JP5569164B2 - Lead acid battery - Google Patents

Description

  The present invention relates to a lead storage battery, and more particularly to a lead storage battery that is used as an emergency power source at the time of a power failure in a hospital or a building that requires a long life.

  The above-mentioned lead storage battery is required to have a long life because such a lead storage battery is used as an assembled battery in which a number of cells are connected in series, and a constant voltage called float charging is applied to compensate for its self-discharge. One of the causes of shortening the service life is the corrosion of the positive grid that is caused by constant application of a constant voltage to the positive grid. .

  On the other hand, as a method for extending the life of a lead-acid battery, it is known to increase the corrosion resistance of the positive electrode grid by thickening the bone of the positive electrode grid and increasing the thickness of the positive electrode plate.

  However, when the above-described thick positive electrode plate is used, the positive electrode active material hardly contributes to the discharge to the inside, resulting in a problem that a discharge capacity corresponding to the amount of the positive electrode active material cannot be obtained. was there.

  As a solution to the above problem, Patent Document 1 discloses a sealed lead-acid battery in which a grid made of a lead-calcium-tin alloy is filled with a paste in which 10 to 3000 ppm of barium is added to an active material to form a positive electrode plate. Further, Patent Document 2 includes a positive electrode in which an active material layer is formed on a lead alloy lattice surface not containing antimony, and the positive electrode has sulfuric acid between the lead alloy lattice surface and the active material layer. A lead storage battery having a layer containing barium is disclosed, and Patent Document 3 discloses that a positive electrode active material is held in a lattice and a positive electrode and a negative electrode are stacked via a separator, and the total amount of the positive electrode active material is A lead storage battery containing 0.5% by mass or more and 5% by mass or less of barium sulfate, wherein the barium sulfate is concentrated on the surface of the positive electrode active material and is slanted toward the inside. Disclosed, and The Patent Document 4, electrode plate for a lead storage battery which contains 0.1 to 2% by weight of lead-acid barium are disclosed in the active material.

Japanese Patent No. 3577709 JP 2000-353518 A JP 2004-72110 A Japanese Patent No. 2553962

According to Patent Document 1, adding Ba to the positive electrode active material means that in an open lead-acid battery, the active material becomes soft and falls off the lattice, resulting in a short life. Since the separator is pressed, the active material is unlikely to fall off, and by adding Ba in a small amount of 10 to 3000 ppm, the active material is appropriately softened, and the active material and the lattice formed by volume expansion due to corrosion of the lattice It has been disclosed that the surface of PbO ₂ generated by lattice corrosion becomes difficult to be formed in the interstitial cracks and voids, and the PbSO ₄ insulating layer is covered with an insulating layer of PbSO ₄ so as not to reach the end of its life early. The relationship with the material density is not mentioned, and in Patent Document 2, the lead alloy lattice containing no antimony has poor adhesion between the active material and the lattice. As the process repeats, a gap is formed between the active material and the grid, and the electrolyte enters the gap, and the generated corrosion layer discharges first, and the grid surface is covered with a lead sulfate insulating layer and can be discharged. Although it has been disclosed that a positive electrode is provided with a layer containing barium sulfate between the lead alloy lattice surface and the active material layer to prevent this, it is disclosed that the positive electrode active material has barium sulfate. In patent document 3, a lead-acid battery using a positive electrode plate filled with an active material at a high density and a sealed lead-acid battery assembled in a highly pressurized state are assembled. In addition, 0.5% by mass or more and 5% by mass or less of barium sulfate is added in a total amount so that the barium sulfate is concentrated on the surface of the positive electrode active material and is inclined and sparse toward the inside. So, dense lead sulfate is formed on the positive electrode surface. Although suppression is disclosed, the relationship with the positive electrode active material density is not mentioned, and Patent Document 4 discloses that the active material has acid resistance, oxidation resistance, and high conductivity, and is a battery. Although it is disclosed that the utilization rate of the active material is improved by containing 0.1 to 2% by weight of barium lead acid that does not elute impurities harmful to the positive electrode active material, Is not mentioned.

  In contrast, as a result of verifying the effect of mixing barium in the active material in relation to the active material density, the present invention contributes to extending the life in relation to the thickness of the positive electrode plate. By finding out, it aims at solving the above-mentioned subject.

That is, the present invention forms a positive electrode plate holding a positive electrode active material containing barium, contains 10 ppm or more and 1000 ppm or less of barium in the average value per sheet in the positive electrode plate after conversion, and after conversion When the active material density of the electrode plate is 3.1 g / cc or more and 4.2 g / cc or less on an average per sheet, the barium content is X and the active material density is Y In addition,
−0.29 log X + 3.6 ≦ Y ≦ −0.29 log X + 4.7
It is characterized by satisfying.

