JP7132417B2 - Flame-retardant sheets, assembled batteries and battery packs - Google Patents

Description

TECHNICAL FIELD The present invention relates to, for example, a fireproof sheet used for assembled batteries in electric tools, vehicles, etc., and assembled batteries and battery packs housed in electric tools, vehicles, etc. and used as power sources for electric motors and the like.

In general, electric tools include those that are used by connecting to a so-called commercial power source, and those that house an assembled battery to serve as a power source for an electric motor for driving. Power tools containing are widely used from the viewpoint of excellent operability.
The assembled battery is formed by connecting a plurality of battery cells in series or in parallel. For example, each battery cell is housed and integrated in a battery case made of polycarbonate or the like, and housed inside the power tool.

As battery cells housed in power tools, lithium-ion secondary batteries, which are capable of high capacity and high output, are mainly used compared to lead-acid batteries, nickel-metal hydride batteries, and the like. However, when thermal runaway occurs in one battery cell due to an internal short circuit or overcharging of the battery (i.e., in the case of an "abnormality"), heat is propagated to other adjacent battery cells, It may cause thermal runaway of other battery cells.

In recent years, from the viewpoint of environmental protection, the development of electric vehicles or hybrid vehicles driven by electric motors has been vigorously advanced. The electric vehicle, hybrid vehicle, or the like is equipped with an assembled battery in which a plurality of battery cells are connected in series or in parallel to serve as a power source for an electric drive motor. Lithium-ion secondary batteries capable of high capacity and high output are mainly used in such battery cells used in vehicles. Thermal runaway of the cell may occur.

As a measure against the occurrence of thermal runaway as described above, for example, Patent Document 1 discloses that when abnormal heat generation occurs due to reasons such as overcurrent flowing into a certain battery cell, fire spreads to adjacent battery cells. An assembled battery capable of suppressing this has been proposed. The assembled battery described in Patent Document 1 is composed of a plurality of battery cells and a block made of a metal material for holding the cells, and the block is composed of a plurality of small blocks. Also, the size of the gap between the block and the battery cell is adjusted.

According to the assembled battery according to Patent Document 1 configured in this way, heat can be rapidly diffused because the blocks holding the battery cells are made of a metal material.

Further, Patent Literature 2 discloses a battery pack intended to improve heat dissipation of a secondary battery and improve performance deterioration. The battery pack described in Patent Document 2 has a plurality of secondary batteries housed in a case, and has a thermal conductivity equal to or higher than a predetermined value between the plurality of secondary batteries and the case, A plate-shaped rubber sheet that changes its shape with pressure is arranged.

According to Patent Document 2, it is described that the heat of the secondary battery can be discharged satisfactorily through the case because the thermal conductivity of the rubber sheet is relatively high. In addition, since the rubber sheet has elasticity, the battery pack can be prevented from being damaged when dropped.

JP 2014-96271 A JP-A-2004-146161

By the way, when thermal runaway occurs in a battery cell, gas is generated inside the battery, and the internal pressure rises, causing deformation of the battery cell. If this deformation is large, the case may be destroyed. .
Such deformation of the battery cells occurs slightly even when the assembled battery cells are subjected to charge-discharge cycles (i.e., during normal use). When the internal pressure is repeatedly increased and decreased, the battery cell is repeatedly pressed and relieved by the case, which causes the performance of the battery to deteriorate.

In the assembled battery according to Patent Document 1, since the blocks that hold the battery cells are made of a metal material, heat can be quickly diffused. not considered.
In addition, the assembled battery described in Patent Document 1 requires a plurality of blocks, and the gaps between the blocks and the battery cells can be changed. , block design is required. Therefore, there is a problem that the design of the block and the assembly of the assembled battery are complicated.

Furthermore, in the battery pack described in Patent Document 2, no consideration is given to suppressing thermal runaway of other adjacent battery cells when thermal runaway occurs in a battery cell.

The present invention has been made in view of the above problems, and it is an object of the present invention to suppress breakage of the battery case and degradation of battery performance due to deformation of the battery cells while suppressing heat propagation between the battery cells in the event of an abnormality. Flame-retardant sheet, and an assembled battery and a battery pack that can suppress the breakage of the battery case and the deterioration of the performance of the battery while suppressing the heat transfer between each battery cell, and are easy to design and assemble intended to provide

The above object of the present invention is achieved by the following configuration [1] relating to the flameproof sheet.

[1] A set in which a plurality of battery cells having an electrode surface having an electrode and an outer peripheral surface orthogonal to the electrode surface, and arranged such that the outer peripheral surfaces face each other, are connected in series or in parallel. A flameproof sheet for use in batteries,
A flameproof sheet comprising a pair of flameproof materials and an elastic member arranged between the pair of flameproof materials.

Further, preferred embodiments of the present invention related to the flameproof sheet relate to the following [2] to [10].

[2] The flameproof sheet according to [1], wherein the elastic member has a plurality of grooves extending from one end surface to the other end surface perpendicular to the surface facing the flameproof material.

[3] The flameproof sheet according to [1] or [2], wherein the elastic member has a plurality of through holes penetrating from one end face to the other end face perpendicular to the face facing the fireproof material.

[4] The flameproof sheet according to any one of [1] to [3], wherein the elastic member is made of rubber or elastomer.

[5] The flameproof sheet according to any one of [1] to [4], wherein the flameproof material contains at least one of inorganic particles, organic fibers and inorganic fibers.

[6] According to [5], the inorganic particles are particles made of at least one inorganic material selected from oxide particles, carbide particles, nitride particles and inorganic hydrate particles. flame retardant sheet.

[7] The flame retardant material has a first inorganic fiber and a second inorganic fiber that are different from each other in at least one property selected from average fiber diameter, shape, and glass transition point, [ 1] The flameproof sheet according to any one of [6].

[8] The average fiber diameter of the first inorganic fibers is larger than the average fiber diameter of the second inorganic fibers,
The flameproof sheet according to [7], wherein the first inorganic fibers are linear or acicular, and the second inorganic fibers are dendritic or crimped.

[9] The first inorganic fibers are amorphous fibers,
The second inorganic fibers are at least one fiber selected from amorphous fibers having a glass transition point higher than that of the first inorganic fibers and crystalline fibers,
The flameproof sheet according to [7], wherein the average fiber diameter of the first inorganic fibers is larger than the average fiber diameter of the second inorganic fibers.

[10] The flameproof material contains inorganic particles, and the inorganic particles include at least one selected from nanoparticles, hollow particles and porous particles,
The first inorganic fibers are amorphous fibers,
The second inorganic fiber according to [7], wherein the second inorganic fiber is at least one inorganic fiber selected from amorphous fibers having a higher glass transition point than the first inorganic fibers and crystalline fibers. flame retardant sheet.

Further, the above object of the present invention is achieved by the following configurations [11] and [12] relating to the assembled battery.

[11] An assembled battery comprising a plurality of battery cells and the flameproof sheet according to any one of [1] to [10], wherein the plurality of battery cells are connected directly or in parallel.

[12] A set in which a plurality of battery cells having an electrode surface having an electrode and an outer peripheral surface perpendicular to the electrode surface, and arranged such that the outer peripheral surfaces face each other, are connected in series or in parallel. a battery,
the battery cell;
a flameproof material covering at least a portion of the outer peripheral surface of the battery cell;
and an elastic member that covers at least a part of the region of the outer peripheral surface of the battery cell that is covered with the flameproof material.

Further, preferred embodiments of the present invention relating to assembled batteries relate to the following [13] to [16].

[13] The assembled battery according to [12], wherein the elastic member covers the region covered with the fireproof material in the circumferential direction of the battery cell and presses the battery cell.

[14] The assembled battery according to [13], wherein the elastic member is a tubular body with both ends opened.

[15] The assembled battery according to [14], wherein the elastic member has a plurality of grooves extending from one end to the other end of the tubular body on the inner surface of the tubular body.

[16] The assembled battery according to [14] or [15], wherein the elastic member has a plurality of through holes penetrating from one end to the other end of the cylindrical body.

Further, the above object of the present invention is achieved by the following configuration [17] relating to the battery pack.

[17] A battery pack in which the assembled battery according to any one of [11] to [16] is accommodated in a battery case.

Since the flameproof sheet of the present invention has a pair of flameproof materials and an elastic member arranged between the pair of flameproof materials, it is possible to suppress heat propagation between battery cells in the event of an abnormality. At the same time, the elastic member deforms flexibly in response to the deformation of the battery cell, thereby suppressing breakage of the battery case and deterioration of battery performance.

