WO2009093464A1 - Positive electrode composition for secondary battery, process for production thereof, and secondary battery using positive electrode composition for secondary battery - Google Patents

Abstract

Disclosed is a secondary battery in which the coefficient of use of a positive electrode active material is improved and the amount of a raw material for an active material is reduced, and which can be produced at a low cost and has a reduced weight. Specifically disclosed is a positive electrode composition for a secondary battery, which comprises a kneading product produced by kneading a raw material for an active material mainly composed of a metal oxide with a carbon and a silica porous material, wherein the kneading product has a bulk density of 2.6 x 10-1 ml/g or more after the kneading product is filled in a grid-like current collector or applied on a sheet-like current collector and the filled or applied kneading product is dried and before the dried kneading product is chemically converted.

Description

Secondary battery positive electrode composition, manufacturing method thereof, and secondary battery using secondary battery positive electrode composition

The present invention relates to a positive electrode composition for a secondary battery, a method for producing the same, and a secondary battery using the positive electrode composition for a secondary battery.

Conventionally, various secondary batteries are known. For example, there are lead storage batteries as inexpensive ones and lithium ion batteries as high energy density ones. Needless to say, a secondary battery that is both inexpensive and has a high energy density is ideal. In particular, there is a great demand for an inexpensive and high energy density storage battery in applications such as a hybrid vehicle or an electric vehicle that performs start-up drive by the storage battery. The price of a storage battery is most dependent on its material cost. For example, in a hybrid vehicle, an expensive nickel metal hydride storage battery is used, but nickel used for the positive electrode of the nickel metal hydride storage battery and noble metal used for the negative electrode are very expensive materials. In addition, the lithium ion secondary battery is also forced to use an expensive material.

On the other hand, in a conventional lead-acid battery, dilute sulfuric acid is added to an active material raw material called lead powder obtained by oxidizing lead to make a paste-like composition, and this paste is filled into a grid-shaped current collector to form an electrode plate. The manufacturing method to form is common. Then, by forming this, the positive electrode contains an active material called lead dioxide and the negative electrode contains spongy lead. These active materials change to lead sulfate (discharge active material) when the battery is discharged. Since the particle volume increases with the change to the discharge active material, the pores of the porous structure in the electrode plate become small, making it difficult to diffuse the electrolytic solution into the active material.

Also, electrical resistance increases by changing to lead sulfate, which is an electrical insulator. Generally, when lead sulfate exceeds 70%, the electrical resistance increases rapidly. Therefore, it has been theoretically impossible to discharge the active material by 70% or more, that is, to set the utilization factor of the active material to 70% or more. Actually, since it is also affected by the magnitude of the discharge current, the utilization rate of low-rate discharge is generally about 35%, and the utilization rate of high-rate discharge is about 17%. That is, theoretically, the utilization rate can be taken up to about 70%, but it is far from this in normal use.

In order to increase the utilization factor of the active material, it is a necessary condition to increase the bulk density of the electrode plate containing the active material, that is, the porosity.

Lead storage batteries are preferable in that the raw materials are inexpensive, but the amount of lead used has to be increased due to the low utilization rate of the active material. As a result, the weight of lead, which has a higher weight density than other materials, has to be increased. This further increases the energy density with respect to the weight. The current energy density of lead-acid batteries is insufficient for hybrid vehicles and electric vehicles and cannot be used.

As a prior art regarding the positive electrode plate of a lead storage battery, there exists patent document 1, for example.
In patent document 1, the manufacturing method of the lead storage battery positive electrode plate excellent in chemical conversion efficiency is disclosed.

Specifically, for Patent Document 1, the positive electrode paste is a mixture of lead oxide, metal lead and lead sulfate, water, dilute sulfuric acid, and a conductive material prepared in advance on a lattice made of a lead alloy containing no antimony. In this case, 2 g (0.17 mol) or less of carbon black treated at a predetermined pressure and temperature is used as a conductive material with respect to 1 mol of lead.
JP 2002-324552 A

There is a demand for a secondary battery that is both inexpensive and has a high energy density, but these have been considered to have a contradictory relationship and have not yet been realized. In Patent Document 1, carbon black is added to improve conductivity, and the improvement of the active material utilization rate due to the porosity is not a problem.

As described above, the main cause of the low energy density of lead-acid batteries is that the electrical resistance increases, so that the active material utilization rate cannot be raised to the upper limit theoretical value of about 70%. In addition, the utilization rate of the active material is further lowered in the usage mode in which the discharge is performed with a large current.

On the other hand, the high cost of nickel-metal hydride secondary batteries and lithium ion secondary batteries is due to their essential materials, so it is difficult to reduce costs.

As described above, the present invention improves the utilization ratio of the positive electrode active material by adding a material not conventionally used to the lead powder as the active material raw material as the positive electrode composition for the secondary battery.

In order to achieve the above object, the present invention provides the following configuration.
(1) The positive electrode composition for a secondary battery according to claim 1 is:
Bulk density after drying and unformed state of a kneaded material filled in a grid-like current collector or coated on a sheet-like current collector and containing an active material material mainly composed of metal oxide and carbon and silica porous material Is 2.6 × 10 ⁻¹ ml / g or more.
(2) The positive electrode composition for a secondary battery according to claim 2 is characterized in that in claim 1,
A first kneaded material produced by kneading the carbon with an aqueous polyvinyl alcohol solution is a kneaded material produced by mixing and kneading the active material raw material and the porous silica material.
(3) The positive electrode composition for a secondary battery according to claim 3 is, in claim 1,
It is a kneaded product produced by mixing and kneading the active material raw material with a first kneaded product produced by kneading the carbon and the silica porous body with an aqueous polyvinyl alcohol solution. .
(4) The positive electrode composition for a secondary battery according to claim 4 is:
It is characterized by comprising a kneaded material in which carbon and silica porous material are contained in an active material raw material mainly composed of a metal oxide.
(5) The positive electrode composition for a secondary battery according to claim 5 is, in claim 4,
A first kneaded material produced by kneading the carbon with an aqueous polyvinyl alcohol solution is a kneaded material produced by mixing and kneading the active material raw material and the porous silica material.
(6) The positive electrode composition for a secondary battery according to claim 6 is, in claim 4,
It is a kneaded product produced by mixing and kneading the active material raw material with a first kneaded product produced by kneading the carbon and the silica porous body with an aqueous polyvinyl alcohol solution. .
(7) The positive electrode composition for a secondary battery according to claim 7 is:
After drying a kneaded material filled with a grid-like current collector or coated on a sheet-like current collector, containing a porous silica in an active material raw material mainly composed of metal oxide and not containing carbon, the bulk in an unformed state The density is 2.5 × 10 ⁻¹ ml / g or more.
(8) The positive electrode composition for a secondary battery according to claim 8 is:
It is characterized by comprising a kneaded material containing a porous silica in an active material raw material mainly composed of a metal oxide and containing no carbon.
(9) The positive electrode composition for a secondary battery according to claim 9 is any one of claims 1 to 8,
It is a kneaded material containing 7.3 mole percent or more of the porous silica in the active material raw material.
(10) The positive electrode composition for a secondary battery according to claim 10 is any one of claims 1 to 9,
The silica porous material contained in the kneaded material is diatomaceous earth, perlite, or shirasu balloon.
(11) A positive electrode composition for a secondary battery according to an eleventh aspect is characterized in that in any one of the first to tenth aspects, the kneaded material contains a trace amount of sulfuric acid.
(12) The positive electrode composition for a secondary battery according to claim 12 is
It is characterized by comprising a kneaded material in which carbon and hollow fibers are contained in an active material raw material mainly composed of a metal oxide.
(13) The positive electrode composition for a secondary battery according to claim 13 is, in claim 12,
A kneaded product produced by kneading the carbon with an aqueous polyvinyl alcohol solution is produced by mixing and kneading an active material raw material mainly composed of a metal oxide and the hollow fiber.
(14) The positive electrode composition for a secondary battery according to claim 14 is, in claim 12,
It is produced by mixing and kneading the active material raw material in a kneaded product produced by kneading carbon and hollow fibers with a polyvinyl alcohol aqueous solution.
(15) A method for producing a positive electrode composition for a secondary battery according to claim 15 comprises:
A first kneaded material produced by kneading the carbon with an aqueous polyvinyl alcohol solution is a kneaded material produced by mixing and kneading the active material raw material and the porous silica material.
(16) A method for producing a positive electrode composition for a secondary battery according to claim 16 comprises:
It is a kneaded product produced by mixing and kneading the active material raw material with a first kneaded product produced by kneading the carbon and the silica porous body with an aqueous polyvinyl alcohol solution. .
(17) The method for producing a positive electrode composition for a secondary battery according to claim 17 is characterized in that, in claim 15 or 16, the porous silica contained in the kneading is diatomaceous earth, pearlite or shirasu balloon. To do.
(18) The method for producing a positive electrode composition for a secondary battery according to claim 18 is characterized in that in any one of claims 15 to 17, the kneaded product contains a trace amount of sulfuric acid.
(19) A secondary battery according to claim 19 is provided.
A secondary battery produced by using the positive electrode composition for a secondary battery according to any one of claims 1 to 14 or by the method for producing a positive electrode composition for a secondary battery according to any one of claims 15 to 18. A positive electrode composition for use is used.

