Pre-Intercalated Cation Optimizing Proton Topochemistry for High-Performance Aqueous Zinc-Ion Batteries.

Cation pre-intercalated oxides have been widely explored as cathode materials for aqueous zinc-ion batteries (AZIBs). Although the influence of intercalants on the material structure and Zn2+ storage capacity has been adequately studied, an in-depth understanding of the influence of intercalants on proton storage is still lacking. Especially, proton transport exhibits ultrafast kinetics as an ideal charge carrier, playing a crucial role in the performance of AZIBs. We show that pre-intercalated K+ in K0.5V6O13 (KVO) not only reinforces the [VO] framework but also optimizes the hydrogen-bonded network composed of confined lattice water, achieving ultrafast proton transport. Benefiting from the optimization of proton topochemistry, the capacity, rate performance, and cycling stability of KVO improve significantly. KVO delivers a high reversible capacity of 462.9 mAh g-1 at 0.2 A g-1 and 82.3% retention after 20000 cycles at 20 A g-1. Even with the high mass loading of 19.2 mg cm-2, a KVO||Zn pouch cell with 539.2 mAh capacity can achieve stable cycling for more than 300 cycles at 0.5 A g-1. This work provides new insights into how pre-intercalated cations affect the proton topochemistry and electrochemical performance of inorganic cathodes.