Method, device and storage medium for detecting lithium precipitation of battery

Abstract

The application discloses a method, device and storage medium for detecting lithium precipitation of a battery, and the method comprises the following steps: performing constant-current charging on the battery at a charging rate of 3C within a temperature range of-30-45 DEG C; after the voltage of the battery reaches a rated cut-off voltage, the constant-voltage charging process is converted to the constant-voltage charging process at the cut-off voltage, and the charging is stopped until the current of the battery reaches a set lower limit current; the charging current of the battery in the constant-voltage charging process is recorded to obtain a charging current-time curve; when the tangent slope of the charging current-time curve changes from a negative value to a positive value, it is determined that the lithium precipitation reaction of the battery is detected. When the negative electrode current of the battery in the constant-voltage charging process includes the lithium precipitation / lithium dissolution side reaction current, the curve characteristics of the corresponding charging current-time curve are used to realize the lithium precipitation detection of the battery.

Description

Technical Field

[0001] This application belongs to the field of battery technology, and in particular relates to a method, equipment and storage medium for detecting lithium plating in batteries. Background Technology

[0002] Lithium-ion batteries are prone to lithium plating at the negative electrode under conditions of high state of charge (SOC), low temperature, and high charging rate. Lithium plating leads to reduced cell capacity, increased impedance, and reduced safety. Therefore, non-destructive testing methods for lithium plating are particularly important for ensuring the safety and lifespan of batteries during use.

[0003] In related technologies, lithium battery charging / discharging experiments are conducted using experimental methods, and lithium plating is judged based on the voltage curve characteristics of the post-charging resting stage and the post-charging discharge process. However, due to limitations in cost and implementation methods, detecting lithium plating based on experimental methods is not applicable to all situations, and experimental methods cannot effectively detect trace amounts of lithium plating.

[0004] Once accurate battery parameter values ​​are obtained, an electrochemical model simulating the battery mechanism can be constructed. This model can simulate the internal state of the battery and reflect its working mechanism. However, there is currently no solution for detecting lithium plating in batteries based on this electrochemical model. Summary of the Invention

[0005] The purpose of this application is to provide a method, device and storage medium for detecting lithium plating in batteries. By introducing a lithium plating / lithium dissolution side reaction equation, the current curve change characteristics of the constant voltage charging stage simulated by the electrochemical model are made closer to reality, so as to realize the detection of lithium plating in batteries using simulation results.

[0006] In a first aspect, this application provides a method for detecting lithium plating in batteries, the method comprising:

[0007] Within the temperature range of -30 to 45°C, the battery is charged at a constant current rate of 3C.

[0008] After the battery voltage reaches the rated cutoff voltage, it switches to a constant voltage charging process at the cutoff voltage until the battery current reaches the set lower limit current and then charging is stopped.

[0009] Record the charging current of the battery during the constant voltage charging process to obtain the charging current-time curve;

[0010] When the slope of the tangent line of the charging current-time curve changes from a negative value to a positive value, it is determined that a lithium plating reaction has been detected in the battery.

[0011] In one possible implementation, the method further includes:

[0012] Differentiate the charging current-time curve to obtain the differential curve of the charging current-time curve;

[0013] If a characteristic peak is detected in the differential curve of the charging current-time curve, it is determined that a lithium plating reaction has been detected in the battery.

[0014] Secondly, this application provides a method for detecting lithium plating in batteries, the method comprising:

[0015] Obtain the battery parameters and initialize the model parameters of the pre-established electrochemical model used to simulate the battery mechanism;

[0016] Based on the model parameters, the electrochemical model is used to simulate the constant current charging process of the battery at a charging rate of 3C to the rated cutoff voltage within the temperature range of -30 to 45°C, and then switching to constant voltage charging at the cutoff voltage until the battery current reaches the set lower limit current and charging is stopped.

[0017] The charging current of the constant voltage charging process is simulated using the electrochemical model to obtain the simulated charging current-time curve. The simulated charging current includes the simulated lithium insertion / delithiation reaction current and lithium plating / lithium dissolution side reaction current at the negative electrode.

[0018] When the simulated charging current-time curve coincides with the measured charging current-time curve of the battery during constant voltage charging, and when the slope of the tangent of the simulated charging current-time curve changes from negative to positive, it is determined that a lithium plating reaction has been detected in the battery, and the amount of lithium plating is calculated based on the simulated lithium plating / lithium dissolution side reaction current.

[0019] In one possible implementation, the electrochemical model is used to simulate the lithium plating / lithium dissolution side reaction current at the negative electrode of the battery during the constant voltage charging process using the following formula, based on the model parameters:

[0020]

[0021]

[0022]

[0023] j Li C represents the current density for the lithium plating / lithium dissolution side reaction. Li η Li i 0，Li T and C are both parameters representing the battery state changes during the constant voltage charging process. Li η is the concentration of elemental lithium. Li i is the overpotential for the lithium plating / lithium dissolution side reaction. 0，LiThe exchange current density is denoted as , and T is the thermodynamic temperature of the battery under test.

