WO2016079821A1

WO2016079821A1 - Lithium ion battery and production method therefor

Info

Publication number: WO2016079821A1
Application number: PCT/JP2014/080595
Authority: WO
Inventors: 新平尼崎; 利光野口; 祐介加賀; 和明直江
Original assignee: 株式会社日立製作所
Priority date: 2014-11-19
Filing date: 2014-11-19
Publication date: 2016-05-26

Abstract

This invention comprises, in an electrode wound body wherein a positive electrode, a separator, and a negative electrode are layered and wound, forming at the positive electrode a high-porosity positive electrode mixture layer and a low-porosity positive electrode mixture layer alternating in a winding direction on the surface of a current collector foil, and, forming at the negative electrode a high-porosity negative electrode mixture layer and a low-porosity negative electrode mixture layer alternating in the winding direction on the surface of a current collector foil. By providing the high-porosity positive electrode mixture layer and the negative electrode mixture layer, the infiltration rate of the electrolytic solution into the electrode wound body is increased. In addition, by equalizing the particle size distributions for the active substances contained respectively in the high-porosity positive electrode mixture layer and the low-porosity positive electrode mixture layer, and by equalizing the particle size distributions for the active substances contained respectively in the high-porosity negative electrode mixture layer and the low-porosity negative electrode mixture layer, the internal resistance during charging-discharging is lowered.

Description

Lithium ion battery and manufacturing method thereof

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

As background art in this technical field, there are JP 2013-008523 A (Patent Document 1) and JP 2011-175739 A (Patent Document 2).

Patent Document 1 states that “a mixture layer containing an active material is formed on the surface of a current collector, and this mixture layer has a different porosity depending on the position along the surface of the current collector. The battery electrode having "" is described.

Patent Document 2 states that “the electrode film formed on the electrode surface is a mixture layer having a small gap and a small active material density, but a high active material density; "A lithium ion battery having an electrode film structure combined with a mixture layer having a large void size that easily penetrates" is described.

JP 2013-008523 A JP 2011-175739 A

Lithium ion batteries are required to achieve both improved productivity and improved battery characteristics.

Patent Document 1 describes a lithium ion battery electrode that secures a migration path of lithium ions in an electrode mixture layer and improves input / output characteristics, and a manufacturing method thereof. However, no mention is made regarding the permeation time of the electrolytic solution, and the structure of the lithium ion battery electrode of Patent Document 1 is not optimal for shortening the permeation time of the electrolytic solution.

Patent Document 2 discloses a lithium ion battery that uses an active material from which fine powder has been removed and uses an electrode mixture layer having a large void size as an electrolyte solution supply path, thereby reducing the electrolyte solution penetration time. Is described. However, since fine powder has the characteristics that the diffusion distance of lithium ions in the active material is short and the reaction area per active material weight is large, the active material containing fine powder is suitable for improving input / output characteristics. ing. Therefore, an active material from which fine powder has been removed is disadvantageous for improving input / output characteristics. Furthermore, in the method for producing an electrode film of Patent Document 2, the number of steps for removing fine powder increases and the number of steps for applying an electrode mixture increases to two, leading to an increase in the number of electrode production steps.

Therefore, the present invention provides a lithium ion battery capable of achieving both improvement in productivity and improvement in battery characteristics by shortening the permeation time of the electrolytic solution and reducing the internal resistance during charging and discharging. A manufacturing method thereof is provided.

In order to solve the above-mentioned problems, a lithium ion battery according to the present invention has a positive electrode, a separator, and a negative electrode that are stacked in an outer can having a can lid and a can bottom at positions facing each other. An electrode winding body wound around is provided. In the positive electrode, a positive electrode mixture layer having a high porosity and a positive electrode mixture layer having a low porosity are alternately formed in the winding direction on the surface of the current collector foil. In addition, a negative electrode mixture layer having a high porosity and a negative electrode mixture layer having a low porosity are alternately formed in the winding direction. Furthermore, the particle size distribution of the active material contained in each of the positive electrode mixture layer having a high porosity and the positive electrode mixture layer having a low porosity is the same, and the negative electrode mixture layer having a high porosity and the negative electrode mixture having a low porosity are used. The particle size distribution of the active material contained in each of the layers is the same.

According to the present invention, it is possible to provide a lithium ion battery and a method for manufacturing the same that can achieve both improvement in productivity and improvement in battery characteristics.

Issues, configurations, and effects other than those described above will be clarified by the following description of embodiments.

2 is a cross-sectional view showing an internal structure of a cylindrical lithium ion battery according to Example 1. FIG. (A), (b) and (c) are schematic views showing a metal member for drying used in the drying step after slurry application according to Example 1, a positive electrode mixture layer during drying, and a positive electrode mixture layer after drying, respectively. It is. (A) And (b) is the schematic diagram of the 1st example and 2nd example of the electrode winding body by which the two electrode mixture layers by which the porosity from Example 1 differs mutually were formed alternately in the winding direction, respectively It is. (A), (b), and (c) are a drying metal member, a positive electrode mixture layer being dried, and a positive electrode mixture layer after drying, respectively, used in the drying step after slurry application according to the modification of Example 1. It is a schematic diagram shown. It is a schematic diagram of the 3rd example of the electrode winding body by which the two electrode mixture layers by which the porosity is mutually different by the modification of Example 1 were alternately formed in the winding direction. It is a schematic diagram which expands and shows a part of cross section of the electrode by which the electrode mixture layer with a low porosity by Example 1 and the electrode mixture layer with a high porosity were formed alternately. It is a graph which shows the porosity of the electrode mixture layer with a low porosity, and the porosity of an electrode mixture layer with a high porosity. (A) And (b) is a principal part top view which shows the other example of two positive mix layers from which the porosity in Example 1 differs. It is a graph which shows the osmosis | permeation rate of the electrolyte solution in the electrode by Example 1, and the electrode by a comparative example. It is a graph which shows the internal resistance in a battery provided with the electrode provided with the electrode by Example 1, and the battery provided with the comparative example. (A), (b) and (c) are schematic diagrams showing a drying metal member, a positive electrode mixture layer being dried, and a positive electrode mixture layer after drying, respectively, used in the drying step after slurry application according to Example 2. It is. It is a schematic diagram of the 4th example of the electrode winding body which has the electrode in which the area | region with the high porosity by Example 2 was formed in the grid | lattice form. (A), (b), and (c) are the schematic diagrams which respectively show the shielding board used at the drying process after slurry application | coating by Example 3, the positive mix layer during drying, and the positive mix layer after drying. .

