Isolated metallic lithium formation in lithium-metal batteries

Isolated metallic lithium (“dead” lithium) formation is one of the key challenges to enabling the practical application of lithium-metal anodes. Here, we identify a charge-discharge asymmetry mechanism through linear stability analysis and phase-field modeling and propose a simple symmetry parameter to quantify the difficulty of forming isolated metallic lithium. Our results suggest that this symmetry parameter is highly correlated with the experimentally measured Coulombic efficiency. The symmetry parameter provides a mechanistic understanding of the interconnected relationship between the battery's performance and various factors, like material, geometry, and loading parameters. Our results show that completely suppressing dendrites is unnecessary as long as they are controllable and do not form isolated metallic lithium. Our analysis provides insights into mitigating isolated metallic lithium and guidelines for lithium-metal battery design.