JP2004111242A

JP2004111242A - Battery pack

Info

Publication number: JP2004111242A
Application number: JP2002272997A
Authority: JP
Inventors: Yuji Tanjo; 丹上　雄児
Original assignee: Nissan Motor Co Ltd
Current assignee: Nissan Motor Co Ltd
Priority date: 2002-09-19
Filing date: 2002-09-19
Publication date: 2004-04-08
Anticipated expiration: 2022-09-19
Also published as: JP4082147B2

Abstract

<P>PROBLEM TO BE SOLVED: To respond to the desire of obtaining a high energy density while keeping a fixed high output density or more in a battery pack as a secondary battery used for an electric vehicle or hybrid vehicle, particularly, a battery pack comprising the parallel-connected combination of a high output density type secondary battery and a high energy density type secondary battery. <P>SOLUTION: This battery pack 15 is constituted by connecting the high output density type secondary battery 15A and high energy density type secondary battery 15B differed in open circuit voltage in parallel. <P>COPYRIGHT: (C)2004,JPO

Description

【０００１】
【発明の属する技術分野】
本発明は、例えば、電気自動車やハイブリッド車両に用いられる二次電池としての組電池に関し、特に、高出力密度型二次電池と高エネルギ密度型二次電池とを並列接続して組み合わせた組電池に関するものである。
【０００２】
【従来の技術】
従来から電気自動車やハイブリッド車両に負荷との間で電力を充放電する二次電池として、高出力密度型二次電池と高エネルギ密度型二次電池とをセル数を同一にしたうえで、並列に接続した組電池が提案されている（例えば、特許文献１参照）。
【０００３】
これは、高出力密度型二次電池によって負荷との間で充放電を行ない、高出力密度型二次電池の充電状態ＳＯＣが５０％を超えている場合には、高出力密度型二次電池の電力によって高エネルギ密度型二次電池を充電すると共に、高出力密度型二次電池の充電状態ＳＯＣが５０％以下の場合には、高エネルギ密度型二次電池の電力によって高出力密度型二次電池を充電するようにしている。
【０００４】
この結果、一般に充電状態ＳＯＣが５０％を下回ると出力が急激に低下する高出力密度型二次電池の充電状態ＳＯＣを常に５０％以上に保つことができ、高出力で且つ高エネルギーな二次電池を提供することができる。
【０００５】
【特許文献１】
特開平１１−３３２０２３号公報
【０００６】
【発明が解決しようとする課題】
しかしながら、上記従来例では、高出力密度型二次電池と高エネルギ密度型二次電池のそれぞれの端子電圧を同じにして、高出力且つ高エネルギーな電池を得るようにしているが、電池に要求される性能として、一定以上の高出力密度を維持しつつ高エネルギ密度を得たい場合や一定以上の高エネルギ密度を維持しつつ高出力密度を得たい場合があり、このような場合には従来の技術では対応することができない可能性があった。
【０００７】
そこで本発明は、上記問題点に鑑みてなされたもので、様々な要求される特性に応じた組電池を提供することを目的とする。
【０００８】
【課題を解決するための手段】
本発明は、開回路電圧の異なる高出力密度型二次電池と高エネルギ密度型二次電池を並列に接続して組電池を構成した。
【０００９】
【発明の効果】
したがって、本発明では、開回路電圧が異なる高出力密度型二次電池と高エネルギ密度型二次電池を並列に接続して組電池を構成したため、開回路電圧が等しい電池の組み合わせに比較して、一定以上の高出力密度を維持しつつ高エネルギ密度を得たい場合や一定以上の高エネルギ密度を維持しつつ高出力密度を得たい場合等の様々な要求される特性に応じた入出力特性を改善する高性能な電池を実現できる。
【００１０】
【発明の実施の形態】
以下、本発明の組電池を各実施形態に基づいて説明する。
【００１１】
（第１実施形態）
図１〜図５は、本発明を適用した組電池の第１実施形態を示し、図１は適用例を示すハイブリッド車両のシステム構成図、図２は組電池の構成を示す接続図、図３は並列接続する各電池のＤＯＤと開放電圧との関係および並列接続された組電池の放電深度ＤＯＤと開放電圧との関係を示すグラフ、図４は組電池における放電深度ＤＯＤと出力電力との関係を示すグラフ、図５は各電池および組電池の容量と開回路電圧との関係を示すグラフである。
【００１２】
図１により、本発明をハイブリッド車両に適用した実施の形態を説明する。なお、本発明はハイブリッド車両に限定されず、一般の電気自動車を始め、電気自動車以外の各種装置に適用することができる。
【００１３】
図１において、太い実線は機械力の伝達経路を示し、太い破線は電力線を示す。また、細い実線は制御線を示し、二重線は油圧系統を示す。この車両のパワートレインは、モータ１、エンジン２、クラッチ３、モータ４、無段変速機５、減速装置６、差動装置７および駆動輪８から構成される。モータ１の出力軸、エンジン２の出力軸およびクラッチ３の入力軸は互いに連結されており、また、クラッチ３の出力軸、モータ４の出力軸および無段変速機５の入力軸は互いに連結されている。
【００１４】
クラッチ３締結時はエンジン２とモータ４が車両の推進源となり、クラッチ３解放時はモータ４のみが車両の推進源となる。エンジン２および／またはモータ４の駆動力は、無段変速機５、減速装置６および差動装置７を介して駆動輪８へ伝達される。無段変速機５には油圧装置９から圧油が供給され、ベルトのクランプと潤滑がなされる。油圧装置９のオイルポンプ（不図示）はモータ１０により駆動される。
【００１５】
モータ１，４，１０は三相同期電動機または三相誘導電動機などの交流機であり、モータ１は主としてエンジン始動と発電に用いられ、モータ４は主として車両の推進と制動に用いられる。また、モータ１０は油圧装置９のオイルポンプ駆動用である。なお、モータ１，４，１０には交流機に限らず直流電動機を用いることもできる。また、クラッチ３締結時に、モータ１を車両の推進と制動に用いることもでき、モータ４をエンジン始動や発電に用いることもできる。
【００１６】
クラッチ３はパウダークラッチであり、伝達トルクを調節することができる。なお、このクラッチ３に乾式単板クラッチや湿式多板クラッチを用いることもできる。無段変速機５はベルト式やトロイダル式などの無段変速機であり、変速比を無段階に調節することができる。
【００１７】
モータ１，４，１０はそれぞれ、インバータ１１，１２，１３により駆動される。なお、モータ１，４，１０に直流電動機を用いる場合には、インバータの代わりにＤＣ／ＤＣコンバータを用いる。インバータ１１〜１３は共通のＤＣリンク１４を介してメインバッテリ１５に接続されており、メインバッテリ１５の直流充電電力を交流電力に変換してモータ１，４，１０へ供給するとともに、モータ１，４の交流発電電力を直流電力に変換してメインバッテリ１５を充電する。インバータ１１〜１３は互いにＤＣリンク１４を介して接続されているので、回生運転中のモータにより発電された電力をメインバッテリ１５を介さずに直接、力行運転中のモータへ供給することができる。なお、この明細書では電池とバッテリとを同義として用いる。
【００１８】
コントローラ１６は、マイクロコンピュータとその周辺部品や各種アクチュエータなどを備え、エンジン２の回転速度、出力およびトルク、クラッチ３の伝達トルク、モータ１，４，１０の回転速度およびトルク、無段変速機５の変速比、メインバッテリ１５の充放電などを制御する。
【００１９】
図２はメインバッテリ１５の詳細な構成を示す図である。メインバッテリ１５は、高エネルギ密度型二次電池１５Ａと、高出力密度型二次電池１５Ｂとを並列に接続した組電池に構成している。以下、組電池に符号１５を付して詳細に説明する。
【００２０】
図２において、組電池１５は、図中右側にあって１１２セルを直列接続した高エネルギ密度型二次電池１５Ａと、図中左側にあって９６セルを直列接続した高出力密度型二次電池１５Ｂと、を並列接続して構成している。
【００２１】
前記高エネルギ密度型二次電池１５Ａのセルは、リチウム金属リン酸化合物（ＬｉＦｅＰＯ_４やＬｉＭｎＰＯ_４等）を正極材料として用いるもの、およびまたは、黒鉛系（グラファイト）炭素材料を負極材料として用いる。例えば、正極材料としてオリビン型リチウム鉄リン酸化合物（ＬｉＦｅＰＯ_４）を、また、負極材料としてグラファイトを用いて、リチウムイオン二次電池セルとし、このセルを直列に１１２個接続して容量が１２Ａｈとなる高エネルギ密度型二次電池１５Ａとする。高エネルギ密度型二次電池１５Ａは、前記した正極材料もしくは負極材料を選択することにより、開回路電圧（開放電圧、無負荷電圧）が放電深度ＤＯＤの増加に対して一定となる特性を持つ電池とすることが出来る。
【００２２】
前記高出力密度型二次電池１５Ｂのセルは、リチウム金属酸化物（ＬｉＭｎ_２Ｏ_４、ＬｉＮｉＯ_２、ＬｉＣｏＯ_２等）を正極材料として用いるもの、およびまたは、非晶質系炭素材料（ハードカーボン）を負極材料として用いる。例えば、正極材料としてスピネル型リチウムマンガン酸化物（ＬｉＭｎ_２Ｏ_４）を、また、負極材料としてハードカーボンを用いて、リチウムイオン二次電池セルとし、このセルを直列に９６個接続して容量が３Ａｈとなる高出力密度型二次電池１５Ｂとする。高出力密度型二次電池１５Ｂは、前記した正極材料もしくは負極材料を選択することにより、開回路電圧（開放電圧、無負荷電圧）を放電深度ＤＯＤの増加に対して徐々に低下する傾きを持つ特性の電池とすることが出来る。
【００２３】
図３は、上記高エネルギ密度型二次電池１５Ａ、高出力密度型二次電池１５Ｂ、および、両者を並列に接続した組電池１５の特性を示す図であり、各電池の放電深度ＤＯＤに対する開回路電圧（開放電圧）の関係を表している。ただし、高エネルギ密度型二次電池１５Ａは１１２セルを直列接続した状態の特性であり、高出力密度型二次電池１５Ｂは９６セルを直列接続した状態の特性である。
【００２４】
図３に示すように、高エネルギ密度型二次電池１５Ａは、特性Ａに示すように、放電深度ＤＯＤが９０％以上となるまで一定の開回路電圧特性を備える一方、高出力密度型二次電池１５Ｂは、特性Ｂに示すように、放電深度ＤＯＤが増加するに連れて徐々に低下する開回路電圧特性を備える。このため、両電池を並列接続した組電池１５は、特性Ｃに示すように、放電深度ＤＯＤが約８０％となるまでは、高エネルギ密度型二次電池１５Ａの容量が使われ、残り２０％の放電深度ＤＯＤの増加時に高出力密度型二次電池１５Ｂの容量が使われる。
【００２５】
一般的に、電池１５から負荷に対して電力を供給している場合には、内部抵抗の小さい高出力密度型二次電池１５Ｂから電力が供給され、高出力密度型二次電池１５Ｂ単体で見ると高出力密度型二次電池１５Ｂの容量が低下する、すなわち高出力密度型二次電池１５Ｂ単体の電圧が低下することになる。そして、負荷への電力供給を停止すると、並列接続された電池１５Ａ、１５Ｂ間で電圧を合わそうとするために、高エネルギ密度型二次電池１５Ａから高出力密度型二次電池１５Ｂに対して充電が行なわれる。ここで、高エネルギ密度型二次電池１５Ａは、図３に示す特性のように放電深度ＤＯＤが７７％までは、開回路電圧が変化しないことになるので、高エネルギ密度型二次電池１５Ａの放電深度ＤＯＤが０〜７７％の範囲では、両方の電池１５Ａ、１５Ｂ単体および組電池１５としての開回路電圧が所望の値（４００Ｖ）を維持できる。そして、高エネルギ密度型二次電池１５Ａの放電深度ＤＯＤが７７％を超えると、高エネルギ密度型二次電池１５Ａの電圧もドロップしてしまう、言い換えると、高エネルギ密度型二次電池１５Ａの容量が空になってしまうので、その後は高出力密度型二次電池１５Ｂの持っている能力でしか電力を供給することができなくなる。従って、組電池１５としての開回路電圧が低下することになる。
【００２６】
図４は電池の使用可能容量（Ａｈ）を横軸とし開回路電圧Ｖを縦軸としたグラフであり、図４（Ａ）は高エネルギ密度型二次電池１５Ａの開回路電圧の変化を示し、図４（Ｂ）は高出力密度型二次電池１５Ｂの開回路電圧の変化を示し、図４（Ｃ）は組電池１５の開回路電圧の変化を示したものである。
【００２７】
そして、並列接続された組電池１５は、高エネルギ密度型二次電池１５Ａの使用可能容量が１２Ａｈであり（図４（Ａ）参照）、高出力密度型二次電池１５Ｂの使用可能容量が３Ａｈであり（図４（Ｂ）参照）、組電池１５全体の使用可能容量としては、１５Ａｈ（＝１２Ａｈ＋３Ａｈ）の容量を持っている（図４（Ｃ）参照）。
【００２８】
そして、図４（Ａ）に示すように、高エネルギ密度型二次電池１５Ａの使用可能容量は１２Ａｈであり、消費容量１１．５Ａｈまで（組電池のＤＯＤとしては７７％に相当）は、開回路電圧がある一定の値を維持でき、その後急速に開回路電圧が低下する。
【００２９】
一方、図４（Ｂ）に示すように、高出力密度型二次電池１５Ｂの使用可能容量は３Ａｈであり、消費容量（消費容量＝使用可能容量−残存容量）の増加に従って、開回路電圧も低下する特性を示す。
【００３０】
従って、高エネルギ密度型二次電池１５Ａの残存容量があるうち（消費容量が１１．５Ａｈまでの領域Ｄの範囲）は、高出力密度型二次電池１５Ｂで消費した容量分を高エネルギ密度型二次電池１５Ａからの充電により補うことができ、消費容量が１１．５Ａｈを超えて使用すると、高エネルギ密度型二次電池１５Ａで高出力密度型二次電池１５Ｂの消費使用分を補えなくなり、開回路電圧が低下する（領域Ｅ参照）ことになる。
【００３１】
この結果、この組電池の放電深度ＤＯＤと出力の関係は、図５に示すように、放電深度ＤＯＤが約８０％（７７％）までは、高出力密度型二次電池１５Ｂの放電深度ＤＯＤが０％に維持されるため、高出力密度型二次電池１５Ｂの出力特性（４０ｋＷ）の高出力を組電池１５から出力でき、組電池１５の出力特性が向上するという効果が得られることになる。
【００３２】
図６、７は、比較例の特性を示すものである。この比較例においては、図示しないが、高エネルギ密度型二次電池を、正極にオリビン型リチウム鉄リン酸化合物（ＬｉＦｅＰＯ_４）、負極にハードカーボンを用いた１２Ａｈの二次電池とし、高出力密度型二次電池を、正極にスピネル型リチウムマンガン酸化物（ＬｉＭｎ_２Ｏ_４）、負極にグラファイトを用いた３Ａｈの二次電池としている。そして、上記実施形態と同様に、高エネルギ密度型二次電池を１１２セル、高出力密度型二次電池を９６セル直列に接続し、それぞれを並列に接続して組電池とした。負極の材料を交換して開放電圧を変化させた以外は、全て上記実施形態と同じ仕様としてある。
【００３３】
図６に高エネルギ密度型二次電池、高出力密度型二次電池の放電深度ＤＯＤと開放電圧Ｆ、Ｇの関係、および、組電池の放電深度ＤＯＤと開放電圧Ｈの関係を示す。図より明らかなように、この比較例では放電深度ＤＯＤの２０％までは高出力密度型二次電池が使われ、残り８０％で高エネルギ密度型二次電池の容量が使われることが分かる。
【００３４】
図７に比較例の放電深度ＤＯＤと出力の関係を示す。この比較例においては、放電深度ＤＯＤが２０％までは高出力密度型二次電池がもっぱら使用されるため高出力密度型二次電池の出力特性となる（図中特性Ｊ参照）。ＤＯＤ２０％以降は高出力密度型二次電池のＤＯＤが１００％近くになってしまうため出力特性が低下する（図中特性Ｋ参照）。
【００３５】
これらの結果より、本実施形態のように、高出力密度型二次電池１５Ｂの開回路電圧を高エネルギ密度型二次電池１５Ａの開回路電圧よりも低くすることにより、高出力密度型二次電池１５Ｂの放電深度ＤＯＤが高エネルギ密度型二次電池１５Ａの放電深度ＤＯＤより小さくなり、図５に示すように、出力特性が向上することが理解できる。
【００３６】
本実施形態においては、以下に記載する効果を奏することができる。
【００３７】
（ア）開回路電圧が異なる高出力密度型二次電池１５Ｂと高エネルギ密度型二次電池１５Ａを並列に接続して組電池１５を構成しているため、開回路電圧が等しい電池の組み合わせに比較して、様々な要求される特性に応じた組電池を実現可能である。
【００３８】
（イ）高エネルギ密度型二次電池１５Ａの開回路電圧を高出力密度型二次電池１５Ｂの開回路電圧より高くしたため、高出力密度型二次電池１５Ｂの放電深度ＤＯＤが高エネルギ密度型二次電池１５Ａの放電深度ＤＯＤより小さくでき、電池の出力特性が向上できる。
【００３９】
