JP2009016235A - Power storage device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power storage device capable of preventing overcharging or the like to a power storage body in a simple structure. <P>SOLUTION: The power storage device includes a power storage body (3) and a conductive member (37) to be in contact with a power storage body (35) and connected with a wire (38) used for charge and discharge of the power storage body. A contact area with the power storage body (35) is changed by thermal deformation of the conductive material in accordance with temperature. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a power storage device capable of limiting a current flowing through a power storage body at a high temperature.

Conventionally, secondary batteries are used as batteries for electric vehicles (EV), hybrid vehicles (HEV), and fuel cell vehicles (FCV). Here, in the secondary battery, gas may be generated due to a chemical change in the battery during overcharge or the like. Therefore, there are some which are provided with a control circuit for avoiding such an abnormal state of the secondary battery.
JP 2004-235068 A

  However, the control circuit described above has a problem that the circuit configuration becomes complicated and the cost is excessive.

  The power storage device according to the present invention includes a power storage unit, and a conductive member that is in contact with the power storage unit and to which wiring used for charging and discharging the power storage unit is connected. The contact area with the power storage unit is changed by thermal deformation.

  Here, a part of the conductive member is deformed in a direction away from the power storage unit in response to a rise in the temperature of the conductive member, and is deformed in a direction in contact with the power storage unit in accordance with a decrease in the temperature of the conductive member. be able to. Further, the power storage unit can be configured such that the positive electrode body and the negative electrode body are stacked with the electrolyte layer interposed therebetween, and the conductive member is brought into contact with at least one end surface of both end surfaces in the stacking direction of the power storage unit. Can do.

  On the other hand, the connection portion of the conductive member with the wiring can be fixed to the power storage unit. Moreover, a conductive material (for example, conductive grease) can be applied to at least one of the contact surfaces of the power storage unit and the conductive member. Furthermore, a bimetal or a shape memory alloy can be used as the conductive member.

  According to the present invention, the conductive member to which the wiring used for charging / discharging the power storage unit is connected is thermally deformed according to the temperature to change the contact area with the power storage unit, thereby overcharging the power storage unit. Can be suppressed. That is, if the contact area between the conductive member and the power storage unit is reduced, the charging current for the power storage unit can be suppressed, and overcharging can be suppressed.

  Moreover, in the present invention, since the conductive member is thermally deformed according to the temperature, the above-described effects can be obtained with a simple configuration in which only the conductive member is provided.

  Examples of the present invention will be described below.

  A battery pack as a power storage device that is Embodiment 1 of the present invention will be described with reference to FIGS. 1 to 3. Here, FIG. 1 is a schematic view showing the configuration of the battery pack of this embodiment, and FIG. 2 is an external perspective view showing the configuration of a part of the laminated battery included in the battery pack. FIG. 3 is a side view showing the configuration of the laminated battery in the present embodiment, a side view (A) when the laminated battery is in a normal state and a side view (B) when the laminated battery is in a high temperature state. ).

  As shown in FIG. 1, the battery pack 1 of the present embodiment includes a case 2, a laminated battery (power storage unit) 3 and a heat exchange medium 4 housed in the case 2. Here, the battery pack 1 is mounted on the vehicle body 5. Examples of the vehicle body 5 include a floor panel and a vehicle frame.

  The case 2 is preferably formed of a material excellent in durability and corrosion resistance. Specifically, a metal such as aluminum can be used as this material. Here, in order to improve the heat dissipation of the case 2, a cooling gas (air or the like) is supplied to the outer surface of the case 2 (surface opposite to the surface in contact with the heat exchange medium 4). be able to. This gas can be supplied using a fan or the like. In addition, in order to improve the heat dissipation in the case 2, it is also possible to provide a radiating fin on the outer surface of the case 2.

  On the other hand, the heat exchange medium 4 accommodated in the case 2 is a gas or liquid used for cooling the laminated battery 3 by heat exchange with the laminated battery 3.

