JP6688491B2 - Lead acid battery - Google Patents

Description

  The present invention relates to a lead storage battery, and more particularly to a lead storage battery that has a long life even when repeatedly deeply discharged.

There is a demand for longer operating times for forklifts, and in order to meet this demand from the side of lead-acid batteries, it is necessary to improve the life performance when deep discharge is repeated. Patent Document 1 (JP2013-218894A) uses acid-type lignin sulfonic acid instead of Na salt, the density of the negative electrode material is 3.7 g / cm ³ or more, and the electrode material contains 0.2 to 1.2 mass% of carbon. By doing so, it is disclosed that the life performance is improved. Patent Document 1 discloses an example in which the barium sulfate concentration in the negative electrode material is 0.6 mass%.

  Patent Document 2 (JP2010-529619A) discloses a preferable composition of the negative electrode material for each application of the lead storage battery. For industrial power applications such as forklifts, barium sulfate is contained at 1.4 to 2.25 mass%, which is a higher concentration than that for automobiles. This suggests that there is an empirical rule that high concentration barium sulfate is effective for repeated deep discharge.

JP2013-218894A JP2010-529619A

  An object of the present invention is to improve the life performance of a lead storage battery for a cycle in which deep discharge is repeated.

The lead acid battery of the present invention has a theoretical capacity of the electrolytic solution of 30% or more of the theoretical capacity of the negative electrode material, the negative electrode material contains more than 0 and less than 0.6 mass% barium sulfate, and further the density of the negative electrode material. Is higher than 3.6 g / cm ³ . Preferably, the theoretical capacity of the electrolytic solution is 40% or more of the theoretical capacity of the negative electrode material.

If the negative electrode material contains more than 0 and less than 0.6 mass% barium sulfate and the density of the negative electrode material is higher than 3.6 g / cm ^{3, the} amount of electricity equivalent to 30% or more of the theoretical capacity of the negative electrode material The capacity can be maintained high even if the discharge of is repeated (FIGS. 1 to 3). In addition, hereinafter, the discharge of the amount of electricity corresponding to 30% or more of the theoretical capacity of the negative electrode material, "discharge with a utilization rate of the negative electrode material of 30% or more" or "discharge with a negative electrode utilization rate of 30% or more" May be expressed as There is an empirical rule that the barium sulfate content should be higher in applications involving deep discharge (see, for example, Patent Document 2), and setting the barium sulfate content to less than 0.6 mass% exceeds this empirical rule. Is. Further, it is a finding obtained for the first time in the present invention that a combination of a specific barium sulfate content and a negative electrode material density higher than 3.6 g / cm ³ is important. For example, in Patent Document 1, the combination of the carbon content and the density of the negative electrode material is important.

  In the lead acid battery of this invention, since the theoretical capacity of the electrolytic solution is 30% or more of the theoretical capacity of the negative electrode material, it is possible to perform deep discharge such as discharge in which the utilization rate of the negative electrode material is 30% or more. . This battery can have a larger capacity than the theoretical capacity of the electrolyte solution is less than 30% of the theoretical capacity of the negative electrode material. The theoretical capacity of the electrolytic solution is preferably 40% or more of the theoretical capacity of the negative electrode material. This is because the amount of the sulfuric acid component remaining when the discharge reaction proceeds increases, so that the increase in the reaction overvoltage due to the decrease in the sulfuric acid concentration in the electrolytic solution is suppressed, and as a result, the higher lead-acid battery This is because the capacity can be increased. Since this effect is excellent, the theoretical capacity of the electrolytic solution is preferably 43% or more, more preferably 57% or more of the theoretical capacity of the negative electrode material. Since the lead storage battery of the present invention has a long life even if deep discharge is repeated, when a lead storage battery for a forklift, an electric vehicle, etc. is used, the operating time per cycle can be lengthened.

If the content and density of barium sulfate in the negative electrode material satisfy one of the following ranges, the life of the negative electrode material can be extended when deep discharge is repeated.
i) barium sulfate content greater than 0.1 mass% and density greater than 3.7 g / cm ³ ,
ii) Barium sulfate content greater than 0.2 mass% and density greater than 3.6 g / cm ^3.

