JP2009259607A - Battery pack - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a battery pack composed of a combination of a secondary battery pack and an accumulating element for the detection of a voltage which can easily and accurately obtain the charging/discharging state of the battery from the voltage of the accumulating element, and can prevent the deterioration of functions in the battery pack. <P>SOLUTION: The battery pack 10 is composed by having a plurality of secondary batteries 12 and at least one accumulating element 14 for voltage detection which is different from the secondary battery 12 and serially connected. The accumulating element 14 is provided with a positive electrode including active carbon as a positive electrode material and a negative electrode containing a negative electrode substance which has the same composition as that of the secondary battery 12. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an assembled battery, and in particular, to an assembled battery constructed by combining a plurality of main secondary batteries and at least one voltage detection storage element.

  Lithium-ion batteries, nickel-metal hydride batteries and other secondary batteries are used as single batteries, and assembled batteries constructed by connecting a plurality of the single batteries in series are used as power sources for obtaining high output for mounting on vehicles such as hybrid cars. The importance is increasing as a power source or a power source of a personal computer and a portable terminal. In particular, an assembled battery in which a plurality of lithium-ion batteries that are lightweight and have a high energy density are connected in series as single cells is expected to be preferably used as a high-output power source for mounting on vehicles.

  As one form of an assembled battery, a battery constructed by combining two types of batteries (single cells) having different characteristics from each other is known. In an assembled battery constructed by combining different types of single batteries (secondary batteries), the assembled battery can be imparted with characteristics different from those of an assembled battery constructed with only a single type of secondary battery.

For example, in Patent Document 1, in addition to a lithium ion battery that is a secondary battery including a nonaqueous electrolyte (hereinafter referred to as “nonaqueous secondary battery”), a secondary battery including a water soluble electrolyte (hereinafter referred to as “aqueous solution system”). An assembled battery including a relatively low capacity nickel-metal hydride battery is described as “secondary battery”. The assembled battery having such a configuration includes a nickel-metal hydride battery having a smaller capacity than that of the lithium ion battery, so that it becomes easy to detect the end of charge from the battery voltage of the entire assembled battery, thereby overcharging the lithium ion battery. The characteristic (effect) that can be prevented is obtained. Patent Document 2 discloses a plurality of non-aqueous secondary batteries (lithium ion batteries) and at least one voltage detection non-aqueous secondary battery (lithium ion battery) having a different electrode active material from the secondary battery. ) Are described.
JP-A-9-180768 JP 2007-220658 A

  As described above, an assembled battery composed of a combination of a non-aqueous secondary battery and an aqueous secondary battery as described in Patent Document 1 is the voltage of the assembled battery from the voltage of the entire assembled battery at the time of charging. While the state of charge can be easily detected, due to the difference in battery characteristics during discharge, the aqueous secondary battery is more likely to deteriorate than the nonaqueous secondary battery due to the overdischarge phenomenon. The deterioration of the aqueous secondary battery due to such an overdischarge phenomenon is not preferable because it causes a decrease in performance and a shortened life of the entire assembled battery.

  In addition, for an assembled battery configured by a combination of non-aqueous secondary batteries having different electrode active materials as described in Patent Document 2, performance degradation or shortness of the entire assembled battery is reduced by a combination of single cells having different battery characteristics. Since there exists a possibility of causing lifetime extension, it is not preferable.

  The present invention was created to solve the conventional problems in such an assembled battery, and one object of the present invention is an assembled battery constituted by a combination of a secondary battery and a voltage detection power storage element. Thus, it is an object of the present invention to provide an assembled battery that can easily and accurately detect the charge / discharge state of the assembled battery from the voltage of the power storage element and can prevent the performance of the assembled battery from being deteriorated.

  The assembled battery provided by the present invention to achieve the above object is an assembled battery in which a plurality of secondary batteries and at least one voltage detection storage element different from the secondary battery are connected in series. . And the electrical storage element which comprises this assembled battery is equipped with the positive electrode containing activated carbon as a positive electrode material, and the negative electrode containing the negative electrode active material of the same composition as the said secondary battery.

  In an assembled battery in which a plurality of main secondary batteries and a voltage detection storage element (for example, a secondary battery) are connected, the secondary battery has a stable output (voltage) regardless of discharge capacity during discharge. ), That is, a voltage that does not easily change regardless of the discharge capacity is preferable. Such secondary batteries typically have a discharge characteristic that exhibits a flat (plateau) discharge curve or a discharge curve having a flat region (typically over a wide range) (ie, a flat discharge curve). Discharge curve characteristics). On the other hand, the voltage detecting storage element preferably has a voltage that varies greatly depending on the discharge capacity. Such a storage element has a discharge characteristic with a large slope of the discharge curve. Here, when manufacturing an electrical storage element having different discharge characteristics (output characteristics), typically, an electrical storage element (battery) including an electrode having a different electrode active material from the secondary battery is manufactured. Examples of such a combination of the secondary battery and the voltage detecting storage element include a lithium secondary battery and a nickel hydride battery, and a lithium secondary battery having a different positive electrode active material. However, in an assembled battery in which an electricity storage element having electrodes with different electrode active materials is connected to a plurality of secondary batteries in this way, as described above, the overall performance of the assembled battery is degraded (typically, Lowering) and shortening the service life.

