JP6996274B2 - Lead-acid battery - Google Patents

Description

The present disclosure relates to lead acid batteries.

In recent years, various fuel efficiency improvement measures have been studied for automobiles in order to prevent air pollution or global warming. Vehicles with measures to improve fuel efficiency include, for example, micro-hybrid vehicles such as idling stop system vehicles (hereinafter referred to as "ISS vehicles") that reduce engine operating time, and power generation control vehicles that reduce alternator power generation by engine power. A car is being considered.

In lead-acid batteries, large current charging may be repeated due to regenerative charging or the like. When relatively deep charging / discharging is repeated, if the high rate discharging performance of the lead storage battery is insufficient, for example, when the engine is restarted after idling stop, the battery voltage drops and restarting cannot be performed. In particular, in recent years, it has become an important issue to improve low-temperature and high-rate discharge performance so that it can be used even in low-temperature areas such as those used below freezing point.

On the other hand, Patent Document 1 below discloses a technique for improving low temperature and high rate discharge performance by using a lignin sulfonate having a conjugated double bond as the lignin sulfonate contained in the negative electrode active material. ing.

Japanese Unexamined Patent Publication No. 9-147771

By the way, it is known that when high current charging is repeated in a lead storage battery, electrolysis of water in the electrolytic solution occurs. When electrolysis occurs, oxygen gas and hydrogen gas generated by the decomposition of water are discharged to the outside of the battery, so that the amount of water in the electrolytic solution is reduced. As a result, the concentration of sulfuric acid in the electrolytic solution increases, and the capacity decreases due to corrosion deterioration of the electrodes (positive electrode and the like). For this reason, when the amount of water in the electrolyte of the lead-acid battery decreases, it is necessary to replenish the reduced amount of water for maintenance. Therefore, lead-acid batteries are required to suppress the decrease (reduction) of water in the electrolytic solution from the viewpoint of maintenance-free, and in particular, suppress the decrease of the electrolytic solution in the overcharged state. Is required.

The present disclosure has been made in view of the above circumstances, and an object of the present invention is to provide a lead storage battery capable of suppressing a decrease in the electrolytic solution in an overcharged state.

In one aspect of the present disclosure, the positive electrode potential that gives an oxygen generation current of 5 mA / Ah in the overcharged state is 1.27 V or more with the mercury / primrose sulfate electrode as a reference electrode, and 5 mA / Ah in the overcharged state. Provided is a lead-acid battery having a negative electrode potential that gives a hydrogen generation current of −1.07 V or less with a mercury / primary mercury sulfate electrode as a reference electrode.

According to the lead storage battery according to one aspect of the present disclosure, it is possible to suppress the decrease of the electrolytic solution in the overcharged state.

According to the present disclosure, it is possible to provide a lead storage battery capable of suppressing a decrease in the electrolytic solution in an overcharged state. According to the present disclosure, it is possible to provide a micro-hybrid vehicle (for example, an ISS vehicle and a power generation control vehicle) equipped with such a lead storage battery. According to the present disclosure, the application of lead-acid batteries to micro-hybrid vehicles can be provided. According to the present disclosure, it is possible to provide an application of a lead storage battery to an ISS vehicle. According to the present disclosure, it is possible to provide an application of a lead storage battery to a power generation control vehicle.

It is a perspective view which shows the whole structure and the internal structure of the lead storage battery which concerns on one Embodiment. It is a perspective view which shows the electrode group of the lead storage battery which concerns on one Embodiment. It is a figure which shows the bag-shaped separator and the electrode accommodated in the bag-shaped separator. It is a figure which shows an example of a separator. It is sectional drawing which shows an example of the arrangement of a separator and an electrode plate. It is a figure which shows the relationship between the electrode potential and the amount of current. It is a figure which shows the relationship between the electrode potential and the amount of current.

Hereinafter, embodiments of the present disclosure will be described with reference to the drawings as appropriate. In the numerical range described stepwise in the present specification, the upper limit value or the lower limit value of the numerical range of one step can be arbitrarily combined with the upper limit value or the lower limit value of the numerical range of another step.

FIG. 1 is a perspective view showing the overall configuration and internal structure of the lead storage battery (liquid type lead storage battery) according to the present embodiment. As shown in FIG. 1, the lead-acid battery 1 according to the present embodiment includes an electric tank 2 having an open upper surface and a lid 3 for closing the opening of the electric tank 2. The battery case 2 and the lid 3 are made of polypropylene, for example. The lid 3 is provided with a positive electrode terminal 4, a negative electrode terminal 5, and a liquid port plug 6 for closing the liquid injection port provided in the lid 3.

Inside the battery case 2, there are an electrode group 7, a positive electrode column (not shown) connecting the electrode group 7 to the positive electrode terminal 4, a negative electrode column 8 connecting the electrode group 7 to the negative electrode terminal 5, and an electrolytic solution. Is housed. The electrolytic solution contains, for example, sulfuric acid. The electrolytic solution may further contain aluminum ions. The electrolytic solution containing aluminum ions can be obtained, for example, by mixing sulfuric acid and aluminum sulfate.

