JP2015204257A - Method for manufacturing nonaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a nonaqueous electrolyte secondary battery, by which an electrode plate can be manufactured without causing liquid dripping.SOLUTION: A method for manufacturing a nonaqueous electrolyte secondary battery comprises the steps of: providing a first mixture paste including an active material on a collector so that an end portion of the collector in its widthwise direction is exposed; providing a second mixture paste including the active material, of which the liquid amount is less than that of the first mixture paste, at a boundary between a coated part of the collector coated with the first mixture paste and an uncoated part of the collector exposed from the first mixture paste; and forming an electrode plate by rolling the collector having the first mixture paste and the second mixture paste provided.

Description

  The present invention relates to a method for producing a nonaqueous electrolyte secondary battery including a step of forming an electrode plate using a mixture paste.

  In Patent Document 1 (Japanese Patent Laid-Open No. 2012-74359), it is possible to apply an alumina paste on both sides of a current collector foil, adjacent to both end portions of a previously applied mixture paste layer. Have been described. In this document, since the alumina paste contains γ-type alumina particles, the bonding strength between the alumina paste and the current collector foil is excellent. Therefore, the separation of the mixture layer and the active material can be prevented when the battery is manufactured or used. It is also described that falling off is prevented.

JP 2012-74359 A

  When the mixture paste is provided on the current collector, the mixture paste may enter the non-coating region from the coating region. As a result, the thickness of the mixture paste may be locally reduced at the end of the coating region located on the non-coating region side. Hereinafter, this phenomenon is referred to as “drip”.

  In places where dripping occurs, it is difficult to apply pressure during rolling. As a result, since the adhesion of the active material to the current collector is reduced, the active material may be detached from the current collector during production or use, etc., resulting in the occurrence of an internal short circuit and a decrease in battery capacity. cause. In addition, since the basis weight of the active material is reduced and the density of the active material is reduced, precipitation of lithium may be caused. The objective of this invention is providing the manufacturing method of the nonaqueous electrolyte secondary battery which can manufacture an electrode plate, without generating dripping.

  Various methods are conceivable as methods for adhering the active material or the like to the current collector. However, if a paste containing an active material or the like is provided on the current collector, excellent coating properties are exhibited, which contributes to mass production of nonaqueous electrolyte secondary batteries. Therefore, a method of providing the mixture paste on the current collector without causing dripping is necessary.

  Then, this inventor examined providing a mixture paste, after providing a water-repellent material in a non-coating area | region. However, when a part of the mixture paste adheres to the non-coating region, the mixture paste may be stabilized as droplets. If left as it is, a new problem may be caused, so it is necessary to remove the droplet from the non-coating area. As a result, the productivity of the nonaqueous electrolyte secondary battery is reduced.

  Next, this inventor examined providing a mixture paste, after a masking tape was affixed on a non-coating area | region. However, when the masking tape is peeled off, a part of the active material or the like may be peeled off together with the masking tape. Moreover, it is difficult to provide the mixture paste so that the mixture paste does not adhere to the masking tape. Therefore, the active material attached to the masking tape is wasted.

  Then, this inventor examined using the alumina paste of patent document 1. FIG. However, since the current collector is provided with a material that does not contribute to the battery reaction, the battery performance is degraded.

  The present inventor has further studied based on the above and completed the method for producing the nonaqueous electrolyte secondary battery of the present invention. The method for producing a non-aqueous electrolyte secondary battery according to the present invention includes a step of providing a first mixture paste containing an active material on a current collector so that an end in a width direction of the current collector is exposed, The boundary between the coating part coated with the first mixture paste and the non-coating part where the current collector is exposed from the first mixture paste contains an active material, and the liquid amount is the first mixture. A step of providing a second mixture paste less than the agent paste, and a step of forming an electrode plate by rolling a current collector provided with the first mixture paste and the second mixture paste.

  The liquid amount of the second mixture paste is smaller than the liquid amount of the first mixture paste. Therefore, the second mixture paste is inferior in fluidity to the first mixture paste. By providing such a second mixture paste at the boundary between the coating part and the non-coating part, it is possible to prevent the first mixture paste from entering the non-coating part.

