Secondary battery

Abstract

Provided is a secondary battery in which it is difficult to open a hole in a battery case. The present invention provides a secondary battery provided with a battery case, an electrode body, and an insulating film disposed between the battery case and the electrode body. The insulating film includes: a first metal layer comprising a first metal; and a second metal layer that is disposed closer to the battery case than the first metal layer, and that is composed of a second metal having a linear expansion coefficient greater than that of the first metal. At least the surface of the insulating film facing the battery case and the surface of the insulating film facing the electrode body are covered with an insulating material.

Description

Technical Field

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

[0002] A secondary battery typically includes a battery case and an electrode body housed in the battery case. As prior art documents related to secondary batteries, International Publication No. 2013 / 027296 and Japanese Patent Application Publication No. 2022-148731 are cited. For example, International Publication No. 2013 / 027296 discloses a secondary battery further including an insulating film made of a synthetic resin disposed between the battery case and the electrode body.

[0003] Patent Document 1: International Publication No. 2013 / 027296

[0004] Patent Document 2: Japanese Patent Application Publication No. 2022-148731

[0005] According to the research of the inventors, if the insulating film is made of a synthetic resin such as polypropylene (PP), the insulating film may partially melt when the temperature in the battery rises due to overcharging, etc. As a result, in the portion where the insulating film is melted, the heat inside the battery is easily transferred to the battery case, which may cause local concentration of heat. As a result, it is possible to open a hole in the battery case. Furthermore, the contents of the secondary battery (such as fragments of the active material layer, etc.) may be discharged to the outside from the portion with the hole, and then scattered to the surroundings. Summary of the invention

[0006] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a secondary battery that can suppress local concentration of heat on a battery case and makes it difficult for a hole to be opened in the battery case.

[0007] The present invention provides a secondary battery, which comprises a battery case, an electrode body contained in the battery case, and an insulating film disposed between the battery case and the electrode body. The insulating film comprises: a first metal layer, the first metal layer being composed of a first metal; and a second metal layer, the second metal layer being disposed at a position closer to the battery case than the first metal layer and being composed of a second metal having a linear expansion coefficient greater than that of the first metal, and at least the surface of the insulating film facing the battery case and the surface facing the electrode body are covered with an insulating material.

[0008] In the present invention, since the linear expansion coefficient of the second metal layer is relatively large, if heat is transferred from the first metal layer on the electrode body side to the second metal layer on the battery case side, the second metal layer expands greatly. Heat also moves with this expansion, thereby allowing heat to be diffused over a wide range. As a result, it is possible to suppress heat from being locally concentrated in the battery case, and it is possible to suppress opening holes in the battery case. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 It is a perspective view schematically showing a secondary battery according to one embodiment.

[0010] Figure 2 Yes Figure 1 A three-dimensional view of a secondary battery in which the top and bottom are reversed.

[0011] Figure 3 It is schematically indicated Figure 1 A longitudinal sectional view of the internal structure of a secondary battery.

[0012] Figure 4 It is a perspective view schematically showing an electrode assembly attached to a sealing plate.

[0013] Figure 5 It is a cross-sectional view schematically showing the structure of an insulating film according to one embodiment.

[0014] Figure 6 It is a development view of an insulating film according to one embodiment.

[0015] Figure 7 It is a perspective view schematically showing a cooling plate according to one embodiment.

[0016] Figure 8 It is a perspective view schematically showing an example of arrangement of cooling plates.

[0017] Description of reference numerals:

[0018] 10…battery case; 12…case body; 12a…bottom surface; 13…exhaust valve; 14…sealing plate; 20…electrode body; 50…insulating film; 51…first metal layer; 52…second metal layer; 58…substrate portion; 70…cooling plate (gap forming portion); 100…secondary battery. DETAILED DESCRIPTION

[0019] Hereinafter, several embodiments of the technology disclosed herein are described in detail with reference to the accompanying drawings. In addition, in addition to the matters specifically mentioned in this specification, the circumstances required for implementing the technology disclosed herein (for example, the general structure and manufacturing process of the secondary battery that do not characterize the technology disclosed herein) can be understood as design matters based on the prior art in this field by those skilled in the art. The technology disclosed herein can be implemented based on the content disclosed in this specification and the technical common sense in this field. In addition, in the following drawings, the same figure marks are used to illustrate the components and parts that play the same role.

[0020] In addition, in this specification, "secondary battery" refers to a whole electrical storage device that can be repeatedly charged and discharged by charge carriers moving between the positive electrode and the negative electrode via an electrolyte. In this specification, the description of "A to B" indicating a range includes the meaning of greater than A and less than B, and the meaning of "greater than A" and "less than B".

[0021] Figure 1 It is a perspective view of a secondary battery 100 according to one embodiment. Figure 2 Yes Figure 1 FIG. 1 is a perspective view of a secondary battery 100 in which the upper and lower parts are reversed. Figure 3 express Figure 1 The internal structure of the secondary battery 100. In addition, in the following description, the reference numerals L, R, F, Rr, U, and D in the drawings represent left, right, front, back, top, and bottom, and the reference numerals X, Y, and Z in the drawings represent the short side direction, the long side direction orthogonal to the short side direction, and the up and down direction orthogonal to the short side direction and the long side direction of the secondary battery 100, respectively. However, these directions are determined for the convenience of description and do not limit the arrangement of the secondary battery 100 in any way.

[0022] like Figure 3 As shown, the secondary battery 100 includes a battery case 10, an electrode body 20, a positive terminal 30, a negative terminal 40, and an insulating film 50. Although not shown in the figure, the secondary battery 100 also includes an electrolyte. Here, the secondary battery 100 is a lithium ion secondary battery. The secondary battery 100 is preferably a lithium ion secondary battery. The secondary battery 100 is characterized in that it includes the insulating film 50 disclosed herein, and the other structures can be the same as before.