(A) The positive electrode composition for a secondary battery according to the first aspect of the present invention is filled in a grid-like current collector or coated on a sheet-like current collector, and carbon is used as an active material raw material mainly composed of a metal oxide. And the kneaded product containing the porous silica is dried and in an unformed state, the bulk density is 2.6 × 10 ⁻¹ ml / g or more, and the bulk density is increased, so the porosity is increased. The utilization rate of the positive electrode active material improved.
(B) A positive electrode composition for a secondary battery according to a second aspect of the present invention, the first kneaded material produced by kneading the carbon with an aqueous polyvinyl alcohol solution, the active material raw material and the porous silica material, Is mixed and kneaded to produce a kneaded product, in which carbon is dispersed in water, and the porous density is increased due to the inclusion of a porous silica, so that the porosity of the cathode active material using this is increased. Utilization rate is improved.
(C) The positive electrode composition for a secondary battery according to the third aspect of the present invention is obtained by adding the active material raw material to the first kneaded material produced by kneading the carbon and the porous silica with an aqueous polyvinyl alcohol solution. Is a kneaded product produced by mixing and kneading the carbon, and since the carbon is dispersed in water and the silica porous material is included, the bulk density is increased and the porosity is increased. The utilization rate of substances is improved.
(D) The positive electrode composition for a secondary battery according to the fourth aspect of the present invention is a metal oxide in which the positive electrode composition for a secondary battery is filled in a grid-like current collector or coated on a sheet-like current collector. The bulk density of the kneaded product containing the silica porous material in the active material raw material mainly composed of carbon and not containing carbon is 2.5 × 10 ⁻¹ ml / g or more after drying, and the bulk density is increased. Therefore, the porosity is increased, and the utilization rate of the positive electrode active material using the same is improved.
(E) The positive electrode composition for a secondary battery according to the fifth aspect of the present invention is a positive electrode composition for a secondary battery in which a metal oxide is added to a kneaded product produced by kneading the carbon with an aqueous polyvinyl alcohol solution. The active material raw material and the hollow fiber are mixed and kneaded to produce carbon, and the carbon is dispersed in water. Since the hollow fiber is contained, the bulk density is increased and the porosity is increased. The utilization rate of is improved.
(F) The positive electrode composition for a secondary battery according to the sixth aspect of the present invention is the above-described kneaded product produced by kneading carbon and hollow fibers with an aqueous polyvinyl alcohol solution. Produced by mixing and kneading the active material, carbon is dispersed in water, and hollow fibers are included, so the bulk density increases and the porosity increases, and the utilization rate of the positive electrode active material using this increases. .

First, an outline of an embodiment of the present invention will be described. Details will be described in the following embodiments.
Prior to the description, terms in the following description such as each example will be defined.
(1) A porous body mainly composed of silicon dioxide is referred to as “silica porous body” or abbreviated as “silica”.
(2) Pearlite made of vitreous pearlite that has been rapidly heated and expanded is simply called “pearlite”.
The positive electrode composition for secondary batteries according to the present invention is substantially intended for lead acid batteries. This positive electrode composition is a paste-like kneaded product in which an active material raw material is a main component and other necessary components are added. The paste-like kneaded product is filled in a positive electrode plate which is a grid-like current collector, aged and dried (unformed state), and then the positive electrode plate is incorporated into a storage battery case, and a chemical conversion process is performed to obtain an active material raw material. It becomes an active material and is completed as a lead-acid battery. Therefore, the “active material raw material” in the claims and the specification of the present application refers to the raw material. The “active material raw material” refers to a raw material that is a target product that is converted into an active material.

The kneaded product of the positive electrode composition mainly composed of the active material raw material according to the present invention contains the active material material mainly composed of the metal oxide and the porous silica without containing carbon and silica or carbon. Moreover, as a porous body, it is set as a silica porous body or a hollow fiber (it calls a hollow fiber in an Example). Further, the porous silica material has diatomaceous earth, pearlite, shirasu balloon, or similar properties. The active material raw material is lead powder. Then, after drying the kneaded material containing at least carbon and silica porous body in the active material raw material mainly composed of metal oxide filled in the grid-shaped current collector or coated on the sheet-shaped current collector and in an unformed state The bulk density is 2.6 × 10 ⁻¹ ml / g or more. In the case of the kneaded product not containing carbon, the bulk density is 2.5 × 10 ⁻¹ ml / g or more.

Further, the porous silica material for improving the bulk density is contained in an amount of 7.3 mole percent or more based on the active material raw material. The positive electrode composition produced by kneading is usually filled in a grid-like current collector before chemical conversion or applied to a sheet-like current collector, and then aged and dried.

As carbon, for example, acetylene black or furnace carbon can be used, and these may be mixed and used.

The kneaded material in Examples 1 to 3 of the positive electrode composition according to the present invention contained a trace amount of sulfuric acid, whereas the kneaded material in Example 4 showed an example in which no sulfuric acid was contained, but in Examples 1 to 3, sulfuric acid was added. It may not be contained, and in Example 4, a trace amount of sulfuric acid may be contained. This small amount of sulfuric acid is used to slightly increase the viscosity of the paste and make it easier to fill the grid-shaped current collector with the paste, and is irrelevant to the basic performance of the battery.

Furthermore, when adding carbon, polyvinyl alcohol (PVA) is contained with respect to said kneaded material. Polyvinyl alcohol is added for the purpose of improving the dispersibility of carbon or the like, but also contributes to increasing the adhesion strength and shape retention strength of the positive electrode composition when the kneaded product is filled in a grid-like current collector. Furthermore, it has a coating action to prevent oxidation of carbon in the positive electrode.
When polyvinyl alcohol is included, warm water is added to PVA in advance to dissolve it in order to facilitate kneading with carbon, and the temperature of the warm water is about 90 ° C., which assists in dissolving PVA. Hereinafter, such conditions are the same also in each Example containing PVA.
The kneaded product produced in one step and another step is mixed and kneaded, but the kneaded product produced in the one step is mixed with the raw material before kneaded product to be produced in another step May be mixed and kneaded.

The manufacturing method of the positive electrode composition of Examples 1, 3 and 4 is as follows. In one kneading step, carbon is kneaded with water to obtain a product. In another kneading process, lead powder as an active material raw material and diatomaceous earth (Example 1), diatomaceous earth, perlite or shirasu balloon (Example 3) or hollow fiber for the product in the one kneading process. (Example 4) is added and further kneaded to obtain a kneaded product. The obtained kneaded material is the above positive electrode composition. When PVA is contained, it is added in the one kneading step.

In the method for producing the positive electrode composition of Example 2, the two kinds of kneading steps in Examples 1, 3 and 4 were not carried out, and lead powder as an active material raw material was kneaded.

