JP6932165B2 - Non-aqueous electrolyte secondary battery - Google Patents

Description

The present invention relates to a non-aqueous electrolyte secondary battery.

In recent years, as the functionality of small information devices has increased, higher performance, smaller size, and higher energy density of secondary batteries have been required. In particular, non-aqueous electrolyte secondary batteries using a non-aqueous electrolyte solution such as lithium ion secondary batteries can increase the battery voltage and can increase the energy density, and thus research and development. Is being actively carried out. Among them, a non-aqueous electrolyte secondary battery in which a laminate is used as an exterior material and an electrode laminate (an electrode and a separator are sequentially laminated) and an electrolytic solution are stored therein has a high degree of freedom in shape. It is attracting attention because it can be made thinner.

By the way, in the manufacturing process of the non-aqueous electrolyte secondary battery, the electrode laminate may be pressed. For example, when the electrode laminate is a flat winding element, the electrode laminate is pressed. Hereinafter, the manufacturing process of the flat winding element will be briefly described. First, an electrode laminate is produced by sequentially laminating a positive electrode, a negative electrode, and a separator. Here, a current collecting tab (also referred to as a current collecting lead) is welded to the positive electrode and the negative electrode before laminating. Then, the electrode laminate is wound in a cylindrical shape to produce a cylindrical winding element. Here, the current collecting tab is arranged at the innermost peripheral portion of the winding element. Then, by pressing (crushing) the cylindrical winding element, a flat winding element is produced.

Japanese Unexamined Patent Publication No. 2003-157888 Japanese Unexamined Patent Publication No. 2006-164956 Japanese Unexamined Patent Publication No. 2012-174387

By the way, the electrode laminate is provided with a current collecting tab as described above. The current collector tab is a structure that protrudes in the thickness direction of the electrode laminate. Therefore, the portion of the electrode laminate on which the current collecting tab is formed is thicker than the other portions by the thickness of the current collecting tab. Therefore, when the electrode laminate is pressed, the pressure is unevenly applied to the electrode laminate. For example, when manufacturing a flat winding element, a cylindrical winding element is pressed. Here, a space surrounded by the electrode laminate and the current collecting tab is formed around the surface direction (direction perpendicular to the thickness direction) of the current collecting tab. Therefore, when the electrode laminate is pressed, different pressures are applied to the portion existing in the thickness direction of the current collecting tab and the portion existing in the thickness direction of the space. That is, the pressure is applied non-uniformly to the electrode laminate. As a result, the thicknesses of the electrodes and separators constituting the electrode laminate may vary. If the thickness of the electrode and the separator varies, the current density may become non-uniform during charging and discharging. As a result, strain is generated in the electrode laminate, and buckling and the like may occur. Due to such strain and buckling, precipitation of lithium metal and the like occur, and as a result, the winding element becomes thick.

As described above, in the conventional non-aqueous electrolyte secondary battery, there is a problem that the thickness of the non-aqueous electrolyte secondary battery increases due to the non-uniformity of the thickness due to the current collecting tab. This problem was particularly remarkable when the exterior material was a laminated film. That is, when the exterior material is a metal can, the exterior material can suppress the deformation of the winding element to some extent. On the other hand, since the strength of the laminated film is smaller than that of the metal can, it is difficult to suppress the deformation of the winding element. On the other hand, Patent Documents 1 to 3 disclose techniques relating to winding elements, but these techniques have not been able to solve the above problems at all.

Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to suppress the non-uniformity of pressure and, by extension, to suppress the increase in the thickness of the non-aqueous electrolyte secondary battery. It is an object of the present invention to provide a new and improved method for manufacturing a non-aqueous electrolyte secondary battery and a non-aqueous electrolyte secondary battery.

In order to solve the above problems, according to a certain viewpoint of the present invention, an electrode laminate in which electrodes and separators are sequentially laminated, a current collecting tab provided on a part of the surface of the electrode, and a surface of the current collecting tab. Provided is a non-aqueous electrolyte secondary battery comprising a filling member provided around the direction.

From this point of view, the filling member can fill the space surrounded by the electrode laminate and the current collecting tab, thereby suppressing the pressure non-uniformity and, by extension, the thickness of the non-aqueous electrolyte secondary battery. The increase can be suppressed.

Here, the surface of the filling member and the surface of the current collecting tab may be flush with each other.

From this point of view, the filling member can more reliably fill the space surrounded by the electrode laminate and the current collecting tab, thereby suppressing the pressure non-uniformity and, by extension, the non-aqueous electrolyte secondary battery. The increase in thickness can be suppressed.

Further, the electrode laminate is a winding element in which an electrode and a separator are wound, a current collecting tab is provided in the innermost peripheral portion of the winding element, and a filling member is surrounded by the winding element and the electrode. It may be provided in the space where it is used.

From this point of view, the filling member can more reliably fill the space surrounded by the electrode laminate and the current collecting tab, thereby suppressing the pressure non-uniformity and, by extension, the non-aqueous electrolyte secondary battery. The increase in thickness can be suppressed.

Further, the region on the separator is divided into a thick region in which the electrode is formed and a thin region in which the electrode is not formed, and the filling member provided on the thin region is larger than the filling member provided on the thick region. It may be thick.

From this point of view, the filling member can more reliably fill the space surrounded by the electrode laminate and the current collecting tab, thereby suppressing the pressure non-uniformity and, by extension, the non-aqueous electrolyte secondary battery. The increase in thickness can be suppressed.

According to another aspect of the present invention, a step of forming a current collecting tab on a part of the surface of the electrode, a step of providing a filling member around the surface direction of the current collecting tab, and forming the current collecting tab and the filling member. Provided is a method for manufacturing a non-aqueous electrolyte secondary battery, which comprises a step of producing an electrode laminate and a step of pressing the electrode laminate by sequentially laminating the electrode and the separator. Will be done.

