JP2016018681A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte secondary battery which allows less entry of foreign matters therein.SOLUTION: A nonaqueous electrolyte secondary battery comprises: electrode sheets 206, 207 composed of e.g. a positive electrode sheet and a negative electrode sheet. The electrode sheets 206, 207 are each composed of an electrode sheet having a belt-shaped collector foil 201, and an active material layer 204 or 205 formed on the collector foil 201, in which the active material layers 204 and 205 are each formed on the collector foil 201 except an exposed part 202 or 203 provided along an edge of the collector foil 201 on one side in a widthwise direction thereof. The active material layers 204 and 205 are each composed of a mold arranged by molding of powder of granulated particles including at least active material particles and a binder. Edges of the active material layers 204 and 205 are not cut out on both sides in a widthwise direction thereof.SELECTED DRAWING: Figure 9

Description

  The present invention relates to a non-aqueous electrolyte secondary battery. Here, in the present specification, the “secondary battery” refers to a battery that can be repeatedly charged. “Nonaqueous electrolyte secondary battery” refers to a secondary battery using a nonaqueous electrolyte composed of a nonaqueous solvent in which an electrolyte salt is dissolved. “Lithium ion secondary battery”, which is a kind of “non-aqueous electrolyte secondary battery”, uses lithium ions as electrolyte ions, and is a secondary in which charge and discharge are realized by the movement of charges associated with lithium ions between positive and negative electrodes A battery.

  For example, JP-A-2005-340188 discloses granulated particles for anode and granulated particles for cathode. The granulated particles for the anode are granulated particles obtained by binding particles containing an active material with a binder containing conductive auxiliary particles. The granulated particles for the cathode are granulated particles prepared by respectively forming particles containing an active material with a binder containing conductive auxiliary particles, and formed for the cathode. Then, these granulated particles are laminated on an anode or cathode current collector, respectively, and these laminates are hot-rolled so that an anode or cathode current collector has an active material layer, respectively. Is formed.

  Further, for example, as disclosed in JP 2010-225291 A, in a non-aqueous electrolyte secondary battery, a positive electrode sheet and a negative electrode sheet are each formed into a strip-shaped electrode sheet, and an active material along the longitudinal direction thereof. A form in which a layer is formed is known. In such a form, an exposed portion where the current collector is exposed is set along one side in the width direction of the electrode sheet. And the active material layer is formed in the longitudinal direction of the sheet along the opposite side of the width direction of the electrode sheet except for the exposed portion. Here, the exposed portion is a portion where the active material layer is not formed, and may be referred to as an active material layer non-formed portion. Moreover, the area | region (area | region set as an exposed part) in which an active material layer is not formed among current collection foil is also called an active material layer non-formation area | region.

JP-A-2005-340188 JP 2010-225291 A

  By the way, in the nonaqueous electrolyte secondary battery, the electrode sheet has a band shape, and an exposed portion where the current collector is exposed is set along one side in the width direction, and the opposite side in the width direction except for the exposed portion. There is a form in which an active material layer is formed along the longitudinal direction of the sheet. In this form, when producing an electrode sheet, for example, an electrode sheet having a width of two strips is prepared, and then slit (cut) in the longitudinal direction to produce two single-width electrode sheets. At this time, when the active material layer is cut, the cutting powder may be included in the non-aqueous electrolyte secondary battery as a foreign substance. Further, when the active material layer is formed by powder molding, there is a tendency that a large amount of foreign matter is generated when the active material layer is cut. Forming the active material layer by powder molding has various advantages, but on the other hand, it is desirable that the foreign matter contained in the nonaqueous electrolyte secondary battery is as few as possible.

  The proposed nonaqueous electrolyte secondary battery includes a strip-shaped current collector foil and an active material layer formed on the current collector foil. The active material layer is formed except for an exposed portion provided along an edge on one side in the width direction of the current collector foil. The active material layer is a molded body in which the powder of granulated particles including at least active material particles and a binder is formed. None of the edges on both sides in the width direction of the active material layer is cut. Here, the edges on both sides in the width direction of the active material layer are not cut, and foreign substances resulting from the cut of the active material layer are hardly included.

  Here, the edge of the current collector foil on the side where the exposed portion is provided in the width direction of the current collector foil may be cut after the active material layer is formed. The edge of the current collector foil on the side where the active material layer is formed in the width direction of the current collector foil is cut before the active material layer is formed. In addition, the electrode sheet proposed here is a strip-shaped current collector foil, an exposed portion set in the middle in the width direction of the strip-shaped current collector foil, and the width of the strip-shaped current collector foil excluding the exposed portion. The active material layer in which the powder of the granulated particle which contains an active material particle and a binder at least is shape | molded is provided in the area | region of the both sides of a direction. In such an electrode sheet, for example, an exposed portion set in an intermediate portion in the width direction of the belt-shaped current collector foil may be cut at a center portion in the width direction. Thus, an active material layer in which an exposed portion is provided on one side in the width direction of the current collector foil, and excluding the exposed portion, a powder of granulated particles including at least active material particles and a binder is formed. The provided two strip-shaped electrode sheet is obtained.

