An antioxidant high electric stability electrode paste and a preparation method thereof

Abstract

The present application relates to the technical field of electrode paste production, and provides an antioxidant high-electric-stability electrode paste and a preparation method thereof.The raw materials for preparing the electrode paste are BN thick-coated coarse SiC, BN thin-coated fine SiC, carbon-coated graphite, ZrO2@carbon composite microspheres, fillers and a binder, with a mass ratio of (16-19):(11-14):(29-32):(7-10):(13-16):(15-18).The coarse SiC particles and the fine SiC particles are respectively subjected to BN thick coating and BN thin coating to balance the oxidation resistance and the electrical conductivity;the flaky graphite is subjected to mild oxidation and carbon coating modification to promote electron transfer while isolating oxygen, thereby avoiding the problem of isolation of the conductive phase caused by the antioxidant layer;the ZrO2@carbon composite microspheres are prepared to improve the structural stability and form a complementary antioxidant barrier, thereby achieving the synergistic improvement of the oxidation resistance and the electrical conductivity of the electrode paste.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electrode paste production, and particularly relates to an oxidation-resistant high-electric-stability electrode paste and a preparation method thereof. BACKGROUND

[0002] As the core conductive material of electric furnace equipment such as electric arc furnaces and calcium carbide furnaces, electrode paste is mainly formed by kneading carbonaceous aggregates such as semi-graphitized anthracite, residual electrode, graphite scrap and calcined petroleum coke with pitch binder, and forms a conductive framework by self-baking at high temperature, which needs to meet the strict requirements of high conductivity, oxidation resistance and mechanical strength. Taking the electric furnace steelmaking furnace as an example, the electrode paste needs to withstand a large current, which will cause a large amount of heat to be generated inside the electrode paste, the temperature will rise sharply, and the resistivity fluctuation range will increase. In addition, the electrode paste will also be subjected to the splashing of molten steel and the erosion of oxidizing gas entering from the furnace mouth. Under these harsh conditions, the performance of the electrode paste faces severe challenges. At present, the improvement of the oxidation resistance and electric stability of the traditional electrode paste is mainly focused on adjusting the proportion of raw materials or the type of pitch. For example, increasing the amount of residual electrode or graphite scrap can improve the conductivity, but it is easy to cause the interface bonding force of the aggregate to decrease and the high-temperature oxidation to be aggravated. Using modified pitch can increase the coking value, but the softening point is increased, which increases the kneading process temperature and pitch fume emission. Such methods essentially rely on physical mixing or simple chemical modification, and have limitations such as weak interface bonding and poor process compatibility, which cannot meet the long-term working requirements of large-scale electric arc furnaces. SUMMARY

[0003] In view of the deficiencies of the prior art, the present application aims to provide an oxidation-resistant high-electric-stability electrode paste and a preparation method thereof. By gradiently coating SiC particles with BN, on the one hand, thick BN coating of coarse SiC particles blocks the oxygen erosion, and on the other hand, thin BN coating of fine SiC particles serves as a conductive bridge to fill the gap between particles, balancing the oxidation resistance and conductivity. By micro-oxidizing and carbon-coating modification of flake graphite, oxygen is isolated while electron transfer is promoted, avoiding the problem of isolation of conductive phase caused by the oxidation-resistant layer. The prepared ZrO2@carbon composite microspheres improve the structural stability of the electrode paste through the ZrO2 framework, and the carbon phase blocks oxygen, thereby forming a complementary oxidation-resistant barrier with the carbon-coated graphite, so as to achieve the synergistic improvement of the oxidation resistance and conductivity of the electrode paste.

[0004] To achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0005] In a first aspect, the present application provides an oxidation-resistant high-electric-stability electrode paste, and the preparation raw materials include: thick BN-coated coarse SiC, thin BN-coated fine SiC, carbon-coated graphite, ZrO2@carbon composite microspheres, fillers and a binder, and the mass ratio is (16-19):(11-14):(29-32):(7-10):(13-16):(15-18).

[0006] The thick BN-coated coarse SiC is obtained by mixing coarse SiC particles, a first BN sol and a first silane coupling agent and then performing a first calcination; and the thin BN-coated fine SiC is obtained by mixing fine SiC particles, a second BN sol and a second silane coupling agent and then performing a second calcination.

[0007] The carbon-coated graphite is obtained by carbonizing phenolic resin pre-mixed with a catalyst on the surface of micro-oxidized graphite; and the micro-oxidized graphite is obtained by micro-oxidizing flake graphite.

[0008] The ZrO2@carbon composite microspheres are obtained by dispersing 3Y-ZrO2 pre-mixed with phenolic resin, adding graphene fragments and ultra-fine carbon black, and then carbonizing; and the dispersing 3Y-ZrO2 is obtained by modifying 3Y-ZrO2 nano-powder with a silane coupling agent and then dispersing by a high-molecular polymer.

[0009] Further, the first and second silane coupling agents are KH-550; the particle size of the coarse SiC particles is 5-10 μm, and the concentration of the first BN sol is 8%-10%; the particle size of the fine SiC particles is 1-3 μm, and the concentration of the second BN sol is 3%-5%.

[0010] As a silane coupling agent, KH-550 can form a covalent bond with the hydroxyl groups on the surface of SiC through the silicon-oxygen groups in the molecule, and the amino groups can combine with the functional groups -OH in the BN sol, which can significantly improve the interfacial strength.

[0011] By adjusting the concentration of the BN sol, gradient coating of SiC can be achieved. After HF etching and coupling with KH-550, active adsorption sites with relatively fixed density are formed on the surface of SiC, and the concentration of the BN sol directly determines the number of BN nanoparticles with a particle size of 5-10 nm that can participate in adsorption per unit volume; for coarse SiC particles with a specific surface area of 1-5 m 2 / g, the total number of active sites per unit mass of particles is small, and 8%-10% high-concentration BN sol can provide sufficient particles so that all active sites are saturatedly adsorbed, and 5-8 layers of BN particles are formed on the surface of SiC through hydrogen bonding and electrostatic interaction; for fine SiC particles with a specific surface area 4-5 times larger, the specific surface area is 10-20 m 2 / g, the total number of active sites per unit mass of particles is significantly more, and 3%-5% low-concentration BN sol has a total amount of particles that is just enough for the saturated adsorption of these active sites, and only 1-2 layers of BN particle accumulation can be formed, and the subsequent centrifugal process can remove the unadsorbed free BN particles, ensuring that the thickness of the coating layer is completely determined by the matching relationship between the sol concentration and the adsorption capacity of SiC, and finally achieving precise regulation of the two thicknesses.

[0012] Further, the catalyst used for the carbon-coated graphite is Fe(NO3)3; the mass ratio of the micro-oxidized graphite to the pre-mixed phenolic resin and Fe(NO3)3 is 20:1; the mass of the Fe(NO3)3 is 0.5%-0.8% of the mass of the phenolic resin; and the particle size of the flake graphite is 5-10 μm, and the fixed carbon is ≥99%.

