WO2023149108A1

WO2023149108A1 - Battery pack

Info

Publication number: WO2023149108A1
Application number: PCT/JP2022/046940
Authority: WO
Inventors: 喜幸坂内
Original assignee: 株式会社村田製作所
Priority date: 2022-02-03
Filing date: 2022-12-20
Publication date: 2023-08-10

Abstract

A battery pack according to one embodiment of the present technology comprises a plurality of batteries, and buried members buried in the gaps between the batteries. The buried members have a porous body impregnated with an endothermic agent. The porous body has a flow path through which the endothermic agent can leak to the outside due to capillarity.

Description

battery pack

This technology relates to battery packs.

Due to the widespread use of electronic devices, batteries are being developed as power sources for such electronic devices. In this case, a battery pack including a plurality of batteries has been proposed in order to handle the plurality of batteries easily and safely.

Various studies have been conducted on technologies related to the configuration of battery packs. Specifically, a heat-absorbing member is in contact with the side surface of the battery unit, and the heat-absorbing member contains a heat-absorbing agent (liquid or gel-like fluid) inside the exterior film (see, for example, Patent Document 1). .

WO 2010/098067 pamphlet

However, in the invention described in Patent Document 1, when the exterior film melts due to abnormal heat generation of the battery, a large amount of the heat-absorbing agent leaks out at once. Therefore, the heat-absorbing agent cannot remain on the surface of the abnormally heated battery, and the heat-absorbing effect due to the sensible heat and latent heat of vaporization of the heat-absorbing agent may be reduced. Therefore, it is desirable to provide a battery pack that can efficiently cool the abnormally heated battery.

A battery pack according to one aspect of the present technology includes a plurality of batteries and an embedding member embedded in gaps between the plurality of batteries. The embedded member has a porous body impregnated with an endothermic agent. The porous body has flow paths through which the heat-absorbing agent can leak out due to capillary action.

According to the battery pack according to one aspect of the present technology, a porous body impregnated with an endothermic agent is provided in an embedding member embedded in a gap between a plurality of batteries, and capillary action is generated through a flow path of the porous body. Since the heat-absorbing agent is made to leak outside, a large amount of the heat-absorbing agent does not leak out at once, and it is possible to efficiently cool the abnormally heated battery.

It should be noted that the effects of the present technology are not necessarily limited to the effects described here, and may be any of a series of effects related to the present technology described below.

FIG. 1 is a diagram illustrating a perspective configuration example of a battery pack according to an embodiment of the present technology. FIG. 2 is a diagram showing a perspective configuration example of a battery module housed in a battery pack. FIG. 3 is a view showing an example of the exploded perspective configuration of the battery module. FIG. 4A is a diagram showing a perspective configuration example of an embedding member. FIG. 4B is a diagram showing a cross-sectional configuration example of the embedding member. FIG. 5 is a diagram showing a perspective configuration example of a porous body. FIG. 6 is a diagram showing how the embedding member and a plurality of batteries are in close contact with each other. FIG. 7 is a diagram showing a modified example of the batteries and the embedded member accommodated in the battery pack. FIG. 8 is a diagram showing a state in which the battery and the embedding member in FIG. 7 are overlaid. FIG. 9 is a diagram showing an example of an experimental apparatus for verifying capillary action. FIG. 10A is a cross-sectional view showing the state before heating by the heater. FIG. 10B is a cross-sectional view showing the state during heating by the heater.

EMBODIMENT OF THE INVENTION Hereinafter, the form for implementing this technique is demonstrated in detail with reference to drawings. The order of explanation is as follows.
1. Battery pack 1-1. Configuration 1-2. Effect 2. Modification 3. Application of battery pack 4 . Validation of capillarity

<1. Battery pack>
First, a battery pack according to an embodiment of the present technology will be described.

The battery pack described here is a power supply with multiple batteries, and is applied to various applications such as electronic devices. The details of the application of the battery pack will be described later. Since the type of battery is not particularly limited, it may be a primary battery or a secondary battery. The type of secondary battery is not particularly limited, but specifically, it is a lithium ion secondary battery in which battery capacity is obtained by utilizing absorption and release of lithium ions. The number of batteries is not particularly limited and can be set arbitrarily. A case where the battery is a secondary battery (lithium ion secondary battery) will be described below. That is, the battery pack described below is a power supply that includes a plurality of secondary batteries.

