JP2008258131A - Positive electrode composition for secondary battery and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a positive electrode composition that improves a utilization factor of an active material and assures a high energy density by using raw materials of cost comparable to a conventional storage battery especially for a positive electrode plate for a secondary battery. <P>SOLUTION: A positive electrode composition for a secondary battery is a mixed paste material containing a raw active material including a metal and its metal oxide, and carbon in the amount equivalent to total oil absorption of 9.6 milliliters or more relative to one mole of the raw active material. A bulk density in a non-formation state after the mixed paste material is filled and dried in a lattice-like collector is 2.2×10<SP>-1</SP>milliliters/gram or more, and carbon is acetylene black and/or furnace carbon. Preferably, the mixed paste material contains additional sulphuric acid. As a manufacturing method, a first mixed pasting is performed with water and carbon, and then lead powder and water are added to the resultant product for second mixed pasting to obtain the mixed paste material. When the mixed paste material contains sulphuric acid, the sulphuric acid is added in the second mixed pasting. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a positive electrode composition for a secondary battery that has a high energy density and can be produced at low cost, and a method for producing the same.

  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, lithium-ion batteries are also forced to use expensive materials.

  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 volume increases with the change to the discharge active material, the pores of the porous structure in the electrode plate become small, and it becomes difficult to diffuse the electrolytic solution into the active material.

  Moreover, 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 rate 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, but it has been known that the charge / discharge cycle life is drastically reduced as a contradiction. Therefore, maintaining the charge / discharge cycle life, increasing the porosity of the electrode plate, and improving the utilization rate of the active material are considered to be extremely difficult and remain unsolved.

  Lead storage batteries are preferable in that the raw materials are inexpensive, but because the utilization rate of the active material is low, the amount of lead used must be increased, and as a result, the weight of lead, which is higher in density than other materials, It further increases, leading to a decrease in energy density. 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 exist patent document 1 and 2, 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, 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 in a lattice made of a lead alloy containing no antimony, Carbon black treated at a predetermined pressure and temperature as a conductive material is used in an amount of 2 g (0.17 mol) or less per 1 mol of lead.

In Patent Document 2, improvements are made by giving examples of the prior art as follows. As a first example, in the positive electrode plate manufactured by the above-described conventional technology, in order to increase the porosity of the active material in order to improve the utilization factor of the active material of the positive electrode plate, the particles between the particles generally constituting the active material As a result, the active material falls off the positive electrode plate, and the adhesion between the active material and the lattice body deteriorates, particularly when deep charge / discharge is repeated. As a result, the current collection efficiency was reduced and the battery life was shortened. " The second is, “On the other hand, the lead storage battery using the positive electrode containing the tin-based additive does not undergo oxidative decomposition like the carbon-based additive even after repeated charge and discharge, The conductive network is maintained, but on the other hand, micropores on the surface of the positive electrode plate, in particular, tend to decrease in porosity, making it difficult to diffuse sulfuric acid necessary for the discharge reaction, resulting in the use of active materials. There was a problem that the rate decreased and the capacity of the battery decreased. " Therefore, Patent Document 2 has the following description as a solution means. “To solve the above-mentioned problems and to provide a positive electrode plate for a lead storage battery that achieves the above-mentioned object, characterized in that the positive electrode active material contains a carbon-based additive and a tin-based additive. According to the invention, the positive electrode plate for a lead storage battery capable of reliably obtaining the above excellent characteristics is provided, and the addition amount of the carbon-based additive and the tin-based additive is the number of moles of lead in the positive electrode active material. On the other hand, it is 0.05 to 5 mol%, and the blending ratio of both additives is 1 to 5: 5 to 1. " The meaning of “containing a carbon-based additive and a tin-based additive in the positive electrode active material” means that, as the prior art, the first and second each alone cannot improve and improve the life and utilization of the storage battery. It is essential to contain both a carbon-based additive and a tin-based additive.
JP 2002-324552 A JP 2001-43861 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 in order to improve conductivity, and it is not intended to improve both the utilization factor and the life due to the porosity. Although patent document 2 makes the subject the improvement of both the utilization factor by porosity, and the improvement of a lifetime, the utilization factor of about 70% or more of active materials which can obtain a high energy density is not implement | achieved.

  As described above, the main cause of the low energy density of the lead storage battery is that the utilization factor cannot be increased to about 70% because the electrical resistance increases. In addition, the utilization factor is further reduced in the usage mode in which discharging is performed with a large current. Moreover, it is said that the utilization factor and lifetime of an active material have a contradictory relationship. That is, when the utilization rate is increased, there is a fatal problem that the charge / discharge cycle life is reduced.

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

  Accordingly, an object of the present invention is to provide a storage battery, that is, a secondary battery that can obtain a high energy density by using a raw material having a cost comparable to that of a lead storage battery. More specifically, an object of the present invention is to provide a positive electrode composition for a secondary battery in which the utilization factor of the active material is improved with a low-cost raw material for the positive electrode plate of the secondary battery.

In order to achieve the above object, the present invention provides the following configurations.
The positive electrode composition for a secondary battery according to claim 1 comprises an active material raw material mainly composed of a metal oxide, and an amount of carbon having a total oil absorption of 9.6 ml or more with respect to 1 mol of the active material raw material. It is a kneaded material to be contained.
The positive electrode composition for a secondary battery according to claim 2 is the positive electrode composition for a secondary battery according to claim 1, wherein the bulk density of the dried positive electrode composition for a secondary battery is 2.2 × 10 ⁻¹ milliliter / gram or more. It is characterized by that.
The positive electrode composition for a secondary battery according to claim 3 is characterized in that, in claim 1 or 2, the carbon is acetylene black and / or furnace carbon.
The manufacturing method of the positive electrode composition for secondary batteries which concerns on Claim 4 is a manufacturing method of the positive electrode composition for secondary batteries in any one of Claims 1-3, Comprising: The mixture containing the said carbon and water at least. It has the 1st process of kneading | mixing, and the 2nd process of adding the said active material raw material to the product obtained by the said 1st process, and also kneading | mixing.
The positive electrode composition for a secondary battery according to a fifth aspect is characterized in that in any one of the first to third aspects, the kneaded material further contains sulfuric acid.
A method for producing a positive electrode composition for a secondary battery according to claim 6 is a method for producing a positive electrode composition for a secondary battery according to claim 5, wherein the mixture containing at least the carbon and water is kneaded. And a second step of adding and kneading the active material raw material and the sulfuric acid to the product obtained by the first step.

