Secondary battery and battery pack

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 JP 2005-038773 A (Patent Document 1), JP 2001-126693 A (Patent Document 2), JP 2001-307707 A (Patent Document 3), JP 2001-345083 A (Patent Document 4), and JP 2001-266812 A (Patent Document 5). The explosion-proof valves formed of thin-walled parts and the like provided in these secondary batteries are provided on the side surface that is perpendicular to the terminal surface and has a large area. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2005-038773 A [Patent Document 2] JP 2001-126693 A [Patent Document 3] JP 2001-307707 A [Patent Document 4] JP 2001-345083 A [Patent Document 5] JP 2001-266812 A 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 standalone batteries, but for in-vehicle and power 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 provided perpendicular to the terminal surface and on the surface with the larger area.

[0006] The present technology has been made to solve the above-mentioned problems, and has an object to provide a highly reliable secondary battery and battery pack that can fully ensure the rupture function of an explosion-proof valve composed 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 body including a first electrode and a second electrode having a polarity different from that of the first electrode; and a case accommodating the electrode body, 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, the case body including a pair of first wall portions opposed to each other and a pair of second wall portions opposed to each other, an area of ​​the first wall portions being larger than an area of ​​the second wall portions, and at least one of the first wall portions having a thin-walled portion that breaks when pressure inside the case reaches or exceeds a predetermined value and discharges gas inside the case to the outside of the case.

[0009] [2] The secondary battery described in [1], wherein the thin-walled portion is provided near an end portion of one of the first wall portions facing the first sealing plate, and near an end portion of the other of the second wall portions facing the second sealing plate.

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

[0011] [4] The secondary battery described in any one of [1] to [3], wherein the thin portion is formed in at least one of a region facing between an end of the main body of the electrode body on the first sealing plate side and the first sealing plate, and a region facing between an 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 having a pair of curved outer surfaces, and the thin-walled portion is formed at 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, the secondary batteries 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, 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 sealing the first opening, and a second sealing plate sealing the second opening, the case body including a pair of first wall portions opposed to each other and a pair of second wall portions opposed to each other, an area of ​​the first wall portions being larger than an area of ​​the second wall portions, at least one of the first wall portions having a thin portion that breaks when pressure inside the case reaches or exceeds a predetermined value and discharges gas inside the case to the outside of the case, and each of the secondary batteries has an inter-cell separator disposed between adjacent and opposing first wall portions.

[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 an opposing area between the heat-resistant layer and the thin portion is larger than an opposing area between the elastic layer and the thin portion. Effect of the Invention

[0021] According to the present technology, it is possible to provide a highly reliable secondary battery and battery pack capable of ensuring a sufficient rupture area for the explosion-proof valve formed of the fragile portion. [Brief description of the drawings]

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

[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 will not be repeated.

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

[0025] In this specification, the words "comprise", "include" and "have" are open-ended, i.e., when a certain configuration is included, other configurations may or may not be included.

[0026] Furthermore, when geometric terms and terms expressing positional and directional relationships, such as "parallel," "orthogonal," "45° diagonal," "coaxial," and "along" are used in this specification, 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 one state, and the relative positional relationships can be inverted 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 of the secondary battery is the X direction as a first direction, the Y direction is the short side direction of the electrode body that is perpendicular to the first direction and seen from the first direction as a second direction, and the Z direction is the long side direction of the electrode body that is perpendicular to the first direction and seen from the first direction as a third direction. In addition, in order to make the invention easier to understand, the dimensions of each component in the drawings are sometimes 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 structure of secondary battery) The overall configuration of the secondary battery will be described with reference to Fig. 1 to Fig. 6. Fig. 1 is a perspective view of the secondary battery 1, Fig. 2 is a front view, and Fig. 3 to Fig. 5 are views showing the secondary battery 1 shown in Fig. 1 as viewed from the directions of arrows III, IV, and V, respectively. Fig. 6 is a front cross-sectional view of the secondary battery 1 shown in Fig. 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 on 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 an assembled battery including the 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 restraining member to form a battery module, or the assembled battery may be directly supported on the side surface of a battery pack case without using a restraining 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 can be formed into a square tube shape, for example, by abutting the ends of bent plate-like members (joint 115 exemplified in FIG. 3) and joining them together (for example, by laser welding). The corners of the "square tube" may have an R shape. The joint 115 in this embodiment extends in a first direction (X direction) on the outer circumferential surface of the case body 110.

