A salt-philic, solvent-phobic interfacial coating design for lithium metal electrodes

A key challenge to enable Li metal batteries as next-generation energy storage devices is to stabilize the interface between the Li metal and the electrolyte. A promising strategy is to promote the formation of a salt-derived robust and stable solid electrolyte interphase (SEI). Here we report a salt-philic, solvent-phobic (SP2) polymer coating for Li metal electrode that selectively transports salt over solvent and thus promotes salt-derived SEI formation. Unlike previously reported artificial SEIs, this SP2 coating approach resulted in enhanced cycling performance in several types of solvent, such as ether, carbonate and fluorinated ether. Specifically, the SP2 coating further enhanced the cycle life of a recently reported high-performance fluorinated ether electrolyte to give a ~400 cycle life (50 µm Li, 2.5 mAh cm−2 nickel manganese cobalt oxide and 80% capacity retention). Our coating design concept can be further fine tuned as promising electrolytes become available.