When the content of barium sulfate and the density of the negative electrode material satisfy one of the following ranges, the life of deep discharge can be further extended.
i) barium sulfate content of less 0.15 mass% or more 0.5 mass%, and density of 3.8 g / cm ³ or more 4.0 g / cm ³ or less,
ii) Barium sulfate content of 0.3 mass% or more and 0.5 mass% or less and density of 3.7 g / cm ³ or more and 4.0 g / cm ³ or less

Preferably, the negative electrode material has a carbon content of 0.2 mass% or less, for example 0.2 mass% or less and 0.1 mass% or more. In Patent Document 1, the capacity is maintained by containing a high concentration of carbon, but in the present invention, the density of the negative electrode material is 3.6 / cm ³ or more, and the barium sulfate content is less than 0.6 mass% and more than 0. Therefore, the capacity can be maintained. And it does not require more than 0.2 mass% carbon.

  The lead-acid battery of the present invention can be used in applications including a discharging process in which the utilization rate of the negative electrode material is 30% or more, and particularly in applications in which the average utilization rate of the negative electrode material per cycle is 30% or more. . Preferably, it can be used in applications including a discharge process in which the utilization rate of the negative electrode material is 40% or more, and particularly in applications in which the average utilization rate of the negative electrode material is 30% or more per cycle.

  Further, by setting the theoretical capacity of the positive electrode material to, for example, 86% or more of the theoretical capacity of the negative electrode, deterioration of the positive electrode such as softening can be suppressed.

Characteristic diagram showing cycle test results when the negative electrode material density is 3.8 g / cm ³ and the barium sulfate concentration is 0.1 to 0.8 mass% Negative electrode material density 3.6 g / cm ³ and 3.7 g / cm ^3, characteristic diagram showing barium sulfate concentration is in 0.2~0.6mass%, the cycle test results Negative electrode material density 3.9 g / cm ³ and 4.0 g / cm ^3, characteristic diagram showing barium sulfate concentration is in 0.3~0.8mass%, the cycle test results A characteristic diagram showing the relationship between the content of barium sulfate and the ratio of the discharge capacity to the theoretical capacity of the negative electrode material at the 1400th cycle of discharge at a utilization rate of 44%. Characteristic diagram showing the relationship between the content of barium sulfate and the ratio of the discharge capacity to the theoretical capacity of the negative electrode material at the 1400th cycle of discharge at a utilization rate of 20%

  The best embodiment of the present invention will be described below. In carrying out the present invention, the embodiments can be appropriately modified according to the common sense of those skilled in the art and the disclosure of the prior art. In the examples, the negative electrode material may be referred to as a negative electrode active material, and the positive electrode material may be referred to as a positive electrode active material. The negative electrode plate is composed of a negative electrode current collector such as a negative electrode grid and a negative electrode material (negative electrode active material), and the positive electrode plate is composed of a positive electrode current collector such as a core metal and a positive electrode material (positive electrode active material). The solid components other than the current collector belong to the electrode material. In this specification, when a range is indicated by “to”, the upper limit and the lower limit are included.

Five paste type negative plates having a height of 300 mm, a width of 140 mm and a thickness of 3.5 mm and four tube type positive plates having the same outer shape and a tube diameter of 10 mm were respectively placed through a polyethylene micropore separator after tank formation. They were stacked to form a lead storage battery for forklifts. The density of the negative electrode material of the negative electrode plate and ^{3.6g / cm 3 ~4.0g / cm 3} , relative to the negative electrode material, 0.2 mass% of acetylene black as carbon, lignin sulfonate 0.2 mass%, the barium sulfate 0.1 A negative electrode plate containing ~ 0.8 mass% was prepared. The acetylene black may be replaced with other carbon black, and the kind of carbon is arbitrary. In addition, there was no significant difference in the results whether the sulfonic acid group of lignin sulfonic acid was H type bound with H ⁺ or Na type bound with Na ⁺ . Instead of ligninsulfonic acid, a sulfonated bisphenol condensate or the like may be used. The barium sulfate used had a peak particle size of 1.20 μm and a volume average particle size of 1.40 μm, but the properties such as the particle size are arbitrary.

