Dual–ion Symmetric Hybrid Supercapacitor Built by Vanadium Oxide with Expanded Interlayers: the Intercalation of Cation–anion Pair and Reversible Redox of Anion Excited by Al3+

The development of aluminum ion batteries (AIBs) is retarded by the low capacity of intercalation cathode and ineffective aluminum dissolution/deposition at Al anode. To solve the issues, benzoquinone(BQ)-preinserted hydrated vanadium oxide formulated as (BQ)(0.04)V2O5.0.87H(2)O (BQ-VO) with a large interlayer spacing of 13.3 angstrom was synthesized, which was used as both cathode and anode with Al(ClO4)(3) acetonitrile (AN) electrolyte to fabricate a symmetric aluminum-ion supercapacitor. BQ-VO delivers a large capacity of similar to 152 mAh g(-1) at 0.2 A g(-1) in the range of 0-1.5 V, which is associated with the intercalation of ion (such as ClO4-, Al3+ or Al3+ - ClO4- pair) into BQ-VO and the reversible redox reaction of ClO4- <-> Cl-, giving rise to a novel symmetric dual-ion hybrid supercapacitor. The reversible conversion of ClO4- <-> Cl- is not observed in NaClO4 AN electrolyte, which is only excited by Al3+, leading to a continuous increasing capacity in the early stage of the cycling test. On the contrary, in the NaClO4 AN electrolyte, BQ-VO illustrates a surface-controlled capacitive performance with excellent cycling stability. Molecular dynamic (MD) simulations reveal that Al3+ and Na+ possess different solvation/anion sheaths, leading to different electrochemical performances of BQ-VO in the Al(ClO4)(3) and NaClO4 electrolytes. The present work provides a routine to utilize the redox reaction of halide for energy storage.