A method for testing the uniformity of the electrochemical activity of a negative electrode material of a water-based ionic battery

Abstract

The present application relates to the technical field of aqueous ion battery, and particularly relates to a method for testing electrochemical activity uniformity of negative electrode material of aqueous ion battery. The method comprises the following steps: preparing a sample pool, wherein the sample pool comprises a substrate layer and a negative electrode material layer to be tested on the substrate; placing the sample pool in a photo-assisted scanning electrochemical microscope system, and performing leveling, wherein the photo-assisted scanning electrochemical microscope system comprises a scanning electrochemical microscope system and a side-viewing CCD camera; and calculating the electrochemical activity uniformity of the surface of the negative electrode material to be tested. The method has the advantages of high speed and high precision by using the photo-assisted scanning electrochemical microscope system for leveling. The method does not depend on the assumption of the electrochemical activity uniformity of the surface to be tested in the actual operation of the traditional SECM system. The leveling time is less than 10 minutes each time, which is much less than 30 minutes required by the ordinary approximation curve leveling method. Therefore, the electrochemical property detection method in the present application is suitable for large-scale electrode screening, and has good application prospect.

Description

Technical Field

[0001] This invention relates to the field of aqueous ion battery technology, and in particular to a method for testing the electrochemical activity uniformity of anode materials in aqueous ion batteries. Background Technology

[0002] Aqueous-based ion batteries (such as zinc-ion and aluminum-ion batteries) have shown great potential in large-scale energy storage due to their high safety, low cost, and environmental friendliness. However, under real-world operating conditions, battery performance and lifespan largely depend on the spatial uniformity of the initial electrochemical properties of the negative electrode metal (such as zinc or aluminum). Inhomogeneous electrochemical activity can lead to localized preferential dissolution / deposition, causing problems such as dendrite growth and accelerated corrosion, thereby accelerating battery failure.

[0003] Currently, characterization of electrode material surface properties primarily employs non-in-situ techniques such as scanning electron microscopy (SEM) and X-ray diffraction (XRD), which struggle to reflect the spatial distribution of electrochemical activity in actual electrolyte environments with micrometer-level resolution in real time. Scanning electrochemical microscopy (SECM), as a high-resolution electrochemical imaging technique, can characterize the localized electrochemical activity of the substrate surface in situ by measuring the feedback current collected as a microprobe scans the electrode surface. Its core principle is based on the "feedback effect" between the probe and the substrate: when the probe approaches an active substrate, the substrate can regenerate the probe reactants, generating positive feedback and increasing the probe current; when it approaches an insulating region, material diffusion is hindered, generating negative feedback and decreasing the probe current. However, traditional SECM techniques and theoretical analysis models mainly target conductors or insulating substrates with relatively uniform surface electrochemical properties, where the feedback behavior (positive or negative) is relatively well-defined. This is entirely different from the actual situation of the negative electrode surface in aqueous ion batteries.

[0004] In practical studies, especially for metal anodes (such as Zn, Al, and Cu) in aqueous batteries that are prone to oxide layer formation or have complex surface states, SECM test results often exhibit strong inhomogeneity. The electrochemical activity of the substrate surface is not a simple binary division of "active" or "inert," but rather includes regions with uneven activity or moderate reaction kinetic rates. Existing SECM testing methods are too inefficient and cannot directly and quantitatively correlate this complex SECM feedback signal (including positive, negative, and anomalous feedback) with the spatial distribution and uniformity of the intrinsic electrochemical activity of the electrode material. Furthermore, they have failed to standardize it as an effective means of evaluating electrode material quality.

[0005] Therefore, existing technologies need to be improved. Summary of the Invention

[0006] In view of the shortcomings of the prior art, the purpose of this invention is to provide a method for testing the electrochemical activity uniformity of anode materials in aqueous ion batteries, aiming to solve the problems of insufficient spatial resolution and testing efficiency of existing micro-area electrochemical characterization techniques.

[0007] The technical solution of the present invention is as follows: A method for testing the electrochemical activity uniformity of anode materials in aqueous ion batteries includes the following steps: S1. Sample cell preparation: Prepare a sample cell for testing the electrochemical activity uniformity of the negative electrode material of an aqueous ion battery. The sample cell includes a substrate layer and a layer of the negative electrode material to be tested located on the substrate. S2. Leveling: The sample cell is placed in the light-assisted scanning electrochemical microscope system for leveling. The light-assisted scanning electrochemical microscope system includes a scanning electrochemical microscope system and a side-viewing CCD camera. S3. Calculate the surface electrochemical activity uniformity: After leveling, add electrolyte to the sample cell, and then use a light-assisted scanning electrochemical microscope system to perform an approximation curve test on the surface of the sample cell to confirm the current feedback mode. Then, perform two-dimensional surface scanning imaging. Based on the statistical analysis of the scanning imaging data, calculate the surface electrochemical activity uniformity of the negative electrode material to be tested according to Formula 1. , Among them, (I) T ) i This represents the current data obtained from the i-th probe scan; μ For all electrochemical current data I T Divide by I ∞ The average value represents the population mean; N represents the total number of data points in the population, and σ represents the standard deviation. Based on the calculated σ, a value greater than 0.05 indicates non-uniform electrochemical properties, while a value less than 0.05 indicates uniform electrochemical activity.

