Secondary batteries and battery packs

Abstract

To provide a secondary battery and a battery pack, which are highly reliable and can sufficiently ensure a cleavage function of an explosion-proof valve constituted of a vulnerable portion.SOLUTION: A secondary battery 1 includes an electrode assembly 200 and a case 100 accommodating the electrode assembly 200. The case 100 includes a case body 110 having a first opening 113 at one end portion thereof and a second opening 114 at another end portion thereof, a first sealing plate 121 sealing the first opening 223, and a second sealing plate 122 sealing the second opening 114. The case body 110 includes a pair of first wall portions 110Y facing each other, and a pair of second wall portions 110Z facing each other. An area of the first wall portion 110Y is larger than an area of the second wall portion 110Z. At least one of the first wall portions 110Y includes a thin portion 151 that, when pressure in the case 100 becomes equal to or more than a predetermined value, is fractured to discharge gas in the case 100 to outside of the case 100.SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[0002] Prior art documents disclosing the configuration of secondary batteries include Japanese Patent Application Laid-Open No. 2005-038773 (Patent Document 1), Japanese Patent Application Laid-Open No. 2001-126693 (Patent Document 2), Japanese Patent Application Laid-Open No. 2001-307707 (Patent Document 3), Japanese Patent Application Laid-Open No. 2001-345083 (Patent Document 4), and Japanese Patent Application Laid-Open No. 2001-266812 (Patent Document 5). The explosion-proof valves formed of thin-walled portions and the like provided in these secondary batteries are provided on the side surface that is perpendicular to the terminal surface and has a larger area. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-038773 [Patent Document 2] Japanese Patent Application Laid-Open No. 2001-126693 [Patent Document 3] Japanese Patent Application Laid-Open No. 2001-307707 [Patent Document 4] Japanese Patent Application Laid-Open No. 2001-345083 [Patent Document 5] Japanese Patent Application Laid-Open No. 2001-266812 Summary of the Invention [Problem to be solved by the invention]

[0004] Secondary batteries for consumer use, such as in smartphones, are installed in devices as a single battery, but for automotive and energy storage applications, secondary batteries are used in a stacked state to obtain output and capacity.

[0005] When secondary batteries are used in a stacked state, the explosion-proof valve is required to operate stably even if it is perpendicular to the terminal surface and is provided on the surface with the larger area.

[0006] The present technology has been made to solve the above-mentioned problems, and aims to provide a highly reliable secondary battery and battery pack that can fully ensure the rupture function of an explosion-proof valve made of a fragile portion. [Means for solving the problem]

[0007] The present technology provides the following secondary battery.

[0008] [1] A secondary battery comprising: an electrode assembly including a first electrode and a second electrode having a polarity different from that of the first electrode; and a case accommodating the electrode assembly, wherein the case includes a case body having a first opening at one end and a second opening at the other end, a first sealing plate that seals the first opening, and a second sealing plate that seals the second opening, wherein the case body includes a pair of first wall portions opposed to each other and a pair of second wall portions opposed to each other, wherein the area of ​​the first wall portions is larger than the area of ​​the second wall portions, and at least one of the first wall portions has a thin-walled portion that ruptures when pressure inside the case reaches or exceeds a predetermined value, and that discharges gas inside the case to the outside of the case.

[0009] [2] A portion of the first wall portion near the end of the first sealing plate and a portion of the second wall portion near the end of the first sealing plate are 1 The secondary battery according to [1], wherein the thin-walled portion is provided in the vicinity of the end of the wall portion on the second sealing plate side and in the vicinity of the end of the wall portion on the second sealing plate side.

[0010] [3] The secondary battery according to [1] or [2], wherein the thin-walled portion is provided near the end of one of the first walls on the side of the first sealing plate and near the end of the other of the first walls on the side of the second sealing plate.

[0011] [4] The secondary battery according to any one of [1] to [3], wherein the thin-walled portion is formed in at least one of an area facing the end of the main body of the electrode body on the first sealing plate side and the first sealing plate, and an area facing the end of the main body of the electrode body on the second sealing plate side and the second sealing plate.

[0012] [5] The secondary battery according to any one of [1] to [4], wherein the electrode body is a flat wound electrode body, has a curved portion with a pair of curved outer surfaces, and the thin-walled portion is formed in a position opposite the curved portion.

[0013] [6] The secondary battery according to any one of [1] to [5], wherein the thin portion has a first straight portion and a plurality of second straight portions intersecting the first straight portion.

[0014] The present technology provides the following assembled battery.

[0015] [7] An assembled battery including a plurality of secondary batteries, wherein the secondary batteries comprise an electrode assembly including a first electrode and a second electrode having a polarity different from that of the first electrode, and a case accommodating the electrode assembly, the case including a case body having a first opening at one end and a second opening at the other end, a first sealing plate that seals the first opening, and a second sealing plate that seals the second opening, the case body including a pair of first wall portions facing each other and a pair of second wall portions facing each other, the area of ​​the first wall portions being larger than the area of ​​the second wall portions, at least one of the first wall portions having a thin portion that ruptures when pressure inside the case reaches or exceeds a predetermined value and discharges gas inside the case to the outside, and each of the secondary batteries has an inter-cell separator disposed between the first wall portions that are adjacent and arranged opposite each other.