In the following embodiments, when necessary for the sake of convenience, the description will be divided into a plurality of sections or embodiments. However, unless otherwise specified, they are not irrelevant to each other, and one is the other. There are some or all of the modifications, details, supplementary explanations, and the like.

Further, in the following embodiments, when referring to the number of elements (including the number, numerical value, quantity, range, etc.), especially when clearly indicated and when clearly limited to a specific number in principle, etc. Except, it is not limited to the specific number, and 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.

In addition, when referring to “consisting of A”, “consisting of A”, “having A”, and “including A”, other elements are excluded unless specifically indicated that only that element is included. It goes without saying that it is not what you do. 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.

Also, in the drawings used in the following embodiments, hatching may be added to make the drawings easy to see even if they are plan views. In all the drawings for explaining the following embodiments, components having the same function are denoted by the same reference numerals in principle, and repeated description thereof is omitted. Hereinafter, the present embodiment will be described in detail with reference to the drawings.

In the following description, the positive electrode and the negative electrode are collectively referred to as “electrode”, and the positive electrode mixture and the negative electrode mixture are collectively referred to as “electrode mixture”. In the following description, the positive electrode material, the negative electrode material, and the insulating material before the drying process using the drying furnace are substances having fluidity including liquids such as a binder solution and an organic solvent. In the following description, “the surface of the current collector foil” refers to only the front surface, not the entire surface including the front surface and the back surface of the current collector foil.

≪Configuration of lithium-ion battery≫
An example of the configuration of the lithium ion battery according to the first embodiment will be described with reference to FIG. FIG. 1 is a cross-sectional view showing the internal structure of a cylindrical lithium ion battery according to the first embodiment.

As shown in FIG. 1, the lithium ion battery LIB has a cylindrical outer can CS having a bottom, and inside the outer can CS, an electrode container made up of a positive electrode PEL, separators SP1, SP2, and a negative electrode NEL. A circular WRF is formed. Specifically, the electrode winding body WRF is laminated so as to sandwich the separator SP1 (or SP2) between the positive electrode PEL and the negative electrode NEL, and is wound around the axis CR at the center of the outer can CS. Has been.

And the positive electrode current collection tab PTAB formed in the positive electrode PEL is arrange | positioned at the upper part side of the electrode winding body WRF, and is electrically connected with the positive electrode lead board PT provided in the upper part of the armored can CS. . 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 is electrically connected to the negative electrode lead plate NT provided on the lower part (bottom part) of the outer can CS. Has been.

The electrolyte is injected into the electrode winding body WRF formed inside the outer can CS. The outer can CS is sealed with a battery lid CAP. The outer can CS is made mainly of, for example, iron (Fe) or stainless steel. In FIG. 1, the symbol PR indicates a positive electrode ring, and the symbol NR indicates a negative electrode ring.

The positive electrode PEL is formed by applying a positive electrode mixture layer PEF made of a positive electrode active material, a binder (binder) and a conductive additive to the current collector foil PEP.

Examples of the positive electrode active material include, but are not limited to, lithium cobaltate, lithium nickelate, and lithium manganate. Specifically, the positive electrode active material is a material capable of inserting / extracting lithium ions, and may be any lithium-containing transition metal oxide in which a sufficient amount of lithium (Li) has been previously inserted. It may be a simple substance such as manganese (Mn), nickel (Ni), cobalt (Co) or iron (Fe), or a material mainly composed of two or more kinds of transition metals. Further, the crystal structure such as the spinel crystal structure or the layered crystal structure is not particularly limited as long as the above-described site and channel are ensured. Furthermore, some transition metals or lithium (Li) in the crystal are replaced with elements such as iron (Fe), cobalt (Co), nickel (Ni), chromium (Cr), aluminum (Al) or manganese (Mg). The obtained material may be used as the positive electrode active material. Alternatively, a material doped with an element such as iron (Fe), cobalt (Co), nickel (Ni), chromium (Cr), aluminum (Al) or manganese (Mg) in the crystal may be used as the positive electrode active material. Good.

As the binder, 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 net-like metal made of a conductive metal such as aluminum (Al) is used.

The negative electrode NEL is formed by applying a negative electrode mixture layer NEF made of a negative electrode active material, a binder (binder) and a conductive additive to the current collector foil NEP.

Examples of the negative electrode active material include a crystalline carbon material and an amorphous carbon material, but are not limited thereto. Specifically, the negative electrode active material may be any carbon material that can insert and desorb lithium ions, and carbon materials such as natural graphite, various artificial graphite agents, and coke can be used. In addition to the above carbon materials, oxides such as silicon oxide, niobium oxide or titanium oxide, or silicon (Si), tin (Sn), germanium (Ge), lead (Pb) or aluminum (Al) A material that forms an alloy with lithium (Li), which is typified, 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 or a lump shape are applicable.

As the binder, for example, polyvinylidene fluoride or polytetrafluoroethylene can be used. Furthermore, for the current collector foil NEP, for example, a metal foil or a net-like metal made of a conductive metal such as copper (Cu) is used.

The separators SP1 and SP2 have a function as a spacer that allows lithium ions to pass through while insulating between the positive electrode and the negative electrode and preventing electrical contact. In recent years, high-strength and thin microporous membranes are used as the separators SP1 and SP2. The separators SP1 and SP2 composed of the microporous membrane are composed of, for example, polyethylene (PE (polyethylene)) or polypropylene (PP (polypropylene)), or a combination of these materials.

A nonaqueous electrolytic solution is used as an electrolytic solution in which a charge / discharge reaction is performed between the positive electrode and the negative electrode. 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 an 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 electrolytic solution, an aqueous solution cannot be used as the electrolytic solution as in the conventional battery. For this reason, in the lithium ion battery LIB, a non-aqueous electrolyte is used as the electrolyte.

Specifically, as _the electrolyte of the nonaqueous _{_{_{electrolyte, LiPF 6, LiClO 4, LiAsF}}} 6, LiBF 4, LiB (C 6 H 5) 4, such as CH 3 _SO 3 Li or _CF 3 _SO 3 Li, or their Mixtures can be used. Moreover, as an organic solvent, ethylene carbonate, dimethyl carbonate, ethyl methyl carbonate, propylene carbonate, or diethyl carbonate can be used. Further, examples of the organic solvent include 1,2-dimethoxyethane, 1,2-diethoxyethane, γ-butyrolactone, tetrahydrofuran, 1,3-dioxolane, 4-methyl-1,3-dioxolane, diethyl ether, sulfolane, methylsulfolane. Acetonitrile or propionitrile can be used. Furthermore, as the organic solvent, the above-mentioned mixed liquid of organic solvents can be used.

