Preparation and electrochemical properties of EVOH-SO₃Li/poly(vinylidene fluoride-hexafluoropropylene)/hydroxyapatite lithium-ion battery separator

Abstract

EVOH-SO3Li/P(VDF-HFP)/HAP lithium ion battery separator was prepared by high-pressure blending electrospinning using polyethylene-vinyl alcohol sulfonate (EVOH-SO3Li), poly(vinylidene fluoride-hexafluoropropylene) (P(VDF-HFP)) and nano hydroxyapatite (HAP) as raw materials. The performance of the separator was characterized by FTIR, SEM, electrochemical workstation and battery detection system. The results show that the EVOH-SO3Li/P(VDF-HFP) composite separator forms an uniform and dense three-dimensional network structure, and the EVOH-SO3Li/P(VDF-HFP)/HAP composite separator presents a three-dimensional network of dendritic shapes after adding P(VDF-HFP) and HAP, which improves the porosity and liquid absorption rate of the separator. Compared with the pure EVOH-SO3Li separator, the porosity and liquid absorption rate of the EVOH-SO3Li/P(VDF-HFP)/HAP composite separator are increased by 37.5% and 91.6%, respectively. Meanwhile, the excellent electrochemical performance is also exhibited. The electrochemical stability window of the assembled lithium-ion battery is 5.65 V, and the interfacial impedance is decreased to 184.24 Ω, and the ionic conductivity is increased to 2.686×10-3 S·cm-1; Lithium-ion batteries assembled with EVOH-SO3Li/P(VDF-HFP)/HAP composite separator have a capacity retention rate of 96.69% after 100 cycles at 0.5 C discharge current, the properties of EVOH-SO3Li/P(VDF-HFP)/HAP composite separator are improved compared with EVOH-SO3Li.

Keywords

• lithium-ion battery separator
• poly(vinylidene fluoride-hexafluoropropylene)
• evoh-so₃li
• nano hydroxyapatite
• electrospinning