Functional Copolymer Derived Self‐Adapting LiF‐Rich Interphase Toward Deep Cycling Lithium Metal Batteries

Abstract Lithium metal batteries (LMBs) are the best candidates for high‐energy density system. However, the unstable solid electrolyte interphase (SEI) caused by notorious lithium dendrite growth and huge volume fluctuation under practical conditions hinders its commercialization. Here, a functional copolymer composed of monomer is designed with ordered −CF 2 − groups grafted to viscoelastic backbone to provide homogeneous and self‐adapting in situ LiF‐rich interface. Hence, the robust interface facilitates rapid Li + flux and suppresses dendritic Li growth. Furthermore, an elastic composite lithium metal anode (FELMA) based on the designed functional copolymer is fabricated through a cost‐effective approach. The FELMA shows excellent cycle stability with ultra‐low volume expansion rate of 0.16% per cycle after 200 cycles at the condition of 3 mA cm −2 –3 mAh cm −2 . The full batteries assembled with high‐loading LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811, 4.1 mAh cm −2 ) cathode can maintain 80% capacity retention after 320 cycles under N/P = 2.17 and E/C = 2.68 g Ah −1 , with the cycling life increased by 220% than Li||NCM811. A prototype 418 Wh kg −1 pouch cell (5.16 Ah) with N/P ratio of 0.88 and E/C ratio of 2.39 g Ah −1 shows stable cycling.