JP6227168B1 - Lithium ion battery and manufacturing method thereof - Google Patents

Abstract

The lithium ion battery includes a positive electrode including a positive electrode mixture layer (positive electrode mixture PEF), a negative electrode including a negative electrode mixture layer (negative electrode mixture NEF), the positive electrode mixture layer, and the negative electrode mixture layer. And a separator layer (separator SP) that insulates the positive electrode and the negative electrode, and an electrolytic solution that performs a charge / discharge reaction between the positive electrode and the negative electrode. Furthermore, the relationship between the film thickness Ts of the separator layer and the film thickness Te of the electrode mixture layer on which the separator layer is formed is Ts + Te ≦ 40 μm and Ts / Te ≦ 4/3. The formed separator layer has a curved structure, and the maximum curvature radius of the curve is 2 mm.

Description

  The present invention relates to a lithium ion battery and a manufacturing technique thereof.

  Background art in this technical field includes International Publication No. 2005/098996 (Patent Document 1) and Japanese Patent Application Laid-Open No. 2014-49184 (Patent Document 2). Patent Document 1 describes “a lithium ion battery including a sheet-like separator interposed between a positive electrode and a negative electrode, and a porous electronic insulating film bonded to the surface of the negative electrode”. Patent Document 2 states that “in a lithium ion secondary battery in which an electrode material for a positive electrode or a negative electrode is applied and an insulating material to be a separator is applied, a mixed layer formed at the interface between the electrode material layer and the insulating material layer is thinned. The manufacturing method and manufacturing apparatus of a lithium ion battery that can be performed "are described.

International Publication No. 2005/098996 JP 2014-49184 A

  Lithium ion batteries have high energy density, long cycle life, low self-discharge characteristics, and high operating voltage, so they are used as power sources for portable electronic devices, batteries for electric vehicles, and batteries for power storage. Research and development is underway. However, since the lithium ion battery has a high operating voltage and high energy density, sufficient countermeasures against abnormal heat generation due to an internal short circuit or an external short circuit are required.

  Patent Document 1 describes a lithium ion battery including a porous electronic insulating film bonded to the surface of a negative electrode. By adhering the porous electronic insulating film to the negative electrode, the heat resistance is improved, so that the safety can be improved. However, in Patent Document 1, since a sheet-like separator and a porous electronic insulation film are used in combination, the number of materials not involved in charge / discharge increases, which is disadvantageous in terms of improving energy density.

  Patent Document 2 describes a lithium ion battery using only an insulating material coated on an electrode as a separator. Since a sheet-like separator is not used in combination, it is advantageous from the viewpoint of improving energy density.

  However, as a result of studies by the present inventors, it has been found that when an electrode coated with an insulating material such as a cylindrical battery or a rectangular battery is bent and stored in a container, a crack may occur in the insulating layer. That is, the present inventors have found a problem that when a crack occurs in the insulating layer, the insulation between the positive and negative electrodes cannot be ensured, and the reliability of the lithium ion battery is reduced, such as battery performance deterioration or internal short circuit. It was.

  An object of the present invention is to provide a technique capable of improving the reliability of a lithium ion battery.

  The above and other objects and novel features of the present invention will be apparent from the description of this specification and the accompanying drawings.

  Of the inventions disclosed in this application, the outline of typical ones will be briefly described as follows.

  The lithium ion battery according to the present invention includes a positive electrode including a positive electrode mixture layer including a positive electrode active material, a negative electrode including a negative electrode mixture layer including a negative electrode active material, the positive electrode mixture layer, and the negative electrode mixture layer. And a separator that insulates the positive electrode and the negative electrode, and an electrolyte that performs a charge / discharge reaction between the positive electrode and the negative electrode. Further, the separator is made of a mixture of insulating particles and a binder, and the relationship between the thickness Ts of the separator and the thickness Te of the electrode mixture layer on which the separator is formed is Ts + Te ≦ 40 μm and Ts. / Te ≦ 4/3, and the separator formed in the electrode mixture layer has a curved structure, and the maximum curvature radius of the curve is 2 mm.

  In addition, the method for producing a lithium ion battery according to the present invention includes (a) a step of applying a slurry-like electrode material on an electrode foil, and (b) an electrode combination formed on the electrode material or by drying the electrode material. Applying a slurry-like insulating material on the agent layer. Furthermore, (c) the electrode material and the insulating material are dried in separate steps or the same step, an electrode mixture layer made of the electrode material on the electrode foil, and the insulating material on the electrode mixture layer And (d) after the step (c), the step of bending the separator and storing the electrode foil, the electrode mixture layer and the separator in a container. Furthermore, the insulating material includes a mixture of insulating particles and a binder, and the relationship between the film thickness Ts of the separator and the film thickness Te of the electrode mixture layer on which the separator is formed is Ts + Te ≦ 40 μm and Ts / Te ≦ 4/3, and in the step (d), the separator is curved so that its maximum radius of curvature is 2 mm.

  Of the inventions disclosed in the present application, effects obtained by typical ones will be briefly described as follows.

  Insulation failure of the separator can be prevented and the reliability of the lithium ion battery can be improved.

FIG. 2 is a schematic cross-sectional view and an enlarged partial cross-sectional view showing an example of an internal structure of a cylindrical lithium ion battery in an embodiment of the present invention. FIG. 2 is an enlarged partial cross-sectional view showing an example of a structure of part A of the lithium ion battery shown in FIG. It is a manufacturing flow which shows an example of the manufacturing procedure of the lithium ion battery shown in FIG. It is a schematic diagram which shows an example of the 1st coating state in the manufacturing procedure of the lithium ion battery shown in FIG. It is a schematic diagram which shows an example of the 2nd coating state in the manufacturing procedure of the lithium ion battery shown in FIG. It is a schematic diagram which shows an example of the evaluation method of the presence or absence of the crack generation in the separator of the lithium ion battery shown in FIG. It is a data figure which shows the SEM image of the surface of the separator in Examples 1-3 and Comparative Examples 1-3 of this invention, and the evaluation result of the presence or absence of a crack. It is a data figure which shows the SEM image of the surface of the separator in Example 4-5 of this invention, and comparative example 4-5, and the evaluation result of the presence or absence of a crack. It is a data figure which shows the evaluation result of the insulation of the separator in Examples 6-11 of this invention, and Comparative Examples 6-8. It is the data figure which put together the evaluation result of the insulation in Examples 6-11 of this invention, and Comparative Examples 6-8 in the table | surface.