[0016] [8] The battery pack according to [7], wherein at least a portion of the thin-walled portion is positioned so as not to overlap the inter-cell separator when viewed from a direction perpendicular to the first wall portion.

[0017] [9] The battery pack according to [7] or [8], wherein the inter-cell separator has a first region that is thinner than other portions, and at least a portion of the thin-walled portion faces the first region.

[0018]

[10] The battery pack according to [9], wherein the first region is a tapered portion.

[0019]

[11] The battery pack according to any one of [7] to

[10] , wherein the inter-cell separator has an elastic layer, and at least a portion of the thin portion faces the elastic layer.

[0020]

[12] The battery pack according to any one of [7] to

[11] , wherein the inter-cell separator includes an elastic layer and a heat-resistant layer, and the opposing area between the heat-resistant layer and the thin portion is larger than the opposing area between the elastic layer and the thin portion. [Effects of the Invention]

[0021] According to the present technology, it is possible to provide a highly reliable secondary battery and battery pack that can ensure a sufficient rupture area for the explosion-proof valve made of the fragile portion. [Brief explanation of the drawings]

[0022] FIG. 1 is a perspective view showing a configuration of a secondary battery according to an embodiment of the present technology. FIG. 2 is a front view showing a configuration of a secondary battery according to an embodiment of the present technology. FIG. 3 is a diagram showing the secondary battery shown in FIG. 1 as viewed from the direction of arrow III. FIG. 4 is a diagram showing the secondary battery shown in FIG. 1 as viewed from the direction of arrow IV. FIG. 5 is a diagram showing the secondary battery shown in FIG. 1 as viewed from the direction of arrow V. As shown in FIG. Figure 6 shows the secondary battery shown in Figure 1. Pond FIG. FIG. 7 is a cross-sectional view showing a weak portion (thin portion) that constitutes the gas release valve. FIG. 8 is a cross-sectional view showing another weak portion (thin portion) that constitutes the gas release valve. FIG. 9 is a diagram showing another arrangement of the gas release valve. FIG. 10 is a diagram showing still another arrangement of the gas release valve. FIG. 11 is a diagram showing still another arrangement of the gas release valve. FIG. 12 is a diagram showing another embodiment of the gas release valve. FIG. 13 is a diagram showing still another embodiment of the gas release valve. FIG. 14 is a schematic diagram showing the configuration of a battery pack. FIG. 15 is a schematic diagram of a battery pack in which only an elastic layer is provided between stacked secondary batteries. FIG. 16 is a schematic diagram showing a state in which the first gas release valve is opened when gas is released from the battery pack shown in FIG. FIG. 17 is a schematic diagram of a battery pack in which only a heat-resistant layer is provided between stacked secondary batteries. FIG. 18 is a schematic diagram showing a state in which the first gas release valve is opened when gas is released from the battery pack shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0023] Hereinafter, embodiments of the present technology will be described. Note that the same or corresponding parts are denoted by the same reference characters, and description thereof may not be repeated.

[0024] In the embodiments described below, when numbers, amounts, etc. are mentioned, the scope of the present technology is not necessarily limited to those numbers, amounts, etc., unless otherwise specified. Furthermore, in the following embodiments, each component is not necessarily essential to the present technology, unless otherwise specified. Furthermore, the present technology is not necessarily limited to those that achieve all of the effects and advantages mentioned in the present embodiments.

[0025] In this specification, the terms "comprise," "include," and "have" are open-ended. That is, when a certain feature is included, other features may or may not be included.

[0026] Furthermore, when geometric terms and terms expressing positional and directional relationships are used in this specification, such as "parallel," "orthogonal," "45° diagonal," "coaxial," and "along," these terms allow for manufacturing errors and slight variations. When terms expressing relative positional relationships, such as "upper side" and "lower side," are used in this specification, these terms are used to indicate relative positional relationships in a single state, and the relative positional relationships can be reversed or rotated to any angle depending on the installation direction of each mechanism (for example, by turning the entire mechanism upside down).

[0027] In this specification, the term "secondary battery" is not limited to lithium ion batteries, but may include other secondary batteries such as nickel-metal hydride batteries and sodium ion batteries. In this specification, the term "electrode" may collectively refer to a positive electrode and a negative electrode.

[0028] In the drawings, the direction along the winding axis of the electrode body provided in the secondary battery is the X direction as a first direction, the Y direction as a second direction which is perpendicular to the first direction and the short side direction of the electrode body as seen from the first direction, and the Z direction as a third direction which is perpendicular to the first direction and the long side direction of the electrode body as seen from the first direction. Also, to make the invention easier to understand, the dimensions of each component in the drawings may be shown differently from the actual dimensions.

[0029] In this specification, the first direction (X direction) may be referred to as the "width direction" of the secondary battery or the case body, the second direction (Y direction) may be referred to as the "thickness direction" of the secondary battery or the case body, and the third direction (Z direction) may be referred to as the "height direction" of the secondary battery or the case body.

[0030] (Overall configuration of secondary battery) The overall configuration of the secondary battery will be described with reference to Figures 1 to 6. Figure 1 is a perspective view of the secondary battery 1, Figure 2 is a front view, and Figures 3 to 5 are views showing the secondary battery 1 shown in Figure 1 as viewed from the directions of arrows III, IV, and V, respectively. Figure 6 is a front cross-sectional view of the secondary battery 1 shown in Figure 1.

