JP4161396B2 - Non-aqueous electrolyte secondary battery - Google Patents
Non-aqueous electrolyte secondary battery Download PDFInfo
- Publication number
- JP4161396B2 JP4161396B2 JP01750798A JP1750798A JP4161396B2 JP 4161396 B2 JP4161396 B2 JP 4161396B2 JP 01750798 A JP01750798 A JP 01750798A JP 1750798 A JP1750798 A JP 1750798A JP 4161396 B2 JP4161396 B2 JP 4161396B2
- Authority
- JP
- Japan
- Prior art keywords
- negative electrode
- positive electrode
- mixture layer
- graphite
- aqueous electrolyte
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
Images
Classifications
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Landscapes
- Carbon And Carbon Compounds (AREA)
- Secondary Cells (AREA)
- Battery Electrode And Active Subsutance (AREA)
Description
【０００１】
【発明の属する技術分野】
本発明は非水電解液二次電池に関し、特に放電負荷特性及び充放電サイクル特性の改善に関する。
【０００２】
【従来の技術】
近年、電子機器の小型軽量化に伴って、電源となる二次電池に対して高いエネルギー密度を有することが求められるようになっている。そのような要求に応える二次電池として非水電解液二次電池が期待されている。
【０００３】
非水電解液二次電池としては、負極材料にリチウム金属やリチウム合金を用い、正極材料にリチウム含有化合物を用いたものが提案されている。
【０００４】
しかしながら、リチウム金属やリチウム合金を負極に用いた場合、充電過程において負極上でリチウム金属がデンドライト状に析出し易い。このデンドライト結晶の先端では非常に高い電流密度になるため、非水電解液が分解してサイクル寿命が低下したり、また負極から析出したデンドライト結晶が正極にまで到達し、電池の内部短絡が発生するといった問題がある。
【０００５】
これに対して、リチウムイオンをドープ・脱ドープすることが可能な炭素材料を負極材料に用いた非水電解液二次電池が提案されている。この炭素材料としては、易黒鉛化性炭素、難黒鉛化性炭素、黒鉛類が用いられ、これらについては結晶構造パラメータを制御したものが特開平２−８２４６６号公報、特開平４−６１１７４７号公報、特開平４−１１５４５８号公報、特開平４−１８４８６２号公報等で提案されている。
【０００６】
このような炭素材料を用いる非水電解液二次電池では、リチウム金属やリチウム合金を負極に用いる電池と異なり、電池系内でリチウムが金属状態で存在しないためにデンドライトの形成が抑制され、良好なサイクル特性が得られる。特に黒鉛類は体積当たり、または重量当たりのリチウムイオン吸蔵量が大きいため、大きな放電容量が得られ、また放電電圧を平坦にできるという利点がある。
【０００７】
ところで、非水電解液二次電池の正極材料としては、ＬｉＣｏＯ2やＬｉＮｉＯ2が多く用いられている。しかし、コバルトやニッケルは資源が稀少であり、これらを含有するコバルト化合物やニッケル化合物は、鉛やマンガン化合物よりも高価になり、正極材料を多量に使用する大型電池に用いるには無理がある。
【０００８】
そこで、比較的資源が豊富なＭｎを含有するリチウムマンガン酸化物の使用が検討され、例えば米国特許４３６６２１５号、米国特許４８２８８３４号、米国特許４９８０２５１号、特開平７−１９２７６８号公報等においてスピネル型リチウムマンガン酸化物を正極材料として用いることが提案されている。
【０００９】
【発明が解決しようとする課題】
しかしながら、リチウムマンガン酸化物を正極材料として使用した場合、ＬｉＣｏＯ2やＬｉＮｉＯ2を正極材料として用いる場合に比べてどうしても電池性能が劣ってしまう。
【００１０】
すなわち、リチウムマンガン酸化物を正極材料として使用した電池では、充放電に伴って可逆性が失われ、それによる容量低下が著しい。また、特に高温環境下で連続して充放電を行った場合には、充放電サイクルの進行に伴って容量が大きく低下する。さらに、大電流条件での充放電では、充放電サイクルにリチウムの出入りが追従できず、放電容量が損なわれるといった問題がある。
【００１１】
そこで、本発明はこのような従来の実情に鑑みて提案されたものであり、リチウムマンガン酸化物を正極材料として使用する二次電池であって、優れた放電負荷特性と充放電サイクル特性が得られる非水電解液二次電池を提供することを目的とする。
【００１２】
【課題を解決するための手段】
上述の目的を達成するために、本発明の非水電解液二次電池は、リチウムマンガン酸化物を含有する正極合剤層が正極集電体に保持されてなる正極と、黒鉛を含有する負極合剤層が負極集電体に保持されてなる負極と、非水溶媒にリチウム塩が０．５〜２ｍｏｌ／ｌ溶解されてなる非水電解液を有してなり、上記正極合剤層に含有されるリチウムマンガン酸化物と上記負極合剤層に含有される黒鉛との重量比が、２．０：１〜２．９：１であり、リチウムマンガン酸化物は、ＬｉｘＭｎＯｙ（但し、ｘは０．５０５〜０．５２５であり、ｙは１．９６〜２．００である）で表され、Ｘ線回折による（３１１）回折ピークと（４００）回折ピークの比が１：１．１０〜１：１．２０であり、上記黒鉛のＸ線回折法によって測定される（００２）面の面間隔ｄが０．３４ｎｍ以下であり、真密度が２．０ｇ／ｃｍ３以上であり、上記負極合剤層の充填密度が、１．４〜１．７ｇ／ｃｍ３であり、正極と負極の厚さの比が、１．１５：１〜１．６：１であることを特徴とする。
【００１３】
リチウムマンガン酸化物を含有する正極合剤層が正極集電体に保持されてなる正極と、黒鉛を含有する負極合剤層が負極集電体に保持されてなる負極と、非水溶媒にリチウム塩が０．５〜２ｍｏｌ／ｌ溶解されてなる非水電解液とを用いる本発明の非水電解液二次電池において、正極合剤層に含有されるリチウムマンガン酸化物と負極合剤層に含有される黒鉛の重量比が２．０：１〜２．９：１の範囲になされていると、放電容量及び充放電サイクル特性が改善される。そして、さらに負極合剤層の充填密度が１．４〜１．７ｇ／ｃｍ３、正極と負極の厚さの比が１．１５：１〜１．６：１の範囲になされていると、放電負荷特性及び充放電サイクル特性がより一層改善される。また、本発明の非水電解液二次電池では、正極を構成するリチウムマンガン酸化物がＬｉｘＭｎＯｙ（但し、ｘは０．５０５〜０．５２５であり、ｙは１．９６〜２．００である）であり、Ｘ線回折による（３１１）回折ピークと（４００）回折ピークの比が１：１．１０〜１：１．２０であることによって、充放電サイクルの繰り返しに伴う低級マンガン化合物の発生が抑えられ、容量の低下を防止することができる。また、本発明の非水電解液二次電池では、黒鉛のＸ線回折法によって測定される（００２）面の面間隔ｄが０．３４ｎｍ以下であることによって、黒鉛構造の結晶性が崩壊し難く、電解液の分解を抑えることができる。また、本発明の非水電解液二次電池では、黒鉛の真密度を２．０ｇ／ｃｍ３以上とすることによって、負極の充填密度を高くでき、容量の増大させることができる。
【００１４】
【発明の実施の形態】
本発明の具体的な実施の形態について説明する。
【００１５】
本発明の非水電解液二次電池は、炭素材料を含有する負極合剤層が負極集電体に保持されてなる負極と、リチウムマンガン酸化物を含有する正極合剤層が正極集電体に保持されてなる正極と、非水溶媒に電解質塩が溶解されてなる非水電解液を有して構成される。
【００１６】
まず、負極において、負極合剤層はリチウムイオンのドープ・脱ドープがなされる炭素材料が含有される層であり、少なくとも前記炭素材料と、この炭素材料を負極集電体に保持するための結着剤によって構成される。
【００１７】
