New insight into Li metal protection: Regulating the Li-ion flux via dielectric polarization

Abstract

Protective surface layer (PSL) is emerging as a popular strategy for lithium (Li) metal protection. Previous reports regarding PSL primarily focus on the two indexes of ionic conductivity and elastic modulus under the precondition of chemical compatibility. Herein, the dielectric property of PSL on Li metal is thoroughly investigated. Although this physical characteristic of the ion conductor has a consequential effect on lithium deposition, it has been surprisingly neglected in the past. Accordingly, the detailed information on how the dielectric feature of PSL affects the current/potential distribution during lithium deposition is elucidated in this study. Indeed, an optimal range of relative dielectric constants is proposed for PSL selection. The mathematical simulation and experimental results show that the dielectric properties of PSL can significantly affect the Li-ion flux distribution on the lithium metal surface. • The dielectric effect of the protective surface layer during the Li deposition was analyzed in detail. • The dielectric and concentration polarization together act as a shock absorber to any sudden changes in the current densities. • In galvanostatic mode, the potential distribution on the Li metal surface was much more uniform under ε r =5–13. • The experimental results can verify the simulated optimal value range of relative dielectric constants through symmetrical Li-Li cells.