Reasons for capacity fading of LiCoPO4 cathodes in LiPF6 containing electrolyte solutions

The reasons for capacity fading of LiCoPO4 cathodes in 1 M LiPF6 EC/DMC 1:1 electrolyte solutions were investigated using 19F, 31P NMR and XPS spectroscopy. The origin of the poor performance of LiCoPO4 cathodes in LiPF6 containing electrolyte solutions is a nucleophilic attack of F− anions in solution on the P atoms, resulting in the breaking of the P―O bonds of the phosphate anions and the formation of soluble LiPO2F2 moieties.

► Reasons for capacity fading of LiCoPO4 cathodes in LiPF6 containing electrolytes.
► Nucleophilic attack of F− anions on the P atoms of LiCoPO4.
► Breaking of the P―O bonds of the phosphate anions with the formation of LiPO2F2.