Non-flammable LiNi0.8Co0.1Mn0.1O2 cathode via functional binder; stabilizing high-voltage interface and performance for safer and high-energy lithium rechargeable batteries

Abstract Demands of increased energy density and high-safety of lithium-ion and lithium metal batteries are growing for advanced electronics, electric vehicles and energy storage systems. Nickel-rich layered oxides such as LiNi0.8Co0.1Mn0.1O2 (NCM811) are appealing as promising high-capacity cathode materials. Their reversible capacity increases further by charging to higher voltages than conventional 4.2 V, which is however difficult to make because of unstable cathode-electrolyte interface and structural degradation. Herein, we report the combination of NCM811 cathode active material with non-aqueous functional polyimide binder to imparts enhanced thermal stability and highly stable interface originating from in situ building-up of surface protective polyimide layer at cathode through monodentate metal-carboxylate chemical bonds during slurry preparation, which permits to charge to 4.4 V despite in commercial electrolyte without any additive. This unique active material-binder combination not only suppresses metal-dissolution and cathode degradation and produces increased reversible capacity higher than 200 mAh g−1 but also provides unprecedented non-flammable characteristics contrary to the case of conventional binder, enabling a stable operation of higher energy and safer batteries.