WO2015140912A1 - Negative electrode for nonaqueous electrolyte secondary battery, nonaqueous electrolyte secondary battery and battery pack - Google Patents

Abstract

According to an embodiment, provided is a negative electrode for a nonaqueous electrolyte secondary battery, said negative electrode comprising a negative electrode collector, a negative electrode active material layer and an oxide insulator layer. The negative electrode active material layer is formed at least on one surface of the negative electrode collector. The oxide insulator layer coats at least a part of the outer periphery of the negative electrode active material layer.

Description

Anode for non-aqueous electrolyte secondary battery, non-aqueous electrolyte secondary battery and battery pack

Embodiments of the present invention relate to a negative electrode for a nonaqueous electrolyte secondary battery, a nonaqueous electrolyte secondary battery, and a battery pack.

Conventionally, there are nonaqueous electrolyte secondary batteries such as lithium ion secondary batteries. Nonaqueous electrolyte secondary batteries have already been put into practical use as power sources in a wide range of fields, from small items such as various electronic devices to large items such as electric vehicles.
Currently, in non-aqueous electrolyte secondary batteries, there are demands from users for further miniaturization, weight reduction, and longer life. In order to meet such demands, it is necessary to further increase the capacity and cycle characteristics of non-aqueous electrolyte secondary batteries.

Some nonaqueous electrolyte secondary batteries use a carbon material as a negative electrode active material and a layered oxide containing nickel, cobalt, manganese, or the like as a positive electrode active material. However, when a carbon material is used as the negative electrode active material, there is a limit to improving the charge / discharge capacity. Further, low-temperature calcined carbon has attracted attention as a carbon material from which a high capacity battery can be obtained. However, since the low-temperature calcined carbon has a low density, it is difficult to increase the charge / discharge capacity per unit volume. Therefore, in order to realize a battery with a higher capacity, it is necessary to develop a new negative electrode active material.

As a material for the negative electrode active material from which a battery having a higher capacity than a carbon material can be obtained, a simple metal such as aluminum (Al), silicon (Si), germanium (Ge), tin (Sn), or antimony (Sb) may be used. Proposed. In particular, when Si is used as the negative electrode active material, a high capacity of 4200 mAh per unit weight (1 g) can be obtained. However, the negative electrode active material composed of these simple metals is liable to cause microscopic pulverization of elements due to repeated insertion and extraction of Li. For this reason, in a battery using these negative electrode active materials, high cycle characteristics may not be obtained.

It has been proposed to use amorphous tin oxide or silicon oxide as a material for a negative electrode active material with high cycle characteristics. By using these oxides as a material for the negative electrode active material, it is possible to achieve both high battery capacity and high cycle characteristics. Furthermore, the volume change of the negative electrode active material accompanying charging / discharging can be suppressed by combining these oxides with a carbon material and using it as a negative electrode active material.

However, even when tin oxide or silicon oxide combined with a carbon material is used as the negative electrode active material, the volume change of the negative electrode active material due to the volume expansion during charging and the contraction during discharging is still large.

Conventionally, in a nonaqueous electrolyte secondary battery, an internal short circuit may occur due to charge / discharge. In particular, the internal short circuit of the battery was likely to occur when a material having a large volume change of the negative electrode active material accompanying charging / discharging such as tin oxide or silicon oxide was used as the negative electrode active material.

JP 2010-92696 A

The problem to be solved by the present invention is to provide a negative electrode for a non-aqueous electrolyte secondary battery that can prevent an internal short circuit of the battery.

The negative electrode for a nonaqueous electrolyte secondary battery of the embodiment has a negative electrode current collector, a negative electrode active material layer, and an oxide insulating layer. The negative electrode active material layer is formed on one side or both sides of the negative electrode current collector. The oxide insulating layer covers at least a part of the outer edge of the negative electrode active material layer.

The expanded cross-section schematic diagram which showed the negative electrode for nonaqueous electrolyte secondary batteries of 1st Embodiment. The cross-sectional schematic diagram for demonstrating an example of the nonaqueous electrolyte secondary battery which has the negative electrode for nonaqueous electrolyte secondary batteries of 1st Embodiment. Sectional drawing which shows an example of the flat type nonaqueous electrolyte battery which concerns on 2nd Embodiment. The expanded sectional view of the A section shown in FIG. The partial notch perspective view which shows typically the other example of the flat type nonaqueous electrolyte battery which concerns on 2nd Embodiment. FIG. 6 is a schematic enlarged cross-sectional view of a portion B in FIG. 5. The disassembled perspective view which shows the battery pack which concerns on 3rd Embodiment. The block diagram which shows the electric circuit with which the battery pack shown in FIG. 7 was equipped.

Hereinafter, a negative electrode for a non-aqueous electrolyte secondary battery and a non-aqueous electrolyte secondary battery (hereinafter may be abbreviated as “battery”) according to embodiments will be described with reference to the drawings. The drawings shown below are schematic diagrams for explaining the nonaqueous electrolyte secondary battery and the negative electrode for a nonaqueous electrolyte secondary battery according to the embodiment, and the shapes, dimensions, ratios, and the like thereof are different from those of the actual apparatus. Although there are places, these can be appropriately modified in consideration of the following description and known techniques.

(First embodiment)
FIG. 1 is an enlarged schematic cross-sectional view showing a negative electrode for a nonaqueous electrolyte secondary battery according to the first embodiment.
A negative electrode 3 for a non-aqueous electrolyte secondary battery shown in FIG. 1 (hereinafter sometimes abbreviated as “negative electrode”) has a negative electrode current collector 3 a, a negative electrode active material layer 3 b, and an oxide insulating layer 13. .

As shown in FIG. 1, a negative electrode active material layer 3b is formed on the entire surface of one surface 11a (upper surface in FIG. 1) and the other surface 11b (lower surface in FIG. 1) of the negative electrode current collector 3a. Yes. As shown in FIG. 1, the oxide insulating layer 13 includes an outer edge 12a on the one surface 11a side and an end surface of the negative electrode current collector 3a from the outer peripheral portion 12b of the negative electrode active material layer 3b formed on the one surface 11a. 11c and the outer edge 12a of the negative electrode active material layer 3b formed on the other surface 11b are continuously formed up to the outer peripheral portion 12b of the negative electrode active material layer 3b on the other surface 11b side.

A negative electrode 3 shown in FIG. 1 has a rectangular shape in plan view, a negative electrode current collector 3a defining the planar shape of the negative electrode 3, and a negative electrode active material layer 3b formed on the entire surface of the negative electrode current collector 3a. Are substantially the same shape in plan view. The oxide insulating layer 13 is continuously formed along the four sides of the negative electrode 3 in the cross-sectional shape shown in FIG. Therefore, the oxide insulating layer 13 covers the entire outer edge 12a of the negative electrode active material layer 3b.

As the negative electrode current collector 3a, a metal foil such as a stainless steel foil, a copper foil, a copper alloy foil, an aluminum foil, an aluminum alloy foil, a titanium foil, or a nickel foil can be used.
The negative electrode current collector 3a is preferably a metal foil having a tensile strength of 500 N / mm ² or more and 2000 N / mm ² or less. Examples of the negative electrode current collector 3a having a tensile strength in the above range include a stainless steel foil and a copper alloy foil.
In addition, the tensile strength of a negative electrode electrical power collector is the numerical value measured by the method based on JISZ2241: 2011.

If the tensile strength of the negative electrode current collector 3a is at 500 N / mm ² or more, as a negative electrode active material contained in the anode active material layer 3b, in case of using a large volume change of the negative electrode active material associated with charge and discharge Even if it exists, it will become difficult to produce the deformation | transformation of the negative electrode collector 3a by the volume change of a negative electrode active material. The tensile strength of the negative electrode current collector 3a is more preferably 550 N / mm ² or more in order to more effectively prevent deformation of the negative electrode current collector 3a.