[0023] The battery case 10 is a case that contains the electrode body 20, the insulating film 50, and the electrolyte. Figure 1 , Figure 2 As shown, here, the battery case 10 has a flat and bottomed rectangular parallelepiped (square) shape. The battery case 10 is preferably square. The material of the battery case 10 can be the same as the material used in the past, and is not particularly limited. The battery case 10 is preferably made of metal, and more preferably, for example, aluminum, aluminum alloy, iron, iron alloy, etc.

[0024] like Figure 3 As shown, here, the battery case 10 includes a case body 12 having a pair of openings 12h, and two sealing plates 14 that block the pair of openings 12h. The battery case 10 is integrated by joining the sealing plates 14 (for example, by welding) to the periphery of the pair of openings 12h of the case body 12. The battery case 10 is hermetically sealed (sealed).

[0025] The shell body 12 is in the shape of a square tube. Figure 1As shown, the housing body 12 has a substantially rectangular bottom surface 12a, a pair of long side surfaces 12b extending from the long sides of the bottom surface 12a and facing each other, and a top surface 12c connecting the upper ends of the pair of long side surfaces 12b. The top surface 12c is substantially rectangular. The top surface 12c faces the bottom surface 12a. The housing body 12 is formed, for example, by bending a sheet of metal plate into a cylindrical shape and joining the seams (for example, by welding). Here, the welded joint 12d is located on the top surface 12c. An exhaust valve 13 is provided on the bottom surface 12a.

[0026] The exhaust valve 13 is configured to break when the pressure in the battery case 10 becomes above a predetermined value, thereby discharging the gas in the battery case 10 to the outside. In addition, in the present embodiment, the number of the exhaust valve 13 is 1, but it may be 2 or more. In addition, in the present embodiment, the exhaust valve 13 is provided on the bottom surface 12a, but in other embodiments, the exhaust valve 13 may also be provided on a surface other than the bottom surface 12a, such as the long side surface 12b, the top surface 12c, the sealing plate 14, etc. In addition, the area of ​​the exhaust valve 13 is arbitrary.

[0027] In the present embodiment, the exhaust valve 13 is a cross-shaped cutout. However, the shape of the exhaust valve 13 is not particularly limited. In other embodiments, the exhaust valve 13 may be, for example, a linear cutout (only a vertical line or a horizontal line), or may be an existing well-known elliptical valve (having a cutout inside it), a circular valve (having a cutout inside it), etc. In addition, the size (length, depth) of the cutout is arbitrary, and may be appropriately determined, for example, considering the pressure resistance of the battery case 10, etc.

[0028] The sealing plate 14 is a plate-shaped component that seals the opening 12h. The sealing plate 14 is roughly rectangular when viewed from above. The area of ​​the sealing plate 14 is smaller than the long side 12b. An injection hole 15 is provided in the sealing plate 14. The injection hole 15 is used to inject electrolyte into the interior of the battery case 10 after the sealing plate 14 is assembled to the case body 12. The injection hole 15 is sealed by the sealing component 16 after the electrolyte is injected. In addition, in the present embodiment, the injection hole 15 is provided on the sealing plate 14, but in other embodiments, the injection hole 15 may also be provided on the case body 12. In addition, in the present embodiment, the injection hole 15 is provided on a different surface from the exhaust valve 13, but in other embodiments, the injection hole 15 may also be provided on the same surface as the exhaust valve 13.

[0029] The positive terminal 30 and the negative terminal 40 are fixed to the battery case 10, respectively. Here, the positive terminal 30 and the negative terminal 40 are fixed to the mutually opposing surfaces of the battery case 10 (specifically, the sealing plate 14). In detail, the positive terminal 30 is installed on one side ( Figure 1 , Figure 2The negative terminal 40 is installed on the other side ( Figure 1 , Figure 2 In addition, in the present embodiment, the positive terminal 30 and the negative terminal 40 are provided on the sealing plate 14, but in other embodiments, the positive terminal 30 and the negative terminal 40 may also be provided on the case body 12. In addition, in the present embodiment, the positive terminal 30 and the negative terminal 40 are provided on a different surface from the exhaust valve 13, but in other embodiments, the positive terminal 30 and the negative terminal 40 may also be provided on the same surface as the exhaust valve 13.

[0030] The positive terminal 30 and the negative terminal 40 are respectively exposed on the surface of the outer side of the sealing plate 14. Here, the positive terminal 30 and the negative terminal 40 are arranged on an axis extending along the long side direction Y and passing through the center of the sealing plate 14. However, in other embodiments, the axis may also deviate from the center of the sealing plate 14 in the short side direction X, for example. In addition, the positive terminal 30 and the negative terminal 40 may not be arranged on the axis. For example, it may also be that one of the positive terminal 30 and the negative terminal 40 deviates in one direction of the short side direction X, and the other direction deviates in the other side of the short side direction X.

[0031] The positive electrode terminal 30 is preferably made of metal, and more preferably, it is made of aluminum or an aluminum alloy. The negative electrode terminal 40 is preferably made of metal, and more preferably, it is made of copper or a copper alloy.

[0032] like Figure 3 As shown in FIG. 1 , the positive terminal 30 is electrically connected to the positive electrode 23 of the electrode body 20 via the positive electrode collector 32 inside the battery case 10. The negative terminal 40 is electrically connected to the negative electrode 24 of the electrode body 20 via the negative electrode collector 42 inside the battery case 10. The positive terminal 30 and the negative terminal 40 are insulated from the case body 12 by the insulating film 50. The positive terminal 30 and the negative terminal 40 are connected by the insulating member 60 (see FIG. 1 ). Figure 4 ) is insulated from the sealing plate 14.

