Patent Description:
A battery pack is required to be sealable in order to protect a secondary battery housed inside from dust and water. In addition, since the secondary battery may generate gas during abnormality, the battery pack is also required to have a gas exhaust function in order to prevent rupture. PTL <NUM> discloses a battery pack in which a battery case with a seal member sandwiched between an upper lid and a lower lid is used to ensure sealability. During abnormality, the seal member is dissolved by the heat of gas generated from a secondary battery to form an exhaust path. PTL <NUM> discloses an energy storage device provided with a housing having a wall in which a gas release valve is formed. PTL <NUM> discloses battery modules including a plurality of batteries accommodated in a case. PTL <NUM> discloses a rechargeable battery. PTL <NUM> discloses a battery pack in which a battery element formed by winding or laminating a positive electrode and a negative electrode with a separator interposed therebetween is wrapped in a laminate film, and a protection circuit board for the battery is integrated with the battery pack. PTL <NUM> discloses venting of equipment used in water and more particularly a vent valve provided between a battery housing arranged in the equipment and an outer wall of the equipment. PTL <NUM> discloses a power storage apparatus including a pressure release valve. PTL <NUM> discloses. PTL <NUM> discloses a battery pack.

In the battery pack disclosed in PTL <NUM>, it takes time to form the exhaust path, and thus there is a possibility that exhaust cannot happen in time when gas is rapidly released from the secondary battery.

Therefore, an object of the present invention is to provide a battery pack that can be exhausted in accordance with an increase in internal pressure.

A battery pack according to an aspect of the present invention includes a secondary battery and a battery case that houses the secondary battery. The battery case includes an exhaust section that exhausts gas exhausted from the secondary battery to outside of the battery case. The exhaust section includes at least one slit that is opened along with deformation of the exhaust section occurring in accordance with an increase in pressure in the battery case.

According to the battery pack of an aspect of the present invention, it is possible to normally seal the inside of the battery case so as to protect the inside of the battery case from dust and water, and to suppress rupture of the battery case during abnormality.

Exemplary embodiments according to the present invention will be described below in detail with reference to the accompanying drawings. Note that in a case where a plurality of exemplary embodiments and modified examples are included in the following, it is assumed from the beginning to construct a new exemplary embodiment by appropriately combining feature parts of them. The plurality of drawings includes schematic views, and dimensional ratios such as depth, width, and height of each member do not necessarily coincide among different drawings. Those configuration elements described in the following that are not recited in independent claims representing the highest concept are illustrated herein as optional configuration elements and are not essential. In the present description, the term "substantial/substantially" is used in the same meaning as the term "approximate/approximately," and the requirement "substantially. " is satisfied if being substantially the same.

In the following exemplary embodiment, a case where battery pack <NUM> has a substantially rectangular parallelepiped shape will be described as an example. In the drawings and the description of the examples, an X direction indicates the depth direction of battery pack <NUM> (battery case <NUM>), a Y direction indicates the width direction of battery pack <NUM> (battery case <NUM>), and a Z direction indicates the height direction of battery pack <NUM> (battery case <NUM>). The X, Y, and Z directions are orthogonal to each other.

First, an outline of battery pack <NUM> will be described with reference to <FIG> is a perspective view of a battery pack that is an example of the exemplary embodiment. <FIG> is a planar cross-sectional view taken along line A-A of <FIG> (a cross-sectional view taken along an XZ plane passing through the center of battery pack <NUM> in the width). <FIG> is a front cross-sectional view taken along line B-B of <FIG> (a cross-sectional view taken along a YZ plane passing through secondary battery <NUM> in the depth of battery pack <NUM>). Battery pack <NUM> can be used as a power source for various electric devices, and may be, for example, a small-capacity battery pack for small portable devices such as a personal computer (PC) or an electric cleaner.

Battery pack <NUM> includes battery case <NUM>. The shape of battery case <NUM> is not particularly limited, but battery case <NUM> may have a substantially rectangular parallelepiped shape such as that illustrated in <FIG>. Battery case <NUM> is formed of a metal material or a resin material, for example. Battery case <NUM> has a function of protecting internally housed secondary battery <NUM> from dust and water.

Battery case <NUM> includes exhaust section <NUM> that exhausts gas exhausted from secondary battery <NUM> to the outside of battery case <NUM>. The position, number, size, and the like at which exhaust section <NUM> is provided are not particularly limited, but one exhaust section <NUM> may be provided on a part of one side surface in the depth direction of battery case <NUM>, such as illustrated in <FIG>. In addition, the size of exhaust section <NUM> may be any size as long as gas exhausted from secondary battery <NUM> can be exhausted to suppress rupture of battery case <NUM>. Although details will be described later, exhaust section <NUM> has a function of normally sealing the inside of battery case <NUM>, and deforming and opening in accordance with an increase in pressure in battery case <NUM> during abnormality. As a result, it is possible to suppress rupture of battery case <NUM> while suppressing intrusion of dust and water into battery case <NUM>.