[0013] Fe(NO3)3 as a catalyst, firstly, Fe 3+ can form a coordination bond with the phenolic hydroxyl group in the phenolic resin, promote the directional arrangement and adsorption of the phenolic resin molecules on the surface of the graphite, and improve the uniformity of the coating; secondly, during the drying and preheating stages before high-temperature calcination, Fe 3+ as a Lewis acid, can activate the reactivity of the phenolic hydroxyl group and formaldehyde in the phenolic resin, accelerate the crosslinking and curing process, and enable the phenolic resin to form a preliminary crosslinked network structure at a lower temperature, thereby avoiding uneven coating caused by resin flow during subsequent high-temperature calcination; and thirdly, during high-temperature calcination, Fe 3+ is reduced to Fe nanoparticles, which can act as a catalyst for carbon graphitization, reduce the activation energy in the carbonization process of the phenolic resin, promote the ordered arrangement of the carbon layer, and improve the electrical conductivity and density of the coated carbon phase.

[0014] Further, the mass ratio of the dispersed 3Y-ZrO2 and the phenolic resin is 25:75; the silane coupling agent is KH-550; and the high-molecular polymer is PEG-4000.

[0015] Since the 3Y-ZrO2 nanopowder is an inorganic phase and the phenolic resin is an organic polymer, the interface compatibility between the two is poor, and therefore KH-550 is introduced as a silane coupling agent. The siloxane group in the molecular structure of the silane coupling agent can form a stable covalent bond (-Si-O-Zr) with the hydroxyl group on the surface of the 3Y-ZrO2 nanopowder, and the amino group at the other end can be combined with the phenolic hydroxyl group in the subsequent phenolic resin through hydrogen bonding or acid-base interaction. This bridging action can significantly improve the interface compatibility between the 3Y-ZrO2 and the organic carbon phase, and reduce interface defects. Moreover, the 3Y-ZrO2 nanopowder modified by the silane coupling agent is still prone to agglomeration, and therefore PEG-4000 is added as a dispersant. The ether bond in the molecule of PEG-4000 has hydrophilicity, and can be combined with the residual polar groups on the surface of the 3Y-ZrO2 nanopowder modified by the silane coupling agent through hydrogen bonding, while the long-chain alkyl part extends into the aqueous phase to form a steric hindrance layer, thereby effectively inhibiting agglomeration.

[0016] Further, in the mixture of dispersing 3Y-ZrO2 and phenolic resin, the mass ratio of graphene fragments and ultrafine carbon black is (0.1-0.2):(0.3-0.4); the particle size of the graphene fragments is 5-10 μm, and the thickness is ≤10 nm; the particle size of the ultrafine carbon black is 20-30 nm, and the specific surface area is ≥1000 m 2 / g.

[0017] The graphene fragments, as a kind of carbon material with excellent electrical conductivity and mechanical properties, can be used as a conductive reinforcing phase, uniformly dispersed in the carbon matrix to form a conductive network, thereby significantly improving the electrical conductivity of the microspheres. The laminar structure of graphene can enhance the mechanical properties of the carbon matrix through "skeleton support" effect, thereby improving the impact resistance of the composite microspheres. The abundant π bonds on the surface of graphene can form π-π stacking with the aromatic rings in the phenolic resin molecules, thereby promoting the interface bonding between graphene and the carbon matrix. The ultrafine carbon black, as an auxiliary carbon source and conductive filler, can fill the gaps between graphene fragments, thereby cooperating with graphene to build a more complete conductive network, thereby further improving the electrical conductivity of the composite microspheres. On the other hand, the high specific surface area and surface activity of the carbon black particles can enhance the interaction with the phenolic resin, thereby promoting the densification of the carbon matrix. In addition, during the calcination process, the carbon black particles can act as a graphitization promoter to induce the transformation of the disordered amorphous carbon layer formed during the carbonization process of the phenolic resin into an ordered structure, thereby improving the crystallinity of the carbon matrix.

[0018] Further, the filler includes electro-calcined anthracite, ZrB2, B4C, and nano-graphite sheets in a mass ratio of (45-53):(35-42):(15-22):(35-43); the particle size of the electro-calcined anthracite is 5-10 μm, and the fixed carbon is ≥98%; the particle size of the ZrB2 is 5-8 μm; the particle size of the B4C is 1-3 μm; the diameter of the nano-graphite sheet is 5-10 μm, and the thickness is ≤5 nm.

[0019] The electrically calcined anthracite is a key carbonaceous filler in the electrode paste, which can be used as a conductive framework. The electrically calcined anthracite has a high carbon content and a certain graphitization degree, and can form a continuous conductive network in cooperation with a carbon-coated graphite and a BN-coated SiC, thereby improving the overall conductivity of the electrode paste. Meanwhile, the electrically calcined anthracite fills the gaps between coarse SiC particles in the form of irregular particles, thereby enhancing the bulk density and mechanical strength of the electrode paste. The surface of the electrically calcined anthracite has polar functional groups, which can enhance the interface bonding with the binder. The nano-graphite sheet can be used as a conductive reinforcing filler. The nano-graphite sheet has a large aspect ratio and excellent conductivity, and can form a bridge in the electrode paste to connect conductive particles such as BN-thin-coated fine SiC and carbon-coated graphite, and to span the insulating interface of the BN-thick-coated layer, thereby making up for the electrically calcined anthracite in the fine gap. The conjugated pi bond on the surface of the nano-graphite sheet can have a pi-pi stacking effect with the aromatic ring in the carbon-coated layer, and the functional groups such as the hydroxyl group on the edge of the nano-graphite sheet can form a hydrogen bond with the binder, thereby further strengthening the interface bonding. In addition, the low friction coefficient of the nano-graphite sheet can reduce the frictional resistance between particles during the electrode paste forming process, thereby promoting uniform mixing and dense packing of the material, and improving the forming quality.

[0020] ZrB2 and B4C can be used as ceramic fillers to jointly enhance the oxidation resistance and structural stability. ZrB2 is oxidized to form ZrO2 and low-melting-point B2O3 at a temperature higher than 1000°C, and the B2O3 can form a molten glass phase to block pores and resist oxygen. B4C is also oxidized to form B2O3, which forms a composite glass phase with ZrO2 to enhance the oxygen resistance effect. ZrB2 and B4C are both high-hardness ceramics. ZrB2 can improve wear resistance and impact resistance through dispersion strengthening, and has good electrical conductivity without affecting the conductive network. B4C fills the gaps in the form of micrometer-sized particles to improve the bulk density and reduce the porosity, thereby reducing the oxygen permeation channel. In addition, B4C has chemical inertness, which can improve the corrosion resistance of the electrode paste and prolong the service life.

