Investigating the effect of lithiation on polycrystalline NMC811 Li-ion battery cathode cracking using in situ SEM micromechanical testing

The mechanical degradation of polycrystalline NMC811 cathode particles during electrochemical cycling was investigated using in situ powder compression and nanoindentation. The research demonstrates a significant reduction in particle strength upon the first delithiation, with only partial recovery upon (re)lithiation. Continuous cycling within the normal operating window leads to further mechanical degradation, likely due to cracking and potential rock-salt layer formation. This method can be applied to other materials chemistries and used as a reliable and quick method to quantify the mechanical stability of other spherical particles exposed to electrochemical cycling.