Method for evaluating the electrical conductivity of a battery electrode sheet

Abstract

This invention relates to the field of lithium-ion battery technology and discloses a method for evaluating the conductivity of battery electrodes, comprising: obtaining target electrodes of the same polarity to form a first symmetrical coin cell, and measuring the resistance R of the first symmetrical coin cell. sol The first AC impedance diagram was obtained; the target electrode was fabricated into a coin cell, and the coin cell was formed using a small current. After the target electrode underwent small current charging and discharging, it was fabricated into a second symmetrical coin cell, and the resistance R of the second symmetrical coin cell was measured. sol The first and second AC impedance diagrams are used to obtain the resistance R of the target electrode by combining the first and second AC impedance diagrams. ion With resistance R ct And based on resistance R sol Resistance R ion With resistance R ct The total resistance of the target electrode is calculated, and the conductivity of the target electrode is evaluated based on the total resistance. This invention solves the problem of low testing accuracy in existing battery evaluation methods.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, and in particular to a method for evaluating the conductivity of battery electrodes. Background Technology

[0002] The internal resistance of a lithium battery is one of the important indicators for battery performance evaluation. It plays a crucial role in measuring the current quality of the battery throughout its entire lifecycle, from design and manufacturing to usage and eventual disposal. Lithium battery internal resistance is generally divided into ohmic internal resistance and polarization internal resistance. Ohmic internal resistance is composed of the electrode materials, electrolyte, separator resistance, and contact resistance of various components. Polarization internal resistance refers to the resistance caused by polarization during the electrochemical reaction, including electrochemical polarization internal resistance and concentration polarization internal resistance. Methods for measuring lithium battery internal resistance generally fall into two categories: DC measurement and AC measurement. In practical applications, most cell manufacturers use AC internal resistance values ​​to evaluate the quality of cell production. The AC internal resistance method is applicable to all batteries. Because the applied AC current is small, it maintains the battery's integrity, and the testing process is fast. Its measured value approximates the battery's ohmic internal resistance, providing a realistic assessment of the cell manufacturing process. Ohmic internal resistance is mainly divided into three parts: ionic resistance, electronic resistance, and contact resistance. Therefore, it is of practical significance to effectively identify the components of ohmic internal resistance and take targeted measures to reduce it.

[0003] In the field of lithium-ion batteries, the conductivity of different material formulations is often evaluated by the four-probe film impedance test method. However, this value only reflects the electronic impedance of the material itself and cannot comprehensively and effectively reflect the conductivity of the material. Summary of the Invention

[0004] This invention provides a method for evaluating the conductivity of battery electrodes to address the problem of low testing accuracy in existing battery evaluation methods.

[0005] To achieve the above objectives, the present invention employs the following technical solution:

[0006] This invention provides a method for evaluating the conductivity of battery electrodes, comprising:

[0007] Obtain the same target electrode to form a first symmetrical coin cell, and measure the resistance R of the first symmetrical coin cell. sol And the first AC impedance diagram;

[0008] Obtain a target electrode sheet of different polarity and fabricate it into a coin cell. Perform low-current formation on the coin cell. After low-current charging and discharging, fabricate the target electrode sheet into a second symmetrical coin cell and measure the resistance R of the second symmetrical coin cell. sol Second AC impedance diagram;

[0009] The resistance R of the target electrode is obtained by combining the first AC impedance diagram and the second AC impedance diagram. ion With resistance R ct And based on the resistance R sol The resistor R ion With the resistor R ct Calculate the total resistance of the target electrode and evaluate its conductivity based on the total resistance.

[0010] Optionally, obtaining the same-pole target electrode includes:

[0011] Obtain the positive electrode or the negative electrode.

[0012] Optionally, both the first symmetrical button cell and the second symmetrical button cell are batteries containing the same electrode sheet, a separator, and an electrolyte.

