Composite polymer electrolyte based on poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP) for solid-state batteries

Abstract

Using solid-state electrolytes (SSEs) with excellent thermal and electrical stability to replace liquid electrolytes, and assembling solid-state lithium-ion batteries (SSLIBs) is considered the best solution to these safety issues. However, it is difficult for a single electrolyte to have the characteristics of high ionic conductivity, low interface resistance, and high stability of the counter electrode at the same time. In this work, the composite polymer electrolyte membrane (CPE) of inorganic Li_1.3Al_0.3Ti_1.7(PO₄)₃ (LATP) and organic poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP) polymer was successfully prepared by traditional casting method. The addition of LATP (10 wt %) ceramic powder makes CPE membrane (CPE-10) exhibit excellent electrochemical performance: the lithium-ion transference number and electrochemical window are as high as 0.60 and 4.94 V, respectively. Moreover, the CPE-10 showed excellent Li-metal stability, thereby enabling the Li–Li symmetric cells to stably run for over 300 h at 0.1 mA/cm² with effective lithium dendrite inhibition. When paired with a high-voltage LiNi_0.6Co_0.2Mn_0.2O₂ (NCM622) cathode, the Li/CPE-10/NCM622 cell exhibited excellent electrochemical performance: the highest specific discharge capacity of 152 mAh/g could be conducted at 0.2C after 50 cycles corresponding to 100% Coulombic efficiencies. The prepared CPE-10 demonstrates excellent electrochemical performance, providing an effective design strategy for SSLMBs.