Method and electronic device for determining charging cut-off voltage of lithium-ion battery

Abstract

The present application discloses a method and electronic device for determining the charging cut-off voltage of a lithium-ion battery. The method includes charging and discharging the first cycle according to the maximum operating voltage of the lithium-ion battery to determine the initial charging cut-off voltage; setting the initial charging cut-off voltage as the current charging cut-off voltage, and charging and discharging the lithium-ion battery for a preset number of cycles according to the current charging cut-off voltage; obtaining the current voltage data and the current capacity data during the last charging cycle; constructing the current differential capacity curve according to the current voltage data and the current capacity data; determining the current charging cut-off voltage from the voltage corresponding to the characteristic peak of the current differential capacity curve, and returning to the step of charging and discharging the lithium-ion battery for a preset number of cycles according to the current charging cut-off voltage until the current capacity data meets the preset conditions. By determining different charging cut-off voltages for lithium-ion batteries, the battery is charged within a healthy voltage range, thereby extending the battery life.

Description

Technical Field

[0001] The present application belongs to the technical field of lithium-ion batteries, and in particular, relates to a method for determining a charging cut-off voltage of a lithium-ion battery and an electronic device. Background Art

[0002] With the gradual expansion of the application of lithium-ion batteries in the field of new energy vehicles, the research on lithium-ion batteries has also received widespread attention.

[0003] At present, during the charging process of lithium-ion batteries, due to the failure to design a reasonable charging cut-off voltage, the crystal structure of the battery's electrode material changes, which in turn causes a sharp decline in the battery's capacity, reducing the battery's service life. Summary of the invention

[0004] The embodiments of the present application provide a method and electronic device for determining a charging cut-off voltage of a lithium-ion battery, thereby enabling the battery to be charged within a healthy voltage range, thereby extending the battery's service life.

[0005] Other features and advantages of the present application will become apparent from the following detailed description, or may be learned in part by the practice of the present application.

[0006] According to a first aspect of an embodiment of the present application, a method for determining a charging cut-off voltage of a lithium-ion battery is provided, the method comprising:

[0007] Performing a first cycle of charging and discharging the lithium-ion battery according to the maximum operating voltage of the lithium-ion battery to determine an initial charging cut-off voltage;

[0008] The initial charge cut-off voltage is set as the current charge cut-off voltage, and the lithium-ion battery is charged and discharged for a preset number of cycles according to the current charge cut-off voltage;

[0009] Get the current voltage data and current capacity data during the last cycle of charging;

[0010] constructing a current differential capacity curve according to the current voltage data and the current capacity data;

[0011] The current charging cut-off voltage is determined from the voltage corresponding to the characteristic peak of the current differential capacity curve, and the step of charging and discharging the lithium-ion battery for a preset number of cycles according to the current charging cut-off voltage is returned until the current capacity data meets a preset condition.

[0012] In some embodiments of the present application, based on the above scheme, charging and discharging the lithium-ion battery for a first cycle according to the maximum operating voltage of the lithium-ion battery to determine the initial charging cut-off voltage includes:

[0013] Charging the lithium-ion battery for a first cycle;

[0014] When the voltage of the lithium-ion battery reaches the maximum operating voltage, stopping charging;

[0015] Acquiring initial voltage data and initial capacity data during the first cycle charging process;

[0016] constructing an initial differential capacity curve according to the initial voltage data and the initial capacity data;

[0017] The initial charge cut-off voltage is determined from a voltage corresponding to a characteristic peak of the initial differential capacity curve.

[0018] In some embodiments of the present application, based on the above solution, the method is applied to a vehicle, the vehicle includes a battery management system and a battery of the same type as the lithium-ion battery, and the method further includes:

[0019] The initial charge cut-off voltage and the current charge cut-off voltage are stored in the battery management system, so that the battery management system controls the charging of the battery according to the initial charge cut-off voltage and the current charge cut-off voltage.

