CN115975607A - Heat absorption composite material, heat absorption composite structure and preparation method thereof, and lithium ion battery unit - Google Patents
Heat absorption composite material, heat absorption composite structure and preparation method thereof, and lithium ion battery unit Download PDFInfo
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Abstract
The invention relates to the technical field of lithium ion batteries, in particular to a heat absorption composite material, a heat absorption composite structure, a preparation method of the heat absorption composite structure and a lithium ion battery unit. The heat absorption composite material comprises a first organic material and a second organic material which are uniformly mixed, wherein the first organic material contains at least one of acid anhydride groups, ester groups, isocyanate groups and aldehyde groups, the second organic material contains at least one of hydroxyl groups, carboxyl groups and amino groups, and the heat absorption composite material is suitable for being arranged on the outer surface of the battery core. The heat absorption composite material is arranged on the outer surface of the battery core, so that the safety of the lithium ion battery unit can be improved.
Description
Technical Field
The invention relates to the technical field of lithium ion batteries, in particular to a heat absorption composite material, a heat absorption composite structure, a preparation method of the heat absorption composite structure and a lithium ion battery unit.
Background
With the development of new energy automobiles, lithium ion batteries are gradually replacing gasoline as a power source of automobiles. However, the safety performance of the lithium ion battery has a great restriction on the development of the electric vehicle. The lithium ion battery contains an oxidant, a reducing agent and flammable electrolyte, and has potential safety hazards of fire and explosion all the time. When a certain battery cell in the battery pack abnormally generates heat due to short circuit or unbalanced electrical property in the charging and discharging process, once the temperature of the certain battery cell exceeds the critical temperature (generally about 150 ℃) of thermal runaway), the material inside the battery cell can continuously generate thermal decomposition exothermic reaction, so that the temperature of the battery cell rapidly rises to generate the thermal runaway, the battery cell fires, and the temperature of the battery cell can exceed more than 500 ℃ during the thermal runaway. If there is not the excellent thermal-insulated structure of heat-proof quality between the adjacent electric core, then the heat that electric core thermal runaway released can spread to neighbouring electric core rapidly to arouse that adjacent electric core also takes place thermal runaway, finally lead to whole battery package to take place comprehensive thermal runaway, produce violent burning exothermic reaction, can even produce the explosion when serious. Therefore, the control of the thermal spread is crucial to the improvement of the safety of the lithium ion battery.
At present, a heat insulation film is generally arranged between adjacent cells to prevent heat spreading after thermal runaway of a single cell, and the material of the heat insulation film comprises heat insulation materials such as aerogel or mica sheets. However, the heat insulation effect of the heat insulation material is limited, and the heat insulation material is not enough to insulate heat generated when the battery core is out of control due to heat, so that the battery pack still has certain potential safety hazards.
Disclosure of Invention
Therefore, the technical problem to be solved by the present invention is how to improve the safety of the lithium ion battery, thereby providing a heat absorption composite material, a heat absorption composite structure, a preparation method thereof, and a lithium ion battery unit.
In a first aspect, the present invention provides an endothermic composite comprising a first organic material containing at least one of an acid anhydride group, an ester group, an isocyanate group, and an aldehyde group, and a second organic material containing at least one of a hydroxyl group, a carboxyl group, and an amino group, which are uniformly mixed, the endothermic composite being adapted to be disposed on an outer surface of a battery cell.
Optionally, the first organic material contains at least one of a polybasic acid anhydride, a polybasic ester, a polybasic isocyanate, and a polybasic aldehyde.
Optionally, the first organic material is subjected to end capping treatment by using an end capping agent, and the difference between the deblocking temperature of the first organic material and the thermal runaway critical temperature of the lithium ion battery is-50 ℃ to 20 ℃.
Optionally, the unblocking temperature is greater than or equal to 130 ℃; the blocking agent comprises at least one of nonyl phenol, caprolactam, methyl ethyl ketoxime, dimethyl pyrazole, ethylene-propylene-amine, diethyl malonic acid, imidazole and phenol.