The kneaded material obtained in this way is undried and can be filled into the grid-like current collector, and in the following examples, it is referred to as “paste”. In the conventional positive electrode composition, kneading in two steps as in Example 1 was not performed. In Example 1 of the present invention, a positive electrode composition having a suitable bulk density could be obtained through two kneading steps. The one kneading step can be replaced by means such as stirring and mixing.

The utilization rate of the active material made of the positive electrode composition according to Example 1 is about 44% to 65% for a low rate discharge (equivalent to about 40 hour rate discharge) of 0.06 ampere discharge when a grid-like current collector is used. In the case of a high rate discharge (corresponding to a rate discharge of about 10 minutes) that is 6%, the discharge rate was about 20% to 38%. See Table 1-2 for both. At any discharge rate in the low rate discharge and the high rate discharge, the utilization rate was remarkably improved as compared with the conventional lead acid battery.
In the low-rate discharge to the high-rate discharge, the active material utilization rate was about 1.3 to 2 times that of the comparative paste No. 1 of the prior art.
These values are approximate because they vary depending on the amount of carbon and the amount of diatomaceous earth.

Further, the utilization rate of the active material comprising the positive electrode composition according to Example 2 that does not contain carbon is about 38% to 65%, 6 amperes in a low rate discharge (equivalent to about 40 hours rate discharge) that is 0.06 ampere discharge. In a high rate discharge (equivalent to a rate discharge for about 10 minutes) which is a discharge, it was about 18% to 43%. Refer to Table 3-2 for both.
In Example 3, active material utilization rates are compared using various porous silica materials. It is about 54% to 73% for low rate discharge (equivalent to about 40 hour rate discharge) which is 0.06 ampere discharge, and about 21% to 29% for high rate discharge (equivalent to about 10 minute rate discharge) which is 6 ampere discharge. there were. See Table 4 for both.
The active material utilization of Example 4 using hollow fibers is about 55% to 73% for a low rate discharge (equivalent to about 40 hour rate discharge) of 0.06 ampere discharge, and a high rate discharge (about about 6 ampere discharge). 10% rate discharge) was about 27% to 48%. Refer to Table 5-2 for both.
With low rate discharge and high rate discharge, the comparative paste No. The active material utilization rate of about 2.1 times and 2.7 times of 1 was obtained, respectively.

As the current collector, a conventional lattice can be used, or the positive electrode composition can be applied to a sheet-like material such as a lead sheet. When filling the grid-like current collector, a certain degree of viscosity is required, so that the amount of water as the kneading medium is set to be small relative to the other components to obtain a paste-like kneaded product. On the other hand, when applying to a sheet | seat, the quantity of water is increased and viscosity is made low and it is set as a slurry-like kneaded material. Whether the kneaded product before application to the electrode plate is a paste or a slurry, the effects of the present invention can be obtained similarly.
Since the paste of the prior art kneads lead powder with sulfuric acid, it was necessary to strictly control the amount of water added to this, but the amount of water in the paste of the present invention does not affect the active material utilization rate, By making it easy to fill the current collector with the paste, the amount of water can be adjusted flexibly, and any desired value can be taken.

An electrode plate in which a grid current collector is filled with paste can basically be used for all uses of conventional lead-acid batteries, and can be lighter with the same battery capacity. A lead-acid battery using a sheet electrode can form a cylindrical battery. In that case, by winding the electrode plate in a spiral, a battery having excellent high-rate discharge and strong vibration resistance is obtained. This is particularly suitable for hybrid vehicles and electric vehicles. Currently, nickel hydride secondary batteries and lithium ion secondary batteries are being used or studied in hybrid vehicles, but they all have a problem of high cost. The lead storage battery according to the present invention is much lower in cost than a nickel hydride secondary battery and a lithium ion secondary battery, and is suitable for practical use because of simple charge / discharge management.

As described above, the lead-acid battery using the positive electrode composition according to the present invention can be discharged by a large current, has a high active material utilization rate, has a small amount of lead powder used, and is low in cost. Compared to lithium ion secondary batteries and nickel metal hydride storage batteries, charge / discharge management is simple. Its optimal use is the hybrid use of engine and storage battery in automotive applications. In this application, regenerative electric power during braking of an automobile is charged into a storage battery, and electric power is taken out from the storage battery at the time of starting, thereby reducing gasoline consumption. Since automobile companies are environmentally favorable due to energy saving and exhaust gas reduction, they are focusing on hybrid cars now and in the future, and it can be said that the industrial applicability of the present invention is extremely high.

Moreover, a general storage battery is often used for float charging. This is a system that supplies power from a storage battery to a load in the event of a power failure, and is generally discharged at a rate of about 10 minutes. When such a storage battery is used with a conventional lead storage battery, a short-time discharge, that is, a large current discharge is generated, so that the utilization factor of the active material which is not originally high further decreases. Therefore, a lead storage battery having a large rated capacity must be prepared, which is large and heavy. The lead storage battery using the positive electrode composition of the present invention has an active material utilization rate as high as about twice that of a conventional lead storage battery, is suitable for discharging by a large current, and has a high utilization rate, so the amount of lead is high. Reduced and lighter.
Recently, with the development of the Internet, the demand for lead storage batteries in data centers has increased, and there has been a demand for an improvement in the utilization rate in such a large current discharge.
Hereinafter, each Example of this invention regarding the positive electrode plate of the lead acid battery using a grid | lattice-like collector is described.

In Example 1, when manufacturing a paste which is a positive electrode composition (a mixture of various substances in lead powder which is an active material raw material mainly composed of metal oxide), the amount of carbon added as an additive is set as a parameter. As such, various test results such as active material utilization rate when the amount of diatomaceous earth added is mainly changed will be described.

<Preparation of sample>
Table 1 is for preparing a positive electrode composition (a paste-like material, a dried material, or constituents of each raw material before kneading. The same applies hereinafter) subjected to the test in Example 1. It is a list which shows an ingredient composition and quantity. The paste referred to in the description of the present invention means a kneaded product in a paste state after kneading these components and before drying.
In Table 1, lead powder is set to a constant amount of 200 g, the amount of carbon is changed to 3 g, 6 g, and 9 g, and the bulk density is measured by changing the amount of diatomaceous earth within the same amount of carbon. It is confirmed that the bulk density increases as the amount of diatomaceous earth increases at the same carbon amount, and the bulk density increases as the carbon amount increases. In addition, the amount of water is increased as the amount of carbon and the amount of diatomaceous earth increase. This is because the amount of carbon to be kneaded and the amount of diatomaceous earth increase, and the amount of PVA is also increased in conjunction with the amount of carbon. Further, the upper limit value of the diatomaceous earth content addition is decreased as the carbon amount increases.
The amount of water in Table 1 is the same as that used to dissolve polyvinyl alcohol (same as in Example 1, Example 3 and Example 4) and when lead powder is mixed (same as in Examples 1 to 4). However, the amount of water is not strict, and water may be appropriately poured in consideration of the paste viscosity at the time of kneading. The same applies to other embodiments.

“No.” in Table 1 is a paste number. 1 is manufactured by the prior art. Paste No. 2 to 16 are pastes according to the present invention.

<Description of main raw materials>
Lead powder is an active material raw material which is a main constituent of the positive electrode composition, and has an oxidation degree of about 75 to 80 percent. Acetylene black having an oil absorption of 160 ml / 100 g was used for carbon, and a degree of polymerization of 2400 was used for polyvinyl alcohol (manufactured by Kuraray Co., Ltd.). The oil absorption amount indicates the DBP oil absorption amount. This indicates the amount of dibutyl phthalate absorbed per 100 grams of carbon.

