Synergistic design of a interface-enhanced composite solid electrolyte through in-situ polymerization within a tri-layer ceramic framework for solid-state Li-metal batteries

The solid-state electrolyte (SSE) has promising applications for next-generation high-energy-density and safe solid-state Li-metal batteries (SSLMBs). However, the signifcant challenge of achieving both high ionic conductivity and good compatibility with electrodes has limited the development of high-performance CSEs for SSLMBs. To overcome these challenges, an unique in situ composite solid electrolytes (CSEs) was fabricated. In brief, employing a tape-casting method to preparate a tri-layer porous-dense-porous ceramic films with nano-sized Li₆.₄La₃Zr₁.₄Ta₀.₆O₁₂ (LLZTO). Subsequently, the vinylene ethylene carbonate (VEC)-based small-molecule polymer monomers are injected into the tri-layer ceramic framework for in-situ polymerization to produce the CSE. Blocking cell tests demonstrated that the CSE has an excellent ionic conductivity of 0.933 mS·cm⁻¹. The Li|CSE|Li symmetric cells exhibited a high Li⁺ transference number of 0.565 and the Li|CSE|SS asymmetric cells behaved an electrochemical stability window of 5.17 V. All of which due to the multifunctional synergistic effect of the tri-layer LLZTO ceramic fillers with the polymer electrolyte. The Li|CSE|LiFePO₄ cell showed a high reversible specific capacity of 146.2 mAh·g⁻¹ with a capacity retention of 91% after 150 cycles at 30°C and 0.5 C. The Graphite|CSE|LiFePO₄ full cells delivered an initial discharge capacity of 142.1 mAh·g⁻¹ at 0.5 C with a capacity retention of 83.1% after 100 cycles. The schematic diagram of the ultra-thin tri-layer porous-dense-porous CSE fabrication process. • A ultra-thin tri-layer LLZTO structure was fabricated by a new tape-casting method. • The in-situ CSE exhibits excellent interfacial compatibility and ionic conductivity. • The Li|CSE|LiFePO₄ exhibited a high capacity retention rate of 91.0%.