Battery and method, device and system for estimating state of health (SOH) thereof

Abstract

The application provides a battery and a SOH estimation method, device and system thereof. The battery comprises an indicator electrode and a first electrode. The rated capacity of the indicator electrode is less than that of the first electrode. The first static voltage of the first electrode after the terminal voltage of the first electrode changes from a first voltage to a second voltage is obtained, and the second static voltage of the indicator electrode after the terminal voltage of the first electrode changes from the first voltage to the second voltage and is connected in parallel with the indicator electrode with the initial terminal voltage being the second voltage is obtained. The capacity difference when the terminal voltage of the indicator electrode changes from the second voltage to the second static voltage is calculated as the real-time capacity difference corresponding to the terminal voltage of the first electrode changing from the first static voltage to the second static voltage. The standard capacity difference corresponding to the terminal voltage of the first electrode changing from the first static voltage to the second static voltage is calculated. The SOH value of the battery is obtained by dividing the real-time capacity difference by the standard capacity difference. The SOH state of the battery is calculated in the manner of detecting the change of the terminal voltage, which is low in cost and can be conveniently applied to the vehicle end.

Description

Technical Field

[0001] This application relates to the field of power battery technology for electric vehicles, and in particular to a battery and its SOH estimation method, apparatus and system. Background Technology

[0002] Lithium-ion batteries, as a driving force for new energy vehicles, have been widely used in the field due to their green, environmentally friendly, recyclable, and small size characteristics. With the widespread adoption of electric vehicles, the safety of lithium-ion power batteries (hereinafter referred to as batteries) has become increasingly prominent. State of health (SOH) reflects the battery's healthy lifespan, including its charge, energy, and charge / discharge power. Accurate assessment of SOH allows for a comprehensive understanding of the battery's current condition, enabling maintenance plans to be developed based on underlying assumptions, correcting various performance parameters, reducing or avoiding risks, and replacing individual cells whose performance does not meet usage requirements, thereby reducing operating costs.

[0003] Among related technologies, the traditional coulomb counting method, while the most accurate, requires a full charge and discharge cycle, resulting in extremely low efficiency and making it unsuitable for practical vehicle applications. Electrochemical impedance spectroscopy (EIS) measurement, while highly practical, necessitates adding EIS measurement equipment to the vehicle, significantly increasing costs, and there is no clear direct interpretation between EIS and battery state of equilibrium (SOH). Methods that infer SOH using curves such as Differential Potential Analysis (DTV), Differential Terminal Voltage (DVA), and Incremental Capacity Analysis (ICA) present technical challenges, including difficulties in smoothing the curves and their susceptibility to variations in sampling frequency, temperature, and charge / discharge rate. Summary of the Invention

[0004] The purpose of this application is to provide a battery and its SOH estimation method, device and system, which calculates the real-time SOH state of the battery by pre-installing an indicator electrode inside the battery and measuring the small changes in the terminal voltage during battery operation. This method is low in cost and can be easily applied to the whole vehicle.

[0005] In a first aspect, this application provides a method for estimating the state of harmonics (SOH) of a battery. The battery includes an indicator electrode and a first electrode. The rated capacity of the indicator electrode is less than the rated capacity of the first electrode. The method includes: obtaining a first resting voltage after the terminal voltage of the first electrode changes from a first voltage to a second voltage, and a second resting voltage after the terminal voltage of the first electrode changes from the first voltage to the second voltage and is connected in parallel with the indicator electrode whose initial terminal voltage is the second voltage; calculating the capacity difference when the terminal voltage of the indicator electrode changes from the second voltage to the second resting voltage, as the real-time capacity difference when the terminal voltage of the first electrode changes from the first resting voltage to the second resting voltage; and calculating the standard capacity difference when the terminal voltage of the first electrode changes from the first resting voltage to the second resting voltage; and obtaining the SOH value of the battery by dividing the real-time capacity difference by the standard capacity difference.

[0006] Furthermore, the step of obtaining the first resting voltage after the terminal voltage of the first electrode changes from the first voltage to the second voltage includes: adjusting the electrode load of the first electrode so that the terminal voltage of the first electrode is the first voltage; charging / discharging the first electrode, and stopping the charging / discharging when the first voltage changes to the second voltage; detecting the current terminal voltage of the first electrode when the terminal voltage change of the first electrode within a specified time is less than a preset voltage threshold, and obtaining the first resting voltage.

[0007] Further, the step of obtaining the second static voltage after the first electrode changes from the first voltage to the second voltage and is connected in parallel with the indicator electrode whose initial terminal voltage is the second voltage includes: adjusting the electrode load of the first electrode and the indicator electrode respectively so that the terminal voltage of the first electrode is the first voltage and the terminal voltage of the indicator electrode is the second voltage; connecting the first electrode to the charging / discharging circuit for charging / discharging, and stopping charging / discharging when the first voltage changes to the second voltage; simultaneously connecting the indicator electrode in parallel to the charging / discharging circuit of the first electrode; and detecting the current terminal voltage of the first electrode when the terminal voltage change of the first electrode within a specified time is less than a preset voltage threshold to obtain the second static voltage.

[0008] Furthermore, the positive and negative terminals of the aforementioned indicator electrode are not connected to the positive and negative terminals of the first electrode; the step of adjusting the electrode load for the first electrode and the indicator electrode respectively includes: when the positive and negative terminals of the first electrode are connected to the load adjustment circuit, the first electrode is loaded with a first preset current until the terminal voltage is the first voltage; when the positive and negative terminals of the indicator electrode are connected to the load adjustment circuit, the indicator electrode is loaded with a second preset current until the terminal voltage is the second voltage; when the first voltage is less than the second voltage, the first preset current is less than the second preset current; when the first voltage is greater than the second voltage, the first preset current is greater than the second preset current.

