Secondary batteries

Abstract

To provide a secondary battery which can suppress the impact on an outer package caused by a heat dissipation member.SOLUTION: A secondary battery 100 comprises: a power generation element 10 which has a positive electrode, a negative electrode facing the positive electrode, and a solid electrolyte layer 12 provided between the positive electrode and the negative electrode; an outer package covering the power generation element 10; and a heat dissipation member 20 which includes a first surface in contact with the power generation element, a second surface in contact with the outer package, and an intermediate part provided between the first surface and the second surface, and disposed at a position overlapping at least one of the first surface and the second surface in plan view. A cross section of the intermediate part in a direction facing the first surface and the second surface has an area smaller than an area of at least one of the first surface and the second surface.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a secondary battery. [Background technology]

[0002] Development of secondary batteries such as all-solid-state lithium secondary batteries is progressing vigorously. One type of secondary battery known is the so-called lithium deposition type secondary battery. In this lithium deposition type secondary battery, lithium metal is deposited on the surface of the negative electrode current collector during charging. This lithium metal becomes lithium ions during discharging. That is, as the battery is charged and discharged, the lithium metal is deposited and disappears, causing a change in the volume of the power generating element.

[0003] For example, a secondary battery has an exterior body that encloses the power generating element, and a heat dissipation member is provided inside the exterior body together with the power generating element (for example, Patent Document 1). Heat generated in the power generating element is dissipated to the exterior body via the heat dissipation member. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2020-113496 Summary of the Invention [Problem to be solved by the invention]

[0005] In such a secondary battery, if the size of the power generating element enclosed in the exterior body changes, the heat dissipation member will deform accordingly, and the deformed heat dissipation member may affect the exterior body.

[0006] Therefore, an object of the present invention is to provide a secondary battery that can suppress the influence of a heat dissipation member on an exterior body. [Means for solving the problem]

[0007] A secondary battery according to one embodiment of the present invention comprises a power generating element having a positive electrode, a negative electrode facing the positive electrode, and a solid electrolyte layer disposed between the positive electrode and the negative electrode; an exterior body covering the power generating element; and a heat dissipation member including a first surface in contact with the power generating element, a second surface in contact with the exterior body, and an intermediate portion disposed between the first surface and the second surface and positioned so as to overlap at least one of the first surface and the second surface in a planar view, wherein the cross-sectional area of ​​the intermediate portion facing the first surface and the second surface is smaller than the area of ​​at least one of the first surface and the second surface. [Effects of the Invention]

[0008] According to the present invention, the heat dissipation member has an intermediate portion whose cross-sectional area is smaller than the area of ​​at least one of the first and second surfaces. This prevents the intermediate portion from expanding outward from the first and second surfaces when the size of the power generating element changes and stress is applied to the heat dissipation member. This makes it possible to reduce the effect of the heat dissipation member on the exterior body. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a cross-sectional view schematically illustrating the configuration of a secondary battery according to one embodiment of the present invention. [Figure 2] 2 is an enlarged cross-sectional view of the heat dissipation member and its vicinity shown in FIG. 1. [Figure 3] FIG. 3 is a diagram illustrating a cross-sectional configuration taken along line III-III′ shown in FIG. 2. [Figure 4] 2(A) to 2(C) are cross-sectional views sequentially illustrating the manufacturing process of the secondary battery shown in FIG. [Figure 5] 2 is a perspective view illustrating an example of a state in which the secondary battery illustrated in FIG. 1 is used. [Figure 6] FIG. 6 is a side view seen from the direction A shown in FIG. 5. [Figure 7] 2 is a cross-sectional view showing the secondary battery shown in FIG. 1 in a fully charged state. [Figure 8] FIG. 10 is a cross-sectional view illustrating the configuration of a secondary battery according to a comparative example. [Figure 9] FIG. 10 is a cross-sectional view illustrating the configuration of a secondary battery according to a modified example. [Figure 10] 3 is a cross-sectional view illustrating another example of the heat dissipation member shown in FIG. 2. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0010] The present embodiment will be described below with reference to the drawings, but the technical scope of the present invention should be determined based on the description of the claims and is not limited to the following embodiment. Note that the dimensional proportions in the drawings are exaggerated for the convenience of explanation and may differ from the actual proportions.

[0011] <Embodiment> [Configuration of secondary battery 100] FIG. 1 is a cross-sectional view schematically illustrating the configuration of a stacked-type (internal parallel connection type) all-solid-state lithium secondary battery (hereinafter also simply referred to as a "secondary battery") according to one embodiment of the present invention. The secondary battery 100 includes, for example, a power generating element 10, a heat dissipation member 20, and a laminate film 30. Charging and discharging reactions occur in the power generating element 10. The power generating element 10 is sealed within the laminate film 30. The heat dissipation member 20 is enclosed within the laminate film 30 together with the power generating element 10. Here, the laminate film 30 corresponds to a specific example of an exterior body of the present invention. The configurations of the power generating element 10, the heat dissipation member 20, and the laminate film 30 will be described below.

[0012] (Power generating element 10) The power generating element 10 has, for example, a laminated structure of a plurality of unit cell layers 1. The unit cell layers 1 include, for example, a positive electrode active material layer 11, a solid electrolyte layer 12, a negative electrode protective layer 13, a positive electrode current collector 14, and a negative electrode current collector 15. The positive electrode of the present invention includes the positive electrode active material layer 11 and the positive electrode current collector 14, and the negative electrode of the present invention includes a negative electrode active material layer (metal layer 16 in FIG. 7 described below) and the negative electrode current collector 15. For example, a negative electrode current collector and a positive electrode current collector (not shown) are attached to the negative electrode current collector 15 and the positive electrode current collector 14, respectively, and these negative electrode current collectors and positive electrode current collectors are extended to the outside of the laminate film 30. The negative electrode current collector and the positive electrode current collector may be attached to the negative electrode current collector 15 and the positive electrode current collector 14 via a negative electrode terminal lead and a positive electrode terminal lead (not shown), respectively, by ultrasonic welding, resistance welding, or the like, as necessary.

[0013] In the cell layer 1, for example, a positive electrode current collector 14 and a negative electrode current collector 15 are provided facing each other. Between the positive electrode current collector 14 and the negative electrode current collector 15, a positive electrode active material layer 11, a solid electrolyte layer 12, and a negative electrode protective layer 13 are arranged in this order from the positive electrode current collector 14 side. For example, the positive electrode current collector 14 and the negative electrode current collector 15 are shared by two stacked cell layers 1. In the following description, the stacking direction of the cell layers 1 may be referred to as the Z direction, and the directions parallel to the main surfaces of each layer may be referred to as the X direction and the Y direction. In the following description, "planar view" refers to the XY planar view unless otherwise specified. The planar shape (XY plane) of the power generating element 10 is, for example, a quadrangle such as a rectangle, a circle, or an ellipse.

