Cyclic stability improvement in a blended P(VdF-HFP)/P(BMA-AN-St)-based gel electrolyte by electrospinning for high voltage lithium ion batteries

The cyclic stability of traditional poly (vinylidenefluoride-co-hexafluoropropylene) (P(VdF-HFP)) and our newly developed poly (butyl methacrylate-acrylonitrile-styrene) (P(BMA-AN-St)) copolymer-based gel polymer electrolyte (GPE) must still be improved to satisfy the increasingly rigid demands of lithium ion batteries that have higher energy densities. Series ratios of P(VdF-HFP) and P(BMA-AN-St) blended membranes were prepared using an electrospinning method to compensate for the disadvantages of a single copolymer-based membrane. The results showed that the compositions of P(VdF-HFP) and P(BMA-AN-St) had sizeable effects on the physical and electrochemical characterization of GPE, in which the P4 membrane and the GPE blending ratio of P(VdF-HFP): P(BMA-AN-St) = 1: 4 had the best properties. Because the P4 membrane showed the best interconnected pore structure and highest porosity, the GPE exhibited the highest ionic conductivity, with a value of 1.4 × 10⁻³ S cm⁻¹ at ambient temperature. Due to the better compatibility of the P4-based GPE with a lithium anode and its considerably electrochemical stability, the LiNi_0.5Mn_1.5O₄/GPE/Li coin cell had an excellent cyclic performance, in which a 98% capacity retention under a 1C rate was maintained after 150 cycles compared to the coin cell that used a pure P(VdF-HFP)-based GPE that maintained 86% of its discharge capacity under the same test conditions. Furthermore, the acceptable rate characterization of the P4-based GPE was presented with a discharge capacity at a 5C rate that retained 92% of its counterpart at 1C.