An electro-polymerized conductive polymer modified aluminum current collector, and a preparation method and application thereof

Abstract

This invention provides an electropolymer-modified aluminum current collector, its preparation method, and its application, relating to the field of aluminum foil current collector technology. By modifying the current collector surface, it primarily addresses the interface problem between the current collector and the active material, thereby improving the performance of lithium-ion batteries. This invention uses an aluminum foil current collector as the anode, a graphite plate as the cathode, and an acidic solution of a conductive polymer monomer as the electrolyte. Anodizing electropolymerization is performed using a constant current or constant voltage method, followed by washing and drying to obtain the electropolymer-modified aluminum current collector. The conductive polymer monomer is at least one of aniline, thiophene, and pyrrole; the concentration of the conductive polymer monomer in the electrolyte is 0.1-1.0 mol / L; and the polymerization time is 5-10 min. This invention effectively reduces the contact resistance between the current collector and the active material, improves the bonding strength between the coating and the substrate, and enhances the corrosion resistance of the current collector, showing promising application prospects.

Description

Technical Field

[0001] This invention relates to the field of aluminum foil current collector technology, and in particular to an electropolymerized conductive polymer modified aluminum current collector, its preparation method and application. Background Technology

[0002] Aluminum foil has become the most widely used current collector material in lithium-ion battery cathodes due to its excellent conductivity, moderate electrochemical stability, and low cost. However, the smooth and flat surface of traditional aluminum foil results in poor interfacial compatibility with the cathode active material slurry, leading to insufficient bonding strength and high interfacial contact resistance, which in turn restricts the overall rate performance of the battery. Furthermore, during long-term charge-discharge cycles, aluminum foil is susceptible to corrosion from electrolytes containing corrosive ions. The corrosion products on the surface not only continuously increase the battery's internal resistance, but the micro-fragments that detach from the corrosion can also puncture the separator, causing internal short circuits and other problems.

[0003] To address these issues, researchers have attempted to introduce functional coatings onto the surface of aluminum foil, using materials including carbon-based materials, microporous materials, and conductive polymers. Among these, conductive polymers are considered the most promising candidates for current collector modification due to their excellent intrinsic conductivity, high flexibility, and compatibility with active materials. However, existing conductive polymer modification methods have several limitations: physical vapor deposition (such as magnetron sputtering) requires stringent conditions like high vacuum, resulting in large equipment investments and low target utilization; chemical oxidative polymerization methods struggle to precisely control coating morphology and thickness; and some conductive polymer raw materials are expensive, with complex synthesis processes, leading to high overall preparation costs and hindering large-scale deployment.

[0004] Therefore, developing a simple, parameter-controllable, and low-cost surface modification method for aluminum foil current collectors is of great practical significance. Summary of the Invention

[0005] In view of this, the present invention provides an electropolymerized conductive polymer-modified aluminum current collector, its preparation method, and its application. The present invention uses an aluminum foil current collector as the anode and an acidic solution of conductive polymer monomers as the electrolyte, employing a constant current or constant voltage anodic oxidation electrochemical polymerization process to construct an in-situ conductive polymer coating with a honeycomb nanostructure on the surface of the aluminum foil current collector. This achieves precise control of the interfacial properties of the aluminum foil current collector, effectively reducing the contact resistance between the current collector and the active material, improving the bonding strength between the coating and the substrate, and enhancing the corrosion resistance of the current collector, thus showing promising application prospects.

[0006] A method for preparing an electropolymer-modified aluminum current collector includes the following steps: Using an aluminum foil current collector as the anode, a graphite plate as the cathode, and an acidic solution of conductive polymer monomers as the electrolyte, anodic oxidation electropolymerization is carried out by constant current or constant voltage, followed by washing and drying to obtain an electropolymerized conductive polymer modified aluminum current collector.

[0007] Preferably, the aluminum foil current collector is pretreated before use, and the method is as follows: remove dirt and oxide layer from the surface of the aluminum foil current collector with a low-concentration acidic solution; the acidic solution is a 0.1-1 mol / L hydrochloric acid, phosphoric acid or sulfuric acid solution.

