JPWO2014128902A1 - Secondary battery deterioration diagnosis method and apparatus using the same - Google Patents

Abstract

The present invention diagnoses the deterioration rate of each active material and the potential with respect to the battery capacity in a non-destructive and simple method for a secondary battery using an electrode in which two or more kinds of active materials are mixed. With the goal. The deterioration diagnosis method for a secondary battery according to the present invention acquires charge / discharge characteristics of the secondary battery, acquires information about a plurality of active materials stored in a memory, and acquires information about the plurality of active materials and the charge / discharge The mixing ratio of the positive electrode or the negative electrode is determined from the characteristics, the charging / discharging characteristics of the secondary battery are predicted based on the mixing ratio, and the predicted charging / discharging characteristics are compared with the charging / discharging characteristics of the secondary battery. When the predicted charge / discharge characteristics match the charge / discharge characteristics of the secondary battery, the potential of the mixed positive electrode predicted using the mixing ratio or the mixed negative electrode predicted using the mixing ratio The deterioration parameter is calculated based on the potential.

Description

  The present invention relates to a secondary battery deterioration diagnosis method and a device having the function.

  In recent years, efforts have been made to efficiently use energy by using a secondary battery such as a lithium ion battery as a power source for mounting on a vehicle or a power source for power storage in a smart house. In order to maximize the energy utilization efficiency, it is important to optimize the initial characteristics of the secondary battery in accordance with the use conditions. Moreover, since it is assumed that the power supply of such an application will be used for a long time, it is also important to suppress the deterioration of the characteristics of the secondary battery. As means for optimizing characteristics and suppressing deterioration, it is known to use a mixture of two or more active materials as the positive electrode / negative electrode active material constituting the secondary battery.

  Moreover, in order to optimize the energy utilization efficiency in the long term, it is necessary to accurately predict the characteristic deterioration of the secondary battery and to select an optimal battery usage method according to the prediction. At this time, if the deterioration states of the positive electrode, the negative electrode, and the electrolyte constituting the secondary battery can be quantitatively evaluated, it is expected that the prediction accuracy of the characteristic deterioration is improved. For example, Patent Document 1 describes a method for quantitatively evaluating the deterioration states of the positive electrode, the negative electrode, and the electrolyte solution in a nondestructive manner by using a charge / discharge curve of a secondary battery.

JP2009-80093

  Patent Document 1 describes a method for determining a state of a secondary battery. Based on a charge / discharge curve of a positive electrode and a negative electrode stored in advance, the charge / discharge curve of the secondary battery is reproduced by calculation. It describes a method for obtaining the effective weight of the positive electrode active material, the effective weight of the negative electrode active material, the amount of change in the use position between the positive electrode and the negative electrode, or the value of the parameter corresponding thereto.

  However, in the method of Patent Document 1, it is assumed that one type of active material is used for each of the positive electrode and the negative electrode active material. In order to diagnose the deterioration state of a secondary battery using a mixed positive electrode or a mixed negative electrode formed by mixing two or more types of active materials by the method of Patent Document 1, for example, the mixed active material is used as a virtual active material. After considering it as a substance, the charge / discharge curve in the initial state of the mixed positive electrode or the mixed negative electrode must be stored in advance to determine the effective mass of the virtual active material.

  However, in practice, the active material constituting the mixed positive electrode or the mixed negative electrode does not deteriorate at the same rate, so the mixing ratio changes with the progress of deterioration, and the charge / discharge curve shape of the unit mass of the mixed positive electrode or the mixed negative electrode changes. .

  In this case, there is a problem that it is difficult to reproduce the charge / discharge curve of the secondary battery after deterioration based on the charge / discharge curve of the initial mixed positive electrode or mixed negative electrode.

  This invention is made | formed in view of this subject, and the deterioration state is nondestructive and simple with respect to the secondary battery using the mixed positive electrode or mixed negative electrode formed by mixing two or more types of active materials. It is an object of the present invention to provide means for diagnosing by a method, or means for enhancing the safety and extending the life of a secondary battery by control based on the diagnosis result.

  Means for solving the above problems are as follows, for example.

  The deterioration diagnosis method for a secondary battery according to the present invention acquires charge / discharge characteristics of the secondary battery, acquires information about a plurality of active materials stored in a memory, and acquires information about the plurality of active materials and the charge / discharge The mixing ratio of the positive electrode or the negative electrode is determined from the characteristics, the charging / discharging characteristics of the secondary battery are predicted based on the mixing ratio, and the predicted charging / discharging characteristics are compared with the charging / discharging characteristics of the secondary battery. When the predicted charge / discharge characteristics match the charge / discharge characteristics of the secondary battery, the potential of the mixed positive electrode predicted using the mixing ratio or the mixed negative electrode predicted using the mixing ratio The deterioration parameter is calculated based on the potential.

