Battery testing method and computer readable storage medium

Abstract

The invention provides a battery testing method and a computer readable storage medium. The battery testing method comprises the following steps: acquiring an electrochemical impedance spectrum and an electrode effective reaction area of a tested battery; wherein the tested battery is a lithium ion half battery in a preset charge state; fitting the electrochemical impedance spectrum of the tested battery to obtain the charge transfer impedance of the tested battery; calculating the reference exchange current density of the measured battery according to the charge transfer impedance of the measured battery and the effective reaction area of the electrode; according to the reference exchange current density of the tested battery and the preset electrolyte concentration and the lithium intercalation concentration of the tested battery, the reaction rate constant of the tested battery is obtained through calculation. The battery testing method has the advantages of being small in testing difficulty, high in reliability and stability and low in cost.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a battery testing method and a computer-readable storage medium. Background Art

[0002] Lithium-ion batteries have the advantages of small size, high energy density, and long cycle life. They are widely used in portable electronic devices, electric vehicles, and energy storage systems. Therefore, it is of great significance to study and analyze lithium-ion batteries. At present, three-electrode batteries are basically used to measure the electrochemical kinetic parameters of lithium-ion batteries. However, the current testing methods still have the disadvantages of high testing difficulty, poor reliability and stability, and high cost. Summary of the invention

[0003] In view of this, the present application provides a battery testing method and a computer-readable storage medium, which can solve the problems of existing testing methods such as high testing difficulty, high cost, and poor reliability and stability of test results.

[0004] In a first aspect, the present application provides a battery testing method, which includes: obtaining an electrochemical impedance spectrum and an effective electrode reaction area of ​​a battery under test; wherein the battery under test is a lithium ion half-cell in a preset state of charge; fitting the electrochemical impedance spectrum of the battery under test to obtain a charge transfer impedance of the battery under test; calculating a reference exchange current density of the battery under test based on the charge transfer impedance and the effective electrode reaction area of ​​the battery under test; and calculating a reaction rate constant of the battery under test based on the reference exchange current density of the battery under test, a preset electrolyte concentration of the battery under test, and a lithium insertion concentration.

[0005] In one embodiment, the reference exchange current density of the battery under test is calculated based on the charge transfer impedance and the effective electrode reaction area of ​​the battery under test, including: calculating the reference exchange current density of the battery under test based on a preset first calculation model according to the charge transfer impedance and the effective electrode reaction area of ​​the battery under test; wherein the first calculation model is used to indicate that there is a negative correlation between the reference exchange current density and the charge transfer impedance, and between the reference exchange current density and the effective electrode reaction area. By calculating with a mathematical model, the reference exchange current density of the battery under test can be obtained quickly and accurately.

[0006] In one embodiment, the reaction rate constant of the battery under test is calculated based on the reference exchange current density of the battery under test, the preset electrolyte concentration of the battery under test, and the lithium insertion concentration, including: the reaction rate constant of the battery under test is calculated based on a preset second calculation model according to the reference exchange current density of the battery under test, the preset electrolyte concentration of the battery under test, the maximum lithium insertion concentration, and the lithium insertion concentration at the preset electrolyte concentration; wherein the second calculation model is used to indicate that there is a positive correlation between the reaction rate constant and the reference exchange current density, between the reaction rate constant and the preset electrolyte concentration, and between the reaction rate constant and the maximum lithium insertion concentration, and there is a negative correlation between the reaction rate constant and the lithium insertion concentration at the preset electrolyte concentration. The reaction rate constant of the battery under test can be quickly and accurately obtained by calculating with a mathematical model.

[0007] In one embodiment, obtaining an electrochemical impedance spectrum of a battery under test includes: obtaining an electrochemical impedance spectrum of the battery under test from an electrochemical testing device; wherein the electrochemical testing device is used to perform an electrochemical impedance spectrum test on the battery under test under preset conditions, the preset conditions including a preset ambient temperature, and an electrical signal applied to the battery under test being in a preset frequency range and reaching a preset amplitude.

[0008] In one embodiment, the battery under test is located in a thermostatic box, and the internal temperature of the thermostatic box reaches a preset ambient temperature.

[0009] In one embodiment, the preset frequency range includes 0.05 Hz-500 kHz; the preset amplitude is in the range of 2 mV to 5 mV.

[0010] In one embodiment, the preset state of charge is in the range of 10% to 90%.

[0011] In one embodiment, the process of fitting the electrochemical impedance spectrum of the battery under test to obtain the charge transfer impedance of the battery under test includes: constructing an equivalent circuit model of the battery under test; fitting the electrochemical impedance spectrum of the battery under test according to the equivalent circuit model; and using the charge transfer impedance in the equivalent circuit model obtained after fitting as the charge transfer impedance of the battery under test. This design can very intuitively and accurately simulate the charge and discharge behavior of the battery under test and obtain accurate charge transfer impedance.