From this point of view, the filling member can more reliably fill the space surrounded by the electrode laminate and the current collecting tab, thereby suppressing the pressure non-uniformity and, by extension, the non-aqueous electrolyte secondary battery. The increase in thickness can be suppressed.

As described above, according to the present invention, according to this viewpoint, the filling member can fill the space surrounded by the electrode laminate and the current collecting tab, so that the non-uniformity of pressure can be suppressed, and thus the non-uniformity of pressure can be suppressed. , It is possible to suppress an increase in the thickness of the non-aqueous electrolyte secondary battery.

It is a plan sectional view which shows the schematic structure of the winding element which concerns on embodiment of this invention. It is explanatory drawing which shows the schematic structure of the positive electrode, the positive electrode current collecting tab, the separator, and the positive electrode filling member which concerns on this embodiment. It is explanatory drawing which shows the schematic structure of the negative electrode, the negative electrode current collecting tab, the separator, and the negative electrode filling member which concerns on this embodiment. It is a side sectional view which shows the modification of the non-aqueous electrolyte secondary battery. It is a plan sectional view which shows the state of pressing a conventional winding element.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the present specification and the drawings, components having substantially the same functional configuration are designated by the same reference numerals, so that duplicate description will be omitted.

<1. Examination by the present inventor>
The present inventor diligently studied the winding element, and as a result, came up with the non-aqueous electrolyte secondary battery according to the present embodiment. Therefore, first, the study conducted by the present inventor will be described with reference to FIG.

FIG. 5 is an explanatory diagram showing a state in which the conventional winding element 100 is pressed. First, a method for manufacturing a winding element will be briefly described. First, an electrode laminate is produced by laminating a band-shaped separator 120a, a band-shaped positive electrode 110, a band-shaped separator 120b, and a band-shaped negative electrode 130 in this order. A current collecting tab 115 is welded to the end of the positive electrode 110 in the length direction (MD direction) before laminating. Similarly, the current collecting tab 135 is welded to the end portion of the negative electrode 130 in the length direction before laminating.

Then, the electrode laminate is wound in a cylindrical shape to produce a cylindrical winding element 100. Here, the current collecting tabs 115 and 135 are arranged at the innermost peripheral portion of the winding element 100. Then, the cylindrical winding element 100 is pressed (crushed) to produce a flat winding element 100. The arrow P shown in FIG. 5 indicates the pressing direction. Here, as is clear from FIG. 5, the current collector tabs 115 and 135 are structures that protrude in the thickness direction of the electrode laminate. Therefore, in the electrode laminate, the portion where the current collecting tabs 115 and 135 are formed is thicker than the other portions by the thickness of the current collecting tab.

Therefore, when the electrode laminate is pressed, the pressure is unevenly applied to the electrode laminate. Specifically, as the electrode laminate is pressed, the surface of the negative electrode current collecting tab 135 (the surface that is not welded to the negative electrode 30) comes into contact with the separator 20a. At this point, spaces 150 and 160 surrounded by the electrode laminate and the current collector tabs 115 and 135 are formed around the current collector tabs 115 and 135 in the plane direction (direction perpendicular to the thickness direction). .. When the electrode laminate is further pressed from this state, different pressures are applied to the portion of the electrode laminate that exists in the thickness direction of the current collector tabs 115 and 135 and the portion that exists in the thickness direction of the space. .. That is, the pressure is applied non-uniformly to the electrode laminate. As a result, the thicknesses of the positive electrode 110, the negative electrode 130, and the separators 120a and 120b may vary. When the thicknesses of the positive electrode 110, the negative electrode 130, and the separators 120a and 120b vary, the current densities may become non-uniform during charging and discharging. As a result, strain is generated in the electrode laminate, and buckling and the like may occur.

Therefore, the present inventor has diligently studied a method for reducing the spaces 150 and 160, which are the causes of pressure non-uniformity. As a result, the present inventor has come up with the idea of reducing the volume of the spaces 150 and 160 by filling the spaces 150 and 160 with a filling member. Then, based on such knowledge, the present inventor came up with the non-aqueous electrolyte secondary battery according to the present embodiment.

<2. Configuration of winding element>
Next, the configuration of the non-aqueous electrolyte secondary battery according to the present embodiment will be described with reference to FIGS. 1 to 3. The non-aqueous electrolyte secondary battery 1 includes a flat winding element 1a, a positive electrode current collecting tab 15, a positive electrode filling member 51, a negative electrode current collecting tab 35, a negative electrode filling member 61, a non-aqueous electrolyte solution, and the like. It is equipped with an exterior material.

The winding element 1a is an electrode laminate in which a band-shaped separator 20a, a band-shaped positive electrode 10, a band-shaped separator 20b, and a band-shaped negative electrode 30 are laminated in this order, wound in the longitudinal direction, and pressed in the arrow P direction.

(Structure of strip-shaped positive electrode and positive electrode current collecting tab)
The band-shaped positive electrode 10 (hereinafter, also simply referred to as “positive electrode 10”) has a positive electrode current collector and positive electrode active material layers formed on both sides of the positive electrode current collector. The positive electrode active material layer contains at least the positive electrode active material, and may further contain a conductive agent and a binder. The positive electrode active material is not particularly limited as long as it is a substance capable of reversibly storing and releasing lithium ions, and is, for example, lithium cobalt oxide (LCO), lithium nickel oxide, lithium nickel cobalt oxide, and nickel cobalt aluminum acid. Lithium (hereinafter sometimes referred to as "NCA"), lithium nickel cobalt manganate (hereinafter sometimes referred to as "NCM"), lithium manganate, lithium iron phosphate, nickel sulfide, copper sulfide, sulfur , Iron oxide, vanadium oxide and the like. These positive electrode active materials may be used alone or in combination of two or more.

