Evaporation boat for preparing current collector as well as preparation method and application of evaporation boat

Abstract

The invention provides an evaporation boat for preparing a current collector and a preparation method and application of the evaporation boat. The evaporation boat comprises modified metal boride, and modified metal boride particles comprise metal boride particles and a coating layer coating the metal boride particles; the metal borides comprise metal borides of IVB and VB group metals; the coating layer comprises at least one of a ceramic coating layer and a carbon coating layer; the ceramic coating layer is prepared from at least one of SiO2, Al2O3, Y2O3, ZrO2, SiC, Si3N4 and Ti3SiC2; the carbon coating layer includes amorphous carbon. The current collector, especially an aluminum or composite aluminum current collector prepared by using the evaporation boat, has the advantages that the problems of uneven surface and the like are effectively improved, so that the problem that a grinding surface is easy to break when a scraper is rolled due to the problems of uneven surface and the like subsequently is further improved; the subsequent processing performance of the composite current collector and the subsequent application performance in the battery can be improved, and the battery performance is further optimized.

Description

Technical Field

[0001] This invention belongs to the field of evaporation boat and current collector technology, specifically relating to an evaporation boat for preparing current collectors, its preparation method and application. Background Technology

[0002] In the manufacturing of components such as lithium-ion batteries and capacitors, a layer of aluminum with a thickness of micrometers is typically vacuum-deposited onto the surface of a polymer film (such as PET or PI film) to form a metallized film that serves as the current collector for the product. Resistance heating vacuum evaporation is the core process for preparing this aluminum current collector, while the evaporation boat is a key consumable in this process, and its performance directly determines the coating quality, production rate, and cost.

[0003] Evaporation boats need to withstand temperatures exceeding 1300°C during operation and contain molten aluminum. Therefore, uneven heating is very likely to occur during the evaporation process, which can cause the molten aluminum in the metal layer to splash. This can cause some particles inside the evaporation boat to splash onto the film surface, resulting in unevenness on the surface of the composite aluminum current collector.

[0004] However, composite aluminum current collectors suffer from surface irregularities, which can lead to surface breakage during the rolling process over a scraper, making it difficult to meet the requirements of continuous production. Furthermore, these surface irregularities not only affect the uniformity of the composite aluminum current collector's appearance but also cause uneven local resistance, potentially becoming hotspots or breakdown points in subsequent electrochemical cycles or high-voltage applications, severely reducing the reliability and safety of the final component. Summary of the Invention

[0005] To address the problems and shortcomings of existing technologies, this invention provides an evaporation boat for preparing current collectors, its preparation method, and its application. The current collectors prepared using this evaporation boat, especially aluminum or composite aluminum current collectors, have significantly improved surface unevenness. This further mitigates the problem of surface breakage during roller pressing and scraping caused by uneven surface unevenness, thus improving the processing performance of subsequent composite current collectors and their application performance in batteries, thereby further optimizing battery performance.

[0006] According to a first aspect of the present invention, an evaporation boat for preparing a current collector is provided. The evaporation boat includes a modified metal boride, wherein the modified metal boride particles include metal boride particles and a coating layer covering the metal boride particles; the metal boride includes metal borides of group IVB and group VB metals; the coating layer includes at least one of a ceramic coating layer and a carbon coating layer; the ceramic coating layer includes at least one of SiO2, Al2O3, Y2O3, ZrO2, SiC, Si3N4, and Ti3SiC2; and the carbon coating layer includes amorphous carbon.

[0007] During its long-term research and development process, the applicant discovered that during the preparation of current collectors such as composite aluminum current collectors, a certain number and size of particles are present on the surface of the current collector. These particles cause the current collector film to be uneven, which can easily lead to film breakage during subsequent rolling and scraping.

[0008] Analysis of the surface particles of the composite aluminum current collector revealed that most of the particles were metal boride particles such as TiB2. Although the surface of the evaporation boat was cleaned before each evaporation deposition, a large amount of metal boride such as TiB2 was still generated during use. Furthermore, as the usage time increased, the TiB2 and other metal boride particles grew larger, exacerbating the formation of sputtering holes and large bumps on the film surface. In addition, during subsequent coating processes, the bump particles could lead to film breakage.

[0009] Therefore, in order to further solve the problems encountered in the preparation of aluminum or composite aluminum current collectors, the evaporation boat for preparing current collectors provided by the present invention introduces a modified metal boride with a unique coating layer structure. The coating layer constitutes a physical and chemical barrier, which can effectively inhibit the abnormal growth of metal boride particles at long-term high temperature. Secondly, the coating layer isolates the direct contact between metal boride particles, reducing the probability of them agglomerating due to van der Waals forces or surface diffusion during high-temperature sintering and use, so that they can be dispersed in the evaporation boat matrix in a finer and more uniform isolated state. Therefore, the two effects mentioned above can keep the metal boride particles in a small and uniform initial state, which directly avoids the generation of large hard particles that can serve as "nucleation cores" or "embeddings" from the source. This greatly eliminates the direct physical source of the formation of protrusion defects (bumps) on the aluminum film surface. As a result, it can effectively reduce the number of large metal boride particles or clusters that peel off from the evaporation boat substrate, sputter out and contaminate the coating. This makes the aluminum current collector film layer deposited on the PET and other base films purer, denser and more uniform. The macroscopic unevenness and other defects are significantly reduced, which greatly improves the appearance quality and functional consistency of the coating.

