Preparation process of ultra-high capacitance MLCC ultra-fine particle size roller printing nickel electrode paste

Abstract

This invention belongs to the field of nickel electrode paste preparation technology, and discloses a preparation process for ultra-fine particle size nickel electrode paste for ultra-high capacity MLCC roller printing. It aims to solve the problems of easy oxidation of ultra-fine nickel powder, high cost of nitrided nickel powder, easy damage and agglomeration of coating during dispersion, and poor paste performance in the prior art. The process maintains a high-purity nitrogen atmosphere throughout and consists of three steps: raw material pretreatment, material dispersion and nitriding simultaneously, and post-treatment and nitrogen protection. The pretreatment removes impurities and prevents oxidation. The dispersion and nitriding are carried out in a coordinated manner by graded control parameters through a sand mill and an ultra-high pressure homogenizer. The post-treatment includes filtration, inspection, and double-layer vacuum sealing. The raw materials are composed in a specific ratio, and the key parameters are precisely controlled to finally obtain a paste that meets the requirements of roller printing compatibility and co-firing. It eliminates the need for independent nitriding and reduction processes, reduces costs, improves paste uniformity, dispersion stability and MLCC reliability, and can be mass-produced.

Description

Technical Field

[0001] This invention relates to the field of electrode paste preparation technology, and in particular to the preparation process of ultra-high capacitance MLCC ultra-fine particle size roller-printed nickel electrode paste. Background Technology

[0002] Multilayer ceramic capacitors (MLCCs) are among the most widely used and fastest-growing electronic components in the electronics and information industry. Their performance directly affects the stability and reliability of electronic devices. With the miniaturization and high integration of electronic products, MLCCs have increasingly higher requirements for capacitance density, reliability, and size. This inevitably requires thinner and more numerous electrode layers inside MLCCs. Nickel electrode paste is a key material for the internal electrodes of MLCCs, and its performance directly affects the electrical performance and reliability of MLCCs.

[0003] In existing nickel electrode slurry preparation technologies, the surface oxidation of ultrafine nickel powder, as a conductive component, has always been one of the bottlenecks restricting the improvement of MLCC performance. Oxidation of nickel powder not only reduces the conductivity of the slurry but also affects the sintering performance and service life of MLCC. To solve the problem of nickel powder oxidation, various methods have been tried in the existing technology. For example, Chinese patent CN103456493A discloses a method for coating nickel nitride on the surface of nickel particles in an internal electrode conductive slurry to effectively control shrinkage during sintering. However, the production cost of existing nickel nitride-coated nickel powder is high, the coating is easily damaged in the dispersion process, and nickel nitride-coated nickel powder is prone to agglomeration during dispersion, affecting the dispersion effect. This makes it difficult for the uniformity and dispersion stability of the slurry to meet the requirements of ultra-high capacitance MLCC for ultrafine electrode linewidth and layer thickness, leading to short circuit and other failure problems when the thickness of the MLCC dielectric layer is further reduced. Summary of the Invention

[0004] The technical problem to be solved by the present invention is that in the prior art, ultrafine nickel powder is easy to oxidize, nickel nitride powder has high production cost, the coating is easily damaged and agglomerates during the dispersion process, and the slurry has poor uniformity and dispersion stability. To this end, we propose a preparation process for ultrafine particle size roller-printed nickel electrode slurry for ultra-high capacity MLCCs.

[0005] To achieve the above objectives, this application adopts the following technical solution: a preparation process for ultra-high capacitance MLCC ultra-fine particle size roller-printed nickel electrode paste, comprising the following steps:

[0006] S1. Raw material pretreatment and nitrogen atmosphere construction: Each raw material is pretreated, and a nitrogen atmosphere is established and maintained throughout the process to remove impurities and prevent oxidation, providing a foundation for the simultaneous dispersion-nitriding process. The nitrogen gas is high-purity nitrogen with a purity ≥99.999%, oxygen content ≤1ppm, and moisture content ≤5ppm, specifically including:

[0007] S101. Vacuum dehydration and deoxidation of nickel powder with nitrogen protection: After vacuum dehydration and deoxidation, ultrafine nickel powder is filled with high-purity nitrogen to atmospheric pressure and transferred to a nitrogen-sealed double planetary mixer under a nitrogen atmosphere to ensure that the oxygen content of the nickel powder is ≤0.2%;

[0008] S102. Ceramic additive modification under nitrogen atmosphere: In a nitrogen-sealed environment, the ceramic additive is mixed and ground with a silane coupling agent to obtain a modified ceramic additive, which is then transferred to the dual planetary mixer under a nitrogen atmosphere.

[0009] S103. Preparation of organic carrier under nitrogen protection: In a nitrogen-sealed environment, the solvent, binder and dispersant are mixed and dissolved, filtered, and the oxygen content of the carrier is controlled to be ≤0.1%. The carrier is then sealed and kept for later use under a nitrogen atmosphere.

[0010] S2. Material Dispersion and Nitriding: By adjusting nitrogen parameters and equipment operation, material dispersion and nickel powder nitriding are carried out synergistically to gradually achieve the target particle size and nitriding layer requirements. Specifically, this includes:

[0011] S201. Nitrogen-sealed premix: Nitrogen powder treated with S101, modified ceramic additives treated with S102, and part of the pre-prepared organic carrier are added sequentially to a nitrogen-sealed double planetary mixer and stirred to form a uniform premix.

[0012] S202. Primary dispersion and low-temperature nitriding start-up: The premix is ​​transferred to a nitrogen-sealed sand mill under a nitrogen atmosphere, the high-purity nitrogen is introduced and the nitrogen partial pressure is adjusted, grinding media is added and the sand mill is started, the temperature is raised and held to start the nitriding reaction and generate Ni3N initial crystal nuclei;

[0013] S203. Fine dispersion and nitrided layer growth: The primary dispersed material is transferred to a nitrogen-sealed ultra-high pressure homogenizer under a nitrogen atmosphere. The partial pressure and temperature of high-purity nitrogen are adjusted, and the homogenizer is started to achieve simultaneous fine dispersion of particles and growth of nitrided layer.

