Coated anode with intermediate layer improved by composite additive and preparation method and application thereof

Abstract

The invention discloses a coating anode with an intermediate layer improved by a composite additive and a preparation method and application of the coating anode, and belongs to the technical field of electrodes, and the preparation method comprises five steps of titanium substrate pretreatment, intermediate layer coating liquid preparation, intermediate layer preparation, active layer coating liquid preparation and active layer preparation. In the middle layer coating liquid preparation step, an alcohol solvent and polyether modified polysiloxane are added into a middle layer base solution, the volume ratio of the middle layer base solution to the alcohol solvent to the polyether modified polysiloxane is 10: (1-5): (0.5-2), and the base solution containing the composite additive is prepared after uniform mixing. According to the method, the alcohol solvent and the polyether modified polysiloxane are added into the conventional titanium-tantalum base solution according to a specific proportion, so that cracks on the surface of the material are effectively reduced, and the compactness of the middle layer is enhanced. According to the method, the binding force of the coating is improved, and the problem of failure of an anode plate caused by passivation of a titanium base material due to surface cracks of a traditional intermediate layer is solved, so that the service life of the coating titanium anode is remarkably prolonged.

Description

Technical Field

[0001] This invention mainly relates to the field of electrode technology, specifically to a coated anode with an improved intermediate layer using composite additives, its preparation method, and its application. Background Technology

[0002] Traditional coated titanium anodes use a titanium substrate as the conductive base, and form a composite structure by coating the surface with a titanium-tantalum interlayer and an iridium-tantalum active catalyst layer. The titanium-tantalum interlayer, as a functional transition layer, must simultaneously meet the requirements of thermal expansion matching with the titanium substrate, high conductivity, and strong adhesion to the active layer.

[0003] However, in traditional processes, the titanium-tantalum interlayer is mainly formed by dissolving titanium (such as TiCl4) and tantalum (such as TaCl5) sources in hydrochloric acid solution, followed by spraying or brushing and high-temperature sintering. However, the hydrochloric acid evaporates rapidly during the drying stage, and the volume of the solvent inside the coating decreases sharply as it evaporates, leading to uneven coating shrinkage and localized stress concentration. High surface tension results in insufficient solution wettability, making it difficult for the coating to spread evenly and forming microscopic defects. Furthermore, the difference in thermal expansion coefficients between the titanium substrate and the titanium-tantalum alloy interlayer leads to high thermal stress during sintering and cooling, exacerbating interfacial stress and causing cracks on the interlayer surface. This crack structure not only significantly reduces the bonding strength between the interlayer and the substrate but also becomes the main channel for the penetration of active oxygen (O*) during electrolysis. In a high-concentration sulfuric acid electrolyte environment, active oxygen diffuses through the cracks to the titanium substrate surface, triggering an irreversible oxidation reaction to form a titanium dioxide (TiO2) insulating layer. As the electrolysis time increases, the oxide film thickness increases, leading to an increase in electrode resistance. When the cell voltage rises above the process threshold, the copper foil deposition rate becomes unbalanced, resulting in uneven thickness or even localized ablation, forcing the electrodes to fail prematurely. Therefore, the existing intermediate layer fabrication process needs further optimization, as the electrodes are prone to failure during long-term operation, severely restricting the continuity of copper foil production and product yield.

[0004] To address the aforementioned issues, existing technologies attempt to improve the performance of the intermediate layer by optimizing the sintering process (such as gradient heating), introducing rare earth doping (such as CeO2), or employing plasma spraying. However, rare earth doping requires the additional introduction of rare earth raw materials and the achievement of uniform dispersion through ball milling or co-precipitation processes, significantly increasing production steps and energy consumption. Gradient heating sintering requires precise control of multi-stage temperature profiles, extending the process cycle by 30% to 50%, and only providing localized relief of thermal stress. While plasma spraying can reduce crack density, it involves high equipment investment and stringent requirements for substrate roughness, making it difficult to adapt to complex workpieces. In short, these methods suffer from drawbacks such as complex processes, high costs, or only limited reduction in crack density. Summary of the Invention

[0005] The present invention addresses the problem of overly simplistic solutions in existing technologies by providing a significantly different solution. It primarily offers a coating anode with an improved intermediate layer using composite additives, along with its preparation method and application. This solves the technical problem mentioned in the background section where traditional titanium-tantalum intermediate layer preparation methods lead to crack formation on the intermediate layer surface, and significantly reduces crack density. The process is simple and cost-effective.

