JP2004319390A - Non-aqueous electrolyte secondary battery - Google Patents

Abstract

Provided is a non-aqueous electrolyte secondary battery which suppresses swelling of the battery during charge and discharge, and has a high capacity and excellent cycle characteristics.
A non-aqueous electrolyte comprising an electrode plate group and a non-aqueous electrolyte in which a positive electrode capable of inserting and extracting lithium and a negative electrode capable of inserting and extracting lithium are alternately laminated via a separator. In a secondary battery, the positive electrode 12 includes a positive electrode active material layer and a core material supporting the same, the negative electrode 13 includes a negative electrode active material layer and a core material supporting the same, and the negative electrode active material layer includes a group 4B element. And the negative electrode active material layer has a volume capacity density of 500 mAh / cc or more.
[Selection diagram] Fig. 1

Description

【００５７】
【表２】

【００５８】
負極活物質を構成する各元素の粉体またはブロックを、加熱溶解槽中で溶融し、その溶融物をロール急冷法で急冷、凝固させて、結晶相からなる凝固物を得た。その凝固物を遊星ボールミル容器中に投入した後、１５Ｇが印加されるように駆動モータの回転数を３７００ｒｐｍに設定し、直径１５ｍｍのステンレス鋼製ボールを用い、メカニカルグラインディング処理を３０分間または４０時間行った。未処理の凝固物およびメカニカルグラインディング処理後に得られた材料を、それぞれ篩で４５μｍ以下に分級することにより、種々の負極活物質を得た。
【００５９】
得られた負極活物質を電子顕微鏡を用いて観察した結果、表２に示す複合材料においては、核粒子表面の全面または一部が表面層によって被覆されていることを確認した。また、表１および表２に示すメカニカルグラインディングを行う前の凝固物について、Ｘ線回折測定を行い、その結晶構造を確認したところ、検出された各回折ピークがシャープであり、凝固物は良好な結晶相であった。一方、メカニカルグラインディング処理を３０分間行った材料については、検出された各回折ピークがブロード化し始めていたことから、結晶状態が崩れ始めていることが確認できた。これらの材料には、結晶子サイズ５〜１００ｎｍの微結晶相が残存しており、低結晶相であった。また、このときのピークの半価幅は０．００１〜０．１°であった。メカニカルグラインディング処理を４０時間行った材料については、各回折ピークは完全に消失しており、結晶指数の帰属が不可能な非晶質相であった。
【００６０】
このように作製した負極活物質粉末材料を用いて、負極板を作製した。負極活物質７５重量部に対し、導電剤である炭素粉末２０重量部と結着剤であるポリフッ化ビニリデン樹脂５重量部を混合し、これらを脱水Ｎ−メチル−２−ピロリドンに分散させて、スラリー状の負極合剤を調製した。この負極合剤を銅箔からなる芯材上に塗布し、乾燥後、圧延して、負極活物質層を形成した。こうして負極板を完成した。
【００６１】
（１−２）薄膜の負極活物質を用いた負極板の作製
本実施例で用いた負極活物質を表３に示す。
ここでは、シリコン薄膜を例に挙げて説明するが、スズ薄膜も、一般的に知られた同様の方法で作製することができる。
【００６２】
【表３】

【００６３】
芯材には、厚みが１８μｍの電解銅箔を用いた。
電解銅箔上に、Ａｒガス雰囲気中でのＲＦスパッタリング法により、厚さ５μｍのシリコン薄膜を形成し、この薄膜を負極活物質層とした。薄膜作製条件は、単結晶シリコンをターゲットとし、ＲＦ電力：４００Ｗ、Ａｒガス流量：５０ｓｃｃｍ、チャンバー内圧力：０．２Ｐａとした。基板は加熱しなかった。
【００６４】
上記条件で作製したシリコン薄膜は、ラマン分光分析により、非晶質薄膜であることがわかった。薄膜の厚みを表面粗さ計で測定したところ、５μｍであった。この値は、スズ薄膜の場合でも同様であった。
【００６５】
このようにして得られた薄膜を不活性ガス中で熱処理することによって結晶子サイズが５〜１００ｎｍになるまで微結晶化させた。このときのＸ線回折パターンのピークの半価幅は０．６°以上であった。さらに、熱処理温度などを制御することによって結晶子サイズが１００ｎｍを超えるまで結晶化させた。それぞれの薄膜電極には、マスキング処理によって薄膜が形成されていない部分を設け、銅箔の露出部から負極リードを引き出して、負極板を完成させた。
【００６６】
（２）積層型電池の作製
図１に示すような積層型リチウム二次電池を作製した。
正極板１２は次のように作製した。コバルト酸リチウム粉末８５重量部と、導電剤の炭素粉末１０重量部と、結着剤のポリフッ化ビニリデン樹脂５重量部とを混合し、これらを脱水Ｎ−メチル−２−ピロリドンに分散させて、スラリー状の正極合剤を作製した。この正極合剤をアルミニウム箔からなる芯材上に塗布し、乾燥後、圧延して、正極活物質層を形成し、正極板を完成した。
非水電解質には、エチレンカーボネートとエチルメチルカーボネートとの混合溶媒（体積比１：１）に、１．５ｍｏｌ／ｌの濃度でＬｉＰＦ_６を溶解したものを用いた。
【００６７】
上記作製した負極板１３と正極板１２とを、セパレータ１４を介して交互に積層し、スタック型の極板群を作製した。負極板１３の芯材から負極リード１６を引き出し、正極板１２の芯材から正極リード１５を引き出した。負極板１枚、正極板２枚を用いて積層した。
スタック状に積層した極板群を、両面に樹脂シートを有するアルミニウム箔（Ａｌラミネートシート）からなる電池ケース１１の内部に挿入した後、電池ケース１１内に非水電解質を注液し、リード部溶着シール１７で電池ケース１１の開口部を封口した。
【００６８】
また、黒鉛を活物質とした負極を用いる以外は、上記実施例と同様にして、比較例の積層型電池を作製した。
【００６９】
（３）捲回型電池の作製
積層型電池を作製したときに用いたものと同様の材料を用いて長尺状の正極板と負極板を作製し、これらを用いて積層型と同じ容量の、図２に示すような捲回型リチウム二次電池を作製した。
負極板２３と正極板２２とをセパレータ２４を介してスパイラル状に捲回し、プレス加工によって扁平化した極板群を作製した。極板群は電池ケース２１内に収納した。負極板２３からリードを引き出して電池ケース２１の底部に接続した。正極板２２からリードを引き出して正極端子（図示せず）に接続した。そして、非水電解質を電池ケース２１内に注液し、電池ケース２１の開口部を封口板で密封した。
【００７０】
また、黒鉛を活物質とした負極を用いる以外は、上記実施例と同様にして、比較例の捲回型電池を作製した。
【００７１】
（４）電池の評価
電池を１Ａの定電流で、４．１Ｖになるまで充電した後、１Ａの定電流で２．５Ｖになるまで放電し、これを１サイクルとした。また、１サイクル目の放電容量（ｍＡｈ）を測定した。この充放電サイクルを１００回繰り返し、１サイクル目の放電容量に対する１００サイクル目の放電容量の割合を百分率で求め、１００サイクル後の容量維持率Ｘ（％）とした。また、１００サイクル目の充電状態の電池の厚さＹ（ｍｍ）を測定した。充放電開始前の電池の厚さは５ｍｍであった。試験は２０℃の恒温槽中で行った。結果を表１〜３に示す。
【００７２】
［単体金属または合金の負極活物質を用いた電池の評価］
表１の結果から分かるように、積層型または捲回型のいずれの電池の場合でも、１サイクル目の放電容量は９００ｍＡｈであり、負極活物質を黒鉛としたときの放電容量（７００ｍＡｈ）よりも高かった。
積層型電池において、活物質が低結晶相の場合、容量維持率Ｘは８０〜９０％、電池の厚さＹは５ｍｍであった。また、活物質が非晶質相の場合、容量維持率Ｘは９０〜９５％、電池の厚さＹは５ｍｍであった。負極活物質が低結晶相または非晶質相の電池では、高い容量維持率を保持したまま、電池の厚さに変化は見られなかった。つまり、負極活物質を黒鉛とした場合と同様に、高サイクル特性を維持したまま、電池の膨れを抑制することができた。
これは、低結晶相または非晶質相においては、結晶子が不規則に配向されているため、リチウムが挿入されても粒子全体の体積変化があまり起こらないためと考えられる。また、非晶質相においては、より不規則に結晶子が配向されているため、低結晶相の負極活物質を用いた場合よりも高い容量維持率Ｘが得られた。
【００７３】
活物質が結晶相の場合、すべての負極活物質において、電池の厚さＹに変化が見られなかったものの、容量維持率Ｘが３０〜５０％まで低下した。
これは、結晶相においては、結晶子サイズが大きいため、リチウム挿入時に大きな体積変化が起こるためと考えられる。
【００７４】
一方、捲回型電池の場合、活物質が結晶相または低結晶相、あるいは非晶質相のとき、すべての負極活物質において、容量維持率Ｘの値は、積層構造の場合とほぼ同様の値であった。しかし、電池の厚さＹは６ｍｍであり、電池の膨れが生じた。比較として、負極活物質を黒鉛とした捲回型電池では、電池の膨れは見られなかった。
これは、捲回型電池の極板群のＲ部が強く固定された状態となっているために、挫屈による膨れが加わって、電池の膨れをより大きなものにしていると考えられる。
【００７５】
［複合粒子の負極活物質を用いた電池の評価］
表２の結果から分かるように、負極活物質を複合粒子とした場合でも表１と同様の傾向の測定結果を得た。負極活物質が低結晶相または非晶質相の積層型電池では、高い容量維持率を保持したまま、電池の厚さに変化は見られなかった。
これは、複合粒子を構成する核粒子および表面層のうち、少なくともいずれか一方が低結晶相または非晶質相を有することにより、リチウムが挿入されても粒子全体の応力緩和が可能となるためと考えられる。
活物質が結晶相の積層型電池においても、電池の厚さＹに変化が見られなかったものの、容量維持率Ｘは５０〜７０％まで低下した。
一方、電池の構造を捲回型とした場合でも、表１と同様に全ての負極活物質において、電池の膨れが見られた。
【００７６】
［薄膜の負極活物質を用いた電池の評価］
表３の結果から分かるように、負極活物質をＳｉまたはＳｎの薄膜とした場合でも、表１と同様の傾向の測定結果を得た。負極活物質が低結晶相または非晶質相の積層型電池では、高い容量維持率を保持したまま、電池の厚さに変化は見られなかった。
これは、低結晶相または非晶質相においては、結晶子が不規則に配向されているため、リチウムが挿入されても粒子全体の体積変化があまり起こらないためと考えられる。
活物質が結晶相の積層型電池においても、電池の厚さＹに変化が見られなかったものの、容量維持率Ｘは５０％まで低下した。
一方、電池の構造を捲回型とした場合でも、表１と同様に全ての負極活物質において、電池の膨れが見られた。
【００７７】
《実施例２》
負極容量密度の範囲について詳細に検討するために、Ｓｉの薄膜の負極活物質を用いて、積層型および捲回型の電池を作製した。負極容量密度は、薄膜の成膜密度を変化させることにより、４００〜１２００ｍＡｈ／ｃｃの範囲で１００ｍＡｈ／ｃｃ毎に変化させて測定した。
【００７８】
電池を１Ａの定電流で、４．１Ｖになるまで充電した後、１Ａの定電流で２．５Ｖになるまで放電し、これを１サイクルとした。また、１サイクル目の放電容量（ｍＡｈ）を測定した。この充放電サイクルを１００回繰り返し、１サイクル目の放電容量に対する１００サイクル目の放電容量の割合を百分率で求め、１００サイクル後の容量維持率Ｘ（％）とした。また、１００サイクル目の充電状態の電池の厚さＹ（ｍｍ）を測定した。充放電開始前の電池の厚さは５ｍｍであった。試験は２０℃の恒温槽中で行った。その結果を表４に示す。
【００７９】
【表４】