[0008] Optionally, the sample cell further includes an annular hydrophobic film covering the negative electrode material layer to be tested, wherein the inner periphery of the annular hydrophobic film covers the negative electrode material layer to be tested and encapsulates the outer edge of the electrolyte.

[0009] Optionally, the annular pore size of the annular hydrophobic film is 5-10 mm, and the thickness of the annular hydrophobic film is 50-100 μm.

[0010] Optionally, the volume of the electrolyte is 50-200 microliters.

[0011] Optionally, the light-assisted scanning electrochemical microscope system includes: The sample cell, dual potentiostat, sample stage with built-in leveling knob, ultra-microelectrode probe (micrometer-diameter needle tip), reference electrode, counter electrode, three-dimensional stepper motor, computer, and side-viewing CCD camera.

[0012] Optionally, the CCD camera is positioned 5-30 cm away from the test sample and the needle tip, and the spatial resolution of the CCD camera reaches 2-10 micrometers.

[0013] Optionally, in S2, leveling includes the following steps: S21. Randomly select three non-linear locations on the edge of the central circular hole on the surface of the negative electrode material in the sample cell. At each location, perform the following steps: control the microelectrode probe to advance at a speed of 5-20 micrometers / second to a distance of 10-20 micrometers from the surface of the negative electrode material; use the three-dimensional stepper motor configured by SECM to control the microelectrode probe to advance (advance speed 0.2 micrometers / second), stop when the probe tip touches the surface, and record the total actual advance distance by the computer, then retract the probe to the initial advance position. S22. Use the built-in leveling knob on the sample stage to fine-tune the base level until the three positions on the same scanning plane are at the same distance from the sample to be tested.

[0014] The optically assisted SECM method proposed in this application for rapid adjustment of the substrate level combines high-resolution optical imaging and tip contact technology. After performing three-point leveling, the angle between the substrate and the horizontal plane in the area within the three points can be less than 0.02°, which is superior to the traditional leveling technology based on approximation curves (leveling accuracy is only 0.2°).

[0015] Optionally, a CCD camera can be used to determine the distance between the microelectrode probe and the surface of the negative electrode material.

[0016] Optionally, the distance between two adjacent location points is 1-4 mm.

[0017] Optionally, in S3, before using a light-assisted scanning electrochemical microscope system to perform an approximation curve test on the sample cell surface to confirm the current feedback mode, the cyclic voltammetry curve of the ultramicroelectrode probe is measured at a distance of 1 mm from the sample cell surface to confirm that the ultramicroelectrode probe has reached a diffusion-controlled state in the prepared electrolyte.

[0018] Beneficial Effects: This invention provides a method for testing the electrochemical activity uniformity of anode materials in aqueous ion batteries. The method employs a light-assisted scanning electrochemical microscope (SECM) system for leveling, offering advantages of high speed and accuracy. This method does not rely on the assumption of uniform electrochemical activity on the test surface in traditional SECM systems. Each leveling session takes less than 10 minutes, significantly less than the 30 minutes required by conventional approximation curve-based leveling methods. Therefore, the electrochemical property detection method in this invention is suitable for large-scale electrode screening and has promising application prospects. Furthermore, this method can achieve micron- and sub-micron-scale electrochemical current imaging in environments close to real aqueous batteries, revealing the microscopic non-uniformity underlying the macroscopic performance of aqueous battery anode materials. Based on single-point approximation curves, multiple representative sites can be rapidly screened, while the area scanning mode can obtain large-area information. This method is applicable to various aqueous battery metal anode materials (such as Zn, Al, Cu, etc.). Attached Figure Description

[0019] Figure 1 This is a flowchart illustrating the process of testing the electrochemical activity uniformity of the negative electrode material in an aqueous ion battery according to the present invention.

[0020] Figure 2 This is a schematic diagram of the light-assisted scanning electrochemical microscope (SECM) system of the present invention.

[0021] Figure 3 This is a top view of the sample cell of the present invention, wherein points 1-3 correspond to the three needle insertion points in the method of adjusting the substrate level, and the white circle represents the hydrophobic film.

[0022] Figure 4 The figure shows the cyclic voltammetry curves of the ultramicroelectrode probe in the electrolyte. The black line corresponds to the electrolyte containing chloride ions, and the red line corresponds to the electrolyte without chloride ions. The distance d from the probe tip to the surface is greater than 1 mm.

[0023] Figure 5 These are the approximation curves of the ultramicroelectrode probes in Examples 1 and 3.

