Protecting Lithium Metal Anodes in Solid-State Batteries

Lithium metal is considered a highly promising anode material because of its low reduction potential and high theoretical specific capacity. However, lithium metal is prone to irreversible side reactions with liquid electrolytes, resulting in the consumption of metallic lithium and electrolytes due to the high reactivity of lithium metal. The uneven plating/stripping of lithium ions leads to the growth of lithium dendrites and battery safety risks, hindering the further development and commercial application of lithium metal batteries (LMBs). Constructing solid-state electrolyte (SSE) systems with high mechanical strength and low flammability is among the most effective strategies for suppressing dendrite growth and improving the safety of LMBs. However, the structural defects, intrinsic ionic conductivity, redox potential and solid-solid contacts of SSEs can cause new electrochemical problems and solid-phase dendrite growth drawbacks in the application of solid-state batteries (SSBs). In this review, the mechanisms of lithium dendrite growth in SSEs are comprehensively summarized. Strategies to suppress lithium dendrite growth, stabilize the interface, and enhance ion transport in organic, inorganic and composite SSEs are emphasized. We conclude with not only relevant experimental findings but also computational predictions to qualitatively and quantitatively characterize the ionic conductivity, interfacial stability and other properties of SSEs based on both chemical and physical principles. The development direction and urgent problems of SSEs are summarized and discussed.