[0012] In one embodiment, the battery under test is a button-type battery, which is easy to prepare and is conducive to improving test efficiency and reducing costs.

[0013] A second aspect of the present application provides a computer-readable storage medium, which stores computer-readable instructions. When the computer-readable instructions are executed by a processor, the battery testing method described in the first aspect or any one of the embodiments of the first aspect is implemented.

[0014] Compared with the prior art, this application has at least the following advantages:

[0015] The present application provides a new battery testing method, using a lithium ion half-cell as the battery to be tested, by obtaining the electrochemical impedance spectrum and electrode effective reaction area of ​​the battery to be tested, fitting the electrochemical impedance spectrum of the battery to be tested, obtaining the charge transfer impedance of the battery to be tested, and then calculating the reference exchange current density of the battery to be tested according to the charge transfer impedance and electrode effective reaction area of ​​the battery to be tested, and finally calculating the reaction rate constant of the battery to be tested according to the reference exchange current density of the battery to be tested, the preset electrolyte concentration of the battery to be tested and the lithium insertion concentration. Since the preparation of lithium ion half-cells is easy and low in cost, and the test steps of the embodiments of the present application are simple, highly operable, and repeatable, and can be cross-validated, therefore, compared with the currently commonly used test method based on three-electrode batteries, the test method of the present application has lower test difficulty, lower cost, better stability, reliability and consistency of the test results, and is more suitable for battery material performance testing, which is helpful for the overall and global test analysis of subsequent batteries and the research and design of finished batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a flow chart of the battery testing method provided in the embodiment of the present application.

[0017] Figure 2 This is a structural diagram of a lithium-ion half-cell.

[0018] Figure 3 This is a test scenario diagram for a lithium-ion half-battery.

[0019] Figure 4 yes Figure 1 A flow chart of step S20 in FIG.

[0020] Figure 5 A schematic diagram of the electrochemical impedance spectroscopy of a lithium-ion half-cell.

[0021] Figure 6 It is a schematic diagram of the charge transfer impedance curve of a lithium-ion half-cell.

[0022] Figure 7 Schematic diagram of a battery testing device provided in an embodiment of the present application.

[0023] Figure 8 It is a schematic diagram of an electronic device provided in an embodiment of the present application.

[0024] Main component symbols

[0025] 100 - tested battery, 101 - working electrode, 102 - lithium electrode, 103 - electrolyte, 104 - diaphragm, 105 - upper shell, 106 - lower shell,

[0026] 200- constant temperature box, 300- electrochemical test equipment, 400- computer equipment, 500- battery test device, 501- acquisition module,

[0027] 502-fitting module, 503-first calculation module, 504-second calculation module, 600-electronic device, 601-processor,

[0028] 602-Memory. DETAILED DESCRIPTION

[0029] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present application.

[0030] In the description of the present application, it should be understood that the terms "first", "second", "third", etc. are used to distinguish different objects rather than to describe a specific order. The terms "include" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product, or device that includes a series of steps or modules is not limited to the listed steps or modules, but may optionally include steps or modules that are not listed, or may optionally include other steps or modules that are inherent to these processes, methods, products, or devices. The following different embodiments and features in the embodiments may be combined with each other without conflict.

[0031] Lithium-ion batteries have the advantages of small size, high energy density, and long cycle life, and are widely used in portable electronic devices, electric vehicles, and energy storage systems. Therefore, it is of great significance to study and analyze lithium-ion batteries.

[0032] At present, three-electrode batteries are basically used to measure the electrochemical kinetic parameters of lithium-ion batteries (such as exchange current density, reaction rate constant, etc.), mainly using the relaxation voltage curve method and linear sweep voltammetry (LSV). The relaxation voltage curve method calculates the exchange current density by recording the curve Ut of the relaxation voltage of the battery after charging is completed, and performing a first-order exponential fit on the Ut curve. The linear sweep voltammetry method calculates the exchange current density by recording the voltammetric curve of the working electrode and the slope of the approximate linear part of the voltammetric curve.

[0033] Since the three-electrode battery needs to introduce a reference electrode, the structure is relatively complex, and the reference electrode may also affect the battery's charge and discharge process. Therefore, the preparation of the three-electrode battery is difficult, the cost is high, and the stability and test consistency are also poor. Therefore, these current test methods still have the disadvantages of high test difficulty, poor reliability and stability, and high cost.

[0034] Therefore, the embodiment of the present application proposes a new battery testing method, which has the advantages of low testing difficulty, high reliability and stability, and low cost.

