JP2023063739A - Electrode manufacturing method - Google Patents

Abstract

To provide an electrode manufacturing method capable of manufacturing an intermittent coating type electrode sheet without requiring a complicated device or control.SOLUTION: An electrode manufacturing method comprises the steps of: preparing a granulated body including an electrode active material, a binder, and a solvent; supplying the granulated body to a first gap between a first roll and a second roll and forming an electrode mixture layer by compression-molding the granulated body; and arranging the electrode mixture layer on an electrode current collector by supplying the electrode mixture layer transported on the second roll and the electrode current collector transported on the third roll to a second gap between the second roll and the third roll. The third roll includes an intermittent recess and a salient, which is a portion other than the recess on the outer peripheral surface. The electrode mixture layer is arranged only in a portion corresponding to the salient of the third roll on a surface of the electrode current collector.SELECTED DRAWING: Figure 2

Description

The present disclosure relates to methods of manufacturing electrodes.

A lithium ion secondary battery or the like is produced by a method of preparing a granule containing an electrode mixture, molding the granule, and arranging an electrode mixture layer on an electrode current collector (granule molding method). There is known a method of manufacturing an electrode for manufacturing a sheet-like electrode used in the field.

Here, as an electrode sheet, which is often used in high-energy-density batteries, an electrode mixture layer formed part (coated part) and non-formed part (non-coated part) are alternately formed on the electrode current collector. intermittent coating type electrode sheets are known.

Examples of methods for producing such an intermittent coating type electrode sheet using the granule forming method include Patent Document 1 (Japanese Patent Application Laid-Open No. 2011-3365) and Patent Document 2 (Japanese Patent Application Laid-Open No. 2012-2012). 228649), Patent Document 3 (JP 2013-17962) and Patent Document 4 (JP 2013-52353).

Japanese Unexamined Patent Application Publication No. 2011-3365 JP 2012-228649 A JP 2013-17962 A JP 2013-52353 A

However, in the method of Patent Document 1, a mechanism for forming cuts at appropriate intervals in the electrode mixture layer before being placed on the electrode current collector, and an electrode current collector according to the positions of the cuts A mechanism is needed to control the distance between the rolls for placing the electrode compound layer thereon.

In the method described in Patent Document 2, a mask is formed on a portion of the electrode current collector where the electrode mixture layer is not provided, and the mask is separated from the electrode current collector after the electrode mixture layer is formed. However, a complex mechanism for mask formation and detachment is required.

In the methods described in Patent Documents 3 and 4, a separate roll is required for intermittently removing the electrode mixture layer before placing the electrode mixture layer on the electrode current collector.

As described above, the conventional method has the problem that a complicated apparatus or control is required to produce an intermittent coating type electrode sheet.

Accordingly, it is an object of the present disclosure to provide an electrode manufacturing method capable of producing an intermittent coating type electrode sheet without the need for complicated equipment or controls.

[1] The method for manufacturing an electrode of the present disclosure includes:
a step of producing a granule containing an electrode active material, a binder and a solvent;
forming an electrode mixture layer by supplying the granules to a first gap between a first roll and a second roll and compression-molding the granules;
The electrode mixture layer conveyed on the second roll and the electrode current collector conveyed on the third roll are supplied to the second gap between the second roll and the third roll. and disposing the electrode mixture layer on the electrode current collector.
The third roll has intermittent recesses and protrusions other than the recesses on its outer peripheral surface,
The electrode mixture layer is arranged only on the portion of the surface of the electrode current collector corresponding to the convex portion of the third roll.

According to the production method of [1] above, an intermittent coating type electrode sheet can be produced without requiring a complicated device or control.
That is, by providing recessed portions 33 b corresponding to portions where the electrode mixture layer 12 is not provided on the outer peripheral surface of the third roll 33 , the electrode mixture layer 12 is formed on the electrode current collector 13 at positions corresponding to the recessed portions 33 b. Therefore, the electrode mixture layer 12 is not formed on the electrode current collector 13, and the electrode mixture layer is formed only on the portions (convex portions 33a) other than the concave portions 33b on the outer peripheral surface of the third roll 33. placed. This allows continuous electrode assembly on the electrode current collector 13 as shown in FIG. The intermittent coating type electrode sheet 11 in which the electrode mixture layer 12 is intermittently formed on the electrode current collector 13 can be manufactured by a simple apparatus and control similar to the method of forming the material layer 12 . .

