JP4097337B2 - Non-aqueous electrolyte battery - Google Patents
Non-aqueous electrolyte battery Download PDFInfo
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- JP4097337B2 JP4097337B2 JP31122398A JP31122398A JP4097337B2 JP 4097337 B2 JP4097337 B2 JP 4097337B2 JP 31122398 A JP31122398 A JP 31122398A JP 31122398 A JP31122398 A JP 31122398A JP 4097337 B2 JP4097337 B2 JP 4097337B2
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- lithium
- positive electrode
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- 239000011255 nonaqueous electrolyte Substances 0.000 title claims description 14
- 239000007774 positive electrode material Substances 0.000 claims description 38
- 229910052744 lithium Inorganic materials 0.000 claims description 31
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims description 29
- 239000010955 niobium Substances 0.000 claims description 29
- 229910013733 LiCo Inorganic materials 0.000 claims description 26
- 239000003792 electrolyte Substances 0.000 claims description 23
- 150000002822 niobium compounds Chemical class 0.000 claims description 16
- 229910000484 niobium oxide Inorganic materials 0.000 claims description 16
- URLJKFSTXLNXLG-UHFFFAOYSA-N niobium(5+);oxygen(2-) Chemical compound [O-2].[O-2].[O-2].[O-2].[O-2].[Nb+5].[Nb+5] URLJKFSTXLNXLG-UHFFFAOYSA-N 0.000 claims description 16
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 15
- KMTRUDSVKNLOMY-UHFFFAOYSA-N Ethylene carbonate Chemical compound O=C1OCCO1 KMTRUDSVKNLOMY-UHFFFAOYSA-N 0.000 claims description 15
- 229910002804 graphite Inorganic materials 0.000 claims description 14
- 239000010439 graphite Substances 0.000 claims description 14
- 239000002131 composite material Substances 0.000 claims description 11
- WMFOQBRAJBCJND-UHFFFAOYSA-M Lithium hydroxide Chemical compound [Li+].[OH-] WMFOQBRAJBCJND-UHFFFAOYSA-M 0.000 claims description 10
- 239000012046 mixed solvent Substances 0.000 claims description 10
- 229910000428 cobalt oxide Inorganic materials 0.000 claims description 9
- IVMYJDGYRUAWML-UHFFFAOYSA-N cobalt(ii) oxide Chemical compound [Co]=O IVMYJDGYRUAWML-UHFFFAOYSA-N 0.000 claims description 9
- -1 imide salt Chemical class 0.000 claims description 8
- 229920000642 polymer Polymers 0.000 claims description 8
- 229910052751 metal Inorganic materials 0.000 claims description 7
- 239000007787 solid Substances 0.000 claims description 7
- 239000002184 metal Substances 0.000 claims description 6
- 229910013385 LiN(SO2C2F5)2 Inorganic materials 0.000 claims description 5
- 229910000625 lithium cobalt oxide Inorganic materials 0.000 claims description 5
- BFZPBUKRYWOWDV-UHFFFAOYSA-N lithium;oxido(oxo)cobalt Chemical compound [Li+].[O-][Co]=O BFZPBUKRYWOWDV-UHFFFAOYSA-N 0.000 claims description 5
- 239000000463 material Substances 0.000 claims description 5
- GUCVJGMIXFAOAE-UHFFFAOYSA-N niobium atom Chemical compound [Nb] GUCVJGMIXFAOAE-UHFFFAOYSA-N 0.000 claims description 5
- IIPYXGDZVMZOAP-UHFFFAOYSA-N lithium nitrate Chemical compound [Li+].[O-][N+]([O-])=O IIPYXGDZVMZOAP-UHFFFAOYSA-N 0.000 claims description 4
- 150000003839 salts Chemical class 0.000 claims description 4
- 229910052758 niobium Inorganic materials 0.000 claims description 3
- IBXOPEGTOZQGQO-UHFFFAOYSA-N [Li].[Nb] Chemical compound [Li].[Nb] IBXOPEGTOZQGQO-UHFFFAOYSA-N 0.000 claims description 2
- XGZVUEUWXADBQD-UHFFFAOYSA-L lithium carbonate Chemical compound [Li+].[Li+].[O-]C([O-])=O XGZVUEUWXADBQD-UHFFFAOYSA-L 0.000 claims description 2
- 229910052808 lithium carbonate Inorganic materials 0.000 claims description 2
- 150000002642 lithium compounds Chemical class 0.000 claims description 2
- 230000000052 comparative effect Effects 0.000 description 26
- 239000008151 electrolyte solution Substances 0.000 description 16
- 238000002474 experimental method Methods 0.000 description 11
- 239000007789 gas Substances 0.000 description 11