[0035] The battery testing method of the embodiment of the present application is introduced below with reference to the accompanying drawings.

[0036] See also Figure 1 , shows a flow chart of a battery testing method provided in an embodiment of the present application. The battery testing method may be executed by a computer device 400. In other embodiments, the battery testing method may also be executed by a dedicated battery testing device or electronic device.

[0037] like Figure 1 As shown, the battery testing method includes the following steps:

[0038] Step S10, obtaining the electrochemical impedance spectrum and electrode effective reaction area of ​​the battery 100 under test.

[0039] The battery 100 under test is a lithium ion half-cell. In practical applications, since button cells are easy to prepare and use less materials, lithium ion half-cells can be made into button cells (also called button cells).

[0040] like Figure 2 As shown, the button cell includes a working electrode 101 (also referred to as a single-sided electrode), a counter electrode, an electrolyte 103, a diaphragm 104, an upper shell 105 and a lower shell 106. The upper shell 105 and the lower shell 106 are arranged relative to each other and assembled together to form a receiving space. The counter electrode, the diaphragm 104 and the working electrode 101 are all received in the receiving space. The diaphragm 104 is arranged between the counter electrode and the working electrode 101, and the receiving space is filled with an electrolyte 103. Among them, the working electrode 101 material is usually made of lithium metal oxide, such as lithium cobalt oxide (LiCoO2), lithium manganese oxide (LiMn2O4), lithium iron oxide (LiFePO4), etc. The counter electrode can be, for example, a lithium electrode 102. The electrolyte 103 is usually made of an organic solvent containing a lithium salt. The diaphragm 104 is usually made of a porous medium with lithium ion selective permeability (i.e., basically only lithium ions are allowed to pass), such as a PE film, a PP film or a combination thereof. The upper shell 105 and the lower shell 106 may be made of materials such as steel or aluminum.

[0041] When the lithium-ion half-cell is connected to an external circuit, an electrochemical reaction will occur. Specifically, when the working electrode 101 and the counter electrode are connected to an external power supply (that is, when the lithium-ion half-cell is charged), lithium ions are released from the working electrode 101, and the lithium ions move to the counter electrode through the electrolyte 103 and the diaphragm 104 and are embedded, and a redox reaction occurs with the counter electrode. At the same time, electrons flow from the counter electrode to the working electrode 101 through the external circuit, thereby forming a charging current. When the working electrode 101 and the counter electrode are connected to an external load (that is, when the lithium-ion half-cell is discharged), lithium ions are released from the counter electrode, and the lithium ions move to the working electrode 101 through the electrolyte 103 and the diaphragm 104 and are embedded, and a redox reaction occurs with the working electrode 101. At the same time, electrons flow from the working electrode 101 to the counter electrode through the external circuit, thereby forming a discharge current to power the external load. Among them, the proportion or concentration of lithium ions in the electrode material during the charge and discharge process is the lithium insertion concentration of the electrode material, and the lithium insertion concentration is directly related to the state of charge (State of Charge, SOC).

[0042] It can be understood that, compared with a three-electrode battery, a lithium-ion half-cell does not need to be provided with a reference electrode, has fewer components, a simpler structure, uses fewer materials, and does not require additional testing and calibration to ensure the accuracy and stability of the reference electrode, so the preparation difficulty and cost are lower, and the stability and test consistency are better. Therefore, using a lithium-ion half-cell as the battery 100 under test, the test difficulty and cost are lower, and the test reliability and stability are higher.

[0043] In the embodiment of the present application, several batteries 100 to be tested can be prepared according to actual needs. The electrolyte 103 of each battery 100 to be tested reaches the corresponding preset electrolyte concentration. The electrolyte concentration can be understood as the molar concentration of the lithium salt in the electrolyte 103, that is, how many moles (mol) of lithium salt are dissolved in each liter of the electrolyte 103. At least one of the working electrode 101 materials and the preset electrolyte concentration of different batteries 100 to be tested can be different. For example, there are three batteries 100 to be tested in step S10, and the electrolyte concentrations of the three batteries 100 to be tested are: 0.5mol / L (or 0.5M), 1.0mol / L (or 1.0M), 2.0mol / L (or 2.0M), where 0.5mol / L is a relatively low concentration, 1.0mol / L is a relatively conventional concentration, and 2.0mol / L is a relatively high concentration.

