JP2019046733A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

To provide a non-electrolytic secondary battery in which both suppression of increase in battery resistance and suppression of increase in battery temperature at the time of abnormality are achieved.SOLUTION: A nonaqueous electrolyte secondary battery includes at least an electrode mixture layer, a separator, and an intermediate layer. The intermediate layer is disposed between the electrode mixture layer and the separator. The intermediate layer includes a combustion inhibitor layer and a heat resistant layer. The combustion inhibitor layer includes a combustion inhibitor. The heat resistant layer includes an inorganic filler and does not include a combustion inhibitor. The heat resistant layer is disposed between the combustion inhibitor layer and the electrode mixture layer.SELECTED DRAWING: Figure 1

Description

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

  Japanese Patent Application Laid-Open No. 2015-118841 (Patent Document 1) discloses that at least one of a positive electrode and a negative electrode contains a part of an intermediate layer containing a combustion inhibitor such as melamine polyphosphate, that is, an electrode mixture layer. Is disclosed to contain a combustion inhibitor. In addition, the “electrode mixture layer” in the present specification is a general term for the positive electrode mixture layer and the negative electrode mixture layer, and when it means the positive electrode mixture layer, when it means the negative electrode mixture layer, or It may mean both the positive electrode mixture layer and the negative electrode mixture layer.

Japanese Patent Laying-Open No. 2015-118841

  However, in a non-aqueous electrolyte secondary battery (hereinafter also simply referred to as “battery”) in which a positive electrode mixture layer contains a combustion inhibitor, the combustion inhibitor is oxidized and decomposed under the influence of the positive electrode potential. Resistance may increase. In addition, in a battery in which a combustion inhibitor is included in the negative electrode mixture layer, the combustion inhibitor may be reduced and decomposed under the influence of the negative electrode potential, resulting in an increase in battery resistance. Therefore, the battery in which the combustion inhibitor is included in the positive electrode mixture layer or the negative electrode mixture layer (that is, the electrode mixture layer) has room for improvement in suppression of battery resistance.

  In addition, in the battery in which the electrode mixture layer contains the combustion inhibitor, the combustion inhibitor may be decomposed as described above. Therefore, the battery temperature may increase in an abnormal state (for example, during nail penetration). There is a possibility that the suppression will be insufficient.

  An object of the present disclosure is to provide a nonaqueous electrolyte secondary battery in which suppression of increase in battery resistance and suppression of increase in battery temperature at the time of abnormality are compatible.

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

  The nonaqueous electrolyte secondary battery includes at least an electrode mixture layer, a separator, and an intermediate layer. The intermediate layer is disposed between the electrode mixture layer and the separator. The intermediate layer includes a combustion inhibitor layer and a heat resistant layer. The combustion inhibitor layer includes a combustion inhibitor. The heat-resistant layer contains an inorganic filler and does not contain a combustion inhibitor. The heat-resistant layer is disposed between the combustion inhibitor layer and the electrode mixture layer.

  In the combustion inhibitor layer, a heat-resistant layer not containing a combustion inhibitor is disposed between the combustion inhibitor layer and the electrode mixture layer so that the combustion inhibitor does not directly contact the electrode mixture layer. Therefore, it is thought that decomposition | disassembly of the combustion inhibitor contained in a combustion inhibitor layer is suppressed, and the increase in battery resistance is suppressed. Furthermore, since the decomposition of the combustion inhibitor is suppressed, it is considered that the rise in battery temperature is suppressed at the time of an abnormality in which the positive electrode and the negative electrode are short-circuited through the conductive foreign matter, for example, during a nail penetration test. Specifically, when the nail is pierced, the electrode and the combustion inhibitor are brought into contact with each other to be affected by the potential, the combustion inhibitor is decomposed, and a decomposition product of the combustion inhibitor is generated. Such a decomposition product functions as a catalyst to carbonize the electrolytic solution and the binder, and a carbonized layer is formed around the positive electrode active material. Oxygen supply from the positive electrode active material is blocked by the carbonized layer formed around the positive electrode active material, combustion is suppressed, and an increase in battery temperature is suppressed. In the battery according to the present disclosure, since decomposition of the combustion inhibitor contained in the intermediate layer is suppressed, a sufficient amount of carbonized layer is formed around the positive electrode active material, and an increase in battery temperature is expected to be suppressed. The That is, it is expected that suppression of increase in battery resistance and suppression of increase in battery temperature at the time of abnormality are compatible.

FIG. 1 is a cross-sectional view illustrating a detailed configuration of the battery according to the present embodiment. FIG. 2 is a cross-sectional view showing another detailed configuration of the battery according to the present embodiment.

