JP2020112535A - Device for detecting degree of deterioration and energy accumulation remaining amount of power storage element - Google Patents

Abstract

To provide a device for detecting a degree of deterioration and an energy accumulation remaining amount of a power storage element capable of recognizing a battery state by precisely and instantly detecting a degree of deterioration SOH and an energy accumulation remaining amount SOC of a power storage element.SOLUTION: A device 1 for detecting a degree of deterioration and an energy accumulation remaining amount of a secondary battery 10 for detecting a degree of deterioration SOH and an energy accumulation remaining amount SOC of the secondary battery 10 includes measurement means for measuring voltage and current of the secondary battery 10 and a control part having computation means for executing a predetermined computation. The control part 14 obtains an overvoltage δ in operation of the secondary battery by computation by using a battery equation shown in the following expression 1 on the basis of measurement values of a rising voltage and current when starting charging of the secondary battery.SELECTED DRAWING: Figure 5

Description

The present invention relates to a state of charge (SOC) indicating the remaining amount of energy of a storage element such as a secondary battery, and a degree of deterioration of the storage performance (SOH) indicating how much the storage performance has deteriorated or matured compared to the initial stage. ) Of the storage element and a remaining storage amount detection device.

Secondary batteries are widely used in electronic devices, electric devices, vehicles, and the like. Examples of the secondary battery include a lead battery, a nickel hydrogen battery, a lithium ion battery and the like. The secondary battery is a battery that can be used by repeatedly discharging and charging. When such a secondary battery is used, the degree of deterioration of the secondary battery (SOH; State Of Health, current performance when the initial is taken as 100%), the remaining charge of the secondary battery (SOC; State Of Charge, It is also known as the depth of charge. When "empty" is 0% and "full" is 100%, it is possible to properly use the secondary battery.

Various techniques have been conventionally proposed as a technique for estimating the SOH and SOC of a secondary battery (see, for example, Patent Documents 1 to 3).

In addition, while secondary batteries are widely used in various fields, there is no means for accurately detecting the remaining charge of the secondary battery, and for users of devices that use the secondary battery as a power source, the device suddenly becomes It is the current situation that people are stuck with the trouble and anxiety that they become inoperable due to the exhaustion of.

The reason for this is that if a method of measuring the terminal voltage of the secondary battery and estimating the remaining power storage amount in association with the terminal voltage is adopted, as shown in FIG. The higher the performance of the secondary battery, the terminal voltage V with respect to the remaining amount hardly changes except in the limit of “empty (EMPTY)” or “FULL”, so it is difficult to determine the remaining amount with the terminal voltage. However, there is a problem that the required detection accuracy exceeds the practical range.

In addition, as a method of detecting the remaining charge of the secondary battery other than the above, a method of estimating the remaining charge by time-integrating the input/output of the current and adding/subtracting the increase/decrease in the amount of electricity from the battery from the reference value is used. ing. In this case, there is a problem in setting the reference value, for example, whether the reference value is fully charged or the remaining amount is zero, and further, the loss inside the battery during charging and discharging is caused by the stored amount of electricity. There is a problem that it is not reflected in, and it becomes a sweet residual amount recognition as a whole.

The technology for accurately detecting the remaining charge of the secondary battery is indispensable not only for electric vehicles that will become even more popular in the future, but also for devices that are driven by the electric energy stored in the battery, and the establishment of that technology is essential. I'm in a hurry.

The secondary battery has two poles, a negative pole and a positive pole, and the material forming the pole is selected so that the chemical potential of the negative pole is higher than that of the positive pole. Further, when the working medium deposited on the negative electrode, for example, a lithium ion battery, slides down to the positive electrode, energy proportional to the difference in chemical potential and the number of lithium ions is released to the external electric circuit to give energy. .. This is the discharging process of the secondary battery.

In addition, the charging process of the secondary battery is a process in which the potential of the positive electrode is made higher than that of the negative electrode and the working medium deposited on the positive electrode is dropped to the negative electrode, but this process requires an external power source for increasing the potential.

As described above, the operation inside the secondary battery can be said to be merely the operation of transferring the working medium between the positive electrode and the negative electrode, but it is accompanied by an electrochemical reaction of oxidation/reduction in the electrode or at the electrode interface. The quantification of the reaction amount per unit or the control of the amount change becomes an extremely complicated and important device configuration.

However, regarding the use of electric energy by the secondary battery, since the device circuit or the electronic device is composed only of the flow of electrons, if it is possible to grasp the electrochemical reaction efficiently and promptly, It should be possible to establish appropriate battery status recognition and remedies. Therefore, it is desired to understand the battery state based on the electrochemical reaction in such a secondary battery.

Specifically, in a system that takes out electric energy from a stored secondary battery and converts the electric energy into motive power such as an electric vehicle such as an electric vehicle or a hybrid vehicle to perform work, the remaining amount of electric power stored during the process. It is desirable as a basic performance to be able to accurately measure and confirm in a short time. However, in the current technology, there are many cases in which the remaining battery charge can be recognized only in a very vague manner, causing unexpected trouble for the user, or the electric vehicle not being able to operate as expected. It

Batteries used in these electric devices, electric vehicles, and the like are so-called secondary batteries such as lead batteries, nickel-hydrogen batteries, and lithium-ion batteries, and batteries that can be repeatedly discharged and charged. For example, charging and discharging of a lithium-ion battery is performed by moving lithium ions in a secondary battery between a positive electrode and a negative electrode through a non-aqueous electrolyte solution, and inserting and desorbing lithium ions into the active material of the positive electrode or the negative electrode. Be seen.

These secondary batteries are repeatedly charged/discharged a large number of times, or are overcharged/overdischarged, resulting in deterioration of the electrolyte, which is an internal structure added to the electrolytic solution of the secondary battery, and damage to the electrode plate. Due to a change in the state, the storage capacity changes compared to the initial state, and the performance deterioration progresses. Eventually, the secondary battery cannot be used.

