JP2017073307A - Electrode sheet for nonaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the worsening of a performance accompanying the high-rate cycle of an electrode sheet.SOLUTION: An electrode sheet for a nonaqueous electrolyte secondary battery comprises: an electrode collector plate; a first electrode mixture material layer disposed on one face of the electrode collector plate; and a second electrode mixture material layer disposed on the other face of the electrode collector plate. At one end in a widthwise direction of the electrode sheet, the first electrode mixture material layer has a plurality of first non-opposing parts along an edge face extending in a longitudinal direction, which are not opposed to the second electrode mixture material layer in its thickness direction, and the second electrode mixture material layer has a plurality of second non-opposing parts along the edge face extending the longitudinal direction, which are not opposed to the first electrode mixture material layer in its thickness direction. The ratio of a total area of the plurality of first non-opposing parts to a total area of the plurality of second non-opposing parts is 0.2 to 5. The sum total of the area of the area of the plurality of first non-opposing parts and the area of the plurality of second non-opposing parts is 100-1009 mmper one meter of the electrode sheet in the longitudinal direction.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an electrode sheet for a non-aqueous electrolyte secondary battery.

  JP-A-10-228930 (Patent Document 1) describes that the electrode mixture layers on both sides are shifted in the longitudinal direction of the electrode sheet, but the electrode mixture layers are shifted in the width direction of the electrode sheet. Is not listed.

Japanese Patent Laid-Open No. 10-228930

  In the electrode sheet described in Patent Document 1, since the electrode mixture layers on both sides are not misaligned in the width direction of the electrode sheet, the density of the entire electrode mixture layer arranged on both surfaces is near the end surface extending in the longitudinal direction. As high as the central part in the width direction. Therefore, since the void volume in the electrode mixture layer in the vicinity of the end face is small, the electrolyte solution once extruded during the high-rate cycle cannot be held in the vicinity of the end face, and the electrolyte solution is difficult to return into the electrode mixture layer. For this reason, the holding | maintenance of electrolyte solution is low and the performance fall accompanying a high-rate cycle tends to arise.

  An object of this invention is to suppress the performance fall accompanying the high-rate cycle of such an electrode sheet.

An electrode sheet for a non-aqueous electrolyte secondary battery is disposed on an electrode current collector plate, a first electrode mixture layer disposed on one surface of the electrode current collector plate, and the other surface of the electrode current collector plate. And a second electrode composite material layer. At one end in the width direction of the electrode sheet, the first electrode mixture layer has a plurality of first non-opposing portions that do not face the second electrode mixture layer in the thickness direction along the end surface extending in the longitudinal direction, and The second electrode mixture layer has a plurality of second non-opposing portions that do not face the first electrode mixture layer in the thickness direction along the end surface extending in the longitudinal direction. The ratio of the total area of the plurality of first non-opposing parts to the total area of the plurality of second non-opposing parts is 0.2 or more and 5 or less. Total area of the second non-facing portion area and the plurality of plurality of first non-facing portion, longitudinal 1m per 100 mm ² or more electrode sheets 1009mm ² or less.

  According to the above, it is possible to suppress the performance degradation associated with the high rate cycle of the electrode sheet. The reason is considered as follows.

  In an example of a conventional electrode sheet, as shown in FIGS. 10A and 10B, the first electrode mixture layer 121 is disposed on one surface (first surface 11a) of the electrode current collector plate 11. The second electrode mixture layer 122 is arranged on the other surface (second surface 11b). And as shown in FIG.10 (b), the electrode compound-material layers 121 and 122 of both surfaces are not shifted in the width direction of an electrode sheet (the end surface 121b and the end surface 122b are aligning).

  In this case, the overall density of the electrode mixture layers 121 and 122 arranged on both surfaces is high in the vicinity of the end surfaces 121b and 122b extending in the longitudinal direction, similarly to the central portion in the width direction. That is, since the void volume in the electrode mixture layer in the vicinity of the end face is small, the electrolyte solution once extruded during the high-rate cycle cannot be held in the vicinity of the end face, and the electrolyte solution is difficult to return into the electrode mixture layer. For this reason, the holding | maintenance of electrolyte solution is low and the performance fall accompanying a high-rate cycle tends to arise.

  As a modification of FIG. 10B, as shown in FIG. 10C, it is conceivable that the electrode mixture layers 121 and 122 on both sides are shifted in the width direction of the electrode sheet. In this case, since there is a portion (non-opposing portion 121c) in which the electrode mixture layer exists only on one side of the electrode current collector plate along the end surface 121b, the total amount of the electrode mixture layer on both surfaces decreases. . For this reason, when compressing the electrode mixture layers on both sides with a roll or the like, the compressive force applied to the non-opposing portion 121c becomes small, and the void volume of the non-opposing portion 121c becomes larger than other portions.

  Accordingly, with respect to the first electrode mixture layer 121, the electrolyte solution once extruded during the high rate cycle is held in the vicinity of the end surface 121b, and the electrolyte solution easily returns into the electrode mixture layer. Thereby, the retainability of electrolyte solution is improved and the performance fall accompanying the high-rate cycle of the 1st electrode compound-material layer 121 is suppressed.

  However, about the 2nd electrode compound-material layer 122 arrange | positioned at the other surface, the retainability of electrolyte solution is low similarly to the case shown in FIG.10 (b), and the performance fall accompanying a high-rate cycle tends to arise. For this reason, as a whole electrode sheet, the performance degradation accompanying a high rate cycle cannot be controlled.

