水介质中Na_(0.44)MnO_2/C复合电极的制备与性能研究

Study on preparation and performance of Na_(0.44)MnO_2/C composites in aqueous medium

高温固相法合成Na_(0.44)MnO_2,分别与纳米粒状乙炔黑(cb)和中孔管状线性碳纳米管(CNT)进行非原位复合,探讨了导电剂种类、分散方式和加入量对Na_(0.44)MnO_2/C复合电极在含锌、锰离子中性水溶液中电化学性能的影响。结果表明,Na_(0.44)MnO_2与碳纳米管复合宜采用液相搅拌方式,而乙炔黑与Na_(0.44)MnO_2复合则更适宜采用机械混合方式。与Na_(0.44)MnO_2/cb复合电极相比,Na_(0.44)MnO_2/CNT复合电极具有更优的动力学特征,突出表现为大电流充放性能明显改善,且低电流密度下易获得高的起始放电比容量,且随循环次数的增加,可较快地增至稳定(~300 mAh/g,100 mA/g);添加量增大,电极性能得以进一步改善,但容量并未成比例地提高。

Na0.44MnO2 was synthesized by a high-temperature solid state method.And then Na0.44MnO2 was complexed in situ with nano granular acetylene black(cb)and mesoporous tubular linear carbon nanotubes(CNT),respectively.The influences of conductivity types,dispersion method,and addition amount on the electrochemical performance of Na0.44MnO2/C composites in the neutral aqueous solutions containing Zn2+and Mn2+ions were investigated.The results show that it is suitable for Na0.44MnO2 to be complexed with CNTs by liquid mixing,while it is better for Na0.44MnO2 to be complexed with cb by mechanical mixing.Compared with Na0.44MnO2/cb composites,the more favorable kinetic characteristics of Na0.44MnO2/CNT composites are exhibited.The outstanding performance for the high current rate capability is obviously improved.Thus,the Na0.44MnO2/CNT composite shows a higher initial discharge specific capacity at a low current rate,and then maintained steady at 300 mAh/g relatively quickly with the increase of cycling number.The performance of the composites can be improved further,but the capacity is not enhanced proportionally.