Among the examples of the positive electrode active material mentioned above, the positive electrode active material is particularly preferably a lithium salt of a transition metal oxide having a layered rock salt type structure. The lithium salt of a transition metal oxide having such a layered rock-salt structure, for _{example, Li 1-x-y-} z Ni x Co y Al z O 2 (NCA) or _{Li 1-x-y-z} Ni lithium salt of _{x Co y Mn z O 2 (} NCM) (0 <x <1,0 <y <1,0 <z <1, and x + y + z <1) 3 -component transition metal oxide which is expressed by Can be mentioned.

The conductive agent is, for example, carbon black such as Ketjen black or acetylene black, natural graphite, artificial graphite, or the like, but is not particularly limited as long as it is for increasing the conductivity of the positive electrode.

The binder binds the positive electrode active materials to each other and also binds the positive electrode active material and the positive electrode current collector. The type of the binder is not particularly limited, and any binder used for the positive electrode active material layer of the conventional lithium ion secondary battery can be used. For example, polyvinylidene fluoride fluoride, vinylidene fluoride (VDF) -hexafluoropropylene (HFP) copolymer, vinylidene fluoride-perfluorovinyl ether copolymer, vinylidene fluoride-tetrafluoroethylene ( tetrafluoroethylene copolymer, vinylidene fluoride-trifluoroethylene copolymer, ethylenepropylenediene ternary copolymer, styrene butadiene rubber (styrene-butadiene rubber) rubber acrylicyl-butadiene rubber, fluororubber, polyvinyl acetate, polymethylmethacrylate, polyethylene, polyethylene, nitrocellulose, etc. There is no particular limitation as long as it can be bound on the positive electrode current collector.

The positive electrode current collector may be any conductor, and is made of, for example, aluminum, stainless steel, nickel-plated steel, or the like. A positive electrode terminal is connected to the positive electrode current collector.

As shown in FIG. 2, the length (length in the left-right direction (MD direction) in FIG. 2) and width (length in the vertical direction (TD direction) in FIG. 2) of the positive electrode 10 are the strip-shaped separator 20b (hereinafter, hereinafter, It is preferably smaller than (also referred to simply as "separator 20b"). This is to suppress a short circuit with the negative electrode 30. Therefore, on the separator 20b, there is a region in which the positive electrode 10 is formed (thick-walled region) and a region in which the positive electrode 10 is not formed (thin-walled region). Region 70 in FIGS. 1 and 2 indicates a thin-walled region.

The positive electrode 10 is produced, for example, by the following method. That is, a positive electrode mixture slurry is formed by dispersing the material of the positive electrode active material layer in an organic solvent or water, and the positive electrode mixture slurry is applied onto the current collector. As a result, a coating layer is formed. Then, the coating layer is dried. Then, the dried coating layer is rolled together with the positive electrode current collector. As a result, the positive electrode 10 is produced.

The positive electrode current collector tab 15 is made of, for example, the same material as the positive electrode current collector. Positive electrode current collector tab 15
Is welded to the tip of the positive electrode 10 in the length direction. Further, the positive electrode current collecting tab 15 is arranged at the innermost peripheral portion of the winding element 1a.

(Structure of positive electrode filling member)
Next, the configuration of the positive electrode filling member 51 will be described with reference to FIGS. 1 and 2. The positive electrode filling member 51 is provided around the positive electrode current collecting tab 15 in the plane direction, more specifically, in a region surrounded by the positive electrode current collecting tab 15 and the electrode laminate (that is, the space 150 shown in FIG. 5). The positive electrode filling member 51 is a member for filling the space 150.

Of the positive electrode filling member 51, the portion 51b provided in the thin-walled region is preferably thicker than the portion 51a provided in the thick-walled region. As a result, it is preferable that the surface of the positive electrode filling member 51 (the surface facing the separator 20a) is flush with the surface of the positive electrode current collecting tab 15 (the surface not welded to the positive electrode 10). The thickness of the portion 51a provided on the thick region may be thicker than the thickness of the positive electrode current collecting tab 15.

Further, the width of the positive electrode filling member 51 is preferably the same as the width of the separator 20a (hereinafter, also simply referred to as “separator 20a”) and the separator 20b. In FIG. 2, the outer edge of the positive electrode filling member 51 is drawn inside the outer edge of the separator 20b in order to make it easier to understand the overlapping state of each layer. Further, the length L1 of the positive electrode filling member 51 is preferably set so that the entire space 150 can be filled.

The material constituting the positive electrode filling member 51 is not particularly limited, but a material that is stable in the presence of an electrolyte is preferable. Specifically, an insulating material is preferable. Examples of the insulating material include materials used for the separators 20a and 20b. As a material other than the insulating material, an aluminum foil or the like can be mentioned as a material that can be used for the positive electrode filling member 51.

(Construction of negative electrode and negative electrode current collector tab)
The band-shaped negative electrode 30 (hereinafter, also simply referred to as “negative electrode 30”) includes a negative electrode current collector and negative electrode active material layers formed on both sides of the negative electrode current collector.

The negative electrode active material layer may be any material as long as it is used as the negative electrode active material layer of the lithium ion secondary battery. For example, the negative electrode active material layer may contain a negative electrode active material and may further contain a binder. The negative electrode active material is, for example, graphite active material (artificial graphite, natural graphite, a mixture of artificial graphite and natural graphite, natural graphite coated with artificial graphite, etc.), silicon (Si) or tin (Sn), or an oxide thereof. Mixtures of fine particles of graphite and graphite active material, fine particles of silicon or tin, alloys using silicon or tin as a basic material, titanium oxide (TiO _x ) compounds such as _{Li 4} Ti ₅ O _{12 and the like can be used.} .. The oxide of silicon is represented by SiO _x (0 ≦ x ≦ 2). In addition to these, as the negative electrode active material, for example, metallic lithium or the like can be used.

