Layered electrode resistance parameter inversion method and system based on multi-probe measurement

Abstract

The invention relates to the technical field of electrical performance measurement, in particular to a layered electrode resistance parameter inversion method and system based on multi-probe measurement, and the method comprises the following steps: obtaining basic physical parameters of an electrode pole piece, and placing the electrode pole piece on an insulating support structure to enable an active layer to face upwards; arranging at least four probes along a preset direction, controlling part of the probes to inject or recycle test current, and collecting potential signals by the rest of the probes to obtain measurement data; constructing a discrete node electrical model based on a layered structure, regarding an active layer and a current collector layer as different conductive areas, and introducing interface resistance parameters; the active layer body resistivity and the interface resistance serve as parameters to be inverted, the basic physical parameters and the potential measurement data serve as input constraints, and data optimization and parameter inversion are achieved through iterative calculation. According to the invention, synchronous analysis of the resistivity and the interface resistance of the active layer under the same measurement condition is realized, and the stability and the consistency of an electrical parameter solving process are improved, so that the reliability of a measurement result is improved.

Description

Technical Field

[0001] This invention relates to the field of electrical performance measurement technology, specifically a method and system for inverting the resistance parameters of layered electrodes based on multi-probe measurement. Background Technology

[0002] In the manufacturing process of lithium-ion batteries, electrode sheets are typically composed of a metal current collector and an active layer stacked together. Their conductivity depends not only on the resistivity of the active layer but also on the interfacial resistance between the two. Excessive or uneven interfacial resistance can hinder current transmission and exacerbate local polarization, thereby affecting the battery's internal resistance, power performance, and lifespan. Therefore, quantitatively evaluating the resistivity of the active layer and the interfacial resistance while maintaining the integrity of the electrode structure is a crucial technical requirement for electrode quality control and performance analysis.

[0003] Several measurement methods have been proposed to address the above needs, but all of them have certain limitations: 1) Mechanical methods (such as peel tests and cross-cut tests) are mainly used to evaluate interfacial adhesion. They are destructive tests and it is difficult to establish a direct correlation with electrical properties. 2) Although the overall electrical method (such as the four-probe method and through resistance measurement) can obtain the equivalent resistance value, its analysis model is based on the assumption of a single-layer conductor. When applied to the electrode structure composed of layers of different materials, it cannot effectively distinguish the contribution of the active layer bulk resistance and the interface resistance. 3) Although electrochemical impedance spectroscopy can obtain impedance information related to the interface, its results depend on equivalent circuit fitting. The correspondence between the physical meaning of the parameters and the actual geometric structure of the electrode is weak, which leads to deviations between the analysis results and the actual interface characteristics.

[0004] Furthermore, existing patents propose acquiring electrical information of electrode surfaces or local areas through multi-probe or scanning methods to assess conductivity or interface states. For example, patents such as CN201710657859 and CN201710608281 measure electrode surface potential or resistance signals using a multi-probe array and estimate interface resistance based on predetermined calculation relationships. Foreign patents such as US6218846B1 and WO2023143638A1 also acquire sample surface electrical distribution through probe arrays or scanning measurements. These techniques can reflect interface conductivity characteristics to some extent, but their analysis is mostly based on preset calculation formulas or empirical processing methods, and a unified calculation framework for modeling and inverting the potential information obtained from multi-point measurements with the layered structural parameters inside the electrode has not yet been established. When both the active layer resistivity and interface resistance affect the measurement results, the above methods still struggle to achieve stable and independent quantitative solutions for both. Summary of the Invention

[0005] In view of the shortcomings of existing methods for measuring electrode interface resistance and resistivity in terms of destructiveness, non-separability of parameters, and model correspondence, the purpose of this invention is to provide a method and system for quantitatively analyzing the resistivity of the active layer and the interface resistance in a layered electrode while maintaining the integrity of the electrode structure.

