Battery charging current determination method and device

Abstract

The invention provides a battery charging current determination method and device, and the method comprises the steps: obtaining a plurality of charging current groups of a battery, and each charging current group comprises the charging current corresponding to at least one charge state stage of charging from a first charge state to a second charge state; respectively inputting the plurality of charging current groups into a pre-established simulation battery charging model to obtain battery temperature variation, charging time and capacity attenuation corresponding to each charging current group; based on a multi-target genetic algorithm, determining at least one candidate charging current group according to each charging current group and the corresponding battery temperature variation, charging time and capacity attenuation; and determining a target charging current group in the at least one candidate charging current group according to a preset charging demand.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a method and device for determining a battery charging current. Background Art

[0002] In the prior art, the charging current used when charging the battery is determined by whether the potential of the negative electrode among the three electrodes is greater than 0. The charging current needs to ensure that the voltage value of the negative electrode of the battery is greater than 0 during the charging stage to prevent lithium deposition in the battery during the charging stage. The current technical solutions mainly focus on how to reduce the risk of lithium deposition of the negative electrode potential during fast charging, while ignoring other factors that affect the battery life, which can easily lead to reduced battery life and increased costs. Summary of the invention

[0003] In view of this, the purpose of the present application is to at least provide a method and device for determining battery charging current, by splitting the battery charging stage into at least one state of charge stage, and obtaining the charging current corresponding to each state of charge stage of the battery in the battery charging stage for multiple times, so as to obtain multiple charging current groups accordingly, and determine the battery temperature change, charging time and capacity attenuation corresponding to the multiple charging current groups according to the pre-built simulated battery charging model, so as to determine at least one candidate charging current group in combination with a multi-objective genetic algorithm, and determine the target charging current value in at least one candidate charging current group according to the preset charging requirements, so as to charge the battery according to the target charging current group. The technical problem that only considering how to prevent lithium deposition during the charging process in the prior art easily leads to a reduction in battery life is solved, and the technical effect of increasing battery life to reduce costs is achieved.

[0004] This application mainly includes the following aspects:

[0005] In a first aspect, an embodiment of the present application provides a method for determining a battery charging current, the method comprising: obtaining a plurality of charging current groups of a battery, each charging current group comprising a charging current corresponding to at least one state of charge stage from a first state of charge to a second state of charge; inputting the plurality of charging current groups into a pre-built simulated battery charging model, respectively, to obtain a battery temperature change, charging time, and capacity attenuation corresponding to each charging current group; based on a multi-objective genetic algorithm, determining at least one candidate charging current group according to each charging current group and its corresponding battery temperature change, charging time, and capacity attenuation; and determining a target charging current group from at least one candidate charging current group according to a preset charging requirement.

[0006] Optionally, at least one candidate charging current group is determined in the following manner: taking the multiple charging current groups as a parent population; processing the parent population through a genetic algorithm to obtain multiple newly added charging current groups, and taking the multiple newly added charging current groups as child populations; inputting the child population into the simulated battery charging model to obtain the battery temperature change, charging time and capacity attenuation corresponding to each newly added charging current group; performing non-dominated sorting and congestion calculation on the child population and the parent population according to the battery temperature change, charging time and capacity attenuation corresponding to the child population and the parent population respectively; generating a new parent population based on the results of the non-dominated sorting and the congestion calculation, and increasing the number of iterations by one, returning to the process of processing the parent population through a genetic algorithm to obtain multiple newly added charging current groups and re-executing until the number of iterations reaches a preset number of iterations, and taking the charging current group in the Pareto solution set corresponding to the preset number of iterations as at least one candidate charging current group.

[0007] Optionally, non-dominated sorting is performed in the following manner: among the charging current groups of the child population and the parent population, a group of non-dominated charging current groups is determined according to the battery temperature change, charging time and capacity attenuation, and the non-dominated order of the group of non-dominated charging current groups is marked as one; the charging current group with a non-dominated order of one is deleted, and the next group of non-dominated charging current groups is determined among the remaining charging current groups according to the battery temperature change, charging time and capacity attenuation, and the non-dominated order is increased by one, until the corresponding non-dominated order is determined for the charging current groups of the child population and the parent population.

[0008] Optionally, the Pareto solution set corresponding to the preset number of iterations refers to a charging current group whose non-dominated order is one in the sorting result of the non-dominated sorting corresponding to the preset number of iterations.

[0009] Optionally, the congestion degree is calculated in the following manner: in the charging current groups of the child population and the parent population, the charging current groups are sorted according to the battery temperature change, charging time and capacity attenuation; according to the sorting results, the difference between two adjacent charging current values ​​of each charging current group corresponding to the battery temperature change, charging time and capacity attenuation is calculated, and the differences are summed to obtain the congestion degree corresponding to each charging current group.

[0010] Optionally, the simulated battery charging model includes an electrochemical and thermal coupling model and a capacity attenuation model of the battery, wherein the charging current corresponding to each charge state stage in the charging current group is less than or equal to a preset maximum charging current, and the preset maximum charging current refers to the maximum charging current corresponding to the negative electrode voltage value of the battery in each charge state stage predicted by the electrochemical and thermal coupling model to be greater than zero.

[0011] Optionally, the simulated battery charging model includes an electrochemical and thermal coupling model and a capacity attenuation model of the battery, and the battery temperature change, charging time and capacity attenuation corresponding to each charging current group are obtained in the following manner: each charging current group is input into the electrochemical and thermal coupling model to obtain the battery temperature change and charging time corresponding to each charging current group; each charging current group and its corresponding charging time are input into the capacity attenuation model to obtain the capacity attenuation corresponding to each charging current group.

[0012] Optionally, the capacity decay model includes a stage capacity decay model corresponding to each state of charge stage, and the charging time corresponding to each charging current group includes the stage charging time of each state of charge stage. The capacity decay amount corresponding to each charging current group is obtained in the following manner: for each charging current group, the charging current and stage charging time of the charging current group in each state of charge stage are input into the corresponding stage capacity decay model to determine the stage capacity decay amount of the charging current group in each state of charge stage; and the sum of the stage capacity decay amounts of each charging current group in each state of charge stage is determined as the capacity decay amount corresponding to each charging current group.