When the tensile strength of the negative electrode current collector 3a is 2000 N / mm ² or less, the oxide insulating layer 13 can effectively prevent an internal short circuit.
More specifically, when forming the negative electrode 3, as described later, a step of forming the negative electrode active material layer 3 b on the negative electrode current collector 3 a and cutting it into a predetermined shape corresponding to the negative electrode 3 is performed. Is going. In this step, burrs may be formed on the outer edge 12a of the negative electrode active material layer 3b located at the upper and lower ends of the cut surface. The burr is composed of the negative electrode current collector 3a and the negative electrode active material layer 3b, and has a sharp shape. Further, the negative electrode 3 forming the battery is disposed to face the positive electrode through a separator. The negative electrode 3 may be deformed by the volume expansion of the negative electrode active material accompanying charging of the battery, and the outer peripheral portion may be warped. When the warped negative electrode 3 has a burr on the outer edge 12a of the negative electrode active material layer 3b, the burr is pressed against the separator through the oxide insulating layer 13. At this time, if the burr breaks through the oxide insulating layer 13 and the separator, a hole may be formed in the separator and an internal short circuit may occur.

When the negative electrode current collector 3a has a tensile strength of 2000 N / mm ² or less, even if burrs are formed on the outer edge 12a of the negative electrode active material layer 3b, the burr strength is low. Therefore, even if burrs are formed on the outer edge 12a of the negative electrode active material layer 3b, the oxide insulating layer 13 can effectively prevent the burrs pressed against the separator from breaking through the separator. Therefore, the internal short circuit of the battery due to the burr of the negative electrode 3 can be effectively prevented. In order to more effectively prevent an internal short circuit in the battery having the negative electrode 3, the tensile strength of the negative electrode current collector 3a is more preferably 1500 N / mm ² or less.

The negative electrode active material layer 3b includes a negative electrode active material and a binder.
As the negative electrode active material, silicon, silicon-containing oxide, tin, tin-containing oxide, anatase type titanium dioxide TiO ₂ , β-type titanium dioxide, ramsdellite type lithium titanate Li ₂ Ti ₃ O ₇ , spinel type titanium Li ₄ Ti ₅ O ₁₂ that is lithium acid, niobium oxide, niobium-containing composite oxide, or the like can be used. These negative electrode active materials may be mixed and used.

The negative electrode active material preferably contains one or more selected from silicon, silicon-containing oxides, tin, and tin-containing oxides. By making the battery having the negative electrode 3 containing these negative electrode active materials, it is possible to achieve both high battery capacity and high cycle characteristics.
The silicon-containing oxide, SiO, SiO ₂ and the like. SiO and SiO ₂ may have Si deposited on the surface. The tin-containing oxide, SnO, SnO ₂ and the like. SnO and SnO ₂ may have Sn deposited on the surface.

The negative electrode active material may be a composite of silicon-containing oxide and / or tin-containing oxide coated with carbon. Compared with the case where a silicon-containing oxide and / or a tin-containing oxide that is not complexed is included, the volume of the negative electrode active material accompanying charge / discharge is reduced by using the negative electrode 3 including such a negative electrode active material. Change can be suppressed. Therefore, it is possible to prevent the outer peripheral portion of the negative electrode 3 from warping while achieving both high battery capacity and high cycle characteristics, and effectively prevent an internal short circuit.

As binders, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluorine-based rubber, ethylene-butadiene rubber (SBR), polypropylene (PP), polyethylene (PE), carboxymethylcellulose (CMC), polyimide (PI), polyacrylimide (PAI), and the like can be used.

In addition to the negative electrode active material and the binder, the negative electrode active material layer 3b may contain a negative electrode conductive agent as necessary.
As the negative electrode conductive agent, for example, a carbon material can be used. As the carbon material, it is preferable to use a material having high alkali metal occlusion and conductivity. Examples of such a carbon material include hard carbon (non-graphitizable carbon), acetylene black, carbon black, and highly crystalline graphite.
In order to improve the cycle performance of the negative electrode active material itself, the negative electrode active material layer 3b may contain a small amount of elements different from the negative electrode active material.

In the negative electrode active material layer 3b, the blending ratio of the negative electrode active material, the negative electrode conductive agent, and the binder is 70 to 95% by mass of the negative electrode active material, 0 to 25% by mass of the negative electrode conductive agent, and 2 to 10% by mass of the binder. It is preferable that When the negative electrode active material contains silicon element, the atomic ratio of silicon element to carbon element in negative electrode active material layer 3b ((number of silicon atoms / number of carbon atoms) × 100 (atomic%)) is 5 to 50 atomic%. It is preferable that When the negative electrode active material contains tin element, the atomic ratio of tin to carbon element in the negative electrode active material layer 3b ((tin atom number / carbon atom number) × 100 (atomic%)) is 5 to 50 It is preferably atomic%.

The oxide insulating layer 13 is an insulator containing an oxide and a binder. Here, the insulator means that the electrical resistivity is 10 ⁶ Ωm or more.
As the binder, polyvinylidene fluoride (PVdF), an acrylic binder, or the like can be used.

Any oxide may be used as long as the oxide insulating layer 13 having the above electrical resistivity can be obtained. Specifically, the oxide preferably contains one or more selected from SiO ₂ , Al ₂ O ₃ , and ZrO ₂ . When the oxide contained in the oxide insulating layer 13 is at least one selected from these, the oxide insulating layer 13 having a sufficiently high electrical resistivity can be obtained. These oxides are preferable as a material for the oxide insulating layer 13 because they can suppress side reactions between HF contained in the nonaqueous electrolyte and the negative electrode active material layer 3b.
Oxide contained in the oxide insulating layer _13, that when it is _{SiO 2, Al 2 O 3,} 1 or more selected from ZrO _2, average particle diameter of the oxide is in the range of 0.5 ~ 10 [mu] m preferable. When the average particle diameter is outside the above range, the oxide insulator layer 13 causes a short circuit, or when the oxide insulating layer 13 is formed by a method of applying a slurry containing an oxide and a binder, It may become difficult to apply.

The oxide insulating layer 13 preferably has a thickness t1, t2 in the direction perpendicular to the surface of the negative electrode active material layer 3b shown in FIG. When the thicknesses t1 and t2 in the direction perpendicular to the surface of the negative electrode active material layer 3b of the oxide insulating layer 13 are 1 μm or more, even if burrs are formed on the outer edge 12a of the negative electrode active material layer 3b, the oxide insulating layer 13 Thus, it is possible to effectively prevent the burr pressed against the separator from breaking through the separator. Therefore, the internal short circuit in the battery having the negative electrode 3 can be more effectively prevented. The thicknesses t1 and t2 of the oxide insulating layer 13 are more preferably 5 μm or more in order to further improve the effect of preventing an internal short circuit in the battery having the negative electrode 3.

When the oxide insulating layer 13 has thicknesses t1 and t2 in the direction perpendicular to the surface of the negative electrode active material layer 3b of 15 μm or less, the portion where the oxide insulating layer 13 is formed on the negative electrode active material layer 3b; The step difference from the portion where the oxide insulating layer 13 is not formed is small. For this reason, the level | step difference of the surface of the negative electrode 3 resulting from the thickness of the oxide insulating layer 13 does not affect the shape of the battery which has the negative electrode 3, and is preferable. The thicknesses t1 and t2 of the oxide insulating layer 13 are more preferably 10 μm or less.

