Apparatus and method for detecting battery condition

Abstract

Disclosed are an apparatus and a method for detecting a battery condition. The apparatus can include a storage that stores a battery model modeling a voltage change and an internal impedance of a battery as an electrical circuit, and a control configured to estimate a distribution state of lithium ions within a positive electrode active material of the battery, detect a distortion region remaining in a boundary portion of two in-phase regions in the positive electrode active material based on the distribution state, estimate an overvoltage caused by the distortion region, correct the battery model by using a correction parameter corresponding to the overvoltage, and estimate a condition of the battery by using the battery model.

Description

Technical Field

[0001] This disclosure relates to apparatus and methods for detecting battery condition, and more specifically, to apparatus and methods for detecting the battery condition of lithium iron phosphate (LiFePO4) batteries. Background Technology

[0002] Rechargeable batteries are batteries that can be charged and discharged, unlike primary batteries that cannot be recharged. Low-capacity rechargeable batteries are used in portable small electronic devices such as smartphones, feature phones, laptops, digital cameras, and camcorders, while high-capacity rechargeable batteries are widely used as motor drive power and energy storage devices, such as in hybrid and electric vehicles. A rechargeable battery includes an electrode assembly, a housing that houses the electrode assembly, and electrode terminals connected to the electrode assembly. The electrode assembly includes a positive electrode, a negative electrode, and a separator inserted between the positive and negative electrodes.

[0003] Typically, a rechargeable battery includes an electrode assembly comprising a positive electrode, a negative electrode, and a separator inserted between the positive and negative electrodes; a housing containing the electrode assembly; and electrode terminals electrically connected to the electrode assembly. An electrolyte solution is injected into the housing to enable the battery to be charged and discharged through an electrochemical reaction between the positive and negative electrodes and the electrolyte solution. The shape of the housing (such as cylindrical or rectangular) depends on the purpose of the battery.

[0004] Lithium iron phosphate (LiFePO4) batteries, a type of lithium-ion battery, are secondary batteries that use lithium iron phosphate (LiFePO4) with an olivine structure as the positive electrode active material.

[0005] The information disclosed in this Background section is intended only to enhance the understanding of the background of this disclosure and may therefore contain information that does not constitute prior art known to those skilled in the art within the country. Summary of the Invention

[0006] This disclosure attempts to provide apparatus and methods for detecting battery condition, thereby improving the accuracy of battery condition detection by reflecting overvoltage due to the memory effect in a battery model of a lithium iron phosphate (LiFePO4) battery.

[0007] However, the technical problems to be solved by this disclosure are not limited to those herein, and those skilled in the art will understand from the following description other purposes not mentioned herein.

[0008] An apparatus for detecting battery condition may include a storage device and a control device. The storage device stores a battery model that models voltage changes and internal impedance of the battery as an electrical circuit. The control device is configured to estimate the distribution of lithium ions within the positive electrode active material of the battery, detect distortion zones remaining at the boundary between two in-phase regions in the positive electrode active material based on the distribution, estimate overvoltages caused by the distortion zones, correct the battery model using correction parameters corresponding to the overvoltages, and estimate the battery condition using the battery model.

[0009] The positive electrode active material may include LiFePO4. The distribution state may include Li... x Li-rich phase regions containing FePO4 (x ≥ 0.9) phase and Li-containing phases y The distribution of the Li-depleted phase region of FePO4 (y ≤ 0.05) within the positive electrode active material particles. The two co-phase regions can be either two Li-rich phase regions or two Li-depleted phase regions.

[0010] The control device can be configured to model the region between the outer boundary and the center of the positive electrode active material particle as a one-dimensional coordinate system, and estimate the position information of the Li-rich phase region and the Li-poor phase region within the positive electrode active material particle by using the one-dimensional coordinate system.

[0011] The control device can be configured to estimate a first distance between two Li-rich phase regions or a second distance between two Li-depleted phase regions based on location information. The control device can be configured to determine that a distorted region is formed in the boundary portion between the two Li-rich phase regions if the first distance decreases below a threshold during constant current discharge. The control device can be configured to determine that a distorted region is formed in the boundary portion between the two Li-depleted phase regions if the second distance decreases below a threshold during constant current charging.

[0012] The control device can be configured to determine that the distorted region has been eliminated if the distorted region exists in the boundary portion of two Li-rich phase regions, or if the distorted region transitions to a Li-rich phase region through discharge or to a Li-depleted phase region through charging.

[0013] The control device can be configured to determine that the distortion region has been eliminated if the distortion region exists in the boundary portion of two Li-depleted phase regions, or if the distortion region is transformed into a Li-depleted phase region by charging or a Li-rich phase region by discharging.

[0014] The control device can be configured to estimate the location information of the distortion region using a one-dimensional coordinate system. The control device can be configured to predict the state of charge (SOC) when lithium ions are deintercalated or intercalated into the distortion region during a subsequent charging or discharging section based on the location information of the distortion region.

[0015] The control device can be configured to determine overvoltages using a first overvoltage and a second overvoltage, the first overvoltage being estimated using a first overvoltage function and the second overvoltage being estimated using a second overvoltage function. The first overvoltage function can be a normal distribution function centered on the state of charge (SOC), deriving the first overvoltage appearing in the distortion region for each SOC of the battery. The second overvoltage function can be an exponential function, deriving the second overvoltage appearing in the distortion region for each SOC of the battery.

[0016] The storage device can be configured to store a function table including multiple first overvoltage functions and multiple second overvoltage functions corresponding to different charging and discharging states. The control device can be configured to select the first overvoltage function and the second overvoltage function from the function table depending on the current charging and discharging state of the battery.

[0017] The calibration parameters may include a calibration resistor or a calibration voltage. The control device can be configured to add the calibration resistor or calibration voltage to the internal parameters of the battery model.

[0018] Methods for detecting battery condition may include: based on the distribution of lithium ions in the positive electrode active material according to the battery's charging and discharging history, detecting the distortion region remaining at the boundary between two in-phase regions in the positive electrode active material based on the distribution state, estimating the overvoltage caused by the distortion region, correcting the battery model by using correction parameters corresponding to the overvoltage, and estimating the battery condition by using the battery model. The battery model can model the battery's voltage changes and internal impedance as an electrical circuit.

[0019] The positive electrode active material may include LiFePO4. The distribution state may include Li... x Li-rich phase regions containing FePO4 (x ≥ 0.9) phase and Li-containing phases y The distribution of the Li-depleted phase region of FePO4 (y ≤ 0.05) within the positive electrode active material particles. The two co-phase regions can be either two Li-rich phase regions or two Li-depleted phase regions.

[0020] The record may include estimating the location information of the Li-rich phase region and the Li-depleted phase region within the positive electrode active material particle by using a one-dimensional coordinate system that models the region between the outer boundary and the center of the positive electrode active material particle.

[0021] Detecting the distortion region may include estimating a first distance between two Li-rich phase regions or a second distance between two Li-poor phase regions based on location information. If the first distance decreases below a threshold during constant current discharge, it is determined that the distortion region is formed in the boundary portion between the two Li-rich phase regions. And if the second distance decreases below a threshold during constant current charging, it is determined that the distortion region is formed in the boundary portion between the two Li-poor phase regions.

[0022] The method may further include: if the distorted region exists in the boundary portion of two Li-rich phase regions, and if the distorted region is transformed into a Li-rich phase region by discharge or into a Li-depleted phase region by charging, then it is determined that the distorted region has been eliminated.

[0023] The method may further include: if the distorted region exists in the boundary portion of two Li-depleted phase regions, and if the distorted region is transformed into a Li-depleted phase region by charging or into a Li-rich phase region by discharging, then it is determined that the distorted region has been eliminated.

[0024] The method may further include: estimating the location information of the distortion region by using a one-dimensional coordinate system, and predicting the state of charge (SOC) when lithium ions are deintercalated or intercalated into the distortion region during subsequent charging or discharging segments based on the location information of the distortion region.

[0025] Estimating overvoltage may include estimating a first overvoltage using a first overvoltage function, estimating a second overvoltage using a second overvoltage function, and determining the overvoltage using both the first and second overvoltages. The first overvoltage function may be a normal distribution function centered on the state of charge (SOC), deriving the first overvoltage appearing in the distortion region for each SOC of the battery. The second overvoltage function may be an exponential function, deriving the second overvoltage appearing in the distortion region for each SOC of the battery.

[0026] The method may further include: storing a function table comprising a plurality of first overvoltage functions and a plurality of second overvoltage functions corresponding to different charging and discharging conditions; and selecting the first overvoltage function and the second overvoltage function from the function table depending on the current charging and discharging condition of the battery.

[0027] Calibration parameters can include calibration resistors or calibration voltages. Calibration can be achieved by adding calibration resistors or calibration voltages to the internal parameters of the battery model.

[0028] According to this disclosure, the accuracy of a battery model can be improved by reflecting overvoltage caused by the memory effect in the battery model of a lithium iron phosphate (LiFePO4) battery. Furthermore, the accuracy of battery condition detection can be improved by using a battery model with improved accuracy to detect the condition value of a lithium iron phosphate (LiFePO4) battery.