[0031] The secondary battery 1 can be mounted in an electric vehicle (BEV: Battery Electric Vehicle), a plug-in hybrid electric vehicle (PHEV: Plug-in Hybrid Electric Vehicle), a hybrid electric vehicle (HEV: Hybrid Electric Vehicle), etc. However, the use of the secondary battery 1 is not limited to being mounted in a vehicle.

[0032] 1 to 5, the secondary battery 1 includes a case 100, an electrode assembly 200, and a current collector 400. The case 100 includes a case body 110, a first sealing plate 121, and a second sealing plate 122.

[0033] When configuring a battery pack including secondary batteries 1, multiple secondary batteries 1 are stacked in their thickness direction. The stacked secondary batteries 1 may be constrained in the stacking direction (Y direction) by a constraining member to form a battery module, or the battery pack may be directly supported on the side surface of a battery pack case without using a constraining member.

[0034] The case body 110 is made of a cylindrical, preferably rectangular, member. This results in a rectangular secondary battery 1. The case body 110 is made of metal. Specifically, the case body 110 is made of aluminum, an aluminum alloy, iron, an iron alloy, or the like.

[0035] 1 and 2, a first sealing plate 121 and a second sealing plate 122 are provided at both ends of the case body 110. The case body 110 is made by, for example, abutting the edges of bent plate-shaped members (the joint shown in FIG. 3). 115 ) and joined together (for example, by laser welding), it can be formed into a square tube shape. The corners of the "square tube shape" may have an R shape. 115 extends on the outer peripheral surface of the case body 110 in the first direction (X direction).

[0036] In this embodiment, the case body 110 is formed so that it is longer in the width direction (X direction) of the secondary battery 1 than in the thickness direction (Y direction) and height direction (Z direction) of the secondary battery 1. The dimension (width) of the case body 110 in the X direction is preferably about 30 cm or more. This allows for the construction of a relatively large (high-capacity) secondary battery 1. The dimension (height) of the case body 110 in the Z direction is preferably about 20 cm or less, more preferably about 15 cm or less, and even more preferably about 10 cm or less. This allows for the construction of a relatively low-height secondary battery 1, which improves, for example, the mountability in a vehicle.

[0037] The case main body 110 includes a pair of first side surface portions 110Y and a pair of second side surface portions 110Z. The pair of first side surface portions 110Y constitute part of the side surfaces of the case 100. The pair of second side surface portions 110Z constitute the bottom surface portion and the top surface portion of the case 100. The pair of first side surface portions 110Y and the pair of second side surface portions 110Z are arranged to intersect with each other. The pair of first side surface portions 110Y and the pair of second side surface portions 110Z are connected to the first sealing plate 121 and the second sealing plate 122 at their respective ends. It is desirable that each of the pair of first side surface portions 110Y has a larger area than each of the pair of second side surface portions 110Z. It is desirable that each of the pair of first side surface portions 110Y has a larger area than each of the first sealing plate 121 and the second sealing plate 122.

[0038] 4, a first opening 113 is provided at a first end in a first direction (X direction) of case body 110. First opening 113 is sealed by a first sealing plate 121. First opening 113 and first sealing plate 121 have a substantially rectangular shape with the Y direction as the short side direction and the Z direction as the long side direction.

[0039] A negative electrode terminal 131 (first electrode terminal) and a liquid inlet 124 are provided on the first sealing plate 121. A configuration in which a gas release valve is provided on the first sealing plate 121 can also be adopted, but in this embodiment, a gas release valve made of a fragile portion is provided on the first side surface portion 110Y as described below, and therefore, in this embodiment, no gas release valve is provided on the first sealing plate 121. The positions of the negative electrode terminal 131 and the liquid inlet 124 can be changed as appropriate.

[0040] 5, a second opening 114 is provided at an end of a second side of case body 110 opposite to the first direction in the first direction (X direction). Second opening 114 is sealed by a second sealing plate 122. Second opening 114 and second sealing plate 122 have a generally rectangular shape with the Y direction as the short side direction and the Z direction as the long side direction.

[0041] A positive electrode terminal 132 (second electrode terminal) and a liquid inlet hole 134 are provided on the second sealing plate 122. A configuration in which a gas release valve is provided on the second sealing plate 122 can also be adopted, but in this embodiment, a gas release valve made of a fragile portion is provided on the first side surface portion 110Y as described below, and therefore, in this embodiment, a gas release valve is not provided on the second sealing plate 122. The positions of the positive electrode terminal 132 and the liquid inlet hole 134 can be changed as appropriate.

[0042] First sealing plate 121 and second sealing plate 122 are made of metal. Specifically, first sealing plate 121 and second sealing plate 122 are made of aluminum, an aluminum alloy, iron, an iron alloy, or the like.

[0043] In this embodiment, it is preferable that the thickness of each of first sealing plate 121 and second sealing plate 122 is greater than the thickness of case body 110 (plate thickness).

[0044] The negative electrode terminal 131 is electrically connected to the negative electrode of the electrode body 200. The negative electrode terminal 131 is attached to the first sealing plate 121, that is, the case 100.

[0045] The positive electrode terminal 132 is electrically connected to the positive electrode of the electrode body 200. The positive electrode terminal 132 is attached to the second sealing plate 122, that is, the case 100.

