Toward Practical Solid‐State Lithium Batteries With High‐Nickel Cathodes: An Interface‐Centered Perspective

ABSTRACT The global transition toward renewable energy and carbon neutrality has sharply increased the demand for energy‐storage systems with higher energy density, improved safety, and extended service life. Despite the dominance of lithium‐ion batteries, their development is greatly limited by the flammability and electrochemical instability of liquid electrolytes. Solid‐state lithium batteries (SSLBs) provide a promising alternative because solid‐state electrolytes (SSEs) eliminate electrolyte leakage, enhance thermal stability, and enable the use of high‐voltage cathodes and lithium‐metal anodes. Among candidate cathode materials, high‐nickel layered oxides (LiNi x Co y Mn 1‐ x ‐ y O 2 , x ≥ 0.8) are the most viable for practical deployment, owing to their high specific capacity, moderate cost, and industrial maturity. However, their integration with SSEs introduces severe challenges, including structural degradation, oxygen release, and interfacial instability, which collectively impede lithium‐ion transport and compromise cycling durability. This review summarizes recent progress in SSLBs with high‐nickel cathodes, focusing on (1) structural and surface engineering of high‐nickel cathodes, (2) optimization of oxide‐, sulfide‐, halide‐, and polymer‐based SSEs, and (3) interface‐engineering strategies, including buffer layers and in situ interfacial design. Finally, perspectives are provided on material innovation, interfacial characterization, and scalable manufacturing, aiming to guide the development of next‐generation SSLBs that combine high energy density with intrinsic safety.