JP2008276980A - Raw material of active material for lead-acid storage battery, and lead-acid storage battery using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve forming efficiency of a positive electrode active material, improve softening resistance of the positive electrode active material, and improve cycle life characteristics in a lead-acid storage battery. <P>SOLUTION: A raw material of the active material comprises secondary particles 10 which are formed by means that primary particles 12 having Pb<SB>3</SB>O<SB>4</SB>as the main body and primary particles 13 having PbO as the main body are mixed and aggregated around the center part 11 where the primary particles containing at least one of PbO and Pb are aggregated. Accordingly, when the active material raw material is added, the forming efficiency is improved. Moreover, since the surface of the secondary particles are not completely converted to Pb<SB>3</SB>O<SB>4</SB>and PbO exists, if the raw material of the active material is kneaded with a material of an active material paste, since the primary particles 13 containing PbO in the secondary particles 10 are bonded to each other and PbO or the like existing on the surface of the secondary particles 10 is bonded to PbO in the paste, a bonding force between the active materials becomes strong and firm, and the softening resistance can be improved more than in the case of publicly known technique in which minium is added. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention relates to a lead-acid battery active material and a lead-acid battery using the same.
In general, “active material for lead-acid batteries” (hereinafter simply referred to as “active material”) includes all of the necessary materials for making an active material paste, including lead powder, water, sulfuric acid, red lead and other additives. It is a word that means the raw material. However, in the claims and specifications of the present invention, the term “active material raw material” is used as a word indicating only the raw material containing Pb ₃ O ₄ described in the present invention and comparative examples. The terms “powder”, “water”, “sulfuric acid”, and “other additives” are used separately from “active material raw materials”.

  As a method for improving the conversion efficiency of a lead-acid battery, a technique of including lead oxide in a positive electrode active material is known. However, normally, adding lead without any ingenuity breaks the network between the active material particles and weakens the bond between the active material particles, causing the active material to soften and fall off early, resulting in cycle life characteristics. There was a problem that decreased.

As a method for solving this problem, a method of adding a raw material (refer to Patent Document 1) in which a part containing Pb ₃ O ₄ as a main component and a part containing PbO as a main component in one particle is added, or metal Pb. A method of adding a raw material (see Patent Document 2) containing PbO and a surface layer of Pb ₃ O ₄ has been proposed.
JP 2005-44772 A Japanese Patent Laid-Open No. 10-270029

When the raw material described in Patent Document 1 is contained in the positive electrode active material paste and kneaded and aged, the PbO portion is bonded to the metal Pb, PbO and basic lead sulfate in the paste during the aging, so The bond of Pb ₃ O ₄ is difficult to bond to these (metal Pb, PbO, etc.). In the raw material described in Patent Document 1, the part containing Pb ₃ O ₄ as the main component and the part containing PbO as the main component are not mixed, but are unevenly distributed. In the positive electrode active material paste, a portion that is partially bonded to the metal Pb or PbO and the basic lead sulfate in the paste is generated.

In addition, the raw material described in Patent Document 2 contains metal Pb and PbO, but the surface layer is formed of Pb ₃ O ₄ , so when it is included in the positive electrode active material paste and kneaded and aged. Furthermore, it is difficult to bind to the metal Pb, PbO and basic lead sulfate in the paste.

  Therefore, when the raw materials described in Patent Document 1 and Patent Document 2 are used, although the strengthening of the bonding force between the active material particles is improved as compared with the case where the normal lead is included, it is sufficient. However, it cannot sufficiently prevent the active material from softening and dropping due to repeated charge and discharge.

  The present invention has been completed on the basis of the above circumstances, and in a lead-acid battery, the conversion efficiency of the positive electrode active material is improved, and the positive electrode active material is more effective than the known technology including lead tan. The object is to improve the softening resistance and, in turn, the cycle life characteristics.

As a means for achieving the above object, the present invention provides an active material material for a lead storage battery comprising secondary particles formed by aggregating primary particles, wherein the secondary particles are as shown in FIG. In addition, primary particles 12 mainly composed of Pb ₃ O ₄ and primary particles 13 mainly composed of PbO are mixed around the central portion 11 formed by agglomeration of primary particles including at least one of PbO and Pb. Active material raw material for a lead storage battery, characterized in that the secondary particles 10 are aggregated and formed and the surface is not completely converted to Pb ₃ O ₄ , and the active material raw material for the lead storage battery Is a lead storage battery characterized in that is used for a positive electrode active material paste.

