Battery and battery pack

Abstract

The invention relates to the field of batteries, in particular to a battery and a battery pack. The battery comprises a top cover, a patch is arranged on the outer side of the top cover, and the patch comprises polyimide and a porous material. According to the battery, a composite material containing a porous material and polyimide is used as a patch of a battery top cover, so that a liquid low-boiling-point solvent overflowing when an explosion-proof valve of the battery is opened can be absorbed, and meanwhile, an inorganic adsorption material is compounded in a heat insulation layer on the inner side of an upper cover of a battery pack; a gaseous low-boiling-point organic solvent and combustible smoke generated by valve opening or thermal runaway of the battery can be absorbed under the condition that the thermal insulation effect of the thermal insulation layer is not influenced, so that the arc discharge risk caused by overflowing of the low-boiling-point solvent and a large amount of smoke in the thermal runaway process of the quick-charging power battery is effectively relieved on the two layers of the battery monomer and the battery pack; and the thermal diffusion intensity of the battery pack is reduced.

Description

Technical Field

[0001] The present invention relates to the field of batteries, and in particular to a battery and a battery pack. Background Art

[0002] With the rapid development of the electric vehicle market, consumers have higher and higher requirements for battery charging speed. In order to meet this demand, the fast charging performance of power batteries has been continuously improved. However, with the continuous improvement of the fast charging performance of power batteries, the content of low-boiling point solvents such as dimethyl carbonate (DMC), ethyl methyl carbonate (EMC) and ethyl acetate (EA) in the electrolyte has continued to increase, and the electrolyte overflow phenomenon when the battery explosion-proof valve is opened is more significant, posing a new challenge to the protection of the battery pack system level. During the opening stage of the battery explosion-proof valve, low-boiling point solvents will gush out of the battery in both liquid and gaseous forms. The outflow of liquid low-boiling point solvents will directly affect the high-voltage insulation protection of the battery pack and may cause the risk of high-voltage arcing; the overflow of gaseous low-boiling point solvents will diffuse, permeate and condense and liquefy inside the battery pack. The condensed and liquefied low-boiling point solvents will not only affect the high-voltage insulation protection of distant batteries, but may also be ignited, thereby worsening the thermal diffusion results. In addition, the smoke emitted by the thermal runaway of the battery contains combustible gases such as CO and CH4. Under extreme conditions, these combustible gases may explode and worsen the thermal diffusion process of the battery pack.

[0003] Therefore, there is an urgent need to provide a product that can effectively reduce the negative impact of low-boiling point solvent overflow and large amounts of smoke, thereby alleviating the problem of thermal diffusion in battery packs. Summary of the invention

[0004] The present invention aims to solve at least one of the technical problems in the related art to a certain extent. To this end, the present invention provides a battery and a battery pack, which uses a composite material comprising a porous material and polyimide as a patch of the battery top cover, which can absorb the liquid low-boiling point solvent overflowing from the battery explosion-proof valve, and at the same time, the inorganic adsorption material is compounded in the thermal insulation layer on the inner side of the battery pack cover, which can absorb the gaseous low-boiling point organic solvent and combustible smoke generated by the battery valve opening or thermal runaway without affecting the thermal insulation effect of the thermal insulation layer, thereby effectively alleviating the arcing risk caused by the overflow of low-boiling point solvents and a large amount of smoke during the thermal runaway of fast-charging power batteries at both the battery cell and battery pack levels, and reducing the severity of thermal diffusion of the battery pack.

[0005] To this end, a first aspect of the present invention provides a battery, the battery comprising a top cover, a patch is disposed on the outer side of the top cover, and the patch is composed of polyimide and a porous material.

[0006] The battery provided by the present invention uses a polyimide composite material containing a porous material to replace the traditional polycarbonate material as a patch on the battery top cover, which can effectively absorb the liquid low-boiling point solvent overflowed when the battery explosion-proof valve is opened, thereby reducing the severity of thermal runaway of the battery pack and alleviating the problem of thermal diffusion of the battery pack. In addition, the thermal stability of the polyimide material is significantly better than that of the traditional polycarbonate material.

[0007] According to an embodiment of the present invention, the porous material includes at least one of molecular sieves, zeolites, porous alumina, porous silicon carbide, and metal organic framework materials.