  Here, the present inventors have proposed a granule forming method as a method for producing an electrode sheet for a non-aqueous electrolyte secondary battery different from the paste method. The granulated body forming method is a method in which a granulated body is prepared, the granulated body is formed, and a sheet-like electrode mixture layer is disposed on an electrode current collector plate. The granulated body is an aggregate of granulated particles (composite particles) containing an electrode active material, a binder, a small amount of solvent, and the like. The granulated body becomes a sheet-like electrode mixture layer by, for example, roll forming and is disposed on the electrode current collector plate.

  When producing an electrode sheet by the granulated body forming method, the granulated particles are compressed by roll molding or the like unless the end surface extending in the longitudinal direction is particularly flattened. Concavities and convexities corresponding to the size of the granulated particles are formed on the end face.

  In this case, since the electrode mixture layers on both sides have irregularities on the end faces in the longitudinal direction, the mixture density in the vicinity of the end faces decreases. However, as a result of the study by the present inventors, it has been found that this alone cannot suppress the performance degradation associated with the high rate cycle. The cause is considered as follows. Even if the end surface of the electrode mixture layer has irregularities, when the irregularities are arranged in the same shape on the front and back so as to overlap in the thickness direction, the amount of the mixture in the thickness direction is as shown in FIG. Similarly, it remains as high as the central portion in the width direction. For this reason, compression at the time of molding applies a strong compressive force on the end surface as well as the central portion in the width direction, and the void volume of the granulated particles is reduced, so that the electrolyte solution retainability on the end surface of the electrode mixture layer is reduced. It is considered that the deterioration in performance due to the high rate cycle could not be suppressed.

  On the other hand, as shown in FIG. 1A, the electrode sheet 10 of the present invention has both sides (first surface 11 a side and second surface 11 b side) at one end in the width direction of the electrode sheet 10. Each of the electrode mixture layers has a plurality of portions (non-opposing portions) that do not face the opposite electrode mixture layer along the end face in the longitudinal direction. That is, the first electrode mixture layer 121 has a plurality of first non-facing portions 121a that do not face the second electrode mixture layer 122 in the thickness direction along the end surface 121b, and the second electrode mixture layer 122. Has a plurality of second non-facing portions 122a that do not face the first electrode mixture layer 121 in the thickness direction along the end surface 122b.

  1A is a schematic top view of a portion corresponding to the region A of the electrode sheet 10 shown in FIG. In FIG. 1A, the end surface 122b is indicated by a dotted line, which means that the second non-facing portion 122a is actually on the back side of the electrode current collector plate and cannot be seen in the top view. FIG. 1B is a cross-sectional view in the cross-section (A-A ′ cross section) in the width direction including the plurality of first non-opposing portions 121 a in FIG. FIG. 1C is a cross-sectional view in a cross section (B-B ′ cross section) in the width direction including the second non-facing portion 122 a in the width direction of FIG. In addition, the arrows shown in FIGS. 1B and 1C conceptually indicate the magnitude of the amount of electrolyte flowing in and out. The left arrow indicates the amount of electrolyte entering the electrode mixture layer, the right arrow indicates the amount of electrolyte exiting the electrode mixture layer, and if the left arrow is longer than the right arrow, the electrolyte is retained. It means that the nature is high.

  Thus, when each of the electrode mixture layers on both sides has a non-facing portion (front and back misalignment), the non-facing portion where the electrode mixture layer exists only on one side is shown in FIG. Similar to the one-electrode mixture layer 121, the electrolyte retention is improved. On the other hand, on the opposite side of the non-opposing portions 121a and 122a, the electrolyte retention is poor. However, as shown in FIG. 1 (b) and FIG. 1 (c), there is always a portion where the electrolyte solution retainability is reversed, so that the electrolyte solution retainability is improved in the electrode mixture layers on both sides. It is done. For this reason, the performance degradation accompanying a high-rate cycle can be suppressed with respect to the electrode mixture layers on both sides. Therefore, it becomes possible to suppress the performance deterioration accompanying the high-rate cycle as the whole electrode sheet.

  However, when there are many non-opposing portions only on the electrode mixture layer on one surface and there are few non-opposing portions on the electrode mixture layer on the other surface, the electrode is substantially the same as in FIG. As a whole sheet, it is not possible to suppress a decrease in performance associated with a high rate cycle. For this reason, when the ratio of the total area of the plurality of first non-opposing portions to the total area of the plurality of second non-opposing portions is 0.2 or more and 5 or less, the electrode sheet as a whole suppresses the performance degradation associated with the high rate cycle. It becomes possible to do.

In addition, even if the electrode mixture layers on both sides have a plurality of non-opposing portions, when the area of the non-opposing portions is very small, it is substantially the same as FIG. It is not possible to increase the electrolyte retention of the layer. On the other hand, when the area of the non-opposing portion is too large, the area of the effective electrode mixture layer disposed on the electrode current collector plate is reduced, and the resistance of the original electrode sheet is increased. Therefore, the total area of the second non-facing portion area and the plurality of plurality of first non-facing portion, when the longitudinal 1m per 100 mm ² or more electrode sheets 1009mm ² or less, the electrolyte of the electrode mixture layer It becomes possible to improve the liquid retention and to suppress the performance degradation accompanying the high rate cycle.

