JP2013069633A - Manufacturing method of nonaqueous electrolyte secondary battery and nonaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a nonaqueous electrolyte secondary battery which allows for suitable coating of an electrode core material with a paste by limiting rapid rise in viscosity of the paste when transmitting through a filter, and to provide a nonaqueous electrolyte secondary battery.SOLUTION: A negative electrode active material having one peak in the particle size distribution is used. The particle size distribution of the negative electrode active material satisfies relations of 0.90≤A/(D50)≤2.0 and 1.30≤B/(D50)≤3.0, where (D50:median diameter, A:half value width of particle size distribution, B:quarter value width of particle size distribution). A negative electrode active material of this particle size distribution, a binder, and a thickening material are charged to a solvent and kneaded thus producing a paste for negative electrode. A negative electrode plate N is manufactured by coating a negative electrode core material with the paste for negative electrode.

Description

  The present invention relates to a method for producing a nonaqueous electrolyte secondary battery and a nonaqueous electrolyte secondary battery. More specifically, the present invention relates to a non-aqueous electrolyte secondary battery manufacturing method and a non-aqueous electrolyte secondary battery in which a coating solution can be suitably applied to an electrode core material.

  Non-aqueous electrolyte secondary batteries include lithium ion secondary batteries. The electrode body of a lithium ion secondary battery is prepared by applying a coating solution to an electrode core material and drying it. The coating liquid includes a positive electrode paste and a negative electrode paste.

  These pastes are prepared by putting an active material, a binder or the like into a solvent and kneading with a kneader. The paste thus prepared is filtered through a filter before being applied to the electrode core material from the coating device. This is to remove undispersed aggregates in the paste. This is because if the paste contains agglomerates, coating stripes may occur in the coating layer when the paste is applied. In a battery having electrode stripes on the electrode body, the desired output may not be exhibited. Further, in such a battery, there is a possibility that lithium is deposited at the location of the coating stripe.

  Accordingly, various techniques for removing aggregates from the coating liquid have been developed. For example, Patent Document 1 discloses a battery manufacturing method in which paste is stirred by a stirring device including a stirring blade and undispersed aggregates are removed using a filter (claim 1 of Patent Document 1). And paragraph [0013] and FIG. 1 etc.).

JP-A-9-213310

  By the way, when the paste passes through the filter, a shearing force is applied to the paste as it passes through the mesh gap. When shear force is applied to the paste, the viscosity of the paste may change only during the period when the shear force is applied. The viscosity of the paste may increase only during the period when shear force is applied to the paste. Such a phenomenon that the viscosity of the paste increases due to the shearing force is called dilatancy.

  When the viscosity of the paste rises rapidly, it becomes difficult for the paste to pass through the filter. That is, the amount (flow rate) of the paste permeating the filter per unit time is reduced. If it does so, the flow volume of the paste which flows out out of a coating device will also decrease. This reduces the productivity of the electrode body. In addition, due to the reduced flow rate of the paste, coating cannot be performed with the prescribed thickness and width, which may result in poor coating. Therefore, it is preferable to suppress a rapid increase in viscosity when the paste passes through the filter.

  The present invention has been made to solve the above-described problems of the prior art. That is, the problem is that a non-aqueous electrolyte secondary battery manufacturing method and a non-aqueous electrolyte secondary battery capable of suitably applying the paste to the electrode core material while suppressing a rapid increase in the viscosity of the paste when passing through the filter are provided. It is to provide a battery.

The method for producing a non-aqueous electrolyte secondary battery according to one aspect of the present invention for solving this problem is to apply a negative electrode paste containing a negative electrode active material to a negative electrode core material after passing through a filter and dry it. A negative electrode plate forming step to form a negative electrode plate, an electrode body preparing step to form an electrode body by placing the negative electrode plate and the positive electrode plate with a separator between them, and injecting the electrode body and electrolyte into the battery container And a battery assembling step for sealing. In the negative electrode plate forming step, the particle size distribution of the negative electrode active material has one peak, and the following relational expression 0.90 ≦ A / D50 ≦ 2.0.
1.30 ≦ B / D50 ≦ 3.0
D50: Median diameter
A: Half width of particle size distribution
B: A negative electrode active material satisfying the quarter width of the particle size distribution is used. In such a non-aqueous electrolyte secondary battery manufacturing method, the negative electrode paste smoothly passes through the filter. For this reason, coating defects are less likely to occur during coating.

