JP2013211157A

JP2013211157A - Battery pack, and power storage device and lifetime determination method using the same

Info

Publication number: JP2013211157A
Application number: JP2012080251A
Authority: JP
Inventors: Yu Nishimura; 悠西村; Shinichiro Kakehi; 真一朗筧
Original assignee: TDK Corp
Current assignee: TDK Corp
Priority date: 2012-03-30
Filing date: 2012-03-30
Publication date: 2013-10-10

Abstract

PROBLEM TO BE SOLVED: To provide a battery pack of lithium ion secondary batteries and a power storage device in which the lifetime can be determined precisely even under various environmental temperatures.SOLUTION: Lifetime of the battery pack can be determined, regardless of an external environmental temperature, by using the power storage device comprising: the battery pack in which first single cells and second single cells 16, having a cycle deterioration rate higher than that of the first single cells and a battery capacity larger than that of the first single cells, are connected in series, and each single cell has wiring for monitoring the voltage; a voltage measurement device for monitoring the voltage of the first and second single cells; and an electric circuit for determining the lifetime of the battery pack from the voltage value of the voltage measurement device.

Description

本発明は、複数の二次電池を直列に接続してなる組電池と、その寿命を判定する機能を有する蓄電装置と、その組電池を用いた寿命判定方法に関する。 The present invention relates to an assembled battery formed by connecting a plurality of secondary batteries in series, a power storage device having a function of determining the life thereof, and a life determining method using the assembled battery.

昨今、電気自動車や自然エネルギーを活かしたスマートグリッドなどによる省エネルギー社会を目指した発展が望ましい。その中で、二次電池は蓄電装置として大きな役割を持つ。特に、リチウムイオン二次電池は、容量・出力ともにすぐれ、システムの小型化に貢献しうる。その際、一つのリチウムイオン電池では電力量が小さいため、直列・並列に組み合わされたリチウムイオン二次電池の組電池として利用される場合が多い。この場合、様々な使用条件により変化する組電池全体の劣化の状態を逐次把握することは必須な技術である。例えば、リチウムイオン二次電池が劣化し貯蔵できる電池容量が減ってくると、十分な電力を供給できなくなり、電力供給をうけるデバイスがうまく動作しなくなるなどの不具合が発生する。 In recent years, it is desirable to develop an energy-saving society by using electric vehicles and smart grids that make use of natural energy. Among them, the secondary battery has a large role as a power storage device. In particular, lithium ion secondary batteries have excellent capacity and output, and can contribute to downsizing of the system. In that case, since the amount of electric power is small in one lithium ion battery, it is often used as an assembled battery of lithium ion secondary batteries combined in series and in parallel. In this case, it is an indispensable technique to sequentially grasp the deterioration state of the entire assembled battery that changes depending on various use conditions. For example, when a lithium ion secondary battery deteriorates and the battery capacity that can be stored decreases, sufficient power cannot be supplied, and problems such as failure of a device that receives power supply to operate properly occur.

従来、単電池・組電池の劣化状態を評価するのには、リチウムイオン二次電池のインピーダンスを測定し、所定の基準と比べることで評価する技術が知られている。特許文献１では、組電池全体のインピーダンスを評価し規定インピーダンス以上を示した場合には組電池を寿命と判定している。 Conventionally, in order to evaluate the deterioration state of a single battery or an assembled battery, a technique is known in which the impedance of a lithium ion secondary battery is measured and compared with a predetermined standard. In patent document 1, when the impedance of the whole assembled battery is evaluated and it shows more than a specified impedance, the assembled battery is determined to have a lifetime.

しかしながら、特許文献１のようにインピーダンスを用いる手法では、外部の環境によって判定精度が落ちる場合がある。リチウムイオン二次電池は外部の温度に敏感であり、例えば、温度が高い場合であると、インピーダンスは低い値となり、温度が低い場合であると、インピーダンスは高い値となる。温度が高い条件においては、本来寿命と判断すべきインピーダンスの大きさになっていても、低く見積もられ使用可と判断され、逆に温度が低い条件下においては、本来、正常とされるはずのインピーダンスであるのに、大きく見積もられ寿命と判断されてしまう場合がある。また、論理回路での温度補正を行うこともできるが、初期だけでなく劣化後の各温度のインピーダンスの特性をあらかじめ正確に把握する必要があり、現実的ではない。 However, in the technique using impedance as in Patent Document 1, the determination accuracy may be reduced depending on the external environment. The lithium ion secondary battery is sensitive to an external temperature. For example, when the temperature is high, the impedance is a low value, and when the temperature is low, the impedance is a high value. Under conditions where the temperature is high, even if the impedance is supposed to be considered as a lifetime, it is estimated to be low and can be used. Conversely, under conditions where the temperature is low, it should be normal. In some cases, it is estimated that the life is long estimated even though the impedance is. In addition, although it is possible to perform temperature correction by a logic circuit, it is necessary to accurately grasp the impedance characteristics of each temperature after deterioration as well as the initial stage, which is not realistic.

特開平９−１１４５８８号公報JP-A-9-114588

本発明は、外部の環境温度によらず、精度よく組電池の寿命判定が可能な組電池およびそれを用いた蓄電装置と、その寿命判定方法を提供することを目的とする。 An object of the present invention is to provide an assembled battery that can accurately determine the life of the assembled battery regardless of the external environmental temperature, a power storage device using the assembled battery, and a method for determining the life thereof.

本発明にかかる蓄電装置は、複数の単電池が直列接続された蓄電装置において、複数の単電池は第１単電池と第２単電池とを含み、第１単電池は第２単電池よりも容量が小さく、且つ第２単電池よりも早く放電終了電圧に達する初期状態を持ち、且つ第１単電池は、第２単電池よりもサイクル劣化速度が遅く、第１単電池の電圧を監視する第１の電圧測定装置と、第２単電池の電圧を監視する第２の電圧測定装置と、第１単電池の電圧と第２単電池の電圧を監視し、充放電後に、第２単電池が第１単電池より先に放電終了電圧に達するときに蓄電装置の寿命と判断する電気回路と、を有することを特徴とする蓄電装置である。 A power storage device according to the present invention is a power storage device in which a plurality of single cells are connected in series, wherein the plurality of single cells includes a first single cell and a second single cell, and the first single cell is more than the second single cell. It has a small capacity and has an initial state in which the discharge end voltage is reached earlier than the second unit cell, and the first unit cell has a slower cycle deterioration rate than the second unit cell, and monitors the voltage of the first unit cell. The first voltage measuring device, the second voltage measuring device for monitoring the voltage of the second unit cell, the voltage of the first unit cell and the voltage of the second unit cell, and after charging / discharging, the second unit cell And an electric circuit that determines that the life of the power storage device is reached when the discharge end voltage is reached before the first unit cell.

この構成によれば、充放電過程において、第１単電池と第２単電池の各電圧を監視し、第２単電池よりも早く第１単電池が放電終了電圧に達する正常状態から、第１単電池よりも先に第２単電池が放電終了電圧に達する状態を寿命と判断するものである。つまり先に放電終了となる電池が、第１単電池から第２単電池に入れ代わる際に寿命と判断されうる。このように蓄電装置内に併設された前記二種の単電池を相対評価することで、環境温度によらず組電池の寿命を精度良く判断することができる。なお、第１単電池と第２単電池の容量差は、本発明の効果を発現する程度であれば特に限定されるものではないが、たとえば３％以上の差をもって設計すれば、高感度な論理回路を用いずとも判別可能である。 According to this configuration, in the charging / discharging process, each voltage of the first unit cell and the second unit cell is monitored, and from the normal state in which the first unit cell reaches the discharge end voltage earlier than the second unit cell, A state in which the second unit cell reaches the discharge end voltage before the unit cell is determined as the life. That is, it can be determined that the battery whose discharge has ended first is replaced with the second battery when the first battery is replaced with the second battery. Thus, by relatively evaluating the two types of unit cells provided in the power storage device, it is possible to accurately determine the life of the assembled battery regardless of the environmental temperature. Note that the capacity difference between the first unit cell and the second unit cell is not particularly limited as long as the effect of the present invention is exhibited. However, for example, if the design is made with a difference of 3% or more, high sensitivity is achieved. The determination can be made without using a logic circuit.

本発明にかかる組電池の寿命判定方法は、複数の単電池が直列に接続されてなる組電池の寿命判定方法であって、複数の単電池は第１単電池と第２単電池とを有し、第１単電池の電圧と第２単電池の電圧とをそれぞれ監視し、放電時に、第１単電池が先に放電終了電圧となった際は、正常と判定し、充放電の繰り返しにより、第２単電池が先に放電終了電圧となった際に、蓄電装置の寿命と判断する組電池の寿命判定方法である。 The battery life determination method according to the present invention is a battery life determination method in which a plurality of single cells are connected in series, and the plurality of single batteries includes a first battery cell and a second battery cell. The voltage of the first unit cell and the voltage of the second unit cell are respectively monitored, and when the first unit cell reaches the discharge end voltage at the time of discharging, it is determined as normal and the charge / discharge is repeated. This is a method of determining the life of the assembled battery, in which the life of the power storage device is determined when the second cell reaches the discharge end voltage first.

この手法によれば、組電池に併設された前記二種の単電池の電圧を相対評価することで、環境温度によらず組電池の寿命を精度良く判断することができる。 According to this method, the life of the assembled battery can be accurately determined regardless of the environmental temperature by relatively evaluating the voltages of the two types of single cells provided in the assembled battery.

