JP4710214B2 - Lithium secondary battery - Google Patents
Lithium secondary battery Download PDFInfo
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- JP4710214B2 JP4710214B2 JP2003047075A JP2003047075A JP4710214B2 JP 4710214 B2 JP4710214 B2 JP 4710214B2 JP 2003047075 A JP2003047075 A JP 2003047075A JP 2003047075 A JP2003047075 A JP 2003047075A JP 4710214 B2 JP4710214 B2 JP 4710214B2
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- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 title claims description 31
- 229910052744 lithium Inorganic materials 0.000 title claims description 31
- 239000011163 secondary particle Substances 0.000 claims description 67
- 239000011164 primary particle Substances 0.000 claims description 56
- 239000002245 particle Substances 0.000 claims description 38
- 239000007774 positive electrode material Substances 0.000 claims description 32
- 239000013078 crystal Substances 0.000 claims description 13
- 239000011255 nonaqueous electrolyte Substances 0.000 claims description 8
- KLARSDUHONHPRF-UHFFFAOYSA-N [Li].[Mn] Chemical compound [Li].[Mn] KLARSDUHONHPRF-UHFFFAOYSA-N 0.000 claims description 4
- 230000002776 aggregation Effects 0.000 claims 1
- 238000004220 aggregation Methods 0.000 claims 1
- 230000000052 comparative effect Effects 0.000 description 87
- 229910021445 lithium manganese complex oxide Inorganic materials 0.000 description 34
- 238000006243 chemical reaction Methods 0.000 description 11
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 10
- 229910001416 lithium ion Inorganic materials 0.000 description 10
- 238000012360 testing method Methods 0.000 description 10
- 229910052596 spinel Inorganic materials 0.000 description 7
- 239000011029 spinel Substances 0.000 description 7
- 230000007423 decrease Effects 0.000 description 6
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- 239000002033 PVDF binder Substances 0.000 description 4
- 229910052782 aluminium Inorganic materials 0.000 description 4
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 4
- 239000011248 coating agent Substances 0.000 description 4
- 238000000576 coating method Methods 0.000 description 4
- 239000000463 material Substances 0.000 description 4
- 229910052760 oxygen Inorganic materials 0.000 description 4
- 239000001301 oxygen Substances 0.000 description 4
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- 239000002002 slurry Substances 0.000 description 4
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- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 3
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- XTHFKEDIFFGKHM-UHFFFAOYSA-N Dimethoxyethane Chemical compound COCCOC XTHFKEDIFFGKHM-UHFFFAOYSA-N 0.000 description 2
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- 101150058243 Lipf gene Proteins 0.000 description 2
- MQHWFIOJQSCFNM-UHFFFAOYSA-L Magnesium salicylate Chemical compound [Mg+2].OC1=CC=CC=C1C([O-])=O.OC1=CC=CC=C1C([O-])=O MQHWFIOJQSCFNM-UHFFFAOYSA-L 0.000 description 2
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- 239000003792 electrolyte Substances 0.000 description 2
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- 239000011572 manganese Substances 0.000 description 2
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- BQCIDUSAKPWEOX-UHFFFAOYSA-N 1,1-Difluoroethene Chemical compound FC(F)=C BQCIDUSAKPWEOX-UHFFFAOYSA-N 0.000 description 1
- LZDKZFUFMNSQCJ-UHFFFAOYSA-N 1,2-diethoxyethane Chemical compound CCOCCOCC LZDKZFUFMNSQCJ-UHFFFAOYSA-N 0.000 description 1
- OFHQVNFSKOBBGG-UHFFFAOYSA-N 1,2-difluoropropane Chemical compound CC(F)CF OFHQVNFSKOBBGG-UHFFFAOYSA-N 0.000 description 1
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- KXJGSNRAQWDDJT-UHFFFAOYSA-N 1-acetyl-5-bromo-2h-indol-3-one Chemical compound BrC1=CC=C2N(C(=O)C)CC(=O)C2=C1 KXJGSNRAQWDDJT-UHFFFAOYSA-N 0.000 description 1
- PPDFQRAASCRJAH-UHFFFAOYSA-N 2-methylthiolane 1,1-dioxide Chemical compound CC1CCCS1(=O)=O PPDFQRAASCRJAH-UHFFFAOYSA-N 0.000 description 1
- SBUOHGKIOVRDKY-UHFFFAOYSA-N 4-methyl-1,3-dioxolane Chemical compound CC1COCO1 SBUOHGKIOVRDKY-UHFFFAOYSA-N 0.000 description 1
- NLHHRLWOUZZQLW-UHFFFAOYSA-N Acrylonitrile Chemical compound C=CC#N NLHHRLWOUZZQLW-UHFFFAOYSA-N 0.000 description 1
- 229910000838 Al alloy Inorganic materials 0.000 description 1
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
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- KRHYYFGTRYWZRS-UHFFFAOYSA-M Fluoride anion Chemical compound [F-] KRHYYFGTRYWZRS-UHFFFAOYSA-M 0.000 description 1
- 229910015015 LiAsF 6 Inorganic materials 0.000 description 1
- 229910015044 LiB Inorganic materials 0.000 description 1
- 229910013063 LiBF 4 Inorganic materials 0.000 description 1
- 229910013684 LiClO 4 Inorganic materials 0.000 description 1
- 229910014689 LiMnO Inorganic materials 0.000 description 1
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 1
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- 229910000831 Steel Inorganic materials 0.000 description 1
- 230000004931 aggregating effect Effects 0.000 description 1
- 229910021383 artificial graphite Inorganic materials 0.000 description 1
- MTAZNLWOLGHBHU-UHFFFAOYSA-N butadiene-styrene rubber Chemical compound C=CC=C.C=CC1=CC=CC=C1 MTAZNLWOLGHBHU-UHFFFAOYSA-N 0.000 description 1
