JP6217928B2 - Lead acid battery and positive electrode plate thereof - Google Patents

Description

  The present invention relates to a lead-acid battery whose positive electrode material contains Sb element and a positive electrode plate thereof.

It is known that a positive electrode material of a lead storage battery contains an Sb element (Patent Document 1 JP 2013-140678 A). As for the Sb element in the positive electrode material, the following is known.
-Sb element increases the bond strength between particles of the positive electrode material. Thereby, the softening / dropping of the positive electrode material can be suppressed.
• Sb element increases self-discharge at the positive electrode and diffuses to the negative electrode to reduce hydrogen overvoltage.

JP2013-140678

The inventor examined the following possibilities. When composite particles in which a lead oxide core is coated with a segregation layer of an element different from lead such as Sb are added to the positive electrode material, the following effects can be expected.
-Since the different elements are unevenly distributed in the segregation layer at the start of use of the lead storage battery, the adverse effect of the different metal elements on the positive electrode material can be reduced.
-After the start of use, dissimilar elements gradually diffuse from the segregation layer to the entire positive electrode material, and exert effects such as strengthening the bond between the positive electrode material particles.
・ The lead oxide of the core is shielded by the segregation layer and does not participate much in the electromotive reaction until after the chemical conversion. However, as the dissimilar elements such as Sb diffuse during the charge / discharge cycle, the proportion of the lead oxide in the core that contributes to the electromotive reaction increases, and the decrease in the discharge capacity is delayed.

The inventor succeeded in producing a composite particle having a multilayer structure in which a lead oxide core is covered with a segregation layer of a different metal element such as Sb. When using a positive electrode material containing these composite particles,
・ The discharge capacity declines slowly due to use.
・ The decrease in strength of the positive electrode material due to use is slow,
・ Even with low-density positive electrode material, it is possible to suppress the loss of positive electrode material
I found out.

  An object of the present invention is to improve the performance of a lead storage battery and its positive electrode plate by composite particles in which a lead oxide core is coated with a segregation layer in which an element different from lead is segregated.

The present invention relates to a lead-acid battery having a positive electrode plate having a positive electrode material mainly composed of lead oxide (PbO ₂ ) and a current collector, a negative electrode plate, and an electrolyte, wherein the positive electrode material is lead acid The compound core includes composite particles covered with a segregation layer in which a metal element different from lead is segregated.

  The present invention also provides a positive electrode plate for a lead-acid battery having a positive electrode material mainly composed of lead oxide and a current collector, wherein the positive electrode material is a metal element whose lead oxide core is different from lead It contains composite particles covered with a segregating layer in which segregates.

  When the composite particles of the present invention are contained in the positive electrode material, the different metal elements are gradually contained in the positive electrode material during use, unlike the case where the different metal elements are uniformly distributed in the positive electrode material from the beginning. It spreads to show its function. For this reason, for example, the performance deterioration of the positive electrode plate after the start of use of the lead-acid battery can be delayed, and for example, the adverse effect of the dissimilar metal element at the start of use can be reduced. As long as the lead oxide of the core is coated on the segregation layer, the participation in the electromotive reaction is limited, and the participation in the electromotive reaction gradually increases after the use of the lead storage battery is started. For this reason, the same phenomenon as when a new positive electrode active material is added after the start of use occurs, and the life performance of the lead storage battery is improved. The total amount of the positive electrode material need not be composed of the composite particles of the present invention. A normal positive electrode material other than the composite particles supports the performance of the lead-acid battery at the start of use, and the composite particles of the present invention gradually exert an effect after the start of use. Therefore, the positive electrode material preferably includes both the composite particles of the present invention and the normal positive electrode material.

  When the dissimilar metal element is Sb, the concentration of Sb in the positive electrode material is 0.02 mass% or more and 0.5 mass% or less. The effect of the composite particles of the present invention is influenced by the concentration of different metal elements in the segregation layer, the thickness of the segregation layer, the density of the segregation layer, the presence or absence of the shell described later, and the above concentration range is absolute. Not something.

  Preferably, in at least some of the composite particles, the segregation layer is covered with a lead oxide layer (shell) from which a different metal element is not segregated. The lead oxide shell is involved in the electromotive reaction from the beginning, and delays the disappearance of the segregation layer. That is, the shell can delay the time when the different metal element of the segregation layer starts to act. When the shell is sufficiently thick, a positive electrode material made only of composite particles is also possible.