[0009] Furthermore, the step of connecting the first electrode to the charging / discharging circuit for charging / discharging includes: connecting the positive and negative terminals of the first electrode to the charging / discharging circuit, and charging / discharging the first electrode with a third preset current; the third preset current is greater than the maximum value of the first preset current and the second preset current.

[0010] Further, the step of calculating the capacity difference when the terminal voltage of the indicator electrode changes from the second voltage to the second resting voltage includes: finding the first SOC value corresponding to the second voltage and the second SOC value corresponding to the second resting voltage from the OCV-SOC curve corresponding to the indicator electrode; calculating the difference between the first SOC value and the second SOC value to obtain the first SOC difference; and calculating the product of the first SOC difference and the rated capacity of the indicator electrode to obtain the capacity difference when the terminal voltage of the indicator electrode changes from the second voltage to the second resting voltage.

[0011] Furthermore, the step of calculating the standard capacity difference corresponding to the change in terminal voltage of the first electrode from the first set voltage to the second set voltage includes: finding the third SOC value corresponding to the first set voltage and the fourth SOC value corresponding to the second set voltage from the OCV-SOC curve corresponding to the first electrode; calculating the difference between the third SOC value and the fourth SOC value to obtain the second SOC difference; and calculating the product of the second SOC difference and the rated capacity corresponding to the first electrode to obtain the standard capacity difference corresponding to the change in terminal voltage of the first electrode from the first set voltage to the second set voltage.

[0012] Further, the target electrode includes an indicator electrode or a first electrode; the process of plotting the OCV-SOC curve of the target electrode is as follows: the target electrode is charged and discharged using a specified current; during the charging and discharging processes, the open-circuit voltage and the corresponding SOC value are collected; based on the open-circuit voltage and SOC value during the charging process, a first OCV-SOC curve is plotted with SOC as the horizontal axis and OCV as the vertical axis; based on the open-circuit voltage and SOC value during the discharging process, a second OCV-SOC curve is plotted with SOC as the horizontal axis and OCV as the vertical axis; the average of the vertical axes of the first OCV-SOC curve and the second OCV-SOC curve is taken to obtain the OCV-SOC curve of the target electrode.

[0013] Furthermore, the constituent material of the aforementioned indicator electrode is a material with a high specific surface area, including one of the following: activated carbon, graphene, or acetylene black.

[0014] Secondly, this application also provides a battery SOH estimation device, the battery including an indicator electrode and a first electrode; the rated capacity of the indicator electrode is less than the rated capacity of the first electrode; the device includes: a voltage acquisition module, used to acquire a first resting voltage after the terminal voltage of the first electrode changes from a first voltage to a second voltage, and a second resting voltage after the terminal voltage of the first electrode changes from the first voltage to the second voltage and is connected in parallel with the indicator electrode whose initial terminal voltage is the second voltage; a rated capacity difference calculation module, used to calculate the capacity difference when the terminal voltage of the indicator electrode changes from the second voltage to the second resting voltage, as the real-time capacity difference corresponding to the terminal voltage of the first electrode changing from the first resting voltage to the second resting voltage; and to calculate the standard capacity difference corresponding to the terminal voltage of the first electrode changing from the first resting voltage to the second resting voltage; and an SOH calculation module, used to divide the real-time capacity difference by the standard capacity difference to obtain the SOH value of the battery.

[0015] Thirdly, this application also provides a battery SOH estimation system, the system including a controller and a battery including an indicator electrode and a first electrode; the rated capacity of the indicator electrode is less than the rated capacity of the first electrode; the controller is used to perform the method as described in the first aspect.

[0016] Fourthly, this application also provides a battery, the battery including an indicator electrode and a first electrode; the rated capacity of the indicator electrode is less than the rated capacity of the first electrode; the SOH value of the battery is determined by the method as described in the first aspect.

[0017] Furthermore, the aforementioned first electrode comprises multiple electrodes; the multiple first electrodes are stacked; the positive and negative terminals of the stacked first electrodes are not connected to the positive and negative terminals of the indicator electrode. The battery, its SOH estimation method, apparatus, and system provided in this application include an indicator electrode and a first electrode; the rated capacity of the indicator electrode is less than the rated capacity of the first electrode; firstly, the first resting voltage of the first electrode after its terminal voltage changes from a first voltage to a second voltage is obtained, and the second resting voltage after the first voltage changes to the second voltage and is connected in parallel with the indicator electrode whose initial terminal voltage is the second voltage is obtained; then, the capacity difference when the terminal voltage of the indicator electrode changes from the second voltage to the second resting voltage is calculated as the real-time capacity difference when the terminal voltage of the first electrode changes from the first resting voltage to the second resting voltage; and the standard capacity difference when the terminal voltage of the first electrode changes from the first resting voltage to the second resting voltage is calculated; finally, the SOH value of the battery is obtained by dividing the real-time capacity difference by the standard capacity difference. This application calculates the real-time SOH state of the battery by pre-installing an indicator electrode inside the battery and by measuring the small changes in the terminal voltage during battery operation, which is low-cost and can be easily applied to vehicle-mounted systems. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the specific embodiments of this application or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0019] Figure 1 A schematic diagram of a battery structure with an indicator electrode provided for an embodiment of this application; Figure 2 A schematic diagram of the external structure of a battery with an indicator electrode provided in an embodiment of this application; Figure 3 A flowchart illustrating a method for estimating the state of harm (SOH) of a battery, as provided in this application embodiment; Figure 4 This application provides a schematic diagram of a SOH estimation process. Figure 5 A circuit diagram provided for an embodiment of this application; Figure 6 A schematic diagram of test data provided in an embodiment of this application; Figure 7 An OCV-SOC curve of an indicator electrode provided for an embodiment of this application; Figure 8 An OCV-SOC curve of a first electrode provided in an embodiment of this application; Figure 9 This is a structural block diagram of a battery SOH estimation device provided in an embodiment of this application. Detailed Implementation

[0020] The technical solutions of this application will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0021] SOH estimation methods can be divided into two types: direct measurement and indirect measurement.