[0021] Further, the binder comprises low-volatile coal tar pitch, liquid phenolic resin and coal tar in a mass ratio of (56-63):(63-74):(33-43). The low-volatile coal tar pitch has a softening point of 60-70°C, an ash content of ≤0.3%, and a volatile content of ≤15%. The liquid phenolic resin has a softening point of 80-90°C and a solid content of ≥90%. The coal tar has a density of 1.15-1.20 g / cm3 and a moisture content of ≤1%. 3

[0022] ​Low volatile coal pitch, liquid phenolic resin and coal tar are used as composite binder. The low volatile coal pitch is the core binder phase, which has a softening point matching the molding temperature, can quickly melt and coat the surface of the particles, and gradually carbonize in the subsequent drying and use due to its high carbon content, forming a continuous carbon skeleton, which not only ensures the bonding strength between particles, but also avoids introducing insulation impurities due to low ash content, and maintains the integrity of the conductive network. The liquid phenolic resin is used as a reinforcing binder, which forms a temperature gradient with the coal pitch, and after the coal pitch is melted and coated, the phenolic resin begins to crosslink and solidify, forming a dense carbon film through thermosetting reaction, and the aromatic rings in the molecules form π-π interaction with carbon-coated graphite and nano-graphite sheets, strengthening the interface bonding, and improving the oxidation resistance and mechanical strength of the electrode paste. The coal tar is used as a flowability regulator, which can reduce the viscosity of the mixed system due to its good wettability, help the binder penetrate into the gap between fine particles, and ensure the integrity of the coating.

[0023] In a second aspect, the application provides a preparation method of an antioxidant high electrical stability electrode paste, comprising the following steps:

[0024] S1, the coarse SiC particles are pretreated by hydrofluoric acid, mixed with the first BN sol and the first silane coupling agent, calcined at 900-1000℃ under nitrogen atmosphere for 2-2.5h to obtain BN thick-coated coarse SiC; the fine SiC particles are pretreated by hydrofluoric acid, mixed with the second BN sol and the second silane coupling agent, calcined at 900-1000℃ under nitrogen atmosphere for 1-1.5h to obtain BN thin-coated fine SiC;

[0025] S2, the flake graphite is micro-oxidized to obtain micro-oxidized graphite; the micro-oxidized graphite is mixed with a phenolic resin ethanol solution containing a catalyst, sheared at 700-800r / min for 20-30min, ultrasonicated at 30-50kHz for 20-30min, dried at 80-90℃ for 2-3h, and calcined at 700-800℃ under nitrogen atmosphere for 1.5-2h to obtain carbon-coated graphite;

[0026] S3, the 3Y-ZrO2 nano-powder is treated with 1wt%-2wt% silane coupling agent, and 0.3wt%-0.4wt% PEG-4000 is added for mixing to obtain dispersed 3Y-ZrO2; the dispersed 3Y-ZrO2 is mixed with phenolic resin, and graphene fragments and ultrafine carbon black pretreated by ethanol ultrasonic dispersion for 30-50min are added, stirred at 900-1000r / min for 30-40min, filtered by screening, and then spray dried, with the inlet air temperature of 100-110℃ and the outlet air temperature of 70℃, to collect microspheres; the microspheres are calcined at 800℃ under nitrogen atmosphere for 2-3h, broken and sieved to obtain ZrO2@carbon composite microspheres with a particle size of 5-10μm;

[0027] S4, dry-mixing the BN thick-coated coarse SiC and the electrically calcined anthracite at 300-400 r / min for 5-10 min, adding the BN thin-coated fine SiC, ZrB2 and B4C, and continuing to dry-mix at 500-600 r / min for 10-15 min, adding the carbon-coated graphite and the nano-graphite sheet, and dry-mixing at 500-600 r / min for 8-10 min, adding the ZrO2@carbon composite microspheres, and dry-mixing until uniform, to obtain dry materials; heating low-volatile coal pitch to melting in a water bath at 80°C, adding liquid phenolic resin and coal tar, stirring until uniform, and then pouring the mixture onto the dry materials, and stirring at 70-80°C for 20-30 min to obtain a mixture;

[0028] S5, pouring the mixture into a mold coated with silicon oil release agent, pre-pressing at 8 MPa for 30 s, pressing at 15 MPa for 8-10 min, and pressing at 5 MPa for 3-5 min, and then performing stepwise drying: from 40°C to 60°C and then to 80°C, with 4-6 h of drying at each stage, and then cooling and demolding to obtain an electrode paste blank.

[0029] Further, the step of surface pretreatment by hydrofluoric acid includes: soaking coarse SiC particles or fine SiC particles with a solid-liquid ratio of 1:5 with 10wt% hydrofluoric acid for 30-40 min, washing with deionized water until pH=7.0, and then drying at 70-80°C for 2-3 h, and then dispersing at 200-300 r / min for 30-40 min, to obtain coarse SiC particles or fine SiC particles that have been surface pretreated.

[0030] The surface pretreatment by hydrofluoric acid is for coarse SiC particles and fine SiC particles. Since the SiO2 on the surface of SiC will hinder the subsequent adhesion and combination of BN sol, the strong corrosiveness of hydrofluoric acid reacts with the naturally formed SiO2 oxide layer on the surface of SiC, dissolving and removing the insulating SiO2 oxide layer, to ensure uniform and continuous BN coating, and to provide a basis for subsequent oxygen resistance and conductive balance.

[0031] Further, the step of micro-oxidation includes: mixing flake graphite with a solid-liquid ratio of 1:6 with 30% hydrogen peroxide, adding 0.05wt%-0.07wt% phosphoric acid relative to the mass of the flake graphite, stirring in a water bath at 50-60°C for 60 min, vacuum filtering for 10-15 min, adjusting the pH to 7.0, and then vacuum drying at 70-80°C for 2-2.5 h, to obtain micro-oxidized graphite.

[0032] Micro-oxidation is to generate hydroxyl radicals by hydrogen peroxide under the catalysis of phosphoric acid, and the surface of flake graphite is slightly oxidized. Since the original flake graphite surface is inert and has poor compatibility with phenolic resin, direct coating is prone to interface gap. After introducing oxygen-containing functional groups such as hydroxyl and carboxyl, the subsequent carbon coating layer can be combined with phenolic resin through hydrogen bond or chemical bond, so that the subsequent carbon coating layer is thinner and more continuous.

[0033] Compared with the prior art, the beneficial effects achieved by the present application are:

[0034] The present application realizes the balance between oxidation resistance and electrical conductivity by thickly coating the coarse SiC particles with BN to effectively block the oxygen erosion, and thinly coating the fine SiC particles with BN to serve as a conductive bridge to fill the inter-particle gap. The thin and continuous carbon layer formed by micro-oxidation and carbon coating modification of flake graphite reduces the interfacial gap between graphite and carbon, reduces the electron transfer resistance between particles, improves the oxidation resistance, and promotes electron transfer, avoiding the problem of isolation of conductive phase caused by the oxidation resistance layer. By preparing ZrO2@carbon composite microspheres, the ZrO2 skeleton improves the structural stability of the electrode paste, and the carbon phase formed on the surface plays a role in oxygen resistance, thereby forming a complementary oxygen resistance barrier with the carbon-coated graphite, thereby synergistically improving the oxidation resistance and electrical stability of the electrode paste. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 It is a preparation process schematic diagram of the anti-oxidation high electrical stability electrode paste of the present application.

[0036] Figure 2 It is a physical picture of the anti-oxidation high electrical stability electrode paste blank of example 1 of the present application. DETAILED DESCRIPTION

[0037] In order to make the technical problems, technical solutions and beneficial effects of the present application clearer, the present application will be further described in detail below in conjunction with examples. However, it should not be understood as limiting the scope of the present application to the following examples. Without departing from the method idea of the present application, all other examples obtained by those skilled in the art without making creative labor are within the scope of protection of the present application.