  In the following embodiments, the description of the same or similar parts will not be repeated in principle unless particularly necessary.

  Further, in the following embodiment, when it is necessary for the sake of convenience, the description will be divided into a plurality of sections or embodiments, but they are not irrelevant to each other unless otherwise specified. The other part or all of the modifications, details, supplementary explanations, and the like are related.

  Also, in the following embodiments, when referring to the number of elements (including the number, numerical value, quantity, range, etc.), particularly when clearly indicated and when clearly limited to a specific number in principle, etc. Except, it is not limited to the specific number, and it may be more or less than the specific number.

  Further, in the following embodiments, the constituent elements (including element steps) are not necessarily indispensable unless otherwise specified and clearly considered essential in principle. Needless to say.

  Further, in the following embodiments, regarding constituent elements and the like, when “consisting of A”, “consisting of A”, “having A”, and “including A” are specifically indicated that only those elements are included. It goes without saying that other elements are not excluded except in the case of such cases. Similarly, in the following embodiments, when referring to the shapes, positional relationships, etc. of the components, etc., the shapes are substantially the same unless otherwise specified, or otherwise apparent in principle. And the like are included. The same applies to the above numerical values and ranges.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that components having the same function are denoted by the same reference symbols throughout the drawings for describing the embodiments, and the repetitive description thereof will be omitted. Further, even a plan view may be hatched for easy understanding of the drawing.

(Embodiment)
<Configuration of lithium ion battery>
A configuration example of the lithium ion battery LIB of the present embodiment will be described. FIG. 1 is a schematic cross-sectional view and an enlarged partial cross-sectional view showing an example of the internal structure of a cylindrical lithium ion battery according to an embodiment of the present invention, and FIG. It is an enlarged partial sectional view showing an example.

  As shown in FIG. 1, an electrode winding body WRF composed of a positive electrode PEL, separators SP1 and SP2, which are separator layers, and a negative electrode NEL is formed inside a cylindrical outer can (container) CS having a bottom. Yes. Specifically, the electrode winding body WRF is stacked so as to sandwich the separator SP1 (SP2) between the positive electrode PEL and the negative electrode NEL, and is wound around the axis CR in the center of the outer can CS. . And the positive electrode current collection tab PTAB formed in the positive electrode PEL is arranged on the upper side of the electrode winding body WRF, and passes through the positive electrode lead plate PT and the positive electrode current collection ring PR provided on the upper part of the outer can CS. Are electrically connected.

  On the other hand, the negative electrode current collecting tab NTAB formed on the negative electrode NEL is disposed on the lower side of the electrode winding body WRF, and passes through the negative electrode lead plate NT provided on the bottom of the outer can CS and the negative electrode current collecting ring NR. Are electrically connected. An electrolyte EL is injected into the electrode winding body WRF formed inside the outer can CS. The electrolyte EL is present in a state of permeating into a positive electrode mixture PEF and a negative electrode mixture NEF, separators SP1 and SP2, which will be described later. The outer can CS is sealed with a battery lid CAP. The outer can CS is made of, for example, iron (Fe) or stainless steel as a main material.

  As shown in FIG. 2, the positive electrode PEL is obtained by applying a positive electrode mixture PEF composed of a positive electrode active material PAS, a binder PBD, and a conductive auxiliary agent PCA to a current collector foil (electrode foil) PEP. Examples of the positive electrode active material PAS include, but are not limited to, lithium cobaltate, lithium nickelate, and lithium manganate. Specifically, the positive electrode active material PAS is a material into which lithium can be inserted and desorbed, and may be any lithium-containing transition metal oxide in which a sufficient amount of lithium has been previously inserted. , Nickel (Ni), cobalt (Co), iron (Fe) or the like, or a material mainly composed of two or more transition metals. Further, the crystal structure such as spinel crystal structure and layered crystal structure is not particularly limited as long as it is a structure capable of inserting / extracting lithium ions. Further, a material in which a part of the transition metal or lithium in the crystal is replaced with an element such as Fe, Co, Ni, Cr, Al, Mg, or an element such as Fe, Co, Ni, Cr, Al, Mg in the crystal A material doped with may be used as the positive electrode active material PAS. For the binder PBD, for example, polyvinyl fluoride, polyvinylidene fluoride, polytetrafluoroethylene, or the like can be used. Furthermore, for the current collector foil PEP, for example, a metal foil or a mesh metal made of a conductive metal such as aluminum is used.

  On the other hand, the negative electrode NEL is obtained by applying a negative electrode mixture NEF comprising a negative electrode active material NAS, a binder NBD, and a conductive auxiliary agent NCA to a current collector foil (electrode foil) NEP. Examples of the negative electrode active material NAS include a crystalline carbon material and an amorphous carbon material, but are not limited thereto. Specifically, the negative electrode active material NAS may be any material that can insert and desorb lithium ions. The negative electrode active material NAS is typified by natural graphite, various artificial graphite agents, carbon materials such as coke, oxides such as silicon oxide, niobium oxide, titanium oxide, silicon, tin, germanium, lead, aluminum, etc. A material that forms an alloy with lithium or a mixture thereof can be used. And also in the particle shape, various particle shapes such as a scale shape, a spherical shape, a fiber shape, and a lump shape are applicable. For the binder NBD, for example, polyvinyl fluoride, polyvinylidene fluoride (PVDF), polytetrafluoroethylene, polyimide, styrene butadiene rubber, or a mixture thereof can be used. Furthermore, for the current collector foil NEP, for example, a metal foil made of a conductive metal such as copper or a mesh metal is used.

