JP2004047353A - Lithium secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lithium secondary battery having battery capacity hardly degraded even by repetition of charge and discharge, and having an excellent cycle characteristic and excellent storage stability. <P>SOLUTION: This lithium secondary battery is equipped, in a battery case, with an internal electrode composed by rolling or stacking a positive electrode containing a positive electrode active material and a negative electrode containing a negative electrode active material by interposing a separator, and filled with a nonaqueous electrolytic solution containing a lithium compound as an electrolyte. The lithium secondary battery is characterized by including an oxidizer (excluding the positive electrode active material) in the battery case. <P>COPYRIGHT: (C)2004,JPO

Description

【００２０】電池ケース内部に酸化剤を含有することにより、上述した充放電の繰り返しによっても電池容量が低下し難く、サイクル特性、及び保存性に優れるといった効果を奏するメカニズムの詳細は不明であるが、酸化剤が発生する酸素によって、電解液の分解等を抑える容量劣化しにくいＳＥＩ層が電極表面に形成されることにより、電池特性の劣化が抑制されるものと推測される。
【００２１】即ち、本発明のリチウム二次電池では、酸化剤は正・負両電極、及び非水電解液に直接接触する箇所に含有される。従って、本発明においては、酸化剤を、正極、負極、及び非水電解液からなる群より選択される少なくともいずれかに含有することが好ましい。また、これらの箇所に酸化剤を含有することは、電池の製造過程において簡単に実施できるために、電池特性の向上のみならず、製造コストの面においても好ましい。
【００２２】本発明においては、酸化剤を、正極及び／又は負極に含有する場合に、この酸化剤を、正極及び／又は負極の表面に偏在した状態で含有することが好ましい。ここで、「正極及び／又は負極の表面に偏在した状態で含有する」とは、酸化剤が、正極及び／又は負極の表面であって、非水電解液に直接的に接触する部位に偏在し、電極活物質と均一に混ざり合っていない状態のことを意味する。このように構成することにより、電池特性の劣化が更に抑制される。なお、このメカニズムについては明らかではないが、非水電解液が酸化剤と直接的に接触することで何らかの化学変化等を起こし、次いで電極活物質と接触することにより、組成が変化したＳＥＩ層が電極表面に形成され、電池特性の劣化が抑制されるものと推測される。
【００２３】本発明においては、酸化剤を正極及び／又は負極に含有する場合、酸化剤の、正極活物質又は負極活物質に対する含有割合が０．１〜２０質量％であることが好ましく、０．５〜１５質量％であることが更に好ましく、１〜１０質量％であることが特に好ましい。０．１質量％未満であると、酸化剤を含有した効果が発揮され難くなるために好ましくなく、２０質量％超であると、電池容量の低下等、かえって他の電池特性に影響を及ぼす場合も想定されるために好ましくない。
【００２４】本発明においては、酸化剤が粉末状であるとともに、平均粒径が０．０５〜１０μｍであることが好ましい。このような規定を満足する粉末状の酸化剤は酸素を放出し易く、この酸化剤を電池ケース内部に含有する本発明のリチウム二次電池は、より長期保存性及びサイクル特性に優れている。また、より一層優れた長期保存性及びサイクル特性をリチウム二次電池に付与するといった観点からは、酸化剤の平均粒径は０．１〜５μｍであることが更に好ましく、０．３〜１μｍであることが特に好ましい。
【００２５】次に、本発明の別の側面について説明する。本発明の別の側面は、電池ケース内部に、正極活物質を含む正極及び負極活物質を含む負極を、セパレータを介して捲回又は積層してなる内部電極体を備えるとともに、リチウム化合物を電解質とする非水電解液が充填されたリチウム二次電池であり、電池ケース内部に、バナジウム化合物を含有することを特徴とするものである。以下、その詳細について説明する。
【００２６】電池ケース内部にバナジウム化合物を含有する本発明のリチウム二次電池は、バナジウム化合物を含有しないリチウム二次電池に比して充放電の繰り返しによっても電池容量が低下し難く、サイクル特性に優れており、また、長期間に渡って保存する場合であっても、そのサイクル特性は劣化し難いものである。なお、酸化剤に代えてバナジウム化合物を含有すること以外の電池の構成は、既に述べた通りである。
【００２７】本発明においては、バナジウム化合物を、正極及び／又は負極に含有することが好ましい。また、これらの箇所にバナジウム化合物を含有させることは、電池の製造過程において簡単に実施できるために、電池特性の向上のみならず、製造コストの面においても好ましい。また、本発明においては、バナジウム化合物を、正極及び／又は負極の表面に偏在した状態で含有することが好ましい。このように構成することにより、電池特性の劣化が更に抑制される。なお、このメカニズムについては明らかではないが、前述の、酸化剤を含有する場合と同様であると推測される。
【００２８】本発明においては、バナジウム化合物の、正極活物質又は負極活物質に対する含有割合が０．１〜２０質量％であることが好ましく、０．５〜１５質量％であることが更に好ましく、１〜１０質量％であることが特に好ましい。０．１質量％未満であると、バナジウム化合物を含有した効果が発揮され難くなるために好ましくなく、２０質量％超であると、電池容量の低下等、かえって他の電池特性に影響を及ぼす場合も想定されるために好ましくない。
【００２９】本発明においては、バナジウム化合物が粉末状であるとともに、平均粒径が０．０５〜１０μｍであることが好ましい。このような規定を満足する粉末状のバナジウム化合物は、非水電解液との単位体積当りの接触面積が十分に大きく、このバナジウム化合物を電池ケース内部に含有する本発明のリチウム二次電池は、より長期保存性及びサイクル特性に優れている。また、より一層優れた長期保存性及びサイクル特性をリチウム二次電池に付与するといった観点からは、バナジウム化合物の平均粒径は０．１〜５μｍであることが更に好ましく、０．３〜１μｍであることが特に好ましい。
【００３０】本発明においては、サイクル特性等の向上といった効果の面、及び取扱いや入手容易性といった観点から、バナジウム化合物が五酸化二バナジウム（Ｖ_２Ｏ_５）であることが好ましい。
【００３１】次に、本発明の更に別の側面について説明する。本発明の更に別の側面は、電池ケース内部に、正極活物質を含む正極及び負極活物質を含む負極を、セパレータを介して捲回又は積層してなる内部電極体を備えるとともに、リチウム化合物を電解質とする非水電解液が充填されたリチウム二次電池であり、電池ケース内部に、過塩素酸塩を含有することを特徴とするものである。以下、その詳細について説明する。
【００３２】電池ケース内部に過塩素酸塩を含有する本発明のリチウム二次電池は、過塩素酸塩を含有しないリチウム二次電池に比して充放電の繰り返しによっても電池容量が低下し難く、サイクル特性に優れており、また、長期間に渡って保存する場合であっても、そのサイクル特性は劣化し難いものである。なお、酸化剤やバナジウム化合物に代えて過塩素酸塩を含有すること以外の電池の構成は、既に述べた通りである。
【００３３】更に、本発明においては、過塩素酸塩を非水電解液に含有することが好ましく、電池特性の向上のみならず、電池の製造過程において簡単に含有させることができるために、製造コストの面においても好ましい。また、本発明においては、過塩素酸塩の、電解質に対する含有割合が０．１〜２０ｍｏｌ％であることが好ましく、０．５〜１５ｍｏｌ％であることが更に好ましく、１〜１０ｍｏｌ％であることが特に好ましい。０．１ｍｏｌ％未満であると、過塩素酸塩を含有した効果が発揮され難くなるために好ましくなく、２０ｍｏｌ％超であると、電池容量の低下等、かえって他の電池特性に影響を及ぼす場合も想定されるために好ましくない。なお、過塩素酸塩の具体例としては過塩素酸リチウム（ＬｉＣｌＯ_４）を挙げることができる。
