KR102555493B1 - Non-aqueous electrolyte rechargeable battery - Google Patents

Abstract

In order to provide a novel and improved non-aqueous electrolyte secondary battery and method for manufacturing a non-aqueous electrolyte secondary battery capable of suppressing pressure non-uniformity and consequently suppressing an increase in the thickness of the non-aqueous electrolyte secondary battery, the present invention provides an electrode electrode and an electrode stack in which separators are sequentially stacked, a current collecting tab installed on a part of the surface of the electrode, and a charging member installed around the surface of the current collecting tab.

Description

Non-aqueous electrolyte secondary battery {NON-AQUEOUS ELECTROLYTE RECHARGEABLE BATTERY}

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

In recent years, high performance, miniaturization, and high energy density of secondary batteries are required according to the high functionality of small-sized information devices.

In particular, non-aqueous electrolyte secondary batteries using non-aqueous electrolytes such as lithium ion secondary batteries have been actively researched and developed because they can increase battery voltage and enable high energy density.

Among them, a non-aqueous electrolyte secondary battery in which a laminate is used as an exterior material and an electrode laminate (electrodes and separators are sequentially laminated) and an electrolyte is accommodated therein has a high degree of freedom in shape and can be thinned. In this respect, it is attracting attention.

By the way, in the manufacturing process of a non-aqueous electrolyte secondary battery, an electrode laminated body may be pressed.

For example, when manufacturing an electrode laminate with a flat winding element, the electrode laminate is pressed.

Hereinafter, the manufacturing process of the flat type winding element is briefly demonstrated.

First, an electrode laminate is manufactured by sequentially stacking an anode, a cathode, and a separator.

Here, a current collecting tab (also referred to as a current collecting lead) is welded to the positive and negative electrodes before lamination.

Next, by winding the electrode laminate in a cylindrical shape (according to the flat shape described above), a cylindrical winding element is produced.

Here, the current collecting tab is disposed on the innermost circumferential portion of the winding element.

Next, the cylindrical winding element is pressed to produce a flat winding element.

Patent Document 1. Japanese Patent Laid-Open No. 2003-157888 Patent Document 2. Japanese Patent Laid-Open No. 2006-164956 Patent Document 3. Japanese Patent Laid-Open No. 2012-174387

As described above, the current collecting tab is installed in the electrode laminate.

At this time, the current collection tab has a structure protruding in the thickness direction of the electrode laminate. For this reason, in the electrode stack, the portion where the collecting tab is formed is thicker than the other portion by the thickness of the collecting tab. Therefore, when the electrode laminate is pressed, pressure is applied unevenly to the electrode laminate.

Further, for example, when manufacturing a flat type 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 of the current collecting tab (direction perpendicular to the thickness direction).

Therefore, when the electrode laminate is pressed, different (different) pressures are applied to the portion of the current collector tab in the thickness direction and the portion of the space in the thickness direction of the space. That is, pressure is non-uniformly applied to the electrode laminate.

As a result, variations may occur in the thicknesses of the electrodes and separators constituting the electrode stack.

When the thickness of the electrode and the separator is varied, the current density may become non-uniform during charging and discharging. As a result, distortion or deformation may occur in the electrode laminate, and buckling may occur. Due to such distortion or deformation and buckling, precipitation of lithium metal or the like occurs, and consequently, 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 non-uniformity in the thickness of the current collecting tab.

This problem is particularly remarkable when the exterior material is made of a laminated film. That is, when the packaging material is a metal can, the packaging material can suppress the deformation of the winding element to some extent. However, since the strength of the laminate film is lower than that of a metal can, it is difficult to suppress deformation of the winding element.

On the other hand, Patent Literatures 1 to 3 disclose technologies relating to winding elements, but the above problems could not be solved at all with these technologies.

Therefore, the present invention is to solve the above problems, and an object of the present invention is to suppress non-uniformity of pressure, and furthermore, to suppress the increase in the thickness of a non-aqueous electrolyte secondary battery, a novel and improved non-aqueous water It is to provide a method for manufacturing an electrolyte secondary battery and a non-aqueous electrolyte secondary battery.

In order to solve the above problems, in one aspect, the present invention includes an electrode stack in which electrodes and separators are sequentially stacked, a current collecting tab installed on a part of the surface of the electrode, and a charging member installed around the surface direction of the current collecting tab. A nonaqueous electrolyte secondary battery is provided.

At this time, since the filling member can fill the space surrounded by the electrode laminate and the current collecting tab, pressure unevenness can be suppressed, and consequently, an increase in the thickness of the non-aqueous electrolyte secondary battery can be suppressed.

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

In this case, since the filling member can more reliably fill the space surrounded by the electrode laminate and the current collecting tab, pressure unevenness can be suppressed, and consequently, an increase in the thickness of the non-aqueous electrolyte secondary battery can be suppressed.

Further, the electrode laminate may be a winding element in which electrodes and separators are wound, a collector tab may be provided at the innermost circumferential portion of the winding element, and a filling member may be provided in a space surrounded by the winding element and the electrode.

In this case, since the filling member can more reliably fill the space surrounded by the electrode laminate and the current collecting tab, pressure unevenness can be suppressed, and consequently, an increase in the thickness of the non-aqueous electrolyte secondary battery can be suppressed.

