JPWO2019187130A1 - Electrode group, battery, and battery pack - Google Patents

Abstract

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 includes a band-shaped positive electrode current collector, a positive electrode current collector tab provided on one side thereof, and a positive electrode active material-containing layer supported on the positive electrode current collector. The positive electrode active material-containing layer includes a first end portion and a second end portion parallel to one side of the positive electrode current collector. The negative electrode includes a band-shaped negative electrode current collector, a negative electrode current collector tab provided on one side thereof, and a negative electrode active material-containing layer supported on the negative electrode current collector and containing a titanium-containing oxide. The negative electrode active material-containing layer includes a third end portion and a fourth end portion parallel to 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 positive electrode current collecting tab projects in the first direction parallel to the winding axis. The fourth end is located on the positive electrode current collecting tab side from the first end. The negative electrode current collecting tab projects in the second direction opposite to the first direction. The third end is located on the negative electrode current collecting tab side from the second end. The second deviation width between the second end and the third end is wider than the first deviation width between the first end and the fourth end.

Description

Embodiments of the present invention relate to electrode groups, batteries, and battery packs.

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 becomes high. The niobium-titanium composite oxide and the rectangular titanium-containing composite oxide have a low reaction potential for inserting and removing lithium among the titanium oxides, and can increase the battery voltage when used for the negative electrode. On the other hand, due to the low reaction potential, the electrolyte is easily reduced and decomposed, and the self-discharge reaction is likely to proceed along with the reduction and decomposition reaction. As a countermeasure, it is possible to suppress the self-discharge reaction by coating the surface of the active material with an inorganic substance or the like, or by including a substance that forms a film on the surface of the active material in the electrolyte to cover the surface of the active material. It is done.

Self-discharge can also occur due to an internal short circuit in the battery. Therefore, it is desirable to ensure resistance to internal short circuits and suppress self-discharge of the battery.

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

It is an object of the present invention 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 a band-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 at least the positive electrode current collector tab except for the positive electrode current collector tab. It includes a positive electrode active material-containing layer. The positive electrode active material-containing layer includes a first end portion and a second end portion parallel to the above-mentioned one side of the positive electrode current collector. The negative electrode is supported on 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 current collector except for at least the negative electrode current collector tab. It includes a negative electrode active material-containing layer containing a contained oxide. The negative electrode active material-containing layer includes a third end portion and a fourth end portion 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 positive electrode current collecting tab projects in the 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 projects 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 deviation width between the second end portion and the third end portion is wider than the first deviation 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 embodiment, 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 expanded. FIG. 3 is a plan view schematically showing an example 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 part 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

Internal short circuits that occur in non-aqueous electrolyte batteries are broadly classified into short circuits due to dendrite precipitation of lithium metal, short circuits due to defects in insulating members such as separators, and short circuits due to the inclusion of minute metal pieces. Among them, the internal short circuit due to the precipitation of lithium metal, which is said to be difficult to suppress, is a material that can occlude and release lithium into the negative electrode active material at a potential (noble potential) significantly higher than the lithium precipitation potential, for example, about 1. By using lithium titanate or the like, which can occlude and release lithium at .5 V (vs. Li / Li ⁺ ), dendrite precipitation of the lithium metal can be suppressed almost completely.

However, when a 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 becomes low, and the energy density of the battery decreases.

Hereinafter, embodiments will be described with reference to the drawings. In addition, the same reference numerals are given to common configurations throughout the embodiment, and duplicate description will be omitted. In addition, each figure is a schematic view for explaining the embodiment and promoting its understanding, and the shape, dimensions, ratio, etc. of the figure are different from those of the actual device, but these are described below and known techniques. The design can be changed as appropriate by taking into consideration.

(First Embodiment)
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 a band-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 at least the positive electrode current collector tab except for the positive electrode current collector tab. It includes a positive electrode active material-containing layer. The positive electrode active material-containing layer includes a first end portion and a second end portion parallel to the above-mentioned one side of the positive electrode current collector.
The negative electrode is supported on 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 current collector except for at least the negative electrode current collector tab. It includes a negative electrode active material-containing layer containing a contained oxide. The negative electrode active material-containing layer includes a third end portion and a fourth end portion 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 cylindrically wound structure. Alternatively, the laminate may have a structure wound in a flat shape.
The positive electrode current collecting tab projects in the 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 projects 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 deviation width between the second end portion and the third end portion is wider than the first deviation 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. 1 to 3.

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 expanded. FIG. 3 is a plan view schematically showing an example electrode group according to the embodiment.

The electrode group 3 shown in FIGS. 1 to 3 includes a positive electrode 4, a negative electrode 5, and an electrically insulating member 6. In the electrode group 3, as shown in FIG. 2, a laminate including a positive electrode 4, a negative electrode 5, and an electrically insulating member 6 arranged 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 band-like shape. The positive electrode active material-containing layer 4b is supported on the positive electrode current collector 4a. The positive electrode current collector tab 4c is provided at one side of the positive electrode current collector 4a, for example, at an end parallel to the long side of the strip shape.

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

The positive electrode current collector tab 4c can be a part of the positive electrode current collector 4a. Of the positive electrode current collector 4a, at least the positive electrode current collector tab 4c is not supported by the positive electrode active material-containing layer 4b, 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 band-like 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 one side of the negative electrode current collector 5a, for example, at an end parallel to the long side of the strip shape.