[0046] The negative electrode terminal 131 is made of a conductive material (more specifically, a metal), and may be made of, for example, copper or a copper alloy. The outer surface of the negative electrode terminal 131 may be provided with a portion or layer made of aluminum or an aluminum alloy.

[0047] The positive electrode terminal 132 is made of a conductive material (more specifically, a metal), and may be made of, for example, aluminum or an aluminum alloy.

[0048] The liquid inlet holes 124 and 134 are sealed with a sealing member (not shown), which may be, for example, a blind rivet or other metal member.

[0049] The electrode assembly 200 is a flat-shaped electrode assembly having a positive electrode plate and a negative electrode plate. The electrode assembly 200 is a wound-type electrode assembly in which a strip-shaped positive electrode plate and a strip-shaped negative electrode plate are wound together via a strip-shaped separator (not shown). However, in this specification, the term "electrode assembly" is not limited to a wound-type electrode assembly, but may also be a stacked-type electrode assembly in which multiple positive electrode plates and multiple negative electrode plates are alternately stacked. The strip-shaped separator may be made of, for example, a polyolefin microporous membrane. The electrode assembly may include multiple positive electrode plates and multiple negative electrode plates, and the positive electrode tabs provided on each positive electrode plate may be stacked to form a positive electrode tab, or the negative electrode tabs provided on each negative electrode plate may be stacked to form a negative electrode tab.

[0050] 6, case 100 houses electrode assembly 200. Electrode assembly 200 is housed in case 100 so that its winding axis is parallel to the X direction.

[0051] Specifically, one or more wound electrode bodies 200 are housed together with an electrolytic solution (electrolyte) (not shown) inside an insulating sheet 600 arranged in the case 100. The electrolytic solution (nonaqueous electrolytic solution) can be, for example, a nonaqueous solvent obtained by mixing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in a volume ratio (25°C) of 30:30:40, in which LiPF6 is dissolved at a concentration of 1.2 mol / L. A solid electrolyte may be used instead of the electrolytic solution.

[0052] The insulating sheet 600 may be made of, for example, resin. More specifically, the material of the insulating sheet 600 may be, for example, polypropylene (PP), polyethylene terephthalate (PET), polyphenylene sulfide (PPS), polyimide (PI), or polyolefin (PO).

[0053] The insulating sheet 600 does not necessarily have to cover the entire surface of the electrode assembly 200. The insulating sheet 600 preferably covers approximately 50% or more, and more preferably approximately 70% or more, of the area of ​​the outer surface of the electrode assembly. Of the six faces of the substantially rectangular parallelepiped (flat) electrode assembly 200, the insulating sheet 600 preferably covers the entire four faces other than at least the two faces on which the negative electrode tab group 220 and the positive electrode tab group 250, which will be described later, are formed.

[0054] The electrode assembly 200 includes a main body portion (a portion where positive electrode plates and negative electrode plates are stacked with a separator interposed therebetween), a negative electrode tab group 220 (first electrode tab group), and a positive electrode tab group 250 (second electrode tab group).

[0055] The main body is composed of negative and positive electrode plates, which will be described later. The negative electrode tab group 220 is located at the end of a first side of the electrode body 200 in a first direction (X direction) relative to the main body. In this embodiment, the first side is the first sealing plate 121 side. The positive electrode tab group 250 is located at the end of a second side in the first direction (X direction) relative to the main body. In this embodiment, the second side is the second sealing plate 122 side.

[0056] The negative electrode tab group 220 and the positive electrode tab group 250 are formed so as to protrude from the center portion of the electrode body 200 toward the first sealing plate 121 or the second sealing plate 122, respectively.

[0057] The current collector 400 includes a negative electrode current collector 410 (first current collector) and a positive electrode current collector 420 (second current collector). The negative electrode current collector 410 and the positive electrode current collector 420 are each made of a plate-shaped member. The electrode assembly 200 is electrically connected to the negative electrode terminal 131 and the positive electrode terminal 132 via the current collector 400.

[0058] The negative electrode current collector 410 is disposed on the first sealing plate 121 via a resin insulating member. The negative electrode current collector 410 is electrically connected to the negative electrode tab group 220 and the negative electrode terminal 131. The negative electrode current collector 410 is made of a conductive material (more specifically, a metal), and may be made of, for example, copper or a copper alloy.

[0059] The positive electrode current collector 420 is disposed on the second sealing plate 122 via a resin insulating member. The positive electrode current collector 420 is electrically connected to the positive electrode tab group 250 and the positive electrode terminal 132. The positive electrode current collector 420 is made of a conductive material (more specifically, a metal), and may be made of, for example, aluminum or an aluminum alloy. The positive electrode tab group 250 may be electrically connected to the second sealing plate 122 directly or via the positive electrode current collector 420. In this case, the second sealing plate 122 may serve as the positive electrode terminal 132.

[0060] Both the negative electrode tab group 220 and the positive electrode tab group 250 are housed in the case 100 in a curved folded state.