The oxide insulating layer 13 may have the same thickness t1 and t2 in the direction perpendicular to the surface of the negative electrode active material layer 3b on the one surface 11a side and the other surface 11b side of the negative electrode current collector 3a. It may be good or different.
In the oxide insulating layer 13 shown in FIG. 1, the thicknesses t1 and t2 in the direction perpendicular to the surface of the negative electrode active material layer 3b are different on the one surface 11a side and the other surface 11b side of the negative electrode current collector 3a. Yes. In the oxide insulating layer 13 shown in FIG. 1, the thickness t1 of the oxide insulating layer 13 on the one surface 11a side is thicker than the thickness t2 of the oxide insulating layer 13 on the other surface 11b side.

The widths D1 and D2 of the oxide insulating layer 13 illustrated in FIG. 1 are dimensions from the outer edge 12a of the negative electrode active material layer 3b to the inner end of the oxide insulating layer 13 in plan view. The widths D1 and D2 of the oxide insulating layer 13 are preferably 1 mm to 1 cm.
When the widths D1 and D2 of the oxide insulating layer 13 are 1 mm or more, even if the oxide insulating layer 13 of the warped negative electrode 3 is pressed against the separator, even if the separator has a hole, the positive electrode side through the hole The part exposed to is likely to be only the oxide insulating layer 13. Since the oxide insulating layer 13 is an insulator, an internal short circuit of the battery is prevented even when exposed to the positive electrode side. Further, when the oxide insulating layer 13 is formed by a method of applying a slurry containing an oxide and a binder, the width D1 and D2 of the oxide insulating layer 13 is 1 mm or more. The dimensions corresponding to the widths D1 and D2 of the insulating layer 13 can be easily controlled.

When the widths D1 and D2 of the oxide insulating layer 13 are 2 mm or more, the internal short circuit of the battery is much less likely to occur. Moreover, when the oxide insulating layer 13 is formed by the method of applying the slurry, it is more preferable that the widths D1 and D2 of the oxide insulating layer 13 be 2 mm or more because the application width of the slurry can be controlled with high accuracy. .

When the widths D1 and D2 of the oxide insulating layer 13 are 1 cm or less, reduction of the charge / discharge reaction area on the negative electrode active material layer 3b due to the formation of the oxide insulating layer 13 can be suppressed. In order to secure a charge / discharge reaction area on the negative electrode active material layer 3b, the widths D1 and D2 of the oxide insulating layer 13 are more preferably 7 mm or less.

The widths D1 and D2 of the oxide insulating layer 13 may be the same or different on the one surface 11a side and the other surface 11b side of the negative electrode current collector 3a.
The widths D1 and D2 of the oxide insulating layer 13 shown in FIG. 1 are different on the one surface 11a side and the other surface 11b side of the negative electrode current collector 3a. In the oxide insulating layer 13 shown in FIG. 1, the width D1 of the oxide insulating layer 13 on the one surface 11a side is larger than the width D2 of the oxide insulating layer 13 on the other surface 11b side.

Next, the manufacturing method of the negative electrode 3 of this embodiment is demonstrated.
First, the negative electrode active material layer 3b is formed on the entire surfaces of the negative electrode current collector 3a. In order to form the negative electrode active material layer 3b, first, a slurry in which the negative electrode active material, the negative electrode conductive agent, and the binder are dispersed in an organic solvent is prepared. Next, the slurry is applied to the entire surface of the negative electrode current collector 3a, dried, and then pressed.
Examples of the organic solvent used in the slurry for forming the negative electrode active material layer 3b include N-methyl-2-pyrrolidone (NMP) and dimethylformamide (DMF).

Thereafter, the negative electrode current collector 3 a on which the negative electrode active material layer 3 b is formed is cut into a predetermined shape corresponding to the negative electrode 3. At this time, burrs may be formed on the outer edge 12a of the negative electrode active material layer 3b located at the upper and lower ends of the cut surface.

Next, the oxide insulating layer 13 that covers the entire outer edge 12a of the negative electrode active material layer 3b is formed. In order to form the oxide insulating layer 13, first, a slurry in which an oxide and a binder are dispersed in an organic solvent is prepared.
As the organic solvent used in the slurry for forming the oxide insulating layer 13, for example, N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), or the like can be used.

Next, the oxide insulating layer 13 is formed on the outer edge 12a of the negative electrode active material layer 3b formed on the one surface 11a of the negative electrode current collector 3a with the one surface 11a of the negative electrode current collector 3a facing upward. The slurry is applied so as to have a thickness t1 and a width D1. At this time, a part of the slurry applied to the outer edge 12a protrudes from the negative electrode active material layer 3b to the end face 11c side of the negative electrode current collector 3a. As a result, the slurry is also applied to the end face 11c of the negative electrode current collector 3a.

Next, with the other surface 11b of the negative electrode current collector 3a facing upward, the oxide insulating layer 13 is formed on the outer edge 12a of the negative electrode active material layer 3b formed on the other surface 11b of the negative electrode current collector 3a. The slurry is applied so as to have a thickness t2 and a width D2. At this time, a part of the slurry applied to the outer edge 12a protrudes from the negative electrode active material layer 3b to the end face 11c side of the negative electrode current collector 3a. Thus, from the outer peripheral portion 12b of the negative electrode active material layer 3b formed on the one surface 11a of the negative electrode current collector 3a, the outer edge 12a on the one surface 11a side, the end surface 11c of the negative electrode current collector 3a, and the negative electrode The slurry is continuously applied to the outer peripheral portion 12b of the negative electrode active material layer 3b on the other surface 11b side, covering the outer edge 12a of the negative electrode active material layer 3b formed on the other surface 11b of the current collector 3a. The
Thereafter, the applied slurry is dried and pressed to obtain the oxide insulating layer 13 having the cross-sectional shape shown in FIG.

The negative electrode 3 of this embodiment includes a negative electrode current collector 3a, a negative electrode active material layer 3b formed on both surfaces of the negative electrode current collector 3a, and an oxide insulating layer 13 that covers all the outer edges 12a of the negative electrode active material layer 3b. It has. For this reason, even if the negative electrode 3 has a burr on the outer edge 12a of the negative electrode active material layer 3b, the burr is covered with the oxide insulating layer 13. Moreover, since the negative electrode 3 has the oxide insulating layer 13, in the battery using this, the deformation accompanying the volume change of the negative electrode active material is difficult to occur.

That is, in the battery using the negative electrode 3 of the present embodiment, even if the negative electrode active material expands during charging, the outer periphery of the negative electrode 3 hardly warps, and even if the outer periphery warps, The burrs are pressed against the separator through the oxide insulating layer 13. Therefore, the burr pressed against the separator can be prevented from breaking through the separator, and an internal short circuit of the battery due to the burr of the negative electrode 3 can be prevented.

In addition, since the oxide insulating layer 13 is an insulator, even if the oxide insulating layer 13 of the warped negative electrode 3 is pressed against the separator and a hole is formed in the separator, the oxide insulating layer 13 is exposed to the positive electrode side through the hole. In the case where only the oxide insulating layer 13 is present, the internal short circuit of the battery does not occur. Therefore, the battery having the negative electrode 3 of the present embodiment is less likely to cause an internal short circuit.

In the negative electrode 3 of the present embodiment, the outer edge 12a of the negative electrode active material layer 3b is covered with the oxide insulating layer 13. The outer edge 12a of the negative electrode active material layer 3b is a portion where lithium deposition is likely to occur due to current density concentration in a battery using the negative electrode active material layer 3b. In the battery using the negative electrode 3 of the present embodiment, the outer edge 12a of the negative electrode active material layer 3b in which lithium is likely to precipitate does not contact the nonaqueous electrolyte. For this reason, in the negative electrode 3, it can prevent that lithium precipitates on the outer peripheral part 12b of the negative electrode active material layer 3b.

