Protective material layer, battery, energy storage apparatus, and electric device

Abstract

A protective material layer, a battery, an energy storage apparatus, and an electric device. The protective material layer is suitable for being provided on the surface of the shell of a battery, and the protective material layer is made of an insulating material, the surface resistivity of which is greater than or equal to 1015Ω. In an infrared spectrum of the protective material layer that is measured by means of Fourier transform infrared spectroscopy, the relative intensity ratio I of the strongest peak at a 1072±3 cm-1 wavelength to the strongest peak at a 1724±3 cm-1 wavelength is 1.3-1.9. The protective material layer has good heat conduction capability, insulating flame-retardant capability, thermal stability and adhesion capability, and thus can be reliably coated on the surface of a shell, thereby preventing a safety accident caused by thermal runaway of a battery.

Description

Protective material layer, battery, energy storage device and electrical equipment

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on July 6, 2023, with application number 202310819825.5 and application name “Protective material layer, battery, energy storage device and electrical equipment”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application generally relates to the field of new energy materials, and specifically relates to a protective material layer, a battery, an energy storage device, and electrical equipment. Background Art

[0003] Currently, large-capacity (≥280Ah) lithium iron phosphate (LFP) batteries are plagued by safety issues such as overcharge thermal runaway and the potential for thermal runaway to spread, hindering the rapid development of the energy storage industry. When overcharged or heated, internal heat accumulates until the diaphragm melts and ruptures, causing an internal short circuit. This can cause instantaneous thermal runaway and generate large amounts of heat and flammable gases, posing a risk of combustion and explosion. To improve battery safety, particularly within the battery or system, external flammable components must be flame-retarded or replaced with appropriate flame-retardant materials.

[0004] In related technologies, battery cells are usually attached with top stickers and blue films for insulation. However, the existing top stickers are generally made of hard PC material, and the blue film is made of PET material, both of which are flammable polymer materials. Therefore, it is necessary to find suitable insulating and flame-retardant materials. On the one hand, they must meet the insulating properties of polymer materials and meet the assembly requirements of battery cell modules. On the other hand, they must meet the flame-retardant and heat-resistant properties to improve the safety performance of battery cell products.

[0005] Summary of the Invention

[0006] In view of the above-mentioned defects or deficiencies in the prior art, it is desired to provide a protective material layer, a battery, an energy storage device and an electrical equipment, wherein the protective material layer has good insulation and flame retardant properties and can effectively avoid safety accidents caused by thermal runaway of the battery.

[0007] In a first aspect, the present application provides a protective material layer, which is suitable for being arranged on the surface of the shell of the battery cell, and the surface resistivity of the protective material layer is greater than or equal to 10 15 Ω, the infrared spectrum of the protective material layer measured by Fourier transform infrared spectroscopy was 1072±3cm -1 The strongest peak at wavelength is at 1724±3cm -1 The relative intensity ratio I of the strongest peak at the wavelength is 1.3-1.9.

[0008] According to this solution, the protective material layer has good thermal conductivity, insulation flame retardancy and thermal stability, as well as good adhesion ability. It can be reliably coated on the surface of the shell without falling off, thereby reliably protecting the battery and avoiding safety accidents caused by thermal runaway.

[0009] In a second aspect, the present application provides a battery comprising an electrode assembly, a housing mounted externally to the electrode assembly, and the protective material layer of the first aspect, the protective material layer being disposed on the outer surface of the housing. This solution exhibits excellent insulation and flame retardancy, as well as excellent heat dissipation properties, ensuring internal heat dissipation from the battery while preventing safety incidents caused by thermal runaway.

[0010] In a third aspect, the present application provides an energy storage device comprising the battery according to the second aspect. The energy storage device can effectively reduce safety accidents caused by thermal runaway.

[0011] In a fourth aspect, the present application provides an electrical device, which includes an energy storage device as described in the third aspect, and the energy storage device supplies power to the electrical device. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments of the present application will be described below.