[0061] (Configuration of the first gas exhaust valve 151) Next, the arrangement and configuration of the first gas release valve 151 in this embodiment will be described with reference to Figures 1, 2, and 6 to 13. Figure 7 is a cross-sectional view showing a weak portion (thin portion) that constitutes the gas release valve, Figure 8 is a cross-sectional view showing a weak portion (thin portion) of another configuration that constitutes the gas release valve, Figures 9 to 11 are diagrams showing other arrangements of the gas release valve, and Figures 12 and 13 are diagrams showing other forms of the gas release valve. In each diagram, a black triangle is used to conveniently indicate the position where the first gas release valve 151 is provided.

[0062] 1, in secondary battery 1 of the present embodiment, groove-shaped first gas release valves 151 made of fragile portions are provided on one first side surface portion 110Y of case body 110, and are provided in two locations: near the end on the first sealing plate 121 side and near the end on the second sealing plate 122 side. The fragile portions in the present embodiment may be configured so that when the pressure inside case body 110 reaches or exceeds a predetermined value, the fragile portions rupture before other regions do, thereby discharging gas inside case body 110 to the outside of case body 110.

[0063] It is preferable that first gas exhaust valves 151 are provided near the end on the first sealing plate 121 side and near the end on the second sealing plate 122 side. When one first gas exhaust valve 151 breaks to form a first opening, gas is exhausted to the outside of case 100 through this first opening. At this time, even if a component such as electrode body 200 disposed inside case 100 blocks the first opening, the other first gas exhaust valve 151 will then break to form a second opening. This allows gas to be exhausted to the outside of case 100 through the second opening. This results in a secondary battery 1 with higher reliability.

[0064] 6, the length (L1) of the first gas release valve 151 in the Z direction (height direction of the secondary battery 1) is preferably at least 1 / 2, and more preferably at least 2 / 3, of the height (H1) of the secondary battery 1. The width (W1) of the first gas release valve 151 in the X direction (width direction of the secondary battery 1) is preferably 0.05 mm or more. The width (W1) of the first gas release valve 151 in the X direction is preferably 10 mm or less, more preferably 5 mm or less, and even more preferably 2 mm or less.

[0065] It is preferable that the width (W1) in the X direction of the first gas exhaust valve 151 is 1 / 3 or less of the width between the end of the negative electrode active material layer of the electrode body 200 and the inner surface of the first sealing plate 121 (D1 in the figure) or the width between the end of the negative electrode active material layer of the electrode body 200 and the inner surface of the second sealing plate 122 (D2 in the figure).

[0066] In this embodiment, the winding axis of the electrode body 200 extends in the X direction, whereas the first gas release valve 151 is linear and extends in the Z direction intersecting the X direction.

[0067] 6, the area where the first gas release valve 151 is formed is preferably provided on the first side surface portion 110Y, which is the large-area side of the case body 110. Furthermore, it is preferable that the first gas release valve 151 be provided in a position that does not face the electrode assembly 200. Specifically, on the large-area side of the case body 110, on the first sealing plate 121 side, it is preferable that the first gas release valve 151 be provided in a region between the end of the negative electrode active material layer of the electrode assembly 200 and the inner surface of the first sealing plate 121 (D1 in the figure). Although this depends on the capacity of the secondary battery 1, it is preferable that the first gas release valve 151 be provided in a region within approximately 3 cm of the inner surface of the first sealing plate 121.

[0068] Similarly, on the second sealing plate 122 side, it is preferable to provide the first gas release valve 151 in the region between the end of the negative electrode active material layer of the electrode body 200 and the inner surface of the second sealing plate 122 (D2 in the figure). Although it depends on the capacity of the secondary battery 1, it is preferable to provide the first gas release valve 151 in a region within approximately 3 cm from the inner surface of the second sealing plate 122.

[0069] As shown in Fig. 7, the first gas exhaust valve 151 may have a groove structure with a triangular cross section recessed in the thickness direction of the case body 110. As shown in Fig. 8, the first gas exhaust valve 151 may have a groove structure with a concave cross section that is thinner than other regions. For example, in either groove structure, the remaining thickness (t2) of the case body 110 (t1) may be 1 / 3 or less (t2 ≦ (t1 / 3)) It is preferable that the width of the groove is smaller than the width of the recessed groove as shown in FIG.

[0070] By providing the first gas release valve 151 as described above, the first gas release valve 151 is positioned opposite the negative electrode tab group 220 and the positive electrode tab group 250 that are accommodated in a curved folded state inside the case 100. This makes it possible to easily operate the first gas release valve 151, resulting in a highly reliable secondary battery.

[0071] When the first side surface portion 110Y is viewed in a plane, a portion of the first gas exhaust valve 151 may overlap with the main body portion of the electrode body 200, but it is preferable that the first gas exhaust valve 151 is positioned so that, for example, 50% or more, more preferably 70% or more of the total area of ​​the first gas exhaust valve 151 does not overlap when viewed in a plane.

[0072] By providing the first gas exhaust valve 151 in this manner, the first gas exhaust valve 151 becomes more susceptible to breakage, and is more likely to function as an explosion-proof valve. In particular, even if gas is generated near either the end of the electrode body 200 on the first sealing plate 121 side or the end of the electrode body 200 on the second sealing plate 122 side, the first gas exhaust valve 151 on the closer side will operate, shortening the gas exhaust path and improving gas exhaust performance. Furthermore, by providing the first gas exhaust valve 151 in the above-mentioned region, for example, when the secondary batteries 1 are stacked to form an assembled battery, do Even when used, the high-temperature gas discharged from the first gas discharge valve 151 is prevented from being directly blown onto the adjacent secondary battery 1 (preventing the spread of fire). Furthermore, clogging of the disposal path inside the secondary battery 1 can be prevented. The configuration of the battery pack will be described later.

