Preparation method of battery metal shell with gradient structure heat insulation coating and battery monomer

Abstract

The invention relates to the technical field of battery monomers, in particular to a preparation method of a battery metal shell with a gradient structure heat insulation coating and a battery monomer. Comprising the following steps: S1, pretreating a battery metal shell, and carrying out physical vapor deposition on the outer surface of the battery metal shell to obtain a coated battery metal shell; the coating film is a Ti coating film or a TiZr coating film; s2, carrying out surface nitriding treatment on the coated battery metal shell, and at least obtaining a nitriding layer on the surface of the coated film, so as to obtain the battery metal shell with a gradient structure heat insulation coating; the heat insulation coating structurally comprises a metal diffusion bonding layer and a nitriding layer from inside to outside in sequence, and the metal diffusion bonding layer is at least one intermetallic compound layer; the heat insulation coating with the gradient structure is prepared on the battery metal shell, so that the problems of low surface hardness, poor mechanical stability and poor heat insulation performance of an existing battery monomer aluminum alloy shell are solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of battery cells, in particular to a preparation method of a battery metal shell with a gradient structure heat insulation coating and a battery cell. BACKGROUND

[0002] Energy storage technology is crucial to the stable operation of the power grid, and the performance of energy storage batteries as the core component of the energy storage system directly affects the efficiency and stability of the entire system.

[0003] Thermal runaway propagation is a harmful behavior that occurs between battery modules and systems. When a battery cell is triggered by mechanical, electrical and thermal triggers, it can cause a certain battery cell to undergo thermal runaway. The temperature of the single battery cell rapidly rises after thermal runaway, with a surface temperature of about 1000℃, and rapidly transfers heat to adjacent batteries, causing the surrounding batteries to undergo thermal runaway. In response to the problem of battery thermal runaway, current energy storage system fireproofing measures can be broadly divided into two categories: active suppression and passive suppression. The former is mainly based on battery thermal management systems and safety warning systems to control the battery temperature within a reasonable range in advance and issue early warning signals to avoid unnecessary losses. Passive suppression of thermal runaway propagation involves using heat protection materials within the battery system to insulate, absorb heat and extinguish fires to reduce the transfer of heat from the runaway battery to the non-runaway battery. Passive suppression schemes mainly use thermal insulation materials, which include thermal resistance materials, heat absorption materials and composite materials.

[0004] However, the reported fireproofing measures are all additional components independent of the battery exterior, requiring a large physical space and even a separate control system, which severely reduces the energy density of the battery system. In addition, the battery manufacturer needs to cooperate to redesign the battery module architecture, which limits the feasibility of large-scale application. Furthermore, aluminum alloys are widely used in battery cell housings, which have low melting points and low mechanical strength, reducing the safety of the battery cell. Moreover, the aluminum alloy housing of the battery cell is extremely thin, usually no more than 3 mm, and is greatly affected by heat. SUMMARY

[0005] To solve the technical problem of increased risk of battery cell thermal runaway propagation caused by the high thermal conductivity of the existing thin-walled battery metal shell, a preparation method of a battery metal shell with a gradient structure heat insulation coating and a battery cell are provided. The present application prepares a gradient structure heat insulation coating on the battery metal shell, which has good heat insulation effect and reduces the risk of battery cell thermal runaway propagation.

[0006] To achieve the above purpose, the present application realizes the following technical scheme:

[0007] The application provides a preparation method of a battery metal shell with a gradient structure thermal insulation coating.

[0008] S1, pretreating the battery metal shell, performing physical vapor deposition on the outer surface of the battery metal shell to obtain a plated battery metal shell; the plating film is a Ti plating film or a TiZr plating film;

[0009] S2, performing surface nitriding treatment on the plated battery metal shell to obtain a nitriding layer at least on the surface of the plating film, thereby obtaining a battery metal shell with a gradient structure thermal insulation coating.

[0010] Further, the overall thickness of the gradient structure thermal insulation coating of the battery metal shell is 4-25 microns, and the thermal insulation coating comprises a metal diffusion bonding layer and a nitriding layer from inside to outside;

[0011] The metal diffusion bonding layer is at least one intermetallic compound layer, and the thickness of the metal diffusion bonding layer is 2.5-22.5 microns;

[0012] The thickness of the nitriding layer is 1.5-4 microns.

