Poly(vinylidenefluoride-hexafluoropropylene)/cellulose/carboxylic TiO2 composite separator with high temperature resistance for lithium-ion batteries

To improve the safety performance of lithium-ion batteries, the research of composite separator with high temperature resistance is one of the strategies. Herein, a poly(vinylidene fluoride-hexafluoropropylene)/cellulose/carboxylic titanium dioxide (PVDF-HFP/cellulose/C-TiO2) composite separator is prepared by the phase inverse method. The composite separator has higher porosity (63.65%) and electrolyte uptake (210.3%) than PP separator, exhibiting good heat resistance that can keep its shape and size under 160 °C for 0.5 h. Additionally, it has a superior ionic conductivity of 1.24–1.49 mS cm−1 and a lower charge transfer impedance at a room temperature, which brings about better cycle and rate performance. Promisingly, the cell assembled with the PVDF-HFP/cellulose/C-TiO2 composite separator has a high electrochemical working window and a high current charge of ability, and can undergo 10 charge-discharge cycles normally under 120 °C. The PVDF-HFP/cellulose/C-TiO2 composite separator has promising potentials for high current and voltage charging, which can improve the safety performance of the lithium-ion battery.