Research progress of cathode materials for ammonium-ion batteries

Aqueous secondary batteries, among many, offer low cost and high safety and are eco-friendly, showing great promise as next-gen storage batteries. Non-metal ions, compared to metal ones, have wide sources, are environmentally friendly, with small molecular weights and ion sizes, possessing unique transport and diffusion advantages and better prospects in aqueous batteries. Among non-metal carriers, NH4+ is cost-effective, less corrosive, and less likely to cause side reactions like hydrogen evolution, fitting for new non-metal ion battery (aqueous ammonium ion batteries, AAIBs) development. Currently, AAIBs face challenges such as low energy density and limited operating potential. Therefore, developing electrode materials with highly reversible NH4+ accommodation capacity is of paramount importance for constructing high-performance AAIBs. This paper focuses on aspects such as structure, performance, and energy storage mechanism, and systematically reviews the cathode materials applied to AAIBs in recent years, including Prussian blue analogs, organic compounds, MXene, manganese oxides, and vanadium oxides. The key development directions of AAIBs cathode materials in the future are discussed, providing guiding ideas for the development of cathode materials with excellent ammonium storage performance. To promote the development of aqueous ammonium ion batteries, cathode materials with excellent ammonium storage properties were integrated. [Display omitted] •Recent cathode materials for AAIBs were summarized.•Focused on developing new high - performance materials for AAIBs cathode.•Advantages and disadvantages of various cathode materials were described.•Structure and performance of existing cathode materials were discussed.•Future research directions were proposed.