An Electron Energy-Loss Spectrometry Study of Charge Compensation in LiNi0.8Co0.2O2

Changes in the electronic structure of Li1-xNi0.8Co0.2O2 during delithiation (charge) are elucidated by changes in the O K-edge and transition-metal (TM) L2,3-edge. Electron energy-loss spectrometry was used to investigate the O 2p and TM 3d occupancy over a wide range of lithium concentrations. Quantitative analysis of the TM L2,3 white lines indicates that the Ni ion accommodates no more than one-half of an electron, whereas the net Co valence is unaffected by delithiation. In contrast with the small changes observed in the TM L2,3-edge, a large decrease in state occupancy is observed in the near-edge structure of the O K-edge, suggesting that much of the electron charge is accommodated by the anion.