【００３４】本発明のリチウム二次電池は、電池ケース内部に、酸化剤、バナジウム化合物、又は過塩素酸塩を含有することを特徴とし、充放電の繰り返しによっても電池容量が低下し難く、サイクル特性、及び保存性に優れるといった効果を奏するものである。従って、その他の材料や電池構造には何ら制限はない。以下、リチウム二次電池の構造、及びこれを構成する主要部材、並びにリチウム二次電池の製造方法について概説する。
【００３５】リチウム二次電池を構成する内部電極体の構造の一例として、容量の大きい電池に用いられる捲回型電極体を挙げることができる。図１の斜視図に示されるように、捲回型電極体１は、正極板２と負極板３とを、多孔性ポリマーからなるセパレータ４を介して正極板２と負極板３とが直接に接触しないように巻芯１３の外周に捲回して構成される。正極板２及び負極板３（以下、「電極板２，３」と記す）に取り付けられている電極リード５，６の数は最低１本あればよく、複数の電極リード５，６を設けて集電抵抗を小さくすることもできる。
【００３６】内部電極体の他の構造としては、コイン電池に用いられる単セル型の電極体を複数段に積層してなる積層型内部電極体を挙げることができる。図２に示すように、積層型電極体７は、所定形状の正極板８と負極板９（以下、「電極板８，９」と記す）とをセパレータ１０を挟み交互に積層したもので、１枚の電極板８，９に少なくとも１本の電極リード１１，１２を取り付ける。電極板８，９の使用材料や作製方法等は、図１に示す捲回型電極体１における電極板２，３等と同様である。
【００３７】次に、図１に示す捲回型電極体１を例に、その構成について更に詳細に説明する。正極板２は集電基板の両面に正極活物質を塗工することによって作製される。集電基板としては、アルミニウム箔やチタン箔等の正極電気化学反応に対する耐蝕性が良好である金属箔が用いられるが、箔以外にパンチングメタル又はメッシュ（網）を用いることもできる。また、正極活物質としては、マンガン酸リチウム（ＬｉＭｎ_２Ｏ_４）やコバルト酸リチウム（ＬｉＣｏＯ_２）、ニッケル酸リチウム（ＬｉＮｉＯ_２）等のリチウム遷移金属複合酸化物が好適に用いられる。なお、これらの正極活物質にアセチレンブラック等の炭素微粉末を導電助剤として加えることが好ましい。
【００３８】ここで、本発明においては、ＬｉとＭｎを主成分とした立方晶スピネル構造を有するマンガン酸リチウム（以下、単に「マンガン酸リチウム」と記す）を用いると、他の正極活物質を用いた場合と比較して、電極体の抵抗を小さくすることができるために好ましい。前述した、本発明の「充放電の繰り返しによっても電池容量が低下し難い」という効果は、この内部抵抗の低減の効果と組み合わせることで、より顕著に現れて電池のサイクル特性の向上が図られるために好ましい。
【００３９】なお、マンガン酸リチウムは、このような化学量論組成（ストイキオメトリー組成）のものに限定されるものではなく、Ｍｎの一部を１以上の他の元素で置換した、一般式ＬｉＭ_ＸＭｎ_２−ＸＯ_４（Ｍは置換元素、Ｘは１分子中における置換元素Ｍの構成比を示す）で表されるマンガン酸リチウムも好適に用いられる。このような元素置換を行ったマンガン酸リチウムにおいては、Ｌｉ／Ｍｎ比が０．５超となる。
【００４０】置換元素Ｍとしては、以下、元素記号で列記するが、Ｌｉ、Ｆｅ、Ｍｎ、Ｎｉ、Ｍｇ、Ｚｎ、Ｂ、Ａｌ、Ｃｏ、Ｃｒ、Ｓｉ、Ｔｉ、Ｓｎ、Ｐ、Ｖ、Ｓｂ、Ｎｂ、Ｔａ、Ｍｏ、Ｗを挙げることができ、理論上、Ｌｉは＋１価、Ｆｅ、Ｍｎ、Ｎｉ、Ｍｇ、Ｚｎは＋２価、Ｂ、Ａｌ、Ｃｏ、Ｃｒは＋３価、Ｓｉ、Ｔｉ、Ｓｎは＋４価、Ｐ、Ｖ、Ｓｂ、Ｎｂ、Ｔａは＋５価、Ｍｏ、Ｗは＋６価のイオンとなり、ＬｉＭｎ_２Ｏ_４中に固溶する元素である。但し、Ｃｏ、Ｓｎについては＋２価の場合、Ｆｅ、Ｓｂ及びＴｉについては＋３価の場合、Ｍｎについては＋３価、＋４価の場合、Ｃｒについては＋４価、＋６価の場合もあり得る。
【００４１】従って、各種の置換元素Ｍは混合原子価を有する状態で存在する場合があり、また、酸素の量については、必ずしもストイキオメトリー組成で表されるように４であることを必要とせず、結晶構造を維持するための範囲内で欠損して、又は過剰に存在していても構わない。
【００４２】正極活物質の塗工は、正極活物質粉末に溶剤や結着剤等を添加して作製したスラリー又はペーストを、ロールコータ法等を用いて、集電基板に塗布・乾燥することで行われ、その後に必要に応じてプレス処理等が施される。
【００４３】負極板３は、正極板２と同様にして作製することができる。負極板３の集電基板としては、銅箔又はニッケル箔等の負極電気化学反応に対する耐蝕性が良好な金属箔が好適に用いられる。負極活物質としては、ソフトカーボンやハードカーボンといったアモルファス系炭素質材料や人造黒鉛や天然黒鉛等の高黒鉛化炭素質粉末が用いられる。
【００４４】本発明において、酸化剤又はバナジウム化合物を正極及び／又は負極に含有する場合には、上述の方法により正極板及び負極板を作製した後、少なくとも一方の電極板の表面に所定量の酸化剤を散布し（振り掛け）、次いで、プレス加工を施せばよい。酸化剤又はバナジウム化合物の散布に際しては、略均一に電極板の表面を覆うように散布すればよく、またプレス加工に際しては、散布された酸化剤又はバナジウム化合物が容易に脱落しない程度の適度の圧力で実施すればよい。
【００４５】セパレータ４としては、マイクロポアを有するＬｉイオン透過性のポリエチレンフィルム（ＰＥフィルム）を、多孔性のＬｉイオン透過性のポリプロピレンフィルム（ＰＰフィルム）で挟んだ三層構造としたものが好適に用いられる。これは、電極体の温度が上昇した場合に、ＰＥフィルムが約１３０℃で軟化してマイクロポアが潰れ、Ｌｉイオンの移動即ち電池反応を抑制する安全機構を兼ねたものである。そして、このＰＥフィルムをより軟化温度の高いＰＰフィルムで挟持することによって、ＰＥフィルムが軟化した場合においても、ＰＰフィルムが形状を保持して正極板２と負極板３の接触・短絡を防止し、電池反応の確実な抑制と安全性の確保が可能となる。
【００４６】この電極板２，３とセパレータ４の捲回作業時に、電極板２，３において電極活物質の塗工されていない集電基板が露出した部分に、電極リード５，６がそれぞれ取り付けられる。電極リード５，６としては、それぞれの電極板２，３の集電基板と同じ材質からなる箔状のものが好適に用いられる。電極リード５，６の電極板２，３への取り付けは、超音波溶接やスポット溶接等を用いて行うことができる。
【００４７】次に、本発明のリチウム二次電池に用いられる非水電解液について説明する。溶媒としては、エチレンカーボネート（ＥＣ）、ジエチルカーボネート（ＤＥＣ）、ジメチルカーボネート（ＤＭＣ）、プロピレンカーボネート（ＰＣ）といった炭酸エステル系のものや、γ−ブチロラクトン、テトラヒドロフラン、アセトニトリル等の単独溶媒又は混合溶媒が好適に用いられる。本発明においては、特に電解液の電導度及び高温安定性等の観点から、環状カーボネートと鎖状カーボネートの混合溶媒を好適に用いることができる。
【００４８】電解質としては、六フッ化リン酸リチウム（ＬｉＰＦ_６）やホウフッ化リチウム（ＬｉＢＦ_４）等のリチウム錯体フッ素化合物、又は過塩素酸リチウム（ＬｉＣｌＯ_４）といったリチウムハロゲン化物を挙げることができ、これらのうちの１種類、又は２種類以上を上述した有機溶媒（混合溶媒）に溶解して用いる。特に、本発明においては、酸化分解が起こり難く非水電解液の導電性の高いＬｉＰＦ_６を用いることが好ましい。
【００４９】本発明において、酸化剤、バナジウム化合物、又は過塩素酸塩を非水電解液に含有する場合には、上述の方法により調製した非水電解液に所定量の酸化剤、バナジウム化合物、又は過塩素酸塩を溶解すればよい。
【００５０】リチウム二次電池の組立に当たっては、先ず、電流を外部に取り出すための端子との電極リード５，６との導通を確保しつつ、作製した捲回型電極体１を電池ケースに挿入して安定な位置にホールドした後、上述した非水電解液を含浸させる。次いで、電池ケースを封止して、本発明のリチウム二次電池を得ることができる。なお、電池ケース内部に含有させる酸化剤が、空気、酸素又はオゾン等の気体である場合には、これらの気体を含む雰囲気下において電池の組み立て、非水電解液の含浸を行えばよい。
【００５１】以上、本発明に係るリチウム二次電池について、その実施形態を示しながら説明してきたが、本発明が上記の実施形態に限定されるものでないことはいうまでもない。また、本発明に係るリチウム二次電池は、特に、電池容量が２Ａｈ以上である大型の電池に好適に採用されるが、このような容量以下の電池に適用することを妨げるものではない。また、本発明のリチウム二次電池は、大容量、低コスト、高信頼性という特徴を生かし車載用電池として、さらには、電気自動車又はハイブリッド電気自動車のモータ駆動用電源に用いることが好ましいとともに、高電圧を必要とされるエンジン起動用としても好適に用いることができる。
【００５２】
