Energy storage device structure for reducing fire risk

Abstract

This invention provides an energy storage device structure that can reduce the risk of fire occurring in the event of abnormalities such as damage or overcharging of energy storage devices, particularly energy storage device stacks which consist of multiple stacked energy storage devices. [Solution] The energy storage device structure consists of an energy storage device and a casing that encloses the energy storage device with a gap between them. The gap between the energy storage device and the casing is filled with a molded body containing an acrylic resin, or a molded body containing a copolymer of a monomer used for polymerization of the acrylic resin and other monomers. This molded body is preferably in the form of a film, sheet, or plate.

Description

Technical Field

[0001] The present invention relates to a power storage device structure that encloses a power storage device such as a lithium-ion battery, a lithium-ion capacitor, or an electric double-layer capacitor, and particularly to a power storage device structure capable of reducing the risk of ignition during abnormal conditions such as when the power storage device is damaged or overcharged.

Background Art

[0002] In recent years, as a power source for high-output portable devices and electric vehicles, power storage devices such as secondary batteries, lithium-ion capacitors, and electric double-layer capacitors in which a power storage device using a non-aqueous electrolyte is housed in a casing have been used.

[0003] Such power storage devices usually have a defined upper limit voltage and are controlled so as not to exceed the upper limit voltage in combination with an appropriate protection circuit. However, when the protection circuit malfunctions and exceeds the upper limit voltage, when charging and discharging are repeated, or when a short circuit occurs due to an external factor, the power storage device falls into an overcharged state, and the electrolytic solution reacts with the electrode material and gas is generated, and the internal pressure increases due to this generated gas. The generated gas may contain flammable gases such as electrolytic solution methane, carbon monoxide, ethylene, ethane, and propane, and when released to the outside of the power storage device, there is a risk of causing ignition or explosion.

[0004] In recent years, in power storage devices such as lithium-ion capacitors and electric double-layer capacitors, higher output and larger capacity have been demanded, and the opportunity to use a large current in a single power storage device or in a module configuration in which a plurality of power storage devices are stacked has been increasing. For example, in a module in which a plurality of power storage devices are stacked, when one power storage device falls into an overcharged state, even after gas is released together with the electrolytic solution, other power storage devices may continue to function, and thus a large current may continue to flow. Therefore, it may be severely overheated due to a short circuit, and the risk of causing ignition or explosion as described above increases.

[0005] As a technology to prevent such energy storage devices from catching fire, for example, a method has been proposed in which gas generated inside the lithium-ion battery is absorbed by a flammable gas absorbent to prevent the battery from rupturing (Patent Documents 1, 2).

[0006] On the other hand, a method has been proposed to reduce the temperature of the gas released to the outside when the safety valve opens due to an increase in internal pressure caused by gas generation inside the lithium-ion battery by placing a fire extinguishing agent inside the battery (Patent Document 3). Furthermore, a method has been proposed to prevent ignition caused by gas generated from lithium-ion batteries by placing a non-flammable gas, an aqueous solvent, or a porous material in which a non-flammable solvent is adsorbed in the pores and on the surface inside the lithium-ion battery (Patent Document 4). [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2001-155790 [Patent Document 2] Japanese Patent Publication No. 2003-077549 [Patent Document 3] Japanese Patent Publication No. 2010-287488 [Patent Document 4] Japanese Patent Publication No. 2010-287488 [Overview of the project] [Problems that the invention aims to solve]

[0008] However, in the event of electrical abnormalities or thermal runaway, a large amount of gas is instantaneously generated. Therefore, methods of placing gas adsorbents inside energy storage devices, as described in Patent Documents 1 and 2, are insufficient in terms of both gas adsorption amount and gas adsorption rate for the limited space of an energy storage device, and thus cannot completely suppress gas ejection from the energy storage device. Furthermore, as described in Patent Documents 3 and 4, methods of placing fire extinguishing agents or materials that adsorb non-combustible gases or aqueous solvents or non-combustible solvents inside an energy storage device to lower the internal temperature of a lithium-ion battery have the problem that if the amount of gas adsorbed is insufficient, the effect will not be fully realized, and gas ejection cannot be completely suppressed.

