JP2015138648A - battery module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a battery module using a molten salt battery, the battery module capable of being rapidly altered in temperature.SOLUTION: A battery module according to the present invention includes rectangular cells 20, each cell 20 consisting of a molten salt battery having molten salt as electrolyte, planar heaters 30, each heater 30 being provided against the largest side of the exterior of the cell 20 for heating and thermal insulation of the cells 20, frame-like spacers 40, each spacer 40 being provided between the cells 20 such that the heater 30 is held between the cell 20 and the spacer 40 to press an outer edge of the heater 30, and a case 50 to hold a required number of the spacer 40, the cell 20, the heater 30, and the spacer 40 overlapped repeatedly in this order with the spacers 40 placed at both ends.

Description

  The present invention relates to a battery module including an assembled battery formed by assembling batteries and a heating function.

  As secondary batteries with excellent energy density, for example, lithium ion batteries, sodium sulfur batteries, and nickel metal hydride batteries are known, but in recent years, secondary batteries have a strong advantage of nonflammability in addition to high energy density. As such, molten salt batteries using a molten salt as an electrolyte have attracted attention (see Patent Document 1 and Non-Patent Document 1). Further, since the molten salt battery has a wide operating temperature range in addition to nonflammability, it is suitable for forming an assembled battery by concentrating a large number of batteries, and thus a compact assembled battery can be formed.

  Therefore, an assembled battery formed by assembling molten salt batteries is expected to be used for hybrid vehicles (HEV, PHEV) and electric vehicles (EV), in addition to power storage applications in medium-scale power networks and homes. The operating temperature range of the molten salt battery is, for example, 57 ° C. to 190 ° C. From the viewpoint of stability of electrical characteristics, battery cycle life, temperature durability of the electrode portion, and the like, a more preferable temperature is, for example, 90 It is considered to be around degrees. In order to obtain such a temperature, a heater is used.

  In order to heat and keep the assembled battery in a state where a large number of batteries are densely packed with a heater, for example, if one unit of the assembled battery is a battery module, a sheet-like heater may be applied to the entire bottom surface of the battery module. (For example, refer to Patent Document 2 and FIG. 13). In this case, each battery constituting the battery module is heated from the bottom by the heater.

JP 2009-67644 A Japanese Patent No. 4925680

"SEI WORLD" March 2011 issue (VOL. 402), Sumitomo Electric Industries, Ltd.

  However, it takes a considerable amount of time to apply a heater to the bottom of the battery module to raise the temperature of the molten salt battery at room temperature to around 90 ° C. Therefore, when a battery module of a molten salt battery is mounted on a vehicle such as an electric vehicle that does not operate continuously, once the temperature of the molten salt battery drops to, for example, room temperature, it takes time to reach an appropriate temperature again. Take it. If you want to use it quickly, it is not preferable to take time.

  In view of this problem, an object of the present invention is to provide a battery module capable of rapidly raising the temperature of a molten salt battery.

  The battery module of the present invention is a rectangular parallelepiped cell constituted by a molten salt battery using a molten salt as an electrolyte, and a planar shape that is provided in contact with the widest side surface among the outer surfaces of the cell and heats the cell. The heater is sandwiched between the heater and a frame-like spacer that holds the outer edge of the heater, and both ends are the spacers. The cell, the heater, and the spacer are arranged in the order. And a case in which a necessary number of the sheets are superposed so as to be repeated.

  ADVANTAGE OF THE INVENTION According to this invention, the battery module which can perform rapid temperature rising of a molten salt battery can be provided.

1 is a schematic diagram showing in principle the basic structure of a power generation element in a molten salt battery. It is a cross-sectional view which shows simply the laminated structure of a molten salt battery main body (main-body part as a battery). It is a perspective view which shows the outline of the external appearance of one cell when a molten salt battery main body is accommodated in a battery container. It is a perspective view of a battery module. It is a perspective view of the battery module seen from the opposite side to FIG. It is a disassembled perspective view of a battery module. It is a perspective view which shows the state which covered the battery module with the heat insulating material. It is a perspective view which shows the 1st example of a heater. It is a figure which shows the characteristic regarding heat_generation | fever density. It is a perspective view which shows the 2nd example of a heater. It is a perspective view which shows the 3rd example of a heater.

