JPWO2013157132A1 - Secondary battery system, secondary battery deterioration state judgment method - Google Patents

Abstract

The secondary battery system includes a secondary battery, a charge / discharge control unit, a differential curve calculation unit that calculates a differential curve Q-dV / dQ, and a deterioration state that calculates a feature point parameter in the differential curve Q-dV / dQ. A calculation unit and a battery state detection unit that determines a deterioration state of the secondary battery. The deterioration state calculation unit uses, as a feature point parameter, a difference σi between the battery capacity Q1 at the first feature point and the battery capacity Q2 at the second feature point of the differential curve Q-dV / dQ within a predetermined state detection range. And at least one of the difference hi between the differential value dV1 / dQ1 at the first feature point and the differential value dV2 / dQ2 at the second feature point. The battery state detection unit is based on at least one of a comparison result between the difference σi and the initial value σ0 of the difference σi stored in advance and a comparison result between the difference hi and the initial value h0 of the difference hi stored in advance. The deterioration state of the secondary battery is determined.

Description

  The present invention relates to a secondary battery system and a secondary battery deterioration state determination method.

  Conventionally, a value of dV / dQ, which is a ratio of a change amount dV of the battery voltage V to a change amount dQ of the storage amount Q at the time of charge / discharge of the secondary battery, is calculated, and the values of the storage amount Q and the dV / dQ values A technique for determining a deterioration state of a secondary battery based on a Q-dV / dQ curve representing the relationship is known. Patent Document 1 discloses that when the difference value of the storage amount Q at two specific feature points selected from a plurality of feature points appearing on the Q-dV / dQ curve is smaller than a preset reference difference value, A secondary battery system for determining that the secondary battery has deteriorated is disclosed.

Japanese Unexamined Patent Publication No. 2010-257984

  In the conventional secondary battery deterioration determination method used in the secondary battery system disclosed in Patent Document 1, in order to make two feature points appear at distant positions on the Q-dV / dQ curve, It is necessary to change the state of charge of the battery greatly. Therefore, it cannot be applied when the change in the state of charge of the secondary battery is small. Further, the present invention cannot be applied to a case where the characteristic points on the Q-dV / dQ curve are difficult to discriminate due to progress of deterioration of the secondary battery. As described above, in the conventional secondary battery deterioration determination method, the deterioration state of the secondary battery may not be accurately determined.

  An object of the present invention is to eliminate the above-described problems in the conventional secondary battery deterioration determination method and accurately determine the deterioration state of the secondary battery.

A secondary battery system according to the present invention includes a secondary battery having a positive electrode, a negative electrode including an active material that undergoes phase change due to charge / discharge, a charge / discharge control unit that controls charge / discharge of the secondary battery, and a secondary battery. A differential curve calculation unit that calculates a differential curve Q-dV / dQ indicating a relationship between the battery capacity Q of the battery and a differential value dV / dQ that is a ratio of the change amount dV of the battery voltage V to the change amount dQ of the battery capacity Q; A deterioration state calculation unit that calculates the parameter of the feature point in the differential curve Q-dV / dQ, and a battery state detection unit that determines the deterioration state of the secondary battery based on the parameter of the feature point. Deterioration state calculating unit, as parameters of the feature point, differential curve Q-dV / dQ in the battery capacity Q _1, the state detection range of the first feature point of the differential curve Q-dV / dQ in a predetermined state detection range And the differential value dV ₁ / dQ ₁ at the first feature point of the differential curve Q-dV / dQ within the state detection range and the difference σ _i with the battery capacity Q ₂ at the second feature point difference _{h i} of the differential value _dV 2 / dQ ₂ at the second characteristic point of the differential curve Q-dV / dQ in calculates at least one of. Battery state detecting unit, a result of comparison between the initial value sigma ₀ of the difference sigma _i and the pre-stored differential sigma _i, and, in comparison with the initial value h ₀ of the difference h _i a previously stored difference h _i The deterioration state of the secondary battery is determined based on at least one.
A secondary battery deterioration state determination method according to the present invention is a secondary battery deterioration state determination method that includes a positive electrode and a negative electrode containing an active material that undergoes phase change by charging and discharging. A differential curve Q-dV / dQ indicating the relationship between the battery capacity Q at the time and the differential value dV / dQ, which is the ratio of the change amount dV of the battery voltage V to the change amount dQ of the battery capacity Q, is calculated. as a parameter of the feature points in the dV / dQ, of the differential curve Q-dV / dQ in the battery capacity Q _1, the state detection range of the first feature point of the differential curve Q-dV / dQ in a predetermined state detection range the The difference σ _{i from} the battery capacity Q _{2 at two} feature points, the differential value dV ₁ / dQ ₁ at the first feature point of the differential curve Q-dV / dQ within the state detection range, and the differentiation within the state detection range Curve Q-dV / dQ Comparison between the difference h _i, the calculated at least one difference sigma _i the initial value sigma ₀ of previously stored the difference sigma _i the differential value dV 2 _/ dQ ₂ at the characteristic points, and the difference h _i And the deterioration value of the secondary battery are determined based on at least one of the comparison results between the difference H _i stored in advance and the initial value h ₀ of the difference h _i .

  According to the present invention, it is possible to accurately determine the deterioration state of the secondary battery.

