WO2019187130A1

WO2019187130A1 - Electrode group, battery, and battery pack

Info

Publication number: WO2019187130A1
Application number: PCT/JP2018/013922
Authority: WO
Inventors: 圭吾保科; 政典田中; 大典高塚; 康宏原田; 高見　則雄
Original assignee: 株式会社東芝
Priority date: 2018-03-30
Filing date: 2018-03-30
Publication date: 2019-10-03
Also published as: JPWO2019187130A1; JP6952876B2

Abstract

One embodiment according to the present invention provides an electrode group comprising a laminate including a positive electrode, a negative electrode, and an electrical insulating member. The positive electrode is provided with: a belt-like positive electrode current collector; a positive electrode current collector tab disposed at one edge thereof; and a positive electrode active material-containing layer which is supported on the positive electrode current collector. The positive electrode active material-containing layer includes a first end part and a second end part that are oriented parallel to one of the edges of the positive electrode current collector. The negative electrode is provided with a belt-like negative electrode current collector, a negative electrode current collector tab disposed on one edge thereof, and a negative electrode active material-containing layer which is supported on the negative electrode current collector and which comprises a titanium-containing oxide. The negative electrode active material-containing layer includes a third end part and a fourth end part that are oriented parallel to one of the edges of the negative electrode current collector. The electrical insulating member is interposed between the positive electrode active material-containing layer and the negative electrode active material-containing layer. The laminate is rolled. The positive electrode current collector tab protrudes in a first direction parallel to the rolling axis. The fourth end part is positioned close to the side of the positive electrode current collector tab as compared with the first end part. The negative electrode current collector tab protrudes in a second direction that is opposite to the first direction. The third end part is positioned closer to the side of the negative electrode current collector tab as compared with the second end part. A first deviation width between the first end part and the fourth end part is wider than a second deviation width between the second end part and the third end part.

Description

Electrode group, battery, and battery pack

Embodiments of the present invention relate to an electrode group, a battery, and a battery pack.

One of the means for increasing the energy density of a battery such as a non-aqueous electrolyte battery is to design the battery so that the battery voltage is increased. The niobium titanium composite oxide and the tetragonal titanium-containing composite oxide have a low reaction potential for lithium insertion / extraction among titanium oxides, and can increase the battery voltage when used as a negative electrode. On the other hand, due to the low reaction potential, the electrolyte is easily reductively decomposed, and the self-discharge reaction is likely to proceed along with the reductive decomposition reaction. As countermeasures, it is possible to suppress the self-discharge reaction by coating the surface of the active material by coating the surface of the active material with an inorganic substance or by including a material that forms a film on the surface of the active material in the electrolyte. Has been done.

Self-discharge can also occur due to an internal short circuit in the battery. For this reason, it is desirable to secure resistance to internal short circuit and suppress self-discharge of the battery.

JP 2014-167890 A Japanese Unexamined Patent Publication No. 2017-91677

An object of the present invention is to provide an electrode group capable of realizing a battery in which self-discharge is suppressed, a battery in which self-discharge is suppressed, and a battery pack including the battery.

According to the embodiment, an electrode group including a laminate including a positive electrode, a negative electrode, and an electrically insulating member is provided. The positive electrode was supported on the positive electrode current collector, a positive electrode current collector tab provided at an end parallel to one side of the positive electrode current collector, and at least excluding the positive electrode current collector tab. A positive electrode active material-containing layer. The positive electrode active material-containing layer includes a first end and a second end parallel to the one side of the positive electrode current collector. The negative electrode includes a strip-shaped negative electrode current collector, a negative electrode current collector tab provided at an end parallel to one side of the negative electrode current collector, and a titanium supported on the negative electrode current collector excluding at least the negative electrode current collector tab A negative electrode active material-containing layer containing a containing oxide. The negative electrode active material-containing layer includes a third end portion and a fourth end portion that are parallel to the one side of the negative electrode current collector. The electrically insulating member is interposed between the positive electrode active material-containing layer and the negative electrode active material-containing layer. The laminate is wound. A positive electrode current collecting tab protrudes in a first direction parallel to the winding axis. The fourth end is located closer to the positive electrode current collector tab than the first end. The negative electrode current collector tab protrudes in the second direction opposite to the first direction. The third end is located closer to the negative electrode current collector tab than the second end. The second shift width between the second end portion and the third end portion is wider than the first shift width between the first end portion and the fourth end portion.

According to another embodiment, a battery including the electrode group according to the above embodiment is provided.

According to still another example, a battery pack including the battery according to the above embodiment is provided.

FIG. 1 is a perspective view schematically showing an example electrode group according to the embodiment. FIG. 2 is a perspective view schematically showing a state in which the electrode group is partially developed. FIG. 3 is a plan view schematically showing an example of an electrode group according to the embodiment. FIG. 4 is a schematic cross-sectional view of an example flat battery according to the embodiment. FIG. 5 is an enlarged cross-sectional view of a portion A in FIG. FIG. 6 is a schematic exploded perspective view of an example battery pack according to the embodiment. FIG. 7 is a block diagram showing an electric circuit of the battery pack of FIG.

Embodiment

The internal short circuit generated in the nonaqueous electrolyte battery is roughly classified into a short circuit due to lithium metal dendrite deposition, a short circuit due to a failure of an insulating member such as a separator, and a short circuit due to mixing of minute metal pieces. In particular, internal short-circuiting due to lithium metal deposition, which is said to be difficult to suppress, is a material that can occlude and release lithium in the negative electrode active material at a potential (a noble potential) significantly higher than the lithium deposition potential, for example, about 1 When lithium titanate that can occlude and release lithium at 0.5 V (vs. Li / Li ⁺ ) or the like is used, dendritic precipitation of lithium metal can be suppressed almost completely.

However, when the negative electrode active material having such a noble potential is used, there is a problem that the battery voltage that can be taken out as a difference from the positive electrode potential is lowered and the energy density of the battery is lowered.

Hereinafter, embodiments will be described with reference to the drawings. In addition, the same code | symbol shall be attached | subjected to a common structure through embodiment, and the overlapping description is abbreviate | omitted. Each figure is a schematic diagram for promoting explanation and understanding of the embodiment, and its shape, dimensions, ratio, etc. are different from the actual device, but these are the following explanations and known techniques. The design can be changed as appropriate.

(First embodiment)
The electrode group according to the first embodiment includes a laminate including a positive electrode, a negative electrode, and an electrical insulating member.
The positive electrode was supported on the positive electrode current collector, a positive electrode current collector tab provided at an end parallel to one side of the positive electrode current collector, and at least excluding the positive electrode current collector tab. A positive electrode active material-containing layer. The positive electrode active material-containing layer includes a first end and a second end parallel to the one side of the positive electrode current collector.
The negative electrode includes a strip-shaped negative electrode current collector, a negative electrode current collector tab provided at an end parallel to one side of the negative electrode current collector, and a titanium supported on the negative electrode current collector excluding at least the negative electrode current collector tab A negative electrode active material-containing layer containing a containing oxide. The negative electrode active material-containing layer includes a third end portion and a fourth end portion that are parallel to the one side of the negative electrode current collector.
The electrically insulating member is interposed between the positive electrode active material-containing layer and the negative electrode active material-containing layer.
The laminate is wound. The laminate may have a structure wound in a cylindrical shape. Or a laminated body may have the structure wound by the flat shape.
A positive electrode current collecting tab protrudes in a first direction parallel to the winding axis. The fourth end is located closer to the positive electrode current collector tab than the first end. The negative electrode current collector tab protrudes in the second direction opposite to the first direction. The third end is located closer to the negative electrode current collector tab than the second end.
The second shift width between the second end portion and the third end portion is wider than the first shift width between the first end portion and the fourth end portion.

The electrode group according to the embodiment will be described with reference to FIGS.

FIG. 1 is a perspective view schematically showing an example of an electrode group according to the embodiment. FIG. 2 is a perspective view schematically showing a state in which the electrode group is partially developed. FIG. 3 is a plan view schematically showing an example of an electrode group according to the embodiment.

1 to 3 includes a positive electrode 4, a negative electrode 5, and an electrical insulating member 6. As shown in FIG. 2, in the electrode group 3, a laminate including a positive electrode 4, a negative electrode 5, and an electrically insulating member 6 disposed between the positive electrode 4 and the negative electrode 5 is wound into a flat shape. Has a structure.

As shown in FIG. 3, the positive electrode 4 includes a positive electrode current collector 4a, a positive electrode active material-containing layer 4b, and a positive electrode current collector tab 4c. The positive electrode current collector 4a has a strip shape. The positive electrode active material-containing layer 4b is supported on the positive electrode current collector 4a. The positive electrode current collecting tab 4c is provided at an end portion parallel to one side of the positive electrode current collector 4a, for example, the long side of the belt-like shape.

The positive electrode active material-containing layer 4 b includes a first end 41 and a second end 42. The first end portion 41 and the second end portion 42 are arranged in parallel to the one side of the positive electrode current collector 4a (one side parallel to the end portion where the positive electrode current collector tab 4c is provided).

The positive electrode current collector tab 4c may be a part of the positive electrode current collector 4a. The positive electrode active material-containing layer 4b is not supported on at least the positive electrode current collector tab 4c of the positive electrode current collector 4a, and the positive electrode current collector tab 4c protrudes from the first end 41 of the positive electrode active material-containing layer 4b. ing.

On the other hand, the negative electrode 5 includes a negative electrode current collector 5a and a negative electrode active material-containing layer 5b. The negative electrode current collector 5a has a strip shape. The negative electrode active material-containing layer 5b is supported on the negative electrode current collector 5a. The negative electrode current collector tab 5c is provided at an end parallel to one side of the negative electrode current collector 5a, for example, the long side of the strip shape.

The negative electrode active material-containing layer 5 b includes a third end portion 53 and a fourth end portion 54. The third end portion 53 and the fourth end portion 54 are in a position parallel to the one side of the negative electrode current collector 5a (one side parallel to the end portion where the negative electrode current collecting tab 5c is provided).

The negative electrode current collector tab 5c may be a part of the negative electrode current collector 5a. The negative electrode active material-containing layer 5b is not supported on at least the negative electrode current collector tab 5c of the negative electrode current collector 5a, and the negative electrode current collector tab 5c protrudes from the third end 53 of the negative electrode active material-containing layer 5b. ing.