[0033] The electrode body 20 is accommodated in the battery case 10 . Figure 4 1 is a perspective view of the electrode body 20 mounted on the sealing plate 14. Figure 4 As shown in FIG. 1 , the electrode body 20 is arranged inside the battery case 10 in a state covered by an insulating film 50 described later. In this embodiment, a plurality of (in Figure 4 However, the number of electrode bodies 20 housed in one battery case 10 is not particularly limited, and in other embodiments, the number may be three or more, or may be one.

[0034] like Figure 3As shown, the electrode body 20 includes a positive electrode 23 and a negative electrode 24. Here, the electrode body 20 is a wound electrode body. Specifically, the electrode body 20 is formed by winding a stacked body formed by stacking a strip-shaped positive electrode 23 and a strip-shaped negative electrode 24 through a strip-shaped separator in the long side direction with a winding axis as the center. However, in other embodiments, the electrode body 20 may also be a stacked electrode body in which a square positive electrode and a square negative electrode are stacked in an insulated state.

[0035] Here, the outer shape of the electrode body 20 is a flat shape. The electrode body 20 has a pair of curved portions and a pair of flat surfaces connecting the pair of curved portions. Here, the electrode body 20 is housed inside the battery case 10 with the winding axis oriented along the long side direction Y. The electrode body 20 is a so-called horizontally wound type. A pair of curved portions of the electrode body 20 are respectively opposed to the bottom surface 12a and the top surface 12c of the shell body 12. A pair of flat surfaces of the electrode body 20 are respectively opposed to a pair of long side surfaces 12b of the shell body 12. However, the electrode body 20 can also be housed inside the battery case 10 with the winding axis oriented along the up-down direction Z, for example. The electrode body 20 can also be a so-called longitudinally wound type. The various components (positive electrode, negative electrode, separator, etc.) constituting the electrode body 20 can be the same as those of a conventional secondary battery, without particular restrictions.

[0036] Typically, the positive electrode 23 has a positive electrode current collector and a positive electrode active material layer fixed on at least one surface of the positive electrode current collector. Here, the positive electrode current collector is in a strip shape. The positive electrode current collector is composed of, for example, a conductive metal such as aluminum, an aluminum alloy, nickel, or stainless steel. Here, the positive electrode current collector is a metal foil, specifically, an aluminum foil.

[0037] The positive electrode active material layer is arranged in a strip shape along the long side direction of the strip-shaped positive electrode collector. The positive electrode active material layer has a positive electrode active material that can reversibly absorb and release charge carriers. As the positive electrode active material, it is preferred to contain an oxide of at least one of Ni, Co, and Mn, for example, lithium transition metal composite oxides such as lithium cobalt oxide, lithium manganese oxide, lithium nickel oxide, lithium nickel manganese composite oxide, and lithium nickel cobalt composite oxide. As for the positive electrode active material, for example, it is preferred to contain a lithium nickel composite oxide in which the Ni content in the composite oxide containing Ni and Li is in the range of 70 to 100 mol% relative to the total molar number of constituent elements other than Li and oxygen in the composite oxide. In addition, the positive electrode active material also includes a positive electrode active material in which a part of Ni, Co, and Mn is replaced by Al, Ti, Zr, P, B, Si, Nb, C, etc., and a positive electrode active material in which the particle surface is covered with a compound containing Al, Ti, Zr, W, P, B, Si, Nb, C, etc. The total amount of substitution and addition is about 0.1 to 7%.

[0038] Typically, the negative electrode 24 includes a negative electrode current collector and a negative electrode active material layer fixed on at least one surface of the negative electrode current collector. Here, the negative electrode current collector is in a strip shape. The negative electrode current collector is composed of, for example, a conductive metal such as copper, a copper alloy, nickel, or stainless steel. Here, the negative electrode current collector is a metal foil, specifically, a copper foil.

[0039] The negative electrode active material layer is arranged in a strip shape along the long side direction of the strip-shaped negative electrode current collector. The negative electrode active material layer has a negative electrode active material that can reversibly absorb and release charge carriers. Examples of the negative electrode active material include carbon materials such as graphite and carbon, and metals and compounds thereof that can absorb lithium such as Si, SiO, SiC, and Sn.

[0040] The separator is a component that insulates the positive electrode active material layer and the negative electrode active material layer. As the separator, a porous resin sheet composed of a polyolefin resin such as polyethylene (PE) and polypropylene (PP) is preferred. A heat resistance layer (Heat Resistance Layer: HRL) containing an inorganic filler may also be provided on the surface of the separator. As the inorganic filler, for example, alumina, boehmite, aluminum hydroxide, titanium dioxide, etc. may be used.

[0041] The electrolyte and the electrode body 20 are housed together in the battery case 10. The electrolyte can be the same as the electrolyte of a conventional secondary battery and is not particularly limited. Typically, the electrolyte is a non-aqueous liquid electrolyte (non-aqueous electrolyte) containing a non-aqueous solvent and a supporting salt. The non-aqueous solvent contains carbonates such as ethylene carbonate (EC), ethyl carbonate (EMC), and dimethyl carbonate (DMC). Regarding the non-aqueous solvent, it is preferred to mix EC, EMC, and DMC in the range of 1 to 99% so that the total ratio becomes 100% of the non-aqueous solvent. The supporting salt is, for example, a fluorine-containing lithium salt. Regarding the fluorine-containing lithium salt, it is preferred to contain lithium hexafluorophosphate (LiPF6), bis(fluorosulfonyl)imide lithium (F2LiNO4S2) called LiFSI, or a fluorine-containing lithium salt of a mixture thereof. The concentration of the supporting salt is preferably 0.6 to 1.8 mol of the supporting salt per 1L of the non-aqueous solvent.