[0013] Other features, objects and advantages of the present application will become more apparent upon reading the detailed description of non-limiting embodiments made with reference to the following drawings:

[0014] FIG1 is an EDX photograph of the protective material layer of Example 1;

[0015] FIG2 is a peak intensity diagram of each element of the protective material layer of Example 1;

[0016] FIG3 is a Fourier transform infrared image of the protective material layer of Example 1;

[0017] FIG4 is a SEM photograph of the protective material layer coated on the surface of the housing in Example 1;

[0018] FIG5 is a cross-sectional SEM photograph of the protective material layer coated on the housing of Example 1;

[0019] FIG6 is a photo of thermal runaway of the battery in Example 1;

[0020] Figure 7 is a photo of the battery thermal runaway of Comparative Example 1;

[0021] FIG8 is a photo of the battery thermal runaway of Comparative Example 2. DETAILED DESCRIPTION

[0022] The present invention will be further described in detail below with reference to the embodiments. It should be understood that the specific embodiments described herein are only used to explain the relevant invention, rather than to limit the invention.

[0023] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the embodiments.

[0024] In the first aspect, the protective material layer provided in the embodiment of the present application is suitable for being arranged on the shell surface of the battery cell, and the surface resistivity of the protective material layer is greater than or equal to 10 15 The insulating material and protective material layer of Ω were measured by Fourier transform infrared spectroscopy to obtain the infrared spectrum at 1072±3cm -1 The strongest peak at wavelength is at 1724±3cm -1 The relative intensity ratio I of the strongest peak at the wavelength is 1.3-1.9.

[0025] The infrared spectrum test method is as follows: the protective material layer sample is tested in reflection mode using Bruker's INVENIO S infrared equipment with a frequency range of 400-4000cm, a resolution of 4cm, and a grating of 6mm;

[0026] The test method of surface resistivity is as follows: Use VICTOR tester to test the surface resistivity of the protective material layer sample, and the value can be read directly.

[0027] It should be noted that in actual use, the protective material layer is applied to the surface of the housing. Of course, the protective material layer can also be made into a mold and bonded to the surface of the housing; the protective material layer can be applied to the outer surface of the housing, and of course, it can also be applied to the inner surface of the housing. The embodiments of this application do not specifically limit the above. In a preferred embodiment, the protective material layer is applied to the outer surface of the housing, which is convenient for processing and manufacturing and does not affect the normal operation of the internal electrode assembly.

[0028] The protective material layer of the embodiment of the present application has good insulation performance and a surface resistivity greater than or equal to 10 15 Any one or more of the above inorganic materials and organic materials can be used. For example, the protective material layer may include an inorganic insulating component, such as, but not limited to, a material selected from silicon dioxide, zirconium oxide, titanium dioxide, aluminum oxide, silicon carbide, and ceramics, and an organic component, such as, but not limited to, various rubber materials such as PAA, or resins such as phenolic resin, polyester resin, polyamide resin, polyvinyl chloride resin, etc.

[0029] The infrared spectrum of the protective material layer was measured by Fourier transform infrared spectroscopy, as shown in Figure 3, at 1072±3cm -1Wavelength and 1724±3cm -1 The wavelength shows a strong peak, among which 1724±3cm -1 The wavelength corresponds to the C=O stretching peak, which can be a functional group such as aldehyde, ketone, or acid; 1072±3cm -1 The wavelength corresponds to the CH in-plane bending vibration, CO stretching vibration, and CC skeleton vibration. Since the bonding force of C=O is better than that of CH, CC and other groups due to the presence of hydrogen bonds, the higher the C=O content, the better the bonding theoretically, and the corresponding thermal stability will be worse. Conversely, the worse the bonding, the better the thermal stability will be.

[0030] The embodiment of the present application is at 1072±3cm -1 The strongest peak at wavelength is at 1724±3cm -1 The relative intensity ratio I of the strongest peak at the wavelength, I has a value range of 1.3-1.9. Specifically, the value of I can be, but is not limited to, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8 or 1.9. The value range of the relative intensity I of this embodiment is conducive to ensuring the appropriate amount of C=O, CH, CO and CC, and ensuring that the protective material layer has suitable adhesion and thermal stability. When the relative intensity ratio is less than 1.3, it means that there are many C=O bonds, good adhesion but poor thermal stability, and it is easy to decompose, resulting in the failure of the protective material layer; when the relative intensity ratio is greater than 1.9, the CH, CO and CC contents are relatively high, the thermal stability is good, but the adhesion is poor, and it cannot be guaranteed that the protective material layer is reliably adhered to the surface of the shell.