1 is a partially cutaway perspective view of a non-aqueous secondary battery used in a secondary battery system according to an embodiment of the present invention. 1 is a schematic configuration diagram of a secondary battery system according to an embodiment of the present invention. It is a system block diagram of the battery controller 51 and the battery system controller 52 which concern on one Embodiment of this invention. It is a flowchart of the judgment process of the battery deterioration state in the secondary battery system which concerns on one Embodiment of this invention. It is a figure which shows the example of the discharge curve (QV) of the assembled battery. It is a figure which shows the example of the discharge differential curve (Q-dV / dQ) of the assembled battery. It is the figure which expanded the part of the peak shape in a state detection range among the discharge differential curves (Q-dV / dQ) of the assembled battery. It is a figure which shows the example of the initial value of the discharge differential curve (Q-dV / dQ) of the assembled battery. It is the figure which expanded the part of the peak shape in a state detection range among the initial values of the discharge differential curve (Q-dV / dQ) of the assembled battery. It is a flowchart of the pre-processing in the secondary battery system which concerns on one Embodiment of this invention.

  Hereinafter, a secondary battery system according to an embodiment of the present invention will be described with reference to the drawings. Here, the embodiment described below shows one application example of the present invention. The present invention is not limited to this content, and various changes and modifications can be made by those skilled in the art within the scope of the technical idea disclosed in this specification.

  In the following embodiments, the case where the deterioration state of the battery is determined by paying attention to the discharge characteristics of the battery will be described. Judgment can be made. That is, according to the present invention, the deterioration state of the battery is determined based on the change in the battery capacity during charging / discharging of the battery. When determining the deterioration state of the battery from the charging characteristics of the battery, “discharge” may be replaced with “charge” in the following description.

  FIG. 1 is a partially cutaway perspective view of a non-aqueous secondary battery (hereinafter also simply referred to as a battery) used in a secondary battery system according to an embodiment of the present invention. The battery shown in FIG. 1 has a positive electrode plate 11 that functions as a positive electrode and a negative electrode plate 12 that functions as a negative electrode.

  The battery shown in FIG. 1 can be manufactured, for example, as follows. First, a positive electrode plate 11 using a composite lithium oxide or the like as a positive electrode active material and a negative electrode plate 12 using a material holding lithium ions as a negative electrode active material are spirally formed around a winding shaft 21 via a separator 13. The electrode winding group 22 is produced by winding the electrode. Next, the produced electrode winding group 22 is accommodated inside a cylindrical battery can 26 having a bottom, and the negative electrode tab 24 led out from the lower part of the electrode winding group 22 is welded to the bottom of the battery can 26, The positive electrode tab 23 led out from the upper part of the electrode winding group 22 is welded to a battery lid 25 attached with an insulating gasket (not shown) around it. Then, after injecting a predetermined electrolyte into the battery can 26, the battery can 26 is sealed by attaching the battery lid 25 to the opening of the battery can 26 and caulking.

  The positive electrode plate 11 is coated with a positive electrode active material and a positive electrode conductive material, and these are bonded to the positive electrode plate 11 with a positive electrode binder. Examples of the positive electrode active material include lithium cobaltate and modified products thereof (such as lithium cobaltate in which aluminum or magnesium is dissolved), lithium nickelate and modified products thereof (partly nickel-substituted cobalt). , Lithium manganate and modified products thereof, and composite oxides thereof (nickel, cobalt, manganese), and the like. In addition, an olivine-based compound or a spinel-type lithium manganese compound can be used alone as a positive electrode active material, or an oxide obtained by combining them can be used as a positive electrode active material.

  Examples of the positive electrode conductive material include carbon blacks such as acetylene black, ketjen black (registered trademark), channel black, furnace black, lamp black, thermal black, and various graphites, or a combination of these. Can be used.

  As the positive electrode binder, for example, polyvinylidene fluoride (PVdF), a modified polyvinylidene fluoride, polytetrafluoroethylene (PTFE), a rubber particle binder having an acrylate unit, or the like can be used. Moreover, it is also possible to mix the acrylate monomer and acrylate oligomer which introduce | transduced the reactive functional group into the binder for positive electrodes.

  On the other hand, a negative electrode active material and a negative electrode conductive material are applied to the negative electrode plate 12, and these are bound to the negative electrode plate 12 by a negative electrode binder. As the negative electrode active material, a material that undergoes phase change due to charging / discharging of the battery is used. For example, various kinds of natural graphite, artificial graphite, silicon-based composite materials such as silicide, and the like can be used as the negative electrode active material.

  As the negative electrode conductive material, for example, carbon blacks such as acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, and various graphites are used alone, as in the case of the positive electrode conductive material described above. Or these can be used combining multiple types.

  As the binder for the negative electrode, various binders such as PVdF and modified products thereof can be used in the same manner as the binder for the positive electrode described above. From the viewpoint of improving the lithium ion acceptability, a small amount of cellulose resin such as carboxymethyl cellulose (CMC) is added to the styrene-butadiene copolymer (SBR) or its modified product to make these negative electrodes. More preferably, it is used in combination as a binder.

  As long as the separator 13 has a composition that can withstand the use range of the lithium ion secondary battery, the material and the structure thereof are not particularly limited. However, it is common and preferable to use the olefin-based microporous film such as polyethylene or polypropylene as the separator 13 in a single layer or a plurality of layers. The thickness of the separator 13 is not particularly limited, but is preferably about 10 to 40 μm.

  With respect to the electrolyte injected into the battery can 26, various lithium compounds such as LiPF6 and LiBF4 can be used as the electrolyte salt. As the solvent, ethylene carbonate (EC), dimethyl cardnate (DMC), diethyl carbonate (DEC), or the like can be used alone or in combination of two or more thereof. Furthermore, in order to form a good film on the positive electrode plate 11 or the negative electrode plate 12 and to ensure stability during overcharge / discharge, vinylene carbonate (VC), cyclohexylbenzene (CHB), or a modified product thereof is used. You may add to electrolyte solution.