A nonaqueous electrolytic solution is used as the electrolytic solution EL in which a charge / discharge reaction is performed between the positive electrode PEL and the negative electrode NEL. The lithium ion battery LIB is a battery that performs charging / discharging by using insertion / extraction of lithium ions in an active material, and lithium ions move in the electrolyte EL. Lithium is a strong reducing agent and reacts violently with water to generate hydrogen gas. Therefore, in the lithium ion battery LIB in which lithium ions move in the electrolytic solution EL, an aqueous solution cannot be used for the electrolytic solution EL unlike a conventional battery. For this reason, in the lithium ion battery LIB, a non-aqueous electrolyte is used as the electrolyte EL. Specifically, as the electrolyte of the nonaqueous _{electrolyte, LiPF 6, LiClO 4, LiAsF} 6, LiBF 4, LiB (C 6 H 5) 4, CH 3 SO 3 Li, CF 3 SO 3 Li , etc., and mixtures thereof Can be used. Moreover, as an organic solvent, ethylene carbonate, dimethyl carbonate, ethyl methyl carbonate, propylene carbonate, diethyl carbonate, etc. can be used. Further, 1,2-dimethoxyethane, 1,2-diethoxyethane, γ-butyrolactone, tetrahydrofuran, 1,3-dioxolane, 4-methyl-1,3-dioxolane, diethyl ether, sulfolane, methylsulfolane, acetonitrile, propio Nitrile or the like, or a mixed solution thereof can be used.

  The separator SP has a function as a spacer that allows lithium ions to pass through while insulating between the positive electrode PEL and the negative electrode NEL and preventing electrical contact.

  In the present embodiment, as shown in FIG. 2, the separator SP is composed of insulating particles SPP and binder SBD, and is applied to the surface of at least one of the positive electrode mixture PEF and the negative electrode mixture NEF. Is formed. FIG. 2 shows, as an example, a schematic cross-sectional view in which separators SP are formed on both surfaces of the positive electrode PEL and the negative electrode NEL shown in FIG. 1, but insulation between the positive electrode PEL and the negative electrode NEL is ensured. If so, the surface on which the separators SP1 and SP2 are formed may be either the positive electrode PEL or the negative electrode NEL.

  Examples of the insulating particles SPP shown in FIG. 2 include, but are not limited to, silicon dioxide, aluminum oxide, polypropylene, polyethylene, and mixtures thereof.

  Furthermore, for example, polyvinyl fluoride, polyvinylidene fluoride (PVDF), polytetrafluoroethylene, polyimide, styrene butadiene rubber, or a mixture thereof can be used as the binder SBD.

  The feature of the present embodiment is that the qualitatively the total thickness of the electrode mixture layer that is the positive electrode mixture PEF or the negative electrode mixture NEF and the separator (separator layer) SP formed on the surface of the electrode mixture layer. And simultaneously controlling the particle size of the electrode active material (positive electrode active material PAS or negative electrode active material NAS) and the insulating particles SPP with respect to the thickness of the separator (separator layer) SP. is there.

  By reducing the total thickness of the electrode mixture layer and the separator layer formed on the surface of the electrode mixture layer, the stress applied to the separator layer when the electrode (electrode sheet) is curved is reduced. The generation of cracks in can be prevented. However, if the separator is simply made thin, the separator layer is easily affected by the unevenness of the electrode mixture layer, which is the application surface, when the separator material is applied. Here, the defect generated in the separator layer when the separator material is applied means that the electrode mixture is exposed because the insulating particles SPP are not uniformly formed on the surface of the electrode mixture layer, and electrical insulation cannot be secured. I mean.

  In the present invention, in addition to reducing the total thickness of the electrode mixture layer and the separator layer formed on the surface of the electrode mixture layer, the particle sizes of the electrode active material and the insulating particles are set to the thickness of the separator layer. It has been found that by controlling, the occurrence of cracks in the separator layer and the occurrence of defects during the application of the separator material can be prevented at the same time, and the insulation of the separator layer can be secured.

<Method for producing lithium ion battery>
3 is a manufacturing flow showing an example of a manufacturing procedure of the lithium ion battery shown in FIG. 1, FIG. 4 is a schematic diagram showing an example of a first coating state in the manufacturing procedure of the lithium ion battery shown in FIG. 3, and FIG. It is a schematic diagram which shows an example of the 2nd coating state in the manufacturing procedure of the lithium ion battery shown in FIG.

  Hereinafter, the manufacturing method of a lithium ion battery will be specifically described along the flow shown in FIG.

  Each of the positive electrode PEL and the negative electrode NEL constituting the lithium ion battery LIB shown in FIG. 1 is basically manufactured by the same process, although there are differences in the material of the electrode foil and the material of the film applied to the electrode foil. The Below, it demonstrates without dividing each manufacturing process of positive electrode PEL and negative electrode NEL. For example, the electrode material EF, which is a coating material shown in FIG. 4 to be described later, includes a case where it is a positive electrode material and a case where it is a negative electrode material. The Here, it goes without saying that in the manufacturing process of the positive electrode PEL, an electrode foil and a coating material made of a positive electrode material are used, and a material used only in the manufacturing process of the negative electrode NEL is not used. Similarly, in the manufacturing process of the negative electrode NEL, it is needless to say that the electrode foil and the coating material made of the negative electrode material are used and the material used only for the manufacturing process of the positive electrode PEL is not used.

1. Production of electrode plates (positive and negative plates) [Kneading / mixing process]
In the manufacturing process of the lithium ion battery LIB according to the present embodiment, first, the electrode material EF shown in FIG. 4 for forming the positive electrode PEL or the negative electrode NEL of the lithium ion battery LIB is kneaded and mixed.

[First coating process (electrode material)]
Next, the adjusted slurry-like electrode material EF shown in FIG. 4 is thinly and uniformly applied on the surface of the film-like current collector foil (electrode foil) EP using the coater 100. In the first coating process, for example, a slit die coater can be used as the coater 100, but another apparatus may be used as an apparatus for applying the electrode material EF.

[Drying process]
Next, the current collector foil EP coated with the electrode material EF in the first coating process is transported into a drying furnace such as a hot air drying furnace to dry the electrode material EF, and the positive electrode mixture PEF or the negative electrode mixture is dried. An electrode mixture layer that is the agent NEF is formed.

