The electrochemical performance of polymer lithium-ion batteries was studied as a function of the hexafluoro propylene (HFP) content in the PVDF-HFP copolymers used as electrode binders and separator membranes. The HFP content in electrode binders was found to have a significant impact on the cycle life performance at elevated temperatures. Best results were achieved with a 5% HFP level, where good cycle life was demonstrated at 60 degreesC, combined with good rate capabilities and low temperature performance. In contrast to electrode binders, the HFP content in separator membranes was found to have no significant impact on cell performance.