Improved Low-Temperature Performance of Rocking-Chair Sodium-Ion Hybrid Capacitor by Mitigating the De-Solvation Energy and Interphase Resistance

摘要

Hybrid capacitors, which bear the advantages of secondary batteries andsupercapacitors, can deliver high power with a relatively fair amount ofenergy. However, its kinetic performance, especially at low temperatures, isstrongly limited by the battery-type electrode and electrolyte. In this work,Na-ion, which has a lower solvation energy than Li-ion, is chosen as thecharge carrier to build the hybrid capacitor. A sodium-ion hybrid capacitor isbuilt with an activated carbon cathode and a pre-sodiated hard carbon anode.To achieve a better kinetic performance, the de-solvation energy and interphaseresistance is decreased through replacing conventional carbonate electrolytewith a diethylene glycol dimethyl ether (DEGDME) based electrolyte.As a result, the sodium-ion capacitor delivers an energy density of 42 Wh kg~(–1)and a high power of 4565 W kg~(–1) for 3000 cycles at 2.5 A g~(–1). Furthermore,this capacitor could sustain an energy density of 36 Wh kg~(–1) at the lowtemperature of ?30 ℃ and maintain 70% of the capacity after 500 cycles. Thestrategies of reducing de-solvation energy and optimizing the solid electrolyteinterphase property offers a clear path for developing electrochemical energystorage devices at lower temperatures.