[Second coating process (insulating material)]
Next, the slurry-like insulating material SPF shown in FIG. 5 is thinly and uniformly applied on the surface of the electrode mixture layer (positive electrode mixture PEF, negative electrode mixture NEF) using the coater 200. In the second coating step, for example, a slit die coater can be used as the coater 200, but another device may be used as a device for applying the insulating material SPF.

[Drying process]
Next, the current collector foil EP coated with the insulating material SPF in the second coating step is transported into a drying furnace, which is a hot air drying furnace, and the insulating material SPF is dried to separate the separator (separator layer) SP. Form.

  In addition, about formation of the electrode mixture layer by electrode material EF, and formation of separator SP by insulating material SPF, coating of electrode material EF and coating of insulating material SPF is performed continuously, and on current collection foil EP In this state, the electrode material layer EF and the insulating material SPF are laminated, and the electrode mixture layer and the separator SP are formed on the current collector foil EP by drying them together in a drying furnace or the like in this state. Good.

[Processing process]
Next, the separator foil electrode sheet 20 shown in FIG. 2 is formed by performing processing such as compression and cutting on the current collector foil EP. The electrode sheet may be the electrode sheet 10 in which only the electrode mixture layer is formed on the current collector foil EP. That is, the electrode sheet 10 in which the separator SP is not formed may be used.

2. Battery cell assembly [winding process]
Next, the positive electrode PEL and the separators SP1 and SP2 shown in FIG. 1 are cut out from the positive electrode plate (electrode sheet with separator 20) necessary for the battery cell. Similarly, the negative electrode NEL and separators SP1 and SP2 having a size necessary for the battery cell are cut out from the negative electrode plate (electrode sheet with separator 20). Subsequently, after stacking the positive electrode PEL having the separator SP formed on the surface thereof and the negative electrode NEL having the separator SP formed on the surface thereof, the laminated body is bonded together.

[Welding and assembly process]
Next, a group of electrode pairs of a positive electrode PEL and a negative electrode NEL that are joined together with the separator SP interposed therebetween is assembled and welded. In this welding / assembly process, for example, an aluminum ribbon is wound around the positive electrode current collecting tab PTAB, and the positive electrode current collecting tab PTAB is connected to the aluminum ribbon by ultrasonic welding. The same applies to the negative electrode current collecting tab NTAB.

[Liquid extraction process]
Next, after arranging the group of these welded electrode pairs in the outer can CS shown in FIG. 1, the electrolyte EL is injected.

  A nonaqueous electrolytic solution is used as the electrolytic solution EL. The lithium ion battery LIB is a battery that performs charging / discharging using insertion of lithium ions into an active material and desorption of lithium ions from the active material, and the lithium ions move in the electrolytic solution. Lithium is a strong reducing agent and reacts violently with water to generate hydrogen gas. Therefore, in the lithium ion battery LIB in which lithium ions move in the electrolyte EL, the aqueous solution cannot be used as the electrolyte EL. For this reason, in the lithium ion battery LIB, a non-aqueous electrolyte is used as the electrolyte EL.

[Sealing process]
Next, a battery cell is produced by completely sealing the outer can CS.

[Charging / discharging process]
Next, the formed battery cell is repeatedly charged and discharged.

[Battery cell inspection process]
Next, the battery cell performance and reliability are inspected (for example, the capacity and voltage of the battery cell, and the current and voltage during charging or discharging). Thereby, the battery cell of the lithium ion battery LIB is completed.

3. Module Assembly Next, in the module assembly process, a battery module is configured by combining a plurality of battery cells in series, and a battery module (battery system) is configured by connecting a controller for charge / discharge control (module assembly). . Thereafter, in the module inspection process, the battery module assembled in the module assembly process is inspected for performance and reliability (for example, inspection of the capacity and voltage of the battery module, current and voltage during charging or discharging) (module inspection). ).

  In the assembly of the separator-attached electrode sheet 20, the case where the separator SP is formed by applying the insulating material SPF, which is an insulating material, to both the positive electrode sheet 20 with a separator and the negative electrode sheet 20 with a separator will be described. did. However, in the lithium ion battery LIB of the present embodiment, the insulating material SPF is applied to only one of the positive electrode PEL and the negative electrode NEL to form the separator SP, and the electrode sheet 20 with the separator is wound. May be.

  Thus, the assembly of the lithium ion battery LIB as shown in FIG. 1 is completed.

  Next, a characteristic separator and electrode structure in this embodiment and a specific method for manufacturing the electrode will be described.

<Relationship of film thickness between electrode mixture layer and separator layer formed on surface of electrode mixture layer>
[Example 1]
First, the manufacturing method of the electrode in the present Example 1 is demonstrated. As materials, the positive electrode active material PAS uses lithium manganese cobalt nickel composite oxide, graphite powder as the conductive auxiliary agent PCA, polyvinylidene fluoride (PVDF) as the binder PBD, and 15 μm thick aluminum foil as the current collector foil PEP. In addition, the lithium manganese cobalt nickel composite oxide used for the positive electrode active material PAS has a D90 particle size of 6 μm (D50 particle size of 4 μm) measured using Microtrac MT3000 (manufactured by Nikkiso).

  Here, the D90 particle size, the D50 particle size, and the like are indices indicating how much particles are contained in what ratio in the material. For example, when the D90 particle size is 6 μm, it means a material in which particles with a particle size of 6 μm or less occupy 90% of the total, and when the D50 particle size is 4 μm, It means a material in which particles of 4 μm or less occupy 50% of the whole.

  And these were mixed so that the weight% of positive electrode active material PAS, conductive support agent PCA, and binder PBD might be 93.0%, 3.5%, and 3.5%, and also N-methyl-2- By dispersing in pyrrolidone (NMP), a positive electrode slurry (a slurry-like positive electrode material EF) is produced. After the production, as shown in FIG. 4, the slurry-like electrode material EF is applied onto an aluminum foil which is a current collector foil (electrode foil) PEP and dried in a hot air drying oven at 120 ° C. Thereafter, the dried film is press-compressed to form a positive electrode PEL having a positive electrode mixture (electrode mixture layer) PEF film thickness of 15 μm.