[0036] In this embodiment, the case body 110 is formed to be 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 a relatively large (high capacity) secondary battery 1 to be configured. 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 a relatively low height (low height) secondary battery 1 to be configured, improving the mountability in a vehicle, for example.

[0037] The case 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 a part of the side surface 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 provided so as 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. Each of the pair of first side surface portions 110Y is preferably larger in area than each of the pair of second side surface portions 110Z. Each of the pair of first side surface portions 110Y is preferably larger in 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 a short side direction in the Y direction and a long side direction in the Z direction.

[0039] A negative electrode terminal 131 (first electrode terminal) and a liquid injection hole 124 are provided on the first sealing plate 121. A configuration in which a gas exhaust valve is provided on the first sealing plate 121 can also be adopted, but in this embodiment, since a gas exhaust valve made of a fragile portion is provided on the first side surface portion 110Y as described below, a gas exhaust valve is not provided on the first sealing plate 121 in this embodiment. The positions of the negative electrode terminal 131 and the liquid injection hole 124 can be changed as appropriate.

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

[0041] A positive electrode terminal 132 (second electrode terminal) and a liquid injection hole 134 are provided on the second sealing plate 122. A configuration in which a gas exhaust valve is provided on the second sealing plate 122 can also be adopted, but in this embodiment, since a gas exhaust valve made of a weak portion is provided on the first side surface portion 110Y as described below, in this embodiment, a gas exhaust valve is not provided on the second sealing plate 122. The positions of the positive electrode terminal 132 and the liquid injection 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 the present embodiment, it is preferable that the thickness of each of first sealing plate 121 and second sealing plate 122 is set to be 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, i.e., 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 by a sealing member (not shown) which may be, for example, a blind rivet or other metal member.

[0049] The electrode body 200 is a flat-shaped electrode body having a positive electrode plate and a negative electrode plate. The electrode body 200 is a wound-type electrode body in which a band-shaped positive electrode plate and a band-shaped negative electrode plate are both wound via a band-shaped separator (not shown). However, in this specification, the "electrode body" is not limited to a wound-type electrode body, and may be a laminated electrode body in which a plurality of positive electrode plates and a plurality of negative electrode plates are alternately laminated. The band-shaped separator may be composed of, for example, a polyolefin microporous film. The electrode body may include a plurality of positive electrode plates and a plurality of negative electrode plates, and the positive electrode tabs provided on each positive electrode plate may be laminated to form a positive electrode tab, or the negative electrode tabs provided on each negative electrode plate may be laminated 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 (non-aqueous electrolytic solution) is, for example, a non-aqueous solvent in which ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a volume ratio (25° C.) of 30:30:40, and LiPF 6 A solution having a concentration of 1.2 mol / L can be used. 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 body 200. The insulating sheet 600 preferably covers an area of ​​about 50% or more, and more preferably about 70% or more, of the outer surface of the electrode body. Of the six faces of the substantially rectangular parallelepiped (flat) electrode body 200, the insulating sheet 600 preferably covers the entire four faces other than at least two faces on which the negative electrode tab group 220 and the positive electrode tab group 250 described below are formed, respectively.

[0054] The electrode body 200 includes a main body portion (a portion in which positive electrode plates and negative electrode plates are stacked with a separator 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 part is composed of a negative electrode plate and a positive electrode plate, which will be described later. The negative electrode tab group 220 is located at an end of a first side of the electrode body 200 in a first direction (X direction) with respect to the main body part. The first side in this embodiment is the first sealing plate 121 side. The positive electrode tab group 250 is located at an end of a second side in the first direction (X direction) with respect to the main body part. The second side in this embodiment 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 body 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 within 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 exhaust 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 exhaust valve, Figure 8 is a cross-sectional view showing a weak portion (thin portion) of another configuration that constitutes the gas exhaust valve, Figures 9 to 11 are diagrams showing other arrangements and configurations of the gas exhaust valve, and Figures 12 and 13 are diagrams showing other forms of the gas exhaust valve. In each diagram, a black triangular shape is used to conveniently indicate the position where the first gas exhaust valve 151 is provided.