【実施例】以下、本発明の具体的な実施結果を説明する。
【００５３】
（実施例１〜１３）
ＬｉＭｎ_２Ｏ_４スピネルを正極活物質とし、これに導電助剤としてアセチレンブラックを外比で４質量％添加したものに、更に溶剤、バインダを加えて調製した正極剤スラリーを、厚さ２０μｍのアルミニウム箔の両面にそれぞれ約１００μｍの厚みとなるように塗工し、その表面上に、表２に示す含有量（質量％）となるようにＶ_２Ｏ_５粉末を均一に振り掛けた後にプレス加工して、正極板を作製した。なお、用いたＶ_２Ｏ_５の平均粒径は表２に示す通りである。
【００５４】グラファイトを負極活物質として、厚さ１０μｍの銅箔の両面にそれぞれ約８０μｍの厚みとなるように塗工して負極板を作製した。得られた正極板と負極板とを、セパレータ（ＰＰ／ＰＥ／ＰＰ（三層））を介して捲回することにより、図１に示すような構成の捲回型電極体１を作製した。
【００５５】ＥＣ、ＤＭＣ、及びＤＥＣの各種有機溶媒を体積比で１：１：１となるように混合して混合溶媒を調製し、これに１ｍｏｌ／ｌの濃度となるように電解質であるＬｉＰＦ_６を溶解して非水電解液を調製した。
【００５６】捲回型電極体を収納した電池ケースに非水電解液を充填し、電池ケースを封止して電池を作製した（実施例１〜１３）。なお、電池の作製は全てドライプロセスにより行った。更に、電池の封止不良等による電池外部からの水分浸入等の影響も排除した。なお、各電池の初回充電後の電池容量は約８Ａｈであった。
【００５７】
（実施例１４〜２６）
Ｖ_２Ｏ_５粉末を用いないこと以外は、前述の実施例１〜１３の場合と同様の方法により、正極板を作製した。また、グラファイトを負極活物質として、厚さ１０μｍの銅箔の両面にそれぞれ約８０μｍの厚みとなるように塗工し、その表面上に、表２に示す含有量（質量％）となるようにＶ_２Ｏ_５粉末を均一に振り掛けた後にプレス加工して、負極板を作製した。なお、用いたＶ_２Ｏ_５の平均粒径は表２に示す通りである。得られた正極板と負極板とを、セパレータ（ＰＰ／ＰＥ／ＰＰ（三層））を介して捲回することにより、図１に示すような構成の捲回型電極体１を作製した。
【００５８】次いで、実施例１〜１３の場合と同様の方法により、捲回型電極体を収納した電池ケースに非水電解液を充填し、電池ケースを封止して電池を作製した（実施例１４〜２６）。なお、各電池の初回充電後の電池容量は約８Ａｈであった。
【００５９】
（実施例２７）
Ｖ_２Ｏ_５粉末に代えてＢｉ_２Ｏ_３粉末を用いること以外は、前述の実施例１〜１３の場合と同様の方法により電池を作製した（実施例２７）。なお、作製した電池の初回充電後の電池容量は約８Ａｈであった。
【００６０】
（実施例２８〜３４）
Ｖ_２Ｏ_５粉末を用いず、かつ、ＬｉＣｌＯ_４を非水電解液に溶解すること以外は、前述の実施例１〜１３の場合と同様の方法により電池を作製した（実施例２８〜３４）。なお、ＬｉＣｌＯ_４の含有量（ｍｏｌ％）は表２に示す通りである。また、作製した各電池の初回充電後の電池容量は約８Ａｈであった。
【００６１】
（比較例１）
Ｖ_２Ｏ_５粉末を用いないこと以外は、前述の実施例１〜１３の場合と同様の方法により電池を作製した（比較例１）。なお、作製した電池の初回充電後の電池容量は約８Ａｈであった。
【００６２】
（電池特性の評価）
１．サイクル試験：上述した実施例１〜３４、及び比較例１の各リチウム二次電池についてサイクル試験行った。１サイクルは、放電深度５０％の充電状態の電池を、８Ａ定電流、４．１Ｖ定電圧にて放電後、８Ａ定電流で再び５０％の充電状態とするパターンに設定した。また、０．２Ｃの電流強さで充電停止電圧４．１Ｖ、放電停止電圧２．５Ｖとした容量測定を行い、１００サイクル経過後の電池容量を初回の電池容量で除することにより、容量維持率（％：ｎ＝５平均）を求めた。結果を表２に示す。
【００６３】２．内部抵抗の測定：各電池の内部抵抗を、８Ａで放電を開始したときの電圧降下から計算した。即ち、充電後の休止中放電直前の電池端子電圧と放電開始直後（本試験では１秒後とした。）の電池端子電圧との差を、放電電流である８Ａで除して得た値を各電池の内部抵抗（ｍΩ）とした。
【００６４】３．内部抵抗上昇率の算出：上述したサイクル試験を１００サイクル経過後の内部抵抗（ｍΩ）をサイクル試験実施前の内部抵抗（ｍΩ）で除して得た値を内部抵抗上昇率（サイクル後／前）とした。結果を表２に示す。
【００６５】
【表２】

【００６６】
（評価）
表２に示す結果から明らかなように、実施例１〜３４のリチウム二次電池は、比較例１のリチウム二次電池に比して１００サイクル経過後の容量維持率が高く、内部抵抗上昇率が低いことが判明した。即ち、本発明のリチウム二次電池の優れたサイクル特性を確認することができた。また、酸化剤（Ｂｉ_２Ｏ_３）やバナジウム化合物（Ｖ_２Ｏ_５）を含有する箇所については、正極表面又は負極表面のいずれの箇所であっても良好なサイクル特性を示すことが明らかである。
【００６７】
【発明の効果】以上説明したように、本発明のリチウム二次電池は、電池ケース内部に酸化剤、バナジウム化合物、又は過塩素酸塩を含有するものであるため、充放電の繰り返しによっても電池容量が低下し難く、サイクル特性、及び保存性に優れている。
【図面の簡単な説明】
【図１】捲回型電極体の構造を示す斜視図である。
【図２】積層型電極体の構造を示す斜視図である。
【符号の説明】
１…捲回型電極体、２…正極板、３…負極板、４…セパレータ、５…電極リード、６…電極リード、７…積層型電極体、８…正極板、９…負極板、１０…セパレータ、１１…電極リード、１２…電極リード、１３…巻芯。[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lithium secondary battery, and more particularly, to a lithium secondary battery having excellent long-term storage characteristics and cycle characteristics.
[0002]
2. Description of the Related Art In recent years, portable electronic devices such as mobile phones, VTRs, and notebook computers have been rapidly reduced in size and weight. As a power supply battery, a lithium composite oxide has been used as a positive electrode active material. Secondary batteries using an organic electrolyte obtained by dissolving a carbonaceous material as a negative electrode active material and a Li ion electrolyte in an organic solvent as an electrolyte have been used.
[0003] Such a battery is generally called a lithium secondary battery or a lithium ion battery, and has a high energy density and a high cell voltage of about 4 V. Electric vehicles (hereinafter, referred to as “EV”) or hybrid electric vehicles (hereinafter, referred to as “EV”), which are actively promoted as low-emission vehicles in the background of recent environmental problems, as well as electronic devices. It is also drawing attention as a power source for driving a motor of “HEV”.