【００８０】
表４の結果から分かるように、負極容量密度が４００ｍＡｈ／ｃｃのとき、積層型電池では、すべての結晶構造において、実施例１と同様の値を得た。一方、捲回型電池では、すべての結晶構造において、実施例１の結果よりも電池の厚さＹ（５．５ｍｍ）を抑制することができた。しかし、いずれの電池においても、１サイクル目の放電容量は６００ｍＡｈであり、負極活物質を黒鉛とした場合の放電容量（７００ｍＡｈ）の値よりも低かった。
これは、負極板の負極容量密度が小さいと、それにともなって活物質量も少なくなるため、吸蔵されるリチウムの量が黒鉛の場合よりも少なくなったためと考えられる。
【００８１】
負極容量密度が５００〜１０００ｍＡｈ／ｃｃのとき、捲回型電池では、すべての負極活物質において、負極容量密度が高くなるほど、電池の厚さＹも大きくなった。一方、積層型電池では、すべての負極活物質において、実施例１と同様の値を得た。また、いずれの電池においても１サイクル目の放電容量は、負極容量密度が高くなるほど高い値を得た。それらの値は、負極活物質を黒鉛とした場合の放電容量（７００ｍＡｈ）よりも高い値であった。
【００８２】
負極容量密度が１２００ｍＡｈ／ｃｃのとき、積層型および捲回型のいずれの電池においても、１サイクル目の放電容量は最も高い値を得た。しかし、容量維持率Ｘは急激に低下した。
これは、負極板が過剰に大きな負極容量密度を有すると、活物質量も過剰になり、極板中の空間部分が少なくなるため、そこに注入される電解液の量も少なくなる。そのため、リチウムイオンの輸送に必要な電解液の量が、活物質量に対して不十分となる。従って、負極板の電荷移動抵抗が大きくなり、サイクル特性が悪くなると考えられる。
【００８３】
負極活物質を構成する元素の混合比率は、特に限定されるものではない。負極活物質が複合粒子の場合、核粒子がＳｎ、Ｓｉを主な元素とした相であり、表面層が核粒子表面の全部または一部を被覆し、かつ少なくともいずれか一方の相が非晶質状態であればよく、仕込み組成を特に限定するものではない。さらに、核粒子は、Ｓｎ、Ｓｉのみからだけではなく、それ以外にも、例えば、Ｏ、Ｃ、Ｎ、Ｓ、Ｃａ、Ｍｇ、Ａｌ、Ｆｅ、Ｗ、Ｖ、Ｔｉ、Ｃｕ、Ｃｒ、Ｃｏ、Ｐなどの元素が微量に存在していてもよい。表面層は表２に示した合金のみからだけではなく、それ以外にも、例えば、Ｏ、Ｃ、Ｎ、Ｓ、Ｃａ、Ｍｇ、Ａｌ、Ｆｅ、Ｗ、Ｖ、Ｔｉ、Ｃｕ、Ｃｒ、Ｃｏ、Ｐなどの元素が微量に存在していてもよい。
【００８４】
負極板の作製法は、上述した方法以外にも、真空蒸着法、イオンプレーティング法、スパッタリング法、化学気相反応法、電解メッキ法を用いてもよい。また、これらの方法により作製された電池についても、充放電サイクルによる容量維持率が高いことを確認した。
【００８５】
なお本実施例では正極活物質としてＬｉＣｏＯ_２を用いたが、ＬｉＭｎ_２Ｏ_４、ＬｉＮｉＯ_２などをはじめとする、充放電に対して可逆性を有する正極活物質と組み合わせた場合にも同様の効果を得ることができることはいうまでもない。
【００８６】
《実施例３》
本発明の電池ケースの構造について検討を行った。
（１）正極板の作製
正極活物質、９０重量部と、導電剤のアセチレンブラック、５重量部と、結着剤のポリフッ化ビニリデン樹脂、５重量部とを混合し、これらを脱水Ｎ−メチル−２−ピロリドンに分散させて、スラリー状の正極合剤を調製した。この正極合剤をアルミニウム箔からなる芯材上に塗布し、乾燥後、圧延して正極活物質層を形成して、正極板を完成した。
【００８７】
（２）負極板の作製
ＴｉＳｉ_２粉末、９０重量部と、導電剤の黒鉛、５重量部と、結着剤のポリフッ化ビニリデン樹脂、５重量部とを混合し、これらを脱水Ｎ−メチル−２−ピロリドンに分散させて、スラリー状の負極合剤を調製した。この負極合剤を銅箔からなる芯材上に塗布し、乾燥後、圧延して負極活物質層を形成して、負極板を完成した。
【００８８】
（３）積層型電池の作製
上記作製した正極板と負極板とを、セパレータを介して交互に積層しスタック型の極板群を作製した。負極板の芯材から負極リードを引き出し、正極板の芯材から正極リードを引き出した。負極板１枚、正極板２枚を用いて積層した。
スタック状に積層した極板群を、両面に樹脂シートを有するアルミニウム箔（Ａｌラミネートシート）からなる電池ケースの内部に挿入した後、電池ケース１１に非水電解質を注液し、リード部溶着シールで電池ケースの開口部を封口した。非水電解質には、エチレンカーボネートとエチルメチルカーボネートとの混合溶媒（体積比１：１）に、１．５ｍｏｌ／ｌの濃度でＬｉＰＦ_６を溶解したものを用いた。
【００８９】
（４）捲回型電池の作製
積層型電池を作製したときに用いたものと同様の材料を用いて長尺状の正極板と負極板を作製し、これらを用いて積層型と同じ容量の捲回型リチウム二次電池を作製した。
負極板と正極板とをセパレータを介してスパイラル状に捲回し、プレス加工によって扁平化した極板群を作製した。極板群は電池ケース内に収納した。負極板からリードを引き出して電池ケースの底部に接続した。正極板からリードを引き出して正極端子に接続した。そして、非水電解質を電池ケース内に注液し、電池ケースの開口部を封口板で密封した。
【００９０】
（５）電池ケースの成形
本実施例の電池ケースの原料には、純アルミニウム系（ＪＩＳ−１０００系）の組成材料を用い、多段プレス法によって、電池ケースの成形を行った。そして、ケースを最終的に封口する工程を行う前に、電池ケース内を減圧することにより、ケースの電極面に対向する面を電池ケースの内側に凹ませた。図３に電池ケースの一例の断面概略図を示す。電池ケースの端部の厚さＡ（ｍｍ）と中央部の厚さＢ（ｍｍ）との比（Ｂ／Ａ）が、０．５≦Ｂ／Ａ≦１．０の範囲について、実施例１と同様に、１サイクル目の放電容量（ｍＡｈ）と、１００サイクル後の容量維持率Ｘ（％）と電池の厚さＹ（ｍｍ）とを測定した。
【００９１】
［電池の評価］
電池を１Ｃの放電電流で２．５Ｖまで放電し、電池の形状について測定した。その結果を表５に示す。
【００９２】
【表５】