[0022] The direct measurement method refers to analyzing the collected experimental data such as current, voltage, and temperature of the power battery to obtain certain characteristic parameters that can reflect the degradation of the power battery, thereby achieving the calibration of the power battery's SOH.

[0023] Coulomb counting (CC) is the simplest and most direct method for estimating State of Charge (SOH). It involves two steps: First, determine the battery's Qact by discharging the battery to 0% State of Charge (SOC) and integrating the discharge current over time. Second, divide Qact by the nominal capacity Qnom to obtain the SOH value.

[0024] The main battery parameters that this method needs to measure and control are: charge / discharge current, voltage, capacity, and temperature. If two of these parameters are calculated in each discharge cycle, the method can easily be transformed into an adaptive approach. During charge / discharge cycles, it can be observed that the Qact value decreases continuously with the increase in the number of charge / discharge cycles, leading to a continuous decrease in the SOH value as the battery is used. Clearly, the accuracy of this method is highly dependent on the precision of the measuring equipment, therefore, regular calibration of the measuring equipment is necessary.

[0025] Electrochemical impedance spectroscopy (EIS) is a non-destructive method for parameter determination and an effective method for measuring battery kinetics. A small-amplitude sinusoidal voltage signal with frequency w1 is applied to the battery system, which generates a sinusoidal current response with frequency w2. The change in the ratio of the excitation voltage to the response current is the impedance spectrum of the electrochemical system.

[0026] Electrochemical interfacial reaction (EIS) is highly practical, as this testing method can achieve wide-range electrochemical interfacial reaction studies from very low frequency scans (a few μHz) to very high frequencies (a few MHz). Currently, most domestic research is still in the early exploratory stage, focusing primarily on EIS curve analysis and related electrochemical interpretation.

[0027] The State of Health (SOH) estimation method based on sample entropy of discharge voltage is an indirect approach. Sample entropy is extracted from the discharge curve and input into the Relative Dynamic Valve Model (RVM) to estimate the SOH. Sample entropy provides a calculation method for assessing the predictability of time series data and quantifies the regularity of the data sequence. Therefore, when applied to discharge temperature data, it can serve as an indicator of battery health, effectively capturing battery degradation processes and localized changes. A smoothed capacity increment curve is fitted, peak values ​​and their locations are extracted, and a function relating the SOH to the peak value is established to estimate the SOH.

[0028] However, smoothing DTV, DVA, and ICA curves has always been a challenge. The same variable extracted using different smoothing techniques may not be equal, and curves with different sampling frequencies also differ. Temperature and charge / discharge rates also affect model parameters. Therefore, the performance of the above three methods is not stable.

[0029] Based on this, embodiments of this application provide a battery and its SOH estimation method, apparatus and system. By pre-setting an indicator electrode inside the battery and measuring the minute changes in the terminal voltage during battery operation, the real-time SOH state of the battery is calculated. This method is low-cost and can be easily applied to the whole vehicle.

[0030] To facilitate understanding of this embodiment, the structure of a battery disclosed in this application embodiment will be described in detail first. This application provides a battery, see embodiment of the present application. Figure 1 As shown, the battery includes an indicator electrode and first electrodes; there can be one or more first electrodes; the figure shows multiple first electrodes; the first electrode is actually a conventional electrode structure for lithium batteries, such as a conventional positive electrode + separator + negative electrode combination; all the positive and negative electrodes of the first electrodes are stacked together and connected to conventional positive and negative terminals respectively; the indicator electrode is a combination of positive electrode + separator + negative electrode; the positive and negative terminals are connected to the positive and negative terminals of the indicator electrode respectively. The positive and negative terminals of the conventional electrodes are insulated from and not connected to the positive and negative terminals of the indicator electrode. A schematic diagram of the external structure of the battery is shown below. Figure 2 Show.

[0031] The main difference between the indicator electrode and the first electrode lies in their material composition, which leads to different degrees of polarization and rated capacities. The rated capacity of the indicator electrode is significantly smaller than that of the first electrode, and its polarization is also much lower. The conventional electrodes inside the battery are the standard positive and negative electrodes, such as lithium iron phosphate or NCM ternary (LiNi) batteries for the positive electrode. x Co Materials such as MnzO2, lithium manganese oxide, and lithium iron manganese phosphate are used as the negative electrode, while graphite and silicon are used as the negative electrode. This type of electrode has a large capacity, with a rated capacity of Q0. However, this type of electrode will produce significant polarization when current passes through it.

[0032] The indicator electrode inside the battery is a special electrode added separately to estimate the battery's state of harm (SOH). This electrode has extremely excellent electrochemical performance, with a very high exchange current density. Under normal battery current, the electrode polarization is very small, and the electrode's terminal voltage can be approximated as its open circuit voltage (OCV). Due to its excellent electrochemical performance, the rated capacity q0 of this electrode is very small (relative to the rated capacity Q0 of a normal electrode), and the capacity does not decay during long-term use. The constituent materials of this electrode are usually materials with high specific surface area, such as activated carbon, graphene, and acetylene black.

[0033] The SOH value of the battery, which includes the indicator electrode and the first electrode, is determined by the method described below.