[Summary of Embodiment]
The gist of the embodiment of the present invention includes at least the following.

(1) This battery module is provided in contact with a rectangular parallelepiped cell constituted by a molten salt battery using a molten salt as an electrolyte, and the widest side surface of the outer surfaces of the cell, and is a surface for heating and maintaining the cell. A frame-like spacer provided between the cell and the cell, the frame-shaped spacer holding the outer edge of the heater, and both ends as the spacer, and the cell, the heater, and the spacer in the middle. And a case that holds the necessary number of layers so as to be repeated.
Such a battery module is suitable for a case where rapid heating is necessary by stacking the heaters between the cells. Accordingly, the molten salt battery can be quickly brought into an operating state at an appropriate temperature. Moreover, the interference by the expansion | swelling of an adjacent cell can be avoided by putting on and putting a frame-shaped spacer between cells.

(2) In the battery module of (1), it is preferable that the outer edge region is larger than the inner region with respect to the heat generation density of the heater.
In this case, the heat generation amount of the outer edge region per the same area is larger than the heat generation amount of the inner region. In the vicinity of the outer edge of the cell, the temperature tends to be lower in the entire cell, but the outer edge region has a larger amount of heat generation than the inner region, so that a uniform temperature distribution can be obtained for the entire cell.

(3) In the battery module of (1) or (2), regarding the heat generation density of one surface of the heater, the heaters at both ends in the overlapping direction may be larger than the heaters between them. preferable.
In this case, the heating value of the heaters at both ends is larger than the heating value of the heater between them at the same area. The temperature of the cells at both ends tends to be low in the battery module, but the heat generation amount of the heaters at both ends is larger than the heat generation amount of the heater between them, so that a uniform temperature distribution is obtained as a whole battery module. be able to.

(4) Moreover, in the battery module according to any one of (1) to (3), the heater may have a configuration in which the heating elements meander along the base material and are spread and spread over one surface.
In this case, the meandering heating element can be slightly expanded and contracted along the surface of the heater. Therefore, together with the base material, the heater can be slightly expanded and contracted, and can flexibly adapt to temperature changes.

(5) Moreover, the battery module in any one of (1)-(3) WHEREIN: The structure by which the heat generating body spreads in the spiral form along the base material may be sufficient.
In this case, the heating element spreading in a spiral shape can be slightly expanded and contracted along the surface of the heater. Therefore, together with the base material, the heater can be slightly expanded and contracted, and can flexibly adapt to temperature changes. In particular, it can sufficiently withstand deformation in a direction perpendicular to the surface. Therefore, it is possible to flexibly adapt to cell bulge.

(6) Moreover, in the battery module according to any one of (1) to (3), in the heater, the heating element spirals along the base material and extends along the contour shape of the base material. It may be a configuration.
In this case, the heating element spreading in a spiral shape can be slightly expanded and contracted along the surface of the heater. Therefore, together with the base material, the heater can be slightly expanded and contracted, and can flexibly adapt to temperature changes. In particular, it can sufficiently withstand deformation in a direction perpendicular to the surface. Therefore, it is possible to flexibly adapt to cell bulge. Furthermore, the heating element spreading over the entire substrate contributes to uniform heating to every corner.

(7) Moreover, in the battery module according to any one of (1) to (6), a circuit board that electrically connects the plurality of heaters to each other may be provided.
In this case, the heater connection can be realized on the battery module side. A control circuit and a temperature monitoring circuit can be mounted on the circuit board.

[Details of the embodiment]
<Basic structure of molten salt battery>
FIG. 1 is a schematic diagram showing in principle the basic structure of a power generation element in a molten salt battery. In the figure, the power generation element includes a positive electrode 1, a negative electrode 2, and a separator 3 interposed therebetween. The positive electrode 1 is composed of a positive electrode current collector 1a and a positive electrode material 1b. The negative electrode 2 includes a negative electrode current collector 2a and a negative electrode material 2b.

