Flame-retardant composition, flame-retardant layer and new energy automobile power battery comprising the same

Abstract

The present application relates to a flame-retardant composition, a flame-retardant layer and a new energy automobile power battery comprising the flame-retardant layer. The flame-retardant composition comprises: 50-68 wt% of a base resin which is a mixture of polycarbonate and polyphenyl ether in a weight ratio of 1:1-3:1; 15-28 wt% of a composite flame retardant comprising a phosphoric acid ester flame retardant, a cyanamide flame retardant and an inorganic flame retardant in a weight ratio of 1:0.5-0.8:2-2.5, wherein the inorganic flame retardant is selected from one or more of the group consisting of aluminum hydroxide, diantimony trioxide, magnesium hydroxide and zinc borate; 10-20 wt% of a heat-conducting agent; 5-10 wt% of a silane coupling agent; and 1-3 wt% of a lubricant. The flame-retardant layer formed by the flame-retardant composition is arranged between the power battery module and the aluminum shell of the new energy automobile power battery, has good flame-retardant, heat-conducting and mechanical properties, and can meet the use requirements of the new energy automobile power battery.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of new energy vehicles, and particularly relates to a flame-retardant composition for a new energy vehicle power battery, a flame-retardant layer formed from the composition, and a new energy vehicle power battery comprising the flame-retardant layer. BACKGROUND

[0002] In the face of increasingly severe global energy crisis and environmental problems, new energy vehicles have become an important direction for the transformation and upgrading of the automotive industry due to their energy-saving and environmentally-friendly advantages. As the core component of new energy vehicles, the safety, reliability and performance of power batteries directly affect the development and application of new energy vehicles. With the increasing requirement for the cruising range of new energy vehicles, the energy density of power batteries is also continuously improving, which makes power batteries face higher risks of heat generation and safety hazards during operation. Once the power battery experiences thermal runaway, it will not only cause vehicle damage, but also may cause serious safety accidents such as fire and explosion, threatening the safety of passengers. Therefore, how to improve the safety of power batteries has become a key problem to be solved in the field of new energy vehicles.

[0003] Flame-retardant technology is one of the important means to improve the safety of power batteries. Currently, the commonly used flame-retardant materials for power batteries on the market mainly include flame-retardant plastics, flame-retardant rubbers, and flame-retardant coatings. However, these traditional flame-retardant materials have many shortcomings in practical application. For example, although some flame-retardant plastics have good flame-retardant properties, they have poor thermal conductivity and cannot dissipate the heat generated by power batteries in time, which easily leads to heat accumulation and further exacerbates the risk of thermal runaway. On the other hand, some materials with good thermal conductivity have difficulty in meeting the safety requirements of power batteries in terms of flame-retardant properties. In addition, the mechanical properties of traditional flame-retardant materials often cannot meet the use requirements of power batteries, and they are prone to cracking, deformation and other problems under the action of external forces such as vibration and impact, affecting the overall performance and service life of power batteries.

[0004] In the existing structure of power batteries, the flame-retardant layer between the battery module and the aluminum shell is an important component to ensure the safety of power batteries. This flame-retardant layer not only needs to have excellent flame-retardant properties to prevent the spread of fire when the battery experiences thermal runaway, but also needs to have good thermal conductivity to conduct the heat generated by the battery in time and reduce the battery temperature. At the same time, this flame-retardant layer should also have high mechanical strength to withstand various external forces during the installation and use of the battery module, ensuring the stability of the battery structure. However, there is currently a lack of a flame-retardant material that can simultaneously meet the requirements of flame-retardant, thermal conductivity and mechanical properties for the flame-retardant layer between the power battery module and the aluminum shell.

[0005] Some existing flame-retardant compositions often improve the flame-retardant performance by adding a large amount of flame retardant, but this will cause the mechanical properties and processing properties of the material to decrease, and will also affect the thermal conductivity of the material. For example, inorganic flame retardants such as aluminum hydroxide, magnesium hydroxide, etc. have good flame-retardant effect, but when the amount added is large, the material becomes brittle and hard, and the tensile strength and bending strength decrease significantly. While organic flame retardants such as phosphate ester flame retardants have less effect on the mechanical properties of the material, but when used alone, the flame-retardant effect is limited, and they need to be used in combination with other flame retardants, which increases the complexity and cost of the formulation.

[0006] In terms of thermal conductivity, existing flame-retardant materials usually improve the thermal conductivity by adding thermal conductive fillers such as graphene, aluminum powder, carbon nanotubes, etc. However, the amount and dispersibility of these thermal conductive fillers have an important influence on the thermal conductivity and mechanical properties of the material. When the amount of thermal conductive fillers is insufficient, the thermal conductivity of the material cannot meet the requirements; while when the amount is too large, the fillers will agglomerate in the matrix resin, affecting the mechanical properties and processing properties of the material. In addition, the compatibility problem between the thermal conductive fillers and the matrix resin will also affect the overall performance of the material.

[0007] In terms of mechanical properties, power batteries are subjected to various external forces such as vibration, impact, temperature change, etc. during use, so the flame-retardant layer is required to have high tensile strength, bending strength and toughness. Some existing flame-retardant materials have unreasonable formulation design, and are difficult to meet the use requirements of power batteries in terms of mechanical properties. For example, the mechanical properties of some flame-retardant materials will decrease significantly at high temperature, which cannot guarantee the structural stability of the power battery during long-term use.