[0034] Figure 3 The flowchart illustrates a method for estimating the state of harmonics (SOH) of a battery, as provided in this application embodiment. The battery includes an indicator electrode and a first electrode; the rated capacity of the indicator electrode is less than the rated capacity of the first electrode; the first electrode here is the conventional electrode described later. The method specifically includes the following steps: Step S302: Obtain the first static voltage of the first electrode after the terminal voltage changes from the first voltage to the second voltage, and the second static voltage after the terminal voltage of the first electrode changes from the first voltage to the second voltage and is connected in parallel with the indicator electrode whose initial terminal voltage is the second voltage; A prerequisite for this step is that the initial terminal voltage of the first electrode has been adjusted to the first voltage, and the initial terminal voltage of the indicator electrode has been adjusted to the second voltage.

[0035] The method of changing the first voltage to the second voltage may include: charging or discharging the first electrode; if charging, the second voltage will be greater than the first voltage; if discharging, the second voltage will be less than the first voltage.

[0036] The first settling voltage is the terminal voltage detected when the terminal voltage of the first electrode changes from a first voltage to a second voltage, and no further charging or discharging occurs, and the change in terminal voltage is less than a threshold within a specified time period. During this process, the indicator electrode does not participate in the circuit, which is equivalent to an open circuit state.

[0037] Based on this, the first electrode is charged or discharged again. After the terminal voltage of the first electrode changes from the first voltage to the second voltage, the charging or discharging is stopped. At the same time, the indicator electrode is connected in parallel to the circuit. In this case, the terminal voltage detected when the terminal voltage change is less than the threshold within a specified time is the second resting voltage.

[0038] Step S304: Calculate the capacity difference when the terminal voltage of the indicator electrode changes from the second voltage to the second resting voltage, and use it as the real-time capacity difference when the terminal voltage of the first electrode changes from the first resting voltage to the second resting voltage; and calculate the standard capacity difference when the terminal voltage of the first electrode changes from the first resting voltage to the second resting voltage. If the first electrode has not decayed, the two measured static voltages should be the same. However, if there has been decay, the two measured static voltages will inevitably be different.

[0039] The main difference between the two static voltage acquisition processes is that an indicator electrode is connected in parallel. This means that the real-time capacity difference caused by the two static voltage acquisition processes is converted into the capacity difference during the charging process of the indicator electrode.

[0040] Therefore, by calculating the capacity difference when the terminal voltage of the indicator electrode changes from the second voltage to the second resting voltage, the real-time capacity difference when the terminal voltage of the first electrode changes from the first resting voltage to the second resting voltage can be determined. Additionally, the standard capacity difference when the terminal voltage of the first electrode changes from the first resting voltage to the second resting voltage also needs to be calculated. By calculating the ratio of these two values, the current SOH value of the battery can be estimated, as in step S306.

[0041] Step S306: Divide the real-time capacity difference by the standard capacity difference to obtain the SOH value of the battery.

[0042] The SOH estimation method for batteries provided in this application embodiment estimates the SOH value by setting a specific indicator electrode in a regular battery and then estimating the SOH value by observing the changes in the voltage of the two electrode terminals during charging or discharging and during the resting process after stopping charging or discharging. This method is low in cost and can be easily applied to vehicle-end applications.

[0043] This application also provides another method for estimating the state of harm (SOH) of a battery, which is implemented based on the previous embodiment. This embodiment focuses on explaining the principle and testing process.

[0044] In step S102 above, "obtaining the first static voltage after the terminal voltage of the first electrode changes from the first voltage to the second voltage" is achieved through the following steps: (1) Adjust the electrode load of the first electrode so that the terminal voltage of the first electrode is the first voltage; (2) Charge / discharge the first electrode, and stop charging / discharging when the first voltage changes to the second voltage; (3) When the voltage change of the first electrode within a specified time is less than the preset voltage threshold, the current voltage of the first electrode is detected to obtain the first static voltage.

[0045] The step S102 above, "obtaining the second static voltage after the first electrode changes from the first voltage to the second voltage, and then connecting it in parallel with the indicator electrode whose initial terminal voltage is the second voltage," is achieved through the following steps: (1) Adjust the electrode load of the first electrode and the indicator electrode respectively so that the terminal voltage of the first electrode is the first voltage and the terminal voltage of the indicator electrode is the second voltage; In specific implementation, when the positive and negative terminals of the first electrode are connected to the load adjustment circuit, the first electrode is charged with a first preset current until the terminal voltage is the first voltage; when the positive and negative terminals of the indicator electrode are connected to the load adjustment circuit, the indicator electrode is charged with a second preset current until the terminal voltage is the second voltage; when the first voltage is less than the second voltage, the first preset current is less than the second preset current; when the first voltage is greater than the second voltage, the first preset current is greater than the second preset current.

[0046] Because a specific voltage value needs to be adjusted here, a small current is used for processing. This results in less battery polarization and a more stable voltage value after voltage regulation. For example, if a very small current is used to adjust it to 3.5V, the voltage will remain stable at 3.5V after the adjustment is complete. However, if a larger current is used, the voltage will drop back to 3.4V or 3.3V after reaching 3.5V due to greater polarization, resulting in poor voltage regulation.

[0047] (2) Connect the first electrode to the charging / discharging circuit for charging / discharging; In specific implementation, the positive and negative terminals of the first electrode are connected to the charging / discharging circuit, and the first electrode is charged / discharged with a third preset current; the third preset current is greater than the maximum value of the first preset current and the second preset current. The third preset current here is much larger than the maximum value of the first and second preset currents. The purpose is to ensure that after the battery is charged / discharged, it has a relatively large voltage rebound before the indicator electrode can be charged.

[0048] (3) When the first voltage changes to the second voltage, stop charging / discharging; at the same time, connect the indicator electrode in parallel to the charging / discharging circuit of the first electrode; (4) When the voltage change of the first electrode within a specified time is less than the preset voltage threshold, the current voltage of the first electrode is detected to obtain the second static voltage.

