JP2004055425A - Laminated secondary battery and battery element body - Google Patents

Laminated secondary battery and battery element body Download PDF

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Publication number
JP2004055425A
JP2004055425A JP2002213466A JP2002213466A JP2004055425A JP 2004055425 A JP2004055425 A JP 2004055425A JP 2002213466 A JP2002213466 A JP 2002213466A JP 2002213466 A JP2002213466 A JP 2002213466A JP 2004055425 A JP2004055425 A JP 2004055425A
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positive electrode
negative electrode
active material
positive
secondary battery
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Yuji Tanjo
丹上　雄児
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Nissan Motor Co Ltd
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Nissan Motor Co Ltd
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    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

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  • Battery Electrode And Active Subsutance (AREA)

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laminated secondary battery with excellent life characteristics. <P>SOLUTION: With the laminated secondary battery 10 with a plurality of positive electrode plates 101 and negative electrode plates 103, immersed in an electrolyte solution capable of inserting and removing lithium ion and mediating transport of the lithium ion, laminated with an interposition of a separator 102 and electrically connected in parallel, the positive electrode includes one or a plurality of first positive electrode layers 41a, 42a with lithium manganese complex oxide as an active material and one or a plurality of second positive electrode layers 41b, 42b with lithium nickel complex oxide as an active material. <P>COPYRIGHT: (C)2004,JPO

Description

【０００１】
【技術分野】
本発明は、リチウム含有複合酸化物を活物質とする積層型二次電池に関する。
【０００２】
【背景技術】
この種の積層型二次電池に関し、寿命特性の向上の観点から、リチウムマンガン複合酸化物とリチウムニッケル複合酸化物との混合酸化物を正極活物質とする電池が提案されている（特開平１０−１１２３１８号公報、特開２０００−７７０７１号公報参照）。この技術によれば、充放電サイクル、充放電寿命等の改善を図ることができる。
【０００３】
しかしながら、リチウムマンガン複合酸化物とリチウムニッケル複合酸化物とを混合した混合酸化物を正極活物質とした電池では、十分な寿命特性を実現することができないという問題があった。
【０００４】
【発明の開示】
本発明は、優れた寿命特性を有する積層型二次電池を提供することを目的とする。
【０００５】
本発明によれば、リチウムイオンの挿入脱離が可能であるとともに、前記リチウムイオンの輸送を媒介する電解液に浸漬される複数の正極及び負極が、セパレータを挟んで積層されるとともに電気的に並列接続された積層型二次電池であって、前記正極は、リチウムマンガン複合酸化物を活物質とする一又は複数の第１の正極と、リチウムニッケル複合酸化物を活物質とする一又は複数の第２の正極とを含む積層型二次電池が提供される。
【０００６】
これにより、本発明は寿命特性に優れた積層型二次電池を提供することができる。
【０００７】
【発明の実施の形態】
以下、本発明の実施形態を図面に基づいて説明する。
【０００８】
図１（Ａ）は本発明の実施形態に係る薄型の積層型二次電池１０の全体を示す平面図、図１（Ｂ）は（Ａ）のＢ−Ｂ線に沿う断面図である。図１は一つの積層型二次電池１０を示す。この積層型二次電池１０を複数積層することにより所望の電圧、容量の組電池を構成することができる。
【０００９】
本発明の実施形態に係る積層型二次電池１０は、リチウム系の薄型の積層型二次電池であり、図１に示すように、複数の正極板１０１および負極板１０３と、正極板１０１と負極板１０３との間に挟まれたセパレータ１０２と、正極端子１０４と、負極端子１０５と、上部電池外装１０６と、下部電池外装１０７と、特に図示しない電解質とから構成されている。正極板１０１，セパレータ１０２，負極板１０３の枚数は何ら限定されず、必要に応じて正極板１０１、負極板１０３およびセパレータの枚数を選択して構成することができる。
【００１０】
＜第１の実施形態＞
図２は、第１の実施形態に係る積層型二次電池１０の内部を具体的に示す。本実施形態では、３枚の正極板１０１と３枚の負極板１０３とが、５枚のセパレータ１０２を挟むように積層され、その最上層の上と最下層の下とに２枚のセパレータ１０２がさらに積層されている。
【００１１】
負極板１０２は、負極端子１０５へと負極リード１０５ｃを介して接続される負極側集電体１０５ａと、この負極側集電体１０５ａの両主面に形成された負極層５１，５２とを有する。また、正極板１０１は、正極端子１０４へと正極リード１０４ｃを介して接続される正極側集電体１０４ａと、この正極側集電体１０４ａの両主面に形成された正極層４１，４２を有する。この正極層４１，４２は、リチウムマンガン複合酸化物またはリチウムニッケル複合酸化物のいずれかを正極活物質とする。本発明においてリチウムマンガン複合酸化物およびリチウムニッケル複合酸化物の組成は、特に限定されず、定比化合物であってもよく、不定比化合物であってもよい。
【００１２】
図２では、リチウムマンガン複合酸化物を正極活物質とする正極層４１，４２を第１の正極層４１ａ，４２ａと示し、リチウムニッケル複合酸化物を正極活物質とする正極層４１，４２を第２の正極層４１ｂ，４２ｂと示す。正極層４１ａ，４２ａの数と正極層４１ｂ，４２ｂの数とは特に限定されることなく、任意に決定することができる。本実施形態では、図２に示すように、６層の正極層（３枚の正極板１０１の両主面に形成された６層の正極層）のうち、４層の正極層（２枚の正極板１０１の両主面に形成された４層の正極層）を、第１の正極層（正極活物質：ＬｉＭｎ２Ｏ４）とし、残りの２層の正極層（１枚の正極板１０１の両主面に形成された２層の正極層）を第２の正極層（正極活物質：ＬｉＮｉＯ２）とした。
【００１３】
ちなみに、本発明では少なくとも１層以上の正極層４１ａ，４２ａと、少なくとも１層以上の正極層４１ｂ，４２ｂとが含まれていればよい。また、本例では、一の正極側集電体１０４ａの両主面に形成される正極層の正極活物質を同じ材料としたが、正極側集電体１０４ａの一方の主面にはリチウムマンガン複合酸化物を正極活物質とする正極層４１ａ，４２ａを形成し、他方の主面にはリチウムニッケル複合酸化物を正極活物質とする正極層４１ｂ，４２ｂを形成してもよい。
【００１４】
本実施形態では、第１の正極層４１ａ，４２ａの正極活物質をＬｉＭｎ２Ｏ４とし、第２の正極層４１ｂ，４１ｂの正極活物質をＬｉＮｉＯ２とした。また、この正極活物質に添加される導電材を炭素材料に属するカーボンブラックとし、さらに正極活物質と導電材とを結着させる結着材をポリフッ化ビニリデン（ＰＶＤＦ）とした。
【００１５】
第１の正極層４１ａ，４２ａは、正極活物質としてのＬｉＭｎ２Ｏ４と導電材としてのカーボンブラックとを混合し、結着剤としてのポリフッ化ビニリデン（ＰＶＤＦ）を溶解させたＮメチル−２−ピロリドン（ＮＭＰ）中に均一に分散させてスラリーを作製し、このスラリーを正極側集電体１０４ａとなるアルミ金属箔上に均一に塗布し、ＮＭＰを蒸発させ、ローラープレス機により圧延し、アルミ金属箔１０４ａ上に正極層４１ａ，４２ａを作製する。混合されるＬｉＭｎ２Ｏ４と、カーボンブラックと、ポリフッ化ビニリデン（ＰＶＤＦ）との重量比は、８：１：１である。第２の正極層４１ｂ，４２ｂは、正極活物質をＬｉＮｉＯ２とし、第１の正極層４１ａ，４２ａと同様の手法で作製する。混合されるＬｉＮｉＯ２と、カーボンブラックと、ポリフッ化ビニリデン（ＰＶＤＦ）との重量比は、８：１：１である。このように作製された正極層４１ａ，４２ａ，４１ｂ，４２ｂは、所定の大きさに切断され、正極板１０２が得られる。
【００１６】
