JPH11250884A - Battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent bursting or explosion of a battery even if a large volume of gas is generated by enlarging the flow path cross section of a gas ejecting part after a safety valve is operated by the physical or chemical reaction of gas ejecting from a battery when the safety valve is operated with a safety valve constituting material. SOLUTION: A suppressing spring 7 and a valve body 9 are arranged between a battery cover 5 and a positive terminal 6 to block a gas ejection hole 10 with the valve body 9. A valve seat 8 is formed with a material having a function enlarging the gas ejecting hole 10 by passing of ejecting gas. For example, if a halogen based electrolyte containing chlorine is used for making an electrolyte nonflammable, when the inner pressure is raised and a valve body starts operation, chlorine in ejecting gas quickly reacts with tellurium of the valve seat 8 to be converted to tellurium chloride, and when the ejecting gas becomes 175 deg.C or higher, the valve seat 8 is melted. Thereby, the region of the valve seat 8 becomes a gas ejection hole to enlarge a gas flow path. Preferably, a shape memorizing alloy deforming at 80-130 deg.C is used in a safety valve, and a low melting point alloy melting at 80-130 deg.C is used in the valve seat 8 or the valve body 9.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery, and more particularly, to a battery having a safety mechanism for preventing explosion or explosion of the battery.

[0002]

2. Description of the Related Art Among batteries, for example, a lithium ion secondary battery (hereinafter, referred to as a lithium battery) is widely used as a lightweight and high-capacity secondary battery as a power source for mobile phones and personal computers. This battery has a high energy density and generates a large amount of heat during charging and discharging. Furthermore, the electrolyte may be decomposed by overcharging or overcurrent during charging, and the reaction heat generated at the same time may accelerate the reaction and lead to an explosion. For this reason, this lithium battery-equipped device is provided with a protection circuit that monitors the voltage and temperature of the battery during charging and discharging, and performs operations such as shutting off the circuit when these abnormalities are detected. . In addition, the battery itself is equipped with a PTC element that increases the resistance when the temperature rises due to overcurrent, a function to cut off the current, and a safety device such as a safety valve that operates against an increase in internal pressure. I have. In particular, the safety valve provided in the battery is made of an elastic body so that gas can be released even if the coil spring of the safety valve malfunctions (Japanese Patent Application Laid-Open No. HEI-5-1993).
Various improvements have been disclosed, such as those disclosed in Japanese Patent Application Laid-Open No. 4-325241 and Japanese Patent Application Laid-Open No. 4-328241, in which the safety valve is filled with grease in order to enhance the sealing property at normal times.

[0003]

As shown in the prior art, for example, a lithium ion secondary battery is usually
Various safety mechanisms are provided. Of these, the last safety measure in the event that the organic electrolyte used in the battery is decomposed and the internal pressure rises or this decomposition reaction runs away due to the generated heat and eventually explodes or explodes, This is a danger avoidance by letting out the gas generated in the above. For this reason, a normal lithium ion secondary battery is provided with a safety valve which operates when the internal pressure rises due to gas generation in the battery for some reason and becomes equal to or higher than a set pressure. However, when a battery is dropped into a fire or when a protection circuit breaks down and becomes overcharged, a large amount of gas is rapidly generated. In this case, the amount of gas to be ejected cannot be completely released, and even though the safety valve operates, the battery may explode or explode.

The present invention makes it possible to operate a safety valve more effectively than in the prior art against such a battery abnormality, and to prevent the battery from exploding or exploding even when a large amount of gas is generated. Aim.

[0005]

In order to solve the above-mentioned problems, in the present invention, the constituent material of the safety valve reacts with exhaust gas discharged from the battery and is consumed, thereby increasing the cross-sectional area of the gas outlet. Have a function. In other words, when the safety valve is activated and gas inside the battery is released from the orifice, the ejected gas chemically or physically reacts with the material that constitutes the safety valve such as the orifice, causing the safety valve to become powdered and consumed or melted. This causes deformation and the like, and as a result, it is possible to discharge a large amount of gas by expanding the cross-sectional area of the gas outlet. For this reason, after the safety valve is operated, it is possible to prevent the battery from exploding or exploding even if a sudden gas is generated.

