JP6794973B2 - Non-aqueous electrolyte secondary battery - Google Patents

Description

The present disclosure relates to a non-aqueous electrolyte secondary battery.

Japanese Unexamined Patent Publication No. 2009-064560 (Patent Document 1) discloses an aluminum alloy foil for a current collector.

JP-A-2009-064560

Patent Document 1 discloses an aluminum alloy foil for a current collector, which contains manganese, iron, magnesium, and the balance is aluminum and unavoidable impurities. It is considered that the aluminum alloy foil for the current collector does not have lower corrosion resistance than the aluminum foil, and even if the thickness of the foil is 15 μm or less, it does not break in the electrode manufacturing process.

However, it is considered that the current collector manufactured by using the aluminum alloy foil for the current collector disclosed in Patent Document 1 has a melting point of about 630 ° C. or higher and 660 ° C. or lower. Therefore, when a short circuit occurs due to nail sticking or the like, it takes time to blow the current collector, and the short circuit may continue for a long time. Therefore, the heat generated by the battery becomes large, and the battery temperature may rise, resulting in insufficient safety. Further, due to the nature of a battery (for example, an in-vehicle battery), it is desired that the battery capacity is maintained even after high temperature storage.

An object of the present disclosure is to provide a non-aqueous electrolyte secondary battery in which both suppression of temperature rise during nailing and maintenance of battery capacity after high temperature storage are achieved.

Hereinafter, the technical configuration and the action and effect of the present disclosure will be described. However, the mechanism of action of the present disclosure includes estimation. The scope of claims should not be limited by the correctness of the mechanism of action.

[1] A non-aqueous battery includes a positive electrode having a positive electrode current collector and a positive electrode mixture layer provided on the surface of the positive electrode current collector. The positive electrode current collector is an aluminum (Al) alloy. The aluminum (Al) alloy contains at least copper (Cu) and, if desired, magnesium (Mg). The amount α (mass%) of magnesium (Mg) contained in the positive electrode current collector and the amount β (mass%) of copper (Cu) contained in the positive electrode current collector satisfy the following (1) to (3). ..
0 ≦ α ≦ 1.5 ・ ・ ・ (1)
2.7 ≤ β ≤ 5.0 ... (2)
3.4 ≤ (α + β) ≤ 5.9 ... (3)

FIG. 1 is a conceptual diagram of a first cross section for explaining the mechanism of action of the present disclosure.
FIG. 1 shows a part of a non-aqueous electrolyte secondary battery (hereinafter, also simply referred to as “battery”) when nail sticking occurs. The battery includes a positive electrode 10 having a positive electrode current collector 11 and a positive electrode mixture layer 12 provided on the surface of the positive electrode current collector 11.

As shown in FIG. 1, when nail piercing occurs, the positive electrode 10 and the negative electrode are short-circuited with low resistance via the nail 70, which is a low resistor, and a large Joule heat is generated. It is considered that the Joule heat melts the separator around the nail 70 and causes the positive electrode mixture layer 12 and the negative electrode mixture layer to come into contact with each other, and a larger short-circuit current continuously flows to generate heat, leading to thermal runaway. The Joule heat is the heat generated when a current flows through a conductor having resistance (for example, the positive electrode 10), and the amount of heat is the square of the flowing current, the resistance of the conductor, and the time during which the current flows. Is proportional to the product of. That is, the longer the short circuit time, the more Joule heat is generated.

FIG. 2 is a conceptual diagram of a second cross section for explaining the mechanism of action of the present disclosure.
As shown in FIG. 2, when the nail 70 is stuck in the battery according to the present disclosure, it is expected that the battery temperature rise at the time of nail sticking is suppressed by the following events (1) and (2).
(1) It is considered that the melting point of the positive electrode current collector 11 (Al alloy) is lowered by containing a predetermined amount of Cu and, if desired, a predetermined amount of Mg in the Al alloy (positive electrode current collector 11). Further, it is considered that the electron resistivity of the positive electrode current collector 11 increases and the specific heat of the positive electrode current collector 11 decreases (that is, the temperature of the positive electrode current collector 11 tends to increase).
(2) The temperature of the positive electrode current collector 11 around the nail 70 rises due to the heat generated by the short circuit. It is considered that the heat generation rate of the positive electrode current collector 11 is increased as compared with the normal because the specific heat of the positive electrode current collector 11 is lowered as described above. In addition, it is considered that the melting point of the positive electrode current collector 11 has decreased. Therefore, it is considered that the positive electrode current collector 11 around the nail 70 is blown in a short time, the blown portion 71 is formed, and the short circuit is completed in a short time. This is expected to reduce Joule heat generated before the end of the short circuit (that is, suppress the rise in battery temperature).