[0014] The positive electrode current collector 14 is a conductive member that functions as a flow path for electrons that are released from the positive electrode toward an external load or that flow from a power source toward the positive electrode as the battery reaction (charge / discharge reaction) progresses. There are no particular limitations on the material that constitutes the positive electrode current collector 14. Examples of materials that can be used for the positive electrode current collector 14 include metals and conductive resins.

[0015] Specifically, examples of metals include aluminum, nickel, iron, stainless steel, titanium, and copper. Other examples include clad materials of nickel and aluminum, and clad materials of copper and aluminum. Foils in which aluminum is coated on the metal surface are also acceptable. Among these, aluminum, stainless steel, copper, and nickel are preferred from the viewpoints of electronic conductivity, battery operating potential, and the like. The surfaces of these metals may be carbon-coated.

[0016] The latter conductive resin may be a resin in which a conductive filler is added to a non-conductive polymer material.

[0017] The current collector may have a single layer structure made of a single material, or may have a laminate structure made of an appropriate combination of layers made of these materials. From the viewpoint of reducing the weight of the current collector, it is preferable that the current collector includes at least a conductive resin layer made of a resin having conductivity. Furthermore, from the viewpoint of blocking the movement of lithium ions between the single cell layers 1, a metal layer may be provided on a part of the current collector.

[0018] There are no particular restrictions on the thickness of the positive electrode current collector 14, but an example is 10 to 100 μm.

[0019] The positive electrode active material layer 11 is provided between the positive electrode current collector 14 and the solid electrolyte layer 12. The positive electrode active material layer 11 is disposed, for example, inside the periphery of the positive electrode current collector 14 in a plan view.

[0020] The positive electrode active material layer 11 contains a positive electrode active material. There are no particular limitations on this positive electrode active material, as long as it is a material that can release lithium ions during the charging process of the secondary battery and absorb lithium ions during the discharging process. An example of such a positive electrode active material is one that contains an M1 element and an O element, and the M1 element contains at least one element selected from the group consisting of Li, Mn, Ni, Co, Cr, Fe, and P. Examples of such positive electrode active materials include layered rock salt active materials such as LiCoO2, LiMnO2, LiNiO2, and Li(Ni-Mn-Co)O2; LiMn2O4; and LiNi 0.5 Mn 1.5 Examples of oxide active materials include spinel-type active materials such as LiFePO4 and LiMnPO4, olivine-type active materials such as LiFeSiO4 and LiMnSiO4, and Si-containing active materials such as LiFeSiO4 and LiMnSiO4. 12 , LiVO2.

[0021] In some cases, two or more positive electrode active materials may be used in combination. Of course, positive electrode active materials other than those mentioned above may also be used.

[0022] In a preferred embodiment, the positive electrode active material layer 11 constituting the secondary battery 100 contains, from the viewpoint of output characteristics, a layered rock salt type active material containing lithium and cobalt (for example, Li(Ni-Mn-Co)O2) as the positive electrode active material.

[0023] The shape of the positive electrode active material may be, for example, particulate (spherical, fibrous), thin film, etc. When the positive electrode active material is particulate, its average particle size (D 50 ) is, for example, preferably in the range of 1 nm to 100 μm, more preferably in the range of 10 nm to 50 μm, even more preferably in the range of 100 nm to 20 μm, and particularly preferably in the range of 1 to 20 μm. In this specification, the average particle size (D 50 The value of can be measured by a laser diffraction scattering method.

[0024] The content of the positive electrode active material in the positive electrode active material layer 11 is not particularly limited, but for example, it is preferably within the range of 30 to 99% by mass, more preferably within the range of 40 to 90% by mass, and even more preferably within the range of 45 to 80% by mass.

[0025] The positive electrode active material layer 11 preferably further contains a solid electrolyte. Examples of the solid electrolyte include sulfide solid electrolytes and oxide solid electrolytes. From the viewpoint that this solid electrolyte exhibits excellent lithium ion conductivity and can better follow the volume change of the electrode active material accompanying charge and discharge, it is preferably a sulfide solid electrolyte containing S element, more preferably a sulfide solid electrolyte containing Li element, M element and S element, and the M element is at least one element selected from the group consisting of P, Si, Ge, Sn, Ti, Zr, Nb, Al, Sb, Br, Cl and I, and even more preferably a sulfide solid electrolyte containing S element, Li element and P element.

[0026] The sulfide solid electrolyte may have a Li3PS4 skeleton, a Li4P2S7 skeleton, or a Li4P2S6 skeleton. Examples of the sulfide solid electrolyte having a Li3PS4 skeleton include LiI-Li3PS4, LiI-LiBr-Li3PS4, and Li3PS4. Further, examples of the sulfide solid electrolyte having a Li4P2S7 skeleton include a Li-P-S-based solid electrolyte called LPS. Further, as the sulfide solid electrolyte, for example, Li (4-x) Ge (1-x) P x S4 (where x satisfies 0 < x < 1), such as LGPS, may be used. More specifically, for example, LPS (Li2S-P2S5), Li7P3S 11 、Li 3.2 P 0.96 S、Li 3.25 Ge 0.25 P 0.75 S4、Li 10 GeP2S 12, or Li6PS5X (where X is Cl, Br, or I). The term "Li2S-P2S5" refers to a sulfide solid electrolyte obtained using a raw material composition containing Li2S and P2S5, and the same applies to other terms. Among these, sulfide solid electrolytes are preferably LPS (Li2S-P2S5), Li6PS5X (where X is Cl, Br, or I), Li7P3S, etc., from the viewpoint that they have high ionic conductivity and a low bulk modulus and can therefore follow the volume change of the electrode active material during charge and discharge. 11 , Li 3.2 P 0.96 S and Li3PS4.

[0027] The content of the solid electrolyte in the positive electrode active material layer 11 is not particularly limited, but is preferably within the range of 1 to 70 mass %, more preferably within the range of 10 to 60 mass %, and even more preferably within the range of 20 to 55 mass %.

[0028] The positive electrode active material layer 11 may further contain at least one of a conductive additive and a binder in addition to the positive electrode active material and the solid electrolyte.

[0029] The thickness of the positive electrode active material layer 11 varies depending on the intended configuration of the lithium secondary battery, but is preferably within the range of 0.1 to 1000 μm, and more preferably 40 to 100 μm, for example.

[0030] The solid electrolyte layer 12 provided between the positive electrode and the negative electrode is disposed between the positive electrode active material layer 11 and the negative electrode protective layer 13 during full discharge (FIG. 1). The solid electrolyte layer 12 is provided wider than the positive electrode active material layer 11 and the negative electrode protective layer 13 in a plan view, and its periphery is disposed outside the periphery of the positive electrode active material layer 11 and the periphery of the negative electrode protective layer 13. By widening the solid electrolyte layer 12 from the positive electrode active material layer 11 and the negative electrode protective layer 13, it is possible to suppress the occurrence of short circuits at the ends of the positive electrode active material layer 11 and the negative electrode active material layer (metal layer 16 in FIG. 7 described below).