In the negative electrode 3 of the present embodiment, when the negative electrode active material layer 3b includes a negative electrode active material containing one or more selected from silicon, silicon-containing oxides, tin, and tin-containing oxides, High cycle characteristics can be achieved at the same time.
Note that the negative electrode active material including one or more selected from silicon, silicon-containing oxide, tin, and tin-containing oxide has a large volume change of the negative electrode active material accompanying charge / discharge. For this reason, in the negative electrode 3 using these negative electrode active materials, the outer peripheral portion is likely to warp. Therefore, in the past, batteries having a negative electrode using these negative electrode active materials have been particularly prone to internal short circuits.

On the other hand, in the negative electrode 3 of the present embodiment, as described above, the warpage of the outer peripheral portion can be suppressed by the oxide insulating layer 13. Moreover, in the negative electrode 3 of the present embodiment, even if the outer peripheral portion is warped, the oxide insulating layer 13 can prevent an internal short circuit of the battery using the negative electrode 3. Therefore, in the battery using the negative electrode 3 of the present embodiment, the negative electrode active material layer 3b including the negative electrode active material including one or more selected from silicon, silicon-containing oxide, tin, and tin-containing oxide is formed. Thus, high capacity and high cycle characteristics can be realized while suppressing internal short circuit.

In the negative electrode 3 of the above embodiment, the negative electrode active material layer is formed on the entire surface of both surfaces of the negative electrode current collector, but the negative electrode active material layer may be formed only on one surface of the negative electrode current collector. Further, the negative electrode active material layer on one surface and / or the other surface of the negative electrode current collector is formed only on a part of the surface of the negative electrode current collector and has a region where the negative electrode active material layer is not formed. There may be.
In the negative electrode of the above embodiment, the oxide insulating layer covers all of the outer edge of the negative electrode active material layer, but may cover only a part of the outer edge of the negative electrode active material layer.

Moreover, when the negative electrode active material layer is formed on both surfaces of the negative electrode current collector 3a, the oxide insulating layer is formed on both the first surface 11a and the other surface 11b of the negative electrode current collector 3a. It is preferable that the outer edge of the negative electrode active material layer is covered, but the outer edge of the negative electrode active material layer formed on the one surface 11a may be covered.

The oxide insulating layer may cover the end surface 11c of the negative electrode current collector 3a, but the oxide insulating layer 13 may not be formed on the end surface 11c of the negative electrode current collector 3a. Part or all of the end face 11c of the current collector 3a may be exposed.
The planar shapes of the negative electrode 3, the negative electrode current collector 3a, and the negative electrode active material layer 3b are appropriately determined according to the shape of the battery in which the negative electrode 3 is used, and are not particularly limited.

In the negative electrode 3 of the present embodiment, for example, instead of the oxide insulating layer 13, it may be possible to form an insulating layer having the same shape as the oxide insulating layer 13 using a resin. However, the resin is not suitable as compared with the oxide from the viewpoints of solvent resistance, reduction resistance, handling, and the like.

(Second Embodiment)
FIG. 2 is a schematic cross-sectional view for explaining an example of a non-aqueous electrolyte secondary battery having the negative electrode for a non-aqueous electrolyte secondary battery according to the first embodiment.
A non-aqueous electrolyte secondary battery 10 shown in FIG. 2 includes the negative electrode 3, the positive electrode 5, the separator 4 disposed between the negative electrode 3 and the positive electrode 5, and a non-aqueous electrolyte (not shown). Have.
As shown in FIG. 2, the positive electrode 5 includes a positive electrode current collector 5a and a positive electrode active material layer 5b formed on both surfaces of the positive electrode current collector 5a.

The battery 10 shown in FIG. 2 has a first region 14 in which the region where the negative electrode active material layer 3b of the negative electrode 3 is formed and the region where the positive electrode active material layer 5b of the positive electrode 5 are formed overlap in a plan view. is doing. In addition, the battery 10 shown in FIG. 2 has a second region 15 in which the positive electrode 5 is not disposed and the negative electrode active material layer 3 b of the negative electrode 3 is formed outside the first region 14.
The battery 10 shown in FIG. 2 has the second region 15, so that concentration of current density in the outer peripheral portion 12 b of the negative electrode active material layer 3 b can be suppressed, and lithium is deposited on the outer peripheral portion 12 b of the negative electrode active material layer 3 b. Can be prevented.

Next, the positive electrode 5 will be described.
As shown in FIG. 2, a positive electrode active material layer 5b is formed on the entire surface of both surfaces of the positive electrode current collector 5a.
As the positive electrode current collector 5a, a metal foil such as a stainless steel foil, a copper foil, a copper alloy foil, an aluminum foil, an aluminum alloy foil, a titanium foil, or a nickel foil can be used.

The positive electrode active material layer 5b includes a positive electrode active material and a binder.
As the positive electrode active material, for example, a lithium composite oxide can be used. Examples of the lithium composite oxide include lithium manganese composite oxide (for example, LiMn ₂ O ₄ or LiMnO ₂ ), lithium nickel composite oxide (for example, LiNiO ₂ ), lithium cobalt composite oxide (LiCoO ₂ ), and lithium nickel cobalt composite oxide. (For example, LiNi _1-x Co _x O ₂ , 0 <x ≦ 1), lithium manganese cobalt composite oxide (for example, LiMn _2-x Co _x O ₄ , 0 <x ≦ 1), lithium copper composite oxide (for example, Li ₂ Cu _x Ni _1-x O ₄ , 0 <x ≦ 1), lithium composite phosphate compound (for example, LiMn _x Fe _1-x PO ₄ , 0 <x ≦ 1), and the like.

As a binder, the thing similar to the binder contained in the negative electrode active material layer 3b of the negative electrode 3 can be used. Specifically, as a binder contained in the positive electrode active material layer 5b, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluorine-based rubber, ethylene-butadiene rubber (SBR), polypropylene (PP), Polyethylene (PE), carboxymethylcellulose (CMC), polyimide (PI), polyacrylimide (PAI), and the like can be used.

In addition to the positive electrode active material and the binder, the positive electrode active material layer 5b may contain a positive electrode conductive agent as necessary.
As the positive electrode conductive agent, for example, a carbon material can be used. Examples of the carbon material include acetylene black, carbon black, and graphite.
In the positive electrode active material layer 5b, the mixing ratio of the positive electrode active material, the positive electrode conductive agent and the binder is 80 to 95% by mass of the positive electrode active material, 3 to 20% by mass of the positive electrode conductive agent, and 2 to 7% by mass of the binder. It is preferable that

The positive electrode 5 can be formed by a conventionally known method.
For example, a slurry is prepared by dispersing a positive electrode active material, a positive electrode conductive agent, and a binder in an organic solvent. As the organic solvent used in the slurry for forming the positive electrode active material layer 5b, for example, N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), or the like can be used. Next, the slurry is applied to the entire surface of the positive electrode current collector 5a, dried, and then pressed. Thereby, the positive electrode 5 is obtained.

Next, the separator 4 will be described.
As the separator 4, for example, a porous film or a resin nonwoven fabric can be used. Examples of the porous film include those made of polyethylene and polypropylene. Such a separator 4 is easy to add a shutdown function that melts and closes the pores when the temperature of the battery 10 rises and reaches a certain temperature, and greatly attenuates the charge / discharge current. It is preferable because safety can be improved. Moreover, you may use what consists of a cellulose-type material as the separator 4 from a viewpoint of cost reduction.