- 238000000034 method Methods 0.000 description 11
- 239000002904 solvent Substances 0.000 description 10
- 239000000203 mixture Substances 0.000 description 9
- RUOJZAUFBMNUDX-UHFFFAOYSA-N propylene carbonate Chemical compound CC1COC(=O)O1 RUOJZAUFBMNUDX-UHFFFAOYSA-N 0.000 description 9
- 230000007423 decrease Effects 0.000 description 8
- OIFBSDVPJOWBCH-UHFFFAOYSA-N Diethyl carbonate Chemical compound CCOC(=O)OCC OIFBSDVPJOWBCH-UHFFFAOYSA-N 0.000 description 7
- 239000007773 negative electrode material Substances 0.000 description 7
- 239000000571 coke Substances 0.000 description 6
- 238000007599 discharging Methods 0.000 description 6
- 230000000694 effects Effects 0.000 description 5
- 239000003575 carbonaceous material Substances 0.000 description 4
- 230000003197 catalytic effect Effects 0.000 description 4
- 238000000354 decomposition reaction Methods 0.000 description 4
- 239000002245 particle Substances 0.000 description 4
- 239000000126 substance Substances 0.000 description 4
- RTZKZFJDLAIYFH-UHFFFAOYSA-N Diethyl ether Chemical compound CCOCC RTZKZFJDLAIYFH-UHFFFAOYSA-N 0.000 description 3
- 229910013870 LiPF 6 Inorganic materials 0.000 description 3
- 239000011149 active material Substances 0.000 description 3
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 3
- 239000011230 binding agent Substances 0.000 description 3
- LBFUKZWYPLNNJC-UHFFFAOYSA-N cobalt(ii,iii) oxide Chemical compound [Co]=O.O=[Co]O[Co]=O LBFUKZWYPLNNJC-UHFFFAOYSA-N 0.000 description 3
- 238000004320 controlled atmosphere Methods 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- 238000002156 mixing Methods 0.000 description 3
- PXHVJJICTQNCMI-UHFFFAOYSA-N nickel Substances [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 3
- 229910052760 oxygen Inorganic materials 0.000 description 3
- 239000001301 oxygen Substances 0.000 description 3
- XTHFKEDIFFGKHM-UHFFFAOYSA-N Dimethoxyethane Chemical compound COCCOC XTHFKEDIFFGKHM-UHFFFAOYSA-N 0.000 description 2
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 2
- 239000002202 Polyethylene glycol Substances 0.000 description 2
- WYURNTSHIVDZCO-UHFFFAOYSA-N Tetrahydrofuran Chemical compound C1CCOC1 WYURNTSHIVDZCO-UHFFFAOYSA-N 0.000 description 2
- 229910052782 aluminium Inorganic materials 0.000 description 2
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 2
- 229910052799 carbon Inorganic materials 0.000 description 2
- 239000011248 coating agent Substances 0.000 description 2
- 238000000576 coating method Methods 0.000 description 2
- 125000004386 diacrylate group Chemical group 0.000 description 2
- QHGJSLXSVXVKHZ-UHFFFAOYSA-N dilithium;dioxido(dioxo)manganese Chemical compound [Li+].[Li+].[O-][Mn]([O-])(=O)=O QHGJSLXSVXVKHZ-UHFFFAOYSA-N 0.000 description 2
- 238000001035 drying Methods 0.000 description 2
- 238000010304 firing Methods 0.000 description 2
- 239000011245 gel electrolyte Substances 0.000 description 2
- 230000020169 heat generation Effects 0.000 description 2
- 229910001416 lithium ion Inorganic materials 0.000 description 2
- 229910052759 nickel Inorganic materials 0.000 description 2
- 229920001223 polyethylene glycol Polymers 0.000 description 2
- 238000005096 rolling process Methods 0.000 description 2
- WNXJIVFYUVYPPR-UHFFFAOYSA-N 1,3-dioxolane Chemical compound C1COCO1 WNXJIVFYUVYPPR-UHFFFAOYSA-N 0.000 description 1
- OKAMTPRCXVGTND-UHFFFAOYSA-N 2-methoxyoxolane Chemical compound COC1CCCO1 OKAMTPRCXVGTND-UHFFFAOYSA-N 0.000 description 1
- RTEZVHMDMFEURJ-UHFFFAOYSA-N 2-methylpentan-2-yl 2,2-dimethylpropaneperoxoate Chemical compound CCCC(C)(C)OOC(=O)C(C)(C)C RTEZVHMDMFEURJ-UHFFFAOYSA-N 0.000 description 1
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 description 1
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 1
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- YCKRFDGAMUMZLT-UHFFFAOYSA-N Fluorine atom Chemical compound [F] YCKRFDGAMUMZLT-UHFFFAOYSA-N 0.000 description 1