上記炭素材料としては、例えば黒鉛構造を有するもの、すなわち炭素六角網面が規則的に積層された結晶構造を有するもの（黒鉛）が用いられる。このような黒鉛は、Ｘ線回折法によって得られる（００２）面の面間隔ｄが０．３４ｎｍ以下であるのが望ましい。面間隔ｄが０．３４ｎｍ以下の黒鉛は、黒鉛結晶構造が適度に発達しており、炭素六角網面同士の間にリチウムイオンがスムースに吸蔵・放出される。面間隔ｄが０．３４ｎｍを超える黒鉛は、黒鉛構造が発達し過ぎているため、炭素六角網面間へのリチウムイオンの吸蔵・放出がスムースに行われない。このため、このような黒鉛を電池の負極材料として用いると、充放電の繰り返しによる容量の低下や充放電時の過電圧が大きくなり、放電時の電位の平坦性が失われる。
【００１８】
また、一般に、黒鉛を負極材料として用いた場合、電解液の分解が問題になる。このような電解液の分解は、充放電サイクルに伴って黒鉛構造の結晶性が崩壊し、この崩壊の際に生じる活性点に起因するものと推定されている。これに対して、面間隔ｄが０．３４ｎｍ以下の黒鉛では、黒鉛構造の結晶性が崩壊し難く、電解液の分解が抑えられる。
【００１９】
なお、面間隔ｄのより好ましい範囲は、０．３３５ｎｍ〜０．３３８ｎｍである。
【００２０】
また、上記黒鉛は、負極の充填密度を高くし、容量の増大を図る点から、真密度が２．０ｇ／ｃｍ3以上であるのが好ましく、さらには粒子径が１μｍ〜１００μｍ、平均粒径が５０μｍ以下、Ｎ2ガス吸着のＢＥＴ法による比表面積が０．１〜２０ｍ2／ｇであるのが望ましい。
【００２１】
炭素材料としては、このような黒鉛の他、メソフェーズマイクロビーズ、熱分解炭素繊維、メソフェーズ系炭素繊維、高温処理ピッチカーボン等であって、Ｘ線回折法によって得られる（００２）面の面間隔ｄが０．３４ｎｍ以下のものも用いることができる。
【００２２】
炭素材料を負極集電体に保持するための結着剤や負極集電体としては、通常用いられるものを使用することができる。例えば、結着剤としてはポリフッ化ビニリデン等のフッ素系樹脂、集電体としては銅箔等が使用される。
【００２３】
一方、正極において、正極合剤層は正極活物質となるリチウムマンガン酸化物が含有される層であり、少なくとも前記リチウムマンガン酸化物と、導電剤及びこれらを正極集電体に保持するための結着剤によって構成される。
【００２４】
上記リチウムマンガン酸化物としては、例えばスピネル構造を有するＬｉＭｎ2Ｏ4またはＬｉＭｎ2Ｏ4に所定量のＬｉを添加したもの、すなわちＬｉxＭｎＯy（但し、ｘは０．５０５〜０．５２５であり、ｙは１．９６〜２．００である）で表されるものが用いられる。このうちＬｉＭｎ2Ｏ4に所定量のＬｉを添加したＬｉxＭｎＯyは、７００〜７５０℃で８時間以上の加熱処理を行った後に、粉末Ｘ線回折測定で観測される（３１１）回折面と（４００）回折面のピーク比［（３１１）回折面：（４００）回折面］が１：１．１０〜１：１．２０であるのが望ましい。ピーク比がこの範囲にあるＬｉxＭｎＯyは、スピネル型類似の結晶構造を有する。ピーク比がこの範囲から外れる場合には充放電サイクルの繰り返しに伴い低級マンガン化合物が発生し、容量が低下する虞がある。なお、正極の材料としては、この他にＬｉ4Ｍｎ5Ｏ12も用いることができる。
【００２５】
このようなリチウムマンガン酸化物は、水酸化リチウム等のリチウム源と、マンガン源を混合し、酸素存在雰囲気下で熱処理することによって合成される。
【００２６】
マンガン源としては、炭酸マンガンや硝酸マンガン、硫酸マンガン、酢酸マンガンもしくはこれらを加熱・酸化したもの、電解二酸化マンガン、化学合成二酸化マンガン、Ｍｎ2Ｏ3、Ｍｎ3Ｏ4等が使用でき、このうち電解二酸化マンガンを使用するのが望ましい。
【００２７】
正極に導電性を付与するための導電剤、正極活物質を正極集電体に保持するための結着剤及び正極集電体としては通常用いられているものが使用できる。例えば導電剤としてはグラファイト、結着剤としてはポリフッ化ビニリデン等のフッ素系樹脂、正極集電体としてはアルミニウム箔がそれぞれ使用される。
【００２８】
負極と正極は以上のような構成とされるが、本発明の非水電解液二次電池では特に、これら負極と正極において、（正極合剤層に含有されるリチウムマンガン酸化物の重量）：（負極合剤層に含有される炭素材料の重量）が、２．０：１〜２．９：１に規制される。
【００２９】
正極合剤層に含有されるリチウムマンガン酸化物と負極合剤層に含有される炭素材料の重量比が上記範囲となされていると、充放電に当たって電極へのリチウムの出入りが円滑に行われるようになり、大きな放電容量が得られるとともに充放電サイクル特性が改善される。また、高温保存性能も向上する。さらにこの正極合剤層に含有されるリチウムマンガン酸化物と負極合剤層に含有される炭素材料の重量比のより好ましい範囲は、２．４：１〜２．７：１である。
【００３０】
また、電池の充放電容量は電極の充填密度に負うところが大きく、大きな充放電容量を得るためには負極合剤層の充填密度が１．４〜１．７ｇ／ｃｍ3であるのが望ましい。さらにこれに加えて、（正極の厚さ）：（負極の厚さ）が１．１５：１〜１．６：１の範囲になされていると電池性能がより一層改善される。
【００３１】
なお、この非水電解液二次電池において非水電解液の非水溶媒、電解質塩としては例えば次のようなものが用いられる。
【００３２】
非水溶媒としては、炭酸プロピレン，炭酸エチレン，炭酸ブチレン等の環状カーボネート、炭酸ジメチル，炭酸ジエチル，炭酸ジプロピル，炭酸エチルメチル等の鎖状カーボネート、ジメトキシエタン，テトラヒドロフラン等のエーテル化合物、γ−ブチロラクトン等の環状エステル類、スルホラン類等が単独もしくは混合して用いられる。
【００３３】
また、電解質塩としてはＬｉＰＦ6、ＬｉＢＦ4、ＬｉＣＦ3ＳＯ3、ＬｉＣｌＯ4、ＬｉＡｓＦ6等のリチウム塩が使用される。これら電解質塩は０．５〜２ｍｏｌ／ｌなる濃度で非水溶媒に溶解される。
【００３４】
本発明は各種タイプの非水電解液二次電池に適用でき、特に帯状正極と帯状負極をセパレータを介して積層、巻回してなる巻回電極体を用いる円筒型電池や、板状正極と帯状負極をセパレータを介して積層した積層電極体を用いる角形電池等に適用して好適である。
【００３５】
このうち円筒型非水電解液二次電池の一例を図１に示す。
【００３６】
この非水電解液二次電池は、図１に示すように、負極集電体９の両面に負極合剤層１５を形成してなる負極１と、正極集電体１０の両面に正極合剤層１６を形成してなる正極２とを、ポリプロピレンやポリエチレン等よりなる微多孔膜セパレータ３を介して巻回し、この巻回体の上下に絶縁体４を載置した状態で電池缶５に収納してなるものである。
【００３７】
前記電池缶５には電池蓋７が封口ガスケット６を介してかしめることによって取付けられ、それぞれ負極リード１１及び正極リード１２を介して負極１あるいは正極２と電気的に接続され、電池の負極あるいは正極として機能するように構成されている。
【００３８】
そして、この電池では、前記正極リード１２は電流遮断用薄板８に溶接されて取り付けられ、この電流遮断用薄板８と感熱抵抗素子１３を介して電池蓋７との電気的接続が図られている。
【００３９】
この電池においては、電池内部の圧力が上昇すると、前記電流遮断等薄板８が押し上げられて変形する。すると、正極リード１２が電流遮断用薄板８と溶接された部分を残して切断され、電流が遮断される。
【００４０】
このような円筒型電池において、正極合剤層に含有されるリチウムマンガン酸化物と負極合剤層に含有される炭素材料の重量比が２．０：１〜２．９：１の範囲とされ、さらに負極合剤層の充填密度が１．４〜１．７ｇ／ｃｍ3、正極と負極の厚さの比が１．１５：１〜１．６：１となされていると、大きな放電容量が得られるとともに良好な充放電サイクル特性が得られることになる。なお、この電池では、正極合剤層及び負極合剤層が集電体の両面に形成されるが、このように合剤層が集電体の両面に形成されている場合、両面の合剤層を合わせたリチウムマンガン酸化物と炭素材料の重量比が上述の範囲に規制される。
【００４１】
【実施例】
以下、本発明の実施例について実験結果に基づいて説明する。
【００４２】
実施例１
（正極合剤層に含有されるリチウムマンガン酸化物の重量）：（負極合剤層に含有される黒鉛粉末の重量）＝２．３：１、負極合剤層の充填密度＝１．５０ｇ／ｃｍ3、（正極の厚さ）：（負極の厚さ）＝１．２３：１となされた非水電解液二次電池の例である。
【００４３】
このような非水電解液二次電池を次のように作製した。
【００４４】
まず、正極を次のようにして作製した。
【００４５】
水酸化リチウムと、３０μｍ以下の粒径に粉砕した電解二酸化マンガンをＬｉ：Ｍｎ（原子比）が１．０４：２となるように計量し、乳鉢に投入した。
【００４６】