<1-1. Overall configuration>
FIG. 1 shows a perspective configuration example of a battery pack 1 . FIG. 2 shows a perspective configuration example of the battery module 30 housed in the battery pack 1 . FIG. 3 shows an example of an exploded perspective configuration of the battery module 30. As shown in FIG.

For example, as shown in FIG. 1, the battery pack 1 includes an exterior case 10, battery modules 30 housed in the exterior case 10, and a control board (not shown). The control board is connected to, for example, the positive and negative terminals of the battery module 30, and measures the voltage of the battery and the battery module, detects the remaining capacity of the battery module 30, measures the current output from the battery module 30, and detects excess current. It has a circuit that detects the presence or absence of current.

The exterior case 10 is provided with an external terminal 20 connected to the control board. A battery module 30 is connected to the external terminal 20 via a control board. The battery pack 1 has a discharge mode in which the power output from the battery module 30 is supplied to the load via the external terminal 20 . Battery pack 1 may further have a charge mode in which power supplied from a power supply connected to external terminal 20 via external terminal 20 is stored in battery module 30 . When the battery 31 described below is a secondary battery, the control board switches between a discharge mode and a charge mode according to the type of the connected object connected to the external terminal 20 . When the battery 31, which will be described later, is a primary battery, the control board executes only the discharge mode.

The battery module 30 has a plurality of batteries 31 as shown in FIGS. 2 and 3, for example. The plurality of batteries 31 are electrically connected via

lead plates

34a, 34b, and 34c, as shown in FIGS. 2 and 3, for example. For example, when a plurality of batteries 31 that are a part of the plurality of batteries 31 are connected in series with each other, and the plurality of batteries 31 connected in series with each other are referred to as series units, the plurality of series units are connected in parallel with each other. In addition, the connection mode of the plurality of batteries 31 is not limited to the above.

Each battery 31 is a primary battery or a secondary battery. When each battery 31 is a secondary battery, the type of the secondary battery is not particularly limited, but specifically, it is a lithium ion secondary battery in which battery capacity is obtained by utilizing absorption and release of lithium ions. . A case where each battery 31 is a secondary battery (lithium ion secondary battery) will be described below. That is, the battery pack 1 described below is a power source that includes a plurality of secondary batteries.

The battery module 30 further includes, for example, as shown in FIGS. 2 and 3, a battery holder 32 that supports the plurality of batteries 31, and an embedding member 33 that is embedded in the gaps between the plurality of batteries 31. . The battery holder 32 has a structure that supports a plurality of batteries 31 in layers with predetermined gaps therebetween.

FIG. 4(A) shows a perspective configuration example of the embedding member 33 . FIG. 4B shows a cross-sectional configuration example of the embedding member 33 . The embedded member 33 has a shape corresponding to the shape of the gaps between the batteries 31 supported by the battery holder 32 . The embedded member 33 is in contact with the surface of the plurality of batteries 31 . Like the battery 31, the embedded member 33 has an elongated columnar shape. In the embedding member 33, the cross section in the direction perpendicular to the extending direction of the embedding member 33 has, for example, a substantially diamond shape. Hereinafter, the extending direction of the embedding member 33 will be referred to as the vertical direction for convenience, and the direction perpendicular to the extending direction of the embedding member 33 will be referred to as the lateral direction for convenience.

The embedded member 33 contains a heat-absorbing agent, and is configured so that the heat-absorbing agent leaks to the outside when the battery 31 generates abnormal heat. The embedding member 33 has, for example, a porous body 33b impregnated with an endothermic agent and a film 33a covering the entire porous body 33b, as shown in FIGS. 4(A) and 4(B). ing.

The porous body 33 b has a shape corresponding to the shape of the gaps between the batteries 31 supported by the battery holder 32 . Like the battery 31, the porous body 33b has an elongated columnar shape. In the porous body 33b, a cross section in a direction (horizontal direction) perpendicular to the extending direction of the porous body 33b is, for example, substantially diamond-shaped. The porous body 33b has a hardness that allows it to stand on its own from the viewpoint of improving handling. The porous body 33b is also made of a material with a heat resistance temperature higher than the abnormal heat generation temperature of the battery 31 (for example, about 600° C.). The porous body 33b is made of, for example, sintered metal, ceramics, or nonflammable fibers. When the porous body 33b is made of incombustible fibers, the incombustible fibers are solidified into a predetermined shape by applying heat or the like. As a result, even if the battery 31 generates abnormal heat, the porous body 33b will not melt, and clogging will not occur in the porous body 33b.

