Energy storage devices

Abstract

To improve the safety of a power storage device.SOLUTION: A power storage device 10 includes: an electrode body 20 which has a positive electrode and a negative electrode; a case 41 which stores the electrode body 20; and a safety device 50 which is provided in the case 41. The safety device 50 comprises a fire-extinguishing agent release part 52 which includes a microcapsule M that contains a fire-extinguishing agent and a storage part 52a that stores the microcapsule M. The fire-extinguishing agent release part 52 is configured so that the microcapsule M is released from the storage part 52a in conjunction with the activation of the safety device 50.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an electricity storage device. [Background technology]

[0002] Japanese Patent Application Laid-Open No. 2010-73595 discloses a non-aqueous electrolyte secondary battery including an electrode assembly and a battery can containing the electrode assembly. The inner wall of the battery can of the non-aqueous electrolyte secondary battery disclosed in this publication is coated with responsive microcapsules, each of which has a core material containing a flame-retardant component and a wall material covering the core material. Such a non-aqueous electrolyte secondary battery is said to effectively prevent thermal runaway.

[0003] Japanese Patent Laid-Open Publication No. 6-283206 discloses a battery having a negative electrode, a positive electrode, a separator, and an electrolyte solution. At least one of the separator and the electrolyte solution contains microcapsules containing chemical substances. Such a battery is said to be highly safe and have a high energy density. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-73595 [Patent Document 2] Japanese Patent Application Publication No. 6-283206 Summary of the Invention [Problem to be solved by the invention]

[0005] The present inventors wish to improve the safety of electricity storage devices. [Means for solving the problem]

[0006] The electricity storage device disclosed herein includes an electrode body having a positive electrode and a negative electrode, a case that houses the electrode body, and a safety device provided in the case. The safety device includes a fire extinguishing agent release section that includes microcapsules containing a fire extinguishing agent and a storage section that houses the microcapsules. The fire extinguishing agent release section is configured to release the microcapsules from the storage section in conjunction with the activation of the safety device. Such an electricity storage device has improved safety. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a partial cross-sectional view of an electricity storage device 10. As shown in FIG. [Figure 2] FIG. 2 is a schematic diagram showing the mounting structure of the positive electrode terminal 42 and the current collector 44. As shown in FIG. [Figure 3] FIG. 3 is a schematic diagram showing the mounting structure of the positive electrode terminal 42 and the current collector 44. As shown in FIG. [Figure 4] FIG. 4 is a schematic diagram showing a safety device 150 according to another embodiment. [Figure 5] FIG. 5 is a schematic diagram showing a safety device 150 according to another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] An embodiment of the technology disclosed herein will be described below with reference to the drawings. The embodiment described here is, of course, not intended to limit the present invention. The drawings are schematic and do not necessarily reflect the actual product. Furthermore, the same reference numerals are appropriately used for components and parts that perform the same function, and redundant explanations will be omitted where appropriate.

[0009] <Electricity Storage Device 10> FIG. 1 is a partial cross-sectional view of an electricity storage device 10. FIG. 1 illustrates a state in which the interior is exposed along one wide surface of a substantially rectangular parallelepiped case 41. In this specification, the term "electricity storage device" refers to a device that can charge and discharge. Electricity storage devices include batteries generally referred to as lithium ion batteries and lithium secondary batteries, as well as lithium polymer batteries and lithium ion capacitors. Secondary batteries generally refer to batteries that can be repeatedly charged and discharged as charge carriers move between positive and negative electrodes. Here, as an example, a lithium ion secondary battery is used as an electricity storage device.

[0010] The electricity storage device 10 is a so-called sealed battery. As shown in Fig. 1, the electricity storage device 10 includes an electrode assembly 20, a case 41, and a safety device 50. The electricity storage device 10 includes electrode terminals 42, 47 (a positive electrode terminal 42 and a negative electrode terminal 47) and a conductive path 55. The electricity storage device 10 includes current collectors 44, 49 that connect the electrode terminals 42, 47 and the electrode assembly 20.

[0011] <Electrode body 20> The electrode assembly 20 is housed in a case 41 while being covered with an insulating film (not shown) or the like. The electrode assembly 20 has a positive electrode sheet 21 as a positive electrode, a negative electrode sheet 22 as a negative electrode, and separator sheets 31 and 32 as separators. The positive electrode sheet 21, the negative electrode sheet 22, and the separator sheets 31 and 32 are each a long, strip-shaped member.

[0012] The positive electrode sheet 21 has a positive electrode current collector foil 21a (e.g., aluminum foil) of a predetermined width and thickness, and a positive electrode active material layer 21b containing a positive electrode active material formed on both sides thereof, except for an unformed portion 21a1 set at one end of the width direction with a fixed width. In a lithium-ion secondary battery, the positive electrode active material is, for example, a material that can release lithium ions during charging and absorb lithium ions during discharging, such as a lithium transition metal composite material. Generally, various positive electrode active materials have been proposed in addition to lithium transition metal composite materials, and there is no particular limitation to the positive electrode active material.