[0024] a、C Li * k 0，Li α a，Li α c，Li C e * R, F are model parameters, a is the reactive surface area of ​​the battery's active material, and C is the reactive surface area of ​​the active material. Li * K is the concentration constant of elemental lithium. 0，Li α is the thermodynamic equilibrium constant. a，Li α is the transfer coefficient of the anodic reaction in the lithium plating / lithium dissolution side reaction. c，Li C is the transfer coefficient of the cathode reaction in the lithium plating / lithium dissolution side reaction. e * Let R be the bulk concentration of the electrolyte, R be the gas constant, and F be the Faraday constant.

[0025] In one possible implementation, the amount of lithium deposited is calculated based on the simulated lithium plating / lithium dissolution side reaction current, including:

[0026] Using the electrochemical model, the lithium plating / lithium dissolution side reaction current-time curve of the negative electrode of the battery during the constant voltage charging process was obtained based on the simulated lithium plating / lithium dissolution side reaction current.

[0027] The amount of lithium deposited in the battery is determined based on the current-time curve of the lithium plating / lithium dissolution side reaction.

[0028] In one possible implementation, determining the amount of lithium plating in the battery based on the lithium plating / lithium dissolution side reaction current-time curve includes:

[0029] The amount of lithium deposited in the battery is determined by integrating the current-time curve of the lithium plating / lithium dissolution side reaction on the time axis.

[0030] In one possible implementation, the electrochemical model is used to simulate the lithium insertion / deintercalation reaction current at the negative electrode of the battery during the constant-voltage charging process using the following formula, based on the model parameters:

[0031]

[0032]

[0033] j gr C represents the current density for the lithium insertion / delithiation reaction. s，i C e η gr i 0，grT and C are both parameters representing the battery state changes during the constant voltage charging process. s，i C represents the lithium concentration on the surface of the graphite particles. e η represents the electrolyte concentration in the localized region within the battery where lithium insertion / deintercalation reactions occur. gr i is the overpotential for the lithium insertion / delithiation reaction. 0，gr is the exchange current density of the lithium insertion / delithiation reaction, and T is the thermodynamic temperature of the battery under test;

[0034] a、α a，gr α c，gr k gr C s，max R and a are model parameters, where a is the reactive surface area of ​​the battery's active material, and α is the reactive surface area. a，gr α is the transfer coefficient of the anolyte reaction in the lithium insertion / delithiation reaction. c，gr k is the transfer coefficient of the cathode reaction in the lithium insertion / delithiation reaction. gr C is the reaction rate constant. s，max R represents the maximum solid-phase lithium concentration in the graphite material, and R is the gas constant.

[0035] In one possible implementation, the method further includes:

[0036] When the amount of lithium plating reaches a preset threshold, the system will alert the user, change the charging strategy, or prompt the user to return the device to the factory.

[0037] Thirdly, this application provides an apparatus including at least one processor; and a memory communicatively connected to the at least one processor; wherein the memory stores instructions executable by the at least one processor, the instructions being executed by the at least one processor to enable the at least one processor to perform a battery lithium plating detection method as described in any of the first aspects of this application, or to perform a battery lithium plating detection method as described in any of the second aspects of this application.

[0038] Fourthly, embodiments of this application also provide a computer-readable storage medium, wherein when the instructions in the computer-readable storage medium are executed by a processor of a terminal device, the terminal device is able to perform a battery lithium plating detection method as described in any of the first aspects of this application, or perform a battery lithium plating detection method as described in any of the second aspects of this application.

[0039] The technical solutions provided by the embodiments of this application bring at least the following beneficial effects:

[0040] The purpose of this application is to provide a method, device, and storage medium for detecting lithium plating in batteries. The lithium plating / lithium dissolution side reaction equation is obtained by correcting the traditional electrode process kinetic equation using a correction term related to lithium concentration. This makes the current curve variation characteristics of the constant voltage charging stage simulated by the electrochemical model more realistic, ensuring that when the remaining lithium metal content is close to zero, the lithium dissolution current is also close to zero. Utilizing the simulation results of the electrochemical model to detect lithium plating in batteries allows for the detection of trace or even minute amounts of lithium plating signals, improving the detection accuracy and facilitating timely adjustments to application strategies for safer battery use. Attached Figure Description

[0041] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0042] Figure 1 This is a schematic flowchart of a battery lithium plating detection method provided in an embodiment of this application;

[0043] Figure 2 Reference graph of current variation during constant voltage charging stage based on experiments provided for embodiments of this application;

[0044] Figure 3 This is a schematic flowchart of another battery lithium plating detection method provided in an embodiment of this application;

[0045] Figure 4 Simulated current curves for charging under different operating conditions provided in the embodiments of this application;