  In the present invention, by including a small amount of barium in the positive electrode active material, the positive electrode active material becomes moderately soft and fills the gap between the lattice-active material interface, thereby improving the overcharge life performance and suppressing the early capacity decrease. However, if the active material density of the positive electrode plate after chemical conversion changes, the amount of barium to be contained must be changed accordingly. Thus, as a result of finding the relationship between the barium content and the positive electrode active material density, in which the above-described effects can be obtained, it is possible to contribute to an increase in discharge capacity commensurate with the increase in active material.

It is the figure which plotted for every sample, making the positive electrode active material density after chemical conversion into the vertical axis | shaft (Y-axis) the content of barium on the horizontal axis (X-axis), and writing the cycle number together.

  Hereinafter, although the details of the present invention are explained by one embodiment, the present invention is not limited to this.

(Production of lead-acid battery)
150 g of a positive electrode paste prepared by dry-mixing barium sulfate (manufactured by Nacalai Tesque, first grade reagent) with lead powder having an oxidation degree of 75%, and then kneading with appropriate addition of water and dilute sulfuric acid. Filled with a positive electrode grid made of Pb-0.1 mass% Ca-1.0 mass% Sn produced by casting with a thickness of 110 mm and a thickness of 3.8 mm, and a non-formed positive electrode with a thickness of 4.0 mm A plate is prepared, and the positive electrode plate is interposed one by one between three negative electrode plates separately prepared by a known method, and a known separator is interposed between the negative electrode plate and the positive electrode plate to form an electrode plate group. Two battery-regulated lead-acid batteries with a rated voltage of 2 V and a nominal capacity of 20 Ah (10 hour rate) are prepared, and one is used for measuring the barium content. Induction for measurement of positive electrode active material density after chemical conversion While measuring the barium content in the positive electrode active material after chemical conversion with a combined plasma mass spectrometer (model 7700S, manufactured by Agilent Technologies, Inc.), and using a pore distribution measuring device (manufactured by Shimadzu Corporation, Autopore III 9405) The density of the positive electrode active material after chemical conversion was measured, and the measurement results are shown in Table 1. In addition, the barium content and the positive electrode active material density in Table 1 are shown as average values of two positive electrode plates. Separately, a material that does not contain barium and has a positive electrode active material density of 4.2 g / cc after chemical conversion was also produced. Table 1 attaches the symbols a to t to the barium content, attaches the numbers 1 to 15 to the positive electrode active material density, and indicates each sample by a combination of the symbols and the numbers.

  Next, for another cycle life test, after discharging for 3 hours at a constant current of 0.07 CA (C is a current value corresponding to the nominal capacity) in an atmosphere at 25 ° C., 2.23 V A cycle in which charging is performed for 69 hours at a constant voltage of 1 is defined as 1 cycle, and the number of cycles when the voltage at the end of discharge falls below 1.8 V is measured. The results are shown in Table 2.

  The results of Table 1 and Table 2 above are plotted for each sample, with the barium content on the horizontal axis (X axis) and the positive electrode active material density after conversion on the vertical axis (Y axis). This is shown in FIG.

  Of the samples plotted in FIG. 1, the number of cycles of the sample (a13) containing no barium and having a positive electrode active material density of 4.2 g / cc after chemical conversion was 29. As a result of discriminating the combination of the barium content and the density of the positive electrode active material after chemical conversion with a cycle number of more than 29 as the present invention and the cycle number of 29 or less as a comparative example, the barium content Is 10 ppm, the positive electrode active material density is 3.3 g / cc, 3.8 g / cc, 4.2 g / cc (d4, d9, d13), the barium content is 24 ppm, and the positive electrode active material density is 3.2 g / cc, 4.2 g / cc samples (f3, f13), barium content of 33 ppm, positive electrode active material density of 3.6 g / cc (g7), barium content Sample (h2, h13) having an amount of 52 ppm and a positive electrode active material density of 3.1 g / cc, 4.2 g / cc, a barium content of 110 ppm and a positive electrode active material density of 4.1 g / cc Sample (j12), sample (k7) having a barium content of 120 ppm and a positive electrode active material density of 3.6 g / cc, barium content of 210 ppm and a positive electrode active material density of 3.1 g / cc Sample (m2), sample (n11) having a barium content of 240 ppm and a positive electrode active material density of 4.0 g / cc, barium content of 320 ppm and a positive electrode active material density of 3.4 g / cc Sample (o5), sample having barium content of 1000 ppm and positive electrode active material density of 3.1 g / cc, 3.4 g / cc, 3.8 g / cc (r2, r5 r9) is the present invention, a sample (b3) having a barium content of 5 ppm and a positive electrode active material density of 3.2 g / cc, a barium content of 6 ppm and a positive electrode active material density of 3.6 g / cc 4.2 g / cc samples (c7, c13), barium content 11 ppm, positive electrode active material density 3.2 g / cc, 4.3 g / cc samples (e3, e14), barium Sample (i1) having a content of 100 ppm and positive electrode active material density of 3.0 g / cc, sample (l15) having a barium content of 160 ppm and positive electrode active material density of 4.4 g / cc, Sample (o1) with a content of 320 ppm and a positive electrode active material density of 3.0 g / cc, a sample with a barium content of 490 ppm and a positive electrode active material density of 4.0 g / cc Sample (q12) having a barium content of 980 ppm and a positive electrode active material density of 4.1 g / cc, barium content of 1130 ppm and a positive electrode active material density of 3.2 g / cc It can be seen that sample (s3), sample (t10) having a barium content of 1180 ppm and a positive electrode active material density of 3.9 g / cc is a comparative example.