そして、これらを十分混合した後アルミナ製坩堝に入れ、酸素存在雰囲気となされた電気炉内で、３５０℃で２時間熱処理し、さらに７８０℃で１２時間熱処理し、室温まで冷却した後、粗く粉砕することでリチウムマンガン酸化物を得た。
【００４７】
このリチウムマンガン酸化物について粉末Ｘ線回折法による測定を行ったところ、観測されたピークはスピネル型ＬｉＭｎ2Ｏ4のピークに一致していた。なお、（３１１）回折面と（４００）回折面のピーク比［（３１１）回折面：（４００）回折面］は１：１．１２であった。
【００４８】
この正極材料９０重量部、導電剤となるグラファイト６重量部、結着剤となるポリフッ化ビニリデン（ＰＶＤＦ）４重量部を混合し、さらに溶剤となるＮ−メチル−２−ピロリドンを加えて混合することによって正極合剤ミックスを調製した。次に、この正極合剤ミックスを、厚さ２０μｍのアルミニウム箔（正極集電体）の両面に、リード溶着部を除いて均一に塗布し、乾燥させることで正極合剤層を形成し、電極寸法に裁断した。そして、正極集電体のリード溶着部にアルミニウム製リード体を溶着することで正極を作製した。
【００４９】
負極を次のようにして作製した。
【００５０】
２８００℃の熱処理によって得られた粒状人造黒鉛粉末を用意した。この黒鉛粉末についてＸ線回折法で（００２）面の面間隔ｄを測定したところ０．３３５ｎｍであった。
【００５１】
この黒鉛粉末９０重量部、結着剤となるポリフッ化ビニリデン１０重量部を混合し、さらに溶剤となるＮ−メチル−２−ピロリドンを加えて混合することによって負極合剤ミックスを調製した。次に、この負極合剤ミックスを、厚さ１０μｍの銅箔（負極集電体）の両面に、リード溶着部を除いて均一に塗布し、乾燥させることで負極合剤層を形成し、電極寸法に裁断した。そして、負極集電体のリード溶着部にニッケル製リード体を溶着することで負極を作製した。ここで負極合剤層の充填密度は１．５０ｇ／ｃｍ3、正極合剤層に含有されるリチウムマンガン酸化物と負極合剤層に含有される人造黒鉛粉末の重量比は２．３：１、正極と負極の厚さ比は１．２３：１であった。
【００５２】
このようにして作製された正極と負極を、セパレータとなるポリプロピレン製微多孔膜を介して積層し、多数回巻回することで渦巻状電極素子を作製した。
【００５３】
そして、この渦巻状電極素子に絶縁板を取り付けて電池缶に挿入し、負極リード体を電池缶に溶接するとともに正極リード体を電流遮断用薄板に溶接した。次いで、炭酸プロピレンと炭酸ジメチル混合液にＬｉＰＦ6を１ｍｏｌ／ｌなる濃度で溶解させた電解液を電池缶に注入し、電流遮断用薄板上に電池蓋を載置した。そして、電池缶の上部を、カシメ機を用いてかしめることで缶を密閉し、外径１８ｍｍ、高さ６５ｍｍの円筒型電池を作製した。
【００５４】
実施例２〜実施例５
（正極合剤層に含有されるリチウムマンガン酸化物の重量）：（負極合剤層に含有される黒鉛粉末の重量）、負極合剤層の充填密度、（正極の厚さ）：（負極の厚さ）を表１に示すように変えたこと以外は実施例１と同じ構成の電池の例である。
【００５５】
比較例１，比較例２
（正極合剤層に含有されるリチウムマンガン酸化物の重量）：（負極合剤層に含有される黒鉛粉末の重量）、負極合剤層の充填密度、（正極の厚さ）：（負極の厚さ）を表１に示すように変えたこと以外は実施例１と同じ構成の電池の例である。
【００５６】
【表１】
このようにして作製された電池について、電流０．３Ａ，上限電圧４．２Ｖで８時間充電し、次に電流０．５Ａで終止電圧２．５Ｖまで放電させた。そして、電流１Ａ，上限電圧４．２Ｖで３時間充電した後、電流１Ａで終止電圧２．５Ｖまで放電を行うといった充放電サイクルを５サイクル行った。
【００５８】
この後、次のような放電負荷試験及び充放電サイクル試験を行い、電池の性能を評価した。
【００５９】
放電負荷試験：電流１Ａ，上限電圧４．２Ｖで３時間充電した後、終止電圧２．５Ｖまで放電させた。なお、放電に際する電流は２〜５Ａの範囲で変化させた。
【００６０】
充放電サイクル試験：電流１Ａ，上限電圧４．２Ｖで３時間充電した後、電流０．５Ａで終止電圧２．５Ｖまで放電させるといった充放電サイクルを１００回行った。
【００６１】
放電負荷特性を図２に、充放電サイクル特性を図３に示す。また、正極と負極の厚さの比と容量維持率（１００サイクル時容量／初期サイクル時容量）の関係を図４に示す。
【００６２】
図２に示すように、正極合剤層の含有されるリチウムマンガン酸化物と負極合剤層に含有される黒鉛粉末の重量比、負極合剤層の充填密度、正極と負極の厚さの比が所定範囲内にある実施例１〜実施例５の電池は、放電電流を上げた場合でも大きな放電容量が得られ、比較例１，比較例２の電池に比べて優れた放電負荷特性が得られる。
【００６３】
また、図３に示す充放電特性についても、実施例１〜実施例５の電池は充放電サイクルの繰り返しに伴う容量低下が小さく、比較例１，比較例２の電池に比べて優れている。
【００６４】
さらに、図４から、容量維持率は特に正極と負極の厚さの比に依存し、この比を１．１５：１〜１．６：１にすることによって８０％以上の容量維持率が得られるようになることがわかる。
【００６５】
このことから、正極合剤層に含有されるリチウムマンガン酸化物と負極合剤層に含有される炭素材料の重量比を２．０：１〜２．９：１、負極合剤層の充填密度を１．４〜１．７ｇ／ｃｍ3、正極と負極の厚さの比を１．１５：１〜１．６：１とすることによって電池の放電負荷特性や充放電サイクル特性が改善されることがわかった。
【００６６】
【発明の効果】
以上の説明からも明らかなように、本発明の非水電解液二次電池は、リチウムマンガン酸化物を含有する正極合剤層が正極集電体に保持されてなる正極と、黒鉛を含有する負極合剤層が負極集電体に保持されてなる負極と、非水溶媒にリチウム塩が０．５〜２ｍｏｌ／ｌ溶解されてなる非水電解液とを有してなり、正極合剤層に含有されるリチウムマンガン酸化物と負極合剤層に含有される黒鉛の重量比が２．０：１〜２．９：１、負極合剤層の充填密度が１．４〜１．７ｇ／ｃｍ３、正極と負極の厚さの比が１．１５：１〜１．６：１であるので、大きな放電容量が得られるとともに良好な充放電サイクル特性が得られる。また、本発明の非水電解液二次電池は、正極を構成するリチウムマンガン酸化物がＬｉｘＭｎＯｙ（但し、ｘは０．５０５〜０．５２５であり、ｙは１．９６〜２．００である）であり、Ｘ線回折による（３１１）回折ピークと（４００）回折ピークの比が１：１．１０〜１：１．２０であることによって、充放電サイクルの繰り返しに伴う低級マンガン化合物の発生が抑えられ、容量の低下を防止することができる。また、本発明の非水電解液二次電池は、黒鉛のＸ線回折法によって測定される（００２）面の面間隔ｄが０．３４ｎｍ以下であることによって、黒鉛構造の結晶性が崩壊し難く、電解液の分解を抑えることができる。また、本発明の非水電解液二次電池は、黒鉛の真密度を２．０ｇ／ｃｍ３以上とすることによって、負極の充填密度を高くでき、容量の増大させることができる。また、本発明の非水電解液二次電池で正極材料として使用するリチウムマンガン酸化物は、リチウムコバルト複合酸化物やリチウムニッケル複合酸化物のように資源が稀少なＣｏ，Ｎｉを含んでいないので入手が容易である。したがって、本発明の非水電解液二次電池は、正極材料を多量に使用する大型電池としても好適である。
【図面の簡単な説明】
【図１】本発明を適用した非水電解液二次電池の一例を示す概略縦断面図である。
【図２】非水電解液二次電池の放電負荷特性を示す特性図である。
【図３】非水電解液二次電池の充放電サイクル特性を示す特性図である。
【図４】正極と負極の厚さの比と、容量維持率の関係を示す特性図である。
【符号の説明】
１ 負極、２ 正極、９ 負極集電体、１０ 正極集電体、１５ 負極合剤層、１６ 正極合剤層[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a non-aqueous electrolyte secondary battery, and more particularly to improvement of discharge load characteristics and charge / discharge cycle characteristics.
[0002]
[Prior art]
In recent years, with the reduction in size and weight of electronic devices, it has been required to have a high energy density for a secondary battery serving as a power source. Non-aqueous electrolyte secondary batteries are expected as secondary batteries that meet such requirements.
