JP6730406B2 - Lead acid battery - Google Patents

Description

The present invention relates to a lead storage battery.

2. Description of the Related Art In recent years, lead acid batteries for automobiles have been used severely due to an increase in electrical components and an improvement in fuel consumption. Therefore, lead-acid batteries for automobiles are required to have the performance to withstand severe use. In particular, idling stop cars (ISS cars) are rapidly becoming widespread, and the number of times a car is cranked is increasing.
On the other hand, a lead storage battery is operated in a partial state of charge (PSOC) in order to maintain high charge acceptability. Therefore, the SOC (State of charge; state of charge; charging rate: ratio of the remaining capacity to the full charge capacity) of the lead storage battery is always low. If the SOC is too low, the voltage drops sharply during cranking. Then, the engine may stop without ignition.

Further, when the SOC becomes low at a low temperature, the resistance of the electrolytic solution increases, and as a result, the engine may not start. In particular, in lead-acid batteries that have not been used for a long period of time, the SOC decreases due to self-discharge and sulfation (crystals of non-conductive lead sulfate swell on the negative electrode plate, and even when charged, this lead sulfate returns to spongy lead. It becomes easy to cause a situation in which electricity cannot be supplied.
Therefore, it is important to suppress sulfation and stratification in order to improve the performance of the lead storage battery, and various methods for suppressing sulfation and stratification have been proposed so far.
One of the methods is a method of adding a carbon material to the negative electrode active material.

In Patent Document 1, carbon black is added to the negative electrode active material in order to suppress sulfation. However, when the amount of addition is large, the negative electrode active material paste becomes hard and the negative electrode active material paste is used as a collector. It is described that it is difficult to fill the lattice.
In order to solve this problem, the amount of carbon black is limited to 1.0 mass% or more and 2.5 mass% or less per 100 mass% of spongy lead. Further, the bisphenol condensate is added at a ratio of 0.1 mass% or more and 0.9 mass% or less per 100 mass% of spongy lead. Furthermore, the median value of pore diameters on a volume basis (pore diameter of 50 vol% in cumulative distribution of pore diameters) is 0.5 μm or less, and porosity (pore diameter is 300 μm or less, pore volume is (Accumulated value) is 0.22 ml/g or more and 0.4 ml/g or less.

In Patent Document 2, carbon black is added to the negative electrode active material in order to suppress sulfation. However, addition of a large amount causes various problems, and therefore the addition amount is substantially active. It is described that only about 0.01 to 0.5 wt% of the substance can be used.
Then, in order to solve this problem, in the negative electrode plate, 0.01 to 1 wt% of carbon fibers or/and carbon whiskers is added to the negative electrode active material, and carbon powder is added to 0.01 to 10 wt% of the negative electrode active material. It is described to add. It is also described that carbon powder is loaded with a shrinkproofing agent.

Further, the applicant of the present invention discloses in Patent Document 3 that by adding powdery or fibrous carbon to the negative electrode, the carbon enters into the gap between the crystals of lead sulfate generated on the surface of the negative electrode to form a conductive path. However, it is disclosed that the effect of extending the life is limited and is insufficient for various industrial practical applications.
To solve this problem, 1 to 5 parts by weight of carbon is added to 100 parts by weight of the negative electrode active material, and 0.01 to 0.1 parts by weight of bismuth is added to 100 parts by weight of the negative electrode active material. It is proposed to add at least one selected from K, Ca, and Al to the sulfuric acid electrolytic solution in an amount of 5 to 50 g/l in terms of sulfate. When Al is added, 5 to 50 g/l in terms of sulfate corresponds to a ratio of aluminum ion concentration to carbon concentration of 0.016 ppm or more and 0.16 ppm or less.

As a method different from the method of adding a carbon material to the negative electrode active material and a method of suppressing sulfation, for example, the method described in Patent Document 4 can be mentioned.
In Patent Document 4, since the amount of the electrolytic solution contained in the active material can be increased by increasing the pore volume of the active material of the electrode plate, the rate of charge/discharge reaction occurring in the electrode plate increases, It is described that the progress of stratification can be delayed. Further, if the pore volume is simply increased, the active material density becomes low, so that the softening of the active material is accelerated in the positive electrode plate, and the binding force between the active materials is weakened in the negative electrode plate, resulting in a decrease in conductivity and a reaction. Is non-uniform and promotes stratification.

In order to solve this problem, the total volume Vp+Vn of the total pore volume Vp of the positive electrode active material and the total pore volume Vn of the negative electrode active material included in the electrode plate group, the volume Ve of the electrode plate group. (Vp+Vn)/Ve to 0.27 to 0.32, and the ratio Vp/Ve of the total pore volume Vp of the positive electrode active material to the volume Ve of the electrode plate group is 0.13 to 0. 15 is described. The volume Ve of the electrode plate group is calculated by the formula “Ve=(Sp+) using the electrode plate area Sp of the positive electrode plate, the electrode plate area Sn of the negative electrode plate, and the inner dimension D of the battery case in the electrode plate stacking direction of the electrode plate group. Sn)×D/2”.

