WO2021186716A1

WO2021186716A1 - Electrode, multilayer body and secondary battery

Info

Publication number: WO2021186716A1
Application number: PCT/JP2020/012460
Authority: WO
Inventors: 佑磨菊地
Original assignee: 株式会社東芝
Priority date: 2020-03-19
Filing date: 2020-03-19
Publication date: 2021-09-23

Abstract

One embodiment of the present invention provides an electrode which comprises: a first current collector; a first current collection tab that extends in a first direction from at least a part of a first lateral surface of the first current collector; a first active material-containing layer; and a first insulating layer that contains an inorganic material. The back surface of the first active material-containing layer is supported by at least an edge of the front surface and/or the back surface of the first current collector, said edge being adjacent to the first lateral surface. The first active material-containing layer comprises a first end face that is adjacent to the first current collection tab. The first insulating layer covers at least a part of the first end face of the first active material-containing layer and portions of the front surface and the back surface of the first current collection tab, said portions being adjacent to the first end face.

Description

Electrodes, laminates and rechargeable batteries

Embodiments of the present invention relate to electrodes, laminates and secondary batteries.

In a secondary battery such as a lithium secondary battery, a porous separator is arranged between the positive electrode and the negative electrode in order to avoid contact between the positive electrode and the negative electrode. A free-standing film separate from the positive electrode and the negative electrode is used for the separator. An example of this is a microporous membrane made of a polyolefin resin. Such a separator is produced, for example, by extruding a melt containing a polyolefin-based resin composition into a sheet, extracting and removing a substance other than the polyolefin-based resin, and then stretching the sheet.

In order to improve the volumetric energy density of the battery, it is desirable that the separator is thin. This is because the positive electrode and the negative electrode are laminated or wound with a separator interposed therebetween, so that if the separator is thick, the number of layers of the positive electrode and the negative electrode that can be stored per unit volume of the battery is limited. Because. However, since the resin film separator needs to have mechanical strength so as not to break during the production of the battery, it is difficult to make it thinner than a certain level. When the separator is made thin, there is a problem that burrs existing on the end face of the current collector or the current collecting tab of the positive electrode or the negative electrode easily break through the separator. When the burr of the electrode current collector breaks through the separator, it comes into contact with the counter electrode to cause a short circuit, and as a result, a high-capacity battery cannot be obtained.

Japanese Patent Application Laid-Open No. 2017-188371

According to the embodiment, an electrode having an improved problem of an internal short circuit that hinders an increase in capacity, a laminate containing the electrode, and a secondary battery including the laminate are provided.

According to the embodiment, a first current collector having a front surface and a back surface and a first side surface intersecting the front surface and the back surface, and at least a part of the first side surface of the first current collector in the first direction. An electrode comprising an extended first current collecting tab, a first active material-containing layer, and a first insulating layer containing an inorganic material is provided. The back surface of the first active material-containing layer is supported on the front surface and / or the back surface of the first current collector at an end adjacent to at least the first side surface. The first active material-containing layer includes a first end face adjacent to the first current collecting tab. The first insulating layer covers at least a part of the first end surface of the first active material-containing layer and a portion of the front surface and the back surface of the first current collecting tab adjacent to the first end surface. ing.

According to another embodiment, a laminate including the electrodes of the embodiment is provided.

According to another embodiment, a secondary battery including the laminate of the embodiment is provided.

FIG. 2 is a cross-sectional view showing an example of the laminated body of the embodiment. FIG. 3 is a perspective view showing a first electrode included in the laminate shown in FIG. The plan view which shows the 1st electrode shown in FIG. FIG. 5 is a plan view showing a state before being covered with the second insulating layer of the second electrode included in the laminate shown in FIG. 1. FIG. 5 is a perspective view showing a state in which the second electrode shown in FIG. 4 is covered with the second insulating layer. FIG. 2 is a cross-sectional view showing another example of the laminated body of the embodiment. The perspective view which shows another example of the laminated body of an embodiment. FIG. 2 is a cross-sectional view showing another example of the laminated body of the embodiment. FIG. 2 is a cross-sectional view showing another example of the laminated body of the embodiment. FIG. 2 is a cross-sectional view showing another example of the laminated body of the embodiment. FIG. 2 is a cross-sectional view showing another example of the laminated body of the embodiment. FIG. 5 is a plan view showing another example of the first electrode. FIG. 2 is a perspective view of the first electrode shown in FIG. FIG. 5 is a plan view showing another example of the second electrode. FIG. 6 is a perspective view showing a state in which the second electrode shown in FIG. 14 is covered with the second insulating layer. The perspective view which shows another example of the 1st electrode. FIG. 2 is a cross-sectional view showing another example of the laminated body of the embodiment. The schematic diagram of one step in the manufacturing method of the laminated body of an embodiment. The schematic diagram of one step in the manufacturing method of the laminated body of an embodiment. A partially cutaway perspective view showing an example of the secondary battery of the embodiment. Exploded view of another example of the secondary battery of the embodiment. The schematic diagram of one step in the manufacturing method of the laminated body of an embodiment. The schematic diagram of one step in the manufacturing method of the laminated body of an embodiment.

(1st embodiment and 2nd embodiment)
The electrodes according to the first embodiment and the laminate according to the second embodiment will be described with reference to the drawings.

FIG. 1 is a cross-sectional view showing an example of the laminated body of the embodiment. The cross-sectional view of FIG. 1 is a cross-sectional view of the laminated body 100 cut in the first direction, which is the extending direction of the current collecting tab. The laminate 100 shown in FIG. 1 includes a first electrode 1, a second electrode 2, and a separator 3. As shown in FIGS. 1 and 2, the first electrode 1 includes a first current collector 1a, a first active material-containing layer 1b, and a first current collector tab 1c. The electrode according to the first embodiment is, for example, the first electrode 1. The first active material-containing layer 1b has a first front surface 40 and a first back surface 41. The first current collector tab 1c extends from a part or the whole of one side surface (first side surface) of the first current collector 1a in the first direction 51. In the case of FIGS. 2 and 3, the first current collector tab 1c is a plurality of strips protruding from a plurality of locations on one side surface (first side surface) of the first current collector 1a. The first current collector 1a is a conductive sheet having a front surface and a back surface. One main surface of the first current collector 1a is the front surface, and the other main surface is the back surface. Each of the four side surfaces of the first current collector 1a intersects (for example, orthogonally) the front surface and the back surface.

The first active material-containing layer 1b is held so as to include at least an end portion of the front surface and / or back surface of the first current collector 1a adjacent to the first side surface. Specifically, the first active material-containing layer 1b is held on the front surface and / or back surface of the first current collector 1a, in addition to the above-mentioned end portion, at least on a portion facing the opposite electrode. .. In a preferred embodiment, the first active material-containing layer 1b is held on the entire surface and / or the back surface of the first current collector 1a. When a battery is manufactured using the first electrode having this form, the volume of the first active material-containing layer 1b per unit volume in the exterior member having a certain volume can be increased. That is, the volumetric energy density of the battery can be increased. The first active material-containing layer 1b is not supported on each of the front surface and the back surface of the first current collecting tab 1c. Of the first front surface 40 and the first back surface 41 of the first active material-containing layer 1b, the surface in contact with the first current collector 1a is the first back surface 41.

The first active material-containing layer 1b has two sets of end faces facing each other. One set of end faces is perpendicular to the first direction 51. One end face of this set of end faces is the first end face 52 adjacent to the first current collecting tab 1c. The first end surface 52 faces the second end surface 53 in the first direction 51.

As shown in FIGS. 2 and 3, the first electrode 1 includes a first insulating layer 4 containing an inorganic material. As shown in FIG. 2, the first insulating layer 4 includes at least a portion of the first end surface 52 of the first active material-containing layer 1b adjacent to the first current collecting tab 1c and the first one. Of the front surface and the back surface of the current collecting tab 1c, the first end surface 52 and the adjacent portion 48 are covered. The first insulating layer 4 is formed on the front surface and the back surface of each of the plurality of first current collecting tabs 1c.

As shown in FIG. 5, the second electrode 2 includes a second current collector 2a, a second active material-containing layer 2b, and a second current collector tab 2c. The second active material-containing layer 2b has a second front surface 42 and a second back surface 43. The second current collector tab 2c extends from the second current collector 2a in the second direction 54. The second direction 54 may be in substantially the same direction as the first direction 51, or may be in a direction opposite to that of the first direction 51. For example, in the laminated body 100 shown in FIG. 1, the direction in which the first current collecting tab 1c of the first electrode 1 extends and the second current collecting tab 2c of the second electrode 2 extend. The directions are opposite to each other. In FIGS. 7 and 17, which will be described later, the first current collecting tab 1c of the first electrode 1 and the second current collecting tab 2c of the second electrode 2 extend in the same direction. Shows the case.

