First-row transition metal compounds for aqueous metal ion batteries

Abstract

In recent years, a series of aqueous metal ion batteries (AMIBs) has been developed to improve the safety and cost-efficiency of portable electronics and electric vehicles. However, the significant gaps in energy density, power density, and cycle stability of AMIBs directly hinder them from replacing the currently widely used non-aqueous metal ion batteries, which stems from the lack of reasonable configuration and performance optimization of electrode materials. First-row transition metal compounds (FRTMCs), with the advantages of optional voltage ranges (from low to high), adjustable crystal structures (layered and tunnel types with large spacing), and designable morphology (multi-dimensional nanostructures), are widely used to construct high-performance AMIBs. However, no comprehensive review papers were generated to highlight their specific and significant roles in AMIBs. In this review, we first summarize the superiority and characteristics of FRTMCs in AMIBs. Then, we put forward control strategies of FRTMCs from subsurface engineering to inner construction to promote capacitance control and diffusion control energy storage. After that, the electrochemical performance of the FRTMCs regulation strategies in AMIBs is reviewed. Finally, we present potential directions and challenges for further enhancements of FRTMCs in AMIBs. The review aims to provide an in-depth understanding of regulation strategies for enhancing energy storage to build high-performance AMIBs that meet practical applications.