Li-concentration dependent elastic modulus. Nanoindentation mechanical experiments and first-principles calculations reveal that the elastic modulus of NMC cathodes is highly dependent on the lithiation state , as shown in Fig. and Fig. . Full delithiation of NMC cathodes significantly reduces their elastic mechanical properties . The elastic modulus at fully lithiated and delithiated states thus represents the upper and lower bound for NMC cathodes. Fig. show the effect of the elastic modulus of NMC cathodes on the formation of dislocations and stress distribution at the interface between cathodes and electrolytes, at a discharge rate of 1 C. The reduction in the elastic modulus of NMC cathodes leads to a decrease of the average dislocation shear from 0.09 to around 0.03 within the cathodes. However, the maximum principal stress distribution at the interface between cathodes and solid electrolytes is minimally impacted by the decrease in the elastic modulus of NMC. Fig. shows that high tensile stress persists at the interface, regardless of whether the elastic modulus corresponds to the fully lithiated or delithiated state.