Modification Of Polyaniline And Application In Lithium Batteries

Polyaniline with its good redox reversibility and environment-friendly features can be used as an cathode material in lithium battery, but the specific capacity of polyaniline is low. In this paper, the electrochemical performance of polyaniline is improved by complex modification and secondary doping modification.The PANi/CNTs composites in emeraldine base are prepared by in situ polymerization on the functionalized carbon nanotubes. When the mass ratio of CNTs and PANi is 1:10, the discharge capacities of the composites were the highest. The IR spectrum indicated the CNTs are functionalized with NH2 groups, RSO3 H groups and COOH groups on their surfaces. SEM and TEM indicate that the composites form the core-shell structure. The XRD shows that PANi/CNTs composites have higher crystallinity. The EIS shows the charge-transfer resistance of PANi/CNTs composites much lower than that of pure PANi and the charge-transfer resistance of the PANi/c-CNTs composites are the lowest. The initial discharge capacities of the PANi/c-CNTs composites are higher than other composites at 0.2 C rate, reaching 135.1 m Ah/g. The discharge capacity of composites with 95% coulombic efficiency can be retained at 111.8 m Ah/g after 100 th cycle, but initial capacity of the pure PANi only reaches 74.8 m Ah/g.The PANi/CNTs composites in leucoemeraldine base has been prepared with the optimized ratio. The absorption of C=N structure in leucoemeraldine base significantly decrease, indicating a good reduction. The PANi/CNTs composites in leucoemeraldine base have a better crystallinity, lower charge-transfer resistance and greater discharge capacity compared with the composites in emeraldine base. The initial discharge capacities of the PANi/c-CNTs composites in leucoemeraldine base reach 181.8 m Ah/g, higher than other composites at 0.2 C rate. The discharge capacity of composites with 95% coulombic efficiency can be retained at 13 9.4 m Ah/g after 100 th cycle. Besides, it also has the better rate performance than other composites. The CV tests indicate that the PANi/c-CNTs composites have the largest lithium-ion diffusion coefficient. The above description shows the reduction of the composites and Carboxylic acid functionalization have achieved the best results.The PANi/CNTs composites and pure PANi in emeraldine base have been further secondary doped and dedoped to obtain a modified materials. The modified composites in emeraldine base have a better crystallinity and lower charge-transfer resistance. The CV tests indicate that the modified composites have better redox reversibility compared with the unmodified composites in emeraldine base. The tafel tests show the modified composites have a higher exchange current density, which represents better electrode reaction reversibility. The UV-Vis spectra showed the conjugated structure of modified composite has been enhanced. The initial discharge capacities of the modified composites and pure PANi in emeraldine base with 97% coulombic efficiency reach 152.1 m Ah/g and 97 m Ah/g respectively, higher than other unmodified composites at 0.2 C rate. Finally, the market prospects and the economic cost of the material have been investigated. Compared with other cathode materials, polyaniline has low production cost and environmentally friendly advantages.