[0073] The position at which the first gas exhaust valve 151 is provided is not limited to the structure in which two first gas exhaust valves 151 are provided on one first side surface portion 110Y as described above. For example, as shown in Fig. 9, the first gas exhaust valve 151 may be provided on both first side surface portions 110Y. Furthermore, as shown in Fig. 10, the first gas exhaust valve 151 may be provided on one end side of one first side surface portion 110Y, and the first gas exhaust valve 151 may be provided on the other end side of the other first side surface portion 110Y.

[0074] The first gas exhaust valve 151 described above is provided near the end on the first sealing plate 121 side and / or near the end on the second sealing plate 122 side, and extends in the Z direction. However, as shown in FIG. 11 , the first gas exhaust valve 151 may extend in the X direction so as to include the end on the first sealing plate 121 side and the end on the second sealing plate 122 side. It is not necessary for both ends of the first gas exhaust valve 151 to be located near the end on the first sealing plate 121 side and the end on the second sealing plate 122 side; it is sufficient if either end is located at the end on the sealing plate side. Note that, as shown in FIG. 11 , when the first gas exhaust valve 151 extends in the X direction, it is preferable that the electrode body 200 is a wound electrode body and that the winding axis of the electrode body 200 is arranged to extend in the X direction. In this case, it is preferable that the first gas exhaust valve 151 be arranged at a position facing a curved portion formed at the end of the wound electrode body.

[0075] The shape of the first gas exhaust valve 151 is not limited to a shape consisting of only a straight line (first straight line portion) as described above. As shown in Fig. 12, second gas exhaust valves 152, which are second straight line portions extending in a direction intersecting the first gas exhaust valve 151, which is the first straight line portion, may be provided at both ends and the center of the first gas exhaust valve 151. As shown in Fig. 13, second gas exhaust valves 152, which are second straight line portions extending in a direction intersecting the first gas exhaust valve 151, which is the first straight line portion, may be provided so as to extend from both ends of the first gas exhaust valve 151 toward the electrode assembly 200. The number of second gas exhaust valves 152 provided is not limited to the number described above and can be selected appropriately.

[0076] By selecting the position where the second gas exhaust valve 152 is installed, it is possible to increase the rupture area when the first gas exhaust valve 151 and the second gas exhaust valve 152 are ruptured during thermal runaway. Furthermore, by increasing the rupture area, it is possible to improve the gas exhaust capacity. Furthermore, by selecting the position where the second gas exhaust valve 152 is installed, it is possible to control how the first gas exhaust valve 151 and the second gas exhaust valve 152 open.

[0077] By providing the first gas exhaust valve 151 and / or the second gas exhaust valve 152 on the first side surface portion 110Y, there is no need to provide gas exhaust valves in other areas such as the second side surface portion 110Z, the first sealing plate 121, and the second sealing plate 122, so there is no need for space to provide gas exhaust valves in other areas, making it possible to achieve higher energy and higher density secondary batteries.

[0078] (Battery pack 1000) The configuration of a battery pack 1000 in which the above-described secondary batteries 1 are stacked will be described below with reference to Figs. 14 to 18. Fig. 14 is a schematic diagram showing the configuration of the battery pack 1000. Fig. 15 is a schematic diagram of the battery pack 1000 in which only elastic layers are provided between stacked secondary batteries. Fig. 16 is a schematic diagram showing the open state of the first gas release valve 151 when gas is released from the battery pack 1000 shown in Fig. 15. Fig. 17 is a schematic diagram of the battery pack in which only heat-resistant layers are provided between stacked secondary batteries. Fig. 18 is a schematic diagram showing the open state of the first gas release valve 151 when gas is released from the battery pack 1000 shown in Fig. 17. Each figure illustrates the battery pack 1000 in which two secondary batteries 1 are stacked, but the number is not limited thereto, and the same applies to a battery pack in which two or more secondary batteries 1 are stacked.

[0079] 14, the battery pack 1000 has two secondary batteries 1 stacked with an inter-cell separator 300 between them, with the first side surface portions 110Y of the cases 100 facing each other. The battery pack 1000 may have various configurations, such as a configuration in which the two secondary batteries 1 are housed in a frame, a configuration in which the batteries are housed in a box-shaped frame, or a configuration in which a pair of end plates are used and the end plates are restrained by bind bars.

[0080] Inter-cell separator 300 is preferably a resin plate, a rubber sheet, a heat insulating material, or a laminate of these. The laminate is preferably an insulating and heat-resistant material. Inter-cell separator 300 shown in FIG. 14 includes elastic layer 310 and heat-resistant layer 320.

[0081] The elastic layer 310 may be made of silicone rubber, fluororubber, urethane rubber, natural rubber, styrene butadiene rubber, butyl rubber, ethylene propylene rubber (EPM, EPDM), butadiene rubber, isoprene rubber, norbornene rubber, etc. The thickness of the elastic layer 310 is preferably, for example, 0.5 mm or more and 10 mm or less.

