JP2008171628A - Partitioning plate for heat dissipation of battery case - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a partitioning plate for heat dissipation of a battery case which has superior oxidation resistance and alkaline corrosion resistance in addition to heat dissipation characteristic. <P>SOLUTION: In the battery case in which a plurality of unit batteries are laminated and stored, the partitioning plate 1 for heat dissipation in which neighboring unit batteries are sectioned is composed of aluminum base material having a surface treatment film, has a thickness of δ (mm) along the lamination direction of the unit battery and a length of L (mm) along the direction perpendicular to the lamination direction, and equipped with one or more ventilation holes D penetrating along the longitudinal direction. If the maximum width of the ventilation hole in the lamination direction is F (mm) and the cross-sectional area of the ventilation hole in the lamination direction is S (mm<SP>2</SP>), then F/δ≤0.6 and 3≤L/S≤45 are satisfied in the partitioning plate for heat dissipation. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a heat dissipation partition plate for battery cases of various secondary batteries (nickel cadmium battery, nickel metal hydride secondary battery, lithium ion secondary battery, etc.), and more specifically, in addition to heat dissipation, oxidation resistance and The present invention relates to a heat radiating partition plate excellent in alkali corrosion resistance.

  Various secondary batteries that can be charged and used repeatedly are widely used regardless of consumer use or industrial use because of their high convenience. For example, a nickel metal hydride secondary battery is a high-performance battery that has a high energy density and uses environmentally friendly materials. Furthermore, higher-performance lithium ion secondary batteries have been developed and are used not only as power sources for various electronic devices, but also recently in transportation equipment such as electric vehicles and hybrid cars.

  The unit cell electromotive force of various secondary batteries is about 1.2 V for nickel cadmium batteries and nickel metal hydride secondary batteries, and about 3.6 V for lithium ion secondary batteries. To obtain the desired voltage and output characteristics In general, batteries are connected in series or in parallel.

  These secondary batteries may generate heat during charging and discharging. This is because the conversion efficiency of electric energy and chemical energy is not 100%, and energy that has not been converted is released as heat. When the temperature exceeds a predetermined temperature, the battery performance such as safety and battery life is adversely affected, and thus the battery needs to be cooled.

  In the secondary batteries connected in series or in parallel, many batteries are often stored in a limited space, and it is not easy to cool each battery equally. In addition to the battery characteristics such as the output characteristics and the lifespan, in addition to the battery characteristics such as the output characteristics and the lifespan, it is desired to reduce the weight of the battery for transportation equipment.

Various proposals have been made for battery cooling methods. In all the examples shown below, the unit cell container is cooled from the outside, and the heat from the heat generation source is transmitted through the unit cell container, so there is a possibility that the unit cell container may not be cooled uniformly. Patent Document 1 describes that a heat transfer member is filled between a nickel metal hydride secondary battery and a container. Patent Document 2 describes that a beam-like spacer is provided in a case that houses a square Li-ion battery. Patent Document 3 describes that air in a holder case of a battery module is forced to flow in one direction and cooled by a pressure-feed fan. Patent Document 4 describes that the electrical connection portion is protected while cooling the battery cell group by disposing the cooling air passage and the end face of the battery cell group in separate spaces by partition walls. Patent Document 5 describes that an air-cooled spacer having irregularities is provided between a plurality of prismatic secondary batteries. However, the cooling methods described in these documents have a problem that a sufficient heat dissipation effect cannot be obtained.
: JP-A-5-36392 : JP-A-8-212986 : JP-A-10-270095 : JP 2003-142051 A : JP-A-10-112301

  The present invention provides a heat dissipation partition plate that efficiently suppresses temperature rise of a plurality of single cells housed in a battery case, and also has a heat dissipation partition plate that also has oxidation resistance and alkali corrosion resistance. This also leads to a reduction in the weight and cost of the battery.

The present invention provides a heat dissipation partition plate for partitioning adjacent unit cells in a battery case in which a plurality of unit cells are stacked and stored, and comprising an aluminum base material having a surface treatment film. One or more ventilation holes having a thickness δ (mm) along the direction and a length L (mm) along a direction orthogonal to the stacking direction, and penetrating along the length direction F / δ ≦ 0.6, where F (mm) is the maximum width of the ventilation holes in the stacking direction, and S (mm ² ) is the cross-sectional area of the ventilation holes along the stacking direction. 3 ≦ L / S ≦ 45. A heat dissipation partition plate was obtained.

