Investigation of lead tin fluorides as possible negative electrodes for Li-ion batteries

Lead tin fluorides are well known fast ion conductors. In this study the electrochemical behaviour of materials as negative electrodes in lithium rechargeable batteries was investigated. The initial reduction with lithium occurs at much higher potentials for fluorides than oxides. This correlates well with the standard energies of formation of metals and lithium oxide/fluoride on lithium insertion. Lead rich compounds present a greater degree of crystallinity than tin rich materials and it is also observed that fluoride matrices exhibit greater crystallinity after cycling than their oxide counterparts. Tin oxide exhibits the best cycling performance and this seems to correlate with the low degree of crystallinity observed in this system.