  In the assembled battery having the configuration disclosed by the present invention, the secondary battery and the voltage detection storage element include negative electrodes having positive electrodes different from each other in positive electrode materials (positive electrode active materials) and having negative electrode active materials having the same composition. It has. And the said electrical storage element contains activated carbon as a positive electrode material.

  In a positive electrode including activated carbon as a positive electrode material, a reaction (charge / discharge reaction) related to transfer of charges (electrons) is based on an adsorption reaction (non-Faraday reaction) between activated carbon and ions. For this reason, the electricity storage device provided with such a positive electrode is (1) largely dependent on the charge / discharge capacity, and the slope of the charge / discharge curve, as compared with the case where an electrode whose charge / discharge reaction is an electrochemical reaction (Faraday reaction) is provided. Have large charge / discharge characteristics, and (2) an irreversible side reaction or the like does not occur at the time of charge / discharge, so that the deterioration of performance is suppressed and the life is long (high durability). With such a property, a power storage element including such a positive electrode is suitable as a voltage detection power storage element, and the life of the power storage element itself is extended.

  On the other hand, a power storage device including such a positive electrode has the above properties (1) and (2), but can also have the property that (3) resistance has low temperature dependence. On the other hand, the resistance of the secondary battery whose charge / discharge reaction is based on the Faraday reaction is highly temperature dependent as a result of the activation energy accompanying the reaction. Here, when a secondary battery having a resistance having different temperature dependence and a power storage element are combined as an assembled battery, the balance of resistance between the secondary battery and the power storage element with respect to a temperature change is lost. For this reason, even when charging / discharging is performed in an appropriate voltage range, an overload is generated in the secondary battery, and the performance of the secondary battery may be reduced and the life may be shortened.

  However, in the assembled battery having the configuration disclosed by the present invention, the negative electrode of the voltage detection power storage element has the same composition as the secondary battery in the negative electrode active material. As a result, the same Faraday reaction as that of the secondary battery is caused and the temperature dependency of resistance is approximated to that of the secondary battery, so that the load that can be generated in the secondary battery is alleviated, and the short-circuit of the secondary battery is reduced. The lifetime can be prevented and the durability can be improved. Accordingly, the assembled battery having the configuration disclosed by the present invention includes a power storage element suitable for voltage detection, and prevents deterioration in performance of both the power storage element and a plurality of main secondary batteries. The overall performance can be guaranteed to be reliable over the long term.

  In a preferred embodiment of the assembled battery disclosed herein, the secondary battery is a lithium secondary battery.

  A lithium secondary battery (typically a lithium ion battery) has a larger electric capacity than other secondary batteries (single batteries), and is preferable as a secondary battery constituting an assembled battery. The assembled battery of this configuration includes a voltage detection storage element in addition to the lithium secondary battery. For this reason, even for an assembled battery mainly composed of a lithium secondary battery having a flat discharge curve characteristic, the state of the assembled battery (typically the discharge capacity) at the time of discharging is measured. Fluctuations) can be easily detected. And as above-mentioned, the said voltage detection electrical storage element is equipped with the positive electrode containing activated carbon as a positive electrode material, and the negative electrode active material (for example, graphite-type carbon material) of the same composition as the said lithium secondary battery, The assembled battery whole As a result, performance degradation can be prevented. As described above, according to the present invention, it is possible to provide an assembled battery mainly composed of a lithium secondary battery having high durability and long life.

  In a further preferred embodiment of the assembled battery disclosed herein, the power storage element includes an electrolyte containing lithium having the same composition as the secondary battery.

  In the assembled battery having such a configuration, the power storage element includes an electrolyte (typically, an electrolyte) containing lithium with the same composition as the lithium secondary battery (typically a lithium ion battery) that is the secondary battery. Therefore, the behavior and environment of charge at the time of charge / discharge, such as the moving speed of the charge (lithium ions) in the electrolyte in the storage element and the reaction field related to occlusion / release of lithium at the negative electrode, are further approximated to the secondary battery. As a result, the performance degradation of the power storage element and the secondary battery can be further prevented, and the performance of the assembled battery as a whole can be guaranteed to be more reliable.

  Since the assembled battery having the above configuration can improve the durability and extend the life of the entire assembled battery, the assembled battery disclosed herein is a battery (battery) mounted on a vehicle that requires high durability and the like. Module). Therefore, according to the present invention, a vehicle (for example, an automobile) provided with such an assembled battery is provided.

  Moreover, this invention provides the state detection method which concerns on the assembled battery of the structure disclosed here. That is, the state detection method prepares an assembled battery in which a correlation between the voltage of the voltage detecting storage element at the time of charging and discharging and the capacity of the assembled battery is determined in advance, and at the time of charging and discharging the assembled battery, By measuring the voltage of the storage element, the state of the assembled battery is detected from the measured voltage value based on the correlation.

