Nanograin-boundary-driven anomalous pseudocapacitance in hierarchical Co3O4 nanorods for high-performance lithium-ion batteries
Avvaru V.S., Vincent M., Fernandez I.J., Hinder S.J., Rodriguez M.C., Etacheri V.
Article, Journal of Energy Storage, 2026, DOI Link
View abstract ⏷
Applications of secondary lithium-ion batteries are greatly hindered by their low energy (<300 Wh kg−1) and power density (<400 W kg−1) due to the use of low-capacity graphite anodes possessing sluggish Li-ion diffusion kinetics. Herein, we report a high energy (451 Wh kg−1) and power density (980 W kg−1) lithium-ion full-cell enabled by nanograin-boundary induced pseudocapacitance of hierarchical Co3O4 nanorods. This highly pseudocapacitive (∼81 %) anode exhibited high reversible capacity (1593 mAh g−1 @ 50 mA g−1), rate-performance (800 mAh g−1@ 30 A g−1), cycling stability (∼60 % after 1000 cycles @ 1 A g−1), coulombic efficiency (∼100 %) and ultrafast-charging (∼35 s @ 30 A g−1). These Li-ion storage performances are significantly better than the previously reported conversion type anodes. Li-ion full-cell composed of Co3O4 nanorod anode and LiNiMnCoO2 cathode demonstrated excellent stability (∼85 % after 200 cycles @ 1 A g−1). Mechanistic studies including in-situ XRD and EELS mapping illustrated unique Li-ion storage at nanograin boundaries. Outstanding performance of Co3O4 nanorods anode is credited to the synergy between conversion reaction and pseudocapacitive Li-ion storage at numerous Li2O/Co/Li1.47Co3O3.72 nanointerfaces. This strategy of nanograin-boundary induced pseudocapacitance can be extended for various transition metal-oxide anodes for next-generation high energy/ power density rechargeable batteries.
High performance Mg-Li dual metal-ion batteries based on highly pseudocapacitive hierarchical TiO2-B nanosheet assembled spheres cathodes
Vincent M., Avvaru V.S., Haranczyk M., Etacheri V.
Article, Nanotechnology, 2025, DOI Link
View abstract ⏷
Although Mg-Li dual metal-ion batteries are proposed as a superior system that unite safety of Mg-batteries and performance of Li-ion based systems, its practical implantation is limited due to the lack of reliable high-performance cathodes. Herein, we report a high-performance Mg-Li dual metal-ion battery system based on highly pseudocapacitive hierarchical TiO2-B nanosheet assembled spheres (NS) cathode. This 2D cathode displayed exceptional pseudocapacitance (a maximum of 93%) specific capacity (303 mAh g −1 at 25 mA g−1 ), rate performance (210 mAh g −1 at 1 A g−1 ), consistent cycling (retain ∼100% capacity for 3000 cycles at 1 A g−1 ), Coulombic efficiency (nearly 100%) and fast-charging (∼12.1 min). These properties are remarkably dominant to the existing Mg-Li dual metal-ion battery cathodes. Spectroscopic and microscopic mechanistic studies confirmed negligible structural changes during charge-discharge cycles of the TiO2-B nanosheet assembled spheres electrodes. Exceptional electrochemical properties of the 2D electrode is ascribed to remarkable pseudocapacitive Mg-Li dual metal-ion diffusion via the numerous nanointerfaces of TiO2-B caused by its hierarchical microstrucrure. Large surface area, nanosheet morphology, mesoporous structure and ultrathin nature also acted as secondary factors facilitating improved electrode-electrolyte contact. Demonstrated approach of pseudocapacitive type Mg-Li dual metal-ion intercalation through hierarchical nanointerfaces may be further utilized for the designing of numerous top-notch electrode materials for futuristic Mg-Li dual metal-ion batteries.
Ultrathin (15 nm) Carbon Sheets with Surface Oxygen Functionalization for Efficient Pseudocapacitive Na-ion Storage
Etacheri V., Maca R.R., Avvaru V.S., Hong C.N., Alazemi A., Pol V.G.
Article, ChemElectroChem, 2024, DOI Link
View abstract ⏷
Disordered carbon is the state of the art anode material for Na-ion batteries due to their increased interlayer spacing and good electronic conductivity. However, its practical application is hindered by average specific capacity, poor rate performance, low coulombic efficiency and limited cycling stability. Herein, we report the superior pseudocapacitance enhanced Na-ion storage of in situ surface functionalized carbon nanosheets. Anodes composed of ultrathin (~15 nm) carbon nanosheets demonstrated excellent reversible specific capacity (375 mAh/g at 25 mA/g), rate performance (150 mAh/g at 2 A/g), long-term cycling performance (1000 cycles at 1 A/g) and coulombic efficiency (~100 %). Considerably higher pseudocapacitance (up to ~78 %) is also identified in this case compared to amorphous carbon particles. Spectroscopic and electrochemical studies proved Na-ion intercalation in to the disordered carbon and pseudocapacitive storage driven by oxygen-containing surface functional groups. Outstanding electrochemical performance is credited to the synergy between diffusion limited intercalation and pseudocapacitive surface Na-ion storage. The demonstrated synthetic method of in situ functionalized carbon nanosheets is inexpensive and scalable. The strategy of functional group and morphology induced pseudocapacitive Na-ion storage offer new prospects to design high-performance Na-ion battery electrodes.
Transition Metal Oxide Nanomaterials for Sodium-Ion Batteries and Hybrid Capacitors
Avvaru V.S., Vincent M., Etacheri V.
Book chapter, Materials for Energy Storage, 2024,
Defect-driven ion storage on hexagonal boron nitride for fire-safe and high-performance lithium-ion batteries
Lei Y., Avvaru V.S., Ward Z., Liu H., Fujisawa K., Bepete G., Zhang N., Carreno A.F., Terrones H., Etacheri V., Terrones M.
Article, Chemical Engineering Journal, 2024, DOI Link
View abstract ⏷
The mass market adoption of electric vehicles has increased the risk of safety concerns, such as overheating and flammability. Rational design of fire-safe and high-capacity anodes with thermal tolerance, capable of fast-charging and long cycle-life, is crucial for the development of next generation Li-ion batteries operating under extreme conditions. Here we report a defect engineered hexagonal boron nitride (hBN) anode to mediate the safety dilemma. We demonstrate that the defects generated via cryomilling catalyze the reversible LiF formation and enable the pseudocapacitive type Li-ion storage on hBN. The non-flammability and excellent thermal tolerance of hBN allows high specific capacity (880 mAh/g @ 25 mA/g), rate performance (480 mAh/g @ 5 A/g) and stable cycling (5000 cycles) at 60 °C. The Li-ion full-cell with the defective hBN anode and the conventional cathode (LiNiMnCoO2) delivers significantly higher energy (400 Wh kg−1) and power density (1 kW kg−1) when compared to graphite/LiNiMnCoO2 full-cells (121 Wh kg−1 and 250 W kg−1). First-principles calculations confirm that nitrogen antisite (NBVN) defects are responsible for the electrochemical activation of otherwise inactive hBN. The strategy of defect-induced electrochemical activation opens up new avenues in the design of high-performance electrode materials for numerous secondary batteries.
High-energy sodium-ion hybrid capacitors through nanograin-boundary-induced pseudocapacitance of Co3O4 nanorods
Feng W., Avvaru V.S., Hinder S.J., Etacheri V.
Article, Journal of Energy Chemistry, 2022, DOI Link
View abstract ⏷
Sodium-ion hybrid capacitors (SICs) have been proposed to bridge performance gaps between batteries and supercapacitors, and thus realize both high energy density and power density in a single configuration. Nevertheless, applications of SICs are severely restricted by their insufficient energy densities (<100 Wh/kg) resulted from the kinetics imbalance between cathodes and anodes. Herein, we report a nanograin-boundary-rich hierarchical Co3O4 nanorod anode composed of ∼20 nm nanocrystallites. Extreme pseudocapacitance (up to 72%@1.0 mV/s) is achieved through nanograin-boundary-induced pseudocapacitive-type Na+ storage process. Co3O4 nanorod anode delivers in this case highly reversible capacity (810 mAh/g@0.025 A/g), excellent rate capability (335 mAh/g@5.0 A/g), and improved cycle stability (100 cycles@1.0 A/g with negligible capacity degradation). The outstanding performance can be credited to the hierarchical morphology of Co3O4 nanorods and the well-designed nanograin-boundaries between nanocrystallites that avoid particle agglomeration, induce pseudocapacitive-type Na+ storage, and accommodate volume variation during sodiation-desodiation processes. Nitrogen-doping of the Co3O4 nanorods not only generates defects for extra surficial Na+ storage but also increases the electronic conductivity for efficient charge separation and lowers energy barrier for Na+ intercalation. Synergy of conventional reaction mechanism and pseudocapacitive-type Na+ storage enables high specific capacity, rapid Na+ diffusion, and improved structural stability of the Co3O4 nanorod electrode. The SIC integrating this highly pseudocapacitive anode and activated carbon cathode delivers exceptional energy density (175 Wh/kg@40 W/kg), power density (6632 W/kg@37 Wh/kg), cycle life (6000 cycles@1.0 A/g with a capacity retention of 81%), and coulombic efficiency (∼100%).
Unusual pseudocapacitive lithium-ion storage on defective Co3O4nanosheets
Avvaru V.S., Vincent M., Fernandez I.J., Hinder S.J., Etacheri V.