[0046] Figure 5 Differential curves of simulated current curves under different operating conditions provided in the embodiments of this application;

[0047] Figure 6 Negative electrode current decomposition curves under different operating conditions are provided for embodiments of this application;

[0048] Figure 7 Simulated lithium plating variation curves under different charging conditions provided for embodiments of this application;

[0049] Figure 8 A flowchart illustrating a management method of a battery management system (BMS) based on the aforementioned battery lithium plating detection method, provided as an embodiment of this application;

[0050] Figure 9 This is a schematic diagram of the device provided in an embodiment of this application. Detailed Implementation

[0051] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. The described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0052] Lithium plating refers to the phenomenon during charging where lithium ions, after being extracted from the positive electrode, cannot be equally inserted into the negative electrode. These uninserted lithium ions gain electrons near the negative electrode, forming elemental lithium. Lithium plating is prone to occur at the negative electrode of lithium batteries under conditions of high state of charge (SOC), low temperature, and high charging rate. Lithium plating leads to reduced cell capacity, increased impedance, and decreased safety. Therefore, non-destructive testing methods for lithium plating are crucial for ensuring battery safety and lifespan during use.

[0053] In related technologies, lithium battery charging / discharging experiments are conducted using experimental methods, and lithium plating is judged based on the voltage curve characteristics of the post-charging resting stage and the post-charging discharge process. However, due to limitations in cost and implementation methods, detecting lithium plating based on experimental methods is not applicable to all situations, and experimental methods cannot effectively detect trace amounts of lithium plating and the corresponding amount of lithium plating.

[0054] Once accurate battery parameter values ​​are obtained, an electrochemical model simulating the battery mechanism can be constructed. This model can simulate the internal state of the battery and reflect its working mechanism. However, there is currently no solution for detecting lithium plating in batteries based on this electrochemical model.

[0055] In view of the above problems, this application provides a method, device and storage medium for detecting lithium plating in batteries. The lithium plating / lithium dissolution side reaction equation is obtained by correcting the traditional electrode process kinetic equation with a correction term related to lithium concentration. This makes the current curve change characteristics of the constant voltage charging stage simulated by the electrochemical model closer to reality. Thus, the simulation results of the electrochemical model are used to detect lithium plating in batteries, which helps to adjust the application strategy in a timely manner so as to use the battery more safely.

[0056] To detect whether lithium plating occurs in a battery, it is usually necessary to conduct a certain number of charge-discharge cycle experiments at different charging rates and temperatures. By recording the charge-discharge data of the battery during the charging and discharging process, parameters that can characterize the lithium plating characteristics of the battery are extracted from it. These parameters are then post-processed to evaluate the lithium plating of the battery.

[0057] like Figure 1The diagram shown is a schematic flowchart of a battery lithium plating detection method provided in an embodiment of this application. The method includes the following steps:

[0058] Step 11: Charge the battery at a constant current rate of 3C within a temperature range of -30 to 45°C.

[0059] The charging rate is measured in C, which represents how many times the charging current during constant current charging is compared to the rated current of the battery under test. For example, if the rated current is 1A and the charging rate is set to 0.5C, then the charging current is 0.5A.

[0060] Step 12: After the battery voltage reaches the rated cutoff voltage, switch to a constant voltage charging process at the cutoff voltage until the battery current reaches the set lower limit current and then stop charging.

[0061] It should be noted that the rated cutoff voltage mentioned above can be the voltage corresponding to the battery when it reaches the set state of charge (SOC), and the set lower limit current mentioned above can be the current corresponding to the battery when it reaches the set state of charge (SOC), or it can be the rated cutoff current of the battery under test. This application does not limit it in this regard.

[0062] Step 13: Record the charging current of the battery during the constant voltage charging process to obtain the charging current-time curve;

[0063] During the battery charging and discharging process, the analyzed lithium undergoes three subsequent processes.

[0064] In process 1, during constant voltage charging, the overpotential returns to above 0V, and the deposited lithium re-inserts into the graphite anode.

[0065] In process 2, during the resting period after charging, the deposited lithium is reinserted into the graphite anode;

[0066] In process 3, the electrode is embedded into the positive electrode during the subsequent discharge process.

[0067] The above three processes are carried out in sequence. If the deposited lithium is completely reinserted into the negative electrode in a certain step, the next process will not occur. The lithium in processes 1-3 is called reversible lithium. There is also some lithium that reacts with the electrolyte to form a solid electrolyte interface (SEI film). This part of the lithium loses electrical contact with the negative electrode material and cannot return to the solution in subsequent reactions. It is called dead lithium.

[0068] Based on process 1 above, if lithium plating occurs during battery charging, the total charging current of the graphite anode during constant voltage charging should include both the lithium insertion / deintercalation reaction current and the lithium plating / lithium dissolution side reaction current.

[0069] Step 14: When the slope of the tangent line of the charging current-time curve changes from negative to positive, it is determined that a lithium plating reaction has been detected in the battery.