The positive electrode active material was mainly composed of lead dioxide, and the theoretical capacity of four positive electrode plates was 710 ± 5 Ah and the theoretical capacity of five negative electrode plates was 575 ± 3 Ah. Attach the envelope-shaped separator to the negative electrode plate so as to enclose the three sides except the upper side, put the electrode group in the battery case, inject 2800 cm ³ (theoretical capacity about 357 Ah) of dilute sulfuric acid with a specific gravity of 1.28 (20 ° C), Trial batteries were manufactured for each 3 cells for each type of negative electrode plate.

  The theoretical capacity of the positive electrode material is preferably 86% or more of the theoretical capacity of the negative electrode. By doing so, it is possible to suppress the performance deterioration of the positive electrode plate due to the charge / discharge cycle. Since this effect is further improved, the theoretical capacity of the positive electrode material is preferably 114% or more, more preferably 125% or more of the theoretical capacity of the negative electrode. By suppressing the deterioration of the performance of the positive electrode plate due to the charge / discharge cycle, the life performance of the negative electrode plate has a large influence on the life performance of the entire battery, so that the significance of the present invention is increased.

The type of negative electrode active material is represented by a symbol such as "3D2". The leading "3" indicates that it contains 0.3 mass% of barium sulfate, and "D" indicates that the density of the already formed negative electrode active material is 3.8g / cm ³ , And "2" at the end indicates that the data is shown as an average of 2 cells. Density of the negative electrode active material noted previously Kasei, B is 3.6g / cm ^3, C is 3.7g / cm ^3, E is 3.9g / cm ^3, F is 4.0 g / cm ^3. For example, at 5C2, the already-formed negative electrode active material contains 0.5 mass% of barium sulfate and has a density of 3.7 g / cm ³ .

  The prototype battery was discharged at 45 A in a 30 ° C. water bath, and the amount of electricity discharged when the terminal voltage fell below 1.7 V was measured and found to be about 252 Ah regardless of the type of negative electrode plate. Therefore, the reference capacity of the battery was set to 252 Ah (44% in utilization rate (negative electrode utilization rate) with respect to the theoretical capacity of the negative electrode). The prototype battery was put into the following cycle life test. That is, in a 30 ℃ water tank, discharge is 67A current for 3 hours (negative electrode utilization rate 35%), charge is 48A current for 5 hours, cycle of alternately discharging and charging is repeated, 30 ℃, 45A every 100 cycles, A discharge capacity test with a final voltage of 1.7 V was performed. During the cycle life test, one cell of each battery was disassembled immediately before the 100th cycle discharge capacity test, and the BET specific surface area was measured. The BET specific surface area increased with the barium sulfate content, demonstrating that barium sulfate prevents the negative electrode active material from shrinking. In the above battery, the theoretical capacity of the electrolytic solution is about 62% of the theoretical capacity of the negative electrode material. With this configuration, a deep discharge that greatly exceeds the negative electrode utilization rate of 30% can be achieved.

  The remaining two cells were put into a cycle life test up to 1400 cycles, and the content of lead sulfate in the negative electrode active material was measured after 1400 cycles. Contrary to expectations, the lead sulfate content increased with the barium sulfate content, indicating that barium sulfate accumulates lead sulfate with repeated deep discharges. In addition, the behavior of the capacity up to 400 cycles and the behavior of the capacity after 1000 cycles are different, and a phenomenon in which the capacity is rapidly decreased from around 1000 cycles even in a battery with a stable capacity up to 400 cycles was observed. These facts suggest that at the 100th cycle, barium sulfate suppresses the decrease in the BET specific surface area and maintains the capacity, but at the 1400th cycle, barium sulfate promotes the accumulation of lead sulfate and decreases the capacity. .

Density of the negative electrode active material results in the D series of 3.8 g / cm ³ in FIG. 1, the results of the C series of B-series and 3.7 g / cm ³ of 3.6 g / cm ³ in FIG. 2, 3.9 g / the results of the F series of E-series and 4.0 g / cm ³ of cm ³ shown in FIG.

In the D series of Fig. 1, when the barium sulfate content is 0.1 mass%, the capacity decrease at the 100th cycle is remarkable, at 0.8mass%, the capacity decrease after the 300th cycle is remarkable, and at 0.6mass%, the capacity decrease after the 600th cycle. Was remarkable. When the barium sulfate content is 0.15 mass%, the capacity is low, but it is stable, suggesting that it is important to reduce the barium sulfate content for durability against repeated deep discharge. A high capacity was obtained at the 1400th cycle when the barium sulfate content was 0.15 mass% to 0.5 mass%, indicating that this range is optimal when the density is 3.8 g / cm ³ .