  According to the above, it is possible to suppress the performance degradation associated with the high rate cycle of the electrode sheet.

It is a conceptual diagram which shows an example of the electrode sheet which concerns on embodiment of this invention. (A) is a schematic top view, (b) is a sectional view in the width direction of (a), and (c) is a sectional view in another section in the width direction of (a). (A) is an upper surface schematic diagram which shows the modification of the electrode sheet which concerns on embodiment of this invention. (B) is an upper surface schematic diagram which shows another modification of the electrode sheet which concerns on embodiment of this invention. It is a photograph of an example of an electrode sheet. (A) is a photograph of the first surface, and (b) is a photograph of the second surface. It is a flowchart which shows the outline of the manufacturing method of the electrode sheet which concerns on embodiment of this invention. It is the schematic which illustrates the arrangement | positioning process in manufacture of an electrode sheet. It is the schematic which shows an example of an electrode sheet. It is the schematic which shows another example of an electrode sheet. It is the schematic which shows an example of a structure of an electrode group. It is a schematic sectional drawing which shows an example of a structure of a nonaqueous electrolyte secondary battery. (A) is an upper surface schematic diagram which shows an example of the conventional electrode sheet. (B) is a longitudinal cross-sectional schematic diagram of (a). (C) is a longitudinal cross-sectional schematic diagram of the modification of (b). 10 is a schematic diagram illustrating an arrangement process of Comparative Example 2. FIG.

  Hereinafter, an example of an embodiment of the present invention (hereinafter also referred to as “this embodiment”) will be described. However, this embodiment is not limited to these. In this specification, that is, the “electrode sheet” indicates at least one of the “negative electrode sheet” or the “positive electrode sheet”, and the “electrode mixture layer” is the “negative electrode mixture layer” or the “positive electrode mixture layer”. “Electrode active material” indicates at least one of “negative electrode active material” or “positive electrode active material”, and “electrode current collector plate” indicates “negative electrode current collector plate” or “positive electrode current collector”. At least one of “plate” is shown.

<Electrode sheet>
Referring to FIG. 1, an electrode sheet 10 for a non-aqueous electrolyte secondary battery includes an electrode current collector plate 11 and electrode mixture layers disposed on both surfaces thereof (that is, one surface of the electrode current collector plate 11). The first electrode mixture layer 121 and the second electrode mixture layer 122 arranged on the other surface of the electrode current collector plate 11 are provided.

  At one end of the electrode sheet 10 in the width direction, the first electrode mixture layer 121 extends along the end surface 121b extending in the longitudinal direction of the plurality of first non-facing portions 121a that do not face the second electrode mixture layer 122 in the thickness direction. Have. And in the said one end, the 2nd electrode compound-material layer 122 has the some 2nd non-opposing part 122a which does not oppose the 1st electrode compound-material layer 121 in the thickness direction along the end surface extended in a longitudinal direction. The “width direction” is the short side direction of the electrode sheet 10, and the “longitudinal direction” is the long side direction of the electrode sheet 10 (see FIG. 6). The electrode sheet 10 is wound in the long side direction to form a wound electrode group.

  As a specific aspect in which the electrode mixture layers on both sides have a plurality of non-opposing portions, in FIG. 1A, end surfaces 121b and 122b (a plurality of non-opposing portions 121a, 122a) shows an example in which the unevenness period differs between the front and back sides. However, the present invention is not limited to such a mode, and as shown in FIG. 2A, the size of the unevenness (height: length in the width direction) of the end surfaces (the plurality of non-opposing portions 121a and 122a) is different between the front and back sides. Alternatively, as shown in FIG. 2B, the unevenness width (length in the longitudinal direction) of the end face may be different between the front and back sides.

In the present embodiment, the ratio of the total area of the plurality of first non-facing portions to the total area of the plurality of second non-facing portions (hereinafter, sometimes referred to as “the front-back ratio of the non-facing portion area”) is 0. .2 or more and 5 or less. Further, the sum of the areas of the plurality of first non-opposing portions and the areas of the plurality of second non-opposing portions (hereinafter sometimes referred to as “non-opposing portion total area”) is 100 mm per 1 m in the longitudinal direction of the electrode sheet. ² or more and 1009 mm ² or less. Here, “area” means an area in a plan view as shown in FIG.

[Electrode current collector]
The electrode current collector plate may be, for example, a copper foil or an aluminum foil. The thickness of the electrode current collector plate may be about 5 to 30 μm.

(Electrode compound layer)
The electrode mixture layer is formed, for example, by placing an electrode mixture containing an electrode active material and a binder on an electrode current collector plate. The thickness of the electrode mixture layer may be, for example, about 10 to 150 μm.

(Electrode active material)
The electrode active material may be a negative electrode active material or a positive electrode active material. In addition, this embodiment is more effective when applied to a negative electrode active material (negative electrode sheet) that has a large volume fluctuation especially during a high-rate cycle.

  The negative electrode active material may be a carbon-based negative electrode active material such as graphite, graphitizable carbon, and non-graphitizable carbon, or may be an alloy-based negative electrode active material containing silicon (Si), tin (Sn), or the like. . The average particle diameter of the negative electrode active material may be about 5 to 25 μm, for example.

The positive electrode active material may be a lithium (Li) -containing metal oxide such as LiNi _1/3 Co _1/3 Mn _1/3 O ₂ . The average particle diameter of the positive electrode active material may be about 5 to 25 μm, for example.