[0020] In some embodiments of the present application, based on the above solution, charging the lithium-ion battery for a first cycle includes:

[0021] Using a plurality of preset temperatures and a plurality of preset charging cut-off currents to charge the lithium-ion battery for a first cycle;

[0022] Accordingly, determining the initial charging cut-off voltage from the voltage corresponding to the characteristic peak of the initial differential capacity curve includes:

[0023] Determine a plurality of the initial charge cut-off voltages from voltages corresponding to characteristic peaks of a plurality of the initial differential capacity curves;

[0024] The determining the current charging cut-off voltage from the voltage corresponding to the characteristic peak of the current differential capacity curve comprises:

[0025] The plurality of current charge cut-off voltages are determined from voltages corresponding to characteristic peaks of the plurality of current differential capacity curves.

[0026] In some embodiments of the present application, based on the above solution, storing the initial charging cut-off voltage and the current charging cut-off voltage in the battery management system includes:

[0027] The preset temperature, the preset charge cut-off current, the initial charge cut-off voltage and the current charge cut-off voltage are correspondingly stored in the battery management system.

[0028] In some embodiments of the present application, based on the aforementioned solution, the preset condition includes: a ratio of the current capacity data to the initial capacity data is less than or equal to 0.8.

[0029] In some embodiments of the present application, based on the above scheme, the current voltage data includes a plurality of voltage data, the current capacity data includes a plurality of capacity data, the voltage data corresponds to the capacity data one by one, and constructing a current differential capacity curve according to the current voltage data and the current capacity data includes:

[0030] Determine the voltage difference between two adjacent voltage data;

[0031] determining a capacity difference between two capacity data corresponding to the two voltage data;

[0032] The ratio of the voltage difference to the capacity difference is used as the ordinate value of the current differential capacity curve, and the larger value of the two voltage data is used as the abscissa value of the current differential capacity curve.

[0033] In some embodiments of the present application, based on the above solution, determining the current charging cut-off voltage from the voltage corresponding to the characteristic peak of the current differential capacity curve includes:

[0034] Determine the voltage at the H2-H3 phase transition position from the voltage corresponding to the characteristic peak of the current differential capacity curve;

[0035] The voltage at the H2-H3 phase change position is determined as the current charging cut-off voltage.

[0036] In some embodiments of the present application, based on the above scheme, determining the voltage at the H2-H3 phase transition position from the voltage corresponding to the characteristic peak of the current differential capacity curve includes:

[0037] The maximum voltage among the voltages corresponding to the characteristic peaks of the current differential capacity curve is determined as the voltage at the H2-H3 phase transition position.

[0038] According to a second aspect of an embodiment of the present application, an electronic device is provided, including a memory and a processor, wherein the memory stores a computer program, and the processor implements the steps of the above method when executing the computer program.

[0039] In the present application, the lithium-ion battery is charged and discharged for the first cycle according to the maximum operating voltage of the lithium-ion battery to determine the initial charge cut-off voltage; the initial charge cut-off voltage is set as the current charge cut-off voltage, and the lithium-ion battery is charged and discharged for a preset number of cycles according to the current charge cut-off voltage; the current voltage data and the current capacity data in the last cycle of charging are obtained; the current differential capacity curve is constructed according to the current voltage data and the current capacity data; the current charge cut-off voltage is determined from the voltage corresponding to the characteristic peak of the current differential capacity curve, and the step of charging and discharging the lithium-ion battery for a preset number of cycles according to the current charge cut-off voltage is returned until the current capacity data meets the preset conditions, and different charge cut-off voltages are determined for the life cycle of the lithium-ion battery, so that the battery is charged within a healthy voltage range, thereby extending the service life of the battery.

[0040] It should be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The drawings herein are incorporated into the specification and constitute a part of the specification, showing embodiments consistent with the present application, and together with the specification, are used to explain the principles of the present application. Obviously, the drawings described below are only some embodiments of the present application, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work. In the drawings:

[0042] Figure 1 A schematic flow chart of a method for determining a charging cut-off voltage of a lithium-ion battery in one embodiment;

[0043] Figure 2 is a schematic diagram of a differential capacity curve in one embodiment;

[0044] Figure 3 is a schematic diagram of a differential capacity curve in another embodiment;

[0045] Figure 4 is a flow chart of step 101 in one embodiment;