<Manufacturing method>
Diatomaceous earth is baked and refined what is called diatomaceous earth shell. It is made of silica component and is a porous body with fine pores of about 1μ, so we thought it could contribute to the improvement of the bulk density of the electrode plate. . Moreover, since it is a silica, it is excellent in acid resistance and oxidation resistance. Here, Radiolite # 300 was used as diatomaceous earth. As an element indicating the properties of the positive electrode plate (positive electrode composition), the relationship between the bulk density, the active material utilization rate, and the battery capacity was examined. The bulk density was controlled by the amount of carbon and water. The bulk density is shown in Table 1.

First, polyvinyl alcohol is dissolved in warm water having a temperature of about 90 ° C., and when the dissolution is completed, an aqueous solution having a polyvinyl alcohol concentration of about 6% is manufactured. The upper part of the container is covered with a sheet such as a wrap in the container to be dissolved so that the water does not evaporate during the dissolution.
Carbon is added to this polyvinyl alcohol aqueous solution and kneaded for about 30 minutes. Thereafter, 200 g of lead powder is mixed into the kneaded product, and a small amount of sulfuric acid (1.3 g of sulfuric acid in Table 1) and 0.3 g of cut fiber are added. After kneading for about 25 minutes, diatomaceous earth was added and kneading was continued for about 5 minutes. However, the kneading time of about 30 minutes, 25 minutes and 5 minutes is an approximate guide, and the kneading for the last 5 minutes varies depending on the amount of diatomaceous earth. Moreover, the addition time of diatomaceous earth may be mixed. That is, diatomaceous earth may be mixed when carbon is added to a polyvinyl alcohol aqueous solution and kneaded. Alternatively, diatomaceous earth may be mixed when the lead powder is mixed in the subsequent process.
The paste No. according to the prior art prepared for comparison with the present invention. 1 is simply kneaded according to the amount in Table 1, and contains 11 grams of pure sulfuric acid.

The paste thus prepared was filled in a 3.7 mm thick grid-shaped current collector, then aged at 98% humidity and a temperature of 45 ° C. for 24 hours, and then dried at 60 ° C. for 24 hours. A positive electrode unformed plate was formed. Hereinafter, a paste that is a positive electrode composition filled in a grid current collector, aged and dried, and further formed is collectively referred to as a positive electrode active material or an active material, or a positive electrode plate or an electrode plate.

Next, in order to show the characteristics of the positive electrode composition, the bulk density of the non-chemical electrode plate was measured. Table 2 shows a method for measuring the bulk density.

The bulk density of the unformed positive electrode composition is calculated by the following formula.
Bulk density of unformed positive electrode composition = volume of unformed positive electrode composition / weight of unformed positive electrode composition = (D−B) / (C−A)
Paste No. 1 prepared according to Table 1. FIG. 1 shows the relationship between the amount of carbon and diatomaceous earth of 2 to 16 and the amount of the paste filled into the grid as the positive electrode current collector.
In FIG. 1, there are three types of plot rows (carbon amount, 3 g, 6 g, and 9 g) and a line connecting them, which uses the carbon amount as a parameter.
The horizontal axis represents the change in the amount of diatomaceous earth. When the carbon amount is 3 g, the diatomaceous earth amount of 4 g to 31 g is plotted 6 points, when the carbon amount is 6 g, the diatomaceous earth amount is 4 g to 26 g of plot 5 It becomes a point.
A vertical axis | shaft represents the filling amount of the paste to the grating | lattice according to the change of bulk density. All units are g and are absolute values. It can be seen that as the addition amount of diatomaceous earth or carbon increases, the filling amount decreases. Comparison paste No1 which is a prior art has the largest filling amount.
As shown in Table 1, the upper limit of the amount of diatomaceous earth is 31 g, 26 g, and 20 g depending on the amount of carbon (3 g, 6 g, and 9 g), which can be confirmed in FIG. This is because the diatomaceous earth is bulky and the oil absorption amount of carbon is large, so as shown in the bulk density column of Table 1, comparative paste No. It means that it is a bulky positive electrode composition compared with 1. Therefore, the lower limit of the bulk density in the claims is set to 0.26 ml / g based on 3 g of carbon and 4 g of diatomaceous earth in Table 1.
Being a bulky positive electrode active material means that the amount of lead powder used is of course physically reduced.
The filling amount of the positive electrode composition is the filling result shown in FIG. 1, and Table 1 shows the preparation and bulk density of the paste raw material, so the filling amount is not shown in Table 1.

A fine glass fiber separator was brought into contact with both sides of one positive electrode plate in which each paste prepared in Table 1 was filled in a grid, and further, one negative electrode plate was brought into contact with each outside. Note that the negative electrode plate uses a conventional technique. By setting it as such a structure, the theoretical capacity | capacitance of an active material becomes large excessively in a negative electrode, and the utilization factor of the target positive electrode active material of this invention can be evaluated. The electrode plate group was inserted into the battery case, and the gap between the battery case and the electrode plate group was filled with an ABS resin spacer. The dilute sulfuric acid having a specific gravity of 1.223 was injected into the battery case, and 300% of the amount of electricity of the theoretical capacity of the positive electrode was passed to perform chemical conversion. The specific gravity of the electrolytic solution after chemical conversion was set to 1.320.

Next, a capacity test (discharge test) was performed in order to calculate the positive electrode active material utilization rate and measure the capacity (Ah) of the lead storage battery. Two types of capacity tests were performed: 0.06 amp discharge and 6 amp discharge. The 0.06 ampere discharge corresponds to a rate of about 40 hours, and the 6 ampere discharge corresponds to a rate discharge of about 10 minutes. Each discharge end voltage was set to 1.7 volts and 1.2 volts per cell. The temperature is 25 ° C.
FIG. 2 and Table 1-2 show the measurement results of the utilization rate of the positive electrode active material of 0.06 ampere discharge, which is a low rate, and 6 ampere discharge, which is a high rate, with respect to changes in the amount of diatomaceous earth using the carbon amount as a parameter.

As described above, lead powder as a raw material is mainly lead oxide, but also includes lead that is not oxidized and in a metallic state. Lead oxide reacts with sulfuric acid in the electrolytic solution, and changes to lead dioxide, which is a positive electrode active material, by chemical conversion. Lead dioxide thus produced is regarded as an active material. Whether or not the metal lead originally contained is regarded as an active material is debated. Here, the utilization rate of the active material in the discharge was calculated on the assumption that the metal lead originally contained in the raw material became an active material.
In other words, when the weight of the lead powder filled in the electrode plate is E,
F = E × 239/223 × (1 / 4.463)
Here, F is the capacity when it is assumed that the lead powder has all changed to lead dioxide by chemical conversion, that is, the theoretical capacity, 239 is the molecular weight of lead dioxide (PbO ₂ ), 223 is the molecular weight of lead oxide (PbO) Yes, 4.463 is the amount of lead dioxide required to discharge 1 ampere hour (Ah), assuming that all lead dioxide has been discharged to lead sulfate. Active material utilization rate (%) Active material utilization rate (%) = positive electrode discharge capacity / F × 100
Can be calculated as When the utilization factor of the active material is represented in each diagram representing the utilization factor of the present invention, this percentage is indicated.
In addition, in this specification, when representing the utilization factor of the active material in each table representing the utilization factor,
Active material utilization rate = positive electrode discharge capacity / F
As a percent (%) notation. However, Table 4 is in% notation.
In the present invention, the calculation was made assuming that all of the lead dioxide is formed after the chemical conversion, but in practice, the lead dioxide after the chemical conversion is generally about 85%, so that the utilization rate of the active material is 100/85. The value multiplied by is the actual utilization rate.