[0031] The protective material layer of the present invention solves the problem that existing battery casings, while meeting insulation requirements, lack flame retardancy and are prone to thermal runaway. The protective material layer of the present invention has excellent insulation and flame retardancy, thermal stability, and good adhesion, allowing it to be reliably applied to the casing surface without falling off, thereby reliably protecting the battery and preventing safety accidents caused by thermal runaway.

[0032] As a practical approach, the surface resistivity of the protective material layer is in the range of 10 15 Ω-10 18 Ω. The surface resistivity of the protective material layer can be but is not limited to 10 15 Ω, 10 16 Ω, 10 17 Ω or 10 18 Ω, etc. The protective material layer of this embodiment has good insulation, is simple to prepare, and has low raw material cost. When the surface resistivity of the protective material layer is lower than 10 15 Ω, it has no insulating effect. When the surface resistivity of the protective material layer is higher than 10 18 Ω, the manufacturing cost is high.

[0033] As an achievable method, the protective material layer satisfies the following formula: Specifically, it can be, but is not limited to, 0.166, 0.5, 1, 5, 10, 12, 16, 20, 25, 29, 30, 35, 37 or 39.9, etc.

[0034] Wherein, T is the thickness of the protective material layer provided on the surface of the battery cell shell, k is the thermal conductivity of the protective material layer, and α is the thermal diffusion coefficient of the protective material layer.

[0035] Wherein, T is the protective material layer provided on the surface of the battery cell shell, k is the thermal conductivity, which can be used to indicate the thermal conductivity of the protective material layer, and α is the thermal diffusion coefficient, which can be used to indicate the speed at which the protective material layer transfers temperature and can be used to indicate the heat dissipation performance. The test method for the thermal conductivity and thermal diffusion coefficient (which can be measured by the same device) is as follows: Using the NETZSCH LFA analysis equipment, place the protective material layer sample on the sample stage, set a 457nm laser, a 100% laser filter, an Ar gas flow rate of 150mL / min, and a temperature of 30°C.

[0036] The embodiment of the present application It can be any value within this range. By controlling the composition ratio of the protective material layer, the physical parameters of the protective material layer can be effectively regulated, thereby ensuring that the protective material layer conforms to the above formula. The protective material layer of the embodiment of the present application can ensure good thermal conductivity, insulation and flame retardancy, and good adhesion, and can be well adhered to the surface of the aluminum shell without falling off. When it is less than 0.166, the protective material layer has insufficient heat dissipation and poor insulation and flame retardant effects, which can easily cause thermal runaway and fire of the battery. When it is greater than 39.9, it means that the protective material layer is too thick and contains too much inorganic components, and the protective material layer cannot be attached to the surface.

[0037] Furthermore, in a preferred embodiment, the thickness T of the protective material layer provided on the surface of the battery cell shell is 40um-120um. Specifically, the thickness T of the protective material layer coated on the surface of the battery shell can be, but is not limited to, 40um, 50um, 60um, 70um, 80um, 90um, 100um, 110um or 120um, etc. The thickness disclosed in this embodiment is conducive to ensuring that the protective material layer has good heat dissipation performance while also playing an insulating and flame-retardant role. When the thickness of the protective layer coated on the surface of the battery shell is less than 40um, the coating thickness is too thin and cannot play an insulating effect. When the thickness of the protective layer coated on the surface of the battery shell is greater than 120um, the coating thickness is too thick, resulting in poor heat dissipation of the entire battery, which is not conducive to the normal operation of the battery.

[0038] As a feasible approach, the thermal conductivity k of the protective material layer is 0.01W / mK-0.1W / mK. The thermal conductivity k of the protective material layer of this embodiment is conducive to ensuring that the protective material layer has good thermal conductivity. When the thermal conductivity k is lower than 0.01W / mK, the thermal conductivity of the protective material layer is poor and it cannot effectively dissipate the heat generated by the battery, which may cause the battery to malfunction. When the thermal conductivity k is higher than 0.1W / mK, the protective material layer may contain too many inorganic components and cannot be reliably adhered to the housing.