The porous body 33b has channels (continuous pores) through which the endothermic agent can leak out due to capillary action. The diameter of the channel provided in the porous body 33b is on the order of microns or submicrons, and is preferably within the range of 0.1 μm to 100 μm, for example. If the diameter is less than 0.1 μm, depending on the components of the fluid, clogging is likely to occur due to components, impurities, etc. in the liquid. Also, if it is larger than 100 μm, depending on the components of the fluid and the surface condition of the porous body, the capillary pressure may decrease and the movement of the fluid may be hindered.

Note that the heat-absorbing agent may be hydrogel as long as it has a viscosity that allows capillary force to be obtained. When the heat-absorbing agent is hydrogel, the speed of movement through the flow path in the porous body 33b is slower than when the heat-absorbing agent is a liquid containing water. However, since the heat-absorbing agent can be supplied for a longer period of time, it becomes possible to cool the part generating abnormal heat for a long period of time. When hydrogel is used as the endothermic agent, it is preferable to use a synthetic polymer gel. Examples of synthetic polymer gel materials include sodium polyacrylate (PNaAA), polyvinyl alcohol (PVA), polyhydroxyethyl methacrylate (PHE-MA), and silicone hydrogel.

The film 33a covers the entire porous body 33b as described above. The film 33a is in close contact with the porous body 33b and has a shape that follows the surface of the porous body 33b. The film 33a is made of a material with a heat resistance temperature lower than the abnormal heat generation temperature of the battery 31 (for example, about 600.degree. C.). As a result, when the battery 31 generates abnormal heat, the film 33a melts and the porous body 33b is exposed. The film 33a is made of, for example, a resin material such as polyethylene, polystyrene, polypropylene, or polycarbonate.

FIG. 5 shows a perspective configuration example of the porous body 33b. FIG. 6 shows how the embedding member 33 and the plurality of batteries 31 are brought into close contact with each other.

For example, as shown in FIGS. 5 and 6, the porous body 33b has a plurality of grooves 33b1 on a surface (that is, a side surface) facing the plurality of batteries 31. For example, as shown in FIG. 5, each groove 33b1 extends from the upper end (first end face S1) of the porous body 33b to the lower end (second end face S2) of the porous body 33b. As a result, when the battery 31 generates abnormal heat, the heat-absorbing agent leaking out of the porous body 33b is heated by the abnormally-heating battery 31 and evaporates. , through the groove 33b1. If the groove portion 33b1 were not provided, the gaseous heat-absorbing agent would form a vapor film, separating the battery 31 and the porous body 33b, which could lead to a decrease in cooling efficiency. When the groove portion 33b1 is provided, the gaseous endothermic agent is discharged, thereby preventing formation of a vapor film.

Each groove 33b1 may be linear as shown in FIG. 5, or may be curved. Although each groove portion 33b1 reaches both the first end surface S1 and the second end surface S2, it may reach only one of the first end surface S1 and the second end surface S2. The width of each groove portion 33b1 may be uniform as shown in FIG. 5, or may gradually widen from the vicinity of the vertical center of the porous body 33b toward the first end surface S1 or the second end surface S2. You can say

<1-2. Effect>
Next, effects of the battery pack 1 will be described.

However, in the invention described in Patent Document 1, when the exterior film melts due to abnormal heat generation of the battery, a large amount of the heat-absorbing agent leaks out at once. Therefore, the heat-absorbing agent cannot remain on the surface of the abnormally heated battery, and the heat-absorbing effect due to the sensible heat and latent heat of vaporization of the heat-absorbing agent may be reduced.

On the other hand, in the present embodiment, the embedding member 33 embedded in the gaps between the plurality of batteries 31 is provided with a porous body 33b impregnated with an endothermic agent. The endothermic agent leaks out due to capillary action. As a result, a large amount of the endothermic agent does not leak out at once. Further, since capillary action is used, for example, even if the heat absorbing agent is arranged below the battery 31 that has generated abnormal heat, the heat absorbing agent can be supplied to the heat generating portion regardless of gravity. Therefore, the abnormally heated battery 31 can be efficiently cooled.