FIG. 2 is a perspective view showing the electrode group 7. As shown in FIG. 2, the electrode group 7 includes a positive electrode plate (positive electrode) 9, a negative electrode plate (negative electrode) 10, and a separator 11 arranged between the positive electrode plate 9 and the negative electrode plate 10. The positive electrode plate 9 has a positive electrode current collector 13 and a positive electrode active material filling portion 14, and the positive electrode active material is filled in the positive electrode current collector 13 to form the positive electrode active material filling portion 14. There is. The negative electrode plate 10 has a negative electrode current collector 15 and a negative electrode active material filling portion 16, and the negative electrode active material is filled in the negative electrode current collector 15 to form a negative electrode active material filling portion 16. There is. In the present specification, the positive electrode plate after chemical conversion from which the positive electrode current collector is removed is referred to as "positive electrode active material", and the negative electrode plate after chemical conversion from which the negative electrode current collector is removed is referred to as "negative electrode active material". ..

The electrode group 7 has a structure in which a plurality of positive electrode plates 9 and negative electrode plates 10 are alternately laminated in a direction substantially parallel to the opening surface of the electric tank 2 via a separator 11. The number of the positive electrode plate 9 and the negative electrode plate 10 in the electrode group 7 may be, for example, 7 negative electrode plates with respect to 6 positive electrode plates.

In the electrode group 7, the selvage portions 9a of the plurality of positive electrode plates 9 are collectively welded by the positive electrode side strap 17. Similarly, the selvage portions 10a of the plurality of negative electrode plates 10 are collectively welded by the negative electrode side strap 18. Then, each of the positive electrode side strap 17 and the negative electrode side strap 18 is connected to the positive electrode terminal 4 and the negative electrode terminal 5 via the positive electrode column and the negative electrode column 8.

The separator 11 is formed in a bag shape, and the negative electrode plate 10 is housed in the separator 11. FIG. 3 is a diagram showing a bag-shaped separator 11 and a negative electrode plate 10 housed in the separator 11. FIG. 4 is a diagram showing an example of a separator. FIG. 4A is a front view showing a sheet-like object 20 used for manufacturing the bag-shaped separator 11, and FIG. 4B is a cross-sectional view of the sheet-like object 20. FIG. 5 is a cross-sectional view of the separator 11 and the electrode plate (positive electrode plate 9 and negative electrode plate 10).

As shown in FIG. 4, the sheet-shaped object 20 includes a flat plate-shaped base portion 21, a plurality of convex ribs 22, and mini ribs 23. The base portion 21 supports the rib 22 and the mini rib 23. A plurality of ribs 22 are formed so as to extend in the longitudinal direction of the sheet-like object 20 at the center in the width direction of the sheet-like object 20. The plurality of ribs 22 are arranged substantially parallel to each other on one surface 20a of the sheet-like object 20. One end of the rib 22 in the height direction is integrated with the base portion 21, and the other end of the rib 22 in the height direction is in contact with the positive electrode plate 9 (see FIG. 5). The base portion 21 faces the positive electrode plate 9 in the height direction of the rib 22. No rib is arranged on the other surface 20b of the sheet-like material 20, and the other surface 20b of the sheet-like material 20 is in contact with the negative electrode plate 10 (see FIG. 5).

Next, the details of the positive electrode plate 9 and the negative electrode plate 10 will be described.

The positive electrode active material contains PbO ₂ as a Pb component, and further contains a Pb component other than PbO ₂ (for example, PbSO ₄ ) and an additive described later, if necessary. As will be described later, the positive electrode active material is obtained by aging and drying a positive electrode active material paste containing a raw material for the positive electrode active material to obtain an unchemical positive electrode active material, and then forming an unchemicald positive electrode active material. be able to. The raw material of the positive electrode active material is not particularly limited, and examples thereof include lead powder. The lead powder is, for example, lead powder produced by a ball mill type lead powder manufacturing machine or a barton pot type lead powder manufacturing machine (in a ball mill type lead powder manufacturing machine, a mixture of powder of the main component PbO and scaly metal lead). ). Lead tan (Pb ₃ O ₄ ) may be added as a raw material for the positive electrode active material.

The content of the Pb component in the positive electrode active material may be 90 to 100% by mass based on the total mass of the positive electrode active material. The positive electrode active material contains at least β-PbO ₂ as a Pb component. The positive electrode active material may contain α-PbO ₂ and may not contain α-PbO ₂ . The content of the positive electrode active material may be 40 to 60% by mass based on the total mass of the positive electrode plate.

The positive electrode current collector serves as a conductive path for the current from the positive electrode active material and holds the positive electrode active material. The positive electrode current collector has, for example, a grid pattern. Examples of the composition of the positive electrode current collector include lead alloys such as lead-calcium-tin alloys and lead-antimony-arsenic alloys. Selenium, silver, bismuth and the like may be appropriately added to the positive electrode current collector depending on the intended use. A positive electrode current collector can be obtained by forming these lead alloys in a grid pattern by a gravity casting method, an expanding method, a punching method, or the like.

In the process of manufacturing the positive electrode plate, for example, the positive electrode active material paste is filled in the positive electrode current collector and then aged and dried to obtain a positive electrode plate having an unchemicald positive electrode active material. The unchemical positive electrode active material may contain tribasic lead sulfate as a main component. The positive electrode active material paste contains, for example, a raw material for the positive electrode active material, and may further contain other predetermined additives and the like.