  The deterioration parameter is calculated based on a secondary battery capacity, a capacity of the mixed positive electrode, and a capacity of the mixed negative electrode.

  The information on the active material includes a capacity per unit weight q (Ah / g), a capacity Q (Ah), an electrode potential V (V), a potential change ΔV / ΔQ (V / Ah) or ΔV / Δq (Vg / Ah), capacitance change with respect to potential change ΔQ / ΔV (Ah / V) or Δq / ΔV (Ah / Vg), state of charge SOC, specific heat c (J / Kg) or heat capacity C (J / K), It is any information of electrical resistance R (Ω).

  The secondary battery system according to the present invention includes a secondary battery having a mixed positive electrode or a mixed negative electrode obtained by mixing at least two active materials, and a deterioration diagnosis device that diagnoses deterioration of the secondary battery, The deterioration diagnosis apparatus includes an input unit, a deterioration diagnosis unit, and a memory, the input unit acquires charge / discharge characteristics of the secondary battery, and the deterioration diagnosis unit includes a plurality of active materials stored in the memory. And the charge / discharge characteristics of the secondary battery, determine the mixing ratio of the positive electrode or the negative electrode from the information on the plurality of active materials and the charge / discharge characteristics, and based on the determined mixing ratio The charging / discharging characteristics of the secondary battery are predicted, and the predicted charging / discharging characteristics and the charging / discharging characteristics of the secondary battery are matched by comparing the predicted charging / discharging characteristics with the charging / discharging characteristics of the secondary battery. In the case predicted using the mixing ratio Using potential or the mixing ratio of the case the positive electrode on the basis of the potential of the predicted the mixed anode and calculates a deterioration parameter.

The deterioration diagnosis unit may determine an upper limit value or a lower limit value of a use voltage of the secondary battery based on the predicted potential of the mixed positive electrode or the predicted potential of the mixed negative electrode.
In addition, the deterioration diagnosis apparatus includes a prediction unit that predicts charge / discharge characteristics of the secondary battery based on the mixture ratio and the deterioration parameter calculated at regular intervals.

  According to the present invention, for a secondary battery using an electrode in which two or more kinds of active materials are mixed, the deterioration state of each active material and the potential with respect to the battery capacity are diagnosed by a non-destructive and simple method. be able to.

  Further, the control based on the diagnosis result can increase the safety and the life of the secondary battery using the mixed electrode. Problems, configurations, and effects other than those described above will be clarified by the following description of embodiments.

Deterioration diagnosis apparatus in first embodiment of the present invention Flow chart of degradation diagnosis method according to the present invention Discharge characteristics per unit weight of positive electrode active materials Li (Ni _1/3 Mn _1/3 Co _1/3 ) O 2 and LiMn ₂ O ₄ Discharge characteristics of the entire mixed cathode and discharge characteristics of each active material Comparison of potential change rate of mixed positive electrode, active material 1 and active material 2 An example of deterioration diagnosis according to the present invention It is a figure explaining the setting of the lower limit voltage (or upper limit voltage) in 2nd embodiment of this invention. Deterioration diagnosis apparatus according to third embodiment of the present invention

Hereinafter, embodiments of the present invention will be described with reference to the drawings. The following description shows specific examples of the contents of the present invention, and the present invention is not limited to these descriptions. Various modifications by those skilled in the art are within the scope of the technical idea disclosed in this specification. Changes and modifications are possible. In all the drawings for explaining the present invention, components having the same function are denoted by the same reference numerals, and repeated description thereof may be omitted.
<First embodiment>
FIG. 1 shows an example of an embodiment of a secondary battery deterioration diagnosis apparatus according to the present invention. Hereinafter, a lithium ion battery will be described as a secondary battery, but the present invention is not limited to this.

  The deterioration diagnosis apparatus 1 includes an input unit 11 to which battery information of charge / discharge characteristics, a data table of charge / discharge characteristics, and the like are input, a deterioration diagnosis unit 12 such as a CPU, a memory 13 such as a RAM and a ROM, and deterioration diagnosis information. The output unit 13 is an interface that outputs to the output.

  The input unit 11 includes a data table of charge / discharge characteristics of the battery measured separately, the type or charge / discharge characteristics and composition ratio of the battery reaction material (active material) included in the battery, and initial values of deterioration parameters used for deterioration diagnosis. Etc. are entered.

  The battery information input to the input unit 11 is output to the deterioration diagnosis unit 12 and used for information of deterioration diagnosis. Note that the degradation diagnosis method performed here will be described separately. The deterioration diagnosis unit 12 reads information from the memory 13 or writes information to the memory 13 as necessary, and calculates the battery by performing calculations based on the charge / discharge characteristics of the input battery reaction material and the deterioration parameter group. Estimate charge / discharge characteristics.