The material of the positive electrode current collector 1a is, for example, an aluminum nonwoven fabric (wire diameter: 100 μm, porosity: 80%). The positive electrode material 1b is a mixture of, for example, NaCrO ₂ as a positive electrode active material, acetylene black, PVDF (polyvinylidene fluoride), and N-methyl-2-pyrrolidone at a mass ratio of 85: 10: 5: 100. It is a thing. And what was kneaded in this way is filled in the positive electrode collector 1a of an aluminum nonwoven fabric, and after drying, it presses at 100 Mpa, and it forms so that the thickness of the positive electrode 1 may be set to about 1 mm.
On the other hand, in the negative electrode 2, an Sn—Na alloy containing, for example, tin as a negative electrode active material is formed on the aluminum negative electrode current collector 2a by plating.

  The separator 3 interposed between the positive electrode 1 and the negative electrode 2 is obtained by impregnating a glass non-woven fabric (thickness 200 μm) or a polyolefin sheet (thickness 50 μm) with a molten salt as an electrolyte. This molten salt is, for example, a mixture of 56 mol% NaFSA and 44 mol% KFSA (potassium bisfluorosulfonylamide), and has a melting point of 57 ° C. At a temperature equal to or higher than the melting point, the molten salt melts and becomes an electrolytic solution in which high-concentration ions are dissolved, and touches the positive electrode 1 and the negative electrode 2. Moreover, this molten salt is nonflammable. The operating temperature range of this molten salt battery is 57 ° C to 190 ° C, and a particularly preferable temperature range is around 90 ° C.

In addition, although the material, component, and numerical value of each part mentioned above are suitable examples, it is not limited to these.
For example, in addition to the above, a mixture of NaFSA and LiFSA, KFSA, RbFSA or CsFSA is also suitable as the molten salt. In addition, other salts composed of organic cations and the like may be mixed. In general, (a) a mixture containing NaFSA, (b) a mixture containing NaTFSA, and (c) a mixture containing NaFTA are suitable as the molten salt. . It is also possible to mix two or more of (a) to (c). In these cases, since the molten salt of each mixture has a relatively low melting point, a state in which high-concentration ions are dissolved with a small amount of heating can be realized, and the molten salt battery can be operated.

  In the above example, the molten salt battery in which the electrolyte is solidified at a room temperature of about 20 ° C. has been described, but other than this, for example, NaFSA and Py13FSA (N-methyl-N-propylpyrrolidinium FSA) Can be applied as an electrolytic solution / electrolyte having a melting point lower than 57 ° C., for example, a molten state even at a room temperature of about 20 ° C. However, even in this case, it is necessary to raise the temperature to a particularly preferable temperature range.

<Specific structure of molten salt battery>
Next, a more specific configuration of the power generation element of the molten salt battery will be described. FIG. 2 is a cross-sectional view schematically showing a laminated structure of the molten salt battery main body (main body portion as a battery) 10.
In FIG. 2, a plurality (six are shown) of rectangular flat plate-like negative electrodes 2 and a plurality (five are shown) of rectangular flat plates each accommodated in a bag-like separator 3 are shown. The positive electrodes 1 face each other and are stacked in the vertical direction in FIG. 2, that is, in the stacking direction, forming a stacked structure.

  The separator 3 is interposed between the positive electrode 1 and the negative electrode 2 adjacent to each other. In other words, the positive electrode 1 and the negative electrode 2 are alternately stacked via the separator 3. For example, 20 positive electrodes 1 and 21 negative electrodes 2 and 20 separators 3 as “bags”, but 40 intervening between positive electrodes 1 and 2 are actually stacked. is there. The separator 3 is not limited to a bag shape, and may be 40 separated.

  In FIG. 2, the separator 3 and the negative electrode 2 are drawn so as to be separated from each other, but they are in close contact with each other when the molten salt battery is completed. Naturally, the positive electrode 1 is also in close contact with the separator 3. In addition, the vertical and horizontal dimensions of the positive electrode 1 are smaller than the vertical and horizontal dimensions of the negative electrode 2 in order to prevent the generation of dendrites, and the outer edge of the positive electrode 1 passes through the separator 3. Thus, it faces the peripheral edge of the negative electrode 2.