[0008] According to an embodiment of the present invention, the mass of the porous material accounts for 5%-55% of the total mass of the patch.

[0009] According to an embodiment of the present invention, the interior of the patch is a porous structure with a pore size of 10 μm-50 μm.

[0010] According to an embodiment of the present invention, the porosity of the patch is 10%-75%.

[0011] According to an embodiment of the present invention, the thickness of the patch is 0.1 mm-5 mm.

[0012] A second aspect of the present invention provides a battery pack, comprising the battery described in the first aspect.

[0013] The battery pack provided by the present invention, since it includes the battery described in the first aspect, can effectively absorb the liquid low-boiling point solvent overflowing when the battery explosion-proof valve is opened, thereby reducing the severity of thermal runaway of the battery pack and alleviating the problem of thermal diffusion of the battery pack.

[0014] According to an embodiment of the present invention, the battery pack includes an upper cover, and a heat insulation layer is provided on the inner side of the upper cover. The raw materials constituting the heat insulation layer include mica, inorganic adsorption material and silicone resin material.

[0015] The battery pack provided by the present invention has a composite inorganic adsorption material in the insulation layer on the inner side of the upper cover, which can absorb gaseous low-boiling point organic solvents and combustible smoke generated by battery valve opening or thermal runaway without affecting the insulation effect of the insulation layer, thereby effectively reducing the severity of thermal runaway of the battery pack and alleviating the problem of heat diffusion of the battery pack.

[0016] According to an embodiment of the present invention, the inorganic adsorption material includes at least one of molecular sieve, zeolite and diatomaceous earth.

[0017] According to an embodiment of the present invention, the mass proportion of the inorganic adsorption material in the heat insulation layer is 5%-35%.

[0018] According to an embodiment of the present invention, the mass proportion of the mica in the thermal insulation layer is 30%-75%.

[0019] According to an embodiment of the present invention, the thickness of the thermal insulation layer is 5 mm-15 mm.

[0020] The beneficial effects of the present invention compared to the prior art are as follows:

[0021] The present invention starts from the two aspects of battery cell and battery pack design, adopts a composite material including porous material and polyimide as a patch of the battery top cover, which can absorb the liquid low-boiling point solvent overflowing when the battery explosion-proof valve is opened. At the same time, the inorganic adsorption material is compounded in the insulation layer on the inner side of the battery pack cover, which can absorb the gaseous low-boiling point organic solvent and combustible smoke generated by battery valve opening or thermal runaway without affecting the insulation effect of the insulation layer, thereby solving the problem of low-boiling point solvent overflow during thermal runaway of fast-charging power batteries and the deterioration of heat diffusion caused by combustible smoke in the battery pack.

[0022] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0024] Figure 1 The performance comparison diagram of the lithium iron phosphate battery prepared in Example 1 of the present invention and in Comparative Example 1 under the condition of 700W external heating triggering thermal runaway is shown. Among them, Figure a is a performance diagram of the lithium iron phosphate battery prepared in Comparative Example 1 under the condition of 700W external heating triggering thermal runaway; Figure b is a performance diagram of the lithium iron phosphate battery prepared in Example 1 under the condition of 700W external heating triggering thermal runaway;

[0025] Figure 2 The performance comparison diagram of the lithium iron phosphate battery prepared in Example 1 of the present invention and in Comparative Example 2 under the condition of 700W external heating triggering thermal runaway is shown. Among them, Figure a is a performance diagram of the lithium iron phosphate battery prepared in Comparative Example 2 under the condition of 700W external heating triggering thermal runaway; Figure b is a performance diagram of the lithium iron phosphate battery prepared in Example 1 under the condition of 700W external heating triggering thermal runaway;

[0026] Figure 3 The figures show the interior of the lithium iron phosphate battery packs prepared in Example 1 of the present invention and in Comparative Example 3 after the thermal diffusion test. Figure a is a figure showing the interior of the lithium iron phosphate battery pack prepared in Comparative Example 3 after the thermal diffusion test; Figure b is a figure showing the interior of the lithium iron phosphate battery pack prepared in Example 1 after the thermal diffusion test. DETAILED DESCRIPTION

[0027] The embodiments of the present invention are described in detail below. The embodiments described below are exemplary and are only used to explain the present invention, and should not be understood as limiting the present invention.

[0028] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. Further, in the description of the present invention, unless otherwise specified, the meaning of "plurality" is two or more.