[0070] As a feasible implementation method, in this embodiment of the application, the current change curve during the constant voltage charging phase is used to detect whether lithium plating occurs. Figure 2 The figure shown is a reference diagram of current variation during the constant voltage charging stage based on experiments, provided in an embodiment of this application. Figure 2 The current change curve was obtained by charging a soft-pack battery with a rated capacity of 2.05A at a charging rate of 4C at an ambient temperature of 45℃. The positive electrode active material of the soft-pack battery is NCM523, the negative electrode active material is graphite, and the voltage upper and lower limits are 2.75 to 4.35V. By disassembling the battery, it can be determined that lithium plating has occurred in the tested battery.

[0071] As shown in step 13, during constant voltage charging, the total charging current of the graphite anode includes not only the lithium insertion / extraction reaction current but also the lithium plating / dissolution side reaction current. Due to the presence of this side reaction current, the rate of change of the total charging current of the graphite anode during constant voltage charging decreases. Therefore, the total charging current of the graphite anode should not decrease exponentially according to the Butler-Volmer equation, but rather decrease accordingly. Figure 2 The current change curve in the test battery shows a characteristic peak of non-exponential decline resembling a "bulge," indicating that the tangent slope of the charging current-time curve changes from a negative value to a positive value. Therefore, lithium plating in the battery can be detected by judging whether the tangent slope of the charging current-time curve changes from a negative value to a positive value during constant voltage charging.

[0072] In one or more embodiments, in addition to detecting lithium plating by determining whether the slope of the tangent of the charging current-time curve changes from a negative value to a positive value, lithium plating can also be detected by determining whether there is an upward characteristic peak in the differential curve of the charging current-time curve.

[0073] As a feasible implementation method, lithium plating in the battery is detected by determining whether a rising characteristic peak exists in the differential curve of the charging current-time curve, including:

[0074] Differentiate the charging current-time curve to obtain the differential curve of the charging current-time curve;

[0075] If a characteristic peak is detected in the differential curve of the charging current-time curve, it is determined that a lithium plating reaction has been detected in the battery.

[0076] Due to limitations in cost and implementation methods, implementation was based on experimental methods. Figure 1The method for detecting lithium plating in batteries shown is not applicable to all situations, therefore, as Figure 3 As shown in the schematic diagram, another battery lithium plating detection method provided in this application embodiment includes the following steps:

[0077] Step 31: Obtain the battery parameters and initialize the model parameters of the pre-established electrochemical model used to simulate the battery mechanism;

[0078] For example, this application selects a pseudo-two-dimensional (P2D) lithium battery model as the electrochemical model for simulating battery mechanism. Other electrochemical models for simulating battery mechanism may also be selected in other embodiments, and this application does not limit this.

[0079] The P2D model, based on porous electrode theory and concentrated solution theory, is the most commonly used electrochemical model for studying the internal state of batteries. The P2D model consists of a set of partial differential equations with numerous parameters, clearly describing the internal working mechanism of the battery, including diffusion transport, ion migration, and electrochemical reactions. Therefore, using the P2D model allows for a better understanding of the battery's working mechanism, correlating the battery's internal state with its external behavior. When accurate model parameter values ​​are obtained, the P2D model can accurately simulate the battery's internal state during charging and discharging. To simulate the changes in the battery state of the tested battery under set operating conditions using an electrochemical model, and further simulate the current changes of the tested battery during the constant voltage charging phase, it is necessary to obtain the battery parameters of the tested battery and use these battery parameters to initialize the pre-established electrochemical model used to simulate the battery mechanism. The battery parameters of the tested battery are derived from the actual parameters of the tested battery itself.

[0080] Step 32: Based on the model parameters, the electrochemical model is used to simulate the constant current charging process of the battery at a charging rate of 3C to the rated cutoff voltage within the temperature range of -30 to 45°C, and then switching to constant voltage charging at the cutoff voltage until the battery current reaches the set lower limit current and charging is stopped.

[0081] Step 33: Use the electrochemical model to simulate the charging current of the constant voltage charging process to obtain the simulated charging current-time curve. The simulated charging current includes the simulated lithium insertion / delithiation reaction current and lithium plating / lithium dissolution side reaction current of the negative electrode.

[0082] Based on the Butler-Volmer equation, the above P2D electrochemical model can simulate the current change of the battery during the charging process based on the set model parameters.

[0083] Refer again Figure 2It can be seen that when lithium plating occurs in the battery, the rate of change of current decreases, and the corresponding reaction current density should also show a decreasing trend. The current change curve of the corresponding constant voltage charging process shows a process in which the tangent slope changes from a negative value to a positive value, and a characteristic peak of non-exponential decrease appears, resembling a "bulge". Currently, when using the Butler-Volmer equation to simulate the current change of the battery during the charging process, when the lithium deposited before the negative electrode dissolves again, the lithium metal concentration gradually approaches zero, and the reaction rate (i.e., the reaction current density) still shows an increasing trend, which is inconsistent with reality.