Note that Patent Document 5 describes the pore volume of the negative electrode active material, although the purpose is different from the purpose of suppressing sulfation. Specifically, as a negative electrode plate for a lead storage battery capable of preventing an increase in trickle current, lead having a volume ratio of pores having a pore diameter of 2 μm or less with respect to the volume of all pores of the negative electrode active material is 50 to 70%. A negative electrode plate for a storage battery is described.
In Patent Document 5, when the pore diameter in the negative electrode active material is reduced, hydrogen gas is likely to remain in the pores of the negative electrode active material, and thus the electrolyte solution is less likely to enter the pores in the negative electrode active material, It is described that the apparent reaction area of the negative electrode active material decreases and the negative electrode overvoltage increases. Further, when the negative electrode overvoltage rises, the overvoltage of the positive electrode plate decreases during trickle charging, and the amount of oxygen gas generated from the positive electrode plate decreases.Therefore, by reducing the pore size in the negative electrode active material, the trickle current is reduced. It is described that the rise of the can be prevented.

However, the lead storage batteries described in Patent Documents 1 to 5 have room for improvement in terms of low-temperature starting characteristics in a low SOC state. Moreover, in Patent Documents 1 to 5, there is no description regarding the presence of aluminum ions in carbon added to the negative electrode active material (lead), and the mixture (composition containing lead and carbon) retained on the current collector is disclosed. ), there is no description about the ratio (Vt/Vs) of the total volume Vt of the holes whose hole diameter is 0.1 μm or more and 1.0 μm or less to the total volume Vs of all the holes present in (1).

Japanese Patent No. 6015427 JP, 9-283147, A Japanese Patent No. 3936157 Japanese Patent No. 6176180 Japanese Patent No. 3518123

An object of the present invention is to provide a novel lead acid battery having excellent low temperature starting characteristics in a low SOC state.

In order to solve the above problems, a lead storage battery of one embodiment of the present invention has a negative electrode that holds a mixture containing lead, carbon having pores, and aluminum ions, and is included in the mixture. The ratio (Ma/Mc) of the total mass Ma of the aluminum ions existing on the surface of the carbon and the aluminum ions existing in the pores to the mass Mc of the carbon is 10 ppm or more and 25 ppm or less. ..

ADVANTAGE OF THE INVENTION According to this invention, the novel lead acid battery excellent in the low temperature starting characteristic in the state where SOC is low is provided.

[One mode of lead-acid battery]
The lead-acid battery of one embodiment of the present invention contains “carbon having pores” in the mixture of the negative electrode so that the lead present around the carbon at the time of discharge is highly reactive sulfuric acid having a non-uniform crystal structure. Lead is produced. Further, the aluminum ions contained in the mixture of the negative electrode also make the crystal structure of lead sulfate non-uniform and increase the reactivity when lead changes to lead sulfate during discharge. The “aluminium ion existing on the carbon surface” includes the case where it is attached to the surface of carbon and the case where it is taken up in the carbon pores while being dissolved in the electrolytic solution.

Thereby, even if the SOC is low, the sulfation is suppressed and the deterioration of the charge/discharge performance is prevented. As a result, the low temperature starting characteristic in the state where the SOC is low is improved. If the ratio (Ma/Mc) is less than 10 ppm, this effect cannot be obtained. If the ratio (Ma/Mc) exceeds 25 ppm, the function of forming conductive paths by carbon having pores may be impaired, and the charge/discharge performance may deteriorate.
In the lead storage battery of one aspect, the ratio (Vt/Vs) of the total volume Vt of the holes having a hole diameter of 0.1 μm or more and 1.0 μm or less to the total volume Vs of all the holes present in the negative electrode mixture is: It is preferably 0.50 or more and 0.75 or less. As a result, the state of the hole in the negative electrode mixture becomes a state in which the sulfate ions of the electrolytic solution can be sufficiently diffused, and it is possible to cope with a sudden large-current charge/discharge, so that it can be charged even in a state where the SOC is low at a low temperature. Discharge reaction becomes possible. Therefore, it is possible to perform cranking that requires instantaneous large-current discharge even at a low temperature and a low SOC.

When discharged at a low current, the diffusivity of sulfate ions in the negative electrode mixture does not matter so much, but when discharged at a high current, the charge-discharge reaction in the part where sulfate ions are difficult to diffuse Is unlikely to occur. On the other hand, when the ratio (Vt/Vs) is 0.50 or more, the diffusivity of sulfate ions in the mixture of the negative electrode is high, and thus it is presumed that large current discharge is possible even in a low SOC state. It Further, when the ratio (Vt/Vs) is 0.70 or more, the diffusibility of sulfate ions in the mixture of the negative electrode becomes higher, which is more preferable.
If the ratio (Vt/Vs) exceeds 0.75, the strength of the negative electrode mixture may decrease, and the strength of the negative electrode may become insufficient.