[0029] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0030] In order to make the present invention more easily understood, certain technical and scientific terms are specifically defined below. Unless otherwise clearly defined elsewhere in this document, all other technical and scientific terms used herein have the meanings commonly understood by those skilled in the art to which the present invention belongs.

[0031] In this document, the terms “include” or “comprising” are open expressions, that is, including the contents specified in the present invention but not excluding other contents.

[0032] As used herein, the terms "optionally", "optional" or "optionally" generally mean that the subsequently described event or circumstance may but need not occur, and that the description includes instances where the event or circumstance occurs and instances where it does not.

[0033] As consumers' requirements for electric vehicle energy replenishment continue to increase, the proportion of fast-charging power batteries in power batteries will continue to increase, but the challenges that fast-charging power batteries bring to thermal diffusion protection are also increasing.

[0034] According to an embodiment of the present invention, a first aspect of the present invention provides a battery, the battery includes a top cover, a patch is provided on the outer side of the top cover, and the patch is composed of polyimide and a porous material.

[0035] At the battery cell level, the use of polyimide composite materials containing porous materials instead of traditional polycarbonate materials as patches on the battery top cover can effectively absorb the liquid low-boiling point solvents that overflow when the battery explosion-proof valve is opened, thereby reducing the severity of thermal runaway of the battery pack and alleviating the problem of thermal diffusion of the battery pack. Among them, polyimide, as the matrix of the composite material, can be used normally at a high temperature of up to 350°C. The melting point of traditional polycarbonate materials is only 200°C, and the top cover temperature during the battery thermal runaway process is higher than 200°C. Polyimide can still maintain a normal form during the battery thermal runaway process; porous materials such as molecular sieves have high adsorption properties and can absorb low-boiling point organic solvents that overflow when the battery valve is opened.

[0036] According to a specific embodiment of the present invention, the type of the porous material is not particularly limited. As some specific examples, the porous material includes at least one of molecular sieves, zeolites, porous alumina, porous silicon carbide, and metal organic framework materials.

[0037] According to a specific embodiment of the present invention, the mass of the porous material accounts for 5%-55% of the total mass of the patch. As some specific examples, the mass of the porous material may account for 5%, 10%, 25%, 40%, 55%, etc. of the total mass of the patch.

[0038] According to a specific embodiment of the present invention, the interior of the patch is a porous structure with a pore size of 10 μm-50 μm. As some specific examples, the pore size may be 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, etc.

[0039] According to a specific embodiment of the present invention, the porosity of the patch is 10%-75%. As some specific examples, the porosity of the patch may be 10%, 30%, 45%, 60%, 75%, etc.

[0040] According to a specific embodiment of the present invention, the thickness of the patch is 0.1 mm-5 mm. As some specific examples, the thickness of the patch may be 0.1 mm, 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, etc.

[0041] According to a specific embodiment of the present invention, the method for preparing the patch is not particularly limited. As some specific examples, the method for preparing the patch may be a cast film curing process.

[0042] According to an embodiment of the present invention, a second aspect of the present invention provides a battery pack, the battery pack comprising the battery described in the first aspect.

[0043] The battery pack provided by the present invention, since it includes the battery described in the first aspect, can effectively absorb the liquid low-boiling point solvent overflowing when the battery explosion-proof valve is opened, thereby reducing the severity of thermal runaway of the battery pack and alleviating the problem of thermal diffusion of the battery pack.

[0044] According to a specific embodiment of the present invention, the battery pack includes an upper cover, and a heat insulation layer is provided on the inner side of the upper cover. The raw materials constituting the heat insulation layer include mica, inorganic adsorption material and silicone resin material.

[0045] At the battery pack level, an inorganic adsorption material is composited in the insulation layer on the inner side of the battery pack cover. This type of inorganic adsorption material is not only resistant to high temperatures above 1000°C, but also has excellent liquid and gas adsorption properties. Moreover, when a specific content of inorganic adsorption material is used, it can absorb gaseous low-boiling point organic solvents and combustible smoke generated by battery valve opening or thermal runaway without affecting the insulation effect of the insulation layer, thereby effectively reducing the severity of thermal runaway of the battery pack and alleviating the problem of thermal diffusion of the battery pack.

