| Lead-acid batteries have the highest market share among all secondary batteries and thus it is of great significance to improve their energy storage characteristics and increase their specific energy.In this dissertation,the electrolyte,the positive and negative current collectors,active material are studied,including the design and preparation a layered-carbon/PbSO4 composite additive for negatively active material(NAM)and a Ti4O7 nanowire additive for positive active material(PAM),rare-earth ion additive for electrolyte,as well as light-weight polymer-graphite composite negative grid and titanium base composite positive grid.This dissertation studies the effects of using these key materials and techniques in the system of lead-acid batteries to improve the specific energy,the rate performance and the cyclability of lead-acid batteries.It also gives an in-depth discussion on the structure-activity relationship and mechanisms.In order to improve the cyclability of the lead-acid batteries and inhibit hydrogen and oxygen evolution of the batteries,rare earth elements are studied as an additive for lead-acid battery electrolytes.The results show that the radius of rare earth ions has a regular effect on the charge-discharge performance of the battery.Rare earth elements with small ionic radius are not easy to be absorbed on the surface of active substances,which can improve the ionic conductivity of the electrolyte without reducing the capacity of the battery,improve the reversibility of charging/discharging of the batteries and thus significantly improve the cyclability performance.Moreover,the addition of rare earth ions in the electrolyte inhibits the hydrogen and oxygen evolution and inhibits the sulfation of NAM and PAM.A novel polymer-graphite composite grid is designed as the negative current collector(grid)for lead-acid batteries.With this novel grid,the NAM can deliver a specific capacity of 170 mAh·g-1(11.5%increase)at a rate of 0.1 C.Through the structural optimization,additional lead pastes can be loaded and the cycle stability of the battery is enhanced.By using the optimized grid,the weight of the negative current collector can be remarkably reduced by 50%?60%.Fine PbSO4 particles are deposited by chemical treatment on the surface of the polymer-graphite composite grid,which could inhibit the hydrogen evolution of the grid surface and build an excellent interface between the grid and the lead pastes.The cells employing the PbSO4-deposition grids exhibit excellent cycling stability(the capacity retention rate is 85%after 100 cycles at 0.1 C)as well as low polarization and then high Coulombic efficiency.In order to meet the requirements of HRPSoC(high-rate partial-state-of-charge)operation,we constructed a layered-carbon/PbSO4 composite negative additive by a chemical vapor deposition method and a subsequent in situ ion exchange process using potassium carbonate as the template.The composite can be uniformly mixed with lead pastes,improving the electronic conductivity and the ionic conductivity of NAM,inhibiting NAM's sulfation during HRPSoC operation,inhibiting the hydrogen evolution of the layered-carbon itself.As a result,the specific capacity,rate performance,and HRPSoC cycling performance of the NAM are significantly enhanced.The NAM with 2.00 wt.%composite additive(the content of layered-carbon in NAM is 0.10 wt.%)delivers a specific discharge capacity of 61 mAh·g-1(30%increase)at a high rate of 10 C rate,and has achieved a HRPSoC cycle life of 160,000 cycles(300%increase).A Magneli phase Ti4O7 nanowire with good conductivity,oxidation resistance and corrosion resistance is designed and prepared as an additive for PAM,which enabled the batteries to have a good charging receptivity.The specific capacity of PAM could be improved by nearly 15%,the utilization rate of PAM reached 59.6%.The cycling performance of the PAM with Ti4O7 nanowires is significantly higher than that of the PAM with Ti4O7 powder.In addition,the titanium grid was treated with an intermediate conductive layer and PbO2 electrodeposited on the surface.By using this grid,the PAM can deliver a specific capacity of 126.0 mAh·g-1 at 0.1 C rate,and the weight of the positive current collector can be remarkably reduced by more than 50%. |
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