[Embodiment]
Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to the embodiments described below. In the embodiments described below, technically preferable limitations are made for carrying out the present invention, but the limitation is not an essential requirement of the present invention.
The lead storage battery of the embodiment of the present invention has a conventionally known monoblock type battery case, a lid, and six electrode plate groups. The battery case is divided into six cell chambers by partition walls. The six cell chambers are arranged along the longitudinal direction of the battery case. One electrode plate group is arranged in each cell chamber. Each electrode plate group has a plurality of negative electrode plates and positive electrode plates, a separator, a negative electrode strap, a positive electrode strap, a negative electrode intermediate pole column rising from the negative electrode strap, and a positive electrode intermediate pole column rising from the positive electrode strap.

The negative electrode plate has a negative electrode substrate that holds a mixture containing a negative electrode active material, and ears that project upward from the negative electrode substrate. The positive electrode plate has a positive electrode substrate that holds a mixture containing a positive electrode active material, and ears that project upward from the positive electrode substrate. A plurality of negative electrode plates and positive electrode plates are alternately arranged with a separator interposed therebetween. The number M _n of negative electrode plates forming the electrode plate group is one more than the number M _p of positive electrode plates.
The mixture containing the negative electrode active material contains lead as the negative electrode active material, carbon black (carbon having pores), aluminum ions, reinforcing fibers and the like. Carbon black is contained in a proportion of 0.1 to 1.0 mass% with respect to lead.

Further, the ratio (Ma/Mc) of the total mass Ma of the aluminum ions existing on the surface of the carbon black and the aluminum ions existing in the pores to the mass Mc of the carbon black contained in the mixture containing the negative electrode active material. Is 10 ppm or more and 25 ppm or less. Furthermore, the ratio (Vt/Vs) of the total volume Vt of the holes having a hole diameter of 0.1 μm or more and 1.0 μm or less to the total volume Vs of all the holes existing in the mixture is 0.70 or more and 0.75 or more. It is below.
The mixture containing the positive electrode active material has the same structure as the conventional product. Specifically, it contains lead dioxide, which is a positive electrode active material, and reinforcing fibers.
The negative electrode substrate and the ears and the positive electrode substrate and the ears are integrally formed of an alloy mainly containing lead. Further, in each cell chamber, the negative electrode strap and the positive electrode strap are arranged above all the negative electrode plates and the positive electrode plates, and the ears of the same polarity are connected to each other in the thickness direction of the electrode plate group.

The lead storage battery can be manufactured by a conventionally known method, for example, by the following method.
First, a negative electrode plate and a positive electrode plate before forming the electrode plate group are formed. The negative electrode plate before formation is made by forming a current collector in the form of a lead alloy on the grid-shaped negative electrode substrate with the ears integrated, filling the negative electrode substrate grid with the negative electrode mixture forming paste, and then drying. And by aging. As the paste for forming the negative electrode mixture, a paste containing water, lead as the negative electrode active material, carbon black, reinforcing fibers and the like is prepared.
Examples of “carbon having pores” other than carbon black include carbon nanotubes, activated carbon, fullerenes and the like.

By using carbon black having a specific surface area of 50 to 800 m ² /g, the ratio (Ma/Mc) of the aluminum ions adhering to the surface of the carbon black and entering the pores in the battery case formation described below is 10 ppm or more. It can be set to 25 ppm or less.
Further, for example, by adjusting the water content of the paste for forming a negative electrode mixture before filling and the amount of sulfate ions to be mixed with this paste, and performing aging, drying, and chemical conversion according to conventionally known conditions, the mixture after chemical conversion The ratio (Vt/Vs) of the total volume Vt of holes having a hole diameter of 0.1 μm or more and 1.0 μm or less to the total volume Vs of all holes existing in the agent is 0.70 or more and 0.75 or less. .. When adjusting the content of water and the amount of sulfate ions with respect to the amount of lead powder in order to set the ratio (Vt/Vs) to a predetermined value, the ratio (Vt/Vs) increases as the content of water increases. The more sulfate ions, the smaller the tendency.

The positive electrode plate before formation is made by forming a current collector in the form of ears integrated on a grid-like positive electrode substrate with a lead alloy, filling the positive electrode mixture forming paste in the positive electrode substrate grid, and then drying. And by aging. As the paste for forming the positive electrode mixture, a paste containing water, lead dioxide as the positive electrode active material, and reinforcing fibers is prepared.
The positive electrode plate and the negative electrode plate before chemical conversion are alternately laminated with a separator made of polyethylene or the like sandwiched therebetween to obtain a laminate (a group of electrode plates on which no strap is formed). At this time, after sandwiching the positive electrode plate or the negative electrode plate between separators, the left and right ends may be sealed with a gear seal or the like to form a bag-shaped separator.

