A method and device for detecting the starting potential of lithium plating of soft-pack battery cells

Abstract

The present application belongs to the field of battery cell testing technology, and discloses a method and device for detecting the lithium plating starting point potential of a soft-pack battery cell. By combining a variety of electrode materials and a preset reference electrode, a soft-pack battery cell with a simple process and a shorter cycle can be prepared, and multiple groups of test capacity parameters are generated according to the nominal capacity determined by the soft-pack battery cell, so that the soft-pack battery cell can be tested based on the voltage relaxation method without causing damage to the soft-pack battery cell and waste. Secondly, the voltage-time curve obtained after the test process and the corresponding differential voltage-time curve can be combined to determine the lithium plating starting point potential of the soft-pack battery cell at a specific rate in the negative electrode to lithium potential curve, which not only ensures the accuracy of the lithium plating starting point potential, but also makes the subsequent step-charging strategy formulation more reasonable, thereby improving the overall testing experience.

Description

Technical Field

[0001] The present application belongs to the field of battery cell testing technology, and in particular relates to a method and device for detecting the starting potential of lithium plating of a soft-pack battery cell. Background Art

[0002] The lithium plating window (LPW) of a lithium battery refers to the voltage range within which the negative electrode material can stably accept and release lithium ions without producing lithium metal deposition during the charge and discharge process. Under normal operating conditions, lithium ions are deintercalated from the positive electrode, migrate through the electrolyte to the negative electrode, and then embed themselves within the negative electrode material. However, when the lithium battery is overcharged, undergoing high-current rapid charging, or experiencing a rapid increase in lithium ion concentration near the negative electrode surface, lithium ions may not be effectively embedded within the internal structure of the negative electrode material. In this case, the lithium ions receive electrons on the negative electrode surface and are reduced to metallic lithium, a phenomenon known as lithium plating.

[0003] Currently, the lithium plating window test for lithium batteries mainly uses power cells and makes reference electrodes. The starting point of lithium plating is determined by monitoring the potential of the negative electrode to the reference electrode to be 0 volts. However, this method of determining the starting point of lithium plating is not applicable. For example, for some soft-pack cells, there is a large error between the determined starting point of lithium plating and the actual starting point of lithium plating, which leads to unreasonable formulation of subsequent step-charging strategies and affects the overall testing experience. Summary of the Invention

[0004] This application aims to solve the above-mentioned problem of using 0 volts of potential of the negative electrode relative to the reference electrode as the starting point of lithium deposition. However, this method of determining the starting point of lithium deposition is not applicable. For example, for some soft-pack batteries, there is a large error between the determined starting point of lithium deposition and the actual starting point of lithium deposition, which leads to unreasonable formulation of subsequent step charging strategies and affects the overall test experience. Technical defects such as a method and device for detecting the starting point potential of lithium deposition of soft-pack batteries are proposed. The technical solution is as follows:

[0005] In a first aspect, an embodiment of the present application provides a method for detecting the lithium plating starting potential of a soft-pack battery cell, comprising:

[0006] Prepare samples of at least two electrode materials to obtain positive and negative electrode test electrodes, and prepare soft-pack batteries based on the positive and negative electrode test electrodes and preset reference electrodes;

[0007] Determine the nominal capacity based on the soft-pack battery cell and two sets of preset charge and discharge parameters;

[0008] Generate at least two sets of test capacity parameters according to the nominal capacity, and test the soft-pack battery cells in turn according to each set of test capacity parameters to obtain corresponding voltage-time curves and negative electrode to lithium potential curves;

[0009] Each voltage-time curve is differentiated to obtain the corresponding differential voltage-time curve, and the lithium plating starting potential of the soft-pack battery cell is determined based on all voltage-time curves, all differential voltage-time curves and the negative electrode lithium potential curve.

[0010] In an optional solution of the first aspect, preparing samples of at least two electrode materials to obtain positive and negative electrode test electrodes includes:

[0011] Mixing artificial graphite, conductive carbon black, sodium carboxymethyl cellulose and styrene-butadiene rubber latex according to a preset first ratio to obtain a negative electrode slurry;

[0012] performing a coating and drying process on the negative electrode slurry according to a preset first coating surface density, and performing a roller pressing process on the negative electrode slurry after the coating and drying process according to a preset first compaction density;

[0013] Cutting the negative electrode slurry after the roll pressing process according to a preset first size to obtain at least two negative electrode test pieces;

[0014] Mixing lithium iron phosphate, conductive carbon black, polyvinylidene fluoride, and carbon nanotubes in a preset second ratio to obtain a positive electrode slurry;

[0015] performing a coating and drying process on the positive electrode slurry according to a preset second coating surface density, and performing a roller pressing process on the positive electrode slurry after the coating and drying process according to a preset second compaction density;

[0016] The positive electrode slurry after the roll pressing process is cut according to a preset second size to obtain at least two positive electrode test electrodes.

[0017] In another optional solution of the first aspect, a soft-pack battery cell is prepared according to the positive and negative test electrodes and a preset reference electrode, including:

[0018] Performing lithium plating on a preset reference electrode according to preset lithium plating parameters;

[0019] Based on the preset number of stacked layers, the number of negative test electrodes, the number of positive test electrodes, the preset number of reference electrodes after lithium plating, and the number of diaphragms are determined respectively, and soft-pack battery cells are prepared according to the number of negative test electrodes, the number of positive test electrodes, the preset number of reference electrodes after lithium plating, and the number of diaphragms.

[0020] In another optional solution of the first aspect, the two sets of preset charge and discharge parameters include a discharge parameter consisting of a charge and discharge rate and a discharge cut-off voltage, and a charge parameter consisting of a charge and discharge rate and a charge cut-off voltage, and the discharge cut-off voltage is less than the charge cut-off voltage;

[0021] Based on the soft-pack battery cell and two sets of preset charge and discharge parameters, the nominal capacity is determined, including:

[0022] The soft-packed battery cells are placed in a static state according to a preset static time, and the soft-packed battery cells are discharged according to discharge parameters after the static state;

[0023] The soft-packed battery cells after discharge treatment are placed on hold according to a preset placement time, and the soft-packed battery cells after placement are charged according to charging parameters;

[0024] The soft-packed battery cells after the charge treatment are placed for a preset placement time, and the soft-packed battery cells after the placement treatment are discharged according to the discharge parameters, so as to use the corresponding discharge capacity as the nominal capacity.

[0025] In another optional solution of the first aspect, generating at least two sets of test capacity parameters according to the nominal capacity includes:

[0026] Obtaining a first set of test capacity parameters based on the nominal capacity, a preset first charge ratio parameter, and a preset relaxation time;

[0027] Obtaining a second set of test capacity parameters based on the nominal capacity, a preset second charging ratio parameter, and a preset relaxation time;

[0028] Based on the nominal capacity, the preset third charging ratio parameter and the preset relaxation time, a third set of test capacity parameters is obtained; wherein the difference between the preset second charging ratio parameter and the preset first charging ratio parameter is consistent with the difference between the preset third charging ratio parameter and the preset second charging ratio parameter.

[0029] In another optional solution of the first aspect, determining the lithium deposition starting potential of the soft-pack battery cell according to all voltage-time curves, all differential voltage-time curves, and the negative electrode to lithium potential curve includes:

[0030] When an abnormal slope change is detected in the voltage-time curve corresponding to the nth group of test capacity parameters, it is determined whether a characteristic peak exists in the corresponding differential voltage-time curve; wherein n is a positive integer greater than 1;

[0031] When a characteristic peak is detected in the differential voltage-time curve, the starting potential of lithium deposition of the soft-pack battery cell is determined according to the voltage-time curve, differential voltage-time curve and negative electrode lithium potential curve corresponding to the n-1th group of test capacity parameters.

[0032] In another optional solution of the first aspect, the lithium plating starting potential of the soft-pack battery cell is determined according to the voltage-time curve, the differential voltage-time curve, and the negative electrode to lithium potential curve corresponding to the n-1th group of test capacity parameters, including:

[0033] When no abnormal slope change is detected in the voltage-time curve corresponding to the n-1th group of test capacity parameters, it is determined whether there is a characteristic peak in the corresponding differential voltage-time curve;

[0034] When no characteristic peak is detected in the differential voltage-time curve, a first potential corresponding to the nth group of test capacity parameters and a second potential corresponding to the n-1th group of test capacity parameters are respectively determined in the negative electrode to lithium potential curve;

[0035] The lithium deposition starting point potential of the soft-pack battery cell is determined according to the potential range formed by the first potential and the second potential.