FIG. 1 is a conceptual diagram of a first cross section for explaining the mechanism of action of the present disclosure. FIG. 2 is a conceptual diagram of a second cross section for explaining the mechanism of action of the present disclosure. FIG. 3 is a schematic view showing an example of the configuration of the non-aqueous electrolyte secondary battery of the present embodiment. FIG. 4 is a schematic view showing an example of the configuration of the electrode group of the present embodiment. FIG. 5 is a schematic view showing an example of the configuration of the positive electrode of the present embodiment. FIG. 6 is a schematic view showing an example of the configuration of the negative electrode of the present embodiment.

Hereinafter, embodiments of the present disclosure (also referred to as “the present embodiment” in the present specification) will be described. However, the following description does not limit the scope of claims.

<Structure of non-aqueous electrolyte secondary battery>
The battery of the present disclosure can have a conventionally known configuration as long as it includes the positive electrode current collector, the positive electrode mixture layer, and the positive electrode described below. The conventionally known configuration includes, for example, a configuration in which an electrode group having a positive electrode, a negative electrode, and a separator arranged between the positive electrode and the negative electrode is provided, and the electrode group is arranged in a battery case together with a non-aqueous electrolyte. To say. The electrode group can be in a flatly wound form (wound electrode group).

FIG. 3 is a schematic view showing an example of the configuration of the non-aqueous battery of the present embodiment. The battery 100 includes a battery case 80. The battery case 80 has a square shape (flat rectangular parallelepiped shape). However, the battery case of this embodiment may have a cylindrical shape. The battery case 80 may be made of a metal material such as Al alloy, stainless steel (SUS), iron (Fe), or a resin material. The battery case 80 may be made of a composite material of a metal material and a resin material (for example, a bag made of an aluminum laminated film).

The battery case 80 is hermetically sealed. The battery case 80 is provided with a terminal 81. The battery case 80 may include a current cutoff mechanism (CID), a gas discharge valve, a liquid injection hole, and the like (none of which are shown). The battery case 80 houses the electrode group 50 and the electrolytic solution. The electrode group 50 is electrically connected to the terminal 81.

FIG. 4 is a schematic view showing an example of the configuration of the electrode group of the present embodiment. The electrode group 50 is a winding type. That is, the electrode group 50 is configured by laminating the positive electrode 10, the separator 30, the negative electrode 20, and the separator 30 in this order, and further winding them in a spiral shape. The electrode group 50 may be formed in a flat shape. In the winding type electrode group 50, the positive electrode current collector 11 is under tension. Therefore, it is expected that the positive electrode current collector 11 is likely to be blown when nailed. However, the electrode group of this embodiment may be a laminated type. The laminated electrode group can be configured such that a plurality of positive electrodes and negative electrodes are alternately laminated while sandwiching a separator, such as a separator, a positive electrode, a separator, and a negative electrode. According to this embodiment, even if the electrode group is a laminated type, it is expected that the temperature rise at the time of nailing will be small.

<Positive electrode>
FIG. 5 is a schematic view showing an example of the configuration of the positive electrode of the present embodiment. The positive electrode 10 is a strip-shaped sheet. The positive electrode 10 includes a positive electrode current collector 11 and a positive electrode mixture layer 12. The positive electrode mixture layer 12 is formed on the surface of the positive electrode current collector 11. The positive electrode mixture layer 12 contains a positive electrode active material. That is, the battery 100 includes at least a positive electrode current collector 11 that supports a positive electrode active material. The positive electrode 10 may have a portion where the positive electrode current collector 11 is exposed from the positive electrode mixture layer 12 as a connection position with the terminal 81.

