KR20140024600A - Lithium ion secondary battery cell and module comprising phase change material - Google Patents

Abstract

The present invention relates to a lithium secondary battery cell and a module which include phase change materials. According to an embodiment of the present invention: the lithium secondary battery cell which comprises the lithium secondary battery cell including an electrode-separation film assembly which includes a positive electrode, a negative electrode, and a separation film interposed between the positive and negative electrodes, and pouches which surround the external front surface of the electrode-separation film assembly, and in which at least one surface of the inside or outside of the pouch is coated with phase change materials; and the lithium secondary battery module which comprises one or more of electrode-separation film assemblies including the positive electrode, negative electrode, and separation film interposed between the positive and negative electrodes, the pouches which respectively surround the external front surface of the electrode-separation film assemblies, and one or more covers which surround external front surface of pouches, and in which one or more between the pouches and between the pouch and the cover are coated with the phase change materials are provided. According to the present invention, the lithium secondary battery to which the phase change materials are applied absorbs heat and maintains an insulation state between electrodes or between an electrode and a penetration object if the temperature of the object is drastically increased, or the object is penetrated from the outside in order to enhance safety of the battery by suppressing ignite and explosion of the battery.

Description

Lithium ion secondary battery cell and module comprising phase change material

The present invention relates to a lithium ion secondary battery cell and module including a phase change material (PCM).

BACKGROUND ART [0002] With the recent development of the information communication industry, as electronic devices have become smaller, lighter, thinner, and portable, there is a growing demand for higher energy density of batteries used as power sources for such electronic devices. Lithium-ion secondary batteries are the batteries that can best meet these needs, and research is being actively conducted on them.

However, when the lithium ion secondary battery is overcharged due to misuse or failure of a charger, or an internal short circuit occurs due to a design defect, penetration, or external shock of the battery itself, the temperature of the battery may increase rapidly. have. When the temperature of such a battery rises rapidly, the battery becomes very unstable due to the reaction between the electrolyte and lithium or the oxidation of the positive electrode, and the solvent of the electrolyte is decomposed to generate gas. The decomposition gas of the solvent may ignite and lead to explosion of the battery.

As a means for improving the stability problem, there is a method of forcibly discharging the electrolyte, the method for protecting the battery in a control PTC (Positive Temperature Coefficient) circuit of the pack to which the battery is connected. However, this method has a limit that is likely to cause a malfunction if a circuit problem occurs. In addition, there have been attempts to apply a device that cuts off the current using a force that the cell expands, such as a current blocking element, but there is still a need to make it work faster.

As a result, there is still a need for an effort to suppress sudden temperature rise during the abnormal behavior of battery cells and modules, and to block current flow to improve stability.

Therefore, the problem to be solved by the present invention, when the temperature of the lithium ion secondary battery rapidly rises or the object penetrates from the outside, absorbs heat and interferes with the electrical flow by the penetrating object, stable lithium ion secondary battery cells and lithium It is to provide an ion secondary battery module.

In order to achieve the above object, according to an aspect of the present invention, an electrode-membrane assembly having an anode, a cathode and a separator interposed between the anode and the cathode, and a pouch surrounding the outer front of the electrode-separator assembly ( A pouch) is provided, and a lithium ion secondary battery cell coated with a phase change material on at least one surface of the inside or outside of the pouch is provided.

According to another aspect of the invention, at least one electrode-membrane assembly having an anode, a cathode and a separator interposed between the anode and the cathode, and a pouch surrounding the outer front of each of the electrode-membrane assembly, the at least one pouch A lithium ion secondary battery module having a cover surrounding an outer front surface of all, and coated with a phase change material between at least one of the pouches and between the pouch and the cover is provided.

According to the present invention, a lithium ion secondary battery to which a phase change material is applied may absorb heat and maintain insulation between electrodes or between an electrode and a penetrating object when its temperature rises rapidly or an object penetrates from the outside. By suppressing ignition and explosion, the safety of the battery can be improved.

1 is a schematic diagram illustrating absorption of heat due to a temperature change of an electrode-membrane assembly by a phase change phenomenon of a phase change material.
FIG. 2 is a schematic diagram illustrating that when a battery cell is penetrated, an electric flow of the penetrating object is disturbed by surrounding the object by a phase change of the phase change material.
3 illustrates an embodiment of a battery cell to which a phase change material is applied.
4 illustrates another embodiment of a battery cell to which a phase change material is applied.
5 illustrates an embodiment of a battery module to which a phase change material is applied.
6 illustrates another embodiment of a battery module to which a phase change material is applied.

