Fireproof heat-insulating coating for outer package of lithium battery as well as preparation method and application of fireproof heat-insulating coating

Abstract

The invention relates to the field of lithium ion battery manufacturing, in particular to a lithium ion battery outer package fireproof heat-insulating coating as well as a preparation method and application thereof. The fireproof heat-insulating coating for packaging comprises the following components in parts by weight: 31-42% of epoxy resin, 21-27% of ammonium polyphosphate, 11-18% of an epoxy curing agent, 1.5-3% of expansible graphite, 0-1% of titanium dioxide, 0-5% of montmorillonite, 6-10% of zinc borate, 6-9% of glass fiber, 0-9% of melamine, 0-3% of polyether phosphate and 0.5-4% of a diluent. The fireproof heat-insulating coating for the external package of the lithium ion battery can effectively solve the problem that thermal runaway in the battery is further caused when the lithium battery is in an external fire environment or a high-temperature environment, and compared with a traditional heat-insulating mode, the fireproof heat-insulating coating for the external package of the lithium ion battery can effectively prevent the secondary explosion risk of the lithium battery in the high-risk environment.

Description

Technical Field

[0001] The present invention relates to the field of lithium-ion battery manufacturing, and in particular to a fireproof and heat-insulating coating for lithium-ion battery outer packaging, a preparation method thereof, and an application thereof. Background Art

[0002] Currently, thermal runaway protection for lithium-ion batteries in the market primarily relies on contactless air isolation to prevent heat transfer from a runaway lithium-ion battery to the surrounding environment or adjacent lithium-ion batteries. However, this approach is only effective for batteries with smaller capacity and lower energy. As the heat released during thermal runaway increases, existing air isolation methods become increasingly ineffective. Because air has a low specific heat capacity, it easily heats a runaway battery cell, causing it to rise in temperature, potentially heating surrounding batteries and components. In particular, with the increasing use of lithium-ion battery-powered new energy vehicles (NEVs), and their rapid growth in major cities, the inherent safety characteristics and temperature sensitivity of lithium-ion batteries have led to frequent safety incidents in hot weather, primarily involving battery fires in the battery pack, which in turn can lead to vehicle fires. Furthermore, lithium-ion batteries are electrochemical power sources, and thermal runaway reactions are rapid and nearly uncontrollable, accompanied by intense flames reaching temperatures as high as 1600°C. Currently, effective fire prevention measures are difficult to implement to prevent the flames from spreading to other areas of the vehicle.

[0003] At present, the best way to solve the thermal management of automotive power battery modules is to suppress the spread of thermal runaway of a single module and block the conduction of high temperature. On the one hand, it can curb the occurrence of fire and explosion of electric vehicles, and on the other hand, it can provide drivers and passengers with a longer escape time. Since my country's special fire-retardant coatings for power batteries started relatively late, although there are many heat-insulating and fire-proof materials on the market, most of them are fire-retardant coatings for construction and are not suitable for high-density chemical lithium-ion batteries. Such fire-retardant coatings must have low density, low thermal conductivity, and high heat shock resistance. There are very few coatings that are suitable for workshop assembly line processes. It is applied to the inner wall or shell of the power battery pack and is used for fire protection inside and outside the battery pack. Under open flame conditions, the thin coating will instantly expand by more than 25 times its own thickness. The coating has good electrical insulation properties, and the expanded layer produced after the fire still maintains high insulation performance. Therefore, there is an urgent need in this field to provide an excellent lithium-ion outer packaging fire-retardant and heat-insulating coating. Summary of the Invention

[0004] To address the above technical issues, the present invention provides a fire-resistant and heat-insulating coating for lithium-ion battery packaging, as well as its preparation method and application. The fire-resistant and heat-insulating coating for lithium-ion battery packaging provided by the present invention can effectively address the problem of thermal runaway within lithium batteries caused by external fire or high-temperature environments. Compared with traditional thermal insulation methods, it can effectively prevent the risk of secondary explosions in lithium batteries in such high-risk environments.

