Battery parameter detection method and device

Abstract

The application relates to a battery parameter detection method and device. The method comprises the following steps: presetting a theoretical positive electrode surface capacity / negative electrode surface capacity (N / P) ratio gradient, preparing positive electrode half-cells and negative electrode half-cells corresponding to different theoretical N / P ratios, reversely connecting the positive electrode half-cells and the negative electrode half-cells with the same theoretical N / P to obtain full cells corresponding to the theoretical N / P ratios, and performing charge-discharge tests on the reversely connected full cells to detect the charge capacity and the discharge capacity of the full cells under different N / P gradients. In the method, the positive electrode half-cells and the negative electrode half-cells are reversely connected to form full cells, the working environment of actual full cells is simulated, the interference of an alkali metal counter electrode in traditional half-cell tests is eliminated, and the gram capacity obtained by the test is closer to the actual value of the material in the actual full cell.

Description

Technical Field

[0001] This application relates to the field of battery testing technology, and in particular to a method and apparatus for testing battery parameters. Background Technology

[0002] In the research, design, and mass production of alkali metal ion secondary batteries (including lithium-ion and sodium-ion batteries), key battery parameters, such as specific capacity and the capacity matching relationship between the positive and negative electrodes (N / P ratio), are crucial for battery safety, cycle life, energy density, rate performance, and cost control. Reasonably determining and accurately testing these battery parameters is a vital prerequisite for battery design, material selection, and process matching. However, current battery design phases lack quantitative testing data and mostly rely on theoretical parameters for design development. In actual mass production, factors such as batch differences in positive and negative electrode materials, process fluctuations, and interfacial side reactions lead to distorted and unreliable test data, resulting in deviations between actual performance and design specifications. This can cause safety and reliability issues such as lithium plating, increased polarization, rapid capacity decay, and internal short circuits.

[0003] Traditional battery parameter testing methods suffer from several drawbacks: insufficient accuracy, with limited precision in calculating key parameters such as the N / P ratio; lack of synergy, often involving independent testing of single indicators, failing to support multi-parameter collaborative optimization; cumbersome operation, poor practicality, long testing cycles, and difficulty in quickly providing feedback on design optimization directions; and poor data reliability, highly susceptible to environmental and operational errors, making it difficult to provide support for design. With the increasing prevalence of high-density cells and new anode materials, battery design demands higher parameter accuracy and data reliability. Existing testing methods are no longer sufficient, necessitating a battery parameter testing method that is accurate, highly synergistic, easy to operate, practical, and provides reliable data to support battery design optimization. Summary of the Invention

[0004] Therefore, it is necessary to provide a battery parameter detection method and device that features high detection accuracy, synergistic optimization of multiple performance indicators, and simple operation to address the aforementioned technical problems.

[0005] In a first aspect, this application provides a battery parameter detection method, including the following steps: a preset theoretical positive electrode surface capacity / negative electrode surface capacity (N / P) ratio gradient, and based on the theoretical specific capacity and mass of the positive electrode material and the negative electrode material, preparing positive electrode half-cells and negative electrode half-cells corresponding to different theoretical N / P ratios;

[0006] By connecting the positive electrode half-cell and the negative electrode half-cell with the same theoretical N / P ratio in reverse series, a full cell with the corresponding theoretical N / P ratio is obtained.

[0007] The full battery was subjected to charging and discharging tests to obtain the standard positive electrode charging specific capacity versus theoretical N / P curve, the standard positive electrode discharging specific capacity versus theoretical N / P curve, the standard negative electrode charging specific capacity versus theoretical N / P curve, and the standard negative electrode discharging specific capacity versus theoretical N / P curve.

[0008] Identify the critical points corresponding to the standard positive electrode charging capacity versus theoretical N / P curve, the standard positive electrode discharging capacity versus theoretical N / P curve, the standard negative electrode charging capacity versus theoretical N / P curve, and the standard negative electrode discharging capacity versus theoretical N / P curve, respectively.

[0009] Based on the critical point, the standard charge capacity, standard discharge capacity, standard charge capacity, and standard discharge capacity of the positive electrode material are obtained.

[0010] Secondly, this application also provides a battery parameter detection device, comprising:

[0011] A half-cell module is used to prepare positive and negative half-cells with different theoretical N / P ratios based on the preset theoretical positive electrode surface capacity / negative electrode surface capacity (N / P) ratio gradient and the theoretical specific capacity and mass of positive and negative electrode materials.

[0012] A reverse series module is used to connect the positive electrode half-cell and the negative electrode half-cell with the same theoretical N / P ratio in reverse series to obtain a full cell with the corresponding theoretical N / P ratio.

[0013] The testing module is used to perform charging and discharging tests on the full battery to obtain standard positive electrode charging specific capacity versus theoretical N / P curves, standard positive electrode discharging specific capacity versus theoretical N / P curves, standard negative electrode charging specific capacity versus theoretical N / P curves, and standard negative electrode discharging specific capacity versus theoretical N / P curves.

[0014] The identification module is used to identify the critical points corresponding to the standard positive electrode charging capacity and theoretical N / P curve, the standard positive electrode discharging capacity and theoretical N / P curve, the standard negative electrode charging capacity and theoretical N / P curve, and the standard negative electrode discharging capacity and theoretical N / P curve, respectively.

[0015] The acquisition module is used to acquire the standard charge capacity, standard discharge capacity, standard charge capacity, and standard discharge capacity of the positive electrode material based on the critical point.

[0016] The above-mentioned battery parameter detection method and device form a full cell by connecting the positive electrode half cell and the negative electrode half cell in reverse series, and perform charge and discharge tests on the reverse-connected full cell to detect the charging capacity and discharge capacity of the full cell under different N / P gradients; it has the following beneficial effects: 1. High detection accuracy: By connecting the positive electrode half cell and the negative electrode half cell in reverse series to form a full cell, the working environment of the actual full cell is simulated, eliminating the interference of alkali metals on the electrodes in traditional half cell tests, and making the specific capacity obtained by the test closer to the true value of the material in the actual full cell;

[0017] 2. Considering the N / P effect: By constructing different theoretical N / P gradients, the influence of the N / P ratio on the specific capacity of the positive and negative electrode materials is comprehensively analyzed. By identifying the critical point of the curve, the actual specific capacity of the positive and negative electrode materials is accurately obtained, providing a reliable basis for the N / P optimization design of the full cell.