[0029] However, the effects that can be obtained through this disclosure are not limited to those herein, and those skilled in the art will clearly understand, based on the following disclosure, other effects not mentioned herein. Attached Figure Description

[0030] The accompanying drawings illustrate preferred embodiments of the present disclosure and, together with the foregoing disclosure, serve to provide a further understanding of the technical features of the present disclosure; therefore, the present disclosure is not to be construed as limited to the drawings.

[0031] Figure 1 An example of an equivalent circuit model of a battery is shown.

[0032] Figure 2 A battery system according to an embodiment is illustrated schematically.

[0033] Figures 3A to 3D An example of modeling the distribution of lithium ions within the active material particles of the positive electrode of a battery is shown.

[0034] Figures 4A to 4D An example is shown where the distribution of lithium ions within the positive electrode active material particles changes according to charging and discharging history.

[0035] Figures 5A to 5D This is a diagram illustrating a method for recording the distribution of lithium ions within positive electrode active material particles using an apparatus for detecting battery condition according to an embodiment.

[0036] Figures 6A to 6D An example of a residual zone appearing within the positive electrode active material particles is shown.

[0037] Figure 7A and Figure 7B This is a diagram used to explain the method by which the apparatus for detecting battery condition according to an embodiment detects residual areas.

[0038] Figure 8A and Figure 8B It is a graph used to explain the trend of overvoltage caused by residual regions.

[0039] Figure 9A and Figure 9B An example is shown where additional overvoltages due to the residual region are defined by using two voltage curves.

[0040] Figure 10A and Figure 10B An example of a device for detecting battery condition and calibrating a battery model according to an embodiment is shown.

[0041] Figure 11 A method for detecting battery condition according to an embodiment is illustrated schematically. Detailed Implementation

[0042] In the following, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. Before the description, it should be understood that the terms and words used in the specification and appended claims should not be construed as having ordinary and dictionary meanings, but should be interpreted in light of the inventor's ability to appropriately define the concepts of terms and words to best describe his / her own disclosure, and are to be interpreted as having meanings and concepts corresponding to the technical concepts of the present disclosure. Therefore, since the embodiments described in the specification and the configurations shown in the drawings are merely the most preferred embodiments and configurations of the present disclosure, they do not represent all the technical concepts of the present disclosure, and it should be understood that various equivalents and modifications of the embodiments are possible when this application is filed. It should also be understood that the terms “comprising,” “including,” “including…,” and / or “containing…”, when used in this specification, specify the presence of the stated features, elements, steps, operations, components, and / or parts, but do not exclude the presence or addition of one or more other features, elements, steps, operations, components, and / or groups thereof. The use of “can / may” in describing embodiments of the present disclosure may include “one or more embodiments of the present disclosure.”

[0043] Furthermore, to aid in understanding this disclosure, the drawings are not drawn to scale, and the dimensions of some components may be exaggerated. Additionally, in different embodiments, the same reference numerals may be assigned to the same elements.

[0044] When interpreting two objects as "identical," it means that these objects are "substantially identical." Therefore, substantially identical objects can include those considered to have low deviations in the field, such as deviations within 5%. Furthermore, when interpreting that certain parameters are uniform across a predetermined region, this can mean that the parameters are uniform in average across the corresponding region.

[0045] Although the terms "first," "second," etc., are used to describe various constituent elements, these constituent elements are not limited by these terms. These terms are used to distinguish one element from another, and unless otherwise stated, the first element can be the second element.

[0046] Throughout this specification, unless otherwise stated, each element may be singular or plural.

[0047] When one element is "above (or below)" or "on (or below)" another element, the element may be on the upper (or lower) surface of the other element, and an intermediate element may exist between the element and the other element above (or below) the element.

[0048] Furthermore, when a component is referred to as “connected,” “coupled,” or “linked” to another component, the component may be directly connected or coupled to that other component. However, it should be understood that intermediate components may exist between each component, or each component may be “connected,” “coupled,” or “linked” to each other through another component. When a component is referred to as being coupled (e.g., electrically coupled or connected) to another component, the component may be directly coupled to that other component or indirectly coupled to that other component via one or more intermediate components.

[0049] Throughout this specification, unless otherwise stated, “A and / or B” means A, B, or A and B. In other words, the term “and / or” includes all or various combinations of the related and listed items. Unless otherwise stated, “C to D” means C or greater and D or less.

[0050] Figure 1 An example of the equivalent circuit model (ECM) of a battery is shown.

[0051] refer to Figure 1 An ECM is a battery model in which the battery's internal impedance and voltage changes are modeled as an electrical circuit. The parameters constituting the ECM can include the open circuit voltage (OCV) Vocv, series resistance Rs, and parallel impedances (parallel resistance Rp and parallel capacitance Cp). The series resistance Rs represents the battery's internal ohmic resistance and is related to the voltage drop during battery discharge and the voltage rise during battery charging. The parallel resistance Rp and parallel capacitance Cp represent the charge transfer resistance and charge transfer capacitance, respectively, and are related to the battery's dynamic characteristics.

[0052] Compared to other lithium-ion batteries that use cobalt, nickel, manganese, etc. as positive electrode active materials, lithium iron phosphate (LiFePO4, hereinafter referred to as "LFP") batteries have various unique characteristics. In LFP batteries, lithium ions (Li+) are intercalated or deintercalated during the charging or discharging process, resulting in a Li-rich phase (Li... x FePO4 (x ≥ 0.9) phase and Li-depleted phase (Li yFePO4 (y ≤ 0.05) phase coexists in the positive electrode, thus exhibiting two-phase transition characteristics in which a transformation occurs between the two phases. These two-phase transition characteristics can be represented by the following reaction formula.

[0053] [Reaction Formula]

[0054]

[0055] In the above reaction equation, Li + and e - Let x represent lithium ions and electrons, respectively, and let y represent the composition range. The composition range refers to the range within which the relative ratios of the corresponding constituent elements in a particular compound can vary. In the following text, for better understanding and ease of description, Li... x The FePO4 phase is called the "Li-rich phase," and Li y The FePO4 phase is referred to as the "Li-poor phase". The Li-rich phase can include a state in which lithium ions are maximally intercalated, making x equal to 1 (i.e., LiFePO4). Conversely, the Li-poor phase can include a state in which lithium ions are completely deintercalated, making y equal to 0 (i.e., FePO4).

[0056] In LFP cells, due to the structural differences between the Li-rich and Li-depleted phases, distortion regions may form within the positive electrode active material during the transition between the two phases. During this transition, different orientations and volume changes may occur due to the structural differences between the two phases, making the crystal structure transition uneven and potentially leading to distortion regions.

[0057] During the charging and discharging process of LFP batteries, a concentration gradient may appear within the positive electrode active material due to the insertion / extraction of lithium ions, and this concentration gradient may intensify with increasing lithium ion insertion / extraction rates. In other words, compared to constant voltage (CV) charging and CV discharging, where lithium ion insertion / extraction rates are relatively low, the concentration gradient may be more pronounced during constant current (CC) charging and CC discharging, where lithium ion insertion / extraction rates are high. As the concentration gradient intensifies during the phase transition, the migration velocity of lithium ions and the phase transition within the positive electrode active material particles may become non-uniform, potentially exacerbating the distortion region. As the phase transition proceeds and the lithium ion concentration becomes more uniform across the various phase regions, the distortion region may gradually decrease and disappear.

[0058] Meanwhile, LFP batteries can exhibit a memory effect when specific conditions are met during their charge and discharge history (or charge and discharge path). This effect occurs at the boundary between two phase regions of the same phase within the positive electrode active material (between two Li-rich phase regions or between two Li-poor phase regions). When the LFP battery is subsequently charged or discharged, the distorted region remaining due to the memory effect (hereinafter referred to as the "residual region") can generate additional overvoltage. In sections where the same phase persists (i.e., sections where the Li-rich or Li-poor phases persist), the activation energy barrier is low, allowing for continuous lithium-ion insertion / extraction with minimal energy during charging or discharging. However, when charging or discharging continues and phase transitions begin to occur in the residual region (i.e., when lithium-ions begin to insert or extract into the residual region), additional overvoltage may occur due to the altered activation energy barrier, potentially affecting the voltage behavior of the LFP battery.

[0059] In the embodiments described herein, the accuracy of the battery model can be improved by predicting additional overvoltages due to the memory effect characteristics of LFP batteries and reflecting the predicted overvoltages in the battery model.

[0060] Figure 2 A battery system according to an embodiment is illustrated schematically.

[0061] refer to Figure 2 The battery system 1 may include a battery 20 and a device 10 for detecting the battery status.

[0062] Battery 20 may be an LFP battery (or an LFP cell) that uses LFP as the positive electrode active material.

[0063] The device 10 for detecting battery condition can measure the voltage, current, temperature, etc. of the battery 20, and can predict the state of charge (SOC), state of health (SOH), open circuit voltage (OCV), internal resistance, etc. of the battery 20 by using the measured values ​​and the battery model 111. The device 10 for detecting battery condition may include a storage device 11, a measuring device 12, and a control device 13.

[0064] The storage device 11 can store information, data, etc., processed by the device 10 for detecting battery status.