  As shown in FIG. 1, the shape of the electrode winding group 22 is not necessarily a true cylindrical shape, and may be, for example, a long cylindrical shape having an elliptical cross section or a prism shape having a rectangular cross section. As a typical form of the battery used in the secondary battery system of this embodiment, as shown in FIG. 1, a cylindrical battery can 26 in which the electrode winding group 22 is accommodated is filled with an electrolytic solution. It is preferable that the positive electrode tab 23 and the negative electrode tab 24 for taking out current from the positive electrode plate 11 and the negative electrode plate 12 are sealed in a state of being welded to the battery lid 25 and the battery can 26, respectively. However, it is not particularly limited to such a form.

  For the battery can 26, it is preferable to use a material excellent in strength, corrosion resistance, workability, etc., such as iron or stainless steel plated for corrosion resistance. It is also possible to use an aluminum alloy or various engineering plastics in combination with a metal. The material used for the battery can 26 is not particularly limited to these.

  Next, the secondary battery system according to the present embodiment will be described with reference to FIG. FIG. 2 is a schematic configuration diagram of a secondary battery system according to an embodiment of the present invention. This secondary battery system includes a battery system controller 52 and a plurality of secondary battery modules 40 connected in parallel to the battery system controller 52.

  The secondary battery module 40 includes an assembled battery 41, a current detection unit 42, a voltage detection unit 43, a temperature detection unit 44, a current control unit 45, and a battery controller 51.

  The assembled battery 41 is configured by combining a plurality of batteries (single cells) as described in FIG. 1 in series, in parallel, or in series-parallel. The number of unit cells and the combination form in the assembled battery 41 are determined so that a desired output voltage and battery capacity can be achieved.

  The voltage detection part 42 is a part for detecting the battery voltage of the assembled battery 41, and is constituted by a voltmeter or the like. The voltage detection unit 42 measures the battery voltage for each unit cell constituting the assembled battery 41 as the battery voltage of the assembled battery 41, or measures the battery voltage in units of battery groups in which a plurality of unit cells are connected in series. Or the battery voltage can be measured for the assembled battery 41 as a whole. The battery voltage measured by the voltage detection unit 42 is not particularly limited to this content.

  The current detection unit 43 is a part for detecting the charging / discharging current of the assembled battery 41, and includes an ammeter or the like. As an ammeter used in the current detection unit 43, for example, a galvanometer, an ammeter using a shunt resistor, a clamp meter, or the like can be considered. Note that the current detection method in the current detection unit 43 is not limited to this, and any method can be used as long as the current value flowing in the assembled battery 41 is detected.

  The temperature detection unit 44 is a part for detecting the temperature of the assembled battery 41, and is configured using a temperature sensor such as a thermocouple or a thermistor. In addition, the temperature sensor used in the temperature detection part 44 is not specifically limited to these contents. As a part of the assembled battery 41 from which the temperature detection unit 44 detects the temperature, for example, the surface or the inside of the assembled battery 41 can be considered. Further, the surface temperature of the housing in which the assembled battery 41 is stored, the ambient temperature of the assembled battery 41, and the like may be detected as the temperature of the assembled battery 41.

  The voltage detection unit 42, the current detection unit 43, and the temperature detection unit 44 described above are parts for detecting the state of the assembled battery 41. That is, the secondary battery module 40 uses the voltage detection unit 42, the current detection unit 43, and the temperature detection unit 44 to detect the battery voltage, the charge / discharge current, and the temperature of the assembled battery 41, respectively. Thus, the state of the assembled battery 41 can be known.

  The current controller 45 is a part for controlling the charge / discharge current of the assembled battery 41, and its operation is controlled by the battery controller 51. For example, the current control unit 45 can be realized by controlling opening / closing of a switch such as a semiconductor switch or a mechanical switch according to the magnitude of the charge / discharge current. Further, a power conversion device such as an inverter or a DC-DC converter may be used as the current control unit 45. As long as the battery controller 51 can control the current value when the assembled battery 41 is charged and discharged, the current control unit 45 is not limited to these.

  The battery controller 51 controls charging / discharging of the assembled battery 41 in accordance with a command from the battery system controller 52, and includes a microcomputer that operates according to a predetermined program, a CPU, a ROM, a RAM, and the like. The battery voltage, charge / discharge current, and temperature of the assembled battery 41 detected by the voltage detector 42, the current detector 43, and the temperature detector 44 are output to the battery controller 51. The battery controller 51 calculates the battery capacity Q of the assembled battery 41 at the time of discharging based on the state detection results of these assembled batteries 41, and the change amount of the battery voltage V with respect to the change amount dQ of the battery capacity Q. A differential value dV / dQ which is a ratio of dV is obtained. Then, a discharge differential curve (Q−dV / dQ) indicating the relationship between the battery capacity Q and the differential value dV / dQ is calculated, and data of the discharge differential curve (Q−dV / dQ) is transmitted to the battery system controller 52. To do. In addition, a timer is provided in the battery controller 51, and a time related to charging / discharging of the assembled battery 41, for example, an elapsed time after starting discharging, is measured using the timer.