【００９３】
表５の結果から分かるように、Ｂ／Ａが０．５のとき、積層型および捲回型のいずれの電池においても、容量維持率Ｘがかなり小さい値であった。
これは、ケースの凹部が過剰な凹みを有しているため、極板群へ大きな圧迫力がかかるためと考えられる。特に、充電過程では、電解液が電極板やセパレータ内部から押し出される状態となり、電気化学的反応が円滑に行れなくなるため、サイクル特性が悪化するものと考えられる。
【００９４】
Ｂ／Ａが０．６〜０．９５のとき、捲回型電池では、Ｂ／Ａの値が大きくなるほど、電池の厚さＹも大きくなった。積層型電池では、電池の厚さＹに変化はなかった。
これは、電池の充放電サイクルにより生じる極板群の膨れを、電池ケースの凹部を外側へ押し出すことにより、緩和することができるためである。なお、極板群の膨れにより、電池ケースの端部の厚さＡが変化することはない。
【００９５】
Ｂ／Ａが１．０のとき、積層型および捲回型のいずれの電池においても、容量維持率Ｘがかなり小さい値であった。
これは、極板群への圧迫力が非常に小さくなるため、Ｂ／Ａが１．０より小さい場合よりも、極板群内部での粒子間接触が不十分となって、電子抵抗が大きくなり、電気化学的反応が円滑に行われなくなるため、サイクル特性が悪化するものと考えられる。
【００９６】
なお、本実施例の電池ケースは、純アルミニウム系（ＪＩＳ−１０００系）組成材料を用いて作製したが、組成としてはこの他に鉄、ニッケル、銅、ステンレス、またはＡｌ−Ｍｎ系などのアルミニウム合金、チタン、亜鉛などを用いても良い。
また、電池ケ−スの作製方法は、多段プレス法による以外にも、鋳造や熱間圧延、冷間圧延、焼鈍などの方法を用いても良い。また、一体成形でなく、溶接やカシメなどの製造方法によってもよい。
また、凹部の調整は上記のように、組み立ての最終工程で封口する前に、ケ−ス内を減圧することによって行ってもよく、これ以外にも、ケ−ス作製時に凹部の形状を作製してもよい。
【００９７】
【発明の効果】
本発明によれば、負極活物質を改良するとともに積層型の極板群を採用することにより、充放電時の電池の膨れを抑制し、かつ、高容量でサイクル特性に優れた非水電解質二次電池を提供することができる。また、非水電解質二次電池を収容する電池ケースにおいて、電極面に対向する面がケースの内側に凹みを有することにより、充放電時に生じる極板群の膨れが凹部を外側に押し出すことにより、電池ケースの端部の厚みを変更させることがない。
【図面の簡単な説明】
【図１】本発明の実施例１による角形の積層型リチウム二次電池の一例の断面概略図である。
【図２】比較例による角形の捲回型リチウム二次電池の一例の断面概略図である。
【図３】本発明の実施例３による電池ケースの一例の断面概略図である。
【符号の説明】
１１、２１ 電池ケース
１２、２２ 正極板
１３、２３ 負極板
１４、２４ セパレータ
１５ 正極リード
１６ 負極リード
１７ リード部溶着シール[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a prismatic non-aqueous electrolyte secondary battery having improved negative electrode material, long life and high reliability. The non-aqueous electrolyte secondary battery of the present invention is suitable for a portable information terminal, a portable electronic device, a small household power storage device, a motorcycle powered by a motor, an electric vehicle, a hybrid electric vehicle, and the like.
[0002]
[Prior art]
In recent years, non-aqueous electrolyte secondary batteries having features such as high electromotive force and high energy density, particularly lithium secondary batteries, have been used as power sources for mobile communication devices and portable electronic devices. When a single lithium metal is used as the negative electrode material, a lithium secondary battery having the highest energy density can be obtained, but there is a problem that dendrite easily grows on the negative electrode surface during charging. When the dendrite pierces the separator and reaches the positive electrode side during repeated charging and discharging, an internal short circuit occurs. In addition, the dendrite deposited on the negative electrode surface has a high specific surface area, so the reaction activity is high, and reacts with the solvent in the electrolytic solution to form a solid electrolyte-like interface film lacking electron conductivity on the surface. . Therefore, the dendrite also causes a reduction in the charge / discharge efficiency of the battery. As described above, the lithium secondary battery using the lithium metal alone as the negative electrode material has problems in reliability and cycle life characteristics.
[0003]
At present, a carbon material capable of occluding and releasing lithium ions has been put to practical use as a negative electrode material replacing lithium metal. Since the carbon material usually stores lithium therein, problems such as internal short circuit due to dendrite can be avoided. However, the theoretical capacity of a carbon material is considerably smaller than the theoretical capacity of lithium metal alone. For example, graphite, a kind of carbon material, has a theoretical capacity of 372 mAh / g, which is only about one tenth of that of lithium metal alone, and is not sufficient.
[0004]
As a negative electrode material expected to have a higher capacity than a carbon material, for example, a simple metal material or a simple nonmetal material that forms a compound with lithium is known. For example, silicon (Si) and tin (Sn) are respectively Li₂₂Si₅, Li₂₂Sn₅It is possible to occlude lithium until the composition shown by Normally, metallic lithium does not precipitate within the above composition range, so that problems such as internal short circuit due to dendrite can be avoided. The theoretical capacities of the above materials are 4199 mAh / g and 993 mAh / g, respectively, which are much larger than the theoretical capacities of carbon materials such as graphite.
[0005]
Further, as another anode material for forming a compound with lithium, at least one selected from the group consisting of a non-ferrous metal silicide composed of a transition element (for example, see Patent Document 1), a Group 4B element, and P and Sb Consisting of an intermetallic compound containing the element₂For example, a material of any one of a mold type, a ZnS type, and an AlLiSi type (for example, see Patent Document 2) has been proposed. These are used for the purpose of improving discharge cycle characteristics.
[0006]
Attempts have also been made to improve the above-mentioned metal-based materials to achieve more excellent cycle characteristics. For example, a negative electrode material composed of a solid solution composed of two solid phases or an intermetallic compound has been proposed (for example, see Patent Document 3). By using such a negative electrode material, it is possible to obtain a battery having a higher capacity and an excellent charge / discharge cycle than when a carbon material is used.
There has also been proposed a negative electrode in which a particulate electrode material having a controlled particle diameter is supported on a flat current collector (for example, see Patent Document 4). According to this negative electrode, it is possible to obtain a battery having a long cycle life, a high capacity, a high energy density, and a somewhat suppressed volume expansion / contraction during charge / discharge.
[0007]
[Patent Document 1]
JP-A-7-240201
[Patent Document 2]
JP-A-9-63651
[Patent Document 3]
JP 2000-30703 A
[Patent Document 4]
JP-A-11-242954
[0008]
[Problems to be solved by the invention]
However, in recent years, there has been an active trend toward higher functionality of portable devices and larger batteries such as electric vehicles, and the demand for longer life of batteries as power sources for driving has been further increased. . It is difficult for conventional negative electrode materials to sufficiently meet such demands.
[0009]
The negative electrode materials described in Patent Literatures 1 to 3 have improved composition, phase structure, and alloy structure of the alloy material, so that the cycle characteristics can be improved to a certain extent, but the volume change during charge and discharge is reduced. The deterioration of the cycle characteristics due to the large size has not been solved. Deterioration of cycle characteristics due to such a volume change is a common problem for metals and alloys capable of storing lithium.
[0010]
Considering the expansion coefficient of the active material during charging based on crystallographic values, for example, when the active material is made of silicon or tin, the maximum insertion amount of lithium per mole of each active material is , 4.4 moles. On the other hand, the theoretical volume expansion coefficients after the insertion before and after the lithium insertion calculated from the crystal lattice volume are 410% for silicon and 358% for tin. When a negative electrode active material having such a large expansion coefficient is used to manufacture an electrode or a battery by a conventional configuration or process, the cycle is caused by deformation of the electrode plate group during charging and discharging and uneven distribution of the electrolyte. The characteristics may be deteriorated, or in the worst case, the appearance of the battery may be deformed.
[0011]
If the negative electrode material described in Patent Document 4 is used, fine pores are present inside the electrode plate, so that volume expansion of the metal active material during charging can be suppressed to some extent. However, in order to completely absorb the volume expansion, an advanced design technique for the pore size is required, which is not industrially easy.
[0012]
[Means for Solving the Problems]
The present invention is based on the following findings.
When the charge / discharge cycle of a rectangular battery having a wound electrode group having a substantially elliptical cross section is repeated over a long period of time, it is difficult to suppress battery swelling due to electrode plate expansion. Here, the wound electrode plate group has a structure in which a separator is interposed between a long negative electrode plate and a long positive electrode plate, and these are spirally wound.
[0013]
In the volume expansion of the negative electrode plate occurring during charging, since the expansion rate in the thickness direction of the negative electrode plate is large, the wound electrode group having a substantially elliptical cross section is mainly in the short axis direction of the electrode group section. Causes swelling. On the other hand, at a corner portion (hereinafter, referred to as an R portion) of such an electrode plate group, since a relatively strong tension is applied to the electrode plate, the R portion is in a strongly fixed state, and a space for expansion is provided. There is not enough room. For this reason, during charging, an excessive force is generated in the direction of the center of the electrode group, and the electrode plates inside the group are deformed. As a result, not only swelling due to expansion of the negative electrode plate in the thickness direction but also swelling due to deformation of the electrode plate (hereinafter referred to as “buckling”) is applied to the wound electrode group during charging. It is considered that the bulging of the sphere becomes larger.
[0014]
In the present invention, in order to suppress the swelling of the battery during charge and discharge, and to provide a non-aqueous electrolyte secondary battery with high capacity and excellent cycle characteristics, the anode active material is improved and a laminated electrode plate is provided. Adopt a group.
[0015]
That is, the present invention provides a non-aqueous electrolyte secondary comprising an electrode group and a non-aqueous electrolyte in which a positive electrode capable of inserting and extracting lithium and a negative electrode capable of inserting and extracting lithium are alternately laminated via a separator. In the battery, the positive electrode includes a positive electrode active material layer and a core material supporting the same, the negative electrode includes a negative electrode active material layer and a core material supporting the same, and the negative electrode active material layer includes a group 4B element. The negative electrode active material layer is a nonaqueous electrolyte secondary battery having a volume capacity density of 500 mAh / cc or more, comprising at least one selected from the group consisting of a simple metal and an alloy containing a Group 4B element. The volume capacity density is preferably from 600 to 1000 mAh / cc.
[0016]
It is preferable to use at least one element selected from the group consisting of Si and Sn as the group 4B element. Further, at least one selected from the group consisting of the simple metals and alloys has at least one state selected from the group consisting of an amorphous phase and a low crystalline phase, or has a crystallite size of 5 to 100 nm. Is preferred.
[0017]
The alloy is M_αSn_βSi_γIt is preferable to have the following composition. In the above composition, (a) M is at least one selected from the group consisting of Ti, Ni, Cu and Fe, (b) 0.1 ≦ α ≦ 10, (c) 0 ≦ β ≦ 10, and (D) 0 ≦ γ ≦ 30 is satisfied, and β and γ are not simultaneously 0.
As the alloy, composite particles composed of core particles and a surface layer covering all or a part of the surface of the core particles may be used. The core particles include at least one selected from the group consisting of Si and Sn. The surface layer is preferably a solid solution or an intermetallic compound containing at least one selected from the group consisting of Ti, Ni, Cu and Fe, and at least one selected from the group consisting of Si and Sn.
[0018]
The electrode group and the non-aqueous electrolyte are usually housed in a battery case. It is preferable that a surface of the battery case facing the electrode surface is recessed inside the case. It is preferable that the ratio B / A of the thickness (A) of the end portion of the case to the thickness (B) of the central portion satisfies 0.6 <B / A <0.95.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
The nonaqueous electrolyte secondary battery of the present invention includes an electrode group and a nonaqueous electrolyte in which a positive electrode capable of inserting and extracting lithium and a negative electrode capable of inserting and extracting lithium are alternately stacked via a separator. . The positive electrode includes a positive electrode active material layer and a core material supporting the same, and the negative electrode includes a negative electrode active material layer and a core material supporting the same. The negative electrode active material layer is made of at least one selected from the group consisting of a simple metal composed of a Group 4B element and an alloy containing a Group 4B element, and has a volume capacity density of 500 mAh / cc or more. If the volume capacity density is less than 500 mAh / cc, buckling does not occur, but the capacity is not sufficient because the charge / discharge cycle has a value similar to that of the carbon material. The volume capacity density is preferably from 600 to 1000 mAh / cc.
[0020]
Even when a negative electrode having a high capacity density is used, it is possible to obtain an electrode group in which deformation (buckling) of an internal electrode plate does not occur during charging by forming an electrode group having a laminated structure. In the case of a stacked electrode group, the negative electrode plate expands in the thickness direction during charging, but the factor of buckling of the electrode group is eliminated. Therefore, a square non-aqueous electrolyte secondary battery having excellent cycle characteristics can be obtained without swelling of the battery more than necessary.
[0021]
In the nonaqueous electrolyte secondary battery of the present invention, the group 4B element is preferably at least one selected from the group consisting of Si and Sn, since a high capacity is obtained. Further, it is preferable that at least one selected from the group consisting of the simple metals and the alloy comprises at least one selected from the group consisting of an amorphous phase and a low crystalline phase.
[0022]
Here, in the present invention, the amorphous phase refers to a phase that gives a broad scattering band having a peak in the range of 20 ° to 40 ° in 2θ value by an X-ray diffraction method using CuKα radiation. The low crystalline phase is a phase that gives a crystalline diffraction pattern, and refers to a phase in which the half width of the strongest diffraction peak is 0.6 ° or more. When the half width of the diffraction peak is less than 0.6 °, the diffraction peak becomes sharp and the crystallinity increases. When the alloy is a composite alloy having two or more types of phases, at least one phase may be an amorphous phase or a low crystalline phase, and it is particularly preferable that all phases are amorphous phases.
[0023]
When a single metal or alloy composed of an amorphous phase absorbs lithium, the generated lithium alloy phase or lithium insertion phase is extremely small. Furthermore, since the crystallites constituting them can be oriented irregularly, stress can be relaxed as a whole of the active material particles even if lithium is inserted during charging.
[0024]
On the other hand, in a single metal or alloy composed of a crystalline phase, crystallites having a relatively large size are regularly oriented, so that when lithium is inserted, stress distortion occurs at the crystal grain boundaries or the structure becomes finer. Or trigger. An active material composed of such a phase is more strongly affected by a volume change which causes isolation of an active site. In other words, in the case of an active material composed of a crystalline phase, structural changes within crystallites or between crystallites increase when lithium is inserted due to the high crystallinity, and stress distortion occurs around a grain boundary connecting crystallites. Tends to occur. Depending on the amount of lithium absorbed (depth of charge), the crystallites that make up the polycrystal undergo a volume change that cannot maintain their own structure, cutting off the electron conduction path at the grain boundaries and partially isolating active sites. Invite. As a result, it is considered that the reversibility of charge and discharge is reduced.
[0025]
The use of a single metal or alloy composed of an amorphous phase or a low crystalline phase can prevent such isolation of active sites beforehand, and the occlusion and release of lithium can proceed smoothly and uniformly, and cycle deterioration can occur. It will be possible to minimize it.
[0026]
The positive electrode and the negative electrode used in the present invention have, as a core material, a mixture layer containing a positive electrode active material or a negative electrode active material capable of electrochemically and reversibly absorbing and releasing lithium ions, a conductive agent, a binder and the like. The active material layer is not limited to the one in which the active material layer is formed by being carried, but may be a thin film electrode in which the active material layer is formed by a physical method or a chemical method.
Methods for producing simple metals or alloys composed of a low crystalline phase or an amorphous phase include gas atomization, liquid quenching, ion beam sputtering, vacuum evaporation, plating, gas phase chemical reaction, mechanical alloying, etc. Can be applied. In particular, a method for forming a thin-film active material layer made of an amorphous phase on a core material is not particularly limited, and examples thereof include a CVD method, a sputtering method, a vapor deposition method, a thermal spray method, and a plating method. Are preferred. Among these thin film forming methods, it is particularly preferable to use a CVD method, a sputtering method, or an evaporation method.
[0027]
When the single metal or alloy is in the form of particles, if the particle diameter exceeds 45 μm, the thickness of the negative electrode active material layer of a practical battery is about 80 μm, so the number of irregularities on the negative electrode surface increases, and the battery characteristics decrease. . For this reason, the preferred particle size is 30 μm or less.
Further, the core material may be plated with a sheet-shaped or porous single metal or alloy to form the negative electrode active material. As the plating method, an electroless plating method, an electroplating method, a molten salt electrolytic method, or the like can be applied.
[0028]
In the nonaqueous electrolyte secondary battery of the present invention, it is preferable that at least one selected from the group consisting of the above-mentioned simple metals and alloys has a crystallite size of 5 to 100 nm. Here, a crystal having a crystallite size in the range of 5 to 100 nm is also referred to as a microcrystal.
[0029]