  In the present invention, in order to improve the utilization rate of the positive electrode active material used in the secondary battery, the electrolyte solution (dilute sulfuric acid) and the active material can be sufficiently in contact with each other, and a configuration that does not cause an increase in electrical resistance has been realized. . In the present invention, a carbon conductive network is formed on a positive electrode plate (that is, a positive electrode of a battery including the positive electrode composition for a secondary battery of the present invention; the same applies hereinafter), and the network supports a number of electrolytes. Therefore, the amount of oil absorption in the positive electrode plate is increased. In other words, by increasing the porosity, the amount of the electrolyte present in the positive electrode plate is increased, and by allowing the electrolyte to penetrate and diffuse from outside the positive electrode plate, It constituted so that it could fully supply. Specifically, in the kneaded material containing the positive electrode active material raw material, the total oil absorption amount of carbon with respect to 1 mol of the active material raw material (mainly composed of metal oxide) is 9.6 ml (milliliter) or more.

In the positive electrode plate, a conductive network can be formed by containing carbon which is a particle chain structure material. A particle chain structure substance refers to a substance in a state in which a plurality of particulate substances are fused to each other and extend in a chain shape as a whole (including a branched chain structure such as a branch). A positive electrode composition which is a kneaded material obtained by adding this to lead powder which is an active material raw material is prepared. The produced positive electrode composition increases in bulk density by including the particle chain structure material. The kneaded product preferably has a bulk density of 2.2 × 10 ⁻¹ ml / g or more in an unformed state after drying.

  In this kneaded product, carbon, which is a particle chain structure material, is entangled vertically and horizontally to form a three-dimensional network, and lead powder, which is an active material raw material, is distributed almost uniformly in this conductive network. . At the same time, countless pores are formed to form a porous structure. After the active material raw material becomes an active material by chemical conversion, these holes can hold a sufficient amount of electrolyte. In addition, good conductivity can be maintained with carbon. In order to maintain the discharge, the dilute sulfuric acid retained in these holes is continuously supplied to the dispersed active material. As a result, the conductive network can prevent a rapid increase in electrical resistance immediately before the discharge partition.

  In this way, by including a particle chain structure material having a predetermined oil absorption amount, the porosity of the positive electrode composition is improved, the oil absorption amount is increased, and the supply of the electrolyte solution is promoted, whereby the utilization rate of the positive electrode active material is increased. It has become possible to exceed 70%, which has been regarded as a theoretical limit. If the utilization rate of the conventional general low rate discharge was 35%, a utilization rate of about twice was realized. Similarly, an improvement of about twice was also observed in high rate discharge.

  As the carbon, a high utilization factor can be obtained by using either acetylene black and / or furnace carbon. Furnace carbon is preferred because it is inexpensive.

  In the first embodiment of the present invention, the positive electrode composition that is a kneaded product does not contain sulfuric acid. On the other hand, in 2nd Embodiment, the positive electrode composition which is a kneaded material contains a sulfuric acid.

  The manufacturing method of the positive electrode composition according to the first embodiment includes a first step of kneading carbon with water, and a second step of adding an active material raw material to the product obtained in the first step and further kneading. And have. Such two-stage kneading has not been performed in the past, but this two-stage kneading forms a carbon conductive network with a suitable bulk density, improving the active material utilization rate by about two times. I was able to. In the first embodiment, such a good result was obtained even though only water was used as the kneading medium and sulfuric acid was not used as in the prior art.

  In the method for producing a positive electrode composition according to the second embodiment, a first step of kneading carbon with water, and a second step of adding an active material raw material and sulfuric acid to the product obtained in the first step and further kneading are performed. It has these processes. The second embodiment contains sulfuric acid, but unlike a conventional manufacturing method in which sulfuric acid is kneaded in a single step, the active material is obtained by mixing in two stages and kneading sulfuric acid in the second step. The utilization rate could be further improved. That is, compared with the first embodiment using only water as the kneading medium, the second embodiment further improves the utilization rate of the positive electrode active material by several percent in both the low rate discharge and the high rate discharge. It could be improved by about 20%.

  According to the present invention, it has become possible to greatly improve the active material utilization rate which has been practically about 35%. Since the actual utilization rate of low-rate discharge has nearly doubled, the lead powder, which is an active material raw material required to exhibit the desired battery capacity, can be reduced to about 1/2 of the conventional amount. Is possible. This can be expressed as utilization rate = actual capacity / theoretical capacity. When the utilization rate is doubled, the theoretical capacity can be halved to ensure the same actual capacity as before. That is, the amount of lead powder used can be halved. (In this calculation of the utilization rate, the ratio is simply shown, but in the embodiment shown below, it is displayed as 100%.)

  By reducing the amount of lead powder, the cost of the storage battery can be further reduced, and the energy density can be greatly improved. As a result, the conventional storage battery can be reduced in weight with the same battery capacity. As a result, the battery becomes extremely suitable for a hybrid vehicle storage battery and an electric vehicle. Although significant improvements in active material utilization have been impossible over the past hundred years, the present invention has made it possible for the first time. It can be said that its industrial value is extremely high.

  In addition, by using the positive electrode composition of the present invention, a lead storage battery having a markedly improved charge / discharge cycle life that has been impossible in the past could be produced.

