JP2019079712A - Non-aqueous electrolyte secondary battery - Google Patents

Abstract

To provide a non-aqueous electrolyte secondary battery having an improved effect of suppressing heat generation at the time of short circuit due to nailing or the like.SOLUTION: A non-aqueous electrolyte secondary battery includes a positive electrode and a negative electrode. The positive electrode includes a positive electrode current collector, a positive electrode mixture layer, and an intermediate layer interposed between the positive electrode current collector and the positive electrode mixture layer. The intermediate layer includes an extreme pressure agent.SELECTED DRAWING: Figure 1

Description

  The present disclosure relates to non-aqueous electrolyte secondary batteries.

  Japanese Patent Application Laid-Open No. 2016-072221 (Patent Document 1) has high thermal conductivity and high resistivity, in which the thermal conductivity, the specific resistance, etc. of the main component are specified between the positive electrode current collector and the positive electrode mixture layer. A non-aqueous electrolyte secondary battery comprising an intermediate layer is disclosed.

JP, 2016-072221, A

  Referring to FIG. 2, in the non-aqueous electrolyte secondary battery disclosed in Patent Document 1, an intermediate layer 14 with high thermal conductivity and high resistance is disposed between positive electrode current collector 11 and positive electrode mixture layer 12. Thus, in the nailing test, even if a short circuit current (arrows in the drawing) occurs via the nail 6, heat can be efficiently dissipated from the short circuit location by the intermediate layer 14. In addition, when the nail 6 does not reach the positive electrode, the short circuit current between the positive electrode current collector 11 and the negative electrode 20 can be suppressed. Therefore, the effect of suppressing heat generation at the time of short circuit is expected. However, when the nail 6 reaches the positive electrode current collector 11 as shown in FIG. 2, the short circuit current between the positive electrode current collector 11 and the negative electrode 20 can not be suppressed, and the short circuit current is sufficiently There is room for improvement in the effect of suppressing the heat generation at the time of a short circuit due to the nail 6.

  An object of the present disclosure is to provide a non-aqueous electrolyte secondary battery having an improved effect of suppressing heat generation at the time of a short circuit due to nailing or the like.

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

A non-aqueous electrolyte secondary battery comprises a positive electrode and a negative electrode.
The positive electrode includes a positive electrode current collector, a positive electrode mixture layer, and an intermediate layer interposed between the positive electrode current collector and the positive electrode mixture layer.
The middle layer contains an extreme pressure agent.

  In the present disclosure, by providing the intermediate layer 13 between the positive electrode current collector 11 and the positive electrode mixture layer 12, a non-aqueous electrolyte secondary battery in which the effect of suppressing heat generation at the time of short circuit due to nailing or the like is improved. Provided.

FIG. 1 is a conceptual diagram for explaining the action mechanism of the present disclosure.
In the positive electrode 10 of the non-aqueous electrolyte secondary battery of the present disclosure, as shown in FIG. 1A, the intermediate layer 13 is provided between the positive electrode current collector 11 and the positive electrode mixture layer 12.

  For example, as shown in FIG. 1B, in the nailing test, it is conceivable that the positive electrode 10 (particularly, the positive electrode current collector 11) and the negative electrode 20 short-circuit through the nail 6. As a result, a short circuit current (an arrow shown in FIG. 1B) is generated, and heat generation occurs around the heat generating portion 7.

  However, since the intermediate layer 13 is provided between the positive electrode current collector 11 and the positive electrode mixture layer 12, the temperature in the intermediate layer 13 is increased by raising the temperature of the short circuit portion (heat generation portion 7) accompanying heat generation at the time of nailing. The extreme pressure agent reacts with the constituent metals of the nail 6 to form an insulating compound 8 in the vicinity of the intermediate layer 13 on the surface of the nail 6 (FIG. 1 (b)). The insulating compound 8 can efficiently suppress the short circuit current between the positive electrode 10 (particularly, the positive electrode current collector 11) and the negative electrode 20.

