Pumping Electrons from Oxygen-Bridged Cobalt for Low-Charging-Voltage Zn-Air Batteries
Yuchao Wang, Q. X. Li, Meng Wang, Houzheng Ou, Danni Deng, Huanran Zheng, Yu Bai, Lirong Zheng, Zhiyan Chen, Weijie Li, Guozhao Fang, Yongpeng Lei
Abstract
Reducing the charging voltage is a prerequisite for improving the chargeability and energy efficiency of Zn-air batteries (ZABs). Herein, Fe 3+ pumps electrons from oxygen-bridged cobalt (Fe–O–Co) and induces the accelerated charging kinetics. For the liquid ZABs, a charging voltage of around 1.94 V at 10 mA cm –2 was displayed, which slightly increased 2% after continuous cycles for 180 h. A steady charging voltage of around 1.87 V at 10 mA cm –2 was also exhibited for quasi-solid-state ZABs. Control experiments and characterization show that the interactions between the O 2– and Fe 3+ sites are relatively weaker than those between the O 2– and Co 3+ sites. Compared with Mn 3+, Zn 2+, and Cu 2+, Fe 3+ effectively pumps electrons from Co sites to generate the active species for the oxygen evolution reaction. Thus, the deprotonation behavior and *OH conversion were improved. This work demonstrates the oxygen electron bridge modulated electron transfer between dual metal sites, contributing to the improvement of low-charging-voltage ZABs.