Three-dimensional LLZO/PVDF-HFP fiber network-enhanced ultrathin composite solid electrolyte membrane for dendrite-free solid-state lithium metal batteries

Composite solid electrolyte (CSE) membranes for lithium metal batteries attract great attention with excellent safety and suitable flexibility. Herein, we construct a polyethylene oxide-based ultrathin CSE membrane that is enhanced by a 3D fiber network composed of Poly (vinylidene fluoride-co-hexafluoropropylene) fibers and Li₇La₃Zr₂O₁₂ particles directly fabricated on the cathode. The 3D fiber network facilitates the rapid transport and uniform deposition of Li⁺, and enhances the mechanical strength of the electrolyte membrane, thereby effectively inhibiting the growth of lithium dendrites. Moreover, the unique preparation method reduces the interfacial impedance, and it can also greatly reduce the electrolyte thickness, which is beneficial to increasing the energy density of the battery. The lithium symmetric battery shows stable cycling over 1500 h under 0.2 mA cm⁻². Li/LiFePO₄ battery with the CSE membrane exhibits a high reversible capacity of 155.8 mAh·g⁻¹ at 0.2 C for 100 cycles and the capacity retention rate is 98.0%. Furthermore, the obtained CSE membrane has a broadened electrochemical window of 4.83 V, and the reversible capacity of the Li/LiNi_0.8Co_0.1Mn_0.1O₂ battery is 160.6 mAh·g⁻¹ at 0.2 C for 100 cycles. These findings showed that the structure proposed here is a viable electrolyte strategy for advanced solid-state lithium metal batteries.