Table 1-2 describes the measurement and calculation of the active material utilization rate in each blend of the carbon amount and diatomaceous earth amount of the present invention according to Table 1. FIG. 2 is a graph of Table 1-2, where the mass of diatomaceous earth is changed from a minimum of 4 g to a maximum of 31 g when the carbon mass is 3 g, 6 g, and 9 g, respectively. Represents changes in diatomite content. The vertical axis represents the active material utilization rate (%).
In addition, the active material utilization shown in Table 1-2 is not a percentage (%) notation but only a rate. The active material utilization shown on the vertical axis in FIG. 2 is expressed in percentage (%). The utilization rate shown in the table for other examples (except for Example 4) is not expressed in percentage (%), and the utilization rate shown on the vertical axis in each figure of other examples is expressed in percentage (%). .
In FIG.
(1) The plot group ◆ (carbon 3 g), ■ (carbon 6 g), and ▲ (carbon 9 g) at the top of the graph are the utilization rate of the positive electrode active material of the low rate discharge (0.06 ampere discharge) of the present invention,
(2) Plot groups （(carbon 3 g), □ (carbon 6 g), and Δ (carbon 9 g) at the bottom of the graph are the positive electrode active material utilization rate of the high rate discharge (6 ampere discharge) of the present invention.
(3) The amount of diatomaceous earth 0 g is a comparative paste No. of the prior art 1. Low-rate discharge plot ● and high-rate discharge plot ○.
In FIG.
(4) The utilization rate of the low rate discharge active material increases as carbon and diatomaceous earth increase, and shows a maximum value of about 65% with 6 g of carbon and 14 g of diatomaceous earth. The value was much higher than 1.
(5) In the high rate discharge, the active material utilization rate increased as carbon and diatomaceous earth increased, and the maximum value of the active material utilization rate was about 38% when the carbon amount was 9 g and the diatomaceous earth amount was 20 g.
(6) In high rate discharge, the average amount of carbon is 6 g, and about 26 g of diatomaceous earth has a high active material utilization rate.
(7) The bulk density which is the maximum value of the active material utilization rate of low rate discharge is 0.37 ml / g (paste No. 10 in Table 1).
(8) The bulk density which is the maximum value of the active material utilization rate of high rate discharge is 0.44 ml / g (paste No. 16 in Table 1).
See Table 1-2 for specific values of active material utilization.
Comparison paste No. made of conventional manufacturing method recipe. Compared to 1, all of the pastes of the present invention had high utilization rates, and both the low rate and high rate discharges had an active material utilization rate of approximately twice the maximum.
In addition, comparative paste No. which is a positive electrode active material of the prior art. 1 is indicated on the horizontal axis where the carbon amount is 0 g and the diatomaceous earth amount is 0 g. This also applies to FIG. 3 (lead storage battery capacity graph) described later. As shown in Table 1-2 and FIG.
(9) 33.0%, 34.5% with low rate discharge
(10) 15.8% and 17.6% for high rate discharge.
Thus, as can be seen from Table 1-2 and FIG. 2, even in the active material utilization rate at the minimum bulk density of 3 g of carbon and 4 g of diatomaceous earth according to the present invention, the conventional technology is also used in low rate discharge and high rate discharge. The utilization rate of the positive electrode active material is exceeded.
Therefore, as described above, the bulk density of 0.26 ml / g (see Table 1) in the blending of the carbon amount and the diatomaceous earth amount is set as the lower limit value of the bulk density of the present invention in which the positive electrode active material utilization rate of the present invention is suitable. It was described in the scope of claims.
In addition, paste No. which is a prior art with respect to the lower limit of the bulk density and the positive electrode active material utilization rate in the carbon amount 3 g and the diatomaceous earth amount 4 g of the invention. The ratio between the bulk density of 1 and the utilization ratio of the positive electrode active material is calculated as follows.
(1) Bulk density ratio 0.26 (present invention) /0.24 (prior art) = 1.08
(2) Low rate discharge utilization ratio: 0.440 / 0.338 = 1.30
(3) High rate discharge utilization ratio: 0.202 / 0.167 = 1.21
Thus, the ratio of the present invention to the prior art is higher in the active material utilization ratio than in the bulk density ratio. This is because even if the bulk density of the present invention and the bulk density of the prior art are the same value, the active material utilization rate of the present invention is higher than that of the prior art.
In addition, the active material utilization factor of said (2) and (3) is an average value of 2 samples.

As can be seen by comparing the bulk density shown in Table 1, the comparative paste No. 1 of the prior art is used. While the bulk density of No. 1 was 0.24 ml / g, The pastes 2 to 16 showed high values from 0.26 ml / g to 0.44 ml / g. That is, it is judged that the high bulk density due to carbon and diatomaceous earth led to a high utilization rate.
Conventional paste No. If the bulk density is higher than the bulk density of 0.24 ml / g, it means that the utilization rate is higher than that of the conventional paste.

If the bulk density is small, the porosity is small, and it is necessary to supply more sulfuric acid electrolyte necessary for discharging the active material from the outside of the electrode plate. Since a large amount of sulfuric acid electrolyte can be retained, it becomes easier to discharge, resulting in a high utilization rate as shown in FIG.
The utilization factor is an absolutely necessary item for improving the energy density of the battery. Moreover, since the active material raw material (lead powder) of a battery can be decreased if a utilization factor is high, the meaning as a cost reduction has a big thing.

As mentioned above, utilization is a very important factor, but in some cases you may want the absolute capacity of the battery. Regarding the relationship between carbon mass (g) and diatomaceous earth mass (g) and lead storage battery capacity (Ah), the lead storage battery capacities of 0.06 ampere discharge which is low rate discharge and 6 ampere discharge which is high rate discharge are shown in Table 1-3. And shown in FIG.
FIG. 3 is a graph of Table 1-3, which uses the same positive electrode active material as the utilization factor shown in Table 1-2. For this reason, the lead storage battery capacity (Ah) can be compared with the utilization rate of the positive electrode active material.
FIG. 3 is a graph in which the mass of carbon is a parameter according to Table 1, and the diatomaceous earth mass is discretely changed from 4 g to a maximum of 31 g in the case of 3 g, 6 g, and 9 g, respectively. The ▲ is the low rate discharge, and the plot group ◇, □, △ at the bottom of the graph is the high rate discharge.
The capacity at low rate discharge is the positive paste No. Some were below 1. When the bulk density is large, the amount of lead powder as an active material raw material is relatively small, so that the capacity that can be taken out is reduced even when the utilization factor is high. In contrast, the high rate discharge capacity is the same as that of the comparative paste No. of the prior art in the entire range tested. The value was higher than 1, and the capacity was almost constant even when the addition amount of carbon or diatomaceous earth was different.
In high-rate discharge, the value of a battery is evaluated by how efficiently it is discharged with a large current. In the lead storage battery of the present invention, since carbon and diatomaceous earth mixed in the active material contain a large amount of dilute sulfuric acid that is the electrolyte of the lead storage battery, the electrolyte in the vicinity of the active material is immediately supplied to the active material, so that a large current Good characteristics. Since the positive electrode active material of the prior art has only lead as the active material, it is supplied from an electrolyte solution outside the active material, so that the large current discharge characteristics are poor.
Therefore, a positive electrode composition in which the amount of carbon and the amount of diatomaceous earth are increased when the high current characteristic is emphasized is exactly suitable.

In Example 1, the bulk density of the electrode plate was increased with carbon and diatomaceous earth, but in order to evaluate the effect of diatomaceous earth alone, a test was conducted with a positive electrode composition having the contents shown in Table 3.
Table 3 is a list of compositions of each positive electrode paste subjected to the test, and also describes the bulk density of each paste.
In Table 3, since there is no carbon, the amount of diatomaceous earth is increased accordingly. No. No. 1 paste is the same prior art as in Table 1. 17 to 23 are pastes of the present invention in which the amount of diatomaceous earth is changed.

<Description of main raw materials>
Lead powder, which is an active material raw material mainly composed of metal oxide, is the main constituent material of the active material, and has an oxidation degree of about 75 to 80 percent. Acetylene black having an oil absorption of 160 ml / 100 g was used for carbon, and a degree of polymerization of 2400 was used for polyvinyl alcohol (manufactured by Kuraray Co., Ltd.). Radiolite # 300 was used as diatomaceous earth.

<Manufacturing method>
First, a small amount of sulfuric acid (1.3 g of sulfuric acid in Table 3) was added to the lead powder and water in the mass shown in Table 3 and kneaded for 40 minutes, then diatomaceous earth was added, and the kneading was continued for 5 minutes. I did it. However, diatomaceous earth may be mixed from the beginning. The kneading time of 40 minutes is an approximate guide, and the kneading for the last 5 minutes varies depending on the amount of diatomaceous earth.

