A Robust Protective Layer Based on Polymer Brush for Long-Term Cycling of Li Metal Anodes

Lithium metal anodes are promising candidates for next-generation high-energy density batteries. Unstable lithium–electrolyte interfaces caused by uncontrolled dendrite growth and side reactions still hinder its practical process. In this work, an all-organic solid electrolyte interphase (SEI) film coupling hardness with softness has been prepared to achieve a dendrite-free lithium metal anode by designing polymer brushes rationally (poly(diethylene glycol methyl ether methacrylate) (PEGM) and poly(2,2,2-trifluoroethyl acrylate) (PTFEA) from bacterial cellulose (BC), denoted as BC-g-P(EGM-co-TFEA)). The rigid BC skeleton can significantly enhance the mechanical strength to depress Li dendrite growth. Furthermore, flexible P(EGM-co-TFEA) side chains are able to homogenize lithium-ion flux, inducing the generation of LiF, boost ion conductivity, and maintain good electrode interface contact. As a result, Li/Li symmetric cells with a BC-g-P(EGM-co-TFEA)-protective film enable long-term (1500 h) reversible lithium plating/stripping at a high current density of 10 mA cm–2, while the Li@BC-g-P(EGM-co-TFEA)/LiFePO4 cell maintains a small capacity decay per cycle of 4% during 500 cycles at 3 C. This work could provide an innovative strategy to develop superior artificial SEI films for inhibiting Li dendrite growth on the Li metal anode.