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

The negative electrode current collector tab 5c can be a part of the negative electrode current collector 5a. Of the negative electrode current collector 5a, at least the negative electrode current collector tab 5c is not supported with the negative electrode active material-containing layer 5b, 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 face each other via the electrically insulating member 6 (FIG. 2). The positive electrode current collecting tab 4c protrudes from the negative electrode active material-containing layer 5b and the electrically insulating member 6 in the first direction parallel to the winding axis of the laminated body. Further, the negative electrode current collecting tab 5c protrudes from the positive electrode 4 and the electrically insulating member 6 in the second direction, which is opposite to the first direction. Therefore, in the electrode group 3, the positive electrode current collecting tab 4c wound in a flat spiral shape is located on the first end surface orthogonal to the winding axis. Further, the negative electrode current collecting tab 5c wound in a flat spiral shape is located on the second end surface orthogonal to the winding axis. As described above, the positive electrode current collecting tab 4c is located on the opposite side of the wound laminate from the negative electrode current collecting 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 5b is the width of the negative electrode active material-containing layer 5b in a direction perpendicular to the third end 53 and fourth end 54. In other words, the width W _N of the negative electrode active material-containing layer 5b corresponds to the width between the third end portion 53 and the fourth end portion 54. The width W _P and width W _N of the active material-containing layer of each of the positive and negative electrodes are also widths in the 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 toward the positive electrode current collecting tab 4c side from the first end portion 41. Then, the third end portion 53 of the negative electrode active material-containing layer 5b protrudes outside the second end portion 42 of the positive electrode active material-containing layer 4b. That is, the third end portion 53 is located at a position shifted toward the negative electrode current collecting tab 5c side from the second end portion 42. In other words, the negative electrode active material-containing layer 5b has both directions (first direction and second direction) parallel to the winding axis on the side where the positive electrode current collecting tab 4c is located and the side where the negative electrode current collecting tab 5c is located in the electrode group 3. Protrudes from the positive electrode active material-containing layer 4b.

The first deviation width A (the protrusion 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. It 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 deviation width B (the protrusion 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. It corresponds to the distance at which the negative electrode active material-containing layer 5b protrudes on the current collecting tab 5c side. The second deviation width B is wider than the first deviation width A.

When a negative electrode active material having a low (base) potential for occlusion and release of lithium is used for the purpose of obtaining a high battery energy density, the ends of the negative electrode active material-containing layer 5b (third end 53 and fourth end 54) are used. Metal precipitation, for example, formation of lithium dendrite is likely to occur. The third end 53 and the fourth end 54 of the negative electrode active material-containing layer 5b protrude to the outside of the first end 41 and the second end 42 of the positive electrode active material-containing layer 4b, so that the positive electrode is positive due to metal precipitation. Short circuit between 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 A part of the substance-containing layer 4b overlaps with each other via the electrically insulating member 6. In that case, an electrical short circuit may occur between the positive and negative electrodes due to the metal precipitation at the fourth end 54. Further, since the portion of the positive electrode active material-containing layer 4b that does not face the negative electrode active material-containing layer 5b increases, there is also an aspect that the energy density decreases.

The larger the second deviation 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 separated from each other, the risk that the second end portion 42 and the third end portion 53 come into contact with each other during the production of the electrode group is reduced. Further, by increasing the second deviation width B, the distance between the second end portion 42 and the negative electrode current collecting tab 5c can be increased. By leaving a distance between the second end 42 of the positive electrode active material-containing layer 4b and the negative electrode current collecting tab 5c, the negative electrode current collecting tab 5c is deformed by a force applied from the outside of the battery such as a physical impact. At that time, contact between the second end portion 42 and the negative electrode current collecting tab 5c is unlikely to occur. 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 54 of the negative electrode active material-containing layer 5b projects outward from the first end 41 of the positive electrode active material-containing layer 4b, there is a distance between the fourth end 54 and the edge of the positive electrode current collecting tab 4c. The distance is shorter than the width of the positive electrode current collector 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 portion 54 and the positive electrode current collecting tab 4c.

Further, from the viewpoint of ensuring the energy density of the battery, it is preferable to reduce the first deviation width A. By keeping the first shift width A 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 smaller the first deviation width A, the higher the energy density.

However, in order to suppress a short circuit due to metal precipitation 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 with the positive electrode active material-containing layer 4b. Therefore, the first deviation width A exceeds zero.

The first shift width A, the ratio of the width _{W N} of the negative electrode active material-containing layer may be 0.008 to 0.02. That is, the first shift width A and the width W _N can satisfy the relationship of 0.008 ≦ A / W _N ≦ 0.02. On the other hand, the second shift width B, the ratio of the width _{W N} of the negative electrode active material-containing layer may be 0.01 or more 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 the 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. The insulating sheet 10 covers, for example, 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 band-shaped positive electrode current collector. Therefore, the positive electrode can have a band 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 the 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 the 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 support a positive electrode active material-containing layer on both sides thereof, or can support a positive electrode active material-containing layer on one side thereof. The positive electrode active material-containing layer includes a first end portion and a second end portion.

Further, the positive electrode includes a positive electrode current collector 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 support a positive electrode active material-containing layer on its 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 contain, 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 or may contain two or more kinds of compounds in combination as the positive electrode active material. Examples of oxides and sulfides include compounds capable of inserting and desorbing Li or Li ions.

Such compounds include, for example, manganese dioxide (MnO ₂ ), iron oxide, copper oxide, nickel oxide, lithium manganese composite oxide (eg Li _x Mn ₂ O ₄ or Li _x MnO ₂ ; 0 <x ≦ 1). , Lithium-nickel composite oxide (eg Li _x NiO ₂ ; 0 <x ≦ 1), Lithium cobalt composite oxide (eg Li _x CoO ₂ ; 0 <x ≦ 1), Lithium nickel-cobalt composite oxide (eg Li _x Ni) _1-y Co _y O ₂ ; 0 <x ≦ 1, 0 <y <1), lithium manganese cobalt composite oxide (for example, Li _x Mn _y Co _1-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 N _y O ₄ ; 0 <x ≦ 1, 0 <y <2), Lithium phosphorus 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), iron sulfate (Fe ₂₎ (SO _{4) 3),} vanadium oxide (e.g. V ₂ O _5), and a 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.

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

When a room temperature molten salt is used as the electrolyte of the battery, 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. Since these compounds have low reactivity with the molten salt at room temperature, 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 promote the diffusion of 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. A positive electrode active material having a specific surface area of 0.1 m ² / g or more can sufficiently secure an occlusion / release site for Li ions. A 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 gaps between the dispersed positive electrode active materials and to bind the positive electrode active material and the positive electrode current collector. Examples of binders include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluororubber, polyacrylic acid compounds, imide compounds, and carboxyl methyl cellulose (CMC). , And CMC salts. 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 conductive agents include carbon blacks such as Vapor Grown Carbon Fiber (VGCF), acetylene black and carbonaceous materials such as graphite. One of these may be used as a conductive agent, or two or more of them may be used as a conductive agent in combination. Moreover, 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 in a proportion of 80% by mass or more and 98% by mass or less and 2% by mass or more and 20% by mass or less, respectively.