In addition, since the assembled battery of the present invention has the flameproof material covering at least a part of the outer peripheral surface of the battery cell, it is possible to suppress heat transfer between the battery cells in the event of an abnormality. Since the elastic member covers at least a part of the outer peripheral surface, the elastic member deforms flexibly in response to the deformation of the battery cell, thereby suppressing breakage of the battery case and deterioration of battery performance. Furthermore, if the elastic member is a cylindrical body, the elastic member has stretchability, so that it is not necessary to change the design of the elastic member and the battery case according to the type of battery cell, and the elastic member can be easily attached to each battery cell. be able to.

Since the battery pack of the present invention accommodates the assembled battery described above, it is possible to suppress heat transfer between battery cells, prevent a chain of thermal runaways, and facilitate assembly. .

FIG. 1 is a cross-sectional view schematically showing an assembled battery using a flameproof sheet according to an embodiment of the present invention. FIG. 2 is a cross-sectional view schematically showing a battery pack according to an embodiment of the invention. FIG. 3 is a cross-sectional view schematically showing a flameproof material containing two kinds of inorganic particles. FIG. 4 is a perspective view showing a shape example of an elastic member applied to the assembled battery according to the embodiment of the present invention. FIG. 5 is a perspective view showing another shape example of the elastic member applied to the assembled battery according to the embodiment of the present invention. FIG. 6 is a perspective view showing still another shape example of the elastic member applied to the assembled battery according to the embodiment of the present invention.

The present inventor provides an assembled battery that suppresses heat transfer between battery cells in the event of an abnormality, and does not affect the performance of the battery case and the battery even when the battery cells are deformed. Therefore, we conducted an intensive study.
As a result, the present inventors have solved the above problem by covering at least a portion of the outer peripheral surface of each battery cell with a flameproof material and covering at least a portion of the region covered with the flameproof material with an elastic member. I found a solution.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. It should be noted that the present invention is not limited to the embodiments described below, and can be arbitrarily modified without departing from the gist of the present invention.

[Flame-retardant sheet]
FIG. 1 is a cross-sectional view schematically showing an assembled battery using a flameproof sheet according to an embodiment of the present invention.
Each battery cell 2 has an electrode surface 2a having an electrode 3 and an outer peripheral surface 2b that is perpendicular to the electrode surface 2a, and each battery cell 2 is arranged so that the outer peripheral surfaces 2b face each other. , electrodes 3 and connectors (not shown).
A flameproof sheet 10 is arranged between the plurality of battery cells 2 . The flameproof sheet 10 has a pair of flameproof materials 4 and an elastic member 5 arranged between the pair of flameproof materials 4 . That is, as shown in FIG. 1, the flameproof material 4 covers at least a portion of the outer peripheral surface of the battery cell 2, and the elastic member 5 covers at least a portion of the region covered by the flameproof material 4. covered. The assembled battery 100 is configured by housing the plurality of battery cells 2 and the flameproof material 4 in the battery case 30 .

In the flame-retardant sheet 10 configured in this manner, when thermal runaway occurs in one of the battery cells in the event of an abnormality when placed between the battery cells 2, the flame-retardant material 4 prevents the adjacent battery cell from being exposed to heat. Heat propagation is suppressed. Therefore, one battery cell adjacent to the other battery cell can be prevented from receiving heat, and a chain of thermal runaway can be prevented.

In addition, the flameproof sheet 10 has an elastic member 5 between the pair of flameproof members 4, and the elastic member 5 has the effect of suppressing the deformation of the battery cell 2 and the effect of absorbing the deformation of the battery cell 2. and That is, when the battery cell 2 is deformed in an abnormal state, the elastic member 5 deforms flexibly in response to the deformation of the battery cell 2 while suppressing the deformation of the battery cell 2 . Therefore, application of unnecessary pressure to the battery cell 2 can be suppressed.

Furthermore, in this embodiment, the flameproof material 4 is arranged so as to contact a part of the outer peripheral surface 2 b of the battery cell 2 , and the elastic member 5 is not in contact with the battery cell 2 . With such a configuration, when the temperature of the battery cell 2 becomes high in an abnormal state, the heat does not easily reach the elastic member 5, so that the elastic member 5 can be prevented from melting. Also, even if the temperature of the battery cell 2 changes during normal operation, since the flameproof material 4 is arranged between the elastic member 5 and the elastic member 5, the temperature change given to the elastic member 5 is small. Deterioration of the elastic member 5 can be prevented.

However, depending on the material constituting the elastic member 5, a flameproof sheet configured to contact the outer peripheral surface 2b of the battery cell 2, that is, to place the flameproof material 4 between the pair of elastic members 5 may be used. can also be used. Specifically, the elastic member 5 is arranged at the position of the flameproof material 4 shown in FIG. As will be described later, the flameproof material 4 may contain inorganic particles with extremely small particle diameters, such as nanoparticles. , the inorganic particles can be prevented from falling off from the flameproof material 4 . Thus, it is preferable to appropriately select the positional relationship between the elastic member 5 and the flameproof material 4 in consideration of the material of the flameproof material 4 and the heat resistance, elasticity, durability, and the like of the elastic member 5 .

It should be noted that the battery cell 2 is slightly deformed even during charge/discharge cycles during normal use. That is, when the gap between the plurality of battery cells 2 is small, when the battery cell 2 expands, the battery cell 2 receives pressure from the opposing battery cell 2, and when the battery cell 2 contracts, the pressure is Disappear. In this way, repeated pressing and relaxing of the battery cell 2 causes deterioration of the battery performance.
In the present embodiment, the elastic member 5 deforms flexibly even when the battery cell 2 is slightly deformed during the charging/discharging cycle during normal use, so that deterioration of the battery performance of the battery cell 2 can be suppressed. can.

In this embodiment, the battery cells 2 may be rectangular or round.
Moreover, although the flameproof sheet 10 is arranged between the plurality of battery cells 2 in the present embodiment, the flameproof sheet 10 may cover the outer peripheral surfaces 2b of the battery cells 2 in the circumferential direction. For example, a flameproof sheet 10 is used in which the flameproof material 4 is arranged so as to be wound in the circumferential direction around the outer peripheral surface 2b of the battery cell 2, and only the elastic member 5 is arranged between the adjacent battery cells 2. can do. In addition, the flameproof material 4 is arranged so as to be wound around the outer peripheral surface 2b of the battery cell 2 in the circumferential direction, and the elastic member 5 is arranged so as to be wound around the outer peripheral surface 2b of the flameproof material 4. may be

An example of an assembled battery in which the flameproof material 4 and the elastic member 5 are arranged so as to cover the outer peripheral surface 2b of the battery cell 2 in the circumferential direction, and a battery pack including this assembled battery will be described in detail below.

[Battery pack]
FIG. 2 is a cross-sectional view schematically showing a battery pack according to an embodiment of the invention.
The battery pack 1 includes a battery case 7 made of resin or the like and an assembled battery 6 which will be described in detail below.

[Assembled battery]
Each battery cell 2 has an electrode surface 2a having an electrode 3 and an outer peripheral surface 2b that is perpendicular to the electrode surface 2a, and each battery cell 2 is arranged so that the outer peripheral surfaces 2b face each other. , electrodes 3 and connectors (not shown).
The outer peripheral surface 2b of the battery cell 2 is covered with a flameproof material 4, and the outer peripheral surface of the flameproof material 4 is further covered with an elastic member 5, whereby the assembled battery 6 is constructed. The elastic member 5 is a tubular body with both ends opened, and covers the outer peripheral surfaces of the battery cells 2 and the flameproof material 4 in the circumferential direction. In this embodiment, both ends of the elastic member 5 (cylindrical body) refer to both one end and the other end in the longitudinal direction of the elastic member 5 (vertical direction in FIG. 2). means the open end of the body.

In the assembled battery 6 configured in this manner, the outer peripheral surfaces 2b of the battery cells 2 are covered with the flameproof material 4. Therefore, if thermal runaway occurs in one of the battery cells in an abnormal situation, the flameproof material 4 This suppresses heat propagation to the surroundings. Therefore, one battery cell adjacent to the other battery cell can be prevented from receiving heat, and a chain of thermal runaway can be prevented.

Further, the elastic member 5 that covers the outer peripheral surfaces of the battery cell 2 and the flameproof material 4 and presses the battery cell 2 has the effect of suppressing the deformation of the battery cell 2 and the effect of absorbing the deformation of the battery cell 2. have That is, when the battery cell 2 is deformed in an abnormal state, the elastic member 5 deforms flexibly in response to the deformation of the battery cell 2 while suppressing the deformation of the battery cell 2 . Therefore, breakage of the battery case 7 can be suppressed.
Furthermore, even if the battery cell 2 becomes hot and ruptures due to an increase in internal pressure in the event of an abnormality, the battery cell 2 is covered with the elastic member 5. It is possible to prevent the organic electrolyte and the like existing in the battery cell 2 from reaching other battery cells 2 and exerting an adverse effect.