  Sb delays the decrease in the strength of the positive electrode material, thereby suppressing the falling off of the positive electrode material. Moreover, since the bond between the particles of the positive electrode material can be strengthened and the dropout can be reduced, the reduction in the discharge capacity is delayed. For the same reason, durability is improved when a low-density positive electrode material is used. When this invention is applied to a low-density positive electrode material, effects such as a reduction in the weight of the lead-acid battery and an improvement in the utilization factor of the positive electrode material can be obtained.

The present invention is characterized in that composite particles having a lead oxide core and a segregation layer such as Sb are used, and the content of the Sb element in the positive electrode material is arbitrary. The effect of the Sb segregation layer increases with the Sb concentration, and becomes significant when the concentration in the positive electrode material converted to Sb metal is 0.02 mass% or more, such as 0.04 mass% or more, and particularly 0.06 mass% or more. Further, when the concentration of Sb element exceeds 0.5 mass% in terms of metal, adverse effects of Sb such as an increase in self-discharge may appear. For this reason, the Sb content in the positive electrode material is preferably 0.02 mass% or more and 0.5 mass% or less, more preferably 0.04 mass% or more and 0.5 mass% or less, particularly preferably 0.06 mass% or more and 0.5 mass% or less, Most preferably, it is 0.1 mass% or more and 0.5 mass% or less. If the Sb segregation layer is covered with a lead oxide shell, the diffusion of the Sb element into the positive electrode material can be further delayed. Therefore, the above upper limit is not absolute. In this specification, Sb content is shown in terms of metal Sb, and the mass ratio of Sb: Sb ₂ O ₃ is about 1: 1.2.

The provision of a segregation layer of Sb element, presumably in the form of Sb, can slow down the strength of the positive electrode material, so that a low-density electrode material can be used. The density of the positive electrode material is preferably 3.1 g / cm ³ or more and 5.0 g / cm ³ or less, more preferably 3.1 g / cm ³ or more and 4.6 g / cm ³ or less. In the present invention, even in low-density positive electrode material such as ^{3.1g / cm 3 ~4.0g / cm 3} , can be reduced electrode material from falling off the positive electrode plate. As is well known, a low-density positive electrode material has a large capacity per mass. In this specification, PbO ₂ is mainly used as a positive electrode material containing an additive such as Sb element, and metal Pb is mainly used as an additive such as carbon, barium sulfate, synthetic fiber and lignin. This is called a negative electrode material. In the following examples, the electrode material is referred to as an active material.

Electron micrograph showing the structure of an unformed positive electrode active material (positive electrode material) in the lead storage battery of the example. Electron micrograph showing the structure of the formed positive electrode active material in the lead storage battery of the example The electron micrograph which shows the structure of the positive electrode active material in the lead acid battery of an Example EPMA photo showing element distribution in the positive electrode active material of lead-acid battery

  Hereinafter, an optimum embodiment of the present invention will be described. In carrying out the present invention, the embodiments can be appropriately changed in accordance with common sense of those skilled in the art and disclosure of prior art.

Preparation of positive electrode active material (positive electrode material) Lead powder is prepared by an appropriate method such as a ball mill method, a harding method, or a Burton pot method. The lead powder may contain lead or the like, and may contain a reinforcing agent such as synthetic fiber and an additive such as carbon. Sb element was added to the lead powder in the form of Sb ₂ O ₃ powder. Metal Sb powder, powders of other oxides such as Sb ₂ O ₅ , or compounds other than oxides such as Sb ₂ O ₂ SO ₄ and Sb ₂ (SO ₄ ) ₃ , containing Sb element Also good. An amount of sulfuric acid having a mass ratio of 4: 1 with the lead powder was added to the lead powder and kneaded to form a paste. Since the sulfuric acid was excessive as compared with the normal paste, the lead powder was not uniformly dispersed in the sulfuric acid, and the lead powder was agglomerated and formed into lumps, and the liquid portion was mainly composed of sulfuric acid and the lead powder concentration was low.

  The amount of sulfuric acid (total mass of sulfuric acid itself and water) is preferably 0.3 or more and 0.5 or less, for example, when the mass of lead powder is 1 when the specific gravity at 20 ° C. is 1.02 to 1.10. The added Sb element is considered to form composite particles by segregating so as to surround the lead powder particles that have become lumpy. From the lead powder paste containing Sb element, excess water is filtered off with a filter press, etc., then filled into a glass fiber tube that wraps the cored bar, dried and aged to obtain an unformed positive electrode plate . The core metal is a Pb—Sb—As alloy, but the composition is arbitrary.

The density of the paste affects the ease of filling and the density of the positive electrode active material. there,
As described above, the sulfuric acid is filtered off and adjusted to an appropriate density, and then packed.
・ Filtering and filling sulfuric acid at the same time.
・ Kneading with ordinary paste without composite particles,
Thereby, the density of a paste can be adjusted and the density of the positive electrode active material after chemical conversion can also be adjusted by this. In the last method, the Sb concentration can be adjusted simultaneously.

