Operando Synchrotron Measurement of Strain Evolution in Individual Alloying Anode Particles within Lithium Batteries

Alloying anode materials offer high capacity for next-generation batteries, but the performance of these materials often decays rapidly with cycling because of volume changes and associated mechanical degradation or fracture. The direct measurement of crystallographic strain evolution in individual particles has not been reported, however, and this level of insight is critical for designing mechanically resilient materials. Here, we use operando X-ray diffraction to investigate strain evolution in individual germanium microparticles during electrochemical reaction with lithium. The diffraction peak was observed to shift in position and diminish in intensity during reaction because of the disappearance of the crystalline Ge phase. The compressive strain along the [111] direction was found to increase monotonically to a value of -0.21%. This finding is in agreement with a mechanical model that considers expansion and plastic deformation during reaction. This new insight into the mechanics of large-volume-change transformations in alloying anodes is important for improving the durability of high-capacity batteries.