[0036] In a second aspect, an embodiment of the present application provides a device for detecting the starting potential of lithium deposition in a soft-pack battery cell, comprising:

[0037] A cell preparation module is used to prepare samples of at least two electrode materials to obtain positive and negative electrode test electrodes, and to prepare soft-pack cells based on the positive and negative electrode test electrodes and a preset reference electrode;

[0038] A capacity determination module is used to determine the nominal capacity based on the soft-pack battery cell and two sets of preset charge and discharge parameters;

[0039] A data generation module is used to generate at least two sets of test capacity parameters according to the nominal capacity, and test the soft-pack battery cells in turn according to each set of test capacity parameters to obtain corresponding voltage-time curves and negative electrode to lithium potential curves;

[0040] The result determination module is used to perform differential processing on each voltage-time curve to obtain the corresponding differential voltage-time curve, and determine the lithium plating starting potential of the soft-pack battery cell based on all voltage-time curves, all differential voltage-time curves and the negative electrode lithium potential curve.

[0041] In a third aspect, an embodiment of the present application further provides a device for detecting the lithium plating starting potential of a soft-pack battery cell, comprising a processor and a memory;

[0042] The processor is connected to the memory;

[0043] a memory for storing executable program code;

[0044] The processor runs the program corresponding to the executable program code by reading the executable program code stored in the memory, so as to implement the method for detecting the lithium plating starting point potential of the soft-pack battery cell provided by the first aspect of the embodiment of the present application or any one of the implementation methods of the first aspect.

[0045] In the fifth aspect, an embodiment of the present application provides a computer storage medium, which stores a computer program. The computer program includes program instructions. When the program instructions are executed by a processor, the method for detecting the lithium plating starting point potential of a soft-pack battery cell provided by the first aspect of the embodiment of the present application or any one of the implementation methods of the first aspect can be implemented.

[0046] In an embodiment of the present application, when detecting the lithium plating starting potential of a soft-pack battery cell, samples can be prepared according to at least two electrode materials to obtain positive and negative electrode test electrodes, and a soft-pack battery cell can be prepared based on the positive and negative electrode test electrodes and a preset reference electrode; the nominal capacity is determined based on the soft-pack battery cell and two sets of preset charge and discharge parameters; at least two sets of test capacity parameters are generated according to the nominal capacity, and the soft-pack battery cell is tested in turn according to each set of test capacity parameters to obtain a corresponding voltage-time curve and a negative electrode to lithium potential curve; each voltage-time curve is differentiated to obtain a corresponding differential voltage-time curve, and the lithium plating starting potential of the soft-pack battery cell is determined based on all voltage-time curves, all differential voltage-time curves and the negative electrode to lithium potential curve. By combining a variety of electrode materials and preset reference electrodes, soft-pack batteries with simple processes and shorter cycles can be prepared, and multiple sets of test capacity parameters are generated according to the nominal capacity determined for the soft-pack batteries, so that the soft-pack batteries can be tested based on the voltage relaxation method without causing damage to and waste of the soft-pack batteries. Secondly, the voltage-time curve obtained after the test and the corresponding differential voltage-time curve can be combined to determine the lithium plating starting potential of the soft-pack batteries at a specific rate in the negative electrode to lithium potential curve. This not only ensures the accuracy of the lithium plating starting potential, but also makes the subsequent step-charging strategy formulation more reasonable, thereby improving the overall testing experience. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0048] Figure 1 This is an overall flow chart of a method for detecting the starting potential of lithium deposition in a soft-pack battery cell provided in an embodiment of the present application;

[0049] Figure 2 A schematic diagram of a voltage-time curve and a differential voltage-time curve of a soft-pack battery cell provided in an embodiment of the present application;

[0050] Figure 3A schematic diagram of a voltage-time curve and a differential voltage-time curve of another soft-pack battery cell provided in an embodiment of the present application;

[0051] Figure 4 A schematic diagram of a negative electrode to lithium potential curve of a soft-pack battery cell provided in an embodiment of the present application;

[0052] Figure 5 A schematic structural diagram of a device for detecting the starting potential of lithium deposition in a soft-pack battery cell according to an embodiment of the present application;

[0053] Figure 6 A schematic structural diagram of another device for detecting the starting potential of lithium deposition in a soft-pack battery cell according to an embodiment of the present application. DETAILED DESCRIPTION

[0054] The technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application.

[0055] In the following introduction, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance. The following introduction provides multiple embodiments of the present application. Different embodiments can be replaced or combined, so the present application can also be considered to include all possible combinations of the same and / or different embodiments described. Therefore, if one embodiment includes features A, B, and C, and another embodiment includes features B and D, then the present application should also be considered to include embodiments containing one or more of all other possible combinations of A, B, C, and D, even though the embodiment may not be clearly described in the following text.

[0056] The following description provides examples and does not limit the scope, applicability, or examples set forth in the claims. Changes may be made to the function and arrangement of the elements described without departing from the scope of the present application. Various examples may appropriately omit, replace, or add various processes or components. For example, the described method may be performed in an order different from the order described, and various steps may be added, omitted, or combined. In addition, features described in some examples may be combined in other examples.

[0057] See also Figure 1 , Figure 1 The figure shows an overall flow chart of a method for detecting the starting potential of lithium deposition in a soft-pack battery cell provided in an embodiment of the present application.

[0058] like Figure 1 As shown, the method for detecting the lithium plating starting potential of the soft-pack battery cell may include at least the following steps:

[0059] Step 102: Prepare samples using at least two electrode materials to obtain positive and negative electrode test electrodes, and prepare soft-pack batteries based on the positive and negative electrode test electrodes and a preset reference electrode.

[0060] In an embodiment of the present application, the method for detecting the lithium deposition starting potential of a soft-pack battery cell can be, but is not limited to, applied to a test terminal, which can establish connections with a battery preparation device and a battery testing device, respectively, to control the battery preparation device to prepare a soft-pack battery cell according to a variety of electrode materials, corresponding electrode parameters, and a preset reference electrode, and the soft-pack battery cell can be placed in the battery testing device for testing and processing to determine the lithium deposition starting potential of the soft-pack battery cell based on the test results fed back by the battery testing device.

[0061] Among them, the battery preparation device can be understood as a collection of processing equipment that coats, dries, rolls, and die-cuts a variety of electrode materials to obtain positive and negative electrode test electrodes, and performs lamination, liquid injection, formation, and capacity separation on the positive and negative electrode test electrodes and the preset reference electrodes. It can process the corresponding multiple electrode materials and the preset reference electrode according to the preparation process of the positive and negative electrode test electrodes output by the test terminal and the preparation process of the soft-pack battery cell. When laminating the positive and negative electrode test electrodes and the preset reference electrode, the preset reference electrode can also be fixed in the middle of the diaphragm corresponding to the positive and negative electrode test electrodes, and the nickel sheet can be used as the tab of the preset reference electrode, that is, the preset reference electrode is welded to the nickel sheet through a tin bar to ensure the potential stability of the reference electrode. Here, all processing equipment contained in the battery preparation device can be conventional equipment in this field, and its related control procedures or execution principles will not be described in detail.

[0062] Among them, the battery testing device can be understood as a test cabinet and a test equipment set for charging and discharging soft-pack batteries. The prepared soft-pack batteries can be placed in the test cabinet through a test terminal or manually, and the soft-pack batteries can be tested according to the various test capacity parameters output by the test terminal. For example, but not limited to, the soft-pack batteries are charged and discharged at a specified current rate, so that the remaining capacity of the soft-pack batteries meets the specified charging ratio parameter (that is, the ratio of the energy of the battery after current charging to the energy when it is fully charged, referred to as SOC), and the current is cut off. The battery testing device can record the changing trend of the soft-pack battery cell as the voltage naturally relaxes over time, thereby generating a voltage-time curve of the soft-pack battery cell under different discharge ratio parameters. In addition, the battery testing device can also synchronously record the negative electrode to lithium potential (i.e., the voltage between the negative electrode of the soft-pack battery cell and a preset reference electrode) of the soft-pack battery cell as time increases through a multi-channel meter during the test process, so as to generate a corresponding negative electrode to lithium potential curve based on the negative electrode to lithium potential, and can feed back all the above-mentioned voltage-time curves and the negative electrode to lithium potential curve to the test terminal. Here, all the test equipment included in the battery testing device can be conventional equipment in this field, and its related control procedures or execution principles will not be described in detail.