（ウ）高出力密度型二次電池１５Ｂの開回路電圧を放電深度ＤＯＤに対して徐々に低下する特性とし、高エネルギ密度型二次電池１５Ａの開回路電圧が放電深度ＤＯＤに対して一定で変化しない特性としたため、高出力密度型二次電池１５Ｂの開回路電圧を高エネルギ密度型二次電池１５Ａの開回路電圧より低くすることができる。
【００４０】
（エ）高エネルギ密度型二次電池１５Ａの開回路電圧が高出力密度型二次電池１５Ｂの開回路電圧より高い開回路電圧で放電深度ＤＯＤに対して一定で変化しない特性としたため、高出力密度型二次電池１５Ｂの放電深度ＤＯＤを０％付近の一定に保つことができ、組電池１５の放電深度ＤＯＤによらず一定の出力特性を確保できる。
【００４１】
（オ）高出力密度型二次電池１５Ｂの開回路電圧を放電深度ＤＯＤに対して徐々に低下する特性とし、高エネルギ密度型二次電池１５Ａの開回路電圧が放電深度ＤＯＤに対して一定で変化しない特性としたため、開回路電圧が放電深度ＤＯＤに対して一定の高エネルギ密度型二次電池１５Ａのみを用いた場合における残存容量の算出が電圧測定のみでは困難であったが、開回路電圧が放電深度ＤＯＤに対して傾きを持つ高出力密度型二次電池１５Ｂを並列に接続していることから、充放電末期時は高出力密度型二次電池１５Ｂの開回路電圧が変化し、電圧を測定するだけで組電池１５の充放電末期を正確に知ることが可能である。
【００４２】
（カ）高出力密度型二次電池１５Ｂは負極材料に非晶質系炭素材料（ハードカーボン）を用い、高エネルギ密度型二次電池１５Ａは負極に黒鉛系（グラファイト）炭素材料を用いるため、高出力密度型二次電池１５Ｂの開回路電圧を、高エネルギ密度型二次電池１５Ａの開回路電圧よりも低くすることができる。
【００４３】
（キ）また、高出力密度型二次電池１５Ｂは負極材料に非晶質系炭素材料（ハードカーボン）を用い、高エネルギ密度型二次電池１５Ａは負極に黒鉛系（グラファイト）炭素材料を用いるため、高出力密度型二次電池１５Ｂをその開回路電圧が放電深度ＤＯＤに対して傾きを持つ電池とでき、高エネルギ密度型二次電池１５Ａをその開回路電圧が放電深度ＤＯＤに対して一定の電池とできる。
【００４４】
（ク）高出力密度型二次電池１５Ｂは正極材料にリチウム金属酸化物（ＬｉＭｎ_２Ｏ_４、ＬｉＮｉＯ_２、ＬｉＣｏＯ_２等）を用い、高エネルギ密度型二次電池１５Ａは正極材料にリチウム金属リン酸化合物（ＬｉＦｅＰＯ_４、ＬｉＭｎＯ_４等）を用いるため、高出力密度型二次電池１５Ｂをその開回路電圧が放電深度ＤＯＤに対して傾きを持つ電池とでき、高エネルギ密度型二次電池１５Ａをその開回路電圧が放電深度ＤＯＤに対して一定の電池とできる。
【００４５】
（ケ）また、高出力密度型二次電池１５Ｂは正極材料にリチウム金属酸化物（ＬｉＭｎ_２Ｏ_４、ＬｉＮｉＯ_２、ＬｉＣｏＯ_２等）を用い、前記高エネルギ密度型二次電池１５Ａは正極材料にリチウム金属リン酸化合物（ＬｉＦｅＰＯ_４、ＬｉＭｎＯ_４等）を用いるため、出力が要求される用途にも、出力特性の劣るリチウム金属リン酸化合物を正極に用いた電池を使用することが可能となる。
【００４６】
（第２実施形態）
図８〜図１１は、本発明を適用した組電池の第２実施形態を示し、図８は組電池の構成を示す接続図、図９は高出力密度型二次電池と高エネルギ密度型二次電池の開回路電圧（開放電圧）特性を示すグラフ、図１０は組電池と組電池を構成する各電池との放電深度ＤＯＤの特性を示すグラフ、図１１は組電池の入出力特性を示すグラフである。本実施形態においては、前実施形態のように電池の出しうる最大出力の特性を得ることに代えて最低入力の範囲を広げるようにしたものである。なお、前実施形態と同一部品には同一符号を付して説明を簡略化若しくは省略する。
【００４７】
図８において、ハイブリッド車両のメインバッテリとしての組電池１６は、図中右側にあって１３０セルを直列接続した高エネルギ密度型二次電池１６Ａと、図中左側にあって９６セルを直列接続した高出力密度型二次電池１６Ｂと、を並列接続して構成する。なお、各電池のセル数は、放電深度ＤＯＤが０％のときの各単一のセルの開回路電圧が異なるため、９６セルが直列接続された高出力密度型二次電池全体（１６Ｂ）の放電深度０％時の開回路電圧と、１３０セルが直列接続された高エネルギ密度型二次電池全体（１６Ａ）の放電深度０％時の開回路電圧とが、同じＬ［Ｖ］という値を示すことを意味している。
【００４８】
前記高エネルギ密度型二次電池１６Ａのセルには、負極に金属リチウム、正極にバナジウム酸化物を用いるリチウムイオン電池とし、前記高出力密度型二次電池１６Ｂのセルは、例えば、負極に炭素材料、正極にリチウムマンガン酸化物を用いるリチウムイオン電池とする。高エネルギ密度型二次電池１６Ａと高出力密度型二次電池１６Ｂの電極材料は上記例に限られるものではない。要するに、開回路電圧（開放電圧）の高い方を高出力密度型二次電池１６Ｂとしている。従って、セルの直列接続数を調整することによっても高出力密度型二次電池１６Ｂの開回路電圧を高エネルギ密度型二次電池１６Ａの開回路電圧より高くすることができる。
【００４９】
電池の高出力化は、電極を薄くし、電極面積を大きくとることによっても可能である。また、開回路電圧の高い正極若しくは負極を用いることによっても電池の高出力化が可能である。また、高出力密度型二次電池１６Ｂに電解液を、高エネルギ密度型二次電池１６Ａに固体電解質を用いることによっても、高出力密度型二次電池１６Ｂと高エネルギ密度型二次電池１６Ａを作ることが可能であり、高出力密度型二次電池１６Ｂと高エネルギ密度型二次電池１６Ａとの差が明確となる。また、高エネルギ密度型二次電池１６Ａは正負電極の活物質を厚くした高容量仕様のリチウムイオン電池を用い、高出力密度型二次電池１６Ｂは正負電極の活物質を薄くして電池の内部抵抗を下げたリチウムイオン電池を用いることで、両者は比較的容易に製作できる。
【００５０】
図９は、上記組電池１６で使用する高出力密度型二次電池１６Ｂと高エネルギ密度型二次電池１６Ａの特性を示す図であり、各電池の放電深度ＤＯＤに対する開回路電圧（開放電圧）の関係を表している。ただし、高出力密度型二次電池１６Ｂは９６セルを直列接続した状態の特性であり、高エネルギ密度型二次電池１６Ａは１３０セルを直列接続した状態の特性である。
【００５１】
図９に示すように、並列接続される２つの電池は、放電深度ＤＯＤが０［％］のときの開回路電圧がともにＬ［Ｖ］であり、放電深度ＤＯＤが７０［％］のときの開回路電圧がともにＮ［Ｖ］であるが、それ以外の放電深度ＤＯＤのときには異なる開回路電圧となっている。即ち、放電深度ＤＯＤが０〜７０［％］の範囲では高出力密度型二次電池１６Ｂの開回路電圧が高エネルギ密度型二次電池１６Ａの開回路電圧より高くなっており、放電深度ＤＯＤが７０［％］より大きい範囲では高出力密度型二次電池１６Ｂの開回路電圧と高エネルギ密度型二次電池１６Ａの開回路電圧の大小関係が逆転する。
【００５２】
このような２つの電池を並列接続した組電池１６では、組電池１６全体としての放電深度ＤＯＤが０［％］のとき開回路電圧がＬ［Ｖ］となり、２つの電池の放電深度ＤＯＤも０［％］となる。同様にして、組電池１６全体としての放電深度ＤＯＤが７０［％］のとき開回路電圧がＮ［Ｖ］となり、２つの電池の放電深度ＤＯＤも７０［％］となる。しかしながら、組電池１６全体としての放電深度ＤＯＤが０あるいは７０［％］以外のときは組電池１６全体としての放電深度ＤＯＤと各電池１６Ａ、１６Ｂの放電深度ＤＯＤが等しくならない。例えば、組電池１６の開回路電圧（＝各電池の電圧）がＭ［Ｖ］であるときの高出力密度型二次電池１６Ｂの放電深度ＤＯＤは約４４［％］であり、高エネルギ密度型二次電池１６Ａの放電深度ＤＯＤは約１６［％］である。
【００５３】
図１０は、組電池１６全体としての放電深度ＤＯＤと各電池１６Ａ、１６Ｂの放電深度ＤＯＤとの関係を示したものである。図１０において、例えば、組電池１６の放電深度ＤＯＤが３０［％］であるときの高出力密度型二次電池１６Ｂの放電深度ＤＯＤは約４４［％］であり、高エネルギ密度型二次電池１６Ａの放電深度ＤＯＤは約１６［％］である。このように、高出力密度型二次電池１６Ｂの開回路電圧が高エネルギ密度型二次電池１６Ａの開回路電圧より高くなる放電深度ＤＯＤの範囲では、高出力密度型二次電池１６Ｂの放電深度ＤＯＤが組電池１６の放電深度ＤＯＤより高くなり、高エネルギ密度型二次電池１６Ａの放電深度ＤＯＤが組電池１６の放電深度ＤＯＤより低くなる。
【００５４】
なお、図中に一点鎖線で示したのは放電深度ＤＯＤに対する開回路電圧の特性が等しい２つの電池を並列接続した組電池（以下、比較例）の特性であり、この場合は組電池の放電深度ＤＯＤと各電池の放電深度ＤＯＤとが常に等しくなる。
【００５５】
図１１は、本実施形態の組電池１の放電深度ＤＯＤとその入出力電力との関係を示す図である。ただし、組電池１６の入出力電力は高出力密度型二次電池１６Ｂの入出力電力でほぼ決まるため、組電池１６の放電深度ＤＯＤと高出力密度型二次電池１６Ｂの入出力電力との関係を示す図であると見て差し支えない。図１１から明らかなように、高出力密度型二次電池１６Ｂの開回路電圧が高エネルギ密度型二次電池１６Ａの開回路電圧より高くなる放電深度ＤＯＤの範囲の入力電力（図中の実線）は、比較例の入力電力（図中の一点鎖線）より大きくなる。これは、入力電力即ち充電パワーは放電深度ＤＯＤの増加に対応して増加するものであり、この範囲における組電池１６の一方である高出力密度型二次電池１６Ｂの放電深度ＤＯＤが比較例の放電深度ＤＯＤより高いためである。
【００５６】
一般に、ハイブリッド車両の電源として二次電池を使用する場合、一定以上の出力電力と一定以上の入力電力とが常に確保できるよう電池の放電深度ＤＯＤを制御する必要がある。例えば、常に確保すべき最低出力電力ＰｏｍｉｎがＰ［ｋＷ］であり、常に確保すべき最低入力電力ＰｉｍｉｎがＲ［ｋＷ］である場合、鎖線図示の比較例の組電池では放電深度ＤＯＤを３５〜７０［％］の範囲に制御する必要がある。これに対し本実施形態の組電池１６では、同じ入出力電力を確保するための放電深度ＤＯＤの範囲を２５〜７０［％］に拡大することができる。これは、入出力制御（充放電制御）がより柔軟に行えることを意味しており、ハイブリッド車両の電源として非常に有利な特性である。
【００５７】
なお、上記の効果を確実に得るため、開回路電圧の大小関係が逆転する放電深度ＤＯＤ（この例では７０［％］）における組電池１６の出力（この例ではＰ［ｋＷ］）が最低出力Ｐｏｍｉｎ以上であり、かつ、開回路電圧の大小関係が逆転する放電深度ＤＯＤにおける組電池１６の入力（この例ではＱ［ｋＷ］）が最低入力Ｐｉｍｉｎ以上である組電池を使用する。
【００５８】
本実施形態においては、以下に記載する効果を奏することができる。
【００５９】
（コ）開回路電圧が異なる高出力密度型二次電池１６Ｂと高エネルギ密度型二次電池１６Ａを並列に接続して組電池１６を構成しているため、開回路電圧が等しい電池の組み合わせに比較して、入出力特性を改善する高性能な電池を実現可能である。
【００６０】
（サ）組電池１６の高出力密度型二次電池１６Ｂの開回路電圧を高エネルギ密度型二次電池１６Ａの開回路電圧よりも高くしたため、高出力密度型二次電池１６Ｂの放電深度（ＤＯＤ）を組電池１６の放電深度ＤＯＤに比べ大きくでき、電池の入力特性を向上できる。
【００６１】
（シ）高出力密度型二次電池１６Ｂの開回路電圧と高エネルギ密度型二次電池１６Ａの開回路電圧が等しくなる組電池１６の放電深度（ＤＯＤ）が存在し、この放電深度の前後で夫々の電池１６Ａ、１６Ｂの放電深度と組電池１６の放電深度との大小関係が逆転するため、入出力特性等の特性が得られる組電池１６の放電深度（ＤＯＤ）範囲を設定することができる。
【００６２】
（ス）高出力密度型二次電池１６Ｂの開回路電圧と高エネルギ密度型二次電池１６Ａの開回路電圧が等しくなる組電池１６の放電深度（ＤＯＤ）の前後で夫々の電池の放電深度と組電池１６の放電深度との大小関係を逆転させる場合において、高出力密度型二次電池１６Ｂの開回路電圧を高エネルギ密度型二次電池１６Ａの開回路電圧よりも高くすると、充電時には高出力密度型二次電池１６Ｂの放電深度を組電池１６の放電深度より大きくなり組電池１６への入力特性を向上でき、放電状態では高出力密度型二次電池１６Ｂの放電深度を組電池１６の放電深度より小さくでき組電池１６からの出力特性を向上できる。
【００６３】
（セ）高出力密度型二次電池１６Ｂの正極または負極に高エネルギ密度型二次電池１６Ａより電池として開回路電圧の高いの正極または負極を用いるため、高出力密度型二次電池１６Ｂの開回路電圧を高エネルギ密度型二次電池１６Ａより大きくすることが可能となる。
【００６４】
（ソ）高出力密度型二次電池１６Ｂおよびまたは高エネルギ密度型二次電池１６Ａのセルの直列接続数を調整することでも、高出力密度型二次電池１６Ｂの開回路電圧を高エネルギ密度型二次電池１６Ａの開回路電圧より高くすることが可能となる。
【００６５】
（タ）組電池１６の使用する放電深度ＤＯＤ範囲を高出力密度型二次電池１６Ｂの開回路電圧が高エネルギ密度型二次電池１６Ａの開回路電圧より高くなる放電深度ＤＯＤ範囲とすることにより、高出力密度型二次電池１６Ｂの放電深度（ＤＯＤ）を組電池１６の放電深度ＤＯＤに比べ大きくでき、電池の入力特性を向上できる。
【００６６】
（チ）高出力密度型二次電池１６Ｂには電解液を用いた電池とし、高エネルギ密度型二次電池１６Ａには全固体電池とすることにより、高出力密度型二次電池１６Ｂと高エネルギ密度型二次電池１６Ａの特性差が明確となり、上記した効果を寄り発揮させることができる。
【図面の簡単な説明】
【図１】本発明の組電池の適用例を示すハイブリッド車両のシステム構成図。
【図２】本発明の第１実施形態の組電池の構成を示す接続図。
【図３】並列接続する各電池のＤＯＤと開放電圧との関係および並列接続された組電池の放電深度ＤＯＤと開放電圧との関係を示すグラフ。
【図４】組電池における放電深度ＤＯＤと出力電力との関係を示すグラフ。
【図５】各電池および組電池の容量と開回路電圧との関係を示すグラフ。
【図６】比較例の並列接続する各電池のＤＯＤと開放電圧との関係および並列接続された組電池の放電深度ＤＯＤと開放電圧との関係を示すグラフ。
【図７】比較例の各電池および組電池の容量と開回路電圧との関係を示すグラフ。
【図８】本発明の第２実施形態を示す組電池の概略構成図。
【図９】同じく高出力密度型二次電池と高エネルギ密度型二次電池の開回路電圧（開放電圧）特性を示すグラフ。
【図１０】同じく組電池と組電池を構成する各電池との放電深度ＤＯＤの特性を示すグラフ。
【図１１】組電池の入出力特性を示すグラフ。
【符号の説明】
１、４、１０　モータ
２　エンジン
３　クラッチ
５　無段変速機
６　減速装置
７　差動装置
８　駆動輪
９　油圧装置
１１〜１３　インバータ
１４　ＤＣリンク
１５、１６　メインバッテリ、組電池
１５Ａ、１６Ａ　高エネルギ密度型二次電池
１５Ｂ、１６Ｂ　高出力密度型二次電池[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a battery pack as a secondary battery used for, for example, an electric vehicle or a hybrid vehicle, and in particular, to a battery pack in which a high power density secondary battery and a high energy density secondary battery are connected in parallel and combined. It is about.
[0002]
[Prior art]
Conventionally, high-power-density secondary batteries and high-energy-density secondary batteries have the same number of cells. (For example, see Patent Document 1).
[0003]
This is because the high-power-density secondary battery charges and discharges with the load, and when the state of charge SOC of the high-power-density secondary battery exceeds 50%, the high-power-density secondary battery When the state of charge of the high power density secondary battery is 50% or less, the high energy density secondary battery is charged by the power of the high energy density secondary battery. The next battery is charged.
[0004]
As a result, the state of charge SOC of a high-power density secondary battery, in which the output generally drops sharply when the state of charge SOC falls below 50%, can always be maintained at 50% or more, and a high-output and high-energy secondary battery can be maintained. A battery can be provided.