[0003]
As a nonaqueous electrolyte secondary battery, a battery using lithium metal or a lithium alloy as a negative electrode material and a lithium-containing compound as a positive electrode material has been proposed.
[0004]
However, when lithium metal or a lithium alloy is used for the negative electrode, the lithium metal is likely to precipitate in a dendrite shape on the negative electrode during the charging process. Since the end of this dendrite crystal has a very high current density, the non-aqueous electrolyte decomposes and the cycle life decreases, and the dendrite crystal deposited from the negative electrode reaches the positive electrode, causing an internal short circuit of the battery. There is a problem such as.
[0005]
On the other hand, a non-aqueous electrolyte secondary battery using a carbon material that can be doped / undoped with lithium ions as a negative electrode material has been proposed. As this carbon material, graphitizable carbon, non-graphitizable carbon, and graphites are used, and those having crystal structure parameters controlled are disclosed in JP-A-2-82466 and JP-A-4-611747. JP-A-4-115458, JP-A-4-184862, and the like.
[0006]
In a non-aqueous electrolyte secondary battery using such a carbon material, unlike batteries using lithium metal or a lithium alloy as a negative electrode, formation of dendrites is suppressed because lithium does not exist in a metal state in the battery system, which is favorable. Cycle characteristics can be obtained. In particular, graphite has an advantage that a large discharge capacity can be obtained and the discharge voltage can be flattened because the lithium ion storage amount per volume or weight is large.
[0007]
By the way, LiCoO 2 and LiNiO 2 are often used as positive electrode materials for non-aqueous electrolyte secondary batteries. However, resources such as cobalt and nickel are scarce, and cobalt compounds and nickel compounds containing these are more expensive than lead and manganese compounds, and are unsuitable for use in large batteries that use a large amount of positive electrode material.
[0008]
Therefore, the use of lithium manganese oxide containing Mn which is relatively abundant in resources has been studied. For example, spinel lithium is disclosed in US Pat. No. 4,366,215, US Pat. No. 4,828,834, US Pat. No. 4,980,251, JP-A-7-192768, and the like. It has been proposed to use manganese oxide as the positive electrode material.
[0009]
[Problems to be solved by the invention]
However, when lithium manganese oxide is used as the positive electrode material, the battery performance is inevitably inferior to the case where LiCoO 2 or LiNiO 2 is used as the positive electrode material.
[0010]
That is, in a battery using lithium manganese oxide as a positive electrode material, the reversibility is lost with charge and discharge, and the capacity reduction due to the loss is significant. In particular, when charging / discharging is performed continuously in a high temperature environment, the capacity greatly decreases as the charging / discharging cycle progresses. Furthermore, in charging / discharging under a large current condition, there is a problem in that lithium does not follow the charging / discharging cycle, and the discharge capacity is impaired.
[0011]
Therefore, the present invention has been proposed in view of such a conventional situation, and is a secondary battery using lithium manganese oxide as a positive electrode material, which has excellent discharge load characteristics and charge / discharge cycle characteristics. It is an object to provide a non-aqueous electrolyte secondary battery.