(Positive current collector)
The positive electrode current collector 11 is an Al alloy. The Al alloy contains at least Cu and, if desired, Mg. The amount α (mass%) of Mg contained in the positive electrode current collector 11 and the amount β (mass%) of Cu contained in the positive electrode current collector 11 satisfy the following (1) to (3). By satisfying these (1) to (3), it is expected that a non-aqueous electrolyte secondary battery having both suppression of temperature rise at the time of nailing and maintenance of battery capacity after high temperature storage can be obtained. To. As the Al contained in the Al alloy, not only pure Al (pure Al) but also, for example, JIS1000 series Al alloy may be used.
0 ≦ α ≦ 1.5 ・ ・ ・ (1)
2.7 ≤ β ≤ 5.0 ... (2)
3.4 ≤ (α + β) ≤ 5.9 ... (3)

When the amount of Mg α (mass%) contained in the positive electrode current collector 11 in the above (1) exceeds 1.5% by mass, it is considered that there is room for improvement in maintaining the battery capacity after high temperature storage.

In the above (2), when the amount of Cu β (mass%) contained in the positive electrode current collector 11 is less than 2.7% by mass, it is considered that the melting point of the positive electrode current collector 11 does not sufficiently decrease. Since the melting point of the positive electrode current collector 11 does not drop sufficiently, it is considered that it takes time to blow the positive electrode current collector 11 at the time of a short circuit, and the short circuit time becomes long. As a result, it is considered that there is room for improvement in reducing the total calorific value of the battery 100 (that is, there is room for improvement in suppressing the rise in battery temperature during nailing). Further, in the above (2), when the amount of Cu β (mass%) contained in the positive electrode current collector 11 exceeds 5.0% by mass, it is considered that there is room for improvement in maintaining the battery capacity after high temperature storage. Be done.

In the above (3), when the sum of the Mg amount α (mass%) and the Cu amount β (mass%) contained in the positive electrode current collector 11 (hereinafter, also referred to as “α + β”) is less than 3.4% by mass. Since the melting point of the positive electrode current collector 11 does not drop sufficiently, it is considered that it takes time to blow the positive electrode current collector 11 at the time of a short circuit, and the short circuit time becomes long. As a result, it is considered that there is room for improvement in suppressing the rise in battery temperature during nailing. Further, in the above (3), when "α + β" exceeds 5.9% by mass, it is considered that there is room for improvement in maintaining the battery capacity after high temperature storage.

(Coating layer)
For example, a coating layer having a thickness of 3 μm or more and 10 μm or less may be provided on the surface of the positive electrode current collector 11. The coating layer may contain a conductive material such as acetylene black (AB). As a result, it is expected that the battery capacity will be maintained after high temperature storage. The "battery capacity" in the present specification is, for example, the discharge capacity when the battery 100 is completely charged at the rated charging voltage and then the battery 100 is discharged to the rated discharge voltage (final voltage) at a discharge rate of 1C. To say. The discharge rate 1C means discharging at a discharge current [A] in which the time required to reach the rated discharge voltage is one hour.

(Manufacturing method of current collector)
The method for manufacturing the current collector 11 is not particularly limited, but the current collector 11 can be manufactured by, for example, the following method. First, a molten metal containing at least a pure Al plate and Cu and further containing Mg is prepared if desired. By solidifying the molten metal, for example, a plate-shaped ingot is produced. The current collector 11 can be manufactured by subjecting the ingot to hot rolling or cold rolling. The thickness of the current collector 11 can be appropriately changed according to the thickness of the target current collector 11. The current collector 11 may have a thickness of, for example, 15 to 20 μm.

(Positive electrode mixture layer)
The positive electrode mixture layer 12 is formed on the surface (both front and back surfaces) of the positive electrode current collector 11. The positive electrode mixture layer 12 may have a thickness of, for example, 10 to 200 μm. The positive electrode mixture layer 12 may include, for example, 80 to 98% by mass of the positive electrode active material, 1 to 15% by mass of the conductive material, and the binder of the rest thereof.

The positive electrode active material should not be particularly limited. The positive electrode active material is, for example, LiCoO ₂ , LiNiO ₂ , LiMnO ₂ , LiNi _1/3 Co _1/3 Mn _1/3 O ₂ , LiNi _0.82 Co _0.15 Al _0.03 O ₂ , LiMn ₂ O ₄ , LiFePO _{4 and the} like. One kind of positive electrode active material may be used alone, or two or more kinds of positive electrode active materials may be used in combination. The positive electrode active material may have, for example, an average particle size of 1 to 30 μm. The average particle size of the present specification indicates a particle size in which the cumulative volume from the fine particle side is 50% of the total volume in the volume-based particle size distribution measured by the laser diffraction / scattering method.

