Rational Design of Sandwich-Like "Gel-Liquid-Gel" Electrolytes for Dendrite-Free Lithium Metal Batteries

Issues of lithium dendrite growth still hinder the popular application of lithium metal batteries (LMBs). Herein, we demonstrate that "gel-liquid-gel"electrolytes effectively suppress the growth of dendrites. This sandwich structure is based on introducing gel polymer coating layers, which consist of polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), onto both sides of a Celgard separator. The PVDF-HFP layers improve the overall liquid electrolyte retention and compatibility with lithium anodes. They also lead to a uniform Li-ion flux at the polymer/lithium interface, which results in the suppression of dendrite nucleation. Impressively, Li|Cu cells operate stably for over 400 cycles with a high Coulombic efficiency of ∼98%. Li|Li symmetric cells enable highly stable Li plating/stripping cycling for over 1200 h at 1 mA cm-2. Li|LiFePO4 full cells also exhibit excellent cycling performance. We expect this work to have great potential in the application of simple composite gel polymer electrolytes to achieve highly safe LMBs.