[0005] In the first aspect, the present invention provides a fireproof and heat-insulating coating for lithium-ion battery outer packaging, which includes the following components by weight: 31-42% epoxy resin, 21-27% ammonium polyphosphate, 11-18% epoxy curing agent, 1.5-3% expandable graphite, 0-1% titanium dioxide, 0-5% montmorillonite, 6-10% zinc borate, 6-9% glass fiber, 0-9% melamine, 0-3% polyether phosphate, and 0.5-4% diluent. In the present invention, the lithium battery fireproof and heat-insulating coating using specific raw materials and dosages solves the problem of timely absorption of the large amount of heat generated instantly during thermal runaway of the lithium battery and the problem that the lithium battery in an external fire environment or high temperature environment will further cause thermal runaway inside the battery. Compared with traditional insulation methods, it can effectively prevent the risk of secondary explosion of lithium batteries in the above-mentioned high-risk environments. The ultra-thin coating material used in the present invention can quickly absorb heat within tens of seconds and provide drivers and passengers with longer escape time.

[0006] Preferably, the epoxy resin is bisphenol A epoxy resin. The present invention uses bisphenol A epoxy resin and epoxy curing agent to cross-link, and can better form a fireproof and heat-insulating coating in combination with other raw materials.

[0007] Preferably, the ammonium polyphosphate is high-polymerization type II ammonium polyphosphate, and the particle size is preferably 10-20 μm. The ammonium polyphosphate used in the present invention can better play a role in the system, dehydrate at high temperature and form a carbonized expanded carbon layer to better isolate heat and oxygen.

[0008] Preferably, the particle size of the expandable graphite is 10-50 μm, preferably 10-30 μm. Using expandable graphite of the preferred particle size and ammonium polyphosphate to fill microscopic pores can form a denser insulation layer, blocking heat conduction and absorbing harmful gases.

[0009] Preferably, the glass fiber is a long rod glass fiber with a diameter ranging from 3-8 μm and a length of 20-100 μm, preferably 30-50 μm. In the present invention, by using the long rod glass fiber, the interaction with other raw materials can further improve the mechanical properties of the coating, prevent the coating from cracking, and better adapt to battery deformation.

[0010] Preferably, the fireproof and thermal-insulating coating for lithium-ion battery outer packaging comprises the following components by weight: 31-40% epoxy resin, 21-27% ammonium polyphosphate, 11-18% epoxy curing agent, 1.5-3% expandable graphite, 0-1% titanium dioxide, 0-3% montmorillonite, 6-10% zinc borate, 6-8% glass fiber, 5-9% melamine, 0-2% polyether phosphate, and 0.5-2% diluent. By optimizing the types and amounts of each component, the present invention can further enhance the overall performance of the coating. The synergistic effect of multiple components can better address the risk of thermal runaway in lithium batteries exposed to fire. The coating combines the advantages of high flame retardancy, rapid expansion, electrical insulation, low density, low thermal conductivity, and thermomechanical resistance, providing key safety assurance for new energy vehicles and energy storage.

[0011] More preferably, the composition comprises the following components by weight: 31-40% epoxy resin, 21-23% ammonium polyphosphate, 11-16% epoxy curing agent, 2-3% expandable graphite, 0-1% titanium dioxide, 0-3% montmorillonite, 6-10% zinc borate, 6-9% glass fiber, 7-8% melamine, 0.5-1% polyether phosphate, and 0.5-2% diluent. The present invention achieves better overall effects when the preferred amounts of the components are used.

[0012] In a second aspect, the present invention provides a method for preparing the fire-retardant and heat-insulating coating for lithium battery outer packaging, which comprises: 1) Epoxy resin, titanium dioxide, zinc borate, montmorillonite, glass fiber, melamine, expandable graphite, polyether phosphate, and diluent are mixed and stirred to obtain component A.

[0013] 2) Mix ammonium polyphosphate and epoxy curing agent and stir to obtain component B.

[0014] Preferably, in step 1), titanium dioxide, zinc borate, montmorillonite, glass fiber, melamine, expandable graphite, polyether phosphate and diluent are added to the epoxy resin in sequence, and each time a material is added, the mixture is stirred at 6000-8000 r / min for 8-10 minutes.

[0015] Preferably, in step 2), ammonium polyphosphate and an epoxy curing agent are mixed and stirred at 6000-8000 rpm for 8-10 minutes to obtain component B. Optionally, components A and B are mixed and stirred at 6000-8000 rpm for 2-3 minutes. The present invention optimizes the mixing sequence of the raw materials and process parameters to produce a fire-retardant and heat-insulating coating for lithium battery packaging with superior performance.