  In the method for manufacturing a non-aqueous electrolyte secondary battery described above, a depth filter having a pore diameter 2.5 to 7 times the median diameter of the negative electrode active material may be used as the filter. This is because the negative electrode paste passes through the filter more smoothly.

A nonaqueous electrolyte secondary battery according to another aspect of the present invention has a positive electrode plate, a negative electrode plate, and a separator, and the particle size distribution of the negative electrode active material contained in the negative electrode plate has one peak. The following relational expression: 0.90 ≦ A / D50 ≦ 2.0
1.30 ≦ B / D50 ≦ 3.0
D50: Median diameter
A: Half width of particle size distribution
B: satisfies the quarter width of the particle size distribution. In such a non-aqueous electrolyte secondary battery, coating unevenness hardly occurs in the coating layer of the negative electrode plate. Therefore, the variation in battery performance that can occur from lot to lot is small.

  According to the present invention, there is provided a non-aqueous electrolyte secondary battery manufacturing method and a non-aqueous electrolyte secondary battery in which a paste viscosity can be suitably applied to an electrode core material while suppressing a sudden increase in the viscosity of the paste during filter permeation. Is provided.

It is a perspective view for demonstrating schematic structure of the assembled battery which concerns on embodiment. It is sectional drawing for demonstrating schematic structure of the battery which concerns on embodiment. It is a perspective view for demonstrating the winding electrode body of the battery which concerns on embodiment. It is an expanded view for demonstrating the winding structure of the winding electrode body of the battery which concerns on embodiment. It is a perspective sectional view for explaining the sectional structure of the positive electrode plate (negative electrode plate) of the battery according to the embodiment. It is a schematic block diagram for demonstrating the coating apparatus used for the manufacturing method of the battery which concerns on embodiment. It is a schematic diagram for demonstrating the transmission rate of the paste in the filter used for the manufacturing method of the battery which concerns on embodiment, and the area | region before and behind that. It is a graph which illustrates the particle size distribution of a negative electrode active material. It is a graph which shows the half value width and quarter value width in the particle size distribution of a negative electrode active material. It is a schematic block diagram for demonstrating the experimental equipment used in the experiment which concerns on an Example. It is a graph which shows the particle size distribution of the negative electrode active material used in the experiment which concerns on an Example. It is a graph for demonstrating the difference in the permeation | transmission speed of the filter by the particle size distribution of the negative electrode active material used in the experiment which concerns on an Example.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments embodying the present invention will be described below in detail with reference to the accompanying drawings. In this embodiment, the present invention is embodied in a method for manufacturing a lithium ion secondary battery.

1. Battery structure 1-1. The assembled battery BP of this embodiment is an assembled battery in which batteries 100 are connected in series as shown in FIG. The battery 100 is a square cell. In the assembled battery BP, as shown in FIG. 1, the positive terminal of the battery 100 and the negative terminal of the battery 100 adjacent to the battery 100 are fastened via a bus bar 190. This fastening is made with bolts and nuts.

1-2. Single Battery The battery 100 is a single battery of a lithium ion secondary battery. A schematic configuration of the battery 100 is shown in a cross-sectional view of FIG. FIG. 2 shows the battery 100 taken out from the assembled battery BP shown in FIG. As shown in FIG. 2, the battery container 110 includes a battery container main body 120 and a sealing plate 130. A wound electrode body 10 is disposed inside the battery container 110. The wound electrode body 10 is a power generation element that actually contributes to power generation. The sealing plate 130 is for closing the opening of the battery container main body 120. Therefore, it is joined to the battery container body 120.

  An electrolyte is injected into the battery container 110. This electrolytic solution is obtained by dissolving an electrolyte in an organic solvent. Examples of organic solvents include propylene carbonate (PC), ethylene carbonate (EC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), 1,2-dimethoxyethane, 1,2-diethoxyethane. , Tetrahydrofuran, 2-methyltetrahydrofuran, dioxane, 1,3-dioxolane, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, acetonitrile, propionitrile, nitromethane, N, N-dimethylformamide, dimethyl sulfoxide, sulfolane, γ-butyrolactone, etc. A solvent or a combination of these can be used.

Further, as a salt that is an electrolyte, lithium perchlorate (LiClO ₄ ), lithium borofluoride (LiBF ₄ ), lithium hexafluorophosphate (LiPF ₆ ), lithium hexafluoroarsenate (LiAsF ₆ ), LiCF ₃ SO _{3 , LiC 4 F 9 SO 3,} LiN (CF 3 SO 2) 2, LiC (CF 3 SO 2) 3, can be used a lithium salt such as LiI.