- 229910000733 Li alloy Inorganic materials 0.000 description 1
- 229910015015 LiAsF 6 Inorganic materials 0.000 description 1
- 229910013063 LiBF 4 Inorganic materials 0.000 description 1
- 229910013684 LiClO 4 Inorganic materials 0.000 description 1
- 229910013553 LiNO Inorganic materials 0.000 description 1
- 239000004594 Masterbatch (MB) Substances 0.000 description 1
- 239000002033 PVDF binder Substances 0.000 description 1
- 239000004698 Polyethylene Substances 0.000 description 1
- 239000004721 Polyphenylene oxide Substances 0.000 description 1
- 239000004743 Polypropylene Substances 0.000 description 1
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 description 1
- QCWXUUIWCKQGHC-UHFFFAOYSA-N Zirconium Chemical compound [Zr] QCWXUUIWCKQGHC-UHFFFAOYSA-N 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- 229910052797 bismuth Inorganic materials 0.000 description 1
- JCXGWMGPZLAOME-UHFFFAOYSA-N bismuth atom Chemical compound [Bi] JCXGWMGPZLAOME-UHFFFAOYSA-N 0.000 description 1
- 238000009835 boiling Methods 0.000 description 1
- 229910052796 boron Inorganic materials 0.000 description 1
- 239000003054 catalyst Substances 0.000 description 1
- 229910052804 chromium Inorganic materials 0.000 description 1
- 239000011651 chromium Substances 0.000 description 1
- 239000010941 cobalt Substances 0.000 description 1
- 229910017052 cobalt Inorganic materials 0.000 description 1
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 description 1
- 239000006258 conductive agent Substances 0.000 description 1
- 229920001577 copolymer Polymers 0.000 description 1
- 239000011889 copper foil Substances 0.000 description 1
- 229920006037 cross link polymer Polymers 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 238000010790 dilution Methods 0.000 description 1
- 239000012895 dilution Substances 0.000 description 1
- IEJIGPNLZYLLBP-UHFFFAOYSA-N dimethyl carbonate Chemical compound COC(=O)OC IEJIGPNLZYLLBP-UHFFFAOYSA-N 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- JBTWLSYIZRCDFO-UHFFFAOYSA-N ethyl methyl carbonate Chemical compound CCOC(=O)OC JBTWLSYIZRCDFO-UHFFFAOYSA-N 0.000 description 1
- 239000011737 fluorine Substances 0.000 description 1
- 229910052731 fluorine Inorganic materials 0.000 description 1
- 239000011888 foil Substances 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 230000002427 irreversible effect Effects 0.000 description 1
- 239000011244 liquid electrolyte Substances 0.000 description 1
- 239000001989 lithium alloy Substances 0.000 description 1
- GQYHUHYESMUTHG-UHFFFAOYSA-N lithium niobate Chemical compound [Li+].[O-][Nb](=O)=O GQYHUHYESMUTHG-UHFFFAOYSA-N 0.000 description 1
- 229910003002 lithium salt Inorganic materials 0.000 description 1
- 159000000002 lithium salts Chemical class 0.000 description 1
- WPBNNNQJVZRUHP-UHFFFAOYSA-L manganese(2+);methyl n-[[2-(methoxycarbonylcarbamothioylamino)phenyl]carbamothioyl]carbamate;n-[2-(sulfidocarbothioylamino)ethyl]carbamodithioate Chemical compound [Mn+2].[S-]C(=S)NCCNC([S-])=S.COC(=O)NC(=S)NC1=CC=CC=C1NC(=S)NC(=O)OC WPBNNNQJVZRUHP-UHFFFAOYSA-L 0.000 description 1
- 229920002239 polyacrylonitrile Polymers 0.000 description 1
- 239000004417 polycarbonate Substances 0.000 description 1
- 229920000515 polycarbonate Polymers 0.000 description 1
- 229920000570 polyether Polymers 0.000 description 1
- 229920000573 polyethylene Polymers 0.000 description 1
- 239000005518 polymer electrolyte Substances 0.000 description 1
- 239000002861 polymer material Substances 0.000 description 1
- 239000003505 polymerization initiator Substances 0.000 description 1
- 229920001155 polypropylene Polymers 0.000 description 1
- 229920002981 polyvinylidene fluoride Polymers 0.000 description 1
- 230000002250 progressing effect Effects 0.000 description 1
- 238000010298 pulverizing process Methods 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 229920005989 resin Polymers 0.000 description 1