First, an outline of an embodiment of the present invention will be described. Details will be described in the following embodiments.
The positive electrode composition for secondary batteries according to the present invention is substantially intended for lead acid batteries. The positive electrode composition is a paste-like kneaded product obtained by adding an active material raw material as a main component and other necessary components. The paste-like kneaded product is filled into 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 and a chemical conversion step is performed to activate the active material material. It becomes a substance 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 according to the present invention contains an active material material mainly composed of a metal oxide and carbon. The active material raw material is lead powder. And carbon is made into the quantity from which a total oil absorption becomes 9.6 ml or more with respect to 1 mol of active material raw materials. The “total oil absorption amount” is the total oil absorption amount of carbon in the carbon content relative to 1 mol of the active material raw material in the relationship between the relative content of carbon and the active material raw material contained in the positive electrode composition (described later). This is a value different from the DBP oil absorption, which is an indicator of carbon characteristics.

As a measure of the porosity of the positive electrode composition of the present invention, the bulk density is 2.2 × 10 ⁻¹ ml / g or more in the unformed state after being dried. In addition, the positive electrode composition produced | generated by kneading | mixing is normally filled in a grid | lattice-shaped electrical power collector before chemical formation, and is age | cure | ripened and dried.

  As carbon, for example, acetylene black or furnace carbon can be used, and these may be mixed and used. Both acetylene black and furnace carbon yielded almost the same high active material utilization rate.

  The kneaded product in the first embodiment of the positive electrode composition according to the present invention does not contain sulfuric acid. Therefore, the kneading medium of the first embodiment may be water only. On the other hand, the kneaded product of the second embodiment contains sulfuric acid in addition to the components of the first embodiment. Therefore, in the second embodiment, water and dilute sulfuric acid are used as the kneading medium.

  Furthermore, you may contain polyvinyl alcohol (PVA) 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.

  The manufacturing method of the positive electrode composition of 1st Embodiment which does not contain a sulfuric acid is as follows. In the first kneading step, carbon is kneaded with water to obtain a product. Next, in the second kneading step, lead powder as an active material raw material is added to the product of the first kneading step 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 first kneading step.

  Moreover, in the manufacturing method of the positive electrode composition of the second embodiment containing sulfuric acid, the first kneading step is the same as that of the first embodiment. In the second kneading step, lead powder and sulfuric acid, which are raw materials for the active material, are added to the product of the first kneading step and further kneaded to obtain a kneaded product. When PVA is contained, it is added in the first kneading step.

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

  The utilization rate of the active material comprising the positive electrode composition according to the first embodiment containing no sulfuric acid is about 68% for 40 hour rate discharge (low rate discharge) and 10 minute rate discharge when using a grid current collector. (High rate discharge) was about 38%. 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.

  Moreover, the utilization factor of the active material comprising the positive electrode composition according to the second embodiment containing sulfuric acid was further improved as compared with the case where no sulfuric acid was contained. When sulfuric acid was contained, the utilization rate was improved by about 20% in the low rate discharge and the high rate discharge as compared with the utilization rate of the first embodiment not containing sulfuric acid.

  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.

  An electrode plate in which a paste is filled in a grid-like current collector can be basically used for all uses of conventional lead-acid batteries, and can be made 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. In hybrid vehicles, nickel-metal hydride battery storage batteries and lithium ion batteries are currently being used or studied, but both have the problem of high costs. The lead storage battery according to the present invention is much lower in cost than a nickel hydride battery storage battery and a lithium ion 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 long life, has a high active material utilization rate, and is low in cost. Compared with lithium ion batteries and nickel metal hydride 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 acid 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 acid battery, can be discharged by a large current, and can be lightweight.

  Hereinafter, each example of the present invention when applied to a positive electrode plate using a grid-like current collector will be described.

In Example 1, a kneaded product of a positive electrode composition with different bulk density was prepared without using sulfuric acid, and a test was performed on a positive electrode plate in which the kneaded product was packed in a grid-like current collector.
<Preparation of sample>
Table 1 is a list showing the component composition when preparing a kneaded product of the positive electrode composition subjected to the test. The “positive electrode paste” means a kneaded product in a paste state after kneading these components and before drying.

  The lead powder of component 1 is a raw material for the positive electrode active material, and the oxidation degree of lead is about 75 to 80%. As the component 2 carbon, acetylene black having a DBP oil absorption of 175 ml / 100 g was used. As the component 3, polyvinyl alcohol (manufactured by Kuraray Co., Ltd.) having a polymerization degree of 2400 was used. The amount of polyvinyl alcohol was set to about 10% of the amount of carbon.

  The DBP oil absorption indicates the amount of dibutyl phthalate absorbed per 100 g of the substance, and is one index indicating the liquid absorbency of the substance. Here, it is used as a parameter of the bulk density, which is a property of the electrode plate using the positive electrode active material raw material. In the examples of the present invention, the characteristics of the positive electrode composition according to the present invention are clearly related to the DBP oil absorption amount or the total oil absorption amount converted based on the DBP oil absorption amount and the active material utilization rate and the battery capacity. The relationship between the utilization rate and battery capacity was clarified. The bulk density was controlled by the amount of carbon and water.

  When carbon is used (positive electrode pastes 1 to 7), these are first kneaded for 30 minutes together with water and polyvinyl alcohol (first kneading step), and then lead powder is added to the kneaded material, followed by further kneading. This was performed for 30 minutes (second kneading step).

  A positive electrode paste 8 produced as a conventional example (hereinafter sometimes referred to as “conventional paste”) is obtained by simply kneading lead powder and dilute sulfuric acid in the amounts shown in Table 1. 49 g of dilute sulfuric acid in the positive electrode paste 8 corresponds to 11 g in terms of pure sulfuric acid.

  The positive electrode pastes 1 to 8 thus prepared were filled in a 3.7 mm thick grid-shaped current collector, then aged at 98% humidity and 45 ° C. for 24 hours, and then dried at 60 ° C. for 24 hours. Thus, a positive electrode plate was formed. Similarly, the positive electrode paste 8 as a conventional example was filled in a grid-shaped current collector and subjected to the same treatment.

  Polyvinyl alcohol exhibits an effect as a dispersant for the kneaded material while ensuring the conductivity of carbon, and can also improve the adhesion of the positive electrode paste to the electrode plate. Polyvinyl alcohol prevents the collapse of the carbon network structure by covering and protecting the carbon, thereby improving the service life. Since polyvinyl alcohol is relatively inexpensive, a higher active material utilization rate can be obtained without increasing the material cost.