Also, in the present embodiment, the porous body 33b has a shape corresponding to the shape of the gaps between the plurality of batteries 31 supported by the battery holder 32 . As a result, the contact area between the embedding member 33 and the battery 31 can be made sufficiently large. It is possible to reliably supply the agent. Therefore, the abnormally heated battery 31 can be efficiently cooled.

In addition, in the present embodiment, the porous body 33b has a hardness that allows it to stand on its own, and is made of a sintered metal, ceramics, or nonflammable fibers. As a result, handling of the embedded member 33 when assembling the battery module 30 can be improved.

In addition, in the present embodiment, the diameter of the flow path provided in the porous body 33b is on the order of microns or submicrons, for example, 0.1 μm or more and 100 μm or less. As a result, the heat-absorbing agent can be leaked to the outside through the flow path of the porous body 33b by capillarity, so that the heat-absorbing agent can be reliably supplied to the heat-generating portion. Therefore, the abnormally heated battery 31 can be efficiently cooled.

Also, in the present embodiment, the endothermic agent is a liquid containing water. As a result, heat-generating locations can be efficiently cooled.

Further, in the present embodiment, a plurality of grooves 33b1 are provided on the side surface of the porous body 33b (the surface facing the plurality of batteries 31). As a result, when the battery 31 generates abnormal heat, the heat-absorbing agent leaking from the porous body 33b is heated by the abnormally-heating battery 31 to evaporate, and the gaseous heat-absorbing agent thus generated is removed. , the groove portion 33b1 can be discharged to the outside. As a result, it is possible to prevent the formation of a vapor film separating the battery 31 and the porous body 33b, so that the heat-generating portion can be efficiently cooled without lowering the cooling efficiency.

Moreover, in the present embodiment, each groove 33b1 reaches the end of the porous body 33b. As a result, the gaseous endothermic agent can be efficiently discharged to the outside. As a result, it is possible to prevent the formation of a vapor film separating the battery 31 and the porous body 33b, so that the heat-generating portion can be efficiently cooled without lowering the cooling efficiency.

Further, in the present embodiment, the porous body 33b is made of a material with a heat resistance temperature higher than the abnormal heat generation temperature of the battery 31. As a result, even if the battery 31 generates abnormal heat, the porous body 33b will not melt and clogging will not occur. As a result, the heat-generating portion can be efficiently cooled.

Further, in the present embodiment, the entire porous body 33b is covered with the film 33a having a heat-resistant temperature lower than the abnormal heat generation temperature of the battery 31. As a result, when the battery 31 generates abnormal heat, the film 33a melts and the porous body 33b is exposed. As a result, the heat-absorbing agent leaks from the exposed portion, so that the heat-generating portion can be efficiently cooled. In a normal case where the battery 31 does not generate abnormal heat, the film 33a can prevent the heat-absorbing agent in the porous body 33b from leaking to the outside.

<3. Variation>
Next, a modification of the battery pack 1 according to the above embodiment will be described.

(Modification A)
In the above embodiment, the battery 31 has a cylindrical shape, the embedded member 33 has an elongated columnar shape like the battery 31, and the cross section in the direction perpendicular to the extending direction of the embedded member 33 has a substantially diamond shape. It was. However, in the above embodiment, for example, as shown in FIGS. , a flat-shaped embedding member 36 may be used. FIG. 7 shows a modified example of the battery 35 and the embedded member 36 accommodated in the battery pack 1. As shown in FIG. FIG. 8 shows how the battery 35 and the embedding member 36 of FIG. 7 are overlaid.

The plurality of batteries 35 are electrically connected, for example, via predetermined lead plates. For example, a plurality of batteries 35 that are part of the plurality of batteries 35 are connected in series with each other. Furthermore, when a plurality of batteries 35 connected in series with each other is referred to as a series unit, the plurality of series units may be connected in parallel with each other. In addition, the connection mode of the plurality of batteries 35 is not limited to the above.

Each battery 35 is a primary battery or a secondary battery. When each battery 35 is a secondary battery, the type of the secondary battery is not particularly limited, but specifically, it is a lithium ion secondary battery in which battery capacity is obtained by utilizing absorption and release of lithium ions. .

