Nondestructive battery degraded state estimation method, nondestructive battery degraded state estimation program, and battery utilization method

Abstract

To solve the problem of a conventional characteristic degraded state estimation process that batteries of unknown origin are unusable.SOLUTION: A nondestructive characteristic degraded state estimation process involves performing: a current resistance value measurement process S31 of measuring the current battery resistance of a battery cell; a characteristic degradation factor analysis process S32 of estimating a current value for each degradation factor parameter which is a characteristic degradation factor of the battery cell on the basis of the difference between a preliminarily estimated battery resistance of the battery cell in a new product state and the current battery resistance; and a salt concentration unevenness moderation process S33 of taking a degradation factor parameter at the time as the determined value, in response to an event that the current battery resistance measured after a charging-discharging process in which the charging-discharging rates are limited has started to rise and a change amount between the previous current battery resistance and the latest current battery resistance became to fall within a preset certain range. When the current battery resistance measured in the salt concentration unevenness moderation process S33 is lower than the previous current battery resistance, the characteristic degradation factor analysis process S32 is executed based on a newly measured current battery resistance.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a non-destructive battery degradation state estimation method, a non-destructive battery degradation state estimation program, and a battery usage method that estimate battery parameters that indicate battery characteristic degradation caused by usage history, for example, without destroying a battery whose manufacturing process or usage history is unknown. [Background technology]

[0002] In recent years, secondary batteries that have been used for a specific purpose have come to be recycled for other purposes. However, when using secondary batteries, if the battery parameters for grasping the state of the secondary battery cannot be grasped, a problem occurs in which the battery control becomes unstable due to overcharging, overdischarging, etc. of the secondary battery. Thus, technologies for grasping the deterioration state of a secondary battery are disclosed in Patent Documents 1 to 4.

[0003] The battery degradation estimation device described in Patent Document 1 is a battery degradation estimation device that estimates battery degradation based on a positive electrode capacity retention rate, a negative electrode capacity retention rate, and a positive and negative electrode composition correspondence mismatch capacity, and has a mismatch capacity calculation unit that calculates the positive and negative electrode composition correspondence mismatch capacity, a measurement unit that measures an open circuit voltage curve (actual measured value) that indicates a change in open circuit voltage relative to a change in battery capacity, a capacity retention rate calculation unit that calculates a positive electrode capacity retention rate and a negative electrode capacity retention rate using the positive and negative electrode composition correspondence mismatch capacity to specify an open circuit voltage curve (estimated value) that approximately coincides with the open circuit voltage curve (actual measured value), and a degradation estimation unit that estimates the degradation state of the battery using the calculated positive electrode capacity retention rate, negative electrode capacity retention rate, and positive and negative electrode composition correspondence mismatch capacity.

[0004] The method for estimating the state of a secondary battery described in Patent Document 2 includes a capacity loss amount specifying step of specifying a capacity loss amount, which is the amount of loss in battery capacity from the initial capacity of the secondary battery; a first step of specifying a first capacity loss amount resulting from a positive / negative electrode capacity mismatch based on a positive electrode potential and temperature; a second step of specifying a second capacity loss amount resulting from a side reaction in which a coating is formed on the positive electrode active material based on the positive electrode potential and temperature; and a third step of calculating a third capacity loss amount due to a structural change in the positive electrode active material by subtracting the first capacity loss amount and the second capacity loss amount from the capacity loss amount.

[0005] In the battery information processing system described in Patent Document 3, a storage device stores a wear deterioration curve and a lithium precipitation deterioration curve defined on a characteristic diagram. The wear deterioration curve is a curve showing the correlation between the internal resistance and wear capacity of a lithium ion secondary battery in which wear deterioration has occurred. The lithium precipitation deterioration curve is a curve showing the correlation between the internal resistance and wear capacity of a lithium ion secondary battery in which deterioration due to lithium precipitation has occurred in addition to wear deterioration. When the internal resistance and wear capacity of a module are plotted on a characteristic diagram, the determination device determines that the module can be reused if the plot is included in a region on the high resistance side of the determination curve defined between the wear deterioration curve and the lithium precipitation deterioration curve.

[0006] The battery system described in Patent Document 4 includes a secondary battery, a battery capacity acquisition means, an internal resistance acquisition means, and a discrimination means for determining whether the state of the secondary battery is in any of the degradation modes, namely, degradation due to wear, degradation due to precipitation of charge carriers at the negative electrode, and degradation due to bias in the salt concentration distribution of the non-aqueous electrolyte, based on the acquired battery capacity and internal resistance using a map showing the correspondence between the amount of decrease in battery capacity, the amount of increase in internal resistance, and the degradation mode. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2017-190979 A [Patent Document 2] Patent Publication No. 2022-21445 [Patent Document 3] JP 2020-85653 A [Patent Document 4] JP 2017-126462 A Summary of the Invention [Problem to be solved by the invention]

[0008] When recycling secondary batteries, it becomes necessary to use secondary batteries of unknown origin, in which the usage history of the secondary battery to be recycled is unknown, or information on the materials used in the secondary battery, manufacturing process, etc. is unknown. However, while the techniques described in Patent Documents 1-4 can determine the deterioration of a secondary battery and estimate its deterioration state, it is difficult to grasp the degree to which deterioration factors contribute to the deterioration and to perform optimal control according to the deterioration state, and there is a problem in that the performance of a secondary battery of unknown origin cannot be fully achieved.