[0084] Therefore, embodiments of this application introduce a correction term C related to lithium concentration. Li The lithium plating / lithium dissolution side reaction equation obtained by correcting the traditional Butler-Volmer equation is used to simulate the lithium plating / lithium dissolution side reaction current during battery charging, so that the current curve change characteristics of the constant voltage charging stage simulated by the electrochemical model are closer to reality.

[0085] As a feasible implementation method, this application embodiment utilizes the electrochemical model and employs the following Butler-Volmer equation to simulate the lithium insertion / deintercalation reaction current in the negative electrode charging current based on the model parameters:

[0086]

[0087]

[0088] j gr C represents the current density for the lithium insertion / delithiation reaction. s，i C e η gr i 0，gr T and C are both parameters representing the battery state changes during the constant voltage charging process. s，i C represents the lithium concentration on the surface of the graphite particles. e η represents the electrolyte concentration in the localized region within the battery where lithium insertion / deintercalation reactions occur. gr i is the overpotential for the lithium insertion / delithiation reaction. 0，gr is the exchange current density of the lithium insertion / delithiation reaction, and T is the thermodynamic temperature of the battery under test;

[0089] a、α a，gr α c，gr k gr C s，max R and a are model parameters, where a is the reactive surface area of ​​the battery's active material, and α is the reactive surface area. a，gr α is the transfer coefficient of the anolyte reaction in the lithium insertion / delithiation reaction. c，gr k is the transfer coefficient of the cathode reaction in the lithium insertion / delithiation reaction. gr C is the reaction rate constant.s，max R represents the maximum solid-phase lithium concentration in the graphite material, and R is the gas constant.

[0090] As a feasible implementation method, this application embodiment utilizes the electrochemical model and employs the following Butler-Volmer equation, based on the model parameters, to simulate the lithium plating / lithium dissolution side reaction current in the negative electrode charging current:

[0091]

[0092]

[0093]

[0094] j Li C represents the current density for the lithium plating / lithium dissolution side reaction. Li η Li i 0，Li T and C are both parameters representing the battery state changes during the constant voltage charging process. Li η is the concentration of elemental lithium. Li i is the overpotential for the lithium plating / lithium dissolution side reaction. 0，Li The exchange current density is denoted as , and T is the thermodynamic temperature of the battery under test.

[0095] a、C Li * k 0，Li α a，Li α c，Li C e * R, F are model parameters, a is the reactive surface area of ​​the battery's active material, and C is the reactive surface area of ​​the active material. Li * K is the concentration constant of elemental lithium. 0，Li α is the thermodynamic equilibrium constant. a，Li α is the transfer coefficient of the anodic reaction in the lithium plating / lithium dissolution side reaction. c，Li C is the transfer coefficient of the cathode reaction in the lithium plating / lithium dissolution side reaction. e * Let R be the bulk concentration of the electrolyte, R be the gas constant, and F be the Faraday constant.

[0096] Equation (3) serves to ensure that matter conforms to the law of conservation.

[0097] It should be noted that the concentration constant C of the above-mentioned elemental lithium... Li * The coefficient used to eliminate the concentration-related coefficient of lithium in the formula. The dimensions of the term.

[0098] It should be noted that the current density of the reaction obtained from the above two sets of formulas is in amperes per square meter. Multiplying it by the cross-sectional area of ​​the negative electrode will give the corresponding reaction current.

[0099] Step 34: When the simulated charging current-time curve coincides with the measured charging current-time curve of the battery during constant voltage charging, and when the slope of the tangent of the simulated charging current-time curve changes from negative to positive, it is determined that a lithium plating reaction has been detected in the battery, and the amount of lithium plating is calculated based on the simulated lithium plating / lithium dissolution side reaction current.

[0100] Based on the aforementioned two sets of formulas, the electrochemical model can simulate the charging current of the negative electrode, the lithium insertion / delithiation reaction current, and the lithium plating / lithium dissolution side reaction current. The charging current of the negative electrode can be obtained by adding the lithium insertion / delithiation reaction current and the lithium plating / lithium dissolution side reaction current.

[0101] During constant-voltage charging, when the overpotential returns above 0V, the deposited lithium metal dissolves, leading to a decrease in lithium metal concentration. Based on the aforementioned lithium deposition / dissolution side reaction equation, when the lithium metal concentration decreases to a certain value, the coefficient related to the concentration of elemental lithium approaches 0, causing the lithium metal concentration to gradually approach zero. As a result, the simulated rate of change of the negative electrode charging current during constant-voltage charging shows a decreasing trend, which is consistent with reality.

[0102] In one or more embodiments, when the simulated charging current-time curve of the battery during constant voltage charging coincides with the measured charging current-time curve of the battery during constant voltage charging, and the slope of the tangent of the simulated charging current-time curve changes from negative to positive, the simulation results of the characterization model are consistent with reality, and the amount of lithium plating can be calculated based on the simulated lithium plating / lithium dissolution side reaction current using the model.

