A resistivity measurement sensor, measurement system, and measurement method

Abstract

This invention belongs to the field of lithium battery slurry measurement, and particularly relates to a resistivity measurement sensor, measurement system, and measurement method. The sensor includes a conductivity cell tube and leads. The conductivity cell tube is a tubular structure open at both ends, with seven annular grooves on its inner wall. An inner electrode is installed in each annular groove. Electrode lead ports, corresponding one-to-one with the annular grooves, are provided on the right side wall of the conductivity cell tube, penetrating the right side wall of the conductivity cell tube. One end of each lead is connected to the inner electrode through the electrode lead port and fixed at the electrode lead port; the other end is connected to the sensor interface and then connected to a downstream calculation circuit through the sensor interface. The sensor of this invention features high stability and ease of cleaning, enabling in-situ measurement of slurry resistivity, meeting the requirements for rapid and high-precision measurement, and offering the advantage of simple operation.

Description

Technical Field

[0001] This invention belongs to the field of lithium battery slurry measurement, and particularly relates to an in-situ, fast-response, high-precision slurry resistivity measurement sensor, measurement system, and measurement method. Background Technology

[0002] Lithium-ion batteries, as a high-energy-density and lightweight battery technology, are widely used in electric vehicles, portable devices, and energy storage systems. With the continuous advancement of energy storage technology and the rapid development of the electric vehicle market in my country, the demand for high-performance lithium-ion batteries is increasing daily. Therefore, developing new lithium-ion batteries with higher energy density, longer cycle life, and faster charge / discharge speeds is of great significance for promoting the development of my country's new energy industry, improving energy efficiency, and achieving the sustainable use of clean energy.

[0003] Slurry preparation, as the first step in lithium-ion battery production, occupies a core position in the lithium battery manufacturing process. Lithium-ion battery slurry is a complex mixture, typically composed of active materials, conductive agents, binders, and solvents. The selection and proportion of each component significantly impact battery performance and cycle life. By precisely controlling the formulation and preparation process of lithium-ion battery slurry, the performance and safety of lithium-ion batteries can be improved.

[0004] Slurry resistivity measurement can reflect the conductivity of slurry, monitor slurry sedimentation, and distinguish slurry formulations. It is of great significance for slurry quality control and process optimization, thus profoundly affecting the key performance of lithium batteries such as stability, cycle life and energy transfer efficiency.

[0005] To monitor slurry settling, the conductivity measurement of the slurry must have the capability for in-situ and rapid measurement; to differentiate slurry formulations, the conductivity measurement of the slurry must have the capability for high-precision measurement. In addition, for slurry measurement on the production line, the measurement method also needs to have advantages such as stable measurement, simple operation, and easy cleaning of the measuring device.

[0006] Currently, resistivity measurement suffers from a technical bottleneck where in-situ measurement, rapid response, and high precision cannot be simultaneously achieved, and there is no suitable slurry resistivity measurement device that adequately meets these requirements. For example, the invention patent CN 107884622B designs a cylindrical test chamber with electrodes at both ends. After the slurry is moved into the chamber, an AC current is applied to it using an electrochemical workstation via AC impedance spectroscopy, and the impedance is measured. Finally, the actual resistivity of the slurry is obtained through the geometric parameters of the test chamber. While this patent accurately measures the slurry resistivity under different excitation currents and frequencies, it also has the following shortcomings: First, using a specially designed test chamber requires filling the chamber with slurry using a pipette, making the operation complex and unsuitable for in-situ slurry resistivity measurement. Second, while using an electrochemical workstation for impedance measurement allows for a relatively comprehensive analysis of slurry impedance at different frequencies, the workstation is complex to use, requires professional personnel, and the frequency sweep measurement takes a long time, making it unsuitable for rapid slurry resistivity measurement. Summary of the Invention

[0007] To address the aforementioned problems, this invention provides a resistivity measurement sensor, measurement system, and measurement method. This sensor features high stability and ease of cleaning, enabling in-situ measurement of slurry resistivity, meeting the requirements for rapid and high-precision measurement, and offering the advantage of simple operation.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] A resistivity measurement sensor includes a conductivity cell tube and leads. The conductivity cell tube is a tubular structure open at both ends, with seven annular grooves along its inner circumference on its inner wall. An inner electrode is installed in each annular groove. Electrode lead ports corresponding to the annular grooves are provided on the right side wall of the conductivity cell tube, and the electrode lead ports penetrate the right side wall of the conductivity cell tube. One end of the lead is connected to the inner electrode through the electrode lead port and fixed at the electrode lead port, while the other end is connected to the sensor interface and connected to the back-end calculation circuit through the sensor interface.

[0010] Furthermore, the conductivity cell tube is made of quartz, and the internal electrode is made of platinum.