[0009] The present invention has been made in view of the above circumstances, and has as its object to promote reuse of secondary batteries of unknown origin while fully utilizing their performance. [Means for solving the problem]

[0010] One aspect of the non-destructive battery degradation state estimation method of the present invention automatically performs the following processes by a computer: a current resistance value measurement process for charging and discharging a battery cell, and measuring the current battery resistance of the battery cell based on the charge / discharge current and the output voltage of the battery cell; a characteristic degradation factor analysis process for estimating current values ​​for each degradation factor parameter that is a characteristic degradation factor of the battery cell based on the difference between a previously estimated battery resistance of a new battery cell and the current battery resistance; and a salt concentration unevenness mitigation process for setting the degradation factor parameter at that time as a determined value when the current battery resistance measured after a certain period of charge / discharge processing in which the charge / discharge current is limited to a predetermined charge / discharge rate changes from a decrease to an increase and the amount of change between the current battery resistance at the previous measurement and the current battery resistance at the current measurement falls within a predetermined range. If the current battery resistance measured in the salt concentration unevenness mitigation process is lower than the current battery resistance at the previous measurement, the characteristic degradation factor analysis process is executed based on the newly measured current battery resistance.

[0011] One aspect of the non-destructive battery degradation state estimation program of the present invention causes a computer to execute a current resistance value measurement process in which a battery cell is charged and discharged, and a current battery resistance of the battery cell is measured based on the charge / discharge current and the output voltage of the battery cell; a characteristic degradation factor analysis process in which a current value is estimated for each degradation factor parameter that is a characteristic degradation factor of the battery cell based on the difference between a previously estimated battery resistance of a new battery cell and the current battery resistance; and a salt concentration unevenness mitigation process in which, when the current battery resistance measured after a certain period of charge / discharge processing in which the charge / discharge current is limited to a predetermined charge / discharge rate changes from a decrease to an increase, and when the amount of change between the current battery resistance at the previous measurement and the current battery resistance at the current measurement falls within a predetermined range, the degradation factor parameter at that time is set as a determined value. If the current battery resistance measured in the salt concentration unevenness mitigation process is lower than the current battery resistance at the previous measurement, the characteristic degradation factor analysis process is executed based on the newly measured current battery resistance.

[0012] One aspect of the battery utilization method of the present invention includes a first determination process for receiving input of product information including at least information on the battery type of a battery cell, determining a first provisional battery parameter set in advance based on the product information, and determining whether or not the battery type is a target battery type; a battery characteristic estimation process for measuring the dimensions of the battery cell determined to be the target battery type, and then assembling the battery cell into a state in which the battery cell can be charged and discharged, estimating a degree of deterioration of the battery cell and a current electrode capacity that is a current electrode capacity of the battery cell based on charge and discharge current values ​​and an output voltage value of the battery cell obtained by charging and discharging the assembled battery cell, and estimating a thickness of an active material layer of the battery cell based on the measurement results of the dimensions of the battery cell; and a battery characteristic estimation process for estimating an amount of change in battery resistance of the battery cell calculated from current and voltage values ​​obtained when the assembled battery cell is repeatedly charged and discharged multiple times. a characteristic degradation state estimation process that estimates a parameter that is an index of a degree of degradation of the characteristic of the battery cell based on the value estimated by the battery characteristic estimation process and the characteristic degradation state estimation process; a second determination process that determines whether the battery cell is usable for the intended use based on the values ​​estimated by the battery characteristic estimation process and the characteristic degradation state estimation process; a battery parameter adaptation process that sets the parameters estimated by the battery characteristic estimation process and the characteristic degradation state estimation process as battery parameters to be used for controlling the battery cell for the battery cell that has been determined to be usable for the intended use; and a battery utilization process that updates the power limit of the battery cell in accordance with the degree of degradation while performing a charging rate and degradation degree estimation process using the battery parameters set in the battery parameter adaptation process, and continues utilization of the battery cell until it is determined that the battery life of the battery cell has expired. Effect of the Invention

[0013] The non-destructive battery degradation state estimation method, non-destructive battery degradation state estimation program, and battery utilization method of the present invention can promote reuse of secondary batteries of unknown origin while fully utilizing their performance. [Brief description of the drawings]

[0014] [Figure 1]10 is a flowchart illustrating the flow of a method of using a battery when the battery specifications are known. [Diagram 2] 4 is a flowchart illustrating a method of using a battery according to the first embodiment. [Diagram 3] 4 is a flowchart illustrating a flow of a battery characteristics estimation process according to the first embodiment. [Figure 4] 4 is a flowchart illustrating a flow of a characteristic degradation state estimation process according to the first embodiment. [Diagram 5] 1 is a flowchart illustrating a flow of a current resistance value measurement process according to the first embodiment. [Figure 6] 1 is a flowchart illustrating a flow of a characteristic degradation cause analysis process according to the first embodiment. [Figure 7] 1 is a graph illustrating the relationship between the rate of increase in resistance and the change in capacitance due to the SEI film. [Figure 8] 11 is a graph illustrating the location where a capacitance deviation occurs for each degradation cause. [Figure 9] 4 is a flowchart illustrating a procedure for reducing salt concentration unevenness according to the first embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] In order to clarify the description, the following description and drawings are omitted and simplified as appropriate. In addition, each element shown in the drawings as a functional block performing various processes can be configured in hardware with a CPU (Central Processing Unit), memory, and other circuits, and in software, can be realized by a program loaded into memory. Therefore, it is understood by those skilled in the art that these functional blocks can be realized in various forms by hardware alone, software alone, or a combination thereof, and are not limited to any one of them. In addition, the same elements are given the same symbols in each drawing, and duplicated explanations are omitted as necessary.

[0016] Moreover, the above-mentioned program includes a set of instructions (or software code) for making the computer perform one or more functions described in the embodiment when the program is read into the computer. The program may be stored in a non-transitory computer-readable medium or a tangible storage medium. By way of example and not limitation, the computer-readable medium or the tangible storage medium includes random-access memory (RAM), read-only memory (ROM), flash memory, solid-state drive (SSD) or other memory technology, CD-ROM, digital versatile disc (DVD), Blu-ray (registered trademark) disk or other optical disk storage, magnetic cassette, magnetic tape, magnetic disk storage or other magnetic storage device. The program may be transmitted on a transitory computer-readable medium or a communication medium. By way of example and not limitation, the transitory computer-readable medium or the communication medium includes electrical, optical, acoustic, or other forms of propagating signals.

