JP2016219368A - Laminate type secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laminate type secondary battery capable of quickly absorbing exothermic heat exceeding normal battery usage time within a battery.SOLUTION: The laminate type secondary battery comprises a heat absorbing sheet between constitutional units and/or in a constitutional unit. The heat absorbing sheet includes a metal porous foil (11), on which a plurality of holes (10) are formed, and a heat absorbing material (12) filling the holes of the porous foil.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a stacked secondary battery. In particular, the present invention relates to a stacked secondary battery having an endothermic material.

  With the rapid spread of information-related equipment and communication equipment such as personal computers, video cameras, and mobile phones in recent years, development of batteries that are used as power sources has been regarded as important. Also in the automobile industry, development of high-power and high-capacity batteries for electric vehicles or hybrid vehicles is being promoted. Currently, among various batteries, lithium ion batteries are attracting attention from the viewpoint of high energy density.

  Currently, commercially available lithium ion batteries use an organic solvent as an electrolyte. Therefore, a problem has been pointed out that the amount of heat generated by the battery may increase when the battery is overcharged or when a short circuit occurs inside the battery.

  On the other hand, in order to solve the above problems, research has been conducted on gel polymer electrolytes in which a polymer material is impregnated with an organic solvent that is an electrolytic solution and a battery using a solid electrolyte that does not use an organic solvent as an electrolyte. ing.

  However, even if the battery uses a gel polymer electrolyte or a solid electrolyte as the electrolyte, the battery may generate heat when the battery is overcharged or when the battery is short-circuited. .

  In these batteries, there is a problem that when the temperature inside the battery becomes high, the electrolyte causes a chemical reaction and the performance of the electrolyte is lowered. In particular, in laminated type secondary batteries, the heat dissipation inside the battery is poor, so if the amount of heat generated inside the battery increases, heat accumulates inside the battery, and the temperature of the battery rises above the normal use temperature. Therefore, it is highly necessary to provide means for suppressing heat generation inside the battery.

  On the other hand, by inserting a polymer layer as an endothermic material between the structural unit cells of a stacked secondary battery and absorbing the heat generated inside the battery with the endothermic material, it exceeds the normal battery usage. A multilayer secondary battery that can prevent excessive heat generation is known. (Patent Document 1)

JP 11-233145 A

  In the case of a stacked secondary battery as in Patent Document 1, when heat generation exceeding the normal battery use occurs inside the battery, the heat absorbing material absorbs the heat inside the battery by an endothermic reaction or the like, It takes time to suppress the temperature rise. This is presumably because heat absorption materials generally have low thermal conductivity, so that it is difficult to transfer the heat generated inside the battery to a wide range in the in-plane direction of the heat absorption materials. Therefore, in the case of the stacked secondary battery of Patent Document 1, in order to improve the endothermic speed of the endothermic material, it is necessary to increase the thickness of the endothermic material, in which case the energy density of the battery is reduced. End up.

  Accordingly, an object of the present invention is to provide a stacked secondary battery that can quickly suppress an increase in temperature inside a battery when heat generation beyond the normal battery use occurs inside the battery.

  If the present invention is used, it is not necessary to increase the thickness of the endothermic material, and the endothermic speed can be improved without reducing the energy density of the battery.

  The present inventor has found that the above problem can be solved by the following means.

  A laminated type having an endothermic sheet between and / or inside constituent unit cells, the endothermic sheet having a metal porous foil having a plurality of holes formed therein, and an endothermic material filled in the holes of the porous foil. Secondary battery.

  According to the multilayer secondary battery of the present invention, when heat generation exceeding the normal battery use occurs inside the battery, the temperature rise inside the battery can be quickly suppressed.

FIG. 1 is a structural example of a structural unit cell in a stacked secondary battery of the present invention. FIG. 2 is a simplified diagram of the laminated secondary battery of the present invention. FIG. 3 is a view of an endothermic sheet prepared by filling a hole in the (a) metal porous foil and (b) the metal porous foil with an endothermic material. FIG. 4 is an example of an endothermic sheet in which an endothermic material is disposed so as to cover not only the hole of the metal porous foil but also one surface of the metal porous foil. FIG. 5 is a diagram when the endothermic sheet is used as a negative electrode current collector. FIG. 6 shows the results of comparison of discharge capacities when the endothermic sheet is used as a current collector and when a metal foil without holes is used as a current collector.