[0006] To achieve the above objectives, the technical solution specifically adopted by the present invention is as follows: Unlike existing multi-probe measurement techniques, the layered electrode resistance parameter inversion method of this invention, based on multi-probe measurement, does not directly calculate the resistance parameters based on a single potential difference or empirical formula. Instead, it introduces a discrete nodal electrical model corresponding to the layered structure of the electrode at the computational level. In this model, the resistivity of the active layer and the interface resistance are treated as unknown parameters to be solved. The theoretical potential distribution under given parameter conditions is obtained through model calculation and compared with the multi-probe measured potential. Based on the deviation between the two, an iterative optimization algorithm is used to gradually correct the parameters, thereby obtaining a parameter combination consistent with the actual electrode conductivity state. The specific steps are as follows: S1. Obtain the basic physical parameters of the electrode sheet to be tested. The basic physical parameters include at least the total thickness of the electrode sheet, the thickness of the current collector, the type of current collector material and its conductivity. S2. Place the electrode sheet on the insulating support structure with its active layer surface facing upwards and exposed. S3. At least four probes are arranged on the surface of the electrode sheet along a predetermined direction, each probe forming a stable electrical contact with the surface of the electrode sheet, and a fixed distance is maintained between adjacent probes. S4. Control some probes to inject or recover test current into the electrode plate, and at the same time collect the potential signal at the corresponding position under the energized state through the other probes to obtain a set of potential measurement data. S5. Based on the layered structure of the electrode sheet, a discrete node electrical model is constructed. The model regards the active layer and the current collector layer as conductive regions with different electrical properties, and introduces an interface resistance parameter between them. S6. Using the volume resistivity and interface resistance of the active layer as parameters to be inverted, and taking the basic physical parameters and the potential measurement data as input constraints, the parameters to be inverted are adjusted through an iterative optimization algorithm so that the theoretical potential distribution calculated by the discrete node electrical model matches the potential measurement data, thereby resolving the volume resistivity and interface resistance values ​​of the active layer that correspond to the actual conductive state of the electrode.

[0007] Furthermore, in step S3, by changing the combination of energized probes or the direction of current, multiple sets of spatially distributed potential data are obtained without moving the electrode plates, and these data are used together as a set of overall measurement data for subsequent parameter analysis.

[0008] Furthermore, in step S5, the construction of the discrete node electrical model specifically includes: i. Discretize the electrode sheet in three dimensions along the thickness direction and the in-plane direction to form a node network; ii. Based on Kirchhoff's voltage law, establish the potential relationship between adjacent nodes in the node network to form a computable linear equation system. The coefficients of the equation system are determined by the active layer volume resistivity and interface resistance parameters of the current iteration.

[0009] This invention also provides a layered electrode resistance parameter inversion system based on multi-probe measurement. This system uses the aforementioned inversion method to invert the layered electrode resistance parameters, including: An insulated sample stage is used to support the electrode sheet to be tested. The multi-probe measurement unit employs a probe array, with each probe fixedly arranged along a straight line at equal or non-equal intervals on a probe holder, and can be synchronously raised and lowered to establish or de-establish electrical contact with the electrode surface. The current injection and switching unit is electrically connected to a selected probe in the multi-probe measurement unit and is used to inject or recover test current into the electrode plate. The potential measurement unit is electrically connected to the other probes in the multi-probe measurement unit and is used to synchronously acquire the potential signals at each probe contact point. The data processing and control unit, communicatively connected to the current injection and switching unit and the potential measurement unit, is configured to: Control probe contact, switch current injection modes, and acquire potential data; Receive and store the basic physical parameters of the electrode plates input by the user and the collected potential measurement data; Run the built-in discrete node electrical model and iterative optimization algorithm to perform parameter inversion calculations and output analytical results of the active layer volume resistivity and interface resistance.

[0010] Furthermore, the probe array is a linear array or a two-dimensional array consisting of four or more probes.

[0011] Furthermore, the data processing and control unit also includes a model building module, which is used to automatically generate the corresponding discrete node network and initialize the electrical equations based on the basic physical parameters of the input electrode sheet under test.

[0012] A computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements steps S1 to S6 of the measurement method described above.