  “The width direction of the current collector” means a direction perpendicular to the longitudinal direction of the current collector in a state where an electrode body described later is not formed and is different from the thickness direction of the current collector. The “width direction end portion of the current collector plate” may mean one end in the width direction of the current collector plate, but preferably means both ends in the width direction of the current collector plate. “Non-coated portion” means a portion of the current collector where the first mixture paste is not provided. “Liquid amount” means the total amount of liquid contained in the mixture paste.

  According to the method for producing a non-aqueous electrolyte secondary battery of the present invention, the first mixture paste can be prevented from entering the non-coated portion, so that the electrode plate can be produced without causing dripping.

It is a flowchart which shows the manufacturing method of the nonaqueous electrolyte secondary battery of one Embodiment of this invention. (A)-(c) is a side view which shows the manufacturing method of the nonaqueous electrolyte secondary battery of one Embodiment of this invention in order of a process. It is a graph which shows the result of an Example. It is a graph which shows the result of an Example.

  The present invention will be described below with reference to the drawings. In the drawings of the present invention, the same reference numerals represent the same or corresponding parts. In addition, dimensional relationships such as length, width, thickness, and depth are changed as appropriate for clarity and simplification of the drawings, and do not represent actual dimensional relationships.

[Manufacture of non-aqueous electrolyte secondary batteries]
FIG. 1 is a flowchart showing a part of the method for producing the nonaqueous electrolyte secondary battery of the present embodiment. FIG. 2 is a side view showing a part of the manufacturing method of the nonaqueous electrolyte secondary battery of the present embodiment in the order of steps. FIG. 2 shows one end side in the width direction of the current collector plate. In this embodiment, since the electrode plate 13 (at least one of the positive electrode and the negative electrode) is manufactured according to the method described below, the occurrence of dripping can be prevented. Thereby, precipitation of lithium can be prevented, an internal short circuit can be prevented, and a decrease in battery capacity can be prevented. Therefore, it is possible to provide a non-aqueous electrolyte secondary battery having excellent safety and high capacity. Therefore, the produced non-aqueous electrolyte secondary battery can be used as a large battery used for, for example, an automobile power source such as a hybrid vehicle or an electric vehicle, a factory power source, or a household power source.

(Step of providing the first mixture paste)
In step S101, the first mixture paste 113 is provided on the current collector 13A so that both ends in the width direction of the current collector 13A are exposed (FIG. 2A). As a result, a coated portion 13C in which the current collector 13A is covered with the first mixture paste 113 and a non-coated portion 13D in which the current collector 13A is exposed from the first mixture paste 113 are formed. The

  The current collector 13A only needs to have a known configuration as a positive electrode current collector or a negative electrode current collector of a nonaqueous electrolyte secondary battery.

  The 1st mixture paste 113 should just have a well-known structure as a positive mix paste or a negative mix paste of a nonaqueous electrolyte secondary battery. That is, when producing a positive electrode, the first mixture paste 113 includes a positive electrode active material, a binder, and a conductive agent, and preferably further includes a thickener. When producing a negative electrode, the first mixture paste 113 includes a negative electrode active material and a binder, and preferably further includes a thickener. Each content such as the active material in the first mixture paste 113 may be a general content as each content of the active material in the positive electrode mixture paste or the negative electrode mixture paste of the nonaqueous electrolyte secondary battery. .

  The first mixture paste 113 may be provided on the current collector 13A as long as it is a known method as a method of providing the positive electrode mixture paste on the positive electrode current collector or a method of providing the negative electrode mixture paste on the negative electrode current collector. For example, a die coating method or a comma coating method can be used.

  The first mixture paste 113 may be dried after being provided on the current collector 13A. The method for drying the first mixture paste 113 may be any method known as a method for drying the positive electrode mixture paste or the negative electrode mixture paste.

(Step of providing the second mixture paste)
In step S102, the 2nd mixture paste 114 is provided in the boundary of the coating part 13C and the non-coating part 13D (FIG.2 (b)). The liquid amount of the second mixture paste 114 is smaller than the liquid amount of the first mixture paste 113. Therefore, the second mixture paste 114 is inferior in fluidity to the first mixture paste 113. By providing such a second mixture paste 114 at the boundary between the coating part 13C and the non-coating part 13D, the first mixture paste 113 can be prevented from entering the non-coating part 13D. That is, the occurrence of dripping can be prevented.