From FIG. 1, the barium content is 10 ppm or more and 1000 ppm or less on average per sheet, and the positive electrode active material density after conversion is 3.1 g / cc or more and 4.1 g on average per sheet. Of the range below / cc,
When the barium content is X and the active material density is Y,
−0.29 log X + 3.6 ≦ Y ≦ −0.29 log X + 4.7
It was found that those satisfying the condition exceeded 29 cycles.

  From FIG. 1, sample b3 (cycle number = 15), sample c7 (cycle number = 18) and sample c13 (cycle number = 21) having a barium content of less than 10 ppm and a cycle number of 29 or less are as follows: Even if the softening of the positive electrode active material by barium is insufficient, lead sulfate is generated on the surface of the positive electrode grid, and it is considered that the life performance has deteriorated early, even if the barium content exceeds 1000 ppm, the same In the sample s3 (cycle number = 27) and the sample t10 (cycle number = 25) in which a tendency is seen, the softening of the positive electrode active material has progressed too much, and the binding property between the positive electrode active materials is lowered, resulting in early life performance. It is thought that it fell.

  Further, from FIG. 1, sample i1 (cycle number = 27) and sample o1 (cycle number = 28) having a positive electrode active material density of less than 3.1 g / cc and having a cycle number of 29 or less are shown in FIG. It is conceivable that gaps are likely to be generated between the positive electrode active materials, and lead sulfate produced on the surface of the positive electrode lattice body enters the gaps, so that the life performance deteriorates early, and the positive electrode active material density after the formation is 4 Sample e14 (cycle number = 28) and sample l15 (cycle number = 22), which show the same tendency even when exceeding .2 g / cc, are less likely to cause a gap between the positive electrode active materials, and the electrolyte does not diffuse. It is conceivable that the positive electrode active material was insufficiently charged without being sufficiently performed.

  In FIG. 1, both the samples b3, c7, and c13 having a barium content of less than 10 ppm and the samples s3 and t10 having a barium content exceeding 1000 ppm have a larger number of cycles as the density of the positive electrode active material after chemical conversion increases. This is considered to be because the generated lead sulfate is difficult to enter the gap due to the high density of the positive electrode active material after chemical conversion.

  Further, in FIG. 1, sample e3 (cycle number = 28) and sample e14 (cycle number = 28) having a barium content of about 60 ppm or less had a positive electrode active material density of 3.1 g / cc or more after chemical conversion. However, although the number of cycles is 29 or less, it is difficult to form a gap between the positive electrode active materials, but because the barium content is small, it was not possible to sufficiently suppress the entry of lead sulfate into the generated gap. Sample p11 (cycle number = 28) and sample q12 (cycle number = 16) having a barium content of about 60 ppm or more had a positive electrode active material density of 4.2 g / cc or less after chemical conversion. However, when the number of cycles is 29 or less, the electrolyte solution is sufficiently diffused, but the softening of the positive electrode active material has progressed too much, and the binding property between the positive electrode active materials is lowered. It is conceivable that life performance is lowered.

  The above test was performed using a positive electrode plate having a thickness of 4.0 mm, but almost the same result was obtained even if the test was performed under the same conditions instead of the thicknesses of 2.0 mm and 6.0 mm. It was.

  As described above, the present invention relates to the positive electrode active material density after chemical conversion and the variability in the positive electrode active material. By finding an appropriate relationship with the content of um, it is possible to obtain a lead-acid battery that can contribute to an improvement in life performance, and thus its industrial applicability is great.

Claims (1)

A positive electrode plate holding a positive electrode active material containing barium is formed, and the positive electrode plate after conversion contains 10 ppm or more and 1000 ppm or less of barium on an average per sheet, and the active electrode plate after conversion is activated. When the average density per sheet is 3.1 g / cc or more and 4.2 g / cc or less, the barium content is X, and the active material density is Y,
−0 . 29logX + 3.6 ≦ Y ≦ −0.29 logX + 4.7
Lead acid battery characterized by satisfying.