  In addition, the deterioration diagnosis unit 12 compares the estimated value of the charge / discharge characteristics of the battery with the input measurement value of the charge / discharge characteristics of the battery, and adjusts the value of the deterioration parameter group so that they match.

  Then, the deterioration diagnosis unit 12 outputs to the output unit 14 the value of the adjusted deterioration parameter group and the charge / discharge characteristics of the positive electrode, the negative electrode, and the battery calculated based on the value of the deterioration parameter.

  The deterioration diagnosis information output to the output unit 14 is output to the control unit 16 at a higher level than the display 15 of the personal computer or the deterioration diagnosis device 1 as necessary. The deterioration information can be confirmed by the information output to the display 15. The control unit 16 (for example, a battery module controller) receives information from the deterioration diagnosis device 1 and performs charge / discharge control of the battery. In addition, although the example which outputs to the display 15 of a personal computer was given as an example in which deterioration information is output here, you may end only with other display apparatuses or simple exchange of information.

  Next, a specific operation of the deterioration diagnosis unit 12 will be described with reference to FIG.

  First, when the deterioration diagnosis is started, the charge / discharge characteristics of the battery are measured and input to the input unit 11 in step S1. The charge / discharge characteristics of the battery measured here include capacity Q (Ah), battery voltage V (V), voltage change ΔV / ΔQ (V / Ah), capacity change ΔQ / ΔV (Ah / V) with respect to voltage change, state of charge SOC normalized with a predetermined reference capacity, heat capacity C (J / K), electric resistance R (Ω), or the like Value.

  In step S <b> 2, the measured charge / discharge characteristics described above are output from the input unit 11 to the deterioration diagnosis unit 12. The charge / discharge characteristics used in this deterioration diagnosis include the above-mentioned continuous energization or intermittent energization, during charging or discharging, the capacity Q (Ah), the battery voltage V (V), and the voltage change with respect to the capacity change. ΔV / ΔQ (V / Ah), capacitance change with respect to voltage change ΔQ / ΔV (Ah / V), state of charge SOC standardized with a predetermined reference capacity, heat capacity C (J / K), electric resistance R (Ω ) Or similar values may be used in combination.

  In the present embodiment, a case will be described in which a combination of capacity Q, battery voltage V, and voltage change ΔV / ΔQ during continuous discharge with a minute current is used.

  As the number of points in the measured data table, it is desirable that the combination of (Q, V, ΔV / ΔQ) is one point, and there are 10 or more data points between the upper limit value and the lower limit value of the battery voltage. More preferably, the number of data points is 50 or more.

  Subsequently, the charge / discharge characteristics of the active material stored in the memory 13 in step S <b> 3 are output to the deterioration diagnosis unit 12 and read into the deterioration diagnosis unit 12. When the type of active material or charge / discharge characteristics input to the degradation diagnosis unit 12 is input, it is as follows.

  For example, when the active material contained in the battery is known and the charge / discharge characteristics of the active material are held in the memory 13, the data is transmitted to the deterioration diagnosis unit 12.

  Further, for example, the active material contained in the battery is unknown, but it is assumed that the battery is included in a plurality of active materials whose charge / discharge characteristics are retained (stored) in the memory 13. When all the active materials to be processed are included, the deterioration diagnosis unit 12 reads the charge / discharge characteristics of any one or more input active materials from the memory 13 and uses them for subsequent deterioration diagnosis.

  On the other hand, when the active material contained in the battery is known or assumed, but the charge / discharge characteristics of the corresponding active material are not held (stored) in the memory 13 of the deterioration diagnosis device 1, Separately, the charge / discharge characteristics are obtained and input to the deterioration diagnosis unit 12. At this time, it is desirable to add the input charge / discharge characteristics of the active material to the library of the memory 13 and to read the charge / discharge characteristics by designating the active material in the subsequent operations.

  The charge / discharge characteristics of these active materials include capacity q (Ah / g) per unit weight, capacity Q (Ah), electrode potential V (V), potential change ΔV / ΔQ (V / Ah) with respect to capacity change, or ΔV / Δq (Vg / Ah), capacitance change with respect to potential change ΔQ / ΔV (Ah / V) or Δq / ΔV (Ah / Vg), state of charge SOC standardized with a predetermined reference capacity, within a specific material The lithium composition ratio x, specific heat c (J / Kg) or heat capacity C (J / K), electric resistance R (Ω), or similar values may be used in combination.

  In the present embodiment, a combination of capacity q, electrode potential V, and potential change ΔV / Δq during continuous discharge with a minute current will be described.

  As the number of points in the data table to be used, it is desirable that the combination of (q, V, ΔV / Δq) is one point, and there are 10 or more data points between the upper limit value and the lower limit value of the battery voltage. It is more desirable that there are 50 or more data points.

  In step S4, the composition ratio of the active material input in the deterioration diagnosis unit 12 is set, and the discharge curves of the positive electrode and the negative electrode are calculated. The parameters used in this step will be described in detail later.

