Battery manufacturing method

Abstract

To suppress the amount of release agent added to a positive electrode in order to prevent a positive electrode from cracking when the positive electrode is removed from a molding die.SOLUTION: A battery manufacturing method includes granulating a first powder containing manganese dioxide MnO2 and graphite C, separating the first powder into a plurality of second powders having different particle sizes, separating each of the plurality of third powders from the plurality of second powders, generating a positive electrode mixture by mixing the plurality of third powders, and molding the positive electrode mixture into a positive electrode.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The technology of the present disclosure relates to a battery manufacturing method and a battery.

Background Art

[0002] An alkaline dry battery in which a positive electrode and a negative electrode are immersed in an electrolytic solution is known. The positive electrode is produced by molding a positive electrode mixture powder containing manganese dioxide MnO2 and graphite C using a molding die (Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In order to prevent cracks from occurring in the positive electrode when the positive electrode is taken out of the molding die, a release agent is added to the positive electrode mixture powder. Since the required amount of the release agent changes when the particle size distribution of the positive electrode mixture powder is different, the release agent is added in an excessive amount to the positive electrode mixture powder. When an excessive amount of the release agent is added to the positive electrode mixture powder in an alkaline dry battery, the amount of the electrolytic solution injected into the battery may be reduced accordingly, and the discharge performance may deteriorate.

[0005] The disclosed technology has been made in view of such a point, and an object thereof is to provide a battery manufacturing method and a battery that suppress the amount of the release agent.

Means for Solving the Problems

[0006] A battery manufacturing method according to an aspect of the present disclosure includes granulating a first powder containing manganese dioxide and graphite, separating the first powder into a plurality of second powders having different particle sizes from each other, and respectively obtaining a plurality of third powders from the plurality of second powders MeasureAnd, Add a release agent in an amount calculated based on the amount of each of the plurality of third powders to the plurality of third powders, The method includes mixing the plurality of third powders to produce a positive electrode mixture, and molding the positive electrode mixture into a positive electrode. [Effects of the Invention]

[0007] The disclosed battery manufacturing method and battery can reduce the amount of mold release agent used. [Brief explanation of the drawings]

[0008]

Figure 1

Figure 2

[0009] Hereinafter, a battery manufacturing method and a battery according to embodiments disclosed herein will be described with reference to the drawings. Note that the following description does not limit the technology of the present disclosure. In addition, in the following description, the same components are given the same reference numerals, and duplicated descriptions will be omitted.

[0010] [Battery 1 of the embodiment] The battery 1 of this embodiment is a so-called alkaline battery, and as shown in FIG. 1, includes a battery case 2, a positive electrode 3, a negative electrode 5, a current collector 6, and a separator 7. FIG. 1 is a cross-sectional view showing the battery 1 of this embodiment. The battery case 2 includes a positive electrode can 11, a negative electrode terminal plate 12, and a sealing gasket 14. The positive electrode can 11 is formed from a conductor, such as a metal. The positive electrode can 11 is formed in a cylindrical shape with a bottom, and includes a side portion 15 and a bottom portion 16. The side portion 15 is formed from a bent plate so as to fit along the side surface of the cylinder. The bottom portion 16 is disposed along one bottom surface of the cylinder. The bottom portion 16 is integrally connected to the side portion 15 so that an edge of the bottom portion 16 is adjacent to one end of the bottom portion 16.

[0011] A positive electrode terminal portion 17 is formed in the center of the bottom portion 16. The positive electrode terminal portion 17 is formed so as to protrude from the inside of the positive electrode can 11 toward the outside. An opening 18 is formed in the positive electrode can 11. The opening 18 is formed in a portion of the side portion 15 that corresponds to the other bottom surface of the cylinder. A beading portion 21 is formed in the side portion 15. The beading portion 21 is formed in the side portion 15 near the opening 18. The beading portion 21 is formed so that the inner diameter of a portion of the side portion 15 near the opening 18 is smaller.