[0014] S204. Cooling to terminate nitriding and nitrogen pressure maintenance to prevent oxidation: Turn off the heating device, cool down to the preset temperature, maintain nitrogen partial pressure to prevent air from entering;

[0015] S205. Viscosity adjustment under nitrogen atmosphere: In a nitrogen-sealed environment, add the remaining organic carrier and additives, stir and mix evenly, and adjust the slurry viscosity to the preset range;

[0016] S206. Nitrogen-protected vacuum degassing: The slurry after viscosity adjustment is transferred to a nitrogen-protected vacuum degassing machine to remove air bubbles and trace by-products from the slurry;

[0017] S3. Post-processing and nitrogen protection throughout the entire process: The slurry treated by S2 is purified, inspected, and packaged, with nitrogen protection maintained throughout the process, specifically including:

[0018] S301. Nitrogen-sealed fine filtration: Under nitrogen protection, the deaerated slurry is passed through a nitrogen-sealed precision filter to remove large particulate impurities.

[0019] S302. Nitrogen Temporary Storage and Finished Product Inspection: The filtered slurry is temporarily stored in a nitrogen atmosphere and tested according to standards;

[0020] S303. Nitrogen Encapsulation and Storage: Qualified slurry is packaged in a double-layer vacuum system. The inner layer is filled with the high-purity nitrogen, and the outer layer is sealed to prevent moisture. It is stored under preset environmental conditions. The high-purity nitrogen has two core functions: First, it serves as a dedicated nitrogen source for the nitriding reaction, providing a material basis for the initial formation of Ni3N crystal nuclei and the growth of the nitrided layer. Second, it serves as a protective atmosphere against oxidation throughout the process, maintaining the oxygen content of the system at ≤1ppm and isolating air to inhibit the oxidation and degradation of nickel powder, slurry system, and nitrided layer. Finally, a nickel electrode slurry with an electrode layer thickness of ≤1μm that meets the requirements for roller printing compatibility and co-firing performance is obtained, without the need for separate nitriding pretreatment and reduction processes.

[0021] Furthermore, the raw materials are composed of the following by weight percentage: 40-60% ultrafine nickel powder, 5-10% ceramic additives, 20-35% solvent, 5-15% binder, 1.5-3% dispersant, 0.5-0.8% antioxidant, and 0.1-0.3% defoamer; the ultrafine nickel powder is a spherical powder with D50=30-60nm, Span≤0.8, and purity≥99.9%; the ceramic additive is barium titanate / calcium strontium titanate with a particle size≤30nm and a thermal expansion coefficient deviation ≤5% from that of the MLCC medium; the amount of silane coupling agent added is 0.5% of the weight of the ceramic additives.

[0022] Furthermore, the dual function of nitrogen is ensured by real-time monitoring through an online gas analysis system. This system records the nitrogen purity, oxygen content, and moisture content in real time, and automatically alarms and replenishes nitrogen when the oxygen content is ≥1ppm.

[0023] Furthermore, in S101, the specific operation of vacuum dehydration and deoxidation is as follows: ultrafine nickel powder is loaded into the vacuum dehydration and deoxidation hopper, the feed port is closed, and the vacuum pump is started to evacuate to -0.098MPa and maintained for 10 minutes; the temperature is raised to 80℃±2℃ and held for 30 minutes; the temperature is lowered to 25℃ and then the high-purity nitrogen gas is introduced to atmospheric pressure; nitrogen is continuously introduced during the transfer process.

[0024] Furthermore, in S102, the oxygen content in the grinding environment is ≤1ppm, the grinding time is 30min, and the D50 of the modified ceramic additive is ≤20nm; before starting the raw material grinding mill, high-purity nitrogen is introduced to replace the air in the mill 3 times, and the pressure is maintained for 5min after each replacement.

[0025] Furthermore, in S103, the organic carrier dissolution vessel is purged with high-purity nitrogen three times before starting; during mixing and dissolution, the temperature is raised to 55℃±2℃ and stirred for 2 hours until completely dissolved and no particles are visible to the naked eye; a 1μm filter element is used for filtration.

[0026] Furthermore, in S201, the chamber of the double planetary mixer is purged with high-purity nitrogen three times in advance, with each pressurization lasting 5 minutes, and the sealed oxygen content is ≤1ppm; the added organic carrier is 50% of the total amount of the pre-prepared organic carrier; the stirring parameters are: speed 600rpm, temperature 25℃, and stirring time 1h.

[0027] Furthermore, in S202, the specific operation of the sand mill is as follows: the sand mill chamber is purged with nitrogen three times in advance, and the sealed oxygen content is ≤1ppm; the two-stage palladium molecular sieve deoxygenation device is turned on, high-purity nitrogen is introduced and the nitrogen partial pressure is adjusted to 0.12MPa±0.01MPa; the grinding media is 0.1-0.3mm zirconia balls, and the sand mill speed is 1500rpm; the temperature is raised to 120℃±2℃ and kept at that temperature for 2h, so that the oxygen content of the material in this stage is ≤0.25%; the inspection standard is: particle size D50≤80nm, and the proportion of Ni3N characteristic peaks detected by XPS is 5%-8%.

[0028] Furthermore, in S203, the specific operation of the ultra-high pressure homogenizer is as follows: the homogenizer chamber is purged with nitrogen three times in advance, and the sealed oxygen content is ≤1ppm; the partial pressure of high-purity nitrogen is adjusted to 0.15MPa±0.01MPa, and the temperature is raised to 140℃±2℃; the homogenizer pressure is adjusted to 2000bar, and the material passes through a 400μm+100μm multi-stage homogenization chamber; the cyclic homogenization dispersion-nitriding process is repeated three times, with a total time of 1.5h; the inspection standards are: particle size D50=30-60nm, Span≤0.8, Ni3N characteristic peak ratio 15-20%, resistivity ≥5×10 -8 Ω・m; if the particle size detection D50 > 60 nm or Span > 0.8, add ≤ 2 cycles while maintaining a nitrogen partial pressure of 0.15 MPa and a temperature ≤ 140 °C.