  To adjust the ratio of composite particles and other lead powder particles, for example, create a lead powder paste containing composite particles at a high concentration as described above, and create a lead powder paste other than composite particles by a regular method. These may be mixed. Further, by controlling the amount of Sb added, the concentration of the Sb element in the positive electrode active material was changed in the range of 0 mass% to 0.84 mass% in terms of Sb metal. Further, a positive electrode active material paste was prepared with a sulfuric acid amount according to a conventional method, and a positive electrode active material distributed uniformly without segregating Sb element was prepared. Further, the density of the positive electrode active material was changed by changing the density of the positive electrode active material paste at the time of filling.

Manufacture of lead-acid batteries
Carbon, barium sulfate, lignin, and a synthetic fiber reinforcing agent are added to lead powder to which no Sb element is added, and paste is formed with sulfuric acid having a mass ratio of 1: 0.2 to lead powder to obtain an unformed negative electrode active material paste. . The composition of the negative electrode active material is arbitrary. The negative electrode active material paste is filled in a current collector composed of a Pb-Sb lattice (composition is optional), dried and aged to form an unformed negative electrode plate, and the unformed positive electrode plate together with the unformed positive electrode plate. It was housed and a dilute sulfuric acid was added to form a battery case to obtain a clad lead acid battery (2V-165Ah / 5hR).

  The composition of the negative electrode active material, the formation conditions of the positive electrode active material and the negative electrode active material are arbitrary, and a paste type lead-acid battery may be used instead of the clad type, and whether it is a VRLA type or a liquid type is arbitrary. The feature of the present invention resides in the use of composite particles in which a lead oxide core is coated with a segregation layer of a different metal element such as Sb, and other points can be changed as appropriate. The segregation layer does not need to completely cover the core. For example, the segregation layer may cover the core except for a part thereof, such as a segregation layer that looks C-shaped on the image.

Composite Particles FIGS. 1 to 3 show electron micrographs in a cross section of a positive electrode active material including composite particles having a segregation layer of Sb element. FIG. 1 shows a cross section of an unformed positive electrode active material, in which a composite particle having a bright circular core and a dark coating layer covering the core is visible. FIG. 2 shows a cross-section of the preformed positive electrode active material, and composite particles in which a bright circular core is covered with a dark coating layer can be seen. In many of the composite particles shown in FIG. 2, the coating layer is coated with a bright lead oxide layer (shell). In FIG. 1 and FIG. 2, composite particles having a clear structure are selected and marked. However, many particles having a core covered with a dark coating layer can be seen.

FIG. 3 shows a cross section of the positive electrode active material after chemical conversion, a core made of dense PbO ₂ , a dark coating layer (Sb segregation layer of Sb element) around the core, and a shell made of dense PbO ₂ covering the coating layer. Can be seen. 1 to 3, the magnification is 85 times.

FIG. 4 shows the distribution of Pb element, S element, and Sb element measured by EPMA. The left column of the figure shows no Sb added, the central column shows 0.2 mass% of Sb concentration in the positive electrode active material (in this example, Sb ₂ O ₃ conversion), and the right column shows Sb ₂ O ₃ conversion in the positive electrode active material The concentration of is 0.7 mass%. In the middle row and the right row, a coating layer with a high concentration of Sb can be seen, and the Pb core can be seen inside.

Measurement method The observation method of composite particles, the measurement method of Sb concentration, etc. The composite particles can be confirmed by observing the cross section of the positive electrode plate with an electron microscope, and the segregation layer of Sb and the core of lead oxide (mainly PbO ₂ ) can be observed by EPMA. In the case of composite particles, the segregation layer decomposes with use, and therefore it is preferable to observe the composite particles before use or immediately after the use. To measure the Sb concentration, after charging, if necessary, the active material is separated from the positive electrode plate, the sulfuric acid is removed by washing with water and drying, and the dry weight of the active material is measured. Next, the Sb concentration is measured by atomic absorption or ICP, for example, by comparison with a standard sample. For the positive electrode active material that has been washed and dried, the density of the positive electrode active material is determined from the pore volume determined by, for example, a mercury intrusion method.

Performance of lead-acid battery The discharge performance of the lead-acid battery was measured. Next, in a 30 ° C environment, a cycle life test was conducted with a discharge of 0.25CA (41.25A) x 3h (DOD75%) and a charge of 0.18CA (29.7A) x 5h (120%). The discharge capacity of CA (33A) was measured. In addition, the battery was disassembled after the capacity test, and the strength of the positive electrode active material and the amount of the active material dropped after 1200 cycles were measured.