FIG. 1 is a conceptual diagram for explaining the action mechanism of the present disclosure. FIG. 2 is a schematic view for explaining an example of a conventional non-aqueous electrolyte secondary battery. 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 (referred to herein as “the embodiments”) will be described. However, the following description does not limit the scope of the claims. Hereinafter, "non-aqueous electrolyte secondary battery" may be abbreviated as "battery".

<Non-aqueous electrolyte secondary battery>
FIG. 3 is a schematic view showing an example of the configuration of the non-aqueous electrolyte secondary battery of the present embodiment.
Battery 100 includes case 90. The case 90 is square (flat rectangular parallelepiped). Of course, the case may be cylindrical. The case 90 includes a container 91 and a lid 92. The lid 92 is joined to the container 91 by, for example, laser welding. The case 90 is sealed. Case 90 may be made of, for example, an aluminum (Al) alloy. The case may be, for example, a pouch made of an Al laminated film, as long as the case can be sealed. That is, the battery may be a laminate type battery.

  The lid 92 is provided with an external terminal 93. The lid 92 may be provided with, for example, a liquid injection hole, a current shutoff mechanism (CID), a gas discharge valve, and the like.

  In the case 90, an electrode assembly 50 and an electrolyte (the alternate long and short dashed lines in FIG. 3 indicate the liquid level of the electrolyte) are accommodated. The electrolyte is also present in the air gap in the electrode assembly 50. Electrode group 50 includes at least positive electrode 10 and negative electrode 20. Thus, the battery 100 includes the positive electrode 10 and the negative electrode 20.

"Electrolytes"
The electrolyte is a non-aqueous electrolyte. That is, the electrolyte (electrolyte solution) contains an aprotic solvent and a support salt. The aprotic solvent should not be particularly limited. Aprotic solvents may, for example, comprise cyclic carbonates and linear carbonates. The mixing ratio of the cyclic carbonate and the linear carbonate may be, for example, “cyclic carbonate / linear 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.

  The linear carbonate may be, for example, dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC) or the like.

  Aprotic solvents may include, for example, lactones, cyclic ethers, linear ethers, carboxylic esters, and the like. The lactone may be, for example, γ-butyrolactone (GBL), δ-valerolactone or the like. The cyclic ether may be, for example, tetrahydrofuran (THF), 1,3-dioxolane, 1,4-dioxane and the like. The chain ether may be 1,2-dimethoxyethane (DME) or the like. The carboxylic acid ester may be, for example, methyl formate (MF), methyl acetate (MA), methyl propionate (MP) and the like.

The electrolyte may contain, for example, a support salt of about 0.5 to 2 mol / L. The supporting salt may be, for example, LiPF ₆ , LiBF ₄ , Li [N (FSO ₂ ) ₂ ], Li [N (CF ₃ SO ₂ ) ₂ ] or the like.

The electrolyte may further include various functional additives in addition to the aprotic solvent and the support salt. The electrolyte may contain, for example, about 1 to 5% by mass of a functional additive. Examples of the functional additive include gas generating agents (so-called overcharge additives), solid electrolyte interface (SEI) film forming agents, and the like. The gas generating agent may be, for example, cyclohexylbenzene (CHB), biphenyl (BP) or the like. Examples of SEI film forming agents include vinylene carbonate (VC), vinyl ethylene carbonate (VEC), Li [B (C ₂ O ₄ ) ₂ ], LiPO ₂ F ₂ , propanesultone (PS), ethylene sulfite (ES) Or the like.

<< Electrode group >>
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 wound type. That is, the electrode group 50 is formed by stacking 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. Of course, the electrode group may be of a stacked type. The stack-type electrode group can be formed by alternately laminating the positive electrode and the negative electrode. A separator is disposed between each of the electrodes.

<< 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 of the present embodiment is a belt-like sheet. The positive electrode 10 includes a positive electrode current collector 11, a positive electrode mixture layer 12, and an intermediate layer 13 interposed between the positive electrode current collector and the positive electrode mixture layer.

