JP2021162511A - Secondary battery life prediction method, life prediction device, and vehicle - Google Patents

Abstract

To provide a method with which it is possible to estimate storage degradation using a physical model and predict the battery life of a secondary battery with good accuracy in a short time.SOLUTION: Provided is a method for predicting the battery life of a secondary battery 100. This method comprises: a step for acquiring a first physical quantity when the open-circuit state 330B of an electric circuit 300 begins and a second physical quantity when the open-circuit state 330B terminates and calculating a difference between the first and the second physical quantities; a step for calculating, on the basis of the difference, a self-discharge current amount ΔI which is the amount of current discharged while the electric circuit 300 is in the open-circuit state 330B; a step for calculating, on the basis of the self-discharge current amount ΔI, an increment of generated amount of a side reaction product generated in the interface between the surfaces of positive and negative active materials 112, 122 of the secondary battery 100 and the electrolyte; a step for calculating, on the basis of the generated amount of side reaction product, the increment of interface resistance of the secondary battery 100; and a step for estimating, on the basis of the increment of interface resistance, the degradation characteristic of the secondary battery 100 in the open-circuit state 330B.SELECTED DRAWING: Figure 1

Description

The present disclosure relates to a method for predicting the life of a secondary battery, a life prediction device, and a vehicle equipped with the life prediction device.

Conventionally, the deterioration characteristics of a secondary battery have been estimated using a physical model (see, for example, Patent Document 1).

In Patent Document 1, when modeling the increase in the internal resistance of the secondary battery due to charging / discharging, a physical model including a negative electrode SEI growth model (negative electrode passivation growth model) is used in consideration of the growth of the passivation film on the negative electrode. Is disclosed.

Japanese Unexamined Patent Publication No. 2014-167406

By the way, the deterioration characteristics of the secondary battery are the deterioration during the cycle when the secondary battery is working to the outside (cycle deterioration) and the deterioration characteristic when the secondary battery is not working to the outside during storage. It is roughly divided into two types: deterioration of the next battery (preservation deterioration).

For example, the technique described in Patent Document 1 can be applied to the estimation of cycle deterioration, but cannot be applied to the estimation of storage deterioration.

In addition, conventional storage deterioration uses a statistical model based on empirical rules, but there is a problem that it takes a huge amount of time, labor, and cost to create a statistical model, and the material of the secondary battery changes. Then, there is a problem that the prediction accuracy is lowered.

Therefore, in the present disclosure, it is possible to estimate storage deterioration using a physical model, and provide a method capable of accurately predicting the battery life of a secondary battery in a shorter period of time, the device thereof, and a vehicle equipped with the device. Make it an issue.

In order to solve the above problems, in the present disclosure, the deterioration characteristics during storage are modeled in consideration of the amount of current consumed by the side reaction product formation reaction at the interface between the active material surface of the electrode and the electrolytic solution. I tried to do it.

That is, the secondary battery life prediction method disclosed herein is a method of predicting the battery life of the secondary battery, and the secondary battery when the open circuit state of the electric circuit including the secondary battery starts. The first physical quantity, which is the physical quantity of, and the second physical quantity, which is the physical quantity of the secondary battery when the open circuit state ends, are acquired, and the difference between the first physical quantity and the second physical quantity is calculated. A step of calculating the self-discharge current amount, which is the amount of current discharged by the electric circuit during the open circuit state, and the self-discharge, based on the step and the difference between the first physical amount and the second physical amount. Based on the step of calculating the amount of by-product produced at the interface between the surface of the active material and the electrolytic solution contained in the electrode of the secondary battery based on the amount of current, and the amount of by-product produced. A step of calculating the increase amount of the interfacial resistance of the secondary battery and a step of estimating the deterioration characteristics of the secondary battery in the open circuit state based on the increase amount of the interfacial resistance are provided. It is characterized by that.

While the electric circuit including the secondary battery is in the open circuit state, the secondary battery is in a stored state in which it does not work to the outside. The secondary battery deteriorates with the passage of time even when it is in a stored state. However, when the secondary battery is in the stored state, the electric circuit is in the open circuit state and the charge / discharge current does not flow. Therefore, for example, the deterioration characteristics of the secondary battery in the stored state should be estimated using a cycle deterioration model. Can't.

Here, the inventors of the present application have found that when a fully charged secondary battery is stored for a certain period of time and then subjected to a discharge test, the amount of charge / discharge current decreases after storage as compared with that before storage. It is considered that this decrease in the amount of charge / discharge current was consumed by the reaction of producing a side reaction product at the interface between the surface of the active material and the electrolytic solution contained in the electrode. That is, even during storage, the formation of side reactants at the interface causes the sidereactor layer to grow as part of the passivation film, increasing the interface resistance and increasing the internal resistance of the secondary battery, that is, secondary. It is probable that the battery has deteriorated.

In this configuration, the current discharged during the open circuit state is based on the difference between the first physical quantity when the open circuit state of the electric circuit starts and the second physical quantity when the open circuit state of the electric circuit ends. The quantity, that is, the amount of self-discharge current is calculated. Then, the amount of the side reaction product produced at the interface is calculated from the amount of self-discharge current. Further, based on the amount of production, the amount of increase in interface resistance at the interface is calculated, and the deterioration characteristics of the secondary battery during storage are estimated.

That is, in this configuration, it is assumed that the deterioration of the secondary battery during storage is due to an increase in side reactants at the interface between the surface of the electrode active material and the electrolytic solution, and the amount of self-discharge current and the reaction of producing side reactants Build a physical model that considers relationships. Then, since the deterioration characteristics of the secondary battery during storage are estimated using the physical model, it is possible to predict the life of the secondary battery with high accuracy in a short period of time.

In the present specification, "when the open circuit state of the electric circuit starts" is when the target open circuit state starts, for example, the electric circuit changes from the previous closed circuit state to the open circuit state. This includes when switching and when the electric circuit changes from the previous open circuit state to the open circuit state. Further, "when the closed circuit state of the electric circuit ends" is when the target open circuit state ends, for example, when the electric circuit switches from the open circuit state to the next closed circuit state, and This includes when the electric circuit changes from the open circuit state to the next open circuit state. Moreover, "time" is a concept including the moment, immediately before, and immediately after. Further, the "physical quantity" is a time, a current value, and / or a voltage value or the like.

In a preferred embodiment, the electric circuit is in a closed circuit state before and after the open circuit state, and when the open circuit state starts, the electric circuit switches from the previous closed circuit state to the open circuit state. The time when the open circuit state ends is when the electric circuit switches from the open circuit state to a later closed circuit state.

When the electric circuit is in the closed circuit state, the secondary battery does work to the outside, that is, during the cycle. Considering the general use of the secondary battery by the user, it is quite possible that there will be a storage time between multiple cycle times. In such a case, the time when the target open circuit state starts is the time when the electric circuit switches from the previous closed circuit state to the open circuit state. Further, the time when the target open circuit state ends is the time when the electric circuit switches from the open circuit state to the next closed circuit state. According to this configuration, it is possible to predict the life of the secondary battery by reflecting the actual usage status of the secondary battery.