  As shown in FIG. 2, the battery 100 includes a positive electrode terminal 50, a negative electrode terminal 60, an insulating member 150, and an insulating member 160. The insulating member 150 is a member for insulating the positive electrode terminal 50 and the sealing plate 130. The insulating member 160 is a member for insulating the negative electrode terminal 60 and the sealing plate 130.

  As shown in FIG. 2, a liquid injection hole 140 is provided in the sealing plate 130. The liquid injection hole 140 is a through hole that penetrates the sealing plate 130. The liquid injection hole 140 is for injecting the electrolyte into the battery container 110. The lid 170 is a liquid injection hole lid for closing the liquid injection hole 140 of the sealing plate 130. Therefore, the lid body 170 covers the opening portion of the liquid injection hole 140. The lid 170 is seam welded to the sealing plate 130 from the outside of the sealing plate 130.

1-3. FIG. 3 is a perspective view showing the wound electrode body 10. As shown in FIG. 3, the wound electrode body 10 has a flat shape. A positive electrode end portion 30 projects from one end portion of the wound electrode body 10. As will be described later, the positive electrode end 30 is a portion where the positive electrode core material of the positive electrode plate protrudes. A negative electrode end 40 protrudes from the other end of the wound electrode body 10. The negative electrode end 40 is a portion where the negative electrode core material of the negative electrode plate protrudes, as will be described later.

  FIG. 4 is a development view showing a wound structure of the wound electrode body 10. As shown in FIG. 4, the wound electrode body 10 is wound in a state where the positive electrode plate P, the separator S, the negative electrode plate N, and the separator T are stacked in this order from the inside. That is, the wound electrode body 10 is configured such that the positive plates P and the negative plates N are alternately arranged with the separators S and T interposed therebetween.

  The positive electrode plate P is obtained by applying a composite material containing a positive electrode active material capable of inserting and extracting lithium ions to an aluminum foil as a positive electrode core material. The negative electrode plate N is obtained by applying a composite material containing a negative electrode active material capable of occluding and releasing lithium ions to a copper foil as a negative electrode core material.

  As shown in FIG. 4, the positive electrode plate P has a positive electrode coating part P1 and a positive electrode non-coating part P2. The positive electrode coating part P1 is a place where a positive electrode mixture layer containing a positive electrode active material or the like is formed on a positive electrode core material. The positive electrode non-coated portion P2 is a portion where the positive electrode mixture layer is not formed on the positive electrode core material. The negative electrode plate N includes a negative electrode coating portion N1 and a negative electrode non-coating portion N2. The negative electrode coating portion N1 is a portion where a negative electrode mixture layer containing a negative electrode active material or the like is formed on a negative electrode core material. The negative electrode non-coated portion N2 is a portion where the negative electrode mixture layer is not formed on the negative electrode core material.

  An arrow A in FIG. 4 indicates the width direction (lateral direction in FIG. 3) of the positive electrode plate P, the negative electrode plate N, and the separators S and T. An arrow B in FIG. 4 indicates the longitudinal direction of the positive electrode plate P, the negative electrode plate N, the separators S and T (the circumferential direction of the wound electrode body 10 in FIG. 3).

  The separators S and T are porous films such as polyethylene and polypropylene. The thicknesses of the separators S and T are about 10 to 50 μm. Here, the separator S and the separator T are made of the same material. For the understanding of the above winding order, only the codes are distinguished as S and T.

1-4. FIG. 5 is a perspective sectional view of the positive electrode plate P (or the negative electrode plate N). In FIG. 5, each symbol outside the parentheses indicates each part in the case of the positive electrode, and each symbol in the parenthesis indicates each part in the case of the negative electrode. The direction indicated by the arrow A in FIG. 5 is the same as the direction indicated by the arrow A in FIG. That is, it is the width direction of the positive electrode plate P (or the negative electrode plate N). The direction indicated by arrow B in FIG. 5 is the same as the direction indicated by arrow B in FIG. That is, it is the longitudinal direction of the positive electrode plate P (or the negative electrode plate N).

