Preparation method of battery reference electrode with high specific surface area

Abstract

The invention belongs to the technical field of battery preparation, and particularly relates to a preparation method of a high-specific-surface-area battery reference electrode, which comprises the following steps: pre-treating a metal wire, annealing, placing the metal wire in a preset acid environment, and applying a specified negative overpotential to the metal electrode through an external circuit to obtain the high-specific-surface-area battery reference electrode. Pores are introduced into the surface of the metal wire through cathode corrosion to prepare a porous material to increase the specific surface area of the reference electrode. According to the preparation method disclosed by the invention, the battery reference electrode with high stability and high specific surface area can be prepared, and the prepared reference electrode has extremely high application value.

Description

Technical Field

[0001] The invention belongs to the technical field of battery preparation, and particularly relates to a method for preparing a battery reference electrode with a high specific surface area. Background Art

[0002] In the research and preparation of secondary batteries, a reference electrode is often required to study the potential changes of the positive or negative electrode during charge and discharge. By measuring the potential changes of a single electrode, detailed information about the internal battery reactions can be obtained. In existing technologies, the reference electrodes used are simply ordinary metal objects, which cannot accurately guarantee the potential measurement process and, consequently, cannot fully evaluate the performance of the battery electrodes. Therefore, how to prepare a battery reference electrode with high stability and high specific surface area, and then accurately detect the potential changes of the positive or negative electrode during charge and discharge, has become a current research focus and difficulty. Summary of the Invention

[0003] The purpose of the present invention is to provide a method for preparing a battery reference electrode with a high specific surface area in response to the deficiencies of the existing technology, which can not only ensure the preparation of a battery reference electrode with high stability and high specific surface area, but also make the prepared reference electrode have extremely high application value.

[0004] In order to achieve the above object, the present invention adopts the following technical solutions:

[0005] A method for preparing a battery reference electrode with a high specific surface area comprises the following steps:

[0006] Step 1: pre-treating the metal wire by immersing it in a specified acid solution for 90 to 130 minutes, then rinsing the surface of the acid-immersed metal wire, and then annealing the metal wire in an inert gas environment at a temperature of 380° C. to 430° C. for 50 to 70 minutes;

[0007] Step 2: Use the inert material electrode as the counter electrode, the metal wire annealed in step 1 as the working electrode, and a reference electrode. Connect the counter electrode, reference electrode, and working electrode to an electrochemical workstation. Simultaneously, immerse the counter electrode, reference electrode, and working electrode in a preset acid environment and let them stand for 280s to 320s. Then, use the open circuit potential method to measure the potential difference between the reference electrode and the working electrode.

[0008] Step 3: Based on the potential difference between the reference electrode and the working electrode measured in Step 2, a negative overpotential of -100 mV or more is applied to the metal wire, and the metal wire is continuously charged in a preset acid environment for more than 10 hours to produce a porous metal wire, wherein the applied overpotential is removed every 1.5 to 2.5 hours during the charging period, and the wire is allowed to stand for 280 to 320 seconds after removal, and then the potential difference between the reference electrode and the working electrode is remeasured;

[0009] Step 4: Clean the porous metal wire obtained in step 3 to remove surface impurities and solution residues on the porous metal wire, and then dry the porous metal wire to obtain the desired porous reference electrode.

[0010] Furthermore, the reagents used for surface rinsing in step 1 include deionized water, anhydrous ethanol, acetone, ethyl acetate, etc.

[0011] Furthermore, in the step 1, the metal wire after acid immersion and then rinsing is subjected to high temperature annealing in an inert gas atmosphere, and the inert gas includes nitrogen, argon, helium, etc.

[0012] Furthermore, the step 2 also includes: first adding the required metal salt to a preset acid solution to form a required acid environment, then immersing the metal wire in the acid environment, and performing cathode corrosion to generate the required pores on the surface of the metal wire to increase the specific surface area of ​​the electrode.

[0013] Furthermore, the addition of metal salts such as lithium chloride, sodium chloride, potassium chloride, etc. in step 2 can improve the conductivity of the solution and accelerate the initiation of cathode corrosion.

