Preparation And Electrochemical Capacitive Properties Of Polyaniline Doped With Transition Metal Ions

Supercapacitors are new energy storage, combining the advantages of the high specific power of dielectric capacitors and the high specific energy of rechargeable batteries. Electrode materials are core and key to effecting on performaces of supercapacitor. Polyaniline (PANI) has been most actively investigated due to its unique doping/dedoping behavior, facile synthesis and good environmental stability.In this paper, PANI was synthesized by simple chemical oxidation polymerization. The capacitive behavior of PANI doped with transition metal salts was investigated. PANI doped with ZnCl2 was selected. Then, the capacitive behavior of PANI co-doped with Zn2+ and H+ was characterized, and the methods of doping were also studied. The process of the in-situ doping was confirmed. Then, the composite materials of PANI and actived carbon were prepared by in-situ polymerization. And the effect of the mass of actived carbon on the capacitive behavior of the composite materials was investigated. On the basis, the capacitive behavior of PANI co-doped with Zn2+ and H+/actived carbon was studied. The main research results and conclusions are as follows:(1) Polyaniline doped with ZnCl2(PZn) and polyanline doped with FeCl3 (PFe) were prepared using ZnCl2 and FeCl3 as doping transiton metal salt, respectively. PZn shows a specific capacitance of 340 F·g-1 at the current density of 0.1 A·g-1, which is much higher than that value exhibited by PFe (90 F·g-1). After 500 cycles, the specific capacitance of PZn remains 268 F·g-1. And the decrease in the specific capacitance of PZn is only 12.1%.(2) Polyaniline co-doped with Zn2+ and H+ was obtained using many doping methods. Compared with PANI doped with H+ (PH), Polyaniline co-doped with Zn2+ and H+ through in-situ doping (P1) shows a higher specific capacitance and better cycleablity. The specific capacitance of 369 F·g-1 was obtained at the current density of 0.1 A·g-1, which is 15 F·g-1 higher than the value exhibited by PH. After 1000 cycles, the decrease in the specific capacitance of P1 is 10%. (3) Polyaniline doped with HCl and carbon composites were prepared in situ polymerization. Polyaniline doped with HCl and acitived carbon composite material in which the mass of active carbon is 30% of the mass of aniline shows the lowest charge transfer resistance and good rate capability and cycleablity. The specific capacitance is 364 F·g-1 at current density of 0.1 A·g-1. This value reduces to 338 F·g-1 at current density of 0.5 A·g-1. The specific capacitance remains 290 F·g-1 after 1000 cycles. Polyaniline doped with HCl and acitived carbon composite material in which the content of active carbon is 10% shows the largest specific capacitance of 370 F·g-1 at current density of 0.1 A·g-1.(4) The composite material of PANI co-doped with Zn2+ and H+ and actived carbon (PCZN) was prepared with 30% active carbon content. Compared with PANI doped with HCl/actived carbon, PCZN exhibits higher specific capacitance of 376 F·g-1 at the current density of 0.1 A·g-1. The specific capacitane is 340 F·g-1 at 0.5 A·g-1. The specific capacitance remains 305 F·g-1 after 1000 cycles, and the capacitance loss is 10%.