A lithium secondary battery having a relatively large capacity which is preferably used for an EV, an HEV, etc., has an internal electrode body to which an electrode lead 5, 6 as shown in FIG. A wound electrode body 1 formed by winding the plates (the positive electrode plate 2 and the negative electrode plate 3) around the outer periphery of the winding core 13 with the separator 4 interposed therebetween so as not to contact each other is suitably employed. In a lithium secondary battery having such a configuration, the charging reaction occurs when Li ions in the positive electrode active material move through the nonaqueous electrolyte to the negative electrode active material and are trapped. A reaction occurs.
[0005]
When the lithium secondary battery having the above-described structure is charged and discharged, the electrode active material and the non-aqueous electrolyte are in direct contact with each other. Due to the activity of the ions, the Li ions react with the non-aqueous electrolyte to form a composition layer called SEI (Solid Electrolyte Interface, hereinafter simply referred to as “SEI”). Depending on the composition ratio and the like of the SEI layer to be formed, Li ions are easily wasted, and in particular, when the charge / discharge cycle is repeated, the battery characteristics (cycle characteristics) are remarkably reduced, and the battery capacity after the charge / discharge cycle elapses is reduced. There is a problem that it becomes easy to do.
In addition, a positive electrode active material reacts with hydrogen fluoride (HF) generated due to a trace amount of water inevitably present in a non-aqueous electrolyte, and a transition metal element constituting the positive electrode active material Elution of manganese (Mn), for example, also contributes to a decrease in battery capacity. Further, even when the battery is simply stored without discharging, it is known that a phenomenon such as a gradual decrease in battery capacity occurs, and it is necessary to take measures to suppress such a phenomenon. .
The present invention has been made in view of the above-mentioned problems of the prior art, and it is an object of the present invention to make it difficult for the battery capacity to be reduced even by repeated charge and discharge, and to improve the cycle characteristics and storage. An object of the present invention is to provide a lithium secondary battery having excellent performance.
[0008]
That is, according to the present invention, an internal electrode is formed by winding or laminating a positive electrode containing a positive electrode active material and a negative electrode containing a negative electrode active material inside a battery case via a separator. A lithium secondary battery comprising a body and filled with a non-aqueous electrolyte containing a lithium compound as an electrolyte, wherein the battery case contains an oxidizing agent (excluding the positive electrode active material) inside. Is provided.
In the present invention, the oxidizing agent is preferably contained in at least one selected from the group consisting of a positive electrode, a negative electrode, and a non-aqueous electrolyte. In the present invention, when the oxidizing agent is contained in the positive electrode and / or the negative electrode, the oxidizing agent is preferably contained in a state unevenly distributed on the surface of the positive electrode and / or the negative electrode. The content ratio to the negative electrode active material is preferably from 0.1 to 20% by mass, and the oxidizing agent is preferably in a powder form, and the average particle size is preferably from 0.05 to 10 µm.
According to the present invention, a battery case is provided with an internal electrode body formed by winding or laminating a positive electrode containing a positive electrode active material and a negative electrode containing a negative electrode active material with a separator interposed therebetween. There is provided a lithium secondary battery filled with a non-aqueous electrolyte containing a compound as an electrolyte, wherein the battery case contains a vanadium compound inside the battery case.