また、本実施形態では、非晶質系の炭素系材料に属するハードカーボンを負極活物質とし、ポリフッ化ビニリデン（ＰＶＤＦ）を結着剤として採用した。ハードカーボンとポリフッ化ビニリデン（ＰＶＤＦ）とを９：１の重量比で混合し、これをＮメチル−２−ピロリドン（ＮＭＰ）に分散させてスラリーを作製し、このスラリーを負極側集電体である銅金属箔１０５ａ上に均一に塗布し、ＮＭＰを蒸発させ、ローラープレス機により圧延し、銅金属箔１０５ｂ上に負極層５１，５２を作製する。作製された負極層５１，５２は所定の大きさに切断され、負極板１０１が得られる。本実施形態の負極活物質は、ハードカーボンをはじめとする非晶質炭素、難黒鉛化炭素、易黒鉛化炭素、または黒鉛などのように、正極活物質のリチウムイオンを吸蔵および放出する材料を用いることができる。
【００１７】
また、セパレータ１０２は、上述した正極板１０１と負極板１０３との短絡を防止するもので、電解質を保持する機能を備えてもよい。セパレータ１０２は、例えばポリエチレン（ＰＥ）やポリプロピレン（ＰＰ）などのポリオレフィン等から構成される微多孔性膜であり、過電流が流れると、その発熱によって膜の空孔が閉塞され電流を遮断する機能をも有する。なお、本発明のセパレータ１０２は、ポリオレフィンなどの単層膜にのみ限られず、ポリプロピレン層をポリエチレン層でサンドイッチした三層構造や、ポリオレフィン微多孔膜と有機不織布などを積層したものも用いることができる。セパレータ１０２を複層化することで、過電流の防止機能、電解質保持機能およびセパレータの形状維持（剛性向上）機能などの諸機能を付与することができる。また、セパレータ１０２の代わりにゲル電解質又は真性ポリマー電解質等を用いることもできる。
【００１８】
以上の正極板１０１と負極板１０３とが交互に、且つ当該正極板１０１と負極板１０２との間にセパレータ１０２が位置するような順序で積層され、さらに、その最上部及び最下部にセパレータ１０２が一枚ずつ積層され、発電要素体が得られる。
【００１９】
そして、２枚の正極板１０１のそれぞれは、正極側集電体１０４ａを介して、金属箔製の正極端子１０４に接続される一方で、２枚の負極板１０３は、負極側集電体１０５ａを介して、同じく金属箔製の負極端子１０５に接続されている。なお、正極端子１０４も負極端子１０５も電気化学的に安定した金属材料であれば特に限定されないが、正極端子１０４としてはアルミニウムやアルミニウム合金などを挙げることができ、負極端子１０５としてはニッケル、銅またはステンレスなどを挙げることができる。また、本例の正極側集電体１０４ａも負極側集電体１０５ａの何れも、正極板１０１および負極板１０３の集電体を構成するアルミニウム箔やニッケル箔、銅箔を延長して構成されているが、別途の材料や部品により当該集電体１０４ａ，１０５ａを構成することもできる。
【００２０】
以上の正極板１０１、負極板１０３、セパレータ１０２等は、上部電池外装１０６及び下部電池外装１０７により封止されている。これら上部電池外装１０６および下部電池外装１０７は、例えばポリエチレンやポリプロピレンなどの樹脂フィルムや、アルミニウムなどの金属箔の両面をポリエチレンやポリプロピレンなどの樹脂でラミネートした、樹脂−金属薄膜ラミネート材など、柔軟性を有する材料で形成されている。
【００２１】
そして、これらの上部電池外装１０６及び下部電池外装１０７によって、上述した正極板１０１、負極板１０３、セパレータ１０２、正極側集電体１０４ａ、正極端子１０４の一部、負極側集電体１０５ａおよび負極端子１０５の一部を包み込み、当該電池外装１０６、１０７により形成される空間に、有機液体溶媒に過塩素酸リチウム、ホウフッ化リチウム等のリチウム塩を溶質とした液体電解質を注入したのち、上部電池外装１０６及び下部電池外装１０７の外周縁を熱融着などの方法により封止する。
【００２２】
電池外装に封入される液体電解質の有機液体溶媒として、プロピレンカーボネート（ＰＣ）、エチレンカーボネート（ＥＣ）、ジメチルカーボネート（ＤＭＣ）などのエステル系溶媒を例示することができるが、本発明の有機液体溶媒はこれにのみ限定されることなく、エステル系溶媒に、γ−ブチラクトン（γ−ＢＬ）、ジエトシキエタン（ＤＥＥ）等のエーテル系溶媒その他を混合、調合した有機液体溶媒も用いることができる。
【００２３】
なお、封止された電池外装１０６、１０７の一方の端部から、正極端子１０４が導出するが、正極端子１０４の厚さ分だけ上部電池外装１０６と下部電池外装１０７との接合部に隙間が生じるので、積層型二次電池１０内の封止性を維持するために、当該正極端子１０４と電池外装１０６、１０７とが接触する部分に、ポリエチレンやポリプロピレンから構成されたシールフィルムを熱融着などの方法により介在させることもできる。同様に、封止された電池外装１０６、１０７の他方の端部からは、負極端子１０５が導出するが、ここにも正極端子１０４側と同様に、当該負極端子１０５と電池外装１０６、１０７とが接触する部分にシールフィルムを介在させることもできる。なお、正極端子１０４および負極端子１０５の何れにおいても、シールフィルムは電池外装１０６，１０７を構成する樹脂と同系統の樹脂から構成することが熱融着性の点から望ましい。
【００２４】
このように構成された本実施形態に係る積層型二次電池について、サイクル寿命特性を検証した。
【００２５】
＜実験１＞
実験に用いた実施例１には、図２を参照して説明した第１の実施形態に係る積層型二次電池１０を用いた。
【００２６】
また、比較例１として、リチウムマンガン複合酸化物（ＬｉＭｎ２Ｏ４）とリチウムニッケル複合酸化物（ＬｉＮｉＯ２）とを２：１の重量比で混合した混合酸化物を、正極活物質とする正極板１０１を作製した。正極板１０１に形成される正極層の数は、実施例１と同じ６層とし、正極層の大きさ、厚さ等も実施例１と同じとした。また、比較例１の正極を構成するリチウムマンガン複合酸化物（ＬｉＭｎ２Ｏ４）に対するリチウムニッケル複合酸化物（ＬｉＮｉＯ２）の存在比は、実施例１の正極層４１ａ，４２ａ，４１ｂ，４２ｂを構成するリチウムマンガン複合酸化物（ＬｉＭｎ２Ｏ４）に対するリチウムニッケル複合酸化物（ＬｉＮｉＯ２）の存在比と同じ値とした。
【００２７】
実施例１と比較例１について、充放電サイクルにおける容量維持率をそれぞれ測定した。容量維持率（％）は、１サイクル目の放電容量を１００％としたときの、所定回数のサイクル時における放電容量を百分率で示したものである。放電容量は、放電容量（Ａｈ）＝放電電流（Ａ）　×　放電時間（ｈ）により算出する。
【００２８】
この１充放電サイクルは、電池を６０℃において、以下の条件における充電−充電休止−放電−放電休止の４ステップからなる。
【００２９】
放電条件：
電流値１ＣＡ：（１時間で全容量を放電させる電流値）
放電終止電圧：２．５Ｖ（電圧が２．５Ｖとなったら放電終了）
充電条件：
電流値１ＣＡ：（１時間で全容量を放電させる電流値）
充電終止電圧：４．２Ｖ（電圧が４．２Ｖとなったら充電終了）
休止条件：
休止時間：１０分
このように、定電流で電池を充放電させてサイクル毎に放電容量を測定し、充放電サイクル数と容量維持率との関係を求めた。結果を表１及び図４に示した。
【００３０】
【表１】

Figure 2004055425
表１および図４に示すように、本実施例１は、比較例１に比べて高い容量維持率を保つことができる。
【００３１】
比較例１は、ＬｉＭｎ２Ｏ４とＬｉＮｉＯ２の混合酸化物を正極活物質とし、混合酸化物内には物理的特性の異なるＬｉＭｎ２Ｏ４とＬｉＮｉＯ２とが混在する。充放電反応においてはこの混合酸化物内でリチウムイオンの挿入脱離が起きるが、充放電時のＬｉイオンの挿入脱離に伴う結晶の膨張収縮率および結晶の膨張収縮のタイミングは、混在するＬｉＭｎ２Ｏ４とＬｉＮｉＯ２とにおいて相違する。このため、充放電が繰り返されるたびに混合酸化物結晶内で不均一な膨張または収縮が繰り返されることとなる。このようにミクロ的に不均一な膨張または収縮が繰り返されると、ＬｉＭｎ２Ｏ４およびＬｉＮｉＯ２の結晶構造や電気化学的特性が変化するものと考えられる。
【００３２】
発明者は、このような混合酸化物内のＬｉＭｎ２Ｏ４およびＬｉＮｉＯ２の結晶構造や電気化学的特性の変化が、正極活物質と導電材との接触抵抗を増加させるなど電気化学的特性に影響を与え電池の寿命特性を劣化させるものと考え、本実施例において、ＬｉＭｎ２Ｏ４を正極活物質とする第１の正極層４１ａ，４２ａと、ＬｉＮｉＯ２を正極活物質とする第２の正極層４１ｂ，４２ｂとの２種の正極層を設けることとした。
【００３３】
このため、本実施例１は、比較例１に見られるような結晶構造や電気化学的特性の変化が生じないため、比較例１よりも高い寿命特性を奏することができる。
【００３４】
また、リチウムマンガン複合酸化物を正極活物質とする場合、充放電反応において正極層からマンガンイオンの溶出が起こる場合がある。溶出したマンガンイオンが負極に析出すると、析出物が負極におけるリチウムイオンの挿入脱離経路をふさぎ、リチウムイオンの吸蔵脱離を妨害して容量が低下する場合がある。
【００３５】
比較例１では、すべての正極層にマンガンイオンが含まれるため、すべての負極層にマンガンイオンが析出して負極層を劣化させる。
【００３６】
これに対し、本実施例１では、リチウムマンガン複合酸化物（ＬｉＭｎ２Ｏ４）を正極活物質とする第１の正極層４１ａ，４２ａと、リチウムニッケル複合酸化物（ＬｉＮｉＯ２）を活物質とする第２の正極層４１ａ，４２ａとに分けたため、リチウムマンガン複合酸化物（ＬｉＭｎ２Ｏ４）を正極活物質とする正極層から溶出するマンガンイオンは、この正極層に対向する負極層にのみ析出し、リチウムニッケル複合酸化物（ＬｉＮｉＯ２）を活物質とする正極層に対向する負極層にまで析出しない。
【００３７】
このように、本実施例は、一部ではあるが負極層の劣化を防ぐことができ、比較例１よりも高い容量維持率を保ち、寿命特性を向上させることができる。
【００３８】
＜第２実施形態＞
図４は、第２実施形態に係る積層型二次電池１０の内部構造を示す。第１の実施形態との相違点は、第１の正極層４１ａ、４２ａに対向する第１の負極層５１ｃ，５２ｃの活物質と、第２の正極層４１ｂ，４２ｂに対向する負極層５１ｄ，５２ｄの活物質とを、異なる炭素材料とした点にある。第１の実施形態と共通する他の点についての説明は省略する。
【００３９】
図４に示すように、第１の負極層５１ｃ、５２ｃは、少なくとも第１の正極層４１ａ，４２ａと対向するように積層され、第２の負極層５１ｄ，５２ｄは、少なくとも第２の正極層４１ｂ，４２ｂと対向するように積層されている。本形態では、一の正極側集電体１０４ａ、負極側集電体１０５ａの各主面に、異なる材料を活物質とする正極層または負極層を形成したが、同じ材料を活物質とする正極層または負極層を形成してもよい。
【００４０】
このように形成される負極層５１，５２の負極活物質は、黒鉛系の炭素系材料または非晶質系の炭素材料（ハードカーボン系炭素材料、またはソフトカーボン系炭素材料に属するものを含む）のいずれかから選択されることが好ましい。
