JP2007134308A - Battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a battery which has an improved heat radiation property and can demonstrate a high stability even in a case of an internal heat generation due to a misuse. <P>SOLUTION: Inside an outer package member 10 is provided a battery element 20. A side surface of a battery can 11 made of stainless steel or the like of the outer package member 10 is coated with a coating member 18 composed of a thermoplastic sheet such as polypropylene. A side surface of the outer package member 10, namely, 70% or more of an area of the outer surface of the coated member 18 is set to have a radiant ratio of 0.6 or more to improve a heat radiation property by radiation and a temperature rise is prevented to delay starting of a thermorunaway. If necessary, a character or a pattern can be written on the outer surface of the coated member 18. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a battery in which a battery element is housed in an exterior member such as a battery can.

  In recent years, many portable electronic devices such as a camera-integrated VTR (video tape recorder), a mobile phone, or a notebook personal computer have appeared, and their size and weight have been reduced. Batteries used as portable power sources for these electronic devices, particularly secondary batteries, are actively used as key devices for research and development aimed at improving energy density. Among them, non-aqueous electrolyte secondary batteries (for example, lithium ion secondary batteries) can provide a larger energy density than conventional lead batteries and nickel cadmium batteries, which are conventional aqueous electrolyte secondary batteries. Considerations are being made in various directions.

Development of safety technology related to conventional lithium-ion batteries has been performed assuming various misuse situations. From the viewpoint of suppressing heat generation, it can be further divided into two categories: improvement of the physical properties of the battery material and utilization of the structure / mechanism of the battery. Development of flame retardant electrolytes, adoption of positive and negative electrode active materials with low calorific value, etc. entered the former domain, prevention of overcharge and overdischarge by external protection circuit, reduction of internal pressure at gas ejection by safety valve, etc. Goes into the latter.
JP 2002-208439 A Tee. Di. Hatcher (TDHatchard) “Importance of Heat Transfer by Radiation in Li-ion Batteries during Thermal Abuse”, Electro Chemical and Solid State Letters State Letters), 2000, Vol. 3, No. 7, p. 305-308 JP-A-62-119859

  However, it is currently difficult to adopt battery materials with high safety considering the trade-off relationship with performance such as battery capacity and the period for searching for new substances. On the other hand, prevention of heat generation by a new battery structure / mechanism has been waiting for the next step.

  From the viewpoint of heat dissipation, which is another approach to safety technology development, it is considered that the adoption of battery materials with good thermal conductivity leads to this purpose. However, because of this trade-off relationship with performance, it could not be changed easily.

  Regarding a structure for improving heat conduction, there is one in which one of an anode and a cathode is in thermal contact with a metal package (see Patent Document 1). With regard to heat radiation promotion, conventionally, only the heat conduction inside the battery and the heat transfer between the outer surface of the battery and the external atmosphere have been focused on, so that no new action has been taken out. In addition, battery exterior materials have been improved for the purpose of battery durability, battery capacity, cost reduction in battery production, and the like. (See Patent Document 2.)

  By the way, for heat dissipation, heat conduction and heat transfer, in addition to releasing heat by a heat flux proportional to the temperature difference, a phenomenon of heat radiation giving a heat flux proportional to the fourth power of the temperature is known. There have been few attempts to take advantage of this phenomenon. Behind that, heat radiation becomes dominant when the temperature in question is several thousand degrees, which is extremely large compared to room temperature, so prejudice that the internal heat generation of batteries at most several hundred degrees is not effective. It is speculated that there was. By the way, in Non-Patent Document 1, there is a label with an emissivity (an index indicating the efficiency of heat radiation: taking a value from 0 to 1) when the outer can of the lithium ion battery has a label and when the stainless steel can is exposed. It was reported that it was harder to run out of heat in the hot box test. It has also been reported that the emissivity when black ink is applied to a stainless steel can is about 0.9. However, it has been difficult to apply black ink to the outer can in terms of the manufacturing process.

  The present invention has been made in view of such problems, and an object thereof is to provide a battery that can improve the heat dissipation of the battery and can exhibit high safety even in the case of internal heat generation due to misuse. There is to do.