From the above, there is a demand for a technique capable of accurately and instantaneously detecting SOH and SOC of a storage element such as a secondary battery.

Japanese Patent No. 3752249 US Pat. No. 7,075,269 Chinese Patent No. 100395939

Matsuda et al. "Introduction to Electrochemistry" (Maruzen Publishing) Shiro Haruyama, "Electrochemistry for Surface Engineers" (Maruzen Publishing)

An object of the present invention is to provide a degree-of-deterioration and a state-of-charge-remaining detection device for a state-of-charge storage element capable of accurately and instantaneously detecting the degree of deterioration SOH and the state-of-charge SOC of a storage element such as a secondary battery to recognize the battery state. Is to provide.

The problem to be solved by the present invention is as described above, and means for solving the problem will be described below.

但し、［数１］においてΔνは前記蓄電素子の端子電圧ｖ、と起電力ηｅｑ＊の差電圧であり、Δν_１は動作時に電極面での酸化／還元反応に伴い発生する電位差となる。また、定数ｆはファラディ定数、ボルツマン定数、及び絶対温度からなる物理定数である。 That is, in claim 1,
A deterioration degree of a storage element and a remaining charge level detection device for detecting a deterioration degree SOH and a remaining charge level SOC of a power storage element,
A control unit having a calculation means for executing a predetermined calculation;
Measuring means for measuring the voltage and current of the storage element,
The control unit is
Based on the measured values of the rising voltage and the current at the start of charging of the storage element, the overvoltage δ during operation of the storage element is calculated by using the battery equation shown in [Formula 1] below.

However, in [Equation 1], Δν is a difference voltage between the terminal voltage v of the storage element and the electromotive force ηeq*, and Δν ₁ is a potential difference generated due to the oxidation/reduction reaction on the electrode surface during operation. The constant f is a physical constant composed of the Faraday constant, Boltzmann constant, and absolute temperature.

That is, in the degree of deterioration of the electricity storage device and the remaining amount of electricity storage detection device according to claim 1, the control unit measures the rising voltage at the start of charging of the electricity storage device, and determines “overvoltage δ” from the difference from the equilibrium voltage. The "potential difference associated with the internal resistance" is separately calculated using the "battery equation" shown in [Equation 1], and the "dynamic internal resistance" associated with the electrode reaction is detected from the current value simultaneously measured.
The details of the “battery equation” will be described later.

In claim 2,
The control unit is
The overvoltage δ during the operation is determined based on the condition that the two expressions in [Equation 1] are equal.

In claim 3,
The control unit is
The time course of the fall voltage when the charge of the power storage element is cut off is measured, and the electrolyte characteristic of the power storage element is calculated.
Accordingly, the operation of the working medium (for example, lithium ions) in the electrolyte filled between the electrodes can be accurately and precisely determined. Consequently, the quality of the characteristics of the electrolyte, which is a battery constituent member that influences the battery characteristics, can be determined.
In addition, the electrolyte characteristics are the numerical values of the diffusion resistance, the electrophoretic resistance, and the capacitor component formed by the repulsion between ions, which are shown as the electrical characteristic values of the electrolyte. An electrical equivalent circuit can be created, and the SOC and SOH can be accurately identified by making a correction in consideration of the electrolyte characteristics even during charging or discharging.

In claim 4,
The control unit is
The dynamic internal resistance Dir at the time of charging is obtained by using the measured value of the voltage and the battery equation shown in [Equation 1], and the deterioration degree SOH is calculated from the Dir.

Specifically, in the degree of deterioration of the electricity storage element and the remaining electricity amount detecting device according to claim 4,
The control unit is
The dynamic internal resistance Dir at the time of charging is obtained by using the measured value of the voltage and the battery equation shown in the above [Formula 1], and the battery is calculated from the minimum Dir obtained by calculating the Dir minimum value with reference to the state of charge SOC. The capacity of is calculated.

In claim 5,
The control unit is
A battery capacity is derived by determining a battery-specific coefficient of [Equation 2], which is a voltage-current characteristic expression for the overvoltage δ, using the measured value of the voltage and the battery equation shown in [Equation 1]. Is.

但し、［数１］においてΔνは前記蓄電素子の端子電圧ｖ、と起電力ηｅｑ＊の差電圧であり、Δν_１は動作時に電極面での酸化／還元反応に伴い発生する電位差となる。また、定数ｆはファラディ定数、ボルツマン定数、及び絶対温度からなる物理定数である。 In claim 6,
A deterioration degree of a storage element and a remaining charge level detection device for detecting a deterioration degree SOH and a remaining charge level SOC of a power storage element,
Measuring means for measuring the voltage and current of the storage element,
A control unit having a calculation means for executing a predetermined calculation,
The control unit is
The overvoltage δ during operation of the secondary battery is calculated by using the battery equation shown in the following [Equation 1] based on a predetermined condition for charging or discharging the storage element.

However, in [Equation 1], Δν is a difference voltage between the terminal voltage v of the storage element and the electromotive force ηeq*, and Δν ₁ is a potential difference generated due to the oxidation/reduction reaction on the electrode surface during operation. The constant f is a physical constant composed of the Faraday constant, Boltzmann constant, and absolute temperature.

In claim 7,
The predetermined condition is a lapse of time of the falling voltage at the start of discharge.

In claim 8,
The predetermined condition is a measured value of the rising voltage when the discharge is cut off.

In claim 9,
The predetermined condition is a measured value of the rising voltage when the charging current is increased or when the discharging current is decreased.

In claim 10,
The predetermined condition is a lapse of time of the falling voltage when the charging current is decreased or the discharging current is increased.

In claim 11,
The predetermined condition is a lapse of time of the falling voltage when the charging is changed to the discharging.

In claim 12,
The predetermined condition is a measured value of the rising voltage when the discharge is changed to the charge.

According to the present invention, it is possible to accurately and instantaneously detect the deterioration degree SOH and the remaining charge SOC of a storage element such as a secondary battery.

