Enhanced Performance of High Energy Density Lithium Metal Battery with PVDF-HFP/LAGP Composite Separator

Abstract

The development of high energy density lithium ion batteries puts forward requirements for separators. In this article, poly(vinylidene fluoride-hexafluoropropylene)/Li1.5Al0.5Ge1.5(PO4)3 composite membrane (PL) has been fabricated by electrospinning and with use of the dip-coating method as the separator of the lithium ion battery. With reference to the physical properties, PL has better mechanical strength than does its base membrane electrospun poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP), and thermal stability and electrolyte uptake (215%) higher than those of the PP separator; with reference to the electrochemistry parameters, PL has an ionic conductivity of up to 3.18 mS cm–1 at RT and a wide electrochemical window of 5.3 V (vs Li+/Li). The NCM811||Li battery that uses the PL separator exhibits a longer cycle life (144.7 mAh g–1 after 500 cycles at 0.2 C), a lower interfacial resistance change (71.19 Ω), and a higher rate capability as compared to the batteries that use the PP and electrospun PVDF-HFP separator. The above results reveal that the PL separator is an ideal choice for high energy density lithium batteries.