  Note that the battery controller 51 may calculate a discharge differential curve (Q−dV / dQ) for the entire assembled battery 41, or each unit cell constituting the assembled battery 41 or a plurality of unit cells in series. A discharge differential curve (Q-dV / dQ) may be calculated for each connected battery group.

  Similar to the battery controller 51, the battery system controller 52 includes a CPU, a ROM, a RAM, and the like, and includes a microcomputer that operates according to a predetermined program. The battery system controller 52 determines the deterioration state of the assembled battery 41 of each secondary battery module 40 based on the data of the discharge differential curve (Q−dV / dQ) transmitted from the battery controller 51 of each secondary battery module 40. to decide. Based on this determination result, the battery system controller 52 outputs a charge / discharge control command to the battery controller 51 of each secondary battery module 40. The battery controller 51 of each secondary battery module 40 performs charge / discharge control of the corresponding assembled battery 41 in response to a command from the battery system controller 52.

  The battery system controller 52 can determine the deterioration state of the assembled battery 41 for each unit of calculation of the discharge differential curve (Q−dV / dQ) in the battery controller 51 described above. That is, when the discharge differential curve (Q−dV / dQ) is calculated for the entire assembled battery 41, the battery system controller 52 determines the deterioration state for the entire assembled battery 41. On the other hand, when a discharge differential curve (Q−dV / dQ) is calculated for each single cell constituting the assembled battery 41, or for each battery group in which a plurality of single cells are connected in series, the discharge differential curve (Q−dV / dQ). ) Is calculated, the battery system controller 52 determines the deterioration state of the assembled battery 41 for each single cell or for each battery group.

  FIG. 3 is a system block diagram of the battery controller 51 and the battery system controller 52 according to an embodiment of the present invention. As shown in FIG. 3, the battery controller 51 functionally includes a charge / discharge control unit 511 and a differential curve calculation unit 512. Further, the battery system controller 52 functionally includes a data recording unit 521, a deterioration state calculation unit 522, and a battery state detection unit 523.

  The charge / discharge control unit 511 controls charging / discharging of the assembled battery 41 in accordance with a command from the battery system controller 52. In addition, the battery voltage, charge / discharge current, and temperature detection results of the assembled battery 41 are received from the voltage detection unit 42, the current detection unit 43, and the temperature detection unit 44, and are output to the differential curve calculation unit 512.

  The differential curve calculation unit 512 is based on the detection results of the battery voltage, the charge / discharge current and the temperature of the assembled battery 41 output from the charge / discharge control unit 511, the elapsed time from the start of discharge measured by the timer described above, and the like. Then, the battery capacity Q of the assembled battery 41 at the time of discharging is calculated every predetermined time, the ratio of the change amount dV of the battery voltage V to the change amount dQ of the battery capacity Q is obtained, and the differential value dV / dQ is calculated. Then, a discharge differential curve (Q−dV / dQ) indicating the relationship between the battery capacity Q and the differential value dV / dQ is calculated and transmitted to the battery system controller 52.

  The data recording unit 521 records the data of the discharge differential curve (Q−dV / dQ) transmitted from the battery controller 51 of each secondary battery module 40. Further, initial data of the discharge differential curve (Q-dV / dQ) for the assembled battery 41 of each secondary battery module 40, that is, data of the discharge differential curve (Q-dV / dQ) before the use of the assembled battery 41 is started. Are also recorded and stored in the data recording unit 521.

  The deterioration state calculation unit 522 determines the deterioration state of the assembled battery 41 of each secondary battery module 40 based on the data of the discharge differential curve (Q−dV / dQ) recorded in the data recording unit 521. Calculate the parameters. A specific parameter calculation method by the deterioration state calculation unit 522 will be described later.

  The battery state detection unit 523 determines the deterioration state of the assembled battery 41 in each secondary battery module 40 based on the parameter calculated by the deterioration state calculation unit 522. As a result, when it is determined that the assembled battery 41 has deteriorated, a predetermined command is output to the battery controller 51 connected to the assembled battery 41. Upon receiving this command, the battery controller 51 controls the current control unit 45 to change the maximum allowable current during charging / discharging of the assembled battery 41 or change the maximum allowable battery voltage. In addition, when it is determined that the battery pack 41 has deteriorated and reached the end of its life, a predetermined signal indicating that the battery pack 41 should be replaced is output to the outside.

  As described above, according to the secondary battery system of the present embodiment, a plurality of secondary battery modules 40 including the assembled battery 41 and the battery controller 51 are connected in parallel to the battery system controller 52. In each secondary battery module 40, the battery controller 51 detects the state of the assembled battery 41, and based on the state of the assembled battery 41, a discharge differential curve (Q that indicates the relationship between the battery capacity Q and the differential value dV / dQ. -DV / dQ). In the battery system controller 52, the life of the assembled battery 41 is determined using this discharge differential curve (Q-dV / dQ), and a command to the battery controller 51 is output based on the determination result. Perform charging control. Thereby, the capacity | capacitance fall of the assembled battery 41 can be suppressed and a long-life secondary battery system can be provided.

  Next, a method for determining a battery deterioration state in the secondary battery system of the present embodiment will be described. FIG. 4 is a flowchart of a battery deterioration state determination process in the secondary battery system according to the embodiment of the present invention.

