Mechanical properties of commercial LixMn2O4 cathode under different States of Charge

Elastic and hardness properties of LiMn2O4 particles extracted from commercially available Li-ion batteries are investigated under different States of Charge (SoC). Instrumented indentation was used for quantitative measurements. It was found that the particles become stiffer for increasing SoC, ranging from 87 GPa (0% SoC) to 104 GPa (100% SoC). Nanoindentation could also detect dissimilar properties between particles of a same cathode. As its spatial resolution is limited, atomic force acoustic microscopy (AFAM) was used to generate stiffness maps. By combining it with micro-Raman spectroscopy as well as Electron Back-Scattered Diffraction (EBSD), elastic isotropy and homogeneity within single particles were found. On the other hand, different neighboring particles present different states of lithiation and stiffnesses. For reference, a {1 1 1} LiMn2O4 wafer was also synthesized and characterized.