[0049] Furthermore, the step of "calculating the capacity difference when the terminal voltage of the indicator electrode changes from the second voltage to the second resting voltage" in step S104 above includes: (1) From the OCV-SOC curve corresponding to the indicator electrode, find the first SOC value corresponding to the second voltage and the second SOC value corresponding to the second resting voltage; SOC is the state of charge of the battery.

[0050] (2) Calculate the difference between the first SOC value and the second SOC value to obtain the first SOC difference; (3) Calculate the product of the first SOC difference and the rated capacity of the indicator electrode to obtain the capacity difference when the terminal voltage of the indicator electrode changes from the second voltage to the second static voltage.

[0051] Furthermore, the step S104 above, "calculating the standard capacitance difference corresponding to the change in terminal voltage of the first electrode from the first settling voltage to the second settling voltage," includes: (1) From the OCV-SOC curve corresponding to the first electrode, find the third SOC value corresponding to the first static voltage and the fourth SOC value corresponding to the second static voltage. (2) Calculate the difference between the third SOC value and the fourth SOC value to obtain the second SOC difference; (3) Calculate the product of the second SOC difference and the rated capacity corresponding to the first electrode to obtain the standard capacity difference when the terminal voltage of the first electrode changes from the first static voltage to the second static voltage.

[0052] Furthermore, the target electrode mentioned above includes an indicator electrode or a first electrode; the process of plotting the OCV-SOC curve of the target electrode is as follows: (1) The target electrode is charged and discharged using a current of a specified magnitude; (2) During the charging and discharging processes, the open-circuit voltage and the corresponding SOC value are collected; (3) Based on the open voltage and SOC value during the charging process, plot the first OCV-SOC curve with SOC as the horizontal axis and OCV as the vertical axis; based on the open voltage and SOC value during the discharging process, plot the second OCV-SOC curve with SOC as the horizontal axis and OCV as the vertical axis. (4) Take the average of the vertical axis of the first OCV-SOC curve and the second OCV-SOC curve to obtain the OCV-SOC curve of the target electrode.

[0053] The following explanation uses the discharge method as an example; see [link / reference]. Figure 4 The flowchart of another method for estimating the SOH of a battery is shown below: Step 1: Adjust the voltage of the indicator electrode to V 目标 (Equivalent to the aforementioned second voltage), the conventional battery electrode voltage is V0 (equivalent to the aforementioned first voltage), and V0 > V 目标 ; The specific circuit diagram is as follows: Figure 5 As shown, by closing K1 and opening K2, a current of 0.01Q0 can be used to adjust the charge of the conventional electrode to the terminal voltage V0; by opening K1 and closing K2, a current of 0.01q0 can be used to adjust the charge of the indicator electrode to the terminal voltage V. 目标 .

[0054] Step 2: Connect the external circuit to the positive and negative terminals of a conventional battery, apply a specified current to the battery (typically 400 amps), and wait for the battery voltage to drop from the initial V0 to the stated V. 目标 Remove the current, keep the positive and negative terminals of the indicator electrode disconnected, and let the sample stand for a specified time (usually 1 hour) until the voltage reaches equilibrium and the battery voltage rebounds to V1 (equivalent to the aforementioned first settling voltage). Step 3: Connect the external circuit to the positive and negative terminals of a conventional battery, apply a specified current to the battery (typically 400 amps), and wait for the battery voltage to drop from the initial V0 to the stated V. 目标Remove the current and connect the indicator electrode post to the circuit. Let the sample stand for a specified time (usually 1 hour) until the voltage reaches equilibrium and the battery voltage rebounds to V2 (equivalent to the aforementioned second settling voltage). Step 4: The change in the indicator electrode value from Step 3 (from V) 目标 To V2), by referring to the OCV-SOC curve of the indicator electrode, V is obtained. 目标 SOC value corresponding to voltage V2 V目标 SOC V2 And calculate ΔSOC = SOC V2 -SOC V目标 The capacity difference q after charging the indicator electrode is derived as q = q0 × (SOC). V2 -SOC V目标 The capacity difference q can characterize the real-time capacity difference under the corresponding ΔSOC state in the conventional electrode decay state.

[0055] Step 5: Using the rebound voltages V1 and V2 obtained in Steps 2 and 3 after resting, reverse the OCV-SOC curve of the conventional electrode to obtain the corresponding SOC values ​​(SOC) at voltages V1 and V2. V1 SOC V2 And calculate ΔSOC = SOC V1 - SOC V2 The standard capacity difference under the corresponding ΔSOC at the BOL (fresh battery) state is calculated as Q = Q0 × (SOC). V1 -SOC V2 ).

[0056] The steps that are the same in steps 2 and 3 are: close K1, open K2, and discharge the conventional electrode with a current of 4Q0 until V. 目标 The capacitance difference during this process is denoted as ΔQ. However, the difference between steps 2 and 3 is: in step 2, K2 remains open throughout, and only a capacitance difference of ΔQ occurs at the output of the conventional electrode, causing the voltage of the conventional electrode to drop from V0 to V1. In step 3, K2 closes after applying a current of 4Q0. At the instant of closure, the voltages of both the conventional electrode and the indicator electrode are V... 目标 However, after a large current discharge, the conventional electrode undergoes a depolarization process, causing its voltage to rebound and rise. This results in the conventional electrode charging the indicator electrode additionally. Consequently, the capacitance difference output by the conventional electrode is greater than ΔQ in step 2. This additional capacitance difference q can be determined by the indicator electrode voltage from V... 目标 Calculated at V2, q = q0 × (SOC) V2 -SOC V目标 ).