【００４１】
さらに、この負極活物質の選択において、第１の正極層４１ａ、４２ａとこれに対向する第１の負極層５１ｃ，５２ｃとが示す任意の放電深さ（％）に対する開回路電圧（Ｖ）が、第２の正極層４１ｂ，４２ｂとこれに対向する第２の負極層５１ｄ，５２ｄとが示すその任意の放電深さ（％）に対する開回路電圧（Ｖ）と異なるように、第１の負極層５１ｃ，５２ｃの活物質と第２の負極層５１ｄ，５２ｄの活物質とを選択することが好ましい。
【００４２】
さらにまた、少なくとも放電終期において、又は常に、第１の正極層４１ａ、４２ａとこれに対向する第１の負極層５１ｃ，５２ｃとが示す任意の放電深さ（％）に対する開回路電圧（Ｖ）が、第２の正極層４１ｂ，４２ｂとこれに対向する第２の負極層５１ｄ，５２ｄとが示す、その任意の放電深さ（％）の開回路電圧（Ｖ）よりも低い値となるように、第１の負極の活物質と第２の負極の活物質とを選択することが好ましい。
【００４３】
このような放電深さ（％）と開回路電圧（Ｖ）との関係は、以下の実験により確認することができ、上記関係を示す負極活物質を選択することができる。
【００４４】
開回路電圧（Ｖ）は、電池を充放電装置により満充電とし、各放電深さ（ＤＯＤ％）となる時間と電圧とを調整し、調整された時間と電圧とに基づいて電池を放電させる。その後、電池の電圧が安定するまで放置し、電圧を測定する。これを電池が放電状態となるまでの各放電深さにおいて繰り返す。この各放電深さにおいて測定された電圧が開回路電圧（Ｖ）である。
【００４５】
具体的な充放電条件を以下に示す。
充電条件
定電流−定電圧充電　（一定の電流値で充電し、満充電電圧となったら、その電圧で充電時間だけ一定に保持する）
電流値：　１ＣＡ（１時間で全容量を放電させる電流値）
満充電電圧：４．２Ｖ
充電時間：２．５時間
放電条件
定電流放電（一定の電流値で放電させる）
電流値：　１ＣＡ（１時間で全容量を放電させる電流値）
充電時間：６分（ＤＯＤ１０％ごとに６分）
休止時間：１０分
本発明者は、第１の正極層４１ａ，４２ａおよび第２の正極層４１ｂ，４２ｂと、異なる種類の炭素材料を負極活物質とする負極層とを幾とおりも組み合わせ、実験を繰り返した結果、図５に示すように上記の関係を満たす放電深さ（％）と開回路電圧（Ｖ）とを得る負極活物質を選択した。図５の関係を示す正極層４１，４２と負極層５１，５２との組み合わせは、「正極活物質をリチウムマンガン複合酸化物とする第１の正極層４１ａ，４２ａと、非晶質炭素を負極活物質とする第１の負極層５１ｃ，５２ｃ」と、「リチウムニッケル複合酸化物を正極活物質とする第２の正極層４１ｂ，４２ｂと、黒鉛系炭素を負極活物質とする第２の負極層５１ｄ，５２ｄ」との組み合わせである。
【００４６】
このような関係を示す負極活物質を選択することが好ましいのは、以下の理由による。
【００４７】
図５のような任意の放電深さにおいて異なる開回路電圧を示す、電池１（第１正極層（正極活物質：ＬｉＭｎ２Ｏ４）＋第１負極層（負極活物質：非晶質炭素）からなる電池）および電池２（第２正極層（正極活物質：ＬｉＮｉＯ２）＋第２負極層（負極活物質：黒鉛系炭素））の２つの電池同士が電気的に並列接続されると、各電池が示す開回路電圧は等しい電圧となる。
【００４８】
図５において任意の放電深さ（％）をＸ％とする。電池１の放電深さＸ％における開回路電圧（Ｖ）は点Ｏのｙ座標値（Ｏｙ）が示す電圧となる。また電池２の放電深さＸ％における閉回路電圧（Ｖ）は点Ｐのｙ座標値（Ｐｙ）が示す電圧となる。電池１と電池２とを並列接続すると、これらの電圧が等しくなるため、電池１の開回路電圧（Ｏｙ）は上昇し、電池２の開回路電圧（Ｐｙ）は下降して、同じく点Ｓにおける電圧Ｓｙ（点Ｓにおけるｙ座標値）を示す。
【００４９】
電池１の開回路電圧Ｓｙに対応する電池１の放電深さ（％）は点Ｑのｘ座標値（Ｑｘ）となる。すなわち、電池１と電池２との並列接続によって、電池１の電圧を上昇させ、この電圧上昇によって放電深さ（％）をＸ％からＱｘ（点Ｑのｘ座標値）に減少させる。言い換えると、電池１の放電深さ（％）と開回路電圧（Ｖ）との関係は、充電側（満充電：ＤＯＤ＝０％）にシフトする。
【００５０】
一方、電池２の開回路電圧Ｓｙに対応する電池２の放電深さ（％）は点Ｒのｘ座標値（Ｒｘ）となる。すなわち、電池１と電池２との並列接続によって、電池２の電圧を下降させ、この電圧下降によって放電深さ（％）をＸ％からＲｘ（点Ｒのｘ座標値）に増加させる。言い換えると、電池２の放電深さ（％）と開回路電圧（Ｖ）との関係は、放電側（放電完了：ＤＯＤ＝１００％）にシフトする。このように、電池１と電池２とを並列に接続することによって、放電が行われる環境を充電側または放電側へと移行させることができる。
【００５１】
リチウムマンガン複合酸化物を正極活物質とする電池１は、放電が進行した環境（放電側）において電池特性劣化の進行度が大きい傾向がある。また、リチウムニッケル複合酸化物を正極活物質とする電池は充電が進行した環境において電池特性の劣化進行度が大きい傾向がある。
【００５２】
発明者はこの事実を考察し、放電深さに対する開回路電圧が異なる２つの電池を電気的に並列に接続することにより、放電深さと開回路電圧との関係を放電側または充電側へシフトさせ、電池特性の劣化が進行しにくい環境を実現させる。図５に示すように電池１の示す任意の放電深さＸ％に対する開回路電圧が、電池２の示す放電深さＸ％に対する開回路電圧よりも低い電圧を示すように負極層の炭素材料を選択すれば、電池１の放電深さ（％）と開回路電圧（Ｖ）との関係を充電側へシフトさせることができる。また、この関係はすべての放電深さにおいて見られることが好ましいが、少なくとも、放電終期において電池１の示す任意の放電深さに対する開回路電圧が、電池２の示す該任意の放電深さに対する開回路電圧よりも低い電圧を示すように負極層の炭素材料を選択すれば、放電が進行した環境（放電側）において電池特性劣化の進行度が大きいリチウムマンガン複合酸化物を正極活物質とする電池１の劣化を抑制することができる。
【００５３】
このように、本実施形態は、正極活物質がリチウムマンガン複合酸化物である電池の環境を電池特性の劣化が進みにくい充電側へシフトさせることができ、同じく正極活物質がリチウムニッケル複合酸化物である電池の環境を電池特性の劣化が進みにくい放電側へシフトさせることができ、積層型二次電池１０の寿命特性を向上させることができる。
【００５４】
＜実験２＞
図５のような関係を示す第１の正極層４１ａ，４２ａおよび第２の負極層５１ｃ，５２ｃと、第２の正極層４１ｂ，４２ｂおよび第２の負極層５１ｄ，５２ｄとを有する積層型二次電池１０に関し、寿命特性を検討した。
【００５５】
実験に用いた実施例２に係る積層型二次電池１０は、第１の正極層４１ａ，４２ａの正極活物質をＬｉＭｎ２Ｏ４とするとともに、これに対向する第１の負極層５１ｃ，５２ｃの負極活物質をハードカーボンとし、第２の正極層４１ｂ，４２ｂの正極活物質をＬｉＮｉＯ２とするとともに、これに対向する第２の負極層５１ｄ，５２ｄの負極活物質をグラファイトとした積層型二次電池１０（図４参照）を用いた。第１の正極層４１ａ，４２ｂａと第１の負極層５１ｃ，５２ｃとからなる電池１と、第２の正極層４１ｂ，４２ｂと第２の負極層５１ｄ，５２ｄとからなる電池２とは電気的に並列接続されている。
【００５６】
第１の正極層４１ａ，４２ａは、ＬｉＭｎ２Ｏ４と、カーボンブラックと、ポリフッ化ビニリデン（ＰＶＤＦ）とからなり、その重量比は、８：１：１である。第２の正極層４１ｂ，４２ｂは、ＬｉＮｉＯ２と、カーボンブラックと、ポリフッ化ビニリデン（ＰＶＤＦ）とからなり、その重量比は、８：１：１である。
【００５７】
また、第１の負極層５１ｃ，５２ｃは、非晶質系の炭素系材料に属するハードカーボンと、ポリフッ化ビニリデン（ＰＶＤＦ）（結着剤）とからなり、その重量比は９：１である。第２の負極層５１ｄ，５２ｄは、黒鉛系の炭素系材料に属するグラファイトと、ポリフッ化ビニリデン（ＰＶＤＦ）（結着剤）とからなり、その重量比は９：１である。なお、製造方法等の他の点については、上述した第２実施形態の積層型二次電池１０と同じである。
【００５８】
また、比較例２として、第１の正極層４１ａ，４２ａの正極活物質をＬｉＭｎ２Ｏ４とし、第２の正極層４１ｂ，４２ｂの正極活物質をＬｉＮｉＯ２とし、これら第１の正極層４１ａ，４２ａおよび第２の正極層４１ｂ，４２ｂに対向する負極層５１，５２の負極活物質をいずれもハードカーボンとした。正極層および負極層を構成する組成の混合比は実施例２と同じ値とした。
【００５９】
このように用意された実施例２と比較例２について、充放電サイクルにおける容量維持率をそれぞれ測定した。容量維持率（％）は、１サイクル目の放電容量を１００％としたときの、所定回数のサイクル時における放電容量を百分率で示すものであって、実験１と同様の手法により、定電流で電池を充放電させてサイクル毎に放電容量を測定し、充放電サイクル数と容量維持率との関係を求めた。結果を表２及び図６に示した。
【００６０】
【表２】
Figure 2004055425
表２および図６に示すように、本実施例２は、比較例２に比べて高い容量維持率を保つことができる。
【００６１】
このように、実施例２が高い容量維持率を保持できるのは、第１正極層と第１負極層との間（電池１）に生じる電圧と第２正極層と第２負極層との間（電池２）に生じる電圧とが異なるように負極活物質を選択したため、異なる開回路電圧を示す単位電池１と単位電池２とを電気的に並列接続することにより開回路電圧を変化させることができ、この開回路電圧の変化によって各単位電池の放電深さを変化させることができたためである。これにより、第１の正極層４１ａ，４２ａと第１負極層５１ｃ，５２ｃとの間（単位電池１）の開回路電圧を上昇させて放電深さを充電側にシフトさせることができ、放電側で劣化が進みやすい第１の正極層（正極活物質：ＬｉＭｎ２Ｏ４）の劣化を抑制することができる。同様に第２の正極層４１ｂ，４２ｂと第２の負極層５１ｄ，５２ｄとの間（単位電池２）の開回路電圧を降下させて放電深さを放電側にシフトさせることができ、充電側で劣化が進みやすい第２の正極層（正極活物質：ＬｉＮｉＯ２）の劣化を抑制することができる。このように、本実施形態は、第１の正極層４１ａ，４２ａおよび第２の正極層４１ｂ，４２ｂの劣化を抑制することができるため、積層型二次電池１０の寿命特性を向上させることができる。
【００６２】
＜第３の実施形態＞