[0013] Further, the physical vapor deposition adopts high-frequency pulse magnetron sputtering to deposit the plating film, and the specific process is as follows: in a high-frequency pulse magnetron sputtering plating furnace, vacuumizing, heating, then introducing argon, performing glow cleaning on the outer surface of the battery metal shell, then running a plating film program, opening a Ti target to deposit, or opening Ti and Zr targets to deposit, and obtaining a battery metal shell with a Ti plating film or a TiZr plating film after deposition.

[0014] Further, the conditions of the glow cleaning are as follows: the vacuum degree of the furnace cavity of the high-frequency pulse magnetron sputtering plating furnace is less than 1x10 -3 mbar, the temperature of the vacuum chamber is 250-400℃, the rotation speed is 1-5 rpm, the amount of introduced argon is 100-500sccm, the substrate bias voltage is greater than -70 V, and the glow cleaning time is 10-30 min.

[0015] Further, the conditions of opening the Ti target to deposit and obtain the Ti plating film are as follows: the vacuum degree of the furnace cavity of the high-frequency pulse magnetron sputtering plating furnace is kept less than 1x10 -2 mbar, the deposition time is 1-3 h under the conditions of a substrate bias voltage greater than -70 V and a Ti target power of 12-18 kW.

[0016] Further, the conditions of opening the Ti and Zr targets to deposit and obtain the TiZr plating film are as follows: the vacuum degree of the furnace cavity of the high-frequency pulse magnetron sputtering plating furnace is kept less than 1x10 -2mbar, under the condition that the base bias is greater than -70 V, the Ti target power is 8-15 kW, and the Zr target power is 3-6 kW, and the deposition time is 1-3 h.

[0017] Further, the surface nitriding treatment is carried out by placing the product of S1 in an ion nitriding furnace, and the specific conditions are as follows: vacuumizing to less than 50 Pa, adjusting the voltage to 650-750 V, then introducing hydrogen into the furnace, heating the battery metal shell to 460-520 DEG C through thin gas glow discharge and keeping the temperature, introducing nitrogen-containing gas at 600-1000 sccm, keeping the pressure of the ion nitriding furnace at 100-250 Pa, and permeating and keeping warm for at least 5 h; after the keeping warm is finished, cooling to room temperature under a nitrogen atmosphere, so that a nitriding layer is obtained on the surface of the plated film.

[0018] Preferably, the nitrogen-containing gas is composed of 200-400 sccm of nitrogen and 400-600 sccm of hydrogen; and the voltage is adjusted to 600-800 V.

[0019] Further, the pretreatment method of the battery metal shell is as follows: sanding the surface to be treated, then cleaning with an alcohol solvent, then polishing, and then cleaning and drying again.

[0020] The sandpaper is SiC sandpaper with a mesh size of 80-2500.

[0021] Further, the battery metal shell is an aluminum shell.

[0022] Another aspect of the present application provides a battery monomer comprising the battery metal shell with the gradient-structure thermal insulation coating prepared by the above preparation method.

[0023] Beneficial technical effects: the present application adopts a physical vapor deposition and ion nitriding combined processing technology to treat the battery metal shell, constructs a gradient-structure thermal insulation coating of a thermal insulation functional layer and a metal diffusion bonding layer on the surface of the battery monomer in situ under the premise of being compatible with the current energy storage system production process, develops a new energy storage system complete component, realizes efficient thermal protection of the energy storage system without increasing the complexity of the system and without compromising the performance, and improves the operation safety of the energy storage system.

