Negative electrode plate manufacturing method, negative electrode plate, and secondary battery manufacturing method

Abstract

To provide a manufacturing method for a negative electrode plate capable of improving battery performance, a negative electrode plate, and a secondary battery.SOLUTION: The negative electrode plate for a secondary battery 1 is formed by kneading a negative electrode active material and a negative electrode additive to form a negative electrode mixture paste, which is then applied to a negative electrode collector and allowed to dry. The blackness of the material mixed with the negative electrode active material and the negative electrode additive is greater than or equal to 4 and less than or equal to 16. The viscosity of the negative electrode thickening material contained in the negative electrode additive is greater than or equal to 13000 mPa-s and less than or equal to 21000 mPa-s when the shear rate is assumed to be 0.01 s-1.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a method for manufacturing a negative electrode plate, a negative electrode plate, and a secondary battery. Manufacturing method Regarding. [Background technology]

[0002] Conventionally, as disclosed in Patent Document 1, there is a known inspection method for judging the quality of a negative electrode paste in a lithium secondary battery based on the blackness of a primary kneaded material obtained in the process of preparing the negative electrode paste. If the blackness of the primary kneaded material is within a predetermined reference blackness range, the inspection result of the primary kneaded material is deemed "good" and it is used as a material for producing a negative electrode paste. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2010-272287 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, the quality of battery performance, such as resistance characteristics and life characteristics, is not determined only by the blackness, but also by other indices. However, Patent Document 1 only discloses judging the quality of battery performance from the viewpoint of the blackness, and does not consider the quality of battery performance from the viewpoint of multiple indices. Therefore, further consideration was needed to optimize battery materials.

[0005] An object of the present invention is to provide a method for manufacturing a negative electrode plate, a negative electrode plate, and a secondary battery that can improve battery performance. [Means for solving the problem]

[0006] The method for manufacturing a negative electrode plate that solves the above-mentioned problem is a method for manufacturing a negative electrode plate for a secondary battery by kneading a negative electrode active material and a negative electrode additive to form a negative electrode composite paste, applying the negative electrode composite paste to a negative electrode current collector and drying the paste, the method comprising: setting the blackness of a material obtained by mixing the negative electrode active material and the negative electrode additive to 4 or more and 16 or less; setting the viscosity of a negative electrode thickener contained in the negative electrode additive to a shear rate of 0.01 s -1 The viscosity was set to 13,000 mPa s or more and 21,000 mPa s or less.

[0007] The negative electrode plate that solves the above-mentioned problems includes a negative electrode current collector that is a base material of a negative electrode of a secondary battery, and a negative electrode mixture formed by applying a negative electrode mixture paste obtained by kneading a negative electrode active material and a negative electrode additive to the negative electrode current collector and drying the negative electrode mixture. The blackness of the material obtained by mixing the negative electrode active material and the negative electrode additive is set to 4 or more and 16 or less, and the viscosity of the negative electrode thickener contained in the negative electrode additive is set to a shear rate of 0.01 s -1 The viscosity was set to 13,000 mPa s or more and 21,000 mPa s or less.

[0008] The secondary battery that solves the above-mentioned problems includes a negative electrode plate used for a negative electrode, a positive electrode plate used for a positive electrode, and a separator disposed between the negative electrode plate and the positive electrode plate. The negative electrode plate includes a negative electrode current collector that is a base material of the negative electrode, and a negative electrode mixture formed by applying a negative electrode mixture paste, which is obtained by kneading a negative electrode active material and a negative electrode additive, to the negative electrode current collector and drying the negative electrode mixture. The blackness of the material obtained by mixing the negative electrode active material and the negative electrode additive is set to 4 or more and 16 or less, and the viscosity of the negative electrode thickener contained in the negative electrode additive is set to a shear rate of 0.01 s -1 The viscosity was set to 13,000 mPa s or more and 21,000 mPa s or less. Effect of the Invention

[0009] The present invention can improve the battery performance of a secondary battery. [Brief description of the drawings]