Further, the region on the separator is divided into a thick region where electrodes are formed and a thin region where electrodes are not formed, and the filling member installed on the thin region may be thicker than the filling member installed on the thick region.

In this case, since the filling member can more reliably fill the space surrounded by the electrode laminate and the current collecting tab, pressure unevenness can be suppressed, and consequently, an increase in the thickness of the non-aqueous electrolyte secondary battery can be suppressed.

In another aspect, the present invention provides a step of forming a collecting tab on a part of the surface of an electrode, a step of providing a charging member around the surface of the collecting tab, and sequentially forming an electrode and a separator on which the collecting tab and the charging member are formed. Provided is a method for manufacturing a non-aqueous electrolyte secondary battery including a step of manufacturing an electrode laminate by laminating, and a step of pressing the electrode laminate.

In this case, since the filling member can more reliably fill the space surrounded by the electrode laminate and the current collecting tab, pressure unevenness can be suppressed, and consequently, an increase in the thickness of the non-aqueous electrolyte secondary battery can be suppressed.

As described above, according to the present invention, since the filling member can fill the space surrounded by the electrode laminate and the current collecting tab, pressure unevenness can be suppressed, and furthermore, an increase in the thickness of the non-aqueous electrolyte secondary battery can be suppressed. .

1 is a cross-sectional plan view showing a schematic configuration of a winding element according to an embodiment of the present invention.
2 is an explanatory diagram showing a schematic configuration of a positive electrode, a positive electrode current collector tab, a separator, and a positive electrode charging member in a winding element according to an embodiment of the present invention.
3 is an explanatory view showing a schematic configuration of a negative electrode, a negative electrode current collector tab, a separator, and a negative electrode charging member in a winding element according to an embodiment of the present invention.
4 is a cross-sectional side view showing a modified example of a non-aqueous electrolyte secondary battery.
Fig. 5 is a cross-sectional plan view showing a state in which a conventional winding element is being pressed.

EMBODIMENT OF THE INVENTION Preferred embodiment of this invention is described in detail, referring an accompanying drawing below.

Meanwhile, in the present specification and drawings, the same reference numerals are given to components having substantially the same functional configuration, and redundant descriptions are omitted.

<1. Review by the present inventors>

As a result of repeated studies on the winding element, the present inventors have completed a non-aqueous electrolyte secondary battery according to the present embodiment. Therefore, first, based on FIG. 5, the examination conducted by the present inventors will be described.

Fig. 5 is an explanatory diagram showing a conventional winding element 100 being pressed.

With reference to this, the manufacturing method of the winding element will be briefly described.

First, a strip-shaped separator 120a, a strip-shaped positive electrode 110, a strip-shaped separator 120b, and a strip-shaped negative electrode 130 are sequentially stacked to form an electrode stack.

Meanwhile, a current collecting tab 115 is welded to an end of the positive electrode 110 in the longitudinal direction (MD direction) before lamination.

Similarly, a current collecting tab 135 is welded to the longitudinal end of the negative electrode 130 before lamination.

Next, the electrode laminate is wound into a cylindrical shape to produce a cylindrical winding element 100 . Here, the current collecting tabs 115 and 135 are disposed on the innermost circumferential portion of the winding element 100 .

Next, the flat winding element 100 is produced by pressing the cylindrical winding element 100 . An arrow P shown in FIG. 5 indicates a press direction.

Here, as clearly shown from FIG. 5 , the collecting tabs 115 and 135 have a structure protruding in the thickness direction of the electrode laminate. For this reason, the portion of the electrode stack in which the collecting tabs 115 and 135 are formed is thicker than other portions by the thickness of the collecting tab.

Therefore, when the electrode laminate is pressed, pressure is applied unevenly to the electrode laminate. Specifically, when the electrode stack is pressed, the surface of the negative electrode current collector tab 135 (the surface not welded to the negative electrode 30) comes into contact with the separator 20a.

At this time, spaces 150 and 160 surrounded by the electrode stack and the current collecting tabs 115 and 135 are formed around the surface direction (direction perpendicular to the thickness direction) of the collecting tabs 115 and 135 .

When the electrode stack is further pressed in this state, a different pressure is applied to a portion of the electrode stack that exists in the thickness direction of the current collecting tabs 115 and 135 and a portion that exists in the thickness direction of the space. That is, pressure is non-uniformly applied to the electrode laminate.

As a result, variations may occur in the thicknesses of the positive electrode 110, the negative electrode 130, and the separators 120a and 120b. As described above, when the thicknesses of the positive electrode 110, the negative electrode 130, and the separators 120a and 120b vary, current densities may become non-uniform during charging and discharging. As a result, distortion or the like may occur in the electrode laminate, and buckling or the like may occur. Therefore, the present inventors studied a method for reducing the spaces 150 and 160, which is a cause of pressure non-uniformity.

As a result, the present inventor came up with reducing the volume of the spaces 150 and 160 by filling the spaces 150 and 160 with a filling member. Based on this knowledge, the present inventors have completed a non-aqueous electrolyte secondary battery according to the present embodiment.

<2. Configuration of Winding Element>

Next, the configuration of the nonaqueous electrolyte secondary battery according to the present embodiment will be described based on FIGS. 1 to 3 .