  In the present embodiment, for example, the optimum value is determined using the previous diagnosis result. In that case, for example, the steepest descent method, the common benefit gradient method or the like may be used.

  Alternatively, a specific value may be given every time, and the optimum value may be determined based on the result.

  Furthermore, when there is no previous diagnosis result, the user may give an initial value.

  Subsequently, in step S5, the effective mass of the positive electrode and the negative electrode and the initial value of the capacity deviation are set in the deterioration diagnosis unit 12.

  In step S6, a battery discharge curve is calculated based on the information in steps S4 and S5. Details of the contents will be described below.

  Finally, in step S7, the actual charge / discharge curve measured in step S2 is compared with the charge / discharge curve of the battery calculated in step S6 to determine whether or not they match. If they match, the battery deterioration state is diagnosed based on the parameters calculated in step S6.

  On the other hand, if the actual charge / discharge curve measured in step S2 does not match the charge / discharge curve of the battery calculated in step S6, the process returns to step S4 to calculate the parameters of the battery again. The calculation is repeated until it matches the measured charge / discharge curve. If they match, the deterioration diagnosis ends.

  Hereinafter, each step as a point of the present invention will be described in more detail.

  First, the parameters used in step S4 will be briefly described.

  The composition ratio of the active material includes, for example, the weight or volume of the total active material contained in the positive electrode or the negative electrode, the weight or volume of the positive electrode or the negative electrode, the weight of the total active material included in the positive electrode or the negative electrode (effective The ratio of the effective weight or effective volume of each active material to the weight) or volume (effective volume) may be used. Moreover, you may use the effective weight or effective volume of each active material as it is.

  In the present embodiment, the case where the ratio of the effective weight of each active material to the total effective weight of the positive electrode or the negative electrode active material is used will be described.

  When there are N kinds of active materials constituting the mixed positive electrode or the mixed negative electrode, the composition ratio of the active material i (i = 1, 2, 3,..., N) is defined as ri, and 0 ≦ ri ≦ 1, r1 + r2 + ... should be selected so that + rN = 1. The composition ratio ri is used as an initial value for deterioration diagnosis.

In the present embodiment, the active material constituting the mixed positive electrode is two types of Li (Ni _1/3 Mn _1/3 Co _1/3 ) O ₂ and LiMn ₂ O ₄ , and the composition ratio is 0.5: 0.5, The case where the active material constituting the negative electrode is one kind of amorphous carbon will be described. That is, this example corresponds to the case where the active material species is known.

  The parameter group used for the deterioration diagnosis may be configured with parameters corresponding to the positive and negative electrode capacities and parameters indicating the correspondence between the positive electrode capacity or potential and the negative electrode capacity or potential.

  Examples of the former include total effective weights mp (g) and mn (g) of the positive and negative electrode active materials, and total effective volumes of the positive and negative electrode active materials.

  Examples of the latter include, for example, differences δp (Ah), δn (Ah) between the capacity origin of the charge / discharge characteristics of the battery and the capacity origin of the charge / discharge characteristics of the positive electrode and the negative electrode, and the charge / discharge characteristics of the positive electrode / negative electrode. There is a difference in capacity origin (δp−δn) (Ah), or a positive or negative potential at a predetermined battery voltage.

  In the present embodiment, a case will be described in which the total effective weights mp and mn of the positive and negative electrode active materials and the differences δp and δn between the positive and negative electrode capacity origins are used.

  As the process performed in step S4, the deterioration diagnosis unit 12 first creates charge / discharge characteristics of the mixed positive electrode and the mixed negative electrode based on the input information on the type and composition ratio of the active material and charge / discharge characteristics. What is necessary is just to determine a preparation method suitably with the value used as a charging / discharging characteristic and a structure ratio. Creation of more specific charge / discharge characteristics when a mixed positive electrode is used is performed with reference to FIGS. 3, 4, and 5.

FIG. 3 shows discharge characteristics per unit weight of the positive electrode active material 1, that is, Li (Ni _1/3 Mn _1/3 Co _1/3 ) O ₂ and the positive electrode active material 2, ie, LiMn ₂ O ₄ , of this embodiment. .

  In this embodiment, the capacity qpx, potential Vpx, and potential change ΔV / Δqpx of the mixed positive electrode are the capacity qp1, potential Vp1, potential change ΔV / Δqp1 of the positive electrode active material 1, and capacity qp2, potential Vp2, potential change of the positive electrode active material 2. It is expressed using ΔV / Δqp2 and mixing ratios rp1 and rp2.