[0013] The negative electrode sheet 22 has a negative electrode current collector foil 22a (copper foil in this case) of a predetermined width and thickness, and a negative electrode active material layer 22b containing a negative electrode active material formed on both sides thereof, except for an unformed portion 22a1 set at a fixed width on one edge in the width direction. In a lithium-ion secondary battery, the negative electrode active material is, for example, a material such as natural graphite that can absorb lithium ions during charging and release the absorbed lithium ions during discharging. Generally, various negative electrode active materials other than natural graphite have been proposed, and there is no particular limitation.

[0014] For example, a porous resin sheet having required heat resistance and allowing the electrolyte to pass through is used for the separator sheets 31 and 32. Various separator sheets 31 and 32 have been proposed, and there is no particular limitation.

[0015] The width of the negative electrode active material layer 22b can be wider than that of the positive electrode active material layer 21b. The width of the separator sheets 31 and 32 is wider than that of the negative electrode active material layer 22b. The unformed portion 21a1 of the positive electrode current collector foil 21a and the unformed portion 22a1 of the negative electrode current collector foil 22a face opposite each other in the width direction. The positive electrode sheet 21, the separator sheet 31, the negative electrode sheet 22, and the separator sheet 32 ​​are aligned in the length direction and stacked in order and wound. The negative electrode active material layer 22b covers the positive electrode active material layer 21b with the separator sheets 31 and 32 interposed therebetween. The negative electrode active material layer 22b is covered by the separator sheets 31 and 32. The unformed portion 21a1 of the positive electrode current collector foil 21a protrudes from one side of the separator sheets 31 and 32 in the width direction. The unformed portion 22a1 of the negative electrode current collector foil 22a protrudes from the separator sheets 31 and 32 on the opposite side in the width direction.

[0016] Here, the electrode assembly 20 is a so-called wound-type electrode assembly. The structure of the electrode assembly 20 is not limited to this form. The structure of the electrode assembly 20 may be, for example, a laminated structure in which positive electrode sheets and negative electrode sheets are alternately laminated with separator sheets interposed therebetween.

[0017] Case 41 The case 41 houses the electrode assembly 20. Multiple electrode assemblies 20 may be housed inside the case 41. The case 41 includes a case body 41a and a lid 41b. The electrode assembly 20 is flattened along a plane including the winding axis so that it can be housed in the case body 41a. The electrode assembly 20 is housed in the case 41 such that, along the winding axis of the electrode assembly 20, the unformed portion 21a1 of the positive electrode current collector foil 21a is arranged on one side, and the unformed portion 22a1 of the negative electrode current collector foil 22a is arranged on the other side.

[0018] The case 41 may contain an electrolyte (not shown) together with the electrode assembly 20. A non-aqueous electrolyte obtained by dissolving a supporting salt in a non-aqueous solvent may be used as the electrolyte. Examples of non-aqueous solvents include carbonate-based solvents such as ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate. Examples of supporting salts include fluorine-containing lithium salts such as LiPF6.

[0019] <Case body 41a> The case body 41a has a generally rectangular parallelepiped shape with one side open. The case body 41a has a generally rectangular bottom surface 61, a pair of wide surface portions (not shown), and a pair of narrow surface portions 64, 65. The pair of wide surface portions each rise from a long side of the bottom surface 61. The pair of narrow surface portions 64, 65 each rise from a short side of the bottom surface 61. An opening 41a1 surrounded by the pair of wide surface portions and the pair of narrow surface portions 64, 65 is formed on one side of the case body 41a.

[0020] <Lid 41b> The lid 41b is attached to the opening 41a1 of the case body 41a, which is surrounded by the long sides of the pair of wide surface portions and the short sides of the pair of narrow surface portions 64, 65. The peripheral edge of the lid 41b is joined to the edge of the opening 41a1 of the case body 41a. This joining may be achieved, for example, by continuous welding without any gaps. This welding may be achieved, for example, by laser welding. The lid 41b may be provided with a safety valve 41b1 that operates at a predetermined pressure to release internal pressure. The safety valve 41b1 may be provided approximately in the center of the lid 41b.

[0021] Electrode terminals 42 and 47 are attached to the case 41. In this embodiment, a positive electrode terminal 42 and a negative electrode terminal 47 are attached to the lid 41b. The electrode terminals 42 and 47 are attached to the outside of the lid 41b via external insulating members 71, respectively.

[0022] The negative electrode current collector 49 is formed in a plate shape. The current collector 49 has a base 49a and a connecting piece 49b. The base 49a extends along the lid 41b. The connecting piece 49b is bent from the base 49a and extends into the inside of the case body 41a. The connecting piece 49b is connected to the unformed portion 22a1. The base 49a of the negative electrode current collector 49 is attached to the inside of the lid 41b via an internal insulating member 72.

[0023] A conductive path 55 is set between the positive electrode terminal 42 and the electrode body 20. In other words, the conductive path 55 connects the positive electrode terminal 42 and the electrode body 20. The conductive path 55 is provided inside the lid 41b.

