JP2004265718A

JP2004265718A - Nonaqueous electrolyte secondary cell

Info

Publication number: JP2004265718A
Application number: JP2003054466A
Authority: JP
Inventors: Tatsuyuki Kuwabara; 達行桑原; Tetsuya Yamashita; 哲哉山下; Tadashi Teranishi; 正寺西
Original assignee: Sanyo Electric Co Ltd
Current assignee: Sanyo Electric Co Ltd
Priority date: 2003-02-28
Filing date: 2003-02-28
Publication date: 2004-09-24
Anticipated expiration: 2023-02-28
Also published as: JP4162510B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte secondary cell that enhances the cell capacity per unit volume and improves the expansion of the cell and the short cycle-life. <P>SOLUTION: The nonaqueous electrolyte secondary cell comprises the basic unit of the cell that has a composite negative electrode plate, a pair of positive electrode plates opposite to respective surfaces of the composite negative electrode plate, and electrolytes disposed between the positive and negative electrode plates. The composite negative electrode plate is composed of a porous metal base filled with a lithium-ion absorbable/releasable carbon material, and a porous metal base filled with silicon wherein both the bases are lapped and joined to each other. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、負極活物質としてケイ素を利用した非水電解質二次電池に関する。
【従来の技術】
リチウムイオン二次電池に代表される非水電解質二次電池は、高いエネルギー密度を有しかつ高容量であるので、移動情報端末等の駆動電源として有用である。
このようなリチウムイオン電池の負極には、従来、リチウムイオンを吸蔵・放出することのできる炭素材料が使用され、正極には複合金属酸化物が使用されている。この構成の電池は、リチウムが金属状態で存在しないので安全性に優れ、リチウムデンドライトが生じないので、サイクル特性に優れているという長所を有する。
【０００２】
しかしながら、近年、携帯電話やノートパソコン等の移動情報端末の小型・軽量化が急速に進展しており、その電源としての電池にはさらなる高容量化が要求されており、このような現状から、負極活物質に炭素材料を用いた上記構成のリチウムイオン電池の電池容量は十分でない。
【０００３】
そこで、炭素材料よりも充放電容量を大きくできる可能性を有するケイ素が負極活物質として注目され、種々な検討が行われている。ところが、ケイ素は、黒鉛等の炭素材料に比較し負荷特性が悪いといった問題や、充放電に伴う体積変化が大きく、サイクルの進行に伴って電池が膨張収縮するといった問題、集電体からケイ素が脱落するためサイクル特性が劣化し易いといった問題を有しており、未だ十分な性能の電池を開発できていない。
【０００４】
このため、このようなケイ素の弱点を補うために、ケイ素と炭素材料とを組み合わせて用いることにより、負荷特性を改善する試みがなされている。しかし、この方法によると電池のサイクル特性が劣化する等のため、期待したような電池容量が得られていない。なぜなら、ケイ素は炭素材料より充電時の電位が高いため、リチウムイオンがケイ素に優先的に吸蔵される結果、炭素材料が電池容量を確保する活物質としてほとんど寄与しなくなるからである。
【０００５】
他方、負極集電体の一方面に黒鉛を塗布し、他方面にハードカーボンや非晶質酸化物等の非黒鉛材料を塗布した負極を用い、この負極の各々の面に正極を対向配置することにより電池容量を高めようとする技術が提案されている（特許文献１参照。）。
【０００６】
【特許文献１】
特開２００１−２１０３１６号公報（第２−３頁）
【０００７】
この技術によると、黒鉛層とこれに対向する正極との間、及び非黒鉛材料からなる層とこれに対向する正極との間で、それぞれリチウムイオンの吸蔵・放出が行われるため、各々の活物質の長所を引き出すことができるので、高容量で電圧平坦性の高い電池を実現することができるとされる。しかし、この技術により、高容量で電圧平坦性の高い電池を実現するためには、電池の充放電を複数の充放電整流器を用いて制御しなければならない。このため、この技術には充放電システムが複雑化し電池製造コストが上昇するという問題がある。
【０００８】
更に、この技術で使用されている黒鉛や、ハードカーボンや非晶質酸化物等の非黒鉛材料は、ケイ素に比べて充放電容量が小さいため、ケイ素を用いた電池ほどには電池容量を高めることができない。その一方、この技術にケイ素を組み合わせると、充放電に伴うケイ素の体積変化によって電池が大きくふくれるといった問題や、ケイ素の体積変化によってケイ素相互及び負極集電体とケイ素との接触性が劣化し、サイクル特性が低下するという問題が生じる。
【０００９】
【発明が解決しようとする課題】
本発明は以上の事情に鑑みなされたものであって、負極活物質としてケイ素を用いることにより単位体積当たりの電池容量を高めるとともに、ケイ素に原因する電池の膨張やサイクル寿命の短さを改善し得た非水電解質二次電池を提供することを目的とする。