It should be noted that the battery cell 2 is slightly deformed even during charge/discharge cycles during normal use. That is, when the gap between the battery cell 2 and the battery case 7 is small, the battery cell 2 receives pressure from the battery case 7 when the battery cell 2 expands, and receives pressure from the battery case 7 when the battery cell 2 contracts. disappears. In this way, repeated pressing and relaxing of the battery cell 2 causes deterioration of the battery performance.
In the present embodiment, the elastic member 5 deforms flexibly even when the battery cell 2 is slightly deformed during the charging/discharging cycle during normal use, so that deterioration of the battery performance of the battery cell 2 can be suppressed. can.

In this embodiment, the battery cells 2 may be rectangular or round.
Further, as shown in FIG. 2, it is preferable that the flameproof material 4 covers the entire outer peripheral surface of the battery cell 2 and presses the battery cell 2. As shown in FIG. 1, a configuration in which a part of the region is not covered can also be preferably used if necessary, as long as the chain can be suppressed.
Furthermore, the elastic member 5 does not have to cover the entire outer peripheral surface of the battery cell 2 covered with the flameproof material 4, and it is sufficient if the effect of the elastic member 5 as described above can be expected. For example, as shown in FIG. 1, a part of the outer peripheral surface 2b of the battery cell 2 may be covered. Even with such a configuration, the effects of the elastic member 5 can be sufficiently obtained as described above.

Next, the flameproof material 4 and the elastic member 5 that constitute the assembled battery according to this embodiment will be described in detail.

[Flameproof material]
The flameproof material 4 used in the assembled battery 6 according to this embodiment preferably contains at least one of organic fibers and inorganic fibers, and more preferably contains inorganic particles as necessary. In the present embodiment, these materials can be processed into sheets, for example, and used. Since it is important for the material constituting the flameproof material 4 to have heat insulating properties, materials with high heat insulating performance are selected.

Thermal conductivity can be cited as an index representing heat insulating performance. It is more preferably less than (W/m·K), more preferably less than 0.2 (W/m·K). Furthermore, the thermal conductivity of the flameproof material 4 is more preferably less than 0.1 (W/m·K), more preferably less than 0.05 (W/m·K), and more preferably less than 0.02 (W/m·K). It is particularly preferably less than (W/m·K).

The thermal conductivity of the flameproof material 4 can be measured according to JIS R 2251, "Testing Method for Thermal Conductivity of Refractories".

<Inorganic particles>
The inorganic particles are preferably composed of a compound having heat resistance, and inorganic particles of a single material may be used, or inorganic particles of two or more materials may be used in combination. . When two or more kinds of inorganic particles having different heat transfer suppression effects are used in combination, the heating element can be cooled in multiple stages, and the endothermic action can be expressed in a wider temperature range, so that the heat insulation performance can be improved. When two or more kinds of inorganic particles are contained, the preferable material, shape and particle size of each inorganic particle are described below.

FIG. 3 is a cross-sectional view schematically showing a flameproof material 4 containing two types of inorganic particles. As an example, the flameproof material 4 shown in FIG. 32), organic fibers 43 and binder 9 are also included.

As the first inorganic particles 41 and the second inorganic particles 12, at least one inorganic material selected from oxide particles, carbide particles, nitride particles and inorganic hydrate particles is used from the viewpoint of heat transfer suppression effect. It is preferred to use particles consisting of, more preferably oxide particles. Inorganic balloons such as silica nanoparticles, metal oxide particles, microporous particles and hollow silica particles, particles made of thermally expandable inorganic materials, particles made of water-containing porous bodies, and the like can also be used. Hereinafter, the inorganic particles will be described in more detail, with small-diameter inorganic particles as the first inorganic particles 41 and large-diameter inorganic particles as the second inorganic particles 12 .

<First inorganic particles>
(Oxide particles)
Since oxide particles have a high refractive index and a strong effect of diffusely reflecting light, the use of oxide particles as the inorganic particles can suppress radiant heat transfer, especially in a high temperature range such as abnormal heat generation. As oxide particles, silica (SiO ₂ ), titania (TiO ₂ ), mullite (Al ₆ O ₁₃ Si ₂ ), zirconia (ZrO ₂ ), magnesia (MgO), zircon (ZrSiO ₄ ), barium titanate (BaTiO ₃ ), zinc oxide (ZnO), alumina (Al ₂ O ₃ ), etc., but not limited thereto. That is, among the oxide particles that can be used as inorganic particles, only one kind may be used, or two or more kinds of oxide particles may be used. In particular, silica is a component with high heat insulation, and titania is a component with a higher refractive index than other metal oxides, and is highly effective in blocking radiant heat by diffusely reflecting light in a high temperature range of 500 ° C. or higher. Therefore, it is most preferable to use silica and titania as oxide particles.

(Average primary particle diameter of oxide particles: 0.001 μm or more and 50 μm or less)
Since the particle size of oxide particles may affect the effect of reflecting radiant heat, limiting the average primary particle size to a predetermined range makes it possible to obtain even higher heat insulation.
That is, when the average primary particle diameter of the oxide particles is 0.001 μm or more, it is sufficiently larger than the wavelength of the light that contributes to heating, and the light is diffusely reflected efficiently. Radiation heat transfer of heat in the material 4 is suppressed, and heat insulation can be further improved.
On the other hand, when the average primary particle diameter of the oxide particles is 50 μm or less, the number of contact points between particles does not increase even when compressed, and it is difficult to form paths for conductive heat transfer, so conductive heat transfer is particularly dominant. It is possible to reduce the influence on heat insulation in the normal temperature range.
In the present invention, the average primary particle size can be determined by observing particles under a microscope, comparing with a standard scale, and averaging 10 arbitrary particles.

(Nanoparticles)
In the present invention, nanoparticles refer to nanometer-order particles having an average primary particle diameter of less than 1 μm and having a spherical or nearly spherical shape. Since nanoparticles have a low density, conductive heat transfer is suppressed, and when nanoparticles are used as inorganic particles, voids are dispersed more finely, so that excellent heat insulation properties that suppress convective heat transfer can be obtained. For this reason, it is preferable to use nanoparticles because heat conduction between adjacent nanoparticles can be suppressed when the battery is normally used in the normal temperature range.

Furthermore, if nanoparticles with a small average primary particle size are used as the oxide particles, the flameproof material will be compressed due to expansion due to thermal runaway of the battery cell, and the density inside the flameproof material 4 will increase. Also, an increase in conductive heat transfer of the flameproof material 4 can be suppressed. This is presumably because fine voids are likely to be formed between nanoparticles due to the repulsive force of static electricity, and the particles are packed so as to have cushioning properties due to their low bulk density.

In the present invention, when nanoparticles are used as the inorganic particles, the material is not particularly limited as long as it conforms to the above definition of nanoparticles. For example, in addition to being a material with high heat insulating properties, silica nanoparticles have small contact points between particles, so the amount of heat conducted by silica nanoparticles is smaller than when silica particles with a large particle size are used. Become. In addition, generally available silica nanoparticles have a bulk density of about 0.1 (g/cm ³ ). Even when a large compressive stress is applied to the material, the size (area) and number of contact points between silica nanoparticles in the flame retardant do not significantly increase, and heat insulation can be maintained. . Therefore, it is preferable to use silica nanoparticles as the nanoparticles. As silica nanoparticles, wet silica, dry silica, aerogel, and the like can be used.

(Average primary particle size of nanoparticles: 1 nm or more and 100 nm or less)
By limiting the average primary particle size of the nanoparticles to a predetermined range, even higher heat insulating properties can be obtained.
That is, when the average primary particle diameter of the nanoparticles is 1 nm or more and 100 nm or less, it is possible to suppress convective heat transfer and conductive heat transfer of heat in the flameproof material 4, particularly in a temperature range of less than 500°C, and heat insulation. can be further improved. In addition, even when compressive stress is applied, voids remaining between nanoparticles and contact points between many particles suppress conductive heat transfer, and the heat insulation of the flameproof material 4 can be maintained. .
The average primary particle size of the nanoparticles is more preferably 2 nm or more, and even more preferably 3 nm or more. On the other hand, the average primary particle size of the nanoparticles is more preferably 50 nm or less, even more preferably 10 nm or less.