[0039] As a practical approach, the thermal diffusion coefficient α of the protective material layer is 0.5 mm 2 / s-15mm 2 / s. The thermal diffusion coefficient disclosed in the embodiment of the present application is conducive to ensuring that the protective material layer can quickly dissipate the heat generated inside the battery while playing the role of insulation and flame retardancy. When the thermal diffusion coefficient of the protective material layer is less than 0.5mm 2 / s, the heat dissipation performance is poor; when the thermal diffusion coefficient of the protective material layer is greater than 15mm 2 / s, the protective material layer may contain too many inorganic components and cannot be reliably adhered to the shell.

[0040] As an achievable method, the protective material layer includes Al2O3, TiO2, Na2SiO3 and a binder. The component raw materials of the protective material layer of this embodiment are low in cost, have good insulation and flame retardant properties, and can reliably adhere to the surface of the battery cell shell.

[0041] It should be noted that the Al2O3, TiO2, and Na2SiO3 inorganic components in the examples of this application are all inorganic ceramic materials with excellent insulation and flame retardancy, as well as good thermal conductivity. Compared to other inorganic materials, the inorganic components in the examples of this application are high-temperature resistant, have good thermal conductivity, are low-cost, have no resource constraints, and can be produced on a large scale, thus having good economic value.

[0042] The adhesive can be any rubber adhesive as long as it has good thermal stability and does not burn or decompose at high temperatures, thereby effectively ensuring that the inorganic components are firmly adhered to the surface of the shell. The embodiments of this application do not limit the specific adhesive.

[0043] In actual use, the above-mentioned inorganic components Al2O3, TiO2 and Na2SiO3 can be directly purchased as commercial products as needed. By adding Al2O3, TiO2, Na2SiO3 and a binder into a dispersant, stirring and mixing to reach a certain concentration and viscosity range, they can be directly sprayed on the shell surface. The binder can reliably adhere the above-mentioned inorganic components to the shell surface.

[0044] As an achievable manner, the protective material layer includes the following components by mass percentage: 20%-40% Al2O3, 20%-40% TiO2, 20%-40% Na2SiO3, and 5%-20% binder. The mass percentage of Al2O3 can be 20%, 25%, 30%, 35%, or 40%, etc., the mass percentage of TiO2 can be 20%, 25%, 30%, 35%, or 40%, etc., the mass percentage of Na2SiO3 can be 20%, 25%, 30%, 35%, or 40%, etc., and the mass percentage of binder can be 5%, 10%, 15%, or 20%, etc. The component ratios disclosed in the embodiments of the present application are conducive to ensuring that the protective material layer has an appropriate amount of inorganic components to reliably play an insulating and flame-retardant role, and can also ensure that the binder is in an appropriate amount, ensuring that the protective material layer reliably adheres to the surface of the shell and does not fall off. When the content of any one of Al2O3, TiO2 or Na2SiO3 is less than 20%, the insulation and flame retardant properties will be reduced. When the content of any one of Al2O3, TiO2 or Na2SiO3 is higher than 40%, on the one hand, the insulation and flame retardant properties will be affected, and on the other hand, the amount of adhesive used will be reduced, resulting in the protective material layer being unable to reliably adhere to the surface of the battery cell shell.

[0045] In some embodiments, the binder includes at least one of nitrile rubber (NBR), styrene butadiene rubber (SBR), resin, and polyacrylic acid (PAA). The binder in this embodiment is low-cost and can evenly adhere to the surface of the inorganic component particles, thereby allowing the protective material layer to reliably adhere to the surface of the housing.

[0046] In a preferred embodiment, the particle size of the protective material layer is 200nm-5um. The particle size of the protective material layer of the present application is conducive to ensuring good thermal conductivity and adhesion properties. When the particle size of the protective material layer is less than 200nm, in order to ensure the insulation and flame retardant properties of the protective layer, the protective layer may be applied too thickly, resulting in poor heat dissipation performance. When the particle size of the protective material layer is greater than 5um, the thermal conductivity and adhesion of the protective material layer are reduced.

[0047] In summary, the protective material layer of the embodiment of the present application includes Al2O3, TiO2, Na2SiO3 and a binder. Al2O3, TiO2, Na2SiO3 and the binder form a mixed slurry, which is evenly coated on the surface of the battery shell, and can effectively play the role of insulation and flame retardancy. Among them, regulating the physical properties of the protective material layer is conducive to ensuring that the protective material layer has good thermal conductivity and insulation and flame retardancy, and has good adhesion, and can be reliably coated on the surface of the shell without falling off, thereby reliably protecting the battery and preventing the battery from thermal runaway.

