A Robust Protective\nLayer Based on Polymer Brush for\nLong-Term Cycling of Li Metal Anodes

Lithium metal anodes are promising candidates for next-generation\nhigh-energy density batteries. Unstable lithium–electrolyte\ninterfaces caused by uncontrolled dendrite growth and side reactions\nstill hinder its practical process. In this work, an all-organic solid\nelectrolyte interphase (SEI) film coupling hardness with softness\nhas been prepared to achieve a dendrite-free lithium metal anode by\ndesigning polymer brushes rationally (poly(diethylene glycol methyl\nether methacrylate) (PEGM) and poly(2,2,2-trifluoroethyl acrylate)\n(PTFEA) from bacterial cellulose (BC), denoted as BC-<i>g</i>-P(EGM-<i>co</i>-TFEA)). The rigid BC skeleton can significantly\nenhance the mechanical strength to depress Li dendrite growth. Furthermore,\nflexible P(EGM-<i>co</i>-TFEA) side chains are able to homogenize\nlithium-ion flux, inducing the generation of LiF, boost ion conductivity,\nand maintain good electrode interface contact. As a result, Li/Li\nsymmetric cells with a BC-<i>g</i>-P(EGM-<i>co</i>-TFEA)-protective film enable long-term (1500 h) reversible lithium\nplating/stripping at a high current density of 10 mA cm<sup>–2</sup>, while the Li@BC-<i>g</i>-P(EGM-<i>co</i>-TFEA)/LiFePO<sub>4</sub> cell maintains a small capacity decay per cycle of 4% during\n500 cycles at 3 C. This work could provide an innovative strategy\nto develop superior artificial SEI films for inhibiting Li dendrite\ngrowth on the Li metal anode.