- 229920005549 butyl rubber Polymers 0.000 description 1
- OJIJEKBXJYRIBZ-UHFFFAOYSA-N cadmium nickel Chemical compound [Ni].[Cd] OJIJEKBXJYRIBZ-UHFFFAOYSA-N 0.000 description 1
- YACLQRRMGMJLJV-UHFFFAOYSA-N chloroprene Chemical compound ClC(=C)C=C YACLQRRMGMJLJV-UHFFFAOYSA-N 0.000 description 1
- 229910052804 chromium Inorganic materials 0.000 description 1
- 229910017052 cobalt Inorganic materials 0.000 description 1
- 239000010941 cobalt Substances 0.000 description 1
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 description 1
- 239000004020 conductor Substances 0.000 description 1
- 239000011889 copper foil Substances 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- QHGJSLXSVXVKHZ-UHFFFAOYSA-N dilithium;dioxido(dioxo)manganese Chemical compound [Li+].[Li+].[O-][Mn]([O-])(=O)=O QHGJSLXSVXVKHZ-UHFFFAOYSA-N 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 229920001971 elastomer Polymers 0.000 description 1
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- XUCNUKMRBVNAPB-UHFFFAOYSA-N fluoroethene Chemical compound FC=C XUCNUKMRBVNAPB-UHFFFAOYSA-N 0.000 description 1
- 239000000446 fuel Substances 0.000 description 1
- 229910002804 graphite Inorganic materials 0.000 description 1
- 239000010439 graphite Substances 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 238000004898 kneading Methods 0.000 description 1
- 229920000126 latex Polymers 0.000 description 1
- 239000004816 latex Substances 0.000 description 1
- 229910002102 lithium manganese oxide Inorganic materials 0.000 description 1
- 229910003002 lithium salt Inorganic materials 0.000 description 1
- 159000000002 lithium salts Chemical class 0.000 description 1
- 229910021437 lithium-transition metal oxide Inorganic materials 0.000 description 1
- VLXXBCXTUVRROQ-UHFFFAOYSA-N lithium;oxido-oxo-(oxomanganiooxy)manganese Chemical compound [Li+].[O-][Mn](=O)O[Mn]=O VLXXBCXTUVRROQ-UHFFFAOYSA-N 0.000 description 1
- 229910052748 manganese Inorganic materials 0.000 description 1
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- HXJUTPCZVOIRIF-UHFFFAOYSA-N sulfolane Chemical compound O=S1(=O)CCCC1 HXJUTPCZVOIRIF-UHFFFAOYSA-N 0.000 description 1
- 229910052717 sulfur Inorganic materials 0.000 description 1
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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
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- Secondary Cells (AREA)
- Battery Electrode And Active Subsutance (AREA)
Description
【０００１】
【発明の属する技術分野】
本発明はリチウム二次電池に係り、特に、正極活物質にリチウムマンガン複酸化物を用い、電極群を非水電解液に浸潤させたリチウム二次電池に関する。
【０００２】
【従来の技術】
従来、再充電可能な二次電池の分野では、鉛電池、ニッケル−カドミウム電池、ニッケル−水素電池等の水溶液系電池が主流であった。しかしながら、電気機器の小型化、軽量化が進むにつれ、高エネルギー密度を有するリチウム二次電池が着目され、その研究、開発及び商品化が急速に進められた結果、現在では、携帯電話やノートパソコン向けに小型民生用リチウム二次電池が広く普及している。
【０００３】
一方、地球温暖化や燃料枯渇の問題から電気自動車（ＥＶ）や駆動の一部を電気モータで補助するハイブリッド電気自動車（ＨＥＶ）が各自動車メーカーで開発され、その電源としてより高容量で高出力な二次電池が求められるようになってきた。このような要求に合致する電源として、高電圧を有する非水溶液系のリチウム二次電池が注目されている。
【０００４】
リチウム二次電池の正極活物質には一般にリチウム遷移金属酸化物が用いられており、中でも容量やサイクル特性等のバランスからコバルト酸リチウムが広く用いられているが、原料であるコバルトは資源量が少なくコスト高となることから、電気自動車用やハイブリッド電気自動車用電池の正極活物質としてはリチウムマンガン複酸化物が有望視され開発が進められている。
【０００５】
例えば、正極活物質にリチウムマンガン複酸化物を用いたリチウム二次電池に、平均粒子径０．５μｍ付近の層状マンガン酸リチウム（例えば、特許文献１参照）や平均粒子径８μｍ程度のスピネル型リチウムマンガン複合酸化物（例えば、特許文献２参照）を用いることにより高容量の電池が得られることが開示されている。また、平均粒径０．０１μｍ以上５．０μｍ以下の一次粒子が凝集してなる平均粒径０．１μｍ以上１５μｍ以下の一次粒子凝集体を用いた電池が開示されている（例えば、特許文献３参照）。
【０００６】
【特許文献１】
特開２００１−２０２９４７号公報（段落番号「００１４」、「００７２」、表２、表４）
【特許文献２】
特開２００１−１４６４２６号公報（段落番号「００１０」、「００１７」、「００２１」）
【特許文献３】
特開平６−３２５７９１号公報（段落番号「０００９」、「００４７」）
【０００７】
【発明が解決しようとする課題】
しかしながら、リチウムマンガン複酸化物を正極活物質に用いたリチウム二次電池の出力特性は、電気自動車用を想定した場合に必ずしも十分とは言えない。これに対して、電極面積を広くして電池を高容量化することが検討されているが、電池サイズが大きくなり、車載スペースを考慮すると実用上難点を生じる。
【０００８】
本発明は上記事案に鑑み、電池サイズを大きくすることなく出力特性を向上させたリチウム二次電池を提供することを課題とする。
【０００９】
【課題を解決するための手段】
上記課題を解決するために、本発明は、正極活物質にリチウムマンガン複酸化物を用い、電極群を非水電解液に浸潤させたリチウム二次電池において、前記リチウムマンガン複酸化物が層状結晶構造を有しており、分級することによって、一次粒子が凝集した二次粒子の平均粒子径が５．０μｍ以上１５μｍ以下であり、かつ、前記一次粒子の平均粒子径が０．５μｍ乃至１．５μｍであり、前記二次粒子の粒子径の最大値ａと最小値ｂとの比ａ／ｂが２１以上３２以下であることを特徴とする。
【００１０】
本発明によれば、正極活物質に層状結晶構造のリチウムマンガン複酸化物が用いられるので、リチウムマンガン複酸化物が酸素層間にリチウム単独の二次元拡散層を有することから、スピネル結晶構造に比べリチウムの拡散係数が小さくリチウムの挿入、脱離が容易となるため、内部抵抗が低減すると共に、二次粒子の平均粒子径が５．０μｍ未満では、非水電解液との反応面積は増加するが結晶の成長が不十分なため、反応抵抗が増大して出力を低下させ、逆に、二次粒子の平均粒子径が１５μｍを超えると、反応面積が減少し正極活物質重量当たりの電流密度が大きくなるため、出力低下を招くので、分級することによって、二次粒子の平均粒子径を５．０μｍ以上１５μｍ以下とすることで反応面積が適正化され、かつ、一次粒子の平均粒子径を０．５μｍ乃至１．５μｍとし、二次粒子の粒子径の最大値ａと最小値ｂとの比ａ／ｂを２１以上３２以下とすることで、電極表面の凹凸が減少し均一な厚みの電極作製が可能となるため、電池内部での微小短絡が抑制されるので、電池サイズを大きくすることなく出力特性を向上させたリチウム二次電池を得ることができる。
【００１２】
【発明の実施の形態】
＜第１実施形態＞
以下、図面を参照して、本発明を電気自動車用電源として用いられる円筒型リチウムイオン二次電池に適用した第１の実施の形態について説明する。
【００１３】
（正極活物質）
正極活物質として層状岩塩型結晶構造を有するリチウムマンガン複酸化物を用いた。使用したリチウムマンガン複酸化物は、分級装置により粒子径制御することで一次粒子の平均粒子径（以下、一次粒子平均径という。）が０．１〜２．０μｍ、一次粒子が凝集した二次粒子の平均粒子径（以下、二次粒子平均径という。）が２．０〜２５μｍの平均粒子径材料とした。平均粒子径はレーザー回折式粒度分布測定装置により測定した。
【００１４】
（正極板）
上述した平均粒子径材料のリチウムマンガン複酸化物粉末と、導電材として鱗片状黒鉛と、結着剤としてポリフッ化ビニリデン（ＰＶＤＦ）と、を重量比８５：１０：５で混合し、これに分散溶媒のＮ−メチルピロリドン（ＮＭＰ）を添加、混練したスラリを、厚さ２０μｍのアルミニウム箔の両面に塗布した。このとき、正極長寸方向の一方の側縁に幅３０ｍｍの未塗布部を残した。その後、乾燥、プレス、裁断することにより厚さ１７０μｍの正極板を得た。側縁に残した未塗布部に切り欠きを入れ、切り欠き残部を正極リード片２とした。隣り合う正極リード片２を５０ｍｍ間隔とし、正極リード片２の幅を５ｍｍとした。
【００１５】
（負極板）
負極活物質として人造黒鉛粉末９０質量部に対し、結着剤としてＰＶＤＦを１０質量部添加し、これに分散溶媒のＮＭＰを添加、混練したスラリを、厚さ１０μｍの電解銅箔の両面に塗布した。このとき、負極長寸方向の一方の側縁に幅３０ｍｍの未塗布部を残した。その後乾燥、プレス、裁断することにより厚さ１３０μｍの負極板を得た。側縁に残した未塗布部に正極と同様に切り欠きを入れ、切り欠き残部を負極リード片３とした。隣り合う負極リード片３を５０ｍｍ間隔とし、負極リード片３の幅を５ｍｍとした。