本発明にかかる組電池は、複数の単電池が直列に接続されており、第１単電池と、第２単電池と、第１単電池と第２単電池それぞれの電圧を監視して比較するための引き出し線と、を含み、第１単電池は第２単電池より容量が小さく、且つ、第２単電池よりサイクル劣化速度が遅いことを特徴とする組電池である。 In the assembled battery according to the present invention, a plurality of single cells are connected in series, and the voltages of the first single cell, the second single cell, and the first single cell and the second single cell are monitored and compared. The first unit cell has a smaller capacity than the second unit cell and has a cycle deterioration rate slower than that of the second unit cell.

この構成によれば、組電池内に併設された、第１単電池と第２単電池の劣化特性差を利用し、組電池のサイクル寿命を判定することができる組電池を提供しうる。この際、組電池内に併設された前記二種の単電池の電池容量を相対評価することで、環境温度によらず組電池の寿命を精度良く判断することができる。 According to this configuration, it is possible to provide an assembled battery that can be used to determine the cycle life of the assembled battery by using the deterioration characteristic difference between the first and second single batteries provided in the assembled battery. At this time, by relatively evaluating the battery capacities of the two types of unit cells provided in the assembled battery, it is possible to accurately determine the life of the assembled battery regardless of the environmental temperature.

また、第１単電池と第２単電池は組電池中で隣接して構成されていることが望ましい。 Moreover, it is desirable that the first unit cell and the second unit cell are configured adjacent to each other in the assembled battery.

また、第１単電池と第２単電池の正極活物質が同種のものであり、且つ、前記第１単電池の正極活物質の平均粒径は、前記第２単電池の正極活物質の平均粒径よりも大きいことを特徴とする、組電池であることが望ましい。 Moreover, the positive electrode active materials of the first unit cell and the second unit cell are of the same type, and the average particle size of the positive electrode active material of the first unit cell is the average of the positive electrode active material of the second unit cell. It is desirable to be an assembled battery characterized by being larger than the particle size.

この構成によれば、正極活物質は小さいと劣化特性が悪くなる傾向があるため、第１単電池の正極活物質の平均粒径を第２単電池の平均粒径よりも大きくすることで、第１単電池と第２単電池に比較的容易にサイクル劣化による特性差を持たせることができ、環境温度によらず組電池の寿命を判定することができる。 According to this configuration, if the positive electrode active material is small, the deterioration characteristics tend to deteriorate, so by making the average particle size of the positive electrode active material of the first unit cell larger than the average particle size of the second unit cell, The first single battery and the second single battery can have a characteristic difference due to cycle deterioration relatively easily, and the life of the assembled battery can be determined regardless of the environmental temperature.

前記第１単電池の単位面積当たりの正極活物質の電気容量に対する、対向する単位面積当たりの負極活物質の電気容量の比率が、前記第２単電池よりも小さく、且つ１より大きいことを特徴とする、組電池であることが望ましい。 The ratio of the electric capacity of the negative electrode active material per unit area opposed to the electric capacity of the positive electrode active material per unit area of the first unit cell is smaller than that of the second unit cell and greater than 1. It is desirable that the battery is an assembled battery.

この構成によれば、前記第１単電池の単位面積当たりの正極活物質の容量に対する、対向する単位面積当たりの負極活物質の容量の比率を、前記第２単電池よりも小さくすることで、第１単電池のサイクル劣化を第２単電池よりも遅くすることができるとともに、前記比率を１以上とすることで、安全性がより向上しうる。 According to this configuration, by making the ratio of the capacity of the negative electrode active material per unit area opposed to the capacity of the positive electrode active material per unit area of the first unit cell smaller than that of the second unit cell, The cycle deterioration of the first unit cell can be made slower than that of the second unit cell, and safety can be further improved by setting the ratio to 1 or more.

前記第１単電池の正極活物質層に用いているバインダーの平均分子量は、前記第２単電池の正極活物質層に用いているバインダーの平均分子量よりも大きいことを特徴とする組電池であることが望ましい。 In the assembled battery, the average molecular weight of the binder used for the positive electrode active material layer of the first unit cell is larger than the average molecular weight of the binder used for the positive electrode active material layer of the second unit cell. It is desirable.

この構成によれば、正極活物質層に用いているバインダーの分子量が大きいとサイクル劣化特性がよくなる傾向があるため、第１単電池の正極活物質層に用いたバインダーの平均分子量を第２単電池の正極活物質層に用いた平均分子量よりも大きくすることで、第１単電池と第２単電池にサイクル劣化による特性差を持たせることができ、環境温度によらず組電池の寿命を判定することができる。 According to this configuration, if the molecular weight of the binder used in the positive electrode active material layer is large, cycle deterioration characteristics tend to be improved. Therefore, the average molecular weight of the binder used in the positive electrode active material layer of the first unit cell is set to the second unit. By making it larger than the average molecular weight used for the positive electrode active material layer of the battery, it is possible to give a difference in characteristics due to cycle deterioration between the first unit cell and the second unit cell, and the life of the assembled battery can be extended regardless of the environmental temperature. Can be determined.

前記第１単電池の正極活物質層中のＮＭＰ（Ｎ−メチルピロリドン）は、前記第２単電池の正極活物質層中に含有される量よりも少ないことを特徴とする組電池であることが望ましい。 The assembled battery is characterized in that NMP (N-methylpyrrolidone) in the positive electrode active material layer of the first unit cell is less than the amount contained in the positive electrode active material layer of the second unit cell. Is desirable.

この構成によれば、正極活物質層中に、ＮＭＰを含有させることで、リチウムイオン二次電池のサイクル劣化特性を比較的容易にコントロールすることができ、第１単電池の正極活物質層に含まれるＮＭＰ含有量を第２単電池の正極活物質層中に含まれるＮＭＰよりも少なくすることで、第１単電池と第２単電池にサイクル劣化による特性差を持たせることができ、環境温度によらず組電池の寿命を判定することができる。 According to this configuration, by including NMP in the positive electrode active material layer, the cycle deterioration characteristics of the lithium ion secondary battery can be controlled relatively easily. By making the NMP content contained smaller than that of the NMP contained in the positive electrode active material layer of the second unit cell, the first unit cell and the second unit cell can have a characteristic difference due to cycle deterioration. The lifetime of the assembled battery can be determined regardless of the temperature.

本発明によれば、組電池の環境温度によらず、精度よく組電池の寿命判定を行える寿命判定方法、そのために用いる組電池およびそれを用いた蓄電池を提供することが可能となる。 ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the lifetime determination method which can determine the lifetime of an assembled battery accurately, irrespective of the environmental temperature of an assembled battery, the assembled battery used for it, and a storage battery using the same.

本発明に適用可能な実施形態の蓄電装置を模式的に示す図である。It is a figure which shows typically the electrical storage apparatus of embodiment applicable to this invention. 本発明に係るリチウムイオン二次電池の構成例を示す概略断面図である。It is a schematic sectional drawing which shows the structural example of the lithium ion secondary battery which concerns on this invention. 実施例１の第１単電池と第２単電池のサイクル劣化特性を現したグラフである。4 is a graph showing cycle deterioration characteristics of the first unit cell and the second unit cell of Example 1; 実施例１の組電池の第１単電池と第２単電池の各々の電圧と充電状態の関係を示したグラフである。4 is a graph showing a relationship between a voltage and a charge state of each of the first cell and the second cell of the assembled battery of Example 1. 実施例２の手法で単電池のサイクル劣化特性を設計した際の、サイクル数と電池容量の関係を示したグラフである。6 is a graph showing the relationship between the number of cycles and the battery capacity when the cycle deterioration characteristics of a single cell are designed by the method of Example 2. 実施例３の手法で単電池のサイクル劣化特性を設計した際の、サイクル数と電池容量の関係を示したグラフである。6 is a graph showing the relationship between the number of cycles and the battery capacity when the cycle deterioration characteristics of a single cell are designed by the method of Example 3. 実施例４の手法で単電池のサイクル劣化特性を設計した際の、サイクル数と電池容量の関係を示したグラフである。6 is a graph showing the relationship between the number of cycles and the battery capacity when the cycle deterioration characteristics of a single cell are designed by the method of Example 4. 比較例の組電池の各温度での、インピーダンスとサイクル劣化特性の関係を示したグラフである。It is the graph which showed the relationship of the impedance and cycle deterioration characteristic in each temperature of the assembled battery of a comparative example.

本発明を実施するための形態（実施形態）につき、図面を参照しつつ詳細に説明する。なお、本明細書において特に言及している事項以外の事柄であって本発明の実施に必要な事柄（たとえば、組電池の構築手段、単電池を構成する電極体ユニットや電解質の構成、電池構築のためのプロセス等）は、当該分野における技術常識に基づいて、変形可能である。 DESCRIPTION OF EMBODIMENTS Embodiments (embodiments) for carrying out the present invention will be described in detail with reference to the drawings. It should be noted that matters other than the matters specifically mentioned in the present specification and necessary for the implementation of the present invention (for example, the construction means of the assembled battery, the construction of the electrode body unit or the electrolyte constituting the unit cell, the construction of the battery Can be modified based on common technical knowledge in the field.

本明細書において、「単電池」とは、組電池を構成するために相互に直列接続され得る個々の電池をいう。本明細書において「電池」とは、リチウムイオン二次電池をいい、特に限定しない限り種々の組成を有するリチウムイオン二次電池を包含する。 In the present specification, the “unit cell” refers to individual cells that can be connected in series to each other to form an assembled battery. In the present specification, the “battery” refers to a lithium ion secondary battery, and includes lithium ion secondary batteries having various compositions unless otherwise specified.