Here, when expanding the gas ejection hole by chemically reacting the ejection gas with the constituent material of the safety valve, it reacts with active components such as carbon monoxide and chlorine contained in the decomposition gas of the electrolytic solution to powder. A material that is consumed by the above process is used for the ejection hole. In the case of causing a physical reaction, a material that reacts with the temperature of the jet gas to cause physical phenomena such as melting and sublimation and changes the shape of the gas jet portion of the safety valve is used.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Normally, the pressure at which a battery safety valve operates is set at 10 to ²⁰ kg / cm ^{2. When} the battery internal pressure approaches this set value, the safety valve opens slightly and gas inside leaks. start. In such a state, the temperature of the gas to be ejected is also as high as 80 ° C. or more at which the electrolytic solution is decomposed. Moreover, this gas contains active components such as carbon monoxide and chlorine generated by decomposition of the electrolytic solution. When a material that causes a chemical reaction with these active components and is consumed by powdering the constituent material or the like is used for the ejection hole of the safety valve, the ejection gas acts to erode the ejection hole. For this reason, since the erosion of the ejection hole portion rapidly progresses simultaneously with the gas ejection, the ejection hole is enlarged, and a larger amount of gas can be released. Further, as a case of utilizing the physical reaction between the ejected gas and the material constituting the safety valve, there is a case where the heat of the ejected gas acts on the material constituting the safety valve. In this case, a shape memory alloy or a low melting point material that responds to the temperature of the jet gas is used as the material of the jet hole. At this time, when the safety valve starts operating, the heat of the gas passing through the ejection hole is transmitted to the constituent material of the ejection hole portion and acts to increase the temperature. When the constituent material reaches the set temperature, in the case of the shape memory alloy, the shape memory can be operated so as to enlarge the ejection hole. When a low-melting-point alloy is used, the material itself melts and flows out at a set temperature, and thus acts to enlarge the ejection hole portion. Therefore, compared to the conventional safety valve structure according to the present invention, the gas release operation of the safety valve after the start of gas leakage enables a large amount of gas to be released instantaneously, and prevents the explosion or explosion of the battery with high reliability. Has the effect of doing

Hereinafter, the present invention will be described with reference to examples. FIG.
1 shows a manganese-based lithium ion secondary battery having a cross-sectional structure of a battery having an explosion-proof function according to an embodiment of the present invention. In the battery of this embodiment, a positive electrode 1 using manganese oxide and a negative electrode 2 using coke-based carbon are wound around a separator (not shown in the figure because the thickness is small) and placed in a battery can 3. This is a cylindrical lithium ion battery. The battery has a battery cover 5 held by an insulating packing 4.
The safety valve function according to the present invention is provided between the positive electrode terminal 6 and the positive electrode terminal 6. In this embodiment, the configuration of the safety valve is almost the same as that of the conventional one, and a holding spring 7 and a valve body 9 of the safety valve are placed between the battery cover 5 and the positive electrode terminal 6. Is closed by a valve body 9. In the present embodiment, the valve seat 8 constituting the ejection hole portion of the battery cover 5 is made of a material having a function of expanding the ejection hole by passing the ejection gas. As a material for imparting the function of the present invention to the valve seat 8, for example, when a halogen-based electrolyte containing a large amount of chlorine is used to make the electrolyte used for the battery nonflammable, a large amount of gas is generated. Since chlorine is contained, the use of tellurium which reacts with the chlorine to form a powder provides a safety valve having the function of the present invention. The operation in this case will be described below.