<Calculation of theoretical capacity>
The theoretical capacity of the positive electrode active material was calculated for each unformed positive electrode plate produced according to Table 1 assuming each chemical conversion. In the calculation of the theoretical capacity, it was assumed that the lead powder as a raw material changed to lead dioxide in the chemical conversion process, and that all of lead dioxide contributed to the discharge. And 4.463 g of lead dioxide is converted into a capacity of 1 Ah. However, as will be described later, the lead powder is composed of 75% to 80% lead oxide and 25% to 20% lead (not oxidized). Therefore, this lead is not completely changed to lead dioxide in the chemical conversion process, and only part of it is converted to lead dioxide. Further, all lead dioxide does not contribute to the discharge and is about 70% as described above. Therefore, under this assumption, the theoretical capacity increases, and thus the utilization rate evaluation of the present invention works in a severe direction.

  FIG. 1 is a graph showing the relationship between the amount of carbon of an unformed positive electrode plate produced from positive electrode pastes 1 to 8 and the theoretical capacity as if the filled active material material was formed based on the calculation results. It can be seen that the theoretical capacity decreases as the proportion of carbon increases. That is, when the ratio of carbon increases, the total filling amount of the active material raw material in the unformed positive electrode plate relatively decreases. This means that the bulk of the positive electrode composition is increased due to the formation of the carbon network.

<Measurement of bulk density>
Next, the bulk density showing one of the characteristics of the positive electrode composition 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)

FIG. 2 is a graph showing the relationship between the amount of carbon in the unformed positive electrode composition prepared from the positive electrode pastes 1 to 8 and the bulk density of the unformed positive electrode composition based on the measurement result of the bulk density. It can be seen that as the amount of carbon increases, the bulk density of the unformed positive electrode composition increases. The bulk density of the unformed positive electrode composition produced by the conventional positive electrode paste 8 was about 2.2 × 10 ⁻¹ ml / g. Therefore, when the amount of carbon is about 5 g or more, the bulk density of the positive electrode composition of the present invention exceeds that of the conventional one.

<Measurement of utilization and capacity>
A fine glass fiber separator was brought into contact with both sides of one unformed positive electrode plate, and further, one negative electrode plate was brought into contact with the outside thereof. With such a configuration, the theoretical capacity of the active material is such that the negative electrode has a large excess, so that the utilization factor of the target positive electrode (that is, the active material) can be evaluated. These electrode plate groups were inserted into the battery case, and an ABS resin spacer was loaded in the gap between the battery case and the electrode plate group. The dilute sulfuric acid having a specific gravity of 1.223 was injected into the battery case, and the amount of electricity of 300% 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.

  Then, the capacity | capacitance test was done about the electrode group inserted in said battery case. Two types of capacity tests, 0.06 A (ampere) and 6 A, were used. 0.06A is a low rate discharge with a rate of about 40 hours, and 6A is a high rate discharge with a rate of about 10 minutes. The respective discharge end voltages were 1.7 V (volt) and 1.2 V per cell. The temperature is 25 ° C.

  FIG. 3A is a graph showing the relationship between the amount of carbon and the utilization rate based on the measurement result of the utilization rate. FIG. 3B is a graph showing the relationship between the bulk density and the utilization factor by replacing the horizontal axis of FIG. 3A with the bulk density based on the measurement result of the bulk density shown in FIG. “P1” or the like in the legend of the graph means “positive electrode paste 1” or the like. The rhombus plot in each graph of FIG. 3A and FIG. 3B shows the measurement result of the low rate discharge, and the square plot shows the measurement result of the high rate discharge. The measured values of low rate discharge and high rate discharge (2 samples are measured for each paste) are also shown in Table 1.

  In addition, although the lead powder which is an active material raw material is mainly lead oxide, it also includes metallic lead that is not oxidized. Lead oxide reacts with sulfuric acid in the electrolytic solution, and changes to lead dioxide as an active material by chemical conversion. In general, lead dioxide thus produced is regarded as an active material. Then, in the calculation of the utilization rate of the active material, whether or not the metal lead originally contained is regarded as a raw material that changes into the active material is a matter of debate. Perhaps metal lead contributes as an active material to a much lower extent than lead oxide, but here, the metal lead originally contained in the lead powder is changed to an active material as well as lead oxide. The active material utilization rate in the discharge was calculated. When the contribution to the utilization ratio of metallic lead is low, the utilization ratio of the original active material of the present invention (when only lead oxide contributes as the active material) is higher than that shown in this embodiment. The same applies to other embodiments.

As shown in FIG. 3A and FIG. 3B, when using positive electrode pastes 1 to 7 which are implementation pastes, both the low rate discharge and the high rate discharge increase the utilization rate when the amount of carbon increases, and reach a maximum value. It gradually decreases. In the low rate discharge, when the amount of carbon was about 11.5 g, that is, when the bulk density was about 3.25 × 10 ⁻¹ ml / g, about 68% which was the maximum value of the utilization rate was obtained. In the high rate discharge, when the amount of carbon was about 13.5 g, that is, when the bulk density was about 3.6 × 10 ⁻¹ ml / g, about 38% which was the maximum value of the utilization rate was obtained. These values are values read from the combined lines of the utilization plots of FIGS. 3A and 3B.

When the practical paste is used, the carbon content is about 5 g, that is, the bulk density is about 2.2 × 10 ⁻¹ ml / g or more in both low rate discharge and high rate discharge. Even the utilization rate increased. More preferably, the carbon amount is 5.7 g, that is, the bulk density is 2.3 × 10 ⁻¹ ml / g or more. In the conventional positive electrode paste 8, the utilization factor is about 33.8% in the low rate discharge and about 16.7% in the high rate discharge (these values are average values of actual measured values). This is the same as the upper limit value of the utilization rate known conventionally.