The embedding member 36 is arranged between the two batteries 35 and is in contact with the surfaces of the two batteries 35 . The embedding member 36 contains a heat-absorbing agent, and is configured such that the heat-absorbing agent leaks to the outside when the battery 35 generates abnormal heat. The embedding member 36 has, for example, a porous body 33b impregnated with an endothermic agent, and a film 33a covering the entire porous body 33b, similarly to the embedding member 33 . In this modified example, the porous body 33b has a flat shape like the battery 35 does.

Thus, even when the flat-shaped battery 35 is used instead of the cylindrical battery 31 and the flat-shaped embedding member 36 is used instead of the pillar-shaped embedding member 33, the above-described implementation is possible. As with the shape, heat-generating locations can be efficiently cooled.

(Modification B)
In the above embodiment and its modification, the heat-absorbing agent is included (impregnated) in the porous body 33b. However, in the above-described embodiment and its modification, a gap sufficiently larger than the flow path may be provided inside the porous body 33b, and the heat-absorbing agent may be stored in the gap. Even in this case, when the

batteries

31 and 35 generate abnormal heat, the heat-absorbing agent stored inside the porous body 33b leaks to the outside through the flow path described above. As a result, the heat-generating portion can be efficiently cooled as in the above-described embodiment and its modification.

(Modification C)
In the above embodiment and its modification, the embedded

members

33 and 36 are provided with the porous body 33b. However, in the above-described embodiment and its modification, instead of the porous body 33b, a heat-absorbing agent is included so that the heat-absorbing agent leaks to the outside when the

batteries

31 and 35 generate abnormal heat. You may use the member which carried out. Even in this case, it is possible to efficiently cool the heat-generating portion similarly to the above-described embodiment and its modification.

<3. Application of battery pack>
The battery pack 1 is used in machines, devices, instruments, devices, and systems (aggregates of multiple devices, etc.) that can use the battery pack 1 as a power source for driving and a power storage source for power storage. If there is, it is not particularly limited.

The battery pack 1 used as a power source may be a main power source or an auxiliary power source. A main power source is a power source that is preferentially used regardless of the presence or absence of other power sources. The auxiliary power supply may be, for example, a power supply that is used in place of the main power supply, or may be a power supply that is switched from the main power supply as needed. When using a battery pack as an auxiliary power supply, the main power supply is not limited to the battery pack.

An example of the usage of the battery pack 1 is as follows. Electronic devices (including portable electronic devices) such as video cameras, digital still cameras, mobile phones, notebook personal computers, cordless phones, headphone stereos, portable radios, portable televisions, and portable information terminals. It is a portable household appliance such as an electric shaver. Backup power and storage devices such as memory cards. Power tools such as power drills and power saws. Medical electronic devices such as pacemakers and hearing aids. It is an electric vehicle such as an electric vehicle (including a hybrid vehicle). It is an electric power storage system such as a home battery system that stores electric power in preparation for emergencies. Of course, the battery pack may be used for purposes other than those described above.

<4. Verification of Capillary Phenomenon>
For example, it is possible to verify whether or not capillary action occurs in the channel provided in the porous body 33b as follows. FIG. 9 shows an example of an experimental device for verifying the presence or absence of capillarity. In this experiment, the presence or absence of capillary action is verified by the following procedure.
(1) Place a portion of the porous body 33b in the center of a glass petri dish 110 having a diameter of 50 mm under an environment of 20° C.±5° C.; At this time, the volume of the porous body 33b placed in the center of the petri dish 110 is 4500 mm<3>.
(2) Pour the liquid 120 into the petri dish 110 until approximately half or more of the porous body 33b is submerged. At this time, the liquid 120 is sufficiently impregnated into the porous body 33b. In FIG. 10A, the liquid 120 impregnated in the porous body 33b is referred to as an impregnated liquid 120a.
(3) In order to block the heat of the heater 130 to be installed later, the sheet 140 is installed so that the porous body 33b is exposed when viewed from above and the liquid 120 is covered (see FIG. 10A). The sheet material is preferably mica, glass or metal.
(4) Place the heater 130 on the porous body 33b and record the liquid level height ha at that time (see FIG. 10(A)).
(5) The temperature of the heater 130 is set to 100° C. to 150° C., and the temperature of the heater 130 is increased (see FIG. 10B).
(6) After the temperature of the heater 130 reaches the set temperature, the temperature is maintained for 30 minutes.
(7) After 30 minutes, record the liquid level hb (see FIG. 10(B)).
(8) When hb-ha is 1 mm or more, it is determined that capillary action is occurring in the flow path provided in the porous body 33b. Conversely, when hb-ha is less than 1 mm, it is determined that capillary action does not occur in the channel provided in the porous body 33b.