[2] In the electrode manufacturing method of the present disclosure, it is preferable that the depth of the recesses in the third roll is 0.05 to 100 mm.
In this case, the electrode mixture layer 12 is not pressed against the electrode current collector 13 more reliably at the position corresponding to the recess 33 b of the third roll 33 , so that the electrode mixture layer 12 is formed on the electrode current collector 13 . not. Therefore, a desired intermittent coating type electrode sheet can be produced more reliably.

[3] In the electrode manufacturing method of the present disclosure, the non-volatile content in the granules is preferably 70% by mass or more and less than 100% by mass.
In this case, the electrode mixture layer 12 is more reliably not formed on the electrode current collector 13 at the positions corresponding to the recesses 33b of the third roll 33, and the protrusions 33a of the third roll 33 (portions other than the recesses) The electrode mixture layer 12 is more reliably formed on the electrode current collector 13 at the position corresponding to . Therefore, a desired intermittent coating type electrode sheet can be produced more reliably.

[4] In the electrode manufacturing method of the present disclosure, it is preferable to reuse the electrode mixture layer that is not placed on the electrode current collector in the placement step.
In this case, the material of the electrode mixture layer can be effectively used, and the material cost can be reduced.

1 is a flow chart showing an outline of a method for manufacturing an electrode according to an embodiment; 1 is a conceptual diagram showing an apparatus used to manufacture electrodes in an embodiment; FIG. 1 is a schematic perspective view showing an apparatus used for manufacturing electrodes in an embodiment; FIG. It is a schematic diagram showing an example of an electrode sheet. 1 is a conceptual diagram showing equipment used in the manufacture of electrodes in the prior art; FIG.

An embodiment of the present disclosure will be described below. However, the present disclosure is not limited to these. In this specification, "positive electrode" and "negative electrode" are collectively referred to as "electrode".

FIG. 1 is a flow chart showing an outline of the electrode manufacturing method of this embodiment. As shown in FIG. 1, the electrode manufacturing method of the present embodiment includes at least a granule preparation step (S10), an electrode mixture layer formation step (S20), and an arrangement step (S30).

In addition, the electrode manufactured by this embodiment is a sheet-like electrode (electrode sheet) for lithium ion secondary batteries, for example. The electrodes may be positive or negative.

<<Granular Body Production Step (S10)>>
In the granule preparation step, granules (wet granules) containing an electrode active material, a binder and a solvent are prepared. The granules are aggregates of a plurality of granulated particles (composite particles) containing an electrode active material, a binder and a solvent.

Granules can be produced, for example, by mixing (granulating) an electrode active material, a binder, a solvent, and the like. As a granulation method, for example, a stirring granulation method can be used. Examples of various granulation operations used in the granule production step include stirring granulation, fluidized bed granulation, and tumbling granulation. Various granulating devices such as a stirring mixer can be used for these granulating operations. When the stirring and mixing device has stirring blades (rotor blades), the rotation speed of the stirring blades is, for example, about 10 to 5000 rpm.

(electrode active material)
The electrode active material may be a positive electrode active material or a negative electrode active material.

Examples of positive electrode active materials include lithium-containing metal oxides and lithium-containing phosphates. Lithium-containing metal oxides include, for example, LiCoO ₂ , LiNiO ₂ , and LiNi _a Co _b O ₂ (where a+b=1, 0<a<1, 0<b<1). compound, LiMnO ₂ , LiMn ₂ O ₄ , general formula LiNi _a Co _b Mn _c O ₂ (where a + b + c = 1, 0 < a < 1, 0 < b < 1, 0 < c < 1 ), LiFePO ₄ and the like. Here, examples _of the compound represented by _the general _{formula LiNiaCobMncO2} include LiNi1 _/3Co1 / _{3Mn1 / 3O2} . Lithium-containing phosphates include, for example, LiFePO ₄ and the like.

The average particle size of the positive electrode active material may be, for example, about 0.1 to 25 μm. Here, the "average particle size" means the particle size (D50) at an integrated value of 50% in the volume-based particle size distribution measured by the laser diffraction/scattering method.

Examples of negative electrode active materials include carbon-based negative electrode active materials such as graphite, graphitizable carbon, and non-graphitizable carbon, and alloy-based negative electrode active materials containing silicon (Si), tin (Sn), and the like. mentioned. The average particle size (D50) of the negative electrode active material may be, for example, about 1 to 25 μm.

The mixing ratio of the electrode active material to the total solid content of the granules (that is, the content of the electrode active material in the electrode mixture layer) is, for example, about 94 to 99.7% by mass.