[0012] The negative electrode terminal plate 12 is made of a conductor such as a metal and is formed in a generally disk shape. The negative electrode terminal plate 12 is arranged along the other bottom surface of the cylinder so as to close the opening 18 of the positive electrode can 11. Inside the battery case 2, the negative electrode terminal plate 12 closes the opening 18, thereby forming an internal space 23 surrounded by the positive electrode can 11 and the negative electrode terminal plate 12.

[0013] The sealing gasket 14 is formed from an insulator such as resin and is generally ring-shaped. The sealing gasket 14 surrounds the edge of the negative electrode terminal plate 12 and is disposed in the opening 18 of the positive electrode can 11. The sealing gasket 14 is sandwiched between the edge of the negative electrode terminal plate 12 and the positive electrode can 11, sealing the gap formed between the edge of the negative electrode terminal plate 12 and the positive electrode can 11. The negative electrode terminal plate 12 is fixed to the positive electrode can 11 via the sealing gasket 14 by being sandwiched between the edge of the negative electrode terminal plate 12 and the positive electrode can 11. The negative electrode terminal plate 12 is electrically insulated from the positive electrode can 11 via the sealing gasket 14 by being sandwiched between the edge of the negative electrode terminal plate 12 and the positive electrode can 11.

[0014] The positive electrode 3 is formed from a positive electrode active material, a binder, an aqueous potassium hydroxide solution, and a release agent, and is formed in a hollow cylindrical shape. The positive electrode active material contains electrolytic manganese dioxide MnO2 and graphite C. The binder is for adhering powders to each other to form a solid, and contains, for example, a polymer compound. The release agent contains calcium stearate. The positive electrode 3 is disposed in the internal space 23 of the battery case 2 and is in close contact with the inner peripheral surface of the side portion 15 of the positive electrode can 11 so that the positive electrode active material is electrically connected to the positive electrode can 11. The negative electrode 5 is formed from a negative electrode active material and is formed in a gel shape. The negative electrode active material contains zinc alloy powder and an aqueous potassium hydroxide solution. The negative electrode 5 is disposed inside the positive electrode 3 in the internal space 23 of the battery case 2.

[0015] The current collector rod 6 is formed from a conductor and is formed in a rod shape. The current collector rod 6 is disposed in the internal space 23 along the central axis of the cylinder. The current collector rod 6 is further embedded in the negative electrode 5 so as to be electrically connected to the negative electrode active material of the negative electrode 5. The current collector rod 6 further penetrates the center of the sealing gasket 14. One end of the current collector rod 6 is joined to the negative electrode terminal plate 12 so that the current collector rod 6 is electrically connected to the negative electrode terminal plate 12.

[0016] The separator 7 is formed of a polypropylene nonwoven fabric. The separator 7 is formed in a bottomed hollow cylindrical shape and includes a side surface portion 25 and a bottom surface portion 26. The side surface portion 25 is disposed between the positive electrode 3 and the negative electrode 5 in the internal space 23. The bottom surface portion 26 is disposed between the negative electrode 5 and the bottom surface portion 16 of the positive electrode can 11 in the internal space 23. The bottom surface portion 26 is integrally connected to the side surface portion 25 such that the region in the internal space 23 where the negative electrode 5 is disposed is separated from the region in the internal space 23 where the positive electrode 3 and the positive electrode can 11 are disposed. By being disposed in this manner, the separator 7 separates the positive electrode 3 and the negative electrode 5 and separates the negative electrode 5 and the positive electrode can 11. The negative electrode 5 is electrically insulated from the positive electrode 3 via the separator 7 because the separator 7 separates the positive electrode 3 and the negative electrode 5, and is electrically insulated from the positive electrode can 11 via the separator 7 because the separator 7 separates the negative electrode 5 and the positive electrode can 11. The battery 1 further includes an electrolyte. The electrolyte is formed from an aqueous solution containing potassium hydroxide KOH. The electrolyte has penetrated into the separator 7.

