Insights into Metal/Metalloid-Based Alloying Anodes for Potassium Ion Batteries

Potassium ion batteries (PIBs) are one of the front runners among energy storage alternatives to the popular but relatively high-cost lithium ion batteries. The anode material, which is one of the critical battery components, influences the electrochemical performance as well as the commercialization in a significant way. Metal/metalloid-based materials operating through alloying reactions to store K+ are predominantly interesting, because of their appealing theoretical volumetric capacities. However, this type of anode is far from satisfactory and faces several obstacles, requiring an analysis concentrating on the reaction mechanisms and identifying the development challenges, which is absent in the literature. This Review starts with evaluating the theoretical volumetric capacities and trend of metal/metalloid-based alloying anodes in PIBs, in addition to discussing their general reaction mechanisms. It then focuses on their detailed potassiation mechanism, enhancement strategies, and structure–performance relationship, besides the influence from the electrolyte, binder, and separator. In the end, this critical review sheds light on what are learned from the previous results and proposes potential solutions to further elevate metal/metalloid-based alloying anodes, which could benefit the development of PIBs significantly.