  According to a second aspect of the present invention, the surface treatment film includes at least one of a phosphate chromate film and a zircon phosphate film, and the thickness of the surface treatment film is 10 nm or more and less than 50 nm.

  According to a third aspect of the present invention, the surface treatment film includes at least one of an electric nickel plating film and an electroless nickel phosphorus plating film, and the thickness of the surface treatment film is 5 to 50 μm.

  With the heat radiating partition plate according to the present invention, the temperature rise of the plurality of single cells housed in the battery case can be suppressed with high efficiency. Furthermore, the heat-radiating partition plate according to the present invention is excellent in oxidation resistance and corrosion resistance, and can achieve a reduction in weight and cost of the battery.

A. Material of heat dissipation partition plate The base material of the heat dissipation partition plate is an aluminum base material made of aluminum or an aluminum-based alloy. As various aluminum-based alloys, 1000 series, 3000 series, 5000 series, 6000 series, and 7000 series can be used, but A1050 material is preferably used from the viewpoint of corrosion resistance and workability. On such an aluminum base material, as a surface treatment film, a phosphate chromate film, a chemical conversion film of a zirconate phosphate film, or a plating film of an electric nickel plating film or an electroless nickel phosphorus plating film is formed.

B. Structure of heat dissipation partition plate FIG. 1 shows an example of a heat dissipation partition plate 1. In this example, the heat radiating partition plate 1 has a flat plate shape and includes a side A in the thickness direction and other sides B and C. The length of sides B and C is sufficiently larger than A. In this example, the surface defined by the sides B and C forms a square, but can be any shape such as a rectangle, a circle, or an ellipse. The heat radiating partition plate 1 is usually formed by extrusion molding. The heat radiating partition plate 1 is provided with a plurality of ventilation holes D penetrating from the end surface E1 defined by the sides A and C to the opposite end surface E2. In this example, the cross section of the ventilation hole D is a square, but it can be an arbitrary cross sectional shape such as a circle, an ellipse, a triangle, a rectangle, a pentagon or more polygon.

The heat dissipation partition plate 1 according to the present invention has a thickness δ (mm) along the stacking direction of the unit cells and a length L (mm) along a direction orthogonal to the stacking direction. The ventilation hole D has a maximum width F (mm) in the stacking direction and a cross-sectional area of the ventilation hole along the stacking direction S (mm ² ). In the present invention, it is necessary to satisfy the relationship of F / δ ≦ 0.6 and 3 ≦ L / S ≦ 45 between these dimensions and the area.

  Here, F / δ is a parameter representing the strength of the heat radiating partition plate in the battery stacking direction. The strength of the heat radiating partition plate is uniquely determined by the ratio of F and δ. In order to obtain the required strength, it is necessary to satisfy F / δ ≦ 0.6. When F / δ is larger than 0.6, the thickness of the material above and below the ventilation hole is too thin, and the strength is insufficient when used as a heat radiating partition plate. As long as the vent hole is provided, F / δ is a positive number.

  The cooling air flowing through the ventilation hole receives a passage resistance from the hole wall, and this passage resistance is generally proportional to L and inversely proportional to S. The relationship between the battery cooling effect described later and L / S, which is a parameter representing the passage resistance, was experimentally determined, and it was found that a favorable battery cooling effect was obtained when 3 ≦ L / S ≦ 45 was satisfied. did. When L / S exceeds 45, the length L of the ventilation hole is too long or the cross-sectional area is too small, so that the passage resistance increases and the amount of heat generation increases, so the overall cooling effect decreases. . On the other hand, when L / S is less than 3, the length L of the ventilation hole is too short and the cooling air passes through the ventilation hole before it sufficiently absorbs the heat generated from the battery, Since the cross-sectional area of the ventilation hole is too large, only the cooling air in the vicinity of the hole wall is involved in heat absorption, so that a sufficient heat dissipation effect cannot be obtained.

  Here, in the example shown in FIG. 1, since the cross section along the laminating direction of the ventilation holes D forms a square, the maximum width F is equal to the length of one side of the square. As shown in FIG. 2, when the cross section along the laminating direction of the ventilation holes is circular, the maximum width F is equal to the diameter. Furthermore, as shown in FIG. 3, when the cross section along the stacking direction of the ventilation holes is a rectangle whose side along the side A is short, the maximum width F is equal to the length of the short side.

