KR101066021B1 - Secondary Battery Including Microcapsule Containing Safety Security Material - Google Patents

Abstract

The present invention relates to a secondary battery in which an electrode assembly having a cathode / membrane / cathode structure is embedded in a battery case, and a microcapsule containing a material for securing safety ('safety collateral') directly affects operation of the battery. It is applied to a portion that does not reach, the coating portion provides a secondary battery, characterized in that the position where the thermal accumulation phenomenon and short circuit due to the internal pressure / external pressure easily occurs when an abnormality such as static or physical impact of the battery.

Description

Secondary battery containing microcapsules containing safety collateral materials {Secondary Battery Including Microcapsule Containing Safety Security Material}

1 is a vertical cross-sectional perspective view of a cylindrical cell comprising a jelly-roll electrode assembly;

Figure 2 is a schematic diagram of the structure before the winding of the jelly-roll type electrode assembly according to an embodiment of the present invention;

3 is a perspective view of a center pin mounted to a cylindrical secondary battery according to another embodiment of the present invention;

4 is a horizontal cross-sectional view taken along the straight line A-A of FIG. 3.

The present invention relates to a secondary battery including a microcapsule containing a built-in safety collateral material, and more particularly, to the heat accumulation phenomenon and the internal pressure / external pressure inside a battery structure in a state in which a material for securing safety is embedded in a capsule. The secondary battery which greatly improves the safety of the battery by suppressing the ignition or explosion caused by the abnormal operation of the battery by applying the short circuit caused by the short-circuit by more than other parts, without affecting the operation performance of the battery. to provide.

In secondary batteries, which are increasingly in demand due to the development of portable electronic devices, the temperature increase inside the battery causes many problems. Representative problems related to the temperature rise inside the battery are as follows.

For example, the heat generated during charging and discharging in a normal operating state causes the secondary battery to operate at a higher temperature than the outside, and such high temperature formation during operation ultimately promotes the deterioration rate of the battery. Moreover, rapid temperature rise inside the cell under abnormal operating conditions may be a major cause of the battery's potential for explosion.

Although a certain amount of heat generation helps the operation of the secondary battery, at least a temperature rise and a rapid temperature rise above a certain temperature are undesirable in view of the life and safety of the secondary battery.

Thus, in an attempt to solve this problem, in order to prevent the risk of explosion of the battery due to rapid temperature rise, a method of incorporating a flame retardant into some of the components of the battery, or causing curing of the electrolyte above a certain temperature, etc. Developed. However, some of these methods can be used as a way to prevent the explosion when the secondary battery is in an abnormal operating state, but does not fundamentally solve the ignition or explosion of the battery.

Therefore, in order to solve these problems, Japanese Patent Application Laid-Open No. 1998-270084 contains a substance that inhibits battery reaction in a nonaqueous electrolyte secondary battery, and a thermosensitive material that releases the battery reaction inhibitor as the battery temperature rises. A technique for applying a microcapsule to a separator or electrode mixture surface is disclosed. In addition, Japanese Patent Application Laid-Open Publication No. 1994-283206 discloses a technique for impregnating a microcapsule containing a chemical or a flame retardant into a separator or an electrolyte solution.

However, the above techniques are applied or impregnated with a microcapsule in a separator, an electrode mixture or an electrolyte solution, thereby preventing the microcapsule particles from blocking pores formed in the separator, or reducing the movement of lithium ions in the electrode mixture or electrolyte solution during charge and discharge, It has the disadvantage that the operating performance of the battery is greatly reduced.

Accordingly, an object of the present invention is to solve the problems of the prior art and the technical problem that has been requested from the past.

That is, an object of the present invention is to provide a secondary battery that can ensure the safety of the battery by minimizing the impact on the size and performance of the battery, while suppressing a sudden temperature rise in an abnormal operating state.