[0046] Figure 5 A schematic flow chart of a method for determining a charging cut-off voltage of a lithium-ion battery in another embodiment;

[0047] Figure 6 FIG. 4 is a diagram showing the internal structure of an electronic device in one embodiment. DETAILED DESCRIPTION

[0048] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0049] In addition, described feature, structure or characteristic can be combined in one or more embodiments in any suitable manner. In the following description, many specific details are provided to provide a full understanding of the embodiments of the present application. However, those skilled in the art will appreciate that the technical scheme of the present application can be put into practice without one or more of the specific details, or other methods, components, devices, steps, etc. can be adopted. In other cases, known methods, devices, realizations or operations are not shown or described in detail to avoid blurring the various aspects of the application.

[0050] The flowcharts shown in the accompanying drawings are only exemplary and do not necessarily include all the contents and operations / steps, nor must they be executed in the order described. For example, some operations / steps can be decomposed, and some operations / steps can be combined or partially combined, so the actual execution order may change according to actual conditions.

[0051] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the objects used in this way can be interchanged where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than those shown or described.

[0052] Figure 1 FIG. 1 is a flow chart of a method for determining a charging cut-off voltage of a lithium-ion battery in one embodiment. Figure 1 As shown, a method for determining a charging cut-off voltage of a lithium-ion battery is provided, and the method may include the following steps:

[0053] Step 101 , charging and discharging the lithium-ion battery in a first cycle according to the maximum operating voltage of the lithium-ion battery to determine an initial charging cut-off voltage.

[0054] Among them, the lithium-ion battery is a test battery. By testing the lithium-ion battery, the charging cut-off voltage of the lithium-ion battery throughout its life cycle is determined. When the vehicle is installed with this type of lithium-ion battery, the lithium-ion battery can be controlled to be charged according to the above-determined charging cut-off voltage, so that the lithium-ion battery in the vehicle is always charged within a healthy voltage range, extending the battery life.

[0055] Specifically, the tester can charge the lithium-ion battery for the first cycle until the voltage of the lithium-ion battery reaches the maximum operating voltage, then stop charging, let it stand, and then discharge it. During the charging process, the initial voltage data and initial capacity data are continuously obtained, and the initial charging cut-off voltage is determined based on the initial voltage data and initial capacity data.

[0056] It should be understood that the steps in this embodiment can be implemented manually by a tester or automatically through program settings, and there is no limitation on the execution subject of this embodiment.

[0057] Step 102, setting the initial charge cut-off voltage as the current charge cut-off voltage, and charging and discharging the lithium-ion battery for a preset number of cycles according to the current charge cut-off voltage.

[0058] The preset number may be 50, 100, 200 or other numbers, which are not limited in this embodiment. For ease of description, the following description is made by taking the preset period of 100 as an example.

[0059] It is understandable that after obtaining the initial charge cut-off voltage, the lithium-ion battery can be charged and discharged for 100 cycles. Specifically, the lithium-ion battery can be charged until the voltage reaches the current charge cut-off voltage, and then the lithium-ion battery can be left standing and discharged, and this cycle can be repeated 100 times.

[0060] Step 103, obtaining the current voltage data and the current capacity data during the last cycle of charging.

[0061] Specifically, when the lithium-ion battery is charged and discharged for the 100th cycle, the voltage and capacity during the 100th cycle of charging are collected and used as current voltage data and current capacity data, respectively.

[0062] Step 104: construct a current differential capacity curve according to the current voltage data and the current capacity data.

[0063] Since charging is a continuous process, multiple voltage data and multiple capacity data can be obtained during the 100th week of charging, and the voltage data and capacity data at the same moment are corresponding. Therefore, the current voltage data can include multiple voltage data, and the current capacity data can include multiple capacity data, and the voltage data and the capacity data correspond one to one.

[0064] In this case, the voltage difference between two adjacent voltage data can be determined; the capacity difference between two capacity data corresponding to the two voltage data can be determined; the ratio of the voltage difference to the capacity difference is used as the vertical coordinate value of the current differential capacity curve, and the larger value of the two voltage data is used as the horizontal coordinate value of the current differential capacity curve.