[0005]
[Patent Document 1]
JP-A-11-332023
[0006]
[Problems to be solved by the invention]
However, in the above-mentioned conventional example, the high output density type secondary battery and the high energy density type secondary battery are made to have the same terminal voltage to obtain a high output and high energy type battery. There are two types of performances: one is to obtain a high energy density while maintaining a certain high power density, and the other is to obtain a high power density while maintaining a certain high energy density. There was a possibility that this technology could not cope.
[0007]
Then, this invention was made in view of the said problem, and an object of this invention is to provide the assembled battery according to various required characteristics.
[0008]
[Means for Solving the Problems]
According to the present invention, an assembled battery is configured by connecting a high output density type secondary battery having a different open circuit voltage and a high energy density type secondary battery in parallel.
[0009]
【The invention's effect】
Therefore, in the present invention, the high output density type secondary battery and the high energy density type secondary battery having different open circuit voltages are connected in parallel to form an assembled battery. Input / output characteristics according to various required characteristics, such as when it is desired to obtain a high energy density while maintaining a high output density above a certain level or when it is desired to obtain a high output density while maintaining a high energy density above a certain level And a high-performance battery can be realized.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the assembled battery of the present invention will be described based on each embodiment.
[0011]
(1st Embodiment)
1 to 5 show a first embodiment of an assembled battery to which the present invention is applied, FIG. 1 is a system configuration diagram of a hybrid vehicle showing an application example, FIG. 2 is a connection diagram showing a configuration of the assembled battery, and FIG. Is a graph showing the relationship between the DOD of each battery connected in parallel and the open voltage, and the relationship between the depth of discharge DOD and the open voltage of the assembled battery connected in parallel, and FIG. 4 is the relationship between the depth of discharge DOD and the output power in the assembled battery. FIG. 5 is a graph showing the relationship between the capacity of each battery and the assembled battery and the open circuit voltage.
[0012]
Referring to FIG. 1, an embodiment in which the present invention is applied to a hybrid vehicle will be described. Note that the present invention is not limited to a hybrid vehicle, and can be applied to various devices other than an electric vehicle, including a general electric vehicle.
[0013]
In FIG. 1, a thick solid line indicates a transmission path of mechanical force, and a thick broken line indicates a power line. A thin solid line indicates a control line, and a double line indicates a hydraulic system. The power train of this vehicle includes a motor 1, an engine 2, a clutch 3, a motor 4, a continuously variable transmission 5, a reduction gear 6, a differential gear 7, and driving wheels 8. The output shaft of the motor 1, the output shaft of the engine 2, and the input shaft of the clutch 3 are connected to each other, and the output shaft of the clutch 3, the output shaft of the motor 4, and the input shaft of the continuously variable transmission 5 are connected to each other. ing.
[0014]
When the clutch 3 is engaged, the engine 2 and the motor 4 serve as propulsion sources for the vehicle. When the clutch 3 is released, only the motor 4 serves as a propulsion source for the vehicle. The driving force of the engine 2 and / or the motor 4 is transmitted to the driving wheels 8 via the continuously variable transmission 5, the reduction gear 6, and the differential gear 7. Pressure oil is supplied from the hydraulic device 9 to the continuously variable transmission 5 to clamp and lubricate the belt. An oil pump (not shown) of the hydraulic device 9 is driven by a motor 10.
[0015]
The motors 1, 4, and 10 are AC machines such as a three-phase synchronous motor or a three-phase induction motor. The motor 1 is mainly used for starting and generating electric power, and the motor 4 is mainly used for propulsion and braking of a vehicle. The motor 10 is for driving the oil pump of the hydraulic device 9. The motors 1, 4, and 10 are not limited to AC machines, but DC motors can be used. Further, when the clutch 3 is engaged, the motor 1 can be used for propulsion and braking of the vehicle, and the motor 4 can be used for starting the engine and generating power.
[0016]
The clutch 3 is a powder clutch, and can adjust the transmission torque. It should be noted that a dry single-plate clutch or a wet multi-plate clutch can be used as the clutch 3. The continuously variable transmission 5 is a continuously variable transmission of a belt type, a toroidal type, or the like, and can continuously adjust the speed ratio.
[0017]
The motors 1, 4, and 10 are driven by inverters 11, 12, and 13, respectively. When a DC motor is used for the motors 1, 4, and 10, a DC / DC converter is used instead of the inverter. The inverters 11 to 13 are connected to a main battery 15 via a common DC link 14, convert DC charging power of the main battery 15 into AC power and supply the AC power to the motors 1, 4, and 10. 4 is converted into DC power to charge the main battery 15. Since the inverters 11 to 13 are connected to each other via the DC link 14, the power generated by the motor during the regenerative operation can be directly supplied to the motor during the power running operation without passing through the main battery 15. In this specification, a battery and a battery are used synonymously.
[0018]
The controller 16 includes a microcomputer and its peripheral parts, various actuators, and the like. The rotation speed, output and torque of the engine 2, the transmission torque of the clutch 3, the rotation speed and torque of the motors 1, 4, and 10, the continuously variable transmission 5 Of the main battery 15 and the like.
[0019]
FIG. 2 is a diagram showing a detailed configuration of the main battery 15. The main battery 15 is configured as an assembled battery in which a high energy density secondary battery 15A and a high power density secondary battery 15B are connected in parallel. Hereinafter, the battery assembly will be described in detail with reference numeral 15.
[0020]
In FIG. 2, the assembled battery 15 includes a high energy density secondary battery 15A having 112 cells connected in series on the right side in the figure and a high power density secondary battery having 96 cells connected in series on the left side in the figure. 15B are connected in parallel.
[0021]
The high energy density secondary battery 15A has a lithium metal phosphate compound (LiFePO4). ₄ And LiMnPO ₄ Etc.) as a positive electrode material and / or a graphite (graphite) carbon material as a negative electrode material. For example, an olivine-type lithium iron phosphate compound (LiFePO ₄ ) Is used as a negative electrode material to form a lithium ion secondary battery cell using graphite as a negative electrode material, and 112 cells are connected in series to form a high energy density secondary battery 15A having a capacity of 12 Ah. The high energy density type secondary battery 15A is a battery having such characteristics that the open circuit voltage (open voltage, no-load voltage) becomes constant with the increase of the depth of discharge DOD by selecting the above-mentioned positive electrode material or negative electrode material. It can be.