Although the present technology has been described above while citing one embodiment, the present technology is not limited to the aspect described in the above-described one embodiment, and various modifications of the present technology are possible.

Specifically, the case where the battery structure of the secondary battery is cylindrical has been described, but the battery structure of the secondary battery applied to the battery pack of the present technology is not particularly limited. Specifically, the battery structure of the secondary battery may be a laminate film type, a square type, a coin type, or the like.

Also, although the case where the secondary battery has a wound structure has been described, the structure of the secondary battery is not particularly limited. Specifically, the secondary battery may have other structures such as a laminated structure.

Also, although lithium was used as the electrode reactant of the secondary battery, the type of the electrode reactant is not particularly limited. Specifically, the electrode reactant may be another group 1 element in the long period periodic table such as sodium and potassium, a group 2 element in the long period periodic table such as magnesium and calcium, or aluminum Other light metals such as

Since the effects described in this specification are merely examples, the effects of the present technology are not limited to the effects described in this specification. Accordingly, other advantages may be obtained with respect to the present technology.

In addition, this technique can also take the following structures.
<1>
a plurality of batteries;
and an embedding member embedded in the gaps between the plurality of batteries,
The embedding member has a porous body impregnated with an endothermic agent,
The porous body has a flow path through which the heat-absorbing agent can leak out due to capillary action.
<2>
further comprising a battery holder that supports the plurality of batteries;
The battery pack according to <1>, wherein the porous body has a shape corresponding to a shape of a gap between the plurality of batteries supported by the battery holder.
<3>
The battery pack according to <2>, wherein the porous body is hard enough to stand on its own.
<4>
The battery pack according to <3>, wherein the porous body is made of sintered metal, ceramics, or nonflammable fiber.
<5>
The battery pack according to any one of <1> to <4>, wherein the flow path has a diameter of 0.1 μm or more and 100 μm or less.
<6>
The battery pack according to any one of <1> to <5>, wherein the endothermic agent is a liquid containing water.
<7>
The battery pack according to any one of <1> to <6>, wherein the porous body has a plurality of grooves on a surface facing the plurality of batteries.
<8>
The battery pack according to <7>, wherein each of the grooves reaches an end of the porous body.
<9>
The battery pack according to any one of <1> to <8>, wherein the porous body is made of a material having a heat resistance temperature higher than an abnormal heat generation temperature of the battery.
<10>
The embedding member further has a film with a heat resistance temperature lower than the abnormal heat generation temperature of the battery,
The battery pack according to <9>, wherein the film covers the entire porous body.

Claims

a plurality of batteries;
and an embedding member embedded in the gaps between the plurality of batteries,
The embedding member has a porous body impregnated with an endothermic agent,
The porous body has a flow path through which the heat-absorbing agent can leak out due to capillary action.
further comprising a battery holder that supports the plurality of batteries;
The battery pack according to claim 1, wherein the porous body has a shape corresponding to the shape of the gaps between the plurality of batteries supported by the battery holder.
The battery pack according to claim 2, wherein the porous body has a hardness that enables it to stand on its own.
The battery pack according to claim 3, wherein the porous body is made of a sintered metal, ceramics, or nonflammable fiber.
The battery pack according to any one of claims 1 to 4, wherein the diameter of the flow path is 0.1 µm or more and 100 µm or less.
The battery pack according to any one of claims 1 to 5, wherein the endothermic agent is a liquid containing water.
The battery pack according to any one of claims 1 to 6, wherein the porous body has a plurality of grooves on a surface facing the plurality of batteries.
The battery pack according to claim 7, wherein each of said grooves reaches an end of said porous body.
The battery pack according to any one of claims 1 to 8, wherein the porous body is made of a material having a heat resistance temperature higher than an abnormal heat generation temperature of the battery.
The embedding member further has a film with a heat resistance temperature lower than the abnormal heat generation temperature of the battery,
The battery pack according to claim 9, wherein the film covers the entire porous body.