A cyano cobalt "electron transfer bridge" boosting the two-electron reaction of a MnO cathode with long lifespan in aqueous zinc batteries

• Published in: Energy & environmental science Vol. 17; no. 7; pp. 2521 - 2529
• Main Authors: Liu, Yaozhi, Lin, Lu, Zhang, Tengsheng, Xue, Zhiqing, Liu, Jie, Chao, Dongliang, Sun, Xiaoqi
• Format: Journal Article
• Published: 02.04.2024
• ISSN: 1754-5692; 1754-5706
• DOI: 10.1039/d3ee03711h

The dissolution/deposition reaction of MnO 2 cathode materials in aqueous zinc batteries provides two-electron transfers and delivers high theoretical capacity. However, this process usually requires an acidic environment and pre-added Mn 2+ salts in electrolytes. Herein, we present an "electron transfer bridge" at the cathode to enhance the two-electron transfer contribution in MnO 2 in conventional zinc cells. A composite material with MnO 2 and CoO x connected by Mn-N&z.tbd;C-Co interactions was synthesized. Mechanism studies demonstrate that the facile redox center of Co 3+ /Co 2+ receives/donates electrons during discharge/charge processes, and electrons effectively transport to the Mn centers thanks to the narrowed band gap and charge delocalization. The dolosse-like hollow morphology formed through the inside-out Ostwald ripening process during the discharge further provides abundant reaction sites. These factors largely activate the dissolution/deposition process of MnO 2 material. In aqueous zinc cells with the conventional ZnSO 4 electrolyte, the composite cathode achieves a high capacity of 425 mA h g −1 at 0.1 A g −1 , and an ultra-long life of over 25 000 cycles is realized at 2 A g −1 . This work presents an effective strategy to promote the high-capacity reaction path of MnO 2 in zinc batteries. An electron transfer bridge based on Mn-N&z.tbd;C-Co interactions is applied for a MnO 2 cathode to boost its reversible two-electron reaction in conventional zinc cells.