  Furthermore, since the occurrence of dripping can be prevented without providing a water repellent material or masking tape or the like in the non-coated portion 13D, the productivity of the non-aqueous electrolyte secondary battery can be maintained high, and the active material is wasted. Can be prevented. Since the occurrence of dripping can be prevented without providing the current collector 13A with a material that does not contribute to the battery reaction, the battery performance of the nonaqueous electrolyte secondary battery can be maintained high.

  The 2nd mixture paste 114 should just be provided in the boundary of the coating part 13C and the non-coating part 13D at least. Therefore, a part of the second mixture paste 114 may be provided so as to cover a part of the first mixture paste 113 in the coating part 13C, or one part of the current collector 13A in the non-coating part 13D. It may be provided so as to cover the part.

  The amount of the second mixture paste 114 is preferably 20% by mass or less, more preferably 2% by mass or more and 20% by mass or less, and further preferably 10% by mass or more and 20% by mass or less. If the amount of the second mixture paste 114 is 20% by mass or less, the second mixture paste 114 can be dried without using a separate drying furnace. When the amount of the second mixture paste 114 is 2% by mass or more, the active material can be brought into close contact with the current collector 13A. As a method for measuring the liquid amount of the second mixture paste 114, the second mixture paste 114 is dried, a mass difference before and after drying is obtained, and the mass difference is regarded as the liquid amount of the second mixture paste 114. Is mentioned.

  The second mixture paste 114 may have a known configuration as the positive electrode mixture paste or the negative electrode mixture paste of the nonaqueous electrolyte secondary battery except for the liquid amount. The binder is preferably a redispersion of active material and binder and particles or particles formed by integrally combining an active material, binder, conductive agent and thickener. For example, the second mixture paste 114 can be prepared by preparing composite particles using any of the following first to third methods and dispersing the obtained composite particles in a solvent. Below, it demonstrates centering on the case where a negative electrode is produced.

(Production of composite particles)
In the first method, composite particles are produced by spray drying. First, an active material and a thickener are mixed. When producing a positive electrode, a conductive agent is added and mixed. A solvent (for example, water) is added to the obtained mixture and kneaded. A solvent (for example, water) is further added to the obtained solid to lower the solid content, and then a binder is added and kneaded. A slurry is thus obtained.

  Next, when the obtained slurry is put into a spray dryer, the slurry is made into particles by the centrifugal force of the rotating body. When the particles are dried in a drying furnace, composite particles are obtained.

  In the second method, composite particles are produced by rolling granulation. First, after making an active material into a fluid state using gas etc., the solution containing a binder, a thickener, etc. is sprayed with respect to the active material. When producing a positive electrode, the solution which further contains a electrically conductive agent is sprayed. Next, the active material is dried using a heater or irradiation with electromagnetic waves. Thereby, composite particles are obtained.

  In the third method, composite particles are produced by a mechanochemical method. First, an active material, a binder, a thickener and the like are mixed. When producing a positive electrode, a conductive agent is added and mixed. Next, compression and shear are applied to the mixture. In this way, composite particles are obtained.

(Dispersion of composite particles)
The composite particles obtained according to any one of the first to third methods are dispersed in a solvent (for example, water). The composite particles may be lightly moistened, and it is not necessary to melt the thickener. Therefore, for example, a solvent may be sprayed on the composite particles. In this way, the second mixture paste 114 is obtained.

  In the second method, it is necessary to control the spraying conditions so that only the solution sprayed on the active material does not aggregate and form droplets. In the third method, it is necessary to control the mixing conditions of the active material and the binder so that the surface of the active material is not broken and powder is not generated. Therefore, it is preferable to prepare the second mixture paste 114 according to the first method. In any of the first to third methods, the thickener is arbitrary.

  The method for providing the second mixture paste 114 on the current collector 13A is not particularly limited. For example, a method of extruding the second mixture paste 114 to the boundary between the coating part 13C and the non-coating part 13D can be used.