  In the following description, the charge / discharge control method of the present invention will be described with reference to the results of a verification test using the following lithium ion secondary battery. In this lithium ion secondary battery, as a positive electrode active material, a material obtained by mixing LiMn2O4 and LiNi0.8Co0.15Al0 · 05 in a ratio of 3: 7 is used as a positive electrode active material, and carbon black is used as a positive electrode conductive material. Polyvinylidene fluoride was used as the adhesive. Further, natural graphite was used as the negative electrode active material, and a material in which a styrene-butadiene copolymer (binder resin) and carboxymethyl cellulose were mixed at a ratio of 98: 1: 1 was used as the negative electrode binder. Using these materials, a cylindrical lithium ion secondary battery having a diameter of 18 mm and a length of 65 mm was manufactured as a verification battery, and a verification test was performed using this.

  When the charge / discharge control is started in step S001 of FIG. 4, the battery system controller 52 transmits a command to start discharging the assembled battery 41 to the battery controller 51 of each secondary battery module 40. In response to this command, the charge / discharge control unit 511 of each battery controller 51 starts discharging the corresponding assembled battery 41.

  After starting the discharge of the assembled battery 41, in each secondary battery module 40, the voltage detection unit 42 determines the battery voltage V of the assembled battery 41, the current detection unit 43 calculates the discharge current I of the assembled battery 41, and the temperature detection unit 44. Thus, the battery temperature T of the assembled battery 41 is measured every predetermined time. Further, the discharge time t (elapsed time from the start of discharge) is measured by a timer.

  In step S002, the differential curve calculation unit 512 in the battery controller 51 of each secondary battery module 40 calculates the battery capacity Q from the product of the measured discharge current I and the discharge time t. Then, a discharge curve (Q-V) is calculated from the calculation result of the battery capacity Q and the measurement result of the battery voltage V.

  FIG. 5 shows an example of a discharge curve (QV) calculated from a verification test using the verification battery as described above. In FIG. 5, the horizontal axis represents the battery capacity Q (Ah), and the vertical axis represents the battery voltage V (V).

  In step S003, the differential curve calculation unit 512 calculates a differential value dV / dQ that is a ratio of the change amount dV of the battery voltage V to the change amount dQ of the battery capacity Q from the discharge curve (Q-V) calculated in step S002. The discharge differential curve (Q−dV / dQ) is calculated from the relationship between this and the amount of change dQ of the battery capacity Q.

  FIG. 6 shows an example of the discharge differential curve (Q-dV / dQ) of the assembled battery 41 calculated from the discharge curve (Q-V) of FIG. In FIG. 6, the horizontal axis represents the battery capacity Q (Ah), and the vertical axis represents the differential value dV / dQ (V / Ah). This discharge differential curve (Q-dV / dQ) is the discharge differential curve (Q-dV / dQ) in the deteriorated state when the battery capacity when discharged at 1 C is reduced by 3.3% compared to the initial state. It is an example. Note that 1C represents a current value at which a theoretical electric capacity that can be theoretically accumulated at a maximum by a lithium ion battery can be discharged in one hour. In FIG. 6, a portion surrounded by a dotted line indicates a state detection range used in the process of step S004 described later. This state detection range is set in advance so as to include a characteristic peak shape based on an initial value of a discharge differential curve (Q-dV / dQ) shown in FIG.

  After calculating the discharge differential curve (Q−dV / dQ) in step S003, the differential curve calculation unit 512 transmits the data to the battery system controller 52. The data of the discharge differential curve (Q−dV / dQ) is recorded in the data recording unit 521 in the battery system controller 52.

  In step S004, the deterioration state calculation unit 522 in the battery system controller 52 reads out the data of the discharge differential curve (Q-dV / dQ) recorded in the data recording unit 521, and the discharge differential curve (Q-dV). / DQ) to calculate the feature of the peak shape. The specific method will be described below with reference to FIG.

FIG. 7 is an enlarged view of the peak shape portion in the state detection range in the discharge differential curve (Q−dV / dQ) of the assembled battery 41 shown in FIG. 6. In step S004, the deterioration state calculation unit 522 is located at the feature point 71 located at the skirt portion of the peak shape and the apex portion of the peak shape in the discharge differential curve (Q-dV / dQ) within this state detection range. The feature points 72 are specified, and the difference σ _i between the battery capacity Q ₁ and the battery capacity Q _{2 at} these points is calculated. Further, a difference h _i between the differential value dV ₁ / dQ ₁ at the feature point 71 and the differential value dV ₂ / dQ ₂ at the feature point 72 is calculated.

  In FIG. 7, as an example of the feature point 71 located at the bottom of the peak shape, the value of the battery capacity Q is smaller than the feature point 72 in the discharge differential curve (Q−dV / dQ) within the state detection range. The local minimum point is shown. In addition, as an example of the feature point 72 positioned at the peak portion of the peak shape, the maximum point of the discharge differential curve (Q−dV / dQ) within the state detection range is shown. However, the feature points 71 and 72 are not limited to these as long as they are respectively located at the skirt portion and the apex portion of the peak shape. For example, the minimum point on the side where the value of the battery capacity Q is larger than the feature point 72 is used as the feature point 71, and the minimum value and the maximum value of the discharge differential curve (Q−dV / dQ) within the state detection range are each characterized. Points 71 and 72 can also be used.

In step S005, the deterioration state calculating unit 522 records the differential sigma _i and the difference _{h i} calculated in step S004, the data recording unit 521 as a parameter of the feature point in the discharge derivative curve (Q-dV / dQ) . At this time, the values of the battery capacities Q ₁ and Q _{2 and} the values of the differential values dV ₁ / dQ ₁ and dV ₂ / dQ ₂ are further recorded in the data recording unit 521, thereby discharging within the state detection range. Record the positions of the feature points 71 and 72 in the differential curve (Q-dV / dQ).