If the internal pressure rises and the safety valve starts operating when there is external heating due to a fire drop or the like, the temperature of the gas to be ejected is high, so that chlorine in the ejected gas and tellurium in the valve seat rapidly increase. In response, the valve seat changes into tellurium dichloride sequentially from the portion in contact with the gas. Tellurium dichloride melting point 175 ° C
Because of the above-mentioned substance, the gas ejected at a higher temperature will melt. As a result, the entire configuration area of the valve seat 8 becomes an ejection hole, and the gas ejection flow path is enlarged. Further, in the electrolytic solution that generates such a gas containing chlorine, it is also effective to use selenium for the valve seat. In this case, selenium tetrachloride is generated by the reaction with the ejected gas. Selenium tetrachloride is 19
Because of the property of sublimation at 6 ° C, when a gas with a higher temperature is ejected, the generated selenium tetrachloride gasifies and blows off instantly when it reaches the sublimation temperature. It is effective. Also, in the case of a battery using a normal organic electrolyte, since the gas generated by decomposition contains carbon monoxide, the gas reacts well with this to form a volatile metal carbonyl compound. Metal is effective.

In the above embodiment, the case where the ejection hole of the safety valve is expanded by utilizing the chemical reaction with the ejected gas is explained. Next, the ejection is performed by utilizing the heat of the ejected gas as a physical reaction. An example in which the function of enlarging a hole is realized will be described. This can be realized, for example, by configuring the valve seat 8 with a low melting point metal alloy such as low melting point solder in the battery configuration of FIG. For example, when a low-melting-point metal having a ratio of Sn: Pb: Bi of 22:28:50 is used for the valve seat 8, it melts at 100 ° C., so that the temperature does not reach such a high temperature by using a normal battery. The valve seat and valve body held by the spring maintain airtightness. However, when the internal pressure rises due to the decomposition of the electrolyte and gas starts to leak from the safety valve, a high temperature gas of 100 ° C. or more passes through the ejection hole of the valve seat, so that the temperature of the valve seat immediately rises and the valve seat is opened. The orifice is easily enlarged for melting. This phenomenon will be described below using an actual measurement example of temperature and pressure when the battery is overcharged.

FIG. 2 shows an example in which the relationship between battery internal pressure and temperature in an overcharge region of a battery provided with a normal safety valve is measured. As shown in this figure, when the electrolyte is decomposed by overcharging, the internal pressure gradually increases. In this measurement example, the overcharge ratio is about 155% (shown by a thin broken line in the figure) and the pressure rise gradient is earlier than that. Temporarily smaller. This is considered to indicate that the generated gas has begun to leak. At this time, the battery surface temperature is considered to be 50 ° C. and does not affect the battery, but has reached 70 ° C. inside the battery, which promotes decomposition of the electrolytic solution. The gas that has begun to leak has the same temperature as the temperature inside the battery, and then rapidly rises due to thermal runaway. As is clear from the measurement example, since the temperature rise changes more than the internal pressure rise, the gas of 100 ° C or more passes through the safety valve before reaching the set pressure (here, 0.2 MPa) at which the safety valve fully operates. Become. As a result, the valve seat 8 is heated and melted by the high-temperature blast gas. As a result, a larger amount of gas can be released from the melted and expanded orifice as compared with the conventional safety valve structure, and the battery can be prevented from exploding due to an increase in internal pressure.

As shown in FIG. 3, in the battery of the present embodiment, if the diameter of the ejection hole 10 is d1, the outer diameter of the valve seat 8 is d2, and the areas of the two are S1 and S2, the ratio of this diameter is d2 /. The ratio S2 / S1 of the enlarged flow path cross-sectional area to d1 increases with the ratio of the square of the diameter ratio. For example, if the safety valve is d2 / d1
= 3, up to 9 more than the conventional safety valve
It can be seen that the gas discharge flow path can be doubled and has a very high gas discharge capacity in an abnormal condition.

FIG. 4 shows an embodiment in which a safety valve is made to respond to temperature by using a shape memory alloy. The figure shows an enlarged view of the safety valve structure of the battery lid. The spring for holding the valve body 9 is a combination of a normal holding spring 7 used in a conventional safety valve and a spring 12 made of a shape memory alloy as shown in the figure. Examples have been given. However, shape memory alloy spring 1
The upper part 2 is fixed to the positive electrode terminal 6.