- 239000011347 resin Substances 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
- 230000008961 swelling Effects 0.000 description 1
- YLQBMQCUIZJEEH-UHFFFAOYSA-N tetrahydrofuran Natural products C=1C=COC=1 YLQBMQCUIZJEEH-UHFFFAOYSA-N 0.000 description 1
- 150000003609 titanium compounds Chemical class 0.000 description 1
- 229910052725 zinc Inorganic materials 0.000 description 1
- 239000011701 zinc Substances 0.000 description 1
- 229910052726 zirconium Inorganic materials 0.000 description 1
Images
Classifications
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- 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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- Inorganic Compounds Of Heavy Metals (AREA)
- Primary Cells (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、正極活物質を含む正極と、負極と、電解質とが外装体内に装填された非水電解質電池に関する。
【０００２】
【従来の技術】
近年、コバルト酸リチウムやマンガン酸リチウムを正極材料とする一方、金属リチウム又はリチウムイオンを吸蔵、放出し得る合金又は炭素材料を負極材料とするリチウムイオン電池が、高容量化が可能な電池として注目されている。
しかしながら、コバルト酸リチウムやマンガン酸リチウムを正極活物質として用いた電池では、充放電を繰り返すことによって次第に充放電容量や充放電効率が低下し、十分なサイクル寿命が得られないという欠点がある。この充放電容量や充放電効率が低下する原因としては、正極活物質の結晶構造の変化に起因して、一部に活物質の非可逆的な変化が起こること、及び、正極の電位が基準値よりも高くなる充電や基準値よりも低くなる充電により電解液が分解すること等が考えられる。このため、下記に示すように、様々な金属元素を正極活物質中に部分置換することによって上記課題の解決が試みられている。
【０００３】
まず、特公昭６３−５９５０７号公報においては、Ｌｉx Ｍy Ｏ2 （ＭはＮｉまたはＣｏから成り、またｘ＜０．８、ｙ≒１である）を正極活物質として用い、リチウム金属を負極として用いた非水電解質電池が提案されている。このような構成であれば、４Ｖ以上の起電力を有し、高エネルギー密度を有するという利点があるものの、上記に示したようなサイクル劣化等の問題は解決されていなかった。
【０００４】
そこで、例えば、特開平４−３２９２６７号公報及び特開平５−１３０８２号公報に示されるように、チタン化合物をコバルト酸リチウムに固溶させたものを正極活物質として用い、又は、特開平４−３１９２６０号公報に示されるように、コバルト酸リチウムにジルコニウムを固溶させたものを正極活物質として用い、或いは特開平４−２５３１６２号公報に示されるように、コバルト酸リチウムに鉛、ビスマス、ホウ素が固溶されたもの等を正極活物質として用いた電池が提案されている。これらの正極活物質を用いた電池においては、他金属元素をコバルト酸リチウムに部分元素置換することによって上記に示した問題は改善できる。しかしながら、発熱開始温度が低下するために安全性が低下したり、電池初期容量が低下する等の問題があった。
【０００５】
また、近年、携帯電話等の携帯機器の普及に伴い、サイクル特性が良好であることはもちろん、作動電圧が高くしかも低温特性の良い電池の必要性が高まっている。
更に、携帯機器の小型化に伴って電池の薄型化が急速に進む中、ラミネート外装体を用いた薄型電池においては、電池性能に加えて電池の膨れが大きな問題となっており、この電池の膨れを防止すべく、ガス発生を減少させる技術の開発が必要となってきた。
【０００６】
【発明が解決しようとする課題】
本発明は、以上の事情に鑑みなされたものであって、作動電圧が高く且つ低温特性に優れると共に、安全性の向上とガス発生の低減とを図ることができる非水電解質電池の提供を目的とする。
【０００７】
【課題を解決するための手段】
上記目的を達成するために、本発明のうちで請求項１に記載の発明は、正極活物質を含む正極と、負極と、電解質とが外装体内に装填された非水電解質電池において、上記正極活物質として、ＬｉＣｏ1-x Ｎｂx Ｏ2 〔０．００００１≦ｘ≦０．０５〕で示されるリチウム含有複合酸化物が用いられ、上記負極として黒鉛を主体とする材料が用いられ、上記電解質としてエチレンカーボネートを主体とする混合溶媒が用いられていることを特徴とする。
また、請求項２記載の発明は、請求項１記載の発明において、上記正極活物質として、ＬｉＣｏ 1-x Ｎｂ x Ｏ 2 〔０．００１≦ｘ≦０．０３〕で示されるリチウム含有複合酸化物が用いられていることを特徴とする。
【０００８】
上記構成の如く、正極活物質としてＬｉＣｏ1-x Ｎｂx Ｏ2 〔０．００００１≦ｘ≦０．０５（特に、０．００１≦ｘ≦０．０３）〕で示されるリチウム含有複合酸化物を用いる（即ち、コバルト酸リチウムの表面にニオブ化合物を固溶させる）と、正極活物質としてコバルト酸リチウムを用いた場合に比べて、放電作動電圧が０．１Ｖ以上上昇するので、低温特性が飛躍的に向上する。尚、リチウム含有複合酸化物のｘを０．００００１≦ｘ≦０．０５に規制するのは、リチウム含有複合酸化物のｘが０．００００１未満では低温特性の向上が十分に発揮されない一方、リチウム含有複合酸化物のｘが０．０５を超えると重量エネルギー密度が小さくなって、放電容量の低下を招くからである。
【０００９】
また、負極として黒鉛を主体とする材料を用いれば、コークスを主体とする材料を用いた場合に比べて低温での放電容量が増大する。また、電解質としてエチレンカーボネートを主体とする混合溶媒が用いられていれば、エチレンカーボネートに起因する電解液被膜が、ニオブ酸化物等の触媒効果によって分解されるため、粒子界面での表面抵抗が減少し、イオン伝導性が向上する。
【００１０】
また、請求項３記載の発明は、請求項１または２記載の発明において、上記電解質の塩として、少なくとも構造式ＬｉＮ（ＳＯ2 Ｃ2 Ｆ5 ）2 で示されるイミド塩が含まれているものが用いられていることを特徴とする。
電解質塩としてＬｉＮ（ＳＯ2 Ｃ2 Ｆ5 ）2 で示されるイミド塩を用いた電池では、電解質塩等が高電位状態や高温状態で分解するのが抑制されるので、ガスの発生量が著しく減少する。
【００１１】
また、請求項４記載の発明は、請求項３記載の発明において、上記外装体がラミネート外装体から成ることを特徴とする。
このように柔らかなラミネート外装体を用いた電池では、電池の変形による破裂や漏液を生じ易いが、上記の如くガスの発生量が著しく減少すれば破裂や漏液を抑制できるので、飛躍的に安全性が向上する。
【００１２】
また、請求項５記載の発明は、請求項１、２、３又は４記載の発明において、上記電解質がゲル状の固体高分子であることを特徴とする。
低温領域では界面抵抗が増加する傾向があり、このことはゲル状電解質において顕著であるが、コバルト酸リチウム中にニオブ酸化物等を添加した場合には界面抵抗が低下するために、低温領域での放電容量の低下が抑制され、低温特性の低下を抑えることができる。
【００１３】
また、請求項６記載の発明は、請求項１、２、３、４又は５記載の発明において、上記正極活物質として、酸化コバルトと、ニオブ化合物とを焼成してニオブ化合物混合酸化コバルトを作製した後、このニオブ化合物混合酸化コバルトと、水酸化リチウム、炭酸リチウム、硝酸リチウムから成るリチウム化合物から選択される少なくとも一種とを混合し、更に焼成したものを用いることを特徴とする。
上記のような正極活物質を用いた場合には、量産性にすぐれると共に製造コストを低減でき、しかも発熱開始温度が高いので、電池の安全性がより向上する。
【００１４】
また、請求項７記載の発明は、請求項１、２、３、４又は５記載の発明において、上記正極活物質として、コバルト酸リチウムに酸化ニオブ及び／又は金属ニオブを混合し、更に焼成したものを用いることを特徴とする。