[0006] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows: A method for preparing a coated anode with an improved intermediate layer using composite additives includes five steps: titanium substrate pretreatment, intermediate layer coating solution preparation, intermediate layer preparation, active layer coating solution preparation, and active layer preparation. In the intermediate layer coating solution preparation step, an alcohol solvent and a polyether-modified polysiloxane are added to the intermediate layer base solution. The volume ratio of the intermediate layer base solution: alcohol solvent: polyether-modified polysiloxane is 10:(1~5):(0.5~2). After uniform mixing, a base solution containing composite additives is obtained. Through the synergistic effect of the composite additives in controlling volatilization during the drying stage and in the microporous structure and particle rearrangement during the sintering process, a highly dense intermediate layer is ultimately obtained.

[0007] In the intermediate layer preparation step, after the primer containing composite additives is fully coated onto the pretreated titanium substrate surface, it is first dried in an oven, then sintered in a sintering furnace, and then naturally cooled to room temperature after being removed from the furnace. During coating, the liquid volume used in a single application is 20~30 mL / m2.

[0008] This invention achieves synergistic control of the microstructure of the intermediate layer by adding an alcohol solvent and a polyether-modified polysiloxane composite additive to the intermediate layer substrate in the coated titanium anode, combined with multiple adjustment strategies. ① During the drying stage, the composite additive delays solvent evaporation through hydroxyl-metal coordination bonds, improves wetting and leveling properties by combining with polyether segments, and synergistically controls coating shrinkage stress and interfacial behavior, significantly reducing microcracks caused by stress concentration. ② In the early stage of sintering, alcohol molecules undergo controlled pyrolysis, generating carbonaceous intermediates that are uniformly distributed at the titanium-tantalum grain boundaries, laying a good foundation for the subsequent formation of a nanoscale porous structure; simultaneously, the polyether-modified polysiloxane, due to the effect of its polyether segments, still enables the coating to shrink uniformly in the early stage of sintering. ③ In the high-temperature sintering stage, the carbonaceous intermediates oxidize to form nanopores that absorb thermal stress, and the gaseous products generated by the pyrolysis of polyether segments promote particle rearrangement, thereby obtaining a dense intermediate layer. In summary, the synergistic effect of alcohol solvents and polyether-modified polysiloxanes can effectively reduce crack formation and improve material density.

[0009] Unlike existing technologies that add surfactants to the active layer, this invention introduces a composite additive of alcohol solvents and polyether-modified polysiloxanes into the intermediate layer, resulting in a significantly different mechanism of action. Existing technologies, by adding surfactants to the active layer, primarily focus on physical dispersion and wetting during the coating stage, aiming to improve catalyst particle distribution and achieve a smooth active layer. In contrast, this invention introduces a composite additive of alcohol solvents and polyether-modified polysiloxanes into the intermediate layer, employing a synergistic regulatory mechanism throughout the drying and sintering process. This mechanism not only reduces initial defects through physical actions (such as improved wettability) but, more importantly, achieves a deep reconstruction of the intermediate layer's microstructure through chemical behaviors (such as hydroxyl coordination to delay volatilization, controlled pyrolysis to generate nanopores, and the formation of a composite structure at high temperatures). This multi-stage, combined physical and chemical synergistic regulation is key to solving the unique cracking problem of the intermediate layer and improving its density and bonding strength.

[0010] For titanium anodes, the intermediate layer requires high density, high bonding strength, and high conductivity, while the active coating layer requires high catalytic activity and corrosion resistance. Existing technologies typically add surfactants to the active layer coating solution, possibly to disperse catalyst particles and improve catalytic activity and corrosion resistance. However, this invention differs from existing technologies by adding composite additives to the intermediate layer coating solution primarily to enhance its density and bonding strength.