By the way, as an example of a method for injecting the electrolytic solution, a method of injecting the electrolytic solution from the can bottom side and infiltrating the electrolytic solution from the can bottom side of the electrode winding body WRF toward the can lid side, or the electrolytic solution Is injected from the can lid side, and the electrolyte solution penetrates from the can lid side of the electrode winding body WRF toward the can bottom side. In order to shorten the injection time, the electrode winding body WRF has a path through which the electrolyte can easily penetrate in the direction of the can lid-can bottom (the direction from the can lid to the can bottom or the direction from the can bottom to the can lid). It is effective to provide it. Therefore, in Example 1, as a path through which the electrolytic solution easily permeates, an electrode mixture layer having a high porosity in the direction of the can lid-can bottom of the electrode winding body WRF, for example 40 An electrode mixture layer having a porosity of about volume% was formed.

The characteristic electrode structure of the lithium ion battery according to Example 1 and the manufacturing method thereof will be described in detail below.

≪Characteristics of electrode for lithium ion battery≫
Details of the characteristics of the electrode for a lithium ion battery according to the first embodiment will be described together with an example of a manufacturing method and an evaluation method thereof. In Example 1, a lithium ion battery electrode in which two or more electrode mixture layers having different porosities are formed in the winding direction is formed through a drying process described below. Further, each of the two or more electrode mixture layers having different porosity from one side of the current collector foil along the winding direction toward the other side of the current collector foil along the winding direction. It is formed.

(Electrode and electrode winding body manufacturing method)
The manufacturing method of the electrode and electrode winding body according to the first embodiment will be described below.

(1) First, the coating process will be described. Here, although the manufacturing method of a positive mix layer is demonstrated, the manufacturing method of a negative mix layer is also the same.

Lithium manganese cobalt nickel composite oxide for the positive electrode active material, graphite powder for the conductive additive, polyvinylidene fluoride (PVDF) for the binder, and aluminum foil for the current collector foil To do. These were mixed so that the weight percentages of the positive electrode active material, the conductive additive and the binder were 93.0, 3.5 and 3.5, respectively, and further N-methyl-2-pyrrolidone (NMP (N-methylpyrrolidone ); Hereinafter simply referred to as NMP) to produce a positive electrode slurry (slurry positive electrode material). At this time, the weight of NMP is adjusted so that the solid content ratio (weight of the solid content (positive electrode active material, conductive additive and binder) with respect to the slurry weight) is 66% by weight, and the slurry viscosity is 1 Pa · s. adjust. By apply | coating the said positive electrode slurry on the surface of current collection foil, the positive mix layer by which the positive electrode slurry was apply | coated by uniform density can be formed on the surface of current collection foil.

(2) Next, the drying process will be described with reference to FIGS. 2 (a), (b) and (c). Here, the manufacturing method of the positive electrode will be described, but the manufacturing method of the negative electrode is substantially the same. 2 (a), 2 (b), and 2 (c) show a drying metal member, a positive electrode mixture layer during drying, and a positive electrode mixture layer after drying, respectively, used in the drying step after slurry application according to the first embodiment. It is a schematic diagram shown.

First, a drying metal member MD1 shown in FIG. 2 (a) is prepared. The drying metal member MD1 includes a plurality of metal lines MW arranged with a first pitch P1 in the first direction, and a metal plate MP connected to one end of the plurality of metal lines MW. That is, the metal plate MP and the plurality of metal wires MW are integrally formed, and the plurality of metal wires MW are fixed by the metal plate MP. The line width of the plurality of metal lines MW is, for example, 0.1 to 1.0 mm, and the first pitch P1 in the first direction of the plurality of metal lines MW is, for example, 10 mm. The drying metal member MD1 (the metal plate MP and the plurality of metal wires MW) is made of, for example, stainless steel, iron (Fe), gold (Au), silver (Ag), iron (Fe) alloy, nickel (Ni) alloy, or the like. . The cross section along the first direction of the metal line MW is substantially circular, but is not limited thereto, and may be, for example, a substantially square shape.

Next, as shown in FIG. 2B, the current collector foil PEP having the positive electrode mixture layer PEF applied on the surface thereof is mounted on the metal member MD1 for drying. At this time, the current collector foil PEP is mounted such that one of the two sides along the conveying direction of the current collector foil PEP is placed on the metal plate MP of the drying metal member MD1. That is, the first direction coincides with the conveying direction of the current collector foil PEP. Thereafter, the current collector foil PEP mounted on the drying metal member MD1 is conveyed into, for example, a 120 ° C. hot-air drying furnace, and applied to the surface of the current collector foil PEP. The layer PEF is dried. The conveying speed of the current collector foil PEP is, for example, 5 to 100 m / min. At the time of mass production, productivity can be maintained by conveying the drying metal member MD1 together with the current collector foil PEP in the hot air drying furnace at a constant speed.

By passing through the drying step, as shown in FIG. 2 (c), the porosity of the positive electrode mixture layer PEFH that is not located on the metal plate MP and the plurality of metal wires MW of the metal member MD1 for drying, It becomes higher than the porosity of the positive electrode mixture layer PEFL located on the metal plate MP and the plurality of metal wires MW of the drying metal member MD1. Thereby, for example, a positive electrode mixture layer PEFL with a width of 5 mm and a low porosity and a positive electrode mixture layer PEFH with a width of 5 mm and a high porosity are alternately formed in the conveying direction of the current collector foil PEP. In addition, a positive electrode composite having a low porosity is formed on a portion having a predetermined width from one side of the current collector foil PEP along the conveying direction of the current collector foil PEP (a portion where the current collector foil PEP and the metal plate MP overlap). The agent layer PEFL is formed. Then, a positive electrode is manufactured by press-compressing the dried positive electrode mixture layer PEF. The negative electrode can be produced in the same manner.

(3) Next, the winding process will be described with reference to FIGS. 3 (a) and 3 (b). 3 (a) and 3 (b) respectively show a first example of an electrode winding body having electrodes in which two electrode mixture layers having different porosities according to Example 1 are alternately formed in the winding direction. It is a schematic diagram of the 2nd example.

As shown in FIG. 3A, the first example of the electrode winding body WRF includes a positive electrode PEL wound around the axis CR, separators SP1 and SP2, and a negative electrode NEL. In the positive electrode PEL, the positive electrode mixture layer PEFH having a high porosity and the positive electrode mixture layer PEFL having a low porosity are alternately formed in the winding direction. In the negative electrode NEL, the negative electrode mixture layer having a high porosity. NEFH and a negative electrode mixture layer NEFL having a low porosity are alternately formed in the winding direction.