[0010] Furthermore, regarding the coating layer, ceramic and / or carbon coating layers are selected. The ceramic coating layer further enhances the chemical inertness between the boride particles and the molten aluminum, significantly reducing the driving force of interfacial reactions and avoiding side reactions such as the formation of brittle aluminum-titanium compounds. This ensures the stability of the bond between the boride particles (such as TiB2) and the substrate, preventing them from "loosening" and detaching due to interfacial corrosion or weakening, thus becoming sputtering material. The carbon coating layer, when the evaporation boat is subjected to severe thermal cycling, acts like an "elastic cushion," absorbing and dissipating the micro-stress caused by the mismatch in thermal expansion coefficients between the boride particles (such as TiB2) and other materials in the evaporation boat substrate. This significantly reduces the initiation and propagation of microcracks around the particles, preventing the particles from becoming sputtering sources due to "debonding." In particular, the carbon coating layer containing amorphous carbon has a long-range disordered amorphous carbon structure, so the film formed on the surface of metal borides is more continuous, dense and uniform. This means that it can more completely encapsulate metal borides such as TiB2 particles, achieving coating without dead corners and a more thorough physical barrier effect. At the same time, the amorphous carbon can be more tightly connected to the metal boride particles, making it less likely to fall off and more likely to remain stable in subsequent high-temperature processes.

[0011] It should be further explained that the ceramic coating and / or carbon coating are tightly bonded to the surface of the metal boride particles and have high stability. Even during the subsequent high-temperature sintering process, the coating is not easy to fall off, so it can play a good role in long-term barrier. Moreover, these coating materials do not have obvious adverse reactions with other materials of the evaporation boat, so they will not reduce the original performance of the evaporation boat, and may even show improved performance such as improved stability of the evaporation boat.

[0012] Preferably, the carbon coating layer is an amorphous carbon coating layer. The difference between amorphous carbon and crystalline carbon can be determined by XRD testing; the absence of obvious crystalline peaks indicates amorphous carbon. In the subsequent calcination process of this invention, a very small amount of amorphous carbon may convert to crystalline carbon (which is negligible), but the majority remains amorphous carbon (the conversion temperature to crystalline carbon needs to be greater than 2500°C).

[0013] Preferably, the carbon coating layer contains dopant elements, including at least one of nitrogen, sulfur, potassium, phosphorus, and boron. Introducing these dopant elements into the carbon coating layer serves two purposes: First, they anchor the carbon network, acting as a "pinning" mechanism to suppress disordered rearrangement and structural relaxation of carbon atoms at high temperatures, thus improving the thermal stability of the amorphous carbon coating layer. Simultaneously, doping optimizes the electronic interactions between the carbon layer and metal borides such as TiB2 cores, enhancing interfacial bonding and making the coating layer less prone to peeling under thermal stress. Second, the dopant elements can subtly adjust the surface chemical state of the carbon coating layer, reducing its interfacial energy with molten aluminum and enhancing its "non-wetting" properties. This strengthens the coating layer's effect as an isolation barrier, preventing molten aluminum from penetrating and reacting with the metal borides such as TiB2 cores. Therefore, this invention further modifies the carbon coating layer through elemental doping, achieving a synergistic upgrade in conductivity, thermal stability, and interface properties, constructing a more robust and intelligent multifunctional barrier. This significantly suppresses the deterioration and shedding of TiB2 particles, ensuring the smoothness and cleanliness of the aluminum current collector film. Preferably, the carbon coating layer contains doping elements, specifically nitrogen and sulfur, and / or potassium, and / or nitrogen, sulfur, and potassium.

[0014] Preferably, the metal boride particles include titanium diboride (TiB2) particles. Titanium diboride (TiB2) is chosen as the metal boride particle because it represents a conductive phase material that achieves the best balance between conductivity, high-temperature stability, interfacial characteristics with molten aluminum, and synergy with the coating layer / substrate. Therefore, the prepared evaporation boat exhibits superior thermal stability and lower sputtering during the preparation of the aluminum current collector, which is beneficial for obtaining an aluminum current collector with higher surface flatness.

[0015] Preferably, the average particle size of the modified metal boride particles is 40-60 μm; and / or, the thickness of the coating layer in the modified metal boride particles is 5-60 nm. The average particle size of the modified titanium diboride particles is 40-60 μm. Particles in this size range can achieve the densest packing in the composite material, reducing porosity in the matrix while avoiding severe agglomeration problems caused by excessively fine particles (e.g., submicron size). This ensures a uniform distribution of the conductive phase in the evaporation boat matrix, which is the basis for achieving uniform current and thermal field, and thus also appropriately reduces particle sputtering. The coating layer thickness of 5-60 nm ensures the formation of a continuous and dense coating layer while having almost no impact on the overall density, conductivity, and other intrinsic properties of the metal boride particles, avoiding the "diluting" of the conductive phase function or the introduction of additional internal stress due to an excessively thick coating layer.

