Reconfiguring the Hydrogen Networks of Aqueous Electrolyte to Stabilize Iron Hexacyanoferrate for High-Voltage pH-Decoupled Cell.

Prussian blue analogs (PBAs) are promising insertion-type cathode materials for different types of aqueous batteries, capable of accommodating metal or non-metal ions. However, their practical application is hindered by their susceptibility to dissolution, which leads to a shortened lifespan. Herein, we have revealed that the dissolution of PBAs primarily originates from the locally elevated pH of electrolytes, which is caused by the proton co-insertion during discharge. To address this issue, the water-locking strategy has been implemented, which interrupts the generation and Grotthuss diffusion of protons by breaking the well-connected hydrogen bonding network in aqueous electrolytes. As a result, the hybrid electrolyte enables the iron hexacyanoferrate to endure over 1000 cycles at a 1 C rate and supports a high-voltage pH-decoupled cell with an average voltage of 1.95 V. These findings provide insights for mitigating the dissolution of electrode materials, thereby enhancing the viability and performance of aqueous batteries.