Ionically Conductive Polymer Cathode Interface Interlayer for High-Performance All-Solid-State Lithium Battery

All-solid-state Li-metal batteries (ASSLMBs) incorporating garnet-type Li6.4La3Zr1.4Ta0.6O7 (LLZTO) electrolytes are promising alternatives to conventional lithium-ion batteries (LIBs) due to their nonflammability, robustness, safety, wide electrochemical window (∼5 V vs Li+/Li), and chemical stability in contact with Li metal. To obtain a high energy density of ASSLMBs, layered nickel-rich manganese cobalt oxides (NMC) are promising cathode materials owing to high operating voltage (∼4.3 V), high specific capacity (>180 mAh g–1), and cost-effectiveness by reduced cobalt content. However, insufficient interfacial contact between the cathode and electrolyte remains a critical challenge. To address this, we incorporate a highly functional polyoxanorbornene-based ionically conductive polymer (ICP) at the LLZTO electrolyte–cathode interface to improve the interfacial contact, Li-ion transport, and performance of the ASSLMBs. The resultant ASSLMB shows improved electrochemical performance, including a specific capacity of 174.4 mAh g–1 at 0.1C and long-term stability of 73.3% at 0.3C up to 300 cycles.