[0017] In addition, the battery utilization method according to the first embodiment described below is performed by an automatic process in which multiple programs executed on separate computers are prepared for each process in the flow of battery utilization in cooperation with each other.

[0018] First embodiment In the following description, a method of using a battery that reuses a secondary battery will be described. Therefore, in the following description, the secondary battery will simply be referred to as a battery. Furthermore, in the method of using a battery according to the first embodiment, regardless of whether the battery is used as a battery pack made up of a combination of multiple batteries, the battery parameters and performance will be evaluated for each individual battery cell, so in the description, the term battery cell will be used.

[0019] First, before explaining the battery utilization method according to the first embodiment, a battery utilization method in which the non-destructive battery degradation state estimation method implemented in the battery utilization method according to the first embodiment is not used will be explained as a comparative example.

[0020] Fig. 1 shows a flowchart explaining the flow of a method of using a battery when the battery specifications are known (a method of using a battery according to a comparative example). As shown in Fig. 1, in the method of using a battery according to the comparative example, detailed product information of the battery is input when starting to use the battery cell (step S101). Specifically, in step S101, the detailed product information includes the capacity of the new battery cell when it starts to be used, design information such as the thickness of the active material layers that make up the electrode plates, characteristic variations of the battery cell caused by manufacturing variations, and life characteristics of the battery cell.

[0021] Next, in the battery usage method according to the comparative example, the product information acquired in step S101 is used to acquire the characteristics of the battery cell and diagnose the battery cell (step S102). In this step S102, the battery cell is repeatedly charged and discharged to acquire information such as the full charge capacity of the battery cell, the terminal resistance value of the battery cell (hereinafter referred to as battery resistance), the input / output characteristics of the battery cell, and the degree of capacity deterioration compared to a new battery cell. When a battery cell is reused, its usage history up to that point is unknown, and by performing the process of step S102, information necessary for appropriately controlling the battery cell is obtained. The process of step S102 usually takes several months to about half a year.

[0022] Next, based on the information acquired in steps S101 and S102, it is determined whether the battery cell has the performance required for the intended use (step S103). If it is determined in step S103 that the battery cell does not have the performance required for the intended use, the battery cell is considered for recycling for another use.

[0023] On the other hand, if it is determined in step S103 that the battery cell has the performance required for the intended use, a battery parameter adaptation process is performed in which the information (e.g., battery parameters) acquired in steps S101 and S102 is set in the system that uses the battery cell as battery parameters to be used in controlling the battery cell (step S104). Also, a power limit according to the performance of the battery cell is set in the system that uses the battery cell (step S105).

[0024] Thereafter, in the battery cell utilization method according to the comparative example, the charging rate (SOC: State Of Charge) and deterioration degree (SOH: State Of Health) of the battery cell are estimated (step S106) and the lifespan of the battery cell is predicted (step S107), and the battery cell is utilized until it is determined that the predicted lifespan has expired (YES branch of step S108).

[0025] As described above, in the battery usage method according to the comparative example, in order to use a battery cell, it is necessary to obtain information that can only be known by the battery manufacturer, such as the capacity of the battery cell when it is new, design information, characteristic variations, and life characteristics, and there is a problem that battery cells with unknown origins cannot be used. In addition, in the battery usage method according to the comparative example, it takes several months to understand the changes in battery characteristics caused by the use of the battery cell, so there is a problem that the period during which the battery cell cannot be used is extended. Furthermore, in the battery usage method according to the comparative example, in step S102, charging and discharging are repeated to obtain and diagnose the characteristics of the battery cell, so there is a problem that power not used for a specific purpose is required.

[0026] However, the battery usage method according to the first embodiment makes it possible to recycle even battery cells whose origins are unknown and whose information on the design and manufacture of the battery cell is difficult to obtain. Also, the battery usage method according to the first embodiment improves the accuracy of information for understanding the current characteristics of the battery cell while using the battery for a specific purpose, thereby shortening the unused period of the battery cell. The battery usage method according to the first embodiment will be specifically described below.

[0027] Fig. 2 shows a flowchart for explaining the battery usage method according to the first embodiment. In the battery usage method according to the first embodiment, first, product information including at least information on the battery type of the battery cell is input, and a first determination process is performed to determine first provisional battery parameters set in advance based on the product information and determine whether the battery type is a target one. In the example shown in Fig. 2, the first determination process is divided into steps S1 to S3.

[0028] In step S1, regardless of whether the identity of the battery cell is known or not, product information of the battery cell is input at the start of use (step S1). Specifically, in the battery usage method according to the first embodiment, information including at least the battery type of the battery cell to be used is input to the computer as product information in step S1. Here, secondary batteries are classified into lead-acid batteries, nickel-metal hydride batteries, lithium-ion batteries, etc., depending on the type of active material used. Therefore, in the battery usage method according to the first embodiment, information on the material from which the battery cell to be used is manufactured, such as a lead-acid battery, nickel-metal hydride battery, or lithium-ion battery, is provided to the computer as the battery type.

[0029] Next, in step S2, first provisional battery parameters (e.g., standard parameters) preset for each battery type of the battery cell to be used are provisionally determined as battery parameters (step S2). Here, the standard parameters in the battery utilization method according to the first embodiment are publicly available information, and are, for example, values ​​determined in advance by a business entity that reuses battery cells based on information published on a website or the like by a material manufacturer that is a supplier of the material for the battery cells. For example, the standard parameters include the thickness of the electrode foil, the thickness of the separator, the density of the active material layer coated on the electrode foil, the specific capacity of the active material layer, and the electrode capacity of the active material layer.