(Positive current collector)
The positive electrode current collector 11 may be, for example, an Al foil or the like. The positive electrode current collector 11 may have a thickness of, for example, 5 μm to 50 μm.

  In the present embodiment, the thickness of each component can be measured, for example, by a micrometer or the like. The thickness of each component may be measured in a cross-sectional microscope image or the like of each component. Thickness can be measured in at least three places. An arithmetic mean of three thicknesses may be taken as the measurement result. It is desirable that the intervals between measurement points be approximately equal.

(Positive material layer)
The positive electrode mixture layer 12 is formed on the surface of the positive electrode current collector 11 described later (see FIG. 1 and the intermediate layer 13 is omitted in FIG. 5) described later. . The positive electrode mixture layer 12 may be formed on both sides of the positive electrode current collector 11 with the intermediate layer 13 interposed therebetween. The positive electrode mixture layer 12 may have a thickness of, for example, 10 μm to 200 μm. The portion where the positive electrode current collector 11 protrudes outside the positive electrode mixture layer 12 in the x-axis direction of FIG. 5 can be used for connection with the external terminal 93.

The positive electrode mixture layer 12 contains at least a positive electrode active material. The positive electrode mixture layer 12 may contain, for example, a positive electrode active material, a conductive material, and a binder. The positive electrode active material should not be particularly limited. The positive electrode active material is, for example, LiCoO ₂ , LiNiO ₂ , LiMnO ₂ , LiMn ₂ O ₄ , Li (Ni, Co, Mn) O ₂ (eg LiNi _1/3 Co _1/3 Mn _1/3 O ₂ etc.), It may be Li (Ni, Co, Al) O ₂ (eg LiNi _0.82 Co _0.15 Al _0.03 O ₂ etc.), LiFePO ₄ etc. One type of positive electrode active material may be used alone. Two or more positive electrode active materials may be used in combination.

  The conductive material should not be particularly limited. The conductive material may be, for example, acetylene black (AB) or the like. The conductive material may be, for example, 1 part by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the positive electrode active material.

  The binder should not be particularly limited. The binder may be, for example, polyvinylidene fluoride (PVDF) or the like. The binder may be, for example, 0.5 parts by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the positive electrode active material.

(Intermediate layer)
The intermediate layer 13 is interposed between the positive electrode current collector 11 and the positive electrode mixture layer 12. The mid layer 13 contains an extreme pressure agent.

  The extreme pressure agent is a compound which reacts with a metal (such as iron) at high temperature (under a predetermined temperature) to form an insulating compound. The extreme pressure agent is also referred to as an "extreme pressure additive", and is generally used as an additive for lubricating oils. In this case, the insulating compound functions as an insulating solid lubricating film. In the present embodiment, the extreme pressure agent is a metal material (such as Al) contained in the positive electrode current collector and a metal material (Li, Ni, Co, etc.) contained in the positive electrode mixture layer in order to suppress the increase in battery resistance. It is preferable that it is a material which hardly reacts with Mn and the like.

  Examples of the extreme pressure agent include chlorine-based extreme pressure agents, sulfur-based extreme pressure agents, and phosphorus-based extreme pressure agents.

  Examples of chlorinated extreme pressure agents include chlorinated hydrocarbons (chlorinated paraffin and the like) and chlorinated fatty acid esters (methyl trichlorostearate and the like).

  Examples of sulfur-based extreme pressure agents include sulfides, sulfurized oils and fats, and sulfurized esters. Examples of the sulfide include monosulfide, disulfide (such as dibenzyl disulfide) and polysulfide (such as alkyl polysulfide and olefin polysulfide). Examples of sulfurized fats and oils include sulfurized spum oil. Examples of sulfurized esters include sulfurized fatty acid esters.

  Examples of the phosphorus-based extreme pressure agent include phosphoric acid compounds (such as tricresyl phosphate).