A nonaqueous electrolyte secondary battery 1 includes a flat winding element 1a, a positive electrode current collector tab 15, a positive electrode charger 51, a negative electrode collector tab 35, a negative electrode charger 61, and a non-aqueous electrolyte secondary battery. An electrolyte solution and an exterior material are provided.

The winding element 1a is obtained by winding an electrode laminate in which a strip separator 20a, a strip anode 10, a strip separator 20b, and a strip cathode 30 are stacked in this order in this order in the longitudinal direction and pressed in the direction of arrow P. will be.

(Configuration of strip-type positive electrode and positive electrode current collector tab)

The strip-shaped positive electrode 10 (hereinafter, simply referred to as "positive electrode 10") has a positive electrode current collector and a positive electrode active material layer formed on both surfaces of the positive electrode current collector.

The positive electrode active material layer contains at least a 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 material capable of reversibly occluding and releasing lithium ions, and examples thereof include lithium cobalt oxide (LCO), lithium nickel oxide, lithium nickel cobalt oxide, and lithium nickel cobalt aluminum oxide (hereinafter, " Sometimes referred to as "NCA"), nickel cobalt lithium manganate (hereinafter sometimes referred to as "NCM"), lithium manganate, lithium iron phosphate, nickel sulfide, copper sulfide, sulfur, iron oxide, vanadium oxide, etc. can

These positive electrode active materials may be used alone or in combination of two or more.

The cathode active material is preferably a lithium salt of a transition metal oxide having a layered rock salt type structure among the examples of the above-mentioned cathode active materials.

Lithium salts of transition metal oxides having such a layered rock salt structure include, for example, Li _{1 -xyz} Ni _x Co _y Al _z O ₂ (NCA) or Li _{1 -xy- z} Ni _x Co _y Mn _z O ₂ ( NCM) (0<x<1, 0<y<1, 0<z<1, also x+y+z<1), and lithium salts of ternary transition metal oxides.

The conductive agent is, for example, carbon black such as Ketjenblack or acetylene black, natural graphite or artificial graphite, but is not particularly limited as long as it is used to increase the conductivity of the anode.

The binder binds the positive electrode active material to each other and simultaneously binds the positive electrode active material and the positive electrode current collector.

The type of binder is not particularly limited, and any binder used in a conventional positive electrode active material layer of a lithium ion secondary battery can be used.

For example, polyvinylidene fluoride, vinylidene fluoride (VDF)-hexafluoropropylene (HFP) copolymer, vinylidene fluoride-perfluorovinyl ether copolymer, vinylidene fluoride- Tetrafluoroethylene copolymer, vinylidene fluoride-trifluoroethylene copolymer, ethylene-propylene-diene terpolymer, styrene-butadiene rubber, acrylo Nitrile-butadiene rubber, fluororubber, polyvinyl acetate, polymethylmethacrylate, polyethylene, cellulose nitrate, etc., but cathode active materials and As long as the conductive agent can be bound on the positive electrode current collector, it is not particularly limited.

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

As shown in FIG. 2, the length (the length in the left-right direction (MD direction) in FIG. 2) and the width (the length in the top-down direction (TD direction) in FIG. , and is also simply referred to as "separator 20b"). This is to suppress a short circuit with the cathode 30.

For this reason, on the separator 20b, there are areas where the anode 10 is formed (thick area) and areas where the anode 10 is not formed (thin area).

Region 70 in FIGS. 1 and 2 represents this thin region.

The anode 10 is manufactured, 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 coated on the current collector.

Thus, a coating layer is formed.

Next, the coating layer is dried.

Next, the dry coating layer is rolled together with the positive electrode current collector.

Thus, the anode 10 is fabricated.

The positive electrode current collector tab 15 is made of the same material as the positive electrode current collector, for example.

The positive electrode current collector tab 15 is welded to the front end of the positive electrode 10 in the longitudinal direction.

In addition, the positive electrode current collector tab 15 is disposed on the innermost circumferential portion of the winding element 1a.

(Configuration of cathode filling member)

Next, the configuration of the positive electrode charging member 51 will be described based on FIGS. 1 and 2 .

The positive electrode charging member 51 is installed around the positive electrode collector tab 15 in the plane direction, more specifically, in an area surrounded by the positive electrode collector tab 15 and the electrode stack (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 charging member 51, the portion 5lb installed in the thin area is preferably thicker than the portion 51a installed in the thick area.

As a result, the surface of the positive electrode charging member 51 (the surface facing the separator 20a) is flush with the surface of the positive electrode current collector tab 15 (the surface that is not welded to the positive electrode 10); It is preferable to be in a flat state or a horizontal state without a step difference).

On the other hand, the thickness of the portion 51a provided on the thick region may be thicker than the thickness of the positive electrode current collector tab 15.

The width of the positive electrode filling member 51 is preferably the same as that of the separator 20a (hereinafter, simply referred to as "separator 20a") and the separator 20b.

Meanwhile, in FIG. 2 , the outer end of the positive electrode charging member 51 is drawn inward than the outer end of the separator 20b in order to easily understand the overlapping state of each layer.

In addition, it is preferable that the length L1 of the positive electrode filling member 51 is set so as to fill the entire space 150 .

The material constituting the positive electrode charging 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.