[0065] Storage device 11 can store battery model 111. Battery model 111 can simulate the electrical characteristics (internal impedance, voltage changes, etc.) of battery 20 using OCV, resistors, capacitors, etc. For example, battery model 111 may include a reference... Figure 1The described ECM. Storage device 11 can store parameter values ​​constituting battery model 111 in the form of tables or functions based on charging and discharging conditions (temperature, SOC, SOH, etc.) (see...). Figure 1 The Vocv, Rs, Rp and Cp are used to store the battery model 111.

[0066] Storage device 11 can store an overvoltage function table. The overvoltage function table can include an overvoltage function for estimating the overvoltage value caused by the memory effect characteristics of battery 20.

[0067] The storage device 11 can store programs for operating the control device 13, which will be described later.

[0068] Storage device 11 may include at least one memory (not shown). The memory may be a computer-readable recording medium and includes various forms of volatile or non-volatile recording media. The memory may include various forms of recording media, such as flash memory, hard disk, card (e.g., SD or XD memory), random access memory (RAM), static random-access memory (SRAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), and programmable read-only memory (PROM).

[0069] The measuring device 12 can periodically measure the condition values ​​of the battery 20, such as voltage, current, temperature, etc. The measuring device 12 may include at least one sensor or measuring circuit for measuring the condition values ​​of the battery 20. The measuring device 12 may be integrated into at least one analog front end (AFE) integrated circuit (IC).

[0070] The control device 13 can control the overall operation of the device 10 used to detect battery status.

[0071] The control device 13 can obtain measured values ​​(voltage, current, temperature, etc.) through the measuring device 12. The control device 13 can detect the condition values ​​of the battery 20, such as SOC, SOH, OCV, internal resistance, etc., by using the measured values ​​and the battery model 111. The control device 13 may include a lithium condition estimator 131, a calibrator 132, and a battery condition estimator 133.

[0072] The lithium condition estimator 131 can estimate the distribution of lithium ions (or lithium ion concentration profile) in the positive electrode active material of the battery 20.

[0073] In battery 20 using LFP as the positive electrode active material, the distribution of lithium ions within the positive electrode active material can vary according to the charging and discharging history. The charging and discharging history represents the history of changes in the state of charge (SOC, or depth of discharge (DOD)) of battery 20 during charging and discharging. When comparing the case of continuously discharging battery 20 from 100% SOC to 50% SOC with the case of continuously charging battery 20 from 0% SOC to 50% SOC, although the discharging and charging of battery 20 terminate at the same SOC of 50%, the charging and discharging history up to when the SOC has reached 50% is different. Therefore, when the charging and discharging history is different, even if the SOC of battery 20 is the same, the distribution of lithium ions within the positive electrode active material may differ from one another.

[0074] Therefore, the lithium condition estimator 131 can monitor the charging and discharging history of the battery 20 to estimate the distribution state of lithium ions in the positive electrode active material of the battery 20.

[0075] In the following text, reference will be made to Figures 3A to 3D , Figures 4A to 4D and Figures 5A to 5D The method of lithium condition estimator 131 estimating and recording the distribution state of lithium ions in the positive electrode active material of battery 20 is described in detail.

[0076] Figure 3A and Figure 3B An example of modeling the distribution of lithium ions within the positive electrode active material particles of battery 20 is shown. Figure 3A and Figure 3B This is an example of modeling the distribution of lithium ions within a circular positive electrode active material particle using radial modeling. Figure 3A An example of the change in the distribution state of lithium ions within the positive electrode active material particles during charging is shown, and Figure 3B An example of the change in the distribution state of lithium ions within the positive electrode active material particles during discharge is shown.

[0077] refer to Figure 3A In the fully discharged state of battery 20, only the Li-rich phase can exist within the positive electrode active material particles. Subsequently, during charging of battery 20, lithium ions (Li... +Lithium ions (Li₂) can be deintercalated from the outer boundary of the positive electrode active material particles and move to the negative electrode. Furthermore, a Li-depleted phase region can be generated on the outer side of the positive electrode active material particles, resulting in phase separation where the Li-depleted and Li-rich phases exist at the outer boundary and center of the positive electrode active material particles, respectively. As charging progresses, the Li-depleted phase region can increase, and the boundary (or interface) between the Li-depleted and Li-rich phase regions can gradually move towards the center of the positive electrode active material particles. When the battery 20 is fully charged, all lithium ions (Li₂) can be deintercalated from the outer boundary of the positive electrode active material particles and move to the negative electrode. + The particles are released and migrate toward the negative electrode, resulting in only the Li-depleted phase existing within the active material particles of the positive electrode.

[0078] refer to Figure 3B In the fully charged state of battery 20, only the Li-depleted phase can exist within the positive electrode active material particles. Subsequently, during the discharge of battery 20, lithium ions (Li... + Li-rich phase regions can be embedded from the outer boundary of the positive electrode active material particles. Furthermore, Li-rich phase regions can form on the outer side of the positive electrode active material particles, resulting in phase separation where the Li-rich and Li-depleted phases exist at the outer boundary and center of the positive electrode active material particles, respectively. As discharge proceeds, the Li-rich phase region can increase, and the boundary (or interface) between the Li-rich and Li-depleted phase regions gradually moves towards the center of the positive electrode active material particles. When the battery 20 is fully discharged, the positive electrode active material particles can be embedded by lithium ions (Li... + The material is completely filled, so that only the Li-rich phase exists within the positive electrode active material particles.

[0079] Figure 3C and Figure 3D Other examples of modeling the distribution of lithium ions within the positive electrode active material particles of battery 20 are shown. Figure 3C and Figure 3D This is an example of modeling the distribution of lithium ions within the active material particles of the positive electrode using a bar chart. Figure 3C An example of the change in the distribution state of lithium ions within the positive electrode active material particles during charging is shown, and Figure 3D An example of the change in the distribution state of lithium ions within the positive electrode active material particles during discharge is shown.

[0080] exist Figure 3C and Figure 3D In the diagram, the bar chart represents the lithium ion (Li) ratio between the center and outer boundary of the positive electrode active material particles, based on a transformation to a one-dimensional coordinate system. +This is obtained by modeling the distribution of the positive electrode active material particles. In the bar chart, the left endpoint A represents the outer boundary (surface) of the positive electrode active material particles, and the right endpoint B represents the center of the positive electrode active material particles. The coordinate values ​​0 to 100 in the bar chart can represent relative distances from the outer boundary of the positive electrode active material particles. Figure 3C and Figure 3D For example, in a bar chart, coordinate values ​​can decrease to the left (i.e., closer to the outer boundary of the positive electrode active material particles) and increase to the right (i.e., closer to the center of the positive electrode active material particles). Furthermore, in the bar chart, depending on the amount of lithium ions inserted or extracted, the Li-rich or Li-poor phase region can be modeled as increasing or decreasing linearly. That is, in the bar chart, depending on the SOC of battery 20, the Li-rich or Li-poor phase region can be modeled, and according to changes in the SOC of battery 20, the Li-rich or Li-poor phase region can be modeled as increasing or decreasing linearly. By using such a bar chart, the distribution state of lithium ions within the positive electrode active material particles can be converted into coordinate values. Furthermore, the history of changes in the distribution state of lithium ions within the positive electrode active material particles can be stored as a history corresponding to changes in the SOC of battery 20.

[0081] at the same time, Figures 3A to 3D The illustration shows the scenario where battery 20 is continuously charged from a fully discharged state to a fully charged state, or continuously discharged from a fully charged state to a fully discharged state. However, during actual use of battery 20, there may be frequent instances where only a portion of battery 20's capacity is repeatedly charged and discharged.

[0082] Therefore, depending on the charging and discharging history of the battery 20, multiple boundaries between the Li-depleted phase region and the Li-rich phase region can exist within the positive electrode active material particles.

[0083] Figures 4A to 4D This is a graph used to explain how the distribution of lithium ions changes within the positive electrode active material particles according to charge and discharge history, and is obtained by using a reference... Figure 3C and Figure 3D The described bar chart illustrates the modeling of the distribution of lithium ions.

[0084] exist Figures 4A to 4D In the diagram, R(i) and P(i) represent the Li-rich phase region and the Li-depleted phase region located at the i-th position from the outer boundary (surface) of the positive electrode active material particle, respectively.

[0085] exist Figure 4A and Figure 4B In the middle, the battery 20 can be charged from 40% SOC to 55% SOC. However, in Figure 4A and Figure 4BIn this study, the distribution of Li-rich and Li-poor phase regions appears to differ depending on the charging and discharging history up to 40% SOC.

[0086] refer to Figure 4A At a SOC of 40% for battery 20, Li-depleted phase regions P(1) and P(2) can exist on the outer boundary (surface) and center of the positive electrode active material particles, respectively, and a Li-rich phase region R(1) can exist between the two Li-depleted phase regions P(1) and P(2). Subsequently, when charging of battery 20 is initiated, lithium ions are released from the Li-rich phase region R(1). Therefore, the boundary between the Li-depleted phase region P(1) and the Li-rich phase region R(1) can gradually move towards the center of the positive electrode active material particles (see the bar charts at SOC 45% and SOC 55%).