[0008] In summary, the flame-retardant materials for new energy vehicle power batteries in the prior art have the problem that the flame-retardant performance, thermal conductivity and mechanical properties are difficult to balance, and cannot meet the requirements of new energy vehicles for the safety and reliability of power batteries. Therefore, it is urgent to develop a flame-retardant composition with good flame-retardant performance, thermal conductivity and mechanical properties, which is used for the flame-retardant layer between the power battery module and the aluminum shell of the power battery, so as to improve the safety and reliability of the power battery and promote the healthy development of the new energy vehicle industry. SUMMARY

[0009] The present application aims to provide a flame-retardant composition for new energy vehicle power batteries, a flame-retardant layer formed by the flame-retardant composition is arranged between the battery module and the aluminum shell of the new energy vehicle power battery, and the flame-retardant layer has good flame-retardant performance, thermal conductivity and mechanical properties (tensile strength and bending strength), so as to solve the above-mentioned problems existing in the prior art.

[0010] Specifically, according to one aspect of the present application, a flame-retardant composition is provided, which comprises, based on the total weight thereof:

[0011] 50-68 wt% of a matrix resin, the matrix resin being a mixture of polycarbonate and polyphenylene ether in a weight ratio of 1 : 1 to 3 : 1;

[0012] 15-28 wt% of a composite flame retardant, the composite flame retardant comprising a phosphoric ester-based flame retardant, a cyanamide-based flame retardant, and an inorganic flame retardant in a weight ratio of 1 : 0.5 to 0.8 : 2 to 2.5, wherein the inorganic flame retardant is selected from one or more of the group consisting of aluminum hydroxide, diantimony trioxide, magnesium hydroxide, and zinc borate;

[0013] 10-20 wt% of a thermal conductive agent;

[0014] 5-10 wt% of a silane coupling agent; and

[0015] 1-3 wt% of a lubricant.

[0016] According to certain preferred embodiments of the present application, the polycarbonate has a weight average molecular weight in the range of 25,000-60,000 g / mol, preferably 30,000-40,000 g / mol, more preferably 30,000-35,000 g / mol.

[0017] According to certain preferred embodiments of the present application, the polycarbonate is selected from one or more of the group consisting of bisphenol A type polycarbonate, bisphenol S type polycarbonate, silicone-modified polycarbonate, and polyester-modified polycarbonate.

[0018] According to certain preferred embodiments of the present application, the polycarbonate is a bisphenol A type polycarbonate.

[0019] According to certain preferred embodiments of the present application, the polyphenylene ether has a weight average molecular weight in the range of 5,000-25,000 g / mol, preferably 10,000-25,000 g / mol, more preferably 15,000-23,000 g / mol.

[0020] According to certain preferred embodiments of the present application, the phosphoric ester-based flame retardant is selected from one or more of the group consisting of triphenyl phosphate (TPP), tricresyl phosphate (TCP), and tris(2-ethylhexyl) phosphate (TEHP).

[0021] According to certain preferred embodiments of the present application, the cyanamide-based flame retardant is selected from one or more of the group consisting of melamine cyanurate (MCA), melamine, and dicyandiamide.

[0022] According to certain preferred embodiments of the present application, the silane coupling agent is selected from one or more of the group consisting of vinyltriethoxysilane, gamma-aminopropyltriethoxysilane, vinyltrimethoxysilane and gamma-mercaptopropyltrimethoxysilane.

[0023] According to certain preferred embodiments of the present application, the composite flame retardant comprises triphenyl phosphate (TPP), melamine cyanurate (MCA) and aluminum hydroxide in a weight ratio of 1 : 0.6-0.65 : 2.3-2.5.

[0024] According to certain preferred embodiments of the present application, the heat conducting agent is selected from one or more of the group consisting of graphene, aluminum powder, nickel powder, carbon nanotubes and carbon fibers.

[0025] According to certain preferred embodiments of the present application, the lubricant is selected from one or more of the group consisting of stearic acid, calcium stearate and paraffin wax.

[0026] According to certain preferred embodiments of the present application, the flame retardant composition further comprises 1-3 wt% of an antioxidant, based on the total weight thereof.

[0027] According to certain preferred embodiments of the present application, the antioxidant is a mixture of a hindered phenolic antioxidant and a phosphite antioxidant in a weight ratio of 1 : 1-2 : 1.

[0028] According to certain preferred embodiments of the present application, the hindered phenolic antioxidant is selected from one or more of the group consisting of 2,6-di-tert-butyl-p-cresol, 2,6-di-tert-butylphenol and 2,4,6-tri-tert-butylphenol.

[0029] According to certain preferred embodiments of the present application, the phosphite antioxidant is selected from one or more of the group consisting of pentaerythrityl didephenyl phosphate, triphenyl phosphite, tris(2,4-di-tert-butylphenyl) phosphite and diphenyl isodecyl phosphite.

[0030] According to certain preferred embodiments of the present application, the flame retardant composition further comprises a colorant.

[0031] According to certain preferred embodiments of the present application, the flame retardant composition comprises 2 wt% or less of the colorant, based on the total weight thereof.

[0032] According to another aspect of the present application, there is provided a flame retardant layer comprising the flame retardant composition described above.

[0033] According to certain preferred embodiments of the present application, the thickness of the flame retardant layer is in the range of 0.5 mm-5 mm, preferably 1 mm-3 mm.