本明細書において、「電池容量」とは、特に限定しない限り、リチウムイオン二次電池に蓄えることのできる電気量の最大量をいい、通常Ａｈの単位を用いる。また、あらかじめ定められた放電終了の電圧から充電し、あらかじめ定められた充電終了となる電圧まで充電した際にリチウムイオン二次電池に蓄えられる電気量と同等である。このとき充電終了電圧になった後に、あらかじめ定められた時間及びあらかじめ定められた電流値になるまで定電圧充電をしてもよい。 In this specification, “battery capacity” means the maximum amount of electricity that can be stored in a lithium ion secondary battery, unless otherwise limited, and usually uses units of Ah. Further, it is equivalent to the amount of electricity stored in the lithium ion secondary battery when charged from a predetermined voltage at the end of discharge and charged to a voltage at which the predetermined charge is completed. At this time, after the charging end voltage is reached, constant voltage charging may be performed until a predetermined time and a predetermined current value are reached.

本明細書において、「放電終了電圧」とは、特に限定しない限り、個々のリチウムイオン二次電池に設定される使用下限電圧をいい、通常Ｖの単位を用いる。設定される電圧値は、使用される正極活物質、負極活物質の組み合わせによって変わる。また、使用目的によっても異なり、電池容量を最大限に使用したい場合は、低い電圧（たとえば３Ｖ以下）を選ぶことができ、電池容量の数十％のみを使用することで安全、長寿命化したい場合は、高い電圧（たとえば３．７Ｖ程度）を選ぶことができる。 In the present specification, the “discharge end voltage” means a use lower limit voltage set for each lithium ion secondary battery unless otherwise specified, and usually uses a unit of V. The set voltage value varies depending on the combination of the positive electrode active material and the negative electrode active material used. Also, depending on the purpose of use, if you want to use the battery capacity to the maximum, you can select a low voltage (for example, 3V or less) and use only tens of percent of the battery capacity to increase the safety and service life. In this case, a high voltage (for example, about 3.7V) can be selected.

図１に本実施形態の蓄電装置を模式的に示す。本実施形態の蓄電装置４０は、第１単電池１４と、第２単電池１６と、が直列に接続されている組電池において、第１単電池１４と第２単電池１６の関係は、第１単電池１４の電池容量が第２単電池１６よりも所定量以上小さく、第１単電池１４のサイクル劣化速度が第２単電池１６よりも遅く、且つ第２単電池よりも早く放電終了電圧に達する初期状態を持ち、第１単電池１４と第２単電池１６にそれぞれ、電圧測定装置３０、電圧測定装置３５が並列に接続されていて、電圧測定装置３０、電圧測定装置３５で得られた、電圧を元に、蓄電装置の寿命を判断する電気回路３８にて組電池の寿命を判定する蓄電装置である。必要に応じて、組電池の大部分を占める単電池１２と直列に接続されていても良い。また、図面では、割愛してあるが、直列に接続された各単電池は、それぞれ、個別に同等の単電池を並列に接続してもよく、組電池の大部分を占める単電池１２もそれぞれ個別に、過放電や過充電防止のため電圧測定装置を設け、あわせて制御回路を設けてもてもよい。 FIG. 1 schematically shows the power storage device of this embodiment. The power storage device 40 of the present embodiment is a battery pack in which the first unit cell 14 and the second unit cell 16 are connected in series, and the relationship between the first unit cell 14 and the second unit cell 16 is as follows. The discharge capacity voltage of the single cell 14 is smaller than the second cell 16 by a predetermined amount or more, the cycle deterioration rate of the first cell 14 is slower than that of the second cell 16 and earlier than the second cell. The voltage measuring device 30 and the voltage measuring device 35 are connected in parallel to the first unit cell 14 and the second unit cell 16, respectively, and are obtained by the voltage measuring device 30 and the voltage measuring device 35. In addition, the electric storage device determines the life of the assembled battery by the electric circuit 38 that determines the life of the electric storage device based on the voltage. As needed, you may connect in series with the cell 12 which occupies most assembled batteries. Moreover, although omitted in the drawings, each unit cell connected in series may be individually connected to the same unit cell in parallel, and each unit cell 12 that occupies most of the assembled battery is also each. Individually, a voltage measurement device may be provided to prevent overdischarge and overcharge, and a control circuit may be provided.

第１単電池１４と、第２単電池１６との、電池容量差は、たとえば、単電池の製造時での電池容量差以上（たとえば３％以上）であることが望ましい。また、通常、単電池を組電池化する際には、グルーピングによって同等程度の単電池を選び組電池化するため、第１単電池１４と、第２単電池１６との、電池容量差は、グルーピング時の電池容量ばらつきである１％程度以上あれば十分である。 It is desirable that the battery capacity difference between the first unit cell 14 and the second unit cell 16 is, for example, not less than the difference in battery capacity at the time of manufacturing the unit cell (for example, 3% or more). In addition, when a unit cell is assembled into an assembled battery, in order to select a unit cell of the same degree by grouping into a group battery, the difference in battery capacity between the first unit cell 14 and the second unit cell 16 is A battery capacity variation of about 1% or more during grouping is sufficient.

なお、サイクル劣化とは、純粋な充放電サイクル負荷による劣化だけでなく、高温状態での使用や、長期保存、温度ショック等による様々なユーザーによる使用環境によって影響しうる諸要因を加味し、充電、放電を繰り返し行うことによる通常使用による劣化を加味しうるものである。 Note that cycle deterioration is not only deterioration due to pure charge / discharge cycle load, but also charging by taking into account various factors that can be affected by various user environments such as use at high temperatures, long-term storage, temperature shock, etc. In addition, deterioration due to normal use due to repeated discharge can be taken into account.

本実施形態の蓄電装置は、初期において、第１単電池１４が第２単電池よりも早く放電終了電圧に達するように設定されているが、通常運用時も、第１単電池１４が第２単電池よりも早く放電終了電圧に達する。このとき、蓄電装置の寿命を判断する電気回路３８にて使用可能状態と判定する。蓄電装置を使用しサイクル回数が増加していくと、第１単電池、第２単電池共に劣化が進み、電池容量が減少していく。第１単電池よりも第２単電池の劣化が早いため、最終的に、第１単電池よりも先に第２単電池が放電終了となる。このとき、蓄電装置の寿命を判断する電気回路３８にて、組電池の寿命と判定する。また、この際、第１単電池と第２単電池は、組電池内で同等の環境にある。このため、環境温度の変化があっても、比較すべき第１単電池と第２単電池の特性は、同等程度に変化しているため、環境温度によらず放電終了を正しく判定することがきる。 The power storage device of the present embodiment is initially set so that the first unit cell 14 reaches the discharge end voltage earlier than the second unit cell, but the first unit cell 14 is the second unit even during normal operation. The end-of-discharge voltage is reached earlier than the unit cell. At this time, the electric circuit 38 that determines the life of the power storage device determines that the battery is usable. As the number of cycles increases using the power storage device, the deterioration of both the first cell and the second cell progresses, and the battery capacity decreases. Since the second unit cell deteriorates faster than the first unit cell, the second unit cell is finally discharged before the first unit cell. At this time, the electric circuit 38 that determines the life of the power storage device determines that the battery life is long. At this time, the first unit cell and the second unit cell are in the same environment in the assembled battery. For this reason, even if there is a change in the environmental temperature, the characteristics of the first cell and the second cell to be compared are changed to the same extent, so that it is possible to correctly determine the end of discharge regardless of the environmental temperature. Yes.

第１単電池と第２単電池の劣化特性と電池容量を設計し、適切な充電状態にて直列に接続することで、設定された組電池の寿命となるときに、前記第２単電池が、直列に接続された第１単電池よりも早く放電電圧となり、環境温度によらず組電池の寿命を判定することができる。このとき、第１単電池と第２単電池の温度特性はほぼ同等であることが望ましい。 By designing the deterioration characteristics and battery capacity of the first unit cell and the second unit cell and connecting them in series in an appropriate state of charge, the second unit cell is The discharge voltage becomes faster than the first unit cells connected in series, and the life of the assembled battery can be determined regardless of the environmental temperature. At this time, it is desirable that the temperature characteristics of the first cell and the second cell are substantially equal.

組電池の寿命は、組電池の主となるリチウムイオン２次電池についてあらかじめサイクル劣化試験を行い、劣化後にて諸特性（出力特性・入力特性・温度特性・安全性など）を満たすことが確認されている最大数か、最大数よりも少ないサイクル数での劣化を上限として、設定することができる。 As for the life of the assembled battery, a cycle deterioration test is conducted in advance on the lithium ion secondary battery, which is the main battery of the assembled battery, and it is confirmed that the characteristics (output characteristics, input characteristics, temperature characteristics, safety, etc.) are satisfied after the deterioration. It is possible to set the upper limit to deterioration at the maximum number or the number of cycles smaller than the maximum number.

第１単電池と第２単電池の劣化特性は、例えば、活物質の選択、導電助剤の量、バインダーの分子量、サイクル寿命をコントロールしうる添加剤、対向する正極と負極の単位面積当たりの塗工量比率などによって設計することが好ましい。 The deterioration characteristics of the first unit cell and the second unit cell include, for example, the selection of the active material, the amount of the conductive additive, the molecular weight of the binder, the additive capable of controlling the cycle life, and the unit area of the opposing positive and negative electrodes. It is preferable to design according to the coating amount ratio.

また、第１単電池と第２単電池の電池容量調整は、単位面積当たりに塗工される正極活物質層６１、負極活物質層７１の質量を大きくしたり、積層型単電池の場合は積総数を多くしたり、捲回型単電池の場合は、捲回数を多くしたりすることによって、設定された組電池の寿命となる際に第２単電池が先に放電終了となるように電池容量を設計することができる。 In addition, the battery capacity adjustment of the first unit cell and the second unit cell can be performed by increasing the mass of the positive electrode active material layer 61 and the negative electrode active material layer 71 applied per unit area or in the case of a stacked unit cell. When the total number of products is increased, or in the case of wound type cells, the number of times of winding is increased so that the second cell ends the discharge first when the set battery life is reached. Battery capacity can be designed.