In the present invention, the vanadium compound is preferably contained in the positive electrode and / or the negative electrode, and the vanadium compound is preferably contained in a state unevenly distributed on the surface of the positive electrode and / or the negative electrode. In the present invention, the content ratio of the vanadium compound to the positive electrode active material or the negative electrode active material is preferably 0.1 to 20% by mass, and the vanadium compound is in a powder form and has an average particle diameter of 0.05%. It is preferably from 10 to 10 μm. In the present invention, the vanadium compound is divanadium pentoxide (V ₂ O ₅ ) Is preferable.
According to the present invention, a battery case is provided with an internal electrode body formed by winding or laminating a positive electrode containing a positive electrode active material and a negative electrode containing a negative electrode active material with a separator interposed therebetween. There is provided a lithium secondary battery filled with a non-aqueous electrolyte containing a compound as an electrolyte, wherein the battery case contains a perchlorate inside.
In the present invention, the perchlorate is preferably contained in the non-aqueous electrolyte, and the content ratio of the perchlorate to the electrolyte is preferably 0.1 to 20 mol%. In the present invention, the perchlorate is lithium perchlorate (LiClO). ₄ ) Is preferable.
In the present invention, the positive electrode active material is preferably lithium manganate having a cubic spinel structure, and the negative electrode active material is preferably a highly graphitized carbon material or hard carbon.
The lithium secondary battery of the present invention is suitably used for a large battery having a battery capacity of 2 Ah or more, and is used as a power source for driving a motor of an electric vehicle or a hybrid electric vehicle in which a large current is frequently discharged. It is preferably used.
[0016]
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be described below, but the present invention is not limited to the following embodiments, and is within the scope of the present invention. It should be understood that design changes, improvements, etc. may be made as appropriate based on the knowledge of.
The lithium secondary battery of the present invention includes an internal electrode body formed by winding or laminating a positive electrode containing a positive electrode active material and a negative electrode containing a negative electrode active material via a separator inside a battery case. A lithium secondary battery filled with a non-aqueous electrolyte using a lithium compound as an electrolyte, characterized in that the battery case contains an oxidizing agent (excluding a positive electrode active material). Hereinafter, the details will be described.
The lithium secondary battery of the present invention contains an oxidizing agent inside a battery case in which an internal electrode body is housed and filled with a non-aqueous electrolyte. By adopting such a configuration, that is, a configuration including an oxidizing agent inside the battery case, the lithium secondary battery of the present invention can be repeatedly charged and discharged as compared with a lithium secondary battery not including an oxidizing agent. The battery capacity is hardly reduced and the cycle characteristics are excellent, and even when stored for a long period of time, the cycle characteristics are hardly deteriorated. In the present invention, the term "oxidizing agent" refers to permanganic acid (salt), chromic acid or its related compound, nitric acid or its related compound, halogen, halogen compound, peroxide, peroxoic acid, metal salts, oxygens And other oxides and the like, which are classified in addition to these, and specifically, the compounds shown in Table 1. In the chemical formulas in Table 1, the metal element represented by "M" is, for example, an alkali metal.
[0019]
[Table 1]

Although the battery case contains an oxidizing agent, the details of the mechanism which has the effect of making it difficult for the battery capacity to be reduced even by the repetition of the above-mentioned charge and discharge, and having excellent cycle characteristics and storage stability are unknown. It is presumed that the SEI layer that suppresses the decomposition of the electrolytic solution and the like that hardly deteriorates is formed on the electrode surface by the oxygen generated by the oxidizing agent, so that the deterioration of the battery characteristics is suppressed.
That is, in the lithium secondary battery of the present invention, the oxidizing agent is contained in both the positive and negative electrodes and at a portion which is in direct contact with the non-aqueous electrolyte. Therefore, in the present invention, it is preferable that the oxidizing agent is contained in at least one selected from the group consisting of a positive electrode, a negative electrode, and a non-aqueous electrolyte. Including an oxidizing agent in these portions is preferable not only in terms of battery characteristics but also in terms of manufacturing cost because the oxidizing agent can be easily implemented in the battery manufacturing process.
In the present invention, when the oxidizing agent is contained in the positive electrode and / or the negative electrode, the oxidizing agent is preferably contained in a state unevenly distributed on the surface of the positive electrode and / or the negative electrode. Here, “contains in a state of being unevenly distributed on the surface of the positive electrode and / or the negative electrode” means that the oxidizing agent is unevenly distributed on the surface of the positive electrode and / or the negative electrode and in direct contact with the nonaqueous electrolyte. However, it does not mean that it is uniformly mixed with the electrode active material. With such a configuration, deterioration of battery characteristics is further suppressed. Although the mechanism is not clear, the non-aqueous electrolyte directly contacts the oxidizing agent to cause some chemical change, and then contacts the electrode active material to form the SEI layer whose composition has changed. It is presumed that it is formed on the electrode surface and the deterioration of battery characteristics is suppressed.
In the present invention, when the oxidizing agent is contained in the positive electrode and / or the negative electrode, the content ratio of the oxidizing agent to the positive electrode active material or the negative electrode active material is preferably 0.1 to 20% by mass. It is more preferably from 0.5 to 15% by mass, particularly preferably from 1 to 10% by mass. If the amount is less than 0.1% by mass, it is not preferable because the effect containing the oxidizing agent is hardly exerted. If the amount is more than 20% by mass, the battery capacity is reduced and other battery characteristics are adversely affected. Is also not preferable because it is assumed.
In the present invention, it is preferable that the oxidizing agent is in the form of a powder and has an average particle diameter of 0.05 to 10 μm. A powdered oxidizing agent satisfying such a rule easily releases oxygen, and the lithium secondary battery of the present invention containing this oxidizing agent inside the battery case has more excellent long-term storage characteristics and cycle characteristics. Further, from the viewpoint of imparting even more excellent long-term storage properties and cycle characteristics to the lithium secondary battery, the average particle size of the oxidizing agent is more preferably 0.1 to 5 μm, and more preferably 0.3 to 1 μm. It is particularly preferred that there is.
Next, another aspect of the present invention will be described. Another aspect of the present invention is to provide, inside a battery case, an internal electrode body formed by winding or laminating a positive electrode including a positive electrode active material and a negative electrode including a negative electrode active material via a separator, and using a lithium compound as an electrolyte. A lithium secondary battery filled with a non-aqueous electrolyte, characterized in that the battery case contains a vanadium compound inside. Hereinafter, the details will be described.
The lithium secondary battery of the present invention containing a vanadium compound inside the battery case is less likely to have a reduced battery capacity by repeated charge / discharge than a lithium secondary battery not containing a vanadium compound, and has improved cycle characteristics. It is excellent, and its cycle characteristics are hardly deteriorated even when stored for a long period of time. The configuration of the battery other than containing a vanadium compound instead of the oxidizing agent is as described above.
In the present invention, a vanadium compound is preferably contained in the positive electrode and / or the negative electrode. Including a vanadium compound in these portions is preferable not only from the viewpoint of improving the battery characteristics but also from the viewpoint of the manufacturing cost, since it can be easily carried out in the process of manufacturing the battery. Further, in the present invention, it is preferable that the vanadium compound is contained in a state of being unevenly distributed on the surface of the positive electrode and / or the negative electrode. With such a configuration, deterioration of battery characteristics is further suppressed. Although this mechanism is not clear, it is presumed that the mechanism is the same as that described above containing an oxidizing agent.
