• Miao Shui

      Articles written in Bulletin of Materials Science

    • GITT studies on oxide cathode LiNi1/3Co1/3Mn1/3O2 synthesized by citric acid assisted high-energy ball milling

      Weidong Zheng Miao Shui Jie Shu Shan Gao Dan Xu Liangliang Chen Lin Feng Yuanlong Ren

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      Layered LiNi1/3Co1/3Mn1/3O2 was synthesized by a citric acid assisted solid-state method. The structure and electrochemical properties of the LiNi1/3Co1/3Mn1/3O2 materials were investigated. XRD analysis indicated the as-synthesized LiNi1/3Co1/3Mn1/3O2 was with the layered 𝛼-NaFeO2 structure. The discharge capacity was about 154 m.Ahg-1 at 0.1 °C rate in the range of 2.0–4.5 V. The kinetics of the LiNi1/3Co1/3Mn1/3O2 materials was investigated by the galvanostatic intermittent titration technique (GITT) method. The lithium ion diffusion coefficient of the LiNi1/3Co1/3Mn1/3O2 was determined in the range of 10-8−10-9 cm2.s-1 as a function of voltage of 3.7−4.5 V.

    • Distribution of relaxation times investigation of Co$^{3+}$ doping lithium-rich cathode material Li[Li$_{0.2}$Ni$_{0.1}$Mn$_{0.5}$Co$_{0.2}$]O$_2$


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      The element Co$^{3+}$ was introduced into lithium-rich material 0.5Li$_2$MnO$_3$ $\cdot$ 0.5LiNi$_{0.5}$Mn$_{0.5}$O$_2$ by apolyacrylamide-assisted sol–gel method to form Li[Li$_{0.2}$Ni$_{0.1}$Mn$_{0.5}$Co$_{0.2}$]O$_2$ and better electro-chemical performances were observed. Electrochemical impedance spectroscopy spectra were measured on 11 specific open circuit voltage levels on the initial charge profile. Then they were converted to the distribution of relaxation times (DRTs) $g(\tau)$ by self-consistent Tikhonov regularization method. The obtained DRTs offered a higher resolution in the frequency domain and providedthe number and the physical origins of loss processes clearly. Through the analysis of DRTs, the rapid augmentation of resistance to electronic conduction and charge transfer within the voltage range 4.46–4.7 V where the removal of Li$_2$O from Li$_2$MnO$_3$ component took place was the most remarkable phenomenon and the Co$^{3+}$ doping greatly reduced the resistanceto electronic conduction Re. This gave us more evidence about the complicated ‘structurally integrated’ composite character of the material.

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