By using a single metal or alloy composed of microcrystals as the negative electrode active material, it is thought that the dislocation movement accompanying the expansion of the crystallites storing lithium can be stopped at the grain boundaries between the crystallites, and the generation of particle cracks is considered. Generation can be suppressed. Further, by suppressing the particle cracking of the negative electrode active material, a battery with less deterioration due to charge / discharge cycles can be obtained.
[0030]
When the crystallite size is larger than 100 nm, the grain boundary between crystallites decreases, and the effect of suppressing particle cracking decreases. When the crystallite size is less than 5 nm, the number of grain boundaries between crystallites becomes too large, and conversely, electron conductivity may be reduced. When the electron conductivity decreases, the overvoltage increases, which causes a reduction in battery capacity.
[0031]
The crystallite size can be determined, for example, by wide-angle X-ray diffraction (hereinafter, referred to as WAXD) measurement. First, WAXD measurement of a single metal or alloy is performed, and the half-value width β (rad) of a peak belonging to a predetermined crystal plane in the obtained diffraction pattern is calculated by Scherrer's formula:
D (nm) = 0.9 × λ / (β × cos θ) (1)
By substituting into the above, the crystallite size D (nm) can be obtained.
In Equation (1), λ is the X-ray wavelength (nm) (1.5405 nm in the case of CuKα radiation), and θ is half the value (rad) of the peak angle 2θ.
[0032]
When there are a plurality of peaks belonging to the crystal plane in the diffraction pattern obtained by the WAXD measurement, the crystallite size may be obtained by applying the Scherrer equation to the main peak having the largest intensity.
[0033]
As a method for measuring the crystallite size, in addition to the above methods, AFM (atomic force microscope; atomic force microscope), TEM (transmission electron microscope), or the like can be used.
[0034]
In the non-aqueous electrolyte secondary battery of the present invention, the alloy includes M_αSn_βSi_γIt is preferable to use one having the following composition: In the above composition, (a) M is at least one selected from the group consisting of Ti, Ni, Cu and Fe, (b) 0.1 ≦ α ≦ 10, (c) 0 ≦ β ≦ 10 and ( d) It is preferable that 0 ≦ γ ≦ 30 is satisfied, and β and γ are not simultaneously 0. When α is less than 0.1, the state is substantially the same as that when M is not contained, meaning of the composition M is lost, and when it exceeds 10, M becomes an excessive state and occludes Li. The amount of Sn or Si to be reduced decreases, and the capacitance becomes small. When β exceeds 10, the content of M is relatively reduced and the capacity is increased, but there is no meaning of the existence of M. On the other hand, if γ exceeds 30, the content of M is relatively reduced and the capacity is increased, but the presence of M is meaningless.
[0035]
The alloy may be a composite particle comprising a core particle and a surface layer covering all or a part of the surface of the core particle. The core particles include at least one member selected from the group consisting of Si and Sn, and the surface layer has at least one member selected from the group consisting of Ti, Ni, Cu, and Fe, and a group consisting of Si and Sn. It is preferably a solid solution or an intermetallic compound containing at least one selected from. At least one of the core particles and the surface layer is preferably composed of microcrystals having a crystallite size of 5 to 100 nm.
[0036]
The core particles play an essential role of an active material that charges and discharges lithium. When the core particles have an amorphous phase, a low crystal phase, or a fine crystallite size, stress relaxation of the entire active material particles can be achieved even if lithium is absorbed. However, the core particles have a problem that the discharge capacity is low in spite of the high capacity density of lithium. On the other hand, the surface layer has a problem that the electrical conductivity is as high as graphite and the cycle characteristics are excellent, but the capacity density is low. Therefore, by using a composite particle composed of a core particle and a surface layer as a negative electrode active material, a non-aqueous electrolyte secondary battery having a high capacity density that can compensate for both problems and has excellent cycle characteristics is provided. can do.
[0037]
Hereinafter, an example of a method for producing a composite particle will be described.
First, the core particles and the powder or block of each element constituting the surface layer are melted in a heating and melting tank, and the melt is rapidly cooled and solidified at an ultra-high speed. According to this method, when the melt is quenched and solidified, core particles are formed, and a surface phase is deposited on at least a part of the surface to coat the core particles, thereby obtaining composite particles. However, it is generally difficult to completely amorphize the composite particles by such a synthesis method, and the composite particles may include a large amount of a crystalline phase. Then, by applying mechanical shearing force to the composite particles using a ball mill, composite particles composed of an amorphous phase or a low crystalline phase can be obtained. Then, the particle size is adjusted by pulverization, classification, and the like as necessary.
By heat-treating the composite particles, the homogeneity of each of the core particles and the surface phase can be increased, but the heat treatment is not necessarily performed. In addition, the method of rapid cooling and solidification is not limited to the method described above.
[0038]
A method for producing another composite particle different from the above will be described. Composite particles can be obtained by attaching an element constituting the surface phase, which is different from the element constituting the core particles, to the surface of the powder of the element constituting the core particles and subjecting the whole to a heat treatment. By this heat treatment, the elements in the core particles are diffused into a layer made of the elements attached to the surface, and a surface layer is formed. As a method of attaching the element constituting the surface layer to the surface of the core particles, a plating method, a mechanical alloying method, or the like can be performed, but is not limited thereto. In the mechanical alloying method, composite particles can be obtained without performing heat treatment.
[0039]
Note that it is difficult to completely remove the crystal phase by the above-described method for producing composite particles. In order to further amorphize the composite particles, it is effective to repeatedly perform grinding, milling, or the like. By these methods, the microstructure can be refined, and the alloy phase having a non-stoichiometric composition at the minute portion can be isotropically arranged by the mechanochemical reaction. That is, the alloy phase can be uniformly dispersed and arranged in the particles.
Amorphous composite particles can also be produced by processing metal powder of a desired starting material with a predetermined composition using a grinding or milling method without producing composite particles. It is.
[0040]
In the nonaqueous electrolyte secondary battery of the present invention, it is preferable to use a case in which the surface facing the electrode surface is recessed inside the case, as the battery case that houses the electrode group and the nonaqueous electrolyte. The ratio B / A of the thickness (A) at the end of the case to the thickness (B) at the center preferably satisfies 0.6 <B / A <0.95. When B / A is less than 0.6, a large pressing force is applied to the electrode plate group, so that the electrochemical reaction is not smoothly performed, and the cycle characteristics deteriorate. On the other hand, when B / A exceeds 0.95, the pressing force on the electrode group becomes very small, but the contact between particles inside the electrode group becomes insufficient and the electronic resistance becomes large. As a result, the electrochemical reaction is not performed smoothly, so that the cycle characteristics deteriorate.
[0041]
In the present invention, a conventionally known positive electrode active material can be used. For example, Li_xCoO₂, Li_xNiO₂, Li_xMnO₂, Li_xCo_yNi_1-yO₂, Li_xCo_yM_1-yO_z, Li_xNi_1-yM_yO_z, Li_xMn₂O₄, Li_xMn_2-yM_yO₄(M = at least one of Na, Mg, Sc, Y, Mn, Fe, Co, Ni, Cu, Zn, Al, Cr, Pb, Sb and B, x = 0 to 1.2, y = A transition metal oxide containing lithium such as 0 to 0.9 and z = 2.0 to 2.3) is used. The above-mentioned x value is a value before the start of charging and discharging, and increases and decreases due to charging and discharging. In addition, positive electrode active materials such as transition metal chalcogenides, vanadium oxides and their lithium compounds, niobium oxides and their lithium compounds, conjugated polymers using organic conductive materials, and Chevrel phase compounds can also be used. It is. It is also possible to use a mixture of a plurality of different positive electrode active materials. The average particle size of the positive electrode active material particles can be used without any particular limitation, but is preferably 1 to 30 μm.
[0042]
As the conductive agent for the positive electrode or the negative electrode, any electronic conductive material that does not cause a chemical change at the charge / discharge potential of the positive electrode or the negative electrode active material to be used may be used. For example, graphite such as natural graphite (flaky graphite, etc.), artificial graphite, etc., carbon blacks such as acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, and conductive materials such as carbon fiber and metal fiber Conductive powders such as conductive fibers, carbon fluoride, and aluminum; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and organic conductive materials such as polyphenylene derivatives. These can be included as a mixture. Among these conductive agents, artificial graphite and acetylene black are particularly preferred. The amount of the conductive agent is not particularly limited, but is preferably 1 to 50% by weight, more preferably 1 to 30% by weight, based on the positive electrode active material. For carbon and graphite, 2 to 15% by weight is particularly preferred.
[0043]
Either a thermoplastic resin or a thermosetting resin can be used as the binder for the positive electrode or the negative electrode. For example, polyethylene (PE), polypropylene (PP), polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), styrene butadiene rubber (SBR), tetrafluoroethylene-hexafluoroethylene copolymer, tetrafluoroethylene-hexa Fluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-chlorotrifluoroethylene copolymer, ethylene-tetra Fluoroethylene copolymer (ETFE resin), polychlorotrifluoroethylene (PCTFE), vinylidene fluoride-pentafluoropropylene copolymer, propylene-tetrafluoroethylene copolymer , Ethylene-chlorotrifluoroethylene copolymer (ECTFE), vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, vinylidene fluoride-perfluoromethylvinyl ether-tetrafluoroethylene copolymer, ethylene-acrylic acid copolymer The polymer or the (Na⁺) Ion crosslinked product, ethylene-methacrylic acid copolymer or (Na⁺) Ion crosslinked product, ethylene-methyl acrylate copolymer or (Na)⁺) Ion crosslinked product, ethylene-methyl methacrylate copolymer or (Na⁺And ionic cross-linked products, and these materials can be used alone or as a mixture. Among these binders, it is particularly preferable to use polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE) as the binder for the positive electrode. As the binder for the negative electrode, styrene-butadiene rubber (SBR), polyvinylidene fluoride (PVDF), ethylene-acrylic acid copolymer or (Na⁺) Ion crosslinked product, ethylene-methacrylic acid copolymer or (Na⁺) Ion crosslinked product, ethylene-methyl acrylate copolymer or (Na)⁺) Ion crosslinked product, ethylene-methyl methacrylate copolymer or (Na⁺) It is preferable to use an ion crosslinked product.
[0044]
As the positive electrode core material, any electron conductive material that does not cause a chemical change according to the charge / discharge potential of the positive electrode active material to be used may be used. For example, in addition to stainless steel, aluminum, titanium, carbon, conductive resin, and the like, there is a material obtained by treating the surface of aluminum or stainless steel with carbon or titanium. Among these core materials, aluminum or an aluminum alloy is particularly preferable. The surface of these materials can be oxidized and used. Also, it is desirable to form irregularities on the surface of the core material by surface treatment. As the shape of the core material, in addition to a foil, a film, a sheet, a net, a punched material, a lath body, a porous body, a foam, a group of fibers, a molded article of a nonwoven fabric, and the like are used. The thickness of the core material is not particularly limited, but is preferably 1 to 500 μm.
[0045]
The negative electrode core material may be any electronic conductor that does not cause a chemical change in the manufactured battery. For example, in addition to stainless steel, nickel, copper, titanium, carbon, a conductive resin, and the like, there are copper and stainless steel surfaces in which carbon, nickel, or titanium is treated. Among these core materials, copper or a copper alloy is particularly preferable. The surface of these materials can be oxidized and used. Also, it is desirable to form irregularities on the surface of the core material by surface treatment. As the shape of the core material, in addition to a foil, a film, a sheet, a net, a punched material, a lath body, a porous body, a foamed body, a molded body of a fiber group, and the like are used. The thickness of the core material is not particularly limited, but a thickness of 1 to 500 μm is preferable.
[0046]
The non-aqueous electrolyte is composed of a solvent and a lithium salt dissolved in the solvent. Examples of the non-aqueous solvent include cyclic carbonates such as ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), and vinylene carbonate (VC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethyl. Chain carbonates such as methyl carbonate (EMC) and dipropyl carbonate (DPC); aliphatic carboxylic esters such as methyl formate, methyl acetate, methyl propionate and ethyl propionate; and γ-lactones such as γ-butyrolactone Chain ethers such as 1,2-dimethoxyethane (DME), 1,2-diethoxyethane (DEE) and ethoxymethoxyethane (EME), cyclic ethers such as tetrahydrofuran and 2-methyltetrahydrofuran, dimethyl Rusulfoxide, 1,3-dioxolane, formamide, acetamide, dimethylformamide, dioxolane, acetonitrile, propyl nitrile, nitromethane, ethyl monoglyme, phosphoric acid triester, trimethoxymethane, dioxolane derivative, sulfolane, methyl sulfolane, 1,3- Aprotic organic solvents such as dimethyl-2-imidazolidinone, 3-methyl-2-oxazolidinone, propylene carbonate derivative, tetrahydrofuran derivative, ethyl ether, 1,3-propanesultone, anisole, dimethylsulfoxide, N-methylpyrrolidone And the like, and these can be used alone or in combination of two or more. Among these non-aqueous electrolytes, a mixed system of a cyclic carbonate and a chain carbonate or a mixed system of a cyclic carbonate, a chain carbonate and an aliphatic carboxylic acid ester is particularly preferable.
[0047]
As the lithium salt, for example, LiClO₄, LiBF₄, LiPF₆, LiAlCl₄, LiSbF₆, LiSCN, LiCl, LiCF₃SO₃, LiCF₃CO₂, Li (CF₃SO₂)₂, LiAsF₆, LiN (CF₃SO₂)₂, LiB₁₀Cl_{1 0}, Lithium lower aliphatic carboxylate, LiBr, LiI, lithium chloroborane, lithium tetraphenylborate, imides, and the like. These may be used alone or in combination of two or more in an electrolytic solution using them. it can. Among these lithium salts, in particular, LiPF₆Is preferred.
[0048]
Among the non-aqueous electrolytes, in particular, at least ethylene carbonate (EC) is contained, and LiPF is used as a supporting salt.₆An electrolytic solution containing The amount of the nonaqueous electrolyte added to the battery is not particularly limited, but a necessary amount can be used depending on the amount of the positive electrode or negative electrode active material and the size of the battery. The amount of the supporting electrolyte dissolved in the nonaqueous solvent is not particularly limited, but is preferably 0.2 to 2 mol / l. In particular, it is more preferably 0.5 to 1.5 mol / l.
[0049]
Further, it is effective to add another compound to the electrolyte for the purpose of improving the discharge and charge / discharge characteristics. For example, using triethyl phosphite, triethanolamine, cyclic ether, ethylenediamine, n-glyme, pyridine, hexaphosphoric triamide, nitrobenzene derivative, crown ethers, quaternary ammonium salt, ethylene glycol dialkyl ether, phosphate ester, etc. Can be.
[0050]
In addition to the conductive agent and the binder, fillers, dispersants, ionic conductors, pressure enhancers and other various additives can be used for the electrode mixture. The filler can be used without limitation as long as it does not cause a chemical change in the configured battery. For example, an olefin-based polymer such as polyethylene (PE) or polypropylene (PP), or a fiber such as glass or carbon is used. The amount of the filler added is not particularly limited, but is preferably 30% by weight or less based on the electrode mixture.
[0051]
As the separator, an electronically insulating microporous thin film having high ion permeability and predetermined mechanical strength is used. As the material of this thin film, there are polypropylene resin, polyethylene resin, etc. from the viewpoint of organic solvent resistance and hydrophobicity, and further, from the viewpoint of heat resistance, aramid resin alone or a laminate or composite of these. Can be used.
The separator may have a thickness of 5 to 100 μm, and particularly preferably 5 to 20 μm.
[0052]
In the configuration of the negative electrode plate and the positive electrode plate in the present invention, it is preferable that the negative electrode mixture surface or the thin film negative electrode active material surface is present at least on the surface facing the positive electrode mixture surface.
[0053]
The shape of the battery includes a coin type, a button type, a sheet type, a laminated type, a cylindrical type, a flat type, a square type, and a large type used for an electric vehicle and the like, and the present invention can be applied to any shape. The non-aqueous electrolyte secondary battery of the present invention can be used for portable information terminals, portable electronic devices, household small power storage devices, motorcycles, electric vehicles, hybrid electric vehicles, etc., but is not particularly limited to these. is not.
[0054]
【Example】
Hereinafter, the present invention will be specifically described based on examples, but the present invention is not limited to the following examples.
[0055]
<< Example 1 >>
(1) Preparation of negative electrode plate
(1-1) Production of negative electrode plate using negative electrode active material powder
Tables 1 and 2 show the negative electrode active materials used in this example. Table 1 shows a negative electrode active material of a simple metal composed of a Group 4B element or an alloy containing a Group 4B element, and Table 2 shows a composite particle composed of a core particle and a surface layer. As the composite particles, those composed of 20% by weight of core particles and 80% by weight of a surface layer were used.
[0056]
[Table 1]