In one embodiment, the physical quantity is a time, and when the physical quantity is the time, the difference between the first physical quantity and the second physical quantity is defined as the time during which the secondary battery is in the open circuit state. In the step of calculating the self-discharge current amount, the storage time calculated in the step of calculating the difference, and the storage time and self-discharge of the secondary battery obtained experimentally in advance. The self-discharge current amount is calculated based on the relationship with the current amount.

When the physical quantity is a time, the first physical quantity is the time when the open circuit state starts. The second physical quantity is the time when the open circuit state ends. If the first physical quantity is the time at the moment when the open circuit state starts, the second physical quantity is also the time at the moment when the open circuit state ends. The difference between the first physical quantity and the second physical quantity corresponds to the time during which the secondary battery is in the open circuit state, that is, the storage time. In this case, for example, if the relationship between the storage time of the secondary battery whose life is to be predicted and the amount of self-discharge current during storage is obtained on a trial basis, the storage time, which is the difference between the first physical quantity and the second physical quantity, can be obtained. The amount of self-discharge current at the time of storage can be calculated based on the value and the relationship. Since the storage time is easy and highly accurate, and has excellent stability, the accuracy and accuracy can be calculated by calculating the self-discharge current amount based on the relationship between the storage time and the relationship obtained on a trial basis in advance. It is possible to predict the life with excellent stability.

In one embodiment, the physical quantity is a voltage value or a current value, and the first physical quantity is the voltage value or the current value immediately before the electric circuit switches from the previous closed circuit state to the open circuit state. The second physical quantity is the voltage value or the current value immediately after the electric circuit is switched from the open circuit state to the next closed circuit state.

When the physical quantity is a voltage value or a current value, the voltage value or the current value immediately before switching from the previous closed circuit state to the target open circuit state is acquired as the first physical quantity, and the second physical quantity is obtained from the open circuit state. Acquires the voltage value or current value immediately after switching to the next closed circuit state. The difference between the first physical quantity and the second physical quantity is the decrease in the voltage value or current value that occurs during the open circuit state, that is, the storage state, and the self-discharge current amount is obtained from this decrease in the voltage value or current value. Can be done.

In the present specification, the "voltage value / current value immediately before switching from the closed circuit state to the open circuit state" means that the voltage value / current value is zero because the electric circuit changes from the closed circuit state to the open circuit state. It can be the voltage value / current value before 0 seconds or less and 0.5 seconds or less from the moment when the voltage value becomes, or the average value of the voltage value / current value or the like. The "voltage value / current value immediately after switching from the open circuit state to the closed circuit state" is from the moment when the voltage value / current value becomes non-zero due to the electric circuit changing from the open circuit state to the closed circuit state. It can be the voltage value / current value after 0 seconds or more and 0.5 seconds or less, or the average value of the voltage value / current value.

In a preferred embodiment, the life cycle of the secondary battery has a plurality of the open circuit states, and the self-discharge current amount calculated for each of the plurality of open circuit states is the time before the open circuit. It decreases as the circuit becomes open later than the state.

The inventors of the present application have found that the rate of increase in the amount of self-discharge current of the secondary battery decreases as the integrated amount of storage time in the life cycle of the secondary battery increases. In other words, the amount of self-discharge current during storage gradually decreases as the storage time increases. According to this configuration, since the relationship between the storage time and the self-discharge current amount is reflected in the estimation of the deterioration characteristics, it is possible to predict the life of the secondary battery with high accuracy.

In a preferred embodiment, the electric circuit is in a closed circuit state at least one before and after the open circuit state, and when the electric circuit is in the closed circuit state, it is based on the charge / discharge current of the secondary battery. Therefore, a step of calculating the amount of increase in the interfacial resistance of the interface is further provided.

When the electric circuit is closed, that is, when it is cycled, the charge / discharge current of the secondary battery flows through the electric circuit. Therefore, based on this charge / discharge current information, the deterioration characteristics of the secondary battery can be estimated using a general cycle deterioration model. According to this configuration, the cycle deterioration model is used during cycling, while the deterioration characteristics of the secondary battery are estimated using the storage deterioration model based on the amount of self-discharge current during storage, thereby accurately predicting the life of the secondary battery. It can be carried out.

In a preferred embodiment, the life cycle of the secondary battery has a plurality of the closed circuit states and the plurality of the open circuit states, and the calculation is performed for each of the plurality of the closed circuit states and the plurality of the open circuit states. In the step of estimating the deterioration characteristic of the secondary battery, which further comprises a step of integrating the increase amount of the interfacial resistance, deterioration in the entire life cycle of the secondary battery based on the integrated value of the increase amount of the interfacial resistance. Estimate the characteristics.

In this configuration, a cycle deterioration model is used for a plurality of closed circuit states, a storage deterioration model is used for a plurality of open circuit states, and the amount of increase in interfacial resistance calculated for each of the closed circuit state and the open circuit state is calculated. Accumulate over the entire life cycle of the next battery. With this configuration, it is possible to accurately predict the life of the entire life cycle of the secondary battery in a short period of time.

Preferably, the secondary battery is a secondary battery mounted on a vehicle. Further, preferably, the secondary battery is a lithium ion secondary battery.

According to this configuration, it is possible to accurately predict the life of a secondary battery mounted on a vehicle, preferably a lithium ion secondary battery, in a short period of time.

In this case, preferably, the physical quantity is a time, the first physical quantity is the time when the vehicle is ignited off, and the second physical quantity is ignited only after the vehicle is ignited off. The difference between the first physical quantity and the second physical quantity is the time from the ignition off to the ignition on of the vehicle.

According to this configuration, the deterioration characteristics of the secondary battery when the engine of the vehicle is off can be estimated accurately.

Preferably, the by-reactant forms a passivation film on the surface of the active material, and the increase in interfacial resistance is due to an increase in the amount of low ion conductive molecules contained in the molecules constituting the passivation film. It is a thing.

According to this configuration, since the increase in the amount of low-ion conductive molecules among the molecules constituting the passivation film is taken into consideration, the battery life of the secondary battery can be predicted accurately and in a short period of time.

The secondary battery life prediction device disclosed herein is a device that predicts the battery life of the secondary battery, and is the device of the secondary battery when the open circuit state of the electric circuit including the secondary battery starts. An acquisition unit that acquires a first physical quantity that is a physical quantity and a second physical quantity that is the physical quantity of the secondary battery when the open circuit state of the electric circuit ends, and the first physical quantity and the second physical quantity. The first calculation unit that calculates the difference between the two, the second calculation unit that calculates the self-discharge current amount, which is the amount of current discharged by the electric circuit during the open circuit state, and the self. A third calculation unit that calculates the amount of by-reactant produced at the interface between the surface of the active material and the electrolytic solution contained in the electrode of the secondary battery based on the amount of discharge current, and the said by-product. A fourth calculation unit that calculates the amount of increase in the interfacial resistance of the interface based on the amount of generation, and an estimation that estimates the deterioration characteristics of the secondary battery in the open circuit state based on the amount of the increase in the interfacial resistance. It is characterized by having a part and.

