JPH10241733A - Nonaqueous electrolytic secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the abnormal temperature rise in a battery to improve safety by installing a refrigerant vessel in the center part of a battery case, and when the pressure in the refrigerant vessel exceeds a set value, releasing the sealing of the refrigerant vessel to vaporize the refrigerant remove the heat in a battery by vaporization heat. SOLUTION: An electrolyte is injected from the opening part of a battery case 10 for sealing an upper lid 11, and then a refrigerant vessel 20, wherein a refrigerant 21 is sealed, is inserted into the hollow cylinder 10b of the inner diameter part of the battery case 10 to be fitted by a fixing screw 34 and a presser bush 25. When the vapor pressure of the refrigerant 21 in the refrigerant vessel 20, corresponding to the temperature in a battery, reaches a set pressure corresponding to or less than the oxygen-separation starting temperature for a positive electrode active material, a pressure valve mechanism 22 is opened continuously, to make the heat in the battery be absorbed by the refrigerant 21, and vaporized and gasified in air, thereby preventing the temperature rise in the battery. Operating lower limit pressure of a pressure valve is decided from the relation between an in-battery temperature rise characteristic within the practical temperature range of the battery and the temperature deterioration characteristic of the battery, and the vapor pressure of the refrigerant 21 is preferably one which corresponds to 100 deg.C in the temperature in a battery group 15.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a unit battery used as a power source for products such as mobile devices such as electric vehicles and electric carts, portable devices such as video cameras and personal computers, backup devices in the event of a power failure, and security devices. Capacity of 20
The present invention relates to safety of a battery for preventing ignition and explosion due to abnormal heat generation of a medium capacity, high capacity type non-aqueous electrolyte secondary battery of Wh or more.

[0002]

2. Description of the Related Art As a conventional safety protection device for a non-aqueous electrolyte secondary battery, as shown in Japanese Patent Application Laid-Open No. 7-192753, as a core for winding a positive electrode and a negative electrode in a spiral shape, polypropylene, polyethylene or the like is used. When the battery temperature rises rapidly due to a short circuit or the like and exceeds the set temperature, the core material of the polymer material melts and absorbs the surrounding heat by the heat of fusion, thereby increasing the battery temperature. Methods to prevent this are known.

[0003]

However, the heat of fusion at which the core of the polymer material is melted has a small heat capacity, and the heat is not sufficiently dissipated because the melted polymer material remains sealed in the battery case. , Battery size is 186
It is effective only for a battery having a small capacity of about 50 (18D × 65L), and cannot be used for a battery having a large capacity. Further, when the polymer material is resistant to a non-aqueous electrolyte, the material is limited, the melting temperature cannot be set freely, and the battery cannot be operated at an optimal temperature for protecting the battery.

The present invention has been made in view of the above-mentioned problems of the prior art, and has as its object to increase the abnormal temperature rise of a non-aqueous electrolyte secondary battery of a medium / high capacity type which generates a large amount of heat. Another object of the present invention is to provide a non-aqueous electrolyte secondary battery with good assemblability, while improving safety by suppressing pressure.

[0005]