[0046] According to a specific embodiment of the present invention, the type of the inorganic adsorption material is not particularly limited. As some specific examples, the inorganic adsorption material includes at least one of molecular sieves, zeolites, and diatomaceous earth.

[0047] According to a specific embodiment of the present invention, the type of the mica is not particularly limited. As some specific examples, the mica includes at least one of synthetic mica and muscovite mica.

[0048] According to a specific embodiment of the present invention, the mass proportion of the inorganic adsorption material in the thermal insulation layer is 5%-35%. As some specific examples, the mass proportion of the inorganic adsorption material in the thermal insulation layer may be 5%, 10%, 20%, 30%, 35%, etc.

[0049] According to a specific embodiment of the present invention, the mass proportion of the mica in the thermal insulation layer is 30%-75%. As some specific examples, the mass proportion of the mica in the thermal insulation layer may be 30%, 40%, 50%, 60%, 75%, etc.

[0050] According to a specific embodiment of the present invention, the thickness of the thermal insulation layer is 5 mm-15 mm. As some specific examples, the thickness of the thermal insulation layer may be 5 mm, 10 mm, 15 mm, etc.

[0051] The scheme of the present invention will be explained below in conjunction with the embodiments. It will be appreciated by those skilled in the art that the following embodiments are only used to illustrate the present invention and should not be considered as limiting the scope of the present invention. Where specific techniques or conditions are not indicated in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. The reagents or instruments used are not indicated by the manufacturer and are all conventional products that can be obtained commercially.

[0052] Example 1

[0053] The polyimide powder and molecular sieve are dispersed with N-methylpyrrolidone solution at the same time, and the solid content of polyimide in the dispersion is 45% and the solid content of molecular sieve is 5%. Then, a polyimide composite patch containing molecular sieve is obtained by a casting film curing process. Due to the presence of molecular sieve, the internal pore size of the polyimide composite patch is 50μm and the porosity is 20%. The thickness of the composite patch is adjustable. The thickness of the composite patch used in this embodiment is 0.15mm. The composite patch is glued to the surface of the top cover according to the size of the battery top cover to obtain a finished battery.

[0054] A 5mm thick thermal insulation layer is affixed to the inner side of the upper cover of the battery pack containing the battery. The mica used in the thermal insulation layer is high-temperature resistant synthetic mica. The thermal insulation layer is obtained by uniformly mixing, drying and curing synthetic mica particles, methylsilicone phenyl resin aqueous solution and molecular sieves in a mass ratio of 70%:20%:10%.

[0055] Example 2

[0056] The polyimide powder and molecular sieve are dispersed with N-methylpyrrolidone solution at the same time, and the solid content of polyimide in the dispersion is 30% and the solid content of molecular sieve is 10%. Then, a polyimide composite patch containing molecular sieve is obtained by a film casting curing process. Due to the presence of molecular sieve, the internal pore size of the polyimide composite patch is 30μm and the porosity is 25%. The thickness of the composite patch is adjustable. The thickness of the composite patch used in this embodiment is 0.20mm. The composite patch is glued to the surface of the top cover according to the size of the battery top cover to obtain a finished battery.

[0057] A 10mm thick thermal insulation layer is affixed to the inner side of the upper cover of the battery pack containing the battery. The mica used in the thermal insulation layer is high-temperature resistant muscovite mica. The thermal insulation layer is obtained by uniformly mixing, drying and curing muscovite mica particles, methylsilicone phenyl resin aqueous solution and molecular sieves in a mass ratio of 67%:18%:15%.

[0058] Comparative Example 1

[0059] The only difference between this comparative example and Example 1 is that polycarbonate is used instead of polyimide.

[0060] The results show that under the same external heating triggering conditions, the lithium iron phosphate battery prepared in this comparative example uses a patch made of polycarbonate. After the battery thermal runaway, all the patches are burned, leaving the residue of the burned patches above the battery top cover (such as Figure 1 As shown); and the lithium iron phosphate battery prepared in Example 1 uses a polyimide patch, the battery patch still maintains its original morphology after thermal runaway, and there is no large amount of residue above the battery top cover.

[0061] Comparative Example 2

[0062] The only difference between this comparative example and Example 1 is that no molecular sieve is added when preparing the patch.

