Self‐Assembled Layer of Organic Phosphonic Acid Enables Highly Stable MnO2 Cathode for Aqueous Znic Batteries
Xilin Xiao, Lei Zhang, Wenli Xin, Min Yang, Yaheng Geng, Mengfan Niu, Hui Zhang, Zhiqiang Zhu
Abstract
Abstract Manganese dioxide (MnO 2 ) is an attractive cathode material for aqueous zinc batteries (AZBs) owing to its environmental benignity, low cost, high operating voltage, and high theoretical capacity. However, the severe dissolution of Mn 2+ leads to rapid capacity decay. Herein, a self‐assembled layer of amino‐propyl phosphonic acid (AEPA) on the MnO 2 surface, which significantly improves its cycle performance is successfully modified. Specifically, AEPA can be firmly attached to MnO 2 through a strong chemical bond, forming a hydrophobic, and uniform organic coating layer with a few nanometers thickness. This coating layer can significantly inhibit the dissolution of Mn 2+ by avoiding the direct contact between the electrolyte and cathode, thus enhancing the structural integrity and redox reversibility of MnO 2 . As a result, the MnO 2 @AEPA cathode achieves a high reversible capacity of 223 mAh g −1 at 0.5 A g −1 and a high capacity retention of 97% after 1700 cycles at 1 A g −1 . This work provides new insights in developing stable Mn‐based cathodes for aqueous batteries.