[0011] Ethylene glycol may coordinate with ions in metal salt solutions, while polyether-modified polysiloxanes may be unstable in acidic or high-ionic-strength solutions, leading to gelation or precipitation and making them unsuitable for stable use in intermediate layer formulations. This indicates a compatibility issue between alcohol solvents such as ethylene glycol and polyether-modified polysiloxanes. Furthermore, excessive or insufficient proportions of composite additives can affect the uniformity and performance of the coating. Additionally, improper control of parameters such as drying time, heating rate, and sintering holding time may lead to increased coating cracking.

[0012] This invention prevents metal salt precipitation by balancing the additive ratio, avoiding gelation between polyether-modified polysiloxane and metal ions; controls drying time and heating rate to accommodate slow solvent evaporation, thereby slowly releasing stress and avoiding microcracks caused by uneven shrinkage; and controls holding time to ensure sufficient oxidation of the metal.

[0013] The improved interlayer, with its nanopores and dense structure, enhances its mechanical interlocking with the titanium substrate, reduces interfacial thermal stress, and improves the bonding strength between the two. Uniform grain boundaries reduce electron transport impedance, increase the interlayer conductivity, and promote charge transfer between the iridium-tantalum active layer and the substrate. The denser structure and reduced microcrack density block electrolyte penetration pathways, decreasing the oxidation rate of the titanium substrate and extending the anode's lifespan. This innovative process improves upon the structural defects of traditional titanium-tantalum interlayers, providing a new approach for developing highly stable coated titanium anodes.

[0014] Specifically, the alcohol solvent is at least one of ethylene glycol, isopropanol, and glycerol.

[0015] Preferably, the volume ratio of the base liquid: ethylene glycol: polyether-modified polysiloxane is 10:3:1.

[0016] Preferably, the drying temperature of the intermediate layer is 40~70 ℃, more preferably 45 ℃; the drying time is 10~60 min, more preferably 30 min.

[0017] Specifically, the sintering temperature of the intermediate layer is 510~550℃; the sintering time is 30~60 min; wherein, the heating rate during the heating stage is 5~9 ℃ / min, and the holding time during the holding stage is 10~35 min.

[0018] Preferably, in the titanium substrate pretreatment step, the pretreatment includes: sandblasting the substrate with one or more of 14-24 mesh bearing steel grit, brown corundum, and quartz sand at a working pressure of 0.4-0.6 MPa to give the substrate surface a certain roughness; then acid etching with one or more of sulfuric acid, hydrochloric acid, and oxalic acid solutions with a mass fraction of 10%-25% for an etching time of 10-60 min; using etching to remove the oxide layer on the substrate surface and increase the specific surface area of ​​the substrate; finally, cleaning and drying the substrate for later use.

[0019] Preferably, in the intermediate layer coating preparation step, TiCl4 and TaCl5 with a Ti:Ta molar ratio of (1~2):(1~2) are prepared in hydrochloric acid solution and stirred thoroughly to obtain the intermediate layer bottom liquid.

[0020] Preferably, in the preparation step of the active coating solution, H2IrCl6 and TaCl5 are prepared in hydrochloric acid solution at a molar ratio of Ir:Ta of (6~8):(2~4) to obtain an active coating solution with a concentration of 50~1000 g / L.

[0021] Preferably, in the active layer preparation step, the active layer coating solution is uniformly coated onto the titanium substrate containing the intermediate layer, with a single iridium weight gain of 1.5~2 g / cm2; then it is placed in a sintering furnace, with a heating rate of 5~10 ℃ / min, preferably 7 ℃ / min, sintered to 300~550 ℃, preferably 520 ℃, held for 10~35 min, preferably 15 min, and the sintering time is 30~60 min; then it is removed from the furnace and naturally cooled to room temperature; the coating-sintering-cooling process is repeated until the iridium content in the titanium anode coating reaches 15~25 g / m2.

[0022] A coated anode with an improved intermediate layer using composite additives, prepared by the above method, can reduce the cell voltage to 3.54V, achieve a coating adhesion of 63 N, and have a service life of over 1600 hours.