[0029] Furthermore, in S204, the temperature is lowered to 30℃±2℃, and the nitrogen partial pressure is maintained at 0.1MPa during the cooling process.

[0030] Furthermore, in S205, the additives include antioxidants and defoamers; the stirring parameters are a speed of 300 rpm and a stirring time of 30 min; the viscosity is adjusted by adding ≤5% of the total solvent or by letting it stand for ≤30 min, with a target viscosity range of 20000-40000 mPa・s.

[0031] Furthermore, in S206, the vacuum degassing machine is purged with nitrogen three times in advance; the vacuum is drawn to -0.095MPa, and the degassing time is 25min. After degassing, the slurry has no visible bubbles and has uniform fluidity.

[0032] Furthermore, in S301, the precision filter is pre-purged with nitrogen three times to ensure the sealed oxygen content is ≤1ppm; the filtration pressure is controlled at 0.1-0.3MPa, and a 0.5μm filter element is used; the content of impurities >1μm after filtration is ≤0.1%; the filter element is replaced for each batch, and the pressure change before and after filtration is recorded.

[0033] Furthermore, in S302, the full range of inspection standards include: particle size distribution D50=30-60nm, Span≤0.8; nitrided layer thickness 2-5nm, Ni3N characteristic peak ratio 15-20%; oxygen content ≤0.3%; viscosity; dispersion stability; roll printing adaptability, thickness deviation ±0.08μm, defect rate ≤0.8%; and co-firing shrinkage rate ≤3%.

[0034] Furthermore, in S303, the inner layer is filled with high-purity nitrogen gas to 0.05 MPa; the storage environment conditions are: temperature 4-25℃, relative humidity ≤40%, and shelf life of 6 months.

[0035] Furthermore, the dispersant is a phosphate ester with an HLB value of 8-10, and the absolute value of the zeta potential of the slurry after its addition is ≥30mV.

[0036] Furthermore, during the raw material storage stage, ultrafine nickel powder and ceramic additives are stored in nitrogen-protected sealed silos with storage conditions of 4-25℃ and relative humidity ≤40%, and must be used within 72 hours after opening.

[0037] Furthermore, the dual function of nitrogen is integrated throughout the entire process of raw material pretreatment, dispersion-nitriding synchronization, post-treatment, and packaging; the sealed oxygen content of all equipment in contact with materials is ≤1ppm; through precise parameter control and synergy with the nitrogen atmosphere, dispersion-nitriding synchronization under large-scale production is achieved.

[0038] The technical effects and advantages of this invention are as follows:

[0039] This invention achieves simultaneous material dispersion and nickel powder nitriding reaction by controlling nitrogen partial pressure and temperature in stages. The particle size of nickel powder and the growth of the Ni3N nitriding layer are gradually completed in a sand mill and an ultra-high pressure homogenizer. This simultaneous process effectively avoids the problem of damage to the nitriding layer in the traditional process of nitriding first and then dispersing, ensuring the integrity and uniformity of the nitriding layer. At the same time, it eliminates the need for separate nitriding pretreatment and reduction processes, greatly simplifying the process and reducing production costs. Attached Figure Description

[0040] The disclosure of this invention is illustrated with reference to the accompanying drawings. It should be understood that the drawings are for illustrative purposes only and are not intended to limit the scope of protection of this invention. In the drawings, the same reference numerals are used to refer to the same parts:

[0041] Figure 1 This is a schematic diagram of the process flow of the present invention. Detailed Implementation

[0042] The technical solutions of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. The components of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of this application, but merely represents selected embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application. It should be noted that similar reference numerals and letters in the following drawings indicate similar items; therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings. Furthermore, in the description of this application, the terms "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0043] Example 1: See Figure 1 The preparation process of the ultra-fine particle size roller-printed nickel electrode paste for ultra-high capacitance MLCCs in this embodiment includes the following steps:

[0044] S1. Raw material pretreatment and nitrogen atmosphere construction:

[0045] First, all raw materials undergo pretreatment. Throughout the entire preparation process, a nitrogen atmosphere is established and maintained to remove impurities and prevent oxidation of the raw materials, providing a foundation for the subsequent simultaneous dispersion-nitriding process. The nitrogen gas used is high-purity nitrogen with a purity ≥99.999%, oxygen content ≤1ppm, and moisture content ≤5ppm. This is ensured by real-time monitoring using an online gas analysis system. This system records nitrogen purity, oxygen content, and moisture content in real time. When the oxygen content is ≥1ppm, an alarm is automatically triggered and nitrogen is replenished to ensure the strict purity of the nitrogen atmosphere and its anti-oxidation effect.

[0046] S101. Nickel powder vacuum dehydration and deoxidation with nitrogen protection:

[0047] Ultrafine nickel powder is loaded into the vacuum dehydration and deoxidation hopper of the nickel powder vacuum dehydration and deoxidation device. After the feed inlet is closed, a vacuum is drawn to -0.098 MPa using vacuum pump 101 and maintained for 10 minutes. Subsequently, the temperature is raised to 80℃±2℃ using heating unit 102 and held for 30 minutes for dehydration and deoxidation. After cooling to 25℃, high-purity nitrogen is introduced to atmospheric pressure. Throughout the transfer process, high-purity nitrogen is continuously introduced for protection, ensuring that the oxygen content of the ultrafine nickel powder is ≤0.2% before being transferred to the nitrogen-sealed double planetary mixer. In this embodiment, the raw material composition of the ultrafine nickel powder is a spherical powder with D50=30-60nm, Span≤0.8, and purity≥99.9%.