[0013] Optionally, a stage capacity decay model corresponding to each state of charge stage is constructed in the following manner: a battery is subjected to multiple charge and discharge operations at the state of charge stage and a stage charge capacity and a stage discharge capacity corresponding to each charge and discharge operation are obtained, wherein the multiple charge and discharge operations correspond to different charge and discharge rates; the stage capacity decay amount corresponding to each charge and discharge operation of the battery at the state of charge stage is determined through the stage charge capacity and the stage discharge capacity corresponding to each charge and discharge operation; and a stage capacity decay model corresponding to the state of charge stage is constructed according to the stage capacity decay amounts corresponding to the multiple charging operations.

[0014] In a second aspect, an embodiment of the present application further provides a battery charging current determination device, the battery charging current determination device comprising: an acquisition module, used to acquire multiple charging current groups of the battery, each charging current group comprising a charging current corresponding to at least one charge state stage from a first charge state to a second charge state; a model prediction module, used to input the multiple charging current groups into a pre-built simulated battery charging model, respectively, to obtain the battery temperature change, charging time and capacity attenuation corresponding to each charging current group; a first determination module, used to determine at least one candidate charging current group based on a multi-objective genetic algorithm according to each charging current group and its corresponding battery temperature change, charging time and capacity attenuation; a second determination module, used to determine a target charging current group from at least one candidate charging current group based on a preset charging requirement.

[0015] A method and device for determining a battery charging current are provided in an embodiment of the present application. The method for determining a battery charging current includes: obtaining multiple charging current groups of a battery, each charging current group including a charging current corresponding to at least one state of charge stage from a first state of charge to a second state of charge; inputting the multiple charging current groups into a pre-built simulated battery charging model to obtain a battery temperature change, charging time, and capacity attenuation corresponding to each charging current group; based on a multi-objective genetic algorithm, determining at least one candidate charging current group according to each charging current group and its corresponding battery temperature change, charging time, and capacity attenuation; and determining a target charging current group from at least one candidate charging current group according to a preset charging requirement. By splitting the battery charging stage into at least one state of charge stage, and obtaining the charging current corresponding to each state of charge stage of the battery in the battery charging stage for multiple times, a plurality of charging current groups are obtained accordingly, and the battery temperature change, charging time and capacity attenuation corresponding to the plurality of charging current groups are determined according to the pre-built simulation battery charging model, and at least one candidate charging current group is determined in combination with a multi-objective genetic algorithm, and a target charging current value is determined in at least one candidate charging current group according to the preset charging requirements, so as to charge the battery according to the target charging current group. The technical problem that only considering how to prevent lithium deposition during the charging process in the prior art may lead to a reduction in the battery life is solved, and the technical effect of increasing the battery life to reduce the cost is achieved.

[0016] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, preferred embodiments are specifically cited below and described in detail with reference to the attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0018] Figure 1 A flow chart of a method for determining a battery charging current provided in an embodiment of the present application is shown.

[0019] Figure 2 A functional module diagram of a battery charging current determination device provided in an embodiment of the present application is shown.

[0020] Figure 3 A schematic structural diagram of an electronic device provided in an embodiment of the present application is shown. DETAILED DESCRIPTION

[0021] To make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. It should be understood that the drawings in the present application only serve the purpose of explanation and description and are not used to limit the scope of protection of the present application. In addition, it should be understood that the schematic drawings are not drawn in real proportion. The flowchart used in this application shows the operations implemented according to some embodiments of the present application. It should be understood that the operations of the flowchart can be implemented out of sequence, and the steps without logical context can be reversed in order or implemented simultaneously. In addition, those skilled in the art, under the guidance of the content of the present application, can add one or more other operations to the flowchart, or remove one or more operations from the flowchart.

[0022] In addition, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application described and shown in the drawings here can be arranged and designed in various configurations. Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the application claimed for protection, but merely represents the selected embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without making creative work belong to the scope of protection of the present application.

[0023] In the context of the rapid development of new energy technologies, lithium-ion batteries, as the key power source of energy storage equipment, have become the focus of research, especially their charging efficiency and safety. In order to meet the needs of both fast and safe charging, it is necessary to determine a battery charging strategy that can shorten the charging time and improve the service life and safety of the battery. In the prior art, the main battery charging strategies include an optimized charging strategy based on the polarization voltage of the whole battery and a charging technology based on the negative electrode potential in a three-electrode battery. These methods generally use a three-electrode battery and measure the negative electrode potential. By ensuring that the negative electrode potential is greater than 0V during charging, the battery is prevented from lithium plating during the charging stage. If the negative electrode potential is less than 0V, it is adjusted by depolarization treatment to achieve lithium plating-free charging. However, the current technical solutions mainly focus on the risk of lithium plating caused by the negative electrode potential during fast charging, but rarely pay attention to the joint influence of multiple factors such as charging time, service life and temperature changes on the formulation of charging strategies.

[0024] Based on this, the embodiment of the present application provides a method and device for determining battery charging current, which divides the battery charging stage into at least one state of charge stage, and obtains the charging current corresponding to each state of charge stage of the battery in the battery charging stage multiple times, so as to obtain multiple charging current groups accordingly, and determines the battery temperature change, charging time and capacity attenuation corresponding to the multiple charging current groups according to the pre-built simulated battery charging model, so as to determine at least one candidate charging current group in combination with a multi-objective genetic algorithm, and determines the target charging current value in at least one candidate charging current group according to the preset charging requirements, so as to charge the battery according to the target charging current group. It solves the technical problem that the prior art only considers how to prevent lithium deposition during the charging process, which easily leads to a reduction in battery life, and achieves the technical effect of increasing battery life to reduce costs, as follows:

[0025] See also Figure 1 , Figure 1 This is a flow chart of a method for determining a battery charging current provided by an embodiment of the present application. Figure 1 As shown, the method for determining the battery charging current provided in the embodiment of the present application includes the following steps:

[0026] S101: Acquire multiple charging current groups of a battery.

