Ultrathin Yet Robust Single Lithium‐Ion Conducting Quasi‐Solid‐State Polymer‐Brush Electrolytes Enable Ultralong‐Life and Dendrite‐Free Lithium‐Metal Batteries

Abstract

Quasi-solid-state polymer electrolytes are one of the most promising candidates for long-life lithium-metal batteries. However, introduction of plasticizers for high ion conductivity at room temperature inevitably gives rise to poor mechanical strength and requires a very thick electrolyte membrane, which is detrimental to safety and energy density of the batteries. Herein, inspired by tube brushes coupling hardness with softness, a novel superstructured polymer bottlebrush BC-g-PLiSTFSI-b-PEGM (BC = bacterial cellulose; PLiSTFSI = poly(lithium 4-styrenesulfonyl-(trifluoromethylsulfonyl) imide); PEGM = poly(diethylene glycol monomethyl ether methacrylate)) with a hard nanofibril backbone and soft functional polymer side-chains is reported as an effective strategy to well balance the mechanical strength and ion conductivity of quasi-solid-state polymer electrolytes. The resulting single lithium-ion conducting quasi-solid-state polymer-brush electrolytes (SLIC-QSPBEs) integrate the features of the ultrathin membrane thickness (10 µm), the nanofibril backbone-strengthened porous nanonetwork (Young's modulus = 1.9 GPa), and the high-rate single lithium-ion conducting diblock copolymer brushes. As a result, the ultrathin yet robust SLIC-QSPBEs enable ultralong-term (over 3300 h) reversible and stable lithium plating/stripping in Li/Li symmetrical cell at a current density of 1 mA cm^-2 for lithium anode. This work affords a promising strategy to develop advanced electrolytes for solid-state lithium-metal batteries.