[0031] The solid electrolyte layer 12 contains a solid electrolyte (usually as a main component). The specific form of the solid electrolyte contained in the solid electrolyte layer 12 is the same as that described above, and therefore a detailed description thereof will be omitted here.

[0032] The content of the solid electrolyte in the solid electrolyte layer 12 is, for example, preferably in the range of 10 to 100 mass %, more preferably in the range of 50 to 100 mass %, and even more preferably in the range of 90 to 100 mass %, relative to the total mass of the solid electrolyte layer.

[0033] The solid electrolyte layer 12 may further contain a binder in addition to the above-mentioned solid electrolyte.

[0034] The thickness of the solid electrolyte layer 12 varies depending on the configuration of the intended lithium secondary battery, but is preferably within the range of 0.1 to 1000 μm, and more preferably 10 to 40 μm, for example.

[0035] An insulating elastic member 41 is provided between the solid electrolyte layer 12 and the positive electrode current collector 14, together with the positive electrode active material layer 11. The elastic member 41 is disposed in the same layer as the positive electrode active material layer 11, and covers the periphery of the positive electrode active material layer 11. The elastic member 41 is provided, for example, in a frame shape around the periphery of the positive electrode active material layer 11, and covers the entire periphery of the positive electrode active material layer 11. By providing such an elastic member 41, even if the solid electrolyte layer 12 is pressed during manufacturing, localized force is less likely to be applied to the solid electrolyte layer 12, and cracks in the solid electrolyte layer 12 during manufacturing can be suppressed.

[0036] The thickness (natural length) of the elastic member 41 provided in the same layer as the positive electrode active material layer 11 is preferably within a range of, for example, 0.1 to 1000 μm, and more preferably 40 to 100 μm.

[0037] The elastic member 41 preferably has an elastic modulus equal to or less than that of the positive electrode active material layer 11. As a result, when a confining pressure is applied in the stacking direction of the cell layers 1 during operation of the secondary battery 100, the elastic member 41 deforms to the same extent as the positive electrode active material layer 11. Therefore, a predetermined confining pressure is applied to the positive electrode active material layer 11, and the secondary battery 100 exhibits desired battery performance. The elastic member 41 deforms in accordance with the volume change of the positive electrode active material layer 11 during charge and discharge of the secondary battery 100.

[0038] The elastic modulus of the elastic member 41, specifically the compressive elastic modulus, is, for example, 0.1 GPa to 100 GPa, and preferably 1 GPa to 10 GPa. The elastic modulus of the elastic member 41 is preferably the same as the elastic modulus of the positive electrode active material layer 11. This makes it possible to more effectively prevent damage to the solid electrolyte layer 12 during production.

[0039] The elastic member 41 is made of, for example, a powder compact of polyimide, polyethylene, or inorganic powder containing a binder, etc. The elastic member 41 may also be made of aluminum oxide (Al2O3, bulk), zirconia (ZrO2), polyethylene terephthalate (PET), Kapton (registered trademark), epoxy resin, polytetrafluoroethylene (PTFE), rubber (natural rubber, synthetic rubber), etc.

[0040] The negative electrode current collector 15 is a conductive member that functions as a flow path for electrons that are released from the negative electrode toward the power source as the battery reaction (charge / discharge reaction) progresses, or that flow from an external load toward the negative electrode. There are no particular restrictions on the material that constitutes the negative electrode current collector 15. For example, metals and conductive resins can be used as the material that constitutes the negative electrode current collector 15. There are no particular restrictions on the thickness of the negative electrode current collector 15, but an example is 10 to 100 μm.

[0041] The outermost layer of the power generating element 10, i.e., the end portion of the power generating element 10 in the Z direction, is made of, for example, a negative electrode current collector 15. One main surface of this outermost negative electrode current collector 15 is in contact with the heat dissipation member 20. When the negative electrode current collector 15 is in contact with the heat dissipation member 20, it is preferable that the negative electrode current collector 15 be made of a material with high thermal conductivity, such as copper or nickel. This reduces the interfacial thermal resistance between the power generating element 10 and the heat dissipation member 20, thereby improving heat dissipation.

[0042] The negative electrode of the secondary battery 100 includes a negative electrode current collector 15 and a negative electrode active material layer (metal layer 16 in FIG. 7 described later). This negative electrode active material layer is formed on the surface of the negative electrode current collector 15 during the charging process of the secondary battery 100. In other words, the layer made of lithium metal deposited on the negative electrode current collector 15 is the negative electrode active material layer of the secondary battery 100. Therefore, the thickness of the negative electrode active material layer increases as the charging process progresses, and the thickness of the negative electrode active material layer decreases as the discharging process progresses. The negative electrode active material layer does not need to be present during full discharge, but in some cases, a negative electrode active material layer made of a certain amount of lithium metal may be present during full discharge. The thickness of the negative electrode active material layer during full charge is not particularly limited, but is typically 0.1 to 1000 μm.

[0043] The anode protective layer 13 is provided between the anode current collector 15 and the solid electrolyte layer 12 (FIG. 1), and is disposed between the anode active material layer and the solid electrolyte layer 12 during full charge (FIG. 7, which will be described later). The anode protective layer 13 is disposed at a position overlapping the solid electrolyte layer 12 in plan view, and its periphery is disposed inside the periphery of the solid electrolyte layer 12.

[0044] The anode protective layer 13 has lithium ion conductivity and suppresses the reaction between the lithium metal (anode active material layer) and the solid electrolyte. By providing this anode protective layer 13, it is possible to prevent the degradation of the solid electrolyte and the decrease in battery capacity caused by the reaction between the lithium metal (anode active material layer) and the solid electrolyte without impeding the progress of the battery reaction.

[0045] Here, a material "has lithium ion conductivity" means that the lithium ion conductivity of the material at 25°C is 1×10 -4 On the other hand, a material "does not have lithium ion conductivity" means that the lithium ion conductivity of the material at 25°C is 1 x 10 -4 The lithium ion conductivity of the material constituting the negative electrode protective layer 13 at 25°C is less than 1×10 -4 [S / cm] or more, preferably 1.5 × 10 -4 [S / cm] or more, more preferably 2.0 × 10 -4 [S / cm] or more, and more preferably 2.5 × 10 -4 [S / cm] or more, and particularly preferably 3.0 × 10 -4 [S / cm] or more.

[0046] There are no particular limitations on the constituent material of the anode protective layer 13, and various materials capable of exhibiting the above-mentioned functions can be used. Examples of constituent materials of the anode protective layer 13 include silver and carbon. It is preferable that the anode protective layer 13 contains both silver and carbon.