[0034] According to still another aspect of the present application, there is provided a new energy automobile power battery, comprising:

[0035] a power battery module;

[0036] an aluminum shell encapsulating the power battery module; and

[0037] the above-mentioned flame-retardant layer is arranged between and in contact with the power battery module and the aluminum shell. DETAILED DESCRIPTION

[0038] It should be understood that other various embodiments can be conceived and modified according to the teachings of the present specification by those skilled in the art without departing from the scope or spirit of the present disclosure. Therefore, the following detailed description is not intended to be limiting in nature.

[0039] Unless otherwise indicated, all numbers expressing features, quantities and physical characteristics used in the specification are to be understood as being modified in all instances by the term "about" to encompass amounts that can vary from those stated by reason of measurement uncertainty. Unless otherwise indicated, the numerical values listed in the specification are approximations that can vary depending on the desired properties sought to be obtained by the person skilled in the art using the teachings disclosed herein, and appropriate variations thereof are to be made.

[0040] As mentioned above, the existing flame-retardant materials for new energy automobile power batteries have many shortcomings: materials with good flame-retardant properties have poor thermal conductivity, which is prone to heat accumulation; materials with good thermal conductivity have insufficient flame-retardant properties; and the mechanical properties are poor and are prone to cracking and deformation under external force. In addition, there is a contradiction between the amount of flame retardant added and the performance of the material, and there is a lack of materials that can simultaneously meet the requirements of flame retardant, thermal conductivity and mechanical properties for the flame-retardant layer between the battery module and the aluminum shell.

[0041] The present application found in the research that the polycarbonate and polyphenyl ether are compounded as the base resin according to a specific weight ratio (1:1-3:1), which can give full play to the impact resistance of polycarbonate and the heat resistance of polyphenyl ether, form a stable framework with complementary performance, and lay a foundation for the mechanical properties of the material. Further research shows that the phosphoric acid ester flame retardant, cyanamide flame retardant and inorganic flame retardant are compounded according to a specific weight ratio (1:0.5-0.8:2-2.5), which can improve the flame-retardant efficiency while reducing the total amount of addition through the synergistic effect of gas-phase flame retardation and condensed-phase flame retardation, and the effect is optimal when the triphenyl phosphate (TPP), melamine cyanurate (MCA) and aluminum hydroxide are compounded according to a ratio of 1:0.6-0.65:2.3-2.5. In addition, the addition of 10-20% by weight of the thermal conductive agent can construct an efficient thermal conduction network, and 5-10% by weight of the silane coupling agent can improve the interfacial compatibility of each component, solving the problem that the flame-retardant, thermal conductivity and mechanical properties are difficult to be considered in traditional materials, so that the composition can meet the comprehensive performance requirements of the power battery flame-retardant layer.

[0042] Based on the above, the present application particularly relates to a flame-retardant composition for a new energy automobile power battery, a flame-retardant layer formed from the composition, and a new energy automobile power battery comprising the flame-retardant layer. The present application aims to solve the problem in the prior art that the flame-retardant material for a new energy automobile power battery is difficult to simultaneously meet the requirements of flame-retardant performance, heat-conducting performance and mechanical performance, and to provide a flame-retardant composition with excellent comprehensive performance, and a flame-retardant layer prepared therefrom and a new energy automobile power battery comprising the flame-retardant layer.

[0043] Specifically, according to one aspect of the present application, a flame-retardant composition is provided, which comprises, based on the total weight thereof:

[0044] 50-68% by weight of a matrix resin, the matrix resin being a mixture of polycarbonate and polyphenyl ether in a weight ratio of 1:1-3:1;

[0045] 15-28% by weight of a composite flame retardant, the composite flame retardant comprising a phosphoric ester flame retardant, a cyanamide flame retardant and an inorganic flame retardant in a weight ratio of 1:0.5-0.8:2-2.5, wherein the inorganic flame retardant is selected from one or more of the group consisting of aluminum hydroxide, diantimony trioxide, magnesium hydroxide and zinc borate;

[0046] 10-20% by weight of a heat-conducting agent;

[0047] 5-10% by weight of a silane coupling agent; and

[0048] 1-3% by weight of a lubricant.

[0049] According to the technical solution of the present application, the flame-retardant composition comprises 50-68% by weight of a matrix resin, the matrix resin being a mixture of polycarbonate and polyphenyl ether in a weight ratio of 1:1-3:1.

[0050] Polycarbonate (PC) is an engineering plastic with excellent impact resistance, heat resistance and light transmission, and its molecular chain contains carbonate groups, which endow the material with good mechanical properties and flame-retardant potential. Polyphenyl ether (PPO) has excellent heat resistance, chemical corrosion resistance and electrical insulation, but its processing performance is relatively poor. By mixing polycarbonate and polyphenyl ether in a specific ratio, the present application can fully exert the synergistic effect of the two, that is, polycarbonate can improve the processing performance and impact resistance of polyphenyl ether, and polyphenyl ether can improve the heat resistance and dimensional stability of the material, thereby providing a good mechanical performance basis for the flame-retardant composition.

[0051] Specifically, when the weight ratio of polycarbonate and polyphenyl ether is 1:1-3:1, the best performance balance can be achieved. If the proportion of polycarbonate is too high, the heat resistance of the material may be reduced; and if the proportion of polyphenyl ether is too high, the processing difficulty of the material is increased and the impact performance is reduced.

[0052] In a preferred embodiment of the present application, the weight average molecular weight of the polycarbonate is in the range of 25,000-60,000 g / mol, preferably 30,000-40,000 g / mol, more preferably 30,000-35,000 g / mol. The molecular weight of polycarbonate has an important influence on its performance, and a too high molecular weight will result in poor melt flowability of the material, which is not conducive to processing; and a too low molecular weight will result in a decrease in the mechanical properties of the material. By selecting a polycarbonate with the above-mentioned molecular weight range, the mechanical properties of the material can be ensured while ensuring good processing performance.

