Poly (vinylidene fluoride) binder reinforced poly (propylene carbonate)/3D garnet nanofiber composite polymer electrolyte toward dendrite-free lithium metal batteries

To realize high energy density solid-state lithium (Li) metal batteries with enhanced safety, composite polymer electrolyte (CPE) that combines the advantages of both inorganic and polymer electrolytes is widely investigated. However, conventional CPE typically possesses low ionic conductivity and generate uneven ion distribution at the electrolyte-electrode interface, which can result in large internal resistance and severe Li dendrite growth. Herein, a novel CPE with high ionic conductivity of 3.1 × 10−4 S cm−1 and Li+ transference number is prepared to achieve dendrite-free Li deposition. Three-dimensional (3D) Li6.4La3Zr1.4Ta0.6O12 (LLZTO) nanofiber is incorporated into poly(propylene carbonate) (PPC) and further reinforced by poly(vinylidene fluoride) (PVDF) binder. The anions immobilized by the polymer matrix and ceramic fillers in the CPE help to guide uniform Li+ distribution without dendrite formation. Consequently, the Li symmetric cell assembled with CPE exhibits a stable potential and robust cyclic performance beyond 3200 h at 0.1 mA cm−2. A high discharge capacity and capacity retention are also achieved by Li/CPE/LiFePO4 cell after cycling for 200 cycles at 0.2C.