Core-shell structure niobium-tantalum oxide capacitor composite anode material, preparation method and application

Abstract

This invention discloses a core-shell structured niobium oxide-tantalum capacitor composite anode material, its preparation method, and its application. The composite anode material includes a conductive core, a diffusion barrier layer, a metal shell, and a dielectric layer. The conductive core is an NbO conductive core prepared from high-purity NbO powder; the diffusion barrier layer is an NbN layer coated on the NbO conductive core with a thickness of 5–50 nm; the metal shell is a Ta metal shell coated on the diffusion barrier layer with a thickness of 50–200 nm; and the dielectric layer is a Ta₂O₅ dielectric layer, generated in situ from the Ta metal shell through a two-stage anodizing process. The core-shell structure is expressed as NbO@NbN@Ta / Ta₂O₅. The preparation method employs a core-shell composite strategy, using NbO as the conductive core, NbN as the barrier layer, and an outer layer of tantalum metal. A high-quality Ta₂O₅ dielectric layer is then generated in situ using a standard anodizing process, balancing the high conductivity and safety of NbO with the high dielectric strength and high stability of Ta₂O₅.

Description

Technical Field

[0001] This invention belongs to the field of capacitor anode material technology, specifically relating to core-shell structure niobium oxide-tantalum capacitor composite anode material, its preparation method, and its application. Background Technology

[0002] As high-end electronic systems rapidly evolve towards miniaturization, high power density, and high reliability, the performance requirements for solid-state electrolytic capacitors, as key passive components, are constantly increasing. Tantalum capacitors, due to their excellent dielectric stability and miniaturization potential, are widely used in various high-end electronic devices. However, traditional tantalum powder anodes face two major bottlenecks: first, tantalum resources are scarce, with low abundance in the earth's crust and high prices, resulting in high device costs; second, pure tantalum anodes are prone to thermal runaway under high ripple current conditions, posing a risk of fire and explosion, and thus insufficient safety.

[0003] Niobium monoxide (NbO) offers significant advantages as a novel candidate material for capacitor anodes: it does not directly short-circuit upon breakdown, but instead enters a high-resistance mode, effectively preventing heat accumulation and fundamentally solving the thermal runaway problem, resulting in extremely high safety; niobium's crustal abundance is approximately 10 times that of tantalum, while its price is only 1 / 3 to 1 / 2 that of tantalum, exhibiting low resource dependence and a clear cost advantage; simultaneously, NbO possesses metal-like conductivity, with superior conductivity compared to porous tantalum frameworks, effectively reducing the equivalent series resistance (ESR) of devices and increasing power density.

[0004] However, NbO has a significant drawback: its surface is prone to spontaneously forming a non-stoichiometric oxide layer (NbO). x (x>1), the oxide layer has a loose structure and high defect density, resulting in large interface leakage current and poor withstand voltage performance, making it difficult to apply directly to high voltage and high reliability capacitor scenarios. Summary of the Invention

[0005] In view of this, embodiments of the present invention disclose a core-shell structured niobium oxide-tantalum capacitor composite anode material. The preparation method adopts a core-shell structure composite strategy, with NbO as the conductive core, NbN as the barrier layer, and tantalum metal as the outer layer. Then, a high-quality Ta2O5 dielectric layer is generated in situ through a standard anodic oxidation process, which takes into account the high conductivity and high safety of NbO and the high dielectric strength and high stability of Ta2O5.

[0006] On one hand, some embodiments disclose core-shell structured niobium oxide-tantalum capacitor composite anode materials, including a conductive core, a diffusion barrier layer, a metallic shell, and a dielectric layer; wherein:

[0007] The conductive core is an NbO conductive core prepared from high-purity NbO powder;

[0008] The diffusion barrier layer is an NbN layer coated on the NbO conductive core, with a thickness of 5–50 nm;

[0009] The metal shell is a metal Ta shell coated on the diffusion barrier layer, with a thickness of 50–200 nm;

[0010] The dielectric layer is a Ta2O5 dielectric layer, which is generated in situ by two-stage anodic oxidation of a metal Ta shell;

[0011] The core-shell structure is represented as NbO@NbN@Ta / Ta2O5.

