Thermal Instability of Olivine-Type LiMnP04 Cathodes

The remarkable thermal stability of LiFePO{sub 4} and its charged counterpart, FePO{sub 4}, have been instrumental in its commercialization as a lithium ion battery cathode material. Despite the similarity in composition and structure, and despite the high thermal stability of the parent compound, LiMnPO{sub 4}, we find that the delithiated phase Li{sub y}MnPO{sub 4}, (which contains a small amount of residual lithium), is relatively unstable and reactive toward a lithium ion electrolyte. The onset temperature for heat evolution in the presence of 1M LiPF{sub 6} in 1:1 ethylene carbonate/propylene carbonate is around 150 C, and the total evolved heat is 884 J/g, comparable to that produced under similar conditions by charged LiCoO{sub 2} electrodes