As an insulating material, the material used for separators 20a and 20b is mentioned.

On the other hand, as materials other than the insulating material that can be used for the anode charging member 51, aluminum foil and the like can be cited.

(Composition of cathode and cathode current collector tab)

The strip-shaped negative electrode 30 (hereinafter, 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.

Any negative electrode active material layer may be used as long as it is used as a negative electrode active material layer of a lithium ion secondary battery.

For example, the negative electrode active material layer contains the negative electrode active material and may further contain a binder.

The negative electrode active material includes, for example, graphite active material (artificial graphite, natural graphite, a mixture of artificial graphite and natural graphite, natural graphite coated with artificial graphite, etc.), fine particles of silicon (Si) or tin (Sn) or their oxides, and graphite. Mixtures of active materials, fine particles of silicon or tin, alloys based on silicon or tin, titanium oxide (TiO _x ) compounds such as Li ₄ Ti ₅ O ₁₂ , and the like can be used.

On the other hand, the oxide of silicon is SiO _x It is represented by (0≤x≤2).

In addition, as the negative electrode active material, for example, metal lithium or the like can be used in addition to these.

The anode current collector is not particularly limited as long as it is a conductor, and may be composed of, for example, one or more selected from the group consisting of copper, stainless steel, and nickel-plated steel.

As shown in FIG. 3, the length (length in the left-right direction (MD direction) in FIG. 3) and width (length in the top-down direction (TD direction) in FIG. 3) of the cathode 30 are smaller than those of the separator 20b. It is desirable to have This is to suppress a short circuit with the positive electrode 10.

However, the length and width of the cathode 30 may be greater than the length and width of the anode 10 . For this reason, on the separator 20b, a region where the cathode 30 is formed (thick region) and a region where the cathode 30 is not formed (thin region) exist. Area 71 in FIGS. 1 and 3 represents a thin area.

Cathode 30 is produced, for example, by 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 (eg, coated) on the negative electrode current collector and dried to form a negative electrode active material layer.

In addition, the negative electrode active material layer is compressed to a desired thickness by a compressor.

Thus, the negative electrode 30 is manufactured.

Here, the thickness of the negative electrode active material layer is not particularly limited, but may be the thickness of the negative electrode active material layer of the lithium ion secondary battery.

In the case of using metallic lithium as the negative electrode active material layer, a metallic lithium foil may be overlapped on the negative electrode current collector.

The negative electrode current collector tab 35 is made of the same material as the negative electrode current collector, for example.

The negative electrode current collector tab 35 is welded to the front end of the negative electrode 30 in the longitudinal direction.

In addition, the negative electrode current collector tab 35 is disposed on the innermost circumferential portion of the winding element 1a.

(Configuration of negative electrode charging member)

Next, the configuration of the negative electrode filling member 61 will be described based on FIGS. 1 and 3 .

The negative electrode charging member 61 is basically the same as the positive electrode charging member 51 .

That is, the negative electrode charging member 61 is located around the negative electrode current collector tab 35 in the plane direction, more specifically, in the area surrounded by the negative electrode current collector tab 35 and the electrode stack (that is, the space 160 shown in FIG. 5). installed

The negative electrode filling member 61 is a member for filling the space 160 .

Of the negative electrode charging member 61, the portion 6lb provided in the thin region is preferably thicker than the portion 61a provided in the thick region.

As a result, the surface of the negative electrode charging member 61 (the surface that contacts the negative electrode 30 when the winding element 1a is pressed) is the surface of the negative electrode current collector tab 35 (the side that is not welded to the negative electrode 30). It is preferable that it is made of cotton) and cotton.

On the other hand, the thickness of the portion 61a provided on the thick region may be thicker than the thickness of the negative electrode current collector tab 35.

Also, the width of the negative electrode filling member 61 is preferably the same as that of the separators 20a and 20b.

Meanwhile, in FIG. 3, the outer edge of the negative electrode charging member 61 is drawn on the inner side of the outer edge of the separator 20b in order to easily understand the overlapping state of each layer.

In addition, the length L2 of the negative electrode filling member 61 is preferably set to fill the entire space 160 .

The material constituting the negative electrode charging member 61 may be the same as that of the positive electrode charging member 51 .

(Configuration of Separator)

The separators 20a and 20b are not particularly limited, and may be any as long as they are used as separators for lithium ion secondary batteries.

As the separators 20a and 20b, it is preferable to use a porous film or non-woven fabric that exhibits excellent high-rate discharge performance alone or in combination.

Resins constituting the separators 20a and 20b include, for example, polyolefin resins represented by polyethylene, polypropylene, etc., polyethylene terephthalate, polybutylene terephthalate ( Polyester resin represented by polybutylene terephthalate, etc., PVDF, vinylidene fluoride (VDF)-hexafluoropropylene (HFP) copolymer, vinylidene fluoride-perfluorovinyl ether (par fluorovinyl ether) copolymer , Vinylidene fluoride-tetrafluoroethylene copolymer, vinylidene fluoride-trifluoroethylene copolymer, vinylidene fluoride-fluoroethylene copolymer, vinylidene fluoride-hexafluoroacetone (hexafluoroacetone) copolymer, vinylidene fluoride-ethylene (ethylene) copolymer, vinylidene fluoride-propylene copolymer, vinylidene fluoride-trifluoro propylene copolymer, vinylidene fluoride-tetrafluoro and ethylene (tetrafluoroethylene)-hexafluoropropylene (hexafluoropropylene) copolymer, vinylidene fluoride-ethylene (ethylene) -tetrafluoroethylene (tetrafluoroethylene) copolymer and the like.

