JP2010277740A - Electrode sheet, wound electrode group as well as nonaqueous electrolyte secondary battery using this and manufacturing method of electrode sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To restrain generation of wrinkles in a mixture non-coated part of an electrode for a nonaqueous electrolyte secondary battery. <P>SOLUTION: An electrode 3 has a first and a second mixture layers 7a, 7b formed on either face of a collector 6 made of a metal foil. At least at either of side edge parts 61, 62 along a length direction of the collector 6, a mixture non-formed part where neither of mixture layers 7a, 7b is formed with the metal foil exposed therein, is continuously formed on both faces of the collector in a length direction, and, as seen from a thickness direction of the electrode 3, a formation position of an end edge part of each mixture layer 7a, 7b nearer to the mixture non-formed part is in a position shifted from each other in a short side direction, so that the mixture layers 7a, 7b of the electrode sheet are formed so as to satisfy a formula (1): 0.1≤X/Y≤1.0 (X is a shift width (mm) between the end edge part of the first mixture and the end edge part of the second mixture layer nearer to the mixture layer non-formed part, and Y is an average density (g/cm<SP>3</SP>) of the mixture). <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an electrode sheet, a wound electrode group using the same, a nonaqueous electrolyte secondary battery, and a method for producing the electrode sheet.

  As a large non-aqueous electrolyte secondary battery used for a power source of an electric vehicle or the like, a secondary battery having high weight energy density and volume energy density is required. As a secondary battery, a positive electrode sheet formed by forming an electrode mixture layer on both sides of a current collector made of metal foil and a negative electrode sheet are opposed to each other with a separator interposed therebetween, and a wound electrode group is not wound. A non-aqueous electrolyte secondary battery is known that is immersed in a water electrolyte solution and accommodated in an electrode exterior body. As a non-aqueous electrolyte, for example, in a lithium ion battery as a secondary battery, an electrolytic solution in which a supporting salt containing lithium in an organic solvent is dissolved can be used.

  In a non-aqueous electrolyte secondary battery, a positive electrode sheet and a negative electrode sheet (sometimes referred to as an electrode sheet as a superordinate concept indicating a positive electrode sheet or a negative electrode sheet) are manufactured as follows. That is, an active material and a binder determined according to the positive electrode sheet and the negative electrode sheet, and an electrode mixture layer coating liquid in which a conductive material is kneaded and dispersed in a solvent as necessary (for each of the positive electrode sheet and the negative electrode sheet) A positive electrode mixture layer coating liquid and a negative electrode mixture layer coating liquid) are prepared, and a positive electrode mixture layer coating liquid and a negative electrode mixture layer coating liquid are respectively applied to both sides of the current collector. Thus, a coating film is formed, and the coating film is dried, so that the coating film forms an electrode mixture layer.

  Furthermore, the density of the electrode mixture layer is usually increased by pressing the electrode mixture layer in the thickness direction in order to increase the capacity of the secondary battery and increase the weight energy density. Thus, an electrode sheet such as a positive electrode sheet or a negative electrode sheet is obtained.

  By the way, in order to attach an electrode lead to a wound electrode group used in a large non-aqueous electrolyte secondary battery, in the electrode sheet, an exposed region of a current collector in which an electrode mixture layer is not formed in advance (that is, A region where the electrode mixture layer coating solution is not applied (uncoated portion); an electrode mixture layer non-formation region) is formed along one side edge of the wound electrode group in the winding direction. Yes. The wound electrode group is electrically connected to an external terminal of the battery exterior body via an electrode lead attached to the uncoated portion.

  Therefore, if it is going to obtain the electrode sheet which raised the density of the electrode mixture layer, an electrode mixture layer and a collector will be pressed.

  As described above, when the step of pressing the electrode mixture layer and the current collector, that is, the pressing step, is performed, the current collector is pressed and stretched together with the electrode mixture layer in the formation region of the electrode mixture layer. It is. However, the current collector is not pressurized and stretched in the region where the electrode mixture layer is not applied. For this reason, the surface of the electrode sheet finally obtained after pressing may be wavy, curved, or distorted, and further, wrinkles may occur in the uncoated portion of the electrode mixture layer coating solution. When an electrode sheet having such wrinkles is used as a positive electrode sheet or a negative electrode sheet when forming a wound electrode group, there arises a problem that the electrode sheet breaks.

  Then, in manufacturing an electrode sheet, it has been proposed to suppress the generation of wrinkles in the electrode sheet by adding a step of processing an uncoated portion into a strip shape (Patent Document 1). Further, in addition to forming uncoated portions extending in the direction (width direction) perpendicular to the flow direction at positions at both ends in the flow direction of the current collector, predetermined positions between both ends in the flow direction of the current collector In addition, it has been proposed to further add an intermediate uncoated portion extending in the width direction to suppress the occurrence of distortion of the electrode sheet (Patent Document 2). Furthermore, it has been proposed to suppress generation of wrinkles on the electrode sheet by locally heating the uncoated portion before pressing the current collector having the electrode mixture layer and the uncoated portion (Patent Document). 3).

JP-A-9-92339 JP 2005-339926 A JP 2007-273390 A

  In the techniques of Patent Documents 1 and 3, there are problems that the number of steps is increased and the number of steps is increased, which increases the manufacturing cost of the electrode sheet. In the technique of Patent Document 2, when forming the wound electrode group, when the positive electrode sheet and the negative electrode sheet are wound facing each other through the separator, the positions of the respective intermediate uncoated portions of the positive electrode sheet and the negative electrode sheet Need to be matched, and the design of the positive electrode sheet and the negative electrode sheet becomes complicated.

  The present invention provides an electrode sheet capable of suppressing generation of wrinkles in an unapplied portion without adding a process, and a wound electrode group formed using this electrode sheet and capable of preventing breakage of the electrode sheet It is another object of the present invention to provide a non-aqueous electrolyte secondary battery using the wound electrode group and a method for producing such an electrode sheet.