Sufficient electrode strength can be obtained by setting the amount of the binder to 2% by mass or more. Also, 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 contained 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 in a ratio.

By setting the amount of the conductive agent to 3% by mass or more, the above-mentioned effect can be exhibited. Further, by setting the amount of the conductive agent to 15% by mass or less, the proportion of the conductive agent in contact with the electrolyte can be reduced. 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 or both sides of the positive electrode current collector. Next, the applied slurry is dried to obtain a laminated structure of a positive electrode active material-containing layer and a positive electrode current collector. Then, the laminated structure is pressed. In this way, the positive electrode is produced.

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

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

[Negative electrode]
The negative electrode includes a band-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 the potential at which lithium (Li) is inserted and removed from the titanium-containing oxide as the 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. A current collector having such a thickness can balance the strength and weight reduction of the electrodes.

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 support a negative electrode active material-containing layer on both sides thereof, or can support a negative electrode active material-containing layer on one side thereof. The negative electrode active material-containing layer includes a third end portion and a fourth end portion.

Further, the negative electrode 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 support a negative electrode active material-containing layer on its surface. The negative electrode current collecting 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 the negative electrode active material. The negative electrode active material-containing layer can further contain, for example, a conductive agent and a binder.

The titanium-containing oxide contained in the active material-containing layer can include, for example, a monoclinic niobium-titanium composite oxide and an orthorhombic titanium-containing composite oxide. The titanium-containing oxide may be one kind of compound or a mixture of two or more kinds 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. Each subscript in the composition formula is 0 ≦ x ≦ 5, 0 ≦ y <1, 0 ≦ z <2, −0.3 ≦ δ ≦ 0.3. Specific examples of the monoclinic niobium-titanium composite oxide include 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. Each subscript in the composition formula is 0 ≦ x ≦ 5, 0 ≦ y <1, 0 ≦ z <2, −0.3 ≦ δ ≦ 0.3.

Examples of the orthorhombic titanium-containing composite oxide include compounds 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. Each subscript in the composition formula is 0 ≦ a ≦ 6, 0 ≦ b <2, 0 ≦ c <6, 0 ≦ d <6, −0.5 ≦ σ ≦ 0.5. Specific examples of the orthorhombic 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 orthorhombic titanium-containing composite oxide have low (basely) lithium occlusion / release potentials (potentials at which lithium is inserted and removed). Therefore, a battery having a high energy density can be obtained by using these titanium-containing oxides. When the lithium storage / release potential is low, lithium dendrite is likely to precipitate, but as described above, the electrode group according to the embodiment is unlikely to cause a short circuit due to precipitation.

As another titanium-containing oxide, for example, spinel-type lithium titanate such as a compound represented by Li _{4 + w} Ti ₅ O ₁₂ (0 ≦ w ≦ 3) can be mentioned. Spinel-type lithium titanate has a high lithium storage / release potential (noble), so it is difficult to obtain a high energy density. Further, since metal precipitation is unlikely to occur due to the 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 faces the positive electrode active material-containing layer of the negative electrode active material-containing layers. This means that the missing parts are unnecessarily increased, and the energy density is reduced. Therefore, it is desirable to select the titanium-containing oxide from the monoclinic niobium-titanium composite oxide and the orthorhombic titanium-containing composite oxide.

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

The titanium-containing oxide particles that can be contained in the active material-containing layer may include a phase containing 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 preferably used.

The crystallinity of the carbon material can be determined by analyzing the carbon material by Raman spectroscopy using a measurement light source of 532 nm. In the Raman chart for carbon materials, 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 defective 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.

A ratio _IG / _ID greater than 1.2 means, for example, insufficient carbon amorphization. Further, in this case, impurities contained in the carbon source may be contained. Such impurities promote a side reaction with the electrolyte, which adversely affects the input / output performance and life performance of the battery.

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 amount of amorphous carbon decreases due to the preferential oxidation of the amorphous carbon component whose carbon-carbon bond is unstable over the graphite structure, and the ratio _IG / _ID may be greater than 1.2.

Further, when the ratio _IG / _ID is smaller than 0.8, it means that the carbon component derived from the graphite structure is small.

Therefore, it is preferable to use a carbon material having a ratio _IG / _ID of 0.8 or more and 1.2 or less because better electron 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 particles, or may be supported on a part of the surface of the titanium-containing oxide particles. More preferably, the conductivity of the entire active material particles (titanium-containing oxide particles and composite particles containing a phase containing a carbon material) is uniformly complemented, and the surface reaction between the active material particles and the electrolyte is suppressed. From the 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 presence or absence of a phase containing a carbon material can be confirmed, for example, by observation by a transmission electron microscope (TEM) 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 conductive agents include carbon blacks such as Vapor Grown Carbon Fiber (VGCF), acetylene black and carbonaceous materials such as graphite. One of these may be used as a conductive agent, or two or more of them may be used as a conductive agent in combination. Alternatively, instead of using a conductive agent, a carbon coat or an electron conductive inorganic material coat may be applied to the surface of the active material particles.

The binder is blended to fill the gaps between the dispersed negative electrode active materials and to bind the negative electrode active material and the negative electrode current collector. Examples of binders include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluororubber, styrene butagen rubber, polyacrylic acid compounds, imide compounds, and carboxyl cellulose. Methyl cellulose; CMC), and salts of CMC are included. 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 or more and 96% by mass or less, 2% by mass or more and 30% by mass or less, and 2% by mass or more, respectively. It is preferable to blend in a proportion of 30% by 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, it is preferable that the conductive agent and the binder are each 30% by mass or less in order to increase the capacity.