Next, after arranging this laminated body in each cell chamber of a battery case, the positive electrode strap which the ears of the positive electrode plate were connected and the ears of the negative electrode plate were connected using the COS (cast on strap) type casting device. Form the negative electrode strap.
Next, resistance welding is performed to electrically connect the adjacent cells in series while the electrode plate group is arranged in each cell chamber of the battery case. Next, the upper surface of the battery case and the lower surface of the lid are melted by heat, the lid is placed on the battery container, and the lid is fixed to the battery container by heat welding. When the lid is placed on the battery case, the pole is passed through the through hole of the lid.

After that, after injecting the electrolytic solution (containing aluminum ions by adding aluminum sulfate to sulfuric acid) into the cell chamber through the injection hole provided as a hole penetrating the lid, the injection hole is closed, etc. The assembly of the lead-acid battery is completed by performing the normal process of. Then, by performing battery case formation under normal conditions, the electrolytic solution enters the holes existing in the mixture of the negative electrode plate and the positive electrode plate, and aluminum ions adhere to the surface of carbon black forming the mixture of the negative electrode plate. At the same time, aluminum ions are taken into the pores of carbon black while being dissolved in the electrolytic solution.

In the lead acid battery of this embodiment, the mixture of the negative electrode plate contains carbon black and aluminum ions, and the aluminum ions present on the surface of the carbon black and the aluminum present in the pores with respect to the mass Mc of the carbon black. The ratio (Ma/Mc) of the total mass Ma of ions is 10 ppm or more and 25 ppm or less.
In the lead-acid battery of this embodiment, by including carbon black in the mixture of the negative electrode plate, lead sulfate having a non-uniform crystal structure is generated by lead existing around the carbon black during discharge. The aluminum ions contained in the mixture of the negative electrode plate also make the crystal structure of lead sulfate non-uniform when lead changes to lead sulfate during discharge. As a result, in the lead storage battery of this embodiment, sulfation is suppressed and charging/discharging is possible even when the SOC is low. As a result, the low temperature starting characteristic in the state where the SOC is low is improved.

Furthermore, the ratio (Vt/Vs) of the total volume Vt of the holes having a hole diameter of 0.1 μm or more and 1.0 μm or less to the total volume Vs of all the holes existing in the mixture is 0.70 or more and 0.75 or more. It is below. Therefore, the lead acid battery of this embodiment can discharge a large current even at a low temperature and a low SOC.
In the above embodiment, a negative electrode plate before chemical conversion is prepared using a negative electrode mixture-forming paste that does not contain aluminum ions, and chemical conversion is performed with an electrolytic solution containing aluminum ions, so that the mixture of the negative electrode plate is formed of aluminum. However, aluminum ions may be added to the mixture of the negative electrode plate before formation using a paste for forming a negative electrode mixture containing aluminum ions.

In that case, for example, a mixture of an aqueous solution of aluminum sulfate (concentration: 0.1 mol/l) at a ratio of 2 ml/g with respect to carbon black is used as another material for the negative electrode mixture forming paste (water and , And a lead, which is a negative electrode active material, and a reinforcing fiber) to prepare a negative electrode mixture forming paste to which aluminum ions are added. In this case, the formation may be performed with an electrolytic solution containing no aluminum ion or with an electrolytic solution containing aluminum ion.
If the addition of aluminum ions to either the paste or the electrolytic solution is carried out alone, or if both are carried out, if the total aluminum ion concentration used for the addition is the same, The total amount of aluminum ions existing on the surface and in the pores is the same. Therefore, aluminum ion addition may be performed by any of the above methods.

[Preparation of test battery]
As lead-acid batteries having the same structure as the lead-acid battery of the embodiment, lead-acid batteries No. 1 to No. 20 were prepared. Specifically, a M-42 type (external dimensions and terminal shape is the same as JIS B20) liquid id lead-acid battery for idling stop, a lead-acid battery with a 20-hour capacity of 40 Ah and an operating voltage of 12 V was produced.
As shown in Table 1, the lead-acid batteries of Samples No. 1 to No. 20 differ from each other in at least one of the ratio (Ma/Mc) and the ratio (Vt/Vs) of the negative electrode mixture. All other points have the same configuration.