Optionally, the boiling points of the first organic material and the second organic material are both greater than the deblocking temperature of the first organic material.
Optionally, the first organic material comprises at least one of phthalic anhydride, pyromellitic anhydride, dimethyl terephthalate, benzene diisocyanate, toluene diisocyanate, and terephthalaldehyde; the second organic material comprises at least one of polyethylene glycol, terephthalic acid, adipic acid, suberic acid, hexamethylene diamine, m-phenylenediamine and dichlorodiphenyl sulfone.
Optionally, the ratio of the molar amounts of the first organic material and the second organic material is 1 to 1.5.
Optionally, the endothermic composite further includes a catalyst, the catalyst is uniformly mixed with the first organic material and the second organic material, and the mass of the catalyst is 0.1% to 5% of the total mass of the first organic material and the second organic material.
Optionally, the catalyst is a solid catalyst.
Optionally, the catalyst comprises at least one of bis-dimethylamino ethyl ether, pentamethyl diethylenetriamine, dimethyl cyclohexylamine, dibutyltin dilaurate, organic bismuth and triazine trimerization catalyst.
Optionally, the heat absorption composite material further comprises a thermoplastic material, the thermoplastic material is uniformly mixed with the first organic material and the second organic material, and the mass of the thermoplastic material is 1% -20% of the total mass of the first organic material and the second organic material.
Optionally, the thermoplastic material includes at least one of polyethylene, polypropylene, polyamide, polyimide, polyoxymethylene, polycarbonate, polyetheretherketone, phenolic resin, and amino resin.
Optionally, the heat-absorbing composite material heat-insulating material is uniformly mixed with the first organic material and the second organic material, and the mass of the heat-insulating material accounts for 1% -50% of the total mass of the first organic material, the second organic material and the heat-insulating material.
Optionally, the heat insulating material includes at least one of carbon aerogel, graphene aerogel, silicon-carbon-oxygen aerogel, porous silica, porous alumina, porous titanium dioxide, phenolic aerogel, polyurethane aerogel and polyurea aerogel.
In a second aspect, the present invention provides a method for preparing an endothermic composite structure, comprising the steps of: uniformly mixing the heat-absorbing composite material with a fiber substrate to obtain a mixture; and carrying out hot pressing on the mixture to obtain a heat absorption composite structure, wherein the heat absorption composite structure is suitable for being attached to the outer surface of the battery core.
Optionally, the mass fraction of the fibrous substrate in the mixture is 40% to 70%.
Optionally, the fiber substrate includes at least one of glass fibers, ceramic fibers, carbon fibers, sepiolite fibers, and polyimide fibers.
Optionally, the thickness of the heat absorption composite structure is 0.1 mm-10 mm.
In a third aspect, the invention provides an endothermic composite structure, which is prepared by the preparation method of the endothermic composite structure.
In a fourth aspect, the present invention provides a lithium ion battery unit, which includes a housing and a plurality of battery cells located in the housing, wherein the outer surface of the battery cell is provided with the above heat absorption composite structure.
Optionally, the inner surface of the outer shell is also provided with the heat absorbing composite structure.
The technical scheme of the invention has the following advantages:
1. in the heat-absorbing composite material provided by the invention, acid anhydride groups, ester groups, isocyanate groups or aldehyde groups in the first organic material can be subjected to condensation reaction with active hydrogen in the second organic material, a large amount of heat is absorbed in the condensation reaction process, the heat-absorbing composite material is arranged on the outer surface of a battery cell, the heating rate of an adjacent battery cell can be reduced, and the highest temperature of the adjacent battery cell is controlled below a thermal runaway critical temperature, so that the thermal runaway of the adjacent battery cell is avoided, and the thermal spreading degree is controlled; meanwhile, after the electric core is out of control thermally, the polymer formed by the reaction of the first organic material and the second organic material is cracked when the temperature of the electric core reaches above 400 ℃, the cracking reaction can absorb heat further, so that the heating rate of the adjacent electric core is further reduced, and a large amount of moisture, carbon dioxide and other non-combustible gases generated by the reaction can slow down the outward diffusion of smoke and flame generated by the out of control thermally. In conclusion, the safety of the lithium ion battery unit can be improved by arranging the heat absorption composite material on the outer surface of the battery cell.