As shown in FIG. 4, the second current collector tab 2c may be a plurality of strips protruding from a plurality of locations on one side surface of the second current collector 2a. The second current collector 2a is a conductive sheet having a front surface and a back surface. One main surface of the second current collector 2a is the front surface, and the other main surface is the back surface.

The second current collector 2a has two sets of end faces facing each other. One set of end faces is perpendicular to the second direction 54. One of the end faces is the end face 44 located on the side where the second current collecting tab 2c extends. The end face 44 faces the end face 45 in the second direction 54. Each of the four sides of the second current collector 2a, including the end faces 44 and 45, intersects (eg, orthogonally) the front and back surfaces of the second current collector 2a.

The second active material-containing layer 2b is held on the front surface and the back surface of the second current collector 2a, respectively. The second active material-containing layer 2b is not supported on the front surface and the back surface of the second current collecting tab 2c, respectively. Of the second front surface 42 and the second back surface 43 of the second active material-containing layer 2b, the surface in contact with the second current collector 2a is the second back surface 43. The second active material-containing layer 2b has two sets of end faces facing each other. One set of end faces is perpendicular to the second direction 54. One end face of this set of end faces is the first end face 55 adjacent to the second current collecting tab 2c. The first end surface 55 faces the second end surface 56 in the second direction 54.

As shown in FIG. 1, the separator 3 includes a first insulating layer 4 containing an inorganic material and a second insulating layer 5 containing organic fibers. For each of the two first active material-containing layers 1b, the portion adjacent to the current collecting tab 1c of the first end surface 52 of the four side surfaces intersecting (for example, orthogonal to) the main surface is the first insulating layer 4. It is covered. As shown in FIG. 2, the first insulating layer 4 covers a portion 48 adjacent to the first end surface 52 of the first active material-containing layer 1b. Further, as shown in FIG. 1, the first insulating layer 4 is located near the end surface 45 located on the opposite side to the side on which the second current collecting tab 2c of the second electrode 2 extends. The end face 45 of the second current collector 2a may have burrs that are inevitably formed in the manufacturing process. When this burr comes into contact with the first current collecting tab 1c, an internal short circuit occurs, but since the first electrode 1 includes the first insulating layer 4, the first current collecting tab 1c and the second It is possible to reduce an internal short circuit due to contact with the end face 45 of the current collector 2a. How the first insulating layer 4 is fixed to the first active material-containing layer 1b and the first current collecting tab 1c is not particularly limited, but for example, adhesion or heat fusion. Can be mentioned.

On the other hand, as shown in FIG. 5, the second insulating layer 5 includes a second surface 42 of each of the second active material-containing layers 2b, four side surfaces intersecting (for example, orthogonal to) the second surface 42, and a second surface. The front surface and the back surface of the current collecting tab 2c of No. 2 are covered with the end surface 55 of the second active material-containing layer 2b and the adjacent portion 46. The second active material-containing layer 2b faces the first active material-containing layer 1b via the second insulating layer 5.

As shown in FIG. 5, the second insulating layer 5 may be integrated with the second electrode 2, but is not limited to this. For example, the second insulating layer 5 may be integrated with the first electrode 1 as shown in FIGS. 10 and 11 described later. How the second insulating layer 5 is integrated with the second active material-containing layer 2b is not particularly limited, but for example, the organic fibers in the second insulating layer are the second. Examples thereof include a state in which the active material-containing layer is sunk or stuck in the surface.

FIG. 6 is a cross-sectional view showing a laminated body according to another example. In FIG. 6, the first insulating layer 4 included in the first electrode 1 faces the second current collector 2a via the second active material-containing layer 2b, and the first portion 4a and the second current collector. Includes a second portion 4b that does not face body 2a. The second portion 4b included in the first insulating layer 4 protrudes from the position of the end surface 45 of the second current collector 2a toward the first direction 51 where the first current collector tab 1c extends, for example. ing. In this case, even if the end surface 45 of the second current collector 2a has burrs, it is possible to further prevent the burrs from coming into contact with the first current collector tab 1c of the first electrode 1. Therefore, according to the laminated body 100 shown in FIG. 6, the occurrence of an internal short circuit can be suppressed, and a high-capacity battery can be provided.

FIG. 7 is a perspective view schematically showing another example of the laminated body according to the embodiment. The laminate 100 includes a first electrode 1 and a second electrode 2. The first electrode 1 is a long electrode described with reference to FIGS. 2 and 3. The second electrode 2 is a long electrode described with reference to FIGS. 4 and 5. The laminated body 100 is formed by winding the first electrode 1 and the second electrode 2 so that the second electrode 2 is located on the outer periphery. The plurality of first current collecting tabs 1c of the first electrode 1 and the plurality of second current collecting tabs 2c of the second electrode 2 extend in the same direction. As shown in FIG. 7, the first electrode 1 and the second electrode 2 are laminated so that the plurality of current collecting tabs they have do not overlap. In the laminated body 100, the plurality of first current collecting tabs 1c are overlapped with each other and electrically connected to each other by welding or the like. Further, the plurality of second current collecting tabs 2c are also overlapped with each other and electrically connected to each other by welding or the like. A second insulating layer 5 is integrated with the second electrode 2, and the second insulating layer 5 functions as a separator. Further, as described below, the first insulating layer 4 can also function as a separator.

Each of the plurality of first current collecting tabs 1c has a first insulating layer 4 on the front surface and the back surface. As described with reference to FIG. 2, the first insulating layer 4 includes at least a portion of the first active material-containing layer 1b adjacent to the first current collecting tab 1c on the first end surface 52, and a first. Of the front surface and the back surface of the current collecting tab 1c of No. 1, the first end surface 52 and the adjacent portion 48 are covered.

In FIG. 5, an end surface 44 of the second current collector 2a is a second insulating layer between a second current collector tab 2c and another second current collector tab 2c adjacent thereto. Although the state of being covered with 5, the entire end face 44 of the second current collector 2a may not be covered with the second insulating layer 5. Therefore, in FIG. 7, the end face 44 of the second current collector 2a is exposed between a certain second current collector tab 2c and another second current collector tab 2c adjacent to the second current collector tab 2c. Can be. FIG. 8 schematically shows a cross section of the laminated body 100 at a position between a certain second current collecting tab 2c and another second current collecting tab 2c adjacent thereto. FIG. 8 is a diagram schematically showing a cross section when the laminate 100 is cut along the lines VI-VI in FIG. 7. The end face 44 of the second current collector 2a may have burrs that are inevitably formed in the manufacturing process. When this burr comes into contact with the first current collecting tab 1c, an internal short circuit occurs, but since the first electrode 1 includes the first insulating layer 4, the first current collecting tab 1c and the second It is possible to reduce an internal short circuit due to contact with the end face 44 of the current collector 2a. Further, the first insulating layer 4 shown in FIG. 8 does not face the first portion 4a facing the second current collector 2a and the second current collector 2a via the second active material-containing layer 2b. It includes the second part 4b. In other words, the second portion 4b projects in the first direction from the first portion 4a. Therefore, according to the laminated body 100, it is possible to reduce an internal short circuit due to contact between the burr of the end face 44 of the second current collector 2a and the first current collector 1c.

As shown in the examples described above, in the electrode of the first embodiment, the first insulating layer is formed on at least a part of the first end surface of the first active material-containing layer, the surface of the first current collecting tab, and the surface of the first current collecting tab. It covers a portion of the back surface adjacent to the first end surface. Therefore, in order to obtain a high capacity, when the electrode group (laminated body) is produced by spirally winding or laminating the electrode and the second electrode as a counter electrode, the second electrode is used. Even if the end face of the included second current collector or the second current collector tab has burrs, it is possible to prevent the burrs from coming into contact with the first current collector tab of the first electrode. .. That is, since the burr contacts the first insulating layer instead of contacting the first current collecting tab, the occurrence of an internal short circuit can be suppressed, and a high-capacity battery can be provided.

In FIG. 1, the surface of the first active material-containing layer is not covered with the first insulating layer 4, but the form of the first electrode is not limited to this form. As shown in FIG. 9, the surface of the first active material-containing layer 1b may be coated with the first insulating layer 4. The first insulating layer 4 further covers the entire surface of the first end surface 52 of the first active material-containing layer 1b, and the front and back surfaces of the first current collecting tab, which are adjacent to the first end surface 52. doing. In this case, a first insulating layer 4 and a second insulating layer 5 are present as separators between the first active material-containing layer and the second active material-containing layer. Therefore, the insulation between the first electrode and the second electrode can be made more reliable. Further, the first insulating layer may be formed on both the first electrode and the second electrode.