[0044] After the button cell is prepared, the tested battery 100 is also pre-treated. The pre-treatment process includes: firstly, the tested battery 100 is formed, that is, the tested battery 100 is charged for the first time to activate the active material of the working electrode 101, so that the working electrode 101 forms an electrode surface film (SEI film). During the formation process, the tested battery 100 can be charged at a smaller multiple rate (C rate), such as 0.1C. In this way, the electrode material can undergo a slow and stable chemical reaction to form a high-quality SEI film, which is beneficial to the performance stability and service life of the tested battery 100. After the formation is completed, the tested battery 100 is divided into different capacities, that is, the tested battery 100 is charged and discharged for multiple cycles to detect the battery parameters such as the capacity, voltage, and internal resistance of the tested battery 100. After the capacity division is completed, the tested battery 100 is charged or discharged according to the battery parameters of the tested battery 100, so that the SOC of the tested battery 100 is in a preset state of charge, such as within the range of 10% to 90%. In this way, it is possible to avoid the performance degradation or instability of the tested battery 100 due to too high or too low SOC, thereby affecting the test results.

[0045] After the pretreatment is completed, the electrochemical impedance spectrum (EIS) and the electrode effective reaction area (ECSA) of the battery 100 under test can be measured by a testing device.

[0046] For example, an electrochemical testing device 300 (e.g., an electrochemical workstation) may be used to perform an EIS test under preset conditions. The preset conditions may include, for example, a preset ambient temperature, an electrical signal applied to the battery 100 under test being in a preset frequency range and reaching a preset amplitude. Specifically, Figure 3As shown, the battery 100 under test can be placed in a thermostat 200, and the internal temperature of the thermostat 200 reaches a preset ambient temperature. The preset ambient temperature can be set according to the application scenario of the battery 100 under test, for example, about 25°C, or 40°C to 50°C or higher in a high temperature scenario, or 0°C to -10°C or lower in a low temperature scenario. The working electrode 101 and the counter electrode of the battery 100 under test are connected to the electrochemical testing device 300. The electrochemical testing device 300 can apply a variable frequency alternating current signal to the battery 100 under test, measure the alternating current impedance of the battery 100 under test at different frequencies in a preset frequency range, and obtain a spectrum of impedance variation with frequency, which is the electrochemical impedance spectrum of the battery 100 under test. The preset frequency range can include, for example, 0.05Hz to 500kHz, covering the low frequency band, the medium frequency band and the high frequency band. The preset amplitude may be within the range of 2mV to 5mV, for example, about 3mV (the error is within the preset error range). Such an amplitude may prevent the AC signal amplitude from being too high and causing damage to the battery 100 under test, and may prevent the AC signal amplitude from being too low and affecting the battery test.

[0047] As another example, an electrochemical testing device 300 (eg, an electrochemical workstation) may be used to measure the effective surface area of ​​the electrode surface that can participate in the electrochemical reaction, ie, the electrode effective reaction area S, by cyclic voltammetry (CV) or the like.

[0048] Based on this, in step S10, Figure 3 As shown, the computer device 400 can be connected to the electrochemical testing device 300 and obtain the electrochemical impedance spectrum and electrode effective reaction area of ​​the tested battery 100 from the electrochemical testing device 300 .

[0049] It should be understood that the above-mentioned methods of obtaining electrochemical impedance spectroscopy (EIS) and electrode effective reaction area are illustrative examples provided in this application. In practical applications, other methods can also be used to obtain them according to actual conditions, and this application does not list them one by one.

[0050] Step S20 , fitting the electrochemical impedance spectrum of the battery 100 under test to obtain the charge transfer impedance of the battery 100 under test.

[0051] In the embodiments of the present application, Figure 4 As shown, step S20 may include the following sub-steps:

[0052] Step S21 : constructing an equivalent circuit model of the battery 100 under test.

[0053] Specifically, the computer device 400 can construct an equivalent circuit model of each tested battery 100 through simulation software (such as MATLAB, PSIM, etc.), and the equivalent circuit model can be used to simulate the electrochemical process inside each tested battery 100. The equivalent circuit model can be, for example, a Randles circuit, which includes an electrolyte 103 resistor Rs, a double-layer capacitor Cdl, and a charge transfer impedance Rct, etc. The electrolyte 103 resistor Rs and the charge transfer impedance Rct are connected in series and then connected in parallel with the double-layer capacitor Cdl.

[0054] Among them, the resistance Rs of the electrolyte 103 is used to describe the resistance of the electrolyte 103 and the electrode material itself, reflecting the resistance of electrons when they are transmitted in the electrolyte 103. The charge transfer impedance Rct is used to describe the resistance of electrons transferred from one electrode to another when an electrochemical reaction occurs on the electrode surface. The smaller the charge transfer impedance, the faster the rate of the electrode reaction, and the higher the charge and discharge efficiency of the measured battery 100. The double layer capacitance Cdl is used to describe the double layer behavior of the electrode interface.

[0055] Step S22: fitting the electrochemical impedance spectrum of the tested battery 100 according to the equivalent circuit model.