【００１０】
【課題を解決するための手段】
上記の目的を達成するための本発明は、リチウムイオンを吸蔵・放出可能な炭素材料を充填した多孔性金属基体と、ケイ素を充填した多孔性金属基体とが重ね合わされ、前記金属基体同士が接合されてなる複合負極板と、前記複合負極板の各々の面にそれぞれ対向するように配置された一対の正極板と、正負電極板の間に配置された電解質と、を含んでなるセル基本単位を備えた非水電解質二次電池であることを特徴とする。
【００１１】
この構成によると、負極活物質として炭素材料とともに、炭素より理論容量の大きいケイ素が用いられているため、単位体積当たりの電池容量及び単位重量当たりの電池容量の双方を高めることができる。また、ケイ素はリチウムイオンの吸蔵・放出に伴い大きく体積変化するのであるが、上記構成ではケイ素の充填された多孔性金属基体がケイ素の体積変化を吸収する。このため、電極板からケイ素が脱落しにくく、サイクル劣化が生じない。また、上記構成ではケイ素と炭素材料が併用されており、ケイ素単独で負極容量を賄う場合に比べてケイ素量が少なくて済む。また、上記構成ではケイ素の充填された多孔性金属基体と炭素材料の充填された多孔性金属基体が接合されており、炭素材料の充填された多孔性金属基体もケイ素の体積変化を吸収する。したがって、上述した作用効果が相まって電池の膨張が十分に抑制されることになる。
【００１２】
他方、炭素材料とケイ素を併用すると、充電時にケイ素が優先的にリチウムイオンを吸蔵するため、炭素材料がリチウムイオンの吸蔵に関与しなくなり、結果として電池容量の低下を招くという問題があるが、上記構成においては、負極板中で炭素材料とケイ素が分離されており、炭素材料の充填されている多孔性金属基体と、ケイ素の充填されている多孔性金属基体のそれぞれに対向させて正極板が配置されているので、このような問題が解消される。つまり、上記構成によると、炭素材料とケイ素との双方が負極活物質として十分に機能するので、負極活物質として炭素材料のみを用いた電池に比較し電池容量を大きくでき、負極活物質としてケイ素のみ用いた電池に比較しサイクル特性を格段に向上させることができる。
【００１３】
ここで、上記本発明リチウムイオン電池においては、前記セル基本単位に、正負電極板が互いに対向するようにして、前記複合負極板と前記正極板とからなるセル追加単位を更に１単位以上積層することができる。
【００１４】
ケイ素は黒鉛等の炭素材料よりも電気容量が大きいため、ケイ素と炭素材料を併用した複合負極板は炭素材料単独の負極板に比較し、体積当たりのエネルギー密度が高い。したがって、このような複合負極板と正極板とが交互に複数積層され、複合負極板の両面に必ず正極板が位置するようにした上記構成であると、高容量でコンパクトなリチウムイオン電池が実現でき、しかも極板の積層数に対応して容量が大きくなるので高容量化しても集電効率の低下がなく、正負極の表面積が大きくなる。すなわち、上記構成によると、高レート放電特性に優れた高容量でコンパクトなリチウムイオン電池が実現できる。
【００１５】
また、上記本発明リチウムイオン電池においては、前記複合負極板の多孔性金属基体同士が電気抵抗溶接により接合された構成とすることができる。
【００１６】
多孔性金属基体同士を直接電気抵抗溶接してなる複合負極板であると、多孔性金属基体同士の電気的一体性が良いので、集電効率がよい。
【００１７】
また、前記炭素材料を充填した多孔性金属基体と、前記ケイ素を充填した多孔性金属基体の少なくとも一方の厚みが、０．１０ｍｍ以上０．２０ｍｍ以下である構成とすることができる。
【００１８】
電気抵抗溶接により接合する場合、その接合のしやすさは多孔性金属基体の厚みに大きく影響を受け、接合する多孔性金属基体の両方の厚みが０．２０ｍｍより大きいと、溶接が困難になるため好ましくない。その一方、０．１０ｍｍ以下であると、負極活物質を十分に充填できなくなる。よって、上記範囲内に規制されていることが好ましい。
【００１９】
また、上記本発明リチウムイオン電池においては、前記多孔性金属基体が発泡金属体からなり、前記炭素材料が黒鉛からなる構成とすることができる。
【００２０】
発泡金属体は三次元的空間を多数有するので、負極活物質を高密度に充填でき、しかもこの空間はその内部に充填された活物質の膨張を金属の伸張や空間形状の変形により吸収することができる。したがって、ケイ素の膨張収縮に起因して負極活物質が負極から脱落するといったことがない。また、黒鉛は比較的容量が大きく電圧平坦性がよいので、前記炭素材料として黒鉛を用いると、コンパクト、高容量で電圧平坦性に優れた非水電極質二次電池を実現することができる。
【００２１】
【発明の実施の形態】
本発明の実施の形態を、図面に基づいて以下に詳細に説明する。なお、本発明は下記実施の形態に限定されるものではなく、その要旨を変更しない範囲において適宜変更することが可能である。
【００２２】
図１は本発明の実施の形態に係るコイン型の非水電解質二次電池の断面図、図２は非水電解質二次電池の正極の平面図、図３は非水電解質二次電池の正極集電体の平面図、図４は非水電解質二次電池の負極板Ａの平面図、図５は非水電解質二次電池の負極の平面図、図６は非水電解質二次電池のセパレータの平面図である。
【００２３】
図１に示すように、本発明の非水電解質二次電池は、セパレータ３を介して正極１と負極２とが対向してなる電極体を有している。この電極体は負極缶６と正極缶５との間にある空間に配置されている。正極１は正極缶５に、負極２は負極缶６にそれぞれ接続され、電池内部で生じた化学エネルギーを電気エネルギーとして外部へ取り出し得るようになっている。
【００２４】
また、負極缶６と正極缶５との間にある空間には、エチレンカーボネートとジメチルカーボネートが混合された非水溶媒に、ＬｉＰＦ_６が１Ｍ（モル／リットル）の割合で溶解された電解液が注入されている。また、前記セパレータは、有機溶媒との反応性が低く、安価なオレフィン系樹脂からなる微多孔膜（厚み：０．０２５ｍｍ）から構成されている。
【００２５】
図５に示すように、前記負極２は、図４に示す円形の負極板が２つ並んだ形状の黒鉛が充填された多孔性金属基体からなる負極板Ａ（２ａ）の一方の円形負極板と、ケイ素充填された多孔性金属基体からなる負極板Ｂ（２ｂ）とが、抵抗溶接により接合され複合負極板が形成されており、図１に示すように各負極板の対向する位置に正極板が配置されている。