The second insulating layer 5 may be integrated with the first electrode 1. An example showing the laminated body 100 in this case is shown in FIGS. 10 and 11. In FIG. 10, the first insulating layer 4 covers the first end surface 52 of the first active material-containing layer 1b and the portions of the front surface and the back surface of the first current collecting tab 1c adjacent to the first end surface 52. doing. The second insulating layer 5 includes a surface of the first insulating layer 4, an electrode surface not covered by the first insulating layer 4, that is, a surface of the first active material-containing layer 1b, and a first current collecting tab. 1c covers the three electrode end faces that do not extend.

On the other hand, in FIG. 11, the first insulating layer 4 covers the first active material-containing layer 1b. The second insulating layer 5 includes the surface of the first insulating layer 4 covering the first active material-containing layer 1b and the electrode end face, that is, the first current collector, which is not covered by the first insulating layer 4. The three electrode end faces on which the electric tab 1c does not extend and a portion on the first current collecting tab 1c and adjacent to the first insulating layer 4 are covered.

According to the structure of the laminate described with reference to FIGS. 10 and 11, the first insulating layer contains the first active material while ensuring the necessary insulating properties between the first electrode and the second electrode. It is possible to suppress peeling from the layer. Therefore, the capacity of the battery and the life of the charge / discharge cycle can be improved.

The shape of the first current collector tab 1c of the first electrode is a plurality of strips protruding from a plurality of locations on one side surface (first side surface) of the first current collector 1a as illustrated in FIG. Not limited to. The first current collector tab 1c may, for example, protrude from the entire surface of one side surface (first side surface) of the first current collector 1a, and the protruding portion may have an uneven structure. An example of this is shown in FIGS. 12 and 13. The first current collector tab 1c is a portion extending in the first direction 51 from the entire one side surface (first side surface) of the first current collector 1a. The extending portion has an uneven shape. A plurality of convex portions project along the first direction 51. The first insulating layer 4 covers the front surface and the back surface (excluding the tip portion of the convex portion) of the first current collecting tab 1c. Therefore, the first insulating layer 4 includes the entire surface of the first end surface 52 of the first active material-containing layer 1b, and the front and back surfaces of the first current collecting tab 1c that are adjacent to the first end surface 52. Is covered.

The shape of the second current collector tab 2c of the second electrode is not limited to a plurality of strips protruding from a plurality of locations on one side surface of the second current collector 2a as illustrated in FIG. The second current collector tab 2c may, for example, project from the entire surface of one side surface of the second current collector 2a, and the protruding portion may have an uneven structure. An example of this is shown in FIGS. 14 and 15. The second current collector tab 2c is a portion extending from the entire side surface of the second current collector 2a in the second direction 54. The extending portion has an uneven shape. A plurality of protrusions project along the second direction 54. As shown in FIG. 15, the second insulating layer 5 includes a second surface 42 of each of the second active material-containing layers 2b, four side surfaces intersecting (for example, orthogonal to) the second surface 42, and a second surface. The front surface and the back surface of the current collecting tab 2c are covered with the portion 46 excluding the tip of the convex portion. Therefore, the portion of the front surface and the back surface of the second current collecting tab 2c adjacent to the end surface 55 of the second active material-containing layer 2b is covered with the second insulating layer 5.

As illustrated in FIGS. 5 and 15, the second insulating layer may be formed at a portion of the second electrode excluding the tip of the second current collecting tab 2c. In this case, all of the two sets of end faces of the second active material-containing layer 2b facing each other are covered with the second insulating layer 5. However, the embodiment is not limited to this case. At least a part of the two sets of end faces of the second active material-containing layer facing each other may be covered with the second insulating layer. Of these end faces, it is preferable that at least the end face adjacent to the second current collecting tab is covered with the second insulating layer.

In the above-described embodiment, the first and second insulating layers are directly formed without providing the active material-containing layer on the protruding portions and convex portions of the first and second current collecting tabs, but the present invention is not limited to this. The active material-containing layer may be formed on the protruding portion or the convex portion of the first and second current collecting tabs, and the first and second insulating layers may be formed on the active material-containing layer. An example applied to the first electrode is shown in FIG. The first current collector tab 1c is a portion extending in the first direction 51 from a plurality of positions (first side surface) of one side surface (first side surface) of the first current collector 1a, and is composed of a plurality of protruding portions. The first active material-containing layer 101 is formed on a portion of the front surface and the back surface of the first current collecting tab 1c adjacent to the first end surface 52. The first insulating layer 4 is formed so as to cover the top of each of the first active material-containing layers 101 and the end faces of each of the first active material-containing layers 101. Further, although not shown here, the first insulating layer 4 may cover the surface of the first active material-containing layer 1b. Such a structure exemplified in FIG. 16 can be similarly applied to the second electrode. The active material-containing layer formed on the protruding portion or the convex portion of the first and second current collecting tabs has a small contribution to the charge / discharge reaction. Therefore, when the active material-containing layer contains a titanium-containing oxide as the active material, it can function as an insulating layer. By providing the first insulating layer or the second insulating layer on the active material-containing layer, the insulating performance can be further improved.

The combination of the first electrode and the second electrode is not limited to the one shown above, and is arbitrary. Any of the first electrode and the second electrode shown above may be combined. Further, in the laminated body, the direction in which the first current collecting tab extends and the direction in which the second current collecting tab extends are not limited to opposite directions, and may be the same direction. An example is shown in FIG.

The laminate shown in FIG. 17 includes a first electrode 1 having a structure shown in FIG. 13 and a second electrode 2 having a structure shown in FIG. The first electrode 1 and the second electrode 2 have the same direction 51 in which each of the plurality of first current collecting tabs 1C extends and the direction in which each of the plurality of second current collecting tabs 2c extends. They are stacked so that they face each other. A plurality of second current collecting tabs 2c are not arranged directly under the plurality of first current collecting tabs 1C, and the plurality of second current collecting tabs 2c are used with respect to the plurality of first current collecting tabs 1C. , Are arranged so as to be offset in the direction orthogonal to the direction 51. Further, the first electrode 1 and the second electrode 2 are laminated so that the second active material-containing layer 2b protrudes (or protrudes) from each of the four sides of the first active material-containing layer 1b. A second insulating layer 5 is arranged between the first active material-containing layer 1b and the second active material-containing layer 2b. The first insulating layer 4 located on the portion of the front surface and the back surface of the first current collecting tab 1c adjacent to the first end surface 52 is located in the vicinity of the second current collecting tab 2c. The second insulating layer 5 is located on a portion of the front surface and the back surface of the second current collecting tab 2c adjacent to the end surface 55 of the second active material-containing layer 2b. Even if the second current collecting tab 2c has burrs, the first insulating layer 4 and the second insulating layer 5 can prevent the burrs from coming into contact with the first electrode 1. Therefore, according to the laminated body 100 shown in FIG. 17, the occurrence of an internal short circuit can be suppressed, and a high-capacity battery can be provided.

In the laminate shown in FIG. 17, the second active material-containing layer 2b protrudes or protrudes from each of the four sides of the first active material-containing layer 1b. As a result, it is possible to prevent an uncharged region from being generated in the first active material-containing layer, and thus it is possible to prevent an internal short circuit due to elution of the active material contained in the first electrode. The relationship between the areas of the first active material-containing layer and the second active material-containing layer is not limited to this, and even if the areas of the first active material-containing layer are the same, the area of the first active material-containing layer is the same. May be larger than the area of the second active material-containing layer.

The number of the first electrode 1 and the second electrode 2 constituting the laminated body can be one or more. The number of the first electrode 1 and the second electrode 2 may be the same as or different from each other.

Hereinafter, the first and second electrodes, the first insulating layer, and the second insulating layer will be described.

(1st and 2nd electrodes)
The opposite electrode of the first electrode is the second electrode. The first electrode may be a positive electrode and the second electrode may be a negative electrode, or the first electrode may be a negative electrode and the second electrode may be a positive electrode.

The first electrode includes a porous first active material-containing layer having a first front surface and a first back surface. On the other hand, the second electrode includes a porous second active material-containing layer having a second front surface and a second back surface.

The first electrode may further include a first current collector and a first current collector tab. On the other hand, the second electrode may further include a second current collector and a second current collector tab. In this case, the first and second active material-containing layers may be formed on both the front surface and the back surface of the first and second current collectors, respectively, but they can also be formed on only one side. ..

A positive electrode active material and a negative electrode active material are used as the active material of the first and second active material-containing layers. The type of active material can be one type or two or more types.

As the positive electrode active material, for example, a lithium transition metal composite oxide can be used. For _{_{example, LiCoO 2, LiNi 1-x}} Co x O 2 (0 <x <0.3), LiMn x Ni y Co z O 2 (0 <x <0.5,0 <y <0.5,0 ≦ z <0.5), LiMn _2-x M _x O ₄ (M is at least one element selected from the group consisting of Mg, Co, Al and Ni, 0 <x <0.2), LiMPO ₄ ( M is at least one element selected from the group consisting of Fe, Co and Ni) and the like.

