JP5039866B2 - Battery pack - Google Patents

Description

  The present invention relates to a battery pack in which a plurality of unit cells are accommodated in an exterior body.

In recent years, demands for secondary batteries such as nickel metal hydride, nickel cadmium, and lithium ion that can be used repeatedly are increasing from the viewpoint of resource saving and energy saving. In particular, lithium ion secondary batteries are lightweight but have high electromotive force and high energy density, so various types of mobile phones, digital cameras, video cameras, notebook computers, etc. There is an increasing demand for power sources for driving portable electronic devices and mobile communication devices and power sources for powering cordless power tools. On the other hand, in order to reduce the consumption of fossil fuels such as petroleum and reduce CO ₂ emissions, it is possible to obtain a desired voltage and capacity by combining a plurality of batteries as a power source for driving a motor of an automobile or the like. Battery packs that can be used have been developed.

  As the energy density of batteries increases, the safety of battery packs using them together with the safety of the batteries themselves is becoming more important.

  When a short circuit occurs inside the battery or inside the battery pack due to a strong impact from the outside, an extremely large current flows in the battery pack, which may cause explosion or ignition. In order to prevent this, the conventional battery pack incorporates various protection circuits. However, such a battery pack may cause the protection circuit itself to fail due to an impact.

  In addition, with the reduction in size and weight of equipment, the battery pack itself to be mounted is also limited in weight and shape, so that a design with a higher degree of design freedom is required while ensuring safety.

  Patent Document 1 discloses a battery pack including a release unit that releases a connection state by a connecting unit that connects batteries by detecting an impact received by the battery pack.

  Patent Document 2 discloses a battery pack including an impact absorbing portion that is destroyed when an impact is applied to the battery pack adjacent to a storage portion that stores the battery.

JP-A-9-274906 JP 2003-45392 A

  In the battery pack disclosed in Patent Literature 1, when an impact that greatly deforms the battery pack is applied, the battery itself may come into contact if the connecting means is greatly deformed. Therefore, in order to prevent a short circuit of the battery, it is necessary to make the outer package of the battery pack strong.

  Moreover, since the battery pack disclosed in Patent Document 2 needs to be provided with an impact absorbing portion separately from the storage portion for storing the battery, the shape of the battery pack exterior body is restricted.

  That is, in the conventional battery pack, in order to ensure safety, restrictions are imposed on the strength, form, and the like of the battery pack exterior body, so it is difficult to increase the degree of freedom in designing the battery pack.

  The present invention has been made in view of the above points, and its main purpose is to provide a battery pack having a high degree of freedom in design that is highly flexible during normal times and has a function of protecting the battery when subjected to an impact. It is to provide.

  A battery pack according to the present invention is a battery pack in which an assembled battery in which a plurality of unit cells are connected is housed in an exterior body, and at least a part of the plurality of unit cells is covered with a buffer member having dilatancy characteristics. It is characterized by.

  The buffer member is preferably made of a polymer base material imparting dilatancy characteristics or a resin material or a porous material containing an organic substance. Further, the buffer member may be formed of a bag body filled with a liquid or gel-like substance imparting dilatancy characteristics.

  In a preferred embodiment, the organic material is made of a gel material, and when the shock absorbing member is cured by absorbing an impact, the gel material is bonded to further impart thermal conductivity.

  It is preferable that the said buffer member is provided in the outer surface or inner surface of an exterior body. Moreover, the said buffer member may be comprised with the exterior body.

  The “dilatancy characteristic” in the present invention is a kind of nonlinear viscoelasticity, and usually refers to a characteristic in which the viscosity increases rapidly as the flow rate increases, although the viscosity is usually small. A typical example of the dilatancy characteristic is a characteristic that cures when a momentary impact is applied.

  According to the present invention, it is possible to provide a battery pack having a high degree of freedom in design, which is highly flexible during normal times and has a function of protecting the battery when subjected to an impact.

