多孔五氧化二铌球的合成及其电化学性能研究

Research on the Synthesis and Electrochemical Properties of Porous Nb_2O_5 Spheres

以表面活性剂CTAB为模板,通过水热法及煅烧过程合成了多孔Nb_2O_5微球。对所得产品的表征和电化学性能测试结果表明:合成了正交结构的Nb_2O_5球,且其单分散性能较好,直径为900 nm左右,球上分布有很多孔径为2~70 nm的小孔,形成了独特的多孔结构,该结构增加了材料的比表面积,其比表面积为340 m^2/g。独特的多孔结构和较大的比表面积使得其作为锂离子电池负极材料时表现出优异的电化学性能:首次容量较高,多孔Nb_2O_5球的首次充放电容量分别为297.8和395.9 m A·h·g^(-1);循环性能稳定,在电流密度为20 m A/g下充放电时,第3次循环后的库伦效率几乎达到100%;倍率性能优异,在50,100 m A/g电流密度下,经过20次循环后的容量分别为139.6,117.1 m A·h·g^(-1),容量保持率都为90%以上。

Porous Nb2O5spheres are to be synthesized in a calcination and hydro-thermal process,with its template the surfactant cetyltrimethyl-ammonium chloride(CTAB).Testing results of the characterization and electrochemical properties of the finished products show that a successful synthesis of orthorhombic Nb2O5spheres can be obtained with a better dispersion performance.About900nm in diameter,the spheres are distributed with many porous of2~70nm in aperture,and its unique porous structure helps to increase the specific surface area(as large as340m2/g).As an anode material for lithium-ion batteries,the unique porous structure and relatively large specific surface area contribute to its excellent electrochemical properties:with an initial charge of297.8and a discharge capacity of395.9mA·h·g-1,respectively;stable in its cycling performance,with its coulombic efficiency as high as100%at the current density of20mA/g after the3rd cycle;excellent in its magnification performance,with a capacity of139.6mA·h·g-1at50mA/g,and117.1mA·h·g-1at100mA/g.Meanwhile,the capacity retention at the current density of50and100mA/g reaches as high as over90%after the20th cycle.These results indicate that porous Nb2O5spheres show a high reversible charge/discharge capacity,stable cycling performance and high rate capability.