混合导电剂影响的含碳Li4Ti5O12材料性能

Effect of conductive agents on the properties of carbon-containing Li4Ti5O12 materials

锂离子电容器作为一种新型储能元件,兼具锂离子电池与双电层电容器的优点。颗粒状的Li4Ti5O12(LTO)因其稳定的结构、良好的循环性能、较高的安全性能等优点,成为较理想的锂离子超级电容器(LIC)负极材料。但因其较差的导电性,使其在大电流充放电过程中容量衰减较快。为改善这一性能缺陷,在制备LTO过程中进行碳源掺入,导致制备的含碳颗粒状LTO具备优良的电子、离子电导率。为进一步改善LTO颗粒间的导电性,使用含SP/C、SP/G、SP/C/G的混合导电剂分别制成不同极片(记为LTO-C、LTO-G和LTO-GC)。在充放电过程中(电流密度为2~20 C),3种半电池LTO-G、LTO-C和LTO-GC的比容量分别是162 mAh/g^102 mAh/g、165 mAh/g^110 mAh/g和179 mAh/g^121 mAh/g。在大电流密度下LTO-GC较高的容量保持率说明GC改良的LTO颗粒立体导电网络对其倍率性能及电化学可逆性能的提高至关重要。

As a new type of energy storage elements,lithium-ion capacitors have their advantages of lithium-ion batteries and double-layer capacitors.Li4Ti5O12(LTO)particles are ideal materials for lithium ion supercapacitors because of their stable structures,good cycling performance and high safety.However,their poor conductivity leads to capacity decay in the process of high current charging and discharging.Different carbon sources can be added into the LTO materials in the preparation process to enhance their electronic and ionic conductivity.Liquid conductive agents containing carbon nanotubes,graphene and carbon nanotubes/graphene(1∶1)were used in the experiment(labeled as LTO-C,LTO-G and LTO-GC,respectively).The specific capacities of LTO-G,LTO-C and LTO-GC are 162 mAh/g to 102 mAh/g,165 mAh/g to 110 mAh/g and 179 mAh/g to 121 mAh/g,respectively.The performance analyses reveal that LTO-GC has a high capacity retention rate at high current density,which indicates that improved LTO three-dimensional conductive networks play an important role on improving its rate performance and electrochemical reversibility.