Article, Nanotechnology, 2022, DOI Link
View abstract ⏷
Secondary lithium-ion batteries are restricted in large-scale applications including power grids and long driving electric vehicles owing to the low specific capacity of conventional intercalation anodes possessing sluggish Li-ion diffusion kinetics. Herein, we demonstrate an unusual pseudocapacitive lithium-ion storage on defective Co3O4 nanosheet anodes for high-performance rechargeable batteries. Cobalt-oxide nanosheets presented here composed of various defects including vacancies, dislocations and grain boundaries. Unique 2D holey microstructure enabled efficient charge transport as well as provided room for volume expansions associated with lithiation-delithiation process. These defective anodes exhibited outstanding pseudocapacitance (up to 87%), reversible capacities (1490 mAh g-1 @ 25 mA g-1), rate capability (592 mAh g-1 @ 30 A g-1), stable cycling (85% after 500 cycles @ 1 A g-1) and columbic efficiency (∼100%). Exceptional Li-ion storage phenomena in defective Co3O4 nanosheets is accredited to the pseudocapacitive nature of conversion reaction resulting from ultrafast Li-ion diffusion through various crystal defects. The demonstrated approach of defect-induced pseudocapacitance can also be protracted for various low-cost and/or eco-friendly transition metal-oxides for next-generation rechargeable batteries.
Fast-charging and long-lasting Mg-Na hybrid batteries based on extremely pseudocapacitive bronze TiO2 nanosheet cathodes
Vincent M., Sai Avvaru V., Haranczyk M., Etacheri V.
Article, Chemical Engineering Journal, 2022, DOI Link
View abstract ⏷
Despite of their inexpensive and sustainable characteristics, practical application of Mg-Na hybrid batteries are limited due to the lack of high performance dual-ion compatible cathode materials. This is mainly due to the increased size of Na-ions and improved electrostatic repulsion resulting from the high charge density of Mg-ions. Herein, we report for the first time a fast charging and ultralong-life Mg-Na hybrid battery based on an extremely pseudocapacitive hierarchical bronze TiO2 (TiO2-B) nanosheet cathode. This two dimensional cathode exhibited outstanding pseudocapacitance (up to 94%), specific capacities (195 mAh/g @ 25 mA/g), rate performance (140 mAh/g @ 1A/g), cycling stability (∼76% after 6000 cycles @ 1A/g), coulombic efficiency (∼100%) and fast-charging (∼8 min). These performances are vastly superior to the previously reported metal oxide type Mg-Na hybrid battery cathodes. Mechanistic investigations revealed Mg-Na dual-ion intercalation pseudocapacitance with no significant structural changes. Exceptional electrochemical performance of the TiO2-B nanosheet cathode is credited to the dominant pseudocapacitive Mg-Na dual-ion diffusion through the nanointerfaces resulting from the hierarchical microstructure of TiO2-B nanosheets. High surface area, ultrathin nature and mesoporous structure are also contributed as secondary factors by facilitating superior contact with the electrolyte solution. The demonstrated method of nanointerfaces induced pseudocapacitive Mg-Na dual-ion intercalation provides new opportunities for the development of high-performance Mg-Na hybrid batteries.
High-Performance Mg−Li Hybrid Batteries Based on Pseudocapacitive Anatase Ti1-xCoxO2-y Nanosheet Cathodes
Vincent M., Avvaru V.S., Haranczyk M., Etacheri V.
Article, ChemSusChem, 2022, DOI Link
View abstract ⏷
Despite the proposed safety, performance, and cost advantages, practical implementation of Mg−Li hybrid batteries is limited due to the unavailability of reliable cathodes compatible with the dual-ion system. Herein, a high-performance Mg−Li dual ion battery based upon cobalt-doped TiO2 cathode was developed. Extremely pseudocapacitance-type Ti1-xCoxO2-y nanosheets consist of an optimum 3.57 % Co-atoms. This defective cathode delivered exceptional pseudocapacitance (maximum of 93 %), specific capacities (386 mAh g−1 at 25 mA g−1), rate performance (191 mAh g−1 at 1 A g−1), cyclability (3000 cycles at 1 A g−1), and coulombic efficiency (≈100 %) and fast charging (≈11 min). This performance was superior to the TiO2-based Mg−Li dual-ion battery cathodes reported earlier. Mechanistic studies revealed dual-ion intercalation pseudocapacitance with negligible structural changes. Excellent electrochemical performance of the cation-doped TiO2 cathode was credited to the rapid pseudocapacitance-type Mg/Li-ion diffusion through the disorder generated by lattice distortions and oxygen vacancies. Ultrathin nature, large surface area, 2D morphology, and mesoporosity also contributed as secondary factors facilitating superior electrode-electrolyte interfacial kinetics. The demonstrated method of pseudocapacitance-type Mg−Li dual-ion intercalation by introducing lattice distortions/oxygen vacancies through selective doping can be utilized for the development of several other potential electrodes for high-performance Mg−Li dual-ion batteries.
Quasi-solid-state sodium-ion hybrid capacitors enabled by UiO-66@PVDF-HFP multifunctional separators: Selective charge transfer and high fire safety
Feng W., Zhang J., Yusuf A., Ao X., Shi D., Etacheri V., Wang D.-Y.
Article, Chemical Engineering Journal, 2022, DOI Link
View abstract ⏷
The practical application of sodium-ion hybrid capacitors is limited by their low energy densities resulted from the kinetics mismatch between cathodes and anodes, and the fire safety related to the flammable electrolyte-separator system. Hence, we report a rational design of metal–organic frameworks (MOFs, UiO-66) modified PVDF-HFP separator. High tensile strength and dimensional thermal stability of the separator reduce the risk of electrode short circuit caused by the separator deformation. MCC test demonstrates a reduction of 75% in peak heat release rate (pHRR), indicating an enhanced fire-resistant property of the separator. This is due to the transformation of UiO-66 into ZrO2 accompanied by the consumption of oxygen and the formation of the barrier char that suppresses further heat release. Quasi-solid-state electrolyte prepared based on this separator presents an enhanced ionic conductivity of 2.44 mS cm−1 and Na-ion transference number of 0.55, which are related to the high porosity (>70%) and electrolyte uptake (~320%) of the separator. Moreover, the open metal sites of UiO-66 can capture PF6–and consequently liberate the Na+ for faster migration, thus reducing the kinetics mismatch between cathodes and anodes. Such multifunctional separator enables the quasi-solid-state Na-ion hybrid capacitor to achieve high energy density (182 Wh kg−1 @31 W kg−1) and power density (5280 W kg−1 @22 Wh kg−1), as well as excellent cyclic stability (10,000 cycles @1000 mA g−1).
Extremely pseudocapacitive interface engineered CoO@3D-NRGO hybrid anodes for high energy/ power density and ultralong life lithium-ion batteries
Avvaru V.S., Fernandez I.J., Feng W., Hinder S.J., Rodriguez M.C., Etacheri V.
Article, Carbon, 2021, DOI Link
View abstract ⏷
Although secondary Li-ion batteries are widely used for electrochemical energy storage, low energy (100–300 Wh kg−1) and power density (250–400 W kg−1) are limiting their applications in several areas including long-range electric vehicles. Herein, we demonstrate high energy (400 Wh kg−1) and power density (1 kW kg−1) Li-ion batteries (considering the weight of both electrodes) based on extremely pseudocapacitive interface engineered CoO@3D-NRGO hybrid anodes. These values are 2.8 and 2.3-fold higher respectively compared to graphite‖LiNiMnCoO2 full-cells under similar experimental conditions. Three-dimensional anode architecture presented here composed of ultrafine CoO nanoparticles (∼10 nm) chemically bonded to nitrogen-doped reduced graphene-oxide. This hybrid anode demonstrated excellent pseudocapacitance (∼92%), specific capacity (1429 mAh g−1 @ 25 mA g−1), rate performance (906 mAh g−1 @ 5 A g−1), and cycling stability (990 mAh g−1 after 7500 cycles @ 5 A g−1). Outstanding electrochemical performance of CoO@3D-NRGO‖LiNiMnCoO2 full-cells is credited to the extreme pseudocapacitance of CoO@3D-NRGO anode resulting from Li2O/Co/NRGO nanointerfaces and Co–O–C bonds. The demonstrated strategy of interfacial engineering can also be extended for other environmental friendly/inexpensive transition metal oxide (Fe2O3, MnO2 etc.) anodes for high energy/power density and ultra-long-life Li-ion batteries.
High-performance lithium sulfur batteries based on multidimensional Graphene-CNT-Nanosulfur hybrid cathodes
Donoro A., Munoz-Mauricio A., Etacheri V.
Article, Batteries, 2021, DOI Link
View abstract ⏷
Although lithium-sulfur (Li-S) batteries are one of the promising candidates for nextgeneration energy storage, their practical implementation is limited by rapid capacity fading due to lithium polysulfide (LiPSs) formation and the low electronic conductivity of sulfur. Herein, we report a high-performance lithium-sulfur battery based on multidimensional cathode architecture consisting of nanosulfur, graphene nanoplatelets (2D) and multiwalled carbon nanotubes (1D). The ultrasonic synthesis method results in the generation of sulfur nanoparticles and their intercalation into the multilayered graphene nanoplatelets. The optimized multidimensional graphene-sulfur-CNT hybrid cathode (GNS58-CNT10) demonstrated a high specific capacity (1067 mAh g-1 @ 50 mA g-1), rate performance (539 @ 1 A g-1), coulombic efficiency (~95%) and cycling stability (726 mAh g-1 after 100 cycles @ 200 mA g-1) compared to the reference cathode. Superior electrochemical performances are credited to the encapsulation of nanosulfur between the individual layers of graphene nanoplatelets with high electronic conductivity, and effective polysulfide trapping byMWCNT bundles.