In addition, an adhesive layer is preferably formed on both surfaces of the separators 20a and 20b.

The adhesive layer improves the adhesive strength between each electrode and the separators 20a and 20b, and is made of a porous body.

The adhesive layer is not particularly limited as long as it is used for non-aqueous electrolyte secondary batteries.

Preferable resins constituting the adhesive layer include polyvinylidene fluoride (PVDF)-based fluororesins.

Examples of such a fluororesin include copolymers of vinylidene fluoride (VDF) and other monomers (such as hexafluoropropylene (HFP)) in addition to PVDF.

An adhesive layer containing a fluorine-based resin is formed on the surfaces of the separators 20a and 20b by, for example, the first method or the second method described below.

In the first method, a slurry is prepared by dissolving a fluororesin in an organic solvent such as NMP (N-methylpyrrolidone), dimethylacetamide, or acetone.

Then, after coating the slurry on the separators 20a and 20b, the fluororesin is phase-separated using a poor solvent such as water, methanol, or tripropylene glycol, thereby forming an adhesive layer in which the fluororesin is made porous. do.

In the second method, a heated slurry is prepared by dissolving a fluororesin in a heated electrolyte solution using dimethyl carbonate, propylene carbonate, ethylene carbonate, or the like as a solvent.

Then, the heated slurry is coated on the separators 20a and 20b to form a coated layer.

Then, by cooling the coated layer, the fluororesin is transformed into a gel (a porous film swollen with an electrolyte 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 a laminate, expansion and contraction of the positive electrode 10 and the negative electrode 30 tend to occur according to charging and discharging.

And, as a result of such expansion and contraction, a part where stress is concentrated inside the non-aqueous electrolyte secondary battery 1 occurs, and buckling and distortion of the non-aqueous electrolyte secondary battery 1 may occur from there. .

In addition, due to buckling and distortion, the interelectrode distance between the positive electrode 10 and the negative electrode 30 becomes non-uniform, which may hinder the smooth movement of lithium ions.

As a result, deterioration in capacity and increase in battery thickness accompanying charge/discharge cycles 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 surface of the separators 20a and 20b, the adhesive strength between the separators 20a and 20b and each electrode is improved, thereby suppressing distortion due to the internal stress of the battery and non-uniform interelectrode distance between the positive and negative electrodes. can be expected

However, in order to express the adhesiveness of the adhesive layer, a so-called heat press step of pressing the electrode laminate at a constant pressure and temperature in the presence of an electrolyte solution is required.

The hot press process is performed at a high temperature at which the sol-gel transition of the polymer occurs. As a result, the polymer in the adhesive layer enters the micropores of the electrode or separator (the 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 expressed.

Conditions for the hot press are not particularly limited, but, for example, the temperature is preferably 25 to 150° C. and the pressure is 10 to 100 kgf/cm ² .

When the temperature is less than 25° C., there is a possibility that the adhesive force between the separators 20a and 20b and the positive electrode 10 and the negative electrode 30 may not be sufficient.

When the temperature exceeds 150°C, there is a possibility that the electrolyte solution boils and gas is generated.

When the pressure is less than 10 kgf/cm ² , there is a possibility that the adhesive force between the separators 20a and 20b and the positive electrode 10 and the negative electrode 30 may not be sufficient.

When the pressure exceeds 100 kgf/cm ² , there is a possibility that the electrode laminate is excessively compressed and the characteristics are rather deteriorated.

In this embodiment, since the filling members 51 and 61 are provided around the surface direction of the collector tabs 15 and 35, the pressure applied to the electrode laminate during hot pressing can be more uniform.

As a result, the adhesive strength 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 be made more uniform.

As a result, distortion, buckling, and the like of the non-aqueous electrolyte secondary battery 1 can be suppressed.

Meanwhile, a heat-resistant filler may be added to the adhesive layer in order to improve heat resistance of the non-aqueous electrolyte secondary battery 1 .

The heat-resistant filler is, for example, ceramic particles, more specifically, metal oxide particles.

Examples of the metal oxide particles include fine particles of alumina, boehmite, titania, zirconia, magnesia, zinc oxide, aluminum hydroxide, and magnesium hydroxide.

(Composition of non-aqueous electrolyte solution)

A non-aqueous electrolyte solution is a solution in which an electrolyte is dissolved in an organic solvent. At this time, the electrolyte is not particularly limited, and for example, a lithium salt may be used in the present embodiment.

