Probing the degradation of LiCoO2 in batteries subjected to high-voltage cycling with 17O solid-state NMR spectroscopy

Abstract

The long-term cycling stability of LiCoO₂ under high-voltage operation in lithium-ion batteries is still not satisfactory and the mechanism of capacity decay is not well understood. Here we mainly apply ¹⁷O MAS NMR spectroscopy to probe the phase transformation of cycled LiCoO₂ cathodes in both liquid cells and solid cells. It turns out that deterioration into the spinel phase is the main cause.