X. Sun et al.
(a)
(b)
(c)
(d)
Fig. 3. SEM images of AMP (a), CMP (b), CMP after cycles (c), photograph of bending CMP (d).
than the AMP of 25.69 m 2 /g. Though the pores of the two samples presented a similar distribution, the average pore diameter of AMP is 23.36 nm, and 17.95 nm for CMP. The number of greater-sized pores on the surface was decreased after the car- bonization treatment, while the number of tiny- sized pore on the surface was increased according to the BET. The increasing tiny-sized pores might improve the capacity of battery with the CMP. The nonisothermal experiment was operated under air atmosphere. The temperature was set from ambient temperature to 1000 at a heating rate of 5 /min. The TGA curves of the AMP and CMP were shown in Fig. 5. CMP curve (b) indi- cated that the MWCNTs were oxidized from 630 . Before the oxidation temperature, the loss of the sample resulted from oxidation of amorphous car- bon which was deposited in carbonization process. TGA for AMP (curve a) exhibited four stages
during combustion process. Below 280 , 2.5%mass loss happened owing to the evaporation of water in the paper. The second stage (from 280 to 350 Þ presented the thermal degradation of paper ¯ber which resulted in the formation of solid char and the evaporation of organic materials. The third stage (350 – 470 Þ was attributed to the oxidation of the chars. The weight loss reached 51% in this stage at 470 . Thus, it can be calculated that the weight content of cellulose in the AMP is about 46.5%. The fourth stage presented the combustion of MWCNTs. The residue only holds a 3.4% after 1000 . The residue mainly contained metal- lic oxides. It can be concluded that AMP only contains 48.6% weight content of MWCNTs. The CMP shows higher thermal stability than AMP. After 5 cycles of discharging and charging, EIS was performed under a fully discharge state by ap- plying a sine wave of 5 mV amplitude over a
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