[0018] 3. Simple operation and strong feasibility: The entire testing process does not require complex equipment and processes, the steps are clear, and the test parameters can be flexibly adjusted according to different types of battery materials. It is suitable for the specific capacity testing of various battery positive and negative electrode materials.

[0019] 4. Comprehensive and reliable data: Four core curves are obtained through charge-discharge testing, combined with potential measurement data, which can comprehensively reflect the electrochemical performance of the material and provide multi-dimensional data support for battery performance evaluation and quality control. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of this application or related technologies, the drawings used in the description of the embodiments of this application or related technologies will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a flowchart illustrating a battery parameter detection method in one embodiment;

[0022] Figure 2 This is a schematic diagram of the battery test curve in one embodiment;

[0023] Figure 3 This is a schematic diagram of the structure of a battery parameter detection device in one embodiment. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0025] It should be noted that the terms "comprising" and "having," and any variations thereof, as used in this application, are intended to cover non-exclusive inclusion. The term "multiple" as used in this application refers to two or more.

[0026] Currently, traditional battery material parameter testing methods mostly employ half-cell testing, which involves pairing positive and negative electrode materials with lithium metal to create half-cells. The specific capacity or lithium-to-metal potential is then directly calculated by charging and discharging these half-cells. However, this method has significant drawbacks: the testing environment (unlimited lithium source, no interference from the counter electrode) differs fundamentally from the actual operating conditions of a full battery where the positive and negative electrodes are coupled. During testing, lithium metal acts as the counter electrode, and its electrochemical behavior differs from that of the negative (or positive) electrode in a full battery. This leads to discrepancies between the measured specific capacity or lithium-to-metal potential and the actual data in a full battery, making it difficult to directly apply to full battery design. Furthermore, traditional half-cell testing methods fail to consider the impact of the capacity matching relationship (N / P ratio) between the positive and negative electrodes on the specific capacity. The N / P ratio is a crucial parameter in full battery design; different N / P ratios result in different actual operating states for the positive and negative electrode materials, leading to variations in their specific capacity. This further reduces the accuracy of traditional testing methods, making it unreliable for providing optimal parameter support for full battery design. In addition, high-precision electrode potential monitoring usually requires the introduction of a third reference electrode (lithium wire, gold wire, etc.), which requires specialized equipment and complex operation, making it difficult to promote on conventional production lines.

[0027] However, if the positive and negative electrode materials are directly assembled into a full cell for testing, only the total voltage of the full cell can be output. It is impossible to separate and measure the actual lithium potential of the positive and negative electrodes, making it difficult to pinpoint the root cause of the performance limitation (insufficient positive electrode capacity or risk of lithium plating in the negative electrode).

[0028] Therefore, there is an urgent need for a method to adapt to the design of the target full cell, that is, to eliminate the test deviation between half cell and full cell, and to directly measure the actual positive and negative electrode parameters under full cell operating conditions by combining the N / P ratio gradient, including the actual lithium potential of the positive and negative electrodes and the actual specific capacity of the positive and negative electrode materials.

[0029] Based on the aforementioned traditional technologies, the battery parameter detection method provided in this application involves connecting a positive half-cell and a negative half-cell in reverse series to form a full cell, performing charge and discharge tests on the reverse-connected full cell, detecting the charging and discharging capacity of the full cell under different N / P gradients, and directly determining the actual specific capacity of the positive and negative electrode materials under full cell operating conditions by combining the N / P ratio gradient. The data is accurate, and the operation is simple and highly feasible.

[0030] The technical solution of this application and how the technical solution of this application solves the above-mentioned technical problems are described in detail below with specific embodiments. These specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments. The embodiments of this application will be described below with reference to the accompanying drawings.

[0031] In one exemplary embodiment, such as Figure 1 As shown, a battery parameter detection method is provided, including the following steps 102 to 105:

[0032] Step 101: Preset the theoretical positive electrode surface capacity / negative electrode surface capacity (N / P) ratio gradient, and prepare positive electrode half-cells and negative electrode half-cells with different theoretical N / P ratio gradients based on the theoretical specific capacity and mass of the positive electrode material and the negative electrode material.

[0033] In specific embodiments, the positive electrode material and the negative electrode material are selected according to specific needs; the specific positive electrode material can be ternary material, lithium iron phosphate (LFP), lithium cobalt oxide (LCO), lithium manganese oxide, etc.; the negative electrode material can be artificial graphite, natural graphite, silicon-based negative electrode, lithium titanate (LTO), etc.

[0034] In an exemplary embodiment, the preset theoretical N / P ratio gradient can be implemented using the theoretical charging N / P ratio. Specifically, the theoretical N / P ratio gradient can include an undermatched region, a matched region, and an overmatched region, wherein the theoretical N / P ratio of the undermatched region is less than 1, the theoretical N / P ratio of the matched region is equal to 1, and the theoretical N / P ratio of the overmatched region is greater than 1. In practice, it can be designed as needed; for example, the undermatched region can be designed to include at least 3 gradients, and the overmatched region can include at least 3 gradients.

[0035] Furthermore, the theoretical N / P ratio gradient range is typically 0.85-1.15. For example, if the under-matched region includes three gradients and the over-matched region includes three gradients, then the theoretical N / P ratio gradients can be set to: 0.85, 0.90, 0.95, 1.00, 1.05, 1.10, and 1.10. Positive and negative electrode half-cells are prepared according to the theoretical charging N / P ratio corresponding to each gradient. The number of positive electrode half-cell samples for each gradient is generally no less than three, and the number of negative electrode half-cells is the same as that of the positive electrode half-cells. Multiple samples are used to eliminate random errors during testing. All half-cells use the same electrolyte and separator system as the target full cell, and the process parameters such as the electrode compaction density and coating areal density are consistent with the target full cell.

[0036] Specifically, the theoretical charge N / P ratio gradient is the ratio of the theoretical charge specific capacity and mass product of the positive electrode material in the positive half-cell to the theoretical charge specific capacity and mass product of the negative electrode material in the negative half-cell. For example:

[0037] .