The negative electrode current collector may be any conductor, and is made of, for example, copper, stainless steel, nickel-plated steel, or the like.

As shown in FIG. 3, the length (length in the left-right direction (MD direction) in FIG. 3) and width (length in the vertical direction (TD direction) in FIG. 3) of the negative electrode 30 are smaller than those of the separator 20b. It is preferable that This is to suppress a short circuit with the positive electrode 10. However, the length and width of the negative electrode 30 may be larger than the length and width of the positive electrode 10. Therefore, on the separator 20b, there is a region in which the negative electrode 30 is formed (thick-walled region) and a region in which the negative electrode 30 is not formed (thin-walled region). Region 71 in FIGS. 1 and 3 indicates a thin-walled region.

The negative electrode 30 is manufactured by, for example, the following method. First, a slurry is formed by dispersing a mixture of a negative electrode active material and a binder in a desired ratio in an organic solvent (for example, N-methyl-2-pyrrolidone). Next, the slurry is formed (for example, coated) on the negative electrode current collector and dried to form the negative electrode active material layer. Further, the negative electrode active material layer is compressed to a desired thickness by a compressor. As a result, the negative electrode 30 is manufactured. Here, the thickness of the negative electrode active material layer is not particularly limited as long as it is the thickness of the negative electrode active material layer of the lithium ion secondary battery. When metallic lithium is used as the negative electrode active material layer, the metallic lithium foil may be laminated on the negative electrode current collector.

The negative electrode current collector tab 35 is made of, for example, the same material as the negative electrode current collector. The negative electrode current collecting tab 35 is welded to the tip of the negative electrode 30 in the length direction. Further, the negative electrode current collecting tab 35 is arranged at the innermost peripheral portion of the winding element 1a.

(Structure of negative electrode filling member)
Next, the configuration of the negative electrode filling member 61 will be described with reference to FIGS. 1 and 3. The negative electrode filling member 61 is basically the same as the positive electrode filling member 51. That is, the negative electrode filling member 61 is provided around the negative electrode current collecting tab 35 in the plane direction, more specifically, in a region surrounded by the negative electrode current collecting tab 35 and the electrode laminate (that is, the space 160 shown in FIG. 5). .. The negative electrode filling member 61 is a member for filling the space 160.

Of the negative electrode filling member 61, the portion 61b provided in the thin-walled region is preferably thicker than the portion 61a provided in the thick-walled region. As a result, the surface of the negative electrode filling member 61 (the surface that comes into contact with the negative electrode 30 when the winding element 1a is pressed) is flush with the surface of the negative electrode current collector tab 35 (the surface that is not welded to the negative electrode 30). It is preferable that it is. The thickness of the portion 61a provided on the thick region may be thicker than the thickness of the negative electrode current collecting tab 35.

Further, the width of the negative electrode filling member 61 is preferably the same as the width of the separators 20a and 20b. In FIG. 3, the outer edge of the negative electrode filling member 61 is drawn inside the outer edge of the separator 20b in order to make it easier to understand the overlapping state of each layer. Further, the length L2 of the negative electrode filling member 61 is preferably set so that the entire space 160 can be filled. The material constituting the negative electrode filling member 61 may be the same as that of the positive electrode filling member 51.

(Structure of separator)
The separators 20a and 20b are not particularly limited, and may be any as long as they are used as a separator for a lithium ion secondary battery. As the separators 20a and 20b, it is preferable to use a porous film, a non-woven fabric, or the like exhibiting excellent high-rate discharge performance alone or in combination. Examples of the resins constituting the separators 20a and 20b include polyolefin-based resins typified by polyethylene, polypropylene, etc., polyethylene terephthalate, polybutylene terephthalate, and the like. Polyethylene resin, PVDF, vinylidene fluoride (VDF) -hexafluoropropylene (HFP) copolymer, vinylidene fluoride-perfluorovinyl ether copolymer, vinylidene fluoride-tetrafluoro Ethylene (tellafluoroethylene) copolymer, vinylidene fluoride-trifluoroethylene copolymer, vinylidene fluoride-fluoroethylene copolymer, vinylidene fluoride-hexafluoroacetone copolymer, fluorine. Vinylidene-ethylene (ethylene) copolymer, vinylidene fluoride-propylene (polyethylene) copolymer, vinylidene fluoride-trifluoropropylene copolymer, vinylidene fluoride-tetrafluoroethylene-hexa Fluoropropylene (hexafluoropolyethylene) copolymers, vinylidene fluoride-ethylene (ethylene) -tetrafluoroethylene (terrafluoropolyethylene) copolymers and the like can be mentioned.

Further, it is preferable that an adhesive layer is formed on both surfaces of the separators 20a and 20b. The adhesive layer improves the adhesive force between each electrode and the separators 20a and 20b, and is a porous body. The adhesive layer is not particularly limited as long as it is used for a non-aqueous electrolyte secondary battery. Preferred resins constituting the adhesive layer include polyvinylidene fluoride (PVDF) -based fluororesins. Examples of such a fluororesin include, in addition to PVDF, a copolymer of vinylidene fluoride (VDF) and another monomer (hexafluoropropylene (HFP), etc.).

The adhesive layer containing the fluororesin is formed on the surfaces of the separators 20a and 20b by, for example, the following first method or second method.