[0010] [Figure 1]1 is a perspective view of a secondary battery according to an embodiment; [Diagram 2] FIG. 2 is a diagram showing the configuration of an electrode body. [Diagram 3] FIG. 2 is a diagram showing a procedure for producing a negative electrode composite paste. [Figure 4] 1 is a table summarizing the index values ​​of the comparative examples and examples. [Diagram 5] FIG. 4 is a characteristic diagram showing changes in shear viscosity of a negative electrode composite paste with respect to changes in shear rate. [Figure 6] FIG. 6 is a partially enlarged view of FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, an embodiment of a method for manufacturing a negative electrode plate, a negative electrode plate, and a secondary battery will be described. (Secondary battery 1) As shown in FIG. 1, a cell 2 of a secondary battery 1 includes a rectangular parallelepiped battery case 5 with an opening 3 closed by a lid 4. The battery case 5 is made of a metal such as an aluminum alloy. The inside of the battery case 5 forms a sealed battery container. The battery case 5 includes an electrode assembly 6 in which positive and negative electrodes are stacked. The inside of the battery case 5 is filled with a nonaqueous electrolyte 7. The lid 4 of the cell 2 includes a positive electrode external terminal 8 and a negative electrode external terminal 9 electrically connected to the electrode assembly 6. The secondary battery 1 is, for example, a lithium ion type that uses lithium ions as the ions that move between the positive and negative electrodes.

[0012] (electrode body 6) As shown in Fig. 2, the electrode body 6 includes a negative electrode plate 12, a positive electrode plate 13, and a separator 14. The negative electrode plate 12, the positive electrode plate 13, and the separator 14 are stacked in the thickness direction of the electrode body 6 (Z-axis direction in Fig. 2). Specifically, the negative electrode plates 12 and the positive electrode plates 13 are alternately arranged, and the separator 14 is arranged between the negative electrode plates 12 and the positive electrode plates 13 in these layers. The electrode body 6 is wound in the length direction of the electrode body 6 (X-axis direction in Fig. 2). The electrode body 6 is formed in a flat shape when viewed from a direction perpendicular to the length direction (Y-axis direction in Fig. 2).

[0013] (Negative electrode plate 12) The negative electrode plate 12 includes a negative electrode current collector 16 and a negative electrode mixture 17. The negative electrode current collector 16 is an electrode base material of the negative electrode. The negative electrode current collector 16 is made of, for example, copper (copper foil). The negative electrode mixture 17 is provided, for example, on both sides of the negative electrode current collector 16. The negative electrode mixture 17 includes, for example, a negative electrode active material and a negative electrode additive. The negative electrode mixture 17 is formed on the negative electrode current collector 16 by kneading the negative electrode active material and the negative electrode additive, and then applying the kneaded negative electrode mixture paste to the negative electrode current collector 16 and drying it.

[0014] The negative electrode active material is, for example, composed of a material capable of absorbing and releasing lithium ions. As the negative electrode active material, for example, a powdered carbon material made of graphite or the like is used. The negative electrode additive includes, for example, a negative electrode solvent, a negative electrode binder, and a negative electrode thickener. As the negative electrode solvent, for example, water or the like is used. The negative electrode additive may further include, for example, a negative electrode conductive material or the like.

[0015] The negative electrode binder may be, for example, a polymer material that disperses in water. Examples of the polymer material include rubbers such as vinyl acetate copolymer, styrene butadiene block copolymer (SBR), acrylic acid modified SBR resin (SBR-based latex), and gum arabic. Examples of the polymer material include fluorine-based resins such as polyethylene oxide (PEO), polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), and ethylene-tetrafluoroethylene copolymer (ETFE). The polymer materials may be used alone or in combination of two or more.

[0016] The negative electrode thickener may be, for example, a polymer that is insoluble in organic solvents and dissolves in water to provide viscosity. The polymer may be, for example, a cellulose derivative such as carboxymethylcellulose (CMC) or methylcellulose (MC).

[0017] The negative electrode current collector 16 has a negative electrode connection portion 18 that is connected to the negative electrode external terminal 9. The negative electrode connection portion 18 is, for example, a portion on both sides of the negative electrode current collector 16 where the negative electrode mixture 17 is not provided, and is configured to be exposed from the positive electrode plate 13 and the separator 14.