  In the present invention, “mainly” means “occupies a majority quantity (mass basis)”.

The active material for lead-acid battery of the present invention (hereinafter also simply referred to as active material) is mainly composed of Pb ₃ O ₄ around a central portion formed by agglomeration of primary particles containing at least one of PbO and Pb. Primary particles mainly composed of PbO and secondary particles formed by agglomerating and agglomerating, so that when this is included in the positive electrode active material paste and aged, PbO contained in the secondary particles The primary particles containing are bonded to each other.

In addition, since the active material raw material of the present invention is secondary particles whose surface is not completely converted to Pb ₃ O ₄ , PbO is present on the surface, and this PbO is present in PbO or basic sulfuric acid in the paste. Combines with lead.

As a result, since PbO around Pb ₃ O ₄ is bonded more strongly than when using a conventional active material material, the bonding force between the active materials is strengthened, and the network between the active materials is destroyed during the formation. Can be suppressed.

  Therefore, according to the present invention, the softening resistance of the active material can be improved and the cycle life characteristics can be improved even when the red lead is included in the active material paste.

Further, in the raw active material of the present invention, since include _{Pb 3 O 4, Pb 3 O} 4 that generates and PbO ₂ high reactivity to the PbSO ₄ and the conductive sulfuric acid in the electrolyte, chemical Efficiency can be improved.

As shown in FIG. 1, the secondary particles 10 contained in the active material raw material of the present invention have Pb ₃ O ₄ around the central portion 11 formed by agglomeration of primary particles containing at least one of PbO and Pb. The primary particles 12 mainly composed of the primary particles 13 and the primary particles 13 mainly composed of PbO are mixed and formed.

The surface of the secondary particle 10 is not completely converted to Pb ₃ O ₄ and PbO exists in the surface layer. The pH of the supernatant after stirring the water completely converted to Pb ₃ O ₄ in water is about 7.8, and when PbO remains, the pH is around 10. Therefore, the pH of the supernatant obtained by stirring and mixing the active material raw material of the present invention in water is about 10.

The active material raw material of the present invention is produced by firing secondary particulate lead powder (details will be described later) usually at 350 to 450 ° C. By adjusting the firing conditions (temperature, time, etc.) at the time of firing, the surface is not completely converted to Pb ₃ O ₄ (the state where PbO remains on the surface), and the active material The Pb ₃ O ₄ content in the raw material can be adjusted. In this specification, the Pb ₃ O ₄ content refers to the ratio (mass%) of Pb ₃ O _{4 in} the active material raw material (calcined product when lead powder is fired to form Pb ₃ O ₄ ). manner to is expressed by a value obtained by multiplying by 100 a value obtained by dividing the mass of the calcined product when Pb ₃ O ₄ turned into by firing Namariko mass of Pb ₃ O _4.
The Pb ₃ O ₄ content (% by mass) can be quantified by the following titration operation.
First, an acetic acid-ammonium acetate solution and a 0.1N sodium thiosulfate solution are added to the active material raw material and stirred to dissolve completely.
To this sample solution, starch solution is used as an indicator, 0.1N iodine solution is added dropwise, and the thiosulfate ion remaining in the solution is taken as the end point when purple coloration by iodine starch reaction is shown. Titrate. The blank experiment was performed in the same manner, and the Pb ₃ O ₄ content (% by mass) was calculated from the amount of the iodine solution used for the titration using the following formula.
Pb ₃ O ₄ content (% by mass) = [0.3428 × (b′−b) × f] / S ×
100
b ′: Amount of iodine solution consumed during titration in the blank experiment (ml)
b: Amount of iodine solution consumed for titration of sample (ml)
f: Factor of iodine solution S: Amount of sample (g)

The Pb ₃ O ₄ content in the active material raw material of the present invention is preferably 20 to 80% by mass. If the Pb ₃ O ₄ content is less than 20% by mass, the effect of improving the chemical conversion efficiency cannot be exhibited. If the Pb ₃ O ₄ content exceeds 80% by mass, early softening and falling off of the active material tends to occur.