[0012]
[Means for Solving the Problems]
In order to achieve the above object, the non-aqueous electrolyte secondary battery of the present invention includes a positive electrode in which a positive electrode mixture layer containing lithium manganese oxide is held by a positive electrode current collector, and a negative electrode containing graphite. A negative electrode in which a mixture layer is held by a negative electrode current collector, and a non-aqueous electrolyte solution in which a lithium salt is dissolved in a non-aqueous solvent in an amount of 0.5 to 2 mol / l. The weight ratio of the lithium manganese oxide contained and the graphite contained in the negative electrode mixture layer is 2.0: 1 to 2.9: 1, and the lithium manganese oxide is Li x MnO y (however, , X is 0.505 to 0.525, and y is 1.96 to 2.00), and the ratio of (311) diffraction peak to (400) diffraction peak by X-ray diffraction is 1: 1. .10 to 1: 1.20, measured by X-ray diffraction of the above graphite (002 ) The face spacing d is 0.34 nm or less, the true density is 2.0 g / cm 3 or more, and the packing density of the negative electrode mixture layer is 1.4 to 1.7 g / cm 3 . The thickness ratio between the positive electrode and the negative electrode is 1.15: 1 to 1.6: 1.
[0013]
A positive electrode in which a positive electrode mixture layer containing lithium manganese oxide is held by a positive electrode current collector, a negative electrode in which a negative electrode mixture layer containing graphite is held in a negative electrode current collector , and lithium in a nonaqueous solvent In the nonaqueous electrolyte secondary battery of the present invention using a nonaqueous electrolyte solution in which a salt is dissolved in an amount of 0.5 to 2 mol / l, the lithium manganese oxide contained in the cathode mixture layer and the anode mixture layer When the weight ratio of the contained graphite is in the range of 2.0: 1 to 2.9: 1, the discharge capacity and charge / discharge cycle characteristics are improved. Further, when the filling density of the negative electrode mixture layer is 1.4 to 1.7 g / cm 3 and the ratio of the thickness of the positive electrode to the negative electrode is in the range of 1.15: 1 to 1.6: 1, Discharge load characteristics and charge / discharge cycle characteristics are further improved. In the nonaqueous electrolyte secondary battery of the present invention, the lithium manganese oxide constituting the positive electrode is Li x MnO y (where x is 0.505 to 0.525, and y is 1.96 to 2. And the ratio of the (311) diffraction peak and the (400) diffraction peak by X-ray diffraction is 1: 1.10 to 1: 1.20, so that the lower manganese accompanying the repeated charge / discharge cycle Generation of a compound is suppressed, and a decrease in capacity can be prevented. Further, in the non-aqueous electrolyte secondary battery of the present invention, the crystallinity of the graphite structure collapses because the (002) plane spacing d measured by X-ray diffraction of graphite is 0.34 nm or less. It is difficult to suppress the decomposition of the electrolytic solution. Moreover, in the non-aqueous electrolyte secondary battery of the present invention, by setting the true density of graphite to 2.0 g / cm 3 or more, the packing density of the negative electrode can be increased and the capacity can be increased.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
A specific embodiment of the present invention will be described.
[0015]
The non-aqueous electrolyte secondary battery of the present invention includes a negative electrode in which a negative electrode mixture layer containing a carbon material is held by a negative electrode current collector, and a positive electrode mixture layer containing lithium manganese oxide as a positive electrode current collector. And a non-aqueous electrolyte solution in which an electrolyte salt is dissolved in a non-aqueous solvent.
[0016]
First, in the negative electrode, the negative electrode mixture layer is a layer containing a carbon material to which lithium ions are doped / dedoped, and at least the carbon material and a bond for holding the carbon material in the negative electrode current collector. Consists of an adhesive.
[0017]
As the carbon material, for example, a material having a graphite structure, that is, a material having a crystal structure in which carbon hexagonal network surfaces are regularly stacked (graphite) is used. Such graphite desirably has a (002) plane spacing d obtained by an X-ray diffraction method of 0.34 nm or less. Graphite with an interplanar spacing d of 0.34 nm or less has a moderately developed graphite crystal structure, and lithium ions are smoothly occluded and released between the hexagonal carbon surfaces. Graphite having an interplanar spacing d exceeding 0.34 nm has an excessively developed graphite structure, so that lithium ions are not smoothly occluded / released between the hexagonal carbon surfaces. For this reason, when such graphite is used as the negative electrode material of the battery, the capacity is reduced due to repeated charging and discharging, the overvoltage during charging and discharging is increased, and the flatness of the potential during discharging is lost.
[0018]
In general, when graphite is used as a negative electrode material, the decomposition of the electrolytic solution becomes a problem. Such decomposition of the electrolytic solution is presumed to be caused by the active points generated during the collapse of the crystallinity of the graphite structure with the charge / discharge cycle. On the other hand, in the case of graphite having an interplanar spacing d of 0.34 nm or less, the crystallinity of the graphite structure is difficult to collapse, and decomposition of the electrolytic solution is suppressed.
[0019]
In addition, the more preferable range of the surface interval d is 0.335 nm to 0.338 nm.
[0020]
The graphite preferably has a true density of 2.0 g / cm 3 or more from the viewpoint of increasing the packing density of the negative electrode and increasing the capacity, and further has a particle diameter of 1 μm to 100 μm and an average particle diameter. Is preferably 50 μm or less, and the specific surface area by the BET method of N 2 gas adsorption is 0.1 to 20 m 2 / g.
[0021]
Examples of the carbon material include mesophase microbeads, pyrolytic carbon fibers, mesophase carbon fibers, high-temperature-treated pitch carbon, and the like, as well as such graphite, and a (002) plane spacing d obtained by an X-ray diffraction method. Those having a thickness of 0.34 nm or less can also be used.
[0022]
As the binder and the negative electrode current collector for holding the carbon material on the negative electrode current collector, those usually used can be used. For example, a fluorine resin such as polyvinylidene fluoride is used as the binder, and a copper foil or the like is used as the current collector.
[0023]
On the other hand, in the positive electrode, the positive electrode mixture layer is a layer containing a lithium manganese oxide serving as a positive electrode active material, and at least the lithium manganese oxide, a conductive agent, and a binder for holding them in the positive electrode current collector. Consists of an adhesive.
[0024]
As the lithium manganese oxide, for example, LiMn 2 O 4 having a spinel structure or LiMn 2 O 4 with a predetermined amount of Li added, that is, Li x MnO y (where x is 0.505 to 0.525) And y is 1.96 to 2.00). Among these, Li x MnO y in which a predetermined amount of Li is added to LiMn 2 O 4 is observed by powder X-ray diffraction measurement after heat treatment at 700 to 750 ° C. for 8 hours or more (311) diffraction plane And the (400) diffraction plane peak ratio [(311) diffraction plane: (400) diffraction plane] is preferably 1: 1.10 to 1: 1.20. Li x MnO y having a peak ratio in this range has a spinel-like crystal structure. When the peak ratio is out of this range, a lower manganese compound is generated as the charge / discharge cycle is repeated, and the capacity may be reduced. In addition, Li 4 Mn 5 O 12 can also be used as the positive electrode material.
[0025]
Such a lithium manganese oxide is synthesized by mixing a lithium source such as lithium hydroxide and a manganese source and performing a heat treatment in an oxygen-existing atmosphere.