  The heat exchange medium 4 is in contact with the outer surface of the laminated battery 3 and the inner wall surface of the case 2. Here, when the temperature of the laminated battery 3 rises due to charge / discharge or the like, heat exchange is performed between the heat exchange medium 4 in contact with the outer surface of the laminated battery 3 and the laminated battery 3, thereby the laminated battery. 3 is suppressed. The heat exchange medium 4 having heat by heat exchange with the stacked battery 3 circulates inside the case 2 and contacts the inner wall surface of the case 2, thereby transferring heat to the case 2. Here, the heat exchange medium 4 may be naturally convected according to a temperature difference, or may be forced to flow using a stirring member provided inside the case 2. The heat transmitted to the case 2 is released into the atmosphere or transmitted to the vehicle body 5.

  When gas is used as the heat exchange medium 4, specifically, dry gas such as air or nitrogen gas can be used. Further, when a liquid is used as the heat exchange medium 4, specifically, insulating oil or inert liquid can be used. Here, silicon oil or the like is used as the insulating oil. As the inert liquid (insulating liquid), fluorinated inert liquids such as Fluorinert (registered trademark), Novec HFE (hydrofluoroether), Novec 1230 (manufactured by 3M), and the like can be used.

  Next, a specific configuration of the laminated battery 3 will be described with reference to FIG.

  The laminated battery 3 has a configuration in which a plurality of bipolar electrodes (electrode bodies) 30 are laminated via a solid electrolyte layer 34. In other words, the laminated battery 3 is an assembled battery in which a plurality of unit cells are laminated. Here, the unit cell is a power generation element including a solid electrolyte layer 34 and electrode layers 32 and 33 arranged on both sides of the solid electrolyte layer 34 in the stacking direction (vertical direction in FIG. 2). is there.

  Note that the number of unit cells to be stacked can be set as appropriate. In this embodiment, the case where a single battery as a secondary battery is used will be described. However, the present invention can be applied to the case where an electric double layer capacitor (capacitor) is used.

  A positive electrode layer (electrode layer) 32 is formed on one surface of the current collector 31, and a negative electrode layer (electrode layer) 33 is formed on the other surface. The electrode layers 32 and 33 and the current collector 31 constitute a bipolar electrode 30. The electrode layers 32 and 33 can be formed on the surface of the current collector 31 by using an inkjet method or the like.

  Here, the current collector 31 positioned at both ends in the stacking direction of the stacked battery 3 has an electrode layer (positive electrode layer or negative electrode layer) formed only on one surface. In addition, electrode tabs (a negative electrode tab 35 and a positive electrode tab 36 to be described later) for extracting a current generated in the laminated battery 3 are electrically and mechanically connected to the other surface.

  Each electrode layer 32, 33 contains an active material corresponding to the positive electrode and the negative electrode. In addition, each electrode layer 32, 33 includes a conductive agent, a binder, an inorganic solid electrolyte for improving ion conductivity, a polymer gel electrolyte, a polymer solid electrolyte, an additive, and the like as necessary.

For example, nickel - the hydrogen battery, as the active material of the positive electrode layer 32, using a nickel oxide as the active material of the negative electrode layer _{33, MmNi (5-x-} y-z) Al x Mn y Co z (Mm: misch A hydrogen storage alloy such as (metal) can be used. In the lithium ion battery, a lithium-transition metal composite oxide can be used as the active material of the positive electrode layer 32, and carbon can be used as the active material of the negative electrode layer 33. As the conductive agent, acetylene black, carbon black, graphite, carbon fiber, or carbon nanotube can be used.

  In the present embodiment, the case where the bipolar electrode 30 is used has been described. However, the present invention is not limited to this. For example, an electrode body (positive electrode body) in which a positive electrode layer is formed on both surfaces of a current collector and an electrode body (negative electrode body) in which a negative electrode layer is formed on both surfaces of the current collector can also be used. In this case, the electrode body provided with the positive electrode layer and the electrode body provided with the negative electrode layer are alternately arranged (laminated) via the solid electrolyte layer.

  The current collector 31 can be formed of, for example, an aluminum foil or a plurality of metals (alloys). In addition, a metal (excluding aluminum) whose surface is covered with aluminum can be used as the current collector 31.