The terms used in the specification and claims should not be construed as limited to ordinary or dictionary terms and the inventor may properly define the concept of a term to describe its invention in its best possible way And should be construed in accordance with the principles and meanings and concepts consistent with the technical idea of the present invention. Therefore, the embodiments described in the specification and the drawings shown in the drawings are only one of the most preferred embodiments of the present invention and do not represent all of the technical idea of the present invention, it is possible to replace them at the time of the present application It should be understood that there may be various equivalents and variations.

FIG. 1 exemplifies absorption of heat due to a phase change phenomenon of the phase change material 3 due to an increase in the temperature of the electrode-separation membrane assembly 1 when an external short circuit and overcharge occurs, for example, of a battery cell surrounded by the pouch 2. 2 illustrates that the battery cell penetrates the object by the phase change of the phase change material 3, thereby disturbing the electrical flow of the penetrating object 4.

In secondary batteries, materials such as carbon-based materials are generally used as a negative electrode (not shown), materials such as lithium-based oxides are used as a positive electrode (not shown), and lithium salts are dissolved in an organic solvent as an electrolyte. If the battery is overcharged, the electrolyte may be decomposed at the positive electrode, the metal may be precipitated at the negative electrode, resulting in deterioration of battery characteristics, and there may be a risk of heat generation or ignition. In addition, since the polymer electrolyte is locally overheated during charging and discharging, the polymer electrolyte, which is weak to heat, may be partially dissolved or softened, resulting in nonuniformity of current and potential, thereby causing a risk of short circuit, fire, and explosion.

3 illustrates one embodiment of a battery cell to which a phase change material is applied, and FIG. 4 illustrates another embodiment of a battery cell to which a phase change material is applied.

3 and 4, the present invention relates to a lithium ion secondary battery cell having a pouch 2 surrounding an outer front surface of an electrode-membrane assembly 1. By applying a phase change material (3) on at least one side was to solve the above-mentioned problems of the lithium ion secondary battery. Here, the electrode-membrane assembly 1 may include an anode (not shown), a cathode (not shown), and a separator (not shown) interposed between the anode and the cathode.

Referring to FIG. 3 as an example, a phase change material 3 is applied to an upper surface of the pouch 2 surrounding the outer front surface of the electrode-membrane assembly 1. In this embodiment, in the case of a rapid temperature rise inside or outside the cell or in the case of penetration of an external object, the phase change material 3 having a specific range of phase change temperature T _PC , as described in FIG. 1 or 2. The heat in the battery can be removed or the insulating state in the battery can be maintained as it is. In addition, the phase change material 3 may be applied to one surface other than the upper surface of the pouch 2 mentioned above, for example, a lower surface or a side surface.

As another example, referring to FIG. 4, a phase change material may be formed on the top surface of the electrode-membrane assembly 1 within the space between the pouch 2 and the electrode-membrane assembly 1, specifically, inside the pouch 2. 3) is applied. Similar to FIG. 3, in the case of a rapid temperature rise inside or outside of a battery or in the penetration of an external object, as described in FIG. 1 or 2, a phase change material having a specific range of phase change temperature T _PC ( 3), the heat in the battery can be removed or the insulating state in the battery can be maintained as it is. In addition, the phase change material 3 is formed in a space between the pouch 2 other than the upper surface of the electrode-membrane assembly 1 and the electrode-membrane assembly 1, such as the pouch 2, inside the pouch 2 mentioned above. ) May be applied to the lower surface or the side of the electrode-membrane assembly 1.

The phase change material refers to a material used for the purpose of storing energy or keeping a temperature constant by using the latent heat absorption or release effect of the material. Here, the latent heat means heat absorbed or released at the same temperature as the material changes phase, that is, from solid to liquid or from liquid to solid, from liquid to gas, or from gas to liquid, and latent heat refers to sensible heat (phase Very much greater than the amount of heat absorbed or released without change). As described above, the phase change material gradually increases the temperature when the ambient temperature is high, and gradually decreases the temperature when the ambient temperature is low. Specifically, if the phase change material has its own phase change temperature (T _PC ) or if a constant temperature is stored for the material, the phase change material releases heat or stores heat while changing the phase in the temperature range. To increase or decrease the ambient temperature. Therefore, when moving from a low temperature place to a high temperature place, the solid phase is changed into a liquid phase to take away the surrounding heat, thereby cooling the surroundings. It can release the heat to increase the ambient temperature.

