JP7056528B2 - Battery information processing system - Google Patents

Description

The present disclosure relates to a battery information processing system, and more specifically, to a battery information processing system for determining whether or not a lithium ion secondary battery can be reused.

Vehicles equipped with secondary batteries are becoming more widespread. When these vehicles are used on the market, the secondary batteries deteriorate over time or with use. Then, the secondary battery is collected when the vehicle is scrapped. From the viewpoint of environmental protection, it is desirable to reuse the recovered secondary battery. Therefore, a technique for determining whether or not the secondary battery can be reused has been proposed.

For example, the control device for an assembled battery disclosed in Japanese Patent Application Laid-Open No. 2014-20818 (Patent Document 1) uses the open circuit voltage value, the internal resistance value, and the full charge capacity value of each battery as evaluation parameters of the assembled battery. Determine if it can be reused.

Japanese Unexamined Patent Publication No. 2014-20818

In general, deterioration of a lithium ion secondary battery includes deterioration due to wear (wear deterioration) and deterioration due to lithium precipitation (lithium precipitation deterioration). Abrasion deterioration means that the performance (lithium receiving capacity) of the positive electrode and the negative electrode deteriorates due to energization or neglect. As a cause of wear deterioration, for example, the active material of the positive electrode and the active material of the negative electrode are worn. On the other hand, lithium precipitation deterioration refers to deterioration in which lithium ions used in the battery reaction precipitate as metallic lithium on the surface of the negative electrode so that the lithium ions do not contribute to the battery reaction.

In determining whether or not the lithium ion secondary battery can be reused, it is preferable to consider not only wear deterioration but also the degree of progress of lithium precipitation deterioration.

The present disclosure has been made to solve the above problems, and an object thereof is to determine whether or not a lithium ion secondary battery can be reused in consideration of the degree of progress of lithium precipitation deterioration.

The battery information processing system according to a certain aspect of the present disclosure determines whether or not the target battery, which is a lithium ion secondary battery, can be reused. The battery information processing system includes a storage device and a determination device. The storage device is the first and second units defined on a plane defined by the internal resistance axis of the lithium ion secondary battery and the wear deterioration axis which is the full charge capacity of the lithium ion secondary battery in which wear deterioration has occurred. Memorize the deterioration curve. The first deterioration curve is a curve showing the correlation between the internal resistance of the lithium ion secondary battery in which wear deterioration has occurred and the wear capacity. The second deterioration curve is a curve showing the correlation between the internal resistance of the lithium ion secondary battery in which deterioration due to lithium precipitation occurs in addition to the wear deterioration and the wear capacity. When the determination device plots the internal resistance and wear capacity of the target battery on a plane, the determination device is located in a region higher than the curve defined between the first deterioration curve and the second deterioration curve. When it is included, it is determined that the target battery can be reused.

Details will be described later, but when the plot of the internal resistance and wear capacity of the target battery is included in the region closer to the first deterioration curve than the curve defined between the first deterioration curve and the second deterioration curve, Lithium precipitation on the surface of the negative electrode has not progressed relatively. Therefore, it can be determined that the target battery can be reused. As described above, according to the above configuration, it is possible to determine whether or not the lithium ion secondary battery can be reused in consideration of the progress of lithium precipitation deterioration.

According to the present disclosure, it is possible to determine whether or not a lithium ion secondary battery can be reused in consideration of the degree of progress of lithium precipitation deterioration.

It is a figure which shows one aspect of the physical distribution from the collection of the assembled battery to the manufacture / sale in Embodiment 1. FIG. It is a flowchart which shows the flow of processing in the battery distribution model shown in FIG. It is a figure which shows the configuration example of the battery management system applied to the battery distribution model shown in FIG. It is a functional block diagram of the processing system 200 which concerns on Embodiment 1. FIG. It is a figure which shows an example of the characteristic diagram in Embodiment 1. FIG. It is a conceptual diagram for demonstrating the active material model in Embodiment 1. FIG. It is a figure which shows typically the relationship between the local SOC of a positive electrode and the positive electrode open potential, and the relationship between the local SOC of a negative electrode and the negative electrode open potential. It is a figure for demonstrating the composition correspondence deviation between a positive electrode and a negative electrode. It is a figure which shows the correlation between SOC and resistance of a module. It is a flowchart which shows the deterioration determination processing in Embodiment 1. It is a figure which shows an example of the characteristic diagram in Embodiment 2. It is a flowchart which shows the deterioration determination processing in Embodiment 2.

Hereinafter, the present embodiment will be described in detail with reference to the drawings. The same or corresponding parts in the drawings are designated by the same reference numerals, and the description thereof will not be repeated.

In the present disclosure, the assembled battery is configured to include a plurality of modules (also referred to as blocks). The plurality of modules may be connected in series or may be connected in parallel with each other. Each of the plurality of modules includes a plurality of cells (cells) connected in series.

In the present disclosure, "manufacturing" of an assembled battery means that at least a part of a plurality of modules constituting the assembled battery is replaced with another module (replacement module) to manufacture the assembled battery. The replacement module is basically a reusable module taken out of the recovered assembled battery, but may be a new module.