The present invention is (1) an electrode sheet in which a first electrode mixture layer and a second electrode mixture layer are formed on one side and the other side of a long current collector made of a metal foil,
The portion where the metal foil is exposed and neither the first electrode mixture layer nor the second electrode mixture layer is formed on at least one side of the side edges of the current collector along the longitudinal direction of the current collector An electrode mixture layer non-formation part formed continuously on the both sides of the current collector in the longitudinal direction of the current collector,
When viewed in the thickness direction of the electrode sheet, the first electrode mixture layer and the second electrode mixture layer have the formation position of the edge portion closer to the electrode mixture layer non-forming portion in each, It is formed so as to be shifted from each other in the short direction of the current collector,
An electrode sheet, wherein the first electrode mixture layer and the second electrode mixture layer are formed to satisfy the following (Equation 1):
(Equation 1) 0.1 ≦ X / Y ≦ 1.0
(However, X is the second electrode mixture closer to the edge portion of the first electrode mixture layer and the electrode mixture layer non-formed portion closer to the electrode mixture layer non-formed portion. deviation width between the edges of the layer (mm), Y is the average density of the current collector electrode mixture layers formed on both surfaces of (g / cm ³⁾⁾
(2) A positive electrode sheet in which a positive electrode mixture layer is formed on both sides of a positive electrode current collector made of metal foil, and a negative electrode electrode mixture layer on both sides of the negative electrode current collector made of metal foil A negative electrode sheet formed with a wound electrode group that is faced and wound through a separator,
As the positive electrode sheet and / or the negative electrode sheet, a wound electrode group in which the electrode sheet according to (1) is used,
(3) A non-aqueous electrolyte secondary battery in which the wound electrode group according to (2) is accommodated in a battery outer body,
(4) A method for producing an electrode sheet in which a first electrode mixture layer and a second electrode mixture layer are formed on one side and the other side of a current collector made of a metal foil,
An electrode mixture layer coating solution containing an electrode active material is applied to a predetermined region inside the side edge of the current collector along the longitudinal direction of the current collector on the current collector surface to form a coating film, A coating and drying step in which an electrode sheet formed body is formed by drying the coating film;
A pressing step of pressing a predetermined portion of the electrode sheet forming body in the thickness direction of the electrode sheet forming body, and
In the coating and drying step, by applying an electrode mixture layer coating solution, a first coating film and a second coating film as a coating film are formed on one side and the other side of the current collector, respectively, At least one of the side edges of the current collector along the longitudinal direction of the current collector is a portion where the metal foil is exposed and neither the first coating film nor the second coating film is formed. When a non-formed part formed continuously in the longitudinal direction of the current collector is formed on both surfaces of the electrode sheet, and when viewed in the thickness direction of the electrode sheet formed body, the first one closer to the non-formed part The side edge of the second coating film closer to the side edge of the coating film and the non-formed part is formed at a position shifted from each other in the short direction of the current collector,
In the pressing step, a portion of the electrode sheet forming body forming both the first coating film and the second coating film is pressed, and the first electrode mixture layer and the second electrode mixture layer are pressed. Is formed as a layer satisfying the following (Equation 2), a method for producing an electrode sheet,
(Expression 2) 0.1 ≦ X / Y ≦ 1.0
(However, X represents the edge of the first electrode mixture layer and the second electrode combination closer to the side edge of the side edge of the current collector where the metal foil is exposed). Deviation width (mm) between the edge of the agent layer and Y is the average density (g / cm ³ ) of the electrode mixture layer formed on both sides of the current collector
Is the gist.

  ADVANTAGE OF THE INVENTION According to this invention, without accompanying a new manufacturing process, generation | occurrence | production of the wrinkle of an electrode mixture layer uncoated part can be suppressed, and it becomes possible to prevent a fracture | rupture of an electrode sheet. In particular, by applying an electrode mixture layer coating solution containing an electrode active material on both sides of the current collector to form a coating film, and further pressing the current collector on which the coating film has been formed in the thickness direction When the electrode sheet is formed and the electrode sheet is wound to form a wound electrode group, a series of steps until the wound electrode group is formed are carried out in a form that goes through a pressing step. Can be prevented.

  According to the present invention, the electrode mixture layer is formed so that the relationship between the mutual displacement width of the electrode mixture layer and the average density satisfies the above (Equation 1). According to the present invention, the deviation width X satisfies the above (Equation 1), so that the breakage of the electrode sheet can be more effectively prevented.

  Further, by forming a wound electrode group using this electrode sheet, it is possible to prevent the electrode sheet from being broken. In addition, by using the wound electrode group, it is possible to efficiently provide a non-aqueous electrolyte secondary battery in which breakage of the electrode sheet is suppressed.

  According to the production method of the present invention, it is possible to obtain an electrode sheet in which the generation of wrinkles in the electrode mixture layer uncoated portion is suppressed, and the current collector is broken in a series of steps until a wound electrode group is formed. It is possible to obtain an electrode sheet capable of preventing the occurrence of the above.

(A) It is a cross-sectional schematic diagram for demonstrating one of the Examples of the electrode sheet formation body for forming the electrode sheet used as the positive electrode sheet or negative electrode sheet of the winding electrode group of this invention. (B) It is a cross-sectional schematic diagram for demonstrating the slit processing position of an electrode sheet formation body. (C) It is a cross-sectional schematic diagram for demonstrating the other Example of the electrode sheet used as a positive electrode sheet or a negative electrode sheet of the winding electrode group of this invention. (D) It is a cross-sectional schematic diagram for demonstrating the other Example of the electrode sheet used as a positive electrode sheet or a negative electrode sheet of the winding electrode group of this invention. It is a partial top view for demonstrating one of the Examples of the electrode sheet used as a positive electrode sheet or a negative electrode sheet of the winding electrode group of this invention. (A) It is sectional drawing for demonstrating one of the winding electrode groups of this invention. (B) It is an expanded section schematic diagram showing typically the state where a part of winding electrode group of the invention was expanded. (A) It is a cross-sectional schematic diagram for demonstrating typically the state in which the positive electrode sheet, the negative electrode sheet, and a separator overlap when forming the winding electrode group of this invention. (B) It is a schematic diagram explaining the method of manufacturing the winding electrode group of this invention. It is a schematic diagram which shows one of the Examples of the non-aqueous field liquid secondary battery using the winding electrode group of this invention.

  The present invention is an electrode sheet 3 that can be used for the positive electrode sheet 2 and the negative electrode sheet 5 of the wound electrode group 1 as shown in FIGS. Here, the wound electrode group 1 is formed by winding the positive electrode sheet 2 and the negative electrode sheet 5 with the separator 4 facing each other.

  In this specification, when the positive electrode sheet 2 and the negative electrode sheet 5 are wound through the separator 4, the winding direction (winding direction) is the positive electrode sheet 2 and the negative electrode sheet 5 before winding. Is a direction along the longitudinal direction of the long current collector 6 to be described later. Further, the winding direction is the arrow T direction in the example of FIG. 3 when viewed from the wound electrode group 1. Further, the direction perpendicular to the winding direction in the in-plane direction of the electrode sheet 3 is the short direction of the long current collector 6.

  Regarding the positive electrode sheet 2 and the negative electrode sheet 5, the positive electrode sheet 2 is formed by forming the positive electrode mixture layer 17 on both surfaces of the positive electrode current collector 16, and the negative electrode sheet 5 is the negative electrode current collector. An electrode mixture layer 27 for the negative electrode is formed on both surfaces of 26 (FIGS. 3A and 3B).