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

<Configuration of non-aqueous electrolyte secondary battery>
The nonaqueous electrolyte secondary battery of the present disclosure has a conventionally known configuration as long as it includes an electrode mixture layer (a positive electrode mixture layer and / or a negative electrode mixture layer), a separator, and an intermediate layer described below. Can do. The conventionally known configuration includes, for example, an electrode group having a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode, and the electrode group is disposed in a battery case together with a nonaqueous electrolyte. Say. The electrode group can have a flatly wound form (winding electrode group) or a laminated form (laminated electrode group).

<Positive electrode>
The positive electrode includes a positive electrode current collector and a positive electrode mixture layer formed on the main surface of the positive electrode current collector. The positive electrode current collector may be, for example, an aluminum (Al) foil. The positive electrode current collector may have a thickness of 10 to 30 μm, for example.

<< Positive electrode mixture layer >>
The positive electrode mixture layer includes a positive electrode active material, a conductive material, and a binder. The positive electrode mixture layer may include, for example, 80 to 98% by weight of the positive electrode active material, 1 to 15% by weight or less of a conductive material, and 1 to 5% by weight or less of a binder. The positive electrode mixture layer may have a thickness of 100 to 200 μm, for example.

(Positive electrode active material, conductive material and binder)
The positive electrode active material, the conductive material, and the binder should not be particularly limited. Examples of the positive electrode active material include LiCoO ₂ , LiNiO ₂ , LiNi _1/3 Co _1/3 Mn _1/3 O ₂ (NCM), LiNi _0.8 Co _0.15 Al _0.05 O ₂ (NCA), LiMnO _2. LiMn ₂ O ₄ , LiFePO ₄ or the like may be used. The conductive material may be, for example, acetylene black (AB), furnace black, vapor grown carbon fiber (VGCF), graphite or the like. The binder may be, for example, polyvinylidene fluoride (PVdF), styrene butadiene rubber (SBR), polytetrafluoroethylene (PTFE), or the like.

<Negative electrode>
The negative electrode includes a negative electrode current collector and a negative electrode mixture layer formed on the main surface of the negative electrode current collector. The negative electrode current collector may be, for example, a copper (Cu) foil. The negative electrode current collector may have a thickness of about 5 to 20 μm, for example.

<Negative electrode mixture layer>
The negative electrode mixture layer includes a negative electrode active material and a binder. The negative electrode mixture layer may include, for example, 95 to 99% by mass of a negative electrode active material and 1 to 5% by mass of a binder. The negative electrode mixture layer may have a thickness of about 50 to 150 μm, for example.

(Negative electrode active material and binder)
The negative electrode active material and the binder should not be particularly limited. Examples of the negative electrode active material include amorphous coated graphite (graphite particles whose surface is coated with amorphous carbon), graphite, graphitizable carbon, non-graphitizable carbon, silicon, silicon oxide, tin, tin oxide, and the like. It may be. The binder may be, for example, carboxymethyl cellulose (CMC), styrene butadiene rubber (SBR), or the like.

<Separator>
The separator electrically isolates the positive electrode and the negative electrode. The separator is preferably a microporous film such as polyethylene (PE) or polypropylene (PP). The separator may have a single-layer structure of PE, or may have a three-layer structure in which a PP film, a PE film, and a PP film are stacked in this order. The thickness of the separator may be about 9 to 30 μm, for example. When the separator has the above-described three-layer structure, the thickness of the PE layer may be, for example, about 3 to 10 μm, and the thickness of the PP layer may be, for example, about 3 to 10 μm. The separator may include a heat resistant layer on the surface thereof. The heat resistant layer includes a heat resistant material. Examples of the heat resistant material include metal oxide particles such as alumina, and a high melting point resin such as polyimide.

《Middle layer》
As shown in FIG. 1, the intermediate layer 20 is disposed between the electrode mixture layer and the separator 300. The intermediate layer 20 includes a combustion inhibitor layer 11 and a heat resistant layer 12. The electrode mixture layer may be the positive electrode mixture layer 102 or the negative electrode mixture layer 202. As shown in FIG. 2, the intermediate layer 20 may be formed on both sides of the separator 300.

  The intermediate layer 20 may have a thickness of, for example, 5 μm or more and 100 μm or less. The “layer thickness” herein can be measured in an electron microscope (SEM) image of a cross section in the thickness direction of the layer. The cross-sectional sample for SEM imaging may be subjected to, for example, focused ion beam (FIB) processing. The layer thickness can be measured in at least three places. The arithmetic average of at least three thicknesses can be the layer thickness. It is desirable that the intervals between the measurement points be uniform. It is desirable that the measurement locations are separated from each other by 10 mm or more.