In general, "reuse" of assembled batteries is roughly divided into reuse, rebuild and recycling. In the case of reuse, the collected assembled battery is shipped as a reused product as it is after undergoing the necessary shipping inspection. In the case of rebuilding, the recovered battery pack is once disassembled into modules (which may be cells), for example. Then, among the disassembled modules, the modules that can be used after the performance recovery (may be the modules that can be used as they are) are combined, and a new assembled battery is manufactured. The newly manufactured assembled battery is shipped as a rebuilt product after undergoing a shipping inspection. On the other hand, in recycling (resource recycling), since the recyclable material is taken out from each cell, the recovered assembled battery is not used as another assembled battery.

In the embodiment described below, the assembled battery recovered from the vehicle is once disassembled into modules, and then the performance is inspected in module units. As a result of the performance inspection, the assembled battery is manufactured from the module determined to be reusable. Therefore, in the following, a reusable module means a module that can be rebuilt. However, depending on the configuration of the assembled battery, it is possible to perform the performance inspection as the assembled battery without disassembling the assembled battery into modules. "Reuse" in such cases can include both reuse and rebuild.

Further, in the present embodiment, each cell included in the module is a lithium ion secondary battery. As the positive electrode, the separator and the electrolytic solution, conventionally known configurations and materials as the positive electrode, the separator and the electrolytic solution of the lithium ion secondary battery can be used, respectively. As an example, the positive electrode is a ternary material in which a part of lithium cobalt oxide is replaced with nickel and manganese. The negative electrode is a carbon-based material such as graphite. The separator is a polyolefin (eg polyethylene or polypropylene). The electrolytic solution is an organic solvent (for example, a mixed solvent of DMC (dimethyl carbonate), EMC (ethyl methyl carbonate) and EC (ethylene carbonate)), a lithium salt (for example, LiPF ₆ ), and an additive (for example, LiBOB (lithium bis). (oxalate) boron) or Li [PF ₂ (C2O4) ₂ ]) and the like. However, this is merely an example of a specific cell configuration, and the cell configuration to which the present disclosure is applicable is not limited to this.

The "lithium ion secondary battery" in the present disclosure is a secondary battery that charges and discharges using lithium as a charge carrier, and is a general lithium ion secondary battery (electrolyte solution) using a liquid electrolyte (for example, an organic solvent). It can include not only a type lithium ion secondary battery) but also an all-solid-state battery (all-solid-state lithium ion secondary battery) using a solid electrolyte.

[Embodiment 1]
<Battery logistics model>
FIG. 1 is a diagram showing one aspect of physical distribution from collection of assembled batteries to manufacturing / sales according to the first embodiment. Hereinafter, the mode of distribution shown in FIG. 1 will be referred to as a “battery distribution model”. FIG. 2 is a flowchart showing a processing flow in the battery distribution model shown in FIG.

With reference to FIGS. 1 and 2, in this battery distribution model, used assembled batteries are recovered from a plurality of vehicles equipped with assembled batteries, and a reusable module included in the recovered assembled batteries is used. Assembled batteries are manufactured and sold. Then, the assembled battery mounted on the vehicle 90 of a certain user is replaced.

The collection company 10 collects the used assembled batteries from the vehicles 91 to 93. The assembled batteries 910 to 930 are mounted on the vehicles 91 to 93, respectively. Note that FIG. 1 shows only three vehicles due to space limitations, but in reality, the assembled batteries are collected from more vehicles. The collection company 10 disassembles the collected assembled battery and takes out a plurality of modules from the assembled battery (step S1, hereinafter, the step is abbreviated as "S").

In this battery distribution model, identification information (ID) for identifying the module is assigned to each module, and the information of each module is managed by the management server 80. Therefore, the collection company 10 transmits the ID of each module taken out from the assembled battery to the management server 80 using the terminal 71 (see FIG. 3).

The inspection company 20 inspects the performance of each module collected by the collection company 10 (S2). Specifically, the inspector 20 inspects the characteristics of the recovered module. For example, the inspector 20 inspects electrical characteristics such as full charge capacity, resistance value, OCV (Open Circuit Voltage), and SOC (State Of Charge). Then, the inspection company 20 separates the reusable module and the non-reusable module based on the inspection result, hands over the reusable module to the performance recovery company 30, and the non-reusable module. Will be handed over to the recycling company 60. The inspection result of each module is transmitted to the management server 80 using the terminal 72 (see FIG. 3) of the inspection company 20.

The performance recovery company 30 performs a process for recovering the performance of the module that has been made reusable by the inspection company 20 (S3). As an example, the performance recovery company 30 recovers the fully charged capacity of the module by charging the module to an overcharged state. However, the performance recovery process by the performance recovery company 30 may be omitted for the module for which the performance deterioration is determined to be small in the inspection by the inspection company 20. The performance recovery result of each module is transmitted to the management server 80 using the terminal 73 (see FIG. 3) of the performance recovery company 30.

The manufacturer 40 manufactures the assembled battery using the module whose performance has been restored by the performance recovery manufacturer 30 (S4). In the first embodiment, information (assembly information) for manufacturing the assembled battery is generated in the management server 80 and transmitted to the terminal 74 (see FIG. 3) of the manufacturer 40. The manufacturer 40 replaces the module included in the assembled battery of the vehicle 90 according to the assembly information, and manufactures (rebuilds) the assembled battery of the vehicle 90.