[0018] (Positive electrode plate 13) The positive electrode plate 13 includes a positive electrode current collector 20 and a positive electrode mixture 21. The positive electrode current collector 20 is an electrode base material of the positive electrode. The positive electrode current collector 20 is made of, for example, aluminum (aluminum foil, aluminum alloy foil). The positive electrode mixture 21 includes, for example, a positive electrode active material and a positive electrode additive. The positive electrode mixture 21 is formed on the positive electrode current collector 20 by kneading the positive electrode active material and the positive electrode additive, and then applying the kneaded positive electrode mixture paste to the positive electrode current collector 20 and drying it.

[0019] The positive electrode active material is, for example, a material capable of absorbing and releasing lithium ions. The positive electrode active material is, for example, a ternary (NMC) lithium-containing composite oxide containing nickel, manganese, and cobalt, such as lithium nickel cobalt manganese oxide (LiCOMNO). 2 ) is used as the positive electrode active material. For example, lithium cobalt oxide (LiCoO 2 ), lithium manganate (LiMn 2 O 4 ), lithium nickel oxide (LiNiO 2 As the positive electrode active material, for example, a lithium-containing composite oxide containing nickel, cobalt, and aluminum (NCA) may be used.

[0020] The positive electrode additive includes, for example, a positive electrode solvent, a positive electrode conductive material, and a positive electrode binder (binder). As the positive electrode solvent, for example, a non-aqueous solvent such as NMP (N-methyl-2-pyrrolidone) solution is used. As the positive electrode conductive material, for example, carbon fibers such as carbon nanotubes (CNT) and carbon nanofibers (CNF) can be used, but graphite, acetylene black (AB), Ketjen black, and other carbon blacks may also be used. As the positive electrode binder, for example, the same material as the negative electrode binder may be used. The positive electrode additive may further include, for example, a positive electrode thickener.

[0021] The positive electrode current collector 20 has a positive electrode connection portion 22 that is connected to the positive electrode external terminal 8. The positive electrode connection portion 22 is, for example, a portion on both sides of the positive electrode current collector 20 where the positive electrode composite material 21 is not provided, and is configured to be exposed from the negative electrode plate 12 and the separator 14.

[0022] (Separator 14) The separator 14 is, for example, a nonwoven fabric made of a porous resin such as polypropylene. For example, a porous polymer membrane such as a porous polyethylene membrane, a porous polyolefin membrane, or a porous polyvinyl chloride membrane, or a lithium ion or ion conductive polymer electrolyte membrane, either alone or in combination, is used as the separator 14. When the electrode body 6 is immersed in the nonaqueous electrolyte 7, the nonaqueous electrolyte 7 permeates the separator 14.

[0023] (Non-aqueous electrolyte 7) The non-aqueous electrolyte 7 is a composition in which a supporting salt is contained in a non-aqueous solvent. For example, ethylene carbonate (EC) is used as the non-aqueous solvent. The non-aqueous solvent may be one or more materials selected from the group consisting of propylene carbonate (PC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and the like.

[0024] The supporting electrolyte is LiPF 6 , LiBF 4 , LiClO 4, LiAsF 6 , LiCF 3 SO 3 , LiC 4 F 9 SO 3 , LiN(CF 3 SO 2 ) 2 , LiC(CF 3 SO 2 ) 3 , LiI, etc. One or more lithium compounds (lithium salts) selected from these may be used. Thus, the non-aqueous electrolyte 7 contains a lithium compound.

[0025] (Procedure for preparing negative electrode mixture paste) As shown in Fig. 3, when preparing the negative electrode composite paste, first, a mixed powder is prepared by mixing the negative electrode active material and the negative electrode thickener at a predetermined mixing ratio. Then, an aqueous solvent is added to this mixed powder and kneaded to prepare a primary kneaded material 24. When preparing the primary kneaded material 24, the aqueous solvent may be added and kneaded in several batches in order to uniformly and sufficiently disperse the negative electrode active material and the negative electrode thickener in the aqueous solvent.

[0026] Next, a negative electrode binder is added to this primary kneaded material 24, and this material is further kneaded to prepare a negative electrode composite paste. The negative electrode composite paste is then applied to the surface of the negative electrode current collector 16. Note that various known devices (e.g., agitators, etc.) can be appropriately used as the kneading device. Examples of the kneading device include an agitator with rotating blades, a fill mixer, a media agitation mill, and a planetary mixer.