[0048] Furthermore, the coating thickness of the protective material layer disclosed in the embodiment of the present application is conducive to ensuring that the protective material layer has good heat dissipation performance while also playing an insulating and flame-retardant role.

[0049] In a second aspect, the present application provides a battery comprising an electrode assembly, a housing mounted externally to the electrode assembly, and the protective material layer of the first aspect, the protective material layer being disposed on the outer surface of the housing. It is understood that the battery possesses all the features and advantages of the protective material layer described above, and further description thereof will not be given here. In general, the battery has excellent insulation and flame retardancy, as well as excellent heat dissipation performance, capable of ensuring internal heat dissipation of the battery while avoiding safety incidents caused by thermal runaway.

[0050] In a third aspect, the present application provides an energy storage device comprising the battery of the second aspect. It will be appreciated that this energy storage device possesses all the features and advantages of the aforementioned battery, which will not be elaborated upon here. In general, this energy storage device can effectively reduce safety incidents caused by thermal runaway.

[0051] In a fourth aspect, the present application provides an electrical device comprising the energy storage device of the third aspect, which supplies power to the electrical device. For example, the electrical device may be an electric vehicle. Thus, the electrical device possesses all the features and advantages of the protective material layer described above, and further description thereof is omitted.

[0052] The present application is described below through specific examples. It should be noted that the following specific examples are only for illustrative purposes and do not limit the scope of the present application in any way. In addition, unless otherwise specified, methods without specific conditions or steps are conventional methods, and the reagents and materials used can be obtained from commercial channels.

[0053] Example 1

[0054] According to the mass ratio of 30:30:30:10, Al2O3, TiO2, Na2SiO3 and binder are uniformly dispersed and mixed to obtain a slurry of the protective material layer. Taking 320Ah lithium iron phosphate square shell battery as an example, the slurry is coated on the shell surface of the battery cell and dried, and the battery cells are assembled in series to form a battery; wherein the surface resistivity of the protective material layer is 10 16 Ω, after testing, the coating thickness of the protective material layer is about 80um, the thermal conductivity k is 0.07W / mK, and the thermal diffusion coefficient α is 3mm 2 / s, the Fourier infrared spectrum is shown in Figure 3, and the calculated value is 1072±3cm -1 The strongest peak at wavelength is 1724±3cm -1 The relative intensity ratio I of the strongest peak at wavelength is 1.76. The value is 4.03.

[0055] The protective material layer prepared in the above embodiment 1 was subjected to EDX analysis, as shown in Figure 1. The test results show that the protective material layer contains Al, Ti, Si, Na, C, and O elements. Figure 2 shows the peak intensity diagram of each element, and Table 1 shows the content of each element. It can be seen from Figure 2 and Table 1 that the content of Al and Si is greater than that of Ti and Na, and the content of carbon and oxygen elements is relatively high, indicating that the material prepared in Example 1 has insulating flame retardancy and good adhesion. The surface of the shell of Example 1 was photographed by SEM, as shown in Figures 4 and 5. It can be seen from Figure 4 that the protective material layer on the surface of the shell is evenly distributed, and it can be seen from Figure 5 that the coating thickness of the protective material layer is about 80um.

[0056] Table 1. Element content of protective material layer

[0057] Example 2

[0058] According to the mass ratio of 25:25:40:10, Al2O3, TiO2, Na2SiO3 and binder are uniformly dispersed and mixed to obtain a protective material layer slurry. Taking 320Ah lithium iron phosphate square shell battery as an example, the slurry is coated on the shell surface of the battery cell and dried, and the battery cells are assembled in series to form a battery; wherein the surface resistivity of the protective material layer is 10 15 Ω, after testing, the coating thickness of the protective material layer is about 40um, the thermal conductivity k is 0.01W / mK, and the thermal diffusion coefficient α is 0.5mm 2 / s,1072±3cm -1 The strongest peak at wavelength is 1724±3cm -1 The relative intensity ratio I of the strongest peak at wavelength is 1.9, The value is 0.166.