[0087] refer to Figure 4B At a SOC of 40% for battery 20, Li-rich phase regions R(1) and R(2) can exist on the outer boundary (surface) and center of the positive electrode active material particles, respectively, and a Li-depleted phase region P(1) can exist between the two Li-rich phase regions R(1) and R(2). Subsequently, when charging of battery 20 is initiated, lithium ions are released from the outer boundary of the Li-rich phase region R(1), and the Li-depleted phase region P(1) can be generated on the outer boundary of the positive electrode active material particles (see the bar chart at SOC 45%). When charging continues and the SOC of battery 20 exceeds 50%, all the previous Li-rich phase regions R(1) can be transformed into Li-depleted phase regions P(1), and only one Li-depleted phase region P(1) and one Li-rich phase region R(1) can exist on the outer boundary and center of the positive electrode active material particles, respectively (see the bar chart at SOC 55%).

[0088] exist Figure 4C and Figure 4D In this configuration, battery 20 can discharge from 50% SOC to 35% SOC. However, in... Figure 4C and Figure 4D In this study, the distribution of Li-rich and Li-poor phase regions appears to differ depending on the charging and discharging history up to 50% SOC.

[0089] refer to Figure 4CAt a SOC of 50% for battery 20, Li-depleted phase regions P(1) and P(2) can exist on the outer boundary (surface) and center of the positive electrode active material particles, respectively, and a Li-rich phase region R(1) can exist between the two Li-depleted phase regions P(1) and P(2). Subsequently, when battery 20 starts discharging, due to lithium ion insertion, the Li-rich phase region R(1) can be generated on the outer boundary of the positive electrode active material particles (see the bar chart at SOC 45%). When discharge continues and the SOC of battery 20 has decreased to below 40%, all the previous Li-depleted phase regions P(1) can be transformed into Li-rich phase regions R(1). Therefore, only one Li-rich phase region R(1) and one Li-depleted phase region P(1) can exist on the outer boundary and center of the positive electrode active material particles, respectively (see the bar chart at SOC 35%).

[0090] refer to Figure 4D At a SOC of 50% for battery 20, Li-rich phase regions R(1) and R(2) can exist on the outer boundary (surface) and center of the positive electrode active material particles, respectively, and a Li-poor phase region P(1) can exist between the two Li-rich phase regions R(1) and R(2). Subsequently, when battery 20 starts discharging, due to the insertion of lithium ions, the boundary between the Li-rich phase region R(1) and the Li-poor phase region P(1) can gradually move towards the center of the positive electrode active material particles (see the bar charts at SOC 45% and SOC 35%).

[0091] As discussed in this article, even if the SOC of the battery 20 is the same, the distribution of lithium ions within the positive electrode active material particles can vary depending on the charging and discharging paths that the battery 20 has previously experienced.

[0092] Therefore, the lithium condition estimator 131 can continuously monitor the charging and discharging history (i.e., SOC change history) of the battery 20 and record the distribution state of lithium ions within the positive electrode active material particles of the battery 20. The lithium condition estimator 131 can obtain positional information representing the lithium ion distribution state by converting the estimated lithium ion distribution state into coordinate information. The lithium condition estimator 131 can store the positional information obtained in this way in the storage device 11 in correspondence with the corresponding SOC to record the distribution state of lithium ions within the positive electrode active material particles.

[0093] Figures 5A to 5D This is a diagram illustrating the method used by the lithium condition estimator 131 to interpret the distribution of lithium ions within the positive electrode active material particles of the battery 20.

[0094] Figures 5A to 5DAn example is shown where the region between the center and outer boundary of the positive electrode active material particle is converted into a one-dimensional coordinate system in bar chart format, and the position information (start position S(i) and end position E(i)) of each Li-rich phase region R(i) is recorded using such a one-dimensional coordinate system.

[0095] In this description, S(i) and E(i) are the positional information of the Li-rich phase region R(i) located at the i-th position from the outer boundary of the positive electrode active material particle, and respectively indicate the start and end positions of the Li-rich phase region R(i). Furthermore, the i-th Li-rich phase region R(i) can refer to the i-th Li-rich phase region located at the outer boundary (or surface) of the positive electrode active material particle, and the i-th Li-depleted phase region P(i) can refer to the i-th Li-depleted phase region located at the outer boundary (or surface) of the positive electrode active material particle.

[0096] by Figure 5A For example, the location information of the first Li-rich phase region R(1) can be determined as (S(1), E(1)) = (10, 70) when the SOC is 40%, as (S(1), E(1)) = (15, 70) when the SOC is 45%, and as (S(1), E(1)) = (25, 70) when the SOC is 55%. Figure 5B For example, the location information of the first Li-rich facies region R(1) can be determined as (S(1), E(1)) = (0, 10) when the SOC is 40%, (S(1), E(1)) = (5, 10) when the SOC is 45%, and (S(1), E(1)) = (55, 100) when the SOC is 55%. The location information of the second Li-rich facies region R(2) can be determined as (S(2), E(2)) = (50, 100) when the SOC is 40%, and (S(2), E(2)) = (50, 100) when the SOC is 45%. Figure 5C For example, the location information of the first Li-rich facies region R(1) can be determined as (S(1), E(1)) = (10, 60) when the SOC is 50%, as (S(1), E(1)) = (0, 5) when the SOC is 45%, and as (S(1), E(1)) = (0, 65) when the SOC is 35%. The location information of the second Li-rich facies region R(2) can be determined as (S(2), E(2)) = (10, 60) when the SOC is 45%. Figure 5DFor example, the location information of the first Li-rich phase region R(1) can be determined as (S(1), E(1)) = (0, 10) when the SOC is 50%, (S(1), E(1)) = (0, 15) when the SOC is 45%, and (S(1), E(1)) = (0, 25) when the SOC is 35%. The location information of the second Li-rich phase region R(2) can be determined as (S(2), E(2)) = (60, 100) when the SOC is 50%, (S(2), E(2)) = (60, 100) when the SOC is 45%, and (S(2), E(2)) = (60, 100) when the SOC is 35%.

[0097] Once the location information (start position S(i) and end position E(i)) of each Li-rich phase region R(i) is determined, the lithium condition estimator 131 can record it together with the corresponding SOC in the storage device 11. Therefore, the SOC change history of the battery 20 and the change history of its corresponding Li-rich phase region R(i) can be recorded in the storage device 11.

[0098] exist Figures 5A to 5D In this embodiment, the distribution of lithium ions within the positive electrode active material particles is recorded by recording the position information (start position S(i) and end position E(i)) of the Li-rich phase region R(i). However, in another embodiment, the distribution of lithium ions within the positive electrode active material particles can be recorded by recording the position information (start position and end position) of the Li-poor phase region P(i) or by recording the position information of all Li-rich phase regions R(i) and Li-poor phase regions P(i). When Li-rich and Li-poor phase regions coexist within the positive electrode active material particles, once the position information of one phase region is determined, the lithium condition estimator 131 can use it to estimate the position information of the remaining phase regions.

[0099] The positive electrode of battery 20 may include multiple positive electrode active material particles, and even at the same point in time, the lithium-ion distribution state may differ for each positive electrode active material particle. Lithium condition estimator 131 may estimate the lithium-ion distribution state relative to a single positive electrode active material particle in a manner described herein. Subsequently, lithium condition estimator 131 may assume that the estimated lithium-ion distribution state relative to a single positive electrode active material particle is the average lithium-ion distribution state of the multiple positive electrode active material particles included in the positive electrode of battery 20.

[0100] When the distribution of lithium ions in the positive electrode of battery 20 is estimated, lithium condition estimator 131 can check whether a residual area exists in the positive electrode of battery 20.

[0101] In the following text, reference will be made to Figure 6A and Figure 6B as well as Figure 7A and Figure 7B The method for detecting residual areas by lithium condition estimator 131 is described in detail.

[0102] Figures 6A to 6D An example of a residual region appearing within the positive electrode active material particles of battery 20 is shown. Figures 6A to 6D You can use the reference Figure 3C and Figure 3D The bar graphs described are used to explain the behavior of lithium ions within the active material particles of the positive electrode.

[0103] refer to Figure 6A First, in the first discharge phase, battery 20 can discharge from SOC 50% to SOC 0%. At SOC 50%, the Li-depleted phase region P(1) and the Li-rich phase region R(1) can exist at the outer boundary and center of the positive electrode active material particles of battery 20, respectively. Subsequently, when discharge starts, due to lithium ion insertion, the Li-rich phase region R(1) can be generated at the outer boundary of the positive electrode active material particles of battery 20. As discharge proceeds, within the positive electrode active material particles of battery 20, the Li-depleted phase region P(1) can gradually transform into the Li-rich phase region R(1).

[0104] When the battery discharges at 20 CC, due to the characteristics of CC discharge, when the distance between two adjacent Li-rich phase regions R(1) and R(2) approaches a predetermined distance, a residual region D can be generated in the boundary portion between the two Li-rich phase regions R(1) and R(2). The residual region D may appear because lithium ions are not sufficiently embedded in the boundary portion between the two Li-rich phase regions R(1) and R(2), resulting in the retention of the Li-poor phase portion. Figure 6A For example, even if battery 20 is discharged to SOC 0%, due to the characteristics of CC discharge, the residual region D can still exist in the boundary part between the two Li-rich phase regions R(1) and R(2).