Tables 1 to 5 show the storage performance and battery life performance of the lead storage battery. In addition, Sb was added by two methods of adding uniformly by a conventional method and adding using composite particles, and the density of the positive electrode active material shown in Tables 1 to 4 was 3.3 g / cm ³ . When adding using composite particles, the lead storage battery is long by making the Sb concentration 0.02 mass% or more and 0.5 mass% or less, preferably 0.04 mass% or more and 0.5 mass% or less, particularly 0.06 mass% or more and 0.5 mass% or less. It was found that the service life was extended.

  The active material strength after the life test in Table 2 shows the positive electrode activity before and after the cycle life test in the case where Sb is uniformly added without generating composite particles and in the case where Sb is segregated in the composite particles. Indicates material strength. The positive electrode active material strength indicates the maximum force required until a cylindrical bar (for example, φ1 mm) of an arbitrary size is pressed against the positive electrode plate against the active material and penetrated or cracked. When composite particles having an Sb segregation layer were used, the decrease in the strength of the positive electrode active material could be delayed. When Sb was uniformly distributed at the same concentration as in the example (Sb: 0.17%), the strength was low from the beginning.

  Table 3 shows the relationship between the amount of Sb added and the amount of the positive electrode active material that had fallen off. The amount of Sb added is metal equivalent. The amount of the positive electrode active material falling off was measured by collecting the precipitate accumulated at the bottom of the battery case and the reduced deposit adhering to the negative electrode plate, washing with water, drying, and mass when performing the life cycle test. did. When composite particles having an Sb segregation layer are used, the amount of the positive electrode active material falling off decreases, so that the density of the positive electrode active material can be reduced. From Table 3, the dropout amount could be reduced as the Sb content increased. However, as shown in Table 1, the Sb content has a characteristic upper limit.

Table 4 shows the 5 hour rate capacity ratio at the end of the life test (after 1200 cycles) when Sb is uniformly added and when Sb is added as a deviated composite particle. In Tables 4 and 5, the 5-hour rate capacity ratio is shown with a conventional product having no active material Sb and an active material density of 3.80 g / cm ³ as 1. In any amount of Sb added, the life performance was further improved in the case where Sb was deflected in the composite particles than in the case where Sb was uniformly added.

Table 5 shows the relationship between the active material density, the additive addition method, and the capacity at the end of the life test. When Sb was not added, a significant decrease in capacity was confirmed with a low density electrode plate of 3.10 g / cm ³ or less, and comparison was not possible. In the case where Sb was uniformly added, the capacity at the end of life decreased to about 70% of the conventional product when the density was 3.10 g / cm ³ . On the other hand, in the case of the Sb composite particle addition of the example, the capacity could be maintained until the end of the life even when the density was 3.10 g / cm ³ . When the density was lower than 3.10 g / cm ³ and higher than 5.0 g / cm ³ , the effect of adding Sb was not observed.

The results in Tables 1 to 5 suggest the following effects.
• Sb is gradually released from the segregation layer. For this reason, a difference from the uniform addition of Sb occurs.
-Sb diffused from the segregation layer into the surrounding positive electrode active material strengthens the bond between the positive electrode active material particles and reduces the amount of the positive electrode active material falling off.
・ When Sb diffuses from the segregation layer to the surroundings, the core lead oxide is more involved in the electromotive reaction. A reduction in discharge capacity can be reduced by a synergistic effect between this fact and the ability to prevent the positive electrode active material from falling off.

Claims (5)

In a lead storage battery having a positive electrode plate having a positive electrode material mainly composed of lead oxide and a current collector, a negative electrode plate, and an electrolyte solution,
The lead-acid battery, wherein the positive electrode material contains composite particles in which a lead oxide core is covered with a segregation layer in which Sb is segregated. The lead storage battery according to claim 1, wherein the segregation layer is covered with a lead oxide layer in which the Sb is not segregated in at least some of the composite particles. The lead acid battery according to claim 1 or 2 , wherein the positive electrode material contains 0.02 mass% or more and 0.5 mass% or less of Sb in terms of Sb metal. The lead acid battery according to claim 1, wherein the density of the positive electrode material is 3.1 g / cm ³ or more and 5.0 g / cm ³ or less. A positive electrode plate for a lead storage battery having a positive electrode material mainly composed of lead oxide and a current collector,
The positive electrode plate for a lead-acid battery, wherein the positive electrode material includes composite particles in which a lead oxide core is covered with a segregation layer in which Sb is segregated.