  As the current collector 31, a so-called composite current collector in which a plurality of metal stays are bonded together can be used. In the case of using this composite current collector, aluminum or the like can be used as the material for the positive electrode current collector, and nickel, copper, or the like can be used as the material for the negative electrode current collector. In addition, as the composite current collector, one in which the positive electrode current collector and the negative electrode current collector are in direct contact is used, or a conductive layer is provided between the positive electrode current collector and the negative electrode current collector. The provided one can be used.

  The solid electrolyte layer 34 includes a particle group composed of a plurality of particles and a binder for binding the particle group. Here, as the solid electrolyte layer 34, an inorganic solid electrolyte or a polymer solid electrolyte can be used.

As the inorganic solid electrolyte, for example, a nitride, halide, oxyacid salt, or phosphorus sulfide compound of Li can be used. More _{specifically, Li 3 N, LiI, Li} 3 N-LiI-LiOH, LiSiO 4, LiSiO 4 -LiI-LiOH, Li 3 PO 4 -Li 4 SiO 4, Li 2 SiS 3, Li 2 O-B _{2 O 3, Li 2 O 2} -SiO 2, Li 2 S-GeS 4, Li 2 S-P 2 S 5, LiI-Li 2 S-P 2 S 5 can be used.

  As the polymer solid electrolyte, for example, a substance composed of the above electrolyte and a polymer that dissociates the electrolyte, or a substance having an ion dissociation group in the polymer can be used. As the polymer for dissociating the electrolyte, for example, a polyethylene oxide derivative and a polymer containing this derivative, a polypropylene oxide derivative, a polymer containing this derivative, and a phosphate ester polymer can be used. An inorganic solid electrolyte and a polymer solid electrolyte can be used in combination.

  Moreover, although the present Example demonstrated the case where the solid electrolyte layer 34 was used, it is not restricted to this, A gel-like or liquid electrolyte layer can also be used. For example, a non-woven fabric as a separator containing an electrolyte can be used. In this case, it is necessary to use a sealing material in order to prevent the liquid electrolyte or the like from leaking outside the laminated battery 3. Specifically, a sealing material can be disposed between the current collectors 31 adjacent to each other in the stacking direction.

  In FIG. 3, a negative electrode tab 35 and a positive electrode tab 36 for taking out a current generated in the laminated battery 3 are provided at both ends in the lamination direction of the laminated battery 3. The negative electrode tab 35 and the positive electrode tab 36 are connected to the current collectors 31 located at both ends in the stacking direction of the stacked battery 3 as described above.

  In FIG. 3, between the negative electrode tab 35 and the positive electrode tab 36, a plurality of unit cells 3a as the power generation elements described above are stacked. The negative electrode tab 35 and the positive electrode tab 36 are connected to an electronic device (for example, a motor used for running the vehicle) mounted on the vehicle via a bimetal 37 and wirings 38 and 39.

  Further, a bimetal (conductive member) 37 is provided on one surface of the negative electrode tab 35 (the surface opposite to the surface in contact with the unit cell 1a). The bimetal 37 is obtained by bonding together a first metal plate 37a and a second metal plate 37b having different thermal characteristics (coefficient of thermal expansion). Here, the second metal plate 37 b is disposed to face the negative electrode tab 35 and is in contact with the surface of the negative electrode tab 35. Further, the first metal plate 37a is located on the opposite side of the negative electrode tab 35 side with respect to the second metal plate 37b.

  A wiring 38 is electrically and mechanically connected to one end of the bimetal 37, and one end of the bimetal 37 is fixed to the negative electrode tab 35 by a fastening mechanism using a bolt or the like or welding. The wiring 39 is electrically and mechanically connected to one end of the positive electrode tab 36.

  Invar (an alloy of 36 wt% nickel and 64 wt% iron) can be used as the first metal plate 37a constituting the bimetal 37, and aluminum or lead is used as the second metal plate 37b. be able to.

  The material of the first and second metal plates 37a and 37b is not limited to this. That is, as will be described later, the bimetal 37 only needs to be deformable at a predetermined temperature, and the second metal plate 37b has a thermal expansion coefficient larger than that of the first metal plate 37a. I just need it. Here, the predetermined temperature is a temperature set in advance before the stacked battery 3 reaches an abnormal state (for example, a state where gas is generated) due to overcharging or the like.