In the B series (density 3.6 g / cm ³ ) of the B series and the C series in FIG. 2, the capacity at the 1400th cycle was low regardless of the barium sulfate content. This indicates that when the density of the negative electrode active material is low, durability against repeated deep discharge cannot be obtained. In the C series (density 3.7 g / cm ³ ), the barium sulfate contents were 0.3 mass% (3C2) and 0.5 mass% (5C2), and the capacity at the 1400th cycle was high.

In the E series (density 3.9 g / cm ³ ) and F series (density 4.0 g / cm ³ ) in FIG. 3, if the barium sulfate content is 0.6 mass% or more, the 1400th cycle will be irrespective of the barium sulfate content. The capacity was low. On the other hand, the density of the negative electrode active material was 3.9 g / cm ³ , the barium sulfate content was 0.3 mass%, and the capacity at the 1400th cycle was high. As described above, it was common to all densities that the barium sulfate content was less than 0.6 mass%.

Of the above evaluation results, those and 3.6 g / cm ³ boiled for density of the negative electrode active material 3.8 g / cm ^3, respectively the relationship between the discharge capacity and the content of the barium sulfate 1400 cycle in FIG. 4 . As a comparison, Fig. 5 shows the result of separately evaluating the tendency when the depth of discharge is shallower. The results of FIG. 5 are obtained by changing the discharge condition of the above test to 20% of the theoretical capacity of the negative electrode material (that is, the negative electrode utilization rate of 20%). The discharge capacity at the 1400th cycle was evaluated by the ratio to the theoretical capacity of the negative electrode material.

  From FIG. 4, when the density of the negative electrode active material is 3.8 g / cm3 and when discharging is performed with the negative electrode utilization rate of 44%, the barium sulfate content is in the range of 0.4 mass% to 0.8 mass%, the content becomes small. Therefore, it can be seen that the discharge capacity at the 1400th cycle is greatly improved. On the other hand, it can be seen from FIGS. 4 and 5 that such a tendency is not observed in the case where the negative electrode density is 3.6 g / cm 3 or the discharge in which the negative electrode utilization rate is 20%. These include an electrolyte solution capable of discharging a capacity equivalent to 44% of the theoretical capacity of the negative electrode material, and the density of the negative electrode material is 3.8 g / cm3, and the barium sulfate content is reduced. It means that the effect of improving the life performance is remarkably obtained by reducing the amount.

  It is presumed that the above phenomenon is related to the degree of influence of barium sulfate on the conductivity of the negative electrode material. That is, since barium sulfate has low conductivity, when added to the negative electrode material, the conductivity of the negative electrode material decreases, but under certain conditions, this decrease is presumed to be the cause of accelerating lead sulfate accumulation. It At a shallow depth of discharge with a negative electrode utilization rate of about 20%, the entire negative electrode plate is in a substantially uniform discharge state, and the conductivity of the negative electrode material is high even during charging, so the addition amount of barium sulfate is 0.6 mass. If it is about%, the inside of the negative electrode material can maintain sufficient conductivity. This is also clear from the fact that the content of barium sulfate in the prior art is 1.4 to 2.25 mass%. Therefore, in the conventional lead-acid battery, the phenomenon that about 0.6 mass% barium sulfate accelerates the accumulation of lead sulfate does not occur. On the other hand, as in the above test, when the negative electrode utilization rate is discharged to a deep discharge depth such as 44%, the non-uniformity of the discharge state in the negative electrode plate becomes remarkable, and for example, locally exceeds 50%. Particularly, a part having a deep discharge depth is generated. In such a place, the conductivity of the negative electrode material during charging is particularly low, and it is difficult to accept charging. Under such circumstances, the effect of the decrease in conductivity due to the addition of barium sulfate is large, and it is presumed that the conductivity was decreased to such an extent that lead sulfate accumulation was accelerated.

