As a renewable and clean energy technology, flexible wearable rechargeable batteries have attracted widespread attention from the scientific and engineering circles. In particular, compared with other energy supply equipment (such as lithium batteries and other Zn-based batteries), flexible Zn-air batteries (ZAB) have unique advantages, a higher theoretical energy density (1086 Wh kg-1), and competition Cost, operational safety and environmental friendliness. Recently, the combination of a new solid electrolyte and a high-efficiency electrocatalyst can assemble ZAB with excellent low-temperature adaptability and electrochemical performance, thereby designing a low-temperature-resistant flexible ZAB for the next generation of flexible electronic products. However, in order to achieve future commercialization, it is necessary to solve the problems of the rechargeability and poor energy conversion efficiency of the flexible ZAB, which is mainly due to the slow reaction kinetics of oxygen in the air cathode. To overcome these obstacles, it is necessary to explore a high-performance electrocatalysis for oxygen reduction reaction (ORR) and oxygen release reaction (OER).

Recently, the research group of Professor Zilong Wang and Shaozao Tan of Jinan University and the research group of Professor Zonglong Zhu of City University of Hong Kong have collaborated to synthesize a NiCo2O4 nanocrystal-MXene hybrid with strong Ni/Co-F bonds. The prepared MXene-based composite material exhibits excellent ORR and OER electrocatalytic activity. This is the best performance reported for the MXene-based flexible air ZAB cathode, which can be compared with some precious metal catalysts. In addition, even after cutting and stitching, the flexible solid ZAB device can still be customized and has high performance.

The results were published in the internationally renowned academic journal ACS Applied Materials & Interfaces, with the title Strongly Coupled NiCo2O4 Nanocrystals-MXene Hybrid through in-situ Ni/Co-F Bonds for Efficient Wearable Zn-Air Batteries

Flow chart 1. Schematic diagram of the preparation of NiCo2O4 / MXene

Figure 1. Physical characterization of NiCo2O4 / MXene composite

Figure 2. Electrocatalytic performance of NiCo2O4 / MXene composite

Figure 3. The performance of NiCo2O4 / MXene composite in liquid ZAB

Figure 4. Schematic diagram and performance of flexible ZAB

In this paper, the NiCo2O4/MXene dual-function electrocatalyst was prepared on a few-layer MXene frame by in-situ anchoring. NiCo2O4 nanocrystals can be grown via Ni/Co-F bonds, which serve as electrocatalytic sites for ORR and OER. It is proved by NEXAFS that the Ni/Co-F bond brings the synergistic effect of electron cloud migration. Due to the synergistic effect, the electrocatalyst exhibits enhanced hydrophilicity and excellent ORR/OER bifunctional activity, which is similar to noble metal-based catalysts. The charging liquid ZAB based on NiCo2O4/MXene positive electrode exhibits a PPD with a peak power density of 277 mWcm-2 and a long-term durability of more than 1000 charge-discharge cycles, which is the best performance of MXene-based liquid ZAB that has been reported. Wearable ZAB using NiCo2O4/MXene air cathode provides high open circuit voltage Voc (1.4 V), ultra-high peak power density PPD (55.1mW cm-2) and excellent stability of 100 cycles. In addition, after our wearable ZAB is cut and sewn with carbon fiber, it can maintain similar performance to the original. When two devices are connected in series, 48 red LED indicators can be easily lit under various operating conditions. Our current work not only shows that the dual-function ORR/OER catalyst based on MXene is effective and successful in the practical application of wearable ZABs, but also opens up a new way for MXene-based materials to be used in other energy storage devices.

Literature link:

DOI: 10.1021/acsami.0c11185

Information source: MXene Frontier

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