It is the perspective view which showed the structure of the battery pack in one Embodiment of this invention. FIG. 2 is a cross-sectional view taken along the line X-X ′ of the battery pack of FIG. 1. It is the fragmentary sectional perspective view which showed the structure of the single battery accommodated in a battery pack. It is the perspective view which showed the structure of the assembled battery which connected the several cell. It is sectional drawing which showed the structure of the buffer member in other embodiment of this invention. It is sectional drawing which showed the structure of the buffer member in other embodiment of this invention. It is sectional drawing which showed the structure of the buffer member in other embodiment of this invention. It is sectional drawing which showed the structure of the buffer member in other embodiment of this invention. It is sectional drawing which showed the structure of the buffer member in other embodiment of this invention. It is sectional drawing which showed the structure of the buffer member in other embodiment of this invention. It is sectional drawing which showed the structure of the buffer member in other embodiment of this invention. It is sectional drawing which showed the structure of the buffer member in other embodiment of this invention. (A), (b) is the perspective view which showed the structure of the buffer member in other embodiment of this invention. It is sectional drawing which showed the structure of the buffer member in other embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, this invention is not limited to the following embodiment. Moreover, it can change suitably in the range which does not deviate from the range which has the effect of this invention. Furthermore, combinations with other embodiments are possible.

  FIG. 1 is a perspective view showing a configuration of a battery pack 1 according to an embodiment of the present invention. FIG. 2 is a cross-sectional view taken along the line X-X ′ of the battery pack 1 shown in FIG. 1.

  As shown in FIG. 1, a battery pack 1 houses an assembled battery 4 that is configured by electrically connecting a plurality of cylindrical unit cells 3 inside a substantially rectangular box-shaped housing 2. Yes.

  As shown in FIG. 2, the housing 2 includes a battery pack exterior body 7 and a buffer member (protective layer) 8 having dilatancy characteristics. In the present embodiment, the outer surface of the exterior body 7 is covered with the buffer member 8, so that the plurality of single cells 3 are covered with the buffer member 8.

  Here, the exterior body 7 is made of a heat-resistant metal such as iron, nickel, aluminum, titanium, copper, stainless steel or the like, a nonflammable material, liquid crystalline wholly aromatic polyester, polyethersulfone, aromatic polyamide, or the like. A certain resin or a laminate of a metal and a resin is used.

  The buffer member 8 is made of a polymer base material imparting dilatancy characteristics or a resin material or a porous material containing an organic substance.

  For example, the buffer member 8 is made of a composite material in which a polymer base material imparting dilatancy characteristics is contained in pores of an open-cell foam such as a polyurethane foam or a cellulose foam.

  Examples of the polymer base material that imparts dilatancy characteristics include silicone bouncing putties. Here, the silicone bouncing putty is a boron-containing siloxane polymer obtained by polymerizing dimethylsiloxane using boric acid as a catalyst. This material is a shear-thickening material that is sensitive to deformation speed, and becomes a viscous flow at low-speed strain deformation, but sufficiently increases viscosity at high-speed strain deformation.

  In addition, examples of the organic material imparting dilatancy characteristics include a liquid or gel substance that is a dispersion of solid particles in a viscous fluid. In addition, these organic materials can be filled in the bag body to constitute the buffer member 8.

  As the bag body, a resin material that is lightweight, flexible, and relatively easy to process is desirable. For example, a processed material such as a film, a sheet, or a fiber can be used. Further, by processing the resin material into a hollow body or a foam, it is possible to enclose an organic material that imparts dilatancy characteristics inside the resin.

  According to the present invention, by covering the plurality of single cells 3 with the buffer member 8 having dilatancy characteristics, when the battery pack 1 receives an impact from the outside, the buffer member 8 is cured, whereby the single cell 3. Can be protected from impact. Moreover, since the buffer member 8 can be comprised with the polymer base material which provides a dilatancy characteristic, or the resin material or porous material containing the organic substance, it can be normally utilized in a lightweight and flexible form. it can. Thereby, the battery pack 1 which is safe and has a high degree of design freedom can be realized.

  In addition, when a gel-like substance is used as an organic substance that imparts dilatancy characteristics, the buffer member 8 further imparts thermal conductivity by bonding the gel-like substance when cured by absorbing an impact. Can do. Thereby, even if an excessive impact is applied to the battery pack, an internal short circuit occurs in the unit cell, and the unit cell generates heat, the generated heat is transferred to the outside through the buffer member 8 provided with thermal conductivity. I can escape. As a result, it is possible to prevent thermal runaway due to a rise in temperature of normal cells other than the unit cell in which an internal short circuit has occurred.