次に第３の実施形態を説明する。第３の実施形態が第２の実施形態と異なる点は、リチウムマンガン複合酸化物を正極活物質とする第１の正極層４１ａ，４２ａが積層型二次電池１０の外装近傍に位置するように、正極及び負極を積層した点である。第２の実施形態と共通する他の点についての説明は省略する。この積層の状態の一例を図４に示した。第１正極層４１ａ，４２ａは積層型二次電池１０の最端層に積層されており、他方、リチウムニッケル複合酸化物を正極活物質とする第２正極層４１ｂ，４２ｂは電池外装から比較的離れた位置、すなわち積層型二次電池１０の中心付近に位置するように積層されている。本実施形態の負極層５１，５２の負極活物質は特に限定されず、非晶質系の炭素材料、黒鉛系の炭素材料、または非晶質系の炭素材料および黒鉛系の炭素材料を用いてもよい。
【００６３】
＜実験３＞
実験に用いる実施例３に係る積層型二次電池１０は、図４に示すような３枚の正極板１０１ａ，１０１ｂ，１０１ｃを有している。このうち外装近傍に位置する正極板１０１ａおよび１０１ｃの正極活物質は、ＬｉＭｎ２Ｏ４である。また、積層型二次電池１０の中心付近に位置する正極板１０１ｂの正極活物質は、ＬｉＮｉＯ２である。これら正極層４１，４２に対向する負極層５１，５２の負極活物質はすべて非晶質系の炭素材料であるハードカーボンである。
【００６４】
第１の正極層４１ａ，４２ａは、ＬｉＭｎ２Ｏ４と、カーボンブラックと、ポリフッ化ビニリデン（ＰＶＤＦ）とからなり、その重量比は、８：１：１である。第２の正極層４１ｂ，４２ｂは、ＬｉＮｉＯ２と、カーボンブラックと、ポリフッ化ビニリデン（ＰＶＤＦ）とからなり、その重量比は、８：１：１である。
【００６５】
また、負極層５１，５２は、非晶質系の炭素系材料に属するハードカーボンと、ポリフッ化ビニリデン（ＰＶＤＦ）（結着剤）とからなり、その重量比は９：１である。なお、製造方法等の他の点については、上述した第２の実施形態の積層型二次電池１０と同じとした。
【００６６】
また、比較例３は、実施例３と同様に、図４に示すような３枚の正極板１０１ａ，１０１ｂ，１０１ｃを有している。このうち外装近傍に位置する正極板１０１ａおよび１０１ｃに形成される正極層の正極活物質をＬｉＮｉＯ２とした。また、積層型二次電池１０の中心付近に位置する正極板１０１ｂに形成される正極層の正極活物質をＬｉＭｎ２Ｏ４とした。これら正極層４１，４２に対向する負極層５１，５２の負極活物質はすべて非晶質系の炭素材料であるハードカーボンである。他の点については、実施例３と同じとした。
【００６７】
このように用意された実施例３と比較例３とについて、充放電サイクルにおける容量維持率をそれぞれ測定した。容量維持率（％）は、１サイクル目の放電容量を１００％としたときの、所定回数のサイクル時における放電容量を百分率で示すものであって、実験１と同様の手法により、定電流で電池を充放電させてサイクル毎に放電容量を測定し、充放電サイクル数と容量維持率との関係を求めた。結果を表３及び図７に示した。
【００６８】
【表３】
Figure 2004055425
表３及び図７に示すように、本実施例３は比較例３に比べて高い容量維持率を保つことができる。
【００６９】
正極活物質をリチウムマンガン複合酸化物とする電池は、特に高熱環境下において劣化が進行する傾向がある。本実施例は、リチウムマンガン複合酸化物を正極活物質とする正極層４１ａ，４２ａを、温度が比較的低い電池の外装近傍に位置するように積層したため、リチウムマンガン複合酸化物を正極活物質とする正極層４１ａ，４２ａの劣化を抑制することができ、積層型二次電池１０の寿命特性を向上させることができる。
【００７０】
なお、以上説明した実施形態は、本発明の理解を容易にするために記載されたものであって、本発明を限定するために記載されたものではない。したがって、上記の実施形態に開示された各要素は、本発明の技術的範囲に属する全ての設計変更や均等物をも含む趣旨である。
【図面の簡単な説明】
【図１】図１（Ａ）は本発明の実施形態に係る積層型二次電池の全体を示す平面図、図１（Ｂ）は本発明の本実施形態に係る積層型二次電池の内部構造を示す断面図である。
【図２】第１実施形態に係る積層型二次電池の内部構造を示す図である。
【図３】第１実施例に係る積層型二次電池のサイクル数（回）と容量維持率（％）との関係を示す図である。
【図４】第２実施形態に係る積層型二次電池の内部構造を示す図である。
【図５】第２実施形態に係る積層型二次電池の放電深さ（％）と開回路電圧（Ｖ）との関係を示す図である。
【図６】第２実施例に係る積層型二次電池のサイクル数（回）と容量維持率（％）との関係を示す図である。
【図７】第３実施例に係る積層型二次電池のサイクル数（回）と容量維持率（％）との関係を示す図である。
【符号の説明】
１０…積層型二次電池
１０１…正極板
１０２…セパレータ
１０３…負極板
１０４…正極端子
１０４ａ…正極側集電体
１０４ｂ…正極層
４１ａ，４２ａ…第１の正極層（第１の正極）
４１ｂ，４２ｂ…第２の正極層（第２の正極）
１０５…負極端子
１０５ａ…負極側集電体
１０５ｂ…負極層
５１ｃ，５２ｃ…第１の負極層（第１の負極）
５１ｄ，５２ｄ…第２の負極層（第１の負極）
１０６…上部電池外装
１０７…下部電池外装
１０８…ヒートシール部（外周縁）
１０９…発電要素（正極板、負極板、セパレータ、電解液、正極端子、負極端子を含む）[0001]
【Technical field】
The present invention relates to a stacked secondary battery using a lithium-containing composite oxide as an active material.
[0002]
[Background Art]
With respect to this type of stacked secondary battery, a battery using a mixed oxide of a lithium manganese composite oxide and a lithium nickel composite oxide as a positive electrode active material has been proposed from the viewpoint of improving the life characteristics (Japanese Patent Application Laid-Open No. Hei 10 (1998)). -112318, JP-A-2000-77071). According to this technique, it is possible to improve a charge / discharge cycle, a charge / discharge life, and the like.
[0003]
However, there has been a problem that a battery using a mixed oxide obtained by mixing a lithium manganese composite oxide and a lithium nickel composite oxide as a positive electrode active material cannot achieve sufficient life characteristics.
[0004]
DISCLOSURE OF THE INVENTION
An object of the present invention is to provide a stacked secondary battery having excellent life characteristics.
[0005]
According to the present invention, insertion and desorption of lithium ions are possible, and a plurality of positive electrodes and negative electrodes immersed in an electrolytic solution that mediates the transport of lithium ions are stacked with a separator interposed therebetween and electrically connected. A stacked secondary battery connected in parallel, wherein the positive electrode includes one or more first positive electrodes using a lithium manganese composite oxide as an active material, and one or more first positive electrodes using a lithium nickel composite oxide as an active material. And a second positive electrode including the second positive electrode.
[0006]
Thus, the present invention can provide a stacked secondary battery having excellent life characteristics.
[0007]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0008]
FIG. 1A is a plan view showing the entire thin stacked secondary battery 10 according to the embodiment of the present invention, and FIG. 1B is a cross-sectional view taken along line BB of FIG. FIG. 1 shows one stacked secondary battery 10. By stacking a plurality of such stacked secondary batteries 10, a battery pack having a desired voltage and capacity can be formed.