[0105] In the next first charging phase, battery 20 can be charged from SOC 0% to SOC 100%. At SOC 0%, two Li-rich phase regions R(1) and R(2) can exist in the outer boundary and center of the positive electrode active material particles of battery 20, respectively, and the residual region D exists in the boundary portion between the two Li-rich phase regions R(1) and R(2). Subsequently, when charging starts, due to the deintercalation of lithium ions, the Li-poor phase region P(1) can be generated in the outer boundary of the positive electrode active material particles of battery 20. As charging proceeds, the Li-rich phase region R(1) can gradually transform into the Li-poor phase region P(1). When charging continues and the SOC of battery 20 becomes higher than 50%, all lithium ions can also be deintercalated from the residual region D, so the residual region D can be transformed into the Li-poor phase region P(1), thereby eliminating the residual region D.

[0106] Therefore, in the next second discharge phase, when battery 20 discharges from 100% SOC to 0% SOC again, the residual region D may no longer exist in the positive electrode active material particles of battery 20.

[0107] refer to Figure 6B First, in the first charging phase, battery 20 can be charged from 50% SOC to 100%. At 50% SOC, the Li-depleted phase region P(1) and the Li-rich phase region R(1) can exist in the center and outer boundary of the positive electrode active material particles of battery 20, respectively. Subsequently, when charging starts, due to the deintercalation and intercalation of lithium ions, the Li-depleted phase region P(1) can be generated in the outer boundary of the positive electrode active material particles of battery 20. As charging progresses, the Li-rich phase region R(1) can gradually transform into the Li-depleted phase region P(1).

[0108] When the battery is charged at 20 CC, due to the characteristics of CC charging, when the distance between two adjacent Li-depleted phase regions P(1) and P(2) approaches a predetermined distance, a residual region D may appear in the boundary portion between the two Li-depleted phase regions P(1) and P(2). The residual region D may appear because lithium ions are not fully released from the boundary portion between the two Li-depleted phase regions P(1) and P(2), resulting in the retention of the Li-rich phase. Figure 6B For example, even if battery 20 is charged to 100% SOC, due to the characteristics of CC charging, the residual region D can still exist in the boundary portion between the two Li-depleted phase regions P(1) and P(2).

[0109] In the subsequent first discharge phase, battery 20 can discharge from SOC 100% to SOC 0%. At SOC 100%, within the positive electrode active material particles of battery 20, two Li-depleted phase regions P(1) and P(2) can exist at the outer boundary and center of the positive electrode active material particles, respectively, and the residual region D exists in the boundary portion between the two Li-depleted phase regions P(1) and P(2). When discharge starts, due to lithium ion insertion, the Li-rich phase region R(1) can be generated at the outer boundary of the positive electrode active material particles of battery 20. As discharge proceeds, within the positive electrode active material particles, the Li-depleted phase region P(1) can gradually transform into the Li-rich phase region R(1). When discharge continues and the SOC of battery 20 becomes below 50%, lithium ions can also be fully inserted into the residual region D, thus the residual region D can be transformed into the Li-rich phase region R(1), thereby eliminating the residual region D.

[0110] Therefore, in the next second charging phase, when battery 20 is charged again from SOC 0% to SOC 100%, the residual region D may no longer exist in the positive electrode active material particles of battery 20.

[0111] refer to Figures 6A to 6B When two adjacent Li-rich phase regions R(1) and R(2) are within a predetermined distance during CC discharge, or when two adjacent Li-poor phase regions P(1) and P(2) are within a predetermined distance during CC charging, a residual region D can be generated in the boundary portion between the two adjacent in-phase regions. This residual region D can be maintained until lithium ions are fully filled into or fully released from the residual region D.

[0112] Meanwhile, depending on the charging and discharging history, multiple residual regions D can exist within the positive electrode active material particles. Figure 6C For example, when battery 20 is charged from 0% SOC to 50%, then discharged back to 0% SOC by CC, and then charged to 30% SOC, and then discharged back to 0% SOC by CC, the residual region D can be formed both when discharging from 50% SOC to 0% and when discharging from 30% SOC to 0%. Figure 6D For example, when battery 20 is discharged from SOC 100% to SOC 50%, then CC-charged back to SOC 100%, and then discharged to SOC 30%, and then CC-charged back to SOC 100%, the residual region D can be formed when charging from SOC 50% to SOC 100% and when charging from SOC 30% to SOC 100%, respectively.

[0113] Figure 7A and Figure 7BThis is a diagram used to explain the lithium condition estimator 131's method of detecting residual areas based on the lithium ion distribution state.

[0114] In the CC discharge section, the position information (start position and end position) of each Li-rich phase region can be continuously estimated. When two or more Li-rich phase regions exist within the positive electrode active material particles, the lithium condition estimator 131 can estimate the relative distance (distance in a one-dimensional coordinate system) between two adjacent Li-rich phase regions based on the position information of each Li-rich phase region.

[0115] by Figure 7A For example, as battery 20 discharges from 50% SOC to 20% SOC, a new Li-rich phase region R(1) can be generated at the outer boundary of the positive electrode active material particles. Therefore, two Li-rich phase regions R(1) and R(2) can exist within the positive electrode active material particles. The lithium condition estimator 131 can continuously estimate the positional information of these two Li-rich phase regions R(1) and R(2). Furthermore, the lithium condition estimator 131 can estimate the relative distance between the two Li-rich phase regions R(1) and R(2) based on the positional information of each of the Li-rich phase regions R(1) and R(2). The lithium condition estimator 131 can estimate the relative distance between the two Li-rich phase regions R(1) and R(2) by subtracting the ending position E(1) of the later-generated Li-rich phase region R(1) (located on the outer boundary of the positive electrode active material particle) from the starting position S(2) of the first-generated Li-rich phase region R(2) (located at the center of the positive electrode active material particle) in the two Li-rich phase regions R(1) and R(2) using the value (S(2)-E(1)).

[0116] When the relative distance (S(2)-E(1)) between two Li-rich phase regions R(1) and R(2) decreases below a threshold through CC discharge, the lithium condition estimator 131 can determine that a residual region D is formed between the two Li-rich phase regions R(1) and R(2). When it is determined that the residual region D is formed between the two Li-rich phase regions R(1) and R(2), the lithium condition estimator 131 can record the starting position E(1) of the residual region D in the storage device 11. The lithium condition estimator 131 can continuously detect the starting position E(1) of the residual region D until the relative distance (S(2)-E(1)) between the two Li-rich phase regions R(1) and R(2) becomes 0, and update the information recorded in the storage device 11. When the relative distance (S(2)-E(1)) between the two Li-rich phase regions R(1) and R(2) becomes 0, the lithium condition estimator 131 can detect the boundary (E(1) or S(2)) between the two Li-rich phase regions R(1) and R(2) as the starting position of the residual region D and update the information recorded in the storage device 11.

[0117] When the CC discharge lasts for a predetermined time or longer, or when the CV discharge occurs after the relative distance (S(2)-E(1)) between the two Li-rich phase regions R(1) and R(2) becomes 0, the lithium condition estimator 131 can determine that the residual region D has disappeared. Therefore, the lithium condition estimator 131 can delete the location information of the residual region D from the storage device 11. In addition, the lithium condition estimator 131 can determine that the two Li-rich phase regions R(1) and R(2) are combined to form a Li-rich phase region R(1), and can update the location information of the Li-rich phase region R(1).

[0118] On the other hand, if the CC discharge is interrupted when the residual region D is determined to remain, the lithium condition estimator 131 can maintain the location information of the residual region D stored in the storage device 11. Figure 7A For example, the lithium condition estimator 131 can estimate that the residual region D remains at the boundary between the two Li-rich phase regions R(1) and R(2) because the discharge of the battery 20 is interrupted due to the SOC of the battery 20 reaching 0%. Therefore, the lithium condition estimator 131 can maintain the location information E(1) of the residual region D detected at SOC 0% as recorded in the storage device 11.

[0119] The residual region D generated during CC discharge can be eliminated when charging continues and lithium ions are fully released from the residual region D.

[0120] by Figure 7AFor example, in the charging phase after CC discharge, battery 20 can be charged to 80% SOC. When charging starts, lithium ions begin to deintercalate from the Li-rich phase region R(1), allowing the Li-rich phase region R(1) to gradually transform into the Li-poor phase region P(1). Subsequently, as charging continues and the SOC of battery 20 becomes 50%, the Li-rich phase region R(1), which was previously located on the outer boundary side, may lose all lithium ions, thus transforming into the Li-poor phase region P(1). In addition, lithium ions may begin to be released from the residual region D. Therefore, the lithium condition estimator 131 can change the Li-rich phase region R(2), which was previously located in the center of the positive electrode active material particles, into the Li-rich phase region R(1), and can change the position information S(2) and E(2) of the Li-rich phase region R(2) into the position information S(1) and E(1) of the new Li-rich phase region R(1), and store them in the storage device 11. In addition, the lithium condition estimator 131 can delete the location information S(2) and E(2) of the past Li-rich phase region R(2) from the storage device 11.