(Combustion inhibitor layer)
The combustion inhibitor layer 11 contains at least a combustion inhibitor. That is, the combustion inhibitor layer 11 includes a combustion inhibitor. Combustion inhibitors include phosphate esters (eg, triphenyl phosphate), polyphosphates (eg, ammonium polyphosphate, magnesium polyphosphate, barium polyphosphate, zinc polyphosphate, nickel polyphosphate, aluminum polyphosphate), etc. Organic phosphorus flame retardants, and melamine flame retardants such as melamine cyanurate, melamine sulfate, melamine cyanurate, and melamine polyphosphate may be used. These flame retardants may be used individually by 1 type, and may be used in combination of multiple types.

  The amount of the combustion inhibitor contained in the combustion inhibitor layer 11 may be 0.3 parts by mass or more and 15 parts by mass or less with respect to 100 parts by mass of the positive electrode active material contained in the positive electrode mixture layer 102. The amount is desirably 0.5 parts by mass or more and 10 parts by mass or less, and more desirably 1 part by mass or more and 5 parts by mass or less. When the content of the combustion inhibitor in the combustion inhibitor layer 11 is less than 0.3 parts by mass with respect to 100 parts by mass of the positive electrode active material, there is a possibility that sufficient combustion suppression effects cannot be obtained. When the content of the combustion inhibitor in the combustion inhibitor layer 11 exceeds 15 parts by mass with respect to 100 parts by mass of the positive electrode active material, the battery capacity may be insufficient.

  The combustion inhibitor layer 11 may contain a binder and a thickener in addition to the combustion inhibitor. The binder may be an acrylic resin, polyvinylidene fluoride (PVdF), aramid, styrene butadiene rubber (SBR), polytetrafluoroethylene (PTFE), or the like. The thickener may be, for example, carboxymethylcellulose (CMC). The distribution of the combustion inhibitor and the binder in the combustion inhibitor layer 11 may be “combustion inhibitor: binder = 93 to 99: 1 to 7” in mass ratio.

(Heat resistant layer)
As shown in FIGS. 1 and 2, the heat-resistant layer 12 is disposed between the combustion inhibitor layer 11 and the electrode mixture layer. By disposing the heat-resistant layer 12 in this way, the combustion inhibitor such as melamine polyphosphate contained in the combustion inhibitor layer 11 is in contact with the positive electrode mixture layer 102 and is oxidatively decomposed, or the combustion inhibitor is mixed with the negative electrode composite. Reducing and decomposing in contact with the material layer 202 is suppressed. The heat-resistant layer 12 may have a thickness of 3 μm or more and 10 μm or less.

  The heat-resistant layer 12 only needs to be disposed between the combustion inhibitor layer 11 and the electrode mixture layer. For example, when manufacturing the battery, the combustion inhibitor layer 11 is formed on the separator 300 and the electrode mixture layer is formed on the electrode mixture layer. The heat-resistant layer 12 may be formed, or after the heat-resistant layer 12 is formed on the electrode mixture layer, the combustion inhibitor layer 11 may be formed on the heat-resistant layer 12, or the combustion is suppressed on the separator 300. After forming the agent layer 11, the heat-resistant layer 12 may be formed on the combustion inhibitor layer 11.

The heat-resistant layer 12 contains an inorganic filler and does not contain a combustion inhibitor. The inorganic filler contained in the heat-resistant layer 12 is, for example, alumina (α-alumina, Al ₂ O ₃ ), boehmite (AlOOH), titania (TiO ₂ ), zirconia (ZrO ₂ ), magnesia (MgO), aluminum hydroxide [Al (OH) ₃ ], magnesium hydroxide [Mg (OH) ₂ ] and the like may be used. These inorganic fillers may be used alone or in combination of two or more. Since the heat-resistant layer 12 does not contain a combustion inhibitor, it is considered that the battery resistance does not increase due to decomposition of the combustion inhibitor even if it contacts the electrode mixture layer.

  The heat-resistant layer 12 may contain a binder in addition to the inorganic filler. The binder may be an acrylic resin, polyvinylidene fluoride (PVdF), aramid, styrene butadiene rubber (SBR), polytetrafluoroethylene (PTFE), or the like. These binders may be used individually by 1 type, and may be used in combination of multiple types. The heat-resistant layer 12 may contain, for example, a binder of 2% by mass to 30% by mass.