FIG. 1 is a cross-sectional view showing a lithium ion secondary battery. FIG. 2 is a diagram showing an electrode body incorporated in a lithium ion secondary battery. FIG. 3 is a diagram illustrating a process of applying a composite paste containing active material particles to a current collector foil. FIG. 4 is a diagram showing a step of pressing a layer (active material layer) of the composite paste applied to the current collector foil and dried. FIG. 5 is a diagram showing a step of cutting the current collector foil on which the layer (active material layer) of the composite paste is formed. FIG. 6 is a schematic view schematically showing the granulated particles 240 obtained here. FIG. 7 is a diagram illustrating a process in which a powder of granulated particles in which a binder component is attached to active material particles is deposited on a current collector foil. FIG. 8 is a diagram showing a step of pressing the deposited layer (active material layer) deposited on the current collector foil. FIG. 9 is a diagram illustrating a process of cutting the current collector foil on which the deposited layer (active material layer) is formed.

  Hereinafter, an embodiment of the proposed nonaqueous electrolyte secondary battery will be described. The embodiments described herein are, of course, not intended to limit the present invention in particular. Each drawing is schematically drawn. For example, the dimensional relationship (length, width, thickness, etc.) in each drawing does not reflect the actual dimensional relationship. Moreover, the same code | symbol is attached | subjected to the member and site | part which show | plays the same effect | action, and the overlapping description is abbreviate | omitted or simplified suitably.

  Here, first, a lithium ion secondary battery 10 is taken as an example of a nonaqueous electrolyte secondary battery, and a structural example of the lithium ion secondary battery 10 that can be applied will be described. Then, the structure proposed here about the lithium ion secondary battery 10 is demonstrated.

<< Lithium ion secondary battery 10 >>
FIG. 1 is a cross-sectional view showing a lithium ion secondary battery 10. FIG. 2 is a diagram showing an electrode body 40 housed in the lithium ion secondary battery 10. Note that the lithium ion secondary battery 10 shown in FIGS. 1 and 2 is merely an example of a lithium ion secondary battery to which the present invention can be applied, and is a lithium ion secondary battery to which the present invention can be applied. There is no particular limitation.

  As shown in FIG. 1, the lithium ion secondary battery 10 includes a battery case 20 and an electrode body 40 (in FIG. 1, a wound electrode body).

<Battery case 20>
The battery case 20 includes a case body 21 and a sealing plate 22. The case body 21 has a box shape having an opening at one end. Here, the case main body 21 has a bottomed rectangular parallelepiped shape in which one surface corresponding to the upper surface in the normal use state of the lithium ion secondary battery 10 is opened. In this embodiment, the case body 21 is formed with a rectangular opening. The sealing plate 22 is a member that closes the opening of the case body 21. The sealing plate 22 is a rectangular plate. The sealing plate 22 is welded to the peripheral edge of the opening of the case body 21 to form a substantially hexahedral battery case 20.

  As the material of the battery case 20, for example, a battery case 20 mainly composed of a metal material that is lightweight and has good thermal conductivity can be preferably used. Examples of such a metal material include aluminum, stainless steel, nickel-plated steel, and the like. The battery case 20 (case body 21 and sealing plate 22) according to the present embodiment is made of aluminum or an alloy mainly composed of aluminum.

  In the example shown in FIG. 1, a positive electrode terminal 23 (external terminal) and a negative electrode terminal 24 (external terminal) for external connection are attached to the sealing plate 22. A safety valve 30 and a liquid injection port 32 are formed on the sealing plate 22. The safety valve 30 is configured to release the internal pressure when the internal pressure of the battery case 20 rises to a predetermined level (for example, a set valve opening pressure of about 0.3 MPa to 1.0 MPa) or more. Further, FIG. 1 shows a state in which the injection port 32 is sealed with a sealing material 33 after the electrolyte solution 80 is injected. An electrode body 40 is accommodated in the battery case 20.

<< Electrode body 40 (winding electrode body) >>
As shown in FIG. 2, the electrode body 40 includes a strip-shaped positive electrode (positive electrode sheet 50), a strip-shaped negative electrode (negative electrode sheet 60), and strip-shaped separators (separators 72 and 74).

<< Positive electrode sheet 50 >>
The positive electrode sheet 50 includes a strip-shaped positive electrode current collector foil 51 and a positive electrode active material layer 53. For the positive electrode current collector foil 51, a metal foil suitable for the positive electrode can be suitably used. For the positive electrode current collector foil 51, for example, a strip-shaped aluminum foil having a predetermined width and a thickness of about 15 μm can be used. An exposed portion 52 is set along the edge portion on one side in the width direction of the positive electrode current collector foil 51. In the illustrated example, the positive electrode active material layer 53 is formed on both surfaces of the positive electrode current collector foil 51 except for the exposed portion 52 set on the positive electrode current collector foil 51. Here, the positive electrode active material layer 53 is held by the positive electrode current collector foil 51 and contains at least a positive electrode active material.

As the positive electrode active material, one type or two or more types of materials conventionally used in lithium ion batteries can be used without particular limitation. As a preferred example, an oxide containing lithium and a transition metal element as constituent metal elements such as lithium nickel oxide (for example, LiNiO ₂ ), lithium cobalt oxide (for example, LiCoO ₂ ), and lithium manganese oxide (for example, LiMn ₂ O ₄ ). And a phosphate containing lithium and a transition metal element as constituent metal elements, such as lithium oxide (lithium transition metal oxide), lithium manganese phosphate (LiMnPO ₄ ), and lithium iron phosphate (LiFePO ₄ ). The positive electrode active material is used in the form of particles and can be appropriately referred to as positive electrode active material particles.