<Preparation of positive electrode plate and negative electrode plate before formation>
<<Preparation of substrate>>
Using a Pb-Ca-Sn alloy, a base material for a positive electrode plate and a negative electrode plate (a current collector in which ears are integrated with a grid-shaped substrate) was produced.
Specifically, the positive electrode base material is a JIS-B size gravity cast substrate with a weight of about 35 g per sheet, and the negative electrode base material is a JIS-B size continuous cast substrate per sheet. It was made with a weight of about 32 g. In addition, the grid design of the substrate was determined by the current/potential analysis simulation so that the potential distribution was as uniform as possible while considering the castability and the amount of lead. Specifically, the amount of lead in the area around the ears where current concentrates was increased, and the grid design was designed so that the radiating points were centered on the ears.

<<Preparation of paste for forming positive electrode mixture>>
For 100 parts by weight of lead powder for a battery (mixed powder of lead and lead oxide having a particle size of several μm to several 30 μm, and a mixing ratio by mass ratio of lead:lead oxide=about 25:75), 0.07 parts by weight of bismuth oxide powder and 0.1 parts by weight of polyester fiber (reinforcing fiber) were added and mixed. An aqueous sulfuric acid solution having a specific gravity D of 1.37 at 20° C. is added to the mixture thus obtained so that the sulfuric acid content is 5.41 parts by weight with respect to 100 parts by weight of the lead powder, and the mixture is kneaded. Thus, a positive electrode mixture forming paste was obtained. The water content of this positive electrode mixture forming paste was 16.0 parts by mass with respect to 100 parts by mass of the lead powder. The obtained paste was filled in the above-mentioned grid-shaped substrate of the base material, and an aging and drying step was performed under normal conditions to obtain a positive electrode plate before chemical conversion.

<<Preparation of paste for forming negative electrode mixture>>
(Sample No.1)
For 100 parts by weight of lead powder for a battery (mixed powder of lead and lead oxide having a particle size of several μm to several 30 μm, and a mixing ratio by mass ratio of lead:lead oxide=about 25:75), 0.2 parts by weight of carbon black having a specific surface area of 5 m ² /g (10 m ² /g or less), 1.0 part by weight of barium sulfate, and 0.1 parts by weight of polyester fiber (reinforcing fiber) were added. Mixed.
After adding an aqueous lignin solution containing 0.2 parts by weight of lignin to 100 parts by weight of lead powder, the specific gravity D at 20° C. was 1.37. A certain sulfuric acid aqueous solution was added to 100 parts by weight of lead powder so that the sulfuric acid content was 4.15 parts by weight and kneaded to obtain a paste for forming a negative electrode mixture. The water content of this negative electrode mixture forming paste was 21.0 parts by mass with respect to 100 parts by mass of lead powder.
The obtained paste was filled in the above-mentioned matrix substrate of the base material, and an aging and drying step was performed under normal conditions to obtain a negative electrode plate before chemical conversion.

(Sample No.2)
When the lignin aqueous solution was added, the amount of water was made smaller than that of Sample No. 1 to obtain a negative electrode mixture forming paste having a water content of 20.0 parts by mass relative to 100 parts by mass of lead powder. A negative electrode plate before chemical conversion was produced in the same manner as in Sample No. 1 except that this paste was used.
(Sample No.3)
When the lignin aqueous solution was added, the amount of water was made smaller than that of Sample No. 2 to obtain a negative electrode mixture forming paste having a water content of 19.5 parts by mass with respect to 100 parts by mass of lead powder. A negative electrode plate before chemical conversion was produced in the same manner as in Sample No. 1 except that this paste was used.

(Sample No.4)
When the lignin aqueous solution was added, the amount of water was made smaller than that of Sample No. 3, to obtain a negative electrode mixture forming paste having a water content of 19.0 parts by mass relative to 100 parts by mass of lead powder. A negative electrode plate before chemical conversion was produced in the same manner as in Sample No. 1 except that this paste was used.
(Sample No.5)
When the lignin aqueous solution was added, the amount of water was made smaller than that of Sample No. 4, to obtain a negative electrode mixture forming paste having a water content of 18.0 parts by mass with respect to 100 parts by mass of lead powder. A negative electrode plate before chemical conversion was prepared in the same manner as in Sample No. 1 except that this paste was used.

(Sample No.6)
The water content is 21.0 parts by mass with respect to 100 parts by mass of the lead powder by the same method as in Sample No. 1 except that carbon black having a specific surface area of 70 m ² /g was used as the carbon black to be added. A negative electrode mixture forming paste was obtained. A negative electrode plate before chemical conversion was prepared in the same manner as in Sample No. 1 except that this paste was used.
(Sample No.7)
The water content is 20.0 parts by mass with respect to 100 parts by mass of the lead powder by the same method as in Sample No. 2 except that carbon black having a specific surface area of 70 m ² /g was used as the carbon black to be added. A negative electrode mixture forming paste was obtained. A negative electrode plate before chemical conversion was produced in the same manner as in Sample No. 1 except that this paste was used.

