**2. Fabrication and characterization of MWCNTs**

MWCNTs were prepared by chemical vapor deposition (CVD), and benzene (Aladdin Co. Ltd., Shanghai) was used as carbon source, ferrocene (Aladdin Co. Ltd., Shanghai) as catalyst, and thiophene (Aladdin Co. Ltd., Shanghai) as accelerant. Ferrocene and thiophene were added into benzene and stirred uniformly; the flow rate was controlled by a micropump. Hydrogen and argon were used as carrier gas. The flow rate was controlled by a mass flow meter. The carbon source was fed into reactor with carrier gas. The MWCNTs were synthesized in a tube furnace with appropriate contents of ferrocene and thiophene and the ratio of benzene to

**Figure 1.** *(a) FESEM and (b) HRTEM images of MWCNTs.*

**75**

*Performance and Applications of Lithium Ion Capacitors*

hydrogen in a certain temperature gradient. The obtained MWCNTs were further graphitized under the condition of vacuum at 2800°C for 24 h with the heating rate of 10°C/min. Finally, the graphitized MWCNTs were milled in a planetary ball mill

**3. SLMP/MWCNTs composite anode for lithium-ion capacitors**

The activated carbon (AC) was dispersed by sonication in N-methyl-2 pyrrolidone (NMP) for 2 h. The surfactant of polyvinylpyrrolidone (PVP, YueMei chemical Co. Ltd., Guangzhou) was added to improve the dispersion performance. The polyvinylidene fluoride (PVDF) was used as binder. The super carbon black (SP) was added to improve the conductivity. The activated carbon slurry was completed after a high-speed (FA25) cutting under 10,000 r/min for 1 h, and the mass ratio of AC:SP:PVDF was 85:5:10. The prepared slurry was coated on Al foil and dried at 60°C under vacuum, and cut into a disc of 14 mm

The MWCNT powders were dispersed by sonication in N-methyl-2-pyrrolidone (NMP) for 2 h. The surfactant of polyvinylpyrrolidone was added to improve the dispersion performance. The polyvinylidene fluoride (PVDF) was used as binder. The slurry was completed after a high-speed (FA25) cutting under 10,000 r/min for 1 h. The mass ratio of MWCNTs:SP:PVDF was 8:1:1. The prepared slurry was coated on Cu foil and dried at 60°C under vacuum. A mixture of 0.5% polystyrene (PS) and 0.5% styrene butadiene rubber (SBR) was selected as a polymer binder, xylene as a solvent, and two groups were mixed to produce a binder solution. SLMP (FMC Corporation) was dispersed in the binder solution to obtain SLMP suspension with 0.5 wt%. Then the SLMP suspension was evenly coated on anode. After dried in vacuum, the SLMP coating is pressed between two glass plates for activating SLMP

The two-electrode CR-2025 button lithium-ion capacitors were assembled with activated carbon as cathode and SLMP/MWCNT composites as anode in an argonfilled dry glove box. The electrolyte was 1 mol/L LiPF6 in a mixed solvent system of EC/DMC (ethylene carbonate/diethyl carbonate) at a ratio of 1:1, and polypropyl-

**Figure 1(a)** showed FESEM image of MWCNTs. The MWCNTs presented linear and smooth structure. The diameters of the MWCNTs range from 100 to 120 nm with a large aspect ratio, and the MWCNTs have a small probability of bending around each other in space. Because of this particular microstructure makes the MWCNTs dispersed easily, simultaneously excellent conductivity and lithiumions adsorption capacity, and other characteristics. **Figure 1(b)** showed HRTEM image of graphitized MWCNTs; the MWCNTs exhibited one-dimensional hollow structure, smooth wall, low defects, thin wall thickness, and regular and orderly

*DOI: http://dx.doi.org/10.5772/intechopen.80353*

at 200 r/min for 3 h [33].

arrangement of carbon atoms

*3.1.1 Preparation of cathode electrode*

*3.1.2 Preparation of anode electrode*

and then cut into a disc of 14 mm diameter.

*3.1.3 Fabrication and characterization of lithium-ion capacitors*

ene microporous membrane was used as the separator.

**3.1 Experiment**

diameter.

*Performance and Applications of Lithium Ion Capacitors DOI: http://dx.doi.org/10.5772/intechopen.80353*

hydrogen in a certain temperature gradient. The obtained MWCNTs were further graphitized under the condition of vacuum at 2800°C for 24 h with the heating rate of 10°C/min. Finally, the graphitized MWCNTs were milled in a planetary ball mill at 200 r/min for 3 h [33].

**Figure 1(a)** showed FESEM image of MWCNTs. The MWCNTs presented linear and smooth structure. The diameters of the MWCNTs range from 100 to 120 nm with a large aspect ratio, and the MWCNTs have a small probability of bending around each other in space. Because of this particular microstructure makes the MWCNTs dispersed easily, simultaneously excellent conductivity and lithiumions adsorption capacity, and other characteristics. **Figure 1(b)** showed HRTEM image of graphitized MWCNTs; the MWCNTs exhibited one-dimensional hollow structure, smooth wall, low defects, thin wall thickness, and regular and orderly arrangement of carbon atoms