[0038] Of course, in practice, only the mass of the positive electrode active material and the mass of the negative electrode active material can be used as precise and controllable matching parameters, and the materials can be grouped according to the preset active material mass ratio gradient to ensure that the theoretical N / P ratio corresponding to each gradient covers the target range.

[0039]

[0040] in, This refers to the mass of the positive electrode material (positive electrode active material) in the positive electrode half-cell. The mass of the negative electrode material (negative electrode active material) in the negative electrode half-cell. The values ​​include 0.85, 0.90, 0.95, 1.00, 1.05, 1.10, and 1.15.

[0041] Furthermore, in a specific embodiment, the positive electrode material used in both the positive and negative electrode half-cells is ternary material NCM811 (chemical formula LiNi). 0.8 Co 0.1 Mn 0.1 O2), the negative electrode material is artificial graphite, the electrolyte is 1M LiPF6, and the solvent system is EC / DMC / EMC. Preset theoretical charge. Set multiple gradients, i.e., preset The gradient of the value must include at least seven gradients: 0.85, 0.90, 0.95, 1.00, 1.05, 1.10, and 1.10; each of these gradients... At least 5 parallel samples were prepared using the gradient of the value, resulting in at least 35 parallel samples in total. Each parallel sample consisted of one positive half-cell and one negative half-cell, and the mass ratio of the active material in the positive half-cell to the negative half-cell in that parallel sample was the corresponding value. Value, specifically corresponding The value is the ratio of the mass of the positive electrode active material in the positive half-cell to the mass of the negative electrode active material in the negative half-cell of the parallel samples. It should be noted that the formulations of the positive electrode and negative electrode in each parallel sample are completely identical to those of the target full cell, meaning the positive electrode material, negative electrode material, solvent system, and electrolyte are completely identical. Specifically, The number of gradients is not limited to seven; under suitable conditions, nine, eleven, or thirteen gradients are all possible. Gradient preparation typically involves 5 sets of parallel samples. To avoid false positives later, more samples can be prepared, such as at least 7 or 9 sets for each gradient.

[0042] Furthermore, after the positive and negative half-cells are prepared, all of them can be pretreated. Specifically, they can be statically activated without charging or discharging.

[0043] In a specific embodiment, the pretreatment generally involves activating at least 35 parallel samples for 12-24 hours under a constant temperature of 20-30℃±1℃ (preferably 25±1℃). No charging or discharging operations are performed during this stage. The experimental equipment used for the static activation of each parallel sample can be the same as that used for the static activation of the target full cell.

[0044] Furthermore, after pretreatment (static activation), an initial inspection can be performed on each set of parallel samples. Specifically, the open-circuit voltage of multiple sets of parallel samples (positive half-cell and negative half-cell) for each gradient is tested, and samples with abnormal open-circuit voltages are discarded to retain positive and negative half-cell samples with good parallelism for subsequent testing.

[0045] Specifically, the open-circuit voltage of the positive and negative half-cells in each group of parallel samples is tested and recorded. Samples with abnormal open-circuit voltages are excluded if they are abnormal samples from at least five positive half-cells and at least five negative half-cells within the same gradient, where the voltage fluctuation is >5mV. Specifically, an abnormal positive half-cell is defined as one whose minimum or maximum open-circuit voltage deviates by more than 5mV from the minimum or maximum open-circuit voltage of other positive half-cells within the same gradient, and / or an abnormal negative half-cell is defined as one whose minimum or maximum open-circuit voltage deviates by more than 5mV from the minimum or maximum open-circuit voltage of other negative half-cells within the same gradient. Specific deviation data should be based on the actual battery design.

[0046] In one exemplary embodiment, system zero-point offset calibration can also be performed. Specifically, a high-precision digital voltmeter and its matching test leads are used. The voltmeter and test leads are connected according to the test requirements to obtain a test system. After the voltmeter and test leads are connected, the two probes of the test system are short-circuited, and the displayed value of the voltmeter is read. This refers to the zero-point offset of the test system. In a specific embodiment, the value displayed on the voltmeter in the test system is read. This embodiment determines the zero-point offset of the voltage measurement system using the probe short-circuit method, which can then be subtracted from all potential measurements to eliminate the inherent bias of the test system.

[0047] Step 102: Connect the positive half-cell and the negative half-cell with the corresponding theoretical N / P ratio in reverse series to obtain the full cell with the corresponding theoretical N / P ratio.

[0048] In an exemplary embodiment, positive and negative half-cells of the same gradient are connected in reverse series to form a full cell. Specifically, the negative electrode shells of positive and negative half-cells with the same N / P ratio are electrically connected, with the positive electrode shell of the positive half-cell serving as the positive terminal of the full cell and the positive electrode shell of the negative half-cell serving as the negative terminal. Because this full cell is connected in reverse series, subsequent testing does not require a third reference electrode and does not rely on non-standard specialized testing equipment; conventional testing equipment can be used directly. Furthermore, the positive and negative half-cells in each set of pre-treated parallel samples are connected in reverse series, with the lithium metal negative electrode shells interconnected, and positive and negative electrode tabs are led out for subsequent testing, forming a full cell C1. This full cell C1 does not require a third reference electrode; the positive electrode shells of the positive and negative half-cells in the same set of parallel samples are used directly as the positive and negative electrode tabs of the full cell C1.

[0049] Step 103: Perform charging and discharging tests on the full battery to obtain the standard positive electrode charging specific capacity versus theoretical N / P curve, the standard positive electrode discharging specific capacity versus theoretical N / P curve, the standard negative electrode charging specific capacity versus theoretical N / P curve, and the standard negative electrode discharging specific capacity versus theoretical N / P curve.

[0050] In one exemplary embodiment, the charging test may include:

[0051] For full batteries with different theoretical N / P ratios, constant current is applied at a preset first current to charge the full battery to its upper limit voltage, and then constant voltage is applied at the upper limit voltage to charge to a preset second current to complete the charging and obtain the charging capacity of the full battery.