Accordingly, the secondary battery according to the present invention is a secondary battery in which an electrode assembly having a cathode / separation membrane / cathode structure is built in a battery case, and a microcapsule battery containing a material for securing safety ('safety collateral material') It is applied to a portion that does not directly affect the operation of the, the application portion is characterized in that the position where the thermal accumulation phenomenon and short circuit due to the internal pressure / external pressure easily occurs when an abnormality such as static abnormality, physical impact of the battery.

According to the present invention, a microcapsule containing a safety collateral material is a portion that does not directly affect the performance or operation of the battery inside the battery, and at the same time, structurally difficult to dissipate heat, and thus high risk of ignition due to high heat accumulation, By applying to areas where internal short circuits are likely to occur due to internal pressure or external pressure due to factors, it is possible to simultaneously achieve two purposes of optimizing battery performance and preventing battery ignition and explosion.

The safety collateral material is not particularly limited as long as it is a material capable of preventing heat generation or ignition of the battery, and may be, for example, a fire extinguishing material ('extinguishing agent'), a heat absorbing material, and the like. desirable.

In general, a secondary battery may cause an internal short circuit due to repeated expansion or contraction of a volume due to external impact, dropping of a battery, inflow of foreign matter, continuous charging and discharging, or an abnormal battery operation state such as overcharge or static. Fever or explosion may result.

In an abnormal operating state of the battery, such as an internal short circuit or overcharge, the temperature of the secondary battery is rapidly increased or gradually rises. In this case, while the temperature of the secondary battery reaches a predetermined temperature, the microcapsules are melted or the microcapsules are destroyed by an increase in internal pressure, and ultimately, the safety collateral material is discharged to the outside of the capsule. In some cases, the safety collateral material may be discharged while the shell of the capsule is destroyed by the physical impact.

Considering various reaction environments inside the battery during charging and discharging, the method of discharging the safety collateral material by melting the microcapsules has a difficult side to ensure reliable operation. On the other hand, the safety collateral material is a material that vaporizes or generates gas at a predetermined temperature, and the method of discharging vaporized material or gas by breaking the microcapsules while increasing the internal pressure by vaporization or gas generation of the material is relatively high. Provides reliability Therefore, the latter manner is more preferred.

In one preferred embodiment, the safety collateral material may be an inert gas that exhibits an extinguishing function, or a substance that generates an inert gas by a chemical reaction ('gas generator').

The inert gas is not particularly limited as long as it is a non-flammable gas. For example, the inert gas may be nitrogen, carbon dioxide, helium, argon, neon, freon, and the like, but is not limited thereto. It may be used as. The inert gas may be embedded in the microcapsules, for example, in the form of a small volume of gas phase or liquid phase by high pressure, and may be a substance that changes from a liquid phase to a gas phase based on a predetermined critical temperature ('phase conversion material'). May be embedded in the microcapsule while maintaining the liquid state at the normal operating temperature of the cell.

The gas generator is a substance generating an inert gas by high heat, for example, potassium hydrogen carbonate (K ₂ CO ₃ ), sodium hydrogen carbonate (NaHCO ₃ ), manganese carbonate ( MnCO ₃ ) and the like, but are not limited thereto.

As used herein, the term "specific temperature" means a temperature that can threaten the safety of a battery in a certain number of repetitive or transient states. The predetermined temperature may be determined according to the type of secondary battery, and one preferred example may be determined in a temperature range of 100 to 150 ° C, more preferably in a temperature range of 110 to 140 ° C.

For example, in the cylindrical secondary battery, the cathode active material decomposes around 130 ° C., causing heat generation of the battery, which causes gas generation and internal pressure within the secondary battery to cause ignition or explosion.

In one preferred embodiment, the safety collateral material may be composed of a fire extinguishing agent to evaporate or generate gas at 100 to 150 ℃. That is, when the temperature of the secondary battery reaches 100 to 150 ℃, the safety collateral material is changed to the gas phase to suppress the heat generation and ignition caused by the decomposition reaction of the electrode active material.

The material of the shell in which the microcapsules contain and seal the safety collateral material is not particularly limited as long as the material exhibits an inertness in the battery's internal environment and can be melted or destroyed under the conditions described above. For example, it may be various kinds of polymers.