In the electrode group 3, the positive electrode active material-containing layer 4b of the positive electrode 4 and the negative electrode active material-containing layer 5b of the negative electrode 5 are opposed to each other with the electrical insulating member 6 interposed therebetween (FIG. 2). In the first direction parallel to the winding axis of the multilayer body, the positive electrode current collecting tab 4 c protrudes from the negative electrode active material-containing layer 5 b and the electrical insulating member 6. Further, the negative electrode current collecting tab 5 c protrudes from the positive electrode 4 and the electrical insulating member 6 in a second direction that is opposite to the first direction. Therefore, in the electrode group 3, the positive electrode current collection tab 4c wound by the flat spiral shape is located in the 1st end surface orthogonal to a winding axis | shaft. Moreover, the negative electrode current collection tab 5c wound by the flat spiral shape is located in the 2nd end surface orthogonal to a winding axis | shaft. Thus, the positive electrode current collection tab 4c is located on the opposite side of the wound laminate from the negative electrode current collection tab 5c.

In FIG. 3, the electrical insulating member 6 is omitted. As shown in FIG. 3, the width _{W P} of the positive electrode active material-containing layer 4b is smaller than the width _{W N} of the negative electrode active material-containing layer 5b. Width W _P of the positive electrode active material-containing layer 4b is the width of the positive electrode active material-containing layer 4b in a direction perpendicular to the first end 41 and second end 42. In other words, the width W _P of the positive electrode active material-containing layer 4b corresponds to the width between the first end 41 and second end 42. Similarly, the width W _N of the negative electrode active material-containing layer 5 b is the width of the negative electrode active material-containing layer 5 b in the direction orthogonal to the third end portion 53 and the fourth end portion 54. That is, the width W _N of the negative electrode active material-containing layer 5 b corresponds to the width between the third end portion 53 and the fourth end portion 54. The width W _P and the width W _N of the active material-containing layer of each of the positive and negative electrodes are also widths in a direction parallel to the winding axis of the wound laminate.

Width W _P of the positive electrode active material-containing layer 4b is smaller than the width W _N of the negative electrode active material-containing layer 5b, the first end 41 and second end part of the anode active material-containing layer 5b positive electrode active material-containing layer 4b It protrudes outward in the width direction from the portion 42. Specifically, the fourth end portion 54 of the negative electrode active material-containing layer 5b protrudes outside the first end portion 41 of the positive electrode active material-containing layer 4b. That is, the fourth end portion 54 is located at a position shifted from the first end portion 41 toward the positive electrode current collecting tab 4c. And the 3rd end part 53 of the negative electrode active material content layer 5b protrudes outside the 2nd end part 42 of the positive electrode active material content layer 4b. That is, the third end portion 53 is located at a position shifted from the second end portion 42 toward the negative electrode current collecting tab 5c. In other words, the negative electrode active material-containing layer 5b is in both directions (first direction and second direction) parallel to the winding axis of the electrode group 3 on the side where the positive electrode current collecting tab 4c is located and on the side where the negative electrode current collecting tab 5c is located. And protrudes from the positive electrode active material-containing layer 4b.

The first shift width A (the protruding width of the fourth end portion 54) between the first end portion 41 of the positive electrode active material-containing layer 4b and the fourth end portion 54 of the negative electrode active material-containing layer 5b is a positive electrode current collecting tab. This corresponds to the distance at which the negative electrode active material-containing layer 5b protrudes on the 4c side. On the other hand, the second shift width B (the protruding width of the third end portion 53) between the second end portion 42 of the positive electrode active material-containing layer 4b and the third end portion 53 of the negative electrode active material-containing layer 5b is the negative electrode. This corresponds to the distance at which the negative electrode active material-containing layer 5b protrudes on the current collecting tab 5c side. The second shift width B is wider than the first shift width A.

If a negative electrode active material having a low (occluded) lithium occlusion / release potential is used for the purpose of obtaining a high battery energy density, the end portions (third end portion 53 and fourth end portion 54) of the negative electrode active material-containing layer 5b are used. Metal deposition, for example, formation of lithium dendrite is likely to occur. The third end portion 53 and the fourth end portion 54 of the negative electrode active material-containing layer 5b protrude outside the first end portion 41 and the second end portion 42 of the positive electrode active material-containing layer 4b. Short circuit between the negative electrodes can be suppressed.

If the first end portion 41 and substantially increasing the width W _P of the positive electrode active material-containing layer 4b is made to project outward from the fourth end portion 54 of the negative electrode active material-containing layer 5b, the cathode active and fourth end portions 54 Part of the substance-containing layer 4b overlaps with the electrically insulating member 6 interposed therebetween. In that case, an electrical short circuit may occur between the positive and negative electrodes due to metal deposition at the fourth end 54. Moreover, since the part which does not oppose the negative electrode active material content layer 5b among the positive electrode active material content layers 4b increases, there also exists an aspect that an energy density falls.

The larger the second displacement width B, the longer the distance between the second end portion 42 of the positive electrode active material-containing layer 4b and the third end portion 53 of the negative electrode active material-containing layer 5b. Since the second end portion 42 and the third end portion 53 are further away from each other, the risk of the second end portion 42 and the third end portion 53 coming into contact with each other during the manufacture of the electrode group is reduced. Further, by increasing the second displacement width B, the distance between the second end portion 42 and the negative electrode current collecting tab 5c can be increased. By separating a distance between the second end portion 42 of the positive electrode active material-containing layer 4b and the negative electrode current collector tab 5c, the negative electrode current collector tab 5c is deformed by a force applied from the outside of the battery such as a physical impact, for example. When it does, contact with the 2nd end part 42 and negative electrode current collection tab 5c does not occur easily. Therefore, an electrical short circuit on the negative electrode current collecting tab 5c side can be suppressed.

On the other hand, it is desirable that the first deviation width A is not too large. Since the fourth end portion 54 of the negative electrode active material-containing layer 5b protrudes outside the first end portion 41 of the positive electrode active material-containing layer 4b, it is between the fourth end portion 54 and the edge of the positive electrode current collecting tab 4c. The distance is shorter than the width of the positive electrode current collecting tab 4c. As the first deviation width A becomes wider, the distance between the fourth end portion 54 and the edge of the positive electrode current collecting tab 4c becomes shorter. Then, for example, when the positive electrode current collecting tab 4c is deformed by a force applied from the outside of the battery such as a physical impact, an electrical short circuit is likely to occur between the fourth end 54 and the positive electrode current collecting tab 4c.

Also, from the viewpoint of securing the energy density of the battery, it is preferable to reduce the first deviation width A. By suppressing the first deviation width A to be small, the area where the positive electrode active material-containing layer 4b and the negative electrode active material-containing layer 5b face each other can be increased. Therefore, the energy density can be increased as the first deviation width A is smaller.

However, in order to suppress a short circuit due to metal deposition at the fourth end portion 54 of the negative electrode active material-containing layer 5b, it is desirable that the fourth end portion 54 does not overlap the positive electrode active material-containing layer 4b. Therefore, the first deviation width A exceeds zero.

The ratio of the first deviation width A to the width W _N of the negative electrode active material-containing layer may be 0.008 or more and 0.02 or less. That is, the first deviation width A and the width W _N can satisfy the relationship of 0.008 ≦ A / W _N ≦ 0.02. On the other hand, the ratio of the second displacement width B to the width W _N of the negative electrode active material-containing layer may be 0.01 or more and 0.022 or less. That is, the second shift width B and the width W _N can satisfy the relationship of 0.01 ≦ B / W _N ≦ 0.022.

Further, it is preferable that the difference AB between the first deviation width A and the second deviation width B is 1 mm or more and 3 mm or less.

As shown in FIG. 1, when the electrode group 3 is mounted on a battery, the positive electrode lead 17 and the negative electrode lead 18 can be connected to the electrode group 3, or the insulating sheet 10 can be provided on the electrode group 3. The positive electrode lead 17 is electrically connected to the positive electrode current collecting tab 4c. The negative electrode lead 18 is electrically connected to the negative electrode current collecting tab 5c. For example, the insulating sheet 10 covers a portion of the outermost periphery of the electrode group 3 excluding the positive electrode current collecting tab 4c and the negative electrode current collecting tab 5c.

Next, the electrode group according to the embodiment will be described in more detail.

[Positive electrode]
The positive electrode includes a strip-shaped positive electrode current collector. Therefore, the positive electrode can have a strip shape.

The positive electrode current collector is preferably an aluminum foil or an aluminum alloy foil containing one or more elements selected from Mg, Ti, Zn, Ni, Cr, Mn, Fe, Cu and Si.

The thickness of the aluminum foil or aluminum alloy foil is preferably 5 μm or more and 20 μm or less, and more preferably 15 μm or less. The purity of the aluminum foil is preferably 99% by mass or more. The content of transition metals such as iron, copper, nickel, and chromium contained in the aluminum foil or aluminum alloy foil is preferably 1% by mass or less.

The positive electrode further includes a positive electrode active material-containing layer supported on the positive electrode current collector. The positive electrode current collector can carry a positive electrode active material-containing layer on both sides thereof, or can carry a positive electrode active material-containing layer on one side. The positive electrode active material-containing layer includes a first end and a second end.

The positive electrode also includes a positive electrode current collecting tab provided at an end parallel to one side of the positive electrode current collector. The positive electrode current collector tab may be a portion of the positive electrode current collector that does not carry the positive electrode active material-containing layer on the surface. The positive electrode current collecting tab protrudes from the first end of the positive electrode active material-containing layer.

The positive electrode active material-containing layer can include, for example, a positive electrode active material, a conductive agent, and a binder.

As the positive electrode active material, for example, an oxide or a sulfide can be used. The positive electrode may contain one kind of compound alone as a positive electrode active material, or may contain two or more kinds of compounds in combination. Examples of oxides and sulfides include compounds that can insert and desorb Li or Li ions.