[0056] Specifically, the computer device 400 can fit the electrochemical impedance spectrum data of each tested battery 100 with the equivalent circuit model through EIS data fitting software (such as ZView, EC-Lab, MATLAB, etc.), wherein the component parameters of the equivalent circuit model can be adjusted using a fitting algorithm (such as complex nonlinear least squares method, etc.) to find the best fitting value of each component parameter in the equivalent circuit model, and the difference between the best fitting value and the electrochemical impedance spectrum data is minimized.

[0057] Step S23 : using the charge transfer impedance in the equivalent circuit model obtained after fitting as the charge transfer impedance of the battery 100 under test.

[0058] That is to say, for each tested battery 100, the best fitting value of the charge transfer impedance in its equivalent circuit model is its charge transfer impedance Rct.

[0059] Step S30: Calculate the reference exchange current density of the battery 100 under test according to the charge transfer impedance and the effective electrode reaction area of ​​the battery 100 under test.

[0060] Where, the reference exchange current density j 0(Reference Exchange Current Density) refers to the current of the oxidation reaction or reduction reaction on the unit area of ​​the electrode surface at the equilibrium potential, when the overpotential η=0, the oxidation reaction and the reduction reaction rate are equal, and the net current is 0. Reference exchange current density j 0 It reflects the ability of the electrode material to gain or lose electrons and the difficulty of the electrode reaction. 0 The larger the value, the stronger the ability of the working electrode 101 to participate in the redox reaction is, the smaller the reaction overpotential during the charge and discharge process is, and the higher the reversibility is.

[0061] Reference exchange current density j 0 It can be understood as a reference value of the actual exchange current density j of the tested battery 100. In the actual battery charging and discharging process, the net current on the electrode surface is not 0. At this time, the relationship between the actual exchange current density j and the reference exchange current density is described by the BV equation:

[0062]

[0063] Where α is a dimensionless coefficient. F is the Faraday constant. R refers to the molar gas constant. T is the temperature in Kelvin, that is, the absolute temperature. η is the overpotential (also known as superpotential, overpotential, overpotential), which refers to the difference between the actual potential and the equilibrium potential when the actual potential in the electrochemical reaction is higher than the equilibrium potential, which can serve as the driving force of the electrochemical reaction.

[0064] Furthermore, in the EIS test, the BV equation is linearized when the overpotential η is small, and the following is obtained:

[0065]

[0066] The relationship between the overpotential η, the charge transfer impedance Rct, and the electrode effective reaction area S can be as follows:

[0067] η=jSR ct (3)

[0068] Where S is the effective reaction area of ​​the electrode.

[0069] Furthermore, based on equations (2) and (3), the following expression for the reference exchange current density can be obtained:

[0070] j 0 =RT / (SFR ct ) (4)

[0071] It can be seen that the expression of the reference exchange current density indicates the reference exchange current density j 0It is negatively correlated with the charge transfer impedance Rct, referring to the exchange current density j 0 There is a negative correlation between the effective reaction area S of the electrode.

[0072] Accordingly, the computer device 400 can pre-establish a corresponding mathematical model related to the reference exchange current density (i.e., a first calculation model, such as formula (4)) for each battery under test 100, and then in step S30, the charge transfer impedance Rct and the electrode effective reaction area S of the battery under test 100 can be substituted into the first calculation model, and the reference exchange current density j of the battery under test 100 can be calculated using the reference exchange current density module. 0 .

[0073] Taking into account that the reference exchange current density varies with the lithium insertion concentration (or SoC) of the electrode material and the electrolyte concentration, therefore, in step S30, the corresponding reference exchange current density can be calculated for the battery 100 under test with different lithium insertion concentrations (or SoC) and different preset electrolyte concentrations, and then the reaction rate constant is calculated in step S40.

[0074] Step S40, calculating the reaction rate constant of the battery 100 under test according to the reference exchange current density of the battery 100 under test, the preset electrolyte concentration of the battery 100 under test, and the lithium insertion concentration.

[0075] The reaction rate constant k 0 It refers to the rate of electrode reaction when the concentration of reactants is unit concentration. The reaction rate constant determines the speed of charging and discharging of the tested battery 100 under the conditions of preset electrode materials, preset ambient temperature and preset electrolyte 103 concentration.

[0076] In the embodiment of the present application, the computer device 400 can pre-establish the corresponding reaction rate constant k for each battery 100 under test. 0 The related mathematical model (ie, the second calculation model) is used to calculate the reaction rate constant of the battery 100 under test.

[0077] In one embodiment, the second computational model can be used to indicate the reaction rate constant k 0 The exchange current density j with the reference 0 , the correlation between lithium insertion concentration. The lithium insertion concentration includes the maximum lithium insertion concentration and at a preset electrolyte concentration c e The lithium insertion concentration c s .