[0016] Preferably, the thickness of the coating layer in the modified metal boride particles is 20~60 nm.

[0017] Preferably, the evaporation boat further includes nitrides or carbides, and boron nitride (BN); the nitrides or carbides include at least one of aluminum nitride (AlN), silicon carbide (SiC), and alumina (Al2O3). The composite material system formed by the aforementioned evaporation boat materials and the modified metal boride not only ensures the high-temperature strength, thermal shock resistance, and long lifespan of the evaporation boat itself, but more importantly, the synergistic effect between the aforementioned materials and the modified metal boride is superior, creating an extremely stable working interface and environment. This fundamentally guarantees the stability of the coating process and effectively improves the unevenness of the aluminum current collector surface.

[0018] Preferably, the current collector includes a metal layer, and the material of the metal layer includes aluminum.

[0019] Preferably, the current collector is a composite aluminum current collector, which includes a polymer substrate layer and an aluminum-containing metal layer disposed on at least one surface of the polymer substrate layer. Preferably, the aluminum-containing metal layer is an aluminum metal layer. The evaporation boat provided by this invention is more suitable for the preparation of composite aluminum current collectors. If used for the preparation of other current collectors such as composite copper current collectors, the raw material formulation needs to be adjusted for further adaptation.

[0020] Preferably, the mass ratio of modified metal borides, nitrides or carbides to boron nitride is 1~5:2~8:3~9.

[0021] Preferably, the mass ratio of modified metal boride, nitride or carbide, and boron nitride is 2.5~3.5:3.5~4.5:4.5~5.5. More preferably, the mass ratio of modified metal boride, nitride or carbide, and boron nitride is 3:4:5.

[0022] According to a second aspect of the present invention, a method for preparing an evaporation boat for preparing a current collector as described above is provided, characterized in that the specific operation is as follows: modified metal borides, nitrides or carbides, and boron nitride are mixed in a certain proportion, mechanically ground, and the resulting mixed powder is filled into a mold. The mixture is then sintered in a first inert atmosphere at 1800~2400℃ for 3.5~6h. After cooling, an evaporation boat is obtained. At the above calcination temperature and time, sufficient densification of the modified metal borides, nitrides or carbides, and boron nitride can be ensured, forming a uniform and dense composite material structure at the microscale, obtaining a high-strength matrix, thereby ensuring that the material design concept of "inhibiting the growth and shedding of metal boride particles" is fully realized in the final product.

[0023] Preferably, during the preparation of the evaporation boat, the mass ratio of modified metal boride, nitride or carbide, and boron nitride is 1~5:2~8:3~9. Controlling the mass ratio of these substances within a specific range allows for the formation of an ideal multiphase composite structure with BN as the continuous matrix, uniformly dispersed metal boride, and reinforced and connected interfaces by nitrides or carbides. This achieves the optimal ratio across multiple performance requirements, including electrical, thermal, mechanical, and chemical properties, enabling the evaporation boat to simultaneously possess uniform heating, high strength, thermal shock resistance, and resistance to molten aluminum erosion. In particular, the powder mixture at this ratio exhibits good sintering activity, facilitating the production of a high-density, low-porosity sintered body under the aforementioned process. This maximizes the design function of each component, thereby ensuring the preparation of high-quality aluminum current collectors and improving surface unevenness issues.

[0024] Preferably, during the preparation of the evaporation boat, the mass ratio of modified metal borides, nitrides or carbides, and boron nitride is 1~5:2~8:3~9.

[0025] Preferably, during the preparation of the evaporation boat, the mass ratio of modified metal borides, nitrides or carbides, and boron nitride is 2.5~3.5:3.5~4.5:4.5~5.5. More preferably, the mass ratio of modified metal borides, nitrides or carbides, and boron nitride is 3:4:5.

[0026] Preferably, the gas pressure is controlled at 30~50 MPa during the sintering process.

[0027] Preferably, the first inert atmosphere comprises argon.

[0028] Preferably, mechanical grinding includes ball milling.

[0029] According to a third aspect of the invention, there is an application of the evaporation boat as described above in the preparation of a current collector.

[0030] According to a fourth aspect of the present invention, a current collector is provided, comprising an aluminum-containing metal layer, which is prepared by using an evaporation boat as described above or an evaporation boat prepared by the methods described above. Current collectors (such as aluminum or composite aluminum current collectors) prepared using the evaporation boat provided by the present invention have a relatively smooth and flat surface with no macroscopically visible "sputtering points" or "black spots," effectively solving the core problem of unevenness on the surface of aluminum current collectors caused by contaminant particles in traditional processes, and providing an ideal substrate for subsequent coating processes.

[0031] Preferably, the current collector is a composite aluminum current collector, which includes a polymer substrate layer and an aluminum-containing metal layer disposed on at least one surface of the polymer substrate layer. Preferably, the aluminum-containing metal layer is an aluminum metal layer.

