Solid electrolyte interphase-ization of Mg2+-blocking layers for lithium ions in anode-free rechargeable lithium metal batteries

A novel concept of solid electrolyte interphase (SEI)-ization of Mg2+-blocking layers for Li+ ions and its effect on their deposition in anode-free rechargeable Li-metal batteries (AFLMBs) has been introduced. The deposition quality of Li on Cu current collectors (CCs) has been improved by the addition of a moderate amount of Mg(N(CF3SO2)2)2 co-salt in Li+-containing carbonate-based electrolytes (Li–Mg electrolytes). Additional analyses revealed that thin, dense, and stable surface layers exhibiting permeability for Li+ and impermeability for Mg2+ ions were formed in Li–Mg electrolytes, significantly suppressing the Li dendrite growth and enhancing the deposited Li metal/Cu CC surface binding. As a result, the Mg2+-blocking layers acted as effective SEI layers from the perspective of Li+ ions, positively influencing the electrochemical performance of the AFLMB full cells.