<< Negative Electrode Sheet 60 >>
As shown in FIG. 2, the negative electrode sheet 60 includes a strip-shaped negative electrode current collector foil 61 and a negative electrode active material layer 63. For the negative electrode current collector foil 61, a metal foil suitable for the negative electrode can be suitably used. As the negative electrode current collector foil 61, a strip-shaped copper foil having a predetermined width and a thickness of about 10 μm is used. On one side of the negative electrode current collector foil 61 in the width direction, an exposed portion 62 is set along the edge portion. The negative electrode active material layer 63 is formed on both surfaces of the negative electrode current collector foil 61 except for the exposed portion 62 set on the negative electrode current collector foil 61. The negative electrode active material layer 63 is held by the negative electrode current collector foil 61 and contains at least a negative electrode active material.

  As the negative electrode active material, one type or two or more types of materials conventionally used in lithium ion batteries can be used without any particular limitation. Preferable examples include carbon-based materials such as graphite carbon and amorphous carbon, lithium transition metal oxides, lithium transition metal nitrides, and the like. The negative electrode active material is used in the form of particles and can be appropriately referred to as negative electrode active material particles. The positive electrode active material particles and the negative electrode active material particles described above can be appropriately referred to as active material particles. Moreover, the positive electrode active material particles and the negative electrode active material particles can be appropriately used in powder form.

  Here, the positive electrode active material layer 53 and the negative electrode active material layer 63 may appropriately include a conductive material, a binder, and a thickener.

<Conductive material>
Examples of the conductive material include carbon materials such as carbon powder and carbon fiber. One kind selected from such conductive materials may be used alone, or two or more kinds may be used in combination. Examples of the carbon powder include acetylene black, oil furnace black, graphitized carbon black, carbon black, graphite, and ketjen black.

<Binder, thickener>
Further, the binder adheres the positive electrode active material and the conductive material particles contained in the positive electrode active material layer 53, or adheres these particles and the positive electrode current collector foil 51. As such a binder, a polymer that can be dissolved or dispersed in a solvent to be used can be used. For example, in an aqueous solvent, fluororesin (for example, polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), etc.), rubbers (styrene butadiene copolymer (SBR), acrylic, etc. A water-soluble or water-dispersible polymer such as an acid-modified SBR resin (SBR latex) or the like, polyvinyl alcohol (PVA), a vinyl acetate copolymer, or an acrylate polymer can be preferably used. In the non-aqueous solvent, a polymer (polyvinylidene fluoride (PVDF), polyvinylidene chloride (PVDC), polyacrylonitrile (PAN) or the like) can be preferably used. As the thickener, a cellulose polymer such as carboxymethylcellulose (CMC) or hydroxypropylmethylcellulose (HPMC) is preferably used.

<< Separators 72, 74 >>
As shown in FIG. 2, the separators 72 and 74 are members that separate the positive electrode sheet 50 and the negative electrode sheet 60. In this example, the separators 72 and 74 are made of a strip-shaped sheet material having a predetermined width and having a plurality of minute holes. For the separators 72 and 74, a porous film made of a resin, for example, a separator having a single layer structure or a separator having a laminated structure made of a porous polyolefin resin can be used. In this example, the width b1 of the negative electrode active material layer 63 is slightly wider than the width a1 of the positive electrode active material layer 53, as shown in FIG. Furthermore, the widths c1 and c2 of the separators 72 and 74 are slightly wider than the width b1 of the negative electrode active material layer 63 (c1, c2>b1> a1).

  The separators 72 and 74 insulate the positive electrode active material layer 53 and the negative electrode active material layer 63 and allow the electrolyte to move. Although not shown, the separators 72 and 74 may have a heat-resistant layer formed on the surface of a base material made of a plastic porous film. The heat-resistant layer is composed of a filler and a binder. The heat-resistant layer is also referred to as HRL (Heat Resistance Layer).

<< Attachment of electrode body 40 >>
In this embodiment, as shown in FIG. 2, the electrode body 40 is flatly pushed and bent along one plane including the winding axis WL. In the example shown in FIG. 2, the exposed portion 52 of the positive electrode current collector foil 51 and the exposed portion 62 of the negative electrode current collector foil 61 are spirally exposed on both sides of the separators 72 and 74, respectively. As shown in FIG. 1, the electrode body 40 has positive and negative exposed portions 52 and 62 protruding from the separators 72 and 74, and tip portions 23 a and 24 a in which the positive and negative electrode terminals 23 and 24 are disposed inside the battery case 20. It is welded to.

  In the form shown in FIG. 1, a flat wound electrode body 40 is accommodated in the battery case 20 along one plane including the winding axis WL. An electrolyte is further injected into the battery case 20. The electrolytic solution 80 enters the electrode body 40 from both axial sides of the winding shaft WL (see FIG. 2).