【００２６】
正極材料としては、リチウム含有遷移金属複合酸化物を単独で、あるいは二種以上混合して用いることができる。具体例として、コバルト酸リチウム、ニッケル酸リチウム、マンガン酸リチウム、鉄酸リチウム、またはこれらの酸化物に含まれる遷移金属の一部を他の元素で置換した酸化物等があげられる。また、リチウム含有オリビン型リン酸化合物を用いることもできる。
【００２７】
また、負極の炭素材料としては、天然黒鉛、人造黒鉛等の黒鉛系炭素質物が好適に使用できる。そして、本発明の効果を奏する限りにおいて、該黒鉛系炭素質物にカーボンブラック、コークス、ガラス状炭素、炭素繊維、あるいはこれらの焼成体等の炭素質物を、さらに含んでもよい。
【００２８】
また、炭素材料やケイ素の充填量は、前記多孔性金属基体の面密度や空孔率に大きく影響を受けるため、好ましくは面密度が４００ｇ／ｍ^２以下、空孔率９０％以上の多孔性金属基体を用いる。このような多孔性金属基体を用いると、電池容量の向上を十分に図れる。多孔性金属基体の材質は特に限定する必要はないが、ケイ素の導電性が低いため、導電性の高い金属の多孔体を用いることが好ましく、またリチウムと合金化しない金属が好ましい。なお、本明細書中において「多孔性金属基体」とは、金属メッシュのような網状の金属ではなく、発泡金属や、燒結金属のように三次元的に多孔を有する金属のことを意味する。
【００２９】
また、電解液に用いる非水電解質としては、エチレンカーボネート、プロピレンカーボネート、ブチレンカーボネート、γ−ブチロラクトン等のリチウム塩の溶解度が高い高誘電率溶媒と、ジエチルカーボネート、ジメチルカーボネート、エチルメチルカーボネート、１，２−ジメトキシエタン、テトラヒドロフラン、アニソール、１，４−ジオキサン、４−メチル−２−ペンタノン、シクロヘキサノン、アセトニトリル、プロピオニトリル、ジメチルホルムアミド、スルホラン、蟻酸メチル、蟻酸エチル、酢酸メチル、酢酸エチル、酢酸プロピル、プロピオン酸エチル等の低粘性溶媒とを、それぞれ単独で、あるいは二種以上を混合して用いることができる。
【００３０】
また、電解質塩としては、ＬｉＮ（Ｃ_２Ｆ_５ＳＯ_２）_２、ＬｉＮ（ＣＦ_３ＳＯ_２）_２、ＬｉＣｌＯ_４、ＬｉＰＦ_６、ＬｉＢＦ_４等が単独で、あるいは２種以上混合して使用することができる。また、前期非水溶媒に対する溶解量は０．５〜２．０モル／リットルとすることが好ましい。
【００３１】
次に実施例に基づいて本発明の内容を更に具体的に説明する。
【００３２】
（実施例１）
実施例にかかる非水電解質二次電池を、次のようにして作製した。
【００３３】
（正極の作製）
コバルト酸リチウム（ＬｉＣｏＯ_２）からなる正極活物質８９質量部と、アセチレンブラックからなる導電剤８質量部と、ポリフッ化ビニリデン３質量部と、Ｎ−メチルピロリドンとを混合し、正極活物質スラリーとした。その後、φ１７．９×０．８０ｍｍの円形部２個を連結部で連結したひょうたん型のペレット型内に、図３に示す形状を有するアルミニウムエキスパンドメタル製正極集電体５を挿入した後、正極活物質スラリーを注入し、６０℃で２時間乾燥させた。その後、ペレット型枠を取り外し、φ１８．０ｍｍの円形部２個を連結部で連結したひょうたん型の金型内で加圧調厚したものを、図２に示す正極１とした。この正極１の円形部のサイズはφ１８．０×０．５５ｍｍ、正極活物質充填密度３．２ｇ／ｃｍ^２であった。
【００３４】
（負極の作製）
増粘剤としてカルボキシメチルセルロース（ＣＭＣ）水性ディスパージョンに、黒鉛（ｄ＝０．３３５ｎｍ、平均粒径２０μｍ）と、結着剤としてポリテトラフルオロエチレン（ＰＴＦＥ）水溶液を添加して、負極活物質スラリーＡとした。この負極活物質スラリーＡの混合比は質量比で黒鉛：ＣＭＣ：ＰＴＦＥ＝９８：１：１となるよう調整した。この負極活物質スラリーを発泡状ニッケル（空孔率９５％、面密度４００ｇ／ｍ^２）に充填し、１００℃で乾燥し、調厚して打ち抜いて、図４に示す負極板Ａとした。この負極板Ａの円形部のサイズはφ１９．０×０．３０ｍｍであり、負極活物質充填密度１．３ｇ／ｃｍ^２であった。
【００３５】
ケイ素粉末（平均粒径１０μｍ）９９質量部と、ポリイミドバインダー１質量部と、Ｎ−メチルピロリドンとを混合して、負極活物質スラリーＢとした。この負極活物質スラリーＢを発泡状ニッケル（空孔率９５％、面密度４００ｇ／ｍ^２）に充填し、１００℃で乾燥し、４００℃で熱処理し、調厚して打ち抜いて、負極板Ｂとした。この負極板Ｂのサイズはφ１９．０×０．１５ｍｍ、負極活物質充填密度０．６ｇ／ｃｍ^２であった。
【００３６】
上記で作製した負極板Ａ、Ｂを抵抗溶接して、図５に示す複合負極２となした。
【００３７】
（セパレータの作製）
図６に示す形状（φ２２．０×０．０２５ｍｍ）のポリプロピレン製微多孔膜からなるセパレータ３を準備した。
【００３８】
（電解液の作製）
エチレンカーボネート（ＥＣ）と、ジエチルカーボネート（ＤＥＣ）と質量比で３：７となるように混合した混合溶媒に、電解質塩としてＬｉＰＦ_６を１Ｍ（モル／リットル）になるよう溶解させ、電解液を作製した。
【００３９】
正極缶５内に、８０℃、８時間乾燥させた正・負極１、２と、常温乾燥させたセパレータ３とを図１のように重ねた。この電極積層体の厚さは２．２０ｍｍである。この電極積層体を正極缶５内に挿入し、ガスケット７を装着した後、電解液を４００ｍｇ注入した。その後、負極缶６をかぶせ、かしめ封口して、φ２４．０×３．０ｍｍのコイン型電池を作製した。この電池を実施例１に係る本発明電池とした。
【００４０】
（比較例１）
黒鉛を充填した負極板Ａ（厚み０．４５ｍｍ）のみを用いて負極板を作製し、図７に示すＳＵＳ網集電体（厚み０．０６ｍｍ）に溶接して負極２となし、電池全高が実施例１と同じとなるように正極の厚みを変化させたこと以外は、上記実施例１と同様にして、比較例１に係る電池を作製した。
【００４１】
（比較例２）
ケイ素を充填した負極板Ｂ（厚み０．２７ｍｍ）のみを用いて負極板を作製し、図７に示すＳＵＳ網集電体（厚み０．０６ｍｍ）に溶接して負極２となし、電池全高が実施例１と同じとなるように正極の厚みを変化させたこと以外は、上記実施例１と同様にして、比較例１に電池を作製した。
【００４２】
（比較例３）