[0053] Preferably, the polycarbonate can be selected from one or more of the group consisting of bisphenol A type polycarbonate, bisphenol S type polycarbonate, silicone modified polycarbonate and polyester modified polycarbonate, and bisphenol A type polycarbonate is preferred. Bisphenol A type polycarbonate is a widely used polycarbonate variety, which has excellent comprehensive performance and relatively low cost, and can meet the performance requirements of the base resin of the present application.

[0054] Preferably, the weight average molecular weight of the polyphenyl ether is in the range of 5,000-25,000 g / mol, preferably 10,000-25,000 g / mol, more preferably 15,000-23,000 g / mol. The molecular weight of polyphenyl ether also affects the performance of the material, and an appropriate molecular weight can ensure that the material has good heat resistance and mechanical properties, and is easy to process with polycarbonate.

[0055] According to the technical solution of the present application, the flame-retardant composition comprises 15-28% by weight of a composite flame retardant, and the composite flame retardant comprises a phosphoric acid ester type flame retardant, a cyanamide type flame retardant and an inorganic flame retardant in a weight ratio of 1:0.5-0.8:2-2.5, wherein the inorganic flame retardant is selected from one or more of the group consisting of aluminum hydroxide, antimony trioxide, magnesium hydroxide and zinc borate. The present application adopts a composite flame retardant system, and through the synergistic effect between different types of flame retardants, the flame-retardant performance of the material can be significantly improved while reducing the total amount of the flame retardant, thereby avoiding the adverse effects of a large amount of a single flame retardant on other properties of the material.

[0056] Specifically, the flame-retardant mechanism of the phosphate ester flame retardant is mainly to generate substances such as phosphoric acid at high temperatures, which can inhibit the combustion reaction of combustible materials and form a carbon layer on the surface of the material to prevent the transfer of heat and oxygen. In the present application, the phosphate ester flame retardant can be selected from one or more of the group consisting of triphenyl phosphate (TPP), tricresyl phosphate (TCP) and tris (2-ethylhexyl) phosphate (TEHP). These phosphate ester flame retardants have good flame-retardant effect and compatibility with the base resin, which can effectively improve the flame-retardant performance of the material.

[0057] The flame-retardant mechanism of the cyanamide flame retardant is mainly to play a role through heat absorption, release of non-combustible gas to dilute oxygen, and formation of an expanded carbon layer. In the present application, the cyanamide flame retardant can be selected from one or more of the group consisting of melamine cyanurate (MCA), melamine and dicyandiamide. Among them, melamine cyanurate (MCA) is an excellent cyanamide flame retardant with high flame-retardant efficiency, low toxicity, good synergistic effect with other flame retardants, etc., and is the preferred choice of the present application.

[0058] Inorganic flame retardants have the advantages of long-lasting flame-retardant effect, non-toxicity, environmental protection, etc., and their flame-retardant mechanism is mainly achieved through heat absorption decomposition, release of water vapor and other non-combustible gases, and formation of a protective layer on the surface of the material. In the present application, the inorganic flame retardant is selected from one or more of the group consisting of aluminum hydroxide, antimony trioxide, magnesium hydroxide and zinc borate. Aluminum hydroxide and magnesium hydroxide will decompose to produce a large amount of water vapor at high temperatures, while absorbing a large amount of heat, which can effectively reduce the temperature of the material surface and inhibit the combustion reaction; antimony trioxide has limited flame-retardant effect, but when used in combination with other flame retardants (such as phosphate ester flame retardants), it can produce a significant synergistic flame-retardant effect; zinc borate has good smoke suppression and flame-retardant performance, which can further improve the flame-retardant effect of the material.

[0059] According to the technical solution of the present application, by compounding the phosphate ester flame retardant, the cyanamide flame retardant and the inorganic flame retardant in a weight ratio of 1:0.5-0.8:2-2.5, the best synergistic flame-retardant effect can be achieved. Within this ratio range, the three flame retardants each play their advantages, complement each other, and form an efficient flame-retardant system. Specifically, the phosphate ester flame retardant can play a flame-retardant role in both the gas phase and the condensed phase, the cyanamide flame retardant can promote the formation and expansion of the carbon layer, and the inorganic flame retardant can enhance the flame-retardant effect through heat absorption and release of non-combustible gases.

[0060] In a particularly preferred embodiment of the present application, the composite flame retardant comprises triphenyl phosphate (TPP), melamine cyanurate (MCA) and aluminum hydroxide in a weight ratio of 1:0.6-0.65:2.3-2.5. Experimental results show that when the composite flame retardant with the specific ratio is used, the flame-retardant composition can achieve the best flame-retardant effect, the limiting oxygen index (LOI) is significantly improved, and the strict requirements of new energy automobile power batteries on flame-retardant performance can be met.

[0061] According to the technical solution of the present application, the flame-retardant composition comprises 10-20 wt% of the heat-conducting agent. In the working process of the new energy automobile power battery, a large amount of heat is generated, which will cause the temperature of the battery to rise if not dissipated in time, affecting the performance and service life of the battery, and even causing safety accidents. Therefore, the flame-retardant material for power batteries not only needs to have good flame-retardant performance, but also needs to have excellent heat-conducting performance.