In the first method, a slurry is prepared by dissolving a fluororesin in an organic solvent such as NMP (N-methylpyrrolidone), dimethylacetamide, and acetone. Then, after applying this slurry to the separators 20a and 20b, the fluororesin is phase-separated using a poor solvent such as water, methanol, or tripropylene glycol to form an adhesive layer in which the fluororesin is made porous. In the second method, a heated slurry is prepared by dissolving a fluororesin in a heated electrolytic solution using dimethyl carbonate, propylene carbonate, ethylene carbonate or the like as a solvent. Then, the coating layer is formed by applying this heated slurry to the separators 20a and 20b. Then, by cooling the coating layer, the fluororesin is transferred to a gel (a porous film swollen with an electrolytic solution). That is, an adhesive layer is produced.

The purpose of forming such an adhesive layer on the surfaces of the separators 20a and 20b is as follows. That is, when the exterior material is laminated, the positive electrode 10 and the negative electrode 30 are likely to expand and contract with charging and discharging. Then, as a result of such expansion and contraction, a portion where the stress inside the non-aqueous electrolyte secondary battery 1 is concentrated is generated, and buckling and distortion of the non-aqueous electrolyte secondary battery 1 may occur from that portion. Further, due to buckling and distortion, the distance between the electrodes of the positive electrode 10 and the negative electrode 30 becomes non-uniform, and the smooth movement of lithium ions is hindered. As a result, the capacity deterioration and the increase in the battery thickness due to the charge / discharge cycle become remarkable.

Therefore, in order to suppress buckling and distortion of the non-aqueous electrolyte secondary battery 1, an adhesive layer is formed on the surfaces of the separators 20a and 20b. By forming the adhesive layer on the surfaces of the separators 20a and 20b, the adhesive force between the separators 20a and 20b and each electrode is improved, so that the battery is distorted due to internal stress and the distance between the positive and negative electrodes becomes non-uniform. It can be expected to suppress this.

However, in order to develop the adhesiveness of the adhesive layer, a so-called heat pressing step of pressing the electrode laminate at a constant pressure and temperature in the presence of an electrolytic solution is required. This heat press process is performed at a high temperature such that a sol-gel transition of the polymer occurs. As a result, the polymer in the adhesive layer enters the micropores of the electrode or separator (so-called anchor effect). In addition, the polymer in the adhesive layer interacts with the binder present on the electrode surface. By these actions, the adhesive force between the electrodes is developed. The conditions of the heat press are not particularly limited, but for example, the temperature is preferably 25 to 150 ° C. and the pressure is preferably 10 to 100 kgf / cm ² . If the temperature is lower than 25 ° C., the adhesive force between the separators 20a and 20b and the positive electrode 10 and the negative electrode 30 may not be sufficient. If the temperature exceeds 150 ° C., the electrolytic solution may boil and gas may be generated. If the pressure is ^{less than 10 kgf / cm 2} , the adhesive force between the separators 20a and 20b and the positive electrode 10 and the negative electrode 30 may not be sufficient. If the pressure exceeds 100 kgf / cm ² , the electrode laminate may be excessively compressed and the characteristics may be deteriorated.

In the present embodiment, since the filling members 51 and 61 are provided around the current collecting tabs 15 and 35 in the plane direction, the pressure applied to the electrode laminate during heat pressing can be made more uniform. As a result, the adhesive force of the adhesive layer can be made more uniform on the interface between the positive electrode 10 and the negative electrode 30, and the thickness of the adhesive layer can also be made more uniform. As a result, distortion, buckling, etc. of the non-aqueous electrolyte secondary battery 1 can be suppressed.

A heat-resistant filler may be added to the adhesive layer in order to improve the heat resistance of the non-aqueous electrolyte secondary battery 1. The heat-resistant filler is, for example, ceramic particles, and more specifically, metal oxide particles. Examples of the metal oxide particles include fine particles such as alumina, boehmite, titania, zirconia, magnesia, zinc oxide, aluminum hydroxide, and magnesium hydroxide.

(Composition of non-aqueous electrolyte solution)
The non-aqueous electrolyte solution is a solution in which an electrolyte is dissolved in an organic solvent. The electrolyte is not particularly limited, and for example, in this embodiment, a lithium salt can be used. Examples of the lithium _{salt, LiClO 4, LiBF 4, LiAsF} 6, LiPF 6, LiPF 6-x (C n F 2n + 1) x ( where, 1 <x <6, n = 1or2), LiSCN, LiBr, LiI, Inorganic ion salts containing one of lithium (Li), sodium (Na) or potassium (K) such as Li ₂ SO ₄ , Li ₂ B ₁₀ Cl ₁₀ , NaClO ₄ , NaI, NaSCN, NaBr, KClO _{4, KSCN, etc.} LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , LiN (CF ₃ SO ₂ ) (C ₄ F ₉ SO ₂ ), LiC (CF ₃ SO ₂ ) ₃ , LiC (C ₂ F ₅ SO ₂ ) ₃ , (CH ₃ ) ₄ NBF ₄ , (CH ₃ ) ₄ NBr, (C ₂ H ₅ ) ₄ NClo ₄ , (C ₂ H ₅ ) ₄ NI, (C ₃ H ₇₎ ) ₄ NBr, (n-C ₄ H ₉ ) ₄ NClo ₄ , (n-C ₄ H ₉ ) ₄ NI, (C ₂ H ₅ ) ₄ N-maleate, (C ₂ H ₅ ) ₄ N-benzoate, ( C ₂ H ₅ ) ₄ N-phtalate, lithium stearyl sulfonate (stearyl sulphonic acid lithium), lithium octyl sulfonate (octyl sulphonic acid), lithium dodecylbenzene sulfonate (dodecil benzene sulphonic acid, etc.), etc. These ionic compounds can be used alone or in combination of two or more. The concentration of the electrolyte salt may be the same as that of the non-aqueous electrolyte solution used in the conventional lithium secondary battery, and is not particularly limited. In the present embodiment, a non-aqueous electrolytic solution containing an appropriate lithium compound (electrolyte salt) at a concentration of about 0.8 to 1.5 mol / L can be used.