[0009] The present invention has been made in view of the above problems, and aims to provide an energy storage device structure that can reduce the risk of fire occurring in the event of abnormalities such as damage or overcharging of an energy storage device, particularly an energy storage device stack comprising multiple stacked energy storage devices. [Means for solving the problem]

[0010] To solve the above problems, the present invention provides an energy storage device structure comprising an energy storage device and a casing that encloses the energy storage device with a void, wherein a molded body containing an acrylic resin, or a molded body containing a copolymer of a monomer used for polymerization of acrylic resin and other monomers, is placed in the void between the energy storage device and the casing (Invention 1).

[0011] According to this invention (Invention 1), by placing a molded body containing acrylic resin, or a molded body containing a copolymer of a monomer used for polymerization of acrylic resin and other monomers, in the space of the casing that encloses the energy storage device, rather than inside the energy storage device, the risk of fire spreading outside the casing when ignition occurs inside the energy storage device can be reduced.

[0012] In the above invention (Invention 1), it is preferable that the energy storage device uses a non-aqueous electrolyte (Invention 2).

[0013] In the above inventions (Inventions 1 and 2), it is preferable that the molded article containing the acrylic resin, or the molded article containing a copolymer of a monomer used for polymerization of the acrylic resin and other monomers, contains 10% by weight or more of the acrylic resin portion (Invention 3).

[0014] According to this invention (Invention 3), it is possible to effectively prevent the spread of fire to the outside when ignition occurs inside the energy storage device.

[0015] In the above inventions (Inventions 1 to 3), it is preferable that the acrylic resin is a polymer of acrylic acid ester or methacrylic acid ester (Invention 4).

[0016] In the above inventions (Inventions 1 to 4), it is preferable that the acrylic resin is a polymer of methyl methacrylate (Invention 5).

[0017] In the above inventions (Inventions 1 to 5), it is preferable that the molded article containing the acrylic resin, or the molded article containing a copolymer of a monomer used for polymerization of the acrylic resin and another monomer, be in the form of a film, a sheet, or a plate (Invention 6).

[0018] According to this invention (Invention 6), by making it in the form of a film, sheet, or plate, it can be attached to the inside of a casing, inserted into gaps, and has a wide variety of installation options, and is easy to handle.

[0019] In the above invention (Invention 6), it is preferable that the film-like, sheet-like, or plate-like molded body has a thickness of 1 μm to 50,000 μm (Invention 7). In particular, in the above invention (Invention 6 or 7), the weight per unit area of ​​the film-like, sheet-like, or plate-like molded body is 10 g to 20,000 g / m². 2 It is preferable that this is the case (Invention 8).

[0020] According to such an invention (Inventions 7 and 8), by disposing a film-shaped, sheet-shaped or plate-shaped molded body having a predetermined thickness and weight in the gap between the power storage device and the casing, it is possible to suitably exhibit the effect of preventing the spread of fire to the outside when ignition occurs in the power storage device.

[0021] Furthermore, a molded body containing the acrylic resin or a molded body containing a copolymer of a monomer used for polymerization of the acrylic resin and another monomer may be a power storage device structure used as a battery case, a storage case or storage film of the power storage device, or a casing that wraps the power storage device (Invention 9).

[0022] In the above inventions (Inventions 1 to 9), a plurality of the power storage devices may be stacked (Invention 10).

[0023] In a power storage device stack in which a plurality of power storage devices are stacked, even if one power storage device falls into an overcharged state, the other power storage devices continue to function and a large current flows, so it becomes extremely overheated and a combustible gas is likely to reach a temperature above the ignition temperature. At this time, according to such an invention (Invention 10), even if a combustible gas jets out from the power storage device and flows out into the space of the casing, since the material of the present invention affects the combustible gas, the risk of the fire spreading outside the casing can be significantly reduced, so it can be particularly suitably applied to the power storage device stack.

Effects of the Invention

[0024] I n the present invention, by disposing a molded body containing an acrylic resin or a molded body containing a copolymer of a monomer used for polymerization of the acrylic resin and another monomer in the gap between the power storage device and the casing, components generated by thermal decomposition of the acrylic resin due to high-temperature ejecta or ejecta gas released from the power storage device due to a short circuit or the like of the power storage device can significantly reduce the risk of ignition of the power storage device structure.