  The state detection method disclosed here relates to the state (typically charge / discharge capacity, particularly discharge capacity) of the secondary battery constituting the assembled battery, and correlation between the state and the measured voltage value of the voltage detection storage element. It is a method that can grasp the state of the whole assembled battery by detecting based on the property. By this method, even in an assembled battery including a plurality of secondary batteries having a flat charge / discharge curve characteristic (particularly, a discharge curve characteristic), when the assembled battery is used (during charge / discharge), the secondary battery From the correlation between the capacity and the voltage value of the power storage element corresponding to the capacity, the state of the assembled battery can be suitably detected (understood). For this reason, the overcharge or overdischarge of the secondary battery can be effectively prevented. This method can be more preferably applied to an assembled battery formed by connecting secondary batteries (for example, lithium secondary batteries, typically lithium ion batteries) having extremely flat charge / discharge curve characteristics. It is particularly preferably used when it is desired to grasp the capacity within a range where the charge / discharge curve of the secondary battery is flat (voltage change is substantially constant).

  Hereinafter, a preferred embodiment of the present invention will be described with reference to FIGS. 1 and 2. FIG. 1 is an explanatory view schematically showing a configuration of an assembled battery according to the present invention. FIG. 2 is an explanatory view schematically showing a configuration of a preferred embodiment of a power supply device incorporating the assembled battery according to the present invention. It should be noted that matters other than matters specifically mentioned in the present specification (for example, the composition of secondary batteries and power storage elements) and matters necessary for the implementation of the present invention (for example, battery assembly procedures, single cells, etc.) The electrode body unit to be configured, the configuration of the electrolyte, and various processes for battery construction) can be grasped as design matters of those skilled in the art based on the prior art in this field. The present invention can be carried out based on the contents disclosed in this specification and common technical knowledge in the field.

  In the present specification, the “unit cell” is a term that refers to individual cells that can be connected to each other in series to form an assembled battery. Unless specifically limited, batteries and power storage elements of various compositions are included. In this specification, the term “battery” refers to various types of chemical batteries (for example, lithium ion batteries) such as electric double layer capacitors in addition to so-called chemical batteries such as lithium secondary batteries, nickel hydride batteries, nickel cadmium batteries, and lead storage batteries. And a storage element (physical battery) that can be used in the same industrial field.

  The assembled battery disclosed here is an assembled battery characterized by connecting a plurality of secondary batteries connected in series with voltage detection storage elements different from the secondary battery in series. Yes, it is not limited by the type of secondary battery (unit cell) constituting the assembled battery, the number of unit cells included in the assembled battery, and the like.

  Although the secondary battery which comprises the assembled battery disclosed here is not specifically limited, Although a various secondary battery can be included, a nonaqueous secondary battery, ie, a secondary battery provided with a nonaqueous electrolyte, is more preferable. A typical example is a lithium secondary battery such as a lithium ion battery. In particular, a lithium ion battery is a secondary battery that can achieve a high output at a high energy density, and is therefore a preferable battery for constructing a high-performance assembled battery, particularly an assembled battery for a vehicle (battery module).

There are no particular limitations on the constituent material of the lithium ion battery used as the unit cell constituting the assembled battery of the present invention. For example, lithium manganate (LiMn ₂ ) which has been conventionally used as a positive electrode material (positive electrode active material). O ₄ ), lithium cobaltate (LiCoO ₂ ), lithium nickelate (LiNiO ₂ ) and the like can be used. As the non-aqueous electrolyte, a non-aqueous solvent containing an appropriate amount of an appropriate electrolyte (for example, a lithium salt such as lithium hexafluorophosphate (LiPF ₆ )), for example, a mixed solvent of diethyl carbonate and ethylene carbonate is preferably used. Can do.

In the assembled battery according to the present invention, the state of the assembled battery during charge / discharge (typically, the discharge capacity of the assembled battery during discharge) is determined by including the voltage detection storage element. It can be easily detected from fluctuations in the potential of the positive and negative electrodes). Accordingly, a lithium secondary battery can be cited as a battery having a flat charge / discharge curve characteristic and difficult to detect the state. In the present invention, as described above, a state detection of a battery having such a flat charge / discharge curve characteristic is provided. Can be easily performed. Therefore, the lithium secondary battery as described above can be preferably used as a constituent cell. For example, a lithium ion battery using a compound having an olivine structure such as LiFePO ₄ and LiMnPO ₄ as a positive electrode active material (olivine-based positive electrode material) is a lithium ion battery that exhibits a very flat discharge curve characteristic (voltage behavior). It is particularly suitable as a non-aqueous secondary battery (unit cell) constituting the assembled battery of the present invention. Olivine _{LiFe 1-x} M _x PO ₄ compound represented by the preferred examples of the cathode material (wherein M is Mn, Cr, Co, Cu, Ni, V, Mo, Ti, Zn, Al, Ga, Mg, B And at least one selected from Nb, and x is a real number satisfying 0 ≦ x ≦ 0.5.

