Surface-Treated Composite Polymer as a Stable Artificial Solid Electrolyte Interphase Layer for Lithium Metal Anodes

Lithium (Li) metal batteries (LMBs) are some of the most promising high energy density batteries to meet the demands of electric transportation. However, the practical applications of LMBs are hindered by short cycle life and safety concerns, mainly associated with the side reactions between Li metal anode and liquid electrolyte and the growth of Li dendrites during cycling. In this study, we develop a stable artificial solid electrolyte interphase (aSEI) layer, which consists of a surface-treated (ST) PEO–Li6.4Ga0.2La3Zr2O12 composite polymer coating layer (CPL) on a Li metal anode. The developed aSEI is stable against a selected electrolyte and enables a uniform electrodeposition of Li. Therefore, STCPL@Li||LiNi0.8Mn0.1Co0.1O2 (NMC811) cells exhibit improved cycling stability compared with bare Li||NMC811 cells at moderate to high current densities. Notably, using a 50 μm-thick Li and a practical NMC811 cathode (∼4.8 mAh cm–2), a capacity retention of 85% is obtained for STCPL@Li||NMC811 cells at a current density of 2.4 mA cm–2 after 300 cycles compared with 24% for bare Li||NMC811 cells. Furthermore, STCPL@Li||NMC811 cells demonstrate higher capacities at charge current densities of 2.4, 4.8, and 7.2 mA cm–2 compared with bare Li||NMC811 cells. These findings suggest that STCPL is promising for high current density practical LMBs.