In order to achieve the above object, the present invention provides a power generating element in which a non-aqueous electrolyte is impregnated into a group of electrodes wound with a positive electrode and a negative electrode facing each other via a separator. At the center of the sealed battery case, a refrigerant container containing a refrigerant is installed.When the pressure inside the refrigerant container exceeds a set value, the sealing of the refrigerant container is opened, and the battery is heated by vaporization heat in which the refrigerant evaporates into the atmosphere. To prevent the temperature of the non-aqueous electrolyte secondary battery from rising.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the nonaqueous electrolyte secondary battery according to the present invention will be described below with reference to the drawings. FIG. 1 is a structural sectional view showing one embodiment of the non-aqueous electrolyte secondary battery of the present invention. In FIG. 1, reference numeral 1 denotes a positive electrode, and a positive electrode mixture 1b using an inorganic lithium intercalation material as a positive electrode active material on both surfaces of a positive electrode current collector 1a made of aluminum foil.
(For example, a mixture prepared by mixing and adjusting carbon as a conductive agent and polyvinylidene fluoride as a binder, such as LiMn2O4, LiCoO2, and LiNiO2 as an active material). Reference numeral 2 denotes a negative electrode, and a negative electrode mixture 2b (for example, a mixture of graphite as an active material and polyvinylidene fluoride as a binder) on both surfaces of a negative electrode current collector 2a formed of a copper foil and having a lithium intercalation carbon material as a negative electrode active material. Adjusted). Reference numeral 3 denotes a separator made of a microporous polyethylene film or polypropylene film. When the temperature of the polyethylene film rises, the shutdown start temperature at which the micropores close due to melting of the film itself is about 130 ° C., and the shutdown start temperature of the polypropylene film is about 150 ° C.
It is. The positive electrode 1 and the negative electrode 2 are spirally wound in a state where they face each other with the separator 3 interposed therebetween to form an electrode group 15, and the core has an electrode group inner diameter space. In this case, the separator 3 is wound slightly wider than the positive electrode 1 and the negative electrode 2, and is further wound several times alone at the core portion and the end portion of the winding, so that the separator 3 can be wound between the positive electrode and the negative electrode and around the electrode group. Has insulation properties. This electrode group 15
Is immersed in a non-aqueous electrolyte (not shown) to become a power generating element. The non-aqueous electrolyte is LiPF6, LiBF4, LiClO4, LiAsF6
And the like are dissolved in an organic solvent (single or mixture of propylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate, etc.) as an electrolyte. Reference numeral 10 denotes a battery case made of stainless steel, nickel-plated iron or aluminum, and a bottomed double cylindrical type having an outer diameter portion cylinder 10a and an inner diameter portion hollow cylinder 10b as the electrode group 15 and a power generation element composed of a non-aqueous electrolyte. And covered with the upper lid 11 and sealed by welding or caulking. In addition, an insulating plate 1 is provided on the upper lid 11 side and the container bottom 10c in the battery case 10 in order to maintain electrical insulation between the battery charging section and the battery case 10.
2a and 12b are provided. Reference numeral 4 denotes a positive electrode lead made of an aluminum material, which is connected to the positive electrode current collector 1a of the positive electrode 1 and the positive electrode terminal 6 by welding or the like. Reference numeral 5 denotes a nickel or copper negative electrode lead, which is connected to the negative electrode current collector 2a of the negative electrode 2 and the negative electrode terminal 7 by welding or the like. Numeral 13 denotes an insulating destant, which is a space 1 for collectively housing the positive electrode lead 4 and the negative electrode lead 5 between the electrode group 15 and the upper lid 11.
6, and the electrode group 15 is pressed so as not to move in the battery case 10. The positive electrode terminal 6 and the negative electrode terminal 7 are fixed to the upper lid 11 of the battery case 10 by a hermetic seal 8 which is electrically insulated with a glass or plastic layer interposed and has a hermetic property. Reference numeral 9 denotes an explosion-proof valve, which is made of a metal plate or a thin-film metal plate having a weak portion such as a notch. The explosion-proof valve is opened when the pressure in the battery case 10 becomes high due to an abnormal temperature rise. I do. The operating pressure of the explosion-proof valve 9 is determined based on the temperature inside the battery case and the strength of the battery case itself and the strength at which the welded portion and the caulked portion do not break first.
Kg / cm2-20 kg / cm2 is desirable. Reference numeral 20 denotes a refrigerant container, which is a bottomed cylindrical container made of a metal material having good heat conductivity such as stainless steel, nickel-plated iron, copper, and aluminum. A refrigerant 21 which is a cooling medium solution is sealed in the refrigerant container 20, and a pressure valve mechanism 22 is caulked to an opening of the refrigerant container 20 via a gasket 23 and hermetically sealed. HFC-based refrigerants (HFC-134a, HFC-143a, HFC-32, HFC-12) which are friendly to the global environment and have a low ozone depletion potential and a low global warming potential
5 or the like alone or in mixtures) and inert gas solutions are safe and suitable. The refrigerant container 20 is fixed in the hollow cylinder 10b of the inner diameter part of the battery case 10 by a fixing screw 24 and a hollow pressing bush 25 so that the pressure valve mechanism 22 communicates with the outside air. That is, the refrigerant container 20 is
It is located at the center of the electrode group 15 which is a heat source inside, and is installed such that the refrigerant 21 evaporates into the atmosphere when the pressure valve mechanism 22 is opened. This location is the location that receives the heat generated by the power generating element most.It has the advantage of good response to temperature change and little time lag for abnormal temperature detection, and also the central part of the battery that has the best cooling effect when the refrigerant evaporates. There is an effect that can be cooled from. The pressure valve mechanism 22 is such that when the pressure becomes equal to or higher than a set pressure, the pressure valve is continuously opened. There is a metal thin film destruction type pressure valve.