  Next, the manufacturing method of separator SP is demonstrated. As materials, silicon dioxide is used for the insulating particles SPP, and polyvinylidene fluoride (PVDF) is used for the binder SBD. As the silicon dioxide of the insulating particles SPP, those having a D90 particle size of 3 μm (D50 particle size of 1 μm) measured using Microtrac MT3000 (made by Nikkiso) are used.

  Then, these are mixed so that the weight percentage of the insulating particles SPP and the binder SBD are 89.3% and 10.7%, and further dispersed in N-methyl-2-pyrrolidone (NMP). A separator slurry (slurry insulating material SPF) is prepared. After the production, as shown in FIG. 5, the slurry-like insulating material SPF is applied to the surface of the positive electrode mixture (electrode mixture layer) PEF prepared in advance, and dried in a hot air drying oven at 120 ° C., thereby A separator layer (separator SP) having a thickness of 10 μm is formed.

  As described above, the electrode mixture layer (positive electrode mixture PEF) and the separator layer (separator SP) are formed, and the film thickness (thickness) Te of the electrode mixture layer (positive electrode mixture PEF) and the separator layer (separator SP). The relationship of the film thickness (thickness) Ts was Te + Ts = 25 μm and Ts / Te = 2/3. Note that the obtained film may or may not be pressed when Te + Ts = 25 μm and Ts / Te = 2/3. Moreover, although the manufacturing method in the case of forming a separator layer on the surface of a positive mix layer was demonstrated in the present Example 1, when forming a separator layer on the surface of a negative mix layer, it can form similarly.

  Next, after forming the positive electrode mixture layer and the separator layer, the separator layer is bent and the current collector foil PEP, the electrode mixture layer, and the separator SP are accommodated in an outer can (container) CS.

  Here, a method for evaluating the presence or absence of cracks when the electrode mixture layer on which the separator SP is formed is curved will be described. FIG. 6 is a schematic diagram showing an example of an evaluation method for the presence or absence of cracks in the separator of the lithium ion battery shown in FIG.

  As shown in FIG. 6, a current collector foil PEP and an electrode mixture layer (positive electrode) are formed on a cylindrical rod (cylindrical rod having a radius of 2 mm) 300 made of stainless steel (SUS) and having a radius R of 2 mm. A film composed of a mixture (PEF) and a separator layer (separator SP) was spread, and a tension of 16 gf / mm was applied. Then, it observed with SEM (Scanning Electron Microscope) in the observation part 400, and the presence or absence of the crack was discriminate | determined. The radius of curvature of 2 mm is the maximum curvature of a general 18650 type cylindrical battery. The tension of 16 gf / mm is a tension of a general winding device.

[Example 2]
In Example 2, the presence / absence of cracks was evaluated under the following conditions.

  Except that the film thickness Te of the electrode mixture layer is 15 μm and the film thickness Ts of the separator layer is 20 μm, it is the same as Example 1 (Te + Ts = 35 μm, Ts / Te = 4/3).

[Example 3]
In Example 3, the presence / absence of cracks was evaluated under the following conditions.

  Same as Example 1 except that the electrode mixture layer thickness Te is 30 μm and the separator layer thickness Ts is 10 μm (Te + Ts = 40 μm, Ts / Te = 1/3).

[Comparative Example 1]
In Comparative Example 1, the presence or absence of cracks was evaluated under the following conditions.

  Except that the film thickness Te of the electrode mixture layer is 15 μm and the film thickness Ts of the separator layer is 30 μm, it is the same as Example 1 (Te + Ts = 45 μm, Ts / Te = 2).

[Comparative Example 2]
In Comparative Example 2, the presence or absence of cracks was evaluated under the following conditions.

  Except that the film thickness Te of the electrode mixture layer is 30 μm and the film thickness Ts of the separator layer is 20 μm, it is the same as Example 1 (Te + Ts = 50 μm, Ts / Te = 2/3).

[Comparative Example 3]
In Comparative Example 3, the presence or absence of cracks was evaluated under the following conditions.

  Except that the film thickness Te of the electrode mixture layer is 30 μm and the film thickness Ts of the separator layer is 30 μm, it is the same as Example 1 (Te + Ts = 60 μm, Ts / Te = 1).

  FIG. 7 is a data diagram showing SEM images of the separator surfaces and evaluation results of the presence or absence of cracks in Examples 1 to 3 and Comparative Examples 1 to 3 of the present invention.

  As shown in FIG. 7, in Examples 1-3, no crack was generated, while in Comparative Examples 1-3, a crack was generated. From this result, it was found that when the maximum radius of curvature is 2 mm, the occurrence of cracks can be prevented when 0 <Te + Ts ≦ 40 μm and 0 <Ts / Te ≦ 4/3. Qualitatively, the stress applied to the separator layer can be reduced by reducing the film thickness Te of the electrode mixture layer and the film thickness Ts of the separator layer.

[Example 4]
In Example 4, as in Example 1, the thickness Te of the positive electrode mixture layer was 15 μm, and the film thickness Ts of the separator layer was 10 μm (Te + Ts = 25 μm, Ts / Te = 2/3). Was evaluated. For the evaluation of crack generation, a cylindrical rod (cylindrical rod with a radius of 1 mm) 300 shown in FIG. 6 made of stainless steel and having a radius R of 1 mm was used. A curvature radius of 1 mm is the maximum curvature of a general prismatic battery.

[Example 5]
In Example 5, the film thickness Te of the positive electrode mixture layer was set to 30 μm, and the film thickness Ts of the separator layer was set to 10 μm (Te + Ts = 40 μm, Ts / Te = 1/3). Was made. Evaluation of crack generation was performed in the same manner as in Example 4.

[Comparative Example 4]
In Comparative Example 4, the film was formed in the same manner as in Example 1 except that the film thickness Te of the positive electrode mixture layer was 15 μm and the film thickness Ts of the separator layer was 20 μm (Te + Ts = 35 μm, Ts / Te = 4/3). Produced. Evaluation of crack generation was performed in the same manner as in Example 4.