Effect of vinylene carbonate electrolyte additive on the surface chemistry and pseudocapacitive sodium-ion storage of tio2 nanosheet anodes
Article, Batteries, 2021, DOI Link
View abstract ⏷
Although titanium dioxide has gained much attention as a sodium-ion battery anode material, obtaining high specific capacity and cycling stability remains a challenge. Herein, we report significantly improved surface chemistry and pseudocapacitive Na-ion storage performance of TiO2 nanosheet anode in vinylene carbonate (VC)-containing electrolyte solution. In addition to the excellent pseudocapacitance (~87%), the TiO2 anodes also exhibited increased high-specific capacity (219 mAh/g), rate performance (40 mAh/g @ 1 A/g), coulombic efficiency (~100%), and cycling stability (~90% after 750 cycles). Spectroscopic and microscopic studies confirmed polycarbonate based solid electrolyte interface (SEI) formation in VC-containing electrolyte solution. The superior electrochemical performance of the TiO2 nanosheet anode in VC-containing electrolyte solution is credited to the improved pseudocapacitive Na-ion diffusion through the polycarbonate based SEI (coefficients of 1.65 × 10−14 for PC-VC vs. 6.42 × 10−16 for PC). This study emphasizes the crucial role of the electrolyte solution and electrode–electrolyte interfaces in the improved pseudocapacitive Na-ion storage performance of TiO2 anodes.
Realization of High Energy Density Sodium-Ion Hybrid Capacitors through Interface Engineering of Pseudocapacitive 3D-CoO-NrGO Hybrid Anodes
Feng W., Avvaru V.S., Maca R.R., Hinder S.J., Rodriguez M.C., Etacheri V.
Article, ACS Applied Materials and Interfaces, 2021, DOI Link
View abstract ⏷
Sodium-ion hybrid capacitors (SHCs) have attracted great attention owing to the improved power density and cycling stability in comparison with sodium-ion batteries. Nevertheless, the energy density (<100 Wh·kg-1) is usually limited by low specific capacity anodes (<150 mAh·g-1) and "kinetics mismatch"between the electrodes. Hence, we report a high energy density (153 Wh·kg-1) SHC based on a highly pseudocapacitive interface-engineered 3D-CoO-NrGO anode. This high-performance anode (445 mAh·g-1 @0.025 A·g-1, 135 mAh·g-1 @5.0 A·g-1) consists of CoO (∼6 nm) nanoparticles chemically bonded to the NrGO network through Co-O-C bonds. Exceptional pseudocapacitive charge storage (up to ∼81%) and capacity retention (∼80% after 5000 cycles) are also identified for this SHC. Excellent performance of the 3D-CoO-NrGO anode and SHC is owing to the synergistic effect of the CoO conversion reaction and pseudocapacitive sodium-ion storage induced by numerous Na2O/Co/NrGO nanointerfaces. Co-O-C bonds and the 3D microstructure facilitating efficient strain relaxation and charge-transfer correspondingly are also identified as vital factors accountable for the excellent electrochemical performance. The interface-engineering strategy demonstrated provides opportunities to design high-performance transition metal oxide-based anodes for advanced SHCs.
Erratum: High-Energy-Density Sodium-Ion Hybrid Capacitors Enabled by Interface-Engineered Hierarchical TiO2Nanosheet Anodes (ACS Appl. Mater. Interfaces (2020) 12: 4 (4443-4453) DOI: 10.1021/acsami.9b17775)
Erratum, ACS Applied Materials and Interfaces, 2021, DOI Link
View abstract ⏷
In the original version of this article, the affiliation of Wenliang Feng is changed from "Department of Materials Science, Polytechnic University of Madrid, E.T.S. de Ingenieros de Caminos, 28040, Madrid, Spain" to "Universidad Politécnica de Madrid, E.T.S. de Ingenieros de Caminos, 28040 Madrid, Spain". This correction does not affect any conclusions of the work.
High-rate and ultralong-life Mg–Li hybrid batteries based on highly pseudocapacitive dual-phase TiO2 nanosheet cathodes
Vincent M., Avvaru V.S., Rodriguez M.C., Haranczyk M., Etacheri V.
Article, Journal of Power Sources, 2021, DOI Link
View abstract ⏷
Although Mg–Li hybrid batteries are proposed as an alternative to Mg-batteries, the lack of dual-ion compatible cathodes are limiting their practical application. Herein, we report a high-rate and ultralong-life Mg–Li hybrid battery based on a dual-phase TiO2 cathode. Highly pseudocapacitive hierarchical two-dimensional TiO2 consists of anatase (60%) and bronze (40%) nanocrystallites forming interfaces due to crystal structure mismatch. This dual-phase hierarchical cathode exhibits excellent pseudocapacitance (up to 92%), specific capacities (235 mAh/g @ 25 mA/g), rate performance (120 mAh/g @ 1A/g) cycling stability (~87% after 3000 cycles @ 1A/g) and coulombic efficiency (~100%). These results are vastly superior to the previously reported values for TiO2 based Mg–Li hybrid battery cathodes. Only minimal structural changes are observed during the charge-discharge of two-dimensional TiO2 electrode. Outstanding electrochemical performance of dual-phase TiO2 nanosheet cathode is attributed to the superior pseudocapacitive Mg/Li-ion diffusion through nanointerfaces between anatase and bronze crystallites. While other structural features such as 2D-morphology, ultrathin nature, mesoporosity, and high surface area act as secondary factors. The demonstrated approach for efficient pseudocapacitive Mg/Li-ion intercalation enhanced by nanointerfaces can be further exploited in the development of other high performance electrodes for advanced Mg–Li hybrid batteries.
Iron oxide−iron sulfide hybrid nanosheets as high-performance conversion-type anodes for sodium-ion batteries
Etacheri V., Tirado J.L., Rubio S., Maca R.R., Ortiz G.F., Vicente C.P., Lavela P.
Article, ACS Applied Energy Materials, 2020, DOI Link
View abstract ⏷
Commercialization of Na-ion batteries is hindered by the shortage of abundant and environmentally benign electrode materials with high electrochemical performance. Most of the high-capacity alloying- and conversion-type anodes face rapid capacity loss during prolonged cycling. Herein, we report superior Na-ion storage performance of iron oxide−iron sulfide hybrid nanosheet anodes. Composite anodes containing Fe2O3−FeS and Fe3O4−FeS hybrid nanosheets demonstrated high specific capacities of 487 and 364 mA h g−1, respectively, at a 0.1C rate. These electrodes also exhibited excellent cycling performance, maintaining 330 mA h g−1 after 50 galvanostatic cycles at a 1C rate with ∼100% coulombic efficiency. Mechanistic investigations revealed a high degree of pseudocapacitive-type Na-ion storage (up to ∼65%) in these iron oxide−iron sulfide hybrid nanosheet anodes. Spectroscopic studies confirmed the complete disappearance of the starting oxide and sulfide structures. 57Fe Mössbauer spectroscopy confirmed Na-ion storage through the conversion reaction of iron oxide−iron sulfide hybrid anodes. Excellent Na-ion storing performance in these hybrid anodes compared with that of previously investigated iron sulfide- and iron oxide-based electrodes is accredited to the enhanced pseudocapacitive Na-ion diffusion caused by the two-dimensional microstructure, high surface area, and crystal mismatch between the iron oxide−iron sulfide nanograins of the hierarchical nanosheets.
Nanointerface-driven pseudocapacitance tuning of TiO2 nanosheet anodes for high-rate, ultralong-life and enhanced capacity sodium-ion batteries
Maca R.R., Cintora Juarez D., Castillo Rodriguez M., Etacheri V.
Article, Chemical Engineering Journal, 2020, DOI Link
View abstract ⏷
Titanium dioxide recently gained attention as sodium-ion battery anode material. However, its practical application is hindered by low specific capacity (~150 mAh/g), and mediocre cycling stability. Here we report for the first time, nanointerface-driven Na-ion intercalation pseudocapacitance tuning as a strategy to substantially improve the performance of TiO2 anodes. This is achieved by tuning the crystal mismatch between anatase and bronze crystallites of hierarchical TiO2 nanosheets. Hybrid TiO2 nanosheets composed of ~10 nm sized anatase (~85%) and bronze (~15%) crystallites exhibited significantly higher pseudocapacitive Na-ion storage compared to phase-pure bronze and anatase TiO2 nanosheets. High specific capacity of 290 mAh/g (~0.87 mol Na-ions) at a current density of 25 mA/g is obtained for this composition. Hybrid TiO2 maintained a specific capacity of 120 mAh/g even at a high current density of 1 A/g. Coulombic efficiency (~100%) and cycling stability are outstanding, retaining 90% of the initial capacity after 2500 galvanostatic cycles. These electrochemical performances are noticeably superior to amorphous and crystalline TiO2 reported earlier. Mechanistic studies proved Na-ion intercalation pseudocapacitance without considerable structural changes. Excellent electrochemical performance of dual-phase hierarchical TiO2 nanosheets is credited to the superior Na-ion intercalation pseudocapacitance resulting from anatase-bronze nanointerfaces. The demonstrated strategy of nanointerface-driven pseudocapacitance tuning provides new opportunities for the designing of advanced Na-ion battery anodes.
Hierarchical Co3O4 nanorods anchored on nitrogen doped reduced graphene oxide: A highly efficient bifunctional electrocatalyst for rechargeable Zn-air batteries
Sanchez J.S., Maca R.R., Pendashteh A., Etacheri V., De La Pena O'Shea V.A., Castillo-Rodriguez M., Palma J., Marcilla R.
Article, Catalysis Science and Technology, 2020, DOI Link
View abstract ⏷
Zn-air batteries are amongst the most promising energy storage technologies due to high theoretical energy density for which their practical application is tied to development of low-cost, effective bifunctional catalysts. Herein, a highly efficient bifunctional electrocatalyst was synthesized by hybridizing hierarchical spinel Co3O4 nano-rods with N-rGO. A rational design of the nano-hybrid was realized through optimizing catalytic activity of the pure Co3O4 NRs followed by their grafting onto N-rGO nanosheets. The optimized hybrid (N-rGO/Co3O4 NRs) showed an excellent bifunctional (ORR/OER) catalytic activity with ΔE = Ej=10 - E1/2 as small as 0.78 V, outperforming state-of-the-art noble-metal catalysts (e.g. PtRuC). Rechargeable Zn-air batteries assembled with a N-rGO/Co3O4 NRs hybrid delivered a specific capacity of 875 mA h gZn-1 (corresponding to an exceptional energy density of 1115 W h kgZn-1), a peak power density of 47 mW cm-2 and a stable cycling stability compared to Zn-air batteries based on PtRuC commercial catalyst. Outstanding electrochemical performance of the hybrid ORR/OER catalyst is credited to the hierarchical nature of Co3O4 NRs, optimized Co3+/Co2+ ratio, particle agglomeration prevention and superior electrical conductivity resulting from the hybridization with N-rGO. Rational design of atomic-scale interfaces in the spinel metal oxide-carbon hybrid structures demonstrated here provides new insights for the designing and fabrication of high-performance bifunctional non-precious electrocatalysts for rechargeable Zn-air batteries.