The conductive material should not be particularly limited. The conductive material may be, for example, acetylene black (AB), thermal black, furnace black, scaly graphite, vapor-grown carbon fiber or the like. One kind of conductive material may be used alone, or two or more kinds of conductive materials may be used in combination.

Binders should not be particularly limited either. The binder is, for example, polyvinylidene fluoride (PVdF), vinylidene fluoride-hexafluoropropylene copolymer (PVdF-HFP), polytetrafluoroethylene (PTFE), polyacrylic acid (PAA), carboxymethyl cellulose (CMC), or the like. There may be. One kind of binder may be used alone, or two or more kinds of binders may be used in combination.

<Negative electrode>
FIG. 6 is a schematic view showing an example of the configuration of the negative electrode of the present embodiment. The negative electrode 20 is a strip-shaped sheet. The negative electrode 20 includes a negative electrode current collector 21 and a negative electrode mixture layer 22. The negative electrode mixture layer 22 is supported on the surface of the negative electrode current collector 21 (current collector). The negative electrode mixture layer 22 contains a negative electrode active material. That is, the battery 100 includes at least a current collector that supports the negative electrode active material. The negative electrode 20 may have a portion where the negative electrode current collector 21 is exposed from the negative electrode mixture layer 22 as a connection position with the terminal 81.

(Negative electrode current collector)
The negative electrode current collector 21 may have a thickness of, for example, 5 to 30 μm. The negative electrode current collector 21 may be, for example, a Cu foil. The Cu foil may be a pure Cu foil or a Cu alloy foil. When the negative electrode 20 has a potential higher than the reaction potential of Li ions (charge carrier) and Al in the battery 100 (for example, when the negative electrode active material is lithium titanate), the above-mentioned positive electrode current collector 11 may be used as the negative electrode current collector 21. That is, the current collector of this embodiment may be a negative electrode current collector.

(Negative electrode mixture layer)
The negative electrode mixture layer 22 is formed on the surface (both front and back surfaces) of the negative electrode current collector 21. The negative electrode mixture layer 22 may have a thickness of, for example, 10 to 200 μm, or may have a thickness of 50 to 150 μm. The negative electrode mixture layer 22 contains, for example, 80 to 99.5% by mass of a negative electrode active material, 0 to 15% by mass of a conductive material, and the remaining binder thereof.

The negative electrode active material should not be particularly limited. The negative electrode active material may be, for example, graphite, graphitizable carbon, non-graphitizable carbon, silicon, silicon oxide, tin, tin oxide, lithium titanate or the like. One kind of negative electrode active material may be used alone, or two or more kinds of negative electrode active materials may be used in combination. For example, a material (also referred to as "amorphous coated graphite") in which natural graphite is coated with amorphous carbon such as graphitizable carbon and non-graphitizable carbon may be used. The negative electrode active material may have, for example, an average particle size of 1 to 30 μm.

The conductive material should not be particularly limited. The conductive material may be, for example, acetylene black, thermal black, furnace black or the like. One kind of conductive material may be used alone, or two or more conductive materials may be used in combination. When a negative electrode active material having high electron conductivity (for example, graphite) is used, the conductive material may not be used.

Binders should not be particularly limited either. The binder may be, for example, styrene butadiene rubber (SBR), carboxymethyl cellulose (CMC) or the like. One kind of binder may be used alone, or two or more kinds of binders may be used in combination.

<Separator>
The separator 30 is a strip-shaped sheet. The separator 30 is interposed between the positive electrode 10 and the negative electrode 20. The separator 30 is an electrically insulating porous film. The separator 30 may have a thickness of, for example, 9 to 30 μm (typically 16 μm). The separator 30 may be made of, for example, polyethylene (PE), polypropylene (PP), or the like. The separator 30 may have a multi-layer structure. The separator 30 may be configured, for example, by laminating a porous film made of PP, a porous film made of PE, and a porous film made of PP in this order.

The separator 30 may have a heat-resistant layer on its surface (one side or both sides). The heat-resistant layer may have a thickness of, for example, 3 to 10 μm (typically 5 μm). The heat resistant layer may include heat resistant materials and binders. The heat-resistant material may be, for example, an oxide material (for example, alumina, boehmite, titania, zirconia, magnesia, etc.), a resin material (for example, aramid, polyimide, etc.) or the like. The binder may be, for example, PVdF, PVdF-HFP, PTFE, ethylene-acrylic acid ester copolymer, SBR or the like. The amount of the binder contained in the heat-resistant layer may be, for example, 2 to 30% by mass (typically 4% by mass).