Lithium salts include, for example, LiClO ₄ , LiBF ₄ , LiAsF ₆ , LiPF ₆ , LiPF _{6 -x} (Cn(F) _{2n + 1} ) _x (provided that 1 < x < 6, n = 1 or 2), One of lithium (Li), sodium (Na) or potassium (K) such as LiSCN, LiBr, LiI, Li ₂ SO ₄ , Li ₂ B ₁₀ Cl ₁₀ , NaClO ₄ , NaI, NaSCN, NaBr, KClO ₄ , KSCN Inorganic ionic salts containing 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 )4NBF ₄ , (CH3)4NBr, (C ₂ H ₅ )4NClO ₄ , (C ₂ H ₅ )4NI, (C ₃ H ₇ )4NBr, (nC ₄ H ₉ )4NClO ₄ , (n-C4H ₉ )4NI, (C ₂ F ₅ )4N-malate, (C ₂ H ₅ )4N-benzoate, (C ₂ H ₅ ) organic ion salts such as 4N-phthalate, stearyl sulfonic acid lithium, octyl sulfonic acid lithium, and dodecyl benzene sulphonic acid; may be used alone or in combination of two or more.

On the other hand, the concentration of the electrolyte salt may be the same as that of the non-aqueous electrolyte used in conventional lithium secondary batteries, and is not particularly limited.

In this embodiment, a non-aqueous electrolyte containing an appropriate lithium compound (electrolyte salt) at a concentration of about 0.8 to 1.5 mol/L can be used.

In addition, as the organic solvent, for example, propylene carbonate (propylene carbonate), ethylene carbonate (ethylene carbonate), butylene carbonate (ethylene carbonate), chloroethylene carbonate (chloroethylene carbonate), vinylene carbonate (vinylene carbonate), such as cyclic carbonic acid esters; cyclic esters such as γ-butyrolactone and γ-valerolactone; Chain carbonates such as dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate; methyl formate, methyl acetate, and methyl butyric acid , chain esters such as ethyl acetate and ethyl propionate; Tetrahydrofuran or its derivatives; 1,3-dioxane, 1,4-dioxane, 1,2-dimethoxyethane, 1,4-dibutoxyethane ), ethers such as methyl diglyme; nitriles such as acetonitrile and benzonitrile; Dioxolane or its derivatives; ethylene sulfide, sulfolane, sultone, or a derivative thereof, or the like alone or in a mixture of two or more thereof, but is not limited thereto.

The non-aqueous electrolyte solution is impregnated into the separators 20a and 20b.

On the other hand, known conductive additives, additives, and the like may be appropriately added to each of the electrodes.

(Composition of exterior materials)

The configuration of the exterior material is not particularly limited, and any material applicable to the 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 by this embodiment is especially remarkable.

Meanwhile, in FIG. 1, the charging member is provided around the positive electrode current collector tab 15 and the negative electrode current collector tab 35, but it may be installed only around either one.

Even in this case, the increase in thickness can be suppressed.

Of course, it is preferable to provide charging members both around the positive electrode current collector tab 15 and around the negative electrode current collector 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.

(Production of strip-shaped anode and attachment of current collector tab)

The anode 10 is manufactured, for example, by the following method.

That is, the material of the positive electrode active material layer is dispersed in an organic solvent or water to form a positive electrode mixture slurry, and the positive electrode mixture slurry is coated on the current collector.

Thus, a coating layer is formed.

Next, the coating layer is dried.

Then, the dry coating layer is rolled together with the positive electrode current collector.

Thus, the anode 10 is fabricated.

Subsequently, the positive electrode current collector tab 15 is welded to the longitudinal end of the positive electrode 10 .

(Production of strip-shaped negative electrode and attachment of collecting tab)

Cathode 30 is produced, for example, by 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 (eg, water, an organic solvent (eg, N-methyl-2-pyrrolidone), etc.).

Next, the slurry is formed (for example, coated) on the negative electrode current collector and dried to form a negative electrode active material layer.

In addition, the negative electrode active material layer is compressed to a desired thickness by a compressor.

Thus, the negative electrode 30 is manufactured.

Here, the thickness of the negative electrode active material layer is not particularly limited, and may be as long as the thickness of the negative electrode active material layer of the lithium ion secondary battery.

In the case of using metallic lithium as the negative electrode active material layer, a metallic lithium foil may be overlapped on the negative electrode current collector.

Next, the negative electrode current collector tab 35 is welded to the end of the negative electrode 30 in the longitudinal direction.

(Manufacturing method of winding element and battery)

Next, the positive electrode 10 is laminated on one surface of the separator 20b.

Next, the positive electrode charging member 51 is installed around the positive electrode collector tab 15 in the surface direction.

Here, among the positive electrode filling member 51, the portion 5lb installed on the thin region is preferably thicker than the portion 51a installed on the thick region.

That is, it is preferable that the surface of the positive electrode current collector tab 15 and the surface of the positive electrode charging member 51 are flush (flat or horizontal without a step).

In addition, it is preferable that the width of the anode charging member 51 is the same as that of the separator 20b. The length L1 of the positive electrode filling member 51 is preferably such that the entire space 150 can be filled. On the other hand, it is preferable that adhesive layers are previously formed on both surfaces of the separator 20b.

Next, the negative electrode 30 is laminated on the other surface of the separator 20b.

Next, the negative electrode charging member 61 is installed around the negative electrode current collector tab 35 in the surface direction. Here, among the negative electrode charging member 61, the portion 6lb provided on the thin region is preferably thicker than the portion 61a provided on the thick region.

That is, the surface of the negative electrode current collector tab 35 and the surface of the negative electrode charging member 61 are preferably flush. Also, the width of the negative electrode filling member 61 is preferably the same as that of the separator 20b. At this time, the length L2 of the negative electrode charging member 61 is preferably a length capable of filling the entire space 160 .

