Anionic Activity in Fast-Charging Batteries: Recent Advances, Prospects, and Challenges

The increasing demand for fast-charging batteries to expedite the widespread adoption of electric vehicles calls for continual improvements of the anode materials to confer high energy and power densities. However, the fundamental limitations of the mainstream graphite and Li-metal anodes for fast-charging applications include the capacity fading and safety issues mainly caused by the Li plating, as well as the sluggish transport kinetics at large current densities. Recently, great attention has been paid to the emergence of large-capacity anodes by tailoring the bonding covalency to modulate the electronic structure and alter the insertion voltage for boosting fast-charging ability and suppressing metal plating. Development of new fast-charging materials by tailoring anionic activity allows us to better understand the key aspects of the bond covalency and band positioning for cation/anion doping and interface/surface engineering. This Review provides an overview of the recent advances in the development of fast-charging anodes around tuning the bonding covalency by bimetal modulation; alloying hard and soft anions to alter the electronic structure and metal plating voltage; constructing anion-derived interfacial films; and surface substituting the ordered terminal groups. Furthermore, we highlight the practical limits of capacity fading at large current densities and describe potential strategies of anionic redox in phosphides and interfacial energy storage of conversion-type anodes to offer additional capacities. We also discuss the prospects for the commercial adoption of high-performance anodes containing various elements to rival the prevalent graphite or Li anodes for fast-charging applications.