Examples of the organic solvent include propylene carbonate (propylene carbonate), ethylene carbonate (etherylene carbonate), butylene carbonate (ethylene carbonate), chloroethylene carbonate (chloroethylene carbonate), vinylene carbonate (vinylene carbonate), and the like. Esters; Cyclic esters such as γ-butyrolactone, γ-valerolactone; dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, etc. Carbonates; Chain esters such as methyl formate, methyl acetate, methyl butyric acid methyl, ethyl acetate, ethyl propionate, etc .; tetrahydrofuran (ethylene) Or derivatives thereof; 1,3-dioxane, 1,4-dioxane, 1,2-dimethoxyethane, 1,4-dibutoxyether, methyldilyme. Ethers such as ester; nitriles such as acetonitrile and benzonitrile, dioxolane or derivatives thereof; ethylene sulfide, sulfolane, sultone and the like. Alternatively, alone or a mixture of two or more of them, such as a derivative thereof, can be mentioned, but the present invention is not limited thereto. The non-aqueous electrolyte solution is impregnated into the separators 20a and 20b. A known conductive auxiliary agent, additive, or the like may be appropriately added to each of the above electrodes.

(Composition of exterior material)
The composition of the exterior material is not particularly limited, and any material applicable to a non-aqueous electrolyte secondary battery can be suitably used in the present embodiment. For example, the exterior material may be a laminate such as an aluminum laminate. When the exterior material is a laminate, it is difficult for the exterior material to suppress the shape change of the electrode laminate. Therefore, the effect of this embodiment is particularly remarkable.

In FIG. 1, the filling member is provided around the positive electrode current collecting tab 15 and around the negative electrode current collecting tab 35, but it may be provided only around one of them. Even in this case, the increase in thickness can be suppressed. Of course, it is preferable to provide the filling member both around the positive electrode current collecting tab 15 and around the negative electrode current collecting tab 35.

<3. Manufacturing method of non-aqueous electrolyte lithium-ion secondary battery ＞
Next, a method for manufacturing a non-aqueous electrolyte lithium ion secondary battery will be described.
(Making a strip-shaped positive electrode and attaching a current collecting tab)
The positive electrode 10 is produced, for example, by the following method. That is, a positive electrode mixture slurry is formed by dispersing the material of the positive electrode active material layer in an organic solvent or water, and the positive electrode mixture slurry is applied onto the current collector. As a result, a coating layer is formed. Then, the coating layer is dried. Then, the dried coating layer is rolled together with the positive electrode current collector. As a result, the positive electrode 10 is produced. Then, the positive electrode current collecting tab 15 is welded to the tip of the positive electrode 10 in the length direction.

(Making a strip-shaped negative electrode and attaching a current collecting tab)
The negative electrode 30 is manufactured by, for example, the following method. First, a slurry is formed by dispersing a mixture of a negative electrode active material and a binder in a desired ratio in a solvent (for example, water, an organic solvent (for example, N-methyl-2-pyrrolidone), etc.). Next, the slurry is formed (for example, coated) on the negative electrode current collector and dried to form the negative electrode active material layer. Further, the negative electrode active material layer is compressed to a desired thickness by a compressor. As a result, the negative electrode 30 is manufactured. Here, the thickness of the negative electrode active material layer is not particularly limited as long as it is the thickness of the negative electrode active material layer of the lithium ion secondary battery. When metallic lithium is used as the negative electrode active material layer, the metallic lithium foil may be laminated on the negative electrode current collector. Then, the negative electrode current collecting tab 35 is welded to the tip of the negative electrode 30 in the length direction.

(Manufacturing method of winding element and battery)
Then, the positive electrode 10 is laminated on one surface of the separator 20b. Next, a positive electrode filling member 51 is provided around the positive electrode current collecting tab 15 in the surface direction. Here, in the positive electrode filling member 51, the portion 51b provided on the thin-walled region is preferably thicker than the portion 51a provided on the thick-walled region. That is, it is preferable that the surface of the positive electrode current collecting tab 15 and the surface of the positive electrode filling member 51 are flush with each other. Further, the width of the positive electrode filling member 51 is preferably the same as the width of the separator 20b. The length L1 of the positive electrode filling member 51 is preferably a length that can fill the entire space 150. It is preferable that adhesive layers are formed in advance on both surfaces of the separator 20b.

Then, the negative electrode 30 is laminated on the other surface of the separator 20b. Next, a negative electrode filling member 61 is provided around the negative electrode current collecting tab 35 in the surface direction. Here, in the negative electrode filling member 61, the portion 61b provided on the thin-walled region is preferably thicker than the portion 61a provided on the thick-walled region. That is, it is preferable that the surface of the negative electrode current collecting tab 35 and the surface of the negative electrode filling member 61 are flush with each other. Further, the width of the negative electrode filling member 61 is preferably the same as the width of the separator 20b. The length L2 of the negative electrode filling member 61 is preferably a length that can completely fill the space 160.