[Comparative Example 5]
In Comparative Example 5, the film was formed in the same manner as in Example 1 except that the film thickness Te of the positive electrode mixture layer was 30 μm and the film thickness Ts of the separator layer was 20 μm (Te + Ts = 50 μm, Ts / Te = 2/3). Produced. Evaluation of crack generation was performed in the same manner as in Example 4.

  FIG. 8 is a data diagram showing SEM images of the separator surfaces and evaluation results of the presence or absence of cracks in Examples 4 to 5 and Comparative Examples 4 to 5 of the present invention.

  As shown in FIG. 8, when the radius of curvature is 1 mm, it has been found that the occurrence of cracks can be prevented when 0 <Te + Ts ≦ 40 μm and 0 <Ts / Te ≦ 2/3. Qualitatively, since the stress applied to the separator layer increases when the radius of curvature is 1 mm as compared with the case where the radius of curvature is 2 mm, cracks are likely to occur. However, by setting 0 <Ts / Te ≦ 2/3, the stress applied to the separator layer can be reduced and the occurrence of cracks can be prevented.

  From the above, the relationship between the film thickness Te of the electrode mixture layer and the film thickness Ts of the separator layer for preventing the occurrence of cracks when the separator layer is curved is such that 0 <Te + Ts ≦ 40 μm when the radius of curvature is 2 mm and It may be 0 <Ts / Te ≦ 4/3. Preferably, when the radius of curvature is 2 mm, the relationship between the film thickness Te of the electrode mixture layer and the film thickness Ts of the separator layer may be 0 <Te + Ts ≦ 40 μm and 0 <Ts / Te ≦ 2/3.

<Relationship between the particle size of the electrode active material and the particle size of the insulating particles relative to the thickness of the separator layer>
In Examples 6 to 11 and Comparative Examples 6 to 8 below, the particle diameters of the insulating particles and the electrode active material are described, and all of them are measured with Microtrac MT3000 (made by Nikkiso).

[Example 6]
In Example 6, the thickness Ts of the separator layer is 5 μm, the D90 particle size Ds of the insulating particles SPP is 3 μm (D50 particle size is 1 μm), and the D90 particle size De of the electrode active material is 10 μm (D50 particle size is 6 μm). The film was produced in the same manner as in Example 1 except that. (Ds / Ts = 0.6, De / Ts = 2).

  Here, a method for evaluating the insulation of the separator layer will be described. A stainless steel plate was placed on the surface of the separator layer formed on the surface of the electrode mixture layer, and the resistance between the stainless steel plate and the current collector foil was measured with a tester. When the resistance value exceeded the upper limit value of the tester (for example, 40 MΩ), it was determined that there was insulation (◯).

[Example 7]
In Example 7, the thickness Ts of the separator layer is 10 μm, the D90 particle size Ds of the insulating particles SPP is 3 μm (D50 particle size is 1 μm), the D90 particle size De of the electrode active material is 6 μm (D50 particle size is 4 μm). The film was produced in the same manner as in Example 1 except that. (Ds / Ts = 0.3, De / Ts = 0.6). The insulation evaluation of the separator layer was performed in the same manner as in Example 6.

[Example 8]
In Example 8, the thickness Ts of the separator layer is 10 μm, the D90 particle size Ds of the insulating particles SPP is 3 μm (D50 particle size is 1 μm), and the D90 particle size De of the electrode active material is 10 μm (D50 particle size is 6 μm). The film was produced in the same manner as in Example 1 except that. (Ds / Ts = 0.3, De / Ts = 1.0). The insulation evaluation of the separator layer was performed in the same manner as in Example 6.

[Example 9]
In Example 9, the thickness Ts of the separator layer is 10 μm, the D90 particle size Ds of the insulating particles SPP is 3 μm (D50 particle size is 1 μm), and the D90 particle size De of the electrode active material is 16 μm (D50 particle size is 10 μm). The film was produced in the same manner as in Example 1 except that. (Ds / Ts = 0.3, De / Ts = 1.6). The insulation evaluation of the separator layer was performed in the same manner as in Example 6.

[Example 10]
In Example 10, the separator layer thickness Ts is 20 μm, the D90 particle size Ds of the insulating particles SPP is 12 μm (D50 particle size is 5 μm), and the D90 particle size De of the electrode active material is 6 μm (D50 particle size is 4 μm). The film was produced in the same manner as in Example 1 except that. (Ds / Ts = 0.6, De / Ts = 0.3). The insulation evaluation of the separator layer was performed in the same manner as in Example 6.

[Example 11]
In Example 11, the separator layer thickness Ts is 20 μm, the D90 particle size Ds of the insulating particles SPP is 12 μm (D50 particle size is 5 μm), and the D90 particle size De of the electrode active material is 10 μm (D50 particle size is 6 μm). The film was produced in the same manner as in Example 1 except that. (Ds / Ts = 0.6, De / Ts = 0.5). The insulation evaluation of the separator layer was performed in the same manner as in Example 6.

[Comparative Example 6]
In Comparative Example 6, the separator layer thickness Ts is 5 μm, the D90 particle size Ds of the insulating particles SPP is 3 μm (D50 particle size is 1 μm), and the D90 particle size De of the electrode active material is 32 μm (D50 particle size is 14 μm). A film was produced in the same manner as in Example 1 except that. (Ds / Ts = 0.6, De / Ts = 6.4). The insulation evaluation of the separator layer was performed in the same manner as in Example 6.

[Comparative Example 7]
In Comparative Example 7, the thickness Ts of the separator layer is 10 μm, the D90 particle size Ds of the insulating particles SPP is 12 μm (D50 particle size is 5 μm), and the D90 particle size De of the electrode active material is 6 μm (D50 particle size is 4 μm). A film was produced in the same manner as in Example 1 except that. (Ds / Ts = 1.2, De / Ts = 0.6). The insulation evaluation of the separator layer was performed in the same manner as in Example 6.

[Comparative Example 8]
In Comparative Example 8, the thickness Ts of the separator layer is 10 μm, the D90 particle size Ds of the insulating particles SPP is 12 μm (D50 particle size is 5 μm), and the D90 particle size De of the electrode active material is 10 μm (D50 particle size is 6 μm). A film was produced in the same manner as in Example 1 except that. (Ds / Ts = 1.2, De / Ts = 1.0). The insulation evaluation of the separator layer was performed in the same manner as in Example 6.