[0012] On the other hand, some embodiments disclose a method for preparing a core-shell structured niobium oxide-tantalum capacitor composite anode material, including the following steps:

[0013] S1. NbO powder is treated with low-temperature hydrogen plasma to remove the non-stoichiometric NbO oxide layer on the surface. x x>1; Activated NbO powder is obtained;

[0014] S2. An NbN diffusion barrier layer is generated in situ on the activated NbO powder to obtain NbO@NbN powder;

[0015] S3. Using liquid-phase chemical reduction, a metal Ta shell layer is uniformly coated on the surface of NbO@NbN powder to obtain NbO@NbN@Ta core-shell composite powder.

[0016] S4. A composite anode is prepared by using NbO@NbN@Ta core-shell composite powder;

[0017] S5. An anodizing electrochemical system consisting of a composite anode, a stainless steel cathode, and a phosphoric acid solution is formed. Under a set voltage, Ta2O5 is formed in situ on the surface of the Ta shell, resulting in a composite anode material with a core-shell structure of NbO@NbN@Ta / Ta2O5.

[0018] Furthermore, some embodiments disclose a method for preparing a core-shell structured niobium oxide-tantalum capacitor composite anode material, wherein step S1 specifically includes:

[0019] S101. Spread NbO powder evenly on the sample holder of the plasma reaction chamber and evacuate to a vacuum degree ≤1Pa.

[0020] S102. Introduce high-purity hydrogen gas, control the hydrogen flow rate to 50 mL / min, and continue purging for 10-15 min.

[0021] S103. Turn on the radio frequency or microwave plasma generator, adjust the power to 50~100W, raise the temperature of the reaction chamber to 200~300℃, maintain this temperature and power, and perform surface activation treatment on NbO powder for 2~5 minutes.

[0022] S104. Continue to introduce hydrogen gas until the temperature of the reaction chamber drops to room temperature, and then obtain activated NbO powder.

[0023] The preparation method of the core-shell structured niobium oxide-tantalum capacitor composite anode material disclosed in some embodiments includes step S2 specifically:

[0024] The activated NbO powder was placed in a tube furnace, and a mixed atmosphere of NH3 and N2 with a volume ratio of 1:1~3 was introduced. The temperature was raised to 450~650℃ at a heating rate of 2~5℃ / min and held for 30~120min to generate an in-situ NbN barrier layer with a thickness of 5~50nm.

[0025] The preparation method of the core-shell structured niobium oxide-tantalum capacitor composite anode material disclosed in some embodiments includes step S3 specifically:

[0026] S301. In an argon-filled glove box, anhydrous toluene or tetrahydrofuran is used as the dispersion medium. The mass ratio of powder to dispersion medium is 1:10~20. The mixture is ultrasonically dispersed for 20~30 minutes to form a uniformly dispersed suspension.

[0027] S302. Slowly add the tantalum source to the suspension. The tantalum source can be K2TaF7 or TaCl5. Control the mass ratio of tantalum source to NbO@NbN powder to be 0.3~0.5:1. Stir evenly to fully dissolve and disperse the tantalum source in the suspension.

[0028] S303. At room temperature, the stirring rate is 200~500 r / min; the reducing agent LiAlH4 or NaBH4 is slowly added dropwise, and the molar ratio of the reducing agent to the tantalum source is 2~3:1. After the addition is complete, the stirring reaction continues for 10~60 min. The tantalum source is reduced in situ on the surface of NbO@NbN powder to form a metallic Ta shell with a thickness of 50~200 nm.

[0029] S304. After the reaction is complete, unreacted LiAlH4 is carefully quenched with ethyl acetate under an inert atmosphere; then centrifuged, the precipitate is collected and washed; and then vacuum dried at 80~100℃ and vacuum degree ≤10Pa for 2~4h to obtain NbO@NbN@Ta core-shell composite powder.

[0030] In some embodiments of the preparation method of core-shell structured niobium oxide-tantalum capacitor composite anode material, in step S3, the centrifugal separation speed is 3000~5000 r / min and the time is 10~15 min.

[0031] The preparation method of the core-shell structured niobium oxide-tantalum capacitor composite anode material disclosed in some embodiments includes step S5 specifically:

[0032] Using the composite anode obtained in step S4 as the anode and the stainless steel mesh as the cathode, an electrode with a conductivity of 350 μS·cm was placed in the solution. -1 In an H3PO4 solution, the solution is heated to 60°C and energized at a high voltage of 150V.

[0033] In some embodiments of the preparation method of core-shell structured niobium oxide-tantalum capacitor composite anode material, step S5, the energy-enabling process includes two stages:

[0034] The first stage is constant current charging, with a charging current of 55mA / g;

[0035] The second stage is constant voltage charging, with a charging voltage of 150V and a time of 1~6 hours.