The figure which shows the change of the electromotive force with respect to SOC by the difference in a battery type. FIG. 3 is a block diagram showing a basic configuration of a degree of deterioration of a secondary battery and a remaining power storage amount detection device according to an embodiment of the present invention. The characteristic diagram which asks for the solution of the battery equation which shows the battery operation at the time of charge. The figure which shows the electric circuit equivalent circuit inside a battery at the time of charge. A characteristic diagram immediately after applying a current from a long-term stationary state. The diagram which combined the battery equation and the current-voltage characteristic. The figure which shows the time characteristic of the rise/fall of voltage-current.

Next, a measurement principle for measuring the deterioration degree SOH and the remaining charge SOC of a storage element such as a secondary battery according to the present invention will be described with reference to the drawings. In the following, the present invention will be specifically described by taking a secondary battery as an example of a power storage element. In the following, the secondary battery may be simply referred to as a battery.

[Measurement principle]
In order to accurately detect the remaining charge of the secondary battery, the relationship between the increase/decrease in electromotive force (Electro Motive Force) and the increase/decrease in the remaining charge is accurately quantified, and the electromotive force is measured to determine the remaining charge. Digitization is one method. However, if the original remaining charge amount is accurately known, the used amount is extracted from the original remaining charge amount while weighing, and the current remaining charge amount is obtained from the deduction account, but the original remaining charge amount is calculated accurately. If it cannot be measured, the remaining amount after that becomes unreliable. In particular, the injection of the amount of electricity during charging and the extraction of the amount of electricity during discharging are accompanied by heat loss due to the internal electrical resistance (internal resistance) inside the battery, which causes errors in the deduction amount, making it impossible to accurately measure the remaining charge Close to.

Another method of accurately measuring the remaining charge of the secondary battery is to measure the electromotive force of the battery. However, the voltage during operation does not show an electromotive force, and when the operation is stopped, the measured value fluctuates very slowly. For example, when the charge is cut off, the voltage value gradually decreases and stabilizes at a constant value over a long period of time. When the discharge is cut off, the voltage gradually rises and also converges to a constant value over a long period of time.

This converged voltage is the electromotive force of the battery and serves as an index of the state of charge (SOC) of the battery. That is, it takes an extremely long time to measure the electromotive force, and once the battery is charged and discharged, the electromotive force cannot be measured unless it is left for many hours after that. (Power) cannot be measured and measured moment by moment, which makes it difficult to control the equipment to which the battery is applied and makes the use of the battery cumbersome.

FIG. 1 is a diagram showing changes in the battery voltage with respect to the remaining charge of the secondary battery. That is, FIG. 1 shows the relationship between the remaining charge x (SOC) and the electromotive force V depending on the type of battery (lithium ion battery, lead battery). The converged voltage in FIG. 1 is the electromotive force of the battery and serves as an index of the state of charge (SOC) of the battery.
As shown in FIG. 1, the lead battery has a large variation range of the electromotive force V with respect to the remaining storage amount x (SOC), but the lithium ion battery has a small change. It becomes difficult to identify x(SOC).

The measurement principle relating to the deterioration degree of the secondary battery and the remaining charge detection device of the present invention is based on the result of the battery reaction theory for the purpose of instantaneous and accurate measurement of the remaining charge in the secondary battery. The equation is applied.
The “battery equation” is specifically an equation derived from the theory of a battery reaction relating to a secondary battery, and is a circuit equation based on an overvoltage and a reaction resistance associated with an oxidation/reduction reaction.

The present invention also instantaneously measures the dynamic internal resistance Dir (Dynamic Internal Resistance) from the battery equation when specifying the battery capacity of the secondary battery, and uses the constants specific to the secondary battery to measure the dynamic internal resistance Dir (Dynamic Internal Resistance). The remaining capacity (SOC) or deterioration degree (also called SOH or soundness), which is the current capacity, is calculated.

In addition, as another method different from the above, the present invention uses a battery equation and a voltage-current formula in combination to instantly measure the current characteristic coefficient, and immediately measures the capacity proportional to this coefficient to obtain the current battery. The amount of remaining electricity (SOC) or the degree of deterioration (SOH), which is the capacity, is calculated.

Here, an outline of the logic regarding the battery reaction will be described, and a description will be added regarding the “battery equation” established by the inventors of the present application.
It should be noted that the description below is based on the configuration of the lithium-ion battery for convenience, but the battery type is not particularly limited.

First, the battery reaction of the negative electrode is set as the rate-determining reaction rate, and the overvoltage and current are considered. In addition, here, a description will be added regarding rate limiting. A battery is mainly composed of a positive electrode, a negative electrode, and an electrolyte that controls ionic conduction between them, but the amount of electrons or the amount of ions passing through each of them is equal from the continuous logic. Therefore, it is called rate-determining because the amount of flow through the most difficult member controls the overall flow.

The oxidation/reduction reaction is mathematically expressed as follows based on the Arrhenius theory, and when each sign in the formula is defined, the current density is given by the following formula.

Since the current is zero at equilibrium, the equilibrium voltage ηeq can be easily calculated from [Equation 1].

That is, the equilibrium voltage ηeq takes different values depending on the concentration ratio c ₀ (0,t)/cr(0,t).

The concentration at the reaction interface has a certain constant value when the time t elapses infinitely. This is expressed by the following equation.

Therefore, by substituting these into [Equation 2], the following Nernst equation is obtained.

Here, the Ec ⁰ ′ is represented as follows.

The balanced voltage in the transient state is expressed based on the voltage in the balanced state when sufficient time is taken. It is considered that the charging current is flowing until time t ₀₋ , and therefore the concentration of the oxidant at the interface is maintained at this concentration immediately after the current is cut off at time t ₀₊ (see FIG. 7).
The equilibrium voltage at this time is represented by [Equation 3], and the equilibrium overvoltage after being left for a long time is represented by [Equation 4]. Taking the difference gives the following formula.