[0014] Furthermore, the step one also includes: selecting copper wire or copper-based alloy wire as the metal wire.

[0015] Furthermore, the acid solution specified in step one is concentrated sulfuric acid or dilute hydrochloric acid, and the related operations in step one are related preparations before the metal wire is subjected to cathode corrosion treatment.

[0016] Furthermore, the preset acid solution in step 2 contains concentrated sulfuric acid, and the concentration of the concentrated sulfuric acid may be 97.5% to 98.3%.

[0017] Furthermore, the inert material electrode in step 2 is platinum wire or graphite, and one of a saturated calomel electrode, a silver / silver chloride electrode, and a mercury / mercurous sulfate electrode is selected as the reference electrode in step 2.

[0018] Furthermore, in step three, the metal wire is continuously charged in a preset acid environment for 15 to 18 hours, and a specified negative overpotential is applied to the metal electrode through an external circuit during the charging process.

[0019] Furthermore, a plurality of micron-level and nanometer-level corrosion holes are formed on the surface of the metal wire. The diameter of the micron-level corrosion holes may be 0.1 μm to 5 μm, and the diameter of the nanometer-level corrosion holes may be 1 nm to 100 nm.

[0020] Furthermore, the pore size of the micron-level corrosion pores can be 0.1μm~1μm, 1μm~2μm, 2μm~3μm, 3μm~4μm, 4μm~5μm, and the pore size of the nano-level corrosion pores can be 1nm~10nm, 10nm~25nm, 25nm~50nm, 50nm~75nm, 75nm~100nm.

[0021] Furthermore, step 4 further includes ultrasonic cleaning of the surface of the porous metal wire for 2 to 4 minutes. After the cathode corrosion treatment in steps 2 and 3 is completed, the porous metal wire needs to be rinsed and ultrasonically cleaned multiple times to remove the solution residue and various compound residues attached to the electrode surface. The rinse solution used includes deionized water and organic solvents such as acetone, ethanol, acetone, and ethyl acetate.

[0022] Furthermore, the method further includes: Step 5, introducing a porous reference electrode into the battery, connecting the positive electrode of the battery and the porous reference electrode after the battery manufacturing process is completed, and using a constant current for lithium plating.

[0023] The beneficial effects of the present invention are as follows: during the processing of the reference electrode, the present invention controls the pore distribution and specific surface area of ​​the metal wire surface by controlling the annealing parameters, corrosion overpotential and corrosion time, adjusts the grain and grain boundary distribution of the metal wire by annealing, and improves the service life of the metal wire; introduces corrosion pores on the metal wire surface by cathode corrosion to make a porous material so that the metal wire surface is rough and the specific surface area of ​​the metal wire is increased, so that more lithium plating reaction sites are present on the surface of the metal wire when lithium is plated, significantly improving the lithium plating reaction rate and the amount of lithium plating; and the rough metal wire surface will also greatly improve the stability of the metallic lithium on the metal wire surface, ensuring the preparation of a battery reference electrode with high stability and high specific surface area. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Schematic diagram of the reference electrode of the present invention.

[0025] Figure 2 This is a comparison diagram of corrosion differences of corrosion solutions containing different cations of the present invention.

[0026] Figure 3 This is a comparison diagram of the differences in corrosion marks caused by different cation concentrations in the acid solution of the present invention.

[0027] Figure 4Schematic diagram of the potential stability of the existing lithium-plated copper wire during cycling that has not been treated with the acid solution corrosion of the present invention.

[0028] Figure 5 This is a schematic diagram of the potential stability of the lithium-plated copper wire obtained by first subjecting the porous copper wire to a short-time acid corrosion treatment and then plating lithium in the cycle according to the present invention.

[0029] Figure 6 This is a schematic diagram of the potential stability of the lithium-plated copper wire obtained by first subjecting the porous copper wire to a long-term acid corrosion treatment and then plating lithium in the cycle according to the present invention. DETAILED DESCRIPTION

[0030] If certain words are used in the specification and claims to refer to specific components, those skilled in the art should understand that manufacturers may use different terms to refer to the same component. This specification and claims do not use differences in name as a way to distinguish components, but rather use differences in the functions of the components as the criteria for distinction. For example, the term "including" mentioned throughout the specification and claims is an open-ended term and should be interpreted as "including but not limited to". "Approximately" means that within an acceptable error range, those skilled in the art can solve technical problems within a certain error range and basically achieve technical effects.

