Electrochemistry
Online ISSN : 2186-2451
Print ISSN : 1344-3542
ISSN-L : 1344-3542
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The 69th special feature “Frontiers of Molten Salts and Ionic Liquids”
  • Qilin YUAN, Xin LU, Osamu TAKEDA, Hongmin ZHU
    2024 Volume 92 Issue 6 Pages 063001
    Published: June 11, 2024
    Released on J-STAGE: June 11, 2024
    Advance online publication: May 17, 2024
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    The influence of fluoride ions on electrochemical behavior of lanthanum and neodymium ions in molten LiCl at 1073 K was experimentally investigated. Cyclic voltammetry and square wave voltammetry were conducted using a molybdenum working electrode. Galvanostatic electrolysis using a molybdenum electrode as cathode in molten LiCl-5 mol%LaCl3, LiCl-5 mol%NdCl3, and LiCl-30 mol%LiF-5 mol%NdCl3 were conducted to investigate the influence of fluoride ions. The result indicates that the cathodic process for La3+ in molten LiCl is a one-step reaction, i.e., La3+ + 3e = La. The cathodic process of Nd3+ in molten LiCl is a two-step reaction, including Nd3+ + e = Nd2+ and Nd2+ + 2e = Nd. With the introduction of fluoride ions, however, the current of the first cathodic reaction decreases and when the molar ratio of F to Nd3+ reaches to 6, the cathodic process of Nd3+ turns to a one-step process: Nd3+ + 3e = Nd. The results indicate that the addition of fluoride ions makes Nd3+ stabler and thus inhibits the reaction to Nd2+ in molten chloride. The deposited neodymium metal was dispersed in the electrolyte in pure chloride melt due to the shuttle of disproportionation and proportionation reactions of neodymium ions. With the addition of enough LiF to melt, the deposited neodymium metal adhered on the cathode. The current efficiency of neodymium electrolysis was remarkably improved and reached the similar value as that for lanthanum electrolysis.

Regular Paper
  • Jian KANG, Takeshi YABUTSUKA, Takeshi YAO, Shigeomi TAKAI
    2024 Volume 92 Issue 6 Pages 067001
    Published: June 14, 2024
    Released on J-STAGE: June 14, 2024
    Advance online publication: May 25, 2024
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    The structural relaxation analysis has been carried out on LixNi0.8Co0.1Mn0.1O2 (NCM-811) and LixNi0.55Co0.20Mn0.25O2 (NCM-552025) after the lithium extraction at 0.1 C-rate to the high-voltage region (x ≤ 0.12). For NCM-811, the H3 phase appeared as the major phase with a small amount of the H2 phase after the lithium extraction. At the relaxation period, no significant phase change was observed and the structural variation including Li- and Ni-interlayer distances was small. On the other hand, NCM-552025 exhibited the single phase of the H2 even at deep lithium extraction up to x = 0.06. In the H2 phase, a slight increase in c-length was observed during the relaxation, which is the result of an increase in the Li-interlayer distance with a decrease in the Ni-interlayer. The relaxation behavior of interlayer distances can be explained by the localization of a small number of mobile lithium-ions.

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