<Nonaqueous electrolyte>
The non-aqueous electrolyte includes a lithium salt, an additive, and a solvent. The lithium salt may be, for example, LiPF ₆ or LiFSI. Examples of the additive include Li [B (C ₂ O ₄ )], LiPO ₂ F ₂ , vinylene carbonate (VC), vinyl ethylene carbonate (VEC), fluoroethylene carbonate (FEC), ethylene sulfite (ES), and propanesulfur. Ton (PS), lithium bis (trifluoromethanesulfonyl) imide (LiTFSI), LiBF ₂ (C ₂ O ₄ ), LiPF ₂ (C ₂ O ₄ ) _{2, and the} like. The solvent may be, for example, a mixture of cyclic carbonate and chain carbonate. The mixing ratio of the cyclic carbonate and the chain carbonate may be a volume ratio, for example, cyclic carbonate: chain carbonate = 1: 9 to 5: 5. Examples of the cyclic carbonate may include ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), and the like. The chain carbonate may be, for example, dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC) or the like.

<Battery case>
The battery case may be, for example, a rectangular shape (flat rectangular parallelepiped), a cylindrical shape, or a bag shape. For example, a metal such as aluminum (Al) or an Al alloy constitutes the battery case. However, as long as the battery case has a predetermined sealing property, for example, a composite material of metal and resin may constitute the battery case. Examples of the composite material of metal and resin include an aluminum laminate film. The battery case may include an external terminal, a liquid injection hole, a gas discharge valve, a current interruption mechanism (CID), and the like.

<Application>
The battery shown in the present disclosure is used as a power source for a hybrid vehicle (HV), a plug-in hybrid vehicle (PHV), an electric vehicle (EV), and the like. However, the use of the battery shown in the present disclosure should not be limited to such in-vehicle use. The battery shown in the present disclosure is applicable to all uses.

  Hereinafter, examples of the present disclosure will be described. However, the following description does not limit the scope of the claims.

<Manufacture of non-aqueous electrolyte secondary batteries>
Example 1
1. Production of positive electrode The following materials were prepared: Positive electrode active material: LiNi _0.8 Co _0.15 Al _0.05 O ₂ (NCA)
Conductive material: AB
Binder: PVdF
Solvent: N-methyl-2-pyrrolidone (NMP)
Current collector foil: Aluminum (Al) foil (thickness = 15 μm)

  With a planetary mixer, 93 parts by weight of NCA, 4 parts by weight of AB, 3 parts by weight of PVdF and NMP were mixed. As a result, a paste-like positive electrode mixture (hereinafter referred to as “positive electrode mixture paste”) was prepared. The positive electrode mixture paste was applied to the surface (both front and back surfaces) of the current collector foil by a die coater and dried. Thereby, the positive electrode mixture layer 102 was formed. The positive electrode mixture layer 102 was compressed by a roll mill. This produced a positive electrode. The positive electrode was cut to a predetermined size. The thickness of the positive electrode mixture layer 102 was 150 μm.

2. Production of negative electrode The following materials were prepared.
Negative electrode active material: amorphous coated graphite / SiO = 90/10
Thickener: CMC
Binder: SBR
Solvent: Water Negative electrode current collector foil: Cu foil (thickness 10 μm)

  Amorphous coated graphite, CMC, SBR and water were put into a stirring tank of a stirring device 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 “amorphous coated graphite / SiO: CMC: SBR = 98: 1: 1” by mass ratio. The negative electrode mixture layer paste was applied to the surface (both front and back surfaces) of the negative electrode current collector and dried. Thereby, the negative electrode mixture layer 202 was formed. Thus, a negative electrode was formed. The negative electrode was rolled and cut into strips. The thickness of the negative electrode mixture layer 202 was 80 μm.

3. Production of Combustion Inhibitor Layer 11 The following materials were prepared.
Separator base material: PE separator (thickness 16 μm)
Combustion inhibitor: Melamine polyphosphate (MPP)
Binder: PVdF
Solvent: N-methyl-2-pyrrolidone (NMP)

  A slurry was prepared by mixing MPP, PVdF and NMP. The mass of MPP contained in the slurry was 3 parts by mass with respect to 100 parts by mass of NCA contained in the positive electrode mixture layer 102. The mixing ratio is “MPP: PVdF = 95: 5 (mass ratio)”. The slurry was applied on the substrate (one side) of the PE separator 300 by a gravure coater and dried, whereby the combustion inhibitor layer 11 was formed on the PE separator 300. The thickness of the combustion inhibitor layer 11 was 5 μm.