[0057] The reason why the final equilibrium voltage of the conventional electrode differs after steps 2 and 3 is that step 3 involves the conventional electrode charging the indicator electrode. From the OCV-SOC curve of the conventional electrode, it can be seen that, without capacity decay, the standard capacity difference corresponding to the voltage equilibrium at V1 and V2 is Q = Q0 × (SOC) V1 -SOC V2 For a fresh, undiminished battery, q = Q; however, as the storage capacity of conventional electrodes decreases with use, q < Q, which can be given by the formula SOH = q / Q, as described in steps 4 and 5 above.

[0058] The test data diagrams for steps 2 and 3 above are shown below. Figure 6 As shown: The q value mentioned above is equivalent to the capacity change of the battery after the conventional electrode aging and decay. However, this ΔSOC value should be Q based on the capacity difference corresponding to the battery's BOL (fresh battery) state. Q>q, and the real-time SOH value of the battery can be obtained by using the formula SOH = q / Q.

[0059] The SOH estimation method for batteries provided in this application can obtain the SOH value of a battery relatively accurately by implanting an indicator electrode in a conventional battery and performing simple pulse discharge, voltage testing, and table lookup.

[0060] To verify the effectiveness of the above method, a commercial ternary lithium battery was selected. The capacity of the battery's conventional electrodes was Q0 = 10Ah, the indicator electrode capacity was q0 = 0.1Ah, the initial voltage was V0 = 3.8V, and the voltage V... 目标 =3.0V, rebound voltage V1=3.62V, rebound voltage V2=3.60V, the OCV-SOC curve of the indicator electrode is as follows Figure 7 The OCV-SOC curve of a conventional electrode is as follows: Figure 8 As shown.

[0061] OCV-SOC curve test of conventional electrode and indicator electrode: According to the respective capacities of the two electrodes, charge and discharge the two electrodes with a current of 0.01C respectively to obtain the charging and discharging OCV-SOC curves. Sum the two curves and take the average value to obtain the respective OCV-SOC curve.

[0062] Testing process: Step 1: Adjust the voltage of the indicator electrode to V 目标 =3.0V, while the electrode voltage of a conventional battery is V0=3.8V; Step 2: Connect the external circuit to the positive and negative terminals of a conventional battery, apply a specified current of 40A to the battery, and wait for the battery voltage to drop from the initial V0 = 3.8V to the specified V.目标 =3.0V, remove the current, keep the positive and negative terminals of the indicator electrode disconnected, and let the sample stand for 1 hour until the voltage reaches equilibrium (usually defined as the voltage change of the battery within 5 minutes is less than 0.001V). The battery voltage rebounds to V1=3.62V. Step 3: Connect the external circuit to the positive and negative terminals of a conventional battery, apply a specified current of 40A to the battery, and wait for the battery voltage to drop from the initial V0 = 3.8V to the specified V. 目标 =3.0V, remove the current, and at the same time connect the indicator electrode post to the circuit. Let the sample stand for 1 hour until the voltage reaches equilibrium. The battery voltage rebounds to V2=3.60V. Step 4: The change in the indicator electrode value from Step 3 (from V) 目标 From V1=3.0V to V2=3.60V), by referring to the OCV-SOC curve of the indicator electrode, the capacity difference q after charging the indicator electrode in this process is found to be 0.05Ah. q=0.1Ah×(50%-0%)=0.05Ah; Step 5: From the rebound voltages V1=3.62V and V2=3.60V after resting in Steps 2 and 3, the SOC values ​​are found to be 35.6% and 35.0% respectively by referring to the OCV-SOC curves of the conventional electrodes. Therefore, the standard capacity difference under ΔSOC corresponding to this voltage change in the BOL (fresh battery) is Q: Q=10Ah×(35.6%-35.0%)=0.06Ah; The real-time SOH value of the battery is obtained from the formula SOH = q / Q, and the real-time SOH value of the battery is 83.3%. That is, SOH = q / Q = 0.05Ah / 0.06Ah = 83.3%.

[0063] Based on the above method embodiments, this application also provides a battery SOH estimation device, wherein the battery includes an indicator electrode and a first electrode; the rated capacity of the indicator electrode is less than the rated capacity of the first electrode; see also Figure 9 As shown, the device includes: a voltage acquisition module 92, used to acquire the first static voltage after the terminal voltage of the first electrode changes from the first voltage to the second voltage, and the second static voltage after the terminal voltage of the first electrode changes from the first voltage to the second voltage and is connected in parallel with the indicator electrode whose initial terminal voltage is the second voltage; a capacity difference calculation module 94, used to calculate the capacity difference when the terminal voltage of the indicator electrode changes from the second voltage to the second static voltage, as the real-time capacity difference corresponding to the terminal voltage of the first electrode changing from the first static voltage to the second static voltage; and to calculate the standard capacity difference corresponding to the terminal voltage of the first electrode changing from the first static voltage to the second static voltage; and a SOH calculation module 96, used to divide the real-time capacity difference by the standard capacity difference to obtain the SOH value of the battery.

[0064] Furthermore, the voltage acquisition module 92 is used to adjust the electrode load of the first electrode so that the terminal voltage of the first electrode is the first voltage; to charge / discharge the first electrode, and to stop charging / discharging when the first voltage changes to the second voltage; and to detect the current terminal voltage of the first electrode when the terminal voltage change of the first electrode within a specified time is less than a preset voltage threshold, thereby obtaining the first resting voltage.

[0065] Furthermore, the voltage acquisition module 92 is used to adjust the electrode load of the first electrode and the indicator electrode respectively, so that the terminal voltage of the first electrode is the first voltage and the terminal voltage of the indicator electrode is the second voltage; to connect the first electrode to the charging / discharging circuit for charging / discharging, and to stop charging / discharging when the first voltage changes to the second voltage; at the same time, to connect the indicator electrode in parallel to the charging / discharging circuit of the first electrode; and to detect the current terminal voltage of the first electrode when the change in the terminal voltage of the first electrode within a specified time is less than a preset voltage threshold, thereby obtaining the second static voltage.