[0022]
The cells of the high power density secondary battery 15B are made of lithium metal oxide (LiMn). ₂ O ₄ , LiNiO ₂ , LiCoO ₂ ) As an anode material and / or an amorphous carbon material (hard carbon) as an anode material. For example, as a positive electrode material, spinel type lithium manganese oxide (LiMn) ₂ O ₄ ) Is also used as a negative electrode material to form a lithium ion secondary battery cell using hard carbon, and 96 of these cells are connected in series to form a high output density secondary battery 15B having a capacity of 3 Ah. The high output density type secondary battery 15B has a slope in which the open circuit voltage (open voltage, no-load voltage) gradually decreases as the depth of discharge DOD increases by selecting the above-described positive electrode material or negative electrode material. A battery having characteristics can be obtained.
[0023]
FIG. 3 is a diagram showing characteristics of the high energy density secondary battery 15A, the high power density secondary battery 15B, and the assembled battery 15 in which both are connected in parallel. It shows the relationship between the circuit voltage (open circuit voltage). However, the high energy density secondary battery 15A has the characteristics in a state where 112 cells are connected in series, and the high power density secondary battery 15B has the characteristics in a state where 96 cells are connected in series.
[0024]
As shown in FIG. 3, the high energy density secondary battery 15A has a constant open circuit voltage characteristic until the depth of discharge DOD becomes 90% or more, as shown in a characteristic A, while the high power density secondary battery 15A The battery 15B has an open circuit voltage characteristic that gradually decreases as the depth of discharge DOD increases, as indicated by the characteristic B. For this reason, as shown in the characteristic C, the assembled battery 15 in which both batteries are connected in parallel uses the capacity of the high energy density secondary battery 15A until the depth of discharge DOD becomes about 80%, and the remaining 20% When the depth of discharge DOD increases, the capacity of the high power density secondary battery 15B is used.
[0025]
Generally, when power is supplied from the battery 15 to the load, power is supplied from the high power density secondary battery 15B having a small internal resistance, and the high power density secondary battery 15B alone is viewed. Therefore, the capacity of the high power density secondary battery 15B decreases, that is, the voltage of the high power density secondary battery 15B alone decreases. When the power supply to the load is stopped, the high-energy-density secondary battery 15A is switched to the high-power-density secondary battery 15B in order to match the voltage between the batteries 15A and 15B connected in parallel. Charging is performed. Here, the open-circuit voltage of the high-energy-density secondary battery 15A does not change until the depth of discharge DOD reaches 77% as shown in the characteristic shown in FIG. When the depth of discharge DOD is in the range of 0 to 77%, the open circuit voltage of both the batteries 15A and 15B alone and the assembled battery 15 can maintain a desired value (400 V). If the depth of discharge DOD of the high energy density secondary battery 15A exceeds 77%, the voltage of the high energy density secondary battery 15A also drops. In other words, the capacity of the high energy density secondary battery 15A Becomes empty, so that power can be supplied only with the capability of the high power density secondary battery 15B thereafter. Therefore, the open circuit voltage of the battery pack 15 decreases.
[0026]
FIG. 4 is a graph in which the available capacity (Ah) of the battery is plotted on the horizontal axis and the open circuit voltage V is plotted on the vertical axis. FIG. 4 (A) shows a change in the open circuit voltage of the high energy density secondary battery 15A. 4 (B) shows the change in the open circuit voltage of the high power density secondary battery 15B, and FIG. 4 (C) shows the change in the open circuit voltage of the battery pack 15.
[0027]
In the assembled battery 15 connected in parallel, the usable capacity of the high energy density type secondary battery 15A is 12 Ah (see FIG. 4A), and the usable capacity of the high power density type secondary battery 15B is 3 Ah. (See FIG. 4B), and the usable capacity of the entire assembled battery 15 is 15 Ah (= 12 Ah + 3 Ah) (see FIG. 4C).
[0028]
As shown in FIG. 4A, the usable capacity of the high-energy-density secondary battery 15A is 12 Ah, and the capacity is 11.5 Ah (corresponding to 77% as the DOD of the assembled battery). The circuit voltage can maintain a certain value, after which the open circuit voltage drops rapidly.
[0029]
On the other hand, as shown in FIG. 4B, the usable capacity of the high power density type secondary battery 15B is 3 Ah, and the open circuit voltage also increases as the consumed capacity (consumed capacity = usable capacity−remaining capacity) increases. It shows a decreasing characteristic.
[0030]
Therefore, while the high-energy-density secondary battery 15A has the remaining capacity (the range of the area D whose consumed capacity is up to 11.5 Ah), the capacity consumed by the high-power-density secondary battery 15B is determined by the high-energy-density type It can be supplemented by charging from the secondary battery 15A, and if the consumption capacity exceeds 11.5 Ah, the consumption of the high power density secondary battery 15B cannot be compensated for by the high energy density secondary battery 15A, The open circuit voltage will decrease (see region E).
[0031]
As a result, as shown in FIG. 5, the relationship between the depth of discharge DOD and the output of this assembled battery is that the depth of discharge DOD of the high power density secondary battery 15B is not increased until the depth of discharge DOD is about 80% (77%). Since it is maintained at 0%, a high output of the output characteristics (40 kW) of the high power density type secondary battery 15B can be output from the assembled battery 15, and the effect of improving the output characteristics of the assembled battery 15 can be obtained. .
[0032]
6 and 7 show the characteristics of the comparative example. In this comparative example, although not shown, a high-energy-density secondary battery was prepared by using an olivine-type lithium iron phosphate compound (LiFePO ₄ ), A 12 Ah secondary battery using hard carbon for the negative electrode, a high power density secondary battery, and a spinel lithium manganese oxide (LiMn) for the positive electrode. ₂ O ₄ ), A 3 Ah secondary battery using graphite for the negative electrode. Then, similarly to the above embodiment, 112 cells of the high energy density type secondary battery and 96 cells of the high power density type secondary battery were connected in series, and each was connected in parallel to form an assembled battery. All the specifications are the same as in the above embodiment, except that the open circuit voltage is changed by replacing the material of the negative electrode.
[0033]