C. Surface Treatment Film The heat dissipation partition plate of the present invention is also desired to withstand oxidation in the air and maintain surface conductivity. Further, in the unlikely event that an electrolyte leakage is assumed, it is also desired to have resistance to the electrolyte components of various secondary batteries. Therefore, in order to protect the surface of the heat radiating partition plate, a chemical conversion film made of a phosphate chromate film or a zircon phosphate film, or a plating film made of an electric nickel plating film or an electroless nickel phosphorus plating film is used as a surface treatment film. It is preferred to use a formed aluminum substrate. About the electro nickel plating film, corrosion resistance to a KOH aqueous solution, which is an electrolytic solution of a nickel cadmium battery or a nickel hydride secondary battery, can also be expected.
In the case of providing such a surface treatment film, it is only necessary to provide at least the upper surface H1, the lower surface H2, the right side surface I1, and the left side surface I2 of the heat dissipation partition plate shown in FIG. 1, and the front surface E1, the rear surface E2, and the ventilation are provided. It may or may not be provided on the inner surface of the hole D.

  With respect to the phosphate chromate film and the zirconium phosphate film, oxidation resistance in the atmosphere is exhibited as long as the film thickness is 10 nm or more. In terms of cost, it is acceptable if the film thickness is less than 50 nm. Therefore, from the viewpoint of oxidation resistance and cost, the film thickness needs to be 10 nm or more and less than 50 nm, and is preferably 20 to 40 nm.

  The electro nickel plating film is crystalline, and exhibits sufficient oxidation resistance and alkali corrosion resistance when the film thickness is 5 μm or more. From the viewpoint of cost, it is acceptable up to 50 μm. Therefore, from the viewpoint of oxidation resistance, alkali corrosion resistance and cost, the film thickness needs to be 5 to 50 μm, preferably 10 to 30 μm.

  In the electroless nickel phosphorus plating film, the crystallinity of the film changes depending on the amount of phosphorus contained. In the present invention, a crystalline or microcrystalline film having a phosphorus content of 1 to 8% by weight (that is, a low phosphorus content region to a medium phosphorus content region) is formed. Since the electroless nickel phosphorus plating film is inferior in corrosion resistance to alkali as compared with the electrolytic nickel plating film, the film thickness needs to be 10 to 50 μm, and from the viewpoint of cost, it is preferably 20 to 30 μm.

D. As shown in FIG. 4, the heat dissipation partition plate 1 according to the present invention is incorporated in a battery case 2 in which unit cells are stacked. In the figure, reference numeral 3 denotes a unit cell, and the heat radiating partition plate 1 is disposed so as to partition adjacent unit cells 3. The front surface of the heat radiating partition plate 1 in FIG. 4 is the right side surface I1 or the left side surface I2 shown in FIG. 1, and the cooling air flows through the ventilation holes (not shown) along the arrow X. On the left and right ends of FIG. 4, positive and negative side current collecting plates 4 and 4 are disposed. Such an assembled battery is accommodated in the body 5 of the battery case.

Examples 1-28 and Comparative Examples 1-4
(1) Molding of heat dissipation partition plate base material In Examples 1 to 28 and Comparative Examples 1 to 3, Al050 alloy was used as the heat dissipation partition plate base material. In Examples 1 to 24, in FIG. 1, the length of the side A is 5 mm, the length of the sides B and C is 50 mm, the F of the ventilation hole D having a square cross section is 3 mm, and the wall portion that separates the ventilation holes D A heat radiating partition plate substrate having a thickness G of 3 mm and a number of vent holes D of 7 was prepared by extrusion molding. In Examples 25 to 28 and Comparative Example 2, only the lengths (ie, L) of sides B and C in Examples 1 to 24 were changed so that L / S different from Examples 1 to 24 was obtained. . In Comparative Example 3, F / δ and L / S different from those in Comparative Example 2 were obtained by changing the lengths of sides B and C in Comparative Example 2 (ie, L) and the length of side A (ie, δ). I was able to get it. In Comparative Example 1, a heat radiating partition base material having a side A of 5 mm and sides B and C of 50 mm and having no ventilation holes was produced by extrusion molding. In Comparative Example 4, a steel plate was used as the heat radiating partition base, and a side A having a length of 5 mm and sides B and C having a length of 50 mm was produced by press molding, but extrusion molding could not be applied. Ventilation holes are not provided.