  For example, when the capacity q with respect to the potential V is expressed as q (V), the capacity qpx (Vpx) when the potential Vpx of the mixed positive electrode is equal to the capacity qp1 of the positive electrode active material 1 and the positive electrode active material 2 corresponding to Vx, and qp2 is obtained from the data table, weighted by the mixture ratios rp1 and rp2, and added. That is, qpx (Vpx) = rp1 * qp1 (Vpx) + rp2 * qp2 (Vpx) may be obtained. Thus, since the mixing ratio rp1 and rp2 of each positive electrode active material is calculated to calculate the capacity qpx of the mixed positive electrode, it is possible to calculate an accurate capacity regardless of the mixing ratio of the positive electrode active material. It becomes possible. Therefore, by performing the prediction of the mixture ratio, the accuracy of battery control and life prediction based on the diagnosis result is improved.

  FIG. 4 shows the discharge characteristics qpx (Vpx) of the whole mixed positive electrode and the discharge characteristics rp1 * qp1 (Vpx) and rp2 * qp2 (Vpx) of the positive electrode active material 1 and the positive electrode active material 2 inside the mixed positive electrode. Vpx (qpx) indicating the potential Vpx with respect to the capacitor qpx can be obtained by switching the relationship of the qpx (Vpx). Further, the potential change ΔV / Δq (qpx) with respect to the capacitance qpx may be obtained from the difference between adjacent data points by arranging the obtained Vpx (qpx) data table in ascending or descending order of qpx.

  FIG. 5 (a) is a diagram showing the electrode potential V with respect to the capacity q per unit weight, and FIG. 5 (b) shows the potential change rate ΔV / Δq (qpx) of the mixed positive electrode obtained by the above procedure, The potential change rates ΔV / Δq (qp1) and ΔV / Δq (qp2) of the positive electrode active material 1 and the positive electrode active material 2 (that is, the data obtained by differentiating the data shown in FIG. 5A) are shown.

  In the deterioration diagnosis unit 12 of the present embodiment, the differential value of the voltage (shown in FIG. 5B) can be used for fitting. By using such a fitting, the curve shape is rich in change, and if it is not calculated with a correct value, it will not match the actual measurement value. Therefore, more accurate prediction is possible.

Further, by using the differential value of the voltage (shown in FIG. 5B), it is possible to make the constant term zero when differentiated. Therefore, the influence of the voltage drop included in the discharge curve of the battery is suppressed, the change due to the discharge curve specific to the material is emphasized, and the accuracy of deterioration diagnosis by fitting is further improved.
Regarding the discharge characteristics of the negative electrode, since the negative electrode active material is one kind of amorphous carbon in this embodiment, the discharge characteristics qn (Vn), Vn (qn), and ΔV / Δq (qn) of amorphous carbon are Use it as is. As described above, charge / discharge characteristics per unit weight of the active material of the mixed positive electrode and the negative electrode can be acquired by performing the above calculation in the deterioration diagnosis unit 12.

  A method for reproducing the discharge characteristics per unit weight of the positive electrode and the negative electrode and the discharge characteristics of the battery based on the deterioration parameters mp, mn, δp, and δn is as follows.

  The battery voltage V (Q) at the capacity Q of the battery is V (Q) = Vpx (qpx) Vn (qn) using the potential Vpx (qpx) of the mixed positive electrode and the potential Vn (qn) of the negative electrode. , And Q = mp * qpx + δp = mn * qn + δn.

  Similarly, the battery voltage change rate ΔV / ΔQ (Q) when the battery capacity Q is ΔV / ΔQ (Q) = (1 / mp) * ΔVpx / Δq (qpx) (1 / mn) * ΔVpx / Δq ( qn), and Q = mp * qpx + δp = mn * qn + δn. The method for calculating the deterioration parameter by this method corresponds to step S6 described above.

  FIG. 6A shows estimated values of discharge characteristics of the battery, the mixed positive electrode, and the negative electrode in the present embodiment.

  To compare the obtained estimated value of the discharge characteristic V (Q) or ΔV / ΔQ (Q) of the battery with the measured value of the input discharge characteristic of the battery and adjust the value of the composition ratio and the deterioration parameter group, For example, there is a method of comparing the sum of squares of the difference between the battery voltage V or the voltage change rate ΔV / ΔQ for the same capacity Q. What is necessary is just to hold | maintain the said square sum with respect to the value of a certain composition ratio and a degradation parameter group, and to search for the value of a composition ratio and a degradation parameter group that the said square sum becomes the minimum.

  The output unit 14 displays to the user the finally obtained types and composition ratios of the mixed positive electrode and mixed negative electrode active materials, the degradation parameter group, the data table of the discharge characteristics of the battery, mixed positive electrode, and mixed negative electrode, and the like. Output to device, battery operation controller, battery life predictor, etc.

  FIG. 6B is obtained by differentiating FIG. 6A with voltage. As with the positive electrode described above, the negative electrode can be handled using a differential value of the voltage.

