Patent Description:
In recent years, from the viewpoint of environmental protection, electric vehicles or hybrid vehicles driven by electric motors have been actively developed. The electric vehicle or the hybrid vehicle is equipped with a battery pack in which battery cells are connected in series or in parallel to serve as a power source for an electric drive motor.

For the battery cell, a lithium-ion secondary battery capable of high capacity and high output is mainly used as compared with a lead-acid battery, a nickel-metal hydride battery, and the like, but when thermal runaway occurs in one battery cell due to an internal short circuit, an overcharge, or the like of the battery (that is, in the case of "abnormality"), the propagation of heat to other adjacent battery cells may cause thermal runaway of the other adjacent battery cells.

For example, <CIT> discloses a power storage device that can achieve effective heat insulation between power storage elements such as lithium-ion secondary batteries. In the power storage device described in <CIT>, a first plate member and a second plate member are disposed between a first power storage element and a second power storage element adjacent to each other. Between the first plate member and the second plate member, a low thermal conductive layer, which is a layer of a substance having a lower thermal conductivity than that of the first plate member and the second plate member, is formed.

In the power storage device according to <CIT> configured as described above, radiant heat from the first power storage element to the second power storage element or radiant heat from the second power storage element to the first power storage element is blocked by the first plate member and the second plate member. Heat transfer from one plate member to another plate member is also suppressed by the low thermal conductive layer.

However, in the above power storage device, since only a heat-insulating layer is provided between the first power storage element and the second power storage element, it is impossible to effectively cool the battery cell that generates heat during a charge and discharge cycle.

Therefore, <CIT> proposes a heat-absorbing sheet for a battery pack that can cool battery cells during normal use while suppressing the propagation of heat between the battery cells when an abnormality occurs. The heat-absorbing sheet described in <CIT> contains two or more substances having different dehydration temperatures. At least one of the two or more substances can be dehydrated during normal use of the battery cell, and at least one other substance can be dehydrated when the battery cell is abnormal.

<CIT> relates to a heat transfer suppressing sheet in which a flat sheet including a heat absorbing material and/or a heat insulating material is formed on both surfaces of a corrugated sheet including a heat absorbing material and/or a heat insulating material.

<CIT> describes a heat transfer suppression sheet which has a heat transfer suppression layer containing inorganic particles and/or inorganic fibers, wherein the heat transfer suppression layer has grooves communicating with the end faces in the in-plane direction in the heat transfer suppression layer, and the surface of the grooves has an irregular shape.

<CIT> relates to a heat insulating sheet that includes a heat insulating layer comprising at least inorganic fibers or inorganic powder, and an endothermic layer formed on both surfaces of the heat insulating layer and comprising at least inorganic hydrate.

<CIT> describes an electric power storage module which includes a plurality of storage devices arranged along a first direction and a separator that is disposed between two adjacent storage devices and insulates a space between the two storage devices. Each storage device includes an outer can having an opening, a sealing plate that blocks the opening, and a joint section where the outer can and the sealing plate are joined. The separator has an abutting region that contacts a surface of the outer cans facing in the first direction, and a separated region that overlaps the joint sections when viewed from the first direction and that is recessed in a direction away from the outer cans than the abutting region.

When battery cells assembled into a battery pack are subjected to a charge and discharge cycle (that is, in the case of "during normal use"), in order to sufficiently exhibit the charge and discharge performance of the battery cells, it is necessary to maintain the surface temperature of the battery cells at a predetermined value or lower (for example, <NUM> or less).

When an abnormal situation occurs in which the temperature of the battery cells is, for example, <NUM> or more, it is necessary to effectively cool the battery cells.

As described above, a heat transfer suppression means capable of maintaining the surface temperature of battery cells during normal use and capable of effectively cooling the battery cells in the case of abnormality of high temperature has been required to be further improved in recent years.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a battery pack and a heat transfer suppression sheet for a battery pack that is used in a battery pack in which battery cells are connected in series or in parallel, and that can cool the individual battery cells during normal use while suppressing the propagation of heat between the battery cells when an abnormality occurs.

The above object of the present invention is achieved by a heat transfer suppression sheet for a battery pack according to independent claim <NUM>.

The above object of the present invention is also achieved by a battery pack as defined in claim <NUM>.

The heat transfer suppression sheet for a battery pack of the present invention is a heat transfer suppression sheet used in a battery pack in which battery cells are connected in series or in parallel, and a sealed gap is formed between the heat-insulating material and the covering material. Therefore, during normal use of the battery pack, moisture evaporated from the heat-insulating material can stay in the gap, and at this time, the battery cells can be effectively cooled by utilizing the heat of vaporization.

When the battery pack is abnormal, since a communication opening that allows the gap to communicate with the outside of the covering material is formed, the heated steam is released to the outside through the communication opening. Therefore, it is possible to suppress the propagation of heat between the battery cells.

In the battery pack of the present invention, since the heat transfer suppression sheet is interposed between the battery cells, the individual battery cells can be cooled during normal use, the propagation of heat between the battery cells can be suppressed when an abnormality occurs, and the chain of thermal runaway can be prevented.

The present inventors have intensively studied to provide a heat transfer suppression sheet for a battery pack that can cool individual battery cells during normal use in which relatively low-temperature heat is generated while suppressing the propagation of heat between the battery cells in the case of abnormality in which high-temperature heat is generated.

As a result, the present inventors have found that when a sealed gap is formed between a heat-insulating material and a covering material during normal use, and when a communication opening that allows the gap to communicate with the outside of the covering material is formed at a temperature of <NUM> or more, the above problems can be solved.

That is, during normal use in which the temperature of the battery cells is relatively low, since a sealed gap is present, the moisture evaporated from the heat-insulating material can stay in the gap, and the battery cells can be effectively cooled by utilizing the heat of vaporization during evaporation.