  As shown in FIG. 5, the positive electrode plate P is obtained by forming a positive electrode mixture layer PA on a part of both surfaces of a strip-like positive electrode core material PB. On the left side in FIG. 5, the positive electrode non-coated portion P2 of the positive electrode plate P protrudes in the width direction. The positive electrode non-coated portion P2 is formed in a strip shape. The positive electrode non-coated portion P2 is a region where the positive electrode active material is not applied to both surfaces of the positive electrode core material PB. Therefore, in the positive electrode non-coating portion P2, the positive electrode core material PB is still exposed. On the other hand, there is no protrusion corresponding to the positive electrode non-coated portion P2 on the right side in FIG. In the positive electrode coating part P1, the positive electrode mixture layer PA is formed with a uniform thickness on both surfaces of the positive electrode core material PB.

The positive electrode mixture layer PA is formed by applying a composite material including a conductive material, a binder, and a thickener in addition to the positive electrode active material capable of occluding and releasing lithium ions to the aluminum foil as the positive electrode core material PB. Layer. Lithium composite oxidation such as lithium nickelate (LiNiO ₂ ), lithium manganate (LiMn ₂ O ₄ ), lithium cobaltate (LiCoO ₂ ), LiNi _1/3 Co _1/3 Mn _1/3 O ₂ as the positive electrode active material Things are used.

  Carbon materials such as carbon powder and carbon fiber can be used as the conductive material for the positive electrode. For example, carbon powder such as acetylene black, furnace black, ketjen black, etc., graphite powder, etc.

  The binder for the positive electrode is preferably a polymer that is insoluble (or hardly soluble) in the electrolyte and is dispersed in the solvent used for the positive electrode paste. For example, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), ethylene-tetrafluoro Fluorine resin such as ethylene copolymer (ETFE), vinyl acetate copolymer, styrene butadiene rubber (SBR), acrylic acid-modified SBR resin (SBR latex), rubber such as gum arabic can be used. Alternatively, a combination of these may be used. The binder is not necessarily limited to the above polymer.

  As the thickener for the positive electrode, cellulose such as carboxymethylcellulose (CMC), methylcellulose (MC), cellulose acetate phthalate (CAP), hydroxypropylmethylcellulose (HPMC), hydroxypropylmethylcellulose phthalate (HPMCP) or the like is used. However, it is not necessarily limited to cellulose as described above, and can be used.

  An example of the solvent is water. In addition, N-methyl-2-pyrrolidone (NMP, hereinafter referred to as NMP) may be used. Other lower alcohols and lower ketones can also be used.

  As indicated by the reference numerals in parentheses in FIG. 5, the negative electrode plate N is obtained by forming a negative electrode mixture layer NA on a part of both surfaces of a strip-shaped negative electrode core material NB. On the left side in FIG. 5, a negative electrode non-coated portion N2 of the negative electrode plate N protrudes in the width direction. The negative electrode non-coated portion N2 is formed in a strip shape. The negative electrode non-coated portion N2 is a region where the negative electrode active material is not applied to both surfaces of the negative electrode core material NB. Therefore, in the negative electrode non-coating portion N2, the negative electrode core material NB is still exposed. On the other hand, there is no protrusion corresponding to the negative electrode non-coated portion N2 on the right side in FIG. In the negative electrode coating portion N1, the negative electrode mixture layer NA is formed with a uniform thickness on both surfaces of the negative electrode core material NB. However, as shown in FIG. 4, at the time of winding, the positive electrode non-coated portion P2 and the negative electrode non-coated portion N2 are wound in a state of protruding to the opposite side.

  The negative electrode mixture layer NA is a layer obtained by applying a mixture containing a negative electrode active material, a binder, and a thickener to a copper foil as the negative electrode core material NB and drying it. The negative electrode active material is a material that can occlude and release lithium ions. As the negative electrode active material, a carbon-based material containing a graphite structure at least partially is used. For example, amorphous carbon, non-graphitizable carbon (hard carbon), graphitizable carbon (soft carbon), graphite (graphite), or a carbon material having a combination thereof can be used.

  The binder for the negative electrode may be a polymer that is insoluble (or hardly soluble) in the electrolyte and is dispersed in the solvent used for the negative electrode paste. For example, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), ethylene-tetrafluoro Fluorine resin such as ethylene copolymer (ETFE), vinyl acetate copolymer, styrene butadiene rubber (SBR), acrylic acid-modified SBR resin (SBR latex), rubber such as gum arabic can be used. Alternatively, a combination of these may be used. The binder is not necessarily limited to the above polymer.

  As the thickener for the negative electrode, cellulose such as carboxymethylcellulose (CMC), methylcellulose (MC), cellulose acetate phthalate (CAP), hydroxypropylmethylcellulose (HPMC), and hydroxypropylmethylcellulose phthalate (HPMCP) is used. However, it is not necessarily limited to cellulose as described above, and can be used.