[0103] In one or more embodiments, by analyzing the results output by the model, it can be determined at what set temperature and charging rate the battery under test will undergo lithium plating and output the corresponding amount of lithium plating. Therefore, by using the electrochemical model, trace amounts or even trace amounts of lithium plating signals can be detected, which improves the detection accuracy of lithium plating and helps to adjust the battery application strategy in a timely manner so as to use the battery more safely.

[0104] In the embodiments of this application, at least one of the following three methods is used to determine whether a lithium plating reaction in the battery is detected.

[0105] Method 1: Based on the simulated charging current-time curve, determine whether lithium plating reaction of the battery is detected.

[0106] In one or more embodiments, a lithium plating reaction is determined to have been detected when the simulated charging current-time curve coincides with the measured charging current-time curve of the battery during constant voltage charging and the slope of the tangent of the simulated charging current-time curve changes from negative to positive.

[0107] Method 2: Determine whether lithium plating reaction is detected based on the differential curve of the simulated charging current-time curve.

[0108] In one or more embodiments, the simulated charging current-time curve is differentiated to obtain the differential curve of the charging current-time curve. If the differential curve of the simulated charging current-time curve coincides with the differential curve of the battery charging current-time curve during the actual constant voltage charging process and a characteristic peak is present, it is determined that a lithium plating reaction of the battery has been detected.

[0109] Method 3: Based on the simulated lithium plating / lithium dissolution side reaction current-time curve, determine whether lithium plating reaction of the battery is detected.

[0110] In one or more embodiments, when the simulated charging current-time curve coincides with the measured charging current-time curve of the battery during constant voltage charging, it indicates that the simulation results are close to reality. At this time, the electrochemical model is used to obtain the lithium plating / lithium dissolution side reaction current-time curve based on the simulated changes in lithium plating / lithium dissolution side reaction current during the constant voltage charging stage.

[0111] Based on the lithium plating / lithium dissolution side reaction current-time curve, when the lithium plating / lithium dissolution side reaction current is detected, it is determined that a lithium plating reaction in the battery has been detected.

[0112] In one or more embodiments, the amount of lithium deposited in the battery is determined based on the current-time curve of the lithium plating / lithium dissolution side reaction.

[0113] As a feasible implementation method, the amount of lithium plating in the battery is determined based on the current-time curve of the lithium plating / lithium dissolution side reaction, including:

[0114] The amount of lithium deposited in the battery is determined by integrating the current-time curve of the lithium plating / lithium dissolution side reaction on the time axis.

[0115] In one or more embodiments, when the amount of lithium plating reaches a preset threshold, the user is alerted, the charging strategy is changed, or a return to the factory is requested.

[0116] It should be noted that, in the embodiments of this application, the reminder operation performed after determining that the lithium plating amount has reached the preset threshold is not limited to warning the user, changing the charging strategy, or prompting the user to return to the factory. It can also be a reminder method such as uploading data to the backend or reminding the user by customer service phone. This application does not limit this.

[0117] The following provides a specific implementation method for the battery lithium plating detection method provided in this application.

[0118] First, an electrochemical model was established based on the battery under test with a ternary cathode and a graphite anode. The voltage range of the battery is 2.8-4.35V, and the 1C current is 2A.

[0119] After establishing the electrochemical model, the model was run under simulated operating conditions. The simulated operating conditions were: starting from 3.56V at an ambient temperature of 25℃, constant current charging and constant voltage charging were performed at six different charging rates of 1C, 1.5C, 2C, 2.5C, 3C, and 3.5C to 4.35V, and then the model was left to stand until the running time reached 4500s.

[0120] like Figure 4 As shown, the simulated current curves for charging under different operating conditions provided in the embodiments of this application can be seen within the dashed box. Under the three charging rates of 2.5C, 3C, and 3.5C, the slope of the tangent line of the current curve changes from negative to positive. That is, when there is a characteristic peak of non-exponential decrease, it means that the battery under test will exhibit lithium plating when charged at the three charging rates of 2.5C, 3C, and 3.5C at an ambient temperature of 25°C.

[0121] like Figure 5 As shown, the differential curves of the simulated current curves under different charging conditions provided in the embodiments of this application can be seen. It can be seen that under the three charging rate conditions of 2.5C, 3C and 3.5C, the differential curves have rising characteristic peaks, which means that the battery under test will exhibit lithium plating when charged at the three charging rates of 2.5C, 3C and 3.5C at an ambient temperature of 25°C.

[0122] like Figure 6 The figure shows the negative electrode current decomposition curves under different charging conditions provided in the embodiments of this application. The dashed line represents the lithium plating / lithium dissolution side reaction current curve, and the solid line represents the lithium insertion / deposition reaction current curve. It can be seen that the sum of the absolute values ​​of the lithium plating / lithium dissolution side reaction current and the absolute values ​​of the lithium insertion / deposition reaction current equals... Figure 4 The magnitude of the charging current at the same time.