[0024] The present application has a gradient-structure strengthening layer on the surface of the battery metal shell; the outer layer is TiN 0.3TiN-based titanium-nitrogen solid solution phase, which plays a heat insulation effect; the inner layer is an intermetallic compound layer mainly composed of aluminum-based intermetallic compounds, and the intermetallic compound layer is formed by interdiffusion of the coating and the base element, which plays the effect of a bonding layer; the present application can solve the problems of low surface hardness, poor mechanical stability and poor heat insulation performance of the existing battery monomer shell; the method of the present application can obtain a heat insulation coating with controllable thickness, high mechanical performance and good heat insulation performance on the surface of the battery monomer shell, which can effectively improve the safety and mechanical stability of the battery monomer, and reduce the risk of heat runaway of the battery monomer caused by mechanical incentives; the hardness of the heat insulation coating of the present application is up to 727.1 Hv, and the wear rate is as low as 7.41*10 -14 m 3 / N·m, the bonding force reaches HF1, and the thermal conductivity is as low as 117.21 W / m·k;

[0025] In the present application, ion nitriding at a lower temperature (460℃~ 520℃) obtains a thicker coating, which meets the energy saving requirement; the heat insulation coating obtained by the composite process of physical vapor deposition and ion nitriding in the present application has a fast formation speed and good bonding force with the substrate, and through optimization of the combination of treatment temperature and treatment time, energy can be effectively saved. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 XRD patterns of battery metal shells with gradient structure heat insulation coatings prepared in Example 1 to Example 3, Example 7 to Example 9;

[0027] Figure 2 Cross-section microstructure SEM images of battery metal shells with gradient structure heat insulation coatings prepared in Example 1 and Example 7, (a) and (a') are Example 1, (b) and (b') are Example 7;

[0028] Figure 3 Rockwell indentation test patterns of battery metal shells with gradient structure heat insulation coatings prepared in Example 1 and Example 7;

[0029] Figure 4 Thermal conductivity column chart of battery metal shells with gradient structure heat insulation coatings of Example 1 and Example 7. DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the embodiments of the present application and the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. The following description of at least one example embodiment is merely illustrative in nature and is in no way limiting on the application or its applications or uses. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of the present application.

[0031] Unless specifically stated otherwise, the numerical values stated in these embodiments do not limit the scope of the present application. Techniques, methods known to those of ordinary skill in the relevant art can not be discussed in detail, but should be considered part of the specification where appropriate. In all examples shown and discussed herein, any specific value should be interpreted as merely exemplary, and not as a limitation. Thus, other examples of the example embodiments can have different values. It should be noted that, for example, values expressed as "in the range of a-b", "between a-b", do not include the end point values a and b; values expressed as "a-b", "is a-b", "a-b", include the end point values a and b.

[0032] The experimental methods in the following embodiments not specified in the specific conditions are generally determined according to the national standard; if there is no corresponding national standard, they are carried out according to the general standard requirements or general methods.

[0033] Example 1

[0034] The preparation method of the battery metal shell with the gradient structure thermal barrier coating includes the following steps:

[0035] S1, pretreating the battery metal shell: polishing the outer surface of the aluminum alloy shell (material is 3031 aluminum alloy base material) with 80 mesh to 2500 mesh SiC sandpaper, then placing it in anhydrous ethanol for ultrasonic cleaning for 15-30 min, taking it out and using diamond polishing paste to polish the outer surface, then placing it in anhydrous ethanol for ultrasonic cleaning for 15-30 min, taking it out and blowing dry, to obtain the pretreated battery metal shell;

[0036] Placing the pretreated battery metal shell in a high-frequency pulse magnetron sputtering plating furnace, adjusting the turret so that the polished surface of the pretreated battery metal shell always faces the target, vacuumizing the arc ion plating furnace chamber to less than 5x10 -5After 5x10-3mbar, the vacuum chamber is heated to 360℃, the rotation speed is set to 3 rpm, then 250 sccm of argon is introduced, the substrate bias is set to -60 V, and the surface of the battery metal shell is pretreated by glow cleaning for 10 min; then the film coating program is run, the Ti target is turned on, the substrate bias is set to -60 V, the Ti target power is 18 kw, the vacuum degree in the high-frequency pulsed magnetron sputtering furnace cavity is kept at 5x10-3mbar, the Ti film is deposited on the surface of the battery metal shell under the condition of 360℃ of temperature, -60 V of substrate bias and 18 kW of Ti target power for 3 h, and the Ti film coated battery metal shell is obtained. -3 After 5x10-3mbar, the vacuum chamber is heated to 360℃, the rotation speed is set to 3 rpm, then 250 sccm of argon is introduced, the substrate bias is set to -60 V, and the surface of the battery metal shell is pretreated by glow cleaning for 10 min; then the film coating program is run, the Ti target is turned on, the substrate bias is set to -60 V, the Ti target power is 18 kw, the vacuum degree in the high-frequency pulsed magnetron sputtering furnace cavity is kept at 5x10-3mbar, the Ti film is deposited on the surface of the battery metal shell under the condition of 360℃ of temperature, -60 V of substrate bias and 18 kW of Ti target power for 3 h, and the Ti film coated battery metal shell is obtained.