[0063] It can be understood that when the test terminal detects the lithium plating starting potential of the soft-pack battery cell, it can control the above-mentioned battery preparation device to prepare a soft-pack battery cell with a simple process and a shorter cycle by combining a variety of electrode materials and a preset reference electrode, and generate multiple sets of test capacity parameters according to the nominal capacity determined by the soft-pack battery cell, so as to control the above-mentioned battery testing device to test and process the soft-pack battery cell according to the multiple sets of test capacity parameters, without causing damage to the soft-pack battery cell and waste; secondly, after receiving all the voltage-time curves and the negative electrode to lithium potential curves fed back by the battery testing device, the lithium plating starting potential of the soft-pack battery cell at a specific rate can be determined in the negative electrode to lithium potential curve according to all the voltage-time curves and the corresponding differential voltage-time curves. This not only ensures the accuracy of the lithium plating starting potential, but also makes the subsequent step charging strategy formulation more reasonable, thereby improving the overall testing experience.

[0064] Specifically, when detecting the lithium plating starting potential of the soft-pack battery cell, the test terminal can, but is not limited to, generate the preparation process of the positive and negative test electrodes and the preparation process of the soft-pack battery cell according to the names of the various electrode materials, the preset reference electrode and the preset electrode parameters input by the staff, and can send the preparation process of the positive and negative test electrodes and the preparation process of the soft-pack battery cell to the battery preparation device, so that the battery preparation device first coats and dries the various electrode materials according to the preparation process of the positive and negative test electrodes, rolls, and die-cuts them, and then stacks, injects, forms and divides the positive and negative test electrodes and the preset reference electrode according to the preparation process of the soft-pack battery cell, thereby obtaining a soft-pack battery cell with higher stability. Here, the preset electrode parameters can be, but are not limited to, the material ratio, coating surface density, and size parameters corresponding to the positive test electrode, the material ratio, coating surface density, and size parameters corresponding to the negative test electrode, and the number of positive and negative test electrode layers in the stacking process.

[0065] As an option in the embodiment of the present application, a sample preparation process is performed on at least two electrode materials to obtain positive and negative electrode test electrodes, including:

[0066] Mixing artificial graphite, conductive carbon black, sodium carboxymethyl cellulose and styrene-butadiene rubber latex according to a preset first ratio to obtain a negative electrode slurry;

[0067] performing a coating and drying process on the negative electrode slurry according to a preset first coating surface density, and performing a roller pressing process on the negative electrode slurry after the coating and drying process according to a preset first compaction density;

[0068] Cutting the negative electrode slurry after the roll pressing process according to a preset first size to obtain at least two negative electrode test pieces;

[0069] Mixing lithium iron phosphate, conductive carbon black, polyvinylidene fluoride, and carbon nanotubes in a preset second ratio to obtain a positive electrode slurry;

[0070] performing a coating and drying process on the positive electrode slurry according to a preset second coating surface density, and performing a roller pressing process on the positive electrode slurry after the coating and drying process according to a preset second compaction density;

[0071] The positive electrode slurry after the roll pressing process is cut according to a preset second size to obtain at least two positive electrode test electrodes.

[0072] Specifically, taking the example of a soft-pack battery cell whose positive electrode active material is lithium iron phosphate and whose negative electrode active material is artificial graphite, after the test terminal sends the preparation process of the positive and negative electrode test electrodes to the battery preparation device, the battery preparation device can first mix the artificial graphite (C), conductive carbon black (SP), sodium carboxymethyl cellulose (CMC), and styrene-butadiene rubber emulsion (SBR) according to a preset first ratio, and use deionized water as a solvent to obtain a negative electrode slurry. The proportions of artificial graphite, conductive carbon black, sodium carboxymethyl cellulose, and styrene-butadiene rubber emulsion in the preset first ratio can be, but are not limited to, 96.1%, 1.0%, 1.3%, and 1.6%, respectively. Of course, in the embodiment of the present application, the proportion of artificial graphite can also be controlled between 94% and 97%, the proportion of conductive carbon black can be controlled between 1% and 3%, the proportion of sodium carboxymethyl cellulose can be controlled between 1% and 3%, and the proportion of styrene-butadiene rubber emulsion can be controlled between 1% and 3%, and the proportion of styrene-butadiene rubber emulsion can be controlled between 1% and 3%, and the above are not limited thereto.

[0073] Next, after obtaining the negative electrode slurry, the negative electrode slurry can be coated on a 6 μm thick copper foil by a battery preparation device, and a continuous oven set at a temperature between 60-65°C is used to coat and dry the negative electrode slurry according to a preset first coating surface density. The preset first coating surface density can be, but is not limited to, 173 g / m 2 , and a roller press with a roller pressure set to 50T can be used to roller-press the negative electrode slurry after the coating and drying treatment according to a preset first compaction density. The preset first compaction density can be but is not limited to 1.6g / cm 3 Of course, the first coating surface density preset in the embodiment of the present application can also be controlled at 150-200 g / m 2 Between (for example but not limited to 150g / m 2 , 160g / m 2 , 170g / m 2 , 180g / m 2 , 190g / m 2 Or 200g / m 2 ), the preset first compaction density can also be controlled at 1.4-1.7g / cm 3 between (for example but not limited to 1.4 g / cm 3 , 1.45g / cm 3 , 1.5g / cm 3 , 1.55g / cm 3 , 1.6g / cm 3 , 1.65g / cm 3 or 1.7g / cm 3 ) to ensure the stability of the negative electrode.

[0074] Next, after the negative electrode slurry is rolled, the battery preparation device can also use a cutter to cut the rolled negative electrode slurry according to a preset first size to obtain a plurality of negative electrode test electrodes. The preset first size can be, but is not limited to, a width of 62 mm and a length of 93 mm, and the number of the negative electrode test electrodes can also be determined according to the preset number of laminate layers input by the user. For example, when the preset number of laminate layers is 12 layers, the number of negative electrode test electrodes can be, but is not limited to, set to 13, and is not limited to this.

[0075] Then, after preparing multiple negative electrode test electrodes, the battery preparation device can also mix lithium iron phosphate (LiFePO4), conductive carbon black (SP), polyvinylidene fluoride (PVDF) and carbon nanotubes (CNT) according to a preset second ratio, and use N-methylpyrrolidone (NMP) as a solvent to obtain a positive electrode slurry. The proportions of lithium iron phosphate, conductive carbon black, polyvinylidene fluoride and carbon nanotubes in the preset second ratio can be, but are not limited to, 96.5%, 1.0%, 2.0% and 0.5%, respectively. Of course, in the embodiment of the present application, the proportion of lithium iron phosphate can also be controlled between 95% and 98%, the proportion of conductive carbon black can also be controlled between 1% and 3%, the proportion of polyvinylidene fluoride can also be controlled between 1% and 3%, and the proportion of carbon nanotubes can also be controlled between 0% and 2%, and are not limited to these.

[0076] Next, after obtaining the positive electrode slurry, the positive electrode slurry can be coated on a 14 μm thick carbon-coated aluminum foil by a battery preparation device, and a continuous oven set at a temperature between 100-120°C is used to coat and dry the positive electrode slurry according to a preset second coating surface density. The preset second coating surface density can be, but is not limited to, 370 g / m 2 The negative electrode slurry after the coating and drying treatment can also be roller pressed by a roller press with a roller pressing pressure set to 60T according to a preset second compaction density. The preset second compaction density can be, but is not limited to, 2.55g / cm 3 Of course, the second coating surface density preset in the embodiment of the present application can also be controlled at 350-410 g / m 2 Between (for example but not limited to 350g / m 2 , 360g / m 2 , 370g / m 2 , 380g / m 2 , 390g / m 2 , 400g / m 2 or 410g / m 2 ), the preset second compaction density can also be controlled at 2.4-2.8 g / cm 3between (for example but not limited to 2.4 g / cm 3 , 2.5g / cm 3 , 2.6g / cm 3 , 2.7g / cm 3 , or 2.8g / cm 3 ) to ensure the stability of the positive electrode.

[0077] Next, after the positive electrode slurry is rolled, the battery preparation device can also use a cutting device to cut the rolled positive electrode material according to a preset second size to obtain a plurality of positive electrode test electrodes. The preset second size can be, but is not limited to, a width of 59 mm and a length of 90 mm, and the number of the positive electrode test electrodes can also be determined according to the preset number of laminate layers input by the user. For example, when the preset number of laminate layers is 12 layers, the number of positive electrode test electrodes can be, but is not limited to, set to 12, and is not limited to this.

[0078] As another option of the embodiment of the present application, a soft-pack battery cell is prepared according to the positive and negative test electrodes and a preset reference electrode, including:

[0079] Performing lithium plating on a preset reference electrode according to preset lithium plating parameters;

[0080] Based on the preset number of stacked layers, the number of negative test electrodes, the number of positive test electrodes, the preset number of reference electrodes after lithium plating, and the number of diaphragms are determined respectively, and soft-pack battery cells are prepared according to the number of negative test electrodes, the number of positive test electrodes, the preset number of reference electrodes after lithium plating, and the number of diaphragms.