  A battery according to the present invention includes a battery element having external connection terminals on the upper and lower surfaces, and an exterior member that covers the side surface of the battery element and has 70% or more of the area of the side surface of which has an emissivity of 0.6 or more. is there.

  The emissivity varies depending on the material composition and thickness of the exterior member (mainly polymer heat-shrinkable tube), and the emissivity value itself is a value measured by a reflection measurement method.

  According to the battery of the present invention, since 70% or more of the area of the side surface of the exterior member is set to an emissivity of 0.6 or more, heat can be efficiently released to the outside air by heat radiation from the side surface. Therefore, even if some internal heat generation occurs due to misuse, it is possible to suppress the risk of gas ejection or rupture due to thermal runaway and to obtain high safety.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the figure, each component schematically shows the shape, size, and arrangement relationship to the extent that the present invention can be understood, and is different from the actual size.

  FIG. 1 shows the appearance of a battery according to an embodiment of the present invention, and FIG. 2 shows its cross-sectional structure. This battery is a so-called cylindrical lithium ion secondary battery, and has a battery element 20 inside a substantially hollow cylindrical exterior member 10.

  The exterior member 10 is obtained by covering the side surface of the battery can 11 with a covering member 18. The battery can 11 is for housing the battery element 20 and is made of, for example, stainless steel, and has one end closed and the other end open. Inside the battery can 11, a pair of insulating plates 12 and 13 are arranged perpendicular to the winding peripheral surface so as to sandwich the battery element 20. At the open end of the battery can 11, a battery lid 14, a safety valve mechanism 15 and a thermal resistance element (Positive Temperature Coefficient; PTC element) 16 provided inside the battery lid 14, have a gasket 17 in between. The battery can 11 is attached by being caulked, and the inside of the battery can 11 is sealed. The battery lid 14 is made of, for example, the same material as the battery can 11. The safety valve mechanism 15 is electrically connected to the battery lid 14 via the heat sensitive resistance element 16, and the disk plate 15A is reversed when the internal pressure of the battery exceeds a certain level due to an internal short circuit or external heating. Thus, the electrical connection between the battery lid 14 and the battery element 20 is cut off. When the temperature rises, the heat sensitive resistance element 16 limits the current by increasing the resistance value and prevents abnormal heat generation due to a large current. The gasket 17 is made of, for example, an insulating material, and asphalt is applied to the surface.

  Here, the end surface of the open end of the battery can 11, that is, the end surface closed by the battery lid 14 is the upper surface, and the end surface of the closed end of the battery can 11, that is, the end surface facing the battery lid 14 is the lower surface. All surfaces orthogonal to the upper and lower surfaces of the battery can 11 are referred to as side surfaces.

  The covering member 18 is made of a thermoplastic sheet such as polyvinyl chloride. Note that the covering member 18 may be provided so as to cover the entire side surface of the battery can 11 and slightly cover the edges of the upper surface and the lower surface in order to prevent dropping.

  In order to effectively suppress an increase in the temperature of the battery element 20, the side surface of the exterior member 10, that is, the outer surface of the covering member 18, is 70% or more of the area, for example, black and has an emissivity of 0.6. That's it. Thereby, in this battery, heat radiation property can be improved and safety can be improved. Here, the side surface of the exterior member 10 refers to the side surface farthest from the battery element 20, and the outer surface of the covering member 18 refers to the surface opposite to the contact surface with the battery can 11.

  As such a covering member 18, for example, a member in which 70% or more of the area of the outer surface is colored black is preferable. This is because radiation is a physical phenomenon whose surface properties are highly effective. Further, it is desirable that the covering member 18 itself is made of a black material such as a black resin, and that the outer surface of the covering member 18 is smooth and has no unevenness.

  Being black means a color in which all of C (cyan), M (magenta), and Y (yellow) are 70 or more in the CMY color model.

  Characters, patterns, and the like may be written on the outer surface of the covering member 18 as necessary. The color, shape, or arrangement of the characters and patterns is not particularly limited, and the characters and patterns do not need to be concentrated on a part of the outer surface. Regardless of the form of these letters and patterns, 70% of the area of the entire outer surface may be an emissivity of 0.6 or more.