[0065] Specifically, the voltage data of the n+1th data point can be subtracted from the voltage data of the nth data point to obtain a dV data, and the power data of the n+1th data point can be subtracted from the power data of the nth data point to obtain a dQ data. All data are processed in sequence to obtain a series of dV and dQ data. Then the dV is divided by the corresponding dQ to obtain another data dV / dQ. All dV / dQ are used as the vertical coordinates, and the voltage corresponding to dV / dQ, the capacitance or SOC corresponding to dV / dQ, etc. are used as the horizontal coordinates to obtain the differential capacity curve of capacitance and voltage, which is used as the current differential capacity curve. According to this curve, the phase change of the positive and negative electrodes of the lithium-ion battery during the charging and discharging process can be analyzed.

[0066] It should be noted that when the horizontal coordinate of the current differential capacity curve is the voltage corresponding to dV / dQ, the tester can quickly determine the current charge cut-off voltage through the curve, thereby improving the efficiency of determining the current charge cut-off voltage.

[0067] Step 105, determining the current charge cut-off voltage from the voltage corresponding to the characteristic peak of the current differential capacity curve, and returning to the step of charging and discharging the lithium-ion battery for a preset number of cycles according to the current charge cut-off voltage until the current capacity data meets the preset conditions.

[0068] It should be noted that dV / dQ is the capacity of the material within a unit voltage range. Both the positive and negative electrode materials have a voltage platform. The negative electrode capacity is higher on the voltage platform, which means that there is a lot of capacity within a very small voltage fluctuation range. Therefore, it is represented as a characteristic peak on the differential capacity curve. The characteristic peak refers to the maximum or minimum point in the differential capacity curve. The peak that appears on the differential capacity curve represents the phase transition of the material. The movement of each peak and the change in peak shape represent different attenuation mechanisms. Due to the different reaction potentials of different materials, the position and height of the characteristic peaks in the differential capacity curve will also be different.

[0069] In one example, when the abscissa of the differential capacity curve is the voltage corresponding to dV / dQ, the tester can directly find the voltage corresponding to the characteristic peak from the current differential capacity curve and determine the current charge cut-off voltage therefrom.

[0070] In a specific implementation, the tester can also determine the voltage at the H2-H3 phase change position from the voltage corresponding to the characteristic peak of the current differential capacity curve; and determine the voltage at the H2-H3 phase change position as the current charging cut-off voltage.

[0071] It should be understood that during the charge and discharge process of lithium-ion batteries, in order to obtain higher energy density, more lithium ions are released from the positive electrode material. Along with the embedding and extraction of lithium ions in the electrode material, the capacity will drop sharply within the cycle range. This phenomenon is a capacity attenuation failure.

[0072] The root cause of battery capacity attenuation is material failure, and it is also closely related to objective factors such as battery manufacturing process and battery use environment. When the positive electrode material is charged and de-lithium is removed, the voltage ends and the H2 to H3 phase transition occurs, which will cause the lattice to shrink in the c direction, resulting in volume change and local stress. After the H2-H3 phase transition, the H3 phase is formed, and the irreversible phase transition will cause microcracks and structural deformation. After the microcracks form new crystal planes, they will react with the electrolyte.

[0073] Therefore, the voltage at the H2-H3 phase change position can be used as the current charging cut-off voltage. In this way, during the charging process, the failure of the electrode material can be effectively avoided, thereby achieving the purpose of protecting the lithium-ion battery.

[0074] Among them, the tester can determine the maximum voltage among the voltages corresponding to the characteristic peaks of the current differential capacity curve as the voltage at the H2-H3 phase transition position.

[0075] Figure 2 is a schematic diagram of a differential capacity curve in one embodiment, Figure 3 is a schematic diagram of a differential capacity curve in another embodiment, wherein: Figure 3 : is a differential capacity curve obtained after charging according to the initial charging cut-off voltage and the current charging cut-off voltage of this embodiment. Figure 2 The position and shape of the characteristic peaks in Figure 3 The position and shape of the characteristic peaks change little, and the loss of the battery's reversible capacity is small.