High-Energy-Density Sodium-Ion Hybrid Capacitors Enabled by Interface-Engineered Hierarchical TiO2 Nanosheet Anodes
Article, ACS Applied Materials and Interfaces, 2020, DOI Link
View abstract ⏷
Sodium-ion hybrid capacitors are known for their high power densities and superior cycle life compared to Na-ion batteries. However, low energy densities (<100 Wh kg-1) due to the lack of high-capacity (>150 mAh g-1) anodes capable of fast charging are delaying their practical implementation. Herein, we report a high-performance Na-ion hybrid capacitor based on an interface-engineered hierarchical TiO2 nanosheet anode consisting of bronze (∼15%) and anatase (∼85%) crystallites (∼10 nm). This pseudocapacitive dual-phase anode demonstrated exceptional specific capacity of 289 mAh g-1 at 0.025 A g-1 and excellent rate capability (110 mAh g-1 at 1.0 A g-1). The Na-ion hybrid capacitor integrating a dual-phase hierarchical TiO2 nanosheet anode and an activated carbon cathode exhibited a high energy density of 200 Wh kg-1 (based on the total mass of active materials in both electrodes) and power density of 6191 W kg-1. These values are in the energy and power density range of Li-ion batteries (100-300 Wh kg-1) and supercapacitors (5000-15 »000 W kg-1), respectively. Furthermore, exceptional capacity retention of 80% is observed after 5000 charge-discharge cycles. Outstanding electrochemical performance of the demonstrated Na-ion hybrid capacitor is credited to the enhanced pseudocapacitive Na-ion intercalation of the two-dimensional TiO2 anode resulting from nanointerfaces between bronze and anatase crystallites. Mechanistic investigations evidenced Na-ion storage through intercalation pseudocapacitance with minimal structural changes. This approach of nanointerface-induced pseudocapacitance presents great opportunities toward developing advanced electrode materials for next-generation Na-ion hybrid capacitors.
Blocking Polysulfides in Graphene–Sulfur Cathodes of Lithium–Sulfur Batteries through Atomic Layer Deposition of Alumina
Hong C.N., Kye D.K., Mane A.U., Elam J.W., Etacheri V., Pol V.G.
Article, Energy Technology, 2019, DOI Link
View abstract ⏷
A lithium–sulfur (Li–S) battery is one of the post-lithium-ion battery chemistry candidates due to the high theoretical capacity of the sulfur cathode (1672 mAh g−1). However, low electronic conductivity of sulfur and severe capacity fading during the charge–discharge process limit the commercial realization of Li–S batteries. The origin of capacity fading is mainly due to the polysulfide shuttling effect, resulting from the dissolution of sulfur in the electrolyte solution. Herein, atomic layer deposition (ALD) (6–8 Å thickness) of alumina is presented as a strategy to suppress capacity degradation on the 2D graphene–sulfur hybrid electrode. Low-temperature ALD prevents sulfur sublimation from the composite electrode. Despite the insulating property of alumina, atomic layer coating maintains good electrical conductivity, thereby yielding lower charge transfer resistance. Alumina-coated graphene–sulfur hybrid electrodes (AGS) exhibit a high specific capacity of 960 mAh g−1 at a current density of 50 mA g−1 and retain 519 mAh g−1 after 100 galvanostatic cycles. Superior electrochemical performance is credited to the combination of the high electronic conductivity of multilayered graphene platelets and low charge transfer resistance, resulting from effective polysulfide blocking by the atomic scale Al2O3 coating.
Superior electrochemical performance of TiO2 sodium-ion battery anodes in diglyme-based electrolyte solution
Rubio S., Maca R.R., Aragon M.J., Cabello M., Castillo-Rodriguez M., Lavela P., Tirado J.L., Etacheri V., Ortiz G.F.
Article, Journal of Power Sources, 2019, DOI Link
View abstract ⏷
Sodium-ion batteries are considered a promising alternative to lithium-ion batteries due to its low cost and potential applications for large-scale energy storage. In this work, we focus on improving the Na-ion storage electrochemical performance of TiO2 anodes by using diglyme-based electrolyte solutions. Significantly better performances are observed for the first time in diglyme-based electrolyte solution, as compared to conventional carbonate electrolyte solutions with and without additives such as fluoroethylene carbonate (FEC) and vinylene (VC). The best TiO2 electrode demonstrated a high specific capacity of 248 mA h g−1 at 25 mA g−1 current density, ∼100% coulombic efficiency, superior pseudocapacitive Na-ion storage, and good capacity retention on extended galvanostatic charge-discharge cycles. A full-cell assembled with TiO2 anode, Na3V2(PO4)3 cathode and NaPF6-diglyme electrolyte solution demonstrated an energy density as high as 440 W h kg−1. Superior electrochemical performance of TiO2 anodes in diglyme-based electrolyte is credited to the enhanced passivation and Na-ion conducting properties of polyether-based solid electrolyte interfaces (SEI) compared to polycarbonate-based counterparts. Carbon coating also resulted in the reduced decomposition of both diglyme and carbonate based electrolyte solutions. These results potentially encourage the use of ether-based electrolyte solutions for further improving the electrochemical performance and commercialization of rechargeable Na-ion batteries.
Carbon-based integrated devices for efficient photo-energy conversion and storage
Gayen R.N., Avvaru V.S., Etacheri V.
Book chapter, Carbon Based Nanomaterials for Advanced Thermal and Electrochemical Energy Storage and Conversion, 2019, DOI Link
View abstract ⏷
Increasing energy demand and depleting fossil fuel resources require exploration of sustainable energy resources and efficient storage of the generated energy. There have been numerous efforts to develop solar cells and batteries/capacitors for energy conversion and storage, respectively. Integration of energy conversion and storage components into a single device has been recently demonstrated as effective to increase the efficiency and reduce size/weight of the hybrid devices. Photo-rechargeable integrated energy storage devices are promising candidates for portable applications. As of now, efficiency of around 5% was obtained in a complete device with dye-sensitized solar cell and supercapacitor. Carbon nanostructures have already possessed a great place in the modern-day energy research mainly due to the immense possibility in realization of environmentally friendly, cost-effective, flexible devices that can efficiently convert and store energy. Application of various carbonaceous materials in integrated devices for efficient photo-energy conversion and storage are summarized in this chapter.
Carbon nanomaterials for rechargeable lithium-sulfur batteries
Donoro A., Cintora-Juarez D., Etacheri V.
Book chapter, Carbon Based Nanomaterials for Advanced Thermal and Electrochemical Energy Storage and Conversion, 2019, DOI Link
View abstract ⏷
Rechargeable lithium-sulfur (Li-S) batteries are capable candidates for next generation high performance devices including long-range electric vehicles. Historically, most of the commercialized battery technologies consist of various carbonaceous materials, and Li-S batteries are no exception. This technology has received significant interest for the last 30 years after the development of sulfur-carbon composite cathode in which carbon played crucial roles in ensuring electrical conductivity and confinement of the active material. The main focus of the Li-S battery cathode design involves engineering carbon materials of required electrical, morphological, textural, chemical, and other functional properties to enable the efficient utilization of the sulfur-based cathode, which is covered in the first part of this chapter. Furthermore, as reviewed in the second part of the chapter, the application of carbon, either as an anode material or as a component of lithium-based anodes, results in the development of safer and high-energy density Li-ion sulfur batteries.
Carbon based nanomaterials for advanced thermal and electrochemical energy storage and conversion
Paul R., Etacheri V., Wang Y., Lin C.-T.
Book, Carbon Based Nanomaterials for Advanced Thermal and Electrochemical Energy Storage and Conversion, 2019, DOI Link
View abstract ⏷
Carbon Based Nanomaterials for Advanced Thermal and Electrochemical Energy Storage and Conversion presents a comprehensive overview of recent theoretical and experimental developments and prospects on carbon-based nanomaterials for thermal, solar and electrochemical energy conversion, along with their storage applications for both laboratory and industrial perspectives. Large growth in human populations has led to seminal growth in global energy consumption, hence fossil fuel usage has increased, as have unwanted greenhouse gases, including carbon dioxide, which results in critical environmental concerns. This book discusses this growing problem, aligning carbon nanomaterials as a solution because of their structural diversity and electronic, thermal and mechanical properties.
Carbon nanotubes, graphene, porous carbon, and hybrid carbon-based materials: Synthesis, properties, and functionalization for efficient energy storage
Paul R., Vincent M., Etacheri V., Roy A.K.
Book chapter, Carbon Based Nanomaterials for Advanced Thermal and Electrochemical Energy Storage and Conversion, 2019, DOI Link
View abstract ⏷
Reliable energy generation at lowest expenditure has become essential for fulfilling present energy requirements. For this purpose, development of low-cost, scalable, efficient, and reliable catalysts is essential. Carbon-based materials are very promising for various energy storage application. Carbon-based heteroatom doped mesoporous electrodes have become very popular as catalysts for electrochemical energy conversion and storage. Various carbon allotropes can be utilized for cost-effective mass production of electrode materials. 3D porous carbon electrodes provide multiple advantages, including a large surface area for maximized active site exposure, 3D conductive pathways for efficient electron transport, and porous channels to facilitate electrolyte diffusion. However, it is challenging to synthesize and functionalize 3D carbon structures. In this chapter, we summarize various synthesis processes of porous carbon materials together with 3D architectures to understand how their physical and chemical properties together with heteroatom doping dictate the electrochemical catalytic performance. Prospects of attractive 3D carbon structural materials for energy conversion, and efficient integrated energy systems are also discussed.