2. In the heat-absorbing composite material provided by the invention, the first organic material is subjected to end capping treatment by adopting an end capping agent, the difference between the deblocking temperature of the first organic material and the thermal runaway critical temperature of the lithium ion battery is-50-20 ℃, the first organic material and the second organic material are suitable for endothermic reaction after deblocking, namely, when the temperature of a battery core is about to reach the thermal runaway critical temperature or just reaches the thermal runaway critical temperature, the first organic material and the second organic material can perform endothermic reaction, heating caused by normal operation of the battery core can not induce the endothermic reaction of the heat-absorbing composite material, the heat-absorbing composite material is completely used for the battery core about to generate thermal runaway or just generate thermal runaway, so that the failure of the heat-absorbing composite material caused by complete reaction of the heat-absorbing composite material before the thermal runaway of the battery core is avoided, and the degree of thermal spreading can be controlled by the heat-absorbing composite material when the thermal runaway of the battery core is generated, and further the thermal runaway of an adjacent battery core is avoided.
3. In the heat-absorbing composite material provided by the invention, the boiling points of the first organic material and the second organic material are both greater than the deblocking temperature of the first organic material, so that the first organic material and the second organic material are prevented from being volatilized and gasified before the temperature of the battery core reaches the deblocking temperature, the heat-absorbing composite material is ensured to be capable of generating a heat-absorbing reaction when the battery core is out of control due to heat, and the heat-absorbing composite material is prevented from being invalid.
4. In the heat-absorbing composite material provided by the invention, the first organic material contains at least one of polybasic acid anhydride, polybasic ester, polybasic isocyanate and polybasic aldehyde, and on one hand, the first organic material is a macromolecular material and has higher stability; on the other hand, if the number of the active groups in the first organic material is larger, the reaction rate is higher, and more heat can be absorbed in unit time, so that the heating rate of the adjacent battery cell is further reduced, and the thermal runaway of the adjacent battery cell is more effectively avoided.
5. In the heat absorption composite material provided by the invention, the reaction rate can be increased by adding the catalyst, so that more heat can be absorbed in unit time, the heating rate of the adjacent electric core is further reduced, and the thermal runaway of the adjacent electric core is further effectively avoided.
6. The heat absorption composite material provided by the invention also comprises a thermoplastic material, wherein the thermoplastic material can load materials such as a first organic material, a second organic material and the like; the thermoplastic material can be melted after the temperature of the battery cell rises, so that phase change heat absorption is generated, the heating rate of the adjacent battery cell can be further reduced, and thermal runaway of the adjacent battery cell is more effectively avoided.
7. The heat absorption composite material provided by the invention also comprises a heat insulation material, wherein the heat insulation material can prevent heat generated by the battery cell from being transferred to an adjacent battery cell, and can further reduce the heating rate of the adjacent battery cell, so that thermal runaway of the adjacent battery cell is more effectively avoided.
8. The heat absorption composite structure provided by the invention can be used for controlling the degree of heat spreading by attaching the heat absorption composite structure to the outer surface of the battery cell, and the using method is simple.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.
Fig. 1 is a schematic structural view of an endothermic composite structure provided in example 2 of the present invention;
FIG. 2 is a schematic view of the structure in the test process of Experimental example 1;
fig. 3 is a variation curve of the temperature and the voltage of the first cell and the second cell;
fig. 4 is a variation curve of the temperature and the voltage of the third cell and the fourth cell;
description of reference numerals:
1-a heat absorbing composite structure; 11-a heat absorbing composite; 12-a fibrous substrate; 2-a first cell; 3-a second cell; 4-heating plate.
Detailed Description
The technical solutions of the present invention are described clearly and completely below, and it is obvious that the described embodiments are some, not all embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention. In the description of the present invention, the terms "first", "second", and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
The examples do not show the specific experimental steps or conditions, and can be performed according to the conventional experimental steps described in the literature in the field. The reagents or instruments used are conventional reagent products which are commercially available, and manufacturers are not indicated.