[0017] [Battery Manufacturing Method of Embodiment] The battery manufacturing method of the embodiment is a method for manufacturing the battery 1 and includes preparation of a positive electrode mixture, molding of the positive electrode, and assembly of the battery. FIG. 2 is a flowchart showing the preparation of the positive electrode mixture in the battery manufacturing method of the embodiment. In the preparation of the positive electrode mixture, electrolytic manganese dioxide MnO2, graphite C, a binder, an electrolyte, and ion-exchanged water are prepared. A predetermined amount of manganese dioxide is measured out from the electrolytic manganese dioxide MnO2 (step S1). A predetermined amount of graphite C is measured out from the graphite C (step S2). A predetermined amount of the binder is measured out from the binder (step S3). The measured electrolytic manganese dioxide MnO2, graphite C, and binder are dry-mixed, and a dry mixture is produced by the dry mixing (step S4).

[0018] A predetermined amount of electrolyte is measured out from the electrolyte (step S5). A predetermined amount of ion-exchanged water is measured out from the ion-exchanged water (step S6). The dry mixture is added with the measured electrolyte and ion-exchanged water and wet-mixed (step S7), and a wet mixture is generated by the wet mixing. The wet mixture is mixed with a recycled agent powder to be described later (step S8), and a mixture is generated by the mixing. The mixture is compressed by rolling with a roll press or the like (step S9), and a solid is generated by the compression. The solid is granulated by being pulverized (step S10), and a first powder is generated by the granulation.

[0019] The first powder is sieved and separated into a plurality of second powders (step S11). For example, the plurality of second powders include ~16 mesh powder, 16 - 20 mesh powder, 20 - 30 mesh powder, 30 - 60 mesh powder, 60 - 80 mesh powder, and 80 - mesh powder. The ~16 mesh powder does not pass through a 16-mesh sieve. The 16 - 20 mesh powder passes through a 16-mesh sieve without passing through a 20-mesh sieve. The 20 - 30 mesh powder passes through a 20-mesh sieve without passing through a 30-mesh sieve. The 30 - 60 mesh powder passes through a 30-mesh sieve without passing through a 60-mesh sieve. The 60 - 80 mesh powder passes through a 60-mesh sieve without passing through an 80-mesh sieve. The 80 - mesh powder passes through an 80-mesh sieve.

[0020] A plurality of third powders are respectively measured from the plurality of second powders. The plurality of third powders include 16-20 mesh powder after weighing, 20-30 mesh powder after weighing, 30-60 mesh powder after weighing, and 60-80 mesh powder after weighing. That is, a predetermined amount of 16-20 mesh powder after weighing is measured from the 16-20 mesh powder (step S12). A predetermined amount of 20-30 mesh powder after weighing is measured from the 20-30 mesh powder (step S13). A predetermined amount of 30-60 mesh powder after weighing is measured from the 30-60 mesh powder (step S14). A predetermined amount of 60-80 mesh powder after weighing is measured from the 60-80 mesh powder (step S15).

[0021] The 16- to 20-mesh powder and the 80-mesh powder are mixed into the wet mixture as a recycled mixture powder (step S8). A release agent is prepared, and a predetermined amount of the release agent is measured out from the release agent (step S16). The amount of the release agent is calculated based on the particle size distribution of the plurality of third powders, for example, based on the amount of the weighed 16- to 20-mesh powder, the amount of weighed 20- to 30-mesh powder, the amount of weighed 30- to 60-mesh powder, and the amount of weighed 60- to 80-mesh powder. The measured release agent and the plurality of third powders are mixed using a drum mixer (step S17), and a positive electrode mixture is produced by this mixing.