【００１６】
（電池の作製）
図１に示すように、作製した正負極板を、これら両極板が直接接触しないように、厚さ４０μｍのポリエチレン製セパレータと共に捲回して捲回群６を作製した。捲回の中心には、ポリプロピレン製の中空円筒状の軸芯１を用いた。このとき、正極リード片２と負極リード片３とが、それぞれ捲回群６の互いに反対側の両端面に位置するようにした。
【００１７】
正極リード片２を変形させ、その全てを正極集電リング４の周囲から一体に張り出した鍔部周面付近に集合、接触させた後、正極リード片２と鍔部周面とを超音波溶接して正極リード片２を鍔部周面に接続した。一方、負極集電リング５と負極リード片３との接続操作も、正極集電リング４と正極リード片２との接続操作と同様に実施した。その後、正極集電リング４の鍔部及び捲回群６周面全周に絶縁被覆を施し、捲回群６をニッケルメッキが施されたスチール製の電池容器７内に挿入した。
【００１８】
負極集電リング５には、予め電気的導通のための負極リード板８を溶接しておき、電池容器７に捲回群６を挿入後、電池容器７の底部と負極リード板８とを溶接した。一方、正極集電リング４には、予め複数枚のアルミニウム製のリボンを重ね合わせて構成した正極リード９の一端を溶接しておき、正極リード９の他端を、電池容器７を封口するための電池蓋の下面に溶接した。電池蓋は、蓋ケース１２と、蓋キャップ１３と、気密を保つ弁押え１４と、アルミニウム合金製で薄板状の内圧低減機構の開裂弁１１とで構成されており、これらが積層されて蓋ケース１２の周縁をカシメることによって組立てられている。開裂弁１１の開裂圧は約９×１０５Ｐａに設定した。
【００１９】
捲回群６全体を浸潤可能な所定量の非水電解液を電池容器７内に注入し、その後、正極リード９を折りたたむようにして電池蓋で電池容器７に蓋をし、ＥＰＤＭ樹脂製ガスケット１０を介してカシメて密封し、容量９．０Ａｈの円筒型リチウムイオン二次電池２０を完成させた。
【００２０】
非水電解液には、エチレンカーボネート（ＥＣ）とジメチルカーボネート（ＤＭＣ）とジエチルカーボネート（ＤＥＣ）とを体積比１：１：１の割合で混合した混合溶媒中へ６フッ化リン酸リチウム（ＬｉＰＦ６）を１モル／リットル溶解したものを用いた。
【００２１】
＜第２実施形態＞
次に、本発明を電気自動車用電源として用いられる円筒型リチウムイオン二次電池に適用した第２の実施の形態について説明する。本実施形態では、第１実施形態の平均粒子径制御に加えて二次粒子の粒子径範囲を制限したものである。なお、本実施形態において、第１実施形態と同一の部材には同一の符号を付してその説明を省略し、異なる箇所のみ説明する。
【００２２】
本実施形態では、正極活物質のリチウムマンガン複酸化物は、二次粒子平均径が５．０〜１５μｍ、二次粒子の粒子径の最大値ａと最小値ｂとの比ａ／ｂが３２以下の粒子径範囲材料とした。粒子径の最大値ａ及び最小値ｂはレーザー回折式粒度分布測定装置により測定した。
【００２３】
【実施例】
次に、以上の実施形態に従って作製した円筒型リチウムイオン二次電池２０の実施例について説明する。なお、以下に示す実施例１〜１０は参考のために記載したものである。また、比較のために作製した比較例の電池についても併記する。
【００２４】
（実施例１）
下表１に示すように、実施例１は第１実施形態に従い、正極活物質に二次粒子平均径が２．０μｍ、一次粒子平均径が０．１μｍの層状構造リチウムマンガン複酸化物粉末を用いた。
【００２５】
【表１】
（実施例２〜実施例１０）
表１に示すように、実施例２〜実施例１０では、二次粒子平均径及び一次粒子平均径を変える以外は実施例１と同様にした。二次粒子平均径は、実施例２では３．０μｍ、実施例３では４．０μｍ、実施例４では５．０μｍ、実施例５では７．５μｍ、実施例６では１０．０μｍ、実施例７では１２．５μｍ、実施例８では１５．０μｍ、実施例９では２０．０μｍ、実施例１０では２５．０μｍとし、一次粒子平均径は、実施例２では０．１μｍ、実施例３及び実施例４では０．５μｍ、実施例５及び実施例６では１．０μｍ、実施例７及び実施例８では１．５μｍ、実施例９及び実施例１０では２．０μｍとした。
【００２７】
（比較例１〜比較例４）
表１に示すように、比較例１〜比較例４では、二次粒子平均径及び一次粒子平均径を変える以外は実施例１と同様にした。二次粒子平均径は、比較例１では１．０μｍ、比較例２では１．５μｍ、比較例３では３０．０μｍ、比較例４では３５．０μｍとし、一次粒子平均径は、比較例１及び比較例２では０．０５μｍ、比較例３では２．５μｍ、比較例４では３．０μｍとした。
【００２８】
（比較例５）
表１に示すように、比較例５では、正極活物質に二次粒子平均径が２．０μｍ、一次粒子平均径が０．１μｍのスピネル構造リチウムマンガン複酸化物粉末を用いる以外は実施例１と同様にした。
【００２９】
（比較例６〜比較例９）
表１に示すように、比較例６〜比較例９では、二次粒子平均径及び一次粒子平均径を変える以外は比較例５と同様にした。二次粒子平均径は、比較例６では５．０μｍ、比較例７では１０．０μｍ、比較例８では１５．０μｍ、比較例９では３０．０μｍとし、一次粒子平均径は、比較例６では０．５μｍ、比較例７では１．０μｍ、比較例８では１．５μｍ、比較例９では２．５μｍとした。
【００３０】
（実施例１１）
下表２に示すように、実施例１１は第２実施形態に従い、正極活物質に二次粒子平均径が５．０μｍ、一次粒子平均径が０．５μｍ、二次粒子の粒子径の最大値ａが２１．１０μｍ、最小値ｂが１．０１μｍの層状構造リチウムマンガン複酸化物粉末を用いた。この最大値ａと最小値ｂとの比ａ／ｂは２１となる。
【００３１】
【表２】
（実施例１２）
表２に示すように、実施例１２では、二次粒子平均径を７．０μｍ、一次粒子平均径を１．０μｍ、最大値ａを２９．８５μｍ、最小値ｂを１．０１μｍとする以外は実施例１１と同様にした。比ａ／ｂは３０となる。
【００３３】
（実施例１３〜実施例１４）
表２に示すように、実施例１３〜実施例１４では、二次粒子平均径を変える以外は実施例１２と同様にした。実施例１３では７．５μｍ、実施例１４では８．０μｍとした。比ａ／ｂは、実施例１３、実施例１４共に３０となる。
【００３４】
（実施例１５）
表２に示すように、実施例１５では、二次粒子平均径を８．５μｍ、一次粒子平均径を１．０μｍ、最大値ａを２１．１０μｍ、最小値ｂを０．６６μｍとする以外は実施例１１と同様にした。比ａ／ｂは３２となる。
【００３５】
（実施例１６）
表２に示すように、実施例１６では、二次粒子平均径を９．０μｍとする以外は実施例１２と同様にした。比ａ／ｂは３０となる。
【００３６】
（実施例１７）
表２に示すように、実施例１７では、二次粒子平均径を１０．０μｍ、一次粒子平均径を１．０μｍとする以外は実施例１１と同様にした。比ａ／ｂは２１となる。
【００３７】
（実施例１８）
表２に示すように、実施例１８では、二次粒子平均径を１２．５μｍ、一次粒子平均径を１．５μｍとする以外は実施例１２と同様にした。比ａ／ｂは３０となる。
【００３８】
（実施例１９）
表２に示すように、実施例１９では、二次粒子平均径を１５．０μｍ、一次粒子平均径を１．５μｍ、最大値ａを４２．２０μｍ、最小値ｂを１．６９μｍとする以外は実施例１１と同様にした。比ａ／ｂは２５となる。
【００３９】
（比較例１０）
表２に示すように、比較例１０では、正極活物質に二次粒子平均径が５．０μｍ、一次粒子平均径が０．５μｍ、最大値ａが１９．９０μｍ、最小値ｂが１．１５μｍのスピネル構造リチウムマンガン複酸化物粉末を用いる以外は実施例１１と同様にした。比ａ／ｂは１７となる。
【００４０】
（比較例１１）
表２に示すように、比較例１１では、二次粒子平均径を５．５μｍ、一次粒子平均径を０．５μｍ、最大値ａを２２．８０μｍ、最小値ｂを１．１５μｍとする以外は比較例１０と同様にした。比ａ／ｂは２０となる。
【００４１】
（比較例１２）
表２に示すように、比較例１２では、二次粒子平均径を６．０μｍ、一次粒子平均径を０．５μｍ、最大値ａを２２．８０μｍ、最小値ｂを１．３２μｍとする以外は比較例１０と同様にした。比ａ／ｂは１７となる。
【００４２】
（比較例１３）
表２に示すように、比較例１３では、二次粒子平均径を６．５μｍ、一次粒子平均径を０．５μｍ、最大値ａを１９．９０μｍ、最小値ｂを１．３２μｍとする以外は比較例１０と同様にした。比ａ／ｂは１５となる。
【００４３】
（比較例１４）
表２に示すように、比較例１４では、二次粒子平均径を７．５μｍ、一次粒子平均径を１．０μｍ、最大値ａを２２．８０μｍ、最小値ｂを１．５１μｍとする以外は比較例１０と同様にした。比ａ／ｂは１５となる。
【００４４】
（比較例１５）
表２に示すように、比較例１５では、二次粒子平均径を９．０μｍ、一次粒子平均径を１．０μｍ、最大値ａを２９．９１μｍ、最小値ｂを１．５１μｍとする以外は比較例１０と同様にした。比ａ／ｂは２０となる。
【００４５】
（比較例１６）
表２に示すように、比較例１６では、二次粒子平均径を１０．５μｍ、一次粒子平均径を１．０μｍ、最大値ａを３７．００μｍ、最小値ｂを１．０６μｍとする以外は比較例１０と同様にした。比ａ／ｂは３５となる。
【００４６】
（比較例１７）
表２に示すように、比較例１７では、二次粒子平均径を１３．０μｍ、一次粒子平均径を１．５μｍ、最大値ａを５２．３３μｍ、最小値ｂを２．１２μｍとする以外は比較例１０と同様にした。比ａ／ｂは２５となる。
【００４７】
（比較例１８）
表２に示すように、比較例１８では、二次粒子平均径を１３．５μｍ、一次粒子平均径を１．５μｍ、最大値ａを３７．００μｍ、最小値ｂを３．００μｍとする以外は比較例１０と同様にした。比ａ／ｂは１２となる。
【００４８】
（比較例１９）
表２に示すように、比較例１９では、二次粒子平均径を１４．０μｍ、一次粒子平均径を１．５μｍ、最大値ａを４４．００μｍ、最小値ｂを２．５２μｍとする以外は比較例１０と同様にした。比ａ／ｂは１７となる。
【００４９】
（比較例２０）
表２に示すように、比較例２０では、二次粒子平均径を１４．５μｍとする以外は比較例１９と同様にした。比ａ／ｂは１７となる。
【００５０】
（比較例２１）
表２に示すように、比較例２１では、二次粒子平均径を１５．０μｍ、一次粒子平均径を１．５μｍ、最大値ａを４７．９８μｍ、最小値ｂを２．５２μｍとする以外は比較例１０と同様にした。比ａ／ｂは１９となる。
【００５１】
（比較例２２）
表２に示すように、比較例２２では、二次粒子平均径を９．５μｍ、一次粒子平均径を１．０μｍ、最大値ａを４２．２０μｍ、最小値ｂを１．０１μｍとする以外は実施例１１と同様にした。比ａ／ｂは４２となる。
【００５２】
（比較例２３）
表２に示すように、比較例２３では、二次粒子平均径を１１．５μｍ、一次粒子平均径を１．０μｍ、最大値ａを４２．２０μｍ、最小値ｂを０．６６μｍとする以外は実施例１１と同様にした。比ａ／ｂは６４となる。
【００５３】
（比較例２４）
表２に示すように、比較例２４では、二次粒子平均径を１０．０μｍ、一次粒子平均径を１．０μｍ、最大値ａを４４．００μｍ、最小値ｂを１．０６μｍとする以外は比較例１０と同様にした。比ａ／ｂは４２となる。
【００５４】
（比較例２５）
表２に示すように、比較例２５では、二次粒子平均径を１３．５μｍ、一次粒子平均径を２．０μｍ、最大値ａを１０４．７０μｍ、最小値ｂを１．７８μｍとする以外は比較例１０と同様にした。比ａ／ｂは５９となる。
【００５５】
＜試験・評価＞
（出力測定試験）
以上のように作製した実施例及び比較例の各電池について、約５時間で放電することができる電流値（０．２Ｃ）で４．２Ｖ定電圧制御し、８時間充電して満充電状態とした後、１０Ａ、２０Ａ、４０Ａ、６０Ａの電流値でそれぞれ３０秒間放電し、３０秒目の電池電圧を測定して、その電圧を電流値に対してプロットした直線が３．２Ｖに到達の電流値（Ｉａ）から、出力（（Ｗ）＝Ｉａ×３．２）を算出し、その出力を電池重量で除して出力密度を算出する出力測定試験を行った。この測定は２５±２°Ｃの雰囲気で行った。