[0076] It should be noted that after determining the current charging cut-off voltage V100 of the 100th cycle, the tester continues to perform the next 100 cycles of charge and discharge cycles on the lithium-ion battery using the current charging cut-off voltage V100, and obtains the current charging cut-off voltage V200 of the 200th cycle. The tester continues to perform the next 100 cycles of charge and discharge cycles on the lithium-ion battery using the current charging cut-off voltage V200, and obtains the current charging cut-off voltage V300 of the 300th cycle... and so on, until the ratio of the current capacity data to the initial capacity of the lithium-ion battery is less than or equal to 0.8.

[0077] After all the charging cut-off voltages in the battery life cycle are obtained through cycling, the initial charging cut-off voltage and all current charging cut-off voltages can be used as the charging cut-off voltages for batteries of the same type as lithium-ion batteries. The battery can be charged according to the charging cut-off voltages to ensure that the battery is charged within a healthy voltage range.

[0078] This embodiment performs a first cycle of charging and discharging of the lithium-ion battery according to the maximum operating voltage of the lithium-ion battery to determine an initial charging cut-off voltage; sets the initial charging cut-off voltage as the current charging cut-off voltage, and performs a preset number of cycles of charging and discharging of the lithium-ion battery according to the current charging cut-off voltage; obtains current voltage data and current capacity data during the last cycle of charging; constructs a current differential capacity curve according to the current voltage data and the current capacity data; determines the current charging cut-off voltage from the voltage corresponding to the characteristic peak of the current differential capacity curve, and returns to the step of performing a preset number of cycles of charging and discharging of the lithium-ion battery according to the current charging cut-off voltage until the current capacity data meets the preset conditions, thereby determining different charging cut-off voltages for the life cycle of the lithium-ion battery, so that the battery is charged within a healthy voltage range, thereby extending the service life of the battery.

[0079] Figure 4 FIG. 1 is a flow chart of step 101 in an embodiment, as shown in FIG. Figure 4 As shown, charging and discharging the lithium-ion battery for the first cycle according to the maximum operating voltage of the lithium-ion battery to determine the initial charging cut-off voltage may include the following steps:

[0080] Step 401, charging the lithium-ion battery for the first cycle;

[0081] Step 402, when the voltage of the lithium-ion battery reaches the maximum operating voltage, stop charging;

[0082] Step 403, obtaining initial voltage data and initial capacity data during the first cycle charging process;

[0083] Step 404, constructing an initial differential capacity curve according to the initial voltage data and the initial capacity data;

[0084] Step 405 , determining an initial charging cut-off voltage from a voltage corresponding to a characteristic peak of the initial differential capacity curve.

[0085] In a specific implementation, the tester can charge the lithium-ion battery for the first cycle using a specified temperature and current, for example, using a commonly used temperature and a commonly used current for charging, or using multiple temperatures and multiple currents for charging.

[0086] It should be understood that if the vehicle is still in the plug-in state after being fully charged, the lithium-ion battery will be repeatedly charged several times, or charged with a very small trickle current, which will cause the battery to always be fully charged or exceed the remaining power (State Of Charge, SOC) window usage state, reducing the battery service life. Different operating conditions at the charging end (such as different temperatures and different rates) will lead to different cut-off dynamic voltages. At the same cut-off voltage, the higher the temperature and the smaller the rate, the more capacity is charged. In response to the problem of SOC exceeding the upper limit, the calibration can be differentiated by charging the battery at different temperatures and currents.

[0087] In one example, the tester can charge the lithium-ion battery for the first cycle using multiple preset temperatures and multiple preset charge cutoff currents. Accordingly, determining the initial charge cutoff voltage from the voltage corresponding to the characteristic peak of the initial differential capacity curve includes: determining multiple initial charge cutoff voltages from the voltages corresponding to the characteristic peaks of the multiple initial differential capacity curves. Determining the current charge cutoff voltage from the voltage corresponding to the characteristic peak of the current differential capacity curve includes: determining multiple current charge cutoff voltages from the voltages corresponding to the characteristic peaks of the multiple current differential capacity curves.

[0088] That is to say, when the tester uses multiple preset temperatures and multiple preset charging cut-off currents to charge the lithium-ion battery for the first cycle, each preset temperature and preset charging cut-off current can obtain a corresponding initial charging cut-off voltage, as well as multiple corresponding current charging cut-off voltages.

