Polymer Coating for Li‐Metal Anode in Polyethylene Oxide‐Based Electrolyte Batteries

The push to use metallic lithium‐based batteries motivates a shift toward the use of solid polymer electrolytes. To improve the ionic conductivity values of such electrolytes, liquid additives (plasticizers) are usually added. However, the improvement in conductivity comes at the expense of a deterioration of the anode–electrolyte interface, resulting in poorer electrochemical cell performance. In this study, the use of a polymer coating consisting of polyethylene oxide, LiTFSI, and LiNO ₃ is proposed. The coating shows improved electrochemical performance and stability, delayed cell failure and a more uniform distribution of Li deposits. These improvements are attributed to the increased stability of the solid electrolyte interphase, which is confirmed by using a combination of electrochemical impedance spectroscopy, scanning electron microscopy, and X‐ray photoelectron spectroscopy. In contrast, it is found that the interphase in uncoated Li electrodes is likely affected by continuous reactions with the plasticizer, further confirming the need to use such protective coatings to achieve long‐term operation in practical solid‐state Li metal batteries.