A pretreatment method for an electrode foil

Abstract

The present invention relates to the technical field of electrode foil pretreatment, and specifically to a pretreatment method for electrode foil, which comprises the following steps: S1, pickling of electrode foil; S2, organic liquid washing of electrode foil; S3, primary formation treatment; S4, treating the electrode foil with γ-methacryloxypropyltrimethoxysilane, polyvinylpyrrolidone, trimellitic acid, ethanol and deionized water; S5, secondary formation treatment; S6, tertiary formation treatment; S7, heating after drying. The electrode foil prepared by the present invention not only has low energy consumption and is convenient to process, but also has a high specific capacitance and a small leakage current for the prepared electrode foil.

Description

Technical Field

[0001] The present invention relates to the technical field of electrode foil pretreatment, and specifically to a pretreatment method for electrode foil. Background Art

[0002] Electrode foil is a key raw material for manufacturing aluminum electrolytic capacitors. Aluminum electrode foil is an important component of aluminum electrolytic capacitors, and the preparation process involves technologies and related industries in multiple disciplines such as machinery, chemical engineering, electronics, and metal materials.

[0003] Before becoming a finished product, aluminum electrode foil requires two processing steps, namely corrosion and formation. The formation process determines the quality of the oxide film. Therefore, during the formation process, the compactness of the oxide film can be improved by increasing the number of formation steps. Sometimes, even more than 5 steps of formation are required, and the subsequent formation consumes a large amount of electricity and often requires a voltage of more than 300V. This formation technology obviously increases the cost of formation and reduces the formation efficiency at the same time.

[0004] Therefore, in view of the problems raised in the above background art, those skilled in the art have proposed a pretreatment method for electrode foil. In this method, after three-stage formation, the voltage requirement is relatively low, and at the same time, the prepared electrode foil has strong comprehensive performance. Summary of the Invention

[0005] The purpose of the present invention is to provide a pretreatment method for electrode foil to solve the problems raised in the above background art.

[0006] To achieve the above purpose, the present invention provides the following technical solutions:

[0007] A pretreatment method for electrode foil includes the following steps:

[0008] S1. Put the electrode foil into a nitric acid solution with a mass fraction of 2 - 4%, immerse it at 60 - 70°C for 2 - 10 min, and then wash it clean with sufficient deionized water;

[0009] S2. Put the electrode foil treated in step S1 into a mixed solution of propanol, acetone, and ethylene glycol and perform ultrasonic treatment for 5 - 10 min;

[0010] S3. Put the electrode foil treated in step S2 into a mixed solution of 2 - 8 wt% ammonium adipate and 1 - 10 wt% sodium adipate for primary formation treatment, and then wash it clean with sufficient deionized water;

[0011] S4. Put the electrode foil treated in step S3 into a mixed solution of γ-methacryloxypropyltrimethoxysilane, polyvinylpyrrolidone, trimesic acid, ethanol, and deionized water, heat it to 50 - 65°C for impregnation treatment for 0.5 - 1 h, and then wash it clean with deionized water;

[0012] S5. Place the electrode foil processed in step S4 into a mixed solution of 0.5 - 5 wt% modified titanium dioxide and 2 - 6 wt% boric acid for secondary formation treatment, and then wash it clean with deionized water;

[0013] S6. Place the electrode foil processed in step S5 into a mixed solution of 2 - 8 wt% ammonium adipate and 1 - 10 wt% sodium adipate for tertiary formation treatment, and then wash it clean with sufficient deionized water;

[0014] S7. After drying the electrode foil processed in step S6 at room temperature, heat - treat it at 300 - 450 °C for 1 - 3 h to obtain the pre - treated electrode foil.

[0015] Further, the mass ratio of propanol, acetone and ethylene glycol in step S2 is 1:(1 - 2):(0.5 - 3).

[0016] Further, in the primary formation treatment of step S3, the applied voltage is 16 - 25 V, the formation temperature is 30 - 45 °C, and the formation time is 5 - 10 min.

[0017] Further, the mass ratio of γ - methacryloxypropyltrimethoxysilane, polyvinylpyrrolidone, trimesic acid, ethanol and deionized water in step S4 is 1:(1 - 5):(0.5 - 2):(15 - 20):(100 - 150).

[0018] Further, in the secondary formation treatment of step S5, the applied voltage is 50 - 80 V, the formation temperature is 55 - 70 °C, and the formation time is 5 - 10 min.

