Abstract
For the use of the zinc anode in secondary batteries, it is necessary to solve the “shape change” deterioration issue in that zinc species agglomerate in the center of the electrode to fade the available capacity. The local chemical compositions of the zinc electrodes during “shape change” were precisely analyzed using the synchrotron X-ray diffraction mapping analysis of practical zinc-nickel cells in a non-destructive manner. The in situ Zn/ZnO mapping shows that metallic Zn deposition chiefly occurs in the periphery of ZnO while ZnO are left in the center of electrode like a hill on charging. On discharging, the ZnO hill grows to the perpendicular direction on the electrode while metallic zinc is oxidized and dissolved. These findings allow us to propose a mechanism for the shape change; thus dissolved zincate species are decomposed on the ZnO hill during discharging to be accumulated in the center of the electrode. It is suggested that suppressing zincate dissolution and non-uniform zinc deposition slow the growth rate of the ZnO hill to enhance the cyclability of zinc-based secondary batteries.
Highlights
Akiyoshi Nakata,1,a Hajime Arai,[1] Haruno Murayama,[1] Katsutoshi Fukuda,[1] Tomokazu Yamane,[1] Toshiro Hirai,[1] Yoshiharu Uchimoto,[2] Jun-ichi Yamaki,[1] and Zempachi Ogumi1 1Office of Society-Academia Collaboration for Innovation, Kyoto University, Gokasho, Uji 611-0011, Japan 2Graduate School of Human and Environmental Studies, Kyoto University, Yoshida-nihonmatsu-cho, Sakyo-ku, Kyoto 606-8501, Japan (Received 31 October 2017; accepted 15 December 2017; published online 11 January 2018). Secondary batteries such as lithium ion batteries are widely used for mobile device such as cellular phones, personal computers, and electric vehicles (EVs)
To enlarge their operating time and enhance their usability, batteries with further high energy density are required and those using metals as the negative electrodes are generally promising with their high specific capacity and strong reducing power.[1,2]
Their insufficient cycle life due the deterioration modes such as zinc dendrite formation, densification, and shape change has limited the widespread use of the zinc-based secondary batteries.[4,7]
Summary
Secondary batteries such as lithium ion batteries are widely used for mobile device such as cellular phones, personal computers, and electric vehicles (EVs). For analyzing zinc electrodes in alkaline electrolytes, it is important to observe the shape change behavior without disassembling the cells to avoid metallic zinc oxidation during the analysis.
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