Full-solid secondary battery

Abstract

To provide a full-solid secondary battery capable of suppressing a transmission of a resistance heat generation at a bonding portion of a current collector foil and a tab lead to a power generation element main body.SOLUTION: A full-solid secondary battery of the present invention, comprises: a power generation element containing a single battery in which a negative electrode having a negative electrode active material onto a current collector foil front surface, a sulfide solid electrolyte, and a positive electrode having a positive electrode active material to the current collector foil front surface are laminated in this order; an outer casing body that houses and seals the power generation element; and a tab lead that inputs and outputs a power by being bonded to the collector foil front. Then, since at least one part of a bonding portion with the tab lead and the collector foil front is arranged to an outside of the outer casing, a transmission of a resistance heat generation main body at the bonding portion is suppressed.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an all-solid-state secondary battery, and more particularly to an all-solid-state secondary battery using a sulfide solid electrolyte as an electrolyte. (Related thereto.)

Background Art

[0002] Lithium-ion secondary batteries have been widely popularized as secondary batteries having a high energy density. Since a generally flammable organic solvent is used in the electrolyte of this lithium-ion secondary battery, there are cases where the safety against heat becomes a problem, and a solid battery using an inorganic solid electrolyte has been proposed in place of the organic liquid electrolyte.

[0003] Patent Document 1 discloses an all-solid-state secondary battery in which a heat conductor in contact with the exterior body and the power generation element is provided inside the exterior body, and heat is transferred from the heat conductor to the exterior body for heat dissipation.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, heat generation during charge and discharge is caused not only by the power generation element but also by the resistance at the joint between the current collector foil of the power generation element and the tab lead that is joined to the current collector foil for input and output of electricity.

[0006] And, the sulfide solid electrolyte used in the all-solid-state secondary battery has a smaller heat capacity than the electrolyte, and the temperature of the all-solid-state secondary battery using the sulfide solid electrolyte easily rises. Therefore, the temperature rise of the battery body due to resistance heat generation at the joint between the current collector foil and the tab lead cannot be ignored.

[0007] The present invention has been made in view of the problems of such conventional technologies, and an object thereof is to provide an all-solid-state secondary battery that suppresses heat transfer of resistance heat generation at the joint portion between the current collector foil and the tab lead to the main body of the power generation element.

Means for Solving the Problems

[0008] As a result of intensive studies to achieve the above object, the present inventor has found that the above object can be achieved by disposing the joint portion between the current collector foil and the tab lead outside the exterior body, and has completed the present invention.

[0009] That is, the all-solid-state secondary battery of the present invention includes a power generation element including a single battery in which a negative electrode having a negative electrode active material on the surface of a current collector foil, a sulfide solid electrolyte, and a positive electrode having a positive electrode active material on the surface of the current collector foil are laminated in this order, an exterior body that houses and seals the power generation element, and a tab lead that is joined to the current collector foil and inputs / outputs power. And at least a part of the joint portion between the tab lead and the current collector foil is disposed outside the exterior body.

Effects of the Invention

[0010] According to the present invention, since the joint portion between the current collector foil and the tab lead is disposed outside the exterior body, heat transfer of resistance heat generation at the joint portion to the main body of the power generation element is suppressed, and an all-solid-state secondary battery that can suppress a temperature rise of the main body of the power generation element can be provided.

Brief Description of the Drawings

[0011]

Figure 1

Modes for Carrying Out the Invention

[0012] The all-solid-state secondary battery of the present invention will be described in detail. The all-solid-state secondary battery of the present invention includes a power generation element including a single battery in which a negative electrode having a negative electrode active material on the surface of a current collector foil, a sulfide solid electrolyte, and a positive electrode having a positive electrode active material on the surface of a current collector foil are laminated in this order.

[0013] In the above power generation element, the negative electrode side current collector foil and the positive electrode side current collector foil are joined to a negative electrode tab lead and a positive electrode tab lead by ultrasonic welding, resistance welding, etc., respectively, and power is input and output through the above tab leads.

[0014] When charging and discharging the all-solid-state secondary battery, heat is generated due to the resistance at the joint between the tab lead and the current collector foil, and this heat is transferred to the power generation element body through the current collector foil to increase the temperature of the power generation element body.

[0015] In the present invention, the "joint between the tab lead and the current collector foil" refers to the entire overlapping portion of the tab lead and the current collector foil, and does not mean only the welded joint portion of the tab lead and the current collector foil.

[0016] The above sulfide solid electrolyte has a heat capacity of about 1000 (J / Kg·K) and is less than 1 / 2 of the heat capacity of a general organic electrolyte used in a lithium-ion secondary battery. Therefore, in an all-solid-state battery using a sulfide solid electrolyte as the electrolyte, the temperature easily rises during charging and discharging.

[0017] In the all-solid-state secondary battery of the present invention, the above power generation element is housed and sealed in the above outer package with a part of its current collector foil exposed to the outside of the outer package, and the joint between the above tab lead and the current collector foil is exposed from the outer package. Therefore, it is easy to dissipate the heat generated at the joint between the above tab lead and the current collector foil.

[0018] Therefore, in the all-solid-state secondary battery of the present invention, the temperature rise at the above joint is suppressed, and the heat transfer from the heat generation at the above joint to the power generation element through the current collector foil can be suppressed.

[0019] In addition, the temperature of the joint portion decreases, increasing the temperature difference with the power generation element, and the heat of the power generation element is easily transferred to the joint portion and dissipated. Therefore, the temperature rise of the power generation element can be suppressed, and the deterioration of the all-solid-state secondary battery can be suppressed.

[0020] It is preferable that the all-solid-state secondary battery of the present invention includes a heat dissipation member at the joint portion between the current collector foil and the tab lead. Thereby, the heat dissipation property of the joint portion is improved, and the temperature rise of the power generation element main body can be further suppressed.