黒鉛とケイ素とカルボキシメチルセルロースとを質量比８９．１：０．９：１で混合してスラリーとし、発泡ニッケルに充填して厚み０．３４ｍｍの負極板を作製し、図７に示すＳＵＳ網集電体（厚み０．０６ｍｍ）に溶接して負極２となし、電池全高が実施例１と同じとなるように正極の厚みを変化させたこと以外は上記実施例１と同様にして、比較例３に係る電池を作製した。
【００４３】
（比較例４）
黒鉛を充填した厚み０．６４ｍｍの負極板Ａと、ケイ素を充填した厚み０．１５ｍｍの負極板Ｂとを、図７に示すＳＵＳ網集電体（厚み０．０６ｍｍ）に溶接して負極２となし、負極板Ａを電池中央に配置し、電池全高が実施例１と同じとなるように正極の厚みを変化させたこと以外は上記実施例１と同様にして、比較例４に係る電池を作製した。
【００４４】
（比較例５）
負極板Ｂを電池中央に配置したこと以外は上記比較例４と同様にして、比較例５に係る電池を作製した。
【００４５】
（電池特性試験）
本発明電池、比較電池それぞれを下記条件で充放電し、その放電容量と、充電状態、放電状態の電池厚みを測定し、電池厚みの変化量を算出した。その結果を下記表１に示す。
【００４６】
充電条件：定電流１０ｍＡ、定電圧４．２Ｖ、１６時間
放電条件：定電流１０ｍＡ、終止電圧３．０Ｖ
ΔＴ（電池厚みの変化、ｍｍ）：（充電状態の電池厚み）−（放電状態の電池厚み）
【００４７】
【表１】

負極積層厚さとは、折り曲げて２枚となった負極板の合計厚さのことを示す。
【００４８】
表１の結果から、ケイ素を充填した負極板と、黒鉛を充填した負極板とを張り合わせた実施例１では、放電容量が９８ｍＡｈと高く、且つ電池のふくれが０．１４ｍｍと小さい電池が得られていることがわかる。
【００４９】
このことは、次のように考えられる。ケイ素は黒鉛よりも容量が大きいため、高容量化が可能となる。さらに、ケイ素を充填した負極板と、黒鉛を充填した負極板それぞれに対向する位置に正極板が配置されているため、充放電反応がこの対向する正負極板間に制限される。この結果、充電状態の電位がケイ素よりも低い黒鉛にも均一に充電されるので、活物質の利用効率が向上して高容量となったと考えられる。
また、ケイ素の体積変化を発泡金属と、ケイ素充填発泡金属に接合された黒鉛充填発泡金属とが吸収するため、電池のふくれが抑制されたと考えられる。
【００５０】
また、黒鉛のみからなる負極板を用いた比較例１では、電池のふくれは０．０６ｍｍと小さいものの、放電容量が８６ｍＡｈと十分なものではない。これは、黒鉛の放電容量が、ケイ素に比べて小さいことによるものと考えられる。
【００５１】
また、ケイ素のみからなる負極板を用いた比較例２では放電容量が９２ｍＡｈと高いものの、電池のふくれが０．３２ｍｍと大きい。これは、充放電に伴うケイ素の体積変化を、発泡金属のみでは十分に吸収できなかったことによるものと考えられる。
【００５２】
また、ケイ素と黒鉛とを混合した負極板を用いた比較例３では電池のふくれが０．１９ｍｍと実施例１より大きく、放電容量が６５ｍＡｈと十分なものではない。放電容量が小さいのは、ケイ素の充電電位が黒鉛に比べて高く、ケイ素が優先的に充電され、黒鉛がほとんど充放電に寄与しないことによるものと考えられる。
また、電池のふくれが実施例１より大きいのは、ケイ素の体積変化を、ケイ素と混合されている黒鉛と、発泡金属とでは十分に吸収できなかったためと考えられる。
【００５３】
また、ケイ素が充填された負極板と黒鉛が充填された負極板とを別々に負極集電体に張り合わせた負極を用いた比較例４、５では電池のふくれが０．１９〜０．２４ｍｍと実施例１と比べて大きく、放電容量が７６−８０ｍＡｈと十分なものではない。放電容量が小さいのは、ケイ素の充電電位が黒鉛に比べて高く、ケイ素が優先的に充電され、黒鉛がほとんど充放電に寄与しないことによると考えられる。
また、電池のふくれが実施例１より大きいのは、ケイ素の体積変化を発泡金属のみでは十分に吸収できなかったことによるものと考えられる。
【００５４】
（実施例２）
図９に示すように、上記実施例１における正極板−複合負極板−正極板からなるセル基本単位の外側に更にケイ素充填負極板Ｂ−正極板を追加し（ただし、負極缶６と対向している正極面にはアルミニウム箔を貼り付けている）、電極積層体の厚さを３．２０ｍｍ、φ２４．０×４．０ｍｍとし、複合負極板２と負極缶６とを電気的に接続する負極リード８を設けたこと以外は、実施例１と同様にして電池を作製した。この電池における黒鉛理論容量の全負極理論容量は１８０ｍＡｈ、全正極理論容量は１６０ｍＡｈである。
【００５５】
この電池を実施例１と同様な条件で測定した放電容量は１３１ｍＡｈと高容量であり、電池の厚み変化ΔＴは０．２４ｍｍと比較例２よりも小さかった。上記結果は、実施例１で考察したものと同じ理由によるものと考えられる。
【００５６】
また、この電池は積層することによって集電性能の低下は見られず、正負極表面積が増加したことから、高レート放電特性が向上したことが確認された。
【００５７】
なお、本発明は上記実施例に限定されることはなく、多層積層型の電池にも応用することができる。
【００５８】
また、上記実施例ではコイン型の電池を作製したが、この形状に限定されるものではなく、極板を積層した角型電池等他の形状の電池を作製することもできる。
【００５９】
【発明の効果】
上記の結果から明らかなように、本発明電池では、電池容量が大きく、さらにリチウムイオンが吸蔵、放出する際の体積変動が小さい、という優れた効果を奏する。
【図面の簡単な説明】
【図１】本発明に係る非水電解質二次電池の断面図。
【図２】本発明に係る非水電解質二次電池に使用する正極の平面図。
【図３】本発明に係る非水電解質二次電池に使用する正極集電体の平面図。
【図４】本発明に係る非水電解質二次電池に使用する負極板Ａの平面図。
【図５】本発明に係る非水電解質二次電池に使用する複合負極の平面図。
【図６】本発明に係る非水電解質二次電池に使用するセパレータの平面図。
【図７】比較例１に係る非水電解質二次電池に使用する負極集電体の平面図。
【図８】比較例１に係る非水電解質二次電池に使用する負極の平面図。
【図９】実施例２に係る非水電解質二次電池の断面図。
【符号の説明】
１正極
２複合負極
３セパレータ
４正極集電体
５正極缶
６負極缶
７ガスケット
８負極リード[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a nonaqueous electrolyte secondary battery using silicon as a negative electrode active material.