This Δη eq (t) is the lithium ion in the electrolyte in the melted form offshore far from the electrode, and the diffusion of the lithium ion in the oxidation/reduction field in the vicinity of the electrode, or in the electric field. It is a potential that appears by forming a tank circuit of a capacitor and a resistance in an electrical equivalent circuit by electrophoresis (see Fig. 4). During steady charging, the charge is cut off at a certain point, and the change in voltage every moment thereafter is changed. It was clarified by the following procedure that the conductivity of lithium ion in the electrolyte and the capacitor component as the electric double layer can be identified by measuring.
The electric double layer is a layer in which positive charges and negative charges are opposed to each other and are arranged at a very short distance at the interface between the electrode and the electrolytic solution.

[Regarding the formation process of Δηeq(t)]
When the charging current I is raised from the long-term stationary state, for example, the reduction reaction of the negative electrode corresponds to t=0 at the concentration of the oxidant c ₀ (0,t) existing on the reaction surface, and this value is the long-term stationary state. Equal to c ₀ *. By the negative electrode reaction, this concentration is consumed, reduced, converted into _cr *, and stored.
In order to replenish the above-mentioned consumption, replenishment inflow of oxidant from the offshore is required, and the natural logarithm of the ratio of initial c ₀ * and replenishing c ₀ (0,t) is multiplied by a physical constant. Δηeq(t).
In this Δηeq(t), the ions that have reached the brave reaction surface are repelled by the guest ions, the ion counter zone is formed as a so-called electric double layer, and at the same time, it becomes a stable tank circuit by diffusion. This formation process is expressed by the following equation.

If the battery is cut off after being charged for a time (τ=t _{° C.} ), the potential difference of the tank circuit immediately after the cutoff is given by the following equation.

The voltage ν(t) after the interruption is given by the following general formula.

This equation has Δηeq(0), T, ηeq*, ₁ as unknowns, and this unknown constant is fixed from three simultaneous equations.

Here, if t ₂ =2t ₁ is set, voltage at three points is measured at equal time intervals, and further, e ^−t1/T =x is set, the above three equations become the following algebraic equations.

この方程式の解は次のように求まる。

The solution of this equation is found as follows.

Using this relationship, if the voltages ν(0), ν(t ₁ ), and ν(2t ₁ ) after interruption are measured, the tank circuit voltage Δηeq(0) is completely discharged according to the charging current. The electromotive force ηeq*, ₁ corresponding to time and the tank circuit time constant T are determined, and the characteristics of the electrolyte are quantified.

As shown in FIG. 7, Δηeq(0) exists at the time of charging interruption, and thereafter, the charge amount in the tank circuit disappears with time due to the parallel resistance, and Δηeq(∞)=0 after the lapse of time.

ここで、［数１］、［数２］、［数３］、［数４］の関係式、及び、移動度α_ｃ＝１／２、荷電子数ｎ＝１と置いて演算した。 [Regarding charge transfer process by electrode reaction]
Next, the battery reaction of the negative electrode is set as the rate-determining reaction rate, and the overvoltage and current are considered.
The current flows only after the overvoltage δ exceeding the equilibrium voltage (Δηeq+η*eq) is added. When the relation of η=δ+Δηeq+η*eq is introduced and transformed in [Equation 1], the following equation is obtained.

Here, the relational expressions of [Equation 1], [Equation 2], [Equation 3], and [Equation 4], the mobility α _c =1/2, and the number of charged electrons n=1 were used for the calculation.

[Equation 13] is a relational expression that gives a current density that holds for displacement δ from an arbitrary equilibrium voltage. The current I is obtained by multiplying this formula by the effective electrode area S, and therefore the current-potential relational expression is as follows.

ここで、［数１４］のＫｘは以下のように表せる。

Here, Kx in [Equation 14] can be expressed as follows.

δ is an overvoltage value that exceeds the virtual equilibrium (equilibrium voltage; η*eq+Δηeq). However, the current value is determined by δ+Δηeq which exceeds the balanced voltage η*eq.
η*eq is a potential determined by the concentration ratio of the oxidizing agent and the reducing agent at the electrode interface in the stable period, and Δηeq corresponds to the excess concentration at the reaction interface required according to the operating current during the operation reaction. The equilibrium potential is changed (see Fig. 3).

The dependence of the current I on the minute overvoltage δ is the conductance at the operating point, and the reciprocal thereof is the resistance at the operating point, that is, the dynamic internal resistance Dir. When this is written, it becomes the following formula.

Also, K _X is transformed as follows using [Equation 6].

The product of the dynamic internal resistance Dir derived from [Equation 16] and the current I obtained from [Equation 14] is a function dependent only on the operating overvoltage δ regardless of the battery, as shown in the following Equation [18].

Since the elements (δ, Δηeq, Dir, I) that determine the voltage-current characteristics can be determined as described above, a schematic diagram of the characteristics (see FIG. 3) and an equivalent circuit of the battery (see FIG. 4) can be drawn.

[Battery equation (general formula)]
During operation, the electric double layer described above is formed at the electrode interface due to the flow of ions in the electrolyte, and the addition of the equilibrium potential of Δηeq shown in FIGS. 3 and 4 occurs.
FIG. 3 is a voltage-current characteristic diagram during charging.
From FIG. 3, the terminal voltage Δv at startup satisfies the following equation.

Here, the current equation is as follows.

Further, Dir at the operating point is obtained by the following equation.

Therefore, the following equation can be derived.

Substituting this into [Equation 19], the following equation "battery equation" is established.

FIG. 3 is a diagram showing the overvoltage δ.

[Battery equation (special solution)]
When rising from the stationary state, the current equation is as follows. Since the electric double layer in the electrolyte is not yet formed on the surface of the electrode, the general formula is Δηeq=0.

FIG. 5 is a voltage-current characteristic diagram at the time of rising and charging from a stationary state.
From FIG. 5, the terminal voltage Δv at startup satisfies the following equation.

The dynamic internal resistance Dir from the stationary state can be expressed by the following equation.

The product of Dir and I can be shown as:

The above can be summarized into the following three expressions.