Various phase change materials may be used for the lithium ion secondary battery cells and modules of the present invention. Since the phase change material is used to remove heat generated due to abnormal operation or penetration of an external object in the battery, the phase change temperature T _{PC thereof} is not limited. For example, a phase change material present in the solid phase at room temperature, such as less than about 60 ° C., or less than about 25 to about 50 ° C., changes to a liquid phase at a phase change temperature T _{PC of} at least about 50 ° C. Changing materials may be used but are not limited to these. Basically, the operating temperature range of the cell is up to about 60 ° C., the range for maintaining the solid phase is about 25 to about 50 ° C., and the temperature for the liquid phase is about 50 to about 95 ° C. In addition, since the degree of heat generation varies slightly depending on the type of battery, it has a phase change temperature (T _PC ) of about 50 ° C. or more, preferably about 50 ° C. to about 90 ° C., and more preferably about 50 ° C. to about 70 ° C. Phase change materials can be used.

As also shown in FIG. 2, when the external object 4 penetrates the cell, in particular the electrode-membrane assembly 1, when the external object 4 is conductive, the conductive object 4 is in contact with the electrode. Although the flow of electricity may result and overheat, if the phase change material 3 is a phase change material having the above-described properties (eg, phase change temperature T _PC ), such phase change material may be in contact with and If the ambient ambient temperature rises above at least approximately 50 ° C., the solid phase of the phase change material will turn into a liquid phase and take away ambient heat. In other words, excessively generated heat in the battery can be removed.

Examples of such phase change materials may be, but are not limited to, one or two or more mixtures selected from the group consisting of paraffins such as C ₂₀ -C ₄₅ paraffins, inorganic salts, salt hydrates and mixtures thereof, carboxylic acids and sugar alcohols, and the like. not. Preferably, examples of the phase change material include tetracoic acid (melting point about 53 ° C), hexacoic acid (melting point about 56 ° C), nonacoic acid (melting point about 63 ° C), sodium acetate trihydrate (melting point about 58 ° C), sodium Hydroxide monohydrate (melting point about 64 ° C), a mixture of lithium nitrate and magnesium nitrate hexahydrate (melting point about 75 ° C), trisodium phosphate dodecahydrate (melting point about 75 ° C), magnesium nitrate hexahydrate ( Melting point about 89 ° C.), myristic acid (melting point about 52 ° C.), stearic acid (melting point about 69 ° C.), xylitol (melting point about 93-95 ° C.), etc. It is not limited.

In addition, in order to increase the thermal conductivity of the phase change material, at least one auxiliary agent having excellent thermal conductivity may be further applied to the lithium ion secondary battery cell or module together with the above-described phase change material. The one or more adjuvants may be materials or compositions with good thermal conductivity, in particular metal powders, metal granules or graphite.

The method of applying the phase change material on the inner and outer surfaces of the pouch of the lithium ion secondary battery cell may use a conventional coating method known in the art, for example, melting the phase change material above the melting point to melt The coating may be applied in various ways such as dip coating, die coating, roll coating, comma coating, or a mixture thereof.

The application amount of the phase change material may vary greatly depending on the type of battery used, for example, a battery used in a mobile phone, HEV, PHEV, EV, and the like. For example, the amount of application of the phase change material may vary depending on the area of the pouch facing the electrode-membrane assembly, the amount of heat generated by the cell, and the like. Since the area and the calorific value of the pouch vary depending on the battery used, the coating amount of the phase change material of the present invention may also vary greatly according to the area of the pouch and the calorific value of the battery that vary depending on the cell used. In addition, the calorific value of the battery varies greatly depending on the capacity of a battery that is commonly used. When the capacity of the battery is large, the calorific value of the battery increases accordingly, and the coating amount may also increase. In addition, the coating amount can be increased in proportion to the thickness of the battery used. For example, the coverage of the phase change material can be the same as the pouch area, and the applied thickness of the phase change material can be the same as the thickness of the cell.

Typically, the phase change material is formed of the electrode-membrane assembly in various spaces to which it is applied, such as the top of the aforementioned electrode-membrane assembly, the space between the pouch and the electrode-membrane assembly, such as inside the pouch. When present in an appropriate amount in whole or in part on the lower surface or side, etc., it is possible to sufficiently absorb the heat generated rapidly inside the battery, and after the heat dissipation, if the battery recovers to a normal state, the phase change material present in the interior thereof is room temperature. For example, back to the solid phase at less than about 50 ° C., thereby allowing the cell to be reused.