[Prior art]
A non-aqueous electrolyte secondary battery represented by a lithium ion secondary battery has a high energy density and a high capacity, and thus is useful as a drive power source for mobile information terminals and the like.
Conventionally, a carbon material capable of occluding and releasing lithium ions has been used for the negative electrode of such a lithium ion battery, and a composite metal oxide has been used for the positive electrode. The battery of this configuration has an advantage of excellent safety because lithium does not exist in a metal state, and has excellent cycle characteristics because lithium dendrite does not occur.
[0002]
However, in recent years, mobile information terminals such as mobile phones and laptop computers have been rapidly becoming smaller and lighter, and batteries as power sources have been required to have higher capacities. The battery capacity of the lithium ion battery having the above configuration using a carbon material as the negative electrode active material is not sufficient.
[0003]
Therefore, silicon having a possibility of increasing the charge / discharge capacity as compared with the carbon material has attracted attention as a negative electrode active material, and various studies have been made. However, silicon has problems such as poor load characteristics as compared with carbon materials such as graphite, a problem that a volume change due to charge and discharge is large, and a battery expands and contracts as the cycle progresses, and silicon is generated from a current collector. There is a problem that the battery tends to fall off and the cycle characteristics are easily deteriorated, and a battery with sufficient performance has not yet been developed.
[0004]
For this reason, attempts have been made to improve load characteristics by using a combination of silicon and a carbon material in order to compensate for such weaknesses of silicon. However, according to this method, the expected battery capacity is not obtained because the cycle characteristics of the battery are deteriorated. This is because silicon has a higher potential at the time of charging than a carbon material, and lithium ions are preferentially occluded by silicon, so that the carbon material hardly contributes as an active material for securing battery capacity.
[0005]
On the other hand, a negative electrode in which graphite is applied to one surface of the negative electrode current collector and a non-graphite material such as hard carbon or amorphous oxide is applied to the other surface is used, and the positive electrode is arranged to face each surface of the negative electrode. Thus, a technique for increasing the battery capacity has been proposed (see Patent Document 1).
[0006]
[Patent Document 1]
JP 2001-210316 A (pages 2-3)
[0007]
According to this technique, lithium ions are absorbed and released between a graphite layer and a positive electrode facing the graphite layer, and between a layer made of a non-graphite material and a positive electrode facing the graphite layer. It is said that since the advantages of the substance can be brought out, a battery having high capacity and high voltage flatness can be realized. However, in order to realize a battery with high capacity and high voltage flatness by using this technique, the charge and discharge of the battery must be controlled using a plurality of charge / discharge rectifiers. For this reason, this technique has a problem that the charge / discharge system becomes complicated and the battery manufacturing cost increases.
[0008]
Furthermore, graphite and non-graphite materials such as hard carbon and amorphous oxides used in this technology have a smaller charge / discharge capacity than silicon, and thus increase the battery capacity as much as batteries using silicon. I can't. On the other hand, when silicon is combined with this technology, the problem that the battery is greatly increased due to the volume change of silicon due to charge and discharge, and the contact between silicon and the negative electrode current collector and silicon are deteriorated by the volume change of silicon, There is a problem that the cycle characteristics deteriorate.
[0009]
[Problems to be solved by the invention]
The present invention has been made in view of the above circumstances, and increases the battery capacity per unit volume by using silicon as a negative electrode active material, and improves the expansion and short cycle life of a battery caused by silicon. An object is to provide the obtained non-aqueous electrolyte secondary battery.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a porous metal substrate filled with a carbon material capable of occluding and releasing lithium ions, and a porous metal substrate filled with silicon, which are joined together. A composite negative electrode plate, and a pair of positive electrode plates disposed so as to face each surface of the composite negative electrode plate, and an electrolyte disposed between the positive and negative electrode plates, comprising a cell basic unit including: A non-aqueous electrolyte secondary battery.
[0011]
According to this configuration, since silicon having a larger theoretical capacity than carbon is used together with the carbon material as the negative electrode active material, both the battery capacity per unit volume and the battery capacity per unit weight can be increased. In addition, silicon changes its volume greatly in accordance with insertion and extraction of lithium ions, but in the above-described configuration, the porous metal substrate filled with silicon absorbs the volume change of silicon. For this reason, silicon does not easily fall off the electrode plate, and cycle deterioration does not occur. Further, in the above configuration, silicon and a carbon material are used in combination, and the amount of silicon can be reduced as compared with a case where silicon alone covers the negative electrode capacity. Further, in the above configuration, the porous metal substrate filled with silicon and the porous metal substrate filled with the carbon material are joined, and the porous metal substrate filled with the carbon material also absorbs a change in volume of silicon. Therefore, the expansion of the battery is sufficiently suppressed in combination with the above-described functions and effects.
[0012]
On the other hand, when a carbon material and silicon are used in combination, silicon preferentially absorbs lithium ions at the time of charging, so that the carbon material does not participate in the absorption of lithium ions, resulting in a problem that the battery capacity is reduced. In the above configuration, the carbon material and silicon are separated in the negative electrode plate, and the positive electrode plate is opposed to the porous metal substrate filled with the carbon material and the porous metal substrate filled with silicon, respectively. Are arranged, so that such a problem is solved. In other words, according to the above configuration, both the carbon material and silicon sufficiently function as the negative electrode active material, so that the battery capacity can be increased as compared with a battery using only the carbon material as the negative electrode active material, and silicon as the negative electrode active material. The cycle characteristics can be remarkably improved as compared with the battery using only the battery.
[0013]
Here, in the lithium ion battery of the present invention, one or more additional cell units composed of the composite negative electrode plate and the positive electrode plate are further laminated on the basic cell unit such that the positive and negative electrode plates face each other. be able to.
[0014]
Since silicon has a larger electric capacity than a carbon material such as graphite, a composite negative electrode plate using both silicon and a carbon material has a higher energy density per volume than a negative electrode plate using only a carbon material. Therefore, with the above-described configuration in which a plurality of such composite negative electrode plates and positive electrode plates are alternately stacked and the positive electrode plate is always located on both surfaces of the composite negative electrode plate, a high capacity and compact lithium ion battery is realized. In addition, since the capacity increases in accordance with the number of stacked electrode plates, even if the capacity is increased, the current collection efficiency does not decrease and the surface area of the positive and negative electrodes increases. That is, according to the above configuration, a high-capacity, compact lithium-ion battery having excellent high-rate discharge characteristics can be realized.