High rate hybrid MnO2@CNT fabric anodes for Li-ion batteries: Properties and a lithium storage mechanism study by: In situ synchrotron X-ray scattering
Rana M., Sai Avvaru V., Boaretto N., De La Pena O'Shea V.A., Marcilla R., Etacheri V., Vilatela J.J.
Article, Journal of Materials Chemistry A, 2019, DOI Link
View abstract ⏷
High-performance anodes for rechargeable Li-ion batteries are produced by nanostructuring of transition metal oxides on a conductive support. Here, we demonstrate a hybrid material of MnO2 directly grown onto fabrics of carbon nanotube fibres, which exhibits notable specific capacities over 1100 and 500 mA h g-1 at discharge current densities of 25 mA g-1 and 5 A g-1, respectively, with a coulombic efficiency of 97.5%. Combined with 97% capacity retention after 1500 cycles at a current density of 5 A g-1, both capacity and stability are significantly above literature data. Detailed investigations involving electrochemical and in situ synchrotron X-ray scattering studies reveal that during galvanostatic cycling, MnO2 undergoes an irreversible phase transition to LiMnO2, which stores lithium through an intercalation process, followed by a conversion mechanism and pseudocapacitive processes. This mechanism is further confirmed by Raman spectroscopy and X-ray photoelectron spectroscopy. The fraction of pseudocapacitive charge storage ranges from 27% to 83%, for current densities from 25 mA g-1 to 5 A g-1. The firm attachment of the active material to the built-in current collector makes the electrodes flexible and mechanically robust, and ensures that the low charge transfer resistance and the high electrode surface area remain after irreversible phase transition of the active material and extensive cycling.
Spherical cobalt/cobalt oxide – Carbon composite anodes for enhanced lithium-ion storage
Patrinoiu G., Etacheri V., Somacescu S., Teodorescu V.S., Birjega R., Culita D.C., Hong C.N., Calderon-Moreno J.M., Pol V.G., Carp O.
Article, Electrochimica Acta, 2018, DOI Link
View abstract ⏷
Herein we report a simple and scalable route to synthesize porous cobalt/cobalt oxide - carbon sphere composites as anode material for rechargeable lithium-ion batteries. It involves the impregnation of starch-derived hydrochar spheres with a cobalt salt, followed by a heat treatment (700 °C) under inert atmosphere. The obtained high surface area (∼670 m2 g−1), submicron spheres (∼300 nm diameter) with high-degree of microporosity (81%) consist of an amorphous carbon matrix with embedded Co/CoO nanoparticles (∼6 nm sized), having a total cobalt content of 6.2 wt%. The hybrid sphere anodes demonstrated superior specific capacity, rate performance and cycling stability. Discharge capacities of 520 and 310 mA h g−1 are observed at charge-discharge rates of 0.1 and 1C respectively. No significant capacity fading is identified on prolonged cycling at various current densities. The electrode also demonstratedexcellent structural stability during extended charge-discharge processes.
Cobalt Nanoparticles Chemically Bonded to Porous Carbon Nanosheets: A Stable High-Capacity Anode for Fast-Charging Lithium-Ion Batteries
Etacheri V., Hong C.N., Tang J., Pol V.G.
Article, ACS Applied Materials and Interfaces, 2018, DOI Link
View abstract ⏷
A two-dimensional electrode architecture of ∼25 nm sized Co nanoparticles chemically bonded to ∼100 nm thick amorphous porous carbon nanosheets (Co@PCNS) through interfacial Co-C bonds is reported for the first time. This unique 2D hybrid architecture incorporating multiple Li-ion storage mechanisms exhibited outstanding specific capacity, rate performance, and cycling stabilities compared to nanostructured Co3O4 electrodes and Co-based composites reported earlier. A high discharge capacity of 900 mAh/g is achieved at a charge-discharge rate of 0.1C (50 mA/g). Even at high rates of 8C (4 A/g) and 16C (8 A/g), Co@PCNS demonstrated specific capacities of 620 and 510 mAh/g, respectively. Integrity of interfacial Co-C bonds, Co nanoparticles, and 90% of the initial capacity are preserved after 1000 charge-discharge cycles. Implementation of Co nanoparticles instead of Co3O4 restricted Li2O formation during the charge-discharge process. In situ formed Co-C bonds during the pyrolysis steps improve interfacial charge transfer, and eliminate particle agglomeration, identified as the key factors responsible for the exceptional electrochemical performance of Co@PCNS. Moreover, the nanoporous microstructure and 2D morphology of carbon nanosheets facilitate superior contact with the electrolyte solution and improved strain relaxation. This study summarizes design principles for fabricating high-performance transition-metal-based Li-ion battery hybrid anodes.
Electrospun nanoporous TiO2 nanofibers wrapped with reduced graphene oxide for enhanced and rapid lithium-ion storage
Thirugunanam L., Kaveri S., Etacheri V., Ramaprabhu S., Dutta M., Pol V.G.
Article, Materials Characterization, 2017, DOI Link
View abstract ⏷
A high reversible Li-ion storage capacity (200 mAh/g) with C/10 rate and good rate capability is achieved in reduced graphene oxide (rGO) wrapped anatase mesoporous TiO2 nanofiber anodes fabricated by electrospinning. X-ray analysis of rGO wrapped TiO2 nanofibers confirmed the crystalline anatase structure of TiO2, while Raman spectroscopy established high frequency shift caused by the interaction of TiO2 with 2–4 layers of rGO. FT-IR analysis of rGO wrapped TiO2 nanofibers revealed disappearance of C–C, C–O, and C–OH stretching frequencies suggesting the successful reduction of GO to graphene, further confirmed by X-ray Photoelectron spectroscopy. The BET surface area of TiO2 nanofibers (54 m2 g− 1) increased to 105 m2 g− 1 after wrapping rGO leading to mesoporous structure with pore diameters 5–20 nm, complementary observations with scanning and transmission electron microscopies. The oxidation/reduction peaks revealed lithium insertion and lithium extraction mechanism, from 1D TiO2 fibers with superior electrode/electrolyte contacts, with shorter Li-ion diffusion length and improved ionic conductivity. Successful anchoring of rGO on TiO2 nanofiber with Ti3 +-C bonds energetically favors the electrochemical reaction yielding high rate and specific TiO2 capacity as a promising anode of lithium ion battery.
Enhanced Lithium- and Sodium-Ion Storage in an Interconnected Carbon Network Comprising Electronegative Fluorine
Hong S.-M., Etacheri V., Hong C.N., Choi S.W., Lee K.B., Pol V.G.
Article, ACS Applied Materials and Interfaces, 2017, DOI Link
View abstract ⏷
Fluorocarbon (CxFy) anode materials were developed for lithium- and sodium-ion batteries through a facile one-step carbonization of a single precursor, polyvinylidene fluoride (PVDF). Interconnected carbon network structures were produced with doped fluorine in high-temperature carbonization at 500-800 °C. The fluorocarbon anodes derived from the PVDF precursor showed higher reversible discharge capacities of 735 mAh g-1 and 269 mAh g-1 in lithium- and sodium-ion batteries, respectively, compared to the commercial graphitic carbon. After 100 charge/discharge cycles, the fluorocarbon showed retentions of 91.3% and 97.5% in lithium (at 1C) and sodium (at 200 mA g-1) intercalation systems, respectively. The effects of carbonization temperature on the electrochemical properties of alkali metal ion storage were thoroughly investigated and documented. The specific capacities in lithium- and sodium-ion batteries were dependent on the fluorine content, indicating that the highly electronegative fluorine facilitates the insertion/extraction of lithium and sodium ions in rechargeable batteries.
Biomineralization-inspired crystallization of monodisperse α-Mn2O3 octahedra and assembly of high-capacity lithium-ion battery anodes
Henzie J., Etacheri V., Jahan M., Rong H., Hong C.N., Pol V.G.
Article, Journal of Materials Chemistry A, 2017, DOI Link
View abstract ⏷
Uniform colloidal building-blocks enable the creation of more stable, structurally sophisticated materials. Here we describe a simple polymer-mediated approach to generate grams of monodisperse, single-crystal α-Mn2O3 nanocrystals bound by {111} facets. The technique is inspired in part by biomineralization, where organisms use macromolecular matrices or compartments to trigger the oriented nucleation and growth of crystalline phases. Polyvinylpyrrolidone (PVP) behaves as a polymeric nano-reactor by coordinating to the manganese (Mn) precursor while recruiting the NOx oxidizing agent from solution to drive the co-precipitation of the manganese oxide. PVP also serves as a molecular template to guide the nucleation of trigonal bipyramids composed of Mn3O4. The porosity of the Mn3O4 particles indicates that they form non-classically via oriented attachment instead of atom-by-atom. The particles are further oxidized and transform into single-crystal α-Mn2O3 octahedra. This co-precipitation approach is advantageous because it can generate large amounts of monodisperse nanocrystals at low economic cost. α-Mn2O3 is an alternative lithium ion battery (LIB) anode material that is earth abundant and has ∼2.7 times higher capacity than conventional graphite anodes. We assembled the monodisperse α-Mn2O3 octahedra into LIB anodes to examine their performance in a realistic device. The α-Mn2O3 octahedra exhibit good rate performance, cycling stability, coulombic efficiency and morphology retention during extended lithiation-delithiation cycles compared to previous reports for this material. We attribute the improved electrochemical performance of the α-Mn2O3 octahedra to the lack of agglomeration in the uniformly distributed electrode and improved lithiation of single crystalline α-Mn2O3 nanoparticles.
