介孔石墨烯/炭黑复合导电剂在锂离子电容器负极中的应用

Application of mesoporous graphene/carbon black composite conductive additive in lithium-ion capacitor anode

将介孔石墨烯与炭黑的复合导电剂(G/SC)应用于硬碳负极材料,并与炭黑(SC)、石墨烯纳米片/碳纳米管/炭黑的导电浆料(GNC/SC)、碳纳米管/炭黑的导电浆料(CNC)3种导电剂进行对比研究。采用扫描电镜和X射线衍射表征了G、SC、GNC、CNC导电剂和硬碳的形貌与结构。硬碳负极的电化学阻抗谱表明,G/SC导电剂可以降低电极电荷转移电阻和固态电解质界面电阻。相比于其它3种导电剂,添加G/SC的硬碳电极具有最高的比容量(155 mA·h/g)和最佳的倍率性能(在2 A/g时比容量为60 mA·h/g)。循环伏安曲线的分析表明,随着扫速的增大,锂离子在电极中的法拉第固相扩散转变为电极表面快速扩散,G/SC导电剂在硬碳负极中构筑了有效的"点-面"导电网络,促进了硬碳负极的电子转移和锂离子在电极表面的快速扩散。基于添加G/SC的硬碳负极和活性炭正极制备出锂离子电容器,能量密度为81.1 W·h/kg,功率密度可达22.3 kW/kg,在20 C倍率下循环2000周后,容量保持率为98.7%。

Mesoporous graphene/carbon black（G/SC） composite conductive additive has been applied for lithium ion capacitor anode.G/SC conductive additive has been comparatively studied with carbon black（SC）,graphene nanosheets/carbon nanotube/carbon black conductive slurry（GNC/SC）,and carbon nanotube/carbon black（CNC）.The morphologies and structures of G,SC,GNC,CNC and hard carbon have been characterized by scanning electron microscopy and X-ray diffraction,respectively.The electrochemical impedance spectra of hard carbon anode shows that the G/SC conductive additive can decrease the charge transfer resistance and the solid electrolyte interphase resistance.Compared with other conductive additives,the hard carbon anode with G/SC has the highest specific capacity（155 mA·h·g-1）,best rate capability（60 mA·h·g-1 at the current density of 2 A·g-1）.The cyclic voltammetry analysis indicates that the faradaic diffusion of lithium ion in the electrode bulk transforms into rapid diffusion on the anode surface as the scan rate increases,G/SC conductive additive and hard carbon have formed ＂point-to-plane＂ conducting network,which promotes the electron transfer in hard carbon anode and the lithium ion diffusion on anode surface..Lithium ion capacitors have been fabricated with hard carbon anode and activated carbon cathode,which shows excellent electrochemical performances.The energy density of lithium ion capacitor with G/SC is 81.1 W·h·kg-1,and the power density is 22.3 kW·kg-1,the capacity retention ratio is 98.7% after 2000 cycles at a C-rate of 20 C.