[0048] S102. Ceramic additives modified under nitrogen atmosphere:

[0049] In a nitrogen-sealed environment, the ceramic additive and silane coupling agent are mixed and ground to obtain the modified ceramic additive. In this embodiment, the oxygen content of the grinding environment is ≤1ppm, and the grinding time is 30min, so that the D50 of the modified ceramic additive is ≤20nm. Before starting the raw material grinding mill, the air in the mill is purged with high-purity nitrogen three times, and the pressure is maintained for 5min after each purging to ensure an oxygen-free environment during the grinding process. In this embodiment, the ceramic additive is barium titanate / calcium strontium titanate with a particle size ≤30nm and a thermal expansion coefficient deviation ≤5% from that of the MLCC medium; the amount of silane coupling agent added is 0.5% of the weight of the ceramic additive. The modified ceramic additive is transferred to the double planetary mixer under a nitrogen atmosphere to prevent it from getting damp or oxidized during the transfer process.

[0050] S103. Preparation of organic carrier under nitrogen protection:

[0051] Before starting the organic carrier dissolution vessel, high-purity nitrogen was purged three times. Then, the solvent, binder, and dispersant were mixed and dissolved. During dissolution, the temperature was raised to 55℃±2℃, and the mixture was stirred for 2 hours until completely dissolved and free of visible particles. After dissolution, the mixture was filtered using a 1μm filter to remove any possible minute impurities. The pre-prepared organic carrier was then sealed under a nitrogen atmosphere, with its oxygen content controlled to ≤0.1%, ensuring the purity and stability of the organic carrier. In this embodiment, the dispersant is preferably a phosphate ester with an HLB value between 8 and 10. After addition, the absolute value of the zeta potential of the slurry is ≥30mV, which helps to improve the dispersion stability of the nickel powder. The raw materials were configured by weight percentage as follows: 50% ultrafine nickel powder, 7.5% ceramic additive, 28% solvent, 7.5% binder, 2% dispersant, 0.7% antioxidant, and 0.2% defoamer.

[0052] S2. Material dispersion and nitriding:

[0053] By adjusting nitrogen parameters and equipment operation, material dispersion and nickel powder nitriding can be carried out in a coordinated manner, gradually achieving the target particle size and nitriding layer requirements.

[0054] S201. Nitrogen-sealed premixing:

[0055] Nickel powder treated with S101, modified ceramic additives treated with S102, and a portion of the pre-prepared organic carrier were sequentially added to a nitrogen-sealed double planetary mixer. The mixture was stirred to form a homogeneous premix. The mixer chamber was purged three times with high-purity nitrogen, maintaining the pressure for 5 minutes each time to ensure an oxygen content ≤1 ppm. The added organic carrier constituted 50% of the total pre-prepared organic carrier. The stirring parameters were: 600 rpm, 25°C, and 1 hour. This step aims to achieve preliminary homogeneous mixing of the components, laying the foundation for subsequent fine dispersion and nitriding reactions.

[0056] S202. Primary dispersion and low-temperature nitriding start-up:

[0057] The premix was transferred to a nitrogen-sealed sand mill under a nitrogen atmosphere. The mill chamber was pre-purged with nitrogen three times to ensure an oxygen content of ≤1ppm. A two-stage palladium molecular sieve deoxidation device was activated, high-purity nitrogen was introduced, and the nitrogen partial pressure was adjusted to 0.12MPa±0.01MPa. 0.1–0.3mm zirconia balls were added as grinding media, and the sand mill was started at 1500rpm. Simultaneously, the temperature was raised to 120℃±2℃ via a heating / cooling jacket and held for 2 hours. In this low-temperature, high-pressure nitrogen environment, the nickel powder particles came into contact with nitrogen during grinding, initiating a nitriding reaction and generating initial Ni3N crystal nuclei. The oxygen content of the material at this stage was ≤0.25%. The testing standards were: particle size D50 ≤80nm, and XPS detection showing a Ni3N characteristic peak percentage of 5%–8%. This stage achieved preliminary dispersion and nitriding, preparing for the next stage of fine dispersion and nitrided layer growth.

[0058] S203. Fine dispersion and nitrided layer growth:

[0059] The primary dispersed material was transferred to a nitrogen-sealed ultra-high pressure homogenizer under a nitrogen atmosphere. The homogenizer chamber was pre-purged with nitrogen three times to ensure an oxygen content ≤1ppm. The partial pressure of high-purity nitrogen was adjusted to 0.15MPa±0.01MPa using a nitrogen partial pressure controller, and the temperature was raised to 140℃±2℃ using a temperature controller. The ultra-high pressure homogenizing pump was started, and the homogenizer pressure was adjusted to 2000bar. The material underwent a circulating homogenization and dispersion-nitriding process three times through a 400μm+100μm multi-stage homogenizing chamber 402, with a total time of 1.5 hours. Under this high temperature, high pressure, and strong shearing action, the nickel powder particles were finely dispersed, and the Ni3N nitrided layer further grew. The inspection standards were: particle size D50=30-60nm, Span≤0.8, Ni3N characteristic peak ratio of 15-20%, and resistivity ≥5×10⁻⁶. -8 Ω・m. If the particle size detection D50 > 60 nm or Span > 0.8, add ≤ 2 cycles while maintaining a nitrogen partial pressure of 0.15 MPa and a temperature ≤ 140 °C to ensure that the target particle size and distribution are achieved.

[0060] S204. Cooling to terminate nitriding and nitrogen pressure maintenance to prevent oxidation:

[0061] Turn off the heating device and cool down to 30℃±2℃. During the cooling process, maintain the nitrogen partial pressure at 0.1MPa to prevent air from entering, ensure that the nitriding reaction is terminated at the appropriate temperature, and prevent the formed nitriding layer and nickel powder from being oxidized.

[0062] S205. Viscosity adjustment under nitrogen atmosphere:

[0063] In a nitrogen-sealed environment, add the remaining organic carrier and additives, and stir until homogeneous. The stirring parameters are 300 rpm and 30 min. Adjust the viscosity of the slurry by adding ≤5% of the total solvent or by letting it stand for ≤30 min. The target viscosity range is 20,000-40,000 mPa·s. This step aims to make the slurry reach the ideal viscosity suitable for subsequent roller printing processes. At the same time, the addition of additives further improves the stability and processing performance of the slurry.