[0057]
[Table 2]

[0058]
The powder or block of each element constituting the negative electrode active material was melted in a heating and melting tank, and the melt was quenched and solidified by a roll quenching method to obtain a solidified material comprising a crystal phase. After the solidified product was put into a planetary ball mill container, the rotation speed of the drive motor was set to 3700 rpm so that 15 G was applied, and mechanical grinding was performed for 30 minutes or 40 minutes using stainless steel balls having a diameter of 15 mm. Time went. The untreated coagulated material and the material obtained after the mechanical grinding treatment were each classified with a sieve to 45 μm or less to obtain various negative electrode active materials.
[0059]
As a result of observing the obtained negative electrode active material using an electron microscope, it was confirmed that in the composite material shown in Table 2, the entire surface or a part of the surface of the core particles was covered with a surface layer. In addition, X-ray diffraction measurement was performed on the solidified product before the mechanical grinding shown in Tables 1 and 2 to confirm the crystal structure. As a result, each of the detected diffraction peaks was sharp, and the solidified product was good. Crystalline phase. On the other hand, with respect to the material subjected to the mechanical grinding treatment for 30 minutes, each of the detected diffraction peaks began to broaden, so that it was confirmed that the crystalline state had begun to collapse. In these materials, a microcrystalline phase having a crystallite size of 5 to 100 nm remained, which was a low crystalline phase. The half width of the peak at this time was 0.001 to 0.1 °. For the material subjected to the mechanical grinding treatment for 40 hours, each diffraction peak completely disappeared, indicating that the material was an amorphous phase in which a crystal index could not be assigned.
[0060]
A negative electrode plate was manufactured using the negative electrode active material powder material thus manufactured. For 75 parts by weight of the negative electrode active material, 20 parts by weight of carbon powder as a conductive agent and 5 parts by weight of polyvinylidene fluoride resin as a binder were mixed, and these were dispersed in dehydrated N-methyl-2-pyrrolidone. A slurry negative electrode mixture was prepared. This negative electrode mixture was applied on a core material made of copper foil, dried, and then rolled to form a negative electrode active material layer. Thus, a negative electrode plate was completed.
[0061]
(1-2) Preparation of negative electrode plate using thin film negative electrode active material
Table 3 shows the negative electrode active materials used in this example.
Here, a silicon thin film will be described as an example, but a tin thin film can also be manufactured by a generally known method.
[0062]
[Table 3]