  Hereinafter, embodiments of the present invention will be described in detail. Note that the present invention is not limited to the following embodiments, and can be implemented with various modifications within the scope of the gist of the present invention.

  The laminated secondary battery of the present invention has an endothermic sheet between constituent unit cells and / or inside the constituent unit cell, and the endothermic sheet is formed in a metal porous foil in which a plurality of holes are formed, and a hole in the porous foil. It has a filled endothermic material.

  As a result of research, the present inventors have found that the heat absorption material suppresses the temperature rise inside the battery when the heat generation exceeding the normal battery use time occurs in the battery in the multilayer secondary battery of Patent Document 1. I found that it takes time.

  Although not limited by the principle, the principle of action in which the heat absorbing material absorbs the heat inside the battery in Patent Document 1 and the present invention is considered as follows.

  In the case of the stacked secondary battery of Patent Document 1, when the temperature rises in the constituent unit cell inside the battery, mainly through the contact portion between the heating part and the endothermic material heated by the heat generated by the constituent unit cell, Temperature transfer from the structural unit cell to the endothermic material occurs. Thereafter, it is considered that the endothermic material reaches a predetermined temperature due to heat transfer in the endothermic material, the endothermic reaction of the endothermic material occurs, and the battery temperature decreases.

  In this mechanism, since the heat conductivity of the endothermic material is generally low, a portion of the endothermic material that is away from the contact portion between the heating portion of the structural unit cell and the endothermic material due to heat transfer in the endothermic material is predetermined. It takes time to reach temperature. For this reason, it is considered that it takes time until the heat absorbing material absorbs the heat inside the battery after the temperature rises inside the battery.

  On the other hand, in the case of the present invention, heat generation inside the battery is suppressed by using a metal porous foil in which a plurality of holes are formed and a heat absorbing sheet having a structure having a heat absorbing material filled in the holes of the porous foil. The mechanism is considered as follows.

  When the temperature rises in the structural unit cell inside the battery, temperature transfer from the structural unit cell to the endothermic material occurs via the contact portion between the structural unit cell heating portion and the endothermic material, and the heated portion of the structural unit cell. The temperature is transferred from the structural unit cell to the metal porous foil through the contact portion between the metal porous foil and the metal porous foil. After that, in the endothermic material, the part away from the contact portion between the heated portion of the structural unit cell and the endothermic material is added via the contact portion between the metal porous foil and the endothermic material in addition to the heat transfer in the endothermic material. The temperature is transferred from the metal porous foil to the heat absorbing material. Thereafter, it is considered that a substantial part of the endothermic material reaches a predetermined temperature due to heat transfer in the endothermic material, an endothermic reaction of the endothermic material occurs, and the battery temperature decreases.

  In order for the endothermic material to cause an endothermic reaction, the endothermic material needs to reach a predetermined temperature. The time taken for the endothermic material to reach a predetermined temperature becomes shorter as the ratio of the amount of heat conducted to the endothermic material per unit time with respect to the volume of the endothermic material is larger. The amount of heat conducted to the endothermic material per unit time is proportional to the size of the surface area of the portion where heat generated from the constituent unit cell is transferred to the endothermic material.

  Therefore, the larger the ratio of the surface area of the portion where heat generated from the structural unit cell is transferred to the endothermic material to the volume of the endothermic material, the farther the endothermic material is from the contact portion between the heated portion of the structural unit cell and the endothermic material. It is considered that the time taken for the end portion to undergo an endothermic reaction is shortened.

  In the case of the patent document, the heat of the structural unit cell is mainly conducted to the endothermic material through the surface where the endothermic material is in contact with the portion of the structural unit cell that is heated by heat generation.

  On the other hand, in this invention, since the heat conductivity of metal foil is high, the heat which generate | occur | produced from the structural unit cell is transmitted to the whole metal foil in a short time. Therefore, the heat generated from the structural unit cell is mainly conducted to the endothermic material through the contact portion between the heated portion of the structural unit cell and the endothermic material and the metal foil through the contact portion with the endothermic material.