Incidentally, in the state of not being completely Pb ₃ O ₄ the surface of the secondary particles 10, by cutting the portion of the surface of the surface layer is completely Pb ₃ O ₄ phased baked product, exposing the PbO You may let them. For example, when pulverization or the like is performed, a part of the surface layer of the fired product that has been converted to Pb ₃ O ₄ can be shaved, so this method is also possible.

  As the secondary particulate lead powder for producing the active material raw material of the present invention, the one formed by agglomerating primary particles mainly composed of PbO around the primary particles mainly composed of metal Pb is used. be able to. Content of the metal Pb in this secondary particulate lead powder is 10-30 mass% normally with respect to the mass of the whole lead powder.

  The secondary particulate lead powder for producing the active material raw material of the present invention uses a ball mill type lead powder production machine capable of producing fine particles as compared with a Balton type lead powder production machine. It is produced by setting the air volume and wind speed to appropriate conditions.

  More specifically, using a general ball mill type lead powder production machine, the average particle diameter is small when the air speed of the air to be fed is reduced and the air speed is made slower than when producing conventional lead powder. Primary particulate lead powder is produced. Since this primary particulate lead powder has a small average particle diameter, it aggregates to form secondary particulate lead powder.

  Further, among the primary particles forming the secondary particulate lead powder, those arranged on the outside have many portions that come into contact with air, and therefore, the oxidation from Pb to PbO easily proceeds. As a result, secondary particulate lead powder in which primary particles mainly composed of PbO are aggregated is formed around a central portion formed by agglomerating primary particles mainly composed of metal Pb.

Next, a method for producing a lead storage battery (hereinafter also simply referred to as “battery”) using the active material material of the present invention will be described.
First, the active material raw material of the present invention is added to the lead powder and mixed by a conventional method.

  It is preferable that the addition amount of the active material raw material of this invention is 10-30 mass% with respect to the total mass of lead powder and the active material raw material of this invention. If the addition amount of the active material raw material of the present invention is less than 10% by mass, the effect of improving the chemical conversion efficiency is hardly exhibited, and if it exceeds 30% by mass, the active material is likely to be softened and dropped early.

  After mixing the active material raw material and the lead powder of the present invention, water and sulfuric acid are added and kneaded to prepare a positive electrode active material paste, this paste is applied to a lead alloy grid for a lead storage battery, and aged at room temperature After aging in the chamber, it is dried to produce an unformed positive electrode plate.

  Next, an unformed positive electrode plate and an unformed negative electrode plate prepared by a conventional method are combined through a separator mainly composed of microporous polyethylene, and an electrode plate group is prepared and inserted into a battery case. After welding the lid, a predetermined amount of electrolytic solution is injected, and the battery is formed, and the lead storage battery of the present invention is obtained.

<Examples and Comparative Examples>
Hereinafter, examples to which the present invention is specifically applied and comparative examples regarding comparative products will be described.
(1) Production of active material material for lead-acid battery Primary particles mainly composed of PbO around the central part formed by agglomeration of primary particles mainly composed of Pb with a content of metal Pb of 10 to 30% by mass The active material raw materials of the present invention having different Pb ₃ O ₄ contents were prepared by adjusting the firing time at a firing temperature of 450 ° C. using secondary particle-shaped ball mill type lead powder in which agglomerates were aggregated. Those having a Pb ₃ O ₄ content of 20% by mass, 50% by mass, 80% by mass, and 90% by mass are referred to as active material raw materials 1, 2, 3, and 4 of the present invention, respectively.

Also, using a primary particle-shaped Barton-type lead powder containing Pb at the center of spherical particles and containing PbO at the center of spherical particles with a Pb content of 10 to 30% by mass, firing time is 450 ° C. to prepare a Pb ₃ O ₄ in different comparative content raw active material by adjusting. Those having Pb ₃ O ₄ content of 20% by mass, 50% by mass, 80% by mass, 90% by mass, and 97% by mass are referred to as comparative active material materials 5, 6, 7, 8, and 9, respectively.
The amount of Pb ₃ O ₄ includes an error of ± 3% by mass.