The manufacturing method of the microcapsules is not particularly limited as long as it is a technique for manufacturing a capsule containing a safety collateral material as in the present invention. For example, the phase change material may be prepared by dispersing in an aqueous solution through an emulsification process and polymerizing a polymer on the surface of its oil phase. In this case, as the polymerization method, interfacial polymerization, in-situ polymerization, coacervation method, or the like may be used.

The microcapsule preferably has a particle size of about 1 to 500 μm. In view of exhibiting rapid reactivity with temperature change, a small particle size having a large surface area per unit weight is preferable. However, too small particle diameter may have difficulty in producing the capsule particle itself, and may have difficulty in the process of applying it to a specific part of the battery, so that it may be appropriately determined in the above range.

The microcapsules may be applied to a corresponding site in a battery using a binder as a coating substrate. For example, the microcapsules may be mixed with an appropriate solvent to prepare a slurry, and then applied to a specific site within the battery as a thin film or a film. Can be made and attached.

One of the important features of the present invention is that the microcapsule is applied to a specific site, i.e., a site which is prone to short-circuit due to thermal accumulation and internal pressure / external pressure when the battery malfunctions. Is that it is.

For example, in the structure of a cylindrical battery or a square battery, a portion centered on an electrode terminal (electrode tab) located at the center of a jelly-roll type electrode assembly ('jelly-roll') is more likely to radiate heat than other portions of the battery. Therefore, heat accumulation is likely to occur. In addition, the portion is likely to be short-circuited by various causes such as external impact, dropping of the battery, concentration of stress due to expansion and contraction of the volume during charging and discharging.

However, even as described above, as described above, when the microcapsules are applied or added to a separator, an electrode mixture, an electrolyte solution, or the like, the capsule particles may greatly degrade the performance of the battery, thus affecting the operation of the battery. It needs to be added to the part which is not.

Therefore, the site to which the microcapsules are applied needs to be selected in consideration of these points, and the following examples are preferable.

First, when the secondary battery is a cylindrical battery, the microcapsule may be applied to the inner uncoated portion, the center pin, or the electrode tab on the inner uncoated portion of the current collector where the electrode mixture is not applied.

Second, when the secondary battery is a rectangular battery, the microcapsule may be applied to an inner plain portion, which is a portion of the current collector to which the electrode mixture is not applied, or an electrode tab on the inner plain portion.

The cylindrical secondary battery may be manufactured by inserting a jelly-roll prepared by winding a positive electrode sheet and a negative electrode sheet in a state where a separator is interposed into a cylindrical can, injecting an electrolyte solution, and sealing the can.

The rectangular secondary battery may be manufactured by the same method as the cylindrical secondary battery, except that the rounded jelly-roll is flattened and inserted into the rectangular can.

In particular, the inner plain portion located at the center portion of the jelly-roll, due to the protruding shape of the electrode tab coupled thereto, presses the adjacent separator by expansion and contraction during charging and discharging, and in some cases, Bursting and penetrating may cause internal short circuits. This internal short circuit is also caused by the deformation of the center pin by external force.

Therefore, the microcapsule coating layer applied to the electrode tab or the center pin on the inner uncoated portion may serve as an insulating layer to prevent the internal short circuit as described above.

The secondary battery according to the present invention can be preferably used in a medium-large battery module of high output large capacity, in which safety is a problem. Since the medium-large battery module includes a plurality of secondary batteries as unit cells, safety may be greatly threatened by a chain reaction when an abnormality occurs in some unit cells.

Accordingly, the present invention also relates to a medium-large battery module including the secondary battery as a unit cell.

The medium-large battery module is not particularly limited as long as it is a battery module electrically connecting two or more secondary batteries. For example, the medium-large battery module is used for a power source of a notebook computer, an e-bike, an electric vehicle, a hybrid electric vehicle, and the like. It may be a battery module.