[0024] Figure 6 The curves are anomalous approximation curves of the ultramicroelectrode probe in Comparative Example 2.

[0025] Figure 7 This is a high-resolution image of the electrochemical current on the surface of the aluminum electrode in Example 1.

[0026] Figure 8 This is a high-resolution image of the electrochemical current on the surface of the copper electrode in Example 2.

[0027] Figure 9 This is a high-resolution image of the electrochemical current on the zinc electrode surface in Example 3.

[0028] Figure 10 This is a high-resolution image of the electrochemical current on the surface of the aluminum electrode in Comparative Example 1.

[0029] Figure 11 This is a high-resolution image of the electrochemical current on the surface of the aluminum electrode in Comparative Example 2.

[0030] Figure 12 This is a high-resolution image of the electrochemical current on the surface of the copper electrode in Comparative Example 3.

[0031] Figure 13 This is a high-resolution image of the electrochemical current on the surface of the copper electrode in Comparative Example 4.

[0032] Figure 14 This is a high-resolution image of the electrochemical current on the zinc electrode surface in Comparative Example 5.

[0033] Figure 15 This is a high-resolution image of the electrochemical current on the surface of the zinc electrode in Comparative Example 6. Detailed Implementation

[0034] This invention provides a method for testing the electrochemical activity uniformity of anode materials in aqueous ion batteries. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention is further described in detail below. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0035] This embodiment provides a method for testing the electrochemical activity uniformity of anode materials in aqueous ion batteries, such as... Figure 1 As shown, it includes the following steps: S1. Sample cell preparation: Prepare a sample cell for testing the electrochemical activity uniformity of the negative electrode material of an aqueous ion battery. The sample cell includes a substrate layer and a layer of the negative electrode material to be tested located on the substrate. S2. Leveling: The sample cell is placed in the light-assisted scanning electrochemical microscope system for leveling. The light-assisted scanning electrochemical microscope system includes a scanning electrochemical microscope system and a side-viewing CCD camera. S3. Calculate the uniformity of surface electrochemical activity: After leveling, add electrolyte to the sample cell, and then use a light-assisted scanning electrochemical microscope system to perform an approximation curve test on the surface of the sample cell to confirm the current feedback mode (including positive feedback, negative feedback, and anomalous feedback). Then, perform two-dimensional surface scanning imaging. Based on the statistical analysis of the scanning imaging data, calculate the uniformity of surface electrochemical activity of the negative electrode material to be tested according to Formula 1. , Among them, (I) T ) i This represents the current data obtained from the i-th probe scan; μFor all electrochemical current data I T Divide by I ∞ The average value represents the population mean; N represents the total number of data points in the population, and σ represents the standard deviation. Based on the calculated σ, a value greater than 0.05 indicates non-uniform electrochemical properties, while a value less than 0.05 indicates uniform electrochemical activity.

[0036] It should be noted that the method in this embodiment uses a light-assisted scanning electrochemical microscope system for leveling, which has the advantages of high speed and high accuracy. This method does not rely on the assumption of uniform electrochemical activity on the test surface in the actual operation of traditional SECM systems. Each leveling time is less than 10 minutes, far less than the 30 minutes required by ordinary approximation curve-based leveling methods. Therefore, the electrochemical property detection method in this invention is suitable for large-scale electrode screening and has good application prospects. Furthermore, this method can achieve micron- and sub-micron-scale electrochemical current imaging in an environment close to that of real aqueous batteries, revealing the root causes of microscopic non-uniformity behind the macroscopic performance of aqueous battery anode materials. Based on single-point approximation curves, multiple representative sites can be rapidly screened, while the area scanning mode can obtain large-area information. This method is applicable to various aqueous battery metal anode materials (such as Zn, Al, Cu, etc.).

[0037] In one implementation, such as Figure 2 As shown, the sample cell also includes an annular hydrophobic film covering the negative electrode material layer to be tested. The outer periphery of the annular hydrophobic film covers the outer periphery of the negative electrode material layer to be tested and encapsulates the outer edge of the electrolyte. It should be noted that a 5-10 mm diameter circular hole can be punched in the hydrophobic film using a puncher. The perforated film is then placed over the negative electrode material to be tested, and the exposed negative electrode material from the circular hole contacts the SECM-specific electrolyte. The central area is the testing area, and the edge area is used to adjust the level of the sample. Despite the open design, the test stability and signal-to-noise ratio remain very high because the sample cell is placed within a Faraday cage. For example, in the embodiment of this invention, the current noise is less than 0.1 nA and can be maintained for more than 8 hours. This configuration enables the light-assisted SECM system to obtain the ability to observe the tip position in situ, which is beneficial for rapid and accurate leveling of the substrate. The use of the hydrophobic film slows down the droplet evaporation rate, allowing for more efficient and accurate leveling of the substrate each time. 80μm 2 Electrochemical current imaging of the area was performed for more than 15 minutes, and the electrochemical current signal remained stable.