In this configuration, it is assumed that the deterioration of the secondary battery during storage is due to an increase in side reactants at the interface between the surface of the electrode active material and the electrolytic solution, and the relationship between the amount of self-discharge current and the reaction of producing sidereactors is determined. Build a physical model that takes into account. Then, since the deterioration characteristics of the secondary battery during storage are estimated using the physical model, it is possible to predict the life of the secondary battery with high accuracy in a short period of time.

Further, the vehicle disclosed here is a vehicle including the secondary battery and the above-mentioned secondary battery life prediction device.

According to this configuration, it is possible to provide a vehicle capable of accurately predicting the life of an in-vehicle secondary battery in a short period of time.

As described above, according to the present disclosure, it is assumed that the deterioration of the secondary battery during storage is due to an increase in side reactants at the interface between the surface of the electrode active material and the electrolytic solution, and the amount of self-discharge current and sidereactors. A physical model is constructed in consideration of the relationship with the generation reaction of. Then, since the deterioration characteristics of the secondary battery during storage are estimated using the physical model, it is possible to predict the life of the secondary battery with high accuracy in a short period of time.

It is a block diagram which shows an example of the power-source system which incorporated the life prediction device of the secondary battery which concerns on one Embodiment. It is a flow chart for demonstrating the life prediction method of the secondary battery which concerns on one Embodiment. It is a conceptual diagram of the physical model used for the life prediction method. It is a figure which shows typically the structure of the secondary battery. It is a graph which shows the change of the internal resistance with respect to the number of cycles. It is a schematic diagram for demonstrating an example of the conduction mechanism of lithium ion at the time of a cycle in the negative electrode of a secondary battery. It is a graph which shows the charge curve before the preservation test and the discharge curve after the preservation test of an NMC battery cell. It is a schematic diagram for demonstrating the mechanism which the self-discharge current flows in the negative electrode of a secondary battery at the time of storage. It is a flow chart of the storage deterioration analysis process using a self-discharge current model. It is a graph which plotted the integrated value of the self-discharge current amount calculated by the preservation test with respect to the preservation time. It is a graph which shows the state of deterioration with time of a secondary battery schematically. It is a graph which shows the change of the internal resistance increase rate with respect to the storage time of an Example and a comparative example.

Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. The following description of preferred embodiments is merely exemplary and is not intended to limit the disclosure, its application or its use at all.

(Embodiment 1)
<Secondary battery life prediction device>
FIG. 1 shows a configuration example of the secondary battery life prediction device 200 according to the present embodiment. The life prediction device 200 is a device that predicts the battery life of the secondary battery 100 by using a physical model corresponding to the secondary battery 100.

The secondary battery 100 is not particularly limited, and is, for example, a lithium ion secondary battery such as NMC (Lithium Nichel Manganese Cobalt Oxide) type, lithium cobalt oxide type, lithium manganate type, nickel (NCA) type, or nickel. It may be a hydrogen battery, a lead storage battery, or the like.

The life prediction device 200 is incorporated in the power supply system 400 as shown in FIG. 1, for example, and is used to predict the life of the secondary battery 100. The power supply system 400 includes an electric circuit 300. The electric circuit 300 includes a secondary battery 100, a load 301 such as an electric motor driven by the secondary battery 100, a current sensor 310 for detecting a current value, a voltage sensor 320 for detecting a voltage value, and an electric circuit 300. Includes a switch 330 that switches between the closed circuit state 330A and the open circuit state 330B. The power supply system 400 includes a charging device for the secondary battery 100, but the illustration is omitted for the sake of simplicity. The current value and voltage value information detected by the current sensor 310 and the voltage sensor 320 by the charge / discharge operation of the secondary battery 100 are sent to the life prediction device 200 as the above-mentioned charge / discharge operation information.

The power supply system 400 can be mounted on, for example, a vehicle such as a hybrid vehicle or an electric vehicle provided with an electric motor driven by a secondary battery 100 as a driving force source. Further, the secondary battery 100 is mounted on a vehicle such as an automobile for the main purpose of supplying power to the starter motor when the engine is started and when the interior lighting or audio equipment is used when the engine is stopped. The next battery may be used. Further, the secondary battery 100 is not limited to a vehicle, and may be a secondary battery mounted on various electronic devices, various portable devices, and the like.

The life prediction device 200 is, for example, a device based on a well-known computer, and is a control unit 210, an input unit 220, an output unit 230, a storage unit 240, and a calculation unit 250 (acquisition unit, first calculation unit, second calculation unit). , Third calculation unit, fourth calculation unit, estimation unit) and timekeeping unit 260. The life prediction device 200 can also serve as a controller already mounted on an object such as various vehicles, various electronic devices, and various mobile devices on which the secondary battery 100 is mounted.

Various sensors such as the above-mentioned current sensor 310 and voltage sensor 320, various display means such as a display, and various control targets are electrically or wirelessly connected to the life prediction device 200. Detection signals from various sensors are input to the input unit 220. The output unit 230 outputs signals to various display means and various control targets. The storage unit 240 stores information about the secondary battery 100 whose life is to be predicted, information about charge / discharge conditions, charge / discharge operation information, information about calculations in the calculation unit 250, a program for executing calculation processing, and the like. In particular, the storage unit 240 stores a battery model, which will be described later, as a physical model for use in life prediction. The calculation unit 250 performs a predetermined calculation based on the detection signal input to the input unit 220 and the information stored in the storage unit 240. The control unit 210 predicts the life of the target battery based on the calculation result of the calculation unit 250.

The timing unit 260 switches from the open circuit state 330B to the next closed circuit state 330A together with the first time (first physical quantity) which is the moment (physical quantity) at which the switch 330 switches from the closed circuit state 330A to the open circuit state 330B. Acquires the second time (second physical quantity), which is the time of the moment (physical quantity). Then, the time measuring unit 260 measures the difference between the first time and the second time, that is, the time when the electric circuit 300 is in the open circuit state 330B as the storage time.

When the life prediction device 200 according to the present embodiment is mounted on the vehicle, for example, the first time is the time when the vehicle is ignited off, and the second time is the time when the vehicle is ignited for the first time after the ignition is turned off. Can be. In this case, the difference between the first time and the second time is the time from the ignition off of the vehicle to the ignition on.

Although not shown in FIG. 1, the power supply system 400 may be equipped with a temperature sensor for detecting the temperature of the secondary battery 100, and the temperature sensor provides temperature information of the secondary battery 100. It can be acquired and reflected in the life prediction. Further, the power supply system 400 of FIG. 1 is merely an example, and the power supply system to which the life prediction device 200 according to the present embodiment is applied may include other configurations.

<Method of predicting the life of secondary batteries>
FIG. 2 shows an example of a life prediction method for the secondary battery 100 using the life prediction device 200. The life prediction method shown in FIG. 2 includes an initial condition setting step S100, a charge / discharge analysis step S200, a physical quantity recording step S300, an interface resistance increase amount calculation step S400, a cycle count determination step S500, and an interface resistance increase amount integration. It includes a step S600, a deterioration characteristic estimation step S700, and a battery life prediction step S800.

