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 perspectival 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.