[0011] Furthermore, the inner electrode includes electrode 1, electrode 2, electrode 3, electrode 4, electrode 5, electrode 6, and electrode 7. Electrodes 1, 2, 3, 4, 5, 6, and 7 are arranged parallel to each other, and electrodes 1, 2, 3 and 7 are symmetrically arranged with electrode 6, 5, and 7 as the center. At the same time, electrodes 1, 2, 3, 4, 5, 6, and 7 are all perpendicular to the inner wall of the conductivity cell tube.

[0012] Furthermore, the electrode lead opening has a tapered structure, with its tip positioned close to the inner electrode and its tail extending outside the conductivity cell tube.

[0013] The present invention also provides a resistivity measurement system, including an AC excitation module, a standard resistor R0, an instrumentation amplifier, a microcontroller, an ADC acquisition module, and the aforementioned sensor; wherein, electrodes one and seven are grounded; the output of the AC excitation module is connected to electrode four through a standard resistor R0; the inputs of the three instrumentation amplifiers are respectively connected to the two ends of electrodes two and three, the two ends of electrodes five and six, and the two ends of the standard resistor R0, and the outputs of the instrumentation amplifiers are connected to the ADC acquisition module, with output voltages u1, u2, and u0, respectively;

[0014] The excitation signal generated by the AC excitation module under the control of the microcontroller is collected by the ADC acquisition module and fed back to the microcontroller, which then calculates the resistivity of the slurry.

[0015] According to the formula for calculating conductor resistance: The formula for calculating the resistivity of slurry is as follows:

[0016]

[0017] Where R represents the conductor resistance, r represents the slurry resistivity, l represents the conductor length, and d represents the inner diameter of the conductivity cell. This represents the cell conductivity constant.

[0018] When the sensor conductivity cell is filled with slurry, the slurry between electrodes 2 and 3, and between electrodes 5 and 6, can be considered as two conductors with equal resistance, R. From Kirchhoff's current law, we can obtain:

[0019]

[0020] From equation (3), we can obtain:

[0021]

[0022] From equation (2), we can obtain the formula for calculating the resistivity of the slurry:

[0023]

[0024] Where R0 represents the resistance value of the standard resistor R0, r represents the resistivity of the conductor, u1 represents the output voltage of the instrumentation amplifier connected to the two ends of electrode 2 and electrode 3, u2 represents the output voltage of the instrumentation amplifier connected to the two ends of electrode 5 and electrode 6, and u0 represents the output voltage of the instrumentation amplifier connected to the two ends of the standard resistor R0.

[0025] The present invention also provides a resistivity measurement method, which uses the above-described resistivity measurement system to measure the resistivity of slurry.

[0026] The present invention has the following beneficial effects:

[0027] The sensor of this invention exhibits excellent stability. The electrodes utilize high-purity platinum electrode material with high chemical stability and low polarization potential, while the conductivity cell is made of quartz material known for its stability.

[0028] The sensor of this invention has the advantages of high throughput and easy cleaning. The large diameter of the conductivity cell is conducive to the flow of slurry, and the designed sensor can easily measure even highly viscous positive electrode slurry; the large diameter of the conductivity cell also makes the sensor easy to clean, and the outer surface of the sensor and the inner surface of the conductivity cell can be quickly cleaned with water and a brush.

[0029] The testing system of this invention features high precision. The sensor electrode structure is a ring-shaped seven-electrode structure. By separating the current electrode and the voltage electrode, the excitation signal is input from the central electrode to generate an excitation electric field, with the electric field lines ultimately flowing to the grounding electrodes at both ends. This layout effectively confines the electric field lines while effectively shielding against interference from outside the conductivity cell, ensuring a closed loop of the electric field within the cell and thus avoiding the influence of external factors on the measurement results.

[0030] The testing method of this invention can perform in-situ measurements of slurry and is easy to operate. The sensor is placed in the slurry to be measured and connected to the calculation circuit via a cable, allowing for convenient in-situ measurements of the slurry without the need for large analytical instruments.

[0031] The testing method of this invention has a rapid response characteristic. The sensor calculation circuit uses a fixed-frequency AC excitation method, which does not require the frequency sweep process of electrochemical impedance spectroscopy analysis, so it can quickly respond to changes in the conductivity of the slurry. Attached Figure Description

[0032] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0033] Figure 1 This is a schematic diagram of the structure of a resistivity measuring sensor according to an embodiment of the present invention.

[0034] Figure 2 This is a circuit block diagram of a resistivity measurement system according to an embodiment of the present invention.

[0035] Figure 3 This is a schematic diagram of the slurry resistivity measurement system in an embodiment of the present invention.

