关键词: 锂离子电池, 单离子传导聚合物电解质, 孔隙率, 离子电导率, 磺化氧化石墨烯

Abstract:

Herein, the lithiated sulfonated graphene oxide (Li-SGO) was successfully prepared via three steps by sulfonation of graphene oxide with 3-merraptnpropylt rimethnxysilane, oxidation of thiol into sulfonate with hydrogen peroxide and lithiation of sulfonate with aqueous lithium hydroxide. The as-prepared Li-SGO was then introduced into the semi-interpenetrating networks of single ion conducting polymer electrolyte (Li-SGO-FPAS) and poly vinylidenefluoride-hexafluoro propylene (PVDF-HFP) binder by in-situ polymerization to fabricate the porous single ion conducting polymer electrolyte membrane (Li-SGO-po-FPAS) generated from the poor compatibility between aromatic Li-SGO-FPAS and aliphatic PVDF-HFP binder. The key properties such as morphology, porosity, solvent uptake, mechanical strength, flexibility, lithium ion transference number, ionic conductivity and rate-capacity were successfully investigated. In addition, the neat single ion polymer electrolyte membrane without Li-SGO (FPAS) (po-FPAS) was prepared for comparison. The Li-SGO-po-FPAS possessed the high porosity of 55.9% and electrolyte uptake of 139.3wt.%, which are much higher than the values derived from the PP separator. As a result, the enhanced ionic conductivities of 0.23 mS·cm^-1 and 1.84 mS·cm^-1 were obtained at room temperature and 80℃, respectively, comparing to those of 0.14 mS·cm^-1 and 1.20 mS·cm^-1 for the po-FPA membrane. Furthermore, the mechanical strength of 9.9 MPa was obtained for the Li-SGO-po-FPAS, which is acceptable for the application in Li-ion batteries. The electrochemical characterizations indicate the better compatibility between the single ion conducting polymer electrolyte and the electrode interface after doping with the Li-SGO. The Li-SGO-po-FPAS showed the lithium ion transference number of 0.91 and electrochemical window of 4.6 V vs. Li⁺/Li. The Li|LiFePO₄ Li-ion battery assembled from the Li-SGO-po-FPAS exhibited good cyclability and higher C-rate capacity. The results suggest that the treatment of GO by lithiation and sulfonation processes is useful for application in single ion conducting polymer electrolyte, and it is also favorable for improving the comprehensive performance of single ion conducting polymer electrolyte, subsequently superior battery performance.

Key words: lithium-ion battery, single-ion conducting polymer electrolyte, porosity, ionic conductivity, sulfonated graphene oxide