[0062] 1, in the secondary battery 1 of the present embodiment, a groove-shaped first gas release valve 151 made of a fragile portion is provided on one first side surface portion 110Y of the case body 110, and is provided in two locations, near the end portion on the first sealing plate 121 side and near the end portion on the second sealing plate 122 side. The fragile portion in the present embodiment may be configured to break prior to other regions when the pressure inside the case body 110 reaches or exceeds a predetermined value, thereby having the function of releasing gas inside the case body 110 to the outside of the case body 110.

[0063] It is preferable that a first gas exhaust valve 151 is provided near the end on the first sealing plate 121 side and near the end on the second sealing plate 122 side. When one of the first gas exhaust valves 151 breaks to form a first opening, gas is exhausted to the outside of the case 100 from this first opening. At this time, even if a component such as the electrode body 200 arranged in the case 100 blocks the first opening, the other first gas exhaust valve 151 next breaks to form a second opening. This allows gas to be exhausted to the outside of the case 100 from 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 1 / 2 or more, and more preferably 2 / 3 or more, 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 ⅓ 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 the present 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 region 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 region does not face the electrode body 200. Specifically, on the large area side of the case body 110, on the first sealing plate 121 side, the first gas release valve 151 may be provided in a region 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). Although it depends on the capacity of the secondary battery 1, the first gas release valve 151 may be provided in a region within about 3 cm from the inner surface of the first sealing plate 121.

[0068] Similarly, on the second sealing plate 122 side, the first gas release valve 151 may be provided 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, the first gas release valve 151 may be provided in a region within about 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 plate 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, it is preferable that the remaining thickness (t2) is 1 / 3 or less (t2<(t1 / 3)) of the plate thickness (t1) of the case body 110. Note that a groove with an even smaller width (for example, a notch) may be provided at the bottom of the groove with a concave cross section as shown in Fig. 8.

[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 within the case 100. This allows the first gas release valve 151 to operate easily, resulting in a highly reliable secondary battery.

[0071] When the first side portion 110Y is viewed in a plan view, a part of the first gas exhaust valve 151 may overlap with the main body portion of the electrode body 200; however, for example, it is preferable that the first gas exhaust valve 151 is positioned so that it does not overlap with at least 50% of the total area thereof, more preferably at least 70% thereof, when viewed in a plan view.

[0072] By providing the first gas exhaust valve 151 in this way, the first gas exhaust valve 151 becomes more likely to break, and the function as an explosion-proof valve can be easily realized. In particular, even if gas is generated in either the vicinity of the end of the electrode body 200 on the first sealing plate 121 side or the vicinity of the end of the electrode body 200 on the second sealing plate 122 side, the first gas exhaust valve 151 on the closer side operates, so that the gas exhaust path is shortened and the gas exhaust performance can be improved. Furthermore, by providing the first gas exhaust valve 151 in the above-mentioned region, for example, even when the secondary batteries 1 are stacked and used as a battery pack, the high-temperature gas exhausted from the first gas exhaust valve 151 is prevented from being directly blown onto the adjacent secondary batteries 1 (fire prevention). Furthermore, clogging of the disposal path inside the secondary batteries 1 can be prevented. The configuration of the battery pack will be described later.

[0073] The position where the first gas exhaust valve 151 is provided is not limited to the structure where two first gas exhaust valves 151 are provided on one first side surface portion 110Y 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 above-mentioned first gas exhaust valve 151 is provided in a position 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 be provided extending in the X direction so as to include the vicinity of the end on the first sealing plate 121 side and the vicinity of the end on the second sealing plate 122 side. It is not necessary that both ends of the first gas exhaust valve 151 are located near the end on the first sealing plate 121 side and the end on the second sealing plate 122 side, and it is sufficient that either one 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 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 is arranged at a position facing a curved portion formed at the end of the wound electrode body.

[0075] The form of the first gas exhaust valve 151 is not limited to a form consisting of only a straight line (first straight line portion) as described above. As shown in Fig. 12, the second gas exhaust valve 152, which is a second straight line portion 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, the second gas exhaust valve 152, which is a second straight line portion 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 body 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 provided, 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 provided, it is possible to control the manner in which the first gas exhaust valve 151 and the second gas exhaust valve 152 are opened.