[0038] The singular forms "is", "or", "a", "any" and "the" used in the present application are intended to include plural forms, unless the context clearly indicates otherwise. In addition, if the terms "first", "second" appear, they are only used for description purposes, and cannot be understood as indicating or implying relative importance.

[0039] Example 1

[0040] As Figure 1 shown, a preparation method of an antioxidant high electrical stability electrode paste comprises the following steps:

[0041] (1) 100 g of coarse SiC particles or fine SiC particles with a solid-liquid ratio of 1:5 are soaked in 10 wt% hydrofluoric acid for 30 min, repeatedly washed with deionized water until pH=7, placed in an 80°C air drying oven for drying for 2 h, dispersed by a planetary ball mill (agate ball, ball-to-material ratio 5:1, 200 r / min) for 40 min to obtain pretreated coarse SiC or fine SiC; the pretreated coarse SiC with a solid-liquid ratio of 1:5 is mixed with 8% BN sol and 0.5 wt% KH-550 (previously diluted 10 times with ethanol, magnetically stirred for 20 min, uniformly dispersed in the BN sol) relative to the mass of the BN sol, placed in an ultrasonic cleaner and ultrasonically treated at 40 kHz and 300 W for 30 min, transferred to a centrifuge tube, centrifuged at 3000 r / min for 10 min, the supernatant is discarded, washed twice with ethanol, placed in a vacuum drying oven, vacuumed at 0.08 MPa for 10 min to remove bubbles, dried at 120°C for 3 h, transferred to a tube furnace, nitrogen gas with a flow rate of 50 mL / min is introduced, calcined at 1000°C for 2 h, taken out after natural cooling, sieved through a 200-mesh sieve to obtain BN thick-coated coarse SiC; the pretreated fine SiC with a solid-liquid ratio of 1:5 is mixed with 3% BN sol and 0.5 wt% KH-550 (previously diluted 10 times with ethanol, magnetically stirred for 20 min, uniformly dispersed in the BN sol) relative to the mass of the BN sol, the same ultrasonic treatment, centrifugation and washing process as above, dried at 120°C for 3 h, then transferred to a tube furnace, calcined at 1000°C for 1 h in a nitrogen atmosphere with a flow rate of 50 mL / min to obtain BN thin-coated fine SiC.

[0042] (2) 100 g of flake graphite with a solid-liquid ratio of 1:6 is mixed with 30% hydrogen peroxide, 0.05 wt% phosphoric acid relative to the mass of the flake graphite is added, stirred in a water bath at 50°C for 60 min, then vacuum filtered for 10 min, 1 mol / L NaOH solution is added to neutralize to pH 7.0, vacuum dried at 70°C for 2.5 h to obtain micro-oxidized graphite; 50 g of micro-oxidized graphite with a mass ratio of 20:1 is mixed with a 5 wt% pre-mixed Fe(NO3)3 phenolic resin ethanol solution, the mass of Fe(NO3)3 is 0.5% of the mass of the phenolic resin, sheared in a high-shear mixer at 800 r / min for 20 min, ultrasonically treated at 50 kHz for 20 min, then dried in an 80°C air drying oven for 3 h, transferred to a tube furnace, calcined at 800°C for 1.5 h in a nitrogen atmosphere with a flow rate of 50 mL / min, cooled and reserved for use to obtain carbon-coated graphite.

[0043] (3) 30g 3Y-ZrO2 nano-powder with solid-liquid ratio of 1:5 was dissolved in deionized water, 1wt% KH-550 was added, and the mixture was stirred at 50°C for 30min, 0.3wt% PEG-4000 was added, and the mixture was continuously stirred for 10min and then transferred into a planetary ball mill (ZrO2 ball, 300r / min, 60min) to obtain dispersed 3Y-ZrO2; the dispersed 3Y-ZrO2 and phenolic resin were mixed at a mass ratio of 25:75, graphene fragments and ultrafine carbon black were pre-ultrasonic dispersed in ethanol at a mass ratio of 0.1:0.3 for 30min, and then added, stirred in a high-shear mixer at 1000r / min for 30min, filtered through a 300-mesh sieve, and then spray dried, with the inlet air temperature being 110°C and the outlet air temperature being 70°C, to collect the microspheres; the microspheres were transferred into a tube furnace, calcined at 800°C for 2h in a nitrogen atmosphere with a flow rate of 50mL / min, cooled, broken by an airflow crusher, sieved through a 300-mesh sieve, and then classified to obtain ZrO2@carbon composite microspheres with a size of 5-10μm.

[0044] (4) 180g BN thick-coated coarse SiC, 50g electrically calcined anthracite were added into a 5L double-planetary mixer, and dry-mixed for 5min at a rotation speed of 400r / min; 130g BN thin-coated fine SiC, 40g ZrB2, 20g B4C were added, the rotation speed was adjusted to 600r / min, and dry-mixed for 10min, during which the tank wall adhered materials were cleaned with a scraper, 300g carbon-coated graphite, 40g nano-graphite sheet were continuously added, the rotation speed was kept at 600r / min, and dry-mixed for 8min, then 90g ZrO2@carbon composite microspheres were added, and dry-mixed for 5min, until the material was uniformly gray-black, to obtain dry material; 60g low-volatile coal tar pitch was heated to melt in a 80°C water bath, 70g liquid phenolic resin, 40g coal tar were added, and stirred uniformly by a magnetic stirrer, then slowly poured onto the dry material, the rotation speed was adjusted to 400r / min, and stirred for 20min, during which the tank bottom material was turned over every 5min to ensure that the particles were completely coated with the binder, to obtain a mixture.

[0045] (5) The mixture was poured into a mold coated with silicon oil release agent on the inner wall, and the surface was scraped flat with a scraper to avoid air bubbles being entrapped; the mold was placed on the workbench of a four-column hydraulic press, and a stepwise pressing mode was adopted: in the first stage, 8MPa pre-pressing for 30s; in the second stage, 15MPa pressure maintaining for 8min; in the third stage, pressure releasing to 5MPa pressure maintaining for 3min; after the pressing was completed, the mold was kept horizontal, and transferred into a forced air drying oven for stepwise temperature rising drying: from 40°C to 60°C, and then to 80°C, and each stage was dried for 6h; the mold was taken out, cooled to room temperature, and demolded to obtain an electrode paste blank.

[0046] The prepared electrode paste blank physical map is shown in Figure 2 The surface is gray-black and flat and dense.

