Modification And Electrochemical Performance Of Activated Carbon Based On Lead Carbon Battery

Adding a certain amount of activated carbon with high specific area and high conductivity into the negative of lead-acid battery can obtain the advantages of the lead-acid battery and supercapacitor at the same time,and then to get lead-carbon battery with super long cycle life.However,the hydrogen evolution overpotential of activated carbon is lower than metal Pb,which will promote hydrogen evolution in the process of charging.In this thesis,we modify the activated carbon by different methods.The results showed that the modified activated carbon exhibit higher overpotential of hydrogen evolution and higher specific capacitance in sulfuric acid solution.The main research contents are as follows:1.We synthesize a new nitrogen-doped nano-porous carbon coated activated carbon composite materials which named C-ZIF-8@AC by liquid phase synthesis and high temperature calcination under the condition of argon.Then,we investigated the electrochemical performance of composite materials in 1 M H₂SO₄ solution.The experimental results showed that C-ZIF-8@AC exhibits excellent electrochemical performance as the electrode materials for supercapacitor.The specific capacitance increases from 130 F/g to 181 F/g at the current density of 1 A/g.It shows good rate capability and excellent cycling stability with a 98%capacitance retention rate after 6000 cycles at the current density of 5 A/g,which is higher than the value of activated carbon that is 90%in the same condition.The method of increasing the specific capacitance of the activated carbon can reduce the addition of the activated carbon in the negative electrode and effectively reduce the hydrogen evolution in the negative electrode of the lead-carbon battery.2.Nitrogen-doped activated carbon?NAC?with different nitrogen contents have been successfully prepared by a facile and cost-effective approach of high-temperature pyrolysis of polyaniline?PANI?/activated carbon?AC?composites under the condition of argon.The electrochemical testing results showed that this nitrogen-doped activated carbon?NAC?exhibits lower current density of hydrogen evolution and higher specific capacitance in 1 M H₂SO₄ solution.The current density of hydrogen evolution of nitrogen-doped activated carbon?NAC?is only-3.7 A/g at the potential of-0.9 V?vs.SCE?,which is lower than the value of original activated carbon?-20.2A/g?.What's more,the specific capacitance increases from 207.5 F/g to 314.5 F/g at a scan rate of 20mv/s.XPS results show that these excellent electrochemical properties of the material is due to the role of nitrogen in the material,especially pyrrole nitrogen which is easy to combine with hydrogen atoms in the hydrogen evolution reaction process,thereby inhibiting the hydrogen atoms into hydrogen gas,and inhibiting the hydrogen evolution in the solution.3.In order to enhance the effect of pyrrole nitrogen in inhibiting hydrogen evolution,polypyrrole/activated carbon?PPy/AC?composite materials were prepared by in situ polymerization using pyrrole as nitrogen source and ferric ion as oxidant.The experimental results showed that with the increase of polypyrrole content in the composite materials,the onset potential of hydrogen evolution gradually decreases from-0.56 V to-0.68 V and the overpotential increases by 0.12 V.When the mass ratio of PPy to AC was 1:1,the PPy/AC₁ exhibited a current density of-15.4 A/g at-0.9 V?vs.SCE?,which was superior than that of activated carbon?-20.2 A/g?.Polypyrrole in the composite material has a better performance of inhibiting the hydrogen evolution,and can increase the performance of inhibiting hydrogen evolution of activated carbon.