FIG. 6 shows the relationship between the depth of discharge DOD and the open voltages F and G of the high energy density secondary battery and the high output density type secondary battery, and the relationship between the depth of discharge DOD and the open voltage H of the assembled battery. As is clear from the figure, in this comparative example, the high power density type secondary battery is used up to 20% of the depth of discharge DOD, and the capacity of the high energy density type secondary battery is used in the remaining 80%.
[0034]
FIG. 7 shows the relationship between the depth of discharge DOD and the output of the comparative example. In this comparative example, the output characteristics of the high power density type secondary battery are obtained because the high power density type secondary battery is exclusively used up to the depth of discharge DOD of 20% (see the characteristic J in the figure). After DOD 20%, the DOD of the high power density type secondary battery becomes close to 100%, so that the output characteristics are reduced (see characteristics K in the figure).
[0035]
From these results, as in the present embodiment, by setting the open circuit voltage of the high power density secondary battery 15B lower than the open circuit voltage of the high energy density secondary battery 15A, the high power density secondary battery It can be understood that the depth of discharge DOD of the battery 15B is smaller than the depth of discharge DOD of the high energy density secondary battery 15A, and the output characteristics are improved as shown in FIG.
[0036]
In the present embodiment, the following effects can be obtained.
[0037]
(A) Since the assembled battery 15 is configured by connecting the high power density type secondary battery 15B and the high energy density type secondary battery 15A having different open circuit voltages in parallel, the combination of batteries having the same open circuit voltage is achieved. In comparison, it is possible to realize an assembled battery according to various required characteristics.
[0038]
(A) Since the open circuit voltage of the high energy density secondary battery 15A is higher than the open circuit voltage of the high power density secondary battery 15B, the discharge depth DOD of the high power density secondary battery 15B is high. The discharge depth DOD of the secondary battery 15A can be made smaller, and the output characteristics of the battery can be improved.
[0039]
(C) The open circuit voltage of the high power density type secondary battery 15B is gradually decreased with respect to the depth of discharge DOD, and the open circuit voltage of the high energy density type secondary battery 15A is constant with respect to the depth of discharge DOD. Since the characteristics do not change, the open circuit voltage of the high power density secondary battery 15B can be lower than the open circuit voltage of the high energy density secondary battery 15A.
[0040]
(D) Since the open circuit voltage of the high energy density type secondary battery 15A is higher than the open circuit voltage of the high output density type secondary battery 15B, the characteristic is constant and does not change with respect to the depth of discharge DOD. The depth of discharge DOD of the density type secondary battery 15B can be kept constant near 0%, and a constant output characteristic can be secured regardless of the depth of discharge DOD of the battery pack 15.
[0041]
(E) The open circuit voltage of the high power density type secondary battery 15B is gradually decreased with respect to the depth of discharge DOD, and the open circuit voltage of the high energy density type secondary battery 15A is constant with respect to the depth of discharge DOD. Since the characteristics do not change, it is difficult to calculate the remaining capacity only by voltage measurement when using only the high energy density type secondary battery 15A having a constant open circuit voltage with respect to the depth of discharge DOD. Is connected in parallel to the high power density secondary battery 15B having a slope with respect to the depth of discharge DOD, so that at the end of charging and discharging, the open circuit voltage of the high power density secondary battery 15B changes, Is measured, it is possible to accurately know the end of charge and discharge of the battery pack 15.
[0042]
(F) Since the high power density secondary battery 15B uses an amorphous carbon material (hard carbon) for the negative electrode material and the high energy density secondary battery 15A uses a graphite (graphite) carbon material for the negative electrode, The open circuit voltage of the high power density secondary battery 15B can be lower than the open circuit voltage of the high energy density secondary battery 15A.
[0043]
(G) The high output density secondary battery 15B uses an amorphous carbon material (hard carbon) as a negative electrode material, and the high energy density secondary battery 15A uses a graphite (graphite) carbon material as a negative electrode. Therefore, the high power density secondary battery 15B can be a battery whose open circuit voltage has a gradient with respect to the depth of discharge DOD, and the high energy density secondary battery 15A has a constant open circuit voltage with respect to the depth of discharge DOD. Can be with batteries.
[0044]
(H) The high power density secondary battery 15B uses a lithium metal oxide (LiMn) as a positive electrode material. ₂ O ₄ , LiNiO ₂ , LiCoO ₂ And the like, and the high energy density secondary battery 15A uses a lithium metal phosphate compound (LiFePO ₄ , LiMnO ₄ Etc.), the high power density type secondary battery 15B can be a battery whose open circuit voltage has a slope with respect to the depth of discharge DOD, and the high energy density type secondary battery 15A has an open circuit voltage whose depth of discharge is DOD. Can be a constant battery.
[0045]
(G) The high-power-density secondary battery 15B uses a lithium metal oxide (LiMn) as a positive electrode material. ₂ O ₄ , LiNiO ₂ , LiCoO ₂ And the like, and the high energy density secondary battery 15A uses a lithium metal phosphate compound (LiFePO ₄ , LiMnO ₄ And the like), it is possible to use a battery using a lithium metal phosphate compound having poor output characteristics for the positive electrode even in an application requiring output.
[0046]
(2nd Embodiment)
8 to 11 show a second embodiment of an assembled battery to which the present invention is applied. FIG. 8 is a connection diagram showing the configuration of the assembled battery. FIG. 9 is a high power density secondary battery and a high energy density secondary battery. FIG. 10 is a graph showing the open circuit voltage (open-circuit voltage) characteristics of the secondary battery, FIG. 10 is a graph showing the characteristics of the depth of discharge DOD of the assembled battery and each battery constituting the assembled battery, and FIG. 11 is the input / output characteristics of the assembled battery. It is a graph. In the present embodiment, the range of the minimum input is expanded instead of obtaining the maximum output characteristic that the battery can produce as in the previous embodiment. The same components as those in the previous embodiment are denoted by the same reference numerals, and the description will be simplified or omitted.
[0047]