(2) Chemical conversion treatment (phosphate chromate treatment, zircon phosphate treatment)
After performing the alkali degreasing and the desmut treatment as pretreatment on the heat radiating partition base material produced as described above, in Examples 1 to 3, 7 and 8, phosphoric acid chromate treatment was performed. After performing the same pretreatment as described above, in Examples 4 to 6, 9, and 10, zircon phosphate treatment was performed. As a treatment solution, Alsurf 301 or Alsurf 407/47 manufactured by Nippon Paint Co., Ltd. was used, and the film thickness was adjusted according to the treatment time in accordance with standard treatment conditions.

(3) Plating treatment After the zincate treatment was applied as a pretreatment to the heat radiating partition plate base material produced as described above, in Examples 11 to 15, 21, 22, 25 to 28 and Comparative Examples 1 to 4, electricity was used. Nickel plating treatment was performed under the following conditions. In Examples 16 to 19, 23, and 24, electroless nickel phosphorus plating treatment was performed under the following conditions.
In Example 20, neither chemical conversion treatment nor plating treatment was performed. As described above, the heat radiating partition plate 1 subjected to the chemical conversion treatment or the plating treatment was produced.

Electrolytic nickel plating treatment conditions A Watt bath (containing nickel sulfate, nickel chloride and boric acid) is used, the heat-radiating partition plate is used as a cathode electrode, the Ni plate is used as an anode electrode, and both electrodes are connected to a DC power source. The electrolytic treatment was carried out at a temperature of 2 ° C., a current density of 2 A / dm ² , and a film formation rate of 0.4 μm / min while stirring with air until a predetermined film thickness was obtained.

Electroless nickel phosphorus plating treatment An electroless plating treatment was performed at a plating temperature of 90 ° C. and a film formation rate of 0.2 to 0.3 μm / min until a predetermined film thickness was obtained. As said plating solution, Okuno Pharmaceutical Co., Ltd. top nicolon series BL, ALT, etc. can be used, for example.

(4) Production of battery and its operation The above-produced heat dissipation partition plate 1 was sandwiched between the single cells, and an assembled battery in which three sets of single cells were stacked was constructed. A single battery having a capacity of about 2000 mAh was used. Cooling air was circulated from the outside through the ventilation holes D of the heat radiating partition plate 1 at 200 mL / min to discharge the heat generated by each battery, thereby cooling the batteries.

  About Examples 1-10, the battery cooling effect, oxidation resistance, cost, and intensity | strength were evaluated. The results are shown in Table 1. Table 1 also shows the average film thickness, the vent hole diameter (F), F / δ, L / S, and the specific gravity of the heat radiating partition plate, measured as follows. Shown together.

  In Examples 11 to 28 and Comparative Examples 1 to 4, the battery cooling effect, oxidation resistance, alkali corrosion resistance, cost and strength were evaluated. The results are shown in Table 2. Table 2 also shows the average film thickness, the vent hole diameter (F), F / δ, L / S, and the specific gravity of the heat radiating partition plate measured as described below.

Measurement of film thickness The film thickness of phosphate chromate and zircon phosphate was measured by TEM (transmission electron microscope) observation. The plating film thickness was measured with a fluorescent X-ray film thickness measuring device.

Measurement of specific gravity of heat radiating partition plate The specific gravity of the heat radiating partition plate was calculated by measuring the volume and weight.

Battery cooling effect At ambient temperature of 25 ° C., the temperature change of the cell surface during charging was measured at 1 C, and the temperature rise during 120% charging was evaluated according to the following criteria. Here, “1C” indicates a current value when the rated capacity of the battery is discharged in one hour. ◎ and ○ were accepted, and x was rejected.
A: Temperature rise is less than 15 ° C B: Temperature rise is 15 ° C or more and less than 25 ° C X: Temperature rise is 25 ° C or more

The oxidation-resistant heat radiation partition plate was left in an environment of a temperature of 50 ° C. and a humidity of 100% for 1 day, and the contact resistance before and after being left was measured to determine the increase. For the contact resistance, a Loresta GP made by Mitsubishi Chemical was used, and the resistance value was measured by pressing the two-terminal electrode against the material. Judgment was made based on the following criteria. ◎ and ○ were accepted, and △ and x were rejected.
◎: No increase ○: Increase is less than 1% △: Increase is 1% or more and less than 10% ×: Increase is 10% or more