[0009]
The stacked secondary battery 10 according to the embodiment of the present invention is a lithium-based thin stacked secondary battery, and includes a plurality of positive electrode plates 101 and negative electrode plates 103, It is composed of a separator 102 sandwiched between a negative electrode plate 103, a positive electrode terminal 104, a negative electrode terminal 105, an upper battery exterior 106, a lower battery exterior 107, and an electrolyte (not shown). The number of the positive electrode plate 101, the separator 102, and the negative electrode plate 103 is not limited at all, and the number of the positive electrode plate 101, the negative electrode plate 103, and the number of the separators can be selected as needed.
[0010]
<First embodiment>
FIG. 2 specifically shows the inside of the stacked secondary battery 10 according to the first embodiment. In this embodiment, three positive electrode plates 101 and three negative electrode plates 103 are stacked so as to sandwich five separators 102, and two separators 102 are provided above the uppermost layer and below the lowermost layer. Are further laminated.
[0011]
The negative electrode plate 102 includes a negative electrode current collector 105a connected to the negative terminal 105 via a negative electrode lead 105c, and negative electrode layers 51 and 52 formed on both main surfaces of the negative electrode current collector 105a. . The positive electrode plate 101 includes a positive electrode side current collector 104a connected to a positive electrode terminal 104 via a positive electrode lead 104c, and positive electrode layers 41 and 42 formed on both main surfaces of the positive electrode side current collector 104a. Have. The positive electrode layers 41 and 42 use either a lithium manganese composite oxide or a lithium nickel composite oxide as a positive electrode active material. In the present invention, the composition of the lithium manganese composite oxide and the lithium nickel composite oxide is not particularly limited, and may be a stoichiometric compound or a non-stoichiometric compound.
[0012]
In FIG. 2, the positive electrode layers 41 and 42 using a lithium manganese composite oxide as a positive electrode active material are shown as first positive electrode layers 41a and 42a, and the positive electrode layers 41 and 42 using a lithium nickel composite oxide as a positive electrode active material are referred to as first and second positive electrode layers. 2 are shown as positive electrode layers 41b and 42b. The number of the positive electrode layers 41a and 42a and the number of the positive electrode layers 41b and 42b are not particularly limited, and can be arbitrarily determined. In the present embodiment, as shown in FIG. 2, of the six positive electrode layers (six positive electrode layers formed on both main surfaces of the three positive electrode plates 101), four positive electrode layers (two The four positive electrode layers formed on both main surfaces of the positive electrode plate 101 were replaced with a first positive electrode layer (a positive electrode active material: LiMn). 2 O 4 ) And the remaining two positive electrode layers (two positive electrode layers formed on both main surfaces of one positive electrode plate 101) as a second positive electrode layer (a positive electrode active material: LiNiO 2 ).
[0013]
Incidentally, in the present invention, at least one or more positive electrode layers 41a and 42a and at least one or more positive electrode layers 41b and 42b may be included. Further, in this example, the positive electrode active material of the positive electrode layer formed on both main surfaces of one positive electrode current collector 104a is the same material. Positive electrode layers 41a and 42a using a composite oxide as a positive electrode active material may be formed, and positive electrode layers 41b and 42b using a lithium nickel composite oxide as a positive electrode active material may be formed on the other main surface.
[0014]
In the present embodiment, the positive electrode active material of the first positive electrode layers 41a and 42a is LiMn. 2 O 4 The positive electrode active material of the second positive electrode layers 41b, 41b is LiNiO 2 And The conductive material added to the positive electrode active material was carbon black belonging to a carbon material, and the binder for binding the positive electrode active material and the conductive material was polyvinylidene fluoride (PVDF).
[0015]
The first positive electrode layers 41a and 42a are made of LiMn as a positive electrode active material. 2 O 4 And carbon black as a conductive material, and uniformly dispersed in N-methyl-2-pyrrolidone (NMP) in which polyvinylidene fluoride (PVDF) as a binder is dissolved to prepare a slurry. Is uniformly applied on an aluminum metal foil serving as a positive electrode side current collector 104a, NMP is evaporated, and the resultant is rolled by a roller press to form positive electrode layers 41a and 42a on the aluminum metal foil 104a. LiMn to be mixed 2 O 4 And the weight ratio of carbon black to polyvinylidene fluoride (PVDF) is 8: 1: 1. The second positive electrode layers 41b and 42b are made of LiNiO 2 The first positive electrode layers 41a and 42a are manufactured in the same manner. LiNiO mixed 2 And the weight ratio of carbon black to polyvinylidene fluoride (PVDF) is 8: 1: 1. The positive electrode layers 41a, 42a, 41b, and 42b thus manufactured are cut into a predetermined size, and a positive electrode plate 102 is obtained.
[0016]
In the present embodiment, hard carbon belonging to an amorphous carbon-based material is used as a negative electrode active material, and polyvinylidene fluoride (PVDF) is used as a binder. Hard carbon and polyvinylidene fluoride (PVDF) were mixed at a weight ratio of 9: 1, and this was dispersed in N-methyl-2-pyrrolidone (NMP) to prepare a slurry. This slurry was used as a negative electrode-side current collector. The negative electrode layers 51 and 52 are formed on the copper metal foil 105b by uniformly applying the solution on a certain copper metal foil 105a, evaporating NMP, and rolling by a roller press. The produced negative electrode layers 51 and 52 are cut into a predetermined size, and a negative electrode plate 101 is obtained. The negative electrode active material of the present embodiment is made of a material that occludes and releases lithium ions of the positive electrode active material, such as amorphous carbon including hard carbon, non-graphitizable carbon, graphitizable carbon, or graphite. Can be used.
[0017]
Further, the separator 102 is for preventing a short circuit between the positive electrode plate 101 and the negative electrode plate 103 described above, and may have a function of retaining an electrolyte. The separator 102 is a microporous film made of, for example, a polyolefin such as polyethylene (PE) or polypropylene (PP). When an overcurrent flows, the heat generated by the separator 102 closes the pores of the film and cuts off the current. It also has Note that the separator 102 of the present invention is not limited to a single-layer film of polyolefin or the like, and may be a three-layer structure in which a polypropylene layer is sandwiched by a polyethylene layer, or a laminate of a polyolefin microporous film and an organic nonwoven fabric. . By forming the separator 102 into multiple layers, various functions such as a function of preventing an overcurrent, a function of retaining an electrolyte, and a function of maintaining the shape of the separator (improving rigidity) can be provided. Further, a gel electrolyte, an intrinsic polymer electrolyte, or the like can be used instead of the separator 102.
[0018]
The positive electrode plate 101 and the negative electrode plate 103 are alternately stacked in such an order that the separator 102 is located between the positive electrode plate 101 and the negative electrode plate 102, and further, the separators 102 are provided on the uppermost and lowermost portions thereof. Are laminated one by one to obtain a power generating element body.
[0019]
Each of the two positive plates 101 is connected to a metal foil positive terminal 104 via a positive current collector 104a, while the two negative plates 103 are connected to a negative current collector 105a. Is connected to the negative electrode terminal 105 also made of metal foil. Note that the positive electrode terminal 104 and the negative electrode terminal 105 are not particularly limited as long as they are electrochemically stable metal materials. Examples of the positive electrode terminal 104 include aluminum and an aluminum alloy. Or stainless steel. In addition, both the positive-side current collector 104a and the negative-side current collector 105a of the present example are formed by extending aluminum foil, nickel foil, and copper foil constituting the current collectors of the positive electrode plate 101 and the negative electrode plate 103. However, the current collectors 104a and 105a may be formed of separate materials and components.
[0020]
The above-described positive electrode plate 101, negative electrode plate 103, separator 102, and the like are sealed by an upper battery exterior 106 and a lower battery exterior 107. The upper battery casing 106 and the lower battery casing 107 are made of a flexible material such as a resin film of polyethylene or polypropylene or a resin-metal thin film laminated material in which both surfaces of a metal foil such as aluminum are laminated with a resin such as polyethylene or polypropylene. Is formed of a material having:
[0021]
Then, the above-described positive electrode plate 101, negative electrode plate 103, separator 102, positive electrode side current collector 104a, part of the positive electrode terminal 104, negative electrode side current collector 105a and negative electrode After enclosing a part of the terminal 105 and injecting a liquid electrolyte in which a lithium salt such as lithium perchlorate or lithium borofluoride is dissolved in an organic liquid solvent into a space formed by the battery outer casings 106 and 107, the upper battery The outer peripheral edges of the outer case 106 and the lower battery outer case 107 are sealed by a method such as heat fusion.
[0022]
Examples of the organic liquid solvent of the liquid electrolyte sealed in the battery casing include ester solvents such as propylene carbonate (PC), ethylene carbonate (EC), and dimethyl carbonate (DMC). The organic solvent is not limited thereto, and an organic liquid solvent obtained by mixing and preparing an ether-based solvent such as γ-butylactone (γ-BL) and diethoxyethane (DEE) and the like to the ester-based solvent can also be used.
[0023]
The positive electrode terminal 104 is led out from one end of the sealed battery outer casings 106 and 107. However, a gap is formed between the upper battery outer casing 106 and the lower battery outer casing 107 by the thickness of the positive electrode terminal 104. Therefore, in order to maintain the sealing property in the stacked secondary battery 10, a sealing film made of polyethylene or polypropylene is heat-sealed to a portion where the positive electrode terminal 104 and the battery casings 106 and 107 are in contact with each other. It can also be interposed by such a method. Similarly, a negative electrode terminal 105 is led out from the other end of the sealed battery outer casings 106 and 107. Here, similarly to the positive terminal 104 side, the negative electrode terminal 105 and the battery outer casings 106 and 107 are connected. A seal film may be interposed in a portion where the contact is made. In any of the positive electrode terminal 104 and the negative electrode terminal 105, it is preferable that the seal film is formed of the same resin as the resin forming the battery casings 106 and 107 from the viewpoint of heat fusion.