  Examples of such a gel substance include a heat conductive silicone grease. Specifically, the silicone polymer includes aluminum, silver, copper, nickel, zinc oxide, alumina, magnesium oxide, aluminum nitride, boron nitride, silicon nitride, diamond, graphite, carbon nanotube, metallic silicon, carbon fiber, fullerene, etc. Examples thereof include materials containing at least one kind of heat conductive material.

  FIG. 3 is a partial cross-sectional perspective view schematically showing the configuration of the unit cell 3 housed in the battery pack 1. In the present invention, the type of unit cell 3 housed in the battery pack 1 is not particularly limited. The single battery 3 illustrated in FIG. 3 is a cylindrical lithium ion secondary battery.

  As shown in FIG. 3, an electrode group 28 in which a positive electrode plate 17 and a negative electrode plate 19 are wound through a separator 21 is housed in a battery case 24 together with an electrolytic solution (not shown). Insulating plates 22 and 23 are respectively provided above and below the electrode group 28, and the opening of the battery case 24 is sealed with a gasket 25, a sealing plate 26, and a positive electrode terminal 27. The positive electrode plate 17 is connected to the sealing plate 26 and the positive electrode terminal 27 through the positive electrode lead 18, and the negative electrode plate 19 is connected to the bottom of the battery case 24 that also serves as the negative electrode terminal through the negative electrode lead 20. Yes.

  A circular groove 29 is formed at the center of the sealing plate 26. When gas is generated in the battery case 24 and the internal pressure exceeds a predetermined pressure, the groove 29 is broken. Further, the convex portion of the positive electrode terminal 27 is provided with an opening 30 (discharge port). When the groove 29 is broken, the gas generated in the battery case 24 is discharged from the opening 30 to the outside. It has become.

The positive electrode plate 17 has a positive electrode active material coated on the surface of a positive electrode current collector made of aluminum foil or the like. As the positive electrode active material, a transition metal-containing composite oxide containing lithium, for example, a transition metal-containing composite oxide such as LiCoO ₂ or LiNiO ₂ can be used.

  The negative electrode plate 19 has a negative electrode active material coated on the surface of a negative electrode current collector made of a metal foil such as a copper foil. As the negative electrode active material, a carbon material, a lithium-containing composite oxide, a material that can be alloyed with lithium, a material that can reversibly store and release lithium, a metallic lithium, and the like can be used.

  FIG. 4 is a perspective view showing a configuration of the assembled battery 4 in which a plurality of unit cells 3 are connected.

  The assembled battery 4 illustrated in FIG. 4 is configured by connecting a plurality of unit cells 3 in series by a connection plate 12. An insulation sheet 13 is wound around the outer periphery of the unit cell 3, and connection lead wires 14 for connection to external devices extend from the unit cells 3 at both ends of the assembled battery 4. In addition, the cell 3 which comprises the assembled battery 4 may be connected in parallel.

  In the present invention, as shown in FIG. 2, the buffer member 8 is cured when the battery pack 1 receives an impact from the outside by covering the plurality of single cells 3 with the buffer member 8 having dilatancy characteristics. Thus, the unit cell 3 can be protected from impact.

  Here, the form in which the buffer member 8 covers the plurality of single cells 3 is not limited to the configuration illustrated in FIG. 2, and may take various forms.

  Hereinafter, the structure of the buffer member 8 in other embodiment is demonstrated, referring FIGS. 5-14.

  The battery pack 1 shown in FIG. 5 is configured by configuring the buffer member 8 with an exterior body of the battery pack 1. For example, the buffer member 8 can be made of a resin material in which plastic, rubber, or fiber containing an organic substance imparting dilatancy characteristics is woven. In this case, the buffer member 8 also serves to protect the unit cell 3 as an exterior body of the battery pack 1.

  The battery pack 1 shown in FIG. 6 has a buffer member 8 attached to a part of the surface of the exterior body 7. For example, the shock can be effectively absorbed by attaching the buffer member 8 to a portion where the strength of the exterior body 7 is weak.