[0032] The composite aluminum current collector was prepared by the following steps: A polymer substrate layer was prepared, and the tension at the unwinding end was set to 110~130N, and at the winding end to 95~105N. After the winding carriage entered the evaporation chamber, a vacuum was applied to 4.5~5.5×10⁻⁶ N. -3 At Pa, the winding carriage is started, with the speed controlled at 280-300 m / min. Simultaneously, the evaporation boat is heated and aluminum wire is fed at a speed of 300-350 mm / min. Oxygen is simultaneously introduced to form an aluminum oxide layer on at least one side of the polymer substrate layer. The vacuum degree is controlled at 4.5~5.5 × 10⁻⁶. -2 Pa; then, the vacuum is broken and an aluminum layer is formed on at least one side of the product structure obtained above in the same manner to obtain a composite aluminum current collector.

[0033] Preferably, the thickness of the alumina layer is 1~5 nm. The alumina serves as the underlayer, which can improve the adhesion between the polymer base film layer and the metal layer (such as the aluminum layer).

[0034] Preferably, the thickness of the aluminum layer is 0.5~2μm.

[0035] According to a fifth aspect of the present invention, a battery is provided, comprising the aforementioned current collector. The highly flat and clean surface of the current collector ensures uniform adhesion and close contact of the active material coating. This significantly reduces the interfacial impedance of the electrodes, promotes uniform insertion / extraction of lithium ions during charging and discharging, effectively mitigates the failure and shedding of active materials caused by interfacial instability or uneven local reactions, thereby significantly reducing the battery's capacity decay rate and extending its cycle life.

[0036] In summary, this invention effectively inhibits the growth and aggregation of metal borides such as TiB2 particles at high temperatures by specifically coating and modifying them, thereby reducing their interfacial reactivity with molten aluminum. Furthermore, the coating layer enhances the thermal shock resistance of the composite material and eliminates localized overheating, fundamentally preventing the formation of large-sized hard sputterings due to the coarsening and shedding of conductive phase particles such as TiB2. The evaporation boat prepared from these specifically modified metal boride particles not only possesses uniform and efficient resistance heating, excellent thermal shock resistance, superior resistance to molten aluminum erosion, and high mechanical strength, but more importantly, the aluminum current collector prepared using this evaporation boat is smooth, pure, and uniform. This effectively improves the unevenness caused by sputterings and optimizes its electrical performance, thus further enabling downstream batteries prepared using this current collector to have higher cycle life and safety performance. Detailed Implementation

[0037] To enable those skilled in the art to better understand the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0038] Example 1 1. Preparation of modified metal boride particles The modified boride particles prepared in this embodiment are SiO2-modified TiB2 particles, that is, SiO2-coated TiB2 particles. The specific preparation steps are as follows: TEOS (ethyl silicate):EtOH (ethanol):H2O = 1:3:4 (mass ratio) was mixed, and ammonia water (pH=10) was added for catalytic reaction at room temperature for 2 hours to form a gel. TiB2 powder was ultrasonically dispersed for 1 hour, and the above gel was added and stirred for coating. The stirring time was 3 hours and the speed was 120 rpm. After drying, SiO2-coated TiB2 particles were obtained with an average particle size (D50) of 56 μm and a coating thickness (average thickness) of 52 nm.

[0039] 2. Preparation of evaporation boat and composite aluminum current collector TiB2 particles coated with BN, AlN, and SiO2 (modified metal boride particles) were mixed in a mass ratio of 5:4:3 and then ball-milled for 12 hours. The mixed powder was then filled into a mold and sintered at 2100℃ for 4.5 hours under an argon atmosphere with a controlled pressure of 40 MPa. The formed evaporation boat was then cooled and used for vapor deposition. A 6μm PET base film was used for deposition, with the tension at the unwinding end set to 120 N and the tension at the winding end set to 100 N. After the winding carriage entered the evaporation chamber, a vacuum of 5 × 10⁻⁶ was applied. -3 At Pa, start the winding carriage, controlling the speed at 280-300 m / min. Simultaneously, heat the evaporation boat and feed the aluminum wire at a speed of 300-350 mm / min. At the same time, start the oxygen intake to form an aluminum oxide layer (undercoat) on both sides of the PET base film, with a thickness of approximately 3 nm. Maintain a vacuum level of 5 × 10⁻⁶. -2 Pa; then, the vacuum was broken and aluminum layers were formed on both sides of the product structure obtained above in the same way, with a thickness of 1 μm, to obtain a composite aluminum current collector.

[0040] Example 2 1. Preparation of modified metal boride particles The modified boride particles prepared in this embodiment are Al2O3-modified TiB2 particles, that is, Al2O3-coated TiB2 particles. The specific preparation steps are as follows: Aluminum isopropoxide and H2O were mixed in a ratio of 1:4 (mass ratio), and ammonia (pH=10) was added for a catalytic reaction at room temperature for 2 hours to form an alumina sol solution. TiB2 powder was ultrasonically dispersed for 1 hour, and the above alumina sol solution was added for coating. The stirring time was 3 hours at a speed of 120 rpm. After drying, TiB2 particles coated with Al2O3 were obtained with an average particle size (D50) of 53 μm and an average coating thickness of 41 nm.

