In-Situ Plasticized LLZTO-PVDF Composite Electrolytes for High-Performance Solid-State Lithium Metal Batteries

Solid polymer electrolytes (SPEs) are seen as the key component in the development of solid-state lithium batteries (SSLBs) by virtue of their good processability and flexibility. However, poor mechanical strength, low room-temperature lithium-ion (Li-ion) conductivity and unsatisfactory interfacial compatibility with electrodes limit their practical application. In this work, a composite electrolyte consisting of polyvinylidene fluoride and polyvinylidene carbonate with a Li6.4La3Zr1.4Ta0.6O12(LLZTO) active filler (PFPC: LLZTO-SPE) is reported to achieve excellent ionic conductivity (4.25 × 10−4 S cm−1 at 30 °C), a wide electrochemical window (>4.6 V), a high Li-ion transference number (tLi+ = 0.49) and good interfacial compatibility with the electrode. Incorporating LLZTO as an active filler not only increases the ionic conductivity of the electrolyte, but also homogenizes Li-ion flux and stabilizes the electrode/electrolyte interface, thereby preventing lithium dendrites from piercing the electrolyte. As a result, Li/Li symmetrical cells using PFPC: LLZTO-SPEs deliver more than 800 h of cyclability at 0.1 mA cm−2 and a high critical current density (CCD) of 2.6 mA cm−2. The assembled Li/PFPC: LLZTO/LFP SSLBs achieve 87% capacity retention after 150 cycles at 0.2 C and 89% capacity retention for 100 cycles at 0.5 C. This work inspires new insights into designing high-performance SPEs.