上記のような正極活物質を用いた場合には、請求項６記載の作用と同様の作用がある。
【００１５】
また、請求項８記載の発明は、請求項１、２、３、４又は５記載の発明において、上記正極活物質として、コバルト酸リチウムにリチウム−ニオブ複合酸化物を混合し、更に焼成したものを用いることを特徴とする。
上記のような正極活物質を用いた場合には、請求項６記載の作用と同様の作用がある。
【００１６】
【発明の実施の形態】
本発明の第１の形態〜第４の形態を、以下に説明する。
（第１の形態）
先ず、酸化ニオブと酸化コバルト粉末とを混合し、大気中で焼成（６００℃）することによって、ニオブ化合物混合酸化コバルト粉末を合成した。次に、このニオブ化合物混合酸化コバルト粉末と、リチウム源であるＬｉＯＨとを混合し、酸素分圧制御雰囲気下で焼成（８００℃）して室温までゆっくりと冷却し、更にこれを粉砕することによりＬｉＣｏ1-x Ｎｂx Ｏ2 〔０．００００１≦ｘ≦０．０５（特に、０．００１≦ｘ≦０．０３）〕で示されるリチウム含有複合酸化物から成る正極活物質を得た。このようにして合成した正極活物質と、炭素導電剤、グラファイト及びフッ素樹脂系結着剤とを一定の割合で混合して正極合剤を作成した後、この正極合剤をアルミ箔の両面に塗着し、乾燥後圧延することにより、正極を作製した。
一方、負極は、負極活物質としての炭素材料（黒鉛）と結着剤としてのフッ素樹脂結着剤を一定の割合で混合して負極合剤を作成した後、この負極合剤を銅箔の両面に塗着し、乾燥後圧延することにより作製した。
【００１７】
次いで、上記のようにして作製した正負極に、それぞれにリードを取り付けた後、ポリプロピレン製のセパレータを介して正負極を渦巻き状に巻き取って渦巻き電極体を作製した後、この渦巻き電極体を電池ケース内に収納した。最後に、上記電池ケース内に電解液を注入した後、封口することにより、容量が４８０ｍＡｈの電池を作製した。尚、電解液としては、エチレンカーボネート（ＥＣ）とジエチルカーボネート（ＤＥＣ）の等容積混合溶媒に、６フッ化リン酸リチウム（ＬｉＰＦ6 ）を１モル／ｌの割合で溶解したものを用いた。
【００１８】
ここで、リチウム源としては、上記ＬｉＯＨに限定するものではなく、例えばＬｉ2 ＣＯ3 ／ＬｉＮＯ3 等を用いることも可能である。
また、ニオブ化合物混合酸化コバルトとしては、酸化ニオブ（ニオブ化合物）と酸化コバルトとの混合物を焼成することにより得たものに限定するものではなく、例えば金属ニオブ粉末と酸化コバルトを混合して、これを大気中で焼成（６００℃）することによっても得ることができる。
【００１９】
（第２の形態）
正極活物質の製造方法として、コバルト酸リチウムにリチウム−ニオブ複合酸化物を混合し、酸素分圧制御雰囲気下で焼成（８００℃）して室温までゆっくりと冷却し、さらに粉砕する方法を用いた他は、上記第１の形態と同様にして電池を作製した。
【００２０】
（第３の形態）
正極活物質の製造方法として、コバルト酸リチウムに金属ニオブ粉末或いはＮｂ2 Ｏ5 などのニオブ化合物を混合し、酸素分圧制御雰囲気下で焼成（８００℃）して室温までゆっくりと冷却し、さらに粉砕する方法を用いた他は、上記第１の形態と同様にして電池を作製した。
【００２１】
（第４の形態）
電解質としてゲル状ポリマー電解質を用いると共に、外装体としてラミネート外装体を用いる他は、前記第１の形態と同様にして電池を作製した。具体的には、以下の通りである。
先ず、前記第１実施例の実施例１と同様の正極と負極とをポリエチレン多孔質体で挟み込んで、これをラミネート外装体内に挿入する。次に、ラミネート外装体内に、ポリエチレングリコールジアクリレート（分子量：１０００）と、ＥＣ及びＤＥＣの等容積混合溶媒にＬｉＰＦ6 を１モル／ｌの割合で溶解したものとを、重量比で１：１０の割合で混合し、これに重合開始剤としてのｔ−ヘキシルパーオキシピバレートを５０００ｐｐｍ添加したものを３ｍｌ注入した後、６０℃で３時間加熱処理して硬化させることにより作製した。
【００２２】
尚、ニオブ化合物を均一にコバルト酸リチウム中に分散させる方法としては、樹脂工業等でよく用いられるマスターバッチ法（初め高い混合比率で均一に混合しておき、順次希釈倍率をあげて混合する方法である。このような方法を用いるのは、少量添加の場合にはこの方法でないと均一に混ざらないためである）で行った。
【００２３】
また、本発明に用いられる負極材料としては上記炭素材料の他、リチウム金属、リチウム合金等が好適に用いられる。更に、電解液の溶媒としては上記のものに限らず、例えばエチレンカーボネートとジメチルカーボネート、メチルエチルカーボネート、テトラヒドロフラン、１，２−ジメトキシエタン、１，３−ジオキソラン、２−メトキシテトラヒドロフラン、ジエチルエーテル等の低粘度低沸点溶媒とを適度な比率で混合した溶媒を用いることができる。また、電解液の溶質としては、上記ＬｉＰＦ6 の他、ＬｉＮ（ＳＯ2 Ｃ2 Ｆ5 ）2 、ＬｉＡｓＦ6 、ＬｉＣｌＯ4 、ＬｉＢＦ4 、ＬｉＣＦ3 ＳＯ3 等を用いることができる。
【００２４】
更に、ゲル状の固体高分子としては、ポリエチレングリコールジアクリレートの他、ポリエーテル系の固体高分子、ポリカーボネート系の固体高分子、ポリアクリロニトリル系の固体高分子、及びこれらの２種以上からなる共重合体、もしくは架橋した高分子材料、ポリフッ化ビニリデン等のようなフッ素系の固体高分子と、リチウム塩、電解液とを組み合わせて用いることもできる。
【００２５】
【実施例】
（第１実施例）
〔実施例１〕
実施例１としては、上記第３の形態に示す方法と同様の方法（コバルト酸リチウムに酸化ニオブを混合し、焼成するという方法）で電池を作製した。尚、ＬｉＣｏ1-x Ｎｂx Ｏ2 におけるｘは０．０１である。
このようにして作製した電池を、以下、本発明電池Ａ１と称する。
【００２６】
〔実施例２〕
負極活物質として黒鉛の代わりにコークスを用いた他は、上記実施例１と同様にして電池を作製した。
このようにして作製した電池を、以下、本発明電池Ａ２と称する。
【００２７】
〔実施例３〕
負極活物質として黒鉛の代わりにコークスを用いると共に、電解液の溶媒としてＥＣとＤＥＣとの等容積混合溶媒の代わりにプロピレンカーボネート（ＰＣ）とＤＥＣの等容積混合溶媒を用いた他は、上記実施例１と同様にして電池を作製した。
このようにして作製した電池を、以下、本発明電池Ａ３と称する。
【００２８】
〔実施例４〜７〕
上記ＬｉＣｏ1-x Ｎｂx Ｏ2 におけるｘを、それぞれ０．００００１、０．０００１、０．０２、０．０３、０．０５とする他は、上記実施例１と同様にして電池を作製した。
このようにして作製した電池を、以下それぞれ、本発明電池Ａ４〜Ａ８と称する。
【００２９】
〔比較例１〕
上記ＬｉＣｏ1-x Ｎｂx Ｏ2 におけるｘを０とする（酸化ニオブを固溶させない）他は、上記実施例１と同様にして電池を作製した。
このようにして作製した電池を、以下、比較電池Ｘ１と称する。
〔比較例２〕
負極活物質として黒鉛の代わりにコークスを用いた他は、上記比較例１と同様にして電池を作製した。
このようにして作製した電池を、以下、比較電池Ｘ２と称する。
【００３０】
〔比較例３〕
負極活物質として黒鉛の代わりにコークスを用いると共に、電解液の溶媒としてＥＣとＤＥＣとの等容積混合溶媒の代わりにＰＣとＤＥＣの等容積混合溶媒を用いる他は、上記比較例１と同様にして電池を作製した。
このようにして作製した電池を、以下、比較電池Ｘ３と称する。
【００３１】
〔比較例４〕
上記ＬｉＣｏ1-x Ｎｂx Ｏ2 におけるｘを、０．１とする他は、上記実施例１と同様にして電池を作製した。
このようにして作製した電池を、以下、比較電池Ｘ４と称する。
【００３２】
〔実験１〕
上記本発明電池Ａ１〜Ａ３及び比較電池Ｘ１〜Ｘ３を、−２０℃、−１０℃、０℃及び２５℃という温度下で定電流充放電試験を行ったので、その結果を、図１〜図３に示す。尚、充放電条件は、充電電流４８０ｍＡ（１Ｃ）で充電終止電圧４．１Ｖまで充電した後、放電電流４８０ｍＡ（１Ｃ）で放電終止電圧２．７５Ｖまで放電するという条件である。
【００３３】
図１及び図２から明らかなように、負極がコークス或いは黒鉛であるに係わらず、ＥＣ（エチレンカーボネート）を含む電解液を用いた場合には、酸化ニオブが固溶された本発明電池Ａ１、Ａ２は、酸化ニオブを含まない比較電池Ｘ１、Ｘ２に比べて、−２０℃〜０℃の低温時に大幅に作動電圧が上昇しており、低温特性が大きく向上していることが認められる。但し、図３から明らかなように、ＰＣ（プロピレンカーボネート）を含む電解液を用いた場合には、酸化ニオブが固溶された本発明電池Ａ３は、酸化ニオブを含まない比較電池Ｘ３に比べて、−２０℃〜０℃の低温時に作動電圧が余り上昇しておらず、低温特性の向上は認められなかった。
【００３４】
この実験結果となったのは、以下に示す理由によるものと考えられる。
