Fabrication and characterization of P(VDF-HFP)/SBA-15 composite membranes for Li-ion batteries

This study reports on the preparation of a composite polymer electrolyte for secondary lithium-ion battery. Poly(vinylidiene fluoride-hexafluoropropylene) (P(VDF-HFP)) was used as the polymer host, and mesoporous SBA-15 (silica) ceramic fillers used as the solid plasticizer were added into the polymer matrix. The SBA-15 fillers with mesoporous structure and high specific surface can trap more liquid electrolytes to enhance the ionic conductivity. The ionic conductivity of P(VDF-HFP)/SBA-15 composite polymer electrolytes was in the order of 10(-3) S cm(-1) at room temperature. The characteristic properties of the composite polymer membranes were examined by using FTIR spectroscopies, scanning electron microscopy (SEM), and an AC impedance method. For comparison, the LiFePO4/Li composite batteries with a conventional microporous polyethylene (PE) separator and pure P(VDF-HFP) polymer membrane were also prepared and studied. As a result, the LiFePO4/Li composite battery comprised the P(VDF-HFP)/10 wt.% m-SBA-15 composite polymer electrolyte, which achieves an optimal discharge capacity of 88 mAh g(-1) at 20 C rate with a high coulomb efficiency of 95%. It is demonstrated that the P(VDF-HFP)/m-SBA-15 composite membrane exhibits as a good candidate for application to LiFePO4 polymer batteries.