In the first example of the electrode winding body WRF, the positive electrode mixture layer PEFL having a low porosity formed along the conveying direction of the current collector foil PEP is wound so as to be positioned on the positive electrode current collector tab PTAB side. The negative electrode mixture layer NEFL having a low porosity formed along the conveying direction of the current collector foil NEP is wound so as to be positioned on the positive electrode current collector tab PTAB side. Accordingly, the first example of the electrode winding body WRF includes the positive electrode PEL on which the positive electrode mixture layer PEFH having a high porosity is formed from the can bottom side toward the can lid direction, and the can bottom side toward the can lid direction. A negative electrode mixture layer NEFH having a high porosity.

Further, as shown in FIG. 3B, the second example of the electrode winding body WRF is similar to the first example of the electrode winding body WRF, the positive electrode PEL wound around the axis CR, the separator SP1 and SP2 and negative electrode NEL are comprised. In the positive electrode PEL, the positive electrode mixture layer PEFH having a high porosity and the positive electrode mixture layer PEFL having a low porosity are alternately formed in the winding direction. In the negative electrode NEL, the negative electrode mixture layer having a high porosity. NEFH and a negative electrode mixture layer NEFL having a low porosity are alternately formed in the winding direction.

However, in the second example of the electrode winding body WRF, unlike the first example of the electrode winding body WRF, the positive electrode mixture layer PEFL having a low porosity formed along the conveying direction of the current collector foil PEP is formed as the negative electrode collector. The negative electrode mixture layer NEFL having a low porosity formed along the conveying direction of the current collector foil NEP is wound so as to be positioned on the negative electrode current collector tab NTAB side. ing. Therefore, the second example of the electrode winding body WRF includes the positive electrode PEL on which the positive electrode mixture layer PEFH having a high porosity is formed from the can lid side toward the can bottom direction, and the can lid side toward the can bottom direction. A negative electrode mixture layer NEFH having a high porosity.

(Variation of manufacturing method of electrode and electrode winding body)
Next, the manufacturing method of the electrode and electrode winding body by the modification of a present Example 1 is demonstrated below.

(1) First, the positive electrode mixture layer PEF is formed on the surface of the current collector foil PEP, and the negative electrode mixture layer NEF is formed on the surface of the current collector foil NEP, in the same manner as the coating step described above.

(2) Next, a drying process is demonstrated using FIG. 4 (a), (b) and (c). Here, the manufacturing method of the positive electrode will be described, but the manufacturing method of the negative electrode is substantially the same. 4 (a), (b) and (c) respectively show the metal member for drying used in the drying step after slurry application according to the modified example of Example 1, the positive electrode mixture layer during drying, and the positive electrode mixture after drying. It is a schematic diagram which shows an agent layer.

First, a drying metal member MD2 shown in FIG. 4 (a) is prepared. The drying metal member MD2 is composed of a plurality of metal lines MW arranged with a second pitch P2 in the first direction. One end and the other end of the plurality of metal wires MW are connected by a support member, and the plurality of metal wires MW are fixed. The line width of the plurality of metal lines MW is, for example, 0.1 to 1.0 mm, and the second pitch P2 in the first direction of the plurality of metal lines MW is, for example, 10 mm. The plurality of metal wires MW are made of, for example, stainless steel, iron (Fe), gold (Au), silver (Ag), iron (Fe) alloy, nickel (Ni) alloy, or the like. The cross section along the first direction of the metal line MW is substantially circular, but is not limited thereto, and may be, for example, a substantially square shape.

Next, as shown in FIG. 4B, the current collector foil PEP having the positive electrode mixture layer PEF applied on the surface thereof is mounted on the drying metal member MD2. At this time, the current collector foil PEP is mounted on the plurality of metal wires MW of the drying metal member MD2. Thereafter, the current collector foil PEP mounted on the drying metal member MD2 is conveyed into, for example, a 120 ° C. hot-air drying furnace, and applied to the surface of the current collector foil PEP. The layer PEF is dried. Here, the said 1st direction and the conveyance direction of current collection foil PEP correspond. The conveying speed of the current collector foil PEP is, for example, 5 to 100 m / min. At the time of mass production, productivity can be maintained by conveying the drying metal member MD2 together with the current collector foil PEP in the hot air drying furnace at a constant speed.

By passing through the drying step, as shown in FIG. 4C, the porosity of the positive electrode mixture layer PEFH that is not located on the plurality of metal wires MW of the drying metal member MD2 is reduced to the drying metal member MD2. It becomes higher than the porosity of the positive electrode mixture layer PEFL located on the plurality of metal wires MW. Thereby, for example, a positive electrode mixture layer PEFL with a width of 5 mm and a low porosity and a positive electrode mixture layer PEFH with a width of 5 mm and a high porosity are alternately formed in the conveying direction of the current collector foil PEP. Then, a positive electrode is manufactured by press-compressing the dried positive electrode mixture layer PEF. The negative electrode can be produced in the same manner.

(3) Next, the winding process will be described with reference to FIG. FIG. 5 is a schematic diagram of a third example of an electrode winding body having electrodes in which two electrode mixture layers having different porosity are alternately formed in the winding direction according to a modification of the first embodiment.

As shown in FIG. 5, the third example of the electrode winding body WRF includes a positive electrode PEL wound around the axis CR, separators SP1 and SP2, and a negative electrode NEL. In the positive electrode PEL, the positive electrode mixture layer PEFH having a high porosity and the positive electrode mixture layer PEFL having a low porosity are alternately formed in the winding direction. In the negative electrode NEL, the negative electrode mixture layer having a high porosity. NEFH and a negative electrode mixture layer NEFL having a low porosity are alternately formed in the winding direction.

In the third example of the electrode winding body WRF, the other side of the current collector foil PEP along the winding direction extends from one side of the current collector foil PEP along the winding direction in the direction of the can lid-can bottom. A positive electrode PEL on which a positive electrode mixture layer PEFH having a high porosity reaching 1 is formed. Further, in the third example of the electrode winding body WRF, the other side of the current collector foil NEP along the winding direction from one side of the current collector foil NEP along the winding direction in the direction of the can lid-can bottom. The negative electrode NEL in which the negative electrode mixture layer NEFH having a high porosity reaching the upper limit is formed.

(Electrode structure)
Next, the structure of the electrode according to Example 1 will be described below with reference to FIGS. FIG. 6 is a cross section of an electrode in which an electrode mixture layer having a low porosity and an electrode mixture layer having a high porosity are alternately formed according to Example 1 (cross section in the direction along the conveying direction of the current collector foil). It is a schematic diagram which expands and shows a part of. FIG. 7 is a graph showing the porosity of an electrode mixture layer having a low porosity and the porosity of an electrode mixture layer having a high porosity. In addition, an electrode mixture layer with a low porosity is a location (for example, a region closer to 2.5 mm from the metal wire) near the metal wire in the drying process, and an electrode mixture layer with a high porosity is used in the drying process. It is a portion that is not near the metal line (for example, a far region away from the metal wire by 2.5 mm or more).