Then, the separator 20a is laminated on the surfaces of the positive electrode current collecting tab 15 and the positive electrode filling member 51. It is preferable that adhesive layers are formed in advance on both surfaces of the separator 20a. As a result, an electrode laminate is produced. Then, the electrode laminate is wound around the winding core to produce a cylindrical winding element 1a. Then, the cylindrical winding element 1a is pressed in the direction of the arrow P (if an adhesive layer is present, heat pressing is performed). The conditions of the heat press are not particularly limited, but for example, the temperature is preferably 25 to 150 ° C. and the pressure is preferably 10 to 100 kgf / cm ² . The pressure of the press is preferably 10 to ^{100 kgf / cm 2 even without heating.}

As a result, the flat winding element 1a is manufactured. Filling members 51 and 61 are provided around the current collecting tabs 15 and 35 in the surface direction. Therefore, the pressure applied to the portion of the winding element 1a existing in the thickness direction of the filling members 51 and 61 can be brought close to the pressure applied to the portion of the current collecting tabs 15 and 35 in the thickness direction. That is, the pressure non-uniformity can be suppressed. As a result, strain and buckling in the non-aqueous electrolyte secondary battery 1 can be suppressed, and eventually, an increase in the thickness of the non-aqueous electrolyte secondary battery 1 can be suppressed.

Then, the flat winding element 1a is inserted into the exterior body (for example, a laminated film) together with the non-aqueous electrolyte solution, and the exterior body is sealed to produce the non-aqueous electrolyte secondary battery 1. When sealing the exterior body, the current collector tabs 15 and 35 are projected to the outside of the exterior body.

<4. Modification example>
FIG. 4 shows a modified example of this embodiment. In this modification, the positive electrode 10, the separator 20, and the negative electrode 30 are sequentially laminated to form the electrode laminated body 1b, and the positive electrode current collecting tabs 15 and the negative electrode current collecting tabs 35 are formed at both ends of the electrode laminated body 1b in the thickness direction. Is formed. Then, the electrode laminate 1b is housed in the exterior material 200. In this modification, a space is formed in a region surrounded by the exterior material 200, the positive electrode current collecting tab 15, and the electrode laminate 1b. Similarly, a space is formed in a region surrounded by the exterior material 200, the negative electrode current collecting tab 35, and the electrode laminate 1b. Therefore, in this modification, a filling member that fills these spaces is formed in each space. Specifically, the positive electrode filling member 51 is formed around the surface direction of the positive electrode current collecting tab 15, and the negative electrode filling member 61 is formed around the surface direction of the negative electrode current collecting tab 35. The specific configurations of the positive electrode filling member 51 and the negative electrode filling member 61 are the same as those in the above-described embodiment. The same effect as that of the above-described embodiment can be obtained by this modification.

(Example 1)
(Preparation of positive electrode)
A positive electrode mixture slurry was prepared by dissolving and dispersing lithium cobalt oxide, acetylene black, and polyvinylidene fluoride (PVDF) in N-methylpyrrolidone at a mass ratio of solid content of 98: 1: 1. Then, the positive electrode mixture slurry was applied to both sides of the aluminum foil current collector having a thickness of 12 μm, and then dried. A positive electrode active material layer was prepared by rolling the coated layer after drying. That is, the positive electrode 10 was produced. The total thickness of the positive electrode 10 was 120 μm. Then, an aluminum lead wire having a thickness of 80 μm was welded to the tip of the positive electrode 10 in the length direction as the positive electrode current collecting tab 15. The length and width of the positive electrode 10 were made smaller than the separators 20a and 20b described later. Therefore, a thin-walled region is formed around the positive electrode 10.

(Preparation of negative electrode)
A negative electrode mixture slurry was prepared by dissolving and dispersing natural graphite, carboxymethyl cellulose, and SBR (styrene butadiene rubber) in an aqueous solvent at a mass ratio of solid content of 98: 1: 1. Then, this negative electrode mixture slurry was applied to both sides of a copper foil current collector having a thickness of 8 μm, and then dried. A negative electrode active material layer was obtained by rolling the coated layer after drying. That is, the negative electrode 30 was manufactured. The total thickness of the negative electrode 30 was 120 μm. Then, the nickel lead wire was welded to the tip of the negative electrode 30 as the negative electrode current collecting tab 35. The length and width of the negative electrode 30 were larger than the length and width of the positive electrode 10 and smaller than the widths of the separators 20a and 20b. Therefore, a thin-walled region is formed around the negative electrode 30.

(Making a separator)
As the separators 20a and 20b, corona-treated porous polyethylene separator films having a thickness of 12 μm were prepared. On the other hand, a slurry was prepared by dissolving PVDF in NMP. Here, the solid content concentration of the slurry was set to 8% by mass. Then, this slurry was applied to both surfaces of the separators 20a and 20b to form a coating layer. Then, the separators 20a and 20b containing the coating layer were washed to phase-separate the PVDF. As a result, an adhesive layer was formed. The thickness of the adhesive layer was 2 μm.

(Manufacturing of winding element and battery)
Then, the positive electrode 10 was laminated on one surface of the separator 20b. Next, a porous polyethylene separator film having a thickness of 80 μm (that is, the same thickness as the positive electrode current collecting tab 15) was prepared as the positive electrode filling member 51. Further, the length L1 of the positive electrode filling member 51 was set to 30 mm, and the width was set to be the same as that of the separators 20a and 20b. Then, the positive electrode filling member 51 is provided around the positive electrode current collecting tab 15 in the surface direction.

Then, the negative electrode 30 was laminated on the other surface of the separator 20b. Next, a porous polyethylene separator film having a thickness of 80 μm (that is, the same thickness as the negative electrode current collecting tab 35) was prepared as the negative electrode filling member 61. Further, the length L2 of the negative electrode filling member 61 was set to 30.3 mm, and the width was set to be the same as that of the separators 20a and 20b. Next, a negative electrode filling member 61 was provided around the negative electrode current collecting tab 35 in the surface direction.