Using [Equation 29], the overvoltage δ is used as a variable to perform a numerical calculation regarding the overvoltage δ, and the result is shown in FIG. The graph of FIG. 6 holds regardless of the type and size of the battery.
Here, the horizontal axis in FIG. 6 is the overvoltage δ. The vertical axis of the upper graph in FIG. 6 is Δv, and the vertical axis of the lower graph is I/K ₀ described later.

Specifically, the graph of FIG. 6 shows that when a voltage higher than the battery voltage (electromotive force), that is, the equilibrium voltage (ηeq*) at that time, is applied to the battery, the Δv( =ν-ηeq*) alone means that the operating point δ is determined. That is, the battery reaction is expressed by the same formula for any battery, and the difference in battery type and performance suggests that the operating point δ determines the current and the battery internal resistance. is there.
The graph data (map data) as shown in FIG. 6 is stored in the measurement controller 14 of the detection device 1 described later.

[Example of solution guidance (application example of FIG. 6)]
Actually, all of the microcomputers installed inside the detection device 1 (measurement controller 14) will calculate, but the following description will be added regarding what kind of calculation process the microcomputer presents the calculation result. Keep it.
When charging the secondary battery,
1) Apply current.
2) Measure Δv and find the intersection of Δv _{1 and} the curve graph using FIG. The δ value corresponding to this intersection is determined.
3) The current function with respect to δ has different coefficients depending on the SOC, and becomes a characteristic curve corresponding to the SOC as shown in FIG. This is because the coefficient equation can be modified and expressed as follows.

この式から以下の式が導かれる。

The following equation is derived from this equation.

この式が図６の電流式である。

This equation is the current equation in FIG.

Therefore, if the SOC during operation is known, the point (δ, I/K ₀₀ Sc) passing through the intersection (I/K ₀₀ Sc) depending on the electrode type is determined, and this point corresponds to the SOC. It becomes the operating point.
When the right side of the equation (31) is determined, and the measured current I on the left side is introduced, the characteristic value K ₀₀ and the effective electrode area Sc specific to the battery type are determined.

In the characteristic diagram shown in FIG. 6, the current value I with respect to the overvoltage δ greatly differs depending on the charging state (that is, SOC). That is, in order to obtain a constant current value when the SOC is small, a large δ value is charged again, and the overvoltage δ is minimized when the SOC is around 50%, and δ is increased again when the charging is further advanced. During the charging process from "empty" to "full" of the battery, the operating point changes along the arrow shown in FIG. SOC; 50% can be fixed by some method, and if the currents I and δ are fixed from the SOC=0.5 curve in FIG. 6, [Equation 12] becomes the following equation.

From this equation, SOH which is the battery performance index indicating the current performance of the battery is determined, and SOH which is the battery performance index is determined from the diagram shown in FIG.
The above is the principle for detecting the degree of deterioration and the remaining charge of the secondary battery based on the "battery equation".

Here, the relation between the mathematical expression analysis and the qualitative phenomenology will be explained.
[Battery electromotive force and dynamic internal resistance]
FIG. 4 shows an electrical equivalent circuit showing the concept of charging.
Next, the battery electromotive force Vemf and the dynamic internal resistance Dir will be described using the equivalent circuit of the battery (secondary battery 10 in this embodiment) shown in FIG.
If a battery is represented by an equivalent circuit, it becomes a simple electric circuit. That is, it is represented by a series connection of a battery element having a charge amount (storage capacity) Q (unit is Coulomb), which is electric energy, and a pure resistance (conductance) directly connected to the battery. Specifically, as shown below, the voltage between the battery terminals (A-B) is V, the current flowing between the battery terminals (A-B) is I, the dynamic internal resistance is Dir, and the battery electromotive force is Vemf. Then, as shown in FIG. 4, the battery can be represented by an equivalent circuit.
V: Voltage between battery terminals (A-B) I: Current flowing between battery terminals (AB) Dir: Dynamic internal resistance (Dynamic Internal Resistance)
Vemf (=ηeq*); Battery electromotive force (potential difference between positive and negative electrodes at rest)

The battery electromotive force Vemf means the voltage between the battery terminals (AB) when the battery is not connected to an external circuit and no current is flowing (at rest). For example, in the case of a lithium ion battery, which is an example of a secondary battery, the battery electromotive force Vemf is not the flow of lithium ions Li ⁺ or electrons e ⁻ , but the difference in ion potential between the cathode and the anode. Therefore, the difference in ion potential is represented by the difference in the site occupancy of lithium ions Li ⁺ between the cathode and the anode.

In the case of a lithium ion battery, for example, the storage capacity Q means the size of the space where the lithium ion Li ⁺ is stored in the cathode. That is, the large storage capacity Q means that the cathode and the anode have large volumes (the number of sites is large) (the K ₀ value of [Equation 32] is large), and the action surface is large ([Equation 32]). Has a large Sc value), which means that the penetration of lithium ions Li ⁺ into both electrodes is rapid and large.
The storage capacity Q decreases as the secondary battery 10 deteriorates. The deterioration of the secondary battery 10 means that the dynamic internal resistance Dir increases and lithium ions do not contact the battery electrodes and do not function. The cause of the increase in the dynamic internal resistance Dir is considered to be an increase in the resistance of the lithium ion during electrophoresis, a decrease in the reaction rate, a decrease in the diffusion rate, a decrease in the number of lithium ion sites in the anode and the cathode, and the like. The dynamic internal resistance Dir increases due to repeated charging and discharging, resulting in deterioration of the secondary battery 10.

Although the dynamic internal resistance Dir is caused by the battery reaction, it decreases as the reaction area increases. In addition, the battery capacity Q increases as the reaction area increases. The relationship between the storage capacity Q and the dynamic internal resistance Dir will be specifically described below.