  In the present specification, the “average particle diameter” is also referred to as a particle diameter (“d50”, “median diameter”) at an integrated value of 50% in a volume-based particle size distribution measured by a laser diffraction / scattering method. ).

(Binder)
The binder may be, for example, sodium salt of carboxymethyl cellulose (CMC-Na), styrene butadiene rubber (SBR), polyacrylic acid Li, or the like. The binder content of the negative electrode mixture layer may be, for example, about 1 to 10% by mass.

(Other ingredients)
The electrode mixture layer may contain a conductive material or the like. As the conductive material, for example, carbon blacks such as acetylene black and thermal black may be used.

[Composition of electrode mixture layer]
The composition of the electrode mixture layer is, for example, as follows: Electrode active material: about 90 to 99% by mass Binder: about 1 to 5% by mass Conductive material: about 0 to 5% by mass.

<Manufacture of electrode sheet>
FIG. 4 is a flowchart showing an outline of a method for producing an electrode sheet according to the present embodiment. As shown in FIG. 4, the manufacturing method includes a granule forming step (S10) and an arrangement step (S20).

[Granulated body forming step (S10)]
In this step, a granulated body made of the electrode active material, the binder and the like and a solvent is formed.

  The solvent may be, for example, water, N-methylpyrrolidone (NMP) or the like. What is necessary is just to adjust the usage-amount of a solvent, for example so that the solid content ratio of a granule may be about 60-90 mass%. Here, the “solid content ratio” indicates the ratio of the mass of components (nonvolatile components) other than the solvent to the total mass of all raw materials including the solvent.

  The granulated body can be produced, for example, by mixing the above-mentioned electrode active material, binder and the like with a solvent. Examples of various granulation operations used for producing the granulated body include stirring granulation, fluidized bed granulation, rolling granulation and the like. Moreover, you may produce a granulated body by shape | molding granulated particles by a predetermined | prescribed shape (for example, cylindrical shape) by extrusion granulation. The average particle diameter of the granulated body is about 0.1 to 5 mm.

[Arrangement Step (S20)]
In the arranging step (S20), the granulated body is arranged in a sheet shape on the electrode current collector plate. Thereby, a granulation body turns into an electrode compound-material layer. FIG. 5 is a schematic view illustrating the arrangement step (S20). Hereinafter, the placement process will be described with reference to FIG.

  First, an electrode manufacturing apparatus 90 shown in FIG. 5 was prepared. An electrode manufacturing apparatus 90 shown in FIG. 5 includes a feeder 95 and three rolls (A roll 91, B roll 92, and C roll 93). The curved arrows drawn on each roll indicate the rotation direction of each roll. The granulated body is supplied to the feeder 95. The feeder 95 supplies the granulated body 8 between the A roll 91 and the B roll 92. The granulated body 8 is conveyed on the A roll 91 or the B roll 92 and supplied to the gap between the A roll 91 and the B roll 92. A predetermined load is applied to the A roll 91. In the gap between the A roll 91 and the B roll 92, the granulated body is consolidated and formed into a sheet shape. The basis weight (mass per unit area) of the granulated material in sheet form can be adjusted by the gap.

Next, the granulated body 8a in the form of a sheet is placed on the electrode current collector plate.
As shown in FIG. 5, the electrode current collector 11 is conveyed on the C roll 93 and supplied to the gap between the B roll 92 and the C roll 93. After leaving the gap between the A roll 91 and the B roll 92, the granulated body 8 a is conveyed on the B roll 92 and supplied to the gap between the B roll 92 and the C roll 93.

  In the gap between the B roll 92 and the C roll 93, the granulated body 8 a is pressed against the electrode current collector plate 11, and the granulated body 8 a is separated from the B roll 92 and pressed onto the electrode current collector plate 11. That is, the granulated body 8 a is transferred (arranged) from the B roll 92 to the electrode current collector plate 11.

  Here, unlike the apparatus shown in FIG. 11, the regulating plate 94 b between the B roll 92 and the C roll 93 was not used on the end face side where the unevenness of the electrode mixture layer 121 was to be formed. By doing in this way, the unevenness | corrugation according to the magnitude | size of granulated particle is formed in the end surface 121b extended in the longitudinal direction of the electrode compound-material layer 121. FIG.

  After arrange | positioning the granulated body 8a on the electrode current collecting plate 11 in a sheet form, in order to volatilize the solvent which remain | survives in a granulated body, you may perform a drying process. The drying step can be performed, for example, in a hot air drying furnace (not shown) provided on the pass line after the C roll 93.

  Further, the electrode current collector plate with the granule disposed on one surface is supplied again to the C roll 93, and the granule is disposed on the other surface in the same manner, whereby the electrode current collector plate is formed on both surfaces of the electrode current collector plate. Place the granules. In addition, you may make it arrange | position a granulated body simultaneously on both surfaces of an electrode current collecting plate.

  Here, by controlling the rotation cycle of the roll while reading the position (cycle) of the end surface unevenness of the electrode mixture layer on one surface with a sensor, the end unevenness cycle can be shifted on the front and back sides.

  In this manner, the granulated body becomes an electrode mixture layer disposed on both surfaces of the electrode current collector plate. Thereafter, a compression step may be performed in order to adjust the thickness and density of the electrode mixture layer. The compression step can be performed using, for example, a roll mill. The thickness of each layer of the electrode mixture layer finally obtained may be about 10 to 150 μm, for example.