[0052] Specifically, each... Each full cell C1 under the gradient is subjected to constant current-constant voltage charging (CC-CV charging). Specifically, taking a preset first current of 0.05C, an upper limit voltage of 4.2V, and a preset second current of 0.01C as an example, each full cell C1 can first be charged with a constant current of 0.05C until the voltage of full cell C1 reaches 4.2V, and then charged with a constant voltage of 4.2V with a cutoff current of 0.01C. The charging capacity of each full cell C1 during the charging process is recorded. Based on this, the charging capacity of each full battery C1 was recorded. Mass of positive electrode material in a full cell and a half cell The mass of the negative electrode material in the negative half-cell This yields the standard positive charge capacity: , which represents the capacity embedded by the cathode material during the full-cell C1 charging process;

[0053] Standard negative electrode charging capacity: , which is the capacity embedded by the negative electrode material during the full cell C1 charging process (including SEI consumption).

[0054] Based on the actual positive and negative charge capacity of each full cell obtained above, and the theoretical N / P ratio of each full cell, the standard positive charge capacity versus theoretical N / P curve and the standard negative charge capacity versus theoretical N / P curve can be obtained.

[0055] It should be noted that CC-CV charging is used here, specifically with a preset first current (minimum current 0.05C) and a preset second current (cutoff current 0.01C). This can control the potential deviation caused by ohmic polarization due to factors such as the double-layer separator, double the electrode spacing, and common lithium sheet to within 1%, ensuring test accuracy. This deviation is negligible in engineering applications and requires no additional correction.

[0056] In one exemplary embodiment, the charging test further includes: testing each group that has completed charging. After the full cell C1 under gradient was left to stand for a preset time, each corresponding parallel sample (including the positive half cell and the negative half cell) was disassembled. The charging-to-lithium potential of each parallel sample was quickly measured using the aforementioned test system, that is, the charging-to-lithium potential of the positive half cell and the charging-to-lithium potential of the negative half cell.

[0057] Furthermore, the resting time for each full cell C1 after the charging test is preset, which can be set to 5-15 minutes (preset time) to eliminate concentration polarization. Each full cell can be disassembled in an inert atmosphere or dry chamber environment to obtain each set of parallel samples. The charging-to-lithium potential of the positive electrode half-cell in each set of parallel samples is quickly measured and recorded using the testing system. The charging effect of the negative electrode half-cell on the lithium potential .

[0058] In one exemplary embodiment, the discharge test may include:

[0059] After disassembling the charging test, the positive half-cell and the half-cell in each group of parallel samples are reconnected in reverse in the same way to obtain the full cell C2 (C1 and C2 here are only to distinguish whether they have been disassembled to avoid ambiguity later, but in fact they are the same positive half-cell and the same negative half-cell connected in reverse in the same way); the full cell C2 is discharged at a preset third current constant current to the lower limit voltage of the full cell to obtain the discharge capacity of the full cell C2.

[0060] Specifically, each... Each full cell C2 under the gradient is subjected to constant current discharge (CC discharge). Specifically, the third current is preset to be 0.05C and the lower limit voltage is preset to be 2.8V. Each full cell C2 is discharged at a constant current of 0.05C until the discharge voltage of that full cell C2 reaches 2.8V, and the discharge capacity of each full cell C2 during the discharge process is recorded. Based on this, the discharge capacity of each full cell C2 was recorded. and the mass of the positive electrode material of the positive half-cell of the full cell. The mass of the negative electrode material in the negative half-cell The standard positive electrode discharge specific capacity can then be obtained: , represents the capacity of the positive electrode material embedded during the C2 discharge process of the full cell; standard negative electrode discharge specific capacity: , which represents the capacity embedded by the negative electrode material during the C2 discharge process of the full cell.

[0061] In one exemplary embodiment, the discharge test further includes: disassembling the full battery C2 into individual cells. For each group of parallel samples under gradient conditions, the discharge-to-lithium potential of the positive half-cell and the discharge-to-lithium potential of the negative half-cell were measured.

[0062] Furthermore, unlike the disassembly after charging tests, after discharging tests, it is necessary to disassemble each full cell (C2). Specifically, disassembly can be performed in an inert atmosphere or a dry room environment to obtain each set of parallel samples. The discharge-to-lithium potential of the positive electrode half-cell in each set of parallel samples is then quickly measured and recorded using a testing system. The discharge of the negative electrode half-cell affects the lithium potential. .

[0063] Specifically, the charging capacity and discharging capacity data obtained in the charging and discharging tests need to be processed. For example, abnormal data are removed from each group of parallel samples in the same gradient, and other data with good parallelism are retained. The average value of the other data is calculated by summing them up, which gives the corresponding detection data under that gradient.

[0064] In one exemplary embodiment, standard positive electrode charge capacity and standard positive electrode discharge capacity of different gradients are obtained by combining the positive electrode active material mass of positive electrode half-cells with different theoretical N / P ratios with charging capacity and discharge capacity.

[0065] Based on the mass of the negative electrode active material in negative electrode half-cells with different theoretical N / P ratios, combined with the charging capacity and discharging capacity, standard negative electrode charging capacity and standard negative electrode discharging capacity of different gradients are obtained.

[0066] Specifically, due to each mass ratio The positive and negative half-cells in each set of parallel samples under the gradient were prepared independently, and the mass of their active materials was known (mass of positive active material). Quality of negative electrode active materials The capacity is processed as shown in Table 1 below.

[0067] Table 1. Types of Capacity and Calculation Formulas

[0068] Capacity type Calculation formula Physical meaning Standard positive electrode discharge capacity The capacity released by the positive electrode during the full discharge of the battery Standard positive charge capacity The capacity embedded in the positive electrode during full battery charging Standard negative charge capacity The capacity embedded in the negative electrode during full battery charging (including SEI consumption). Standard negative electrode discharge capacity The capacity released by the negative electrode during full cell discharge

[0069] It should be further noted that the charging-to-lithium potential of the positive electrode half-cell measured in the above embodiments... The charging effect of the negative electrode half-cell on the lithium potential The discharge of the positive electrode half-cell affects the lithium potential. The discharge of the negative electrode half-cell affects the lithium potential All of these were detected by the test system used for zero-point offset calibration in the aforementioned embodiments. Specifically, a high-precision digital voltmeter and its matching test leads were used. The voltmeter and the matching test leads were connected according to the test requirements to obtain the test system. Based on this test system, the lithium potential was obtained, and based on the zero-point offset of the test system already measured in the aforementioned embodiments... This allows for the calibration of the corresponding lithium potential. Specifically, zero-point offset is subtracted from all potential measurements. The inherent bias of the test system is eliminated; in all the aforementioned potential measurements, the true potential is calculated using the following formula: .