[0016] In a third aspect, the present invention provides a lithium ion outer packaging fireproof and heat-insulating coating, which is obtained from the above-mentioned lithium ion outer packaging fireproof and heat-insulating coating or the lithium ion outer packaging fireproof and heat-insulating coating obtained by the above-mentioned preparation method.

[0017] In a fourth aspect, the present invention provides the use of the above-mentioned lithium ion outer packaging fireproof and heat-insulating coating or the lithium ion outer packaging fireproof and heat-insulating coating obtained by the above-mentioned preparation method in lithium ion batteries.

[0018] The present invention has at least the following beneficial effects: the fireproof and thermal-insulating coating for lithium battery outer packaging prepared by the present invention solves the problem of timely absorption of the large amount of heat generated instantly during thermal runaway of lithium batteries, and also addresses the problem of further internal thermal runaway of lithium batteries caused by external fire or high-temperature environments. Compared with traditional thermal insulation methods, it can effectively prevent the risk of secondary explosion of lithium batteries in such high-risk environments. The ultra-thin coating material provided by the present invention uses commonly available raw materials, can rapidly absorb heat within tens of seconds, quickly expand and isolate heat, and provide drivers and passengers with longer escape time. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the present invention or the prior art, a brief introduction is given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0020] Figure 1 This is a picture of the fire-retardant and heat-insulating coating provided in an embodiment of the present invention after testing.

[0021] Figure 2 This is a picture of the fire-retardant and heat-insulating coating after testing provided as a comparative example of the present invention.

[0022] Figure 3 These are pictures of the fire-retardant and heat-insulating coatings provided in the embodiments and comparative examples of the present invention after testing.

[0023] Figure 4 These are pictures of the fire-retardant and heat-insulating coatings provided in the embodiments and comparative examples of the present invention after testing. DETAILED DESCRIPTION

[0024] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention are described clearly and completely below. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0025] The endpoints of the ranges and any values ​​disclosed herein 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 endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to form one or more new numerical ranges, and these numerical ranges should be considered to be specifically disclosed in the present invention.

[0026] Any embodiment described herein as "exemplary" is not necessarily to be construed as preferred over other embodiments. Although various aspects of the embodiments are presented in the drawings, the drawings are not necessarily drawn to scale unless specifically noted.

[0027] It should be noted that the following detailed descriptions are illustrative and are intended to provide further explanation of the present application. Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which this application belongs. Where specific techniques or conditions are not specified in the embodiments of the present invention, the techniques or conditions described in the literature in this field, or the product instructions, are used. For devices, instruments, reagents, etc. used, where the manufacturer is not specified, they are all conventional products that can be purchased through regular channels. The experimental reagents and raw materials involved are all commercially available products.

[0028] In the following embodiments, the bisphenol A epoxy resin and curing agent used are E51 type purchased from Suzhou HNSAT Industrial Co., Ltd.; ammonium polyphosphate uses high polymerization degree II ammonium polyphosphate with a particle size of 15 μm, purchased from Zhenjiang Xingxing Flame Retardant Co., Ltd.; melamine is purchased from Zhenjiang Xingxing Flame Retardant Co., Ltd.; the expandable graphite used has a particle size of 10-30 μm and is purchased from Anage Chemical Reagent Co., Ltd.; the glass fiber used is a long rod glass fiber of 30-50 μm, purchased from China Jushi Co., Ltd.; the titanium dioxide used is 100-300 nm and is purchased from Shijiazhuang Tingde Chemical Technology Co., Ltd.; the zinc borate used is purchased from Kunshan Shengheng Chemical Materials Co., Ltd.; the montmorillonite used is purchased from Lingshou County Shunze Mineral Products Processing Plant; the polyether phosphate used is purchased from Zhejiang Alpha Chemical Technology Co., Ltd.; and the diluent used is purchased from Guangdong Zhongke Hongtai New Materials Co., Ltd.

[0029] In the following examples, the preparation method of the fireproof and heat-insulating coating for the outer packaging of lithium batteries is as follows: according to the weight ratio of the components, epoxy resin is added to a homogenizing cup, and titanium dioxide, zinc borate, montmorillonite, glass fiber, melamine, expandable graphite, polyether phosphate, and diluent are added in sequence. Each time a material is added, it is stirred with a homogenizer at 6800-7200 r / min for 8.5±0.5 min to obtain component A, and then ammonium polyphosphate is added to the epoxy curing agent and stirred with a homogenizer at 6800-7200 r / min for 8.5±0.5 min to obtain component B; then, component A and component B are mixed and homogenized at 6800-7200 r / min for 3 min before use.

