Electrochemical and X-ray photospectroscopy studies of polytetrafluoroethylene and polyvinylidene fluoride in Li/C batteries

The stability of polytetrafluorethylene (PTFE) and polyvinylidene fluoride (PVDF) used as the anode binders in lithium-ion batteries was studied by electrochemical and X-ray photospectroscopy (XPS) measurements. The characteristic discharge/charge curves for PTFE and PVDF were obtained. It is shown that the behavior of PTFE and PVDF exhibits much discrepancy when they are attacked by high active lithium ion in electrochemical cells. PTFE reacts with lithium easily and decomposes during the first discharge process, which is indicated by a long plateau appearing around 1.2 V in the first discharge curve of Li/Ni(PTFE) cell. XPS results show that PTFE decomposes after one discharge/charge cycle. PVDF is rather stable due to a possible surface passivation process.