[0027] (Blackness of negative electrode mixture paste) The negative electrode composite paste is prepared by kneading various materials in a predetermined compounding ratio, and therefore can have different characteristics depending on the state of preparation. Fluctuations in the characteristics of the negative electrode composite paste lead to qualitative fluctuations in the negative electrode (negative electrode plate 12), and thus have a significant impact on the battery performance of the secondary battery 1. Therefore, optimizing the characteristics of the negative electrode composite paste is one of the important points for improving the performance of the secondary battery 1.

[0028] It is known that the quality of the negative electrode composite paste is correlated with, for example, the blackness of the primary kneaded material 24. The blackness is an index showing, for example, the properties of the negative electrode active material, such as cracking, peeling, and chipping. The blackness varies depending on, for example, the amount of the negative electrode thickener and the properties of the primary kneaded material 24. The properties of the primary kneaded material 24 refer to, for example, the share of materials when the primary kneaded material 24 is produced, and specifically corresponds to an index of whether the negative electrode active material and the negative electrode thickener are uniformly and sufficiently dispersed in the primary kneaded material 24. The properties of the primary kneaded material 24 vary depending on, for example, the compounding ratio of the materials and the kneading method.

[0029] Incidentally, when the share of kneading is increased, the viscosity of the primary kneaded material 24 (negative electrode composite paste) relatively decreases. This is because the negative electrode thickener is finely divided by kneading, so that the negative electrode active material and the negative electrode thickener are mixed uniformly and sufficiently. On the other hand, when the share of kneading is insufficient, the viscosity of the primary kneaded material 24 (negative electrode composite paste) relatively increases. In this way, the viscosity of the primary kneaded material 24 (negative electrode composite paste) takes a state according to the share of kneading.

[0030] (Parameter setting of material for negative electrode composite 17) FIG. 4 shows a table summarizing the index values ​​of the comparative examples and the examples. For example, the table in FIG. 4 shows the blackness, the solid content of the kneaded mixture [%], the viscosity of the negative electrode composite paste [mPa s] (shear rate: 2 [s -1 ]), coating property, viscosity of negative electrode thickener [mPa s] (shear rate: 0.01 [s -1 ]), resistance characteristics, and life characteristics are listed as indexes. Then, while Comparative Example 1 was used as the standard for sample comparison, measurements were carried out on ten patterns of samples from "Example 1" to "Example 10." The meanings of each index are as follows: Blackness: Blackness of the primary kneaded material 24 Solid content [%]: Proportion of mixed powder (negative active material and negative thickener) in primary kneaded material 24 (negative active material, negative thickener, aqueous solvent) · Viscosity of negative electrode mixture paste [mPa·s]… Viscosity of negative electrode mixture paste Coating property: Whether or not the negative electrode composite paste can be discharged from the coating equipment - Viscosity of negative electrode thickener [mPa·s]... Viscosity of negative electrode thickener Resistance characteristics: Change in resistance value of battery compared to Comparative Example 1 Life characteristics: Change in battery life compared to Comparative Example 1 The viscosity of the negative electrode thickener is measured by a rheometer whose rotation speed can be changed as desired. The rheometer measures the viscosity from the phase difference between stress and strain when a sinusoidal stress is applied to the object to be measured, for example. In addition, the larger the value of the life characteristic, the better. The smaller the value of the resistance characteristic, the better.

[0031] It can be seen that as the blackness of the primary kneaded material 24 increases, the life characteristics of the secondary battery 1 improve. However, conversely, if the blackness becomes too high, the phenomenon of improved life characteristics does not occur. For this reason, it can be seen that there is an optimal range for the blackness. Based on this, in this example, the blackness of the material (in this example, the primary kneaded material 24) in which the negative electrode active material and the negative electrode additive are mixed is set to a value of 4 or more and 16 or less.