Further, as a negative electrode material (negative electrode active material) of a lithium ion battery, carbon-based materials such as graphite carbon and amorphous carbon, lithium-containing transition metal oxides, transition metal nitrides, and the like can be used. A carbon-based material such as graphite (graphite) is preferable in order to realize a high voltage of the entire assembled battery. As a carbon-based material suitable for constructing a lithium ion battery having a flat charge / discharge curve characteristic (potential flatness) that can easily enjoy the effects of the present invention, the interlayer distance d of the graphite structure is relatively small and calculated from the d value. Particularly preferred are natural graphite materials having a relatively large lattice constant C ₀ (= 2d) crystallite size Lc and artificial graphite materials such as mesocarbon microbeads. For example, a natural graphite material (for example, C _o = 0.67 nm, Lc = 27 nm) having an average particle diameter of about 10 to 30 μm (for example, 20 μm) and a degree of graphitization of 0.9 or more is preferable.

  In order to construct the assembled battery disclosed here, the voltage sensing storage element used together with the secondary battery as described above (lithium secondary battery, typically lithium ion battery) is activated carbon as a positive electrode material. A power storage element including a positive electrode including a negative electrode including a negative electrode active material having the same composition as the secondary battery can be preferably used. That is, the voltage detecting power storage element may be a battery having a form in which the positive electrode active material (lithium-containing transition metal oxide) of the secondary battery is replaced with a positive electrode material containing an amorphous carbon material (activated carbon). . Moreover, it is preferable to use the same electrolytic solution as that used in the secondary battery as the electrolytic solution of the power storage element. When a lithium ion battery is used as the secondary battery, the positive electrode containing activated carbon, the negative electrode containing the negative electrode material (graphite) as described above, and lithium An electric storage element provided with a non-aqueous electrolyte composed of a non-aqueous solvent containing a salt, so-called lithium ion capacitor, can be preferably used. The above-described power storage element configured to include activated carbon in the positive electrode has a large voltage change with respect to the capacity change (the slope of the charge / discharge curve is large), and a substantially constant gradient with respect to the capacity change over a wide capacity range (that is, almost the same). The voltage changes linearly. Therefore, the storage element having such a configuration detects a change in capacity (especially a change in discharge capacity) during use (charge / discharge, particularly during discharge) of the assembled battery mainly composed of the secondary battery, and detects a voltage change of the storage element. It is possible to grasp accurately.

  Moreover, in the said electrical storage element, although activated carbon is included as a positive electrode material, a negative electrode active material is the same composition as the said secondary battery (lithium secondary battery, typically a lithium ion battery). For this reason, the power storage device having such a configuration has a resistance temperature dependency on the secondary battery as compared with a power storage device in which both the positive electrode material and the negative electrode material are activated carbon (so-called electric double layer capacitor). You can get closer. This effect is further exhibited by making the electrolytic solution the same (non-aqueous electrolytic solution containing a lithium salt). Therefore, for example, one or two to three power storage elements (lithium ion capacitors) having the above-described configuration and a plurality of (for example, 5 to 30) lithium ion batteries exhibiting flat charge / discharge curve characteristics (voltage behavior). When an assembled battery is constructed in combination, it is possible to reduce the difference in resistance balance caused by temperature changes during use of the battery or the difference in the behavior of lithium ions and the interface environment between the electrode and electrolyte. The load on the lithium ion battery can be reduced. As a result, it is possible to provide a highly reliable assembled battery for a long period of time, preventing performance degradation and shortening of the life of the assembled battery as a whole.

  In addition, as the voltage detection storage element, a battery having a capacity that is approximately the same as or larger than the battery capacity of the secondary battery to be combined can be used. As a result, overcharging of the battery element is prevented during charging of the battery pack, and charging end of the battery pack is not limited to charging end of the battery element, so that it can be used in a wide capacity range. it can.

  Even when a battery element with a large battery capacity is used, the voltage change relative to the capacity change of the battery element is large within the capacity range of the battery element corresponding to the capacity range that the secondary battery can take when using the assembled battery. Thus, it can be preferably employed as a voltage detection element. Here, in the storage element including activated carbon as the positive electrode material, the voltage changes with a substantially constant slope over a wide capacity range, and the voltage change amount is larger than the voltage change amount within the capacity range of the secondary battery. Since it is sufficiently large, the above storage element having a large battery capacity can be preferably employed as the voltage detection storage element.