<Electrolytic solution>
The battery 100 may include an electrolytic solution. The electrolyte contains at least a lithium (Li) salt and a solvent. The electrolytic solution may contain, for example, a Li salt of 0.5 mL / l or more and 2 mL / l or less. Li salt is a supporting electrolyte. The Li salt is dissolved in the solvent. The Li salt may be, for example, LiPF ₆ , LiBF ₄ , Li [N (FSO ₂ ) ₂ ], Li [N (CF ₃ SO ₂ ) ₂ ], or the like. One Li salt may be used alone. Two or more kinds of Li salts may be used in combination.

The solvent is aprotic. That is, the electrolytic solution of this embodiment is a non-aqueous electrolyte. The solvent may be, for example, a mixture of cyclic carbonate and chain carbonate. The mixing ratio may be, for example, "cyclic carbonate: chain carbonate = 1: 9 to 5: 5 (volume ratio)".

The cyclic carbonate may be, for example, ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), fluoroethylene carbonate (FEC), or the like. One type of cyclic carbonate may be used alone. Two or more cyclic carbonates may be used in combination.

The chain carbonate may be, for example, dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC) or the like. One type of chain carbonate may be used alone. Two or more chain carbonates may be used in combination.

The solvent may include, for example, lactone, cyclic ether, chain ether, carboxylic acid ester and the like. The lactone may be, for example, γ-butyrolactone (GBL), δ-valerolactone and the like. The cyclic ether may be, for example, tetrahydrofuran (THF), 1,3-dioxolane, 1,4-dioxane or the like. The chain ether may be 1,2-dimethoxyethane (DME) or the like. The carboxylic acid ester may be, for example, methylformate (MF), methylacetate (MA), methylpropionate (MP) or the like.

The electrolytic solution may further contain various functional additives in addition to the Li salt and the solvent. The electrolytic solution may contain, for example, 1% by mass or more and 5% by mass or less of a functional additive. Examples of the functional additive include a gas generating agent (overcharge additive), a SEI (solid electrolyte interface) film forming agent, and the like. The gas generating agent may be, for example, cyclohexylbenzene (CHB), biphenyl (BP) or the like. Examples of the SEI film-forming agent include vinylene carbonate (VC), vinylethylene carbonate (VEC), Li [B (C ₂ O ₄ ) ₂ ], LiPO ₂ F ₂ , propane sulton (PS), and ethylene sulfide (ES). ) Etc. may be used.

The battery 100 of the present embodiment may contain a gel electrolyte and a solid electrolyte instead of the electrolytic solution (liquid electrolyte). The battery 100 may further contain a gel electrolyte and a solid electrolyte in addition to the electrolyte.

<Use, etc.>
The battery 100 of the present embodiment is expected to have both suppression of temperature rise at the time of nail sticking and maintenance of battery capacity after high temperature storage. Examples of applications in which such characteristics are utilized include driving power sources for hybrid vehicles (HVs), plug-in hybrid vehicles (PHVs), electric vehicles (EVs), and the like. However, the use of the battery 100 of the present embodiment should not be limited to in-vehicle use. The battery 100 of this embodiment can be applied to all uses.

Examples will be described below. However, the following examples do not limit the scope of claims.

<Example 1>
1. 1. Manufacture of positive electrode current collector The following materials were prepared.
Pure Al plate: (Mg: 0.1% by mass or less, Cu: 0.1% by mass or less, Al: 99.3% by mass or more)
Cu source: Copper powder (Cu)

The pure Al plate and copper powder were melted by high frequency induction heating. As a result, a molten metal containing pure Al and Cu was prepared. An ingot was produced by solidifying the molten metal. The obtained ingot was homogenized at a temperature of 600 ° C. for 10 hours and then rolled to a thickness of 1 mm by hot rolling. Then, it was rolled to a thickness of 15 μm by performing hot rolling and cold rolling. From the above, the positive electrode current collector 11 (thickness 15 μm) was manufactured. The positive electrode current collector 11 contained 3.4% by mass of Cu.

