Compatibility of Li Alloy Anodes with Solid-State Electrolytes: An Evaluation

The quest to achieve high energy density anode materials in solid-state batteries has sparked significant interest in metal alloy anodes due to their superior theoretical capacities, higher safety, and greater electrochemical stability. Lithium-alloying materials such as silicon, tin, silver, and aluminum offer advantages by reducing the risks of short circuits and battery failure, which are often caused by interfacial fluctuations at the solid–solid interface due to lithium metal deposition, unlike other anode materials used in liquid electrolyte batteries or lithium metal in solid-state batteries. However, during the alloying/dealloying reactions, large volume changes occur, causing the accumulation of stress in solid-state systems, thereby degrading the structural integrity. Additionally, the sluggish lithium-ion kinetics, diffusional lithium trapping, and electrochemical fatigue mechanism during each cycle of alloying/dealloying are identified as the main causes of severe capacity fading observed in alloy anodes. This review explores the recent developments in metal alloy anodes, highlighting their compatibility with solid-state electrolytes. We also assess the degradation mechanisms in alloy anodes that hinder their widespread adoption and commercialization while suggesting strategies to overcome these barriers for improved anode performance. With the promise of revolutionizing the next generation of batteries, metal alloy anodes in solid-state systems represent a cutting-edge approach to achieving safer, more efficient, and longer-lasting energy storage solutions.