Modes for Carrying Out the Invention

[0025] The following energy storage device structure of the present invention will be described in detail based on the following embodiments.

[0026] [Energy storage device structure] The energy storage device structure of this embodiment comprises an energy storage device and a casing that encloses the energy storage device with a void, and has a structure in which a molded body containing an acrylic resin, or a molded body containing a copolymer of a monomer used for polymerization of acrylic resin and other monomers, is placed in the void between the energy storage device and the casing.

[0027] (Energy storage device) In this embodiment, there are no particular restrictions on the energy storage device, and either a primary battery or a secondary battery can be used, but a secondary battery is preferred. There are no particular restrictions on the type of secondary battery, and for example, lithium-ion batteries, lithium-ion polymer batteries, all-solid-state batteries, lead-acid batteries, nickel-metal hydride batteries, nickel-cadmium batteries, nickel-iron batteries, nickel-zinc batteries, silver oxide-zinc batteries, metal-air batteries, polyvalent cation batteries, capacitors, etc., can be used. Among these, those using a non-aqueous electrolyte can be suitably used. Among these secondary batteries, lithium-ion batteries, lithium-ion polymer batteries, lithium-ion capacitors, all-solid-state batteries, etc., can be suitably used as suitable applications for the battery packaging material of the present invention.

[0028] As the above non-aqueous electrolyte, for example, a mixed solution of cyclic carbonates such as propylene carbonate (PC) and ethylene carbonate (EC) and chain carbonates such as dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) can be used. Furthermore, the above non-aqueous electrolyte may, if necessary, contain a dissolved lithium salt such as lithium hexafluoride phosphate as the electrolyte. For example, a mixture of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) in a 1:1:1 ratio, or a mixture of propylene carbonate (PC), ethylene carbonate (EC), and diethyl carbonate (DEC) in a 1:1:1 ratio to which 1 mol / L of lithium hexafluoride phosphate can be added can be used.

[0029] The energy storage devices described above may also be in the form of an energy storage device stack consisting of multiple devices stacked on top of each other. An energy storage device stack is particularly suitable because, even if one energy storage device enters an overcharge state, the other energy storage devices continue to function and supply a large current, making it easier for the temperature to exceed the ignition temperature when flammable gas is generated due to the non-aqueous electrolyte.

[0030] (Casing) In this embodiment, the casing is not particularly limited as long as it can enclose the energy storage device (energy storage device stack) with an air gap, and includes cases for housing energy storage devices (energy storage device stacks) such as battery cases, and housings for equipment that uses energy storage devices (energy storage device stacks). The material of this casing is not limited to synthetic resin, metal, etc.

[0031] (Flame-resistant material) In this embodiment, the fire prevention material to be placed in the gap between the energy storage device and the casing is a molded body containing acrylic resin, or a molded body containing a copolymer of a monomer used for polymerization of acrylic resin and other monomers.

[0032] Acrylic resins are polymers of acrylic acid esters or methacrylic acid esters, and among them, polymers of methyl methacrylate are widely used, but are not limited to these.

[0033] Other monomers copolymerized with the monomer used for polymerization of acrylic resin include, but are not limited to, acrylonitrile, methyl acrylate, acrylamide, vinyl acetate, vinyl chloride, vinylidene chloride, and styrene. It is preferable that the other monomers constitute 90% by weight or less, and particularly 40% by weight or less, relative to 100% by weight of the total of the monomer used for polymerization of the acrylic resin and the other monomers. If the amount of other monomers becomes too high, the effect of reducing the risk of fire in the energy storage device structure will be insufficient.