8, a battery pack 16 as a main battery of the hybrid vehicle has a high energy density type secondary battery 16A on the right side in the drawing and 130 cells connected in series, and 96 cells on the left side in the drawing. The high power density type secondary battery 16B is connected in parallel. In addition, since the open circuit voltage of each single cell differs when the depth of discharge DOD is 0%, the number of cells of each battery is equal to that of the entire high power density secondary battery (16B) in which 96 cells are connected in series. The open circuit voltage at a discharge depth of 0% and the open circuit voltage at a discharge depth of 0% of the entire high energy density type secondary battery (16A) in which 130 cells are connected in series have the same value of L [V]. Means to show.
[0048]
The cell of the high energy density secondary battery 16A is a lithium ion battery using metal lithium for the negative electrode and vanadium oxide for the positive electrode. The cell of the high power density secondary battery 16B is, for example, a carbon material for the negative electrode. A lithium ion battery using a lithium manganese oxide for the positive electrode is provided. The electrode materials of the high energy density type secondary battery 16A and the high power density type secondary battery 16B are not limited to the above examples. In short, the one with the higher open circuit voltage (open voltage) is defined as the high output density type secondary battery 16B. Therefore, by adjusting the number of cells connected in series, the open circuit voltage of the high power density secondary battery 16B can be made higher than the open circuit voltage of the high energy density secondary battery 16A.
[0049]
The output of the battery can be increased by making the electrode thinner and increasing the electrode area. The use of a positive electrode or a negative electrode having a high open circuit voltage can also increase the output of the battery. Also, by using an electrolyte for the high power density type secondary battery 16B and a solid electrolyte for the high energy density type secondary battery 16A, the high power density type secondary battery 16B and the high energy density type secondary battery 16A can be formed. Therefore, the difference between the high power density type secondary battery 16B and the high energy density type secondary battery 16A becomes clear. The high-energy density secondary battery 16A uses a high-capacity lithium ion battery in which the active materials of the positive and negative electrodes are thickened, and the high power density secondary battery 16B uses a thin active material of the positive and negative electrodes to reduce the inside of the battery. By using a lithium ion battery with reduced resistance, both can be manufactured relatively easily.
[0050]
FIG. 9 is a diagram showing characteristics of the high power density type secondary battery 16B and the high energy density type secondary battery 16A used in the battery pack 16, and the open circuit voltage (open voltage) with respect to the discharge depth DOD of each battery. Represents the relationship. However, the high output density type secondary battery 16B has the characteristics in a state where 96 cells are connected in series, and the high energy density type secondary battery 16A has the characteristics in a state where 130 cells are connected in series.
[0051]
As shown in FIG. 9, the two batteries connected in parallel have an open circuit voltage of L [V] when the depth of discharge DOD is 0 [%], and have an open circuit voltage of 70 [%] when the depth of discharge DOD is 70 [%]. The open circuit voltages are both N [V], but at other discharge depths DOD, they are different open circuit voltages. That is, when the depth of discharge DOD is in the range of 0 to 70 [%], the open circuit voltage of the high power density type secondary battery 16B is higher than the open circuit voltage of the high energy density type secondary battery 16A. In a range larger than 70%, the magnitude relationship between the open circuit voltage of the high power density type secondary battery 16B and the open circuit voltage of the high energy density type secondary battery 16A is reversed.
[0052]
In the battery pack 16 in which such two batteries are connected in parallel, the open circuit voltage becomes L [V] when the discharge depth DOD of the battery pack 16 as a whole is 0 [%], and the discharge depth DOD of the two batteries is also 0. [%]. Similarly, when the depth of discharge DOD of the entire assembled battery 16 is 70 [%], the open circuit voltage is N [V], and the depth of discharge DOD of the two batteries is also 70 [%]. However, when the depth of discharge DOD of the entire assembled battery 16 is other than 0 or 70 [%], the depth of discharge DOD of the entire assembled battery 16 does not become equal to the depth of discharge DOD of each of the batteries 16A and 16B. For example, when the open circuit voltage (= voltage of each battery) of the assembled battery 16 is M [V], the discharge depth DOD of the high power density type secondary battery 16B is about 44 [%], and the high energy density type The discharge depth DOD of the secondary battery 16A is about 16 [%].
[0053]
FIG. 10 shows the relationship between the depth of discharge DOD of the battery pack 16 as a whole and the depth of discharge DOD of each of the batteries 16A and 16B. In FIG. 10, for example, when the depth of discharge DOD of the battery pack 16 is 30 [%], the depth of discharge DOD of the high power density type secondary battery 16B is about 44 [%], and the high energy density type secondary battery is The discharge depth DOD of 16A is about 16 [%]. Thus, in the range of the depth of discharge DOD where the open circuit voltage of the high power density type secondary battery 16B is higher than the open circuit voltage of the high energy density type secondary battery 16A, the discharge depth of the high power density type secondary battery 16B The DOD is higher than the discharge depth DOD of the battery pack 16, and the discharge depth DOD of the high energy density secondary battery 16A is lower than the discharge depth DOD of the battery pack 16.
[0054]
The dashed line in the figure shows the characteristics of an assembled battery (hereinafter, comparative example) in which two batteries having the same open circuit voltage characteristics with respect to the depth of discharge DOD are connected in parallel. The depth DOD and the discharge depth DOD of each battery are always equal.
[0055]
FIG. 11 is a diagram showing the relationship between the depth of discharge DOD of the battery pack 1 of the present embodiment and its input / output power. However, since the input / output power of the battery pack 16 is substantially determined by the input / output power of the high power density secondary battery 16B, the relationship between the depth of discharge DOD of the battery pack 16 and the input / output power of the high power density secondary battery 16B is determined. May be seen as a diagram showing As is apparent from FIG. 11, the input power in the range of the depth of discharge DOD where the open circuit voltage of the high power density type secondary battery 16B is higher than the open circuit voltage of the high energy density type secondary battery 16A (solid line in the figure). Is larger than the input power of the comparative example (the dashed line in the figure). This is because the input power, that is, the charging power increases in accordance with the increase in the depth of discharge DOD, and the depth of discharge DOD of the high power density secondary battery 16B which is one of the assembled batteries 16 in this range is the comparative example. This is because it is higher than the discharge depth DOD.