  As at least one of the positive electrode sheet 2 and the negative electrode sheet 5, an electrode sheet 3 composed of an electrode sheet forming body 30 (FIGS. 1A and 2) formed as follows can be used (FIG. 1C). (D)). FIG. 2 is a partial plan view for explaining one example of the electrode sheet forming body 30, and a cross-sectional view taken along the line II in FIG. 2 corresponds to FIG.

[Configuration of Electrode Sheet 3]
As shown in FIGS. 1 (c) and 1 (d), the electrode sheet 3 includes electrode mixture layers 7 (first electrode mixture layer 7 a and second electrode mixture layer 7 b) on both sides of the current collector 6. Formed. At this time, when viewed in the thickness direction of the electrode sheet 3, the electrode mixture layers 7 (the first electrode mixture layer 7 a and the second electrode mixture layer 7 b) on both surfaces of the current collector 6 are wound electrodes. The edge portion 8 (8a, 8b) of the electrode mixture layer 7 is formed inside at least one of the side edges 61, 62 of the current collector 6 extending in the winding direction of the group 1, and the edge thereof The portions 8a and 8b are arranged between the electrode mixture layers 7a and 7b (first electrode mixture layer 7a and second electrode mixture layer 7b) on both sides of the current collector 6 and They are formed at positions shifted in the direction crossing the turning direction (FIGS. 1C and 1D).

  In addition, the state where “the end edge portions 8a and 8b are shifted” means “the combination and / or the end edge portions (8a1 and 8b1) near the one end edge of the current collector 6”. Regarding the combination of the edge portions (8a2, 8b2), when the position of the edge portion 8 is viewed in the thickness direction of the electrode sheet 3, the edge portions 8a1, 8b1 do not overlap and / or the edge portion 8a2. , 8b2 shows a state in which they do not overlap.

  In the electrode sheet 3, the current collector 6 is formed with a region where the electrode mixture layer 7 is not formed (a region indicated by a symbol K in FIG. 1). The non-formation region is a region where the metal foil forming the current collector 6 is exposed. This electrode sheet 3 is a portion in which the first electrode mixture layer 7a and the second electrode mixture layer 7b are formed on one side and the other side of the current collector 6, respectively (the electrode mixture layer 7 is formed on both sides). The electrode mixture layer non-double-sided forming part excluding the electrode mixture layer double-sided forming part, and the electrode mixture layer non-double-sided forming part is formed only on one surface of the current collector 6. The electrode mixture layer single-sided formation part, which is the part where the layer 7 is formed, and the part where neither the first electrode mixture layer nor the second electrode mixture layer is formed on the current collector 6 (both surfaces of the current collector 6) The electrode mixture layer 7 is a portion where the electrode mixture layer 7 is not formed).

  In the electrode sheet 3, when the non-formation region K of the electrode mixture layer 7 is formed on both side edges of the current collector 6, one of the side edges of the current collector 6 (the side edge 61 in FIG. 1C). ) Formed in the non-forming region K (K1) is larger than the non-forming region K (K2) formed in the other of the side edges of the current collector 6 (the side edge 62 in FIG. 1C). When the wound electrode group using the electrode sheet 3 is incorporated into a non-aqueous electrolyte secondary battery, the larger non-formation region K (K1) serves as an electrode lead attachment portion.

  In the example of FIG. 1 (c), the electrode mixture layer 7a, both of the side edges 61 and 62 of the current collector 6 extending in the winding direction of the wound electrode group 1 on the inner side of the side edges 61 and 62, 7b end edges 8a and 8b are formed. The positions of the end edge 8a1 and the end edge 8b1 closer to the side edge 61 of the end edges 8a and 8b are perpendicular to the winding direction of the wound electrode group 1 (the EF direction; In the short direction of the current collector 6, they are shifted from each other by a shift width X <b> 1. The positions of the end edge 8a2 and the end edge 8b2 closer to the side edge 62 of the end edges 8a and 8b are shifted from each other by the shift width X2 in the EF direction. In this example, the electrode sheet 3 includes a region of a portion from the side edges 61 and 62 of the current collector 6 toward the edge portions 8a and 8b of the electrode mixture layers 7a and 7b and an electrode mixture from the side edges 62. The non-formation area | region K (K1, K2) of the electrode mixture layer 7 is formed in the area | region of the part which goes to the edge part 8a, 8b of layer 7a, 7b. At this time, when viewed in the thickness direction of the current collector 6, the relative positions of the end edge portion 8 a 1 and the end edge portion 8 b 1 closer to the electrode mixture layer non-forming portion on the side edge 61 side, the side edge 62. Both of the relative positions of the end edge portion 8a2 and the end edge portion 8b2 closer to the side where the electrode mixture layer is not formed are shifted from each other.

  In the electrode sheet 3, the electrode mixture layers 7 on both sides of the current collector 6 are positioned at the edge portions 8 a and 8 b between the first electrode mixture layer 7 a and the second electrode mixture layer 7 b. It suffices if it is formed so as to cause a deviation.

  The electrode mixture layers 7a and 7b are formed so that the edge portions 8a1, 8b1, 8a2 and 8b2 of the electrode mixture layers 7a and 7b are alternately arranged in the EF direction in a plan view. However, in addition to (1), (2) the edge portions 8b1 and 8b2 are formed between the edge portions 8a1 and 8a2, or (3) outside the edge portions 8a1 and 8a2. It is preferable that the end edge portions 8b1 and 8b2 are positioned at the end. In the cases of (2) and (3), the electrode mixture layer 7a and the electrode mixture layer 7b have the other layer formed inside either one of the layers in plan view (FIG. 1 (a)). ). In FIG. 1A, an electrode mixture layer 7b is formed inside the electrode mixture layer 7a. In this case, after forming the electrode mixture layer 7a, in forming the electrode mixture layer 7b from the coating film formed by application of the electrode mixture layer coating solution, the edge portion 8 of the electrode mixture layer 7b is formed. The collapse of the shape of the coating film at the position is prevented.

(Current collector 6)
The current collector 6 is formed in a long shape. Here, the current collector 6 only needs to be long in a predetermined direction, and the length in the longitudinal direction is not particularly limited. As a material for the current collector 6, a thin sheet metal body, that is, a metal foil is used. As the current collector 16 (6) for the positive electrode sheet 2, aluminum, nickel, or the like is used, and as the current collector 26 (6) for the negative electrode sheet 5, copper, nickel, stainless steel, or the like is used. The current collector 16 for the positive electrode sheet 2 is preferably an aluminum foil, and the current collector 26 for the negative electrode sheet 5 is preferably a copper foil. The thickness of these metal foils is usually about 5 to 30 μm, preferably 5 to 20 μm. Such a metal foil is usually prepared in the state of a roll formed by winding a long belt-like sheet.

(Electrode mixture layer 7)
The electrode mixture layer 7 contains at least an active material and a binder, and contains a conductive material as necessary. The electrode active material includes a positive electrode active material for the positive electrode sheet 2 and a negative electrode active material for the negative electrode sheet 5.

