JP2013253940A - Life estimating device and life estimating method for electricity storage element, and electricity storage system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a life estimating device that can accurately estimate the remaining useful live of an electricity storage element.SOLUTION: A life estimating device 100 for estimating the remaining useful life of an electricity storage element 200, which is the cumulative period in which the element can be used, comprises a relational expression acquiring unit 110 that acquires a relational expression of the DC resistance or the AC resistance of the electricity storage element 200, which is the cumulative period in which the element can be used, at the time the cumulative period of use has elapsed, in a mathematical expression containing a term of the exponential function of the cumulative period of use, and a remaining life estimating unit 120 that estimates the remaining useful life of the electricity storage element 200 by using the acquired relational expression.

Description

  The present invention relates to a life estimation apparatus, a life estimation method, and a power storage system including a power storage element and the life estimation apparatus.

  Power storage elements such as lithium ion secondary batteries have been used as power sources for mobile devices such as notebook computers and mobile phones, but have recently been used in a wide range of fields such as power sources for electric vehicles. And in such an electrical storage element, it is very important to grasp | ascertain accurately the remaining lifetime which is the accumulation remaining period which can be used for an electrical storage element. Here, conventionally, in order to estimate the remaining life of the power storage element, a technique for estimating the change with time of the DC resistance of the power storage element has been proposed (for example, see Non-Patent Document 1).

  Non-Patent Document 1 discloses a technique for estimating the time-dependent change in DC resistance at a predetermined test time based on an empirical formula in which the time-dependent change in DC resistance of a battery is represented by an N-order function of the test time. Here, N in the above empirical formula is 1/2, 1, or 1.52, and varies depending on the test mode.

J. et al. Belt et al. , Journal of Power Sources 196 (2011), 10213-10221.

  However, the conventional technology has a problem that the remaining life of the electricity storage element cannot be accurately estimated.

  That is, in the conventional technique for estimating the change with time of the direct current resistance of the power storage element, it is difficult to predict the value of N because the value of N in the above empirical formula changes according to the test mode. Further, even if the value of N can be predicted, the estimated value of the DC resistance with time is not sufficiently accurate. For this reason, in the prior art, it is impossible to accurately estimate the remaining life of the power storage element.

  The present invention has been made to solve the above-described problem, and an object thereof is to provide a life estimation apparatus, a life estimation method, and a power storage system that can accurately estimate the remaining life of a power storage element.

  In order to achieve the above object, a life estimation apparatus according to an aspect of the present invention is a life estimation apparatus that estimates a remaining life, which is a cumulative remaining period in which a power storage element can be used. A relational expression obtaining unit that obtains a relational expression in which a direct current resistance or an alternating current resistance value of the power storage element at the time of the cumulative use period being a cumulative value is represented by an expression including an exponential term of the cumulative use period; And a remaining life estimation unit that estimates the remaining life using the acquired relational expression.

  According to this, the life estimation apparatus obtains a relational expression in which the resistance value of the direct current resistance or the alternating current resistance of the power storage element at the time when the cumulative use period has elapsed is represented by an expression including an exponential function term of the cumulative use period, The remaining life of the power storage element is estimated using the relational expression. Here, the resistance value increases at an accelerated rate as the cumulative use period elapses. As a result of intensive studies and experiments, the inventors of the present application have found that the temporal change of the resistance value is represented by an exponential function with the cumulative use period as a variable. For this reason, since the lifetime estimation apparatus can accurately represent the relationship between the resistance value and the cumulative usage period by using the above relational expression, the remaining lifetime of the power storage element can be accurately estimated. .

  Further, the relational expression acquisition unit may acquire the relational expression in which the resistance value is proportional to an exponential function having a value obtained by multiplying the cumulative use period by a predetermined constant.

  According to this, the life estimation apparatus acquires a relational expression in which the resistance value is proportional to an exponential function having a variable obtained by multiplying the cumulative use period by a predetermined constant. Here, as a result of intensive studies and experiments, the inventors of the present application have found that the relational expression proportional to an exponential function having a variable obtained by multiplying the cumulative use period by a predetermined constant is a change with time of the resistance value. Was found to be accurately expressed. For this reason, since the lifetime estimation apparatus can accurately represent the relationship between the resistance value and the cumulative usage period by using the above relational expression, the remaining lifetime of the power storage element can be accurately estimated. .

  The remaining life estimation unit obtains a first resistance value that is the resistance value at a predetermined time and a second resistance value that is the resistance value when the life of the power storage element is reached. A value acquisition unit, and a first cumulative usage period that is a cumulative usage period in the first resistance value obtained from the relational expression, and a cumulative usage period in the second resistance value obtained from the relational expression. A period acquisition unit that acquires two cumulative use periods; and a remaining life calculation unit that calculates a remaining life of the power storage element from the predetermined time point by subtracting the first cumulative use period from the second cumulative use period May be provided.

  According to this, the life estimation apparatus obtains the first resistance value at a predetermined time point and the second resistance value at the time when the life of the power storage element is reached, and in the first resistance value obtained from the above relational expression. Obtain the first cumulative usage period and the second cumulative usage period at the second resistance value, and subtract the first cumulative usage period from the second cumulative usage period to calculate the remaining life of the storage element from a predetermined point in time . In this way, the lifetime estimation apparatus can accurately estimate the remaining lifetime of the power storage element.

  The remaining life estimation unit further includes a relational expression correction unit that corrects the relational expression acquired by the relational expression acquisition unit, and estimates the remaining life using the corrected relational expression. May be.

  According to this, the life estimation apparatus corrects the above relational expression, and estimates the remaining life using the corrected relational expression. In this way, the life estimation apparatus can accurately estimate the remaining life by correcting the relational expression and improving the accuracy of the relational expression.

  The power storage device is a lithium ion secondary battery including a lithium transition metal oxide having a layered structure as a positive electrode active material, and the relational expression acquiring unit acquires the relational expression regarding the lithium ion secondary battery. The remaining life estimation unit may estimate the remaining life of the lithium ion secondary battery.