As such a compound, for example, manganese dioxide (MnO ₂ ), iron oxide, copper oxide, nickel oxide, lithium manganese composite oxide (for example, Li _x Mn ₂ O ₄ or Li _x MnO ₂ ; 0 <x ≦ 1) Lithium nickel composite oxide (for example, Li _x NiO ₂ ; 0 <x ≦ 1), lithium cobalt composite oxide (for example, Li _x CoO ₂ ; 0 <x ≦ 1), lithium nickel cobalt composite oxide (for example, Li _x Ni _{_{_{1-y Co y O 2;}}} 0 <x ≦ 1,0 <y <1), lithium-manganese-cobalt composite oxide (e.g., _{_{_{Li x Mn y Co 1-y}}} O 2; 0 <x ≦ 1,0 <y < 1) a lithium manganese nickel composite oxide having a spinel structure (for example, Li _x Mn _{2 -y} Ni _y O ₄ ; 0 <x ≦ 1, 0 <y <2), a lithium phosphorous oxide having an olivine structure (for example, Li _x FePO _4; 0 _{_{x ≦ 1, Li x Fe 1}} -y Mn y PO 4; 0 <x ≦ 1,0 <y <1, Li x CoPO 4; 0 <x ≦ 1), ferrous sulfate _{_{_{(Fe 2 (SO 4) 3}}} ) , Vanadium oxide (for example, V ₂ O ₅ ), and lithium nickel cobalt manganese composite oxide (Li _x Ni _1-yz Co _y Mn _z O ₂ ; 0 <x ≦ 1, 0 <y <1, 0 <z <1, y + z <1).

Among the above, examples of compounds more preferable as the positive electrode active material include lithium manganese composite oxide having a spinel structure (for example, Li _x Mn ₂ O ₄ ; 0 <x ≦ 1), lithium nickel composite oxide (for example, Li _x). NiO ₂ ; 0 <x ≦ 1), lithium cobalt composite oxide (for example, Li _x CoO ₂ ; 0 <x ≦ 1), lithium nickel cobalt composite oxide (for example, Li _x Ni _1-y Co _y O ₂ ; 0 < x ≦ 1, 0 <y <1), lithium manganese nickel composite oxide having a spinel structure (for example, Li _x Mn _2-y Ni _y O ₄ ; 0 <x ≦ 1, 0 <y <2), lithium manganese cobalt composite oxides (e.g., _{_{_{Li x Mn y Co 1-y}}} O 2; 0 <x ≦ 1,0 <y <1), lithium iron phosphate (e.g. _{_{Li x FePO 4; 0 <x}} ≦ 1), and lithium Nickel cobalt manganese composite Oxide _{_{(Li x Ni 1-yz Co}} y Mn z O 2; 0 <x ≦ 1,0 <y <1,0 <z <1, y + z <1) are included. When these compounds are used for the positive electrode active material, the positive electrode potential can be increased.

When room temperature molten salt is used as the battery electrolyte, lithium iron phosphate, Li _x VPO ₄ F (0 ≦ x ≦ 1), lithium manganese composite oxide, lithium nickel composite oxide, lithium nickel cobalt composite oxide, or these It is preferable to use a positive electrode active material containing a mixture of the above. Since these compounds have low reactivity with room temperature molten salts, the cycle life can be improved. Details of the room temperature molten salt will be described later.

The primary particle size of the positive electrode active material is preferably 100 nm or more and 1 μm or less. A positive electrode active material having a primary particle size of 100 nm or more is easy to handle in industrial production. A positive electrode active material having a primary particle size of 1 μm or less can smoothly diffuse lithium ions in a solid.

The specific surface area of the positive electrode active material is preferably 0.1 m ² / g or more and 10 m ² / g or less. The positive electrode active material having a specific surface area of 0.1 m ² / g or more can sufficiently ensure the storage / release sites of Li ions. The positive electrode active material having a specific surface area of 10 m ² / g or less is easy to handle in industrial production and can ensure good charge / discharge cycle performance.

The binder is blended to fill the gap between the dispersed positive electrode active materials and to bind the positive electrode active material and the positive electrode current collector. Examples of the binder include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluorine-based rubber, polyacrylic acid compound, imide compound, carboxymethyl cellulose (CMC). , And salts of CMC. One of these may be used as a binder, or a combination of two or more may be used as a binder.

The conductive agent is blended in order to improve the current collecting performance and suppress the contact resistance between the positive electrode active material and the positive electrode current collector. Examples of the conductive agent include vapor grown carbon fibers (Vapor Grown Carbon Fiber; VGCF), carbon black such as acetylene black, and carbonaceous materials such as graphite. One of these may be used as a conductive agent, or a combination of two or more may be used as a conductive agent. Further, the conductive agent can be omitted.

In the positive electrode active material-containing layer, the positive electrode active material and the binder are preferably blended at a ratio of 80% by mass to 98% by mass and 2% by mass to 20% by mass, respectively.

Sufficient electrode strength can be obtained by setting the amount of the binder to 2% by mass or more. In addition, the binder can function as an insulator. Therefore, when the amount of the binder is 20% by mass or less, the amount of the insulator included in the electrode is reduced, so that the internal resistance can be reduced.

When a conductive agent is added, the positive electrode active material, the binder, and the conductive agent are 77% by mass or more and 95% by mass or less, 2% by mass or more and 20% by mass or less, and 3% by mass or more and 15% by mass or less, respectively. It is preferable to mix | blend in a ratio.

By making the amount of the conductive agent 3% by mass or more, the above-described effects can be exhibited. Moreover, the ratio of the electrically conductive agent which contacts an electrolyte can be made low by making the quantity of an electrically conductive agent into 15 mass% or less. When this ratio is low, decomposition of the electrolyte can be reduced under high temperature storage.

The positive electrode can be produced, for example, by the following method. First, a positive electrode active material, a conductive agent, and a binder are suspended in a solvent to prepare a slurry. This slurry is applied to one side or both sides of the positive electrode current collector. Next, the applied slurry is dried to obtain a laminated structure of the positive electrode active material-containing layer and the positive electrode current collector. Thereafter, the laminated structure is pressed. In this way, a positive electrode is produced.

Alternatively, the positive electrode may be produced by the following method. First, a positive electrode active material, a conductive agent, and a binder are mixed to obtain a mixture. The mixture is then formed into pellets. Subsequently, a positive electrode can be obtained by arranging these pellets on a positive electrode current collector.

The width of the positive electrode active material-containing layer can be controlled by appropriately adjusting the width of the slurry applied to the positive electrode current collector or the range of the pellets arranged on the positive electrode current collector. If necessary, the produced positive electrode is cut to adjust the dimensions.

[Negative electrode]
The negative electrode includes a strip-shaped negative electrode current collector. Therefore, the negative electrode can have a strip shape.

As the negative electrode current collector, a material that is electrochemically stable at a potential at which lithium (Li) is inserted into and desorbed from a titanium-containing oxide as a negative electrode active material is used. The negative electrode current collector is preferably made of, for example, copper, nickel, stainless steel, or aluminum, or an aluminum alloy containing one or more elements selected from Mg, Ti, Zn, Mn, Fe, Cu, and Si. . The thickness of the negative electrode current collector is preferably 5 μm or more and 20 μm or less. The current collector having such a thickness can balance the strength and weight reduction of the electrode.

The negative electrode further includes a negative electrode active material-containing layer supported on the negative electrode current collector. The negative electrode current collector can carry a negative electrode active material-containing layer on both sides thereof, or can carry a negative electrode active material-containing layer on one side. The negative electrode active material-containing layer includes a third end and a fourth end.

The negative electrode also includes a negative electrode current collector tab provided at an end parallel to one side of the negative electrode current collector. The negative electrode current collector tab may be a portion of the negative electrode current collector that does not carry the negative electrode active material-containing layer on the surface. The negative electrode current collector tab protrudes from the third end of the negative electrode active material-containing layer.

The negative electrode active material-containing layer contains a titanium-containing oxide. The titanium-containing oxide can be contained in the negative electrode active material-containing layer as a negative electrode active material. The negative electrode active material-containing layer can further include, for example, a conductive agent and a binder.

The titanium-containing oxide contained in the active material-containing layer can include, for example, monoclinic niobium titanium composite oxide and orthorhombic titanium-containing composite oxide. The titanium-containing oxide may be one type of compound or a mixture of two or more types of compounds.

Examples of the monoclinic niobium titanium composite oxide include compounds represented by Li _x Ti _1-y M1 _y Nb ₂ -z M2 _z O _{7 + δ} . Here, M1 is at least one selected from the group consisting of Zr, Si, and Sn. M2 is at least one selected from the group consisting of V, Ta, and Bi. The subscripts in the composition formula are 0 ≦ x ≦ 5, 0 ≦ y <1, 0 ≦ z <2, and −0.3 ≦ δ ≦ 0.3. A specific example of the monoclinic niobium titanium complex oxide is Li _x Nb ₂ TiO ₇ (0 ≦ x ≦ 5).

Another example of the monoclinic niobium titanium composite oxide is a compound represented by Li _x Ti _1-y M3 _{y + z} Nb ₂ -z O _7-δ . Here, M3 is at least one selected from Mg, Fe, Ni, Co, W, Ta, and Mo. The subscripts in the composition formula are 0 ≦ x ≦ 5, 0 ≦ y <1, 0 ≦ z <2, and −0.3 ≦ δ ≦ 0.3.

Examples of the tetragonal titanium-containing composite oxide include a compound represented by Li _{2 + a} M (I) _{2 -b} Ti _{6 -c} M (II) _d O _{14 + σ} . Here, M (I) is at least one selected from the group consisting of Sr, Ba, Ca, Mg, Na, Cs, Rb and K. M (II) is at least one selected from the group consisting of Zr, Sn, V, Nb, Ta, Mo, W, Y, Fe, Co, Cr, Mn, Ni, and Al. The subscripts in the composition formula are 0 ≦ a ≦ 6, 0 ≦ b <2, 0 ≦ c <6, 0 ≦ d <6, and −0.5 ≦ σ ≦ 0.5. Specific examples of the tetragonal titanium-containing composite oxide include Li _{2 + a} Na ₂ Ti ₆ O ₁₄ (0 ≦ a ≦ 6).

Among the titanium-containing oxides, the monoclinic niobium titanium composite oxide and the tetragonal titanium-containing composite oxide have a low lithium insertion / extraction potential (potential at which lithium is inserted and desorbed). Therefore, a battery having a high energy density can be obtained by using these titanium-containing oxides. When the lithium occlusion / release potential is low, lithium dendrite is likely to precipitate. However, as described above, the electrode group according to the embodiment is less likely to cause a short circuit due to precipitation.

