Acta Phys. -Chim. Sin. ›› 2007, Vol. 23 ›› Issue (08): 1265-1268.doi: 10.3866/PKU.WHXB20070824

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Drawing and Application of Phase Diagram Related to Eutectic Mixed Lithium Salts

TANG Hong-Wei; ZHU Zhi-Hong; CHANG Zhao-Rong; CHEN Zhong-Jun   

  1. College of Chemistry and Environmental Science, Henan Normal University, Xinxiang 453007, Henan Province, P. R. China; College of Chemical Engineering and Environment, Beijing Institute of Technology, Beijing 100080, P. R. China
  • Received:2007-01-30 Revised:2007-04-02 Published:2007-08-03
  • Contact: CHANG Zhao-Rong

Abstract: Eutectic mixed lithium salts were studied with thermal analysis method. The cooling curves and T-x phase diagrams of lithium salts were plotted in this article. The result showed that these binary systems were simple eutectic systems and had the lowest melt points. The lowest melt points of the eutectic mixed LiOH-LiNO3, LiOH-LiCl, LiOH-Li2CO3, and LiNO3-LiCl were 175.7, 294.5, 418.2, and 221.6 ℃, respectively. Eutectic mixture of LiNO3-LiOH was used as lithium salt with different precursors to prepare cathode materials LiNiO2, LiNi0.8Co0.2O2, and LiNi1/3Co1/3Mn1/3O2 for lithium ion battery. XRD results showed that the prepared cathode materials possessed an ordered NaFeO2 layer structure. The intensity ratios of XRD lines I(003)/I(104) of the prepared cathode materials were all greater than 2.0, which means the samples had a better-developed layer structure. Electrochemical property tests testified that for charge-discharge current density of 0.1C and voltage of 2.7-4.3 V(vs Li/Li+), the initial charge specific capacities of prepared LiNiO2, LiNi0.8Co0.2O2, and LiNi1/3Co1/3Mn1/3O2 were 168.0, 225.4, and 194.0 mAh·g-1, and the discharge specific capacities were 138.4, 165.8, and 157.7 mAh·g-1, respectively. Therefore it was a novel and efficient approach that eutectic mixed salts were used to prepare the cathode materials for lithiumion battery.

Key words: Cooling curve, Phase diagram, Eutectic mixed salt, Lithiumion battery