AZ61 and AZ61-La Alloys as Anodes for Mg-Air Battery
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JMEPEG https://doi.org/10.1007/s11665-019-03985-5
AZ61 and AZ61-La Alloys as Anodes for Mg-Air Battery Yiping Wu, Zhifeng Wang, Yu Liu, Guofeng Li, Shaohui Xie, Hui Yu, and Hanqing Xiong (Submitted June 14, 2018; in revised form February 27, 2019) AZ61 and AZ61-0.5La (wt.%) alloys are prepared by the conventional casting method and then, AZ61 and AZ61-0.5La alloy sheets are obtained with multi-pass hot rolling. Microstructures and electrochemical properties of four alloys are investigated, and discharge properties are tested by an assembled Mg-air battery using alloy anode sheets with a dimension of 70 3 100 3 2.5 mm. Results show that Al11La3 phases are formed in as-cast AZ61-0.5La alloy and promote the grain refinement and the formation of uniform microstructure in as-rolled AZ61-0.5La alloy. As-rolled AZ61-0.5La alloy exhibits a weak self-corrosion tendency but a strong discharge activity. After discharge test for 5 h, the Mg-air battery based on the asrolled AZ61-0.5La sheet can provide the maximum power output of 1.625 W, and as-rolled AZ61-0.5La anode can supply the maximum energy density of 1417 mWhg21. In addition, the relationship between microstructures and discharge properties is sufficiently described and discussed in this paper. Keywords
air battery, discharge property, hot rolling, magnesium alloy, microstructure
1. Introduction In recent decades, magnesium–air (Mg-air) battery has attracted increasing attention as promising electrochemical energy storages and conversion devices because Mg alloys possess high theoretical energy density (6.8 kWh kg1), high specific capacity density (2.2 Ah kg1) and low cost (Ref 1). Mg-air battery is composed of air cathode, electrolyte and Mg (or Mg alloys) anode. It also exhibits higher theoretical voltage (3.1 V) comparing with Zn-air (1.65 V) battery and Al-air (2.71 V) battery (Ref 2). Nevertheless, Mg-air battery is now still not as popular as the two metal–air batteries mentioned above. Two factors impede the use of Mg-air battery, low coulombic efficiency and irreversible polarization (Ref 3). The negative difference effect means of both cathode current and anode current are increased with the increase in applied potential, which accelerates the hydrogen evolution and decreases the coulombic efficiency of Mg anodes. The severe self-corrosion of Mg anode is owing to its high activity and impurities (such as Fe) (Ref 4). During the discharge process of Mg anodes, discharge products adhered to their surface, such as Mg(OH)2, decreases the reaction surface area leading to the irreversible polarization (Ref 5). For reducing the self-discharge rate and improving the electrochemical performance of Mg anodes, one effective method is to add other elements, such as Al, Zn, Mn and RE. Yiping Wu, Yu Liu, Guofeng Li, and Shaohui Xie, Department of Mechanical and Electronic Engineering, Changsha University, Changsha 410083, China; Zhifeng Wang and Hui Yu, School of Materials Science and Engineering, Hebei University of Technology, Tianjin 300130, China; and Hanqing Xiong, De
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