[0008] Preferably, the electrolyte is prepared as follows: a conductive polymer monomer is dissolved in an acidic solution and heated and stirred until homogeneous; the conductive polymer monomer is at least one of aniline, thiophene, and pyrrole; the acidic solution is a phosphoric acid solution, sulfuric acid solution, or hydrochloric acid solution with a concentration of 0.1-1.0 mol / L; the heating and stirring temperature is 20-50℃; and the concentration of the conductive polymer monomer in the electrolyte is 0.1-1.0 mol / L.

[0009] Preferably, the current is 0.001-0.010 A / cm. 2 The voltage is 0.01-10 V / cm. 2 That is, a voltage of 0.01-10 V is applied for each square centimeter of aluminum foil area, and the polymerization time is 5-10 min.

[0010] Preferably, the washing and drying process is repeated 1-2 times, and the drying temperature is 40-80℃.

[0011] The second aspect of the present invention is to provide a modified aluminum current collector prepared according to the above method, wherein the current collector is coated with a conductive polymer coating, and the surface has a circular honeycomb structure with a diameter of 10-50 nm and a thickness of 100-500 nm.

[0012] A third aspect of the present invention is to provide the application of the above-mentioned modified aluminum current collector in lithium-ion batteries or sodium-ion batteries, specifically by coating a positive electrode material slurry onto the surface of the modified aluminum current collector and then assembling the battery.

[0013] Preferably, the cathode material slurry is a lithium iron phosphate cathode material, a ternary cathode material, or a sodium-ion battery cathode material.

[0014] Compared with the prior art, the beneficial technical effects of the present invention are as follows: This invention employs an electrochemical polymerization method to deposit a conductive polymer coating on the surface of aluminum foil in situ. The entire process is completed in a normal pressure and low temperature liquid phase environment, without the need for harsh conditions such as high vacuum or high temperature. The equipment requirements are low, the operation is convenient, which helps to reduce production costs and realize large-scale continuous preparation.

[0015] This invention can precisely adjust the pore size and thickness of the honeycomb nanostructure of the coating by controlling parameters such as current density, monomer concentration and polymerization time. The resulting three-dimensional porous network structure significantly increases the effective contact area between the current collector and the active material, improves the interfacial bonding strength, and effectively reduces the contact resistance.

[0016] The uniform and dense conductive polymer coating on the modified current collector of this invention forms a physical shield for the aluminum foil substrate, effectively blocking the direct contact between corrosive ions in the electrolyte and the aluminum foil, inhibiting the self-corrosion and electrochemical corrosion of the aluminum foil, helping to maintain the structural integrity of the current collector during long-term cycling, and reducing the rate of increase in battery internal resistance.

[0017] The modified aluminum foil current collector prepared by this invention can be used to assemble lithium-ion or sodium-ion batteries, which can significantly improve the rate performance and cycle stability of the battery and has good application value in practical applications. Attached Figure Description

[0018] The present invention will be further described below with reference to the accompanying drawings.

[0019] Figure 1 The image shows the FT-IR spectrum of the electropolymer-modified aluminum current collector of Example 1 of this invention. Figure 2 This is a surface SEM image of the electropolymer-modified aluminum current collector of Example 1 of the present invention; Figure 3 This is a cross-sectional SEM image of the electropolymer-modified aluminum current collector of Example 1 of the present invention; Figure 4 This is a comparison chart of the performance test results of lithium iron phosphate batteries assembled with electropolymerized conductive polymer-modified aluminum current collectors and unmodified aluminum current collectors in Example 1 of the present invention. Detailed Implementation

[0020] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0021] In the following examples and comparative examples, the thickness data and capacity retention rate data in step S4 are all rounded to multiples of 5.

[0022] Unless otherwise specified, all experiments were repeated three times, and the results are expressed as averages.