≪Initial condition setting process≫
In the initial condition setting step S100, data such as the battery configuration related to the secondary battery 100 stored in the storage unit 240 in advance, that is, the specifications of the separator including the positive electrode, the negative electrode, and the electrolytic solution is read, and the data is set as the initial condition. do.

≪Charging / discharging analysis process≫
In the charge / discharge analysis step S200, the secondary battery 100 is charged and discharged in an arbitrary cycle, and the charge / discharge operation information such as the current value and the voltage value obtained by the charge / discharge operation is included in the battery model described later. The charge / discharge analysis of the secondary battery 100 is performed based on the charge / discharge operation model.

≪Physical quantity recording process≫
In the physical quantity recording step S300, as a part of the charge / discharge operation information, the physical quantity related to the secondary battery 100, specifically, the time information acquired by the measuring unit 260, the current value detected by the current sensor 310, and the voltage. The voltage value or the like detected by the sensor 320 is recorded and stored in the storage unit 240.

≪Process for calculating the amount of increase in interfacial resistance≫
In the interface resistance increase amount calculation step S400, the secondary battery 100 is based on the charge / discharge operation information, the charge / discharge analysis result obtained in the charge / discharge analysis step S200, and the deterioration model included in the battery model described later. Calculate the amount of increase in the interfacial resistance of.

Specifically, the interface resistance increase amount calculation step S400 includes a circuit state determination step S410, a cycle deterioration analysis step S420, and a storage deterioration analysis step S430.

-Circuit state determination process-
The circuit state determination step S410 determines whether or not the electric circuit 300 is in the closed circuit state 330A, that is, whether or not it is in the closed circuit state 330A or the open circuit state 330B.

-Cycle deterioration analysis process-
If it is determined in the circuit state determination step S410 that the electric circuit 300 is in the closed circuit state, the process proceeds to the cycle deterioration analysis step S420. Then, the amount of increase in the interfacial resistance during the cycle is calculated based on the charge / discharge operation information, the charge / discharge analysis result, and the cycle deterioration model which is a deterioration model during the cycle.

-Preservation deterioration analysis process-
If it is determined in the circuit state determination step S410 that the electric circuit 300 is in the open circuit state, the process proceeds to the storage deterioration analysis step S430. Then, the amount of increase in the interfacial resistance at the time of storage is calculated based on the recorded information of the physical quantity and the storage deterioration model which is a deterioration model at the time of storage.

≪Cycle count determination process≫
In the cycle number determination step S500, it is determined whether or not the number of cycles of the charge / discharge cycle has reached a predetermined value. If it is determined that the number of cycles has not reached a predetermined value, the process returns to the charge / discharge analysis step S200, and the charge / discharge analysis step S200 to the cycle number determination step S500 are repeated. On the other hand, when it is determined that the number of cycles has reached a predetermined value, the process proceeds to the next interfacial resistance increase amount integration step S600.

≪Process for integrating increase in interfacial resistance≫
The life cycle of the secondary battery 100 has a plurality of closed circuit states 330A and a plurality of open circuit states 330B. In the interface resistance increase amount integration step S600, the interface resistance increase amount calculated for each of the plurality of closed circuit states 330A and the open circuit state 330B is integrated.

<< Deterioration characteristic estimation process >>
In the deterioration characteristic estimation step S700, the internal resistance increase rate, capacity retention rate, etc. in the entire life cycle of the secondary battery 100 are calculated based on the integrated value of the interface resistance increase amount calculated in the interface resistance increase amount integration step S600. And estimate its deterioration characteristics.

≪Battery life prediction process≫
In the battery life prediction step S800, the battery life of the secondary battery 100 is predicted based on the deterioration characteristics estimated in the deterioration characteristic estimation step S700.

The battery life prediction step S800 can include a step of notifying the user of the battery life prediction result. Specifically, for example, a process is conceivable in which a threshold value for the remaining battery life is set in advance, and when the threshold value falls below the threshold value, a signal prompting the user to replace the battery is output to the display means.

Further, when the threshold value of the remaining battery life is exceeded, the switch 330 of the electric circuit 300 may be forcibly set to the open circuit state 330B. In this case, for example, the output unit of the life prediction device 200 may output a control signal forcibly setting the open circuit state 330B to the switch 330.

The life prediction method according to the present embodiment can also be used for predicting only storage deterioration. In this case, in FIG. 2, it may be assumed that the predetermined number of cycles is set to 0, and after the initial condition setting step S100, for example, a plurality of open circuit states 330B are repeated at predetermined time intervals. Then, the time at the moment when the target open circuit state 330B starts is set to the first time, and the time at the moment when the target open circuit state 330B starts is set to the second time. Calculate the amount of increase. Then, the amount of increase in the obtained interface resistance can be integrated to estimate the deterioration characteristics, and the battery life can be predicted.

<Battery model>
As a physical model for predicting battery life, for example, the battery model shown in FIG. 3 can be used. The battery model is composed of a battery charge / discharge operation model and a deterioration model. The deterioration model is composed of a cycle deterioration model and a storage deterioration model. The cycle deterioration model is composed of a structural transition phase growth model on the positive electrode side and a Li movement inhibition model on the negative electrode side. Further, in the present embodiment, the self-discharge current model is adopted as the storage deterioration model.

≪Charging / discharging operation model≫
The charge / discharge operation model is, for example, a model of the structure of the secondary battery 100 shown in FIG.

As the secondary battery 100, for example, an NMC-based lithium ion secondary battery will be described as an example. As shown in FIG. 4, the secondary battery 100 includes a positive electrode 110, a negative electrode 120, and a separator 130. The separator 130 is configured by, for example, infiltrating the electrolytic solution 140 into a resin arranged between the positive electrode 110 and the negative electrode 120.

The positive electrode 110 and the negative electrode 120 are each composed of, for example, an aggregate of spherical active materials. That is, as shown in FIG. 4, the positive electrode 110 contains the positive electrode active material 112, and the negative electrode 120 contains the negative electrode active material 122 (hereinafter, the positive electrode active material 112 and the negative electrode active material 122 are collectively referred to as “active material 112, 122”. May be called). In the positive electrode 110 and the negative electrode 120, the electrolytic solution 140 permeated into the separator 130 permeates between the positive electrode active materials 112 adjacent to each other and between the negative electrode active materials 122 adjacent to each other, and the surfaces of the active materials 112 and 122 and the electrolytic solution 140. An interface with is created.

Two at the time of battery 100 of the discharge, the lithium ion Li ⁺ and electrons e on the interface of the positive electrode active material 112 ^- along with the chemical reaction of absorbing is performed, lithium ions Li ⁺ and electrons e on the interface of the negative electrode active material 122 ^- The chemical reaction that releases On the other hand, at the time of charging, the reverse reaction proceeds. In the secondary battery 100, charging / discharging is performed by the transfer of ^{lithium ion Li + via the separator 130, and a charging / discharging current is generated.}

The charge / discharge operation model includes, for example, definite parameters such as the particle size of the active materials 112 and 122, the electrical conductivity, the open circuit potentials of the positive electrode 110 and the negative electrode 120, the salt diffusion coefficient in the electrolytic solution 140, and the salt concentration, and for example, the active material. It can be constructed by a known method by determining fluctuation parameters such as the Li diffusion coefficient of 112 and 122, the lithium ion concentration, and the reaction rate constants at the positive electrode 110 and the negative electrode 120.