(Sample No.8)
The water content is 19.5 parts by mass with respect to 100 parts by mass of the lead powder by the same method as in Sample No. 3, except that carbon black having a specific surface area of 70 m ² /g was used as the carbon black to be added. A negative electrode mixture forming paste was obtained. A negative electrode plate before chemical conversion was prepared in the same manner as in Sample No. 1 except that this paste was used.
(Sample No.9)
The water content is 19.0 parts by mass with respect to 100 parts by mass of the lead powder by the same method as in Sample No. 4, except that carbon black having a specific surface area of 70 m ² /g was used as the carbon black to be added. A negative electrode mixture forming paste was obtained. A negative electrode plate before chemical conversion was prepared in the same manner as in Sample No. 1 except that this paste was used.

(Sample No.10)
The water content is 18.0 parts by mass with respect to 100 parts by mass of the lead powder by the same method as in Sample No. 5, except that carbon black having a specific surface area of 70 m ² /g was used as the carbon black to be added. A negative electrode mixture forming paste was obtained. A negative electrode plate before chemical conversion was prepared in the same manner as in Sample No. 1 except that this paste was used.
(Sample No.11)
The water content is 21.0 parts by mass with respect to 100 parts by mass of the lead powder by the same method as in Sample No. 1 except that carbon black having a specific surface area of 800 m ² /g was used as the carbon black to be added. A negative electrode mixture forming paste was obtained. A negative electrode plate before chemical conversion was prepared in the same manner as in Sample No. 1 except that this paste was used.

(Sample No.12)
The water content is 20.0 parts by mass relative to 100 parts by mass of the lead powder by the same method as in Sample No. 2 except that carbon black having a specific surface area of 800 m ² /g was used as the carbon black to be added. A negative electrode mixture forming paste was obtained. A negative electrode plate before chemical conversion was prepared in the same manner as in Sample No. 1 except that this paste was used.
(Sample No.13)
The water content is 19.5 parts by mass with respect to 100 parts by mass of the lead powder in the same manner as in Sample No. 3, except that carbon black having a specific surface area of 800 m ² /g was used as the carbon black to be added. A negative electrode mixture forming paste was obtained. A negative electrode plate before chemical conversion was prepared in the same manner as in Sample No. 1 except that this paste was used.

(Sample No.14)
The water content is 19.0 parts by mass with respect to 100 parts by mass of the lead powder in the same manner as in Sample No. 4, except that carbon black having a specific surface area of 800 m ² /g was used as the carbon black to be added. A negative electrode mixture forming paste was obtained. A negative electrode plate before chemical conversion was prepared in the same manner as in Sample No. 1 except that this paste was used.
(Sample No.15)
The water content is 18.0 parts by mass with respect to 100 parts by mass of the lead powder in the same manner as in Sample No. 5, except that carbon black having a specific surface area of 800 m ² /g was used as the carbon black to be added. A negative electrode mixture forming paste was obtained. A negative electrode plate before chemical conversion was prepared in the same manner as in Sample No. 1 except that this paste was used.

(Sample No.16)
The water content is 21.0 parts by mass with respect to 100 parts by mass of the lead powder by the same method as in Sample No. 1 except that carbon black having a specific surface area of 1200 m ² /g was used as the carbon black to be added. A negative electrode mixture forming paste was obtained. A negative electrode plate before chemical conversion was prepared in the same manner as in Sample No. 1 except that this paste was used.
(Sample No.17)
The water content is 20.0 parts by mass with respect to 100 parts by mass of the lead powder by the same method as in Sample No. 2 except that carbon black having a specific surface area of 1200 m ² /g was used as the carbon black to be added. A negative electrode mixture forming paste was obtained. A negative electrode plate before chemical conversion was prepared in the same manner as in Sample No. 1 except that this paste was used.

(Sample No.18)
The water content is 19.5 parts by mass with respect to 100 parts by mass of the lead powder in the same manner as in Sample No. 3, except that carbon black having a specific surface area of 1200 m ² /g was used as the carbon black to be added. A negative electrode mixture forming paste was obtained. A negative electrode plate before chemical conversion was prepared in the same manner as in Sample No. 1 except that this paste was used.
(Sample No.19)
The water content is 19.0 parts by mass with respect to 100 parts by mass of the lead powder in the same manner as in Sample No. 4, except that carbon black having a specific surface area of 1200 m ² /g was used as the carbon black to be added. A negative electrode mixture forming paste was obtained. A negative electrode plate before chemical conversion was prepared in the same manner as in Sample No. 1 except that this paste was used.
(Sample No.20)
The water content is 18.0 parts by mass with respect to 100 parts by mass of the lead powder in the same manner as in Sample No. 5, except that carbon black having a specific surface area of 1200 m ² /g was used as the carbon black to be added. A negative electrode mixture forming paste was obtained. A negative electrode plate before chemical conversion was prepared in the same manner as in Sample No. 1 except that this paste was used.