2. 2. Manufacture of positive electrode The following materials were prepared.
Positive electrode active material: LiNi _1/3 Co _1/3 Mn _1/3 O ₂ (NCM)
Conductive material: AB
Binder: PVdF
Solvent: N-methyl-2-pyrrolidone (NMP)

A positive electrode paste was prepared by mixing NCM, AB, PVdF and NMP. The positive electrode paste was applied to the surfaces (both front and back surfaces) of the positive electrode current collector 11 obtained above and dried. As a result, the positive electrode mixture layer 12 was formed. The positive electrode mixture layer 12 was rolled. The positive electrode mixture layer 12 after rolling had a thickness of 150 μm. As a result, the positive electrode 10 was manufactured. The positive electrode 10 was cut into a strip shape.

3. 3. Manufacture of negative electrode The following materials were prepared.
Negative electrode active material: Amorphous coated graphite binder: CMC, SBR
Solvent: Water (ion-exchanged water)
Negative electrode current collector: Cu foil (thickness: 10 μm)

Amorphous coated graphite, CMC, SBR and water were added and stirred to prepare a paste-like negative electrode mixture (hereinafter, referred to as “negative electrode mixture paste”). In the negative electrode mixture paste, the solid content was set to "amorphous coated graphite: CMC: SBR = 98: 1: 1" in terms of mass ratio. The paste for the negative electrode mixture layer was applied to the surface (both front and back surfaces) of the negative electrode current collector 21 and dried. As a result, the negative electrode mixture layer 22 was formed. As a result, the negative electrode was formed. The negative electrode was rolled and cut into strips. The thickness of the negative electrode mixture layer 22 was set to 80 μm.

4. Assembly A strip-shaped separator 30 was prepared. The separator 30 has a thickness of 16 μm. The separator 30 is formed by laminating a porous film made of PP, a porous film made of PE, and a porous film made of PP in this order.

The positive electrode 10, the separator 30, the negative electrode 20, and the separator 30 were laminated in this order, and further wound in a spiral shape to produce an electrode group 50. The electrode group 50 was formed into a flat shape. The width dimension (dimension in the X-axis direction in FIGS. 3 and 4) of the electrode group 50 after molding was set to 130 mm. The height dimension of the electrode group 50 after molding (dimensions in the Z-axis direction of FIGS. 3 and 4) was set to 50 mm. A terminal was connected to the electrode group 50. The electrode group 50 was housed in the battery case 80.

An electrolytic solution having the following composition was prepared.
Solvent: [EC: EMC: DMC = 3: 3: 4]
Li salt: LiPF ₆ (1.1 mol / l)

The electrolyte was injected into the battery case 80. The battery case 80 was sealed. From the above, the battery according to Example 1 was manufactured. The capacity ratio (negative electrode capacity / positive electrode capacity) was 1.8.

<Examples 2 to 6, Comparative Examples 1 to 6>
As shown in Table 1 below, the battery was manufactured in the same manner as in Example 1 except that the composition ratio of each component in the positive electrode current collector 11 was changed. Magnesium nitrate (Mg (NO ₃ ) ₂ ) was used as the Mg source.

<Comparative Example 7>
AB, PTFE and NMP were mixed to prepare a slurry. The solid content was set to "AB: PTFE = 50: 50" in terms of mass ratio. The slurry was applied to the surface (both front and back surfaces) of the positive electrode current collector 11 and dried. As a result, a coating layer was formed. Except that the coating layer having a thickness of 5 μm was provided on the surface (both front and back surfaces) of the positive electrode current collector 11 in this way, and the composition ratio of each component in the positive electrode current collector 11 was changed. A battery was manufactured in the same manner as in Example 1.

<Nail piercing test>
The battery was charged to 4.25V in a 25 ° C environment by the constant current constant voltage (CCCV) method. After that, the battery was heated to 60 ° C. A thermocouple was attached to the battery. A nail having a body diameter of 3 mm (N nail, symbol "N65") was prepared. A nail was stuck in the battery. The temperature of the battery case was monitored at a distance of 1 cm from the position where the nail was inserted. The maximum temperature reached after nailing was measured. The results are shown in the "Achieved temperature" column of Table 1 below. The lower the temperature reached, the more the battery temperature rise during nailing is suppressed.