The dealer 50 sells the assembled battery manufactured by the manufacturer 40 for a vehicle, or sells it for a stationary use that can be used in a house or the like (S5). In the first embodiment, the vehicle 90 is brought to the store 50, where the assembled battery of the vehicle 90 is replaced with a reused product or a rebuilt product manufactured by the manufacturer 40.

The recycler 60 disassembles the module that has been made non-reusable by the inspector 20, and recycles it for use as a raw material for new cells and other products.

In FIG. 1, the collection company 10, the inspection company 20, the performance recovery company 30, the manufacturer 40, and the store 50 are different companies from each other, but the classification of the company is not limited to this. For example, the inspection company 20 and the performance recovery company 30 may be one company. Alternatively, the collection company 10 may be divided into a company that collects the assembled battery and a company that disassembles the collected assembled battery. In addition, the bases of each trader and retailer are not particularly limited. The bases of each trader and the dealer may be different, or a plurality of traders or dealers may be in the same base.

FIG. 3 is a diagram showing a configuration example of a battery management system applied to the battery distribution model shown in FIG. With reference to FIG. 3, the battery management system 100 includes terminals 71 to 75, a management server 80, a communication network 81, and a base station 82.

The terminal 71 is a terminal of the collection company 10. The terminal 72 is a terminal of the inspection company 20. The terminal 73 is a terminal of the performance recovery company 30. The terminal 74 is a terminal of the manufacturer 40. The terminal 75 is a terminal of the store 50.

The management server 80 and the terminals 71 to 75 are configured to be able to communicate with each other via a communication network 81 such as the Internet or a telephone line. The base station 82 of the communication network 81 is configured to be able to exchange information with the vehicle 90 by wireless communication.

The inspector 20 may abbreviate the battery information system (hereinafter, abbreviated as "processing system") for measuring the AC impedance of each module and determining the reuse mode (rebuild or recycling) of the module based on the measurement result. ) 200 is installed. The reuse mode of the module determined by the processing system 200 is transmitted to the management server 80 via, for example, the terminal 72.

In the following, among the plurality of modules included in the assembled battery 910 taken out from the vehicle 91, the deterioration state of a certain module (hereinafter, also referred to as “module M”) is estimated by the processing system 200. Further, based on the estimation result of the deterioration state of the module M, whether or not the module M can be reused (reuse mode) is determined. Module M corresponds to the "target battery" according to the present disclosure.

<Deterioration of lithium-ion secondary battery>
Deterioration of a lithium ion secondary battery may include deterioration due to wear and deterioration due to precipitation of lithium. In the following, deterioration due to wear of a lithium ion secondary battery may be referred to as “wear deterioration”, and deterioration due to lithium precipitation may be referred to as “lithium precipitation deterioration”.

Abrasion deterioration means that the performance (lithium receiving capacity) of the positive electrode and the negative electrode deteriorates due to energization or neglect. As a cause of wear deterioration, for example, the active material of the positive electrode and the active material of the negative electrode are worn. On the other hand, deterioration due to lithium precipitation means deterioration in which lithium ions used in the battery reaction precipitate as metallic lithium on the surface of the negative electrode, and lithium ions change into by-products so that the lithium ions do not contribute to the battery reaction. say.

The processing system 200 according to the first embodiment can determine the deterioration state of the lithium ion secondary battery in detail by distinguishing between wear deterioration and lithium precipitation deterioration.

<Functional block of battery information processing system>
FIG. 4 is a functional block diagram of the processing system 200 according to the first embodiment. With reference to FIG. 4, the processing system 200 includes a capacity calculation device 210, a resistance measuring device 220, a determination device 230, a storage device 240, and a display device 250. It should be noted that these devices may be configured as devices independent of each other, but may be configured as one device.

The capacity calculation device 210 calculates the capacity of the module M. The "capacity" here is a wear capacity C (W) described later. The calculated wear capacity C (W) of the module M is output to the determination device 230 (plot unit 231).

The resistance measuring device 220 measures the internal resistance R of the entire module M. The internal resistance R includes a pure electrical resistance to the movement of electrons at the negative electrode and the positive electrode, and a charge transfer resistance that acts equivalently as an electric resistance when a reaction current is generated at the active material interface. The measured internal resistance R of the module M is output to the determination device 230 (plot unit 231).

The determination device 230 estimates the deterioration state of the module M using the capacity-resistance characteristic diagram of the module (hereinafter, also simply abbreviated as “characteristic diagram”), and determines whether or not the module M can be reused based on the estimation result. do. The determination device 230 includes a plot unit 231, an area determination unit 232, and a reuse determination unit 233. The characteristic diagram (see FIG. 5) corresponds to the “plane” according to the present disclosure.

The storage device 240 stores in advance the wear deterioration curve LP and the lithium precipitation deterioration curve LQ (details will be described later) shown on the characteristic diagram. The storage device 240 outputs each of the curves LP and LQ to the plot unit 231.

FIG. 5 is a diagram showing an example of a characteristic diagram according to the first embodiment. In FIG. 5 and FIG. 11 described later, the horizontal axis represents the wear capacity of the module. The vertical axis represents the internal resistance of the module.