  Therefore, in this invention, compared with the case of patent document 1, it can be said that the ratio with respect to the volume of the endothermic material of the surface area of the part which the heat generated from the structural unit cell is transmitted to the endothermic material is large.

  Therefore, it is considered that the multilayer secondary battery of the present invention can absorb heat faster than the multilayer secondary battery of Patent Document 1.

<Multilayer secondary battery>

  In the present invention, a stacked secondary battery is a battery created by stacking structural unit cells. The stacking method of the stacked secondary battery is not particularly limited, and examples thereof include a method of stacking structural unit cells in series, a method of stacking in parallel, and a combination thereof.

<Unit cell>

  In the present invention, examples of the structural unit cell (6) include the positive electrode current collector (1), the positive electrode active material layer (2), the solid electrolyte layer (3), the negative electrode active material layer (4), and the negative electrode current collector. Although the single battery (FIG. 1) which has a body (5) is mentioned, if it has a function as a single battery, it will not specifically limit. Hereinafter, although the example at the time of using a sulfide solid electrolyte as an electrolyte is given, the structure of a structural unit cell is not limited to this.

1. Positive electrode active material layer The positive electrode active material layer contains a positive electrode active material, and optionally a conductive additive, a binder, and a sulfide solid electrolyte.

As the positive electrode active material, at least one transition metal selected from manganese, cobalt, nickel and titanium and a metal oxide containing lithium, for example, lithium cobaltate (Li _x CoO ₂ ), lithium nickelate (Li _x NiO _2). ), Lithium nickel cobalt manganate (Li _{1 + x} Ni _1/3 Co _1/3 Mn _1/3 O ₂ ), or a combination thereof.

  The average particle diameter of the positive electrode active material is not particularly limited, and examples thereof include 1 μm or more, 3 μm or more, 5 μm or more, or 10 μm or more, and 100 μm or less, 50 μm or less, 30 μm or less, or 20 μm or less. Can do. The average particle diameter of the positive electrode active material is preferably in the range of 1 to 50 μm, more preferably in the range of 1 μm to 20 μm, still more preferably in the range of 1 μm to 10 μm, and particularly preferably in the range of 1 μm to 6 μm.

  Examples of the conductive auxiliary agent include carbon materials such as VGCF, acetylene black, and ketjen black, metals such as nickel, aluminum, and SUS, or combinations thereof.

  The binder is not particularly limited, but a polymer resin such as polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyimide (PI), polyamide (PA), polyamideimide (PAI), butadiene rubber (BR) Styrene-butadiene rubber (SBR), nitrile-butadiene rubber (NBR), styrene-ethylene-butylene-styrene block copolymer (SEBS), carboxymethyl cellulose (CMC), or a combination thereof. From the viewpoint of high temperature durability, the binder is preferably polyimide, polyamide, polyamideimide, polyacryl, carboxymethylcellulose, or a combination thereof.

The sulfide solid electrolyte is not particularly limited, for _{example, 75Li 2 S-25P 2 S} 5, 8Li 2 O · 67Li 2 S · 25P 2 S 5, Li 2 S, P 2 S 5, Li 2 S-SiS _{2, LiI-Li 2 S-} SiS 2, LiI-Li 3 PO 4 -P 2 S 5, LiI-Li 2 S-P 2 S 5, or _{LiI-Li 2 S-B 2} S 3 or the like, or their Combinations can be mentioned.

2. Negative electrode active material layer The negative electrode active material layer contains a negative electrode active material, and optionally a conductive additive, a binder, and an electrolyte.

  The form of the negative electrode active material is preferably a powder. The negative electrode active material is not particularly limited as long as it can occlude / release metal ions such as lithium ions, but metal such as Li, Sn, Si, or In, and Li and Ti, Mg, or Al. An alloy or a carbon material such as hard carbon, soft carbon, graphite, or a combination thereof can be given.

  As the conductive additive, binder, and electrolyte of the negative electrode active material layer, the materials mentioned for the positive electrode active material layer can be used.

3. Sulfide solid electrolyte layer The electrolyte described in the positive electrode active material layer can be used for the sulfide solid electrolyte layer.