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

Examples of solutes include lithium perchlorate (LiClO ₄ ), lithium hexafluorophosphate (LiPF ₆ ), lithium tetrafluoroborate (LiBF ₄ ), lithium arsenic hexafluoride (LiAsF ₆ ), trifluorometa Lithium sulfonate (LiCF ₃ SO ₃ ), lithium bistrifluoromethylsulfonylimide [LiN (CF ₃ SO ₂ ) ₂ ], [LiN (C ₂ F ₅ SO ₂ ) ₂ ], [Li (CF ₃ SO ₂ ) ₃ C ], 1 or more types of lithium salt chosen from LiB [(OCO) ₂ ] _2, etc. are preferable. It is preferable that the solute 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), and vinylene carbonate; chain forms such as diethyl carbonate (DEC), dimethyl carbonate (DMC), and methyl ethyl carbonate (MEC). Carbonates; cyclic ethers such as tetrahydrofuran (THF), 2-methyltetrahydrofuran (2MeTHF), dioxolane (DOX); chain ethers such as dimethoxyethane (DME) and diethoxyethane (DEE); or γ-butyrolactone (GBL) , Acetonitrile (AN), and sulfolane (SL). These organic solvents can be used alone or in the form of a mixed solvent.

Among the above, as a preferable organic solvent, a mixed solvent in which at least two or more of the group consisting of methyl ethyl carbonate (MEC), propylene carbonate (PC), ethylene carbonate (EC) and diethyl carbonate (DEC) are mixed, Another example is a mixed solvent containing γ-butyrolactone (GBL). By using these mixed solvents, a nonaqueous electrolyte battery having excellent high temperature characteristics can be obtained.

Examples of the polymer material constituting the gel-like nonaqueous electrolyte include those containing polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), and polyethylene oxide (PEO).

Also, as the non-aqueous electrolyte, a room temperature molten salt (ionic melt) containing lithium ions can be used. Specifically, for example, when an ionic melt composed of lithium ions, an organic cation and an anion, which is liquid at 100 ° C. or less, preferably at room temperature or less, is selected, An electrolyte battery can be obtained.

The battery 10 shown in FIG. 2 can be manufactured using a conventionally known method.
The battery 10 shown in FIG. 2 can be used as a material for a wound nonaqueous electrolyte battery and a laminated nonaqueous electrolyte battery, as will be described later.
Specifically, for example, a wound electrode group of a wound nonaqueous electrolyte battery can be formed by stacking the battery 10 shown in FIG. 2 on the separator 4 to form a laminate, and winding this into a spiral. .
2 can be stacked to form a stacked battery group of stacked nonaqueous electrolyte batteries. The stacked battery group shown in FIG.

The battery 10 according to the present embodiment includes the negative electrode 3 according to the first embodiment, the positive electrode 5 including the positive electrode active material layer 5b, and the nonaqueous electrolyte. Therefore, an internal short circuit is unlikely to occur.
In addition, as shown in FIG. 2, the battery 10 of the present embodiment has a region in which the negative electrode active material layer 3 b of the negative electrode 3 is formed and a positive electrode active material layer 5 b of the positive electrode 5 in plan view. Since the first region 14 that overlaps with the region and the second region 15 in which the positive electrode 5 is not disposed and the negative electrode active material layer 3b is formed outside the first region 14 are described below. As shown in FIG. 3, the outer periphery of the negative electrode 3 is likely to warp.

That is, since the positive electrode 5 does not exist in the second region 15, the negative electrode 3 in the second region 15 has a larger space that can be deformed than the first region 14 by the volume of the positive electrode 5. For this reason, the negative electrode 3 in the second region 15 is more easily deformed than the negative electrode 3 in the first region 14, and easily absorbs stress due to volume expansion of the negative electrode active material. Therefore, the negative electrode 3 in the second region 15 functions as a stress escape field due to the volume expansion of the negative electrode active material. Therefore, in the battery 10, the stress due to the volume expansion of the negative electrode active material to the negative electrode 3 in the second region 15 is larger than that of the negative electrode 3 in the first region 14, and the outer peripheral portion of the negative electrode 3 is easily warped. .

However, in the battery 10 of the present embodiment, the oxide insulating layer 13 suppresses the warpage of the outer peripheral portion of the negative electrode 3. Even if the outer periphery of the negative electrode 3 is warped, the oxide insulating layer 13 can prevent an internal short circuit of the battery 10. Therefore, in the battery 10 using the negative electrode 3 of the present embodiment, it is possible to prevent lithium from being deposited on the outer peripheral portion 12b of the negative electrode active material layer 3b by providing the second region 15 while suppressing an internal short circuit.

In the battery of the above-described embodiment, the example in which the second region 15 is provided outside the first region 14 has been described as an example, but the second region 15 may be omitted.

The nonaqueous electrolyte battery according to the second embodiment is not limited to the one shown in FIG.
Hereinafter, as another example of the nonaqueous electrolyte battery according to the second embodiment, a flat type nonaqueous electrolyte battery (nonaqueous electrolyte battery) 100 shown in FIGS. 3 and 4 will be described. FIG. 3 is a schematic cross-sectional view of the flat type nonaqueous electrolyte battery 100. FIG. 4 is an enlarged cross-sectional view of a portion A shown in FIG.

A nonaqueous electrolyte battery 100 shown in FIGS. 3 and 4 is a wound nonaqueous electrolyte battery, and includes an exterior material 2, a flat wound electrode group 1 housed in the exterior material 2, and an exterior material 2. And a non-aqueous electrolyte filled therein. The nonaqueous electrolyte battery 100 shown in FIGS. 3 and 4 is a laminate in which the battery 10 shown in FIG. 2 is laminated on the separator 4 and laminated in the order of the negative electrode 3, the separator 4, the positive electrode 5, and the separator 4. Is wound in a spiral shape and has a wound electrode group 1 formed by press molding. As the non-aqueous electrolyte, the same one as described in the battery 10 shown in FIG. 2 can be used.

3 and 4, the negative electrode 3 located on the outermost periphery of the wound electrode group 1 has a configuration in which a negative electrode layer 3b is formed on one surface on the inner surface side of the negative electrode current collector 3a. A portion of the negative electrode 3 other than the outermost periphery has a configuration in which the negative electrode layer 3b is formed on both surfaces of the negative electrode current collector 3a. In place of the separator 4, a gel nonaqueous electrolyte may be used.

In the wound electrode group 1 shown in FIG. 3, the negative electrode terminal 6 is electrically connected to the negative electrode current collector 3a of the outermost negative electrode 3 in the vicinity of the outer peripheral end thereof. The positive electrode terminal 7 is electrically connected to the positive electrode current collector 5 a of the inner positive electrode 5. The negative electrode terminal 6 and the positive electrode terminal 7 are extended to the outside of the exterior material 2 or connected to a take-out electrode provided in the exterior material 2.

The exterior material 2 may be a laminate film formed in a bag shape or a metal container.
When manufacturing the nonaqueous electrolyte battery 100 including the exterior material made of a laminate film, the wound electrode group 1 to which the negative electrode terminal 6 and the positive electrode terminal 7 are connected is mounted on the bag-shaped exterior material 2 having an opening. Enter. Next, a liquid non-aqueous electrolyte is injected from the opening of the exterior material 2. Then, the wound electrode group 1 and the liquid nonaqueous electrolyte are completely sealed by heat-sealing the opening of the bag-shaped outer packaging material 2 with the negative electrode terminal 6 and the positive electrode terminal 7 interposed therebetween.

Moreover, when manufacturing the nonaqueous electrolyte battery 100 provided with the exterior material which consists of metal containers, the winding electrode group 1 to which the negative electrode terminal 6 and the positive electrode terminal 7 were connected is inserted into the metal container which has an opening part. . Next, a liquid non-aqueous electrolyte is injected from the opening of the exterior material 2, and a lid is attached to the metal container to seal the opening.