[0081] Specifically, after preparing a plurality of positive electrode test sheets and a plurality of negative electrode test sheets, the test terminal can also send the preparation process of the soft-pack battery cell to the battery preparation device, so that the battery preparation device first uses the nickel sheet as the tab of the preset reference electrode, welds the nickel sheet to the preset reference electrode through a tin bar, and performs forward charging and reverse discharging lithium plating on the preset reference electrode according to the preset lithium plating parameters, repeating multiple times until a preset total time or a preset lithium layer thickness is reached, thereby ensuring the potential stability of the preset reference electrode. Here, the preset reference electrode can be, but is not limited to, a copper wire, and the preset lithium plating parameters can be, but are not limited to, including a lithium plating current and a lithium plating time. The lithium plating current can be controlled between 5uA and 30uA (for example, but not limited to, 5uA, 10uA, 15uA, 20uA, 25uA, or 30uA), and the lithium plating time can be controlled between 2h and 6h (for example, but not limited to, 2h, 3h, 4h, 5h, or 6h).

[0082] Next, taking the above-mentioned preset number of laminate layers of 12 as an example, it can be determined that the number of negative test sheets is 13, the number of positive test sheets is 12, the number of preset reference electrodes after lithium plating treatment is 12, and the number of diaphragms is 12. The battery preparation device performs a stacking process on all negative test sheets, all positive test sheets, all preset reference electrodes and all diaphragms, and during the stacking process, a diaphragm is provided between each positive test sheet and the adjacent negative test sheet, and a preset reference electrode can be fixed in the middle of each diaphragm. A mixed solution can be prepared, but is not limited to, with an electrolyte of 1 mol / L lithium hexafluorophosphate (LiPF6) solution and a solvent of ethylene carbonate (EC): ethyl carbonate (DMC) in a volume ratio of 1:1, so as to use the mixed solution to perform liquid injection, room temperature standing, chemical formation and volume separation on all sheets after the stacking process in sequence, thereby obtaining a soft-pack battery cell. Here, the type of the separator may be a polyethylene (PE)-based film with a single-sided ceramic, but is not limited thereto.

[0083] Of course, in the embodiment of the present application, all negative test electrodes, all positive test electrodes, all preset reference electrodes and all diaphragms can be stacked, and then all preset reference electrodes can be forward charged and reverse discharged for lithium plating, and the process can be repeated multiple times until the preset total time or the preset lithium layer thickness is reached. The present invention is also not limited to this.

[0084] Step 104: Determine the nominal capacity based on the soft-pack battery cell and two sets of preset charge and discharge parameters.

[0085] Specifically, after the soft-pack battery cell is prepared by the battery preparation device, the test terminal can, but is not limited to, manually or automatically control the transfer of the soft-pack battery cell to the test cabinet for a period of time, and send two sets of preset charge and discharge parameters to the battery testing device, so that the battery testing device can perform multiple charge and discharge processes on the soft-pack battery cell according to the preset charge and discharge parameters, and use the final discharged capacity of the soft-pack battery cell as the nominal capacity. Here, the standing time can be, but is not limited to, set to 6 hours.

[0086] As another option of the embodiment of the present application, the two sets of preset charge and discharge parameters include a discharge parameter consisting of a charge and discharge rate and a discharge cut-off voltage, and a charge parameter consisting of a charge and discharge rate and a charge cut-off voltage, and the discharge cut-off voltage is less than the charge cut-off voltage;

[0087] Based on the soft-pack battery cell and two sets of preset charge and discharge parameters, the nominal capacity is determined, including:

[0088] The soft-packed battery cells are placed in a static state according to a preset static time, and the soft-packed battery cells are discharged according to discharge parameters after the static state;

[0089] The soft-packed battery cells after discharge treatment are placed on hold according to a preset placement time, and the soft-packed battery cells after placement are charged according to charging parameters;

[0090] The soft-packed battery cells after the charge treatment are placed for a preset placement time, and the soft-packed battery cells after the placement treatment are discharged according to the discharge parameters, so as to use the corresponding discharge capacity as the nominal capacity.

[0091] In order to ensure the rationality of charging and discharging, the two sets of preset charging and discharging parameters can be divided into a set of charging parameters and a set of discharging parameters. The charging parameters may include charging and discharging rates and discharge cut-off voltages. The discharging parameters may include charging and discharging parameters and charging cut-off voltages. The charging and discharging rates can be understood as the constant current density corresponding to the specified capacity during the charging and discharging process (for example, charging and discharging xx capacity in one hour), for example, which can be set between 0.01C-2C (for example, but not limited to 0.01C, 0.1C, 0.2C, 0.5C, 1C or 2C).

[0092] Specifically, when the battery testing device performs multiple charge and discharge treatments on the soft-pack battery cells according to preset charge and discharge parameters, it can also be but not limited to after the soft-pack battery cells have been stationary in the test cabinet for a preset standing time (for example, which can be set to 6 hours), and then the soft-pack battery cells after the standing treatment are discharged according to the discharge parameters, for example, but not limited to discharging at a constant current of 1C to a cut-off voltage of 2.5V, and after the discharge treatment of the soft-pack battery cells is completed, the soft-pack battery cells after the discharge treatment are placed for a preset placement time, which can be but not limited to being set to 10 minutes, and then the soft-pack battery cells after the placement treatment are charged according to the charging parameters, for example, but not limited to charging at a constant current of 1C to a cut-off voltage of 3.65V.

[0093] Then, after completing one charge and discharge cycle of the soft-pack battery cell, the battery testing device can also perform multiple charge and discharge cycles on the soft-pack battery cell in the above manner (for example, but not limited to three times), until the soft-pack battery cell after the shelving treatment is finally discharged according to the discharge parameters, and the capacity corresponding to the final discharge process is used as the nominal capacity.

[0094] It should be noted that the test cabinet in the embodiment of the present application can be but is not limited to a Xinwei test cabinet, and the temperature of the entire charging and discharging process is maintained at around 25°C.

[0095] Step 106: Generate at least two groups of test capacity parameters according to the nominal capacity, and test the soft-pack battery cells in turn according to each group of test capacity parameters to obtain corresponding voltage-time curves and negative electrode to lithium potential curves.

[0096] Specifically, after the battery testing device determines the nominal capacity of the soft-pack battery cell, the testing terminal may, but is not limited to, generate multiple sets of test capacity parameters based on the nominal capacity fed back by the battery testing device. Among them, each group of test capacity parameters may include a charging rate corresponding to the nominal capacity, a preset charging ratio parameter and a preset relaxation time. The charging rate can be set between 1C-6C (for example, but not limited to 1C, 2, 3C, 4C, 5C or 6C), and the preset charging ratio parameter can be set between the starting charging ratio and the ending charging ratio (the starting charging ratio can be but not limited to 40%, and the ending charging ratio can be but not limited to 70%, 80%, 90% or 100%). The difference between the two preset charging ratio parameters in any two adjacent groups of test capacity parameters is fixed and can be set between 1%-15% (for example, but not limited to 1%, 2%, 3%, 5%, 10% or 15%), and the preset relaxation time can be set between 10min-60min (for example, but not limited to 10min, 20min, 30min, 40min, 50min or 60min).

[0097] Of course, each set of test capacity parameters in the embodiment of the present application may also include a discharge rate and a cut-off voltage corresponding to the nominal capacity, that is, after processing according to the above-mentioned charging rate, preset charging ratio parameters and preset relaxation time, the voltage of the soft-pack battery cell must be discharged according to the discharge rate to be consistent with the cut-off voltage, and after a specified shelf time, the test can be performed again according to the next set of test capacity parameters.

[0098] As another option of the embodiment of the present application, at least two sets of test capacity parameters are generated according to the nominal capacity, including:

[0099] Obtaining a first set of test capacity parameters based on the nominal capacity, a preset first charge ratio parameter, and a preset relaxation time;

[0100] Obtaining a second set of test capacity parameters based on the nominal capacity, a preset second charging ratio parameter, and a preset relaxation time;

[0101] Based on the nominal capacity, the preset third charging ratio parameter and the preset relaxation time, a third set of test capacity parameters is obtained; wherein the difference between the preset second charging ratio parameter and the preset first charging ratio parameter is consistent with the difference between the preset third charging ratio parameter and the preset second charging ratio parameter.