4). Current collector Examples of the current collector include a positive electrode current collector and a negative electrode current collector. The raw material of the positive electrode current collector or the negative electrode current collector is not particularly limited, and is a current collector of various metals such as Ag, Cu, Au, Al, Ni, Fe, SUS, or Ti, or alloys thereof. The body can be used. From the viewpoint of chemical stability, the positive electrode current collector is preferably an aluminum current collector, and the negative electrode current collector is preferably a copper current collector.

<Endothermic sheet>
The endothermic sheet has a metal porous foil (11) and an endothermic material (12) filled in the holes (10) of the porous foil (FIG. 3). 3A is a diagram of a metal porous foil, and FIG. 3B is a diagram of a metal porous foil in which holes are filled with an endothermic material.

  The endothermic sheet is inserted between the stacked unit cell and / or inside the unit cell. FIG. 2 is a configuration example of a stacked secondary solid battery in which an endothermic sheet is inserted between stacked structural unit cells. In the stacked secondary battery (8) of FIG. 2, unit constituent cells are stacked in parallel, and an endothermic sheet (7) is inserted between the positive electrode current collectors of adjacent constituent unit cells (6). The positive electrode current collector and the negative electrode current collector of each constituent unit cell are each connected to a current collecting tab (9).

  When the endothermic sheet is inserted into the constituent unit cell, the insertion location is not particularly limited. For example, the metal foil portion (11) of the endothermic sheet also serves as the negative electrode current collector and is directly stacked on the negative electrode active material layer (13). Can be mentioned (FIG. 5).

1. Metal porous foil In the present invention, the metal porous foil refers to a metal foil having a plurality of holes. The kind of metal used for the metal porous foil is not limited, and examples thereof include Zn, Al, Au, Ag, Sn, Fe, Cu, Ni, Pt, SUS, and alloys thereof. From the viewpoints of thermal conductivity, ease of processing, metal price, etc., Cu, Al, Ni, SUS and the like are preferable.

  The thickness of the metal porous foil is not particularly limited, but may be 10 μm or more, 20 μm or more, or 40 μm or more from the viewpoints of battery miniaturization and ease of processing such as application of endothermic material. The thickness may be 100 μm or less, 80 μm or less, or 60 μm or less.

  The shape of the holes in the metal porous foil is not particularly limited as long as it can be filled with an endothermic material. Examples of the shape of the holes include a circle, an ellipse, a polygon, and the like. , 60 ° staggered type, square staggered type, parallel type and the like. More specifically, round hole 60 ° staggered type, round hole square staggered type, round hole parallel type, long round hole staggered type, long round hole parallel type, square hole staggered type, square hole parallel type, hexagonal 60 ° A zigzag type, a long-angle hole zigzag type, a long-angle hole parallel type, or a combination thereof can be used. Moreover, the hole includes both the case where it penetrates and the case where it does not penetrate.

  The hole diameter of the metal porous foil is not particularly limited, but from the viewpoint of endothermic efficiency and the like, for example, when the hole shape is a round hole, the average hole diameter may be 25 μm or more, 50 μm or more, or 75 μm or more. Moreover, it may be 200 μm or less, 150 μm or less, or 125 μm or less.

  The aperture ratio of the holes in the porous foil is not particularly limited, but from the viewpoint of endothermic efficiency, for example, in the case of a parallel type of round holes, the aperture ratio (the mouth portion of all the holes with respect to the area of the entire surface of the surface with holes) The area ratio) may be 10% or more and 20% or more. Further, it may be 90% or less and 80% or less.

2. Endothermic material The endothermic material is filled in all or part of the holes of the round-hole porous foil, but may further cover all or part of one or both sides of the porous foil (FIG. 4). In addition, in FIG. 4, (b) is the figure which looked at (a) from the side.

  The endothermic material is not particularly limited as long as it is a substance that can absorb heat from the surroundings, but a material that can absorb heat by an endothermic reaction is preferable. Although it does not specifically limit as an endothermic material, A hydrate, a hydroxide, sugar alcohols, etc. are mentioned. More specifically, mannitol, erythritol, xylitol, galactitol, zinc hydroxide, aluminum hydroxide, zirconium hydroxide, cobalt hydroxide, nickel hydroxide, gypsum, copper sulfate trihydrate, aluminum hydroxide trihydrate Zinc borate, borax, potassium nitrate, dosonite, calcium aluminate and the like, but are not limited thereto.