<< Electrolytic solution (liquid electrolyte) >>
As the electrolytic solution 80, the same non-aqueous electrolytic solution conventionally used in lithium ion batteries can be used without particular limitation. Such a nonaqueous electrolytic solution typically has a composition in which a supporting salt is contained in a suitable nonaqueous solvent. Examples of the non-aqueous solvent include ethylene carbonate (hereinafter referred to as “EC” as appropriate), propylene carbonate, dimethyl carbonate (hereinafter referred to as “DMC” as appropriate), diethyl carbonate, and ethyl methyl carbonate (hereinafter referred to as appropriate). 1), 1,2-dimethoxyethane, 1,2-diethoxyethane, tetrahydrofuran, 1,3-dioxolane, or the like. Examples of the supporting salt include LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiCF ₃ SO ₃ , LiC ₄ F ₉ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiC (CF ₃ SO ₂ ) _{3 and the} like. Lithium salts can be used. As an example, a nonaqueous electrolytic solution in which LiPF ₆ is contained at a concentration of about 1 mol / L in a mixed solvent of ethylene carbonate and diethyl carbonate (for example, a volume ratio of 1: 1) can be mentioned.

  FIG. 1 schematically shows the electrolytic solution 80 injected into the battery case 20, and does not strictly indicate the amount of the electrolytic solution 80 injected into the battery case 20. In addition, the electrolytic solution 80 injected into the battery case 20 sufficiently permeates the voids of the positive electrode active material layer 53 and the negative electrode active material layer 63 in the wound electrode body 40.

  The positive electrode current collector foil 51 and the negative electrode current collector foil 61 of the lithium ion secondary battery 10 are electrically connected to an external device through electrode terminals 23 and 24 penetrating the battery case 20. Hereinafter, the operation of the lithium ion secondary battery 10 during charging and discharging will be described.

<Operation during charging>
During charging, the lithium ion secondary battery 10 is applied with a voltage between the positive electrode sheet 50 and the negative electrode sheet 60, and lithium ions (Li) are released from the positive electrode active material in the positive electrode active material layer 53 to the electrolyte. The charge is released from the positive electrode active material layer 53. In the negative electrode sheet 60, electric charges are stored, and lithium ions (Li) in the electrolytic solution are absorbed and stored in the negative electrode active material in the negative electrode active material layer 63. Thereby, a potential difference is generated between the negative electrode sheet 60 and the positive electrode sheet 50.

<Operation during discharge>
At the time of discharging, the lithium ion secondary battery 10 is charged with electric charge from the negative electrode sheet 60 to the positive electrode sheet 50 due to a potential difference between the negative electrode sheet 60 and the positive electrode sheet 50, and the lithium ions stored in the negative electrode active material layer 63 are electrolyzed. Released into the liquid. In the positive electrode, lithium ions in the electrolytic solution are taken into the positive electrode active material in the positive electrode active material layer 53.

  Thus, in the charge / discharge of the lithium ion secondary battery 10, lithium ions are occluded or released in the positive electrode active material in the positive electrode active material layer 53 and the negative electrode active material in the negative electrode active material layer 63. Then, lithium ions travel between the positive electrode active material layer 53 and the negative electrode active material layer 63 via the electrolytic solution.

  By the way, the positive electrode sheet and the negative electrode sheet of the non-aqueous electrolyte secondary battery have an electrode active material layer formed on, for example, two sheets in order to improve productivity and ensure quality. . And the sheet | seat in which the said electrode active material layer was formed was cut | disconnected along the longitudinal direction, and two 1 sheet | seat sheets are obtained.

<< Manufacturing process of active material layer using composite paste >>
The positive electrode active material layer 53 and the negative electrode active material layer 63 (see FIG. 2) are prepared by, for example, preparing a composite paste containing positive electrode active material particles or negative electrode active material particles, a binder, a thickener, and the like. It can be molded by applying to a current collector foil, drying and pressing.

  Here, FIG. 3 to FIG. 5 are diagrams for explaining a manufacturing process in a case where a mixture paste containing active material particles is applied to a current collector foil, dried and pressed to obtain an electrode sheet. FIG. 3 shows a process of applying a composite paste containing active material particles to a current collector foil. FIG. 4 shows a step of pressing the layer (active material layer) of the composite paste applied to the current collector foil and dried. FIG. 5 shows a step of cutting the current collector foil on which the layer (active material layer) of the composite paste is formed.

  When preparing the composite paste and applying it to the current collector foil, if the composite paste is applied to the edge of the current collector foil, the edge of the composite paste gradually becomes thicker toward the edge of the current collector foil. Inclined to decrease. That is, the edge of the composite paste applied to the current collector foil is maintained by the surface tension of the paste, and has an inclined thickness shape. When the edge of the composite paste applied to the edge of the current collector foil has an inclined thickness, the basis weight and density of the active material layer formed on the edge of the current collector foil deviate from the design value. It is desirable that the active material layer formed on the edge of the current collector foil be as close to the design value as possible in terms of the basis weight and density. When the active material layer is formed by applying the composite paste, applying the composite paste to the edge of the current collector foil makes the basis weight and density of the active material layer in the part as close as possible to the design value. Is not appropriate in terms of

