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.