[0013] This invention has the following characteristics and beneficial effects: 1) By using a multi-probe method to obtain multi-point potential distribution information on the surface of the electrode sheet, the conductivity characteristics can be obtained without damaging the electrode sheet structure. This avoids the damage to the sample structure caused by mechanical methods such as peeling test and cross-cut test, and improves the applicability and repeatability of the detection process.

[0014] 2) By combining the potential data obtained from multi-probe measurements with the discrete node electrical model corresponding to the layered structure of the electrode, a clear correspondence between multi-point measurement information and the internal structural parameters of the electrode is realized, overcoming the problem that existing methods can only obtain the overall equivalent impedance or local contact signal and are difficult to reflect the electrical differences within the layer.

[0015] 3) By using both the active layer resistivity and the interface resistance as parameters to be solved in the model and employing multi-point potential information to jointly constrain them, the synchronous analysis of the active layer resistivity and the interface resistance under the same measurement conditions is achieved, which improves the shortcomings of existing methods where different electrical parameters are coupled to each other and difficult to separate independently.

[0016] 4) By using an iterative optimization algorithm to gradually correct the model parameters, the stability and consistency of the electrical parameter solution process are improved, and the obtained parameter results can maintain a good match with the actual conductivity state of the electrode, thereby improving the reliability of the measurement results.

[0017] 5) By implementing the modeling and calculation under the condition of known electrode thickness, current collector material and structural parameters, the adaptability of this technical solution to different electrode structures and material systems is enhanced, enabling it to be applied to practical engineering scenarios such as electrode quality evaluation and process consistency analysis. Attached Figure Description

[0018] Figure 1 This is a flowchart illustrating the overall process of a method for inverting the resistance parameters of layered electrodes based on multi-probe measurement, according to an embodiment of the present invention.

[0019] Figure 2 This is a schematic diagram of the overall structure of a layered electrode resistance parameter inversion system based on multi-probe measurement according to an embodiment of the present invention; In the diagram, 1 represents the current collector; 2 represents the interface layer; and 3 represents the active layer. , For injection probe; ~ S is the potential measurement probe; S is the electrode surface area; d is the electrode thickness; For the current collector thickness; This represents the thickness of the active layer.

[0020] Figure 3This is a functional block diagram of a layered electrode resistance parameter inversion system based on multi-probe measurement according to an embodiment of the present invention.

[0021] Figure 4 This is a schematic diagram of the mesh structure of the discrete node method model in an embodiment of the present invention.

[0022] Figure 5 This is an example diagram of the equivalent resistance network loop in an embodiment of the present invention.

[0023] Figure 6 This is a schematic diagram of the inversion algorithm calculation process in an embodiment of the present invention. Detailed Implementation