[0013] Optionally, the resistance R of the first symmetrical coin cell is measured. sol And the first AC impedance diagram, including:

[0014] The resistance R of the first symmetrical coin cell was measured using an electrochemical workstation. sol The first AC impedance diagram was obtained using an electrochemical workstation.

[0015] Optionally, the coin cell is a battery containing different electrodes, a separator, and an electrolyte.

[0016] Optionally, the low-current formation of the coin cell includes:

[0017] The button cell battery is charged, and its state of charge is monitored in real time.

[0018] When the state of charge of the button cell reaches a preset charge threshold, charging of the button cell is stopped.

[0019] Optionally, the resistance R of the second symmetrical coin cell is measured. sol The second AC impedance diagram includes:

[0020] The resistance R of the second symmetrical coin cell was measured using an electrochemical workstation. sol The second AC impedance diagram was obtained using an electrochemical workstation.

[0021] Optionally, the resistance R of the target electrode is obtained by combining the first AC impedance diagram and the second AC impedance diagram. ion With resistance R ct ,include:

[0022] Construct a coordinate system and input the first AC impedance diagram and the second AC impedance diagram into the coordinate system;

[0023] When the y-axis of the coordinate system is 0, the x-axis corresponding to the first and second AC impedance diagrams is the resistance R. sol ;

[0024] When the y-axis of the coordinate system is greater than 0, and the first AC impedance diagram and the second AC impedance diagram coincide, the x-axis corresponding to the first AC impedance diagram and the second AC impedance diagram is the resistance R. ion one-third;

[0025] When the y-axis of the coordinate system is greater than 0, and the first AC impedance diagram and the second AC impedance diagram do not coincide, the x-axis corresponding to the second AC impedance diagram is the resistance R. ct Twice as much.

[0026] Optionally, the method based on the resistor R sol The resistor R ion With the resistor R ct Calculate the total resistance of the target electrode, including:

[0027] For the resistor R sol The resistor R ion With the resistor R ct The total resistance R is obtained by summing the results.

[0028] Optionally, the evaluation of the conductivity of the target electrode based on the total resistance includes:

[0029] The larger the value of the total resistance R, the weaker the conductivity of the target electrode; conversely, the smaller the value of the total resistance R, the stronger the conductivity of the target electrode.

[0030] Beneficial effects:

[0031] The battery electrode conductivity evaluation method provided by this invention can identify the various components of the internal resistance in the electrode through AC impedance spectroscopy analysis of symmetrical coin cells; it can quickly identify the conductivity performance of active materials and conductive agents, including not only electronic conductivity but also ionic conductivity, with higher accuracy; the testing method can quickly estimate the internal resistance of its combined battery, thereby establishing a new method for identifying the contribution of positive and negative electrodes to the battery, determining the optimization direction of the formulation process, and reducing evaluation time. Attached Figure Description

[0032] Figure 1 This is a flowchart of a preferred embodiment of the battery electrode conductivity evaluation method of the present invention;

[0033] Figure 2This is a schematic diagram of the first and second AC impedance diagrams according to a preferred embodiment of the present invention.

[0034] Figure 3 This is a schematic diagram of the AC impedance diagram of Embodiment 2 of the present invention;

[0035] Figure 4 This is a schematic diagram of the AC impedance diagram of Embodiment 3 of the present invention;

[0036] Figure 5 This is a schematic diagram of the AC impedance diagram of Embodiment 4 of the present invention;

[0037] Figure 6 This is a schematic diagram of the AC impedance diagram of the full cell in Embodiment 5 of the present invention;

[0038] Figure 7 This is a schematic diagram of the AC impedance diagram of the positive electrode sheet in Embodiment 5 of the present invention;

[0039] Figure 8 This is a schematic diagram of the AC impedance of the negative electrode sheet in Embodiment 5 of the present invention. Detailed Implementation

[0040] The technical solution of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0041] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar terms used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Similarly, the terms "an" or "a" and similar terms do not indicate a quantity limitation, but rather indicate the presence of at least one. The terms "connected" or "linked" and similar terms are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. "Up," "down," "left," "right," etc., are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship also changes accordingly.