Examples of the other titanium-containing oxide include spinel type lithium titanate such as a compound represented by Li _{4 + w} Ti ₅ O ₁₂ (0 ≦ w ≦ 3). Since spinel type lithium titanate has a high lithium storage / release potential (noble), it is difficult to obtain a high energy density. In addition, since metal precipitation is unlikely to occur due to a high potential, making the width of the negative electrode active material-containing layer larger than the width of the positive electrode active material-containing layer is opposite to the positive electrode active material-containing layer in the negative electrode active material-containing layer. The part which is not needed is increased unnecessarily, and the energy density is reduced. Therefore, it is desirable to select the titanium-containing oxide from monoclinic niobium titanium composite oxide and tetragonal titanium-containing composite oxide.

The titanium-containing oxide can be included in the active material-containing layer in the form of primary particles or secondary particles, for example. As used herein, secondary particles refer to particles formed by aggregating a plurality of primary particles.

The titanium-containing oxide particles that can be included in the active material-containing layer can include a phase including a carbon material formed on at least a part of the surface of the particles. By including such a phase, good conductivity can be obtained. For example, composite particles in which a phase containing a carbon material is formed on the particle surface of a niobium titanium composite oxide as a titanium-containing oxide can be suitably used.

When the carbon material is analyzed by Raman spectroscopy using a measurement light source of 532 nm, the crystallinity of the carbon material can be determined. In the Raman chart of the carbon material, the G band observed near 1580 cm ⁻¹ is a peak derived from the graphite structure, and the D band observed near 1330 cm ⁻¹ is a peak derived from the defect structure of carbon. is there. G band and D band is due to various factors, from 1580 cm ^-1 and 1330 cm ^-1, it is possible that each shifted about ± 50 cm ^-1.

Carbon material ratio I _G / I _D between the peak intensity I _D of G peak intensity of the bands I _G and D bands in the Raman chart is 0.8 to 1.2, it has a good crystallinity of graphite Means. Such a carbon material can have excellent conductivity.

That the ratio I _G / _ID is greater than 1.2 means, for example, that the amorphization of carbon is insufficient. In this case, impurities contained in the carbon source may be included. Since such impurities cause side reactions with the electrolyte, the battery input / output performance and life performance are adversely affected.

In addition, for example, when a titanium-containing oxide containing an Nb element such as Nb ₂ TiO ₇ is used, the carbon source may react with the Nb element. When the reaction between the carbon source and the Nb element proceeds, the amorphous carbon component whose carbon-carbon bond is more unstable than the graphite structure is preferentially oxidized, so that the amount of amorphous carbon decreases and the ratio I _G / _ID may be greater than 1.2.

Further, the ratio I _G / _ID being smaller than 0.8 means that the carbon component derived from the graphite structure is small.

Therefore, it is preferable to use a carbon material having a ratio I _G / _ID of 0.8 or more and 1.2 or less because better electronic conductivity can be obtained.

The phase containing the carbon material can exist in various forms. For example, the phase containing the carbon material may cover the entire titanium-containing oxide particle, or may be supported on a part of the surface of the titanium-containing oxide particle. More preferably, the conductivity of the entire active material particle (a composite particle including a titanium-containing oxide particle and a phase containing a carbon material) is uniformly complemented, and the surface reaction between the active material particle and the electrolyte is suppressed. From these two viewpoints, it is preferable that the entire surface of the titanium-containing oxide particles is coated with a phase containing a carbon material. The existence state of the phase containing the carbon material can be confirmed by, for example, transmission electron microscope (TEM) observation and mapping by energy dispersive X-ray spectroscopy (EDX) analysis.

The conductive agent is blended in order to improve the current collecting performance and suppress the contact resistance between the active material and the current collector. Examples of the conductive agent include vapor grown carbon fibers (Vapor Grown Carbon Fiber; VGCF), carbon black such as acetylene black, and carbonaceous materials such as graphite. One of these may be used as a conductive agent, or a combination of two or more may be used as a conductive agent. Alternatively, instead of using a conductive agent, a carbon coat or an electronically conductive inorganic material coat may be applied to the surface of the active material particles.

The binder is blended to fill a gap between the dispersed negative electrode active materials and to bind the negative electrode active material and the negative electrode current collector. Examples of the binder include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluorine rubber, styrene butadiene rubber, polyacrylic acid compound, imide compound, carboxymethyl cellulose (carboxyl). methyl cellulose (CMC), and salts of CMC. One of these may be used as a binder, or a combination of two or more may be used as a binder.

The negative electrode active material (titanium-containing oxide, etc.), the conductive agent and the binder in the negative electrode active material-containing layer are 68% by mass to 96% by mass, 2% by mass to 30% by mass and 2% by mass, respectively. It is preferable to mix | blend in the ratio of 30 mass% or less. By setting the amount of the conductive agent to 2% by mass or more, the current collecting performance of the negative electrode active material-containing layer can be improved. Further, by setting the amount of the binder to 2% by mass or more, the binding property between the negative electrode active material-containing layer and the current collector becomes sufficient, and excellent cycle performance can be expected. On the other hand, the conductive agent and the binder are each preferably 30% by mass or less in order to increase the capacity.

The negative electrode can be produced by a method similar to that of the positive electrode, for example, using a titanium-containing oxide as the negative electrode active material instead of the positive electrode active material and using the negative electrode current collector instead of the positive electrode current collector.

[Electrical insulation]
The electrically insulating member includes a material having an electrically insulating property. The electrically insulating member is, for example, a separator. Further, the electrically insulating member can be an insulating layer containing a material having electrical insulation. The electrically insulating member may be a single member or two or more members. For example, a separator can be used alone, an insulating layer can be used alone, or a separator and an insulating layer can be used in combination.

The separator is formed of, for example, a porous film containing polyethylene (PE), polypropylene (PP), cellulose, or polyvinylidene fluoride (PVdF), or a synthetic resin nonwoven fabric. From the viewpoint of safety, it is preferable to use a porous film formed from polyethylene or polypropylene. This is because these porous films can be melted at a constant temperature to interrupt the current.

Further, the insulating layer can include a non-Li conductive inorganic material or a solid electrolyte particle exhibiting Li conductivity as a material having electrical insulation.

Examples of the inorganic material that does not exhibit conductivity with respect to Li (lithium) include one or more oxides selected from the group consisting of Ba, Al, Zr, Ta, and Si. Specific examples include metal oxides such as aluminum oxide (Al ₂ O ₃ ), barium oxide (BaO), zirconium oxide (ZrO ₂ ), tantalum pentoxide (Ta ₂ O ₅ ), and barium sulfate (BaSO ₄ ). One or more compounds selected from the group consisting of sulfate and silicon oxide (SiO ₂ ) can be used. Other examples include titanium oxide (TiO ₂ ), magnesium oxide (MgO), calcium oxide (CaO), beryllium oxide (BeO), lithium oxide (Li ₂ O), sodium oxide (Na ₂ O), potassium oxide (K ₂ O), zinc oxide (ZnO), antimony oxide (Sb ₂ O ₅ ), metal oxides such as strontium oxide (SrO) indium oxide (In ₂ O ₃ ), arsenic oxide (As ₄ O ₆ ), boron oxide One or more compounds selected from the group consisting of (B ₂ O ₃ ) can be used. Especially, the above-mentioned metal oxide can show the outstanding stability with respect to the nonaqueous electrolyte which a nonaqueous electrolyte battery contains.

Examples of the solid electrolyte exhibiting conductivity with respect to Li include LLZ-based materials such as a compound represented by Li ₇ La ₃ Zr ₂ O ₁₂ , and Li _{1 + x} Al _x M _2-x (PO ₄ ) ₃ (M 1 or more selected from the group consisting of Ti, Zr, and Ge; materials of a family of compounds represented by 0 ≦ x ≦ 0.6) can be used. As the solid electrolyte, one type of compound may be used, or two or more types of compounds may be used in combination. A non-Li conductive inorganic material and a solid electrolyte can also be used together.

The insulating layer may contain a binder. Examples of the binder that can be included in the insulating layer include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluorine-based rubber, styrene butadiene rubber (SBR), carboxymethyl cellulose (CMC), and mixtures thereof. Can be mentioned. The content of the binder in the insulating layer is desirably in the range of 0.01% by mass to 20% by mass.

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

The insulating layer may be a layer formed on at least one of the positive electrode and the negative electrode, for example, including a material having electrical insulation. An electrode in which an insulating layer as an electrical insulating member is formed on the active material-containing layer can be manufactured by the first manufacturing method or the second manufacturing method described below.

In the first manufacturing method, an insulating layer is formed on a manufactured electrode.
An electrode (positive electrode or negative electrode) is produced by the method described above. When producing an electrode, you may abbreviate | omit a press.
Separately, a slurry containing a material having electrical insulation is prepared. The adjusted slurry is applied on the active material-containing layer of the electrode. At this time, the coating width of the slurry is wider than the width of the active material-containing layer, and a part of the slurry is directly applied to a portion of the current collector that does not carry the active material-containing layer (for example, the electrode current collector tab). It may be applied. After drying the slurry, the laminated structure after drying (the electrode on which the insulating layer before pressing is formed) is roll-pressed to obtain an electrode on which the insulating layer is formed.

In the second manufacturing method, the active material-containing layer and the insulating layer of the electrode are formed by simultaneous coating.
A slurry containing an active material and a binder (hereinafter referred to as slurry I) and a slurry containing an electrically insulating material (hereinafter referred to as slurry II) on at least one of the front and back surfaces of the current collector ) At the same time. Almost simultaneously with the application of the slurry I, the slurry II is applied so as to protrude from the application region of the slurry I. Since the slurry II is repeatedly applied to the slurry I before the slurry I dries, the slurry II easily follows the surface shape of the slurry I. Then, after the slurry is dried, the laminated structure after the drying (the current collector on which the active material-containing layer and the insulating layer before pressing are formed) is roll-pressed to form an electrode on which the insulating layer is formed. Get.

<Measurement method>
A method for measuring the electrode group will be described below.

∙ When the electrode group to be measured is built in a fabricated battery, prepare a measurement sample according to the following procedure.

∙ Discharge the battery at a constant current in a constant temperature bath at 25 ℃ until the current value reaches 0.2V at a current value [A] equivalent to 0.2 C. Then, constant voltage discharge is performed at 1.5V for 1 hour.