  The battery element 20 is formed by laminating a positive electrode 21 and a negative electrode 22 with a separator 23 therebetween and winding them in a spiral shape, and a center pin 24 is inserted in the center. The positive electrode 21 is a positive electrode current collector made of, for example, an aluminum foil, and an electrode layer containing a positive electrode active material such as a lithium-containing compound, and the negative electrode 22 is made of, for example, a negative electrode current collector made of copper foil or the like. The body is provided with an electrode layer including a negative electrode active material such as a carbon material capable of inserting and extracting lithium. Moreover, the separator 23 is comprised by porous membranes, such as a polypropylene (PP), for example, The electrolyte solution which dissolved electrolyte salt, such as lithium salt, in non-aqueous solvents, such as carbonate ester, is used for a separator, for example. Impregnated. A positive electrode lead 25 made of aluminum (Al) or the like is connected to the positive electrode 21 of the battery element 20, and a negative electrode lead 26 made of nickel (Ni) or the like is connected to the negative electrode 22. The positive electrode lead 25 is electrically connected to the battery lid 14 by being welded to the safety valve mechanism 15, and the negative electrode lead 26 is welded and electrically connected to the battery can 11A. That is, in this battery element 20, the battery lid 14 on the upper surface is an external connection terminal on the positive electrode side, and the lower surface of the battery can 11A, that is, the back surface portion is an external connection terminal on the negative electrode side.

  This battery can be manufactured, for example, as follows.

  First, the covering member 18 made of the above-described thermoplastic sheet is prepared. For example, by printing, 70% or more of the area of the outer surface is colored black so that the emissivity is 0.6 or more, and characters and patterns are used as necessary. Describe etc. Alternatively, when using the covering member 18 made of a high emissivity resin material such as a black resin, a letter or a pattern is described as necessary by printing, and at that time, 70% or more of the area of the outer surface is increased. The resin with the emissivity is left as it is, and the emissivity is 0.6 or more.

  Next, the covering member 18 is placed on the side surface of the battery can 11 made of the above-described material, for example, by heat shrinkage, and the exterior member 10 is formed.

  Moreover, the battery element 20 is produced. For example, a positive electrode active material, a conductive agent, and a binder are mixed to prepare a positive electrode mixture, and the positive electrode mixture is dispersed in a solvent such as N-methyl-2-pyrrolidone (NMP) to form a paste. The positive electrode mixture slurry. Subsequently, the positive electrode mixture slurry is uniformly applied to the positive electrode current collector using a doctor blade or a bar coater, and the solvent is dried. Then, the positive electrode active material layer is formed by compression and heat molding using a roll press machine or the like. Then, the positive electrode 21 is produced.

  Next, for example, a negative electrode active material and a binder are mixed to prepare a negative electrode mixture, and the negative electrode mixture is dispersed in a solvent such as N-methyl-2-pyrrolidone to obtain a paste-like negative electrode mixture slurry. And Subsequently, the negative electrode mixture slurry is uniformly applied to the negative electrode current collector using a doctor blade or a bar coater, and the solvent is dried. Then, the negative electrode mixture layer is formed by compression and heat molding with a roll press machine. Then, the negative electrode 22 is produced. The roll press machine may be used by heating. Moreover, you may compression-mold several times until it becomes the target physical-property value. Furthermore, you may use press machines other than a roll press machine.

  After producing the positive electrode 21 and the negative electrode 22, the positive electrode lead 25 is attached to the positive electrode 21 by welding or the like, and the negative electrode lead 26 is attached to the negative electrode 22 by welding or the like. After that, the positive electrode 21 and the negative electrode 22 are laminated with the separator 23 interposed therebetween and wound many times to produce the battery element 20.

  After the battery element 20 is manufactured, the battery element 20 is sandwiched between the pair of insulating plates 12 and 13, the negative electrode lead 26 is welded to the battery can 11, and the positive electrode lead 25 is welded to the safety valve mechanism 15. The battery can 11 is accommodated in the battery can 11, and the electrolytic solution is injected into the battery can 11 and impregnated in the separator 23. Thereafter, the battery lid 14, the safety valve mechanism 15, and the heat sensitive resistance element 16 are fixed to the opening end of the battery can 11 by caulking between the gaskets 17. Thereby, the battery shown in FIG. 1 is completed.