[0102] Specifically, taking the number of groups of test capacity parameters as three and the nominal capacity represented as C as an example, the test terminal can also, but is not limited to, set the charging rate to 4C according to the nominal capacity, and set the preset first charging ratio parameter to 40%, and the preset relaxation time to 20min, thereby obtaining a first group of test capacity parameters including a charging rate of 4C, a charging ratio parameter of 40%, and a relaxation time of 20min (of course, the first group of test capacity parameters may also include a discharge rate of 1C and a cut-off voltage of 2.5V); then, the difference between any two adjacent charging ratio parameters may be set to 5%, that is, the preset second charging ratio parameter. The parameter is 45%, thereby obtaining the first set of test capacity parameters including a charge rate of 4C, a charge ratio parameter of 45%, and a relaxation time of 20min (of course, the second set of test capacity parameters may also include a discharge rate of 1C and a cut-off voltage of 2.5V); then, according to the above setting, the difference between any two adjacent charge ratio parameters is 5%, that is, the preset third charge ratio parameter is 50%, thereby obtaining the third set of test capacity parameters including a charge rate of 4C, a charge ratio parameter of 50%, and a relaxation time of 20min (of course, the second set of test capacity parameters may also include a discharge rate of 1C and a cut-off voltage of 2.5V).

[0103] It should be noted that the number of test capacity parameter groups in the embodiment of the present application is not limited to three groups. For example, the charging ratio parameter in the first group of test capacity parameters can be set to 40%, and the charging ratio parameter in the last group of test capacity parameters can be set to 80%. The difference between any two adjacent charging ratio parameters can be set to 5%, generating a total of nine groups, and is not limited to this.

[0104] Furthermore, after generating multiple sets of test capacity parameters, the test terminal can also send all the test capacity parameters to the battery testing device, so that the battery testing device can test and process the soft-pack battery cells according to all the test capacity parameters, and can record the voltage-time curve corresponding to each set of test capacity parameters and the negative electrode to lithium potential curve corresponding to all the test capacity parameters in real time during the test process.

[0105] Here, when the battery testing device tests the soft-pack battery cell according to all test capacity parameters, it can be but is not limited to referring to the above embodiment, so that after the soft-pack battery cell is allowed to stand for 30 minutes, the battery testing device is used to charge the soft-pack battery cell to 40% at a constant current at a charging rate of 4C, with a relaxation time of 20 minutes, and discharge it to 2.5V at a constant current at a discharge rate of 1C; then, the soft-pack battery cell can be left for 30 minutes, charged to 45% at a constant current at a charging rate of 4C, with a relaxation time of 20 minutes, and discharged to 2.5V at a constant current at a discharge rate of 1C; the difference between two adjacent groups of charge ratio parameters in each group of test capacity parameters is set to 5% until it reaches 80%.

[0106] Step 108: Differentiate each voltage-time curve to obtain a corresponding differential voltage-time curve, and determine the lithium deposition starting potential of the soft-pack battery cell based on all voltage-time curves, all differential voltage-time curves, and the negative electrode lithium potential curve.

[0107] Specifically, after the battery testing device obtains the voltage-time curve corresponding to each set of test capacity parameters, the test terminal can receive all voltage-time curves fed back by the battery testing device, and perform differential processing on each voltage-time curve to obtain the corresponding differential voltage-time curve, so as to determine the lithium plating window of the soft-pack battery cell by combining the voltage-time curve corresponding to each set of test capacity parameters and the differential voltage-time curve, and determine the corresponding lithium plating starting potential in the negative electrode to lithium potential curve according to the lithium plating window. Compared with the prior art of taking the negative electrode to lithium potential of 0V as the lithium plating starting point, it can not only ensure the accuracy of the lithium plating starting potential, but also make the subsequent step charging strategy formulation more reasonable, thereby improving the overall testing experience.

[0108] As another option of the embodiment of the present application, the lithium deposition starting potential of the soft-pack battery cell is determined according to all voltage-time curves, all differential voltage-time curves, and the negative electrode to lithium potential curve, including:

[0109] When an abnormal slope change is detected in the voltage-time curve corresponding to the nth group of test capacity parameters, it is determined whether a characteristic peak exists in the corresponding differential voltage-time curve; wherein n is a positive integer greater than 1;

[0110] When a characteristic peak is detected in the differential voltage-time curve, the starting potential of lithium deposition of the soft-pack battery cell is determined according to the voltage-time curve, differential voltage-time curve and negative electrode lithium potential curve corresponding to the n-1th group of test capacity parameters.

[0111] Specifically, when determining the lithium plating starting potential of the soft-pack battery cell, the test terminal may, but is not limited to, perform feature point recognition processing on the voltage-time curve corresponding to each set of test capacity parameters, identify multiple continuous feature points corresponding to each voltage-time curve, and calculate multiple slopes based on the coordinates of two consecutive feature points in the corresponding voltage-time curve. By taking the difference between the two adjacent slopes as the slope change, the test terminal can use whether the slope change is abnormal to determine whether there is a platform in the corresponding voltage-time curve, which indicates that lithium plating may occur. Here, the basis for judging whether the slope change is abnormal can be, but is not limited to, when it is detected that the difference between any two adjacent slope changes exceeds a preset difference threshold, or when it is detected that any slope change is not in a preset slope change range, it can be determined that the slope change is abnormal, otherwise it is not abnormal, and is not limited to this.

[0112] Then, when an abnormal slope change is detected in the voltage-time curve corresponding to any set of test capacity parameters, the test terminal can identify the characteristic peak of the corresponding differential voltage-time curve to determine whether the corresponding test capacity parameter has caused lithium deposition in the soft-pack battery cell by judging whether the differential voltage-time curve has a characteristic peak. It is understandable that the method of identifying the characteristic peak of the differential voltage-time curve can also be determined by calculating the slope of the characteristic point, or by judging whether the differential voltage-time curve has an inflection point, etc., which will not be elaborated here.

[0113] Then, when a characteristic peak is identified in the corresponding differential voltage-time curve, it indicates that when the soft-pack battery cell is tested according to the corresponding test capacity parameters, lithium deposition has occurred in the soft-pack battery cell, and then the voltage-time curve and the differential voltage-time curve determined when the soft-pack battery cell is tested by combining the previous set of test capacity parameters can be used to further determine whether lithium deposition has occurred in the soft-pack battery cell. It is understandable that when the current set of test capacity parameters is used to test the soft-pack battery cell and it is determined that no lithium deposition has occurred, it can be indicated that the lithium deposition window of the soft-pack battery cell is between the preset charge ratio parameters corresponding to the previous set of test capacity parameters and the preset charge ratio parameters corresponding to the current set of test capacity parameters.

[0114] As another optional embodiment of the present application, the lithium plating starting potential of the soft-pack battery cell is determined according to the voltage-time curve, differential voltage-time curve, and negative electrode to lithium potential curve corresponding to the n-1th group of test capacity parameters, including:

[0115] When no abnormal slope change is detected in the voltage-time curve corresponding to the n-1th group of test capacity parameters, it is determined whether there is a characteristic peak in the corresponding differential voltage-time curve;

[0116] When no characteristic peak is detected in the differential voltage-time curve, a first potential corresponding to the nth group of test capacity parameters and a second potential corresponding to the n-1th group of test capacity parameters are respectively determined in the negative electrode to lithium potential curve;

[0117] The lithium deposition starting point potential of the soft-pack battery cell is determined according to the potential range formed by the first potential and the second potential.

[0118] Specifically, when analyzing and processing the voltage-time curve and the differential voltage-time curve corresponding to the n-1th group of test capacity parameters, you can, but are not limited to, refer to the above embodiments, which will not be described in detail here. When it is determined that no abnormal slope change is detected in the voltage-time curve corresponding to the n-1th group of test capacity parameters, and no characteristic peak is detected in the differential voltage-time curve, it indicates that the lithium plating window of the soft-pack battery cell is between the charge ratio parameter within the n-1th group of test capacity parameters and the charge ratio parameter within the nth group of test capacity parameters. Then, the test terminal can find the first potential corresponding to the charge ratio parameter within the nth group of test capacity parameters and the second potential corresponding to the charge ratio parameter within the n-1th group of test capacity parameters in the negative electrode to lithium potential curve. At this time, the lithium plating starting potential of the soft-pack battery cell is within the potential interval formed by the first potential and the second potential.

[0119] Then, after obtaining the potential interval formed by the first potential and the second potential, the test terminal can also, but is not limited to, use any potential within the potential interval as the starting potential for lithium deposition of the soft-pack battery cell. Of course, the median corresponding to the potential interval can also be used as the starting potential for lithium deposition of the soft-pack battery cell, but is not limited to this.