In this case, the curve shape is rich in change, and if it is not calculated with a correct value, it will not match the actual measurement value. Therefore, more accurate prediction is possible.
<Second Embodiment>
In this embodiment, the major part is the same as in the first embodiment. The difference from the first embodiment is that an upper limit voltage or a lower limit voltage for using the battery is determined from the predicted potential of the mixed positive electrode (or mixed negative electrode when a mixed negative electrode is used).

  The deterioration diagnosis apparatus 1 is based on the estimated value of the charge / discharge characteristic of the battery that matches the measured value of the charge / discharge characteristic of the battery, and the charge / discharge characteristic of the mixed positive electrode and the mixed negative electrode corresponding to the estimated value of the charge / discharge characteristic of the battery. Thus, the upper and lower limits of the battery voltage are set so as not to exceed the usable potential region of each active material.

  Even with the same battery voltage, both the positive electrode potential and the negative electrode potential are often higher in a deteriorated battery than in a new battery. For this reason, when the high potential region of the positive electrode is used, there is a possibility that the electrolytic solution cannot withstand and is oxidatively decomposed to increase the internal resistance.

  Further, when the high potential / low potential region of the positive electrode is used, the crystal structure may change and the internal resistance may increase. Furthermore, depending on the manner of deterioration, when the battery is charged, the potential of the negative electrode is lowered, Li metal may be deposited on the surface of the negative electrode, or the electrolytic solution may be reduced and decomposed, resulting in deterioration of capacity and resistance.

  Therefore, the above-described deterioration can be suppressed by setting the predetermined upper limit voltage and lower limit voltage.

In this embodiment, as in Embodiment 1, Li (Ni _1/3 Mn _1/3 Co _1/3 ) O ₂ and LiMn ₂ O ₄ are used as the positive electrode active material, and amorphous carbon is used as the negative electrode active material. Will be described.

  In the present embodiment, the active material composition ratios rp1 and rp2 and the deterioration parameter groups mp, mn, δp, and δn obtained by the deterioration diagnosis described in the first embodiment, and the data table indicating the discharge characteristics of the battery, the positive electrode, and the negative electrode Is sent from the output unit 14 to the control unit 16. The control unit 16 calculates a battery voltage corresponding to the upper limit or the lower limit of the potential region where the predetermined active material can be used based on the received data.

  FIG. 7A is a diagram similar to FIG. 6A, but in FIG. 7A, a description of a method for determining a lower limit value is added. FIG. 7B is also the same diagram as FIG.

  The lower limit value is determined by the following procedure. (In this embodiment, the lower limit value is determined, but the upper limit value is also determined in the same procedure.) For example, as shown in FIG. 7B, the mixed positive electrode promotes deterioration in a region where the capacity is larger than 0.7 Ah. (A region where the capacity is larger than the inflection point indicated by the arrow in FIG. 7B is a region where deterioration is promoted.) That is, deterioration of the mixed positive electrode is promoted in a region where the potential is 3.7 V or less as shown in FIG. Therefore, the potential of the mixed positive electrode needs to be larger than 3.7V.

  In the first embodiment described above, in order to make the potential of the mixed positive electrode larger than 3.7 V, it is necessary to make it smaller than 0.7 Ah. Therefore, in an actual battery, the point where 0.7 Ah and the charge / discharge curve of the battery intersect, that is, 3.0 V is determined as the lower limit voltage.

As another method, when the available lower limit potential of Li (Ni _1/3 Mn _1/3 Co _1/3 ) O ₂ is Vp1l, the capacity Ql corresponding to Vp1l is set as a data table of the discharge characteristics of the positive electrode. Next, there is a method of obtaining the battery voltage Vl with respect to the capacity Ql from the battery discharge characteristic data table. A battery voltage corresponding to the upper limit potential, a battery voltage corresponding to the upper and lower limit potential of LiMn ₂ O ₄ , and a battery voltage corresponding to the upper and lower limit potential of amorphous carbon are obtained. The operating range of the battery voltage can be determined so as not to exceed the upper and lower limit potentials of all the active materials.

  The upper limit voltage can also be determined by one of the above two methods.

  In the present invention, since the charge / discharge characteristics of the active material constituting the mixed positive electrode can be predicted, the upper limit voltage or the lower limit voltage can be set based on the information of each active material type.

  In this case, it becomes possible to slow down the deterioration rate of the active material whose deterioration is promoted, so that the life of the battery can be extended.

As described above, in the present embodiment, it is possible to set the upper limit voltage and the lower limit voltage of the use voltage based on the predicted potential information of the mixed positive electrode. Therefore, it becomes possible to set an appropriate upper limit voltage and lower limit voltage for the mixed positive electrode, and to suppress deterioration of the battery. The upper limit value and the lower limit value can be set by either the deterioration diagnosis unit 12 or the control unit 16.
<Third embodiment>
In another embodiment of the secondary battery deterioration diagnosis device 1 according to the present invention, the remaining battery life is determined based on the battery deterioration diagnosis result and a predetermined capacity lower limit value. In the present embodiment, as in Embodiment 1, Li (Ni _1/3 Mn _1/3 Co _1/3 ) O ₂ and LiMn ₂ O ₄ are used as the positive electrode active material, and amorphous carbon is used as the negative electrode active material. explain.