As shown in FIG. 6, the electrode EL includes a current collector (current collector foil) EP and an electrode mixture layer EF formed on the current collector EP. The electrode mixture layer EF includes the active material AS. , Containing conductive aid CA and binder (binder) BD. The average particle size of the active material AS is, for example, 2 to 10 μm, and the particle size distribution of the electrode mixture layer having a low porosity and the particle size distribution of the electrode mixture layer having a high porosity are the same. Here, “same” does not mean completely the same, but means substantially the same or substantially the same, and includes a certain range in consideration of variations. For example, as described above, the average particle diameter of the active material AS also has a variation of 2 to 10 μm.

Quantitative evaluation of the porosity can be performed, for example, by observing a cross section SEM (Scanning Electron Microscope) of the electrode mixture layer EF. From the SEM image, the void area and the solid content area of the cross section of the electrode mixture layer EF were obtained, and the void ratio was calculated by the formula (1).

Porosity (area%) =
Void area / (Cavity area + Solid content area) × 100 Formula (1)

In cross-sectional SEM observation, it is difficult to quantitatively evaluate the porosity in the depth direction, but the electrode structure is considered to be similar in the vicinity of the observation surface. Therefore, in this experiment, evaluation was performed as porosity (area%) ≈porosity (volume%). The cross section of the electrode mixture layer having a low porosity and the cross section of the electrode mixture layer having a high porosity were each observed at three locations, and the porosity was calculated.

FIG. 7 shows the porosity of the electrode mixture layer having a low porosity and the porosity of the electrode mixture layer having a high porosity. The porosity shown in FIG. 7 is an average value at three locations, and the error bar indicates the maximum value and the minimum value. The porosity of the electrode mixture layer with low porosity is about 18 to 28% by volume, the porosity of the electrode mixture layer with high porosity is about 39 to 43% by volume, and the difference in porosity is about 11 to 25% by volume. Met.

As described above, the reason why the electrode mixture layer having a low porosity and the electrode mixture layer having a high porosity are obtained is considered as follows.

In the drying process, the electrode mixture layer near the metal wire has a faster temperature rise than the electrode mixture layer not near the metal wire, and the volatilization rate of NMP contained in the electrode slurry (slurry electrode material) is high. Conceivable. Therefore, NMP volatilizes and disappears in the electrode mixture layer in the vicinity of the metal wire, and NMP does not volatilize in a portion that is not in the vicinity of the metal wire. When such a state occurs, the NMP flows from the location where the NMP remains to the location where the NMP has evaporated and disappeared. At this time, the solid content of the active material moves simultaneously with the flow of NMP, so the density of the solid content increases in the electrode mixture layer near the metal wire, and the solid content in the electrode mixture layer not near the metal wire. It is thought that the density is lowered. Since the solid contents have different densities, electrode mixture layers having different porosity can be formed.

Further, in order to obtain two or more electrode mixture layers having different porosity, it is only necessary to provide a temperature distribution in the electrode mixture layer in the drying step as described above, and the metal of the metal member for drying in the drying step By controlling the shape of the line, two or more electrode mixture layers having different porosity can be produced in an arbitrary pattern. For example, as shown in FIG. 8 (a), the shape of the positive electrode mixture layer PEFH having a high porosity can be a parallelogram, or as shown in FIG. 8 (b), the positive electrode mixture having a high porosity can be used. The shape of the agent layer PEFH can also be corrugated.

(Various characteristics of lithium-ion battery)
Next, in the lithium ion battery according to Example 1, the results of evaluating the penetration rate of the electrolytic solution from the viewpoint of productivity and the internal resistance (DC resistance) of the battery from the viewpoint of battery characteristics are shown in FIGS. This will be described below. FIG. 9 is a graph showing the permeation rate of the electrolytic solution in the electrode according to the first embodiment and the electrode according to the comparative example. FIG. 10 is a graph showing the internal resistance in the battery including the electrode according to the first embodiment and the battery including the electrode according to the comparative example.

For the electrode according to Example 1 that evaluated the penetration rate of the electrolytic solution and the internal resistance of the battery, for example, an electrode mixture layer having a low porosity and a high porosity every 5 mm shown in FIG. An electrode in which electrode mixture layers were alternately formed was used. In the electrode according to Example 1, the active material density of the electrode mixture layer having a low porosity is about 2.8 g / cm ³ , and the active material density of the electrode mixture layer having a high porosity is about 2.1 g / cm 3. ^3. The area ratio of the electrode mixture layer having a low porosity and the electrode mixture layer having a high porosity is 1: 1.

Further, for the electrode according to the comparative example in which the penetration rate of the electrolytic solution and the internal resistance of the battery were evaluated, an electrode mixture layer in which the electrode slurry was applied at a uniform density on the surface of the current collector foil, for example, hot air at 120 ° C. It dried with the drying furnace and produced the electrode with the uniform porosity. In the electrode according to the comparative example, the active material density of the electrode mixture layer is about 2.7 g / cm ³ .

First, the method for evaluating the penetration rate of the electrolyte and the experimental results will be described.

When 5 μl of the electrolytic solution is dropped on the surface of the electrode mixture layer, the electrolytic solution penetrates through the electrode mixture layer and spreads over the surface of the electrode mixture layer. After the spread of the electrolytic solution is maximized, it is observed that the electrolytic solution penetrates into the electrode mixture layer. The time when the electrolyte solution permeated into the electrode mixture layer and the electrolyte solution was not visible was defined as the penetration end time, and the product of the area where the electrolyte solution spread and the thickness of the electrode mixture layer was defined as the penetration volume. The permeation time (time from immediately after the electrolytic droplet was dropped to the end of permeation) was measured, and the permeation rate was calculated by equation (2).

Permeation rate (μl / (s · cm ³ )) =
Amount of dropped electrolyte / (infiltration volume × infiltration time) Formula (2)

FIG. 9 shows the permeation rate of the electrolytic solution in the electrode according to Example 1 and the electrode according to the comparative example. In FIG. 9, the permeation rate of the electrode according to the comparative example is 1, and the permeation rate is shown as a relative value. Compared with the electrode according to the comparative example, it was confirmed that the penetration rate was improved by 1.2 times in the electrode according to the present Example 1.