[0047] Example 2

[0048] As shown in Figure 1 A preparation method of an antioxidant high electrical stability electrode paste, comprising the following steps:

[0049] (1) 100 g of coarse SiC particles or fine SiC particles with a solid-liquid ratio of 1:5 were soaked in 10 wt% hydrofluoric acid for 35 min, washed repeatedly with deionized water until pH=7, placed in a 75°C air drying oven for drying for 2.5 h, dispersed by a planetary ball mill (agate ball, ball-to-material ratio 5:1, 250 r / min) for 35 min to obtain pretreated coarse SiC or fine SiC; the pretreated coarse SiC with a solid-liquid ratio of 1:5 was mixed with 9% BN sol and 0.5 wt% KH-550 (previously diluted 10 times with ethanol, magnetically stirred for 20 min, uniformly dispersed in the BN sol) relative to the mass of the BN sol, placed in an ultrasonic cleaner and ultrasonically treated at 40 kHz, 300 W for 30 min, transferred to a centrifuge tube, centrifuged at 3000 r / min for 10 min, the supernatant was discarded, washed twice with ethanol, placed in a vacuum drying oven, vacuumed at 0.08 MPa for 10 min to remove bubbles, dried at 120°C for 3 h, transferred to a tube furnace, nitrogen gas was introduced at a flow rate of 50 mL / min, calcined at 950°C for 2.25 h, naturally cooled, taken out, sieved through a 200 mesh sieve to obtain BN thick-coated coarse SiC; the pretreated fine SiC with a solid-liquid ratio of 1:5 was mixed with 4% BN sol and 0.5 wt% KH-550 (previously diluted 10 times with ethanol, magnetically stirred for 20 min, uniformly dispersed in the BN sol) relative to the mass of the BN sol, the same ultrasonic, centrifugal and washing processes were performed, dried at 120°C for 3 h, then transferred to a tube furnace, calcined at 950°C for 1.2 h in a nitrogen atmosphere at a flow rate of 50 mL / min to obtain BN thin-coated fine SiC.

[0050] (2) 100 g of flake graphite with a solid-liquid ratio of 1:6 was mixed with 30% hydrogen peroxide, 0.06wt% of phosphoric acid was added relative to the mass of flake graphite, and after stirring in a water bath at 55°C for 60 min, vacuum filtration was performed for 12 min, 1 mol / L NaOH solution was added for neutralization to pH 7.0, and vacuum drying was performed at 75°C for 2.25 h to obtain micro-oxidized graphite; 50 g of micro-oxidized graphite with a mass ratio of 20:1 was mixed with a 5wt% pre-mixed Fe(NO3)3 phenolic resin ethanol solution, the mass of Fe(NO3)3 was 0.6% of the mass of the phenolic resin, shearing was performed in a high-shear mixer at 750 r / min for 25 min, ultrasonic treatment was performed at 40 kHz for 25 min, and then drying was performed in a 85°C air-drying oven for 2.5 h, and then the product was transferred to a tube furnace, calcination was performed at 750°C for 1.7 h in a nitrogen atmosphere with a flow rate of 50 mL / min, and after cooling, the product was reserved for use, to obtain carbon-coated graphite.

[0051] (3) 30 g of 3Y-ZrO2 nano-powder with a solid-liquid ratio of 1:5 was dissolved in deionized water, 1.5wt% KH-550 was added, magnetic stirring was performed at 50°C for 30 min, 0.35wt% PEG-4000 was added, and after further magnetic stirring for 10 min, the product was transferred to a planetary ball mill (ZrO2 balls, 300 r / min, 60 min) to obtain dispersed 3Y-ZrO2; the dispersed 3Y-ZrO2 was mixed with phenolic resin at a mass ratio of 25:75, graphene fragments and ultrafine carbon black were pre-ultrasonically dispersed in ethanol at a mass ratio of 0.15:0.35 for 40 min, and then added, stirring was performed in a high-shear mixer at 950 r / min for 35 min, filtration was performed through a 300-mesh sieve, and then spray drying was performed, the inlet air temperature was 105°C, the outlet air temperature was 70°C, and microspheres were collected; the microspheres were transferred to a tube furnace, calcination was performed at 800°C for 2.5 h in a nitrogen atmosphere with a flow rate of 50 mL / min, and after cooling, the product was broken up using an airflow crusher, sieved through a 300-mesh sieve, and then 5-10 μm ZrO2@carbon composite microspheres were obtained.

[0052] (4) Put 160 g BN thick-coated coarse SiC and 45 g electrically calcined anthracite into a 5 L double-planetary mixer, set the rotation speed to 350 r / min, and dry mix for 7 min; add 110 g BN thin-coated fine SiC, 35 g ZrB2, and 15 g B4C, and adjust the rotation speed to 550 r / min, and dry mix for 12 min, during which the tank wall adhered material is cleaned with a scraper, continue to add 290 g carbon-coated graphite and 35 g nano-graphite sheets, keep the rotation speed at 550 r / min, and dry mix for 9 min, then add 70 g ZrO2@carbon composite microspheres, and continue to dry mix for 5 min, until the material is uniformly gray-black, to obtain a dry material; melt 54 g low-volatile coal tar pitch at 80°C in a water bath, add 63 g liquid phenolic resin and 33 g coal tar, and magnetically stir until uniform, then slowly pour onto the dry material, adjust the rotation speed to 400 r / min, and stir while adding, set the mixer temperature to 75°C, and stir for 25 min, during which the tank bottom material is turned over every 5 min to ensure that the particles are completely coated with the binder, to obtain a mixture.

[0053] 5) Pour the mixture into a mold coated with silicon oil release agent on the inner wall, and use a scraper to flatten the surface to avoid air bubbles; place the mold on the workbench of a four-column hydraulic press, and use a step-by-step pressing mode: first stage, 8 MPa pre-pressing for 30 s; second stage, 15 MPa pressure maintaining for 9 min; third stage, pressure relief to 5 MPa pressure maintaining for 4 min; after the pressing is completed, keep the mold horizontal, and transfer the mold into a forced air drying oven for stepwise temperature rising drying: from 40°C to 60°C and then to 80°C, each stage drying for 5 h; remove the mold, cool to room temperature, and demold to obtain an electrode paste blank.

[0054] Example 3

[0055] As shown in Figure 1 , a method for preparing an antioxidant high electrical stability electrode paste includes the following steps:

[0056] (1) 100 g of coarse SiC particles or fine SiC particles with a solid-liquid ratio of 1:5 were soaked in 10 wt% hydrofluoric acid for 40 min, washed repeatedly with deionized water until pH = 7, placed in a 70°C air drying oven for drying for 3 h, dispersed by a planetary ball mill (agate ball, ball-to-material ratio 5:1, 300 r / min) for 30 min to obtain pretreated coarse SiC or fine SiC; the pretreated coarse SiC with a solid-liquid ratio of 1:5 was mixed with 10% BN sol and 0.5 wt% KH-550 (previously diluted 10 times with ethanol, magnetically stirred for 20 min, uniformly dispersed in the BN sol) relative to the mass of the BN sol, placed in an ultrasonic cleaner and ultrasonically treated at 40 kHz and 300 W for 30 min, transferred to a centrifuge tube, centrifuged at 3000 r / min for 10 min, the supernatant was discarded, washed twice with ethanol, placed in a vacuum drying oven, vacuumed for 10 min to remove bubbles at 0.08 MPa, dried at 120°C for 3 h, transferred to a tube furnace, and calcined at 900°C for 2.5 h in a nitrogen atmosphere with a flow rate of 50 mL / min, taken out after natural cooling, and sieved through a 200-mesh sieve to obtain BN thick-coated coarse SiC; the pretreated fine SiC with a solid-liquid ratio of 1:5 was mixed with 5% BN sol and 0.5 wt% KH-550 (previously diluted 10 times with ethanol, magnetically stirred for 20 min, uniformly dispersed in the BN sol) relative to the mass of the BN sol, and the same ultrasonic, centrifugal and washing processes were performed, dried at 120°C for 3 h, and then transferred to a tube furnace, calcined at 900°C for 1.5 h in a nitrogen atmosphere with a flow rate of 50 mL / min to obtain BN thin-coated fine SiC.