[0089] When the method is applied to a vehicle, and the vehicle includes a battery management system and a battery of the same type as a lithium-ion battery, the tester stores the initial charge cut-off voltage and the current charge cut-off voltage in the battery management system so that the battery management system controls the battery charging according to the initial charge cut-off voltage and the current charge cut-off voltage.

[0090] When each preset temperature and preset charging cut-off current can obtain a corresponding initial charging cut-off voltage and multiple corresponding current charging cut-off voltages, the tester can store the preset temperature, preset charging cut-off current, initial charging cut-off voltage and current charging cut-off voltage correspondingly in the battery management system.

[0091] In one example, after stopping charging, the tester may also leave the lithium-ion battery at rest and discharge the lithium-ion battery.

[0092] In one example, the specific implementation method of constructing the initial differential capacity curve based on the initial voltage data and the initial capacity data can be the same as the construction method of the current differential curve. Assuming that the initial voltage data includes multiple voltage data, and the initial capacity data includes multiple capacity data, the tester can determine the voltage difference between two adjacent voltage data; determine the capacity difference between two capacity data corresponding to the two voltage data; use the ratio of the voltage difference to the capacity difference as the ordinate value of the initial differential capacity curve, and use the larger value of the two voltage data as the abscissa value of the initial differential capacity curve.

[0093] Specifically, the voltage data of the nth data point can be subtracted from the voltage data of the nth data point to obtain a dV data, and the power data of the nth data point can be subtracted from the power data of the nth data point to obtain a dQ data. All the initial data are processed in sequence to obtain a series of dV and dQ data. Then the dV is divided by the corresponding dQ to obtain another data dV / dQ. Using all dV / dQ as the vertical coordinate, and the voltage corresponding to dV / dQ, the capacitance or SOC corresponding to dV / dQ, etc. as the horizontal coordinate, the differential capacity curve of capacitance and voltage can be obtained, which is used as the initial differential capacity curve.

[0094] In one example, determining the initial charge cut-off voltage from the voltage corresponding to the characteristic peak of the initial differential capacity curve can be the same as determining the current charge cut-off voltage, that is, the voltage at the H2-H3 phase change position can be determined from the voltage corresponding to the characteristic peak of the initial differential capacity curve; the voltage at the H2-H3 phase change position is determined as the initial charge cut-off voltage; wherein the voltage at the H2-H3 phase change position is generally the maximum voltage among the voltages corresponding to the characteristic peak of the initial differential capacity curve.

[0095] In one example, the preset condition includes: a ratio of the current capacity data to the initial capacity data is less than or equal to 0.8.

[0096] It should be understood that, for new batteries, the ratio of current capacity data to initial capacity data is generally greater than 100%. As the battery is used, it ages and the ratio gradually decreases. IEEE Standard 1188-1996 clearly stipulates that when the capacity of the power battery drops to 80%, that is, when the ratio of current capacity data to initial capacity data is less than or equal to 0.8, the battery should be replaced. By setting this preset condition, the charging cut-off voltage of the battery throughout its life cycle can be obtained.

[0097] This embodiment realizes the determination of the initial charging cut-off voltage, improves the accuracy of the charging cut-off voltage of the lithium-ion battery, realizes the charging management of the battery throughout its life cycle, further protects the battery and increases the battery life, and helps to improve the safety level of the vehicle.

[0098] Figure 5 FIG. 1 is a flow chart of a method for determining a charging cut-off voltage of a lithium-ion battery in another embodiment. Figure 5 As shown, the method for determining the charging cut-off voltage of a lithium-ion battery may include the following steps:

[0099] Step 501, charging the lithium-ion battery for the first cycle, and stopping the charging when the voltage of the lithium-ion battery reaches the maximum operating voltage;

[0100] Step 502, obtaining initial voltage data and initial capacity data during the first cycle of charging;

[0101] Step 503, constructing an initial differential capacity curve according to the initial voltage data and the initial capacity data;

[0102] Step 504, determining a first voltage at the H2-H3 phase transition position from the voltage corresponding to the characteristic peak of the initial differential capacity curve, and determining the first voltage as the initial charging cut-off voltage;