[0042] Please see Figure 1-8 :

[0043] Example 1:

[0044] This application provides a method for evaluating the conductivity of battery electrodes, including:

[0045] Obtain the same target electrode to form a first symmetrical coin cell, and measure the resistance R of the first symmetrical coin cell. sol And the first AC impedance diagram;

[0046] Obtain a target electrode sheet of different polarity and fabricate it into a coin cell. Perform low-current formation on the coin cell. After low-current charging and discharging, fabricate the target electrode sheet into a second symmetrical coin cell and measure the resistance R of the second symmetrical coin cell. sol Second AC impedance diagram;

[0047] The resistance R of the target electrode is obtained by combining the first AC impedance diagram and the second AC impedance diagram. ion With resistance R ct And based on the resistance R sol The resistor R ion With the resistor R ct Calculate the total resistance of the target electrode and evaluate its conductivity based on the total resistance.

[0048] In the above embodiments, by analyzing the AC impedance spectrum of symmetrical coin cells, the various components of the internal resistance in the electrode can be identified, and the conductivity of active materials and conductive agents can be quickly identified. This includes not only electronic conductivity but also ionic conductivity, resulting in higher accuracy. This allows for the rapid estimation of the internal resistance of the combined battery, thereby establishing a new method for identifying the contribution of positive and negative electrodes to the battery, determining the optimization direction of the formulation process, and reducing evaluation time.

[0049] Optionally, obtaining the same-pole target electrode includes:

[0050] Obtain the positive electrode or the negative electrode.

[0051] In the above embodiments, the electrode can be either a positive or negative electrode. The main material of the positive electrode can be one of lithium iron phosphate, lithium cobalt oxide, lithium manganese oxide, lithium nickel oxide, or ternary materials. The main material of the negative electrode can be one of graphite, silicon oxide, or silicon carbon. The conductive agent additive can be one of carbon black, acetylene black, graphene, or carbon nanotubes. The coin cell specification can be one of CR2016, CR2032, or CR2430. The test method is AC impedance testing, with a test frequency of 0.01-1000000Hz. e The contact resistance of the electrode mainly reflects the intrinsic resistance of the material.

[0052] Optionally, both the first symmetrical button cell and the second symmetrical button cell are batteries containing the same electrode sheet, a separator, and an electrolyte.

[0053] Optionally, the resistance R of the first symmetrical coin cell is measured. sol And the first AC impedance diagram, including:

[0054] The resistance R of the first symmetrical coin cell was measured using an electrochemical workstation. sol The first AC impedance diagram was obtained using an electrochemical workstation.

[0055] Optionally, the coin cell is a battery containing different electrodes, a separator, and an electrolyte.

[0056] Optionally, the low-current formation of the coin cell includes:

[0057] The button cell battery is charged, and its state of charge is monitored in real time.

[0058] When the state of charge of the button cell reaches a preset charge threshold, charging of the button cell is stopped.

[0059] In the above embodiment, the low current is set to 0.01C for 10 hours. Specifically, the charge / discharge process involves constant current charging at 0.1C to 3.65V, followed by constant current discharging at 0.1C to 50% capacity. The R... ion The value is three times the value of the segment where curves a and b overlap, mainly reflecting the resistance of the ions themselves; the aforementioned R... ct The value is half the diameter of the semicircle of curve b, mainly reflecting the internal resistance of charge transfer; the aforementioned R ion and R ct It can only appear when it participates in an electrochemical reaction.

[0060] Optionally, the resistance R of the second symmetrical coin cell is measured. sol The second AC impedance diagram includes:

[0061] The resistance R of the second symmetrical coin cell was measured using an electrochemical workstation. sol The second AC impedance diagram was obtained using an electrochemical workstation.