<One form of cell>
The molten salt battery main body 10 configured as described above constitutes one physical cell by being housed in a rectangular parallelepiped battery container made of, for example, an aluminum alloy.
FIG. 3 is a perspective view showing an outline of the appearance of one cell (molten salt battery) 20 when the molten salt battery main body 10 is accommodated in the battery container 11x. In addition, from each of the positive electrode 1 and the negative electrode 2 in FIG. 2, the terminals 1t and 2t are pulled out of the battery container 11x while maintaining electrical insulation from the battery container 11x. The terminals 1t and 2t are provided on a lid 11a that seals the battery case 11x. In addition to the terminals 1t and 2t, the lid 11a is provided with a safety valve for releasing pressure when the internal atmospheric pressure rises excessively, but the illustration is omitted here. An assembled battery can be formed by arranging a plurality of such cells 20.

《Battery module》
Next, an embodiment of the battery module will be described with reference to FIGS.
FIG. 4 is a perspective view of the battery module 100. FIG. 5 is a perspective view of the battery module 100 viewed from the side opposite to FIG. FIG. 6 is an exploded perspective view of the battery module 100. In each figure, three directions orthogonal to each other are assumed to be X, Y, and Z. The orientation (posture) of the illustrated battery module 100 is shown in an easy-to-read state for explanation, and is not necessarily the orientation that is actually used.

In FIG. 6, the battery module 100 is stacked between a case 50 configured by fastening a bottom plate 51 and a pressing plate 52 to each other so that three types of elements form a laminated structure. The three types of elements are:
(1) the aforementioned rectangular parallelepiped cell 20,
(2) A planar heater 30 that is provided in contact with the widest side surface of the cell 20 and heats and retains the cell 20, and
(3) A frame-like spacer 40 provided with the heater 30 sandwiched between the cells 20 and holding the outer edge of the heater 30.
The material of the case 50 is, for example, stainless steel, and the material of the spacer 40 is, for example, an aluminum alloy. The heater 30 has a heating element in a heat resistant insulating layer (for example, polyimide).

  In the example of FIG. 6, there are four cells 20, all of which have a heater 30 and a spacer 40 superimposed on each other in the Z direction. Spacers 40 are disposed at both ends in the Z direction. The upper end spacer 40 is provided so that the heater 30 does not directly contact the pressing plate 52. The lower end spacer 40 is provided so that the cell 20 does not directly contact the bottom plate. The elements of the cell 20, the heater 30, and the spacer 40 are overlapped without gaps in the Z direction, and the bottom plate 51 and the pressing plate 52 are fastened together to form a case 50. That is, in the case 50, both ends in the overlapping direction (Z direction) are used as the spacers 40, and the necessary number of the cells 50, the heaters 30 and the spacers 40 are overlapped in the order in the middle. Hold (FIGS. 4 and 5).

In FIG. 4, for example, the terminal 1t (positive electrode) and the terminal 2t (negative electrode) of the cell 20 are reversed for each adjacent cell 20 (that is, the direction of the cell 20 is reversed). If connected, the four cells 20 can be easily connected in series. If the four cells 20 are connected in series, the output voltage of the battery module 100 can be about 12V.
In addition, the notch 52a is formed in the pressing plate 52, and if the temperature sensor (not shown) is attached here, the temperature of the cell 20 can be detected.

  Such a battery module 100 is suitable for a case where rapid heating is required by stacking the heaters 30 between adjacent cells 20. Therefore, the molten salt battery can be quickly brought into an operating state at an appropriate temperature (for example, about 90 ° C.). Such a so-called “rapid temperature rise” battery module 100 is suitable for mounting on a vehicle such as an electric vehicle, even if a molten salt battery is used. In addition, when using as a power supply for vehicle electrical components or auxiliary equipment, even one battery module can be used. Moreover, since the internal resistance of the molten salt battery is smaller than that of the lead storage battery, the battery module 100 is also suitable for absorbing regenerative power when the vehicle decelerates. When used as a main power source for traveling, a large number of battery modules 100 may be connected in series and parallel according to the required voltage / current.