【００５６】
（微小内部短絡発生数測定試験）
以上のように作製した実施例１１〜実施例１９及び比較例１０〜比較例２５の電池のそれぞれ２０セルについて、上述した条件で満充電状態とした後、２５°Ｃ中に放置して電圧低下速度を測定した。このとき、１４日めと２１日めとの電圧差を求め、１日当りの電圧低下速度が、２．７ｍＶ／ｄａｙを超えた電池を微小内部短絡発生電池とした。
【００５７】
下表３に実施例１〜実施例１０及び比較例１〜比較例９の電池について出力測定試験の試験結果を示す。また、下表４に実施例１１〜実施例１９及び比較例１０〜比較例２５の電池について出力測定試験及び微小内部短絡発生数測定試験の試験結果を示す。
【００５８】
【表３】
【表４】
表３に示すように、正極活物質に層状構造を有するリチウムマンガン複酸化物を用い、二次粒子平均径を２．０μｍ未満、一次粒子平均径を０．１μｍ未満とした比較例１、比較例２の電池及び二次粒子平均径が２５．０μｍを超え、一次粒子平均径が２．０μｍを超えた比較例３、比較例４の電池では、上述した測定方法による出力密度が４００〜５２０Ｗ／ｋｇであった。また、正極活物質にスピネル構造リチウムマンガン複酸化物を用いた比較例５〜比較例９の電池では、３２０〜５３０Ｗ／ｋｇの出力密度であった。これに対して、二次粒子平均径が２．０〜２５．０μｍ、一次粒子平均径が０．１〜２．０μｍの層状構造リチウムマンガン複酸化物を用いた実施例１〜実施例１０の電池では、６００〜７５０Ｗ／ｋｇの出力密度であった。また、二次粒子平均径が２．０μｍ、３．０μｍ、一次粒子平均径が０．１μｍの層状構造リチウムマンガン複酸化物を用いた実施例１、実施例２の電池及び二次粒子平均径が２０．０μｍ、２５．０μｍ、一次粒子平均径が２．０μｍの層状構造リチウムマンガン複酸化物を用いた実施例９、実施例１０の電池では、６００〜６８０Ｗ／ｋｇと出力密度が若干低下した。これに対し、正極活物質に二次粒子平均径が４．０〜１５．０μｍ、一次粒子平均径が０．５〜１．５μｍの層状構造リチウムマンガン複酸化物を用いた実施例３〜実施例８の電池は、７３０〜７５０Ｗ／ｋｇの優れた出力密度を示した。
【００６１】
表４に示すように、二次粒子平均径が９．５μｍ、１１．５μｍ、一次粒子平均径が１．０μｍ、比ａ／ｂが３２を超えた層状構造リチウムマンガン複酸化物を正極活物質に用いた比較例２２、比較例２３の電池では、出力密度が７４０Ｗ／ｋｇを示したものの、電池内部での微小短絡の発生を確認した。これに対して、二次粒子平均径が５．０〜１５．０μｍ、一次粒子平均径が０．５〜１．５μｍ、比ａ／ｂが３２以下の層状構造リチウムマンガン複酸化物を用いた実施例１１〜実施例１９の電池では、７３０〜７５０Ｗ／ｋｇの優れた出力密度を示し、微小短絡の発生も確認できなかった。また、スピネル構造リチウムマンガン複酸化物を正極活物質に用いた比較例１０〜比較例２１、比較例２４及び比較例２５の電池は、４９０〜５４０Ｗ／ｋｇの出力密度であった。中でも、比ａ／ｂが３２を超えた比較例２４、比較例２５の電池では、微小短絡も発生した。また、最大値ａが同じ４２．２０μｍの層状構造リチウムマンガン複酸化物を使用した比較例２２、比較例２３の電池と実施例１９の電池とを比較すると、平均粒子径が大きい粉末であっても比ａ／ｂが２１以上３２以下であれば、電池内部での微小短絡の発生はなかった。
【００６２】
以上の試験結果から、二次粒子平均径が２．０μｍ〜２５．０μｍ、一次粒子平均径が０．１〜２．０μｍの層状構造リチウムマンガン複酸化物を正極活物質に用いた電池は優れた出力特性を示すことが判った。中でも、二次粒子平均径が４．０〜１５．０μｍ、一次粒子平均径が０．５〜１．５μｍの層状構造リチウムマンガン複酸化物を正極活物質に用いた電池は出力密度が高いことが判明した。また、二次粒子平均径が５．０〜１５．０μｍ、一次粒子平均径が０．５〜１．５μｍ、比ａ／ｂが２１〜３２の層状構造リチウムマガン複酸化物を正極活物質に使用した電池では、電池内部での微小短絡を発生することなく、より優れた出力特性を示すことが判明した。
【００６３】
上記実施形態では、正極活物質にリチウムマンガン複酸化物のうち層状岩塩型結晶構造のリチウムマンガン複酸化物が用いられる。層状構造はスピネル構造に比べリチウムの拡散性に関しては、酸素層間にリチウム単独の二次元拡散層を持っているため拡散係数が小さい。このため、リチウムの挿入、脱離が容易となり内部抵抗が低減するので、電池サイズを大きくすることなく出力特性を向上させたリチウム二次電池を得ることができる。従って、電気自動車のような高出力を要求され、車載スペースに限りがある場合にも、好適に使用することができる。
【００６４】
また、正極活物質に二次粒子平均径が２．０μｍ未満、一次粒子平均径が０．１μｍ未満の層状構造リチウムマンガン複酸化物を用いると、非水電解液との反応面積は増加するが結晶が十分に成長していないため、反応抵抗が増大してリチウムイオン二次電池の出力を低下させ、逆に、二次粒子平均径が２５μｍを超え、一次粒子平均径が２．０μｍを超える層状構造リチウムマンガン複酸化物を用いると、反応面積が減少し正極活物質重量当たりの電流密度が大きくなるため、リチウムイオン二次電池の出力低下を招く。このため、第１実施形態では、正極活物質に二次粒子平均径が２．０μｍ以上２５μｍ以下、一次粒子平均径が０．１μｍ以上２．０μｍ以下の層状構造リチウムマンガン複酸化物が用いられる。これにより、正極活物質の反応面積が最適化され、電池サイズを大きくすることなく出力特性を向上させたリチウムイオン二次電池を得ることができる。特に、二次粒子平均径を４．０μｍ以上１５μｍ以下、一次粒子平均径を０．５μｍ以上１．５μｍ以下とすることで、出力特性をより向上させることができる。
【００６５】
また、二次粒子の粒子径の最大値ａと最小値ｂとの比ａ／ｂが３２を超えると、正極活物質を含むスラリをアルミニウム箔に塗布する塗工時に塗工面に凹凸が生じて、均一な厚みでの大面積塗工ができない。塗工面の凹凸により電池作製時等にセパレータを破損して微小短絡を引き起こす。これは、粒子サイズの差が大きいためにスラリの混練時に粒子径の小さな粒子が凝集し、粒子径の大きな粒子同士の間に入り、粉砕されないまま残ったことによるものと考えられる。このため、第２実施形態では、正極活物質に二次粒子平均径が５．０μｍ以上１５．０μｍ以下、一次粒子平均径が０．５μｍ以上１．５μｍ以下、比ａ／ｂが２１以上３２以下の層状構造リチウムマガン複酸化物が用いられる。これにより、スラリの塗工時に均一な厚みでの大面積塗工が可能となるため、電池内部での微小短絡を発生することなく、優れた出力特性のリチウムイオン二次電池を得ることができる。このような電池は内部抵抗（反応抵抗）が小さく電極面積を広くしなくても高出力が得られるので、品質を向上することができ、電池サイズの小型化を図る上でも有用である。
【００６６】
なお、本実施形態では、正極活物質に層状岩塩型結晶構造を有するリチウムマンガン複酸化物を例示したが、本発明はこれに限定されるものではなく、予め十分な量のリチウムを挿入した層状結晶構造のリチウムマンガン複酸化物（ＬｉＭｎＯ２）を用いた場合であれば適用可能であり、また、Ａｌ、Ｃｏ、Ｃｒ、Ｆｅ、Ｎｉ等の金属元素で結晶構造中のＭｎの一部を置換又はドープした層状結晶構造リチウムマンガン複酸化物や結晶中の酸素の一部をＳ、Ｐ等で置換又はドープした材料を用いた場合にも適用可能である。
【００６７】
また、本実施形態では、円筒型電池について例示したが、本発明は電池の形状についても限定されず、角形、その他の多角形の電池にも適用可能である。更に、本発明の適用可能な構造としては、上述した電池容器（缶）に電池蓋がカシメによって封口されている構造の電池以外であっても構わない。このような構造の一例として正負外部端子が電池蓋を貫通し電池容器内で軸芯を介して正負外部端子が押し合っている状態の電池を挙げることができる。
【００６８】
更に、本実施形態では、バインダとしてＰＶＤＦを例示したが、ポリテトラフルオロエチレン（ＰＴＦＥ）、ポリエチレン、ポリスチレン、ポリブタジエン、ブチルゴム、ニトリルゴム、スチレン／ブタジエンゴム、多硫化ゴム、ニトロセルロース、シアノエチルセルロース、各種ラテックス、アクリロニトリル、フッ化ビニル、フッ化ビニリデン、フッ化プロピレン、フッ化クロロプレン等の重合体及びこれらの混合体などを使用するようにしてもよい。
【００６９】
また更に、本実施形態では、ＥＣ、ＤＥＣ、ＤＭＣの混合溶媒中にＬｉＰＦ６を溶解した非水電解液を例示したが、一般的なリチウム塩を電解質とし、これを有機溶媒に溶解した非水電解液を用いるようにしてもよく、本発明は用いられるリチウム塩や有機溶媒には特に制限されない。例えば、電解質としては、ＬｉＣｌＯ４、ＬｉＡｓＦ６、ＬｉＢＦ４、ＬｉＢ（Ｃ６Ｈ５）４、ＣＨ３ＳＯ３Ｌｉ、ＣＦ３ＳＯ３Ｌｉ等やこれらの混合物を用いることができる。また、有機溶媒としては、プロピレンカーボネート、エチレンカーボネート、１，２−ジメトキシエタン、１，２−ジエトキシエタン、γ−ブチロラクトン、テトラヒドロフラン、１，３−ジオキソラン、４−メチル−１，３−ジオキソラン、ジエチルエーテル、スルホラン、メチルスルホラン、アセトニトリル、プロピオニトリル等又はこれら２種類以上の混合溶媒を用いるようにしてもよく、混合配合比についても限定されるものではない。
【００７０】
【発明の効果】
以上説明したように、本発明によれば、正極活物質に層状結晶構造のリチウムマンガン複酸化物が用いられるので、リチウムマンガン複酸化物が酸素層間にリチウム単独の二次元拡散層を有することから、スピネル結晶構造に比べリチウムの拡散係数が小さくリチウムの挿入、脱離が容易となるため、内部抵抗が低減すると共に、二次粒子の平均粒子径が５．０μｍ未満では、非水電解液との反応面積は増加するが結晶の成長が不十分なため、反応抵抗が増大して出力を低下させ、逆に、二次粒子の平均粒子径が１５μｍを超えると、反応面積が減少し正極活物質重量当たりの電流密度が大きくなるため、出力低下を招くので、分級することによって、二次粒子の平均粒子径を５．０μｍ以上１５μｍ以下とすることで反応面積が適正化され、かつ、一次粒子の平均粒子径を０．５μｍ乃至１．５μｍとし、二次粒子の粒子径の最大値ａと最小値ｂとの比ａ／ｂを２１以上３２以下とすることで、電極表面の凹凸が減少し均一な厚みの電極作製が可能となるため、電池内部での微小短絡が抑制されるので、電池サイズを大きくすることなく出力特性を向上させたリチウム二次電池を得ることができる、という効果を得ることができる。
【図面の簡単な説明】
【図１】本発明が適用可能な実施形態の円筒型リチウムイオン二次電池の断面図である。
【符号の説明】
２０ 円筒型リチウムイオン二次電池（リチウム二次電池）[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a lithium secondary battery, and more particularly to a lithium secondary battery in which a lithium manganese complex oxide is used as a positive electrode active material and an electrode group is infiltrated with a non-aqueous electrolyte.
[0002]
[Prior art]
Conventionally, in the field of rechargeable secondary batteries, aqueous batteries such as lead batteries, nickel-cadmium batteries, and nickel-hydrogen batteries have been mainstream. However, as electric devices have become smaller and lighter, lithium secondary batteries with high energy density have attracted attention, and as a result of rapid progress in research, development, and commercialization, mobile phones and laptop computers are now available. Small-sized consumer lithium secondary batteries are widely used.