即ち、電池系において、正極粒子表面にＥＣやＰＣなどの電解液は被膜を形成するが、コバルト酸リチウムに固溶した酸化ニオブ等のニオブ化合物はコバルト粒子表面上に存在して触媒作用を発揮するため、ＥＣによる電解液被膜を分解する。したがって、電解液被膜が生成し難い状態となって、粒子界面での表面抵抗が減少し、イオン伝導性が向上する。一方、このようなニオブ化合物の触媒効果はＰＣによる電解液被膜の分解には充分に発揮されないため、ＰＣを含む電解液を用いた場合にはイオン伝導性が向上しないという理由によるものと考えられる。
【００３５】
尚、負極が黒鉛である場合には一般にＰＣは負極を分解してしまうことが既知であるため、負極が黒鉛であってＰＣを含む電解液を用いた電池については、今回実験を行っていない。
また、前記発明の実施の形態における、第１の形態及び第２の形態で作製した正極活物質を用いた場合にも、上記と同様の効果を発揮することを実験により確認している。
【００３６】
〔実験２〕
上記ＬｉＣｏ1-x Ｎｂx Ｏ2 におけるｘを、それぞれ０、０．００００１、０．０００１、０．０１、０．０２、０．０３、０．０５、０．１とする正極活物質を作製し、この正極活物質を用いた正極と金属リチウムから成る参照極とを上記実施例１で示した電解液と同様の電解液中に浸漬し、ＬｉＣｏ1-x Ｎｂx Ｏ2 におけるｘと正極活物質の単位重量当たりの放電容量（以下、単に放電容量と称する）との関係を調べたので、その結果を図４及び図５に示す。
【００３７】
図４及び図５から明らかなように、ＬｉＣｏ1-x Ｎｂx Ｏ2 におけるｘが大きくなるに連れて放電容量が小さく（即ち、正極活物質を用いて電池を作製した場合の重量エネルギー密度が小さく）なることが認められる。したがって、重量エネルギー密度という観点からは、ＬｉＣｏ1-x Ｎｂx Ｏ2 におけるｘがｘ≦０．０５（特に、ｘ≦０．０３）の範囲であることが望ましい。
【００３８】
〔実験３〕
上記本発明電池Ａ１・Ａ４〜Ａ８及び比較電池Ｘ１、Ｘ４を用いて、ＬｉＣｏ1-x Ｎｂx Ｏ2 におけるｘと、−１０℃及び−２０℃での放電容量との関係を調べたので、その結果を図６〜図９（図６及び図７は−１０℃、図８及び図９は−２０℃）に示す。
図６〜図９から明らかなように、ＬｉＣｏ1-x Ｎｂx Ｏ2 におけるｘが大きくなるに連れて放電容量が大きくなることが認められる。ここで、実際に携帯機器に電池を用いる場合には、−１０℃での条件下では初期容量に対して４０％以上（４８０ｍＡｈ×０．４＝１９２ｍＡｈ）、−２０℃での条件下では初期容量に対して２０％以上（４８０ｍＡｈ×０．２＝９６ｍＡｈ）の容量を有しているとが望ましい。したがって、低温でも十分な放電容量を得るという観点からは、ＬｉＣｏ1-x Ｎｂx Ｏ2 におけるｘが０．００００１≦ｘ（特に、０．０００１≦ｘ）の範囲であることが望ましい。
【００３９】
上記実験２及び実験３の結果より、重量エネルギー密度を高めつつ、低温でも十分な放電容量を得るためには、ＬｉＣｏ1-x Ｎｂx Ｏ2 におけるｘが０．００００１≦ｘ≦０．０５（特に、０．０００１≦ｘ≦０．０３）の範囲であることが望ましいことがわかる。
【００４０】
〔実験４〕
コバルト酸リチウムに添加する物質（添加しない場合を含む）と、電解液の溶媒と、電解液の溶質とを変えつつ各種の電池を作製し、これら電池を８０℃で９６時間保存した後のガス発生量を調べたので、その結果を下記表１〜表３に示す。尚、負極には黒鉛系の炭素材料を使用し、電解液としては、ＥＣを主成分とする２成分系の等体積混合溶媒に各溶質を１モル／ｌの割合で溶解させたものを用いた。
【００４１】
【表１】
【表２】
【表３】
上記表１〜表３から明らかなように、いずれの物質をコバルト酸リチウムに添加した場合にも、当該物質は充放電時や高温保存時に触媒として作用するため、電解液の溶媒や溶質と反応してガスを発生することが認められる。このようにガスが発生すると、電池性能が低下するばかりか、近年盛んに開発されている柔らかなラミネート外装体を用いた電池では、電池の変形による破裂や漏液の直接の原因となる結果、安全性が低下する等の問題が生じる。
【００４５】
但し、原因については定かではないが、酸化ニオブが固溶されたコバルト酸リチウムを正極活物質として用いると共に、電解液の溶質としてＬｉＮ（ＳＯ2 Ｃ2 Ｆ5 ）2 で示されるイミド塩を用いた電池では、電解液の溶媒や溶質が高電位状態や高温状態で分解するのを抑制する働きがあることを見出した。したがって、このような電池ではガスの発生量が著しく低減するので、上記のような柔らかなラミネート外装体を用いた電池では、電池の変形による破裂や漏液を抑制でき、この結果安全性が飛躍的に向上する。
尚、上記表１〜表３には示していないが、ニオブの代わりに珪素、鉄、アルミニウム、マンガン、ニッケル、クロム及び亜鉛を用いた場合にも、電解液の溶媒や溶質に係わらず、添加物の触媒作用による電解液の溶媒や溶質の分解に起因するガス発生が認められた。また、ＬｉＣｏ1-x Ｎｂx Ｏ2 におけるｘを０．０００１、０．００１、０．０１及び０．１に変化させて、上記と同様の実験を行ったところ、ガス発生量は異なる（添加物の量が増加するにしたがって、ガス発生量も増加する）ものの、傾向としては、上記表１〜表３と同様の傾向にあることを確認した。
【００４６】
（第２実施例）
〔実施例〕
実施例としては、上記発明の実施の形態における第４の形態に示す方法と同様の方法で電池を作製した。尚、ＬｉＣｏ1-x Ｎｂx Ｏ2 におけるｘは０．０１である。
このようにして作製した電池を、以下、本発明電池Ｂと称する。
【００４７】
〔比較例〕
酸化ニオブが固溶していないコバルト酸リチウムを正極活物質として用いる他は、上記実施例と同様にして電池を作製した。
このようにして作製した電池を、以下、比較電池Ｙと称する。
【００４８】
〔実験〕
上記本発明電池Ｂ及び比較電池Ｙを、−２０℃、−１０℃、０℃及び２５℃という温度下で定電流充放電試験を行ったので、その結果を、図１０に示す。尚、充放電条件は、前記第１実施例の実験１と同様の条件である。
図１０から明らかなように、比較電池Ｙでは放電作動電圧、放電容量共に大幅に低下しているのに対して、本発明電池Ｂでは放電作動電圧、放電容量共に余り低下しておらず、特に−１０℃以下の低温領域における両者の差異が顕著に認められる。
【００４９】
これは、低温領域では界面抵抗が増加する傾向があり、このことは液体電解質よりもゲル状電解質において顕著であが、本発明電池Ｂの如く酸化ニオブが固溶されたコバルト酸リチウムを正極活物質として用いると、界面抵抗を低下させるために、低温特性の低下が抑制されるものと考えられる。
【００５０】
【発明の効果】
以上説明したように、本発明によれば、電池の作動電圧を高くでき、しかも電池の低温特性と安全性の向上とガス発生の低減とを図ることができるといった優れた効果を奏する。
【図面の簡単な説明】
【図１】図１は本発明電池Ａ１及び比較電池Ｘ１における電池電圧と放電容量との関係を示すグラフである。
【図２】図２は本発明電池Ａ２及び比較電池Ｘ２における電池電圧と放電容量との関係を示すグラフである。
【図３】図３は本発明電池Ａ３及び比較電池Ｘ３における電池電圧と放電容量との関係を示すグラフである。
【図４】図４はＬｉＣｏ1-x Ｎｂx Ｏ2 におけるｘと正極活物質の単位重量当たりの放電容量との関係を示すグラフである。
【図５】図５はＬｉＣｏ1-x Ｎｂx Ｏ2 におけるｘと正極活物質の単位重量当たりの放電容量との関係を示すグラフである。
【図６】図６は本発明電池Ａ１・Ａ４〜Ａ８及び比較電池Ｘ１、Ｘ４における、ＬｉＣｏ1-x Ｎｂx Ｏ2 におけるｘと−１０℃での放電容量との関係を示すグラフである。
【図７】図７は本発明電池Ａ１・Ａ４〜Ａ８及び比較電池Ｘ１、Ｘ４における、ＬｉＣｏ1-x Ｎｂx Ｏ2 におけるｘと−１０℃での放電容量との関係を示すグラフである。
【図８】図８は本発明電池Ａ１・Ａ４〜Ａ８及び比較電池Ｘ１、Ｘ４における、ＬｉＣｏ1-x Ｎｂx Ｏ2 におけるｘと−２０℃での放電容量との関係を示すグラフである。
【図９】図９は本発明電池Ａ１・Ａ４〜Ａ８及び比較電池Ｘ１、Ｘ４における、ＬｉＣｏ1-x Ｎｂx Ｏ2 におけるｘと−２０℃での放電容量との関係を示すグラフである。
【図１０】図１０は本発明電池Ｂ及び比較電池Ｙにおける、電池電圧と放電容量との関係を示すグラフである。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a non-aqueous electrolyte battery in which a positive electrode including a positive electrode active material, a negative electrode, and an electrolyte are loaded in an outer package.