  According to this, the electric storage element is a lithium ion secondary battery including a lithium transition metal oxide having a layered structure as a positive electrode active material. Here, as a result of intensive studies and experiments, the inventors of the present application have found that the deterioration state can be accurately expressed by the above relational expression when the storage element is the lithium ion secondary battery. For this reason, the lifetime estimation apparatus can estimate the remaining lifetime of the said lithium ion secondary battery correctly.

  The present invention can be realized not only as such a life estimation apparatus, but also as a power storage system including a power storage element and a life estimation apparatus that estimates the remaining life of the power storage element. In addition, the present invention can be realized as a life estimation method including a characteristic process performed by the life estimation apparatus as a step. The present invention can also be realized as an integrated circuit including a characteristic processing unit included in the life estimation apparatus. In addition, the present invention can be realized as a program for causing a computer to execute characteristic processing included in the life estimation method, or can be realized as a recording medium such as a computer-readable CD-ROM in which the program is recorded. You can also. Needless to say, such a program can be distributed via a recording medium such as a CD-ROM and a transmission medium such as the Internet.

  According to the present invention, it is possible to accurately estimate the remaining life of a power storage element.

It is an external view of an electrical storage system provided with the lifetime estimation apparatus which concerns on embodiment of this invention. It is a block diagram which shows the functional structure of the lifetime estimation apparatus which concerns on embodiment of this invention. It is a figure which shows an example of the electrical storage element data which concerns on embodiment of this invention. It is a figure for demonstrating the relational expression which the relational expression acquisition part which concerns on embodiment of this invention acquires. It is a flowchart which shows an example of the process in which the lifetime estimation apparatus which concerns on embodiment of this invention estimates the remaining lifetime of an electrical storage element. It is a flowchart which shows an example of the process in which the lifetime estimation apparatus which concerns on embodiment of this invention estimates the remaining lifetime of an electrical storage element. It is a figure for demonstrating the effect which the lifetime estimation apparatus which concerns on embodiment of this invention has. It is a figure for demonstrating the effect which the lifetime estimation apparatus which concerns on embodiment of this invention has. It is a figure for demonstrating the effect which the lifetime estimation apparatus which concerns on embodiment of this invention has. It is a figure for demonstrating the effect which the lifetime estimation apparatus which concerns on embodiment of this invention has. It is a block diagram which shows the structure of the lifetime estimation apparatus which concerns on the modification of embodiment of this invention. It is a block diagram which shows the minimum structure of the lifetime estimation apparatus which concerns on embodiment of this invention. It is a block diagram which shows the structure which implement | achieves the lifetime estimation apparatus which concerns on embodiment of this invention with an integrated circuit.

  Hereinafter, a power storage device life estimation apparatus and a power storage system including the life estimation apparatus according to an embodiment of the present invention will be described with reference to the drawings. Each of the embodiments described below shows a preferred specific example of the present invention. The numerical values, shapes, materials, constituent elements, arrangement positions and connecting forms of the constituent elements, steps, order of steps, and the like shown in the following embodiments are merely examples, and are not intended to limit the present invention. In addition, among the constituent elements in the following embodiments, constituent elements that are not described in the independent claims indicating the highest concept of the present invention are described as optional constituent elements that constitute a more preferable embodiment.

  First, the configuration of the power storage system 10 will be described.

  FIG. 1 is an external view of a power storage system 10 including a life estimation apparatus 100 according to an embodiment of the present invention.

  As shown in the figure, the power storage system 10 includes a life estimation device 100, a plurality (six in FIG. 6) of power storage elements 200, and a storage case 300 that stores the life estimation device 100 and the plurality of power storage elements 200. I have.

  The life estimation apparatus 100 is a circuit board on which a circuit that is disposed above the plurality of power storage elements 200 and estimates the life of the plurality of power storage elements 200 is mounted. Specifically, the lifetime estimation apparatus 100 is connected to a plurality of power storage elements 200, acquires information from the plurality of power storage elements 200, and is a remaining life that is a usable remaining remaining period of the plurality of power storage elements 200. Is estimated. The detailed functional configuration of the life estimation apparatus 100 will be described later.

  Here, life estimation apparatus 100 is disposed above a plurality of power storage elements 200, but life estimation apparatus 100 may be disposed anywhere.

  The storage element 200 is a secondary battery such as a nonaqueous electrolyte secondary battery having a positive electrode and a negative electrode. In FIG. 6, six rectangular storage elements 200 are arranged in series to form an assembled battery. Note that the number of power storage elements 200 is not limited to six, but may be other plural numbers or one. Further, the shape of the electricity storage element 200 is not particularly limited.

Here, the power storage element 200 is preferably a lithium ion secondary battery including a lithium transition metal oxide having a layered structure as a positive electrode active material. Specifically, as the positive electrode active material, Li _{1 + x} M _1-y O ₂ (M is one or more transition metal elements selected from Fe, Ni, Mn, Co and the like, 0 ≦ x <1 / It is preferable to use a lithium transition metal oxide having a layered structure such as 3, 0 ≦ y <1/3). Note that as the positive electrode active material, spinel type lithium manganese oxide such as LiMn ₂ O ₄ and LiMn _1.5 Ni _0.5 O ₄ , olivine type positive electrode active material such as LiFePO ₄ , and lithium having the above layered structure You may mix and use a transition metal oxide.

Moreover, as a negative electrode active material, if a negative electrode active material which can occlude / release lithium ion, a well-known material can be used suitably. For example, lithium is occluded in addition to lithium metal and lithium alloys (lithium-containing alloys such as lithium-silicon, lithium-aluminum, lithium-lead, lithium-tin, lithium-aluminum-tin, lithium-gallium, and wood alloys). Releasable alloys, carbon materials (eg, graphite, non-graphitizable carbon, graphitizable carbon, low-temperature calcined carbon, amorphous carbon, etc.), silicon oxide, metal oxide, lithium metal oxide (Li ₄ Ti ₅ O ₁₂ ), polyphosphoric acid compounds, or compounds of transition metals and Group 14 to Group 16 elements such as Co ₃ O ₄ and Fe ₂ P, which are generally called conversion anodes.