Battery pack <NUM> may include covering member <NUM> that covers exhaust section <NUM>. As a result, secondary battery <NUM> housed in battery case <NUM> can be more reliably protected from dust and water. Covering member <NUM> is fixed to battery case <NUM> so as to close exhaust section <NUM> by a fixing means such as an adhesive. Covering member <NUM> may be made of an air-permeable and waterproof material, such as Gore-Tex (registered trademark), that allows exhaust gas from the inside of battery case <NUM> to pass and blocks liquid such as water from the outside.

Battery pack <NUM> includes secondary battery <NUM> housed in battery case <NUM>. The number, shape, size, and the like of secondary battery <NUM> are not particularly limited, but battery pack <NUM> may house a plurality of cylindrical secondary batteries <NUM> in battery case <NUM>, such as illustrated in <FIG>. Examples of secondary battery <NUM> include a non-aqueous electrolyte secondary battery such as a lithium ion battery. Secondary battery <NUM> may have positive electrode terminal 16a and negative electrode terminal 16b at respective ends in the depth. Secondary battery <NUM> includes, for example, an electrode group including a positive electrode and a negative electrode, an exterior can that houses the electrode group together with an electrolyte, and a sealing plate that seals an opening of the exterior can with an insulating gasket. The exterior can may be electrically connected to the negative electrode of the electrode group, and the conductive sealing plate may be connected to the positive electrode. Note that a current collecting member such as a metal plate is connected to positive electrode terminal 16a and negative electrode terminal 16b of secondary battery <NUM>, and a connection terminal with the outside of the positive electrode and the negative electrode is provided in battery case <NUM>. However, in <FIG>, an electrical connecting member such as a current collecting member and a connection terminal is omitted.

As illustrated in <FIG>, battery case <NUM> may include container <NUM> that houses secondary battery <NUM> in an internal space of inner wall <NUM> formed on a peripheral edge. An exhaust passage <NUM> through which a high-temperature gas exhausted from the secondary battery <NUM> during abnormality flows is formed between containers <NUM> and between container <NUM> and inner wall <NUM>. Exhaust passage <NUM> is a passage for gas exhausted from secondary battery <NUM>, and may be cooled by mixing with the air in exhaust passage <NUM> when the gas flows through exhaust passage <NUM>. For example, in <FIG>, when the sealing plate near the positive electrode terminal 16a of secondary battery <NUM> is designed to be broken before the exterior can, high-temperature gas exhausted from secondary battery <NUM> passes through exhaust passage <NUM> over a long distance before reaching exhaust section <NUM>, so that the temperature of the gas can be efficiently lowered. Note that the exterior can may be designed to be broken, and it is preferable that the exterior can be designed to be broken after the sealing plate has been broken.

As illustrated in <FIG>, battery case <NUM> may be divided into two half cases 12a, 12b in the height. By overlapping half cases 12a, 12b in a state of facing each other, secondary battery <NUM> can be entirely covered. In half cases 12a, 12b, only the tip of inner wall <NUM> abuts, and the tips of parts other than inner wall <NUM> face each other with a space therebetween. Thus, a space is formed in battery case <NUM>, and this space is exhaust passage <NUM>.

Next, exhaust section <NUM> will be described in detail with reference to <FIG>.

<FIG> is an enlarged view of a part of exhaust section <NUM> in an example of the exemplary embodiment. Exhaust section <NUM> has at least one slit <NUM>, and preferably has a plurality of slits <NUM> as illustrated in <FIG>. Slits <NUM> are thin lines penetrating exhaust section <NUM> in the thickness. Note that slits <NUM> need not penetrate over their entire length, and a part thereof may be non-penetrating. The width of slits <NUM> is, for example, <NUM> to <NUM>, preferably <NUM> to <NUM>. The thickness of exhaust section <NUM> is not particularly limited as long as slits <NUM> can be opened during abnormality as described later.

As illustrated in <FIG>, slits <NUM> each have the same shape with pointed bent parts 30a, 30b, and may be aligned such that the directions of bent parts 30a, 30b are aligned in the longitudinal direction and are alternately opposite in the lateral direction. Since bent parts 30a, 30b of slits <NUM> are pointed, when the slits <NUM> part is opened as described later, covering member <NUM> is broken and gas can be more easily exhausted from exhaust section <NUM>. In addition, the plurality of slits <NUM> may overlap in the lateral direction as illustrated in <FIG>. The larger overlap width w is, the larger the opening can be widened with respect to the pressure in battery case <NUM> during abnormality.

Since exhaust section <NUM> has slits <NUM>, the slits <NUM> part is preferentially deformed along with deformation of exhaust section <NUM> occurring in accordance with an increase in pressure in battery case <NUM>. Therefore, when gas is exhausted from secondary battery <NUM>, the pressure in battery case <NUM> increases, and exhaust section <NUM> is pushed from the inside of battery case <NUM>, so that the slits <NUM> part is opened, and the gas can be exhausted from exhaust section <NUM> to the outside.

