PVdF-HFP (polyvinylidenefluoride-hexafluoropropylene) polymer electrolytes comprising cross-linkable PEGDMA (polyethylene glycol dimethacrylate) oligomers with thermal shutdown characteristic have been developed. In contrast to the melting mechanism of polyolefin, this new polymer electrolyte possesses a thermal shutdown characteristic by a rapid cross-linking reaction of PEGDMA. The cross-linked PEGDMA network inside the PVdF-HFP matrix can provide the mechanical strength for the electrolytes, while the un-cross-linked PEGDMA oligomers serve as plasticizers for PVdF-HFP to improve the mobility of lithium ions at normal operation temperatures. In addition, the un-cross-linked PEGDMA oligomers can initiate cross-linking upon a sudden rise of temperature and thus provide thermal shutdown protection at elevated temperatures. (c) 2005 Elsevier B.V. All rights reserved.