[0024] 2 and 3 are schematic diagrams showing the mounting structure of the positive electrode terminal 42 and the current collector 44. 2 and 3 show a cross section of the positive electrode terminal 42, the current collector 44, and the safety device 50 mounted on the lid 41b. In FIG. 3, the direction in which the microcapsules M are released is indicated by an arrow.

[0025] 2, the lid 41b has a mounting hole 41b2 for mounting the positive electrode terminal 42 of the positive electrode. The mounting hole 41b2 penetrates the lid 41b at a predetermined position of the lid 41b. The current collector 44 and the positive electrode terminal 42 are mounted in the mounting hole 41b2 of the lid 41b via an external insulating member 71 and an internal insulating member 72. The outside of the mounting hole 41b2 may be provided with a step for attaching the external insulating member 71, a protrusion for positioning the external insulating member 71, or the like.

[0026] <Positive terminal 42> The positive electrode terminal 42 is a member that can be connected to an external connection part such as a bus bar. The positive electrode terminal 42 is made of a metal having required conductivity. The positive electrode terminal 42 may be made of the same type of metal as the positive electrode current collector foil 21a (see FIG. 1), such as aluminum or an aluminum alloy.

[0027] The positive electrode terminal 42 includes a head 42a and a shaft 42b. The head 42a is a portion disposed on the outside of the lid 41b. The head 42a is a generally flat plate-shaped portion that is larger than the mounting hole 41b2. The shaft 42b protrudes downward from the general center of the head 42a. The lower end of the shaft 42b reaches the inside of the case 41 (see FIG. 1). The shaft 42b is a portion that is attached to the mounting hole 41b2 via the external insulating member 71.

[0028] <External insulating member 71> The external insulating member 71 is attached to the upper surface of the lid 41b and around the mounting hole 41b2. The external insulating member 71 includes a seat 71a, a boss 71b, and a sidewall 71c. The seat 71a is located on the outer surface of the lid 41b around the mounting hole 41b2. The seat 71a has a generally flat shape that conforms to the shape of the lid 41b. The boss 71b protrudes from the bottom surface of the seat 71a. The boss 71b has an outer shape that conforms to the inner surface of the mounting hole 41b2 so that it can be attached to the mounting hole 41b2 of the lid 41b. The inner surface of the boss 71b forms an attachment hole into which the shaft 42b of the positive terminal 42 is attached. The sidewall 71c rises upward from the periphery of the seat 71a. The head 42a of the positive terminal 42 is attached to the area surrounded by the sidewall 71c of the external insulating member 71.

[0029] The external insulating member 71 is disposed between the lid 41b and the positive electrode terminal 42, and ensures insulation between the lid 41b and the positive electrode terminal 42. The external insulating member 71 also ensures airtightness of the mounting hole 41b2 of the lid 41b. From this perspective, it is preferable to use a material with excellent chemical resistance. In this embodiment, PFA is used for the external insulating member 71. PFA is a copolymer of tetrafluoroethylene and perfluoroalkoxyethylene (tetrafluoroethylene-perfluoroalkylvinylether copolymer). However, the material used for the external insulating member 71 is not limited to PFA. An internal insulating member 72 is provided on the inner surface of the lid 41b.

[0030] <Internal insulating member 72> The internal insulating member 72 is attached to the inside of the lid 41b around the mounting hole 41b2 of the lid 41b. The internal insulating member 72 includes a bottom wall 72a, a hole 72b, a side wall 72c, and a retaining portion 72d. The bottom wall 72a is disposed along the inner surface of the lid 41b. The bottom wall 72a is a generally flat plate-shaped portion. The bottom wall 72a is disposed along the inner surface of the lid 41b and is sized so as not to protrude from the lid 41b so as to be accommodated in the case body 41a (see FIG. 1). The hole 72b is a hole provided corresponding to the inner surface of the boss portion 71b of the external insulating member 71. The hole 72b is provided in the generally central portion of the bottom wall 72a. The side wall 72c rises downward from the peripheral edge of the bottom wall 72a. Since the internal insulating member 72 is disposed inside the case 41, it is preferable that the internal insulating member 72 have required chemical resistance. In this embodiment, PPS is used for the internal insulating member 72. PPS is a type of polyphenylene sulfide resin. However, the material used for the internal insulating member 72 is not limited to PPS. The internal insulating member 72 houses the conductive member 43, the reversal plate 51, and the base 44a of the current collector 44.

[0031] The holding portion 72d of the internal insulating member 72 is connected to the side wall 72c. The holding portion 72d is interposed between the reversal plate 51 and the current collector 44 and holds the reversal plate 51 and the current collector 44. The holding portion 72d can be configured to be attachable to the side wall 72c.

[0032] <Conductive member 43> The conductive member 43 is interposed between the electrode body 20 and the positive electrode terminal 42 inside the case 41, and constitutes part of the conduction path 55. The conductive member 43 is connected to the positive electrode terminal 42. The conductive member 43 is made of a metal having required conductivity. The same type of metal as the positive electrode terminal 42 may be used as the conductive member 43, and for example, aluminum or an aluminum alloy may be used.

