Atomic‐ and Molecular‐Scale Interphase Engineering for High‐Performance Solid‐State Batteries

Solid‐state batteries (SSBs) promise a decisive advance beyond conventional Li‐ion systems, yet their development remains constrained by persistent solid–solid interfacial instabilities that degrade performance and durability. Interfaces between solid electrolytes and both cathodes and Li metal often exhibit poor wettability, limited physical contact, and high charge–transfer resistance, leading to chemical decomposition, mechanical failure, and impedance growth. Overcoming these limitations requires interphase engineering with atomic‐scale precision—capabilities that conventional coating methods cannot reliably deliver. Atomic layer deposition (ALD) and molecular layer deposition (MLD) uniquely meet this need by enabling ultrathin, conformal, and composition‐tunable films that stabilize reactive surfaces, suppress parasitic reactions, and regulate Li‐metal morphology. Importantly, this Perspective highlights ALD/MLD systems that have already demonstrated effectiveness in liquid‐electrolyte cells and discusses how these validated strategies can be deliberately translated to solid‐state architectures. By grounding future directions in experimentally proven concepts rather than speculative hypotheses, we outline how atomic‐ and molecular‐scale design principles can accelerate the development of robust, high‐performance SSB technologies.