  Next, a detailed functional configuration of the life estimation apparatus 100 will be described.

  FIG. 2 is a block diagram showing a functional configuration of life estimation apparatus 100 according to the embodiment of the present invention.

  The lifetime estimation apparatus 100 is an apparatus that estimates a remaining lifetime that is a cumulative remaining period in which the power storage element 200 can be used. As shown in the figure, the lifetime estimation apparatus 100 includes a relational expression acquisition unit 110, a remaining lifetime estimation unit 120, and a storage unit 130. The storage unit 130 stores relational expression data 131 and power storage element data 132.

  The relational expression acquisition unit 110 is an expression in which the direct current resistance or the resistance value of the alternating current resistance of the power storage element 200 at the time when the cumulative use period has elapsed, which is the cumulative value of the use period of the power storage element 200, includes an exponential function term of the cumulative use period. The relational expression indicated by is acquired. Specifically, the relational expression acquisition unit 110 acquires the relational expression in which the resistance value is proportional to an exponential function having a variable obtained by multiplying the cumulative use period by a predetermined constant.

  Here, the cumulative use period indicates a total period obtained by integrating the periods in which the power storage element 200 is used from the use start time of the power storage element 200 to a predetermined time point. For example, when the power storage element 200 is used intermittently, the cumulative use period indicates a period obtained by subtracting a non-use period in which the power storage element 200 is not used. The method of subtracting the non-use period may not be strict, and the entire use period including the non-use period from the start of use of the power storage element 200 to a predetermined time may be used as the cumulative use period. The unit of the cumulative use period is preferably time or cycle (number of times of charging / discharging), but may be any unit as long as it represents a period such as a month or a day.

  The resistance value of the DC resistance or AC resistance of the electricity storage element 200 is the resistance value of the internal resistance of the electricity storage element 200, for example, the resistance value of the DC resistance at 10 seconds or the AC resistance of 1 kHz. The DC resistance at 10 seconds is measured from the slope of the VI (voltage-current) plot at 10 seconds. The 1 kHz AC resistance is AC resistance (AC impedance) measured by applying an AC voltage or AC current having a frequency of 1 kHz to the storage element 200.

  The relational expression acquisition unit 110 acquires the relational expression by reading the relational expression from the relational expression data 131 stored in the storage unit 130. That is, the relational expression data 131 is data that holds a relational expression for estimating the remaining life of the power storage element 200. Details of the relational expression will be described later.

  The remaining life estimation unit 120 estimates the remaining life of the electricity storage device 200 using the relational expression acquired by the relational expression acquisition unit 110. Here, the remaining life estimation unit 120 includes a resistance value acquisition unit 121, a period acquisition unit 122, and a remaining life calculation unit 123.

  The resistance value acquisition unit 121 acquires a first resistance value that is a resistance value of the power storage element 200 at a predetermined time point (hereinafter referred to as a first time point). That is, the resistance value acquisition unit 121 acquires the measured resistance value of the power storage element 200 at the first time point, and sets the acquired value as the first resistance value.

  In addition, the resistance value acquisition unit 121 acquires a second resistance value that is a resistance value at the time when the life of the power storage element 200 is reached (hereinafter referred to as the second time point). That is, the resistance value acquisition unit 121 acquires a value determined by the user as a resistance value at the end of the life of the storage element 200 by an input from the user, and sets the acquired value as the second resistance value.

  Then, the resistance value acquisition unit 121 stores the acquired first resistance value and second resistance value in the storage element data 132 of the storage unit 130. Details of the storage element data 132 stored in the storage unit 130 will be described later.

  The period acquisition unit 122 acquires a first cumulative use period that is a cumulative use period in the first resistance value obtained from the above relational expression. That is, the period acquisition unit 122 calculates the cumulative use period in the first resistance value acquired by the resistance value acquisition unit 121 using the relational expression acquired by the relational expression acquisition unit 110, so that the above-described first time point is obtained. The first cumulative usage period that is the cumulative usage period is acquired.

  Moreover, the period acquisition part 122 acquires the 2nd cumulative use period which is a cumulative use period in the 2nd resistance value obtained from said relational expression. That is, the period acquisition unit 122 calculates the cumulative use period in the second resistance value acquired by the resistance value acquisition unit 121 using the relational expression acquired by the relational expression acquisition unit 110, so that the above-described second time point is obtained. The second cumulative usage period that is the cumulative usage period is acquired.

  The period acquisition unit 122 reads the first resistance value and the second resistance value from the power storage element data 132 stored in the storage unit 130, and uses the relational expression to calculate the first cumulative use period and the second cumulative value. Obtained by calculating the usage period. Then, the period acquisition unit 122 stores the acquired first cumulative usage period and second cumulative usage period in the power storage element data 132.

  The remaining life calculation unit 123 calculates the remaining life of the electricity storage device 200 from the first time point by subtracting the first accumulated use period from the second accumulated use period acquired by the period acquisition unit 122. Specifically, the remaining life calculation unit 123 reads the first cumulative use period and the second cumulative use period from the storage element data 132 stored in the storage unit 130, and calculates the remaining life. In other words, the remaining life is a cumulative use period in which the power storage device 200 can be used from a predetermined time (first time) to the life reaching time (second time).

  FIG. 3 is a diagram showing an example of the storage element data 132 according to the embodiment of the present invention.

  The storage element data 132 is a collection of data indicating the resistance value of the storage element 200 at a certain point in time and the cumulative use period of the storage element 200 at the certain point in time. That is, as shown in the figure, the storage element data 132 is a data table in which “resistance value” and “cumulative use period” are associated with each other. In the “resistance value”, a value indicating the resistance value of the power storage element 200 at a certain time such as the first time or the second time is stored. In the “cumulative usage period”, a value indicating the cumulative usage period of the power storage element 200 at the certain time is stored.