[0036] On the other hand, some embodiments disclose a solid capacitor anode, which is prepared from the core-shell structure niobium oxide-tantalum capacitor composite anode material disclosed in the embodiments of the present invention.

[0037] On the other hand, some embodiments disclose solid-state capacitors that include the solid-state capacitor electrodes disclosed in the embodiments of the present invention.

[0038] The core-shell structured niobium oxide-tantalum capacitor composite anode material, its preparation method, and its application disclosed in this invention have at least the following beneficial technical effects:

[0039] 1. Significantly improved specific capacitance: Under the same sintering density, the volumetric specific capacitance of the core-shell structure niobium oxide-tantalum capacitor composite anode material is increased by 20-40% compared with pure Ta anode. For capacitors of the same size, the capacitance is higher, which can realize device miniaturization and meet the miniaturization requirements of high-end electronic devices.

[0040] 2. Significantly reduced equivalent series resistance (ESR): Due to the high conductivity of the NbO core and the low resistance of the NbN barrier layer, the ESR of the core-shell structure niobium oxide-tantalum capacitor composite anode is reduced by 30-50% compared to the pure Ta anode at a frequency of 100kHz. This reduces heat generation during device operation, increases power density, and extends device lifespan.

[0041] 3. Significantly improved reliability: The Ta2O5 dielectric layer is dense with low defect density, resulting in a breakdown field strength >500 V / μm and a leakage current ≤0.5CV (at 85℃ and rated voltage); the reverse voltage test pass rate at high temperature and high humidity (e.g., 85℃, 85%RH) is >99%; it does not spontaneously combust or explode during breakdown, making it far safer than pure Ta anodes.

[0042] 4. Significantly reduced costs: Nb resources are abundant and inexpensive. Compared with pure Ta anodes, the amount of Ta used in this invention is reduced by 30-50%, and the material cost is reduced by 20-35%. At the same time, it reduces dependence on tantalum mines in high-risk areas such as the Democratic Republic of Congo, and enhances the market competitiveness of the product.

[0043] 5. High feasibility for industrialization: The preparation process is mild, and the plasma nitriding, liquid phase reduction and other processes used are all mature industrial processes. Moreover, the final product is compatible with existing tantalum capacitor production lines, the production line modification cost is low, and large-scale mass production can be achieved.

[0044] 6. Excellent interface stability: The NbN barrier layer effectively suppresses the interdiffusion of Nb and Ta. During high-temperature sintering at 600~800℃ and long-term service for more than 1000h, the core-shell structure does not fall off or have defects, the electrical performance is stable, and the device life is improved by more than 30%. Attached Figure Description

[0045] Figure 1 , one The flowchart of the preparation method of core-shell structured niobium oxide-tantalum capacitor composite anode material disclosed in these embodiments. Detailed Implementation

[0046] The term "embodiment" used herein, as an example, is not necessarily to be construed as superior to or better than other embodiments. Performance testing in these embodiments of the invention, unless otherwise specified, employs conventional testing methods in the art. It should be understood that the terminology used in these embodiments is merely for describing particular implementations and is not intended to limit the scope of the disclosure of these embodiments.

[0047] Unless otherwise stated, the technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the embodiments of this invention pertain; other experimental methods and technical means not specifically noted in the embodiments of this invention refer to experimental methods and technical means commonly used by one of ordinary skill in the art.

[0048] The terms “basic” and “approximately” as used herein are used to describe small fluctuations. For example, they can mean less than or equal to ±5%, such as less than or equal to ±2%, such as less than or equal to ±1%, such as less than or equal to ±0.5%, such as less than or equal to ±0.2%, such as less than or equal to ±0.1%, such as less than or equal to ±0.05%. Numerical data presented or expressed in range format herein are used for convenience and brevity only, and should therefore be interpreted flexibly to include not only the explicitly listed values ​​that define the range, but also all independent values ​​or subranges contained within that range. For example, a numerical range of “1–5%” should be interpreted to include not only the explicitly listed values ​​from 1% to 5%, but also the independent values ​​and subranges within the indicated range. Thus, this numerical range includes independent values ​​such as 2%, 3.5%, and 4%, and subranges such as 1%–3%, 2%–4%, and 3%–5%, etc. This principle also applies to ranges that list only one value. Furthermore, this interpretation applies regardless of the width of the range or the characteristics described.