  On the other hand, by overlapping with the frame-shaped spacers 40 sandwiched between the cells 20, interference due to the bulging of the adjacent cells 20 can be avoided. If such a spacer 40 is not provided, there arises a problem that the case 50 is deformed in the Z direction due to the bulging of the adjacent cells 20. In addition, when the bulge of the cell 20 returns to the original state, the case 50 may be deformed, so that a gap is formed between the cell 20 and the heater 30 and it may be difficult to heat and keep warm. The battery module 100 does not cause such a problem.

In FIG. 5, the battery module 100 is additionally provided with a circuit board 60 that electrically connects the four heaters 30 to each other. A thin plate-like conductor 31 is drawn out from the end of the heater 30, and necessary connection is made on the circuit board 60.
In this case, since the connection between the plurality of heaters 30 can be realized on the battery module 100 side without depending on an external circuit, the circuit connection is simple. Further, a control circuit and a temperature monitoring circuit (not shown) can be mounted on the circuit board 60.

FIG. 7 is a perspective view showing a state in which the battery module 100 is covered with a heat insulating material 70. By covering with such a heat insulating material 70, heat dissipation can be suppressed and the thermal efficiency for heat insulation can be further increased. As the heat insulating material 70, for example, phenol resin or glass wool is suitable.
Next, a configuration example of the heater 30 will be described.

<< Heater: First example >>
FIG. 8 is a perspective view showing a first example of the heater 30. The heater 30 has a structure in which, for example, two thin heat-resistant insulating (for example, polyimide) base materials 32 are prepared, and a heating element 33 is sandwiched between the layers.
As shown in the figure, the heater 30 extends in the Y direction while the heating element 33 meanders along the base material 32 in an S-shape, and slightly shifts in the X direction near the end of the base material 32 in the Y direction. It spreads over the entire surface while turning back to return to the direction. The end portions 33a and 33b of the heating element are connected to the conductors 31a and 31b, respectively.

  The meandering heating element 33 has elasticity similar to a spring and can be slightly expanded and contracted in the X direction and the Y direction along the surface of the heater 30. Therefore, together with the base material 32, the heater 30 can be slightly expanded and contracted, and can flexibly adapt to temperature changes.

FIG. 9 is a diagram showing characteristics relating to heat generation density (heat generation amount [W / m ² ] per unit area). This is a view focusing only on the heater 30 in FIG. The magnitude of the heat generation density is represented by hatching intervals, and the heat generation density increases as the hatching interval decreases.
When one surface of the heater 30 is divided into an outer edge area 30e and an inner area 30i, the outer edge area 30e is larger than the inner area 30i in terms of heat generation density.
In this case, the heat generation amount of the outer edge region 30e per the same area is larger than the heat generation amount of the inner region 30i. In the vicinity of the outer end of the cell 20 (FIG. 6), the temperature tends to be lower in the entire cell, but the outer edge region 30e generates a larger amount of heat than the inner region 30i. Can be obtained.

Further, when viewed from the whole battery module, regarding the heat generation density of one surface of the heater 30, the heaters 30 at both ends in the overlapping direction (Z direction) are larger than the heaters 30 between them.
In this case, the amount of heat generated by the heaters 30 at both ends is larger than the amount of heat generated by the heaters 30 between them at the same area. The cell 20 (FIG. 6) at both ends tends to be low in temperature in the battery module 100, but the heat generation amount of the heaters 30 at both ends is larger than the heat generation amount of the heaters 30 between them. A uniform temperature distribution can be obtained as a whole.

In order to increase the heat generation density with the heat generator 33 as shown in FIG. 8, for example, the width of the heat generator may be narrowed or the density of the heat generator may be increased. That is, as for the single heater 30, the following may be relatively performed.
Outer edge area: the width of the heating element is narrow or the density of the heating element is high.
Inner region: the width of the heating element is wide or the density of the heating element is low.
In this case, the outer region and the inner region are not separated by a boundary line, but may be gradually changed in this way.