  Next, the relational expression acquired by the relational expression acquisition unit 110 will be described in detail.

  FIG. 4 is a diagram for explaining a relational expression acquired by the relational expression acquisition unit 110 according to the embodiment of the present invention. Specifically, the figure is a graph showing the relationship between the resistance value of the electricity storage element 200 and the cumulative usage period.

The relational expression acquired by the relational expression acquisition unit 110 can be acquired by performing the following experiment. Specifically, the DC resistance or AC resistance until a certain deterioration state is reached (for example, during the period from t ₀ to t _{1 in} the figure) under the usage conditions (current value is defined) assumed to be used repeatedly. The exponential correlation function R = f (t) is calculated from the transition of the resistance value R.

  For example, DC resistance or AC resistance measurement is performed after 0, 100, 200, and 300 cycles, and a data pair of (resistance value R, cumulative usage period t) is acquired. Furthermore, the constants a and b are calculated by substituting the relationship between the two into Ln (R) = a × t + b.

  Here, examples of the method for measuring the resistance value R include the following methods. That is, after the collected battery is left at 25 ° C. for at least 3 hours, constant current discharge (remaining discharge) is performed at a battery rated capacity of 0.05 CA until the SOC (State Of Charge) is 0%.

  The method for obtaining the resistance value R of the DC resistance is not limited. For example, after constant current and constant voltage charging at 0.2 CA is performed for a total of 8 hours until the SOC reaches 50%, 0. Plot the 10th second voltage (V) of discharge current of at least 3 points, such as 2, 0.5, 1CA, etc. against each discharge current (I) and confirm that their slopes show linearity A method for obtaining the resistance value R of the DC resistance from the slope of the VI plot can be exemplified.

  Moreover, when acquiring the resistance value R of AC resistance, the internal impedance (for example, SOC: 0%) of a battery of 1 kHz, for example, is acquired using an AC impedance measuring instrument.

  As described above, as the above relational expression, as shown in the following Expression 1, a relational expression in which the resistance value R is expressed by an exponential function of the cumulative usage period t is acquired.

      R = f (t) = A × exp (B × t) (Formula 1)

  Here, A and B are constants. As described above, as the relational expression acquired by the relational expression obtaining unit 110, as shown in the above-described Expression 1, the DC resistance of the power storage element 200 at the time when the cumulative use period t, which is the cumulative value of the use period of the power storage element 200, or A relational expression in which the resistance value R of the AC resistance is proportional to an exponential function having a value obtained by multiplying the cumulative use period t by a predetermined constant B can be obtained.

  As described above, the graph represented by the above formula 1 is a graph in which the resistance value R increases rapidly with the lapse of the cumulative use period t at the end of the battery life, and the resistance value is accelerated at the end of the battery life. The deterioration state of the battery in which R increases can be accurately expressed. Note that the end of battery life refers to, for example, a case where the internal resistance of the battery has increased to three times or more of the initial value.

  Then, the relational expression shown in Expression 1 above is derived in advance by experiments as described above for each type of power storage element 200 and stored in advance in relational expression data 131 of the storage unit 130. Note that the constants A and B in Equation 1 above are calculated for each type of power storage element 200.

  Next, the process in which the lifetime estimation apparatus 100 estimates the remaining lifetime of the electrical storage element 200 will be described.

  5 and 6 are flowcharts illustrating an example of processing in which the lifetime estimation apparatus 100 according to the embodiment of the present invention estimates the remaining lifetime of the power storage element 200.

  First, as shown in FIG. 5, the relational expression acquisition unit 110 acquires the relational expression shown in the above expression 1 according to the type of the power storage element 200 whose remaining life is estimated (S102). Specifically, the relational expression acquisition unit 110 refers to the relational expression data 131 stored in the storage unit 130 and acquires a relational expression corresponding to the type of the storage element 200. Note that the relational expression acquisition unit 110 may calculate and acquire the relational expression by analyzing the transition of the resistance value of the power storage element 200.

  And the remaining life estimation part 120 estimates the remaining life of the electrical storage element 200 using the relational expression which the relational expression acquisition part 110 acquired (S104). Below, the process in which the remaining lifetime estimation part 120 estimates the said remaining lifetime is demonstrated in detail. FIG. 6 is a flowchart illustrating an example of a process (S104 in FIG. 5) in which the remaining life estimation unit 120 according to the embodiment of the present invention estimates the remaining life.

First, as illustrated in FIG. 6, the resistance value acquisition unit 121 acquires the first resistance value of the power storage element 200 at the first time point (S202). Specifically, as shown in FIG. 4, the resistance value acquisition unit 121, by measuring a first resistance value R ₁ of the electric storage device 200 in the first time, to obtain a first resistance value R _1. Note that the resistance value acquisition unit 121 may acquire the first resistance value R ₁ from the outside such as an input by a user. Then, the resistance value acquisition unit 121 stores the acquired first resistance value R ₁ in the storage element data 132 of the storage unit 130.

Then, returning to FIG. 6, the period acquisition unit 122 acquires a first cumulative use period that is a cumulative use period in the first resistance value obtained from the above relational expression. Specifically, as illustrated in FIG. 4, the period acquisition unit 122 adds the first resistance value R ₁ acquired by the resistance value acquisition unit 121 to the relational expression (graph of FIG. 4) acquired by the relational expression acquisition unit 110. by substituting, for calculating a first cumulative use period t _1. For example, the period acquisition unit 122 calculates the first cumulative usage period t ₁ using the exponential correlation function formula R = f (t) from the relational expression expressed by the above formula 1.

The period acquiring section 122, a storage element data 132 stored in the storage unit 130 reads the first resistance value R _1, calculates a first cumulative use period t ₁ using the relational expression, the first The accumulated usage period t ₁ is stored in the storage element data 132.