[0120] Also see here Figure 2 A schematic diagram of a voltage-time curve and a differential voltage-time curve of a soft-pack battery cell provided in an embodiment of the present application is shown, and Figure 3 Schematic diagram of voltage-time curve and differential voltage-time curve of another soft pack battery cell provided in an embodiment of the present application is shown. Figure 2 As shown in 3, Figure 2 The voltage-time curve and differential voltage-time curve can be obtained by testing the capacity parameter with a charging ratio parameter of 60%. Figure 2 The voltage-time curve in the figure does not have abnormal slope change, and the differential voltage-time curve does not have a characteristic peak; Figure 3 The voltage-time curve and differential voltage-time curve can be obtained by testing the capacity parameter with a charging ratio parameter of 65%. Figure 3 The voltage-time curve in the figure has an abnormal slope change, and the differential voltage-time curve has a characteristic peak, which means that the lithium plating window of the soft-pack battery cell is between 60% and 65% when the charging ratio parameter is set.

[0121] Also see here Figure 4 The schematic diagram of the negative electrode to lithium potential curve of a soft-pack battery provided in an embodiment of the present application is shown in FIG. Figure 4 As shown, combined with the above Figure 2 as well as Figure 3 The lithium plating window of the soft-pack battery cell is determined to be between 60% and 65% of the charging ratio parameter. Figure 4 The potential corresponding to the charging ratio parameter of 60% (-0.048V in the figure) and the potential corresponding to the charging ratio parameter of 65% (-0.055V in the figure) are found respectively. It can be concluded that the starting potential of lithium deposition of the soft-pack battery cell is between -0.048V and -0.055V. It should be noted that if the existing technology is used to take the negative electrode potential of 0 V as the starting potential of lithium deposition of the battery cell, then combined with Figure 2 、 Figure 3 as well as Figure 4 It can be inferred that the corresponding lithium deposition window should be smaller than the charging ratio parameter set at 40% (according to Figure 4 The potential corresponding to the charging ratio parameter of 40% is -0.02V), which is quite different from the actual lithium plating window, which may easily lead to unreasonable formulation of subsequent step charging strategies and affect the overall test experience.

[0122] See also Figure 5 , Figure 5 A schematic structural diagram of a device for detecting the starting potential of lithium deposition in a soft-pack battery cell provided in an embodiment of the present application is shown.

[0123] like Figure 5 As shown, the device for detecting the lithium plating starting potential of a soft-pack battery cell may include at least a battery cell preparation module 501, a capacity determination module 502, a data generation module 503, and a result determination module 504, wherein:

[0124] The battery cell preparation module 501 is used to prepare samples of at least two electrode materials to obtain positive and negative electrode test electrodes, and to prepare soft-pack battery cells based on the positive and negative electrode test electrodes and a preset reference electrode;

[0125] A capacity determination module 502 is configured to determine a nominal capacity based on the soft-pack battery cell and two sets of preset charge and discharge parameters;

[0126] The data generation module 503 is used to generate at least two sets of test capacity parameters according to the nominal capacity, and test the soft-pack battery cells in sequence according to each set of test capacity parameters to obtain corresponding voltage-time curves and negative electrode to lithium potential curves;

[0127] The result determination module 504 is used to perform differential processing on each voltage-time curve to obtain a corresponding differential voltage-time curve, and determine the lithium plating starting potential of the soft-pack battery cell based on all voltage-time curves, all differential voltage-time curves, and the negative electrode lithium potential curve.

[0128] In some possible embodiments, preparing samples of at least two electrode materials to obtain positive and negative electrode test electrodes includes:

[0129] Mixing artificial graphite, conductive carbon black, sodium carboxymethyl cellulose and styrene-butadiene rubber latex according to a preset first ratio to obtain a negative electrode slurry;

[0130] performing a coating and drying process on the negative electrode slurry according to a preset first coating surface density, and performing a roller pressing process on the negative electrode slurry after the coating and drying process according to a preset first compaction density;

[0131] Cutting the negative electrode slurry after the roll pressing process according to a preset first size to obtain at least two negative electrode test pieces;

[0132] Mixing lithium iron phosphate, conductive carbon black, polyvinylidene fluoride, and carbon nanotubes in a preset second ratio to obtain a positive electrode slurry;

[0133] performing a coating and drying process on the positive electrode slurry according to a preset second coating surface density, and performing a roller pressing process on the positive electrode slurry after the coating and drying process according to a preset second compaction density;

[0134] The positive electrode slurry after the roll pressing process is cut according to a preset second size to obtain at least two positive electrode test electrodes.

[0135] In some possible embodiments, a soft-pack battery cell is prepared based on the positive and negative test electrodes and a preset reference electrode, including:

[0136] Performing lithium plating on a preset reference electrode according to preset lithium plating parameters;

[0137] Based on the preset number of stacked layers, the number of negative test electrodes, the number of positive test electrodes, the preset number of reference electrodes after lithium plating, and the number of diaphragms are determined respectively, and soft-pack battery cells are prepared according to the number of negative test electrodes, the number of positive test electrodes, the preset number of reference electrodes after lithium plating, and the number of diaphragms.

[0138] In some possible embodiments, the two sets of preset charge and discharge parameters include a discharge parameter consisting of a charge and discharge rate and a discharge cut-off voltage, and a charge parameter consisting of a charge and discharge rate and a charge cut-off voltage, wherein the discharge cut-off voltage is less than the charge cut-off voltage;

[0139] Based on the soft-pack battery cell and two sets of preset charge and discharge parameters, the nominal capacity is determined, including:

[0140] The soft-packed battery cells are placed in a static state according to a preset static time, and the soft-packed battery cells are discharged according to discharge parameters after the static state;

[0141] The soft-packed battery cells after discharge treatment are placed on hold according to a preset placement time, and the soft-packed battery cells after placement are charged according to charging parameters;

[0142] The soft-packed battery cells after the charge treatment are placed for a preset placement time, and the soft-packed battery cells after the placement treatment are discharged according to the discharge parameters, so as to use the corresponding discharge capacity as the nominal capacity.

[0143] In some possible embodiments, generating at least two sets of test capacity parameters according to the nominal capacity includes:

[0144] Obtaining a first set of test capacity parameters based on the nominal capacity, a preset first charge ratio parameter, and a preset relaxation time;

[0145] Obtaining a second set of test capacity parameters based on the nominal capacity, a preset second charging ratio parameter, and a preset relaxation time;

[0146] Based on the nominal capacity, the preset third charging ratio parameter and the preset relaxation time, a third set of test capacity parameters is obtained; wherein the difference between the preset second charging ratio parameter and the preset first charging ratio parameter is consistent with the difference between the preset third charging ratio parameter and the preset second charging ratio parameter.

[0147] In some possible embodiments, determining the lithium deposition starting potential of the soft-pack battery cell according to all voltage-time curves, all differential voltage-time curves, and the negative electrode to lithium potential curve includes:

[0148] When an abnormal slope change is detected in the voltage-time curve corresponding to the nth group of test capacity parameters, it is determined whether a characteristic peak exists in the corresponding differential voltage-time curve; wherein n is a positive integer greater than 1;

[0149] When a characteristic peak is detected in the differential voltage-time curve, the starting potential of lithium deposition of the soft-pack battery cell is determined according to the voltage-time curve, differential voltage-time curve and negative electrode lithium potential curve corresponding to the n-1th group of test capacity parameters.

[0150] In some possible embodiments, determining the lithium deposition starting potential of the soft-pack battery cell according to the voltage-time curve, the differential voltage-time curve, and the negative electrode to lithium potential curve corresponding to the n-1th group of test capacity parameters includes:

[0151] When no abnormal slope change is detected in the voltage-time curve corresponding to the n-1th group of test capacity parameters, it is determined whether there is a characteristic peak in the corresponding differential voltage-time curve;

[0152] When no characteristic peak is detected in the differential voltage-time curve, a first potential corresponding to the nth group of test capacity parameters and a second potential corresponding to the n-1th group of test capacity parameters are respectively determined in the negative electrode to lithium potential curve;

[0153] The lithium deposition starting point potential of the soft-pack battery cell is determined according to the potential range formed by the first potential and the second potential.

[0154] Those skilled in the art will clearly understand that the technical solutions of the embodiments of the present application can be implemented with the help of software and / or hardware. "Unit" and "module" in this specification refer to software and / or hardware that can independently perform or cooperate with other components to perform specific functions, where the hardware can be, for example, a field-programmable gate array (FPGA) or an integrated circuit (IC).