Next, the structure of the assembled battery according to the present invention will be described with reference to FIG. As schematically shown in FIG. 1, an assembled battery 10 disclosed herein is an assembled battery 10 in which a plurality of secondary batteries 12 and a voltage detection storage element 14 are connected in series, and the assembled battery 10 10 is a secondary battery (for example, a lithium secondary battery, typically a lithium ion battery) 12, and at least one voltage sensing storage element 14 different from the secondary battery 12. It is connected. The position to which the electricity storage element 14 is connected may be at the end of the assembled battery 10 or between the secondary batteries 12 and is not particularly limited. In addition, other configurations, the assembled method of the assembled battery, and the like may be the same as those of the conventional assembled battery, and are not particularly limited. For example, the form of the unit cell constituting the assembled battery and the number of the unit cells may be the same as those of the conventional assembled battery. For example, when a lithium ion battery is adopted as a secondary battery that is a main constituent element of an assembled battery, as one form of the lithium ion battery (single battery), a predetermined battery constituent material (active material of each of positive and negative electrodes, positive and negative electrodes) And a sealed lithium ion battery including an electrode body including each current collector, separator, electrolyte, and the like, and a container for housing the electrode body.
When the assembled battery 10 is connected to a predetermined circuit as a power source, a power supply device (power supply circuit) having the same circuit configuration as the internal configuration of the assembled battery 10 shown in FIG. 1 is provided.

  For example, as schematically shown in FIG. 2, a power supply device (power supply circuit) 40 including a plurality of secondary batteries 12 and a voltage detecting storage element 14, and a plurality of (for example, 5 to 30) secondary batteries. (For example, a non-aqueous secondary battery, preferably a lithium ion battery) 12 and at least one (one or two to three) voltage detection storage elements 14 connected in series to the secondary battery 12. A power supply device (power supply circuit) 40 including the assembled battery 20 configured by the combination of the above and the control unit 30 is provided. For example, when the control unit 30 is provided in a vehicle in advance and a separately prepared removable battery 20 is mounted at a predetermined position, the control unit 30 and the power storage element 14 of the battery pack 20 can be connected in parallel. The power supply device 40 configured as described above is provided (for example, a power supply device for a vehicle power supply). The control unit 30 includes, for example, measuring means for measuring the voltage value of the power storage element 14, capacity of the power storage element 14, capacity of the secondary battery, and further, capacity of the assembled battery 20 as a whole. The detection means etc. which detect from the measured voltage value obtained by 1 are included. The control unit 30 for configuring the power supply device 40 having such a configuration includes various electronic components that are directly connected to or not connected to the assembled battery 20 in addition to the above-described measurement means and detection means. (Elements such as capacitors and transistors) and additional circuits (auxiliary power supply and the like) may be included, but these elements do not characterize the present invention, and thus detailed description thereof is omitted.

  According to the present invention, there is provided a method for detecting the state (typically, discharge capacity during discharge) of an assembled battery having the configuration disclosed herein.

  Such a method prepares an assembled battery in which the correlation between the state of the assembled battery and the voltage value of the voltage detecting storage element constituting the assembled battery is determined in advance by, for example, preliminary charge and discharge processing. This is a method of detecting the state of the assembled battery by measuring the voltage of the voltage detecting storage element at any time during use of the battery and comparing the measured voltage value with the correlation.

  In this method, the correlation is determined by the following procedure, for example. That is, a preliminary charge / discharge process (typically one cycle of charge / discharge process) is performed on one of the secondary batteries as a component of the assembled battery under a predetermined condition (predetermined current condition and voltage condition). To implement. As an example of the preliminary discharge treatment, (i) a constant current condition of a predetermined current value (for example, a current value of about one fifth of the battery capacity predicted from the theoretical capacity at the positive electrode of the secondary battery, for example, 1 A) After the voltage value reaches a predetermined voltage value (charging upper limit voltage), the voltage value is maintained and the current value is attenuated (for example, until it becomes 1/10 of the current value under a constant current condition). (Ii) After this charging process is performed, a predetermined voltage value (for example, the above-described constant current condition) is used under a predetermined current value (for example, the above-described constant current condition). Discharge until it reaches a voltage value of 75% of the charge upper limit voltage). Correlation between the discharge capacity of the secondary battery or the remaining capacity (the capacity obtained by subtracting the discharge capacity from the capacity immediately before the start of discharge or at the end of charge) and the voltage value by such preliminary charge / discharge treatment. Seeking sex. In addition, the same charge / discharge treatment as described above is performed on the power storage element, and the correlation between the discharge capacity (remaining capacity) and the voltage value in the power storage element is obtained.

  Next, the two correlations obtained by the above method (that is, the correlation between the capacity of the secondary battery and the voltage value, and the correlation between the capacity of the storage element and the voltage value) are collated, Corresponding to the capacity value of the secondary battery by determining the capacity value of the power storage element corresponding to the capacity value of the secondary battery and deriving the voltage value of the power storage element from the determined capacity value of the power storage element The voltage value of the storage element can be set. In this way, the correlation between the capacity (state) of the secondary battery and the voltage of the storage element is obtained, and the correlation between the state of the assembled battery and the voltage of the storage element is further determined from the correlation. .

