New Insights into Lithium Hopping and Ordering in LiNiO2 Cathodes during Li (De)intercalation

摘要

In situ ~7Li and ex situ ~6Li nuclear magnetic resonance (NMR) spectroscopy is applied to monitor lithium mobility in a LiNiO2 cathode during Li-ion (de)intercalation. In situ X-ray absorption spectroscopy and galvanostatic intermittent titration are also used to capture changes during the Li-ion deintercalation process. A considerable line broadening was first found by ~7Li NMR spectroscopy. The Jahn-Teller distortion hinders the Li diffusion, thus broadening the NMR signal. The observed NMR shifts are compared to Li/vacancy ordering patterns described earlier by Arroyo y de Dompablo et al. Coupled motions of electrons and Li ions are also discovered by both in situ ~7Li and ex situ ~6Li NMR spectroscopy for the first time. They result in local Li environments with an enhanced number of Ni~(3+) neighbors at highly charged states. This opens a new perspective for understanding the highly delithiated structure.