¡After discharging at constant voltage, place the battery in an argon glove box and disassemble the battery. An electrode coil (rolled electrode group) is taken out from the exterior member in the glove box. At this time, it can be determined that the electrode connected to the negative electrode terminal of the battery is the negative electrode, and the electrode connected to the positive electrode terminal is the positive electrode. The electrode coil can be connected to the electrode terminal via an electrode lead. Carefully remove the electrode coil from the electrode lead. For example, it is possible to remove the connection with the electrode lead using scissors, pliers, a cutter or the like while pressing the electrode coil so that the positions of the positive electrode, the electrically insulating member, and the negative electrode do not move within the electrode coil.

The electrode group isolated in this way was used as a measurement sample, and the width (W _P , W _N ) of the active material-containing layer in the positive and negative electrodes and the end portions (first to fourth end portions) of the active material-containing layer were measured. The gap width (A, B) is measured.

(Method for identifying composition in negative electrode active material-containing layer)
Whether or not the negative electrode active material-containing layer contains a titanium-containing oxide can be confirmed, for example, as follows.

First, the electrode group taken out by the procedure described above is disassembled and the negative electrode is taken out. This negative electrode is washed with a suitable solvent. For example, ethyl methyl carbonate may be used. If the cleaning is insufficient, an impurity phase such as lithium carbonate or lithium fluoride may be mixed under the influence of lithium ions remaining in the negative electrode. In that case, it is preferable to use an airtight container in which the measurement atmosphere can be performed in an inert gas.

The section of the member taken out as described above is cut out by Ar ion milling. The cut section is observed with a scanning electron microscope (SEM). Sampling of the sample should be performed in an inert atmosphere such as argon or nitrogen while avoiding exposure to the air.

Several particles are selected with a 3000 times SEM observation image. At this time, the particle size distribution of the selected particles is selected to be as wide as possible.

Next, elemental analysis is performed on each selected particle by energy dispersive X-ray spectroscopy (EDX). Thereby, the kind and quantity of elements other than Li among the elements contained in each selected particle | grain can be specified.

The crystal structure of the compound contained in each particle selected by SEM can be specified by X-ray diffraction (XRD) measurement.

The measurement is performed in the measurement range of 2θ = 10 to 90 ° using CuKα ray as a radiation source. By this measurement, an X-ray diffraction pattern of the compound contained in the selected particle can be obtained.

As an apparatus for powder X-ray diffraction measurement, SmartLab manufactured by Rigaku is used. Measurement conditions are as follows: Cu target; 45 kV 200 mA; Solar slit: 5 ° for both incidence and reception; Step width: 0.02 deg; Scan rate: 20 deg / min; Semiconductor detector: D / teX Ultra 250; Plate holder: Flat glass sample plate holder (thickness 0.5 mm); Measurement range: 10 ° ≦ 2θ ≦ 90 °. When using other devices, perform measurements using standard Si powder for powder X-ray diffraction so that the same measurement results as above can be obtained, under conditions where the peak intensity and peak top position match those of the above devices. Do.

When the particles to be measured contain a tetragonal titanium-containing composite oxide, an X-ray diffraction pattern belonging to the tetragonal type, such as the space group Cmca or Fmmm, can be confirmed by X-ray diffraction measurement.

XRD measurement for the negative electrode can be performed by cutting the electrode to be measured to the same extent as the area of the holder of the wide-angle X-ray diffractometer and directly attaching it to a glass holder for measurement. If necessary, the insulating layer is previously removed from the active material-containing layer. At this time, an XRD spectrum is measured in advance according to the type of the metal foil of the electrode current collector, and the position where the peak derived from the current collector appears is known. In addition, the presence or absence of a peak of a mixture such as a conductive agent or a binder is also grasped in advance. When the peak of the current collector and the peak of the active material overlap, it is desirable to measure by peeling the active material-containing layer from the current collector. This is for separating overlapping peaks when quantitatively measuring the peak intensity. Of course, if these can be grasped in advance, this operation can be omitted. Although the active material-containing layer may be physically peeled off, it is easily peeled off when ultrasonic waves are applied in a solvent. By measuring the active material-containing layer collected in this manner, wide-angle X-ray diffraction measurement of the active material can be performed.

The composition of the entire active material-containing layer can be measured, for example, by the following procedure.

First, the electrode collected by the procedure described above is washed.
Using the cleaned electrode, the composition of the particles contained in the active material-containing layer is specified by the method described above.

On the other hand, another part of the cleaned electrode is placed in a suitable solvent and irradiated with ultrasonic waves. For example, the active material-containing layer can be peeled from the current collector substrate by placing an electrode in ethyl methyl carbonate placed in a glass beaker and vibrating in an ultrasonic cleaner. Next, vacuum drying is performed to dry the separated active material-containing layer. By pulverizing the obtained active material-containing layer with a mortar or the like, a powder containing an active material to be measured, a conductive agent, a binder, and the like is obtained. By dissolving this powder with an acid, a liquid sample containing an active material can be produced. At this time, hydrochloric acid, nitric acid, sulfuric acid, hydrogen fluoride and the like can be used as the acid. By subjecting this liquid sample to inductively coupled plasma (ICP) emission spectroscopic analysis, the concentration of elements in the active material contained in the active material-containing layer can be known.

As described above, the particles contained in the active material-containing layer are contained in the particles by combining the results of the identification of the composition by SEM and EDX, the identification of the crystal structure by XRD, and the ICP emission spectroscopic analysis. The composition and crystal structure of the compound can be specified.

(Method for confirming phases containing carbon materials)
As a technique for quantitatively evaluating the crystallinity of the carbon component contained in the phase that can be formed on the titanium-containing oxide particles, a micro-Raman measurement apparatus can be used. As the micro Raman apparatus, for example, Thermo Fisher Scientific ALMEGA can be used. The measurement conditions can be, for example, a wavelength of the measurement light source of 532 nm, a slit size of 25 μm, a laser intensity of 10%, an exposure time of 5 s, and an integration count of 10 times.

Raman spectroscopy can be performed, for example, according to the procedure described below.

When evaluating the material incorporated in the battery, the battery is brought into a state where lithium ions are completely desorbed. For example, when a titanium-containing oxide is used as the negative electrode active material, the battery is completely discharged. However, a small amount of lithium ions may remain even in a discharged state.

Next, the battery is disassembled in a glove box filled with argon, and the electrode is washed with an appropriate solvent. At this time, for example, ethyl methyl carbonate may be used. Next, the active material-containing layer is peeled off from the cleaned electrode, and a sample is collected.

Using the collected sample, for example, Raman spectroscopy measurement is performed under the conditions described above.

In the measurement, the presence or absence of Raman activity and the peak position of other components contained in the current collector and the mixture such as the conductive agent and the binder are known. In the case of overlapping, it is necessary to separate peaks relating to components other than the active material.

When an active material (for example, composite particles of active material particles and a phase containing a carbon material) is mixed with a conductive agent in the active material-containing layer, the carbon material contained in the active material and the conductive agent are incorporated. It can be difficult to distinguish between different carbon materials. In such a case, as one method for distinguishing between the two, for example, a method of dissolving and removing the binder with a solvent and then performing centrifugation to extract an active material having a high specific gravity can be considered. According to such a method, since the active material and the conductive agent can be separated, the carbon material contained in the active material can be subjected to measurement while being contained in the active material. it can.

Alternatively, mapping is performed from the spectral component derived from the active material by mapping by microscopic Raman spectroscopy to separate the conductive agent component from the active material component, and then only the Raman spectrum corresponding to the active material component is extracted. It is also possible to take an evaluation method.

The electrode group according to the first embodiment includes a laminate including a positive electrode, a negative electrode, and an electrically insulating member. The positive electrode was supported on the positive electrode current collector, a positive electrode current collector tab provided at an end parallel to one side of the positive electrode current collector, and at least excluding the positive electrode current collector tab. A positive electrode active material-containing layer. The positive electrode active material-containing layer includes a first end and a second end parallel to the one side of the positive electrode current collector. The negative electrode includes a strip-shaped negative electrode current collector, a negative electrode current collector tab provided at an end parallel to one side of the negative electrode current collector, and a titanium supported on the negative electrode current collector excluding at least the negative electrode current collector tab A negative electrode active material-containing layer containing a containing oxide. The negative electrode active material-containing layer includes a third end portion and a fourth end portion that are parallel to the one side of the negative electrode current collector. The electrically insulating member is interposed between the positive electrode active material-containing layer and the negative electrode active material-containing layer. The laminate is wound. A positive electrode current collecting tab protrudes in a first direction parallel to the winding axis. The fourth end portion is located closer to the positive electrode current collecting tab side than the first end portion. The negative electrode current collector tab protrudes in the second direction opposite to the first direction. The third end portion is located closer to the negative electrode current collecting tab side than the second end portion. The second shift width between the second end portion and the third end portion is wider than the first shift width between the first end portion and the fourth end portion. The electrode group can realize a battery in which self-discharge is suppressed.

(Second Embodiment)
The battery according to the second embodiment includes the electrode group according to the first embodiment.

The battery according to the embodiment may further include an electrolyte. The electrolyte can be held on the electrode group.

In addition, the battery according to the embodiment can further include an exterior member that accommodates the electrode group and the electrolyte.

Furthermore, the battery according to the embodiment may further include a negative electrode terminal electrically connected to the negative electrode and a positive electrode terminal electrically connected to the positive electrode.

The battery according to the embodiment may be, for example, a lithium ion secondary battery. The battery includes, for example, a nonaqueous electrolyte battery including a nonaqueous electrolyte as an electrolyte.

Hereinafter, the electrolyte, the exterior member, the negative electrode terminal, and the positive electrode terminal will be described in detail.

[Electrolytes]
As the electrolyte, for example, a liquid non-aqueous electrolyte or a gel non-aqueous electrolyte can be used. The liquid non-aqueous electrolyte is prepared by dissolving an electrolyte salt as a solute in an organic solvent. The concentration of the electrolyte salt is preferably 0.5 mol / L or more and 2.5 mol / L or less.