[0033] The positive electrode terminal 42 is connected to the conductive member 43. The conductive member 43 has a bottom 43a and a side portion 43b. The bottom 43a is a portion that is arranged along the inner surface of the bottom wall 72a of the internal insulating member 72. The bottom 43a is a generally flat plate-shaped portion. The bottom 43a has dimensions that allow it to be housed in the internal insulating member 72. A hole 43a1 is formed in the bottom 43a. The hole 43a1 is a hole that is provided corresponding to the hole 72b of the internal insulating member 72. The lower end of the shaft portion 42b of the positive electrode terminal 42 is inserted through the hole 43a1. The conductive member 43 is connected to the shaft portion 42b of the positive electrode terminal 42 around the hole 43a1.

[0034] The connection form between the conductive member 43 and the positive electrode terminal 42 is not particularly limited. For example, the inner circumferential surface of the hole 43a1 of the conductive member 43 and the lower end of the shaft portion 42b of the positive electrode terminal 42 may be connected by welding or the like. A cylindrical or plate-shaped crimping piece may be provided at the lower end of the shaft portion 42b of the positive electrode terminal 42. The crimping piece of the positive electrode terminal 42 may be connected to the bottom portion 43a of the conductive member 43 by being bent or pressed while inserted into the hole 43a1 of the conductive member 43. To improve conductivity, the crimping piece of the positive electrode terminal 42 may be partially joined to the conductive member 43 by welding or the like.

[0035] The side portion 43b of the conductive member 43 rises downward from the peripheral edge of the bottom portion 43a along the side wall 72c of the internal insulating member 72. The side portion 43b of the conductive member 43 is connected to the current collector 44 connected to the electrode assembly 20 via the reversal plate 51. The form of the conductive member 43 is not limited to this form as long as it is connected to the positive electrode terminal 42. The conductive member 43 may be provided integrally with the positive electrode terminal 42.

[0036] <Current collector 44> The current collector 44 is interposed between the electrode assembly 20 and the positive electrode terminal 42 inside the case 41, and constitutes part of the conductive path 55. The current collector 44 is also referred to as an internal terminal. The current collector 44 is made of a metal having a required conductivity. The same type of metal as the positive electrode current collector foil 21a may be used as the current collector 44, and for example, aluminum or an aluminum alloy may be used.

[0037] The current collector 44 is formed in a plate shape. The current collector 44 has a base 44a and a connecting piece 44b. Like the connecting piece 49b of the negative electrode current collector 49, the connecting piece 44b is bent from the base 44a and extends downward inside the case 41 (see FIG. 1). The connecting piece 44b is connected to the unformed portion 21a1 of the positive electrode current collector foil 21a of the electrode body 20. The base 44a is bent from the connecting piece 44b and extends along the lid 41b. The base 44a is held by the inner surface of the holding portion 72d of the internal insulating member 72.

[0038] The base 44a has a protrusion 44a1. The protrusion 44a1 is a portion that protrudes upward from the base 44a. The protrusion 44a1 is provided in approximately the center of the base 44a. A through-hole 44a2 is formed in the protrusion 44a1. The through-hole 44a2 is provided in approximately the center of the protrusion 44a1. In this embodiment, the through-hole 44a2 is a substantially circular hole. The shape of the through-hole 44a2 is not particularly limited. The current collector 44 is connected to the reversal plate 51 via the protrusion 44a1. The current collector 44 is connected to the positive electrode terminal 42 via the reversal plate 51.

[0039] <Reversal Plate 51> The reversal plate 51 is a member that can deform in response to the internal pressure of the case 41. The reversal plate 51 is interposed between the electrode body 20 and the positive electrode terminal 42 inside the case 41, and constitutes part of the conduction path 55. In this embodiment, the reversal plate 51 is a substantially disk-shaped member. The reversal plate 51 is configured to deform and thereby interrupt the conduction path 55 when the internal pressure of the case 41 becomes higher than a predetermined pressure. The reversal plate 51 is made of a metal having a required conductivity. The same type of metal as the positive electrode current collector foil 21a (see FIG. 1) may be used as the reversal plate 51, and for example, aluminum or an aluminum alloy may be used.

[0040] The reversal plate 51 includes a disk portion 51a, a connecting portion 51b, and a protruding portion 51c. The disk portion 51a is a substantially disk-shaped member in a plan view along the height direction. The disk portion 51a is inclined downward from the peripheral portion toward the center. The disk portion 51a is inclined from the lid 41b toward the base portion 44a of the current collector 44. The connecting portion 51b is provided on the peripheral portion of the disk portion 51a.

[0041] The connection portion 51b is a portion that is connected to the conductive member 43. The connection portion 51b is preferably provided on at least a portion of the periphery of the disk portion 51a. In this embodiment, the connection portion 51b extends downward from the periphery of the disk portion 51a along the side portion 43b of the conductive member 43. The connection portion 51b of the reversal plate 51 is connected to the side portion 43b of the conductive member 43. A protrusion 51c is provided in approximately the center of the reversal plate 51.

