In‐Situ CEI Layer Fabricated by Multifunctional Carboxylate Additive Enabling the Reversible Jahn–Teller Distortion in Manganese Oxides

Abstract Manganese oxides, known for their high theoretical capacity and operating voltage, have garnered significant attention in aqueous zinc‐ion batteries. However, irreversible phase transitions and manganese dissolution in Mn‐free electrolytes result in poor electrochemical performance. To solve those problems, an in‐situ cathode electrolyte interphase (CEI) layer formed by the adsorption of lactate ions (SC − ) on the cathode that allows Zn 2+ and H + de‐intercalation while preventing Mn 2+ from entering the electrolyte during charging is proposed. The inhibited Mn 2+ is reversibly oxidized under an external power source, making the Jahn–Teller distortion reversible. Additionally, SC − can stabilize pH and modulate solvation structure of the electrolyte, which can suppress the side reactions. Consequently, the Zn//manganese oxide batteries deliver a remarkable reversible capacity (294.9 mAh g −1 at 0.1 A g −1 ), outstanding rate capability (119.0 mAh g −1 at 2.0 A g −1 ), and robust cyclic stability (81.7% after 1000 cycles at 0.3 A g −1 ). More importantly, the carboxyl‐Zn 2+ interaction achieves uniform Zn deposition on the (002) plane, enabling high‐performance pouch cells. This study provides new insights into the CEI layers, which will promote the commercialization of Zn//manganese oxide batteries.