[0015]
Further, in the above-described lithium ion battery of the present invention, it is possible to adopt a configuration in which the porous metal substrates of the composite negative electrode plate are joined by electric resistance welding.
[0016]
In the case of a composite negative electrode plate in which the porous metal substrates are directly welded with each other by electric resistance, the electrical integration between the porous metal substrates is good, and thus the current collection efficiency is high.
[0017]
Further, the thickness of at least one of the porous metal substrate filled with the carbon material and the porous metal substrate filled with silicon may be 0.10 mm or more and 0.20 mm or less.
[0018]
In the case of joining by electric resistance welding, the ease of joining is greatly affected by the thickness of the porous metal substrate, and if the thickness of both of the joined porous metal substrates is larger than 0.20 mm, welding becomes difficult. Therefore, it is not preferable. On the other hand, if it is 0.10 mm or less, the negative electrode active material cannot be sufficiently filled. Therefore, it is preferable that the content is regulated within the above range.
[0019]
In the above-described lithium ion battery of the present invention, the porous metal substrate may be made of a foamed metal body, and the carbon material may be made of graphite.
[0020]
Since the foamed metal body has a large number of three-dimensional spaces, it can be filled with the negative electrode active material at a high density, and this space absorbs the expansion of the active material filled inside by the expansion of the metal and the deformation of the space shape. Can be. Therefore, the negative electrode active material does not fall off the negative electrode due to the expansion and contraction of silicon. Further, since graphite has a relatively large capacity and good voltage flatness, if graphite is used as the carbon material, it is possible to realize a non-aqueous electrode type secondary battery which is compact, has a high capacity and is excellent in voltage flatness.
[0021]
BEST MODE FOR CARRYING OUT THE INVENTION
Embodiments of the present invention will be described below in detail with reference to the drawings. The present invention is not limited to the following embodiments, and can be appropriately changed without changing the gist of the present invention.
[0022]
FIG. 1 is a cross-sectional view of a coin-type non-aqueous electrolyte secondary battery according to an embodiment of the present invention, FIG. 2 is a plan view of a positive electrode of the non-aqueous electrolyte secondary battery, and FIG. FIG. 4 is a plan view of a negative electrode plate A of the nonaqueous electrolyte secondary battery, FIG. 5 is a plan view of a negative electrode of the nonaqueous electrolyte secondary battery, and FIG. 6 is a separator of the nonaqueous electrolyte secondary battery. FIG.
[0023]
As shown in FIG. 1, the nonaqueous electrolyte secondary battery of the present invention has an electrode body in which a positive electrode 1 and a negative electrode 2 face each other with a separator 3 interposed therebetween. This electrode body is disposed in a space between the negative electrode can 6 and the positive electrode can 5. The positive electrode 1 is connected to the positive electrode can 5 and the negative electrode 2 is connected to the negative electrode can 6, so that chemical energy generated inside the battery can be taken out as electric energy.
[0024]
In the space between the negative electrode can 6 and the positive electrode can 5, an electrolytic solution in which LiPF ₆ is dissolved at a ratio of 1 M (mol / liter) in a nonaqueous solvent in which ethylene carbonate and dimethyl carbonate are mixed is provided. Has been injected. The separator has a low reactivity with an organic solvent and is formed of a microporous film (thickness: 0.025 mm) made of an inexpensive olefin resin.
[0025]
As shown in FIG. 5, the negative electrode 2 is one of the circular negative electrode plates of a negative electrode plate A (2a) made of a porous metal base filled with graphite in which two circular negative electrode plates shown in FIG. And a negative electrode plate B (2b) made of a porous metal substrate filled with silicon, which is joined by resistance welding to form a composite negative electrode plate. As shown in FIG. A plate is arranged.
[0026]
As the positive electrode material, a lithium-containing transition metal composite oxide can be used alone or in combination of two or more. Specific examples include lithium cobaltate, lithium nickelate, lithium manganate, lithium ferrate, and oxides in which some of the transition metals contained in these oxides are substituted with other elements. Further, a lithium-containing olivine-type phosphate compound can also be used.
[0027]
As the carbon material for the negative electrode, graphite-based carbonaceous materials such as natural graphite and artificial graphite can be suitably used. As long as the effects of the present invention are exhibited, the graphite-based carbonaceous material may further include a carbonaceous material such as carbon black, coke, glassy carbon, carbon fiber, or a fired body thereof.
[0028]
Further, since the filling amount of the carbon material and silicon is greatly affected by the surface density and the porosity of the porous metal substrate, it is preferable that the porous material has a surface density of 400 g / m ² or less and a porosity of 90% or more. A metal substrate is used. The use of such a porous metal substrate can sufficiently improve the battery capacity. The material of the porous metal substrate is not particularly limited. However, since silicon has low conductivity, it is preferable to use a porous body of a metal having high conductivity, and a metal that does not alloy with lithium is preferable. In this specification, the term “porous metal substrate” means not a metal mesh such as a metal mesh but a three-dimensionally porous metal such as a foamed metal or a sintered metal.
[0029]
Further, as the non-aqueous electrolyte used for the electrolytic solution, ethylene carbonate, propylene carbonate, butylene carbonate, a high dielectric constant solvent having a high solubility of lithium salts such as γ-butyrolactone, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, 1, 2-dimethoxyethane, tetrahydrofuran, anisole, 1,4-dioxane, 4-methyl-2-pentanone, cyclohexanone, acetonitrile, propionitrile, dimethylformamide, sulfolane, methyl formate, ethyl formate, methyl acetate, ethyl acetate, propyl acetate And low-viscosity solvents such as ethyl propionate can be used alone or in combination of two or more.
[0030]
As the electrolyte salt, LiN (C ₂ F ₅ SO ₂ ) ₂ , LiN (CF ₃ SO ₂ ) ₂ , LiClO ₄ , LiPF ₆ , LiBF ₄ or the like may be used alone or in combination of two or more. Can be. In addition, the dissolution amount in the non-aqueous solvent is preferably 0.5 to 2.0 mol / liter.
[0031]
Next, the contents of the present invention will be described more specifically based on examples.
[0032]
(Example 1)
A non-aqueous electrolyte secondary battery according to an example was manufactured as follows.