[0038] In some embodiments, the annular pore size of the annular hydrophobic film is 5-10 mm, and the thickness of the annular hydrophobic film is 50-100 μm.

[0039] In some embodiments, the volume of the electrolyte is 50-200 microliters.

[0040] In some embodiments, the electrolyte is an aqueous solution containing a certain concentration of redox active material and supporting electrolyte (such as 1 mM ferrocene methanol + 0.1 M Na2SO4).

[0041] As an example, the redox active substance can be 10 mM potassium ferrocyanide, and the supporting electrolyte can be 0.1 M K2SO4, ZnSO4, KNO3, and KCl.

[0042] To improve the stability of the microelectrode during testing, the inventors discovered that KCl, as a supporting electrolyte, can only be used for 10 minutes of measurement on the same microelectrode, after which the current noise increases from 0.1 pA to over 10 pA; while an electrolyte without chloride ions can be used for continuous measurement on the same microelectrode for more than 1 hour. Therefore, in the embodiments, the electrolyte is preferably an electrolyte without chloride ions.

[0043] For example, the light-assisted scanning electrochemical microscope system, such as Figure 3 As shown, it includes: The system includes a sample cell, dual potentiostats, microelectrode probes (micrometer-diameter tips), a reference electrode, a counter electrode, and a side-viewing CCD camera (and other optical imaging systems). It also includes a three-dimensional stepper motor, a computer, and a sample stage with a built-in leveling knob.

[0044] Specifically, except for the dual potentiostat and the computer, all other components are placed in a Faraday cage to improve shielding against external electromagnetic waves, reduce current noise during the test, and enable accurate measurement of 0.1 nA current. The signal collection end of the dual potentiostat is connected to the computer, and the signal acquisition end is connected to the microelectrode, reference electrode, and counter electrode via wires. These three components form an electrochemical three-electrode testing system. Simultaneously, the dual potentiostat has another wire connected to the conductive substrate under test, allowing the application of a control voltage to the substrate. The conductive substrate, reference electrode, and counter electrode constitute a second three-electrode system. During the test, the tips of the reference electrode, microelectrode probe, and counter electrode contact the electrolyte. The sample stage fixes the sample cell (test sample), and the computer is used to acquire signals from the test probes.

[0045] The ultramicroelectrode probe has the following configuration: the core is a platinum or gold ultramicroelectrode (UME) with a diameter of 10 micrometers or 1 micrometer as the probe, and the outer ring is wrapped with a 100-10 micrometer (outer diameter) SiO2 insulating layer, maintaining the ratio of the outer diameter of the insulating layer to the inner diameter of the inner metal electrode at 10:1, so as to achieve the electrochemical mass transfer diffusion control mode.

[0046] The counter electrode is a 0.5 mm diameter platinum wire.

[0047] The reference electrode is a 0.5 mm diameter silver / silver chloride (Ag / AgCl) wire, which is prepared by immersing a 0.5 mm silver wire in a 1 M FeCl3 aqueous solution for 10 minutes, then rinsing it with deionized water and drying it with nitrogen gas for later use.

[0048] In some embodiments, the CCD camera is positioned 5-30 cm away from the test sample and the needle tip, and the spatial resolution of the CCD camera reaches 2-10 micrometers.

[0049] Optionally, in S2, leveling includes the following steps: S21. Randomly select three non-linear locations on the edge of the central circular hole on the surface of the negative electrode material in the sample cell. At each location, perform the following steps: control the microelectrode probe to advance at a speed of 5-20 micrometers / second to a distance of 10-20 micrometers from the surface of the negative electrode material; control the microelectrode probe to advance (advance speed 0.2 micrometers / second), stop when the probe tip touches the surface, record the total actual advance distance, and retract the probe to the initial advance position. S22. Use the built-in leveling knob on the sample stage to fine-tune the base level until the three positions on the same scanning plane are at the same distance from the sample to be tested.

[0050] This leveling step occurs before the electrolyte is added, and the needle insertion process is monitored by a side-view CCD camera. For example, the specific process is as follows: 1. On the surface of the negative electrode material to be tested, a point is randomly selected in the edge region of the central circular hole (e.g., ...). Figure 2 The probe (number 1) is rapidly advanced to a distance of approximately 10 micrometers from the sample surface at an advancement speed of 10 micrometers per second, with the distance determined based on optical photographs. Figure 3 ); 2. Slowly advance the needle using the 3D stepper motor configured by SECM (inward speed 0.2 micrometers / second). When the needle tip touches the surface, stop manually immediately. At this point, the computer records the total actual needle advance distance, and retracts the needle to the initial inward position; 3. Use a stepper motor to move the needle tip horizontally from the X direction to Figure 2 Point 2, 3mm from point 1, is then moved horizontally to point 3, 3mm from point 2, and the first two needle insertion steps are performed, recording the actual insertion distance. The needle tip is then moved horizontally from the Y direction to point 3, 3mm from point 2, and the first two needle insertion steps are performed, recording the actual insertion distance. The substrate is then fine-tuned using the built-in leveling knob on the sample stage until the three positions on the same scanning plane are at the same distance from the sample under test, indicating successful leveling. The optically assisted SECM rapid leveling method for the substrate proposed in this application combines high-resolution optical imaging and needle tip contact technology. After performing the three-point leveling, the angle between the substrate and the horizontal plane within the three points can be less than 0.02°, which is superior to traditional leveling techniques based on approximation curves (leveling accuracy is only 0.2°).