[0063]
An electrolytic copper foil having a thickness of 18 μm was used as the core material.
A 5 μm-thick silicon thin film was formed on the electrolytic copper foil by an RF sputtering method in an Ar gas atmosphere, and this thin film was used as a negative electrode active material layer. The thin film production conditions were as follows: single crystal silicon was used as a target, RF power: 400 W, Ar gas flow rate: 50 sccm, and chamber pressure: 0.2 Pa. The substrate was not heated.
[0064]
The silicon thin film produced under the above conditions was found to be an amorphous thin film by Raman spectroscopy. When the thickness of the thin film was measured with a surface roughness meter, it was 5 μm. This value was the same in the case of the tin thin film.
[0065]
The thin film thus obtained was heat-treated in an inert gas to be microcrystallized until the crystallite size became 5 to 100 nm. At this time, the half width of the peak of the X-ray diffraction pattern was 0.6 ° or more. Further, crystallization was performed until the crystallite size exceeded 100 nm by controlling the heat treatment temperature and the like. Each thin film electrode was provided with a portion where a thin film was not formed by a masking process, and a negative electrode lead was pulled out from an exposed portion of the copper foil to complete a negative electrode plate.
[0066]
(2) Production of stacked battery
A laminated lithium secondary battery as shown in FIG. 1 was produced.
The positive electrode plate 12 was produced as follows. A mixture of 85 parts by weight of lithium cobalt oxide powder, 10 parts by weight of carbon powder as a conductive agent, and 5 parts by weight of polyvinylidene fluoride resin as a binder was dispersed in dehydrated N-methyl-2-pyrrolidone, A slurry-like positive electrode mixture was prepared. This positive electrode mixture was applied onto a core material made of aluminum foil, dried, and then rolled to form a positive electrode active material layer, thereby completing a positive electrode plate.
The non-aqueous electrolyte was mixed with a mixed solvent of ethylene carbonate and ethyl methyl carbonate (volume ratio 1: 1) at a concentration of 1.5 mol / l LiPF.₆Was used.
[0067]
The negative electrode plate 13 and the positive electrode plate 12 produced as described above were alternately laminated with the separator 14 interposed therebetween, to produce a stack type electrode plate group. The negative electrode lead 16 was pulled out from the core material of the negative electrode plate 13, and the positive electrode lead 15 was drawn out from the core material of the positive electrode plate 12. Lamination was performed using one negative electrode plate and two positive electrode plates.
After inserting the group of electrode plates laminated in a stack into a battery case 11 made of aluminum foil (Al laminated sheet) having resin sheets on both sides, a non-aqueous electrolyte is injected into the battery case 11 and a lead portion is formed. The opening of the battery case 11 was sealed with a welding seal 17.
[0068]
Further, a laminated battery of a comparative example was manufactured in the same manner as in the above example except that a negative electrode using graphite as an active material was used.
[0069]
(3) Production of wound type battery
A long positive electrode plate and a long negative electrode plate were manufactured using the same materials as those used when the stacked battery was manufactured, and these were used and wound into the same capacity as the stacked battery as shown in FIG. A lithium secondary battery was manufactured.
The negative electrode plate 23 and the positive electrode plate 22 were spirally wound with the separator 24 interposed therebetween, and a flattened electrode group was produced by press working. The electrode group was housed in the battery case 21. The lead was pulled out from the negative electrode plate 23 and connected to the bottom of the battery case 21. The lead was pulled out from the positive electrode plate 22 and connected to a positive electrode terminal (not shown). Then, the non-aqueous electrolyte was injected into the battery case 21, and the opening of the battery case 21 was sealed with a sealing plate.
[0070]
Further, a wound type battery of a comparative example was produced in the same manner as in the above example except that a negative electrode using graphite as an active material was used.
[0071]
(4) Battery evaluation
The battery was charged at a constant current of 1 A until it reached 4.1 V, and then discharged at a constant current of 1 A until it reached 2.5 V, which was defined as one cycle. Further, the discharge capacity (mAh) at the first cycle was measured. This charge / discharge cycle was repeated 100 times, and the ratio of the discharge capacity at the 100th cycle to the discharge capacity at the first cycle was determined as a percentage, and was defined as a capacity retention rate X (%) after 100 cycles. Further, the thickness Y (mm) of the battery in the charged state at the 100th cycle was measured. The thickness of the battery before the start of charge / discharge was 5 mm. The test was performed in a thermostat at 20 ° C. The results are shown in Tables 1 to 3.
[0072]
[Evaluation of batteries using single metal or alloy negative electrode active materials]
As can be seen from the results in Table 1, the discharge capacity in the first cycle is 900 mAh in both the stacked type and the wound type batteries, which is higher than the discharge capacity (700 mAh) when graphite is used as the negative electrode active material. it was high.
In the stacked battery, when the active material was in a low crystalline phase, the capacity retention ratio X was 80 to 90%, and the battery thickness Y was 5 mm. When the active material was an amorphous phase, the capacity retention ratio X was 90 to 95%, and the thickness Y of the battery was 5 mm. In a battery in which the negative electrode active material had a low crystalline phase or an amorphous phase, no change was observed in the thickness of the battery while maintaining a high capacity retention ratio. That is, similar to the case where graphite was used as the negative electrode active material, it was possible to suppress swelling of the battery while maintaining high cycle characteristics.
This is presumably because in the low crystalline phase or the amorphous phase, the crystallites are irregularly oriented, so that even if lithium is inserted, the volume of the whole particle does not change much. In the amorphous phase, since the crystallites were more irregularly oriented, a higher capacity retention ratio X was obtained than in the case where the negative electrode active material having a low crystalline phase was used.
[0073]
In the case where the active material was in the crystalline phase, in all of the negative electrode active materials, no change was observed in the thickness Y of the battery, but the capacity retention ratio X was reduced to 30 to 50%.
This is considered to be because the crystal phase has a large crystallite size, and a large volume change occurs when lithium is inserted.
[0074]
On the other hand, in the case of a wound type battery, when the active material is in a crystalline phase, a low crystalline phase, or an amorphous phase, in all the negative electrode active materials, the value of the capacity retention ratio X is substantially the same as in the case of the laminated structure. Value. However, the thickness Y of the battery was 6 mm, and the battery swelled. For comparison, in the wound type battery in which the negative electrode active material was graphite, no swelling of the battery was observed.
This is considered to be due to the fact that the R portion of the electrode group of the wound battery is strongly fixed, so that swelling due to buckling is added, thereby increasing the swelling of the battery.
[0075]
[Evaluation of battery using composite particle negative electrode active material]
As can be seen from the results in Table 2, measurement results having the same tendency as in Table 1 were obtained even when the negative electrode active material was composite particles. In the stacked battery in which the negative electrode active material had a low crystalline phase or an amorphous phase, no change was observed in the thickness of the battery while maintaining a high capacity retention rate.
This is because, since at least one of the core particles and the surface layer constituting the composite particles has a low crystalline phase or an amorphous phase, even if lithium is inserted, stress relaxation of the entire particles becomes possible. it is conceivable that.
Even in a stacked battery in which the active material was a crystalline phase, the capacity retention ratio X was reduced to 50 to 70%, although no change was observed in the battery thickness Y.
On the other hand, even when the structure of the battery was a wound type, the swelling of the battery was observed in all the negative electrode active materials as in Table 1.
[0076]
[Evaluation of battery using thin film negative electrode active material]
As can be seen from the results in Table 3, even when the negative electrode active material was a thin film of Si or Sn, measurement results having the same tendency as in Table 1 were obtained. In the stacked battery in which the negative electrode active material had a low crystalline phase or an amorphous phase, no change was observed in the thickness of the battery while maintaining a high capacity retention rate.
This is presumably because in the low crystalline phase or the amorphous phase, the crystallites are irregularly oriented, so that even if lithium is inserted, the volume of the whole particle does not change much.
Even in a stacked battery in which the active material was a crystalline phase, the capacity retention ratio X was reduced to 50%, although no change was observed in the battery thickness Y.
On the other hand, even when the structure of the battery was a wound type, the swelling of the battery was observed in all the negative electrode active materials as in Table 1.
[0077]
<< Example 2 >>
In order to investigate the range of the negative electrode capacity density in detail, a stacked type and a wound type battery were manufactured using a Si thin film negative electrode active material. The negative electrode capacity density was measured by changing the film formation density of the thin film and changing the density every 400 mAh / cc in the range of 400 to 1200 mAh / cc.
[0078]
The battery was charged at a constant current of 1 A until it reached 4.1 V, and then discharged at a constant current of 1 A until it reached 2.5 V, which was defined as one cycle. Further, the discharge capacity (mAh) at the first cycle was measured. This charge / discharge cycle was repeated 100 times, and the ratio of the discharge capacity at the 100th cycle to the discharge capacity at the first cycle was determined as a percentage, and was defined as a capacity retention rate X (%) after 100 cycles. Further, the thickness Y (mm) of the battery in the charged state at the 100th cycle was measured. The thickness of the battery before the start of charge / discharge was 5 mm. The test was performed in a thermostat at 20 ° C. Table 4 shows the results.
[0079]
[Table 4]