[0063] The results showed that when the square aluminum shell lithium iron phosphate battery was fixed with a steel clamp and externally heated by a heating plate to trigger thermal runaway, the lithium iron phosphate battery prepared in this comparative example would have electrolyte overflow when the explosion-proof valve was opened. The patch of the lithium iron phosphate battery prepared in this comparative example did not contain molecular sieves, and the overflowed electrolyte accumulated on the top cover of the battery. Eventually, the electrolyte was ignited by the sparks ejected by thermal runaway, causing the battery to catch fire (such as Figure 2 As shown); the patch of the lithium iron phosphate battery prepared in Example 1 contains a molecular sieve, which absorbs the overflowed electrolyte, thereby preventing the electrolyte from accumulating on the surface of the battery top cover, so that the thermal runaway of the battery is mainly manifested in smoke without fire, which effectively improves the safety of the thermal runaway of the battery.

[0064] Comparative Example 3

[0065] The only difference between this comparative example and Example 1 is that no molecular sieve is added when preparing the thermal insulation layer.

[0066] The results show that, since the thermal insulation layer on the inner side of the upper cover of the lithium iron phosphate battery pack prepared in this comparative example does not contain molecular sieves, a large amount of liquid remains in the battery pack box after thermal runaway. The liquid is accumulated by the electrolyte spraying during the thermal runaway of multiple batteries in the battery pack. The presence of the electrolyte reduces the insulation protection level inside the battery pack, resulting in large-scale heat diffusion in the battery pack (such as Figure 3 As shown); in contrast, the lithium iron phosphate battery pack prepared in Example 1 benefited from the adsorption of the electrolyte ejected by the battery thermal runaway by the molecular sieve in the thermal insulation layer. No large amount of liquid residue was observed in the box after the test, and the battery pack did not show large-scale battery heat diffusion and spread, which effectively improved the safety protection level of the battery pack.

[0067] Comparative Example 4

[0068] The only difference between this comparative example and Example 1 is that the mass ratio of the synthetic mica particles, the methylsilicone phenyl resin aqueous solution and the molecular sieve when preparing the thermal insulation layer is 15%:10%:75%.

[0069] The performance parameters of the thermal insulation layer in the lithium iron phosphate battery prepared in Comparative Example 4 and Example 1 are shown in Table 1. From the data in Table 1, it can be seen that due to the excessively high molecular sieve content in the thermal insulation layer of the lithium iron phosphate battery prepared in Comparative Example 4, the thermal conductivity of the thermal insulation layer of the lithium iron phosphate battery prepared in Example 1 is only 1.27 W / (m 2 .K), while the thermal conductivity of the thermal insulation layer of the lithium iron phosphate battery prepared in Comparative Example 4 reaches 1.85W / (m 2.K), which seriously affected the thermal insulation performance of the thermal insulation layer, and eventually led to arcing and fire in the thermal diffusion test of the battery pack.

[0070] Table 1

[0071]

[0072] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0073] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A battery, characterized in that: The battery comprises a top cover, a patch is arranged on the outer side of the top cover, and the patch is composed of polyimide and porous material.

2. The battery according to claim 1, characterized in that The porous material includes at least one of molecular sieves, zeolites, porous alumina, porous silicon carbide, and metal organic framework materials.

3. The battery according to claim 1, characterized in that The mass of the porous material accounts for 5%-55% of the total mass of the patch.

4. The battery according to claim 1, characterized in that The interior of the patch is a porous structure with a pore size of 10 μm-50 μm; Optionally, the patch has a porosity of 10%-75%.

5. The battery according to claim 1, characterized in that The thickness of the patch is 0.1mm-5mm.

6. A battery pack, characterized in that: The battery pack comprises the battery according to any one of claims 1 to 5.

7. The battery pack according to claim 6, characterized in that: The battery pack comprises an upper cover, an inner side of which is provided with a heat insulating layer, and the raw materials constituting the heat insulating layer comprise mica, an inorganic adsorption material and a silicone resin material.

8. The battery pack according to claim 7, characterized in that: The inorganic adsorption material includes at least one of molecular sieve, zeolite and diatomaceous earth.

9. The battery pack according to claim 7, characterized in that: The inorganic adsorption material accounts for 5% to 35% by mass in the thermal insulation layer; Optionally, the mass proportion of the mica in the thermal insulation layer is 30%-75%.

10. The battery pack according to claim 7, characterized in that: The thickness of the heat insulation layer is 5mm-15mm.

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