[0027] Each charging current group includes charging currents corresponding to at least one state of charge stage from the first state of charge to the second state of charge.

[0028] That is to say, the first state of charge refers to the battery state of charge (SOC) when the battery starts to be charged, and the second state of charge refers to the battery state of charge when the battery finishes charging. Furthermore, the change in the battery state of charge from the beginning to the end of charging is divided into at least one state of charge stage, and each state of charge stage may be evenly divided or not.

[0029] Exemplarily, if the battery is charged from 0% SOC (state of charge) to 100% SOC and is evenly divided into 10 state of charge stages, the battery charging stage is divided into a first state of charge stage of charging from 0% SOC to 10% SOC, a second state of charge stage of charging from 10% SOC to 20% SOC, ..., a ninth state of charge stage of charging from 80% SOC to 90% SOC, and a tenth state of charge stage of charging from 90% SOC to 100% SOC.

[0030] Furthermore, each state of charge stage corresponds to a charging current value, and the charging current values ​​corresponding to each state of charge stage when the battery is charged from the first state of charge to the second state of charge are grouped into a charging current group.

[0031] That is to say, multiple charging current groups of the battery are obtained in the following manner: the battery is charged multiple times, and for each charge, the battery is charged from a first state of charge to a second state of charge, so as to obtain the charging current values ​​corresponding to each state of charge stage of the battery during the charging process, and obtain the charging current group of the charging.

[0032] S102: Input the plurality of charging current groups into a pre-built simulated battery charging model to obtain the battery temperature change, charging time and capacity attenuation corresponding to each charging current group.

[0033] Among them, the simulated battery charging model includes an electrochemical and thermal coupling model and a capacity attenuation model of the battery. The electrochemical and thermal coupling model is used to simulate the temperature change and voltage change of the battery during the charging process, and the battery is a three-electrode battery, that is, to simulate the overall temperature change of the battery, the positive electrode temperature change, the negative electrode temperature change, the positive electrode voltage change of the positive electrode relative to the reference electrode, the negative electrode voltage value change of the negative electrode relative to the reference electrode, and the battery voltage change (the change in the difference between the positive electrode voltage and the negative electrode voltage) during the charging process, and simulate the charging time according to whether the battery voltage reaches the cut-off voltage corresponding to the completion of charging. The capacity attenuation model is used to simulate the capacity attenuation of the battery during the charging process.

[0034] The battery temperature change, charging time and capacity attenuation corresponding to each charging current group are obtained in the following manner: each charging current group is input into the electrochemical and thermal coupling model to obtain the battery temperature change and charging time corresponding to each charging current group; each charging current group and its corresponding charging time are input into the capacity attenuation model to obtain the capacity attenuation corresponding to each charging current group.

[0035] That is to say, for each charging current group, the charging current group is input into the electrochemical and thermal coupling model to obtain the battery temperature change and charging time corresponding to the charging current group, and the charging current group and charging time are input into the capacity decay model to obtain the capacity decay corresponding to the charging current group. In addition, the battery temperature change, charging time and capacity decay corresponding to different charging battery groups are predicted.

[0036] For example, if the battery is charged from 0% SOC (state of charge) to 100% SOC, and is evenly divided into a first state of charge stage from 0% SOC to 10% SOC, a second state of charge stage from 10% SOC to 20% SOC, ..., a ninth state of charge stage from 80% SOC to 90% SOC, and a tenth state of charge stage from 90% SOC to 100% SOC. Then, for each charging current group, the electrochemical and thermal coupling model simulates the battery temperature change caused by charging according to the charging current corresponding to each state of charge stage, thereby determining the total battery temperature change of the battery after the battery is fully charged, and the electrochemical and thermal coupling model simulates the battery voltage change caused by charging according to the charging current corresponding to each state of charge stage, and then, when the battery voltage changes to the charging completion cut-off voltage corresponding to each state of charge stage, the charging time of each state of charge stage is simulated.

[0037] Among them, the construction method of the electrochemical and thermal coupling model can be constructed through the existing model construction method. The present application does not limit the construction method of the electrochemical and thermal coupling model. It only needs to ensure that the electrochemical and thermal coupling model can obtain voltage changes and temperature changes, and the charging time can be calculated based on the voltage changes.

[0038] Exemplarily, the present application constructs an electrochemical and thermal coupling model in the following manner: setting the battery geometry and material parameters, and also setting boundary conditions such as the initial lithium ion concentration distribution and the initial battery temperature; describing the diffusion and migration of lithium ions in solid active materials by Fick's second law; using the Butler-Volmer equation to react to the electrochemical reaction process on the electrode surface and derive the overpotentials corresponding to the positive and negative electrodes, respectively, to calculate the voltages of the positive and negative electrodes relative to the reference electrode, respectively; calculating the heat generated by the battery, and describing the generation and transfer of heat by the energy conservation equation; coupling the electrochemical model and the thermal model by considering the effect of temperature on the electrochemical parameters; solving the coupled partial differential equations by numerical methods to calculate the battery temperature; and considering adjusting the model parameters to optimize the model.

[0039] Among them, the battery size, electrode material, electrolyte material, battery density, specific heat capacity and thermal conductivity and other geometric shapes and material parameters are defined according to the actual design parameters of the battery, and based on the Newman model, it is assumed that the active material particles inside the battery are spherical particles of uniform size and the radial distance from the center of the spherical particle to the surface is defined. The battery of this application is a lithium-ion battery, and the insertion and extraction of lithium ions occur on the surface of the electrode material. The diffusion and migration of lithium ions in the solid active materials of the positive and negative electrodes are described by Fick's second law, which is expressed by the following formula:

[0040]

[0041] In formula (1), C s refers to the lithium ion concentration of the solid phase active material, t refers to the time, and r refers to the radial distance from the center of the spherical particle to the surface.

[0042] The Butler-Volmer equation describes the relationship between current density, exchange current density and overpotential to reflect the electrochemical reaction process on the positive and negative electrode surfaces.