≪Deteriorated model≫
It is known that the internal resistance of a secondary battery increases with time and as the number of cycles increases, and the output decreases, that is, deteriorates.

-Cycle deterioration model-
FIG. 5 shows the value of the internal resistance with respect to the number of cycles obtained in the <analytical test> described later. As shown in FIG. 5, it can be seen that the internal resistance of the battery increases as the number of cycles increases. It can be seen that the increase in the internal resistance is mainly due to the increase in the interface resistance generated at the interface between the active materials 112 and 122 contained in the electrodes and the electrolytic solution 140. That is, it is considered that the life of the secondary battery 100 can be predicted accurately by adopting the interface resistance increase model that appropriately models the increase in the interface resistance during the cycle.

The cycle deterioration model models the deterioration of the secondary battery 100 according to charging and discharging. The cycle deterioration model includes a structural transition phase growth model that models an increase in interfacial resistance at the positive electrode 110 and a Li movement inhibition model that models an increase in interfacial resistance at the negative electrode 120.

[Structural transition phase growth model]
In the positive electrode 110, a structural transition phase exists on the surface of the positive electrode active material 112, but as charging and discharging are repeated, this structural transition phase progresses inside the active material, and the thickness of the structural transition phase increases. To go. As the thickness of the structural transition phase increases, the interfacial resistance at the positive electrode increases, which causes deterioration of the secondary battery 100. The structural transition phase growth model models such an increase in interfacial resistance at the positive electrode 110 as a result of an increase in the thickness of the structural transition phase. A known model can be adopted as the structural transition phase growth model.

[Li migration inhibition model]
As shown in FIG. 6, in the negative electrode 120, a passivation film 124 is formed at the interface between the surface of the negative electrode active material 122 and the electrolytic solution 140. The passivation film is a layer formed by depositing a side reaction product generated by a chemical reaction occurring on the surface of the negative electrode active material 122 on the surface of the negative electrode active material 122.

The inventors of the present application may include lithium phosphate, lithium carbonate, lithium fluoride, and lithium oxide as the main components of the side reaction product, and among these lithium salts, an increase in lithium phosphate is an interface. It has been found that it greatly contributes to the increase in resistance (see Japanese Patent Application No. 2018-174387).

Specifically, the molecule 126 such as lithium carbonate, lithium fluoride, and lithium oxide ^{is considered to have high conductivity of lithium ion Li +} (hereinafter, the molecule 126 may be referred to as "high ion conductive molecule 126". .). Then, as indicated by reference numeral L in FIG. 6, it is considered that Li ⁺ reaches the negative electrode active material 122 through the position where the highly ionic conductive molecule 126 exists. On the other hand, the molecule 128 such as lithium phosphate ^{has low conductivity of Li +} (hereinafter, the molecule 128 may be referred to as “low ion conductive molecule 128”), and is considered to inhibit the movement of ^{Li +.} Therefore, it is considered that as the proportion of the low ion conductive molecule 128 contained in the passivation film 124 increases, ^{the conductivity of lithium ion Li +} in the passivation film 124 decreases and the interfacial resistance increases.

The Li movement inhibition model models such an increase in interfacial resistance in the negative electrode 120 as a result of an increase in the proportion of low ion conductive molecules 128 in the passivation film 124. As the Li movement inhibition model, for example, the model described in Japanese Patent Application No. 2018-174387 can be preferably adopted.

-Preservation deterioration model-
The storage deterioration model is a model of deterioration of the secondary battery 100 in a stored state over time.

Here, the life prediction method according to the present embodiment is characterized by adopting a self-discharge current model as a storage deterioration model. Hereinafter, the self-discharge current model will be described.

FIG. 7 shows the charge curve of the NMC-based battery cell before the storage test performed in <Comparative Example> described later, and the discharge curve after the storage test. As shown in FIG. 7, it can be seen that the charge / discharge current amount in the discharge curve after the storage test is reduced from I _{1 to I 2} as compared with the charge / discharge current amount in the charge curve before the storage test. This decrease in the amount of charge / discharge current ΔI (= I ₁ −I ₂ ) is a chemical reaction (“side reaction” in the present specification) for producing a side reaction product at the interface between the surface of the active material contained in the electrode and the electrolytic solution. It is considered that it was consumed by.

Specifically, for example, when the secondary battery 100 is an NMC battery cell, at the interface between the surface of the positive electrode active material 112 and the electrolytic solution 140, Li _x (Ni _1/3 Mn _{1/3) which is the positive electrode active material 112} It is considered that, for example, a side reaction as shown by the following formula (1) spontaneously proceeds due to _{Co 1/3} ) O ₂ ^{and Li +} contained in the electrolytic solution 140.

Further, also at the interface between the surface of the negative electrode active material 122 and the electrolytic solution, depending on the graphite which is the negative electrode active material 122 and LiPF ₆ and Li ⁺ contained in the electrolytic solution 140, for example, a sub-type as represented by the following formula (2) The reaction is thought to proceed spontaneously.

Therefore, at the interface on the positive electrode 110 side, (x-2) e ⁻ in the above formula (1), and at the interface on the negative electrode 120 side, (2y-1) / 3e ⁻ in the above formula (2) are the charge / discharge current amounts. It is considered that it corresponds to the decrease ΔI of. The decrease Δ of the charge / discharge current amount can be defined as the “self-discharge current amount” which is the amount of current discharged when the electric circuit 300 is in the open circuit state 330B, that is, during storage.

Then, at the interface on the positive electrode 110 side, a side _{reaction product such as NiO, CoO, MnO, Li 2} O, preferably a low ion conductive molecule such as NiO, CoO, MnO is generated, so that the side reaction product layer is not formed. It grows as part of a dynamic film. Further, at the interface on the negative electrode 120 side, as shown in FIG. 8, a _{side reaction product such as Li x-1} PO _x F _4-x, which is a low ion conductive molecule 128, is generated, thereby forming a side reaction product layer. Grow as part of the passivation film 124. Then, it is considered that the interfacial resistance increases and the deterioration of the secondary battery 100 progresses.

The self-discharge current model considers the amount of side reactants, preferably low-ion conductive molecules, that form the passivation film formed at the interface between the active materials 112 and 122 and the electrolytic solution during storage, and the interfacial resistance. This is an interfacial resistance increase model that models the increase in.

Specifically, the storage deterioration analysis step S430 using the self-discharge current model is based on the physical quantity difference calculation step S431 that calculates the difference between the first physical quantity and the second physical quantity, for example, as shown in FIG. Based on the self-discharge current amount calculation step S432 for calculating the self-discharge current amount, the side reactant production amount calculation step S433 for calculating the side reaction product production amount based on the self-discharge current amount, and the production amount. Therefore, the interfacial resistance increase amount calculation step S434 for calculating the interfacial resistance increase amount is provided.