  An example of the solvent is water. NMP may be used. Other lower alcohols and lower ketones can also be used.

2. Coating Device Next, the coating device 1000 used in the battery manufacturing method of the present embodiment will be described. The coating apparatus 1000 can be used for both the production of the positive electrode plate P and the production of the negative electrode plate N. Here, for the sake of explanation, the negative electrode plate N will be described as an example. A coating apparatus 1000 of this embodiment is shown in FIG. As shown in FIG. 6, the coating apparatus 1000 includes a kneading apparatus 1100, a first filter 1200, a buffer tank 1300, a second filter 1400, a valve 1500, a pump 1600, a third filter 1700, An industrial die 1800 and a backup roller 1900 are provided.

  The kneading apparatus 1100 is for making a negative electrode paste by mixing and kneading the negative electrode active material, the binder, and the thickener in the solvent described above. The first filter 1200 is for removing aggregates from the kneaded negative electrode paste. The buffer tank 1300 is for temporarily storing the negative electrode paste.

  The second filter 1400 is for removing aggregates from the negative electrode paste sent out from the buffer tank 1300. The valve 1500 is for adjusting the opening and closing of the flow path of the negative electrode paste. The pump 1600 is for adjusting the flow rate of the negative electrode paste. The third filter 1700 is for removing agglomerates from the negative electrode paste before coating with the coating die 1800.

  The coating die 1800 is for coating a negative electrode paste on the negative electrode core material NB. The backup roller 1900 is used for conveying the negative electrode core material NB while supporting the negative electrode core material NB from the surface opposite to the surface to be coated on the negative electrode core material NB during coating by the coating die 1800. is there.

  The first filter 1200, the second filter 1400, and the third filter 1700 are the same type of filter. These should be depth filters. A screen filter may also be used. The pore diameter of the filter is preferably about 2.5 to 7 times the median diameter of the negative electrode active material. In particular, it is even better to be about 3 to 5 times the median diameter of the negative electrode active material. The median diameter will be described later.

3. Increase in Viscosity of Negative Electrode Paste As described above, when the viscosity of the negative electrode paste rapidly increases when the negative electrode paste passes through these filters 1200, 1400, 1700, the negative electrode that passes through the filters 1200, 1400, 1700. The permeation amount of the paste is small. In particular, if the amount of the negative electrode paste that passes through the third filter 1700 is insufficient, it is difficult to apply the negative electrode paste with a target coating width and coating thickness. Also, it may cause uneven coating. Therefore, it is preferable to prepare a negative electrode paste that does not increase in viscosity when passing through the filters 1200, 1400, and 1700.

  Dilatancy here, that is, a sudden increase in viscosity, is a reversible change in viscosity. As the paste passes through the filter, shear is applied. Only during this shear is the viscosity of the paste rising. Therefore, the viscosity of the paste after passing through the filter is almost equal to the viscosity of the paste before passing through the filter. Thus, the viscosity increases only when it passes through the filter. Note that this dilatancy, that is, a sharp increase in viscosity during filter permeation, tends to occur as the solid content in the paste increases.

  FIG. 7 shows the state of the paste when passing through the filter. FIG. 7 is a diagram schematically showing the filter mesh and its surroundings. In practice, the filter has a multi-layer structure in which a portion with a mesh and a portion without a mesh appear alternately. As is clear from FIG. 7, the passage 1201 of the particles (negative electrode active material or the like) is narrow at a location (region R2) where the filter mesh is present. There are no obstacles to the permeation of the particles at the front and rear portions (regions R1, R3) of the filter mesh.

Here, the average speed of the paste in the region R1 before the paste passes through the filter mesh is V1. Let V2 be the average velocity of the paste in the region R2 while the paste is passing through the filter mesh. Let V3 be the average velocity of the paste in region R3 after the paste has passed through the filter mesh. Then, the following relational expression holds.
V2 >> V1
V3 ≒ V1

  Here, the particles receive a shearing force in the region R2 that passes through the filter mesh. Under the shearing force, the particles move at a high average speed V2 in the region R2. For these reasons, the viscosity of the paste increases. As mentioned above, this increase in viscosity occurs only when passing through the filter. The viscosity of the paste after passing through the filter is almost the same as the viscosity of the paste before passing through the filter. As will be described later, when the particle size distribution of the negative electrode active material is different, the degree of increase in the viscosity is also different. This embodiment is characterized in that a negative electrode active material having a particle size distribution that does not increase the viscosity of the paste so much is used.