(Inorganic hydrate particles)
When the inorganic hydrate particles receive heat from the heating element and reach a thermal decomposition initiation temperature or higher, they thermally decompose, releasing their own water of crystallization to lower the temperature of the heating element and its surroundings, a so-called "endothermic effect". express. In addition, after the water of crystallization is released, it becomes a porous body and exhibits heat insulating properties due to its numerous air holes.
Specific examples of inorganic hydrates include aluminum hydroxide (Al(OH) ₃ ), magnesium hydroxide (Mg(OH) ₂ ), calcium hydroxide (Ca(OH) ₂ ), zinc hydroxide (Zn(OH) ₂ ), iron hydroxide (Fe(OH) ₂ ), manganese hydroxide (Mn(OH) ₂ ), zirconium hydroxide (Zr(OH) ₂ ), gallium hydroxide (Ga(OH) ₃ ), and the like. .

For example, aluminum hydroxide has about 35% water of crystallization, and as shown in the following formula, it is thermally decomposed to release water of crystallization to exhibit endothermic action. After releasing the water of crystallization, it becomes porous alumina (Al ₂ O ₃ ) and functions as a flameproof material.
2Al ₍ OH) ₃ → _Al2O3 + _3H2O

As will be described later, the flameproof material 4 and the elastic member 5 according to the present embodiment are preferably interposed, for example, between battery cells. The temperature rises sharply to exceed 700°C and continues to rise. Therefore, it is also preferable that the inorganic particles are composed of an inorganic hydrate having a thermal decomposition initiation temperature of 200° C. or higher.
The thermal decomposition initiation temperature of the inorganic hydrates listed above is about 200 ° C. for aluminum hydroxide, about 330 ° C. for magnesium hydroxide, about 580 ° C. for calcium hydroxide, about 200 ° C. for zinc hydroxide, and about 200 ° C. for iron hydroxide. is about 350°C, manganese hydroxide is about 300°C, zirconium hydroxide is about 300°C, and gallium hydroxide is about 300°C. It can be said that it is a preferable inorganic hydrate because it overlaps and can efficiently suppress the temperature rise.

(Average secondary particle size of inorganic hydrate particles: 0.01 μm or more and 200 μm or less)
Further, when inorganic hydrate particles are used as the first inorganic particles 41, if the average particle diameter is too large, the first inorganic particles 41 (inorganic hydrate ), it takes a certain amount of time to reach the thermal decomposition temperature, so the first inorganic particles 41 near the center of the flameproof material 4 may not be thermally decomposed. Therefore, the average secondary particle size of the inorganic hydrate particles is preferably 0.01 μm or more and 200 μm or less, more preferably 0.05 μm or more and 100 μm or less.

(nitride particles)
Boron nitride (BN) and the like are suitable examples of nitride particles.

(carbide particles)
Boron carbide (B ₄ C) and the like are preferably used as the carbide particles.

(Particles made of thermally expandable inorganic material)
Vermiculite, bentonite, mica, perlite, etc., can be mentioned as thermally expandable inorganic materials.

(Particles made of hydrous porous material)
Specific examples of the water-containing porous material include zeolite, kaolinite, montmorillonite, acid clay, diatomaceous earth, wet silica, dry silica, aerogel, mica, vermiculite, and the like.

(inorganic balloon)
The flameproof material 4 used in the present invention may contain inorganic balloons as inorganic particles.
When inorganic balloons are included, convective heat transfer or conductive heat transfer in the flameproof material 4 can be suppressed in a temperature range of less than 500° C., and the heat insulating properties of the flameproof material 4 can be further improved. can be done.
At least one selected from shirasu balloons, silica balloons, fly ash balloons, barlite balloons, and glass balloons can be used as the inorganic balloons.

(Inorganic balloon content: 60% by mass or less with respect to the total mass of the flameproof material)
The content of inorganic balloons is preferably 60% by mass or less with respect to the total mass of the flameproof material.

(Average particle size of inorganic balloon: 1 μm or more and 100 μm or less)
The average particle size of the inorganic balloons is preferably 1 μm or more and 100 μm or less.

<Second inorganic particles>
In the case where the flameproof material 4 contains two types of inorganic particles, the second inorganic particles 12 are not particularly limited as long as they differ from the first inorganic particles 41 in material, particle size, and the like. Examples of the second inorganic particles 12 include oxide particles, carbide particles, nitride particles, inorganic hydrate particles, silica nanoparticles, metal oxide particles, inorganic balloons such as microporous particles and hollow silica particles, and thermally expandable inorganic particles. Particles made of material, particles made of water-containing porous material, etc. can be used, and the details thereof are as described above.

It should be noted that the nanoparticles have extremely low conductive heat transfer and can maintain excellent heat insulating properties even when compressive stress is applied to the flameproof material. In addition, metal oxide particles such as titania are highly effective in blocking radiant heat. Furthermore, when large-diameter inorganic particles and small-diameter inorganic particles are used, the small-diameter inorganic particles enter the gaps between the large-diameter inorganic particles, resulting in a more dense structure and improving the heat transfer suppression effect. can. Therefore, when nanoparticles are used as the first inorganic particles 51, particles made of a metal oxide having a larger diameter than the first inorganic particles 41 are used as the second inorganic particles 12. It is preferable to make the flame material 4 contain it.
Examples of metal oxides include silicon oxide, titanium oxide, aluminum oxide, barium titanate, zinc oxide, zircon, and zirconium oxide. In particular, titania is a component having a higher refractive index than other metal oxides, and has a high effect of diffusely reflecting light and blocking radiant heat in a high temperature range of 500° C. or higher. Therefore, titania is most preferably used.

(Average primary particle size of second inorganic particles)
When the flameproof material 4 contains the second inorganic particles 12 made of a metal oxide, the average primary particle diameter of the second inorganic particles 12 is 1 μm or more and 50 μm or less. can efficiently suppress radiant heat transfer. The average primary particle size of the second inorganic particles 12 is more preferably 5 μm or more and 30 μm or less, and most preferably 10 μm or less.

(Content of first inorganic particles and second inorganic particles)
When the first inorganic particles 41 are silica nanoparticles and the second inorganic particles 12 are metal oxides, the content of the first inorganic particles 41 is the same as that of the first inorganic particles 41 and the second inorganic particles. When it is 60% by mass or more and 95% by mass or less with respect to the total mass of 12, the amount of metal oxide particles necessary to suppress radiation heat transfer, the amount of metal oxide particles necessary to suppress conductive/convective heat transfer, and the cushioning properties required The amount of silica nanoparticles can be optimized.
As a result, it is considered that even if a compressive force is applied from the outside, high heat insulating properties can be obtained in a well-balanced manner over a wide temperature range from the temperature during normal use of the battery to a high temperature of 500° C. or higher.

<Inorganic fiber>
Examples of inorganic fibers include silica fiber, alumina fiber, alumina silicate fiber, zirconia fiber, carbon fiber, soluble fiber, refractory ceramic fiber, airgel composite material, magnesium silicate fiber, alkaline earth silicate fiber, potassium titanate fiber, Examples include ceramic fibers such as potassium titanate whisker fibers, glass fibers such as glass fibers and glass wool, and mineral fibers such as rock wool, basalt fiber and wollastonite.
These inorganic fibers are preferable in terms of heat resistance, strength, availability, and the like. Among the inorganic fibers, silica-alumina fibers, alumina fibers, silica fibers, rock wool, alkaline earth silicate fibers, and glass fibers are particularly preferred from the viewpoint of handleability.

The cross-sectional shape of the inorganic fiber is not particularly limited, and examples thereof include circular cross-section, flat cross-section, hollow cross-section, polygonal cross-section, and core cross-section. Among them, a modified cross-section fiber having a hollow cross section, a flat cross section or a polygonal cross section can be preferably used because the heat insulating properties are slightly improved.