  In the present embodiment, the deterioration diagnosis described in the first embodiment has already been performed on the discharge characteristics of batteries having the same or the same configuration measured in different usage periods.

  A diagram of the degradation diagnosis apparatus 100 in the present embodiment is shown in FIG. The type and composition ratio of the active material obtained by the deterioration diagnosis, the value of the deterioration parameter group, and the battery use status at the time of deterioration diagnosis are held in the memory 13 or input from the outside by the input unit 11. These data are sent to the prediction unit 17. Also, from the input unit 11, a function having the usage status of the composition ratio and the deterioration parameter group as a variable is input.

  Examples of the function form include a straight line, a quadratic function, an exponential function, and a logarithmic function. Examples of the variable include the period of use, the number of charge / discharge cycles, the accumulated charge / discharge amount, temperature, battery voltage, and electrode potential. These functions may be determined by the prediction unit based on data input from the input unit.

  The usage status that becomes the function variable is input from the input section. The predicting unit 17 calculates the composition ratio (mixing ratio) and the deterioration parameter group for each predetermined period based on the input variables and functions, and predicts the charge / discharge characteristics of the battery based on the calculation result.

  Moreover, the magnitude relationship with a predetermined | prescribed upper / lower limit is determined with respect to the charging / discharging characteristic of the estimated battery. When the charging / discharging characteristic of the battery exceeds or falls below a predetermined upper limit value or lower limit value at a certain time t1 in the prediction calculation, this time t1 is regarded as the life of the battery. For example, the predetermined value means that the battery capacity is 70% or less of the initial value, the internal resistance of the battery is 200% or more of the initial value.

  The output unit outputs the time t1 or the time T1 from the current time to the time t1. When the time T1 is shorter than the predetermined shortest time T2, a warning is output. As a specific example of each value, the time point t1 may be set as the date and time when the lifetime comes, the time T1 as the remaining lifetime, the predetermined shortest time T2 as the number of days until the next periodic inspection, and the like. In this way, a warning can be issued when the battery becomes unusable before inspection.

  With the above procedure, the lifetime of the secondary battery using the mixed electrode can be predicted.

  As described above, the present invention is characterized by the following points. Therefore, even when a mixed electrode is used, it is possible to reliably perform deterioration diagnosis.

  First, in the present invention, when estimating the charge / discharge curve of the positive electrode active material, the mixing ratio rp1, rp2 of each positive electrode active material is calculated to calculate the capacity qpx of the mixed positive electrode. Even if it is a ratio, it is possible to calculate an accurate capacity.

  In the present invention, the mixing ratios rp1 and rp2 of the positive electrode active materials are multiplied by the capacity qp1 (Vpx) of the positive electrode active material 1 and the capacity qp1 (Vpx) of the positive electrode active material 2, respectively. It is possible to estimate the mixed positive electrode capacity more accurately than simply calculating the mixed positive electrode capacity qpx based solely on the mixing ratio.

  In the present invention, the estimated charge / discharge curve is compared with the actual charge / discharge curve, and the sum of squares of the difference between the battery voltage V or the voltage change rate ΔV / ΔQ with respect to the same capacity Q is calculated. The current capacity degradation rate can be estimated. For this reason, it is possible to estimate the capacity deterioration more accurately than the conventional method.

  In the present invention, the upper limit value of the battery voltage is set based on the charge / discharge characteristics of the mixed positive electrode corresponding to the estimated value of the charge / discharge characteristics of the battery. That is, using the data of each active material used when estimating the charge / discharge characteristics of the mixed positive electrode, a plurality of active materials used are estimated, and the upper limit operating voltage and the lower limit operating voltage of each active material are calculated. By controlling so that it may satisfy | fill, it becomes possible to provide the diagnosis and battery system which suppressed degradation of each active material of a mixed positive electrode.

  In this case, the active material that is most deteriorated may be determined by the above-described method, and may be controlled so as to satisfy the upper limit use voltage and the lower limit use voltage corresponding to the active material. In this case, since it becomes possible to suppress further deterioration of the active material that has been most deteriorated, it is possible to control to extend the life of the battery.

  Further, in the present invention, by determining whether or not the battery can be used based on the deterioration diagnosis result of the secondary battery obtained by the deterioration diagnosis method, even if the mixed positive electrode is used, It becomes possible to determine availability.

  Further, according to the present invention, the remaining life of the battery can be calculated more accurately by acquiring the remaining life of the secondary battery based on the diagnosis result obtained by the diagnosis earlier than a certain diagnosis result. Become.