With reference to FIGS. 4 and 5, the full charge capacity of a battery is generally reduced by wear deterioration and by lithium precipitation deterioration. The wear capacity is a full charge capacity reduced only by wear deterioration without considering the amount of capacity decrease due to lithium precipitation deterioration. For the fully charged capacity C of the module after deterioration, the initial capacity of the module (for example, the fully charged capacity immediately after the module is manufactured) is expressed as C0, the amount of capacity decrease due to wear deterioration is expressed as ΔC (W), and the capacity due to lithium precipitation deterioration is expressed. When the amount of decrease is expressed as ΔC (Li), it is expressed by the following equation (1).
C = C0-ΔC (W) -ΔC (Li) ... (1)

On the other hand, the wear capacity C (W) is expressed as the following formula (2) because the capacity reduction amount ΔC (Li) due to lithium precipitation deterioration is not included.
C (W) = C0-ΔC (W) ... (2)

The initial capacity C0 of the module is known from the specifications of the module. Alternatively, for example, the initial capacity C0 of the module can be measured at the time of vehicle manufacturing. On the other hand, wear deterioration is more likely to progress in a high temperature environment. Therefore, the capacity decrease amount ΔC (W) due to wear deterioration can be calculated by acquiring the temperature environment in which the module is placed when the module is mounted (before being taken out from the vehicle). Therefore, the wear capacity C (W) can be calculated according to the above equation (2).

The plotting unit 231 plots the wear deterioration curve LP and the lithium precipitation deterioration curve LQ received from the storage device 240 on the characteristic diagram. Further, the plotting unit 231 plots the calculation result of the wear capacity C (W) of the module M and the measurement result of the internal resistance R on the characteristic diagram.

The wear deterioration curve LP is the wear capacity of the module when only the wear deterioration of the module occurs (in other words, when there is almost no lithium precipitation deterioration, more preferably when there is no lithium precipitation deterioration at all). It is a curve showing the correlation between and internal resistance. The lithium precipitation deterioration curve LQ is a curve showing the correlation between the wear capacity of the module and the internal resistance when excessive lithium precipitation deterioration occurs in addition to the wear deterioration of the module. The wear deterioration curve LP corresponds to the "first deterioration curve" according to the present disclosure, and the lithium precipitation deterioration curve LQ corresponds to the "second deterioration curve" according to the present disclosure.

Each curve LP and LQ can be defined as follows. Generally, if the lithium ion secondary battery is maintained in a high temperature state, lithium precipitation can be suppressed, and only wear deterioration can be generated in a state where lithium precipitation is suppressed. By conducting an experiment on whether or not lithium precipitates under a plurality of temperature conditions, it is possible to determine the set temperature when the lithium ion secondary battery is in a high temperature state. On the other hand, if the lithium ion secondary battery is maintained in a low temperature state, wear deterioration can be suppressed, and only lithium precipitation can be performed in a state in which wear deterioration is suppressed. By conducting an experiment on whether or not wear deterioration occurs under a plurality of temperature conditions, it is possible to determine the set temperature when the lithium ion secondary battery is in a low temperature state.

For example, by installing the module in a high temperature constant temperature bath and gradually deteriorating the wear and deterioration of the module, the full charge capacity of the module is gradually reduced by a predetermined amount. Then, each time the full charge capacity of the module is reduced, the internal resistance of the module is measured. Thereby, it is possible to determine the data (wear deterioration curve LP) showing the change in the internal resistance with respect to the change in the capacity of the module when the lithium precipitation does not occur.

Further, by installing the module in a constant temperature bath at a low temperature, the lithium precipitation deterioration of the module is excessively promoted. After that, the module is transferred to a high temperature constant temperature bath (or the temperature of the constant temperature bath is raised), and the wear deterioration of the module is gradually advanced, so that the full charge capacity of the module is gradually reduced. The internal resistance at this time is measured in the same manner as above. This makes it possible to determine data (lithium precipitation deterioration curve LQ) indicating the change in internal resistance with respect to the change in the capacity of the module when lithium precipitation occurs.

FIG. 5 further shows a determination curve LD located between the wear deterioration curve LP and the lithium precipitation deterioration curve LQ. The determination curve LD is determined in consideration of the degree of progress of lithium precipitation deterioration allowed for the reuse of the module. The determination curve LD corresponds to the "curve defined between the first deterioration curve and the second deterioration curve" according to the present disclosure.

The region sandwiched between the wear deterioration curve LP and the determination curve LD is described as "region X" and is shown with diagonal lines. Further, an example of a plot based on the calculation result of the wear capacity C (W) of the module M to be determined whether or not it can be reused and the measurement result of the internal resistance R is shown in (C (W), R). FIG. 5 shows an example in which the plot (C (W), R) is included in the region X.

Since the region X is a region relatively close to the wear deterioration curve LP, it can be said that the region X is a region in which lithium precipitation on the negative electrode surface has not progressed at all or hardly progressed. On the other hand, the region other than the region X, that is, the region located between the determination curve LD and the lithium precipitation deterioration curve LQ (region Y described later) is a region relatively close to the lithium precipitation deterioration curve LQ. It can be said that this is a region where lithium precipitation has progressed to some extent.

The area determination unit 232 determines whether or not the plot (C (W), R) of the module M to be determined is included in the area X. The determination result by the area determination unit 232 is output to the reuse determination unit 233.