[0042] The insulating film 50 and the electrode body 20 are housed together in the battery case 10. The insulating film 50 is disposed between the battery case 10 and the electrode body 20. Figure 4 As shown, the insulating film 50 covers the periphery of the electrode body 20. Specifically, the insulating film 50 preferably covers at least the curved portion facing the bottom surface 12a and a pair of flat surfaces of the electrode body 20. The insulating film 50 is composed of sheet-like members assembled into a box or bag shape, for example.

[0043] Figure 51 is a cross-sectional view showing the structure of an insulating film 50 according to one embodiment. The insulating film 50 includes an insulating substrate portion 58 and a first metal layer 51 and a second metal layer 52 embedded in the substrate portion 58. The first metal layer 51 and the second metal layer 52 overlap in a stacking direction T from the electrode body 20 toward the battery case 10. The insulating film 50 includes a first surface 50a and a second surface 50b that are orthogonal to the stacking direction T. The first surface 50a is a surface facing the electrode body 20, and the second surface 50b is a surface facing the battery case 10.

[0044] Regarding the insulating film 50, at least the surface opposite to the battery case 10 and the surface opposite to the electrode body 20 are covered with an insulating material. In detail, regarding the insulating film 50, at least the first surface 50a and the second surface 50b are respectively composed of a substrate portion 58. On the first surface 50a and the second surface 50b, the first metal layer 51 and the second metal layer 52 are not exposed. In addition, in the present embodiment, both ends of the insulating film 50 in the width direction W orthogonal to the stacking direction T are also covered by the substrate portion 58. However, in other embodiments, for example, in the portion where the insulating film 50 is not in contact with the battery case 10 and the electrode body 20, at the end in the width direction W, the first metal layer 51 and / or the second metal layer 52 may also be exposed.

[0045] exist Figure 5 In the embodiment of the present invention, the first metal layer 51 and the second metal layer 52 are in contact with each other (in direct contact) in the stacking direction T. However, in other embodiments, a base material portion 58 may be interposed between the first metal layer 51 and the second metal layer 52. In addition, for example, an adhesive layer different from the base material portion 58 may be interposed between the first metal layer 51 and the second metal layer 52 instead of the base material portion 58 or in addition to the base material portion 58.

[0046] The first metal layer 51 is arranged on the electrode body 20 side relative to the second metal layer 52. Although not particularly limited, the thickness (the length in the stacking direction T) T1 of the first metal layer 51 is preferably 0.05 to 1.5 mm, more preferably 0.1 to 1 mm, and further preferably 0.2 to 0.5 mm. By making the thickness greater than or equal to a specified value, the effect of the technology disclosed herein can be exerted at a higher level. By making the thickness less than or equal to a specified value, the volume energy density can be increased.

[0047] The first metal layer 51 is composed of a first metal. The first metal is a metal or an alloy (two or more metals). The type of the first metal is not particularly limited as long as the linear expansion coefficient is smaller than that of the second metal described later. Although not particularly limited, the linear expansion coefficient of the first metal is preferably 23×10 －6 / K or less, for example, 0.1 to 22×10 －6 / K. The linear expansion coefficient of the first metal is preferably smaller than the linear expansion coefficient of the metal (for example, aluminum) constituting the battery case 10 .

[0048] The melting point of the first metal is preferably higher than the melting point of the metal (e.g., aluminum or aluminum alloy) constituting the battery case 10. Although not particularly limited, the melting point of the first metal is preferably above 1000°C, more preferably above 1250°C, and further preferably above 1400°C. Thus, the effect of the technology disclosed herein can be exerted at a higher level. From the viewpoint of cost, etc., the melting point of the first metal is below 5000°C, and may also be below 4000°C. In one example, it is below 2000°C. Specific examples of the first metal include copper, beryllium, nickel, iron, titanium, tungsten, stainless steel, carbon steel, nickel steel, duralumin, etc., among which titanium is preferred.

[0049] The second metal layer 52 is arranged on the battery case 10 side than the first metal layer 51. Although not particularly limited, the thickness (length in the stacking direction T) T2 of the second metal layer 52 is preferably 0.05 to 1.5 mm, more preferably 0.1 to 1 mm, and further preferably 0.2 to 0.5 mm. By making the thickness greater than a specified value, the effect of the technology disclosed herein can be exerted at a higher level. By making the thickness less than a specified value, the volume energy density can be increased. Here, although the thickness T2 of the second metal layer 52 is the same as the thickness T1 of the first metal layer 51, in other embodiments, the thicknesses of the first metal layer 51 and the second metal layer 52 may also be different.

[0050] The second metal layer 52 is composed of a second metal having a linear expansion coefficient greater than that of the first metal. Typically, the second metal is a metal or alloy (two or more metals) of a different type from the first metal. The type of the second metal is not particularly limited as long as the linear expansion coefficient is greater than that of the first metal. Although not particularly limited, the linear expansion coefficient of the second metal is preferably 5×10 －6 / K or more, more preferably 10×10 －6 / K or more, for example, 14 to 25×10 －6 / K. Although not particularly limited, the difference between the linear expansion coefficients of the first metal and the second metal ((linear expansion coefficient of the second metal) - (linear expansion coefficient of the first metal)) is preferably 1×10 －6 / K or more, more preferably 5×10 －6 / K or more, more preferably 6×10 －6 / K or more, particularly preferably 7×10 －6 / K or more. Thus, the effect of the technology disclosed herein can be exerted at a higher level.