  In this embodiment, the negative electrode tab 35 and the positive electrode tab 36 are used, but these can be omitted. That is, the bimetal 37 is brought into contact with the negative electrode side current collector 31 positioned at one end in the stacking direction of the stacked battery 3, and the positive electrode side current collector 31 positioned at the other end of the stacked battery 3 is wired. 39 may be connected.

  Next, the operation of the bimetal 37 will be described with reference to FIG.

  FIG. 3A shows a side view when the laminated battery 3 is in a normal state that is not a high temperature state. In the state shown in FIG. 3A, the bimetal 37 (second metal plate 37 b) is in contact with the substantially entire surface of the negative electrode tab 35. Depending on a dimensional error related to the surface shape of the bimetal 37 or the negative electrode tab 35, a part of the bimetal 37 may not contact the negative electrode tab 35. It shall be in contact with.

  In the state shown in FIG. 3A, the current flowing through the entire stacked battery 3 (the entire surface orthogonal to the stacking direction) also flows through the entire bimetal 37. And charging / discharging to the laminated battery 3 is performed via the wirings 38 and 39.

  Here, when the temperature of the laminated battery 3 rises due to overcharge or the like, the temperature of the bimetal 37 in contact with the laminated battery 3 also rises. In this case, the bimetal 37 is deformed in the direction indicated by the arrow A1 in FIG. 3B as the temperature rises, and a part of the bimetal 37 is separated from the surface of the negative electrode tab 35. In other words, since one end portion of the bimetal 37 connected to the wiring 38 is fixed to the negative electrode tab 35, the other end portion is separated from the surface of the negative electrode tab 35 due to thermal deformation.

  In the state shown in FIG. 3B, the contact area between the bimetal 37 and the negative electrode tab 35 is smaller than that in the state shown in FIG. 3A, and the electrical resistance between the bimetal 37 and the negative electrode tab 35 increases. Thereby, the electric current amount which flows into the laminated battery 3 can be suppressed, and the overcharge to the laminated battery 3 can be suppressed. Here, depending on the contact area between the bimetal 37 and the negative electrode tab 35 in the state shown in FIG. 3B, the charging current for the laminated battery 3 can be cut off. In addition, the contact area between the bimetal 37 and the negative electrode tab 35 varies depending on the temperature of the bimetal 37 (in other words, the amount of deformation).

  As described above, by suppressing overcharge of the laminated battery 3, it is possible to suppress an increase in the temperature of the laminated battery 3, and to prevent an abnormal reaction (gas generation or the like) of the laminated battery 3 due to the temperature increase.

  On the other hand, if the overcharge of the laminated battery 3 is continued to be suppressed in the state shown in FIG. 3B, the temperature of the laminated battery 3 is lowered and the temperature of the bimetal 37 is also lowered. As the temperature decreases, the bimetal 37 is deformed in the direction indicated by the arrow A2 in FIG. 3B, thereby contacting the surface of the negative electrode tab 35 and returning to the state shown in FIG.

  Here, a conductive material (for example, conductive grease) can be applied to at least one of the contact surfaces of the bimetal 37 and the negative electrode tab 35. In this case, even if the bimetal 37 operates between the states shown in FIGS. 3A and 3B, a substantially constant contact resistance (conduction) is maintained at the contact portion between the bimetal 37 and the negative electrode tab 35. can do.

  According to the present embodiment, overcharge of the laminated battery 3 can be suppressed with a simple configuration in which the bimetal 37 is simply deformed according to the temperature of the laminated battery 3. As a result, it is possible to omit a control circuit (including a sensor) for avoiding an abnormal state associated with overcharging of the laminated battery 3, thereby reducing costs.

  In the present embodiment, the case where the bimetal 37 is used has been described. However, the present invention is not limited to this. That is, depending on the temperature, any material can be used as long as it can be deformed between a state where it is in contact with the entire surface of the negative electrode tab 35 and a state where it is separated from a part of the negative electrode tab 35 and has conductivity. .