[0037] S2, the Ti film coated battery metal shell prepared in the above step is placed in an ion nitriding furnace, vacuumed to less than 50 Pa, the voltage is adjusted to 750 V, then hydrogen gas is introduced into the furnace, the Ti film coated battery metal shell is heated to 520℃ by means of thin gas glow discharge, 800 sccm of nitrogen-containing gas (400 sccm of nitrogen and 400 sccm of hydrogen) is introduced, the ion nitriding furnace pressure is kept at 200 Pa, then the temperature is kept at 520℃ and the furnace pressure is kept at 200 Pa for 8 h, after the heat preservation is completed, the temperature is cooled to room temperature in a nitrogen atmosphere, and a nitriding layer is obtained on the surface of the film, that is, a battery metal shell with a gradient structure thermal barrier coating is obtained.

[0038] Example Two

[0039] The preparation method of the battery metal shell with a gradient structure thermal barrier coating in this case is the same as that in Example One, except that in S2, the Ti film coated battery metal shell is heated to 490℃ and kept at a temperature of 490℃ in the ion nitriding furnace.

[0040] Example Three

[0041] The preparation method of the battery metal shell with a gradient structure thermal barrier coating in this case is the same as that in Example One, except that in S2, the Ti film coated battery metal shell is heated to 460℃ and kept at a temperature of 460℃ in the ion nitriding furnace.

[0042] Example Four

[0043] The preparation method of the battery metal shell with a gradient structure thermal barrier coating in this case is the same as that in Example One, except that in S2, the nitrogen-containing gas introduced is 200 sccm of nitrogen and 600 sccm of hydrogen.

[0044] Example Five

[0045] The preparation method of the battery metal shell with the gradient structure heat insulation coating in this case is the same as that in Embodiment One, except that the nitrogen-containing gas introduced in S2 is 200 sccm nitrogen and 600 sccm hydrogen, and the Ti-coated battery metal shell is heated to 490°C and kept at the temperature of 490°C in the ion nitriding furnace.

[0046] Embodiment Six

[0047] The preparation method of the battery metal shell with the gradient structure heat insulation coating in this case is the same as that in Embodiment One, except that the nitrogen-containing gas introduced in S2 is 200 sccm nitrogen and 600 sccm hydrogen, and the Ti-coated battery metal shell is heated to 460°C and kept at the temperature of 460°C in the ion nitriding furnace.

[0048] Embodiment Seven

[0049] The preparation method of the battery metal shell with the gradient structure heat insulation coating in this case is the same as that in Embodiment One, except that the film coating procedure in the high-frequency pulse magnetron sputtering plating furnace in S1 is to open the Ti target and the Zr target for deposition, and the Ti target power is set to 15 kW and the Zr target power is set to 6 kW; and the TiZr-coated battery metal shell is obtained in S1.

[0050] Embodiment Eight

[0051] The preparation method of the battery metal shell with the gradient structure heat insulation coating in this case is the same as that in Embodiment One, except that the film coating procedure in the high-frequency pulse magnetron sputtering plating furnace in S1 is to open the Ti target and the Zr target for deposition, and the Ti target power is set to 15 kW and the Zr target power is set to 6 kW; the TiZr-coated battery metal shell is obtained in S1; and the TiZr-coated battery metal shell is heated to 490°C and kept at the temperature of 490°C in the ion nitriding furnace in S2.

