An in-situ polymerized interphase engineering for high-voltage all-solid-state lithium-metal batteries

All-solid-state lithium batteries (ASSLBs) have attracted great interest due to their promising energy density and strong safety. However, the interface issues, including large interfacial resistance between electrode and electrolyte and low electrochemical stability of solid-state electrolytes against high-voltage cathodes, have restricted the development of high-voltage ASSLBs. Herein, we report an ASSLB with stable cycling by adopting a conformal polymer interlayer in-situ formed at the Li_6.4La₃Zr_1.4Ta_0.6O₁₂ (LLZTO)–cathode interfaces. The polymer can perfectly fill the voids and create a stable interface contact between LLZTO and cathodes. In addition, the electric field across the polymer interlayer is reduced compared with pure solid polymer electrolyte (SPE), which facilitates the electrochemical stability with high-voltage cathode. The all-solid-state Li|LLZTO-SPE|LiFe_0.4Mn_0.6PO₄ (LMFP) cells achieve a low interface impedance, high specific capacity, and excellent cycling performance. This work presents an effective and practical strategy to rationally design the electrode–electrolyte interface for the application of high-voltage ASSLBs.