Accordingly, the phase change material of the present invention may improve the safety of the battery by absorbing heat alone or in combination with a thermal conductive aid when the temperature of the battery increases rapidly during overcharging or internal short circuit of the lithium ion secondary battery. .

Meanwhile, the positive electrode, the negative electrode, the separator, the electrolyte solution, the pouch, the cover, and the like used in the present invention can be easily manufactured by processes and / or methods known in the art. As the positive electrode, the negative electrode, and the separator constituting the electrode-separation membrane assembly, all of those conventionally used in manufacturing a lithium ion secondary battery may be used.

Specifically, the positive electrode is prepared in a form in which the positive electrode active material is bound to the positive electrode current collector according to a conventional method known in the art, and serves to store and release lithium ions. As the cathode active material, a conventional cathode active material that can be used for a cathode of a conventional secondary battery can be used, and examples thereof include LiCoO ₂ , LiNiO ₂ , LiMnO ₂ , LiMn ₂ O ₄ , Li (Ni _a Co _b Mn _{c) O 2 (0 <a} <1, 0 <b <1, a + b + c = 1), LiNi 1 - Y Co Y O 2, LiCo 1 - Y Mn Y O 2, LiNi 1 -Y Mn Y O ₂ (where, 0≤Y <1), Li ( Ni a Co b Mn c) O 4 (0 <a <2, 0 <b <2, a + b + c = 2), LiMn 2 - Z Ni _Z O ₄ , LiMn _{2 -Z} Co _Z O ₄ (where 0 <Z <2), LiCoPO ₄ , LiFePO _4, and mixtures thereof. As the positive electrode collector, aluminum, nickel, or a foil produced by a combination of these may be used.

The negative electrode is manufactured by binding an anode active material to an anode current collector according to a conventional method known in the art, and performs a function of intercalating and deintercalating lithium ions in the same manner as the anode. At this time, the negative electrode active material may be carbon such as non-graphitized carbon or graphite carbon; Li _x Fe ₂ O ₃ (0? _X? 1), Li _x WO ₂ (0? _X? 1), Sn _x Me _{1 -x} Me _y O _z (Me: Mn, Fe, Pb, : Metal complex oxides of Al, B, P, Si, Group 1, Group 2, Group 3 elements of the periodic table, halogen, 0 &lt; x &lt; Lithium metal; Lithium alloy; Silicon-based alloys; Tin alloy; _{SnO, SnO 2, PbO, PbO} 2, Pb 2 O 3, Pb 3 O 4, Sb 2 O 3, Sb 2 O 4, Sb 2 O 5, GeO, GeO 2, Bi 2 O 3, Bi 2 O 4, Bi ₂ O ₅ and the like; Conductive polymers such as polyacetylene; Li-Co-Ni-based materials and the like can be used. On the other hand, as the negative electrode collector, stainless steel, nickel, copper, titanium or an alloy thereof can be used.

Separation membrane is provided between the positive electrode and the negative electrode to maintain an insulating state to prevent a short circuit, a polymer membrane such as polyolefin, polypropylene, polyethylene or the like, multiple membranes thereof, microporous film, woven fabric and nonwoven fabric can be used. In addition, an organic / inorganic particle coating layer may be formed over the separator as is known in the art.

Electrolyte solution is A ⁺ B ^- A salt of the structure, such as, A ⁺ is Li ^+, Na ^+, K ⁺ comprises an alkaline metal cation or an ion composed of a combination thereof, such as, and B ^- is PF ₆ ^-, BF ₄ ^{-, Cl -, Br -, I -} , ClO 4 -, AsF 6 -, CH 3 CO 2 -, CF 3 SO 3 -, N (CF 3 SO 2) 2 -, C (CF 2 SO 2) 3 - , such as Salts comprising ions of anions or combinations thereof include propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), dimethyl sulfoxide, aceto Nitrile, dimethoxyethane, diethoxyethane, tetrahydrofuran, N-methyl-2-pyrrolidone (NMP), ethylmethylcarbonate (EMC), gamma butyrolactone (γ-butyrolactone) or mixtures thereof Some are dissolved or dissociated in the organic solvent, but are not limited thereto.