  For this reason, for example, as shown in FIG. 3, a current collector foil 101 having a width corresponding to two strips is prepared, and exposed portions 102 and 103 are respectively set on both sides in the width direction of the current collector foil 101. The composite paste 104 is applied to an intermediate portion excluding the exposed portions 102 and 103. In this case, the composite paste 104 is applied to an intermediate portion in the width direction of the current collector foil 101 and is not applied to the edge of the current collector foil 101. In this case, the mixture paste 104 is applied at an appropriate thickness in an intermediate portion excluding the edges 104a and 104b on the exposed portions 102 and 103 side. Note that the edges 104a and 104b on the exposed portions 102 and 103 side of the mixture paste 104 have an inclined thickness shape in which the thickness of the mixture paste 104 gradually decreases. The layer of the applied composite paste 104 is dried and pressed as shown in FIG. 4 to form the active material layer 104. Here, the active material layer 104 is formed on one surface of the current collector foil 101, but thereafter, the active material layer 104 is also formed on the opposite surface of the current collector foil 101 by the same method. Then, as shown in FIG. 5, the current collector foil 101 and the coated active material layer 104 are cut in the length direction along the center in the width direction of the current collector foil 101. As a result, exposed portions 102 and 103 are provided along one edge in the width direction of the current collector foil 101, and the active material layer 104 is formed on both surfaces of the current collector foil 101 except for the exposed portions 102 and 103. Thus, two striped electrode sheets 105 and 106 are obtained.

  As described above, when the active material layer 104 is formed by applying the composite paste 104 to the current collector foil 101, drying, and pressing, the following problems are raised. The composite paste 104 cannot be applied along the edge in the width direction of the current collector foil 101. For this reason, as shown in FIG. 3, the exposed portions 102 and 103 are set at the edge in the width direction of the current collector foil, and the mixture paste 104 is applied to the center portion in the width direction of the current collector foil. In this case, the edge 104b of the active material layer 104 has an inclined shape in which the thickness of the active material layer 104 is gradually reduced. That is, the thickness cannot be kept substantially constant at the edge 104b of the active material layer 104. Moreover, a lot of energy is required to dry the composite paste 104. In addition, since it is necessary to cut the formed active material layer 104 after pressing, foreign matter derived from the active material layer 104 is likely to be generated.

  As shown in FIG. 4, when pressing the electrode sheet 100 on which the active material layer 104 is formed, for example, the electrode sheet 100 is sandwiched and pressed by rolling rolls 151 and 152. In this case, the portion where the active material layer 104 is molded is pressed with a greater force during pressing than the exposed portions 102 and 103 where the active material layer 104 is not formed. In order to increase the density of the active material particles, the formed active material layer 104 is pressed at a higher pressure. For this reason, when the density is increased, the elongation of the current collector foil 101 may be significantly different between the portion where the active material layer 104 is molded and the exposed portions 102 and 103. For this reason, a wrinkle may arise in an electrode sheet resulting from the stress difference which arises in the current collection foil 101 at the time of a press. Such wrinkles become prominent, for example, when the press pressure is increased to increase the density.

<< Process for producing active material layer using powder >>
On the other hand, the present inventor is considering forming the positive electrode active material layer 53 and the negative electrode active material layer 63 (see FIG. 2) by powder molding for such a nonaqueous electrolyte secondary battery. In this case, a powder of granulated particles containing active material particles and a binder is prepared. FIG. 6 schematically shows the granulated particles 240 obtained here.

  The granulated particles 240 prepared here may include at least active material particles 241 and a binder 242 as shown in FIG. The powder 220 of the granulated particles 240 is obtained, for example, by granulating a mixture (suspension) in which the active material particles 241 and the binder 242 are mixed with a solvent by a spray drying method. In the spray dry manufacturing method, the mixture is sprayed in a dry atmosphere. At this time, the particles contained in the sprayed droplets are roughly granulated as one lump. For this reason, the amount of solid content contained in the granulated particles 240 varies depending on the size of the droplets, and the size and mass of the granulated particles 240 vary. The droplets to be sprayed preferably include at least active material particles 241 and a binder 242. The droplets to be sprayed may contain materials other than the active material particles 241 and the binder 242, and may contain, for example, a conductive material or a thickener. The granulated particles 240 prepared here may have, for example, an average particle size of about 60 μm to 100 μm. In the present specification, unless otherwise specified, the “average particle size” means a particle size at an integrated value of 50% in a particle size distribution measured based on a particle size distribution measuring apparatus based on a laser scattering / diffraction method, that is, 50%. It shall mean the volume average particle diameter.

<Active material particles 241>
The electrode manufacturing method proposed here can be applied to various electrodes. For example, a lithium ion secondary battery can be applied to both a positive electrode and a negative electrode. The active material particles 241 included in the granulated particles 240 differ depending on the electrodes to be produced. For example, when manufacturing an electrode for a positive electrode of a lithium ion secondary battery, the active material particles used for the positive electrode are used as the active material particles 241. Moreover, when manufacturing the electrode for negative electrodes of a lithium ion secondary battery, the active material particle used for the said negative electrode is used.

  Then, a layer of active material particles (electrode active material layer) adhered on the current collector foil by depositing, molding and pressing the powder of such granulated particles on the current collector foil. Can be molded. As another method, a layer of active material particles (electrode active material layer) attached on the current collector foil is obtained by depositing the powder on a roller and transferring the powder to the current collector foil. Can be molded. In the process of forming from the granulated particle powder, such a drying step is unnecessary or simplified, and the manufacturing equipment can be simplified. Moreover, since the fuel cost required in the drying process can be suppressed, the manufacturing cost can be suppressed low.