図２に、単電池となるリチウムイオン二次電池の内部構造を模式的に示す。図２のリチウムイオン二次電池５０は、リチウムイオンを吸蔵放出する材料（正極活物質，負極活物質）を含む正極６０および負極７０と、リチウムイオン伝導性を有する電解質と、正極と負極との間にあって電解質を保持するセパレータ８０と、を含む。 In FIG. 2, the internal structure of the lithium ion secondary battery used as a cell is typically shown. A lithium ion secondary battery 50 in FIG. 2 includes a positive electrode 60 and a negative electrode 70 including materials that absorb and release lithium ions (positive electrode active material, negative electrode active material), an electrolyte having lithium ion conductivity, and a positive electrode and a negative electrode. And a separator 80 that holds the electrolyte therebetween.

本実施形態の第１単電池の電極は、活物質材料と、バインダーと、導電助剤とを含む塗料を集電体に塗布することによって形成することができる。バインダーには、ポリフッ化ビリニデン（ＰＶＤＦ）、スチレンブタジエンゴム（ＳＢＲ）、カルボキシメチルセルロース（ＣＭＣ）などを用いることができる。これらバインダーを溶解させる溶媒には、Ｎ−メチルピロリドン（ＮＭＰ）、純水などを用いることができる。導電助剤には、カーボンブラック、アセチレンブラック、黒鉛などを用いることができる。集電体は、リチウムイオン二次電池に使用されている各種公知の材料を用いることができる。具体的には、負極集電体７２としては銅箔が、正極集電体６２としてはアルミニウム箔が例示される。 The electrode of the first unit cell of this embodiment can be formed by applying a paint containing an active material, a binder, and a conductive additive to a current collector. As the binder, polyvinylidene fluoride (PVDF), styrene butadiene rubber (SBR), carboxymethyl cellulose (CMC), or the like can be used. As a solvent for dissolving these binders, N-methylpyrrolidone (NMP), pure water or the like can be used. Carbon black, acetylene black, graphite or the like can be used as the conductive assistant. As the current collector, various known materials used in lithium ion secondary batteries can be used. Specifically, the negative electrode current collector 72 is exemplified by a copper foil, and the positive electrode current collector 62 is exemplified by an aluminum foil.

正極は、併用する正極活物質と、所定の導電助剤と、所定のバインダーとを混合して作製することができる。正極活物質として、ＬｉＴｉＯ_２、ＬｉＦｅＰＯ_４（以下、「ＬＦＰ」という）、Ｌｉ（Ｎｉ_{１−ｘ−ｙ}Ｃｏ_ｘＭｎ_ｙ）Ｏ_２（以下、「ＮＣＭ」という。０．１≦ｘ≦０．５、０．１≦ｙ≦０．５）、Ｌｉ_ａ（Ｎｉ_{１−ｂ−ｃ}Ｃｏ_ｂＡｌ_ｃ）Ｏ_２（０．９≦ａ≦１．３、０＜ｂ≦０．５、０＜ｃ≦０．７）、ＬｉＶＰＯ_４、ＬｉＶＯＰＯ_４、ＬｉＣｏＯ_２、ＬｉＭｎＰＯ_４、ＬｉＣｏＰＯ_４、ＬｉＮｉＰＯ_４などが例示される。また、例えば、劣化速度の遅い活物質として粒径の大きな正極活物質、劣化速度の速い活物質として粒径の小さい正極活物質を選択することができ、単電池の劣化特性を設計しうる。この塗料を正極集電体６２であるアルミ箔上に塗布し、乾燥させて単電池の正極を形成する。 The positive electrode can be produced by mixing a positive electrode active material to be used in combination, a predetermined conductive auxiliary agent, and a predetermined binder. As the positive electrode active material, LiTiO ₂ , LiFePO ₄ (hereinafter referred to as “LFP”), Li (Ni _1-xy Co _x Mn _y ) O ₂ (hereinafter referred to as “NCM”, 0.1 ≦ x ≦ 0. 5, 0.1 ≦ y ≦ 0.5), Li _a (Ni _1- bc Co _b Al _c ) O ₂ (0.9 ≦ a ≦ 1.3, 0 <b ≦ 0.5, 0 < c ≦ 0.7), LiVPO ₄ , LiVOPO ₄ , LiCoO ₂ , LiMnPO ₄ , LiCoPO ₄ , LiNiPO _{4 and the} like. Further, for example, a positive electrode active material having a large particle size can be selected as an active material having a slow deterioration rate, and a positive electrode active material having a small particle size can be selected as an active material having a high deterioration rate, so that the deterioration characteristics of the unit cell can be designed. This paint is applied on the aluminum foil as the positive electrode current collector 62 and dried to form the positive electrode of the unit cell.

負極は、併用する負極活物質と、所定の導電助剤と、所定のバインダーとを混合して作製することができる。負極活物質として、ハードカーボン、グラファイト、シリコン化合物、スズ化合物などが例示される。たとえば、負極活物質としてグラファイト、導電助剤としてカーボンブラックを、バインダーとしてＰＶＤＦを、溶媒であるＮＭＰに分散させて混合し、負極塗料を作製する。この塗料を負極集電体７２である銅箔上に塗布し、乾燥させて単電池の負極を形成する。このとき、負極活物質層７１となる塗料の塗工量を調整することによって、単電池の劣化特性を設計しうる。 The negative electrode can be prepared by mixing a negative electrode active material to be used in combination, a predetermined conductive assistant, and a predetermined binder. Examples of the negative electrode active material include hard carbon, graphite, a silicon compound, and a tin compound. For example, graphite as a negative electrode active material, carbon black as a conductive assistant, and PVDF as a binder are dispersed and mixed in NMP as a solvent to prepare a negative electrode paint. This paint is applied onto a copper foil as the negative electrode current collector 72 and dried to form a negative electrode of a single cell. At this time, the deterioration characteristics of the unit cell can be designed by adjusting the coating amount of the coating material to be the negative electrode active material layer 71.

作製した正極と負極とは、セパレータを介して積層又は巻回され、電池要素として外装体の中に挿入される。セパレータには特に制限はなく、広く公知の材料を用いることができる。例えば、ポリエチレン、ポリプロピレンなどのポリオレフィン系樹脂の微多孔膜を用いることができる。 The produced positive electrode and negative electrode are laminated or wound via a separator and inserted into the outer package as a battery element. There is no restriction | limiting in particular in a separator, A widely well-known material can be used. For example, a microporous film of a polyolefin resin such as polyethylene or polypropylene can be used.

正極６０、負極７０、セパレータ８０を積層した電池要素を封入する外装体は特に制限はなく、アルミニウムやステンレス製の缶、アルミニウムラミネート製の外装体を適宜選択することができる。 There is no particular limitation on the outer package that encloses the battery element in which the positive electrode 60, the negative electrode 70, and the separator 80 are laminated, and an aluminum or stainless steel can or an aluminum laminate outer package can be selected as appropriate.

この外装体の中に電池要素を挿入した後、電解質が加えられる。電解質は、非水電解液、ゲル状の電解質、無機物あるいは有機物の固体電解質を広く用いることができる。例えば、非水電解液は溶媒と塩を含む物を用いることができ、これは適宜添加物を含んでいてもよい。 After the battery element is inserted into the outer package, an electrolyte is added. As the electrolyte, a nonaqueous electrolytic solution, a gel electrolyte, an inorganic or organic solid electrolyte can be widely used. For example, the non-aqueous electrolyte may be a substance containing a solvent and a salt, which may contain additives as appropriate.

非水電解液の溶媒には、リチウムイオン伝導性のある溶媒が望ましい。例えば、エチレンカーボネート（ＥＣ）、プロピレンカーボネート（ＰＣ）、ブチレンカーボネート（ＢＣ）、ジフルオロカーボネート（ＦＥＣ）等の環状炭酸エステルを単体または適宜組み合わせて使用することができる。電気伝導度を高くし、かつ適切な粘度を有する電解液を得るため、鎖状炭酸エステルとして、ジメチルカーボネート（ＤＭＣ）、メチルエチルカーボネート（ＭＥＣ）、ジエチルカーボネート（ＤＥＣ）等を併用してもよい。非水電解液中の塩には、ＬｉＰＦ_６、ＬｉＢＦ_４、ＬｉＣｌＯ_４などを用いることができる。この後、外装体を真空密封し単電池を得ることができる。 As the solvent for the non-aqueous electrolyte, a solvent having lithium ion conductivity is desirable. For example, cyclic carbonates such as ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), and difluorocarbonate (FEC) can be used alone or in appropriate combination. In order to increase the electric conductivity and obtain an electrolytic solution having an appropriate viscosity, dimethyl carbonate (DMC), methyl ethyl carbonate (MEC), diethyl carbonate (DEC) or the like may be used in combination as the chain carbonate ester. . Salts of the non-aqueous electrolytic _solution, or the like can be used _{_{LiPF 6, LiBF 4, LiClO 4}} . Thereafter, the outer package is vacuum-sealed to obtain a single cell.

また、第１単電池と第２単電池は、それぞれの単電池の温度特性差が小さいことが望ましい。一般に、リチウムイオン二次電池の温度特性の傾向は同じであり、電解液の影響が大きく、第１単電池と第２単電池の電解液は、同等程度の電気伝導度の温度特性を持つことが望ましい。より好ましくは、電解液の電気伝導度の温度特性には、主溶媒の選択が重要であり、第１単電池と第２単電池に用いている、環状炭酸エステルと、鎖状炭酸エステルの混合比率が同等程度であることが望ましい。また、より好ましくは、第１単電池と第２単電池に用いている電解液は、同等の環状炭酸エステルと、同等の鎖状炭酸エステルで構成されていることが望ましい。 Further, it is desirable that the temperature difference between the first cell and the second cell is small. In general, the tendency of the temperature characteristics of lithium ion secondary batteries is the same, and the influence of the electrolyte is large, and the electrolytes of the first cell and the second cell have temperature characteristics of the same degree of electrical conductivity. Is desirable. More preferably, the selection of the main solvent is important for the temperature characteristics of the electrical conductivity of the electrolyte, and the mixture of the cyclic carbonate and the chain carbonate used in the first unit cell and the second unit cell is important. It is desirable that the ratio is comparable. More preferably, the electrolytic solution used for the first unit cell and the second unit cell is composed of an equivalent cyclic carbonate and an equivalent chain carbonate.