Examples of the additive contained in the positive electrode active material paste include carbon materials (excluding carbon fibers) and reinforcing short fibers (acrylic fibers, polyethylene fibers, polypropylene fibers, polyethylene terephthalate fibers, carbon fibers, etc.). Examples of the carbon material include carbon black and graphite. Examples of carbon black include furnace black, channel black, acetylene black, thermal black and ketjen black.

When producing the positive electrode active material paste, lead powder can be used as a raw material for the positive electrode active material. Further, from the viewpoint of shortening the chemical conversion time, lead tan (Pb ₃ O ₄ ) may be added as a raw material for the positive electrode active material. By filling the positive electrode active material paste in a positive electrode current collector (for example, a positive electrode current collector lattice) and then aging and drying, a positive electrode plate having an unchemical positive electrode active material can be obtained. In the positive electrode active material paste, the blending amount of the reinforcing short fibers may be 0.005 to 0.3% by mass based on the total mass of the raw materials of the positive electrode active material.

The positive electrode active material can be obtained, for example, by the following method. First, additives such as reinforcing staple fibers are added to the lead powder and mixed in a dry manner. Next, 4 to 10% by mass of water and 5 to 10% by mass of dilute sulfuric acid (specific gravity 1.28) are added to the mixture containing the lead powder and kneaded to prepare a positive electrode active material paste. Dilute sulfuric acid (specific gravity 1.28) may be added gradually in several portions in order to reduce heat generation. In the preparation of the positive electrode active material paste, sudden heat generation forms a positive electrode active material having a sparse structure, and the bonding force between the active materials during the life is reduced. Therefore, it is desirable to suppress heat generation as much as possible.

The positive electrode active material can be obtained by aging and drying a positive electrode active material paste containing a raw material for the positive electrode active material to obtain an unchemicald positive electrode active material, and then chemicalizing the unchemicald positive electrode active material. The positive electrode active material contains, for example, α-PbO ₂ and β-PbO ₂ .

By filling the positive electrode current collector (casted lattice body, expanded lattice body, etc.) with the positive electrode active material paste and then aging and drying, a positive electrode plate having an unchemical positive electrode active material can be obtained. In the positive electrode active material paste, the blending amount of the reinforcing short fibers is 0.05 to 0.3% by mass based on the total mass of lead powder (the total mass of lead powder and lead tan when lead tan is contained). It's okay.

The aging conditions may be 15 to 60 hours in an atmosphere with a temperature of 35 to 85 ° C. and a humidity of 50 to 98 RH%. The drying conditions may be 15 to 30 hours at a temperature of 45 to 80 ° C.

The negative electrode active material contains at least Pb as a Pb component, and if necessary, further contains a Pb component other than Pb (for example, PbSO ₄ ) and an additive described later. The negative electrode active material may contain porous spongy lead. As will be described later, the negative electrode active material is obtained by aging and drying a negative electrode active material paste containing a raw material for the negative electrode active material to obtain an unchemicald negative electrode active material, and then forming an unchemicald negative electrode active material. be able to. The raw material for the negative electrode active material is not particularly limited, and examples thereof include lead powder. The lead powder is, for example, lead powder produced by a ball mill type lead powder manufacturing machine or a barton pot type lead powder manufacturing machine (in a ball mill type lead powder manufacturing machine, a mixture of powder of the main component PbO and scaly metal lead). ).

The negative electrode current collector serves as a conductive path for the current from the negative electrode active material and holds the negative electrode active material. The composition of the negative electrode current collector may be the same as the composition of the positive electrode current collector described above.

In the process of manufacturing a negative electrode plate, for example, a negative electrode active material paste is filled in a negative electrode current collector (for example, a negative electrode current collector lattice) and then aged and dried to obtain a negative electrode plate having an unchemical negative electrode active material. .. As the negative electrode current collector, the same one as the positive electrode current collector can be used. The unchemical negative electrode active material may contain tribasic lead sulfate as a main component. The negative electrode active material paste contains, for example, a raw material for the negative electrode active material and a resin having a sulfo group and / or a sulfonic acid base, and may further contain other predetermined additives and the like.

The negative electrode active material paste may further contain a solvent and sulfuric acid. Examples of the solvent include water (for example, ion-exchanged water) and an organic solvent.

Resins having a sulfo group and / or a sulfonic acid base include lignin sulfonic acid, lignin sulfonate, and a condensate of phenols, aminoaryl sulfonic acid, and formaldehyde (for example, bisphenol, aminobenzene sulfonic acid, and formaldehyde. It may be at least one selected from the group consisting of (condensates of).

Examples of the additive contained in the negative electrode active material paste include barium sulfate, carbon material (excluding carbon fiber) and short reinforcing fiber (acrylic fiber, polyethylene fiber, polypropylene fiber, polyethylene terephthalate fiber, carbon fiber, etc.). .. Examples of the carbon material include carbon black and graphite. Examples of carbon black include furnace black, channel black, acetylene black, thermal black and ketjen black.

The negative electrode active material paste can be obtained, for example, by the following method. First, a mixture is obtained by mixing a resin having a sulfo group and / or a sulfonic acid base with lead powder and an additive added as needed. Next, sulfuric acid (dilute sulfuric acid or the like) and a solvent (water or the like) are added to this mixture and kneaded to obtain a negative electrode active material paste.