As the negative electrode active material, a carbon material such as graphite, a tin-silicon alloy material, or the like can be used, but it is preferable to use a titanium-containing oxide such as lithium titanate. Further, titanium oxide containing other metals such as (niobium) Nb or lithium titanate is also mentioned as a negative electrode active material. Examples of lithium titanate include Li _{4 + x} Ti ₅ O ₁₂ (0 ≦ x ≦ 3) _{having a spinel structure and Li 2 + y} Ti ₃ O ₇ (0 ≦ y ≦ 3) having a ramsteride structure. Can be mentioned.

When the first active material-containing layer or the second active material-containing layer contains a titanium-containing oxide as the active material, lithium dendrite is precipitated on the first active material-containing layer or the second active material-containing layer. Therefore, the charge / discharge cycle life of the secondary battery can be improved.

The active material can be a single primary particle, a secondary particle in which the primary particles are aggregated, or a mixture of the primary particle and the secondary particle.

The average particle size of the primary particles of the negative electrode active material is preferably in the range of 0.001 or more and 1 μm or less. The average particle size can be determined, for example, by observing the negative electrode active material with SEM. The particle shape may be either granular or fibrous. In the case of fibrous form, the fiber diameter is preferably 0.1 μm or less. Specifically, the average particle size of the primary particles of the negative electrode active material can be measured from an image observed with an electron microscope (SEM). When lithium titanate having an average particle size of 1 μm or less is used as the negative electrode active material, a negative electrode active material-containing layer having a highly flat surface can be obtained. Further, when lithium titanate is used, the negative electrode potential becomes more noble as compared with a lithium ion secondary battery using a general carbon negative electrode, so that precipitation of lithium metal does not occur in principle. Since the negative electrode active material containing lithium titanate has a small expansion and contraction due to the charge / discharge reaction, it is possible to prevent the crystal structure of the active material from collapsing.

The first and second active material-containing layers may contain a binder and a conductive agent in addition to the active material. Examples of the conductive agent include acetylene black, carbon black, graphite, or a mixture thereof. Examples of the binder include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluorinated rubber, styrene-butadiene rubber, and mixtures thereof. The binder has a function of binding the active material and the conductive agent.

In the positive electrode active material-containing layer, the contents of the active material, the conductive agent and the binder are 80% by mass or more and 97% by mass or less, 2% by mass or more and 18% by mass or less, and 1% by mass or more and 17% by mass or less, respectively. It is preferable to have. In the negative electrode active material-containing layer, the contents of the negative electrode active material, the conductive agent and the binder are 70% by mass or more and 98% by mass or less, 1% by mass or more and 28% by mass or less, and 1% by mass or more and 28% by mass or less, respectively. It is preferable to have.

The thickness of the first and second active material-containing layers can be 5 μm or more and 100 μm or less, respectively.

The first and second current collectors can be conductive sheets. Examples of conductive sheets include foils made of conductive materials. Examples of conductive materials include aluminum and aluminum alloys.

The thickness of the first and second current collectors can be 5 μm or more and 40 μm or less, respectively.

The first and second current collector tabs may be formed of the same material as the current collector, but a current collector tab is prepared separately from the current collector and welded to at least one end surface of the current collector. You may use the one connected by the above.

(First insulating layer)
The first insulating layer has a front surface and a back surface, respectively, and contains an inorganic material. One main surface of the first insulating layer corresponds to the front surface, and the other main surface corresponds to the back surface. Examples of inorganic materials include oxides (eg, Li ₂ O, BeO, B ₂ O ₃ , Na ₂ O, MgO, Al ₂ O ₃ , SiO ₂ , P ₂ O ₅ , CaO, Cr ₂ O ₃ , Fe. ₂ O ₃ , ZnO, ZrO ₂ , titanium dioxide (eg anatase, rutile or bronze type TiO ₂ ), magnesium oxide, silicon oxide, alumina, zirconia, titanium oxide and other IIA-VA groups, transition metals, IIIB, IVB Oxide), zeolite (M _{2 / n} O, Al ₂ O ₃ , xSiO ₂ , yH ₂ O (in the formula, M is a metal atom such as Na, K, Ca and Ba, n is the charge of the ^{metal cation Mn +.} The numbers corresponding to, x and y are the _{number of moles of SiO 2} and H ₂ O, 2 ≦ x ≦ 10, 2 ≦ y), nitrides (for example, BN, AlN, Si ₃ N ₄ and Ba ₃ N _{2 and the} like). ), Silicon carbide (SiC), zircon (ZrSiO ₄ ), carbonates (eg _{MgCO 3} and CaCO ₃ etc.), sulfates (eg CaSO ₄ and BaSO ₄ etc.) and composites thereof (eg a type of porcelain). there, steatite (MgO · SiO _2), forsterite (2MgO · SiO ₂₎ and, cordierite _{_{(2MgO · 2Al 2 O 3 ·}} 5SiO 2)), it can be mentioned tungsten oxide or mixtures thereof. oxides As another example, lithium titanium oxide such as lithium titanate having a spinel structure (for example, Li _{4 + x} Ti ₅ O ₁₂ , 0 ≦ x ≦ 3) can be mentioned.

Examples of other inorganic materials include barium titanate, calcium titanate, lead titanate, γ-LiAlO ₂ , LiTIO ₃ , solid electrolytes or mixtures thereof.

Examples of solid electrolytes include solid electrolytes having no or low lithium ion conductivity, solid electrolytes having lithium ion conductivity. Examples of oxide particles having no or low lithium ion conductivity include lithium aluminum oxide (for example, LiAlO ₂ , Li _x Al ₂ O _3, where 0 <x ≦ 1), lithium silicon oxide, and lithium zirconium oxide. Be done.

Examples of solid electrolytes having lithium ion conductivity include oxide solid electrolytes having a garnet-type structure. The garnet-type structure of the oxide solid electrolyte has high reduction resistance and has the advantage of a wide electrochemical window. Examples of solid oxide electrolytes with a garnet-type structure include Li _{5 + x} A _x La _3-x M ₂ O ₁₂ (A is at least one element selected from the group consisting of Ca, Sr and Ba, M is Nb and / Or Ta, x is preferably in the range of 0.5 or less (including 0), Li ₃ M _2-x L ₂ O ₁₂ (M contains Nb and / or Ta, L contains Zr, x is 0 .5 or less (preferably in the range of 0 or less), Li _7-3x Al _x La ₃ Zr ₃ O ₁₂ (x is preferably in the range of 0.5 or less (including 0)), Li ₇ La ₃ Zr ₂ O ₁₂ is included. Among them, Li _6.25 Al _0.25 La ₃ Zr ₃ O ₁₂ , Li _6.4 La ₃ Zr _1.4 Ta _0.6 O _12, Li _6.4 La ₃ Zr _1.6 Ta _0.6 O _{12 ,} Li ₇ La ₃ Zr ₂ O ₁₂ has high ionic conductivity and is electrochemically stable, so that it is excellent in discharge performance and cycle life performance.

Further, an example of the solid electrolyte having lithium ion conductivity includes a lithium phosphate solid electrolyte having a NASICON type structure. An example of a lithium phosphate solid electrolyte having a NASICON type structure is LiM1 ₂ (PO ₄ ) ₃ , where M1 is one or more elements selected from the group consisting of Ti, Ge, Sr, Zr, Sn and Al. included. Preferred examples include Li _{1 + x} Al _x Ge _2-x (PO ₄ ) ₃ , Li _{1 + x} Al _x Zr _2-x (PO ₄ ) ₃ , and Li _{1 + x} Al _x Ti _2-x (PO ₄ ) ₃ . Here, in each case, x is preferably in the range of 0 or more and 0.5 or less. In addition, each of the illustrated solid electrolytes has high ionic conductivity and high electrochemical stability. Both the lithium phosphate solid electrolyte having a NASICON type structure and the oxide solid electrolyte having a garnet type structure may be used as the solid electrolyte having lithium ion conductivity.

The first insulating layer containing at least one kind of inorganic material selected from the above is a porous film composed of an aggregate of inorganic material particles. Although there are inorganic materials having lithium ion conductivity such as solid electrolytes, most of the inorganic materials have low electron conductivity or insulating properties. Therefore, the first insulating layer can function as a partition wall separating the positive electrode and the negative electrode. As a result, the conductivity between the first active material-containing layer and the second active material-containing layer facing the first active material-containing layer via the first insulating layer can be suppressed, so that internal short circuit and self-discharge can be suppressed. Can be done.

Further, since the first insulating layer can retain the non-aqueous electrolyte in the porous portion, it does not hinder the permeation of Li ions.