[0051] Typically, the second metal is a metal having a melting point lower than that of the first metal. Although not particularly limited, the melting point of the second metal is preferably above 500°C, more preferably above 800°C. Thus, the effect of the technology disclosed herein can be exerted at a higher level. The melting point of the second metal is below 2000°C, and may also be below 1500°C. Specific examples of the second metal include aluminum, copper, brass, stainless steel, carbon steel, etc., among which copper is preferred.

[0052] The base material 58 is made of an insulating material. Typically, the base material 58 is made of a material having a melting point lower than that of the first metal and the second metal. The base material 58 is preferably made of a resin, preferably made of olefin resins such as polyethylene (PE), polypropylene (PP / OPP), polymethylpentene (PMP / TPX (trademark)), polyester resins such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), acrylic resin (PMMA), polyimide (PI), polyphenylene ether (PPE), triacetate (TAC), polyphenylene sulfide resin (PPS), polycarbonate (PC), nylon, polytetrafluoroethylene (PTFE) and other fluororesins. Among them, olefin resins and engineering plastics having a heat resistance of more than 100°C are preferred.

[0053] The insulating film 50 preferably has a through hole H at a position facing the exhaust valve 13 (see Figure 6 ). However, in other embodiments, the insulating film 50 may not have the through hole H. Alternatively, the insulating film 50 may be such that only the portion opposing the exhaust valve 13 is composed only of a plastic film such as PP. Furthermore, the size of the through hole H is arbitrary. In the case where the exhaust valve 13 is an elliptical valve or a circular valve, the size of the through hole H is preferably within the range of ±10 mm from the outer edge of the exhaust valve 13. In addition, in the case where the exhaust valve 13 is a cutout as in the present embodiment, in the portion opposing the exhaust valve 13, the insulating film 50 preferably covers a portion of the cutout.

[0054] Since the secondary battery 100 has an insulating film 50, even if an unsafe phenomenon occurs in the battery case 10 due to overcharging, etc., it is difficult for heat to be concentrated locally in the battery case 10. In detail, since the linear expansion coefficient of the second metal constituting the second metal layer 52 is greater than the first metal constituting the first metal layer 51, if fragments of the active material layer generated from the electrode body 20 in the battery case 10 contact the first metal layer 51, the heat is transferred to the second metal layer 52, and the second metal layer 52 expands to a greater extent than the first metal layer 51. At this time, the heat also moves with the expansion, thereby allowing the heat to diffuse to the surroundings. As a result, it is possible to suppress the heat from being concentrated locally in the battery case 10, and it is possible to suppress the opening of holes in the battery case 10.

[0055] Such an insulating film 50 can be produced, for example, by a production method including a preparation step S1 of preparing a film serving as a raw material and a processing step S2 of processing the prepared film.

[0056] In the preparation step S1, for example, first, a metal plate (sheet-shaped, with a thickness of 0.5 to 3 mm) composed of a first metal (including an alloy) and a metal plate (sheet-shaped, with a thickness of 0.5 to 3 mm) composed of a second metal are prepared, and they are rolled into foils of a specified thickness by metal rolling. Next, the two obtained metal foils (including alloy foils) are cut into specified sizes. In addition, the cutting method is not particularly limited. For example, a metal blade can be used for cutting, or a laser can be used. The cut ends are preferably deburred. As a result, in the insulating film 50, it is difficult for the metal ends to penetrate the substrate portion 58.

[0057] Next, adhesive is applied to each of the two metal foils cut to a predetermined size, and the two sides are pressed against the plastic film of the material mentioned above. After that, the metal foils covered with the plastic film are overlapped with each other via the adhesive and pressed again, so that a film having the first metal layer 51 and the second metal layer 52 can be produced.

[0058] Alternatively, as a second method, two metal foils of a specified size may be overlapped, and the non-opposing surfaces of the foils may be pressed against the plastic film by the same method as described above to form a film. In this case, the plastic film may be larger than the metal foil and cover the two metal foils. Afterwards, the unnecessary plastic film portion is removed by cutting. In this case, the end face of the metal foil is not exposed at the cut end face. In addition, the cutting method is not particularly limited, and for example, a metal blade may be used for cutting, or a laser may be used.

[0059] Furthermore, as a third method, a plastic film such as an olefin resin or various engineering plastics (PET, PEN, PI, PPE, fluororesin film, etc.) is placed on a metal foil of a predetermined size without using an adhesive, and the plastic is melted and pressed to form an integrated object of the metal foil and the plastic by heating at a high temperature of up to about 400°C and then overlapping the metal foil covered with the plastic film on the surface of the integrated object and heating and melting again, thereby also forming a film.

[0060] Alternatively, as a fourth method, two different metal foils cut to a predetermined size are overlapped, and plastic films are placed on the two non-opposing surfaces of each foil, and the plastics are melted and pressed at a high temperature of up to about 400°C to form a film. In this case, the plastic film is also sized to cover the entire metal foil. Thereafter, as in the second method described above, the unnecessary plastic film portion is removed by cutting.