  Finally, the electrode sheet 10 shown in FIG. 6 is completed by cutting into a predetermined size using, for example, a slitter. In FIG. 6, the granulated body is an electrode mixture layer 12. Note that, when the cutting process is performed, the end surface of the electrode mixture layer on the cut surface side becomes flat, so that irregularities are formed only on the opposite end surface. However, if the electrode current collector plate is cut to a desired width in advance and the cutting step is not performed after the electrode mixture layer is formed, irregularities can be formed on both end faces in the width direction. It is more effective to form irregularities (non-opposing portions) on both end surfaces, but a sufficient effect can be obtained by forming irregularities (non-opposing portions) only on one end surface.

  FIG. 3 is a photograph of an example of the electrode sheet according to the present embodiment. (A) is a photograph of the first surface, and (b) is a photograph of the second surface. In this way, the height (size) and width of the convex and concave portions of the unevenness can be changed on the front and back sides.

  The measurement of the total area of the non-opposing portion is within a predetermined unit length including the end face of the electrode mixture layer, as shown in FIG. 3 (b) and a photograph of the first surface as shown in FIG. It is possible to take a picture of the second surface and perform image processing to obtain the total area of the portions not overlapping the first surface and the second surface of the electrode mixture layer as the total area of the plurality of non-opposing portions. . The sum of the front and back areas (the areas of the plurality of first non-opposing parts and the areas of the plurality of second non-opposing parts) of the plurality of non-opposing parts is the non-opposing part total area.

  The front / back ratio of the non-opposing portion area is obtained by dividing the total area of the plurality of first non-opposing portions obtained in the same manner by the total area of the plurality of second non-opposing portions.

  In FIGS. 3A and 3B, “width” means the width of the protrusions forming the unevenness (length in the longitudinal direction of the electrode sheet), and “height” forms the unevenness. It means the height of the projection (length in the width direction of the electrode sheet).

  In the said embodiment, the "width" of a convex part is about 0.1-10 mm. The width of the convex portion can be controlled by coating conditions (particularly, the rotation speed ratio of the roll). In addition, it can spread so that the width | variety of the convex part of an end surface may become large, so that the difference of the rotational speed of the opposing roll becomes large.

  The “height” of the convex portion is about 0.1 to 2.0 mm. The height (size) of the convex portion has a correlation with the average particle diameter of the granulated body, and the height of the convex portion increases as the average particle diameter of the granulated body increases.

  Hereinafter, although this embodiment is described using an example, this embodiment is not limited to these.

<Manufacture of electrode sheet>
The electrode sheets (negative electrode sheet) of Examples 1 to 10 and Comparative Examples 1 to 6 and the electrode sheet (positive electrode sheet) of Example 11 were produced as follows.

[Example 1]
1. Granule formation process (S10)
First, the following materials were prepared: Negative electrode active material: natural graphite binder: SBR, CMC-Na.

  A negative electrode active material (97 parts by mass), a binder (SBR: 1 part by mass and CMC-Na: 2 parts by mass) and a solvent (water) are charged into a stirring tank of a stirring granulator and mixed. Granules were formed. The amount of the solvent used was adjusted so that the solid content concentration of the granulated product was 70% by mass. The average particle diameter (d50) of the obtained granulated body was 1 mm.

2. Arrangement process (S20)
An electrode manufacturing apparatus shown in FIG. 5 was prepared. Using the electrode manufacturing apparatus 90, the granulated body 8 was arranged in a sheet form on both surfaces of the electrode current collector plate 11 as described above. In addition, similarly to the apparatus shown in FIG. 11, the exposed portion 13 was provided at one end in the width direction of the electrode current collector plate using a regulating plate 94 a between the A roll 91 and the B roll 92. However, unlike the apparatus shown in FIG. 11, the regulating plate 94b between the B roll 92 and the C roll 93 is not used so that irregularities are formed on the end surface 121b on the exposed portion 13 side of the electrode mixture layer 121. It was.

  Cu foil (thickness 10 μm, width 80.9 mm) was prepared as a negative electrode current collector plate. The negative electrode current collector plate 11 was supplied to the electrode manufacturing apparatus 90 shown in FIG. 5, and a sheet-shaped granule 8 a was disposed on both surfaces of the negative electrode current collector plate 11. In addition, the exposed part 13 which does not arrange | position a granulated material on the 1st surface of the electrode current collecting plate 11 is provided in width 20.5mm along one end surface of the width direction, and the 2nd surface is also along the end surface of the same side. An exposed portion 13 having a width of 21 mm was provided (FIG. 6).

  The granulated body was dried using a drying furnace, and the granulated body was compressed using a roll rolling machine to produce the negative electrode sheet 10 shown in FIG. In FIG. 6, the granulated body is the negative electrode mixture layers 121 and 122. Note that the end surfaces 121b and 122b on the exposed portion 13 side of the negative electrode mixture layers 121 and 122 are drawn flat for simplicity, but as shown in FIG. 122a).

In addition, about the negative electrode sheet of Example 1, when the total area of the non-facing part per 1 m of longitudinal directions of a negative electrode sheet was measured, it was 103 mm < ² >. Further, the front / back ratio of the non-opposing portion area was both about 1.