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

[Electrical insulation member]
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 may be an insulating layer containing a material having an electrically insulating property. The electrically insulating member may be one member or two or more members. For example, the separator can be used alone, the insulating layer can be used alone, or the separator and the insulating layer can be used together.

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

Further, the insulating layer may contain non-Li conductive inorganic material, particles of a solid electrolyte exhibiting Li conductivity, or the like as a material having electrical insulating property.

Examples of the inorganic material that does not exhibit conductivity 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). Metal oxides such as ₂ O), zinc oxide (ZnO), antimony oxide (Sb ₂ O ₅ ), 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. Above all, the above-mentioned metal oxide can exhibit excellent stability with respect to the non-aqueous electrolyte contained in the non-aqueous electrolyte battery.

Examples of the solid electrolyte exhibiting conductivity 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). Can be selected from the group consisting of Ti, Zr, and Ge; one or more; materials of the compound system represented by 0 ≦ x ≦ 0.6) can be used. As the solid electrolyte, one kind of compound may be used, or two or more kinds of compounds may be used in combination. Further, a non-Li conductive inorganic material and a solid electrolyte can be used in combination.

The insulating layer may contain a binder. Binders that can be included in the insulating layer include, for example, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluororubber, styrene butylene rubber (SBR), carboxymethyl cellulose (CMC) or mixtures thereof. Can be mentioned. The content of the binder in the insulating layer is preferably in the range of 0.01% by mass or more and 20% by mass or less.

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

The insulating layer may be, for example, a layer containing a material having electrical insulating properties and formed on at least one electrode of a positive electrode and a negative electrode. An electrode in which an insulating layer as an electrical insulating member is formed on an 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 the manufactured electrode.
An electrode (positive electrode or negative electrode) is manufactured by the method described above. The press may be omitted when the electrode is manufactured.
Separately, a slurry containing a material having electrical insulation is prepared. The prepared slurry is applied onto the active material-containing layer of the electrode. At this time, the coating width of the slurry is made wider than the width of the active material-containing layer, and a part of the slurry is directly applied to the portion of the current collector that does not support the active material-containing layer (for example, the electrode current collector tab). It may be applied. After the slurry is dried, a roll press is applied to the dried laminated structure (the electrode on which the insulating layer before pressing is formed) 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 surface and the back surface of the current collector. ) At the same time. At about the same time as the application of the slurry I, the slurry II is overcoated so as to protrude from the application area of the slurry I. Since the slurry II is overcoated on the slurry I before the slurry I dries, the slurry II can easily follow the surface shape of the slurry I. Then, after the slurry is dried, the dried laminated structure (current collector in which the active material-containing layer and the insulating layer before pressing are formed on the current collector) is roll-pressed to form an electrode on which the insulating layer is formed. To get.

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

If the electrode group to be measured is incorporated in the prepared battery, prepare the measurement sample according to the following procedure.

The battery is discharged at a constant current value [A] equivalent to 0.2 C until it reaches 1.5 V in a constant temperature bath at 25 ° C. After that, constant voltage discharge is performed at 1.5 V for 1 hour.

After constant voltage discharge, put the battery in the argon glove box and disassemble the battery. The electrode coil (winding type 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 terminals via the electrode leads. Carefully remove the electrode coil from the electrode lead. For example, the connection with the electrode lead can be removed using scissors, pliers, a cutter, or the like while holding the electrode coil so that the positions of the positive electrode, the electrically insulating member, and the negative electrode do not move in the electrode coil.

The thus isolated electrodes as a measurement sample, the width of the active material-containing layer in the positive and negative electrode (W _{P, W N),} the ends of the active material-containing layer (first end portion to the fourth end portion) Measure the gap width (A, B) and so on.

(Method for identifying composition in negative electrode active material-containing layer)
Whether or not the titanium-containing oxide is contained in the negative electrode active material-containing layer 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. The negative electrode is washed with a suitable solvent. For example, ethyl methyl carbonate or the like may be used. If cleaning is insufficient, an impurity phase such as lithium carbonate or lithium fluoride may be mixed due to 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 set in an inert gas.

The cross section of the member taken out as described above is cut out by Ar ion milling. The cut out cross section is observed with a scanning electron microscope (SEM). Samples should be sampled in an inert atmosphere such as argon or nitrogen without being exposed to the atmosphere.

Several particles are selected from a 3000x SEM observation image. At this time, the selected particles are selected so that the particle size distribution is as wide as possible.

Next, each selected particle is subjected to elemental analysis by Energy Dispersive X-ray Spectroscopy (EDX). This makes it possible to specify the type and amount of elements other than Li among the elements contained in each of the selected particles.

The crystal structure of the compound contained in each particle selected by SEM can be identified by X-Ray Diffraction (XRD) measurement.

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

As a device for powder X-ray diffraction measurement, a Smart Lab manufactured by Rigaku Co., Ltd. is used. The measurement conditions are as follows: Cu target; 45 kV 200 mA; solar slit: 5 ° for both incident and received light; step width: 0.02 deg; scan speed: 20 deg / min; semiconductor detector: D / teX Ultra 250; sample Plate holder: Flat glass sample plate holder (thickness 0.5 mm); Measurement range: 10 ° ≤ 2θ ≤ 90 °. When using other equipment, measure using standard Si powder for powder X-ray diffraction so that the same measurement results as above can be obtained, and under the conditions that the peak intensity and peak top position match those of the above equipment. Do.

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

The XRD measurement of the negative electrode can be performed by cutting out 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 the glass holder for measurement. If necessary, the insulating layer is removed from the active material-containing layer in advance. At this time, the 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 grasped. In addition, the presence or absence of peaks of the mixture such as the conductive agent and the binder should be grasped in advance. When the peak of the current collector and the peak of the active material overlap, it is desirable to peel off the active material-containing layer from the current collector for measurement. This is to separate the overlapping peaks when the peak intensity is quantitatively measured. Of course, this operation can be omitted if these are known in advance. The active material-containing layer may be physically peeled off, but it is easily peeled off when ultrasonic waves are applied in a solvent. By measuring the active material-containing layer recovered in this way, 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 electrodes collected by the procedure described above are washed.
Using the washed electrodes, the composition of the particles contained in the active material-containing layer is specified by the method described above.

