Polymer Zwitterion-Based Artificial Interphase Layers for Stable Lithium Metal Anodes

Lithium (Li) metal batteries are promising future rechargeable batteries with high-energy density as the Li metal anode (LMA) possesses a high specific capacity and the lowest potential. However, the commercial application of the LMA has been hindered by a low Coulombic efficiency and dendrite growth, which are related to the unstable interphase with poor Li⁺ ion transport. Herein, we report novel polymer zwitterion-based artificial interphase layers (AILs) with improved Li⁺ ion transport and high stability for long-life LMAs. Benefitting from the unique zwitterion effect within the polymer zwitterion-based AILs, a high Li⁺ ion transference number (0.81) and a good ionic conductivity (0.75 × 10^-4 S cm^-1) can be realized simultaneously at the interface. By regulating the weight ratio of the sulfonate group and the phosphate group in polymer zwitterion-based AILs, the modified LMA enables long-term Li plating/stripping for 1400 h at 1 mA cm^-2 and stable cycling in a full cell. This interfacial engineering concept could shed light on the development of safe LMAs.