  Considering based on such a mechanism, the effect of improving the life performance by reducing the content of barium sulfate is that the charge / discharge cycle including discharge in which the utilization rate of the negative electrode material is 30% or more, It is thought that it can be observed particularly clearly. Further, it is considered that it is more remarkably observed when discharging is performed so that the utilization factor of the negative electrode material is 40% or more. When a charge-discharge cycle including discharge in which the utilization rate of the negative electrode material is 30% or more is performed, lead sulfate accumulation is clearly recognized, and when the utilization rate of the negative electrode material is 40% or more. The lead sulfate accumulation becomes more pronounced. And, the situation in which lead sulfate is accumulated means that the conductivity of the active material is lowered in the charging process. Therefore, even if the addition amount of about 0.6 mass%, the conductivity of the entire active material, in particular, in the state where the non-uniformity of the discharge state in the negative electrode plate is remarkable, it becomes a particularly deep discharge depth. It is considered that barium sulfate has a great influence on the conductivity of the portion where it is present. In such a situation, it is estimated that by reducing the amount of barium sulfate, the accumulation of lead sulfate can be remarkably avoided or suppressed. Therefore, the effect is easily exerted in a battery in which the theoretical capacity of the electrolytic solution is 30% or more of the theoretical capacity of the negative electrode material, and is more prominent when the theoretical capacity is 40% or more.

  The effect that the life performance is improved by reducing the content of barium sulfate is not clear for the reason, but it is observed only when the density of the negative electrode material is higher than 3.6 g / cm 3. As shown in FIG. 4, the effect cannot be obtained when the density is 3.6 g / cm 3. On the other hand, it was confirmed that the same tendency was observed when the density of the negative electrode material was 3.7 g / cm3, 3.9 g / cm3 and 4.0 g / cm3. From these, it is estimated that this effect is obtained in the density range higher than 3.6 g / cm3.

  From the above, in the present invention, the effect of improving the life performance obtained by reducing the barium sulfate content, the theoretical capacity of the electrolytic solution is 30% or more of the theoretical capacity of the negative electrode material, and the negative electrode material It can be said that this is a phenomenon that is uniquely confirmed in lead-acid batteries with a density higher than 3.6 g / cm3. The present invention is of great significance in applications where the utilization rate of the negative electrode material is 30% or more, and is even more significant in applications where the utilization rate is 40% or more.

These results are contrary to the guideline of Patent Document 2 that the barium sulfate content in the negative electrode active material is increased in applications involving deep discharge such as for forklifts. Further, it is important to combine the barium sulfate content and the density of the negative electrode active material, it is important that the density of the active material is higher than 3.6 g / cm ³ , and the barium sulfate content is less than 0.6 mass%. It is shown that.

The discharge capacity at the 1400th cycle with respect to the theoretical capacity of the negative electrode is summarized in Table 1, and the gray area is the optimum area. Barium content sulfate may have less than 0.6 mass% with 0.1mass% greater, especially more than 0.15 mass% 0.5 mass% or less, the density of the negative electrode active material 3.8 g / cm ³ or more 4.0 g / cm ³ or less is optimal, density barium sulfate content is superior range of not more than 0.3 mass% or more 0.5 mass% at 3.7 g / cm ³ or more 3.8 g / cm ³ or less. Generalizing these things, it is preferable that the barium sulfate content is more than 0.1 mass% and less than 0.6 mass% and the density is more than 3.7 g / cm ^{3 and} 4.0 g / cm ³ or less. The range of more than 0.15 mass% and less than 0.6 mass% is preferable. It is also preferable that the barium sulfate content is more than 0.2 mass% and less than 0.6 mass% and the density is more than 3.6 g / cm ^{3 and} 4.0 g / cm ³ or less.

It was recognized that the life performance improved by the addition of barium sulfate is approximately proportional to the amount added, but within the preferable range described above, performance improvement exceeding the proportional relationship is recognized. That is, it can be seen from Table 1 that, for example, when the negative electrode density is 3.8 g / cm 3, the discharge capacity is improved from 25% to 31% when the barium sulfate content is changed from 0.1% to 0.15%. For comparison, it can be seen that when the negative electrode density is 3.6 g / cm 3, increasing the barium sulfate content by 0.1% tends to increase the discharge capacity by 1%. This tendency can also be seen in Fig. 4. These contrasting, or 0.15 mass% 0.5 mass% or less, to obtain the density of the negative electrode active material by a 3.8 g / cm ³ or more 4.0 g / cm ³ or less in the range, a remarkable effect as compared with the range You can see that it is being done. The same reason a density of 3.7 g / cm ³ or more that 3.8 g / cm ³ range barium sulfate content less not more than 0.3 mass% or more 0.5 mass% or less even remarkable effect is obtained can be seen.