From the results shown in FIGS. 3A and 3B, it is necessary to set the amount of carbon to about 5 g or more with respect to 200 g of lead powder, and the bulk density of the positive electrode paste to about 2.2 × 10 ⁻¹ ml / g or more. 5 g of carbon corresponds to 46% in terms of molar ratio with respect to 200 g of lead powder. When the oxidation degree of the lead powder is 75%, the molar amount of the lead powder 200 g is expressed as (150 g / 223) + (50 g / 207) from the molecular weight 223 of lead oxide and the molecular weight 207 of lead. From the molecular weight of carbon 12, the molar amount of 5 g of carbon is expressed as 5 g / 12. Therefore, the molar ratio of carbon to lead powder is calculated as (5 g / 12) / (150 g / 223 + 50 g / 207) = 0.456. That is, the molar ratio of carbon to lead powder is about 46%. In addition, when the oxidation degree of lead powder is 80%, the molar ratio of carbon to lead powder is calculated to be 0.458, which is also about 46%.

  When the amount of carbon is small, that is, when the bulk density is small, it is necessary to supply more electrolyte solution (dilute sulfuric acid) necessary for the active material to discharge from the outside of the electrode plate. Since the electrolytic solution can be supplied from the vicinity of the active material (dilute sulfuric acid absorbed by carbon), it is easier to discharge and acts more powerfully. Therefore, the results shown in FIGS. 3A and 3B are obtained. The utilization factor is absolutely necessary for improving the energy density of the battery. In addition, since the battery active material (that is, the active material raw material) can be reduced if the utilization factor is high, the cost reduction is significant.

  As described above, the utilization factor is an extremely important factor, but in some cases, there are applications that require the absolute capacity of the battery. FIG. 4 is a graph showing the relationship between the amount of carbon and the capacity based on the measurement result of capacity. The rhombus plot in the graph of FIG. 4 shows the measurement result of the low rate discharge, and the square plot shows the measurement result of the high rate discharge.

  As shown in FIG. 4, the capacities of the low rate discharge and the high rate discharge each increased monotonously as the carbon amount increased, and then decreased monotonously through a range having a substantially constant value. The range of the amount of carbon in which a capacity larger than that of the conventional positive electrode paste 8 is obtained is about 5 g to about 15 g with respect to 200 g of lead powder for both low rate discharge and high rate discharge. In the region where the amount of carbon is less than 5 g, it is considered that the capacity is lower than the conventional because the bulk density is small, and the capacity is reduced in the region where the amount of carbon exceeds 15 g because the bulk density is large. This is probably because the absolute amount of the substance is reduced. Carbon 5g-15g is equivalent to 46% -137% in molar ratio with respect to 200g of lead powder (by the same calculation as the calculation about the above-mentioned carbon 5g).

From the results of FIGS. 3A, 3B and FIG. 4, in order to improve the utilization rate and obtain a large absolute capacity, the carbon amount is about 5 g, that is, the bulk density is about 2.2 × 10 ⁻¹ ml / g or more. Is preferred.

Here, an important factor that determines the utilization rate of the active material is the total oil absorption amount of carbon, and determines the relationship between the amount of oil absorbed by the entire carbon and the number of moles of lead powder. There is a need. As described above, a value of 5 g was obtained as the minimum amount of carbon for 200 g of lead powder. The amount of liquid retained in the entire 5 g of carbon, that is, the total oil absorption is expressed by 1.75 ml / g × 5 g. On the other hand, the oxidation degree of the lead powder used in the working paste is 75 to 80%. When the degree of oxidation is 75%, the molar amount of 200 g of the lead powder is represented by (150 g / 223 + 50 g / 207). Therefore, the total amount of carbon supplied per mole of lead powder when the degree of oxidation is 75% is 1.75 (ml / g) × 5 g / (150 g / 223 + 50 g / 207) = 9.57 (ml / mol). Further, when the oxidation degree is 80%, the molar amount of 200 g of the lead powder is represented by (160 g / 223 + 40 g / 207), and therefore the total amount of carbon supply per 1 mol of the lead powder when the oxidation degree is 80%. Is 1.75 (ml / g) × 5 g / (160 g / 223 + 40 g / 207) = 9.61 (ml / mol).
From these calculation results, it is necessary that the total oil absorption amount of carbon per mole of the active material raw material is about 9.6 ml or more in order to exceed the utilization rate of the conventional active material.
When 5.7 g of the above carbon amount is contained, the total oil absorption amount of carbon calculated here is about 9.6 ml / mol, and is multiplied by 5.7 / 5, so that the total oil absorption amount of carbon is about 11 ml / mol. Mole. Therefore, more preferably, the total oil absorption amount of carbon per mole of the active material raw material is in the range of about 11 ml or more.

<Life test>
The life test for the charge / discharge cycle was performed on the positive electrode paste 5 (carbon 8.6 g) of the present invention shown in Table 1 and the conventional positive electrode paste 8 (without carbon).
Each of the cells is connected in parallel with three positive electrode plates with a thickness of 3.7 mm and four negative electrode plates with a thickness of 2.2 mm, which are grid-shaped current collectors. The positive electrode plates are filled with positive electrode pastes 5 and 8, respectively. The negative electrode plate was filled with a conventional appropriate negative electrode paste. Thereafter, it was aged for 24 hours at a humidity of 98% and a temperature of 45 ° C., and then dried at 60 ° C. for 24 hours.

  Next, a fine glass fiber separator was brought into contact with each electrode plate, the electrode plate group was inserted into the battery case, and an ABS resin spacer was loaded in the gap between the battery case and the electrode plate group. The dilute sulfuric acid having a specific gravity of 1.223 was injected into the battery case, and the amount of electricity of 300% 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. In this way, a storage battery having a capacity of 7 A · h (ampere hour) was produced.