[0062] Optionally, the resistance R of the target electrode is obtained by combining the first AC impedance diagram and the second AC impedance diagram. ion With resistance R ct ,include:

[0063] Construct a coordinate system and input the first AC impedance diagram and the second AC impedance diagram into the coordinate system;

[0064] When the y-axis of the coordinate system is 0, the x-axis corresponding to the first and second AC impedance diagrams is the resistance R. sol ;

[0065] When the y-axis of the coordinate system is greater than 0, and the first AC impedance diagram and the second AC impedance diagram coincide, the x-axis corresponding to the first AC impedance diagram and the second AC impedance diagram is the resistance R. ion one-third;

[0066] When the y-axis of the coordinate system is greater than 0, and the first AC impedance diagram and the second AC impedance diagram do not coincide, the x-axis corresponding to the second AC impedance diagram is the resistance R. ct Twice as much.

[0067] like Figure 3 As shown, in the above embodiments, R sol Z' is the resistance of the solution, mainly reflecting the conductivity of the electrolyte. When Z” = 0, the corresponding value of Z' is R. sol value.

[0068] Optionally, the method based on the resistor R sol The resistor R ion With the resistor R ct Calculate the total resistance of the target electrode, including:

[0069] For the resistor R sol The resistor R ion With the resistor R ct The total resistance R is obtained by summing the results.

[0070] Optionally, the evaluation of the conductivity of the target electrode based on the total resistance includes:

[0071] The larger the value of the total resistance R, the weaker the conductivity of the target electrode; conversely, the smaller the value of the total resistance R, the stronger the conductivity of the target electrode.

[0072] Example 2:

[0073] A negative electrode slurry with a formulation of graphite SX-1: carbon black SP: dispersant CMC: binder SBS of 95.5:1:1.2:2.3 was prepared and uniformly coated onto a 10μm copper foil. After drying for 12 hours, a negative electrode sheet with an areal density of 8.0 mg / cm2 was obtained. The electrode sheet was then rolled to the appropriate thickness with a compaction density of 1.56 g / cm3. The electrode sheet was then mounted to a size of 13 mm. In a vacuum glove box, three symmetrical cells were assembled: one without a separator and without electrolyte, one with a separator and electrolyte, and one with an electrode sheet / lithium sheet. These were designated SP-1, SP-2, and SP-3, respectively. The SP-3 battery was first formed and then charged and discharged to 50% SOC. Finally, the AC impedance of the three batteries (SP-1, SP-2, and SP-3) was tested, and the R value was obtained from the curves. e R sol R ion R ct Resistance value.

[0074] Example 3:

[0075] A negative electrode slurry with a formulation of graphite SX-1: acetylene black Li435: dispersant CMC: binder SBR of 95.5:1:1.2:2.3 was prepared, uniformly coated on a 10μm copper foil, and dried for 12 hours to obtain an areal density of 8.0 mg / cm³. 2 The negative electrode sheet was compacted to a density of 1.56 g / cm³. 3 The electrode sheets were rolled to the appropriate thickness; the electrode sheets were cut to 13mm in size, and assembled in a vacuum glove box into symmetrical electrode / electrode cells (without separator and without electrolyte), symmetrical electrode / electrode cells (with separator and electrolyte), and asymmetrical electrode / lithium cell cells (labeled Li435-1, Li435-2, and Li435-3), respectively. The Li435-3 cell was first formed and then charged and discharged to 50% SOC. Finally, AC impedance tests were performed on the three cells (Li435-1, Li435-2, and Li435-3), and the RE value was obtained from the curves. e R sol R ion R ct Resistance value.

