低温溶剂热法制备5V级性能优异的LiCr_(0.2)Ni_(0.4)Mn_(1.4)O_4正极材料(英文)

Superior Electrochemical Properties of 5 V LiCr_(0.2)Ni_(0.4)Mn_(1.4)O_4 Cathode Material Prepared by Low-Temperature Solvothermal Method

通过低温溶剂热的方法成功制备出了LiCr0.2Ni0.4Mn1.4O4尖晶石正极材料。通过此法,溶液的饱和蒸汽压急剧降低且在室温(25℃)下即可沸腾。所有的金属离子可在随后的热聚合过程中均匀分散且煅烧后所得材料无杂质相生成。采用了热重分析,X射线衍射,扫描电镜、循环伏安,交流阻抗等测试手段对材料进行了表征。结果表明:此法所得材料含有Mn3+,为Fd3m晶型,且其形貌规则、粒度分布均一。1C和10C下放电容量为140.5和121.0 mAh·g-1,10C下100次循环容量保持率高达96.9%。其优异的电化学性能可归因于均相的前驱体制备过程,高结晶度且无杂相生成,以及较高的锂离子扩散系数诸因素的共同作用。

The Cr-doped spinel LiCr0.2Ni0.4Mn1.4O4 cathode material has been synthesized by a low-temperature solvothermal method.Via this way,the saturated vapor pressure of the solution could be sharply reduced and the ebullition of whole solution can occur at room temperature （25 ℃）.All metal ions are able to be dispersed at a homogeneous state during the subsequent thermal polymerization process without formation of any impurity.Various measurements were used for investigating the morphology,structure,physical property and electrochemical performances,including thermal gravimetric analysis （TG）,X-ray diffraction （XRD）,scanning electron microscopy （SEM）,cyclic voltammetry （CV） and electrochemical impedance spectroscopy （EIS）,etc.The results reveal that the sample synthesized by low-temperature solvothermal method has a space group of Fd3m within a small amount of Mn3＋ and well-shaped morphology with uniform size distribution.Electrochemical test shows that the as-prepared sample exhibits an excellent discharge capacity of 140.5 and 121.0 mAh·g-1 at 1C and 10C,respectively.Moreover,a stable cyclic performance is demonstrated by desirable capacity retention of 96.9％ after 100 cycles at 10C.In summary,homogeneous state during precursor preparation,high crystallinity and structure stability with no impurities,and superior diffusion coefficient of Li＋ together make great contribution to the enhanced electrochemical performances of the as-synthesized sample.