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

The reasons for capacity fading of LiCoPO4 cathodes in 1 M LiFF6 EC/DMC 1:1 electrolyte solutions were investigated using F-19, P-31 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. (C) 2011 Elsevier BM. All rights reserved.