A preferable lower limit of the average fiber length of the inorganic fibers is 0.1 mm, and a more preferable lower limit is 0.5 mm, unless the inorganic fibers have special properties described later. On the other hand, the preferred upper limit of the average fiber length of inorganic fibers is 50 mm, and the more preferred upper limit is 10 mm. If the average fiber length of the inorganic fibers is less than 0.1 mm, the inorganic fibers are less likely to be entangled with each other, and the mechanical strength of the flameproof material 4 may decrease. On the other hand, if the thickness exceeds 50 mm, although a reinforcing effect can be obtained, the inorganic fibers cannot be tightly entangled with each other, or a single inorganic fiber will curl up, which tends to cause continuous voids, resulting in heat insulation. may lead to a decrease in

The lower limit of the average fiber diameter of the inorganic fibers is preferably 1 μm, more preferably 2 μm, and even more preferably 3 μm, unless the inorganic fibers have special properties described later. On the other hand, the upper limit of the average fiber diameter of the inorganic fibers is preferably 15 μm, and the more preferable upper limit is 10 μm. If the average fiber diameter of the inorganic fibers is less than 1 μm, the mechanical strength of the inorganic fibers themselves may decrease. Moreover, from the viewpoint of influence on human health, the average fiber diameter of the inorganic fibers is preferably 3 μm or more. On the other hand, if the average fiber diameter of the inorganic fibers is more than 15 μm, solid heat transfer through the inorganic fibers as a medium may increase, which may lead to a decrease in heat insulating properties, and the formability and strength of the flameproof material may deteriorate. There is a risk.

Incidentally, the inorganic fibers may be used singly or in combination of two or more. As shown in FIG. 3, the flame retardant material 4 includes first inorganic fibers 31 and second inorganic fibers 32 having at least one different property selected from, for example, average fiber diameter, shape, and glass transition point. It is preferable to have By containing two kinds of inorganic fibers having different properties, the mechanical strength of the flame retardant material 4 and the ability to retain inorganic particles can be improved.

(Two types of inorganic fibers with different average fiber diameters and fiber shapes)
When the flameproof material 4 contains two kinds of inorganic fibers, the average fiber diameter of the first inorganic fibers 31 is larger than the average fiber diameter of the second inorganic fibers 32, and the first inorganic fibers 31 Linear or acicular, preferably the second inorganic fibers 32 are dendritic or crimped. The first inorganic fibers 31 having a large average fiber diameter (thick diameter) have the effect of improving the mechanical strength and shape retention of the flameproof material 4 . By making one of the two types of inorganic fibers, for example, the first inorganic fiber 31 larger in diameter than the second inorganic fiber 32, the above effect can be obtained. Since the flame-retardant material 4 may be subjected to an impact from the outside, the inclusion of the first inorganic fibers 31 in the flame-retardant material 4 increases impact resistance. The impact from the outside includes, for example, pressing force due to expansion of the battery cell, wind pressure due to ignition of the battery cell, and the like.
Moreover, in order to improve the mechanical strength and shape retention of the flameproof material 4, it is particularly preferable that the first inorganic fibers 31 are linear or acicular. The linear or needle-like fibers refer to fibers having a degree of crimp of less than 10%, preferably 5% or less, which will be described later.

More specifically, in order to improve the mechanical strength and shape retention of the flameproof material 4, the average fiber diameter of the first inorganic fibers 31 is preferably 1 μm or more, more preferably 3 μm or more. more preferred. If the first inorganic fibers 31 are too thick, the moldability and workability of the flame retardant material 4 may deteriorate. The following are more preferable.
In addition, if the first inorganic fiber 31 is too long, the moldability and workability may be deteriorated, so the fiber length is preferably 100 mm or less. Furthermore, if the first inorganic fiber 31 is too short, the shape retention and mechanical strength are lowered, so the fiber length is preferably 0.1 mm or more.

On the other hand, the second inorganic fibers 32 having a small average fiber diameter (thin diameter) have the effect of improving the retention of other inorganic fibers and inorganic particles, and increasing the flexibility of the flame retardant material 4 . Therefore, it is preferable to make the diameter of the second inorganic fibers 32 smaller than that of the first inorganic fibers 31 .

More specifically, it is preferable that the second inorganic fibers 32 are easily deformable and have flexibility in order to improve the retention of other inorganic fibers, inorganic particles, and the like. Therefore, the fine second inorganic fibers 32 preferably have an average fiber diameter of less than 1 μm, more preferably 0.1 μm or less. However, if the fine-diameter inorganic fibers are too fine, they are likely to break, and the ability to retain other inorganic fibers, inorganic particles, and the like decreases. In addition, the proportion of fibers remaining entangled in the flame retardant material 4 without holding other inorganic fibers, inorganic particles, etc., is increased, and in addition to a decrease in the ability to hold other inorganic fibers, inorganic particles, etc. , the moldability and shape retention are also inferior. Therefore, the average fiber diameter of the second inorganic fibers 32 is preferably 1 nm or more, more preferably 10 nm or more.
The fiber length of the second inorganic fibers 32 is preferably 0.1 mm or less, because if the second inorganic fibers 32 are too long, the moldability and shape retention properties are lowered.

Also, the second inorganic fibers 32 are preferably dendritic or crimped. When the second inorganic fibers 32 have such a shape, they are entangled with other inorganic fibers, inorganic particles, and the like in the flameproof material 4 . Therefore, the ability to retain other inorganic fibers, inorganic particles, and the like is improved. Further, when the flameproof material 4 and the elastic member 5 are subjected to a pressing force or wind pressure, the flameproof material 4 slides and moves due to the entanglement of the first inorganic fibers 31 and the second inorganic fibers 32 . is suppressed, thereby improving the mechanical strength particularly against external pressure and impact.

The dendritic structure is a two-dimensionally or three-dimensionally branched structure, and includes, for example, a feather shape, a tetrapod shape, a radial shape, and a three-dimensional network shape.
When the second inorganic fibers 32 are dendritic, the average fiber diameter can be obtained by measuring the diameters of several trunks and branches by SEM and calculating the average value thereof.

Moreover, the crimped shape is a structure in which the fibers are bent in various directions. As one of the methods for quantifying the crimped form, it is known to calculate the degree of crimp from an electron micrograph. For example, it can be calculated from the following formula.
Crimp degree (%) = (fiber length - distance between fiber ends) / (fiber length) x 100
Here, both the fiber length and the distance between fiber ends are measured values on an electron micrograph. That is, the fiber length and the distance between fiber ends projected onto a two-dimensional plane are shorter than the actual values. Based on this formula, the crimp degree of the second inorganic fibers 32 is preferably 10% or more, more preferably 30% or more. If the degree of crimping is small, the ability to hold other inorganic fibers, inorganic particles, etc., and the entanglement (network) between the second inorganic fibers 32 and between the first inorganic fibers 31 and the second inorganic fibers 32 are formed. become difficult.

In the above-described embodiment, the first inorganic fibers 31 having different average fiber diameters and fiber shapes are used as a method for improving the mechanical strength and shape retention of the flame retardant material 4 and the retention of inorganic particles and inorganic fibers. and second inorganic fibers 32 are used. However, by using the first inorganic fibers 31 and the second inorganic fibers 32 having different glass transition points and average fiber diameters, the mechanical strength, shape retention, and particle retention of the flame retardant material 4 can be improved. can be made

As described above, in this embodiment, it is preferable to use various combinations of inorganic fibers in order to improve the mechanical strength, shape retention, and particle retention of the flameproof material 4 . Hereinafter, a combination of the first inorganic fiber and the second inorganic fiber that is different from the embodiment shown in FIG. 3 will be described. will be used for explanation.

(Two kinds of inorganic fibers having different glass transition points)
When the flameproof material 4 contains two types of inorganic fibers, the first inorganic fibers 31 are amorphous fibers, and the second inorganic fibers 32 have a glass transition point higher than that of the first inorganic fibers 31. At least one type of fiber selected from amorphous fibers having a high D and crystalline fibers is preferred. In addition, by using the first inorganic particles 41 containing at least one selected from nanoparticles, hollow particles and porous particles together with the above two inorganic fibers, the heat insulation performance can be further improved. .

The melting point of crystalline inorganic fibers is usually higher than the glass transition point of amorphous inorganic fibers. Therefore, when the first inorganic fiber 31 is exposed to a high temperature, its surface softens earlier than the second inorganic fiber 32, and binds other inorganic fibers, inorganic particles, and the like. Therefore, by including the first inorganic fibers 31 as described above in the flameproof material 4, the mechanical strength of the heat insulating layer can be improved.
Specifically, inorganic fibers having a melting point of less than 700° C. are preferable as the first inorganic fibers 31, and many amorphous inorganic fibers can be used. Among them, fibers containing SiO ₂ are preferable, and glass fibers are more preferable because they are inexpensive, readily available, and excellent in handleability.

As described above, the second inorganic fibers 32 are fibers made of at least one selected from amorphous fibers having a glass transition point higher than that of the first inorganic fibers 31 and crystalline fibers. Many crystalline inorganic fibers can be used as the second inorganic fibers 32 .
If the second inorganic fibers 32 are made of crystalline fibers or have a glass transition point higher than that of the first inorganic fibers 31, the first inorganic fibers will be Even if 31 softens, the second inorganic fibers 32 do not melt or soften. Therefore, it is possible to maintain the shape and continue to exist between the battery cells even during thermal runaway of the battery cells.
In addition, if the second inorganic fibers 32 are not melted or softened, small spaces are maintained between the particles contained in the flameproof material 4, between the particles and the fibers, and between the fibers, so that heat insulation by air is achieved. The effect is exhibited, and excellent heat transfer suppression performance can be maintained.