4). Method for Producing Negative Electrode Paste The method for producing a lithium ion secondary battery according to the present embodiment is a method characterized by the method for producing the negative electrode paste. Therefore, a method for producing a negative electrode paste will be described.

  This embodiment is characterized by the particle size of the negative electrode active material used. In this embodiment, a negative electrode active material having one peak in the particle size distribution is used. For example, in FIG. 8, the particle size distributions X1 and X2 satisfy this condition. As will be described later, a paste using a negative electrode active material having a double peak in the particle size distribution cannot pass through the filter, as in the particle size distribution X3 in FIG.

Further, the particle size distribution of the negative electrode active material in this embodiment satisfies the following expressions (1) and (2).
0.90 ≦ A / D50 ≦ 2.0 (1)
1.30 ≦ B / D50 ≦ 3.0 (2)
D50: Median diameter
A: Half width of particle size distribution
B: Quarter width of particle size distribution The median diameter is a diameter at which the cumulative number of particles is half (50%) of the total number when the particle sizes are arranged in ascending order. FIG. 9 shows the half width A and the quarter width B of the particle size distribution. As shown in FIG. 9, the half-value width A is the width of the particle size distribution when the value H / 2 is half the peak value H of the particle size distribution. The quarter width B is the width of the particle size distribution when the value H / 4 is 1/4 of the peak value H.

As the negative electrode active material used in this embodiment, a material satisfying the following conditions is used.
Condition 1: The particle size distribution has one peak. Condition 2: The expressions (1) and (2) are satisfied. Of the particle size distributions shown in FIG. 8, the particle size distribution X1 satisfies the conditions 1 and 2. Yes. The particle size distribution X2 satisfies the condition 1, but does not satisfy the condition 2. The particle size distribution X3 is a double peak and does not satisfy even condition 1.

  In this embodiment, a negative electrode active material that satisfies conditions 1 and 2 is used. Although details will be described later in the Examples section, the paste for the negative electrode cannot permeate the filters 1200, 1400, and 1700 when the particle size distribution has a double peak. If a negative active material having a narrow single particle size distribution, that is, a uniform particle size is used, the viscosity of the negative paste rapidly increases when the negative paste passes through the filters 1200, 1400, and 1700. .

  Therefore, when the negative electrode active material satisfying the conditions 1 and 2 is used, the filter passes through the filter, suppresses an abrupt increase in the viscosity of the paste when passing through the filter, and allows an appropriate amount of paste to be sent from the coating die 1800. . Of course, agglomerates can be removed from the paste. As a result, a highly productive battery manufacturing method can be realized.

5. Manufacturing Method of Battery The manufacturing method of the lithium ion secondary battery of the present embodiment is characterized in that the above-described manufacturing method of the negative electrode paste is adopted. And the manufacturing method of the lithium ion secondary battery of this form has the manufacturing process shown next.
(A) Positive electrode plate production process (B) Negative electrode plate production process (C) Electrode body production process (D) Battery assembly process

5-1. (A) Positive electrode plate preparation process A positive electrode active material, a conductive material, a thickener, and a binder are mixed in a solvent and kneaded to prepare a positive electrode paste. The materials described above may be used for each material such as the positive electrode active material used here.

  Then, a positive electrode paste is applied to the positive electrode core material PB using the coating apparatus 1000 to form a positive electrode paste layer. The positive electrode paste layer is a layer before drying of the positive electrode mixture layer PA. Next, the positive electrode paste layer on which the positive electrode paste layer is formed is dried while being conveyed into the drying furnace. Thereby, the positive electrode mixture layer PA is formed on the positive electrode core material PB. Here, the positive electrode mixture layer PA is preferably formed on both surfaces of the positive electrode core material PB. Thereby, the positive electrode plate P is created. The positive electrode plate P may be appropriately subjected to a roll press process or a slit process.

5-2. (B) Negative electrode plate preparation step A negative electrode active material, a binder, and a thickener are mixed in a solvent and kneaded to prepare a negative electrode paste. The negative electrode active material used here satisfies the conditions 1 and 2 as described above. As for other materials, those described above may be used.

  Then, the negative electrode paste is applied to the negative electrode core material NB using the coating apparatus 1000. Therefore, the negative electrode paste is applied to the negative electrode core material NB after passing through the third filter 1700. And the negative electrode plate N is produced by drying the paste layer for negative electrodes in a drying furnace.