  The extreme pressure agent is not limited to the above components, and other extreme pressure agents can also be used. Other extreme pressure agents include, for example, lead naphthenate. Also, as other extreme pressure agents, compounds containing two or more of chlorine, sulfur and phosphorus (chloroalkylxanthates containing chlorine and sulfur, alkylthiophosphate amines containing sulfur and phosphorus, etc.) can also be used. .

  The extreme pressure agent may be, for example, an electrode capable of reacting with the metal under high temperature to form an insulating compound (insulating solid lubricating film) according to the kind of metal having high possibility as a constituent material of the metal foreign matter. A pressure agent may be selected. For example, when the metallic foreign matter is a nail made of iron, an insulating compound (iron chloride, sulfurized at a high temperature by using a chlorine-based extreme pressure agent, a sulfur-based extreme pressure agent, a phosphorus-based extreme pressure agent or the like as an extreme pressure agent. Iron, iron phosphate, etc.) can be produced on the surface of metallic foreign matter. For example, a chlorine-based extreme pressure agent can react with a metal such as iron at a temperature of about 150 ° C. or more to form a chloride (insulating compound) such as iron chloride. Further, the sulfur-based extreme pressure agent can react with a metal such as iron at a temperature of about 200 ° C. or more to form a sulfide (insulating compound) such as iron sulfide. For this reason, it is considered that the chlorine-based extreme pressure agent has a higher effect of suppressing heat generation during a short circuit in the present disclosure than the sulfur-based extreme pressure agent.

  The addition amount of the extreme pressure agent in the intermediate layer 13 is preferably 40% by mass or more in order to more reliably exhibit the effects of the present disclosure. Moreover, it is preferable that it is 80 mass% or less from a viewpoint of suppressing the resistance increase of a battery.

  The intermediate layer 13 may contain a conductive material, a binder and the like in addition to the extreme pressure agent. This is expected to improve the electron conductivity, adhesion, etc. between the positive electrode current collector and the positive electrode mixture layer. As the conductive material and the binder, the same materials as the materials used for the above-mentioned positive electrode mixture layer can be used.

  In the present disclosure, since the intermediate layer 13 containing an extreme pressure agent is interposed between the positive electrode current collector 11 and the positive electrode mixture layer 12, the positive electrode current collector 11 in which a large amount of current flows particularly The short circuit current between the negative electrode 20 and the negative electrode 20 can be suppressed, and the heat generation due to the short circuit current at the nailing test etc. can be effectively suppressed.

<< 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 of the present embodiment is a belt-like sheet. The negative electrode 20 includes a negative electrode current collector 21 and a negative electrode mixture layer 22. Negative electrode current collector 21 may be, for example, a copper (Cu) foil or the like. Negative electrode current collector 21 may have a thickness of, for example, about 5 to 50 μm. The negative electrode mixture layer 22 is formed on the surface of the negative electrode current collector 21. The negative electrode mixture layer 22 may be formed on both the front and back sides of the negative electrode current collector 21. Negative electrode mixture layer 22 may have a thickness of, for example, about 10 to 50 μm. A portion where the negative electrode current collector 21 protrudes outward beyond the negative electrode mixture layer 22 in the x-axis direction of FIG. 6 can be used for connection with the external terminal 93.

  The negative electrode mixture layer 22 contains at least a negative electrode active material. The negative electrode mixture layer 22 may contain, for example, a negative electrode active material and a binder. 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, silicon-based alloy, tin, tin oxide, tin-based alloy and the like. One type of negative electrode active material may be used alone. Two or more negative electrode active materials may be used in combination. The binder may be, for example, 0.5 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the negative electrode active material. The binder should not be particularly limited. The binder may be, for example, carboxymethylcellulose (CMC) and styrene butadiene rubber (SBR).

«Separator»
The separator 30 of the present embodiment is a belt-like sheet. Separator 30 may have a thickness of, for example, about 5 to 50 μm. The separator 30 is porous. The separator 30 is an insulator. The separator 30 may be made of, for example, polyethylene (PE) or polypropylene (PP).