The life test by repeating the charge / discharge cycle was performed under the following conditions.
(A) Discharge: Current 7A
(B) End-of-discharge voltage: 1.6 V / cell (c) Charging: Current I ₁ was set to 7 A until 2.45 V was reached (charging time T ₁ ), then current I ₂ was set to 4.9 A (this The voltage drops slightly. After charging again until it reached 2.45 V (charging time T ₂ ), the current I ₃ was set to 3.4 A (thus lowering the voltage slightly). Thereafter, every time the voltage reached 2.45 V, the charging current I _i was decreased to 2.4 A, 1.7 A, 1.1 A, 0.8 A, and 0.4 A. Each time the current value was changed, the battery was charged until it reached 2.45 V (charging time at each current I _i was T _j ). The battery was charged until the total charge current amounted to about 105% of the discharge amount. That is, the total charging current amount is ΣI _i · T _j, which is the sum of products of the charging current I _i and the charging time T _j (where i = j). The temperature was 25 ° C.

  FIG. 5 is a graph showing the results of the life test. The paste of the present invention maintained a capacity of about 80% of the initial capacity even after 500 cycles. With the conventional paste, it became about 75% of the initial capacity after 500 cycles. In general, it is said that the greater the bulk density, the shorter the life because the active material is more likely to collapse. Longer life than paste. The paste of the present invention is stable even after exceeding 300 cycles, and the conventional paste monotonously decreases after exceeding 300 cycles.

  Although the positive electrode paste according to the present invention has a large bulk density, since the carbon network supports the positive electrode composition including the carbon network itself, even if charging and discharging are repeated, the collapse of the active material is suppressed and the life performance is improved. This has been achieved.

  Thus, according to the present invention, it was possible to achieve both the cycle life performance of the storage battery and the improvement of the utilization factor and capacity of the active material. Conventionally, improvement in the utilization rate and cycle life performance are in a trade-off relationship, and it has been considered that if the utilization rate is increased, the cycle life performance is inevitably reduced. Both can be stretched.

Positive electrode pastes with different types of carbon were prepared without using sulfuric acid in the same manner as in Example 1, and tests were performed on positive electrode plates filled with these positive electrode pastes in a grid-like current collector. Moreover, the bulk density was changed by adding an emulsion to positive electrode pastes having the same carbon content, and tests were also conducted on them.
<Preparation of sample>
Table 3 is a list of component compositions of the positive electrode paste subjected to the test.

  The lead powder of component 1 which is an active material raw material has a lead oxidation degree of about 75 to 80%. For comparison of the types of carbon, acetylene black having a DBP oil absorption of 175 ml / 100 g as component 2 and furnace carbon having a DBP oil absorption of 220 ml / 100 g as component 3 were used. As the component 4, polyvinyl alcohol having a polymerization degree of 2400 was used, and the amount thereof was about 5% of the carbon amount. As the emulsion of component 5, an acrylic styrene emulsion was used. The emulsion was added to change the bulk density of positive electrode pastes 9-12 containing the same amount of acetylene black.

  For the positive electrode pastes 9 to 14, carbon was kneaded with polyvinyl alcohol, an emulsion and water for 30 minutes (first kneading step), and then lead powder was added to the kneaded material and further kneaded for 30 minutes (first) 2 kneading step).

  The positive electrode pastes 9 to 14 thus prepared were filled into a 3.7 mm thick grid-shaped current collector, then aged at 98% humidity and 45 ° C. for 24 hours, and then dried at 60 ° C. for 24 hours. Thus, an unformed positive electrode plate was formed.

<Measurement of bulk density>
In the positive electrode pastes 9 to 12 containing the same amount of carbon, the bulk density decreased when the addition amount of the emulsion was increased. The positive electrode paste 9 is 2.97 × 10 ⁻¹ ml / g, the positive electrode paste 10 is 2.85 × 10 ⁻¹ ml / g, the positive electrode paste 11 is 2.80 × 10 ⁻¹ ml / g, and the positive electrode paste 12 is It was 2.71 × 10 ⁻¹ ml / g.

<Measurement of utilization rate>
Next, a fine glass fiber separator was brought into contact with both sides of one positive electrode plate, and further, one negative electrode plate was brought into contact with the outside thereof. With such a configuration, the theoretical capacity of the active material is such that the negative electrode has a large excess, so that the utilization factor of the target positive electrode (that is, the active material) can be evaluated. These electrode plate groups were inserted into the battery case, and an ABS resin spacer was loaded in the gap between the battery case and the electrode plate group. Dilute sulfuric acid having a specific gravity of 1.223 was injected into the battery case, and 300% of the theoretical capacity of the positive electrode was passed to conduct chemical conversion. The specific gravity of the electrolytic solution after chemical conversion was set to 1.320.

  Then, the capacity | capacitance test was done about the electrode group inserted in said battery case. Two types of capacity tests, 0.06A and 6A, were used. 0.06A is a low rate discharge with a rate of about 40 hours, and 6A is a high rate discharge with a rate of about 10 minutes. The respective discharge end voltages were 1.7 V and 1.2 V per cell. The temperature is 25 ° C.

  FIG. 6 is a graph showing the relationship between the bulk density of the positive electrode paste and the utilization factor by 0.06A low rate discharge. FIG. 7 is a graph showing the relationship between the bulk density of the positive electrode paste and the utilization factor by 6A high rate discharge.

  The relationship between the positive electrode pastes 9 to 12 containing the same amount of carbon and the utilization rate is as follows. As described above, the positive electrode pastes 9 to 12 have progressively smaller bulk densities from the positive electrode pastes 9 to 12. As shown in FIGS. 6 and 7, it was found that the utilization rate was larger as the bulk density of the unformed positive electrode paste was larger even when the amount of carbon was the same. Thereby, it became clear that the improvement of the utilization factor of the active material in the present invention was caused not by the amount of carbon itself but by the formation of a carbon network structure.

  In addition, the positive electrode paste 9 using acetylene black as carbon and the positive electrode paste 14 using furnace carbon as carbon (the amount of carbon is the same in both pastes, and the same applies to emulsions, and comparison is possible. In other words, almost the same utilization rate was obtained for both low rate discharge and high rate discharge. From this result, it can be said that the utilization rate is almost unrelated to the type of carbon. However, in high rate discharge, acetylene black has a slight advantage. The reason why the utilization rate of the positive electrode paste 13 using furnace carbon is higher than the others is that the amount of carbon is large (that is, the bulk density is large). Furnace carbon is advantageous in terms of cost because it is less expensive than acetylene black.