[0047] The anode protective layer 13 may be composed of nanoparticles having lithium ion conductivity. By including nanoparticles in the anode protective layer 13, a lithium secondary battery having excellent functionality can be provided. Here, "nanoparticles" refers to particles having an average particle diameter on the nanometer (nm) scale. The "average particle diameter" of nanoparticles refers to the 50% cumulative diameter (D50) of particle diameters (the maximum distance between any two points on the outline of the observed particles) measured by observing the cross section of a layer containing the nanoparticles with a scanning electron microscope (SEM). The average particle diameter of the nanoparticles is preferably 500 nm or less, more preferably 300 nm or less, even more preferably 150 nm or less, particularly preferably 100 nm or less, and most preferably 60 nm or less. In particular, when the average particle diameter of the nanoparticles is 60 nm or less, a lithium secondary battery having an excellent dendrite growth suppression effect can be provided. While there is no particular limit on the lower limit of the average particle diameter of the nanoparticles, it is usually 10 nm or more, and preferably 20 nm or more.

[0048] From the viewpoint of providing particularly excellent functionality as the anode protective layer 13, such nanoparticles preferably contain one or more elements selected from the group consisting of carbon, gold, platinum, palladium, silicon, silver, aluminum, bismuth, tin, and zinc, and more preferably contain one or more of these elements as simple substances or alloys. Furthermore, the nanoparticles preferably contain silver and carbon. When the anode protective layer 13 contains such nanoparticles, the layer may further contain a binder.

[0049] The method for forming the anode protective layer 13 containing the above-described nanoparticles on the surface of the solid electrolyte layer facing the anode current collector is not particularly limited, and may include, for example, applying a slurry in which the above-described nanoparticles and, if necessary, a binder are dispersed in an appropriate solvent to the surface of the solid electrolyte layer facing the anode current collector, and then drying the solvent. In some cases, the anode protective layer 13 may be formed by forming a continuous layer containing any of the above-described materials by a method such as sputtering, rather than in the form of nanoparticles.

[0050] Although the nanoparticles constituting the anode protective layer 13 have been described above, the anode protective layer 13 may be composed of other constituent materials. Examples of other constituent materials include one or more lithium-containing compounds selected from the group consisting of lithium halides (lithium fluoride (LiF), lithium chloride (LiCl), lithium bromide (LiBr), and lithium iodide (LiI)), composite metal oxides represented by Li-MO (where M is one or more metal elements selected from the group consisting of Mg, Au, Al, Sn, and Zn), and Li-Ba-TiO composite oxides. All of these materials are more stable than solid electrolytes with respect to reductive decomposition upon contact with lithium metal. That is, when comparing the tendency of the solid electrolyte constituting the solid electrolyte layer to undergo reductive decomposition upon contact with lithium metal with the tendency of the lithium-containing compounds constituting the anode protective layer 13 to undergo reductive decomposition upon contact with lithium metal, the latter tendency is smaller. Therefore, the lithium-containing compounds can also function as the anode protective layer 13. There are no particular limitations on the method for forming the anode protective layer 13 containing such a lithium-containing compound. For example, the anode protective layer 13 can be formed by forming a continuous layer containing the above-mentioned lithium-containing compound by a method such as sputtering.

[0051] The average thickness of the anode protective layer 13 is not particularly limited, as long as it is disposed at a thickness that allows the above-described functions to be exhibited. However, if the average thickness of the anode protective layer 13 is too large, it increases the internal resistance, which can cause a decrease in charge / discharge efficiency. For this reason, the average thickness of the anode protective layer 13 is preferably smaller than the average thickness of the solid electrolyte layer 12. Furthermore, if the average thickness of the anode protective layer 13 is too small, the reaction suppression effect of providing the anode protective layer 13 may not be sufficiently obtained. From these viewpoints, when the anode protective layer 13 is a layer containing nanoparticles, the average thickness of the anode protective layer 13 is preferably 300 nm to 20 μm, more preferably 500 nm to 15 μm, and even more preferably 1 to 10 μm. Furthermore, when the layer is a continuous layer made of a lithium-containing compound formed by a method such as sputtering, the average thickness is preferably 0.5 to 20 nm. The "average thickness" of the negative electrode protective layer 13 refers to a value calculated as the arithmetic mean value of thicknesses measured at several to a dozen different positions on the negative electrode protective layer 13.

[0052] (heat dissipation member 20) FIG. 2 shows an enlarged view of the heat dissipation member 20 and its vicinity shown in FIG. 1. The heat dissipation member 20, which is provided between the power generating element 10 and the laminate film 30, functions as a heat transfer path for heat generated in the power generating element 10 and plays a role in improving the heat dissipation performance of the secondary battery 100. By providing the heat dissipation member 20, the interface resistance between the power generating element 10 and the laminate film 30 is reduced compared to when the heat dissipation member 20 is not provided, thereby improving the heat dissipation performance. In particular, the secondary battery 100, which is an all-solid-state battery, tends to have lower heat dissipation performance than a liquid-based secondary battery, so providing the heat dissipation member 20 can effectively improve the heat dissipation performance. The heat dissipation member 20 is provided, for example, on both ends of the power generating element 10 in the Z direction.

[0053] The heat dissipation member 20 is in contact with the power generating element 10 and the laminate film 30. In other words, the heat dissipation member 20 has a first surface S1 that is in contact with the power generating element 10 and a second surface S2 that is in contact with the laminate film 30. The first surface S1 and the second surface S2 are disposed opposite each other. The first surface S1 and the second surface S2 each have a peripheral edge Ps1, Ps2. The peripheral edges Ps1, Ps2 are disposed, for example, at the same position in a plan view and have the same length.

[0054] The peripheral edges Ps1, Ps2 of the first surface S1 and the second surface S2 are preferably arranged in positions that overlap the peripheral edges of the outermost electrodes of the power generating element 10 in a plan view. For example, the peripheral edges Ps1, Ps2 of the first surface S1 and the second surface S2 are arranged in positions that overlap the peripheral edges of the negative electrode current collector 15 in a plan view. This makes it less likely that the heat dissipation member 20 will come into contact with the solid electrolyte layer 12 that has expanded from the negative electrode current collector 15, thereby suppressing deterioration of the solid electrolyte layer 12 due to contact with the heat dissipation member 20.

[0055] In plan view, the first surface S1 preferably covers the main surface (XY plane) of the positive electrode active material layer 11. In other words, in plan view, the periphery Ps1 of the first surface S1 is preferably provided outside the periphery of the positive electrode active material layer 11. This makes it easier to apply a confining pressure to the positive electrode, and the resistance of the power generating element 10 can be reduced.

[0056] The heat dissipation member 20 has an intermediate portion 20M between the first surface S1 and the second surface S2. The intermediate portion 20M is disposed at a position overlapping the first surface S1 and the second surface S2 in a plan view (see FIG. 3 described later). The intermediate portion 20M has a peripheral edge Pm.