[0019] Further, in the tertiary formation treatment of step S6, the applied voltage is 120 - 180 V, the formation temperature is 80 - 90 °C, and the formation time is 2 - 6 min.

[0020] Further, the preparation method of the modified titanium dioxide in step S5 is prepared by the following steps:

[0021] S101. Under ice - bath conditions, drop titanium tetrachloride into deionized water, then add lanthanum nitrate hexahydrate, stir and mix evenly. Continuously drop 20% ammonia water by mass fraction into the system until the pH reaches 9.5, and continuously react for 0.5 - 1 h to obtain a reaction solution;

[0022] S102. Centrifugally filter the reaction solution obtained in step S101. After vacuum - drying the filtered product at 30 - 50 °C, grind it to a particle size of 20 - 50 nm, and then calcine it in a muffle furnace at 500 - 600 °C for 1 - 2 h to obtain lanthanum - doped titanium dioxide;

[0023] S103. Irradiate the lanthanum-doped titanium dioxide in step S102 with ultraviolet light having a wavelength of 254 - 365 nm for 1 - 4 h;

[0024] S104. Disperse the lanthanum-doped titanium dioxide treated in step S103 into a mixed solution of sodium hexametaphosphate, chitosan, glutaraldehyde and deionized water, soak for 4 - 12 h, filter, and vacuum dry at 30 - 50 °C to obtain modified titanium dioxide.

[0025] Further, the mass ratio among lanthanum nitrate hexahydrate, titanium tetrachloride and deionized water in step S101 is 1:(15 - 30):(120 - 200).

[0026] Further, the mass ratio of chitosan, glutaraldehyde, sodium hexametaphosphate, deionized water to titanium tetrachloride in step S101 in step S104 is 1:(0.5 - 2):(5 - 10):(80 - 150):(20 - 30).

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] 1. In the process of preparing the electrode foil in the present invention, by adding modified titanium dioxide in the secondary formation treatment, the performance of the prepared electrode foil can be effectively improved, the specific capacitance of the electrode foil is increased, and the leakage current of the electrode foil is reduced;

[0029] 2. The electrode foil prepared in the present invention undergoes a total of three-stage formation treatment. The formation treatment is less, the voltage requirement is lower, effectively saving the energy consumption and improving the production efficiency. Brief Description of the Drawings

[0030] Figure 1 It is the process flow chart of the electrode foil pretreatment of the present invention;

[0031] Figure 2 It is the process flow chart of preparing modified titanium dioxide of the present invention. Detailed Embodiments

[0032] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0033] Please refer to Figures 1 to 2 , the present invention provides:

[0034] Example 1

[0035] A pretreatment method for an electrode foil, comprising the following steps:

[0036] S1. Put the electrode foil into a nitric acid solution with a mass fraction of 2.5%, impregnate it at 66 °C for 3 min, and then clean it thoroughly with sufficient deionized water;

[0037] S2. Put the electrode foil treated in step S1 into a mixed solution of propanol, acetone and ethylene glycol with a mass ratio of 1:1.5:2 and perform ultrasonic treatment for 6 min;

[0038] S3. Put the electrode foil treated in step S2 into a mixed solution of 4 wt% ammonium adipate and 5 wt% sodium adipate for primary formation treatment. The voltage applied during the primary formation treatment is 22 V, the formation temperature is 35 °C, and the formation time is 8 min. Then clean it thoroughly with sufficient deionized water;

[0039] S4. Put the electrode foil treated in step S3 into a mixed solution of γ-methacryloxypropyltrimethoxysilane, polyvinylpyrrolidone, trimesic acid, ethanol and deionized water with a mass ratio of 1:3:1.5:18:130, heat it to 55 °C and perform impregnation treatment for 0.8 h, and then clean it with deionized water;

[0040] S5. Put the electrode foil treated in step S4 into a mixed solution of 2 wt% modified titanium dioxide and 3 wt% boric acid for secondary formation treatment. The voltage applied during the secondary formation treatment is 75 V, the formation temperature is 62 °C, and the formation time is 7 min. Then clean it with deionized water;

[0041] S6. Put the electrode foil treated in step S5 into a mixed solution of 6 wt% ammonium adipate and 4 wt% sodium adipate for tertiary formation treatment. The voltage applied during the tertiary formation treatment is 165 V, the formation temperature is 88 °C, and the formation time is 3 min. Then clean it thoroughly with sufficient deionized water;

[0042] S7. After drying the electrode foil treated in step S6 at room temperature, heat-treat it at 400 °C for 2.5 h to obtain the pretreated electrode foil;

