High dielectric composite polymer electrolyte for lithium-ion batteries

Poly(vinylidene fluoride) (PVDF)-based solid polymer electrolytes (SPEs) with “lithium salt in polymer” configurations typically exhibit poor lithium salt dissociation and mechanical strength. In this study, we proposed a composite polymer electrolyte (CPE) for solid-state lithium-ion batteries (LIBs) as a novel approach to address the challenges. The CPE incorporates a high dielectric polymer poly(vinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene) (P(VDF-TrFE-CTFE)) as the polymer matrix, and sodium super ionic conductor (NASICON)-type ceramic Li_1.5Al_0.5Ti_1.5(PO₄)₃ (LATP) as fillers. The optimized CPE demonstrates enhanced dissociation of lithium salts, leading to high ionic conductivity (1.1 mS·cm⁻¹) and improved lithium transference numbers ( ${\mathit{t}}_{{\mathbf{L}\mathbf{i}}^{+}}$ = 0.51). Meanwhile, the interaction between LATP inorganic filler and P(VDF-TrFE-CTFE) enhances the elasticity and tensile strength (1.09 MPa) of the CPE. The graphite|CPE|NCM811 (NCM stands for lithium nickel manganese cobalt oxide. Chemical formula of NCM811 is “LiNi_0.8Co_0.1Mn_0.1O₂”) cell achieves a high specific capacity of 160 mAh·g⁻¹ with excellent cycles stably for 300 cycles at 1 C. In addition, the flexible graphite|CPE|NCM811 pouch cell demonstrates exceptional capacity stability under dynamic bending for 10,000 times. Furthermore, the CPE can fulfil the fabrication process needs of flexible stacking-type and winding-type cells, highlighting its versatility and suitability for various LIB configurations in real applications.