Advanced Rechargeable Zinc-Air Batteries with Precious Metal Free Catalysts

Abstract

Rechargeable zinc-air batteries (ZABs) could be promising energy storage devices with high energy and power density, enabling safe and cost-effective operation. ZABs have higher practical specific energy compared to traditional aqueous and lithium-ion batteries [1]. The schematic of rechargeable of ZAB is shown in Figure 1a. The main challenge of the electrically rechargeable ZABs in alkaline electrolytes is the limitation during recharging [2, 3]. The performance of ZAB largely depends on oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Figure 1a shows that the cell rechargeability is realized by the OER and design of the Zn electrode. Hence, advances of the air electrode enabled by bifunctional catalysts as well as the development of the Zn electrode are important.In this presentation, we will discuss rechargeable ZAB with novel NiCo and NiFe catalysts, as well as an advanced Zn electrode that is created with a hybrid method using electrodeposition and powder coating. These catalysts were pre-scanned by using rotating disk electrode (RDE) in the alkaline solution, as shown in Figure 1b. NiCo and NiFe exhibited high catalytic activity towards OER but not towards ORR. These catalysts were applied and tested in the in-house designed ZAB cell. The Zn electrode was made by coating the Zn power on the CuZn mesh that was prepared by electrodeposition. The ZAB in a two-electrode configuration exhibited a discharge cell voltage of ~0.8 V at 20 mA/cm2 (3 hours cycle time), as shown in Figure 1c. To determine which electrode is limiting the efficiency, an additional Zn reference electrode was introduced into the cell to setup a four-electrode configuration. The additional reference is inserted into the cathode compartment enable measurement of the overpotential in solution and for the oxygen electrode. Test results, for different types of catalyst and Zn electrodes will be shown and discussed.