《Proposal of new structure》
Here, a novel structure of a non-aqueous electrolyte secondary battery using such powder molding is proposed.

  The proposed nonaqueous electrolyte secondary battery includes a strip-shaped current collector foil and an active material layer formed on the current collector foil. The current collector foil has an active material layer formed except for an exposed portion provided along one edge in the width direction. The active material layer is a molded body in which a powder of granulated particles including active material particles and a binder is molded, and the edges on both sides in the width direction of the active material layer are not cut.

<New electrode sheet manufacturing process>
FIG. 7 to FIG. 9 are diagrams for explaining a manufacturing process of electrode sheets (positive electrode sheet and negative electrode sheet) of the nonaqueous electrolyte secondary battery proposed here. FIG. 7 shows a process in which a powder of granulated particles containing active material particles and a binder is deposited on a current collector foil. FIG. 8 shows a step of pressing the deposited layer (active material layer) deposited on the current collector foil. FIG. 9 shows a step of cutting the current collector foil on which the deposited layer (active material layer) is formed.

  In the manufacturing process of the electrode sheet of the nonaqueous electrolyte secondary battery proposed here, a current collector foil 201 having a width corresponding to two strips is prepared as shown in FIG. Here, the current collector foil 201 has a current collector foil 201 having a width corresponding to two strips. Separately, a powder of granulated particles used when forming the active material layers (deposited layers 204 and 205) is prepared. Here, for example, a powder of granulated particles including at least active material particles and a binder is prepared.

  For example, here, as the electrode sheet, the positive electrode sheet 50 or the negative electrode sheet 60 (see FIG. 1 or 2) used for the wound electrode body 40 of the nonaqueous electrolyte secondary battery can be produced. When the positive electrode sheet 50 is produced, a powder of granulated particles including at least positive electrode active material particles and a binder is prepared as active material particles. Moreover, when producing the negative electrode sheet 60, the powder of the granulated particle which contains at least a negative electrode active material particle and a binder as an active material particle is prepared. The powder of the granulated particles prepared here may appropriately contain conductive material particles.

  In the central portion of the current collector foil 201 in the width direction, regions where no active material layer is formed (active material layer non-forming regions) are set in regions corresponding to the exposed portions 202 and 203 of the electrode sheet 200, respectively. Then, the deposited layers 204 and 205 are formed on both sides in the width direction of the current collector foil 201 excluding the active material layer non-formation regions (202 and 203), respectively. On the deposited layers 204 and 205, powder of granulated particles is deposited at a predetermined thickness.

  Next, the deposited layers 204 and 205 (active material layers) formed on both sides in the width direction of the current collector foil 201 are pressed. At this time, as shown in FIG. 8, the deposited layers 204 and 205 may be pressed in a state where guides 261 to 263 are provided at the edges of the deposited layers 204 and 205. In the form shown in FIG. 8, guides 261 to 263 that support the edges of the deposited layers 204 and 205 are provided on one of the rolling rolls 251 and 252. Here, as shown in FIG. 8, the guides 261 to 263 are arranged from the outer peripheral surface of the rolling roll 251 at predetermined positions in the axial direction of the rolling roll 251 (positions corresponding to the edges of the deposited layers 204 and 205). It is exciting.

  Here, the edges 261a and 263a of the guides 261 and 263 provided on both sides in the axial direction of the rolling roll 251 are the outer edges 204b and 205b of the deposited layers 204 and 205 along the both side edges in the width direction of the current collector foil. Support. More specifically, the edges 261 a and 263 a of the guides 261 and 263 support the side surfaces of the outer edges 204 b and 205 b of the deposited layers 204 and 205. Further, the edges 262a and 262b of the guide 262 provided on both sides in the axial direction of the rolling roll 251 support the inner edges 204a and 205a of the deposited layers 204 and 205 along the intermediate portion in the width direction of the current collector foil. ing. More specifically, the edges 262a, 262b of the guide 262 support the side surfaces of the inner edges 204a, 205a of the deposited layers 204, 205. Further, the deposited layers 204 and 205 are accommodated between the guides 261 to 263, and are pressed between the rolling roll 251 and the other rolling roll 252. As described above, when the deposited layers 204 and 205 are formed by volume of the granulated particle powder, the edges 204a, 204b, 205a, and 205b are also formed by press forming while supporting the side surfaces. The thickness can be kept substantially constant at the edges 204a, 204b, 205a, 205b of 204, 205.

  The deposited layers 204 and 205 are pressed by this pressing process. When the deposited layers 204 and 205 are pressed, the active material particles and the active material particles and the current collector foil are bonded to each other by the binder contained in the deposited layers 204 and 205. As a result, the active material layers 204 and 205 are formed on both sides of the current collector foil 201 except for the central portion (active material layer non-formation regions 202 and 203).