[0052] Embodiment Nine

[0053] The preparation method of the battery metal shell with the gradient structure heat insulation coating in this case is the same as that in Embodiment One, except that the film coating procedure in the high-frequency pulse magnetron sputtering plating furnace in S1 is to open the Ti target and the Zr target for deposition, and the Ti target power is set to 15 kW and the Zr target power is set to 6 kW; the TiZr-coated battery metal shell is obtained in S1; and the TiZr-coated battery metal shell is heated to 460°C and kept at the temperature of 460°C in the ion nitriding furnace in S2.

[0054] Test Example

[0055] The battery metal shells with the gradient structure heat insulation coating in the above embodiments were subjected to performance testing, and the test results are shown in Table 1 andFigures 1 to 4 .

[0056] X-ray diffraction was performed on the metal casings of batteries with gradient-structured thermal insulation coatings from Examples 1 to 3 and Examples 7 to 9. The XRD patterns are shown below. Figure 1 As shown, by Figure 1 It is known that the coating of the battery metal shell contains a titanium nitride solid solution phase, a titanium nitride phase, and an aluminum-based intermetallic compound phase.

[0057] Microstructural observation of cross-sections of the battery metal casings with gradient structure thermal insulation coatings from Examples 1 and 7 is shown in the SEM images. Figure 2 As shown, by Figure 2 It can be seen that the overall thickness of the coating in Example 1 is 17 micrometers, as observed under magnification. Figure 2 As shown in (a'), the coating structure, from the inside out, consists of a 14.9-micrometer-thick intermetallic compound layer and a 2.1-micrometer-thick nitride layer. The intermetallic compound layer is formed by the interdiffusion of elements between the coating and the substrate, acting as an adhesive layer. Therefore, the coating and substrate interface have good bonding. In Example 7, the overall coating thickness is 6.8 micrometers. After magnification observation, it is found to be... Figure 2 As shown in (b'), the structure of the coating, from the inside out, consists of a 1.7-micrometer-thick Ti-Al intermetallic compound layer, a 1.1-micrometer-thick Ti-Zr-Al intermetallic compound layer, and a 4-micrometer-thick nitride layer. The intermetallic compound layer is formed by the interdiffusion of the coating and the substrate elements, which acts as an adhesive layer. Therefore, the coating and the substrate have a good interface.

[0058] The reciprocating wear performance of the battery metal casings with gradient structure heat-insulating coatings from Examples 1 to 9, as well as the untreated 3031 aluminum alloy casings, was tested. The test conditions were as follows: A ball-and-disc tribo-wear tester (BRUKER UMT TriboLab) was used. The test disc was a 3031 aluminum alloy sample (φ18 mm × 5 mm) strengthened by the method described in this embodiment; the grinding balls were made of GCr15 steel with a diameter of 5 mm; the test was conducted under dry friction conditions, with a normal load of 5 N, a linear velocity of 5 mm / s, a single-pass sliding distance of 2 mm, and a test time of 30 min. The test results are shown in Table 1.

[0059] Vickers hardness tests were performed on the battery metal casings with gradient structure heat-insulating coatings from Examples 1 to 9, as well as on the untreated 3031 aluminum alloy casing. The test results are shown in Table 1. Rockwell indentation test diagrams are shown below. Figure 3 As shown.

[0060] The thermal conductivity of the battery metal casings with gradient structure thermal insulation coatings from Examples 1 to 9, as well as the untreated 3031 aluminum alloy casing, was tested at room temperature using a laser thermal conductivity tester. The thermal conductivity histograms for the battery metal casings with gradient structure thermal insulation coatings from Examples 1 and 7 are shown below. Figure 4 As shown.

[0061] Table 1. Example Data

[0062]

[0063] As shown in Table 1, the hardness of the battery metal casing treated in Examples 1 and 7 is significantly improved, and the hardness of Example 7 is 6 times that of the substrate. The wear rate of the battery metal casing treated in Examples 1 and 7 is reduced by two orders of magnitude compared with the substrate, and the mechanical properties are significantly improved.

[0064] Depend on Figure 4 As shown in Table 1, the thermal conductivity of the battery metal casing after treatment in Examples 1 and 7 was significantly reduced. The thermal conductivity of Example 1 was 117.21 W·m. -1 ·k -1 It is significantly lower than the untreated aluminum alloy shell, and its heat insulation performance is significantly improved.