The reuse determination unit 233 determines whether or not the module M can be reused based on the determination result by the area determination unit 232. Specifically, the reuse determination unit 233 determines lithium in the module M when the plot (C (W), R) of the module M is included in the region X (when the resistance side is higher than the determination curve LD). Assuming that the degree of progress of precipitation deterioration is smaller than the degree of progress of lithium precipitation deterioration allowed for reuse (hereinafter, also referred to as "permissible progress"), the module M can be reused, that is, the module M can also be rebuilt. Judge that there is.

On the other hand, when the plot (C (W), R) of the module M is not included in the region X (when the resistance side is lower than the determination curve LD), the degree of progress of lithium precipitation deterioration in the module M is permissible. Greater than progress. In this case, the reuse determination unit 233 determines that the module M cannot be reused, that is, the module M cannot be rebuilt and the module M should be recycled (recycling of resources or materials). The determination result by the reuse determination unit 233 is output to the display device 250.

The display device 250 is, for example, a liquid crystal display, and displays the determination result by the reuse determination unit 233. This allows the inspector to determine how to handle the module M thereafter. In addition to the determination result by the reuse determination unit 233, the display device 250 may display a plot on the characteristic diagram as shown in FIG.

<Principle of deterioration estimation>
Next, the outline of the deterioration state estimation of the module in the first embodiment will be described. In particular, the reason why the lithium precipitation deterioration curve LQ is shown lower in the figure (lower resistance side) than the wear deterioration curve LP on the characteristic diagram shown in FIG. 5 will be described.

In the concept of deterioration estimation in the first embodiment, a certain active material model (battery model) is used. In this active material model, the positive electrode active material contained in the positive electrode of the module is schematically represented as one particle, and the negative electrode active material is schematically represented as another single particle.

FIG. 6 is a conceptual diagram for explaining the active material model in the first embodiment. With reference to FIG. 6, in the first embodiment, it is assumed that the circumferential lithium concentration distribution in polar coordinates is uniform inside the spherical positive electrode particles, and only the radial lithium concentration distribution in polar coordinates is considered. In other words, the internal model of the positive electrode particles is a one-dimensional model in which the moving direction of lithium is limited to the radial direction.

The positive electrode particles are virtually divided into N (N: 2 or more natural numbers) regions in the radial direction. The regions are distinguished from each other by the subscript k (k = 1 to N). The lithium concentration c _1k in the region k is expressed as a function of the position r _1k of the region k in the radial direction of the positive electrode particles and the time t (see the following equation (3)).

In this embodiment, the lithium concentration _cs1k of each region k is standardized. Specifically, as shown in the following formula (4), the ratio of the lithium concentration c _1k to the maximum value (limit lithium concentration) c _{1 and max} of the lithium concentration can be calculated for each region k. The critical lithium concentration c _{1, max} is a concentration determined according to the type of the positive electrode active material, and is known from the literature.

Hereinafter, the value θ _1k after normalization is referred to as the “local lithium amount” in the region k. The local lithium amount θ ₁ k takes a value in the range of 0 to 1 depending on the amount of lithium contained in the region k of the positive electrode particles. Further, the local lithium amount θ _1N in the outermost peripheral region N (that is, the surface of the positive electrode particles) where k = N is referred to as “local SOC” of the positive electrode and is represented by θ ₁ . Although the positive electrode particles have been described as an example in FIG. 6, the same applies to the negative electrode particles. The local SOC θ 2 _N on the surface of the negative electrode particles is referred to as the “local SOC” of the negative electrode and is represented by θ ₂ .

Further, in the following, when the module is in the non-energized state (no load state), the potential of the positive electrode is referred to as the positive electrode open potential (OCP: Open Circuit Potential) U ₁ , and the potential of the negative electrode is referred to as the negative electrode open potential U ₂ . The reference potential (0V) of these potentials can be arbitrarily set, and for example, the potential of metallic lithium can be set as a reference.

FIG. 7 is a diagram schematically showing the relationship between the local SOC θ ₁ of the positive electrode and the positive electrode open potential U ₁ and the relationship between the local SOC θ ₂ of the negative electrode and the negative electrode open potential U ₂ . The relationship between the local SOC θ ₁ and the positive electrode open potential U ₁ shown in FIG. 7 is in the initial state of the module (for example, immediately after the module is manufactured, the state in which the module is not deteriorated). Similarly, the relationship between the local SOC θ ₂ and the negative electrode open potential U ₂ is the initial state of the module.

The difference between the positive electrode open potential U ₁ and the negative electrode open potential U ₂ corresponds to the open circuit voltage (OCV) of the module. As shown in FIG. 7, the OCV of the module increases as the local SOC θ ₂ goes to the right in the figure. The right direction in the figure is the charging direction of the module (SOC increasing direction), and the left direction in the figure is the discharging direction of the module (SOC decreasing direction).

In general, the decrease in the full charge capacity of a lithium ion secondary battery is mainly caused by a "decrease in unipolar capacity" in the positive electrode and the negative electrode and a "composition correspondence deviation" between the positive electrode and the negative electrode. The decrease in unipolar capacity is a decrease in the capacity to accept lithium ions in each of the positive electrode and the negative electrode. A decrease in the capacity to accept lithium means a decrease in active materials and the like that effectively function for charging and discharging. As explained below, the composition correspondence deviation is the correspondence (combination) between the local SOCθ ₁ (so to speak, the composition of the positive electrode) of the positive electrode and the local SOCθ ₂ (the composition of the negative electrode) of the negative electrode in the initial state of the module. It means to deviate from the relationship.