[0061] Next, in the processing step S2 , for example, first, the film obtained as described above is cut into a shape and size that conforms to the outer shape of the electrode body 20 . Figure 6 FIG. 1 is a development diagram of an insulating film 50 according to one embodiment. Figure 6 In the figure, the bottom surface portion BP is a portion facing the lower end of the electrode body 20 and the bottom surface 12a of the battery case 10, and the side surface portion SP is a portion facing a pair of flat surfaces of the electrode body 20 and a pair of long side surfaces 12b of the battery case 10. In addition, the cutout portions N1 and N2 are respectively connected to the connection portions between the electrode body 20 and the positive electrode current collecting portion 32 (see Figure 3 ), the connection portion between the electrode body 20 and the negative electrode current collecting portion 42 (see Figure 3 ) corresponds to the bottom surface portion BP. Here, the insulating film 50 has a through hole H in the bottom surface portion BP. The through hole H is provided so that at least a portion thereof is opposed to the exhaust valve 13. The through hole H can be formed by cutting off the insulating film 50 or the plastic film and removing the portion opposed to the exhaust valve 13. In addition, at the position of the dotted line, a scribing process (e.g., a grooving process, a punching process, etc.) for folding and forming can also be performed. By folding the film of such a shape along the dotted line, the insulating film 50 can be made.

[0062] In some embodiments, the secondary battery 100 preferably further includes a cooling plate 70 disposed between the battery case 10 and the electrode body 20 so as to be in contact with a portion of the battery case 10 (eg, the bottom surface 12a) (see Figure 7 ). The cooling plate 70 is preferably made of a material with high thermal conductivity, for example, it is more preferably made of a metal material (including alloy material) with aluminum as the main material, or a metal material with copper as the main material. The surface of the cooling plate 70 is preferably covered with a resin such as polypropylene. By having the cooling plate 70, the heat generated in the battery case 10 can be efficiently dissipated, and the safety of the secondary battery 100 can be improved. The cooling plate 70 is an example of a "gap forming portion".

[0063] Figure 7 This is a three-dimensional view of a cooling plate 70 involved in one embodiment. The cooling plate 70 of this embodiment has a base portion 71 and a plurality of (here 3) protrusions 72. The base portion 71 is rectangular. The protrusions 72 are provided on the surface on the electrode body 20 side. The surface of the cooling plate 70 on the electrode body 20 side is a concave-convex shape. Here, the protrusions 72 are prism-shaped along the long sides. However, the number and shape (height, length, etc.) of the protrusions 72 are not particularly limited and are arbitrary.

[0064] Figure 81 is a perspective view showing an example of the configuration of the cooling plate 70. In the present embodiment, the cooling plate 70 is in contact with the bottom surface 12a. The cooling plate 70 is arranged on the bottom surface 12a side of the electrode body 20, that is, the bottom surface 12a is in contact with the electrode body 20 (at Figure 8 However, in other embodiments, the cooling plate 70 may be disposed on the long side surface 12b side, the top surface 12c side, or the sealing plate 14 side of the electrode body 20.

[0065] In this embodiment, a plurality of (in Figure 8 In the embodiment, there are two cooling plates 70. The two cooling plates 70 are arranged in the long side direction Y with the exhaust valve 13 between them. However, the number of cooling plates 70 arranged inside one battery case 10 is not particularly limited, and in other embodiments, it may be more than three or one. For example, in the case where two exhaust valves 13 are provided on the bottom surface 12a, the three cooling plates 70 may be arranged in the long side direction Y with the two exhaust valves 13 between them. Alternatively, in the case where one or more exhaust valves 13 are provided on a portion of the battery case 10 other than the bottom surface 12a, such as the long side surface 12b, the top surface 12c, or the sealing plate 14, a slightly larger cooling plate 70 may be arranged on the bottom surface 12a.

[0066] Although the secondary battery 100 can be used for various purposes, it can be preferably used as a power source (driving power source) for a motor mounted on a vehicle such as a passenger car or a truck. Although the type of vehicle is not particularly limited, examples thereof include a plug-in hybrid electric vehicle (PHEV), a hybrid electric vehicle (HEV), and a battery electric vehicle (BEV).

[0067] Several embodiments related to the present invention will be described below, but the present invention is not intended to be limited to these embodiments.

[0068] <Construction of secondary battery>

[0069] A metal plate (sheet-shaped, with a thickness of 0.5 to 3 mm) composed of the first metal described in Table 1 and a metal plate (sheet-shaped, with a thickness of 0.5 to 3 mm) composed of the second metal are prepared, and they are rolled into foils of the thickness shown in Table 1 by metal rolling. Next, after the two metal foils are cut into a specified size, they are overlapped, and a plastic film (PP) is arranged on the non-opposing side of each foil. In addition, the plastic film is sized to cover the entire metal foil (including the end). Next, the laminate is heated at a high temperature of up to about 400°C to melt the plastic, and further crimped, thereby obtaining a film having a first metal layer and a second metal layer. In addition, the properties (melting point, linear expansion coefficient) of the first metal and the second metal are as described in Table 1. In addition, the difference in linear expansion coefficient is obtained by (linear expansion coefficient of the second metal)-(linear expansion coefficient of the first metal). In addition, Comparative Example 1 uses only PP film.

[0070] Next, a rectangular battery case with an exhaust valve is prepared. In addition, the position and number of the exhaust valves are as shown in Table 1. Next, the film obtained by the above is cut into a specified size and bent to form an insulating film. In addition, at this time, for the example where the through hole is "yes" in Table 1, a through hole is provided at a position opposite to the exhaust valve. Specifically, at least a portion of the metal foil of the portion opposite to the exhaust valve is removed by cutting, thereby providing a through hole. In addition, for the example where the cooling plate is "yes" in Table 1, a cooling plate is also prepared. Next, the electrode body is covered with the prepared insulating film. At this time, one side of the first metal layer is opposite to the electrode body, and one side of the second metal layer is opposite to the battery case. Then, the electrode body covered by the insulating film is accommodated in the battery case, and an electrolyte is further injected into the battery case, thereby prototyping a square secondary battery.