[0030] Example 1 This embodiment provides a fireproof and heat-insulating coating for lithium battery outer packaging, comprising the following components by weight: 31% bisphenol A epoxy resin, 21% ammonium polyphosphate, 1% titanium dioxide, 7% zinc borate, 1% montmorillonite, 9% glass fiber, 7% melamine, 3% expandable graphite, 1% polyether phosphate, 1% diluent (polyether polyol HSH310), and 18% epoxy curing agent (type E51).

[0031] Example 2 This embodiment provides a fireproof and heat-insulating coating for lithium battery outer packaging, comprising the following components by weight: 31% bisphenol A epoxy resin, 23% ammonium polyphosphate, 0% titanium dioxide, 9% zinc borate, 3% montmorillonite, 9% glass fiber, 7% melamine, 3% expandable graphite, 2% polyether phosphate, 2% diluent (polyether polyol HSH310), and 15% epoxy curing agent (type E51).

[0032] Example 3 This embodiment provides a fireproof and heat-insulating coating for lithium battery outer packaging, comprising the following components by weight: 35% bisphenol A epoxy resin, 25% ammonium polyphosphate, 3% titanium dioxide, 6% zinc borate, 1% montmorillonite, 9% glass fiber, 7% melamine, 2% expandable graphite, 2% polyether phosphate, 1% diluent (polyether polyol HSH310), and 11% epoxy curing agent (type E51).

[0033] Example 4 This embodiment provides a fireproof and heat-insulating coating for lithium battery outer packaging, comprising the following components by weight: 40% bisphenol A epoxy resin, 21% ammonium polyphosphate, 0% titanium dioxide, 6% zinc borate, 0% montmorillonite, 6% glass fiber, 7% melamine, 2% expandable graphite, 1% polyether phosphate, 1% diluent (polyether polyol HSH310), and 16% epoxy curing agent (type E51).

[0034] Comparative Example 1 This comparative example provides a lithium battery fire retardant coating, numbered IFR-1-1, which is purchased from a commercial source and includes the following components by weight: 48% bisphenol A epoxy resin, 21% ammonium polyphosphate, 6% zinc borate, 7% melamine, 2% polyether phosphate, and 16% epoxy curing agent (short-chain amine).

[0035] Comparative Example 2 This comparative example provides a lithium battery fire retardant coating, numbered IFR-1-2, which is purchased from a commercial source and includes the following components by weight: 45% bisphenol A epoxy resin, 24% ammonium polyphosphate, 6% glass fiber, 2% zinc borate, 8% melamine, and 15% epoxy curing agent (cashew nut shell oil).

[0036] Comparative Example 3 A lithium battery fire retardant coating, numbered IFR-2-1, is purchased from a commercial source and includes the following components by weight: 50% bisphenol A epoxy resin, 21% ammonium polyphosphate, 3% glass fiber, 1% zinc borate, 3% titanium dioxide, 7% melamine, 1% polyether phosphate, and 14% epoxy curing agent (E60).

[0037] The coatings used in Examples 1-4 and Comparative Examples 1-3 were prepared and tested for limiting oxygen index according to GB / T 5454-1997 "Determination of burning behavior of textiles - Oxygen index method", GB / T 2406-93 "Test method for burning behavior of plastics - Oxygen index method", GB / T 10707-2008 "Rubber - Determination of burning behavior of rubber - Oxygen index method" and GB / T 8924-2005 "Fiber reinforced plastics - Test method for burning behavior of fiber reinforced plastics - Oxygen index method".

[0038] The test conditions and results of coating Examples 1-4 and Comparative Examples 1-3 are shown in Table 1 below.

[0039] Table 1 Test conditions and results of coating examples 1-4 and comparative examples 1-3

[0040] The temperature heating device used in Examples 1-4 and Comparative Examples 1-3 is a 1000°C butane spray gun. Figure 1-3 As shown, Figure 1 In the middle, the left part is Example 1, and the right part is Example 2. Figure 2 In the figure, the left part is Example 3 and the right part is Example 4. It can be seen that the expansion multiples of Examples 1-4 are not much different. Figure 3 The left side is the coating of comparative example 1, and the right side is the coating of comparative example 2. It can be seen that the expansion multiples are different. Figure 1-2 There are significant differences in Comparative Examples 1-4. Figure 4Among them, coating No. 24-1 is the coating of Example 4, and the uncoated one is without any coating shielding. Coating No. 24-2 is the coating of Comparative Example 2. It can be seen that there is a significant difference in back temperature. The effect of the embodiment of the present invention is obviously better than the uncoated comparative solution and comparative example.