  In this battery, when charged, lithium ions are released from the positive electrode 21 and inserted in the negative electrode 22 through the electrolytic solution impregnated in the separator 23. When discharging is performed, lithium ions are released from the negative electrode 22 and inserted in the positive electrode 21 through the electrolytic solution impregnated in the separator 23. At this time, there are two types of heat transfer to the outside of the battery, heat transfer and heat radiation. The heat transfer depends on the type of atmosphere and the flow state, and cannot be controlled by parameters of the battery itself. On the other hand, thermal radiation depends on the material and shape of the outer surface of the covering member 18 that covers the side surface of the exterior member 10, that is, the side surface of the battery can 11. The heat transfer to the outside by heat transfer and heat radiation is as large as heat transfer, assuming that heat radiation is the most efficient black body radiation, so by using heat radiation efficiently Safety is improved.

  Here, 70% or more of the area of the side surface of the exterior member 10, that is, the outer surface of the covering member 18, is set to have an emissivity of 0.6 or more, so that heat is efficiently transferred to the outside air by heat radiation from the side surface. Escaped. Also, even if some internal heat generation occurs due to misuse, more heat generated inside the battery is released, the start of thermal runaway is delayed, and the risk of gas ejection and rupture is suppressed.

  As described above, according to the present embodiment, since 70% or more of the area of the side surface of the exterior member 10 is set to an emissivity of 0.6 or more, the heat radiation can be improved, and internal heat generation due to misuse can be improved. Even in the case, high safety can be exhibited.

  In the above embodiment, the side surface of the battery can 11 is covered with the covering member 18, and 70% or more of the area of the outer surface of the covering member 18 is set to have an emissivity of 0.6 or more. May not necessarily be provided. In this case, if 70% or more of the area of the side surface of the exterior member 10, that is, the side surface of the battery can 11, has an emissivity of 0.6 or more, the heat radiation property of the side surface is increased and is the same as in the above embodiment. The effect of can be obtained. In this case, in order to make the side surface of the battery can 11 have an emissivity of 0.6 or more, for example, a method of coloring by applying a spray is possible.

  Further, specific embodiments of the present invention will be described in detail.

(Examples 1-3)
The battery described in the above embodiment was manufactured. In Example 1, black spray was applied to the entire side surface of the battery can 11 made of stainless steel. In Example 2, black spray was applied to 70% of the side surface area. In Example 3, 70% of the area of the side surface was made emissivity 0.6 or more by covering the battery can 11 with the covering member 18 made of a green polypropylene / polyethylene mixed tube. The value of the emissivity was 0.91 in the spray coating part of Examples 1 and 2 and 0.6 in the tube coating part of Example 3 by reflection measurement. The size and shape of the battery was a cylindrical shape with a diameter of 18 mm and a height of 65 mm.

  As Comparative Example 1 with respect to Examples 1 to 3, a battery was prepared in the same manner as in Examples 1 and 2 except that the spray was not applied to the side surface of the battery can made of stainless steel and the surface was exposed. Produced. The emissivity of Comparative Example 1 was measured by a reflection measurement method and found to be 0.12.

  Further, as Comparative Examples 2 and 3, by applying black spray to the side surface of the battery can made of stainless steel, 60% of the side surface area was made black in Comparative Example 3, and 50% was made black in Comparative Example 4. A battery was prepared in the same manner as in Examples 1 and 2 except for the above.

  About the obtained battery of Examples 1-3 and Comparative Examples 1-3, after charging until a battery voltage reached 4.35V, the 130 degreeC hot box test was done and the change of the surface temperature of a battery was measured. The change in the surface temperature was measured by pressing the sensor head (thermocouple) against the battery surface using a surface temperature sensor manufactured by Anritsu Keiki Co., Ltd. The arrangement of the batteries in the oven was as shown in FIG. The results of Examples 1 and 3 and Comparative Example 1 are shown in FIG. 4, and the results of Examples 1 and 2 and Comparative Examples 2 and 3 are shown in FIG.

  As can be seen from FIG. 4, in Examples 1 and 3, the temperature rise is suppressed more than in Comparative Example 1, and thermal runaway is avoided. That is, if the emissivity is 0.6 or more, the temperature rise can be suppressed. Furthermore, when the ratio of the portion where the side surface area is applied in black is changed from 50% to 70% from FIG. 5, if it is 70% or more, the elapsed time when the battery surface temperature starts to rise, There is a difference of about 10 minutes between the example and the comparative example. That is, the temperature rise can be suppressed by making 70% or more of the side surface area black. From the above, it was found that if 70% or more of the area of the side surface has an emissivity of 0.6 or more, thermal runaway of the battery can be suppressed and safety can be improved.