On the other hand, the other part of the washed electrode is put in a suitable solvent and irradiated with ultrasonic waves. For example, the active material-containing layer can be peeled off from the current collector substrate by placing an electrode in ethyl methyl carbonate placed in a glass beaker and vibrating it in an ultrasonic cleaner. Next, vacuum drying is performed to dry the peeled active material-containing layer. By pulverizing the obtained active material-containing layer in a mortar or the like, a powder containing the active material to be measured, a conductive agent, a binder and the like can be obtained. By dissolving this powder with an acid, a liquid sample containing an active material can be prepared. 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 spectroscopy, 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 composition specification by SEM and EDX, the crystal structure specification by XRD, and the ICP emission spectroscopic analysis. The composition and crystal structure of the compound can be specified.

(Method of confirming the phase containing carbon material)
A microscopic Raman measuring device can be used as a method for quantitatively evaluating the crystallinity of the carbon component contained in the phase that can be formed on the particles of the titanium-containing oxide. 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 number of 10 times.

Raman spectroscopic measurement can be performed, for example, by the procedure described below.

When evaluating the material incorporated in a battery, the battery is left in 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, there may be a small amount of residual lithium ions even in the discharged state.

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

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

At the time of measurement, the presence or absence of Raman activity of the current collector and other components contained in the mixture such as the conductive agent and the binder and the peak position thereof should be grasped. If they overlap, it is necessary to separate peaks related to components other than the active material.

When the active material (for example, composite particles of the active material particles and the phase containing the carbon material) is mixed with the conductive agent in the active material-containing layer, the carbon material contained in the active material material and the carbon material contained in the active material material are incorporated as the conductive agent. It can be difficult to distinguish between carbon materials. In such a case, as one of the methods for distinguishing between the two, for example, a method of dissolving and removing the binder with a solvent and then centrifuging to take out the active material having a large specific gravity can be considered. According to such a method, the active material and the conductive agent can be separated, so that the carbon material contained in the active material can be used for measurement as it is contained in the active material. it can.

Alternatively, mapping is performed from the spectral components derived from the active material material by mapping by microscopic Raman spectroscopy to separate the conductive agent component and the active material material component, and then only the Raman spectrum corresponding to the active material 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 a band-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 at least the positive electrode current collector tab except for the positive electrode current collector tab. It includes a positive electrode active material-containing layer. The positive electrode active material-containing layer includes a first end portion and a second end portion parallel to the above-mentioned one side of the positive electrode current collector. The negative electrode is supported on 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 current collector except for at least the negative electrode current collector tab. It includes a negative electrode active material-containing layer containing a contained oxide. The negative electrode active material-containing layer includes a third end portion and a fourth end portion 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 positive electrode current collecting tab projects in the first direction parallel to the winding axis. The fourth end is located closer to the positive electrode current collector tab side than the first end. The negative electrode current collector tab projects in the second direction opposite to the first direction. The third end is located closer to the negative electrode current collector tab side than the second end. The second deviation width between the second end portion and the third end portion is wider than the first deviation 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 retained in the electrode group.

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

Further, the battery according to the embodiment can 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 can be, for example, a lithium ion secondary battery. Further, the battery includes, for example, a non-aqueous electrolyte battery containing a non-aqueous 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-like 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 hexafluorophosphate (LiAsF ₆ ), and trifluoromethane. Includes lithium salts such as lithium sulfonate (LiCF ₃ SO ₃ ) and bistrifluoromethylsulfonylimide lithium (LiN (CF ₃ SO ₂ ) ₂ ), and mixtures thereof. The electrolyte salt is preferably one that is difficult to oxidize even at a high potential, and LiPF ₆ is most preferable.

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-methyl tetrahydrofuran (2MeTHF), dioxolane (DOX). Cyclic ethers such as; chain ethers such as dimethoxy ethane (DME), diethoxy ethane (DEE); γ-butyrolactone (GBL), acetonitrile (acetonitrile; AN), and sulfolanes. (Sulfolane; SL) is included. These organic solvents can be used alone or as a mixed solvent.

The gel-like non-aqueous electrolyte is prepared by combining a liquid non-aqueous electrolyte and a polymer material. Examples of polymeric materials include polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyethylene oxide (PEO), or mixtures 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. May be good.

The room temperature molten salt (ionic melt) refers to a compound that can exist as a liquid at room temperature (15 ° C. or higher and 25 ° C. or lower) among organic salts composed of a combination of an organic cation and an anion. The room temperature molten salt includes a room temperature molten salt that exists as a liquid by itself, a room temperature molten salt that becomes a liquid when mixed with an electrolyte salt, a room temperature molten salt that becomes a liquid when dissolved in an organic solvent, or a mixture thereof. Is done. Generally, the melting point of a room temperature molten salt used in a secondary battery is 25 ° C. or lower. In addition, 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 substance having Li ion conductivity. As the inorganic solid electrolyte, for example, a solid electrolyte having Li ion conductivity that can be contained in the insulating layer can be used.

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

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

As the laminated film, a multilayer film including a plurality of resin layers and a metal layer interposed between these resin layers is used. The resin layer contains, for example, a polymer material such as polypropylene (PP), polyethylene (PE), nylon, and polyethylene terephthalate (PET). The metal layer is preferably made of aluminum foil or aluminum alloy foil for weight reduction. The laminated film can be molded into the shape of an exterior member by sealing by heat fusion.

The wall thickness of the metal container is, for example, 1 mm or less, more preferably 0.5 mm or less, 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 the aluminum alloy contains a transition metal such as iron, copper, nickel, and chromium, the content thereof is preferably 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, a button type, or the like. The exterior member can be appropriately selected according to the battery size and the application of the battery.