When the second inorganic fiber 32 is crystalline, the second inorganic fiber 32 includes silica fiber, alumina fiber, alumina silicate fiber, zirconia fiber, carbon fiber, soluble fiber, refractory ceramic fiber, and airgel composite. materials, ceramic fibers such as magnesium silicate fiber, alkaline earth silicate fiber, potassium titanate fiber, glass fiber, glass fiber such as glass wool, mineral fiber such as rock wool, basalt fiber, wollastonite, etc. can be done.
Among the fibers mentioned as the second inorganic fibers 32, if the melting point exceeds 1000° C., even if the thermal runaway of the battery cell occurs, the second inorganic fibers 32 will not melt or soften. Since the shape can be maintained, it can be preferably used.
Among the fibers mentioned as the second inorganic fibers 32, it is more preferable to use, for example, silica fibers, ceramic fibers such as alumina fibers and alumina silicate fibers, and mineral fibers. It is more preferable to use one with a temperature higher than 1000°C.

Further, even if the second inorganic fibers 32 are amorphous, any fiber having a glass transition point higher than that of the first inorganic fibers 31 can be used. For example, a glass fiber having a glass transition point higher than that of the first inorganic fiber 31 may be used as the second inorganic fiber 32 .
As the second inorganic fibers 32, various inorganic fibers exemplified may be used singly, or two or more types may be mixed and used.

In addition, as described above, the first inorganic fiber 31 has a lower glass transition point than the second inorganic fiber 32, and when exposed to a high temperature, the first inorganic fiber 31 softens first. The inorganic fibers 31 can bind other inorganic fibers, inorganic particles, and the like. However, for example, when the second inorganic fibers 32 are amorphous and have a fiber diameter smaller than the fiber diameter of the first inorganic fibers 31, the first inorganic fibers 31 and the second inorganic fibers 32 If the glass transition points of and are close to each other, the second inorganic fibers 32 may soften first.
Therefore, when the second inorganic fibers 32 are amorphous fibers, the glass transition point of the second inorganic fibers 32 is preferably higher than the glass transition point of the first inorganic fibers 31 by 100° C. or more. , 300° C. or higher.

The fiber length of the first inorganic fibers 31 is preferably 100 mm or less, and preferably 0.1 mm or more. The fiber length of the second inorganic fibers 32 is preferably 0.1 mm or less. These reasons are as described above.

(Two types of inorganic fibers having mutually different glass transition points and average fiber diameters)
When the flameproof material 4 contains two types of inorganic fibers, the first inorganic fibers 31 are amorphous fibers, and the second inorganic fibers 32 have a glass transition point higher than that of the first inorganic fibers 31. is at least one fiber selected from amorphous fibers and crystalline fibers having a high Large is preferred.

As described above, when the flameproof material 4 according to this embodiment contains two types of inorganic fibers, the average fiber diameter of the first inorganic fibers 31 is preferably larger than that of the second inorganic fibers 32 . In addition, the first inorganic fibers 31 having a large diameter are amorphous fibers, and the second inorganic fibers 32 having a small diameter are amorphous fibers having a glass transition point higher than that of the first inorganic fibers 31, and Fibers made of at least one selected from crystalline fibers are preferred. As a result, the glass transition point of the first inorganic fiber 31 is low, and the first inorganic fiber 31 softens quickly. On the other hand, the second inorganic fibers 32 having a small diameter are fibers made of at least one selected from amorphous fibers having a glass transition point higher than that of the first inorganic fibers 31 and crystalline fibers. Since the second inorganic fibers 32 with a small diameter remain in the form of fibers even when the temperature rises, the structure of the flameproof material 4 can be maintained, and falling off of powder can be prevented.

Even in this case, the fiber length of the first inorganic fibers 31 is preferably 100 mm or less, and preferably 0.1 mm or more. The fiber length of the second inorganic fibers 32 is preferably 0.1 mm or less. These reasons are as described above.

In addition to the first inorganic fibers 31 and the second inorganic fibers 32, the flameproof material 4 may contain different inorganic fibers.

(Each content of the first inorganic fiber and the second inorganic fiber)
When the flameproof material 4 contains two kinds of inorganic fibers, the content of the first inorganic fibers 31 is preferably 3% by mass or more and 30% by mass or less with respect to the total mass of the flameproof material. The content of the second inorganic fibers 32 is preferably 3% by mass or more and 30% by mass or less with respect to the total mass of the flameproof material.

Further, the content of the first inorganic fibers 31 is more preferably 5% by mass or more and 15% by mass or less with respect to the total mass of the flameproof material, and the content of the second inorganic fibers 32 is It is more preferably 5% by mass or more and 15% by mass or less with respect to the total mass of the flame material. With such a content, the shape retention, pressure resistance, and wind pressure resistance of the first inorganic fibers 31 and the ability of the second inorganic fibers 32 to hold inorganic particles are exhibited in a well-balanced manner.

<Organic fiber>
The organic fibers 43 are not particularly limited, but synthetic fibers, natural fibers, pulp, and the like can be used. As synthetic fibers, fibers made of thermosetting resins or thermoplastic resins can be selected. Fiber, nylon fiber, polybutylene terephthalate fiber, polyvinyl alcohol (PVA) fiber, polyurethane fiber, ethylene-vinyl alcohol copolymer fiber, polytrimethylene terephthalate fiber, polyacetal fiber, polytetrafluoroethylene fiber, polyether ether ketone fiber , polyphenylene sulfide fibers, polyamide fibers, polyparaphenylphthalamide fibers, and the like.

The types and structures of the synthetic fibers that can be used in this embodiment will be described in more detail below.
Vinylon: A fiber made of a long-chain synthetic polymer containing at least 65% by mass of vinyl alcohol units.
Vinylal: Fibers composed of long-chain synthetic polymers of polyvinyl alcohol with varying levels of acetalization.
Polyvinyl chloride (chlorofiber): A fiber composed of a long-chain synthetic polymer formed mainly of vinyl chloride units.
Vinylidene chloride ( _chlorofiber ): A fiber composed of a long _- chain synthetic polymer formed mainly of vinylidene chloride units (--CH.sub.2--CCl.sub.2--).
Acrylic: A fiber composed of a long-chain synthetic polymer containing 85% or more by mass of repeating units of acrylonitrile groups.
Modacrylic: A fiber composed of a long-chain synthetic polymer containing 35% or more and less than 85% by mass of repeating units of acrylonitrile groups.
Nylon (polyamide): A fiber consisting of long chain synthetic macromolecules in which more than 85% of the repeating amide bonds are attached to aliphatic or cycloaliphatic units.
Aramid: A long chain in which the amide or imide bonds directly bonded to two benzene rings account for 85% or more by mass, and the number of imide bonds, if any, does not exceed the number of amide bonds. Fibers made of synthetic polymers.
Polyester: A fiber made of a long-chain synthetic polymer containing 85% or more by mass of ester units of terephthalic acid and dihydric alcohol.
Polyethylene terephthalate (PET): A fiber composed of a long-chain synthetic polymer containing 85% or more by mass of ester units of terephthalic acid and ethylene glycol.
Polytrimethylene terephthalate (PTT): A fiber composed of a long-chain synthetic polymer containing 85% or more by mass of ester units of terephthalic acid and 1,3-propanediol.
Polybutylene terephthalate (PBT): A fiber composed of a long-chain synthetic polymer containing 85% or more by mass of ester units of terephthalic acid and 1,4-butanediol.
Polyethylene (PE): A polymer composed of saturated aliphatic hydrocarbons without substituents, and a fiber composed of long-chain synthetic polymers.
Polypropylene (PP): a macromolecule composed of saturated aliphatic hydrocarbons with methyl side chains on every two carbon atoms, stereoregular, long-chain with no other substituents Fibers made of synthetic polymers.
Polyurethane (elastane, polyurethane): A long-chain synthetic high-strength material containing at least 85% by mass of polyurethane segments and which, when stretched to three times its untensioned length, returns to its original length as soon as the tension is removed. A fiber made up of molecules.
Polylactide: A fiber made of a long-chain synthetic polymer containing 50% or more by mass of lactate ester units.
Preferred ranges of the average fiber length and average fiber diameter of the organic fibers 43 are the same as those of the inorganic fibers.