[0024]
The cycle life characteristics of the thus-configured stacked secondary battery according to the present embodiment were verified.
[0025]
<Experiment 1>
In Example 1 used in the experiment, the stacked secondary battery 10 according to the first embodiment described with reference to FIG. 2 was used.
[0026]
As Comparative Example 1, a lithium manganese composite oxide (LiMn 2 O 4 ) And lithium nickel composite oxide (LiNiO) 2 ) Was mixed at a weight ratio of 2: 1 to prepare a positive electrode plate 101 using a mixed oxide as a positive electrode active material. The number of positive electrode layers formed on the positive electrode plate 101 was six, the same as in Example 1, and the size, thickness, and the like of the positive electrode layer were also the same as in Example 1. Further, a lithium manganese composite oxide (LiMn) constituting the positive electrode of Comparative Example 1 2 O 4 Lithium nickel composite oxide (LiNiO) 2 ) Of the lithium manganese composite oxide (LiMn) constituting the positive electrode layers 41a, 42a, 41b, and 42b of Example 1. 2 O 4 Lithium nickel composite oxide (LiNiO) 2 ) Is the same as the abundance ratio.
[0027]
For Example 1 and Comparative Example 1, the capacity retention rates in charge / discharge cycles were measured. The capacity retention ratio (%) is a percentage of the discharge capacity at a predetermined number of cycles when the discharge capacity in the first cycle is 100%. The discharge capacity is calculated by: discharge capacity (Ah) = discharge current (A) × discharge time (h).
[0028]
This one charge / discharge cycle consists of four steps of charging-pausing-discharging-discharging-discharging pause at 60.degree.
[0029]
Discharge conditions:
Current value 1CA: (current value for discharging all capacity in one hour)
Discharge end voltage: 2.5 V (discharge ends when the voltage reaches 2.5 V)
Charging conditions:
Current value 1CA: (current value for discharging all capacity in one hour)
Charge end voltage: 4.2 V (Charge ends when the voltage reaches 4.2 V)
Pause conditions:
Pause time: 10 minutes
As described above, the battery was charged and discharged at a constant current, the discharge capacity was measured for each cycle, and the relationship between the number of charge and discharge cycles and the capacity retention ratio was obtained. The results are shown in Table 1 and FIG.
[0030]
[Table 1]
Figure 2004055425
As shown in Table 1 and FIG. 4, Example 1 can maintain a higher capacity retention ratio than Comparative Example 1.
[0031]
Comparative Example 1 is LiMn 2 O 4 And LiNiO 2 Is used as a positive electrode active material, and LiMn having different physical properties is contained in the mixed oxide. 2 O 4 And LiNiO 2 And are mixed. In the charge / discharge reaction, insertion / desorption of lithium ions occurs in the mixed oxide. 2 O 4 And LiNiO 2 And the difference. Therefore, each time charge and discharge are repeated, uneven expansion or contraction is repeated in the mixed oxide crystal. When the microscopic uneven expansion or contraction is repeated, LiMn 2 O 4 And LiNiO 2 It is considered that the crystal structure and the electrochemical characteristics of are changed.
[0032]
The inventors have found that LiMn in such mixed oxides 2 O 4 And LiNiO 2 It is considered that the change in the crystal structure and the electrochemical characteristics of the battery deteriorates the life characteristics of the battery by affecting the electrochemical characteristics such as increasing the contact resistance between the positive electrode active material and the conductive material. LiMn 2 O 4 Positive electrode layers 41a and 42a having a positive electrode active material of LiNiO 2 And two kinds of positive electrode layers 41b and 42b each having a positive electrode active material.
[0033]
For this reason, in Example 1, since there is no change in the crystal structure and the electrochemical characteristics as seen in Comparative Example 1, it is possible to achieve a higher life characteristic than Comparative Example 1.
[0034]
In the case where a lithium manganese composite oxide is used as the positive electrode active material, manganese ions may be eluted from the positive electrode layer in a charge / discharge reaction. When the eluted manganese ions deposit on the negative electrode, the deposits may block the insertion / desorption path of lithium ions in the negative electrode, hindering the insertion / extraction of lithium ions and reduce the capacity in some cases.
[0035]
In Comparative Example 1, since manganese ions are contained in all the positive electrode layers, manganese ions are deposited on all of the negative electrode layers and deteriorate the negative electrode layers.
[0036]
In contrast, in Example 1, the lithium manganese composite oxide (LiMn 2 O 4 ) As the positive electrode active material, and a lithium nickel composite oxide (LiNiO 2). 2 ) Is divided into the second positive electrode layers 41a and 42a having an active material of lithium manganese composite oxide (LiMn). 2 O 4 ) Eluted from the positive electrode layer having the positive electrode active material as a positive electrode active material is deposited only on the negative electrode layer facing this positive electrode layer, and the lithium nickel composite oxide (LiNiO 2 ) Does not precipitate on the negative electrode layer facing the positive electrode layer using the active material as the active material.
[0037]
As described above, in the present embodiment, although partly, the deterioration of the negative electrode layer can be prevented, the capacity retention ratio is higher than that of Comparative Example 1, and the life characteristics can be improved.
[0038]
<Second embodiment>
FIG. 4 shows the internal structure of the stacked secondary battery 10 according to the second embodiment. The difference from the first embodiment is that the active materials of the first negative electrode layers 51c and 52c facing the first positive electrode layers 41a and 42a and the negative electrode layers 51d and 52d facing the second positive electrode layers 41b and 42b are different. The point is that a different carbon material is used for the 52d active material. Description of other points common to the first embodiment will be omitted.
[0039]
As shown in FIG. 4, the first negative electrode layers 51c and 52c are stacked so as to face at least the first positive electrode layers 41a and 42a, and the second negative electrode layers 51d and 52d are formed at least in the second positive electrode layer. It is laminated so as to face 41b and 42b. In this embodiment mode, a positive electrode layer or a negative electrode layer using a different material as an active material is formed on each main surface of one positive electrode current collector 104a and the negative electrode current collector 105a. A layer or a negative electrode layer may be formed.
[0040]
The negative electrode active material of the negative electrode layers 51 and 52 thus formed is a graphite-based carbon material or an amorphous carbon material (including a hard carbon-based carbon material or a soft carbon-based carbon material). It is preferable to be selected from any of the above.
[0041]
Further, in the selection of the negative electrode active material, the open circuit voltage (V) with respect to an arbitrary discharge depth (%) indicated by the first positive electrode layers 41a and 42a and the first negative electrode layers 51c and 52c opposed thereto is increased. , The second positive electrode layers 41b, 42b and the second negative electrode layers 51d, 52d opposed thereto differ from the open circuit voltage (V) for an arbitrary discharge depth (%) thereof. It is preferable to select the active material of the layers 51c and 52c and the active material of the second negative electrode layers 51d and 52d.
[0042]
Furthermore, at least at the end of discharge or at all times, the open circuit voltage (V) with respect to an arbitrary discharge depth (%) indicated by the first positive electrode layers 41a and 42a and the first negative electrode layers 51c and 52c opposed thereto. Is lower than the open circuit voltage (V) of the arbitrary discharge depth (%) indicated by the second positive electrode layers 41b and 42b and the second negative electrode layers 51d and 52d opposed thereto. In addition, it is preferable to select the active material of the first negative electrode and the active material of the second negative electrode.
[0043]
The relationship between the discharge depth (%) and the open circuit voltage (V) can be confirmed by the following experiment, and a negative electrode active material exhibiting the above relationship can be selected.
[0044]
The open circuit voltage (V) is obtained by fully charging the battery with a charging / discharging device, adjusting the time and voltage at each discharge depth (DOD%), and discharging the battery based on the adjusted time and voltage. . Thereafter, the battery is left until the voltage is stabilized, and the voltage is measured. This is repeated at each discharge depth until the battery is discharged. The voltage measured at each discharge depth is the open circuit voltage (V).
[0045]
Specific charge / discharge conditions are shown below.
Charging conditions
Constant current-constant voltage charge (Charge at a constant current value, and when it reaches a full charge voltage, keep it at that voltage for the charge time)
Current value: 1 CA (current value for discharging all capacity in one hour)
Full charge voltage: 4.2V
Charging time: 2.5 hours
Discharge conditions
Constant current discharge (discharge at a constant current value)
Current value: 1 CA (current value for discharging all capacity in one hour)
Charging time: 6 minutes (6 minutes for every 10% DOD)
Pause time: 10 minutes
The present inventor repeatedly combined the first positive electrode layers 41a and 42a and the second positive electrode layers 41b and 42b with negative electrode layers using different types of carbon materials as negative electrode active materials, and repeated the experiment. As shown in FIG. 5, a negative electrode active material that obtains a discharge depth (%) and an open circuit voltage (V) satisfying the above relationship was selected. The combination of the positive electrode layers 41 and 42 and the negative electrode layers 51 and 52 showing the relationship of FIG. 5 is as follows: “the first positive electrode layers 41 a and 42 a having a lithium manganese composite oxide as the positive electrode active material; A first negative electrode layer 51c, 52c as an active material; a second positive electrode layer 41b, 42b using a lithium nickel composite oxide as a positive electrode active material; and a second negative electrode using graphite-based carbon as a negative electrode active material. Layers 51d and 52d ".
[0046]
It is preferable to select a negative electrode active material having such a relationship for the following reason.
[0047]
Battery 1 (first positive electrode layer (positive electrode active material: LiMn: LiMn) showing different open circuit voltages at arbitrary discharge depths as shown in FIG. 2 O 4 ) + A first negative electrode layer (a negative electrode active material: amorphous carbon) and a battery 2 (a second positive electrode layer (a positive electrode active material: LiNiO)) 2 ) + Second negative electrode layer (negative electrode active material: graphite-based carbon)), when the two batteries are electrically connected in parallel, the open circuit voltage of each battery becomes equal.