Positive electrode paste No. 1 prepared for comparison. 1 is simply kneaded according to the amount of Table 3, and contains 11 grams of pure sulfuric acid. This paste is the same as in Table 1.

The paste thus prepared was filled in a 3.7 mm thick grid-shaped current collector, aged at 98% humidity and at a temperature of 45 ° C. for 24 hours, and then dried at 60 ° C. for 24 hours to form a positive electrode unformed plate. Formed.

A fine glass fiber separator was brought into contact with both sides of one positive electrode plate, and a conventional negative electrode plate was brought into contact with the outside one by one. With such a structure, the theoretical capacity of the active material is excessively large for the negative electrode, and the active material utilization rate of the target positive electrode can be evaluated. The electrode plate group was inserted into the battery case, and the gap between the battery case and the electrode plate group was filled with an ABS resin spacer. The dilute sulfuric acid having a specific gravity of 1.223 was injected into the battery case, and a 300% electric quantity of the theoretical capacity of the positive electrode was passed to perform chemical conversion. The specific gravity of the electrolytic solution after chemical conversion was set to 1.320.

Next, a capacity test (discharge test) was performed in order to calculate the positive electrode active material utilization rate and measure the lead-acid battery capacity. Two types of capacity tests were performed: 0.06 amp discharge and 6 amp discharge.
The 0.06 ampere discharge is equivalent to a rate of about 40 hours, and the 6 ampere discharge is equivalent to a rate of about 10 minutes. Each discharge end voltage was set to 1.7 volts and 1.2 volts per cell. The temperature is 25 ° C.

Table 3-2 and FIG. 4 show the positive electrode active material utilization rates of 0.06 ampere discharge and 6 ampere discharge. In the horizontal axis of FIG. 4, diatomaceous earth is plotted at 0 g (low rate discharge plot ◆ and high rate discharge plot ■). A value of 1 is shown.
FIG. 4 is a graph of Table 3-2. In the present invention, the utilization rate of the positive electrode active material when the mass of diatomaceous earth in Table 3 is discretely changed from 4 g to 43 g is shown.
The plot group ◆ at the top of the graph is low rate discharge, and the plot group ■ at the bottom of the graph is high rate discharge. The active material utilization rate of the low rate discharge increased as the amount of diatomaceous earth added increased, and showed a maximum value of 65% when the amount of diatomaceous earth was 37 g.
On the other hand, the utilization rate of the high rate discharge monotonously increased as more diatomaceous earth was added, and the maximum value was about 43% at 43 g of diatomaceous earth. There is still room for increasing the active material utilization by increasing the amount of diatomaceous earth.
The following discussion will be made with reference to the data in Table 3-2.
Prior art comparative paste no. In 1,
(1) Low rate discharge utilization rate is 33.0%, 34.5% (average 33.8%)
(2) High rate discharge utilization is 15.8%, 17.6% (average 16.7%)
Prior art paste No1. Then, the high rate discharge utilization rate compared to the low rate discharge utilization rate,
(3) 16.7% / 33.8% = 0.49 (high rate discharge utilization / low rate discharge utilization)
It becomes.
In Table 3 and Table 3-2, the paste No. In the active material utilization rate to which 43 g of diatomaceous earth is added, the high rate discharge utilization rate / low rate discharge utilization rate is obtained.
(4) 42.5% / 58.3% = 0.73 (average value of 2 samples)
It can be seen that the ratio of the high rate discharge utilization rate to the low rate discharge utilization rate is as large as 0.73, which is suitable for high rate discharge.
In Table 3 and Table 3-2, paste No. 37 containing 37 g of diatomaceous earth of the present invention was added. 22 and prior art paste no. The utilization rate at the time of low rate discharge and high rate discharge with 1 is compared.
(5) 63.7% / 33.8% = 1.9 ... ratio in the average of samples during low rate discharge (6) 38.4% / 16.7% = 2.3 ... high rate discharge In comparison with the average of the samples at the time, the lead storage battery capacity of the present invention and the prior art at the time of low rate discharge is equivalent in the amount of diatomaceous earth of 37 g of the lead storage battery capacity (Ah) shown in Table 3-3 and FIG. The lead storage battery capacity at the rate discharge is slightly larger in the present invention. Thus, the test result that the lead storage battery capacity is almost equal and the utilization rate of the positive electrode active material is about twice as large as that of the present invention. In the past, this is absolutely impossible.
Table 3-3 shows the lead storage battery capacity for the positive electrode composition shown in Table 3. FIG. 5 is a graph of Table 3-3.

From the graphs of FIGS. 2 and 3 generated from Table 1-2 and Table 1-3, respectively, and the graph results of FIGS. 4 and 5 respectively generated from Table 3-2 and Table 3-3, the graph of FIG. If the amount of diatomaceous earth added to 200 g of the lead powder of the paste is 4 g or more, the utilization rate of the positive electrode active material and the lead storage battery capacity at the time of low rate discharge and high rate discharge are compared with the paste No. It can be seen that it can be higher than 1.
When 200 g of lead powder is a mixture of 150 g of lead oxide and 50 g of metal lead, the number of moles is 150/223 = 0.673 mol and 50/207 = 0.242 mol, and 0.673 + 0.242 = 0. 915 mol, and 4 g of diatomaceous earth is 4/60 = 0.0667 mol. Therefore, the number of moles of diatomaceous earth with respect to the lead powder is 0.0667 / 0.915 = 0.729. However, the molecular weight of lead oxide is 223, the molecular weight of metallic lead is 207, and the molecular weight of diatomaceous earth is 60.
When this is expressed by one calculation formula, the following formula is obtained.
(4/60) / (150/223 + 50/207) = 0.0729 ... 75% of lead oxide
Similarly, when 200 g of lead powder is calculated as a mixture of 160 g of lead oxide and 40 g of metal lead, the following formula is obtained.
(4/60) / (160/223 + 40/207) = 0.0732 ... 80% lead oxide
Therefore, when the number of moles of diatomaceous earth with respect to the lead powder is expressed as a percentage, 7.29 mol% when the lead oxide content of the lead powder is 75% and 7.32 when the lead oxide content of the lead powder is 80%. Mol%.
When these are averaged, diatomaceous earth can be added in an amount of 7.3 mole percent or more with respect to the lead powder. It means that the utilization rate and capacity higher than 1 can be demonstrated. Therefore, in the claims, the number of moles of diatomaceous earth contained in the lead powder is set to 7.3 mol%. This can also be applied to the first embodiment. That is, in this example, 4 g of diatomaceous earth and 3 g of carbon in Table 1 were added.

The positive electrode active material utilization rate and lead acid battery capacity when only diatomaceous earth of Example 2 is added are substantially the same as the positive electrode active material utilization rate and lead acid battery capacity of Example 1 where carbon is also added (however, actually In Example 1, in which carbon was also added, the positive electrode active material utilization rate and the lead-acid battery capacity are slightly larger due to the contribution of the bulk density of carbon. Prior art paste no. It was confirmed that the utilization rate of the positive electrode active material of 1 was exceeded and the performance of the lead storage battery capacity was also exceeded.
Carbon was cheaper than lead powder, and diatomaceous earth was cheaper than carbon, realizing a low-cost lead acid battery. Moreover, in Example 2, since it is not necessary to use polyvinyl alcohol and a manufacturing process can be simplified, the lead acid battery further reduced in cost was implement | achieved.
In each of the examples of the present invention, the maximum positive electrode active material utilization rate is the same as that of the past paste No. Therefore, the amount of lead could be reduced to about ½.
Conventionally, lead-acid batteries have been easy to handle, safe (no fire hazard compared to lithium-ion secondary batteries, etc.) and large-capacity storage batteries, but their weight was the biggest drawback. . In data centers with a large capacity of lead storage batteries, floor weighting has been a problem.
In the present invention, all of these are solved and an ideal lead storage battery is realized as described above.

