The passivity of lithium electrodes in liquid electrolytes for secondary batteries

Rechargeable Li metal batteries are currently limited by safety concerns, continuous electrolyte decomposition and rapid consumption of Li. These issues are mainly related to reactions occurring at the Li metal–liquid electrolyte interface. The formation of a passivation film (that is, a solid electrolyte interphase) determines ionic diffusion and the structural and morphological evolution of the Li metal electrode upon cycling. In this Review, we discuss spontaneous and operation-induced reactions at the Li metal–electrolyte interface from a corrosion science perspective. We highlight that the instantaneous formation of a thin protective film of corrosion products at the Li surface, which acts as a barrier to further chemical reactions with the electrolyte, precedes film reformation, which occurs during subsequent electrochemical stripping and plating of Li during battery operation. Finally, we discuss solutions to overcoming remaining challenges of Li metal batteries related to Li surface science, electrolyte chemistry, cell engineering and the intrinsic instability of the Li metal–electrolyte interface. Rechargeable Li metal batteries are currently limited by electrolyte decomposition and rapid Li consumption. Li plating and stripping greatly depend on the solid electrolyte interphase formed at the Li metal–liquid electrolyte interface. This Review discusses the reactions occurring at this interface from a corrosion science perspective, highlighting the requirements for an ideal passivation layer.