FIG. 8 is a diagram for explaining the composition correspondence deviation between the positive electrode and the negative electrode. In FIG. 8, the vertical axis represents the electric potential. The horizontal axis represents, in order from the top, the local SOC θ ₁ of the positive electrode, the local SOC θ ₂ of the negative electrode in the initial state, the local SOC θ ₁ of the positive electrode, and the local SOC θ ₂ of the negative electrode after deterioration.

When the module is in the initial state, the amount of lithium ions emitted from one of the positive and negative electrodes and the amount of lithium ions received by the other are equal to each other. In this case, the local SOC θ ₁ and the local SOC θ ₂ correspond exactly. However, when the module deteriorates, the correspondence between the local SOC θ ₁ and the local SOC θ ₂ may shift due to the following two factors.

The first factor is that a film is formed on the surface of the negative electrode by the lithium ions emitted from the negative electrode. The lithium ions used to form the film become inactive and do not contribute to subsequent charging and discharging. The second factor is that the lithium ions emitted from the positive electrode are not taken into the negative electrode and are deposited as metallic lithium on the surface of the negative electrode. In this case as well, the lithium ions precipitated as metallic lithium do not contribute to the subsequent charge / discharge. As the deterioration due to the first and second factors progresses, the local SOC θ ₂ of the negative electrode particles decreases as the lithium ions are released from the negative electrode, but the released lithium ions are not taken into the positive electrode, so that the positive electrode particles Local SOC θ ₁ of is not increased. As a result, the correspondence between the local SOC θ ₁ and the local SOC θ ₂ deviates from the correspondence in the initial state of the module. That is, there is a difference in composition correspondence.

When the composition correspondence deviation occurs in the module, the horizontal axis representing the local SOC θ ₂ of the negative electrode is shifted to the right in the figure (the direction in which the local SOC θ ₁ of the positive electrode becomes smaller) by Δθ ₂ as compared with the initial state of the module. Then, the curve showing the relationship between the local SOC θ ₂ after deterioration and the negative electrode open potential U ₂ (represented by U _2B ) is also the curve showing the relationship between the local SOC θ ₂ and the negative electrode open potential U ₂ in the initial state (U _2A ). Compared with (represented by), it is shifted to the right in the figure by Δθ ₂ . Even if the module is deteriorated and the composition correspondence between the positive electrode and the negative electrode is deviated, the horizontal axis representing the local SOC θ ₁ of the positive electrode does not shift.

It is assumed that the OCV of the module reaches a certain value (described as V) when the module is charged and discharged. In the module in the initial state, the local SOC θ ₁ = θ _1A of the positive electrode and the local SOC θ 2 = θ _2A of the negative electrode correspond to each other. On the other hand, in the deteriorated module, as a result of the composition correspondence deviation, the local SOC θ ₁ = θ _1B and the local SOC θ ₂ = θ _2B correspond to each other. That is, when the module deteriorates, the combination of the local SOC θ ₁ and the local SOC θ ₂ in which the OCV of the module becomes V shifts to the right in the figure. As described in FIG. 7, since the right direction in the figure is the charging direction of the module, the shift to the right in the figure has an OCV of a common value V between the module in the initial state and the module after deterioration. However, it means that the SOC becomes high.

FIG. 9 is a diagram showing the correlation between the SOC of the module and the resistance. In FIG. 9, the horizontal axis represents the SOC of the module, and the vertical axis represents the internal resistance of the module.

As shown in FIG. 9, in general, a lithium ion secondary battery has a characteristic that the lower the SOC, the higher the internal resistance. Therefore, when the SOC corresponding to the common OCV increases from S1 to S2 due to the composition correspondence deviation between the positive electrode and the negative electrode, the internal resistance decreases from R1 to R2.

In the case where only the wear deterioration occurs in the module and the case where the lithium precipitation deterioration occurs in addition to the wear deterioration, the latter case has a larger composition correspondence deviation than the former case. Therefore, the latter has a relatively high SOC, and the latter has a relatively low internal resistance. As a result, in FIG. 5, the lithium precipitation deterioration curve LQ is shown lower in the figure than the wear deterioration curve LP.

<Deterioration judgment flow>
FIG. 10 is a flowchart showing the deterioration determination process in the first embodiment. This flowchart is executed by the processing system 200, for example, when the inspector installs the module M in the processing system 200 and operates an operation unit (start button or the like) (not shown).

In the following, the components of the processing system 200 (capacity calculation device 210, resistance measuring device 220, determination device 230, etc. shown in FIG. 2) as the execution body of each processing are not particularly distinguished, and are comprehensively “processed”. It is described as "system 200". Each step is basically realized by software processing by the processing system 200, but a part or all thereof may be realized by hardware (electric circuit) manufactured in the processing system 200.

With reference to FIG. 10, in S11, the processing system 200 acquires the initial capacity C0 of the module M, which is the target of determination of reusability. As described above, since the initial capacity C0 of the module is known from the specifications of the module M or has been measured at the time of manufacturing the vehicle, this value is used between the processing system 200 and the vehicle (or the external management server 80). It can be obtained by communication.