When barium sulfate is used in the negative electrode active material paste, the blending amount of barium sulfate may be 0.01 to 1% by mass based on the total mass of the raw materials of the negative electrode active material. When a carbon material is used, the blending amount of the carbon material may be 0.2 to 1.4% by mass based on the total mass of the raw material of the negative electrode active material. The blending amount of the resin having a sulfo group and / or a sulfonic acid base may be 0.01 to 2% by mass in terms of resin solid content based on the total mass of the raw material of the negative electrode active material.

The aging conditions may be 15 to 60 hours in an atmosphere with a temperature of 35 to 85 ° C. and a humidity of 50 to 98 RH%. The drying conditions may be 15 to 30 hours at a temperature of 45 to 80 ° C.

The lead-acid battery according to the present embodiment can be used for a micro-hybrid vehicle such as an ISS vehicle and a power generation control vehicle. The micro-hybrid vehicle according to the present embodiment (for example, an ISS vehicle and a power generation control vehicle) includes a lead storage battery according to the present embodiment.

The lead-acid battery according to the present embodiment is, for example, charged at a constant voltage in an overcharged state. The "overcharged state" is a state in which charging is continued from a fully charged state. The fully charged state can be obtained, for example, by charging the terminal voltage measured every 15 minutes while charging the 5-hour rate current I ₅ until the terminal voltage shows a constant value three times in a row (battery). Definition of full charge described in the industry association standard SBA S 0101: 2014). As will be described later, the lead-acid battery according to the present embodiment includes a positive electrode having a positive electrode potential giving an oxygen evolution current satisfying a specific range, and a negative electrode having a negative electrode potential giving a hydrogen generating current satisfying a specific range. The details will be described below.

When charging a lead-acid battery in an overcharged state, the following gas generation (positive electrode: oxygen generation, negative electrode: hydrogen generation), corrosion reaction, oxygen recombination reaction (Oxygen recombination), and the like occur. According to the findings of the present inventor, since the influence of the corrosion reaction in the overcharged state is small, the gas generation and the oxygen recombination reaction will be considered below.
(Positive electrode)
Oxygen evolution: H ₂ O ⇒ 1 / 2O ₂ + 2H ⁺ + ^2e-
Corrosion reaction: PbO ₂ + 2H ₂ O ⇒ Pb ₂ + 4H ⁺ + ^4e-
(Negative electrode)
Hydrogen generation: 2H ⁺ + 2e ^- ⇒ H ₂
Oxygen recombination reaction: 1 / 2O ₂ + 2H ⁺ + 2e ^- ⇒H _2O

When charging a lead storage battery in an overcharged state, the following equations (a) to (d) hold (I ⁺ _total : sum of currents derived from the electron transfer reaction (oxygen generation) at the positive electrode, I ^- _total : electron transfer at the negative electrode. Sum of currents derived from reactions (hydrogen generation and oxygen recombination reaction), I ⁺ _O2 : oxygen generation current at the positive electrode, I ^- _H2 : hydrogen generation current at the negative electrode, I ^- _O2rec : oxygen recombination reaction at the negative electrode Derived current).
(A) I ⁺ _total = I ^- _total
(B) I ⁺ _total = I ⁺ _O2
(C) I ^- _total = I ^- _H2 + I ^- _O2rec
(D) I ⁺ _O2 = I ^- _H2 + I ^- _O2rec

Further, the current related to the oxygen gas released to the outside of the battery is expressed by the following formula (e), and the current related to the hydrogen gas released to the outside of the battery is expressed by the following formula (f). As shown in the formulas (e) and (f), each of the currents related to the oxygen gas and the hydrogen gas released to the outside of the battery is expressed as the current obtained by subtracting I ^- _O2rec from I ⁺ _total . The currents are equal to each other (I ⁺ _O2Out = I ^- _H2Out ).
(E) I ⁺ _O2Out = I ⁺ _O2 -I ^- _O2rec = I ⁺ _total -I ^- _O2rec
(F) I ^- _H2Out = I ^- _H2 = I ^- _total -I ^- _O2rec = I ⁺ _total -I ^- _O2rec

Here, assuming that the influence caused by the oxygen recombination reaction is not taken into consideration (I ⁻ _O2rec = 0), the following formula (g) is satisfied. In this case, as shown in FIG. 6A, the liquid reduction rate A1 (when the voltage V) corresponds to the amount of gas released to the outside of the battery is “I ⁺ _O2 ”. FIG. 6A is a diagram showing the relationship between the electrode potential and the amount of current (when the influence caused by the oxygen recombination reaction is not taken into consideration).
(G) I ⁺ _O2Out = I ^- _H2Out = I ^- _H2 = I ⁺ _O2

However, as shown in the formulas (e) and (f), the oxygen recombination reaction contributes to the current (liquid reduction rate) related to the gas released to the outside of the battery, so that the liquid reduction rate is reduced. In order to do so, it is necessary to consider the effects caused by the oxygen recombination reaction. Here, according to the knowledge of the present inventor, about 50% of the generated oxygen gas tends to return to water by oxygen recombination (I ⁻ _O2rec = 0.5I ⁺ _O2 ), and the above formula (e) and The following formula (h) is obtained based on the formula (f). In this case, as shown in FIG. 6B, the liquid reduction rate A2 (when the voltage is V) is "0.5I ⁺ _O2 ", which is higher than the liquid reduction rate A1 because the influence of the oxygen recombination reaction contributes. Few. FIG. 6B is a diagram showing the relationship between the electrode potential and the amount of current (when the influence caused by the oxygen recombination reaction is taken into consideration).
(H) I ⁺ _O2Out = I ^- _H2Out = 0.5I ⁺ _O2

