The Synthesis Of Carbon Foams Derived From Resins And Their Capacitance Performance

Carbon foam,a new type activated carbon,is composed of bubble and bubble wall with three-dimensional reticulated structure.Carbon foam is a good electrode material for supercapacitors due to its abundant raw materials,large specific surface,wide distribution of pore size and chemical stability.Meanwhile,their specific surface area and pore diameter could be easily adjusted and controlled by foaming and carbonizing.In this paper,a series of phenolic foam?PF?,polyurethane foam?PUF?and their composites with carbon fibers?CFs?,CoO_x and CoNiS_x were prepared based on the phenolic resin?PR?and polyurethane?PU?.The obtained electrode materials were characterized and the electrochemical performance of the prepared materials was evaluated by the electrochemical methods.What is more,the obtained electrode materials were assembled into symmetrical or symmetrical capacitors to investigate their utilization potentiality.The detailed work was as follows:1.A series of phenolic foam?PF?was prepared by applying the phenol?P?and polyformaldehyde?F?as the raw materials.Various factors affecting the electrochemical properties of PF were taken in consider,such as the functional ratio?F/P?,the polymerization time?n h?,the mass of blowing agent and foaming temperature?t?.The electrochemical properties were measured by the cyclic voltammetry?CV?,constant-current charge-discharge?CP?and impedance?EIS?.The maximum specific capacitance of PF could be up to 160 F·g^-1 at 0.1 A·g^-1 when the F/P,n,w and t were at 2,3 h,7%and 65?,respectively.2.The composite carbon materials of PR and CFs were prepared by using the same preparation method of PF as the way described in the“1”section.By changing the mass of CFs and carbonizing temperature,a series of PF/CF-t-w was prepared.The experimental results showed that PF/CF-1000-3%exhibited a highest specific capacitance when the content of CFs was 3%and the carbonizing temperature was at1000?.Its specific capacitance was up to 298 F·g^-11 and about twice as much as PF at0.1 A·g^-1.The energy density of symmetrical capacitor PF/CF//PF/CF was up to 14Wh·kg^-1.Meanwhile,PF/CF//PF/CF could retain 90%of its initial specific capacitance after 10000 cycles.3.The hybrid materials PF/CoOx-m were prepared by the solvothermal method.Using PF obtained from the“1”section as the base material and changing the mass of PF,PF/CoOx-m with different content of CFs was prepared.The results of CV,CP and EIS indicated that the capacitance performance of PF/CoO_x-m was obviously better than CO_x.PF/CO_x-10%showed a higher capacitance up to 687 F·g^-1 at 0.5 A·g^-1,and the capacitance still sustained 438 F·g^-1 at 20 A·g^-1.The specific capacitance of PF/CO_x-10%was about three times than that of CO_x(234 F·g^-1)at 0.5 A·g^-1.Furthermore,the asymmetrical capacitor PF/CF//PF/CF also exhibited the excellent electrochemical performance with an energy density of 32 Wh·kg^-1 and 87%capacity retention after 7000 CP cycles.4.Polyurethane foam was prepared by one-step foaming method with MDI and polyester polyol as raw materials.According to the TG curves of polyurethane foam,PUF with complete structure was prepared by changing the carbonizing conditions.When the specific surface area of PUF was 814.8 m²·g^-1 and the content of N element was 4.44%,the capacitance value could reach 325 F·g^-1at 0.1 A·g^-1.5.The hybrid materials PUF/Ni were prepared using the preparation method of PUF as described in“4”section.Using PUF/Ni as nickel source,Co?Ac?₂ as cobalt source and thiourea as reducing agent,PUF/CoNiSx-m composite material was prepared by the hydrothermal method.The results of electrochemical measurement showed that the capacitance of PUF/CoNiSx-15%was excellent and its specific capacitance reached 504 F·g^-1 at 0.5 A·g^-1.The energy density of asymmetric capacitor PUF/CoNiS_x//PUF was up to 41 Wh·kg^-1,suggesting a good application potential of PUF/CoNiSx-m.