Monitoring of electro-chemo-mechanics in Li metal electrodes by optical fibre sensors

Abstract

Battery technology is essential for advancing green energy solutions and achieving sustainable development goals. Li metal batteries have the highest theoretical capacity and are regarded as promising next-generation energy storage systems. However, their application is restricted by dendrite growth and unstable interfaces driven by electro-chemo-mechanical effects. Addressing these challenges requires obtaining direct insights into internal stress evolutionary characteristics, and this process remains uncertain. Here, we embed fibre Bragg grating sensors within Li metal electrodes, enabling real-time monitoring of stress during cycling. The measurements reveal a dynamic stress evolution process that is consistent with the migration behaviour of active Li. This process features a nonuniform stress contribution and a hysteresis effect that are not present in the charge–discharge conversion process. A new parameter, i.e., mechanical efficiency, is introduced to assess intrinsic structural stability, revealing that local microstructural stability can exceed macroscopic electrochemical performance. Furthermore, correlation analysis of stress–evolution curves reveals highly reproducible patterns, offering a potential avenue for investigating the existence of structural memory in Li metal. This study of electro-chemo-mechanics provides insights into enhancing Li-metal battery durability via mechanical regulation.