(2) Observation of cross section of active material raw material The cross sectional observation was performed about the active material raw materials 1-4 of this invention produced by said method, and the comparative active material raw materials 5-9. After embedding the active material raw material particles in the resin, the cut surface was polished and the polished surface was observed using a laser microscope. FIG. 2 is a schematic cross-sectional view of the active material raw material 2 of the present invention, and FIG. 3 is a schematic cross-sectional view of a comparative active material raw material 6.

As a result of observation, the active material raw material 2 of the present invention has a Pb ₃ particle diameter of 0.1 to 9.0 μm around the central portion 11 formed by agglomeration of primary particles containing at least one of PbO and Pb. The primary particles 12 mainly composed of O ₄ and the primary particles 13 mainly composed of PbO are secondary particles 10 formed by agglomeration, and the particle diameter of the secondary particles 10 is 10 to 50 μm. Was confirmed (see FIG. 2). The same applies to the active material materials 1, 3, and 4 of the present invention.

The comparative active material raw material 6 is a primary particle 20 having a particle diameter of 0.5 μm to 15 μm in which a layer 22 made of Pb ₃ O ₄ is formed around a portion 21 made of at least one of PbO and Pb. It was confirmed (see FIG. 3). The same was true for the comparative active material materials 5, 7, 8, and 9.

(3) Confirmation as to whether or not the surface layer of the active material raw material is covered with Pb ₃ O ₄ Next, PbO remains on the surface layer of the active material raw materials 1 to 4 of the present invention. It was confirmed by the following method that it was not in the state covered with Pb ₃ O ₄ .

After stirring and mixing 10 g of the active material raw material of the present invention in 100 ml of ion-exchanged water, the mixture was allowed to stand for 30 minutes and the pH of the supernatant was measured. When PbO is present, the pH is around 10. Therefore, when the pH is 7 to 8, it is judged that the surface layer is completely covered with Pb ₃ O _{4. When} the pH is around 10, It was judged that the surface layer was not completely covered with Pb ₃ O ₄ .

In all of the active material raw materials 1 to 4 of the present invention, since the pH was around 10, it was found that the surface layers of the active material raw materials 1 to 4 of the present invention were not completely covered with Pb ₃ O _4. It was.

(4) Preparation of lead acid battery The amount of addition of the active material raw materials 1 to 4 of the present invention and the amount of addition of the comparative active material raw materials 5 to 9 are listed in Table 1 (total of lead powder and active material raw materials It was mixed with a ball mill type lead powder so as to be 10 to 30% by mass with respect to the mass, and water and sulfuric acid were further added and kneaded to prepare an active material paste. Was also prepared in the same manner as the active material paste also raw active material of the present invention, those not added raw active material and red lead of comparison (i.e., containing no Pb ₃ O ₄ component).

  Each of the active material pastes thus produced was applied to a lead alloy lattice, aged for 40 hours in an aging room at room temperature, and then dried to produce an unformed positive electrode plate.

  This unformed positive electrode plate and an unformed negative electrode plate produced by a conventional method are combined through a separator mainly composed of microporous polyethylene to prepare an electrode plate group, which is inserted into a 34B19 type battery case. Then, the lid was welded to produce a 34B19 type lead acid battery.

  A predetermined amount of dilute sulfuric acid with a specific gravity of 1.15 (20 ° C.) is injected into this lead storage battery, and then the battery is formed by energizing a quantity of electricity 1.8 times the theoretical capacity of the positive electrode for 8 hours. A 27 Ah lead acid battery was obtained. Lead acid batteries produced using the active material materials 1 to 4 of the present invention are Examples 1 to 12, and the lead acid battery produced without adding the active material raw material of the present invention, the comparative active material raw material, and the red lead battery is a comparative example. 1. The lead acid battery produced using the comparative active material raw materials 5-9 was made into Comparative Examples 2-16.

<Test example>
By the above method, four batteries of each of Examples 1 to 12 and Comparative Examples 1 to 16 were produced. Two pieces of each produced battery were subjected to the following chemical conversion efficiency evaluation test and softening resistance evaluation test, and the average value of the test results of the two batteries was adopted as the result of the evaluation test.
(1) Evaluation test of chemical conversion efficiency Since the positive electrode active material of the lead storage battery changes from PbO or basic lead sulfate to PbO ₂ by chemical conversion, the chemical conversion efficiency can be improved by comparing the amount of PbO ₂ in the positive electrode active material after chemical conversion. evaluated. This will be specifically described below.