  In this case, when the deposited layers 204 and 205 (active material layer) provided on both sides in the width direction of the current collector foil 201 are pressed, the current collection at the site where the deposited layers 204 and 205 (active material layer) are formed. The foil 201 is also stretched under stress. Further, in response to this, the active material layer non-formed regions 202 and 203 in the middle portion of the current collector foil 101 are also pulled by the current collector foil 201 at the portion where the deposited layers 204 and 205 (active material layers) on both sides are formed. extend. In this case, since the current collector foil 201 is stretched almost uniformly, wrinkles are unlikely to occur on the sheet after pressing.

  7 and 8 show a process in which the active material layers 204 and 205 are formed on one surface of the current collector foil 201. FIG. Here, the active material layers 204 and 205 are formed on the opposite surface of the current collector foil 201 by the same method, and the active material layers 204 and 205 are formed on both surfaces of the current collector foil 201.

  After the active material layers 204 and 205 are formed on both surfaces of the current collector foil 201, the current collector foil 201 is cut in the length direction along the center in the width direction of the current collector foil 201 as shown in FIG. . Thus, two electrode sheets 206 and 207 are obtained. The two strips of electrode sheets 206 and 207 obtained here are provided with exposed portions 202 and 203 along one side edge of the current collector foil 201 in the width direction. Further, in the two electrode sheets 206 and 207, the active material layers 204 and 205 are formed on the current collector foil 201 except for the exposed portions 202 and 203. Further, in the electrode sheets 206 and 207, as shown in FIG. 8, the portions where the deposited layers 204 and 205 (active material layer) are formed and the active layers where the deposited layers 204 and 205 (active material layer) are not formed are formed. The difference in elongation of the current collector foil 201 during pressing is small between the material layer non-formed regions 202 and 203. For this reason, even when the press pressure is increased to increase the density, wrinkles are unlikely to occur in the electrode sheets 206 and 207.

  Here, as the electrode sheets 206 and 207, the positive electrode sheet 50 or the negative electrode sheet 60 (see FIG. 1 or FIG. 2) used for the wound electrode body 40 of the nonaqueous electrolyte secondary battery can be produced. At this time, when the positive electrode sheet 50 is manufactured, a powder of granulated particles including positive electrode active material particles and a binder may be used when the deposition layers 204 and 205 are manufactured. Further, when the negative electrode sheet 60 is manufactured, it is preferable to use a powder of granulated particles including negative electrode active material particles and a binder when the deposition layers 204 and 205 are manufactured.

  As described above, according to the proposed nonaqueous electrolyte secondary battery, for example, in the positive electrode sheet 50 and the negative electrode sheet 60 (see FIGS. 1 and 2), as shown in FIG. 201 and active material layers 204 and 205 formed on the current collector foil 201. The active material layers 204 and 205 are formed except for the exposed portions 202 and 203 (active material layer non-formed portions) provided along one edge in the width direction of the current collector foil 201. Here, the active material layers 204 and 205 are formed bodies in which powders of granulated particles including active material particles and a binder are formed. The active material particles adhere to each other by the binder, and the current collectors are collected. It adheres to the foil 201. The edges on both sides in the width direction of the active material layers 204 and 205 are not cut. As described above, in the nonaqueous electrolyte secondary battery, the active material layers 204 and 205 are produced by powder molding, but the edges on both sides in the width direction of the active material layers 204 and 205 are not cut. For this reason, there are few foreign materials produced due to the active material layers 204 and 205 being cut.

  In this case, the edge on the side where the exposed portions 202 and 203 are provided in the width direction of the current collector foil 201 may be cut. Moreover, the edge on the side where the active material layers 204 and 205 are formed in the width direction of the current collector foil 201 may be cut. For example, as shown in FIG. 7, when two strips of current collector foil 201 are prepared from a rolled wide foil material, the edges on both sides of the two strips of current collector foil 201 are Disconnected. For this reason, the edge on the side where the active material layers 204 and 205 are formed in the width direction of the current collector foil 201 is cut. Even in such a case, the edge on the side where the active material layers 204 and 205 are formed in the width direction of the current collector foil 201 is cut, but the edge on the side of the active material layers 204 and 205 is not cut. .

  That is, as shown in FIG. 9, according to the proposed nonaqueous electrolyte secondary battery, the edge on the side where the active material layers 204 and 205 are formed in the width direction of the current collector foil 201 is cut. Even in this case, the edges of the active material layers 204 and 205 on the side are not cut. For this reason, there is little generation | occurrence | production of a foreign material. Further, when the active material layers 204 and 205 are pressed, the current collector foil 101 is stretched almost uniformly, so that there is little wrinkle. For this reason, according to the nonaqueous electrolyte secondary battery proposed here, the quality of a nonaqueous electrolyte secondary battery can be improved.

  That is, even when powder molding is used, as shown in FIG. 3, the electrode sheets 105 and 106 can be obtained by a process similar to the manufacturing process using the composite paste. In this case, as shown in FIG. 3, two current collector foils 101 are prepared, and the active material layer 104 is formed in an intermediate portion of the current collector foil 101 in the width direction. And as shown in FIG. 5, it cut | disconnects along a longitudinal direction in the center of the width direction of the current collection foil 101, and the electrode sheets 105 and 106 are obtained. However, in this case, as shown in FIG. 5, in the electrode sheets 105 and 106, the edge on the side where the active material layer 104 is formed in the width direction of the current collector foil 101 is cut, and further, the active material The edge of the layer 104 is also cut off. If the active material layer 104 is formed by powder molding, the active material particles are likely to be lost due to cutting.

