Rational Design of a Robust Flexible Triblock Polyurea Copolymer Protective Layer for High-Performance Lithium Metal Batteries

Dendrite growth and volume expansion in lithium metal are the most important obstacles affecting the actual applications of lithium metal batteries. Herein, we design a robust flexible artificial solid electrolyte interphase layer based on a triblock copolymer polyurea film, which promotes uniform lithium deposition on the surface of the lithium metal electrode and has a high lithium-ion transference number. The high elasticity and close contact of polyurea compounds effectively suppress lithium dendrite growth and volume expansion in the Li anode, which are effectively confirmed by electrochemical characterization and optical microscopy observation. The symmetrical batteries with the PU-Li metal anode can achieve stable and reversible Li plating/stripping over 500 h at a current density of 5 mA cm-2. Matched with the high-mass-loaded S cathode and the commercial NCM523 cathode, this film significantly improves the cycle life of lithium metal batteries.