Suppressed Proton Insertion Enhances Zinc-Ion Storage Kinetics and Stability in Hydrated Vanadate

Preintercalation chemistry is pivotal for tuning the structure of layered hydrated vanadium pentoxide (V2O5·nH2O, VOH) cathodes in aqueous zinc-ion batteries (AZIBs). However, the underlying fundamental impacts on proton insertion accompanied by zinc storage are elusive in the electrochemical process. In this work, 1,3-diaminoguanidine (DG) molecules are preintercalated into the interlayers of VOH. The modified sample (DG-VOH) exhibits enhanced Zn2+ diffusion and storage despite the reduced interlayer spacing. This improvement stems from the charge shielding effect provided by preintercalated DG molecules. Additionally, distortion of [VO6] octahedra modulates the electronic structure, leading to increased electronic conductivity. More importantly, the modulated electronic structure contributes to the effectively suppressed detrimental H+ co-insertion, which alleviates lattice strain, vanadium dissolution, and byproduct formation. As a result, the DG-VOH cathode delivers a high specific capacity of 437.8 mAh/g and outstanding long-term cycling stability, retaining 91% of its capacity after 5000 cycles at 8 A/g. This work elucidates the critical role of organic preintercalants in inhibiting H+ co-intercalation, providing valuable insights for the design of high-performance AZIB cathodes.