[0059] Example 3

[0060] According to the mass ratio of 35:23:35:7, Al2O3, TiO2, Na2SiO3 and binder are uniformly dispersed and mixed to obtain a protective material layer slurry. Taking 320Ah lithium iron phosphate square shell battery as an example, the slurry is coated on the shell surface of the battery cell and dried, and the battery cells are assembled in series to form a battery; wherein the surface resistivity of the protective material layer is 10 16 Ω, after testing, the coating thickness of the protective material layer is about 120um, the thermal conductivity k is 0.1W / mK, and the thermal diffusion coefficient α is 15mm 2 / s,1072±3cm -1 The strongest peak at wavelength is 1724±3cm -1 The relative intensity ratio I of the strongest peak at wavelength is 1.3, The value is 39.9.

[0061] Example 4

[0062] According to the mass ratio of 33:25:34:8, Al2O3, TiO2, Na2SiO3 and binder are uniformly dispersed and mixed to obtain a protective material layer slurry. Taking 320Ah lithium iron phosphate square shell battery as an example, the slurry is coated on the shell surface of the battery cell and dried, and the battery cells are assembled in series to form a battery; wherein the surface resistivity of the protective material layer is 10 16 Ω, after testing, the coating thickness of the protective material layer is about 70um, the thermal conductivity k is 0.06W / mK, and the thermal diffusion coefficient α is 10.54mm 2 / s,1072±3cm -1 The strongest peak at wavelength is 1724±3cm -1 The relative intensity ratio I of the strongest peak at wavelength is 1.8, The value is 12.

[0063] Example 5

[0064] According to the mass ratio of 29:33:33:5, Al2O3, TiO2, Na2SiO3 and binder are uniformly dispersed and mixed to obtain a protective material layer slurry. Taking 320Ah lithium iron phosphate square shell battery as an example, the slurry is coated on the shell surface of the battery cell and dried, and the battery cells are assembled in series to form a battery; wherein the surface resistivity of the protective material layer is 10 16 Ω, after testing, the coating thickness of the protective material layer is about 90um, the thermal conductivity k is 0.08W / mK, and the thermal diffusion coefficient α is 12.53mm 2 / s,1072±3cm -1 The strongest peak at wavelength is 1724±3cm -1 The relative intensity ratio I of the strongest peak at wavelength is 1.6, The value is 21.

[0065] Example 6

[0066] According to the mass ratio of 31:26:37:6, Al2O3, TiO2, Na2SiO3 and binder are uniformly dispersed and mixed to obtain a protective material layer slurry. Taking 320Ah lithium iron phosphate square shell battery as an example, the slurry is coated on the shell surface of the battery cell and dried, and the battery cells are assembled in series to form a battery; wherein the surface resistivity of the protective material layer is 10 16 Ω, after testing, the coating thickness of the protective material layer is about 110um, the thermal conductivity k is 0.09W / mK, and the thermal diffusion coefficient α is 13.35mm 2 / s,1072±3cm -1The strongest peak at wavelength is 1724±3cm -1 The relative intensity ratio I of the strongest peak at wavelength is 1.4, The value is 30.

[0067] Example 7

[0068] According to the mass ratio of 31:26:39:6, Al2O3, TiO2, Na2SiO3 and binder are uniformly dispersed and mixed to obtain a protective material layer slurry. Taking 320Ah lithium iron phosphate square shell battery as an example, the slurry is coated on the shell surface of the battery cell and dried, and the battery cells are assembled in series to form a battery; wherein the surface resistivity of the protective material layer is 10 16 Ω, after testing, the coating thickness of the protective material layer is about 200um, the thermal conductivity k is 0.08W / mK, and the thermal diffusion coefficient α is 14mm 2 / s,1072±3cm -1 The strongest peak at wavelength is 1724±3cm -1 The relative intensity ratio I of the strongest peak at wavelength is 1.31. The value is 43.