In addition, the technical features involved in the different embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
Example 1
The present embodiment provides an endothermic composite, including a first organic material containing at least one of an acid anhydride group, an ester group, an isocyanate group, and an aldehyde group, and a second organic material containing at least one of a hydroxyl group, a carboxyl group, and an amino group, which are uniformly mixed, the endothermic composite being adapted to be disposed on an outer surface of a battery cell.
In the heat-absorbing composite material, acid anhydride groups, ester groups, isocyanate groups or aldehyde groups in the first organic material can perform condensation reaction with active hydrogen in the second organic material, a large amount of heat is absorbed in the condensation reaction process, the heat-absorbing composite material is arranged on the outer surface of the battery cell, the heating rate of the adjacent battery cell can be reduced, and the highest temperature of the adjacent battery cell is controlled below the thermal runaway critical temperature, so that the thermal runaway of the adjacent battery cell is avoided, and the thermal spreading degree is controlled; meanwhile, after the battery core is thermally out of control, the polymer formed by the reaction of the first organic material and the second organic material is cracked when the temperature of the battery core reaches above 400 ℃, the cracking reaction can absorb heat further, so that the heating rate of the adjacent battery core is further reduced, and a large amount of moisture, carbon dioxide and other non-combustible gases generated by the reaction can slow down the outward diffusion of smoke and flame generated by the thermal out of control. In conclusion, the safety of the lithium ion battery unit can be improved by arranging the heat absorption composite material on the outer surface of the battery cell.
Preferably, the first organic material contains at least one of a polybasic acid anhydride, a polybasic ester, a polybasic isocyanate, and a polybasic aldehyde. On one hand, the first organic material is a macromolecular material and has higher stability; on the other hand, if the number of the active groups in the first organic material is larger, the reaction rate is higher, and more heat can be absorbed in unit time, so that the heating rate of the adjacent battery cell is further reduced, and thermal runaway of the adjacent battery cell is further effectively avoided.
In a preferred embodiment, the first organic material is blocked by a blocking agent, the difference between the deblocking temperature of the first organic material and the critical temperature of thermal runaway of the lithium ion battery is-50 ℃ to 20 ℃, and the first organic material and the second organic material are suitable for endothermic reaction after deblocking. That is, only when the cell temperature is about to reach thermal runaway critical temperature or just reaches thermal runaway critical temperature, first organic material can take place endothermic reaction with second organic material, and the generating heat that the normal working process of electric core leads to can not induce endothermic combined material to take place endothermic reaction, endothermic combined material is whole to be used for about to take place thermal runaway or just take place thermal runaway's electric core, this has avoided the endothermic combined material that endothermic combined material reaction leads to completely before thermal runaway takes place at electric core to lose efficacy, the thermal creep's degree can be controlled to endothermic combined material when thermal runaway takes place at electric core, and then avoid neighbouring electric core to take place thermal runaway.
Specifically, the deblocking temperature is greater than or equal to 130 ℃, and is determined by the blocking agent. The blocking agent includes, but is not limited to, at least one of nonylphenol, caprolactam, methyl ethyl ketoxime, dimethylpyrazole, ethylene-propylene-amine, diethyl malonic acid, imidazole, phenol.
Furthermore, the boiling points of the first organic material and the second organic material are both greater than the deblocking temperature of the first organic material, so that the first organic material and the second organic material can be prevented from being volatilized and gasified before the temperature of the battery core reaches the deblocking temperature, endothermic reaction of the endothermic composite material can be ensured when the battery core is out of control due to heat, and the endothermic composite material is prevented from being invalid.