[0048]
In FIG. 5, an arbitrary discharge depth (%) is defined as X%. The open circuit voltage (V) at the discharge depth X% of the battery 1 is the voltage indicated by the y coordinate value (Oy) of the point O. The closed circuit voltage (V) at the discharge depth X% of the battery 2 is the voltage indicated by the y coordinate value (Py) of the point P. When the battery 1 and the battery 2 are connected in parallel, these voltages become equal, so that the open circuit voltage (Oy) of the battery 1 increases, the open circuit voltage (Py) of the battery 2 decreases, and the voltage at the point S The voltage Sy (y coordinate value at the point S) is shown.
[0049]
The discharge depth (%) of the battery 1 corresponding to the open circuit voltage Sy of the battery 1 is the x coordinate value (Qx) of the point Q. That is, the voltage of the battery 1 is increased by connecting the battery 1 and the battery 2 in parallel, and the voltage increase reduces the discharge depth (%) from X% to Qx (x coordinate value of the point Q). In other words, the relationship between the discharge depth (%) of the battery 1 and the open circuit voltage (V) shifts to the charging side (full charge: DOD = 0%).
[0050]
On the other hand, the discharge depth (%) of the battery 2 corresponding to the open circuit voltage Sy of the battery 2 is the x coordinate value (Rx) of the point R. That is, the voltage of the battery 2 is lowered by the parallel connection of the battery 1 and the battery 2, and the discharge depth (%) is increased from X% to Rx (x coordinate value of the point R) by the voltage drop. In other words, the relationship between the discharge depth (%) of the battery 2 and the open circuit voltage (V) shifts to the discharge side (discharge completion: DOD = 100%). As described above, by connecting the battery 1 and the battery 2 in parallel, the environment in which the discharging is performed can be shifted to the charging side or the discharging side.
[0051]
Battery 1 using a lithium-manganese composite oxide as a positive electrode active material tends to have a large degree of deterioration of battery characteristics in an environment where discharge has proceeded (discharge side). Also, batteries using a lithium nickel composite oxide as a positive electrode active material tend to have a large degree of deterioration in battery characteristics in an environment where charging has progressed.
[0052]
The inventor considers this fact, and shifts the relationship between the discharge depth and the open circuit voltage to the discharge side or the charge side by electrically connecting two batteries having different open circuit voltages with respect to the discharge depth in parallel. In addition, an environment in which deterioration of battery characteristics does not easily progress is realized. As shown in FIG. 5, the carbon material of the negative electrode layer was changed so that the open circuit voltage of the battery 1 at an arbitrary discharge depth X% indicated was lower than the open circuit voltage of the battery 2 at the discharge depth X% indicated. If selected, the relationship between the discharge depth (%) of the battery 1 and the open circuit voltage (V) can be shifted to the charge side. It is preferable that this relationship be observed at all discharge depths. However, at least at the end of discharge, the open circuit voltage of the battery 1 for an arbitrary discharge depth indicates that the open circuit voltage of the battery 2 for the arbitrary discharge depth indicates. If the carbon material of the negative electrode layer is selected so as to exhibit a voltage lower than the circuit voltage, a battery using a lithium manganese composite oxide having a large degree of deterioration of battery characteristics in the environment where the discharge has progressed (discharge side) as a positive electrode active material 1 can be suppressed.
[0053]
As described above, according to the present embodiment, the environment of the battery in which the positive electrode active material is the lithium manganese composite oxide can be shifted to the charging side where the deterioration of the battery characteristics does not easily progress. The battery environment can be shifted to the discharge side where deterioration of the battery characteristics does not easily progress, and the life characteristics of the stacked secondary battery 10 can be improved.
[0054]
<Experiment 2>
A stacked type having first positive electrode layers 41a and 42a and second negative electrode layers 51c and 52c and second positive electrode layers 41b and 42b and second negative electrode layers 51d and 52d having the relationship shown in FIG. The life characteristics of the secondary battery 10 were examined.
[0055]
The stacked secondary battery 10 according to Example 2 used in the experiment has a configuration in which the positive electrode active materials of the first positive electrode layers 41a and 42a are LiMn. 2 O 4 The negative electrode active material of the first negative electrode layers 51c and 52c opposed thereto is hard carbon, and the positive electrode active material of the second positive electrode layers 41b and 42b is LiNiO 2. 2 In addition, a stacked secondary battery 10 (see FIG. 4) in which the negative electrode active material of the second negative electrode layers 51d and 52d opposed thereto was graphite was used. The battery 1 including the first positive electrode layers 41a and 42ba and the first negative electrode layers 51c and 52c, and the battery 2 including the second positive electrode layers 41b and 42b and the second negative electrode layers 51d and 52d are electrically connected. Are connected in parallel.
[0056]
The first positive electrode layers 41a and 42a are made of LiMn. 2 O 4 , Carbon black, and polyvinylidene fluoride (PVDF), and the weight ratio is 8: 1: 1. The second positive electrode layers 41b and 42b are made of LiNiO 2 , Carbon black, and polyvinylidene fluoride (PVDF), and the weight ratio is 8: 1: 1.
[0057]
The first negative electrode layers 51c and 52c are made of hard carbon belonging to an amorphous carbon-based material and polyvinylidene fluoride (PVDF) (binder), and the weight ratio is 9: 1. . The second negative electrode layers 51d and 52d are made of graphite belonging to a graphite-based carbon-based material and polyvinylidene fluoride (PVDF) (binder), and the weight ratio thereof is 9: 1. Other points such as a manufacturing method are the same as those of the above-described stacked secondary battery 10 of the second embodiment.
[0058]
As Comparative Example 2, the positive electrode active materials of the first positive electrode layers 41a and 42a were LiMn. 2 O 4 The positive electrode active material of the second positive electrode layers 41b and 42b is LiNiO 2 The negative electrode active materials of the negative electrode layers 51 and 52 facing the first positive electrode layers 41a and 42a and the second positive electrode layers 41b and 42b were hard carbon. The mixing ratio of the compositions constituting the positive electrode layer and the negative electrode layer was the same value as in Example 2.
[0059]
With respect to Example 2 and Comparative Example 2 prepared in this way, the capacity retention ratio in the charge / discharge cycle was measured. The capacity retention ratio (%) indicates the discharge capacity in a predetermined number of cycles when the discharge capacity in the first cycle is 100%, and is expressed as a percentage. The battery was charged / discharged and the discharge capacity was measured for each cycle, and the relationship between the number of charge / discharge cycles and the capacity retention rate was determined. The results are shown in Table 2 and FIG.
[0060]
[Table 2]
Figure 2004055425
As shown in Table 2 and FIG. 6, Example 2 can maintain a higher capacity retention ratio than Comparative Example 2.
[0061]
As described above, Example 2 can maintain a high capacity retention ratio because of the voltage generated between the first positive electrode layer and the first negative electrode layer (battery 1) and the voltage between the second positive electrode layer and the second negative electrode layer. Since the negative electrode active material is selected so that the voltage generated in (battery 2) is different, the open circuit voltage can be changed by electrically connecting the unit batteries 1 and 2 exhibiting different open circuit voltages in parallel. This is because the discharge depth of each unit cell could be changed by the change of the open circuit voltage. As a result, the open circuit voltage between the first positive electrode layers 41a and 42a and the first negative electrode layers 51c and 52c (unit battery 1) can be increased to shift the discharge depth to the charge side, and Positive electrode layer (positive electrode active material: LiMn 2 O 4 ) Can be suppressed. Similarly, the open circuit voltage between the second positive electrode layers 41b and 42b and the second negative electrode layers 51d and 52d (unit cell 2) is lowered to shift the discharge depth to the discharge side, and to reduce the discharge side. Positive electrode layer (positive electrode active material: LiNiO 2 ) Can be suppressed. As described above, according to the present embodiment, the deterioration of the first positive electrode layers 41a and 42a and the second positive electrode layers 41b and 42b can be suppressed, so that the life characteristics of the stacked secondary battery 10 can be improved. it can.
[0062]
<Third embodiment>
Next, a third embodiment will be described. The third embodiment differs from the second embodiment in that the first positive electrode layers 41a and 42a using a lithium manganese composite oxide as a positive electrode active material are located near the exterior of the stacked secondary battery 10. , A positive electrode and a negative electrode are laminated. Description of other points common to the second embodiment will be omitted. FIG. 4 shows an example of this laminated state. The first positive electrode layers 41a and 42a are stacked on the outermost layer of the stacked secondary battery 10, while the second positive electrode layers 41b and 42b using a lithium nickel composite oxide as a positive electrode active material are relatively thin from the battery exterior. They are stacked so as to be separated from each other, that is, near the center of the stacked secondary battery 10. The negative electrode active materials of the negative electrode layers 51 and 52 of the present embodiment are not particularly limited, and may be made of an amorphous carbon material, a graphite carbon material, or an amorphous carbon material and a graphite carbon material. Is also good.
[0063]
<Experiment 3>
The stacked secondary battery 10 according to the third embodiment used in the experiment has three positive plates 101a, 101b, and 101c as shown in FIG. Of these, the positive electrode active materials of the positive plates 101a and 101c located near the exterior are LiMn. 2 O 4 It is. The positive electrode active material of the positive electrode plate 101b located near the center of the stacked secondary battery 10 is LiNiO 2. 2 It is. The negative electrode active materials of the negative electrode layers 51 and 52 opposed to the positive electrode layers 41 and 42 are all hard carbon which is an amorphous carbon material.
[0064]
The first positive electrode layers 41a and 42a are made of LiMn. 2 O 4 , Carbon black, and polyvinylidene fluoride (PVDF), and the weight ratio is 8: 1: 1. The second positive electrode layers 41b and 42b are made of LiNiO 2 , Carbon black, and polyvinylidene fluoride (PVDF), and the weight ratio is 8: 1: 1.