次に組電池の製造方法について述べる。本発明の組電池は、複数の単電池が直列に接続されており、第１単電池と、第２単電池と、第１単電池と第２単電池それぞれの電圧を監視して比較するための引き出し線と、を含み、第１単電池は第２単電池より容量が小さく、且つ、第２単電池よりサイクル劣化速度が遅いことを特徴とする。 Next, a method for manufacturing the assembled battery will be described. In the assembled battery of the present invention, a plurality of unit cells are connected in series, and the first unit cell, the second unit cell, and the respective voltages of the first unit cell and the second unit cell are monitored and compared. The first unit cell is smaller in capacity than the second unit cell and has a slower cycle deterioration rate than the second unit cell.

単電池を直列に接続する際に、前もって、各単電池の充電状態をそろえて接続することが望ましい。ここで充電状態とは、電池容量に対する、実際にたまっている電気容量の割合をいう。より好ましくは、満充電近傍の充電状態で接続することが望ましい。満充電近傍の充電状態で接続すると、満充電近傍での電圧ばらつきが最小となり、過充電状態となってしまう可能性が減り、安全な組電池となりうる。 When connecting the cells in series, it is desirable to connect the cells in the same state of charge in advance. Here, the state of charge refers to the ratio of the electric capacity actually accumulated to the battery capacity. More preferably, it is desirable to connect in a state of charge near full charge. When connected in a charged state near full charge, voltage variation near full charge is minimized, and the possibility of being overcharged is reduced, and a safe assembled battery can be obtained.

次に、第１単電池と第２単電池の劣化速度の設計方法について述べる。リチウムイオン二次電池は電池内で使用される各材料によって種々の特性を持つ。特に正極に用いられている正極活物質、負極に用いられている負極活物質、電解液はリチウムイオン二次電池の主たる特性を決めている。例えば、ここである正極活物質Ａと正極活物質Ｂについて特性を比較した場合、正極活物質Ａの劣化速度が速いとわかった場合では、第２単電池１６に正極活物質Ａを用い、第１単電池１４に正極活物質Ｂを用いればよい。初期での第１単電池１４と第２単電池１６は、組電池の寿命として定められる劣化状態時に、同等の電池容量となるように、設計すればよい。
また好ましくは、活物質ＡとＢは同種異径の活物質であって、粒径が小さくなるとリチウムイオン二次電池としての劣化速度は速くなることを利用すると、劣化特性以外の特性差を小さくすることができ望ましい。たとえば、第１単電池の正極活物質に１０μｍのＮＣＭを、第２単電池の正極活物質として５μｍのＮＣＭを用いることができる。ＬＦＰや他の活物質を用いた構成であってもよい。 Next, a method for designing the deterioration rate of the first cell and the second cell will be described. The lithium ion secondary battery has various characteristics depending on each material used in the battery. In particular, the positive electrode active material used for the positive electrode, the negative electrode active material used for the negative electrode, and the electrolytic solution determine the main characteristics of the lithium ion secondary battery. For example, when the characteristics of the positive electrode active material A and the positive electrode active material B are compared, and it is found that the deterioration rate of the positive electrode active material A is fast, the positive electrode active material A is used for the second unit cell 16, The positive electrode active material B may be used for the single cell 14. What is necessary is just to design the 1st cell 14 and the 2nd cell 16 in an initial stage so that it may become an equivalent battery capacity at the time of the deterioration state defined as a lifetime of an assembled battery.
Preferably, the active materials A and B are active materials of the same type and different diameters, and if the deterioration rate of the lithium ion secondary battery is increased as the particle size is reduced, the characteristic difference other than the deterioration characteristic is reduced. Can be desirable. For example, 10 μm NCM can be used as the positive electrode active material of the first unit cell, and 5 μm NCM can be used as the positive electrode active material of the second unit cell. A configuration using LFP or another active material may be used.

また、正極と負極の活物質層比率を変えることでも、劣化特性を設計することができる。一般に、正極の単位面積当たりに塗工される正極活物質層の電気容量と、対向する負極の単位面積当たりに塗工される負極活物質層の電気容量は、負極活物質層のほうが大きく設計されている。この時の単位面積当たりの正極に対する負極の電気容量の比率が大きくなると、単電池の劣化速度が速くなる傾向がある。たとえば、第１単電池１４の単電池の前記電気容量比率を１．３とし、第２単電池１６の前記電気容量比率を１．８とすることで、第１単電池の劣化速度は、第２単電池よりも遅くすることができ、本実施形態の蓄電装置へ適応しうる。 The deterioration characteristics can also be designed by changing the active material layer ratio between the positive electrode and the negative electrode. In general, the negative electrode active material layer is designed so that the capacitance of the positive electrode active material layer applied per unit area of the positive electrode and the negative electrode active material layer applied per unit area of the opposing negative electrode are larger. Has been. When the ratio of the electric capacity of the negative electrode to the positive electrode per unit area at this time increases, the deterioration rate of the unit cell tends to increase. For example, by setting the electric capacity ratio of the unit cell of the first unit cell 14 to 1.3 and the electric capacity ratio of the second unit cell 16 to 1.8, the deterioration rate of the first unit cell is It can be made slower than the two unit cells, and can be applied to the power storage device of this embodiment.

また、正極活物質層、負極活物質層に用いているバインダー量やバインダーの分子量によって単電池の劣化特性を設計することができる。バインダー量が多い場合や、バインダーの分子量が大きい場合に、活物質層の劣化を抑えることができる。たとえば、第１単電池の正極活物質層中のＰＶＤＦ（ポリフッ化ビニリデン）の分子量を１００万、第２単電池の正極活物質層中のＰＶＤＦの分子量を５０万とすると、第１単電池の劣化速度を、第２単電池よりも遅くすることができ、本実施形態の蓄電装置へ適応しうる。 Further, the deterioration characteristics of the unit cell can be designed according to the amount of binder used in the positive electrode active material layer and the negative electrode active material layer and the molecular weight of the binder. When the amount of the binder is large or when the molecular weight of the binder is large, the deterioration of the active material layer can be suppressed. For example, assuming that the molecular weight of PVDF (polyvinylidene fluoride) in the positive electrode active material layer of the first unit cell is 1,000,000 and the molecular weight of PVDF in the positive electrode active material layer of the second unit cell is 500,000, The deterioration rate can be made slower than that of the second unit cell, and can be applied to the power storage device of the present embodiment.

また、正極活物質層、負極活物質層に、単電池のサイクル劣化特性を設計することができる添加剤を入れ込むことによって、単電池の劣化特性を設計することができる。単電池のサイクル劣化特性を設計することができる添加剤としてＮＭＰがあげられる。正極合材層へのＮＭＰの添加量が少ない方が単電池の劣化が抑えられる傾向がある。たとえば、第１単電池の正極活物質層に重量比で０．１％、第２単電池の正極活物質層に０．５％添加することで、第１単電池の劣化速度を、第２単電池よりも遅くすることができ、本実施形態の蓄電装置へ適応しうる。 Moreover, the deterioration characteristic of a single cell can be designed by putting the additive which can design the cycle deterioration characteristic of a single cell into a positive electrode active material layer and a negative electrode active material layer. NMP is an additive that can be used to design the cycle deterioration characteristics of a unit cell. When the amount of NMP added to the positive electrode mixture layer is small, the deterioration of the unit cell tends to be suppressed. For example, by adding 0.1% by weight to the positive electrode active material layer of the first unit cell and 0.5% to the positive electrode active material layer of the second unit cell, the deterioration rate of the first unit cell can be reduced to the second level. It can be slower than the unit cell, and can be applied to the power storage device of this embodiment.

また、第１単電池と第２単電池の電池容量調整について前述のとおりである。 The battery capacity adjustment of the first cell and the second cell is as described above.

以下、実施例及び比較例に基づいて本発明をより具体的に説明するが、本発明は以下の実施例に限定されるものではない。 EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example and a comparative example, this invention is not limited to a following example.

〔実施例１〕 [Example 1]

第１単電池１４の作製
〔電池電極の作製〕
（正極の作製）
正極活物質として、ＮＣＭ（ＬｉＮｉ_１／３Ｍｎ_１／３Ｃｏ_１／３Ｏ_２）と、導電助剤としてカーボンブラック及び黒鉛、バインダーとしてＰＶＤＦ（ポリフッ化ビニリデン）、を用い正極を作製した。ＮＣＭについては、平均粒径（Ｄ５０）で１０μｍのものを使用した。ＮＣＭを８５ｇ、カーボンブラックを５ｇ、黒鉛を５ｇの混合比率とした。これにＰＶＤＦ（呉羽化学工業（株）製、ＫＦ７３０５）のＮ−メチル−２−ピロリジノン（ＮＭＰ）溶液（５０ｇ、１０ｗｔ％）を加えて混合し、塗料１６５ｇを作製した。この塗料を集電体であるアルミニウム箔（厚み２０μｍ）にドクターブレード法で塗布後、９０℃で乾燥し、圧延した。 Production of first cell 14 [Production of battery electrode]
(Preparation of positive electrode)
A positive electrode was prepared using NCM (LiNi _1/3 Mn _1/3 Co _1/3 O ₂ ) as a positive electrode active material, carbon black and graphite as a conductive additive, and PVDF (polyvinylidene fluoride) as a binder. For NCM, an average particle diameter (D50) of 10 μm was used. The mixing ratio was 85 g of NCM, 5 g of carbon black, and 5 g of graphite. To this, an N-methyl-2-pyrrolidinone (NMP) solution (50 g, 10 wt%) of PVDF (manufactured by Kureha Chemical Industry Co., Ltd., KF7305) was added and mixed to prepare 165 g of paint. This paint was applied to an aluminum foil (thickness 20 μm) as a current collector by a doctor blade method, dried at 90 ° C., and rolled.

