A Nonpresodiate Sodium-Ion Capacitor with High Performance

Sodium-ion capacitors (SICs) have received intensive attention due to their high energy density, high power density, long cycle life, and low cost of sodium. However, the lack of high-performance anode materials and the tedious presodiation process hinders the practical applications of SICs. A simple and effective strategy is reported to fabricate a high-performance SIC using Fe_1−xS as the anode material and an ether-based electrolyte. The Fe_1−xS electrode is found to undergo a reversible intercalation reaction after the first cycle, resulting in fast kinetics and excellent reversibility. The Fe_1−xS electrode delivers a high capacity of 340 mAh g⁻¹ at 0.05 A g⁻¹, 179 mAh g⁻¹ at high current of 5 A g⁻¹ and an ultralong cycling performance with 95% capacity retention after 7000 cycles. Coupled with a carbon-based cathode, a high-performance SIC without the presodiation process is successfully fabricated. The hybrid device demonstrates an excellent energy density of 88 Wh kg⁻¹ and superior power density of 11 500 W kg⁻¹, as well as an ultralong lifetime of 9000 cycles with over 93% capacity retention. An innovative and efficient way to fabricate SICs with both high energy and power density utilizing ether-based electrolytes can be realized to eliminate the presodiation process.