[0057] Fig. 3 shows the cross section (XY cross section) of the middle portion 20M along line III-III' shown in Fig. 2, together with the first surface S1 and the second surface S2. This cross section of the middle portion 20M is a cross section facing the first surface S1 and the second surface S2, and is, for example, substantially parallel to the first surface S1 and the second surface S2.

[0058] In this embodiment, the cross-sectional area of ​​the intermediate portion 20M is smaller than the areas of the first surface S1 and the second surface S2. The areas of the first surface S1 and the second surface S2 are, for example, substantially the same. Here, the length of the periphery Pm of the intermediate portion 20M is shorter than the lengths of the peripheries Ps1, Ps2 of the first surface S1 and the second surface S2, and the periphery Pm of the intermediate portion 20M is located more inward than the peripheries Ps1, Ps2 of the first surface S1 and the second surface S2. As will be described in detail later, this makes it possible to reduce the influence of the heat dissipation member 20 on the laminate film 30 even if the size of the power generating element 10 changes.

[0059] The heat dissipation member 20 is thermally conductive, and preferably has a thermal conductivity of 1 W / mk or more. This reduces the interfacial thermal resistance between the power generating element 10 and the heat dissipation member 20, and between the heat dissipation member 20 and the laminate film 30, thereby improving heat dissipation. The heat dissipation member 20 is preferably insulating.

[0060] The heat dissipation member 20 is deformable in response to stress, and has a resistance of 75 N / mm 2 It is preferable that the heat dissipation member 20 has a Vickers hardness of 0.05 mm or less. As a result, when the size of the power generating element 10 changes, the heat dissipation member 20 deforms in accordance with this change, and contact of the heat dissipation member 20 (first surface S1 and second surface S2) with the power generating element 10 and the laminate film 30 is maintained. Therefore, the interfacial thermal resistance between the power generating element 10 and the heat dissipation member 20 and between the heat dissipation member 20 and the laminate film 30 is reduced, thereby improving heat dissipation.

[0061] The Vickers hardness of the middle portion 20M is preferably greater than the Vickers hardness of the first surface S1 and the second surface S2, so that the middle portion 20M is less likely to deform when stress is applied from the first surface S1 side or the second surface S2 side, and therefore the expansion of the periphery Pm of the middle portion 20M can be more effectively suppressed.

[0062] The heat dissipation member 20 includes, for example, an elastic material and a filler added to the elastic material. Examples of elastic materials include silicone rubber, urethane rubber, nitrile rubber, acrylic rubber, ethylene propylene rubber, and fluororubber. Examples of fillers include boron nitride, silicon nitride, aluminum nitride, alumina, silver, copper, silica, zinc oxide, magnesium oxide, and carbon nanotubes. The heat dissipation member 20 may be made of a metal such as aluminum or an aluminum alloy. The heat dissipation member 20 may be made entirely of the same material, or may be made partially of different materials. The heat dissipation member 20 may be formed by molding a single-layer heat dissipation sheet, or by laminating multiple heat dissipation sheets. The heat dissipation member 20 may be formed by applying thermal grease between the power generation element 10 and the laminate film 30.

[0063] (Laminating film 30) The laminate film 30 housing the power generating element 10 and the heat dissipation member 20 may be, for example, a three-layer laminate film formed by laminating PP (polypropylene), aluminum, and nylon in this order, but is not limited thereto. The three-layer laminate film 30 has excellent high-output and cooling performance and is suitable for use in batteries for large devices such as electric vehicles (EVs) and hybrid electric vehicles (HEVs). Furthermore, it is preferable that the laminate film 30 contain aluminum, since this allows for easy adjustment of the collective pressure applied to the power generating element 10 from the outside. Other exterior bodies may be used instead of the laminate film 30. For example, a known metal can case may be used as the exterior body.

[0064] [Secondary battery manufacturing method] 4(A) to 4(C) show the steps of the method for manufacturing the secondary battery 100 in order.

[0065] First, the positive electrode current collector 14 is formed, and then the positive electrode active material layer 11 and the elastic member 41 are formed on the surface (main surface) of the positive electrode current collector 14 (FIG. 4(A)). The elastic member 41 is formed, for example, by using a mask after the positive electrode active material layer 11 is formed on the positive electrode current collector 14. The positive electrode active material layer 11 and the elastic member 41 may be formed on one main surface and the other main surface of the positive electrode current collector 14.

[0066] After the positive electrode active material layer 11 and the elastic member 41 are formed on the surface of the positive electrode current collector 14, the solid electrolyte layer 12 is formed on the positive electrode active material layer 11 and the elastic member 41 (FIG. 4(B)). The solid electrolyte layer 12 is formed by applying a solid electrolyte onto the positive electrode active material layer 11 and the elastic member 41 using, for example, a die coater. The solid electrolyte layer 12 may also be formed using a transfer method.

[0067] After the solid electrolyte layer 12 is formed, the solid electrolyte layer 12 is pressed using a roll press to adhere the solid electrolyte layer 12 to the positive electrode active material layer 11. The adherence between the solid electrolyte layer 12 and the positive electrode active material layer 11 reduces the contact resistance between the solid electrolyte layer 12 and the positive electrode active material layer 11, improving the battery performance of the secondary battery 100. Here, because the elastic member 41 is formed around the periphery of the positive electrode active material layer 11, localized force is less likely to be applied to the solid electrolyte layer 12 when the solid electrolyte layer 12 is pressed using the roll press. This reduces bending stress on the solid electrolyte layer 12, thereby preventing damage to the solid electrolyte layer 12 during manufacturing. Instead of using the roll press, an isostatic press may be used to adhere the solid electrolyte layer 12 to the positive electrode active material layer 11.

[0068] After the solid electrolyte layer 12 is adhered to the positive electrode active material layer 11, the negative electrode protective layer 13 and the negative electrode current collector 15 are assembled thereto (FIG. 4(C)). Specifically, the negative electrode protective layer 13 is formed on the surface of the negative electrode current collector 15, and then the negative electrode protective layer 13 is adhered to the solid electrolyte layer 12. This forms the unit cell layer 1. The unit cell layers 1 are stacked to form the power generating element 10.

[0069] After forming the power generating element 10, a positive electrode current collector plate is bonded to the positive electrode current collector 14, and a negative electrode current collector plate is bonded to the negative electrode current collector 15. The bonding is performed using, for example, an ultrasonic welding machine. Next, a heat dissipation member 20 is placed so as to contact both end faces of the power generating element 10 in the Z direction. Thereafter, the power generating element 10 and the heat dissipation member 20 are housed in a laminate film 30, and the secondary battery 100 is formed.

[0070] [Secondary battery usage status] Fig. 5 is a perspective view showing a state of use of the secondary battery 100. Fig. 6 is a side view seen from direction A shown in Fig. 5.