As the positive electrode active material for the positive electrode sheet 2, a material conventionally used as a positive electrode active material of a non-aqueous electrolyte secondary battery can be used. For example, lithium transition metal composite oxides such as LiCoO ₂ , LiNiO ₂ or LiMn ₂ O ₄ , or chalcogen compounds such as TiS ₂ , MnO ₂ , MoO ₃ or V ₂ O ₅ can be exemplified.

  The positive electrode active material is preferably a powder having an average particle size of 0.1 to 100 μm in order to uniformly disperse it in the electrode mixture layer 7. These positive electrode active materials may be used alone or in combination of two or more.

  As the negative electrode active material for the negative electrode sheet 5, a material conventionally used as a negative electrode active material of a non-aqueous electrolyte secondary battery can be used. For example, carbonaceous materials such as natural graphite, artificial graphite, amorphous carbon, carbon black, or a carbon composite obtained by adding a different element to these components are preferably used. In addition, materials capable of occluding and releasing lithium ions such as metallic lithium and its alloys, tin, silicon, and alloys thereof can be generally used.

  The particle shape of the negative electrode active material is not particularly limited. For example, scaly, massive, fibrous, or spherical ones can be used. The negative electrode active material is preferably a powder having an average particle size of 0.1 to 100 μm in order to be uniformly dispersed in the electrode mixture layer 7. These negative electrode active materials may be used alone or in combination of two or more.

  The content ratio of the positive electrode active material or the negative electrode active material in the electrode mixture layer 7 is 70 based on the total amount of the blending components excluding the solvent from the coating liquid used for forming the electrode mixture layer 7 (solid content basis). It is -98 weight%, More preferably, it is 80-98 weight%.

  As the binder, for any of the positive electrode sheet 2 and the negative electrode sheet 5, for example, those conventionally used, thermoplastic resins, more specifically polyester resins, polyamide resins, polyacrylate resins, A polycarbonate resin, a polyurethane resin, a cellulose resin, a polyolefin resin, a polyvinyl resin, a fluorine resin, a polyimide resin, or the like can be used. Preferred are binders for cellulose resins such as carboxymethyl cellulose, rubbers such as styrene-butadiene rubber, and fluorine resins. A fluororesin is preferably used as a binder, and among these, polyvinylidene fluoride is particularly preferred. Moreover, you may add another resin and an additive as needed. The content of the binder in the electrode mixture layer 7 is 1 to 20% by weight, more preferably 2 to 15% by weight, based on the solid content.

  As the conductive material, carbonaceous materials such as natural and artificial graphite, carbon black, and carbon fiber can be used. Here, carbon black includes acetylene black, furnace black, thermal black, and the like. More preferred is acetylene black. Furthermore, graphite and carbon fiber can also be added as needed. Here, it is preferable to use vapor grown carbon fiber as the carbon fiber.

  Although the particle shape, size, etc. of the conductive material are not particularly limited, in the battery incorporating the wound electrode group 1 using the electrode sheet 3, the ion contained in the electrolyte in the battery and the electrode mixture layer 7 Since a battery reaction occurs due to the active material to be generated, a gap (a space in which no conductive material or the like exists) in which the electrolytic solution can permeate into the electrode active material layer 7 can be secured in the electrode mixture layer 7, for example, Particles, fibers, porous sheets and the like can be preferably used. When the conductive material is particulate, the average particle size is 0.01 to 20 μm, preferably 0.03 to 5 μm. The content of the conductive material in the electrode mixture layer 7 is 1.5 to 30% by weight, more preferably 3 to 20% by weight, based on the solid content.

(Preparation of electrode sheet 3)
A method for manufacturing the electrode sheet 3 in which the first electrode mixture layer 7a and the second electrode mixture layer 7b are respectively formed on one side and the other side of the current collector made of metal foil will be described. The electrode sheet 3 is produced by applying an electrode mixture layer coating solution containing an electrode active material to the inner side of the current collector 6 along the longitudinal direction of the current collector 6 on the surface of the current collector 6. A coating and drying process comprising: a coating process for coating a predetermined region to form a coating film; and a drying process for removing the solvent to obtain the electrode sheet forming body 30 by drying the coating film; A pressing step of pressing (rolling) a predetermined portion in the thickness direction of the electrode sheet forming body, and slitting the electrode sheet forming body 30 to a desired electrode width as necessary. Have

  As a solvent for preparing the electrode mixture layer coating solution for forming the positive electrode mixture layer and the negative electrode mixture layer, toluene, methyl ethyl ketone, N-methyl-2-pyrrolidone or a mixture thereof, or ion-exchanged water is used. In addition, a solvent capable of dissolving and dispersing the binder can be used. The ratio of the solvent in the coating liquid is 30 to 60% by weight, preferably 45 to 55% by weight, and the coating liquid is prepared in a slurry form. A positive electrode or negative electrode active material, a binder and a conductive material selected as appropriate can be added to a suitable solvent, and mixed and dispersed by a disperser such as a homogenizer, ball mill, sand mill, roll mill or planetary mixer to prepare a slurry. In addition, a thickener, a dispersing agent, etc. can also be added as needed.

The application method is not particularly limited, and for example, die coating, comma coating, or the like can be used. When the viscosity of the coating liquid is low, it can be applied by gravure coating, spray coating, dip coating, or the like. The electrode mixture layer may be formed by repeating the formation of the coating film a plurality of times and the drying of the coating film, or after coating three or more layers, the three or more layers may be dried at once. . The coating amount of the electrode mixture layer coating solution (formation weight of the electrode mixture layer) is 10 to 300 g / m ² (per one side of the current collector), preferably 20 to 250 g / m ² (current collection). Per side of the body).

  After coating, the electrode mixture layer is dried to remove the solvent in the coating film. The method for removing the solvent is not particularly limited, but may be appropriately selected from general techniques such as hot air drying, far-infrared drying, contact drying, reduced pressure drying, freeze drying drying, or a combination of these. it can.

  Specifically, regarding the formation of the electrode sheet forming body 30 in FIG. 1A, first, the electrode sheet 3 is made of a long strip-shaped metal foil depending on whether the electrode sheet 3 is the positive electrode sheet 2 or the negative electrode sheet 5. While preparing the electrical power collector 6, the electrode mixture layer coating liquid containing the active material which comprises the electrode mixture layer 7, a binder, and a electrically conductive material as needed is prepared. The prepared electrode mixture layer coating solution is applied to one surface of the current collector 6 along the longitudinal direction of the current collector 6 to form a coating film. Then, the coating film is dried and solidified to form a cured coating film (first coating film). Next, the prepared electrode mixture layer coating solution is applied to the other surface of the current collector 6 along the longitudinal direction of the current collector 6 to form a coating film. Then, the coating film is dried and solidified to form a cured coating film (second coating film). At this time, the electrode sheet forming body 30 is obtained. In this electrode sheet forming body 30, the metal foil is exposed on at least one side of the side edges of the current collector along the longitudinal direction of the current collector 6, and the first coating film and the second coating film are formed. A non-formed portion is formed by forming portions that are not formed on both sides of the current collector in the longitudinal direction of the current collector. Furthermore, when viewed in the thickness direction of the electrode sheet forming body 30, the side edge of the first coating film closer to the non-formed part and the side edge of the second coating film closer to the non-formed part Are formed at positions shifted from each other in the short direction of the current collector.