[0002]
[Prior art]
In recent years, lithium ion batteries that use lithium cobalt oxide or lithium manganate as a positive electrode material, and metal lithium or an alloy that can occlude and release lithium ions or a carbon material as a negative electrode material, are attracting attention as a battery that can be increased in capacity. Has been.
However, a battery using lithium cobaltate or lithium manganate as a positive electrode active material has a drawback that charging / discharging capacity and charging / discharging efficiency are gradually lowered by repeating charging / discharging, and a sufficient cycle life cannot be obtained. The reason why the charge / discharge capacity and charge / discharge efficiency are reduced is that, due to a change in the crystal structure of the positive electrode active material, an irreversible change of the active material occurs in part, and the positive electrode potential is the standard. It is conceivable that the electrolytic solution is decomposed by charging that is higher than the value or charging that is lower than the reference value. For this reason, as described below, attempts have been made to solve the above problems by partially replacing various metal elements in the positive electrode active material.
[0003]
First, in JP-B-63-59507, Li x M y O 2 ( where M consists of Ni or Co, also x <0.8, a y ≒ 1) used as a positive electrode active material, a lithium metal Nonaqueous electrolyte batteries used as negative electrodes have been proposed. Such a configuration has the advantage of having an electromotive force of 4 V or higher and a high energy density, but problems such as cycle deterioration as described above have not been solved.
[0004]
Therefore, for example, as disclosed in JP-A-4-329267 and JP-A-5-13082, a titanium compound dissolved in lithium cobaltate is used as the positive electrode active material, or As disclosed in Japanese Patent No. 319260, lithium cobaltate in which zirconium is dissolved is used as a positive electrode active material, or as disclosed in Japanese Patent Laid-Open No. 4-253162, lead, bismuth, boron There has been proposed a battery using as a positive electrode active material a material in which is dissolved. In the battery using these positive electrode active materials, the above-described problems can be improved by substituting another metal element with lithium cobaltate as a partial element. However, since the heat generation start temperature is lowered, there is a problem that safety is lowered and initial battery capacity is lowered.
[0005]
In recent years, with the widespread use of mobile devices such as mobile phones, there is an increasing need for batteries having high operating voltage and good low temperature characteristics as well as good cycle characteristics.
In addition, while thinning of batteries is rapidly progressing with downsizing of portable devices, in thin batteries using a laminate outer package, swelling of the batteries has become a big problem in addition to battery performance. In order to prevent blistering, it has become necessary to develop technologies that reduce gas generation.
[0006]
[Problems to be solved by the invention]
The present invention has been made in view of the above circumstances, and an object thereof is to provide a nonaqueous electrolyte battery that has a high operating voltage and excellent low-temperature characteristics, and that can improve safety and reduce gas generation. And
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the invention described in
The invention according to claim 2 is the invention according to
[0008]
As described above, a lithium-containing composite oxide represented by LiCo 1-x Nb x O 2 [0.00001 ≦ x ≦ 0.05 (particularly 0.001 ≦ x ≦ 0.03)] is used as the positive electrode active material. When used (that is, when a niobium compound is dissolved on the surface of lithium cobaltate), the discharge operating voltage rises by 0.1 V or more compared to the case where lithium cobaltate is used as the positive electrode active material, so that the low temperature characteristics are dramatically improved. Improve. Note that the x of the lithium-containing composite oxide is regulated to 0.00001 ≦ x ≦ 0.05 because when the lithium-containing composite oxide x is less than 0.00001, the improvement of the low temperature characteristics is not sufficiently exhibited. This is because if the x of the contained composite oxide exceeds 0.05, the weight energy density decreases and the discharge capacity decreases.
[0009]
Further, when a material mainly composed of graphite is used as the negative electrode, the discharge capacity at a low temperature is increased as compared with the case where a material mainly composed of coke is used. In addition, if a mixed solvent mainly composed of ethylene carbonate is used as the electrolyte, the electrolyte film resulting from ethylene carbonate will be decomposed by the catalytic effect of niobium oxide, etc., reducing the surface resistance at the particle interface. In addition, ion conductivity is improved.
[0010]
The invention according to claim 3 is the invention according to
In a battery using an imide salt represented by LiN (SO 2 C 2 F 5 ) 2 as an electrolyte salt, decomposition of the electrolyte salt or the like in a high potential state or a high temperature state is suppressed. Decrease.
[0011]
According to a fourth aspect of the present invention, in the third aspect of the invention, the exterior body is a laminate exterior body.
In such a battery using a soft laminate outer package, rupture and leakage due to deformation of the battery are likely to occur, but if the amount of gas generated is significantly reduced as described above, rupture and leakage can be suppressed. Safety is improved.
[0012]
The invention according to claim 5 is the invention according to
The interface resistance tends to increase in the low temperature region, which is remarkable in the gel electrolyte, but when niobium oxide or the like is added to lithium cobaltate, the interface resistance decreases, so in the low temperature region. The decrease in the discharge capacity is suppressed, and the decrease in the low temperature characteristics can be suppressed.
[0013]
The invention according to claim 6 is the invention according to
When the positive electrode active material as described above is used, it is excellent in mass productivity and the manufacturing cost can be reduced, and the heat generation start temperature is high, so that the safety of the battery is further improved.
[0014]
Further, the invention according to claim 7 is the invention according to
When the positive electrode active material as described above is used, the same effect as that described in claim 6 is obtained.
[0015]
The invention according to claim 8 is the invention according to
When the positive electrode active material as described above is used, the same effect as that described in claim 6 is obtained.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
The first to fourth embodiments of the present invention will be described below.
(First form)
First, niobium oxide and cobalt oxide powder were mixed and fired in the atmosphere (600 ° C.) to synthesize a niobium compound mixed cobalt oxide powder. Next, this niobium compound mixed cobalt oxide powder and LiOH, which is a lithium source, are mixed, calcined (800 ° C.) in an oxygen partial pressure controlled atmosphere, slowly cooled to room temperature, and further pulverized. A positive electrode active material composed of a lithium-containing composite oxide represented by LiCo 1-x Nb x O 2 [0.00001 ≦ x ≦ 0.05 (particularly 0.001 ≦ x ≦ 0.03)] was obtained. A positive electrode active material synthesized in this way and a carbon conductive agent, graphite, and a fluororesin-based binder are mixed at a certain ratio to create a positive electrode mixture, and then the positive electrode mixture is applied to both sides of the aluminum foil. The positive electrode was produced by applying, drying and rolling.
On the other hand, after preparing a negative electrode mixture by mixing a carbon material (graphite) as a negative electrode active material and a fluororesin binder as a binder at a certain ratio, the negative electrode is mixed with a copper foil. It was prepared by applying to both sides, drying and rolling.