[0043] The preparation method of the modified titanium dioxide in the above step S5 is prepared by the following steps:

[0044] S101. Under ice bath conditions, drop 129.3 g of titanium tetrachloride into 1.29 kg of deionized water, then add 7.2 g of lanthanum nitrate hexahydrate, stir and mix evenly. Continue to drop 20% ammonia water by mass fraction into the system until the pH reaches 9.5, and continuously react for 0.8 h to obtain a reaction solution;

[0045] S102. Centrifuge and filter the reaction solution obtained in step S101. After vacuum drying the filtered product at 45°C, grind it to a particle size of 30 nm, and then calcine it in a muffle furnace at 520°C for 1.2 h to obtain lanthanum-doped titanium dioxide.

[0046] S103. Irradiate the lanthanum-doped titanium dioxide in step S102 with ultraviolet light of wavelength 300 nm for 2 h.

[0047] S104. Disperse the lanthanum-doped titanium dioxide treated in step S103 into a mixed solution of sodium hexametaphosphate, chitosan, glutaraldehyde and deionized water and soak for 8 h. The amounts of sodium hexametaphosphate, chitosan, glutaraldehyde and deionized water are 43 g, 5.4 g, 8.1 g and 650 g respectively. Filter and vacuum dry at 35°C to obtain modified titanium dioxide.

[0048] Example 2

[0049] A pretreatment method for an electrode foil, comprising the following steps:

[0050] S1. Put the electrode foil into a nitric acid solution with a mass fraction of 2%, impregnate it at 60°C for 20 min, and then wash it clean with sufficient deionized water.

[0051] S2. Put the electrode foil treated in step S1 into a mixed solution of propanol, acetone and ethylene glycol with a mass ratio of 1:1:0.5 and perform ultrasonic treatment for 5 min.

[0052] S3. Put the electrode foil treated in step S2 into a mixed solution of 2 wt% ammonium adipate and 1 wt% sodium adipate for primary formation treatment. The voltage applied during the primary formation treatment is 16 V, the formation temperature is 30°C, and the formation time is 5 min. Then wash it clean with sufficient deionized water.

[0053] S4. Put the electrode foil treated in step S3 into a mixed solution of γ-methacryloxypropyltrimethoxysilane, polyvinylpyrrolidone, trimesic acid, ethanol and deionized water with a mass ratio of 1:1:0.5:15:100, heat it to 50°C and perform impregnation treatment for 0.5 h, and then wash it clean with deionized water.

[0054] S5. Put the electrode foil treated in step S4 into a mixed solution of 0.5 wt% modified titanium dioxide and 2 wt% boric acid for secondary formation treatment. The voltage applied during the secondary formation treatment is 50 V, the formation temperature is 55°C, and the formation time is 5 min. Then wash it clean with deionized water.

[0055] S6. Place the electrode foil processed in step S5 into a mixed solution of 2 wt% ammonium adipate and 1 wt% sodium adipate for three-stage formation treatment. The voltage applied during the three-stage formation treatment is 120 V, the formation temperature is 80 °C, and the formation time is 2 min. Then, wash it clean with sufficient deionized water;

[0056] S7. After drying the electrode foil processed in step S6 at room temperature, heat-treat it at 300 °C for 1 h to obtain the pretreated electrode foil;

[0057] The preparation method of the modified titanium dioxide in the above step S5 is prepared through the following steps:

[0058] S101. Under ice bath conditions, drop 128 g of titanium tetrachloride into 1.023 kg of deionized water, then add 8.53 g of lanthanum nitrate hexahydrate, stir and mix evenly. Continue to drop 20% ammonia water by mass fraction into the system until the pH reaches 9.5, and continuously react for 0.5 h to obtain a reaction solution;

[0059] S102. Centrifuge and filter the reaction solution obtained in step S101. After vacuum drying the filtered product at 30 °C, grind it to a particle size of 20 nm, and then calcine it in a muffle furnace at 500 °C for 1 h to obtain lanthanum-doped titanium dioxide;

[0060] S103. Irradiate the lanthanum-doped titanium dioxide in step S102 with ultraviolet light of wavelength 254 nm for 1 h;

[0061] S104. Disperse the lanthanum-doped titanium dioxide processed in step S103 into a mixed solution of sodium hexametaphosphate, chitosan, glutaraldehyde and deionized water and soak for 4 h. The dosages of sodium hexametaphosphate, chitosan, glutaraldehyde and deionized water are 32 g, 6.4 g, 3.2 g and 512 g respectively. Filter and vacuum dry at 30 °C to obtain modified titanium dioxide.

