Investigation of first-cycle voltage hysteresis in Li-rich cathode materials by magnetic Compton scattering experiments.

Lithium-rich layered oxides (LLOs) are among the most promising cathode materials for next-generation lithium-ion batteries featuring reversible capacities of 250 mAh g^-1or higher. However, LLOs suffer from severe voltage hysteresis during the charge/discharge process. In this work, we utilized magnetic Compton scattering spectroscopy to characterize the electronic states of the typical LLO Li_1.2-xNi_0.2Mn_0.6O₂and extract the redox orbitals. By comparing the experimental data with the results of density functional theory calculations, we successfully achieved the first direct observation of spin-polarized oxygen 2p state modifications due to superstructural changes, which were found to be responsible for the voltage hysteresis during the charge/discharge process.