[0070] Specifically, the measured potential is corrected by subtracting the zero-point offset to obtain the actual potential value. The actual charging of the positive electrode half-cell affects the lithium potential. ;

[0071] The actual charge of the negative electrode half-cell relative to the lithium potential ;

[0072] The actual discharge of the positive electrode half-cell versus the lithium potential ;

[0073] The actual discharge of the negative electrode half-cell versus the lithium potential .

[0074] It should be further explained that in this embodiment, the standard positive electrode charging specific capacity versus theoretical N / P curve uses the theoretical N / P ratio as the abscissa, and the standard positive electrode charging specific capacity... The vertical axis represents the standard positive electrode discharge specific capacity versus theoretical N / P ratio curve; the horizontal axis represents the theoretical N / P ratio. The vertical axis represents the standard negative electrode charging specific capacity versus theoretical N / P curve; the horizontal axis represents the theoretical N / P ratio. The vertical axis represents the standard negative electrode discharge specific capacity versus theoretical N / P ratio curve; the horizontal axis represents the theoretical N / P ratio. The vertical axis is denoted by .

[0075] Step 104: Identify the critical points corresponding to the standard positive electrode charging capacity versus theoretical N / P curve, the standard positive electrode discharging capacity versus theoretical N / P curve, the standard negative electrode charging capacity versus theoretical N / P curve, and the standard negative electrode discharging capacity versus theoretical N / P curve, respectively.

[0076] Specifically, the critical point in the standard positive discharge specific capacity versus theoretical N / P curve is the inflection point where the standard positive discharge specific capacity changes from increasing to decreasing. The critical points corresponding to other standard positive charge specific capacity versus theoretical N / P curves, standard negative charge specific capacity versus theoretical N / P curves, and standard negative discharge specific capacity versus theoretical N / P curves are directly obtained based on the theoretical N / P ratio corresponding to the inflection point of the standard positive discharge specific capacity versus theoretical N / P curve.

[0077] Among them, when actually charging When the ratio is less than 1 (negative electrode capacity is insufficient, positive electrode capacity is limited), both the standard positive electrode charging capacity and the standard positive electrode discharging capacity change with the actual charging. The increase is rapid, but the rate of increase gradually decreases; both the standard negative electrode charging capacity and the standard negative electrode discharging capacity increase with actual charging. The rate of increase decreases slowly, but the absolute value of the rate of decrease gradually increases.

[0078] When actual charging When the ratio is equal to 1 (or near 1), the standard positive electrode charging capacity, standard positive electrode discharging capacity, standard negative electrode charging capacity, and standard negative electrode discharging capacity reach the critical point: the standard positive electrode discharging capacity reaches its maximum value; the growth of the standard positive electrode charging capacity slows down significantly; and the standard negative electrode charging and discharging capacity changes from a slow decrease to an accelerated decrease.

[0079] When actual charging When the ratio is greater than 1 (insufficient positive electrode capacity and limited negative electrode capacity), the standard positive electrode charging specific capacity continues to increase, but the growth slows down and the rate of increase further decreases; the standard positive electrode discharging specific capacity then turns to decrease, with a negative slope; both the standard negative electrode charging specific capacity and the standard negative electrode discharging specific capacity increase with actual charging. The rate of increase is relatively fast, but the absolute value of the downward slope gradually decreases, showing an asymptotic trend.

[0080] In practical identification of the critical point, because the standard positive electrode charging capacity increases with the theoretical N / P ratio in the standard positive electrode charging capacity vs. theoretical N / P curve, although the upward slope changes before and after the critical point, it is difficult to identify the inflection point (i.e., the critical point) by visual inspection alone. The standard negative electrode charging capacity vs. theoretical N / P curve and the standard negative electrode discharging capacity vs. theoretical N / P curve are similar; although the downward slope changes before and after the critical point, it is also difficult to identify the inflection point by visual inspection alone. Only the standard positive electrode discharging capacity increases before the critical point and decreases after the critical point, with a clear inflection point. This curve is generally used to confirm the theoretical N / P ratio (i.e., the actual charging capacity vs. theoretical N / P ratio) corresponding to the critical point. =1), based on this theoretical N / P ratio, the standard positive electrode charging capacity is obtained. Standard positive electrode discharge capacity Standard negative charge capacity Standard negative electrode discharge capacity .

[0081] Step 105: Obtain the standard charge capacity, standard discharge capacity, standard charge capacity, and standard discharge capacity of the positive electrode material based on the critical point.

[0082] In an exemplary embodiment, as described above, after identifying the critical point (i.e., inflection point) between the standard positive electrode discharge specific capacity and the theoretical N / P curve, the corresponding theoretical N / P ratio is obtained. To distinguish it from other N / P ratios on the horizontal axis, it is denoted here as... According to this theory, the N / P ratio ( Read the charge / discharge specific capacity of the positive and negative electrode materials and compare it with the standard charge / discharge specific capacity corresponding to the theoretical N / P curve. This is the standard positive electrode charge specific capacity. Standard positive electrode discharge capacity Standard negative charge capacity Standard negative electrode discharge capacity .

[0083] Specifically, in the aforementioned embodiments, the positive electrode material selected for the positive half-cell and the negative electrode half-cell is ternary material NCM811, and the negative electrode material is artificial graphite. The charge and discharge data (theoretical data) of the positive and negative electrodes provided by the raw material supplier are shown in Table 2 below.

[0084] Table 2 Theoretical charge-discharge data for positive and negative electrode materials

[0085] Theoretical data provided by raw material suppliers Charging capacity (mAh / g) Discharge capacity mAh / g First effect Ternary material NCM811 228.9 210.1 91.8% Artificial graphite 383.3 357.6 93.3%

[0086] The theoretical N / P ratio gradients were determined to be 0.85, 0.90, 0.95, 1.00, 1.05, 1.10, and 1.10. Positive and negative half-cells were prepared according to the aforementioned battery parameter detection method. The active material masses in the positive and negative half-cells corresponding to the theoretical N / P ratio gradients are shown in Table 3 below.