[Physical quantity difference calculation process]
As described above, the timekeeping unit 260 is used for the first time when the electric circuit 300 switches from the closed circuit state 330A to the open circuit state 330B and when the electric circuit 300 switches from the open circuit state 330B to the next closed circuit state 330A. Get the second time. The first time and the second time are stored in the storage unit 240. In the physical quantity difference calculation step S431, the calculation unit 250 acquires the first time as the first physical quantity and the second time as the second physical quantity stored in the storage unit 240, and calculates the difference between them. The difference between the first time and the second time is the time when the secondary battery 100 is in the open circuit state 330B, that is, the storage time.

[Self-discharge current amount calculation process]
For example, the storage unit 240 may be tested in advance by using a test method such as a storage test of <Comparative Example> described later or a simulation of a secondary battery having a configuration similar to that of the secondary battery 100 whose life is predicted. The relationship between the desired storage time in the secondary battery 100 and the amount of self-discharge current during storage is stored. In the self-discharge current amount calculation step S432, the self-discharge during storage when the electric circuit 300 is in the open circuit state 330B based on the value of the storage time, which is the difference between the first time and the second time, and the relationship. Calculate the amount of current.

Here, it is desirable that the relationship between the storage time and the self-discharge current amount obtained experimentally in advance has a tendency that the rate of increase of the self-discharge current amount gradually decreases as the storage time increases. Specifically, FIG. 10 shows a test in which the same test as the storage test of <Comparative Example> described later is performed to calculate the self-discharge current amount ΔI, and the integrated value of the self-discharge current amount ΔI is plotted against the storage time. Is. As shown in FIG. 10, when the storage time increases from t ₀ to t ₀ + t ₁ + t ₂ + t _3, the self-discharge current amount calculated for each of the plurality of open circuit states 330B corresponding to the storage times t1, t2, and t3. It can be seen that ΔI ₁ , ΔI ₂ , and ΔI ₃ are temporally reduced so as to be in the later open circuit state 330B as compared with the storage time in the previous open circuit state 330B. That is, in the example of FIG. 10, the rate of increase in the amount of self-discharge current gradually decreases as the storage time increases. Since the relationship between the storage time and the amount of self-discharge current has such a tendency, it is possible to perform a simulation that more accurately reflects the actual condition of the secondary battery 100, which is the life prediction target, and thus the secondary battery. It is possible to accurately predict the life of the battery.

The self-discharge current amount ΔI is an absolute amount of the current amount consumed during storage, and the sizes of the positive electrode 110 and the negative electrode 120 are almost always different from each other. It is preferable to use the current density obtained by dividing the quantity ΔI by the cross-sectional area of the electrode, that is, the self-discharge current density i _0.

[Vaccine production amount calculation process]
In byproducts generated amount calculation step S433, the self-discharge current [Delta] I, preferably based on the self-discharge current density i _0, side reaction products generated in the interface between the surface and the electrolyte solution 140 of active material 112, 122 , Preferably calculate the amount of low ion conductive molecules produced.

[Process for calculating the amount of increase in interfacial resistance]
Then, in the interface resistance increase amount calculation step S434, the increase amount of the interface resistance at the interface is calculated based on the production amount of the side reaction product.

[Concrete example]
Hereinafter, an example of a specific physical model of the by-product production amount calculation step S433 and the interfacial resistance increase amount calculation step S434 will be shown. First, the equations for calculating the amount of side reactants produced can be defined as the following equations (3) to (5).

However, in the formulas (3) to (5), the symbols indicate the following.

J _s : Vaccine reaction current [A]
η _s : side reaction overvoltage [V]
R _film : Vaccine resistance [Ω]
δ: Thickness of side reaction product layer [m]
i ₀ : Self-discharge current density [A / m ² ]
F: Faraday constant [C / mol]
R: Gas constant [J / mol / K]
α: Transition coefficient [-]
J: Interfacial current density [A / m ² ]
η ₀ : Initial overvoltage of side reaction [V]
M: Molecular weight of side reactant [kg / mol]
ρ: Vaccine density [kg / m ³ ]
n: Number of side reaction electrons [-]
In equations (3) to (5), J _s , η _s , R _film , and δ are variable parameters.

Equations (3) and (4) describe the formation of side reactants. _{Equation (3) is an equation for obtaining a side reaction current J s} , which is a current that causes a side reaction that proceeds during storage at the interface between the electrode active material and the electrolytic solution. The value of the self-discharge current density i ₀ calculated as described above is input to the equation (3). _{Note that η s} in the equation (3) is an overvoltage of a side reaction and can be expressed by the equation (4). In formula (4), R _film is the amount of increase in interfacial resistance due to the final output by-product.

Equation (5) is an equation that describes the amount of side reaction product produced as the amount of increase in the thickness δ of the side reaction product layer. The increase in the thickness δ of the side reaction product layer corresponds to the increase in the film thickness of the passivation film during storage.

_{The value of the self-discharge current density i 0} is input to the equations (3) to (5), and as a result of the calculation, the amount of increase in the interfacial resistance due to the increase in the layer thickness δ of the side reaction product layer according to the following equation (6). The R _film is output.

However, in the formula (6), κ is the conductivity [S / m] of the side reactant.

The control factors of the physical model are the electrode material of the secondary battery 100 whose life is predicted, the specifications of the electrolytic solution, the area of the electrode, the size such as the thickness, the SOC, and the like. The error factors are outside air temperature, variation in initial resistance, contact resistance, and the like. By taking these control factors and error factors into consideration and performing iterative calculations using the above physical model, it is possible to predict an increase in interfacial resistance during storage of the secondary battery 100.

Finally, from the amount of increase in interfacial resistance, the rate of increase in internal resistance, the rate of capacity retention, etc. in the entire life cycle of the secondary battery 100 are calculated, and the deterioration characteristics of the secondary battery 100 are estimated. Then, the life of the secondary battery 100 is predicted. Specifically, for example, for the internal resistance value R _t and the internal resistance increase rate R _p of the secondary battery 100, the initial value of the internal resistance value is R ₀ , and the integrated value of the increase amount R _{film of the interfacial resistance is ΣR film.} , Are given by the following equations (7) and (8), respectively.

R _t = R ₀ + ΣR _film ... (7)
R _p = R _t / R ₀ ... (8)

<Effect>
In the method and apparatus for predicting the life of the secondary battery 100 according to the present embodiment, the first time at the moment when the electric circuit 300 switches from the closed circuit state 330A to the open circuit state 330B and the next closed circuit state 330A from the open circuit state 330B Calculate the difference from the second time at the moment of switching to. Then, the self-discharge current amount ΔI at the time of storage is calculated based on the difference between the first time and the second time and the relationship between the difference and the self-discharge current amount ΔI obtained experimentally in advance. .. Then, from the self-discharge current amount ΔI, the amount of the side reaction product produced at the interface is calculated. Further, based on the amount of production, the amount of increase in interface resistance at the interface is calculated, and the deterioration characteristics of the secondary battery during storage are estimated.