5-3. (C) Electrode body creation process Subsequently, the wound electrode body 10 is created. At that time, as shown in FIG. 4, the positive electrode plate P and the negative electrode plate N are wound with the separators S and T interposed therebetween and stacked. Thereby, a cylindrical wound electrode body disposed between the positive electrode plate P and the negative electrode plate N via the separators S and T is created. By compressing the cylindrical wound electrode body from the radial direction of the cylinder, a flat wound electrode body 10 as shown in FIG. 3 is created.

5-4. (D) Battery Assembly Step Next, the wound electrode body 10 is accommodated in the battery container body 120. Further, the sealing plate 130 is joined to the battery container main body 120. Laser welding may be used for this joining. Of course, other joining methods may be used. Then, an electrolyte is injected into the battery container main body 120 from the liquid injection hole 140. Next, the lid 170 is sealed by joining to the sealing plate 130. Thereby, the battery 100 is assembled.

5-5. Other Steps After injecting the electrolytic solution into the battery container 110, the electrolytic solution gradually impregnates the positive electrode mixture layer PA and the negative electrode mixture layer NA of the wound electrode body 10. After the impregnation with the electrolytic solution, an initial charging step, a high temperature aging step, or the like is preferably performed. Further, various other inspection processes may be performed. The assembled battery BP is manufactured through the above steps.

6). Produced Battery When the coating layer of the negative electrode plate N of the battery 100 manufactured by the battery manufacturing method of the present embodiment is disassembled, the particle size distribution of the negative electrode active material contained in the negative electrode plate N is expressed by the above formula (1 ), (2) should be satisfied. And in the battery 100 manufactured with the manufacturing method of the battery of this form, the coating layer is suitably applied to the electrode core material, and there is almost no coating defect. This is because the paste is suitably supplied to the electrode core material at the coating stage. Also, almost no coating streaks are seen.

7). Summary As described above in detail, the battery manufacturing method according to the present embodiment uses a negative electrode active material having a relatively wide single peak. That is, the particle size distribution of the negative electrode active material satisfies the expressions (1) and (2). By using a negative electrode active material having such a particle size distribution, a non-aqueous electrolyte secondary battery manufacturing method and a non-aqueous electrolyte secondary battery that can be suitably applied even when a paste having a high solid content is used Is realized.

  Note that this embodiment is merely an example, and does not limit the present invention. Therefore, the present invention can naturally be improved and modified in various ways without departing from the gist thereof. For example, if it is a battery, it can apply not only to a secondary battery but to a primary battery. Of course, it does not depend on the shape of the electrode body.

A. Experimental Method In this experiment, negative electrode pastes were prepared using negative electrode active materials with different particle size distributions. In this experiment, natural graphite was used as the negative electrode active material. Carboxymethylcellulose (CMC) was used as a thickener. Styrene butadiene rubber (SBR) was used as the binder. The mixing ratio of these powders is negative electrode active material: CMC: SBR = 98: 1: 1 in weight percent. And the solid content rate of the paste finally obtained was 54% by weight ratio.

  The apparatus used in the experiment is shown in FIG. As shown in FIG. 10, the kneaded negative electrode paste is moved from the first tank 2100 to the second tank 2300. At that time, the filter 2200 is transmitted. A depth filter having a pore diameter 3 to 6 times the median diameter of the negative electrode active material was used as the filter. At this time, the first tank 2100 is pressurized with a pressure of 0.13 MPa. The value of this pressure is the same as the value of the pressure applied before permeation of each filter in the coating apparatus 1000 described in the embodiment.

B. Evaluation Item The evaluation item in this experiment is the permeation speed when the negative electrode paste passes through the filter 2200 as described above. The permeation rate after passing through the filter 2200, that is, the flow rate of the negative electrode paste (the amount of negative electrode paste flowing per unit time: g / sec) is measured. For this purpose, the time change of the weight of the second tank 2300 was measured. It is also possible to measure using a flow meter.

C. Experimental Results In this experiment, a negative electrode active material having a particle size distribution as shown in the graph of FIG. 11 was used. Example 1 satisfies the above-described condition 1 and condition 2. Comparative Example 1 satisfies Condition 1, but does not satisfy Condition 2. Comparative example 2 has a double peak and does not satisfy even condition 1.