Examples of electrolyte salts include lithium perchlorate (LiClO ₄ ), lithium hexafluorophosphate (LiPF ₆ ), lithium tetrafluoroborate (LiBF ₄ ), lithium arsenic hexafluoride (LiAsF ₆ ), trifluoromethane Lithium salts such as lithium sulfonate (LiCF ₃ SO ₃ ) and lithium bistrifluoromethylsulfonylimide (LiN (CF ₃ SO ₂ ) ₂ ) and mixtures thereof are included. The electrolyte salt is preferably one that is difficult to oxidize even at a high potential, and LiPF ₆ is most preferred.

Examples of organic solvents include: cyclic carbonates such as propylene carbonate (PC), ethylene carbonate (EC), vinylene carbonate (VC); diethyl carbonate (DEC), dimethyl carbonate (Dimethyl carbonate; DMC), chain carbonates such as methyl ethyl carbonate (MEC); tetrahydrofuran (tetrahydrofuran; THF); 2-methyltetrahydrofuran (2-MeTHF); dioxolane (DOX) Cyclic ethers such as: dimethoxy ethane (DME), chain ethers such as diethoxy ethane (DEE); γ-butyrolactone (GBL), acetonitrile ( acetonitrile; AN) and sulfolane (SL). These organic solvents can be used alone or as a mixed solvent.

The gel-like nonaqueous electrolyte is prepared by combining a liquid nonaqueous electrolyte and a polymer material. Examples of the polymer material include polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyethylene oxide (PEO), or a mixture thereof.

Alternatively, as the non-aqueous electrolyte, in addition to the liquid non-aqueous electrolyte and the gel-like non-aqueous electrolyte, a room temperature molten salt (ionic melt) containing lithium ions, a polymer solid electrolyte, an inorganic solid electrolyte, and the like are used. Also good.

The room temperature molten salt (ionic melt) refers to a compound that can exist as a liquid at room temperature (15 ° C. or more and 25 ° C. or less) among organic salts formed by a combination of an organic cation and an anion. Room temperature molten salt includes room temperature molten salt that exists as a liquid alone, room temperature molten salt that becomes liquid when mixed with electrolyte salt, room temperature molten salt that becomes liquid when dissolved in organic solvent, or a mixture thereof It is. Generally, the melting point of the room temperature molten salt used for the secondary battery is 25 ° C. or less. The organic cation generally has a quaternary ammonium skeleton.

The polymer solid electrolyte is prepared by dissolving an electrolyte salt in a polymer material and solidifying it.

The inorganic solid electrolyte is a solid material having Li ion conductivity. As the inorganic solid electrolyte, for example, a solid electrolyte having Li ion conductivity that can be included in the insulating layer can be used.

[Exterior material]
As the exterior member, for example, a container made of a laminate film or a metal container can be used.

The thickness of the laminate film is, for example, 0.5 mm or less, and preferably 0.2 mm or less.

As the laminate film, a multilayer film including a plurality of resin layers and a metal layer interposed between these resin layers is used. The resin layer includes, for example, a polymer material such as polypropylene (PP), polyethylene (PE), nylon, and polyethylene terephthalate (PET). It is preferable that a metal layer consists of aluminum foil or aluminum alloy foil for weight reduction. The laminate film can be formed into the shape of the exterior member by sealing by heat sealing.

The wall thickness of the metal container is, for example, 1 mm or less, more preferably 0.5 mm or less, and still more preferably 0.2 mm or less.

The metal container is made of, for example, aluminum or an aluminum alloy. The aluminum alloy preferably contains elements such as magnesium, zinc, and silicon. When an aluminum alloy contains transition metals, such as iron, copper, nickel, and chromium, it is preferable that the content is 100 mass ppm or less.

The shape of the exterior member is not particularly limited. The shape of the exterior member may be, for example, a flat type (thin type), a square type, a cylindrical type, a coin type, or a button type. The exterior member can be appropriately selected according to the battery size and the application of the battery.

[Negative terminal]
The negative electrode terminal can be formed from a material that is electrochemically stable at the Li occlusion / release potential of the above-described titanium-containing oxide (negative electrode active material) and has conductivity. Specifically, the negative electrode terminal material includes copper, nickel, stainless steel, or aluminum, or at least one element selected from the group consisting of Mg, Ti, Zn, Mn, Fe, Cu, and Si. An aluminum alloy is mentioned. As a material for the negative electrode terminal, aluminum or an aluminum alloy is preferably used. In order to reduce the contact resistance with the negative electrode current collector, the negative electrode terminal is preferably made of the same material as the negative electrode current collector.

[Positive terminal]
The positive electrode terminal can be formed of a material that is electrically stable and has conductivity in a potential range (vs. Li / Li +) of 3 V to 4.5 V with respect to the oxidation-reduction potential of lithium. Examples of the material of the positive electrode terminal include aluminum or an aluminum alloy containing at least one element selected from the group consisting of Mg, Ti, Zn, Mn, Fe, Cu, and Si. The positive electrode terminal is preferably formed of the same material as the positive electrode current collector in order to reduce contact resistance with the positive electrode current collector.

Next, the battery according to the embodiment will be described more specifically with reference to the drawings.

FIG. 4 is a schematic cross-sectional view of an example flat battery according to the embodiment. FIG. 5 is an enlarged cross-sectional view of a portion A in FIG.

The battery 1 shown in FIGS. 4 and 5 includes a flat wound electrode group 3 shown in FIG. The flat wound electrode group 3 is housed in a bag-shaped exterior member 2 made of a laminate film including a metal layer and two resin films sandwiching the metal layer.

As shown in FIG. 6, the flat wound electrode group 3 is formed by spirally winding a laminate in which the negative electrode 5, the electrical insulating member 6, the positive electrode 4, and the electrical insulating member 6 are laminated in this order from the outside. It is formed by press molding. As shown in FIG. 5, the outermost portion of the negative electrode 5 forms a negative electrode active material-containing layer 5 b containing a negative electrode active material on one surface on the inner surface side of the negative electrode current collector 5 a. In the other part of the negative electrode 5, the negative electrode active material containing layer 5b is formed on both surfaces of the negative electrode current collector 5a. For the positive electrode 4, positive electrode active material-containing layers 4b are formed on both surfaces of the positive electrode current collector 4a.

In the vicinity of the outer peripheral end of the wound electrode group 3, the negative electrode terminal 8 is connected to the negative electrode current collector 5 a in the outermost layer portion of the negative electrode 5, and the positive electrode terminal 7 is the positive electrode of the positive electrode 4 positioned inside. It is connected to the current collector 4a. The negative terminal 8 and the positive terminal 7 are extended to the outside from the opening of the bag-shaped exterior member 2.

4 and 5 further includes an electrolyte (not shown). The electrolyte is accommodated in the exterior member 2 in a state in which the electrode group 3 is impregnated.

The battery according to the second embodiment includes the electrode group according to the first embodiment. Therefore, self-discharge is suppressed in the battery.

[Third Embodiment]
According to the third embodiment, a battery pack is provided. This battery pack includes the battery according to the second embodiment.

The battery pack according to the embodiment may include a plurality of batteries. The plurality of batteries can be electrically connected in series or electrically connected in parallel. Alternatively, a plurality of batteries can be connected in a combination of series and parallel.

For example, the battery pack can include five batteries according to the second embodiment. These batteries can be connected in series. Moreover, the battery connected in series can comprise an assembled battery. That is, the battery pack according to the embodiment can include an assembled battery.

The battery pack according to the embodiment can include a plurality of assembled batteries. The plurality of assembled batteries can be connected in series, parallel, or a combination of series and parallel.

The battery pack according to the embodiment will be described in detail with reference to FIGS. The flat battery shown in FIGS. 1 and 2 can be used as the unit cell.

FIG. 6 is an exploded perspective view schematically showing an example of the battery pack according to the embodiment. FIG. 7 is a block diagram showing an example of an electric circuit of the battery pack 20 shown in FIG.

A plurality of unit cells 21 composed of the flat batteries shown in FIGS. 1 and 2 are laminated so that the negative electrode terminal 8 and the positive electrode terminal 7 extending to the outside are aligned in the same direction. The assembled battery 23 is configured by fastening. These unit cells 21 are electrically connected to each other in series as shown in FIG.

The printed wiring board 24 is arranged to face the side surface of the unit cell 21 from which the negative electrode terminal 8 and the positive electrode terminal 7 extend. On the printed wiring board 24, as shown in FIG. 7, a thermistor 25, a protection circuit 26, and a terminal 27 for energizing external devices are mounted. An insulating plate (not shown) is attached to the surface of the protection circuit board 24 facing the assembled battery 23 in order to avoid unnecessary connection with the wiring of the assembled battery 23.

The positive electrode side lead 28 is connected to the positive electrode terminal 7 located in the lowermost layer of the assembled battery 23, and the tip thereof is inserted into the positive electrode side connector 29 of the printed wiring board 24 and electrically connected thereto. The negative electrode side lead 30 is connected to the negative electrode terminal 8 located in the uppermost layer of the assembled battery 23, and the tip thereof is inserted into and electrically connected to the negative electrode side connector 31 of the printed wiring board 24. These

connectors

29 and 31 are connected to the protection circuit 26 through wiring 32 and wiring 33 formed on the printed wiring board 24.

The thermistor 25 detects the temperature of the unit cell 21, and the detection signal is transmitted to the protection circuit 26. The protection circuit 26 can cut off the plus side wiring 34a and the minus side wiring 34b between the protection circuit 26 and the energization terminal 27 to the external device under a predetermined condition. The predetermined condition is, for example, when the temperature detected by the thermistor 25 is equal to or higher than a predetermined temperature. The predetermined condition is when the overcharge, overdischarge, overcurrent, etc. of the cell 21 are detected. This detection of overcharge or the like is performed for each individual cell 21 or the entire assembled battery 23. When detecting each single cell 21, the battery voltage may be detected, or the positive electrode potential or the negative electrode potential may be detected. In the latter case, a lithium electrode used as a reference electrode is inserted into each unit cell 21. In the case of FIG. 6 and FIG. 7, a wiring 35 for voltage detection is connected to each single cell 21, and a detection signal is transmitted to the protection circuit 26 through these wirings 35.

Protective sheets 36 made of rubber or resin are respectively disposed on the three side surfaces of the assembled battery 23 excluding the side surfaces from which the positive electrode terminal 7 and the negative electrode terminal 8 protrude.