Specifically, the first organic material includes, but is not limited to, at least one of phthalic anhydride, pyromellitic anhydride, dimethyl terephthalate, phenylene diisocyanate, toluene diisocyanate, and terephthalaldehyde, and the second organic material includes, but is not limited to, at least one of polyethylene glycol, terephthalic acid, adipic acid, suberic acid, hexamethylene diamine, m-phenylenediamine, and dichlorodiphenyl sulfone. The ratio of the molar amounts of the first organic material and the second organic material is 1 to 1.5. Illustratively, the ratio of the molar amounts of the first organic material and the second organic material can be 1, 1.1, 1.2, 1.3, 1.4, or 1.5, and any number therein.
As a preferred embodiment, the endothermic composite further includes a catalyst, and the catalyst is uniformly mixed with the first organic material and the second organic material, and the addition of the catalyst can increase the reaction rate, so that more heat can be absorbed in a unit time, thereby further reducing the temperature rise rate of the adjacent cell, and further more effectively avoiding thermal runaway of the adjacent cell.
Specifically, the mass of the catalyst is 0.1% to 5% of the total mass of the first organic material and the second organic material. Illustratively, the mass of the catalyst may be 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, or 5% of the total mass of the first organic material and the second organic material.
Preferably, the catalyst is a solid catalyst. The catalyst includes but is not limited to at least one of bis-dimethylamino ethyl ether, pentamethyl-diethylenetriamine, dimethyl cyclohexylamine, dibutyltin dilaurate, organic bismuth and triazine trimerization catalyst.
As a preferred embodiment, the heat absorbing composite further comprises a thermoplastic material, the thermoplastic material is uniformly mixed with the first organic material and the second organic material, and the thermoplastic material can support the first organic material, the second organic material and the like; the thermoplastic material can be melted after the temperature of the battery cell rises, so that phase change heat absorption is generated, the heating rate of the adjacent battery cell can be further reduced, and thermal runaway of the adjacent battery cell is more effectively avoided.
Specifically, the mass of the thermoplastic material is 1-20% of the total mass of the first organic material and the second organic material. Illustratively, the mass of the thermoplastic material may be 1%, 5%, 10%, 15%, or 20% of the total mass of the first organic material and the second organic material. The thermoplastic material comprises at least one of polyethylene, polypropylene, polyamide, polyimide, polyformaldehyde, polycarbonate, polyether ether ketone, phenolic resin and amino resin.
As a preferred embodiment, the heat absorption composite material further includes a thermal insulation material, the thermal insulation material is uniformly mixed with the first organic material and the second organic material, and the thermal insulation material can hinder heat generated by the battery cell from being transferred to an adjacent battery cell, so that the temperature rise rate of the adjacent battery cell can be further reduced, and thermal runaway of the adjacent battery cell is further effectively avoided.
Specifically, the mass of the heat insulating material accounts for 1-50% of the total mass of the first organic material, the second organic material and the heat insulating material. Illustratively, the mass of the thermal insulation material may account for 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, or 50% of the total mass of the first organic material, the second organic material, and the thermal insulation material. The thermal insulation material includes, but is not limited to, at least one of carbon aerogel, graphene aerogel, silicon-carbon-oxygen aerogel, porous silica, porous alumina, porous titanium dioxide, phenolic aerogel, polyurethane aerogel and polyurea aerogel.
It is to be understood that the heat absorbing composite may further include at least one of a flame retardant material, a fire retardant material, an oxygen barrier material, and a phase change material, which may be uniformly mixed with the first organic material and the second organic material.
In practical use, the heat absorbing composite material provided by this embodiment may be mixed with a solvent to configure a heat absorbing paste, and then the heat absorbing paste is coated on the outer surface of the battery cell and baked to remove the solvent of the heat absorbing paste, so as to obtain the heat absorbing layer. The thickness of the heat absorption layer is 0.1 mm-1.0 mm; illustratively, the heat sink layer may have a thickness of 0.1mm, 0.2mm, 0.3mm, 0.4mm, 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, or 1.0mm.
Example 2
The embodiment provides a preparation method of an endothermic composite structure, which comprises the following steps: uniformly mixing the heat-absorbing composite material provided in example 1 with a fiber substrate to obtain a mixture; and carrying out hot pressing on the mixture to obtain a heat absorption composite structure, wherein the heat absorption composite structure is suitable for being attached to the outer surface of the battery core, and the using method is simple.