<Other materials>
The flameproof material 4 that can be used in this embodiment includes the first inorganic particles 41 and the second inorganic particles 12, the first inorganic fibers 31 and the second inorganic fibers 32, and the organic fibers 43. Ingredients necessary for molding into a flame retardant material, such as binders, coloring agents, etc., may also be included. Other components are also described in detail below.

(Binder)
The flameproof material 4 of the present invention can be formed by sintering or the like even if it does not contain a binder such as the binder 9. Especially when the flameproof material 4 contains silica nanoparticles, In order to maintain the shape of the flameproof material 4, it is preferable to add a binder in an appropriate amount. In the present invention, the binder may be any material as long as it holds the inorganic particles together, and may be in any form such as a binder with adhesion, a fiber that physically entangles the particles, or a heat-resistant resin that adheres with adhesive force. do not have. The first inorganic fibers 31 and the second inorganic fibers 32 also function as binders.

As the binder 9, an organic binder, an inorganic binder, or the like can be used. Although the present invention does not particularly limit these types, as organic binders, polymer aggregates, acrylic emulsions, etc. can be used, and as inorganic binders, silica sol, alumina sol, aluminum sulfate, etc. can be used. can. They act as adhesives when solvents such as water are removed.

In the flameproof material 4 used in the present invention, the binder content is preferably 60% by mass or less, more preferably 50% by mass or less, relative to the total mass of the flameproof material. In the flameproof material 4 used in the present invention, the binder content is preferably 10% by mass or more, more preferably 20% by mass or more, relative to the total mass of the flameproof material.

Although the thickness of the flameproof material 4 used in the present invention is not particularly limited, it is preferably in the range of 0.1 mm or more and 30 mm or less. When the thickness of the flameproof material is within the above range, sufficient heat insulating properties and mechanical strength can be obtained, and the material can be easily molded.

[Elastic member]
The elastic member 5 used in the assembled battery 6 according to the present embodiment has elasticity such that it deforms flexibly in response to deformation of the battery cells 2, and when the flameproof sheet 10 is arranged between the adjacent battery cells 2, When the elastic member 5 is attached to the battery cell 2 covered with the flameproof material 4, the elastic member 5 can absorb the expansion and contraction of the battery cell 2 and has the elasticity to press the battery cell 2. . Rubber or elastomer, for example, can be used as such an elastic member 5 .
The elastic member 5 shown in FIG. 2 is a cylindrical body with both ends opened, and the outer surface and the inner surface are formed smoothly. is not limited to

FIG. 4 is a perspective view showing a shape example of an elastic member applied to the assembled battery according to the embodiment of the present invention. Since all of the elastic member shapes shown below can be used in place of the elastic member 5 of the assembled battery 6 shown in FIG. As a thing, the effect etc. are demonstrated.
As shown in FIG. 4, a plurality of grooves 16 extending from one end portion 15a to the other end portion 15b of the elastic member 15 are formed on the inner surface of the elastic member 15 which is a cylindrical body. In the present embodiment, the one end 15a and the other end 15b of the elastic member 5 (cylindrical body) refer to one end and the other end in the longitudinal direction of the elastic member 5 (vertical direction in FIG. 4), respectively. , i.e. indicating the open end of the tube.

In the assembled battery using the elastic member 15 configured in this way, the propagation of heat is suppressed by the flameproof material 4 when the temperature of the battery cells 2 becomes high, as in the assembled battery 6 shown in FIG. In addition, since the elastic member 15 deforms according to the deformation of the battery cell 2 while suppressing the deformation of the battery cell 2, it is possible to suppress the damage of the battery case 7 and the deterioration of the battery performance of the battery cell 2. can.

Moreover, since the elastic member 15 has grooves 16 on its inner surface, a gap is formed between the elastic member 15 and the flameproof material 4 . Therefore, when part of the heat, whose propagation was difficult to suppress even by the flameproof material 4, is propagated to the elastic member 15 side, the gas in the gap is heated, and the high-temperature gas passes through the gap. is discharged to the one end portion 15 a and the other end portion 15 b of the elastic member 15 . As a result, new gas is introduced into the gap, so that the battery cells 2 can be effectively cooled.

The number, depth, circumferential width, etc. of the grooves 16 formed in the elastic member 15 are not particularly limited. By changing the number, depth, and width of the grooves 16 in the circumferential direction, the elasticity and stretchability of the elastic member 15 can be changed. Different designs are possible depending on the size of the area.
Further, the grooves 16 do not necessarily have to be formed in a direction parallel to the longitudinal direction of the elastic member 15, but in order to prevent the heat of the battery cells 2 from being propagated to the adjacent battery cells 2, the grooves 16 are filled with heated gas. is preferably discharged to the electrode surface 2a side of the battery cell 2 and to the surface side facing the electrode surface 2a. Therefore, when the groove 16 is formed, it may be formed so as to extend from the one end portion 15a of the elastic member 15 to the other end portion 15b.
When the grooves 16 are formed not in parallel with the longitudinal direction of the elastic member 15 but at a predetermined angle with respect to the longitudinal direction, a wider area on the surface of the battery cell 2 can be cooled. . Note that the groove 16 may be formed in a spiral shape, or may be formed in a curved shape.
The predetermined angle is preferably greater than 0° with respect to the parallel direction. On the other hand, when the predetermined angle is 45° or less, the heated high-temperature gas can be efficiently discharged, so it is preferable, and 30° or less is more preferable.

FIG. 5 is a perspective view showing another shape example of the elastic member applied to the assembled battery according to the embodiment of the present invention. As shown in FIG. 5, the elastic member 25, which is a cylindrical body, has smooth inner and outer surfaces similar to the elastic member 5 shown in FIG. A plurality of through holes 27 are formed through the other end portion 25b.

Even in the assembled battery using the elastic member 25 configured in this way, the same effects as in the case of using the elastic member 5 and the elastic member 15 can be obtained. In addition, since the elastic member 25 has the through hole 27 inside in the thickness direction, the inside of the through hole 27 is a gap. Therefore, when the heat generated from the battery cell 2 reaches the elastic member 25 , the gas inside the through hole 27 is heated, and then the high-temperature gas flows through the through hole 27 to the one end portion 15 a of the elastic member 25 . and discharged to the other end 15b side. As a result, new gas is introduced into the through holes 27, so that the battery cells 2 can be effectively cooled.

The number, size, etc. of the through holes 27 formed in the elastic member 25 are not particularly limited. As with the elastic member 15 shown in FIG. 4, various designs can be made according to the required properties of the elastic member 25 and the size of the area of the battery case 7 that accommodates the battery cells 2 .
Moreover, the through hole 27 does not necessarily have to be formed in a direction parallel to the longitudinal direction of the elastic member 25. should be formed to
Cooling a wider area on the surface of the battery cell 2 when the through hole 27 is not formed parallel to the longitudinal direction of the elastic member 25 but at the predetermined angle with respect to the parallel direction. can be done. In addition, the through-hole 27 may be formed in a spiral shape, or may be formed in a curved shape.

FIG. 6 is a perspective view showing still another shape example of the elastic member applied to the assembled battery according to the embodiment of the present invention. As shown in FIG. 6, the elastic member 35, which is a cylindrical body, has a shape in which a plurality of tubes are arranged in parallel in the longitudinal direction and adjacent surfaces are adhered to each other. Therefore, like the elastic member 15 shown in FIG. 4, a plurality of grooves 36 are formed on the inner surface, and like the elastic member 25 shown in FIG. A plurality of through holes 37 are formed through the portion 35b.

Even in the assembled battery using the elastic member 35 configured in this way, the same effects as in the case of using the elastic members 5, 15, and 25 can be obtained. The elastic member 35 also has a groove 36 , a gap formed between the elastic member 35 and the flameproof material 4 , and a through hole 37 . Therefore, the presence of both the gap and the through hole 37 enhances the effect of discharging the heated gas toward the one end portion 35a and the other end portion 35b of the elastic member 35, so that the battery cell can be more effectively discharged. 2 can be cooled.

The number and size of the through-holes 37 formed in the elastic member 35, the depth of the grooves 36, and the like can be appropriately designed.
Further, as in the case of the elastic member 15 and the elastic member 25, the groove 36 and the through hole 37 are not parallel to the longitudinal direction of the elastic member 35, but are arranged at the predetermined angle with respect to the parallel direction. When formed, a wider area on the surface of the battery cell 2 can be cooled. The grooves 36 and the through-holes 37 may be spirally formed or curved.