[0041] 2. Preparation of evaporation boat and composite aluminum current collector The modified metal boride particles were adjusted to the Al2O3-coated TiB2 particles prepared in this embodiment, and the rest were the same as in Example 1.

[0042] Example 3 1. Preparation of modified metal boride particles The modified boride particles prepared in this embodiment are Y2O3-modified TiB2 particles, that is, Y2O3-coated TiB2 particles. The specific preparation steps are as follows: Y(NO3)3:H2O = 1:4 was mixed and ammonia water (pH=10) was added for catalytic reaction at room temperature for 2 hours to form Y(OH)3 sol solution; TiB2 powder was ultrasonically dispersed for 1 hour and the above Y(OH)3 sol solution was added for coating by stirring for 3 hours at a speed of 120 rpm; after drying, Y2O3 coated TiB2 particles were obtained with an average particle size (D50) of 55 μm and a coating layer thickness (average thickness) of 52 nm.

[0043] 2. Preparation of evaporation boat and composite aluminum current collector The modified metal boride particles were adjusted to the Y2O3-coated TiB2 particles prepared in this embodiment, and the rest were the same as in Example 1.

[0044] Example 4 1. Preparation of modified metal boride particles The modified boride particles prepared in this embodiment are amorphous carbon-modified TiB2 particles, that is, amorphous carbon-coated TiB2 particles. The specific preparation steps are as follows: TiB2 powder and 20wt% glucose solution (mass ratio 10:1) were mixed and ball-milled for 4 hours, then spray-dried and carbonized at 650℃ for 2 hours in an argon atmosphere to form amorphous carbon-coated TiB2 particles with an average particle size (D50) of 58 μm and an average coating thickness of 49 nm.

[0045] 2. Preparation of evaporation boat and composite aluminum current collector The modified metal boride particles were adjusted to the amorphous carbon-coated TiB2 particles prepared in this embodiment, and the rest were the same as in Example 1.

[0046] Example 5 1. Preparation of modified metal boride particles The modified boride particles prepared in this embodiment are nitrogen-doped amorphous carbon modified TiB2 particles, that is, nitrogen-doped amorphous carbon coated TiB2 particles. The specific preparation steps are as follows: TiB2 powder, 20wt% glucose solution and pyrrole were mixed (mass ratio 5:2:1) and ball-milled for 4 hours, then spray-dried and carbonized at 650℃ for 2 hours in an argon atmosphere to obtain nitrogen-doped amorphous carbon-coated TiB2 particles with an average particle size (D50) of 49 μm and an average coating thickness of 46 nm.

[0047] 2. Preparation of evaporation boat and composite aluminum current collector The modified metal boride particles were adjusted to the nitrogen-doped amorphous carbon-coated TiB2 particles prepared in this embodiment, and the rest were the same as in Example 1.

[0048] Example 6 1. Preparation of modified metal boride particles The modified boride particles prepared in this embodiment are sulfur-doped amorphous carbon modified TiB2 particles, that is, sulfur-doped amorphous carbon coated TiB2 particles. The specific preparation steps are as follows: TiB2 powder, 20wt% glucose solution and sublimed sulfur were mixed (mass ratio 5:2:1) and ball-milled for 4 hours, then spray-dried and carbonized at 650℃ for 2 hours in an argon atmosphere to obtain sulfur-doped amorphous carbon-coated TiB2 particles with an average particle size (D50) of 52 μm and an average coating thickness of 55 nm.

[0049] 2. Preparation of evaporation boat and composite aluminum current collector The modified metal boride particles were adjusted to the sulfur-doped amorphous carbon-coated TiB2 particles prepared in this embodiment, and the rest were the same as in Example 1.

[0050] Example 7 1. Preparation of modified metal boride particles The modified boride particles prepared in this embodiment are nitrogen-sulfur co-doped amorphous carbon modified TiB2 particles, that is, nitrogen-sulfur co-doped amorphous carbon coated TiB2 particles. The specific preparation steps are as follows: TiB2 powder, 20wt% glucose solution, pyrrole and sublimed sulfur were mixed (mass ratio 5:2:0.5:0.5) and ball-milled for 4 hours, then spray-dried and carbonized at 650℃ for 2 hours in an argon atmosphere to obtain nitrogen-sulfur co-doped amorphous carbon-coated TiB2 particles with an average particle size (D50) of 42 μm and an average coating thickness of 28 nm.

[0051] 2. Preparation of evaporation boat and composite aluminum current collector The modified metal boride particles were adjusted to the nitrogen-sulfur co-doped amorphous carbon-coated TiB2 particles prepared in this embodiment, and the rest were the same as in Example 1.

