Study On Lead-carbon Electrochemical Energy Storage Systems Applied In Start-stop Systems

The energy crisis and environmental pollution have been treated as the two main issues of our society.The fuel cars are rich in oil and emissions,which is difficult to meet the need of sustainable development,and the hybrid vehicle with“electric filling oil” is emerging.The start-stop system is the core of hybrid vehicles.The start-stop system can reduce the idle time during driving,convert the excess heat into the stored energy and reduce the energy consumption of the vehicle.The start-stop battery is the basis of the start-stop system and determines the development level of the hybrid vehicle.The start-stop battery is not only able to be operated at high current,but also provide continuous,stable electrical energy for electronic equipments of vehicles after stalling the engine.The working environment of the start-stop battery is very severe.The lead-acid battery is the most mature start-stop battery.However,with the development of hybrid vehicles,the lead-acid battery is facing a series of serious technical challenges.The lead-carbon battery is known as the next generation of the lead-acid battery,which has higher power density and longer cycle life at high rate.The negative electrode of the lead-carbon battery contains a large number of carbon materials,which can restrain the sulfation process in the negative electrode and improve the performance of the battery at high current.The lead-carbon battery has been widely applied in Japanese and German hybrid vehicles,but the confidentiality degree of relevant technologies is extremely high.Relevant research in our country starts late.In this paper,the positive electrode with silicon dioxide applied in the lead-carbon hybrid capacitor was designed and prepared.The electrochemical behavior of lead ions on the negative electrode of the lead-carbon hybrid capacitor is also analyzed.Furthermore,a series of advanced carbon-coating lead-carbon batteries have been developed.The powder additive applied in the positive electrode and the polyvinyl alcohol gel employed in the negative electrode were also prepared.A new battery failure mechanism about the negative electrode is proposed.The lead-carbon hybrid capacitor and the carbon-coating lead-carbon battery is designed for the development of the start-stop battery.The main work of this paper is listed as follows:?1?The high performance nano-SiO₂/PbO₂ electrode was prepared by anode co-electrodeposition.The nano-SiO₂/PbO₂ electrode is composed of the?-PbO₂ and the nano-SiO₂,which has micro-sized cracks and a large number of mesoporous.The nano-SiO₂ can build inert ion transmission channels within active materials and improve the diffusion ability of the electrolyte.The energy density of lead-carbon hybrid capacitor with the nano-SiO₂/PbO₂ electrode at 3 A g^-1 can reach 41 Wh Kg^-1.After the optimization of co-electrodeposition current density and electrode quality ratio,the energy density of lead-carbon hybrid capacitor with the nano-SiO₂/PbO₂ electrode at 3A g^-1 can reach 61 Wh Kg^-1.The energy density retention rate can reach 91%after cycling 1000 times.After adding nano-SiO₂/PbO₂ powder into the positive electrode of the carbon-coating lead-carbon battery,the nano-SiO₂/PbO₂ additive can build ion transmission channels within the active material,and the ions can be more fully contact with electrodes,improving the energy density and cyclic stability of the battery.Compared with the carbon-coating lead-carbon battery with PbO₂ powder,the energy density of the carbon-coating lead-carbon battery with nano-SiO₂/PbO₂ additive was increased by 12%,and the cycle stability was increased by 10%after cycling 3000 times.?2?A method of coating PVA gel onto the active carbon of the carbon-coating negative electrode is proposed.The mechanism of PVA gel is studied.The results show that the PVA gel can inhibite the hydrogen evolution reaction and enhance the energy density of the carbon material.The cycle stability of the carbon-coating lead-carbon battery with PVA gel was increased by 24% after cycling 15000 times.?3?A new failure mechanism of the carbon-coating lead-carbon battery is reported:During discharging,the lead ions from the positive and negative electrodes will spread through the electrolyte to the surface of the coated carbon.During charging,the lead ions around the coated carbon will be reduced to lead,and then quickly converted to lead sulfate,making the sulfation happened.As the discharge current increasing,the initial voltage of the coated carbon is negative,and the reduction potential of lead ions around the coated carbon is more negative to the reduction potential of the lead paste.The sulfation on the coated carbon is more serious than that on the lead paste at high rate.The PVA gel can prevent the carbon materials from sulfation.The energy retention rate of the carbon-coating lead-carbon battery with PVA gel was increased from 76.01% to 83.75%after cycling 2000 times at 1 A g^-1 under 100%DOD.The charging-discharging efficiency was increased from 44.12% to 97.45%.The cycle stability was increased by 11%.A new failure mechanism of lead-carbon hybrid capacitor is reported:During discharging,part of disoved lead ions from the positive electrode can spread through the electrolyte to the negative electrode.When a certain current density is arrived during charging,lead ions around the negative electrode will be reduced to lead,and then quickly convert to lead sulphates during next discharging,making the sulfation happening.The lower the current density,the more likely the sulfation will be aggravated.Placing the anion exchange membrane between the positive and negative electrode can prevent the spread of lead ions around the negative electrode,and inhibites the lead deposition on the surface of active carbon.The energy density of lead-carbon hybrid capacitor with anion exchange membrane at 3 A g^-1 can reach 73.6 Wh Kg^-1.The energy density retention rate can reach 95%after cycling 10000 times.?4?The 8 V 2 Ah lead-carbon hybrid capacitor and the 12 V 24 Ah carbon-coating lead-carbon battery was designed and prepared.The cycle life of the lead-carbon hybrid capacitor at 50%DOD and at start-stop mode can reach 4926 times and 94761 times,respectively.The cycle life of the carbon-coating lead-carbon battery at 50%DOD and start-stop mode can reach 395 times and 39729 times,respectively.Both these two devices have nice load power,great dynamic charging acceptance ability,outstanding static charging acceptance ability,excellent low temperature starting ability,and meet the national standard requirements both in China and Japan.