Then, the present inventor investigated the liquid depletion rate when the same voltage was applied when the relationship between the oxygen evolution potential at the positive electrode and the hydrogen evolution potential at the negative electrode was adjusted for the lead storage battery in the overcharged state. From the viewpoint of increasing the oxygen generation potential at the positive electrode (making it difficult to generate oxygen gas), the surface area of the positive electrode active material (for example, Pb component) is halved compared to the case of FIG. 6 (b) (FIG. 7 (Fig. 7). From the viewpoint of a)) and increasing the hydrogen generation potential in the negative electrode negatively (making it difficult to generate hydrogen gas), the surface area of the negative electrode active material (for example, Pb component) is halved as compared with the case of FIG. 6 (b). In this case (FIG. 7 (b)), at voltage V, the liquid reduction rate A2 in FIG. 6 (b) is 1, and the liquid reduction rate A3 in FIG. 7 (a) is 0.6, which is FIG. 7 (b). The liquid reduction rate A4 is 0.75. FIG. 7A is a diagram showing the relationship between the electrode potential and the amount of current (when the surface area of the positive electrode active material is halved). FIG. 7B is a diagram showing the relationship between the electrode potential and the amount of current (when the surface area of the negative electrode active material is halved). In the example of FIG. 7, adjusting the surface area of the positive electrode active material is more effective in reducing the liquid reduction rate than the surface area of the negative electrode active material.

As shown in the above calculation results of FIGS. 7 (a) and 7 (b), in order to reduce the liquid reduction rate at the same voltage, the oxygen generation potential at the positive electrode is positively increased (oxygen gas is generated). It is effective to make it difficult), and from the viewpoint of balancing with other battery performance (cycle characteristics, discharge characteristics, charge acceptability, etc.), the hydrogen generation potential at the negative electrode is made too large to be negative, and the positive electrode is used. It is effective not to make the oxygen generation potential in the negative too large. Then, the present inventor sets the values of the oxygen generation current and the hydrogen generation current (values that are sufficiently large and easy to observe and can be detected during actual use of the lead storage battery) of the lead storage battery, which makes it easy to compare the liquid reduction rate. Focusing on 5mA / Ah, which is an example of the oxygen generation current and hydrogen generation current in the overcharged state of 2.4V in a single cell, as a result of examining the potential to give the 5mA / Ah, in order to reduce the liquid reduction rate. We have found effective oxygen generation potential (positive electrode) and hydrogen generation potential (negative electrode). That is, in the lead storage battery according to the present embodiment, the positive electrode potential that gives an oxygen generation current of 5 mA / Ah in the overcharged state is 1.27 V or more with the mercury / primary mercury sulfate electrode as a reference electrode, and in the overcharged state. The negative electrode potential that gives a hydrogen generation current of 5 mA / Ah is −1.07 V or less with the mercury / lead-acid sulfate electrode as a reference electrode.

The positive electrode potential that gives an oxygen evolution current of 5 mA / Ah in the overcharged state is 1.27 V or more with the mercury / primary mercury sulfate electrode as a reference electrode from the viewpoint of suppressing the decrease in the electrolytic solution in the overcharged state. The positive electrode potential that gives the oxygen generation current is preferably 1.28 V or more, preferably 1.285 V or more, with the mercury / mercuric sulfate primary mercury electrode as a reference electrode from the viewpoint of further suppressing the decrease in the electrolytic solution in the overcharged state. More preferably, 1.29V or more is further preferable. The upper limit of the positive electrode potential that gives the oxygen evolution current may be, for example, 1.35V.

The negative electrode potential that gives a hydrogen generation current of 5 mA / Ah in the overcharged state is −1.07 V or less with the mercury / primary mercury sulfate electrode as a reference electrode from the viewpoint of suppressing the decrease in the electrolytic solution in the overcharged state. .. The negative electrode potential that gives the hydrogen generation current is preferably -1.08 V or less, preferably -1.09 V, with the mercury / mercuric sulfate primary mercury electrode as a reference electrode from the viewpoint of further suppressing the decrease in the electrolytic solution in the overcharged state. The following is more preferable. The lower limit of the negative electrode potential that gives the hydrogen generation current may be, for example, -1.15V.

The above-mentioned positive electrode potential and negative electrode potential are potentials in the lead storage battery after chemical conversion. When the lead-acid battery includes a plurality of single cells (single cells), the positive electrode potential and the negative electrode potential mean the positive electrode potential and the negative electrode potential of at least one single cell. When the lead-acid battery has a plurality of single cells, it is sufficient that the lead-acid battery has at least one single cell satisfying the above-mentioned positive electrode potential and negative electrode potential, and all of the single cells have the above-mentioned positive electrode potential and negative electrode potential. May be satisfied.