[0064] S206. Nitrogen-protected vacuum degassing:

[0065] The viscosity-adjusted slurry is transferred to a nitrogen-protected vacuum degassing machine. The vacuum degassing machine is pre-purged with nitrogen three times, evacuated to -0.095 MPa, and degassed for 25 minutes. This step aims to remove any microbubbles that may be present in the slurry and trace byproducts generated during production, ensuring the slurry's density and uniformity. After degassing, the slurry should be free of visible bubbles and have uniform flowability.

[0066] S3. Post-treatment and nitrogen protection throughout the process:

[0067] The slurry treated with S2 is purified, inspected, and packaged, with nitrogen protection maintained throughout the process.

[0068] S301. Nitrogen-sealed fine filtration:

[0069] Under nitrogen protection, the deaerated slurry is passed through a nitrogen-sealed precision filter for filtration. The precision filter is pre-purged with nitrogen three times to ensure an oxygen content of ≤1ppm. The filtration pressure is controlled at 0.1-0.3MPa, using a 0.5μm filter element to remove large particulate impurities. After filtration, the content of particles >1μm is ≤0.1%. The filter element is replaced for each batch, and pressure changes before and after filtration are recorded to ensure filtration effectiveness.

[0070] S302. Nitrogen Temporary Storage and Finished Product Inspection:

[0071] The filtered slurry was temporarily stored under a nitrogen atmosphere. Subsequently, the slurry underwent comprehensive testing according to standards, including: particle size distribution D50 = 30-60 nm, Span ≤ 0.8; nitrided layer thickness 2-5 nm, Ni3N characteristic peak percentage 15-20%; oxygen content ≤ 0.3%; viscosity; dispersion stability; roller printing thickness deviation ±0.08 μm, defect rate ≤ 0.8%; and co-firing shrinkage ≤ 3%. Through rigorous quality control, the final product's qualification was ensured.

[0072] S303. Nitrogen Encapsulation and Storage:

[0073] The qualified slurry is packaged in a double-layer vacuum system. The inner layer is filled with high-purity nitrogen gas up to 0.05 MPa to isolate oxygen and prevent oxidation, and to provide a potential material basis for nitriding reaction. The outer layer is sealed and moisture-proof to ensure a stable storage environment. The storage environment conditions are: temperature 4-25℃, relative humidity ≤40%, and shelf life up to 6 months. This packaging method further ensures the long-term stability and excellent performance of the slurry.

[0074] Finally, the nickel electrode paste prepared by the above method has an electrode layer thickness of ≤1μm, meets the requirements of roll printing compatibility and co-firing performance, and does not require separate nitriding pretreatment and reduction processes.

[0075] Example 2: S1. Raw material pretreatment and nitrogen atmosphere construction:

[0076] The nitrogen gas is high-purity nitrogen with a purity ≥99.999%, oxygen content ≤1ppm, and moisture content ≤5ppm. The online gas analysis system for real-time monitoring and alarm nitrogen replenishment is the same as in Example 1.

[0077] S101. Nickel powder vacuum dehydration and deoxidation with nitrogen protection:

[0078] The operation is the same as in Example 1, and the oxygen content of the ultrafine nickel powder is ≤0.2%.

[0079] S102. Ceramic additives modified under nitrogen atmosphere:

[0080] The operation is the same as in Example 1, with the D50 of the modified ceramic additive ≤ 20nm.

[0081] S103. Preparation of organic carrier under nitrogen protection:

[0082] The operation is the same as in Example 1, with the oxygen content of the carrier ≤0.1%.

[0083] The raw materials are composed of the following by weight percentage: 40% ultrafine nickel powder, 10% ceramic additive, 35% solvent, 5% binder, 3% dispersant, 0.5% antioxidant, and 0.3% defoamer.

[0084] S2. Material dispersion and nitriding:

[0085] S201. Nitrogen-sealed premixing:

[0086] The chamber of the dual planetary mixer was purged with high-purity nitrogen three times beforehand, with each pressurization lasting 5 minutes. The sealed oxygen content was ≤1ppm. The added organic carrier was 50% of the total amount of the pre-prepared organic carrier. The stirring parameters were: 600 rpm, 25℃, and 1 hour.

[0087] S202. Primary dispersion and low-temperature nitriding start-up:

[0088] The mill chamber was pre-purged with nitrogen three times to ensure an oxygen content ≤1ppm. A two-stage palladium molecular sieve deoxygenation device was activated, and high-purity nitrogen was introduced, with the partial pressure adjusted to 0.13MPa±0.01MPa. The grinding media consisted of 0.1–0.3mm zirconia balls. The mill speed was 1500rpm, and the temperature was raised to 125℃±2℃ and maintained for 2 hours. During this stage, the oxygen content of the material was ≤0.25%. The testing standards were: particle size D50 ≤80nm, and XPS detection showing a Ni3N characteristic peak percentage of 6%–9%.

[0089] S203. Fine dispersion and nitrided layer growth:

[0090] The homogenizer chamber was pre-purged with nitrogen three times, ensuring a sealed oxygen content ≤1ppm. The partial pressure of high-purity nitrogen was adjusted to 0.16MPa±0.01MPa, the temperature was raised to 145℃±2℃, and the homogenizer pressure was adjusted to 2000bar. The material was passed through a multi-stage homogenization chamber (400μm + 100μm) and cyclically homogenized, dispersed, and nitrided three times, with a total time of 1.5 hours. The testing standards were: particle size D50 = 30-60nm, Span ≤0.8, Ni3N characteristic peak percentage 16-21%, and resistivity ≥5×10⁻⁶. -8Ω・m. If the particle size D50 is greater than 60 nm or Span is greater than 0.8, add ≤2 cycles while maintaining a nitrogen partial pressure of 0.16 MPa and a temperature of ≤145 °C.

[0091] S204. Cooling to terminate nitriding and nitrogen pressure maintenance to prevent oxidation:

[0092] Cool down to 30℃±2℃, maintaining a nitrogen partial pressure of 0.1MPa during the cooling process.