[Negative electrode terminal]
The negative electrode terminal can be formed from a material that is electrochemically stable and has conductivity at the Li storage / discharge potential of the above-mentioned titanium-containing oxide (negative electrode active material). Specifically, the material of the negative electrode terminal contains at least one element selected from the group consisting of copper, nickel, stainless steel or aluminum, or Mg, Ti, Zn, Mn, Fe, Cu, and Si. Aluminum alloy can be mentioned. As the material of the negative electrode terminal, it is preferable to use aluminum or an aluminum alloy. The negative electrode terminal is preferably made of the same material as the negative electrode current collector in order to reduce the contact resistance with 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 or more and 4.5 V or less with respect to the redox 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 the 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 part A in FIG.

The battery 1 shown in FIGS. 4 and 5 includes the 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 laminated film including a metal layer and two resin films sandwiching the metal layer.

As shown in FIG. 6, the flat spiral electrode group 3 spirally winds a laminated body in which the negative electrode 5, the electrically insulating member 6, the positive electrode 4, and the electrically insulating member 6 are laminated in this order from the outside. , 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 5b containing a negative electrode active material on one surface of the negative electrode current collector 5a on the inner surface side. In the other portion 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. Regarding the positive electrode 4, positive electrode active material-containing layers 4b are formed on both sides of the positive electrode current collector 4a.

The negative electrode terminal 8 is connected to the negative electrode current collector 5a in the outermost layer of the negative electrode 5 in the vicinity of the outer peripheral end of the wound electrode group 3, and the positive electrode terminal 7 is the positive electrode of the positive electrode 4 located inside. It is connected to the current collector 4a. These negative electrode terminals 8 and positive electrode terminals 7 extend outward from the opening of the bag-shaped exterior member 2.

The battery 1 shown in FIGS. 4 and 5 further includes an electrolyte (not shown). The electrolyte is housed in the exterior member 2 in a state of being impregnated with the electrode group 3.

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

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

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

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

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

The battery pack according to the embodiment will be described in detail with reference to FIGS. 6 and 7. As the cell, the flat batteries shown in FIGS. 1 and 2 can be used.

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 the electric circuit of the battery pack 20 shown in FIG.

The plurality of cell cells 21 composed of the flat batteries shown in FIGS. 1 and 2 described above are laminated so that the negative electrode terminals 8 and the positive electrode terminals 7 extending to the outside are aligned in the same direction, and are laminated with an adhesive tape 22. The assembled battery 23 is formed by fastening the batteries. As shown in FIG. 7, these cell cells 21 are electrically connected in series with each other.

The printed wiring board 24 is arranged so as to face the side surface of the cell 21 on which the negative electrode terminal 8 and the positive electrode terminal 7 extend. As shown in FIG. 7, the printed wiring board 24 is equipped with a thermistor 25, a protection circuit 26, and a terminal 27 for energizing an external device. An insulating plate (not shown) is attached to the surface of the protective 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 at the bottom 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. The negative electrode side lead 30 is connected to the negative electrode terminal 8 located on the uppermost layer of the assembled battery 23, and the tip thereof is inserted into the negative electrode side connector 31 of the printed wiring board 24 and electrically connected. These connectors 29 and 31 are connected to the protection circuit 26 through the wiring 32 and the wiring 33 formed on the printed wiring board 24.

The thermistor 25 detects the temperature of the cell 21 and the detection signal is transmitted to the protection circuit 26. The protection circuit 26 can cut off the positive side wiring 34a and the negative side wiring 34b between the protection circuit 26 and the energizing terminal 27 to the external device under predetermined conditions. The predetermined condition is, for example, when the detection temperature of the thermistor 25 becomes equal to or higher than the predetermined temperature. Further, the predetermined condition is when overcharge, overdischarge, overcurrent, etc. of the cell 21 are detected. The detection of overcharging or the like is performed for each individual cell 21 or the entire assembled battery 23. When detecting the individual 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 cell 21. In the case of FIGS. 6 and 7, a wiring 35 for voltage detection is connected to each of the cell 21s, and a detection signal is transmitted to the protection circuit 26 through these wirings 35.

Protective sheets 36 made of rubber or resin are arranged on the three side surfaces of the assembled battery 23 except for the side surfaces on which the positive electrode terminal 7 and the negative electrode terminal 8 project.

The assembled battery 23 is housed in the storage container 37 together with the protective sheet 36 and the printed wiring board 24. That is, the protective sheet 36 is arranged on both inner side surfaces 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 arranged 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.

A heat-shrinkable tape may be used instead of the adhesive tape 22 to fix 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-shrinked to bind the assembled battery.

Although FIGS. 6 and 7 show a form in which the cells 21 are connected in series, they may be connected in parallel in order to increase the battery capacity. The assembled battery packs can also 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.

<Battery production>
(Example 1)
[Manufacturing of negative electrode]
As the negative electrode active material, Ti Nb ₂ O _{7 in the} form of secondary particles to which carbon was attached 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 N-methylpyrrolidone (NMP) at a mass ratio of 80:10:10 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 Al foil in the width direction, a portion where the slurry was not applied was left on any surface. The laminated structure after drying was pressed and further vacuum dried. Next, the active material-containing layer (slurry coating film after drying and pressing) was cut so as to have a width of 180 mm to obtain a negative electrode. When cutting, the side opposite to the portion to which the slurry was not applied was cut. The portion to which the slurry was not applied was used as the negative electrode current collector tab.

[Manufacturing of positive electrode]
LiNi _0.33 Co _0.33 Mn _0.33 O ₂ particles were prepared as the positive electrode active material, carbon black was prepared as the conductive agent, and polyvinylidene fluoride (PVdF) was prepared as the binder. These were mixed at a mass ratio of 90: 5: 5 to obtain a mixture. Next, the obtained mixture was dispersed in an N-methylpyrrolidone (NMP) solvent to prepare a positive electrode slurry. 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 Al foil in the width direction, a portion where the slurry was not applied was left on any surface. The laminated structure after drying was roll-pressed. Then, the active material-containing layer (slurry coating film after drying and pressing) was cut so as to have a size of 175 mm to obtain a positive electrode. When cutting, the side opposite to the portion to which the slurry was not applied was cut. The portion to which the slurry was not applied was used as the positive electrode current collecting tab.