4). Production of heat-resistant layer 12 The following materials were prepared.
Inorganic filler: α-alumina Solvent: N-methyl-2-pyrrolidone (NMP)
Binder: Acrylic resin

  A slurry was prepared by mixing α-alumina, acrylic resin and NMP. The slurry was applied to the positive electrode mixture layer 102 by a gravure coater and dried, whereby the heat resistant layer 12 was formed on the positive electrode mixture layer 102. The thickness of the heat resistant layer 12 was 5 μm, and the content of the acrylic resin in the heat resistant layer 12 was 4 mass%.

5. Preparation of non-aqueous electrolyte An electrolyte having the following composition was prepared.
Solvent composition: [EC: EMC: DMC = 3: 3: 4 (volume ratio)]
Supporting salt: LiPF ₆ (1.1 mol / L)

6). Production of Nonaqueous Electrolyte Secondary Battery A strip-shaped positive electrode, a strip-shaped negative electrode, and a strip-shaped separator were prepared. The heat-resistant layer 12 is disposed on the positive electrode mixture layer 102 included in the positive electrode, and the combustion inhibitor layer 11 is disposed on the separator substrate made of PE. The positive electrode, the separator 300, the negative electrode, and the separator 300 were laminated in this order so that the positive electrode and the negative electrode were opposed to each other with the separator interposed therebetween, and further wound in a spiral shape. Thus, an electrode group was configured. The width of the electrode group was 130 mm, and the height of the electrode group was 50 mm. Terminals were connected to the positive electrode and the negative electrode, respectively. The electrode group was housed in a battery case made of aluminum. A non-aqueous electrolyte was injected into the battery case, and the battery case was sealed. From the above, a battery including the combustion inhibitor layer 11 and the heat-resistant layer 12 (that is, the intermediate layer 20) was manufactured. The intermediate layer 20 is disposed between the positive electrode mixture layer 102 and the separator 300. The battery is cylindrical. The battery is designed to have a rated capacity of 1.0 Ah in the range of 2.5-4.1V. The capacity ratio (negative electrode capacity / positive electrode capacity) was 1.8. Thus, a nonaqueous electrolyte secondary battery according to Example 1 shown in Table 1 was obtained. The heat-resistant layer 12 faces the positive electrode, and the intermediate layer 20 is disposed between the positive electrode mixture layer 102 and the separator 300.

Example 2
A battery was produced in the same manner as in Example 1 except that the combustion inhibitor layer 11 was formed on the heat-resistant layer 12 disposed on the positive electrode mixture layer 102. The heat-resistant layer 12 faces the positive electrode, and the intermediate layer 20 is disposed between the positive electrode mixture layer 102 and the separator 300.

Example 3
A battery was produced in the same manner as in Example 1 except that the heat-resistant layer 12 was formed on the combustion inhibitor layer 11 disposed on the separator substrate (positive electrode side). The heat-resistant layer 12 faces the positive electrode, and the intermediate layer 20 is disposed between the positive electrode mixture layer 102 and the separator 300.

Example 4
A battery was produced in the same manner as in Example 1 except that the heat-resistant layer 12 was formed on the combustion inhibitor layer 11 disposed on the separator substrate (positive electrode side) and melamine sulfate was used as the combustion inhibitor. It was done. The heat-resistant layer 12 faces the positive electrode, and the intermediate layer 20 is disposed between the positive electrode mixture layer 102 and the separator 300.

Example 5
A separator made of PP / PE / PP is used as the separator substrate, the heat-resistant layer 12 is formed on the combustion inhibitor layer 11 disposed on the separator substrate (negative electrode side), and the opposing surface of the heat-resistant layer 12 is the negative electrode. A battery was manufactured in the same manner as in Example 1 except that. The heat-resistant layer 12 faces the negative electrode, and the intermediate layer 20 is disposed between the negative electrode mixture layer 202 and the separator 300.

Example 6
A separator made of PP / PE / PP is used as the separator substrate, the heat-resistant layer 12 is formed on the combustion inhibitor layer 11 disposed on the separator substrate (negative electrode side), and the opposing surface of the heat-resistant layer 12 is the negative electrode. A battery was produced in the same manner as in Example 1 except that aluminum polyphosphate was used as a combustion inhibitor. The heat-resistant layer 12 faces the negative electrode, and the intermediate layer 20 is disposed between the negative electrode mixture layer 202 and the separator 300.

Example 7
Using a separator made of PP / PE / PP as the separator base material, the combustion inhibitor layer 11 is formed on both surfaces of the separator base material, and the heat resistant layer 12 is formed on both sides of the separator base material. A battery was manufactured in the same manner as in Example 1 except that it was formed in the same manner as in Example 1. The heat-resistant layer 12 is opposed to both surfaces of the positive electrode and the negative electrode, and the intermediate layer 20 is disposed between the positive electrode mixture layer 102 and the separator 300 and between the negative electrode mixture layer 202 and the separator 300.