[0093] S205. Viscosity adjustment under nitrogen atmosphere:

[0094] The additives include antioxidants and defoamers. The stirring parameters are 300 rpm and 30 min. The viscosity is adjusted by adding ≤5% of the total solvent or letting it stand for ≤30 min. The target viscosity range is 20000-40000 mPa·s.

[0095] S206. Nitrogen-protected vacuum degassing:

[0096] The vacuum degassing machine was pre-purged with nitrogen three times, and the vacuum was drawn to -0.095MPa. The degassing time was 25 minutes. After degassing, the slurry had no visible bubbles and had uniform fluidity.

[0097] S3. Post-treatment and nitrogen protection throughout the process:

[0098] S301. Nitrogen-sealed fine filtration:

[0099] The precision filter is pre-purged with nitrogen three times to ensure the sealed oxygen content is ≤1ppm. The filtration pressure is controlled between 0.1-0.3MPa. A 0.5μm filter element is used for filtration. After filtration, the content of impurities >1μm particles is ≤0.1%. The filter element is replaced for each batch, and the pressure change before and after filtration is recorded.

[0100] S302. Nitrogen Temporary Storage and Finished Product Inspection:

[0101] The full range of testing standards are the same as those in Example 1.

[0102] S303. Nitrogen Encapsulation and Storage:

[0103] The inner layer is filled with high-purity nitrogen to 0.05 MPa. The storage environment conditions are: temperature 4-25℃, relative humidity ≤40%, and shelf life of 6 months.

[0104] Example 3: S1. Raw material pretreatment and nitrogen atmosphere construction:

[0105] The nitrogen gas is high-purity nitrogen with a purity of ≥99.999%, oxygen content ≤1ppm, and moisture content ≤5ppm. The online gas analysis system for real-time monitoring and alarm nitrogen replenishment is the same as in Example 1.

[0106] S101. Nickel powder vacuum dehydration and deoxidation with nitrogen protection:

[0107] Ultrafine nickel powder is loaded into a vacuum dehydration and deoxidation hopper. After closing the feed inlet, the vacuum pump is started to evacuate to -0.098 MPa and maintained for 15 minutes. Then, the temperature is raised to 82℃±2℃ and held for 35 minutes. After cooling to 25℃, high-purity nitrogen is introduced to atmospheric pressure. Nitrogen is continuously purged during the transfer process. The oxygen content of the nickel powder is ≤0.2%.

[0108] S102. Ceramic additives modified under nitrogen atmosphere:

[0109] The oxygen content in the grinding environment is ≤1ppm, the grinding time is 35min, the D50 of the modified ceramic additive is ≤20nm, and high-purity nitrogen is introduced into the grinding mill to replace the air in the mill 3 times before starting the raw material grinding mill. After each replacement, the pressure is maintained for 5min.

[0110] S103. Preparation of organic carrier under nitrogen protection:

[0111] Before starting the organic carrier dissolution vessel, high-purity nitrogen gas was introduced to purge the mixture three times. During mixing and dissolution, the temperature was raised to 58℃±2℃, and the mixture was stirred for 2.5 hours until it was completely dissolved and no particles were visible to the naked eye. A 1μm filter cartridge was used for filtration.

[0112] The raw materials are composed of the following by weight percentage: 60% ultrafine nickel powder, 5% ceramic additive, 20% solvent, 15% binder, 1.5% dispersant, 0.8% antioxidant, and 0.1% defoamer.

[0113] S2. Material dispersion and nitriding:

[0114] S201. Nitrogen-sealed premixing:

[0115] The chamber of the dual planetary mixer was purged three times with high-purity nitrogen, each time for 5 minutes, with a sealed oxygen content ≤1ppm. The added organic carrier was 50% of the total amount of the pre-prepared organic carrier. The stirring parameters were: 650 rpm, 25℃, and 1.2 h.

[0116] S202. Primary dispersion and low-temperature nitriding start-up:

[0117] The mill chamber was pre-purged with nitrogen three times to ensure an oxygen content of ≤1ppm. A two-stage palladium molecular sieve deoxygenation device was activated, high-purity nitrogen was introduced, and the nitrogen partial pressure was adjusted to 0.11MPa±0.01MPa. The grinding media consisted of 0.1–0.3mm zirconia balls, and the mill speed was 1600rpm. The temperature was raised to 118℃±2℃ and held for 2.5 hours; during this stage, the oxygen content of the material was ≤0.25%. The testing standards were: particle size D50 ≤80nm, and XPS detection showing a Ni3N characteristic peak percentage of 4%–7%.

[0118] S203. Fine dispersion and nitrided layer growth:

[0119] The homogenizer chamber was pre-purged with nitrogen three times to ensure an oxygen content ≤1ppm. The partial pressure of high-purity nitrogen was adjusted to 0.14MPa±0.01MPa, and the temperature was raised to 138℃±2℃. The homogenizer pressure was adjusted to 2000bar, and the material was passed through a multi-stage homogenization chamber of 400μm+100μm. The homogenization-dispersion-nitriding process was repeated three times, with a total time of 1.5 hours. The testing standards were: particle size D50 = 30-60nm, Span ≤0.8, Ni3N characteristic peak percentage 14-19%, and resistivity ≥5×10⁻⁶. -8 Ω・m. If the particle size D50 is greater than 60 nm or Span is greater than 0.8, add ≤2 cycles while maintaining a nitrogen partial pressure of 0.14 MPa and a temperature of ≤138 °C.

[0120] S204. Cooling to terminate nitriding and nitrogen pressure maintenance to prevent oxidation:

[0121] Cool down to 30℃±2℃, maintaining a nitrogen partial pressure of 0.1MPa during the cooling process.

[0122] S205. Viscosity adjustment under nitrogen atmosphere:

[0123] Additives include antioxidants and defoamers. The stirring parameters are 300 rpm and 30 min. The viscosity is adjusted by adding ≤5% of the total solvent or letting it stand for ≤30 min. The target viscosity range is 20,000-40,000 mPa·s.