The first insulating layer containing the above-mentioned type of inorganic material has high insulating property while having Li ion permeability. In consideration of practical use, a first insulating layer containing at least one selected from the group consisting of alumina, titanium oxide and lithium titanium oxide is preferable. The rutile-type titanium dioxide particles are suitable because they are difficult to aggregate and easily disperse uniformly in the first insulating layer. Lithium titanate and titanium dioxide having a spinel structure are each excellent in resistance to hydrogen fluoride (HF) and also excellent in oxidation resistance at the positive electrode. When the first insulating layer containing titanium oxide and / or lithium titanium oxide is formed on at least a part of the surface of the active material-containing layer, wear of the roll used in the roll press described later can be suppressed.

The form of the inorganic material can be, for example, granular or fibrous.

The average particle size D50 of the inorganic material particles can be 0.5 μm or more and 2 μm or less.

It is desirable that the content of the inorganic material in the first insulating layer is in the range of 80% by mass or more and 99.9% by mass or less. Thereby, the insulating property of the first insulating layer can be improved.

The first insulating layer may contain a binder. Examples of the binder include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluorinated rubber, styrene-butadiene rubber, or a mixture thereof. The content of the binder in the first insulating layer is preferably in the range of 0.01% by mass or more and 20% by mass or less.

The thickness of the first insulating layer can be 1 μm or more and 30 μm or less.

(Second insulating layer)
The second insulating layer may contain organic fibers. The second insulating layer can be a porous film in which organic fibers are deposited in the plane direction. The second insulating layer has a front surface and a back surface. One main surface of the second insulating layer corresponds to the front surface, and the other main surface corresponds to the back surface. The second insulating layer may be a porous film containing polyethylene (PE), polypropylene (PP), cellulose, or polyvinylidene fluoride (PVdF), or a non-woven fabric made of synthetic resin.

Organic fibers include, for example, at least one organic material selected from the group consisting of polyamideimide, polyamide, polyolefin, polyether, polyimide, polyketone, polysulfone, cellulose, polyvinyl alcohol (PVA) and polyvinylidene fluoride (PVdF). .. Examples of the polyolefin include polypropylene (PP) and polyethylene (PE). The type of organic fiber may be one type or two or more types. Preferred is at least one selected from the group consisting of polyimide, polyamide, polyamideimide, cellulose, PVdF, and PVA, and more preferred is selected from the group consisting of polyimide, polyamide, polyamideimide, cellulose, and PVdF. At least one type.

Since polyimide is insoluble and insoluble even at 250 to 400 ° C. and does not decompose, a second insulating layer having excellent heat resistance can be obtained.

The organic fiber preferably has a length of 1 mm or more and an average diameter of 2 μm or less, and more preferably an average diameter of 1 μm or less. Since such a second insulating layer has sufficient strength, porosity, air permeability, pore size, electrolyte resistance, oxidation-reduction resistance, and the like, it functions well as a separator. The average diameter of the organic fibers can be measured by observation with a focused ion beam (FIB) device. In addition, the length of the organic fiber is obtained based on the length measured by observation with a FIB device.

Since it is necessary to ensure ion permeability and electrolyte retention, it is preferable that 30% or more of the total volume of the fibers forming the second insulating layer is organic fibers having an average diameter of 1 μm or less, and 350 nm. The following organic fibers are more preferable, and organic fibers having a diameter of 50 nm or less are further preferable.

Further, it is more preferable that the volume of the organic fiber having an average diameter of 1 μm or less (more preferably 350 nm or less, further preferably 50 nm or less) occupies 80% or more of the volume of the entire fiber forming the second insulating layer. .. Such a state can be confirmed by scanning ion microscope (SIM) observation of the second insulating layer. It is more preferable that the organic fibers having a thickness of 40 nm or less occupy 40% or more of the total volume of the fibers forming the second insulating layer. The small diameter of the organic fiber means that the influence of obstructing the movement of ions is small.

It is preferable that a cation exchange group is present on at least a part of the entire surface including the front surface and the back surface of the organic fiber. The cation exchange group promotes the movement of ions such as lithium ions through the separator, thus enhancing the performance of the battery. Specifically, it is possible to perform rapid charging and rapid discharging for a long period of time. The cation exchange group is not particularly limited, and examples thereof include a sulfonic acid group and a carboxylic acid group. Fibers having a cation exchange group on the surface can be formed by, for example, an electrospinning method using a sulfonated organic material.

The second insulating layer has pores, and the average pore diameter of the pores is preferably 5 nm or more and 10 μm or less. The porosity is preferably 70% or more and 90% or less. If such pores are provided, a separator having excellent ion permeability and good electrolyte impregnation can be obtained. The porosity is more preferably 80% or more. The average pore diameter and porosity of the pores can be confirmed by the mercury intrusion method, calculation from volume and density, SEM observation, SIM observation, and gas desorption method. The porosity is preferably calculated from the volume and density of the second insulating layer. Further, it is desirable to measure the average pore size by a mercury intrusion method or a gas adsorption method. A large porosity in the second insulating layer means that the effect of interfering with the movement of ions is small.

It is desirable that the thickness of the second insulating layer is in the range of 12 μm or less. The lower limit of the thickness is not particularly limited, but may be 1 μm.

In the second insulating layer, if the contained organic fibers are in a sparse state, the porosity is increased, so that it is not difficult to obtain a layer having a porosity of about 90%, for example. It is extremely difficult to form such a layer with a large porosity with particles.

The second insulating layer is more advantageous than the deposit of inorganic fibers in terms of unevenness, fragility, electrolyte-containing property, adhesion, bending property, porosity, and ion permeability.

The second insulating layer may contain particles of an organic compound. The particles are made of, for example, the same material as organic fibers. The particles may be formed integrally with the organic fiber.

The thickness of the first insulating layer and the second insulating layer is measured by a method conforming to the JIS standard (JIS B 7503-1997). Specifically, these thicknesses are measured using a contact digital gauge. Place the material on the stone surface plate and use the digital gauge fixed to the stone surface plate. A flat type with a tip of φ5.0 mm is used for the measurement terminal, the measurement terminal is brought closer from a distance of 1.5 mm or more and less than 5.0 mm above the sample, and the distance in contact with the sample is the thickness of the sample.

The second insulating layer is formed by, for example, an electrospinning method. In the electrospinning method, the first electrode or the second electrode, which is the object of forming the second insulating layer, is grounded to be a ground electrode. When forming on the first electrode, the first electrode on which the first insulating layer has been formed is prepared.

The voltage applied to the spinning nozzle charges the liquid raw material (for example, the raw material solution), and the volatilization of the solvent from the raw material solution increases the amount of charge per unit volume of the raw material solution. Due to the continuous volatilization of the solvent and the accompanying increase in the amount of charge per unit volume, the raw material solution discharged from the spinning nozzle extends in the longitudinal direction, and as a nano-sized organic fiber, the first ground electrode. Accumulate on the electrode or the second electrode. A Coulomb force is generated between the organic fiber and the ground electrode due to the potential difference between the nozzle and the ground electrode. Therefore, the contact area with the first insulating layer can be increased by the nano-sized organic fiber, and the organic fiber can be deposited on the first electrode or the second electrode by the Coulomb force. It is possible to increase the peel strength of the insulating layer 2 from the electrode. The peel strength can be controlled by adjusting, for example, the solution concentration, the distance between the sample and the nozzle, and the like.

When the second insulating layer is not formed on the first and second current collecting tabs, it is preferable to mask the first and second current collecting tabs before forming the second insulating layer. An example of this is shown in FIG. FIG. 18 is a perspective view showing a step of forming a second insulating layer on the second electrode. As shown in FIG. 18, the second insulating layer 5 is directly formed by depositing the raw material solution discharged from the nozzle N on the second active material-containing layer 2b and the second current collecting tab 2c as organic fibers. It is formed. One side of the second current collecting tab 2c and its vicinity are covered with the mask M. Therefore, the second insulating layer 5 is deposited so as to straddle the surface of the second active material-containing layer 2b and the portion of the surface of the second current collecting tab 2c adjacent to the second active material-containing layer 2b. It becomes a porous film containing the organic fibers.

By using the electrospinning method, a second insulating layer can be easily formed on the electrode surface. In principle, the electrospinning method forms a single continuous fiber, so that the thin film can ensure resistance to breakage due to bending and cracking of the film. The fact that the organic fibers constituting the second insulating layer are seamless and continuous is advantageous in terms of suppressing self-discharge because the probability of fraying or partial loss of the second insulating layer is low.

As the liquid raw material used for electrospinning, for example, a raw material solution prepared by dissolving an organic material in a solvent is used. Examples of organic materials include those similar to those mentioned for organic materials constituting organic fibers. The organic material is used by being dissolved in a solvent at a concentration of, for example, about 5 to 60% by mass. The solvent for dissolving the organic material is not particularly limited, and any solvent such as dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), N, N'dimethylformamide (DMF), N-methylpyrrolidone (NMP), water, alcohols and the like can be used. A solvent can be used. For organic materials with low solubility, electrospinning is performed while melting the sheet-shaped organic material with a laser or the like. In addition, it is permissible to mix a high boiling organic solvent with a low melting point solvent.