[0049] In this document, including in the claims, conjunctions such as "comprising," "including," "with," "having," "containing," "involving," and "accommodating" are understood to be open-ended, meaning "including but not limited to." Only the conjunctions "consisting of" and "composed of" are closed conjunctions.

[0050] To better illustrate the content of this invention, numerous specific details are provided in the following detailed embodiments. Those skilled in the art should understand that the invention can be practiced even without certain specific details. In the embodiments, some methods, means, instruments, and devices well-known to those skilled in the art are not described in detail, in order to highlight the main points of the invention.

[0051] Without conflict, the technical features disclosed in the embodiments of the present invention can be combined arbitrarily, and the resulting technical solution belongs to the content disclosed in the embodiments of the present invention.

[0052] In some embodiments, the core-shell structured niobium oxide-tantalum capacitor composite anode material includes a conductive core, a diffusion barrier layer, a metallic shell, and a dielectric layer; wherein:

[0053] The conductive core is an NbO conductive core prepared from high-purity NbO powder. Typically, the NbO conductive core uses high-purity NbO powder as the conductive framework of the entire anode material, providing a low-resistance path and significantly reducing the device's equivalent series resistance (ESR). It also possesses high safety characteristics, entering a high-resistance mode upon breakdown to avoid thermal runaway and ensure device safety. Its porous structure increases the specific surface area, laying the foundation for high specific capacitance. Typically, the NbO conductive core is made of high-purity NbO powder with a particle size of 0.1–8 μm; preferably 0.5–5 μm.

[0054] The diffusion barrier layer is an NbN layer coated on the NbO conductive core, with a thickness of 5–50 nm. Typically, the NbN diffusion barrier layer is located between the NbO core and the Ta shell, with a thickness of 5–50 nm. It is prepared by in-situ generation and has the characteristics of high melting point, high conductivity, and thermodynamic stability. The core function of the diffusion barrier layer is to suppress the interdiffusion of Nb and Ta during high-temperature sintering and long-term service, avoid the formation of alloy phases or vacancy defects, and at the same time improve the interfacial bonding force between NbO and Ta, reduce the interfacial defect density, and reduce leakage current.

[0055] In some embodiments, a preferred thickness of the NbN layer is 20 nm.

[0056] The metal shell is a Ta shell coated on the diffusion barrier layer, with a thickness of 50–200 nm. Typically, the Ta shell is coated on the surface of the NbN barrier layer, with a thickness of 50–200 nm, serving as a precursor for the Ta₂O₅ dielectric layer. After anodizing, a high-quality Ta₂O₅ dielectric layer can be generated in situ. Simultaneously, it is fully compatible with existing tantalum capacitor enabling processes, ensuring high dielectric reliability of the device.

[0057] In some embodiments, a preferred thickness of the metal Ta shell is 100 nm.

[0058] The dielectric layer is a Ta2O5 dielectric layer, which is generated in situ by two-stage anodic oxidation of the metal Ta shell. Typically, the Ta2O5 dielectric layer is located on the outermost layer of the core-shell structure. It is generated in situ by two-stage anodic oxidation of the metal Ta shell, with uniform thickness, dense structure, and low defect density. It has the characteristics of high breakdown field strength (>500V / μm), strong self-healing ability, and good dielectric stability, ensuring high withstand voltage and high reliability of the device.

[0059] Typically, the core-shell structure of niobium oxide-tantalum capacitor composite anode materials can be expressed as NbO@NbN@Ta / Ta2O5.

[0060] In some embodiments, the preparation method of the core-shell structured niobium oxide-tantalum capacitor composite anode material includes the following steps:

[0061] S1. NbO powder is treated with low-temperature hydrogen plasma to remove the non-stoichiometric NbO oxide layer on the surface. x x>1; Activated NbO powder is obtained; The surface energy and activity of the activated NbO powder are improved, laying the foundation for the subsequent in-situ generation of the NbN barrier layer and the coating of the Ta shell; Generally, the temperature and time of hydrogen plasma treatment must be controlled within a suitable range to completely remove NbO from the NbO surface. x (x>1) Oxide layer, otherwise it will lead to a decrease in the bonding force of the subsequent NbN barrier layer and an increase in leakage current;

[0062] In some embodiments, step S1 specifically includes:

[0063] S101. Spread NbO powder evenly on the sample holder of the plasma reaction chamber, close the reaction chamber, evacuate to a vacuum degree ≤1Pa, and remove the air.