  Separator 30 may have, for example, a single-layer structure. The separator 30 may be formed only of, for example, a porous sheet made of PE. Separator 30 may have, for example, a multilayer structure. The separator 30 may be formed, for example, by laminating a porous sheet made of PP, a porous sheet made of PE, and a porous sheet made of PP in this order.

  A heat resistant layer may be formed on the surface of the separator 30. The heat-resistant layer may have a thickness of, for example, about 1 to 8 μm. The heat resistant layer contains a heat resistant material. The heat-resistant material may be, for example, alumina or the like.

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

Example 1
<< Manufacturing of positive electrode >>
The following materials were prepared.
(Positive current collector)
Al foil (thickness: 20 μm)
(Material of middle layer)
Extreme pressure agent: Chlorinated paraffin Conducting material: Acetylene black (AB)
Binder: Polyvinylidene fluoride (PVDF)
Solvent: N-Methyl-2-pyrrolidone (NMP)
(Material of positive electrode mixture layer)
Positive electrode active material: Li (Ni, Co, Mn) O ₂
Conductive material: AB
Binder: PVDF
Solvent: NMP

  The intermediate layer paste was prepared by mixing the extreme pressure agent (chlorinated paraffin), which is the material of the intermediate layer, the conductive material and the binder in a solvent. The mixing ratio of the solid content is “extreme pressure agent / conductive material / binder = 60/30/10 (parts by mass). By gravure coating, the intermediate layer paste is on the surface of the positive electrode current collector 11 (both the front and back sides) The intermediate layer 13 was formed by being coated and dried.

  Next, a positive electrode mixture paste was prepared by mixing the positive electrode active material, the conductive material, the binder, and the solvent. The mixing ratio of the solid content is “positive electrode active material / conductive material / binder = 100/8/2 (mass ratio)”. The positive electrode mixture paste was applied to the surfaces of the intermediate layers 13 formed on both surfaces of the positive electrode current collector 11 and dried to form the positive electrode mixture layer 12. The positive electrode mixture layer 12 was rolled. The positive electrode mixture layer 12 and the positive electrode current collector 11 were cut. The positive electrode 10 was manufactured from the above. The positive electrode 10 has the following external dimensions.

Thickness dimension of the positive electrode 10 (dimension in the y-axis direction in FIG. 5): 70 μm
Length dimension of the positive electrode 10 (dimension in the z-axis direction in FIG. 5): 3000 mm
Width dimension of the positive electrode 10 (dimension in the x-axis direction in FIG. 5): 114 mm
Width dimension of the positive electrode mixture layer 12 (dimension in the x-axis direction in FIG. 5): 94 mm

<< Manufacturing of negative electrode >>
The following materials were prepared.
Negative electrode active material: Graphite Binder: CMC and SBR
Solvent: water Negative electrode current collector: Cu foil (thickness: 10 μm)

  The paste was prepared by mixing the negative electrode active material, the binder and water. The mixing ratio of the solid content is “negative electrode active material / binder = 100/2”. CMC and SBR are equivalent. The paste was applied to the surfaces (both front and back) of the negative electrode current collector 21 and dried to form the negative electrode mixture layer 22. The negative electrode mixture layer 22 was rolled. The negative electrode mixture layer 22 and the negative electrode current collector 21 were cut. Thus, the negative electrode 20 was manufactured. The negative electrode 20 has the following external dimensions.

Thickness dimension of the negative electrode 20 (dimension in the y-axis direction in FIG. 6): 80 μm
Length dimension of the negative electrode 20 (dimension in the z-axis direction in FIG. 6): 3300 mm
Width dimension of the negative electrode 20 (dimension in the x-axis direction in FIG. 6): 120 mm
Width dimension of the negative electrode mixture layer 22 (dimension in the x-axis direction in FIG. 6): 100 mm

<< Preparation of Electrolyte >>
An electrolyte was prepared containing the following aprotic solvent and a Li salt.
Li salt: LiPF ₆ (1 mol / L)
Aprotic solvent: [EC / DMC / EMC = 30/35/35 (volume ratio)]

"assembly"
Separator 30 was prepared. The separator 30 has a thickness of 20 μm. The separator 30 is formed by laminating a porous sheet made of PP, a porous sheet made of PE, and a porous sheet made of PP in this order.