In the present invention, the content ratio of the vanadium compound to the positive electrode active material or the negative electrode active material is preferably from 0.1 to 20% by mass, more preferably from 0.5 to 15% by mass. It is particularly preferred that the content is 1 to 10% by mass. If the amount is less than 0.1% by mass, it is difficult to exhibit the effect of containing the vanadium compound, which is not preferable. If the amount is more than 20% by mass, the battery capacity is reduced and other battery characteristics are adversely affected. Is also not preferable because it is assumed.
In the present invention, it is preferable that the vanadium compound is in a powder form and has an average particle diameter of 0.05 to 10 μm. The powdery vanadium compound satisfying such a rule has a sufficiently large contact area per unit volume with the non-aqueous electrolyte, and the lithium secondary battery of the present invention containing the vanadium compound inside the battery case is Superior long-term storage and cycle characteristics. Further, from the viewpoint of imparting more excellent long-term storage characteristics and cycle characteristics to the lithium secondary battery, the average particle size of the vanadium compound is more preferably 0.1 to 5 μm, and more preferably 0.3 to 1 μm. It is particularly preferred that there is.
In the present invention, the vanadium compound is selected from divanadium pentoxide (V) in view of the effect of improving the cycle characteristics and the like, and from the viewpoint of handling and availability. ₂ O ₅ ) Is preferable.
Next, still another aspect of the present invention will be described. Yet another aspect of the present invention is to provide a battery case with an internal electrode body formed by winding or laminating a positive electrode including a positive electrode active material and a negative electrode including a negative electrode active material via a separator, and a lithium compound. A lithium secondary battery filled with a non-aqueous electrolyte serving as an electrolyte, wherein a perchlorate is contained in a battery case. Hereinafter, the details will be described.
In the lithium secondary battery of the present invention containing a perchlorate in the battery case, the battery capacity is less likely to be reduced by repeated charging and discharging as compared with a lithium secondary battery not containing a perchlorate. Cycle characteristics are excellent, and even when stored for a long period of time, the cycle characteristics are hardly deteriorated. The configuration of the battery other than containing a perchlorate in place of the oxidizing agent or the vanadium compound is as described above.
Further, in the present invention, the perchlorate is preferably contained in the non-aqueous electrolyte, which not only improves the battery characteristics but also can be easily contained in the battery manufacturing process. It is also preferable in terms of cost. Further, in the present invention, the content ratio of the perchlorate to the electrolyte is preferably 0.1 to 20 mol%, more preferably 0.5 to 15 mol%, and further preferably 1 to 10 mol%. Is particularly preferred. If the amount is less than 0.1 mol%, it is difficult to exert the effect containing the perchlorate, which is not preferable. If the amount exceeds 20 mol%, other battery characteristics such as a decrease in battery capacity are adversely affected. Is also not preferable because it is assumed. As a specific example of the perchlorate, lithium perchlorate (LiClO ₄ ).
The lithium secondary battery of the present invention is characterized in that the battery case contains an oxidizing agent, a vanadium compound, or a perchlorate, and the battery capacity is hardly reduced even by repeated charging and discharging. It has the effect of being excellent in characteristics and preservability. Therefore, there are no restrictions on other materials or battery structures. Hereinafter, the structure of the lithium secondary battery, its main components, and the method of manufacturing the lithium secondary battery will be outlined.
As an example of the structure of the internal electrode body constituting the lithium secondary battery, there is a wound electrode body used for a battery having a large capacity. As shown in the perspective view of FIG. 1, in the wound electrode body 1, the positive electrode plate 2 and the negative electrode plate 3 are directly connected to each other via a separator 4 made of a porous polymer. It is wound around the outer periphery of the core 13 so as not to contact. The number of the electrode leads 5 and 6 attached to the positive electrode plate 2 and the negative electrode plate 3 (hereinafter referred to as “electrode plates 2 and 3”) may be at least one. The current collecting resistance can be reduced.
As another structure of the internal electrode body, a laminated internal electrode body formed by laminating a plurality of single cell type electrode bodies used in a coin battery can be exemplified. As shown in FIG. 2, the laminated electrode body 7 is obtained by alternately laminating a positive electrode plate 8 and a negative electrode plate 9 (hereinafter, referred to as “electrode plates 8 and 9”) of a predetermined shape with a separator 10 interposed therebetween. At least one electrode lead 11, 12 is attached to one electrode plate 8, 9. The materials used and the manufacturing method of the electrode plates 8 and 9 are the same as those of the electrode plates 2 and 3 in the wound electrode body 1 shown in FIG.
Next, the configuration of the wound electrode body 1 shown in FIG. 1 will be described in more detail. The positive electrode plate 2 is produced by applying a positive electrode active material to both surfaces of a current collecting substrate. As the current collecting substrate, a metal foil having good corrosion resistance to a positive electrode electrochemical reaction, such as an aluminum foil or a titanium foil, is used. Alternatively, a punching metal or a mesh (net) can be used instead of the foil. As the positive electrode active material, lithium manganate (LiMn) ₂ O ₄ ) Or lithium cobaltate (LiCoO) ₂ ), Lithium nickelate (LiNiO) ₂ ) Are suitably used. Note that it is preferable to add carbon fine powder such as acetylene black to these positive electrode active materials as a conductive additive.
In the present invention, when lithium manganate having a cubic spinel structure containing Li and Mn as main components (hereinafter simply referred to as “lithium manganate”) is used, other positive electrode active materials can be used. This is preferable because the resistance of the electrode body can be reduced as compared with the case where it is used. The above-described effect of the present invention that “the battery capacity is hardly reduced even by repeated charge and discharge” is more remarkable when combined with the effect of reducing the internal resistance, thereby improving the cycle characteristics of the battery. Preferred for.
The lithium manganate is not limited to such a stoichiometric composition (stoichiometric composition), but may be a compound represented by a general formula wherein a part of Mn is replaced by one or more other elements. LiM _X Mn _2-X O ₄ Lithium manganate represented by the formula (M is a substitution element, and X is a composition ratio of the substitution element M in one molecule) is also preferably used. In the lithium manganate subjected to such element substitution, the Li / Mn ratio exceeds 0.5.
The substitution elements M are listed below by element symbols. Li, Fe, Mn, Ni, Mg, Zn, B, Al, Co, Cr, Si, Ti, Sn, P, V, Sb, Nb, Ta, Mo, and W can be mentioned. In theory, Li has +1 valence, Fe, Mn, Ni, Mg, and Zn have +2 valence, B, Al, Co, and Cr have +3 valence, Si, Ti, and Sn. Is +4, P, V, Sb, Nb and Ta are +5, Mo and W are +6, and LiMn ₂ O ₄ It is an element that forms a solid solution. However, Co and Sn may be +2, Fe, Sb and Ti may be +3, Mn may be +3 and +4, and Cr may be +4 and +6.
Therefore, various kinds of substitution elements M may exist in a state having mixed valence, and the amount of oxygen needs to be always 4 as represented by the stoichiometric composition. However, it may be missing or excessive within the range for maintaining the crystal structure.