FIG. 2 is an enlarged sectional view showing an embodiment of the pressure valve mechanism 22. The pressure valve 26 has a weak portion 26 such as a notch.
a. The cut depth and shape of the pressure valve 26 are determined so that the weak point portion 26a is split when the pressure exceeds a set pressure. Reference numeral 27 denotes a protective cap having a gas vent hole 27a for covering and protecting the pressure valve 26.

FIG. 3 is an enlarged sectional view showing another embodiment of the pressure valve mechanism 22.
0a, the seal plate 30 and the case 31
A valve 32 and a spring 33 are sandwiched and built in so as to close a, thereby forming a case. At the other end of the valve 32, a hook-shaped latch 32a is provided at a portion penetrating the through hole 31a of the case 31, and a latch spring 34 is in contact with the outside of the latch 32 with its tip facing outward. When the pressure in the refrigerant container 20 reaches the set pressure, the valve 32 is pushed up against the force of the spring 33, the latch 32a rides on the latch spring 34 and is caught, and the valve 32 keeps the discharge port 30a open. The set pressure at which the valve opens can be freely set by changing the pressing force of the spring.

Next, a method of assembling the non-aqueous electrolyte secondary battery according to the present invention will be described. First, the positive electrode lead 4 and the negative electrode lead 5 are attached to the positive electrode 1 and the negative electrode 2, respectively, by spot welding or ultrasonic welding. At this time, the number of leads to be attached is increased or decreased depending on the size of the battery capacity. The positive electrode 1 and the negative electrode 2 are wound with the separator 3 interposed therebetween, and the end of the winding is stopped with a tape or the like to form an electrode group 15. Insulating plate 12 from bottom 10c side of bottomed double cylindrical container
b, the electrode group 15 and the insulating distant 13 are placed in this order, and the positive electrode lead 4 and the negative electrode lead 5 are bundled and put together.
Next, the insulating plate 12 a is placed on the back side of the upper lid 11, and the positive electrode lead 4 and the negative electrode lead 5 are welded to the positive terminal 6 and the negative terminal 7 of the upper lid 11. Next, an electrolytic solution is injected from the opening of the battery case 10, and the upper lid 11 is sealed by welding or caulking. Finally, the refrigerant container 20 in which the refrigerant 21 is sealed is inserted into the hollow cylinder 10b of the inside diameter of the battery case 10 and attached with the fixing screw 24 and the holding bush 25. in this way,
After the battery is completed, the refrigerant container 20 is incorporated into the hollow cylinder 10b of the inner diameter portion of the battery case, so that workability is good.