[0123] like Figure 7 The figure shows simulated lithium plating variation curves under different charging conditions provided in the embodiments of this application. Figure 4It is known that the battery under test will exhibit lithium plating when charged at three charging rates (2.5C, 3C, and 3.5C) at an ambient temperature of 25℃. Accordingly, based on... Figure 6 The integral of the lithium plating / lithium dissolution side reaction current-time curves on the time axis at three charging rates (2.5C, 3C, and 3.5C) determines the following: Figure 7 The changes in lithium plating of the tested battery at ambient temperature of 25℃ and charging rates of 2.5C, 3C, and 3.5C are shown. It can be seen that the change in lithium plating is greatest when charging at a charging rate of 3.5C.

[0124] Based on the lithium plating detection method provided in this application, the lithium plating / lithium dissolution side reaction equation is obtained by correcting the traditional Butler-Volmer equation using a correction term related to lithium concentration. This makes the current curve change characteristics of the constant voltage charging stage simulated by the electrochemical model closer to reality, ensuring that when the remaining lithium metal content is close to zero, the lithium dissolution current is also close to zero. The simulation results of the electrochemical model are used to detect lithium plating in the battery and dynamically decompose the reaction current of the negative electrode to output the change in the amount of lithium plating in real time. This method can detect trace amounts or even trace amounts of lithium plating signals, improve the detection accuracy of lithium plating, and help to adjust application strategies in a timely manner for safer battery use.

[0125] Based on the same inventive concept, such as Figure 8 As shown, this application embodiment also provides a management method for a battery management system (BMS) based on the aforementioned battery lithium plating detection method, the method comprising the following steps:

[0126] Step 81: Real-time acquisition of charging parameters and battery parameters of the monitored battery;

[0127] Step 82: Using the charging parameters and battery parameters, based on the pre-established electrochemical model for simulating battery mechanism, simulate the charging current-time curve and lithium plating / lithium dissolution side reaction current-time curve of the monitored battery during the constant voltage charging stage.

[0128] Step 83: When it is detected that the simulated charging current-time curve coincides with the measured charging current-time curve of the battery during constant voltage charging, and when it is detected that the slope of the tangent of the simulated charging current-time curve changes from a negative value to a positive value, the amount of lithium plating in the monitored battery is determined based on the lithium plating / lithium dissolution side reaction current-time curve of the monitored battery. When it is determined that the amount of lithium plating reaches a threshold, the user is alerted, the charging strategy is changed, or a return to the factory is prompted.

[0129] The specific implementation method of the battery management system (BMS) based on the aforementioned battery lithium plating detection method can be referred to the aforementioned embodiment of the battery lithium plating detection method, and will not be repeated here.

[0130] Based on the same inventive concept, this application also provides a device 900, such as... Figure 9 As shown, it includes at least one processor 902; and a memory 901 communicatively connected to the at least one processor; wherein the memory stores instructions executable by the at least one processor, the instructions being executed by the at least one processor to enable the at least one processor to perform the above-described battery lithium plating detection method.

[0131] The memory 901 is used to store programs. Specifically, the program may include program code, which includes computer operation instructions. The memory 901 may be volatile memory, such as random-access memory (RAM); it may also be non-volatile memory, such as flash memory, hard disk drive (HDD), or solid-state drive (SSD); or it may be any one or a combination of the above-mentioned volatile and non-volatile memory types.

[0132] The processor 902 can be a central processing unit (CPU), a network processor (NP), or a combination of a CPU and an NP. It can also be a hardware chip. This hardware chip can be an application-specific integrated circuit (ASIC), a programmable logic device (PLD), or a combination thereof. The PLD can be a complex programmable logic device (CPLD), a field-programmable gate array (FPGA), a generic array logic (GAL), or any combination thereof.

[0133] Based on the same inventive concept, embodiments of this application provide a computer program medium, wherein the computer storage medium stores a computer program, the computer program being used to cause a computer to execute the above-described method for detecting lithium plating in batteries.

[0134] The aforementioned storage medium may be a non-transitory computer-readable storage medium, such as a ROM, random access memory (RAM), CD-ROM, magnetic tape, floppy disk, and optical data storage device.

[0135] In the above embodiments, implementation can be achieved, in whole or in part, through software, hardware, firmware, or any combination thereof. When implemented in software, it can be implemented, in whole or in part, as a computer program product.

[0136] The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, all or part of the processes or functions described in the embodiments of this application are generated. The computer may be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions may be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another. For example, the computer instructions may be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via wired (e.g., coaxial cable, fiber optic, digital subscriber line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) means. The computer-readable storage medium may be any available medium that a computer can store or a data storage device such as a server or data center that integrates one or more available media. The available medium may be a magnetic medium (e.g., floppy disk, hard disk, magnetic tape), an optical medium (e.g., DVD), or a semiconductor medium (e.g., solid-state disk (SSD)).