When an abnormality occurs in which the temperature of the battery cells is high, a communication opening that allows the gap to communicate with the outside of the covering material is formed, and the heated steam is released to the outside through the communication opening, and thus the propagation of heat between the battery cells can be suppressed.

The present invention is not limited to the embodiments described below, and can be freely changed and implemented without departing from the gist of the present invention.

In the following description, "to" means that the value is equal to or larger than a lower limit value and equal to or smaller than an upper limit value.

Hereinafter, the heat transfer suppression sheet for a battery pack according to the present embodiment will be described in order from a first embodiment to a sixth embodiment. Then, other examples of the heat-insulating material according to the present embodiment, the heat-insulating material, the covering material, and the like constituting the heat transfer suppression sheet for a battery pack according to the present embodiment will be described. Further, a method for manufacturing the heat transfer suppression sheet for a battery pack according to the present embodiment will be described.

<FIG> is a cross-sectional view schematically showing a heat transfer suppression sheet for a battery pack according to the first embodiment. <FIG> is a plan view schematically showing a heat-insulating material used in the heat transfer suppression sheet for a battery pack according to the first embodiment. Hereinafter, a heat transfer suppression sheet <NUM> for a battery pack may be simply referred to as the heat transfer suppression sheet <NUM>.

The heat transfer suppression sheet <NUM> for a battery pack according to the present embodiment includes a heat-insulating material <NUM>, and covering materials <NUM> covering a surface 11a and a back surface 11b which are main surfaces of the heat-insulating material <NUM>. In the present embodiment, the covering material <NUM> does not cover end surfaces 11c of the heat-insulating material <NUM>. As will be described later, when the heat transfer suppression sheet <NUM> and battery cells are laminated, the surface 11a and the back surface 11b of the heat-insulating material <NUM> refer to surfaces facing the battery cells, and the end surfaces 11c refer to four surfaces parallel to a thickness direction of the heat transfer suppression sheet <NUM>.

The heat-insulating material <NUM> contains, for example, inorganic particles and inorganic fibers containing crystal water or adsorbed water, and the crystal water or the adsorbed water has the property of releasing moisture when heated. As shown in <FIG> and <FIG>, concave portions 13a are regularly formed on the surface 11a of the heat-insulating material <NUM>, and a region where the concave portions 13a are not formed substantially constitutes convex portions 13b.

The concave portions 13a have, for example, a rectangular shape in a plan view, and as shown in <FIG>, concave portions whose longitudinal directions are parallel to one side of the heat-insulating material <NUM> and concave portions whose longitudinal directions are perpendicular to one side of the heat-insulating material <NUM> are alternately disposed.

The covering material <NUM> is, for example, a polymer film that melts at a temperature of <NUM> or more, and the convex portion 13b of the heat-insulating material <NUM> is bonded to the covering material <NUM> with an adhesive (not shown). In the present embodiment, an adhesive made of an organic substance or an inorganic substance is used, and the adhesive has the property of melting at <NUM> or more.

Since the region where the concave portions 13a are formed is not in contact with the covering material <NUM>, as a result, gaps <NUM> are formed between the heat-insulating material <NUM> and the covering material <NUM>. Since the convex portions 13b around the gaps <NUM> is bonded to the covering material <NUM>, the gaps <NUM> are always sealed at a temperature of less than <NUM>.

<FIG> is a cross-sectional view schematically showing a battery pack to which the heat transfer suppression sheet for a battery pack according to the first embodiment is applied. A battery pack <NUM> includes a battery case <NUM>, battery cells <NUM> housed in the battery case <NUM>, and the heat transfer suppression sheets <NUM> interposed between the battery cells <NUM>. The battery cells <NUM> are connected in series or in parallel by a bus bar (not shown) or the like.

For example, the battery cell <NUM> is preferably a lithium-ion secondary battery, but is not particularly limited thereto, and may be applied to other secondary batteries.

In the heat transfer suppression sheet <NUM> configured as described above, when the temperature rises in a relatively low temperature range from room temperature (about <NUM>) to about <NUM>, which is a temperature range of the battery cell <NUM> during normal use, heat is also propagated to the heat-insulating material <NUM>. In the present embodiment, since the heat-insulating material <NUM> contains inorganic particles containing crystal water or adsorbed water, and the crystal water or the adsorbed water is a material that releases moisture when heated, moisture is evaporated from the inorganic particles when the heat-insulating material <NUM> is heated. Part of the evaporated moisture stays in the gap <NUM>, and the other part is released from the end surface 11c of the heat transfer suppression sheet <NUM>. At this time, since the heat-insulating material <NUM> loses the heat of vaporization and is cooled, the heat transfer suppression sheet <NUM> can effectively cool the battery cell <NUM>.

When the use (that is, charge and discharge) of the battery pack <NUM> is stopped after the battery cell <NUM> is effectively cooled, the water vapor remaining in the gap <NUM> is cooled and forms water droplets, which are absorbed into the heat-insulating material <NUM> over time. Then, when the battery pack <NUM> is used next time, the moisture in the heat-insulating material <NUM> is evaporated again, the heat-insulating material <NUM> loses the heat of vaporization, and the cycle of cooling the battery cell <NUM> is repeated.

<FIG> is a cross-sectional view schematically showing the heat transfer suppression sheet for a battery pack according to the first embodiment when an abnormality occurs. On the surface 11a of the heat-insulating material <NUM>, the covering material <NUM> is partially melted, and on the back surface 11b, an adhesive for bonding the covering material <NUM> to the heat-insulating material <NUM> is melted due to an increase in temperature.