[0030] Next, in step S3, it is determined whether the battery cell to be used is a battery cell that is suitable for the intended use. Specifically, in step S3, for example, in a battery pack that uses a combination of multiple battery cells, it is necessary to combine battery cells of the same type, and it is determined whether the battery type is a target battery pack to be assembled. Also, in step S3, it may be determined to exclude battery cells that are obviously old, or battery cells whose shape is obviously unsuitable for the intended use.

[0031] Then, if it is determined in step S3 that the battery cell matches the intended use, a battery characteristic estimation process (step S6), a characteristic deterioration state estimation process (step S7), and a second judgment process (step S8) are performed on the target battery cell.

[0032] In the battery characteristic estimation process S6, the dimensions of the battery cell determined to be the target battery type are measured, and then the battery cell is assembled in a state in which it can be charged and discharged, and the deterioration level of the battery cell and the current electrode capacity of the battery cell are estimated based on the charge / discharge current value and the output voltage value of the battery cell obtained by charging and discharging the assembled battery cell, and the thickness of the active material layer of the battery cell is estimated based on the measurement results of the battery cell dimensions. Note that the example of Fig. 2 shows step S4 of measuring the dimensions of the battery cell as a process prior to the battery parameter estimation process, and step S5 of assembling the target battery cell so that it can be charged and discharged.

[0033] Here, the battery characteristic estimation process S6 will be described in more detail. In the battery characteristic estimation process S6, design parameters indicating the characteristics (e.g., capacity, etc.) of the battery cell in a new state and the structure of the battery cell are estimated using the provisional values ​​acquired in S2 and the measured values ​​acquired in step S4. In other words, in the battery characteristic estimation process, design parameters indicating the characteristics (e.g., capacity, etc.) of the battery cell in a new state and the structure of the battery cell are acquired without destroying the battery cell. Here, FIG. 3 shows a flowchart explaining the flow of the battery characteristic estimation process according to the first embodiment. As shown in FIG. 3, in the battery characteristic estimation process, provisional parameter setting process S21, current state measurement process S22, coating portion structure calculation process S23, and active material thickness calculation process S24 are performed.

[0034] In the provisional parameter setting process S21, provisional values ​​for each parameter, for example, aluminum foil thickness, copper foil thickness, separator thickness, positive electrode density, positive electrode specific capacity, negative electrode density, negative electrode specific capacity, initial positive electrode capacity, and initial negative electrode capacity, are set by referring to the standard parameters input in step S2.

[0035] In the current state measurement process S22, the battery cell is charged and discharged while controlling the battery cell using the provisional values ​​set by the provisional parameter setting process, and the degree of deterioration of the battery cell and the current electrode capacities of the battery cell, i.e., the current positive electrode capacity and the current negative electrode capacity, are estimated.

[0036] In the coating structure calculation process S23, the cross-sectional area of ​​the electrode body contained in the battery cell as viewed from a side perpendicular to the electrode stacking direction and the width of the coating portion of the electrode body are calculated based on dimensions that can be measured without destroying the battery cell (for example, the width, height, and thickness of the case that contains the electrode body in the battery cell obtained in step S4).

[0037] In the active material thickness calculation process S24, the thickness of the positive electrode active material layer and the thickness of the negative electrode active material layer are calculated using the aluminum foil thickness, copper foil thickness, separator thickness, positive electrode density, positive electrode specific capacity, negative electrode density, and negative electrode specific capacity whose provisional values ​​were set in step S21, the current positive electrode capacity and current negative electrode capacity whose estimated values ​​were calculated in step S22, and the cross-sectional area of ​​the electrode body and the coated portion width of the electrode body calculated in step S23.

[0038] The values ​​acquired and calculated in steps S21 to S24 are used in the characteristic degradation state estimation process that is performed after the battery characteristic estimation process and subsequent processes.

[0039] Next, the characteristic degradation state estimation process S7 will be described. In the characteristic degradation state estimation process S7, the amount of change in the battery resistance of the battery cell is calculated from the current and voltage values ​​obtained when the battery cell assembled in step S5 is repeatedly charged and discharged multiple times, and a parameter that is an index of the degree of degradation of the battery cell's characteristics is estimated based on the amount of change in the battery resistance of the battery cell. By performing this characteristic degradation state estimation process, it is possible to optimize the control of the battery cell according to the battery degradation state, and to use the battery cell more safely and with higher performance. The characteristic degradation state estimation process S7 will be described in detail later.

[0040] Next, in the second determination process in step S8, it is determined whether the battery cell can be used for the intended use based on the estimated values ​​in the battery characteristic estimation process S6 and the characteristic deterioration state estimation process step S7. If the battery cell is suitable for the intended use in this second determination process S8, the battery parameter adaptation process S9 and the battery use processes S10 to S13 are performed.

[0041] In the battery parameter adaptation process S9, the parameters estimated in the battery characteristic estimation process S6 and the characteristic degradation state estimation process S7 are set as battery parameters to be used for controlling the battery cell.

[0042] In the battery utilization process of steps S10 to S13, the battery control parameters set in the battery parameter adaptation process are used to estimate the charging rate (SOC: State Of Charge) and deterioration level (SOH: State Of Health), while updating the power limit of the battery cell according to the deterioration level, and the battery cell continues to be used until it is determined that the battery life of the battery cell has expired.

[0043] In the battery usage method according to the first embodiment, by using the battery according to the flow shown in Fig. 2, even if the battery cell has an unknown origin, it is possible to safely use the battery cell while extracting higher performance. It becomes possible to use the battery cell in a short period of time. One of the processes for realizing this feature is the characteristic degradation state estimation in step S7. Here, the characteristic degradation state estimation process S7 will be described in detail.