In step S006, the battery state detection unit 523 reads out the differential sigma _i and the difference h _i parameters as above, which is recorded in the data recording unit 521 in step S005 feature point, the deterioration of the battery pack 41 based on these values Determine the state. Here, using the initial data of the discharge differential curve (Q-dV / dQ) recorded in advance in the data recording unit 521, the deterioration state of the assembled battery 41 is determined according to the following procedure.

FIG. 8 shows an example of the initial value of the discharge differential curve (Q-dV / dQ) of the assembled battery 41 using the verification battery from which the discharge differential curve (Q-dV / dQ) of FIG. 6 was obtained. . In FIG. 8, the horizontal axis represents the battery capacity Q (Ah), and the vertical axis represents the differential value dV / dQ (V / Ah). FIG. 9 is an enlarged view of the peak shape portion in the state detection range corresponding to FIG. 7 among the initial values of the discharge differential curve (Q−dV / dQ) of the assembled battery 41 shown in FIG. 8. In FIG. 9, feature points 91 and 92 correspond to the feature points 71 and 72 in FIG. 7, respectively. The data recording unit 521 includes an initial difference σ ₀ between the battery capacity Q ₀₁ of the feature point 91 and the battery capacity Q ₀₂ of the feature point 92, a differential value dV ₀₁ / dQ ₀₁ of the feature point 91, and a differential value of the feature point 92. The initial difference h _{0 from} dV ₁ / dQ ₁ is recorded in advance as initial data of the discharge differential curve (Q−dV / dQ).

In step S006, the battery state detection unit 523 reads the difference σ _i and difference h _i recorded in step S005 and the initial difference σ ₀ and initial difference h ₀ as the initial data from the data recording unit 521. . Then, the difference σ _i is compared with the initial difference σ ₀ , the difference h _i is compared with the initial difference h _0, and the deterioration state of the assembled battery 41 is determined based on these comparison results. For example, differential sigma _i and the initial differential sigma ₀ and the ratio σ _i / σ ₀ is the ratio _h i / _{h 0} is a predetermined threshold value with a predetermined threshold value k is greater than _sigma or delta _{h i} and the initial difference _{h 0,} If k is smaller than _h, it is determined that the battery pack 41 is in a deteriorated state. Note that the determination of the battery deterioration state in step S006 is not limited to the above determination method. As long as the difference σ _i is compared with the initial difference σ ₀ , or the difference h _i is compared with the initial difference h ₀ , the battery deterioration state may be determined by another method.

  In step S007, the battery state detection unit 523 determines whether or not the assembled battery 41 has reached the end of its life based on the determination result of the battery deterioration state in step S006. If it is determined in step S006 that the assembled battery 41 is in a deteriorated state, it is determined that the assembled battery 41 has reached the end of its life, and the process proceeds to step S008. Otherwise, the process proceeds to step S009.

  In step S008, the battery state detection unit 523 determines that the assembled battery 41 has reached the end of its life, and recommends battery replacement. At this time, the battery system controller 52 outputs a predetermined signal to the outside. The external device that has received this signal displays a warning for recommending battery replacement. After execution of step S008, the process proceeds to step S009.

In step S009, the battery state detection unit 523 reduces the battery value so as to decrease one or both of the maximum allowable charge / discharge current value and the maximum allowable battery voltage according to the determination result of the battery deterioration state in step S006. Commands to the controller 51. Here, the ratio σ _i / σ ₀ between the difference σ _i and the initial difference σ ₀ used in the determination of the battery deterioration state in step S006, or the ratio h _i / h ₀ between the difference h _i and the initial difference h ₀ is used. Based on the above, the maximum allowable charge / discharge current value and the maximum allowable battery voltage are changed. For example, the reciprocal of the ratio σ _i / σ ₀ and / or the value of the ratio h _i / h ₀ are added to the initial value of the maximum allowable charging / discharging current value and the maximum allowable battery voltage. By obtaining a value multiplied by a value (average value or the like), the value after the change is determined, and a command corresponding to the result is output to the battery controller 51. Upon receiving this command, the battery controller 51 controls the operation of the current control unit 45 so as to lower the maximum allowable charge / discharge current value according to the value after change, or the maximum allowable battery voltage in the charge control of the assembled battery 41. The maximum allowable charge / discharge current value and the maximum allowable battery voltage are changed by changing the set value.

In step S010, the battery state detection unit 523 determines the ratio σ _i / σ ₀ between the difference σ _i and the initial difference σ ₀ used in the determination of the battery deterioration state in step S006, and the difference h _i and the initial difference h ₀ . The ratio h _i / h ₀ is recorded in the data recording unit 521 as a parameter indicating the determination result of the battery deterioration state. Thereafter, in step S011, the flowchart of FIG. 4 is terminated, and the battery deterioration state determination process is completed.

  Next, pre-processing executed before the determination of the battery deterioration state in the secondary battery system of the present embodiment will be described. In order to perform the battery deterioration state determination process described with reference to the flowchart of FIG. 4, the battery voltage V is detected every predetermined time while changing the battery capacity Q by discharging, and the discharge differential curve (Q−dV / dQ). ) Must be calculated. At this time, if the value of the discharge current is large, the battery capacity Q changes abruptly, so that a characteristic peak shape in the discharge differential curve (Q-dV / dQ) may not be obtained correctly. In order to avoid this, in the secondary battery system according to the present embodiment, before the determination of the battery deterioration state, prior to reducing the discharge current in the period corresponding to the peak shape of the discharge differential curve (Q−dV / dQ). Execute the process.