[0043] In electrochemical kinetics, the intensity of the local lithium ion intercalation reaction is reflected by the reaction current density, and its relationship is determined by the Butler-Volmer equation. The local reaction current density at the solid-liquid interface of the positive electrode sheet and the negative electrode sheet is calculated by the following formula:

[0044]

[0045] In formula (2), i loc refers to the local reaction current density, s refers to the reaction specific surface area, i 0 refers to the exchange current density, α a Refers to the charge transfer coefficient of the positive electrode, α c refers to the charge transfer coefficient of the negative electrode, F refers to the Faraday constant, η refers to the overpotential, and R const refers to the gas constant and T is the battery temperature.

[0046] In the established electrochemical model, the positive electrode and the negative electrode are solid-liquid homogeneous porous electrodes and electrochemical reactions occur. The carriers are both electrons and ions. The transport rules are described by Ohm's law and Nernst-Planck law, respectively. The local reaction current density is calculated by the following formula:

[0047]

[0048] In formulas (3) and (4), i loc refers to the local reaction current density, σ s,eff Refers to the effective electronic conductivity of the porous electrode solid phase, refers to the solid phase potential, σ l,eff Refers to the effective electronic conductivity of the porous electrode liquid phase, refers to the liquid phase potential, R const refers to the gas constant, T is the battery temperature, F refers to the Faraday constant, f refers to the activity coefficient, C l refers to the concentration of lithium ions in the liquid phase, t + Refers to the number of migrations.

[0049] The diaphragm is a porous electrolyte, the carriers are only ions and no electrochemical reaction occurs, so the transport rules conform to The effective conductivity is obtained by correcting the physical parameters of the Bruggeman equation. ε s is the solid phase porosity, ε l is the liquid phase porosity, σ s is the solid phase intrinsic conductivity, σ l is the intrinsic conductivity of the liquid phase. s , ε l , σ s , σ l ,f,C l ,t + All data are pre-input into the model and are set for the electrodes corresponding to the positive and negative electrodes respectively.

[0050] Furthermore, the local reaction current density corresponding to the positive electrode and the negative electrode is calculated by formula (3) and (4), and then the overpotential corresponding to the positive electrode and the negative electrode is inferred by combining formula (2). The initial potentials of the positive electrode and the negative electrode are obtained by the overpotentials corresponding to the positive electrode and the negative electrode and the preset equilibrium potential. Then, based on the difference between the initial potentials of the positive electrode and the negative electrode and the preset constant potential of the reference electrode, the positive electrode voltage value of the positive electrode relative to the reference electrode and the negative electrode voltage value of the negative electrode relative to the reference electrode are obtained, and then the difference between the positive electrode voltage value and the negative electrode voltage value is used as the battery voltage.

[0051] The battery temperature variation corresponding to each charging current group is obtained by simulating the battery heat generation rate generated by charging the battery according to each charging current group through the electrochemical and thermal coupling model, and determining the battery temperature variation corresponding to the battery heat generation rate.

[0052] That is to say, each charging current group is input into the electrochemical and thermal coupling model to simulate the battery heat generation rate generated by charging the battery according to each charging current group through the electrochemical and thermal coupling model, and then, the battery temperature change corresponding to charging the battery according to each charging current group is obtained.

[0053] Specifically, the heat generated by the battery in the model includes reversible heat, polarization heat and ohmic heat, which are calculated by the following formula:

[0054] Q tot =Q rev +Q pol +Q ohn (5)

[0055]

[0056] Q pol=i loc ×η (7)

[0057]

[0058] In formulas (5) to (8), Q tot is the heat generated by the battery, Q rev is the reversible heat, Q pol is the polarization heat, Q ohm is ohmic heat, i loc is the local reaction current density, T is the battery temperature, U is the battery voltage, η refers to the overpotential, is the solid phase potential, is the liquid phase potential, i s is the solid phase current density, i l is the liquid phase current density.

[0059] Considering the heat generated inside the battery and the heat transfer, the thermal changes of the battery are described by the energy conservation equation:

[0060]

[0061] In formula (9), ρ refers to the battery density, C p refers to the battery specific heat capacity, T refers to the battery temperature, t refers to time, k refers to thermal conductivity, Q tot Refers to the heat generated by the battery. Among them, ρ, C p , k is the data pre-input into the model, which can be determined through existing information or actual data of the battery.

[0062] Then, the battery temperature is calculated based on the heat generated by the battery. The heat Q generated by the battery calculated by the electrochemical model is obtained by the electrochemical model. tot As the heat source term of the thermal model, the coupling of the electrochemical and thermal models is realized. At the same time, the temperature distribution calculated by the thermal model will be fed back to the electrochemical model, affecting the kinetic parameters of the electrochemical reaction to achieve the coupling of the electrical model and the thermal model.

[0063] Among them, the temperature-related electrochemical parameter λ in the electrochemical model can be calculated using the Arrhenius equation:

[0064]

[0065] Formula (10), λ refers to the electrochemical parameter related to temperature, λ ref refers to the reference value of λ, E a refers to the activation energy of the reaction, R const refers to the gas constant, T refers to the battery temperature, and Tref Refers to the reference value of battery temperature. Among them, λ includes liquid phase diffusion coefficient, solid phase diffusion coefficient and positive and negative electrode reaction rate constants. Among them, λ ref and E a The data for pre-input into the model may be determined from existing information or actual data of the battery.

[0066] Numerical solutions in electrochemical and thermal coupling models generally use numerical methods, such as finite element method or finite difference method, to solve the established electrochemical-thermal coupling model and obtain the electrochemical behavior and temperature distribution of the battery during the charging and discharging process.

[0067] After constructing the electrochemical and thermal coupling model, the parameters in the model need to be corrected, such as the aforementioned liquid phase diffusion coefficient, solid phase diffusion coefficient, and positive and negative electrode reaction rate constants, so as to predict the temperature change and voltage change of the battery that are more in line with the actual charging process. The battery temperature change and battery voltage change of the same specification of battery cells under different working conditions are determined in actual experiments and / or literature search as standard data to correct the parameters in the model, that is, the battery temperature change, positive electrode temperature change, negative electrode temperature change, positive electrode voltage change relative to the reference electrode, negative electrode voltage change relative to the reference electrode, and battery voltage change (change in the difference between the positive electrode voltage and the negative electrode voltage) in actual experiments and / or literature are used as standard data. Among them, different working conditions refer to different charging rates, charge states before and after charging, and different ambient temperatures, while the battery cell specifications remain unchanged.

