NH4+ Deprotonation at Interfaces Induced Reversible H3O+/NH4+ Co‐insertion/Extraction

Abstract

AbstractIon insertions always involve electrode‐electrolyte interface process, desolvation for instance, which determines the electrochemical kinetics. However, it′s still a challenge to achieve fast ion insertion and investigate ion transformation at interface. Herein, the interface deprotonation of NH4+ and the introduced dissociation of H2O molecules to provide sufficient H3O+ to insert into materials′ structure for fast energy storages are revealed. Lewis acidic ion‐NH4+ can, on one hand provide H3O+ itself via deprotonation, and on the other hand hydrolyze with H2O molecules to produce H3O+. In situ attenuated total reflection‐Fourier transform infrared ray method probed the interface accumulation and deprotonation of NH4+, and density functional theory calculations manifested that NH4+ tend to thermodynamically adsorb on the surface of monoclinic VO2, and deprotonate to provide H3O+. In addition, the inserted NH4+ has a positive effect for stabilizing the VO2(B) structure. Therefore, high specific capacity (>300 mAh g−1) and fast ionic insertion/extraction (<20 s) can be realized in VO2(B) anode. This interface derivation proposes a new path for designing proton ion insertion/extraction in mild electrolyte.