Specifically, the mass fraction of the fiber substrate in the mixture is 40% -70%. Illustratively, the mass fraction of the fibrous substrate in the mixture may be 40%, 50%, 60% or 70%. By limiting the mass fraction of the fiber substrate to the above range, the strength of the heat absorption composite structure can be ensured on the one hand, and the content of the heat absorption composite material in the heat absorption composite structure can be ensured on the other hand, so that the heat absorption effect of the heat absorption composite structure is ensured.
In this embodiment, the substrate is capable of withstanding higher temperatures, and the fibrous substrate includes, but is not limited to, at least one of glass fibers, ceramic fibers, carbon fibers, sepiolite fibers, and polyimide fibers.
It is to be understood that the endothermic composite may contain only the first organic material and the second organic material, only the first organic material, only the second organic material, and only the catalyst, only the first organic material, only the second organic material, and only the thermoplastic material, or only the first organic material, only the second organic material, only the catalyst, and only the thermoplastic material. Preferably, when the heat-absorbing composite material is used for preparing a heat-absorbing composite structure, the heat-absorbing composite material does not contain a thermoplastic material, so that the content of the first organic material and the second organic material in the heat-absorbing material layer can be increased, the reaction degree of the heat-absorbing material layer is increased, more heat can be absorbed in the heat-absorbing composite structure per unit time, and the temperature rise rate of an adjacent electric core can be reduced more effectively.
In the embodiment, the hot pressing pressure is 80MPa to 150MPa, the hot pressing temperature is 25 ℃ to 80 ℃, and the hot pressing time is 0.5h to 8h in the hot pressing process of the mixture. Illustratively, the pressure of hot pressing may be 80MPa, 100MPa, 120MPa, 130MPa or 150MPa, the temperature of hot pressing may be 25 ℃, 40 ℃, 60 ℃, 80 ℃, and the time of hot pressing may be 0.5h, 1h, 3h, 5h, 8h. The larger the pressure and the higher the temperature of the hot pressing, the shorter the hot pressing time.
Referring to fig. 1, the present embodiment also provides an endothermic composite structure 1, which is manufactured by the above-described method for manufacturing an endothermic composite structure, in which the endothermic composite 11 and the fiber substrate 12 are uniformly dispersed in the endothermic composite structure 1. The thickness of the heat absorption composite structure is 0.1 mm-10 mm. Illustratively, the thickness of the heat absorbing composite structure may be 0.1mm, 0.5mm, 0.8mm, 1.0mm, 2.0mm, 3.0mm, 4.0mm, 5.0mm, 6.0mm, 7.0mm, 8.0mm, or 10mm.
Example 3
The present embodiment provides a lithium ion battery unit, including a housing and a plurality of battery cells located in the housing, where an outer surface of the battery cell is provided with the heat absorption composite structure provided in embodiment 2. After thermal runaway occurs in one electric core of the lithium ion battery unit, thermal runaway of adjacent electric cores can not be caused, so that the whole lithium ion battery unit is prevented from generating comprehensive thermal runaway, and the safety of the lithium ion battery unit is improved.
Further, the inner surface of the outer shell may also be provided with the heat absorbing composite structure.
In the present embodiment, the lithium ion battery cell includes, but is not limited to, a lithium ion battery pack.
Specific examples are provided below to demonstrate the effects of the technical solution of the present application.
Example 4
This example provides an endothermic composite structure comprising glass fibers, adipic acid, dibutyltin dilaurate, a phenolic resin, and phthalic anhydride end-capped with nonylphenol, wherein the content of phthalic anhydride end-capped with nonylphenol was 24.7%, the content of adipic acid was 20.3%, the content of dibutyltin dilaurate was 0.45%, the content of phenolic resin was 5%, and the balance was glass fibers. The thickness of the heat absorbing composite structure is 2.5mm.
Comparative example 1
This comparative example provides a silica aerogel sheet of 3.0mm thickness as a heat insulating film.