[0023] The aforementioned coating anode with improved intermediate layer using composite additives can be applied to different coatings in various fields, including but not limited to copper foil production, electrolytic chlorination, water treatment, seawater desalination, and printed circuit board manufacturing.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) This invention introduces alcohol solvents and polyether-modified polysiloxanes into the intermediate layer substrate, resulting in an intermediate layer coating with a relatively dense surface and significantly reduced crack density. This is attributed to the synergistic regulatory effect of the composite additives. On the one hand, during the drying stage, alcohol molecules delay volatilization, and polyether-modified polysiloxanes regulate interfacial tension. Together, they achieve uniform drying of the coating, avoid local stress concentration, and reduce crack generation. On the other hand, alcohol solvents can improve coating uniformity, thereby reducing macroscopic cracks; while polyether-modified polysiloxanes can be used to fill grain boundaries and absorb stress, thereby suppressing microscopic cracks. On the other hand, during the sintering heating stage, alcohol molecules generate carbonaceous intermediates and are uniformly distributed at the titanium-tantalum grain boundaries. These carbonaceous intermediates are oxidized and removed during the high-temperature sintering stage, leaving a uniform nanoscale porous structure that can effectively absorb thermal stress. At the same time, during the high-temperature stage, polyether-modified polysiloxanes decompose to generate SiO2, which forms a composite structure with titanium-tantalum oxides, which is beneficial to improving the density of the coating. The improved intermediate layer, with its dense structure, enhances its bonding strength with the titanium substrate, increases electrical conductivity, blocks electrolyte penetration pathways, and reduces the oxidation rate of the titanium substrate. Compared to traditional intermediate layer preparation processes, this invention significantly reduces crack density and enhances coating adhesion, thereby significantly extending the service life of the titanium anode surface coating.

[0025] (2) The additives in this invention are uniformly dispersed in the base liquid to prevent agglomeration or precipitation; by strictly controlling the drying time, heating rate, sintering temperature and sintering time, the adhesion and service life of the titanium anode surface coating can be further improved.

[0026] (3) By optimizing the formula ratio and adjusting parameters such as drying time, heating rate and holding time, this invention ensures that the additives play an effective role in each stage, solves the problems of compatibility and process synergy, and successfully applies composite additives to the intermediate layer, thereby improving the performance of titanium anodes.

[0027] (4) The preparation method provided by the present invention only requires drying and sintering. The sintering process does not require gradient heating; it does not require the introduction of rare earth doping; and it does not require the use of plasma spraying. The preparation process of the present invention is simple, safe, green and low cost, which is conducive to industrial production. Moreover, experimental testing shows that it can significantly reduce crack density.

[0028] The present invention will be explained in detail below with reference to the accompanying drawings and specific embodiments. Attached Figure Description

[0029] Figure 1 These are SEM images of the intermediate layer prepared in Embodiment 1 of the present invention at different magnifications; Figure 2 These are SEM images of the intermediate layer prepared in Comparative Example 3 of this invention at different magnifications. Figure 3 The cyclic voltammetry curves (Figure a) and polarization curves (Figure b) of Examples 1 to 8 and Comparative Examples 1 to 3 are shown. Detailed Implementation

[0030] To facilitate understanding of the present invention, a more comprehensive description of the present invention will be given below with reference to the accompanying drawings, which illustrate several embodiments of the present invention. However, the present invention can be implemented in different forms and is not limited to the embodiments described in the text. Rather, these embodiments are provided to make the disclosure of the present invention more thorough and complete.

