In-situ measurements of mechanical property and stress evolution of commercial graphite electrode

Li ion concentration-dependent mechanical properties and stress of electrodes are crucial to the performance and durability of lithium-ion batteries. Here, we report in situ measurements of the elastic modulus and stress of a commercial graphite composite electrode during lithiation/delithiation cycling. To realize the in situ measurements, the real-time curvature change of cantilever graphite electrodes in a home-made transparent cell was captured by a CCD camera during cycling. The elastic modulus and stress were derived from the curvature change of cantilever electrodes using a mechanical model, developed in this study. The elastic modulus increases from an initial value of ca.8.9 GPa to ca.31.9 GPa when the state of charge (SOC) is 60% during the second lithiation. The magnitude of the stress increases during lithiation process, and changes from compressive stress to tensile stress in the thickness direction. These findings are helpful for modeling efforts to understand the degradation and optimize the design of commercial graphite electrodes.