The diatomaceous earth described above can be said to be one type of porous silica. Since there are various types and varieties of porous silica, the active material utilization rate was tested.
<Description of main ingredients>
Lead powder, which is an active material raw material mainly composed of metal oxide, is a main constituent material of the active material raw material, and has an oxidation degree of about 75 to 80 percent. Acetylene black having an oil absorption of 160 ml / 100 g was used for carbon, and a degree of polymerization of 2400 was used for polyvinyl alcohol (manufactured by Kuraray Co., Ltd.). The silica porous body shown in Table 4 was tested.
Diatomaceous earth is different in pores, particle size (radiolite grades), manufacturer (Spidix and Dicalite), or naturally produced. Cell Pure S300) was tested. Further, pearlite made porous by expanding and crushing vitreous rock, and shirasu balloon expanded with vitreous rock were tested. These are all materials mainly composed of silicon dioxide.
Table 4 shows a list of these various porous silica materials and the test results of adding them.
Table 4 mainly describes the types of porous silica and the active material utilization rate (%) corresponding to this, and the polyvinyl alcohol dissolved in 3 g of carbon and 63 ml of hot water as an additive to the active material material. .1g is omitted in Table 4 but is actually included.

<Manufacturing method>
First, 3 g of carbon was kneaded with a polyvinyl alcohol aqueous solution in a ratio of 0.1 g of polyvinyl alcohol to 63 ml of warm water of about 90 ° C. for 30 minutes, and then lead powder was added to the kneaded material to add a small amount of sulfuric acid (1.3 g of sulfuric acid in Table 4). ) Was added and kneaded for 25 minutes, and 14 g of each type of porous silica was added one by one, and the kneading was continued for another 5 minutes. This is performed for each silica porous body.
However, the kneading time of about 30 minutes, 25 minutes, and 5 minutes is an approximate guide, and particularly the last kneading for 5 minutes varies depending on the amount of each porous silica material. Moreover, the addition time of each silica porous body may be mixed. That is, each silica porous body may be mixed when carbon is added to a polyvinyl alcohol aqueous solution and kneaded. Or when mixing lead powder in a subsequent process, each porous silica may be mixed.
The paste thus prepared was filled in a 3.7 mm thick grid-shaped current collector, then aged at 98% humidity and a temperature of 45 ° C. for 24 hours, and then dried at 60 ° C. for 24 hours. A positive electrode unformed plate was formed.

A fine glass fiber separator was brought into contact with both sides of one positive electrode plate, and a conventional negative electrode plate was brought into contact with each outside. By setting it as such a structure, the theoretical capacity | capacitance of an active material becomes large excessively in a negative electrode, and the utilization factor of the target positive electrode can be evaluated. The electrode plate group was inserted into the battery case, and the gap between the battery case and the electrode plate group was filled with an ABS resin spacer. Dilute sulfuric acid having a specific gravity of 1.223 was injected into the battery case, and 300% of the amount of electricity of the theoretical capacity of the positive electrode was supplied to perform chemical conversion. The specific gravity of the electrolytic solution after chemical conversion was set to 1.320.

Next, a capacity test (discharge test) was performed to calculate the utilization ratio of the positive electrode active material. Two types of capacity tests were performed: 0.06 amp discharge and 6 amp discharge. The 0.06 ampere discharge is equivalent to a rate of about 40 hours, and the 6 ampere discharge is equivalent to a rate of about 10 minutes. Each discharge end voltage was set to 1.7 volts and 1.2 volts per cell. The temperature is 25 ° C.
Table 4 shows the positive electrode composition subjected to the test and the results.
In Table 4, the active material utilization rate is expressed in%. Except for what is described as “added by adding water to silica” in the remarks column of Table 4, the silica is added without containing water.

Since the results in Table 4 have different test lots, it is better to roughly evaluate them.
Various types of silica porous materials were tested, and the low rate discharge utilization rate was 54 to 73%, and the high rate discharge utilization rate was about 21 to 29%. The active material utilization rate of 1 is exceeded. This is presumably because the porosity of the silica porous material is similar.

In addition to the diatomaceous earth of Example 1 and Example 2, the diatomaceous earth of Example 3, pearlite and shirasu balloon, the porous material to be added to the paste is hollow fiber (in Table 5, Table 5-2 and Table 5-3, hollow fiber) The test was conducted.
Table 5 is a list of positive electrode compositions subjected to the test. Paste No. 1 is the same as in Examples 1 and 2. The paste of the present invention is No. 24 to 29.

<Description of main raw materials>
Lead powder, which is an active material raw material mainly composed of metal oxide, is the main constituent material of the active material, and has an oxidation degree of about 75 to 80 percent. Acetylene black having an oil absorption of 160 ml / 100 g was used for carbon, and a degree of polymerization of 2400 was used for polyvinyl alcohol (manufactured by Kuraray Co., Ltd.). The hollow fiber is a fiber having a hole in the center, and a slit of about 0.1 to 0.25 μ is opened on the side of the fiber. When this is added to the active material, the electrolytic solution can be stored in the central hole, and the electrolytic solution can be moved through the side slit in discharging and charging.

<Manufacturing method>
First, polyvinyl alcohol is dissolved in warm water having a temperature of about 90 ° C., and when the dissolution is completed, an aqueous solution having a polyvinyl alcohol concentration of about 6% is manufactured. The upper part of the container is covered with a sheet such as a wrap in the container to be dissolved so that the water does not evaporate during the dissolution.
Carbon is added to this polyvinyl alcohol aqueous solution and kneaded for about 30 minutes. Thereafter, 200 g of lead powder is mixed into the kneaded product, 0.3 g of cut fiber is added and kneaded for about 25 minutes, and further hollow fibers are added. The kneading was continued for 5 minutes. However, the kneading time of about 30 minutes, 25 minutes, and 5 minutes is an approximate guide, and the kneading for the last 5 minutes varies depending on the amount of hollow fiber. Moreover, the addition time of the hollow fiber may be mixed. That is, the hollow fiber may be mixed when carbon is added to the aqueous polyvinyl alcohol solution and kneaded. Alternatively, the hollow fiber may be mixed when the lead powder is mixed in the subsequent process.
Positive electrode paste No. 1 prepared for comparison. No. 1 is simply kneaded according to the amounts in Table 5 and contains 11 grams of pure sulfuric acid.

A fine glass fiber separator was brought into contact with both sides of one positive electrode plate, and a conventional negative electrode plate was brought into contact with each outside. With such a configuration, the theoretical capacity of the active material is that the negative electrode is excessively large, and the utilization rate of the target positive electrode can be evaluated. The electrode plate group was inserted into the battery case, and the gap between the battery case and the electrode plate group was filled with an ABS resin spacer. Dilute sulfuric acid having a specific gravity of 1.223 was injected into the battery case, and 300% of the amount of electricity of the theoretical capacity of the positive electrode was supplied to perform chemical conversion. The specific gravity of the electrolytic solution after chemical conversion was set to 1.320.

Next, a capacity test (discharge test) was performed in order to obtain the positive electrode active material utilization rate and the lead storage battery capacity. Two types of capacity tests were performed: 0.06 amp discharge and 6 amp discharge. The 0.06 ampere discharge is equivalent to a rate of about 40 hours, and the 6 ampere discharge is equivalent to a rate of about 10 minutes. Each discharge end voltage was set to 1.7 volts and 1.2 volts per cell. The temperature is 25 ° C.

