| As the most widely used chemical power source,lead-acid battery has been widely used in people’s life.In recent years,the vigorous development of the electric bicycle industry has led to the prosperity of the lead-acid battery industry.the lightweight design of the electric bicycle requires the weight loss of the lead-acid battery.as a result,the lead-calcium-based alloy positive grid in use has the phenomenon of creep and growth,resulting in a significant decline in battery life.In this paper,tensile test,creep resistance test,polarization curve test,electrochemical impedance spectroscopy and DC/AC cyclic voltammetry were used to study the mechanical properties,corrosion resistance and oxygen evolution behavior of positive grid alloys for lead-acid batteries,and their creep resistance and corrosion mechanism under different conditions were discussed.A comprehensive and rapid evaluation system for mechanical properties and corrosion resistance of grid alloys was established.The results of metallography,grain size measurement and creep resistance test show that the composition of the alloy has an effect on the grain size.The addition of rare earth La elements in the range of 0.006 to 0.010 wt.%can refine the grain size of the alloy,while the rare earth La of 0.0006 to 0.001 wt.%has no obvious effect on the grain size of the alloy.The grain size of the alloy containing rare earth elements decreases at first and then increases with the increase of Bi content in the alloy.The creep resistance,tensile strength,yield strength and ductility of nine kinds of alloys were compared by room temperature mechanical experiments.The comprehensive mechanical test results show that the addition of rare earth La element can improve the toughness,plasticity and deformability of the alloy,but decrease the creep resistance of the alloy.The creep resistance and tensile strength of lead-calcium alloy without rare earth are higher,but the toughness,plasticity and deformability are poor.The creep resistance of nine kinds of lead alloys was compared and analyzed,and the effect of grain size on creep resistance was discussed by using creep constitutive equation.The corrosion resistance and oxygen evolution properties of different lead grids were studied by polarization curve test and cyclic voltammetry.When the content of Bi in lead alloy is less than 0.003wt.%,the oxygen evolution rate of lead grid anode will increase with the increase of Bi content.The addition of rare earth element La can improve the corrosion resistance of lead alloy.The addition of Ag element will reduce the oxygen evolution overpotential and increase the oxygen evolution capacity of lead grid.The corrosion and oxygen evolution behavior of different lead grids at different potentials were studied by AC electrochemical impedance spectroscopy(EIS).When the potential was 1.458V,the Bi element in the alloy could promote the nucleation of PbSO4 on the anodic film and increase the impedance of the anodic film.When the potential was 1.958V,the rare earth element La could increase the specific gravity of α-PbO2 in the anodic film and increase the corrosion resistance of the alloy.The study on the impedance of alloy anode film by AC cyclic voltammetry shows that the more detailed the grain size of the alloy is,the lower the impedance of alloy anode film is,the better the deep cycle performance of the battery is.The cycle life of the battery made of nine kinds of alloy grid is tested.The addition of rare earth alloy can improve the corrosion resistance of the battery,but also reduce the creep resistance of the alloy,so that the elongation of the grid containing rare earth elements before and after cycle is higher.The creep resistance of the alloy without rare earth elements is good,but the toughness and plasticity is poor,and some alloys will fracture before and after cycling.The test results of battery cycle life are consistent with the results of mechanical and electrochemical experiments. |
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