As shown in <FIG>, when an abnormality occurs, for example, when the temperature of the battery cell <NUM> rises to, for example, <NUM> or more, the covering material <NUM> melts, and communication openings <NUM> that allow the gaps <NUM> to communicate with the outside are formed. In the case of using the covering material <NUM> that does not melt even at a high temperature, when the adhesive melts, the communication openings <NUM> that allow the gaps <NUM> to communicate with the outside of the heat transfer suppression sheet <NUM> are formed.

When the communication opening <NUM> is formed in this manner, the steam evaporated from the inorganic particles, staying in the gap <NUM>, and reaching a high temperature is released to the outside of the heat transfer suppression sheet <NUM> through the communication opening <NUM>. Therefore, even when thermal runaway occurs in the battery cells <NUM>, it is possible to effectively suppress the propagation of heat between the battery cells <NUM>.

Both the polymer film and the adhesive used in the present embodiment have the property of melting at any temperature of <NUM> or more. That is, in a temperature range lower than melting temperatures of the used polymer film and adhesive, the gap <NUM> is always sealed. Since polymer films and adhesives have various melting temperatures depending on kinds thereof, a polymer film or an adhesive having a desired melting temperature in a range of <NUM> or more can be selected as necessary.

The temperature at which a communication opening that allows the gap <NUM> to communicate with the outside of the covering material <NUM> is formed is preferably <NUM> or more, and more preferably <NUM> or more.

On the other hand, an upper limit of the temperature at which a communication opening that allows the gap <NUM> to communicate with the outside of the covering material <NUM> is formed is not particularly limited, but is preferably <NUM> or less, more preferably <NUM> or less, still more preferably <NUM> or less, and particularly preferably <NUM> or less.

<FIG> is a cross-sectional view schematically showing a heat transfer suppression sheet for a battery pack according to the second embodiment.

In <FIG> showing the following second to sixth embodiments, the same or equivalent parts as those in the first embodiment are denoted by the same reference numerals in the drawings, and the description thereof is omitted or simplified. Since all the embodiments described below can be used in place of the heat transfer suppression sheet <NUM> described in the battery pack <NUM> shown in <FIG>, effects and the like will be described assuming that the heat transfer suppression sheets according to the second to sixth embodiments are applied to the battery pack <NUM>.

A heat transfer suppression sheet <NUM> for a battery pack according to the second embodiment includes the heat-insulating material <NUM>, and the covering material <NUM> covering the surface 11a, the back surface 11b, and the end surfaces 11c which are main surfaces of the heat-insulating material <NUM>. In the present embodiment, the concave portions 13a and the convex portions 13b are also formed on the end surfaces 11c of the heat-insulating material <NUM>. That is, the covering material B12 formed in a bag shape with an adhesive (not shown) or the like covers the entire surface of the heat-insulating material <NUM>, and the heat-insulating material <NUM> is completely sealed by the covering material <NUM>.

In the heat transfer suppression sheet <NUM> configured as described above, the same effects as those of the first embodiment can also be obtained during normal use. In the second embodiment, since the heat-insulating material <NUM> is completely covered with the covering material <NUM>, when the heat-insulating material <NUM> is heated during normal use and moisture evaporates from the inorganic particles, all the evaporated moisture stays in the gap <NUM> and is not released to the outside from the heat transfer suppression sheet <NUM>. However, since the moisture is evaporated, the heat-insulating material <NUM> loses the heat of vaporization and is cooled, and the heat transfer suppression sheet <NUM> can effectively cool the battery cell <NUM>.

In the second embodiment, since the evaporated moisture is not released to the outside, when the use of the battery pack is stopped, most of the evaporated moisture is again absorbed into the heat-insulating material <NUM>. Therefore, according to the heat transfer suppression sheet <NUM> for a battery pack according to the second embodiment, it is possible to maintain the effect of cooling the battery cell <NUM> for a long period of time.

Further, when an abnormality occurs, the adhesive for bonding the covering materials <NUM> to each other is melted or the covering material <NUM> is melted to form the communication openings <NUM> between the gaps <NUM> and the outside as in the case shown in <FIG>, and thus the same effects as in the first embodiment can be obtained.

<FIG> is a cross-sectional view schematically showing a heat transfer suppression sheet for a battery pack according to the third embodiment.

A heat transfer suppression sheet <NUM> for a battery pack according to the third embodiment includes a heat-insulating material <NUM>, and covering materials <NUM> covering a surface 51a and a back surface 51b of the heat-insulating material <NUM>. In the present embodiment, as in the first embodiment, the covering material <NUM> does not cover end surfaces 51c of the heat-insulating material <NUM>.

In the third embodiment, the surface of the heat-insulating material <NUM> is flat, and no concave portions or convex portions are formed. On the other hand, the covering material <NUM> is formed of a film, and the surface thereof is subjected to concave and convex processing. On a surface facing the heat-insulating material <NUM> in the covering material <NUM>, concave portions 53a and convex portions 53b are formed. The convex portions 53b of the covering material <NUM> is bonded to the heat-insulating material <NUM> with an adhesive (not shown), and the sealed gaps <NUM> are formed between the concave portions 53a and the heat-insulating material <NUM>.

In the heat transfer suppression sheet <NUM> configured as described above, the same effects as those of the first embodiment can also be obtained during normal use and when an abnormality occurs. By forming a heat transfer suppression sheet to cover the entire surface of the heat-insulating material <NUM> using the covering material <NUM> shown in the third embodiment, it is possible to maintain the effect of cooling the battery cell <NUM> for a long period of time as in the second embodiment.

<FIG> is a cross-sectional view schematically showing a heat transfer suppression sheet for a battery pack according to the fourth embodiment.