  The electrode sheet forming body 30 thus formed is pressed (rolled). In the pressing step, a portion of the electrode sheet forming body forming both the first coating film and the second coating film is pressed, and the first electrode mixture is formed as a layer satisfying the following (Equation 3). The press on which the layer and the second electrode mixture layer are formed is performed using, for example, a metal roll, an elastic roll, a heating roll, or the like. The roll press can continuously press the long belt-like electrode sheet forming body 30. When performing a roll press, either a stereotaxic press or a constant pressure press may be performed. When managing the pressure of a roll press with a linear pressure, although it adjusts according to the diameter of a pressure roll, a linear pressure can be 4.9 N / cm-9800 N / cm.

  In the slit processing, the electrode sheet forming body 30 is cut along the longitudinal direction of the current collector 6 and adjusted to a predetermined width. As the cutting position of the electrode sheet forming body 30, for example, positions G1 to G5 are appropriately selected as shown in FIG. When the electrode sheet forming body 30 is slit in the range from the position G1 to the position G4 in FIG. 1B (when cut at two positions G1 and G4), it is shown in FIG. This is the outer shape of the electrode sheet 3. When the electrode sheet forming body 30 is slit in the range from the position G1 to the position G3 in FIG. 1B, the outer shape of the electrode sheet 3 shown in FIG. Further, when the electrode sheet forming body 30 is cut at the three positions G1, G2, and G5 in FIG. Electrode sheets that form the formation region are formed in a portion from the position G2 to the position G1 and a portion from the position G2 to the position G5, respectively.

  Note that either pressing or slitting may be performed first. However, when it is intended to obtain the electrode sheet 3 in which the side end portions 8 are formed on the side edges 61 and 62 of the current collector (the electrode sheet 3 shown in FIG. 1C), slit processing is performed. After performing, it is preferable to press-work, and when it is going to obtain the electrode sheet 3 as what the side edge part 8 is formed in the one side edge of an electrical power collector (electrode sheet 3 shown in FIG.1 (d)) For this, it is preferable to perform slit processing after press processing.

In this way, the electrode sheet 3 which forms the electrode mixture layer 7 (7a, 7b) on both surfaces of the current collector 6 is obtained.

  By the way, in the electrode sheet 3 that forms at least one of the positive electrode sheet 2 and the negative electrode sheet 5, the electrode mixture layers 7 on both surfaces of the current collector 6 are shifted to the positions of the edge portions 8 (in FIG. X (X1, X2)) exists. Therefore, in forming the coating film made of the electrode mixture layer coating solution, the region where the electrode mixture layer coating solution is applied to each of the front and back surfaces of the current collector 6 is appropriately set in accordance with the deviation width. It is determined. At this time, as shown in FIGS. 1A, 1C, and 1D, the current collector 6 has a portion where a coating film is formed on both surfaces of the current collector 6 (a portion where no exposed region of the metal foil exists). ) (Part D) and a part where the coating film is not formed on both surfaces of the current collector 6 (part where the exposed region of the metal foil exists (part where the electrode mixture layer is not formed)) ( Part N) is formed. By the way, the state immediately before the press working of the current collector 6 is as shown in FIG. 1A when the press working is performed before the slit working, and after the slit working is performed. In the case where press working is performed, the state of the current collector 6 immediately before the press working is as shown in FIG. In any state of the current collector 6, at the time of pressing, the portion D is pressed and the current collector 6 is stretched, and the portion N is not pressed and the current collector 6 is hardly stretched. Here, in the electrode mixture layer 7 on both surfaces of the current collector 6, there is a shift (shift width X) in the position of the edge portion 8, so the portion N is near the boundary with the portion D. A “part where a coating film is formed only on one side of the current collector 6” (part S) is formed. This portion S reinforces the strength of the portion N and suppresses the occurrence of breakage of the electrode sheet 3. In addition, the part D corresponds to the part that becomes the electrode mixture layer double-sided forming part after pressing, the part N corresponds to the part that forms the electrode mixture layer non-double-sided after pressing, and the part S forms the electrode mixture layer on one side after pressing. In the part to be the part, the part excluding the part S from the part N corresponds to the part that becomes the electrode mixture layer non-formed part after pressing.

  In the electrode sheet 3, the current collector layer 7 on both sides of the current collector 6 is formed with a deviation width (X) that satisfies the following (Equation 3).

(Equation 3) 0.1 ≦ X / Y ≦ 1.0

However, X is the second electrode mixture layer closer to the edge part of the first electrode mixture layer closer to the electrode mixture layer non-formed part and the electrode mixture layer non-formed part. The deviation width (mm) between the end edges of the electrode, and Y are the average density (g / cm ³ ) in the electrode mixture layer formed on both surfaces of the current collector 6. Therefore, in the example of FIG. 1, X represents X1 and X2, and indicates the displacement width (mm) of the edge portions 8a and 8b between the electrode mixture layers 7a and 7b formed on both surfaces of the current collector 6. . In the present specification, the “average density” indicated by “Y” indicates the average density of the electrode mixture layer in the electrode sheet 3. Therefore, when the electrode sheet forming body 30 forms the electrode sheet 3 through the pressing process, the average density of the electrode mixture layer after the electrode sheet forming body 30 is pressed, that is, the “average density after pressing” is shown.

  When the electrode sheet 3 is X / Y <0.1, the size of the portion S is reduced, and the strength of the current collector 6 may not be sufficiently reinforced.

  When the electrode sheet 3 is X / Y> 1.0, the electrode mixture layer is prevented from being broken in the winding step when the wound electrode group is formed using the electrode sheet 3, but the electrode mixture layer There is a possibility that the portion becomes small, the battery capacity of the electrode sheet 3 decreases, and it becomes difficult to achieve the original purpose of obtaining a large capacity as a wound electrode group.

  In addition, in the electrode sheet 3, as shown in FIG. 1A, FIG. 2, etc., when there are a plurality of types of displacement width X such as X1 and X2, the above (Equation 3) is satisfied for any of them. Preferably it is.