In Example 3, sulfuric acid was added to prepare a kneaded product of the positive electrode composition, and a test was performed on a positive electrode plate in which the kneaded product was filled in a grid-like current collector.
<Preparation of sample>
Table 4 is a list showing the component composition when preparing a kneaded product of the positive electrode composition subjected to the test.

  The lead powder of component 1 is a raw material for the positive electrode active material, and the oxidation degree of lead is about 75 to 80%. As the component 2 carbon, acetylene black having a DBP oil absorption of 175 ml / 100 g was used. As the component 3, polyvinyl alcohol (manufactured by Kuraray Co., Ltd.) having a polymerization degree of 2400 was used. The amount of polyvinyl alcohol was set to about 10% of the amount of carbon.

  In the positive electrode pastes 20 to 22 (carbon amount 8.6 g), the amount of sulfuric acid was changed to 0 g, 5.5 g, and 11 g, respectively. The positive electrode pastes 23 to 25 (carbon amount 11.4 g) were also obtained by changing the amount of sulfuric acid to 0 g, 5.5 g, and 11 g, respectively. The positive electrode pastes 26 to 28 (carbon amount 14.3 g) were also obtained by changing the amount of sulfuric acid to 0 g, 5.5 g, and 11 g, respectively.

First, the positive electrode pastes 21, 22, 24, 25, 27, and 28 containing sulfuric acid were prepared by kneading component 2 carbon, component 3 polyvinyl alcohol, and component 4 water for 30 minutes (first kneading step). Then, the lead powder of component 1, the sulfuric acid of component 5, and the water of component 6 were added to this kneaded product and further kneaded for 30 minutes (second kneading step). The sulfuric acid of component 5 shows pure sulfuric acid. Usually, the sulfuric acid of component 5 and the water of component 6 are combined and added as dilute sulfuric acid.
The positive electrode pastes 20, 23, and 26 that do not contain sulfuric acid, which is a comparative example (same component ratio as the positive electrode pastes 5, 4, and 3 in Table 1, respectively, but the sample was prepared again), first, carbon of component 2, The polyvinyl alcohol of component 3 and the water of component 4 are kneaded for 30 minutes (first kneading step), and then the lead powder of component 1 and the water of component 6 are added to this kneaded product, and further kneaded. This was performed for 30 minutes (second kneading step).

  The conventional positive electrode paste 8 is the same as the positive electrode paste 8 (conventional) in Table 1 and is simply kneaded of lead powder, sulfuric acid and water (a combination of sulfuric acid and water is a conventional dilute sulfuric acid). It is. However, in Table 4, 49 g of dilute sulfuric acid of the positive electrode paste 8 in Table 1 is converted to 11 g of pure sulfuric acid.

  The positive electrode pastes 20 to 28 thus prepared were filled into a 3.7 mm thick grid-like current collector, then aged at 98% humidity and 45 ° C. for 24 hours, and then dried at 60 ° C. for 24 hours. Thus, a positive electrode plate was formed. The past paste was similarly filled in a grid-shaped current collector and subjected to the same treatment.

<Measurement of utilization rate>
A fine glass fiber separator was brought into contact with both sides of one unformed positive electrode plate, and further, one negative electrode plate was brought into contact with the outside thereof. With such a configuration, the theoretical capacity of the active material is such that the negative electrode has a large excess, so that the utilization factor of the target positive electrode (that is, the active material) can be evaluated. These electrode plate groups were inserted into the battery case, and an ABS resin spacer was loaded in the gap between the battery case and the electrode plate group. Dilute sulfuric acid having a predetermined specific gravity (specific gravity 1.223 for positive electrode paste not containing sulfuric acid and conventional paste, and specific gravity 1.203 for positive electrode paste containing sulfuric acid by reducing the sulfuric acid content) is poured into the battery case. Then, chemical formation was performed by flowing an electric quantity of 300% of the theoretical capacity of the positive electrode. The specific gravity of the electrolytic solution after chemical conversion was set to 1.320.

  Then, the capacity | capacitance test was done about the electrode group inserted in said battery case. Two types of capacity tests, 0.06 A (ampere) and 6 A, were used. 0.06A is a low rate discharge with a rate of about 40 hours, and 6A is a high rate discharge with a rate of about 10 minutes. The respective discharge end voltages were 1.7 V (volt) and 1.2 V per cell. The temperature is 25 ° C.

  8 and 9 are graphs showing the relationship between the amount of sulfuric acid and the utilization rate based on the measurement result of the utilization rate. “P20” or the like in the legend of the graph means “positive electrode paste 20” or the like. The graph of FIG. 8 shows the measurement result of the low rate discharge, and the graph of FIG. 9 shows the measurement result of the high rate discharge. The measured values of low rate discharge and high rate discharge (2 samples are measured for each paste) are also shown in Table 4.

  8 and 9, the utilization rate tended to increase as the amount of sulfuric acid increased. Further, as in Example 1, it was reconfirmed that the greater the amount of carbon, the greater the utilization factor. In Example 1 described above, it has been found that the utilization rate can be improved by a factor of about 2 by containing carbon. However, in Example 3, the utilization rate is further increased by about several percent to about 20% by adding sulfuric acid. It has been found that it can be improved. The conventional paste contains no carbon and is kneaded with sulfuric acid in a single process as usual, but its utilization rate remains at a considerably low level.

  Referring to FIGS. 8 and 9, the amount of change in utilization rate in each sample is substantially proportional to the amount of sulfuric acid. The values obtained by reading the relationship between the sulfuric acid amount (g) and the utilization rate (%) from the line obtained by combining the utilization rate plots of FIGS. 8 and 9 are as shown in Table 5 below.

