Weak Solvation Chemistry in Fluorinated Nonflammable Electrolytes Achieves Stable Cycling in High-Voltage Lithium Metal Batteries.

Abstract

High-voltage (>4.35 V) lithium nickel-cobalt-manganese batteries are star candidates due to their higher energy density for next-generation power batteries. This poses higher demands for electrolyte design, including compatibility with lithium metals, stability on high-voltage cathodes, speedy interfacial ion transport kinetics, and appropriate concentration. However, electrolytes at the current level of research struggle to balance these demands. Here, we took advantage of the reduced affinity with Li+ and enhanced oxidative stability of three fluorinated linear carbonates to design a series of weakly solvating electrolytes (WSEs) at a low salt concentration of 1 M, which contain abundant ionic cluster structures, leading to the optimization of interfacial chemistry. As a result, WSEs can support the stable cycling of 4.6 V high-voltage Li||NCM811 cells for 300 cycles with a capacity retention of nearly 80%. Moreover, benefiting from the lower desolvation energy of Li+, WSEs achieve superior cycling stability and low polarization under -20 °C. Our work extends the application of WSEs for high-voltage LMBs, providing a promising solution in electrolytes for high-specific-energy lithium batteries.