[0023] Example 1: A method for preparing an electropolymer-modified aluminum current collector, comprising the following steps: S1. Soak the aluminum foil current collector in 0.1 mol / L hydrochloric acid solution at room temperature for 2 min to remove dirt and oxide layer from the surface of the aluminum foil current collector; S2. Dissolve aniline in a 0.4 mol / L phosphoric acid solution, heat and stir at 40℃ for 30 min to obtain an electrolyte with an aniline concentration of 0.3 mol / L; S3. Using the above-mentioned aniline solution as the electrolyte, a graphite plate as the cathode, and a treated aluminum foil current collector as the anode, a current is applied at 0.005 A / cm. 2 Electrochemical polymerization was carried out at a constant current at 40°C for 10 min; S4. Wash with water once and dry at 50℃ for 5 min to obtain electropolymerized conductive polymer modified aluminum current collector (PANI / Al-0.4). The current collector has a light green surface and a microstructure of a circular honeycomb structure with a diameter of 20 nm and a thickness of 240 nm. S5. A lithium iron phosphate cathode material slurry was coated onto the surface of the electropolymer-modified aluminum current collector, and a lithium-ion battery was assembled. Electrochemical performance was then tested. The test results are shown below. Figure 4 .

[0024] At 2C rate, the capacity of lithium iron phosphate batteries increased by 10% after modification with aluminum foil current collectors, and maintained 68% of the capacity after 1000 cycles, which is 20% higher than that of batteries with unmodified aluminum foil current collectors (i.e., aluminum foil current collectors pretreated in step S1).

[0025] Example 2 The difference from Example 1 is as follows: S2. Thiophene was dissolved in a 0.3 mol / L sulfuric acid solution and heated and stirred at 40°C for 15 min to obtain an electrolyte with a thiophene concentration of 0.40 mol / L. S3. Using the above-mentioned thiophene solution as the electrolyte, a graphite plate as the cathode, and a treated aluminum foil current collector as the anode, a current is applied at 0.55 V / cm. 2 Electrochemical polymerization was carried out at a constant voltage at 40°C for 8 min. S4. After washing with water twice, the aluminum foil current collector surface turns black after drying at 60℃ for 5 min. The surface microstructure is a circular honeycomb structure with a diameter of 30 nm and a thickness of 220 nm. S5. Coat the surface of the electropolymerized conductive polymer-modified aluminum current collector with lithium iron phosphate cathode material slurry, assemble a lithium-ion battery, and conduct electrochemical performance testing.

[0026] At 2C rate, the capacity of lithium iron phosphate batteries increased by 12% after modification with aluminum foil current collectors, and maintained 65% of the capacity after 1000 cycles, which is 15% higher than that of batteries with unmodified aluminum foil current collectors.

[0027] Example 3 The difference from Example 1 is as follows: S2. Thiophene and aniline were dissolved in a 0.3 mol / L phosphoric acid solution and heated and stirred at 40°C for 30 min. The resulting electrolyte contained 0.20 mol / L thiophene and 0.20 mol / L aniline, respectively. S3. Using the above mixed solution as the electrolyte, a graphite plate as the cathode, and the treated aluminum foil current collector as the anode, a current collector is passed through a flow rate of 0.006 A / cm. 2 Electrochemical polymerization was carried out at a constant current at 40°C for 8 min. S4. After washing with water once and drying at 60℃ for 5 min, the surface of the aluminum foil current collector is gray, and the surface microstructure is a circular honeycomb structure with a diameter of 30 nm and a thickness of 230 nm. S5. Coat the surface of the electropolymerized conductive polymer-modified aluminum current collector with lithium iron phosphate cathode material slurry, assemble a lithium-ion battery, and conduct electrochemical performance testing.

[0028] At 2C rate, the capacity of lithium iron phosphate batteries increased by 9% after modification with aluminum foil current collectors, and maintained 69% of the capacity after 1000 cycles, which is 22% higher than that of batteries with unmodified aluminum foil current collectors.

[0029] Example 4 The difference from Example 1 is as follows: S2. Dissolve pyrrole in a 0.3 mol / L phosphoric acid solution and heat and stir at 40°C for 30 min to obtain an electrolyte with a pyrrole concentration of 0.50 mol / L. S3. Using the above mixed solution as the electrolyte, a graphite plate as the cathode, and a treated aluminum foil current collector as the anode, a current collector is passed through a flow rate of 0.008 A / cm. 2 Electrochemical polymerization was carried out at a constant current at 40°C for 8 min. S4. After washing with water once and drying at 60℃ for 5 min, the surface of the aluminum foil current collector is light gray, and the surface microstructure is a circular honeycomb structure with a diameter of 33 nm and a thickness of 230 nm. S5. Coat the surface of the electropolymerized conductive polymer-modified aluminum current collector with lithium iron phosphate cathode material slurry, assemble a lithium-ion battery, and conduct electrochemical performance testing.