[0042] The protrusion 51c protrudes downward from approximately the center of the disk portion 51a. The protrusion 51c of the reversal plate 51 is connected to approximately the center of the protrusion 44a1 of the current collector 44. A joint 51c1 may be formed by joining the protrusion 51c of the reversal plate 51 to the protrusion 44a1 of the current collector 44 by welding or the like. The protrusion 51c of the reversal plate 51 has a dimension larger than the through-hole 44a2 formed in the protrusion 44a1 of the current collector 44. The reversal plate 51 is connected to the current collector 44 so as to close the through-hole 44a2. Here, the protrusion 51c of the reversal plate 51 is connected to the protrusion 44a1 of the current collector 44 continuously in the circumferential direction around the through-hole 44a2. As a result, the protrusion 51c of the reversal plate 51 closes the through-hole 44a2 of the protrusion 44a1 of the current collector 44.

[0043] The internal pressure of the case 41 is transmitted to the reversal plate 51 through the through-hole 44a2 of the protruding portion 44a1 of the current collector 44. The strength, dimensions, shape, and the like of the reversal plate 51 may be designed so that the reversal plate 51 deforms before other components when a predetermined pressure is reached in the case 41. The reversal plate 51 may be formed thinner than the conductive member 43, the current collector 44, and the like provided in the case 41. In this embodiment, the reversal plate 51 is designed to deform and cut off the conduction path 55 when the internal pressure of the case 41 reaches 1 MPa. In addition, to prevent gas generated in the case 41 from being released to the outside, the reversal plate 51 may be configured to deform at a pressure lower than the pressure at which the safety valve 41b1 (see FIG. 1) activates. The pressure at which the reversal plate 51 activates may be appropriately set depending on the type, usage, design, and the like of the electricity storage device 10.

[0044] The internal pressure of the case 41 is applied to the protruding portion 51c of the reversal plate 51 through the through-hole 44a2. When the internal pressure of the case 41 reaches a predetermined pressure, the protruding portion 51c is pushed. As a result, the disk portion 51a of the reversal plate 51 is deformed, as shown in FIG. 3. In this embodiment, the disk portion 51a of the reversal plate 51 is pushed upward and deformed. The disk portion 51a can be deformed into a shape that slopes upward from the peripheral portion toward the center. As a result, when the internal pressure of the case 41 becomes higher than the predetermined pressure, the conduction path 55 (see FIG. 2) is interrupted. When the disk portion 51a is deformed, the joint portion 51c1 of the disk portion 51a of the reversal plate 51 may come off the protruding portion 44a1 of the current collector 44, thereby interrupting the conduction path 55. When the disk portion 51a is deformed, one of the disk portion 51a of the reversal plate 51 and the protruding portion 44a1 of the current collector 44 may be broken around the joint portion 51c1, thereby interrupting the conductive path 55.

[0045] <Safety device 50> The safety device 50 is a device for suppressing heat generation, for example, when a malfunction occurs in the electricity storage device 10 and heat is generated. In this embodiment, the safety device 50 is provided on the positive electrode terminal 42 side. The configuration of the positive electrode terminal 42 and the safety device 50 will be described below. Note that the safety device 50 may also be provided on the negative electrode terminal 47 side.

[0046] 2, the safety device 50 includes a fire extinguishing agent discharging section 52. The fire extinguishing agent discharging section 52 has microcapsules M and a containing section 52a. In this embodiment, the safety device 50 includes a reversing plate 51.

[0047] <Storage section 52a> The storage section 52a is a portion that stores the microcapsules M. In this embodiment, the storage section 52a is provided in the space between the current collector 44 and the reversal plate 51. As described above, the current collector 44 and the reversal plate 51 are connected at the protrusions 44a1 and 51c, respectively, which are provided approximately in the center. Radially outward from the joint 51c1 where the current collector 44 and the reversal plate 51 are connected, the storage section 52a is surrounded by the base 44a of the current collector 44, the disk portion 51a of the reversal plate 51, the connection portion 51b of the reversal plate 51, and the holding portion 72d of the internal insulating member 72. The through-hole 44a2 of the current collector 44 is blocked by the protrusion 51c of the reversal plate 51. This seals the storage section 52a and isolates it from the interior of the case 41.

[0048] <Microcapsule M> The microcapsules M have an outer shell and a fire extinguishing agent contained in the outer shell. Although not particularly limited, the microcapsules M may be spherical with a diameter of about 10 μm to 100 μm. The microcapsules M are configured to break in response to temperature, releasing the fire extinguishing agent therein.