[0087] Table 3. Mass of active material for positive and negative electrodes corresponding to the theoretical N / P ratio gradient.

[0088] Theoretical N / P ratio gradient Cathode material mass / mg Anode material mass / mg Actual preliminary N / P ratio 0.85 7.961 4.031 0.847887438 0.90 8.008 4.272 0.893305908 0.95 8.024 4.566 0.952879566 1.00 7.984 4.784 1.003375909 1.05 8.032 5.033 1.049291747 1.10 8.016 5.276 1.102148477 1.15 7.992 5.488 1.149877706

[0089] As mentioned above, the positive and negative half-cells in each of the aforementioned parallel samples were connected in reverse series and charged and discharged to obtain the test data shown in Table 4.

[0090] Table 4 Battery parameters obtained after charge-discharge tests

[0091] Theoretical N / P ratio gradient Charging capacity / mAh Discharge capacity / mAh Positive electrode charging capacity (mAh / g) Positive electrode discharge capacity (mAh / g) Negative electrode charging capacity (mAh / g) Negative electrode discharge capacity (mAh / g) 0.85 1.5383 1.4214 193.23 178.55 381.62 352.62 0.90 1.6274 1.5013 203.22 187.48 380.95 351.43 0.95 1.7216 1.5777 214.56 196.62 377.05 345.53 1.00 1.7727 1.5711 222.03 196.78 370.55 328.41 1.05 1.8003 1.5592 224.14 194.12 357.70 309.80 1.10 1.7971 1.5436 224.19 192.56 340.62 292.57 1.15 1.7896 1.5211 223.92 190.33 326.09 277.17

[0092] The standard positive electrode charging specific capacity versus theoretical N / P ratio curves, standard positive electrode discharging specific capacity versus theoretical N / P ratio curves, standard negative electrode charging specific capacity versus theoretical N / P ratio curves, and standard negative electrode discharging specific capacity versus theoretical N / P ratio curves obtained based on the data in Table 4 are attached. Figure 2 As shown, the critical point (inflection point; the inflection point of the curve between the standard positive electrode discharge specific capacity and the theoretical N / P ratio is identified based on existing technology and will not be discussed further here) is theoretical N / P = 0.98 (around 0.98). Therefore, the corresponding standard specific capacity is determined to be the standard positive electrode charging specific capacity. =220.5mAh / g, standard positive electrode discharge capacity Standard negative charge capacity Standard negative electrode discharge capacity .

[0093] The aforementioned battery parameter testing method constructs a full cell by connecting a positive electrode half-cell and a negative electrode half-cell in reverse series. Charge-discharge tests are then performed on this full cell to detect the actual charge and discharge specific capacities of the positive and negative electrode materials under different N / P ratio gradients. This method boasts high accuracy because by connecting the positive and negative electrode half-cells in reverse series to form a full cell, it simulates the working environment of a real full cell, eliminating the interference of lithium metal on the electrodes in traditional half-cell testing. This results in a specific capacity more closely resembling the true value of the material in a real full cell. Furthermore, by constructing different theoretical N / P gradients, the method analyzes the influence of the N / P ratio on the specific capacity of the positive and negative electrode materials and identifies the critical points of the curves. This method accurately obtains the actual specific capacity of positive and negative electrode materials, providing a reliable basis for the N / P optimization design of full batteries. The entire testing process requires no complex equipment or processes, with clear steps. Test parameters can be flexibly adjusted according to different types of battery materials, making it suitable for the specific capacity testing of positive and negative electrode materials in various batteries. Furthermore, during the test, the actual parameters are derived from the measured parameters using the active material mass ratio as a benchmark, avoiding systematic deviations between the data provided by raw material manufacturers and the full battery design. In addition, by obtaining four core curves through charge-discharge testing and combining them with potential measurement data, the electrochemical performance of the materials can be comprehensively reflected, providing multi-dimensional data support for battery performance evaluation and quality control.

[0094] Based on the above battery parameter detection method, in addition to obtaining the standard positive electrode charging capacity, Standard positive electrode discharge capacity Standard negative charge capacity The standard negative electrode discharge capacity can also be used to establish a standardized curve for full cell design based on the detected parameters.

[0095] Specifically, the theoretical charging N / P ratio is first converted, which involves changing the mass ratio of the positive and negative electrode active materials. Unified conversion to standard charging N / P ratio (using symbols) express):

[0096]

[0097] in , The standard charge capacity is determined based on the aforementioned battery parameter detection method.

[0098] Furthermore, the theoretical N / P ratio on the horizontal axis of the original standard positive electrode charging specific capacity versus theoretical N / P ratio curve, standard positive electrode discharging specific capacity versus theoretical N / P ratio curve, standard negative electrode charging specific capacity versus theoretical N / P ratio curve, and standard negative electrode discharging specific capacity versus theoretical N / P ratio curve is directly converted to the standard charging N / P ratio. Figure 2 Taking the curve in the image as an example, the original theoretical N / P ratio of 0.98 is converted to a standard charging N / P ratio of 1.00, that is... Establish a charging N / P ratio A standardized curve with the horizontal axis representing the base and other battery testing parameters representing the vertical axis, including: positive electrode charging capacity. and Standardized curve of the relationship; positive electrode discharge specific capacity and Standardized curve of the relationship; negative electrode charging capacity and Standardized curve of the relationship; negative electrode discharge specific capacity and Standardized curve of the relationship; negative electrode full charge potential and The relationship is standardized curve.

[0099] This allows for the selection of the target charging N / P ratio during subsequent full-battery design, based on the application scenario. The corresponding design parameters are read from the standardized curve, including the positive electrode charging capacity, positive electrode discharging capacity, negative electrode charging capacity, negative electrode discharging capacity, and negative electrode full charge potential; and based on the above design parameters, the required mass ratio of positive electrode material and negative electrode material is obtained.

