Nickel-zinc batteries are promising due to their high output voltage, high theoretical specific energy, high safety, and low cost. However, rechargeable alkaline nickel-zinc batteries face significant challenges associated with the cathodic side reaction of oxygen evolution, which results in low energy efficiency and poor stability.
Now, a research team from the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences has proposed to construct an air-breathing cathode using side oxygen evolution reaction (OER) in nickel-zinc batteries by coupling electrocatalysts for oxygen reduction reactions (ORR) in the cathode.
Such a novel battery, Ni-Zn batteries with air-breathing cathodes (Ni-ZnAB), designed in a pouch-type cell with a lean electrolyte, exhibited an ultralong lifespan and ultrahigh energy efficiency, significantly superior to Ni-Zn battery and Zn-air battery (ZAB).
The inevitable OER in the charging process of Ni-Zn reduces energy efficiency and Coulombic efficiency, leading to poor energy storage and release capabilities. Though the OER in the cathode can be partially suppressed by controlling the charging voltage and using electrolyte additives, these strategies are unfortunately insufficient to completely solve the OER issue in the Ni-Zn system.
The new approach would enable the oxygen generated during charging via the OER to be utilized during discharge, similar to the air-breathing mechanism. In these Ni-ZnAB batteries, the OER in the cathode was no longer an undesirable side reaction during the charging process.
Moreover, the Coulombic efficiency loss from nickel hydroxide could be compensated by the ORR. The novel Ni-ZnAB batteries exhibited significantly improved cycling stability and energy efficiency when compared to conventional Ni-Zn batteries.
Due to the stabilizing effects on the electrolyte and electrode, the pouch-type Ni-ZnAB battery exhibited an excellent cycling performance of 100 hours with a capacity of 45 mAh. Also, it showed an average energy efficiency of 85.1%, indicating the potential of the Ni-ZnAB battery for practical applications.
To further improve the cycling stability, a mold-type Ni-ZnAB battery with a rich electrolyte was designed, which delivered an ultrahigh stability of 500 cycles with an energy efficiency higher than 80%, showing significant improvement compared to Ni-Zn.
“Our results highlight the importance of incorporating air-breathing cathode in Ni-Zn cells to improve their stability and energy efficiency and showcase the potential of Ni-ZnAB batteries as a valuable guide for designing highly stable Ni-Zn batteries,” said Prof. YANG Weishen, lead researcher.
Journal reference:
- Weili Xie, Kaiyue Zhu, Hanmiao Yang, Weikang Jiang, Weijian Li, Zhengsen Wang, Weishen Yang. Enhancing Energy Conversion Efficiency and Durability of Alkaline Nickel-Zinc Batteries with Air-Breathing Cathode. Angewandte Chemie International Edition, 2023; DOI: 10.1002/anie.202303517