A second insulating layer is formed by discharging the raw material from the spinning nozzle over the surface of a predetermined electrode while applying a voltage to the spinning nozzle using a high voltage generator. The applied voltage is appropriately determined according to the solvent / solute species, the boiling point / vapor pressure curve of the solvent, the solution concentration, the temperature, the nozzle shape, the distance between the sample and the nozzle, etc. For example, the potential difference between the nozzle and the work is 0.1 to 1. It can be 100 kV. The supply rate of the raw material is also appropriately determined according to the solution concentration, solution viscosity, temperature, pressure, applied voltage, nozzle shape and the like. In the case of the syringe type, for example, it can be about 0.1 to 500 μl / min per nozzle. Further, in the case of a multi-nozzle or a slit, the supply speed may be determined according to the opening area.

Since the organic fibers are formed directly on the surface of the electrode in a dry state, it is substantially avoided that the solvent contained in the raw material penetrates into the electrode. The residual amount of solvent inside the electrode is as low as ppm level or less. The residual solvent inside the electrode causes a redox reaction and causes a loss of the battery, which leads to a decrease in battery performance. According to the present embodiment, the possibility of such inconvenience occurring is reduced as much as possible, so that the performance of the battery can be improved.

The method of manufacturing the electrodes and the laminate according to the embodiment will be described below.

(First manufacturing method)
A slurry containing the first active material (hereinafter referred to as slurry I) and a slurry containing an inorganic material (hereinafter referred to as slurry II) are simultaneously placed on at least one of the front surface and the back surface of the first current collector. Paint. An example of the coating process is shown in FIGS. 19 and 22. According to this coating example, for example, the first electrode described with reference to FIG. 9 can be manufactured.

The coating device 30 includes a tank 32 for accommodating the slurry I and a tank 33 for accommodating the slurry II, and is configured to simultaneously apply the slurry I and the slurry II to the base material. The width orthogonal to the coating direction at the discharge port of the slurry I corresponds to the coating width of the active material-containing layer. Further, the width orthogonal to the coating direction at the discharge port of the slurry I corresponds to the coating width of the first insulating layer. The long first current collector 1a before being cut to a predetermined size is conveyed to the slurry discharge port of the coating device 30 by the transfer roller 31. In FIG. 22, the slurry I discharge port 32a is located on the upstream side of the current collector with respect to the slurry II discharge port 33a. The width orthogonal to the coating direction of the slurry I discharge port 32a is narrower than the width orthogonal to the coating direction of the slurry II discharge port 33a. Slurry I is applied from the coating device 30 onto the first current collector 1a except for both ends in the short side direction. At about the same time, the slurry II is overcoated so as to protrude from the coating area of the slurry I. Next, after the slurry is dried, the first current collector 1a is punched out together with the dried slurry, so that at least a part of one side surface of the first current collector 1a (in the case of FIG. 9, a plurality of one side surface). A plurality of first current collecting tabs 1c protruding from the locations) are formed. The punched material is roll-pressed and cut to a predetermined size to obtain a first electrode. The first current collector tab 1c may be formed by cutting the first current collector 1a into a target shape with a laser instead of punching the first current collector 1a from the first current collector 1a using a die or the like.

By changing the arrangement of the slurry II discharge port 33a, only the portion of the surface of the first active material-containing layer and the surface of the first current collecting tab that is adjacent to the first end surface is the first. It can be coated with an insulating layer. An example of this is shown in FIG. According to this coating example, for example, the first electrode described with reference to FIG. 1 or FIG. 2 can be manufactured.

As shown in FIG. 23, the slurry II discharge port 33a is arranged on one end in a direction orthogonal to the coating direction of the slurry I discharge port 32a. Slurry I is applied from the coating device 30 onto the first current collector 1a except for both ends in the short side direction. At about the same time, the slurry II is overcoated on one side of the coating region 1b of the slurry I in the coating direction and on the surface of the first current collector 1a adjacent thereto. Next, after the slurry is dried, at least a part of one side surface of the first current collector 1a (one side surface in the case of FIGS. 1 and 2) is punched out together with the dried slurry. A plurality of first current collecting tabs 1c protruding from the plurality of places) are formed. The punched material is roll-pressed and cut to a predetermined size to obtain a first electrode. The first current collector tab 1c may be formed by cutting the first current collector 1a into a target shape with a laser instead of punching the first current collector 1a from the first current collector 1a using a die or the like.

On the other hand, after applying the slurry containing the second active material to the second current collector, the slurry is dried, and the dried one is roll-pressed and cut to a predetermined size to obtain a second electrode. .. A second insulating layer is formed on the second electrode by an electrospinning method. Then, a press may be applied. The pressing method may be a roll press or a flat plate press.

The second current collecting tab can be obtained by, for example, the following method. As a first method, a second current collector having a second current collector tab is used in advance, and necessary treatments such as application of slurry and drying are applied to the second current collector to obtain a second electrode. As a second method, in the cutting step, the second current collector is cut into a target shape to obtain a second current collector tab. As a third method, after forming the second insulating layer by the electrospinning method, the second current collector is cut into a target shape to obtain a second current collector tab. Cutting is performed, for example, by punching with a die or the like, cutting with a laser, or the like.

The first electrode and the second electrode are laminated so that the first active material-containing layer and the second active material-containing layer face each other via the second insulating layer and / or the first insulating layer. To obtain the laminate of the embodiment.

(Second manufacturing method)
A second insulating layer is formed on the first electrode produced by the first manufacturing method by an electrospinning method. Then, a press may be applied.

On the other hand, after applying the slurry containing the second active material to the second current collector, the slurry is dried, and the dried one is roll-pressed and cut to a predetermined size to obtain a second electrode. ..

Whether the laminate obtained by the first or second manufacturing method is used as it is as an electrode group or a stack of a plurality of laminates is used as an electrode group, one set or a plurality of laminates are spirally formed. The wound one may be used as an electrode group. The electrode group may be pressed.

In the above, an example in which the first insulating layer and / or the second insulating layer is used as a separator has been described, but the present invention is not limited to this. An insulating film other than the first and second insulating layers may be used as the separator. A combination of a plurality of types may be used as a separator. Examples of the insulating film include synthetic resin non-woven fabrics, polyethylene porous films, polyolefin porous films such as polypropylene porous films, and cellulosic separators. Further, a separator in which these materials are combined, for example, a separator made of a porous polyolefin film and cellulose can be used. The insulating membrane preferably has a porous structure.

According to the electrode of the first embodiment described above, the first insulating layer containing the inorganic material is at least a part of the first end surface of the first active material-containing layer and the first current collecting tab. It covers the first end surface and the adjacent portion of the front surface and the back surface of the above. Therefore, in order to obtain a high capacity, when the electrode group (laminated body) is produced by winding the electrode and the second electrode as the counter electrode in a spiral shape, the second electrode included in the second electrode is included. Even if the end face of the current collector or the second current collector tab has burrs, it is possible to prevent the burrs from coming into contact with the first current collector tab of the first electrode.

Further, since the laminate according to the second embodiment includes the electrodes according to the first embodiment, it is possible to suppress the occurrence of an internal short circuit and realize a high-capacity battery.

(Third Embodiment)
The secondary battery of the third embodiment includes the laminate of the second embodiment. The secondary battery may further include an electrolyte and an exterior member capable of accommodating the electrolyte and the laminate.

A plurality of laminates laminated so that a separator is located between the first active material-containing layer and the second active material-containing layer may be used as an electrode group in a secondary battery. The shape of the electrode group is not limited to this shape, and one or more laminated bodies wound in a spiral or flat spiral shape may be used as the electrode group. Examples of the separator include an insulating film other than the first and second insulating layers and the first and second insulating layers. A combination of a plurality of types may be used as a separator. Examples of the insulating film are as described above.

The secondary battery may further include a first electrode terminal that is electrically connected to the first current collecting tab and a second electrode terminal that is electrically connected to the second current collecting tab. Is.

As the electrolyte, for example, a non-aqueous electrolyte is used. Examples of the non-aqueous electrolyte include a liquid non-aqueous electrolyte prepared by dissolving the electrolyte in an organic solvent, a gel-like non-aqueous electrolyte in which a liquid electrolyte and a polymer material are combined, and the like. The liquid non-aqueous electrolyte can be prepared, for example, by dissolving the electrolyte in an organic solvent at a concentration of 0.5 mol / L or more and 2.5 mol / L or less.

Examples of the electrolyte include lithium perchlorate (LiClO ₄ ), lithium hexafluorophosphate (LiPF ₆ ), lithium tetrafluoroborate (LiBF ₄ ), lithium arsenic hexafluorophosphate (LiAsF ₆ ), and trifluorometh. Lithium salts such as lithium sulfonate (LiCF ₃ SO ₃ ), bistrifluoromethylsulfonylimide lithium [LiN (CF ₃ SO ₂ ) ₂ ], or mixtures thereof can be mentioned. It is preferable that it is hard to oxidize even at a high potential, and LiPF ₆ is most preferable.