  For example, a shape memory alloy can be used instead of the bimetal 37. Examples of the shape memory alloy include a nickel-titanium alloy and a copper-zinc-aluminum alloy. The material of the shape memory alloy can be selected by the same method as that for selecting the material of the bimetal 37 described above.

  In this embodiment, the bimetal 37 is brought into contact with the negative electrode tab 35, but the present invention is not limited to this. That is, it is sufficient if the bimetal 37 is brought into contact with at least one of the negative electrode tab 35 and the positive electrode tab 36. In this case, the wiring for taking out the output of the laminated battery 3 to the outside is connected to the bimetal 37.

  Furthermore, in this embodiment, the end of the bimetal 37 to which the wiring 38 is connected is fixed to the negative electrode tab 35, but the present invention is not limited to this. That is, a part of the bimetal 37 (arbitrary region) may be fixed to the negative electrode tab 35.

  Specifically, the central portion of the bimetal 37 may be fixed to the negative electrode tab 35, or the end of the bipolar 37 opposite to the end to which the wiring 38 is connected may be fixed to the negative electrode tab 35. Good. If a part of the bimetal 37 is fixed to the negative electrode tab 35 in this way, other regions of the bimetal 37 can be brought into contact with or separated from the negative electrode tab 35 by thermal deformation.

  Here, as in this embodiment, if the end of the bimetal 37 to which the wiring 38 is connected is fixed to the negative electrode tab 35, the position of the wiring 38 is maintained even if the bimetal 37 is deformed by temperature (heat). Will not change.

  On the other hand, in the present embodiment, the stacked battery 3 having a configuration in which a plurality of unit cells 3a are stacked has been described. However, the present invention can be applied to a battery having another configuration. For example, the present invention can also be applied to a cylindrical battery in which a positive electrode and a negative electrode are wound via an electrolyte. Here, the positive electrode, the negative electrode, and the electrolyte are power generation elements in the cylindrical battery.

  In this case, the charging current is reduced by bringing the bimetal into contact with a conductive plate provided at one end (or both ends) of the cylindrical battery in the longitudinal direction and thermally deforming the bimetal to reduce the contact area with the conductive plate. Can be limited. Thereby, overcharge can be suppressed. Here, the conductive plate is a member that is connected to the power generation element of the cylindrical battery and through which a current passes when the cylindrical battery is charged and discharged. The power generation element and the conductive plate correspond to the power storage unit in the present invention.

It is a figure which shows schematic structure of the battery pack which is Example 1 of this invention. 1 is an external perspective view showing a configuration of a part of a laminated battery in Example 1. FIG. It is a side view (A) which shows the structure of the laminated battery in a normal state, and the side view (B) which shows the structure of the laminated battery in a high temperature state.

Explanation of symbols

1: Battery pack (power storage device)
2: Case 3: Stacked battery (power storage unit)
4: Heat exchange medium 30: Bipolar electrode 31: Current collector 34: Solid electrolyte layer 35: Negative electrode tab 36: Positive electrode tab 37: Bimetal (conductive member)
38, 39: Wiring

Claims (6)

A power storage unit;
A conductive member that is in contact with the power storage unit and connected to wiring used for charging and discharging the power storage unit;
The power storage device, wherein the conductive member is thermally deformed according to temperature to change a contact area with the power storage unit.   A part of the conductive member is deformed in a direction away from the power storage unit in response to an increase in the temperature of the conductive member, and in a direction in contact with the power storage unit in response to a decrease in the temperature of the conductive member. The power storage device according to claim 1, wherein the power storage device is deformed. The power storage unit has a configuration in which a positive electrode body and a negative electrode body are stacked with an electrolyte layer interposed therebetween,
3. The power storage device according to claim 1, wherein the conductive member is in contact with at least one end face of both end faces in the stacking direction of the power storage unit.   4. The power storage device according to claim 1, wherein a portion of the conductive member that is connected to the wiring is fixed to the power storage unit. 5.   5. The power storage device according to claim 1, wherein a conductive material is applied to at least one of contact surfaces of the power storage body and the conductive member.   The power storage device according to any one of claims 1 to 5, wherein the conductive member is formed of a bimetal or a shape memory alloy.

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