[0034] In this embodiment, there are no particular restrictions on the shape of the molded body placed in the gap between the energy storage device and the casing, and it can be in the shape of glumes, granules, beads, pellets, films, sheets, plates, honeycomb, etc. Furthermore, considering ease of handling when installing in the gap between the energy storage device and the casing, it is preferable to use a film, sheet, or plate shape. By making the fire prevention material a film, sheet, or plate, it is possible to attach it to the inside of the casing, insert it into gaps, and provide a wide variety of installation options. In this case, in order to increase the contact efficiency with ejected material and gases from the energy storage device in a limited space, the film or sheet molded product can be made into a bellows structure to increase the contact area. Moreover, these fire prevention materials can also be used by adsorbing and imparting materials that exhibit a cooling effect through heat transfer absorption, an effect of suppressing combustion radical reactions, and a flame extinguishing effect that destabilizes the flame on the surface of the adsorbent material to the ejected material and gases from the energy storage device. In this embodiment, the molded article containing acrylic resin, or the molded article containing a copolymer of monomers used for polymerization of acrylic resin and other monomers, does not include woven or nonwoven fabrics of acrylic resin or copolymers of monomers used for polymerization of acrylic resin and other monomers.

[0035] The fire-preventing materials described above may be used individually or in combination of two or more materials.

[0036] Furthermore, the molded article containing the acrylic resin, or the molded article containing a copolymer of a monomer used for polymerization of the acrylic resin and other monomers, may be used as a battery case, a storage case or storage film for an energy storage device, or a casing that encloses an energy storage device, thus forming an energy storage device structure.

[0037] The energy storage device structure of the present invention has been described above. However, the present invention only requires that a molded body containing acrylic resin, or a molded body containing a copolymer of a monomer used for polymerization of acrylic resin and other monomers, be placed in the gap between the energy storage device (energy storage device stack) and the casing. The size and shape of the energy storage device (energy storage device stack) are not particularly limited. Therefore, it can be applied to a wide range of energy storage devices (energy storage device stacks), from smartphones to automotive applications. [Examples]

[0038] The present invention will be described in more detail based on the following specific examples, but the present invention is not limited to the following examples. [Overcharge test]

[0039] (Comparative Example 1) A PP resin container (internal dimensions: 80mm wide x 105mm long x 34mm deep, resin thickness 2mm, with the electrode side of an aluminum laminate lithium-ion battery positioned on the 80mm wide side of the PP resin container, and with five 10mm diameter holes on the 80mm wide side of the container, resulting in an open top) was prepared for use as a container for an energy storage device. A 1500mAh aluminum laminate lithium-ion battery (35mm wide x 75mm long) with a positive electrode ternary system was placed inside this PP resin container, and a 4mm thick PP resin plate was used as a lid. The edges of the lid were sealed with heat-resistant tape to ensure there were no gaps, and the device was configured so that any ejection from the lithium-ion battery due to overcharging would only be released through the five holes.

[0040] A PP resin container, intended as the container for this energy storage device, is placed outside a PP resin container intended as the container for the casing (internal dimensions: 98mm wide x 148mm long x 48mm deep, resin thickness 2mm, with five 10mm diameter holes on the 98mm side and an open top (the holes are drilled on the opposite side from the holes in the PP resin container intended as the container for the energy storage device)). Wiring is done to allow the battery to be overcharged, and a 4mm thick PP resin plate is placed over it as a lid. The edges of the lid are sealed with heat-resistant tape to prevent any gaps, and any battery ejection during overcharging is released only through the five holes, thus forming the energy storage device structure.

[0041] When this energy storage device structure was subjected to overcharging at 15V, 7.5A, the battery was destroyed after approximately 19 minutes, and a violent fire was observed outside the casing.

[0042] (Example 1) In the energy storage device structure used in Comparative Example 1, a plate-shaped molded body of acrylic resin (100% polymer of methyl methacrylate) (thickness 1000 μm, weight per unit area 1150 g / m²) 2 ) is applied to the inner upper surface of the PP resin plate of the lid of a PP resin container, which is intended to be a casing, at a depth of 0.011m 2 The device was then attached using double-sided tape to form a power storage device structure.

[0043] When this energy storage device structure was overcharged under the same conditions as Comparative Example 1, namely 15V and 7.5A, the battery was destroyed after approximately 19 minutes, but no fire was observed outside the casing.

[0044] (Example 2) In the energy storage device structure used in Comparative Example 1, a film-like molded body of acrylic resin (100% polymer of methyl methacrylate) (thickness 200 μm, weight per unit area 230 g / m²) was used. 2 ) is applied to the inner upper surface of the PP resin plate of the lid of a PP resin container, which is intended to be a casing, at a depth of 0.011m 2The device was then attached using double-sided tape to form a power storage device structure.