[0062] In the present application, preferably, the heat-conducting agent is selected from one or more of the group consisting of graphene, aluminum powder, nickel powder, carbon nanotubes and carbon fibers. These heat-conducting agents have a high thermal conductivity coefficient, can form an effective heat-conducting network in the material, and improve the heat-conducting performance of the material, so as to conduct the heat generated by the battery in time.

[0063] Graphene is a two-dimensional material composed of carbon atoms, has an extremely high thermal conductivity coefficient (up to 5000 W / m•K or more), and is one of the best heat-conducting materials known at present. Adding graphene as a heat-conducting agent to the flame-retardant composition can significantly improve the heat-conducting performance of the material. Aluminum powder and nickel powder are common metal heat-conducting agents, have good heat-conducting and electric-conducting properties, and can effectively improve the heat-conducting effect of the material. Carbon nanotubes and carbon fibers also have excellent heat-conducting performance and mechanical properties, and adding them to the material can not only improve the heat-conducting property, but also enhance the mechanical properties of the material.

[0064] The addition amount of the heat-conducting agent has an important influence on the heat-conducting performance and mechanical properties of the material. When the addition amount is too small, an effective heat-conducting network cannot be formed, and the heat-conducting performance of the material is limitedly improved; when the addition amount is too large, the heat-conducting agent is not uniformly dispersed in the matrix resin, and agglomeration phenomenon is easily caused, thereby affecting the mechanical properties and processing performance of the material. The present application selects an addition amount of 10-20 wt% of the heat-conducting agent, which can ensure that the material has good heat-conducting performance while avoiding adverse effects on the mechanical properties and processing performance of the material.

[0065] According to the technical scheme of the present application, the flame-retardant composition contains 5-10 wt% of silane coupling agent. The silane coupling agent is a kind of compound with amphiphilic structure, which contains both groups capable of combining with inorganic materials (such as flame retardant and thermal conductive agent) and groups capable of combining with organic materials (such as matrix resin) in the molecule. The addition of silane coupling agent in the flame-retardant composition can improve the interfacial compatibility between the flame retardant, thermal conductive agent and matrix resin, and enhance the binding force therebetween. Specifically, the silane coupling agent can combine with groups such as hydroxyl groups on the surface of the flame retardant and thermal conductive agent through chemical adsorption or chemical reaction, while its organic groups can chemically react with or physically entangle with the matrix resin, thereby establishing effective chemical bond connection between the inorganic filler and the organic matrix. This not only can improve the dispersibility of the flame retardant and thermal conductive agent in the matrix resin, avoiding the agglomeration phenomenon, but also can enhance the interfacial bonding strength of the material, thereby improving the mechanical properties and processing properties of the material while ensuring the flame-retardant and thermal conductive properties of the material.

[0066] Preferably, the silane coupling agent can be one or more selected from the group consisting of vinyltriethoxysilane, γ-aminopropyltriethoxysilane, vinyltrimethoxysilane and γ-mercaptopropyltrimethoxysilane. These silane coupling agents have good coupling effect and stability, and can meet the use requirements of the present application. The addition amount of the silane coupling agent also needs to be reasonably controlled. If the addition amount is too small, the compatibility between the components cannot be sufficiently improved; if the addition amount is too large, too many interfaces may be formed in the material, which may adversely affect the performance of the material. The present application selects an addition amount of 5-10 wt% of the silane coupling agent, which can achieve the best modification effect.

[0067] According to the technical scheme of the present application, the flame-retardant composition contains 1-3 wt% of lubricant. The lubricant plays an important role in the processing of the flame-retardant composition, and its main function is to improve the melt flowability of the material, reduce the friction and adhesion between the material and the processing equipment, and improve the demolding performance of the material, thereby ensuring the smooth progress of the processing and improving the quality of the product. According to the technical scheme of the present application, preferably, the lubricant can be one or more selected from the group consisting of stearic acid, calcium stearate and paraffin. Stearic acid and calcium stearate are commonly used metal soap lubricants, which have good lubricating effect and thermal stability; paraffin is a hydrocarbon lubricant, which can effectively reduce the melt viscosity of the material and improve its flowability. The addition amount of the lubricant is usually small, and too much addition amount may cause the mechanical properties of the material to decrease, such as tensile strength and bending strength. The present application selects an addition amount of 1-3 wt% of the lubricant, which can meet the requirements of the lubricating performance in the processing, and will not have obvious adverse effects on other properties of the material.

[0068] According to some preferred embodiments of the present application, the flame-retardant composition further comprises 1-3 wt% of an antioxidant based on the total weight of the flame-retardant composition. During the processing and use of the flame-retardant composition, the material can be subjected to heat, oxygen and other factors, and thus is prone to oxidative degradation, which can result in the deterioration of the performance of the material. The addition of an antioxidant can inhibit or delay the oxidation process of the material, and thus can improve the thermal stability and service life of the material. The antioxidant is preferably a mixture of a hindered phenolic antioxidant and a phosphite antioxidant in a weight ratio of 1:1-2:1. The hindered phenolic antioxidant is a kind of efficient primary antioxidant, which can capture free radicals and terminate the chain growth of the oxidation reaction. The phosphite antioxidant is a kind of secondary antioxidant, which can decompose hydroperoxide and prevent the generation of free radicals. The use of the two antioxidants in a specific ratio can produce a synergistic antioxidant effect, and thus can significantly improve the antioxidant performance of the material. Preferably, the hindered phenolic antioxidant can be one or more selected from the group consisting of 2,6-di-tert-butyl-p-cresol, 2,6-di-tert-butylphenol and 2,4,6-tri-tert-butylphenol; and the phosphite antioxidant can be one or more selected from the group consisting of pentaerythritol diisodecyl diphosphite, triphenyl phosphite, tris(2,4-di-tert-butylphenyl) phosphite and diphenyl isodecyl phosphite.