The coating of the positive electrode active material is performed by applying a slurry or paste prepared by adding a solvent, a binder, or the like to the positive electrode active material powder to a current collecting substrate using a roll coater method or the like and drying the slurry. Then, a pressing process or the like is performed as necessary.
The negative electrode plate 3 can be manufactured in the same manner as the positive electrode plate 2. As the current collecting substrate of the negative electrode plate 3, a metal foil having good corrosion resistance to a negative electrode electrochemical reaction such as a copper foil or a nickel foil is suitably used. As the negative electrode active material, an amorphous carbonaceous material such as soft carbon or hard carbon, or a highly graphitized carbonaceous powder such as artificial graphite or natural graphite is used.
In the present invention, when an oxidizing agent or a vanadium compound is contained in the positive electrode and / or the negative electrode, a positive electrode plate and a negative electrode plate are prepared by the above-described method, and then a predetermined amount of An oxidizing agent may be sprayed (sprinkled) and then subjected to press working. At the time of spraying the oxidizing agent or the vanadium compound, it may be sprayed so as to cover the surface of the electrode plate substantially uniformly, and at the time of press working, an appropriate pressure such that the sprayed oxidizing agent or the vanadium compound does not easily fall off. What should be done.
The separator 4 preferably has a three-layer structure in which a Li-ion permeable polyethylene film (PE film) having micropores is sandwiched between porous Li-ion permeable polypropylene films (PP films). Used for When the temperature of the electrode body rises, the PE film softens at about 130 ° C. and the micropores are crushed, which also serves as a safety mechanism for suppressing the movement of Li ions, that is, the battery reaction. By sandwiching the PE film with a PP film having a higher softening temperature, even when the PE film is softened, the PP film retains its shape and prevents contact and short circuit between the positive electrode plate 2 and the negative electrode plate 3. Thus, it is possible to reliably suppress the battery reaction and to ensure the safety.
At the time of winding the electrode plates 2 and 3 and the separator 4, the electrode leads 5 and 6 are attached to portions of the electrode plates 2 and 3 where the current collector substrate on which the electrode active material is not applied is exposed. Can be As the electrode leads 5 and 6, foil-like ones made of the same material as the current collecting substrate of each of the electrode plates 2 and 3 are preferably used. The attachment of the electrode leads 5 and 6 to the electrode plates 2 and 3 can be performed using ultrasonic welding, spot welding, or the like.
Next, the non-aqueous electrolyte used in the lithium secondary battery of the present invention will be described. Examples of the solvent include carbonates such as ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC) and propylene carbonate (PC), and single solvents or mixed solvents such as γ-butyrolactone, tetrahydrofuran, and acetonitrile. It is preferably used. In the present invention, a mixed solvent of a cyclic carbonate and a chain carbonate can be suitably used, particularly from the viewpoint of the conductivity of the electrolytic solution and high-temperature stability.
As the electrolyte, lithium hexafluorophosphate (LiPF) ₆ ) And lithium borofluoride (LiBF) ₄ ) Or lithium perchlorate (LiClO) ₄ ), And one or more of these are dissolved in the above-mentioned organic solvent (mixed solvent) and used. In particular, in the present invention, LiPF having high conductivity of the non-aqueous electrolyte which is unlikely to undergo oxidative decomposition. ₆ It is preferable to use
In the present invention, when the oxidizing agent, the vanadium compound, or the perchlorate is contained in the non-aqueous electrolyte, a predetermined amount of the oxidizing agent, the vanadium compound, Alternatively, the perchlorate may be dissolved.
In assembling the lithium secondary battery, first, while ensuring conduction between the terminal for extracting current to the outside and the electrode leads 5 and 6, the fabricated wound electrode body 1 is inserted into the battery case. Then, after holding at a stable position, the above-mentioned non-aqueous electrolyte is impregnated. Next, the battery case is sealed to obtain the lithium secondary battery of the present invention. If the oxidizing agent contained in the battery case is a gas such as air, oxygen, or ozone, the battery may be assembled and impregnated with the non-aqueous electrolyte in an atmosphere containing these gases.
As described above, the lithium secondary battery according to the present invention has been described with reference to the embodiments, but it goes without saying that the present invention is not limited to the above embodiments. In addition, the lithium secondary battery according to the present invention is particularly suitably used for a large battery having a battery capacity of 2 Ah or more, but does not prevent application to a battery having such a capacity or less. In addition, the lithium secondary battery of the present invention, as a vehicle-mounted battery, taking advantage of the features of high capacity, low cost, and high reliability, further, as well as being preferably used as a power source for driving a motor of an electric vehicle or hybrid electric vehicle, It can also be suitably used for starting an engine that requires a high voltage.
[0052]
DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific results of the present invention will be described below.
[0053]
(Examples 1 to 13)
LiMn ₂ O ₄ A positive electrode slurry prepared by adding 4% by mass of acetylene black as an external additive to the spinel as a positive electrode active material, and further adding a solvent and a binder, was coated on both sides of a 20 μm-thick aluminum foil. Each was coated so as to have a thickness of about 100 μm, and V was applied on the surface so that the content (% by mass) shown in Table 2 was obtained. ₂ O ₅ The powder was uniformly sprinkled and then pressed to produce a positive electrode plate. The used V ₂ O ₅ Are as shown in Table 2.
Graphite was used as a negative electrode active material and applied to both sides of a 10 μm thick copper foil so as to have a thickness of about 80 μm, respectively, to produce a negative electrode plate. The obtained positive electrode plate and negative electrode plate were wound via a separator (PP / PE / PP (three layers)) to produce a wound electrode body 1 having a configuration as shown in FIG.
Various organic solvents of EC, DMC, and DEC were mixed at a volume ratio of 1: 1: 1 to prepare a mixed solvent, and LiPF as an electrolyte was added thereto so as to have a concentration of 1 mol / l. ₆ Was dissolved to prepare a non-aqueous electrolyte.
A battery case containing a wound electrode body was filled with a non-aqueous electrolyte, and the battery case was sealed to produce batteries (Examples 1 to 13). Note that all of the batteries were manufactured by a dry process. Further, the influence of water intrusion from the outside of the battery due to poor sealing of the battery and the like was also eliminated. In addition, the battery capacity after the first charge of each battery was about 8 Ah.
[0057]
(Examples 14 to 26)
V ₂ O ₅ Except that no powder was used, a positive electrode plate was produced in the same manner as in Examples 1 to 13 described above. In addition, graphite was used as a negative electrode active material, and applied to both sides of a copper foil having a thickness of 10 μm so as to have a thickness of about 80 μm, and the content (% by mass) shown in Table 2 was applied to the surface. V ₂ O ₅ The powder was uniformly sprinkled and then pressed to produce a negative electrode plate. The used V ₂ O ₅ Are as shown in Table 2. The obtained positive electrode plate and negative electrode plate were wound via a separator (PP / PE / PP (three layers)) to produce a wound electrode body 1 having a configuration as shown in FIG.
Next, a battery case containing a wound electrode body was filled with a non-aqueous electrolyte and the battery case was sealed in the same manner as in Examples 1 to 13 to produce a battery (Example). Examples 14 to 26). In addition, the battery capacity after the first charge of each battery was about 8 Ah.