A heat transfer suppression sheet <NUM> for a battery pack according to the fourth embodiment includes the heat-insulating material <NUM> and the covering material <NUM> covering the entire surface of the heat-insulating material <NUM>. In the present embodiment, the concave portions 13a and the convex portions 13b are formed in the heat-insulating material <NUM>. On a surface facing the heat-insulating material <NUM> in the covering material, the concave portions 53a recessed in a direction away from the heat-insulating material <NUM> and the convex portions 53b having a shape protruding toward the heat-insulating material <NUM> are also formed. The convex portions 53b of the covering material <NUM> is bonded to the convex portions 13b of the heat-insulating material <NUM> with an adhesive (not shown), and the sealed gaps <NUM> are formed between the concave portions 53a of the covering material <NUM> and the concave portions 13a of the heat-insulating material <NUM>.

In the heat transfer suppression sheet <NUM> configured as described above, the same effects as those of the second embodiment can also be obtained during normal use and when an abnormality occurs. Since the gap <NUM> is formed by the concave portion 13a and the concave portion 53a, a volume of the gap <NUM> is increased as compared with the heat transfer suppression sheets for a battery pack according to the second and third embodiments. Therefore, moisture is easily evaporated from the heat-insulating material <NUM>, and the effect of cooling the battery cell <NUM> during normal use can be further improved.

In the fourth embodiment, the covering material <NUM> covers the end surfaces 11c of the heat-insulating material <NUM>, but the end surfaces 11c of the heat-insulating material <NUM> may be open as in the first embodiment. By opening the end surfaces 11c, since part of the evaporated moisture is released to the outside during normal use, the moisture in the heat-insulating material <NUM> is more easily evaporated, and the cooling effect due to the heat of vaporization can be enhanced.

In the case of abnormality, when the covering material <NUM> that does not melt at a high temperature is used, the communication openings <NUM> that allow the gaps <NUM> to communicate with the outside of the heat transfer suppression sheet <NUM> are formed when the adhesive melts, so that the effect of cooling the battery cell <NUM> can be obtained.

<FIG> is a cross-sectional view schematically showing a heat transfer suppression sheet for a battery pack according to the fifth embodiment. <FIG> is a cross-sectional view schematically showing the heat transfer suppression sheet for a battery pack according to the fifth embodiment when an abnormality occurs.

A heat transfer suppression sheet <NUM> for a battery pack according to the fifth embodiment includes the heat-insulating material <NUM>, and covering materials <NUM> covering the surface 11a and the back surface 11b of the heat-insulating material <NUM>. In the present embodiment, unlike the first embodiment, a covering material (metal plates) <NUM> made of metal is used as the covering material. The convex portions 13b of the heat-insulating material <NUM> is bonded to the covering material <NUM> with an adhesive (not shown), and the sealed gaps <NUM> are formed between the concave portions 13a of the heat-insulating material <NUM> and the covering material <NUM>.

In the heat transfer suppression sheet <NUM> configured as described above, the same effects as those of the first embodiment can also be obtained during normal use.

As shown in <FIG>, when an abnormality occurs, the adhesive bonding the convex portions 13b of the heat-insulating material <NUM> to the covering material <NUM> is melted, and the covering material <NUM> is peeled off from the heat-insulating material <NUM>. Therefore, since the communication openings <NUM> that allow the gaps <NUM> to communicate with the outside of the heat transfer suppression sheet <NUM> are formed, the battery cell <NUM> can be effectively cooled.

<FIG> is a cross-sectional view schematically showing a heat transfer suppression sheet for a battery pack according to the sixth embodiment. <FIG> is a cross-sectional view schematically showing the heat transfer suppression sheet for a battery pack according to the sixth embodiment when an abnormality occurs.

In a heat transfer suppression sheet <NUM> for a battery pack according to the sixth embodiment, not only the surface 11a and the back surface 11b of the heat-insulating material <NUM>, but also the end surfaces 11c are covered with metal covering materials (metal plates) <NUM>. That is, in the present embodiment, all of the surface 11a, the back surface 11b, and the end surfaces 11c in four directions of the heat-insulating material <NUM> are covered with covering materials <NUM>, and the covering materials are also bonded to each other with an adhesive (not shown).

In the heat transfer suppression sheet <NUM> configured as described above, the same effects as those of the second embodiment can also be obtained during normal use.

As shown in <FIG>, when an abnormality occurs, the adhesive bonding the convex portions 13b of the heat-insulating material <NUM> to the covering material <NUM> is melted, and the covering material <NUM> and the heat-insulating material <NUM> are separated from each other. At the same time, the adhesive for bonding the covering materials <NUM> to each other is also melted, and the covering materials <NUM> are separated. As a result, the communication openings <NUM> that allow the gaps <NUM> to communicate with the outside of the heat transfer suppression sheet <NUM> are formed, and the battery cell <NUM> can be effectively cooled.

In the sixth embodiment, the surface 11a, the back surface 11b, and the end surfaces 11c of the heat-insulating material <NUM> are covered with the covering materials <NUM>, and the covering materials <NUM> are bonded to each other with an adhesive, but the present invention may use a single metal sheet. For example, the heat-insulating material <NUM> may be sandwiched between one metal sheet folded in two parts, and in the vicinity of the end surfaces 11c, a contact region between the metal sheet covering the surface 11a of the heat-insulating material <NUM> and the metal sheet covering the back surface 11b can be adhered with an adhesive. With such a configuration, the same effects as those of the sixth embodiment can also be obtained.

The heat transfer suppression sheets for a battery pack according to the first to sixth embodiments have been described in order. Next, another example of the heat-insulating material used in the heat transfer suppression sheets for a battery pack according to the first to sixth embodiments will be described.

<FIG> is a plan view schematically showing another example of the heat-insulating material used in the heat transfer suppression sheets for a battery pack according to the first to sixth embodiments. In the first to sixth embodiments, an example using the heat-insulating material <NUM> shown in <FIG> has been given, but the shape of the heat-insulating material is not particularly limited.

As shown in <FIG>, concave portions 13a are regularly formed on a surface 21a of a heat-insulating material <NUM>, and a region where the concave portions 13a are not formed substantially constitutes the convex portions 13b.

