Ultra‐Soluble 1‐Azaphenothiazine Additive Stabilizes High‐Voltage LiCoO₂ for 500 Wh Kg−1 Lithium Metal Pouch Cells

Abstract High‐voltage LiCoO 2 is a promising cathode candidate for achieving high‐energy lithium metal pouch cells. However, further application is still hindered by irreversible structural degradation and severe interfacial side reactions that accelerate capacity decay. Herein, 1‐Azaphenothiazine (1‐APT) is incorporated as a cathode slurry additive (1 g mL −1 in N‐methyl‐2‐pyrrolidone) to promote the optimization of the LiCoO 2 interface during the electrode coating process. The ultra‐soluble 1‐APT promotes the formation of inorganic‐rich components within the cathode‐electrolyte interphase (CEI), mitigates the reaction of Co 4+ with the electrolyte, and enhances the interfacial stability of LiCoO 2 , thereby enabling 4.7 V LiCoO 2 with an initial capacity of 229.8 mAh g −1 and 73.2% capacity retention after 200 cycles. More importantly, Li||LiCoO 2 ‐1‐APT pouch cells exhibit remarkable electrochemical performance, achieving specific energies of 515.7 , 497.4 , and 484.9 Wh kg −1 at discharge rates of 0.5C, 1C, and 2C, respectively. Notably, the 5 Ah pouch cell exhibited the capability to maintain an energy density of 411.4 Wh kg −1 after 100 cycles at 0.5C. This work presents a practical and effective strategy for optimizing cathode interfaces, thereby enabling the stabilization of high‐voltage cathodes.