[0031] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly associated with those skilled in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0032] Example 1: A method for preparing a coated anode with a modified intermediate layer using composite additives, comprising the following steps: S1. Titanium Substrate Pretreatment: The sample was cut to size using a shearing machine, with the TA1 titanium plate cut to 100*100mm. The cut titanium substrate was then pretreated by sandblasting with G18 steel grit at a pressure of 0.55 MPa to give the substrate surface a certain roughness. The pretreated titanium substrate was then immersed in a 20% hydrochloric acid solution and etched for 30 minutes to remove the oxide layer on the substrate surface and increase the specific surface area. Finally, it was cleaned and dried before use. S2. Preparation of intermediate layer coating solution: TiCl4 and TaCl5 are prepared in hydrochloric acid solution at a Ti:Ta molar ratio of 1:1. After thorough stirring, an intermediate layer base solution is obtained. Ethylene glycol and polyether modified polysiloxane are added to the base solution at a volume ratio of 10:3:1 (base solution: ethylene glycol: polyether modified polysiloxane). The mixture is stirred and sonicated for 30 min to obtain a uniform intermediate layer coating solution containing composite additives. S3. Intermediate Layer Preparation: The intermediate layer coating solution containing composite additives is fully coated onto the surface of the titanium substrate treated in step S1, with a single application volume of 25 mL / m². After coating, the substrate is dried in an oven at 45 ℃ for 30 min. It is then placed in a sintering furnace and sintered to 520 ℃ at a heating rate of 7 ℃ / min for 30 min. After removal from the furnace, the substrate is allowed to cool naturally to room temperature. This coating-drying-sintering-cooling process is repeated four times to obtain a titanium substrate containing an intermediate layer. Its scanning electron microscope (SEM) image is shown below. Figure 1 As shown; by Figure 1 It is evident that the intermediate layer prepared using the above-mentioned optimized formula and process parameters has a dense surface and significantly reduced cracks.

[0033] S4. Preparation of active coating solution: H2IrCl6 and TaCl5 are mixed in hydrochloric acid solution at a ratio of 7:3 to obtain an active coating solution with a concentration of 100 g / L. S5. Preparation of the active layer: The active layer coating solution is uniformly coated onto the titanium substrate containing the intermediate layer, with a single iridium weight gain of 1.5 g / cm2. The coated titanium plate is placed in a sintering furnace, heated at a rate of 7 ℃ / min, sintered to 520 ℃, held at that temperature for 15 min, and then allowed to cool naturally to room temperature. The coating-sintering-cooling process is repeated until the iridium content in the titanium anode coating reaches 23~24 g / m2.

[0034] Example 2: The difference between this example and Example 1 is that: In this embodiment, the drying time in step S3 is 10 min.

[0035] The rest is the same as in Example 1.

[0036] Example 3: The difference between this example and Example 1 is that: In this embodiment, the heat preservation time in step S3 is 15 minutes.

[0037] The rest is the same as in Example 1.

[0038] Example 4: The difference between this example and Example 1 is that: In this embodiment, ethylene glycol in step S2 is replaced with isopropanol.

[0039] The rest is the same as in Example 1.

[0040] Example 5: The difference between this example and Example 1 is that: In this embodiment, the volume ratio of the base liquid: ethylene glycol: polyether-modified polysiloxane in step S2 is 10:2:1.

[0041] The rest is the same as in Example 1.

[0042] Example 6: The difference between this example and Example 1 is that: In this embodiment, the volume ratio of the base liquid: ethylene glycol: polyether-modified polysiloxane in step S2 is 10:3:2.

[0043] The rest is the same as in Example 1.

[0044] Example 7: The difference between this example and Example 1 is that: In this embodiment, in step S1, the substrate is sandblasted with 14-mesh brown corundum at a working pressure of 0.6 MPa; then, it is acid-etched with a 10% oxalic acid solution for 60 min.

[0045] In step S2, the Ti:Ta molar ratio is 2:1; the volume ratio of the intermediate layer bottom liquid: alcohol solvent: polyether-modified polysiloxane is 10:1:0.5; and the alcohol solvent is glycerol.

[0046] In step S3, the single liquid volume is 20 mL / m2; the drying temperature of the intermediate layer is 40℃; the drying time of the intermediate layer is 60 min; the sintering temperature of the intermediate layer is 510℃; the sintering time of the intermediate layer is 30 min; the heating rate of the heating stage is 5℃ / min; and the holding time of the holding stage is 10 min.

[0047] In step S4, the molar ratio of Ir:Ta is 6:4; the concentration of the active coating solution is 50 g / L.