Example 8
Using a separator made of PP / PE / PP as the separator base material, the combustion inhibitor layer 11 is formed on both surfaces of the separator base material, and the heat resistant layer 12 is formed on both sides of the separator base material. A battery was produced in the same manner as in Example 1 except that triphenyl phosphate was used as a combustion inhibitor. The heat-resistant layer 12 is opposed to both surfaces of the positive electrode and the negative electrode, and the intermediate layer 20 is disposed between the positive electrode mixture layer 102 and the separator 300 and between the negative electrode mixture layer 202 and the separator 300.

Example 9
The heat-resistant layer 12 is formed on the combustion inhibitor layer 11 disposed on the separator substrate (positive electrode side), and the mass of MPP contained in the combustion inhibitor layer 11 is 100 parts by mass of NCA contained in the positive electrode mixture layer 102. A battery was produced in the same manner as in Example 1 except that the amount was 0.3 parts by mass. The heat-resistant layer 12 faces the positive electrode, and the intermediate layer 20 is disposed between the positive electrode mixture layer 102 and the separator 300.

Example 10
The heat-resistant layer 12 is formed on the combustion inhibitor layer 11 disposed on the separator substrate (positive electrode side), and the mass of MPP contained in the combustion inhibitor layer 11 is 100 parts by mass of NCA contained in the positive electrode mixture layer 102. A battery was produced in the same manner as in Example 1 except that the content was 0.5 parts by mass. The heat-resistant layer 12 faces the positive electrode, and the intermediate layer 20 is disposed between the positive electrode mixture layer 102 and the separator 300.

Example 11
The heat-resistant layer 12 is formed on the combustion inhibitor layer 11 disposed on the separator substrate (positive electrode side), and the mass of MPP contained in the combustion inhibitor layer 11 is 100 parts by mass of NCA contained in the positive electrode mixture layer 102. A battery was produced in the same manner as in Example 1 except that the amount was 1 part by mass. The heat-resistant layer 12 faces the positive electrode, and the intermediate layer 20 is disposed between the positive electrode mixture layer 102 and the separator 300.

Example 12
The heat-resistant layer 12 is formed on the combustion inhibitor layer 11 disposed on the separator substrate (positive electrode side), and the mass of MPP contained in the combustion inhibitor layer 11 is 100 parts by mass of NCA contained in the positive electrode mixture layer 102. A battery was produced in the same manner as in Example 1 except that the amount was 5 parts by mass. The heat-resistant layer 12 faces the positive electrode, and the intermediate layer 20 is disposed between the positive electrode mixture layer 102 and the separator 300.

Example 13
The heat-resistant layer 12 is formed on the combustion inhibitor layer 11 disposed on the separator substrate (positive electrode side), and the mass of MPP contained in the combustion inhibitor layer 11 is 100 parts by mass of NCA contained in the positive electrode mixture layer 102. A battery was produced in the same manner as in Example 1 except that the content was 10 parts by mass. The heat-resistant layer 12 faces the positive electrode, and the intermediate layer 20 is disposed between the positive electrode mixture layer 102 and the separator 300.

Example 14
The heat-resistant layer 12 is formed on the combustion inhibitor layer 11 disposed on the separator substrate (positive electrode side), and the mass of MPP contained in the combustion inhibitor layer 11 is 100 parts by mass of NCA contained in the positive electrode mixture layer 102. A battery was produced in the same manner as in Example 1 except that the content was 15 parts by mass. The heat-resistant layer 12 faces the positive electrode, and the intermediate layer 20 is disposed between the positive electrode mixture layer 102 and the separator 300.

<< Comparative Example 1 >>
Except that the combustion inhibitor layer 11 was not formed, the combustion inhibitor to be contained in the combustion inhibitor layer 11 was mixed with the positive electrode mixture layer 102, and the heat-resistant layer 12 was formed on the separator substrate (positive electrode side). Thus, a battery was manufactured in the same manner as in Example 1. The heat resistant layer 12 faces the positive electrode. Since the combustion inhibitor layer 11 is not formed, the intermediate layer 20 is not formed between the positive electrode mixture layer 102 and the separator 300.

<< Comparative Example 2 >>
A battery was manufactured in the same manner as in Example 1 except that the combustion inhibitor layer 11 was not formed and the combustion inhibitor to be contained in the combustion inhibitor layer 11 was mixed with the heat-resistant layer 12. Since the combustion inhibitor layer 11 is not formed, the intermediate layer 20 is not formed between the positive electrode mixture layer 102 and the separator 300.

