Constructing stable interface and high-performance solid polymer electrolyte by introducing MgF2 for dendrite-free Li metal batteries

Li metal anode suffers from poor interfacial stability and safety hazards in liquid electrolytes. Designing stable interface on Li metal and replacing liquid electrolytes are critical ways to develop high-energy-density lithium metal batteries (LMBs). In this paper, a superior MgF 2 -containing interface was first studied, and an interface-derived high-performance solid polymer electrolyte (SPE) was prepared by a facile solution casting method. A LiF-rich interface containing Mg atoms is in-situ generated by the reaction between MgF 2 and metallic Li, which simultaneously enhances the interfacial stability and endows dendrite-free Li deposition, enabling the Li metal anodes to realize long-term stable cycling even at 5C (3.04 mA cm −2 ) in commercial carbonate electrolytes. The interface-derived SPE has high room-temperature (RT) ionic conductivity, Li-ion transference number, excellent interfacial compatibility and stability due to the existence of MgF 2 . Under the joint action of stable interface and high-performance SPE, the all-solid-state LMBs can exhibit ultra-stable cycling with high coulombic efficiencies under RT. This work provides a guideline for the development of superior interfaces and high-performance SPEs by learning from each other.