In the present embodiment, the concave portions 13a have, for example, a rectangular shape in a plan view, and all the concave portions 13a are disposed such that longitudinal directions thereof are parallel to one side of the heat-insulating material <NUM>.

The heat-insulating material <NUM> configured as described above can also be applied to the heat transfer suppression sheets for a battery pack according to the first to sixth embodiments, and the same effects as those of the first to sixth embodiments can be obtained.

<FIG> is a plan view schematically showing still another example of the heat-insulating material used in the heat transfer suppression sheets for a battery pack according to the first to sixth embodiments.

In the heat-insulating material <NUM> shown in <FIG> and the heat-insulating material <NUM> shown in <FIG>, all the concave portions 13a are sealed by the covering material, but the present invention is not limited thereto.

As shown in <FIG>, concave portions 13a are regularly formed on a surface 31a of a heat-insulating material <NUM>, and a region where the concave portions 13a are not formed substantially constitutes the convex portions 13b. However, the concave portions 13c formed in the vicinity of end surfaces 31c of the heat-insulating material <NUM> reach the end surfaces 31c of the heat-insulating material <NUM>.

For example, when the heat-insulating material <NUM> in the first embodiment is replaced with the heat-insulating material <NUM>, the concave portions 13c formed in the vicinity of the end surfaces 31c of the heat-insulating material <NUM> do not constitute sealed gaps. However, since sealed gaps are formed between some of the concave portions 13a and the covering material <NUM>, the same effects as those of the first to sixth embodiments can be obtained.

Next, the heat-insulating material, the covering material, the adhesive constituting the heat transfer suppression sheet for a battery pack according to the present embodiment and a thickness of the heat transfer suppression sheet will be described in detail.

The heat-insulating material used in the heat transfer suppression sheet for a battery pack according to the present embodiment contains at least one of inorganic particles or inorganic fibers.

The inorganic particles are preferably inorganic hydrates or hydrous porous materials. The inorganic hydrates receive heat from the battery cell <NUM>, thermally decompose when the temperature is equal to or higher than a thermal decomposition start temperature, and release crystal water thereof, thereby cooling the battery cell <NUM>. The inorganic hydrates form porous bodies after releasing the crystal water, and an effective heat insulation effect can be obtained due to a large number of air holes.

As the inorganic particles, a single kind of inorganic particles may be used, or two or more kinds of inorganic hydrate particles may be used in combination. Since the inorganic hydrates have different thermal decomposition start temperatures depending on their kinds, the battery cell <NUM> can be cooled in multiple stages by using two or more kinds of inorganic hydrate particles in combination.

Specific examples of the inorganic hydrates include aluminum hydroxide (Al(OH)<NUM>), magnesium hydroxide (Mg(OH)<NUM>), calcium hydroxide (Ca(OH)<NUM>), zinc hydroxide (Zn(OH)<NUM>), iron hydroxide (Fe(OH)<NUM>), manganese hydroxide (Mn(OH)<NUM>), zirconium hydroxide (Zr(OH)<NUM>), gallium hydroxide (Ga(OH)<NUM>), and the like.

Examples of the fibrous inorganic hydrates include fibrous calcium silicate hydrates.

Specific examples of the hydrous porous materials include zeolite, kaolinite, montmorillonite, acid clay, diatomaceous earth, sepiolite, wet silica, dry silica, aerogel, mica, vermiculite, and the like.

Further, examples of the inorganic fibers include alumina fibers, silica fibers, alumina silicate fibers, rock wool, magnesium silicate fibers, alkaline earth silicate fibers, glass fibers, zirconia fibers, potassium titanate fibers, and the like. Among these inorganic fibers, magnesium silicate fibers can be suitably used as a material that releases moisture when heated.

As the inorganic fibers, a single kind of inorganic fibers may be used, or two or more kinds of inorganic fibers may be used in combination.

In addition to the inorganic particles and the inorganic fibers, organic fibers, organic binders, or the like may be blended into the heat-insulating material as necessary. The organic fibers and the organic binders are useful for reinforcing the heat-insulating material and improving the moldability thereof.

The inorganic particles and the inorganic fibers contained in the heat-insulating material do not necessarily contain a material that releases moisture when heated. During the manufacture of the heat-insulating material, a small amount of moisture is inevitably contained, and therefore, in a case where the temperature of the battery cell <NUM> rises during normal use and when an abnormality occurs, the moisture contained in the heat-insulating material evaporates, thereby obtaining an effect of cooling the battery cell <NUM>.

In the present embodiment, the heat-insulating material may contain at least one of the inorganic particles or the inorganic fibers, and with respect to a total mass of the heat transfer suppression sheet, a content of the inorganic particles is preferably <NUM>% or more by mass and <NUM>% or less by mass, and a content of the inorganic fibers is preferably <NUM>% or more by mass and <NUM>% or less by mass. By setting the contents as described above, the shape retention, the pressing force resistance, and the wind pressure resistance can be improved by the inorganic fibers, and the retention capacity of the inorganic particles can be secured.

Organic fibers, organic binders, or the like may be blended into the heat transfer suppression sheet according to the present embodiment as necessary. The organic fibers and the organic binders are useful for reinforcing the heat transfer suppression sheet and improving the moldability thereof.

As the covering material, a polymer film or a metal film (metal plate) can be used.

Examples of the polymer film include polyimide, polycarbonate, PET, p-phenylene sulfide, polyetherimide, cross-linked polyethylene, flame-retardant chloroprene rubber, polyvinylidene fluoride, rigid vinyl chloride, polybutylene terephthalate, PTFE, PFA, FEP, ETFE, rigid PCV, flame-retardant PET, polystyrene, polyether sulfone, polyamide-imide, polyacrylonitrile, polyethylene, polypropylene, polyamide, and the like.