[0022] In forming the positive electrode, the positive electrode mixture prepared by preparing the positive electrode mixture is poured into a molding die, pressure is applied, and the mixture is then removed from the molding die to form the positive electrode 3. In assembling the battery, the positive electrode 3 is inserted into the positive electrode can 11 so that the outer peripheral surface of the positive electrode 3 contacts the inner peripheral surface of the positive electrode can 11. After the positive electrode 3 is inserted into the positive electrode can 11, the positive electrode can 11 is processed so that a beading portion 21 is formed at the opening 18 of the positive electrode can 11. The formation of the beading portion 21 in the positive electrode can 11 prevents the positive electrode 3 from slipping out of the positive electrode can 11. After the beading portion 21 is formed in the positive electrode can 11, the separator 7 is inserted inside the positive electrode 3. After the separator 7 is inserted inside the positive electrode 3, a predetermined amount of electrolyte is injected inside the positive electrode 3 and allowed to soak into the separator 7. The amount of the electrolyte is calculated based on the amount of the release agent added to the plurality of third powders.

[0023] In the battery assembly, a gelled negative electrode 5 is further prepared using zinc alloy powder and an aqueous potassium hydroxide solution. The negative electrode 5 is injected into the separator 7 after the separator 7 has been saturated with the electrolyte. After the negative electrode 5 is injected, the current collector 6, negative electrode terminal plate 12, and sealing gasket 14 are attached to the positive electrode can 11 so that the current collector 6 joined to the negative electrode terminal plate 12 is embedded in the negative electrode 5 and so that the negative electrode terminal plate 12 and sealing gasket 14 close the opening 18. After the current collector 6, negative electrode terminal plate 12, and sealing gasket 14 are attached to the positive electrode can 11, the portion of the positive electrode can 11 near the opening 18 is crimped so that the gap formed between the edge of the negative electrode terminal plate 12 and the positive electrode can 11 is sealed with the sealing gasket 14. When the positive electrode can 11 is crimped, the sealing gasket 14 is deformed, the current collector rod 6, the negative electrode terminal plate 12, and the sealing gasket 14 are fixed to the positive electrode can 11, the internal space 23 is sealed from the outside, and the battery 1 is produced.

[0024] In conventional batteries in which the particle size distribution of the powder contained in the positive electrode mixture varies from battery to battery, the required amount of release agent to prevent cracks from occurring in the positive electrode when the positive electrode is removed from the mold varies from battery to battery, and therefore, in conventional batteries in which the particle size distribution of the powder contained in the positive electrode mixture varies from battery to battery, a larger amount of release agent is uniformly added relative to the amount of positive electrode mixture.

[0025] In the batteries fabricated by the above-described battery manufacturing method, the particle size distribution of the powder contained in the positive electrode mixture is generally the same for each battery. In the batteries fabricated by the above-described battery manufacturing method, the particle size distribution is generally the same for each battery, and therefore the required amount of release agent is generally the same for each battery. Therefore, in the batteries fabricated by the above-described battery manufacturing method, it is not necessary to add a large amount of release agent relative to the amount of positive electrode mixture, and an appropriate amount of release agent can be added to the positive electrode. In the batteries fabricated by the above-described battery manufacturing method, the amount of electrolyte injected can be increased by adding an appropriate amount of release agent to the positive electrode. In the batteries fabricated by the above-described battery manufacturing method, the discharge capacity can be increased by increasing the amount of electrolyte injected.

[0026] In the battery manufacturing method described above, the positive electrode mixture is produced by mixing four third powders having different particle sizes. However, the positive electrode mixture may be produced by mixing a plurality of third powders different in particle size from four. For example, the positive electrode mixture may be produced by mixing two third powders having different particle sizes from one another. Examples of the two third powders include a 16-60 mesh powder after weighing and a 60-80 mesh powder after weighing. In this case, the first powder may be sieved and separated into four second powders. The four second powders include a 16-mesh powder, a 16-60 mesh powder, a 60-80 mesh powder, and an 80-mesh powder. The 16-60 mesh powder passes through a 16 mesh sieve but not a 60 mesh sieve. The 60-80 mesh powder passes through a 60 mesh sieve but not an 80 mesh sieve. After weighing, the 16 to 60 mesh powder is weighed out from the 16 to 60 mesh powder. After weighing, the 60 to 80 mesh powder is weighed out from the 60 to 80 mesh powder. Even in this case, the battery manufacturing method can reduce the amount of release agent added to the positive electrode.