Each of the springs used here has a temperature characteristic as shown in FIG. 5, thereby realizing the function of expanding the gas flow path of the present invention. That is, the normal pressing spring has no influence of the temperature in the illustrated temperature range (60 ° C. to 120 ° C.) and always presses the valve body against the valve seat with a constant compressive force. On the other hand, the shape memory alloy spring 12
When the temperature is higher than 90 ° C., a tensile force exceeding the compressive force of the presser spring is generated in an attempt to return to the original shape. For this reason, when the safety valve having the structure as shown in FIG. 4 starts to leak gas due to an increase in the internal pressure and raises the temperature of the spring by the heat of the ejected gas,
When the temperature reaches 90 ° C. or more, the shape memory alloy spring 12 contracts and acts to open the valve. In this state, the safety valve can be operated only by the temperature change regardless of the internal pressure. Therefore, in addition to the conventional push-up of the valve body 9 by only the internal pressure, the push-up of the valve body 9 by the shape memory alloy spring 12 is added. The opening degree of the valve after the start of gas leakage becomes larger than that of the safety valve, and as a result, the cross-sectional area of the gas flow path between the valve seat and the valve element is further increased. Therefore, according to the present invention, even when there is a sudden generation of gas due to an abnormality in the battery, it is possible to avoid an explosion. Although the lithium secondary battery has been described as an example, the present invention can be used for a battery whose internal pressure rises when an abnormality occurs.

[0015]

According to the present invention, there is an effect that the battery can be used safely without rupture or explosion.

[Brief description of the drawings]

FIG. 1 is a diagram showing a battery structure according to one embodiment of the present invention.

FIG. 2 is a diagram showing a measurement example of temperature and pressure during overcharge.

FIG. 3 is a diagram showing an effect of increasing a cross-sectional area of a flow channel.

FIG. 4 is a diagram showing a safety valve structure according to one embodiment of the present invention.

FIG. 5 is a view showing characteristics of a safety valve holding spring.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Positive electrode, 2 ... Negative electrode, 3 ... Battery can, 4 ... Insulating packing,
5: Battery cover, 6: Positive electrode terminal, 7: Pressing spring, 8: Valve seat, 9: Valve body, 10: Jet hole, 12: Shape memory alloy spring.

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor ▲ Toshi ▼ 7-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture Inside the Hitachi Research Laboratory, Hitachi, Ltd. 7-1-1, Hitachi Research Laboratory, Hitachi Research Laboratory

Claims (9)

[Claims] In a battery provided with a safety valve for releasing the internal pressure of the battery, the gas discharged from the battery when the safety valve is operated and the material constituting the safety valve physically or chemically react with each other, whereby the safety valve after the operation of the safety valve is operated. A battery having a function of enlarging a flow path cross-sectional area of a gas ejection part. 2. A battery according to claim 1, wherein the gas ejected when the safety valve is operated and the material for forming the gas ejection portion of the safety valve are chemically reacted and consumed, thereby increasing the cross-sectional area of the passage of the ejected gas. . 3. The battery according to claim 2, wherein the material for forming the gas ejection portion is made of a transition metal such as tellurium, selenium, nickel, or cobalt. 4. The battery according to claim 1, further comprising a function of expanding a flow path cross-sectional area of the gas ejection portion after the safety valve is operated in response to a temperature of gas ejected when the safety valve is operated. 5. The battery according to claim 2, wherein a material which is decomposed and consumed by reacting with carbon monoxide or chlorine is used for a gas ejection portion of the safety valve. 6. The method according to claim 4, wherein the temperature is from 80 ° C. to 130 ° C.
A battery using a shape memory alloy which deforms in a temperature range of ° C. for a safety valve. 7. The method according to claim 4, wherein the temperature is from 80 ° C. to 130 ° C.
A secondary battery characterized in that a low-melting alloy or a thermoplastic plastic that melts in a temperature range of ° C is used for a valve seat or a valve body constituting a gas ejection portion of a safety valve. 8. The method according to claim 4, wherein the temperature ranges from 80 ° C. to 130 ° C.
A battery characterized in that a solid material that sublimates at a temperature of ° C. is used for a valve seat and / or a valve body of a gas ejection part of a safety valve, or both. 9. An electronic device or an electric driving device using the battery according to claim 1.