  Although the present invention has been described with reference to the embodiments and examples, the present invention is not limited to the above embodiments and examples, and various modifications can be made. For example, in the above-described embodiments and examples, the case where the covering member 18 is provided so as to cover the entire side surface of the battery can 11 and slightly cover the edges of the upper surface and the lower surface has been described. You may make it cover only a part of. In that case, it is sufficient that the covering member 18 covers at least the position corresponding to the lower end of the battery element from the side surface of the battery can 11 to the lower end of the caulking portion.

  Moreover, although the said embodiment and Example demonstrated the case where a character, a pattern, etc. were described on the covering member 18 itself, the covering member 18 may be provided separately from the label which described the character, the pattern, etc. Good.

  Further, for example, the material and thickness of each component described in the above embodiment, the manufacturing method and conditions, etc. are not limited, and may be other materials and thicknesses, or other manufacturing methods and conditions. Also good. For example, the battery can 11 may be made of a material other than stainless steel, for example, iron (Fe) plated with nickel (Ni), and the character or pattern of the covering member 18 may be other than printing. It may be described in a method.

  In addition, in the above-described embodiments and examples, the secondary battery using the cylindrical battery can 11 has been specifically described, but the present invention relates to a secondary battery having the square battery can 11. Can be applied similarly. Moreover, although the secondary battery has been described in the above embodiment, the present invention can be similarly applied to other batteries such as a primary battery. Furthermore, the present invention is effective regardless of the charging voltage, and is not defined by the examples.

  Furthermore, in the above embodiment and example, the positive electrode 21 and the negative electrode 22 are wound, but the positive electrode and the negative electrode may be folded or stacked.

  In addition, for example, in the embodiments and examples described above, the case where an electrolytic solution that is a liquid electrolyte is used as a solvent has been described, but another electrolyte may be used instead of the electrolytic solution. Other electrolytes include, for example, a gel electrolyte in which an electrolyte is held in a polymer compound, a solid electrolyte having ionic conductivity, a mixture of a solid electrolyte and an electrolyte, or a solid electrolyte and a gel electrolyte. And a mixture thereof.

  Furthermore, in the above embodiments and examples, the case where lithium is used as the electrode reactant has been described. However, other group 1 elements in the long-period periodic table such as sodium (Na) or potassium (K), or The present invention can also be applied to the case of using elements of Group 2 in the long-period periodic table such as magnesium or calcium (Ca), other light metals such as aluminum, lithium, or alloys thereof. An effect can be obtained. At that time, a negative electrode active material, a positive electrode active material, a solvent, or the like that can occlude and release the electrode reactant is selected according to the electrode reactant.

It is a perspective view showing the external appearance of the battery which concerns on one embodiment of this invention. It is a longitudinal cross-sectional view of the battery shown in FIG. It is a perspective view showing arrangement | positioning of the battery in oven in the Example and comparative example of this invention. It is a figure showing the result of the temperature rise which concerns on the coating | coated member of a battery. It is a figure showing the result of the temperature rise which concerns on the black area with respect to the side surface area of a battery.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Exterior member, 11 ... Battery can, 12, 13 ... Insulating plate, 14 ... Battery cover, 15 ... Safety valve mechanism, 16 ... Heat sensitive resistance element, 17 ... Gasket, 18 ... Cover member, 20 ... Battery element, 21 ... Positive electrode, 22 ... negative electrode, 23 ... separator, 24 ... center pin, 25 ... positive electrode lead, 26 ... negative electrode lead.

Claims (2)

A battery element having external connection terminals on the upper and lower surfaces;
A battery comprising: an exterior member that covers a side surface of the battery element and has 70% or more of the area of the side surface having an emissivity of 0.6 or more. The exterior member is obtained by covering the side surface of the battery can with a covering member,
The battery according to claim 1, wherein 70% or more of the outer surface area of the covering member has an emissivity of 0.6 or more.

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