[Manufacturing of electrode group]
As a separator (electrically insulating member), a cellulose fiber non-woven fabric having a thickness of 15 μm and a porosity of 70% was prepared. Two of these separators and the negative electrode and the positive electrode manufactured as described above were laminated in the order of the negative electrode, the separator, the positive electrode, and the separator to obtain a laminated body. When laminating, the negative electrode current collecting tab and the positive electrode current collecting tab were arranged on opposite sides of the laminated body (each of a pair of sides facing each other in the width direction). At this time, it can be seen that the width of the active material-containing layer is 5 mm longer in the negative electrode than in the positive electrode. The protrusion width of the negative electrode active material-containing layer on the positive electrode current collector tab side was 1.5 mm, and the protrusion 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 in a flat spiral shape.

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

[Battery production]
The electrode group was inserted into a bag-shaped exterior member made of a laminated film.
A liquid non-aqueous electrolyte was injected into a group of electrodes in the exterior member. By sealing the exterior member, a non-aqueous 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 manufactured in the same procedure as in Example 1.
An alumina-containing slurry (slurry II) was prepared by dispersing a mixture of Al ₂ O ₃ particles having an average particle size of 1 μm and PVdF in a mass ratio of 100: 4 in NMP. This slurry was prepared so as to have a viscosity shear rate of 1.0 (1 / s) of 100 Pa · s and a viscosity shear rate of 1000 (1 / s) of 2 Pa · s.

The alumina-containing slurry was applied onto the active material-containing layers on both sides of the negative electrode in an amount of 5 g / m ² . Further, the alumina-containing slurry was applied so that the coating width was 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 laminated body. When laminating, the negative electrode current collecting tab and the positive electrode current collecting tab were arranged on opposite sides of the laminated body (each of a pair of sides facing each other in the width direction). Similar to Example 1, the protrusion width of the negative electrode active material-containing layer on the positive electrode current collecting tab side was 1.5 mm, and the protrusion width of the negative electrode active material-containing layer on the negative electrode current collecting tab side was 3.5 mm. An electrode group was manufactured by winding the laminate.

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

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

(Example 4)
A non-aqueous electrolyte secondary battery was produced in the same manner as in Example 2 except that Li ₇ La ₂ Ta ₃ O ₁₂ particles having an average particle size of 1 μm were used instead of Al ₂ O ₃ for forming the insulating layer.

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

(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 protrusion width of the negative electrode active material-containing layer to the positive electrode current collection tab side was changed to 1 mm, and the protrusion width of the negative electrode active material-containing layer to the negative electrode current collection tab side was changed to 1.5 mm. The electrode group was inserted into a square can having a wall thickness of 0.25 mm and an aluminum alloy (Al purity 99%) having a thickness of 21 mm, a width of 115 mm, and a height of 105 mm instead of a bag-shaped exterior member made of a laminated film.
Except for these changes, a non-aqueous electrolyte secondary battery was produced 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 protrusion width of the negative electrode active material-containing layer to the positive electrode current collection tab side was changed to 1.5 mm, and the protrusion width of the negative electrode active material-containing layer to the negative electrode current collection tab side was changed to 2 mm.
Except for these changes, a non-aqueous electrolyte secondary battery was produced 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 for forming the insulating layer in Example 2 was prepared.
A non-aqueous electrolyte secondary battery was produced in the same manner as in Example 7, except that a negative electrode having an insulating layer formed 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 to the positive electrode current collector tab side was changed to 2 mm, and the protrusion width of the negative electrode active material-containing layer to the negative electrode current collector tab side was changed to 4 mm.
Except for these changes, a non-aqueous electrolyte secondary battery was produced 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 protrusion width of the negative electrode active material-containing layer to the positive electrode current collection tab side was changed to 2 mm, and the protrusion width of the negative electrode active material-containing layer to the negative electrode current collection tab side was changed to 2.5 mm.
Except for these changes, a non-aqueous electrolyte secondary battery was produced 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 protrusion width of the negative electrode active material-containing layer to the positive electrode current collection tab side was changed to 3.5 mm, and the protrusion width of the negative electrode active material-containing layer to the negative electrode current collection tab side was changed to 3.9 mm.
Except for these changes, a non-aqueous electrolyte secondary battery was produced in the same manner as in Example 2.

(Example 12)
A non-aqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that Ti Nb ₂ O ₇ (without carbon phase) having an average particle size of 1 μm was used as the negative electrode active material.

(Example 13)
A non-aqueous electrolyte secondary battery was produced in the same manner as in Example 2 except that Ti Nb ₂ O ₇ (without carbon phase) having an average particle size of 1 μm was used as the negative electrode active material.

(Example 14)
A non-aqueous electrolyte secondary battery was produced in the same manner as in Example 2 except that Ti Nb ₂ O ₇ (without carbon phase) having an average particle size of 0.8 μm was used as the negative electrode active material.

(Example 15)
A non-aqueous electrolyte secondary battery was produced in the same manner as in Example 2 except that Ti Nb ₂ O ₇ (without carbon phase) having an average particle size of 12 μm was used as the negative electrode active material.

(Example 16)
A non-aqueous electrolyte secondary battery was produced in the same manner as in Example 6 except that Ti Nb ₂ O ₇ (without carbon phase) having an average particle size of 1 μm was used as the negative electrode active material.

(Example 17)
A non-aqueous electrolyte secondary battery was produced in the same manner as in Example 7 except that Ti Nb ₂ O ₇ (without carbon phase) having an average particle size of 1 μm 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 collection tab side was changed to 0.5 mm, and the protrusion of the negative electrode active material-containing layer to the negative electrode current collection 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 the negative electrode active material, Li ₂ Na _1.6 Ti _5.6 Nb _0.4 O ₁₄ in the form of secondary particles to which carbon was attached 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 N-methylpyrrolidone (NMP) at a mass ratio of 80:10:10 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 Al foil in the width direction, a portion where the slurry was not applied was left on any surface. The laminated structure after drying was pressed and further vacuum dried. Next, the active material-containing layer (slurry coating film after drying and pressing) was cut so as to have a width of 180 mm to obtain a negative electrode. When cutting, the side opposite to the portion to which the slurry was not applied was cut. The portion to which the slurry was not applied was used as the negative electrode current collector tab.
A non-aqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that this negative electrode was used.