[0057] (2) 100 g of flake graphite with a solid-liquid ratio of 1:6 was mixed with 30% hydrogen peroxide, 0.07 wt% phosphoric acid was added relative to the mass of the flake graphite, and the mixture was stirred in a water bath at 60°C for 60 min, then vacuum filtered for 15 min, and 1 mol / L NaOH solution was added to neutralize to pH 7.0, and vacuum dried at 80°C for 2 h to obtain micro-oxidized graphite; 50 g of micro-oxidized graphite with a mass ratio of 20:1 was mixed with a 6 wt% Fe(NO3)3 pre-mixed phenolic resin ethanol solution, the mass of Fe(NO3)3 was 0.8% of the mass of the phenolic resin, sheared in a high-shear mixer at 700 r / min for 30 min, ultrasonically treated at 30 kHz for 30 min, and then dried in a 90°C air drying oven for 2 h, transferred to a tube furnace, and calcined at 700°C for 2 h in a nitrogen atmosphere with a flow rate of 50 mL / min, and cooled to obtain carbon-coated graphite.

[0058] (3) 30 g 3Y-Zr02nanopowder with solid-liquid ratio of 1:5 was dissolved in deionized water, 2 wt% KH-550 was added, and the mixture was stirred at 50°C for 30 min under magnetic stirring, 0.4 wt% PEG-4000 was added, and the mixture was continuously stirred for 10 min under magnetic stirring and then transferred into a planetary ball mill (Zr02ball, 300 r / min, 60 min) to obtain dispersed 3Y-Zr02; the dispersed 3Y-Zr02and phenolic resin were mixed at a mass ratio of 25:75, graphene fragments and ultrafine carbon black were pre-ultrasonic dispersed in ethanol at a mass ratio of 0.2:0.4 for 50 min, and then added into the mixture, which was stirred at 900 r / min for 40 min in a high-shear mixer, filtered through a 300-mesh sieve, and then spray dried, with the inlet air temperature of 100°C and the outlet air temperature of 70°C, to collect the microspheres; the microspheres were transferred into a tube furnace, calcined at 800°C for 3 h in a nitrogen atmosphere at a flow rate of 50 mL / min, and then broken by an airflow crusher, filtered through a 300-mesh sieve, and then selected by classification to obtain Zr02@carbon composite microspheres with a size of 5-10 μm.

[0059] (4) 190 g BN thick-coated coarse SiC and 53 g electrically calcined anthracite were added into a 5L double-planetary mixer, and dry-mixed for 10 min at a rotation speed of 300 r / min; 140 g BN thin-coated fine SiC, 42 g ZrB2, and 22 g B4C were added, and dry-mixed for 15 min at a rotation speed of 500 r / min, during which the wall of the tank was cleaned with a scraper to remove the adhered materials; 320 g carbon-coated graphite and 43 g nanoparticle graphite were added, and dry-mixed for 10 min at a rotation speed of 500 r / min; then, 100 g Zr02@carbon composite microspheres were added, and dry-mixed for 5 min, until the materials were uniformly gray-black, to obtain dry materials; 63 g low-volatile coal tar pitch was heated to melt in a water bath at 80°C, 74 g liquid phenolic resin and 43 g coal tar were added, and stirred uniformly under magnetic stirring, then slowly poured onto the dry materials, and stirred while adding, with the rotation speed adjusted to 400 r / min, and the temperature of the mixer set to 70°C, and stirred for 30 min, during which the materials at the bottom of the tank were stirred every 5 min to ensure that the particles were completely coated with the binder, to obtain a mixture.

[0060] (5) The mixture was poured into a mold coated with silicon oil release agent on the inner wall, and the surface was scraped flat with a scraper to avoid air bubbles; the mold was placed on the workbench of a four-column hydraulic press, and a stepwise pressing mode was adopted: in the first stage, 8 MPa pre-pressing for 30 s; in the second stage, 15 MPa for 10 min; in the third stage, pressure relief to 5 MPa for 5 min; after the pressing was completed, the mold was kept horizontal, and was transferred into a forced air drying oven for stepwise drying: from 40°C to 60°C, and then to 80°C, with each stage drying for 4 h; the mold was taken out, cooled to room temperature, and demolded to obtain an electrode paste blank.

[0061] Comparative Example 1

[0062] An oxidation-resistant high electrical stability electrode paste and a preparation method thereof, the implementation steps and parameters of which are different from those of Example 1 in that the coarse SiC and the fine SiC are not gradient-coated, i.e., the coarse SiC and the fine SiC are both coated with 3% BN sol, and the remaining steps and parameters are the same.

[0063] Comparative Example 2

[0064] An oxidation-resistant high electrical stability electrode paste and a preparation method thereof, the implementation steps and parameters of which are different from those of Example 1 in that the flake graphite is not subjected to micro-oxidation treatment, and the remaining steps and parameters are the same.

[0065] Comparative Example 3

[0066] An oxidation-resistant high electrical stability electrode paste and a preparation method thereof, the implementation steps and parameters of which are different from those of Example 1 in that Fe(NO3)3 is not added for catalyzing the cross-linking and curing process of the phenolic resin, and the remaining steps and parameters are the same.

[0067] Comparative Example 4

[0068] An oxidation-resistant high electrical stability electrode paste and a preparation method thereof, the implementation steps and parameters of which are different from those of Example 1 in that only 170 g of low-volatile coal tar pitch is used as the binder, and no liquid phenolic resin and coal tar are added, and the remaining steps and parameters are the same.

[0069] Performance test:

[0070] Oxidation resistance: first, the electrode paste blanks prepared in Examples 1-3 and Comparative Examples 1-4 are processed into Φ20 mm x 20 mm cylinders, then the electrode paste samples of each example are placed in a muffle furnace, heated at 10 ℃ / min to 1000 ℃ in an air atmosphere, and held for 5 h, and after cooling, the weight is measured, and the oxidation weight loss rate is calculated: oxidation weight loss rate / %=(mass before calcination-mass after calcination) / mass before calcination x 100%, and the results are shown in Table 1.

[0071] Conductive performance: first, the electrode paste blanks prepared in Examples 1-3 and Comparative Examples 1-4 are processed into Φ20 mm x 10 mm cylinders, a ST2258A four-probe tester is used, the test conditions are 25 ℃ and 10 mA, the volume resistivity of each electrode paste sample is tested, and the average value of three positions of each sample is taken, and the results are shown in Table 1.