[0121] Subsequently, as charging continues, i.e., when the SOC of battery 20 increases to over 50%, the residual region D may lose all lithium ions, thus transforming into the Li-depleted phase region P(1), and lithium ions can begin to be released from the remaining Li-rich phase region R(1). Therefore, the lithium condition estimator 131 can delete the location information of the residual region D from the storage device 11.

[0122] During the CC charging phase, the lithium condition estimator 131 can continuously estimate the location information of each Li-depleted phase region P(i). When two or more Li-depleted phase regions exist within the positive electrode active material particles, the lithium condition estimator 131 can estimate the relative distance (distance in a one-dimensional coordinate system) between two adjacent Li-depleted phase regions based on the location information of each Li-depleted phase region. Subsequently, when the relative distance between two Li-depleted phase regions decreases below a threshold during CC charging, the lithium condition estimator 131 can determine that a residual region is formed between the two Li-depleted phase regions.

[0123] At the same time, such as Figure 7B As shown, when the lithium condition estimator 131 records the lithium ion distribution state within the positive electrode active material particles, if the method of recording the location information of each Li-rich phase region is used, the lithium condition estimator 131 can detect the formation of a residual region in the boundary portion between two Li-poor phase regions based on the change in the location information of the Li-rich phase region located between two Li-poor phase regions.

[0124] by Figure 7BFor example, as the battery 20 is charged from 50% SOC to 80% SOC, a new Li-depleted phase region P(1) can be generated at the outer boundary of the positive electrode active material particles. Therefore, two Li-depleted phase regions P(1) and P(2) can exist within the positive electrode active material particles, and a Li-rich phase region R(1) is located between the two Li-depleted phase regions P(1) and P(2). The lithium condition estimator 131 can continuously estimate the position information S(1) and E(1) of the Li-rich phase region R(1). Furthermore, the lithium condition estimator 131 can calculate the relative distance between the Li-depleted phase regions P(1) and P(2) based on the position information S(1) and E(1) of the Li-rich phase region R(1). The lithium condition estimator 131 can estimate the relative distance between the two Li-depleted phase regions P(1) and P(2) based on the difference between the start position S(1) and the end position E(1) of the Li-rich phase region R(1) (i.e., the width of the Li-rich phase region R(1)).

[0125] When the relative distance (E(1)-S(1)) between two Li-depleted phase regions P(1) and P(2) decreases below a threshold through CC charging, the lithium condition estimator 131 can determine that a residual region D is formed between the two Li-depleted phase regions P(1) and P(2). When it is determined that the residual region D is formed between the two Li-depleted phase regions P(1) and P(2), the lithium condition estimator 131 can record the starting position S(1) of the residual region D in the storage device 11. The lithium condition estimator 131 can continuously detect the starting position S(1) of the residual region D until the relative distance (E(1)-S(1)) between the two Li-depleted phase regions P(1) and P(2) becomes 0, and update the information recorded in the storage device 11. When the relative distance (E(1)-S(1)) between the two Li-depleted phase regions P(1) and P(2) becomes 0, the lithium condition estimator 131 can update the position information of the residual region D by recording the boundary E(1) or S(1) between the two Li-depleted phase regions P(1) and P(2) in the storage device 11 as the starting position of the residual region D.

[0126] When CC charging continues for a predetermined time or longer, or when CV charging is performed after the relative distance (E(1)-S(1)) between the two Li-depleted phase regions P(1) and P(2) becomes 0, the lithium condition estimator 131 can determine that the residual region D has disappeared. Therefore, the lithium condition estimator 131 can delete the location information of the residual region D from the storage device 11. In addition, the lithium condition estimator 131 can determine that the two Li-depleted phase regions P(1) and P(2) are combined to form a Li-depleted phase region P(1), and can update the location information of the Li-depleted phase region P(1).

[0127] On the other hand, CC charging stops while the residual area D still exists, and the lithium condition estimator 131 can maintain the position information of the residual area D stored in the storage device 11. Figure 7B For example, the lithium condition estimator 131 can determine that the residual region D still exists at the boundary of the two Li-depleted phase regions P(1) and P(2) because the CC charging has stopped due to the SOC of the battery 20 reaching 100%, and the location information E(1) or S(1) of the residual region D can be removed from the storage device 11.

[0128] When lithium ions are fully inserted into the residual region D through discharge, the residual region D generated during CC charging can be eliminated.

[0129] by Figure 7B For example, in the discharge phase after CC charging, battery 20 can discharge to SOC 20%. When discharge starts, lithium ions can begin to intercalate into the Li-poor phase region P(1), and the Li-poor phase region P(1) gradually transforms into the Li-rich phase region R(1). Subsequently, when the discharge continues and the SOC of battery 20 becomes 50%, the Li-poor phase region P(1) that was previously located on the outer boundary can fully acquire lithium ions to transform into the Li-rich phase region R(1), and lithium ions can also begin to intercalate into the residual region D.

[0130] Subsequently, as the discharge proceeds further, i.e., when the SOC of battery 20 becomes below 50%, the residual region D can also acquire sufficient lithium ions to transform into the Li-rich phase region R(1), and lithium ions can begin to intercalate into the remaining Li-poor phase region P(1). Therefore, the lithium condition estimator 131 can delete the location information of the residual region D from the storage device 11.

[0131] When recording the location information of the residual region D, the lithium condition estimator 131 can also record the corresponding SOC in the storage device 11 by mapping it to the corresponding SOC. The lithium condition estimator 131 can predict the SOC when starting up through the insertion or deintercalation of lithium ions in the residual region D during charging or discharging, and can store it together with the location information of the residual region D in the storage device 11. Figure 7A and Figure 7BAs shown, when modeling the distribution of lithium ions within the positive electrode active material particles using a bar chart, it can be seen that the proportion of the Li-depleted phase region within the positive electrode active material particles (the proportion of the Li-depleted phase region on the bar chart) is proportional to the SOC of the battery 20. Therefore, the lithium condition estimator 131 can predict the SOC of the battery 20 at the time point when lithium ion insertion or extraction in the residual region D starts (hereinafter referred to as the "memory point") based on the current SOC of the battery 20, the current position information of the Li-depleted phase region within the positive electrode active material particles, and the current position information of the residual region D.

[0132] The residual region D formed in the boundary between two in-phase regions may lead to a change in the activation energy barrier, thereby generating additional overvoltage.

[0133] Figure 8A and Figure 8B It is a graph used to explain the trend of overvoltage caused by residual regions.

[0134] exist Figure 8A Case 1 shows the voltage curve of battery 20 under normal conditions (no residual area) when charged from 0% SOC to 100% SOC and then discharged back to 0% SOC. Case 2 shows the voltage curve of battery 20 after Case 1 has been performed, when charged from 0% SOC to 50% SOC and then discharged back to 0% SOC. Case 3 shows the voltage curve of battery 20 after Case 2 has been performed, when charged from 0% SOC to 100% SOC and then discharged back to 0% SOC.

[0135] For reference Figure 6A As described, after scenario 2, a residual region located in the boundary portion between the two Li-rich phase regions can form within the positive electrode active material particles of battery 20. Therefore, compared to scenario 1 without a residual region, in scenario 3 where a residual region is present, additional overvoltage can be added to the voltage of battery 20.

[0136] Figure 8B It is a voltage curve representing the additional overvoltage (i.e., voltage increase) caused by the residual region in the charging section of case 3. Figure 8B The voltage curve can be derived from the voltage difference between the voltage curve in the charging section of case 3 and the voltage curve in the charging section of case 1.

[0137] As discussed herein, the lithium condition estimator 131 can model the distribution of lithium ions relative to a single positive electrode active material particle based on the state of charge (SOC) and detect the positions of individual phase regions and residual regions within the positive electrode active material particle. However, the positive electrode of an actual battery 20 may include multiple positive electrode active material particles. When the positive electrode comprises multiple positive electrode active material particles, the timing of the appearance of the residual region within the particle and the timing of lithium ion insertion / extraction within the residual region can vary depending on the position of each positive electrode active material particle.

[0138] Therefore, as Figure 8B As shown, the additional overvoltage curve caused by the residual region of the positive electrode active material particles in battery 20 can exhibit a shape similar to a normal distribution curve over a wide SOC range.

[0139] Furthermore, the residual area can reduce the effective capacity of battery 20; therefore, overvoltage can continue to increase until battery 20 is fully charged. Due to these characteristics, in some SOC ranges, such as Figure 8B As shown, additional overvoltage curves may appear in a shape similar to an exponential function.

[0140] Based on the characteristics described in this paper, the additional overvoltage curve caused by the residual region in battery 20 can be defined by using two overvoltage functions (i.e., the normal distribution function and the exponential function).

[0141] Figure 9A and Figure 9B An example is shown where additional overvoltage due to the residual region is defined using two voltage curves, where Figure 9A This represents the overvoltage curve during the charging phase, and Figure 9B This represents the overvoltage curve within the discharge section. (Reference) Figure 9A During the charging phase of battery 20, overvoltages with a normal distribution curve shape can appear in the low SOC range, and subsequently, overvoltages with an exponential function curve shape that gradually increases with increasing SOC can appear. (Reference) Figure 9B In the discharge phase of battery 20, overvoltages with a normal distribution curve shape can appear in the high SOC range, and then overvoltages with an exponential function curve shape that increases as SOC decreases can appear.