[0124] S206. Nitrogen-protected vacuum degassing:

[0125] The vacuum degassing machine was pre-purged with nitrogen three times. The vacuum was then drawn to -0.095 MPa, and the degassing time was 25 minutes. After degassing, the slurry had no visible bubbles and exhibited uniform fluidity.

[0126] S3. Post-treatment and nitrogen protection throughout the process:

[0127] S301. Nitrogen-sealed fine filtration:

[0128] The precision filter is pre-purged with nitrogen three times, ensuring a sealed oxygen content ≤1ppm. The filtration pressure is controlled between 0.1-0.3MPa, using a 0.5μm filter element. After filtration, the content of particles >1μm is ≤0.1%. The filter element is replaced for each batch, and pressure changes before and after filtration are recorded.

[0129] S302. Nitrogen Temporary Storage and Finished Product Inspection:

[0130] The full range of testing standards are the same as those in Example 1.

[0131] S303. Nitrogen Encapsulation and Storage:

[0132] The inner layer is filled with high-purity nitrogen to 0.05 MPa. Storage conditions are: temperature 4-25℃, relative humidity ≤40%, shelf life 6 months.

[0133] In the preparation method of the above embodiments, the oxygen content of all equipment in contact with the materials, such as the double planetary mixer, sand mill, ultra-high pressure homogenizer, and precision filter, is strictly controlled to ≤1ppm. This ensures that the dual function of nitrogen is maintained throughout the entire process of raw material pretreatment, dispersion-nitriding synchronization, post-treatment, and packaging. Through precise parameter control and synergy with a nitrogen atmosphere, this invention can achieve simultaneous dispersion-nitriding in large-scale production, continuously and stably producing high-performance nickel electrode slurry. Furthermore, during the raw material storage stage, ultrafine nickel powder and ceramic additives are stored in nitrogen-protected sealed silos under nitrogen-protected conditions of 4-25℃ and relative humidity ≤40%, and are used within 72 hours of opening. This further ensures the quality and activity of the raw materials, providing a solid foundation for the smooth progress of subsequent processes.

[0134] The above are merely embodiments of this application and are not intended to limit the scope of protection of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A process for preparing ultra-high capacitance MLCC ultra-fine particle size roller-printed nickel electrode paste, characterized in that, Includes the following steps: S1. Raw material pretreatment and nitrogen atmosphere construction: Pretreatment of each raw material, establishment and maintenance of nitrogen atmosphere throughout the process, removal of raw material impurities, prevention of raw material oxidation, and provision of the foundation for the dispersion-nitriding synchronous process; The nitrogen gas is high-purity nitrogen with a purity ≥99.999%, an oxygen content ≤1ppm, and a moisture content ≤5ppm, specifically including: S101. Vacuum dehydration and deoxidation of nickel powder with nitrogen protection: After vacuum dehydration and deoxidation, ultrafine nickel powder is filled with high-purity nitrogen to atmospheric pressure and transferred to a nitrogen-sealed double planetary mixer under a nitrogen atmosphere to ensure that the oxygen content of the nickel powder is ≤0.2%; S102. Ceramic additive modification under nitrogen atmosphere: In a nitrogen-sealed environment, the ceramic additive is mixed and ground with a silane coupling agent to obtain a modified ceramic additive, which is then transferred to the dual planetary mixer under a nitrogen atmosphere. S103. Preparation of organic carrier under nitrogen protection: In a nitrogen-sealed environment, the solvent, binder and dispersant are mixed and dissolved, filtered, and the oxygen content of the carrier is controlled to be ≤0.1%. The carrier is then sealed and kept for later use under a nitrogen atmosphere. S2. Material Dispersion and Nitriding: By adjusting nitrogen parameters and equipment operation, material dispersion and nickel powder nitriding are carried out synergistically to gradually achieve the target particle size and nitriding layer requirements. Specifically, this includes: S201. Nitrogen-sealed premix: Nitrogen powder treated with S101, modified ceramic additives treated with S102, and part of the pre-prepared organic carrier are added sequentially to a nitrogen-sealed double planetary mixer and stirred to form a uniform premix. S202. Primary dispersion and low-temperature nitriding start-up: The premix is ​​transferred to a nitrogen-sealed sand mill under a nitrogen atmosphere, the high-purity nitrogen is introduced and the nitrogen partial pressure is adjusted, grinding media is added and the sand mill is started, the temperature is raised and held to start the nitriding reaction and generate Ni3N initial crystal nuclei; S203. Fine dispersion and nitrided layer growth: The primary dispersed material is transferred to a nitrogen-sealed ultra-high pressure homogenizer under a nitrogen atmosphere. The partial pressure and temperature of high-purity nitrogen are adjusted, and the homogenizer is started to achieve simultaneous fine dispersion of particles and growth of nitrided layer. S204. Cooling to terminate nitriding and nitrogen pressure maintenance to prevent oxidation: Turn off the heating device, cool down to the preset temperature, maintain nitrogen partial pressure to prevent air from entering; S205. Viscosity adjustment under nitrogen atmosphere: In a nitrogen-sealed environment, add the remaining organic carrier and additives, stir and mix evenly, and adjust the slurry viscosity to the preset range; S206. Nitrogen-protected vacuum degassing: The slurry after viscosity adjustment is transferred to a nitrogen-protected vacuum degassing machine to remove air bubbles and trace by-products from the slurry; S3. Post-processing and nitrogen protection throughout the entire process: The slurry treated by S2 is purified, inspected, and packaged, with nitrogen protection maintained throughout the process, specifically including: S301. Nitrogen-sealed fine filtration: Under nitrogen protection, the deaerated slurry is passed through a nitrogen-sealed precision filter to remove large particulate impurities. S302. Nitrogen Temporary Storage and Finished Product Inspection: The filtered slurry is temporarily stored in a nitrogen atmosphere and tested according to standards; S303. Nitrogen Encapsulation and Storage: Qualified slurry is packaged in a double-layer vacuum system. The inner layer is filled with the high-purity nitrogen, and the outer layer is sealed to prevent moisture. It is stored under preset environmental conditions. The high-purity nitrogen has two core functions: First, it serves as a dedicated nitrogen source for the nitriding reaction, providing a material basis for the initial formation of Ni3N crystal nuclei and the growth of the nitrided layer. Second, it serves as a protective atmosphere against oxidation throughout the process, maintaining the oxygen content of the system at ≤1ppm and isolating air to inhibit the oxidation and degradation of nickel powder, slurry system, and nitrided layer. Finally, a nickel electrode slurry with an electrode layer thickness of ≤1μm that meets the requirements for roller printing compatibility and co-firing performance is obtained, without the need for separate nitriding pretreatment and reduction processes.