[0068] Exemplarily, in the actual experiment, a thermocouple is set on the side with the largest area of ​​the battery, or multiple thermocouples are evenly arranged on the side with the largest area of ​​the battery, and the battery is charged from the first state of charge to the second state of charge. The battery temperature collected by a thermocouple during the charging process or the average value of the battery temperature collected by multiple thermocouples is used as the battery temperature corresponding to the current collection time in the actual experiment. Exemplarily, the collection frequency of the thermocouple is set to 1Hz. Then, the battery temperature change when the battery is charged from the first state of charge to the second state of charge can be obtained. Thermocouples can also be arranged on the positive and negative pole pieces of the battery to obtain the temperature change of the positive pole piece and the temperature change of the negative pole piece when the battery is charged from the first state of charge to the second state of charge.

[0069] For example, if the battery temperature change and battery voltage change of the battery are determined through actual experiments, then the working conditions of the actual experiments are input into the electrochemical and thermal coupling model to determine the battery temperature change and battery voltage change output by the electrochemical and thermal coupling model under the working conditions. The root mean square error of the battery temperature change obtained in the actual experiment and the battery temperature change output by the electrochemical and thermal coupling model is calculated, and the root mean square error of the battery voltage change obtained in the actual experiment and the battery voltage change output by the electrochemical and thermal coupling model is calculated. Thus, the root mean square error is reduced by changing various parameters of the electrochemical and thermal coupling model, so that the calibration of various parameters of the electrochemical and thermal coupling model is completed when the root mean square error is less than the preset value.

[0070] The capacity decay model includes a stage capacity decay model corresponding to each state of charge stage, and the stage capacity decay model corresponding to each state of charge stage is constructed in the following manner: obtaining multiple charge and discharge operations of the battery in the state of charge stage and obtaining the stage charge capacity and stage discharge capacity corresponding to each charge and discharge operation, and the multiple charge and discharge operations correspond to different charge and discharge rates; determining the stage capacity decay amount corresponding to each charge and discharge operation of the battery in the state of charge stage through the stage charge capacity and stage discharge capacity corresponding to each charge and discharge operation; and constructing the stage capacity decay model corresponding to the state of charge stage according to the stage capacity decay amounts corresponding to the multiple charging operations.

[0071] That is to say, the stage capacity decay model corresponding to each state of charge stage is used to predict the stage capacity decay amount of each state of charge stage, so that the sum of the stage capacity decay amounts of each state of charge stage can be used as the capacity decay amount of the battery when charging from the first state of charge to the second state of charge.

[0072] In the actual experiment, the battery is divided into multiple state of charge stages from the first state of charge to the second state of charge. Then, for each state of charge stage, the battery is charged from the lower limit value of the state of charge stage to the upper limit value, and then the battery is discharged from the upper limit value of the state of charge stage to the lower limit value, so as to complete a charge and discharge operation of the state of charge stage. In addition, different charge and discharge rates are used to perform multiple charge and discharge operations on the battery in each state of charge stage, and one charge and discharge rate corresponds to one charge and discharge operation of the state of charge stage.

[0073] For example, if the first state of charge stage of the multiple state of charge stages of the battery is charged from 0% SOC to 10% SOC, and the battery is charged from 0% SOC to 10% SOC and then discharged to 0% SOC using a charge and discharge rate of 0.5C, the battery is charged from 0% SOC to 10% SOC and then discharged to 0% SOC using a charge and discharge rate of 1C, and the battery is charged from 0% SOC to 10% SOC and then discharged to 0% SOC using a charge and discharge rate of 2C. Then, in each charge and discharge operation under the first state of charge stage, the stage charge capacity corresponding to the charging stage and the stage discharge capacity corresponding to the discharge stage are obtained, so that the difference between the stage discharge capacity and the stage charge capacity corresponding to each charge and discharge operation is used as the multiple stage capacity attenuation corresponding to the first state of charge stage of the battery.

[0074] Among them, the stage capacity decay model corresponding to each state of charge stage is expressed by the following formula:

[0075]

[0076] In formula (11), Q loss,k Refers to the stage capacity attenuation of the kth state of charge stage, C k Refers to the charging rate at the kth state of charge stage, B k Refers to the pre-exponential factor of capacity attenuation at each state of charge stage, z k refers to the power law factor of capacity decay at the kth state of charge stage, Ah refers to the stage charge capacity at the kth state of charge stage, R const is the gas constant, T W Refers to the ambient temperature. The stage charging capacity of each state of charge stage is calculated by the ampere-hour integration method, that is, the stage charging capacity of each state of charge stage is calculated according to the charging time and charging current corresponding to each state of charge stage in a charging current group. The charging time is obtained by the electrochemical and thermal coupling model based on whether the battery voltage reaches the voltage corresponding to the completion of charging.

[0077] Furthermore, multiple charge and discharge operations are performed at each state of charge stage to obtain multiple stage charging capacities and multiple stage capacity attenuation amounts at each state of charge stage, and the multiple stage charging capacities and multiple stage capacity attenuation amounts at each state of charge stage are substituted into formula (12) to use the parameter estimation method to estimate the capacity attenuation pre-exponential factor and capacity attenuation power law factor that best fit the multiple stage charging capacities and multiple stage capacity attenuation amounts at the state of charge stage, so as to establish a stage capacity attenuation model corresponding to each state of charge stage.

[0078] Among them, the charging current corresponding to each charge state stage in the charging current group is less than or equal to the preset maximum charging current, and the preset maximum charging current refers to the maximum charging current corresponding to the negative electrode voltage value of the battery in each charge state stage predicted by the electrochemical and thermal coupling model when it is greater than zero.