In the present invention, the covering material is configured such that a communication opening that allows the gap to communicate with the outside of the covering material is formed at a temperature of <NUM> or more. As described above, examples of forming the communication opening include melting of the polymer film used as the covering material and melting of the adhesive for bonding the covering materials to each other or bonding the covering material to the heat-insulating material.

To form the communication opening that allows the gap to communicate with the outside of the covering material at a temperature of <NUM> or more, for example, the polymer film may be melted at any temperature of <NUM> or more. Since the polymer film has a melting point of <NUM> to <NUM>, the covering material (polymer film) can reliably seal the gap at a temperature of less than <NUM>, and can form the communication opening at any temperature of <NUM> or more.

In the present embodiment, when a polymer film is used as the covering material, the melting temperature of the polymer film is preferably <NUM> or more, more preferably <NUM> or more, and still more preferably <NUM> or more.

On the other hand, the melting temperature of the polymer film is preferably <NUM> or less, more preferably <NUM> or less, still more preferably <NUM> or less, and particularly preferably <NUM> or less.

Examples of the metal film include aluminum foil, stainless steel foil, and copper foil.

In the present embodiment, as a method of sealing the gap formed between the heat-insulating material and the covering material, a method of bonding the heat-insulating material to the covering material or a method of bonding the covering materials to each other can be applied.

Examples of an adhesive for bonding the heat-insulating material to the covering material include those using urethane, polyethylene, polypropylene, polystyrene, nylon, polyester, vinyl chloride, vinylon, acrylic resin, silicone, and the like as a raw material.

The adhesive can also be applied as an adhesive for bonding the covering materials to each other.

In the present embodiment, when a covering material that does not melt at a temperature of <NUM> or more is used, for example, the melting temperature of the adhesive for bonding the covering materials to each other or bonding the covering material to the heat-insulating material may be <NUM> or more. That is, when the adhesive melts at a temperature of <NUM> or more, the covering material can reliably seal the gap at a temperature of less than <NUM>, and the communication opening that allows the gap to communicate with the outside of the covering material can be formed at any temperature of <NUM> or more.

In this case, the melting temperature of the adhesive is preferably <NUM> or more, more preferably <NUM> or more, and still more preferably <NUM> or more.

On the other hand, the melting temperature of the adhesive is preferably <NUM> or less, more preferably <NUM> or less, still more preferably <NUM> or less, and particularly preferably <NUM> or less.

As a method of sealing the gap formed between the heat-insulating material and the covering material, a method of covering the entire heat-insulating material with the covering material can be applied.

Examples of the method of covering the entire heat-insulating material with the covering material include lamination (dry lamination, thermal lamination), pouch lamination, vacuum packaging, vacuum lamination, shrink packaging, and caramel packaging.

As the adhesive for bonding the heat-insulating material to the covering material or bonding the covering materials to each other, adhesives having different melting temperatures may be used such that the adhesives melt stepwise in regions as the temperature rises. An example using adhesives will be described below with reference to the drawings. The following examples shown in <FIG> are modifications of the heat transfer suppression sheet <NUM> for a battery pack according to the first embodiment shown in <FIG> and <FIG>.

<FIG> is a plan view schematically showing a heat transfer suppression sheet for a battery pack using two kinds of adhesives having different melting temperatures.

As shown in <FIG>, in a heat transfer suppression sheet <NUM> for a battery pack, in a region of the convex portions 13b of the heat-insulating material <NUM>, an adhesive 16b is used in peripheral edges in the vicinity of end surfaces, and an adhesive 16a is used in a region inside the peripheral edges. The adhesive 16a and the adhesive 16b have different melting temperatures, and specifically, the melting temperature of the adhesive 16b is higher than the melting temperature of the adhesive 16a. The melting temperature of the covering material is higher than the melting temperature of the adhesive 16b.

In the heat transfer suppression sheet <NUM> configured as described above, at a temperature lower than the melting temperature of the adhesive 16a in a first stage, gaps between the concave portions 13a and the covering material are sealed. Therefore, when the heat-insulating material <NUM> is heated and moisture is evaporated from the inorganic particles, all the evaporated moisture stays in the gaps and is not released to the outside from the heat transfer suppression sheet <NUM>, and the heat-insulating material <NUM> loses the heat of vaporization and is cooled due to the evaporation of the moisture.

Thereafter, in a second stage, when the temperature of the battery cell further rises to be equal to or higher than the melting temperature of the adhesive 16a and lower than the melting temperature of the adhesive 16b, the region adhered by the adhesive 16a is separated, volumes of the gaps increase, and thus moisture is easily evaporated from the heat-insulating material <NUM>. Since the heated steam does not stay in a fixed position and can move over a wider region than in the first stage, the heat transfer suppression sheet <NUM> can effectively cool the battery cell.

Thereafter, in a third stage, when the temperature of the battery cell is equal to or higher than the melting temperature of the adhesive 16b, the region adhered by the adhesive 16b is separated, and communication openings that allow the gaps to communicate with the outside of the heat transfer suppression sheet <NUM> are formed. As a result, the high-temperature steam staying inside the region of the adhesive 16b is released at once. Therefore, even when thermal runaway occurs in the battery cells, it is possible to effectively suppress the propagation of heat between the battery cells.

<FIG> is a plan view schematically showing another example of the heat transfer suppression sheet for a battery pack using two kinds of adhesives having different melting temperatures.

As shown in <FIG>, in a heat transfer suppression sheet <NUM>, the adhesive 16b having a higher melting temperature is used in the peripheral edges of the region of the convex portions 13b of the heat-insulating material <NUM>, as in the heat transfer suppression sheet <NUM> shown in <FIG>. However, the same adhesive 16a, which is used in the region inside the peripheral edges and has a lower melting temperature, is used only in part of the peripheral edges.