Subsequently, a separator 20a is laminated on the surfaces of the positive electrode current collector tab 15 and the positive electrode charging member 51 .

On the other hand, it is preferable that adhesive layers are previously formed on both surfaces of the separator 20a. In this way, an electrode laminate is produced.

Next, the electrode laminate is wound around a winding core to produce a cylindrical winding element 1a.

Next, the cylindrical winding element 1a is pressed in the direction of the arrow P (when the adhesive layer exists, heat pressing is performed).

Conditions for the hot press are not particularly limited, but, for example, the temperature is preferably 25 to 150° C. and the pressure is 10 to 100 kgf/cm ² . Even when not accompanied by heating, the pressure of the press is preferably 10 to 100 kgf/cm ² .

In this way, a flat winding element 1a is produced.

On the other hand, filling members 51 and 61 are provided around the surface direction of the collecting tabs 15 and 35 . Therefore, the pressure applied to the portion of the winding element 1a in the thickness direction of the filling members 51 and 61 can be brought closer to the pressure applied to the portion in the thickness direction of the collector tabs 15 and 35. there is. That is, it is possible to suppress non-uniformity of pressure.

As a result, distortion and buckling in the non-aqueous electrolyte secondary battery 1 can be suppressed, and furthermore, an increase in the thickness of the non-aqueous electrolyte secondary battery 1 can be suppressed.

Next, the non-aqueous electrolyte secondary battery 1 is fabricated by inserting the flat winding element 1a together with the non-aqueous electrolyte into an exterior body (for example, a laminated film) and sealing the exterior body.

On the other hand, when sealing the exterior body, the collector tabs 15 and 35 protrude outside the exterior body.

<4. Variation>

Fig. 4 shows a modified example of this embodiment.

In this modified example, the electrode stack 1b is formed by sequentially stacking the positive electrode 10, the separator 20, and the negative electrode 30, and positive electrode current collector tabs 15 are formed at both ends of the electrode stack 1b in the thickness direction. , a negative electrode current collector tab 35 is formed.

Then, the electrode laminate 1b is housed in the exterior material 200 .

In this modified example, a space is formed in a region surrounded by the exterior material 200, the positive electrode current collector 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 collector tab 35, and the electrode laminate 1b.

Therefore, in this modified example, filling members for filling these spaces are formed in each space.

Specifically, the positive electrode charging member 51 is formed around the positive electrode current collector tab 15 in the surface direction, and the negative electrode charging member 61 is formed around the negative electrode current collector tab 35 in the surface direction.

The specific configuration of the positive electrode charging member 51 and the negative electrode charging member 61 is the same as in the above-described embodiment.

Even with this modified example, the same effects as those of the above-described embodiment are obtained.

(Example 1)

(Manufacture of anode)

Lithium cobaltate, acetylene black, and polyvinylidene fluoride (PVDF) were dissolved and dispersed in N-methyl pyrrolidone at a solid mass ratio of 98:1:1 to prepare a positive electrode mixture slurry. Subsequently, 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. Next, a positive electrode active material layer was produced by rolling the coated layer after drying. That is, the positive electrode 10 was fabricated. At this time, the total thickness of the positive electrode 10 was 120 μm. Next, an aluminum lead wire having a thickness of 80 μm was welded to the longitudinal end of the positive electrode 10 as the positive electrode current collector tab 15 .

On the other hand, the length and width of the positive electrode 10 were made smaller than those of the separators 20a and 20b described later. Thus, a thin region is formed around the anode 10 .

(Cathode production)

Natural graphite, carboxymethylcellulose, and SBR (styrene butadiene rubber) were dissolved and dispersed in a water solvent at a solid mass ratio of 98:1:1 to prepare a negative electrode mixture slurry. Subsequently, 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. Next, a negative electrode active material layer was obtained by rolling the coated layer after drying. That is, the negative electrode 30 was produced. At this time, the total thickness of the cathode 30 was 120 μm. Thereafter, a nickel lead wire was used as a negative electrode current collector tab 35 and welded to the tip of the negative electrode 30 .

On the other hand, the length and width of the negative electrode 30 were made larger than the length and width of the positive electrode 10 and smaller than the widths of the separators 20a and 20b. Thus, a thin region is formed around the cathode 30 .

(Manufacture of separator)

As the separators 20a and 20b, porous polyethylene separator films having a thickness of 12 μm and subjected to corona treatment were prepared.

On the other hand, PVDF was dissolved in NMP to prepare a slurry. Here, the solid content concentration of the slurry was 8% by mass. And the coating layer was formed by coating this slurry on both surfaces of separators 20a and 20b. Next, the PVDF was phase-separated by washing the separators 20a and 20b including the coated layer. Thus, an adhesive layer was formed. At this time, the thickness of the adhesive layer was 2㎛.

(Manufacture of winding element and battery)

Then, the positive electrode 10 was laminated on one surface of the separator 20b. Next, as the positive electrode charging member 51, a porous polyethylene separator film having a thickness of 80 μm (i.e., the same thickness as the positive electrode current collector tab 15) was prepared. In addition, the length (L1) of the positive electrode charging member 51 was set to 30 mm and the width was the same as that of the separators 20a and 20b. Then, the positive electrode charging member 51 was installed around the positive electrode collector tab 15 in the surface direction.

