Organic flame-retardant-loaded battery separator offers a new opportunity for battery safety. However, its poor thermal stability still poses serious safety issues. Inspired by Tai Chi, an "internal-cultivating and external-practicing" core-shell nanofibrous membrane was prepared by coaxial electrospinning, wherein the shell layer was a mixture of polyvinylidene fluoride, silicon dioxide (SiO2), and graphene oxide (GO) and the core layer contained triphenyl phosphate (TPP). SiO2 and GO enhanced the thermal stability and electrochemical performance. The encapsulated TPP prevented heat transfer and the degradation of electrochemical performance caused by its direct dissolution. This separator exhibited outstanding thermal stability and flame retardancy: it did not burn and remained relatively intact (91.2%) in an open flame for 15 s. The battery assembled with a composite separator showed excellent performance: the initial capacity reached 164 mA h/g and maintained 95% after 100 charge-discharge cycles. This novel strategy endows high-performance lithium batteries with relatively higher safety.
Keywords: battery safety; coaxial electrospinning; flame retardant; high electrochemical performance; thermal stability.