Weakly Solvated Anions in Electrolytes Boost Cathode Performance for Dual-Ion Batteries and Hybrid Ion Capacitors

High Resolution Image Download MS PowerPoint Slide Electrochemical anion storage plays a critical role in the development of hybrid ion capacitors and dual-ion batteries. However, the mechanism of the interaction between electrolytes and anion storage remains unknown. Herein, we systematically investigate the electrochemical anion-storage properties of polypyrrole (PPy) cathodes in different chain-length ether-based electrolytes. In dimethyl ether (DME)-based electrolytes, the PPy cathode delivers a specific capacity of 91 mAh g –1 at 100 mA g –1 after 200 cycles and maintained 60 mAh g –1 at 5 A g –1 . The shorter-chain DME exhibits weaker anion-solvent interactions, enabling rapid anion desolvation behavior, thus enhancing ion storage kinetics. Further experimental analysis and theoretical computation verify that the shorter-chain solvents exhibit reduced solvation energy barriers and optimized interfacial charge transfer. This work highlights the critical role of solvent molecular structure in regulating anion storage kinetics, providing a strategic electrolyte design for approaching high-performance sodium-ion hybrid capacitors and dual-ion batteries.