[0100] Table 2. Selection of target charging N / P ratio based on application scenario

[0101] Application scenarios Design Preferences Target charging N / P ratio range Design basis Consumer batteries High energy density priority 1.03～1.08 Choose a smaller N / P ratio within the safety boundary. power battery Balancing energy density and cycle life 1.08～1.15 Balancing capacity utilization and safety margin Energy storage battery Ultra-long lifespan priority 1.15～1.25 Choosing a larger N / P ratio sacrifices some energy density.

[0102] Based on the above-mentioned battery parameter detection method, the following benefits are achieved in the design of full batteries: Firstly, a complete standardized design curve is established: a complete curve of the charge and discharge capacity of the positive and negative electrodes and the negative electrode potential changes with the charging N / P ratio is obtained. Designers can independently select the target N / P ratio according to the application scenario and directly read all design parameters from the curve. Secondly, through the standardized curve, designers only need to select the target N / P ratio to uniquely determine the mass ratio, capacity utilization and potential boundary, which greatly shortens the R&D cycle, makes the design accurate and reproducible, and improves the success rate of the first design.

[0103] It should be understood that although the steps in the flowcharts of the above embodiments are shown sequentially according to the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless explicitly stated herein, there is no strict order restriction on the execution of these steps, and they can be executed in other orders. Moreover, at least some steps in the flowcharts of the above embodiments may include multiple steps or multiple stages. These steps or stages are not necessarily completed at the same time, but can be executed at different times. The execution order of these steps or stages is not necessarily sequential, but can be performed alternately or in turn with other steps or at least some of the steps or stages in other steps. It is understood that the steps in different embodiments can be freely combined as needed, and all non-contradictory solutions formed by such combinations are within the scope of protection of this application.

[0104] Based on the same inventive concept, this application also provides a battery parameter detection device for implementing the battery parameter detection method described above. The solution provided by this device is similar to the solution described in the above method; therefore, the specific limitations in one or more battery parameter detection device embodiments provided below can be found in the limitations of the battery parameter detection method described above, and will not be repeated here.

[0105] In one exemplary embodiment, such as Figure 3 As shown, a battery parameter detection device is provided, including a battery fabrication module and a testing module, wherein:

[0106] The battery fabrication module is used to prepare positive and negative half-cells with different theoretical N / P ratios based on the theoretical specific capacity of positive and negative electrode materials and the preset theoretical positive / negative electrode surface capacity (N / P) ratio gradient.

[0107] The battery fabrication module is also used to connect positive and negative half-cells with the same theoretical N / P ratio in reverse series to obtain a full cell with the corresponding theoretical N / P ratio.

[0108] The testing module is used to perform charging and discharging tests on the full battery, and obtain the standard positive electrode charging specific capacity versus theoretical N / P curve, the standard positive electrode discharging specific capacity versus theoretical N / P curve, the standard negative electrode charging specific capacity versus theoretical N / P curve, and the standard negative electrode discharging specific capacity versus theoretical N / P curve.

[0109] The test module is also used to identify the critical points corresponding to the standard positive electrode charging capacity and theoretical N / P curve, the standard positive electrode discharging capacity and theoretical N / P curve, the standard negative electrode charging capacity and theoretical N / P curve, and the standard negative electrode discharging capacity and theoretical N / P curve, respectively.

[0110] The testing module is also used to obtain the standard charge capacity, standard discharge capacity, standard charge capacity, and standard discharge capacity of the positive electrode material based on the critical point.

[0111] Specifically, in the battery fabrication module, the theoretical N / P ratio gradient is the ratio of the theoretical specific capacity and mass product of the positive electrode material in the positive half-cell to the theoretical specific capacity and mass product of the negative electrode material in the negative half-cell.

[0112] The theoretical N / P ratio gradient includes: undermatched region, matched region, and overmatched region. The N / P ratio of the undermatched region is less than 1, the N / P ratio of the matched region is equal to 1, and the N / P ratio of the overmatched region is greater than 1.

[0113] In an exemplary embodiment, the testing module is further configured to charge full batteries with different theoretical N / P ratios at a preset first current constant current to the upper limit voltage of the full battery, and then charge them at the upper limit voltage constant voltage to a preset second current to complete the charging and obtain the charging capacity of the full battery.

[0114] In an exemplary embodiment, the testing module is further configured to disassemble the positive half-cell and the negative half-cell after the fully charged battery has been left to stand for a preset time, and to measure the charge-to-lithium potential of the positive half-cell and the charge-to-lithium potential of the negative half-cell, respectively.

[0115] In an exemplary embodiment, the test module is further configured to reconnect the positive half-cell and the half-cell obtained after the charging test is disassembled into a full cell in reverse series.

[0116] The full battery is discharged at a preset third current constant current to the lower limit voltage of the full battery to obtain the discharge capacity of the full battery.

[0117] In an exemplary embodiment, the test module is further configured to disassemble the full battery into a positive electrode half-cell and a negative electrode half-cell, and measure the discharge-to-lithium potential of the positive electrode half-cell and the discharge-to-lithium potential of the negative electrode half-cell, respectively.

[0118] In an exemplary embodiment, the testing module is further configured to obtain standard positive electrode charge capacity and standard positive electrode discharge capacity of different gradients based on the positive electrode active material mass of positive electrode half-cells with different theoretical N / P ratios, combined with charging capacity and discharge capacity.

[0119] Based on the mass of the negative electrode active material in negative electrode half-cells with different theoretical N / P ratios, combined with the charging capacity and discharging capacity, standard negative electrode charging capacity and standard negative electrode discharging capacity of different gradients are obtained.

[0120] In an exemplary embodiment, the battery fabrication module is further configured to perform a static activation pretreatment on each positive electrode half-cell and negative electrode half-cell before connecting the positive electrode half-cell and the negative electrode half-cell with the same theoretical N / P ratio in reverse series to obtain a full cell with the corresponding theoretical N / P ratio.

[0121] The open-circuit voltages of the positive and negative half-cells were tested after static activation pretreatment.

[0122] In an exemplary embodiment, the battery fabrication module connects a positive electrode half-cell and a negative electrode half-cell of the same gradient in reverse series to form a full cell, specifically including:

[0123] The negative electrode casings of positive half-cells and negative half-cells with the same N / P ratio are electrically connected. The positive electrode casing of the positive half-cell serves as the positive terminal of the full cell, and the positive electrode casing of the negative half-cell serves as the negative terminal of the full cell.