  FIG. 10 is a flowchart of pre-processing in the secondary battery system according to the embodiment of the present invention.

  When starting the pre-processing in step S021, the battery system controller 52 prepares to read data from the data recording unit 521.

In step S022, the battery state detection unit 523 performs data recording on the data of the battery capacity range obtained by calculating the characteristics of the peak shape of the discharge differential curve (Q-dV / dQ) in the battery deterioration state determination process performed immediately before. Read from the unit 521. That is, the value of the battery capacity Q ₂ of battery capacity Q ₁ and feature point 72 of the recorded feature point 71 in step S005 of FIG. 4 the previously executed, read from the data recording unit 521.

In step S023, the battery state detection unit 523, based on the battery capacity _{Q 1} and _{Q 2} read in step S022, it sets the battery capacity range of lowering the set value of the discharge current. Here, in the next battery deterioration state determination process, the battery capacity that surely includes the two feature points 71 and 72 respectively located at the bottom and apex portions of the peak shape as shown in FIG. the range is set based on the battery capacity _{Q 1} and _{Q 2.} For example, a starting point the value of the battery capacity Q ₁ minus the predetermined battery capacity, it sets the battery capacity range of the end point of the value obtained by adding a predetermined battery capacity to the battery capacity Q _2. Alternatively, starting from the value obtained by multiplying a following predetermined magnification to battery capacity Q _1, sets the battery capacity range of the end point of the value obtained by multiplying the one or more predetermined magnification to battery capacity Q _2. Note that the battery capacity range set here is not limited to the above as long as the feature points 71 and 72 can be included in the next determination process of the battery deterioration state.

  In step S024, the battery state detection unit 523 transmits to the battery controller 51 an instruction to decrease the set value of the battery capacity range set in step S023. In response to this command, the charge / discharge control unit 511 of the battery controller 51 lowers the set value of the discharge current for the designated battery capacity range from the original set value. Thereafter, the discharge of the assembled battery 41 is started by starting the processing shown in the flowchart of FIG. 4 in step S001. At this time, in the battery capacity range in which the set value of the discharge current is lowered, the battery controller 51 makes the discharge current of the assembled battery 41 lower than the discharge current in other battery capacity ranges in accordance with the set value. As a result, the battery capacity Q is gradually changed, and a characteristic peak shape in the discharge differential curve (Q-dV / dQ) is surely obtained.

  According to the embodiment described above, the following operational effects are obtained.

(1) The secondary battery system includes an assembled battery 41 that is a secondary battery, a charge / discharge control unit 511 that controls charging / discharging of the assembled battery 41, a battery capacity Q of the assembled battery 41, and a differential value dV / dQ. A differential curve calculation unit 512 that calculates a differential curve (Q−dV / dQ) indicating the relationship, a deterioration state calculation unit 522, and a battery state detection unit 523 are provided. Deterioration state calculating unit 522, as a parameter of the feature points in the derivative curve (Q-dV / dQ), and the battery capacity to _{Q 1} in the feature point 71 of the differential curve (Q-dV / dQ) in a predetermined state detection range The difference σ _{i from} the battery capacity Q ₂ at the feature point 72, the differential value dV ₁ / dQ ₁ at the feature point 71 of the differential curve (Q−dV / dQ), and the differential value dV ₂ / at the feature point 72. It calculates a difference _{h i} and dQ ₂ (step S004). The battery state detection unit 523 sets the set based on at least one of the comparison result between the difference σ _i and the previously stored initial difference σ ₀ and the comparison result between the difference h _i and the previously stored initial difference h _0. The deterioration state of the battery 41 is determined (step S006). Since it did in this way, the deterioration state of the assembled battery 41 which is a secondary battery can be judged correctly.

(2) A point located at the bottom of the peak shape of the differential curve (Q−dV / dQ) within the state detection range, more specifically, a minimum point is defined as the feature point 71. Further, a point located at the apex portion of the peak shape of the discharge differential curve (Q−dV / dQ) within the state detection range, more specifically, the maximum point is defined as the feature point 72. Since it did in this way, the feature point of the peak shape in a differential curve (Q-dV / dQ) can be specified reliably.

(3) The battery state detection unit 523 determines that the ratio σ _i / σ ₀ between the difference σ _i and the initial difference σ ₀ is larger than a predetermined threshold k _σ , or the ratio h between the difference h _i and the initial difference h _{0. When i} / h ₀ is smaller than a predetermined threshold value k _h , it is determined that the assembled battery 41 has deteriorated. Since it did in this way, it can be judged easily and reliably whether the assembled battery 41 has deteriorated.

(4) charge and discharge control unit 511, the ratio and σ _i / σ ₀ of the above differential sigma _i and the initial differential sigma _0, based on the ratio _h i / _{h 0} between the difference _{h i} and the initial difference _{h 0,} At least one of the maximum allowable current and the maximum allowable battery voltage during charging / discharging of the assembled battery 41 is changed (step S009). Since it did in this way, optimal charging / discharging control can be performed according to the deterioration degree of the assembled battery 41. FIG.

(5) charge and discharge control unit 511, the charge and discharge current of the battery pack 41 in the battery capacity range based on the battery capacity Q ₁ and battery capacity Q ₂ above, it is lower than the charge and discharge current in the other battery capacity range ( Step S024). Since it did in this way, the characteristic peak shape can be obtained reliably in the differential curve (Q-dV / dQ) when the assembled battery 41 is charged / discharged.