[0078] Specifically, the second calculation model may be, for example, the following expression:

[0079]

[0080] It can be seen that the second calculation model indicates the reaction rate constant k 0 The exchange current density j with the reference 0 There is a positive correlation between them, and the reaction rate constant k 0 With the preset electrolyte concentration c e There is a positive correlation between the reaction rate constant and the maximum lithium insertion concentration. There is a positive correlation between them, and the reaction rate constant k 0 With the preset electrolyte concentration c e The lithium insertion concentration c s There is a negative correlation between them.

[0081] Accordingly, in step S40, the reference exchange current density j of each battery 100 under test may be 0 , the preset electrolyte concentration c of the battery 100 under test e , Maximum lithium insertion concentration and at a preset electrolyte concentration c e The lithium insertion concentration c s Substitute into the corresponding second calculation model, and use the second calculation model module to calculate the reaction rate constant k of the battery 100 under test 0 .

[0082] For better understanding, the whole process of the battery testing method of the present application embodiment is described below with an example. In this example, a graphite negative electrode and a lithium sheet are used, and the concentration c e Several button-type half-cells were made using 1M LiPF6 (lithium hexafluorophosphate) electrolyte 103, wherein a graphite negative electrode was used as a working electrode 101, which used a circular electrode piece with a diameter of 12 mm and a surface loading of 8.47 mg / cm2. A lithium sheet was used as a counter electrode.

[0083] At 25°C, EIS tests were performed on button half-cells with different lithium insertion concentrations (3mV@50mHz~0.5Mhz, i.e., an AC signal with an amplitude of 3mV and a frequency of 50mHz~0.5Mhz was applied to the graphite negative electrode). The measured EIS results (i.e., electrochemical impedance spectroscopy) can be found in Figure 5 . Figure 5 The horizontal axis is the real impedance, which represents the resistance component, mainly the solution resistance and charge transfer impedance. The vertical axis is the imaginary impedance, which represents the polarization impedance or capacitive response (especially the polarization behavior of the electrode surface). Figure 5 It can be seen that different lithium insertion concentrations (0-1.0) correspond to different impedance curves. Among them, the charge transfer impedance curves under different lithium insertion concentrations can be shown as follows Figure 6 As shown in the Exp Rct curve, Figure 6The abscissa is the SOC corresponding to the lithium intercalation state, the left ordinate is the reference exchange current density, and the right ordinate is the charge transfer impedance Rct. The solid dots on the curve represent the charge transfer impedance at a certain lithium intercalation concentration.

[0084] Therefore, through steps S10 - S30 of the embodiments of the present application, the reference exchange current density j of the electrode under different lithium intercalation states can be calculated. 0 , as shown in Figure 6 the EXPj 0 curve. The solid triangles on the curve represent the reference exchange current density at a certain lithium intercalation concentration.

[0085] In this example, in order to more intuitively understand the reference exchange current density and more quickly determine the better reaction rate constant, the reference exchange current densities at several lithium intercalation concentrations can be selected to fit the Figure 6 Fitj 0 curve. The Fitj 0 curve can more clearly reflect the trend of the reference exchange current density changing with the lithium intercalation concentration.

[0086] Furthermore, through step S40 of the embodiments of the present application, the corresponding reaction rate constant k can be calculated according to the Fitj 0 curve. 0 , as shown in Figure 6 the k 0 curve.

[0087] It can be understood that the reference exchange current density j 0 and the reaction rate constant k 0 can be used as the kinetic parameters of the electrochemical reaction of the battery under test 100, to analyze the electrode reaction mechanism and kinetic process of the battery under test 100, and to evaluate the performance and efficiency of the battery, etc. For example, the reference exchange current density and reaction rate constant of the battery under different conditions (such as different preset electrolyte concentrations, electrode materials, temperatures, SOC, etc.) can be measured through the above steps. Among them, the spatial distribution of the actual exchange current density j can be obtained according to the B - V equation (such as formula (1)) and the reference exchange current density j 0 . The overpotential η can be calculated according to formula (3), etc. Based on these measured parameters, an electrochemical model of the battery can be established to simulate the process and kinetic characteristics of the electrochemical reaction between the electrode and the electrolyte 103. For another example, the electrolyte concentration and / or electrode material with a higher reference exchange current density and reaction rate constant can be screened out, which is beneficial to finding the electrolyte concentration and / or electrode material that is easier and faster to undergo electrochemical reactions, so as to study batteries with more efficient charge and discharge.