Hereinafter, although described with reference to the drawings according to an embodiment of the present invention, this is for easier understanding of the present invention, the scope of the present invention is not limited thereto.

1 is a vertical cross-sectional perspective view of a cylindrical battery including a jelly-roll electrode assembly is schematically shown.

Referring to FIG. 1, the cylindrical secondary battery 10 accommodates a jelly-roll type electrode assembly (jelly-roll) 20 in a cylindrical case 30 and injects an electrolyte solution into the cylindrical case 30, and then the case 30. ) Is manufactured by combining the top cap 40 having the electrode terminal (for example, a positive electrode terminal) formed at the open upper end.

The electrode assembly 20 has a structure in which the anode 200, the cathode 300, and the separator 400 are sequentially stacked to be wound in a round shape, and at its core (center of jelly-roll), a cylindrical center pin 50 is formed. Is inserted. The center pin 50 is generally made of a metal material to impart a predetermined strength, and has a structure in which a plate is rounded, and as shown in FIG. It has a hollow cylindrical structure that is not in contact. The center pin 50 serves to fix and support the electrode assembly, and serves as a passage for releasing gas generated by internal reactions under charge and discharge and abnormal operating conditions.

Figure 2 is a schematic diagram of the structure before the winding of the jelly-roll used in the secondary battery of Figure 1 is shown.

Referring to FIG. 2, the jelly-roll 20 separates a positive electrode sheet coated with the positive electrode active material 310 on both sides of the positive electrode plate 320 and a negative electrode sheet coated with the negative electrode active material 210 on both sides of the negative electrode plate 220. It is manufactured by winding round in the direction of the arrow in the state 400 is interposed. At one end of the positive electrode plate 320 is formed a non-coating portion 140 is not coated with the positive electrode active material 310, the positive electrode tab 510 has a lower end portion such that its upper end portion partially protrudes above the non-coating portion 140 To the uncoated portion 140.

Since the uncoated portion 140 is not coated with the positive electrode active material 310, even if a specific material is coated on the surface thereof, the non-coating portion 140 does not affect the operation characteristics of the battery. In particular, since the inner plain portion 140 located at the center of the jelly-roll 20 after winding is not easy to radiate, there is a high risk of ignition or explosion when heat is generated at such a portion.

Therefore, the microcapsule 600 containing the extinguishing agent is applied to the non-coated portion 140 of the positive electrode plate 320, so that an impact from the outside is applied to the jelly roll 20 so that an internal short circuit occurs at the positive electrode tab 510. When the temperature of the non-coating portion 140 reaches approximately 130 ° C., the shell (not shown) of the microcapsule 60 is destroyed, and the internal extinguishing agent is discharged, thereby greatly reducing the risk of fire or explosion of the battery. give. The microcapsule 600 may be applied to the positive electrode tab 510 on the non-coating portion 140 as well as the non-coating portion 140, and the microcapsule coating layer 610 also serves as a kind of insulating layer.

On the other hand, the cathode non-coating portion 240 located outside the jelly-roll 20 after the winding is relatively less dangerous even if heat is generated, compared to the positive electrode non-coating portion 140, which is the negative electrode non-coating portion ( This is because 240 is adjacent to a can (not shown), so there is little possibility of heat accumulation.

FIG. 3 is a perspective view schematically illustrating a center pin according to an embodiment of the present invention included in the cylindrical secondary battery of FIG. 1, and FIG. 4 is a horizontal cross-sectional view along a straight line AA of FIG. 3. It is.

Referring to these figures, the center pin 50 has an outer diameter R _C of 4 mm, and is applied to the hollow body 52 that imparts strength on a horizontal cross section, and the outer surface of the hollow body 52. It consists of including a microcapsule coating layer 610.

The hollow body 52 may be made of a metal material to impart a predetermined mechanical strength, and has a structure bent roundly so that both ends of the metal plate face each other. Through the hollow structure formed by the hollow body 52, the gas generated by the short circuit inside the battery can be smoothly discharged, and this increases the internal pressure of the cylindrical battery, thereby operating the safety vent and / or the CID. It is possible to improve the safety of the battery by blocking the discharge of the gas and the energization of the current, it is possible to prevent the phenomenon of the entire jelly-roll ejected in the harsh environment, such as high temperature to high pressure.