The assembled battery 23 is stored in a storage container 37 together with each protective sheet 36 and the printed wiring board 24. That is, the protective sheet 36 is disposed on each of the inner side surface in the long side direction and the inner side surface in the short side direction of the storage container 37, and the printed wiring board 24 is disposed on the inner side surface on the opposite side in the short side direction. The assembled battery 23 is located in a space surrounded by the protective sheet 36 and the printed wiring board 24. The lid 38 is attached to the upper surface of the storage container 37.

In addition, instead of the adhesive tape 22, a heat shrink tape may be used for fixing the assembled battery 23. In this case, protective sheets are arranged on both side surfaces of the assembled battery, the heat shrinkable tape is circulated, and then the heat shrinkable tape is heat shrunk to bind the assembled battery.

6 and 7 show the configuration in which the unit cells 21 are connected in series, but in order to increase the battery capacity, they may be connected in parallel. The assembled battery packs can be connected in series and / or in parallel.

The battery pack according to the third embodiment includes the battery according to the second embodiment. Therefore, self-discharge is suppressed in the battery pack.

[Example]
Examples will be described below.

<Production of battery>
Example 1
[Manufacture of negative electrode]
As a negative electrode active material, TiNb ₂ O _{7 in the} form of secondary particles attached with carbon was prepared. The average particle size of the secondary particles including the carbon phase was 15 μm. The prepared negative electrode active material, acetylene black, and polyvinylidene fluoride (PVdF) were mixed in a mass ratio of 80:10:10 in N-methylpyrrolidone (NMP) to obtain a slurry. This slurry was applied to both sides of the Al foil with a basis weight of 60 g / m ² and dried. On one side of the width direction of the Al foil, a portion where no slurry was applied was left on either side. The laminated structure after drying was pressed and further vacuum dried. Next, the active material-containing layer (the slurry coating after drying and pressing) was cut so that the width was 180 mm to obtain a negative electrode. When cutting, the side opposite to the portion where the slurry was not applied was cut. In addition, the part which did not apply | coat a slurry was used as a negative electrode current collection tab.

[Production of positive electrode]
LiNi _0.33 Co _0.33 Mn _0.33 O ₂ particles were prepared as a positive electrode active material, carbon black as a conductive agent, and polyvinylidene fluoride (PVdF) as a 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. This slurry was applied to both sides of an aluminum foil having a thickness of 15 μm with a basis weight of 80 g / m ² and dried. On one side of the width direction of the Al foil, a portion where no slurry was applied was left on either side. The laminated structure after drying was roll-pressed. Thereafter, the active material containing layer (slurry coating film after drying and pressing) was cut to have a width of 175 mm to obtain a positive electrode. When cutting, the side opposite to the portion where the slurry was not applied was cut. In addition, the part which did not apply | coat a slurry was used as a positive electrode current collection tab.

[Manufacture of electrode group]
A cellulose fiber nonwoven fabric having a thickness of 15 μm and a porosity of 70% was prepared as a separator (electrically insulating member). Two separators and the negative electrode and positive electrode produced as described above were laminated in the order of negative electrode, separator, positive electrode, and separator to obtain a laminate. When laminating, the negative electrode current collecting tab and the positive electrode current collecting tab were disposed on the opposite side of the laminated body (each of a pair of sides facing each other in the width direction). At this time, the width of the active material-containing layer is found to be 5 mm longer for the negative electrode than for the positive electrode. The protruding width of the negative electrode active material-containing layer on the positive electrode current collecting tab side was 1.5 mm, and the protruding width of the negative electrode active material-containing layer on the negative electrode current collecting tab side was 3.5 mm.
The electrode assembly was manufactured by winding the laminate into a flat spiral shape.

[Preparation of electrolyte]
Propylene carbonate (PC) and diethyl carbonate (DEC) were mixed so that the volume ratio PC: DEC was 1: 2. In this mixed solvent, 1M of LiPF ₆ was dissolved to obtain a liquid non-aqueous electrolyte.

[Production of battery]
The electrode group was inserted into a bag-shaped exterior member made of a laminate film.
The liquid nonaqueous electrolyte was injected into the electrode group in the exterior member. By sealing the exterior member, a nonaqueous electrolyte secondary battery having a thickness of 17 mm, a width of 88 mm, and a height of 240 mm was obtained.

(Example 2)
A negative electrode and a positive electrode were produced in the same procedure as in Example 1.
A mixture of Al ₂ O ₃ particles having an average particle diameter of 1 μm and PVdF mixed at a mass ratio of 100: 4 was dispersed in NMP to prepare an alumina-containing slurry (slurry II). This slurry was prepared so as to be 100 Pa · s at a viscosity shear rate of 1.0 (1 / s) and 2 Pa · s at a viscosity shear rate of 1000 (1 / s).

The alumina-containing slurry was applied on the active material-containing layers on both sides of the negative electrode so as to have an amount of 5 g / m ² . Moreover, it apply | coated so that the coating width of an alumina containing slurry might be set to 180 mm. The alumina-containing slurry was dried to form an insulating layer on the negative electrode.

The negative electrode and the positive electrode on which the insulating layer was formed were alternately laminated to obtain a laminate. When laminating, the negative electrode current collecting tab and the positive electrode current collecting tab were disposed on the opposite side of the laminated body (each of a pair of sides opposed in the width direction). As in Example 1, the protruding width of the negative electrode active material-containing layer on the positive electrode current collector tab side was 1.5 mm, and the protruding width of the negative electrode active material-containing layer on the negative electrode current collector tab side was 3.5 mm. An electrode group was manufactured by winding the laminate.

A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that the obtained electrode group was used.

Example 3
A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 2 except that BaSO ₄ particles having an average particle diameter of 1 μm were used instead of Al ₂ O ₃ for forming the insulating layer.

Example 4
A nonaqueous electrolyte secondary battery was fabricated in the same manner as in Example 2 except that Li ₇ La ₂ Ta ₃ O ₁₂ particles having an average particle diameter of 1 μm were used instead of Al ₂ O ₃ for forming the insulating layer.

(Example 5)
A non-aqueous electrolyte was formed in the same manner as in Example 2 except that Li _1.4 Al _0.4 Zr _1.6 (PO ₄ ) ₃ particles having an average particle diameter of 1 μm were used instead of Al ₂ O ₃ for forming the insulating layer. A secondary battery was produced.

(Example 6)
The width of the negative electrode active material-containing layer was changed to 90 mm, and the width of the positive electrode active material-containing layer was changed to 87.5 mm. The protruding width of the negative electrode active material-containing layer on the positive electrode current collecting tab side was changed to 1 mm, and the protruding width of the negative electrode active material-containing layer on the negative electrode current collecting tab side was changed to 1.5 mm. The electrode group was inserted into a rectangular can made of an aluminum alloy (Al purity 99%) having a wall thickness of 0.25 mm, having a thickness of 21 mm, a width of 115 mm, and a height of 105 mm, instead of the laminated film bag-shaped exterior member.
Except for these changes, a non-aqueous electrolyte secondary battery was fabricated in the same manner as in Example 2.

(Example 7)
The width of the negative electrode active material-containing layer was changed to 180 mm, and the width of the positive electrode active material-containing layer was changed to 176.5 mm. The protruding width of the negative electrode active material-containing layer on the positive electrode current collecting tab side was changed to 1.5 mm, and the protruding width of the negative electrode active material-containing layer on the negative electrode current collecting tab side was changed to 2 mm.
Except for these changes, a non-aqueous electrolyte secondary battery was fabricated in the same manner as in Example 2.

(Example 8)
A slurry (slurry I) similar to the slurry used for producing the negative electrode in Example 1 was prepared.
A slurry (slurry II) similar to the alumina-containing slurry used to form the insulating layer in Example 2 was prepared.
A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 7, except that a negative electrode having an insulating layer formed thereon was produced according to the second production method described above.

Example 9
The width of the negative electrode active material-containing layer was changed to 185 mm, and the width of the positive electrode active material-containing layer was changed to 179 mm. The protrusion width of the negative electrode active material-containing layer on the positive electrode current collector tab side was changed to 2 mm, and the protrusion width of the negative electrode active material-containing layer on the negative electrode current collector tab side was changed to 4 mm.
Except for these changes, a non-aqueous electrolyte secondary battery was fabricated in the same manner as in Example 2.

(Example 10)
The width of the negative electrode active material-containing layer was changed to 118 mm, and the width of the positive electrode active material-containing layer was changed to 113.5 mm. The protruding width of the negative electrode active material-containing layer on the positive electrode current collecting tab side was changed to 2 mm, and the protruding width of the negative electrode active material-containing layer on the negative electrode current collecting tab side was changed to 2.5 mm.
Except for these changes, a non-aqueous electrolyte secondary battery was fabricated in the same manner as in Example 2.

(Example 11)
The width of the negative electrode active material-containing layer was changed to 180 mm, and the width of the positive electrode active material-containing layer was changed to 172.6 mm. The protruding width of the negative electrode active material-containing layer on the positive electrode current collecting tab side was changed to 3.5 mm, and the protruding width of the negative electrode active material-containing layer on the negative electrode current collecting tab side was changed to 3.9 mm.
Except for these changes, a non-aqueous electrolyte secondary battery was fabricated in the same manner as in Example 2.

Example 12
A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that TiNb ₂ O ₇ (no carbon phase) having a primary particle shape of 1 μm in average particle size was used as the negative electrode active material.

(Example 13)
A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 2 except that TiNb ₂ O ₇ (no carbon phase) having a primary particle shape of 1 μm in average particle size was used as the negative electrode active material.

(Example 14)
A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 2 except that TiNb ₂ O ₇ (no carbon phase) having a primary particle shape of 0.8 μm in average particle size was used as the negative electrode active material.

(Example 15)
A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 2, except that TiNb ₂ O ₇ (no carbon phase) in the form of secondary particles having an average particle size of 12 μm was used as the negative electrode active material.

(Example 16)
A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 6 except that TiNb ₂ O ₇ (no carbon phase) having a primary particle shape of 1 μm in average particle size was used as the negative electrode active material.

(Example 17)
A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 7, except that TiNb ₂ O ₇ (no carbon phase) having a primary particle shape of 1 μm in average particle size was used as the negative electrode active material.