  About the 1st composite material layer and the 2nd composite material layer in a present Example, the "width" and "height" of the above-mentioned convex part are shown in Table 1 (the same is true in the following examples and comparative examples).

[Examples 2 and 3]
The coating cycle of Example 1 is controlled to increase the difference between the coating cycles of the front and back sides, and the total area of the non-opposing portion per 1 m in the longitudinal direction of the electrode sheet is 489 mm ² (Example 2), 1009 mm ² (Example) A negative electrode sheet was produced in the same manner as in Example 1 except that 3).

Examples 4 and 5
The longitudinal direction of the electrode sheet is increased by increasing the difference in the average particle diameter of the granulates arranged on the front and back of Example 1 and changing the size (height) of the irregularities on the front and back as shown in FIG. except that the non-facing portions total area per 1m was 521 mm ^2, 498 mm ² is to prepare a negative electrode sheet in the same manner as in example 1.

[Examples 6 and 7]
By controlling the rotation speed ratio of the A roll 91, the B roll 92, and the C roll 93, and changing the width of the unevenness on the front and back as shown in FIG. 2B, the non-opposing portion per 1 m in the longitudinal direction of the electrode sheet except that the total area was 488 mm ^2, 470 mm ² is to prepare a negative electrode sheet in the same manner as in example 1.

Examples 8 and 9
A negative electrode sheet was produced in the same manner as in Example 1 except that the width of the exposed portion in Example 1 was increased on either the first surface (Example 8) or the second surface (Example 9). The total area of the non-opposing portions per 1 m in the longitudinal direction of the negative electrode sheet of Example 8 was 509 mm ² , and the front-back ratio (first non-opposing portion / second non-opposing portion) of the non-opposing portion area was about 0.2. It was. The total area of the non-opposing portions per 1 m in the longitudinal direction of the negative electrode sheet of Example 9 was 500 mm ² , and the front / back ratio of the non-opposing portion area was about 5.

Example 10
The negative electrode sheet was formed in the same manner as in Example 1 except that the exposed portions were provided on both sides of the electrode current collector plate in the width direction, and the end surfaces on both sides of the electrode mixture layer were provided along the exposed portions on both sides. Manufactured. In addition, it was made for the exposed part to be provided in the both sides of the width direction of an electrode current collector plate using the two control boards 94a between the A roll 91 and the B roll 92. FIG. On the other hand, the regulating plate 94b between the B roll 92 and the C roll 93 was not provided on both sides so that irregularities were formed on the end faces on both sides of the electrode mixture layer.

Example 11
A positive electrode sheet made of the following materials was produced in the same manner as the negative electrode sheet of Example 1. Positive electrode active material: LiNi _1/3 Co _1/3 Mn _1/3 O ₂
Binder: Polyvinylidene fluoride (PVDF)
Conductive material: Acetylene black Current collector: Aluminum foil NMP was used as a solvent, and the solid content of the granulated body was 80% by mass. The average particle diameter (d50) of the granulated body was 1 mm. The total area of the non-opposing portions per 1 m in the longitudinal direction of the positive electrode sheet was 470 mm ² , and the front / back ratio of the non-opposing portion area was about 1.2.

[Comparative Example 1]
A negative electrode sheet similar to that of Example 1 was manufactured except that the negative electrode mixture layer was formed using the paste method.

  First, the same negative electrode active material, binder and thickener as in Example 1 were prepared. A negative electrode active material (97 parts by mass), a binder (1 part by mass), a thickener (2 parts by mass) and a solvent (water) were charged into a stirring tank of a planetary mixer and mixed to form a paint. . In addition, the usage-amount of the solvent was adjusted so that solid content concentration might be 50 mass%.

Using a die coater, a coating material was applied to both surfaces of the same negative electrode current collector plate as in Example 1, and dried to form a negative electrode mixture layer. In addition, the exposed part which does not apply a coating material was provided with a width of 20.5 mm on the first surface and a width of 21 mm on the second surface. Thus, the difference is 0.5mm next width of the negative electrode mixture layers on the front and back, the non-opposing portions total area per longitudinal 1m becomes 500 mm ^2. The negative electrode mixture layer was rolled with a roll to obtain a negative electrode sheet. The thickness of each of the negative electrode composite layers on both sides was 100 μm.

[Comparative Example 2]
A negative electrode sheet was produced in the same manner as in Example 1 except that in the arrangement step, the regulating plate 94 was used to prevent the unevenness from being generated on the end surface in the width direction of the negative electrode composite material layer using the apparatus shown in FIG. . As in Comparative Example 1, the exposed portion was provided with a width of 20.5 mm on the first surface and a width of 21 mm on the second surface, so that the difference in the width of the negative electrode mixture layer between the front and back surfaces was 0.5 mm.

[Comparative Example 3]
A negative electrode sheet was produced in the same manner as in Example 1 except that the coating period of the granulated body on the first surface and the second surface was controlled so that the unevenness period was matched between the front and back surfaces. The total area of the non-opposing portions per 1 m in the longitudinal direction of the negative electrode sheet was 56 mm ² .

[Comparative Example 4]
In the same manner as in Example 1 except that the average particle size of the granulated body was increased and the difference in the coating period of the granulated body was increased between the front and back surfaces, so that the total area of the non-opposing portion was further increased. A sheet was produced. The total area of the non-opposing portions per 1 m in the longitudinal direction of the negative electrode sheet was 1201 mm ² .

