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.

The structural relaxation analysis has been carried out on Li_xNi_0.8Co_0.1Mn_0.1O₂ (NCM-811) and Li_xNi_0.55Co_0.20Mn_0.25O₂ (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.