Ma Wenjiao, Li Jinye, Wang Huijian, Lei Chengjun, Liang Xiao
State Key Laboratory of Chem/Bio-Sensing and Chemometrics, Joint International Research Laboratory of Energy Electrochemistry, College of Chemistry and Chemical Engineering, Hunan University, Changsha, 410082, China.
Angew Chem Int Ed Engl. 2024 Dec 20;63(52):e202410994. doi: 10.1002/anie.202410994. Epub 2024 Nov 7.
The multi-electron transfer I/IO redox couple is attractive for high energy aqueous batteries. Shifting from an acidic to an alkaline electrolyte significantly enhances the IO formation kinetics due to the spontaneous disproportionation reaction, while the alkaline environment also offers more favorable Zn anode compatibility. However, sluggish kinetics during the reduction of IO persists in both acidic and alkaline electrolytes, compromising the energy efficiency of this glorious redox couple. Here, we establish the fundamental redox mechanism of the I/IO couple in alkaline electrolytes for the first time and propose that Bi/BiO acts as a redox mediator (RM) to "catalyze" the reduction of IO . This mediation significantly reduces the voltage gap between charge/discharge from 1.6 V to 1 V with improved conversion efficiency and rate capability. By pairing the Zn anode and the Bi/BiO RM cathode, the full battery with I/IO redox mechanism achieves high areal capacity of 12 mAh cm and stable operation at 5 mAh cm for over 400 cycles.
多电子转移I/IO氧化还原对对于高能水系电池具有吸引力。由于自发歧化反应，从酸性电解质转变为碱性电解质会显著提高IO的形成动力学，同时碱性环境也提供了更有利的锌阳极兼容性。然而，在酸性和碱性电解质中，IO还原过程中的动力学都很缓慢，这损害了这种出色氧化还原对的能量效率。在此，我们首次确立了I/IO对在碱性电解质中的基本氧化还原机制，并提出Bi/BiO作为氧化还原介质（RM）来“催化”IO的还原。这种介导显著降低了充放电之间的电压差，从1.6 V降至1 V，同时提高了转换效率和倍率性能。通过将锌阳极与Bi/BiO RM阴极配对，具有I/IO氧化还原机制的全电池实现了12 mAh cm的高面积容量，并在5 mAh cm下稳定运行超过400个循环。