When an electrode mixture layer having a high porosity as shown in FIG. 3A is formed from the can bottom side toward the can lid direction, the electrolyte solution is injected from the can bottom side. Time can be shortened. On the other hand, when forming an electrode mixture layer with a high porosity as shown in FIG. 3 (b) from the can lid side toward the can bottom, by injecting an electrolyte from the can lid side, Injection time can be shortened. From the viewpoint of improving the injection speed, the length (L) of the mixture layer having a high porosity formed from the bottom of the can to the can lid or from the can lid to the bottom of the can is determined from the direction of the can lid to the bottom of the can. The width (W) of the electrode mixture layer is preferably 2/3 or more and 1 or less (2W / 3 <L ≦ W) (see FIG. 3A). The length (L) of the electrode mixture layer having a high porosity formed from the can bottom side toward the can lid direction or from the can lid side toward the can bottom direction is the width of the electrode mixture layer in the can lid-can bottom direction ( If the ratio is less than 2/3 times W), the electrode mixture layer in which the electrolyte solution easily penetrates becomes short, and the effect of shortening the injection time becomes low.

In addition, since the effect of shortening the injection time is the highest, the length (L) of the electrode mixture layer having a high porosity is equal to the width (W) of the electrode mixture layer in the can lid-can bottom direction. More preferably (L = W) (see FIG. 5). In this case, the injection time can be shortened by injecting the electrolyte from either the can bottom side or the can lid side.

Next, the battery internal resistance evaluation method and experimental results will be described.

In both Example 1 and Comparative Example, a positive electrode composed of a lithium manganese cobalt nickel composite oxide, a conductive additive (graphite powder) and a binder (polyvinylidene fluoride), a carbon powder, a conductive additive (graphite), and a binder A negative electrode made of a material (polyvinylidene fluoride) was used. Further, in both Example 1 and Comparative Example, an electrolytic solution comprising a separator made of porous polypropylene having a thickness of 20 μm, an organic solvent (ethyl carbonate, dimethyl carbonate or ethyl methyl carbonate), and an electrolytic salt (lithium hexafluorophosphate). A lithium ion battery was prepared using The prepared lithium ion battery was charged with a constant current at 1 C up to a battery voltage of 4.2 V, and then charged with a constant voltage to obtain a fully charged state. From a fully charged state, the battery was discharged at each current value of C rate: 0.2 to 20.0 C, the battery voltage after 10 seconds was measured, and the slope of the battery voltage with respect to the discharge current was calculated as the internal resistance of the battery. The C rate is an expression of a current value based on a current value for discharging the battery capacity in one hour. For example, the current value when discharging over 1 hour is 1C, and the current value when discharging over 0.5 hour is 2C. The lower the internal resistance, the lower the battery voltage during discharge, which means that the battery can be discharged at a higher output.

FIG. 10 shows the internal resistance of the battery using the electrode according to Example 1 and the battery using the electrode according to the comparative example. In FIG. 10, the internal resistance of the battery using the electrode according to the comparative example is 1, and the internal resistance is shown as a relative value. It was confirmed that the internal resistance can be reduced by about 5% in the battery using the electrode according to Example 1 as compared with the battery using the electrode according to the comparative example.

Thus, according to the first embodiment, the permeation time of the electrolytic solution can be shortened. Furthermore, the internal resistance during charging / discharging of the lithium ion battery can be reduced. As a result, it is possible to improve both the productivity of the lithium ion battery and the battery characteristics.

Next, differences between the first embodiment and Patent Document 1 and Patent Document 2 will be described below.

Patent Document 1 describes a method of forming a plurality of electrode mixture layers having a high porosity along the electrode coating direction. In this case, when the electrode is wound, an electrode mixture layer having a high porosity is not formed in the direction of the can lid-can bottom of the electrode wound body, so that the effect of increasing the permeation rate of the electrolytic solution is small. On the other hand, in Example 1, since the electrode mixture layer having a high porosity is formed in a direction intersecting with the conveying direction of the current collector foil and the surface of the current collector foil, when the electrode is wound, FIG. ) And (b) and as shown in FIG. 5, an electrode mixture layer having a high porosity is formed in the direction of the can lid-can bottom of the electrode winding body. Therefore, at the time of injecting the electrolyte solution, the electrolyte solution penetrates from the bottom of the can to the can lid side or from the can lid side to the can bottom side through the electrode mixture layer having a high porosity. Can be shortened, and productivity can be improved as compared with Patent Document 1. The difference in the permeation speed in the can lid-can bottom direction between Example 1 and Patent Document 1 corresponds to the result shown in FIG.

In Patent Document 2, an electrode mixture layer having a large void size is formed using an active material from which fine powder has been removed, and then an electrode mixture layer having a small void size using an active material from which fine powder has not been removed. A method of forming is described. In Patent Document 2, since an electrode mixture layer having a large gap size can be formed in the direction of the can lid-can bottom, it is possible to reduce the permeation time of the electrolytic solution. However, in addition to requiring a step of removing fine powder from the active material, the step of applying the electrode mixture is required twice, which increases the number of electrode manufacturing steps. On the other hand, in the present Example 1, in the drying process, since only the current collector foil having the electrode mixture layer formed on the surface thereof is disposed on the metal member for drying, in terms of the number of manufacturing steps of the electrode, It can be said that it is more advantageous for improving the productivity than Patent Document 2.

In Patent Document 2, it is necessary to remove the active material in the form of fine powder. The fine powder is characterized by a short diffusion distance of lithium ions in the active material and a large reaction area per weight of the active material. Therefore, removal of fine powder is disadvantageous for reducing internal resistance. On the other hand, in Example 1, active material materials having the same particle size distribution are used in the electrode mixture layer having a high porosity and the electrode mixture layer having a low porosity. Therefore, since fine powder is also present in the electrode mixture layer having a low porosity, an effect of reducing internal resistance can be obtained as compared with Patent Document 2, and input / output characteristics can be improved.

A method for manufacturing the electrode and the electrode winding body according to the second embodiment will be described below.

(1) First, the positive electrode mixture layer PEF is formed on the surface of the current collector foil PEP, and the negative electrode mixture layer NEF is formed on the surface of the current collector foil NEP in the same manner as in the coating step according to Example 1 described above. Form.

(2) Next, a drying process is demonstrated using FIG. 11 (a), (b) and (c). Here, the manufacturing method of the positive electrode will be described, but the manufacturing method of the negative electrode is substantially the same. 11 (a), (b) and (c) respectively show a drying metal member, a positive electrode mixture layer being dried, and a positive electrode mixture layer after being dried used in the drying step after slurry application according to the second embodiment. It is a schematic diagram shown.