[0103] Step 505, setting the initial charge cut-off voltage as the current charge cut-off voltage, and charging and discharging the lithium-ion battery for a preset number of cycles according to the current charge cut-off voltage;

[0104] Step 506, obtaining current voltage data and current capacity data during the last cycle of charging;

[0105] Step 507, constructing a current differential capacity curve according to the current voltage data and the current capacity data;

[0106] Step 508, determining a second voltage at the H2-H3 phase change position from the voltage corresponding to the characteristic peak of the current differential capacity curve, determining the second voltage as the current charge cut-off voltage, and returning to the step of charging and discharging the lithium-ion battery for a preset number of cycles according to the current charge cut-off voltage until the ratio of the current capacity data to the initial capacity data is less than or equal to 0.8.

[0107] It should be understood that, although the various steps in the flowcharts involved in the above-mentioned embodiments are displayed in sequence according to the indication of the arrows, these steps are not necessarily executed in sequence according to the order indicated by the arrows. Unless there is a clear explanation in this article, the execution of these steps does not have a strict order restriction, and these steps can be executed in other orders. Moreover, at least a part of the steps in the flowcharts involved in the above-mentioned embodiments can include multiple steps or multiple stages, and these steps or stages are not necessarily executed at the same time, but can be executed at different times, and the execution order of these steps or stages is not necessarily to be carried out in sequence, but can be executed in turn or alternately with other steps or at least a part of the steps or stages in other steps.

[0108] Based on the same inventive concept, an embodiment of the present application also provides an electronic device. Figure 6 FIG. 1 is a diagram showing the internal structure of an electronic device in an embodiment. Figure 6 As shown, the electronic device includes one or more memories 604, one or more processors 602, and at least one computer program (program code) stored in the memory 604 and executable on the processor 602. When the processor 602 executes the computer program, the method for determining the charging cut-off voltage of a lithium-ion battery as described above is implemented.

[0109] Among them, Figure 6 In the embodiment of the present invention, a bus architecture (represented by bus 600) is shown, which may include any number of interconnected buses and bridges, and bus 600 links various circuits including one or more processors represented by processor 602 and memory represented by memory 604. Bus 600 may also link various other circuits such as peripherals, voltage regulators, and power management circuits, which are well known in the art and are therefore not further described herein. Bus interface 605 provides an interface between bus 600 and receiver 601 and transmitter 603. Receiver 601 and transmitter 603 may be the same element, namely a transceiver, providing a unit for communicating with various other devices over a transmission medium. Processor 602 is responsible for managing bus 600 and general processing, while memory 604 may be used to store data used by processor 602 when performing operations.

[0110] Those skilled in the art will understand that Figure 6 The structure shown in the figure is merely a block diagram of a partial structure related to the scheme of the present application, and does not constitute a limitation on the electronic device to which the scheme of the present application is applied. The specific electronic device may include more or fewer components than shown in the figure, or combine certain components, or have a different arrangement of components.

[0111] The functions described herein may be implemented in hardware, software executed by a processor, firmware, or any combination thereof. If implemented in software executed by a processor, the functions may be stored as one or more instructions or codes on a computer-readable medium or transmitted via a computer-readable medium. Other examples and implementations are within the scope and spirit of the present application and the appended claims. For example, due to the nature of software, the functions described above may be implemented using software executed by a processor, hardware, firmware, hard wiring, or a combination of any of these. In addition, each functional unit may be integrated into a processing unit, each unit may exist physically separately, or two or more units may be integrated into one unit.

[0112] In the several embodiments provided in this application, it should be understood that the disclosed technical content can be implemented in other ways. Among them, the device embodiments described above are only schematic. For example, the division of the units can be a logical function division. There may be other division methods in actual implementation. For example, 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 interfaces, indirect coupling or communication connection of units or modules, which can be electrical or other forms.

[0113] The above description is only an embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent substitution, improvement, etc. made within the spirit and principle of the present application shall be included in the scope of the claims of the present application.

