Polychalcogenides Induced Challenges in Transition Metal Chalcogenide Anodes for Alkali Metal Ion Batteries

Transition metal chalcogenide (TMC) anode materials are highly promising for alkali metal ion batteries (AMIBs) due to their higher capacities, arising from multielectron conversion reactions. However, their practical usage is hindered by classical issues such as volume expansion, voltage hysteresis and sluggish kinetics. Beyond these, a critical yet frequently overlooked issue is the generation and shuttling of polychalcogenides. Here, we systematically present the driving force behind polychalcogenide formation and how it triggers cascading, multifaceted degradation pathways. First, using well-known metal chalcogenide battery chemistry, the nature of polychalcogenides was presented in the context of TMC anodes for AMIBs. Later, the generation, shuttling and simultaneous degradation pathways triggered by polychalcogenides are depicted. Factors governing polychalcogenide generation and outward diffusion towards the metal anode, as well as strategies to inhibit the polychalcogenide shuttle, are elucidated. Finally, perspectives on anode and electrolyte design to improve TMC anode performance are summarized, along with the conclusions.