In S12, the processing system 200 acquires the temperature history (heat history) of the module M collected when the vehicle is used (when the module M is mounted on the vehicle) from the vehicle (or management server 80). Specifically, the processing system 200 can acquire the temperature frequency distribution of the module M detected by the temperature sensor (not shown) provided in the module M. The processing system 200 calculates the degree of progress of wear deterioration (capacity decrease amount) of the module M from the temperature of the module for each unit time. Then, the processing system 200 calculates the capacity reduction amount ΔC (W) of the module M by integrating the capacity reduction amount for each unit time up to the present time.

In S13, the processing system 200 calculates the wear capacity C (W) from the initial capacity C0 of the module M and the capacity reduction amount ΔC (W) according to the above equation (2).

In S14, the processing system 200 acquires the internal resistance R of the module M. The processing system 200 can charge and discharge the module M by using a charging / discharging device (not shown) such as a DC / DC converter, and can calculate the internal resistance R from the voltage value and the current value at that time. Alternatively, the processing system 200 may acquire the value of the internal resistance R measured outside the processing system 200 by communicating with the outside.

In S15, the processing system 200 plots the wear capacity C (W) calculated in S13 and the internal resistance R acquired in S14 on the characteristic diagram (see FIG. 5).

In S16, the processing system 200 determines whether or not the plot (C (W), R) in S15 is included in the region X. When the plot (C (W), R) is in the region X (YES in S16), the processing system 200 determines that the module M can be reused, and classifies the module M as a rebuild application (S17). ). On the other hand, when the plot (C (W), R) is outside the region X (NO in S16), the processing system 200 determines that the module M is not suitable for reuse (cannot be reused), and recycles the module M. It is classified into applications (S18). After that, a series of processes is completed.

As described above, in the first embodiment, the determination curve D between the wear deterioration curve LP and the lithium precipitation deterioration curve LQ on the characteristic diagram (see FIG. 5) and the plot of the module M (C (W)). , R) is used to determine whether the module M can be reused. When the plot (C (W), R) is included in the region X closer to the wear deterioration curve LP than the determination curve D, it is determined that the module M can be reused (rebuilt).

The determination curve D is determined in consideration of the degree of progress (permissible progress) of lithium precipitation deterioration allowed for the reuse of the module. That is, the smaller the allowable progress degree, the closer the determination curve D is to the wear deterioration curve LP, and conversely, the larger the allowable progress degree, the closer to the lithium precipitation deterioration curve LQ. As described above, according to the present embodiment, it is possible to determine whether or not the module M can be reused in consideration of the degree of progress of lithium precipitation deterioration.

Further, according to the present embodiment, the characteristics of the module M can be simply plotted on the characteristic diagram without performing a complicated calculation for distinguishing the deterioration caused in the module M into the wear deterioration and the lithium precipitation deterioration. Whether or not the module M can be reused can be easily determined.

[Embodiment 2]
In the first embodiment, a configuration for determining whether or not the module M can be reused has been described depending on whether or not the plot (C (W), R) of the module M is in the region X. In the second embodiment, a configuration for estimating the deterioration state of the module M in more detail will be described. Since the configuration of the processing system according to the second embodiment is the same as the configuration of the processing system 200 according to the first embodiment (see FIG. 4), detailed description thereof will not be repeated.

FIG. 11 is a diagram showing an example of a characteristic diagram according to the second embodiment. With reference to FIG. 11, in the second embodiment, the wear capacity is divided into three ranges A to C from the higher wear capacity to the lower wear capacity. In the second embodiment, the region sandwiched between the determination curve LD and the lithium precipitation deterioration curve LQ is referred to as “region Y”.

In the range A where the wear capacity is highest, the plot (C (W), R) of the module M is included in the region X, or the plot (C (W), R) is included in the region Y. Even if there is, it is determined that the module M can be reused.

In the range B where the wear capacity is medium, it is determined that the module M can be reused when the plot (C (W), R) of the module M is included in the region X. On the other hand, when the plot (C (W), R) is included in the region Y, it is determined that the module M cannot be reused.

In the range C where the wear capacity is the lowest, it is determined that the module M cannot be reused regardless of the region including the plot (C (W), R) of the module M (that is, regardless of the height of the internal resistance R). Ru.

As described above, in the second embodiment, in the range A near the upper right of the figure where the deterioration of the module M as a whole has not progressed most, the region Y (in other words, the occurrence of some lithium precipitation) is allowed, and the module is used. It is determined that M can be reused. In the range B where the deterioration of the module M as a whole has progressed to some extent, it is determined that the module M cannot be reused in the region Y in order to reduce the allowable amount of lithium precipitation as compared with the range A. In the range C near the upper right of the figure where the deterioration of the module M as a whole is most advanced, it is determined that the module M cannot be reused regardless of the amount of lithium precipitation.

The value of the wear capacity as the boundary between the range A and the range B can be determined experimentally (or by simulation) as follows. As described by the above equation (1), the full charge capacity C of the module M is obtained by subtracting the capacity decrease amount ΔC (Li) due to lithium precipitation from the wear capacity C (W) (C = C (W). ) -ΔC (Li)). That is, the full charge capacity C of the module M is further smaller than the wear capacity C (W). The value of the wear capacity as the boundary between the range A and the range B is set when the module is rebuilt and mounted on a new vehicle 90 in consideration of the existence of the capacity decrease amount ΔC (Li) due to lithium precipitation. It is defined so that the full charge capacity C required for traveling can be secured in the vehicle 90.