[0080]
As can be seen from the results in Table 4, when the negative electrode capacity density was 400 mAh / cc, the same value as in Example 1 was obtained in all the crystal structures in the stacked battery. On the other hand, in the wound type battery, the thickness Y (5.5 mm) of the battery could be suppressed in all crystal structures as compared with the result of Example 1. However, in each of the batteries, the discharge capacity in the first cycle was 600 mAh, which was lower than the value of the discharge capacity (700 mAh) when graphite was used as the negative electrode active material.
This is presumably because the lower the negative electrode capacity density of the negative electrode plate, the smaller the amount of the active material, and the smaller the amount of stored lithium than in the case of graphite.
[0081]
When the negative electrode capacity density was 500 to 1000 mAh / cc, in the wound type battery, in all the negative electrode active materials, the higher the negative electrode capacity density was, the larger the battery thickness Y was. On the other hand, in the stacked battery, the same values as in Example 1 were obtained for all the negative electrode active materials. In each of the batteries, the discharge capacity in the first cycle was higher as the negative electrode capacity density was higher. These values were higher than the discharge capacity (700 mAh) when graphite was used as the negative electrode active material.
[0082]
When the negative electrode capacity density was 1200 mAh / cc, the discharge capacity at the first cycle obtained the highest value in both the stacked type and the wound type batteries. However, the capacity retention ratio X sharply decreased.
This is because, when the negative electrode plate has an excessively large negative electrode capacity density, the amount of the active material becomes excessive and the space in the electrode plate is reduced, so that the amount of the electrolyte injected into the electrode plate is also reduced. Therefore, the amount of the electrolyte required for transporting lithium ions becomes insufficient with respect to the amount of the active material. Therefore, it is considered that the charge transfer resistance of the negative electrode plate increases and the cycle characteristics deteriorate.
[0083]
The mixing ratio of the elements constituting the negative electrode active material is not particularly limited. When the negative electrode active material is a composite particle, the core particle is a phase containing Sn and Si as main elements, the surface layer covers all or a part of the core particle surface, and at least one of the phases is amorphous. As long as it is in a quality state, the charged composition is not particularly limited. Further, the core particles are formed not only from Sn and Si, but also from others, for example, O, C, N, S, Ca, Mg, Al, Fe, W, V, Ti, Cu, Cr, Co, Elements such as P may be present in trace amounts. The surface layer was formed not only from the alloys shown in Table 2 but also from other alloys such as O, C, N, S, Ca, Mg, Al, Fe, W, V, Ti, Cu, Cr, Co, Elements such as P may be present in trace amounts.
[0084]
As a method for manufacturing the negative electrode plate, a vacuum deposition method, an ion plating method, a sputtering method, a chemical vapor reaction method, or an electrolytic plating method may be used in addition to the above-described methods. In addition, it was confirmed that the batteries produced by these methods also had a high capacity retention ratio due to charge / discharge cycles.
[0085]
In this embodiment, LiCoO is used as the positive electrode active material.₂Was used, but LiMn₂O₄, LiNiO₂Needless to say, the same effect can be obtained also in the case of combining with a positive electrode active material having reversibility with respect to charge and discharge.
[0086]
<< Example 3 >>
The structure of the battery case of the present invention was studied.
(1) Production of positive electrode plate
90 parts by weight of the positive electrode active material, 5 parts by weight of acetylene black as a conductive agent, and 5 parts by weight of polyvinylidene fluoride resin as a binder were mixed, and these were dispersed in dehydrated N-methyl-2-pyrrolidone. Thus, a slurry-like positive electrode mixture was prepared. This positive electrode mixture was applied on a core material made of aluminum foil, dried, and then rolled to form a positive electrode active material layer, thereby completing a positive electrode plate.
[0087]
(2) Preparation of negative electrode plate
TiSi₂90 parts by weight of powder, 5 parts by weight of graphite as a conductive agent, and 5 parts by weight of polyvinylidene fluoride resin as a binder, and these were dispersed in dehydrated N-methyl-2-pyrrolidone to obtain a slurry. A negative electrode mixture was prepared. This negative electrode mixture was applied onto a core material made of copper foil, dried, and then rolled to form a negative electrode active material layer, thereby completing a negative electrode plate.
[0088]
(3) Production of stacked battery
The positive electrode plate and the negative electrode plate produced as described above were alternately laminated with a separator interposed therebetween, to produce a stack type electrode plate group. The negative electrode lead was pulled out from the core material of the negative electrode plate, and the positive electrode lead was drawn out from the core material of the positive electrode plate. Lamination was performed using one negative electrode plate and two positive electrode plates.
After inserting the stacked electrode group into a battery case made of aluminum foil (Al laminated sheet) having resin sheets on both sides, a non-aqueous electrolyte is injected into the battery case 11, and a lead portion welding seal is formed. To seal the opening of the battery case. The non-aqueous electrolyte was mixed with a mixed solvent of ethylene carbonate and ethyl methyl carbonate (volume ratio 1: 1) at a concentration of 1.5 mol / l LiPF.₆Was used.
[0089]
(4) Production of wound type battery
A long positive electrode plate and a long negative electrode plate were manufactured using the same materials as those used when manufacturing the stacked battery, and a wound lithium secondary battery having the same capacity as the stacked battery was manufactured using these materials. did.
The negative electrode plate and the positive electrode plate were spirally wound with a separator interposed therebetween, and a flattened electrode plate group was produced by press working. The electrode group was housed in a battery case. The lead was pulled out from the negative electrode plate and connected to the bottom of the battery case. The lead was pulled out from the positive electrode plate and connected to the positive electrode terminal. Then, the nonaqueous electrolyte was injected into the battery case, and the opening of the battery case was sealed with a sealing plate.
[0090]
(5) Battery case molding
A battery case was formed by a multi-stage pressing method using a pure aluminum-based (JIS-1000) composition material as a raw material for the battery case of the present embodiment. Then, before performing the step of finally closing the case, the inside of the battery case was depressurized, so that the surface of the case facing the electrode surface was recessed inside the battery case. FIG. 3 shows a schematic sectional view of an example of the battery case. Example 1 The ratio (B / A) of the thickness A (mm) of the end portion of the battery case to the thickness B (mm) of the center portion was in the range of 0.5 ≦ B / A ≦ 1.0, and the first embodiment Similarly to the above, the discharge capacity (mAh) at the first cycle, the capacity retention X (%) after 100 cycles, and the thickness Y (mm) of the battery were measured.
[0091]
[Evaluation of battery]
The battery was discharged to 2.5 V at a discharge current of 1 C, and the shape of the battery was measured. Table 5 shows the results.
[0092]
[Table 5]