[0064] S102. Introduce high-purity hydrogen gas with a purity of not less than 99.999%, control the hydrogen flow rate to 50 mL / min, and continue purging for 10 to 15 minutes to further remove residual oxygen and impurities in the reaction chamber.

[0065] S103. Turn on the radio frequency or microwave plasma generator, adjust the power to 50~100W, raise the temperature of the reaction chamber to 200~300℃, maintain this temperature and power, and perform surface activation treatment on NbO powder for 2~5 minutes.

[0066] S104. After the process is completed, turn off the plasma generator, continue to introduce hydrogen gas, and wait for the temperature of the reaction chamber to drop to room temperature before stopping the gas supply and taking out the activated NbO powder.

[0067] S2. An NbN diffusion barrier layer is generated in situ on the activated NbO powder to obtain NbO@NbN powder. Typically, during the preparation of the NbN barrier layer, the thickness is strictly controlled at 5~50 nm, the nitriding temperature is 450~650℃ (ammonia thermal nitriding method), and an oxygen-free atmosphere is maintained throughout the process to prevent NbN oxidation and ensure the compactness and conductivity of NbN.

[0068] In some embodiments, step S2 specifically includes: placing the activated NbO powder in a tube furnace, introducing a mixed atmosphere of NH3 and N2 with a volume ratio of 1:1~3, raising the temperature to 450~650℃ at a heating rate of 2~5℃ / min, holding at the temperature for 30~120min, and generating an in-situ NbN barrier layer with a thickness of 5~50nm.

[0069] S3. Using a liquid-phase chemical reduction method, a metal Ta shell layer is uniformly coated onto the surface of NbO@NbN powder to obtain NbO@NbN@Ta core-shell composite powder. Typically, a liquid-phase chemical reduction method is used, employing organic solvents and an inert atmosphere to prevent the tantalum source and reducing agent from reacting with oxygen or water. This method uniformly coats the surface of NbO@NbN powder with a metal Ta shell layer, achieving low-temperature, non-sintering, uniform coating, and controllable thickness, making it suitable for ultrafine porous powders. In some embodiments, step S3 specifically includes:

[0070] S301. In an argon-filled glove box, anhydrous toluene or tetrahydrofuran is used as the dispersion medium. The mass ratio of powder to dispersion medium is 1:10 to 1:20. The mixture is ultrasonically dispersed for 20 to 30 minutes to form a uniformly dispersed suspension.

[0071] S302. Slowly add the tantalum source to the suspension. The tantalum source can be K2TaF7 or TaCl5. Control the mass ratio of the tantalum source to the NbO@NbN powder to be 0.3:1~0.5:1. Stir evenly to ensure that the tantalum source is fully dissolved and dispersed in the suspension.

[0072] S303. At room temperature, the stirring rate is 200~500 r / min; the reducing agent LiAlH4 or NaBH4 is slowly added dropwise, and the molar ratio of the reducing agent to the tantalum source is 2~3:1. After the addition is complete, the stirring reaction continues for 10~60 min. The tantalum source is reduced in situ on the surface of NbO@NbN powder to form a metallic Ta shell with a thickness of 50~200 nm.

[0073] S304. After the reaction is complete, unreacted LiAlH4 is carefully quenched with ethyl acetate under an inert atmosphere; then, the precipitate is collected by centrifugation and washed; and then vacuum dried at 80-100℃ and a vacuum degree ≤10Pa for 2-4 hours to obtain NbO@NbN@Ta core-shell composite powder. In some embodiments, the centrifugation speed is 3000-5000 r / min and the time is 10-15 min.

[0074] S4. Use NbO@NbN@Ta core-shell composite powder to prepare and shape a composite anode; usually, a forming agent can be added, and the composite anode can be shaped into the required shape under a certain pressure, such as the anode for solid capacitors.

[0075] S5. An anodic oxidation electrochemical system is composed of a composite anode, a stainless steel cathode, and a phosphoric acid solution. Energization is performed under a set voltage to form Ta2O5 in situ on the Ta shell surface, resulting in a composite anode material with a NbO@NbN@Ta / Ta2O5 core-shell structure. The Ta2O5 dielectric layer is dense, has low defects, and high breakdown strength.

