Research On Preparation Of Pb-C Composite Anode And Mechanism Of Action Of Carbon

In order to alleviate environmental pollution and energy crisis, our country has begun to develop electric vehicles. Pb-C battery is suitable for hybrid vehicles because of its low cost, long life and good security. It will be charged in high rate when the electric vehicles are braking, and will be discharged in high rate when the electric vehicles are accelerating or climbing.In this paper, functional graphene was prepared and incorporated in the negative lead paste. Other types of carbon were also incorporated in the negative lead paste. The types and quantity of carbon was determined by testing the cycle life of each battery in HEV mode. Morphology and structure of Pb-C battery was characterized by SEM and XRD. We analyzed the role of carbon materials in negative activated materials (NAM) by CV and EIS and then proposed a model of charge/discharge of NAM.SEM analysis showed that the pore structure of graphene became larger when improving oxidation degree and expansion temperature and the lead sulfate would be packaged easier. XRD analysis showed that high temperature had largely enlarged spacing of graphene. Using single factor test and orthogonal, optimum preparation techniques of carbon electrode was ensured as follows: The ratio of AC and AB was 5:1, the proportion of stearic acid was 1 mass%, the proportion of PTFE was 4 mass%, the proportion of CMC was 0.25 mass%, the thickness of the plate was 0.35 mm. Cyclic voltammogram of activated carbon and graphene showed that all of them had capacity in sulfuric acid solution. Activated carbon owned poor rate performance while graphene was much better.We established the optimum content of AB was 0.25 mass% in the anode while AC and graphene was 0.5 mass% through the research of cycle life. Testing the cycle life of the optimum formula in 50%,70% and 90% SoC respectively, the electrode owned the best cycle performance in 70% SoC.Adding carbon materials into NAM affected the microstructure of Pb after formation. As the quantity of the carbon growed, the shape of the lead changed from lump to acicular. The commercial plate contained lead sulfate after capacity-recovery charging while the optimum formula plate contained no lead sulfate. It showed that the particles of lead sulfate in the optimum formula plate were very small after discharge, and the charge progress became much easier. EIS analysis showed that real electrochemical surface area of the lead plate was enlarged by adding carbon materials into NAM. Therefore, the current density of the lead reduced. The experiments we designed showed that the role EAC played was to promote the electron transfer. At last we proposed a model of charge/discharge of NAM. Using the model, we explained the mechanism that carbon materials played an important role in inhibiting sulfation of the anode.