[0003]
On the other hand, electric vehicles (EV) and hybrid electric vehicles (HEV) that assist part of driving with electric motors have been developed by each automobile manufacturer due to problems of global warming and fuel depletion. Rechargeable batteries have been demanded. As a power source that meets such requirements, a non-aqueous lithium secondary battery having a high voltage has attracted attention.
[0004]
In general, lithium transition metal oxides are used as the positive electrode active material of lithium secondary batteries. Among them, lithium cobaltate is widely used from the balance of capacity and cycle characteristics, but the raw material cobalt has a resource amount. Since the cost is low and the cost is high, lithium manganese complex oxide is considered promising as a positive electrode active material for batteries for electric vehicles and hybrid electric vehicles, and is being developed.
[0005]
For example, in a lithium secondary battery using a lithium manganese complex oxide as a positive electrode active material, layered lithium manganate having an average particle size of about 0.5 μm (see, for example, Patent Document 1) or spinel type lithium having an average particle size of about 8 μm It is disclosed that a high-capacity battery can be obtained by using a manganese composite oxide (for example, see Patent Document 2). In addition, a battery using primary particle aggregates having an average particle size of 0.1 μm or more and 15 μm or less formed by aggregating primary particles having an average particle size of 0.01 μm or more and 5.0 μm or less is disclosed (for example, Patent Document 3). reference).
[0006]
[Patent Document 1]
JP 2001-202947 A (paragraph numbers “0014”, “0072”, Table 2, Table 4)
[Patent Document 2]
JP 2001-146426 A (paragraph numbers “0010”, “0017”, “0021”)
[Patent Document 3]
JP-A-6-325791 (paragraph numbers “0009” and “0047”)
[0007]
[Problems to be solved by the invention]
However, the output characteristics of a lithium secondary battery using lithium manganese complex oxide as a positive electrode active material are not necessarily sufficient when an electric vehicle is assumed. On the other hand, it has been studied to increase the battery capacity by widening the electrode area. However, the battery size becomes large, and a practically difficult point arises in consideration of the in-vehicle space.
[0008]
An object of the present invention is to provide a lithium secondary battery with improved output characteristics without increasing the battery size.
[0009]
[Means for Solving the Problems]
In order to solve the above-described problems, the present invention provides a lithium secondary battery in which a lithium manganese complex oxide is used as a positive electrode active material, and an electrode group is infiltrated with a non-aqueous electrolyte. Has a structure, By classifying, The average particle diameter of the secondary particles in which the primary particles are aggregated is 5.0 μm or more and 15 μm or less, and the primary particles Of child The average particle diameter is 0.5 μm to 1.5 μm, and the ratio a / b between the maximum value a and the minimum value b of the secondary particles is 21 or more and 32 or less.
[0010]
According to the present invention, since the lithium manganese complex oxide having a layered crystal structure is used as the positive electrode active material, the lithium manganese complex oxide has a two-dimensional diffusion layer of lithium alone between the oxygen layers. Since the diffusion coefficient of lithium is small and insertion and removal of lithium is easy, the internal resistance is reduced, and the reaction area with the non-aqueous electrolyte increases when the average particle size of the secondary particles is less than 5.0 μm. However, since the crystal growth is insufficient, the reaction resistance increases and the output decreases. Conversely, when the average particle diameter of the secondary particles exceeds 15 μm, the reaction area decreases and the current density per weight of the positive electrode active material. Will cause a decrease in output. By classifying, By making the average particle size of the secondary particles 5.0 μm or more and 15 μm or less, the reaction area is optimized, And, The average particle diameter of the primary particles is 0.5 μm to 1.5 μm, and the ratio a / b between the maximum value a and the minimum value b of the secondary particles is 21 or more and 32 or less. Since an electrode with a uniform thickness can be manufactured and a small short circuit inside the battery is suppressed, a lithium secondary battery with improved output characteristics can be obtained without increasing the battery size.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
<First Embodiment>
Hereinafter, a first embodiment in which the present invention is applied to a cylindrical lithium ion secondary battery used as a power source for an electric vehicle will be described with reference to the drawings.