[0027] [Battery 1 evaluation test] In order to confirm the effects of the battery 1 of the embodiment, multiple battery samples were fabricated and multiple evaluation tests were performed on each of the multiple battery samples. Table 1 shows multiple fabrication conditions and multiple evaluation results corresponding to the multiple battery samples. [Table 1]

[0028] The plurality of battery samples include a battery of Conventional Example 1, a battery of Conventional Example 2, a battery of Conventional Example 3, a battery of Conventional Example 4, a battery of Conventional Example 5, a battery of Conventional Example 6, a battery of Example 1, a battery of Example 2, a battery of Comparative Example 1, and a battery of Comparative Example 2. Each of the plurality of battery samples includes a plurality of batteries fabricated based on the battery manufacturing method described above. Specifically, the plurality of batteries were fabricated based on the battery manufacturing method described above so that the battery size was LR6 and so that a positive electrode mixture was fabricated by mixing 16-60 mesh powder, 60-80 mesh powder, and a release agent.

[0029] A plurality of battery samples are further fabricated such that their fabrication conditions are different from each other, and they are fabricated in the same manner as each other except that their fabrication conditions are different from each other. The fabrication conditions are indicated by the fine powder ratio, the release agent addition amount, and the electrolyte injection amount. The fine powder ratio corresponding to a certain battery sample indicates the ratio in which 60 - 80 mesh powder is mixed with the powder contained in the positive electrode mixture of that battery sample, and represents the value obtained by multiplying the value obtained by dividing the weight of the 60 - 80 mesh powder by the weight of the powder contained in the positive electrode mixture by 100. The release agent addition amount corresponding to a certain battery sample indicates the amount of the release agent added to the positive electrode mixture of that battery sample, and represents the value obtained by multiplying the value obtained by dividing the weight of the release agent added to the positive electrode mixture of that battery sample by the weight of the positive electrode mixture by 100. The electrolyte injection amount corresponding to a certain battery sample indicates the amount of the electrolyte injected into that battery sample, and represents the value obtained by multiplying the value obtained by dividing the weight of the electrolyte injected into that battery sample by the weight of the electrolyte injected into the battery of Comparative Example 1 by 100.

[0030] The fine powder ratio of the battery of Comparative Example 1 is 30. The release agent addition amount of the battery of Comparative Example 1 is 0.10. The electrolyte injection amount of the battery of Comparative Example 1 is 100. The fine powder ratio of the battery of Comparative Example 2 is 30. The release agent addition amount of the battery of Comparative Example 2 is 0.20. The electrolyte injection amount of the battery of Comparative Example 2 is 100. The fine powder ratio of the battery of Comparative Example 3 is 30. The release agent addition amount of the battery of Comparative Example 3 is 0.30. The electrolyte injection amount of the battery of Comparative Example 3 is 100.

[0031] The fine powder ratio of the battery of Comparative Example 4 is 10. The release agent addition amount of the battery of Comparative Example 4 is 0.10. The electrolyte injection amount of the battery of Comparative Example 4 is 100. The fine powder ratio of the battery of Comparative Example 5 is 10. The release agent addition amount of the battery of Comparative Example 5 is 0.20. The electrolyte injection amount of the battery of Comparative Example 5 is 100. The fine powder ratio of the battery of Comparative Example 6 is 10. The release agent addition amount of the battery of Comparative Example 6 is 0.30. The electrolyte injection amount of the battery of Comparative Example 6 is 100.

[0032] The fine powder ratio of the battery of Comparative Example 1 is 30. The amount of release agent added of the battery of Comparative Example 1 is 0.30. The amount of electrolyte injected of the battery of Comparative Example 1 is 110. The fine powder ratio of the battery of Comparative Example 2 is 30. The amount of release agent added of the battery of Comparative Example 2 is 0.10. The amount of electrolyte injected of the battery of Comparative Example 2 is 130.

