3V锂离子电池用层状α-Na_(0.67)MnO_(2.26)的电化学性能

Electrochemical performance of layered α-Na_(0.67)MnO_(2.26) as cathode material of 3 V lithium ion batteries

以Mn(CH3COO)2·4H2O和Na2CO3为原料,通过sol-gel技术合成前驱体,在600℃焙烧前驱体得到一种新的无水层状α-Na0.67MnO2.26材料。用等离子体光谱、X射线衍射仪、扫描电镜、恒流充放电和循环伏安(CV)等对产物的结构、组成、形貌及电化学性能进行研究。结果表明:得到的样品为稳定的六方层状P2结构,且颗粒细小;该样品在充放电电流密度为25mA/g和电压为2.0～4.3V时,首次充电比容量为188mA·h/g,第2次放电比容量为176mA·h/g,充放电库仑效率高达94%;在电压为2.0～4.3V,电流密度为25,50,125和250mA/g充放电条件下,其第2次放电比容量分别为176,168,139和110mA·h/g,40次循环后,其放电比容量分别为150,142,121和105mA·h/g,显示材料有较好的循环稳定性和大电流充放电性能。

The new layered sodium manganese oxides α-Na0.67MnO2.26 was synthesized at 600℃ by the method of solid-state reaction combined with sol-gel process, and using both Mn（CH3COO）2·4H2O and Na2CO3 as the start material. The structure, composition, appearance and electrochemical performances of the product were characterized by Inductively coupled plasma （ICP）, X-ray diffraction （XRD）, scanning electron microscope （SEM）, the constant current charge/discharge and cyclic voltammogram. The results indicate that α-Na0.67MnO2.26 has hexagonal layered P2 structure with small particle size. The first specific charge capacity of the material is 188mA.h/g and the second specific discharge capacity of the material is 176 mA.h/g, and the coulomb efficiency in the first charge-discharge process reaches 94%. Besides, it was found that the sample has the better cycle stability and rapid charge-discharge performance. In the potential window 2.0-4.3V, the second specific discharge capacities of 176, 168, 139 and 110 mA.h/g are obtained at the rate of 25, 50, 125 and 250 mA/g, respectively. After 40 cycles, attractive specific capacities of 150, 142, 121 and 105mA.h/g are obtained, respectively.