Ordinary and low-maintenance batteries lead-antimony alloy, the alloy of the positive electrode plate lead-acid battery, lead is a main material constituting the grid, pure lead is too soft, casting and machining very inconvenient, the use of the alloying material way to improve and enhance The main method of performance. Therefore, binary alloys such as Pb-Sb and Pb-Ca suitable for battery grids are successively produced. In order to further improve the properties and corrosion resistance of these alloys, different elements such as appropriate amounts of As, Ag, Bi, Cd, etc. Multi-component alloys such as Sn, Co, Se, Te, Sr, and Al have also been extensively studied and applied.

Grid alloys can be divided into common type, less maintenance type, maintenance-free type and other types of grids without light or light according to the type of battery. Since the service life of the lead storage battery is mainly determined by the positive electrode, a normal type and a low maintenance type battery grid alloy will be described later.

Ordinary battery grid alloy

Lead-bismuth alloy

Conventional batteries still mostly use lead-bismuth alloys. The main components of the alloy are: Pb and Sb (2% to 12%), but the more widely used compositions are: Pb and Sb (4% to 6%).

Advantages of Pb-Sb alloy:

Its tensile strength, ductility, hardness and grain strengthening are significantly better than pure lead;

Its melting point and shrinkage ratio is lower than that of pure lead, and it has good casting properties;

It has a lower coefficient of thermal expansion than pure lead, so the grid is not easily deformed during cyclic discharge;

Its corrosion is more uniform than pure lead, and Sb has a significant inhibitory effect on the growth of PbO ₂ in the corrosion film of the grid.

The "adhesion" between the grid and the active material is enhanced, which is beneficial to the deep charge and deep discharge capability of the lead storage battery and the cycle charge and discharge life.

In the positive plate of a lead storage battery, the presence of Sb has a significant effect on the formation of PbO ₂ in the cycle life of the plate. Recent studies have shown that the maximum electrochemical capacity achieved by batteries with pure lead is not further increased by repeated charge and discharge of the battery, but the capacity of the Sb-containing Pb-Sb alloy system is found to be repeated with charge and discharge. Gradually increase. This may come from two aspects: one is that Sb promotes two high- mercury forms—the crystal bond between PbO ₂ and β—PbO ₂ ; the other is that Sb acts as a nucleation catalyst for β-PbO ₂ in the corrosion product. Attached to the surface of the grid.

The above overall result is that the particles of PbO ₂ are strengthened, and the surface crystallization is kept small in particle properties, thereby increasing the electrochemical capacity of the battery and prolonging the charge and discharge life of the battery.

Lead-bismuth alloys have the following disadvantages:

The resistance of the alloy is slightly larger than that of pure lead. It is still considered that its corrosion resistance is not as good as that of pure lead. However, the corrosion state of the niobium-containing alloy is more uniform than that of pure lead. Even if the corrosion degree is slightly larger than that of pure lead, it is not suitable for lead storage batteries. The performance has a large impact.

The transfer behavior of Sb accelerates the self-discharge of the battery.

The main disadvantage of the Pb-Sb alloy is that the presence of Sb significantly reduces the hydrogen evolution overpotential of the negative electrode, thereby accelerating the self-discharge of the battery, which is not conducive to battery maintenance. The Sb eluted from the positive electrode grid is transferred by the separator and deposited on the surface of the negative electrode active material, and the hydrogen evolution overcharge is significantly increased due to the low hydrogen evolution potential on the Sb. In addition, under overcharge conditions, Sb also escapes from the highly toxic gas of SbH ₃ , which is one of the defects of the ruthenium-containing grid.

The transfer of Sb in the alloy is unavoidable, that is, the battery produced by using the Pb-Sb alloy as a grid, the large amount of outgas caused by self-discharge and the frequent water maintenance in use are unavoidable. In order to effectively improve the electrochemical performance and service life of lead storage batteries, it is necessary to develop a lead-bismuth multi-alloy with better performance instead of Pb-Sb alloy.

Lead arsenic alloy

The important reason for the damage of modern battery in the corrosion and deformation of lead-bismuth binary alloy grid is that a lot of research work has been done at home and abroad in order to find a better alloy to improve the service life of lead storage battery. Long-term research and practical use show that the current mature alloy is lead-bismuth arsenic alloy. Common compositions of the alloy are: Pb, Sb (4% to 6%) and As (0.1% to 0.15%).