In the heat transfer suppression sheet <NUM> configured as described above, at a temperature lower than the melting temperature of the adhesive 16a in a first stage, gaps between the concave portions 13a and the covering material <NUM> are sealed. Therefore, as in the heat transfer suppression sheet <NUM> shown in <FIG>, moisture is evaporated from the heat-insulating material <NUM> toward the gaps, and the heat-insulating material <NUM> loses the heat of vaporization and is cooled.

Thereafter, in a second stage, when the temperature of the battery cell further rises to be equal to or higher than the melting temperature of the adhesive 16a, the region adhered by the adhesive 16a is separated, and thus moisture is easily evaporated from the heat-insulating material <NUM>. Since the adhesive 16a having a low melting temperature is used only in part of the peripheral edges, this region serves as a communication opening that allows the gaps to communicate with the outside of the heat transfer suppression sheet <NUM>. Therefore, as shown by an arrow in <FIG>, the high-temperature steam is released from the communication opening, and it is possible to effectively suppress the propagation of heat between the battery cells.

As shown in <FIG>, when the same adhesive 16a, which is used in the region inside the peripheral edges and has a lower melting temperature, is used only in part of the peripheral edges, it is possible to easily control the position where the high-temperature steam (moisture) is released. Therefore, it is possible to prevent water exposure to predetermined parts in the battery pack.

<FIG> is a plan view schematically showing still another example of the heat transfer suppression sheet for a battery pack using two kinds of adhesives having different melting temperatures.

As shown in <FIG>, in a heat transfer suppression sheet <NUM>, the adhesive 16b having a high melting temperature is used in the peripheral edges of the region of the convex portions 13b of the heat-insulating material <NUM>, as in the heat transfer suppression sheet <NUM> shown in <FIG>. However, the adhesive 16a having a low melting temperature is used only in part of the peripheral edges, and this region serves as a communication opening at a high temperature. An adhesive 16c having the same melting temperature as that of the adhesive 16b is used in a region separated at a predetermined interval from the peripheral edges inside the region in which the adhesive 16b is used. In the region where the adhesive 16c is used, the adhesive 16a having a low melting temperature is used in part of the opposite side of the region serving as the communication opening.

In the heat transfer suppression sheet <NUM> configured as described above, in a first stage, as in the heat transfer suppression sheet <NUM> shown in <FIG>, moisture is evaporated from the heat-insulating material <NUM> toward the gaps, and the heat-insulating material <NUM> loses the heat of vaporization and is cooled.

Thereafter, when the adhesive 16a is melted in a second stage, a moisture release path is formed as shown by an arrow in <FIG>. As a result, since the high-temperature steam moves along the release path and is released to the outside through the communication opening, the cooling effect can be further improved.

The adhesive 16a, the adhesive 16b, and the adhesive 16c may all have different melting temperatures, and the regions in which the respective adhesives are used can be freely determined according to the purpose.

As described above, the heat transfer suppression sheets <NUM>, <NUM>, and <NUM> shown in <FIG> are designed such that the adhesives melt stepwise in regions as the temperature of the battery cell rises.

Therefore, it is possible to adjust the timing at which the steam staying in the gaps is released, provide a steam release opening at any position, or provide a release path in a free manner.

To obtain the effects described above, the adhesives may melt stepwise in regions as the temperature rises, and in addition to the method of using adhesives having different melting temperatures, a method of applying the adhesive to regions in different application amounts can be used.

In <FIG>, in the heat transfer suppression sheets in which the covering material is bonded to the surface and the back surface of the heat-insulating material <NUM>, the case where the adhesive for bonding the heat-insulating material <NUM> to the covering material melts stepwise has been described, but the present invention is not limited thereto. For example, in a configuration in which the heat-insulating material <NUM> is completely covered with a covering material, a method of adjusting the melting temperature or the application amount of the adhesive depending on the region can also be applied. Specifically, in the case where the covering materials are bonded to each other in the vicinity of the end surfaces of the heat-insulating material <NUM>, by setting a high melting temperature adhesive for bonding the covering materials to each other and a low melting temperature adhesive for bonding the heat-insulating material <NUM> to the covering material, the same effects as those of the heat transfer suppression sheet <NUM> can be obtained.

In the present embodiment, the thickness of the heat transfer suppression sheet is not particularly limited, but is preferably in a range of <NUM> to <NUM>. If the thickness of the heat transfer suppression sheet is less than <NUM>, sufficient mechanical strength cannot be imparted to the heat transfer suppression sheet. On the other hand, if the thickness of the heat transfer suppression sheet exceeds <NUM>, it may be difficult to form the heat transfer suppression sheet.

Next, a method for manufacturing the heat transfer suppression sheet for a battery pack according to the present embodiment will be described.

The heat-insulating material used in the heat transfer suppression sheet according to the present embodiment can be manufactured by molding a material containing at least one of inorganic particles or inorganic fibers by a dry molding method or a wet molding method, for example. As the dry molding method, for example, a press molding method (dry press molding method) and an extrusion molding method (dry extrusion molding method) can be used.

In the dry press molding method, inorganic particles and inorganic fibers, and, if necessary, organic fibers, organic binders, and the like are put into a mixer such as a V-shaped mixer at a predetermined ratio. Then, after the materials put into the mixer are sufficiently mixed, the mixture is put into a predetermined mold and press-molded to obtain a heat-insulating material. During press molding, heating may be performed as necessary.

A heat-insulating material having concave portions and convex portions can be formed by, for example, a pressing method using a mold having a concave and convex shape during press molding.

A press pressure during press molding is preferably in a range of <NUM> MPa or more and <NUM> MPa or less. If the press pressure is less than <NUM> MPa, the strength of the obtained heat-insulating material may not be secured and the heat-insulating material may collapse. On the other hand, if the press pressure exceeds <NUM> MPa, the workability may be deteriorated due to excessive compression, or due to an increase in the bulk density, solid heat transfer may increase and heat insulating properties may be decreased.