[0044] FIG. 4 shows a flow chart for explaining the flow of the characteristic degradation state estimation process S7 according to the first embodiment. As shown in FIG. 4, the characteristic degradation state estimation process according to the first embodiment includes a current resistance value measurement process S31, a characteristic degradation factor analysis process S32, and a salt concentration unevenness mitigation process S33. In the current resistance value measurement process S31, charging and discharging are performed on the battery cell, and the current battery resistance of the battery cell is measured based on the charge and discharge current and the output voltage of the battery cell. In the characteristic degradation factor analysis process S32, a current value is estimated for each degradation factor parameter that is a characteristic degradation factor of the battery cell based on the difference between the battery resistance of the battery cell in a new state estimated in advance and the current battery resistance measured in the current resistance value measurement process S31. In the salt concentration unevenness mitigation process S33, the degradation factor parameter at that time point is set as a determined value in response to the current battery resistance measured after a certain time of charging and discharging process in which the charge and discharge current is limited to a predetermined charge and discharge rate changing from a decrease to an increase, and the amount of change between the current battery resistance at the previous measurement and the current battery resistance at the current measurement falling within a certain range set in advance. In the characteristic degradation state estimation process S7, if the current battery resistance measured in the salt concentration unevenness mitigation process S33 is lower than the current battery resistance measured previously, a characteristic degradation factor analysis process S32 is executed based on the newly measured current battery resistance. Each of the current resistance value measurement process S31, the characteristic degradation factor analysis process S32, and the salt concentration unevenness mitigation process S33 will be described in more detail below.

[0045] FIG. 5 shows a flowchart for explaining the flow of the current resistance value measurement process S31 according to the first embodiment. As shown in FIG. 5, in the current resistance value measurement process S31, first, it is determined whether or not information on a brand new battery cell can be acquired (step S41). The information to be determined whether or not it can be acquired in step S41 is information that includes at least the positive electrode capacity, the negative electrode capacity, and the initial capacity deviation amount of the brand new battery cell. The initial capacity deviation amount is the deviation amount from the full charge capacity according to the specifications immediately after the completion or shipment of the battery cell. Furthermore, the information to be determined whether or not it can be acquired in step S41 is information that can be acquired from the battery manufacturer or the like as the battery cell specifications. Then, if it is determined in step S41 that the information on the brand new battery cell can be acquired, the information is acquired (step S42).

[0046] Following step S42, in a current resistance value measurement process S31, charging and discharging are performed on the battery cell, and a current battery resistance, which is the battery resistance at the present time, is measured based on the charging and discharging current and the output voltage of the battery cell (step S43). After that, using the measurement result of the current battery resistance, the current positive electrode capacity, negative electrode capacity, and capacity deviation amount of the battery cell are calculated (step S44). Furthermore, in the current resistance value measurement process S31, a preliminary adaptation process is performed in which the positive electrode capacity, negative electrode capacity, and initial capacity deviation amount of the new battery cell obtained in step S42 and the current battery resistance measured in step S43 are set as provisional values ​​of battery parameters to be used for controlling the battery cell (step S45).

[0047] On the other hand, if it is determined in step S41 that it is impossible to obtain the information of the new battery cell, the information of the new battery cell calculated as the estimated value in step S7 is obtained as a substitute value for the new battery cell (step S46). The information obtained in step S46 is information of estimated values ​​including at least the positive electrode capacity, the negative electrode capacity, and the initial capacity deviation amount of the new battery cell.

[0048] Following step S46, in the current resistance value measurement process S31, charging and discharging are performed on the battery cell, and the current battery resistance, which is the battery resistance at the present time, is measured based on the charging and discharging current and the output voltage of the battery cell (step S47). After that, using the measurement result of the current battery resistance, the current positive electrode capacity, negative electrode capacity, and capacity deviation amount of the battery cell are calculated (step S48). Furthermore, in the current resistance value measurement process S31, a preliminary adaptation process is performed in which the estimated positive electrode capacity, estimated negative electrode capacity, and estimated initial capacity deviation amount of the new battery cell obtained in step S46, and the current battery resistance measured in step S47 are set as provisional values ​​of battery parameters to be used for controlling the battery cell (step S49).

[0049] Next, Fig. 6 shows a flowchart for explaining the flow of the characteristic degradation factor analysis process S32 according to the first embodiment. In the characteristic degradation factor analysis process S32, the characteristic factor parameters that are characteristic degradation factors among the battery parameters are updated according to the characteristic degradation state of the battery cell, and are brought closer to values ​​that match the actual performance of the battery cell. In the example shown in Fig. 6, at least the positive electrode capacity deviation amount, the SEI film capacity deviation amount, and the lithium deposition amount are defined as the degradation factor parameters.

[0050] As shown in FIG. 6, the characteristic degradation factor analysis process S32 according to the first embodiment performs a positive electrode capacity degradation determination process S51, a first parameter assignment process S52, a tentative SEI coating capacity deviation calculation process S53, a capacity deviation determination process S54, a second parameter assignment process (steps S55 and S56), and a third parameter assignment process (steps S57 and S58).