The main advantages of lead-bismuth arsenic alloys are:

The addition of arsenic significantly improves the corrosion resistance of the battery grid. The corrosion of the arsenic-containing alloy by the weight loss method is not much different from that of the common lead-bismuth alloy, but the fine crystallization of arsenic makes the arsenic-containing alloy. The corrosion life of the battery assembled with Pb-Sb-As grid is increased by 25% to 30%. The results show that arsenic has a certain inhibitory effect on the growth of PbO _{2 ,} PbO and PbSO4 in lead anode film. At the same time, the formed film is looser, but the distribution is more uniform, which is consistent with grain refinement.

The addition of arsenic improves the mechanical strength of the grid, and in particular increases the hardening speed of the grid, thereby delaying the linear "growth" and deformation of the grid.

The "adhesion" between the arsenic-containing grid and the active material is stronger than that of the Pb-Sb alloy, and has a certain inhibitory effect on the active material shedding.

Lead-bismuth arsenic alloys still have shortcomings:

The inherent brittleness of arsenic-containing alloys reduces the castability to a certain extent. Therefore, it is necessary to design the mold correctly and control the casting temperature and cooling conditions reasonably. In this respect, Shanghai Battery Factory has accumulated rich experience, more than ten After years of use, the effect is very significant.

As has certain toxicity, it should be pre-formed into lead ingot or master alloy in the place where the protective conditions are safe, and then used in casting.

Arsenic, lead antimony tin alloy

In order to maintain the above advantages of the Pb—Sb—As alloy and overcome the brittleness of the arsenic-containing alloy, a Pb—Sb—As alloy with an appropriate amount of tin may be used. The main components of the alloy are:

The addition of a small amount of Sn in Pb, Sb (4% to 6%), As (0.1% to 0.15%), and Sn (0.05% to 0.5%) significantly improved the fluidity and castability of the molten As alloy, thereby clearly Reduces brittleness due to the addition of Sb and As.

However, the content of Sn should not exceed 0.5%. The excessive Sn content may contribute to the self-discharge of the battery, and the price of Sn is relatively expensive, which unnecessarily increases the cost.

Lead-bismuth silver alloy

Among the additives for corrosion-resistant alloys currently studied, silver is particularly noteworthy. Studies have shown that even the addition of only 0.1% silver to the Pb-Sb alloy can substantially improve the corrosion resistance of lead-bismuth alloy.

The main components of lead-bismuth silver alloy are:

Pb, Sb (4% to 7%), Ag (0.1% to 0.5%)

The good corrosion resistance of the ternary Pb-Sb-Ag alloy with Ag addition depends mainly on the Ag degranulation. The results of electron microscopy on the anodic corrosion mechanism of Pb-Sb4.5%-Ag0.2% alloy show that in homogeneous Pb-Sb-Ag alloys, corrosion occurs mainly due to matrix grains. Selective oxidation and limited damage to the 锑 phase. Most of the silver adheres to the Sb phase and surrounds the Sb ellipsoid, thereby preventing selective dissolution of the yttrium phase from the etched anode, so that the Ag-containing ternary alloy has good corrosion resistance.

In addition, Ag can cause a significant drop in the overpotential of oxygen, thereby accelerating the oxygen evolution process during charging. And the price of Ag is relatively expensive, and the content of Ag in the alloy should not be too high.

Lead-bismuth copper alloy

In order to replace the more expensive Ag, people tried to use Cu to obtain a Pb-Sb-Cu alloy. The composition of this alloy is generally: Pb—Sb (6%), Cu (0.069%)

The main feature of the alloy is that Cu increases the tensile strength and fluidity of the alloy, reduces the brittleness of the grid, increases the initial hardness of the alloy, and expands the casting temperature range. In addition, the intermetallic compound Cu3Sb composed of Cu and Sb makes the Pb—Sb—Cu alloy have better corrosion resistance than the Pb—Sb alloy.

Although the price of Cu is lower than that of Ag, the properties of the Pb-Sb-Cu alloy are generally not comparable to those of the silver-containing alloy. Another disadvantage of copper-containing alloys is that the brittleness of the grid is still large in the case of overheating of the mold (e.g., above 19 °C).

Lead bismuth arsenide copper alloy

The Pb-Sb-As alloy of good quality results in certain brittleness due to improper casting conditions. Adding a small amount of Cu to the As-containing alloy can play a good role in improving the brittleness and corrosion resistance.

The general composition of this alloy is:

Pb—Sb (6%), As (0.2%), Cu (0.09%)

The advantage of Pb-Sb-As-Cu alloy is that As and Cu react to form Cu ₃ As copper arsenide. Moreover, As can only be used as a better crystallizing agent and nucleation after Cu is formed by Cu. The agent thus has better corrosion resistance than Pb—Sb—Cu.

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