[0041] Table 1 shows that the fireproof and thermal insulation coatings provided in Examples 1-4 of the present invention significantly outperform those in Comparative Examples 1-4 in both fireproofing and thermal insulation. Experimental results demonstrate that the fireproof and thermal insulation coatings for lithium battery packaging provided in the present invention, under the synergistic effect of the aforementioned ammonium polyphosphate, expandable graphite, polyether phosphate, diluent, and various powder fillers, exhibit excellent fireproof, flame-retardant, and thermal insulation properties. The fireproof and thermal insulation coating for lithium battery packaging prepared in Example 4 exhibits the best overall performance. The coatings provided in the present invention also have the advantages of low density and low thermal conductivity, and are resistant to thermal shock, making them suitable for production on assembly lines.

[0042] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A fireproof and heat-insulating coating for lithium-ion battery outer packaging, characterized in that: The invention comprises the following components in parts by weight: 31-42% of epoxy resin, 21-27% of ammonium polyphosphate, 11-18% of epoxy curing agent, 1.5-3% of expandable graphite, 0-1% of titanium dioxide, 0-5% of montmorillonite, 6-10% of zinc borate, 6-9% of glass fiber, 0-9% of melamine, 0-3% of polyether phosphate and 0.5-4% of diluent.

2. The fireproof and heat-insulating coating for lithium-ion battery outer packaging according to claim 1, characterized in that: The epoxy resin is bisphenol A epoxy resin.

3. The fireproof and heat-insulating coating for lithium-ion battery outer packaging according to claim 1 or 2, characterized in that: The ammonium polyphosphate is high-polymerization type II ammonium polyphosphate.

4. The fireproof and heat-insulating coating for lithium-ion battery outer packaging according to any one of claims 1 to 3, characterized in that: The particle size of the expandable graphite is 10-50 μm.

5. The fireproof and heat-insulating coating for lithium-ion battery outer packaging according to any one of claims 1 to 4, characterized in that: The glass fiber is a long rod glass fiber with a length of 20-100 μm.

6. The fireproof and heat-insulating coating for lithium-ion battery outer packaging according to any one of claims 1 to 5, characterized in that: The invention comprises the following components by weight: 31-40% of epoxy resin, 21-27% of ammonium polyphosphate, 11-18% of epoxy curing agent, 1.5-3% of expandable graphite, 0-1% of titanium dioxide, 0-3% of montmorillonite, 6-10% of zinc borate, 6-8% of glass fiber, 5-9% of melamine, 0-2% of polyether phosphate and 0.5-2% of diluent.

7. The method for preparing the fireproof and heat-insulating coating for lithium battery outer packaging according to any one of claims 1 to 6, characterized in that: include: 1) Mixing epoxy resin, titanium dioxide, zinc borate, montmorillonite, glass fiber, melamine, expandable graphite, polyether phosphate and diluent, and stirring to obtain component A; 2) Mix ammonium polyphosphate and epoxy curing agent and stir to obtain component B.

8. The preparation method according to claim 7, characterized in that In step 1), titanium dioxide, zinc borate, montmorillonite, glass fiber, melamine, expandable graphite, polyether phosphate and diluent are added to the epoxy resin in sequence; And / or, in step 2), ammonium polyphosphate and epoxy curing agent are mixed and stirred at 6000-8000 r / min for 8-10 minutes to obtain component B; Optionally, component A and component B are mixed and stirred at 6000-8000 r / min for 2-3 minutes.

9. A fireproof and heat-insulating coating for lithium ion outer packaging, characterized in that: The invention is obtained by the lithium ion outer packaging fireproof and heat-insulating coating according to any one of claims 1 to 6 or the lithium ion outer packaging fireproof and heat-insulating coating obtained by the preparation method according to claim 7 or 8.

10. Use of the lithium ion outer packaging fireproof and heat-insulating coating according to any one of claims 1 to 6 or the lithium ion outer packaging fireproof and heat-insulating coating obtained by the preparation method according to claim 7 or 8 in lithium ion batteries.

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