[0051] Here, the characteristics handled in the characteristic degradation factor analysis process S32 are capacity degradation and resistance degradation, and the relationship between capacity degradation and degradation factor parameters will be described. FIG. 7 shows a graph for explaining the occurrence position of capacity deviation for each degradation factor. The graph shown in FIG. 7 has the charge rate on the horizontal axis and the voltage on the vertical axis, and shows the change in the positive electrode OCP (Open Circuit Potential), which is the voltage value of the positive electrode, and the negative electrode OCP, which is the voltage value of the negative electrode, as a curve. The output voltage of the battery cell is defined by the difference between the positive electrode OCP and the negative electrode OCP. Referring to FIG. 7, when the positive electrode capacity decreases, the curve shape of the positive electrode OCP changes so that the length of the positive electrode OCP in the charge rate direction becomes shorter, thereby causing a capacity deviation in which the capacity decreases. In addition, the capacity deviation caused by lithium deposition or the capacity deviation caused by the growth of the SEI film occurs when the positive electrode OCP shifts to the low charge rate side, thereby reducing the region of the charge rate where the positive electrode OCP and the negative electrode OCP overlap. In other words, the capacity deviation of the battery cell is caused by a combination of the positive electrode capacity deviation amount, the SEI film capacity deviation amount, and the amount of lithium precipitation. In the characteristic degradation factor analysis process S32, the contribution of each of the positive electrode capacity deviation amount, the SEI film capacity deviation amount, and the amount of lithium precipitation to the capacity deviation amount is analyzed to accurately estimate the values ​​of these parameters. Each process will be described in detail below.

[0052] In the positive electrode capacity deterioration determination process S51, it is determined whether the current positive electrode capacity of the battery cell has decreased relative to the positive electrode capacity of the battery cell in a brand new state. More specifically, in the positive electrode capacity deterioration determination process S51, it is determined whether the current positive electrode capacity of the battery cell calculated in step S44 or step S48 of the current resistance value measurement process S31 has decreased relative to the positive electrode capacity of the battery cell in a brand new state acquired in step S42 or step S46. Then, in the characteristic deterioration factor analysis process S32, if it is determined in the positive electrode capacity deterioration determination process S51 that the current positive electrode capacity has decreased relative to the brand new state, a first parameter assignment process S52 is performed to assign the decrease in the positive electrode capacity to the positive electrode deterioration capacity deviation amount. On the other hand, if it is determined in the positive electrode capacity deterioration determination process S51 that the current positive electrode capacity has not decreased relative to the brand new state, a temporary SEI coating capacity deviation amount calculation process S53 is performed without performing the first parameter assignment process S52.

[0053] In the provisional SEI coating capacity deviation calculation process S53, a capacity change rate of the battery cell corresponding to the resistance increase rate of the current battery resistance relative to the battery resistance of a brand new battery cell is calculated using a resistance-capacity relational equation that defines the relationship between the battery resistance increase rate and the capacity decrease amount due to the SEI coating, and a provisional SEI coating capacity deviation amount is calculated based on the calculated capacity change rate. The SEI coating is an abbreviation for Solid Electrolyte Interphase coating, and is a coating formed mainly during charging at the interface between the negative electrode and the electrolyte in a lithium ion battery. The SEI coating is a thin film formed on the negative electrode, and plays a role of appropriately incorporating lithium ions into the negative electrode while preventing the electrolyte from decomposing on the negative electrode. In addition, the thickness of the SEI coating increases or decreases due to charging and discharging, and the capacity of the battery cell decreases due to the immobilization of lithium ions inside the SEI coating, which affects the life and efficiency of the battery.

[0054] Here, the resistance-capacity relational expression may be a formula derived from a graph created from measurements of the battery resistance increase rate and the capacity decrease amount caused by the SEI coating, or may be table data of the relationship between the battery resistance increase rate and the capacity decrease amount shown in the graph. Here, FIG. 8 shows a graph explaining the relationship between the resistance increase rate and the capacity change caused by the SEI coating. The graph shown in FIG. 8 is a graph showing the relationship between the battery resistance increase rate and the capacity decrease rate caused by the thickness of the SEI coating. As shown in FIG. 8, there is a relationship between the resistance increase rate and the capacity decrease rate such that the resistance increase rate decreases as the capacity decrease rate increases, and the relationship is approximately linear. Such a change in the thickness of the SEI coating occurs due to manufacturing variations or the usage status of the battery cell. In the provisional SEI coating capacity deviation calculation process S53, the battery resistance decrease rate is calculated based on the relationship between the battery resistance increase rate and the capacity decrease rate as shown in FIG. 8, and the capacity deviation amount is calculated from the capacity decrease rate, and this capacity deviation amount is set as the provisional SEI coating capacity deviation amount.

[0055] In the capacity deviation determination process S54, it is determined whether the initial capacity deviation amount, which indicates the deviation amount of the capacity of the battery cell in a new state, matches the provisional SEI coating capacity deviation amount. If the initial capacity deviation amount, which indicates the deviation amount of the capacity of the battery cell in a new state, matches the provisional SEI coating capacity deviation amount in the capacity deviation determination process, the amount of lithium deposition is set to zero (step S55), and the remainder obtained by subtracting the positive electrode deterioration capacity deviation amount from the estimated capacity deviation amount, which indicates the magnitude of the deviation amount between the capacity of the battery cell in a new state and the current capacity, is assigned to the SEI coating capacity deviation amount (step S56), in which a second parameter assignment process is performed. On the other hand, if it is determined in the capacity deviation judgment process S54 that the initial capacity deviation amount and the provisional SEI coating capacity deviation amount do not match, the provisional SEI coating capacity deviation amount is assigned to the SEI coating capacity deviation amount (step S57), and the remainder obtained by subtracting the sum of the positive electrode deterioration capacity deviation amount and the SEI coating capacity deviation amount from the estimated capacity deviation amount is assigned to the lithium deposition amount (step S58), in which a third parameter assignment process is performed. Note that the estimated capacity deviation amount in steps S56 and S58 is the deviation amount between the current capacity of the battery cell estimated in steps S44 and S48 of the limited calibration value measurement process S31 and the capacity in a new state.

