High-voltage nickel-rich layered cathodes in lithium metal batteries enabled by a sulfolane / fluorinated ether/ fluoroethylene carbonate-based electrolyte design

Electrolyte system with high electrochemical stability and interfacial compatibility is essential to the high-performance lithium metal battery. Herein, we introduce an electrolyte design of 1 M Lithium bistrifluoromethosulfonimide (LiTFSI) sulfolane/1,1,2,2-Tetrafluoroethyl 2,2,3,3-Tetrafluoropropyl Ether (HFE)/Fluoroethylene carbonate (FEC) to improve the high voltage performance (4.7 V) for LiNi0.8Mn0.1Co0.1O2 based lithium metal batteries. Such a designed electrolyte exhibits a high-voltage limit of 5.1 V，compared to 4.3 V of the carbonated-based electrolyte (1 M Lithium hexafluorophosphate (LiPF6) ethylene carbonate（EC）/dimethyl carbonate (DMC)/ethyl methyl carbonate (EMC) 1:1:1). The cell with the designed electrolyte improves the coulombic efficiency, rate and cycle capability. The cell with the designed electrolyte delivers a reversible capacity of ∼220 mAh g−1 at 0.1C, with a capacity retention of ∼85% after 150 cycles (0.5C charge/discharge, 3.0–4.7 V), while the commercial electrolyte only exerts a capacity retention of 71.60%. X-Ray Powder Diffraction (XRD)，Scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS) analysis reveal the designed electrolyte effectively improve the structural and interfacial stability on cathode. It also suppresses the lithium-dendrite growth and facilitates the stable lithium-plating/stripping on lithium metal anode. While the carbonate-based electrolyte forms thick and unstable interface on cathode and grows dendrite-liked surface on lithium anode.