(Example 20)
A non-aqueous 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 (without carbon phase) having an average particle size of 1 μm was used as the negative electrode active material. ..

(Example 21)
As the negative electrode active material, Li ₄ Ti ₅ O ₁₂ having a primary particle shape with an average particle size of 1 μm was prepared. The prepared negative electrode active material, acetylene black, and polyvinylidene fluoride (PVdF) were mixed in N-methylpyrrolidone at a mass ratio of 80:10:10 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 Al foil in the width direction, a portion where the slurry was not applied was left on any surface. The laminated structure after drying was pressed and further vacuum dried. Next, the active material-containing layer (slurry coating film after drying and pressing) was cut so as to have a width of 180 mm to obtain a negative electrode. When cutting, the side opposite to the portion to which the slurry was not applied was cut. The portion to which the slurry was not applied was used as the negative electrode current collector tab.
A non-aqueous 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 collection tab side was changed to 2.5 mm, and the protrusion of the negative electrode active material-containing layer to the negative electrode current collection 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 collection tab side was changed to 2.5 mm, and the protrusion of the negative electrode active material-containing layer to the negative electrode current collection 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 collection tab side was changed to 4 mm, and the protrusion of the negative electrode active material-containing layer to the negative electrode current collection 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 carried out for each battery prepared in each Example and each Comparative Example.

For each battery, the discharge capacity from 100% SOC was measured. After charging each battery to 100% SOC again, it was stored in a constant temperature bath at 60 ° C. Residual volume was measured after a storage period of 4 weeks.

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 a current of 1 C. At this time, the discharge termination condition was set to the time when the battery voltage reached 1.8 V. The discharged capacity was measured to determine the remaining capacity.

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

Table 1 summarizes the design of each electrode group and the evaluation results of the battery. In particular, as the design of the electrode group, the composition of the compounds used in the negative electrode active material, the width of the negative electrode active material-containing layer (the width W _N), the negative electrode active material-containing layer of the protruding width of the positive electrode current collector tab side (first The deviation width A), the protrusion width of the negative electrode active material-containing layer on the negative electrode current collecting tab side (second deviation width B), and the ratio of the protrusion width on the positive electrode current collection tab side to the width of the negative electrode active material-containing layer (A / W). _N ), the ratio (B / W _N ) of the protrusion width on the negative electrode current collecting tab side to the width of the negative electrode active material-containing layer is shown. In addition, as an evaluation result, the residual capacity retention rate in the high temperature storage test described above is shown.

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

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

In Example 21, Li ₄ Ti ₅ O _12, which has a relatively high (noble) lithium occlusion / release potential, was used as the negative electrode active material. Therefore, the battery of Example 20 was in a condition where lithium precipitation was unlikely to occur even under the conditions of the high temperature storage test. That is, it is presumed that since there was no precipitation of lithium, no electrical short circuit occurred and self-discharge was small.

In Comparative Examples 1 and 2, the protrusion 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 is larger than the protrusion width (deviation width A) of the negative electrode active material-containing layer on the positive electrode current collector tab side. Was narrow.
As described above, in each comparative example, the protrusion 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 design of the electrode group was not appropriate. As a result of the short circuit in each comparative example, it is presumed that self-discharge could not be suppressed.

The electrode group according to at least one embodiment and the above-described embodiment includes a laminate including a positive electrode, a negative electrode, and an electrically insulating member. The positive electrode was supported on a band-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 at least the positive electrode current collector tab except for the positive electrode current collector tab. It includes a positive electrode active material-containing layer. The positive electrode active material-containing layer includes a first end portion and a second end portion parallel to the above-mentioned one side of the positive electrode current collector. The negative electrode is supported on 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 current collector except for at least the negative electrode current collector tab. It includes a negative electrode active material-containing layer containing a contained oxide. The negative electrode active material-containing layer includes a third end portion and a fourth end portion 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 positive electrode current collecting tab projects in the 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 projects 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 deviation width between the second end portion and the third end portion is wider than the first deviation 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 some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other embodiments, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, as well as in the scope of the invention described in the claims and the equivalent scope thereof.

Claims (6)

A band-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 a positive electrode current collector other than at least the positive electrode current collector tab were supported on the positive electrode current collector. A positive electrode active material-containing layer is provided, and the positive electrode active material-containing layer includes a positive electrode including a first end portion and a second end portion parallel to the one side of the positive electrode current collector, and a band-shaped negative electrode current collector. A negative electrode current collecting tab provided at an end parallel to one side of the negative electrode current collector, and a negative electrode active material containing a titanium-containing oxide supported on the negative electrode current collector except for at least the negative electrode current collecting tab. The negative electrode active material-containing layer includes a negative electrode including a third end portion and a fourth end portion parallel to the one side of the negative electrode current collector.
A laminate including an electrically insulating member interposed between the positive electrode active material-containing layer and the negative electrode active material-containing layer is provided.
The laminate is wound, the positive electrode current collecting tab protrudes in the first direction parallel to the winding axis, and the fourth end is located closer to the positive electrode current collecting tab than the first end. Then, the negative electrode current collecting tab protrudes in the second direction opposite to the first direction, and the third end portion is located closer to the negative electrode current collecting tab side than the second end portion.
An electrode group in which the second deviation width between the second end portion and the third end portion is wider than the first deviation width between the first end portion and the fourth end portion. The electrode group according to claim 1, which satisfies the relationship of 0.008 ≤ A / W _N ≤ 0.02 and satisfies the relationship of 0.01 ≤ B / W _N ≤ 0.022:
Here, A is the first shift width, B is the second shift width, and W _N is the width of the negative electrode active material-containing layer parallel to the winding axis. The electrode group according to claim 1 or 2, wherein the difference AB between the first deviation width and the second deviation 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 contains 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.

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