[0051] In some implementations, a CCD camera is used to determine the distance between the microelectrode probe and the surface of the negative electrode material, such as... Figure 3 As shown.

[0052] In some implementations, the distance between two adjacent locations is 1-4 mm.

[0053] In some embodiments, in S3, before using a light-assisted scanning electrochemical microscope system to perform an approximation curve test on the sample cell surface to confirm the current feedback mode, the cyclic voltammetry curve of the ultramicroelectrode probe is measured at a distance of 1 mm from the sample cell surface to confirm that the ultramicroelectrode probe has reached a diffusion-controlled state in the prepared electrolyte.

[0054] In some implementations, in S3, the use of a light-assisted scanning electrochemical microscope system to perform an approximation curve test on the sample cell surface to confirm the current feedback mode specifically involves: The probe is slowly lowered vertically to the sample surface along the Z-axis. The probe is lowered using the feedback current approximation curve of the scanning electrochemical microscope until the current suddenly increases or decreases to the plateau current I. ∞ Stop needle insertion when the current reaches 125% or 75%. For single-point approximation curve testing, the plateau current is I. ∞ .

[0055] Feedback pattern recognition and surface electrochemical activity classification are as follows: Positive feedback curve (i T (Continuously increases as d decreases): This indicates that the substrate surface corresponding to this point has high electrochemical activity and can effectively regenerate key redox active substances; Negative feedback curve (i T (Continues to decrease as d decreases): This indicates that the corresponding substrate surface at this point is a low-activity or inert region; Anomalous feedback curve (i T (Increase first, then decrease): This indicates that an active / inert interleaved structure exists on the substrate surface corresponding to this point.

[0056] In some implementations, in S3, the specific process of two-dimensional surface scanning imaging is as follows: the scanning step size is set to 1 micrometer, and the scanning area is 80. 80μm 2 Collecting current (I) from 6400 needle tips T ) data, each divided by the platform current (I ∞ ), to obtain I T / I ∞ The ratio, calculated by computer, is I T / I ∞ In the three-dimensional diagram of the XY plane, we obtain I. T / I ∞ The mean and standard deviation σ of the ratio.

[0057] The present invention will be further described below through specific embodiments.

[0058] Example 1 In this embodiment, the negative electrode material to be tested is a rolled aluminum electrode. The electrolyte contains 1 mM ferrocene methanol + 0.1 M Na2SO4, and the electrolyte itself has a stability of 3 months.

[0059] This embodiment of a method for testing the electrochemical activity uniformity of an aqueous ion battery anode material includes the following steps: The ultramicro probe used for testing was polished; the open SECM sample cell and sample were placed stably on the sample stage, and the testing platform was leveled (the specific process is as follows: 1. Randomly select points on the surface of the negative electrode material to be tested, in the edge area of ​​the central circular hole region (e.g. Figure 2 The probe (number 1) is rapidly advanced to a distance of approximately 10 micrometers from the sample surface at an advance speed of 10 micrometers per second, with the distance determined based on optical photographs (e.g., ...). Figure 3 ); 2. Slowly advance the needle using the 3D stepper motor configured by SECM (inward speed 0.2 micrometers / second). When the needle tip touches the surface, stop manually immediately. At this point, the computer records the total actual needle advance distance, and retracts the needle to the initial inward position; 3. Use a stepper motor to move the needle tip horizontally from the X direction to Figure 2 Point 2, 3mm from point 1, is then moved horizontally to point 3, 3mm from point 2, and the first two steps of needle insertion are performed, recording the actual insertion distance. 4. The needle tip is moved horizontally from the Y direction to point 3, 3mm from point 2, and the first two steps of needle insertion are performed, recording the actual insertion distance. 5. The substrate is finely adjusted using the built-in leveling knob on the sample stage until the three positions on the same scanning plane are at the same distance from the sample to be tested, indicating successful leveling. The test microelectrode, counter electrode, reference electrode, sample to be tested, and dual potentiostat are connected; the prepared electrolyte is added so that the droplets on the open SECM sample cell are hemispherical; the dual potentiostat test parameters are set, and the three-dimensional stepper motor is controlled to move the test probe to the test area for testing; the software with the set test parameters is run, and the cyclic voltammetry curve of the microelectrode (probe) is measured at a distance of approximately 1mm from the surface of the sample to be tested, confirming that the probe reaches the required level in the prepared electrolyte. Figure 4 The diffusion control state in the curve is represented by an S-shaped curve. A single-point approximation curve test is then performed, controlling the probe to gradually approach multiple statistically representative sites on the electrode surface along the vertical direction (Z direction), and recording the probe current (i) in real time. T The relationship curve between the probe and the substrate distance (d) (i) T -d curve), confirm feedback mode. Tip voltage set to Figure 4The voltage was set to 0.25V; finally, electrochemical current XY plane imaging was performed. The activity uniformity of the entire electrode surface was evaluated, and based on statistical analysis of the scanning imaging data, activity quantification indicators (such as tip collection current (It)) were defined. T ) and plateau current (I ∞ Ratio I T / I ∞ The standard deviation σ is used to calculate the electrochemical activity uniformity of the electrode surface.