  The battery pack 1 shown in FIG. 7 has a buffer member 8 attached to the inside of the exterior body 7. Since the buffer member 8 is hidden inside the battery pack 1 in appearance, the shape and function of the exterior body 7 can be maintained.

  The battery pack 1 shown in FIG. 8 has a buffer member 8 attached to a part of the inside of the exterior body 7 and the cell 3 is fixed by the buffer member 8. Thereby, the cell 3 can be protected more stably.

  The battery pack 1 shown in FIG. 9 is obtained by filling the space between the exterior body 7 and the single battery 3 with a buffer member 8 made of a gel substance. Thereby, the cell 3 can be protected more stably.

  A battery pack 1 shown in FIG. 10 is provided with a buffer member 8 between adjacent unit cells 3. By making the buffer member 8 function as a storage wall for partitioning the unit cell 3, the unit cell 3 can be protected from impact and the structure of the exterior body 7 can be further strengthened.

  The battery pack 1 shown in FIG. 11 is one in which a base material 32 having pores is filled in the exterior body 7, and an organic substance imparting dilatancy characteristics is filled in the pores. As the base material 32, foamed polystyrene, a ceramic porous body, or the like can be used, and the organic material imparting dilatancy characteristics is preferably liquid or gel.

  In the battery pack 1 shown in FIG. 12, the buffer member 8 is formed of a bag filled with a liquid or gel-like substance imparting dilatancy characteristics. As the bag body, for example, a bag made of aluminum foil can be used.

  Further, as shown in FIGS. 13 and 14, the buffer member 8 may be directly attached to the outer periphery of the unit cell 3 or the assembled battery 4.

  FIG. 13A shows an example in which the buffer member 8 is attached to the outer periphery of the cylindrical unit cell 3, and FIG. 13B shows an example in which the buffer member 8 is attached to the outer periphery of the prismatic unit cell 3. . FIG. 14 shows an example in which the buffer member 8 is attached to the outer periphery of the assembled battery 4.

Below, the Example which comprised the battery pack using the lithium ion secondary battery shown in FIG. 3 is described.
(1) Production of positive electrode plate N- of lithium cobaltate powder (85 parts by mass) as a positive electrode active material, carbon powder (10 parts by mass) as a conductive agent, and polyvinylidene fluoride (PVDF) (5 parts by mass) as a binder. A positive electrode mixture was prepared by mixing a methyl-2-pyrrolidone (hereinafter abbreviated as NMP) solution. This positive electrode material mixture was applied to a current collector made of an aluminum foil having a thickness of 15 μm, dried and then rolled to prepare a positive electrode plate 17 having a thickness of 100 μm.
(2) Production of negative electrode plate An artificial graphite powder (95 parts by mass) as a negative electrode active material and an NMP solution of PVDF (5 parts by mass) as a binder were mixed to produce a negative electrode mixture. This negative electrode mixture was applied to a current collector made of a copper foil having a thickness of 10 μm, dried and then rolled to prepare a negative electrode plate 19 having a thickness of 110 μm.
(3) Preparation of non-aqueous electrolyte As a non-aqueous solvent, ethylene carbonate and ethyl methyl carbonate are mixed at a volume ratio of 1: 1 so that lithium hexafluorophosphate (LiPF6) is 1 mol / L. Dissolve to prepare 15 ml of non-aqueous electrolyte.
(4) Production of Secondary Battery After the positive electrode plate 17 and the negative electrode plate 19 are wound through a separator 21 having a thickness of 25 μm to produce a cylindrical electrode group 28, the electrode group 28 is combined with a non-aqueous electrolyte. The cylindrical lithium ion secondary battery 3 having a diameter of 18 mm and a height of 65 mm was produced by housing in a metal battery case 24 and sealing the opening of the battery case 24. The design capacity of the battery was 2000 mAh. The outer periphery of the battery case 24 was covered with a heat-shrinkable tube made of polyethylene terephthalate having a thickness of 80 μm.
(5) Manufacture of an assembled battery Four produced secondary batteries 3 were arranged as shown in FIG. 4 and connected in series with a connection plate 12 made of nickel and having a thickness of 0.2 mm. Furthermore, the assembled battery 4 was manufactured by attaching the connection lead wires 14 for connecting the unit cells 3 connected in series and the terminals of the battery pack 1 to the unit cells 3 at both ends.
(6) Production of Battery Pack The produced assembled battery 4 was accommodated in the outer package 7 to produce the battery pack 1 of Examples 1 to 12 and Comparative Example 1 below.