（負極の作製）
負極活物質として天然黒鉛を４５ｇ、導電助剤としてカーボンブラックを２．５ｇ、をドライミックスした後に、バインダーとしてＰＶＤＦ溶液２２．５ｇを加え負極用の塗料を作製した。この塗料を集電体である銅箔（厚み１６μｍ）にドクターブレード法で塗布後、乾燥（９０℃）、圧延した。 (Preparation of negative electrode)
After dry-mixing 45 g of natural graphite as a negative electrode active material and 2.5 g of carbon black as a conductive additive, 22.5 g of PVDF solution was added as a binder to prepare a negative electrode paint. This paint was applied to a copper foil (thickness 16 μm) as a current collector by a doctor blade method, dried (90 ° C.) and rolled.

〔電池の作製〕
得られた正極、負極を、セパレータ（ポリオレフィン製の微多孔質膜）と共に所定の寸法に切断した。正極、負極には、外部引き出し端子を溶接するために塗料（活物質＋導電助剤＋バインダー）を塗布しない部分を設けた。正極、セパレータ、負極をこの順序で積層した。このとき、リチウムイオン二次電池の容量が２００ｍＡｈになるように積層した。正極、負極には、それぞれ、外部引き出し端子としてアルミニウム箔（幅４ｍｍ、長さ４０ｍｍ、厚み１００μｍ）、ニッケル箔（幅４ｍｍ、長さ４０ｍｍ、厚み１００μｍ）を超音波溶接した。この外部引き出し端子に、ポリプロピレン（ＰＰ）を巻き付け熱接着させた。 [Production of battery]
The obtained positive electrode and negative electrode were cut into predetermined dimensions together with a separator (microporous membrane made of polyolefin). The positive electrode and the negative electrode were provided with portions to which no paint (active material + conductive aid + binder) was applied in order to weld the external lead terminals. A positive electrode, a separator, and a negative electrode were laminated in this order. At this time, the lithium ion secondary battery was laminated so that the capacity was 200 mAh. An aluminum foil (width 4 mm, length 40 mm, thickness 100 μm) and nickel foil (width 4 mm, length 40 mm, thickness 100 μm) were ultrasonically welded to the positive electrode and the negative electrode, respectively, as external lead terminals. Polypropylene (PP) was wrapped around this external lead terminal and thermally bonded.

正極、負極、セパレータを積層した電池要素を、アルミニウムラミネート材料からなる外装体に収容した。外装体の中に電池要素を入れた後、電解液としてエチレンカーボンネート（ＥＣ）とジエチルカーボネート（ＤＥＣ）の混合溶媒（ＥＣ：ＤＥＣ＝３０：７０ｖｏｌ％）にＬｉＰＦ_６を１Ｍに溶解させたものを添加し、外装体を真空密封し、リチウムイオン二次電池を作製した。リチウムイオン二次電池は、封止後、１０ｍＡ（０．０５Ｃ）にて初回充電した。得られたリチウムイオン二次電池の、初期の平均放電容量は、約２００ｍＡｈであった。 A battery element in which a positive electrode, a negative electrode, and a separator were laminated was housed in an exterior body made of an aluminum laminate material. After putting a battery element in the outer package, LiPF ₆ is dissolved in 1M in a mixed solvent of ethylene carbonate (EC) and diethyl carbonate (DEC) (EC: DEC = 30: 70 vol%) as an electrolytic solution. Was added, and the outer package was vacuum-sealed to produce a lithium ion secondary battery. The lithium ion secondary battery was initially charged at 10 mA (0.05 C) after sealing. The initial average discharge capacity of the obtained lithium ion secondary battery was about 200 mAh.

第２単電池１６の作製
正極作製時に、ＮＣＭの平均粒径（Ｄ５０）を５μｍとし、積層数を調節することで、初期の平均放電容量は約２４０ｍＡｈのリチウムイオン二次電池を得た。 Production of Second Single Battery 16 A lithium ion secondary battery having an initial average discharge capacity of about 240 mAh was obtained by adjusting the number of stacked layers by adjusting the average particle size (D50) of NCM to 5 μm during the production of the positive electrode.

第１単電池１４と第２単電池１６のそれぞれの電池に対し、完全放電状態から満充電状態までのサイクル劣化負荷を所定の回数繰り返した。その際の２００サイクルごとに電池容量を評価し、初期での第１単電池の電池容量を１００％として、サイクル劣化特性を評価すると図３のようになった。約１０００サイクル後に容量が同等になり、それ以降のサイクルにて、第２単電池１１６の容量が少なくなることを確かめた。 The cycle deterioration load from the fully discharged state to the fully charged state was repeated a predetermined number of times for each of the first unit cell 14 and the second unit cell 16. The battery capacity was evaluated every 200 cycles at that time, and the cycle capacity characteristics were evaluated as shown in FIG. It was confirmed that the capacity became equivalent after about 1000 cycles, and the capacity of the second unit cell 116 decreased in the subsequent cycles.

組電池の作製
あらかじめ作製しておいた、第１単電池１４を４個と、第２単電池１６を１個とをそれぞれ満充電状態になるまで充電し、直列に接続することで組電池を得た。その際、組電池として放電した際の、第１単電池１４と、第２単電池１６の個々の放電カーブを図４に示す。このとき、組電池の容量は、第１単電池１４の容量とほぼ同値となって２００ｍＡｈを示し、このときの容量を１００％として示した。組電池の放電終了後に、第１単電池１４を取り出してさらに放電させた時の放電カーブを負の領域に示した。なお、実施例１での組電池の寿命は１０００サイクルと設定した。また、放電終了電圧は２．５Ｖと設定した。 Production of assembled battery Charge the four first cell 14 and one second cell 16 prepared in advance until they are fully charged, and connect them in series by connecting them in series. Obtained. At that time, individual discharge curves of the first unit cell 14 and the second unit cell 16 when discharged as an assembled battery are shown in FIG. At this time, the capacity of the assembled battery was approximately the same as the capacity of the first unit cell 14 and showed 200 mAh, and the capacity at this time was shown as 100%. The discharge curve when the first cell 14 was taken out and further discharged after the discharge of the assembled battery was shown in the negative region. In addition, the lifetime of the assembled battery in Example 1 was set to 1000 cycles. The discharge end voltage was set to 2.5V.

その後、第１単電池と第２単電池に電圧測定用の配線を用い、電圧測定装置をそれぞれ並列に取り付けた後、前記電圧測定装置の電圧値を寿命判定装置へ伝えるための配線を施し、蓄電装置とした。 After that, using voltage measurement wiring for the first cell and the second cell, and attaching the voltage measurement devices in parallel, respectively, wiring for transmitting the voltage value of the voltage measurement device to the life determination device, A power storage device was obtained.

（組電池の作製と寿命判定試験）
作製した蓄電装置に、完全放電状態から満充電状態までのサイクル劣化負荷を所定の回数繰り返した後に、各環境温度下にて、寿命判定を行った際の結果を表１に示す。実施例１での蓄電装置を用いれば、環境温度によらず寿命判定をすることができた。 (Production of battery pack and life test)
Table 1 shows the results when the life was determined at each environmental temperature after the cycle deterioration load from the fully discharged state to the fully charged state was repeated a predetermined number of times for the produced power storage device. Using the power storage device in Example 1, it was possible to determine the life regardless of the environmental temperature.

〔実施例２〕
実施例２での第１単電池１４の作製
実施例２では、単位面積当たりの正極活物質の電気容量に対する、対向する単位面積当たりの負極活物質の電気容量の比率を変えることによって、リチウムイオン二次電池の劣化特性を設計した。 [Example 2]
Production of first unit cell 14 in Example 2 In Example 2, lithium ion was changed by changing the ratio of the electric capacity of the negative electrode active material per unit area to the electric capacity of the positive electrode active material per unit area. The degradation characteristics of the secondary battery were designed.

〔電池電極の作製〕
（正極の作製）
実施例１と同等の正極を利用した。 [Production of battery electrode]
(Preparation of positive electrode)
A positive electrode equivalent to that in Example 1 was used.

（負極の作製）
実施例１と同様に塗料を作製し、負極の電極を作製した。その際に、正極の単位面積当たりの電気容量に対する、対向する負極の単位面積あたりの電気容量の比率を１１０％、１３０％、２００％、２５０％となるように、単位面積当たりの銅箔上に塗工される負極合剤の量を調節し、４種類の負極を得た。 (Preparation of negative electrode)
A paint was prepared in the same manner as in Example 1 to prepare a negative electrode. At that time, on the copper foil per unit area, the ratio of the electric capacity per unit area of the opposing negative electrode to the electric capacity per unit area of the positive electrode is 110%, 130%, 200%, 250%. The amount of the negative electrode mixture to be applied to was adjusted to obtain four types of negative electrodes.

〔電池の作製〕
実施例１と同様の要領で、電池化を行い、正極の単位面積当たりの電気容量に対する、負極の電気容量の比率が異なる４種類のリチウムイオン二次電池を得た。得られたそれぞれのリチウムイオン二次電池の、初期の平均放電容量は、約２００ｍＡｈであった。 [Production of battery]
The battery was made in the same manner as in Example 1, and four types of lithium ion secondary batteries with different ratios of the electric capacity of the negative electrode to the electric capacity per unit area of the positive electrode were obtained. Each of the obtained lithium ion secondary batteries had an initial average discharge capacity of about 200 mAh.