[0060] Example 2 Unlike Example 1, the negative electrode material to be tested in this example is a copper electrode.

[0061] This embodiment of a method for testing the electrochemical activity uniformity of an aqueous ion battery anode material includes the following steps: The ultramicro probe for testing was polished. The open SECM sample cell and sample were placed stably on the sample stage, and the test platform was leveled. The ultramicro electrode, counter electrode, reference electrode, sample to be tested, and dual potentiostat were connected. The prepared electrolyte was added so that the droplets on the open SECM sample cell formed a hemispherical shape. The test parameters of the dual potentiostat were set, and the three-dimensional stepper motor was controlled to move the test probe to the test area for testing. The software with the set test parameters was run, and the cyclic voltammetry curve of the ultramicro electrode (probe) was measured at a distance of approximately 1 mm from the surface of the sample to confirm that the probe reached the required stability in the prepared electrolyte. Figure 4 The diffusion control state in the curve is represented by an S-shaped curve. A single-point approximation curve test is then performed, controlling the probe to gradually approach multiple statistically representative sites on the electrode surface along the vertical direction (Z direction), and recording the probe current (i) in real time. T The relationship curve between the probe and the substrate distance (d) (i) T -d curve), confirm feedback mode. Tip voltage set to Figure 4 The voltage was set to 0.25V; finally, electrochemical current XY plane imaging was performed. The activity uniformity of the entire electrode surface was evaluated, and based on statistical analysis of the scanning imaging data, activity quantification indicators (such as tip collection current (It)) were defined. T ) and plateau current (I ∞ Ratio I T / I ∞ The standard deviation σ is used to calculate the electrochemical activity uniformity of the electrode surface.

[0062] Example 3 Unlike Example 1, the negative electrode material to be tested in this example is a zinc electrode.

[0063] This embodiment of a method for testing the electrochemical activity uniformity of an aqueous ion battery anode material includes the following steps: The ultramicro probe for testing was polished. The open SECM sample cell and sample were placed stably on the sample stage, and the test platform was leveled. The ultramicro electrode, counter electrode, reference electrode, sample to be tested, and dual potentiostat were connected. The prepared electrolyte was added so that the droplets on the open SECM sample cell formed a hemispherical shape. The test parameters of the dual potentiostat were set, and the three-dimensional stepper motor was controlled to move the test probe to the test area for testing. The software with the set test parameters was run, and the cyclic voltammetry curve of the ultramicro electrode (probe) was measured at a distance of approximately 1 mm from the surface of the sample to confirm that the probe reached the required stability in the prepared electrolyte. Figure 4 The diffusion control state in the curve is represented by an S-shaped curve. A single-point approximation curve test is then performed, controlling the probe to gradually approach multiple statistically representative sites on the electrode surface along the vertical direction (Z direction), and recording the probe current (i) in real time. T The relationship curve between the probe and the substrate distance (d) (i) T -d curve), confirm feedback mode. Tip voltage set to Figure 4 The voltage was set to 0.25V; finally, electrochemical current XY plane imaging was performed. The activity uniformity of the entire electrode surface was evaluated, and based on statistical analysis of the scanning imaging data, activity quantification indicators (such as tip collection current (It)) were defined. T ) and plateau current (I ∞ Ratio I T / I ∞ The standard deviation σ is used to calculate the electrochemical activity uniformity of the electrode surface.

[0064] Comparative Example 1 The difference between this comparative example and Example 1 is that the method for adjusting the base level is based on the approximation curve leveling method.

[0065] Comparative Example 2 The difference between this comparative example and Example 1 is that the aluminum electrode was treated by soaking in 1M HCl for 15 min.

[0066] Comparative Example 3 The difference between this comparative example and Example 2 is that the copper electrode was treated by soaking in 1 M HCl for 15 minutes.

[0067] Comparative Example 4 The difference between this comparative example and Example 2 is that the copper electrode was treated by soaking in a 0.1M K3Fe(CN)6 aqueous solution for 15 minutes.

[0068] Comparative Example 5 The difference between this comparative example and Example 3 is that the zinc electrode surface is covered with a 2-acrylamide-2-methylpropanesulfonic acid adsorption layer.