[0088] In general, the embodiments of the present application provide a new battery testing method, which uses a lithium-ion half-cell as a battery under test, obtains the electrochemical impedance spectrum and the effective electrode reaction area of ​​the battery under test, fits the electrochemical impedance spectrum of the battery under test, and obtains the charge transfer impedance of the battery under test. Then, based on the charge transfer impedance and the effective electrode reaction area of ​​the battery under test, the reference exchange current density of the battery under test is calculated. Finally, based on the reference exchange current density of the battery under test, the preset electrolyte concentration of the battery under test, and the lithium insertion concentration, the reaction rate constant of the battery under test is calculated.

[0089] Since lithium-ion half-cells are easy to prepare and have low costs, and the test steps of the embodiments of the present application are simple, highly operable, and have good repeatability, compared with the currently commonly used test methods based on three-electrode batteries, the test difficulty of the embodiments of the present application is lower, the material cost is lower, and the stability and consistency of the test results are better.

[0090] Moreover, in the method of the embodiment of the present application, the results between different electrolyte concentrations and different SoCs can be cross-validated, that is, the reaction rate constant and reference exchange current density measured by the method of the embodiment of the present application can be converted into the same other parameters using known formulas. The similarity or consistency of the conversion results can verify that the reaction rate constant and reference exchange current density measured by the method of the embodiment of the present application are stable, accurate and reliable.

[0091] Therefore, in summary, the battery testing method of the embodiment of the present application is very suitable for battery material performance testing, can effectively improve testing efficiency, reduce testing costs, and is helpful for subsequent overall, global testing analysis of batteries and research and design of finished batteries.

[0092] It should be noted that, for the aforementioned method embodiments, for the sake of simplicity of description, they are all expressed as a series of action combinations, but those skilled in the art should know that the present application is not limited by the described order of actions, because according to the present application, certain steps can be performed in other orders or simultaneously.

[0093] In addition, the embodiment of the present application further provides a battery testing device 500. The battery testing device 500 can be used to implement the above-mentioned battery testing method.

[0094] For details, please refer to Figure 7 The battery testing device 500 provided in the embodiment of the present application includes: an acquisition module 501, a fitting module 502, a first calculation module 503 and a second calculation module 504.

[0095] The acquisition module 501 is used to acquire the electrochemical impedance spectrum and the effective electrode reaction area of ​​the battery under test; wherein the battery under test is a lithium-ion half-cell in a preset state of charge.

[0096] The fitting module 502 is used to fit the electrochemical impedance spectrum of the battery under test to obtain the charge transfer impedance of the battery under test.

[0097] The first calculation module 503 is used to calculate the reference exchange current density of the battery 100 under test according to the charge transfer impedance and the effective reaction area of ​​the electrode of the battery under test.

[0098] The second calculation module 504 is used to calculate the reaction rate constant of the battery under test according to the reference exchange current density of the battery under test, the preset electrolyte concentration and the lithium insertion concentration of the battery under test.

[0099] It is understandable that the division of the various modules in the above-mentioned battery testing device 500 is only for illustration. In other embodiments, the battery testing device 500 can be divided into different modules as needed to complete all or part of the functions of the above-mentioned battery testing device 500.

[0100] The specific implementation of each module in the embodiment of the present application can also refer to the corresponding description of the aforementioned method embodiment, so it will not be described in detail here.

[0101] The functional modules in the embodiments of the present application may all be integrated into one processing module / unit, or each module may be a separate module, or two or more modules may be integrated into one module; the above-mentioned integrated modules may be implemented in the form of hardware or in the form of hardware plus software functional modules.

[0102] If the above-mentioned integrated module of the present application is implemented in the form of a software function module and sold or used as an independent product, it can also be stored in a computer-readable storage medium. Based on such an understanding, the technical solution of the embodiment of the present application can be essentially or partly embodied in the form of a software product that contributes to the prior art. The computer software product is stored in a storage medium, including several instructions to enable a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the methods described in each embodiment of the present application. The aforementioned storage medium includes: various media that can store program codes, such as mobile storage devices, ROM, RAM, magnetic disks or optical disks.

[0103] Accordingly, the embodiment of the present application also provides a computer-readable storage medium for storing computer-readable instructions, and when the computer-readable instructions are executed by a processor, all or part of the steps in the above-mentioned battery testing method embodiment are implemented. Among them, the computer-readable storage medium includes volatile and non-volatile, removable and non-removable media implemented in any method or technology for storing information (such as computer-readable instructions, data structures, program modules or other data).

[0104] In addition, an embodiment of the present application further provides an electronic device 600 .

[0105] like Figure 8 As shown, the electronic device 600 may include a processor 601 and a memory 602 .

[0106] The processor 601 may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application specific integrated circuits (ASIC), field programmable gate arrays (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor may be a microprocessor or any conventional processor, etc.

