Surface-Treated\nComposite Polymer as a Stable Artificial\nSolid Electrolyte Interphase Layer for Lithium Metal Anodes

Lithium (Li) metal batteries (LMBs)\nare some of the most promising\nhigh energy density batteries to meet the demands of electric transportation.\nHowever, the practical applications of LMBs are hindered by short\ncycle life and safety concerns, mainly associated with the side reactions\nbetween Li metal anode and liquid electrolyte and the growth of Li\ndendrites during cycling. In this study, we develop a stable artificial\nsolid electrolyte interphase (aSEI) layer, which consists of a surface-treated\n(S<sub>T</sub>) PEO–Li<sub>6.4</sub>Ga<sub>0.2</sub>La<sub>3</sub>Zr<sub>2</sub>O<sub>12</sub> composite polymer coating layer\n(CPL) on a Li metal anode. The developed aSEI is stable against a\nselected electrolyte and enables a uniform electrodeposition of Li.\nTherefore, S<sub>T</sub>CPL@Li||LiNi<sub>0.8</sub>Mn<sub>0.1</sub>Co<sub>0.1</sub>O<sub>2</sub> (NMC811) cells exhibit improved cycling\nstability compared with bare Li||NMC811 cells at moderate to high\ncurrent densities. Notably, using a 50 μm-thick Li and a practical\nNMC811 cathode (∼4.8 mAh cm<sup>–2</sup>), a capacity\nretention of 85% is obtained for S<sub>T</sub>CPL@Li||NMC811 cells\nat a current density of 2.4 mA cm<sup>–2</sup> after 300 cycles\ncompared with 24% for bare Li||NMC811 cells. Furthermore, S<sub>T</sub>CPL@Li||NMC811 cells demonstrate higher capacities at charge current\ndensities of 2.4, 4.8, and 7.2 mA cm<sup>–2</sup> compared\nwith bare Li||NMC811 cells. These findings suggest that S<sub>T</sub>CPL is promising for high current density practical LMBs.