<< Comparative Example 3 >>
Without forming the combustion inhibitor layer 11, the combustion inhibitor to be contained in the combustion inhibitor layer 11 is mixed with the heat-resistant layer 12, the heat-resistant layer 12 is formed on the negative electrode mixture layer 202, and PP is used as a separator substrate. A battery was produced in the same manner as in Example 1 except that a separator made of / PE / PP was used. Since the combustion inhibitor layer 11 is not formed, the intermediate layer 20 is not formed between the negative electrode mixture layer 202 and the separator 300.

<< Comparative Example 4 >>
Except that the combustion inhibitor layer 11 is not formed, the combustion inhibitor to be contained in the combustion inhibitor layer 11 is mixed with the heat resistant layer 12, and the heat resistant layer 12 is formed on the separator substrate (positive electrode side). A battery was manufactured in the same manner as in Example 1. The heat resistant layer 12 faces the positive electrode. Since the combustion inhibitor layer 11 is not formed, the intermediate layer 20 is not formed between the positive electrode mixture layer 102 and the separator 300.

<< Comparative Example 5 >>
Without forming the combustion inhibitor layer 11, a separator made of PP / PE / PP is used as a separator base material, and a combustion inhibitor to be contained in the combustion inhibitor layer 11 is mixed with the heat resistant layer 12. A battery was produced in the same manner as in Example 1 except that it was formed on the separator substrate (negative electrode side). The heat resistant layer 12 faces the negative electrode. Since the combustion inhibitor layer 11 is not formed, the intermediate layer 20 is not formed between the negative electrode mixture layer 202 and the separator 300.

<Deterioration rate measurement test due to high load charge / discharge>
In the thermostat set at a temperature of 25 ° C., the batteries (initial batteries) according to each of the unused Examples and Comparative Examples were placed. Charging was performed at a current of 2.5 C for 240 seconds, and discharging was performed at 30 C for 20 seconds as one cycle. Here, the current of 1C is a constant current that discharges a battery whose state of charge is adjusted to 100% and completes the discharge in just one hour. When performing a plurality of cycles, an interval of 120 seconds was provided between each cycle. The battery resistance after 1 cycle and 1000 cycles was measured, and the battery resistance after 1000 cycles was regarded as 100, and the battery resistance after 1000 cycles was relatively evaluated. The results are shown in the column “Deterioration Evaluation” in Table 1 below. In addition, it shows that the battery resistance after 1000 cycles is increasing, so that the value of deterioration evaluation is large.

<Nail penetration test>
The nail penetration test evaluated the heat generation during an internal short circuit. The test procedure is as follows. First, the battery was charged to 4.1 V at 25 ° C. A thermocouple was attached to the surface of the battery, and the battery was heated to 60 ° C. A φ3 mm nail was prepared. At 60 ° C., a nail was inserted into the center of the battery to forcibly cause an internal short circuit. Using a thermocouple, the maximum temperature reached on the surface of the battery after the short circuit (a place 1 cm away from the nail) was measured and evaluated. The results are shown in the “Achieved temperature” column of Table 1 below.

<Result>
The batteries according to Examples 1 to 14 show that the suppression of the increase in battery resistance and the suppression of the increase in battery temperature at the time of abnormality (when nailing) are compatible with each other in Table 1 above. From this result, in the battery including at least the electrode mixture layer, the separator 300, and the intermediate layer 20, the intermediate layer 20 is disposed between the electrode mixture layer and the separator 300, and the intermediate layer 20 is the combustion inhibitor layer. 11 and a heat-resistant layer 12, the combustion inhibitor layer 11 contains a combustion inhibitor, the heat-resistant layer 12 contains an inorganic filler, does not contain a combustion inhibitor, and the heat-resistant layer 12 In the case of being disposed between the material layers, it was shown that suppression of increase in battery resistance and suppression of increase in battery temperature at the time of abnormality are compatible.

  In Examples 1 to 14, an increase in battery resistance is suppressed as compared with Comparative Examples 1 to 5. In Examples 1 to 14, the combustion inhibitor layer 11 is disposed so as not to contact the positive electrode mixture layer 102 and the negative electrode mixture layer 202. Thereby, it is suppressed that combustion inhibitors such as MPP are in contact with the positive electrode mixture layer 102 and are oxidatively decomposed, and that the combustion inhibitor is in contact with the negative electrode mixture layer 202 and are reduced and decomposed, thereby increasing battery resistance. Is considered to be suppressed. In Comparative Example 1, it is considered that the combustion inhibitor mixed in the positive electrode mixture layer 102 was oxidized and decomposed, and the battery resistance was increased. In Comparative Examples 2 to 5, although the combustion inhibitor is mixed in the heat-resistant layer 12, the heat-resistant layer 12 is in contact with the positive electrode mixture layer 102 and the negative electrode mixture layer 202, so the combustion contained in the heat-resistant layer 12 It is considered that the battery resistance was increased due to oxidative decomposition or reductive decomposition of the inhibitor.