  The above cycle test corresponds to operating the forklift at a negative electrode utilization rate of 35% in the daytime, charging it at night, and omitting even charging on weekends. Under this condition, the ability to maintain the capacity relative to the theoretical capacity of 30% or more for 1400 cycles makes the operating conditions harsh so that the negative electrode utilization rate exceeds 40%, and it is assumed that this will be compensated by equal charge on weekends. In this case, it is suggested that the lead-acid battery for forklift can be used for 5 years under the condition that the negative electrode utilization rate exceeds 40%.

  In addition to the lead-acid battery for a forklift, the present invention is preferably used as long as it has a negative electrode utilization rate of 30% or more and undergoes a discharging process. Further, according to the present invention, a lead storage battery having a rated capacity of 30% or more or 40% or more of the theoretical capacity of the negative electrode active material can be supplied to the market. Even if the user uses the lead storage battery such that 100% of the rated capacity is used up without additional charge, the reduction in capacity when repeatedly charged and discharged is suppressed.

  The quantification method of various materials in the present invention is shown. The lead storage battery after full charge is disassembled, the negative electrode plate is washed with water and dried to remove the sulfuric acid content, and the negative electrode material is collected. Negative electrode material was crushed, 300g / L concentration of hydrogen peroxide solution was added to 20mL per 100g of negative electrode material, and further 60mass% concentrated nitric acid was diluted with 3 times its volume of deionized water (1 + 3) nitric acid. Is added and heated under stirring for 5 hours to dissolve lead as lead nitrate. Then, the carbon black, barium sulfate, and the reinforcing material (if included) are separated by filtration.

The solid content obtained by filtration is dispersed in water. A sieve that does not allow reinforcement to pass through
Using a 1.4 mm sieve, pass the dispersion twice through a sieve to wash with water to remove the reinforcing material. Then, for example, centrifugation is performed at 3000 rpm for 5 minutes, carbon black is extracted from the supernatant and the upper precipitate, and barium sulfate is extracted from the lower precipitate. The barium sulfate and carbon black separated by the above series of operations are washed with water, dried and then weighed.

  The method for measuring the density of the negative electrode material in the present invention is shown below. After washing the already formed fully charged negative electrode electrode material with water and vacuum drying, separating it from the grid and pre-processing so as not to make mercury amalgam, fill the negative electrode material into a container for mercury penetration test, The mass is measured, and then the volume of the negative electrode material is measured when mercury is press-fitted so that the pores of 100 μm or more are filled with mercury. The density of the negative electrode material is calculated by dividing the mass of the negative electrode material by this volume.

Claims (5)

The theoretical capacity of the electrolytic solution is 30% or more of the theoretical capacity of the negative electrode material, the negative electrode material contains more than 0 and less than 0.6 mass% barium sulfate, the density of the negative electrode material is 3.6 g / cm ³ A lead-acid battery that is higher and more open type . The theoretical capacity of the electrolytic solution is 30% or more of the theoretical capacity of the negative electrode material, the negative electrode material contains more than 0 and less than 0.6 mass% barium sulfate, the density of the negative electrode material is 3.6 g / cm ³ A lead acid battery that is higher and for forklifts. The lead storage battery according to claim 1 or 2 , wherein the negative electrode material has a barium sulfate content and density satisfying any of the following ranges.
i) barium sulfate content greater than 0.1 mass% and density greater than 3.7 g / cm ³ ,
ii) Barium sulfate content greater than 0.2 mass% and density greater than 3.6 g / cm ^3. The lead storage battery according to claim 3 , wherein the negative electrode material has a barium sulfate content and a density satisfying any of the following ranges.
i) barium sulfate content of less 0.15 mass% or more 0.5 mass%, and density of 3.8 g / cm ³ or more 4.0 g / cm ³ or less,
ii) Barium sulfate content of 0.3 mass% or more and 0.5 mass% or less and density of 3.7 g / cm ³ or more and 4.0 g / cm ³ or less The lead storage battery according to any one of claims 1 to 4 , wherein the negative electrode material has a carbon content of 0.2 mass% or less.