Examples of the organic solvent include cyclic carbonates such as propylene carbonate (PC), ethylene carbonate (EC) and vinylene carbonate, and chain carbonates such as diethyl carbonate (DEC), dimethyl carbonate (DMC) and methyl ethyl carbonate (MEC). , Cyclic ethers such as tetrahydrofuran (THF), dimethyltetrahydrofuran (2MeTHF), dioxolane (DOX), chain ethers such as dimethoxyethane (DME) and diethoxyethane (DEE), γ-butyrolactone (GBL), Examples thereof include acetonitrile (AN) and sulfolane (SL). Such an organic solvent may be used alone or as a mixture of two or more kinds.

Examples of the polymer material include polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyethylene oxide (PEO) and the like.

As the non-aqueous electrolyte, a room temperature molten salt (ionic melt) containing lithium ions, a polymer solid electrolyte, an inorganic solid electrolyte, or the like may be used.

As the exterior member, for example, a metal container, a laminated film container, or the like can be used.

The form of the secondary battery is not particularly limited, and can be, for example, various forms such as a cylindrical type, a flat type, a thin type, a square type, and a coin type.

FIG. 20 is a partially cutaway perspective view showing an example of the secondary battery according to the embodiment. FIG. 20 is a diagram showing an example of a secondary battery using a laminated film as an exterior member. The secondary battery 10 shown in FIG. 20 includes an exterior member 20 made of a laminated film, an electrode group 12, a first electrode terminal 13, a second electrode terminal 14, and a non-aqueous electrolyte (not shown). .. The electrode group 12 includes a plurality of laminated bodies of the embodiment, and has a structure in which the first electrode and the second electrode are laminated via a separator. A non-aqueous electrolyte (not shown) is retained or impregnated in the electrode group 12. The first current collecting tab of the first electrode is electrically connected to the first electrode terminal 13. The second current collecting tab of the second electrode is electrically connected to the second electrode terminal 14. As shown in FIG. 12, the tips of the first electrode terminal 13 and the second electrode terminal 14 project outward from one side of the exterior member 11 in a state where they are separated from each other.

FIG. 21 is a schematic cross-sectional view showing another example of the secondary battery according to the embodiment. More specifically, FIG. 21 is a cross section obtained by cutting the first current collector 1a to the first current collector 1c along the extending direction. The secondary battery 10 shown in FIG. 21 includes an exterior member 11, and an electrode group 12 in which a plurality of first electrodes 1 and a plurality of second electrodes 2 are alternately laminated. The electrode group 12 is housed in the exterior member 11.

The exterior member 11 is a bag-shaped exterior member made of a laminated film containing two resin layers and a metal layer interposed between them.

As shown in FIG. 21, the electrode group 12 is a laminated electrode group. The laminated electrode group 12 is an example of the aspect of the laminated body according to the second embodiment. Here, the second electrode 2 is regarded as the negative electrode 2, and the first electrode 1 is regarded as the positive electrode 1.

The electrode group 12 includes a plurality of negative electrodes 2. Each of the plurality of negative electrodes 2 includes a negative electrode current collector 2a and a negative electrode active material-containing layer 2b supported on both sides of the negative electrode current collector 2a. The negative electrode current collector 2a of each negative electrode 2 includes a portion 2c on which the negative electrode active material-containing layer 2b is not supported on any surface on one side thereof. The portion 2c functions as a negative electrode current collecting tab 2c. Each negative electrode 2 includes a second insulating layer 5 described with reference to FIG. A plurality of negative electrode current collecting tabs 2c extending from each negative electrode 2 are electrically connected to a band-shaped negative electrode terminal 24. The tip of the strip-shaped negative electrode terminal 24 is pulled out to the outside of the exterior member 11.

Further, the electrode group 12 includes a plurality of positive electrodes 1. Each of the plurality of positive electrodes 1 includes a positive electrode current collector 1a and a positive electrode active material-containing layer 1b supported on both surfaces of the positive electrode current collector 1a. The positive electrode active material-containing layer 1b is provided on the entire front surface and the entire back surface of the positive electrode current collector 1a.

The positive electrode current collector 1a of each positive electrode 1 includes a portion 1c on which the positive electrode active material-containing layer 1b is not supported on any surface on one side thereof. The portion 1c functions as a positive electrode current collecting tab 1c. The positive electrode current collecting tab 1c extends in the direction opposite to the direction in which the negative electrode current collecting tab 2c extends. The positive electrode active material-containing layer 1b has a first end surface adjacent to the positive electrode current collecting tab 1c. On the front surface and the back surface on the positive electrode current collecting tab 1c, the first end surface of the positive electrode active material-containing layer 1b and the portion adjacent to the end surface are supported by the first insulating layer 4. Therefore, even if a part of the end face of the negative electrode current collector 2a has burrs, it is possible to prevent the burrs from penetrating the second insulating layer 5 and coming into contact with the first current collector tab 1c. Can be done.

According to the secondary battery of the third embodiment described above, since the laminated body of the second embodiment is included, the secondary battery excellent in capacity and life performance by suppressing an internal short circuit which hinders the increase in capacity. Batteries can be provided.

A non-aqueous electrolyte battery having the first electrode as the positive electrode and the second electrode as the negative electrode was produced by the following method.

(Example 1)
An insulating inorganic material layer as a first insulating layer included in the positive electrode and a nanofiber layer as a second insulating layer included in the negative electrode were produced by the following methods.

_{LiNi 0.33} Co _0.33 Mn _0.33 O ₂ particles were prepared as the positive electrode active material, carbon black was prepared as the conductive agent, and polyvinylidene fluoride (PVdF) was prepared as the binder. These were mixed at a mass ratio of 90: 5: 5 to obtain a mixture. Next, the obtained mixture was dispersed in an n-methylpyrrolidone (NMP) solvent to prepare a positive electrode slurry.

_{Al 2} O ₃ particles having an average particle size of 1 μm and PVdF were prepared as insulating inorganic materials. These were mixed at a mass ratio of 100: 4 to obtain a mixture. Next, the obtained mixture was dispersed in NMP to prepare an alumina-containing slurry.

Next, the first electrode was produced as follows by the coating method described with reference to FIG. 23. First, the positive electrode slurry was applied onto an aluminum foil having a thickness of 15 μm. At about the same time, the alumina-containing slurry was applied in parallel on one side of the coating area of the positive electrode slurry in the coating direction and on the surface of the aluminum foil adjacent thereto. Next, the positive electrode slurry and the alumina-containing slurry were dried to form a positive electrode active material-containing layer and an insulating inorganic material layer. This was done on both sides of the aluminum foil. Then, after performing a roll press, it was punched out with a die to obtain a first electrode having a plurality of current collector tabs protruding from a plurality of locations on one side surface of the current collector. The obtained first electrode had the structure described with reference to FIG. That is, the insulating inorganic material layer covered the end face of the positive electrode active material-containing layer and the portions adjacent to the end face on each of the front and back surfaces of the plurality of current collector tabs.

The thickness of each of the positive electrode active material-containing layers was 20 μm, and the thickness of the insulating inorganic material layer formed on the aluminum foil protruding from the positive electrode active material-containing layer was 20 μm.

Lithium titanate particles having an average primary particle size of 0.5 μm were prepared as the negative electrode active material, carbon black was prepared as the conductive agent, and polyvinylidene fluoride was prepared as the binder. These were mixed at a mass ratio of 90: 5: 5 to obtain a mixture. The resulting mixture was dispersed in an n-methylpyrrolidone (NMP) solvent to prepare a slurry.

The obtained slurry was applied to both sides of an aluminum foil having a thickness of 15 μm and dried. Then, the dried coating film was pressed to obtain a negative electrode. The thickness of each of the negative electrode active material-containing layers was 30 μm. A portion without a negative electrode active material-containing layer was provided on one long side of the current collector, and this portion was used as a negative electrode current collector tab.

Organic fibers were deposited on this negative electrode by an electrospinning method to form a nanofiber layer. Polyimide was used as the organic material. This polyimide was dissolved in DMAc as a solvent at a concentration of 20% by mass to prepare a raw material solution as a liquid raw material. The obtained raw material solution was supplied from the spinning nozzle to the surface of the negative electrode at a supply rate of 5 μl / min using a metering pump. A voltage of 20 kV was applied to the spinning nozzle using a high voltage generator, and a layer of 2 μm organic fibers was formed on the surface of the negative electrode active material-containing layer while moving the range of 100 × 200 mm with this spinning nozzle. The negative electrode was subjected to the electrospinning method with the surface of the negative electrode current collecting tab masked, except for the portion 10 mm from the boundary with the negative electrode active material-containing layer on both surfaces (main surfaces) of the negative electrode current collecting tab. Obtained.