Then, returning to FIG. 6, the resistance value acquiring unit 121 acquires the second resistance value of the power storage element 200 at the second time point (life reaching time) of the power storage element 200 (S206). Specifically, as illustrated in FIG. 4, the resistance value acquisition unit 121 acquires the second resistance value R ₂ determined by the user as the resistance value at the time of reaching the end of the life of the power storage element 200 by an input from the user or the like. To do. Note that the time point when the storage element 200 reaches the end of life indicates, for example, a case where the internal resistance of the storage element 200 is three times or more of the initial value. Then, the resistance value acquisition unit 121 stores the acquired second resistance value R ₂ in the storage element data 132 of the storage unit 130.

Note that the second resistance value R ₂ may be determined in advance and stored in the storage unit 130, and the resistance value acquisition unit 121 may acquire the second resistance value R ₂ from the storage unit 130. The resistance value acquisition unit 121, by calculating the second resistance value R ₂ according to a predetermined rule may be to obtain a second resistance value R _2.

Then, returning to FIG. 6, the period acquisition unit 122 acquires a second cumulative use period that is a cumulative use period in the second resistance value obtained from the relational expression (S208). Specifically, as illustrated in FIG. 4, the period acquisition unit 122 adds the second resistance value R ₂ acquired by the resistance value acquisition unit 121 to the relational expression (graph of FIG. 4) acquired by the relational expression acquisition unit 110. by substituting, for calculating a second cumulative use period t _2. For example, the period acquisition unit 122 calculates the second cumulative usage period t ₂ by t ₂ = f ⁻¹ (R ₂ ), similarly to the calculation of the first cumulative usage period t ₁ .

The period acquisition unit 122 reads the second resistance value R ₂ from the storage element data 132 stored in the storage unit 130, calculates the second cumulative use period t ₂ using the relational expression, The accumulated use period t ₂ is stored in the storage element data 132. Note that the second cumulative usage period t ₂ may be stored in advance in the storage element data 132, and the period acquisition unit 122 may acquire the second cumulative usage period t ₂ from the storage element data 132.

Then, returning to FIG. 6, the remaining life calculation unit 123 calculates the remaining life of the electricity storage device 200 from the first time point by subtracting the first accumulated use period from the second accumulated use period (S210). Specifically, as shown in FIG. 4, the remaining life calculation unit 123 reads the first cumulative use period t ₁ and the second cumulative use period t ₂ from the storage element data 132 stored in the storage unit 130. Thus, the remaining life T (= t ₂ −t ₁ ) is calculated.

  Thus, the process of estimating the remaining lifetime of the storage element 200 by the lifetime estimation device 100 ends.

  Next, the effect which the lifetime estimation apparatus 100 which concerns on embodiment of this invention show | plays is demonstrated. Specifically, it will be described that the lifetime estimation apparatus 100 can accurately estimate the remaining lifetime of the power storage element 200.

The lithium ion secondary batteries (Battery A and Battery B) used in the following specific examples include a positive electrode, a negative electrode, and a nonaqueous electrolyte. The positive electrode is formed by forming a positive electrode mixture on an aluminum foil that is a positive electrode current collector. The positive electrode mixture includes a positive electrode active material, polyvinylidene fluoride as a binder, and acetylene black as a conductive material. The positive electrode active material is a mixture of a lithium transition metal oxide having a layered structure represented by LiNi _1/3 Co _1/3 Mn _1/3 O ₂ and a spinel type lithium manganese oxide. The negative electrode is formed by forming a negative electrode mixture on a copper foil that is a negative electrode current collector. The negative electrode mixture includes a graphitic carbon material as a negative electrode active material and polyvinylidene fluoride as a binder. Battery A and battery B differ in the particle size and specific surface area values of the positive electrode active material.

  7-10 is a figure for demonstrating the effect which the lifetime estimation apparatus 100 which concerns on embodiment of this invention has. Specifically, FIG. 7 is a diagram for explaining the effect of the life estimation apparatus 100 when the storage element 200 is the battery A and the resistance value R is a DC resistance, and FIG. It is a figure explaining the effect which the lifetime estimation apparatus 100 in case it is the battery A and resistance value R is an alternating current resistance. FIG. 9 is a diagram for explaining the effect exerted by the lifetime estimation device 100 when the storage element 200 is the battery B and the resistance value R is a DC resistance. FIG. It is a figure explaining the effect which there exists and the lifetime estimation apparatus 100 in case the resistance value R is alternating current resistance.

As shown in FIG. 7, the battery A was subjected to a 1C cycle test at 45 ° C., and the relational expression shown in the above equation 1 was calculated. Specifically, a power law relational expression R = f (t) was calculated from the transition of the resistance value R of the DC resistance in the cycle ₀ (t _{0 in} the figure) to 300 cycles (t _{1 in} the figure). As a result, a relational expression R = 121.8 × exp (6.467 × 10 ⁻⁴ × t) was obtained.

Here, in the case of t ₁ = 300 cycles, since R ₁ = 149.7 mOhm, the first resistance value of the battery A at the first time point is R ₁ = 149.7 mOhm, and the first cumulative use period is t ₁ = 300 cycles. Further, the second resistance value of the battery A at the second time point (life reaching time point) is R ₂ = 424.4 mOhm, and the second cumulative use period t ₂ is calculated by t ₂ = f ⁻¹ (R ₂ ). As a result, the second cumulative usage period t ₂ = 1930 cycles was calculated.

Accordingly, the remaining life T is calculated as T = t ₂ −t ₁ = 1630 cycles. Here, since the actual measurement value was 1700 cycles, the remaining life T calculated using the power law relational expression R = f (t) was in good agreement with the actual measurement value.

  Next, as a comparative example, a remaining life prediction was performed by a conventionally used method. Specifically, based on the result of the resistance value R in the above 0 cycle to 300 cycles, the relationship between the resistance value R and the number of cycles is (1) linear rule, (2) root rule, (3) 1 It was estimated that each of the .52 order rules, and a prediction formula was obtained. Each prediction formula is as follows.