[0056] Next, the salt concentration unevenness alleviation process S33 will be described. In a secondary battery such as a lithium ion battery, when it is continuously used with a charge / discharge current of a certain magnitude or more, unevenness in the salt concentration in the electrolyte occurs on the electrode plate. Such an increase in battery resistance caused by the salt concentration unevenness is called a high-rate deterioration phenomenon. However, the high-rate deterioration phenomenon can be recovered to a certain extent by leaving the battery for a long period of time or by suppressing the charge / discharge rate to a level at which salt concentration unevenness does not occur and charging / discharging. In the salt concentration unevenness alleviation process S33, such salt concentration unevenness is alleviated. In the characteristic deterioration state estimation process according to the first embodiment, when the battery resistance decreases due to the salt concentration unevenness being alleviated in the salt concentration unevenness alleviation process S33, the characteristic deterioration factor analysis S32 is performed again to recalculate the value of the deterioration factor parameter.

[0057] FIG. 9 shows a flow chart for explaining the flow of the salt concentration unevenness mitigation process S33 according to the first embodiment. As shown in FIG. 9, in the salt concentration unevenness mitigation process S33, first, a charge / discharge process S61 is performed for a certain time in which the charge / discharge current is limited to a preset charge / discharge rate. In addition, a current battery resistance is calculated from the charge / discharge current during the charge / discharge process and the voltage value of the battery cell (step S62). Then, the current battery resistance at the previous measurement is compared with the current battery resistance at the current measurement, and it is determined whether the current battery resistance at the current measurement is lower than the current battery resistance at the previous measurement (step S63). Then, in step S63, if the current battery resistance at the current measurement is lower than the current battery resistance at the previous measurement, the decrease in the battery resistance is assigned as a salt concentration mitigation resistance component caused by salt concentration unevenness mitigation, and the current battery resistance is replaced with the current battery resistance calculated in step S62 (step S64), and the characteristic deterioration factor analysis process S32 is performed again.

[0058] On the other hand, in step S63, if the current battery resistance measured this time is equal to or greater than the current battery resistance measured last time, it is determined whether the change in the current battery resistance measured this time from the current battery resistance measured last time is within a preset range (step S65). Then, in step S65, if the change in the current battery resistance measured this time from the current battery resistance measured last time exceeds the preset range, the charge / discharge process S61 is performed again. On the other hand, in step S65, if the change in the current battery resistance measured this time from the current battery resistance measured last time is within the preset range, it can be assumed that the Endo soil unevenness has been eliminated, so the current battery parameters are determined as values ​​to be used for battery control (step S66). Then, the processes from steps S61 to S66 are repeated until the charge / discharge being performed at that time is completed (step S67).

[0059] From the above description, in the battery usage method according to the first embodiment, even if the battery cell has an unknown origin, the characteristic deterioration caused by the usage history of the battery cell can be determined for each cause of the characteristic deterioration without destroying the battery cell. In addition, in the battery usage method according to the first embodiment, it is possible to estimate the degree to which each of the deterioration factor parameters that cause the characteristic deterioration contributes to the characteristic deterioration. By estimating the detailed battery parameters in this way, the battery usage method according to the first embodiment can maximize the performance of the battery with unknown origin and promote the reuse of the battery. In addition, in the battery usage method according to the first embodiment, the battery parameters used for control are estimated by calculation and contain many errors, so it is preferable to continue use in a state where performance is suppressed, such as by suppressing the power limit, until the battery usage process of steps S10 to S13 progresses and the accuracy of the battery parameters improves.

[0060] In addition, in the battery usage method according to the first embodiment, charging and discharging are performed in the battery characteristic estimation process S6 and the characteristic degradation state estimation process S7, but the charging and discharging performed in these processes do not need to be performed only for the estimation process. In other words, in the battery usage method according to the first embodiment, the period during which the battery cell cannot be used can be made extremely short compared to the comparative example, since the battery cell is used while changes in battery characteristics caused by the use of the battery cell can be grasped. Furthermore, in the battery usage method according to the first embodiment, since it is not necessary to acquire and diagnose the battery cell characteristics (step S102) in the comparative example in order to grasp the battery parameters, it is possible to reduce the power required during the period when the battery is not used for a specific purpose.

[0061] The present invention is not limited to the above-described embodiment, and can be modified as appropriate without departing from the spirit and scope of the present invention.

Claims

1. a current resistance value measurement process for measuring a current battery resistance of the battery cell based on a charge / discharge current and an output voltage of the battery cell by charging / discharging the battery cell; A characteristic degradation factor analysis process for estimating a current value for each degradation factor parameter that is a characteristic degradation factor of the battery cell based on a difference between a previously estimated battery resistance of a new battery cell and the current battery resistance; a salt concentration unevenness alleviation process in which the deterioration factor parameter at the time point is set as a determined value in response to the current battery resistance measured after a certain period of charge / discharge processing in which a charge / discharge current is limited to a preset charge / discharge rate changing from a decrease to an increase and an amount of change between the current battery resistance measured previously and the current battery resistance measured this time falling within a preset certain range, A non-destructive battery degradation state estimation method in which, when the current battery resistance measured in the salt concentration unevenness mitigation process is lower than the current battery resistance at the previous measurement, the characteristic degradation factor analysis process is performed based on the newly measured current battery resistance.

2. 2. A non-destructive battery degradation state estimation method as described in claim 1, wherein in the current resistance value measurement process, preset provisional values ​​are used as the positive electrode capacity, negative electrode capacity, and capacity deviation of the battery cell in a brand new state, and the current battery resistance measured in the current resistance value measurement process and the provisional values ​​are set as battery parameters used to control the charging and discharging of the battery cell in the salt concentration unevenness mitigation process.

3. The non-destructive battery degradation state estimating method according to claim 2 , wherein the provisional value is a value set based on publicly available information.