2. The preparation process of ultra-fine particle size roller-printed nickel electrode paste for ultra-high capacitance MLCCs according to claim 1, characterized in that, The raw materials are composed of the following by weight percentage: 40-60% ultrafine nickel powder, 5-10% ceramic additives, 20-35% solvent, 5-15% binder, 1.5-3% dispersant, 0.5-0.8% antioxidant, and 0.1-0.3% defoamer; the ultrafine nickel powder is a spherical powder with D50=30-60nm, Span≤0.8, and purity≥99.9%; the ceramic additive is barium titanate / calcium strontium titanate with a particle size≤30nm and a thermal expansion coefficient deviation ≤5% from that of the MLCC medium; the amount of silane coupling agent added is 0.5% of the weight of the ceramic additives.

3. The preparation process of the ultra-fine particle size roller-printed nickel electrode paste for ultra-high capacitance MLCCs according to claim 1, characterized in that, In S101, the specific operation of vacuum dehydration and deoxidation is as follows: ultrafine nickel powder is loaded into the vacuum dehydration and deoxidation hopper, the feed port is closed, the vacuum pump is started to evacuate to -0.098MPa and held for 10 minutes; the temperature is raised to 80℃±2℃ and held for 30 minutes; the temperature is lowered to 25℃ and then the high-purity nitrogen gas is introduced to atmospheric pressure; nitrogen is continuously introduced during the transfer process.

4. The preparation process of ultra-fine particle size roller-printed nickel electrode paste for ultra-high capacitance MLCCs according to claim 1, characterized in that, In S102, the oxygen content in the grinding environment is ≤1ppm, the grinding time is 30min, and the D50 of the modified ceramic additive is ≤20nm. Before starting the raw material grinding mill, high-purity nitrogen is introduced to replace the air in the mill 3 times, and the pressure is maintained for 5min after each replacement.

5. The preparation process of the ultra-fine particle size roller-printed nickel electrode paste for ultra-high capacitance MLCCs according to claim 1, characterized in that, In S201, the chamber of the double planetary mixer is purged with high-purity nitrogen three times in advance, with each pressurization lasting 5 minutes, and the sealed oxygen content is ≤1ppm; the added organic carrier is 50% of the total amount of the pre-prepared organic carrier; the stirring parameters are: speed 600rpm, temperature 25℃, and stirring time 1h.

6. The preparation process of the ultra-fine particle size roller-printed nickel electrode paste for ultra-high capacitance MLCCs according to claim 1, characterized in that, In S202, the specific operation of the sand mill is as follows: the sand mill chamber is purged with nitrogen three times in advance, and the sealed oxygen content is ≤1ppm; the two-stage palladium molecular sieve deoxygenation device is turned on, high-purity nitrogen is introduced and the nitrogen partial pressure is adjusted to 0.12MPa±0.01MPa; the grinding media is 0.1-0.3mm zirconia balls, and the sand mill speed is 1500rpm; the temperature is raised to 120℃±2℃ and kept at that temperature for 2h, so that the oxygen content of the material in this stage is ≤0.25%; the inspection standard is: particle size D50≤80nm, and the proportion of Ni3N characteristic peak detected by XPS is 5%-8%.

7. The preparation process of ultra-fine particle size roller-printed nickel electrode paste for ultra-high capacitance MLCCs according to claim 1, characterized in that, In S203, the specific operation of the ultra-high pressure homogenizer is as follows: The homogenizer chamber is pre-purified with nitrogen three times, ensuring the sealed oxygen content is ≤1ppm; the partial pressure of high-purity nitrogen is adjusted to 0.15MPa±0.01MPa, and the temperature is raised to 140℃±2℃; the homogenizer pressure is adjusted to 2000bar, and the material passes through a 400μm+100μm multi-stage homogenization chamber; the homogenization-dispersion-nitriding process is repeated three times, with a total time of 1.5 hours; the inspection standards are: particle size D50=30-60nm, Span≤0.8, Ni3N characteristic peak ratio 15-20%, resistivity ≥5×10⁻⁶. -8 Ω・m; if the particle size detection D50 > 60 nm or Span > 0.8, add ≤ 2 cycles while maintaining a nitrogen partial pressure of 0.15 MPa and a temperature ≤ 140 °C.

8. The preparation process of ultra-fine particle size roller-printed nickel electrode paste for ultra-high capacitance MLCCs according to claim 1, characterized in that, In S204, the temperature is lowered to 30℃±2℃, and the nitrogen partial pressure is maintained at 0.1MPa during the cooling process.

9. The preparation process of ultra-fine particle size roller-printed nickel electrode paste for ultra-high capacitance MLCCs according to claim 1, characterized in that, In S205, the additives include antioxidants and defoamers; the stirring parameters are a speed of 300 rpm and a stirring time of 30 min; the viscosity is adjusted by adding ≤5% of the total solvent or letting it stand for ≤30 min, with a target viscosity range of 20000-40000 mPa·s.

10. The preparation process of ultra-fine particle size roller-printed nickel electrode paste for ultra-high capacitance MLCCs according to claim 1, characterized in that, In S206, the vacuum degassing machine is purged with nitrogen three times in advance; the vacuum is drawn to -0.095MPa, and the degassing time is 25min. After degassing, the slurry has no visible bubbles and has uniform fluidity.

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