[0071] The secondary battery 100 is used by being sandwiched between two metal plates 200. The two metal plates 200 are fastened together by a fastening member, such as a bolt 300 and a nut 400. The metal plates 200, bolts 300, and nuts 400 function as pressure members that apply pressure (restrain) to the secondary battery 100 (power generating element 10) in the stacking direction. The pressure member is not particularly limited as long as it is a member that can apply pressure to the power generating element 10 in the stacking direction. A typical pressure member is a combination of a plate made of a rigid material, such as the metal plate 200, and the fastening member described above. The fastening member is not limited to the bolts 300 and nuts 400, and may also be a tension plate that fixes the end of the metal plate 200 so as to restrain the power generating element 10 in the stacking direction.

[0072] The lower limit of the load applied to the power generating element 10 (restraint pressure in the stacking direction of the power generating element) is, for example, 0.1 MPa or more, preferably 1 MPa or more, more preferably 3 MPa or more, and even more preferably 5 MPa or more. The upper limit of the restraint pressure in the stacking direction of the power generating element 10 is, for example, 100 MPa or less, preferably 70 MPa or less, more preferably 40 MPa or less, and even more preferably 10 MPa or less.

[0073] [Secondary battery operation] FIG. 7 shows an example of the configuration of the secondary battery 100 in a fully charged state (SOC 100%). The secondary battery 100 operates, for example, with a predetermined confining pressure applied in the stacking direction (Z direction) of the power generating element 10. When the secondary battery 100 is charged, a metal layer 16 is formed between the negative electrode current collector 15 and the solid electrolyte layer 12, more specifically, between the negative electrode current collector 15 and the negative electrode protective layer 13. This metal layer 16 is formed when lithium (Li) ions in the positive electrode active material layer 11 pass through the solid electrolyte layer 12 and the negative electrode protective layer 13 and precipitate as lithium metal (LiM) on the surface of the negative electrode current collector 15, and functions as a negative electrode active material layer. As the metal layer 16 is formed during charging, the volume of the power generating element 10 increases compared to during discharging. As the volume of the power generating element 10 increases, stress is applied to the heat dissipation member 20 from the first surface S1 side and the second surface S2 side.

[0074] On the other hand, when the secondary battery 100 is discharged, lithium ions pass from the metal layer 16 through the anode protective layer 13 and the solid electrolyte layer 12 and are absorbed into the cathode active material layer 11. At an SOC of 0%, the metal layer 16 disappears (FIG. 1). This causes the volume of the power generating element 10 to decrease compared to when it is charged.

[0075] [Action and effect of secondary batteries] In the secondary battery 100 according to this embodiment, the heat dissipation member 20 has a middle portion 20M, and the cross-sectional area (XY cross-section) of this middle portion 20M is smaller than the area of ​​the first surface S1 and the area of ​​the second surface S2. This makes it possible to suppress the influence of the heat dissipation member 20 on the laminate film 30. The effect of this will be described in detail below.

[0076] FIG. 8 shows a cross-sectional structure of a secondary battery (secondary battery 1000) according to a comparative example. The shape of the heat dissipation member 20 in this secondary battery 1000 differs from that of the secondary battery 100 of this embodiment, and it does not have an intermediate portion (intermediate portion 20M in FIG. 2 ). In this secondary battery 1000, if the volume of the power generating element 10 increases during charging, the heat dissipation member 20 may damage the laminate film 30. Specifically, stress is applied to the heat dissipation member 20 from the first surface S1 side and the second surface S2 side, causing the portion between the first surface S1 and the second surface S2 to expand outward beyond the periphery of the first surface S1 and the second surface S2. This expanded heat dissipation member 20 comes into contact with the laminate film 30 and damages it. In particular, if the thickness (size in the Z direction) of the heat dissipation member 20 is reduced, the expansion of the heat dissipation member 20 becomes more pronounced. Damage to the laminate film 30 may result in deterioration of battery performance, such as a decrease in capacity retention rate and an increase in cell resistance.

[0077] In contrast, the heat dissipation member 20 of the secondary battery 100 has an intermediate portion 20M, whose cross-sectional area is smaller than the areas of the first surface S1 and the second surface S2. Here, the length of the periphery Pm of the intermediate portion 20M is shorter than the lengths of the peripheries Ps1 and Ps2 of the first surface S1 and the second surface S2, and the periphery Pm of the intermediate portion 20M is located inward from the peripheries Ps1 and Ps2 of the first surface S1 and the second surface S2 in a plan view. Therefore, even when stress is applied to the intermediate portion 20M from the first surface S1 side or the second surface S2 side, the expansion of the intermediate portion 20M outward from the first surface S1 and the second surface S2 is suppressed. This reduces the likelihood of the intermediate portion 20M coming into contact with the laminate film 30, thereby preventing damage to the laminate film 30. This also reduces the degradation of battery performance due to damage to the laminate film 30.

[0078] Furthermore, even if the thickness of the heat dissipation member 20 is reduced, the expansion of the middle portion 20M is suppressed, so the space inside the laminate film 30 can be used effectively, thereby improving the battery performance.

[0079] Furthermore, by providing the middle portion 20M in the heat dissipation member 20 and suppressing damage to the laminate film 30, it is possible to increase the areas of the first surface S1 and the second surface S2 of the heat dissipation member 20. This improves heat dissipation.

[0080] As described above, in the secondary battery 100 of this embodiment, the heat dissipation member 20 has the middle portion 20M, and the cross-sectional area of ​​this middle portion 20M is smaller than the area of ​​the first surface S1 and the area of ​​the second surface S2. This prevents the middle portion 20M from expanding outward from the first surface S1 and the second surface S2 even when the size of the power generating element 10 changes and stress is applied to the heat dissipation member 20. This makes it possible to reduce the effect of the heat dissipation member 20 on the laminate film 30.

[0081] The following describes modified examples of the secondary battery 100 described in the above embodiment. In order to avoid duplication of explanation, detailed descriptions of the same components as those of the secondary battery described in the above embodiment will be omitted.

[0082] <Modification> 9 shows the configuration of a main part of a secondary battery 100 according to a modified example. In the heat dissipation member 20 of this secondary battery 100, the area of ​​the first surface S1 and the area of ​​the second surface S2 are different from each other. Except for this point, the secondary battery 100 according to the modified example has the same configuration as the secondary battery 100 described in the above embodiment, and provides the same effects.

[0083] The heat dissipation member 20 provided between the power generating element 10 and the laminate film 30 has, for example, a trapezoidal cross section in the thickness direction (Z direction). For example, the area of ​​the first surface S1 in contact with the power generating element 10 is larger than the area of ​​the second surface S2 in contact with the laminate film 30. By making the area of ​​the first surface S1 in contact with the power generating element 10 larger than the area of ​​the second surface S2 in contact with the laminate film 30 in this way, it is possible to improve heat dissipation.