  In Examples 1 to 14, as compared with Comparative Examples 1 to 5, an increase in battery temperature at the time of abnormality (when nailing) is suppressed. In Examples 1-14, it is thought that decomposition | disassembly of a combustion inhibitor is suppressed as mentioned above. Therefore, it is considered that a sufficient carbonized layer was formed around the positive electrode active material during the nail penetration test, and the carbonized layer blocked oxygen supply from the positive electrode active material, thereby suppressing combustion. In Comparative Example 1, it is considered that a sufficient heat generation suppressing effect could not be obtained as a result of the oxidative decomposition of the combustion inhibitor mixed in the positive electrode mixture layer 102. In Comparative Examples 2 to 5, although the combustion inhibitor is mixed in the heat-resistant layer 12, the heat-resistant layer 12 is in contact with the positive electrode mixture layer 102 and the negative electrode mixture layer 202, so the combustion contained in the heat-resistant layer 12 As a result of the oxidative decomposition or reductive decomposition of the inhibitor, it is considered that a sufficient exothermic suppression effect could not be obtained.

  From the evaluation results of Examples 1 to 14, it is sufficient that the heat-resistant layer 12 is disposed between the combustion inhibitor layer 11 and the electrode mixture layer, and the combustion inhibitor layer 11 is formed on the separator 300 during battery production. Then, the heat-resistant layer 12 may be formed on the electrode mixture layer, or after the heat-resistant layer 12 is formed on the electrode mixture layer, the combustion inhibitor layer 11 may be formed on the heat-resistant layer 12. In addition, it was shown that the heat-resistant layer 12 may be formed on the combustion inhibitor layer 11 after forming the combustion inhibitor layer 11 on the separator 300.

  From the evaluation results of Examples 1, 4, 6, and 8, it was shown that MPP, melamine sulfate, aluminum polyphosphate, and triphenyl phosphate can be suitably used as the combustion inhibitor.

  From the evaluation results of Example 1 and 9 to 14, the content of the combustion inhibitor in the combustion inhibitor layer 11 is 0.3 mass with respect to 100 parts by mass of the positive electrode active material contained in the positive electrode mixture layer 102. It may be from 15 parts by weight to 15 parts by weight, preferably from 0.5 parts by weight to 10 parts by weight, and more preferably from 1 part by weight to 5 parts by weight. Example 9 in which the content of the combustion inhibitor in the combustion inhibitor layer 11 is 0.3 parts by mass with respect to 100 parts by mass of the positive electrode active material contained in the positive electrode mixture layer 102 is the ultimate temperature during the nail penetration test Was an acceptable level, but the reached temperature was slightly higher than in the other examples. Further, in Example 14 in which the content of the combustion inhibitor in the combustion inhibitor layer 11 is 15 parts by mass with respect to 100 parts by mass of the positive electrode active material contained in the positive electrode mixture layer 102, the deterioration rate due to high load charge / discharge The increase in battery resistance in the measurement test was at an acceptable level, but the degradation evaluation value was slightly higher than in the other examples.

  From the evaluation results of Example 1 and 5 to 8, it was shown that a PE separator or a PP / PE / PP separator may be used as the separator substrate.

  The embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The technical scope defined by the description of the scope of claims includes all modifications within the meaning and scope equivalent to the scope of claims.

  DESCRIPTION OF SYMBOLS 11 Combustion inhibitor layer, 12 Heat resistant layer, 20 Intermediate layer, 102 Positive electrode mixture layer (electrode mixture layer), 202 Negative electrode mixture layer (electrode mixture layer), 300 Separator.

Claims (1)

An electrode mixture layer;
A separator;
And at least an intermediate layer,
The intermediate layer is disposed between the electrode mixture layer and the separator,
The intermediate layer includes a combustion inhibitor layer and a heat-resistant layer,
The combustion inhibitor layer includes a combustion inhibitor,
The heat-resistant layer contains an inorganic filler and does not contain a combustion inhibitor,
The heat-resistant layer is disposed between the combustion inhibitor layer and the electrode mixture layer.
Non-aqueous electrolyte secondary battery.

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