[0124] Each module in the aforementioned battery parameter detection device can be implemented entirely or partially through software, hardware, or a combination thereof. These modules can be embedded in the processor of the communication device in hardware form or independent of it, or stored in the memory of the communication device in software form, so that the processor can call and execute the corresponding operations of each module.

[0125] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this application.

[0126] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A method for detecting battery parameters, characterized in that, Includes the following steps: By pre-setting the theoretical positive electrode surface capacity / negative electrode surface capacity (N / P) ratio gradient, and based on the theoretical specific capacity and mass of the positive and negative electrode materials, positive and negative electrode half-cells with different theoretical N / P ratios are prepared. By connecting the positive electrode half-cell and the negative electrode half-cell with the same theoretical N / P ratio in reverse series, a full cell with the corresponding theoretical N / P ratio is obtained. The full battery was subjected to charging and discharging tests to obtain the standard positive electrode charging specific capacity versus theoretical N / P curve, the standard positive electrode discharging specific capacity versus theoretical N / P curve, the standard negative electrode charging specific capacity versus theoretical N / P curve, and the standard negative electrode discharging specific capacity versus theoretical N / P curve. The critical points corresponding to the standard positive electrode charging specific capacity and theoretical N / P curve, the standard positive electrode discharging specific capacity and theoretical N / P curve, the standard negative electrode charging specific capacity and theoretical N / P curve, and the standard negative electrode discharging specific capacity and theoretical N / P curve are obtained respectively. Based on the critical point, the standard charge capacity, standard discharge capacity, standard charge capacity, and standard discharge capacity of the positive electrode material are obtained.

2. The battery parameter detection method according to claim 1, characterized in that, The charging test includes: The full cells with different theoretical N / P ratios are charged at a preset first current at a constant current to the upper limit voltage of the full cell, and then charged at the upper limit voltage at a constant voltage to a preset second current to complete the charging and obtain the charging capacity of the full cell.

3. The battery parameter detection method according to claim 2, characterized in that, The charging test also includes: After the full battery has been charged and left to stand for a preset time, the positive half-cell and the negative half-cell are disassembled, and the charging-to-lithium potential of the positive half-cell and the charging-to-lithium potential of the negative half-cell are measured respectively.

4. The battery parameter detection method according to claim 2, characterized in that, The discharge test includes: The positive half-cell obtained after the charging test was disassembled and the half-cell were reconnected in reverse series to form a full cell; The full battery is discharged at a preset third current constant current to the lower limit voltage of the full battery to obtain the discharge capacity of the full battery.

5. The battery parameter detection method according to claim 4, characterized in that, The discharge test also includes: The full cell is disassembled into the positive electrode half-cell and the negative electrode half-cell, and the discharge-to-lithium potential of the positive electrode half-cell and the discharge-to-lithium potential of the negative electrode half-cell are measured respectively.

6. The battery parameter detection method according to claim 4, characterized in that, The method further includes: Based on the mass of the positive active material of the positive half-cell with different theoretical N / P ratios, combined with the charging capacity and the discharging capacity, the standard positive charge capacity and the standard positive discharge capacity with different gradients are obtained. Based on the mass of the negative electrode active material of the negative electrode half-cell with different theoretical N / P ratios, combined with the charging capacity and the discharging capacity, the standard negative electrode charging capacity and the standard negative electrode discharging capacity with different gradients are obtained.

7. The battery parameter detection method according to claim 1, characterized in that, Before connecting the positive electrode half-cell and the negative electrode half-cell with the same theoretical N / P ratio in reverse series to obtain a full cell with the corresponding theoretical N / P ratio, the following steps are included: Each of the positive electrode half-cells and the negative electrode half-cells is pre-treated; The open-circuit voltages of the positive half-cell and the negative half-cell were tested after pretreatment.

8. The battery parameter detection method according to claim 1, characterized in that, The theoretical N / P ratio gradient is the ratio of the theoretical specific capacity and mass product of the positive electrode material of the positive half-cell to the theoretical specific capacity and mass product of the negative electrode material of the negative half-cell. The theoretical N / P ratio gradient includes: an undermatched region, a matched region, and an overmatched region, wherein the N / P ratio of the undermatched region is less than 1, the N / P ratio of the matched region is equal to 1, and the N / P ratio of the overmatched region is greater than 1.

9. The battery parameter detection method according to claim 1, characterized in that, The step of connecting the positive half-cell and the negative half-cell at the same gradient in reverse series to form a full cell includes: The negative electrode casings of the positive half-cell and the negative electrode casing of the negative half-cell, which have the same N / P ratio, are electrically connected. The positive electrode casing of the positive half-cell serves as the positive terminal of the full cell, and the positive electrode casing of the negative half-cell serves as the negative terminal of the full cell.

10. A battery parameter detection device, characterized in that, include: A half-cell module is used to prepare positive and negative half-cells with different theoretical N / P ratios based on the preset theoretical positive electrode surface capacity / negative electrode surface capacity (N / P) ratio gradient and the theoretical specific capacity and mass of positive and negative electrode materials. A reverse series module is used to connect the positive electrode half-cell and the negative electrode half-cell with the same theoretical N / P ratio in reverse series to obtain a full cell with the corresponding theoretical N / P ratio. The testing module is used to perform charging and discharging tests on the full battery to obtain standard positive electrode charging specific capacity versus theoretical N / P curves, standard positive electrode discharging specific capacity versus theoretical N / P curves, standard negative electrode charging specific capacity versus theoretical N / P curves, and standard negative electrode discharging specific capacity versus theoretical N / P curves. The identification module is used to identify the critical points corresponding to the standard positive electrode charging capacity and theoretical N / P curve, the standard positive electrode discharging capacity and theoretical N / P curve, the standard negative electrode charging capacity and theoretical N / P curve, and the standard negative electrode discharging capacity and theoretical N / P curve, respectively. The acquisition module is used to acquire the standard charge capacity, standard discharge capacity, standard charge capacity, and standard discharge capacity of the positive electrode material based on the critical point.

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