[0076] In some embodiments, step S5 specifically includes: using the composite anode obtained in step S4 as the anode and the stainless steel mesh as the cathode, placing an object with a conductivity of 350 μS·cm... -1 In an H3PO4 solution, the solution is heated to 60°C and energized at a high voltage of 150V.

[0077] In some embodiments of the preparation method of core-shell structured niobium oxide-tantalum capacitor composite anode material, step S5, the energy-enabling process includes two stages:

[0078] The first stage is constant current charging, with a charging current of 55mA / g;

[0079] The second stage is constant voltage charging, with a charging voltage of 150V and a time of 1~6 hours.

[0080] Typically, in the first stage of constant current anodic oxidation, the anodic oxidation current is 55 mA / g, and the composite anode is anodicly oxidized at a constant current, with the actual voltage increasing at a relatively constant rate. In the second stage of constant voltage anodic oxidation, the anodic oxidation voltage is 150 V, and the time is 1–6 h. As time progresses, the current through the tantalum anode gradually decreases, and the defects in the oxide film are gradually improved. After anodic oxidation, the anode material is removed, washed with deionized water to remove residual electrolyte, and vacuum dried to obtain the final NbO@NbN@Ta / Ta2O5 core-shell composite anode material.

[0081] Some embodiments disclose solid capacitor anodes prepared from the core-shell structure niobium oxide-tantalum capacitor composite anode material disclosed in the embodiments of the present invention.

[0082] Some embodiments disclose solid-state capacitors that include the solid-state capacitor electrodes disclosed in the embodiments of the present invention.

[0083] The technical details are further illustrated below with reference to the embodiments.

[0084] Example 1

[0085] In Example 1, the preparation method of the core-shell structured niobium oxide-tantalum capacitor composite anode material includes:

[0086] S1. Surface activation: NbO powder is placed in the plasma reaction chamber, vacuumed to 1Pa, purged with 50mL / min high-purity H2 for 10min, radio frequency plasma is turned on at 75W power, treated at 250℃ for 3min, and the activated NbO powder is taken out after cooling.

[0087] S2, NbN barrier layer preparation: Activated NbO powder was placed in a tube furnace, and a mixed gas of NH3 (30 mL / min) and N2 (30 mL / min) was introduced. The temperature was increased to 550℃ at 3℃ / min and held for 60 min. The N2 atmosphere was cooled to room temperature to obtain NbO@NbN powder with an NbN layer thickness of about 20 nm.

[0088] S3, Ta shell coating: In a glove box filled with argon atmosphere, NbO@NbN powder and tetrahydrofuran were mixed at a mass ratio of 1:15 and ultrasonically dispersed for 25 min. K2TaF7 (mass ratio to powder 0.4:1) was added and stirred to dissolve. NaBH4 (molar ratio to K2TaF7 2.5:1) was slowly added dropwise at a stirring rate of 300 r / min and reacted for 30 min. After centrifugation, washing, and vacuum drying at 80℃ for 3 h, NbO@NbN@Ta composite powder was obtained with a Ta shell thickness of approximately 100 nm.

[0089] S4. Shape the composite powder into an anode;

[0090] S5, Anodizing: Prepare a 0.05% H3PO4 electrolyte (conductivity 350 μS·cm). -1 The cathode was subjected to constant temperature of 60℃; a stainless steel mesh was used as the cathode, and the cathode was energized to 150V with a constant current of 55mA / g, and then energized at a constant voltage of 150V for 3 hours; the cathode was washed and dried to obtain the target composite anode material.

[0091] In Example 1, the corresponding indicator testing methods include:

[0092] 1. Volumetric specific volume: Prepare anode blocks of the same external dimensions, test the capacitance with an LCR meter at room temperature, calculate the specific volume based on the volume, and compare it with pure tantalum anodes to calculate the improvement.

[0093] 2. Equivalent series resistance (ESR): An impedance analyzer was used to test the ESR value of the device under normal operating conditions at a test frequency of 100kHz. The reduction ratio was obtained by comparing the measured value with that of a reference sample.

[0094] 3. Leakage current: At an ambient temperature of 85℃, apply a constant voltage of 150V, stabilize the voltage and let it stand for 5 minutes, then read the steady-state leakage current and calculate the value in CV standard units.

[0095] 4. High temperature and high humidity reverse voltage reliability: The test chamber is set at 60℃ and 90% relative humidity. The reverse rated voltage is applied, and batch samples are subjected to long-term aging tests. The pass rate is obtained by statistically analyzing the percentage of qualified samples.