[0059]
(Example 27)
V ₂ O ₅ Bi instead of powder ₂ O ₃ A battery was manufactured in the same manner as in Examples 1 to 13 except that powder was used (Example 27). In addition, the battery capacity after the first charge of the produced battery was about 8 Ah.
[0060]
(Examples 28 to 34)
V ₂ O ₅ No powder and LiClO ₄ Were prepared in the same manner as in Examples 1 to 13 except that was dissolved in a non-aqueous electrolyte (Examples 28 to 34). In addition, LiClO ₄ Is as shown in Table 2. The battery capacity of each of the fabricated batteries after the first charge was about 8 Ah.
[0061]
(Comparative Example 1)
V ₂ O ₅ A battery was produced in the same manner as in Examples 1 to 13 except that no powder was used (Comparative Example 1). In addition, the battery capacity after the first charge of the produced battery was about 8 Ah.
[0062]
(Evaluation of battery characteristics)
1. Cycle test: A cycle test was performed on each of the lithium secondary batteries of Examples 1 to 34 and Comparative Example 1. One cycle was set to a pattern in which a battery in a charged state with a depth of discharge of 50% was discharged at a constant current of 8 A, a constant voltage of 4.1 V, and then charged again at a constant current of 8 A with a charge of 50%. In addition, the capacity was measured at a charge stop voltage of 4.1 V and a discharge stop voltage of 2.5 V at a current strength of 0.2 C, and the capacity was maintained by dividing the battery capacity after 100 cycles by the initial battery capacity. The ratio (%: n = 5 average) was determined. Table 2 shows the results.
2. Measurement of internal resistance: The internal resistance of each battery was calculated from the voltage drop when discharging was started at 8A. That is, the value obtained by dividing the difference between the battery terminal voltage immediately before the discharge during the rest after charging and the battery terminal voltage immediately after the start of the discharge (after 1 second in this test) by 8 A which is the discharge current. The internal resistance (mΩ) of each battery was used.
3. Calculation of internal resistance rise rate: The value obtained by dividing the internal resistance (mΩ) after 100 cycles of the above-described cycle test by the internal resistance (mΩ) before the execution of the cycle test is the internal resistance rise rate (after / before cycle). ). Table 2 shows the results.
[0065]
[Table 2]

[0066]
(Evaluation)
As is clear from the results shown in Table 2, the lithium secondary batteries of Examples 1 to 34 have a higher capacity retention rate after 100 cycles than the lithium secondary batteries of Comparative Example 1, and the internal resistance increase rate. Turned out to be low. That is, excellent cycle characteristics of the lithium secondary battery of the present invention could be confirmed. In addition, an oxidizing agent (Bi ₂ O ₃ ) And vanadium compounds (V ₂ O ₅ It is clear that the portion containing ()) shows good cycle characteristics regardless of whether it is on the positive electrode surface or the negative electrode surface.
[0067]
As described above, since the lithium secondary battery of the present invention contains an oxidizing agent, a vanadium compound, or a perchlorate inside the battery case, the battery can be repeatedly charged and discharged. The capacity is hardly reduced, and the cycle characteristics and the storage stability are excellent.
[Brief description of the drawings]
FIG. 1 is a perspective view showing a structure of a wound electrode body.
FIG. 2 is a perspective view showing a structure of a stacked electrode body.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Wound electrode body, 2 ... Positive electrode plate, 3 ... Negative electrode plate, 4 ... Separator, 5 ... Electrode lead, 6 ... Electrode lead, 7 ... Laminated electrode body, 8 ... Positive electrode plate, 9 ... Negative electrode plate, 10 ... separator, 11 ... electrode lead, 12 ... electrode lead, 13 ... winding core.

Claims (21)

A battery case is provided with an internal electrode body formed by winding or laminating a positive electrode containing a positive electrode active material and a negative electrode containing a negative electrode active material via a separator, and is filled with a non-aqueous electrolytic solution containing a lithium compound as an electrolyte. Lithium secondary battery,
A lithium secondary battery comprising an oxidizing agent (excluding the positive electrode active material) inside the battery case. The lithium secondary battery according to claim 1, wherein the oxidizing agent is contained in at least one selected from the group consisting of the positive electrode and the nonaqueous electrolyte. The lithium secondary battery according to claim 2, wherein when the oxidizing agent is contained in the positive electrode and / or the negative electrode, the oxidizing agent is contained in a state of being unevenly distributed on the surface of the positive electrode and / or the negative electrode. When the oxidizing agent is contained in the positive electrode and / or the negative electrode, a content ratio of the oxidizing agent to the positive electrode active material or the negative electrode active material is 0.1 to 20% by mass. 4. The lithium secondary battery according to 3. The lithium secondary battery according to any one of claims 1 to 4, wherein the oxidizing agent is in a powder form and has an average particle size of 0.05 to 10 µm. A battery case is provided with an internal electrode body formed by winding or laminating a positive electrode containing a positive electrode active material and a negative electrode containing a negative electrode active material via a separator, and is filled with a non-aqueous electrolytic solution containing a lithium compound as an electrolyte. Lithium secondary battery,
A lithium secondary battery containing a vanadium compound inside the battery case. The lithium secondary battery according to claim 6, wherein the vanadium compound is contained in the positive electrode and / or the negative electrode. The lithium secondary battery according to claim 7, wherein the vanadium compound is contained in a state of being unevenly distributed on the surface of the positive electrode and / or the negative electrode. The lithium secondary battery according to claim 7 or 8, wherein a content ratio of the vanadium compound to the positive electrode active material or the negative electrode active material is 0.1 to 20% by mass. The lithium secondary battery according to any one of claims 6 to 9, wherein the vanadium compound is in a powder form and has an average particle size of 0.05 to 10 µm. The vanadium compound, the lithium secondary battery according to any one of claims 6-10 which is vanadium pentoxide (V 2 _{O 5).} A battery case is provided with an internal electrode body formed by winding or laminating a positive electrode containing a positive electrode active material and a negative electrode containing a negative electrode active material via a separator, and is filled with a non-aqueous electrolytic solution containing a lithium compound as an electrolyte. Lithium secondary battery,
A lithium secondary battery comprising a perchlorate in the battery case. The lithium secondary battery according to claim 12, wherein the perchlorate is contained in the nonaqueous electrolyte. The lithium secondary battery according to claim 13, wherein the content ratio of the perchlorate to the electrolyte is 0.1 to 20 mol%. The lithium secondary battery according to claim 12, wherein the perchlorate is lithium perchlorate (LiClO ₄ ). The lithium secondary battery according to any one of claims 1 to 15, wherein the positive electrode active material is lithium manganate having a cubic spinel structure. The lithium secondary battery according to any one of claims 1 to 16, wherein the negative electrode active material is a highly graphitized carbon material or hard carbon. The lithium secondary battery according to any one of claims 1 to 17, wherein the battery capacity is 2 Ah or more. The lithium secondary battery according to any one of claims 1 to 18, which is a vehicle-mounted battery. The lithium secondary battery according to claim 19, which is used for an electric vehicle or a hybrid electric vehicle. 21. The lithium secondary battery according to claim 19, which is used for starting an engine.

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