C-1. Example 1
As shown in Table 1, Y was the half-value width of the particle size distribution in the case of Example 1. For this reason, the half-value width Y of the first embodiment and the following comparative example are based on this half-value width Y. The quarter value width of Example 1 is 1.48Y. In Example 1, the speed at which the paste permeates the filter (hereinafter referred to as “filter permeation speed”) was 21.7 g / sec. This transmission rate is a sufficient value. Although shear is applied when passing through the filter, it is thought that the viscosity of the paste has not increased so much.

C-2. Comparative Example 1
As shown in Table 1, the half value width of the particle size distribution in the case of Comparative Example 1 was 0.72Y. The half value width of Comparative Example 1 is about 70% of the half value width Y of Example 1. That is, the peak of the particle size distribution is narrower than that of Example 1. The quarter value width of Comparative Example 1 was 1.15Y. The quarter width of Comparative Example 1 is also narrower than that of Example 1. In Comparative Example 1, the filter transmission rate was 5.8 g / sec. It is considered that the viscosity of the paste rises rapidly due to the shear applied during the filter transmission, and the permeation rate is low.

C-3. Comparative Example 2
As shown in Table 1, in Comparative Example 2, a negative electrode active material having a double particle size particle size distribution was used. In Comparative Example 2, the paste did not pass through the filter. The filter is clogged, and it is thought that the paste could not pass through the filter.

  Therefore, as shown in FIG. 12, if the filter transmission speed is 10 g / sec or more, it is determined that the product is non-defective. If the filter transmission speed is less than 10 g / sec, it is determined that the filter is defective. From FIG. 12, only Example 1 among Example 1, Comparative Example 1, and Comparative Example 2 satisfies the above conditions.

  Therefore, if the negative electrode active material having the particle size distribution of Example 1 is used, the paste can be suitably applied to the electrode core material by the coating apparatus. As shown in Table 1, even when a negative electrode active material having any particle size distribution is used, the viscosity of the paste tends to decrease as the shear rate is increased.

DESCRIPTION OF SYMBOLS 10 ... Winding electrode body 30 ... Positive electrode end part 40 ... Negative electrode end part 50 ... Positive electrode terminal 60 ... Negative electrode terminal 100 ... Battery 110 ... Battery container 120 ... Battery container main body 130 ... Sealing plate 140 ... Injection hole 150 ... Insulating member 160 ... Insulating member 170 ... Cover 1000 ... Coating device 1100 ... Kneading device 1200 ... First filter 1300 ... Buffer tank 1400 ... Second filter 1500 ... Valve 1600 ... Pump 1700 ... Third filter 1800 ... Coating die 1900 ... Backup Roller BP ... Battery assembly P ... Positive electrode plate P1 ... Positive electrode coating part P2 ... Positive electrode non-coating part N ... Negative electrode plate N1 ... Negative electrode coating part N2 ... Negative electrode non-coating part S, T ... Separator

Claims (3)

A negative electrode plate preparation step in which a negative electrode paste containing a negative electrode active material is coated on a negative electrode core material after passing through a filter and dried to form a negative electrode plate;
An electrode body making step for forming an electrode body by disposing the negative electrode plate and the positive electrode plate between them via a separator;
A battery assembly process for injecting and sealing the electrode body and electrolyte into a battery container, and a method for producing a non-aqueous electrolyte secondary battery,
In the negative electrode plate making process,
The particle size distribution of the negative electrode active material has one peak, and the following relational expression: 0.90 ≦ A / D50 ≦ 2.0
1.30 ≦ B / D50 ≦ 3.0
D50: Median diameter
A: Half width of particle size distribution
B: A method for producing a non-aqueous electrolyte secondary battery, comprising using a negative electrode active material that satisfies a quarter width of a particle size distribution. A method for manufacturing a non-aqueous electrolyte secondary battery according to claim 1, comprising:
As the filter,
A method for producing a non-aqueous electrolyte secondary battery, comprising using a depth filter having a pore diameter 2.5 to 7 times the median diameter of a negative electrode active material. A non-aqueous electrolyte secondary battery having a positive electrode plate, a negative electrode plate, and a separator,
The particle size distribution of the negative electrode active material contained in the negative electrode plate is
It has one peak and the following relational expression 0.90 ≦ A / D50 ≦ 2.0
1.30 ≦ B / D50 ≦ 3.0
D50: Median diameter
A: Half width of particle size distribution
B: A non-aqueous electrolyte secondary battery characterized by satisfying the quarter-value width of the particle size distribution.

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