[0032] As shown in FIG. 4, the resistance characteristics of the secondary battery 1 are correlated with the viscosity of the negative electrode thickener. Specifically, if the viscosity of the negative electrode thickener becomes too high, the resistance characteristics deteriorate. Based on this, in this example, the viscosity of the negative electrode thickener used in the negative electrode mixture 17 is set to 0.01 s -1 The value is set to 13,000 mPa s or more and 21,000 mPa s or less when

[0033] Furthermore, in this embodiment, the thickened solid content of the primary kneaded material 24 is set to 58% or more and 61% or less. The thickened solid content becomes softer as the value decreases, and conversely, the thickened solid content becomes harder as the value increases. By appropriately changing the thickened solid content, it is possible to adjust the shear applied to the negative electrode composite paste.

[0034] (Operation of the embodiment) Next, the operation of the negative electrode plate manufacturing method of this embodiment (secondary battery 1, negative electrode plate 12) will be described.

[0035] As shown in Fig. 4, under certain conditions, for example, the blackness of the primary kneaded material 24 is adjusted by setting the thickened solid content of the primary kneaded material 24 to a target value. For example, when looking at a group of samples with the same viscosity of the negative electrode thickener, it can be seen that the blackness of the primary kneaded material 24 changes when the value of the thickened solid content is changed. As an example, it can be seen that the blackness increases when the thickened solid content is increased in the four samples of "Comparative Example 1" and "Example 1" to "Example 3" (all of which have the same viscosity of the negative electrode thickener at "13000 mPa s").

[0036] Here, if the blackness of the primary kneaded material 24 is too low (for example, see "Example 1"), the life characteristics of the battery are not significantly extended. However, if the blackness is low, the kneading share is insufficient, so the negative electrode thickener does not sufficiently cover the surface of the negative electrode active material. Therefore, the nonaqueous electrolyte 7 decomposes at the active points of the negative electrode, and the battery life is deteriorated. Therefore, it can be said that a blackness that is too low is not good.

[0037] On the other hand, if the blackness of the primary kneaded material 24 is too high (see, for example, "Example 6" and "Example 10"), the battery life characteristics will not change or will deteriorate. If the blackness is high, the kneading share will increase and the coating of the negative electrode thickener will be sufficient, but as the amount of fine powder of the negative electrode active material increases, the phenomenon of decomposition of the nonaqueous electrolyte 7 at the active points of the negative electrode will easily occur. In this way, an increase in localized reactions will lead to a deterioration in the battery life. Therefore, it can be said that a blackness that is too high is also not good.

[0038] When the blackness is adjusted, the resistance characteristics of the battery are affected by the viscosity of the negative electrode thickener. Specifically, as shown in "Example 1" to "Example 5", when the blackness is adjusted under the condition that the viscosity of the negative electrode thickener is "13000 mPa·s or more and 21000 mPa·s or less", the resistance characteristics do not deteriorate. On the other hand, as shown in "Example 7" to "Example 10", when the blackness is adjusted under the condition that the viscosity of the negative electrode thickener is higher than "21000", the resistance characteristics deteriorate. Therefore, it can be seen that the viscosity of the negative electrode thickener is closely related to the resistance characteristics of the battery.

[0039] When the viscosity of the negative electrode thickener is high, the molecular weight of the negative electrode thickener is large, so that the negative electrode active material has a large portion that is not covered by the negative electrode thickener. This is thought to lead to an increase in the resistance value of the battery, that is, a deterioration in the resistance characteristics. Therefore, from the viewpoint of ensuring the resistance characteristics, it is understood that a high viscosity of the negative electrode thickener is not good.

[0040] FIG. 5 shows the shear viscosity change characteristic, which is a logarithmic graph showing the relationship between the shear rate and the shear viscosity of the negative electrode composite paste. In FIG. 5, the shear viscosity waveform S1 of "Example 2" in which the viscosity of the negative electrode thickener is "13000 mPa·s" and the shear viscosity waveform S2 of "Example 8" in which the viscosity of the negative electrode thickener is "96000 mPa·s" are shown. When the shear rate is increased, both "Example 2" and "Example 8" show a right-shouldered waveform in which the shear viscosity gradually decreases after reaching a certain peak value.

[0041] As shown in FIG. 6, in “Example 8”, the shear rate was “10,000 s -1 " When the shear viscosity passes the point where it drops sharply to the right, it suddenly rises, and so-called dilatancy appears (point A in Figure 6). When dilatancy appears, it becomes difficult to discharge the negative electrode mixture paste from the coating equipment, so it is not a material suitable for production. From this point of view, it can be said that it is not desirable to use a negative electrode thickener with a high viscosity.