[0066] Furthermore, the positive and negative terminals of the aforementioned indicator electrode are not connected to the positive and negative terminals of the first electrode; the voltage acquisition module 92 is used to adjust the electrode load of the first electrode with a first preset current until the terminal voltage is the first voltage when the positive and negative terminals of the first electrode are connected to the load adjustment circuit; when the positive and negative terminals of the indicator electrode are connected to the load adjustment circuit, the indicator electrode is adjusted to the terminal voltage with a second preset current until the terminal voltage is the second voltage; when the first voltage is less than the second voltage, the first preset current is less than the second preset current; when the first voltage is greater than the second voltage, the first preset current is greater than the second preset current.

[0067] Furthermore, the voltage acquisition module 92 is used to connect the positive and negative terminals of the first electrode to the charging / discharging circuit, and to charge / discharge the first electrode with a third preset current; the third preset current is greater than the maximum value of the first preset current and the second preset current.

[0068] Furthermore, the aforementioned capacity difference calculation module 94 is used to find the first SOC value corresponding to the second voltage and the second SOC value corresponding to the second resting voltage from the OCV-SOC curve corresponding to the indicator electrode; calculate the difference between the first SOC value and the second SOC value to obtain the first SOC difference; and calculate the product of the first SOC difference and the rated capacity of the indicator electrode to obtain the capacity difference when the terminal voltage of the indicator electrode changes from the second voltage to the second resting voltage.

[0069] Furthermore, the aforementioned capacity difference calculation module 94 is used to find the third SOC value corresponding to the first static voltage and the fourth SOC value corresponding to the second static voltage from the OCV-SOC curve corresponding to the first electrode; calculate the difference between the third SOC value and the fourth SOC value to obtain the second SOC difference; and calculate the product of the second SOC difference and the rated capacity corresponding to the first electrode to obtain the standard capacity difference corresponding to the first electrode when the terminal voltage changes from the first static voltage to the second static voltage.

[0070] Further, the target electrode includes an indicator electrode or a first electrode; the process of plotting the OCV-SOC curve of the target electrode is as follows: the target electrode is charged and discharged using a specified current; during the charging and discharging processes, the open-circuit voltage and the corresponding SOC value are collected; based on the open-circuit voltage and SOC value during the charging process, a first OCV-SOC curve is plotted with SOC as the horizontal axis and OCV as the vertical axis; based on the open-circuit voltage and SOC value during the discharging process, a second OCV-SOC curve is plotted with SOC as the horizontal axis and OCV as the vertical axis; the average of the vertical axes of the first OCV-SOC curve and the second OCV-SOC curve is taken to obtain the OCV-SOC curve of the target electrode.

[0071] Furthermore, the constituent material of the aforementioned indicator electrode is a material with a high specific surface area, including one of the following: activated carbon, graphene, or acetylene black.

[0072] Based on the above method embodiments, this application also provides a battery SOH estimation system, the system including a controller and a battery including an indicator electrode and a first electrode; the rated capacity of the indicator electrode is less than the rated capacity of the first electrode; the controller is used to execute the method as described in the method embodiments.

[0073] This application also provides a computer-readable storage medium storing computer-executable instructions. When the computer-executable instructions are called and executed by a processor, the computer-executable instructions cause the processor to implement the above-described method. For specific implementation details, please refer to the foregoing method embodiments, which will not be repeated here.

[0074] The computer program products of the methods, apparatus, and electronic devices provided in the embodiments of this application include a computer-readable storage medium storing program code. The instructions included in the program code can be used to execute the methods described in the preceding method embodiments. For specific implementations, please refer to the method embodiments, which will not be repeated here.

[0075] Unless otherwise specifically stated, the relative steps, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of this application.

[0076] If the aforementioned functions are implemented as software functional units and sold or used as independent products, they can be stored in a processor-executable, non-volatile, computer-readable storage medium. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or a portion of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0077] In the description of this application, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0078] Finally, it should be noted that the above-described embodiments are merely specific implementations of this application, used to illustrate the technical solutions of this application, and not to limit them. The protection scope of this application is not limited thereto. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any person skilled in the art can still modify or easily conceive of changes to the technical solutions described in the foregoing embodiments, or make equivalent substitutions for some of the technical features, within the technical scope disclosed in this application. Such modifications, changes, or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be covered within the protection scope of this application. Therefore, the protection scope of this application should be determined by the protection scope of the claims.

Claims

1. A method for estimating the state of harmonics (SOH) of a battery, characterized in that, The battery includes an indicator electrode and a first electrode; the rated capacity of the indicator electrode is less than the rated capacity of the first electrode; the method includes: The first static voltage is obtained after the terminal voltage of the first electrode changes from the first voltage to the second voltage, and the second static voltage is obtained after the terminal voltage of the first electrode changes from the first voltage to the second voltage and is connected in parallel with the indicator electrode whose initial terminal voltage is the second voltage. Calculate the capacity difference when the terminal voltage of the indicator electrode changes from the second voltage to the second resting voltage, and use it as the real-time capacity difference when the terminal voltage of the first electrode changes from the first resting voltage to the second resting voltage; and calculate the standard capacity difference when the terminal voltage of the first electrode changes from the first resting voltage to the second resting voltage. The SOH value of the battery is obtained by dividing the real-time capacity difference by the standard capacity difference.

2. The method according to claim 1, characterized in that, The step of obtaining the first resting voltage after the terminal voltage of the first electrode changes from a first voltage to a second voltage includes: The first electrode is subjected to electrode loading adjustment so that the terminal voltage of the first electrode is the first voltage; The first electrode is charged / discharged, and the charging / discharging is stopped when the first voltage changes to the second voltage; When the voltage change of the first electrode within a specified time is less than a preset voltage threshold, the current voltage of the first electrode is detected to obtain the first static voltage.