[0048] In step S5, during coating, the weight gain of iridium per unit is 2 g / cm2; during sintering, the heating rate is 5 ℃ / min, sintering is carried out at 550℃ and held for 10 min; the coating-sintering-cooling process is repeated until the iridium content in the titanium anode coating reaches 15~16 g / m2.

[0049] The rest is the same as in Example 1.

[0050] Example 8: The difference between this example and Example 1 is that: In this embodiment, in step S1, the substrate is sandblasted with 24-mesh quartz sand at a working pressure of 0.4 MPa; then, it is acid-etched with a 25% sulfuric acid solution for 10 min.

[0051] In step S2, the Ti:Ta molar ratio is 1:2; the volume ratio of the intermediate layer bottom liquid: alcohol solvent: polyether modified polysiloxane is 10:5:2.

[0052] In step S3, the single liquid volume is 30 mL / m2; the drying temperature of the intermediate layer is 70℃; the drying time of the intermediate layer is 10 min; the sintering temperature of the intermediate layer is 510 ℃; the sintering time of the intermediate layer is 60 min; the heating rate of the heating stage is 5 ℃ / min; and the holding time of the holding stage is 35 min.

[0053] In step S4, the molar ratio of Ir:Ta is 8:2; the concentration of the active coating solution is 1000 g / L.

[0054] In step S5, during coating, the weight gain of iridium per unit is 2 g / cm2; during sintering, the heating rate is 10 ℃ / min, sintering is carried out at 300℃ and held for 35 min; the coating-sintering-cooling process is repeated until the iridium content in the titanium anode coating reaches 24~25 g / m2.

[0055] The rest is the same as in Example 1.

[0056] Comparative Example 1: In step S2, only ethylene glycol was added, without adding polyether-modified polysiloxane.

[0057] The rest is the same as in Example 1.

[0058] Comparative Example 2: In step S2, only polyether-modified polysiloxane was added, without adding ethylene glycol.

[0059] The rest is the same as in Example 1.

[0060] Comparative Example 3: A method for preparing a coated anode without an additive interlayer, which is basically the same as Example 1, except that in step S2, no alcohol solvent and polyether-modified polysiloxane are added. The conventional interlayer substrate is directly coated onto the etched titanium substrate. Its scanning electron microscope (SEM) image is shown below. Figure 2 As shown.

[0061] Comparative Example 4: The heating rate in step S3 is 10 ℃ / min.

[0062] The rest is the same as in Example 1.

[0063] Comparative Example 5: The sintering temperature in step S3 is 500 ℃.

[0064] The rest is the same as in Example 1.

[0065] Figure 1 The image shows a scanning electron microscope (SEM) image of the intermediate layer modified by the composite additive. It can be clearly observed from the image that the intermediate layer prepared by coating and sintering the titanium substrate after introducing the composite additive into the conventional substrate has a fairly dense surface with only a very few cracks. Figure 2 The results of Comparative Example 3 show that the intermediate layer prepared by coating and sintering a titanium substrate with a conventional substrate without additives has a high surface crack density, which makes the anode prone to passivation failure during the reaction process.

[0066] Performance testing 1. To verify the effect of different treatment processes on electrochemical performance, polarization curve (LSV) tests were performed on Examples 1 to 6 and Comparative Examples 1 to 5, respectively. The test results are as follows: Figure 3 As shown.

[0067] from Figure 3 As can be seen, Example 1 exhibits the best activity, showing a significant improvement in activity compared to Comparative Example 3. Analysis revealed that in Comparative Example 3, cracks weaken the bonding force between the intermediate layer and the surface coating, leading to localized stress in the iridium-tantalum coating during sintering due to substrate unevenness. This stress resulted in micropores or peeling, reducing the effective active area. In Example 1, the uniform, crack-free intermediate layer provides a smooth substrate for the layer-by-layer sintering of the iridium-tantalum coating, promoting the uniform distribution of active layer nanoparticles, forming continuous conductive channels, and accelerating electrochemical reaction kinetics.