As the negative electrode terminal 6, for example, a material having electrical stability and conductivity in a range where the potential with respect to lithium is 1 V or more and 3 V or less can be used. Specifically, aluminum or an aluminum alloy containing elements such as Mg, Ti, Zn, Mn, Fe, Cu, and Si can be given. The negative electrode terminal 6 is more preferably made of the same material as the negative electrode current collector 3a in order to reduce the contact resistance with the negative electrode current collector 3a.

As the positive electrode terminal 7, a material having electrical stability and conductivity in the range of 3 to 4.25 V with respect to lithium can be used. Specifically, aluminum or an aluminum alloy containing an element such as Mg, Ti, Zn, Mn, Fe, Cu, or Si can be given. The positive electrode terminal 7 is preferably made of the same material as the positive electrode current collector 5a in order to reduce the contact resistance with the positive electrode current collector 5a.

Hereinafter, the exterior material 2 will be described in detail.
The exterior material 2 is formed of a laminate film having a thickness of 0.5 mm or less, or a metal container having a thickness of 1 mm or less.
The shape of the exterior material 2 can be appropriately selected from a flat type (thin type), a square type, a cylindrical type, a coin type, and a button type.
Examples of the exterior material 2 include, for example, a small battery exterior material loaded on a portable electronic device, a large battery exterior material loaded on a two-wheel or four-wheel automobile, etc., depending on the battery size. It is.

When the exterior material 2 made of a laminate film is used, a multilayer film in which a metal layer is interposed between resin layers is used. For the metal layer in this case, it is preferable to employ an aluminum foil or an aluminum alloy foil for weight reduction. Moreover, as a resin layer, polymeric materials, such as a polypropylene (PP), polyethylene (PE), nylon, a polyethylene terephthalate (PET), can be used, for example. The laminate film can be molded into the shape of an exterior material by sealing by heat sealing.

When the exterior material 2 made of a metal container is used, one made of aluminum or an aluminum alloy is used. As such an aluminum alloy, an alloy containing elements such as magnesium, zinc, and silicon is preferable. Moreover, when transition metals, such as iron, copper, nickel, and chromium, are contained in an aluminum alloy, it is preferable to suppress the content to 100 mass ppm or less. Moreover, when using the exterior | packing material 2 which consists of metal containers, it is more preferable to use a thing with thickness of 0.5 mm or less.

The nonaqueous electrolyte battery 100 shown in FIG. 3 and FIG. 4 described above has the negative electrode 3 having the oxide insulating layer covering at least a part of the outer edge of the negative electrode active material layer, so that an internal short circuit hardly occurs. .

The nonaqueous electrolyte battery according to the second embodiment may be a battery having the configuration shown in FIGS. 5 and 6. FIG. 5 is a partially cutaway perspective view schematically showing another flat type non-aqueous electrolyte secondary battery according to the second embodiment. 6 is an enlarged cross-sectional view of a portion B in FIG.
The nonaqueous electrolyte battery shown in FIGS. 5 and 6 is a stacked nonaqueous electrolyte battery, and a stacked electrode group 31 is housed in an exterior member 32. The laminated electrode group 31 is a laminate in which the negative electrode 3, the separator 4, the positive electrode 5, and the separator 4 are laminated in this order, and is formed by laminating a plurality of these. As the separator 4 and the nonaqueous electrolyte, the same materials as those described in the battery 10 shown in FIG. 2 can be used.

In the negative electrode 3 forming the stacked electrode group 31, the oxide insulating layer 13 covers the outer edge of the negative electrode active material layer 3b on the three sides of the rectangular negative electrode 3 as shown in FIG. This is different from the negative electrode 3 of FIG. About others, it is the same as the negative electrode 3 of the battery 10 shown in FIG. Therefore, the oxide insulating layer 13 is not formed on one side of the negative electrode 3 and covers only a part of the outer edge of the negative electrode active material layer 3b.
The negative electrode current collector 3 a protrudes from the negative electrode 3 on one side where the oxide insulating layer of the negative electrode 3 is not formed. The protruding negative electrode current collector 3 a is electrically connected to a strip-shaped negative electrode terminal 36. The tip of the strip-shaped negative electrode terminal 36 is drawn out from the exterior member 32 to the outside.

The positive electrode 5 forming the stacked electrode group 31 has the battery shown in FIG. 2 in that the side of the positive electrode current collector 5a opposite to the protruding side of the negative electrode current collector 3a protrudes from the positive electrode 5. 10 different from the positive electrode 5. About others, it is the same as the positive electrode 5 of the battery 10 shown in FIG.
The positive electrode current collector 5 a protruding from the positive electrode 5 is electrically connected to a belt-like positive electrode terminal 37. The front end of the belt-like positive electrode terminal 37 is located on the side opposite to the negative electrode terminal 36 and is drawn out from the exterior member 32 to the outside.

The non-aqueous electrolyte battery shown in FIGS. 5 and 6 described above has the negative electrode 3 having the oxide insulating layer covering at least a part of the outer edge of the negative electrode active material layer, and therefore an internal short circuit hardly occurs.

(Third embodiment)
Next, the battery pack according to the third embodiment will be described in detail.
The battery pack according to the present embodiment has one or more nonaqueous electrolyte batteries (that is, single cells) according to the second embodiment. When the battery pack includes a plurality of single cells, the single cells are electrically connected in series, parallel, or connected in series and parallel.

With reference to FIG. 7 and FIG. 8, the battery pack 200 which concerns on this embodiment is demonstrated concretely. In the battery pack 200 shown in FIG. 7, the flat type nonaqueous electrolyte battery 100 shown in FIG. 3 is used as the unit cell 121.
The plurality of single cells 121 are stacked such that the negative electrode terminal 6 and the positive electrode terminal 7 extending to the outside are aligned in the same direction, and are fastened with an adhesive tape 122 to constitute an assembled battery 123. These unit cells 121 are electrically connected to each other in series as shown in FIGS.

The printed wiring board 124 is disposed to face the side surface of the unit cell 121 from which the negative electrode terminal 6 and the positive electrode terminal 7 extend. As shown in FIG. 7, a thermistor 125 (see FIG. 8), a protection circuit 126, and a terminal 127 for energizing external devices are mounted on the printed wiring board 124. Note that an insulating plate (not shown) is attached to the surface of the printed wiring board 124 facing the assembled battery 123 in order to avoid unnecessary connection with the wiring of the assembled battery 123.

The positive electrode side lead 128 is connected to the positive electrode terminal 7 located in the lowermost layer of the assembled battery 123, and the tip thereof is inserted into the positive electrode side connector 129 of the printed wiring board 124 and electrically connected thereto. The negative electrode side lead 130 is connected to the negative electrode terminal 6 located in the uppermost layer of the assembled battery 123, and the tip thereof is inserted into the negative electrode side connector 131 of the printed wiring board 124 and electrically connected thereto. These connectors 129 and 131 are connected to the protection circuit 126 through wirings 132 and 133 (see FIG. 8) formed on the printed wiring board 124.

The thermistor 125 is used to detect the temperature of the unit cell 121 and is not shown in FIG. 7, but is provided in the vicinity of the unit cell 121 and its detection signal is transmitted to the protection circuit 126. . The protection circuit 126 can cut off the plus-side wiring 134a and the minus-side wiring 134b between the protection circuit 126 and the terminal 127 for energizing external devices under a predetermined condition. Here, the predetermined condition is, for example, when the temperature detected by the thermistor 125 is equal to or higher than a predetermined temperature. Furthermore, the predetermined condition is when an overcharge, overdischarge, overcurrent, or the like of the unit cell 121 is detected. Such detection of overcharge or the like is performed for each single cell 121 or the entire single cell 121. In addition, when detecting the overcharge etc. in each single battery 121, a battery voltage may be detected and a positive electrode potential or a negative electrode potential may be detected. In the latter case, a lithium electrode used as a reference electrode is inserted into each unit cell 121. In the case of FIG. 7 and FIG. 8, a voltage detection wiring 135 is connected to each single cell 121, and a detection signal is transmitted to the protection circuit 126 through these wirings 135.