[0031] The inventors discovered that using conventional lithium-plated copper wire as a reference electrode for research suffers from drawbacks such as prolonged lithium plating time during preparation and poor surface lithium stability in the resulting reference electrode. If the copper wire needs to be re-plated with lithium before each potential measurement, the decomposition of the surface lithium at the end of a long test can lead to inaccurate potential measurements. Consequently, conventional lithium-plated copper wire can lead to inaccurate potential measurements during experiments and increased workload.

[0032] In order to meet the working needs of the reference electrode of lithium-ion batteries and overcome the defects of the existing technology, the inventor introduced corrosion pores on the surface of the copper wire through cathode corrosion before introducing the copper wire into the battery cell to increase the specific surface area of ​​the copper wire, thereby increasing the lithium plating amount and lithium plating stability on the surface of the copper wire.

[0033] The technical solution of the present invention is further described in detail below, but is not intended to limit the present invention.

[0034] A method for preparing a battery reference electrode with a high specific surface area comprises the following steps:

[0035] Step 1: Take a copper wire with a diameter of 0.08mm to 0.1mm (copper content of at least 99.95%) and soak it in concentrated sulfuric acid for 1.8 hours to 2 hours. Then, rinse the surface of the copper wire with deionized water and anhydrous ethanol to ensure that the surface of the copper wire is clean. After rinsing, the copper wire is annealed at 400 degrees Celsius in a nitrogen atmosphere for one hour;

[0036] Step 2: Separately measure 53.45 mL of 98% concentrated sulfuric acid, add deionized water to the 98% concentrated sulfuric acid to dilute it to 1 L, then add 1 g to 1.5 g of NaCl to the concentrated sulfuric acid solution to increase the conductivity of the acidic solution, use a platinum wire as a counter electrode, a saturated calomel electrode as a reference electrode, connect the copper wire treated in step 1 as a working electrode to an electrochemical workstation, immerse the electrode in an acidic solution configured to accelerate cathode corrosion, let it stand for 280 to 300 seconds, turn on the OCP mode in the electrochemical workstation to measure, and obtain the required open circuit potential;

[0037] Step 3: Based on the open circuit potential, an overpotential of -300 mV was applied to the copper wire and charging continued for 16 hours. During this period, the overpotential was removed every 2 hours, the system was allowed to rest for 280-300 seconds, and the open circuit potential was remeasured in this state.

[0038] Step 4: After all treatments are completed, the porous copper wire obtained in step 3 is cleaned with deionized water and acetone, and then the electrode is ultrasonically cleaned in deionized water for 2.5 to 3 minutes to remove impurities, solution residues, and surface compound residues on the copper wire surface. The sample is then dried to obtain a porous reference copper wire.

[0039] Step 5: Introduce the porous reference copper wire into the battery. After the battery manufacturing process is completed, connect the positive electrode of the battery to the porous reference copper wire and use a constant current of 0.5 mA to 1 mA for lithium plating.

[0040] In step one, the optimal immersion time of the copper wire in the acid solution is 90 minutes to 130 minutes, the optimal annealing temperature of the copper wire in an inert gas environment is 380°C to 430°C, and the optimal annealing time is 50 minutes to 70 minutes. By adjusting the grain and grain boundary distribution of the copper wire by annealing, the service life of the copper wire can be effectively improved.

[0041] To make the technical solutions and advantages of the present invention clearer, Figures 1 to 6 The present invention and its beneficial effects are further described in detail with reference to the accompanying drawings, but the embodiments of the present invention are not limited thereto.

[0042] Example 1

[0043] A method for preparing a battery reference electrode with a high specific surface area comprises the following steps:

[0044] Step 1: Take a copper wire with a diameter of 0.08 mm (copper content of 99.98%) and soak it in concentrated sulfuric acid for 2 hours. Rinse the surface of the copper wire three times with deionized water and anhydrous ethanol to ensure the surface is clean. After rinsing, anneal the copper wire at 400°C for 1 hour in a nitrogen atmosphere, cool it to room temperature, and then take it out.