[0013]
(Positive electrode active material)
A lithium manganese complex oxide having a layered rock salt type crystal structure was used as the positive electrode active material. The used lithium manganese complex oxide has a primary particle average particle diameter (hereinafter referred to as primary particle average diameter) of 0.1 to 2.0 μm and secondary particles in which primary particles are aggregated by controlling the particle diameter with a classifier. An average particle size material having an average particle size (hereinafter referred to as secondary particle average size) of 2.0 to 25 μm was used. The average particle size was measured with a laser diffraction particle size distribution analyzer.
[0014]
(Positive electrode plate)
The above-described lithium manganese complex oxide powder having an average particle size material, scaly graphite as a conductive material, and polyvinylidene fluoride (PVDF) as a binder are mixed at a weight ratio of 85: 10: 5 and dispersed therein. A slurry in which N-methylpyrrolidone (NMP) as a solvent was added and kneaded was applied to both surfaces of an aluminum foil having a thickness of 20 μm. At this time, an uncoated portion with a width of 30 mm was left on one side edge in the positive electrode longitudinal direction. Thereafter, drying, pressing, and cutting were performed to obtain a positive electrode plate having a thickness of 170 μm. A notch was left in the uncoated portion left on the side edge, and the remaining notch was used as the positive electrode lead piece 2. Adjacent positive electrode lead pieces 2 were spaced 50 mm apart, and the width of the positive electrode lead pieces 2 was 5 mm.
[0015]
(Negative electrode plate)
10 parts by mass of PVDF as a binder is added to 90 parts by mass of artificial graphite powder as the negative electrode active material, and a slurry obtained by adding and kneading the dispersion solvent NMP is applied to both surfaces of a 10 μm thick electrolytic copper foil. did. At this time, an uncoated part with a width of 30 mm was left on one side edge in the negative electrode longitudinal direction. Thereafter, drying, pressing, and cutting were performed to obtain a negative electrode plate having a thickness of 130 μm. A notch was formed in the uncoated part left on the side edge in the same manner as the positive electrode, and the remaining part of the notch was used as the negative
[0016]
(Production of battery)
As shown in FIG. 1, the produced positive and negative electrode plates were wound together with a polyethylene separator having a thickness of 40 μm so that the bipolar plates were not in direct contact with each other, thereby producing a
[0017]
The positive electrode lead piece 2 is deformed, and all of the positive electrode lead piece 2 is gathered and brought into contact with the vicinity of the buttocks circumferential surface integrally projecting from the periphery of the positive electrode
[0018]
A negative
[0019]
A predetermined amount of non-aqueous electrolyte that can infiltrate the
[0020]
As the non-aqueous electrolyte, lithium hexafluorophosphate (LiPF) was mixed into a mixed solvent in which ethylene carbonate (EC), dimethyl carbonate (DMC), and diethyl carbonate (DEC) were mixed at a volume ratio of 1: 1: 1. 6 ) Was dissolved at 1 mol / liter.
[0021]
<Second Embodiment>
Next, a second embodiment in which the present invention is applied to a cylindrical lithium ion secondary battery used as a power source for an electric vehicle will be described. In this embodiment, in addition to the average particle size control of the first embodiment, the particle size range of secondary particles is limited. In the present embodiment, the same members as those in the first embodiment are denoted by the same reference numerals, description thereof is omitted, and only different portions will be described.
[0022]
In this embodiment, the lithium manganese complex oxide of the positive electrode active material has an average secondary particle diameter of 5.0 to 15 μm, and a ratio a / b between the maximum value a and the minimum value b of the secondary particle diameter is 32. The following particle size range materials were used. The maximum value a and the minimum value b of the particle diameter were measured by a laser diffraction type particle size distribution measuring device.
[0023]
【Example】
Next, examples of the cylindrical lithium ion
[0024]
Example 1
As shown in Table 1 below, Example 1 is a layered structure lithium manganese complex oxide powder having a secondary particle average diameter of 2.0 μm and a primary particle average diameter of 0.1 μm according to the first embodiment. Using.
[0025]
[Table 1]
(Example 2 to Example 10)
As shown in Table 1, Examples 2 to 10 were the same as Example 1 except that the secondary particle average diameter and primary particle average diameter were changed. The average secondary particle diameter is 3.0 μm in Example 2, 4.0 μm in Example 3, 5.0 μm in Example 4, 7.5 μm in Example 5, 10.0 μm in Example 6, and Example 7 12.5 μm, Example 8 15.0 μm, Example 9 20.0 μm, Example 10 25.0 μm, and the average primary particle diameter is 0.1 μm in Example 2, Example 3 and Examples 4 was 0.5 μm, Examples 5 and 6 were 1.0 μm, Examples 7 and 8 were 1.5 μm, Examples 9 and 10 were 2.0 μm.
[0027]
(Comparative Examples 1 to 4)
As shown in Table 1, Comparative Example 1 to Comparative Example 4 were the same as Example 1 except that the secondary particle average diameter and primary particle average diameter were changed. The secondary particle average diameter is 1.0 μm in Comparative Example 1, 1.5 μm in Comparative Example 2, 30.0 μm in Comparative Example 3, and 35.0 μm in Comparative Example 4, and the average primary particle diameter is Comparative Example 1 and In Comparative Example 2, the thickness was 0.05 μm, Comparative Example 3 was 2.5 μm, and Comparative Example 4 was 3.0 μm.
[0028]
(Comparative Example 5)
As shown in Table 1, in Comparative Example 5, Example 1 was used except that the positive electrode active material was a spinel structure lithium manganese complex oxide powder having an average secondary particle diameter of 2.0 μm and an average primary particle diameter of 0.1 μm. And so on.
[0029]
(Comparative Example 6 to Comparative Example 9)
As shown in Table 1, Comparative Example 6 to Comparative Example 9 were the same as Comparative Example 5 except that the secondary particle average diameter and primary particle average diameter were changed. The secondary particle average diameter is 5.0 μm in Comparative Example 6, 10.0 μm in Comparative Example 7, 15.0 μm in Comparative Example 8, 30.0 μm in Comparative Example 9, and the primary particle average diameter is in Comparative Example 6. The thickness was 0.5 μm, Comparative Example 7 was 1.0 μm, Comparative Example 8 was 1.5 μm, and Comparative Example 9 was 2.5 μm.
[0030]
(Example 11)
As shown in Table 2 below, Example 11 is in accordance with the second embodiment. The positive electrode active material has a secondary particle average diameter of 5.0 μm, a primary particle average diameter of 0.5 μm, and a maximum particle diameter of the secondary particles. A layered lithium manganese complex oxide powder having a of 21.10 μm and a minimum value b of 1.01 μm was used. The ratio a / b between the maximum value a and the minimum value b is 21.
[0031]
[Table 2]
(Example 12)
As shown in Table 2, in Example 12, the secondary particle average diameter was 7.0 μm, the primary particle average diameter was 1.0 μm, the maximum value a was 29.85 μm, and the minimum value b was 1.01 μm. Same as Example 11. The ratio a / b is 30.
[0033]
(Example 13 to Example 14)
As shown in Table 2, Examples 13 to 14 were the same as Example 12 except that the average secondary particle diameter was changed. In Example 13, it was 7.5 μm, and in Example 14, it was 8.0 μm. The ratio a / b is 30 for both Example 13 and Example 14.
[0034]
(Example 15)
As shown in Table 2, in Example 15, the secondary particle average diameter was 8.5 μm, the primary particle average diameter was 1.0 μm, the maximum value a was 21.10 μm, and the minimum value b was 0.66 μm. Same as Example 11. The ratio a / b is 32.
[0035]
(Example 16)
As shown in Table 2, Example 16 was the same as Example 12 except that the average secondary particle diameter was 9.0 μm. The ratio a / b is 30.
[0036]
(Example 17)
As shown in Table 2, Example 17 was the same as Example 11 except that the average secondary particle diameter was 10.0 μm and the average primary particle diameter was 1.0 μm. The ratio a / b is 21.
[0037]
(Example 18)
As shown in Table 2, Example 18 was the same as Example 12 except that the average secondary particle diameter was 12.5 μm and the average primary particle diameter was 1.5 μm. The ratio a / b is 30.
[0038]
(Example 19)
As shown in Table 2, in Example 19, the secondary particle average diameter was 15.0 μm, the primary particle average diameter was 1.5 μm, the maximum value a was 42.20 μm, and the minimum value b was 1.69 μm. Same as Example 11. The ratio a / b is 25.
[0039]
(Comparative Example 10)
As shown in Table 2, in Comparative Example 10, the positive electrode active material had an average secondary particle size of 5.0 μm, an average primary particle size of 0.5 μm, a maximum value a of 19.90 μm, and a minimum value b of 1.15 μm. The same procedure as in Example 11 except that the spinel structure lithium manganese double oxide powder was used. The ratio a / b is 17.
[0040]
(Comparative Example 11)
As shown in Table 2, in Comparative Example 11, the secondary particle average diameter was 5.5 μm, the primary particle average diameter was 0.5 μm, the maximum value a was 22.80 μm, and the minimum value b was 1.15 μm. Same as Comparative Example 10. The ratio a / b is 20.
[0041]
(Comparative Example 12)
As shown in Table 2, in Comparative Example 12, the average secondary particle diameter was 6.0 μm, the primary particle average diameter was 0.5 μm, the maximum value a was 22.80 μm, and the minimum value b was 1.32 μm. Same as Comparative Example 10. The ratio a / b is 17.