[0045] When this energy storage device structure was overcharged under the same conditions as Comparative Example 1, namely 15V and 7.5A, the battery was destroyed after approximately 19 minutes, but no fire was observed outside the casing.

[0046] (Example 3) In the energy storage device structure used in Comparative Example 1, a plate-shaped molded body of a copolymer of 49% by weight of methyl methacrylate and 51% by weight of styrene (thickness 1000 μm, weight per unit area 1100 g / m²) 2 ) is applied to the upper inner surface of the PP resin plate of the lid of the PP resin container, which is intended to be a casing, at a depth of 0.011m 2 The device was then attached using double-sided tape to form a power storage device structure.

[0047] When this energy storage device structure was overcharged under the same conditions as Comparative Example 1, namely 15V and 7.5A, the battery was destroyed after approximately 19 minutes, but no fire was observed outside the casing.

[0048] (Example 4) In the energy storage device structure used in Comparative Example 1, the PP resin container intended for the casing was replaced with a container made of 100% methyl methacrylate polymer (internal dimensions: 98mm wide x 148mm long x 48mm deep, resin thickness 2mm, with five 10mm diameter holes on the 98mm side and an open top (a container with holes on the opposite side from where the holes were drilled in the PP resin container intended for the energy storage device)), and the battery was wired to allow overcharging. A 4mm thick PP resin plate was then replaced with a 100% methyl methacrylate polymer plate to cover it, and the edges of the cover were sealed with heat-resistant tape to prevent gaps. The energy storage device structure was designed so that any battery ejection during overcharging would only be released through the five holes.

[0049] When this energy storage device structure was overcharged under the same conditions as Comparative Example 1, namely 15V and 7.5A, the battery was destroyed after approximately 19 minutes, but no fire was observed outside the casing.

Claims

1. A power storage device structure comprising a power storage device and a casing that encloses the power storage device with an air gap, A molded body containing acrylic resin, or a molded body containing a copolymer of a monomer used for polymerization of acrylic resin and other monomers, is placed in the gap between the energy storage device and the casing. A fire-risk-reducing energy storage device structure wherein the molded article containing the acrylic resin, or the molded article containing a copolymer of a monomer used for polymerization of the acrylic resin and other monomers, is in the form of a film, sheet, or plate, and does not contain woven or nonwoven fabrics of fibrous material of the acrylic resin or the copolymer of a monomer used for polymerization of the acrylic resin and other monomers.

2. The energy storage device structure for reducing the risk of ignition according to claim 1, wherein the energy storage device uses a non-aqueous electrolyte.

3. The ignition risk reduction energy storage device structure according to claim 1 or 2, wherein the molded article containing the acrylic resin, or the molded article containing a copolymer of a monomer used for polymerization of the acrylic resin and another monomer, contains 10% by weight or more of the acrylic resin portion.

4. The energy storage device structure for reducing the risk of ignition according to any one of claims 1 to 3, wherein the acrylic resin is a polymer of acrylic acid ester or methacrylic acid ester.

5. The energy storage device structure for reducing the risk of ignition according to any one of claims 1 to 4, wherein the acrylic resin is a polymer of methyl methacrylate.

6. The energy storage device structure for reducing the risk of ignition according to claims 1 to 5, wherein the film-like, sheet-like, or plate-like molded body has a thickness of 1 μm to 50,000 μm.

7. The energy storage device structure for reducing the risk of ignition according to claims 1 to 6, wherein the weight per unit area of ​​the film-like, sheet-like, or plate-like molded body is 10 g to 20,000 g / m2.

8. A fire-risk-reducing energy storage device structure according to any one of claims 1 to 7, wherein the molded article containing the acrylic resin, or the molded article containing a copolymer of a monomer used for polymerization of the acrylic resin and another monomer, is used as a battery case, a storage case or storage film for an energy storage device, or a casing for enclosing an energy storage device.

9. A fire risk reduction energy storage device structure according to any one of claims 1 to 8, wherein a plurality of the aforementioned energy storage devices are stacked.