[0069] According to some preferred embodiments of the present application, the flame-retardant composition further comprises a colorant to meet different appearance requirements. Preferably, the flame-retardant composition comprises 2 wt% or less of the colorant based on the total weight of the flame-retardant composition. The amount of the colorant should not be too much, otherwise it can affect other properties of the material. The colorant can be a commonly used coloring material such as an organic pigment or an inorganic pigment, and the specific type can be selected according to actual needs.

[0070] The method for preparing the flame-retardant composition that can be used in the present application is not particularly limited. Specifically, it can include the following steps:

[0071] The components are weighed according to the formulation ratio, including 50-68 wt% of the base resin (polycarbonate and polyphenyl ether mixed in a ratio of 1:1-3:1), 15-28 wt% of the composite flame retardant (phosphate, cyanamide and inorganic flame retardant mixed in a ratio of 1:0.5-0.8:2-2.5), 10-20 wt% of the thermal conductive agent, 5-10 wt% of the silane coupling agent, 1-3 wt% of the lubricant, and optionally 1-3 wt% of the antioxidant and 2 wt% or less of the colorant. Then, all the components are added to a high-speed mixer and mixed under heating to obtain a mixture. The mixture is added to a twin-screw extruder and subjected to melt blending and extrusion. Finally, the extruded material is cooled by water and then pelletized to obtain flame-retardant composition particles.

[0072] According to another aspect of the present application, there is provided a flame-retardant layer comprising the flame-retardant composition described above. The flame-retardant layer is prepared by subjecting the flame-retardant composition to a suitable processing technique (e.g. extrusion molding, injection molding, casting, etc.).

[0073] The thickness of the flame-retardant layer is in the range of 0.5 mm to 5 mm, preferably 1 mm to 3 mm. The thickness of the flame-retardant layer has a significant impact on its performance. If the thickness is too thin, it can not provide sufficient flame-retardant effect and mechanical strength; if the thickness is too thick, it will increase the weight and volume of the power battery, affecting the energy density of the battery. By selecting a thickness in the range of 0.5 mm to 5 mm, preferably 1 mm to 3 mm, the flame-retardant layer can have good performance while meeting the requirements of light weight and small size for power batteries.

[0074] The flame-retardant layer prepared from the flame-retardant composition of the present application has excellent flame-retardant performance, thermal conductivity and mechanical properties. Its limiting oxygen index (LOI) can reach more than 27%, meeting the requirements of new energy automobile power batteries for flame-retardant performance; the thermal conductivity (W / m・K) can reach more than 0.4 W / m・K, allowing the heat generated by the battery to be dissipated; the tensile strength (MPa) can reach more than 12 MPa, and the bending strength (MPa) can reach more than 120 MPa, thus having basic mechanical strength to withstand various external forces during installation and use of the battery.

[0075] According to still another aspect of the present application, there is provided a new energy automobile power battery comprising:

[0076] a power battery module;

[0077] an aluminum shell enclosing the power battery module; and

[0078] the flame-retardant layer described above, which is arranged between and in contact with the power battery module and the aluminum shell.

[0079] The power battery module is the core part of the new energy vehicle power battery, responsible for storing and providing electric energy. The specific structure of the power battery module usually includes a plurality of single cells (such as lithium ion cells), a bracket or a shell for fixing and connecting the cells, and a tab, a bus bar and other components for realizing the electrical connection between the cells, which together constitute an overall module structure capable of stably outputting electric energy. The aluminum shell has good thermal conductivity and mechanical strength, can protect the battery module, and help the heat dissipation of the battery. The flame-retardant layer of the present application is arranged between the battery module and the aluminum shell, which can fully exert its excellent performance: when the battery is in thermal runaway, the flame-retardant layer can effectively prevent the spread of fire and play a good flame-retardant role; at the same time, it can quickly conduct the heat generated by the battery module to the aluminum shell, and then dissipate to the outside through the aluminum shell, avoiding heat accumulation; in addition, the flame-retardant layer can also provide a certain buffering and supporting effect for the battery module, enhancing the structural stability of the battery and improving the vibration resistance and impact resistance of the battery.

[0080] Compared with the prior art in the art, the present application has the following advantages:

[0081] 1. By mixing the specific ratio of polycarbonate and polyphenyl ether matrix resin, and the compound system of phosphate ester, cyanamide and inorganic flame retardant, the synergistic improvement of flame retardation, thermal conductivity and mechanical properties is realized, and the defects that the performance of traditional materials is difficult to consider are overcome.

[0082] 2. The synergistic effect of the composite flame retardant can improve the flame retardant effect while reducing the addition amount, avoid the performance degradation of the material caused by the large amount of addition of the flame retardant, and solve the contradiction between the flame retardant efficiency and the material performance in the traditional flame retardant system.

[0083] 3. The addition of silane coupling agent enhances the compatibility between the flame retardant, the thermal conductor and the matrix resin, not only ensures the flame retardation and thermal conductivity, but also improves the mechanical strength and processing fluidity of the material, and optimizes the overall interface bonding force.

[0084] 4. The prepared flame-retardant layer has excellent performance in flame-retardant performance, thermal conductivity and mechanical properties, can meet the strict requirements of new energy vehicle power battery in safety, heat dissipation and structural stability, and has significant practical application value.