[0056]
Generally, when a secondary battery is used as a power supply for a hybrid vehicle, it is necessary to control the depth of discharge DOD of the battery so that a certain level of output power and a certain level of input power can always be secured. For example, when the minimum output power Pomin to be always secured is P [kW] and the minimum input power Pimin to be always secured is R [kW], the depth of discharge DOD of the battery pack of the comparative example shown by the dashed line is 35 to It is necessary to control in the range of 70 [%]. On the other hand, in the battery pack 16 of the present embodiment, the range of the depth of discharge DOD for securing the same input / output power can be expanded to 25 to 70%. This means that input / output control (charge / discharge control) can be performed more flexibly, which is a very advantageous characteristic as a power source for a hybrid vehicle.
[0057]
In order to reliably obtain the above-described effect, the output (P [kW] in this example) of the battery pack 16 at the depth of discharge DOD (70 [%] in this example) where the magnitude relationship of the open circuit voltage is reversed is the lowest output. A battery pack whose input (Q [kW] in this example) is equal to or greater than Pomin and whose input (Q [kW] in this example) is equal to or greater than the minimum input Pimin at the depth of discharge DOD where the magnitude relationship of the open circuit voltage is reversed.
[0058]
In the present embodiment, the following effects can be obtained.
[0059]
(G) Since the high-power-density secondary battery 16B and the high-energy-density secondary battery 16A having different open-circuit voltages are connected in parallel to form the battery pack 16, the combination of batteries having the same open-circuit voltage can be obtained. In comparison, a high-performance battery with improved input / output characteristics can be realized.
[0060]
(C) Since the open circuit voltage of the high power density secondary battery 16B of the assembled battery 16 is higher than the open circuit voltage of the high energy density secondary battery 16A, the depth of discharge (DOD) of the high power density secondary battery 16B ) Can be made larger than the depth of discharge DOD of the battery pack 16, and the input characteristics of the battery can be improved.
[0061]
(B) There is a depth of discharge (DOD) of the battery pack 16 in which the open circuit voltage of the high power density type secondary battery 16B is equal to the open circuit voltage of the high energy density type secondary battery 16A. Since the magnitude relationship between the depth of discharge of each of the batteries 16A and 16B and the depth of discharge of the battery pack 16 is reversed, it is possible to set the depth of discharge (DOD) range of the battery pack 16 from which characteristics such as input / output characteristics can be obtained. .
[0062]
(S) Before and after the depth of discharge (DOD) of the battery pack 16 at which the open circuit voltage of the high power density type secondary battery 16B is equal to the open circuit voltage of the high energy density type secondary battery 16A, In the case where the magnitude relationship with the depth of discharge of the battery pack 16 is reversed, if the open circuit voltage of the high power density type secondary battery 16B is higher than the open circuit voltage of the high energy density type secondary battery 16A, the high output during charging is obtained. The discharge depth of the density type secondary battery 16B is larger than the discharge depth of the battery pack 16, so that the input characteristics to the battery pack 16 can be improved. The depth can be made smaller than the depth, and the output characteristics from the assembled battery 16 can be improved.
[0063]
(C) Since a positive electrode or a negative electrode having a higher open circuit voltage is used as a positive electrode or a negative electrode of the high power density secondary battery 16B than the high energy density secondary battery 16A, the high power density secondary battery 16B is opened. The circuit voltage can be made higher than that of the high energy density type secondary battery 16A.
[0064]
(G) The open circuit voltage of the high power density type secondary battery 16B can also be adjusted by adjusting the number of series-connected cells of the high power density type secondary battery 16B and / or the high energy density type secondary battery 16A. It is possible to make the voltage higher than the open circuit voltage of the secondary battery 16A.
[0065]
(T) By setting the range of the depth of discharge DOD used by the assembled battery 16 to the range of the depth of discharge DOD in which the open circuit voltage of the high power density type secondary battery 16B is higher than the open circuit voltage of the high energy density type secondary battery 16A. In addition, the depth of discharge (DOD) of the high power density type secondary battery 16B can be made larger than the depth of discharge DOD of the battery pack 16, and the input characteristics of the battery can be improved.
[0066]
(H) The high power density secondary battery 16B is a battery using an electrolytic solution, and the high energy density secondary battery 16A is an all solid state battery. The characteristic difference of the density type secondary battery 16A becomes clear, and the above-mentioned effect can be further exerted.
[Brief description of the drawings]
FIG. 1 is a system configuration diagram of a hybrid vehicle showing an application example of an assembled battery of the present invention.
FIG. 2 is a connection diagram showing a configuration of a battery pack according to the first embodiment of the present invention.
FIG. 3 is a graph showing the relationship between the DOD of each battery connected in parallel and the open-circuit voltage and the relationship between the depth of discharge DOD and the open-circuit voltage of the assembled battery connected in parallel.
FIG. 4 is a graph showing a relationship between a depth of discharge DOD and output power in a battery pack.
FIG. 5 is a graph showing the relationship between the capacity of each battery and the assembled battery and the open circuit voltage.
FIG. 6 is a graph showing the relationship between the DOD of each battery connected in parallel and the open-circuit voltage of the comparative example, and the relationship between the depth of discharge DOD and the open-circuit voltage of the assembled battery connected in parallel;
FIG. 7 is a graph showing the relationship between the capacity of each battery and the assembled battery of the comparative example and the open circuit voltage.
FIG. 8 is a schematic configuration diagram of a battery pack showing a second embodiment of the present invention.
FIG. 9 is a graph showing open-circuit voltage (open-circuit voltage) characteristics of a high output density secondary battery and a high energy density secondary battery.
FIG. 10 is a graph showing the characteristics of the depth of discharge DOD of the battery pack and the batteries constituting the battery pack.
FIG. 11 is a graph showing input / output characteristics of a battery pack.
[Explanation of symbols]
1, 4, 10 motor
2 Engine
3 clutch
5 continuously variable transmission
6 Reduction gear
7 Differential device
8 drive wheels
9 Hydraulic system
11-13 Inverter
14 DC link
15, 16 Main battery, assembled battery
15A, 16A High energy density secondary battery
15B, 16B High power density secondary battery