First, a drying metal member MD3 shown in FIG. 11 (a) is prepared. The drying metal member MD3 is a metal plate in which a plurality of recesses extending in the first direction and a plurality of recesses extending in the second direction intersecting the first direction are formed, that is, the recesses are in a lattice shape. It consists of a formed metal plate. The interval (pitch) of the lattice is, for example, 10 mm, and the lattice width is, for example, 5 mm. The drying metal member MD3 is made of, for example, stainless steel, iron (Fe), gold (Au), silver (Ag), iron (Fe) alloy, nickel (Ni) alloy, or the like.

Next, as shown in FIG. 11B, the current collector foil PEP having the positive electrode mixture layer PEF applied on the surface thereof is mounted on the drying metal member MD3. Thereafter, the current collector foil PEP mounted on the drying metal member MD3 is conveyed into, for example, a 120 ° C. hot-air drying furnace, and applied to the surface of the current collector foil PEP. The layer PEF is dried. Here, the said 1st direction and the conveyance direction of current collection foil PEP correspond. The conveying speed of the current collector foil PEP is, for example, 5 to 100 m / min. At the time of mass production, productivity can be maintained by conveying the drying metal member MD3 together with the current collector foil PEP in a hot air drying furnace at a constant speed.

By passing through the drying step, as shown in FIG. 11C, the porosity of the lattice-shaped positive electrode mixture layer PEF that is not located on the plurality of convex portions of the drying metal member MD3 is reduced to the drying metal. It becomes higher than the porosity of the positive electrode mixture layer PEF located on the plurality of convex portions of the member MD3. Thereby, for example, a positive electrode mixture layer PEFH having a high porosity of 5 mm in width is formed in a lattice shape. Then, a positive electrode is manufactured by press-compressing the dried positive electrode mixture layer PEF. The negative electrode can be produced in the same manner.

(3) Next, the winding process will be described with reference to FIG. FIG. 12 is a schematic diagram of a fourth example of an electrode winding body having an electrode in which an electrode mixture layer in which a high porosity region according to the second embodiment has a lattice shape is formed.

As shown in FIG. 12, the fourth example of the electrode winding body WRF includes a positive electrode PEL wound around the axis CR, separators SP1 and SP2, and a negative electrode NEL. In the positive electrode PEL, the positive electrode mixture layer PEFH having a high porosity is formed in a lattice shape, and in the negative electrode NEL, the negative electrode mixture layer NEFH having a high porosity is formed in a lattice shape.

In Example 2, the electrode mixture layer having a high porosity is formed in a lattice shape provided at a constant interval (pitch), but is not limited thereto. For example, it is possible to form a mesh shape in which electrode mixture layers having a high porosity are provided at indefinite intervals using a drying metal member on which convex portions are randomly formed.

As described above, according to the second embodiment, since the electrode mixture layer having a high porosity has a lattice shape, a wide diffusion path of lithium ions can be secured. The internal resistance during charging / discharging of the ion battery can be reduced.

The electrode manufacturing method according to the third embodiment will be described below.

The difference between the third embodiment and the first and second embodiments described above is the drying method of the electrode mixture layer formed on the surface of the current collector foil. That is, in Examples 1 and 2 described above, the electrode mixture layer after slurry application was dried with, for example, 120 ° C. hot air in a drying furnace. In Example 3, an infrared lamp was used in the drying furnace. The electrode mixture layer after slurry application is dried.

(2) Next, a drying process is demonstrated using FIG. 13 (a), (b) and (c). Here, the manufacturing method of the positive electrode will be described, but the manufacturing method of the negative electrode is substantially the same. FIGS. 13A, 13B, and 13C are schematic diagrams showing a shielding plate used in the drying step after slurry application according to Example 3, a positive electrode mixture layer being dried, and a positive electrode mixture layer after being dried, respectively. FIG.

First, a shielding plate SH shown in FIG. 13 (a) is prepared. In the shielding plate SH, shielding portions SHP and openings (slits) OP are alternately formed in the first direction. The widths of the shielding part SHP and the opening OP in the first direction are each 1 mm, for example, and the opening OP is formed in a stripe shape extending in the second direction orthogonal to the first direction. A ceramic plate or a metal plate can be used for the shielding plate SH.

Next, as shown in FIG.13 (b), the infrared lamp is installed through the shielding board SH in the direction facing the surface of positive mix layer PEF, and infrared rays are irradiated from an infrared lamp, and positive electrode The mixture layer PEF is dried. As the infrared lamp, a halogen lamp or the like can be used. Here, the shielding plates SH are arranged so that the shielding portions SHP and the openings OP are alternately arranged in the conveying direction of the current collector foil PEP. That is, the shielding plate SH is disposed so that the first direction and the transport direction of the current collector foil PEP coincide with each other and the opening OP extends in a direction intersecting the transport direction of the current collector foil PEP. . During mass production, productivity can be maintained by transporting the shielding plate SH together with the current collector foil PEP through the drying furnace at a constant speed.

By passing through the drying step, as shown in FIG. 13 (c), the porosity of the positive electrode mixture layer PEF that is shielded from infrared rays and is not irradiated is equal to the porosity of the positive electrode mixture layer PEF that is irradiated with infrared rays. Higher than. Thereby, a positive electrode mixture layer having a high porosity and a positive electrode mixture layer having a low porosity are alternately formed in the conveying direction of the current collector foil PEP. The width of the positive electrode mixture layer having a low porosity in the transport direction of the current collector foil PEP and the width of the positive electrode mixture layer having a high porosity are, for example, 1 mm. Then, a positive electrode is manufactured by press-compressing the dried positive electrode mixture layer PEF. The negative electrode can be produced in the same manner.

(3) Next, in the same manner as in Examples 1 and 2, the electrode mixture layer having a high porosity was formed in the can lid-can bottom direction by laminating and winding the electrode and the separator. An electrode winding body is formed.

The drying method using the infrared lamp can be locally heated, and can form a pattern in which the width of the electrode mixture layer having a different porosity is narrower than the hot air drying method used in Examples 1 and 2 described above. it can. Thereby, since the diffusion path | route of lithium ion can be shortened, the internal resistance at the time of charging / discharging of a lithium ion battery can be reduced rather than Example 1, 2 mentioned above.

Further, by forming the opening OP of the shielding plate SH used in the drying process into an arbitrary shape, the electrode mixture layers having different porosity can be formed in an arbitrary pattern (for example, FIGS. 3A and 3B, FIG. 5 or FIG. The electrode winding body formed in a pattern as shown in FIG.

As mentioned above, the invention made by the present inventor has been specifically described based on the embodiment. However, the present invention is not limited to the embodiment, and various modifications can be made without departing from the scope of the invention. Needless to say.