  In the wound electrode group 1, the electrode sheet 3 is used as at least one of the positive electrode sheet 2 and the negative electrode sheet 5, and the electrode sheet 3 is used as both the positive electrode sheet 2 and the negative electrode sheet 5. It is preferable that the electrode sheet 3 satisfying the above (Equation 3) is used.

[Manufacture of wound electrode group]
The wound electrode group 1 of the present invention can be manufactured by appropriately using a well-known direction from the past, for example, as follows. Here, as an example, the wound electrode group 1 uses the electrode sheet 3 for both the positive electrode sheet 2 and the negative electrode sheet 5.

  First, as the positive electrode sheet 2 and the negative electrode sheet 5, the above-described long and belt-like electrode sheet 3 is obtained (FIGS. 1 and 2). The long positive electrode sheet 2, the negative electrode sheet 5, and the separator 4 are prepared in a rolled state. The roll-shaped positive electrode sheet 2, the separator 4 (4a, 4b), and the negative electrode sheet 5 are sent in the direction of arrow L toward the wound electrode group winding shaft 80 of the winding portion 81 as follows (FIG. 4 ( b)). First, the wound electrode group winding shaft 80 rotates in the T direction so that the separator 4a, the negative electrode sheet 2, and further the separator 4b are arranged on the innermost side with respect to the wound electrode group winding shaft 80. These are wound around (FIG. 4B). In this case, the outer peripheral surface of the separator 4b and the separator 4a face each other, but the positive electrode sheet 2 is sent out between the outer peripheral surface of the separator 4b and the separator 4a. Then, in the state in which the positive electrode sheet 2, the separator 4a, the negative electrode sheet 5, and the separator 4b overlap each other in the radial direction (inside and outside direction) of the wound product, A state of being wound is formed. Then, the positive electrode sheet 2, the separator 4a, the negative electrode sheet 2, and the separator 4b are repeated in this order while being wound around the wound electrode group winding shaft 80 so that they are overlapped with each other. When it is wound around the winding electrode group winding shaft 80 a predetermined number of times, the positive electrode sheet 2 is cut. The separators 4 a and 4 b and the negative electrode sheet 5 are further wound around the wound electrode group take-up shaft 80 until they are arranged at the outer peripheral position than the positive electrode sheet 2. And the negative electrode sheet 5 is cut | disconnected and separator 4a, 4b is further cut | disconnected. Thus, a wound product constituting the battery, that is, a wound electrode group 1 is obtained. A separator 4 a or a separator 4 b is interposed between the positive electrode sheet 2 and the negative electrode sheet 5 in the wound electrode group 1.

  The separator 4 is not particularly limited as long as it can insulate the positive electrode sheet 2 and the negative electrode sheet 5 and can pass predetermined ions when immersed in a predetermined electrolytic solution. In particular, in addition to woven fabrics and non-woven fabrics, fine porous membranes made of synthetic resin can be used. As the separator 4, a microporous film made of a synthetic resin is particularly preferably used. Among them, a polyolefin-based microporous film is a microporous film made of another synthetic resin with respect to thickness, strength of the film itself, film resistance, and the like. It is preferably used because it is superior to the porous membrane. As the polyolefin-based microporous membrane, specifically, a microporous membrane made of polyethylene and polypropylene, or a microporous membrane in which these are combined is used.

  The shape of the wound electrode group 1 is not limited to the case where the cross section as shown in FIGS. 3A and 3B is spiral and the appearance is a cylindrical shape, and may be a flat shape or the like.

[Configuration of non-aqueous electrolyte secondary battery]
The wound electrode group 1 of the present invention can be used by being incorporated in a non-aqueous electrolyte secondary battery. Next, an example of a non-aqueous electrolyte secondary battery incorporating the wound electrode group 1 will be described.

  As shown in FIG. 5, the nonaqueous electrolyte secondary battery 50 is formed by accommodating the wound electrode group 1 in the battery outer casing 51 as follows.

  The battery exterior body 51 includes a battery lid 53 including an inner plate 53a and an outer plate 53b that are electrically connected, and a battery can 52. The wound electrode group 1 includes insulators 54 and 55 arranged above and below the wound electrode group 1 (the direction perpendicular to the winding direction is the vertical direction) and is housed in the battery can 52. At the upper end of the wound electrode group 1, a positive electrode lead 70 is connected to the positive electrode sheet 2 so as to be electrically energized and extends upward, and the tip of the positive electrode lead 70 is The battery cover 53 is connected to the inner plate 53a of the battery cover 53 so as to be electrically energized, and the outer plate 53b of the battery cover 53 serves as a positive electrode terminal. Further, a negative electrode lead 71 is connected to the negative electrode sheet 5 so as to be electrically energized at the lower end of the wound electrode group 1 and extends downward, and a tip of the negative electrode lead 71 is connected to the negative electrode lead 71. The bottom surface 57 of the battery can 52 is connected to the bottom surface 57 of the battery can 52 and serves as a negative electrode terminal.

  A predetermined electrolyte solution 72 is poured into the battery can 52, and the wound electrode group 1 is immersed in the electrolyte solution 72. Examples of the electrolyte solution 72 include a solution in which a supporting salt is dissolved in a solvent. When the non-aqueous electrolyte secondary battery 50 is a lithium ion battery, the electrolyte solution 72 is a non-aqueous electrolyte obtained by dissolving a solute lithium salt in an organic solvent.

Examples of the lithium salt include inorganic lithium salts such as LiClO ₄ , LiBF ₄ , LiPF ₆ , LiAsF ₆ , LiCl, and LiBr, LiB (C ₆ H ₅ ) ₄ LiN (SO ₂ CF ₃ ) ₂ , LiC (SO _{2 CF 3) 3, LiOSO 2 CF} 3, LiOSO 2 C 2 F 5, LiOSO 2 C 3 F 7, LiOSO 2 C 4 F 9, LiOSO 2 C 5 F 11, LiOSO 2 C 6 F 13, LiOSO 2 C 7 F An organic lithium salt such as ₁₅ is used.

  Examples of the organic solvent for dissolving the lithium salt include cyclic esters, chain esters, cyclic ethers, chain ethers and the like. More specifically, examples of cyclic esters include propylene carbonate, butylene carbonate, γ-butyrolactone, vinylene carbonate, 2-methyl-γ-butyrolactone, acetyl-γ-butyrolactone, and γ-valerolactone. As chain ester solvents, dimethyl carbonate, diethyl carbonate, dibutyl carbonate, dipropyl carbonate, methyl ethyl carbonate, methyl butyl carbonate, methyl propyl carbonate, ethyl butyl carbonate, ethyl propyl carbonate, butyl propyl carbonate, propionic acid alkyl ester, Examples include malonic acid dialkyl esters and acetic acid alkyl esters. Examples of the cyclic ether solvent include tetrahydrofuran, alkyltetrahydrofuran, dialkyltetrahydrofuran, alkoxytetrahydrofuran, dialkoxytetrahydrofuran, 1,3-dioxolane, alkyl-1,3-dioxolane, 1,4-dioxolane and the like. Furthermore, as the chain ether solvent, 1,2-dimethoxyethane, 1,2-diethoxyethane, diethyl ether, ethylene glycol dialkyl ether, diethylene glycol dialkyl ether, triethylene glycol dialkyl ether, tetraethylene glycol dialkyl ether, etc. It can be illustrated.