[0033]
(Preparation of positive electrode)
89 parts by mass of a positive electrode active material composed of lithium cobalt oxide (LiCoO ₂ ), 8 parts by mass of a conductive agent composed of acetylene black, 3 parts by mass of polyvinylidene fluoride, and N-methylpyrrolidone were mixed together to form a positive electrode active material slurry. did. Then, after inserting a positive electrode current collector 5 made of aluminum expanded metal having the shape shown in FIG. 3 into a gourd-shaped pellet formed by connecting two circular portions having a diameter of 17.9 × 0.80 mm with a connecting portion, The active material slurry was injected and dried at 60 ° C. for 2 hours. After that, the pellet mold was removed, and the pressure was adjusted in a gourd-shaped mold in which two circular portions having a diameter of 18.0 mm were connected by a connecting portion to obtain a positive electrode 1 shown in FIG. The size of the circular portion of the positive electrode 1 was φ18.0 × 0.55 mm, and the packing density of the positive electrode active material was 3.2 g / cm ² .
[0034]
(Preparation of negative electrode)
A negative electrode active material slurry is prepared by adding graphite (d = 0.335 nm, average particle size 20 μm) and an aqueous solution of polytetrafluoroethylene (PTFE) as a binder to an aqueous dispersion of carboxymethyl cellulose (CMC) as a thickener. A. The mixing ratio of the negative electrode active material slurry A was adjusted so that the mass ratio of graphite: CMC: PTFE was 98: 1: 1. This negative electrode active material slurry was filled in foamed nickel (porosity: 95%, area density: 400 g / m ² ), dried at 100 ° C., thickened and punched out to obtain a negative electrode plate A shown in FIG. The size of the circular portion of the negative electrode plate A was φ19.0 × 0.30 mm, and the packing density of the negative electrode active material was 1.3 g / cm ² .
[0035]
A negative electrode active material slurry B was obtained by mixing 99 parts by mass of silicon powder (average particle size: 10 μm), 1 part by mass of a polyimide binder, and N-methylpyrrolidone. This negative electrode active material slurry B was filled into foamed nickel (95% porosity, area density 400 g / m ² ), dried at 100 ° C., heat-treated at 400 ° C., punched after thickness control, and punched out. And The size of the negative electrode plate B was φ19.0 × 0.15 mm, and the negative electrode active material packing density was 0.6 g / cm ² .
[0036]
The negative electrodes A and B produced above were resistance-welded to form a composite negative electrode 2 shown in FIG.
[0037]
(Preparation of separator)
A separator 3 composed of a microporous polypropylene membrane having a shape (φ22.0 × 0.025 mm) shown in FIG. 6 was prepared.
[0038]
(Preparation of electrolyte)
LiPF ₆ was dissolved as an electrolyte salt in a mixed solvent of ethylene carbonate (EC) and diethyl carbonate (DEC) at a mass ratio of 3: 7 so as to have a mass ratio of 1 M (mol / liter). Produced.
[0039]
In the positive electrode can 5, the positive and negative electrodes 1 and 2 dried at 80 ° C. for 8 hours and the separator 3 dried at room temperature were stacked as shown in FIG. The thickness of the electrode laminate is 2.20 mm. This electrode laminate was inserted into the positive electrode can 5, the gasket 7 was attached, and then 400 mg of the electrolyte was injected. Thereafter, the negative electrode can 6 was covered and swaged and sealed to produce a coin-type battery having a diameter of 24.0 × 3.0 mm. This battery was used as the battery of the present invention according to Example 1.
[0040]
(Comparative Example 1)
A negative electrode plate was prepared using only the negative electrode plate A (0.45 mm thick) filled with graphite, and was welded to a SUS net current collector (0.06 mm thick) shown in FIG. A battery according to Comparative Example 1 was produced in the same manner as in Example 1 except that the thickness of the positive electrode was changed so as to be the same as in Example 1.
[0041]
(Comparative Example 2)
A negative electrode plate was prepared using only the negative electrode plate B (thickness 0.27 mm) filled with silicon, and was welded to a SUS net current collector (thickness 0.06 mm) shown in FIG. A battery was made in Comparative Example 1 in the same manner as in Example 1 except that the thickness of the positive electrode was changed so as to be the same as in Example 1.
[0042]
(Comparative Example 3)
Graphite, silicon, and carboxymethylcellulose were mixed at a mass ratio of 89.1: 0.9: 1 to form a slurry, and the mixture was filled with nickel foam to produce a 0.34 mm-thick negative electrode plate. A comparative example was prepared in the same manner as in Example 1 except that the negative electrode 2 was formed by welding to an electric body (thickness 0.06 mm), and the thickness of the positive electrode was changed so that the overall height of the battery was the same as in Example 1. The battery according to No. 3 was produced.
[0043]
(Comparative Example 4)
A negative electrode 2 was prepared by welding a 0.64 mm-thick negative electrode plate A filled with graphite and a 0.15 mm-thick negative electrode plate B filled with silicon to a SUS net current collector (0.06 mm thickness) shown in FIG. In the same manner as in Example 1 except that the negative electrode plate A was arranged at the center of the battery and the thickness of the positive electrode was changed so that the overall height of the battery was the same as in Example 1, the battery according to Comparative Example 4 was manufactured. Was prepared.
[0044]
(Comparative Example 5)
A battery according to Comparative Example 5 was produced in the same manner as in Comparative Example 4 except that the negative electrode plate B was disposed at the center of the battery.
[0045]
(Battery characteristics test)
Each of the battery of the present invention and the comparative battery was charged and discharged under the following conditions, and the discharge capacity, the battery thickness in the charged state and the battery thickness in the discharged state were measured, and the amount of change in the battery thickness was calculated. The results are shown in Table 1 below.
[0046]
Charging conditions: constant current 10 mA, constant voltage 4.2 V, 16 hours discharging conditions: constant current 10 mA, final voltage 3.0 V
ΔT (change in battery thickness, mm): (battery thickness in charged state) − (battery thickness in discharged state)
[0047]
[Table 1]

The term “negative electrode stack thickness” indicates the total thickness of the two negative electrode plates that were bent.
[0048]
From the results shown in Table 1, in Example 1 in which the negative electrode plate filled with silicon and the negative electrode plate filled with graphite were bonded, a battery having a high discharge capacity of 98 mAh and a small battery bulge of 0.14 mm was obtained. You can see that it is.
[0049]
This is considered as follows. Since silicon has a larger capacity than graphite, it is possible to increase the capacity. Furthermore, since the positive electrode plate is disposed at a position facing each of the negative electrode plate filled with silicon and the negative electrode plate filled with graphite, the charge / discharge reaction is limited between the opposed positive and negative electrode plates. As a result, it is considered that graphite having a charged state lower than silicon is uniformly charged, so that the use efficiency of the active material is improved and the capacity is increased.