[Comparative Examples 5 and 6]
In Comparative Example 5, the width of the exposed portion on the first surface side was widened, and in Comparative Example 6, the width of the exposed portion was narrowed. Other than that was carried out similarly to Example 1, and manufactured the negative electrode sheet. The front / back ratio of the non-opposing area was about 0.1 in Comparative Example 5 and about 7 in Comparative Example 6. The non-opposing portions total area per longitudinal 1m of the negative electrode sheet, 490 mm ² in Comparative Example 5, was 510 mm ² in Comparative Example 6.

<Manufacture of non-aqueous electrolyte secondary batteries>
Using the negative electrode sheets of Examples 1 to 10 and Comparative Examples 1 to 6 manufactured above, a non-aqueous electrolyte secondary battery (rectangular lithium ion secondary battery) for evaluation having a rated capacity of 25 Ah was obtained as follows. Manufactured. Hereinafter, the “nonaqueous electrolyte secondary battery” may be simply referred to as “battery”.

1. Positive electrode sheet manufacturing process The positive electrode sheet 20 shown in FIG. 7 was manufactured. First, the following materials were prepared.

Cathode active material: LiNi _1/3 Co _1/3 Mn _1/3 O ₂
Conductive material: Acetylene black Binder: PVDF
Solvent: NMP.

  A positive electrode active material (90 parts by mass), a conductive material (8 parts by mass), a binder (2 parts by mass) and a solvent were put into a stirring tank of a planetary mixer and mixed to form a paint (positive electrode paste). . The usage-amount of the solvent was adjusted so that the solid content concentration of a granulation body might be 50 mass%.

  An Al foil having a thickness of 20 μm and a width of 78.0 mm was prepared as a positive electrode current collector plate. Using a die coater, the positive electrode paste was applied to both surfaces of the positive electrode current collector plate and dried. Thereby, the positive electrode mixture layer 22 was formed. In addition, the exposed part 23 which does not apply | coat a positive electrode paste was provided in the width direction of the width direction of the positive electrode current collecting plate 21 by 20 mm. Furthermore, the positive electrode mixture layer 22 was rolled to a predetermined thickness with a roll to produce the positive electrode sheet 20 shown in FIG.

2. Electrode group manufacturing process A polyethylene separator having a width of 63.0 mm was prepared.

  As shown in FIG. 8, the negative electrode sheet 10 and the positive electrode sheet 20 are sandwiched between the separators 30 so that the exposed portion 13 of the negative electrode current collector plate and the exposed portion 23 of the positive electrode current collector plate are arranged in opposite directions. By laminating and winding these, a wound electrode group was formed. Furthermore, the electrode group was formed into a flat shape using a flat plate press.

3. Case Housing Step As shown in FIG. 9, the electrode group 80 was housed in a battery case 50 (height 75 mm, width 120 mm, thickness 15 mm).

4). Liquid Injection Process An electrolytic solution 81 having the following composition was injected from the liquid injection port of the battery case 50. Thereafter, the liquid injection port was sealed, and the battery case 50 was sealed.

[Electrolytic solution composition]
Supporting electrolyte: LiPF ₆ (1.0 mol / L)
Solvent: Mixed solvent consisting of ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) [EC: DMC: EMC = 3: 5: 2 (volume ratio)].

  As described above, the nonaqueous electrolyte secondary battery 100 for evaluation having a rated capacity of 25 Ah was manufactured.

  Furthermore, using the negative electrode sheet of Comparative Example 1 and using the positive electrode sheet of Example 11 instead of the above positive electrode sheet, a similar non-aqueous electrolyte secondary battery for evaluation was manufactured.

<Evaluation of battery performance: High-rate cycle test>
Each battery obtained above was evaluated as follows. In the following description, the unit of current value “C” indicates a current value at which the rated capacity of the battery can be discharged in one hour. “SOC” (State Of Charge) means a charging rate.

1. Measurement of initial resistance First, the initial resistance of the battery produced above was measured. Specifically, the SOC of the battery was adjusted to 60% in a 25 ° C. environment. At the same temperature, a pulse discharge of 10 C × 10 seconds was performed, and the amount of voltage drop was measured. The IV resistance was calculated by dividing the amount of voltage drop by the current value during pulse discharge. In addition, about each said various battery, IV resistance of 10 batteries was measured, and those average values were made into initial stage resistance.

2. Measurement of rate of increase in resistance after high-rate pulse cycle In a 25 ° C environment, the SOC of the battery whose initial resistance was measured was adjusted to 60% again. Next, a high-rate pulse cycle in which the following “pulse charge → pulse discharge” is one cycle was repeated 2500 times. Pulse charge: 4C × 12 seconds Pulse discharge: 2C × 24 seconds.

  After executing 2500 cycles, the average value of the IV resistance of the battery was determined in the same manner as in “1. Measurement of initial resistance”. The resistance increase rate (percentage) was determined by dividing the resistance after the high rate cycle by the initial resistance. The results are shown in Table 1. It can be said that the smaller the resistance increase rate, the lower the performance degradation associated with the high-rate cycle (the better the high-rate cycle characteristics).

