Constructing vertical Li+ transport “Highways” and interface regulation of composite solid electrolytes for ultra-stable lithium metal batteries

Three-dimensional (3D) interconnected composite solid electrolytes (CSEs) hold significant promise for solid-state batteries by leveraging the combined strengths of ceramic and polymer electrolytes. However, optimizing ion transport in 3D-CSEs remains challenging, with unclear underlying mechanisms. Here, a CSE (marked as 3D-LATP) is developed by integrating 3D vertically aligned Li$_{1.3}$Al$_{0.3}$Ti$_{1.7}$(PO$_{4}$)$_{3}$ (LATP) framework with infiltrated poly(vinylidene fluoride-co-trifluoroethylene-co-chlorofluoroethylene) (P(VDF-TrFE-CFE)) and lithium bis(fluorosulfonyl)imide. The multipath Li+ transfer mechanism and enhanced interfacial stability are thoroughly investigated. The vertically aligned LATP structure provides efficient ion transport “highways” and robust mechanical support. LATP also induces more generation of high dielectric constant β-crystalline phase in PVDF, thereby enhancing ionic transport kinetics at the ceramic/polymer interface. Strong LATP−N, N-dimethylformamide interactions enhance electrochemical stability with lithium metal. The high-dielectric polymer interlayer at the Li|CSE interface enables uniform Li$^+$ deposition, meanwhile significantly enhancing the safety property. ... mehrAs a result, compared to CSEs with an equal amount of randomly distributed LATP fillers, the 3D-LATP electrolyte demonstrates markedly improved ambient ionic conductivity, lithium-ion transference number, and critical current density. Li||LiFePO4 full cells achieve an outstanding cycle lifetime of 2500 cycles (at 1 C rate), presenting a promising approach for designing high-performance CSEs that ensure efficient ion transport and stable interfaces.