  First, the positive electrode active material after battery case formation is washed with water to remove sulfuric acid, dried and pulverized. Next, an acetic acid-ammonium acetate solution and a 0.1 N sodium thiosulfate solution were added to the pulverized positive electrode active material (sample), and the mixture was stirred and completely dissolved.

To this sample solution, a starch solution is added, a 0.1N iodine solution is added dropwise, and the sodium thiosulfate ion remaining in the solution is titrated at the end of the time when purple coloration due to iodine starch reaction is exhibited. did. A blank experiment was performed in the same manner, and the amount of PbO ₂ after conversion (mass%) was calculated from the amount of iodine solution used for titration using the following equation.
PbO ₂ amount (% by mass) = [0.01196 × (b′−b) × f] / S × 100
b ′: Amount of iodine solution consumed during titration in the blank experiment (ml)
b: Amount of iodine solution consumed for titration of sample (ml)
f: Factor of iodine solution S: Amount of sample (g)

Table 1 shows the relative value A when the amount of PbO ₂ after the formation of the battery of Comparative Example 1 is taken as 100. It shows that the larger the relative value A is, the more PbO ₂ is, that is, the chemical conversion efficiency is improved.

(2) Softening resistance evaluation test The positive electrode active material of the lead-acid battery is subjected to cycle life test according to the following procedure because PbO ₂ is softened by repeated charge and discharge, and the capacity that can be gradually dropped and taken out decreases. The amount of the positive electrode active material before and after the test was measured, and the softening resistance was evaluated by comparing the amount of the positive electrode active material remaining after the test with respect to the amount of the positive electrode active material before the test.

(Cycle life test)
At an ambient temperature of 40 ° C. ± 2 ° C., charging / discharging was performed by discharging at 10 A for 30 minutes and charging at 2.5 A for 2 hours and 12 minutes as one cycle. The judgment discharge was performed from the fully charged state every 10 cycles to a final voltage of 10.2 V at 10 A, and the cycle end condition was 150 cycles.

  Table 1 shows the relative value B when the remaining amount of the active material of the battery of Comparative Example 1 is 100. The larger the relative value B, the smaller the amount of the active material that falls off, that is, the higher the softening resistance.

Furthermore, the right end of Table 1 shows the square root value (hereinafter referred to as A × B value) of the product of the relative value A and the relative value B. This A × B value indicates whether the chemical conversion efficiency has been improved and the softening resistance has been improved. If the A × B value is larger than the A × B value (100) of the battery of Comparative Example 1, the chemical conversion It was judged that the efficiency was improved and the softening resistance was improved.
In Table 1, “comparative raw material” indicates “comparative active material raw material”, “raw material of the present invention” indicates “active material raw material of the present invention”, and “Pb ₃ O ₄ content”. And “Pb ₃ O ₄ content (mass%) in the active material raw material”.

<Test results and discussion>
(1) About chemical conversion efficiency In the lead acid battery of Examples 1-12 and the lead acid battery of Comparative Examples 2-16, chemical conversion efficiency improved rather than the comparative example 1. FIG.

In Examples 1-12 and Comparative Examples 2-16, since Pb ₃ O ₄ is contained in the positive electrode active material paste, this Pb ₃ O ₄ reacts with sulfuric acid in the electrolytic solution during chemical conversion. Thus, it is considered that the chemical conversion efficiency is improved by the generation of highly conductive PbO ₂ .

Comparing the chemical conversion efficiencies of the same active material raw material and the same active material raw material addition amount (for example, Examples 5 to 8), the Pb ₃ O ₄ content is in the range of 20 to 90% by mass. Then, as the Pb ₃ O ₄ content increased, the chemical conversion efficiency increased. However, when the Pb ₃ O ₄ content ranged from 80 to 90% by mass, the chemical conversion efficiency changed little.