  The present invention will be described in more detail with reference to the following examples, but it goes without saying that the scope of the present invention is not limited by these examples.

<Example 1>
1. Preparation of positive electrode mixture slurry 52 g of LiNi _0.33 Co _0.33 Mn _0.33 O ₂ (Nichia Corporation) having an average particle diameter D50 of 5 μm, VGCF (Showa Denko), 17 g of sulfide solid electrolyte, binder (PVDF ) 2 g and 52 g of butyl butyrate (Wako Pure Chemical Industries, Ltd.) were weighed and mixed thoroughly to obtain a positive electrode mixture slurry. Note that the surface of LiNi _0.33 Co _0.33 Mn _0.33 O ₂ which is a positive electrode active material was previously coated with LiNbO ₃ .

2. Preparation of Negative Electrode Mixture Slurry A mixture of 36 g of graphite, 25 g of a sulfide solid electrolyte, 2 g of binder, and 42 g of butyl butyrate (Wako Pure Chemical) was used as a negative electrode mixture.

3. Production of Solid Electrolyte Slurry A solid electrolyte slurry was prepared by sufficiently mixing 25 g of sulfide solid electrolyte, 1 g of binder, and 25 g of dehydrated heptane.

4). Preparation of endothermic sheet Zn (OH) _{2 2} g, binder 0.2 g, and butyl butyrate 0.8 g were weighed and mixed thoroughly to obtain an endothermic material slurry. The endothermic material slurry was applied to an Al porous foil (opening ratio: 63%, hole diameter: 100 μm) and dried to prepare an endothermic sheet.

5. Production of Battery A positive electrode mixture slurry was applied to an Al foil, dried, and then cut. The negative electrode mixture slurry was applied to Cu foil, dried and then cut. The solid electrolyte slurry was coated on a substrate and dried, and then cut to prepare a solid electrolyte layer. And the solid electrolyte layer which consists of sulfide solid electrolyte was transcribe | transferred between what applied the positive electrode compound-material slurry to Al foil, and was dry-cut, and what applied the negative electrode compound-material slurry to Cu foil, and dry-cut. Then, a positive electrode mixture slurry coated and dried on an Al foil, a negative electrode mixture slurry coated and dried on a Cu foil, and a solid electrolyte layer were pressed to prepare a structural unit cell. It laminated | stacked putting the endothermic sheet between the produced structural unit cells. The current collecting tab and the cell terminal were ultrasonically welded and vacuum-sealed with an aluminum laminate film to obtain a laminated battery of Example 1 of 0.5 Ah class.

<Example 2 and Comparative Example 1>
Among the preparation methods of Example 1, an endothermic sheet is prepared using the metal foil used in the preparation of the endothermic sheet as a Ni porous foil, and this endothermic sheet is used as a negative electrode current collector to prepare a structural unit cell. The structural unit cell of Example 2 was used. Further, a structural unit cell was created by the creation method of Example 1, and this was used as the structural unit cell of Comparative Example 1. Table 1 shows the configurations of the structural unit cells of the actual example 2 and the comparative example 1.

  The discharge capacities of the structural unit cell of Example 2 and the structural unit cell of Comparative Example 1 were compared. As a result of comparison, as shown in FIG. 6, there was no significant difference in discharge capacity between the structural unit cell of Example 2 and the structural unit cell of Comparative Example 1 (FIG. 6). From this, it can be said that even when the endothermic sheet is used as the negative electrode current collector, the discharge capacity hardly decreases.

DESCRIPTION OF SYMBOLS 1 Positive electrode collector 2 Positive electrode active material layer 3 Solid electrolyte layer 4 Negative electrode active material layer 5 Negative electrode collector 6 Structural unit cell 7 Endothermic sheet 8 The whole laminated battery 9 Current collection tab 10 Hole 11 Metal porous foil 12 Endothermic material 13 Negative electrode active material layer

Claims (1)

Having an endothermic sheet between the structural unit cells and / or inside the structural unit cells;
The endothermic sheet has a metal porous foil in which a plurality of holes are formed, and an endothermic material filled in the holes of the porous foil.
Multilayer secondary battery.

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