[0026]
As the manganese source, manganese carbonate, manganese nitrate, manganese sulfate, manganese acetate or those obtained by heating and oxidation thereof, electrolytic manganese dioxide, chemically synthesized manganese dioxide, Mn 2 O 3 , Mn 3 O 4 and the like can be used. It is desirable to use electrolytic manganese dioxide.
[0027]
As the conductive agent for imparting conductivity to the positive electrode, the binder for holding the positive electrode active material on the positive electrode current collector and the positive electrode current collector, those usually used can be used. For example, graphite is used as the conductive agent, fluorine resin such as polyvinylidene fluoride is used as the binder, and aluminum foil is used as the positive electrode current collector.
[0028]
Although the negative electrode and the positive electrode are configured as described above, in the non-aqueous electrolyte secondary battery of the present invention, particularly in these negative electrode and positive electrode (weight of lithium manganese oxide contained in the positive electrode mixture layer): (Weight of the carbon material contained in the negative electrode mixture layer) is regulated to 2.0: 1 to 2.9: 1.
[0029]
When the weight ratio of the lithium manganese oxide contained in the positive electrode mixture layer and the carbon material contained in the negative electrode mixture layer is in the above range, the lithium can smoothly enter and exit the electrode during charging and discharging. Thus, a large discharge capacity is obtained and the charge / discharge cycle characteristics are improved. Moreover, high temperature storage performance is also improved. Furthermore, the more preferable range of the weight ratio of the lithium manganese oxide contained in this positive electrode mixture layer and the carbon material contained in the negative electrode mixture layer is 2.4: 1 to 2.7: 1.
[0030]
In addition, the charge / discharge capacity of the battery largely depends on the packing density of the electrode. In order to obtain a large charge / discharge capacity, the packing density of the negative electrode mixture layer is preferably 1.4 to 1.7 g / cm 3 . In addition to this, when (the thickness of the positive electrode) :( the thickness of the negative electrode) is in the range of 1.15: 1 to 1.6: 1, the battery performance is further improved.
[0031]
In this non-aqueous electrolyte secondary battery, for example, the following can be used as the non-aqueous solvent and electrolyte salt of the non-aqueous electrolyte.
[0032]
Nonaqueous solvents include cyclic carbonates such as propylene carbonate, ethylene carbonate and butylene carbonate, chain carbonates such as dimethyl carbonate, diethyl carbonate, dipropyl carbonate and ethyl methyl carbonate, ether compounds such as dimethoxyethane and tetrahydrofuran, γ-butyrolactone, etc. These cyclic esters and sulfolanes are used alone or in combination.
[0033]
As the electrolyte salt LiPF 6, LiBF 4, LiCF 3 SO 3, LiClO 4, lithium salt LiAsF 6 or the like is used. These electrolyte salts are dissolved in a non-aqueous solvent at a concentration of 0.5 to 2 mol / l.
[0034]
The present invention can be applied to various types of non-aqueous electrolyte secondary batteries, and in particular, a cylindrical battery using a wound electrode body in which a strip-like positive electrode and a strip-like negative electrode are stacked and wound via a separator, and a plate-like positive electrode and a strip-like battery. It is suitable for application to a prismatic battery using a laminated electrode body in which a negative electrode is laminated via a separator.
[0035]
An example of a cylindrical nonaqueous electrolyte secondary battery is shown in FIG.
[0036]
As shown in FIG. 1, the non-aqueous electrolyte secondary battery includes a
[0037]
A battery lid 7 is attached to the battery can 5 by caulking through a sealing gasket 6 and is electrically connected to the
[0038]
In this battery, the
[0039]
In this battery, when the pressure inside the battery rises, the thin plate 8 such as the current interruption is pushed up and deformed. Then, the
[0040]
In such a cylindrical battery, the weight ratio of the lithium manganese oxide contained in the positive electrode mixture layer and the carbon material contained in the negative electrode mixture layer is in the range of 2.0: 1 to 2.9: 1. Furthermore, when the packing density of the negative electrode mixture layer is 1.4 to 1.7 g / cm 3 and the ratio of the thickness of the positive electrode to the negative electrode is 1.15: 1 to 1.6: 1, a large discharge capacity is obtained. As a result, good charge / discharge cycle characteristics can be obtained. In this battery, the positive electrode mixture layer and the negative electrode mixture layer are formed on both sides of the current collector. When the mixture layer is thus formed on both sides of the current collector, The weight ratio of the lithium manganese oxide and the carbon material combined in the layers is regulated within the above range.
[0041]
【Example】
Examples of the present invention will be described below based on experimental results.
[0042]
Example 1
(Weight of lithium manganese oxide contained in positive electrode mixture layer): (weight of graphite powder contained in negative electrode mixture layer) = 2.3: 1, packing density of negative electrode mixture layer = 1.50 g / This is an example of a nonaqueous electrolyte secondary battery in which cm 3 , (positive electrode thickness) :( negative electrode thickness) = 1.23: 1.
[0043]
Such a non-aqueous electrolyte secondary battery was produced as follows.
[0044]
First, the positive electrode was produced as follows.
[0045]
Lithium hydroxide and electrolytic manganese dioxide ground to a particle size of 30 μm or less were weighed so that the Li: Mn (atomic ratio) was 1.04: 2, and placed in a mortar.
[0046]
Then, after sufficiently mixing them, they are put in an alumina crucible, heat-treated at 350 ° C. for 2 hours, further heat-treated at 780 ° C. for 12 hours, cooled to room temperature, and then roughly crushed As a result, lithium manganese oxide was obtained.
[0047]
When this lithium manganese oxide was measured by a powder X-ray diffraction method, the observed peak coincided with the peak of spinel type LiMn 2 O 4 . The peak ratio of the (311) diffraction surface and the (400) diffraction surface [(311) diffraction surface: (400) diffraction surface] was 1: 1.12.
[0048]
90 parts by weight of the positive electrode material, 6 parts by weight of graphite as a conductive agent, and 4 parts by weight of polyvinylidene fluoride (PVDF) as a binder are mixed, and N-methyl-2-pyrrolidone as a solvent is added and mixed. Thus, a positive electrode mixture was prepared. Next, this positive electrode mixture mix is uniformly applied to both surfaces of an aluminum foil (positive electrode current collector) having a thickness of 20 μm, excluding the lead weld portion, and dried to form a positive electrode mixture layer. Cut to size. And the positive electrode was produced by welding the lead body made from aluminum to the lead welding part of a positive electrode electrical power collector.
[0049]
A negative electrode was produced as follows.
[0050]
A granular artificial graphite powder obtained by heat treatment at 2800 ° C. was prepared. The graphite powder was measured for the (002) plane distance d by X-ray diffraction to find 0.335 nm.
[0051]
90 parts by weight of the graphite powder and 10 parts by weight of polyvinylidene fluoride serving as a binder were mixed, and further N-methyl-2-pyrrolidone serving as a solvent was added and mixed to prepare a negative electrode mixture mix. Next, this negative electrode mixture mix is uniformly coated on both sides of a 10 μm thick copper foil (negative electrode current collector) except for the lead welded portion, and dried to form a negative electrode mixture layer, and the electrode Cut to size. And the negative electrode was produced by welding the lead body made from nickel to the lead welding part of a negative electrode collector. Here, the packing density of the negative electrode mixture layer is 1.50 g / cm 3 , and the weight ratio of the lithium manganese oxide contained in the positive electrode mixture layer to the artificial graphite powder contained in the negative electrode mixture layer is 2.3: 1. The thickness ratio of the positive electrode to the negative electrode was 1.23: 1.