[0082] The elastic modulus of the elastic layer 310 varies depending on the pressing speed, history, pressing range, etc., so the following definition of elastic modulus is used. m's Using a square test piece, an FS curve (pressure rate 30 N / min) is obtained. The horizontal axis represents the compression rate and the vertical axis represents the pressure. The elastic modulus is calculated from the slope of the compression rate from 1% to 20%. The value is preferably 1 MPa or more and 10 MPa or less.

[0083] The heat-resistant layer 320 is made of a material that has a lower elastic modulus and better heat resistance than the elastic layer 310. For example, a high-melting-point resin (a resin with a higher melting point than the resin constituting the elastic layer), a resin member containing ceramic particles, silica aerogel, a porous body mainly made of silica, etc. Preferably, the heat-resistant layer 320 has higher heat insulation properties (lower thermal conductivity per unit volume) than the elastic layer 310. The thickness of the heat-resistant layer 320 is, for example, preferably 0.5 mm or more and 10 mm or less.

[0084] It is preferable that the inter-cell separator 300 is disposed so as not to face the first gas exhaust valve 151. It is not preferable that the inter-cell separator 300 completely blocks the first gas exhaust valve 151, and the first gas exhaust valve 151 may be partially covered by the inter-cell separator 300. As will be described later, there may be cases where it is acceptable even if the first gas exhaust valve 151 is completely blocked by the inter-cell separator 300.

[0085] 14, the elastic layer 310 is disposed on the first side surface portion 110Y on which the first gas exhaust valve 151 is provided, so as not to cover the first gas exhaust valve 151. The heat-resistant layer 320 is disposed on the first side surface portion 110Y on which the first gas exhaust valve 151 is not provided, so as to cover the entire surface of the first side surface portion 110Y. The heat-resistant layer 320 has an area facing the first gas exhaust valve 151. In other words, the area of ​​the heat-resistant layer 320 is larger than the area of ​​the elastic layer 310.

[0086] As a result, when the inter-cell separator 300 is observed in a direction perpendicular to the first side surface portion 110Y (Z direction), the region of the inter-cell separator 300 facing the first gas release valve 151 has a region (first region R1) that is thinner than the region facing the first gas release valve 151. As a result, a space equivalent to the thickness of the elastic layer 310 is provided in the first region facing the first gas release valve 151.

[0087] This prevents the first gas release valve 151 from directly contacting the first region R1, and does not prevent the first gas release valve 151 from deforming or breaking, making it easier for the first gas release valve 151 to exhibit its opening function and improving its gas release capacity. Furthermore, because the elastic layer 310 covers the entire surface of the first side surface portion 110Y, it is also possible to prevent gas from directly contacting the adjacent secondary battery 1.

[0088] The first region R1 provided in the inter-cell separator 300 is thinner than the central portion (portion overlapping with the main body portion of the electrode assembly 200) of the inter-cell separator 300, and is therefore preferably located near the outer peripheral edge portion of the inter-cell separator 300. For example, when viewed from the Y direction, the proportion of the area of ​​the region overlapping with the first region R1 to the total area of ​​the first gas release valve 151 is preferably 20% or more, more preferably 30% or more, and even more preferably 50% or more.

[0089] In terms of the positional relationship between the first gas release valve 151 and the inter-cell separator 300, it is preferable that the opposing area between the heat-resistant layer 320 and the first gas release valve 151 is larger than the opposing area between the elastic layer 310 and the first gas release valve 151. The first gas release valve 151 may be positioned so that part of it overlaps with the inter-cell separator 300. For example, when observed in a direction perpendicular to the first side surface portion 110Y (Y direction), it is preferable that the first gas release valve 151 is positioned so that 50% or more, more preferably 70% or more of the total area thereof does not overlap.

[0090] Next, with reference to Fig. 15 to Fig. 18, other positional relationships between the first gas release valve 151 and the inter-cell separator 300 will be described. The inter-cell separator 300 shown in Fig. 15 and Fig. 16 is provided with only the heat-resistant layer 320. In this configuration, the first regions R1 provided at both ends of the heat-resistant layer 320 have tapered portions whose ends become thinner toward both ends. 320t It has the following characteristics.

[0091] In this way, even when only the heat-resistant layer 320 is used, the tapered portion 320t 16, a gap is formed between the first gas exhaust valve 151 and the first gas exhaust valve 151, and therefore the valve opening function of the first gas exhaust valve 151 and the exhaust capacity of the gas G1 are not impaired.

[0092] 17 and 18 show another arrangement of the first gas release valve 151 and the inter-cell separator 300, in which the inter-cell separator 300 is provided with only the elastic layer 310. In this configuration, the first regions R1 provided at both ends of the elastic layer 310 cover the first gas release valve 151.

[0093] However, even when the first gas exhaust valve 151 is covered by the elastic layer 310, the elastic layer 310 can deform. As a result, when the first gas exhaust valve 151 functions in the first region R1 and the gas G1 is exhausted, the elastic layer 310 deforms. As a result, even with this configuration, the opening function of the first gas exhaust valve 151 and the exhaust capacity of the gas G1 are not impaired.

