Halide SSEs are regarded as ideal candidates for high-energy-density ASSBs owing to their high ionic conductivity, superior electrochemical stability, and good processability. Nevertheless, cathode interfacial instability remains a principal bottleneck in practical applications. Although notable advances have been achieved in materials optimization, interfacial engineering, and structural design, several scientific and engineering challenges remain unresolved.

1) Intrinsic materials stability. Under high-voltage operation, the chemical and electrochemical stability of halide SSEs are still limited. Anion substitution, cation doping, and high-entropy strategies can partially expand these windows, yet their action mechanisms and the governing rules for interfacial electronic-structure modulation are not fully elucidated. Future studies should integrate experiment and theory to establish quantitative links among chemical composition, electronic structure, and stability, considering density of states, space-charge layers, and band alignment at interfaces, to derive design principles for interfacial stabilization.

2) Construction and evolution of interfacial structures. Current efforts focus on electrolyte modification or cathode surface treatments, forming passivating layers from electrolyte decomposition or applying protective coatings to block direct contact between active materials and the electrolyte. Building on this, priority should be given to controllable synthesis that delivers nanoscale, uniform interfacial contact while avoiding byproducts and voids-key to enhancing electrochemical stability. Gradient architectures, core-shell designs, and in situ-formed interphases are promising, but their cycling evolution and mechanical matching require deeper investigation. In parallel, combining single-crystal cathodes with highly stable halide SSEs may offer a new balance between energy density and interfacial stability.

3) Processing and manufacturability. Halide-based ASSBs still face challenges in scalable fabrication and environmental sensitivity. Many halide electrolytes are extremely sensitive to moisture and polar solvents, limiting the direct use of conventional wet processes. Priority should be placed on developing coating, dry pressing, and lamination routes in low-polarity or non-solvent environments, and on mapping how processing parameters (pressure, temperature, atmosphere) affect interfacial structure and performance to unify electrochemical metrics with manufacturability.

In summary, halide SSEs present a compelling suite of advantages for ASSBs, yet cathode interfacial stability remains the key constraint on performance and deployment. Research on halide cathode interfaces is transitioning from mechanistic elucidation to controllable construction and engineering implementation. Future efforts should pursue coordinated advances in materials optimization, structural design, and process development to enable safe, high-energy-density storage. Through the integration of multiple strategies, halide ASSBs hold promise for achieving high energy density, long cycle stability, and industrial viability-advancing ASSBs technology and underpinning safer, more efficient energy-storage systems.