[0068] 2. The electrodes prepared in Examples 1 to 6 and Comparative Examples 1 to 5 were subjected to trench pressure test, accelerated life test and coating adhesion test.

[0069] 1) Cell voltage test: The prepared coated titanium anode and titanium cathode were placed in a 20% H2SO4 electrolyte and electrolyzed using a DC power supply. The temperature was a constant 60℃ water bath. The anode current density was 5 A / cm2, the electrode spacing was 3.3 cm, and the electrode area was 1 cm2. The cell voltage was monitored at the beginning of electrolysis.

[0070] 2) Accelerated Life Test: The prepared coated titanium anode and titanium cathode were placed in a 20% H2SO4 electrolyte. Electrolysis was conducted using a DC power supply. The electrolyte temperature was 60℃, the anode current density was 5 A / cm2, the electrode spacing was 3.3 cm, and the electrode area was 1 cm2. The cell voltage was continuously monitored. When the cell voltage exceeded 5 V, the anode was considered to have failed, and the accelerated life test results were recorded.

[0071] 3) Coating adhesion was tested using an automatic scratch tester under the following conditions: Detection mode: Acoustic emission; Load applied: 100 N; Loading method: Unidirectional continuous loading; Scratch length: 6 mm; Loading rate: 60 N / min.

[0072] Accelerated life testing was conducted when the tank voltage exceeded 5 V, at which point the anode was considered to have failed and the accelerated life test results were recorded. The adhesion test results were the critical load values ​​at which the coating began to fail, and the results are shown in Table 1.

[0073] Table 1. Performance Comparison of Examples 1 to 6 and Comparative Examples 1 to 5

[0074] As shown in Table 1: Comparing Example 1 with Comparative Example 3 reveals that, within the scope provided by this invention, the introduction of composite additives can significantly improve coating adhesion and service life, while also significantly reducing tank pressure. This fully demonstrates the synergistic advantages of composite additives.

[0075] Comparing Example 1 with Comparative Examples 1 and 2 reveals that, compared to a single additive system, the composite additive significantly improves coating adhesion and service life.

[0076] Comparing Example 1 with Comparative Examples 4 and 5 reveals that, with the introduction of composite additives, rapid heating induces thermal stress cracks, and low-temperature sintering results in poor density of the intermediate layer and weak interfacial bonding, thus significantly deteriorating the coating performance.

[0077] Comparing Example 1 with Examples 2, 3, 5, and 6, it can be seen that by introducing composite additives and further controlling the drying time, sintering holding time, and additive ratio, not only can the service life be extended, but also the tank pressure can be reduced and the coating adhesion can be improved.

[0078] Comparing Example 1 and Example 4, it can be found that simply replacing ethylene glycol with isopropanol results in uneven shrinkage of the intermediate layer due to the faster volatilization and weaker coordination ability of isopropanol, leading to a reduction in coating adhesion and service life.

[0079] In summary, the core of performance improvement lies in the multi-dimensional synergistic regulation of a composite additive consisting of alcohol solvents and polyether-modified polysiloxanes in the intermediate layer substrate. Precise control of the additive ratio and process parameters is crucial for maximizing coating performance. Alcohol molecules slow down solvent evaporation, balance drying stress distribution, and improve precursor wettability, thus suppressing uneven coating shrinkage. Polyether-modified polysiloxanes, with their amphiphilic structure, regulate interfacial tension, and their flexible segments buffer coating shrinkage stress. Upon high-temperature pyrolysis, they generate gaseous products that fill grain boundary defects. The synergistic effect of these two additives achieves both evaporation control and microstructure enhancement, significantly reducing coating cracking, blocking electrolyte penetration channels, inhibiting interlayer / substrate interface corrosion, and reducing iridium active component loss, thereby greatly extending anode lifespan.

[0080] The present invention has been described by way of example in conjunction with the accompanying drawings. Obviously, the specific implementation of the present invention is not limited to the above-described manner. Any non-substantial improvement made by adopting the inventive concept and technical solution of the present invention, or the direct application of the inventive concept and technical solution of the present invention to other occasions without modification, shall be within the protection scope of the present invention.