[0065] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for producing a battery metal case having a thermal barrier coating with a gradient structure, characterized by, The method comprises the following steps: S1, pretreating the battery metal shell, performing physical vapor deposition on the outer surface of the battery metal shell to obtain a plated battery metal shell; the plating film is a Ti plating film or a TiZr plating film; S2, performing surface nitriding treatment on the plated battery metal shell to obtain a nitride layer on at least the surface of the plating film, thereby obtaining a battery metal shell with a gradient structure thermal insulation coating.

2. The method of claim 1, wherein the method further comprises: The overall thickness of the gradient structure thermal insulation coating of the battery metal shell is 4-25 microns, and the thermal insulation coating comprises a metal diffusion bonding layer and a nitride layer from inside to outside; The metal diffusion bonding layer is at least one intermetallic compound layer, and the thickness of the metal diffusion bonding layer is 2.5-22.5 microns; The thickness of the nitride layer is 1.5-4 microns.

3. The method of claim 1, wherein the method further comprises: The physical vapor deposition is performed by high-frequency pulse magnetron sputtering to obtain a plating film, and the specific process is as follows: in a high-frequency pulse magnetron sputtering plating furnace, vacuumize, after heating, introduce argon, perform glow cleaning on the outer surface of the battery metal shell, then run the plating film program, open the Ti target for deposition, or open the Ti target and the Zr target for deposition, and after deposition, obtain a battery metal shell with a Ti plating film or a TiZr plating film.

4. The method of claim 3, wherein the method further comprises: The conditions of the glow cleaning are as follows: the vacuum degree of the furnace cavity of the high-frequency pulse magnetron sputtering coating furnace is less than 1×10 -3 mbar, the temperature of the vacuum chamber is 250-400℃, the rotating speed is 1-5 rpm, the amount of argon gas is 100-500sccm, the substrate bias is greater than-70 V, and the glow cleaning time is 10-30 min.

5. The method of claim 3, wherein the method further comprises: The conditions for opening the Ti target to deposit the Ti film are as follows: the vacuum degree in the furnace cavity of the high-frequency pulse magnetron sputtering plating furnace is less than 1x10 -2 mbar, the substrate bias is greater than -70 V, the Ti target power is 12-18 kW, and the deposition time is 1-3 h.

6. The method of claim 3, wherein the method further comprises: The conditions for opening the Ti target and Zr target to deposit and obtain the TiZr plated film are as follows: the vacuum degree in the high-frequency pulse magnetron sputtering plating furnace cavity is less than 1x10 -2 mbar, the substrate bias is greater than -70 V, the Ti target power is 8-15 kW, the Zr target power is 3-6 kW, and the deposition time is 1-3 h.

7. The method of claim 1, wherein the method further comprises: The surface nitriding treatment is performed by placing the product of S1 in an ion nitriding furnace, and the specific conditions are as follows: vacuumize to less than 50 Pa, adjust the voltage to 650-750 V, then introduce hydrogen into the furnace, heat the battery metal shell to 460-520℃ by thin gas glow discharge, and maintain the temperature, introduce nitrogen-containing gas at 600-1000 sccm, maintain the ion nitriding furnace pressure at 100-250 Pa, and permeate and keep warm for at least 5 h, after keeping warm, cool to room temperature in a nitrogen atmosphere, that is, obtain a nitride layer on at least the surface of the plating film.

8. The method of claim 7, wherein the method further comprises: The composition of the nitrogen-containing gas is 200-400 sccm of nitrogen and 400-600 sccm of hydrogen; and the voltage is adjusted to 600-800 V.

9. The method of producing a battery metal case having a thermal barrier coating with a gradient structure according to any one of claims 1 to 8, characterized in that, The pretreatment method of the battery metal shell is as follows: sandpaper polishing the surface to be treated, then alcohol solvent cleaning, then polishing, and then cleaning and drying again; The sandpaper is SiC sandpaper with a mesh size of 80-2500; The battery metal shell is an aluminum shell.

10. A battery cell, characterized by The battery metal shell with a gradient structure thermal insulation coating prepared by the preparation method of any one of claims 1-9.

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