(Example 18)
When manufacturing the electrode group, the protrusion width of the negative electrode active material-containing layer on the positive electrode current collector tab side was changed to 0.5 mm, and the protrusion of the negative electrode active material-containing layer on the negative electrode current collector tab side was changed to 4.5 mm, A non-aqueous electrolyte secondary battery was produced in the same manner as in Example 2.

(Example 19)
As a negative electrode active material, Li ₂ Na _1.6 Ti _5.6 Nb _0.4 O ₁₄ in the form of secondary particles attached with carbon was prepared. The average particle size of the secondary particles including the carbon phase was 15 μm. The prepared negative electrode active material, acetylene black, and polyvinylidene fluoride (PVdF) were mixed in a mass ratio of 80:10:10 in N-methylpyrrolidone (NMP) to obtain a slurry. This slurry was applied to both sides of the Al foil with a basis weight of 100 g / m ² and dried. On one side of the width direction of the Al foil, a portion where no slurry was applied was left on either side. The laminated structure after drying was pressed and further vacuum dried. Next, the active material-containing layer (the slurry coating after drying and pressing) was cut so that the width was 180 mm to obtain a negative electrode. When cutting, the side opposite to the portion where the slurry was not applied was cut. In addition, the part which did not apply | coat a slurry was used as a negative electrode current collection tab.
A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that this negative electrode was used.

(Example 20)
A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 18 except that Li ₂ Na _1.6 Ti _5.6 Nb _0.4 O ₁₄ (no carbon phase) having an average particle diameter of 1 μm as the negative electrode active material was used. .

(Example 21)
Li ₄ Ti ₅ O ₁₂ having a primary particle shape with an average particle diameter of 1 μm was prepared as a negative electrode active material. The prepared negative electrode active material, acetylene black, and polyvinylidene fluoride (PVdF) were mixed at a mass ratio of 80:10:10 in N-methylpyrrolidone to obtain a slurry. This slurry was applied to both sides of the Al foil with a basis weight of 75 g / m ² and dried. On one side of the width direction of the Al foil, a portion where no slurry was applied was left on either side. The laminated structure after drying was pressed and further vacuum dried. Next, the active material-containing layer (the slurry coating after drying and pressing) was cut so that the width was 180 mm to obtain a negative electrode. When cutting, the side opposite to the portion where the slurry was not applied was cut. In addition, the part which did not apply | coat a slurry was used as a negative electrode current collection tab.
A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that this negative electrode was used.

(Comparative Example 1)
When manufacturing the electrode group, the protrusion width of the negative electrode active material-containing layer on the positive electrode current collector tab side was changed to 2.5 mm, and the protrusion of the negative electrode active material-containing layer on the negative electrode current collector tab side was changed to 2.5 mm, A non-aqueous electrolyte secondary battery was produced in the same manner as in Example 1.

(Comparative Example 2)
When manufacturing the electrode group, the protrusion width of the negative electrode active material-containing layer on the positive electrode current collector tab side was changed to 2.5 mm, and the protrusion of the negative electrode active material-containing layer on the negative electrode current collector tab side was changed to 2.5 mm, A non-aqueous electrolyte secondary battery was produced in the same manner as in Example 2.

(Comparative Example 3)
When manufacturing the electrode group, the protrusion width of the negative electrode active material-containing layer on the positive electrode current collector tab side was changed to 4 mm, and the protrusion of the negative electrode active material-containing layer to the negative electrode current collector tab side was changed to 1 mm, A non-aqueous electrolyte secondary battery was produced in the same manner as in Example 2.

<Battery evaluation>
The following high-temperature storage test was implemented with respect to each battery produced in each Example and each Comparative Example.

The discharge capacity from SOC 100% was measured for each battery. Each battery was again charged to 100% SOC and then stored in a constant temperature bath at 60 ° C. The remaining volume was measured after 4 weeks of storage.

The remaining capacity was measured as follows. After the battery surface temperature reached 25 ° C. ± 3 ° C. in a constant temperature bath at 25 ° C., constant current discharge was performed at 1 ° C. current. At this time, the discharge termination condition was the time when the battery voltage reached 1.8V. The discharged capacity was measured to determine the remaining capacity.

The remaining capacity measured after storage for 4 weeks was defined as C4, the discharge capacity from 100% SOC before the storage test was defined as C0, and the ratio of C4 to C0 was calculated to determine the remaining capacity retention ratio (residual capacity retention ratio = C4 / C0 × 100%).

Table 1 summarizes the design of each electrode group and the battery evaluation results. Specifically, as the design of the electrode group, the composition of the compound used for the negative electrode active material, the width of the negative electrode active material-containing layer (width W _N ), the protruding width of the negative electrode active material-containing layer on the positive electrode current collector tab side (first Deviation width A), the protruding width of the negative electrode active material-containing layer on the negative electrode current collecting tab side (second deviation width B), the ratio of the protruding width on the positive electrode current collecting tab side and the width of the negative electrode active material containing layer (A / W) _N ), and the ratio (B / W _N ) between the protrusion width on the negative electrode current collector tab side and the width of the negative electrode active material-containing layer. Moreover, the remaining capacity maintenance rate in the high-temperature storage test demonstrated previously as an evaluation result is shown.

As shown in Table 1, the remaining capacity retention rate in the storage test for the batteries produced in each example was higher than the remaining capacity maintenance rate in the batteries produced in each comparative example. As this result shows, self-discharge was able to be suppressed in each Example.

In Example 1-20, Nb ₂ TiO ₇ or Li ₂ Na _1.6 Ti _5.6 Nb _0.4 O ₁₄ having a relatively low lithium insertion / release potential (base) was used as the negative electrode active material. Therefore, the conditions of the high-temperature storage test using the batteries of these examples were conditions where lithium was likely to precipitate. Nevertheless, since self-discharge was suppressed, it can be determined that no electrical short circuit occurred.

In Example 21, Li ₄ Ti ₅ O ₁₂ having a relatively high lithium absorption / release potential (noble) was used as the negative electrode active material. Therefore, the battery of Example 20 was in a condition in which lithium deposition hardly occurred even under the conditions of the high-temperature storage test. That is, it is presumed that since there was no deposition of lithium, an electrical short circuit did not occur and there was little self-discharge.

In Comparative Examples 1 and 2, the protruding width of the negative electrode active material-containing layer was the same on the positive electrode current collecting tab side and the negative electrode current collecting tab side (first deviation width A = second deviation width B).
In Comparative Example 3, the protrusion width (first deviation width B) of the negative electrode active material-containing layer on the negative electrode current collector tab side was larger than the protrusion width (deviation width A) of the negative electrode active material-containing layer on the positive electrode current collection tab side. Was narrow.
As described above, in each comparative example, the protruding width of the negative electrode active material-containing layer is not wider on the negative electrode current collecting tab side than on the positive electrode current collecting tab side (the second deviation width B is not wider than the first deviation width A), The electrode group design was not appropriate. As a result, it is speculated that self-discharge could not be suppressed as a result of a short circuit in each comparative example.

The electrode group according to at least one embodiment and example described above includes a laminate including a positive electrode, a negative electrode, and an electrically insulating member. The positive electrode was supported on the positive electrode current collector, a positive electrode current collector tab provided at an end parallel to one side of the positive electrode current collector, and at least excluding the positive electrode current collector tab. A positive electrode active material-containing layer. The positive electrode active material-containing layer includes a first end and a second end parallel to the one side of the positive electrode current collector. The negative electrode includes a strip-shaped negative electrode current collector, a negative electrode current collector tab provided at an end parallel to one side of the negative electrode current collector, and a titanium supported on the negative electrode current collector excluding at least the negative electrode current collector tab A negative electrode active material-containing layer containing a containing oxide. The negative electrode active material-containing layer includes a third end portion and a fourth end portion that are parallel to the one side of the negative electrode current collector. The electrically insulating member is interposed between the positive electrode active material-containing layer and the negative electrode active material-containing layer. The laminate is wound. A positive electrode current collecting tab protrudes in a first direction parallel to the winding axis. The fourth end portion is located closer to the positive electrode current collecting tab than the first end portion. The negative electrode current collector tab protrudes in the second direction opposite to the first direction. The third end is located closer to the negative electrode current collecting tab than the second end. The second displacement width between the second end portion and the third end portion is wider than the first displacement width between the first end portion and the fourth end portion. The electrode group can realize a battery in which self-discharge is suppressed and a battery pack including the battery.

Although several 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 forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and the equivalents thereof.

Claims

A belt-shaped positive electrode current collector, a positive electrode current collector tab provided at an end parallel to one side of the positive electrode current collector, and supported on the positive electrode current collector except at least the positive electrode current collector tab A positive electrode active material-containing layer, wherein the positive electrode active material-containing layer includes a positive electrode including a first end and a second end parallel to the one side of the positive electrode current collector, a strip-shaped negative electrode current collector, A negative electrode current collector tab provided at an end parallel to one side of the negative electrode current collector, and a negative electrode active material comprising a titanium-containing oxide supported on the negative electrode current collector excluding at least the negative electrode current collector tab A negative electrode including a third end and a fourth end parallel to the one side of the negative electrode current collector;
Comprising a laminate including an electrically insulating member interposed between the positive electrode active material-containing layer and the negative electrode active material-containing layer;
The laminate is wound, the positive current collecting tab protrudes in a first direction parallel to the winding axis, and the fourth end portion is located closer to the positive current collecting tab than the first end portion. The negative current collector tab protrudes in a second direction opposite to the first direction, and the third end portion is located closer to the negative electrode current collector tab than the second end portion,
The electrode group in which the second shift width between the second end portion and the third end portion is wider than the first shift width between the first end portion and the fourth end portion.
The electrode group according to claim 1, satisfying a relationship of 0.008 ≦ A / W N ≦ 0.02 and satisfying a relationship of 0.01 ≦ B / W N ≦ 0.022.
Here, A represents the first displacement width, B represents the second displacement width, and W N represents a width parallel to the winding axis of the negative electrode active material-containing layer.
The electrode group according to claim 1 or 2, wherein a difference AB between the first shift width and the second shift width is 1 mm or more and 3 mm or less.
The electrode group according to any one of claims 1 to 3, wherein the electrically insulating member includes one or more oxides selected from the group consisting of Ba, Al, Zr, Ta, and Si.
A battery comprising the electrode group according to any one of claims 1 to 4.
A battery pack comprising the battery according to claim 5.