[0042]
(Comparative Example 13)
As shown in Table 2, in Comparative Example 13, the average secondary particle diameter was 6.5 μm, the primary particle average diameter was 0.5 μm, the maximum value a was 19.90 μm, and the minimum value b was 1.32 μm. Same as Comparative Example 10. The ratio a / b is 15.
[0043]
(Comparative Example 14)
As shown in Table 2, in Comparative Example 14, the secondary particle average diameter was 7.5 μm, the primary particle average diameter was 1.0 μm, the maximum value a was 22.80 μm, and the minimum value b was 1.51 μm. Same as Comparative Example 10. The ratio a / b is 15.
[0044]
(Comparative Example 15)
As shown in Table 2, in Comparative Example 15, the secondary particle average diameter was 9.0 μm, the primary particle average diameter was 1.0 μm, the maximum value a was 29.91 μm, and the minimum value b was 1.51 μm. Same as Comparative Example 10. The ratio a / b is 20.
[0045]
(Comparative Example 16)
As shown in Table 2, in Comparative Example 16, the secondary particle average diameter was 10.5 μm, the primary particle average diameter was 1.0 μm, the maximum value a was 37.00 μm, and the minimum value b was 1.06 μm. Same as Comparative Example 10. The ratio a / b is 35.
[0046]
(Comparative Example 17)
As shown in Table 2, in Comparative Example 17, the secondary particle average diameter was 13.0 μm, the primary particle average diameter was 1.5 μm, the maximum value a was 52.33 μm, and the minimum value b was 2.12 μm. Same as Comparative Example 10. The ratio a / b is 25.
[0047]
(Comparative Example 18)
As shown in Table 2, in Comparative Example 18, except that the secondary particle average diameter was 13.5 μm, the primary particle average diameter was 1.5 μm, the maximum value a was 37.00 μm, and the minimum value b was 3.00 μm. Same as Comparative Example 10. The ratio a / b is 12.
[0048]
(Comparative Example 19)
As shown in Table 2, in Comparative Example 19, the secondary particle average diameter was 14.0 μm, the primary particle average diameter was 1.5 μm, the maximum value a was 44.00 μm, and the minimum value b was 2.52 μm. Same as Comparative Example 10. The ratio a / b is 17.
[0049]
(Comparative Example 20)
As shown in Table 2, Comparative Example 20 was the same as Comparative Example 19 except that the average secondary particle diameter was 14.5 μm. The ratio a / b is 17.
[0050]
(Comparative Example 21)
As shown in Table 2, in Comparative Example 21, the secondary particle average diameter was 15.0 μm, the primary particle average diameter was 1.5 μm, the maximum value a was 47.98 μm, and the minimum value b was 2.52 μm. Same as Comparative Example 10. The ratio a / b is 19.
[0051]
(Comparative Example 22)
As shown in Table 2, in Comparative Example 22, the secondary particle average diameter was 9.5 μm, the primary particle average diameter was 1.0 μm, the maximum value a was 42.20 μm, and the minimum value b was 1.01 μm. Same as Example 11. The ratio a / b is 42.
[0052]
(Comparative Example 23)
As shown in Table 2, in Comparative Example 23, the secondary particle average diameter was 11.5 μm, the primary particle average diameter was 1.0 μm, the maximum value a was 42.20 μm, and the minimum value b was 0.66 μm. Same as Example 11. The ratio a / b is 64.
[0053]
(Comparative Example 24)
As shown in Table 2, in Comparative Example 24, the secondary particle average diameter was 10.0 μm, the primary particle average diameter was 1.0 μm, the maximum value a was 44.00 μm, and the minimum value b was 1.06 μm. Same as Comparative Example 10. The ratio a / b is 42.
[0054]
(Comparative Example 25)
As shown in Table 2, in Comparative Example 25, the secondary particle average diameter was 13.5 μm, the primary particle average diameter was 2.0 μm, the maximum value a was 104.70 μm, and the minimum value b was 1.78 μm. Same as Comparative Example 10. The ratio a / b is 59.
[0055]
<Test and evaluation>
(Output measurement test)
About each battery of the Example and comparative example produced as mentioned above, 4.2V constant voltage control is carried out with the electric current value (0.2C) which can be discharged in about 5 hours, it charges for 8 hours, and it is in a full charge state. After that, the battery was discharged for 30 seconds at current values of 10A, 20A, 40A, and 60A, the battery voltage at 30 seconds was measured, and the current obtained by plotting the voltage against the current value reached 3.2V. From the value (Ia), an output ((W) = Ia × 3.2) was calculated, and an output measurement test was performed to calculate the output density by dividing the output by the battery weight. This measurement was performed in an atmosphere of 25 ± 2 ° C.
[0056]
(Test for measuring the number of micro internal short circuits)
About 20 cells of each of the batteries of Examples 11 to 19 and Comparative Examples 10 to 25 produced as described above, after being fully charged under the above-described conditions, the battery was left at 25 ° C. and the voltage was lowered. The speed was measured. At this time, the voltage difference between the 14th day and the 21st day was obtained, and a battery having a voltage drop rate per day exceeding 2.7 mV / day was defined as a micro internal short circuit generating battery.
[0057]
Table 3 below shows the test results of the output measurement test for the batteries of Examples 1 to 10 and Comparative Examples 1 to 9. Table 4 below shows the test results of the output measurement test and the minute internal short circuit occurrence number measurement test for the batteries of Examples 11 to 19 and Comparative Examples 10 to 25.
[0058]
[Table 3]
[Table 4]
As shown in Table 3, Comparative Example 1 in which a lithium manganese complex oxide having a layered structure was used as the positive electrode active material, the secondary particle average diameter was less than 2.0 μm, and the primary particle average diameter was less than 0.1 μm, comparison In the battery of Example 2 and the batteries of Comparative Example 3 and Comparative Example 4 in which the average particle size of the secondary particles exceeds 25.0 μm and the average particle size of the primary particles exceeds 2.0 μm, the output density according to the measurement method described above is 400 to 520 W. / Kg. Moreover, in the batteries of Comparative Examples 5 to 9 using the spinel structure lithium manganese complex oxide as the positive electrode active material, the output density was 320 to 530 W / kg. On the other hand, Examples 1 to 10 using a layered structure lithium manganese complex oxide having a secondary particle average diameter of 2.0 to 25.0 μm and a primary particle average diameter of 0.1 to 2.0 μm. In the battery, the power density was 600 to 750 W / kg. Further, the batteries of Example 1 and Example 2 and the average secondary particle diameter using a layered structure lithium manganese complex oxide having an average secondary particle diameter of 2.0 μm, 3.0 μm, and an average primary particle diameter of 0.1 μm. Are 20.0 μm, 25.0 μm, and the batteries of Examples 9 and 10 using the layered structure lithium manganese complex oxide having an average primary particle diameter of 2.0 μm, the output density is slightly reduced to 600 to 680 W / kg. did. On the other hand, Examples 3 to 3 using a layered lithium manganese complex oxide having a secondary particle average diameter of 4.0 to 15.0 μm and a primary particle average diameter of 0.5 to 1.5 μm as the positive electrode active material. The battery of Example 8 exhibited an excellent power density of 730-750 W / kg.
[0061]
As shown in Table 4, a layered lithium manganese complex oxide having a secondary particle average diameter of 9.5 μm, 11.5 μm, a primary particle average diameter of 1.0 μm, and a ratio a / b exceeding 32 is used as a positive electrode active material. In the batteries of Comparative Example 22 and Comparative Example 23 used for the above, although the output density was 740 W / kg, the occurrence of a micro short circuit inside the battery was confirmed. In contrast, a layered structure lithium manganese complex oxide having an average secondary particle diameter of 5.0 to 15.0 μm, an average primary particle diameter of 0.5 to 1.5 μm, and a ratio a / b of 32 or less was used. The batteries of Examples 11 to 19 showed an excellent output density of 730 to 750 W / kg, and the occurrence of minute short circuits could not be confirmed. Further, the batteries of Comparative Examples 10 to 21, 21 and 24 using the spinel structure lithium manganese complex oxide as the positive electrode active material had a power density of 490 to 540 W / kg. In particular, in the batteries of Comparative Example 24 and Comparative Example 25 in which the ratio a / b exceeded 32, a minute short circuit occurred. Further, when the batteries of Comparative Example 22 and Comparative Example 23 using the same layered lithium manganese oxide having the same maximum value a of 42.20 μm were compared with the battery of Example 19, the powder had a large average particle diameter. However, if the ratio a / b was 21 or more and 32 or less, there was no occurrence of a micro short circuit inside the battery.
[0062]
From the above test results, a battery using a layered structure lithium manganese complex oxide having a secondary particle average diameter of 2.0 μm to 25.0 μm and a primary particle average diameter of 0.1 to 2.0 μm as the positive electrode active material is excellent. It was found that the output characteristics were exhibited. Among them, a battery using a layered structure lithium manganese complex oxide having a secondary particle average diameter of 4.0 to 15.0 μm and a primary particle average diameter of 0.5 to 1.5 μm as a positive electrode active material has high output density. There was found. Further, a layered structure lithium magan complex oxide having an average secondary particle diameter of 5.0 to 15.0 μm, an average primary particle diameter of 0.5 to 1.5 μm, and a ratio a / b of 21 to 32 is used as a positive electrode active material. It was found that the used battery showed better output characteristics without causing a micro short circuit inside the battery.