[0079] That is, the battery is charged according to the charging current corresponding to each state of charge stage through the electrochemical and thermal coupling model and the negative electrode voltage value relative to the reference electrode is predicted. The maximum value of the charging current is determined from the charging current corresponding to each moment when the negative electrode voltage value is greater than zero, and the maximum value of the charging current is used as the preset maximum charging current. Furthermore, by setting each charging current in the charging current group to be less than or equal to the preset maximum charging current, lithium deposition of the battery is prevented.

[0080] The charging time corresponding to each charging current group includes the stage charging time of each state of charge stage, and the capacity attenuation amount corresponding to each charging current group is obtained in the following manner: for each charging current group, the charging current and stage charging time of the charging current group at each state of charge stage are input into the corresponding stage capacity attenuation model to determine the stage capacity attenuation amount of the charging current group at each state of charge stage; the sum of the stage capacity attenuation amounts of each charging current group at each state of charge stage is determined as the capacity attenuation amount corresponding to each charging current group.

[0081] That is to say, for each charging current group, according to the stage charging time and charging current corresponding to each state of charge stage in the charging current group, the stage charging capacity corresponding to each state of charge stage is determined by the ampere-hour integration method, and the stage charging capacity of each state of charge stage is substituted into the corresponding stage capacity attenuation model, and the stage capacity attenuation amount of the charging current group in each state of charge stage is determined in combination with the pre-set charging rate. Therefore, the sum of the stage capacity attenuation amounts of the charging current group in each state of charge stage is used as the capacity attenuation amount of the charging current group.

[0082] S103: Based on a multi-objective genetic algorithm, at least one candidate charging current group is determined according to each charging current group and its corresponding battery temperature change, charging time and capacity attenuation.

[0083] At least one candidate charging current group is determined in the following manner: taking the multiple charging current groups as a parent population; processing the parent population by a genetic algorithm to obtain multiple newly added charging current groups, and taking the multiple newly added charging current groups as child populations; inputting the child population into the simulated battery charging model to obtain the battery temperature change, charging time and capacity attenuation corresponding to each newly added charging current group; performing non-dominated sorting and congestion calculation on the child population and the parent population according to the battery temperature change, charging time and capacity attenuation corresponding to the child population and the parent population respectively; generating a new parent population according to the results of the non-dominated sorting and the congestion calculation, and increasing the number of iterations by one, returning to the step of processing the parent population by a genetic algorithm to obtain multiple newly added charging current groups and re-executing until the number of iterations reaches a preset number of iterations, and taking the charging current group in the Pareto solution set corresponding to the preset number of iterations as at least one candidate charging current group.

[0084] Among them, the charging current value corresponding to each state of charge stage in the newly added charging current group should also be less than or equal to the preset maximum charging current of each state of charge stage to prevent the newly added charging current group from causing lithium deposition in the battery.

[0085] Exemplarily, the parent population is processed by a genetic algorithm to obtain multiple new charging current groups, including: performing crossover mutation on multiple charging current groups of the parent population to generate multiple new charging current groups. There are many other ways to increase the number of samples by genetic algorithms, not limited to generating multiple new charging current groups by crossover mutation.

[0086] Specifically, each charging current group in the parent population and the child population corresponds to three objective functions: battery temperature change, charging time, and capacity attenuation. If a charging current group is not worse than another charging current group in all objective functions and is better in at least one objective function, then one charging current group is said to dominate another charging current group.

[0087] The non-dominated sorting is performed in the following manner: among the charging current groups of the child population and the parent population, a group of non-dominated charging current groups is determined according to the battery temperature change, charging time and capacity attenuation, and the non-dominated order of the group of non-dominated charging current groups is marked as one; the charging current group with the non-dominated order of one is deleted, and the next group of non-dominated charging current groups is determined according to the battery temperature change, charging time and capacity attenuation among the remaining charging current groups, and the non-dominated order is increased by one, until the corresponding non-dominated order is determined for the charging current groups of the child population and the parent population.

[0088] That is, the sub-population and the parent population are non-dominated in the following manner: the charging current groups that are not dominated by any other charging current groups are determined from among all the charging current groups in the parent population and the sub-population, and these charging current groups constitute the first-layer non-dominated solution set F1, and the irank value is set to 1, that is, the non-dominated order is 1. The charging current groups in the first-layer non-dominated solution set F1 are deleted, and the charging current groups that are not dominated by any other charging current groups are determined from among the remaining charging current groups, and these charging current groups constitute the second-layer non-dominated solution set F2, and the irank value is set to 2, that is, the non-dominated order is 2. And so on, until all the charging current groups have determined the corresponding irank values ​​to complete the non-dominated sorting.

[0089] The congestion degree of the sub-population and the parent population is calculated in the following manner: in the charging current groups of the sub-population and the parent population, the charging current groups are sorted according to the battery temperature change, charging time and capacity attenuation; according to the sorting results, the differences between two adjacent charging current values ​​of each charging current group corresponding to the battery temperature change, charging time and capacity attenuation are calculated, and the differences are summed to obtain the congestion degree corresponding to each charging current group.

[0090] Specifically, the congestion is calculated in the following manner: for all charging current groups in the sub-population and the parent population, all charging current groups are sorted according to the data size of the battery temperature change, and the first difference in battery temperature change between two adjacent charging current groups of each charging current group is calculated; all charging current groups are sorted according to the data size of the charging time, and the second difference in charging time between two adjacent charging current groups of each charging current group is calculated; all charging current groups are sorted according to the data size of the capacity attenuation, and the third difference in capacity attenuation between two adjacent charging current groups of each charging current group is calculated; the sum of the first difference, the second difference and the third difference corresponding to each charging current group is used as the congestion of each charging current value.

[0091] Generating a new parent population according to the results of the non-dominated sorting and the congestion calculation includes: controlling the number of charging current groups of the new parent population to be the same as that of the initial parent population through a screening and elimination mechanism according to the results of the non-dominated sorting and the congestion calculation.