(1) Straight line rule R = 0.121 × t + 115.2
(2) Route rule R = 2.19 × t ^1/2 +110.3
(3) 1.52 degree rule R = 5.77 × 10 ⁻³ × t ^1.52 +118.5

Then, similarly to the above power law, the remaining life T = t ₂ −t ₁ was calculated by calculating t ₂ with t ₁ = 300 cycles and the life when R ₂ = 424.4 mOhm was reached. . The calculation results of the remaining lifetime T are (1) 2243 cycles, (2) 20160 cycles, and (3) 982 cycles for (1) linear law, (2) root law, and (3) 1.52 order law, respectively. there were.

  As a result, as shown in FIG. 7B, the difference between these remaining lifetimes T and the actually measured value of 1700 cycles is (1) linear law, (2) root law, and (3) 1.52 order. The rules were (1) 543 cycles, (2) 18460 cycles, and (3) 718 cycles, respectively. As described above, the lifetime estimation apparatus 100 according to the above-described embodiment was able to estimate the remaining lifetime with very high accuracy as compared with a conventionally used method.

Next, as shown in FIG. 8, the battery A was subjected to a 45 ° C., 1 C cycle test, and the resistance value R of the AC resistance in the 0 cycle (t _{0 in} the figure) to 300 cycles (t _{1 in} the figure). The relational expression R = f (t) of the power law was calculated from the transition of. As a result, the relational expression R = 83.9 × exp (6.410 × 10 ⁻⁴ × t) was obtained.

Here, in the case of t ₁ = 300 cycles, since R ₁ = 104.9 mOhm, the first resistance value of the battery A at the first time point is R ₁ = 104.9 mOhm, and the first cumulative use period is t ₁ = 300 cycles. Further, the second resistance value of the battery A at the second time point (life reaching time point) is R ₂ = 291.2 mOhm, and the second cumulative use period t ₂ is calculated by t ₂ = f ⁻¹ (R ₂ ). As a result, the second cumulative usage period t ₂ was calculated to be 1941 cycles.

Accordingly, the remaining life T is calculated as T = t ₂ −t ₁ = 1641 cycles. Here, since the actual measurement value was 1700 cycles, the remaining life T calculated using the power law relational expression R = f (t) was in good agreement with the actual measurement value.

  Next, as comparative examples, prediction formulas were obtained for each of the above (1) straight line rule, (2) root rule, and (3) 1.52 degree rule. Each prediction formula is as follows.

(1) Straight line rule R = 0.147 × t + 63.9
(2) Route rule R = 2.77 × t ^1/2 +56.9
(3) 1.52 order rule R = 6.87 × 10 ⁻³ × t ^1.52 +68.1

Then, similarly to the above power law, the remaining life T = t ₂ −t ₁ was calculated by calculating t ₂ with t ₁ = 300 cycles and assuming the life when R ₂ = 291.2 mOhm was reached. . The calculation results of the remaining life T are (1) 1246 cycles, (2) 6834 cycles, and (3) 629 cycles for (1) linear law, (2) root law, and (3) 1.52 order law, respectively. The difference from the actually measured value of 1700 cycles was (1) 454 cycles, (2) 5134 cycles, and (3) 1071 cycles, respectively. As described above, the lifetime estimation apparatus 100 according to the above-described embodiment was able to estimate the remaining lifetime with very high accuracy as compared with a conventionally used method.

Next, as shown in FIG. 9, the battery B is subjected to a 45 ° C., 1 C cycle test, and the resistance value R of the direct current resistance of 0 cycle (t _{0 in} the figure) to 300 cycles (t _{1 in} the figure). The relational expression R = f (t) of the power law was calculated from the transition of. As a result, the relational expression R = 101.7 × exp (2.875 × 10 ⁻⁴ × t) was obtained.

Here, in the case of t ₁ = 300 cycles, since R ₁ = 112.1 mOhm, the first resistance value of the battery B at the first time point is R ₁ = 112.1 mOhm, and the first cumulative use period is t ₁ = 300 cycles. Further, the second resistance value of the battery B at the second time point (life reaching point) is set as R ₂ = 180 mOhm, and the second cumulative use period t ₂ is calculated by t ₂ = f ⁻¹ (R ₂ ). As a result, the second cumulative usage period t ₂ was calculated as 1985 cycles.

Accordingly, the remaining life T is calculated as T = t ₂ −t ₁ = 1687 cycles. Here, since the actual measurement value was 1700 cycles, the remaining life T calculated using the power law relational expression R = f (t) was in good agreement with the actual measurement value.

  Next, as comparative examples, prediction formulas were obtained for each of the above (1) straight line rule, (2) root rule, and (3) 1.52 degree rule. Each prediction formula is as follows.

(1) Straight line rule R = 0.047 × t + 100.0
(2) Route rule R = 0.902 × t ^1/2 +97.5
(3) 1.52 order rule R = 2.11 × 10 ⁻³ × t ^1.52 +101.4

Then, similarly to the above power law, the remaining life T = t ₂ −t ₁ was calculated by setting t ₁ = 300 cycles and calculating t ₂ with the life when R ₂ = 180 mOhm being reached. The calculation results of the remaining lifetime T are (1) 1402 cycles, (2) 8064 cycles, (3) 717 cycles for (1) linear rule, (2) route rule, and (3) 1.52 order rule, respectively. The difference from the actually measured 1700 cycles was (1) 298 cycles, (2) 6364 cycles, and (3) 983 cycles, respectively. As described above, the lifetime estimation apparatus 100 according to the above-described embodiment was able to estimate the remaining lifetime with very high accuracy as compared with a conventionally used method.

Next, as shown in FIG. 10, the battery B was subjected to a 1C cycle test at 45 ° C., and the resistance value R of the AC resistance for 0 cycle (t _{0 in} the figure) to 300 cycles (t _{1 in} the figure). The relational expression R = f (t) of the power law was calculated from the transition of. As a result, the relational expression R = 59.0 × exp (2.811 × 10 ⁻⁴ × t) was obtained.