Test example 1
Referring to fig. 2, the heat-absorbing composite structure 1 provided in example 4 is placed between a first cell 2 and a second cell 3 that are adjacent to each other, a heating plate 4 is disposed on one side of the first cell 2 away from the heat-absorbing composite structure 1, and the first cell 2 is triggered to generate thermal runaway by controlling the temperature of the heating plate 4; the method includes the steps of testing a temperature T1 of a central position of one side surface of the first battery cell 2 facing the heat absorption composite structure 1 and a temperature T2 of a central position of one side surface of the second battery cell 3 facing the heat absorption composite structure 1 by using a thermocouple, monitoring voltages of the first battery cell 2 and the second battery cell 3, and obtaining a change curve of the temperatures and the voltages of the first battery cell 2 and the second battery cell 3 in a heating process of the first battery cell 2, specifically, see fig. 3, where an abscissa represents test time, a left ordinate represents temperatures of T1 and T2, and a right ordinate represents voltages of the first battery cell 2 and the second battery cell 3.
Similarly, the silica aerogel sheet provided in the comparative example 1 is placed between a third electric core and a fourth electric core which are adjacent to each other, a heating plate is arranged on one side of the third electric core, which is far away from the silica aerogel sheet, and the third electric core is triggered to generate thermal runaway by controlling the temperature of the heating plate; the temperature T3 of the central position of one side surface of the third battery cell, which faces the silica aerogel sheet, and the temperature T4 of the central position of one side surface of the fourth battery cell, which faces the silica aerogel sheet, are tested by a thermocouple, and the voltages of the third battery cell and the fourth battery cell are monitored, so that a change curve of the temperatures and the voltages of the third battery cell and the fourth battery cell in the heating process of the third battery cell is obtained, specifically, see fig. 4, wherein the abscissa represents the test time, the ordinate on the left represents the temperatures of T3 and T4, and the ordinate on the right represents the voltages of the third battery cell and the fourth battery cell.
As can be seen from fig. 3, the first electrical core 2 undergoes a voltage dip at 514s, and the temperature T1 at the surface center position suddenly rises to 840 ℃, so that thermal runaway occurs; t1 decreased to 400 ℃ at 798 s. The temperature of the second electrical core 3 rises when the first electrical core 2 is thermally out of control, and under the action of the heat absorption composite structure 1, the temperature T2 of the central position of the surface of the second electrical core 3 rises to about 255 ℃, and then is cooled, during which the voltage of the second electrical core 3 is kept constant, that is, the second electrical core 3 is not thermally out of control.
As can be seen from fig. 4, when the voltage of the third battery cell suddenly decreases at 328s, the temperature T3 at the center of the surface thereof suddenly increases to about 850 ℃, and thermal runaway occurs; at 615s T3 decreased to 400 ℃. The temperature of the fourth cell also rises when thermal runaway occurs in the third cell, the temperature T4 at the center of the surface of the fourth cell rises to 300 ℃ at 456s, and the temperature T4 rises suddenly at 633s and the voltage of the fourth cell drops, namely thermal runaway occurs.
As can be seen from the above results, the heat-absorbing composite structure 1 provided in embodiment 4 can absorb a large amount of heat generated by the thermal runaway cell, so as to reduce the temperature rise rate and the highest temperature of the neighboring cell, and effectively reduce the risk of thermal runaway occurring in the neighboring cell; meanwhile, compared with the aerogel sheet with the thickness of 3.0mm provided by the comparative example 1, the heat absorption composite structure 1 with the thickness of 2.5mm provided by the example 4 is thinner, which is beneficial to reducing the occupied space of the non-energy part of the lithium ion Chi Baozhong and increasing the energy density of the lithium ion battery pack.
It should be understood that the above examples are only for clarity of illustration and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications derived therefrom are intended to be within the scope of the invention.
Claims (10)
1. An endothermic composite, characterized by comprising a first organic material containing at least one of an acid anhydride group, an ester group, an isocyanate group, and an aldehyde group and a second organic material containing at least one of a hydroxyl group, a carboxyl group, and an amino group, which are uniformly mixed, the endothermic composite being adapted to be disposed on an outer surface of a battery cell.