  A paste was prepared by mixing alumina, an acrylic binder and a solvent. The paste was applied to the surface (one side) of the separator 30 and dried to form a heat resistant layer.

  The positive electrode 10, the separator 30, the negative electrode 20, and the separator 30 were stacked in this order, and further wound in a spiral shape to form an electrode group 50. The separator 30 was disposed such that the heat-resistant layer faced the negative electrode 20. The electrode group 50 was formed into a flat shape. Case 90 (square aluminum case) was prepared. The electrode group 50 was housed in the case 90.

  An electrolyte was injected into case 90. Case 90 was sealed. From the above, the battery 100 (lithium ion secondary battery: non-aqueous electrolyte secondary battery) was manufactured. Battery 100 is designed to have a rated capacity of 4 Ah in a voltage range of 3 to 4.1V.

  The battery 100 was charged to 4.1 V with a current of 4A. The battery 100 was discharged to 3 V by the current of 4A. Thus, the battery 100 was in the initial state.

Example 2
A battery 100 is manufactured in the same manner as in Example 1, except that the addition amount of the extreme pressure agent in the intermediate layer (solid content) is 30% by mass and the addition amount of the conductive material is 60% by mass. Was in the initial state.

Example 3
A battery 100 is manufactured in the same manner as in Example 1, except that the addition amount of the extreme pressure agent in the intermediate layer (solid content) is 40 mass% and the addition amount of the conductive material is 50 mass%. Was in the initial state.

Example 4
A battery 100 is manufactured in the same manner as in Example 1, except that the addition amount of the extreme pressure agent in the intermediate layer (solid content) is 50% by mass and the addition amount of the conductive material is 40% by mass. Was in the initial state.

Example 5
A battery 100 is manufactured in the same manner as in Example 1, except that the addition amount of the extreme pressure agent in the intermediate layer (solid content) is 70% by mass and the addition amount of the conductive material is 20% by mass. Was in the initial state.

Example 6
A battery 100 is manufactured in the same manner as in Example 1, except that the addition amount of the extreme pressure agent in the intermediate layer (solid content) is 80 mass% and the addition amount of the conductive material is 10 mass%. Was in the initial state.

Example 7
A battery 100 is manufactured in the same manner as Example 1, except that the addition amount of the extreme pressure agent in the intermediate layer (solid content) is 90% by mass and the addition amount of the conductive material is 0% by mass. Was in the initial state.

Example 8
A battery 100 was manufactured in the same manner as in Example 1 except that a chlorinated fatty acid ester (chlorinated methyl stearate) was used instead of the chlorinated paraffin as the extreme pressure agent, and the battery 100 was in the initial state. .

Example 9
A battery 100 was manufactured in the same manner as in Example 6 except that a chlorinated fatty acid ester (chlorinated methyl stearate) was used instead of chlorinated paraffin as an extreme pressure agent, and the battery 100 was in an initial state. .

Example 10
A battery 100 was manufactured in the same manner as in Example 1 except that dibenzyl disulfide was used instead of chlorinated paraffin as an extreme pressure agent, and the battery 100 was in an initial state.

Example 11
A battery 100 was manufactured in the same manner as in Example 6 except that dibenzyl disulfide was used instead of chlorinated paraffin as an extreme pressure agent, and the battery 100 was in an initial state.

Comparative Example 1
A battery 100 was manufactured in the same manner as in Example 1 except that the intermediate layer 13 was not formed, and the battery 100 was in an initial state.

<Comparative Examples 2 and 3>
A battery 100 was manufactured in the same manner as in Comparative Example 1 except that an extreme pressure agent (chlorinated paraffin) was added to the positive electrode mixture layer, and the battery 100 was in an initial state. The addition ratio of the extreme pressure agent (mass ratio to the total mass of the positive electrode active material) in each of Comparative Examples 2 and 3 is as shown in Table 1.