[0024] 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, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0025] To establish a clear correspondence between surface potential information obtained from multi-point measurements and the layered structure within the electrode in a layered electrode composed of a metal current collector and an active layer, where the bulk resistivity of the active layer and the interfacial resistance simultaneously affect the current distribution and potential response, and to further achieve stable and independent solutions for each electrical parameter, this invention provides a method for inverting the resistance parameters of a layered electrode based on multi-probe measurements. Figure 1 As shown, it includes the following steps: S1. Obtain basic physical parameters Obtain the basic physical parameters of the electrode sheet to be tested. The basic physical parameters include at least the total thickness of the electrode sheet, the thickness of the current collector, the type of current collector material and its conductivity. S2, Sample Preparation The electrode sheet is placed on an insulating support structure with its active layer surface facing upwards and exposed. S3, Probe Arrangement At least four conductive probes are arranged on the surface of the electrode plate along a predetermined direction (such as a straight line or an array). The perpendicular contact pressure between the probes and the electrode plate surface is controlled within the range of 0.1-1 N to ensure that the probes form a stable ohmic contact with the electrode plate surface. S4, Multi-condition Potential Measurement Without moving the electrodes, by changing the combination of energized probes or the direction of the injected current, different probes are sequentially controlled to inject or recover a constant test current into the electrodes. Simultaneously, the potential signals at corresponding spatial locations under energized conditions are acquired through the remaining probes. This process is repeated to obtain multiple sets of spatially distributed potential response datasets, which together constitute the basic measurement data for subsequent parameter inversion. S5. Perform the following processing on the raw potential measurement data: Outlier removal: The 3σ criterion is used to identify and remove outlier data points that deviate from the mean by three times the standard deviation. Noise filtering: Power frequency interference and high-frequency noise are removed by using a 50Hz notch filter and a low-pass filter (cutoff frequency 1kHz); Normalization: The potential data under different current injection conditions are normalized according to the current intensity to unify the dimensions; S6. Constructing a discrete node electrical model and optimizing the objective function A three-dimensional discrete nodal electrical model is constructed based on the layered structure of the electrode plates. This model treats the active layer and the current collector layer as conductive regions with different electrical properties, and introduces an interface resistance parameter between them. The specific operation is as follows: First, assume the initial electrical parameters: the initial volume resistivity of the active layer is... The initial value of the interface resistance is Secondly, a discrete node equivalent resistance network model is established. The electrode sheet is three-dimensionally discretized in the thickness and in-plane directions to form a discrete node network. In the discrete node network, surface nodes correspond to the actual measurement points of the multi-probe, while longitudinal nodes are used to characterize material layers with different electrical properties. Thirdly, a computable set of mathematical equations is established based on this discrete node network. The core is to establish a voltage rise and fall conservation equation for each basic square closed loop composed of four resistors, based on Kirchhoff's Voltage Law (KVL), requiring that the algebraic sum of voltage rise and fall along the closed loop be zero. In the discrete node equivalent resistance network, adjacent nodes are interconnected through equivalent resistance units. The equivalent resistance at different locations is determined by the resistivity and dimensional parameters of the corresponding materials. At the interface between the active layer and the current collector, an equivalent interface resistance value RI is introduced between the corresponding nodes. Y This is used to characterize the additional voltage drop effect at the interface, allowing the voltage distribution in the cross-interface loop to reflect the influence of the interface's conduction characteristics. By applying voltage rise and fall conservation conditions to each basic closed loop in the entire discrete node network, a system of linear equations with the node potentials as unknowns can be established. Taking the first loop as an example, we have... Similarly, the equations for other loops can be obtained. For simplicity, the following notation is introduced: ; ; ; ; ; ; ; .

[0026] The Kirchhoff linear equations described above can then be expressed in the form of matrix G:

[0027] Subsequently, by solving the above system of linear equations, the equivalent current of each loop under the current resistance parameters is obtained, and thus the V at each node is obtained. i c (ρ1,R s Next, the theoretical potential distribution is compared point-by-point with the actual measured potential data after preprocessing in step S5 at the corresponding spatial locations of the probe, and the difference between the two, i.e., the residual, is calculated. Finally, to evaluate the parameter matching degree and guide optimization, an objective function is constructed. The index i iterates through all measurement points (e.g., ...). 、 , wait), This is the measured potential. The calculated potential is guessed given parameters, where N is the number of measurement points. Set a preset stopping threshold. By minimizing Find the optimal solution and ( (with known information fixed), that is, to construct a nonlinear least squares problem; S7. Using the volume resistivity and interface resistance of the active layer as parameters to be inverted, and taking the basic physical parameters and the potential measurement data as input constraints, the parameters to be inverted are adjusted through an iterative optimization algorithm so that the theoretical potential distribution calculated by the discrete node electrical model matches the potential measurement data, thereby resolving the volume resistivity and interface resistance values ​​of the active layer that correspond to the actual conductive state of the electrode.

[0028] It is worth noting that, as a prerequisite for calculation and analysis, this inversion method assumes that each constituent layer of the electrode sheet is an electrically homogeneous medium within its planar range and satisfies isotropic conductivity in the considered direction. This assumption is used to establish an electrical model corresponding to the actual structure of the electrode sheet and does not constitute a substantial limitation on the material system.