[0155] See also Figure 6 , Figure 6 A structural schematic diagram of another device for detecting the starting potential of lithium deposition in a soft-pack battery cell provided in an embodiment of the present application is shown.

[0156] like Figure 6 As shown, the lithium plating starting point potential detection device 600 for a soft-pack battery cell may include at least one processor 601 , at least one network interface 604 , a user interface 603 , a memory 605 and at least one communication bus 602 .

[0157] The communication bus 602 may be used to implement connection and communication among the above components.

[0158] The user interface 603 may include buttons, and the optional user interface may also include a standard wired interface or a wireless interface.

[0159] The network interface 604 may include, but is not limited to, a Bluetooth module, an NFC module, a Wi-Fi module, and the like.

[0160] Among them, the processor 601 may include one or more processing cores. The processor 601 uses various interfaces and lines to connect the various parts of the lithium deposition starting point potential detection device 600 for the soft-pack battery cell, and executes various functions and processes data of the lithium deposition starting point potential detection device 600 for the soft-pack battery cell by running or executing instructions, programs, code sets or instruction sets stored in the memory 605, and calling data stored in the memory 605. Optionally, the processor 601 can be implemented in at least one hardware form of DSP, FPGA, and PLA. The processor 601 can integrate one or more combinations of CPU, GPU, and modem. Among them, the CPU mainly processes the operating system, user interface, and application programs; the GPU is responsible for rendering and drawing the content to be displayed on the display screen; and the modem is used to handle wireless communications. It is understandable that the above-mentioned modem may not be integrated into the processor 601, but may be implemented separately through a chip.

[0161] The memory 605 may include RAM or ROM. Optionally, the memory 605 includes a non-transitory computer-readable medium. The memory 605 can be used to store instructions, programs, codes, code sets or instruction sets. The memory 605 may include a program storage area and a data storage area, wherein the program storage area may store instructions for implementing an operating system, instructions for at least one function (such as a touch function, a sound playback function, an image playback function, etc.), instructions for implementing the above-mentioned various method embodiments, etc.; the data storage area may store data involved in the above-mentioned various method embodiments, etc. The memory 605 may also be optionally at least one storage device located away from the aforementioned processor 601. As Figure 6 As shown, the memory 605 as a computer storage medium may include an operating system, a network communication module, a user interface module, and an application program for detecting the lithium plating starting potential of the soft-pack battery cell.

[0162] Specifically, the processor 601 may be used to call the lithium plating starting potential detection application for the soft-pack battery cell stored in the memory 605 and specifically perform the following operations:

[0163] Prepare samples of at least two electrode materials to obtain positive and negative electrode test electrodes, and prepare soft-pack batteries based on the positive and negative electrode test electrodes and preset reference electrodes;

[0164] Determine the nominal capacity based on the soft-pack battery cell and two sets of preset charge and discharge parameters;

[0165] Generate at least two sets of test capacity parameters according to the nominal capacity, and test the soft-pack battery cells in turn according to each set of test capacity parameters to obtain corresponding voltage-time curves and negative electrode to lithium potential curves;

[0166] Each voltage-time curve is differentiated to obtain the corresponding differential voltage-time curve, and the lithium plating starting potential of the soft-pack battery cell is determined based on all voltage-time curves, all differential voltage-time curves and the negative electrode lithium potential curve.

[0167] In some possible embodiments, preparing samples of at least two electrode materials to obtain positive and negative electrode test electrodes includes:

[0168] Mixing artificial graphite, conductive carbon black, sodium carboxymethyl cellulose and styrene-butadiene rubber latex according to a preset first ratio to obtain a negative electrode slurry;

[0169] performing a coating and drying process on the negative electrode slurry according to a preset first coating surface density, and performing a roller pressing process on the negative electrode slurry after the coating and drying process according to a preset first compaction density;

[0170] Cutting the negative electrode slurry after the roll pressing process according to a preset first size to obtain at least two negative electrode test pieces;

[0171] Mixing lithium iron phosphate, conductive carbon black, polyvinylidene fluoride, and carbon nanotubes in a preset second ratio to obtain a positive electrode slurry;

[0172] performing a coating and drying process on the positive electrode slurry according to a preset second coating surface density, and performing a roller pressing process on the positive electrode slurry after the coating and drying process according to a preset second compaction density;

[0173] The positive electrode slurry after the roll pressing process is cut according to a preset second size to obtain at least two positive electrode test electrodes.

[0174] In some possible embodiments, a soft-pack battery cell is prepared based on the positive and negative test electrodes and a preset reference electrode, including:

[0175] Performing lithium plating on a preset reference electrode according to preset lithium plating parameters;

[0176] Based on the preset number of stacked layers, the number of negative test electrodes, the number of positive test electrodes, the preset number of reference electrodes after lithium plating, and the number of diaphragms are determined respectively, and soft-pack battery cells are prepared according to the number of negative test electrodes, the number of positive test electrodes, the preset number of reference electrodes after lithium plating, and the number of diaphragms.

[0177] In some possible embodiments, the two sets of preset charge and discharge parameters include a discharge parameter consisting of a charge and discharge rate and a discharge cut-off voltage, and a charge parameter consisting of a charge and discharge rate and a charge cut-off voltage, wherein the discharge cut-off voltage is less than the charge cut-off voltage;

[0178] Based on the soft-pack battery cell and two sets of preset charge and discharge parameters, the nominal capacity is determined, including:

[0179] The soft-packed battery cells are placed in a static state according to a preset static time, and the soft-packed battery cells are discharged according to discharge parameters after the static state;

[0180] The soft-packed battery cells after discharge treatment are placed on hold according to a preset placement time, and the soft-packed battery cells after placement are charged according to charging parameters;

[0181] The soft-packed battery cells after the charge treatment are placed for a preset placement time, and the soft-packed battery cells after the placement treatment are discharged according to the discharge parameters, so as to use the corresponding discharge capacity as the nominal capacity.

[0182] In some possible embodiments, generating at least two sets of test capacity parameters according to the nominal capacity includes:

[0183] Obtaining a first set of test capacity parameters based on the nominal capacity, a preset first charge ratio parameter, and a preset relaxation time;

[0184] Obtaining a second set of test capacity parameters based on the nominal capacity, a preset second charging ratio parameter, and a preset relaxation time;

[0185] Based on the nominal capacity, the preset third charging ratio parameter and the preset relaxation time, a third set of test capacity parameters is obtained; wherein the difference between the preset second charging ratio parameter and the preset first charging ratio parameter is consistent with the difference between the preset third charging ratio parameter and the preset second charging ratio parameter.

[0186] In some possible embodiments, determining the lithium deposition starting potential of the soft-pack battery cell according to all voltage-time curves, all differential voltage-time curves, and the negative electrode to lithium potential curve includes:

[0187] When an abnormal slope change is detected in the voltage-time curve corresponding to the nth group of test capacity parameters, it is determined whether a characteristic peak exists in the corresponding differential voltage-time curve; wherein n is a positive integer greater than 1;

[0188] When a characteristic peak is detected in the differential voltage-time curve, the starting potential of lithium deposition of the soft-pack battery cell is determined according to the voltage-time curve, differential voltage-time curve and negative electrode lithium potential curve corresponding to the n-1th group of test capacity parameters.

[0189] In some possible embodiments, determining the lithium deposition starting potential of the soft-pack battery cell according to the voltage-time curve, the differential voltage-time curve, and the negative electrode to lithium potential curve corresponding to the n-1th group of test capacity parameters includes:

[0190] When no abnormal slope change is detected in the voltage-time curve corresponding to the n-1th group of test capacity parameters, it is determined whether there is a characteristic peak in the corresponding differential voltage-time curve;

[0191] When no characteristic peak is detected in the differential voltage-time curve, a first potential corresponding to the nth group of test capacity parameters and a second potential corresponding to the n-1th group of test capacity parameters are respectively determined in the negative electrode to lithium potential curve;

[0192] The lithium deposition starting point potential of the soft-pack battery cell is determined according to the potential range formed by the first potential and the second potential.

[0193] The present application also provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the above method. The computer-readable storage medium may include, but is not limited to, any type of disk, including a floppy disk, an optical disk, a DVD, a CD-ROM, a microdrive, a magneto-optical disk, a ROM, a RAM, an EPROM, an EEPROM, a DRAM, a VRAM, a flash memory device, a magnetic card or an optical card, a nanosystem (including a molecular memory IC), or any type of medium or device suitable for storing instructions and / or data.

