低共熔混合锂盐相图的绘制及应用

采用热分析法对不同组成的混合锂盐二元体系进行研究, 绘制了混合锂盐体系的步冷曲线和T-x相图, 结果表明体系均为具有最低共熔点的二元体系. LiOH-LiNO3、LiOH-LiCl、LiOH-Li2CO3及LiNO3-LiCl体系的最低共熔点分别为175.7、294.5、418.2及221.6 ℃. 利用低共熔混合物LiNO3-LiOH为锂盐与不同前驱体反应, 制备出了层状结构良好的锂离子电池正极材料LiNiO2、LiNi0.8Co0.2O2及LiNi1/3Co1/3Mn1/3O2. X射线衍射分析表明, 合成的材料具有规整的层状NaFeO2结构, 且XRD衍射峰强度之比I(003)/I(104)>2.0, 电性能测试表明, 在2.7-4.3 V(vs Li/Li+)的电压范围内进行0.1C倍率充放电, LiNiO2、LiNi0.8Co0.2O2、LiNi1/3Co1/3Mn1/3O2首次充电比容量分别达168.0、225.4、194.0 mAh·g-1, 放电比容量分别为138.4、165.8、157.7 mAh·g-1.

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

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.