[0045] Step 2: Separately measure 53.45 mL of 98% concentrated sulfuric acid, dilute the 98% concentrated sulfuric acid to 1 L with deionized water, and then add 1 g of NaCl to the concentrated sulfuric acid solution to increase the conductivity of the acidic solution. Use a platinum wire as a counter electrode and a saturated calomel electrode as a reference electrode. Connect the copper wire treated in step 1 as a working electrode to an electrochemical workstation, immerse each electrode in an acidic solution configured to accelerate cathode corrosion, let it stand for 300 seconds, turn on the OCP mode in the electrochemical workstation for measurement, and obtain the required open circuit potential V0;

[0046] Step 3: Based on the open circuit potential, an overpotential of -300 mV was applied to the copper wire and charging continued for 16 hours. During this period, the overpotential was removed every 2 hours, the system was allowed to rest for 300 seconds, and the open circuit potential was remeasured in this state.

[0047] Step 4: After all treatments are completed, the porous copper wire obtained in step 3 is cleaned with deionized water and acetone, and then the electrode is ultrasonically cleaned in deionized water for 3 minutes to remove impurities, solution residues and surface compound residues on the copper wire surface. The sample is then dried to obtain a porous reference copper wire.

[0048] Step 5: Introduce the porous reference copper wire into the battery. After the battery is manufactured, connect the positive electrode of the battery to the porous reference copper wire, and use a constant current of 0.5mA to 1mA to discharge for lithium plating.

[0049] Example 2

[0050] The difference from Example 1 is that in step 3, the overvoltage is set to -150 mV, the continuous charging time is set to 12 hours, and the 1 g NaCl added in step 2 is changed to 1 g NaOH. The other steps are the same as in Example 1.

[0051] Example 3

[0052] The difference from Example 2 is that 1 g of NaOH in step 2 is replaced with 5 g of NaOH, and the other steps are the same as those in Example 2.

[0053] Example 4

[0054] The difference from Example 1 is that 1 g of NaCl in step 2 is replaced with 1 g of KOH, and the other steps are the same as those in Example 1.

[0055] Example 5

[0056] The difference from Example 1 is that 1 g of NaCl in step 2 is replaced with 1.5 g of LiOH, and the other steps are the same as those in Example 1.

[0057] Example 6

[0058] The difference from Example 1 is that the copper wire with a diameter of 0.08 mm (copper content of 99.98%) in step 1 is changed to a 0.1 mm silver-plated copper wire, and concentrated sulfuric acid is changed to 0.1 mol dilute hydrochloric acid. The other steps are the same as in Example 1.

[0059] Comparative Example 1

[0060] The difference from Examples 1 to 6 is that ordinary copper wire is directly used for lithium plating, and the ordinary copper wire is not processed through steps 1 to 4 of Examples 1 to 6.

[0061] The potential of the reference electrodes obtained in Examples 1 to 6 and Comparative Example 1 was measured, and it was found that the lithium plating amount and lithium plating stability of Examples 1 to 6 were significantly better than those of Comparative Example 1.

[0062] It can be seen that Figure 1 As shown, the present invention provides a high specific surface area lithium-plated copper wire reference electrode for lithium-ion batteries. The above-mentioned preparation method makes the corrosion marks on the surface of the copper wire controllable. At the same time, the corrosion effect can be changed by controlling the time, overpotential, tempering parameters and the type of cations in the acid solution to obtain the most stable lithium plating layer.

[0063] like Figure 2 As shown, in the present invention, different types of cations can be introduced into the same acidic solution in step 2, which will cause different types of corrosion; Figure 3 As shown, in the present invention, different corrosion traces may be caused by different cation concentrations in the same acidic solution in step 2.