A plurality of microcapsules 600 containing a fire extinguishing agent forms a coating layer 610 on the outer surface of the hollow body 52 by a binder such as PVdF, and acts as an insulating layer of the center pin 50. do. In addition, when a high temperature is generated around the center pin 50 due to various causes, the microcapsule 600 is destroyed and the internal extinguishing agent is discharged to reduce the risk of fire or explosion of the battery.

Those skilled in the art to which the present invention pertains will be able to make various applications and modifications within the scope of the present invention based on the above contents.

As described above, according to the present invention, by applying a microcapsule containing a built-in safety collateral material to a portion of the battery that does not directly affect the operation of the battery and at the same time a thermal accumulation phenomenon easily occurs when the battery is abnormal In addition, the battery can be secured by ultimately suppressing the risk of fire or explosion due to rapid temperature rise inside the battery even in an abnormal operating state with little effect on the size, shape and performance of the battery.

Claims (13)

A secondary battery in which an electrode assembly having a cathode / membrane / cathode structure is built in a battery case, and a microcapsule containing a material that guarantees safety ('safety collateral') does not directly affect battery operation. And the coated portion is a position where heat accumulation phenomenon and short circuit due to internal pressure / external pressure are likely to occur when an abnormality occurs in the battery. The secondary battery of claim 1, wherein the security collateral material is a fire extinguishing material ('extinguishing agent') or a heat absorbing material. The method of claim 1, wherein the microcapsules are melted while the temperature of the battery reaches a temperature of 100 to 150 ℃, or the microcapsules are destroyed by an increase in the internal pressure, the safety collateral material is discharged to the outside of the capsule. battery. The method of claim 3, wherein the security material is a material that vaporizes or generates gas at a temperature of 100 to 150 ℃, the microcapsules are destroyed while the internal pressure increases by vaporization or gas generation of the material to destroy the vaporized material or gas Secondary battery, characterized in that the discharge. The secondary battery according to claim 1, wherein the safety collateral material is an inert gas that exhibits a fire extinguishing function or a substance that generates an inert gas by a chemical reaction ('gas generator'). The material according to claim 5, wherein the inert gas is embedded in the microcapsules in the form of a small volume of gas phase or in the form of a liquid by high pressure, or changes from liquid to gas phase based on a critical temperature of 100 to 150 ° C. 7. Phase change material ') is a secondary battery, characterized in that it is embedded in the microcapsules while maintaining a liquid state at the normal operating temperature of the battery. The _secondary gas generator of claim 5, wherein the gas generating agent is potassium bicarbonate (K ₂ CO ₃ ), sodium bicarbonate (NaHCO ₃ ), or manganese carbonate (MnCO ₃ ), which generates pyrolysis and generates carbon dioxide, which is an inert gas. battery. The secondary battery of claim 1, wherein the safety collateral is a fire extinguishing agent that vaporizes or generates gas at 100 to 150 ° C. 3. The secondary battery of claim 1, wherein the microcapsules have a particle size of 1 to 500 μm. The method of claim 1, wherein the battery is a cylindrical battery, the microcapsule is characterized in that applied to the inner uncoated portion, the center pin, or the electrode tab on the inner uncoated portion of the current collector is not applied to the electrode mixture. Secondary battery. The secondary battery according to claim 1, wherein the battery is a rectangular battery, and the microcapsule is applied to an inner plain portion, which is a portion of the current collector to which the electrode mixture is not applied, or an electrode tab on the inner plain portion. A medium-large battery module comprising the secondary battery according to claim 1 as a unit cell. The medium and large battery module of claim 12, wherein the battery module is used for a power source of a notebook computer, an e-bike, an electric vehicle, or a hybrid electric vehicle.

Images