[0049] The outer shell is configured to break at a predetermined temperature and release the fire extinguishing agent stored therein. For use in the electricity storage device 10, the outer shell can be configured to break at approximately 115°C to 125°C. The temperature at which the outer shell breaks can be set depending on the thickness, material, etc., of the outer shell. The outer shell can be made of a polymer resin. The outer shell can be made of, for example, melamine resin, epoxy resin, polyurethane resin, phenolic resin, etc. As the fire extinguishing agent, a halide-based fire extinguishing agent is preferably used, and a fluorocarbon compound-based fire extinguishing agent is particularly preferably used. As the microcapsules M, for example, NOVEC (registered trademark) 1230 manufactured by 3M Company can be used.

[0050] The present inventors have been considering disposing microcapsules containing a fire extinguishing agent inside the case of an electricity storage device from the viewpoint of safety. Their investigations have revealed that microcapsules disposed inside the case may not necessarily exhibit good fire extinguishing properties, depending on various conditions. For example, when microcapsules are disposed inside the case by electrocoating, the timing of the destruction of the microcapsules may differ depending on the location of the microcapsules. In this case, the fire extinguishing properties of the microcapsules may be reduced. Furthermore, when the fire extinguishing agent is dispersed in advance in a separator, an electrolyte, or the like, the contact of the microcapsules with the electrolyte or the like may result in the unintended release of the fire extinguishing agent inside the microcapsules.

[0051] In the above-described embodiment, the electricity storage device 10 includes an electrode assembly 20 having a positive electrode and a negative electrode, a case 41 that houses the electrode assembly 20, and a safety device 50 provided in the case 41. The safety device 50 includes a fire extinguishant releasing unit 52 that has microcapsules M containing a fire extinguishant and a storage unit 52a that stores the microcapsules. The fire extinguishant releasing unit 52 is configured to release the microcapsules M from the storage unit 52a in conjunction with the operation of the safety device 50.

[0052] Before the safety device 50 is activated, the microcapsules M are accommodated in the accommodation portion 52a of the fire extinguishing agent discharging portion 52. Therefore, the microcapsules M are not released into the case 41 until the safety device 50 is activated. When an abnormality occurs in the power storage device 10 and the safety device 50 is activated, the microcapsules M, which were isolated from the inside of the case 41, are released into the case 41. When the microcapsules M are released into the case 41 and the temperature inside the case 41 reaches a predetermined temperature or higher, the outer shell of the microcapsules M is broken and the fire extinguishing agent is released. At this time, the entire amount of the microcapsules M is released into the case 41 by the activation of the safety device 50, making it easy to suppress a temperature rise at an appropriate time when an abnormality occurs in the power storage device 10. Furthermore, when the microcapsules M are released into the case 41, the gas in the case 41 and the fire extinguishing agent contained in the microcapsules M are mixed. For example, even when an abnormality in the electricity storage device 10 causes the internal pressure of the case 41 to rise and gas is ejected to the outside of the electricity storage device 10, the gas ejected to the outside is prevented from igniting.

[0053] In the embodiment described above, the device further includes a positive electrode terminal 42 attached to the case 41, and a conductive path 55 connecting the positive electrode terminal 42 and the electrode body 20. The safety device 50 is configured to activate when the internal pressure of the case 41 exceeds a predetermined pressure, and to cut off the conductive path 55. When the safety device 50 activates and microcapsules M containing a fire extinguishing agent are released into the case 41, the conductive path 55 is also cut off. By cutting off the conductive path 55, current that could flow through each component within the power storage device 10 is cut off, and the risk of a temperature rise in the power storage device 10 in the event of an abnormality can be reduced.

[0054] In the above-described embodiment, the safety device 50 further includes a reversing plate 51 that deforms when the internal pressure of the case 41 exceeds a predetermined pressure, thereby blocking the conduction path 55. The safety device 50 includes the reversing plate 51, which makes it easier to instantly detect an increase in internal pressure. As a result, the conduction path 55 is more likely to be blocked early, and the risk of a temperature rise in the electricity storage device 10 in the event of the above-described abnormality is more likely to be reduced.

[0055] The safety device 50 does not necessarily have to be activated by deformation of the reversal plate 51. The safety device may be activated in conjunction with another pressure-sensitive member, such as a safety valve. The safety device 50 is not necessarily limited to being activated by the internal pressure of the case 41. For example, a safety device activated by temperature, current, or the like may be used.

[0056] In the embodiment described above, the current collector 44 is connected to the electrode terminal 42 via the reversal plate 51. The storage section 52a is provided in the space between the current collector 44 and the reversal plate 51. By providing the storage section 52a in this position, the microcapsules M can be stored without compressing the space inside the case 41. In such an electricity storage device 10, performance can be maintained while safety can be improved.

[0057] The amount of the microcapsules M to be contained may be set appropriately depending on the dimensions of the electricity storage device 10, etc. The amount of the microcapsules M to be contained may be set to, for example, 0.25% or more of the volume of the case 41. This allows a sufficient amount of extinguishing agent to be supplied to the volume of the case 41 when an abnormality occurs in the electricity storage device 10. Furthermore, from the viewpoint of maintaining the performance of the electricity storage device 10, the amount of the microcapsules M to be contained may be, for example, preferably 1.0% or less of the volume of the case 41, and more preferably 0.50% or less.