[0065]
The negative electrode layers 51 and 52 are made of hard carbon belonging to an amorphous carbon-based material and polyvinylidene fluoride (PVDF) (binder), and the weight ratio is 9: 1. Other points such as the manufacturing method are the same as those of the above-described stacked secondary battery 10 of the second embodiment.
[0066]
Further, Comparative Example 3 has three positive plates 101a, 101b, and 101c as shown in FIG. Of these, the positive electrode active material of the positive electrode layer formed on the positive plates 101a and 101c located near the exterior is LiNiO 2 And The positive electrode active material of the positive electrode layer formed on the positive electrode plate 101b located near the center of the stacked secondary battery 10 is LiMn. 2 O 4 And The negative electrode active materials of the negative electrode layers 51 and 52 opposed to the positive electrode layers 41 and 42 are all hard carbon which is an amorphous carbon material. The other points were the same as in Example 3.
[0067]
With respect to Example 3 and Comparative Example 3 prepared as described above, the capacity retention ratio in the charge / discharge cycle was measured. The capacity retention ratio (%) indicates the discharge capacity in a predetermined number of cycles when the discharge capacity in the first cycle is 100%, and is expressed as a percentage. The battery was charged / discharged and the discharge capacity was measured for each cycle, and the relationship between the number of charge / discharge cycles and the capacity retention rate was determined. The results are shown in Table 3 and FIG.
[0068]
[Table 3]
Figure 2004055425
As shown in Table 3 and FIG. 7, Example 3 can maintain a higher capacity retention ratio than Comparative Example 3.
[0069]
A battery using a lithium manganese composite oxide as the positive electrode active material tends to deteriorate particularly in a high temperature environment. In this embodiment, since the positive electrode layers 41a and 42a using the lithium manganese composite oxide as the positive electrode active material are stacked so as to be located near the exterior of the battery having a relatively low temperature, the lithium manganese composite oxide is used as the positive electrode active material. The deterioration of the positive electrode layers 41a and 42a can be suppressed, and the life characteristics of the stacked secondary battery 10 can be improved.
[0070]
The embodiments described above are described for facilitating the understanding of the present invention, and are not described for limiting the present invention. Therefore, each element disclosed in the above embodiment is intended to include all design changes and equivalents belonging to the technical scope of the present invention.
[Brief description of the drawings]
FIG. 1A is a plan view showing an entire stacked secondary battery according to an embodiment of the present invention, and FIG. 1B is an internal view of the stacked secondary battery according to the embodiment of the present invention. It is sectional drawing which shows a structure.
FIG. 2 is a diagram showing an internal structure of the stacked secondary battery according to the first embodiment.
FIG. 3 is a diagram showing the relationship between the number of cycles (times) and the capacity retention ratio (%) of the stacked secondary battery according to the first embodiment.
FIG. 4 is a diagram showing an internal structure of a stacked secondary battery according to a second embodiment.
FIG. 5 is a diagram showing a relationship between a discharge depth (%) and an open circuit voltage (V) of the stacked secondary battery according to the second embodiment.
FIG. 6 is a view showing the relationship between the number of cycles (times) and the capacity retention ratio (%) of the stacked secondary battery according to the second embodiment.
FIG. 7 is a diagram showing the relationship between the number of cycles (times) and the capacity retention ratio (%) of the stacked secondary battery according to Example 3.
[Explanation of symbols]
10 ... Stacked type secondary battery
101 ... Positive electrode plate
102 ... Separator
103 ... Negative electrode plate
104 ... Positive terminal
104a: positive electrode side current collector
104b: positive electrode layer
41a, 42a... First positive electrode layer (first positive electrode)
41b, 42b... Second positive electrode layer (second positive electrode)
105 ... negative electrode terminal
105a: negative electrode side current collector
105b: negative electrode layer
51c, 52c... First negative electrode layer (first negative electrode)
51d, 52d... Second negative electrode layer (first negative electrode)
106: Upper battery exterior
107: Lower battery exterior
108: heat seal portion (outer peripheral edge)
109 ... power generation element (including positive electrode plate, negative electrode plate, separator, electrolyte, positive electrode terminal, negative electrode terminal)

Claims (9)

リチウムイオンの挿入脱離が可能であるとともに、前記リチウムイオンの輸送を媒介する電解液に浸漬される複数の正極及び負極が、セパレータを挟んで積層されるとともに電気的に並列接続された積層型二次電池であって、
前記正極は、リチウムマンガン複合酸化物を活物質とする一又は複数の第１の正極と、リチウムニッケル複合酸化物を活物質とする一又は複数の第２の正極とを含む積層型二次電池。A stacked type in which lithium ions can be inserted and desorbed, and a plurality of positive electrodes and negative electrodes immersed in an electrolytic solution that mediates the transport of the lithium ions are stacked with a separator interposed therebetween and electrically connected in parallel. A secondary battery,
The positive electrode includes a stacked secondary battery including one or more first positive electrodes using a lithium manganese composite oxide as an active material and one or more second positive electrodes using a lithium nickel composite oxide as an active material. . 前記負極は、少なくとも前記第１の正極に対向する一又は複数の第１の負極と、少なくとも前記第２の正極に対向する一又は複数の第２の負極とを含み、
前記第１の負極の活物質と前記第２の負極の活物質とは、異なる炭素系材料である請求項１記載の積層型二次電池。The negative electrode includes at least one or a plurality of first negative electrodes facing the first positive electrode, and at least one or a plurality of second negative electrodes facing the second positive electrode,
2. The stacked secondary battery according to claim 1, wherein the active material of the first negative electrode and the active material of the second negative electrode are different carbon-based materials. 前記第１の負極の活物質または前記第２の負極の活物質は、黒鉛系の炭素材料、および非晶質系の炭素材料から選択される請求項２記載の積層型二次電池。The stacked secondary battery according to claim 2, wherein the active material of the first negative electrode or the active material of the second negative electrode is selected from a graphite-based carbon material and an amorphous-based carbon material. 前記第１の正極とこれに対向する第１の負極とが示す任意の放電深さ（％）に対する開回路電圧（Ｖ）が、前記第２の正極とこれに対向する第２の負極とが示す前記任意の放電深さ（％）に対する開回路電圧（Ｖ）と異なるように、前記第１の負極の活物質と前記第２の負極の活物質とを選択する請求項３記載の積層型二次電池。The open circuit voltage (V) with respect to an arbitrary discharge depth (%) indicated by the first positive electrode and the first negative electrode facing the first positive electrode is equal to the open circuit voltage (V) between the second positive electrode and the second negative electrode opposed thereto. 4. The stacked type according to claim 3, wherein the active material of the first negative electrode and the active material of the second negative electrode are selected so as to be different from the open circuit voltage (V) for the given discharge depth (%). Rechargeable battery. 前記第１の正極とこれに対向する第１の負極とが示す任意の放電深さ（％）に対する開回路電圧（Ｖ）が、少なくとも放電終期において、前記第２の正極とこれに対向する第２の負極とが示す前記任意の放電深さ（％）に対する開回路電圧（Ｖ）よりも低い値となるように、前記第１の負極の活物質と前記第２の負極の活物質とを選択する請求項３または４記載の積層型二次電池。The open-circuit voltage (V) for an arbitrary discharge depth (%) indicated by the first positive electrode and the first negative electrode facing the second positive electrode and the second positive electrode facing the second positive electrode at least at the end of discharge are determined. The active material of the first negative electrode and the active material of the second negative electrode have a lower value than the open circuit voltage (V) for the arbitrary discharge depth (%) indicated by the negative electrode of No. 2 The stacked secondary battery according to claim 3 or 4, which is selected. 前記第１の正極とこれに対向する第１の負極とが示す任意の放電深さ（％）に対する開回路電圧（Ｖ）が、常に、前記第１の正極とこれに対向する第１の負極とが示す前記任意の放電深さに対する開回路電圧（Ｖ）よりも低い電圧値となるように、前記第１の負極の活物質と前記第２の負極の活物質とを選択する請求項３または４記載の積層型二次電池。The open circuit voltage (V) for an arbitrary discharge depth (%) indicated by the first positive electrode and the first negative electrode opposed thereto is always the first positive electrode and the first negative electrode opposed thereto. 4. The active material of the first negative electrode and the active material of the second negative electrode are selected such that the voltage value is lower than the open circuit voltage (V) for the arbitrary discharge depth indicated by Or the stacked secondary battery according to 4. 前記第１の正極に対向する第１の負極の活物質を、非晶質系の炭素材料とするとともに、
前記第２の正極に対向する第２の負極の活物質を、黒鉛系の炭素系材料とする請求項２〜６の何れかに記載の積層型二次電池。The active material of the first negative electrode facing the first positive electrode is an amorphous carbon material,
The stacked secondary battery according to any one of claims 2 to 6, wherein the active material of the second negative electrode facing the second positive electrode is a graphite-based carbon-based material. 前記第１の正極が積層型二次電池の外装近傍に位置するように、前記複数の正極及び負極が積層された請求項１〜８の何れかに記載の積層型二次電池。The stacked secondary battery according to any one of claims 1 to 8, wherein the plurality of positive electrodes and the negative electrode are stacked such that the first positive electrode is located near the exterior of the stacked secondary battery. リチウムイオンの挿入脱離が可能である複数の正極及び負極が、セパレータを挟んで積層された電池要素体であって、
前記正極は、リチウムマンガン複合酸化物を活物質とする一又は複数の第１の正極と、リチウムニッケル複合酸化物を活物質とする一又は複数の第２の正極とを含む電池要素体。A plurality of positive and negative electrodes capable of lithium ion insertion and desorption is a battery element body laminated with a separator interposed therebetween,
A battery element body including: one or more first positive electrodes using a lithium manganese composite oxide as an active material; and one or more second positive electrodes using a lithium nickel composite oxide as an active material.
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