  The state detection of the assembled battery can be performed as follows, for example. An assembled battery in which the correlation between the state of the assembled battery and the voltage of the voltage detecting storage element is determined in advance as described above is prepared, and the assembled battery is charged / discharged (used). The charging / discharging process is performed while measuring the voltage of the power storage element, and the state of the entire assembled battery is detected by comparing the measured voltage value obtained as needed and the correlation. Here, the frequency of voltage measurement of the power storage element is not particularly limited, and may be measured every predetermined time, or the voltage may be continuously monitored.

  The upper limit value and the lower limit value of the capacity range that the secondary battery can take when using the assembled battery are typically the both ends of the flat portion in the charge / discharge curve of the secondary battery (the start and end of the flat portion). Part), each capacity corresponding to the vicinity, but can be appropriately set depending on the output characteristics of a power supply device (for example, power supply device 40 in FIG. 2) in which the assembled battery can be incorporated.

  By the method as described above, the state of the entire assembled battery can be detected from the measured voltage value of the voltage detecting storage element. Moreover, this method can be preferably implemented in, for example, the control unit 30 of the power supply device 40 schematically shown in FIG.

  The following examples further illustrate the invention, but are not intended to limit the construction of the invention to those listed as such examples.

Whether or not there is a difference in durability (discharge capacity retention rate) of the assembled battery by changing the type of the storage element in the assembled battery formed by connecting a secondary battery and a voltage detecting storage element in series evaluated. A specific method for evaluating the durability will be described below.
<Production of secondary battery that is the main component of the assembled battery>
A lithium ion battery was produced as a secondary battery incorporated in the assembled battery. That is, LiFePO ₄ which is a positive electrode active material, acetylene black (AB) which is a conductive additive, and polyvinylidene fluoride (PVDF) which is a binder, LiFePO ₄ / AB / PVDF = 85/5 / A positive electrode active material layer forming paste was prepared by adding to N-methyl-2-pyrrolidone (NMP), which is a dispersion solvent, and mixing well. The obtained paste for forming a positive electrode active material layer was applied on an aluminum foil having a length of 2.7 m, a width of 10 cm, and a thickness of 15 μm, and a treatment by a roll press was performed, so that the positive electrode active material layer was formed on the aluminum foil. A positive electrode current collector sheet formed was produced.

  On the other hand, a natural graphite-based carbon material (graphite) that is a negative electrode active material, a styrene-butadiene copolymer (SBR) that is a binder, and carboxymethyl cellulose (CMC) that is a thickener are graphite / A negative electrode active material layer forming paste was prepared by adding to water as a dispersion solvent so that SBR / CMC = 95 / 2.5 / 2.5 and mixing well. The obtained paste for forming a negative electrode active material layer was applied on a copper foil having a length of 2.9 m, a width of 10 cm, and a thickness of 10 μm, and a treatment by a roll press was performed, so that the negative electrode active material layer was formed on the copper foil. A formed negative electrode current collector sheet was prepared. The amount of paste applied was adjusted so that the ratio between the theoretical capacity of the positive electrode and the theoretical capacity of the negative electrode was 1 (positive electrode): 1.5 (negative electrode).

  The positive electrode current collector sheet and the negative electrode current collector sheet thus obtained were wound together with a separator sheet (two sheets) that is a polypropylene / polyethylene composite porous film having a length of 3.1 m, a width of 11 cm, and a thickness of 25 μm ( A flat wound electrode body for a lithium ion battery was produced by crushing 20 turns) and then crushing.

The lead terminals of the positive and negative electrodes were welded to the wound electrode body thus produced and accommodated in an aluminum box-shaped container (internal volume: about 100 mL) having a shape corresponding to the wound electrode body. An appropriate amount of electrolytic solution (non-aqueous electrolytic solution in which LiPF ₆ having a concentration of 1 M as a lithium salt is dissolved in a mixed solvent of ethylene carbonate, ethyl methyl carbonate and dimethyl carbonate having a mass ratio of 1: 1: 1) is injected into the container. And sealed. This produced the sealed lithium ion battery provided with the wound electrode body used as a single battery of the assembled battery.
<Preparation of voltage sensing power storage element>
Moreover, the following three types of power storage elements (1) to (3) were produced as voltage detection power storage elements to be incorporated into the assembled battery.
<Production of power storage element (1)>
A storage element (1) (lithium ion battery) was produced in the same manner as the above lithium ion battery production method except that the positive electrode active material was changed from LiFePO ₄ to LiNiO ₂ .
<Production of power storage element (2)>
A storage element (2) (lithium ion battery) was produced in the same manner as the above lithium ion battery production method except that the positive electrode active material was changed from LiFePO ₄ to LiCoO ₂ .
<Production of electricity storage element (3)>
Activated carbon (positive electrode active material), AB, which is a conductive additive, and PVDF, which is a binder, are added to NMP, which is a dispersion solvent, so that the mass ratio is activated carbon / AB / PVDF = 80/10/10. The positive electrode active material layer forming paste was prepared by mixing well. The obtained paste for forming a positive electrode active material layer was applied on an aluminum foil having a length of 2.7 m, a width of 10 cm, and a thickness of 15 μm, and a treatment by a roll press was performed, so that the positive electrode active material layer was formed on the aluminum foil. A positive electrode current collector sheet formed was produced. A storage element (3) (so-called lithium ion capacitor) was produced in the same manner as the above-described method for producing a lithium ion battery except for the positive electrode current collector sheet.
Here, each discharge characteristic of the said lithium ion battery (secondary battery) and electrical storage element (1), (2) and (3) was investigated. Specifically, for each of the secondary battery and the storage elements (1) to (3), 5 minutes of the battery capacity (Ah) predicted from the positive electrode theoretical capacity by the constant current and constant voltage under the temperature condition of 25 ° C. Charging was carried out at a current value of 1 up to each charging upper limit voltage. That is, the charging was performed until the final current value during constant voltage charging was 1/10 of the initial current value. After the above charging, in order to evaluate the discharge characteristics of the assembled batteries of Example, Comparative Example 1 and Comparative Example 2, the battery was discharged to 3 V at a current value of 1/5 of the battery capacity (Ah) predicted from the positive electrode theoretical capacity. The capacity values (discharge capacities) of the lithium ion battery and the storage elements (1) to (3) were examined. The obtained capacity value was defined as “capacity value before endurance test” of each of the lithium ion battery and power storage elements (1) to (3).