Further, it is considered that the foaming metal and the graphite-filled foamed metal bonded to the silicon-filled foamed metal absorb the change in volume of silicon, so that the blister of the battery was suppressed.
[0050]
Further, in Comparative Example 1 using the negative electrode plate made of only graphite, the swelling of the battery was as small as 0.06 mm, but the discharge capacity was 86 mAh, which was not sufficient. This is considered to be because the discharge capacity of graphite is smaller than that of silicon.
[0051]
In Comparative Example 2 using a negative electrode plate made of silicon alone, the discharge capacity was as high as 92 mAh, but the bulge of the battery was as large as 0.32 mm. This is considered to be due to the fact that the volume change of silicon due to charge and discharge could not be sufficiently absorbed by the foam metal alone.
[0052]
In Comparative Example 3 using a negative electrode plate in which silicon and graphite were mixed, the bulge of the battery was 0.19 mm, which was larger than that of Example 1, and the discharge capacity was 65 mAh, which was not sufficient. It is considered that the reason why the discharge capacity is small is that the charge potential of silicon is higher than that of graphite, silicon is preferentially charged, and graphite hardly contributes to charge and discharge.
Further, it is considered that the reason why the swelling of the battery was larger than that in Example 1 was that the volume change of silicon could not be sufficiently absorbed by the graphite mixed with silicon and the foamed metal.
[0053]
Further, in Comparative Examples 4 and 5 using negative electrodes in which a negative electrode plate filled with silicon and a negative electrode plate filled with graphite were separately bonded to a negative electrode current collector, the blister of the battery was 0.19 to 0.24 mm. It is larger than that of Example 1, and the discharge capacity is not sufficient, that is, 76 to 80 mAh. It is considered that the reason why the discharge capacity is small is that the charge potential of silicon is higher than that of graphite, silicon is charged preferentially, and graphite hardly contributes to charge and discharge.
It is considered that the reason why the swelling of the battery was larger than that in Example 1 was that the change in volume of silicon could not be sufficiently absorbed only by the foamed metal.
[0054]
(Example 2)
As shown in FIG. 9, a silicon-filled negative electrode plate B-a positive electrode plate was further added to the outside of the basic cell unit composed of the positive electrode plate, the composite negative electrode plate, and the positive electrode plate in Example 1 (provided that the negative electrode can 6 Aluminum foil is stuck on the positive electrode surface), the thickness of the electrode laminate is 3.20 mm, φ24.0 × 4.0 mm, and the composite negative electrode plate 2 and the negative electrode can 6 are electrically connected. A battery was fabricated in the same manner as in Example 1, except that the negative electrode lead 8 was provided. In this battery, the total theoretical theoretical capacity of the graphite is 180 mAh, and the total theoretical capacity of the positive electrode is 160 mAh.
[0055]
The discharge capacity of this battery measured under the same conditions as in Example 1 was as high as 131 mAh, and the thickness change ΔT of the battery was 0.24 mm, which was smaller than Comparative Example 2. The above results are considered to be due to the same reason as discussed in Example 1.
[0056]
In addition, this battery did not show a decrease in current collecting performance due to the lamination, and increased the positive and negative electrode surface areas, confirming that high-rate discharge characteristics were improved.
[0057]
Note that the present invention is not limited to the above-described embodiment, and can be applied to a multilayer laminated battery.
[0058]
In the above embodiment, a coin-type battery is manufactured. However, the present invention is not limited to this shape, and a battery having another shape such as a square battery in which electrode plates are stacked can be manufactured.
[0059]
【The invention's effect】
As is clear from the above results, the battery of the present invention has an excellent effect that the battery capacity is large and the volume fluctuation when lithium ions are inserted and released is small.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a non-aqueous electrolyte secondary battery according to the present invention.
FIG. 2 is a plan view of a positive electrode used in the nonaqueous electrolyte secondary battery according to the present invention.
FIG. 3 is a plan view of a positive electrode current collector used in the nonaqueous electrolyte secondary battery according to the present invention.
FIG. 4 is a plan view of a negative electrode plate A used for a non-aqueous electrolyte secondary battery according to the present invention.
FIG. 5 is a plan view of a composite negative electrode used in the nonaqueous electrolyte secondary battery according to the present invention.
FIG. 6 is a plan view of a separator used in the nonaqueous electrolyte secondary battery according to the present invention.
FIG. 7 is a plan view of a negative electrode current collector used for a nonaqueous electrolyte secondary battery according to Comparative Example 1.
FIG. 8 is a plan view of a negative electrode used for a nonaqueous electrolyte secondary battery according to Comparative Example 1.
FIG. 9 is a sectional view of a non-aqueous electrolyte secondary battery according to Example 2.
[Explanation of symbols]
Reference Signs List 1 positive electrode 2 composite negative electrode 3 separator 4 positive electrode current collector 5 positive electrode can 6 negative electrode can 7 gasket 8 negative electrode lead

Claims

A composite negative electrode plate in which a porous metal substrate filled with a carbon material capable of occluding and releasing lithium ions and a porous metal substrate filled with silicon are overlapped, and the metal substrates are joined to each other;
A pair of positive electrode plates arranged to face each surface of the composite negative electrode plate,
An electrolyte disposed between the positive and negative electrode plates,
A non-aqueous electrolyte secondary battery provided with a cell basic unit comprising:

The non-aqueous electrolyte secondary battery according to claim 1,
A non-aqueous electrolyte secondary battery, wherein at least one additional cell unit composed of the composite negative electrode plate and the positive electrode plate is stacked on the basic cell unit such that positive and negative electrode plates face each other.

The non-aqueous electrolyte secondary battery according to claim 1 or 2,
A non-aqueous electrolyte secondary battery, wherein the porous metal substrates of the composite negative electrode plate are joined by electric resistance welding.

The non-aqueous electrolyte secondary battery according to claim 3,
A nonaqueous electrolyte secondary battery, wherein the thickness of at least one of the porous metal substrate filled with the carbon material and the porous metal substrate filled with silicon is 0.10 mm or more and 0.20 mm or less.

The non-aqueous electrolyte secondary battery according to claim 4,
A non-aqueous electrolyte secondary battery, wherein the porous metal substrate is made of a foamed metal body, and the carbon material is made of graphite.