[0062] Example 3

[0063] A pretreatment method for an electrode foil, comprising the following steps:

[0064] S1. Place the electrode foil into a 4% nitric acid solution by mass fraction, impregnate it at 70 °C for 10 min, and then wash it clean with sufficient deionized water;

[0065] S2. Place the electrode foil processed in step S1 into a mixed solution of propanol, acetone and ethylene glycol with a mass ratio of 1:2:3 and perform ultrasonic treatment for 10 min;

[0066] S3. Place the electrode foil processed in step S2 into a mixed solution of 8 wt% ammonium adipate and 10 wt% sodium adipate for primary formation treatment. The voltage applied during the primary formation treatment is 25 V, the formation temperature is 45 °C, and the formation time is 10 min. Then, wash it thoroughly with sufficient deionized water;

[0067] S4. Place the electrode foil processed in step S3 into a mixed solution of γ-methacryloxypropyltrimethoxysilane, polyvinylpyrrolidone, trimesic acid, ethanol, and deionized water with a mass ratio of 1:5:2:20:150, heat it to 50 - 65 °C, and perform impregnation treatment for 0.5 - 1 h. Then, wash it thoroughly with deionized water;

[0068] S5. Place the electrode foil processed in step S4 into a mixed solution of 5 wt% modified titanium dioxide and 6 wt% boric acid for secondary formation treatment. The voltage applied during the secondary formation treatment is 80 V, the formation temperature is 70 °C, and the formation time is 10 min. Then, wash it thoroughly with deionized water;

[0069] S6. Place the electrode foil processed in step S5 into a mixed solution of 8 wt% ammonium adipate and 10 wt% sodium adipate for tertiary formation treatment. The voltage applied during the tertiary formation treatment is 180 V, the formation temperature is 90 °C, and the formation time is 6 min. Then, wash it thoroughly with sufficient deionized water;

[0070] S7. After drying the electrode foil processed in step S6 at room temperature, heat-treat it at 450 °C for 3 h to obtain the pre-treated electrode foil;

[0071] The preparation method of the modified titanium dioxide in step S5 above is prepared through the following steps:

[0072] S101. Under ice bath conditions, drop 154 g of titanium tetrachloride into 1.026 kg of deionized water, then add 5.13 g of lanthanum nitrate hexahydrate, stir and mix evenly. Continuously drop 20% ammonia water into the system until the pH reaches 9.5, and continuously react for 1 h to obtain a reaction solution;

[0073] S102. Centrifugally filter the reaction solution obtained in step S101. After vacuum drying the filtered product at 50 °C, grind it to a particle size of 50 nm, and then calcine it in a muffle furnace at 600 °C for 2 h to obtain lanthanum-doped titanium dioxide;

[0074] [[ID=2*]]S103. Irradiate the lanthanum-doped titanium dioxide in step S102 with ultraviolet light with a wavelength of 365 nm for 5 h;

[0075] S104. Disperse the lanthanum-doped titanium dioxide processed in step S103 into a mixed solution of sodium hexametaphosphate, chitosan, glutaraldehyde and deionized water, soak for 12 h. The dosages of sodium hexametaphosphate, chitosan, glutaraldehyde and deionized water are 51.3 g, 5.13 g, 10.26 g and 769 g respectively. Filter and vacuum dry at 50 °C to obtain modified titanium dioxide.

[0076] Example 4

[0077] A pretreatment method for an electrode foil, comprising the following steps:

[0078] S1. Put the electrode foil into a nitric acid solution with a mass fraction of 3%, impregnate at 68 °C for 7 min, and then wash it clean with sufficient deionized water;

[0079] S2. Put the electrode foil processed in step S1 into a mixed solution of propanol, acetone and ethylene glycol with a mass ratio of 1:1.5:2.5 and perform ultrasonic treatment for 9 min;

[0080] S3. Put the electrode foil processed in step S2 into a mixed solution of 4 wt% ammonium adipate and 6 wt% sodium adipate for primary formation treatment. The voltage applied during the primary formation treatment is 22 V, the formation temperature is 42 °C, and the formation time is 8 min. Then wash it clean with sufficient deionized water;