〔サイクル劣化特性の評価〕
得られた、４種のリチウムイオン二次電池について、完全放電状態から満充電状態の範囲で充放電を繰り返す試験を行い、２００サイクルごとの電池容量を評価した。正極の単位面積当たりの電気容量に対する、対向する負極の単位面積あたりの電気容量の比率をＡ／Ｃとして表記した。結果を初期での電池容量を１００％となるように図５に示す。図５は、正極の単位面積当たりの電気容量に対する、対向する負極の単位面積あたりの電気容量の比率を調整することで、本発明に利用可能なリチウムイオン二次電池のサイクル劣化特性を設計しうることを確認した。 [Evaluation of cycle deterioration characteristics]
The obtained four types of lithium ion secondary batteries were subjected to a test of repeated charge / discharge in the range from a fully discharged state to a fully charged state, and the battery capacity for every 200 cycles was evaluated. The ratio of the electric capacity per unit area of the opposing negative electrode to the electric capacity per unit area of the positive electrode was expressed as A / C. The results are shown in FIG. 5 so that the initial battery capacity is 100%. FIG. 5 illustrates the cycle deterioration characteristics of a lithium ion secondary battery that can be used in the present invention by adjusting the ratio of the capacitance per unit area of the opposing negative electrode to the capacitance per unit area of the positive electrode. I confirmed it.

〔実施例３〕
実施例３では、正極活物質層に用いるバインダーの分子量をパラメータとすることで、リチウムイオン二次電池のサイクル劣化特性を設計した。 Example 3
In Example 3, the cycle deterioration characteristics of the lithium ion secondary battery were designed by using the molecular weight of the binder used for the positive electrode active material layer as a parameter.

〔電池電極の作製〕
（正極の作製）
正極塗量を作製する際に、ＰＶＤＦの分子量を約２５万と、約５０万と、約１００万と、の３種類をそれぞれ用い、その他は、実施例１の要領で３種類の正極を作製した。 [Production of battery electrode]
(Preparation of positive electrode)
When preparing the coating amount of the positive electrode, three types of PVDF molecular weights of about 250,000, about 500,000, and about 1,000,000 were used, respectively. did.

（負極の作製）
実施例１の負極と同等の負極を使用した。 (Preparation of negative electrode)
A negative electrode equivalent to the negative electrode of Example 1 was used.

〔電池の作製〕
実施例１と同様の要領で、電池化を行い、正極活物質層のバインダーの分子量が異なる３種類のリチウムイオン二次電池を得た。得られたそれぞれのリチウムイオン二次電池の、初期の平均放電容量は、約２００ｍＡｈであった。 [Production of battery]
The battery was made in the same manner as in Example 1 to obtain three types of lithium ion secondary batteries in which the molecular weight of the binder in the positive electrode active material layer was different. Each of the obtained lithium ion secondary batteries had an initial average discharge capacity of about 200 mAh.

〔サイクル劣化特性の評価〕
得られた、３種のリチウムイオン二次電池について、完全放電状態から満充電状態の範囲で充放電を繰り返す試験を行い、２００サイクルごとの電池容量を評価した。結果を図６に示す。図６は、正極活物質層のバインダーの分子量を調整し、本発明に利用可能なリチウムイオン二次電池のサイクル劣化特性を設計しうることを確認した。 [Evaluation of cycle deterioration characteristics]
The obtained three types of lithium ion secondary batteries were subjected to a test for repeated charge and discharge in a range from a fully discharged state to a fully charged state, and the battery capacity for every 200 cycles was evaluated. The results are shown in FIG. FIG. 6 confirms that the cycle deterioration characteristics of the lithium ion secondary battery that can be used in the present invention can be designed by adjusting the molecular weight of the binder of the positive electrode active material layer.

〔実施例４〕
実施例４では、正極活物質層にサイクル劣化を調整しうる添加剤として、ＮＭＰを用いたことでの、リチウムイオン二次電池のサイクル劣化特性を設計した。 Example 4
In Example 4, the cycle deterioration characteristic of the lithium ion secondary battery by using NMP as an additive capable of adjusting the cycle deterioration in the positive electrode active material layer was designed.

〔電池電極の作製〕
（正極の作製）
実施例１と同様に正極を作製した。その後、ＮＭＰの飽和雰囲気下に、作製した電極を置き、時間を調整することで、正極へのＮＭＰ添加量を調整した。ＮＭＰを添加した正極をガスクロマトグラフィーを用いて、ＮＭＰの濃度を測定したところ、正極活物質層の重量に対して、０．３％以下と、約０．８％程度の２種類の正極を得た。 [Production of battery electrode]
(Preparation of positive electrode)
A positive electrode was produced in the same manner as in Example 1. Thereafter, the prepared electrode was placed in a saturated atmosphere of NMP, and the amount of NMP added to the positive electrode was adjusted by adjusting the time. When the concentration of NMP was measured for the positive electrode to which NMP was added using gas chromatography, two types of positive electrodes, about 0.3% or less and about 0.8% with respect to the weight of the positive electrode active material layer, were obtained. Obtained.

〔電池の作製〕
実施例１と同様の要領で、電池化を行い、正極活物質層中へのＮＭＰの添加量が異なる２種類のリチウムイオン二次電池を得た。得られたそれぞれのリチウムイオン二次電池の、初期の平均放電容量は、約２００ｍＡｈであった。 [Production of battery]
Battery formation was performed in the same manner as in Example 1, and two types of lithium ion secondary batteries with different amounts of NMP added to the positive electrode active material layer were obtained. Each of the obtained lithium ion secondary batteries had an initial average discharge capacity of about 200 mAh.

〔サイクル劣化特性の評価〕
得られた、２種のリチウムイオン二次電池について、完全放電状態から満充電状態の範囲で充放電を繰り返す試験を行い、２００サイクルごとの電池容量を評価した。結果を図７に示す。図７は、正極活物質層へのＮＭＰ添加量によって、本発明に利用可能なリチウムイオン二次電池のサイクル劣化特性を設計しうることを確認した。 [Evaluation of cycle deterioration characteristics]
The obtained two types of lithium ion secondary batteries were subjected to a test of repeated charge / discharge in a range from a fully discharged state to a fully charged state, and the battery capacity for every 200 cycles was evaluated. The results are shown in FIG. FIG. 7 confirmed that the cycle deterioration characteristics of the lithium ion secondary battery that can be used in the present invention can be designed according to the amount of NMP added to the positive electrode active material layer.

以上、実施例２〜４で作製した、サイクル劣化特性を設計しうるリチウムイオン二次電池を、実施例１の要領で組電池化し蓄電装置とすることで、環境温度によらず組電池の寿命を評価可能である。 As described above, the lithium ion secondary battery that can be designed for cycle deterioration characteristics manufactured in Examples 2 to 4 is assembled into a battery as described in Example 1 to form a power storage device. Can be evaluated.

〔比較例１〕
（リチウムイオン二次電池の作製）
（正極）
正極活物質として、ＮＣＭ（ＬｉＮｉ_１／３Ｍｎ_１／３Ｃｏ_１／３Ｏ_２）を、導電助剤としてカーボンブラック及び黒鉛、バインダーとしてＰＶＤＦ（ポリフッ化ビニリデン）、を用い正極を作製した。これらはＮＣＭを８５ｇ、ＬＦＰを４２．５ｇ、カーボンブラックを５ｇ、黒鉛を５ｇの混合比率とした、これにＰＶＤＦのＮ−メチル−２−ピロリジノン（ＮＭＰ）溶液（５０ｇ、１０ｗｔ％）を加えて混合し、塗料１６５ｇを作製した。この塗料を集電体であるアルミニウム箔（厚み２０μｍ）にドクターブレード法で塗布後、９０℃で乾燥し、圧延した。 [Comparative Example 1]
(Production of lithium ion secondary battery)
(Positive electrode)
A positive electrode was produced using NCM (LiNi _1/3 Mn _1/3 Co _1/3 O ₂ ) as the positive electrode active material, carbon black and graphite as the conductive assistant, and PVDF (polyvinylidene fluoride) as the binder. These were mixed at a mixing ratio of 85 g of NCM, 42.5 g of LFP, 5 g of carbon black, and 5 g of graphite. 165 g of paint was prepared by mixing. This paint was applied to an aluminum foil (thickness 20 μm) as a current collector by a doctor blade method, dried at 90 ° C., and rolled.

（負極）
負極活物質として天然黒鉛を４５ｇ、導電助剤としてカーボンブラックを２．５ｇ、をドライミックスした後に、バインダーとしてＰＶＤＦ溶液２２．５ｇを加え負極用の塗料を作製した。この塗料を集電体である銅箔（厚み１６μｍ）にドクターブレード法で塗布後、乾燥（９０℃）、圧延した。 (Negative electrode)
After dry-mixing 45 g of natural graphite as a negative electrode active material and 2.5 g of carbon black as a conductive additive, 22.5 g of PVDF solution was added as a binder to prepare a negative electrode paint. This paint was applied to a copper foil (thickness 16 μm) as a current collector by a doctor blade method, dried (90 ° C.) and rolled.