Next, the operation of the nonaqueous electrolyte secondary battery according to the present invention will be described. When the battery is overcharged to a voltage equal to or higher than the set voltage due to a failure in the charging circuit, a chemical reaction other than the battery reaction as lithium intercalation is performed to decompose the electrolytic solution, thereby deteriorating the battery and increasing the temperature of the battery. If the discharge circuit is overdischarged below the set voltage due to a failure of the discharge circuit, lithium metal precipitates on the negative electrode due to the dentite reaction, breaks through the separator 3 and causes a short circuit between the positive electrode and the negative electrode. Become. Furthermore, the battery also generates heat and becomes abnormal temperature due to use at a high temperature exceeding the normal use temperature range of the battery, external short-circuit due to misuse, and internal short-circuit in the battery for some reason.
When the temperature of the non-aqueous electrolyte secondary battery rises, the film of the separator 3 between the positive electrode 1 and the negative electrode 2 becomes 130 ° C. to 150 ° C.
It melts at a temperature of ° C. and acts to shut off the current by a shutdown effect that stops the movement of lithium ions between the positive and negative electrodes by closing the microporous film. However, a polyethylene film or a polypropylene film, which is a material of the separator, melts and shrinks due to a further rise in temperature, and may not be able to secure insulation between the positive and negative electrodes, resulting in a short circuit between the electrodes. If the temperature inside the battery exceeds 150 ° C, the positive electrode active material used for the electrodes will cause thermal runaway, causing smoke and
It is a dangerous temperature range that leads to ignition and explosion. That is, rapid heat generation is caused by an oxygen desorption reaction from a crystal lattice of the positive electrode active material such as LiMn2O4, LiCoO2, and LiNiO2. The oxygen desorption start temperature varies depending on the type of the active material and the composition ratio of each element, but is in the range of 150 ° C to 400 ° C. If the battery abnormally rises in temperature for some reason, the electrolyte in the battery will decompose,
In addition, the electrolytic solution and the active materials of the positive electrode and the negative electrode cause a chemical reaction to generate gas, and the pressure in the battery case rapidly rises. The pressure inside the battery rises and 10kg / cm2 ~ 20kg / c
When the pressure reaches m2, the explosion-proof valve 9 ruptures and discharges gas out of the battery case to reduce the explosive power of the battery. However, the activation of the explosion-proof valve does not eliminate the danger of smoking, ignition and explosion. In order to prevent explosion, it is necessary to keep the temperature inside the battery below the temperature at which oxygen desorption of the positive electrode active material starts. That is, this is the object of the present invention, and the vapor pressure of the refrigerant 21 in the refrigerant container 20 corresponding to the temperature in the battery is:
When the pressure reaches a set pressure equal to or lower than the oxygen desorption start temperature of the positive electrode active material, the pressure valve mechanism 22 is continuously opened, and the refrigerant 21 absorbs the heat of the battery and evaporates into the atmosphere to prevent the battery temperature from rising. . The operating lower limit pressure of the pressure valve is determined from the relationship between the battery temperature rise characteristic and the battery temperature deterioration characteristic in the practical temperature range of the battery.
Is desirably set to the vapor pressure of the refrigerant 21 in the refrigerant container 20 corresponding to The reason why the pressure valve is continuously opened is to completely evaporate the built-in refrigerant, reliably prevent the temperature of the battery from rising due to heat of vaporization, and set the battery in a safe temperature range where thermal runaway does not occur. In addition, since the refrigerant is evaporated and vaporized into the atmosphere, the heat taken from the battery is effectively discharged to the outside of the battery, the cooling effect is large, and the temperature of the battery is rapidly lowered.

[0011]

As described above, according to the present invention, a power generating element composed of a non-aqueous electrolyte and an electrode group in which a positive electrode and a negative electrode are wound opposite to each other with a separator interposed therebetween is used as a bottomed double cylindrical container. In a battery sealed in a battery case consisting of an upper lid, a metal refrigerant container containing a refrigerant is installed in a hollow cylinder serving as a core portion of an electrode group, and when the pressure in the refrigerant container exceeds a set value, the refrigerant container The seal is continuously opened to allow the refrigerant to completely evaporate into the atmosphere, providing good temperature responsiveness when the temperature rises abnormally, preventing the battery temperature from rising due to heat of vaporization, and ensuring battery safety. Can be reliably protected. Further, since the refrigerant container is directly attached to the inside of the hollow cylindrical portion of the battery case from the outside after the battery is completed, the workability of battery assembly is improved, and an inexpensive non-aqueous electrolyte secondary battery can be provided.