That is, in this configuration, it is assumed that the deterioration of the secondary battery 100 during storage is due to an increase in side reactants at the interface between the surfaces of the active materials 112 and 122 and the electrolytic solution 140. Then, a self-discharge current model considering the relationship between the self-discharge current amount ΔI and the side reaction is constructed. Then, since the deterioration characteristics of the secondary battery 100 during storage are estimated using the self-discharge current model, it is possible to predict the life of the secondary battery with high accuracy in a short period of time.

In this configuration, when the electric circuit 300 is in the closed circuit state 330A, that is, during the cycle, the deterioration characteristics of the secondary battery 100 can be estimated by using a general cycle deterioration model. Therefore, when the life cycle of the secondary battery 100 has a plurality of closed circuit states 330A and a plurality of open circuit states 330B, a cycle deterioration model is used for the plurality of closed circuit states 330A, and the plurality of open circuit states 330B are used. Uses a storage deterioration model. Then, the amount of increase in the interfacial resistance is calculated for each of the plurality of closed circuit states 330A and the plurality of open circuit states 330B. Then, the amount of increase in the interfacial resistance is integrated over the entire life cycle of the secondary battery 100.

Specifically, FIG. 11 is a schematic graph showing the state of deterioration of the secondary battery 100 over time. At the time of storage, the secondary battery 100 does not work to the outside. During this time, the secondary battery 100 may gradually deteriorate. During the cycle, the secondary battery 100 works to the outside. During this time, the secondary battery 100 may deteriorate at a speed faster than that at the time of storage. By repeating the storage time and the cycle time a plurality of times, the degree of deterioration that has progressed during the storage time and the cycle time is accumulated over the entire life cycle.

In the life prediction method and apparatus according to the present embodiment, the increase amount of the interfacial resistance calculated for each of the plurality of closed circuit states 330A and the open circuit state 330B is integrated to cover the entire life cycle of the secondary battery 100. Deterioration characteristics can be estimated. Then, it is possible to predict the life of the secondary battery 100 with high accuracy in a short period of time.

Further, in the life prediction method and device according to the present embodiment, time is used as a physical quantity. Since the storage time is easy and highly accurate, and has excellent stability, the accuracy and accuracy can be calculated by calculating the self-discharge current amount based on the relationship between the storage time and the relationship obtained on a trial basis in advance. It is possible to predict the life with excellent stability.

(Embodiment 2)
Hereinafter, other embodiments according to the present disclosure will be described in detail. In the description of these embodiments, the same parts as those of the first embodiment are designated by the same reference numerals, and detailed description thereof will be omitted.

In the first embodiment, the case where the time is used as the physical quantity has been described as an example, but the physical quantity is not limited to the time, and a voltage value, a current value, or the like may be used.

Specifically, for example, when a voltage value is used as the physical quantity, for example, the first physical quantity is the first voltage value which is the voltage value immediately before the electric circuit 300 switches from the closed circuit state 330A to the open circuit state 330B. be able to. Further, the second physical quantity can be a second voltage value which is a voltage value immediately after the electric circuit 300 is switched from the open circuit state 330B to the closed circuit state 330A. The first voltage value and the second voltage value are, for example, V ₁ and V ₂ shown in FIG. 7.

In this case, the calculation unit 250 acquires the first voltage value and the second voltage value stored in the storage unit 240, and calculates the difference between the two. The difference is the open circuit state 330B, that is, the decrease in voltage generated during storage, and the self-discharge current amount ΔI can be calculated from this decrease in voltage.

Similarly, when a current value is used as the physical quantity, for example, the first physical quantity is the current value immediately before the electric circuit 300 switches from the closed circuit state 330A to the open circuit state 330B (hereinafter, referred to as "first current value"). .) Can be. Further, the second physical quantity can be a current value immediately after the electric circuit 300 is switched from the open circuit state 330B to the closed circuit state 330A (hereinafter, referred to as “second current value”). The first current value and the second current value are, for example, I ₁ and I ₂ shown in FIG.

In this case, the calculation unit 250 acquires the first current value and the second current value stored in the storage unit 240, and calculates the difference between the two. The difference is the open circuit state 330B, that is, the decrease in the current generated during storage, and corresponds to the self-discharge current amount ΔI itself.

By using a voltage value or a current value as a physical quantity, modeling can be easily performed and the self-discharge current amount ΔI can be easily calculated. However, from the viewpoint of suppressing a decrease in the calculation accuracy of the self-discharge current amount due to a large error in the detected value of the voltage value / current value due to the on / off of the switch 330, the time of the first embodiment is used as the physical quantity. The configuration is desirable.

(Embodiment 3)
The model for increasing the interfacial resistance of the positive electrode 110 is not limited to the above-mentioned structural transition phase growth model, and may be another physical model. Specifically, for example, a known model such as the Li movement inhibition model applied to the negative electrode 120, or a passivation film growth model in which an increase in interfacial resistance is modeled as a result of an increase in the film thickness of the passivation film. , Or a model in which these are combined.

Specifically, for example, in an NMC-based battery, a reaction similar to the above formula (1) proceeds at the interface between the positive electrode active material 112 and the electrolytic solution 140 even during the cycle, and NiO as a low ion conductive molecule, CoO, MnO, etc. are generated. Then, the passivation film grows. Therefore, since the increase in the interfacial resistance of the positive electrode 110 can be modeled as a result of the increase in the proportion of low ion conductive molecules in the passivation film, the Li movement inhibition model can be adopted as the model for increasing the interfacial resistance of the positive electrode 110. ..

The model for increasing the interfacial resistance of the negative electrode 120 is not limited to the Li movement inhibition model of the first embodiment, and may be another known model such as the above-mentioned structural transition phase growth model or the above-mentioned passivation film growth model. ..

As the interface resistance increase model for the positive electrode 110 and the negative electrode 120, an appropriate one may be appropriately selected according to the assumed battery configuration.

Next, a specific example and a comparative example will be described.

<Comparison example>
A storage test was conducted on the NMC battery cells shown in Table 1. Specifically, the internal resistance value of the battery cell is measured by the IV test after 0 hours, 290 hours, 570 hours, 1050 hours, 1350 hours, and 1470 hours have passed from the start of the test at a temperature of 45 ° C. and 100% SOC. bottom. The IV test was carried out under the condition that a current of 0.5C, 0.7C, 1C and 2C was passed for 10 seconds from a state of a temperature of 25 ° C. and a SOC of 50%. The results are shown in FIG. In FIG. 12, the internal resistance value at 0 hours is set to 100%, and the internal resistance value at each storage time is shown by the internal resistance increase rate (%) as a comparison value with the internal resistance value at 0 hours.

<Example>
For the NMC battery cells shown in Table 1, a self-discharge current model was created by the method described in the first embodiment. The relationship between the storage time of the battery cell and the self-discharge current was determined by the same storage test as in <Comparative Example>. The change curve of the internal resistance increase rate with respect to the storage time obtained by the simulation using the self-discharge current model is shown by the solid line in FIG. The model development period of the self-discharge current model, that is, the period required from the start of creation of the self-discharge current model to the completion was about 0.1 year.