When a single cell has a plurality of positive electrodes (for example, a positive electrode plate), the positive electrode potential that gives the oxygen evolution current means the average value of the plurality of positive electrode potentials (potential of the positive electrode group). When a single cell has a plurality of positive electrodes, the positive electrode potential is measured by measuring the potential of a member (for example, the positive electrode terminal 4 in FIG. 1 or the positive electrode side strap 17 in FIG. 2) that collects electricity from the plurality of positive electrodes. Can be obtained. When a single cell has a plurality of negative electrodes (for example, a negative electrode plate), the negative electrode potential that gives the hydrogen generation current means an average value of the plurality of negative electrode potentials (potential of the negative electrode group). When a single cell has a plurality of negative electrodes, the negative electrode potential is measured by measuring the potential of a member (for example, the negative electrode terminal 5 in FIG. 1 or the negative electrode side strap 18 in FIG. 2) that collects current from the plurality of negative electrodes. Can be obtained.

The positive electrode potential that gives the oxygen generating current and the negative electrode potential that gives the hydrogen generating current adjust the surface area of the electroactive material (positive electrode active material or negative electrode active material), and the reaction of gas generation on the surface of the electrode active material. It can be adjusted by adjusting the sex.

When the surface area of the electrode active material is large, the absolute value of the gas generation potential is reduced as the reaction area is large, so that the above-mentioned gas generation current can be obtained at a potential of a smaller absolute value. The surface area of the electrode active material can be adjusted by adjusting the amount of the electrode active material or the like used, the amount of sulfuric acid used when producing the active material paste, and the like.

The reactivity of gas generation on the surface of the electrode active material can be adjusted by the constituent components of the electrode active material (carbon material, sulfo group and / or resin having a sulfonic acid base, etc.). For example, on the surface of a carbon material, hydrogen generation tends to proceed more easily than the Pb component. Therefore, as the content of the carbon material increases, the hydrogen generation potential is reduced, so that the above-mentioned hydrogen generation current can be obtained at a negative electrode potential having a smaller absolute value. Further, when the negative electrode active material contains a resin having a sulfo group and / or a sulfonic acid base in addition to the carbon material, the resin having a sulfo group and / or a sulfonic acid base is adsorbed on the carbon material to generate hydrogen. The generation is suppressed and the hydrogen generation potential increases. From this point of view, when the negative electrode active material contains a carbon material, the negative electrode active material may contain a carbon material and a resin having a sulfo group and / or a sulfonic acid base.

The amount of positive electrode active material (total amount of positive electrode active material when there are multiple positive electrodes) is larger than the amount of negative electrode active material (total amount of negative electrode active material when there are multiple negative electrodes). May be the same amount or less. The lower limit of the amount of the positive electrode active material may be 100 parts by mass or more, 110 parts by mass or more, or 120 parts by mass or more with respect to 100 parts by mass of the negative electrode active material. The upper limit of the amount of the positive electrode active material is 300 parts by mass or less, 250 parts by mass or less, 200 parts by mass or less, 150 parts by mass or less, 140 parts by mass or less, or 130 parts by mass or less with respect to 100 parts by mass of the negative electrode active material. May be.

The constant voltage charge in the overcharged state when evaluating the liquid reduction rate may be performed at a plurality of voltages. That is, the constant voltage charging may include a plurality of charging steps having different voltages, for example, a first charging step of the first voltage and a second charging step of the second voltage in this order. You may be prepared. In this case, it is sufficient that the above-mentioned positive electrode potential and negative electrode potential are satisfied in at least one charging step, and the above-mentioned positive electrode potential and negative electrode potential may be satisfied in all charging steps. The constant voltage charging may include another charging step (for example, a third charging step) after the first charging step and the second charging step described above. For example, the third charging step may be a charging step of a third voltage different from the first voltage and the second voltage, and may be a charging step of the same voltage as the first voltage. When the voltage of the third charging step is the same as the first voltage, it is sufficient that the positive electrode potential and the negative electrode potential described above are satisfied at least in the first charging step. Each charging step is not limited to being continuously performed, and other steps (constant current charging step, discharging step, resting step, etc.) may be performed between the charging steps.

The conditions for constant voltage charging are not particularly limited. The voltage for constant voltage charging (voltage for a single cell) may be, for example, 2.15 to 2.80 V. The temperature at the time of constant voltage charging may be, for example, 5 to 80 ° C. Constant voltage charging can be performed, for example, at a voltage of 2.40 V and 60 ° C. for a single cell based on the storage battery standard of a 14.4 V battery established by the German Association of the Automotive Industry (VDA: Verband der Automobilindustrie). The time for constant voltage charging (time for maintaining one voltage) may be, for example, 1 to 42 days.

Hereinafter, the present disclosure will be specifically described with reference to Examples. However, the present disclosure is not limited to the following examples.

<Making lead-acid batteries>
(Example 1)
[Preparation of positive electrode current collector]
As a positive electrode current collector, a plate-shaped lead-calcium-tin alloy (lead content: 0.05% by mass, calcium content: 0.5% by mass) is cut and stretched so as to widen the cut. The expanded lattice body prepared in the above was prepared. The positive electrode current collector had a width of 145 mm, a height of 110 mm, and a thickness of 0.9 mm.