[0085] 5. The raw materials used in the flame-retardant composition of the present application are common chemical products in the market, and the preparation process is simple and easy to operate, suitable for industrial production.

[0086] Examples

[0087] In the present application, unless otherwise specified, the reagents used are commercially available products, which are used directly without further purification treatment.

[0088] The raw material information employed in the examples and comparative examples of the present application is listed in Table 1 below.

[0089] Table 1 Raw material information employed in the examples and comparative examples of the present application

[0090]

[0091] Test methods

[0092] According to the methods described below, the flame retardant properties, thermal conductivity properties and mechanical properties (tensile strength and bending strength) of the flame retardant films prepared in each of the following examples and comparative examples were tested, respectively.

[0093] Flame retardant property test

[0094] The flame retardant property test was conducted according to GB / T 2406-1993. GB / T 2406-1993 is used to determine the minimum oxygen concentration required for a material to burn in a mixture of oxygen and nitrogen (oxygen index) to evaluate the combustion performance of the material.

[0095] According to the general industry standard for limiting oxygen index (LOI) test of flame-retardant thermal conductive materials for new energy automobile power batteries according to GB / T 2406-1993, when the limiting oxygen index reaches 27%, it can be considered that the flame-retardant thermal conductive material meets the basic requirements of new energy automobile power batteries on flame retardancy; and when the limiting oxygen index reaches more than 30%, it can be considered that the flame-retardant thermal conductive material performs excellently in terms of flame retardancy.

[0096] Thermal conductivity property test

[0097] The thermal conductivity property test was conducted according to ASTM E1461. ASTM E1461 is a standard test method for determining the thermal diffusivity of solid materials, which is based on the flash method.

[0098] According to the general industry standard for thermal conductivity test of flame-retardant thermal conductive materials for new energy automobile power batteries according to ASTM E1461, when the thermal conductivity (W / m·K) reaches more than 0.4 W / (m·K), it can be considered that the flame-retardant thermal conductive material meets the basic requirements of new energy automobile power batteries on thermal conductivity; and when the thermal conductivity (W / m·K) reaches more than 3 W / (m·K), it can be considered that the thermal conductive material performs excellently in terms of thermal conductivity.

[0099] Tensile strength test

[0100] The tensile strength was tested according to GB / T 1040.1-2006. GB / T 1040.1-2006 is applicable to the tensile property test of plastics and composite materials, especially in the field of automobile batteries.

[0101] According to the general industry standard for testing the tensile strength of the flame-retardant heat-conducting material for new energy automobile power batteries according to GB / T 1040.1-2006, when the tensile strength (MPa) reaches 12 MPa, it can be considered that the flame-retardant heat-conducting material meets the basic requirements of new energy automobile power batteries on mechanical properties related to tensile properties; and when the tensile strength (MPa) reaches 30 MPa or more, it can be considered that the flame-retardant heat-conducting material performs excellently in mechanical properties related to tensile properties.

[0102] Bending strength test

[0103] The bending strength is tested according to ISO 178-93.

[0104] According to the general industry standard for testing the bending strength of the flame-retardant heat-conducting material for new energy automobile power batteries according to ISO 178-93, when the bending strength (MPa) reaches 120 MPa, it can be considered that the flame-retardant heat-conducting material meets the basic requirements of new energy automobile power batteries on mechanical properties related to bending properties; and when the bending strength (MPa) reaches 300 MPa or more, it can be considered that the flame-retardant heat-conducting material performs excellently in mechanical properties related to bending properties.

[0105] Example 1 (E1)

[0106] The following components are weighed by weight %:

[0107] PC (30,000) and PPO (15,000) in a total amount of 55 wt%, with a weight ratio of 1:1;

[0108] TPP, MCA and Al(OH)3 in a total amount of 18 wt%, with a weight ratio of 1:0.6:2.5;

[0109] 15 wt% of the heat-conducting agent graphene;

[0110] 10 wt% of the silane coupling agent vinyltriethoxysilane; and

[0111] 2 wt% of the lubricant calcium stearate.

[0112] The above components are added to a high-speed mixer and mixed at 80℃ for 10 min to obtain a mixed material.

[0113] The mixed material is added to a twin-screw extruder, and the extrusion temperature is set as follows: Zone 1 220℃, Zone 2 230℃, Zone 3 240℃, Zone 4 250℃, Zone 5 260℃, Zone 6 260℃, die 250℃, and the screw speed is 300 r / min, for melt blending extrusion.

[0114] After water cooling, the extruded material is cut into particles to obtain flame-retardant material particles.

[0115] The flame retardant material particles prepared above were made into a flame retardant film 1 having a thickness of 1 mm through a flow casting process.

[0116] Then, the flame retardant film 1 was tested for the flame retardant properties, the thermal conductivity properties, and the mechanical properties (tensile strength and bending strength) according to the methods for measuring the flame retardant properties, the thermal conductivity properties, and the mechanical properties (tensile strength and bending strength) described in detail above, and the test results are shown in Table 2 below.

[0117] Examples 2-9 (E2-E9) and Comparative Examples 1-10 (CE1-CE10)

[0118] The flame retardant films 2-9 and the comparative flame retardant films 1-10 were prepared in a similar manner to Example 1 above, except that the raw material ratios were changed as shown in Table 2 or Table 3 below.