[0142] exist Figure 9A and Figure 9B In this context, the additional overvoltage curve y caused by the residual area in battery 20 can be defined as the sum of two voltage curves (the first voltage curve y1 and the second voltage curve y2) (y=y1+y2).

[0143] The first voltage curve y1 can correspond to the additional overvoltage caused by the change in the activation energy barrier due to the residual region within the positive electrode active material particles, and can be defined by using the normal distribution function f1(x) of Equation 1 below.

[0144] [Equation 1]

[0145]

[0146] Compared to Figure 8A In the case where cases 2 and 3 are executed sequentially, when... Figure 7A When modeling the lithium-ion distribution within the positive electrode active material particles using the method shown, residual region D can be generated within the positive electrode active material particles as case 2 progresses. Furthermore, as case 3 progresses and battery 20 is charged to approximately 50% SOC, lithium ions begin to be released from residual region D, which can alter the activation energy barrier. (Reference) Figure 8A and Figure 8B It can be seen that even in the overvoltage curve of battery 20 where multiple positive electrode active material particles are distributed in the positive electrode, the part of the normal distribution curve also has symmetry centered on SOC 50%.

[0147] Therefore, in Equation 1 above, m, representing the center (or average) of the normal distribution, can be a memory point recorded by the lithium condition estimator 131. As described herein, when recording the location of the residual region D, the lithium condition estimator 131 can predict the state of charge (SOC) at which lithium ions begin to intercalate or deintercalate in the residual region D, and the predicted SOC can then be stored in the storage device 11 as a memory point.

[0148] In Equation 1 above, x can represent the current SOC, and σ can represent the dispersion of the normal distribution curve y1. σ can be determined in advance through experiments and can also be determined by fitting the normal distribution curve y1 to the actual overvoltage curve y of battery 20.

[0149] The second voltage curve y2 can correspond to the additional overvoltage caused by the reduction of the effective capacity of battery 20 due to the residual area, and can be defined by using the exponential function f2(x) of Equation 2 below.

[0150] [Equation 2]

[0151]

[0152] In Equation 2 above, OVmax can represent the maximum value of the overvoltage due to the additional residual region, m can represent the memory point recorded by the lithium condition estimator 131, n can represent the SOC when OVmax occurs, a can correspond to the base of the exponential function, and x can represent the current SOC. OVmax, a, and n can be determined in advance through experiments and can also be determined by fitting the exponential function f2(x) and the actual overvoltage curve y of battery 20.

[0153] refer to Figure 9A In the second voltage curve y2 during battery 20 charging, a > 1 can be set because the voltage value increases with increasing SOC. (Reference) Figure 9B In the second voltage curve y2 when discharging battery 20, 0 < a < 1 can be set because the voltage value decreases as SOC increases.

[0154] refer to Figure 9A The additional overvoltage caused by the residual area in battery 20 during charging can be estimated using the normal distribution function f1(x) and the exponential function f2(x) within the SOC range satisfying 0 < SOC < n. Furthermore, refer to... Figure 9B The additional overvoltage caused by the residual area in battery 20 during discharge can be estimated using the normal distribution function f1(x) and the exponential function f2(x) in the SOC range where n < SOC < 100.

[0155] Return to reference Figure 2 The overvoltage functions (normal distribution function f1(x) and exponential function f2(x)) described in this paper can be calibrated by preliminary experiments on the voltage behavior of battery 20 and then stored in function table 112 of storage device 11.

[0156] The behavior of the additional overvoltage caused by the residual region can vary depending on the charging and discharging conditions (temperature of battery 20, SOH, location of the residual region (or memory point), etc.). Therefore, through preliminary experiments, overvoltage functions (normal distribution function f1(x) and exponential function f2(x)) can be generated for each charging and discharging condition, and each charging and discharging condition and its corresponding overvoltage function (normal distribution function f1(x) and exponential function f2(x)) are stored in function table 112.

[0157] Return to reference Figure 2When the lithium condition estimator 131 estimates that the residual region exists within the positive electrode active material particles, the corrector 132 can extract overvoltage functions (normal distribution function f1(x) and exponential function f2(x)) that match the current charge and discharge conditions from the function table 112. The corrector 132 can calculate the overvoltage value corresponding to the current SOC by using the overvoltage functions (normal distribution function f1(x) and exponential function f2(x)) extracted from the function table 112. When no overvoltage function corresponding to the current charge and discharge conditions is found from the function table 112, the corrector 132 can also extract the overvoltage function of the charge and discharge conditions most similar to the current charge and discharge conditions from the function table 112. In this case, the corrector 132 can correct the overvoltage function extracted from the function table 112 by methods such as interpolation to suit the current charge and discharge conditions.

[0158] When the overvoltage value is calculated, the corrector 132 can use it to generate correction parameters (correction resistance or correction voltage). The corrector 132 can then combine the generated correction parameters with the battery model 111 to correct the battery model 111.

[0159] Figure 10A and Figure 10B This is a diagram used to explain the method by which the calibrator 132 calibrates the battery model 111.

[0160] refer to Figure 10A When the overvoltage value corresponding to the current SOC is calculated, the corrector 132 can obtain the correction resistor Rmem by dividing the calculated overvoltage value by the current measurement value of the battery 20. The corrector 132 can correct the battery model 111 by adding the obtained correction resistor Rmem as an internal parameter of the battery model 111. That is, the corrector 132 can add the correction resistor Rmem as a resistor connected between the series resistor Rs and the open circuit voltage (OCV) Vocv.

[0161] refer to Figure 10B When the overvoltage value corresponding to the current SOC is calculated, the corrector 132 can correct the battery model 111 by adding it as a correction voltage Vmem to the battery model 111. That is, the corrector 132 can add a correction voltage Vmem to the battery model 111, so that it is connected in series with the open circuit voltage (OCV) Vocv.

[0162] Return to reference Figure 2The battery condition estimator 133 can determine the condition value of the battery 20 using the battery model 111 calibrated by the calibrator 132 and the measurements from the measuring device 12. That is, the battery condition estimator 133 can estimate the internal impedance Rs, Rp, and Cp, open-circuit voltage (OCV) Vocv, and state of charge (SOH) of the battery 20 using the calibrated battery model 111 and current and voltage measurements. The battery condition estimator 133 can also calibrate the state of charge (SOC) of the battery 20 using the battery model 111. For example, the battery condition estimator 133 can estimate the SOC of the battery 20 using measurements taken from the battery 20, and then calibrate the SOC using the calibrated battery model 111. Furthermore, the battery condition estimator 133 can detect anomalies in the battery 20, such as internal short circuits and degradation, based on the condition value of the battery 20. Moreover, when an anomaly is detected in the battery 20, the battery condition estimator 133 can perform protection functions for the battery 20, such as blocking charging and discharging currents.

[0163] The control device 13 may include at least one processor for performing the functions of the control device 13 mentioned herein (the functions of the lithium condition estimator 131, the corrector 132, and the battery condition estimator 133). A processor may refer to a data processing device having physically structured circuitry to perform functions expressed by code or instructions included in a program, such as a microprocessor, central processing unit (CPU), processor core, multiprocessor, application-specific integrated circuit (ASIC), field-programmable gate array (FPGA), etc.

[0164] The control device 13 can be integrated into the battery management system (BMS) of the battery system 1.

[0165] Figure 11 A method for detecting battery condition according to an embodiment is illustrated schematically. Figure 11 The method can be found in the reference. Figures 2 to 10B The control device 13 described is executed.

[0166] refer to Figure 11 In step S100, the control device 13 can record the charging and discharging history of the battery 20 and the history of changes in the distribution state of lithium ions within the positive electrode active material particles.

[0167] In step S100, the charging and discharging history may include the history of changes in the SOC of the battery 20. The control device 13 records the charging and discharging history of the battery 20 by continuously detecting the SOC of the battery 20, and stores the detected SOC in the storage device 11 in chronological order.

[0168] In step S100, the lithium-ion distribution state within the positive electrode active material particles can be estimated based on the SOC of the battery 20. The control device 13 can then use a reference... Figure 3C and Figure 3D The bar chart format is used to model the interior of the positive electrode active material particles, and the location information of the Li-rich phase region and the Li-depleted phase region in the one-dimensional coordinate system according to the SOC variation can be estimated. When the location information of the Li-rich phase region and the Li-depleted phase region is determined, the control device 13 can store it in the storage device 11 by mapping it to the corresponding SOC.

[0169] In step S100, the control device 13 can detect the formation of a residual region based on the location information of the Li-rich phase region and the Li-depleted phase region. When it is determined that a residual region has been formed, the control device 13 can record the location information of the residual region in the storage device 11. In addition, the control device 13 can predict the memory point corresponding to the residual region and can record the predicted memory point together in the storage device 11.

[0170] In step S110, when it is determined that the residual region exists within the positive electrode active material particles, in step S120, the control device 13 can generate correction parameters for reflecting the overvoltage caused by the residual region in the battery model 111.