[0063]
In the said embodiment, the lithium manganese complex oxide of a layered rock salt type crystal structure is used for a positive electrode active material among lithium manganese complex oxides. Compared with the spinel structure, the layered structure has a small diffusion coefficient in terms of lithium diffusivity because it has a two-dimensional diffusion layer of lithium alone between oxygen layers. For this reason, lithium insertion and removal are facilitated and the internal resistance is reduced, so that a lithium secondary battery with improved output characteristics can be obtained without increasing the battery size. Therefore, it can be suitably used even when a high output such as an electric vehicle is required and the space on the vehicle is limited.
[0064]
Further, when a layered structure lithium manganese complex oxide having a secondary particle average diameter of less than 2.0 μm and a primary particle average diameter of less than 0.1 μm is used as the positive electrode active material, the reaction area with the non-aqueous electrolyte increases. Since the crystals are not sufficiently grown, the reaction resistance is increased and the output of the lithium ion secondary battery is lowered. Conversely, the secondary particle average diameter exceeds 25 μm, and the primary particle average diameter exceeds 2.0 μm. When the layered structure lithium manganese complex oxide is used, the reaction area is reduced and the current density per weight of the positive electrode active material is increased, resulting in a decrease in the output of the lithium ion secondary battery. For this reason, in the first embodiment, a layered structure lithium manganese complex oxide having an average secondary particle diameter of 2.0 μm to 25 μm and an average primary particle diameter of 0.1 μm to 2.0 μm is used for the positive electrode active material. . Thereby, the reaction area of the positive electrode active material is optimized, and a lithium ion secondary battery with improved output characteristics can be obtained without increasing the battery size. In particular, when the secondary particle average diameter is 4.0 μm or more and 15 μm or less, and the primary particle average diameter is 0.5 μm or more and 1.5 μm or less, the output characteristics can be further improved.
[0065]
Further, when the ratio a / b between the maximum value a and the minimum value b of the secondary particles exceeds 32, unevenness occurs on the coated surface during the coating of the slurry containing the positive electrode active material on the aluminum foil. Large area coating with uniform thickness is not possible. The unevenness of the coated surface breaks the separator during battery production, etc., causing a micro short circuit. This is considered to be due to the fact that the small particle size aggregates when the slurry is kneaded due to the large difference in particle size, and the particles enter between the large particle size particles and remain without being pulverized. For this reason, in the second embodiment, the positive electrode active material has an average secondary particle diameter of 5.0 μm to 15.0 μm, an average primary particle diameter of 0.5 μm to 1.5 μm, and a ratio a / b of 21 to 32. The following layered structure lithium magan complex oxide is used. As a result, large area coating with a uniform thickness is possible during slurry coating, so that a lithium ion secondary battery having excellent output characteristics can be obtained without causing a micro short circuit inside the battery. . Such a battery has a small internal resistance (reaction resistance) and can provide a high output without increasing the electrode area. Therefore, the quality can be improved and the battery can be reduced in size.
[0066]
In the present embodiment, the lithium-manganese complex oxide having a layered rock salt type crystal structure is exemplified as the positive electrode active material, but the present invention is not limited to this, and a layered state in which a sufficient amount of lithium is inserted in advance. Lithium manganese complex oxide with crystal structure (LiMnO 2 And a layered crystal structure lithium manganese composite oxide in which a part of Mn in the crystal structure is substituted or doped with a metal element such as Al, Co, Cr, Fe, Ni, etc. It can also be applied to the case where a material in which part of oxygen in the crystal is substituted or doped with S, P or the like is used.
[0067]
Further, in the present embodiment, the cylindrical battery is exemplified, but the present invention is not limited to the shape of the battery, and can be applied to a rectangular battery and other polygonal batteries. Furthermore, the structure to which the present invention can be applied may be other than a battery having a structure in which a battery lid is sealed with a caulking to the above-described battery container (can). An example of such a structure is a battery in which positive and negative external terminals pass through the battery lid and the positive and negative external terminals are pressed against each other through an axis in the battery container.
[0068]
Furthermore, although PVDF was illustrated as a binder in this embodiment, polytetrafluoroethylene (PTFE), polyethylene, polystyrene, polybutadiene, butyl rubber, nitrile rubber, styrene / butadiene rubber, polysulfide rubber, nitrocellulose, cyanoethylcellulose, various types Polymers such as latex, acrylonitrile, vinyl fluoride, vinylidene fluoride, propylene fluoride, chloroprene fluoride, and mixtures thereof may be used.
[0069]
Furthermore, in this embodiment, LiPF is mixed in a mixed solvent of EC, DEC, and DMC. 6 However, the present invention may use a non-aqueous electrolyte obtained by dissolving a general lithium salt as an electrolyte and dissolving it in an organic solvent. There is no particular restriction. For example, as an electrolyte, LiClO 4 , LiAsF 6 , LiBF 4 , LiB (C 6 H 5 ) 4 , CH 3 SO 3 Li, CF 3 SO 3 Li or the like or a mixture thereof can be used. Examples of the organic solvent include propylene carbonate, ethylene carbonate, 1,2-dimethoxyethane, 1,2-diethoxyethane, γ-butyrolactone, tetrahydrofuran, 1,3-dioxolane, 4-methyl-1,3-dioxolane, Diethyl ether, sulfolane, methyl sulfolane, acetonitrile, propionitrile, etc., or a mixed solvent of two or more of these may be used, and the mixing ratio is not limited.
[0070]
【The invention's effect】
As described above, according to the present invention, since the lithium manganese complex oxide having a layered crystal structure is used as the positive electrode active material, the lithium manganese complex oxide has a two-dimensional diffusion layer of lithium alone between oxygen layers. The lithium diffusion coefficient is small compared to the spinel crystal structure, and insertion and removal of lithium is easy, so that the internal resistance is reduced and the average particle diameter of the secondary particles is less than 5.0 μm. However, when the average particle size of the secondary particles exceeds 15 μm, the reaction area decreases and the positive electrode active is increased. Since the current density per substance weight increases, it causes a decrease in output, By classifying, By making the average particle size of the secondary particles 5.0 μm or more and 15 μm or less, the reaction area is optimized, And, The average particle diameter of the primary particles is 0.5 μm to 1.5 μm, and the ratio a / b between the maximum value a and the minimum value b of the secondary particles is 21 or more and 32 or less. Therefore, it is possible to produce a lithium secondary battery with improved output characteristics without increasing the battery size. The effect that can be obtained.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a cylindrical lithium ion secondary battery according to an embodiment to which the present invention is applicable.
[Explanation of symbols]
20 Cylindrical lithium ion secondary battery (lithium secondary battery)
Claims (1)
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|---|---|---|---|---|
| JPH06243897A (en) * | 1992-12-24 | 1994-09-02 | Fuji Photo Film Co Ltd | Nonaqueous secondary battery |
| JPH07183047A (en) * | 1993-12-22 | 1995-07-21 | Sony Corp | Nonaqueous electrolyte secondary battery |
| JPH111323A (en) * | 1997-04-14 | 1999-01-06 | Sakai Chem Ind Co Ltd | Lithium manganate particular composition, its production and lithium ion secondary cell |
| JP2000203844A (en) * | 1998-05-22 | 2000-07-25 | Toyota Central Res & Dev Lab Inc | Lithium-manganese compound oxide as anodic active material for lithium secondary battery, production of the compound oxide, and lithium secondary battery using the same as anodic active material |
| JP2002321920A (en) * | 2001-04-27 | 2002-11-08 | Sakai Chem Ind Co Ltd | Element substitution lithium manganese compound oxide granulated composition, its manufacturing method and its utilization for secondary battery |
| JP2003017052A (en) * | 2001-06-27 | 2003-01-17 | Matsushita Electric Ind Co Ltd | Positive electrode active material and non-aqueous electrolyte secondary battery containing the same |
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2003
- 2003-02-25 JP JP2003047075A patent/JP4710214B2/en not_active Expired - Lifetime
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH06243897A (en) * | 1992-12-24 | 1994-09-02 | Fuji Photo Film Co Ltd | Nonaqueous secondary battery |
| JPH07183047A (en) * | 1993-12-22 | 1995-07-21 | Sony Corp | Nonaqueous electrolyte secondary battery |
| JPH111323A (en) * | 1997-04-14 | 1999-01-06 | Sakai Chem Ind Co Ltd | Lithium manganate particular composition, its production and lithium ion secondary cell |
| JP2000203844A (en) * | 1998-05-22 | 2000-07-25 | Toyota Central Res & Dev Lab Inc | Lithium-manganese compound oxide as anodic active material for lithium secondary battery, production of the compound oxide, and lithium secondary battery using the same as anodic active material |
| JP2002321920A (en) * | 2001-04-27 | 2002-11-08 | Sakai Chem Ind Co Ltd | Element substitution lithium manganese compound oxide granulated composition, its manufacturing method and its utilization for secondary battery |
| JP2003017052A (en) * | 2001-06-27 | 2003-01-17 | Matsushita Electric Ind Co Ltd | Positive electrode active material and non-aqueous electrolyte secondary battery containing the same |
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