<Life test>
About the positive electrode paste 21 (carbon 8.6g) containing the sulfuric acid of Table 4, the lifetime test with respect to a charging / discharging cycle was done. The test method is the same as the life test of Example 1. For comparison, the positive electrode paste 5 (carbon 8.6 g) in Table 1 and the conventional paste were also tested.
Three positive electrode plates with a thickness of 3.7 mm and four negative electrode plates with a thickness of 2.2 mm, which are grid-shaped current collectors, are filled with positive electrode paste 21, positive electrode paste 5, and conventional paste, respectively. The negative electrode plate was filled with a conventional appropriate negative electrode paste. Thereafter, it was aged for 24 hours at a humidity of 98% and a temperature of 45 ° C., and then dried at 60 ° C. for 24 hours.

  Next, a fine glass fiber separator was brought into contact with each electrode plate, the electrode plate group was inserted into the battery case, and an ABS resin spacer was loaded in the gap between the battery case and the electrode plate group. Dilute sulfuric acid having a predetermined specific gravity (specific gravity 1.223 for positive electrode paste not containing sulfuric acid and conventional paste, and specific gravity 1.203 for positive electrode paste containing sulfuric acid by reducing the sulfuric acid content) is poured into the battery case. Then, chemical formation was performed by flowing an electric quantity of 300% of the theoretical capacity of the positive electrode. The specific gravity of the electrolytic solution after chemical conversion was set to 1.320. In this way, a storage battery having a capacity of 7 A · h (ampere hour) was produced.

The life test by repeating the charge / discharge cycle was performed under the following conditions.
(A) Discharge: Current 7A
(B) End-of-discharge voltage: 1.6 V / cell (c) Charging: Current I ₁ was set to 7 A until 2.45 V was reached (charging time T ₁ ), then current I ₂ was set to 4.9 A (this The voltage drops slightly. After charging again until it reached 2.45 V (charging time T ₂ ), the current I ₃ was set to 3.4 A (thus lowering the voltage slightly). Thereafter, every time the voltage reached 2.45 V, the charging current I _i was decreased to 2.4 A, 1.7 A, 1.1 A, 0.8 A, and 0.4 A. Each time the current value was changed, the battery was charged until it reached 2.45 V (charging time at each current I _i was T _j ). The battery was charged until the total charge current amounted to about 105% of the discharge amount. That is, the total amount of charging current is ΣI _i · T _j, which is the sum of products of the charging current I _i and the charging time T _j (where i = j). The temperature was 25 ° C.

  FIG. 10 is a graph showing the results of a life test of 500 cycles. For the positive electrode paste 21, the test results for two samples are shown. The positive electrode paste 21 containing carbon and sulfuric acid has a large capacity and a stable capacity transition as compared with the positive electrode paste 5 containing carbon and containing no sulfuric acid, and the conventional paste kneaded with sulfuric acid containing no carbon in a single step. Show.

It is the graph which showed the relationship between the carbon amount of the non-formed positive electrode plate produced with the positive electrode paste which does not use the sulfuric acid by this invention, and the conventional positive electrode paste, and the theoretical capacity | capacitance as a filled active material raw material was formed. It is the graph which showed the relationship between the amount of carbon of the non-formed positive electrode plate produced with the positive electrode paste which does not use the sulfuric acid by this invention, and the conventional positive electrode paste based on the measurement result of bulk density, and a bulk density. It is the graph which showed the relationship between the amount of carbon, and a utilization factor based on the measurement result of the utilization factor of the positive electrode paste which does not use the sulfuric acid by this invention, and the conventional positive electrode paste. It is the graph which showed the relationship between a bulk density and a utilization factor by replacing the horizontal axis of FIG. 3A with a bulk density based on the measurement result of the bulk density shown in FIG. It is the graph which showed the relationship between the amount of carbon, and a capacity | capacitance based on the measurement result of the capacity | capacitance of the battery produced with the positive electrode paste which does not use the sulfuric acid by this invention, and the conventional positive electrode paste. It is a graph which shows the result of the cycle life test of the battery produced with the positive electrode paste which does not use the sulfuric acid by this invention, and the conventional positive electrode paste. It is a graph which shows the relationship between the bulk density of the positive electrode paste which does not use the sulfuric acid by this invention, and the utilization factor by 0.06A low rate discharge. It is a graph which shows the relationship between the bulk density of the positive electrode paste which does not use the sulfuric acid by this invention, and the utilization factor by 6A high rate discharge. It is a graph which shows the relationship between the amount of sulfuric acids and the utilization factor by 0.06A low rate discharge of the battery produced with the positive electrode paste using the sulfuric acid by this invention, and the conventional positive electrode paste. It is a graph which shows the relationship between the sulfuric acid amount and the utilization factor by 6A high rate discharge of the battery produced with the positive electrode paste using the sulfuric acid by this invention, and the conventional positive electrode paste. It is a graph which shows the result of the cycle life test of the battery produced by the positive electrode paste using the sulfuric acid by this invention, the positive electrode paste which does not use the sulfuric acid by this invention, and the conventional positive electrode paste.

Claims (6)

  A secondary battery comprising a kneaded material comprising an active material raw material mainly composed of a metal oxide and carbon in an amount of 9.6 milliliters or more of total oil absorption per mole of the active material raw material. Positive electrode composition. 2. The positive electrode composition for a secondary battery according to claim 1, wherein a bulk density of the dried positive electrode composition for a secondary battery is not less than 2.2 × 10 ⁻¹ ml / gram.   The positive electrode composition for a secondary battery according to claim 1 or 2, wherein the carbon is acetylene black and / or furnace carbon.   It is a manufacturing method of the positive electrode composition for secondary batteries in any one of Claims 1-3, Comprising: The 1st process of knead | mixing the mixture containing the said carbon and water at least, It obtains by the said 1st process. And a second step of adding the active material raw material to the product and further kneading the product, and a method for producing a positive electrode composition for a secondary battery.   The positive electrode composition for a secondary battery according to claim 1, wherein the kneaded product further contains sulfuric acid.   It is a manufacturing method of the positive electrode composition for secondary batteries of Claim 5, Comprising: The 1st process of knead | mixing the mixture containing the said carbon and water at least, The product obtained by the said 1st process WHEREIN: And a second step of adding and kneading the active material raw material and the sulfuric acid, and a method for producing a positive electrode composition for a secondary battery.

Images