4. In the characteristic degradation cause analysis process, At least a positive electrode capacity deviation amount, an SEI film capacity deviation amount, and a lithium deposition amount are defined as the deterioration factor parameters, a positive electrode capacity deterioration determination process for determining whether a current positive electrode capacity of the battery cell is decreased with respect to a positive electrode capacity of the battery cell in a new state; a first parameter allocation process in which, when it is determined in the positive electrode capacity deterioration determination process that the current positive electrode capacity of the battery cell is decreased with respect to a new battery state, an amount of decrease in the positive electrode capacity is allocated to an amount of deviation in positive electrode deterioration capacity; a tentative SEI coating capacity deviation calculation process for calculating a capacity change rate of the battery cell corresponding to a resistance increase rate of the current battery resistance relative to the battery resistance of the battery cell in a brand new state using a resistance-capacity relational equation that defines a relationship between a battery resistance increase rate and a capacity decrease amount due to an SEI coating, and calculating a tentative SEI coating capacity deviation amount based on the calculated capacity change rate; a capacity deviation determination process for determining whether an initial capacity deviation amount indicating a capacity deviation amount of the battery cell in a new state coincides with the provisional SEI coating capacity deviation amount; a second parameter allocation process for setting an amount of lithium deposition to zero when it is determined in the capacity deviation determination process that the initial capacity deviation amount and the tentative SEI film capacity deviation amount match, and allocating to an SEI film capacity deviation amount a remainder obtained by subtracting the positive electrode deterioration capacity deviation amount from an estimated capacity deviation amount indicating the magnitude of the deviation amount between the capacity of the battery cell in a new state and the current capacity; a third parameter allocation process for allocating the tentative SEI coating capacity deviation amount to the SEI coating capacity deviation amount when it is determined in the capacity deviation determination process that the initial capacity deviation amount and the tentative SEI coating capacity deviation amount do not match, and allocating a remainder obtained by subtracting a sum of the positive electrode deterioration capacity deviation amount and the SEI coating capacity deviation amount from the estimated capacity deviation amount to an amount of lithium deposition; The non-destructive battery degradation state estimating method according to claim 1 , comprising:

5. The non-destructive battery degradation state estimating method according to claim 1 , wherein the charge / discharge process of the salt concentration unevenness mitigation process comprises charging / discharging with a maximum current value that does not cause a high-rate degradation phenomenon in the battery cell.

6. A current resistance value measurement process for measuring a current battery resistance of the battery cell based on a charge / discharge current and an output voltage of the battery cell by charging / discharging the battery cell; A characteristic degradation factor analysis process for estimating a current value for each degradation factor parameter that is a characteristic degradation factor of the battery cell based on a difference between a previously estimated battery resistance of a new battery cell and the current battery resistance; a salt concentration unevenness mitigation process in which the deterioration factor parameter at a time point is set as a determined value when the current battery resistance measured after a certain period of charge / discharge processing in which a charge / discharge current is limited to a predetermined charge / discharge rate changes from a decrease to an increase and an amount of change in the current battery resistance between the previous measurement and the current measurement falls within a certain range set in advance; A non-destructive battery degradation state estimation program that, when the current battery resistance measured in the salt concentration unevenness mitigation process is lower than the current battery resistance at the previous measurement, executes the characteristic degradation factor analysis process based on the newly measured current battery resistance.

7. a first determination process for receiving product information including at least information on the battery type of the battery cell, determining first provisional battery parameters that are set in advance based on the product information, and determining whether the battery type is a target battery type; a battery characteristic estimation process for measuring the dimensions of the battery cell determined to be a target battery type, and then assembling the battery cell into a state in which the battery cell can be charged and discharged, estimating a degree of deterioration of the battery cell and a current electrode capacity that is a current electrode capacity of the battery cell based on a charge / discharge current value and an output voltage value of the battery cell obtained by charging and discharging the assembled battery cell, and estimating a thickness of an active material layer of the battery cell based on the measurement results of the dimensions of the battery cell; a characteristic degradation state estimation process for estimating a parameter that is an index of a characteristic degradation degree of the battery cell based on an amount of change in battery resistance of the battery cell calculated from current and voltage values ​​obtained when the assembled battery cell is repeatedly charged and discharged a plurality of times; a second determination process for determining whether the battery cell can be used for a desired purpose based on values ​​estimated by the battery characteristic estimation process and the characteristic degradation state estimation process; a battery parameter adaptation process for setting, for the battery cell determined to be usable for the intended use, parameters estimated by the battery characteristic estimation process and the characteristic degradation state estimation process as battery parameters to be used for controlling the battery cell; a battery usage process for updating a power limit of the battery cell according to the degree of deterioration while performing a process of estimating a charging rate and a degree of deterioration using the battery parameters set in the battery parameter adaptation process, and continuing to use the battery cell until it is determined that the battery life of the battery cell has expired; A method of using a battery in which the above is carried out by automatic processing using a computer.

8. In the characteristic degradation state estimation process, a current resistance value measurement process for measuring a current battery resistance of the battery cell based on a charge / discharge current and an output voltage of the battery cell by performing charging / discharging on the battery cell; A characteristic degradation factor analysis process for estimating a current value for each degradation factor parameter that is a characteristic degradation factor of the battery cell based on a difference between a previously estimated battery resistance of a new battery cell and the current battery resistance; a salt concentration unevenness alleviation process in which the deterioration factor parameter at the time point is set as a determined value in response to the current battery resistance measured after a certain period of charge / discharge processing in which a charge / discharge current is limited to a preset charge / discharge rate changing from a decrease to an increase and an amount of change between the current battery resistance measured previously and the current battery resistance measured this time falling within a preset certain range, A method for using a battery as described in claim 7, wherein, when the current battery resistance measured in the salt concentration unevenness mitigation process is lower than the current battery resistance at the time of the previous measurement, the characteristic deterioration factor analysis process is performed based on the newly measured current battery resistance.

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