[Manufacturing of unchemical positive electrode plate]
To the lead powder prepared by the ball mill method, 0.07% by mass of reinforcing short fibers (acrylic fibers) and 0.01% by mass of sodium sulfate were added and then dry-mixed. The blending amount of each of the acrylic fiber and sodium sulfate is based on the total mass of the lead powder. Next, 10% by mass of water and 9% by mass of dilute sulfuric acid (specific gravity 1.28) were added to the mixture containing the lead powder and then kneaded to prepare a positive electrode active material paste (water and dilute sulfuric acid). Each compounding amount is based on the total mass of lead powder). When preparing the positive electrode active material paste, dilute sulfuric acid was added stepwise in order to avoid a rapid temperature rise. Subsequently, the prepared positive electrode active material paste was filled in the positive electrode current collector obtained above, and aged in an atmosphere of a temperature of 50 ° C. and a humidity of 98% for 24 hours. As a result, an unchemical positive electrode plate in which the positive electrode current collector was filled with the unchemical positive electrode active material was obtained. In the unchemical positive electrode plate, the width of the filled portion was 145 mm, the height of the filled portion was 110 mm, and the thickness was 1.5 mm.

[Manufacturing of negative electrode current collector]
As a negative electrode current collector, a plate-shaped lead-calcium-tin alloy (lead content: 0.05% by mass, calcium content: 0.5% by mass) is cut and stretched so as to widen the cut. The expanded lattice body prepared in the above was prepared. The negative electrode current collector had a width of 145 mm, a height of 110 mm, and a thickness of 0.8 mm.

[Manufacturing of unchemical negative electrode plate]
To the lead powder prepared by the ball mill method, 0.1% by mass of reinforcing short fibers (acrylic fibers), 0.2% by mass of acetylene black, and 1.0% by mass of barium sulfate were added and then dry-mixed. The above-mentioned compounding amount is a compounding amount based on the total mass of lead powder. Next, 0.2% by mass of lignin sulfonate (trade name: Vanillex N, manufactured by Nippon Paper Industries, Ltd.) (in terms of resin solid content, the amount is based on the total mass of lead powder) and 10% by mass of water. % (The blending amount based on the total mass of the lead powder) was added and then kneaded. Subsequently, 9.5% by mass of dilute sulfuric acid (specific gravity 1.280) was added little by little based on the total mass of the lead powder and kneaded to prepare a negative electrode active material paste. Subsequently, the prepared negative electrode active material paste was filled in the negative electrode current collector obtained above, and aged in an atmosphere of a temperature of 50 ° C. and a humidity of 98% for 20 hours. As a result, an unchemical negative electrode plate in which the negative electrode current collector was filled with the unchemical negative electrode active material was obtained. In the unchemical negative electrode plate, the width of the filled portion was 145 mm, the height of the filled portion was 110 mm, and the thickness was 1.3 mm.

[Preparation of separator]
A separator (bag) formed by processing a sheet-like material having a plurality of convex ribs on one surface and a base portion supporting the ribs into a bag shape so that the surface on which the ribs are formed is on the outside. (See FIGS. 3 and 4). In the separator, the total thickness is 0.8 mm, the thickness T of the base portion is 0.2 mm, the height H of the rib is 0.6 mm, the upper bottom width B of the rib is 0.4 mm, and the rib. The bottom width A was 0.8 mm.

[Battery assembly]
An unchemical negative electrode plate was housed in the obtained bag-shaped separator. Next, 6 unchemical positive electrode plates and 7 unchemical negative electrode plates housed in a bag-shaped separator were alternately laminated so that the ribs of the separator were in contact with the unchemical positive electrode plates. In the above-mentioned production of the electrode plates, the total amount of the positive electrode active material in the six positive electrode plates was adjusted to 120 parts by mass with respect to 100 parts by mass of the total amount of the negative electrode active material in the seven negative electrode plates. Next, the current collecting portion of the unchemical positive electrode plate and the current collecting portion of the unchemical negative electrode plate were collectively welded to the positive electrode side strap and the negative electrode side strap for each polarity to obtain a electrode plate group. The thickness of the electrode plate group was 3.36 cm.

An electric tank having one cell chamber was prepared. After inserting the electrode plates into the cell chamber of the electric tank, the lid was heat-welded to the electric tank. Then, the liquid spout was opened, and dilute sulfuric acid (electrolyte) was poured into the cell from the liquid pouring port provided on the lid. Next, an electric tank was formed by energizing the battery at an ambient temperature of 40 ° C. and a current of 25 A for 20 hours to produce a single-cell lead-acid battery (corresponding to a D23 size single cell specified in JIS D5301). The specific gravity of the electrolytic solution after chemical conversion was adjusted to 1.29. The content of Pb component in the positive electrode after chemical conversion (based on the total mass of the positive electrode active material) is 99.9% by mass, and the content of the Pb component in the negative electrode after chemical conversion (based on the total mass of the negative electrode active material) is 98. It was 4% by mass.

(Comparative Example 1)
The same as in Example 1 except that the total amount of the positive electrode active material was increased and the total amount of the positive electrode active material in the 6 positive electrode plates was adjusted to 140 parts by mass with respect to 100 parts by mass of the total amount of the negative electrode active material in the 7 negative electrode plates. A lead storage battery was manufactured.

(Comparative Example 2)
Similar to Comparative Example 1 except that the total amount of the negative electrode active material was reduced and the total amount of the positive electrode active material in the 6 positive electrode plates was adjusted to 140 parts by mass with respect to the total amount of 80 parts by mass of the negative electrode active material in the 7 negative electrode plates. A lead storage battery was manufactured.