  FIG. 9 is a data diagram showing the evaluation results of the insulating properties of the separators in Examples 6 to 11 and Comparative Examples 6 to 8 of the present invention, and FIG. 10 is the insulating property in Examples 6 to 11 and Comparative Examples 6 to 8 of the present invention. It is a data figure which put together the evaluation result of this in the table | surface.

  As shown in FIGS. 9 and 10, when 0 <De / Ts ≦ 2 and 0 <Ds / Ts ≦ 0.6, defects (insulating material on the surface of the electrode mixture layer) when the separator material (insulating material SPF) is applied. It has been found that since the SPF is not formed uniformly, the electrode mixture is exposed and the electrical failure cannot be ensured), and the insulation can be secured.

  First, the relationship between the thickness Ts of the separator layer and the D90 particle size De of the electrode active material is described below for the reason that 0 <De / Ts ≦ 2.

  That is, the unevenness of the electrode mixture layer is affected by the particle size of the electrode active material. Even when the film thickness of the electrode mixture layer is smoothed by press compression, unevenness due to the active material particles remains, and the unevenness becomes De / 2 at the maximum. Therefore, in order to cover the surface of the electrode mixture layer with the insulating particles SPP, the film thickness Ts of the separator layer (separator SP) needs to be De / 2 ≦ Ts, that is, De / Ts ≦ 2.

  Next, the relationship Ds / Ts between the thickness Ts of the separator layer and the D90 particle size Ds of the insulating particles SPP, and the insulating relationship are described below.

  When the relationship between the thickness Ts of the separator layer and the D90 particle size Ds of the insulating particles SPP is Ds / Ts> 1, the insulating particles SPP are larger than the thickness of the separator. In such a situation, when the separator material (insulating material SPF) is applied, particles are sandwiched between the coating surface and the coater, and a portion where the insulating particles SPP are not formed on the surface of the electrode mixture layer is generated in a streak shape (insulating material SPF). Is not applied to a uniform film thickness, causing streak-like depressions), and as a result, insulation cannot be secured.

  On the other hand, if the relationship between the thickness Ts of the separator layer and the D90 particle size Ds of the insulating particles SPP is Ds / Ts ≦ 1, the insulating particles SPP can be uniformly formed on the surface of the electrode mixture layer. Insulation can be ensured. Also in the present embodiment, as shown in FIG. 9, it was proved that insulation can be secured under the condition of Ds / Ts ≦ 1.

  Thereby, the relationship between the film thickness Ts of the separator layer that prevents the occurrence of defects during coating, the D90 particle size De of the electrode active material, and the D90 particle size Ds of the insulating particles SPP is 0 <De / Ts ≦ 2. And 0 <Ds / Ts ≦ 1 may be satisfied. More preferably, 0 <De / Ts ≦ 2 and 0 <Ds / Ts ≦ 0.6.

  From the above examination, in order to prevent both the occurrence of cracks when the separator layer is curved and the occurrence of defects when the separator material is applied, and to ensure the insulation of the separator layer, the maximum curvature radius is 2 mm. 0 <Te + Ts ≦ 40 μm and 0 <Ts / Te ≦ 4/3. Preferably, 0 <Te + Ts ≦ 40 μm and 0 <Ts / Te ≦ 2/3, and 0 <De / Ts ≦ 2 and 0 <Ds / Ts ≦ 1. More preferably, 0 <De / Ts ≦ 2 and 0 <Ds / Ts ≦ 0.6.

  In the present embodiment, the electrode mixture is formed when the electrode (electrode sheet) is curved by reducing the total film thickness of the electrode mixture layer and the separator layer formed on the surface of the electrode mixture layer. The stress applied to the layer and the separator layer can be reduced, and the occurrence of cracks in the separator layer can be prevented. However, if the film thickness is simply reduced, the separator layer is likely to be defective because it is affected by the unevenness of the electrode mixture layer that is the application surface when the separator material is applied. The defect generated in the separator layer when the separator material is applied means that the insulating particles SPP are not uniformly formed on the surface of the electrode mixture layer, so that the electrode mixture is exposed and electrical insulation cannot be secured. doing.

  Therefore, in the present embodiment, the total film thickness of the electrode mixture layer that is the positive electrode mixture PEF or the negative electrode mixture NEF and the separator (separator layer) SP formed on the surface of the electrode mixture layer is thinned. And controlling the particle sizes of the electrode active material (positive electrode active material PAS or negative electrode active material NAS) and the insulating particles SPP with respect to the film thickness of the separator (separator layer) SP are simultaneously satisfied.

  Thereby, both generation | occurrence | production of the crack in a separator layer and the defect generation | occurrence | production at the time of separator material application | coating can be prevented, and the insulation of a separator layer can be ensured.

  As a result, the insulation failure of the separator (separator layer) SP can be prevented and the reliability of the lithium ion battery LIB can be improved.

  As mentioned above, the invention made by the present inventor has been specifically described based on the embodiments of the invention. However, the present invention is not limited to the embodiments of the invention, and various modifications can be made without departing from the scope of the invention. It goes without saying that it is possible.

  In addition, this invention is not limited to above-described embodiment, Various modifications are included. For example, the above-described embodiment has been described in detail for easy understanding of the present invention, and is not necessarily limited to one having all the configurations described.

  Further, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. . In addition, it is possible to add, delete, and replace other configurations for a part of the configuration of each embodiment. In addition, each member and relative size which were described in drawing are simplified and idealized in order to demonstrate this invention clearly, and it becomes a more complicated shape on mounting.

  In the above embodiment, the technical idea of the present invention has been described by taking a wound type lithium ion battery as an example. However, the technical idea of the present invention is not limited to a wound type lithium ion battery. The present invention can be widely applied to power storage devices (for example, batteries and capacitors) that include a positive electrode, a negative electrode, and a separator that electrically separates the positive electrode and the negative electrode.