<FIG> is a cross-sectional view taken along line C-C of <FIG>. Part (a) of <FIG> illustrates a normal state in which the pressure in battery case <NUM> is low, and (b) of <FIG> illustrates an abnormal state in which the pressure in battery case <NUM> has increased. Part (c) of <FIG> is a cross-sectional view taken along line D-D of <FIG> in an abnormal state in which the pressure in battery case <NUM> has increased. As illustrated in (a) of <FIG>, exhaust section <NUM> is normally substantially flat, and the width of slits <NUM> in bent parts 30a, 30b is narrowed to such an extent that it is possible to suppress entry of dust and water into battery case <NUM>. However, as illustrated in (b) of <FIG>, exhaust section <NUM> during abnormality receives pressure from the inside of battery case <NUM>, slits <NUM> are pushed to the outside, the width of slits <NUM> in bent parts 30a, 30b is increased, and gas g exhausted from secondary battery <NUM> is exhausted. This can suppress rupture of battery case <NUM>. In addition, since the bending directions of the bent parts of the plurality of slits <NUM> are opposite for each adjacent row, as illustrated in (b) and (c) of <FIG>, the direction in which gas g is exhausted can be differentiated for each adjacent row of slits <NUM>, so that it is possible to reduce the concentration of gas g outside the vicinity of exhaust section <NUM> and to reduce the risk of combustion of gas g.

In exhaust section <NUM>, slits <NUM> reversibly operate due to the pressure in battery case <NUM>. That is, when gas is exhausted and the pressure in battery case <NUM> decreases, slits <NUM> preferably return to normal positions. As a result, since the sealed state can be maintained again after exhaust, it is possible to suppress the spread of fire of secondary battery <NUM> due to inflow of air from the outside.

Exhaust section <NUM> is preferably made of an aluminum material or a stainless steel material. As a result, exhaust section <NUM> is less likely to be corroded by gas exhausted from secondary battery <NUM>, and can operate stably. Further, since aluminum and stainless steel are easily elastically deformed, a deformation range in which exhaust section <NUM> can reversibly operate can be made relatively wide.

Next, other examples of exhaust section <NUM> will be described with reference to <FIG>. Part (a) to (e) of <FIG> are diagrams corresponding to <FIG> in the other examples of the exemplary embodiment.

In (a) of <FIG>, slits <NUM> each have the same shape with pointed bent parts, and are aligned such that the directions of the bent parts are aligned in the longitudinal direction and are alternately opposite in the lateral direction. In addition, the plurality of slits <NUM> do not overlap in the lateral direction.

In (b) of <FIG>, slits <NUM> each have the same shape with round bent parts 30a, 30b, and are aligned such that the directions of the bent parts are aligned in the longitudinal direction and are alternately opposite in the lateral direction. In addition, the plurality of slits <NUM> do not overlap in the lateral direction. As illustrated in (a) and (b) of <FIG>, when the slits do not overlap each other in the lateral direction, exhaust section <NUM> is relatively less likely to be deformed, and thus, is likely to operate reversibly in accordance with the pressure in battery case <NUM>.

In (c) of <FIG>, linear slits <NUM> having the same length and facing two directions orthogonal to each other are periodically aligned, so that the assembly of slits <NUM> forms a lattice pattern. In this case, the exhaust direction of gas g during abnormality as illustrated in (b) of <FIG> is likely to be aligned in the same direction. However, in a case where the concentration of gas g outside the periphery of exhaust section <NUM> is sufficiently low and the risk of combustion of gas g is low, exhaust section <NUM> may have such an assembly of slits <NUM>.

In (d) of <FIG>, each slit <NUM> has a linear shape extending in the lateral direction and having the same length, and is aligned such that both ends thereof are aligned in the longitudinal direction and heights thereof in the longitudinal direction are aligned every other line in the lateral direction. In addition, the plurality of slits <NUM> overlap in the lateral direction.

In (e) of <FIG>, each slit <NUM> has a linear shape extending in the lateral direction and having the same length, and is aligned such that both ends thereof are aligned in the longitudinal direction and heights thereof in the longitudinal direction are aligned every other line in the lateral direction. In addition, the plurality of slits <NUM> do not overlap in the lateral direction. As illustrated in (d) and (e) of <FIG>, when slits <NUM>, <NUM> have a linear shape, the slits can be relatively easily manufactured.

The slits illustrated in <FIG> and <FIG> of <FIG> are examples, and exhaust section <NUM> may include a plurality of types of slits with different shapes.

Claim 1:
A battery pack (<NUM>) comprising:
a secondary battery (<NUM>); and
a battery case (<NUM>) that houses the secondary battery (<NUM>),
wherein
the battery case (<NUM>) includes an exhaust section (<NUM>) through which gas discharged from the secondary battery (<NUM>) is exhausted to outside of the battery case (<NUM>), and
the exhaust section (<NUM>) includes at least one slit (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) that is opened along with deformation of the exhaust section (<NUM>) occurring in accordance with an increase in pressure in the battery case (<NUM>);
wherein in the exhaust section (<NUM>), the at least one slit (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) reversibly operates due to pressure in the battery case (<NUM>).