[0094] Although the embodiments of the present technology have been described above, the embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present technology is defined by the claims, and it is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0095] 1 secondary battery, 100 case, 110 case body, 110Y first side portion, 110Z second side portion, 113 first opening, 114 second opening, 115 joint portion, 121 first sealing plate, 122 second sealing plate, 124, 134 liquid inlet, 131 negative electrode terminal, 132 positive electrode terminal, 151 first gas release valve, 152 second gas release valve, 200 electrode body, 220 negative electrode tab group, 250 positive electrode tab group, 300 inter-cell separator, 310 elastic layer, 320 heat-resistant layer, 400 current collector, 410 negative electrode current collector, 420 positive electrode current collector, 600 insulating sheet, 1000 assembled battery.

Claims

1. an electrode assembly including a first electrode and a second electrode having a polarity different from that of the first electrode; a case that houses the electrode assembly, The case is a case body having a first opening at one end and a second opening at the other end; a first sealing plate that seals the first opening; a second sealing plate that seals the second opening, The case body includes: a pair of first wall portions facing each other and a pair of second wall portions facing each other, The area of ​​the first wall portion is larger than the area of ​​the second wall portion, the electrode body has a first electrode tab group electrically connected to the first electrodes at an end on the first sealing plate side, the electrode body has a second electrode tab group electrically connected to the second electrodes at an end on the second sealing plate side, a first electrode terminal electrically connected to the first electrode tab group is attached to the first sealing plate; second electrode terminals electrically connected to the second electrode tab group are attached to the second sealing plate; At least one of the first walls has a thin-walled portion that breaks when the pressure inside the case reaches a predetermined value or more, and discharges gas inside the case to the outside of the case, the thin-walled portion includes a first thin-walled portion and a second thin-walled portion, the first thin-walled portion is formed in a region facing the first sealing plate and an end of the main body portion of the electrode body on the first sealing plate side, the second thin portion is formed in a region facing the second sealing plate and an end portion of the main body portion of the electrode body on the second sealing plate side, Secondary battery.

2. the thin-walled portion is provided near an end of one of the first wall portions on the first sealing plate side and near an end of the other of the first wall portions on the second sealing plate side, The secondary battery according to claim 1 .

3. the electrode body is a flat, wound electrode body and has a curved portion having a pair of curved outer surfaces; The thin-walled portion is formed at a position opposite to the curved portion. The secondary battery according to claim 1 .

4. The thin-walled portion has a first linear portion and a plurality of second linear portions intersecting the first linear portion. The secondary battery according to claim 1 .

5. The length of the case body in the direction connecting the first opening and the second opening is 30 cm or more. The secondary battery according to claim 1 .

6. In the direction in which the edge of the first opening in the first wall portion extends, the length of the first thin-walled portion is at least 1 / 2 of the length of the case body, and the length of the second thin-walled portion is at least 1 / 2 of the length of the case body. The secondary battery according to claim 1 .

7. A battery pack including a plurality of secondary batteries, The secondary battery includes an electrode assembly including a first electrode and a second electrode having a polarity different from that of the first electrode, and a case that houses the electrode assembly; the case includes a case body having a first opening at one end and a second opening at the other end, a first sealing plate that seals the first opening, and a second sealing plate that seals the second opening, the case body includes a pair of first wall portions opposed to each other and a pair of second wall portions opposed to each other, The area of ​​the first wall portion is larger than the area of ​​the second wall portion, At least one of the first walls has a thin-walled portion that breaks when the pressure inside the case reaches a predetermined value or more, and discharges gas inside the case to the outside of the case, In each of the secondary batteries, an inter-cell separator is disposed between the adjacent first wall portions that are disposed opposite to each other. Battery pack.

8. At least a part of the thin-walled portion is disposed at a position that does not overlap with the inter-cell separator when viewed from a direction perpendicular to the first wall portion. The battery pack according to claim 7 .

9. the inter-cell separator has a first region that is thinner than other portions, At least a portion of the thin-walled portion faces the first region. The battery pack according to claim 7 .

10. the first region is a tapered portion; The battery pack according to claim 9 .

11. the inter-cell separator has an elastic layer, At least a portion of the thin portion faces the elastic layer. The battery pack according to claim 7 .

12. the inter-cell separator includes an elastic layer and a heat-resistant layer, a facing area between the heat-resistant layer and the thin portion is larger than a facing area between the elastic layer and the thin portion; The battery pack according to claim 7 .

13. An electrode body including a first electrode and a second electrode having a polarity different from that of the first electrode; a case that houses the electrode assembly, The case is a case body having a first opening at one end and a second opening at the other end; a first sealing plate that seals the first opening; a second sealing plate that seals the second opening, The case body includes: a pair of first wall portions facing each other and a pair of second wall portions facing each other, The area of ​​the first wall portion is larger than the area of ​​the second wall portion, the electrode body has a first electrode tab group electrically connected to the first electrodes at an end on the first sealing plate side, the electrode body has a second electrode tab group electrically connected to the second electrodes at an end on the second sealing plate side, a first electrode terminal electrically connected to the first electrode tab group is attached to the first sealing plate; second electrode terminals electrically connected to the second electrode tab group are attached to the second sealing plate; At least one of the first walls has a thin-walled portion that breaks when the pressure inside the case reaches a predetermined value or more, and discharges gas inside the case to the outside of the case, the thin-walled portion is formed so as to extend from a region facing between the end of the main body portion of the electrode body on the first sealing plate side and the first sealing plate to a region facing between the end of the main body portion of the electrode body on the second sealing plate side and the second sealing plate. Secondary battery.

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