(rolling)
The current collector 13A provided with the first mixture paste 113 and the second mixture paste 114 is rolled. Thereby, the 1st mixture paste 113 and the 2nd mixture paste 114 become the mixture layer 13B, and the electrode plate 13 is formed (FIG.2 (c)). That is, the electrode plate 13 is provided at the coating portion 13C in which the current collector 13A is covered with the mixture layer 13B and at one end in the width direction or both ends in the width direction of the electrode plate 13, and the current collector 13A is provided in the mixture layer And an uncoated portion 13D exposed from 13B.

  In the present embodiment, the occurrence of dripping is prevented (FIG. 2B). Thereby, since a pressure is applied equally, it can prevent that the adhesive force of the active material to 13 A of collectors falls locally. Therefore, it is possible to prevent the active material from falling off from the current collector 13A during production or use. For example, it is possible to prevent the active material from dropping off at the end (region X) of the coating part 13C located on the non-coating part 13D side. Therefore, the battery capacity can be kept high. Moreover, since the breakage of the separator due to the dropped active material can be prevented, the occurrence of an internal short circuit can be prevented.

  Further, since the pressure is applied evenly, in the region X, the active material weight per unit area can be prevented from being locally reduced, the active material density can be prevented from being locally reduced, and the thickness of the mixture layer 13B. Can be prevented from becoming locally thin. Therefore, precipitation of lithium can be prevented.

  As a method of rolling the current collector 13A applied with the first mixture paste 113 and the second mixture paste 114, a method of rolling the positive electrode collector applied with the positive electrode mixture paste or a negative electrode mixture paste is used. Any known method for rolling the coated negative electrode current collector may be used. For example, rolling may be performed at 50 ° C. or higher and 80 ° C. or lower (hot pressing).

  It is preferable to perform rolling after drying the first mixture paste 113 and the second mixture paste 114. The method for drying the first mixture paste 113 and the second mixture paste 114 may be any method known as a method for drying the positive electrode mixture paste or the negative electrode mixture paste.

(Production of electrode body)
An electrode body is produced using the electrode plate 13 and the separator thus obtained. Although it does not specifically limit as a preparation method of an electrode body, For example, the method shown next can be used. First, a separator is provided between the positive electrode mixture layer and the negative electrode mixture layer, and the positive electrode non-coated portion and the negative electrode non-coated portion are the positive electrode current collector (or the negative electrode current collector). A positive electrode, a negative electrode, and a separator are provided so as to protrude in the opposite direction from the separator in the width direction. Next, a winding shaft is arranged so as to be parallel to the width direction of the positive electrode current collector (or the negative electrode current collector), and the positive electrode, the separator, and the negative electrode are wound using the winding shaft. . A predetermined pressure is applied to the obtained cylindrical electrode body. In this way, a flat electrode body is obtained. In addition, the separator should just have a well-known structure as a separator of a nonaqueous electrolyte secondary battery.

(Sealing)
The obtained electrode body is put in a battery case together with a nonaqueous electrolyte, and then the battery case is sealed. In this way, a nonaqueous electrolyte secondary battery is obtained. In addition, the nonaqueous electrolyte should just have a well-known structure as a nonaqueous electrolyte of a nonaqueous electrolyte secondary battery.

  Hereinafter, the present invention will be specifically described, but the present invention is not limited to the following configurations. In the following examples, a negative electrode was produced, and the film thickness profile of the negative electrode mixture layer and the peel strength of the negative electrode mixture layer were examined.

[Example 1]
(Application of first negative electrode mixture paste)
As a negative electrode active material, a carbon material (average particle size of 5 to 25 μm) having natural graphite as a core material was prepared. The prepared negative electrode active material and sodium carboxymethylcellulose (CMC-Na, thickener) were mixed, and then water was added and kneaded. The aqueous solution obtained by kneading contained 60 mass% to 70 mass% solid content.

  After the kneading, water was further added so that the solid content was 50% by mass to 60% by mass. Styrene butadiene rubber (binder) was added to the aqueous solution and kneaded. In this way, a first negative electrode mixture paste was obtained. The obtained first negative electrode mixture paste contained 98% by mass of a negative electrode active material, 1% by mass of a thickener, and 1% by mass of a binder. Then, the 1st negative mix paste was apply | coated on both surfaces of Cu foil so that the width direction both ends of Cu foil (negative electrode collector) might be exposed. Thereafter, the first negative electrode mixture paste was dried.