[0058] In the embodiment described above, the current collector 44 has a through-hole 44a2 formed therein. The reversal plate 51 is connected to the current collector 44 so as to block the through-hole 44a2. With this configuration, the reversal plate 51 is likely to deform to interrupt the conduction path 55 (see FIG. 2), and the microcapsules M contained in the containing portion 52a are likely to be supplied into the case 41 (see FIG. 3) at approximately the same time. This makes it easier for the microcapsules M to be quickly supplied to the portion containing the electrode body 20 after the conduction path 55 is interrupted. As a result, it is easier to suppress a temperature rise in the electricity storage device 10 during an abnormality.

[0059] The above-described electricity storage device 10 can be manufactured, for example, as follows. The electrode body 20 is prepared. The unformed portion 21a1 of the positive electrode current collector foil 21a of the electrode body 20 and the unformed portion 22a1 of the negative electrode current collector foil 22a are attached to the connecting pieces 44b, 49b of the current collectors 44, 49, which are attached to both longitudinal sides of the lid 41b. The reversal plate 51, which is separate from the current collector 44, is prepared. The microcapsules M are filled into the reversal plate 51. The holding portion 72d of the internal insulating member 72 is attached to the reversal plate 51. The base 44a of the current collector 44 is attached to the holding portion 72d. The protruding portion 44a1 of the current collector 44 and the protruding portion 51c of the reversal plate 51 are joined around the through-hole 44a2. As a result, the microcapsules M are hermetically contained in the containing portion 52a. The electrode body 20, to which the reversal plate 51, the positive electrode current collector 44, the holding portion 72d of the internal insulating member 72, and the negative electrode current collector 49 are attached, is attached to the lid 41b. At this time, the reversal plate 51 and the conductive member 43 are joined by welding or the like, and the electrode body 20 and the positive electrode terminal 42 are electrically connected. The lid 41b to which the electrode body 20 is attached is attached to the case body 41a and sealed. An electrolyte solution is poured into the case 41, and an electricity storage device assembly is prepared. The electricity storage device assembly is subjected to an initial charging process and an aging process by known methods, to manufacture the electricity storage device 10.

[0060] Although one embodiment of the power storage device 10 has been described above, the power storage device disclosed herein is not limited to this embodiment. Figures 4 and 5 are schematic diagrams showing a safety device 150 according to another embodiment. The configuration other than that shown in Figures 4 and 5 can be the same as that of the power storage device 10, and detailed description thereof will be omitted.

[0061] As shown in FIG. 4, the electricity storage device (not shown) includes a current collector 144 and a safety device 150. The safety device 150 includes a reversal plate 151, a container 152, and a lid 153. The container 152 and the lid 153 are made of metal. In this electricity storage device, a conduction path is established among the current collector 144, the container 152, the lid 153, and the reversal plate 151. The container 152 is connected to the current collector 144. The lid 153 is connected to the reversal plate 151. Alternatively, the container 152 may be connected to the reversal plate 151, and the lid 153 may be connected to the current collector 144.

[0062] In this embodiment, the current collector 144 is a plate-shaped member. A container 152 is connected to an upper surface 144a of the current collector 144. A lower surface of the container 152 is connected to the upper surface 144a of the current collector 144. The container 152 is generally cylindrical with an open top. The shape of the container 152 is not particularly limited, and may be, for example, a rectangular container with a polygonal cross section. The configuration of the current collector 144 and the container 152 is not particularly limited as long as the current collector 144 and the container 152 are electrically connected. The current collector 144 and the container 152 may be integrally formed. The current collector 144 and the container 152 may be prepared as separate components and connected by welding or the like. The container 152 contains microcapsules M. The upper surface 144a of the current collector 144 faces the reversal plate 151. The volume of the container 152 can be set, for example, in the same manner as the above-described storage section 52a (see FIGS. 2 and 3).

[0063] Like the reversal plate 51 (see FIGS. 2 and 3), the reversal plate 151 is a member that can deform in response to the internal pressure of the case 41. The reversal plate 151 is interposed between the electrode body and the positive electrode terminal inside the case, and constitutes part of the conduction path. In this embodiment, the reversal plate 51 is a substantially disk-shaped member. The reversal plate 151 may be curved or inclined so as to be convex toward the current collector 144. The lower surface 151a of the reversal plate 151 faces the current collector 144. A lid 153 is provided at a position corresponding to the container 152 in the center of the reversal plate 151. The lid 153 has a shape corresponding to the opening on the top surface of the container 152. As a result, when the lid 153 is closed to the container 152, the container 152 is sealed.

[0064] The configuration of the reversal plate 151 and the lid 153 is not particularly limited as long as the reversal plate 151 and the lid 153 are electrically connected. The reversal plate 151 and the lid 153 may be integrally formed. The reversal plate 151 and the lid 153 may be prepared as separate parts and connected by welding or the like. The container 152 is closed by the lid 153. The storage section 152a that stores the microcapsules M is provided in a space sealed by the container 152 and the lid 153. The reversal plate 51 is configured to deform and cut off the conductive path 55 when the internal pressure of the case 41 becomes higher than a predetermined pressure.