[0036] Figure 4 The resistivity test results are for the positive electrode slurry after static settling.

[0037] Figure 5 The resistivity test results are for different positive electrode slurry formulations. Detailed Implementation

[0038] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. 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. These all fall within the scope of protection of the present invention.

[0039] Example 1

[0040] like Figure 1 As shown, a resistivity measurement sensor includes a conductivity cell tube 9 and leads. The conductivity cell tube 9 is made of quartz and has a tubular structure with open ends. In this embodiment, its length is 50 mm, its inner diameter is 12 mm, and its outer diameter is 16 mm. Seven annular grooves are formed along the inner circumference of the inner wall of the conductivity cell tube 9. The seven annular grooves are all horizontally arranged, and an inner electrode is installed in each annular groove. Electrode lead ports 8 are formed on the right side wall of the conductivity cell tube 9, corresponding to the annular grooves. The electrode lead ports 8 have a conical structure, with their tip close to the inner electrode and their tail extending outside the conductivity cell tube 9, i.e., the electrode lead ports 8 penetrate the right side wall of the conductivity cell tube 9. One end of the lead is connected to the inner electrode through the electrode lead port 8 and fixed at the electrode lead port. The other end is connected to the sensor interface and connected to the back-end calculation circuit through the sensor interface.

[0041] In this embodiment, the inner electrodes are made of platinum metal and are designated as electrode 1, electrode 2, electrode 3, electrode 4, electrode 5, electrode 6, and electrode 7. Electrodes 1, 2, 3, 7, 6, and 5 are arranged symmetrically and parallel to electrode 4, with electrode 4 as the center, and are perpendicular to the inner wall of the conductivity cell tube 9. In this embodiment, electrodes 1, 2, 3, 7, 6, and 5 are all ring electrodes. Electrodes 1, 4, and 7 have the same dimensions and a thickness of 4 mm. Electrodes 2, 3, 5, and 6 have the same dimensions and a thickness of 2 mm. The distance between the horizontal center line of electrode 1 and the horizontal center line of electrode 2 is 8 mm. The distance between the horizontal center line of electrode 2 and the horizontal center line of electrode 3 is 5 mm. The distance between the horizontal center line of electrode 3 and the horizontal center line of electrode 4 is 8 mm. The distance between the horizontal center line of electrode 4 and the horizontal center line of electrode 5 is 8 mm. The distance between the horizontal center line of electrode 5 and the horizontal center line of electrode 6 is 5 mm. The distance between the horizontal center line of electrode 6 and the horizontal center line of electrode 7 is 8 mm.

[0042] Example 2

[0043] like Figure 2 As shown, a resistivity measurement system includes an AC excitation module, a standard resistor R0, an instrumentation amplifier, a microcontroller, an ADC acquisition module, and the sensor described in Example 1; wherein: electrode 1 and electrode 7 are grounded; the output of the AC excitation module is connected to electrode 4 through a standard resistor R0; the inputs of the three instrumentation amplifiers are respectively connected to the two ends of electrode 2 and electrode 3, the two ends of electrode 5 and electrode 6, and the two ends of the standard resistor R0, and the outputs of the instrumentation amplifiers are connected to the ADC acquisition module, with output voltages u1, u2, and u0 respectively;

[0044] The excitation signal generated by the AC excitation module under the control of the microcontroller is collected by the ADC acquisition module and fed back to the microcontroller, which then calculates the resistivity of the slurry.

[0045] The formula for calculating the resistance of a conductor is known:

[0046]

[0047] Where R represents conductor resistance, r represents conductor resistivity, l represents conductor length, and S represents conductor cross-sectional area.

[0048] like Figure 2As shown, taking electrodes 5 and 6 as examples, when the sensor conductivity cell is filled with slurry, the slurry between the two electrodes can be regarded as a conductor resistance. Let the distance between the two electrodes be l, and the diameter of the inner wall of the conductivity cell be d. From equation (1), the formula for calculating the resistivity of the slurry in the conductivity cell is:

[0049]

[0050] Where R represents the conductor resistance, r represents the slurry resistivity, l represents the conductor length, and d represents the inner diameter of the conductivity cell. This represents the cell conductivity constant.

[0051] Since the size parameters of the conductivity cell are fixed, the resistivity of the slurry can be determined by measuring the resistance between the two electrodes.

[0052] During measurement, the slurry between electrode 2 and electrode 3, and between electrode 5 and electrode 6 can be considered as two conductors with equal resistance, R. According to Kirchhoff's current law, we can obtain:

[0053]

[0054] From equation (3), we can obtain:

[0055]

[0056] From equation (2), we can obtain the formula for calculating the resistivity of the slurry:

[0057]

[0058] Where R0 represents the resistance value of the standard resistor R0, r represents the resistivity of the conductor, u1 represents the output voltage of the instrumentation amplifier connected to the two ends of electrode 2 and electrode 3, u2 represents the output voltage of the instrumentation amplifier connected to the two ends of electrode 5 and electrode 6, and u0 represents the output voltage of the instrumentation amplifier connected to the two ends of the standard resistor R0.