Wild Fungus Derived Carbon Fibers and Hybrids as Anodes for Lithium-Ion Batteries
Article, ACS Sustainable Chemistry and Engineering, 2016, DOI Link
View abstract ⏷
We reported a facile synthesis of carbonaceous fibers directly from Tyromyces fissilis wild fungus through a controlled carbonization process. Electron micrograph observations revealed that as-prepared carbon fibers are composed of 40-60 μm long solid and tubular fibers mimicking their natural texture. Raman spectroscopy and X-ray diffraction indicated that these carbon fibers are possessing disordered carbon structure with larger interlayer spacing (0.386 nm) than graphite (0.335 nm). These carbon fibers delivered specific reversible capacity of 340 mAh/g at C/10 rate and 300 mAh/g at C/5 rate. Electrochemical performance of as-prepared carbon fibers was further improved by uniform decoration of cobalt oxide particles via solid state thermal processing. CoO-carbon fiber hybrid anode delivered higher reversible capacity, 530 mAh/g at C/10 rate with only 10 mol % of CoO loading. This improvement is attributed to the synergistic effect, namely conductive network of cross-linked carbon fibers and facile electrochemical reaction with deposited monodispersed CoO nanoclusters. Cyclic voltammetry and electrochemical impedance spectroscopy on both carbon fiber and hybrid anodes were conducted to comprehend the lithiation and delithiation processes.
Highly porous three-dimensional carbon nanotube foam as a freestanding anode for a lithium-ion battery
Paul R., Etacheri V., Pol V.G., Hu J., Fisher T.S.
Article, RSC Advances, 2016, DOI Link
View abstract ⏷
Anodes composed of freestanding, binder-free and hierarchical multiwalled carbon nanotube (MWCNT) foam have been demonstrated. These three-dimensional MWCNT foams are fabricated using a Ti-Al-Fe trilayer catalyst on Ni-foam through a microwave plasma assisted chemical vapor deposition. The MWCNT foam possesses a hierarchical graphitic microstructure, high porosity (99.8%), reduced impedance and specific capacitance of 790 mA h g-1 when cycled between 0 and 3 V for a lower current density (0.1C). At a higher current density (1C), the foam electrode retains a discharge capacity of 390 mA h g-1, significantly higher than that of the commercial graphite anode. Upon extended charge-discharge cycling, MWCNT foams shows stable capacities of 790 and 510 mA h g-1 at current densities of 0.1C and 1C respectively, maintaining a high coulombic efficiency of 99.7%. Preserved structural and chemical stability of the MWCNT foams during lithiation-delithiation cycling can be utilized as a basis for improved electrochemical energy storage in CNT based architectures.
Visible-light activation of TiO2 photocatalysts: Advances in theory and experiments
Etacheri V., Di Valentin C., Schneider J., Bahnemann D., Pillai S.C.
Review, Journal of Photochemistry and Photobiology C: Photochemistry Reviews, 2015, DOI Link
View abstract ⏷
The remarkable achievement by Fujishima and Honda (1972) in the photo-electrochemical water splitting results in the extensive use of TiO2 nanomaterials for environmental purification and energy storage/conversion applications. Though there are many advantages for the TiO2 compared to other semiconductor photocatalysts, its band gap of 3.2eV restrains application to the UV-region of the electromagnetic spectrum (λ≤387.5nm). As a result, development of visible-light active titanium dioxide is one of the key challenges in the field of semiconductor photocatalysis. In this review, advances in the strategies for the visible light activation, origin of visible-light activity, and electronic structure of various visible-light active TiO2 photocatalysts are discussed in detail. It has also been shown that if appropriate models are used, the theoretical insights can successfully be employed to develop novel catalysts to enhance the photocatalytic performance in the visible region. Recent developments in theory and experiments in visible-light induced water splitting, degradation of environmental pollutants, water and air purification and antibacterial applications are also reviewed. Various strategies to identify appropriate dopants for improved visible-light absorption and electron-hole separation to enhance the photocatalytic activity are discussed in detail, and a number of recommendations are also presented.
Upcycling of Packing-Peanuts into Carbon Microsheet Anodes for Lithium-Ion Batteries
Article, Environmental Science and Technology, 2015, DOI Link
View abstract ⏷
Porous carbon microsheet anodes with Li-ion storage capacity exceeding the theoretical limit are for the first time derived from waste packing-peanuts. Crystallinity, surface area, and porosity of these 1 thick carbon sheets were tuned by varying the processing temperature. Anodes composed of the carbon sheets outperformed the electrochemical properties of commercial graphitic anode in Li-ion batteries. At a current density of 0.1 C, carbon microsheet anodes exhibited a specific capacity of 420 mAh/g, which is slightly higher than the theoretical capacity of graphite (372 mAh/g) in Li-ion half-cell configurations. At a higher rate of 1 C, carbon sheets retained 4-fold higher specific capacity (220 mAh/g) compared to those of commercial graphitic anode. After 100 charge-discharge cycles at current densities of 0.1 and 0.2 C, optimized carbon sheet anodes retained stable specific capacities of 460 and 370 mAh/g, respectively. Spectroscopic and microscopic investigations proved the structural integrity of these high-performance carbon anodes during numerous charge-discharge cycles. Considerably higher electrochemical performance of the porous carbon microsheets are endorsed to their disorderness that facilitate to store more Li-ions than the theoretical limit, and porous 2-D microstructure enabling fast solid-state Li-ion diffusion and superior interfacial kinetics. The work demonstrated here illustrates an inexpensive and environmentally benign method for the upcycling of packaging materials into functional carbon materials for electrochemical energy storage.
Porous carbon sphere anodes for enhanced lithium-ion storage
Etacheri V., Wang C., O'Connell M.J., Chan C.K., Pol V.G.
Article, Journal of Materials Chemistry A, 2015, DOI Link
View abstract ⏷
Amorphous and turbostratic porous carbon spheres are synthesized through a template-free spray pyrolysis method. Anodes composed of these non-graphitic carbon spheres outperformed the commercial graphitic carbon anodes in rechargeable Li-ion batteries. A discharge capacity of 378 mA h g<sup>-1</sup>, which is equivalent to the theoretical limit of 372 mA h g<sup>-1</sup>, is achieved at a current density of 0.1 C (37.2 mA g<sup>-1</sup>). At a higher charge-discharge rate of 1 C, electrochemically most active turbostratic carbon spheres exhibited a reversible specific capacity of 270 mA h g<sup>-1</sup>, which is 4-fold higher compared to those of commercial graphitic carbon anodes. After 100 charge-discharge cycles at current densities of 0.1 C and 1 C, carbon spheres retained stable specific capacities of 365 and 250 mA h g<sup>-1</sup>, respectively. Spectroscopic and microscopic investigation of porous carbon anodes after 100 galvanostatic cycles illustrated an excellent structural stability of turbostratic carbon spheres during the lithiation-delithiation process. The notably higher electrochemical performance of carbon spheres is explained by their disordered crystal structure and porosity, which resulted in lower impedance and superior rate performance. This study demonstrates porous turbostratic carbon spheres having a higher charge potential and sloping profile as promising anodes for rechargeable Li-ion batteries.
Ultrasmooth submicrometer carbon spheres as lubricant additives for friction and wear reduction
Alazemi A.A., Etacheri V., Dysart A.D., Stacke L.-E., Pol V.G., Sadeghi F.
Article, ACS Applied Materials and Interfaces, 2015, DOI Link
View abstract ⏷
Ultrasmooth submicrometer carbon spheres are demonstrated as an efficient additive for improving the tribological performance of lubricating oils. Carbon spheres with ultrasmooth surfaces are fabricated by ultrasound assisted polymerization of resorcinol and formaldehyde followed by controlled heat treatment. The tribological behavior of the new lubricant mixture is investigated in the boundary and mixed lubrication regimes using a pin-on-disk apparatus and cylinder-on-disk tribometer, respectively. The new lubricant composition containing 3 wt % carbon spheres suspended in a reference SAE 5W30 engine oil exhibited a substantial reduction in friction and wear (10-25%) compared to the neat oil, without change in the viscosity. Microscopic and spectroscopic investigation of the carbon spheres after the tribological experiments illustrated their excellent mechanical and chemical stability. The significantly better tribological performance of the hybrid lubricant is attributed to the perfectly spherical shape and ultrasmooth surface of carbon sphere additive filling the gap between surfaces and acting as a nanoscale ball bearing.
Ordered network of interconnected SnO2 nanoparticles for excellent lithium-ion storage
Etacheri V., Seisenbaeva G.A., Caruthers J., Daniel G., Nedelec J.-M., Kessler V.G., Pol V.G.
Article, Advanced Energy Materials, 2015, DOI Link
View abstract ⏷
An ordered network of interconnected tin oxide (SnO2) nanoparticles with a unique 3D architecture and an excellent lithium-ion (Li-ion) storage performance is derived for the first time through hydrolysis and thermal self-assembly of the solid alkoxide precursor. Mesoporous anodes composed of these ≈9 nm-sized SnO2 particles exhibit substantially higher specific capacities, rate performance, coulombic efficiency, and cycling stabilities compared with disordered nanoparticles and commercial SnO2. A discharge capacity of 778 mAh g-1, which is very close to the theoretical limit of 781 mAh g-1, is achieved at a current density of 0.1 C. Even at high rates of 2 C (1.5 A g-1) and 6 C (4.7 A g-1), these ordered SnO2 nanoparticles retain stable specific capacities of 430 and 300 mAh g-1, respectively, after 100 cycles. Interconnection between individual nanoparticles and structural integrity of the SnO2 electrodes are preserved through numerous charge-discharge process cycles. The significantly better electrochemical performance of ordered SnO2 nanoparticles with a tap density of 1.60 g cm-3 is attributed to the superior electrode/electrolyte contact, Li-ion diffusion, absence of particle agglomeration, and improved strain relaxation (due to tiny space available for the local expansion). This comprehensive study demonstrates the necessity of mesoporosity and interconnection between individual nanoparticles for improving the Li-ion storage electrochemical performance of SnO2 anodes. A unique nanoarchitecture of interconnected SnO2 particles is demonstrated as a high-performance Li-ion battery anode. Excellent Li-ion storage properties of these SnO2 anodes are attributed to the synergetic effect of ultrafine particle size and interconnected microstructure.