[0065] When the internal pressure of the case 41 (see FIGS. 2 and 3) reaches a predetermined pressure, the reversal plate 151 deforms. As shown in FIG. 5, the reversal plate 151 deforms so as to become convex upward. At this time, the lid 153 comes off the container 152 along with the deformation of the reversal plate 151. When the lid 153 comes off the container 152, the conduction path is interrupted. Furthermore, the microcapsules M contained inside the container 152 are released to the outside of the container 152. As a result, when the current flowing through the electricity storage device is interrupted, a rise in temperature is likely to be suppressed if an abnormality occurs in the electricity storage device.

[0066] The technology disclosed herein has been described in various ways. Unless otherwise specified, the embodiments and the like described herein do not limit the present invention. Furthermore, the technology disclosed herein can be modified in various ways, and as long as no particular problems arise, each component and each process described herein can be omitted or combined as appropriate. Furthermore, this specification includes the disclosures described in the following sections.

[0067] Section 1: an electrode assembly having a positive electrode and a negative electrode; a case in which the electrode body is housed; a safety device provided in the case; Equipped with The safety device comprises: microcapsules having a fire extinguishing agent; a storage section for storing the microcapsules; a fire extinguishing agent discharge section having The extinguishing agent release section is configured to release the microcapsules from the storage section in conjunction with activation of the safety device.

[0068] Section 2: an electrode terminal attached to the case; a conductive path connecting the electrode terminal and the electrode body; Furthermore, Item 1. The power storage device according to item 1, wherein the safety device is configured to activate and cut off the conduction path when the internal pressure of the case becomes higher than a predetermined pressure.

[0069] Section 3: Item 3. The power storage device according to item 2, wherein the safety device further includes a reversal plate that deforms to block the conduction path when the internal pressure of the case exceeds a predetermined pressure.

[0070] Section 4: further comprising a current collector connecting the electrode body and the electrode terminal; the current collector is connected to the electrode terminal via the reversal plate, Item 4. The electricity storage device according to item 3, wherein the storage section is provided in a space between the current collector and the reversal plate.

[0071] Section 5: The current collector has a through hole formed therein, Item 5. The electricity storage device according to item 4, wherein the reversal plate is connected to the current collector so as to block the through-hole.

[0072] Item 6: further comprising a current collector connecting the electrode body and the electrode terminal; the safety device includes a container connected to one of the current collector and the reversal plate, and a lid connected to the other of the current collector and the reversal plate to close the container, Item 4. The power storage device according to item 3, wherein the storage section is provided in a space sealed by the container and the lid. [Explanation of symbols]

[0073] 10. Energy storage devices 20 Electrode body 21 Positive electrode sheet 22 Negative electrode sheet 31,32 Separator sheet 41 cases 41a Case body 41b Lid 41b1 Safety valve 41b2 Mounting hole 42 Positive terminal (electrode terminal) 42a head 42b Shaft 43 Conductive materials 43a bottom 43a1 hole 43b Side 44, 49, 144 Current collector 44a,49a base 44a1 Protrusion 44a2 through hole 44b, 49b Connection piece 47 Negative terminal 50,150 Safety equipment 51,151 Reversal plate 51a Disc section 51b Connection 51c Protrusion 51c1 Joint 52 Fire extinguishing agent discharge section 52a, 152a Storage section 55 Conduction Path 71 External insulating member 72 Internal insulating member 152 Container 153 Lid M Microcapsules

Claims

1. an electrode assembly having a positive electrode and a negative electrode; a case in which the electrode body is housed; a safety device provided in the case; an electrode terminal attached to the case; a conductive path connecting the electrode terminal and the electrode body; Equipped with the safety device is configured to be activated when the internal pressure of the case becomes higher than a predetermined pressure, and to cut off the conductive path; The safety device comprises: microcapsules having a fire extinguishing agent; a storage section for storing the microcapsules; a fire extinguishing agent discharge section having The extinguishing agent release section is configured to release the microcapsules from the storage section in conjunction with activation of the safety device.

2. The power storage device according to claim 1 , wherein the safety device further comprises a reversal plate that deforms to cut off the conductive path when the internal pressure of the case becomes higher than a predetermined pressure.

3. further comprising a current collector connecting the electrode body and the electrode terminal; the current collector is connected to the electrode terminal via the reversal plate, The electricity storage device according to claim 2 , wherein the storage portion is provided in a space between the current collector and the reversal plate.

4. The current collector has a through hole formed therein, The electricity storage device according to claim 3 , wherein the reversal plate is connected to the current collector so as to close the through-hole.

5. further comprising a current collector connecting the electrode body and the electrode terminal; the safety device includes a container connected to one of the current collector and the reversal plate, and a lid connected to the other of the current collector and the reversal plate to close the container, The power storage device according to claim 2 , wherein the storage section is provided in a space sealed by the container and the lid.

Images