[0029] Unlike existing multi-probe measurement techniques, this invention does not rely solely on a single measurement formula or empirical conversion relationship. Instead, it introduces an electrical model corresponding to the electrode geometry, using the potential data obtained from multi-probe measurements as constraints to establish a systematic correlation between multi-point measurement information and intralayer electrical parameters at the computational level. In this way, the measurement results not only reflect surface or local responses but can also be used to analyze key parameters that decisively influence the electrode's conductivity, such as the active layer's bulk resistivity and interfacial resistance.

[0030] like Figure 2As shown, the layered electrode resistance parameter inversion system based on multi-probe measurement used in this embodiment includes a multi-probe measurement unit, a current injection and switching unit, a potential measurement unit, and a data processing unit. The multi-probe measurement unit consists of multiple probes arranged along the electrode surface, with a fixed spacing between each probe, and capable of forming stable electrical contact with the electrode surface. In this embodiment, the multiple probes are a linear array or a two-dimensional array of four or more probes.

[0031] like Figure 3 As shown, during the measurement process, the electrode sheet is placed flat, and the multi-probe measurement unit forms stable contact with the electrode sheet surface. Current is injected at selected probe positions via the current injection and switching unit, while the other probes simultaneously measure the surface potential at the corresponding positions. By changing the combination of the energized probe and the measurement probe, multiple sets of surface potential measurement data can be obtained without altering the electrode sheet's placement. Each set of measurement data corresponds to the potential distribution of the same electrode sheet under different energizing conditions.

[0032] After completing the potential measurement, the electrical parameter calculation process begins. For example... Figure 4 As shown, based on the layered structure of the electrode, the active layer and the current collector are distinguished along the electrode thickness direction in the computational model, and discrete nodes are set at the measurement positions on the electrode surface and between layers. The surface nodes correspond to the actual measurement points of the multi-probe, while the longitudinal nodes are used to characterize the potential states in different material layers. In this way, the continuous electrode structure is transformed into a discrete node network model.

[0033] By adjusting the combination of the energizing probe and the measuring probe, potential data under different measurement conditions can be obtained without changing the electrode placement, thereby improving the integrity and stability of the measurement information.

[0034] In the established discrete node model, adjacent nodes are connected by equivalent resistance. The inter-node resistance within the active layer is determined by the volume resistivity of the active layer. An interface resistance parameter is introduced between nodes located at the interface between the active layer and the current collector to characterize the resistance effect generated when electrons pass through the interface, such as... Figure 5 As shown. The above modeling method enables the computational model to reflect the actual current conduction path inside the electrode.

[0035] In specific calculation implementation, such as Figure 6 As shown, initial values ​​need to be set for the resistivity of the active layer and the interfacial resistance. These initial values ​​can be reasonably set based on the electrode material type, thickness parameters, and existing empirical ranges, and are not limited to a specific numerical form. Given these initial parameters, based on the aforementioned discrete node model, a set of node potential equations is constructed using Kirchhoff's voltage law to calculate the theoretical potential distribution on the electrode surface under these parameters.

[0036] Subsequently, the calculated theoretical potential distribution is compared with the measured potential data under the corresponding energized conditions to obtain the error information between the two. This error is used to evaluate the degree of deviation between the current parameter combination and the actual electrode conductivity state.

[0037] Based on this, such as Figure 6 As shown, the resistivity of the active layer and the interface resistance parameters are updated based on the error information. In this embodiment, the parameter update process adopts an iterative optimization method based on the least squares criterion. By gradually adjusting the parameters, the calculated potential distribution continuously approximates the measured results. The above iterative process terminates when a preset convergence condition is met or a set number of iterations is reached.

[0038] After the iteration is complete, the current parameter combination is output as the calculated results of the active layer resistivity and interface resistance corresponding to that electrode. Through the above implementation process, this invention can achieve quantitative analysis of the electrical parameters in the layered structure of an electrode by utilizing surface potential information obtained from multi-probe measurements without damaging the electrode structure.

[0039] It should be noted that, in different implementations, the node division method, iteration termination condition, or parameter initial value setting can be adjusted according to the electrode material type, measurement accuracy requirements, or computational efficiency requirements, but none of these adjustments will affect the basic principles and technical effects of the technical solution described in this invention.