3. The method according to claim 1, characterized in that, The step of obtaining the second static voltage after the first electrode changes from the first voltage to the second voltage, and then connecting it in parallel with the indicator electrode whose initial terminal voltage is the second voltage, includes: The first electrode and the indicator electrode are respectively subjected to electrode load adjustment so that the terminal voltage of the first electrode is the first voltage and the terminal voltage of the indicator electrode is the second voltage; The first electrode is connected to the charging / discharging circuit for charging / discharging. When the first voltage changes to the second voltage, the charging / discharging is stopped. At the same time, the indicator electrode is connected in parallel to the charging / discharging circuit of the first electrode. When the voltage change of the first electrode within a specified time is less than a preset voltage threshold, the current voltage of the first electrode is detected to obtain the second static voltage.

4. The method according to claim 3, characterized in that, The positive and negative terminals of the indicator electrode are not connected to the positive and negative terminals of the first electrode; the steps of adjusting the electrode load on the first electrode and the indicator electrode respectively include: When the positive and negative terminals of the first electrode are connected to the load adjustment circuit, the first electrode is loaded with a first preset current until the terminal voltage is the first voltage. When the positive and negative terminals of the indicator electrode are connected to the load adjustment circuit, the indicator electrode is loaded with a second preset current until the terminal voltage is the second voltage. When the first voltage is less than the second voltage, the first preset current is less than the second preset current; when the first voltage is greater than the second voltage, the first preset current is greater than the second preset current.

5. The method according to claim 4, characterized in that, The step of connecting the first electrode to the charging / discharging circuit for charging / discharging includes: The positive and negative terminals of the first electrode are connected to the charging / discharging circuit, and the first electrode is charged / discharged with a third preset current; the third preset current is greater than the maximum value of the first preset current and the second preset current.

6. The method according to claim 1, characterized in that, The step of calculating the capacitance difference when the terminal voltage of the indicator electrode changes from the second voltage to the second resting voltage includes: From the OCV-SOC curve corresponding to the indicator electrode, find the first SOC value corresponding to the second voltage and the second SOC value corresponding to the second resting voltage; Calculate the difference between the first SOC value and the second SOC value to obtain the first SOC difference; Calculate the product of the first SOC difference and the rated capacity of the indicator electrode to obtain the capacity difference when the terminal voltage of the indicator electrode changes from the second voltage to the second resting voltage.

7. The method according to claim 1, characterized in that, The step of calculating the standard capacitance difference corresponding to the change in terminal voltage of the first electrode from the first resting voltage to the second resting voltage includes: From the OCV-SOC curve corresponding to the first electrode, find the third SOC value corresponding to the first static voltage and the fourth SOC value corresponding to the second static voltage; Calculate the difference between the third SOC value and the fourth SOC value to obtain the second SOC difference; Calculate the product of the second SOC difference and the rated capacity corresponding to the first electrode to obtain the standard capacity difference corresponding to the change in terminal voltage of the first electrode from the first resting voltage to the second resting voltage.

8. The method according to claim 6 or 7, characterized in that, The target electrode includes an indicator electrode or a first electrode; the process of plotting the OCV-SOC curve of the target electrode is as follows: The target electrode is charged and discharged using a specified current. During the charging and discharging processes, the open-circuit voltage and the corresponding SOC value are collected. Based on the open voltage and SOC value during the charging process, a first OCV-SOC curve is plotted with SOC as the horizontal axis and OCV as the vertical axis; based on the open voltage and SOC value during the discharging process, a second OCV-SOC curve is plotted with SOC as the horizontal axis and OCV as the vertical axis. The OCV-SOC curve of the target electrode is obtained by averaging the vertical axes of the first OCV-SOC curve and the second OCV-SOC curve.

9. The method according to claim 1, characterized in that, The indicator electrode is composed of a material with a high specific surface area, including one of the following: activated carbon, graphene, or acetylene black.

10. A battery SOH estimation device, characterized in that, The battery includes an indicator electrode and a first electrode; the rated capacity of the indicator electrode is less than the rated capacity of the first electrode; the device includes: The voltage acquisition module is used to acquire the first static voltage after the terminal voltage of the first electrode changes from the first voltage to the second voltage, and the second static voltage after the terminal voltage of the first electrode changes from the first voltage to the second voltage and is connected in parallel with the indicator electrode whose initial terminal voltage is the second voltage; The rated capacity difference calculation module is used to calculate the capacity difference when the terminal voltage of the indicator electrode changes from the second voltage to the second resting voltage, which is used as the real-time capacity difference when the terminal voltage of the first electrode changes from the first resting voltage to the second resting voltage; and to calculate the standard capacity difference when the terminal voltage of the first electrode changes from the first resting voltage to the second resting voltage. The SOH calculation module is used to obtain the SOH value of the battery by dividing the real-time capacity difference by the standard capacity difference.

11. A battery SOH estimation system, characterized in that, The system includes a controller and a battery including an indicator electrode and a first electrode; the rated capacity of the indicator electrode is less than the rated capacity of the first electrode; the controller is configured to perform the method as described in any one of claims 1-9.

12. A battery, characterized in that, The battery includes an indicator electrode and a first electrode; the rated capacity of the indicator electrode is less than the rated capacity of the first electrode; the SOH value of the battery is determined by the method according to any one of claims 1-9.

13. The battery according to claim 12, characterized in that, The first electrode includes multiple electrodes; the multiple first electrodes are stacked; the positive and negative terminals of the stacked first electrodes are not connected to the positive and negative terminals of the indicator electrode.

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