[0052] Example 8 1. Preparation of modified metal boride particles The modified boride particles prepared in this embodiment are potassium (potassium carbonate) modified TiB2 particles, that is, potassium (potassium carbonate) coated TiB2 particles. The specific preparation steps are as follows: TiB2 powder, 20wt% glucose solution, and potassium carbonate were mixed (mass ratio 5:2:1) and ball-milled for 4 hours. Then, the mixture was spray-dried and carbonized at 650℃ for 2 hours under argon atmosphere to obtain potassium (potassium carbonate) coated TiB2 particles with an average particle size (D50) of 44 μm and an average coating thickness of 36 nm.

[0053] 2. Preparation of evaporation boat and composite aluminum current collector The modified boron compound particles were adjusted to the potassium (potassium carbonate) coated TiB2 particles prepared in this embodiment, and the rest were the same as in Example 1.

[0054] Example 9 1. Preparation of modified metal boride particles The modified boride particles prepared in this embodiment are nitrogen-sulfur-potassium (potassium carbonate) amorphous carbon modified TiB2 particles, that is, nitrogen-sulfur-potassium (potassium carbonate) amorphous carbon coated TiB2 particles. The specific preparation steps are as follows: TiB2 powder, 20wt% glucose solution, pyrrole, sublimed sulfur and potassium carbonate were mixed (mass ratio 5:2:0.5:0.5:1) and ball-milled for 4 hours. Then, the mixture was spray-dried and carbonized at 650℃ for 2 hours under argon atmosphere to obtain TiB2 particles coated with nitrogen, sulfur and potassium (potassium carbonate) with an average particle size (D50) of 44 μm and an average coating thickness of 23 nm.

[0055] 2. Preparation of evaporation boat and composite aluminum current collector The modified metal boride particles were adjusted to the nitrogen-sulfur-potassium (potassium carbonate) amorphous carbon-coated TiB2 particles prepared in this embodiment, and the rest were the same as in Example 1.

[0056] Example 10 1. Preparation of modified metal boride particles During the preparation process, the metal boride particles were adjusted to zirconium diboride (ZrB2) particles, and the rest was the same as in Example 3. That is, the Y2O3 modified ZrB2 particles (Y2O3 coated ZrB2 particles) were prepared with an average particle size (D50) of 50 μm and a coating thickness (average thickness) of 47 nm.

[0057] 2. Preparation of evaporation boat and composite aluminum current collector The modified metal boride particles were adjusted to the Y2O3-coated ZrB2 particles prepared in this embodiment, and the rest were the same as in Example 3.

[0058] Example 11 1. Preparation of modified metal boride particles During the preparation process, the metal boride particles were adjusted to vanadium diboride (VB2) particles, and the rest was the same as in Example 4. That is, the amorphous carbon modified VB2 particles (amorphous carbon coated VB2 particles) prepared had an average particle size (D50) of 49 μm and a coating thickness (average thickness) of 36 nm.

[0059] 2. Preparation of evaporation boat and composite aluminum current collector The modified metal boride particles were adjusted to the amorphous carbon-coated VB2 particles prepared in this embodiment, and the rest were the same as in Example 4.

[0060] Example 12 1. Preparation of modified metal boride particles During the preparation process, the metal boride particles were adjusted to niobium diboride (NbB2) particles, and the rest was the same as in Example 5. That is, the nitrogen-doped amorphous carbon modified NbB2 particles (nitrogen-doped amorphous carbon coated NbB2 particles) were prepared with an average particle size (D50) of 52 μm and a coating thickness (average thickness) of 54 nm.

[0061] 2. Preparation of evaporation boat and composite aluminum current collector The modified metal boride particles were adjusted to nitrogen-doped amorphous carbon-coated NbB2 particles prepared in this embodiment, and the rest were the same as in Example 5.

[0062] Example 13 1. Preparation of modified metal boride particles During the preparation process, the metal boride particles were adjusted to niobium diboride (NbB2) particles, and the rest was the same as in Example 7. That is, the nitrogen-sulfur co-doped amorphous carbon modified NbB2 particles (nitrogen-sulfur co-doped amorphous carbon coated NbB2 particles) were prepared with an average particle size (D50) of 50 μm and a coating thickness (average thickness) of 22 nm.

[0063] 2. Preparation of evaporation boat and composite aluminum current collector The modified metal boride particles were adjusted to the nitrogen-sulfur co-doped amorphous carbon-coated NbB2 particles prepared in this embodiment, and the rest were the same as in Example 7.

[0064] Example 14 1. Preparation of modified metal boride particles During the preparation process, the metal boride particles were adjusted to hafnium diboride (HfB2) particles, and the rest was the same as in Example 8. That is, the potassium (potassium carbonate) modified HfB2 particles (potassium (potassium carbonate co-doped amorphous carbon coated HfB2 particles) were prepared with an average particle size (D50) of 51 μm and a coating thickness (average thickness) of 55 nm.

[0065] 2. Preparation of evaporation boat and composite aluminum current collector The modified metal boride particles were adjusted to the potassium (potassium carbonate) amorphous carbon-coated HfB2 particles prepared in this embodiment, and the rest were the same as in Example 8.