Furthermore, the elastic members shown in FIGS. 4 to 6 all have a cylindrical shape, but when applied to the flameproof sheet 10 shown in FIG. 1, the elastic member 5 is a cylindrical body. No need. That is, it is possible to use a sheet-shaped elastic member shown in FIGS. Specifically, the elastic member 5 shown in FIG. 1 may have a plurality of grooves extending from one end surface orthogonal to the surface facing the flameproof material 4 toward the other end surface facing this one end surface. good.
Further, the elastic member 5 may have a plurality of through holes penetrating from one end surface orthogonal to the surface facing the flameproof material 4 to the other end surface facing this one end surface.
Furthermore, the elastic member 5 may have the groove and the through hole at the same time.
When using the sheet-like elastic member 5, it is preferable to dispose the elastic member 5 so that the direction in which the grooves and through holes extend is the direction in which heat is desired to be released.

[Support layer]
As described above, the flameproof sheet 10 according to the present embodiment has the flameproof material 4 and, for example, the elastic member 5. Further, a support layer (not shown) is provided between the flameproof material and the elastic member. is preferably arranged. The support layer has the effect of supporting the shape of the flame-retardant material and maintaining the strength of the flame-retardant sheet. It is possible to prevent the flameproof material from being exposed to the flameproof material, and to suppress the breakage of the flameproof material.

As a material constituting the support layer, a material having a lower elastic modulus and a higher hardness than the elastic member can be used. For example, a material containing an organic material or an inorganic material as a main raw material can be used. . When an organic material is used as the main raw material for forming the support layer, the support layer itself has flexibility, so the fireproof sheet can also be flexible, and the assembly work to the assembled battery can be simplified. can be made easier. Moreover, when an inorganic material is used as the main raw material for forming the support layer, the support layer itself has heat resistance, so that the heat resistance of the flameproof sheet can be further improved.

The support layer may have a structure in which two or more layers made of different materials are laminated. At least one surface of the support layer contains either one of the material of the flameproof material and the material of the elastic member, and the support layer and the flameproof material or the elastic member are integrated. good too. In this way, if the support layer and at least one of the flameproof material and the elastic member are integrated with each other, the effect of not only improving the strength of the flameproof sheet but also increasing the strength of the elastic member and the flameproof material It is also possible to obtain the effect of suppressing positional deviation due to slippage, and further, it is possible to obtain the effect of suppressing dust generation. In addition, one surface of the support layer contains the material for the flameproof material, and the other surface contains the material for the elastic member, so that the flameproof material and the elastic member are integrated through the support layer. is more preferable, and thereby the effect of suppressing displacement and the effect of suppressing dust generation can be further improved.

The thickness of the support layer is not particularly limited, but it is preferably thinner than the elastic member in order to obtain a sufficient space for arranging the elastic member and the flameproof material. Therefore, the thickness of the support layer is preferably 0.5% or more and 30% or less, more preferably 1.0% or more and 10% or less, of the thickness of the elastic member. Even in the structure in which the support layer and the elastic member are integrated, the relationship between the thickness of the portion forming the support layer and the thickness of the portion forming the elastic member is preferably within the above range.

<Battery case>
The material and shape of the battery case 7 that accommodates the assembled battery 6 according to the present embodiment as shown in FIG. 2 are not particularly limited. As the material of the battery case 7, in addition to polycarbonate, PP, PET, polyamide (PA; polyamide), aluminum, stainless steel (SUS; Steel Use Stainless), and the like can be used. Moreover, the shape of the battery case 7 can be freely selected according to the equipment such as an electric power tool to be applied.
In addition, in the assembled battery 6 according to the present embodiment shown in FIG. It does not have to be housed in the battery case 7 . For example, a plurality of battery cells 2 covered with flameproof material 4 and elastic member 5 are grouped together and fixed with a band or the like to form an assembled battery, which can be stored as it is inside a device such as an electric power tool. can also In this way, when a plurality of battery cells 2 covered with the flameproof material 4 and the elastic member 5 are arranged adjacently without using the battery case 7, the distance between the adjacent battery cells 2 is as shown in FIG. It has the same configuration as the flameproof sheet 10 .

[Assembly method of assembled battery]
The assembled battery according to the present embodiment shown in FIG. 1 can be easily assembled by interposing the flameproof sheet 10 between the battery cells 2 . In addition, the assembled battery 6 according to the present embodiment shown in FIG. 2 has the above-mentioned effect by simply covering the battery cells 2 with the flameproof material 4 and covering it with the elastic member 5 which is, for example, a cylindrical body. Batteries can be assembled easily. Further, since the flameproof material 4 and the elastic member 5 are attached to each battery cell 2, complicated design of the battery case 7 is not required.
Furthermore, in the present embodiment, if the flameproof material 4 is sheet-shaped, it can easily cover the outer peripheral surface of the battery cell 2 regardless of the shape and size of the battery cell 2. can be processed into In addition, when the elastic member 5 is cylindrical, the elastic member 5 can be attached to various battery cells 2 without being affected by the shape and size of the battery cell 2 because the elastic member 5 has stretchability.

The assembled battery and battery pack according to the present embodiment can be suitably used for power assisted bicycles, electric motorcycles, electric vehicles, etc., in addition to power tools.

In addition, the assembled battery of this embodiment is not limited to the assembled battery illustrated in FIGS. A flameproof sheet 10 can also be placed between the battery case 30).

In the assembled battery configured in this way, when a certain battery cell catches fire, it is possible to suppress the spread of the flame to the outside of the battery case.
For example, the assembled battery according to the present embodiment is used in an electric vehicle (EV) or the like, and may be placed under the floor of a passenger. In this case, even if the battery cell catches fire, the safety of the passenger can be ensured.
In addition, the flameproof sheet 10 can be placed not only between the battery cells, but also between the battery cell 2 and the battery case. It is possible to configure a low-cost and safe assembled battery.

In the assembled battery of this embodiment, when the flameproof sheet 10 is arranged between the battery cell 2 and the battery case, the flameproof sheet 10 and the battery cell 2 have a gap even if they are in contact with each other. may However, even if there is no gap between the flameproof sheet 10 and the battery cell 2, since the flameproof sheet 10 has the elastic member 5, the temperature of any one of the battery cells It is possible to allow deformation of the battery cell when it rises and expands in volume.

1 Battery pack 2 Battery cell 2a Electrode surface 3 Electrode 4 Flameproof material 5, 15, 25, 35 Elastic member 6 Assembled battery 7 Battery case 9 Resin binder 10 Flameproof sheet 12 Second inorganic particles 16, 36 Grooves 27, 37 Through holes 31 First inorganic fibers 32 Second inorganic fibers 41 First inorganic particles 43 Organic fibers

Claims (10)

A plurality of battery cells having an electrode surface having an electrode and an outer peripheral surface orthogonal to the electrode surface, and arranged such that the outer peripheral surfaces face each other are used in an assembled battery connected in series or in parallel. A flame-retardant sheet that can be
having a pair of flameproof materials and an elastic member disposed between the pair of flameproof materials;
The flameproof material comprises at least one inorganic particle selected from nanoparticles, hollow particles and porous particles ;
a first inorganic fiber that is an amorphous fiber ;
A flameproof sheet comprising at least one second inorganic fiber selected from amorphous fibers having a glass transition point higher than that of the first inorganic fibers and crystalline fibers. 2. The flameproof sheet according to claim 1, wherein said elastic member has a plurality of grooves extending from one end surface to the other end surface orthogonal to the surface facing said flameproof material. 3. The flameproof sheet according to claim 1, wherein said elastic member has a plurality of through-holes penetrating from one end face to the other end face perpendicular to the surface facing said flameproof material. The flameproof sheet according to any one of claims 1 to 3, wherein said elastic member is made of rubber or elastomer. The flameproof sheet according to any one of claims 1 to 4, wherein the flameproof material contains organic fibers . Any one of claims 1 to 5, wherein the inorganic particles are particles made of at least one inorganic material selected from oxide particles, carbide particles, nitride particles and inorganic hydrate particles. 1. The flameproof sheet according to item 1 . The flameproof sheet according to any one of Claims 1 to 6, wherein the average fiber diameter of the first inorganic fibers is larger than the average fiber diameter of the second inorganic fibers. 8. The flameproof sheet according to claim 7, wherein said first inorganic fibers are linear or acicular, and said second inorganic fibers are dendritic or crimped. An assembled battery comprising a plurality of battery cells and the flameproof sheet according to any one of claims 1 to 8, wherein the plurality of battery cells are connected directly or in parallel. A battery pack containing the assembled battery according to claim 9 in a battery case.

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