<Relationship between storage capacity and dynamic internal resistance>
Next, a simple modeled concept of the relationship between the storage capacity Q and the dynamic internal resistance Dir will be described.
Letting dS be a minute acting surface element that constitutes a pair of a negative electrode and a positive electrode, the dS allows the battery element to be represented by an equivalent circuit.
Here, the conductance ρ, which means the ease of current flow in the circuit per unit area of action, is
ρ=1/r
And the effective area (reaction area) is S, the dynamic internal resistance Dir is
Dir=1/∫ρdS=1/ρS=r/S (a)
It is represented by. Further, the storage capacity Q of the whole area is q, where q is the electric capacity per unit area.
Q=∫qdS=qS...(b)
It is represented by. From the above equations (a) and (b),
Dir×Q=qr=K...(c)
Can be obtained. Here, K is a constant (constant value) determined by the type of secondary battery.

That is, in the same type of secondary battery having a different storage capacity Q, the value obtained by multiplying the storage capacity Q and the dynamic internal resistance Dir is constant as shown in the above equation (c). The internal resistance Dir decreases in inverse proportion, and when the dynamic internal resistance Dir increases, the storage capacity Q decreases in inverse proportion to it. Further, when the effective acting area S becomes smaller, the storage capacity Q decreases, while the dynamic internal resistance Dir increases. Therefore, the storage capacity Q can be calculated using the value of K by calculating the dynamic internal resistance Dir.
Here, the dynamic internal resistance refers to Dir obtained from the battery equation according to the present embodiment.

[Specific Embodiment of Degradation Degree of Secondary Battery and Remaining Amount of Residual Power Detection Device]
Next, the deterioration degree of the secondary battery 10 and the remaining battery charge detection device 1 (hereinafter, also simply referred to as the detection device 1), which is an embodiment of the present invention, will be described with reference to the drawings. Here, the secondary battery 10 refers to a battery that can be repeatedly charged and discharged, and converts electric energy into chemical energy for storage and, conversely, converts the stored chemical energy into electric energy for use. A battery that can be used. For example, there are nickel-cadmium batteries, nickel-hydrogen metal batteries, lithium-ion batteries and the like.

FIG. 2 shows the basic configuration of the detection device 1. The detection device 1 includes a power supply unit 11 that supplies a charging voltage to the secondary battery 10, a current detector 12 that is a charging current measuring unit, a voltage detector 13 that is a voltage measuring unit, a measurement controller 14, and a display. Means 15 and operation switch 16 are mainly provided. The measurement controller 14 is electrically connected to the power supply unit 11, the current detection circuit 12, the voltage detector 13, the display unit 15, the operation unit 16, and the like.
Note that the configuration of the detection device 1 described in the present embodiment may be any configuration that can realize the functions described in the present embodiment, and can be appropriately changed. The secondary battery 10 is connected to the power supply unit 11 via the current detector 12.

The power supply unit 11 has a transformer/rectifier circuit that converts commercial AC power into DC. The power supply unit 11 is a power supply that provides an output voltage of, for example, about 1.2 times the rated voltage of the secondary battery 10 and a current of about 0.1 C or more of the battery capacity. The power supply unit 11 has an external voltage control terminal (not shown), and is connected to the secondary battery 10 via the external voltage control terminal.

The voltage detector 13 measures the voltage of the secondary battery 10, and detects the voltage between terminals (also referred to as terminal voltage) between the positive electrode (+) and the negative electrode (−) of the secondary battery 10.
The current detector 12 and the voltage detector 13 form a measuring unit that measures the voltage and current of the secondary battery.

The measurement controller 14 has a central processing unit, storage means (ROM, RAM, HDD, etc.), a PC (personal computer) or a microcomputer configured with various I/Fs, and the measurement principle described in this embodiment. It is possible to store the or calculation as a program and execute the program. That is, the measurement controller 14 has a calculation unit that executes a predetermined calculation. Specifically, the measurement controller 14 detects the voltage value between the terminals of the secondary battery 10 and the current detection unit that detects the current value of the current flowing in the secondary battery 10 via the current detector 12. It includes a voltage detection unit that detects the voltage via the device 13, an AD conversion unit that converts the analog signal detected by the current detection unit and the voltage detection unit into a digital signal, and the like. Various processing programs processed in the detection device 1 (for example, based on the measurement principle of the SOH and SOC detection methods described in the present embodiment and detected voltage/current data are used as storage means such as a ROM). And a program for performing a predetermined calculation) are stored.

The display unit 15 displays information indicating the charge state of the secondary battery 10 (for example, deterioration state). The display means 15 is composed of an LCD or the like. As the information indicating the state of charge of the secondary battery 10, the display unit 15 may be, for example, a battery electromotive force Vemf, a dynamic internal resistance Dir, a deterioration degree SOH (State Of Health), and a state of charge SOC (State Of Charge). Can be displayed.

The operation unit 16 is a unit that a user performs an operation or the like to execute the detection of SOH and SOC. The operation unit 16 is, for example, an operation switch, a touch panel such as a liquid crystal, a keyboard, or the like.

As shown in FIG. 2, the secondary battery 10 is connected to the power supply 11 via the current detector 12. The voltage and current signals measured by the voltage detector 13 for measuring the voltage of the secondary battery 10 and the current detector 12 for measuring the charging current are transmitted to the measurement controller 14. The measurement controller 14 receives and operates the signal, controls the output voltage and current of the power supply 11 to appropriate values, and at the same time outputs the numerical values of SOC and SOH as the calculation result, that is, displays them by the display means 15.

FIG. 7 is a diagram showing time characteristics of rising/falling of voltage-current.
FIG. 7 is a diagram illustrating a change with time in voltage-current after the charging operation is started at t=0 when the constant current control is performed. If an overvoltage δ higher than the electromotive force (equilibrium voltage) is applied, the constant current becomes I and the battery terminal voltage becomes v.

From the measured value Δv obtained for the current set value I, the overvoltage δ and the dynamic internal resistance Dir are calculated by using the formula of [Equation 23] or the formula of [Equation 25], and from “empty” to “ The capacity of the new battery cell of the same type is determined from the Dir ratio by using the data of the dynamic internal resistance Dir and the capacity Q, SOC, and ηeq*(=Vemf) measured up to full. Since this required time is a time calculated based on the above-described measurement principle, it is possible to make a battery performance judgment immediately, in less than 1 second.