Claims

1. A method for preparing a coated anode with a modified intermediate layer using composite additives, comprising five steps: titanium substrate pretreatment, intermediate layer coating solution preparation, intermediate layer preparation, active layer coating solution preparation, and active layer preparation; characterized in that: In the intermediate layer coating preparation step, a composite additive is added to the intermediate layer base liquid. The composite additive is a mixture of alcohol solvent and polyether modified polysiloxane, and the volume ratio of the intermediate layer base liquid: alcohol solvent: polyether modified polysiloxane is 10:(1~5):(0.5~2). After mixing evenly, an intermediate layer coating liquid containing the composite additive is obtained.

2. The method for preparing a coated anode with a modified intermediate layer using composite additives according to claim 1, characterized in that: The alcohol solvent is at least one of ethylene glycol, isopropanol, and glycerol.

3. The method for preparing a coated anode with a modified intermediate layer using composite additives according to claim 1, characterized in that: In the intermediate layer preparation step, the intermediate layer coating solution containing composite additives is fully coated onto the pretreated titanium substrate surface, with a single application volume of 20~30 mL / m. 2 First, dry in an oven, then sinter in a sintering furnace, and then cool naturally to room temperature after being taken out of the furnace.

4. The method for preparing a coated anode with a modified intermediate layer using composite additives according to claim 3, characterized in that: The drying temperature of the intermediate layer is 40~70℃; And / or, the drying time for the intermediate layer is 10~60 min.

5. The method for preparing a coated anode with a modified intermediate layer using composite additives according to claim 3, characterized in that: The sintering temperature of the intermediate layer is 510~550 ℃; And / or, the sintering time of the intermediate layer is 30~60 min; The heating rate during the heating stage is 5~9 ℃ / min, and the holding time during the holding stage is 10~35 min.

6. The method for preparing a coated anode with a modified intermediate layer using composite additives according to claim 1, characterized in that: The titanium substrate pretreatment includes the following steps: The substrate is sandblasted using one or more of the following: 14-24 mesh bearing steel grit, brown corundum, and quartz sand, at a working pressure of 0.4-0.6 MPa, to give the substrate surface a certain roughness. Then, it is acid-etched using one or more of the following solutions with a mass fraction of 10%-25%: sulfuric acid, hydrochloric acid, and oxalic acid, for an etching time of 10-60 min. The etching removes the oxide layer on the substrate surface and increases the specific surface area of ​​the substrate. Finally, the substrate is cleaned and dried before use.

7. The method for preparing a coated anode with a modified intermediate layer using composite additives according to claim 1, characterized in that: TiCl4 and TaCl5 were prepared in hydrochloric acid solution with a Ti:Ta molar ratio of (1~2):(1~2), and the mixture was stirred thoroughly to obtain the intermediate bottom liquid.

8. The method for preparing a coated anode with a modified intermediate layer using composite additives according to claim 1, characterized in that: In the preparation step of the active coating solution, H2IrCl6 and TaCl5 are prepared in hydrochloric acid solution according to the molar ratio of Ir:Ta of (6~8):(2~4) to obtain an active coating solution with a concentration of 50~1000 g / L.

9. The method for preparing a coated anode with a modified intermediate layer using composite additives according to claim 1, characterized in that: In the active layer preparation step, the active layer coating solution is uniformly coated onto the titanium substrate containing the intermediate layer, and then sintered in a sintering furnace at a temperature of 300~550 ℃ for 30~60 min. After being removed from the furnace, it is allowed to cool naturally to room temperature. The coating-sintering-cooling process is repeated until the iridium content in the titanium anode coating reaches 15~25 g / m 2 ; And / or, the heating rate during the heating stage is 5~10 ℃ / min, and the holding time during the holding stage is 10~35 min.

10. A coated anode with a modified intermediate layer using composite additives, prepared by the method described in any one of claims 1-9, characterized in that: It can be applied to various coatings in different fields, including but not limited to copper foil production, electrolytic chlorination, water treatment, seawater desalination, and printed circuit board manufacturing.

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