[0092] That is to say, when the number of all charging current groups of the parent population and the child population is greater than the number of charging current groups of the initial parent population, the charging current group with the largest non-dominated order among all charging current groups of the parent population and the child population is deleted; it is determined whether the number of remaining charging current groups is greater than the number of charging current groups of the initial parent population; if the number of remaining charging current groups is greater than the number of charging current groups of the initial parent population, it is determined whether the number of new charging current groups with the largest non-dominated order is greater than the number of charging current groups of the initial parent population after the number of new charging current groups with the largest non-dominated order is deleted; if the number of new charging current groups with the largest non-dominated order is greater than the number of charging current groups of the initial parent population after the number of new charging current groups with the largest non-dominated order is deleted, If the number of charging current groups is greater than the number of charging current groups in the initial parent population after the number of charging current groups with the largest new non-dominated order is deleted, it is re-determined whether it is greater than the number of charging current groups in the initial parent population after the number of charging current groups with the largest new non-dominated order is deleted; if the number of charging current groups with the largest new non-dominated order is less than the number of charging current groups in the initial parent population after the number of charging current groups with the largest new non-dominated order is deleted in order of increasing congestion until the number of remaining charging current groups is equal to the number of charging current groups in the initial parent population, and the remaining charging current groups are used as the new parent population to ensure that the number of charging current groups in the new parent population is the same as that in the initial parent population.

[0093] Among them, preferentially deleting the charging current group with the largest non-dominated order is equivalent to removing the charging current values ​​with lower levels first, and deleting the charging current groups in order of congestion from large to small means selecting the charging current groups that leave less crowded areas in the same non-dominated order and removing the more crowded charging current groups.

[0094] The Pareto solution set corresponding to the preset number of iterations refers to the charging current group whose non-dominated order is 1 in the sorting result of the non-dominated sorting corresponding to the preset number of iterations. That is, in the new parent population generated when the number of iterations reaches the preset number of iterations, the non-dominated solution set with an irank value of 1 is selected as the Pareto solution set for the final solution, and the charging current group in the non-dominated solution set with an irank value of 1 is selected as at least one candidate charging current group.

[0095] S104: Determine a target charging current group from at least one candidate charging current group according to a preset charging requirement.

[0096] The preset charging requirement is set according to the usage scenario of the battery. For example, if the shortest charging time is required, a charging current group with the shortest charging time is determined in the Pareto solution set as the target charging current group.

[0097] Based on the same application concept, the embodiments of the present application also provide a battery charging current determination device corresponding to the battery charging current determination method provided in the above embodiments. Since the principle of solving the problem by the device in the embodiments of the present application is similar to the battery charging current determination method in the above embodiments of the present application, the implementation of the device can refer to the implementation of the method, and the repeated parts will not be repeated.

[0098] like Figure 2 Show, Figure 2 A functional module diagram of a battery charging current determination device provided in an embodiment of the present application. The battery charging current determination device 10 includes: an acquisition module 101, which is used to acquire multiple charging current groups of the battery, each charging current group includes a charging current corresponding to at least one state of charge stage from a first state of charge to a second state of charge; a model prediction module 102, which is used to input the multiple charging current groups into a pre-built simulated battery charging model to obtain the battery temperature change, charging time and capacity attenuation corresponding to each charging current group; a first determination module 103, which is used to determine at least one candidate charging current group based on a multi-objective genetic algorithm according to each charging current group and its corresponding battery temperature change, charging time and capacity attenuation; a second determination module 104, which is used to determine a target charging current group from at least one candidate charging current group according to a preset charging requirement.

[0099] Based on the same application concept, see Figure 3 2 is a schematic diagram of the structure of an electronic device provided in an embodiment of the present application, wherein the electronic device 20 comprises: a processor 201, a memory 202 and a bus 203, wherein the memory 202 stores machine-readable instructions executable by the processor 201, and when the electronic device 20 is running, the processor 201 communicates with the memory 202 through the bus 203, and the machine-readable instructions are executed by the processor 201 when running, as in the steps of the method for determining the battery charging current described in any of the above embodiments.

[0100] Specifically, when the machine-readable instructions are executed by the processor 201, the following processing can be performed: obtaining multiple charging current groups of the battery, each charging current group including a charging current corresponding to at least one charge state stage from a first charge state to a second charge state; inputting the multiple charging current groups into a pre-built simulated battery charging model to obtain the battery temperature change, charging time and capacity attenuation corresponding to each charging current group; based on a multi-objective genetic algorithm, determining at least one candidate charging current group according to each charging current group and its corresponding battery temperature change, charging time and capacity attenuation; and determining a target charging current group from at least one candidate charging current group based on a preset charging requirement.

[0101] Based on the same application concept, an embodiment of the present application further provides a computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, the steps of the battery charging current determination method provided in the above embodiment are executed.

[0102] Specifically, the storage medium can be a general storage medium, such as a mobile disk, a hard disk, etc. When the computer program on the storage medium is run, the above-mentioned battery charging current determination method can be executed, by splitting the battery charging stage into at least one state of charge stage, and obtaining the charging current corresponding to each state of charge stage of the battery in the battery charging stage for multiple times, so as to obtain multiple charging current groups accordingly, and determine the battery temperature change, charging time and capacity attenuation corresponding to the multiple charging current groups according to the pre-built simulation battery charging model, so as to determine at least one candidate charging current group in combination with a multi-objective genetic algorithm, and determine the target charging current value in at least one candidate charging current group according to the preset charging demand, so as to charge the battery according to the target charging current group. The technical problem that only considering how to prevent lithium deposition during the charging process in the prior art easily leads to a reduction in battery life is solved, and the technical effect of increasing battery life to reduce costs is achieved.

[0103] Those skilled in the art can clearly understand that, for the convenience and simplicity of description, the specific working process of the system and device described above can refer to the corresponding process in the aforementioned method embodiment, and will not be repeated here. In the several embodiments provided in the present application, it should be understood that the disclosed system, device and method can be implemented in other ways. The device embodiments described above are merely schematic. For example, the division of the units is only 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 communication interfaces, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms.

[0104] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0105] In addition, each functional unit in each embodiment of the present application may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit.

