Operando X-ray Absorption Spectroscopy Study of Atomic Phase Reversibility with Wavelet Transform in the Lithium-Rich Manganese Based Oxide Cathode

Lithium-rich, Mn-based composites, such as Li(Li 0.2 Mn 0.54 Ni 0.13 Co 0.13 )O 2, retain immense interest for researchers and practitioners as one of the most promising candidates for electric vehicle applications (EV/HEV/PHEV). Enabling the commercialization of this battery system requires reducing intrinsic drawbacks, that is, large capacity fading during first cycle or low-rate capability; it is of great importance to optimize the composite design of the battery cathode. Information about the electronic structure and atomic environment of the transition metals (Mn, Co, and Ni) provides crucial insight into the structure of high-energy density cathodes. In this study, we present precise characterization of the atomic environments of each transition metal by operando X-ray absorption spectroscopy using continuous Cauchy wavelet transform (CCWT) analysis during the first electrochemical cycle at the charge rate of 0.5 C. The CCWT interpretation provides continuous decomposition of extended X-ray absorption fine structure amplitudes and provides new insight into the local environment change during charging, which allows the “atomic phase reversibility” to be identified by this novel approach.