  Further, as shown in FIG. 4, even if the current collector foil 101 is stretched at the portion where the active material layer 104 is formed due to pressing, the current collector foil 101 is not exposed at the exposed portions 102 and 103. It is hard to stretch. For this reason, the difference in elongation of the current collector foil 101 is partially noticeable, and thus wrinkles are likely to occur. That is, in the width direction of the current collector foil 201, the edge on the side where the active material layers 204 and 205 are formed is cut, but the edge on the side of the active material layers 204 and 205 is not cut. 207 cannot be formed by the manufacturing process as shown in FIGS. 3 to 5 in which the active material layer 104 is formed in the middle portion of the current collector foil.

  On the other hand, according to the nonaqueous electrolyte secondary battery proposed here, the edge on the side where the active material layers 204 and 205 are formed in the width direction of the current collector foil 201 is cut, but the active material The edges of the layers 204, 205 on that side are not cut. For this reason, generation | occurrence | production of the foreign material resulting from an active material particle missing from the edge of the active material layers 204 and 205 can be suppressed few. According to the proposed nonaqueous electrolyte secondary battery, wrinkles generated in the current collector foil 101 can be suppressed to be small. For example, the smaller the difference in the elongation rate of the current collector foil 201 between the portion where the active material layers 204 and 205 are formed and the exposed portions 202 and 203, the better. The difference in elongation rate of the current collector foil 201 may be, for example, 10% or less, more preferably 8% or less, further preferably 5% or less, further preferably 3% or less, and further preferably 1%. It is good to be below.

  The nonaqueous electrolyte secondary battery according to one embodiment of the present invention has been described above, but the nonaqueous electrolyte secondary battery proposed here is not limited to the above-described embodiment.

  The proposed non-aqueous electrolyte secondary battery (typically a lithium ion secondary battery) can be used for various applications, but the active material layer has low resistance and high battery performance. . Therefore, it can be preferably used in applications requiring high energy density and power density. As such an application, for example, a power source (drive power source) for a motor mounted on a vehicle can be cited. The type of vehicle is not particularly limited, and examples thereof include plug-in hybrid vehicles (PHV), hybrid vehicles (HV), electric vehicles (EV), electric trucks, motorbikes, electric assist bicycles, electric wheelchairs, electric railways, and the like. . Such a non-aqueous electrolyte secondary battery may be used in the form of an assembled battery formed by connecting a plurality of them in series and / or in parallel.

  For example, the nonaqueous electrolyte secondary battery proposed here is particularly suitable as a vehicle driving battery mounted on a vehicle. Here, the vehicle driving battery may be in the form of an assembled battery formed by connecting a plurality of the above-described non-aqueous electrolyte secondary batteries (typically, lithium ion secondary batteries) in series. Vehicles equipped with such a vehicle drive battery as a power source typically include automobiles, particularly automobiles equipped with electric motors such as hybrid cars (including plug-in hybrid cars) and electric cars. Moreover, as another nonaqueous electrolyte secondary battery, a sodium ion secondary battery is mentioned here, for example.

DESCRIPTION OF SYMBOLS 10 Lithium ion secondary battery 20 Battery case 21 Case main body 22 Sealing plate 23 Positive electrode terminal 24 Negative electrode terminal 30 Safety valve 32 Injection port 33 Sealing material 40 Winding electrode body 50 Positive electrode sheet 51 Positive electrode current collecting foil 52 Exposed part 53 Positive electrode activity Material layer 60 Negative electrode sheet 61 Negative electrode current collector foil 62 Exposed portion 63 Negative electrode active material layer 72, 74 Separator 80 Electrolytic solution 100 Electrode sheet (2 strip width)
101 Current collecting foils 102, 103 Exposed portion 104 Active material layer (applied mixture paste)
105, 106 Electrode sheet (single width)
151, 152 Rolling roll 200 Electrode sheet (2 width)
201 Current collection foil 202, 203 Exposed part (active material layer non-formation area)
204, 205 Active material layer (deposition layer)
206, 207 Electrode sheet (single width)
251,252 Rolling Rolls 261-263 Guide

Claims (4)

A strip-shaped current collector foil,
An active material layer formed on the current collector foil,
The active material layer is
It is formed except for the exposed portion provided along the edge on one side in the width direction of the current collector foil,
A molded body in which a powder of granulated particles containing at least active material particles and a binder is molded,
None of the edges on both sides in the width direction of the active material layer are cut.
Non-aqueous electrolyte secondary battery.   2. The nonaqueous electrolyte according to claim 1, wherein an edge of the current collector foil on a side where the exposed portion is provided in a width direction of the current collector foil is cut after the active material layer is formed. Secondary battery.   The edge of the current collector foil on the side where the active material layer is formed in the width direction of the current collector foil is cut before the active material layer is formed. Non-aqueous electrolyte secondary battery. A strip-shaped current collector foil,
An exposed portion set in an intermediate portion in the width direction of the strip-shaped current collector foil;
An electrode sheet comprising an active material layer in which a powder of granulated particles including at least active material particles and a binder is formed in regions on both sides in the width direction of the belt-shaped current collector foil except for the exposed portion.

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