A heat dissipation partition plate whose outer surface was covered with an alkali-corrosion-resistant plating film was immersed in a 6N-KOH aqueous solution at 25 ° C. to observe the corrosion state, and the time taken for the material to bulge or foam was measured. . The test was conducted for a maximum of 30 days and judged according to the following criteria. ◎ and ○ were accepted, and △ and x were rejected.
◎: Time required is 30 days or more ○: Time required is 20 days or more and less than 30 days △: Time required is 10 days or more and less than 20 days ×: Time required is less than 10 days

Cost was evaluated based on the thickness of the cost chemical conversion film (phosphate chromate film, zircon phosphate film) and plating film (electric nickel plating film, electroless nickel phosphorus plating film). The evaluation criteria are as follows. ◎ and ○ were accepted, and x was rejected.
A: The thickness of the chemical film is 10 nm or more and 30 nm or less. ○: The thickness of the chemical film is more than 30 nm and less than 50 nm. X: The thickness of the chemical film is less than 10 nm or 50 nm or more. A: The thickness of the plating film is 5 μm or more. 30 μm or less ○: The thickness of the plating film exceeds 30 μm and 50 μm or less ×: The thickness of the plating film is less than 5 μm or exceeds 50 μm

In FIG. 1, when a load of 100 kg / cm ² was applied from the upper surface H1 to the lower surface H2 of the heat radiating partition plate, a case where the partition plate was not deformed such as crushing or bending was evaluated as ◯. The case was set to x, and ○ was set to pass x.

  In each of Examples 1 to 28, the evaluation of the battery cooling effect was acceptable. In Examples 1 to 6, 8, 10, 11 to 19, and 21 to 28, the oxidation resistance was also acceptable. In Examples 11-19, 22, and 24-28, the alkali corrosion resistance was also acceptable. In Examples 1 to 7, 9, 11 to 21, 23, 25 to 28, the cost was also acceptable. Furthermore, in Examples 1-28, the strength was also acceptable.

  In Comparative Example 1, the ventilation hole was not provided, and the cooling performance of the battery was inferior. In Comparative Example 2, the L / S condition was not satisfied and the battery cooling performance was insufficient. In Comparative Example 3, the F / δ condition was not satisfied and the strength was insufficient. In Comparative Example 4, ventilation holes could not be formed by extrusion molding, the cooling effect was inferior, and the specific gravity was large and difficult to handle because the steel plate was used as a base material.

  As described above, the heat dissipation partition plate of the present invention can effectively suppress the temperature rise of various secondary batteries. In addition, it is rich in oxidation resistance and alkali corrosion resistance, and can also reduce the weight and cost of the battery.

The perspective view of an example of the heat dissipation partition plate which concerns on this invention is shown. The perspective view of an example of the heat dissipation partition plate which concerns on this invention is shown. The perspective view of an example of the heat dissipation partition plate which concerns on this invention is shown. The front view which shows the battery case structure incorporating the heat-radiating partition plate which concerns on this invention is shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Radiation case partition plate 2 ... Battery case incorporating a cell and battery case partition plate 3 ... Single cell 4 ... Side collector electrode 5 ... Body of battery case A ... Side of heat dissipation partition plate B: Side of heat radiating partition plate C: Side of heat radiating partition plate D: Ventilation hole E1: Front surface of battery case partition plate E2: Rear surface of battery case partition plate F: In the stacking direction of ventilation holes Maximum width G …… Thickness of wall portion separating ventilation holes H1 …… Upper surface of battery case partition plate H2 …… Lower surface of battery case partition plate I1 …… Right side surface of battery case partition plate I2 …… Battery case partition plate Left side of X X Direction of cooling air flow

Claims (3)

In a battery case for stacking and storing a plurality of unit cells, a heat dissipation partition plate that partitions adjacent unit cells, is made of an aluminum base material having a surface treatment film, and has a thickness δ ( mm) and a length L (mm) along a direction perpendicular to the stacking direction, and includes one or more ventilation holes penetrating along the length direction. F / δ ≦ 0.6 and 3 ≦ L / S ≦ 45, where F (mm) is the maximum width in the stacking direction, and S (mm ² ) is the cross-sectional area of the ventilation holes along the stacking direction. A partition plate for heat dissipation, characterized in that   The partition plate for heat dissipation according to claim 1, wherein the surface treatment film includes at least one of a phosphate chromate film and a zircon phosphate film, and the thickness of the surface treatment film is 10 nm or more and less than 50 nm.   The heat dissipation partition plate according to claim 1, wherein the surface treatment film includes at least one of an electric nickel plating film and an electroless nickel phosphorus plating film, and the thickness of the surface treatment film is 5 to 50 µm.