[0081] S4. Put the electrode foil processed in step S3 into a mixed solution of γ-methacryloxypropyltrimethoxysilane, polyvinylpyrrolidone, trimesic acid, ethanol and deionized water with a mass ratio of 1:4:1.5:18:110, heat to 60 °C and perform impregnation treatment for 0.6 h, and then wash it clean with deionized water;

[0082] S5. Put the electrode foil processed in step S4 into a mixed solution of 3 wt% modified titanium dioxide and 5 wt% boric acid for secondary formation treatment. The voltage applied during the secondary formation treatment is 75 V, the formation temperature is 66 °C, and the formation time is 8 min. Then wash it clean with deionized water;

[0083] S6. Put the electrode foil processed in step S5 into a mixed solution of 5 wt% ammonium adipate and 3 wt% sodium adipate for tertiary formation treatment. The voltage applied during the tertiary formation treatment is 175 V, the formation temperature is 85 °C, and the formation time is 3.5 min. Then wash it clean with sufficient deionized water;

[0084] S7. After drying the electrode foil processed in step S6 at room temperature, heat-treat it at 440 °C for 1.2 h to obtain the pretreated electrode foil;

[0085] The preparation method of the modified titanium dioxide in the above step S5 is prepared through the following steps:

[0086] S101. Under ice bath conditions, 144 g of titanium tetrachloride was dropped into 1.48 kg of deionized water, then 8.2 g of lanthanum nitrate hexahydrate was added, and the mixture was stirred evenly. Then, 20% ammonia water was continuously dropped into the system until the pH reached 9.5, and the reaction was continued for 0.6 h to obtain a reaction solution.

[0087] S102. The reaction solution obtained in step S101 was centrifuged and filtered. After the filtered product was vacuum dried at 42 °C, it was ground to a particle size of 40 nm, and then calcined in a muffle furnace at 520 °C for 1.6 h to obtain lanthanum-doped titanium dioxide.

[0088] S103. The lanthanum-doped titanium dioxide in step S102 was irradiated with ultraviolet light with a wavelength of 365 nm for 1 h.

[0089] S104. The lanthanum-doped titanium dioxide treated in step S103 was dispersed in a mixed solution of sodium hexametaphosphate, chitosan, glutaraldehyde and deionized water and soaked for 10 h. The amounts of sodium hexametaphosphate, chitosan, glutaraldehyde and deionized water were 52 g, 6.5 g, 5.4 g and 720 g respectively. After filtration, it was vacuum dried at 35 °C to obtain modified titanium dioxide.

[0090] Comparative Example 1

[0091] The difference between Comparative Example 1 and Example 1 is that step S101 was omitted, thus canceling the addition of lanthanum nitrate hexahydrate, and the remaining steps are exactly the same as those in Example 1.

[0092] Comparative Example 2

[0093] The difference between Comparative Example 2 and Example 1 is that step S103 was omitted, thus canceling the ultraviolet irradiation process, and the remaining steps are exactly the same as those in Example 1.

[0094] Comparative Example 3

[0095] The difference between Comparative Example 3 and Example 1 is that step S104 was omitted, thus canceling the addition of sodium hexametaphosphate, and the remaining steps are exactly the same as those in Example 1.

[0096] Comparative Example 4

[0097] The difference between Comparative Example 4 and Example 1 is that step S104 was omitted, thus canceling the addition of glutaraldehyde and chitosan, and the remaining steps are exactly the same as those in Example 1.

[0098] Comparative Example 5

[0099] The difference between Comparative Example 5 and Example 1 is that the modified titanium dioxide added in step S5 is replaced with ordinary titanium dioxide, and the remaining steps are exactly the same as those in Example 1.

[0100] Comparative Example 6

[0101] The difference between Comparative Example 6 and Comparative Example 5 is that the addition of titanium dioxide is completely cancelled in step S5, and the remaining steps are exactly the same as those in Example 1.

[0102] The electrode foils prepared in the above Examples 1-4 and Comparative Examples 1-6 were subjected to performance tests. The test standard was the national standard SJ / T11140-2012 for electrode foils used in aluminum electrolytic capacitors. The test results are shown in Table 1 below;

[0103] Table 1: Performance test table of electrode foils prepared in Examples 1-4 and Comparative Examples 1-6

[0104]

[0105] It can be seen from the data in Table 1 above that by adding titanium dioxide in the secondary formation process, the present invention can significantly improve the performance of the electrode foil (increase the specific capacitance and reduce the leakage current). At the same time, through the further modification of titanium dioxide in the present invention, including coprecipitation with a small amount of cerium nitrate and treatment with a mixed solution of sodium hexametaphosphate, chitosan, and glutaraldehyde, and irradiation with ultraviolet light before treatment, the performance of the prepared electrode foil can be further improved. At the same time, in the present invention, when preparing the electrode foil, through three formation processes, the number of formation processes is less, saving energy.