(Application of second negative electrode mixture paste)
A first negative electrode mixture paste was prepared according to the method described above, and the first negative electrode mixture paste was put in a spray dryer. As a result, composite particles constituted by integrally combining the negative electrode active material, the thickener, and the binder were obtained.

  The obtained composite particles and water were put into a planetary mixer. The composite particles were dispersed in water at 20 ° C. with a rotation speed of 50 rpm and a dilution time of 10 minutes. In this way, a second negative electrode mixture paste was obtained. Thereafter, the second negative electrode mixture paste is applied to the boundary between the coated portion in which the Cu foil is coated with the first negative electrode mixture paste and the non-coated portion in which the Cu foil is exposed from the first negative electrode mixture paste. Provided.

  When the obtained 2nd negative mix paste was dried and the mass difference before and behind drying was calculated | required, it turned out that the liquid amount of a 2nd mix paste is less than 1 mass%.

(rolling)
When the first negative electrode mixture paste and the second negative electrode mixture paste were dried, the Cu foil provided with them was rolled. In this way, a coated portion in which the Cu foil is coated with the negative electrode mixture layer, and a non-coated portion that is provided at one end in the width direction of the Cu foil and in which the Cu foil is exposed from the negative electrode mixture layer. The negative electrode which has was obtained.

[Examples 2 to 4, Comparative Example 1]
In Examples 2 to 4, negative electrodes were produced according to the method described in Example 1 except that the second negative electrode mixture paste containing the liquid amounts shown in Table 1 was used. In Comparative Example 1, a negative electrode was produced according to the method described in Example 1 except that the second negative electrode mixture paste was applied at the position shown in Table 1. In addition, “in-plane” in Table 1 means a portion located in the center in the width direction of the Cu foil in the coated portion.

(Measurement of film thickness profile)
The thickness of the negative electrode mixture layer of Example 4 and Comparative Example 1 was measured using a film thickness meter. The result is shown in FIG. In FIG. 3, L31 shows the result of Example 4, L32 shows the result of Comparative Example 1, and an enlarged view of region Y is shown in a frame in the graph. Moreover, in FIG. 3, as it goes to the left side (0 mm side) of the horizontal axis and the right side (300 mm side) of the horizontal axis, the boundary between the coated part and the uncoated part (the end side in the width direction of the Cu foil) approaches. . In Example 4, compared with Comparative Example 1, it was possible to prevent the thickness of the mixture layer from being locally reduced at the end of the coating portion located on the boundary side.

(Measurement of 90 ° peel strength)
In accordance with the method specified in JIS Z 0237: 2009 (Adhesive tape / adhesive sheet test method), the peel strength (90 ° peel strength) when the negative electrode mixture layer was peeled from the Cu foil was measured. The result is shown in FIG.

  When the result of the film thickness profile and the result of the 90 ° peel strength are summarized, if the liquid amount of the second mixture paste is 20% by mass or less, the coating positioned on the boundary side between the coated part and the non-coated part is applied. It was possible to prevent the thickness of the mixture layer from being locally reduced at the end of the work part. On the other hand, the 90 ° peel strength is about the same as in Comparative Example 1 if the amount of the second mixture paste is 2% by mass and 10% by mass, and the amount of the second mixture paste is 20% by mass. If it exists, it became higher than the case of the comparative example 1. Therefore, the amount of the second mixture paste is preferably 20% by mass or less, more preferably 2% by mass or more and 20% by mass or less, and further preferably 10% by mass or more and 20% by mass or less. I found out.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  13 electrode plate, 13A current collector, 13B mixture layer, 13C coating part, 13D non-coating part, 113 first mixture paste, 114 second mixture paste.

Claims (1)

Providing the current collector with a first mixture paste containing an active material such that the widthwise end of the current collector is exposed;
The active material is included in a boundary between a coated part in which the current collector is coated with the first mixture paste and a non-coated part in which the current collector is exposed from the first mixture paste. And a step of providing a second mixture paste having a liquid amount smaller than that of the first mixture paste;
And a step of forming an electrode plate by rolling a current collector provided with the first mixture paste and the second mixture paste.