[0137] The technical solutions provided in this application have been described in detail above. Specific examples have been used in this application to illustrate the principles and implementation methods of this application. The description of the above embodiments is only for the purpose of helping to understand the method and core ideas of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

[0138] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0139] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to this application. It should be understood by those skilled in the art from the computer program instructions that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of one or more computer-usable storage media containing computer-usable program code (implementing each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams). These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create a machine for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0140] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0141] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0142] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.

Claims

1. A method for detecting lithium plating in batteries, characterized in that, include: Obtain the battery parameters and initialize the model parameters of the pre-established electrochemical model used to simulate the battery mechanism; Based on the model parameters, the electrochemical model is used to simulate the constant current charging process of the battery at a charging rate of 3C to the rated cutoff voltage within the temperature range of -30~45℃, and then switching to constant voltage charging at the cutoff voltage until the battery current reaches the set lower limit current and charging is stopped. The charging current of the constant voltage charging process is simulated using the electrochemical model to obtain the simulated charging current-time curve. The simulated charging current includes the simulated lithium insertion / delithiation reaction current and lithium plating / lithium dissolution side reaction current at the negative electrode. When the simulated charging current-time curve coincides with the measured charging current-time curve of the battery during constant voltage charging, and when the slope of the tangent of the simulated charging current-time curve changes from negative to positive, it is determined that a lithium plating reaction has been detected in the battery, and the amount of lithium plating is calculated based on the simulated lithium plating / lithium dissolution side reaction current. Using the electrochemical model and the following formula, based on the model parameters, the lithium plating / lithium dissolution side reaction current at the negative electrode of the battery during the constant voltage charging process is simulated: The current density is for the lithium plating / lithium dissolution side reaction. These are all parameters representing changes in the battery state during the constant voltage charging process. This represents the concentration of elemental lithium. This is the overpotential for the lithium plating / lithium dissolution side reaction. The exchange current density is denoted as , and T is the thermodynamic temperature of the battery under test. Here, represents the model parameters, and 'a' represents the reactive surface area of ​​the battery's active material. Let be the concentration constant of elemental lithium. It is the thermodynamic equilibrium constant. The transfer coefficient of the anodic reaction in the lithium plating / lithium dissolution side reaction is given. The transfer coefficient of the cathode reaction in the lithium plating / lithium dissolution side reaction is given. Let R be the bulk concentration of the electrolyte, R be the gas constant, and F be the Faraday constant.

2. The method according to claim 1, characterized in that, The amount of lithium deposited is calculated based on the simulated lithium plating / lithium dissolution side reaction current, including: Using the electrochemical model, the lithium plating / lithium dissolution side reaction current-time curve of the negative electrode of the battery during the constant voltage charging process was obtained based on the simulated lithium plating / lithium dissolution side reaction current. The amount of lithium deposited in the battery is determined based on the current-time curve of the lithium plating / lithium dissolution side reaction.

3. The method according to claim 2, characterized in that, Based on the current-time curve of the lithium plating / lithium dissolution side reaction, the amount of lithium plating in the battery is determined, including: The amount of lithium deposited in the battery is determined by integrating the current-time curve of the lithium plating / lithium dissolution side reaction on the time axis.

4. The method according to claim 1, characterized in that, Using the electrochemical model and the following formula, based on the model parameters, the lithium insertion / deintercalation reaction current at the negative electrode of the battery during the constant voltage charging process is simulated: This represents the current density for the lithium insertion / delithiation reaction. These are all parameters representing changes in the battery state during the constant voltage charging process. The lithium concentration on the surface of the graphite particles. This refers to the electrolyte concentration in the localized region within the battery where lithium insertion / deintercalation reactions occur. This is the overpotential for the lithium insertion / delithiation reaction. is the exchange current density of the lithium insertion / delithiation reaction, and T is the thermodynamic temperature of the battery under test; All are model parameters, where 'a' represents the reactive surface area of ​​the battery's active material. is the transfer coefficient of the anolyte reaction in the lithium insertion / delithiation reaction. is the transfer coefficient of the cathode reaction in the lithium insertion / delithiation reaction. The reaction rate constant is... R represents the maximum solid-phase lithium concentration in the graphite material, and R is the gas constant.

5. The method according to claim 2, characterized in that, Also includes: When the amount of lithium plating reaches a preset threshold, the system will alert the user, change the charging strategy, or prompt the user to return the device to the factory.

6. A device, characterized in that, The method includes at least one processor; and a memory communicatively connected to the at least one processor; wherein the memory stores instructions executable by the at least one processor to enable the at least one processor to perform the method as described in any one of claims 1-5.

7. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores computer instructions that, when executed on a computer, cause the computer to perform the method as described in any one of claims 1-5.

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