High‐Entropy Electrolytes Toward Aqueous Ammonium‐Ion Batteries with High Capacity and Long Lifetime

Abstract Aqueous ammonium‐ion batteries (AAIBs) enjoy the merits of resource affordability, environmental sustainability, and rapid ion transport capabilities. However, achieving both high capacity and long lifetime, which are critical performance metrics for AAIBs, presents a significant challenge. This difficulty arises from the fact that enhancing capacity, such as constructing multiple active sites, often results in the degradation of the electrode structure. It is imperative to devise innovative strategies for enhancing performance of AAIBs. The novel high‐entropy electrolytes (HEEs) exhibit a multi‐component disordered structure that facilitates ion transport and hinders the dissolution of elements in electrode materials, showing great potential to enhance electrochemical performance. Herein, taking Prussian blue analogues (PBAs) as an illustration, high‐performance AAIBs are devised by constructing HEEs. Benefiting from the synergistic effect of multiple cationic additives, ultra‐stable electrode materials are obtained while maintaining their inherent high capacity. When using HEEs, it demonstrates remarkable performance with a specific capacity of 86.8 mAh g −1 and cycling stability of 1700 cycles at 0.2 A g −1 . Furthermore, the assembled full battery presents a stable lifespan, demonstrating the significance of HEEs for the practical application of AAIBs, thus laying out a blueprint for large‐scale energy storage.