Next, the negative electrode 30 was laminated on the other surface of the separator 20b. Next, as the negative electrode charging member 61, a porous polyethylene separator film having a thickness of 80 μm (ie, the same thickness as the negative electrode current collector tab 35) was prepared. In addition, the length L2 of the negative electrode filling member 61 was set to 30.3 mm and the width was the same as that of the separators 20a and 20b.

Next, a negative electrode charging member 61 was placed around the negative electrode current collector tab 35 in the surface direction. Next, a separator 20a was laminated on the surfaces of the positive electrode current collector tab 15 and the positive electrode charging member 51 . Thus, an electrode laminate was produced.

Next, the electrode laminate was wound around a winding core having a diameter of 3 cm. The winding direction was the longitudinal direction of the electrode laminate. In this way, a cylindrical winding element 1a was produced.

After fixing the end of the winding element 1a with tape, the winding core was removed. Next, the winding element 1a was sandwiched between two metal plates with a thickness of 3 cm. Then, while heating the winding element 1a to 98 degrees, it was pressed at a pressure of 730 kPa for 120 seconds. Thus, a flat winding element 1a was obtained.

As a result of visually observing the flat section of the winding element 1a, the positive electrode charging member 51 and the negative electrode charging member 61 filled the spaces 150 and 160 throughout the spaces 150 and 160 in the longitudinal direction. was doing

(production of battery)

The winding element 1a was sealed in a laminated film composed of three layers of polypropylene/aluminum/nylon together with an electrolyte so that the two lead wires came out, and a battery was fabricated. As the electrolyte, a solution obtained by dissolving 1M LiPF ₆ in a solvent in which ethylene carbonate/ethyl methyl carbonate was mixed in a ratio of 3:7 (volume ratio) was used. This battery was sandwiched between two metal plates with a thickness of 3 cm heated to 80 degrees and held for 5 minutes. Through 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, charging was performed under a charging condition of 0.2 C and a constant current constant voltage (CCCV) of 0.05 C cutoff, and discharging was performed with a CC discharge at 0.5 C and a 3.5 V cutoff. After the second cycle, a charge/discharge test was conducted in the same manner with the current amount set to 0.7 C for both charge and discharge.

Meanwhile, 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.

(Comparative example)

The same treatment as in Example 1 was performed except that the positive electrode charging member 51 and the negative electrode charging member 61 were not provided. The evaluation results are summarized and shown in the following [Table 1].

As shown in [Table 1], the examples were able to significantly suppress the increase in thickness compared to the comparative examples.

unit mm 1 cyc 100 cyc 200 cyc 300cyc 400cyc 500 cyc Example 1 4.102 4.150 4.166 4.178 4.199 4.233 comparative example 4.099 4.189 4.256 4.278 4.289 4.389

(Examples 2 to 10)

In addition, the same treatment as in Example 1 was performed except that the thickness of the positive electrode charging member 51 and the negative electrode charging member 61 was set to the thickness shown in Table 2 below.

Specifically, the thickness of each filling member formed on the thick and thin regions was changed. In Example 2, the thickness of the filling member on the thick region is 80 mu m, equivalent to the thickness of the tab, and at the same time, the thickness of the filling member on the thin region is 200 mu m. Therefore, in Example 2, the difference between the thickness of the filling member on the thin region and the thickness of the filling member on the thick region is equal to the thickness of the electrode (=120 μm). That is, the surface of the charging 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 region and the thickness of the filling member on the thin region are changed respectively.

As shown in [Table 2], in Example 2, the cell thickness after 300 cycles was most suppressed. In addition, the cell thickness after 300 cycles was suppressed when the thickness of the filling member in the thick region was thicker than 80 μm than when it was thinner.

Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Example 9 Example 10 Thickness of filling member in thick area
(μm) 80 80 80 40 40 40 120 120 120 Filling member thickness in thin area
(μm) 200 240 160 200 240 160 200 240 160 Cell thickness after 300 cycles (mm) 4.135 4.220 4.211 4.256 4.242 4.210 4.199 4.188 4.201

As mentioned above, although preferred embodiment of this invention was demonstrated in detail referring an accompanying drawing, this invention is not limited to this example.

For those skilled in the art to which the present invention belongs, it is clear that various changes or modifications can be made within the scope of the technical idea described in the claims, and these are of course also It is understood that it falls within the technical scope of the present invention.

1: non-aqueous electrolyte secondary battery
1a: winding element
10: anode
15: positive current collector tab
20a, 20b: separator
30: cathode
35: negative current collector tab
51: positive charging member
61: negative electrode charging member

Claims (5)

delete delete delete delete forming a collecting tab on a part of the surface of the electrode;
providing a filling member around the surface of the collecting tab;
manufacturing an electrode laminate by sequentially stacking an electrode and a separator on which the current collecting tab and the filling member are formed; and
A method for manufacturing a non-aqueous electrolyte secondary battery comprising a step of pressing the electrode laminate,
The method of manufacturing a non-aqueous electrolyte secondary battery, wherein the step of installing the charging member is carried out so as to be filled in a space formed around the electrode laminate and the collecting tab surrounded by the collecting tab in a surface direction.

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