Here, in the case of t ₁ = 300 cycles, since R ₁ = 65.5 mOhm, the first resistance value of the battery B at the first time point is R ₁ = 65.5 mOhm, and the first cumulative use period is t ₁ = 300 cycles. In addition, the second resistance value of the battery B at the second time point (life reaching time point) is R ₂ = 100.4 mOhm, and the second cumulative usage period t ₂ is calculated by t ₂ = f ⁻¹ (R ₂ ). As a result, the second cumulative usage period t ₂ was calculated to be 1891 cycles.

Accordingly, the remaining life T is calculated as T = t ₂ −t ₁ = 1591 cycles. Here, since the actual measurement value was 1700 cycles, the remaining life T calculated using the power law relational expression R = f (t) was in good agreement with the actual measurement value.

  Next, as comparative examples, prediction formulas were obtained for each of the above (1) straight line rule, (2) root rule, and (3) 1.52 degree rule. Each prediction formula is as follows.

(1) Straight line rule R = 0.05 × t + 52.2
(2) Route rule R = 0.811 × t ^1/2 +52.2
(3) 1.52 order rule R = 2.27 × 10 ⁻³ × t ^1.52 +53.8

Then, similarly to the above power law, the remaining life T = t ₂ −t ₁ was calculated by calculating t ₂ with t ₁ = 300 cycles and the life when R ₂ = 100.4 mOhm was reached. . The calculation results of the remaining lifetime T are (1) 664 cycles, (2) 3232 cycles, and (3) 387 cycles for (1) linear law, (2) root law, and (3) 1.52 order law, respectively. The difference from the actually measured value of 1700 cycles was (1) 1036 cycles, (2) 1532 cycles, and (3) 1313 cycles, respectively. As described above, the lifetime estimation apparatus 100 according to the above-described embodiment was able to estimate the remaining lifetime with very high accuracy as compared with a conventionally used method.

  As described above, according to the life estimation apparatus 100 according to the embodiment of the present invention, the direct current resistance or the resistance value of the alternating current resistance of the power storage element 200 at the time when the cumulative use period has elapsed is a term of an exponential function of the cumulative use period. Is obtained, and the remaining lifetime of the electricity storage device 200 is estimated using the relational expression. Here, the resistance value increases at an accelerated rate as the cumulative use period elapses. As a result of intensive studies and experiments, the inventors of the present application have found that the temporal change of the resistance value is represented by an exponential function with the cumulative use period as a variable. For this reason, since the lifetime estimation apparatus 100 can accurately represent the relationship between the resistance value and the cumulative usage period by using the above relational expression, the lifetime estimation apparatus 100 accurately estimates the remaining lifetime of the power storage element 200. Can do.

  Moreover, the lifetime estimation apparatus 100 acquires a relational expression in which the resistance value is proportional to an exponential function having a variable obtained by multiplying the cumulative use period by a predetermined constant. Here, as a result of intensive studies and experiments, the inventors of the present application have found that the relational expression proportional to an exponential function having a variable obtained by multiplying the cumulative use period by a predetermined constant is a change with time of the resistance value. Was found to be accurately expressed. For this reason, since the lifetime estimation apparatus 100 can accurately represent the relationship between the resistance value and the cumulative usage period by using the above relational expression, the lifetime estimation apparatus 100 accurately estimates the remaining lifetime of the power storage element 200. Can do.

  Moreover, the lifetime estimation apparatus 100 acquires the first resistance value at a predetermined time point and the second resistance value at the time point when the life of the electric storage element 200 is reached, and obtains the first resistance value obtained from the above relational expression. The remaining life of the electricity storage device 200 from a predetermined time is calculated by acquiring one accumulated use period and the second accumulated use period at the second resistance value and subtracting the first accumulated use period from the second accumulated use period. . In this way, the lifetime estimation apparatus 100 can accurately estimate the remaining lifetime of the power storage element 200.

  The power storage device 200 is preferably a lithium ion secondary battery including a lithium transition metal oxide having a layered structure as a positive electrode active material. Here, as a result of intensive studies and experiments, the inventors of the present application have found that the deterioration state can be accurately expressed by the above relational expression when the storage element 200 is the lithium ion secondary battery. For this reason, the lifetime estimation apparatus 100 can estimate the remaining lifetime of the said lithium ion secondary battery correctly.

  In addition, the lifetime estimation apparatus 100 can estimate the remaining lifetime at the end of the lifetime of the electricity storage element 200 with high accuracy. Thereby, for example, it is possible to accurately determine the replacement timing of a lithium-ion secondary battery for a moving body such as an electric vehicle. In addition, by performing charge / discharge control in accordance with the estimated lifetime in the power storage element 200, capacity deterioration can be suppressed, and thus life extension measures can be taken.

  The life estimation apparatus 100 and the power storage system 10 according to the embodiment of the present invention have been described above, but the present invention is not limited to this embodiment. That is, the embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  For example, in the above-described embodiment, the remaining life estimation unit 120 estimates the remaining life of the electricity storage device 200 using the relational expression acquired by the relational expression acquisition unit 110 without being changed. However, the remaining life estimation unit may correct the relational expression and estimate the remaining life. FIG. 11 is a block diagram showing a configuration of a life estimation apparatus 100a according to a modification of the embodiment of the present invention. As shown in the figure, the remaining life estimation unit 120a of the life estimation apparatus 100a includes a relational expression correction unit 124 that corrects the relational expression acquired by the relational expression acquisition unit 110, and the relational expression correction unit 124 corrected the relational expression correction unit 124. The remaining life is estimated using the corrected relational expression. Thereby, the lifetime estimation apparatus 100a acquires, for example, a data pair corresponding to the cumulative use period t and the resistance value R during actual use in an automobile or the like, and corrects the above relational expression based on the data pair. By improving the accuracy of the relational expression, the remaining life can be accurately estimated.

  Moreover, in the said embodiment, the lifetime estimation apparatus 100 is provided with the relational expression acquisition part 110, the remaining lifetime estimation part 120, and the memory | storage part 130, and the remaining lifetime estimation part 120 is the resistance value acquisition part 121, the period acquisition part. 122 and the remaining life calculation unit 123 are provided. However, as shown in FIG. 12, the life estimation apparatus only needs to include at least a relational expression acquisition unit and a remaining life estimation unit.