Claims

1. A method for determining a lithium-ion battery charging cut-off voltage, applied to a vehicle, wherein the vehicle comprises a battery management system and a battery of the same type as the lithium-ion battery, characterized in that: The method comprises: Performing a first cycle of charging and discharging the lithium-ion battery according to the maximum operating voltage of the lithium-ion battery to determine an initial charging cut-off voltage; The initial charge cut-off voltage is set as the current charge cut-off voltage, and the lithium-ion battery is charged and discharged for a preset number of cycles according to the current charge cut-off voltage; Get the current voltage data and current capacity data during the last cycle of charging; constructing a current differential capacity curve according to the current voltage data and the current capacity data; Determine the current charge cut-off voltage from the voltage corresponding to the characteristic peak of the current differential capacity curve, and return to the step of charging and discharging the lithium-ion battery for a preset number of cycles according to the current charge cut-off voltage until the current capacity data meets the preset condition; wherein, The charging and discharging of the lithium-ion battery for a first cycle according to the maximum operating voltage of the lithium-ion battery to determine the initial charging cut-off voltage includes: Charging the lithium-ion battery for a first cycle; When the voltage of the lithium-ion battery reaches the maximum operating voltage, stopping charging; Acquiring initial voltage data and initial capacity data during the first cycle charging process; constructing an initial differential capacity curve according to the initial voltage data and the initial capacity data; Determining the initial charge cut-off voltage from the voltage corresponding to the characteristic peak of the initial differential capacity curve; The determining the current charging cut-off voltage from the voltage corresponding to the characteristic peak of the current differential capacity curve comprises: Determine the voltage at the H2-H3 phase transition position from the voltage corresponding to the characteristic peak of the current differential capacity curve; Determine the voltage at the H2-H3 phase change position as the current charging cut-off voltage; The method further comprises: The initial charge cut-off voltage and the current charge cut-off voltage are stored in the battery management system, so that the battery management system controls the charging of the battery according to the initial charge cut-off voltage and the current charge cut-off voltage.

2. The method according to claim 1, characterized in that The charging of the lithium-ion battery for a first cycle includes: Using a plurality of preset temperatures and a plurality of preset charging cut-off currents to charge the lithium-ion battery for a first cycle; Accordingly, determining the initial charging cut-off voltage from the voltage corresponding to the characteristic peak of the initial differential capacity curve includes: Determine a plurality of the initial charge cut-off voltages from voltages corresponding to characteristic peaks of a plurality of the initial differential capacity curves; The determining the current charging cut-off voltage from the voltage corresponding to the characteristic peak of the current differential capacity curve comprises: A plurality of the current charge cut-off voltages are determined from voltages corresponding to characteristic peaks of a plurality of the current differential capacity curves.

3. The method according to claim 2, characterized in that The storing the initial charging cut-off voltage and the current charging cut-off voltage in the battery management system includes: The preset temperature, the preset charge cut-off current, the initial charge cut-off voltage and the current charge cut-off voltage are correspondingly stored in the battery management system.

4. The method according to claim 1, characterized in that: The preset condition includes: a ratio of the current capacity data to the initial capacity data is less than or equal to 0.

8.

5. The method according to claim 1, characterized in that: The current voltage data includes a plurality of voltage data, the current capacity data includes a plurality of capacity data, the voltage data corresponds to the capacity data one by one, and constructing a current differential capacity curve according to the current voltage data and the current capacity data includes: Determine the voltage difference between two adjacent voltage data; determining a capacity difference between two capacity data corresponding to the two voltage data; The ratio of the voltage difference to the capacity difference is used as the ordinate value of the current differential capacity curve, and the larger value of the two voltage data is used as the abscissa value of the current differential capacity curve.

6. The method according to claim 1, characterized in that Determining the voltage at the H2-H3 phase transition position from the voltage corresponding to the characteristic peak of the current differential capacity curve includes: The maximum voltage among the voltages corresponding to the characteristic peaks of the current differential capacity curve is determined as the voltage at the H2-H3 phase transition position.

7. An electronic device, characterized in that: The method comprises a memory and a processor, wherein the memory stores a computer program, and the processor implements the steps of the method according to any one of claims 1 to 6 when executing the computer program.

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