Subsequently, a negative electrode with an integrated nanofiber layer was obtained by punching with a die so that a plurality of negative electrode current collector tabs protruding from a plurality of locations on one side surface of the negative electrode current collector were formed.

As shown in FIGS. 7 and 8, the nanofiber layer is a collection of negative electrodes among four side surfaces intersecting (for example, orthogonal) with each surface of the negative electrode active material-containing layer and the front and back surfaces of the negative electrode active material-containing layer. The three side surfaces excluding the surface on which the negative electrode current collecting tab extends from the electric body, the portion adjacent to the negative electrode current collecting tab on the remaining one side surface, and the negative electrode active material-containing layers on the front and back surfaces of the negative electrode current collecting tab. It covered the end face and the adjacent part.

The produced positive electrode and negative electrode are laminated via a nanofiber layer so that the positive electrode active material-containing layer and the negative electrode active material-containing layer face each other, and then wound and wound as described with reference to FIG. A mold electrode group was prepared.

The obtained electrode group was vacuum-dried at room temperature overnight, and then left in a glove box having a dew point of −80 ° C. or lower for one day. This was housed in a metal container together with the electrolytic solution to obtain a non-aqueous electrolyte battery. _{The electrolytic solution used was a solution of LiPF 6} in ethylene carbonate (EC) and dimethyl carbonate (DMC).

(Example 2)
A non-aqueous electrolyte battery was produced in the same manner as in Example 1 except that lithium titanate particles having an average particle diameter D50 of 0.5 μm were used as the insulating inorganic material constituting the first insulating layer.

(Example 3)
A non-aqueous electrolyte battery was produced in the same manner as in Example 1 except that _{rutile-type titanium dioxide (TiO 2} ) having an average particle diameter D50 of 1 μm was used as the insulating inorganic material constituting the first insulating layer. bottom.

(Example 4)
As the positive electrode slurry, the same slurry as that prepared in Example 1 was prepared.
As the alumina-containing slurry, the same slurry as that prepared in Example 1 was prepared.

Next, the first electrode was produced as follows by the coating method described with reference to FIG. 22. The aluminum foil having a thickness of 15 μm was overcoated with a positive electrode slurry in the lower layer and an alumina-containing slurry in the upper layer, and the alumina-containing slurry in the upper layer protruded, and dried. This was done on both sides of the aluminum foil. Then, after performing a roll press, it was punched out with a die to obtain a first electrode having a plurality of current collector tabs protruding from one side surface of the current collector. The obtained first electrode had the same structure as the first electrode 1 shown in FIG. That is, the insulating inorganic material layer covered the end face of the positive electrode active material-containing layer and the portions adjacent to the end face on each of the front and back surfaces of the plurality of current collector tabs. Further, the insulating inorganic material layer covered the surface of each of the positive electrode active material-containing layers.

The thickness of each of the positive electrode active material-containing layers is 20 μm, the thickness of the insulating inorganic material layer on the positive electrode active material-containing layer is 3 μm, and the insulating inorganic material layer formed on the aluminum foil protruding from the positive electrode active material-containing layer. The thickness of was 20 μm.

Next, a negative electrode was prepared in the same manner as in Example 1.
Then, a non-aqueous electrolyte battery was produced in the same manner as in Example 1.

(Example 5)
A non-aqueous electrolyte battery was produced in the same manner as in Example 4 except that lithium titanate particles having an average particle diameter D50 of 0.5 μm were used as the insulating inorganic material constituting the first insulating layer.

(Example 6)
A non-aqueous electrolyte battery was produced in the same manner as in Example 4, except that _{rutile-type titanium dioxide (TiO 2} ) having an average particle diameter D50 of 1 μm was used as the insulating inorganic material constituting the first insulating layer. bottom.

(Comparison example)
A non-aqueous electrolyte battery was produced in the same manner as in Example 1 except that the formation of the insulating inorganic material layer was omitted when the first electrode was produced.

<Yield evaluation>
Fifty non-aqueous electrolyte batteries according to Example 1 were produced, internal resistance was measured for each non-aqueous electrolyte battery, and a battery having a resistance value of 10 kΩ or more was judged to be a non-defective product, and a battery having a resistance value of less than 10 kΩ. Was evaluated as a defective product. As a result, all 50 non-aqueous electrolyte batteries according to Example 1 were non-defective products. That is, the yield of the non-aqueous electrolyte battery according to Example 1 was 100%.

As for Examples 2 to 6, when 50 non-aqueous electrolyte batteries were prepared and the yield was evaluated in the same manner as in Example 1, the yield was 100% in each case.

On the other hand, when 50 non-aqueous electrolyte batteries were prepared and the yield was evaluated for the comparative example, 16 were good products and 34 were defective. That is, the yield of the non-aqueous electrolyte battery according to the comparative example was 32%.

In each of the positive electrodes included in the non-aqueous electrolyte batteries according to Examples 1 to 6, the insulating inorganic material layer covers the end face of the positive electrode active material-containing layer and a part on the positive electrode current collecting tab adjacent to the end face. Therefore, it is considered that the burr on the end face of the negative electrode current collector and the positive electrode current collector tab could be suppressed from coming into direct contact with each other, and an internal short circuit could be suppressed.

In the electrodes according to at least one embodiment and examples described above, the first insulating layer is at least a part of the first end face of the first active material-containing layer and the first in the first current collecting tab. It covers the end face and the adjacent portion. Therefore, in order to obtain a high capacity, when the electrode group (laminated body) is produced by spirally winding or laminating the electrode and the second electrode as a counter electrode, the second electrode is used. Even if the end face of the containing second current collector or the second current collector tab has burrs, it is possible to prevent the burrs from coming into contact with the first current collector tab of the first electrode. .. As a result, it is possible to suppress an internal short circuit that is a factor that hinders the increase in capacity.

Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other embodiments, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are also included in the scope of the invention described in the claims and the equivalent scope thereof.

1 ... 1st electrode, 1a ... 1st current collector, 1b ... 1st active material-containing layer, 1c ... 1st current collection tab, 2 ... 2nd electrode, 2a ... 2nd current collector , 2b ... Second active material-containing layer, 2c ... Second current collecting tab, 3 ... Separator, 4 ... First insulating layer, 5 ... Second insulating layer, 10 ... Secondary battery, 11 ... Exterior member , 12 ... Electrode group, 13 ... First electrode terminal, 14 ... Second electrode terminal, 20 ... Exterior member, 23 ... Positive terminal, 24 ... Negative terminal, 40 ... First front surface, 41 ... First back surface , 42 ... second front surface, 43 ... second back surface, 45 ... end face of second current collector, 46 ... portion of the second current collection tab including the boundary with the second active material-containing layer, 51. ... 1st direction, 52, 55 ... 1st end face, 53, 56 ... 2nd end face, 54 ... 2nd direction, 100 ... Laminated body.

Claims

A first current collector having a front surface and a back surface and a first side surface intersecting the front surface and the back surface.
A first current collector tab extending in a first direction from at least a part of the first side surface of the first current collector.
It has a front surface and a back surface, and the back surface is supported on at least an end portion of the front surface and / or the back surface of the first current collector adjacent to the first side surface, and the first current collector tab is provided. A first active material-containing layer containing the first end face adjacent to the
Including a first insulating layer containing an inorganic material,
The first insulating layer includes at least a part of the first end surface of the first active material-containing layer, and the first end surface of the front surface and the back surface of the first current collecting tab. An electrode that covers adjacent parts.
The electrode according to claim 1, wherein the first insulating layer further covers the surface of the first active material-containing layer.
The electrode according to claim 1 or 2, wherein the first current collecting tab extends in a first direction from a plurality of locations on the first side surface.
The electrode according to claim 1 or 2, wherein the first current collecting tab extends in the first direction from the entire first side surface.
The first electrode, which is the electrode according to any one of claims 1 to 4,
A laminated body including a second electrode as a counter electrode of the first electrode.
The second electrode is
A second current collector with front and back surfaces,
A second current collector tab extending from the second current collector along the first direction or extending toward the side opposite to the first direction.
A second active material having a front surface and a back surface, the back surface of which is supported on at least a part of the front surface and the back surface of the second current collector and faces the first active material-containing layer. Including the containing layer,
The laminate further includes a second insulating layer containing organic fibers, which is arranged between the first active material-containing layer and the second active material-containing layer.
The first insulating layer includes a first portion facing the second current collector and a second portion not facing the second current collector via the second active material-containing layer. Item 5. The laminated body according to Item 5.
The laminate according to claim 5 or 6, wherein the second active material-containing layer contains a titanium-containing oxide as an active material.
A secondary battery containing the laminate according to any one of claims 5 to 7.