[0119] Then, the flame retardant films 2-9 and the comparative flame retardant films 1-10 were tested for the flame retardant properties, the thermal conductivity properties, and the mechanical properties (tensile strength and bending strength) according to the methods for measuring the flame retardant properties, the thermal conductivity properties, and the mechanical properties (tensile strength and bending strength) described in detail above, and the test results are shown in Table 2 or Table 3 below.

[0120] Table 2 Component ratios of the flame retardant compositions of Examples 1-9 (E1-E9) and the test results of the properties

[0121]

[0122] Table 3 Component ratios of the flame retardant compositions of Comparative Examples 1-10 (CE1-CE10) and the test results of the properties

[0123]

[0124] As can be seen from the results shown in Table 3 and Table 2 above, when a specific content and a base resin, a complex flame retardant, a thermal conductivity agent, a silane coupling agent, and a lubricant of a specific composition are selected within the scope of the present application, a flame retardant composition having good flame retardant properties, thermal conductivity properties, and mechanical properties (tensile strength and bending strength) suitable for use as a flame retardant layer between a battery module and an aluminum case of a new energy automobile power battery can be obtained. In particular, as can be seen by comparing the results of Examples 1-5 with those of Examples 6-9, by further controlling the weight average molecular weight of polycarbonate and polyphenyl ether and selecting a specific weight ratio of triphenyl phosphate (TPP), melamine cyanurate (MCA), and aluminum hydroxide of 1:0.6-0.65:2.3-2.5, excellent effects can be simultaneously obtained in terms of the flame retardant properties, the thermal conductivity properties, and the mechanical properties (tensile strength and bending strength).

[0125] While specific embodiments of the application have been shown and described in detail, it will be understood by those skilled in the art that various substitutions and / or modifications have been made thereto without departing from the scope of the present application. The application is intended to cover any improvements or modifications to the specific embodiments of the application discussed herein. Numerous modifications and variations are possible in light of the above teachings without departing from the scope of the application.

Claims

1. A flame-retardant composition characterized in that, The flame-retardant composition comprises, based on the total weight thereof: 50-68% by weight of a matrix resin which is a mixture of polycarbonate and polyphenylene ether at a weight ratio of 1:1-3:1; 15-28% by weight of a composite flame retardant comprising a phosphoric acid ester-based flame retardant, a cyanamide-based flame retardant, and an inorganic flame retardant at a weight ratio of 1:0.5-0.8:2-2.5, wherein the inorganic flame retardant is selected from one or more of the group consisting of aluminum hydroxide and magnesium hydroxide; 10-20% by weight of a heat conductive agent; 5-10% by weight of a silane coupling agent; and 1-3% by weight of a lubricant.

2. The flame-retardant composition according to claim 1, characterized in that: the weight average molecular weight of the polycarbonate is in the range of 30,000-40,000 g / mol; and / or the polycarbonate is selected from one or more of the group consisting of bisphenol A type polycarbonate, bisphenol S type polycarbonate, silicone-modified polycarbonate, and polyester-modified polycarbonate; and / or the weight average molecular weight of the polyphenylene ether is in the range of 10,000-25,000 g / mol.

3. The flame-retardant composition according to claim 1, characterized in that: the phosphoric acid ester-based flame retardant is selected from one or more of the group consisting of triphenyl phosphate, tricresyl phosphate, and tris(2-ethylhexyl) phosphate; and / or the cyanamide-based flame retardant is selected from one or more of the group consisting of melamine cyanurate, melamine, and dicyandiamide; and / or the silane coupling agent is selected from one or more of the group consisting of vinyltriethoxysilane, γ-aminopropyltriethoxysilane, vinyltrimethoxysilane, and γ-mercaptopropyltrimethoxysilane.

4. The flame retardant composition according to claim 1, characterized in that, the composite flame retardant comprises triphenyl phosphate, melamine cyanurate, and aluminum hydroxide at a weight ratio of 1:0.6-0.65:2.3-2.

5.

5. The flame-retardant composition according to claim 1, characterized in that: the heat conductive agent is selected from one or more of the group consisting of graphene, aluminum powder, nickel powder, carbon nanotube, and carbon fiber; and / or the lubricant is selected from one or more of the group consisting of stearic acid, calcium stearate, and paraffin wax.

6. The flame-retardant composition according to claim 1, characterized in that, The flame-retardant composition further comprises 1-3% by weight of an antioxidant based on the total weight thereof.

7. The flame-retardant composition according to claim 6, characterized in that the antioxidant is a mixture of a hindered phenol-based antioxidant and a phosphite-based antioxidant at a weight ratio of 1:1-2:1, wherein the hindered phenol-based antioxidant is selected from one or more of the group consisting of 2,6-di-tert-butyl-p-cresol, 2,6-di-tert-butylphenol, and 2,4,6-tri-tert-butylphenol, and the phosphite-based antioxidant is selected from one or more of the group consisting of dipentaerythritol diisodecyl diphosphite, triphenyl phosphite, tris(2,4-di-tert-butylphenyl) phosphite, and diphenyl isodecyl phosphite.

8. The flame retardant composition according to claim 1, characterized in that, The flame-retardant composition comprises 2% by weight or less of a colorant based on the total weight thereof.

9. A flame retardant layer characterized by, The flame-retardant layer comprises the flame-retardant composition according to any one of claims 1 to 8, and the thickness of the flame-retardant layer is in the range of 0.5 mm-5 mm.

10. A new energy vehicle power battery, characterized in that, The new energy automobile power battery comprises: A power battery module; An aluminum case that encloses the power battery module; and The fire-retardant layer according to claim 9 is arranged between and in contact with the power battery module and the aluminum case.

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