[0084] In the intermediate portion 20M between the first surface S1 and the second surface S2, the area of ​​a cross section (XY cross section) facing the first surface S1 and the second surface S2 decreases, for example, from the first surface S1 side to the second surface S2 side. The cross-sectional area of ​​this intermediate portion 20M is smaller than the area of ​​the first surface S1 and larger than the area of ​​the second surface S2. In a plan view, the periphery Pm of this intermediate portion 20M is located inside the periphery Ps1 of the first surface S1 and outside the periphery Ps2 of the second surface S2. Therefore, the length of the periphery Pm of the intermediate portion 20M is shorter than the length of the periphery Ps1 of the first surface S1 and longer than the length of the periphery Ps2 of the second surface S2.

[0085] Although not shown, the area of ​​the second surface S2 of the heat dissipation member 20 may be larger than the area of ​​the first surface S1. In this case, for example, the area of ​​the cross section of the intermediate portion 20M facing the first surface S1 and the second surface S2 decreases from the first surface S1 side toward the second surface S2 side. The cross section area of ​​the intermediate portion 20M is smaller than the area of ​​the second surface S2 and larger than the area of ​​the first surface S1.

[0086] In the secondary battery 100 according to this modification, the heat dissipation member 20 has a middle portion 20M, and the cross-sectional area of ​​this middle portion 20M is smaller than either the first surface S1 or the second surface S2. As a result, as described in the above embodiment, even when the size of the power generating element 10 changes and stress is applied to the heat dissipation member 20, the middle portion 20M is prevented from expanding outward from the first surface S1 or the second surface S2. This makes it possible to reduce the effect of the heat dissipation member 20 on the laminate film 30.

[0087] Furthermore, compared to the heat dissipation member 20 (FIG. 2) described in the above embodiment, the cross-sectional area in the thickness direction of the heat dissipation member 20 can be easily increased. This reduces the thermal resistance of the heat dissipation member 20, making it possible to improve heat dissipation performance.

[0088] <Application example> The secondary battery 100 is applied to, for example, an assembled battery. An assembled battery is configured by connecting multiple batteries. Specifically, it is configured by using at least two batteries connected in series, in parallel, or both. By connecting them in series or parallel, it becomes possible to freely adjust the capacity and voltage.

[0089] A small, detachable battery pack can be formed by connecting multiple batteries in series or in parallel. Furthermore, a large-capacity, high-output battery pack suitable for vehicle drive power sources and auxiliary power sources, which require high volumetric energy density and high volumetric power density, can be formed by further connecting multiple batteries in series or in parallel. The number of batteries to be connected to form a battery pack and the number of stacked small batteries to form a large-capacity battery pack can be determined based on the battery capacity and output of the vehicle (electric vehicle) in which it will be installed.

[0090] The secondary battery 100 is applied to, for example, vehicles. The secondary battery 100 has a high energy density per volume. In vehicle applications such as electric vehicles, hybrid electric vehicles, fuel cell vehicles, and hybrid fuel cell vehicles, higher capacity and larger size are required compared to applications in electrical and portable electronic devices. Therefore, the secondary battery 100 can be suitably used as a power source for vehicles, for example, as a vehicle drive power source or auxiliary power source.

[0091] Specifically, a battery or a battery pack formed by combining a plurality of such batteries can be mounted on a vehicle. Since the present invention can provide a high-capacity battery with excellent output characteristics, installing such a battery can enable the construction of plug-in hybrid electric vehicles with long EV driving distances and electric vehicles with long driving distances per charge. For example, a battery or a battery pack formed by combining a plurality of such batteries can be used in hybrid vehicles, fuel cell vehicles, and electric vehicles (all of which include four-wheeled vehicles (commercial vehicles such as passenger cars, trucks, and buses, and light vehicles), as well as two-wheeled vehicles (motorcycles) and three-wheeled vehicles) to provide vehicles with long driving distances. However, the applications are not limited to automobiles, and the battery pack can also be used as a power source for other vehicles, such as trains, and can also be used as an on-board power source for uninterruptible power supplies and the like.

[0092] The secondary battery of the present invention has been described above using the embodiments and modifications. However, those skilled in the art can appropriately add, modify, and omit aspects of the present invention within the scope of the technical concept. For example, the configurations, shapes, sizes, etc. of each layer of the secondary battery described in the above embodiments and modifications are merely examples, and other configurations, shapes, sizes, etc. may be used.

[0093] For example, in the above embodiments, a stacked-type (internal parallel connection type) all-solid-state lithium secondary battery has been described as an example, but the present invention is also applicable to other secondary batteries such as bipolar type. Also, in the above embodiments, the secondary battery 100 having a plurality of unit cell layers 1 has been described, but the secondary battery 100 may have a single layer structure.

[0094] 3 illustrates the heat dissipation member 20 having a rectangular planar shape, the heat dissipation member 20 may have other planar shapes such as a circle or an ellipse. The planar shape of the power generating element 10 may be any shape such as a circle, an ellipse, or a rectangle.

[0095] In the above-described embodiments, an example has been described in which a metal layer 16 containing lithium metal is deposited when the secondary battery 100 is charged. However, in the secondary battery 100, a metal layer 16 containing an alkali metal such as sodium (Na) or potassium (K) may be deposited during charging. Furthermore, the secondary battery 100 does not necessarily have to be one in which a metal layer is deposited during charging. The present invention is suitable for use in batteries in which the volume change of the power generating element between charging and discharging is relatively large, such as secondary batteries using a silicon-based or tin-based negative electrode active material.

[0096] In addition, in the above embodiment, the case where the periphery Pm of the intermediate portion 20M is located inside the peripheries Ps1, Ps2 of the first surface S1 and the second surface S2 in a planar view has been described. However, as long as the cross-sectional area of ​​the intermediate portion 20M is configured to be smaller than the area of ​​at least one of the first surface S1 and the second surface S2, the periphery Pm of the intermediate portion 20M may be located at a position overlapping the peripheries Ps1, Ps2 of the first surface S1 and the second surface S2 in a planar view.

[0097] For example, as shown in FIG. 10, the intermediate portion 20M may have a gap inside the peripheral edge Pm. [Example]

[0098] The present invention will be described in more detail below with reference to examples. However, the technical scope of the present invention is not limited to the following examples. Note that the following operations were performed in a glove box. Furthermore, the instruments and devices used in the glove box were thoroughly dried beforehand.

[0099] <Example> First, LiNi as the positive electrode active material 0.8 Mn 0.1 Co 0.1O2, acetylene black as a conductive additive, and sulfide solid electrolyte (LPS (Li2S-P2S5)) were weighed in a mass ratio of 70:5:25 and mixed in an agate mortar in a glove box. The mixture was then further mixed and stirred in a planetary ball mill. Two parts by mass of styrene-butadiene rubber (SBR) were added to 100 parts by mass of the resulting mixed powder, and mesitylene was added as a solvent to prepare a positive electrode active material slurry. The positive electrode active material slurry was then applied to both sides of a carbon-coated aluminum (Al) foil serving as a positive electrode current collector and dried to form a positive electrode active material layer (100 μm thick on each side). This produced a positive electrode.

