Abstract
Sodium-ion capacitors have received much attention compared
to lithium-based systems, owing to the improved safety and
earth abundancy. Here, we assembled an aqueous sodium-ion
capacitor by using nickel hexacyanoferrate and graphene as
positive and negative electrodes, respectively, in 1 M Na2SO4
electrolyte. The fabricated capacitor can work in a wide
potential window from 0 to 2 V, giving an energy density of
39.35 Whkg1 with better capacitance retention of about 91%,
even after 2000 cycles. Besides, the cost-effective precursors as
well as environmentally friendly and earth-abundant electrolytes
with high safety will ensure that the fabricated sodium-ion
capacitor system is suitable for next-generation energy storage
applications.
