Effect of lithiation on micro-scale fracture toughness of LixMn2O4 cathode

Abstract An optimized nanoindentation pillar splitting technique is used for the fracture toughness measurement of spinel Li x Mn 2 O 4 cathode material under different states of charge (SoC), along with the high-speed nanoindentation results for nanomechanical property mapping. High-speed nanoindentation enables for a robust and efficient evaluation of elastic modulus and hardness as a function of the SoC on strongly heterogeneous materials. The fracture toughness decreases linearly upon de-lithiation, with an overall reduction of 53% from 0% to 100% SoC. Decrease in fracture toughness is associated with the volume change, increase of defect density and stresses related to diffusion of lithium upon de-lithiation.