Roles of Nonflammable Organic Liquid Electrolyte in Stabilizing the Interface of the LiNi_0.8Co_0.1Mn_0.1O₂ Cathode at 4.5 V and Improving the Battery Performance

Abstract

Driven by a high demand for safe lithium-ion batteries (LIBs) with no risk of fire, we develop a nonflammable organic liquid electrolyte, which is composed of 1 M lithium hexafluorophosphate salt and propylene carbonate and fluorinated linear carbonates. Herein, we report the studies of the effects of the nonflammable electrolyte on the surface chemistry and structure of the nickel-rich LiNi0.8Co0.1Mn0.1O2 (NCM811) cathode under the expanded electrochemical voltage window to 4.5 V and their correlation to cycling performance. We provide for the first time the visual evidence for the roles and effectiveness of our nonflammable organic liquid electrolyte in stabilizing both surface and bulk structures, in promoting the formation of a stable surface protective film at the NCM811 cathode and reducing crack formation, metal-dissolution, and structural degradation despite under 4.5 V high-voltage condition and thus resulting in the increased capacity up to 230 mA h g–1 at 0.2 C and unprecedented cycling performance of the NCM811 cathode under high-voltage in not only Li∥NCM811 half-cell for lithium metal batteries but also graphite∥NCM811 full-cell with vinylene carbonate additive for LIBs. The data give an insight into the design principle of nonflammable and high energy-density lithium rechargeable batteries employing a nonflammable electrolyte and stable cathode–electrolyte interface.