[Calculation of SOH (degree of deterioration)]
Next, the deterioration degree SOH, which is an index indicating the progress of deterioration of the secondary battery 10, will be described.
In the detection device 1 of the present embodiment, the measurement controller 14 calculates SOH, which is the deterioration degree indicating the deterioration state of the secondary battery 1 with respect to the charge/discharge cycle. The SOH is an index showing the progress of deterioration of the battery, and is represented by the ratio of the current storage capacity to the initial storage capacity. When the initial storage capacity is Q ₀ , SOH=(Q/Q ₀ )×100 It can be calculated.

Regarding the remaining charge SOC, if the battery electromotive force Vemf can be accurately acquired by the above-described measurement principle or the like, the acquired battery electromotive force is defined as a voltage at which the charging rate of the secondary battery 10 becomes 100%. Good.
The detection device 1 can calculate the current storage capacities Q, SOH, and SOC of the secondary battery 10 in the measurement controller 14, and output them to the display unit 15 to display them.

[Method 1]
As described above, according to the detection device 1 of the present embodiment, the measurement controller 14, which is an example of the control unit, uses the measured values of the rising voltage and the current at the start of charging the secondary battery 10 25] and the equation of [Equation 28], the overvoltage δ during operation of the secondary battery 10 and Dir can be calculated. Furthermore, the deterioration degree SOH can be detected by comparing this Dir with the Dir of a new secondary battery. As a result, the SOH of the secondary battery 10 can be detected accurately and instantaneously. Therefore, the battery state (eg, charge state) of the secondary battery 10 can be recognized at any time.

[Method 2]
Further, according to the detection apparatus 1 of the present embodiment, the measurement controller 14 is obtained from the measured value of the falling voltage when the charging of the secondary battery 10 is cut off and [Equation 9] to [Equation 11]. An accurate change in electromotive force at rest is obtained using Δηeq and ηeq* and the “battery equation”, and the remaining charge SOC is determined by collation with a comparison table in which the electromotive force is measured in advance. As a result, even if the capacity of the secondary battery 10 is reduced due to long-term use, the remaining power storage amount at that time is acquired as a ratio and an absolute value, and the user's anxiety due to energy depletion is eliminated.

Further, according to the detection device 1 of the present embodiment, the measurement controller 14 uses the measured value of the voltage by the voltage detector 13 and the battery equation shown in [Equation 23] to calculate the dynamic internal resistance Dir during charging. Then, the deterioration degree SOH is calculated from the minimum Dir obtained by calculating the Dir minimum value with reference to the remaining charge SOC. As a result, the SOH of the secondary battery 10 can be detected accurately and instantaneously. Therefore, the battery state (for example, deterioration state) of the secondary battery 10 can be recognized at any time.

Further, according to the detection apparatus 1 of the present embodiment, the measurement controller 14 determines the voltage-current characteristic with respect to the overvoltage δ using the voltage measurement value by the voltage detector 13 and the battery equation shown in [Equation 23]. The battery capacity of the secondary battery 10 is derived by determining the coefficient specific to the battery (see [Equation 31]).
That is, as a concrete measure to derive in this way, by applying FIG. 6, the coefficient K ₀ of the current-voltage curve is determined, and the storage element capacity Q ₀ =0. A value obtained by multiplying the K value by 55 (the numerical value is calculated from the electrochemical reaction theory under the optimum charging condition) can be determined as the capacity Q. That is, in the above-described detection device 1, since these are arithmetically processed, it is possible to make an instant performance determination that requires a time of only 1 second. It should be noted that although the capacity of the storage element has an error of about ±10%, it is possible to minimize this error by the above [Method 1].

[Regarding Practical Development of the Present Invention]
In addition, the deterioration degree of the secondary battery and the remaining charge detection device of the present invention are expected to have the following effects.
1) Battery performance is determined by the performance of the electrodes (negative electrode and positive electrode) that control the oxidation/reduction reaction. According to the present invention, the electrode performance is measured by measuring the voltage and the current value applied from the outside of the battery, and the calculation is performed to determine the value in a short time, thereby ensuring the safety and reliability of battery use.
2) Inside the battery, a working medium (for example, lithium ions in a lithium ion battery) is generally present in the polymer dielectric material in a melted form, and a flow is formed during the charging/discharging process. The degree of this flow also greatly affects the battery performance. As in the case of 1) above, this is also converted into a numerical value from the measurement of the external voltage/current, and it is possible to judge the quality.
3) The battery has a life with deterioration. The deterioration degree of the secondary battery and the remaining charge detection device according to the present invention make it possible to predict the deterioration result by analyzing the aged data of the measurement result. This is due to the fact that the present invention enables data acquisition quickly and accurately.

When using the secondary battery, it is essential to be able to always grasp the current remaining charge amount (SOC) and deterioration degree (SOH, power storage performance). However, in the prior art, it is impossible to detect these battery states immediately, and there are many cases in which unexpected "electrical depletion" or "overcharge" is caused and various troubles or hazards are caused.
The degree of deterioration of a secondary battery and the remaining battery level detection device of the present invention relates to the chemical reaction inside the battery having a complicated mechanism and the continuity of the flow of electrons flowing through the external circuit. Is analyzed based on the classical method of chemical reaction theory and summarized in the universal “battery equation” described above. Based on the development of its application and adaptation, the quality of the battery and the performance are accurate in less than 1 second. It was created as a measurable "battery analyzer".
By applying the technology according to the present invention, quick evaluation during battery development, quality control during battery production, individual cell performance adjustment during battery assembly production, operation status grasp of battery system, performance classification during reuse, etc. It can be used at all stages of use and application.