  FIG. 12 is a block diagram showing a minimum configuration of the life estimation apparatus according to the embodiment of the present invention. As shown in the figure, the life estimation apparatus 100b includes a relational expression acquisition unit 110 and a remaining life estimation unit 120b having functions similar to those of the above-described embodiment, and exchanges information with an external storage unit 130. The remaining life is estimated. The remaining life estimation unit 120b only needs to be able to estimate the remaining life using the relational expression acquired by the relational expression acquisition unit 110, and the resistance value acquisition unit 121, the period acquisition unit 122, and the like as in the above embodiment. It is not limited to having the remaining life calculation unit 123.

  Here, the processing unit included in the lifetime estimation apparatus 100 according to the present invention is typically realized as an LSI (Large Scale Integration) that is an integrated circuit. That is, as shown in FIG. 13, the present invention is realized as an integrated circuit 101 including a relational expression acquisition unit 110 and a remaining life estimation unit 120. FIG. 13 is a block diagram showing a configuration for realizing the life estimation apparatus according to the embodiment of the present invention with an integrated circuit.

  Each processing unit included in the integrated circuit 101 may be individually made into one chip, or may be made into one chip so as to include a part or all of them.

  The name used here is LSI, but it may also be called IC, system LSI, super LSI, or ultra LSI depending on the degree of integration.

  Further, the method of circuit integration is not limited to LSI's, and implementation using dedicated circuitry or general purpose processors is also possible. An FPGA (Field Programmable Gate Array) that can be programmed after manufacturing the LSI, or a reconfigurable processor that can reconfigure the connection and setting of circuit cells inside the LSI may be used.

  Furthermore, if integrated circuit technology comes out to replace LSI's as a result of the advancement of semiconductor technology or a derivative other technology, it is naturally also possible to carry out function block integration using this technology. There is a possibility of adaptation of biotechnology.

  Moreover, the present invention can be realized not only as such a life estimation apparatus 100 but also as a life estimation method using characteristic processes performed by the life estimation apparatus 100 as steps.

  In addition, the present invention can be realized as a program for causing a computer to execute characteristic processing included in the life estimation method, or can be realized as a recording medium such as a computer-readable CD-ROM in which the program is recorded. You can also. Needless to say, such a program can be distributed via a recording medium such as a CD-ROM and a transmission medium such as the Internet.

  The present invention can be applied to a lifetime estimation device that can accurately estimate the remaining lifetime of a power storage element.

10, 10a, 10b Power storage system 100, 100a, 100b Life estimation device 101 Integrated circuit 110 Relational expression acquisition unit 120, 120a, 120b Remaining life estimation unit
121 resistance value acquisition unit 122 period acquisition unit 123 remaining life calculation unit 124 relational expression correction unit 130 storage unit 131 relational expression data 132 power storage element data 200 power storage element 300 accommodation case

Claims (8)

A lifetime estimation device that estimates a remaining lifetime that is a cumulative remaining period in which a storage element can be used,
A relational expression in which the direct current resistance or the resistance value of the alternating current resistance of the power storage element at the time when the cumulative use period has elapsed, which is a cumulative value of the use period of the power storage element, is represented by an expression including an exponential function term of the cumulative use period. A relational expression acquisition unit to acquire;
A life estimation apparatus comprising: a remaining life estimation unit that estimates the remaining life using the acquired relational expression. The lifetime estimation apparatus according to claim 1, wherein the relational expression acquisition unit acquires the relational expression in which the resistance value is proportional to an exponential function having a value obtained by multiplying the cumulative use period by a predetermined constant as a variable. The remaining life estimation unit is
A resistance value acquisition unit that acquires the first resistance value that is the resistance value at a predetermined time point, and acquires the second resistance value that is the resistance value at the time when the lifetime of the power storage element is reached;
A first cumulative use period that is a cumulative use period in the first resistance value obtained from the relational expression is acquired, and a second cumulative use period that is a cumulative use period in the second resistance value obtained from the relational expression is obtained. A period acquisition unit to acquire;
The life estimation according to claim 1, further comprising: a remaining life calculation unit that calculates a remaining life of the power storage element from the predetermined time point by subtracting the first cumulative use period from the second cumulative use period. apparatus. The remaining life estimation unit is
And a relational expression correction unit that corrects the relational expression acquired by the relational expression acquisition unit,
The life estimation apparatus according to claim 1, wherein the remaining life is estimated using the corrected relational expression. The power storage element is a lithium ion secondary battery including a lithium transition metal oxide having a layered structure as a positive electrode active material,
The relational expression acquisition unit acquires the relational expression for the lithium ion secondary battery,
The lifetime estimation apparatus according to any one of claims 1 to 4, wherein the remaining lifetime estimation unit estimates the remaining lifetime of the lithium ion secondary battery. A storage element;
A power storage system comprising: the life estimation device according to any one of claims 1 to 5 that estimates a remaining life that is a cumulative remaining time of use of the power storage element. A life estimation method in which a computer estimates a remaining life that is a cumulative remaining life of a storage element,
A relational expression in which the direct current resistance or the resistance value of the alternating current resistance of the power storage element at the time when the cumulative use period has elapsed, which is a cumulative value of the use period of the power storage element, is represented by an expression including an exponential function term of the cumulative use period. A relational expression acquisition step to be acquired;
A remaining life estimation step of estimating the remaining life using the acquired relational expression. An integrated circuit that estimates a remaining lifetime, which is a cumulative remaining period of a storage element,
A relational expression in which the direct current resistance or the resistance value of the alternating current resistance of the power storage element at the time when the cumulative use period has elapsed, which is a cumulative value of the use period of the power storage element, is represented by an expression including an exponential function term of the cumulative use period. A relational expression acquisition unit to acquire;
An integrated circuit comprising: a remaining life estimation unit that estimates the remaining life using the acquired relational expression.

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