Example 1
As shown in FIG. 2, a battery pack 1 having a structure in which a buffer member 8 was provided on the outer peripheral surface of the exterior body 7 was produced. As the buffer member 8, a plastic containing a polymer base material exhibiting dilatancy characteristics was used, and the thickness was set to 0.3 mm. As the polymer base material, a resin material in which silicone oil is the main raw material and boron is bonded is used. Moreover, the exterior body 7 was made of epoxy resin and the thickness was 0.2 mm.

(Example 2)
As shown in FIG. 5, a battery pack 1 having a structure in which the buffer member 8 is configured by an exterior body was produced. As the buffer member 8, a plastic containing a polymer base material exhibiting dilatancy characteristics was used, and the thickness was set to 0.5 mm. As the polymer base material, a resin material in which silicone oil is the main raw material and boron is bonded is used.

(Example 3)
As shown in FIG. 6, the battery pack 1 having a configuration in which the buffer member 8 was attached to a part of the surface of the exterior body 7 was produced. As the buffer member 8, a plastic containing a polymer base material exhibiting dilatancy characteristics was used, and the outer dimensions were 15 mm × 50 mm and the thickness was 0.3 mm. As the polymer base material, a resin material in which silicone oil is the main raw material and boron is bonded is used.

Example 4
As shown in FIG. 7, the battery pack 1 having a configuration in which the buffer member 8 was attached to the inside of the exterior body 7 was produced. As the buffer member 8, a plastic containing a polymer base material exhibiting dilatancy characteristics was used, and the thickness was set to 0.3 mm. As the polymer base material, a resin material in which silicone oil is the main raw material and boron is bonded is used.

(Example 5)
As shown in FIG. 8, the battery pack 1 having a configuration in which the buffer member 8 was attached to a part of the inside of the exterior body 7 and the unit cell 3 was fixed by the buffer member 8 was produced. As the buffer member 8, a plastic containing a polymer base material exhibiting dilatancy characteristics was used, and the outer dimensions were 15 mm × 50 mm and the thickness was 0.3 mm. As the polymer base material, a resin material in which silicone oil is the main raw material and boron is bonded is used.

(Example 6)
As shown in FIG. 9, a battery pack 1 having a configuration in which the space between the exterior body 7 and the single battery 3 was filled with a buffer member 8 made of a gel material was produced. As the buffer member 8, a resin material having a dilatancy characteristic in which silicone oil is the main raw material and boron is bonded is used.

(Example 7)
As shown in FIG. 10, a battery pack 1 having a configuration in which a buffer member 8 was provided between adjacent unit cells 3 was produced. As the buffer member 8, a plastic containing a polymer base material exhibiting dilatancy characteristics was used, and the outer dimensions were 18 mm × 65 mm and the thickness was 0.5 mm. As the polymer base material, a resin material in which silicone oil is the main raw material and boron is bonded is used.

(Example 8)
As shown in FIG. 11, a battery pack 1 having a configuration in which a base material 32 having pores was filled in the exterior body 7 and an organic substance imparting dilatancy characteristics was filled in the pores. As the base material 32, foamed silicone was used, and as the buffer member 8, a resin material fluid having a dilatancy characteristic in which polydiorganosiloxane and boron were bonded together was used.

Example 9
As shown in FIG. 12, a battery pack 1 was produced in which the buffer member 8 was constituted by a bag body filled with a gel-like substance imparting dilatancy characteristics. As the buffer member 8, an aluminum foil bag filled with a polymer base material exhibiting dilatancy characteristics and sealed was used. As a polymer base material exhibiting dilatancy characteristics, a mixture of 80% quartz sand, 16% glycerin, and 4% water was used.

