A separator based on cross-linked nano-SiO2 and cellulose acetate for lithium-ion batteries

Abstract

In this study, we constructed a new membrane, which was prepared by free radical polymerization of a mixture containing vinyl-functionalized SiO2 nanoparticles (M-SiO2), modified cellulose acetate (M-CA) and poly(ethylene glycol)dimethacrylate (PEGDMA). The M-SiO2 was the SiO2 nanoparticles coupled with vinyltrimethoxysilane (VTMO), and the M-CA was the cellulose acetate modified with methacryloyl groups. The effects of M-SiO2 content on the porosity, electrolyte uptake and other properties of the membrane were studied. The results showed that the membrane with a suitable M-SiO2 content had good mechanical strength and other properties. For example, the membrane with 15 wt% of M-SiO2 (named as C-CAS15) possessed the excellent comprehensive performance. The mechanical strength of C-CAS15 membrane was up to 14.30 MPa, and it had no obvious dimension change at 200 °C. Meanwhile, the C-CAS15 membrane exhibited a relatively high ionic conductivity of 1.54 mS cm−1. The LiFePO4/GPE/Li half-cell assembled by the C-CAS15 membrane displayed excellent cycle charge-discharge performance and C-rate discharge performance, in which the discharge specific capacity retention could retain 98% after 100 cycles under 0.5 C/0.5 C and the discharge specific capacity could reach above 100 mAh g−1 under the higher C-rate of 4 C. Compared with the commercial PE membrane and the common membranes reported in previous literatures, the prepared C-CAS15 membrane presented better comprehensive performance, which indicated that the C-CAS15 membrane could be a promising separator for high performance lithium-ion batteries.