In the case of using the dry press molding method, it is preferable to use an ethylene-vinyl acetate copolymer (EVA) as the organic binder, but any organic binder that is generally used in the case of using the dry press molding method can be used without particular limitation.

In the dry extrusion molding method, a paste is prepared by adding water to inorganic particles and inorganic fibers and, if necessary, organic fibers and organic binders as binders, followed by kneading the mixture with a kneader. Then, the obtained paste is extruded from a slit-shaped nozzle using an extruder and further dried to obtain a heat-insulating material. In the case of using the dry extrusion molding method, it is preferable to use methylcellulose, water-soluble cellulose ether, or the like as the organic binder, but any organic binder that is generally used in the case of using the dry extrusion molding method can be used without particular limitation.

Examples of the method for manufacturing the heat-insulating material having concave portions and convex portions by the dry extrusion molding method include a method of scraping a surface of a sheet before drying obtained by the extrusion from a slit-shaped nozzle into a desired concave and convex shape.

In the wet molding method, inorganic particles and inorganic fibers, and, if necessary, organic binders as binders, are mixed in water and stirred with a stirrer to prepare a mixed solution. Then, the obtained mixed solution is poured into a molding machine having a mesh for filtration formed on a bottom surface, and the mixed solution is dehydrated through the mesh, whereby a wet sheet is prepared. Thereafter, the obtained wet sheet is heated and pressurized, whereby a heat-insulating material can be obtained.

Before the heating and pressurizing step, a ventilation drying treatment may be performed in which hot air is passed through the wet sheet to dry the sheet, or the wet sheet may be heated and pressurized in a wet state without performing the ventilation drying treatment.

In the case of using the wet molding method, an acrylic emulsion using polyvinyl alcohol (PVA) can be selected as the organic binder.

Examples of the method for manufacturing a heat-insulating material having concave portions and convex portions by the wet molding method include a method of press-molding a wet sheet using a mold having a concave and convex shape before heating and pressurization.

Examples of the method for manufacturing the covering material having concave portions and convex portions include a method in which the above polymer films or metal films of general purpose manufactured with a desired thickness can be used, and press molding is performed using a mold having a concave and convex shape.

The heat transfer suppression sheet according to the present embodiment can be manufactured, for example, by applying an adhesive to the heat-insulating material or the covering material obtained as described above and bonding the heat-insulating material to the covering material.

Examples of a method of covering the entire heat-insulating material with the covering material include a method of sandwiching the heat-insulating material between two covering materials cut larger than a surface of the heat-insulating material or between folded covering materials, and bonding the covering materials to each other by thermocompression bonding or an adhesive around the heat-insulating material.

A battery pack according to the present embodiment is a battery pack in which battery cells are connected in series or in parallel, and the heat transfer suppression sheet for a battery pack according to the present embodiment is interposed between the battery cells. Specifically, for example, as shown in <FIG>, in the battery pack <NUM>, battery cells <NUM> are disposed side by side, connected in series or in parallel and accommodated in the battery case <NUM>, and the heat transfer suppression sheets <NUM> are interposed between the battery cells <NUM>.

In such a battery pack <NUM>, since the heat transfer suppression sheet <NUM> is interposed between the battery cells <NUM>, the individual battery cells <NUM> can be cooled during normal use.

Even when one of the battery cells <NUM> has thermal runaway and reaches a high temperature, swells, or catches fire, due to the heat transfer suppression sheet <NUM> according to the present embodiment, the propagation of heat between the battery cells <NUM> can be suppressed. Therefore, the chain of thermal runaway can be prevented, and adverse effects on the battery cell <NUM> can be minimized.

Claim 1:
A heat transfer suppression sheet (<NUM>; <NUM>; <NUM>; <NUM>; <NUM>; <NUM>; <NUM>; <NUM>; <NUM>) for a battery pack (<NUM>), the heat transfer suppression sheet (<NUM>; <NUM>; <NUM>; <NUM>; <NUM>; <NUM>; <NUM>; <NUM>; <NUM>) being used in a battery pack (<NUM>) in which battery cells (<NUM>) are connected in series or in parallel and being interposed between the battery cells (<NUM>), the heat transfer suppression sheet (<NUM>; <NUM>; <NUM>; <NUM>; <NUM>; <NUM>; <NUM>; <NUM>; <NUM>) comprising:
a heat-insulating material (<NUM>; <NUM>; <NUM>; <NUM>) containing at least one of inorganic particles or inorganic fibers; and
a covering material (<NUM>; <NUM>; <NUM>; <NUM>) covering at least a part of the heat-insulating material (<NUM>; <NUM>; <NUM>; <NUM>), wherein
a sealed gap (<NUM>) is formed between the heat-insulating material (<NUM>; <NUM>; <NUM>; <NUM>) and the covering material (<NUM>; <NUM>; <NUM>; <NUM>),
characterized in that
the covering material (<NUM>; <NUM>; <NUM>; <NUM>) is configured such that a communication opening (<NUM>) that allows the gap (<NUM>) to communicate with the outside of the covering material (<NUM>; <NUM>; <NUM>; <NUM>) is formed at a temperature of <NUM> or more, wherein
the heat-insulating material (<NUM>; <NUM>; <NUM>; <NUM>) is bonded to the covering material (<NUM>; <NUM>; <NUM>; <NUM>) with an adhesive (16a, 16b, 16c) that melts at a temperature of <NUM> or more and when the adhesive (16a, 16b, 16c) has melted, the communication opening (<NUM>) is formed, and/or
the covering material (<NUM>; <NUM>; <NUM>; <NUM>) is formed of a polymer film that melts at a temperature of <NUM> or more.