In the present embodiment, the technical idea of the present invention has been described by taking a lithium ion battery as an example, but the technical idea of the present invention is not limited to the lithium ion battery. For example, it can be widely applied to an electricity storage device (for example, a battery or a capacitor) including 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 the manufacturing industry for manufacturing batteries represented by, for example, lithium ion batteries.

AS active material BD binder (binder)
CA Conductive aid CAP Battery cover CR Shaft core CS Exterior can EF Electrode mixture layer EL Electrode EP Current collector (current collector foil)
LIB Lithium ion batteries MD1, MD2, MD3 Drying metal member MP Metal plate MW Metal wire NEF Negative electrode mixture layer NEFH High porosity negative electrode mixture layer NEFL Low porosity negative electrode mixture layer NEL Negative electrode NEP Current collector foil NT Negative electrode Lead plate NTAB Negative electrode current collector tab NR Negative electrode ring OP Opening (slit)
P1 First pitch P2 Second pitch PEF Positive electrode mixture layer PEFH High porosity positive electrode mixture layer PEFL Low porosity positive electrode mixture layer PEL Positive electrode PEP Current collecting foil PR Positive electrode ring PT Positive electrode lead plate PTAB Positive electrode current collecting tab SH Shielding plate SHP Shielding part SP1, SP2 Separator WRF Electrode winding body

Claims

A positive electrode in which a positive electrode mixture layer is formed on the surface of the first current collector foil;
A negative electrode in which a negative electrode mixture layer is formed on the surface of the second current collector foil;
A separator for 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;
A lithium ion battery comprising:
The positive electrode mixture layer is composed of two or more mixture layers formed on the surface of the first current collector foil and having different porosity.
The negative electrode mixture layer is composed of two or more mixture layers having different porosity formed on the surface of the second current collector foil,
The particle size distribution of the active material contained in each of the two or more mixture layers constituting the positive electrode mixture layer is the same,
A lithium ion battery in which the particle size distribution of the active material contained in each of the two or more mixture layers constituting the negative electrode mixture layer is the same.
The lithium ion battery according to claim 1,
Inside the outer can having a can lid and a can bottom at positions facing each other, an electrode winding body is formed by winding the stacked positive electrode, the separator, and the negative electrode around an axis,
The positive electrode mixture layer has a first mixture layer having a first porosity, and a second mixture layer having a second porosity higher than the first porosity,
The negative electrode mixture layer has a third mixture layer having a third porosity, and a fourth mixture layer having a fourth porosity higher than the third porosity,
The second mixture layer and the fourth mixture layer are formed from the can bottom side of the outer can toward the can lid or from the can lid side of the outer can to the can bottom. , Lithium ion battery.
The lithium ion battery according to claim 2,
The length of the second mixture layer in the can lid-can bottom direction perpendicular to the winding direction of the electrode winding body is 2/3 times the width of the positive electrode mixture layer in the can lid-can bottom direction. Above and below 1 times
The length of the fourth mixture layer in the can lid-can bottom direction is not less than 2/3 times and not more than 1 times the width of the negative electrode mixture layer in the can lid-can bottom direction. Ion battery.
The lithium ion battery according to claim 2,
The length of the second mixture layer in the can lid-can bottom direction perpendicular to the winding direction of the electrode winding body is equal to the width of the positive electrode mixture layer in the can lid-can bottom direction,
The length of the fourth mixture layer in the can lid-can bottom direction is equal to the width of the negative electrode mixture layer in the can lid-can bottom direction,
The first mixture layer and the second mixture layer are alternately formed in the winding direction,
The lithium ion battery, wherein the third mixture layer and the fourth mixture layer are alternately formed in the winding direction.
The lithium ion battery according to claim 2,
The second porosity of the second mixture layer is 11% by volume to 25% by volume higher than the first porosity of the first mixture layer,
The lithium ion battery, wherein the fourth porosity of the fourth mixture layer is 11 volume% to 25 volume% higher than the third porosity of the third mixture layer.
The lithium ion battery according to claim 1,
The positive electrode mixture layer has a first mixture layer having a first porosity, and a second mixture layer having a second porosity higher than the first porosity,
The negative electrode mixture layer has a third mixture layer having a third porosity, and a fourth mixture layer having a fourth porosity higher than the third porosity,
On the surface of the first current collector foil, a plurality of the first mixture layers are formed apart from each other, and the second mixture layer is formed around the plurality of the first mixture layers,
On the surface of the second current collector foil, a plurality of the third mixture layers are formed apart from each other, and the fourth mixture layer is formed around the plurality of the third mixture layers. Lithium ion battery.
The lithium ion battery according to claim 6,
The second mixture layer is formed in a lattice shape on the surface of the first current collector foil,
The fourth mixture layer is a lithium ion battery formed in a lattice shape on the surface of the second current collector foil.
The lithium ion battery according to claim 6,
The second porosity of the second mixture layer is 11% by volume to 25% by volume higher than the first porosity of the first mixture layer,
The lithium ion battery, wherein the fourth porosity of the fourth mixture layer is 11 volume% to 25 volume% higher than the third porosity of the third mixture layer.
(A) A step of applying a slurry-like electrode material on the surface of the current collector foil to form an electrode mixture layer;
(B) drying the electrode mixture layer on the surface of the current collector foil traveling in the first direction;
Including
In the step (b), a part of the back surface of the current collector foil is brought into contact with a metal member, and the electrode mixture layer is dried in a hot air drying furnace.
In the manufacturing method of the lithium ion battery according to claim 9,
The method of manufacturing a lithium ion battery, wherein the metal member includes a plurality of metal wires that are spaced apart from each other in the first direction.
In the manufacturing method of the lithium ion battery according to claim 9,
The said metal member is a manufacturing method of a lithium ion battery which is a metal plate which has several convex parts arrange | positioned mutually spaced apart.
In the manufacturing method of the lithium ion battery according to claim 11,
The said metal plate is a manufacturing method of a lithium ion battery which has a grid | lattice-shaped recessed part in planar view.
(A) A step of applying a slurry-like electrode material on the surface of the current collector foil to form an electrode mixture layer;
(B) drying the electrode mixture layer on the surface of the current collector foil traveling in the first direction;
Including
The manufacturing method of a lithium ion battery which irradiates infrared rays through the shielding board in which the several opening part was formed in the said (b) process from the surface side of the said collector foil.
In the manufacturing method of the lithium ion battery according to claim 13,
The plurality of openings are spaced apart from each other in the first direction and extend in a second direction intersecting the first direction.
In the manufacturing method of the lithium ion battery according to claim 13,
The other part of the shielding plate in which the plurality of openings are not formed is a lithium ion battery having a lattice shape in plan view.