[0052]
The positive electrode and the negative electrode thus produced were laminated via a polypropylene microporous film serving as a separator, and wound many times to produce a spiral electrode element.
[0053]
Then, an insulating plate was attached to the spiral electrode element and inserted into the battery can, and the negative electrode lead body was welded to the battery can and the positive electrode lead body was welded to the thin plate for current interruption. Next, an electrolytic solution in which LiPF 6 was dissolved in a mixed solution of propylene carbonate and dimethyl carbonate at a concentration of 1 mol / l was poured into the battery can, and the battery lid was placed on the thin plate for current interruption. And the can was sealed by crimping the upper part of a battery can using a caulking machine, and the cylindrical battery of outer diameter 18mm and height 65mm was produced.
[0054]
Example 2 to Example 5
(Weight of lithium manganese oxide contained in positive electrode mixture layer): (weight of graphite powder contained in negative electrode mixture layer), packing density of negative electrode mixture layer, (thickness of positive electrode): (negative electrode This is an example of a battery having the same configuration as that of Example 1 except that (thickness) is changed as shown in Table 1.
[0055]
Comparative Example 1 and Comparative Example 2
(Weight of lithium manganese oxide contained in positive electrode mixture layer): (weight of graphite powder contained in negative electrode mixture layer), packing density of negative electrode mixture layer, (thickness of positive electrode): (negative electrode This is an example of a battery having the same configuration as that of Example 1 except that (thickness) is changed as shown in Table 1.
[0056]
[Table 1]
The battery thus fabricated was charged for 8 hours at a current of 0.3 A and an upper limit voltage of 4.2 V, and then discharged to a final voltage of 2.5 V at a current of 0.5 A. Then, after charging for 3 hours at a current of 1 A and an upper limit voltage of 4.2 V, a charge / discharge cycle of discharging to a final voltage of 2.5 V at a current of 1 A was performed five cycles.
[0058]
Thereafter, the following discharge load test and charge / discharge cycle test were performed to evaluate the performance of the battery.
[0059]
Discharge load test: After charging for 3 hours at a current of 1 A and an upper limit voltage of 4.2 V, the battery was discharged to a final voltage of 2.5 V. In addition, the electric current at the time of discharge was changed in the range of 2-5A.
[0060]
Charging / discharging cycle test: After charging for 3 hours at a current of 1 A and an upper limit voltage of 4.2 V, a charging / discharging cycle of discharging to a final voltage of 2.5 V at a current of 0.5 A was performed 100 times.
[0061]
The discharge load characteristic is shown in FIG. 2, and the charge / discharge cycle characteristic is shown in FIG. FIG. 4 shows the relationship between the ratio between the thickness of the positive electrode and the negative electrode and the capacity retention ratio (capacity at 100 cycles / capacity at initial cycle).
[0062]
As shown in FIG. 2, the weight ratio of the lithium manganese oxide contained in the positive electrode mixture layer and the graphite powder contained in the negative electrode mixture layer, the packing density of the negative electrode mixture layer, the ratio of the thickness of the positive electrode and the negative electrode In the batteries of Examples 1 to 5 in which the battery voltage is within the predetermined range, a large discharge capacity is obtained even when the discharge current is increased, and excellent discharge load characteristics are obtained as compared with the batteries of Comparative Examples 1 and 2. It is done.
[0063]
In addition, with respect to the charge / discharge characteristics shown in FIG. 3, the batteries of Examples 1 to 5 have a smaller capacity drop due to repeated charge / discharge cycles, and are superior to the batteries of Comparative Examples 1 and 2.
[0064]
Furthermore, from FIG. 4, the capacity retention ratio depends particularly on the ratio of the thickness of the positive electrode to the negative electrode, and a capacity retention ratio of 80% or more is obtained by setting this ratio to 1.15: 1 to 1.6: 1. You can see that
[0065]
From this, the weight ratio of the lithium manganese oxide contained in the positive electrode mixture layer and the carbon material contained in the negative electrode mixture layer is 2.0: 1 to 2.9: 1, and the packing density of the negative electrode mixture layer Is 1.4 to 1.7 g / cm 3 , and the ratio of the thickness of the positive electrode to the negative electrode is 1.15: 1 to 1.6: 1, the discharge load characteristics and charge / discharge cycle characteristics of the battery are improved. I understood it.
[0066]
【The invention's effect】
As is clear from the above description, the nonaqueous electrolyte secondary battery of the present invention includes a positive electrode in which a positive electrode mixture layer containing lithium manganese oxide is held by a positive electrode current collector, and graphite. A negative electrode mixture layer having a negative electrode current collector layer held by a negative electrode current collector and a nonaqueous electrolyte solution in which a lithium salt is dissolved in a non-aqueous solvent in an amount of 0.5 to 2 mol / l. The weight ratio of the lithium manganese oxide contained in the graphite and the graphite contained in the negative electrode mixture layer is 2.0: 1 to 2.9: 1, and the packing density of the negative electrode mixture layer is 1.4 to 1.7 g / Since the ratio of the thickness of cm 3 and the positive electrode to the negative electrode is 1.15: 1 to 1.6: 1, a large discharge capacity is obtained and good charge / discharge cycle characteristics are obtained. In the nonaqueous electrolyte secondary battery of the present invention, the lithium manganese oxide constituting the positive electrode is Li x MnO y (where x is 0.505 to 0.525, and y is 1.96 to 2. And the ratio of the (311) diffraction peak and the (400) diffraction peak by X-ray diffraction is 1: 1.10 to 1: 1.20, so that the lower manganese accompanying the repeated charge / discharge cycle Generation of a compound is suppressed, and a decrease in capacity can be prevented. Further, in the non-aqueous electrolyte secondary battery of the present invention, the crystallinity of the graphite structure is collapsed when the interplanar spacing d of the (002) plane measured by the X-ray diffraction method of graphite is 0.34 nm or less. It is difficult to suppress the decomposition of the electrolytic solution. Moreover, the nonaqueous electrolyte secondary battery of this invention can make the filling density of a negative electrode high, and can increase a capacity | capacitance by setting the true density of graphite to 2.0 g / cm < 3 > or more. Further, the lithium manganese oxide used as the positive electrode material in the non-aqueous electrolyte secondary battery of the present invention does not contain Co and Ni, which are rare resources like lithium cobalt composite oxide and lithium nickel composite oxide. Easy to obtain. Therefore, the non-aqueous electrolyte secondary battery of the present invention is also suitable as a large battery that uses a large amount of the positive electrode material.
[Brief description of the drawings]
FIG. 1 is a schematic longitudinal sectional view showing an example of a nonaqueous electrolyte secondary battery to which the present invention is applied.
FIG. 2 is a characteristic diagram showing a discharge load characteristic of a non-aqueous electrolyte secondary battery.
FIG. 3 is a characteristic diagram showing charge / discharge cycle characteristics of a non-aqueous electrolyte secondary battery.
FIG. 4 is a characteristic diagram showing a relationship between a thickness ratio of a positive electrode and a negative electrode and a capacity retention rate.