The battery module 100 as a whole may be configured as follows when, for example, four heaters 30 are connected in series.
Heaters at both ends in the overlapping direction: As a whole, the width of the heating elements is narrow on average or the density of the heating elements is high as a whole.
Heater in the middle between both ends: As a whole, the heater as a whole has a wide width of the heating element or a low density of the heating elements.
In this case as well, when the number of superpositions is large, it may be gradually changed in such a tendency, instead of simply dividing the both ends and the other.

<< Heater: Second example >>
FIG. 10 is a perspective view showing a second example of the heater 30. In the heater 30, the heating element 33 extends in a spiral shape along the base material 32.
In this case, the heating element 33 spreading in a spiral shape can be slightly expanded and contracted along the surface of the heater 30. Therefore, together with the base material 32, the heater 30 can be slightly expanded and contracted, and can flexibly adapt to temperature changes. In particular, it can sufficiently withstand deformation in a direction perpendicular to the surface (Z direction). Accordingly, the cell 20 can be flexibly adapted to bulge.
The other configurations and characteristics related to the heat generation density are the same as in the first example.

<< Heater: Third example >>
FIG. 11 is a perspective view showing a third example of the heater 30. In the heater 30, the heating element 33 extends in a spiral shape along the base material 32 and extends along the contour shape of the base material 32.
In this case, the heating element 33 spreading in a spiral shape can be slightly expanded and contracted along the surface of the heater 30. Therefore, together with the base material 32, the heater 30 can be slightly expanded and contracted, and can flexibly adapt to temperature changes. In particular, it can sufficiently withstand deformation in a direction perpendicular to the surface (Z direction). Accordingly, the cell 20 can be flexibly adapted to bulge. Furthermore, the heating element 33 spreading over the entire base material 32 contributes to heating to every corner.
The other configurations and characteristics related to the heat generation density are the same as in the first example.

<Others>
The number of elements in the structure shown in FIG. 6 is only an example, and the number of elements can be provided as necessary. Also, the shape of the case 50 can be variously modified.

  In addition, according to the structure of the battery module 100 as described above, since the gap is secured by the spacer 40, the swelling of the cell 20 is reflected as the deformation (extension) of the heater 30. That is, when the cell 20 bulges, the heater 30 is pushed and expands (extends). As a result, the resistance value of the heater 30 slightly changes. Therefore, if the resistance value of the cell 20 at a certain temperature is measured by, for example, an ECU (Electronic Control Unit) connected to the battery module 100, the degree of expansion of the cell 20 can be estimated.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

1 positive electrode 1a positive electrode current collector 1b positive electrode material 1t terminal 2 negative electrode 2a negative electrode current collector 2b negative electrode material 2t terminal 3 separator 10 molten salt battery main body 11x battery container 11a lid 20 cell 30 heater 30e outer edge region 30i inner region 31 (31a, 31b) Conductor 32 Base 33 Heating element 33a, 33b End 40 Spacer 50 Case 51 Bottom plate 52 Holding plate 52a Notch 60 Circuit board 70 Heat insulating material 100 Battery module

Claims (7)

A rectangular parallelepiped cell constituted by a molten salt battery using a molten salt as an electrolyte;
Of the outer surface of the cell, provided in contact with the widest side surface, a planar heater for heating and keeping the cell,
A frame-shaped spacer that is provided with the heater sandwiched between the cells and holds the outer edge of the heater;
The case where the both ends are the spacers, and the case is held in a state where the necessary number of the cells, the heaters, and the spacers are overlapped in the order, and are overlapped as necessary.
Battery module equipped with.   The battery module according to claim 1, wherein an outer edge region is larger than an inner region with respect to a heat generation density of the heater.   3. The battery module according to claim 1, wherein the heat density of one surface of the heater is such that the heaters at both ends in the overlapping direction are larger than the heaters between them.   The battery module according to any one of claims 1 to 3, wherein the heater has a heating element meandering along the base material and is spread and distributed over one surface.   The battery module according to any one of claims 1 to 3, wherein the heater has a heating element spreading in a spiral shape along the substrate.   The battery module according to any one of claims 1 to 3, wherein the heater has a heating element spirally along the base material and extends along a contour shape of the base material.   The battery module according to any one of claims 1 to 6, further comprising a circuit board that electrically connects the plurality of heaters to each other.

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