[0171] In step S120, the control device 13 can extract overvoltage functions (normal distribution function f1(x) and exponential function f2(x)) corresponding to the current charging and discharging conditions (temperature of battery 20, state of equilibrium (SOH), and location of residual area (or memory point)) from function table 112. The control device 13 can calculate the overvoltage value corresponding to the current SOC by using the overvoltage functions extracted from function table 112. When the overvoltage value is calculated, the control device 13 can use it to generate correction parameters (correction resistor, or correction voltage).

[0172] When the calibration parameters are generated, in step S130, the control device 13 can calibrate the battery model 111 by combining the calibration parameters into the battery model 111.

[0173] In step S130, the control device 13 may add a correction resistor Rmem as a resistor connected between the series resistor Rs and the open-circuit voltage (OCV) Vocv inside the battery model 111. The control device 13 may also add a correction voltage Vmem to the battery model 111, connecting it in series with the open-circuit voltage (OCV) Vocv.

[0174] When the battery model 111 is calibrated, in step S140, the control device 13 can estimate the condition of the battery 20 by using the calibrated battery model 111.

[0175] In step S140, the control device 13 can estimate the internal impedance Rs, Rp, and Cp, open-circuit voltage (OCV) Vocv, and state of equilibrium (SOH) of the battery 20 using the calibrated battery model 111 and current and voltage measurements. The control device 13 can also estimate the state of charge (SOC) of the battery 20 using the battery model 111. For example, the control device 13 can estimate the SOC of the battery 20 using measurements taken from the battery 20, and then calibrate the SOC using the calibrated battery model 111. Furthermore, the control device 13 can detect anomalies in the battery 20, such as internal short circuits and degradation, using the calibrated battery model 111.

[0176] In addition to the apparatus and / or methods described herein, which are readily achievable by those skilled in the art, the embodiments described herein can also be implemented by a program for implementing functions corresponding to the configuration of the embodiments or by a recording medium for recording the program. Computer-readable recording media can include all types of recording means for storing data that can be read by a computer system. Examples of computer-readable recording means can include ROM, RAM, CD-ROM, DVD_ROM, DVD_RAM, magnetic tape, floppy disk, hard disk, and optical data storage means.

[0177] While this disclosure has been described in conjunction with embodiments now considered practical, it should be understood that this disclosure is not limited to the disclosed embodiments, but rather is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Claims

1. A device for detecting battery status, comprising: Storage devices, which model battery voltage changes and internal impedance as electrical circuits; as well as The control device is configured to estimate the distribution state of lithium ions in the positive electrode active material of the battery, detect a distortion region remaining in the boundary portion of two in-phase regions in the positive electrode active material based on the distribution state, estimate the overvoltage caused by the distortion region, correct the battery model by using a correction parameter corresponding to the overvoltage, and estimate the condition of the battery by using the battery model.

2. The apparatus according to claim 1, wherein: The active material of the positive electrode includes LiFePO4; The distribution state includes Li x Li-rich phase regions containing FePO4 (x ≥ 0.9) phase and Li-containing phases y The distribution of the Li-depleted phase region of FePO4 (y ≤ 0.05) within the positive electrode active material particles; and The two in-phase regions are either two Li-rich phase regions or two Li-poor phase regions.

3. The apparatus according to claim 2, wherein, The control device is configured to: The region between the outer boundary and the center of the positive electrode active material particle is modeled as a one-dimensional coordinate system; By using the one-dimensional coordinate system, the positional information of the Li-rich phase region and the Li-depleted phase region within the positive electrode active material particles is estimated.

4. The apparatus according to claim 3, wherein, The control device is configured to: Based on the location information, estimate the first distance between the two Li-rich phase regions or the second distance between the two Li-poor phase regions; If the first distance decreases below a threshold during constant current discharge, it is determined that the distortion region is formed in the boundary portion between the two Li-rich phase regions; as well as If the second distance decreases below the threshold during constant current charging, it is determined that the distortion region is formed in the boundary portion between the two Li-depleted phase regions.

5. The apparatus according to claim 4, wherein, The control device is configured to: if the distorted region exists in the boundary portion of the two Li-rich phase regions, and if the distorted region is transformed into the Li-rich phase region by discharge or into the Li-depleted phase region by charging, then determine that the distorted region has been eliminated.

6. The apparatus according to claim 4, wherein, The control device is configured to: if the distorted region exists in the boundary portion of the two Li-depleted phase regions, and if the distorted region is transformed into the Li-depleted phase region by charging or the distorted region is transformed into the Li-rich phase region by discharging, then determine that the distorted region has been eliminated.

7. The apparatus according to claim 4, wherein, The control device is configured to: By using the one-dimensional coordinate system, the location information of the distorted region is estimated; and Based on the location information of the distortion region, the state of charge (SOC) is predicted when lithium ions are deintercalated or intercalated into the distortion region during subsequent charging or discharging phases.

8. The apparatus according to claim 7, wherein: The control device is configured to determine the overvoltage by a first overvoltage and a second overvoltage, wherein the first overvoltage is estimated using a first overvoltage function and the second overvoltage is estimated using a second overvoltage function; The first overvoltage function is a normal distribution function centered on the SOC, and the first overvoltage function derives the first overvoltage that appears in the distortion region for each SOC of the battery; and The second overvoltage function is an exponential function, which derives the second overvoltage that occurs in the distortion region for each state of charge (SOC) of the battery.

9. The apparatus according to claim 8, wherein: The storage device is configured to store a function table including a plurality of first overvoltage functions and a plurality of second overvoltage functions corresponding to different charging and discharging conditions; and The control device is configured to select the first overvoltage function and the second overvoltage function from the function table depending on the current charging and discharging status of the battery.

10. The apparatus according to claim 1, wherein: The correction parameters include a correction resistor or a correction voltage; and The control device is configured to add the correction resistor or the correction voltage to the internal parameters of the battery model.

11. A method for detecting battery condition, the method comprising: The distribution state of lithium ions in the positive electrode active material is based on the charging and discharging history of the battery. Based on the distribution state, the distortion region remaining in the boundary portion of the two in-phase regions in the positive electrode active material is detected; Estimate the overvoltage caused by the distortion region; The battery model of the battery is corrected by using correction parameters corresponding to the overvoltage; and The condition of the battery is estimated by using the battery model. The battery model models the voltage changes and internal impedance of the battery as an electrical circuit.

12. The method according to claim 11, wherein: The active material of the positive electrode includes LiFePO4; The distribution state includes Li x Li-rich phase regions containing FePO4 (x ≥ 0.9) phase and Li-containing phases y The distribution of the Li-depleted phase region of FePO4 (y ≤ 0.05) within the positive electrode active material particles; and The two in-phase regions are either two Li-rich phase regions or two Li-poor phase regions.

13. The method according to claim 12, wherein, The recording includes estimating the positional information of the Li-rich phase region and the Li-depleted phase region within the positive electrode active material particle by using a one-dimensional coordinate system that models the region between the outer boundary and the center of the positive electrode active material particle.

14. The method according to claim 13, wherein, The detection of the distorted region includes: Based on the location information, estimate the first distance between the two Li-rich phase regions or the second distance between the two Li-poor phase regions; If the first distance decreases below a threshold during constant current discharge, it is determined that the distortion region is formed in the boundary portion between the two Li-rich phase regions; and If the second distance decreases below the threshold during constant current charging, it is determined that the distortion region is formed in the boundary portion between the two Li-depleted phase regions.

15. The method of claim 14, further comprising: If the distorted region exists in the boundary portion of the two Li-rich phase regions, and if the distorted region transforms into the Li-rich phase region through discharge or transforms into the Li-depleted phase region through charging, then it is determined that the distorted region has been eliminated.

16. The method of claim 14, further comprising: If the distorted region exists in the boundary portion of the two Li-depleted phase regions, and if the distorted region transforms into the Li-depleted phase region through charging or transforms into the Li-rich phase region through discharging, then it is determined that the distorted region has been eliminated.

17. The method of claim 14, further comprising: The location information of the distorted region is estimated by using the one-dimensional coordinate system; as well as Based on the location information of the distortion region, the state of charge (SOC) is predicted when lithium ions are deintercalated or intercalated into the distortion region during subsequent charging or discharging phases.

18. The method according to claim 17, wherein, The estimation of the overvoltage includes: The first overvoltage is estimated using the first overvoltage function; The second overvoltage is estimated by using a second overvoltage function; and The overvoltage is determined by using the first overvoltage and the second overvoltage. Wherein, the first overvoltage function is a normal distribution function centered on the SOC, and the first overvoltage function derives the first overvoltage appearing in the distortion region for each SOC of the battery, and The second overvoltage function is an exponential function, which derives the second overvoltage that occurs in the distortion region for each state of charge (SOC) of the battery.

19. The method according to claim 18, wherein, Also includes: The storage includes a function table containing multiple first overvoltage functions and multiple second overvoltage functions corresponding to different charging and discharging conditions; as well as Depending on the current charging and discharging status of the battery, the first overvoltage function and the second overvoltage function are selected from the function table.

20. The method of claim 11, wherein: The correction parameters include a correction resistor or a correction voltage; and The correction includes correcting the battery model by adding the correction resistor or the correction voltage to the internal parameters of the battery model.

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