Mesoporous, nanocrystalline SnO2 anodes for excellent lithium ion storage
Etacheri V., Seisenbaeva G.A., Kessler V.G., Pol V.G.
Conference paper, Nanomaterials for Energy Applications 2014 - Topical Conference at the 2014 AIChE Annual Meeting, 2014,
Mesoporous, nanocrystalline SnO2 anodes for excellent lithium ion storage
Etacheri V., Seisenbaeva G.A., Kessler V.G., Pol V.G.
Conference paper, International Congress on Energy 2014, ICE 2014 - Topical Conference at the 2014 AIChE Annual Meeting, 2014,
Chemically bonded TiO2-Bronze nanosheet/reduced graphene oxide hybrid for high-power lithium ion batteries
Etacheri V., Yourey J.E., Bartlett B.M.
Article, ACS Nano, 2014, DOI Link
View abstract ⏷
Although Li-ion batteries have attracted significant interest due to their higher energy density, lack of high rate performance electrode materials and intrinsic safety issues challenge their commercial applications. Herein, we demonstrate a simple photocatalytic reduction method that simultaneously reduces graphene oxide (GO) and anchors (010)-faceted mesoporous bronze-phase titania (TiO2-B) nanosheets to reduced graphene oxide (RGO) through Ti 3+-C bonds. Formation of Ti3+-C bonds during the photocatalytic reduction process was identified using electron paramagnetic resonance (EPR) and X-ray photoelectron spectroscopy (XPS) techniques. When cycled between 1-3 V (vs Li+/0), these chemically bonded TiO 2-B/RGO hybrid nanostructures show significantly higher Li-ion storage capacities and rate capability compared to bare TiO2-B nanosheets and a physically mixed TiO2-B/RGO composite. In addition, 80% of the initial specific (gravimetric) capacity was retained even after 1000 charge-discharge cycles at a high rate of 40C. The improved electrochemical performance of TiO2-B/RGO nanoarchitectures is attributed to the presence of exposed (010) facets, mesoporosity, and efficient interfacial charge transfer between RGO monolayers and TiO2-B nanosheets. © 2014 American Chemical Society.
Mesoporous TiO2-B microflowers composed of (1 1 0) facet-exposed nanosheets for fast reversible lithium-ion storage
Etacheri V., Kuo Y., Van Der Ven A., Bartlett B.M.
Article, Journal of Materials Chemistry A, 2013, DOI Link
View abstract ⏷
A new method was developed to synthesize nanosheet-assembled TiO 2-B microflowers for Li-ion batteries. Significantly higher electrochemical performance of these microflowers compared to other TiO 2-B nanostructures was attributed to their hierarchical microstructure and exposed (1 1 0) facets of the individual nanosheets. © 2013 The Royal Society of Chemistry.
Hierarchical activated carbon microfiber (ACM) electrodes for rechargeable Li-O2 batteries
Etacheri V., Sharon D., Garsuch A., Afri M., Frimer A.A., Aurbach D.
Article, Journal of Materials Chemistry A, 2013, DOI Link
View abstract ⏷
Hierarchical activated carbon microfiber (ACM) and ACM/α-MnO 2 nanoparticle hybrid electrodes were fabricated for high performance rechargeable Li-O2 batteries. Various oxygen diffusion channels present in these air-cathodes were not blocked during the oxygen reduction reactions (ORR) in triglyme-LiTFSI (1 M) electrolyte solution. ACM and ACM/α-MnO2 hybrid electrodes exhibited a maximum specific capacity of 4116 mA h gc-1 and 9000 mA h g c-1, respectively, in comparison to 2100 mA h g c-1 for conventional carbon composite air-electrodes. Energy densities of these electrodes were remarkably higher than those of sulfur cathodes and the most promising lithium insertion electrodes. In addition, ACM and ACM/α-MnO2 hybrid electrodes exhibited lower charge voltages of 4.3 V and 3.75 V respectively compared to 4.5 V for conventional composite carbon electrodes. Moreover, these binder free electrodes demonstrated improved cycling performances in contrast to the carbon composite electrodes. The superior electrochemical performance of these binder free microfiber electrodes has been attributed to their extremely high surface area, hierarchical microstructure and efficient ORR catalysis by α-MnO 2 nanoparticles. The results showed herein demonstrate that the air-cathode architecture is a critical factor determining the electrochemical performance of rechargeable Li-O2 batteries. This study also demonstrates the instability of ether based electrolyte solutions during oxygen reduction reactions, which is a critical problem for Li-O2 batteries. © The Royal Society of Chemistry 2013.
A highly efficient TiO2-xCx nano-heterojunction photocatalyst for visible light induced antibacterial applications
Etacheri V., Michlits G., Seery M.K., Hinder S.J., Pillai S.C.
Article, ACS Applied Materials and Interfaces, 2013, DOI Link
View abstract ⏷
Visible-light-induced antibacterial activity of carbon-doped anatase-brookite titania nano-heterojunction photocatalysts are reported for the first time. These heterostructures were prepared using a novel low temperature (100 C) nonhydrothermal low power microwave (300 W) assisted method. Formation of interband C 2p states was found to be responsible for the band gap narrowing of the carbon doped heterojunctions. The most active photocatalyst obtained after 60 min of microwave irradiation exhibits a 2-fold higher visible-light induced photocatalytic activity in contrast to the standard commercial photocatalyst Evonik-Degussa P-25. Staphylococcus aureus inactivation rate constant for carbon-doped nano-heterojunctions and the standard photocatalyst was 0.0023 and -0.0081 min-1, respectively. It is proposed that the photoexcited electrons (from the C 2p level) are effectively transferred from the conduction band of brookite to that of anatase causing efficient electron-hole separation, which is found to be responsible for the superior visible-light induced photocatalytic and antibacterial activities of carbon-doped anatase-brookite nano-heterojunctions. © 2013 American Chemical Society.
On the challenge of electrolyte solutions for Li-air batteries: Monitoring oxygen reduction and related reactions in polyether solutions by spectroscopy and EQCM
Sharon D., Etacheri V., Garsuch A., Afri M., Frimer A.A., Aurbach D.
Article, Journal of Physical Chemistry Letters, 2013, DOI Link
View abstract ⏷
Polyether solvents are considered interesting and important candidates for Li-O2 battery systems. Discharge of Li-O2 battery systems forms Li oxides. Their mechanism of formation is complex. The stability of most relevant polar aprotic solvents toward these Li oxides is questionable. Specially high surface area carbon electrodes were developed for the present work. In this study, several spectroscopic tools and in situ measurements using electrochemical quartz crystal microbalance (EQCM) were employed to explore the discharge-charge processes and related side reactions in Li-O2 battery systems containing electrolyte solutions based on triglyme/lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) electrolyte solutions. The systematic mechanism of lithium oxides formation was monitored. A combination of Fourier transform infrared (FTIR), NMR, and matrix-assisted laser desorption/ionization (MALDI) measurements in conjunction with electrochemical studies demonstrated the intrinsic instability and incompatibility of polyether solvents for Li-air batteries. © 2012 American Chemical Society.
Nanostructured Ti1- xSxO2- yNy heterojunctions for efficient visible-light-induced photocatalysis
Etacheri V., Seery M.K., Hinder S.J., Pillai S.C.
Article, Inorganic Chemistry, 2012, DOI Link
View abstract ⏷
Highly visible-light-active S,N-codoped anatase-rutile heterojunctions are reported for the first time. The formation of heterojunctions at a relatively low temperature and visible-light activity are achieved through thiourea modification of the peroxo-titania complex. FT-IR spectroscopic studies indicated the formation of a Ti4+-thiourea complex upon reaction between peroxo-titania complex and thiourea. Decomposition of the Ti 4+-thiourea complex and formation of visible-light-active S,N-codoped TiO2 heterojunctions are confirmed using X-ray diffraction, Raman spectroscopy, transmission electron microscopy, and UV/vis spectroscopic studies. Existence of sulfur as sulfate ions (S6+) and nitrogen as lattice (N-Ti-N) and interstitial (Ti-N-O) species in heterojunctions are identified using X-ray photoelectron spectroscopy (XPS) and FT-IR spectroscopic techniques. UV-vis and valence band XPS studies of these S,N-codoped heterojunctions proved the fact that the formation of isolated S 3p, N 2p, and η * N-O states between the valence and conduction bands are responsible for the visible-light absorption. Titanium dioxide obtained from the peroxo-titania complex exists as pure anatase up to a calcination temperature as high as 900 °C. Whereas, thiourea-modified samples are converted to S,N-codoped anatase-rutile heterojunctions at a temperature as low as 500 °C. The most active S,N-codoped heterojunction 0.2 TU-TiO2 calcined at 600 °C exhibits a 2-fold and 8-fold increase in visible-light photocatalytic activities in contrast to the control sample and the commercial photocatalyst Degussa P-25, respectively. It is proposed that the efficient electron-hole separation due to anatase to rutile electron transfer is responsible for the superior visible-light-induced photocatalytic activities of S,N-codoped heterojunctions. © 2012 American Chemical Society.