As shown in FIG. 7, protective sheets 136 made of rubber or resin are disposed on the three side surfaces of the assembled battery 123 excluding the side surfaces from which the positive electrode terminal 7 and the negative electrode terminal 6 protrude.

The assembled battery 123 is stored in the storage container 137 together with the protective sheets 136 and the printed wiring board 124. That is, the protective sheet 136 is disposed on each of the inner side surface in the long side direction and the inner side surface in the short side direction of the storage container 137, and the printed wiring board 124 is disposed on the inner side surface opposite to the protective sheet 136 in the short side direction. Be placed. The assembled battery 123 is located in a space surrounded by the protective sheet 136 and the printed wiring board 124. The lid 138 is attached to the upper surface of the storage container 137.

In addition, instead of the adhesive tape 122, a heat shrink tape may be used for fixing the assembled battery 123. In this case, protective sheets are arranged on both side surfaces of the assembled battery, the heat shrinkable tape is circulated, and then the heat shrinkable tape is heat shrunk to bind the assembled battery.

7 and 8 show the configuration in which the unit cells 121 are connected in series. However, in order to increase the battery capacity, the unit cells 121 may be connected in parallel, or the series connection and the parallel connection may be performed. A combined configuration may be used. In addition, the assembled battery packs can be further connected in series and in parallel.
Since the battery pack of the present embodiment described above has a negative electrode having an oxide insulating layer covering at least a part of the outer edge of the negative electrode active material layer, an internal short circuit hardly occurs.

In addition, the aspect of a battery pack is changed suitably according to a use. As a use of the battery pack according to the present embodiment, an electronic device, and further one that is required to exhibit excellent cycle characteristics when a large current is taken out is preferable. Specific examples include a power source for a digital camera, a vehicle for a two- to four-wheel hybrid electric vehicle, a two- to four-wheel electric vehicle, an assist bicycle, and the like. In particular, a battery pack using a nonaqueous electrolyte battery having excellent high temperature characteristics is suitably used for in-vehicle use.

Example 1
<Production of negative electrode>
80% by weight of silicon powder (Si) as a negative electrode active material, 10% by weight of hard carbon powder (negative electrode conductive agent), and 10% by weight of polyimide (PI) (binder) are used as N-methyl as an organic solvent. A slurry was prepared by adding to pyrrolidone (NMP) and mixing.
The obtained slurry was applied to both surfaces of a 10 μm-thick stainless steel foil (tensile strength 1250 N / mm ² ) (negative electrode current collector), dried and then pressed. As a result, a negative electrode current collector having a negative electrode active material layer formed thereon was obtained.
Thereafter, the negative electrode current collector on which the negative electrode active material layer was formed was cut into a rectangle having a length of 55 mm and a width of 870 mm.

Next, in order to form an oxide insulating layer, 90 wt% of SiO ₂ powder (average particle size: 6 μm) and 10 wt% of polyvinylidene fluoride (PVdF) binder are added to NMP and mixed to prepare a slurry. did.
An oxide insulating layer is formed on the outer edge of the negative electrode active material layer formed on one surface of the negative electrode current collector with the slurry facing one surface of the negative electrode current collector on which the negative electrode active material layer is formed facing upward. The slurry was applied so as to have a predetermined thickness t1 and width D1. At this time, a part of the slurry applied on the negative electrode active material layer protruded from the outer peripheral portion of the negative electrode active material layer to the end face side of the negative electrode current collector. As a result, the slurry was also applied to the end face of the negative electrode current collector.

Next, the oxide insulating layer has a predetermined thickness t2 and width D2 on the outer edge of the negative electrode active material layer formed on the other surface of the negative electrode current collector with the other surface of the negative electrode current collector facing upward. The slurry was applied as follows. At this time, a part of the slurry applied on the negative electrode active material layer protruded from the outer peripheral portion of the negative electrode active material layer to the end face side of the negative electrode current collector. By this, from the outer periphery of the negative electrode active material layer formed on one surface of the negative electrode current collector, the outer edge on one surface side, the end surface of the negative electrode current collector, and the other surface of the negative electrode current collector The slurry was continuously applied to the outer periphery of the negative electrode active material layer on the other surface side, covering the outer edge of the formed negative electrode active material layer.
Thereafter, the applied slurry was dried and pressed to obtain a negative electrode of Example 1 having an oxide insulating layer having a cross-sectional shape shown in FIG.

The width D1 of the oxide insulating layer on one surface of the obtained negative electrode was 6 mm, and the thickness t1 in the direction perpendicular to the surface of the negative electrode active material layer was 12 μm. The width D2 of the oxide insulating layer on the other surface of the negative electrode was 4 mm, and the thickness t2 in the direction perpendicular to the surface of the negative electrode active material layer was 8 μm. The electric resistivity of the oxide insulating layer was 3.2 × 10 ⁸ Ωm.

<Preparation of positive electrode>
90% by weight of lithium nickel manganese cobalt composite oxide (LiNi _1/3 Mn _1/3 Co _1/3 O ₂ ) powder as a positive electrode active material, 5% by weight of acetylene black (positive electrode conductive agent), polyvinylidene fluoride ( PVdF) (binder) 5 wt% was added to N-methylpyrrolidone and mixed to prepare a slurry.
The obtained slurry was applied to an aluminum foil (positive electrode current collector) having a thickness of 15 μm, dried, and then pressed. Then, it cut | disconnected into the rectangle of length 54mm and width 850mm, and produced the positive electrode of Example 1 which has a positive electrode active material layer with a density of 3.2 g / cm < ³ >.

<Production of electrode group>
The negative electrode of Example 1, a separator made of a polyethylene porous film, the positive electrode of Example 1, and the separator were laminated in this order to obtain a laminate. The laminate was wound in a spiral shape so that the negative electrode was located on the outermost periphery, and the electrode group of Example 1 was produced.

<Preparation of non-aqueous electrolyte>
Ethylene carbonate (EC) and methyl ethyl carbonate (MEC) were mixed at a volume ratio of 1: 2 to obtain a mixed solvent. A nonaqueous electrolyte was prepared by dissolving 1.0 mol / L of lithium hexafluorophosphate (LiPF ₆ ) in this mixed solvent.

<Preparation of nonaqueous electrolyte secondary battery>
The electrode group of Example 1 and the above non-aqueous electrolyte were each stored in a bottomed cylindrical container made of stainless steel. Subsequently, one end of the negative electrode lead was connected to the negative electrode of the electrode group, and the other end of the negative electrode lead was connected to a bottomed cylindrical container that also served as the negative electrode terminal. In addition, an insulating sealing plate having a positive electrode terminal fitted in the center was prepared. Then, one end of the positive electrode lead was connected to the positive electrode terminal, and the other end of the positive electrode lead was connected to the positive electrode of the electrode group. Thereafter, a cylindrical nonaqueous electrolyte secondary battery having a capacity of 3 Ah was assembled by caulking an insulating sealing plate in the upper opening of the container.
The obtained secondary battery was charged at 4.3 V in a 0.2 C rate and 25 ° C. environment, and then discharged at a 0.2 C rate until 2 V was reached. Thereafter, charge and discharge were repeated once at a 1C rate in a 25 ° C. environment, and the initial discharge capacity was confirmed.