Then, the separator 20a was laminated on the surfaces of the positive electrode current collecting tab 15 and the positive electrode filling member 51. As a result, an electrode laminate was produced. Then, the electrode laminate was wound around a winding core having a diameter of 3 cm. The winding direction was the length direction of the electrode laminate. As a result, a cylindrical winding element 1a was produced. After fixing the end of the winding element 1a with tape, the winding core was removed. Then, the winding element 1a was sandwiched between two metal plates having a thickness of 3 cm. Then, the winding element 1a was pressed at a pressure of 730 kPa for 120 seconds while heating to 98 ° C. As a result, a flat winding element 1a was obtained. When the planosection of the winding element 1a was visually observed, the positive electrode filling member 51 and the negative electrode filling member 61 filled the spaces 150 and 160 over the entire length direction of the spaces 150 and 160.

(Battery production)
A battery was manufactured by sealing the winding element 1a on a laminated film composed of three layers of polypropylene / aluminum / nylon with an electrolytic solution so that the two lead wires were exposed to the outside. As the electrolytic solution, a solvent obtained by dissolving _{1 M of LiPF 6} in a solvent obtained by mixing ethylene carbonate / ethyl methyl carbonate in a ratio of 3: 7 (volume ratio) was used. The battery was sandwiched between two 3 cm thick metal plates heated to 80 ° C. and held for 5 minutes. By the above steps, the non-aqueous electrolyte secondary battery 1 was produced.

(Characteristic evaluation)
A charge / discharge cycle test was conducted using the non-aqueous electrolyte secondary battery 1 prepared as described above. Only in the first cycle, the battery was charged with a constant current constant voltage (CCCV) of 0.05 Cutoff under a charging condition of 0.2 C, and the discharge was CC discharge at 0.5 C and 3.5 V cutoff. From the second cycle onward, the charge / discharge test was performed in the same manner with the current amount set to 0.7 C for both charging and discharging. On the other hand, the thickness of the non-aqueous electrolyte secondary battery 1 during the cycle test was measured by pressing a ^{flat metal plate against the non-aqueous electrolyte secondary battery 1 with a force of 30 g / cm 2.} The thickness was measured after 1 cycle, 100 cycles, 200 cycles, 300 cycles, 400 cycles, and 500 cycles, respectively.

(Comparison example)
The same treatment as in Example 1 was performed except that the positive electrode filling member 51 and the negative electrode filling member 61 were not provided. Table 1 summarizes the evaluation results. As is clear from Table 1, the examples were able to suppress the increase in thickness as compared with the comparative examples.

(Examples 2 to 10)
Further, the same treatment as in Example 1 was performed except that the thicknesses of the positive electrode filling member 51 and the negative electrode filling member 61 were set to the thicknesses shown in Table 2 below. Specifically, the thickness of each filling member formed on the thick region and the thin region was changed. In the second embodiment, the thickness of the filling member on the thick region is 80 μm, which is equivalent to the thickness of the tab, and the thickness of the filling member on the thin region is 200 μm. Therefore, in Example 2, the difference between the thickness of the filling member on the thin-walled region and the thickness of the filling member on the thick-walled region is equal to the thickness of the electrode (= 120 μm). That is, the surface of the filling member and the surface of the current collecting tab are flush with each other. In Examples 3 to 10, the thickness of the filling member on the thick-walled region and the thickness of the filling member on the thin-walled region are changed, respectively. As is clear from Table 2, in Example 2, the cell thickness after 300 cycles was most suppressed. Further, when the thickness of the filling member in the thick region is thicker than 80 μm, the cell thickness after 300 cycles is suppressed as compared with the thinner one.

Although the preferred embodiments of the present invention have been described in detail with reference to the accompanying drawings, the present invention is not limited to such examples. It is clear that a person having ordinary knowledge in the field of technology to which the present invention belongs can come up with various modifications or modifications within the scope of the technical idea described in the claims. , These are also naturally understood to belong to the technical scope of the present invention.

1 Non-aqueous electrolyte secondary battery 1a Winding element 10 Positive electrode 15 Positive electrode current collecting tab 20a, 20b Separator 30 Negative electrode 35 Negative electrode current collecting tab 51 Positive electrode filling member 61 Negative electrode filling member

Claims (4)

An electrode laminate in which a positive electrode, a negative electrode, and a separator are sequentially laminated, and the electrode laminate is a winding element in which the positive electrode, the negative electrode, and the separator are wound .
A positive electrode current collecting tab provided on a part of the surface of the positive electrode , and a negative electrode current collecting tab provided on a part of the surface of the negative electrode .
A positive electrode filling member which is surrounded by a plurality of members including at least the positive electrode and the positive electrode current collecting tab and fills the entire space around the positive electrode current collecting tab in the surface direction, and at least the negative electrode and the negative electrode current collecting tab. A negative electrode filling member surrounded by a plurality of members including the negative electrode and filling the entire space around the negative electrode current collecting tab in the surface direction .
Equipped with a,
The positive electrode filling member and the negative electrode filler member Rukoto have the disposed within so as to sandwich the innermost portion of the winding element of the winding element between the positive electrode filling member wherein the negative electrode filling member A non-aqueous electrolyte secondary battery characterized by. The non-aqueous electrolyte secondary battery according to claim 1, wherein at least one of the positive electrode filling member and the negative electrode filling member is an insulating substance. The surface of the positive electrode filling member and the surface of the positive electrode current collecting tab are flush with each other, and the surface of the negative electrode filling member and the surface of the negative electrode current collecting tab are flush with each other. , The non-aqueous electrolyte secondary battery according to claim 1 or 2. Region on the separator, a thick area in which the cathode is formed, the positive electrode is divided into the thin region is not formed,
The positive electrode filling member provided the thin region on the rather thick than the positive electrode filling member provided on the thick region, or,
The region on the separator is divided into a thick region in which the negative electrode is formed and a thin region in which the negative electrode is not formed.
The non-aqueous electrolyte secondary according to any one of claims 1 to 3, wherein the negative electrode filling member provided on the thin-walled region is thicker than the negative electrode filling member provided on the thick-walled region. battery.

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