The above according to the embodiment described, the feature points 71 and 72 in the discharge derivative curve (Q-dV / dQ), as well as calculating the difference between sigma _i and battery capacity _{Q 1,} the battery capacity _{Q 2,} the differential value calculates the difference _{h i} between the dV ₁ / dQ ₁ and the differential value _{dV 2} / dQ 2, an example was described of determining the deterioration state of the assembled battery 41 by using these calculation results. However, only one of these calculations may be performed, and the deterioration state of the assembled battery 41 may be determined using the calculation result.

  Moreover, although the said embodiment demonstrated the example of the secondary battery system using the wound-type lithium ion secondary battery, it is good also as a secondary battery of another structure. For example, the present invention can also be applied to a secondary battery system using a stacked lithium ion secondary battery in which a plurality of positive plates and a plurality of negative plates are alternately stacked via separators.

  As mentioned above, although an example of embodiment of this invention was demonstrated, this invention is not limited to the said embodiment, In the range which does not deviate from the summary, it can change suitably and can apply.

Claims (9)

A secondary battery having a positive electrode and a negative electrode including an active material accompanied by a phase change by charge and discharge;
A charge / discharge control unit for controlling charge / discharge of the secondary battery;
A differential curve Q-dV / dQ indicating the relationship between the battery capacity Q of the secondary battery and the differential value dV / dQ, which is the ratio of the change amount dV of the battery voltage V to the change amount dQ of the battery capacity Q, is calculated. A differential curve calculation unit;
A deterioration state calculation unit for calculating parameters of feature points in the differential curve Q-dV / dQ;
A battery state detection unit that determines a deterioration state of the secondary battery based on the parameter of the feature point,
The differential curve of the deterioration state calculating unit, as parameters of the feature points, the battery capacity Q ₁ and the state detection range of the first feature point of the differential curve Q-dV / dQ in a predetermined state detection range The difference σ _i between the battery capacity Q ₂ at the second feature point of Q-dV / dQ and the differential value dV ₁ at the first feature point of the differential curve Q-dV / dQ within the state detection range. the difference _{h i} of the differential value _dV 2 / dQ ₂ in the second aspect of the differential curve Q-dV / dQ, of at least one calculated in / dQ ₁ and the inner state detection range,
The battery state detection unit, a result of comparison between the initial value sigma ₀ of the differential sigma _i stored in advance the difference sigma _i, and the difference h _i a previously stored initial value h of the difference h _{i 0} A secondary battery system that determines a deterioration state of the secondary battery based on at least one of the comparison results. The secondary battery system according to claim 1,
The first feature point is a point located at a skirt portion of a peak shape indicated by the differential curve Q-dV / dQ in the state detection range,
The secondary battery system, wherein the second feature point is a point located at an apex portion of the peak shape. The secondary battery system according to claim 2,
The first feature point is a minimum point of the differential curve Q-dV / dQ within the state detection range,
The second feature point is a secondary battery system which is a maximum point of the differential curve Q-dV / dQ within the state detection range. The secondary battery system according to any one of claims 1 to 3,
The battery state detection unit determines that the secondary battery has deteriorated when a ratio σ _i / σ ₀ between the difference σ _i and the initial value σ ₀ is larger than a predetermined threshold k _σ. Next battery system. The secondary battery system according to claim 4,
The charge / discharge control unit is a secondary battery system that changes at least one of a maximum allowable current and a maximum allowable battery voltage during charging / discharging of the secondary battery based on the ratio σ _i / σ ₀ . The secondary battery system according to any one of claims 1 to 3,
The battery state detection unit determines that the secondary battery has deteriorated when a ratio h _i / h ₀ between the difference h _i and the initial value h ₀ is smaller than a predetermined threshold k _h. Next battery system. The secondary battery system according to claim 6,
The charge / discharge control unit is a secondary battery system that changes at least one of a maximum allowable current and a maximum allowable battery voltage during charging / discharging of the secondary battery based on the ratio h _i / h ₀ . The secondary battery system according to any one of claims 1 to 3,
The charging and discharging control unit, the battery capacity Q ₁ and the battery capacity Q charge and discharge current of the secondary battery in the battery capacity range based on _2, the secondary battery to be lower than the charge and discharge current in the other battery capacity range system. A method for determining a deterioration state of a secondary battery having a positive electrode and a negative electrode containing an active material that undergoes phase change by charge and discharge,
A differential curve Q-dV / showing a relationship between the battery capacity Q at the time of charge / discharge of the secondary battery and a differential value dV / dQ which is a ratio of the change amount dV of the battery voltage V to the change amount dQ of the battery capacity Q. dQ is calculated,
The differential in the differential as a parameter of the feature point in the curve Q-dV / dQ, the battery capacity Q ₁ and the state detection range of the first feature point of the differential curve Q-dV / dQ in a predetermined state detection range The difference σ _{i from} the battery capacity Q ₂ at the second feature point of the curve Q-dV / dQ, and the differential value dV at the first feature point of the differential curve Q-dV / dQ within the state detection range. Calculating at least one of ₁ / dQ ₁ and a difference h _i between the differential value dV ₂ / dQ ₂ at the second feature point of the differential curve Q-dV / dQ within the state detection range;
At least one of the comparison result between the difference σ _i and the previously stored initial value σ ₀ of the difference σ _i and the comparison result between the difference h _i and the previously stored initial value h ₀ of the difference h _i A secondary battery deterioration state determination method for determining a deterioration state of the secondary battery based on the above.

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