[0069] Example 8

[0070] According to the mass ratio of 25:32:35:8, Al2O3, TiO2, Na2SiO3 and binder are uniformly dispersed and mixed to obtain a protective material layer slurry. Taking 320Ah lithium iron phosphate square shell battery as an example, the slurry is coated on the shell surface of the battery cell and dried, and the battery cells are assembled in series to form a battery; wherein the surface resistivity of the protective material layer is 10 16 Ω, after testing, the coating thickness of the protective material layer is about 10um, the thermal conductivity k is 0.02W / mK, the thermal diffusion coefficient α is 0.6mm2 / s, 1072±3cm -1 The strongest peak at wavelength is 1724±3cm -1 The relative intensity ratio I of the strongest peak at wavelength is 1.9, The value is 0.14.

[0071] Comparative Example 1

[0072] According to the mass ratio of 22:38:36:4, Al2O3, TiO2, Na2SiO3 and binder are uniformly dispersed and mixed to obtain a protective material layer slurry. Taking 320Ah lithium iron phosphate square shell battery as an example, the slurry is coated on the shell surface of the battery cell and dried, and the battery cells are assembled in series to form a battery; wherein the surface resistivity of the protective material layer is 10 16 Ω, after testing, the coating thickness of the protective material layer is about 60um, the thermal conductivity k is 0.02W / mK, and the thermal diffusion coefficient α is 0.6mm2 / s,1072±3cm -1 The strongest peak at wavelength is 1724±3cm -1 The relative intensity ratio I of the strongest peak at the wavelength is 2.5, The value is 0.284.

[0073] Comparative Example 2

[0074] According to the mass ratio of 32:33:27:8, Al2O3, TiO2, Na2SiO3 and binder are uniformly dispersed and mixed to obtain a protective material layer slurry. Taking 320Ah lithium iron phosphate square shell battery as an example, the slurry is coated on the shell surface of the battery cell and dried, and the battery cells are assembled in series to form a battery; wherein the surface resistivity of the protective material layer is 10 16 Ω, after testing, the coating thickness of the protective material layer is about 85um, the thermal conductivity k is 0.03W / mK, and the thermal diffusion coefficient α is 1.5mm 2 / s,1072±3cm -1 The strongest peak at wavelength is 1724±3cm -1 The relative intensity ratio I of the strongest peak at the wavelength is 0.3, The value is 7.98.

[0075] Comparative Example 3

[0076] According to the mass ratio of 28:28:35:9, Al2O3, TiO2, Na2SiO3 and binder are uniformly dispersed and mixed to obtain a protective material layer slurry. Taking 320Ah lithium iron phosphate square shell battery as an example, the slurry is coated on the shell surface of the battery cell and dried, and the battery cells are assembled in series to form a battery; wherein the surface resistivity of the protective material layer is 10 16 Ω, after testing, the coating thickness of the protective material layer is about 10um, the thermal conductivity k is 0.02W / mK, and the thermal diffusion coefficient α is 0.6mm 2 / s,1072±3cm -1 The strongest peak at wavelength is 1724±3cm -1 The relative intensity ratio I of the strongest peak at the wavelength is 2, The value is 0.134.

[0077] Comparative Example 4

[0078] According to the mass ratio of 28:32:32:8, Al2O3, TiO2, Na2SiO3 and binder are uniformly dispersed and mixed to obtain a protective material layer slurry. Taking 320Ah lithium iron phosphate square shell battery as an example, the slurry is coated on the shell surface of the battery cell and dried, and the battery cells are assembled in series to form a battery; wherein the surface resistivity of the protective material layer is 10 16Ω, after testing, the coating thickness of the protective material layer is about 10um, the thermal conductivity k is 0.01W / mK, and the thermal diffusion coefficient α is 0.5mm 2 / s,1072±3cm -1 The strongest peak at wavelength is 1724±3cm -1 The relative intensity ratio I of the strongest peak at wavelength is 1.2, The value is 0.132.

[0079] The batteries of Examples 1-8 and Comparative Examples 1-4 were pre-treated for overcharge testing according to GB36276. The pre-treated cells were overcharged at 1C, and then the batteries were observed to see if they caught fire after thermal runaway. The test results are shown in Table 2.

[0080] Table 2 Battery test results of Examples 1-8 and Comparative Examples 1-4

[0081] According to the results in Table 2, after thermal runaway, the batteries of Examples 1-6 only emitted smoke but did not catch fire, while the batteries of Comparative Examples 1-4 all caught fire after 5 minutes. Figure 6 shows that the battery of Example 1 did not catch fire after thermal runaway, Figure 7 shows that the battery of Comparative Example 1 caught fire after thermal runaway, and Figure 8 shows that the battery of Comparative Example 2 caught fire after thermal runaway.