Pouches can be used without limitation as long as the material does not dissolve in the electrolyte. The pouch may be configured in the form of interposing a metal thin film, such as an aluminum thin film, in order to improve the electrochemical properties of the battery cell and to improve heat dissipation. In addition, in order to ensure insulation between the battery cell and the outside, the aluminum thin film may include an insulating layer (not shown) coated with an insulating material such as polyethylene terephthalate (PET) resin or nylon (nylon) resin. It may be formed on the outside. The inner surface of the pouch for sealing may form an adhesive layer (not shown) made of a heat adhesive resin. Therefore, the pouch may form an adhesive layer on the inner surface of the metal thin film and an insulating layer on the outer surface thereof, and the heat-adhesive resin coated on the inner surface may be fused and sealed by heating and pressing.

5 illustrates an embodiment of a battery module to which a phase change material is applied, and FIG. 6 illustrates another embodiment of a battery module to which a phase change material is applied.

5 and 6, according to another embodiment of the present invention, an anode (not shown), a cathode (not shown), and a separator interposed between the anode and the cathode (not shown) At least one electrode-membrane assembly (1), and a pouch (2) surrounding the outer front of each of the electrode-membrane assemblies (1), and a cover (5) surrounding the outer front of all of the at least one pouch (2) In the lithium ion secondary battery module having a, characterized in that the phase change material (3) is applied between at least one of the pouches (2) and between the pouch (2) and the cover (5). .

Here, the materials and configurations of the positive electrode, the negative electrode, the separator, the electrode-membrane assembly and the pouch are as described above.

The cover 5 may have the same material and construction as the pouch 2 described above in one embodiment. In other embodiments, the cover 5 may be free of electrolyte therein, so examples of the material may be extensive. Also, the cover 5 forms an insulating layer (not shown) on the outside similarly to the pouch 2 described above, and forms an adhesive layer (not shown) made of a heat-adhesive resin on the inner surface for sealing. can do.

1-electrode-membrane assembly
2 - Pouch
3-phase change material
4-penetrating object
5-cover

Claims (11)

An electrode-membrane assembly having an anode, a cathode and a separator interposed between the anode and the cathode, and a pouch surrounding the outer front surface of the electrode-membrane assembly,
A lithium ion secondary battery cell coated with a phase change material (PCM) on at least one surface of the inside or outside of the pouch. The method of claim 1,
And the phase change material has a phase change temperature (T _PC ) of 50 ° C. or higher. The method of claim 1,
The phase change material is a lithium ion secondary battery cell, characterized in that one or two or more selected from the group consisting of paraffins, inorganic salts, hydrates, carboxylic acids and sugar alcohols. The method of claim 3,
The phase change material may be tetracoic acid, hexacoic acid, nonacoic acid, sodium acetate trihydrate, sodium thiosulfate pentahydrate, sodium hydroxide monohydrate, a mixture of lithium nitrate and magnesium nitrate hexahydrate, trisodium phosphate Lithium ion secondary battery cell, characterized in that one or two or more selected from the group consisting of dodecahydrate, magnesium nitrate hexahydrate, myristic acid, stearic acid and xylitol. The method of claim 1,
A lithium ion secondary battery cell, wherein the at least one auxiliary agent having excellent thermal conductivity is further applied together with the phase change material. 6. The method of claim 5,
Lithium ion secondary battery cell, characterized in that the auxiliary agent is a metal powder, metal granules or graphite. The method of claim 1,
And the coating amount of the phase change material is adjusted according to the area of the pouch facing the electrode-separator assembly, the capacity of the battery, or the amount of heat generated. At least one electrode-membrane assembly having an anode, a cathode and a separator interposed between the anode and the cathode, a pouch surrounding the outer front of each of the electrode-membrane assemblies, and a cover surrounding the outer front of all of the at least one pouch. But
Lithium ion secondary battery module is a phase change material is applied between at least one of the pouch and between the pouch and the cover. 9. The method of claim 8,
The phase change material has a phase change temperature (T _PC ) of 50 ℃ or more lithium ion secondary battery module. 9. The method of claim 8,
The phase change material is a lithium ion secondary battery module, characterized in that one or two or more selected from the group consisting of paraffins, inorganic salts, hydrates, carboxylic acids and sugar alcohols. 9. The method of claim 8,
And the coating amount of the phase change material is adjusted according to the area of the pouch facing the electrode-separator assembly, the capacity of the battery, or the amount of heat generated.

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