Artificial solid electrolyte interphases by atomic and molecular layer deposition

Atomic layer deposition (ALD) and molecular layer deposition (MLD) are techniques known for their unique capability to produce pinhole-free and conformal thin films uniformly, even on complex 3D architectures and powders, with sub-nm thickness control. Owing to these characteristics, they are recognized as highly promising techniques for the fabrication of ultrathin protective coatings on Li-ion battery components to improve battery performance and lifetime. In the early studies, the focus was on archetypal ALD materials such as Al₂O₃, but recently the scope has considerably widened to cover various Li-based materials, aiming at a better ionic conductivity and enhanced Li-ion kinetics in the coating, as well as ALD/MLD-grown metal-organics with enhanced elasticity and mechanical flexibility to better moderate the volume changes in the coated electrode materials during battery charge-discharge cycling. Also, to most closely mimic the solid-electrolyte interphase (SEI) layers that naturally form in state-of-the-art Li-ion batteries, the layer should include carbonate species. In this review, we present a brief account of the current state of this exciting and timely research field, and discuss the foreseen prospects and challenges for progress.