[0059] Application Example 1

[0060] Used for testing slurry settling: Figure 4 The display shows the experimental results of testing the resistivity changes of the upper and lower layers of a large beaker containing positive electrode slurry, using two designed sensors placed at the top and bottom layers (5 cm vertically apart). The results indicate that after several hours of settling, the resistivity of the upper and lower layers of the slurry changed significantly, demonstrating sedimentation and stratification. Furthermore, the designed sensors effectively detected these sedimentation changes.

[0061] Application Example 2

[0062] Used to differentiate slurry formulations: Figure 5 The results shown are experimental findings on the resistivity of cathode slurries with different carbon black ratios, tested using the designed sensor. The active material in the cathode slurry is lithium cobalt oxide (LCO), the conductive agent is carbon black (SP), the binder is polyvinylidene fluoride (PVDF), and the solvent is N-methylpyrrolidone (NMP). The formulation composition is shown in Table 1 below.

[0063] Table 1

[0064]

[0065] It can be seen that the resistivity measured for slurries with different carbon black contents is significantly different, indicating that the designed sensor can effectively distinguish slurries with different formulations.

[0066] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A resistivity measurement system, characterized in that: Includes AC excitation module, standard resistor The instrumentation amplifier, microcontroller, ADC acquisition module, and resistivity measurement sensor are all included; electrodes 1 and 7 are grounded; the output of the AC excitation module is connected to a standard resistor. Then connect electrode number four; the input terminals of the three instrumentation amplifiers are respectively connected to the two ends of electrodes number two and three, the two ends of electrodes number five and six, and the standard resistor. At both ends, the output of the instrumentation amplifier is connected to the ADC acquisition module, and the output voltages are respectively , and ; The excitation signal generated by the AC excitation module under the control of the microcontroller is collected by the ADC acquisition module and fed back to the microcontroller, which then calculates the resistivity of the slurry. The resistivity measurement sensor includes a conductivity cell tube and leads. The conductivity cell tube is a tubular structure open at both ends, with seven annular grooves on its inner wall. An inner electrode is installed in each annular groove. Electrode lead ports corresponding to the annular grooves are provided on the right side wall of the conductivity cell tube, and the electrode lead ports penetrate the right side wall of the conductivity cell tube. One end of the lead is connected to the inner electrode through the electrode lead port and fixed at the electrode lead port. The other end is connected to the sensor interface and connected to the back-end calculation circuit through the sensor interface. According to the formula for calculating conductor resistance: (1) It can be seen that the formula for calculating the resistivity of the slurry is: （2） ； in, Indicates the resistance of a conductor. Indicates the resistivity of the slurry. Indicates the length of the conductor. Indicates the diameter of the inner wall of the conductivity cell. Represents the cell conductivity constant; When the sensor conductivity cell is filled with slurry, the slurry between electrodes 2 and 3, and between electrodes 5 and 6, are considered as two conductors with equal resistance. According to Kirchhoff's current law: （3）； From equation (3), we get: （4）； Then, from equation (2), the formula for calculating the resistivity of the slurry is obtained as follows: （5）； in, Indicates standard resistance The resistance value, Represents the resistivity of a conductor. This represents the output voltage of the instrumentation amplifier connected across electrodes two and three. This represents the output voltage of the instrumentation amplifier connected to electrodes five and six. Indicates connection to a standard resistor The output voltage of the instrumentation amplifier at both ends.

2. The resistivity measurement system as described in claim 1, characterized in that: The resistivity measurement sensor in the resistivity measurement system uses a quartz cell tube and a platinum metal inner electrode.

3. The resistivity measurement system as described in claim 1, characterized in that: The resistivity measurement sensor in the resistivity measurement system has internal electrodes including electrode 1, electrode 2, electrode 3, electrode 4, electrode 5, electrode 6, and electrode 7. Electrodes 1, 2, and 3 are symmetrically and parallelly arranged with electrode 7, 6, and 5 as the center, and are perpendicular to the inner wall of the conductivity cell tube.

4. The resistivity measurement system as described in claim 1, characterized in that: The resistivity measurement sensor in the resistivity measurement system has a tapered electrode lead, with its tip positioned close to the inner electrode and its tail extending outside the conductivity cell tube.

5. A method for measuring resistivity, characterized in that: The resistivity of the slurry is measured using the resistivity measurement system as described in any one of claims 1-4.

Images