(Comparative Example 3)
The same as in Example 1 except that the total amount of the negative electrode active material was increased and the total amount of the positive electrode active material in the 6 positive electrode plates was adjusted to 120 parts by mass with respect to the total amount of 120 parts by mass of the negative electrode active material in the 7 negative electrode plates. A lead storage battery was manufactured.

<Measurement of oxygen evolution potential and hydrogen evolution potential>
The flow rate (gas flow rate) of oxygen gas and hydrogen gas released to the outside of the battery was measured by the following procedure. First, a tube was connected to the battery so that the generated gas would not leak. Moisture and sulfuric acid mist were removed from the gas by filling the tube with silica gel. Next, oxygen gas and hydrogen gas are collected, and a hydrogen concentration meter (HPS-100, manufactured by AMS), a gas flow meter (F-100D, DP-FLOW, manufactured by Bronkhorst) and an oxygen concentration connected in series to each other are collected. Oxygen gas and hydrogen gas were introduced into a meter (GMH3695 / GGO370, manufactured by Greisinger), and the flow rate, oxygen concentration and hydrogen concentration of the mixed gas were measured. Then, the flow rates of the oxygen gas and the hydrogen gas were obtained by multiplying the flow rate of the mixed gas by the concentration of each gas (oxygen concentration or hydrogen concentration).

The oxygen evolution potential (positive electrode) and the hydrogen evolution potential (negative electrode) were obtained by the following procedure based on the current I ⁺ _total or I ^- _total observed by the charge / discharge tester and the gas flow rate obtained above.

That is, since it is "I ^- _H2 = I ^- _H2Out " as shown in the equation (f), I ^- _H2Out obtained by converting the flow rate of the hydrogen gas discharged to the outside of the battery into a current is the hydrogen generation current. In the overcharged state, a voltage at which this hydrogen generation current becomes stable at 5 mA / Ah (voltage when the terminal voltage during charging measured every 15 minutes shows a constant value three times in a row) is applied, and at that time. The negative electrode potential of was obtained as the hydrogen generation potential. The negative electrode potential was determined by measuring the potential difference between the negative electrode terminal and the reference electrode. A mercury / mercuric sulfate primary mercury electrode was used as the reference electrode.

Further, since the relationship of the following formula (i) is established from the formula (e) and the formula (f), I ⁺ _O2Out and I ^- _H2Out obtained by converting the flow rates of oxygen gas and hydrogen gas released to the outside of the battery into currents. , The oxygen evolution current can be determined using the current I ⁺ _total or I ^- _total observed by the charge / discharge tester. In the overcharged state, a voltage at which this oxygen generation current stably reaches 5 mA / Ah (voltage when the terminal voltage during charging measured every 15 minutes shows a constant value three times in a row) is applied, and the voltage is applied. The positive electrode potential at that time was obtained as the oxygen generation potential. The positive electrode potential was determined by measuring the potential difference between the positive electrode terminal and the reference electrode. A mercury / mercuric sulfate primary mercury electrode was used as the reference electrode.
(I) I ⁺ _O2 = I ⁺ _O2Out + I ^- _O2rec = I ⁺ _O2Out + I ⁺ _total (or I ^- _total ) -I ^- _H2Out

<Evaluation of liquid reduction suppression performance>
At the atmospheric temperature (temperature of the water tank) of 60 ° C., constant voltage overcharging was performed at 2.4 V for 42 days. The mass of the electrolytic solution before and after this charging was measured, and the mass difference (the amount of liquid reduction due to overcharging (the amount of liquid reduction)) was compared to evaluate the liquid reduction suppressing performance.

Table 1 shows the oxygen evolution potential (positive electrode), the hydrogen evolution potential (negative electrode), and the liquid reduction rate (liquid reduction suppression performance). The liquid reduction suppressing performance was evaluated by a relative value with the liquid reduction amount in the overcharged state as 100 in Example 1. The smaller this value is, the better the liquid reduction suppressing performance is.

In Example 1, since the absolute values of the positive electrode potential that gives an oxygen evolution current of 5 mA / Ah and the negative electrode potential that gives a hydrogen evolution current of 5 mA / Ah are large, the amount of reduction of the electrolytic solution in the overcharged state is small. .. On the other hand, in Comparative Examples 1 and 2, since the positive electrode potential that gives an oxygen generation current of 5 mA / Ah is small, the amount of the electrolytic solution reduced in the overcharged state is large. In Comparative Example 3, since the absolute value of the negative electrode potential that gives a hydrogen generation current of 5 mA / Ah is small, the amount of reduction of the electrolytic solution in the overcharged state is large.

1 ... Lead-acid battery, 9 ... Positive electrode plate (positive electrode), 10 ... Negative electrode plate (negative electrode).

Claims (1)

The positive electrode potential that gives an oxygen evolution current of 5 mA / Ah in the overcharged state is 1.27 V or more with the mercury / mercuric sulfate primary mercury electrode as a reference electrode.
A lead-acid battery having a negative electrode potential that gives a hydrogen generation current of 5 mA / Ah in an overcharged state of −1.07 V or less with the mercury / primary mercury sulfate electrode as a reference electrode.

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