  Next, the assembled battery according to this example was manufactured by connecting in series the 10 lithium ion batteries and one selected from the storage elements (1) to (3).

  Here, as Example 1, an assembled battery in which 10 lithium ion batteries and one power storage element (1) were connected in series was manufactured.

  Further, as Example 2, an assembled battery in which 10 lithium ion batteries and one power storage element (2) were connected in series was manufactured.

  Furthermore, as Example 3, an assembled battery formed by connecting ten lithium ion batteries and one power storage element (3) in series was manufactured.

  Next, an endurance test (accelerated deterioration test) was performed on each of the three assembled batteries according to Examples 1 to 3. As this endurance test, a cycle test in which charging and discharging at 2C were repeated under a temperature condition of 25 ° C. Specifically, each assembled battery was charged to an upper limit voltage with a constant current of 2C, and then discharged to 3V with a constant current of 2C. This cycle was repeated 100 times. Here, “C” represents a discharge time rate. Therefore, the current density 2C means a current density (A) that can supply an amount of electricity corresponding to the battery capacity (Ah) in 0.5 hours.

  After carrying out the durability test under the above temperature conditions, the lithium ion battery and the storage elements (1) to (3) were separated from each of the assembled batteries according to Examples 1 to 3. One lithium ion battery and storage element (1) according to the assembled battery of Example 1, one lithium ion battery and storage element (2) according to the assembled battery of Example 2, and one according to the assembled battery of Example 3 In order to evaluate the charge / discharge characteristics of the lithium ion battery and the electricity storage element (3), the current of 1/5 of the battery capacity (Ah) predicted from the theoretical capacity of the positive electrode, similarly to the discharge characteristic evaluation before the durability test. After charging up to the charging upper limit voltage, the battery was discharged at the same current value up to 3 V, and the capacity value (discharge capacity) of each assembled battery was examined. The obtained capacity value was defined as “capacity value after endurance test”.

  In addition, the graph which shows the 25 degreeC discharge curve of the lithium ion battery (unit cell) which comprised the assembled battery which concerns on Example 3, and an electrical storage element (3) was shown in FIG.3 and FIG.4, respectively. The vertical axis represents voltage [V], and the horizontal axis represents discharge capacity (Q) [%]. Here, the discharge capacity of 100% is the “capacity value before the durability test” of the lithium ion battery in FIG. 3, and the “capacity value before the durability test” of the power storage element (3) in FIG. is there.

  The capacity retention ratio after the durability test was determined from the capacity values before and after the durability test of each of the lithium ion batteries according to Examples 1 to 3 and the electricity storage devices (1) to (3). This capacity retention ratio is expressed as a percentage obtained by dividing "capacity value after endurance test" by "capacity value before endurance test". Table 1 shows capacity retention rates of the lithium ion batteries and the storage elements (1) to (3) according to Examples 1 to 3.

  As shown in Table 1, the assembled batteries according to Examples 1 and 2 are different from the main secondary battery (lithium ion battery) in the storage element (lithium ion battery) in which the lithium-containing transition metal oxide of the positive electrode active material is different. ) Is incorporated as a voltage detecting power storage element. In this case, the capacity maintenance rate of the voltage detection power storage element itself was decreased, and a decrease in capacity after the endurance test was observed. On the other hand, in the assembled battery according to Example 3, a storage element including activated carbon as a positive electrode material (positive electrode active material) is used as a voltage detection storage element. In this case, both the capacity maintenance rate of the voltage detecting power storage element and the capacity maintenance rate of the main secondary battery are almost 100%, and almost no decrease in capacity after the endurance test was observed, and high durability. It was found to have sex. As a result, a battery element including a positive electrode including activated carbon as a positive electrode material and a negative electrode including a negative electrode active material having the same composition as the secondary battery is incorporated into the assembled battery as a voltage detection power storage element. It has been found that performance degradation and shortening of the life can be prevented, and durability improvement and long life can be realized.