In the method 1 described above, the detection device 1 uses the “measured values of the rising voltage and current at the start of charging” of the secondary battery 10 as the battery equation in [Equation 25] and the equation in [Equation 28]. Is used to calculate the overvoltage δ during operation of the secondary battery 10 and Dir. Here, the “measured value of the rising voltage and current at the start of charging” is an example of the “predetermined condition regarding charging or discharging” of the secondary battery acquired by the measurement controller 14 via various measuring means.

Examples of the above-mentioned “predetermined condition regarding charging or discharging” include the following.
(1) Elapsed time of falling voltage at the start of discharge (2) Measured value of rising voltage at discharge interruption (3) Measured value of rising voltage when increasing charging current or decreasing discharging current ( 4) Time course of falling voltage when charging current is decreased or discharge current is increased (5) Time course of falling voltage when shifting from charging to discharging (6) Transition from discharging to charging Measured value of rising voltage at the time of detection The detection device 1 operates the secondary battery 10 using the battery equation described in [Equation 25] and the equation described in [Equation 28] based on each of these conditions. The overvoltage δ at the time and Dir can be calculated. Therefore, the same effect as the present invention is achieved.

In the present embodiment, the charging/discharging in the case of using the secondary battery has been described, but the present invention is not limited to the secondary battery and can be widely applied to a storage element.
Here, the electricity storage element refers to all elements having an electricity storage function, for example, an element having at least a pair of electrodes and an electrolyte and having a function capable of electricity storage. The power storage element may be a power storage device.

As the storage element, for example, a lithium ion secondary battery, a lead storage battery, a lithium ion polymer secondary battery, a nickel hydrogen storage battery, a nickel cadmium storage battery, a nickel iron storage battery, a nickel/zinc storage battery, a secondary battery such as a silver oxide/zinc storage battery, Liquid circulation type secondary batteries such as redox flow batteries, zinc/chlorine batteries, zinc bromine batteries, aluminum/air batteries, zinc-air batteries, sodium/sulfur batteries, lithium/iron sulfide batteries, etc. A battery or the like can be used. Note that the present invention is not limited to these, and the storage element may be configured using, for example, a lithium ion capacitor, an electric double layer capacitor, or the like.

1 Detection device 10 Secondary battery (electric storage element)
12 Current detector (current measuring means)
13 Voltage detector (voltage measuring means)
14 Measurement controller (control unit)

Claims (12)

A deterioration degree of a storage element and a remaining charge level detection device for detecting a deterioration degree SOH and a remaining charge level SOC of a power storage element,
Measuring means for measuring the voltage and current of the storage element,
A control unit having a calculation means for executing a predetermined calculation,
The control unit is
The overvoltage δ during operation of the storage element is calculated by using the battery equation shown in the following [Equation 1] based on the measured values of the rising voltage and current at the start of charging the storage element. Deterioration degree of power storage element and remaining power storage level detection device.

However, in [Equation 1], Δν is a difference voltage between the terminal voltage v of the storage element and the electromotive force ηeq*, and Δν ₁ is a potential difference generated due to the oxidation/reduction reaction on the electrode surface during operation. The constant f is a physical constant composed of the Faraday constant, Boltzmann constant, and absolute temperature. The control unit is
The deterioration degree of a power storage element and a power storage residual amount detection device according to claim 1, wherein the overvoltage δ during the operation is determined from the condition that the two expressions described in [Equation 1] are equal. The control unit is
The degree of deterioration of a power storage device and the remaining power storage amount detection according to claim 1 or 2, wherein a time lapse of a falling voltage when the charge of the power storage device is cut off is measured to calculate an electrolyte characteristic of the power storage device. apparatus. The control unit is
The deterioration degree SOH is calculated from the Dir by calculating the dynamic internal resistance Dir during charging using the measured value of the voltage and the battery equation shown in [Formula 1]. Item 6. A deterioration degree of a power storage element and a remaining power storage level detection device according to the item. The control unit is
The battery capacity is derived by determining the battery-specific coefficient of [Equation 2], which is the voltage-current characteristic equation for the overvoltage δ, using the measured value of the voltage and the battery equation shown in [Equation 1]. The degree-of-deterioration of the electricity storage element and the remaining electricity storage device according to any one of claims 1 to 4.

A deterioration degree of a storage element and a remaining charge level detection device for detecting a deterioration degree SOH and a remaining charge level SOC of a power storage element,
Measuring means for measuring the voltage and current of the storage element,
A control unit having a calculation means for executing a predetermined calculation,
The control unit is
Based on a predetermined condition for charging or discharging the storage element, an overvoltage δ during operation of the storage element is calculated by using a battery equation shown in the following [Equation 1]. Deterioration level and remaining battery level detection device.

However, in [Equation 1], Δν is a difference voltage between the terminal voltage v of the storage element and the electromotive force ηeq*, and Δν ₁ is a potential difference generated due to the oxidation/reduction reaction on the electrode surface during operation. The constant f is a physical constant composed of the Faraday constant, Boltzmann constant, and absolute temperature. The degree of deterioration of a power storage element and a power storage remaining amount detection device according to claim 6, wherein the predetermined condition is a lapse of time of a falling voltage at the start of discharge. 7. The deterioration degree of a power storage element and a power storage remaining amount detection device according to claim 6, wherein the predetermined condition is a measured value of a rising voltage at the time of discharge interruption. 7. The degree of deterioration of a power storage element and the remaining power storage level detection according to claim 6, wherein the predetermined condition is a measured value of a rising voltage when the charging current is increased or when the discharging current is decreased. apparatus. 7. The degree of deterioration of a storage element and the remaining storage amount according to claim 6, wherein the predetermined condition is a lapse of time of the falling voltage when the charging current is decreased or the discharging current is increased. Detection device. The deterioration level of a power storage element and a remaining power level detection device according to claim 6, wherein the predetermined condition is a lapse of time of a falling voltage when the charging is changed to the discharging. 7. The deterioration degree of a power storage element and a power storage remaining amount detection apparatus according to claim 6, wherein the predetermined condition is a measured value of a rising voltage at the time of shifting from discharging to charging.

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