  In the non-aqueous electrolyte secondary battery 50 shown in the example of FIG. 5, a gas vent hole 74 and an explosion-proof valve body 75 are provided in the battery lid 53 as a safety device, in addition to a PTC element 73 for current interruption. A battery lid 53 is attached to the battery can 52 via a gasket 56 to seal the inside of the battery can 52. In this way, the non-aqueous electrolyte secondary battery 50 is formed.

  Note that the battery is not limited to the nonaqueous electrolyte secondary battery 50 shown in the example of FIG. 5 as long as the battery can incorporate the wound electrode group 1 of the present invention.

  The invention is illustrated in more detail using examples.

  First, various (positive electrode, negative electrode) electrode sheets were prepared as shown below.

Example 1
A positive electrode mixture layer coating solution was prepared as follows as an electrode mixture layer coating solution. 92 parts by weight of lithium cobalt oxide powder (trade name; Cellseed C-10, manufactured by Nippon Kagaku Kogyo Co., Ltd.), 1.5 parts by weight of acetylene black (trade name; Denka Black, manufactured by Denki Kagaku Kogyo Co., Ltd.) and graphite (TIMCAL) Manufactured, trade name: TIMCAL-KS-15) 1.5 parts by weight and 12% N-methylpyrrolidone solution of polyvinylidene fluoride (manufactured by Kureha Chemical Industry Co., Ltd., KF polymer L # 1120) 41.7 parts by weight (solid content) 7 equivalent to 7 parts by weight) was kneaded with a planetary mixer, and N-methylpyrrolidone was added and dispersed for viscosity adjustment, and a positive electrode mixture layer coating solution was prepared as this dispersion.

A long aluminum foil (thickness: 15 μm) was prepared as a current collector, and a positive electrode mixture layer coating solution was applied to one surface of the aluminum foil to form a coating film, and the coating film was dried. . Furthermore, the positive electrode mixture layer coating solution was applied to the other surface of the aluminum foil to form a coating film, and the coating film was dried. At this time, the coating amount of the positive electrode mixture layer coating solution was adjusted so that the coating amount per one side of the current collector was 250 g / m ² with respect to the coating film after drying. The positive electrode mixture layer coating solution was applied to the aluminum foil such that the edge portions of the coating film were positioned on the inner side of both sides of the aluminum foil in the width direction on both sides of the aluminum foil. Furthermore, the position at which the positive electrode mixture layer coating solution is applied to the aluminum foil is determined by the “deviation width” X which is relatively determined between the positive electrode mixture layers finally formed on the front and back surfaces of the aluminum foil. The aluminum foil was adjusted so that X = 0.35 (mm) on both sides of both sides in the width direction of the aluminum foil.

  A long electrode sheet was obtained by pressing (rolling) an aluminum foil having a coating film on both sides with a roll press (pressing), and further slitting. This electrode sheet is a positive electrode sheet in which a positive electrode mixture layer is formed on both surfaces of an aluminum foil.

In addition, in the finally obtained electrode sheet, press working is performed on the density of the electrode mixture layer of the “part where the electrode mixture layer is formed on both sides of the current collector” (the electrode mixture layer on both sides of the aluminum foil). The average density Y was adjusted so that Y = 3.5 g / cm ³ .

  In the slit sheet, the electrode sheet finally obtained has a width of 200 mm as a whole, and the part where the electrode mixture layer is not formed on either side of the current collector (the uncoated region of the electrode mixture layer coating solution) The length in the width direction of the portion where the aluminum foil is exposed) is 15 mm, and the length in the width direction of the electrode mixture layers formed on both sides of the current collector is 185 mm. It was adjusted and implemented.

  In the press working, there was no change in the deviation width before and after pressing.

Example 2
An electrode sheet was produced using the same method and material as in Example 1 except that the deviation width of the positive electrode mixture layer was set to X = 1.75 (mm).

Example 3
An electrode sheet was produced using the same method and material as in Example 1 except that the displacement width of the positive electrode mixture layer was X = 3.50 (mm).

Comparative Example 1
An electrode sheet was produced using the same method and material as in Example 1 except that the deviation width of the positive electrode mixture layer was set to X = 0.00 (mm).

Example 4
A negative electrode mixture layer coating solution was prepared as follows as an electrode mixture layer coating solution. 57. 93 parts by weight of a negative electrode active material (trade name; MCMB-6-28, manufactured by Osaka Gas Chemical Company) and 12% N-methylpyrrolidone solution of polyvinylidene fluoride (manufactured by Kureha Chemical Industry Co., Ltd., KF polymer L # 1120) 3 parts by weight (corresponding to 7 parts by weight of solid content) is kneaded with a planetary mixer, and further N-methylpyrrolidone is added and dispersed for viscosity adjustment, and the negative electrode mixture coating liquid is prepared as this dispersion. It was done.

A long copper foil (thickness: 10 μm) is prepared as a current collector, a negative electrode mixture layer coating solution is applied to one surface of the copper foil to form a coating film, and the coating film is dried. did. Furthermore, the negative electrode mixture layer coating solution was applied to the other surface of the copper foil to form a coating film, and the coating film was dried. At this time, the coating amount of the negative electrode mixture layer coating solution was adjusted so that the coating amount per one side of the current collector was 110 g / m ² with respect to the coating film after drying. The negative electrode mixture layer coating solution was applied to the copper foil so that the edge portions of the coating film were located on the inner side of both sides of the copper foil in the width direction on both sides of the copper foil. Furthermore, the position where the negative electrode mixture layer coating solution is applied to the copper foil is such that the “deviation width” X, which is finally determined relatively between the negative electrode mixture layers formed on the front and back surfaces of the copper foil, is the copper foil. It was adjusted so that it might be set to X = 0.15 (mm) about both sides of the width direction both sides.

  A long foil electrode sheet was obtained by pressing (rolling) a copper foil having a coating film on both sides with a roll press (pressing) and slitting. This electrode sheet is a negative electrode sheet in which a negative electrode mixture layer is formed on both surfaces of a copper foil.

In the finally obtained electrode sheet, the press working is performed on the density of the electrode mixture layer of “the portion where the electrode mixture layer is formed on both sides of the current collector” ) Y was adjusted so that Y was 1.5 g / cm ³ .

