Three-Dimensional Continuous Ion Transport Skeleton-Reinforced Composite Solid Electrolyte for High-Performance Solid-State Lithium Metal Batteries

The Li_1.3Al_0.3Ti_1.7(PO₄)₃ (LATP) electrolyte is recognized as a highly promising solid-state electrolyte for next-generation solid-state lithium batteries due to its high ionic conductivity, low cost, and exceptional air stability. Unfortunately, its practical application is impeded by significant grain boundary impedance and interfacial instability with lithium metal. In this study, we introduced a cost-effective template method to fabricate a three-dimensional LATP (3D-LATP) skeleton featuring continuous porosity, which was combined with the polymer poly(vinylidene fluoride-<i>co</i>-hexafluoropropylene) (PVDF-HFP) to fabricate a three-dimensional composite solid electrolyte (3D-CSE) exhibiting enhanced flexibility and superior interfacial contact. The 3D-LATP skeleton acts as an active filler, establishing continuous transport pathways for lithium ions within the electrolyte and substantially increasing the room-temperature ionic conductivity to 6.89 × 10^-4 S cm^-1. Furthermore, the nonflammability of the 3D-LATP skeleton significantly enhances the thermal stability of the electrolyte. Additionally, the inclusion of the PVDF-HFP polymer improves interfacial contact between the LATP skeleton and the electrodes, thereby mitigating erosion of the LATP skeleton by the lithium metal anode in Li|Li symmetric batteries and LiFePO₄|Li full batteries. Consequently, the Li|3D-CSE|Li symmetric battery demonstrated stable lithium plating-stripping cycles for over 4000 h at 0.1 mA cm^-2. Moreover, the LiFePO₄|3D-CSE|Li full battery exhibited reliable cycling performance over 500 cycles at 0.5C. This high-performance 3D composite electrolyte highlights the potential of LATP for high-energy-density solid-state lithium metal batteries.