(Binder)
Examples of binders include carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyacrylic acid (PAA), and the like. A binder may be used individually by 1 type, and may be used in combination of 2 or more types.

The blending ratio of the binder to the total solid content of the granules (that is, the content of the binder in the electrode mixture layer) is, for example, about 0.3 to 6% by mass.

(solvent)
Examples of solvents include aqueous solvents and organic solvents. An aqueous solvent means water or a mixed solvent containing water and a polar organic solvent.

As the aqueous solvent, water can be preferably used because of its ease of handling. Examples of polar organic solvents that can be used in the mixed solvent include alcohols such as methanol, ethanol and isopropyl alcohol, ketones such as acetone, and ethers such as tetrahydrofuran. Incidentally, the aqueous solvent can be suitably used as a solvent for manufacturing the negative electrode.

Examples of organic solvents include N-methyl-2-pyrrolidone (NMP). In addition, an organic solvent can be used suitably as a solvent for positive electrode manufacture.

The amount of the solvent used is not particularly limited, but the solid content ratio of the granule is adjusted to 70% by mass or more and less than 100% by mass, preferably 70 to 90% by mass, more preferably 70 to 80% by mass. do it. In this case, in an arrangement step (S30) to be described later, the electrode mixture layer 12 is easily fixed to the electrode current collector 13 on the protrusions 33a of the third roll 33, and the electrode current collector on the recesses 33b of the third roll 33 is easily adhered. It becomes difficult for the electrode mixture layer 12 to adhere to the body 13 . If the solid content of the granules is less than 70% by mass, it may be difficult to produce the granules due to the large amount of solvent. The "solid content ratio" means the ratio of the mass of components (non-volatile components) other than the solvent to the total mass of all raw materials including the solvent.

(other ingredients)
The components of the granules may contain other components than the above, and may contain, for example, a conductive material. Examples of conductive materials include carbon black such as acetylene black (AB), thermal black and furnace black, and carbon nanotubes (CNT). The conductive material is expected to improve electronic conductivity.

<<Electrode Mixture Layer Forming Step (S20)>>
In the electrode mixture layer forming step, the electrode mixture layer 12 is formed by supplying the granules 10 to the first gap between the first roll 31 and the second roll 32 and compressing the granules 10 . Form.

In the electrode manufacturing method of the present embodiment, an electrode manufacturing apparatus 3 as shown in FIGS. 2 and 3 is used. The electrode manufacturing apparatus 3 includes a feeder 2 and three rolls (first roll 31, second roll 32 and third roll 33). Each of the first roll 31, the second roll 32 and the third roll 33 has a diameter of, for example, 10 to 1000 mm, and an axial length of, for example, 100 to 2000 mm.

The rotation axes of the first roll 31, the second roll 32 and the third roll 33 are fixed such that the rotation axes of the first roll 31, the second roll 32 and the third roll 33 are parallel to each other. ing. The distance (width) of the first gap between the first roll 31 and the second roll 32 is kept constant. The distance of the second gap between the second roll 32 and the third roll 33 is also kept constant. The first roll 31, the second roll 32 and the third roll 33 are each driven to rotate. In FIGS. 2 and 3, the curved arrow drawn on each roll indicates the direction of rotation of each roll.

The first roll 31 and the second roll 32 are rotationally driven in mutually opposite directions. The granules are supplied between such a pair of rolls (the first roll 31 and the second roll 32), and the granules are compression-molded by the pair of rolls to form a sheet-like electrode mixture layer. It is formed.

The distance of the first gap between the first roll 31 and the second roll 32 is, for example, approximately 50 μm to 10 mm. The distance of the first gap is the linear distance between the first roll 31 and the second roll 32 at the position where the first roll 31 and the second roll 32 are closest to each other.

The feeder 2 is arranged directly above the gap (first gap) between the first roll 31 and the second roll 32 . In this step, first, the granules are supplied to the feeder 2 . The feeder 2 feeds the granules 10 to the first gap between the first roll 31 and the second roll 32 .

The electrode manufacturing apparatus 3 further includes a pair of regulating plates 24 arranged parallel to each other with a predetermined gap in the axial direction of the first roll 31 and the second roll 32 . The granules 10 supplied to the gap (first gap) between the first roll 31 and the second roll 32 are regulated by the pair of regulating plates 24 while the width dimension of the granules 10 is regulated. Rotation of roll 32 (in the direction of the arrow in the figure) draws it under and through the first gap. Thereby, the basis weight (mass per unit area) of the electrode mixture layer 12 can be adjusted. In addition, the pair of restricting plates 24 can provide exposed portions 13b at both ends of the electrode current collector 13 in the width direction (FIG. 4) where the electrode mixture layer 12 is not arranged. The basis weight of the electrode mixture layer 12 can also be adjusted by the distance of the first gap.