From this, when the Pb ₃ O ₄ content exceeds 80% by mass, it is considered that the effect of improving the chemical conversion efficiency by increasing the Pb ₃ O ₄ content is difficult to obtain, and Pb ₃ in the active material raw material It is considered that the O ₄ content is preferably 20 to 80% by mass.

(2) Softening resistance When comparing the Pb ₃ O ₄ content in the active material and the amount of the active material added to the active material paste are the same (for example, Comparative Example 2 and Example 1), The battery had higher softening resistance than the battery of the comparative example.

This is because when the active material raw material of the present invention used in the batteries of Examples 1 to 12 is included in the positive electrode active material paste, primary particles mainly composed of PbO in the secondary particles are bonded to each other and exist on the surface. Since PbO is bonded to other secondary particles or PbO in the paste or basic lead sulfate, PbO around Pb ₃ O ₄ is strongly bonded, so the active material is more active than the batteries of Comparative Examples 2 to 16. This is thought to be due to the strengthening of the bond strength.

The softening resistance decreases as the Pb ₃ O ₄ content in the active material and the amount of the active material added to the active material paste increase (the amount of Pb ₃ O ₄ in the active material paste increases). I understood. Further, the battery of Example 1～4,5,6,9, despite containing the _Pb 3 _{O 4} components, a battery containing no _Pb 3 _{O 4} component (Comparative Example 1) Comparative However, although it was a slight difference, the softening resistance was improved.

(3) Improvement of chemical conversion efficiency and softening resistance (A × B value) The batteries of Examples 1 to 12 had higher A × B values than Comparative Example 1, but in the batteries of Comparative Examples 2 to 16 None had a higher A × B value than Comparative Example 1.

  From this, it is considered that the lead storage battery using the active material material of the present invention has improved chemical conversion efficiency and improved softening resistance.

<Summary>
As described above, according to the present invention, in lead-acid batteries, the conversion efficiency of the positive electrode active material is improved, and the softening resistance of the positive electrode active material is improved as compared with the known technology to which lead is added, and thus the cycle life characteristics are improved. Can be made.

<Other embodiments>
The present invention is not limited to the embodiments described with reference to the above description and drawings. For example, the following embodiments are also included in the technical scope of the present invention.
(1) In the above-described embodiment, the active material raw material having a Pb ₃ O ₄ content of 20, 50, 80% by mass is added 10% by mass, 20% by mass, 30% by mass with respect to the entire active material raw material. However, the Pb ₃ O ₄ content and the addition amount are not limited to this, and for example, a Pb ₃ O ₄ content of 25% by mass and a Pb ₃ O ₄ content of 15% by mass are added. May be added with 25% by mass of 75% by mass.
(2) In the above embodiment, the liquid type battery has been described as an example. However, since the same effect can be obtained even when used as an active material for a VRLA type battery (control valve type lead storage battery), the active material of the present invention. The raw material can also be applied as an active material raw material for a VRLA battery.
(3) In the above embodiment, the method of producing the active material raw material of the present invention using more preferable ball mill type lead powder as a raw material has been shown. However, the particle state of the active material raw material includes at least one of PbO and Pb. If the primary particles mainly composed of Pb ₃ O ₄ and the primary particles mainly composed of PbO are mixed and formed around the central part formed by aggregation of the primary particles, It may be produced by other methods.
(4) The lead acid battery of the present invention may contain organic fibers as an additive.

An enlarged schematic view of an example of the active material raw material of the present invention Schematic diagram of a cross section of the active material raw material of the present invention Schematic diagram of cross section of comparative active material

Explanation of symbols

10 ... primary particles mainly composed of primary particles 13 ... PbO mainly secondary particles 11 ... center 12 ... _Pb 3 _{O 4}

Claims (2)

An active material material for a lead storage battery comprising secondary particles formed by aggregating primary particles,
The secondary particles include a mixture of primary particles mainly composed of Pb ₃ O ₄ and primary particles mainly composed of PbO around a central portion formed by aggregation of primary particles including at least one of PbO and Pb. Agglomerate and form,
And the active material raw material for lead acid batteries characterized in that the surface is not completely converted to Pb ₃ O ₄ . The lead acid battery active material raw material of Claim 1 is used for a positive electrode active material paste, The lead acid battery characterized by the above-mentioned.

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