[0194] In the several embodiments provided in this application, it should be understood that the disclosed devices can be implemented in other ways. For example, the device embodiments described above are merely illustrative. For example, the division of units is only a logical function division. In actual implementation, there may be other division methods, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some service interface, and the indirect coupling or communication connection of devices or units can be electrical or other forms.

[0195] In addition, the functional units in the various embodiments of the present application may be integrated into a single processing unit, or each unit may exist physically separately, or two or more units may be integrated into a single unit. The aforementioned integrated units may be implemented in the form of hardware or software functional units.

[0196] If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable memory. Based on this understanding, the technical solution of the present application, or the part that contributes to the prior art, or all or part of the technical solution can be embodied in the form of a software product. The computer software product is stored in a memory and includes a number of instructions for enabling a computer device (which can be a personal computer, server, or network device, etc.) to execute all or part of the steps of the various embodiments of the present application. The aforementioned memory includes: U disk, read-only memory (ROM), random access memory (RAM), mobile hard disk, magnetic disk, or optical disk, etc., various media that can store program code.

Claims

1. A method for detecting the starting potential of lithium deposition in a soft-pack battery cell, characterized in that: include: Performing sample preparation on at least two electrode materials to obtain positive and negative electrode test electrodes, and preparing soft-pack batteries based on the positive and negative electrode test electrodes and a preset reference electrode; Determining a nominal capacity based on the soft-pack battery cell and two sets of preset charge and discharge parameters; Generating at least two groups of test capacity parameters according to the nominal capacity, and testing the soft-pack battery cells in turn according to each group of test capacity parameters to obtain corresponding voltage-time curves and negative electrode to lithium potential curves; performing a differential processing on each of the voltage-time curves to obtain a corresponding differential voltage-time curve, and when an abnormal slope change is detected in the voltage-time curve corresponding to the nth group of the test capacity parameters, determining whether a characteristic peak exists in the corresponding differential voltage-time curve; wherein n is a positive integer greater than 1; When the characteristic peak is detected in the differential voltage-time curve, the lithium deposition starting potential of the soft-pack battery cell is determined according to the voltage-time curve, the differential voltage-time curve, and the negative electrode to lithium potential curve corresponding to the test capacity parameter of the n-1th group; Wherein, determining the lithium deposition starting potential of the soft-pack battery cell according to the voltage-time curve, the differential voltage-time curve, and the negative electrode to lithium potential curve corresponding to the test capacity parameters of the n-1th group includes: When no abnormal slope change is detected in the voltage-time curve corresponding to the test capacity parameter of the n-1th group, determining whether a characteristic peak exists in the corresponding differential voltage-time curve; When the absence of the characteristic peak is detected in the differential voltage-time curve, determining a first potential corresponding to the nth group of test capacity parameters and a second potential corresponding to the n-1th group of test capacity parameters in the negative electrode to lithium potential curve; The lithium deposition starting point potential of the soft-pack battery cell is determined according to the potential interval formed by the first potential and the second potential.

2. The method according to claim 1, characterized in that The method of preparing samples using at least two electrode materials to obtain positive and negative electrode test electrodes comprises: Mixing artificial graphite, conductive carbon black, sodium carboxymethyl cellulose and styrene-butadiene rubber latex according to a preset first ratio to obtain a negative electrode slurry; performing a coating and drying process on the negative electrode slurry according to a preset first coating surface density, and performing a roller pressing process on the negative electrode slurry after the coating and drying process according to a preset first compaction density; Cutting the negative electrode slurry after the roll pressing process according to a preset first size to obtain at least two negative electrode test pieces; Mixing the lithium iron phosphate, the conductive carbon black, the polyvinylidene fluoride, and the carbon nanotubes in a preset second ratio to obtain a positive electrode slurry; performing a coating and drying process on the positive electrode slurry according to a preset second coating surface density, and performing a roller pressing process on the positive electrode slurry after the coating and drying process according to a preset second compaction density; The positive electrode slurry after the roll pressing process is cut according to a preset second size to obtain at least two positive electrode test electrodes.

3. The method according to claim 2, characterized in that The method of preparing a soft-pack battery cell according to the positive and negative test electrodes and a preset reference electrode includes: Performing lithium plating on a preset reference electrode according to preset lithium plating parameters; Based on the preset number of laminate layers, the number of negative electrode test sheets, the number of positive electrode test sheets, the preset number of reference electrodes after lithium plating, and the number of diaphragms are determined respectively, and according to the number of negative electrode test sheets, the number of positive electrode test sheets, the preset number of reference electrodes after lithium plating, and the number of diaphragms, a soft-pack battery cell is prepared.

4. The method according to claim 1, wherein The two sets of preset charge and discharge parameters include a discharge parameter consisting of a charge and discharge rate and a discharge cut-off voltage, and a charge parameter consisting of the charge and discharge rate and the charge cut-off voltage, wherein the discharge cut-off voltage is less than the charge cut-off voltage; The method of determining the nominal capacity based on the soft-pack battery cell and two sets of preset charge and discharge parameters includes: Performing a rest treatment on the soft-pack battery cell according to a preset rest time, and performing a discharge treatment on the soft-pack battery cell after the rest treatment according to the discharge parameters; Performing a shelf treatment on the soft-packed battery cell after the discharge treatment according to a preset shelf time, and performing a charging process on the soft-packed battery cell after the shelf treatment according to the charging parameters; The soft-packed battery cell after the charging process is placed on hold according to the preset placement time, and the soft-packed battery cell after the placement process is discharged according to the discharge parameters, so as to use the corresponding discharge capacity as the nominal capacity.

5. The method according to claim 1, wherein Generating at least two sets of test capacity parameters according to the nominal capacity includes: Obtaining a first set of test capacity parameters based on the nominal capacity, a preset first charging ratio parameter, and a preset relaxation time; Obtaining a second set of test capacity parameters based on the nominal capacity, the preset second charge ratio parameter, and the preset relaxation time; Based on the nominal capacity, the preset third charging ratio parameter and the preset relaxation time, a third set of test capacity parameters is obtained; wherein, the difference between the preset second charging ratio parameter and the preset first charging ratio parameter is consistent with the difference between the preset third charging ratio parameter and the preset second charging ratio parameter.

6. A device for detecting the starting potential of lithium deposition in a soft-pack battery cell, characterized in that: include: A cell preparation module is used to prepare samples of at least two electrode materials to obtain positive and negative electrode test electrodes, and to prepare soft-pack cells based on the positive and negative electrode test electrodes and a preset reference electrode; a capacity determination module, configured to determine a nominal capacity based on the soft-pack battery cell and two sets of preset charge and discharge parameters; a data generation module, configured to generate at least two sets of test capacity parameters according to the nominal capacity, and test the soft-pack battery cells in sequence according to each set of test capacity parameters to obtain corresponding voltage-time curves and negative electrode to lithium potential curves; a result determination module, configured to perform a differential process on each of the voltage-time curves to obtain a corresponding differential voltage-time curve, and when an abnormal slope change is detected in the voltage-time curve corresponding to the nth group of the test capacity parameters, determine whether a characteristic peak exists in the corresponding differential voltage-time curve; wherein n is a positive integer greater than 1; When the characteristic peak is detected in the differential voltage-time curve, the lithium deposition starting potential of the soft-pack battery cell is determined according to the voltage-time curve, the differential voltage-time curve, and the negative electrode to lithium potential curve corresponding to the test capacity parameter of the n-1th group; Wherein, determining the lithium deposition starting potential of the soft-pack battery cell according to the voltage-time curve, the differential voltage-time curve, and the negative electrode to lithium potential curve corresponding to the test capacity parameters of the n-1th group includes: When no abnormal slope change is detected in the voltage-time curve corresponding to the test capacity parameter of the n-1th group, determining whether a characteristic peak exists in the corresponding differential voltage-time curve; When the absence of the characteristic peak is detected in the differential voltage-time curve, determining a first potential corresponding to the nth group of test capacity parameters and a second potential corresponding to the n-1th group of test capacity parameters in the negative electrode to lithium potential curve; The lithium deposition starting point potential of the soft-pack battery cell is determined according to the potential interval formed by the first potential and the second potential.

7. A device for detecting the starting potential of lithium deposition in a soft-pack battery cell, characterized in that: including a processor and a memory; The processor is connected to the memory; The memory is used to store executable program code; The processor runs a program corresponding to the executable program code by reading the executable program code stored in the memory, so as to execute the steps of the method according to any one of claims 1 to 5.

8. A computer-readable storage medium having a computer program stored thereon, characterized in that: The computer-readable storage medium stores instructions, and when the instructions are executed on a computer or a processor, the computer or the processor executes the steps of the method according to any one of claims 1 to 5.

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