[0033] The fine powder ratio of the battery of Example 1 is 30. The release agent addition amount of the battery of Example 1 is 0.10. The electrolyte injection amount of the battery of Example 1 is 110. The fine powder ratio of the battery of Example 2 is 30. The release agent addition amount of the battery of Example 2 is 0.10. The electrolyte injection amount of the battery of Example 2 is 120.

[0034] The multiple evaluation results include multiple mix crack evaluation results, multiple discharge performance evaluation results, and multiple voltage defect occurrence rate evaluation results. The multiple mix crack evaluation results correspond to multiple battery samples. Among the multiple mix crack evaluation results, a mix crack evaluation result corresponding to a certain battery sample indicates a result derived by performing a mix crack evaluation test on that battery sample, and indicates "o" or "x." In the mix crack evaluation test performed on a certain battery sample, the positive electrode of the battery sample is visually inspected to determine whether or not cracks have occurred in the positive electrode of the battery sample. When the mix crack evaluation result of a certain battery sample among the multiple mix crack evaluation results indicates "o," it indicates that the rate at which cracks occur in the positive electrode of that battery sample is smaller than a predetermined value. When the mix crack evaluation result of a certain battery sample among the multiple mix crack evaluation results indicates "x," it indicates that the rate at which cracks occur in the positive electrode of that battery sample is smaller than a predetermined value.

[0035] The results of the evaluation of multiple composite cracking show that cracking has occurred in the positive electrodes of the batteries of Comparative Example 4 and Comparative Example 5, and that no cracking has occurred in the positive electrodes of the other battery samples. The evaluation results of the composite cracking corresponding to the batteries of Comparative Examples 1 to 6 among the results of the evaluation of multiple composite cracking indicate that cracking is likely to occur in the positive electrode when the fine powder ratio is small. The evaluation results of the composite cracking corresponding to the batteries of Comparative Examples 4 to 6 among the results of the evaluation of multiple composite cracking indicate that cracking is likely to occur in the positive electrode when the release agent is less. The evaluation results of the composite cracking corresponding to the batteries of Comparative Examples 4 to 6 among the results of the evaluation of multiple composite cracking further indicate that even when the fine powder ratio is small, by increasing the amount of the release agent, it is possible to prevent cracking from occurring in the positive electrode. The evaluation results of the composite cracking corresponding to the batteries of Comparative Examples 1 to 6 among the results of the evaluation of multiple composite cracking further indicate that even when the particle size distribution of the positive electrode composite is different, by sufficiently adding a release agent to the positive electrode composite, it is possible to prevent cracking from occurring in the positive electrode.

[0036] The plurality of discharge performance evaluation results correspond to a plurality of battery samples. The discharge performance evaluation result corresponding to a certain battery sample among the plurality of discharge performance evaluation results indicates the result derived by performing a discharge performance evaluation test on that battery sample. The discharge performance evaluation test is based on, for example, the discharge test specified in JIS standard JIS C8515 "Primary Battery Individual Product Specifications". That is, in the discharge performance evaluation test performed on a certain battery sample, a 1-hour discharge pattern is repeatedly executed in an atmosphere of 20°C until the battery voltage of that battery sample becomes less than the cut-off voltage of 1.05V, and the number of discharges is derived. The 1-hour discharge pattern is formed by a 5-minute discharge period and a 55-minute rest period. In the 5-minute discharge period, a 30-second discharge pattern is repeatedly executed 10 times. The 30-second discharge pattern is formed by a 2-second discharge period and a 28-second discharge period. In the 2-second discharge period, that battery sample is electrically connected to a load of 1500 mW. The 28-second discharge period starts immediately after the end of the 2-second discharge period. In the 28-second discharge period, that battery sample is electrically connected to a load of 650 mW for 28 seconds. The 55-minute rest period is executed immediately after the end of the 5-minute discharge period. In the 55-minute rest period, the electrical connection between that battery sample and the load is interrupted for 55 minutes.