(Example 10)
As shown in FIG. 13A, the battery pack 1 having a configuration in which the buffer member 8 is attached to the outer periphery of the unit cell 3 was produced. As the buffer member 8, a plastic containing a polymer base material exhibiting dilatancy characteristics was used, and the thickness was set to 0.3 mm. As the polymer base material, a resin material in which silicone oil is the main raw material and boron is bonded is used.

(Example 11)
As shown in FIG. 14, the battery pack 1 having a configuration in which the buffer member 8 was attached to the outer periphery of the assembled battery 4 was produced. As the buffer member 8, a plastic containing a polymer base material exhibiting dilatancy characteristics was used, and the thickness was set to 0.3 mm. As the polymer base material, a resin material in which silicone oil is the main raw material and boron is bonded is used.

(Comparative Example 1)
In the battery pack 1 of Example 1, the battery pack 1 having a configuration without the buffer member 8 was produced.

  The following evaluations were performed on each battery pack obtained in the above examples and comparative examples.

(7) Drop test In order to confirm safety, a drop test was performed in which the battery pack 1 was dropped from a position of 16 m height onto the concrete wall. Table 1 is a table showing the results. In the table, the cells 3 in which the breakage (including cracks) did not occur are indicated by ◯, and the cells that have been broken are indicated by ×.

  In Examples 1 to 11, the cell 3 was not broken by the drop test, but in the comparative example 1, it was broken. From this, it can be seen that the battery pack 1 having the buffer member 8 has improved safety.

  In the above embodiment, a drop test was performed only on the battery pack. However, even when the battery pack mounted on the device body was actually subjected to an impact, heat generation or leakage, etc. generated by destruction of the single cell, etc. Damage to the main body of the equipment is also minimized. In particular, high safety effects are expected for portable electronic devices and mobile communication devices that are easily dropped and damaged, and automobiles that are subject to a strong impact by collision.

  As mentioned above, although this invention was demonstrated by suitable embodiment, such description is not a limitation matter and of course various modifications are possible. For example, in the above embodiment, the single battery 3 is a lithium ion secondary battery, but other secondary batteries (for example, a nickel metal hydride battery) may be used.

  The present invention is useful as a power source for electronic devices, automobiles, electric motorcycles, electric play equipment, and the like.

1 Battery pack
2 Case
3 cells
4 batteries
7 exterior body
8 cushioning member
12 Connection board
13 Insulation sheet
14 Connection lead wire
17 Positive electrode plate
18 Positive lead
19 Negative electrode plate
20 Negative lead
21 Separator
22, 23 Insulation plate
24 battery case
25 Gasket
26 Sealing plate
27 Positive terminal
28 Electrode group
29 Groove
30 opening
32 Base material

Claims (9)

A battery pack in which an assembled battery in which a plurality of cells are connected is housed in an exterior body,
A battery pack, wherein at least some of the plurality of single cells are covered with a buffer member having a dilatancy characteristic.   2. The battery pack according to claim 1, wherein the buffer member is made of a polymer base material imparting dilatancy characteristics, a resin material containing an organic substance, or a porous material.   The battery pack according to claim 1, wherein the buffer member is formed of a bag body that is filled with a liquid or gel substance that imparts dilatancy characteristics. The organic material is a gel material,
4. The battery pack according to claim 3, wherein when the shock absorbing member absorbs an impact and is cured, the gel-like substance is bonded to further impart thermal conductivity.   The gel material is made of silicone polymer, aluminum, silver, copper, nickel, zinc oxide, alumina, magnesium oxide, aluminum nitride, boron nitride, silicon nitride, diamond, graphite, carbon nanotube, metal silicon, carbon fiber, fullerene. The battery pack according to claim 4, comprising at least one thermally conductive material selected from the group consisting of:   The battery pack according to claim 1, wherein the buffer member is provided on an outer surface or an inner surface of the exterior body.   The battery pack according to claim 1, wherein the buffer member is configured by the exterior body.   The battery pack according to claim 1, wherein the buffer member is provided between the adjacent single cells.   The battery pack according to claim 1, wherein the buffer member is provided on an outer peripheral portion of the unit cell.

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