  In addition, as a method of reliably diagnosing deterioration when a mixed positive electrode or a mixed negative electrode is used without using the above-described method, it is conceivable to store in advance charge / discharge curves of the mixed positive electrode or mixed negative electrode of any mixing ratio. However, there is a problem that the storage capacity necessary for the system becomes extremely large for a mixed positive electrode or mixed negative electrode using three or more kinds of active materials.

  Therefore, by using the above-described deterioration diagnosis method, it becomes possible to cope with charge / discharge curves of mixed positive electrodes or mixed negative electrodes of any mixing ratio without extremely increasing the storage capacity of the system.

  In addition, although the case where the mixed positive electrode was mainly used was demonstrated in the embodiment mentioned above, it can utilize even when a mixed negative electrode is used by replacing the positive electrode mentioned above with the negative electrode and using the present invention.

  Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and various designs can be made without departing from the spirit of the present invention described in the claims. It can be changed. For example, the above-described embodiment has been described in detail for easy understanding of the present invention, and is not necessarily limited to one having all the configurations described. Further, a part of the configuration of an embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of an embodiment. Furthermore, it is possible to add, delete, and replace other configurations for a part of the configuration of each embodiment.

DESCRIPTION OF SYMBOLS 1 Degradation diagnostic apparatus 11 Input part 12 Degradation diagnostic part 13 Memory 14 Output part 15 Display 16 Control part

Claims (7)

In a secondary battery deterioration diagnosis method for diagnosing deterioration of a secondary battery having a mixed positive electrode or a mixed negative electrode formed by mixing at least two active materials,
A first step of acquiring charge / discharge characteristics of the secondary battery;
A second step of acquiring information on a plurality of active materials stored in a memory;
A third step of determining a mixing ratio of the positive electrode or the negative electrode from information of the plurality of active materials and the charge / discharge characteristics;
A fourth step of predicting charge / discharge characteristics of the secondary battery based on the mixing ratio determined in the third step;
When comparing the predicted charge / discharge characteristics and the charge / discharge characteristics acquired in the first step, and when the predicted charge / discharge characteristics and the charge / discharge characteristics acquired in the first step match, A secondary battery comprising a fifth step of calculating a deterioration parameter based on the potential of the mixed positive electrode predicted using a mixing ratio or the potential of the mixed negative electrode predicted using the mixing ratio. Deterioration diagnosis method of The deterioration diagnosis method for a secondary battery according to claim 1,
The degradation parameter of a secondary battery, wherein the degradation parameter is calculated based on a secondary battery capacity, a capacity of the mixed positive electrode, and a capacity of the mixed negative electrode. The deterioration diagnosis method for a secondary battery according to claim 2,
The information on the active material includes a capacity per unit weight q (Ah / g), a capacity Q (Ah), an electrode potential V (V), a potential change ΔV / ΔQ (V / Ah) or ΔV / Δq ( Vg / Ah), capacitance change ΔQ / ΔV (Ah / V) or Δq / ΔV (Ah / Vg), state of charge SOC, specific heat c (J / Kg) or heat capacity C (J / K), electric resistance A method for diagnosing deterioration of a secondary battery, wherein the information is any information of R (Ω). In a secondary battery system having a secondary battery having a mixed positive electrode or a mixed negative electrode obtained by mixing at least two active materials, and a deterioration diagnosis device for diagnosing deterioration of the secondary battery,
The deterioration diagnosis apparatus includes an input unit, a deterioration diagnosis unit, and a memory.
The input unit acquires the charge / discharge characteristics of the secondary battery,
The deterioration diagnosis unit acquires information on a plurality of active materials stored in a memory and charge / discharge characteristics of the secondary battery, and mixes the positive electrode or the negative electrode based on the information on the plurality of active materials and the charge / discharge characteristics. And predicting the charge / discharge characteristics of the secondary battery based on the determined mixing ratio,
When the predicted charge / discharge characteristics and the charge / discharge characteristics of the secondary battery coincide with each other by comparing the predicted charge / discharge characteristics and the charge / discharge characteristics of the secondary battery, the mixture ratio is predicted. A secondary battery system, wherein a deterioration parameter is calculated based on the potential of the mixed negative electrode or the potential of the mixed negative electrode predicted using the mixing ratio. The secondary battery system according to claim 6,
The secondary battery system, wherein the deterioration parameter is calculated based on a battery capacity, a capacity of the mixed positive electrode, and a capacity of the mixed negative electrode. The secondary battery system according to claim 5,
The deterioration diagnosis unit determines an upper limit value or a lower limit value of a use voltage of the secondary battery based on the predicted potential of the mixed positive electrode or the predicted potential of the mixed negative electrode. system. The secondary battery system according to claim 6,
The deterioration diagnosis apparatus includes a prediction unit that predicts a charge / discharge characteristic of the secondary battery based on the mixture ratio and the deterioration parameter calculated at regular intervals.

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