[0071] <Evaluation of Secondary Batteries>

[0072] The trial-produced secondary battery is put into a discharge state, and is clamped from the long sides on both sides by a 3cm thick aluminum metal block through a heat insulating material and an elastomer, and is constrained at a constant pressure of 0.1-1MPa. In addition, a hole of several mm in diameter through which a nail can be inserted is opened in the center of the metal block (the position of the center of gravity (center) of the long side of the secondary battery). The hole has a diameter of about +1-2mm relative to the diameter of the nail. For example, if the diameter of the nail is 3mm, the hole diameter is about 3.1-3.2mm. Next, the secondary battery clamped by the metal block is charged to full charge (SOC100%). Then, the nail penetration test is carried out in the following order.

[0073] In the nail penetration test, a specified nail is inserted into a hole in the center of a metal block to forcibly short-circuit the secondary battery, thereby raising the temperature of the secondary battery. The test temperature is room temperature (about 25°C). In addition, regarding the type of nail, a round nail manufactured by Daido Hunt, SIZE: N65 ( / The shape is optional, and the angle is not specified). In addition, the nail piercing speed is 1 mm / s, and the nail piercing stops when the secondary battery enters a thermal runaway state.

[0074] Then, the morphological changes of the secondary batteries after the thermal runaway were evaluated in six levels, namely, level 0 to level 5. The morphological changes of the secondary batteries in each level are as follows. The results are shown in Table 1.

[0075] Level 0: Emissions only come from the exhaust valve, and there is no change in the battery case.

[0076] Level 1: The ejection is from the cracks in the exhaust valve and its surroundings, and there is no other change in the battery case.

[0077] Level 2: The ejection comes from the exhaust valve and its surroundings, as well as cracks within 3 other locations, and there are no cracks at the two ends.

[0078] Level 3: The ejection comes from the exhaust valve and its surroundings, as well as 4 to 9 other cracks, and there are no cracks at the two ends.

[0079] Level 4: The ejection is from the exhaust valve and its surroundings, as well as 10 or more other cracks, and there are also cracks in both terminal parts.

[0080] Level 5: The ejected matter came from the exhaust valve and its surroundings, and from 10 or more other cracks. There were also cracks in both terminal portions, and the surface of the terminal portion was further separated from the battery case.

[0081]

[0082] As shown in Table 1, Comparative Example 1 is an example of using an insulating film composed of a polypropylene (PP) film with a thickness of about 0.4 mm. Comparative Example 2 is an example of using an insulating film having two metal layers composed of aluminum (Al) with a thickness of 0.2 mm. Comparative Example 3 is an example of using an insulating film having a first metal layer composed of aluminum (Al) with a thickness of 0.2 mm, and a second metal layer made of an alloy composed of hard aluminum (A2017) having a linear expansion coefficient smaller than that of the first metal. Comparative Examples 1 to 3 all have the largest morphological changes in the secondary batteries after thermal runaway, showing a state of Level 5.

[0083] On the other hand, Example 1 is an example of an insulating film using a first metal layer made of an alloy composed of hard aluminum (A2017) with a thickness of 0.2 mm and a second metal layer composed of aluminum (Al) having a linear expansion coefficient greater than that of the first metal. Compared with Comparative Examples 1 to 3, Example 1 can relatively suppress the morphological change of the secondary battery after thermal runaway and present a state of Level 4. The explanation is not intended to be particularly limited, but it is believed that the reason is that since the linear expansion coefficient of the second metal is greater than that of the first metal (alloy), when the ejecta generated from the electrode body inside the battery hits the first metal layer, the second metal layer will expand more than the first metal layer, and heat will also move with the expansion, thereby making it possible to diffuse the heat to the surroundings. As a result, it is possible to suppress the concentration of heat on the battery shell in contact with this part, making it difficult to open a hole in the battery shell.

[0084] Example 2 is an example of an insulating film using a first metal layer composed of copper (Cu) with a thickness of 0.2 mm and a second metal layer made of an alloy composed of brass (Cu 67%, Zn 33%) having a linear expansion coefficient greater than that of the first metal. Compared with Comparative Examples 1 to 3 and Example 1, Example 2 is more capable of suppressing the morphological changes of the secondary battery after thermal runaway and presents a state of Level 3. The explanation is not intended to be particularly limited, but it is believed that the reason is that the melting point of the first metal is higher than that of Example 1. That is, it is believed that if the melting point of the first metal is high, the time for heat diffusion to melting can be prolonged, thereby effectively reducing the heat concentrated in the battery case.

[0085] Example 3 is an example of an insulating film having a first metal layer composed of beryllium (Be) with a thickness of 0.2 mm and a second metal layer composed of copper (Cu) having a linear expansion coefficient greater than that of the first metal. Compared with Comparative Examples 1 to 3 and Examples 1 and 2, Example 3 can further suppress the morphological changes of the secondary battery after thermal runaway and present a state of Level 2. The explanation is not intended to be particularly limited, but it is believed that the reason is that in addition to the melting point of the first metal being higher than that of Example 1, the difference in linear expansion coefficient between the first metal and the second metal is also large. That is, it is believed that when the difference in linear expansion coefficient between the first metal and the second metal is large, the heat diffusion effect based on the second metal is greater, thereby further suppressing the concentration of heat to the battery case.

[0086] Examples 4 to 12 are examples in which the types of the first metal and / or the second metal are different. According to the results of Examples 4 to 12, if the melting point of the first metal is higher, or the difference between the linear expansion coefficients of the first metal and the second metal is larger, the morphological change of the secondary battery after thermal runaway can be suppressed, and the result tends to be better (tends to be improved in grade).