[0072] Resistivity fluctuation amplitude: The electrode paste samples prepared in Examples 1-3 and Comparative Examples 1-4 were fixed on a high-temperature test table using a high-temperature four-probe test system with a temperature control furnace and a direct current stabilized power supply. Nitrogen was introduced at a flow rate of 50 mL / min, and the temperature was raised to 800°C at a rate of 5°C / min. After 30 min of heat preservation, a constant current of 100 mA was applied, and the volume resistivity was recorded every 10 h. The fluctuation amplitude of the resistivity at different time points was calculated based on the initial resistivity after heat preservation at 800°C without applying electricity. The resistivity fluctuation amplitude / % = (resistivity measured at each time point-initial resistivity) / initial resistivity x 100%. The maximum fluctuation amplitude of three parallel samples was taken as the final result, and the results are shown in Table 1.

[0073] Structural stability: First, the electrode paste blanks prepared in Examples 1-3 and Comparative Examples 1-4 were processed into 25mm x 5mm x 5mm cuboids. Using a thermal dilatometer, the electrode paste samples were heated to 800°C at a rate of 5°C / min under a nitrogen atmosphere with a flow rate of 50 mL / min. The thermal expansion coefficient (x10 -6 / ℃) = length change / (initial length x temperature change) was calculated. Each sample was tested three times and the average value was taken. The results are shown in Table 1.

[0074] Table 1 Performance test results of electrode paste

[0075]

[0076] As shown in Table 1, the oxidation loss rate, volume resistivity, thermal expansion coefficient, and resistivity fluctuation amplitude of the electrode paste of Examples 1-3 are lower than those of Comparative Examples 1-4, indicating that the oxidation resistance and electrical stability of the electrode paste of Examples 1-3 are better than those of Comparative Examples 1-4.

[0077] In Comparative Example 1, the coarse SiC and fine SiC were not gradiently coated, and both were coated with 3% BN sol, resulting in a thin BN layer on the surface of the coarse SiC. At high temperatures, oxygen can easily penetrate the coating layer and react with the internal SiC, causing a decrease in oxidation resistance. Although the thin BN layer has little effect on the conductivity of fine SiC, the thin BN layer on coarse SiC is easily oxidized to form a local insulating oxide layer, and lacks the structural support of a thick BN layer for particle accumulation, increasing the gap between particles and blocking the electron transport path, resulting in an increase in volume resistivity and a significant increase in resistivity fluctuation amplitude. For structural stability, the thick BN coating layer has a structural restraining effect, which can inhibit the thermal expansion of coarse SiC particles. In Comparative Example 1, the restraining ability of the thin BN layer is weak, and the particles are easily expanded when heated, resulting in an increase in the overall thermal expansion coefficient.

[0078] Comparative Example 2: The performance of the graphite is reduced because the scale graphite is not subjected to micro-oxidation treatment, which destroys the interface bonding between the graphite and the carbon coating layer. Firstly, the surface of the scale graphite that is not subjected to micro-oxidation has strong inertness, and the combination with the phenolic resin is loose, and the carbon coating layer has micro-gaps, and oxygen is easy to penetrate through the gaps to corrode the graphite, resulting in reduced oxidation resistance. Secondly, the interface gap increases the electron transmission resistance, resulting in increased volume resistivity and expanded resistivity fluctuation range. Thirdly, the poor interface bonding causes the graphite and the carbon layer to easily move relative to each other when heated, and the interface force cannot inhibit the expansion, and the time gap will further expand the thermal expansion space.

[0079] Comparative Example 3: The performance of the graphite is significantly reduced because Fe(NO3)3 is lacking to catalyze the crosslinking of the phenolic resin, resulting in a loose carbon coating layer structure. In the absence of Fe(NO3)3, the crosslinking of the phenolic resin is not complete, and the carbon layer has a large number of micropores and defects, and oxygen can penetrate through the micropores to the surface of the graphite and cause oxidation, resulting in weakened oxidation resistance. The dense carbon layer is the key channel for electron transmission, and the loose carbon layer formed in Comparative Example 3 makes the electron transmission path discontinuous, and the micropores increase the probability of electron scattering. At the same time, the interface bonding between the carbon layer and the graphite is weakened due to insufficient crosslinking, and the interface resistance increases, resulting in increased volume resistivity and the most significant resistivity fluctuation. The loose carbon layer has weak wrapping and restraining ability for the graphite, and the carbon layer itself is easy to expand irregularly due to structural defects when heated, and cannot inhibit the overall expansion together with the ZrO2@carbon composite microspheres.

[0080] Comparative Example 4: The wrapping effect and carbon skeleton performance are reduced because a single coal tar pitch binder is used to replace the “coal tar pitch + phenolic resin + coal tar” composite binder. The single coal tar pitch has insufficient flowability and wettability after melting, and some particles are not completely wrapped, and the carbon layer formed by the carbonization of the single coal tar pitch has poor density, which cannot effectively block oxygen, resulting in reduced oxidation resistance. For the partially wrapped particles, local insulation areas are formed, which block the conductive network. At the same time, the carbon layer formed by the carbonization of the single coal tar pitch has lower conductivity than the graphitized carbon layer formed by the composite binder, and the electron transmission resistance increases, resulting in increased volume resistivity and rising resistivity fluctuation range. For structural stability, the carbon skeleton formed by the single coal tar pitch has insufficient rigidity and is easy to deform when heated, and the inter-particle bonding force is weak and has no effective constraint during expansion.

[0081] Comparative Examples 1-4 respectively lack the key links of the BN gradient wrapping in the coordination system of Example 1, which lays the foundation for the balance between oxidation resistance and electrical stability, graphite micro-oxidation, and Fe(NO3)3 catalysis to ensure the density of the carbon layer, and the composite binder to ensure the integrity of the wrapping and the quality of the carbon skeleton, resulting in the breaking of the coordinated balance between oxidation resistance and electrical stability, and further amplifying the performance short board.

[0082] The above results show and describe the basic principles and main features of the present application, as well as the advantages of the present application.

[0083] The embodiments of the present application are described above with reference to the accompanying drawings, but the present application is not limited to the above-described specific embodiments, and the above-described specific embodiments are merely illustrative, but not restrictive, and a person of ordinary skill in the art can make many forms under the inspiration of the present application without departing from the purpose of the present application and the scope protected by the claims, and these all belong to the protection of the present application.