  In addition to the above durability test under the temperature condition of 25 ° C., the same durability test was performed under the temperature conditions of −30 ° C., 0 ° C., 45 ° C., and 60 ° C. As a result, the result similar to the result shown in Table 1 was recognized under any temperature condition.

As is clear from the graphs of FIGS. 3 and 4, the voltage of the electricity storage element (3) incorporated in the assembled battery according to Example 3 changes with a substantially constant slope with respect to the change in discharge capacity. Was confirmed. On the other hand, the secondary battery (lithium ion battery) constituting the assembled battery according to Example 3 has a flat discharge curve characteristic over a wide discharge capacity range. As a result, in the assembled battery according to Example 3, it was confirmed that the capacity of the secondary battery can be accurately detected by the power storage element. For example, in FIGS. 3 and 4, by adjusting the respective capacities of the secondary battery and the storage element and adjusting the use conditions of the battery pack, the battery pack is used (charge / discharge). The capacity range that the secondary battery (unit cell) can take is, for example, the range of the discharge capacities Q _{1 to} Q _{2 in} FIG. 3, and the discharge capacity of the power storage element corresponding to the capacities Q ₁ and Q ₂ is When the capacity is set to Q ₃ and Q ₄ , respectively, the voltage change in the discharge capacity range Q _{1 to} Q ₂ of the secondary battery is about 0.2 V, whereas the discharge capacity range Q _{3 of the} power storage element. change in voltage to Q ₄ is about 1V. Thus, since the voltage change with respect to the discharge capacity range of the power storage element is larger than the voltage change of the secondary battery, the discharge capacity of the secondary battery can be accurately detected by the power storage element.

  Furthermore, the discharge curve characteristics of the assembled battery mainly composed of the plurality of secondary batteries can be similar to the discharge curve characteristics of the secondary battery (unit cell). As a result, the storage element has a discharge capacity of the entire assembled battery. It can be seen that can be detected accurately.

  In the above examples, the effectiveness of the state detection of the assembled battery at the time of discharging was confirmed by evaluating the discharging characteristics. However, the charging characteristics can also be regarded as the same as described above. The state detection of the assembled battery at the time can be preferably performed.

  As is apparent from the above-described embodiments, according to the present invention, a plurality of secondary batteries (lithium secondary batteries, typically lithium ion batteries) that are the main components, and a voltage detecting storage element connected to the secondary batteries. To provide an assembled battery in which the deterioration of both of the performances is prevented and the entire assembled battery has a long life, and the state of the assembled battery at the time of charging / discharging can be easily detected from the measured voltage value by the power storage element. Can do.

  Therefore, the assembled battery (or a power supply device incorporating the assembled battery) of the present invention is particularly suitable as a power source for a motor (electric motor) mounted on a vehicle such as an automobile. Therefore, as shown in FIG. 5, a vehicle 1 (typically an automobile, particularly a hybrid automobile, an electric automobile, etc.) including the assembled battery 10 (or the power supply device 40 in FIG. 2) configured as described above according to the present invention. An automobile equipped with an electric motor such as a fuel cell automobile) can be provided.

  As mentioned above, although this invention was demonstrated by suitable embodiment and an Example, such description is not a limitation matter and of course, various modifications are possible.

It is explanatory drawing which shows typically the structure of the assembled battery which concerns on this invention. It is explanatory drawing which shows typically the structure of one preferable form of the power supply device incorporating the assembled battery which concerns on this invention. 6 is a graph showing a discharge curve at 25 ° C. of a lithium ion battery constituting the assembled battery according to Example 3. FIG. 10 is a graph showing a discharge curve at 25 ° C. of the electricity storage device (3) constituting the assembled battery according to Example 3. It is a side view which shows typically the vehicle (automobile) provided with the assembled battery of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Vehicle 10, 20 Battery pack 12 Secondary battery 14 Voltage detection electrical storage element 30 Control part 40 Power supply device

Claims (5)

In an assembled battery in which a plurality of secondary batteries and at least one voltage detection storage element different from the secondary battery are connected in series,
The storage element includes a positive electrode including activated carbon as a positive electrode material, and a negative electrode including a negative electrode active material having the same composition as the secondary battery.   The assembled battery according to claim 1, wherein the secondary battery is a lithium secondary battery.   The assembled battery according to claim 2, wherein the power storage element includes an electrolyte containing lithium with the same composition as the secondary battery.   A vehicle comprising the assembled battery according to claim 1. An assembled battery state detection method,
It is an assembled battery in any one of Claims 1-3, Comprising: The assembled battery by which the correlation of the voltage of the said voltage detection electrical storage element at the time of charging / discharging and the capacity | capacitance of an assembled battery was prepared, and the said A method of detecting a state of the assembled battery from the measured voltage value based on the correlation by measuring a voltage of the storage element during charging / discharging of the assembled battery.

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