[0106] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principle and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for pretreating an electrode foil, characterized in that: The steps include: S1. Place the electrode foil in a 2-4% nitric acid solution at 60-70°C for 2-10 minutes, then rinse with sufficient deionized water. S2. Place the electrode foil treated in step S1 into a mixed solution of propanol, acetone, and ethylene glycol and ultrasonically treat for 5-10 minutes; S3, placing the electrode foil treated in step S2 into a mixed solution of 2-8 wt% ammonium adipate and 1-10 wt% sodium adipate for primary chemical treatment, and then washing it with sufficient deionized water; S4, placing the electrode foil treated in step S3 into a mixed solution of γ-methacryloxypropyltrimethoxysilane, polypyrrolidone, trimesic acid, ethanol and deionized water, heating it to 50-65° C. and immersing it for 0.5-1 hour, and then washing it with deionized water; S5, placing the electrode foil treated in step S4 into a mixed solution of 0.5-5 wt% modified titanium dioxide and 2-6 wt% boric acid for secondary chemical treatment, and then washing it with deionized water; S6. Place the electrode foil treated in step S5 into a mixed solution of 2-8 wt% ammonium adipate and 1-10 wt% sodium adipate for a tertiary chemical treatment, and then rinse with sufficient deionized water; S7, drying the electrode foil processed in step S6 at room temperature, and then heating it at 300-450° C. for 1-3 hours to obtain a pre-treated electrode foil; The preparation method of the modified titanium dioxide in step S5 is prepared by the following steps: S101. In an ice bath, titanium tetrachloride was added dropwise to deionized water, followed by addition of lanthanum nitrate hexahydrate, and the mixture was stirred and mixed uniformly. 20% by mass aqueous ammonia was added dropwise to the system until the pH reached 9.5, and the reaction was continued for 0.5-1 h to obtain a reaction solution. S102, centrifugally filtering the reaction solution obtained in step S101, vacuum drying the filtered product at 30-50° C., grinding it to a particle size of 20-50 nm, and then calcining it in a muffle furnace at 500-600° C. for 1-2 hours to obtain lanthanum-doped titanium dioxide; S103, irradiating the lanthanum-doped titanium dioxide in step S102 with ultraviolet light having a wavelength of 254-365 nm for 1-4 hours; S104, dispersing the lanthanum-doped titanium dioxide treated in step S103 into a mixed solution of sodium hexametaphosphate, chitosan, glutaraldehyde and deionized water, soaking the solution for 4-12 hours, filtering the solution, and vacuum drying the solution at 30-50° C. to obtain modified titanium dioxide.

2. The electrode foil pretreatment method according to claim 1, characterized in that: The mass ratio of propanol, acetone and ethylene glycol in step S2 is 1:(1-2):(0.5-3).

3. The electrode foil pretreatment method according to claim 1, characterized in that: In the first-stage formation treatment in step S3, the voltage applied is 16-25V, the formation temperature is 30-45°C, and the formation time is 5-10 minutes.

4. The electrode foil pretreatment method according to claim 1, characterized in that: In step S4, the mass ratio of γ-methacryloxypropyltrimethoxysilane, polypyrrolidone, trimesic acid, ethanol and deionized water is 1:(1-5):(0.5-2):(15-20):(100-150).

5. The electrode foil pretreatment method according to claim 1, characterized in that: In the secondary formation treatment in step S5, the voltage applied is 50-80V, the formation temperature is 55-70°C, and the formation time is 5-10 minutes.

6. The electrode foil pretreatment method according to claim 1, characterized in that: In the three-stage formation treatment in step S6, the voltage applied is 120-180V, the formation temperature is 80-90°C, and the formation time is 2-6 minutes.

7. The electrode foil pretreatment method according to claim 1, characterized in that: In step S101, the mass ratio of lanthanum nitrate hexahydrate, titanium tetrachloride and deionized water is 1:(15-30):(120-200).

8. The electrode foil pretreatment method according to claim 1, characterized in that: The mass ratio of chitosan, glutaraldehyde, sodium hexametaphosphate and deionized water in step S104 to titanium tetrachloride in step S101 is 1:(0.5-2):(5-10):(80-150):(20-30).

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