<Evaluation>
"Peeling test"
The battery 4 was charged to 4.1 V by the current of 4A. A nail was prepared. The nail has a torso diameter of 3 mm. A nail was inserted into the battery 100 at a speed of 1 mm / sec. The amount of voltage drop one second after the nail was inserted into the battery 100 was measured. The results are shown in Table 1. In addition, it is thought that the suppression effect of a short circuit current is so high that the amount of voltage drops is small.

Initial resistance
The battery 100 was charged to 3.7V. In a temperature environment of 25 ° C., the battery 100 was discharged by a current of 40 A (10 C). The amount of voltage drop 10 seconds after the start of discharge was measured. The resistance was calculated by dividing the amount of voltage drop by the current. The results are shown in Table 1. "C" is a unit of current rate. “1 C” indicates a current rate at which SOC (State of Charge) reaches 0% to 100% by charging for one hour.

<Result>
As shown in Table 1, in the batteries of Examples 1 to 11, compared to Comparative Example 1, the amount of voltage drop in the nail penetration test is reduced. This is because the extreme pressure agent contained in the intermediate layer provided between the positive electrode current collector and the positive electrode mixture layer becomes a metal (iron (iron) by raising the temperature due to heat generation at the time of internal short circuit by nailing. Etc.) to form an insulating compound (iron chloride, iron sulfide, etc.) and coat the surface of the nail for insulation, which is considered to be because the short circuit current is suppressed. For this reason, since the short circuit current at the time of nailing is suppressed more than before by Examples 1-11, it is thought that the effect which suppresses the heat_generation | fever at the time of shorting by nailing etc. improves.

  On the other hand, in Comparative Examples 2 and 3 in which an extreme pressure agent was added to the positive electrode mixture layer, the voltage drop amount in the nail penetration test was not significantly reduced as compared with Comparative Example 1. From this, by interposing the intermediate layer containing the extreme pressure agent between the positive electrode current collector and the positive electrode mixture layer, a short circuit current between the positive electrode current collector and the negative electrode through which particularly a large amount of current flows It can be considered that the heat generation due to the short circuit current at the nailing test etc. can be effectively suppressed.

  From the results of Examples 1 to 7, in order to more reliably obtain the reduction effect of the voltage drop amount in the nail penetration test, it is considered preferable to set the addition amount of the extreme pressure agent to 40% by mass or more. On the other hand, in order to suppress the increase in the initial resistance, it is considered preferable to make the additive amount of the extreme pressure agent 80% by mass or less.

  From the results of Examples 1, 6 and 8 to 11, not only chlorinated paraffin but also chlorinated fatty acid esters which are other chlorine based extreme pressure agents and dibenzyl disulfide which is a sulfur based extreme pressure agent are used as extreme pressure agents. Even when used, it is considered that the short circuit current at the time of nailing is suppressed more than in the past, and the effect of suppressing heat generation at the time of shorting due to nailing or the like is improved. In addition, it is thought that the reduction amount of voltage drop (reduction effect of the short circuit current at the time of nailing) tends to be higher for the chlorine-based extreme pressure agent having a lower reaction temperature with the metal than the sulfur-based extreme pressure agent. .

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

  100 battery (non-aqueous electrolyte secondary battery), 10 positive electrode, 11 positive electrode current collector, 12 positive electrode mixture layer, 13, 14 intermediate layer, 20 negative electrode, 21 negative electrode current collector, 22 negative electrode mixture layer, 30 separators, 50 electrode groups, 6 nails, 7 heat generating parts, 8 insulating compounds, 90 cases, 91 containers, 92 lids, 93 external terminals.

Claims (1)

Equipped with positive and negative electrodes,
The positive electrode includes a positive electrode current collector, a positive electrode mixture layer, and an intermediate layer interposed between the positive electrode current collector and the positive electrode mixture layer,
The non-aqueous electrolyte secondary battery, wherein the intermediate layer contains an extreme pressure agent.

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