  The present invention can be widely used in, for example, a manufacturing industry for manufacturing a battery represented by a lithium ion battery.

LIB Lithium ion battery CS outer can (container)
EL Electrolyte NAS Negative electrode active material NCA Conductive auxiliary agent NEF Negative electrode mixture (electrode mixture layer)
NEP current collector foil (electrode foil)
NEL Negative electrode PAS Positive electrode active material PCA Conductive auxiliary agent PEF Positive electrode mixture (electrode mixture layer)
PEP current collector foil (electrode foil)
PEL Positive electrode SPP Insulating particle SP Separator (separator layer)
EF Electrode material SPF Insulating material EP Current collector foil (electrode foil)

Claims (12)

A positive electrode provided with a positive electrode mixture layer containing a positive electrode active material;
A negative electrode including a negative electrode mixture layer containing a negative electrode active material;
A separator formed on the surface of at least one of the positive electrode mixture layer and the negative electrode mixture layer, and insulating the positive electrode and the negative electrode;
An electrolytic solution in which a charge / discharge reaction is performed between the positive electrode and the negative electrode;
Have
The separator is composed of a mixture of insulating particles and a binder,
The relationship between the thickness Ts of the separator and the thickness Te of the electrode mixture layer on which the separator is formed is Ts + Te ≦ 40 μm and Ts / Te ≦ 4/3.
The separator formed in the electrode mixture layer has a curved structure, the maximum curvature radius of the curve is 2 mm,
The relationship between the thickness Ts of the separator, the D 90 particle size Ds of the insulating particles contained in the separator, and the D 90 particle size De of the active material of the electrode mixture layer in which the separator is formed is A lithium ion battery in which De / Ts ≦ 2 and Ds / Ts ≦ 1. The lithium ion battery according to claim 1,
The relationship between the thickness Ts of the separator and the thickness Te of the electrode mixture layer on which the separator is formed is Ts + Te ≦ 40 μm and Ts / Te ≦ 2/3. The lithium ion battery according to claim 2,
The separator formed in the electrode mixture layer has a curved structure, and a maximum curvature radius of the curve is 1 mm. The lithium ion battery according to any one of claims 1 to 3,
The said separator is a lithium ion battery currently formed in the surface of the said positive mix layer, and the surface of the said negative mix layer. The lithium ion battery according to claim 1,
The relationship between the thickness Ts of the separator, the D 90 particle size Ds of the insulating particles contained in the separator, and the D 90 particle size De of the active material of the electrode mixture layer in which the separator is formed is A lithium ion battery in which De / Ts ≦ 2 and Ds / Ts ≦ 0.6. The lithium ion battery according to claim 5,
The relationship between the thickness Ts of the separator and the thickness Te of the electrode mixture layer on which the separator is formed is Ts + Te ≦ 40 μm and Ts / Te ≦ 2/3. The lithium ion battery according to claim 6,
The separator formed in the electrode mixture layer has a curved structure, and a maximum curvature radius of the curve is 1 mm. In the lithium ion battery according to any one of claims 5 to 7,
The said separator is a lithium ion battery currently formed in the surface of the said positive mix layer, and the surface of the said negative mix layer. (A) applying a slurry-like electrode material on the electrode foil;
(B) applying a slurry-like insulating material on the electrode material or an electrode mixture layer formed by drying the electrode material;
(C) The electrode material and the insulating material are dried in separate steps or the same step, and the electrode mixture layer made of the electrode material is formed on the electrode foil, and the insulating material is formed on the electrode mixture layer. A step of forming a separator,
(D) after the step (c), the step of bending the separator and storing the electrode foil, the electrode mixture layer and the separator in a container;
Have
The insulating material includes a mixture of insulating particles and a binder,
The relationship between the thickness Ts of the separator and the thickness Te of the electrode mixture layer on which the separator is formed is Ts + Te ≦ 40 μm and Ts / Te ≦ 4/3.
In the step (d), the separator is curved so that its maximum radius of curvature is 2 mm,
The relationship between the film thickness Ts of the separator, the D 90 particle size Ds of the insulating particles contained in the separator, and the D 90 particle size De of the active material of the electrode mixture layer in which the separator is formed is A method for producing a lithium ion battery, wherein the separator and the electrode mixture layer are formed so that De / Ts ≦ 2 and Ds / Ts ≦ 1. In the manufacturing method of the lithium ion battery according to claim 9,
The separator and the electrode mixture layer are set so that the relationship between the film thickness Ts of the separator and the film thickness Te of the electrode mixture layer on which the separator is formed is Ts + Te ≦ 40 μm and Ts / Te ≦ 2/3. A method for manufacturing a lithium ion battery. (A) applying a slurry-like electrode material on the electrode foil;
(B) applying a slurry-like insulating material on the electrode material or an electrode mixture layer formed by drying the electrode material;
(C) The electrode material and the insulating material are dried in separate steps or the same step, and the electrode mixture layer made of the electrode material is formed on the electrode foil, and the insulating material is formed on the electrode mixture layer. A step of forming a separator,
(D) after the step (c), the step of bending the separator and storing the electrode foil, the electrode mixture layer and the separator in a container;
Have
The insulating material includes a mixture of insulating particles and a binder,
The relationship between the thickness Ts of the separator and the thickness Te of the electrode mixture layer on which the separator is formed is Ts + Te ≦ 40 μm and Ts / Te ≦ 4/3.
In the step (d), the separator is curved so that its maximum radius of curvature is 2 mm,
The relationship between the film thickness Ts of the separator, the D 90 particle size Ds of the insulating particles contained in the separator, and the D 90 particle size De of the active material of the electrode mixture layer in which the separator is formed is A method of manufacturing a lithium ion battery, wherein the separator and the electrode mixture layer are formed so that De / Ts ≦ 2 and Ds / Ts ≦ 0.6. In the manufacturing method of the lithium ion battery according to claim 11,
The separator and the electrode mixture layer are set so that the relationship between the film thickness Ts of the separator and the film thickness Te of the electrode mixture layer on which the separator is formed is Ts + Te ≦ 40 μm and Ts / Te ≦ 2/3. A method for manufacturing a lithium ion battery.

Images