[0087] Examples 13 to 17 are examples in which the thickness of the first metal layer and the second metal layer are different. If the thickness of each metal layer is thinner than 0.05 mm, the uniformity of the film thickness is poor and it is difficult to manufacture. On the other hand, if the thickness of each metal layer is made thicker than 1.5 mm, the total amount of electrode bodies placed in the battery case is greatly reduced, resulting in a reduction in battery capacity. Therefore, the thickness of the first metal layer and the second metal layer is preferably in the range of 0.05 to 1.5 mm. According to the results of Examples 13 to 17, within this range, the thicker the thickness, the more it can suppress the morphological changes of the secondary battery after thermal runaway, and the result is better (improved grade).

[0088] Example 18 is the same as Example 9 except that a through hole is provided at a position of the insulating film facing the exhaust valve. It is found that in both Examples 9 and 18, the morphological change of the secondary battery after thermal runaway can be suppressed at a high level, and the results are good (level 1).

[0089] Example 20 is the same as Example 19 except that a cooling plate is provided between the bottom surface of the battery case and the electrode body. Comparison between Examples 19 and 20 shows that if a cooling plate is provided on the bottom surface to improve heat dissipation, the morphological change of the secondary battery after thermal runaway can be suppressed, resulting in a better result (level improved from 1 to 0).

[0090] The above is a description of the embodiments of the technology disclosed herein. However, the above description is only an example and does not limit the scope of the claims. The technology described in the claims includes various modifications and changes to the specific examples illustrated in the above description.

[0091] As described above, as specific aspects of the technology disclosed herein, aspects described in the following items can be cited.

[0092] Item 1:

[0093] A secondary battery comprises a battery case, an electrode body accommodated in the battery case, and an insulating film arranged between the battery case and the electrode body, wherein:

[0094] The insulating film comprises:

[0095] a first metal layer, the first metal layer being composed of a first metal; and

[0096] a second metal layer disposed closer to the battery case than the first metal layer and composed of a second metal having a linear expansion coefficient greater than that of the first metal,

[0097] At least a surface of the insulating film facing the battery case and a surface facing the electrode body are covered with an insulating material.

[0098] Item 2:

[0099] In the secondary battery described in item 1,

[0100] The battery case is made of metal.

[0101] The melting point of the first metal is higher than the melting point of the metal constituting the battery case. Item 3:

[0102] In the secondary battery according to item 1 or 2,

[0103] The melting point of the first metal is 1250° C. or higher.

[0104] Item 4:

[0105] In the secondary battery according to any one of items 1 to 3,

[0106] The melting point of the first metal is 1400° C. or higher.

[0107] Item 5:

[0108] In the secondary battery according to any one of items 1 to 4,

[0109] The difference in linear expansion coefficient between the first metal and the second metal is 5 / K or more. Item 6:

[0110] In the secondary battery according to any one of items 1 to 5,

[0111] The first metal layer has a thickness of 0.05 mm or more and 1.5 mm or less.

[0112] Item 7:

[0113] In the secondary battery according to any one of items 1 to 6,

[0114] The second metal layer has a thickness of not less than 0.05 mm and not more than 1.5 mm.

[0115] Item 8:

[0116] In the secondary battery according to any one of items 1 to 7,

[0117] The battery housing has a vent valve.

[0118] The insulating film has a through hole at a position facing the exhaust valve.

[0119] Item 9:

[0120] In the secondary battery described in item 8,

[0121] The battery housing includes:

[0122] A shell body, the shell body having a bottom surface, a side surface and an opening; and a sealing plate, the sealing plate seals the opening,

[0123] The exhaust valve is arranged on the bottom surface.

[0124] Item 10:

[0125] In the secondary battery described in item 9,

[0126] The present invention further includes a gap forming portion which is disposed between the bottom surface and the electrode body and has a concavo-convex shape on a surface facing the electrode body.

Claims

1. A secondary battery comprising a battery case, an electrode body accommodated in the battery case, and an insulating film disposed between the battery case and the electrode body, The secondary battery is characterized in that The insulating film comprises: a first metal layer, the first metal layer being composed of a first metal; and a second metal layer disposed closer to the battery case than the first metal layer and composed of a second metal having a linear expansion coefficient greater than that of the first metal, At least a surface of the insulating film facing the battery case and a surface facing the electrode body are covered with an insulating material.

2. The secondary battery according to claim 1, characterized in that: The battery housing is made of metal. The first metal has a melting point higher than a melting point of a metal constituting the battery case.

3. The secondary battery according to claim 1 or 2, characterized in that: The melting point of the first metal is 1250° C. or higher.

4. The secondary battery according to claim 1 or 2, characterized in that: The melting point of the first metal is 1400° C. or higher.

5. The secondary battery according to claim 1 or 2, characterized in that: The difference in linear expansion coefficient between the first metal and the second metal is 5 / K or more.

6. The secondary battery according to claim 1 or 2, characterized in that: The thickness of the first metal layer is greater than or equal to 0.05 mm and less than or equal to 1.5 mm.

7. The secondary battery according to claim 1 or 2, characterized in that: The second metal layer has a thickness of 0.05 mm or more and 1.5 mm or less.

8. The secondary battery according to claim 1 or 2, characterized in that: The battery housing has a vent valve. The insulating film has a through hole at a position facing the exhaust valve.

9. The secondary battery according to claim 8, characterized in that: The battery housing comprises: a housing body having a bottom surface, side surfaces, and an opening; and a sealing plate, the sealing plate sealing the opening, The exhaust valve is arranged on the bottom surface.

10. The secondary battery according to claim 9, characterized in that: The secondary battery further includes a gap forming portion which is disposed between the bottom surface and the electrode body and has a concavo-convex shape on a surface facing the electrode body.

Images