[Explanation of symbols]
1 negative electrode, 2 positive electrode, 9 negative electrode current collector, 10 positive electrode current collector, 15 negative electrode mixture layer, 16 positive electrode mixture layer
Claims (4)
上記正極合剤層に含有されるリチウムマンガン酸化物と上記負極合剤層に含有される黒鉛との重量比が、２．０：１〜２．９：１であり、
リチウムマンガン酸化物は、ＬｉｘＭｎＯｙ（但し、ｘは０．５０５〜０．５２５であり、ｙは１．９６〜２．００である）で表され、Ｘ線回折による（３１１）回折ピークと（４００）回折ピークの比が１：１．１０〜１：１．２０であり、
上記黒鉛のＸ線回折法によって測定される（００２）面の面間隔ｄが０．３４ｎｍ以下であり、真密度が２．０ｇ／ｃｍ３以上であり、
上記負極合剤層の充填密度が、１．４〜１．７ｇ／ｃｍ３であり、
上記正極と上記負極の厚さの比が、１．１５：１〜１．６：１であることを特徴とする非水電解液二次電池。A positive electrode in which a positive electrode mixture layer containing lithium manganese oxide is held by a positive electrode current collector, a negative electrode in which a negative electrode mixture layer containing graphite is held in a negative electrode current collector, and lithium in a nonaqueous solvent A non-aqueous electrolyte solution in which a salt is dissolved in an amount of 0.5 to 2 mol / l ,
The weight ratio of the lithium manganese oxide contained in the positive electrode mixture layer and the graphite contained in the negative electrode mixture layer is 2.0: 1 to 2.9: 1,
The lithium manganese oxide is represented by Li x MnO y (where x is 0.505 to 0.525 and y is 1.96 to 2.00), and (311) diffraction peak by X-ray diffraction. And the (400) diffraction peak ratio is 1: 1.10 to 1: 1.20,
The (002) plane spacing d measured by X-ray diffraction of the above graphite is 0.34 nm or less, the true density is 2.0 g / cm 3 or more,
The packing density of the negative electrode mixture layer is 1.4 to 1.7 g / cm 3 ,
The non-aqueous electrolyte secondary battery, wherein the thickness ratio of the positive electrode to the negative electrode is 1.15: 1 to 1.6: 1.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP01750798A JP4161396B2 (en) | 1998-01-29 | 1998-01-29 | Non-aqueous electrolyte secondary battery |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP01750798A JP4161396B2 (en) | 1998-01-29 | 1998-01-29 | Non-aqueous electrolyte secondary battery |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH11214042A JPH11214042A (en) | 1999-08-06 |
| JP4161396B2 true JP4161396B2 (en) | 2008-10-08 |
Family
ID=11945901
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP01750798A Expired - Fee Related JP4161396B2 (en) | 1998-01-29 | 1998-01-29 | Non-aqueous electrolyte secondary battery |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP4161396B2 (en) |
Families Citing this family (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2000077102A (en) * | 1998-08-28 | 2000-03-14 | Sony Corp | Nonaqueous electrolyte secondary battery |
| US6506518B1 (en) | 1999-04-27 | 2003-01-14 | Shin-Kobe Electric Machinery Co., Ltd. | Lithium secondary battery |
| JP4656710B2 (en) * | 2000-09-29 | 2011-03-23 | 三洋電機株式会社 | Non-aqueous electrolyte secondary battery |
| JP4483618B2 (en) | 2005-02-17 | 2010-06-16 | ソニー株式会社 | Secondary battery |
| JP2007095402A (en) * | 2005-09-28 | 2007-04-12 | Hitachi Maxell Ltd | Lithium secondary battery |
| CN114730862A (en) * | 2019-11-27 | 2022-07-08 | 三洋电机株式会社 | Nonaqueous electrolyte secondary battery |
-
1998
- 1998-01-29 JP JP01750798A patent/JP4161396B2/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| JPH11214042A (en) | 1999-08-06 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| JP4878687B2 (en) | Lithium secondary battery | |
| JP3844733B2 (en) | Nonaqueous electrolyte secondary battery | |
| JP4878683B2 (en) | Lithium secondary battery | |
| JP4963330B2 (en) | Lithium iron composite oxide for positive electrode active material of lithium secondary battery, method for producing the same, and lithium secondary battery using the same | |
| JP2004139743A (en) | Nonaqueous electrolyte secondary battery | |
| JP2008177346A (en) | Energy storage device | |
| JPH0935715A (en) | Manufacture of positive electrode active material and nonaqueous electrolyte secondary battery | |
| JP7169772B2 (en) | Non-aqueous electrolyte battery and manufacturing method thereof | |
| JP3436600B2 (en) | Rechargeable battery | |
| JP2004014405A (en) | Non-aqueous electrolyte secondary battery | |
| JP2002025611A (en) | Nonaqueous electrolyte secondary battery | |
| JP4994628B2 (en) | Nonaqueous electrolyte secondary battery | |
| JP2000040526A (en) | Nonaqueous electrolyte for secondary battery and nonaqueous electrolyte secondary battery | |
| JP3244389B2 (en) | Lithium secondary battery | |
| JP2001222995A (en) | Lithium ion secondary battery | |
| JP2004335439A (en) | Nonaqueous electrolyte secondary battery | |
| JP4161396B2 (en) | Non-aqueous electrolyte secondary battery | |
| JP2004259485A (en) | Nonaqueous electrolyte secondary battery | |
| JP4183412B2 (en) | Non-aqueous secondary battery | |
| JPH0547383A (en) | Nonaqueous electrolyte secondary battery and manufacture thereof | |
| JP4320526B2 (en) | Nonaqueous electrolyte secondary battery | |
| JP4711319B2 (en) | Non-aqueous secondary battery | |
| JP7403474B2 (en) | Non-aqueous electrolyte secondary battery and its manufacturing method | |
| JPH11185822A (en) | Nonaqueous electrolyte secondary battery | |
| JP2001015168A (en) | Lithium secondary battery |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| A621 | Written request for application examination |
Free format text: JAPANESE INTERMEDIATE CODE: A621 Effective date: 20041215 |
|
| A977 | Report on retrieval |
Free format text: JAPANESE INTERMEDIATE CODE: A971007 Effective date: 20070921 |
|
| A131 | Notification of reasons for refusal |
Free format text: JAPANESE INTERMEDIATE CODE: A131 Effective date: 20071009 |
|
| A521 | Written amendment |
Free format text: JAPANESE INTERMEDIATE CODE: A523 Effective date: 20071210 |
|
| A02 | Decision of refusal |
Free format text: JAPANESE INTERMEDIATE CODE: A02 Effective date: 20080129 |
|
| A521 | Written amendment |
Free format text: JAPANESE INTERMEDIATE CODE: A523 Effective date: 20080228 |
|
| A911 | Transfer of reconsideration by examiner before appeal (zenchi) |
Free format text: JAPANESE INTERMEDIATE CODE: A911 Effective date: 20080425 |
|
| TRDD | Decision of grant or rejection written | ||
| A01 | Written decision to grant a patent or to grant a registration (utility model) |
Free format text: JAPANESE INTERMEDIATE CODE: A01 Effective date: 20080701 |
|
| A01 | Written decision to grant a patent or to grant a registration (utility model) |
Free format text: JAPANESE INTERMEDIATE CODE: A01 |
|
| A61 | First payment of annual fees (during grant procedure) |
Free format text: JAPANESE INTERMEDIATE CODE: A61 Effective date: 20080714 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20110801 Year of fee payment: 3 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20110801 Year of fee payment: 3 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20110801 Year of fee payment: 3 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20120801 Year of fee payment: 4 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20120801 Year of fee payment: 4 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20130801 Year of fee payment: 5 |
|
| LAPS | Cancellation because of no payment of annual fees |