[0076] Example 4:

[0077] A negative electrode slurry with a formulation of graphite SX-1: graphene composite conductive agent GCS (graphene:CNT:SP = 4:2:4): dispersant CMC: binder SBR in a ratio of 100:1:1.3:2.0 was prepared, uniformly coated on a 10μm copper foil, and dried for 12 hours to obtain an areal density of 8.0 mg / cm³. 2 The negative electrode sheet was compacted to a density of 1.56 g / cm³. 3 The electrode sheets were rolled to the appropriate thickness; the electrode sheets were cut to 13mm in size, and assembled in a vacuum glove box into symmetrical electrode / electrode cells (without separator and without electrolyte), symmetrical electrode / electrode cells (with separator and electrolyte), and asymmetrical electrode / lithium cell cells (labeled GCS-1, GCS-2, and GCS-3), respectively; the GCS-3 cell was first formed and then charged and discharged to 50% SOC; finally, the AC impedance of the three cells (GCS-1, GCS-2, and GCS-3) was tested, and the R value was obtained from the curve. e R sol R ion R ct Resistance value.

[0078] Please refer to Table 1, which shows the test results of the battery electrodes in Examples 2-4.

[0079] Table 1: Test Results of Examples 2-4

[0080] <![CDATA[R sol (Oh)]]> 1.15 1.104 1.17 <![CDATA[R ion (Oh)]]> 9.873 5.622 5.394 <![CDATA[R ct (Oh)]]> 12.844 11.967 6.482 R total 23.867 18.693 13.046

[0081] Conductive agents, as a crucial component of electrodes, significantly influence their performance. They not only accelerate electron migration but also increase the insertion / extraction rate of lithium ions within the active material, thereby improving conductivity and reducing the electrode's ohmic resistance. Therefore, the use of conductive agent materials in electrode design is a critical factor affecting electrode performance. Common conductive agents include carbon black (zero-dimensional), acetylene black (zero-dimensional), carbon nanotubes (one-dimensional), graphene (two-dimensional), and composite conductive agents (three-dimensional). Each of these agents possesses unique advantages, enabling the construction of a robust conductive network within the material, thus enhancing the capacity, rate capability, and lifespan of lithium-ion batteries.

[0082] The above three implementation examples use the same negative electrode with three different conductive agents. Based on the testing methods, the resistance values ​​of various parts of the negative electrode sheet in Examples 2-4 can be obtained. As shown in the table above, R in the three implementation examples... sol The resistance values ​​are small and not significantly different, while R lion and R ct The proportion of the resistance value to the total resistance value is large, and it is the main factor determining the total resistance value. Implementation Case 2 uses the conventional conductive agent SP, whose R... lion and R ct The resistance values ​​are all relatively high. Implementation Case 3 uses acetylene black Li435, which has a much smaller particle size than SP, resulting in smaller interparticle gaps and a larger contact area with the electrolyte. This leads to more and shorter lithium-ion diffusion paths, thus its R... lion The resistance is significantly reduced. Implementation Case 4 uses a graphene composite conductive agent, and its tested R... lion and R ct The resistance values ​​are all minimized, resulting in the lowest total internal resistance of the electrode. This is because the graphene composite conductive agent contains three conductive agents: graphene, carbon nanotubes, and SP. The three carbon materials are interconnected to form a three-dimensional network of points, lines, and surfaces. Compared with point-to-point and point-to-line structures, this structure not only has highly efficient electronic conduction capabilities and significantly improves the electron mobility of the active material surface, but also the abundant oxygen-containing functional groups in graphene are beneficial for wetting the electrolyte, increasing the lithium-ion diffusion rate, constructing a more three-dimensional electronic and ion conductive pathway, and reducing the movement distance of electrons and ions.

[0083] Example 5:

[0084] The above implementation cases were verified by testing the resistance values ​​of the positive and negative electrodes separately, and then calculating the internal resistance of the combined battery, which was then compared with the actual internal resistance of the fabricated full lithium-ion battery.