[0096] 5. Breakdown safety characteristics: Gradually increase the voltage until the device breaks down and fails, observe the sample status throughout the process, and check for any fire or explosion phenomena.

[0097] 6. Interfacial interdiffusion detection: Using transmission electron microscopy (TEM) combined with energy dispersive spectroscopy (EDS) line scanning, the elemental distribution between particle layers is analyzed to determine whether there is elemental interdiffusion behavior at the layer interface.

[0098] In comparison, the inventors also tested pure Ta anodes; the test results are shown in Table 1.

[0099] The product performance test results of Example 1 show that, compared with pure Ta anode, the composite anode material of Example 1 has a 32% increase in volumetric capacitance, a 41% reduction in ESR at 100 kHz, a leakage current of 0.28 CV (85℃, 150V), a 99.5% pass rate in high temperature and high humidity reverse voltage test, no fire or explosion after breakdown, no interdiffusion phenomenon at the interface, and its performance fully meets the requirements of high-end tantalum capacitors.

[0100] Table 1. List of Anode Performance Tests for Example 1 and Pure Ta

[0101]

[0102] The core-shell structured niobium oxide-tantalum capacitor composite anode material, its preparation method, and its application disclosed in this invention have at least the following beneficial technical effects:

[0103] 1. Significantly improved specific capacitance: Under the same sintering density, the volumetric specific capacitance of the core-shell structure niobium oxide-tantalum capacitor composite anode material is increased by 20-40% compared with pure Ta anode. For capacitors of the same size, the capacitance is higher, which can realize device miniaturization and meet the miniaturization requirements of high-end electronic devices.

[0104] 2. Significantly reduced equivalent series resistance (ESR): Due to the high conductivity of the NbO core and the low resistance of the NbN barrier layer, the ESR of the core-shell structure niobium oxide-tantalum capacitor composite anode is reduced by 30-50% compared to the pure Ta anode at a frequency of 100kHz. This reduces heat generation during device operation, increases power density, and extends device lifespan.

[0105] 3. Significantly improved reliability: The Ta2O5 dielectric layer is dense with low defect density, resulting in a breakdown field strength >500 V / μm and a leakage current ≤0.5CV (at 85℃ and rated voltage); the reverse voltage test pass rate at high temperature and high humidity (e.g., 85℃, 85%RH) is >99%; it does not spontaneously combust or explode during breakdown, making it far safer than pure Ta anodes.

[0106] 4. Significantly reduced costs: Nb resources are abundant and inexpensive. Compared with pure Ta anodes, the amount of Ta used in this invention is reduced by 30-50%, and the material cost is reduced by 20-35%. At the same time, it reduces dependence on tantalum mines in high-risk areas such as the Democratic Republic of Congo, and enhances the market competitiveness of the product.

[0107] 5. High feasibility for industrialization: The preparation process is mild, and the plasma nitriding, liquid phase reduction and other processes used are all mature industrial processes. Moreover, the final product is compatible with existing tantalum capacitor production lines, the production line modification cost is low, and large-scale mass production can be achieved.

[0108] 6. Excellent interface stability: The NbN barrier layer effectively suppresses the interdiffusion of Nb and Ta. During high-temperature sintering at 600~800℃ and long-term service for more than 1000h, the core-shell structure does not fall off or have defects, the electrical performance is stable, and the device life is improved by more than 30%.

[0109] The technical solutions and technical details disclosed in the embodiments of this invention are merely illustrative of the inventive concept of this invention and do not constitute a limitation on the technical solutions of the embodiments of this invention. Any conventional changes, substitutions, or combinations made to the technical details disclosed in the embodiments of this invention have the same inventive concept as this invention and are within the protection scope of the claims of this invention.

Claims

1. A core-shell structured niobium oxide-tantalum capacitor composite anode material, characterized in that, It includes a conductive core, a diffusion barrier layer, a metallic shell, and a dielectric layer; wherein: The conductive core is an NbO conductive core prepared from high-purity NbO powder; The diffusion barrier layer is an NbN layer coated on the NbO conductive core, with a thickness of 5-50 nm. The metal shell is a metal Ta shell coated on the diffusion barrier layer, with a thickness of 50-200 nm. The dielectric layer is a Ta2O5 dielectric layer, which is generated in situ by two-stage anodic oxidation of a metallic Ta shell. The core-shell structure is expressed as NbO@NbN@Ta / Ta2O5.