[0107] The memory 602 may be a read-only memory (ROM) or other types of static storage devices that can store static information and instructions, a random access memory (RAM) or other types of dynamic storage devices that can store information and instructions, or an electrically erasable programmable read-only memory (EEPROM), a compact disc read-only memory (CD-ROM) or other optical disc storage, optical disc storage (including compressed optical disc, laser disc, optical disc, digital versatile disc, Blu-ray disc, etc.), a magnetic disk storage medium or other magnetic storage device, or any other medium that can be used to carry or store the desired program code in the form of instructions or data structures and can be accessed by a computer, but is not limited thereto. The memory 602 may exist independently and be connected to the processor 601 via a bus. The memory 602 may also be integrated with the processor 601.

[0108] The memory 602 is used to store programs, instructions or codes. The processor 601 is used to execute the programs, instructions or codes stored in the memory 602. The programs, instructions or codes stored in the memory 602 can execute some or all of the steps in the above-mentioned battery testing method embodiment.

[0109] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present application and are not intended to limit it. Although the present application has been described in detail with reference to the preferred embodiments, a person of ordinary skill in the art should understand that the technical solution of the present application may be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the present application.

Claims

1. A battery testing method, characterized in that: The battery testing method comprises: Obtaining an electrochemical impedance spectrum and an effective electrode reaction area of ​​a battery under test; wherein the battery under test is a lithium-ion half-cell in a preset state of charge; Fitting the electrochemical impedance spectrum of the battery under test to obtain the charge transfer impedance of the battery under test; Calculating a reference exchange current density of the battery under test according to the charge transfer impedance of the battery under test and the effective reaction area of ​​the electrode; The reaction rate constant of the battery under test is calculated based on the reference exchange current density of the battery under test, the preset electrolyte concentration and the lithium insertion concentration of the battery under test.

2. The battery testing method according to claim 1, characterized in that: Calculating the reference exchange current density of the battery under test according to the charge transfer impedance of the battery under test and the effective reaction area of ​​the electrode includes: According to the charge transfer impedance of the battery under test and the effective reaction area of ​​the electrode, a reference exchange current density of the battery under test is calculated based on a preset first calculation model; The first calculation model is used to indicate that there is a negative correlation between the reference exchange current density and the charge transfer impedance, and between the reference exchange current density and the effective reaction area of ​​the electrode.

3. The battery testing method according to claim 1, characterized in that: The reaction rate constant of the battery under test is calculated according to the reference exchange current density of the battery under test, the preset electrolyte concentration of the battery under test, and the lithium insertion concentration, including: Calculating the reaction rate constant of the battery under test based on a preset second calculation model according to the reference exchange current density of the battery under test, the preset electrolyte concentration of the battery under test, the maximum lithium insertion concentration and the lithium insertion concentration at the preset electrolyte concentration; Among them, the second calculation model is used to indicate that there is a positive correlation between the reaction rate constant and the reference exchange current density, between the reaction rate constant and the preset electrolyte concentration, and between the reaction rate constant and the maximum lithium insertion concentration, and there is a negative correlation between the reaction rate constant and the lithium insertion concentration at the preset electrolyte concentration.

4. The battery testing method according to claim 1, characterized in that: The step of obtaining the electrochemical impedance spectrum of the battery under test comprises: The electrochemical impedance spectrum of the battery under test is obtained from an electrochemical testing device; wherein the electrochemical testing device is used to perform an electrochemical impedance spectrum test on the battery under test under preset conditions, and the preset conditions include a preset ambient temperature, and an electrical signal applied to the battery under test is in a preset frequency range and reaches a preset amplitude.

5. The battery testing method according to claim 1 or 4, characterized in that: The battery under test is located in a thermostatic box, and the internal temperature of the thermostatic box reaches a preset ambient temperature.

6. The battery testing method according to claim 4, characterized in that: The preset frequency range includes 0.05 Hz-500 kHz; the preset amplitude is in the range of 2 mV to 5 mV.

7. The battery testing method according to claim 1, characterized in that: The preset state of charge is in the range of 10% to 90%.

8. The battery testing method according to claim 1, characterized in that: The process of fitting the electrochemical impedance spectrum of the battery under test to obtain the charge transfer impedance of the battery under test includes: Constructing an equivalent circuit model of the battery under test; Fitting the electrochemical impedance spectrum of the tested battery according to the equivalent circuit model; The charge transfer impedance in the equivalent circuit model obtained after fitting is used as the charge transfer impedance of the battery under test.

9. The battery testing method according to claim 1, characterized in that: The battery under test is a button battery.

10. A computer-readable storage medium storing computer-readable instructions, characterized in that: When the computer-readable instructions are executed by a processor, the battery testing method according to any one of claims 1 to 9 is implemented.

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