[0030] At 2C rate, the capacity of lithium iron phosphate batteries increased by 15% after modification with aluminum foil current collectors, and maintained 70% of the capacity after 1000 cycles, which is 23% higher than that of batteries with unmodified aluminum foil current collectors.

[0031] Example 5 The difference from Example 1 is as follows: S2. Thiophene, pyrrole, and aniline were dissolved in a 0.3 mol / L phosphoric acid solution and heated and stirred at 40°C for 30 min. The resulting electrolyte contained 0.15 mol / L, 0.15 mol / L, and 0.20 mol / L, respectively. S3. Using the above mixed solution as the electrolyte, a graphite plate as the cathode, and the treated aluminum foil current collector as the anode, a current collector is passed through a flow rate of 0.003 A / cm. 2 Electrochemical polymerization was carried out at a constant current for 5 min at 40°C. S4. After washing with water once and drying at 60℃ for 5 min, the surface of the aluminum foil current collector is light green, and the surface microstructure is a circular honeycomb structure with a diameter of 30 nm and a thickness of 210 nm. S5. Coat the surface of the electropolymerized conductive polymer-modified aluminum current collector with lithium iron phosphate cathode material slurry, assemble a lithium-ion battery, and conduct electrochemical performance testing.

[0032] At 2C rate, the capacity of lithium iron phosphate batteries increased by 17% after modification with aluminum foil current collectors, and maintained 74% of the capacity after 1000 cycles, which is 24% higher than that of batteries with unmodified aluminum foil current collectors.

[0033] Example 6 The difference from Example 1 is as follows: S2. Thiophene and aniline were dissolved in a 0.3 mol / L phosphoric acid solution and heated and stirred at 40°C for 30 min. The resulting electrolyte contained 0.16 mol / L thiophene and 0.20 mol / L aniline. S3. Using the above mixed solution as the electrolyte, a graphite plate as the cathode, and the treated aluminum foil current collector as the anode, a current collector is passed through a flow rate of 0.006 A / cm. 2 Electrochemical polymerization was carried out at a constant current at 40°C for 8 min. S4. After washing with water once and drying at 60℃ for 5 min, the surface of the aluminum foil current collector is gray, and the surface microstructure is a circular honeycomb structure with a diameter of 30 nm and a thickness of 230 nm. S5. Coat the surface of the electropolymerized conductive polymer-modified aluminum current collector with sodium iron pyrophosphate cathode material slurry, assemble the sodium iron pyrophosphate battery, and conduct electrochemical performance testing.

[0034] At 2C rate, the capacity of the sodium iron pyrophosphate battery increased by 13% after modification with aluminum foil current collector, and maintained 65% of the capacity after 1000 cycles, which is 15% higher than that of the unmodified aluminum foil current collector battery.

[0035] Comparative Example 1 The difference from Example 1 is as follows: Step S3 is modified as follows: The pretreated aluminum foil current collector is immersed in a 0.4 mol / L phosphoric acid solution containing 0.2 mol / L aniline and 10% ammonium persulfate (APS, oxidant), and allowed to stand at 0℃ for 12 min for chemical oxidation polymerization. After removal, it is washed once with water and dried at 50℃ for 5 min to obtain chemically oxidized aniline modified aluminum foil current collector. Its surface microstructure is granular spherical with a particle diameter of 900 nm.

[0036] At a 2C rate, the initial capacity of the lithium iron phosphate battery is 126 mAh·g. -1 After 1000 cycles, the capacity retention rate is 50%.

[0037] Comparative Example 2 The difference from Example 1 is as follows: Step S1 was omitted (i.e., no pretreatment was performed on the aluminum foil current collector, and the original aluminum foil was used directly), while the other conditions remained unchanged. The resulting current collector surface morphology was spherical with a particle diameter of 700 nm.

[0038] At a 2C rate, the initial capacity of the lithium iron phosphate battery is 118 mAh·g. -1 After 1000 cycles, the capacity retention rate is 40%.

[0039] Comparative Example 3 The difference from Example 1 is that: In step S3, the constant current density is changed to 0.0005 A / cm². 2 With all other conditions remaining unchanged, the resulting current collector surface has a honeycomb-like microstructure with a pore size of 5 nm and a coating thickness of 30 nm.