Claims

1. An antioxidant high electrical stability electrode paste, characterized by, The BN thick-coated coarse SiC, the BN thin-coated fine SiC, the carbon-coated graphite, the ZrO2@carbon composite microspheres, the filler and the binder are in a mass ratio of (16-19):(11-14):(29-32):(7-10):(13-16):(15-18). The BN thick-coated coarse SiC is obtained by mixing coarse SiC particles, a first BN sol and a first silane coupling agent and then performing a first calcination; in the BN thick-coated coarse SiC, 5-8 layers of BN are stacked on the surface of the coarse SiC particles, and the particle size of the coarse SiC particles is 5-10 μm; the concentration of the first BN sol is 8%-10%; and the first silane coupling agent is KH-550. The BN thin-coated fine SiC is obtained by mixing fine SiC particles, a second BN sol and a second silane coupling agent and then performing a second calcination; in the BN thin-coated fine SiC, 1-2 layers of BN are stacked on the surface of the fine SiC particles, and the particle size of the fine SiC particles is 1-3 μm; the concentration of the second BN sol is 3%-5%; and the second silane coupling agent is KH-550. The carbon-coated graphite is obtained by carbonizing micro-oxidized graphite coated with an organic resin; the micro-oxidized graphite is obtained by micro-oxidizing flake graphite; the organic resin is a phenolic resin with a pre-mixed catalyst; the catalyst is Fe(NO3)3; the mass ratio of the micro-oxidized graphite to the pre-mixed Fe(NO3)3 phenolic resin is 20:1; the mass of the Fe(NO3)3 is 0.5%-0.8% of the mass of the phenolic resin; and the particle size of the flake graphite is 5-10 μm, and the fixed carbon is ≥99%. The ZrO2@carbon composite microspheres are obtained by carbonizing dispersed 3Y-ZrO2, a phenolic resin, graphene fragments and ultra-fine carbon black; the dispersed 3Y-ZrO2 is obtained by modifying 3Y-ZrO2 nano-powder with a silane coupling agent and then dispersing the modified 3Y-ZrO2 with a high-molecular polymer; The filler includes electro-calcined anthracite, ZrB2, B4C and nano-graphite flakes in a mass ratio of (45-53):(35-42):(15-22):(35-43). The binder includes low-volatile coal pitch, liquid phenolic resin and coal tar in a mass ratio of (54-63):(63-74):(33-43).

2. The antioxidant high electrical stability electrode paste according to claim 1, characterized in that, The mass ratio of the dispersed 3Y-ZrO2 to the phenolic resin is 25:75; in the mixture of the dispersed 3Y-ZrO2 and the phenolic resin, the mass ratio of the graphene fragments to the ultra-fine carbon black is (0.1-0.2):(0.3-0.4); the silane coupling agent is KH-550; and the high-molecular polymer is PEG-4000.

3. The antioxidant high electrical stability electrode paste of claim 1, wherein, The particle size of the 3Y-ZrO2 nanopowder is 25-50 nm, and the tetragonal phase content is greater than or equal to 95%; the particle size of the graphene fragment is 5-10 μm, and the thickness is less than or equal to 10 nm; the particle size of the ultrafine carbon black is 20-30 nm, and the specific surface area is greater than or equal to 1000 m 2 / g; and the particle size of the ZrO2@carbon composite microsphere is 5-10 μm.

4. The antioxidant high electrical stability electrode paste of claim 1, wherein, The particle size of the electro-calcined anthracite is 5-10 μm, and the fixed carbon is ≥98%; the particle size of the ZrB2 is 5-8 μm; the particle size of the B4C is 1-3 μm; and the diameter of the nano-graphite flakes is 5-10 μm, and the thickness is ≤5 nm.

5. The antioxidant high electrical stability electrode paste of claim 1, wherein, The low volatile coal pitch has a softening point of 60-70 DEG C, ash content of ≤0.3%, and volatile content of ≤15%; the liquid phenolic resin has a softening point of 80-90 DEG C, solid content of ≥90%; and the coal tar has a density of 1.15-1.20 g / cm 3 , and moisture content of ≤1%.

6. A process for the preparation of an antioxidant high electrical stability electrode paste as claimed in any one of claims 1 to 5, characterized in that, The method comprises the following steps: S1, after the coarse SiC particles are pretreated on the surface by hydrofluoric acid, the coarse SiC particles are mixed with the first BN sol and the first silane coupling agent, and then are calcined at 900-1000°C under a nitrogen atmosphere for 2-2.5h to obtain BN thick-coated coarse SiC; after the fine SiC particles are pretreated on the surface by hydrofluoric acid, the fine SiC particles are mixed with the second BN sol and the second silane coupling agent, and then are calcined at 900-1000°C under a nitrogen atmosphere for 1-1.5h to obtain BN thin-coated fine SiC; S2, the flake graphite is micro-oxidized to obtain micro-oxidized graphite; the micro-oxidized graphite is mixed with a phenolic resin ethanol solution containing a catalyst, is sheared at 700-800r / min for 20-30min, is ultrasonically treated at 30-50kHz for 20-30min, is dried at 80-90°C for 2-3h, and is calcined at 700-800°C under a nitrogen atmosphere for 1.5-2h to obtain carbon-coated graphite; S3, 3Y-ZrO2 nano-powder is treated with 1wt%-2wt% silane coupling agent, 0.3wt%-0.4wt% PEG-4000 is added, and dispersion 3Y-ZrO2 is obtained; the dispersion 3Y-ZrO2 is mixed with phenolic resin, graphene fragments and super-fine carbon black that are previously ultrasonically dispersed in ethanol for 30-50min are added, the mixture is stirred at 900-1000r / min for 30-40min, and then is filtered by screening and is spray-dried, the inlet air temperature of the spray-drying is 100-110°C, the outlet air temperature is 70°C, and microspheres are collected; the microspheres are calcined at 800°C under a nitrogen atmosphere for 2-3h, are broken and sieved, and ZrO2@carbon composite microspheres with a particle size of 5-10μm are obtained; S4, the BN thick-coated coarse SiC and the electrically calcined anthracite are dry-mixed at 300-400r / min for 5-10min, the BN thin-coated fine SiC, ZrB2 and B4C are added, the speed is adjusted to 500-600r / min, and the dry-mixing is continued for 10-15min, the carbon-coated graphite and nano-graphite sheets are added, the speed is kept at 500-600r / min, and the dry-mixing is continued until uniform, and dry materials are obtained; low-volatile coal tar pitch is heated to melt in a water bath at 80°C, liquid phenolic resin and coal tar are added, the mixture is stirred until uniform, and then is poured on top of the dry materials, and the mixture is stirred at 70-80°C for 20-30min to obtain a mixture; S5, the mixture is poured into a mold coated with silicon oil release agent, is pre-pressed at 8MPa for 30s, is kept at 15MPa for 8-10min, and is kept at 5MPa for 3-5min, and then is dried by stepwise heating: from 40°C to 60°C and then to 80°C, and each stage is dried for 4-6h, and an electrode paste blank is obtained after cooling and demolding.

7. The method of claim 6, wherein the antioxidant high electric stability electrode paste is prepared by adding 0.1 to 0.5 parts by weight of the antioxidant to 100 parts by weight of the electrically conductive material. The step of surface pretreatment by hydrofluoric acid comprises: soaking coarse SiC particles or fine SiC particles with a solid-liquid ratio of 1:5 in 10wt% hydrofluoric acid for 30-40 min, washing with deionized water until pH=7.0, and then drying at 70-80℃ for 2-3 h, and dispersing at 200-300 r / min for 30-40 min to obtain the coarse SiC particles or fine SiC particles after surface pretreatment.

8. The method of claim 6, wherein the antioxidant high electric stability electrode paste is prepared by adding 0.1 to 0.5 parts by weight of the antioxidant to 100 parts by weight of the electrically conductive material. The step of micro-oxidation comprises: mixing flake graphite with a solid-liquid ratio of 1:6 with 30% hydrogen peroxide, adding 0.05wt%-0.07wt% phosphoric acid relative to the mass of the flake graphite, stirring in a water bath at 50-60℃ for 60 min, and then vacuum filtering for 10-15 min, adjusting pH to 7.0, and then vacuum drying at 70-80℃ for 2-2.5 h to obtain the micro-oxidized graphite.

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