[0064] Depend on Figures 4 to 6 It can be seen that the existing lithium-plated copper wire that has not been treated with acid solution corrosion of the present invention has poor potential stability in the cycle, while the lithium-plated copper wire obtained by short-term acid corrosion treatment to obtain porous copper wire and then lithium plating has good potential stability in the cycle. Figure 4 Compared with the previous experiment, the potential stability of the lithium-plated copper wire obtained by long-term acid corrosion treatment and then lithium plating has reached the most ideal state during the cycle. Therefore, it can be determined that the potential stability of the copper wire is significantly improved after the cathode corrosion holes are introduced on the surface of the copper wire.

[0065] Based on the disclosure and teachings of the above description, those skilled in the art will be able to make changes and modifications to the above embodiments. Therefore, the present invention is not limited to the above specific embodiments. Any obvious improvements, substitutions, or modifications made by those skilled in the art based on the present invention fall within the scope of protection of the present invention. In addition, although certain specific terms are used in this description, these terms are only for convenience of description and do not constitute any limitation to the present invention.

Claims

1. A method for preparing a battery reference electrode with a high specific surface area, characterized in that: The following steps are involved: Step 1: pre-treating the metal wire by immersing it in a specified acid solution for 90 to 130 minutes, then rinsing the surface of the acid-immersed metal wire, and then annealing the metal wire in an inert gas environment at a temperature of 380° C. to 430° C. for 50 to 70 minutes; Step 2: Use the inert material electrode as the counter electrode, the metal wire annealed in step 1 as the working electrode, and a reference electrode. Connect the counter electrode, reference electrode, and working electrode to an electrochemical workstation. Simultaneously, immerse the counter electrode, reference electrode, and working electrode in a preset acid environment and let them stand for 280s to 320s. Then, use the open circuit potential method to measure the potential difference between the reference electrode and the working electrode. Step 3: Based on the potential difference between the reference electrode and the working electrode measured in Step 2, a negative overpotential of -100 mV or more is applied to the metal wire, and the metal wire is continuously charged in a preset acid environment for more than 10 hours to produce a porous metal wire, wherein the applied overpotential is removed every 1.5 to 2.5 hours during the charging period, and the wire is allowed to stand for 280 to 320 seconds after removal, and then the potential difference between the reference electrode and the working electrode is remeasured; Step 4: Clean the porous metal wire obtained in step 3 to remove surface impurities and solution residues on the porous metal wire, and then dry the porous metal wire to obtain the desired porous reference electrode.

2. The method for preparing a battery reference electrode with a high specific surface area according to claim 1, wherein: The second step also includes: first adding the required metal salt into a preset acid solution to form a required acid environment, then immersing the metal wire in the acid environment to perform cathode corrosion to generate the required pores on the surface of the metal wire.

3. The method for preparing a battery reference electrode with a high specific surface area according to claim 1, wherein: The step one also includes: selecting copper wire or copper-based alloy wire as the metal wire.

4. The method for preparing a battery reference electrode with a high specific surface area according to claim 1, wherein: The designated acid solution in step 1 is concentrated sulfuric acid or dilute hydrochloric acid.

5. The method for preparing a battery reference electrode with a high specific surface area according to claim 2, wherein: The preset acid solution in step 2 contains concentrated sulfuric acid.

6. The method for preparing a battery reference electrode with a high specific surface area according to claim 1, wherein: The inert material electrode in step 2 is platinum wire or graphite, and one of a saturated calomel electrode, a silver chloride electrode, and a mercurous sulfate electrode is selected as a reference electrode in step 2.

7. The method for preparing a battery reference electrode with a high specific surface area according to claim 2, wherein: A plurality of micron-scale and nanometer-scale corrosion holes are formed on the surface of the metal wire.

8. The method for preparing a battery reference electrode with a high specific surface area according to claim 5, wherein: In the step 3, the metal wire is continuously charged in a preset acid environment for 15 to 18 hours.

9. The method for preparing a battery reference electrode with a high specific surface area according to any one of claims 1 to 8, wherein: The step 4 further includes ultrasonic cleaning the surface of the porous metal wire for 2 minutes to 4 minutes.

10. The method for preparing a battery reference electrode with a high specific surface area according to any one of claims 1 to 8, wherein: The method also includes: Step 5, introducing a porous reference electrode into the battery, connecting the positive electrode of the battery and the porous reference electrode after the battery manufacturing process is completed, and using a constant current for lithium plating.

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