Long-Life and High-Rate-Charging Lithium Metal Batteries Enabled by a Flexible Active Solid Electrolyte Interphase Layer

Commercially, lithium metal batteries are still limited by the growth of lithium dendrites and excessive consumption of the electrolyte. A stable multifunctional solid electrolyte interface is the development strategy of lithium metal batteries in the future. However, most of the artificial solid electrolyte interphases (SEIs) cannot meet the original intention of multifunctional design and cannot form an SEI film with a high conductivity and low nucleation potential. In this work, we report a universal and simple method of adding multifunctional fluorosulfonate to a commercial electrolyte, so increasing the inorganic LiF in the SEI. In addition, the imidazole ring in the fluorosulfonate combines with the alkyl group in the electrolyte to form a flexible interface layer, which inhibits the growth of lithium dendrites and makes lithium deposition more uniform, thereby realizing a stable fast charge cycle. With an ultralow capacity of 2 mAh/cm(2) deposited, the symmetrical battery can be deposited stably for nearly 300 h at a high current density of 20 mA/cm(2). The capacity retention rate of the Li-LiFePO4 (LFP) full cell was still at 90.6% after 1000 cycles at 5 C. Even with 5 C high-rate fast charging, the capacity was maintained at 76.56% after 200 cycles, which is four times that of commercial electrolytes. This simple addition strategy gives insights into the practical application of the new electrolyte and provides a new idea for the construction of a stable SEI for commercial lithium metal batteries.