[0100] A solid electrolyte slurry was prepared by adding 2 parts by mass of styrene-butadiene rubber (SBR) to 100 parts by mass of a sulfide solid electrolyte (LPS (Li2S-P2S5)), and mesitylene as a solvent. The solid electrolyte slurry was then applied to the surface of a stainless steel (SUS) foil support and dried to form a solid electrolyte layer (40 μm thick) on the surface of the stainless steel foil. The positive electrode active material layer of the positive electrode prepared above and the solid electrolyte layer prepared similarly above were then stacked facing each other, and then bonded together using a hydrostatic press (700 MPa, 25°C, 1 minute). The stainless steel foil on the solid electrolyte layer side was peeled off, yielding a positive electrode current collector / positive electrode active material layer / solid electrolyte layer laminate.

[0101] On the other hand, carbon black and silver nanoparticles were prepared as the constituent materials of the negative electrode protective layer. 10 parts by mass of styrene-butadiene rubber (SBR) was added to 100 parts by mass of the carbon black and silver nanoparticles, and mesitylene was added as a solvent to prepare a nanoparticle slurry. The nanoparticle slurry prepared above was then coated on both sides of a stainless steel foil support and dried to form a negative electrode protective layer (10 μm thick on each side) on both sides of the stainless steel foil as a negative electrode current collector.

[0102] Next, the cathode current collector / cathode active material layer / solid electrolyte layer laminate was laminated so that the central portion of the exposed surface of the solid electrolyte layer faced the anode protective layer on the anode current collector prepared above, and then the two were bonded together using a hydrostatic press (700 MPa, 25°C, 1 minute) to form the anode protective layer on the central portion of the solid electrolyte layer, thereby producing a power generating element.

[0103] Next, an Al tab was bonded to the positive electrode current collector foil of this power generating element, and a Ni tab was bonded to the negative electrode current collector foil using an ultrasonic welder. After this, heat dissipation members were placed on both sides of the power generating element. The heat dissipation members were made of a material containing rubber and filler. A middle part with a shape similar to that shown in Figure 2 was formed in the heat dissipation member. Finally, the power generating element together with the heat dissipation member was placed in an exterior body (aluminum laminate film) and vacuum sealed to produce a secondary battery.

[0104] <Comparative Example> The secondary battery of this comparative example was fabricated in the same manner as in the above-described example, except that the heat dissipation member did not have an intermediate portion.

[0105] [Evaluation of secondary batteries 1 (cycle test and visual inspection)] A cycle test was performed at a cell confinement pressure of 3 MPa, at 60°C, with a cell voltage ranging from 3.0 V to 4.3 V, by repeating 100 cycles of charge and discharge at a charge / discharge rate of 0.5 C (charge CCCV mode (0.01 C cutoff), discharge CC mode). After this cycle test, the secondary battery was disassembled and the inner and outer layers of the exterior body (aluminum laminate film) were checked for tears and wrinkles.

[0106] In the secondary battery of the comparative example, wrinkles and tears were observed in the aluminum laminate film, whereas in the secondary battery of the example, no wrinkles or tears were observed in the aluminum laminate film.

[0107] [Evaluation of secondary batteries 2 (resistance measurement during discharge)] After the cycle test, the secondary battery was charged to SOC = 100%. Then, the secondary battery was repeatedly discharged in the following order (1) to (7), and the relationship between the amount of current and the voltage drop was plotted. The resistance during discharge was calculated from the slope of the plotted graph. The capacity retention rate was also calculated. (All discharge conditions were 60°C) (1)0.05C CC discharge 15sec (2) Two-hour break (3)0.1C CC discharge 15sec (4) Two-hour break (5)0.2C CC charge / discharge 15sec (6) Two-hour break (7)0.5C CC discharge 15sec In the secondary battery of the comparative example, the capacity retention rate after 100 cycles was 70% and the cell resistance was 35 Ωcm 2 In contrast, in the secondary battery of the example, the capacity retention rate after 100 cycles was 95% and the cell resistance was 20 Ωcm. 2 It was.

[0108] The above results show that the secondary batteries of the Examples can suppress damage to the laminate film compared to the secondary batteries of the Comparative Examples, and also suppress performance degradation of the secondary batteries caused by damage to the laminate film. [Explanation of symbols]

[0109] 1 power generation element, 11 positive electrode active material layer, 12 solid electrolyte layer, 13 negative electrode protective layer, 14 positive electrode current collector, 15 negative electrode current collector, 16 metal layers, 20 heat dissipation member, 20M middle part, 30 laminating film, 41 Elastic member.

Claims

1. a power generating element including a positive electrode, a negative electrode facing the positive electrode, and a solid electrolyte layer provided between the positive electrode and the negative electrode; an exterior body that covers the power generating element; a heat dissipation member including a first surface in contact with the power generating element, a second surface in contact with the exterior body, and an intermediate portion provided between the first surface and the second surface and disposed continuously at a position overlapping at least one of the first surface and the second surface in a plan view; an area of ​​a cross section of the intermediate portion facing the first surface and the second surface is smaller than an area of ​​at least one of the first surface and the second surface; The intermediate portion has a portion where the cross-sectional area is constant from the first surface side to the second surface side. Secondary battery.

2. The secondary battery according to claim 1 , wherein the peripheral length of the intermediate portion is shorter than the peripheral length of at least one of the first surface and the second surface.

3. The secondary battery according to claim 1 , wherein the cross-sectional area of ​​the intermediate portion is smaller than the area of ​​the first surface and the area of ​​the second surface.

4. The secondary battery according to claim 1 , wherein the periphery of the intermediate portion is located inside the periphery of at least one of the first surface and the second surface in a plan view.

5. The secondary battery according to claim 1 or 2, wherein the first surface and the second surface have different areas.

6. The secondary battery according to claim 5 , wherein the area of ​​the first surface is larger than the area of ​​the second surface.

7. the positive electrode includes a positive electrode active material layer, 7. The secondary battery according to claim 1, wherein the first surface covers a main surface of the positive electrode active material layer.

8. 8. The secondary battery according to claim 1, wherein the Vickers hardness of the intermediate portion is greater than the Vickers hardness of the first surface and the second surface.

9. the negative electrode has a negative electrode current collector containing at least one of copper and nickel, 9. The secondary battery according to claim 1, wherein the first surface is in contact with the negative electrode current collector.

10. 10. The secondary battery according to claim 1, wherein the negative electrode comprises a negative electrode current collector and lithium metal that deposits on the surface of the negative electrode current collector during charging.

11. The secondary battery according to claim 10 , wherein the power generating element further comprises an anode protective layer provided between the anode current collector and the solid electrolyte layer and having lithium ion conductivity.

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