[0066] Example 15 1. Preparation of modified metal boride particles During the preparation process, the metal boride particles were adjusted to tantalum diboride (TaB2) particles, and the rest was the same as in Example 9. That is, the nitrogen-sulfur-potassium (potassium carbonate) amorphous carbon modified TaB2 particles (nitrogen-sulfur-potassium (potassium carbonate) amorphous carbon coated TaB2 particles) were prepared with an average particle size (D50) of 46 μm and a coating thickness (average thickness) of 32 nm.

[0067] 2. Preparation of evaporation boat and composite aluminum current collector The modified metal boride particles were adjusted to the nitrogen-sulfur-potassium (potassium carbonate) amorphous carbon-coated TaB2 particles prepared in this embodiment, and the rest were the same as in Example 9.

[0068] Example 16 1. Preparation of modified metal boride particles During the preparation process, the time of the room temperature catalytic reaction was adjusted to 1 hour, and the rest was the same as in Example 3. The average particle size (D50) of the Y2O3-coated TiB2 particles obtained was 35 μm, and the thickness (average thickness) of the coating layer was 45 nm.

[0069] 2. Preparation of evaporation boat and composite aluminum current collector Consistent with Example 3.

[0070] Example 17 1. Preparation of modified metal boride particles During the preparation process, the carbonization temperature was adjusted to 800℃, and the rest was the same as in Example 4. The average particle size (D50) of the amorphous carbon-coated TiB2 particles obtained was 65μm, and the thickness (average thickness) of the coating layer was 55nm.

[0071] 2. Preparation of evaporation boat and composite aluminum current collector Consistent with Example 4.

[0072] Example 18 1. Preparation of modified metal boride particles Consistent with Example 3.

[0073] 2. Preparation of evaporation boat and composite aluminum current collector During the preparation process, the mass ratio of BN, AlN, and Y2O3-coated TiB2 particles was adjusted to 8:1:3, consistent with Example 3.

[0074] Comparative Example 1 1. Preparation of modified metal boride particles The modified boride particles prepared in this comparative example are graphite-modified TiB2 particles, i.e., graphite-coated TiB2 particles. The specific preparation steps are as follows: TiB2 and graphite were mixed (mass ratio 5:1) and ball-milled for 4 hours to obtain graphite-coated TiB2 particles with an average particle size (D50) of 58 μm and an average coating thickness of 52 nm.

[0075] 2. Preparation of evaporation boat and composite aluminum current collector The modified boron metal particles were adjusted to the graphite-coated TiB2 particles prepared in this comparative example, and the rest were the same as in Example 1.

[0076] Comparative Example 2 This comparative example does not prepare TiB2 particles with specific coating modification. That is, in the process of preparing the evaporation boat in this comparative example, uncoated TiB2 particles are used directly, and the rest is the same as in Example 1.

[0077] Test case 1. Experimental Construction Method The evaporation boat, composite aluminum current collector, and electrode prepared by a composite current collector obtained in all the above embodiments and comparative examples were subjected to the following performance tests, and the specific test methods are as follows: (1) Resistance test: The DC low resistance test method is adopted. The evaporation boat is placed horizontally and stably, and then the four probes of the test fixture are pressed simultaneously, vertically and stably on the standard test points at both ends of the evaporation boat. After the instrument display value stabilizes, the resistance value is read and recorded (unit: milliohm, mΩ).

[0078] (2) Pinhole test: The number of pinholes on the surface of the composite aluminum current collector is tested by a CCD machine. The CCD line scan camera installed on the production line is used to perform real-time synchronous scanning through backlight imaging to capture the light leakage points and calculate the number of holes.

[0079] (3) Surface particles: The size and number of TiB2 particles on the surface of the composite aluminum current collector (coated 2000m) were tested using SEM; the size of TiB2 particles was taken as the average particle size of TiB2 particles.

[0080] (4) Coating and Rolling Test: The selected positive electrode slurry is a ternary positive electrode material with the following formula: 97 parts of nickel-cobalt-manganese 811 (NCM811), 1 part of carbon nanotubes, 0.5 parts of super P, and 1.5 parts of PVDF. The solvent is NMP. The mixture is stirred for 20 minutes. The composite aluminum current collector is placed on the coating machine, and the prepared positive electrode slurry is evenly poured onto the composite aluminum current collector for doctor blade coating with a doctor blade height of 150 μm. Afterward, baking is performed at a temperature of 80℃, followed by rolling. The pressure of the pressure roller is adjusted to 4 kgf / cm, the winding tension is 8 N, the film speed is 6 m / s, and the film length is 100,000 m. The number of tape breaks is recorded.

[0081] 2. Experimental Results The relevant performance test results of the evaporation boat, composite aluminum current collector, and electrode obtained from all the above embodiments and comparative examples are shown in Table 1.

[0082] Table 1. Performance test results of the evaporation boat, composite aluminum current collector, and electrode obtained from the examples and comparative examples.

