High‐voltage LiCoO2 is an attractive cathode for ultra‐high energy lithium‐ion batteries in the 5G era. However, the practical application of LiCoO2 is largely hindered by the unstable structure under high voltage. Herein, dextran sulfate lithium (DSL) is used as a versatile binder to improve the cycling stability of LiCoO2 at 4.6 V. A coulombic efficiency of almost 100% and 93.4% capacity retention after 100 cycles has been achieved. The aqueous DSL binder can be evenly coated onto the surfaces of LiCoO2 particles to function as an artificial interface, significantly preventing the decomposition of electrolyte and the dissolution of Co ions. More importantly, the superior interaction between the sulfate acid groups of DSL chains and the LiCoO2 particles enhances the stability of CoO chemical bonds, further suppressing the detrimental phase transition from O3 to H1‐3 above 4.55 V. The stabilization of high‐voltage LiCoO2 through the binder is facile and enlightening to design high energy battery materials.