2. The method for preparing the core-shell structured niobium oxide-tantalum capacitor composite anode material according to claim 1, characterized in that, Including the following steps: S1. NbO powder is treated with low-temperature hydrogen plasma to remove the non-stoichiometric NbO oxide layer on the surface. x x>1; Activated NbO powder is obtained; S2. An NbN diffusion barrier layer is generated in situ on the activated NbO powder to obtain NbO@NbN powder; S3. Using a liquid-phase chemical reduction method, a metal Ta shell layer is uniformly coated on the surface of NbO@NbN powder to obtain NbO@NbN@Ta core-shell composite powder. S4. A composite anode is prepared by using NbO@NbN@Ta core-shell composite powder; S5. An anodizing electrochemical system consisting of a composite anode, a stainless steel cathode, and a phosphoric acid solution is formed. Under a set voltage, Ta2O5 is formed in situ on the surface of the Ta shell, resulting in a composite anode material with a core-shell structure of NbO@NbN@Ta / Ta2O5.

3. The preparation method according to claim 2, characterized in that, Step S1 specifically includes: S101. Spread NbO powder evenly on the sample holder of the plasma reaction chamber and evacuate to a vacuum degree ≤1Pa. S102. Introduce high-purity hydrogen gas, control the hydrogen flow rate to 50 mL / min, and continue purging for 10-15 min. S103. Turn on the radio frequency or microwave plasma generator, adjust the power to 50~100W, raise the temperature of the reaction chamber to 200~300℃, maintain this temperature and power, and perform surface activation treatment on NbO powder for 2~5 minutes. S104. Continue to introduce hydrogen gas until the temperature of the reaction chamber drops to room temperature, and then obtain activated NbO powder.

4. The preparation method according to claim 2, characterized in that, Step S2 specifically includes: The activated NbO powder was placed in a tube furnace, and a mixed atmosphere of NH3 and N2 with a volume ratio of 1:1~3 was introduced. The temperature was raised to 450~650℃ at a heating rate of 2~5℃ / min and held for 30~120min to generate an in-situ NbN barrier layer with a thickness of 5~50nm.

5. The preparation method according to claim 2, characterized in that, Step S3 specifically includes: S301. In an argon-filled glove box, anhydrous toluene or tetrahydrofuran is used as the dispersion medium. The mass ratio of powder to dispersion medium is 1:10~20. The mixture is ultrasonically dispersed for 20~30 minutes to form a uniformly dispersed suspension. S302. Slowly add the tantalum source to the suspension. The tantalum source can be K2TaF7 or TaCl5. Control the mass ratio of tantalum source to NbO@NbN powder to be 0.3~0.5:

1. Stir evenly to fully dissolve and disperse the tantalum source in the suspension. S303. At room temperature, the stirring rate is 200~500 r / min; the reducing agent LiAlH4 or NaBH4 is slowly added dropwise, and the molar ratio of the reducing agent to the tantalum source is 2~3:

1. After the addition is complete, the stirring reaction continues for 10~60 min. The tantalum source is reduced in situ on the surface of NbO@NbN powder to form a metallic Ta shell with a thickness of 50~200 nm. S304. After the reaction is complete, unreacted LiAlH4 is carefully quenched with ethyl acetate under an inert atmosphere; then centrifuged, the precipitate is collected and washed; and then vacuum dried at 80~100℃ and vacuum degree ≤10Pa for 2~4h to obtain NbO@NbN@Ta core-shell composite powder.

6. The preparation method according to claim 5, characterized in that, In step S3, the centrifugation speed is 3000~5000 r / min and the time is 10~15 min.

7. The preparation method according to claim 2, characterized in that, Step S5 specifically includes: Using the composite anode obtained in step S4 as the anode and the stainless steel mesh as the cathode, an electrode with a conductivity of 350 μS·cm was placed in the solution. -1 In an H3PO4 solution, the solution is heated to 60°C and energized at a high voltage of 150V.

8. The preparation method according to claim 7, characterized in that, In step S5, the enabling process includes two stages: The first stage is constant current charging, with a charging current of 55mA / g; The second stage is constant voltage charging, with a charging voltage of 150V and a time of 1~6 hours.

9. Anode of a solid-state capacitor, characterized in that, It is prepared from the core-shell structured niobium oxide-tantalum capacitor composite anode material as described in claim 1.

10. A solid-state capacitor, characterized in that, It includes the solid capacitor anode as described in claim 9.

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