〔Results and discussion〕
From the results in Table 1, it can be seen that the batteries using the negative electrode sheets of Comparative Examples 1 and 2 have poor high rate cycle characteristics. This is because the non-opposing part total area is 500 mm ² , but the non-opposing part exists only on the first surface, so the electrolyte holding of the negative electrode mixture layer (first electrode mixture layer) on the first surface This is because the electrolyte solution withered in the negative electrode composite material layer (second electrode composite material layer) on the second surface, although the properties were high. Indeed, the negative electrode sheet was collected after high rate cycle, was measured LiPF ₆ of the negative-electrode mixture layer of the double-sided, LiPF ₆ of the negative electrode mixture layer in the first surface than the second surface There were many.

On the other hand, in Examples 1 to 11, excellent high rate cycle characteristics could be obtained. Examples 1-11 are the electrode sheets manufactured by the granulation body shaping | molding method, and a 1st electrode compound-material layer is a several 1st non-opposing part (opposite to a 2nd electrode compound-material layer in at least one end of the width direction. And the second electrode mixture layer has a plurality of second non-opposing portions (portions not opposed to the first electrode mixture layer) at least at one end in the width direction. The front / back ratio of the non-opposing portion area is 0.2 or more and 5 or less. The non-opposing portions total area is 100 mm ² or more 1009Mm ² or less per longitudinal 1 m. In addition, the range of this non-opposing portion total area is a range for one end face in the width direction, and when there are a plurality of non-opposing portions on both end faces in the width direction as in Example 10, each end face is The total area of the plurality of non-opposing portions for both end faces may exceed this range.

In the above embodiment, the high-rate cycle characteristics are improved because a plurality of non-opposing portions are alternately present on the front and back surfaces (first surface and second surface), so that both the first surface and the second surface of the electrode plate This is because the electrolytic solution retention was improved. Indeed, the negative electrode sheet was collected after high rate cycle, it was measured LiPF ₆ of the negative-electrode mixture layer of the double-sided, LiPF ₆ of the negative-electrode mixture layer of the double-sided (first surface and second surface) is Both were equivalent to those of the first surface of Comparative Examples 1 and 2. This means that high liquid retention was obtained. Moreover, when the uncoated part existed in both, the effect was acquired more, and even when it provided in the positive electrode, the effect was acquired.

  On the other hand, in Comparative Examples 3 and 4, the resistance increased due to the high rate cycle, and the high rate cycle characteristics were poor. About the comparative example 3 with a small area of a some non-opposing part, it is thought that it is because the improvement effect of electrolyte solution retainability was not acquired. Moreover, about the comparative example 4 with a large area of a some non-opposing part, when a winding body (winding-type electrode group) is decomposed | disassembled, the part which does not have a negative electrode compound material layer will exist in the part facing the positive electrode sheet did. From this, it can be considered that in Comparative Example 4, the resistance was originally increased. In addition, in order to increase the area of a plurality of non-opposing portions as in Comparative Example 4, when the size (height) of the unevenness on the end surface is increased and the difference in the coating cycle between the front and back is increased, the wound body There are disadvantages in battery design, such as the size of the battery.

  Also, in Comparative Examples 5 and 6, the high rate cycle characteristics were poor. This is because there are many non-opposing parts on either side of the front and back, and there are too few non-opposing parts on the opposite side, so the electrolyte solution retention of the electrode mixture layer on the side with few non-opposing parts is poor It is thought that.

  The nonaqueous electrolyte secondary battery including the electrode sheet of the present embodiment is suitable as a vehicle-mounted battery in which high rate cycle characteristics are important.

  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.

  DESCRIPTION OF SYMBOLS 1 Electrode active material, 8, 8a Granulated body, 10 Negative electrode sheet (electrode sheet), 11 Negative electrode current collector plate, 11a 1st surface, 11b 2nd surface, 12 Negative electrode compound material layer, 121 Electrode compound material layer (1st Electrode composite layer, negative electrode composite layer), 121a non-opposing portion (first non-opposing portion), 121b, 122b end face, 121c non-opposing portion, 122 electrode composite layer (second electrode composite layer, negative electrode composite layer) ), 122b Non-opposing portion (second non-opposing portion), 13 exposed portion, 20 positive electrode sheet (electrode sheet), 21 positive electrode current collector plate, 22 positive electrode composite material layer, 23 exposed portion, 30 separator, 50 battery case, 71 , 72 External terminal, 80 electrode group, 81 electrolyte, 90 electrode manufacturing apparatus, 91 A roll, 92 B roll, 93 C roll, 95 feeder, 94 regulating plate, 100 non-aqueous electrolyte secondary battery.

Claims (1)

An electrode current collector plate, a first electrode mixture layer disposed on one surface of the electrode current collector plate, and a second electrode mixture layer disposed on the other surface of the electrode current collector plate. An electrode sheet for a non-aqueous electrolyte secondary battery,
At one end in the width direction of the electrode sheet,
The first electrode mixture layer has a plurality of first non-facing portions that do not oppose the second electrode mixture layer in the thickness direction along an end surface extending in the longitudinal direction, and the second electrode mixture layer Has a plurality of second non-opposing portions that do not face the first electrode mixture layer in the thickness direction along the end surface extending in the longitudinal direction,
The ratio of the total area of the plurality of first non-opposing portions to the total area of the plurality of second non-opposing portions is 0.2 or more and 5 or less,
Total area of the second non-facing portion area and the plurality of the plurality of first non-facing portion is longitudinally 1m per 100 mm ² or more 1009Mm ² or less of the electrode sheet, the non-aqueous electrolyte solution for a secondary battery Electrode sheet.