(Examples 2 to 7)
The conditions shown in Table 1 as the negative electrode (the material of the negative electrode active material, the tensile strength of the negative electrode current collector, the material of the oxide insulating layer, the width of the oxide insulating layer on one side and the other side (D1 / D2) In the same manner as in Example 1, except that the surface of the negative electrode active material layer of the oxide insulating layer on one side and the other side was used in the vertical direction (t1 / t2), non-aqueous An electrolyte secondary battery was produced and the initial discharge capacity was confirmed.
Table 1 also shows the mass ratio of Examples 5 to 7 using two types of materials as the negative electrode active material and the mass ratio of Examples 5 to 6 using two types of materials as the oxide insulating layer.
The electrical resistivity of the oxide insulating layers of Examples 2 to 7 was 10 ⁶ Ωm or more.

(Example 8)
90% by weight of graphite (natural graphite) as a negative electrode active material and 10% by weight of polyvinylidene fluoride (PVdF) (binder) are added to an organic solvent N-methylpyrrolidone (NMP) and mixed to obtain a slurry. Was prepared.
The resulting slurry was applied onto both sides entire thickness 12μm copper foil (tensile strength 420N / mm 2) ^(negative electrode current collector), dried, and pressed. As a result, a negative electrode current collector having a negative electrode active material layer formed thereon was obtained.
A non-aqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that a negative electrode current collector having a negative electrode active material layer formed in this manner, and the initial discharge capacity was confirmed.
Note that the electrical resistivity of the oxide insulating layer of Example 8 was 10 ⁶ Ωm or more.

Example 9
<Production of negative electrode>
A negative electrode current collector having the same negative electrode active material layer as that of Example 1 was produced. Thereafter, the negative electrode current collector on which the negative electrode active material layer was formed was cut into a rectangular shape having a length of 77 mm and a width of 88 mm. When the negative electrode current collector was cut, it was punched out from the central part of one vertical side leaving a tab for taking out the lead (negative electrode terminal 36 in FIG. 5).
After that, an oxide insulating layer was formed so as to satisfy the conditions shown in Table 1 for three sides other than the one side where the tabs exist.
The electrical resistivity of the oxide insulating layer of Example 9 was 10 ⁶ Ωm or more.

<Preparation of positive electrode>
A positive electrode current collector on which a positive electrode active material layer similar to that in Example 1 was formed was produced. Thereafter, the positive electrode current collector on which the positive electrode active material layer was formed was cut into a rectangular shape having a length of 75 mm and a width of 86 mm. As with the negative electrode, when the positive electrode current collector was cut, it was punched out from the central portion of one vertical side leaving a tab for lead extraction (positive electrode terminal 37 in FIG. 5).

<Production of electrode group>
An electrode group was prepared using the negative electrode and positive electrode prepared above and a polyethylene porous film having a thickness of 20 μm as a separator. The positive electrode, the separator, the negative electrode, and the separator were stacked in this order to form a laminate. This laminate was laminated so that the outermost layer was a negative electrode. The produced laminate was pressed while being heated at 90 ° C. to produce a flat electrode group.

<Preparation of nonaqueous electrolyte secondary battery>
The obtained electrode group was accommodated in a bag-shaped exterior member and vacuum-dried at 80 ° C. for 24 hours. The exterior member is formed of a laminate film having a thickness of 0.1 mm, which includes an aluminum foil having a thickness of 40 μm and a polypropylene layer formed on both surfaces of the aluminum foil.
A non-aqueous electrolyte similar to that in Example 1 was injected into the exterior member that accommodated the electrode group, and sealed to produce a non-aqueous electrolyte secondary battery shown in FIG. This battery had a capacity of 3 Ah. For the nonaqueous electrolyte secondary battery of Example 9, the initial discharge capacity was confirmed in the same manner as in Example 1.

(Comparative Example 1)
A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that the oxide insulating layer was not formed, and the initial discharge capacity was confirmed.
(Comparative Example 2)
A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 8 except that the oxide insulating layer was not formed, and the initial discharge capacity was confirmed.

The non-aqueous electrolyte secondary batteries of Examples 1 to 9 and Comparative Examples 1 and 2 were charged to 4.3 V at a 1C rate in a 25 ° C. environment and then stored in an environment of −30 ° C. for 1 week. After that, a discharge test was conducted up to 2V without charging, the discharge capacity after storage was confirmed, and the remaining capacity ratio (remaining capacity ratio = (discharge capacity after storage / initial discharge capacity) × 100 (%)) Calculated. The remaining capacity rate is an index indicating the degree of internal short circuit of the nonaqueous electrolyte secondary battery. Table 2 shows the results of the remaining capacity ratios of Examples 1 to 9 and Comparative Examples 1 and 2.

In Examples 1 to 7 in which the oxide insulating layer was formed, it was confirmed that the residual capacity ratio was higher than that in Comparative Example 1 in which the oxide insulating layer was not formed.
In Example 8 in which the oxide insulating layer was formed, the residual capacity ratio was higher than that in Comparative Example 2 in which the oxide insulating layer was not formed. In Example 9 in a different form, the residual capacity ratio was high as in Examples 1-7.
From the results of Examples 1 to 9 and Comparative Examples 1 and 2, it is possible to effectively suppress internal short circuit by forming an oxide insulating layer even when a negative electrode active material having a large volume change due to charge / discharge is used. I understood.

According to at least one embodiment described above, the negative electrode current collector, the negative electrode active material layer formed on one or both surfaces of the negative electrode current collector, and the oxidation covering at least a part of the outer edge of the negative electrode active material layer By using a negative electrode having a physical insulating layer, an internal short circuit in a battery using the negative electrode can be prevented.

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

DESCRIPTION OF SYMBOLS 3 ... Negative electrode, 3a ... Negative electrode collector, 3b ... Negative electrode active material layer, 4 ... Separator, 5 ... Positive electrode, 5a ... Positive electrode collector, 5b ... Positive electrode active material layer, 10 ... Nonaqueous electrolyte secondary battery (battery 11a ... one surface, 11b ... the other surface, 11c ... end face, 12a ... outer edge, 12b ... outer periphery, 13 ... oxide insulating layer, 14 ... first region, 15 ... second region

Claims (7)

1. A negative electrode current collector;
   A negative electrode active material layer formed on one or both sides of the negative electrode current collector;
   The negative electrode for nonaqueous electrolyte secondary batteries which has an oxide insulating layer which coat | covers at least one part of the outer edge of the said negative electrode active material layer.
2. The negative electrode for a nonaqueous electrolyte secondary battery according to claim 1, wherein the oxide insulating layer contains one or more selected from SiO ₂ , Al ₂ O ₃ , and ZrO ₂ .
3. 3. The negative electrode for a non-aqueous electrolyte secondary battery according to claim 1, wherein the oxide insulating layer has a thickness in a direction perpendicular to a surface of the negative electrode active material layer of 1 μm or more and 15 μm or less.
4. The negative electrode for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 3, wherein the negative electrode current collector is a metal foil having a tensile strength of 500 N / mm ² or more and 2000 N / mm ² or less.
5. The non-aqueous solution according to any one of claims 1 to 4, wherein the negative electrode active material layer includes a negative electrode active material containing one or more selected from silicon, a silicon-containing oxide, tin, and a tin-containing oxide. Negative electrode for electrolyte secondary battery.
6. A nonaqueous electrolyte secondary battery comprising the negative electrode for a nonaqueous electrolyte secondary battery according to any one of claims 1 to 5, a positive electrode including a positive electrode active material layer, and a nonaqueous electrolyte.
7. A battery pack comprising the nonaqueous electrolyte secondary battery according to claim 6.

Images