Claims

1. A method for layered electrode resistivity parameter inversion based on multi-probe measurements, characterized in that, The method comprises the following steps: S1, obtaining basic physical parameters of the electrode tab to be measured, the basic physical parameters comprising at least total thickness of the electrode tab, thickness of the current collector, type of the current collector material and conductivity thereof; S2, placing the electrode tab on an insulating support structure with the active layer surface exposed upward; S3, arranging at least four probes on the surface of the electrode tab in a predetermined direction, each probe forming stable electrical contact with the surface of the electrode tab, and the adjacent probes maintaining a fixed interval; S4, controlling part of the probes to inject or recover test current to the electrode tab, and collecting potential signals at corresponding positions in the energized state through the remaining probes to obtain a set of potential measurement data; S5, constructing a discrete node electrical model based on the layered structure of the electrode tab, regarding the active layer and the current collector layer as conductive regions with different electrical properties, and introducing an interface resistance parameter between the two layers; S6, taking the volume resistivity of the active layer and the interface resistance as the parameters to be inverted, taking the basic physical parameters and the potential measurement data as input constraints, adjusting the parameters to be inverted through an iterative optimization algorithm, so that the theoretical potential distribution calculated by the discrete node electrical model matches the potential measurement data, thereby analyzing the volume resistivity of the active layer and the interface resistance value consistent with the actual conductive state of the electrode tab.

2. A layered electrode resistivity parameter inversion method based on multi-probe measurements as claimed in claim 1, wherein, In the step S3, a plurality of sets of spatially distributed potential data are obtained by changing the combination mode or the current direction of the probes in the energized state without moving the electrode tab, which are collectively used as a set of overall measurement data for subsequent parameter analysis.

3. The method of claim 1, wherein, In the step S5, the construction of the discrete node electrical model specifically comprises: i. three-dimensionally discretizing the electrode tab in the thickness direction and the in-plane direction to form a node network; ii. establishing the potential relationship between adjacent nodes in the node network according to Kirchhoff's voltage law to form a calculable linear equation set, the coefficients of the equation set being determined by the volume resistivity of the active layer and the interface resistance parameter in the current iteration.

4. A multi-probe measurement based layered electrode resistivity parameter inversion system, characterized in that, The inversion method of any one of claims 1-3 is used to realize the inversion of the resistance parameters of the layered electrode.

5. A layered electrode resistivity parameter inversion system based on multi-probe measurements as claimed in claim 4, wherein, It comprises: an insulating sample table for carrying the electrode tab to be measured; a multi-probe measurement unit using a probe array, each probe being fixedly arranged along a straight line at equal or unequal intervals on a probe holder and being capable of synchronous lifting to establish or release electrical contact with the surface of the electrode tab; a current injection and switching unit electrically connected to selected probes in the multi-probe measurement unit for injecting or recovering test current to the electrode tab; a potential measurement unit electrically connected to the remaining probes in the multi-probe measurement unit for synchronously collecting potential signals at the contact points of the probes; a data processing and control unit communicatively connected to the current injection and switching unit and the potential measurement unit and configured to: control the contact of the probes, the switching of the current injection mode and the collection of potential data; receive and store the basic physical parameters of the electrode tab input by the user and the potential measurement data collected; run the built-in discrete node electrical model and iterative optimization algorithm to perform parameter inversion calculation and output the analysis results of the volume resistivity of the active layer and the interface resistance.

6. A layered electrode resistivity parameter inversion system based on multi-probe measurements as claimed in claim 5, wherein, The probe array is a linear array or a two-dimensional array of four or more probes.

7. A layered electrode resistivity parameter inversion system based on multi-probe measurements as claimed in claim 5, wherein, The data processing and control unit further comprises a model construction module for automatically generating a corresponding discrete node network and initializing an electrical equation set according to the inputted basic physical parameters of the electrode tab to be measured. 8.A computer readable storage medium having stored thereon a computer program which, when executed by a processor, implements steps S1 to S6 of the measurement method according to any one of claims 1 to 3.

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