[0082] Among them, the I value range of the protective material layer in Examples 1-6 is 1.3-1.9, and the physical properties of the protective material layer are in line with the formula range. The values ​​of I in Comparative Examples 1-4 are all outside the range. It can be seen that the value range of I disclosed in the embodiments of the present application is conducive to ensuring that the material can be reliably adhered to the shell of the battery cell. In Comparative Examples 1 and 4, the protective material layer is too thick and has more inorganic components, and the protective layer cannot be attached to the surface of the shell, thereby failing to achieve a good insulation and flame retardant effect; in Comparative Examples 2 and 3, the protective material layer has insufficient heat dissipation and poor insulation and flame retardant effect, causing thermal runaway and fire of the battery.

[0083] According to the test results of Examples 1-6 and 7-8, the batteries of Examples 1-6 only emitted smoke after thermal runaway, while the batteries of Examples 7 and 8 caught fire half an hour after thermal runaway. This shows that the formulas satisfied by I, I, and other physical parameters of the protective material layer of the present application are all within the specified ranges, further ensuring excellent thermal conductivity, insulation, and flame retardancy, as well as good adhesion, allowing it to adhere well to the aluminum shell surface without falling off, thereby ensuring that the battery will not catch fire after thermal runaway.

[0084] The above description is merely a preferred embodiment of the present application and an illustration of the technical principles employed. Those skilled in the art should understand that the scope of the invention herein is not limited to the technical solutions formed by the specific combination of the above-mentioned technical features, but also encompasses other technical solutions formed by any combination of the above-mentioned technical features or their equivalents without departing from the inventive concept. For example, a technical solution formed by replacing the above-mentioned features with (but not limited to) technical features having similar functions disclosed in this application.

Claims

1. A protective material layer, characterized in that: The protective material layer is suitable for being arranged on the surface of the battery shell, and the surface resistivity of the protective material layer is greater than or equal to 10 15 Ω, the infrared spectrum of the protective material layer measured by Fourier transform infrared spectroscopy is 1072±3cm -1 The strongest peak at wavelength is at 1724±3cm -1 The relative intensity ratio I of the strongest peak at the wavelength is 1.3-1.

9.

2. The protective material layer according to claim 1, characterized in that: The surface resistivity of the protective material layer is in the range of 10 15 Ω-10 18 Ω.

3. The protective material layer according to claim 1 or 2, characterized in that: The protective material layer satisfies the following formula: Wherein, T is the thickness of the protective material layer disposed on the surface of the battery cell shell, k is the thermal conductivity of the protective material layer, and α is the thermal diffusion coefficient of the protective material layer.

4. The protective material layer according to claim 3, characterized in that: The thickness T of the protective material layer arranged on the surface of the battery cell shell is 40um-120um.

5. The protective material layer according to claim 3, characterized in that: The protective material layer satisfies at least one of the following conditions: The thermal conductivity k of the protective material layer is 0.01W / mK-0.1W / mK; The thermal diffusion coefficient α of the protective material layer is 0.5 mm 2 / s-15mm 2 / s.

6. The protective material layer according to claim 1 or 2, characterized in that: The protective material layer includes Al2O3, TiO2, Na2SiO3 and a binder.

7. The protective material layer according to claim 1 or 2, characterized in that: The protective material layer comprises the following components according to mass percentage: 20%-40% Al2O3, 20%-40% TiO2, 20%-40% Na2SiO3 and 5%-20% binder.

8. The protective material layer according to claim 7, characterized in that: The binder includes at least one of nitrile rubber, styrene butadiene rubber, resin and polyacrylic acid.

9. A battery, characterized in that: It comprises an electrode assembly, a shell installed outside the electrode assembly and a protective material layer according to any one of claims 1 to 8, wherein the protective material layer is arranged on the outer surface of the shell.

10. An energy storage device, characterized in that: A battery comprising the battery of claim 9.

11. An electrical device, characterized in that: The electrical equipment comprises the energy storage device as claimed in claim 10, and the energy storage device supplies power to the electrical equipment.

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