[0037] The number of discharges indicates the number of times the 1-hour discharge pattern is repeatedly executed on that battery sample before the battery voltage of that battery sample becomes less than the cut-off voltage of 1.05V. The discharge performance evaluation result corresponding to a certain battery sample among the plurality of discharge performance evaluation results indicates the value obtained by multiplying the average of the number of discharges of 9 batteries fabricated as that battery sample by 100 and dividing it by the average of the number of discharges of 9 batteries fabricated as the battery of Comparative Example 1. The plurality of discharge performance evaluation results indicate that the greater the discharge performance evaluation result of a battery sample, the greater the discharge capacity, and the better the discharge performance of the battery sample with the greater discharge performance evaluation result.

[0038] The plurality of discharge performance evaluation results indicate that the discharge performance of the batteries of Comparative Examples 1 and 2 and the discharge performance of the batteries of Examples 1 and 2 are better than the discharge performance of the batteries of Conventional Examples 1 to 6. Among the plurality of discharge performance evaluation results, the discharge performance evaluation results corresponding to the battery of Conventional Example 1, the batteries of Examples 1 and 2, and the battery of Comparative Example 2 indicate that the greater the electrolyte injection amount of the battery sample, the better the discharge performance.

[0039] The plurality of voltage defect occurrence rate evaluation results correspond to a plurality of battery samples. The voltage defect occurrence rate evaluation result corresponding to a certain battery sample among the plurality of voltage defect occurrence rate evaluation results shows the result derived by performing a voltage evaluation test on that battery sample, and indicates "〇" or "×". In the voltage evaluation test performed on a certain battery sample, the battery voltage of that battery sample is measured, and it is determined whether a voltage defect has occurred in that battery sample. For example, in the voltage evaluation test, when the battery voltage of a certain battery sample is not within a preset range, it is determined that a voltage defect has occurred in that battery sample. The plurality of voltage defect occurrence rate evaluation results indicate that when the voltage defect occurrence rate evaluation result corresponding to a certain battery sample shows "〇", the ratio of the occurrence of voltage defects in that battery sample is smaller than a predetermined value. The plurality of voltage defect occurrence rate evaluation results indicate that when the voltage defect occurrence rate evaluation result corresponding to a certain battery sample shows "×", the ratio of the occurrence of voltage defects in that battery sample is greater than a predetermined value.

[0040] The evaluation results of the plurality of voltage defect occurrence rates indicate that voltage defects are likely to occur in the batteries of Comparative Examples 1 and 2, and are less likely to occur in other battery samples. Among the evaluation results of the plurality of voltage defect occurrence rates, the evaluation results corresponding to the battery of Conventional Example 3 and the battery of Comparative Example 1 indicate that when the amount of the electrolytic solution is increased in the case of a large amount of the release agent, voltage defects are likely to occur. Among the evaluation results of the plurality of voltage defect occurrence rates, the evaluation results corresponding to the battery of Comparative Example 1 and the battery of Example 1 indicate that even when the amount of the electrolytic solution is increased, the reduction of the release agent makes it difficult for voltage defects to occur. Among the evaluation results of the plurality of voltage defect occurrence rates, the evaluation result corresponding to the battery of Comparative Example 2 indicates that when the electrolytic solution is excessive even in the case of a small amount of the release agent, voltage defects are likely to occur.

[0041] [Effect of the battery manufacturing method of the embodiment] The battery manufacturing method of the embodiment includes granulating a first powder containing manganese dioxide MnO2 and graphite C, separating the first powder into a plurality of second powders having different particle sizes, respectively weighing a plurality of third powders from the plurality of second powders, generating a positive electrode mixture by mixing the plurality of third powders, and molding the positive electrode mixture into the positive electrode 3.