[0083] As shown in Table 1, the evaporation boat provided by this invention, by introducing a specific ceramic coating layer and a carbon coating layer containing amorphous carbon on the surface of the metal boride, can effectively suppress the abnormal growth of metal boride particles at long-term high temperatures and effectively avoid direct contact between metal boride particles, reducing agglomeration. Therefore, at least two of these aspects enable the evaporation boat prepared using the specifically coated and modified metal boride to effectively reduce the number of large-sized metal boride particles or clusters that peel off from the evaporation boat substrate, sputter out, and contaminate the coating during subsequent aluminum film preparation. This results in a purer, denser, and more uniform aluminum current collector film layer deposited on a base film such as PET, thus effectively reducing the number of band breaks during electrode preparation. See the example data in Table 1 for details.

[0084] In Comparative Example 1, the carbon coating layer is a graphite layer, i.e. a crystalline carbon layer. The crystalline carbon layer is not tightly bonded to the coated metal boride, so it is easy to fall off during the subsequent high-temperature calcination process, resulting in a decrease in protective performance. This leads to an increase in the number of pinholes on the current collector surface and an increase in the average particle size of TiB2 particles, ultimately resulting in an increase in the number of band breaks during the preparation of the positive electrode.

[0085] In Comparative Example 2, uncoated TiB2 particles were used directly. The TiB2 particles lacked the protection of the coating layer, and their various properties were significantly reduced. Therefore, the number of band breaks during the preparation of the positive electrode was also significantly increased.

[0086] Further observation of Examples 1-9 reveals that various properties change to some extent when the type of coating layer changes. Further observation of Examples 3 and 10, 4 and 11, 5 and 12, 7 and 13, 8 and 14, and 9 and 15 shows that changing the metal boride particles also results in certain or significant changes in various properties. This demonstrates that a specific pairing relationship exists between the coating layer and the metal boride particles; when these two materials are combined in a specific way, it is more beneficial to improve various properties.

[0087] Comparing Example 1 with Examples 16 and 17, the average particle size of the modified metal boride particles in Examples 16 and 17 was too small and too large, respectively, which was not conducive to the improvement of various properties. This shows that the particle size also has a certain impact on the performance of the evaporation boat, and thus affects the performance of the aluminum current collector film layer and the electrode.

[0088] Comparing Example 1 and Example 18, the range of raw materials for the evaporation boat in Example 18 was not within the preferred range, which also caused a decrease in various properties. This shows that a suitable raw material ratio is more conducive to obtaining an evaporation boat with excellent performance, resulting in fewer and smaller particles in the process of preparing the aluminum current collector film layer, thereby improving the subsequent processing performance of the aluminum current collector and reducing the number of electrode breakages.

[0089] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention, but such modifications or substitutions are all within the scope of protection of the present invention.

Claims

1. An evaporation boat for preparing a current collector, characterized in that: The evaporation boat includes a modified metal boride, and the modified metal boride particles include metal boride particles and a coating layer covering the metal boride particles. The metal borides include metal borides of group IVB and group VB metals; The coating layer includes at least one of a ceramic coating layer and a carbon coating layer; The ceramic coating layer includes at least one of SiO2, Al2O3, Y2O3, ZrO2, SiC, Si3N4, and Ti3SiC2; The carbon coating layer comprises amorphous carbon.

2. The evaporation boat for preparing a current collector as described in claim 1, characterized in that: The carbon coating layer contains doping elements, including at least one of nitrogen, sulfur, potassium, phosphorus, and boron.

3. The evaporation boat for preparing a current collector as described in claim 1, characterized in that: The boron compound particles include titanium diboride (TiB2) particles.

4. The evaporation boat for preparing a current collector as described in claim 1, characterized in that: The modified metal boride particles have an average particle size of 40~60μm; And / or, in the modified metal boride particles, the thickness of the coating layer is 5~60 nm.

5. The evaporation boat for preparing a current collector as described in claim 1, characterized in that: The evaporation boat also includes nitrides or carbides, boron nitride (BN). The nitride or carbide includes at least one of aluminum nitride (AlN), silicon carbide (SiC), and aluminum oxide (Al2O3).

6. A method for preparing an evaporation boat for preparing a current collector as described in any one of claims 1 to 5, characterized in that, The specific steps are as follows: The modified metal boride, the nitride or carbide, and the boron nitride are mixed in a certain proportion, mechanically ground, and the resulting mixed powder is filled into a mold. The mixture is then sintered at 1800~2400℃ for 3.5~6h in a first inert atmosphere. After cooling, the evaporation boat is obtained.

7. The method for preparing an evaporation boat for preparing a current collector as described in claim 6, characterized in that: The mass ratio of the modified metal boride, the nitride or carbide, and the boron nitride is 1~5:2~8:3~9.

8. The use of the evaporation boat as described in any one of claims 1 to 5 in the preparation of current collectors.

9. A current collector, characterized in that: The current collector includes an aluminum-containing metal layer, which is prepared by using an evaporation boat as described in any one of claims 1 to 5 or an evaporation boat prepared by the method for preparing an evaporation boat as described in any one of claims 6 to 7.

10. A battery, characterized in that: The battery includes the current collector as described in claim 9.

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