[0042] As shown in Fig. 4, a comparison of the indices of the samples of "Example 1" to "Example 10" reveals that the viscosity of the negative electrode thickener is preferably within the range of "13000 mPa·s to 21000 mPa·s". However, as can be seen from Examples 1 and 6, even if the viscosity of the negative electrode thickener is set to a value of "13000 mPa·s to 21000 mPa·s", if the degree of blackness is too low or too high, at least one of the resistance characteristics and the life characteristics will not reach an optimal value.

[0043] In view of the above, in this embodiment, the optimum combination range of the blackness and the viscosity of the negative electrode thickener was set. Specifically, the blackness range of the material (in this embodiment, the primary kneaded material 24) in which the negative electrode active material and the negative electrode additive are mixed is set to "4 or more and 16 or less", and the viscosity range of the negative electrode thickener is set to "13000 mPa·s or more and 21000 mPa·s or less". This makes it possible to manufacture a secondary battery 1 that is excellent in both resistance characteristics and life characteristics. In addition, since the viscosity of the negative electrode thickener is set to a low value, it also serves as a measure against the occurrence of dilatancy during the coating process.

[0044] (Effects of the embodiment) According to the negative electrode plate manufacturing method of the above embodiment (secondary battery 1, negative electrode plate 12), the following effects can be obtained.

[0045] (1) In the negative electrode plate manufacturing method of this example, a negative electrode active material and a negative electrode additive are mixed to form a negative electrode composite paste, and the negative electrode composite paste is applied to a negative electrode current collector 16 and dried to manufacture a negative electrode plate 12 of a secondary battery 1. The blackness of the material obtained by mixing the negative electrode active material and the negative electrode additive is set to 4 or more and 16 or less, and the viscosity of the negative electrode thickener contained in the negative electrode additive is adjusted to a shear rate of 0.01 s -1 The viscosity was set to 13,000 mPa s or more and 21,000 mPa s or less.

[0046] According to this configuration, since the optimum range is set for the blackness of the material obtained by mixing the negative electrode active material and the negative electrode additive, it is difficult for the negative electrode thickener to not sufficiently cover the negative electrode active material, or conversely, for the negative electrode thickener to increase in fine powder. Therefore, it is difficult for the nonaqueous electrolyte 7 to decompose at the active points of the negative electrode to occur, so it is possible to extend the battery life. In addition, since the optimum range is set for the viscosity of the negative electrode thickener, the amount of the negative electrode active material covered by the negative electrode thickener does not increase. Therefore, it is possible to keep the battery resistance low. As a result, the battery performance of the secondary battery 1 can be improved.

[0047] (2) The negative electrode additive includes at least a negative electrode thickener and a negative electrode solvent. The blackness of the material obtained by mixing the negative electrode active material and the negative electrode additive is the blackness of the primary kneaded material 24 produced by kneading the negative electrode active material, the negative electrode thickener, and the negative electrode solvent. With this configuration, the blackness of the primary kneaded material 24 can be optimized, leading to improved battery performance of the secondary battery 1.

[0048] (3) In the negative electrode plate manufacturing method of this example, the thickened solid content of the primary kneaded material 24 is set to 58% or more and 61% or less. With this configuration, the range of the thickened solid content of the primary kneaded material 24 is also optimized, which further contributes to improving the battery performance of the secondary battery 1.

[0049] (Other embodiments) This embodiment can be modified as follows: This embodiment and the following modifications can be combined with each other to the extent that no technical contradiction occurs.

[0050] The blackness is not limited to the blackness of the primary kneaded material 24, but may be, for example, the blackness of a material (negative electrode composite paste) in which the primary kneaded material 24 is mixed with a negative electrode binder. The viscosity of the negative electrode thickener is controlled by a shear rate of 0.01 s -1 The range is not limited to the range specified when the shear rate is set as above, and may be appropriately changed to a range when other shear rates are set as conditions.

[0051] As the negative electrode binder, for example, styrene butadiene rubber (SBR), polyvinylidene fluoride (PVDF), polyvinyl alcohol (PVA), etc. may be used. For both the negative and positive electrodes, any type of active material, conductive material, solvent, and binder can be used.