正極、負極、セパレータを積層した電池要素を、アルミニウムラミネート材料からなる外装体に収容した。外装体の中に電池要素を入れた後、電解液としてエチレンカーボンネート（ＥＣ）とジエチルカーボネート（ＤＥＣ）の混合溶媒（ＥＣ：ＤＥＣ＝３０：７０ｖｏｌ％）にＬｉＰＦ_６を１Ｍに溶解させたものを添加し、外装体を真空密封し、リチウムイオン二次電池を作製した。リチウムイオン二次電池は、封止後、１０ｍＡ（０．０５Ｃ）にて初回充電しリチウムイオン２次電池を得た。その後、充電し初期の平均放電容量を確認したところは約２００ｍＡｈであった。
（リチウムイオン二次電池のインピーダンス評価）
組電池寿命をインピーダンス値から判断するために、得られたリチウムイオン二次電池のインピーダンスを１００サイクルごとに測定した。結果を図８に示す。このことから、１ｋＨｚでの交流インピーダンスが１６０ｍΩ程度になった場合に組電池の寿命と設定（図８の点線１００）した。同様にして、１００サイクルごとに各環境温度にした後にインピーダンスを評価した結果も示した。
（組電池の作製と寿命判定試験）
作製したリチウムイオン二次電池５個を満充電状態にし、５直列に接続し、組電池を得た。組電池をサイクル劣化試験を行った際の寿命判定を、特許文献１と同様に実施すると共に、各環境温度にても同様に実施した。 A battery element in which a positive electrode, a negative electrode, and a separator were laminated was housed in an exterior body made of an aluminum laminate material. After putting a battery element in the outer package, LiPF ₆ is dissolved in 1M in a mixed solvent of ethylene carbonate (EC) and diethyl carbonate (DEC) (EC: DEC = 30: 70 vol%) as an electrolytic solution. Was added, and the outer package was vacuum-sealed to produce a lithium ion secondary battery. The lithium ion secondary battery was initially charged at 10 mA (0.05 C) after sealing to obtain a lithium ion secondary battery. Then, when it charged and the initial average discharge capacity was confirmed, it was about 200 mAh.
(Impedance evaluation of lithium ion secondary battery)
In order to judge the assembled battery life from the impedance value, the impedance of the obtained lithium ion secondary battery was measured every 100 cycles. The results are shown in FIG. From this, when the alternating current impedance at 1 kHz becomes about 160 mΩ, the life of the assembled battery is set (dotted line 100 in FIG. 8). Similarly, the results of evaluating the impedance after each environmental temperature is set every 100 cycles are also shown.
(Production of battery pack and life test)
Five lithium ion secondary batteries produced were fully charged and connected in series to obtain an assembled battery. The life determination when the assembled battery was subjected to a cycle deterioration test was performed in the same manner as in Patent Document 1 and also at each environmental temperature.

その結果を表１に示す。２５℃以外の環境では、誤った判定がなされた。また一度寿命と判定された項目は、それ以降評価はしていない。 The results are shown in Table 1. In an environment other than 25 ° C, an incorrect determination was made. In addition, items that have been determined to have a lifetime have not been evaluated since then.

なお、表１中、５００サイクル後の−１０℃環境下の測定では比較例１は５００サイクル早く寿命と判断し誤判定となり、８００サイクル後の０℃環境下の測定では比較例１は２００サイクル早く寿命と判断し誤判定となり、１１００サイクル後の４５℃環境下の測定では比較例１は１００サイクル遅く寿命と判断し誤判定となった。

In Table 1, in the measurement in the −10 ° C. environment after 500 cycles, Comparative Example 1 was judged as a life cycle earlier by 500 cycles, resulting in an erroneous determination. In the measurement in the 0 ° C. environment after 800 cycles, Comparative Example 1 was 200 cycles. It was judged that the life was early and erroneously judged, and in the measurement in a 45 ° C. environment after 1100 cycles, Comparative Example 1 judged that the life was late by 100 cycles and misjudged.

本発明は、環境温度が大きく異なるような環境においても、複雑な判定回路を必要とせず、精度良く充電深度を評価できるリチウムイオン二次電池の組電池および蓄電装置を提供するため、リチウムイオン二次電池の組電池および蓄電装置の製造、販売に寄与するので、産業上の利用可能性を有する。 The present invention provides an assembled battery and a power storage device of a lithium ion secondary battery that can accurately evaluate the depth of charge without requiring a complicated determination circuit even in an environment where the environmental temperature varies greatly. Since it contributes to the manufacture and sale of secondary battery assemblies and power storage devices, it has industrial applicability.

２組電池の大部分を占める単電池
１４第１単電池
１６第２単電池
２０組電池
３０第１単電池の電圧測定装置
３５第２単電池の電圧測定装置
３８蓄電装置の寿命を判断する電気回路
４０蓄電装置
５０リチウムイオン二次電池
６０正極
６１正極活物質層
６２正極集電箔
７０負極
７１負極活物質層
７２負極集電箔
８０セパレータ
１００組電池の寿命と判定するインピーダンスの上限値 2 Single cell occupying most of the assembled battery 14 1st single cell 16 2nd single cell 20 20 assembled cell 30 voltage measuring device of the first single cell 35 voltage measuring device of the second single cell 38 Electricity for judging the life of the power storage device Circuit 40 Power storage device 50 Lithium ion secondary battery 60 Positive electrode 61 Positive electrode active material layer 62 Positive electrode current collector foil 70 Negative electrode 71 Negative electrode active material layer 72 Negative electrode current collector foil 80 Separator 100 Upper limit value of impedance determined as life of assembled battery

Claims

複数の単電池が直列接続された蓄電装置において、複数の単電池は第１単電池と第２単電池とを含み、前記第１単電池は前記第２単電池よりも容量が小さく、且つ前記第２単電池よりも早く放電終了電圧に達する初期状態を持ち、且つ前記第１単電池は、前記第２単電池よりもサイクル劣化速度が遅く、前記第１単電池の電圧を監視する第１の電圧測定装置と、前記第２単電池の電圧を監視する第２の電圧測定装置と、前記第１単電池の電圧と前記第２単電池の電圧を監視し、充放電後に、前記第２単電池が前記第１単電池より先に放電終了電圧に達するときに蓄電装置の寿命と判断する電気回路と、を有することを特徴とする蓄電装置。 In the power storage device in which a plurality of unit cells are connected in series, the plurality of unit cells include a first unit cell and a second unit cell, and the first unit cell has a smaller capacity than the second unit cell, and the The first unit cell has an initial state of reaching the discharge end voltage earlier than the second unit cell, and the first unit cell has a slower cycle deterioration rate than the second unit cell, and monitors the voltage of the first unit cell. Voltage measuring device, a second voltage measuring device that monitors the voltage of the second cell, the voltage of the first cell and the voltage of the second cell, and after charging and discharging, the second And an electric circuit that determines that the life of the power storage device is reached when the unit cell reaches the discharge end voltage before the first cell.

複数の単電池が直列に接続されてなる組電池の寿命判定方法であって、
複数の単電池は第１単電池と第２単電池とを有し、前記第１単電池の電圧と前記第２単電池の電圧とをそれぞれ監視し、
放電時に、前記第１単電池が先に放電終了電圧となった際は、正常と判定し、充放電の繰り返しにより、前記第２単電池が先に放電終了電圧となった際に、蓄電装置の寿命と判断する組電池の寿命判定方法。 A method for determining the life of an assembled battery comprising a plurality of cells connected in series,
The plurality of unit cells includes a first unit cell and a second unit cell, and monitors the voltage of the first unit cell and the voltage of the second unit cell, respectively.
At the time of discharge, when the first unit cell first reaches the discharge end voltage, it is determined as normal, and when the second unit cell first reaches the discharge end voltage due to repeated charge and discharge, the power storage device A method for judging the life of an assembled battery, which is judged as the life of the battery.

複数の単電池が直列に接続されており、第１単電池と、第２単電池と、前記第１単電池と前記第２単電池それぞれの電圧を監視するための引き出し線と、を含み、第１単電池は第２単電池より容量が小さく、且つ、第２単電池よりサイクル劣化速度が遅いことを特徴とする組電池。 A plurality of unit cells are connected in series, including a first unit cell, a second unit cell, and a lead wire for monitoring the voltage of each of the first unit cell and the second unit cell, The assembled battery, wherein the first unit cell has a smaller capacity than the second unit cell and has a slower cycle deterioration rate than the second unit cell.

第１単電池と第２単電池は組電池中で隣接して構成されている請求項３記載の組電池。 The assembled battery according to claim 3, wherein the first cell and the second cell are adjacent to each other in the assembled battery.

前記第１単電池の正極活物質の平均粒径は、前記第２単電池の正極活物質の平均粒径よりも大きいことを特徴とする請求項３乃至４のいずれかに記載の組電池。 5. The assembled battery according to claim 3, wherein an average particle size of the positive electrode active material of the first unit cell is larger than an average particle size of the positive electrode active material of the second unit cell.

前記第１単電池の単位面積当たりの正極活物質の電気容量に対する、対向する単位面積当たりの負極活物質の電気容量の比率が、前記第２単電池よりも小さく、且つ１より大きいことを特徴とする請求項３乃至５のいずれかに記載の組電池。 The ratio of the electric capacity of the negative electrode active material per unit area opposed to the electric capacity of the positive electrode active material per unit area of the first unit cell is smaller than that of the second unit cell and greater than 1. The assembled battery according to any one of claims 3 to 5.

前記第１単電池の正極活物質層に用いているバインダーの平均分子量は、前記第２単電池の正極活物質層に用いているバインダーの平均分子量よりも大きいことを特徴とする請求項３乃至６のいずれかに記載の組電池。 The average molecular weight of the binder used for the positive electrode active material layer of the first unit cell is larger than the average molecular weight of the binder used for the positive electrode active material layer of the second unit cell. The assembled battery according to any one of 6.

前記第１単電池の正極活物質層中のＮＭＰ（Ｎ−メチルピロリドン）は、前記第２単電池の正極活物質層中に含有される量よりも少ないことを特徴とする請求項３乃至７のいずれかに記載の組電池。
The NMP (N-methylpyrrolidone) in the positive electrode active material layer of the first unit cell is less than the amount contained in the positive electrode active material layer of the second unit cell. The assembled battery according to any one of the above.