<Fixing the positive electrode plate and the negative electrode plate by forming a strap>
First, six positive electrode plates before chemical conversion prepared by the above method and the same seven negative electrode plates before chemical conversion for each sample No. were prepared. Next, each of the seven negative electrode plates before chemical conversion is housed in a bag-shaped separator, and the negative electrode plate-containing separator before chemical conversion and the positive electrode plate before chemical conversion are alternately laminated to form a positive electrode plate before chemical conversion. Six laminated bodies each having six sheets and seven negative electrode plates were obtained for each of sample Nos. 1 to 20.

Next, for each sample No., the obtained six laminated bodies were put into six cell chambers of a polypropylene monoblock type battery case, respectively, and then a COS (cast on strap) type casting device was used. By supplying molten metal (lead alloy) into the cavity and inserting the ears of the laminated body with the ears facing downward, first, the positive and negative straps for connecting the ears are connected. Formed. Next, small pieces and pole columns are formed on the negative electrode straps and the positive electrode straps arranged in the cell chambers at both ends in the arrangement direction, and the positive electrode intermediate pole column and the negative electrode intermediate pole column are formed on the other positive electrode straps and negative electrode straps, respectively. Formed.
Next, the positive electrode intermediate pole column and the negative electrode intermediate pole column, which face each other across the partition wall that partitions the cell chambers of the battery case, were connected by resistance welding at the through-hole portion provided in the partition wall. In this state, the electrode plate group before formation is arranged in each cell of the battery case.
The battery case and the lid in this state were heat-welded by the method described in the embodiment to obtain lead-acid batteries No. 1 to 20 before chemical conversion.

<Battery formation>
Aluminum sulfate was added to sulfuric acid having a specific gravity of 1.22 at 20° C. to prepare an electrolytic solution having an aluminum ion concentration of 0.18 mol/l. This electrolytic solution was injected into each cell chamber of the battery case from the liquid injection hole of the lid of the lead acid batteries No. 1 to 20 before chemical conversion. Then, as a battery case formation, in an atmosphere at a temperature of 40° C., a current of 2 A was charged for 0.4 hours, a current of 6 A was charged for 3.0 hours, a current of 10 A was charged for 8.7 hours, and a current of 10 A was applied for 0. Discharging for 5 hours and charging for 7.0 hours with a current of 10 A were performed in this order. The specific gravity of sulfuric acid after forming the battery case was 1.285 (value converted at 20° C.). Thus, No. 1 to 20 lead-acid batteries were obtained.
The mixture which the negative electrode plate before formation has by the battery case formation contains spongy lead (negative electrode active material), carbon black, and aluminum ions, and aluminum ions are present on the surface and pores of the carbon black. It changed into a mixture. Further, the mixture contained in the negative electrode plate before formation had a very large surface area of lead and contained many holes. Further, the mixture contained in the positive electrode plate after chemical conversion was changed to a mixture containing lead dioxide (positive electrode active material).

[Measurement of ratio (Ma/Mc) and ratio (Vt/Vs)]
Regarding the mixture contained in the negative electrode plate after electrolytic formation that constitutes each lead storage battery of No. 1 to 20, the total volume Vs of all holes existing in the mixture and the hole diameter is 0.1 μm or more by the mercury injection method. The total volume Vt of the holes, which is 1.0 μm or less, was measured to calculate the ratio (Vt/Vs) of both.
Further, the mixture was beaten into the mortar from the negative electrode plate after the electrolysis forming the lead storage batteries No. 1 to 20, and the mixture was ground with a pestle to give a powder. This powder was put into a 30 mass% sodium hydroxide aqueous solution and heated to separate metallic lead and carbon black and obtain a solution in which carbon black having a low specific gravity was dispersed. After filtering this solution with a filter, the solid remaining on the filter was washed with water and dried to obtain an extract containing carbon black.
Nitric acid was added to this extract and heated to elute aluminum ions, and the resulting aqueous solution was subjected to an ICP emission spectroscopic apparatus to determine the total mass Ma of aluminum ions present on the surface of carbon black and aluminum ions present in the pores. Was measured. The ratio (Ma/Mc) was calculated from the measured value Ma and the mass Mc of the carbon black contained in the negative electrode mixture.

[Test and evaluation]
Each of the obtained lead acid batteries was tested by the following method.
<Test to check low temperature startability>
Leave each of the lead-acid batteries No. 1 to 20 in an atmosphere of -15°C for 18 hours or more, and after confirming that the temperature of the electrolytic solution has reached -15°C, discharge at 150A until the voltage becomes 6V. Then, the time taken until that time (discharge duration) was examined. Then, for each of the obtained discharge durations of Nos. 1 to 20, relative values were calculated with the value of No. 6 of the standard configuration being 100. When the discharge duration (relative value) is 100 or more, it can be determined that the predetermined criterion is satisfied.