Claims

A battery pack comprising a high output density secondary battery and a high energy density secondary battery having different open circuit voltages connected in parallel.

The battery pack according to claim 1, wherein an open circuit voltage of the high energy density type secondary battery is higher than an open circuit voltage of the high power density type secondary battery.

The high power density type secondary battery has a characteristic that the open circuit voltage gradually decreases with respect to the depth of discharge DOD, and the high energy density type secondary battery has a constant open circuit voltage with respect to the depth of discharge DOD and does not change. 3. The battery pack according to claim 1, wherein the battery pack has characteristics.

The high power density type secondary battery uses an amorphous carbon material (hard carbon) as a negative electrode material, and the high energy density type secondary battery uses a graphite type (graphite) carbon material as a negative electrode. The battery pack according to claim 2 or 3.

The high power density type secondary battery uses a lithium metal oxide (LiMn ₂ O ₄ , LiNiO ₂ , LiCoO _2, etc.) as a positive electrode material, and the high energy density type secondary battery uses a lithium metal phosphate compound ( 5. The battery pack according to claim 2, wherein LiFePO ₄ , LiMnO ₄ or the like is used.

The battery pack according to claim 1, wherein an open circuit voltage of the high power density type secondary battery is higher than an open circuit voltage of the high energy density type secondary battery.

There is a discharge depth DOD of the battery pack in which the open circuit voltage of the high power density type secondary battery and the open circuit voltage of the high energy density type secondary battery are equal, and the discharge depth of each battery before and after this discharge depth 2. The battery pack according to claim 1, wherein the magnitude relationship between the battery pack and the depth of discharge of the battery pack is reversed. 3.

The assembled battery according to claim 7, wherein an open circuit voltage of the high power density type secondary battery is higher than an open circuit voltage of the high energy density type secondary battery.

The battery pack according to claim 6, wherein the positive electrode of the high power density type secondary battery uses a positive electrode having a higher open circuit voltage than the positive electrode of the high energy density type secondary battery.

The battery pack according to claim 6, wherein the negative electrode of the high power density type secondary battery uses a negative electrode having a higher open circuit voltage than the negative electrode of the high energy density type secondary battery.

The number of series-connected cells of the high power density secondary battery and / or the high energy density secondary battery is such that the open circuit voltage of the high power density secondary battery is higher than the open circuit voltage of the high energy density secondary battery. 7. The battery pack according to claim 6, wherein the battery pack is adjusted so as to be as follows.

The discharge depth DOD range used by the battery pack is a discharge depth DOD range in which the open circuit voltage of the high power density type secondary battery is higher than the open circuit voltage of the high energy density type secondary battery. Item 10. The battery pack according to Item 1.

The battery pack according to claim 1, wherein the high power density type secondary battery is a battery using an electrolyte, and the high energy density type secondary battery is an all solid state battery.