[0106] If the function is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a non-volatile computer-readable storage medium that is executable by a processor. Based on this understanding, the technical solution of the present application, or the part that contributes to the prior art or the part of the technical solution, can be embodied in the form of a software product, and the computer software product is stored in a storage medium, including a number of instructions to enable a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the method described in each embodiment of the present application. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM), random access memory (RAM), disk or optical disk, etc., various media that can store program codes.

[0107] The above are only specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A method for determining a battery charging current, characterized in that: The battery charging current determination method comprises: Acquire multiple charging current groups of the battery, each charging current group including charging currents corresponding to at least one state of charge stage of charging from a first state of charge to a second state of charge; Input the multiple charging current groups into a pre-built simulated battery charging model to obtain the battery temperature change, charging time and capacity attenuation corresponding to each charging current group; Based on a multi-objective genetic algorithm, at least one candidate charging current group is determined according to each charging current group and its corresponding battery temperature change, charging time and capacity attenuation; According to a preset charging requirement, a target charging current group is determined from at least one candidate charging current group.

2. The method for determining battery charging current according to claim 1, characterized in that: At least one candidate charging current group is determined by: taking the plurality of charging current groups as parent populations; Processing the parent population by a genetic algorithm to obtain a plurality of newly added charging current groups, and using the plurality of newly added charging current groups as child populations; Inputting the subpopulation into the simulated battery charging model to obtain the battery temperature change, charging time and capacity attenuation corresponding to each newly added charging current group; According to the battery temperature change, charging time and capacity attenuation corresponding to the sub-population and the parent population respectively, performing non-dominated sorting and congestion calculation on the sub-population and the parent population; According to the results of the non-dominated sorting and the congestion calculation, a new parent population is generated, and the number of iterations is increased by one, and the process of processing the parent population by a genetic algorithm to obtain multiple newly added charging current groups is returned to and re-executed until the number of iterations reaches a preset number of iterations, and the charging current group in the Pareto solution set corresponding to the preset number of iterations is used as at least one candidate charging current group.

3. The method for determining battery charging current according to claim 2, characterized in that: Non-dominated sorting is performed in the following way: In the charging current groups of the child population and the parent population, a group of non-dominated charging current groups is determined according to the battery temperature change, the charging time and the capacity attenuation, and the non-dominated order of the group of non-dominated charging current groups is marked as one; The charging current groups with a non-dominated order of one are deleted, and the next non-dominated charging current group is determined in the remaining charging current groups according to the battery temperature change, charging time and capacity attenuation, and the non-dominated order is increased by one until the charging current groups of the child population and the parent population have determined the corresponding non-dominated order.

4. The method for determining battery charging current according to claim 3, characterized in that: The Pareto solution set corresponding to the preset number of iterations refers to a charging current group whose non-dominated order is one in the sorting result of the non-dominated sorting corresponding to the preset number of iterations.

5. The method for determining battery charging current according to claim 2, characterized in that: The congestion calculation is performed as follows: In the charging current groups of the child population and the parent population, the charging current groups are sorted according to the battery temperature change, charging time and capacity attenuation; According to the sorting results, the differences between the two adjacent charging current values ​​of each charging current group in terms of battery temperature change, charging time and capacity attenuation are calculated, and the differences are summed to obtain the congestion degree corresponding to each charging current group.

6. The method for determining battery charging current according to claim 1 or 2, characterized in that: The battery charging simulation model includes an electrochemical and thermal coupling model and a capacity decay model of the battery. Among them, the charging current corresponding to each charge state stage in the charging current group is less than or equal to the preset maximum charging current, and the preset maximum charging current refers to the maximum charging current corresponding to the negative electrode voltage value of the battery in each charge state stage predicted by the electrochemical and thermal coupling model when it is greater than zero.

7. The method for determining battery charging current according to claim 1, characterized in that: The simulated battery charging model includes an electrochemical and thermal coupling model and a capacity attenuation model of the battery. The battery temperature change, charging time and capacity attenuation corresponding to each charging current group are obtained in the following manner: Inputting each charging current group into the electrochemical and thermal coupling model to obtain the battery temperature change and charging time corresponding to each charging current group; Each charging current group and its corresponding charging time are input into the capacity decay model to obtain the capacity decay amount corresponding to each charging current group.

8. The method for determining battery charging current according to claim 7, characterized in that: The capacity attenuation model includes a stage capacity attenuation model corresponding to each state of charge stage, and the charging time corresponding to each charging current group includes the stage charging time of each state of charge stage. The capacity attenuation corresponding to each charging current group is obtained by the following method: For each charging current group, the charging current and stage charging time of the charging current group at each state of charge stage are input into the corresponding stage capacity decay model to determine the stage capacity decay amount of the charging current group at each state of charge stage; The sum of the stage capacity decay amounts of each charging current group at each state of charge stage is determined as the capacity decay amount corresponding to each charging current group.

9. The method for determining battery charging current according to claim 8, characterized in that: The stage capacity decay model corresponding to each state of charge stage is constructed in the following way: Obtaining multiple charge and discharge operations of the battery at the state of charge stage and obtaining a stage charge capacity and a stage discharge capacity corresponding to each charge and discharge operation, wherein the multiple charge and discharge operations correspond to different charge and discharge rates; Determine the stage capacity attenuation corresponding to each charge and discharge operation of the battery at the state of charge stage through the stage charge capacity and stage discharge capacity corresponding to each charge and discharge operation; According to the stage capacity decay amounts corresponding to the multiple charging operations, a stage capacity decay model corresponding to the state of charge stage is constructed.

10. A device for determining battery charging current, characterized in that: The battery charging current determining device comprises: An acquisition module, used for acquiring a plurality of charging current groups of the battery, each charging current group comprising a charging current corresponding to at least one state of charge stage of charging from a first state of charge to a second state of charge; A model prediction module, used to input the multiple charging current groups into a pre-built simulated battery charging model to obtain the battery temperature change, charging time and capacity attenuation corresponding to each charging current group; A first determination module is used to determine at least one candidate charging current group based on a multi-objective genetic algorithm according to each charging current group and its corresponding battery temperature change, charging time and capacity attenuation; The second determination module is used to determine a target charging current group from at least one candidate charging current group according to a preset charging requirement.

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