Composite polymer electrolytes incorporating gallium-doped Li7La3Zr2O12 nanofillers for high-performance all-solid-state lithium metal batteries

Lithium-ion batteries using organic liquid electrolytes face safety issues, such as flammability and explosion risks, along with low energy density. To address these limitations, we develop a composite polymer electrolyte (CPE) as a safer, higher energy density alternative. The optimized CPE, denoted as CPE-60, contains Li 5.5 Ga 0.5 La 3 Zr 2 O 12 (LGLZO), succinonitrile (SN), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and poly (vinylidene fluoride- co -hexafluoropropylene (PVdF-HFP). LGLZO nanofillers reinforce the PVdF-HFP matrix, enhancing mechanical strength and suppressing Li dendrite growth, while SN and LiTFSI improve lithium-ion transport properties. The solid polymer electrolyte containing SN and LiTFSI delivers an ionic conductivity of 2.45 × 10 −4 S cm −1 , a lithium-ion transference number of 0.52, and an activation energy of 0.27 eV. Incorporation of 60 wt% LGLZO further imparts excellent thermal and electrochemical stabilities, along with robust mechanical strength. The Li-symmetric cell fabricated using CPE-60 demonstrates excellent cycling stability for over 350 h at 0.1 mA cm −2 , maintaining a low overpotential of 108 mV. Furthermore, the Li/CPE-60/LiFePO 4 full cell demonstrates exceptional electrochemical performance, achieving an average Coulombic efficiency of 99.94% over 110 cycles at 0.1C and robust rate capability, retaining 82.1% capacity at 1C. This study highlights LGLZO-modified PVdF-HFP membranes as highly promising electrolytes for high-performance, stable all-solid-state lithium batteries.