<Test to check charge acceptability after leaving over-discharged>
The test of “7.5 Endurance in cycle test with 50% depth of discharge (DoD) at 40° C. and preced deep discard” is performed under the test of “7.5 Endurance in cycle test with 50% depth of discharge” described in “EN 50342-6:2015” of European standard (EN standard). The time required to reach the rated voltage (16 V) by charging after the standing test was examined.

Specifically, first, a 12V, 10W miniature electric bulb was attached to a lead storage battery that was fully charged at an ambient temperature of 25° C. and left for 168 hours (one week). Next, the battery was charged with a constant current of 10 A and a constant voltage of 16 V (CC-CV) for 24 hours, and the time (arrival time) required to reach a constant voltage (16 V) was examined. If this time is early, it can be determined that the internal resistance in the lead storage battery is low and the charge acceptance is good. Then, for each of the obtained arrival times of Nos. 1 to 20, relative values were calculated with the value of No. 6 which is the standard configuration being 100. If the arrival time (relative value) is 100 or less, it can be determined that the predetermined criterion is satisfied.

The results of these tests are shown in Table 1 together with the composition of the negative electrode mixture (different composition is described for each sample No.).

In Table 1, in the column of the composition of the negative electrode mixture, numerical values for which the ratio (Ma/Mc) deviates from the condition (10 ppm or more and 25 ppm or less) of one embodiment of the present invention are underlined. In addition, double underline is given to a numerical value that is out of the preferable aspect of "ratio (Vt/Vs) is 0.50 or more and 0.75 or less". Further, numerical values that satisfy the more preferable aspect of “ratio (Vt/Vs) is 0.70 or more and 0.75 or less” are shown in italics.
As shown in Table 1, the lead storage batteries No. 6 to No. 15 having a ratio (Ma/Mc) of 10 ppm or more and 25 ppm or less had a discharge duration of 100 or more at low temperature starting. On the other hand, in the lead-acid batteries No. 1 to No. 5 and No. 15 to No. 20 in which the ratio (Ma/Mc) does not satisfy 10 ppm or more and 25 ppm or less, the discharge duration time at low temperature starting is less than 100. Was becoming.

Further, among the lead storage batteries of No. 6 to No. 15, the lead storage batteries of No. 7 to No. 9 and No. 12 to No. 14 satisfying the ratio (Vt/Vs) of 0.50 or more and 0.75 or less. Satisfied both the discharge duration of 105 or more at low temperature start and the arrival time of 100 or less until reaching a constant voltage after being left over-discharged. On the other hand, in No. 6, No. 10, No. 11, and No. 15 lead-acid batteries, the discharge duration of 105 or more at low temperature start and the arrival time to constant voltage of 100 or less after being left over-discharged The result did not meet either.
Further, among the lead storage batteries No. 7 to No. 9 and No. 12 to No. 14, No. 8, No. 9, No. 8 satisfying the ratio (Vt/Vs) of 0.70 or more and 0.75 or less. The lead-acid batteries of No. 10 and No. 11 were able to reach the constant voltage of 95 or less after being left over-discharged.

In addition, in the comparison of the lead storage batteries No. 1 to No. 15 having the same ratio (Ma/Mc), when the ratio (Vt/Vs) is 0.75 or less, as the ratio (Vt/Vs) increases, The discharge duration at the low temperature start increases, and the time to reach the constant voltage after the over discharge is left is short.
From the above results, by setting the ratio (Ma/Mc) within the range of 10 ppm or more and 25 ppm or less, the low temperature starting performance becomes good, and in addition to this, the ratio (Vt/Vs) is 0.50 or more and 0.75 or more. It was found that the charge acceptability was improved by setting the ratio within the following range, and the charge acceptability was further improved by setting the ratio (Vt/Vs) within the range of 0.70 or more and 0.75 or less.

Claims (3)

A negative electrode having a mixture containing lead, carbon having pores, and aluminum ions,
The ratio (Ma/Mc) of the total mass Ma of the aluminum ions existing on the surface of the carbon and the aluminum ions existing in the pores to the mass Mc of the carbon contained in the mixture is 10 ppm or more and 25 ppm. The following are lead acid batteries. The ratio (Vt/Vs) of the total volume Vt of the holes having a hole diameter of 0.1 μm or more and 1.0 μm or less to the total volume Vs of all the holes existing in the mixture is 0.50 or more. The lead-acid battery according to claim 1, which is 0.75 or less. The ratio (Vt/Vs) of the total volume Vt of the holes having a hole diameter of 0.1 μm or more and 1.0 μm or less to the total volume Vs of all the holes existing in the mixture is 0.70 or more. The lead-acid battery according to claim 1, which is 0.75 or less.