[0093]
As can be seen from the results in Table 5, when B / A was 0.5, the capacity retention ratio X was a fairly small value in both the stacked type and the wound type batteries.
This is considered to be because the concave portion of the case has an excessive concave portion, and a large pressing force is applied to the electrode plate group. In particular, in the charging process, the electrolyte is pushed out from the inside of the electrode plate or the separator, and the electrochemical reaction cannot be performed smoothly, so that the cycle characteristics are considered to be deteriorated.
[0094]
When B / A was 0.6 to 0.95, in the wound type battery, as the value of B / A increased, the thickness Y of the battery also increased. In the stacked battery, the thickness Y of the battery did not change.
This is because the swelling of the electrode group caused by the charge / discharge cycle of the battery can be reduced by pushing the concave portion of the battery case outward. The thickness A of the end of the battery case does not change due to the swelling of the electrode group.
[0095]
When B / A was 1.0, the capacity retention ratio X was a fairly small value in both the stacked type and the wound type batteries.
This is because the compressive force on the electrode group becomes extremely small, so that the particle-to-particle contact inside the electrode group becomes insufficient compared with the case where B / A is smaller than 1.0, and the electronic resistance becomes large. Therefore, it is considered that the electrochemical reaction is not smoothly performed, so that the cycle characteristics are deteriorated.
[0096]
The battery case of this example was manufactured using a pure aluminum-based (JIS-1000-based) composition material, but other compositions such as iron, nickel, copper, stainless steel, and Al-Mn-based aluminum An alloy, titanium, zinc, or the like may be used.
In addition, a method such as casting, hot rolling, cold rolling, or annealing may be used as a method for producing the battery case, instead of the multi-stage pressing method. Further, a manufacturing method such as welding or caulking may be used instead of integral molding.
Further, as described above, the recess may be adjusted by reducing the pressure inside the case before sealing in the final step of assembly. May be.
[0097]
【The invention's effect】
According to the present invention, by improving the negative electrode active material and employing a stacked electrode plate group, the battery is prevented from swelling during charging and discharging, and has a high capacity and excellent cycle characteristics. A secondary battery can be provided. Further, in the battery case that houses the non-aqueous electrolyte secondary battery, the surface facing the electrode surface has a recess inside the case, so that the swelling of the electrode plate group that occurs during charging and discharging pushes the recess outward. The thickness of the end of the battery case is not changed.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view of an example of a prismatic stacked lithium secondary battery according to Embodiment 1 of the present invention.
FIG. 2 is a schematic cross-sectional view of an example of a rectangular wound lithium secondary battery according to a comparative example.
FIG. 3 is a schematic sectional view of an example of a battery case according to Embodiment 3 of the present invention.
[Explanation of symbols]
11, 21 Battery case
12,22 Positive electrode plate
13,23 Negative electrode plate
14, 24 separator
15 Positive electrode lead
16 Negative electrode lead
17 Lead welding seal

Claims (8)

A non-aqueous electrolyte secondary battery comprising an electrode group and a non-aqueous electrolyte in which a positive electrode capable of inserting and extracting lithium and a negative electrode capable of inserting and extracting lithium are alternately stacked via a separator,
The positive electrode comprises a positive electrode active material layer and a core material supporting the same, and the negative electrode includes a negative electrode active material layer and a core material supporting the same,
The negative electrode active material layer is made of at least one selected from the group consisting of a simple metal composed of a Group 4B element and an alloy containing a Group 4B element,
The non-aqueous electrolyte secondary battery, wherein the negative electrode active material layer has a volume capacity density of 500 mAh / cc or more. The non-aqueous electrolyte secondary battery according to claim 1, wherein the volume capacity density is 600 to 1000 mAh / cc. The non-aqueous electrolyte secondary battery according to claim 1, wherein the group 4B element is at least one selected from the group consisting of Si and Sn. 2. The non-aqueous electrolyte secondary battery according to claim 1, wherein at least one selected from the group consisting of simple metals and alloys is at least one selected from the group consisting of an amorphous phase and a low crystalline phase. The non-aqueous electrolyte secondary battery according to claim 1, wherein at least one crystallite size selected from the group consisting of the elemental metal and the alloy is 5 to 100 nm. The alloy has a composition of M _α Sn _β Si _γ ,
In the above composition,
(A) M is at least one selected from the group consisting of Ti, Ni, Cu and Fe;
(B) 0.1 ≦ α ≦ 10,
(C) 0 ≦ β ≦ 10 and (d) 0 ≦ γ ≦ 30
Is satisfied, and β and γ are not simultaneously 0. The alloy is a composite particle comprising a core layer and a surface layer covering all or a part of the core particle surface,
The core particles include at least one selected from the group consisting of Si and Sn,
The said surface layer is a solid solution or an intermetallic compound containing at least 1 sort (s) selected from the group consisting of Ti, Ni, Cu, and Fe, and at least 1 sort (s) selected from the group consisting of Si and Sn. Non-aqueous electrolyte secondary battery. Furthermore, it has a battery case for housing the electrode group and the non-aqueous electrolyte,
The surface facing the electrode surface of the battery case is recessed inside the case, and the ratio of the thickness (A) at the end of the case to the thickness (B) at the center: B / A is 0.6. The non-aqueous electrolyte secondary battery according to claim 1, wherein <B / A <0.95 is satisfied.

Images