FIG. 12 is a flowchart showing the deterioration determination process in the second embodiment. Since the processes of S21 to S25 are the same as the processes of S11 to S15 (see FIG. 10) in the first embodiment, the description will not be repeated.

With reference to FIG. 12, in S26, the processing system 200 determines which of the ranges A to C the wear capacity C (W) of the module M belongs to.

When the wear capacity C (W) of the module M belongs to the range A (“range A” in S26), the processing system 200 advances the processing to S28, and the wear capacity of the module M plotted on the characteristic diagram in S25. It is determined whether or not the combination of C (W) and the internal resistance R (C (W), R) is included in the region X or the region Y. When the plot (C (W), R) is included in the area X or the area Y (YES in S28), the processing system 200 determines that the module M can be reused, and uses the module M for rebuilding. Classify (S29). On the other hand, when the plot (C (W), R) is not included in either the region X or the region Y (NO in S28), that is, the plot (C (W), R) is below the region Y. If so, the processing system 200 determines that the module M is non-reusable and classifies the module M for recycling (S30).

When the wear capacity C (W) of the module M belongs to the range B (“range B” in S26), the processing system 200 advances the processing to S27. When the plot (C (W), R) is included in the region X (YES in S27), the processing system 200 determines that the module M can be reused (S29). On the other hand, when the plot (C (W), R) is not included in the region X (YES in S27), that is, the plot (C (W), R) is included in the region Y or below the region Y. When it is located on the (low resistance side), the processing system 200 determines that the module M cannot be reused (S30).

When the wear capacity C (W) of the module M belongs to the range C (“range C” in S26), the processing system 200 determines that the module M cannot be reused regardless of the internal resistance R of the module M. (S30).

As described above, in the second embodiment as in the first embodiment, it is determined whether or not the module M can be reused in consideration of the degree of progress of lithium precipitation deterioration and without going through complicated calculations. be able to.

Further, in the second embodiment, the module M is set with the value of the wear capacity as the boundary between the range A and the range B so that the full charge capacity C required for traveling of the vehicle 90 can be secured. When the wear capacity C (W) of is included in the range A, the module M is determined to be reusable even when the plot (C (W), R) of the module M is included in the region Y. .. As a result, it is possible to reuse a larger number (higher ratio) of modules as compared with the first embodiment while securing the full charge capacity C required for traveling.

The embodiments disclosed this time should be considered to be exemplary and not restrictive in all respects. The scope of the present disclosure is set forth by the claims rather than the description of the embodiments described above, and is intended to include all modifications within the meaning and scope of the claims.

10 collectors, 20 inspectors, 30 performance recovery companies, 40 manufacturers, 50 dealers, 60 recyclers, 71-75 terminals, 80 management servers, 81 communication networks, 82 base stations, 90, 91-93 vehicles, 100 Battery management system, 200 processing system, 210 capacity calculation device, 220 resistance measurement device, 230 judgment device, 231 plot unit, 232 area judgment unit, 233 reuse judgment unit, 240 storage device, 250 display device, 910, 920, 930 Battery assembly, M module.

Claims (1)

It is a battery information processing system for determining whether or not the target battery, which is a lithium ion secondary battery, can be reused.
A storage device for storing the first and second deterioration curves defined on a plane defined by the internal resistance axis and the wear deterioration axis of the lithium ion secondary battery is provided.
The wear deterioration shaft is a shaft showing a wear capacity which is a full charge capacity that does not decrease due to lithium precipitation but decreases due to wear deterioration.
The first deterioration curve is a curve showing the correlation between the internal resistance of the lithium ion secondary battery in which the wear deterioration has occurred and the wear capacity, and is a curve when the wear deterioration progresses in a high temperature environment. Obtained by measuring changes in internal resistance with respect to changes in full charge capacity,
The second deterioration curve is a curve showing the correlation between the internal resistance of the lithium ion secondary battery in which deterioration due to lithium precipitation occurs in addition to wear deterioration and the wear capacity, and is a curve showing a correlation under a low temperature environment. Obtained by measuring the change in internal resistance with respect to the change in full charge capacity when the wear deterioration is advanced in a high temperature environment after the lithium deterioration is advanced in
Further equipped with a determination device for determining whether or not the target battery can be reused,
The determination device is
The wear capacity of the target battery calculated from the amount of decrease in the wear capacity of the target battery per unit time according to the temperature of the target battery and the temperature history of the target battery collected when the target battery is used. Acquired,
The internal resistance of the target battery calculated from the voltage value and the current value when the target battery is charged or discharged is acquired.
When the internal resistance and wear capacity of the target battery are plotted on the plane, it is determined that the target battery can be reused when the plot is included in a predetermined area .
The predetermined region includes a determination curve defined between the first deterioration curve and the second deterioration curve based on the progress of lithium precipitation allowed for reuse of the lithium ion secondary battery, and the first. A battery information processing system, which is an area sandwiched between the deterioration curve of 1 .

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