[0040] At a 2C rate, the initial capacity of the lithium iron phosphate battery is 113 mAh·g. -1 After 1000 cycles, the capacity retention rate is 35%.

[0041] Comparative Example 4 The difference from Example 1 is that: In step S3, the constant current density is changed to 0.015 A / cm. 2 With all other conditions remaining unchanged, the resulting current collector surface has a honeycomb-like microstructure with a pore size of 65 nm and a coating thickness of 800 nm.

[0042] At a 2C rate, the initial capacity of the lithium iron phosphate battery is 101 mAh·g. -1 After 1000 cycles, the capacity retention rate is 35%.

[0043] Comparative Example 5 The difference from Example 1 is that: In step S3, the electrochemical polymerization time was changed to 2 min, while the other conditions remained unchanged, and the coating thickness was 20 nm.

[0044] At a 2C rate, the initial capacity of the lithium iron phosphate battery is 105 mAh·g. -1 After 1000 cycles, the capacity retention rate is 40%.

[0045] Comparative Example 6 The difference from Example 1 is that: In step S3, the electrochemical polymerization time was changed to 15 min, while the other conditions remained unchanged, and the coating thickness was 900 nm.

[0046] At a 2C rate, the initial capacity of the lithium iron phosphate battery is 102 mAh·g. -1 After 1000 cycles, the capacity retention rate was 39%.

[0047] Comparative Example 7 The difference from Example 1 is that: In step S2, the concentration of aniline in the electrolyte was changed to 0.05 mol / L, while other conditions remained unchanged. The resulting current collector surface microstructure was a sparse honeycomb structure with small pore size, and the coating thickness was 90 nm.

[0048] At a 2C rate, the initial capacity of the lithium iron phosphate battery is 106 mAh·g. -1 After 1000 cycles, the capacity retention rate was 42%.

[0049] Comparative Example 8 The difference from Example 1 is that: In step S2, the concentration of aniline in the electrolyte was changed to 1.5 mol / L, while the other conditions remained unchanged, and the coating thickness was 95 nm.

[0050] At a 2C rate, the initial capacity of the lithium iron phosphate battery is 104 mAh·g. -1 After 1000 cycles, the capacity retention rate was 42%.

[0051] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for preparing an electropolymer-modified aluminum current collector, characterized in that, Includes the following steps: Using an aluminum foil current collector as the anode, a graphite plate as the cathode, and an acidic solution of conductive polymer monomers as the electrolyte, anodic oxidation electropolymerization is carried out by constant current or constant voltage, followed by washing and drying to obtain an electropolymerized conductive polymer modified aluminum current collector. The conductive polymer monomer is at least one of aniline, thiophene, and pyrrole; The concentration of conductive polymer monomers in the electrolyte is 0.1-1.0 mol / L; The polymerization time is 5-10 min.

2. The preparation method according to claim 1, characterized in that, The aluminum foil current collector is pretreated before use, and the method is as follows: remove dirt and oxide layer from the surface of the aluminum foil current collector with a low-concentration acidic solution.

3. The preparation method according to claim 2, characterized in that, The low-concentration acidic solution is a 0.1-1 mol / L hydrochloric acid, phosphoric acid, or sulfuric acid solution.

4. The preparation method according to claim 1, characterized in that, The electrolyte is prepared as follows: the conductive polymer monomer is dissolved in an acidic solution and heated and stirred until homogeneous.

5. The preparation method according to claim 1, characterized in that, The current is 0.001-0.010 A / cm. 2 .

6. The preparation method according to claim 1, characterized in that, The voltage is 0.01-10 V / cm 2 .

7. An electropolymer-modified aluminum current collector prepared by the method according to any one of claims 1-6.

8. The electropolymer-modified aluminum current collector according to claim 7, characterized in that, The surface of the electropolymerized conductive polymer modified aluminum current collector is coated with a conductive polymer coating, and the surface has a circular honeycomb structure with a diameter of 10-50 nm and a thickness of 100-500 nm.

9. The application of the modified aluminum current collector prepared by the method according to any one of claims 1-6 in lithium-ion batteries or sodium-ion batteries.

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