In addition, it is preferable that the rotation speed of the second roll 32 is faster than the rotation speed of the first roll 31 . For example, the rotational speed of the second roll 32 is approximately three to five times the rotational speed of the first roll 31 . By making the rotation speed of the second roll 32 faster than the rotation speed of the first roll 31, the granules are stretched more on the surface of the second roll 32 than on the surface of the first roll 31, as shown in FIG. As a result, the area of contact of the liquid bridge portion of the granule with the surface of the second roll 32 becomes larger than the area of contact with the surface of the first roll 31 . As a result, the rolled granules 10 (electrode mixture layer 12 ) adhere to the second roll 32 side and are conveyed by the second roll 32 .

<<Placement step (S30)>>
In the placement step, the electrode mixture layer 12 conveyed on the second roll 32 and the electrode current collector conveyed on the third roll 33 are placed in the second gap between the second roll 32 and the third roll 33 . The electrode mixture layer 12 is arranged on the electrode current collector 13 by supplying the body 13 and the electrode mixture layer 12 on the electrode current collector 13 .

For example, the sheet-like electrode mixture layer 12 produced in the electrode mixture layer forming step (S20) is transferred to the electrode current collector 13 (negative electrode current collector), thereby forming the electrode mixture layer 12 as an electrode current collector. Placed on body 13 .

Specifically, the electrode current collector 13 is conveyed on the third roll 33 and supplied to the gap (second gap) between the second roll 32 and the third roll 33 . After leaving the gap (first gap) between the first roll 31 and the second roll 32 , the electrode mixture layer 12 is conveyed on the second roll 32 , and is transferred between the second roll 32 and the third roll 33 . supplied to the gap between The second roll 32 and the third roll 33 are rotationally driven in opposite directions (see curved arrows in FIGS. 2 and 3).

Here, the third roll 33 has intermittent recesses 33b on its outer peripheral surface, and the electrode mixture layer 12 is formed on the portion of the surface of the electrode current collector 13 corresponding to the recesses 33b of the third roll 33. Not placed. In addition, the concave portion 33b is a portion that is lower in height (shorter distance from the rotation axis) than the outer peripheral surface (the convex portion 33a) of the third roll 33 . Then, the portion corresponding to the convex portion 33a on the surface of the electrode current collector 13 (the portion other than the concave portion 33b on the outer peripheral surface of the third roll 33) (the portion opposite to the convex portion 33a on the surface of the electrode current collector 13) , the electrode mixture layer 12 is arranged. It should be noted that the convex portion 33a is preferably a portion having a constant height (distance from the rotation axis).

That is, since the electrode mixture layer 12 is not pressed against the electrode current collector 13 in the gap between the second roll 32 and the concave portion 33b of the third roll 33, the electrode mixture layer 12a is separated from the second roll 32. It is further conveyed on the second roll 32 without being removed. Note that the electrode mixture layer 12 a not disposed on the electrode current collector 13 can be scraped off by the blade 4 and reused as a material for the granule 10 .

On the other hand, in the gap between the second roll 32 and the convex portion 33a of the third roll 33, the electrode mixture layer 12 is pressed against the electrode current collector 13, and the electrode mixture layer 12 is separated from the second roll 32. , is crimped to the electrode current collector 13 . That is, the electrode mixture layer 12 is transferred from the second roll 32 to the electrode current collector 13 .

The depth of the concave portions 33b in the third roll 33 is preferably 0.05 to 100 mm. In this case, the electrode mixture layer 12 is not pressed against the electrode current collector 13 more reliably at the position corresponding to the recess 33 b of the third roll 33 , so that the electrode mixture layer 12 is formed on the electrode current collector 13 . not. The depth of the concave portion 33b means the difference between the diameter of the concave portion 33b (the distance from the rotation axis to the surface of the concave portion 33b) and the diameter of the convex portion 33a. The shape of the concave portion 33b, the inclination of the surface, etc. are not particularly limited.