[0042] In the battery manufacturing method of the embodiment, since the plurality of third powders are respectively weighed from the plurality of second powders, a plurality of positive electrodes can be manufactured such that the particle size distribution of the powders constituting the positive electrode mixture is equal for each of the plurality of positive electrodes. In the battery manufacturing method of the embodiment, since the particle size distribution of the powders of the positive electrode mixture contained in each of the plurality of positive electrodes is equal, it is not necessary to add a large amount of the release agent to the positive electrode mixture, and the addition amount of the release agent can be reduced. In the battery manufacturing method of the embodiment, since the addition amount of the release agent is reduced, the amount of the electrolytic solution injected into the battery including the positive electrode can be increased, and the discharge performance of the battery can be improved.

[0043] In addition, in the battery manufacturing method of the embodiment, the positive electrode mixture is generated by adding a release agent in an amount calculated based on the amount of each of the plurality of third powders to the plurality of third powders. At this time, the battery manufacturing method of the embodiment can add an appropriate amount of the release agent to the positive electrode mixture and can reduce the addition amount of the release agent.

[0044] By the way, the release agent added to the positive electrode mixture of the battery 1 of the above-described embodiment contains calcium stearate, but may contain other compounds different from calcium stearate. As such a compound, zinc stearate is exemplified. Even when such a release agent is used, the battery manufacturing method can reduce the addition amount of the release agent by adding an appropriate amount of the release agent to the positive electrode mixture.

[0045] In addition, in the battery manufacturing method of the embodiment, the amount of the electrolytic solution in which the positive electrode 3 is immersed is calculated based on the amount of the release agent added to the plurality of third powders. At this time, the battery manufacturing method of the embodiment can inject an appropriate amount of the electrolytic solution into the battery and can prevent a voltage failure from occurring in the battery.

[0046] In addition, in the battery manufacturing method of the embodiment, the positive electrode mixture is generated by mixing a plurality of third powders using a drum mixer. The battery manufacturing method of the embodiment can prevent the particles of the plurality of third powders from being broken and can prevent the particle size distribution of the plurality of third powders from changing by mixing the plurality of third powders using a drum mixer. By preventing the particle size distribution of the plurality of third powders from changing, the battery manufacturing method of the embodiment can add an appropriate amount of the release agent to the positive electrode mixture and can suppress the amount of the release agent added to the positive electrode.

[0047] In the battery manufacturing method according to the embodiment described above, the third powders are mixed using a drum mixer. However, if the particle size distribution of the third powders does not change significantly, the third powders may be mixed using a mixer other than a drum mixer. An example of such a mixer is one that rotates a stirrer in a tank containing the third powders. In the battery manufacturing method according to the embodiment, even when such a mixer is used, the amount of release agent added to the positive electrode mixture can be reduced.

[0048] Although the embodiments have been described above, the embodiments are not limited to the above content. Furthermore, the above-described components include those that can be easily imagined by a person skilled in the art, those that are substantially the same, and those that are within the so-called equivalent range. Furthermore, the above-described components can be combined as appropriate. Furthermore, at least one of various omissions, substitutions, and modifications of the components can be made without departing from the spirit of the embodiments. [Explanation of symbols]

[0049] 1:Battery 3: Positive electrode 5: Negative electrode

Claims

1. granulating a first powder containing manganese dioxide and graphite; separating the first powder into a plurality of second powders having different particle sizes from each other; weighing out a plurality of third powders from the plurality of second powders respectively; adding a release agent in an amount calculated based on the amount of each of the plurality of third powders to the plurality of third powders, and mixing the plurality of third powders to produce a positive electrode mixture; forming the positive electrode mixture into a positive electrode A battery manufacturing method comprising the steps of:

2. The release agent contains calcium stearate The battery manufacturing method according to Claim 1.

3. The amount of the electrolyte solution in which the positive electrode is immersed is calculated based on the amount of the release agent added to the plurality of third powders The battery manufacturing method according to Claim 1 or Claim 2.

4. The positive electrode mixture is produced by mixing the plurality of third powders using a drum mixer The battery manufacturing method according to any one of Claims 1 to 3.

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