Mg-doped ZnO nanoparticles for efficient sunlight-driven photocatalysis
Article, ACS Applied Materials and Interfaces, 2012, DOI Link
View abstract ⏷
Magnesium-doped ZnO (ZMO) nanoparticles were synthesized through an oxalate coprecipitation method. Crystallization of ZMO upon thermal decomposition of the oxalate precursors was investigated using differential scanning calorimetry (DSC) and X-ray diffraction (XRD) techniques. XRD studies point toward a significant c-axis compression and reduced crystallite sizes for ZMO samples in contrast to undoped ZnO, which was further confirmed by HRSEM studies. X-ray photoelectron spectroscopy (XPS), UV/vis spectroscopy and photoluminescence (PL) spectroscopy were employed to establish the electronic and optical properties of these nanoparticles. (XPS) studies confirmed the substitution of Zn 2+ by Mg 2+, crystallization of MgO secondary phase, and increased ZnO bond strengths in Mg-doped ZnO samples. Textural properties of these ZMO samples obtained at various calcination temperatures were superior in comparison to the undoped ZnO. In addition to this, ZMO samples exhibited a blue-shift in the near band edge photoluminescence (PL) emission, decrease of PL intensities and superior sunlight-induced photocatalytic decomposition of methylene blue in contrast to undoped ZnO. The most active photocatalyst 0.1-MgZnO obtained after calcination at 600 °C showed a 2-fold increase in photocatalytic activity compared to the undoped ZnO. Band gap widening, superior textural properties and efficient electronhole separation were identified as the factors responsible for the enhanced sunlight-driven photocatalytic activities of Mg-doped ZnO nanoparticles. © 2012 American Chemical Society.
Exceptional electrochemical performance of Si-nanowires in 1,3-dioxolane solutions: A surface chemical investigation
Etacheri V., Geiger U., Gofer Y., Roberts G.A., Stefan I.C., Fasching R., Aurbach D.
Article, Langmuir, 2012, DOI Link
View abstract ⏷
The effect of 1,3-dioxolane (DOL) based electrolyte solutions (DOL/LiTFSI and DOL/LiTFSI-LiNO 3) on the electrochemical performance and surface chemistry of silicon nanowire (SiNW) anodes was systematically investigated. SiNWs exhibited an exceptional electrochemical performance in DOL solutions in contrast to standard alkyl carbonate solutions (EC-DMC/LiPF 6). Reduced irreversible capacity losses, enhanced and stable reversible capacities over prolonged cycling, and lower impedance were identified with DOL solutions. After 1000 charge-discharge cycles (at 60 °C and a 6 C rate), SiNWs in DOL/LiTFSI-LiNO 3 solution exhibited a reversible capacity of 1275 mAh/g, whereas only 575 and 20 mAh/g were identified in DOL/LiTFSI and EC-DMC solutions, respectively. Transmission electron microscopy (TEM) studies demonstrated the complete and uniform lithiation of SiNWs in DOL-based electrolyte solutions and incomplete, nonuniform lithiation in EC-DMC solutions. In addition, the formation of compact and uniform surface films on SiNWs cycled in DOL-based electrolyte solutions was identified by scanning electron microscopic (SEM) imaging, while the surface films formed in EC-DMC based solutions were thick and nonuniform. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) spectroscopy were employed to analyze the surface chemistry of SiNWs cycled in EC-DMC and DOL based electrolyte solutions. The distinctive surface chemistry of SiNWs cycled in DOL based electrolyte solutions was found to be responsible for their enhanced electrochemical performances. © 2012 American Chemical Society.
Effect of fluoroethylene carbonate (FEC) on the performance and surface chemistry of Si-nanowire li-ion battery anodes
Etacheri V., Haik O., Goffer Y., Roberts G.A., Stefan I.C., Fasching R., Aurbach D.
Article, Langmuir, 2012, DOI Link
View abstract ⏷
The effect of FEC as a co-solvent on the electrochemical performance and surface chemistry of silicon nanowire (SiNW) anodes was thoroughly investigated. Enhanced electrochemical performance was observed for SiNW anodes in alkyl carbonates electrolyte solutions containing fluoroethylene carbonate (FEC). Reduced irreversible capacity losses accompanied by enhanced and stable reversible capacities over prolonged cycling were achieved with FEC-containing electrolyte solutions. TEM studies provided evidence for the complete and incomplete lithiation of SiNW's in FEC-containing and FEC-free electrolyte solutions, respectively. Scanning electron microscopy (SEM) results proved the formation of much thinner and compact surface films on SiNW's in FEC-containing solutions. However, thicker surface films were identified for SiNW electrodes cycled in FEC-free solutions. SiNW electrodes develop lower impedance in electrolyte solutions containing FEC in contrast to standard (FEC-free) solutions. The surface chemistry of SiNW electrodes cycled in FEC-modified and standard electrolytes were investigated using X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) spectroscopy. The impact of FEC as a co-solvent on the electrochemical behavior of SiNW electrodes is discussed herein in light of the spectroscopic and microscopic studies. © 2011 American Chemical Society.
Oxygen rich titania: A dopant free, high temperature stable, and visible-light active anatase photocatalyst
Etacheri V., Seery M.K., Hinder S.J., Pillai S.C.
Article, Advanced Functional Materials, 2011, DOI Link
View abstract ⏷
The simultaneous existence of visible light photocatalytic activity and high temperature anatase phase stability up to 900 °C in undoped TiO 2 is reported for the first time. These properties are achieved by the in-situ generation of oxygen through the thermal decomposition of peroxo-titania complex (formed by the precursor modification with H 2O2). Titania containing the highest amount of oxygen (16 H2O2-TiO2) retains 100% anatase phase even at 900 °C, where as the control sample exists as 100% rutile at this temperature. The same composition exhibits a six-fold and two-fold increase in visible light photocatalytic activities in comparison to the control sample and the standard photocatalyst Degussa P-25 respectively. Among the various parameters affecting the photocatalytic action, such as band gap narrowing, textural properties, crystallite size, and anatase phase stability, band gap narrowing was identified as the major factor responsible for the visible light photocatalytic activity. Increased Ti-O-Ti bond strength and upward shifting of the valence band (VB) maximum, which is responsible for the high temperature stability and visible light activity respectively, are identified from FT-IR, XPS, and photoluminescence (PL) spectroscopic studies. It is therefore proposed that the oxygen excess defects present in these titania samples are responsible for the high temperature stability and enhanced visible light photocatalytic activities. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Challenges in the development of advanced Li-ion batteries: A review
Etacheri V., Marom R., Elazari R., Salitra G., Aurbach D.
Review, Energy and Environmental Science, 2011, DOI Link
View abstract ⏷
Li-ion battery technology has become very important in recent years as these batteries show great promise as power sources that can lead us to the electric vehicle (EV) revolution. The development of new materials for Li-ion batteries is the focus of research in prominent groups in the field of materials science throughout the world. Li-ion batteries can be considered to be the most impressive success story of modern electrochemistry in the last two decades. They power most of today's portable devices, and seem to overcome the psychological barriers against the use of such high energy density devices on a larger scale for more demanding applications, such as EV. Since this field is advancing rapidly and attracting an increasing number of researchers, it is important to provide current and timely updates of this constantly changing technology. In this review, we describe the key aspects of Li-ion batteries: the basic science behind their operation, the most relevant components, anodes, cathodes, electrolyte solutions, as well as important future directions for R&D of advanced Li-ion batteries for demanding use, such as EV and load-leveling applications. © 2011 The Royal Society of Chemistry.
Influence of low trivalent iron doping on the electrical characteristics of PZT
Article, Journal of Materials Science: Materials in Electronics, 2010, DOI Link
View abstract ⏷
Piezoelectric materials based on lead zirconium titanium oxide with a composition near the morphotropic phase boundary, (Pb 0.94Sr 0.06)(Zr 0.53Ti 0.47)O 3[PSZT] have been synthesized by sol-gel method. The influence of B-site aliovalent dopant Fe 3+ on the structure, ferroelectric, dielectric, piezoelectric characteristics and microstructure have been investigated. The influence of the transition metal-oxygen vacancy defect-dipoles on the electrical characteristics have also been investigated. © 2009 Springer Science+Business Media, LLC.
Single step morphology-controlled synthesis of silver nanoparticles
Etacheri V., Georgekutty R., Seery M.K., Pillai S.C.
Conference paper, Materials Research Society Symposium Proceedings, 2010,
View abstract ⏷
Silver nanoparticles having different size and plasmon resonances were synthesized through a single step aqueous based method. The current procedure was based on the reduction of silver ions by ascorbic acid in the presence of sodiumborohydride and trisodium citrate. Triangular colloidal nanoparticles having different plasmon resonances (and hence different size and colours) were synthesized by varying only the concentration of ascorbic acid. These nanoparticles were found to be stable without using any surfactants or polymers. This study revealed a strong correlation between particle growth and concentration of constituent chemicals. Crystallinity and phase purity of the silver samples were investigated through powder X-ray diffraction studies (XRD). Absorption spectra of various silver particles were recorded using UV/Vis/NIR spectrometer. Morphological analysis was performed using transmission electron microscopy (TEM) and average edge lengths of nanoparticles were also calculated. © 2010 Materials Research Society.
Highly visible light active TiO2-xNx heterojunction photocatalysts
Etacheri V., Seery M.K., Hinder S.J., Pillai S.C.
Article, Chemistry of Materials, 2010, DOI Link
View abstract ⏷
diaminetetraacetic acid (EDTA) modified sol-gel process.An FT-IR study of EDTA modified TiO2 gel confirms the existence of an ionic intermediate (as indicated by a Δ value of 233 cm-1). Differential scanning calorimetry (DSC), X-ray diffraction (XRD), and Raman spectroscopy are employed to study the phase evolution, phase purity, and crystallite size of samples. Formations of O-Ti-N and N-Ti-N bonds in calcined samples are confirmed using XPS and FT-IR spectroscopy. AllEDTAmodified samples show significantly higher visible light photocatalytic activity than the unmodified sample. The most active nitrogen doped heterojunction obtained at 400 °C exhibits 9-fold visible light activity in comparison to the standard photocatalyst Degussa P-25. It is proposed that the photo excited electrons (from the visible midgap level) are effectively transferred from the conduction band of anatase to that of rutile causing effective electron-hole separation, which is responsible for the higher visible light activity and lower photoluminescence (PL) intensity. © 2010 American Chemical Society.