[0085] The positive electrode formulation is lithium iron phosphate B3: dispersant PVP: conductive agent Tiannai CNT117-44: binder PVDF1800 = 100:0.5:1:3.0. This mixture is uniformly coated onto a 15μm copper foil and dried for 12 hours to obtain an areal density of 15.9 mg / cm³. 2 The positive electrode sheet is compacted to a density of 2.45 g / cm³. 3 The electrode sheet is rolled to the appropriate thickness and then cut to a size of 13mm to obtain the positive electrode sheet;

[0086] The negative electrode formulation is graphite ACR1:SP: dispersant CMC: binder SBR = 100:1:1.3:2.0. After being uniformly coated onto a 10μm copper foil and dried for 12 hours, a surface density of 8.0 mg / cm³ was obtained. 2 The negative electrode sheet was compacted to a density of 1.56 g / cm³. 3 The electrode sheet is rolled to the appropriate thickness and then cut to a size of 13mm to obtain the negative electrode sheet;

[0087] After assembling positive and negative electrodes into symmetrical electrode / electrode cells with separators and electrolytes, and asymmetrical electrode / lithium cell cells (charged to 50% SOC), tests were conducted, and the corresponding R values ​​were calculated. sol R ion R ct The resistance values ​​are shown in Table 2. Simultaneously, 527095 pouch cells were fabricated using the same positive and negative electrode combinations as described above. The electrode formulation, compaction density, separator, and electrolyte were all kept consistent. After charging the full cell to 50% SOC, an AC impedance test was performed to obtain the resistance value R. The ohmic resistance of the battery is generally tested using an AC voltage at a frequency of 1kHz, and its value is approximately equivalent to the 1kHz resistance value in AC impedance testing. The measured resistance of the above full cell was R = 25.1mΩ.

[0088] Table 2: Test Results of Example 5

[0089] <![CDATA[R sol (Oh)]]> 1.348 1.625 <![CDATA[R ion (Oh)]]> 7.209 <![CDATA[R ct (Oh)]]> 5.855 R total 7.203 8.834

[0090] Based on the test method of Example 5 above, the resistance values ​​of the positive and negative electrodes can be obtained.

[0091] At 1kHz, only R was measured on the negative electrode. sol R ion The positive electrode only tested R sol R ct .

[0092] Based on the formulas R = ρL / S and R = Rpositive + Rnegative, the following formula can be derived:

[0093] R(positive, symmetrical) * Ssymmetric = R(positive, calculated) * Spositive electrode;

[0094] R(negative, symmetrical) * Ssymmetric = R(negative, calculated) * Snegative electrode;

[0095] R(total, calculated) = R(positive, calculated) + R(negative, calculated);

[0096] R(positive, symmetric) = R sol +R ct =1.348Ω+5.855Ω=7.203Ω;

[0097] R (negative, symmetric) = R sol +R ct =1.625Ω+7.209Ω=8.834Ω;

[0098] S-symmetric electrode area = πr 2 = 3.14159 × (13 mm / 2) 2 =1.3273cm 2 ;

[0099] Area of ​​the positive electrode (S) = Length * Width = (964 + 812) mm × 85 mm = 1509.6 cm² 2 ;

[0100] Area of ​​negative electrode S = (970 + 850) mm × 87 mm = 1583.4 cm² 2 ;

[0101] Given the values ​​of S (symmetric), S (positive electrode), S (negative electrode), and R (positive, symmetric) and R (negative, symmetric), the total internal resistance R of the battery electrodes can be calculated. 极片 .

[0102] R_electrode = R(negative, symmetrical) * S_symmetric / S_negative_electrode + R(positive, symmetrical) * S_symmetric / S_positive_electrode = 13.73mΩ;

[0103] Since the electrode also contains tabs, R_tab = R_positive_tab + R_negative_tab = 9.65mΩ;

[0104] Final R calculation = R_tab + R_plate = 23.38mΩ;

[0105] Given that the measured R = 25.1 mΩ, with an error value within 1-2 mΩ, and that the error includes the resistance introduced by the accessory tape, the calculated R is basically close to the measured R.