[0069] Comparative Example 6 The difference between this comparative example and Example 3 is that the zinc electrode surface is covered with a polymer coating made of 2-acrylamide-2-methylpropanesulfonic acid.

[0070] The aluminum, copper, and zinc electrodes from Examples 1-3 above were subjected to approximation curve tests, and the characterization results are as follows: Figure 5 and Figure 6 As shown. Cyclic voltammetry was performed on the polished microelectrode probe, and the test results are as follows. Figure 4 As shown.

[0071] from Figure 4 As can be seen, the cyclic voltammetry curve of the polished microelectrode probe exhibits an S-shape. After reaching a voltage of 0.1V relative to the Ag / AgCl reference electrode, the plateau from 0.1V to 0.3V indicates a diffusion-controlled oxidation reaction occurring on the microelectrode. A stable concentration gradient of the active material in the electrolyte is established at the tip of the microelectrode probe, further demonstrating the effectiveness of the polishing treatment. Approximation curve tests were performed on different electrodes with the voltage fixed at 0.25V. Figure 5 The negative feedback curve is often obtained on the Al electrode, while the positive feedback curve is often obtained on the zinc electrode. Figure 6 The anomalous feedback curve corresponding to the "rise then fall" probe current is often obtained on copper electrodes, indicating that the electrochemical activity distribution of copper electrodes is uneven, showing regions with alternating conductive and insulating properties. Aluminum electrodes, however, are essentially inert due to the influence of the oxide film. Zinc electrodes generally exhibit higher electrochemical activity (I0.05). T / I ∞ >1 region), and also inactive region (I T / I ∞ >1), as expected.

[0072] based on Figure 5 and Figure 6 The approximation curve test was performed on the aluminum electrode in Example 1 and the aluminum electrode in Comparative Example 1, and the electrochemical current XY plane imaging was performed. The results are as follows: Figure 7 , Figure 10 As shown in Table 1, in Example 1, the average I of the relatively flat aluminum electrode T / I ∞ The value is 0.892, and the root mean square error σ is only 0.013, indicating that the aluminum electrode has been leveled with high precision using the "light-assisted SECM system for rapid adjustment of the substrate level" method according to this invention. In contrast, leveling the same aluminum electrode using the approximation curve leveling method results in an average I... T / I ∞ The value is 0.685, which is still negative feedback and relatively reasonable. However, the root mean square error σ is as high as 0.113, which is 10 times that of ordinary aluminum electrodes, making the statistic meaningless.

[0073] based on Figure 5 , Figure 6 The approximation curve test was performed on the aluminum, copper, and zinc electrodes in Examples 1-3, and on the electrochemical current XY plane imaging of Comparative Examples 2-6. The results are as follows: Figure 7 , Figure 8 , Figure 9 , Figure 11 , Figure 12 , Figure 13 , Figure 14 , Figure 15 As shown in Table 1. Figure 7 , Figure 11 The comparison showed that after the aluminum electrode was treated with 1M HCl solution for 15 min, the surface electrochemical activity non-uniformity was significantly improved because some oxide layers were destroyed, forming an image of enhanced local activity but overall inertness.

[0074] Figure 8 , Figure 12 , Figure 13 XY plane imaging comparison shows that the copper electrode itself has more electrochemically active regions compared to the aluminum electrode. After treatment with 1M HCl for 15 min, it exhibits a uniform positive feedback response overall because the surface oxide layer is uniformly removed. However, after treatment with 0.1M K3Fe(CN)6, although a uniform electrochemical current response is observed overall, the average Ig... T / I ∞ However, the feedback is negative, indicating that K3Fe(CN)6 has a strong oxidizing property and the reaction rate is too fast, resulting in passivation of the entire surface.

[0075] Figure 9 , Figure 14 , Figure 15 XY plane imaging comparisons show that the zinc electrode surface is relatively active, exhibiting a generally positive feedback response and being highly non-uniform. When used as a negative electrode in zinc-aqueous ion batteries, a polymer coating needs to be applied to the surface to homogenize the surface electric field and suppress possible dendrite growth. In Comparative Examples 5 and 6, the zinc electrode surface was coated with different molecular layers. After adsorption of 2-acrylamide-2-methylpropanesulfonic acid, the surface exhibits uniform electrochemical inertness. Figure 14 When the same molecules are polymerized and spin-coated onto a zinc surface, the surface exhibits a certain level of activity and is very uniform, indicating that this coating is very suitable for electron transport and can conduct ions to a certain extent, with high surface electrochemical coupling efficiency. Figure 15 ).

[0076] The electrochemical parameter results for the examples and comparative examples are shown in Table 1.