<Initial capacity measurement test>
CCCV discharge was performed from 4.25 V to 3.0 V for the batteries according to each Example and Comparative Example, and the initial capacity [Ah] was measured. The conditions are as follows.
CCCV discharge conditions: CC current value 0.3C, termination current 0.1C.

<High temperature storage test>
After charging the batteries according to the Examples and Comparative Examples that have undergone the initial capacity measurement test to 4.25 V at a current value of 0.3 C by CCCV charging (termination current 0.1 C), the temperature is set to 60 ° C. The batteries were stored in a constant temperature bath for 60 days. After 60 days, the battery was taken out and the battery capacity after high temperature storage was measured in the same manner as the initial capacity. The capacity retention rate after high temperature storage was calculated by dividing the battery capacity after high temperature storage by the initial capacity. The results are shown in the column of "Capacity retention rate after high temperature storage" in Table 1. The larger the value of the capacity retention rate after high temperature storage, the larger the battery capacity retention rate after the high temperature storage test.

<Result>
In Examples 1 to 6, both suppression of temperature rise during nailing and maintenance of battery capacity after high temperature storage were achieved.

In Comparative Examples 1 to 4, the temperature rise during the nail piercing test is large. It is probable that the melting point of the positive electrode current collector 11 did not drop sufficiently because the contents of Cu and Mg contained in the positive electrode current collector 11 (Al alloy) were insufficient. Therefore, it is considered that it takes time to melt the positive electrode current collector 11 by Joule heat after nailing, the short circuit time becomes long, and the battery temperature rises.

From the results of Example 3, Comparative Example 2, Comparative Example 3 and Comparative Example 6, when the amount α (mass%) of Mg contained in the positive electrode current collector 11 exceeds 1.5% by mass, it is stored at a high temperature. It can be understood that there is room for improvement in the post-capacity retention rate.

From the results of Example 1, Example 2, Comparative Example 1, Comparative Example 4 and Comparative Example 5, the sum of the amount α (mass%) of Mg and the amount β (mass%) of Cu contained in the positive electrode current collector. When it exceeds 5.9% by mass, it can be understood that although the temperature rise at the time of nailing is suppressed, there is room for improvement in the capacity retention rate after high temperature storage.

From the comparison between Example 1, Example 2 and Comparative Example 5 and Examples 3 to 6, the positive electrode current collector 11 contains both Cu and Mg, and the positive electrode current collector 11 contains both Cu and Mg. The amount α (mass%) of Mg contained and the amount β (mass%) of Cu contained in the positive electrode current collector 11 are 0 ≦ α ≦ 1.5, 2.7 ≦ β ≦ 5.0, and 3. When .4 ≦ (α + β) ≦ 5.9 is satisfied, it can be understood that the suppression of the temperature rise at the time of nailing is remarkably achieved while maintaining the battery capacity after high temperature storage.

From the results of Comparative Example 5 and Comparative Example 7, it can be understood that the capacity retention rate after high temperature storage is improved by providing the coating layer containing the conductive material on the surface of the positive electrode current collector 11.

The above embodiments and examples are exemplary in all respects and are not restrictive. The technical scope defined by the description of the scope of claims includes all changes within the meaning and scope equivalent to the scope of claims.

10 Positive electrode, 11 Positive electrode current collector, 12 Positive electrode mixture layer, 20 Negative electrode, 21 Negative electrode current collector, 22 Negative electrode mixture layer, 30 Separator, 50 Electrode group, 70 nails, 71 Fused part, 80 Battery case, 81 terminals , 100 batteries (non-aqueous electrolyte secondary batteries).

Claims (1)

A positive electrode having a positive electrode current collector and a positive electrode mixture layer provided on the surface of the positive electrode current collector is provided.
A coating layer having a thickness of 3 μm or more and 10 μm or less is provided on the surface of the positive electrode current collector.
The coating layer contains a conductive agent and contains
The positive electrode current collector is an aluminum alloy.
The aluminum alloy contains at least copper and contains
The aluminum alloy further contains magnesium, if desired.
The amount α (mass%) of magnesium contained in the positive electrode current collector and the amount β (mass%) of copper contained in the positive electrode current collector satisfy the following (1) to (3), non-aqueous electrolytes. Secondary battery.
0 ≦ α ≦ 1.5 ・ ・ ・ (1)
2.7 ≤ β ≤ 5.0 ... (2)
3.4 ≤ (α + β) ≤ 5.9 ... (3)

Images