Research On Carbon-Based Suppercapacitor Electrode For Ultrabattery

The development and use of electric vehicles, in particular hybrid electric vehicles (HEV), has been developing the world's hot spots. Ultra-battery which takes the advantage of lead-acid batteries and super-capacitor is an ideal choice for HEV. But because of the working range mismatch between carbon negative electrode and lead negative electrode and severe hydrogen evolution in the end of charging, the development of ultra-battery has been restricted. To solve these problems, we conducted the following research.Two modification methods, including mechanical mixing and chemical deposition,were used to mix 10% lead with carbon material. We investigated hydrogen evolution rate of modified carbon, and found that the chemical deposited carbon has lower hydrogen evolution rate than the mechanical mixed carbon. TEM and SEM images of modified carbons shows that lead can be evenly distributed in the carbon surface and pores by chemical deposition, while mechanical mixing could not. It means chemical deposition is better than mechanical mixing. In subsequent experiments, we adopted chemical deposition method to modify carbon. We deposited a series of amounts of lead and bismuth into activated carbon.The results showed that with the increase of deposited lead, hydrogen evolution rate of modified carbon gradually decreased. Analyzing hydrogen evolution rate of modified carbon electrode at -1.4V, showed that more than 30% lead deposited into carbon, the hydrogen evolution rate decreased slowly. So that 30% lead is the best modification. For bismuth, with the increase of deposition, hydrogen evolution rate of carbon gradually decreased, indicating that bismuth can also inhibit the carbon hydrogen. For the working range of carbon material, lead can make a significant negative shift on working range of carbon, but bismuth has little effect. In order to make ultra-battery, 30% lead modified carbon electrode were prepared and be incorporated into lead-acid battery, paralleling with negative plate. Compared with commercial batteries, ultra-battery had better cycle performance, two times longer.Based on 30% lead modified carbon materials, barium and bismuth were deposited. The results showed that the addition of barium and bismuth will increase hydrogen evolution rate of modified carbon. In addition, the barium can improve the cycle stability of carbon electrodes, while Bi can improve the specific capacity of carbon electrodes. So, certain amount of barium and bismuth on the modified carbon could be beneficial.