[0106] As can be seen from the above inferences, this method is fast and simple. By testing the resistance values ​​of the positive and negative electrodes separately, the internal resistance of the combined full cell can be calculated, which greatly shortens the evaluation cycle of material performance and has high accuracy. It is of reference value for evaluating the conductivity of materials.

[0107] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A method for evaluating the conductivity of battery electrodes, characterized in that, include: A first symmetric button cell is made from the homopolar target disk, and the resistance R of the first symmetric button cell is measured sol and a first AC impedance plot; An anode target sheet is obtained, a button-type full cell is made from the anode target sheet, the button-type full cell is subjected to small-current formation, a second symmetrical button-type full cell is made from the anode target sheet after small-current charge and discharge, and the resistance R of the second symmetrical button-type full cell is measured sol and a second AC impedance diagram, the first symmetrical button-type full cell and the second symmetrical button-type full cell are both cells containing homopolar sheets, with a separator and an electrolyte; The resistance R of the target electrode is obtained by combining the first AC impedance diagram and the second AC impedance diagram. ion With resistance R ct And based on the resistance R sol The resistor R ion With the resistor R ct Calculate the total resistance of the target electrode and evaluate the conductivity of the target electrode based on the total resistance. The resistance R of the target electrode is obtained by combining the first AC impedance diagram and the second AC impedance diagram. ion With resistance R ct ,include: Construct a coordinate system and input the first AC impedance diagram and the second AC impedance diagram into the coordinate system; When the y-axis of the coordinate system is 0, the x-axis corresponding to the first and second AC impedance diagrams is the resistance R. sol ; When the y-axis of the coordinate system is greater than 0, and the first AC impedance diagram and the second AC impedance diagram coincide, the x-axis corresponding to the first AC impedance diagram and the second AC impedance diagram is the resistance R. ion one-third; When the y-axis of the coordinate system is greater than 0, and the first AC impedance diagram and the second AC impedance diagram do not coincide, the x-axis corresponding to the second AC impedance diagram is the resistance R. ct Twice as much.

2. The method for evaluating the conductivity of battery electrodes according to claim 1, characterized in that, The acquisition of the same-polarity target electrode includes: Obtain the positive electrode or the negative electrode.

3. The method for evaluating the conductivity of battery electrodes according to claim 1, characterized in that, The resistance R of the first symmetrical button cell was measured. sol And the first AC impedance diagram, including: The resistance R of the first symmetrical coin cell was measured using an electrochemical workstation. sol The first AC impedance diagram was obtained using an electrochemical workstation.

4. The method for evaluating the conductivity of battery electrodes according to claim 1, characterized in that, The coin cell is a battery containing different electrodes, a separator, and an electrolyte.

5. The method for evaluating the conductivity of battery electrodes according to claim 1, characterized in that, The low-current formation of the coin cell includes: The button cell battery is charged, and its state of charge is monitored in real time. When the state of charge of the button cell reaches a preset charge threshold, charging of the button cell is stopped.

6. The method for evaluating the conductivity of battery electrodes according to claim 1, characterized in that, The resistance R of the second symmetrical button cell was measured. sol The second AC impedance diagram includes: The resistance R of the second symmetrical coin cell was measured using an electrochemical workstation. sol The second AC impedance diagram was obtained using an electrochemical workstation.

7. The method for evaluating the conductivity of battery electrodes according to claim 1, characterized in that, The resistance R sol The resistor R ion With the resistor R ct Calculate the total resistance of the target electrode, including: For the resistor R sol The resistor R ion With the resistor R ct The total resistance R is obtained by summing the results.

8. The method for evaluating the conductivity of battery electrodes according to claim 7, characterized in that, The evaluation of the conductivity of the target electrode based on the total resistance includes: The larger the value of the total resistance R, the weaker the conductivity of the target electrode; conversely, the smaller the value of the total resistance R, the stronger the conductivity of the target electrode.

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