[0077] Table 1. Electrochemical parameters in each example and comparative example

[0078] As can be seen from Table 1, the electrochemical activity of the electrode surface can be determined by I... T / I ∞ The average value is used to determine reactivity. Although all three have excellent electronic conductivity, Al is significantly less reactive than Cu and Zn because the oxide layer on the aluminum surface is denser and more difficult to break. I... T / I ∞ The standard deviation σ value can accurately characterize the uniformity of electrochemical properties. A value greater than 0.05 indicates significant non-uniformity, while a value less than this value can be considered uniform.

[0079] Based on the above, the micro-area electrochemical testing method proposed in this invention has good guiding significance. The intuitive imaging results of the spatial distribution of electrochemical activity provide a direct basis for targeted improvement of electrode materials, electrolyte formulations, and film formation processes. For example, the experiments in Example 3, Comparative Example 5, and Comparative Example 6 show that the Zn anode has intrinsic electrochemical activity heterogeneity. According to the detection method provided in this invention and the optimization of the synthesis method of the 2-acrylamide-2-methylpropanesulfonic acid coating covering its surface, the Zn anode can balance high electrochemical activity and uniformity, which is beneficial to improving the long-term cycle stability of aqueous zinc-ion batteries.

[0080] It should be understood that the application of the present invention is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A method for testing the electrochemical activity uniformity of anode materials in aqueous ion batteries, characterized in that, Includes the following steps: S1. Sample cell preparation: Prepare a sample cell for testing the electrochemical activity uniformity of the negative electrode material of an aqueous ion battery. The sample cell includes a substrate layer and a layer of the negative electrode material to be tested located on the substrate. S2. Leveling: The sample cell is placed in the light-assisted scanning electrochemical microscope system for leveling. The light-assisted scanning electrochemical microscope system includes a scanning electrochemical microscope system and a side-viewing CCD camera. S3. Calculate the surface electrochemical activity uniformity: After leveling, add electrolyte to the sample cell, and then use a light-assisted scanning electrochemical microscope system to perform an approximation curve test on the surface of the sample cell to confirm the current feedback mode. Then, perform two-dimensional surface scanning imaging. Based on the statistical analysis of the scanning imaging data, calculate the surface electrochemical activity uniformity of the negative electrode material to be tested according to Formula 1. (Formula 1) Among them, (I) T ) i This represents the current data obtained from the i-th probe scan; μ For all electrochemical current data I T Divide by I ∞ The mean; N represents the total number of data points, and σ represents the standard deviation; Based on the calculated σ, a value greater than 0.05 indicates non-uniform electrochemical properties, while a value less than 0.05 indicates uniform electrochemical activity.

2. The method for testing the electrochemical activity uniformity of anode materials in aqueous ion batteries according to claim 1, characterized in that, The sample cell also includes an annular hydrophobic film covering the negative electrode material layer to be tested, wherein the inner periphery of the annular hydrophobic film covers the negative electrode material layer to be tested and wraps the outer edge of the electrolyte.

3. The method for testing the electrochemical activity uniformity of anode materials in aqueous ion batteries according to claim 2, characterized in that, The annular hydrophobic film has an annular pore size of 5-10 mm and a thickness of 50-100 μm.

4. The method for testing the electrochemical activity uniformity of anode materials in aqueous ion batteries according to claim 1, characterized in that, The volume of the electrolyte is 50-200 microliters.

5. The method for testing the electrochemical activity uniformity of an aqueous ion battery anode material according to claim 4, characterized in that, The CCD camera is located 5-30 cm away from the test sample and the needle tip, and the spatial resolution of the CCD camera reaches 2-10 micrometers.

6. The method for testing the electrochemical activity uniformity of an aqueous ion battery anode material according to claim 1, characterized in that, In S2, leveling includes the following steps: S21. Randomly select three non-linear locations in the central region of the surface of the negative electrode material to be tested in the sample cell. At each location, perform the following steps: control the microelectrode probe to advance at a speed of 5-20 micrometers / second to a distance of 10-20 micrometers from the surface of the negative electrode material to be tested; control the microelectrode probe to advance until the tip touches the surface, then record the total actual advance distance and retract the probe to the initial advance position. S22. Make fine adjustments to the substrate level until the distance between the three positions on the same scanning plane and the negative electrode material to be tested is the same.

7. The method for testing the electrochemical activity uniformity of an aqueous ion battery anode material according to claim 6, characterized in that, A CCD camera is used to determine the distance between the microelectrode probe and the surface of the negative electrode material.

8. The method for testing the electrochemical activity uniformity of an aqueous ion battery anode material according to claim 6, characterized in that, The distance between two adjacent locations is 1-4 mm.

9. The method for testing the electrochemical activity uniformity of an aqueous ion battery anode material according to claim 1, characterized in that, In S3, before using a light-assisted scanning electrochemical microscope system to perform an approximation curve test on the sample cell surface to confirm the current feedback mode, the cyclic voltammetry curve of the ultramicroelectrode probe is measured at a distance of 1 mm from the sample cell surface to confirm that the ultramicroelectrode probe has reached a diffusion-controlled state in the prepared electrolyte.

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