Further, since the amount of the refrigerant can be sealed by the heat capacity corresponding to the battery size, and the set pressure of the pressure valve mechanism can be freely set, a highly safe non-aqueous electrolyte secondary battery suitable for various uses is provided. A battery is obtained.

[Brief description of the drawings]

FIG. 1 is a structural sectional view showing one embodiment of a non-aqueous electrolyte secondary battery of the present invention.

FIG. 2 is a structural sectional view showing one embodiment of a pressure valve mechanism of the nonaqueous electrolyte secondary battery of the present invention.

FIG. 3 is a structural sectional view showing another embodiment of the pressure valve mechanism of the nonaqueous electrolyte secondary battery of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ‥‥ Positive electrode, 1a ‥‥ Positive electrode collector, 1b ‥‥ Positive electrode mixture, 2 ‥‥ Negative electrode, 2a 負極 Negative electrode collector, 2b ‥‥ Negative electrode mixture, 3 セ パ レ ー タ Separator 4 正極 Positive electrode lead 5 ‥‥ Negative electrode lead 6 正極 Positive electrode terminal 7 ‥‥ Negative electrode terminal 8 ハ ー Hermetic seal 9 爆 Explosion-proof valve 10 ‥‥ Battery case 10 a ‥‥ Outer diameter cylinder 10 b ‥‥ Inner diameter hollow cylinder 10 c ‥‥ Container bottom 11 ‥‥ Upper lids 12a, 12b 絶 縁 Insulating plate 13 絶 縁 Insulating distant 15 ‥‥ Electrode group 16 ‥‥ Electrode upper space 20 ‥‥ Refrigerant container 21 冷媒 Refrigerant 22 ‥‥ Pressure valve mechanism 23 ガ ス Gasket 24 固定 Fixing screw 25 ‥‥ Presser bush 26 ‥‥ Pressure valve 26 a ‥‥ Weak point 27 ‥‥ Protective cap 27 a ‥‥ Gas vent hole 30 シ ー ル Seal plate 30 a ‥‥ Discharge port 31 ‥‥ Scan 31a ‥‥ through hole 32 ‥‥ valve 32a ‥‥ latch 33 ‥‥ spring 34 ‥‥ a latch spring

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Koichi Sato 800, Tomita, Ohira-cho, Ohira-cho, Shimotsuga-gun, Tochigi Prefecture Inside the Cooling and Cooling Division, Hitachi, Ltd. (72) Michiko Sakairi 800, Tomita-Oita, Ohira-cho, Shimotsuga-gun, Tochigi Hitachi, Ltd.

Claims (6)

[Claims] 1. A battery in which a positive electrode and a negative electrode are opposed to each other with a separator interposed therebetween, and a power generation element composed of a spirally wound electrode group and a non-aqueous electrolyte is hermetically housed in a battery case. A refrigerant container in which a refrigerant is sealed is installed in a hollow cylinder serving as a part, and when the pressure in the refrigerant container exceeds a set value, the sealing of the refrigerant container is opened, and the refrigerant evaporates to the atmosphere. Water electrolyte secondary battery. 2. A power generating element comprising an electrode group and a non-aqueous electrolyte,
2. The non-aqueous electrolyte secondary battery according to claim 1, wherein the battery case is sealed in a battery case comprising a bottomed double cylindrical container having an inner diameter hollow cylinder and an outer diameter cylinder. 3. The non-aqueous electrolyte secondary battery according to claim 1, further comprising a pressure valve mechanism for continuously opening the seal when the refrigerant container exceeds a set pressure. 4. The set pressure at which the refrigerant container is opened is a vapor pressure of a refrigerant corresponding to a temperature in a battery case equal to or lower than an electrode group temperature of 100 ° C. or lower and an oxygen desorption starting temperature of a positive electrode active material as a lower limit. The non-aqueous electrolyte secondary battery according to claim 1, wherein: 5. The refrigerant container is made of stainless steel, aluminum,
The non-aqueous electrolyte secondary battery according to claim 1, comprising a metal material such as iron and copper. 6. The non-aqueous electrolyte secondary battery according to claim 1, wherein the refrigerant is a solution of a nonflammable gas in a cooling medium.