At the 2024 SMM 19th Lead-Zinc Conference and Lead-Zinc Technology Innovation Forum - Lead-Acid Battery Technology Forum hosted by SMM, Wu Yongxin, an engineer and doctor of Chaowei Group, shared the relevant impact of bismuth on the performance of lead-acid batteries.
Effect of bismuth on the performance of lead-acid batteries
Polarization curves
It can be seen from the curve trend that the oxygen evolution current density of the alloy increases with the increase of Bi content, and the oxygen evolution rate increases, while the passivation protection potential of the alloy decreases and the corrosion resistance decreases with the increase of Bi content.
Electrochemical impedance test -1.458V
The electrochemical impedance experiments at 1.458 V, 1.958 V, and 2.258 V show that Bi can increase the impedance of the anode film.
The main component of the anode film is PbO2, and the surface impedance of the lead alloy anode is very low, and the film impedance is the highest when the addition content of Bi is about 0.002 wt.%.
The results of the electrochemical impedance test at the polarization voltage of 2.458V are as follows:
The main component of the anode film is PbO2, and the impedance of the anode film is further reduced, and the addition of Bi element will reduce the oxygen evolution impedance of the alloy, resulting in the acceleration of oxygen evolution.
Mechanical properties and grid corrosion resistance test
Through the relevant tests, it can be concluded that the mechanical properties of the alloy grid decreased due to the increase of bismuth content in electrolytic lead, and the corrosion resistance of the alloy grid decreased due to the increase of bismuth content in electrolytic lead.
Battery cycling performance test
In laboratory tests, the cycle life of the low bismuth 0.0008% standard positive plate alloy is better than that of high bismuth alloys.
Battery cyclic water loss performance test
In the laboratory cycle test, the increase in bismuth content of high bismuth alloys increases the water loss rate of the battery.
Through the battery dissection experiment, it can be concluded that the increase of bismuth content in electrolytic lead increases the deformation of the mesh alloy grid, and the increase of bismuth content in electrolytic lead decreases the corrosion resistance of the mesh alloy grid.
Effect of bismuth content in lead powder on battery performance
Composition analysis and the effect of bismuth on water loss performance
1. When recycled lead is used as lead powder, the main factor for the increase of water loss rate is the influence of other impurity elements;
2. The increase of bismuth element content has little effect on the water loss rate.
Effect of bismuth element content on battery cycling performance
Through the comparison of the effect of bismuth content on battery cycle performance, it is found that the use verification of bismuth content in lead powder has been verified in large quantities in the market, and the effect of bismuth on battery performance is smaller than that of other impurities.
Effect of bismuth element content on grid production process
Grid appearance defects
The content of bismuth in recycled lead is high, and the content of bismuth and other impurities can be reduced by blending, which can improve the defects in the process of grid casting/continuous casting.
The content of bismuth in recycled lead is high, and the content of bismuth and other impurities can be reduced by blending, which can improve the mechanical properties of the grid and reduce the production scrap rate.
Through the morphology of 1#, 2# and 3# grid fractures, it can be found that:
1. The high impurity elements in lead lead to the formation of inclusions, some brittle second phases, and needle-like structures, and electrolytic lead can be considered to improve the purity of lead liquid.
2. The appearance of needle-like structure indicates that the second phase is not coherent with the matrix, and in the fracture structure, it is found that some tissues with poor conductivity are lead oxides and other carbon inclusions, and further enhancement of melt impurities can be considered.
3. Continuous atmospheric pores. The formation of continuous pores is caused by the poor fluidity of liquid lead.