Study Of Carbon Nanotubes As Negative Electrode For High Performance Lithium-ion Capacitors

Multi-walled carbon nanotubes have a unique one-dimensional tubular structure and excellent electrical conductivity,which can effectively improve electrochemical performance when used as an electrode material.Multi-walled carbon nanotubes have been synthesized by floating reactant method in a vertical tubular reactor.Pre-lithiated multi-walled carbon nanotube anode was prepared by doping stabilized lithium metal Powder(SLMP)into carbon nanotubes and internal short circuit approach.The structure of multi-walled carbon nanotubes and electrodes were investigated by scanning electron microscopy(SEM)and transmission electron microscopy(TEM).The electrochemical performance of LICs with different MWCNTs content was investigated through galvanostatic charge/discharge and electrochemical impedance.The main research results are as follows.1.Pre-lithiated multi-walled carbon nanotube anode was prepared by internal short approach(IS)for 5min,30 min and 60 min.Lithium ion capacitors(LICs)were assembled using pre-lithiated multi-walled carbon nanotubes as anode and activated carbon(AC)as cathode.The electrochemical tests indicated that pre-lithiation of multi-walled carbon nanotubes greatly improve the charge-discharge performance of LIC.The energy density reached about 4 times over conventional electric double-layer capacitors(EDLCs)at the current density of 100 mA/g.The LICs achived a specific capacitance of 57F/g at the current density of 100 mA/g with 60 min pre-lithiatiation process.The maximum energy density and power density reached 90Wh/kg and 4130 W/kg respectively in the current range of 100mA/g~3200 mA/g.The capacity still remained more than 85% after 1000 cycles.The LIC showed excellent supercapacitor performance.2.An internal short approach process was developed to achieve the pre-lithiated multi-walled carbon nanotube MWCNTs/graphite composite anodes.Lithium-ion capacitors(LICs)were composed of a pre-lithiated multi-walled carbon nanotubes/graphite composite anode and an activated carbon(AC)cathode.The electrochemical performance of LICs with different MWCNTs content was investigated through galvanostatic charge/discharge and electrochemical impedance.The results show that the charge–discharge performance of LICs was greatly improved with the addition of MWCNTs in anodes.LIC25(25 wt% MWCNTs)was found to achieve the optimal electrochemical performance.The LIC25 hold a specific capacitance of 58.2 F/g at the current density of 100 mA/g.The maximum energy density and power density were up to 96 Wh/kg and 10.1 kW/kg,respectively,in the current range of 100~8000 m A/g.The continuous galvanostatic charge–discharge cycling tests revealed that the LIC25 maintained excellent capacity retention of 86% after 3000 cycles.3.Pre-lithiated carbon nanotube anode was prepared by doping stabilized lithium metal Powder(SLMP)into carbon nanotubes.Lithium ion capacitors(LICs)were assembled using pre-lithiated carbon nanotubes anode and activated carbon(AC)cathode.The electrochemical tests indicated that pre-lithiated carbon nanotubes anode lithium-ion capacitor exhibited a specific capacitance of 65.7F/g at the current density of 100 mA/g compared with a specific capacitance of 9.6F/g of conventional electric double-layer capacitors(EDLC).The capacity is roughly 7 times increase than EDLC.The specific energy and specific power reached 50.4Wh/kg and 8.5 Kw/kg respectively at the current density of 200mA/g.