  In the slit sheet, the electrode sheet finally obtained has a width of 200 mm as a whole, and the part where the electrode mixture layer is not formed on either side of the current collector (the uncoated region of the electrode mixture layer coating solution) The length in the width direction of the portion where the copper foil is exposed) is 10 mm, and the length in the width direction of the electrode mixture layer formed on both surfaces of the current collector is 190 mm. It was adjusted and implemented.

Example 5
An electrode sheet was produced using the same method and material as in Example 4 except that the deviation width of the negative electrode mixture layer was set to X = 0.75 (mm).

Example 6
An electrode sheet was produced using the same method and material as in Example 4 except that the displacement width of the negative electrode mixture layer was X = 1.50 (mm).

Comparative Example 2
An electrode sheet was prepared using the same method and material as in Example 4 except that the displacement width of the negative electrode mixture layer was set to X = 0.00 (mm).

  A wound electrode group was prepared using each of the electrode sheets obtained above, and the state of the wound electrode group was evaluated.

(Production of wound electrode group)
Examples 1 to 3, a negative electrode sheet (negative electrode dummy electrode sheet) opposed to the positive electrode sheet of Comparative Example 1 via a separator, and Examples 4 to 6 and a negative electrode sheet of Comparative Example 2 via a separator A positive electrode sheet (positive electrode dummy electrode sheet) opposed to each other was produced as follows.

  An electrode sheet was prepared using the same method and material as in Example 4 except that the electrode mixture layer for the negative electrode was formed on both sides of the copper foil and the entire width direction of the copper foil (width of the electrode sheet; 200 mm). And this electrode sheet was used as a negative electrode dummy electrode sheet.

  An electrode sheet was prepared using the same method and material as in Example 1 except that the electrode mixture layer for the positive electrode was formed on both surfaces of the aluminum foil and in the entire width direction of the aluminum foil (width of the electrode sheet; 200 mm). And this electrode sheet was used as a positive electrode dummy electrode sheet.

The negative electrode dummy electrode sheet and the positive electrode dummy electrode sheet were not substantially distorted.

  The above-described negative electrode dummy electrode sheets were faced to each of the positive electrode sheets of Examples 1 to 3 and Comparative Example 1 through a separator and wound to produce a wound electrode group. The above-mentioned positive electrode dummy electrode sheet was faced through each separator with respect to each of the negative electrode sheets of Examples 4 to 6 and Comparative Example 2, and wound to produce a wound electrode group. In addition, the winding process was performed by performing the winding for each of the electrode sheets of Examples 1 to 6 and Comparative Examples 1 and 2 until each electrode sheet was used 2.5 m in the longitudinal direction. .

(Evaluation of wound electrode group)
Evaluation was performed by the presence or absence and the frequency | count of the fracture | rupture of the electrode sheet in the winding process. The process of producing the wound electrode group using the electrode sheets of Examples 1 to 6 and Comparative Examples 1 and 2 was performed 100 times, and the winding process was performed 100 times. The evaluation was performed by accumulating the number of times the electrode sheet was broken in the 100 winding steps. The results are shown in Table 1.

DESCRIPTION OF SYMBOLS 1 Winding electrode group 2 Positive electrode sheet 3 Electrode sheet 4 Separator 5 Negative electrode sheet 6 Current collector 7 Electrode mixture layer 8 Edge 16 Current collector for positive electrode 17 Electrode mixture layer for positive electrode 26 Current collector for negative electrode Body 27 Electrode mixture layer for negative electrode 30 Electrode sheet forming body

Claims (4)

An electrode sheet in which a first electrode mixture layer and a second electrode mixture layer are respectively formed on one side and the other side of a long current collector made of a metal foil,
The portion where the metal foil is exposed and neither the first electrode mixture layer nor the second electrode mixture layer is formed on at least one side of the side edges of the current collector along the longitudinal direction of the current collector An electrode mixture layer non-formation part formed continuously on the both sides of the current collector in the longitudinal direction of the current collector,
When viewed in the thickness direction of the electrode sheet, the first electrode mixture layer and the second electrode mixture layer have the formation position of the edge portion closer to the electrode mixture layer non-forming portion in each, It is formed so as to be shifted from each other in the short direction of the current collector,
An electrode sheet, wherein the first electrode mixture layer and the second electrode mixture layer are formed so as to satisfy the following (Equation 1).
(Equation 1) 0.1 ≦ X / Y ≦ 1.0
(However, X is the second electrode mixture closer to the edge portion of the first electrode mixture layer and the electrode mixture layer non-formed portion closer to the electrode mixture layer non-formed portion. Deviation width (mm) between edge portions of layers, Y is an average density (g / cm ³ ) of the electrode mixture layer formed on both surfaces of the current collector A positive electrode sheet in which a positive electrode mixture layer was formed on both sides of a positive electrode current collector made of metal foil, and a negative electrode mixture layer was formed on both sides of the negative electrode current collector made of metal foil. A negative electrode sheet is a wound electrode group that is faced and wound through a separator,
A wound electrode group in which the electrode sheet according to claim 1 is used as a positive electrode sheet and / or a negative electrode sheet.   A nonaqueous electrolyte secondary battery comprising the wound electrode group according to claim 2 housed in a battery outer package. A method for producing an electrode sheet in which a first electrode mixture layer and a second electrode mixture layer are formed on one side and the other side of a current collector made of metal foil, respectively,
An electrode mixture layer coating solution containing an electrode active material is applied to a predetermined region inside the side edge of the current collector along the longitudinal direction of the current collector on the current collector surface to form a coating film, A coating and drying step in which an electrode sheet formed body is formed by drying the coating film;
A pressing step of pressing a predetermined portion of the electrode sheet forming body in the thickness direction of the electrode sheet forming body, and
In the coating and drying step, by applying an electrode mixture layer coating solution, a first coating film and a second coating film as a coating film are formed on one side and the other side of the current collector, respectively, At least one of the side edges of the current collector along the longitudinal direction of the current collector is a portion where the metal foil is exposed and neither the first coating film nor the second coating film is formed. When a non-formed part formed continuously in the longitudinal direction of the current collector is formed on both surfaces of the electrode sheet, and when viewed in the thickness direction of the electrode sheet formed body, the first one closer to the non-formed part The side edge of the second coating film closer to the side edge of the coating film and the non-formed part is formed at a position shifted from each other in the short direction of the current collector,
In the pressing step, a portion of the electrode sheet forming body forming both the first coating film and the second coating film is pressed, and the first electrode mixture layer and the second electrode mixture layer are pressed. Is formed as a layer satisfying the following (Equation 2).
(Expression 2) 0.1 ≦ X / Y ≦ 1.0
(However, X represents the edge of the first electrode mixture layer closer to the side edge of the side edge of the current collector where the metal foil is exposed and the second electrode combination. Deviation width (mm) between the edge of the agent layer and Y is the average density (g / cm ³ ) of the electrode mixture layer formed on both sides of the current collector

Images