[0052] The secondary battery 1 is not limited to a lithium ion type, and may be of another type. The secondary battery 1 is not limited to being in a thin plate shape, and may be in another shape, such as a cylindrical shape.

[0053] The secondary battery 1 is not limited to being used in vehicles, but may be used in other applications, such as in ships, aircraft, or stationary applications. The viscosity range of the negative electrode thickener contained in the negative electrode additive can be appropriately changed to a range according to the shear rate. In other words, since the possible shear viscosity value changes depending on the shear rate, the viscosity of the negative electrode thickener may be appropriately changed to a range according to the shear rate.

[0054] Although the present disclosure has been described with reference to the embodiment, it is understood that the present disclosure is not limited to the embodiment or structure. The present disclosure also includes various modifications and modifications within the scope of equivalents. In addition, various combinations and forms, as well as other combinations and forms including only one element, more than one element, or less than one element, are also within the scope and concept of the present disclosure. [Explanation of symbols]

[0055] 1…Secondary battery 2…Cell 3…Aperture 4…Lid 5. Battery case 6...Electrode body 7…Nonaqueous electrolyte 8…Positive external terminal 9…Negative external terminal 12...Negative electrode plate 13…Positive electrode plate 14…Separator 16...Negative electrode current collector 17...Negative electrode composite material 18…Negative electrode connection part 20...Positive electrode current collector 21…Positive electrode mixture 22…Positive electrode connection part 24... Primary kneaded material S1…Shear viscosity waveform S2…Shear viscosity waveform

Claims

1. A method for manufacturing a negative electrode plate for a secondary battery, comprising kneading a negative electrode active material and a negative electrode additive to form a negative electrode mixture paste, applying the negative electrode mixture paste to a negative electrode current collector, and drying the paste, A primary kneaded product in the process of preparing the negative electrode composite paste is prepared by kneading a negative electrode active material made of at least a carbon material and a negative electrode additive containing a negative electrode thickener with an aqueous solvent; The primary kneaded product is subjected to centrifugal separation, and a supernatant liquid containing the negative electrode active material and the thickener liberated from the primary kneaded product is collected; The absorbance spectrum of the collected supernatant is measured in a wavelength range of 400 nm to 700 nm, and the average value of the absorbance in the wavelength range is calculated as the blackness index; The blackness of the material obtained by mixing the negative electrode active material and the negative electrode additive is set to 4 or more and 16 or less, and the viscosity of the negative electrode thickener contained in the negative electrode additive is adjusted to a shear rate of 0.01 s －１ The negative electrode plate manufacturing method is configured to set the viscosity of the negative electrode plate to 13,000 mPa·s or more and 21,000 mPa·s or less when the above condition is met.

2. The method for producing a negative electrode plate according to claim 1 , wherein a thickened solid content of the primary kneaded material is set to 58% or more and 61% or less.

3. A secondary battery comprising: a negative electrode plate used as a negative electrode; a positive electrode plate used as a positive electrode; and a separator disposed between the negative electrode plate and the positive electrode plate, The negative electrode plate includes a negative electrode current collector serving as a base material of the negative electrode, and a negative electrode mixture formed by applying a negative electrode mixture paste, which is obtained by kneading a negative electrode active material and a negative electrode additive, to the negative electrode current collector and drying the paste, A primary kneaded product in the process of preparing the negative electrode composite paste is prepared by kneading a negative electrode active material made of at least a carbon material and a negative electrode additive containing a negative electrode thickener with an aqueous solvent; The primary kneaded product is subjected to centrifugal separation, and a supernatant liquid containing the negative electrode active material and the thickener liberated from the primary kneaded product is collected; The absorbance spectrum of the collected supernatant is measured in a wavelength range of 400 nm to 700 nm, and the average value of the absorbance in the wavelength range is calculated as the blackness index; The blackness of the material obtained by mixing the negative electrode active material and the negative electrode additive is set to 4 or more and 16 or less, and the viscosity of the negative electrode thickener contained in the negative electrode additive is adjusted to a shear rate of 0.01 s －１ The method for manufacturing a secondary battery, wherein the viscosity is set to 13,000 mPa·s or more and 21,000 mPa·s or less when the above condition is met.

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