Effective Suppression of Lithium Dendrite Growth Using a Flexible Single-Ion Conducting Polymer Electrolyte

A novel single-ion conducting polymer electrolyte (SIPE) membrane with high lithium-ion transference number, good mechanical strength, and excellent ionic conductivity is designed and synthesized by facile coupling of lithium bis(allylmalonato) borate (LiBAMB), pentaerythritol tetrakis (2-mercaptoacetate) (PETMP) and 3,6-dioxa-1,8-octanedithiol (DODT) in an electrospun poly(vinylidienefluoride) (PVDF) supporting membrane via a one-step photoinitiated in situ thiol-ene click reaction. The structure-optimized LiBAMB-PETMP-DODT (LPD)@PVDF SIPE shows an outstanding ionic conductivity of 1.32 × 10^-3 S cm^-1 at 25 °C, together with a high lithium-ion transference number of 0.92 and wide electrochemical window up to 6.0 V. The SIPE exhibits high tensile strength of 7.2 MPa and elongation at break of 269%. Due to these superior performances, the SIPE can suppress lithium dendrite growth, which is confirmed by galvanostatic Li plating/stripping cycling test and analysis of morphology of Li metal electrode surface after cycling test. Li|LPD@PVDF|Li symmetric cell maintains an extremely stable and low overpotential without short circuiting over the 1050 h cycle. The Li|LPD@PVDF|LiFePO₄ cell shows excellent rate capacity and outstanding cycle performance compared to cells based on a conventional liquid electrolyte (LE) with Celgard separator. The facile approach of the SIPE provides an effective and promising electrolyte for safe, long-life, and high-rate lithium metal batteries.