2. The heat absorbing composite of claim 1, wherein the first organic material comprises at least one of a polybasic acid anhydride, a polybasic ester, a polybasic isocyanate, and a polybasic aldehyde.
3. The heat absorption composite material as claimed in claim 1 or 2, wherein the first organic material is capped with a capping agent, and the difference between the deblocking temperature of the first organic material and the critical temperature of thermal runaway of a lithium ion battery is-50 ℃ to 20 ℃;
preferably, the deblocking temperature is greater than or equal to 130 ℃; the blocking agent comprises at least one of nonyl phenol, caprolactam, methyl ethyl ketoxime, dimethyl pyrazole, ethylene-propylene-amine, diethyl malonic acid, imidazole and phenol;
preferably, the boiling points of the first organic material and the second organic material are both greater than the deblocking temperature of the first organic material;
preferably, the first organic material includes at least one of phthalic anhydride, pyromellitic anhydride, dimethyl terephthalate, benzene diisocyanate, toluene diisocyanate, and terephthalaldehyde; the second organic material comprises at least one of polyethylene glycol, terephthalic acid, adipic acid, suberic acid, hexamethylene diamine, m-phenylenediamine and dichlorodiphenyl sulfone;
preferably, the ratio of the molar amounts of the first organic material and the second organic material is 1 to 1.5.
4. The endothermic composite of any one of claims 1 to 3, further comprising a catalyst, the catalyst being homogeneously mixed with the first organic material and the second organic material, the mass of the catalyst being 0.1% to 5% of the total mass of the first organic material and the second organic material;
preferably, the catalyst is a solid catalyst;
preferably, the catalyst comprises at least one of bis-dimethylamino ethyl ether, pentamethyl-diethylenetriamine, dimethyl cyclohexylamine, dibutyltin dilaurate, organic bismuth and triazine trimerization catalyst.
5. The heat absorbing composite as claimed in any one of claims 1 to 4, further comprising a thermoplastic material homogeneously mixed with the first organic material and the second organic material, the mass of the thermoplastic material being 1% to 20% of the total mass of the first organic material and the second organic material;
preferably, the thermoplastic material comprises at least one of polyethylene, polypropylene, polyamide, polyimide, polyoxymethylene, polycarbonate, polyetheretherketone, phenolic resin, amino resin.
6. The heat absorbing composite as claimed in any one of claims 1 to 5, further comprising a thermal insulating material uniformly mixed with the first organic material and the second organic material, the thermal insulating material comprising 1% to 50% by mass of the total mass of the first organic material, the second organic material and the thermal insulating material;
preferably, the thermal insulation material comprises at least one of carbon aerogel, graphene aerogel, silicon-carbon-oxygen aerogel, porous silica, porous alumina, porous titanium dioxide, phenolic aerogel, polyurethane aerogel and polyurea aerogel.
7. A method of making an endothermic composite structure, comprising the steps of:
uniformly mixing the heat absorbing composite of any one of claims 1 to 6 with a fibrous substrate to obtain a mixture;
and carrying out hot pressing on the mixture to obtain a heat absorption composite structure, wherein the heat absorption composite structure is suitable for being attached to the outer surface of the battery core.
8. The method of making an endothermic composite structure, as claimed in claim 7, characterized in that the mass fraction of the fibrous substrate in the mixture is 40% to 70%;
preferably, the fiber substrate comprises at least one of glass fibers, ceramic fibers, carbon fibers, sepiolite fibers, and polyimide fibers;
preferably, the thickness of the heat absorption composite structure is 0.1 mm-10 mm.
9. An endothermic composite structure, characterized by being produced by the method for producing an endothermic composite structure according to claim 7 or 8.
10. A lithium ion battery cell comprising a housing and a plurality of cells within the housing, the cells having an outer surface provided with the endothermic composite structure of claim 9;
preferably, the inner surface of the outer shell is also provided with the heat absorbing composite structure.
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