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

[0078] (Battery pack 1000) The configuration of a battery pack 1000 in which the above-mentioned 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 an elastic layer is provided between the stacked secondary batteries, Fig. 16 is a schematic diagram showing the open state of the first gas exhaust valve 151 when gas is exhausted in the battery pack 1000 shown in Fig. 15, Fig. 17 is a schematic diagram of the battery pack in which only a heat-resistant layer is provided between the stacked secondary batteries, and Fig. 18 is a schematic diagram showing the open state of the first gas exhaust valve 151 when gas is exhausted in the battery pack 1000 shown in Fig. 17. In each figure, the battery pack 1000 in which two secondary batteries 1 are stacked is described, but the number is not limited, 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 bound by bind bars.

[0080] The 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 or heat resistant material. The inter-cell separator 300 shown in FIG. 14 includes an elastic layer 310 and a 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 elastic layer 310 varies depending on the pressing speed, history, pressing range, etc., so the following definition of elastic modulus is used. An FS curve (pressure rate 30 N / min) is obtained using a square test piece with one side 5 cm (the surface facing the case 100). The elastic modulus is calculated from the slope of the compression rate from 1% to 20% when the horizontal axis is the compression rate and the vertical axis is the pressure. The above value is preferably 1 MPa or more and 10 MPa or less.

[0083] The heat-resistant layer 320 is made of a material having a lower elastic modulus and a higher heat resistance than the elastic layer 310. For example, a high melting point resin (a resin having 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. are preferable. The heat-resistant layer 320 preferably has higher heat insulation (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 set to be larger than the area of ​​the elastic layer 310.

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

[0087] As a result, the first gas release valve 151 is not in direct contact with the first region R1, and deformation and breakage of the first gas release valve 151 are not hindered, making it easier for the first gas release valve 151 to exhibit its opening function and improving the gas release capacity. Furthermore, since the elastic layer 310 covers the entire surface of the first side portion 110Y, it is also possible to prevent the gas from directly contacting the adjacent secondary battery 1.

[0088] Since the first region R1 provided in the inter-cell separator 300 has a thickness thinner than the central portion (the portion overlapping with the main body portion of the electrode body 200) of the inter-cell separator 300, it is preferable that the first region R1 is located near the outer circumferential 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 exhaust 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 exhaust valve 151 is larger than the opposing area between the elastic layer 310 and the first gas exhaust valve 151. The first gas exhaust valve 151 may be positioned so as to partly overlap 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 exhaust valve 151 is positioned so that 50% or more, more preferably 70% or more of the total area does not overlap.

[0090] Next, other positional relationships between the first gas exhaust valve 151 and the inter-cell separator 300 will be described with reference to Fig. 15 to Fig. 18. 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 310t whose tips become thinner toward both ends.

[0091] In this way, even in the case of only the heat-resistant layer 320, by providing the tapered portion 310t, it is possible to prevent the first gas exhaust valve 151 from being completely blocked in the first region R1. Furthermore, as shown in Fig. 16, a gap is formed between the first gas exhaust valve 151 and the first gas exhaust valve 151, so that the 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 embodiment of the present technology has been described above, the embodiment disclosed herein should be considered as 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 scope and meaning equivalent to 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 injection hole, 131 negative electrode terminal, 132 positive electrode terminal, 151 first gas exhaust valve, 152 second gas exhaust 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 body, 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: The housing includes a pair of first walls opposed to each other and a pair of second walls 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 or exceeds a predetermined value, and discharges gas inside the case to the outside of the case. Secondary battery.

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

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

4. the thin portion is formed in at least one of a region facing between an end portion of the main body of the electrode body on the first sealing plate side and the first sealing plate, and a region facing between an end portion of the main body of the electrode body on the second sealing plate side and the second sealing plate. The secondary battery according to claim 1 .

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

6. The thin portion has a first straight line portion and a plurality of second straight line portions intersecting the first straight line portion. 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 pressure inside the case reaches or exceeds a predetermined value, and discharges gas inside the case to the outside of the case, Each of the secondary batteries has an inter-cell separator disposed between the adjacent first wall portions that are disposed opposite to each other. Battery pack.

8. At least a part of the thin portion is disposed at a position not overlapping 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 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.

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