[0021] Specifically, for the joint portion outside the exterior body, a separate heat dissipation member independent for each of the joint portion of the positive electrode and the joint portion of the negative electrode can be provided, or when providing one continuous heat dissipation member for the joint portion of the positive electrode and the joint portion of the negative electrode, an insulator can be inserted at the contact portion between the joint portion and the heat dissipation member.

[0022] Thereby, while preventing a short circuit between the joint portion of the positive electrode and the joint portion of the negative electrode, the heat dissipation property of the joint portion can be improved.

[0023] The heat dissipation member only needs to be able to increase the surface area of the joint portion to improve the heat dissipation property. For example, a heat sink having fins can be mentioned. As the material for forming the heat dissipation member, for example, a metal having excellent heat conductivity such as aluminum or its alloy can be used.

[0024] When the power generation element is formed by laminating a plurality of single cells, it is preferable to join the current collector foils of the negative electrode of the power generation element and the current collector foils of the positive electrode inside the joint portion between the current collector foil and the tab lead.

[0025] Thereby, the joint strength between the current collector foils is improved, and the heat generation at the joint portion can be suppressed because the conductive path becomes thicker.

[0026] The all-solid-state secondary battery of the present invention can be manufactured by accommodating a power generation element in which a current collector foil and a tab lead are welded and joined in a laminate exterior body such that the joint between the current collector foil and the tab lead protrudes outside the laminate exterior body, inserting a heat-sealing film between the current collector foils on the power generation element side of the joint, and heat-sealing and sealing the laminate exterior body and the heat-sealing film under vacuum degassing.

[0027] Next, the power generation element constituting the all-solid-state secondary battery will be described.

[0028] (Sulfide solid electrolyte) As the above-mentioned sulfide solid electrolyte, for example, LGPS-type sulfide solid electrolytes such as Li 10 GeP2S 12 and alditol-type sulfide solid electrolytes such as Li6PS5Cl can be mentioned.

[0029] (Negative electrode) The negative electrode has a negative electrode active material layer containing a negative electrode active material capable of occluding lithium on the surface of a current collector foil. Examples of the negative electrode active material include carbon materials, such as carbon black, carbon nanotubes (CNT), graphite, hard carbon, and the like.

[0030] The negative electrode active material layer can be formed by applying and transporting a negative electrode active material slurry containing the negative electrode active material, a binder, and, if necessary, a sulfide solid electrolyte or a conductive aid added to the current collector foil.

[0031] Examples of the binder include polybutylene terephthalate, polyethylene terephthalate, polyvinylidene fluoride (PVDF), polyethylene, polypropylene, polymethylpentene, polybutene, polyether nitrile, polytetrafluoroethylene, polyacrylonitrile, polyimide, polyamide, ethylene-vinyl acetate copolymer, polyvinyl chloride, styrene-butadiene rubber (SBR), and the like.

[0032] Examples of the material constituting the current collector foil include aluminum, nickel, iron, stainless steel, titanium, or copper.

[0033] (Positive electrode) The positive electrode has a positive electrode active material layer containing a positive electrode active material capable of reversibly occluding and releasing lithium ions on the surface of the current collector foil.

[0034] As the positive electrode active material, a lithium metal composite oxide can be used. For example, as the lithium metal composite oxide, layered rock salt type compounds such as LiCoO2, LiMnO2, LiNiO2, LiVO2, or Li(Ni-Mn-Co)O2, spinel type compounds such as LiMn2O4 or LiNi 0.5 Mn 1.5 spinel type compounds such as O4, olivine type compounds such as LiFePO4 or LiMnPO4, or Si-containing compounds such as Li2FeSiO4 or Li2MnSiO4 can be mentioned.

[0035] For the positive electrode, the same current collector foil, binder, sulfide solid electrolyte, and conductive assistant as those of the negative electrode can be used, and it can be produced by applying and drying a positive electrode active material slurry containing the positive electrode active material, the binder, the sulfide solid electrolyte, etc.

Explanation of symbols

[0036] 1 Power generation element 11 Negative electrode 12 Negative electrode current collector foil 13 Negative electrode active material layer 21 Sulfide solid electrolyte layer 31 Positive electrode 32 Positive electrode current collector foil 33 Positive electrode active material layer 4 Laminate exterior body 5 Tab lead 6 Joint part

Claims

1. A power generation element including a single cell in which a negative electrode having a negative electrode active material on the surface of a current collector foil, a sulfide solid electrolyte, and a positive electrode having a positive electrode active material on the surface of the current collector foil are laminated in this order, An exterior body that houses and seals the power generation element, A tab lead that is joined to the current collector foil and inputs and outputs power, and is a all-solid-state secondary battery, An all-solid-state secondary battery, characterized in that at least a part of the joint portion between the tab lead and the current collector foil is disposed outside the exterior body.

2. The all-solid-state secondary battery according to claim 1, characterized in that the entire joint portion is disposed outside the exterior body.

3. The all-solid-state secondary battery according to claim 1, characterized in that a heat dissipation member is provided at the joint portion between the current collector foil and the tab lead.

4. The all-solid-state secondary battery according to claim 3, characterized in that the heat dissipation member is divided into a joint portion of the positive electrode and a joint portion of the negative electrode.

5. The all-solid-state secondary battery according to claim 3, characterized in that an insulator is inserted between the heat dissipation member and the joint portion.

6. The power generation element has a plurality of single cells, The all-solid-state secondary battery according to claim 1, characterized in that the current collector foils of the negative electrodes and / or the current collector foils of the positive electrodes are joined inside the joint portion between the current collector foil and the tab lead.

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