Tables 5-2 and 5-3 show the positive electrode active material utilization rate and the lead-acid battery capacity obtained in this test, respectively. FIG. 6 is a graph of Table 5-2. 24 to paste no. For 29, the utilization rate of the low rate 0.06 ampere discharge is shown by the upper plot groups ■ and □ (high utilization rate) in FIG. 6, and the high rate 6 by the lower plot group ■ and □ (small utilization rate) in FIG. The utilization rate of ampere discharge is indicated.
FIG. 7 is a graph of Table 5-3. In FIG. 24 to paste no. 7 shows the lead storage battery capacity of low rate 0.06 ampere discharge by upper plot groups ■ and □ (large capacity) in FIG. 7, and high rate 6 amperes by lower plot groups ■ and □ (small capacity) in FIG. The discharge lead-acid battery capacity is shown.
Prior Art Paste Nos. In FIG. 1, the utilization rate of low rate 0.06 ampere discharge is shown by plots ♦ and ◇ in FIG. 6, and the utilization rate of low rate 0.06 ampere discharge in FIG. 6 is shown.
Also, in Table 5, the conventional paste No. 1 shows the lead storage battery capacity of the low rate 0.06 ampere discharge by plots ♦ and ◇ in FIG. 7, and the plot ■ and □ in FIG. 7 show the lead storage battery capacity of the high rate 6 ampere discharge.
In Tables 5-2 and 5-3, and FIGS. 6 and 7, both the positive electrode active material utilization rate and the lead acid battery capacity are comparative paste Nos. Compared to 1, a high value was shown. In particular, the utilization rate of the positive electrode active material by the paste of the present invention is low and high. It was about twice that of 1.
Since the density of the material of diatomaceous earth is about twice that of hollow fiber, Table 5-2, which is a test result of the utilization rate of hollow fiber, is compared with Table 1-2, which is the result of using diatomaceous earth of Example 1. Then, for example, in comparison with the example of carbon 3g and hollow fiber 9g (paste No. 24), the hollow fiber 9g corresponds to about 18 g of diatomaceous earth when the volumes of both are made uniform.
The hollow fiber added low rate discharge utilization rate is about 55 percent (see Table 5-2. In FIG. 6, the leftmost / top plot), and the high rate discharge utilization rate is about 28 percent (see Table 5-2). The lower rate discharge utilization rate of diatomaceous earth addition of Example 1 is about 56% (in Table 1-2, 20 g of diatomaceous earth is substituted. In FIG. Plot ◆ (diatomaceous earth amount 20 g)), high-rate discharge utilization rate is approximately 28% (in Table 1-2, diatomite amount 20 g is used as a substitute, and in FIG. 2, the central and lower plots ◇ (diatomaceous earth amount 20 g)) To do. That is, even if there is a difference in material, if the bulk density is the same, the utilization factor is considered to be almost the same.

By adding carbon and silica porous material or hollow fiber to the positive electrode active material to obtain a kneaded paste, the utilization factor of the active material was greatly increased. From this test, it was found that a porous material that increases the bulk density contributes greatly to the improvement of the active material utilization rate universally. Therefore, the use of the positive electrode composition to which the hollow fiber is added also makes the active material utilization rate the paste No. of the prior art. It was found that the lead powder raw material can be reduced to almost ½.
It was found that reducing the lead powder raw material is effective as it is as a reduction in the cost of the storage battery, and the energy density can be greatly improved. Thereby, the weight reduction of the conventionally used storage battery was possible, and the possibility as an automobile hybrid storage battery became clear simultaneously. Although a significant improvement in utilization has not been possible for nearly 100 years, the present invention has made it possible for the first time. Its industrial value is extremely high.

These show the paste filling amount to the positive electrode lattice when changing the amount of diatomaceous earth with the amount of carbon according to Example 1 of the present invention as a parameter. These show the utilization rate of the positive electrode active material when the amount of diatomaceous earth with the amount of carbon according to Example 1 of the present invention as a parameter is changed. These show the lead acid battery capacity when changing the amount of diatomaceous earth with the amount of carbon according to Example 1 of the present invention as a parameter. These show the utilization rate of a positive electrode active material when the amount of diatomaceous earth according to Example 2 of the present invention is changed. These show lead acid battery capacity when the amount of diatomaceous earth by Example 2 of the present invention is changed. These show the utilization rate of a positive electrode active material when the amount of hollow fibers according to Example 4 of the present invention is changed. These show lead acid battery capacity when the amount of hollow fibers according to Example 4 of the present invention is changed.

Claims (19)

1. Bulk density after drying and unformed state of a kneaded material filled in a grid-like current collector or coated on a sheet-like current collector and containing an active material material mainly composed of metal oxide and carbon and silica porous material Is a positive electrode composition for a secondary battery, wherein the positive electrode composition is 2.6 × 10 ⁻¹ ml / g or more.
2. The first kneaded material produced by kneading the carbon with an aqueous polyvinyl alcohol solution is a kneaded material produced by mixing and kneading the active material raw material and the porous silica material. 2. The positive electrode composition for a secondary battery according to 1.
3. It is a kneaded product produced by mixing and kneading the active material raw material with a first kneaded product produced by kneading the carbon and the silica porous body with an aqueous polyvinyl alcohol solution. The positive electrode composition for secondary batteries according to claim 1.
4. A positive electrode composition for a secondary battery, comprising a kneaded material in which carbon and silica porous material are contained in an active material raw material mainly composed of a metal oxide.
5. The first kneaded product produced by kneading the carbon with an aqueous polyvinyl alcohol solution is a kneaded product produced by mixing and kneading the active material raw material and the porous silica material. 4. The positive electrode composition for a secondary battery according to 4.
6. It is a kneaded product produced by mixing and kneading the active material raw material with a first kneaded product produced by kneading the carbon and the silica porous body with an aqueous polyvinyl alcohol solution. The positive electrode composition for secondary batteries according to claim 4.
7. After drying a kneaded material filled with a grid-like current collector or coated on a sheet-like current collector, containing a porous silica in an active material raw material mainly composed of metal oxide and not containing carbon, the bulk in an unformed state A positive electrode composition for a secondary battery, wherein the density is 2.5 × 10 ⁻¹ ml / g or more.
8. A positive electrode composition for a secondary battery comprising a kneaded material containing a porous silica in an active material raw material mainly composed of a metal oxide and containing no carbon.
9. The positive electrode composition for a secondary battery according to any one of claims 1 to 8, which is a kneaded product containing 7.3 mol% or more of the porous silica material relative to the active material raw material.
10. The positive electrode composition for a secondary battery according to any one of claims 1 to 9, wherein the porous silica contained in the kneaded material is diatomaceous earth, pearlite, or shirasu balloon.
11. The positive electrode composition for a secondary battery according to any one of claims 1 to 10, wherein the kneaded product contains a small amount of sulfuric acid.
12. A positive electrode composition for a secondary battery, comprising a kneaded material in which carbon and hollow fibers are contained in an active material raw material mainly containing a metal oxide.
13. 13. The kneaded product produced by kneading the carbon with an aqueous polyvinyl alcohol solution is produced by mixing and kneading the active material raw material mainly composed of a metal oxide and the hollow fiber. The positive electrode composition for secondary batteries as described.
14. 13. The secondary battery according to claim 12, wherein the active material raw material is mixed and kneaded into a kneaded product generated by kneading carbon and hollow fibers with a polyvinyl alcohol aqueous solution. Positive electrode composition.
15. A secondary kneaded product produced by mixing and kneading the active material raw material and the porous silica material with a first kneaded product produced by kneading the carbon with an aqueous polyvinyl alcohol solution. A method for producing a positive electrode composition for a battery.
16. It is a kneaded product produced by mixing and kneading the active material raw material with a first kneaded product produced by kneading the carbon and the silica porous body with an aqueous polyvinyl alcohol solution. The manufacturing method of the positive electrode composition for secondary batteries.
17. The method for producing a positive electrode composition for a secondary battery according to claim 15 or 16, wherein the porous silica contained in the kneading is diatomaceous earth, pearlite, or shirasu balloon.
18. The method for producing a positive electrode composition for a secondary battery according to any one of claims 15 to 17, wherein the kneaded product contains a small amount of sulfuric acid.
19. A secondary battery produced by using the positive electrode composition for a secondary battery according to any one of claims 1 to 14 or by the method for producing a positive electrode composition for a secondary battery according to any one of claims 15 to 18. A secondary battery using the positive electrode composition.

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