<Discussion>
As shown in FIG. 12, it can be seen that the prediction results of the examples have high consistency with the actual test results of the comparative examples (error 2.0%). In the comparative example, the internal resistance value at 290 hours was lower than the internal resistance value of the cell at 0 hours, which means that, for example, the aging process at the time of manufacturing the secondary battery was insufficient. It is thought that this is the cause. In predicting the battery life of a secondary battery, it is important to estimate the deterioration characteristics such as after 10 years, so it is considered that the influence of the variation in the internal resistance value at the initial stage is small.

Further, the conventional statistical model is created by collecting the same data as the data shown in the comparative example for a plurality of battery cells while adjusting the test conditions and the like, and using the least squares method or the like. The model development period for such a statistical model, that is, the period required from the start of the storage test to the completion of the statistical model, can extend to at least about two years.

The battery model of the embodiment has an extremely short model development period as compared with such a conventional statistical model.

As described above, according to the method and apparatus for predicting the life of the secondary battery according to the present disclosure, the life of the secondary battery can be predicted accurately in a very short period of time and at low cost.

<Analytical test>
The battery cells shown in Table 2 are charged and discharged by repeating the charging / discharging operation a predetermined number of times (0 times, 400 times, 800 times) under the conditions of a temperature of 55 ° C. and a charging / discharging current of 5.8A (1C) / 5.8A (1C). A discharge test was performed.

The AC impedance of the battery cell after the charge / discharge test was measured, and the obtained Nyquist plot was subjected to fitting analysis to calculate the internal resistance of the battery cell (FIG. 5). The value of the interfacial resistance shown in FIG. 5 is the total value of the interfacial resistance of the positive electrode and the negative electrode calculated from the AC impedance measurement and the fitting analysis result thereof.

The present disclosure enables estimation of storage deterioration using a physical model, and can provide a method capable of accurately predicting the battery life of a secondary battery in a shorter period of time, the device thereof, and a vehicle equipped with the device. So it is extremely useful.

100 Secondary battery 110 Positive electrode 112 Positive electrode active material 120 Negative electrode 122 Negative electrode active material 124 (Negative electrode) Immobility film 126 High ion conductive molecule 128 Low ion conductive molecule 130 Separator 140 Electrolyte 200 Life predictor 210 Control unit 220 Input Unit 230 Output unit 240 Storage unit 250 Calculation unit 260 Measuring unit 300 Electric circuit 301 Load 310 Current sensor 320 Voltage sensor 330 Switch 330A Closed circuit state 330B Open circuit state 400 Power supply system

Claims (11)

It is a method of predicting the battery life of a secondary battery.
The first physical quantity, which is the physical quantity of the secondary battery when the open circuit state of the electric circuit including the secondary battery starts, and the second physical quantity, which is the physical quantity of the secondary battery when the open circuit state ends. A step of acquiring a physical quantity and calculating the difference between the first physical quantity and the second physical quantity, and
A step of calculating the self-discharge current amount, which is the amount of current discharged by the electric circuit during the open circuit state, based on the difference between the first physical quantity and the second physical quantity.
Based on the self-discharge current amount, a step of calculating the amount of by-product produced at the interface between the active material surface and the electrolytic solution contained in the electrode of the secondary battery, and
A step of calculating the amount of increase in the interfacial resistance of the secondary battery based on the amount of the side reaction product produced, and
A method for predicting the life of a secondary battery, which comprises a step of estimating deterioration characteristics of the secondary battery in the open circuit state based on the increase amount of the interfacial resistance. In claim 1,
The electric circuit is in a closed circuit state before and after the open circuit state.
The time when the open circuit state starts is when the electric circuit switches from the previous closed circuit state to the open circuit state.
A method for predicting the life of a secondary battery, wherein the end of the open circuit state is a time when the electric circuit is switched from the open circuit state to a later closed circuit state. In claim 1 or 2,
The physical quantity is time and
When the physical quantity is the time, the difference between the first physical quantity and the second physical quantity is the storage time as the time when the secondary battery is in the open circuit state.
In the step of calculating the self-discharge current amount, the relationship between the storage time calculated in the step of calculating the difference and the storage time of the secondary battery and the self-discharge current amount obtained in advance on a trial basis. A method for predicting the life of a secondary battery, which comprises calculating the self-discharge current amount based on. In claim 2,
The physical quantity is a voltage value or a current value, and is
The first physical quantity is the voltage value or the current value immediately before the electric circuit switches from the previous closed circuit state to the open circuit state.
A method for predicting the life of a secondary battery, wherein the second physical quantity is the voltage value or the current value immediately after the electric circuit is switched from the open circuit state to the next closed circuit state. In any one of claims 1 to 4,
The life cycle of the secondary battery has a plurality of the open circuit states.
The amount of self-discharge current calculated for each of the plurality of open circuit states is reduced in time from the previous open circuit state to the later open circuit state. Life prediction method. In any one of claims 1 to 5,
The electric circuit is in a closed circuit state at least one before and after the open circuit state.
When the electric circuit is in the closed circuit state, the secondary battery is further provided with a step of calculating the amount of increase in the interfacial resistance at the interface based on the charge / discharge current of the secondary battery. Life prediction method. In claim 6,
The life cycle of the secondary battery has a plurality of the closed circuit states and a plurality of the open circuit states.
A step of integrating the increase amount of the interfacial resistance calculated for each of the plurality of closed circuit states and the plurality of open circuit states is further provided.
In the step of estimating the deterioration characteristics of the secondary battery, the deterioration characteristics of the secondary battery over the entire life cycle of the secondary battery are estimated based on the integrated value of the increase amount of the interfacial resistance. Life prediction method. In any one of claims 1 to 7,
A method for predicting the life of a secondary battery, wherein the secondary battery is a secondary battery mounted on a vehicle. In claim 8.
The physical quantity is time and
The first physical quantity is the time when the vehicle is ignited off.
The second physical quantity is the time when the ignition is turned on for the first time after the vehicle is turned off.
A method for predicting the life of a secondary battery, wherein the difference between the first physical quantity and the second physical quantity is the time from the ignition off to the ignition on of the vehicle. A device that predicts the battery life of a secondary battery.
The first physical amount, which is the physical amount of the secondary battery when the open circuit state of the electric circuit including the secondary battery starts, and the secondary battery of the secondary battery when the open circuit state of the electric circuit ends. An acquisition unit that acquires a second physical quantity, which is a physical quantity,
A first calculation unit that calculates the difference between the first physical quantity and the second physical quantity, and
Based on the difference, the second calculation unit that calculates the self-discharge current amount, which is the amount of current discharged by the electric circuit during the open circuit state,
A third calculation unit that calculates the amount of by-reactants produced at the interface between the surface of the active material and the electrolytic solution contained in the electrodes of the secondary battery based on the amount of self-discharge current.
A fourth calculation unit that calculates the amount of increase in interfacial resistance at the interface based on the amount of the side reaction product produced.
A secondary battery life prediction device including an estimation unit that estimates deterioration characteristics of the secondary battery in the open circuit state based on the increase in the interfacial resistance. A vehicle including the secondary battery and the life prediction device for the secondary battery according to claim 10.

Images