In this manner, the sheet-shaped electrode mixture layer 12 can be intermittently arranged only at predetermined positions on the electrode current collector 13 . Therefore, an intermittent coating type electrode sheet can be produced. The intermittent coating type electrode sheet 11 is, for example, an electrode sheet 11 having an exposed portion 13a of an electrode current collector 13 between electrode mixture layers 12, as shown in FIG.

After drying the electrode mixture layer 12, the electrode sheet 11 may be cut into a predetermined size using, for example, a slitter.

The electrode obtained by the production method of the present disclosure can be used, for example, as an electrode for a lithium ion secondary battery (nonaqueous electrolyte secondary battery). The lithium ion secondary battery can be used, for example, as a power source for hybrid vehicles (HV), electric vehicles (EV), plug-in hybrid vehicles (PHV), and the like. However, the electrode obtained by the manufacturing method of the present disclosure is not limited to such in-vehicle use, and can be applied to any use.

The present embodiment will be described below using Examples, but the present embodiment is not limited to these.

[Example 1]
In Example 1, an electrode (negative electrode for a lithium ion secondary battery) sheet is manufactured as follows.

<<Granule manufacturing process>>
In Example 1, first, the following materials are prepared.
Negative electrode active material: natural graphite [average particle size (D50): 22 µm]
Binder: CMC, sodium polyacrylate

A negative electrode active material (98.8 parts by mass), a binder (CMC: 0.5 parts by mass and sodium polyacrylate: 0.8 parts by mass) and a solvent (water) were placed in a stirring tank of a mixer (agitation granulator). are added and mixed to prepare a granule. The amount of solvent used is adjusted so that the solid content concentration of the granules is 76% by mass.

In order to make the coating film thickness 4 μm, the target particle size of the granules is set to 4 mm in average particle size (D90) (100 times the coating thickness), and the goal is to obtain granules with a D90 of 4 mm or less. . In addition, D90 means the particle size at the integrated value of 90% in the volume-based particle size distribution measured using the laser diffraction/scattering method.

<<Electrode mixture layer forming process>>
In this step, the electrode manufacturing apparatus 3 shown in FIGS. 2 and 3 is used to form a sheet-like electrode mixture layer 12 from the granules described above, as in the above embodiment.

In addition, in the electrode manufacturing apparatus 3, the distance between the first roll 31 and the second roll 32 (distance of the first gap) is 50 μm. The distance between the second roll 32 and the third roll 33 (second gap distance) is 20 μm. Moreover, the diameter of each of the first roll 31, the second roll 32 and the third roll 33 is all 100 mm, and the length of each is all 200 mm. The depth of the recess 33b of the third roll 33 is 1 mm.

《Placement process》
In this step, the electrode mixture layer 12 is placed on the electrode current collector 13 using the electrode manufacturing apparatus 3 shown in FIGS. 2 and 3 as in the above embodiment. The electrode current collector 13 (negative electrode current collector) is a copper (Cu) foil. The electrode (negative electrode) of Example 1 is manufactured by drying the electrode mixture layer.

It should be considered that the embodiments and examples disclosed this time are illustrative in all respects and not restrictive. The scope of the present disclosure is indicated by the scope of the claims rather than the above description, and is intended to include all modifications within the scope and meaning equivalent to the scope of the claims.

REFERENCE SIGNS LIST 10 granule 12, 12a electrode mixture layer 13 electrode current collector 13a, 13b exposed portion 2 feeder 24 regulation plate 3 electrode manufacturing apparatus 31 first roll 32 second roll 33 third third Roll, 33a convex, 33b concave, 4 blade.

Claims (4)

a step of producing a granule containing an electrode active material, a binder and a solvent;
forming an electrode mixture layer by supplying the granules to a first gap between a first roll and a second roll and compression-molding the granules;
The electrode mixture layer conveyed on the second roll and the electrode current collector conveyed on the third roll are supplied to the second gap between the second roll and the third roll. By placing the electrode mixture layer on the electrode current collector,
The third roll has intermittent recesses and protrusions other than the recesses on its outer peripheral surface,
The electrode mixture layer is arranged only on a portion of the surface of the electrode current collector corresponding to the convex portion of the third roll,
A method of manufacturing an electrode. 2. The method for manufacturing an electrode according to claim 1, wherein the depth of said recesses in said third roll is 0.05 to 100 mm. 3. The method for producing an electrode according to claim 1, wherein the granule has a non-volatile content of 70% by mass or more and less than 100% by mass. The method for producing an electrode according to any one of claims 1 to 3, wherein the electrode mixture layer not placed on the electrode current collector is reused.

Images