[0017]
Next, after attaching leads to the positive and negative electrodes produced as described above, the positive and negative electrodes were wound in a spiral shape through a polypropylene separator to produce a spiral electrode body, and then the spiral electrode body was Stored in a battery case. Finally, an electrolyte was injected into the battery case and sealed to prepare a battery with a capacity of 480 mAh. As the electrolytic solution, an equal volume mixed solvent of ethylene carbonate (EC) and diethyl carbonate (DEC), was obtained by dissolving lithium hexafluorophosphate and (LiPF 6) at a ratio of 1 mol / l.
[0018]
Here, the lithium source is not limited to the LiOH, and for example, Li 2 CO 3 / LiNO 3 or the like can be used.
Further, the niobium compound mixed cobalt oxide is not limited to those obtained by firing a mixture of niobium oxide (niobium compound) and cobalt oxide. For example, a mixture of metal niobium powder and cobalt oxide may be used. Can be obtained by baking (600 ° C.) in the air.
[0019]
(Second form)
As a method for producing the positive electrode active material, a method in which lithium cobalt oxide was mixed with lithium cobaltate, fired (800 ° C.) in an oxygen partial pressure controlled atmosphere, slowly cooled to room temperature, and further pulverized was used. Otherwise, a battery was fabricated in the same manner as in the first embodiment.
[0020]
(Third form)
As a method for producing a positive electrode active material, lithium niobate is mixed with a metal niobium powder or a niobium compound such as Nb 2 O 5 , fired (800 ° C.) in an oxygen partial pressure controlled atmosphere, and slowly cooled to room temperature. A battery was fabricated in the same manner as in the first embodiment except that the pulverizing method was used.
[0021]
(4th form)
A battery was fabricated in the same manner as in the first embodiment except that a gel polymer electrolyte was used as the electrolyte and a laminate outer package was used as the outer package. Specifically, it is as follows.
First, the same positive electrode and negative electrode as in Example 1 of the first example are sandwiched between polyethylene porous bodies and inserted into a laminate outer package. Next, a polyethylene glycol diacrylate (molecular weight: 1000) and a solution obtained by dissolving LiPF 6 in an equal volume mixed solvent of EC and DEC at a ratio of 1 mol / l in the laminate outer package are in a weight ratio of 1:10. The mixture was mixed at a ratio of 5%, and 3 ml of a mixture obtained by adding 5000 ppm of t-hexylperoxypivalate as a polymerization initiator was injected, and then the mixture was heated at 60 ° C. for 3 hours to be cured.
[0022]
In addition, as a method of uniformly dispersing the niobium compound in lithium cobalt oxide, a masterbatch method often used in the resin industry or the like (a method in which the niobium compound is mixed uniformly at a high mixing ratio at first and then gradually increased in dilution ratio and mixed) The reason why such a method is used is that, when a small amount is added, it is not mixed uniformly unless this method is used).
[0023]
Further, as the negative electrode material used in the present invention, lithium metal, lithium alloy and the like are preferably used in addition to the carbon material. Furthermore, the solvent of the electrolytic solution is not limited to the above, but examples thereof include ethylene carbonate and dimethyl carbonate, methyl ethyl carbonate, tetrahydrofuran, 1,2-dimethoxyethane, 1,3-dioxolane, 2-methoxytetrahydrofuran, diethyl ether and the like. A solvent in which a low-viscosity low-boiling solvent is mixed at an appropriate ratio can be used. As the solute of the electrolytic solution, LiN (SO 2 C 2 F 5 ) 2 , LiAsF 6 , LiClO 4 , LiBF 4 , LiCF 3 SO 3 and the like can be used in addition to the above LiPF 6 .
[0024]
Further, as the gel-like solid polymer, in addition to polyethylene glycol diacrylate, a polyether solid polymer, a polycarbonate solid polymer, a polyacrylonitrile solid polymer, and a co-polymer comprising two or more of these. A polymer, a cross-linked polymer material, a fluorine-based solid polymer such as polyvinylidene fluoride, a lithium salt, or an electrolyte can be used in combination.
[0025]
【Example】
(First embodiment)
[Example 1]
As Example 1, a battery was manufactured by a method similar to the method shown in the third embodiment (a method of mixing niobium oxide with lithium cobaltate and firing it). Note that x in LiCo 1-x Nb x O 2 is 0.01.
The battery thus produced is hereinafter referred to as the present invention battery A1.
[0026]
[Example 2]
A battery was fabricated in the same manner as in Example 1 except that coke was used instead of graphite as the negative electrode active material.
The battery thus produced is hereinafter referred to as the present invention battery A2.
[0027]
Example 3
Other than using coke instead of graphite as negative electrode active material and using equal volume mixed solvent of propylene carbonate (PC) and DEC instead of equal volume mixed solvent of EC and DEC as solvent of electrolyte A battery was produced in the same manner as in Example 1.
The battery thus produced is hereinafter referred to as the present invention battery A3.
[0028]
[Examples 4 to 7]
A battery was fabricated in the same manner as in Example 1 except that x in LiCo 1-x Nb x O 2 was 0.00001, 0.0001, 0.02, 0.03, and 0.05, respectively. .
The batteries thus produced are hereinafter referred to as invention batteries A4 to A8, respectively.
[0029]
[Comparative Example 1]
A battery was fabricated in the same manner as in Example 1 except that x in LiCo 1-x Nb x O 2 was 0 (no niobium oxide was dissolved).
The battery thus produced is hereinafter referred to as comparative battery X1.
[Comparative Example 2]
A battery was fabricated in the same manner as in Comparative Example 1 except that coke was used instead of graphite as the negative electrode active material.
The battery thus produced is hereinafter referred to as comparative battery X2.
[0030]
[Comparative Example 3]
The same as in Comparative Example 1 except that coke is used instead of graphite as the negative electrode active material, and an equal volume mixed solvent of PC and DEC is used instead of an equal volume mixed solvent of EC and DEC as the solvent of the electrolytic solution. A battery was produced.
The battery thus produced is hereinafter referred to as comparative battery X3.
[0031]
[Comparative Example 4]
A battery was fabricated in the same manner as in Example 1 except that x in LiCo 1-x Nb x O 2 was 0.1.
The battery thus produced is hereinafter referred to as comparative battery X4.
[0032]
[Experiment 1]
Since the present invention batteries A1 to A3 and comparative batteries X1 to X3 were subjected to a constant current charge / discharge test at temperatures of -20 ° C, -10 ° C, 0 ° C and 25 ° C, the results are shown in Figs. 3 shows. The charging / discharging conditions are such that after charging to a charging end voltage of 4.1 V at a charging current of 480 mA (1 C), discharging is performed to a discharging end voltage of 2.75 V at a discharge current of 480 mA (1 C).
[0033]
As is apparent from FIGS. 1 and 2, the present invention battery A1, in which niobium oxide is dissolved, is used when an electrolyte containing EC (ethylene carbonate) is used regardless of whether the negative electrode is coke or graphite. It is recognized that the operating voltage of A2 is greatly increased at low temperatures of −20 ° C. to 0 ° C. and the low temperature characteristics are greatly improved as compared with comparative batteries X1 and X2 that do not contain niobium oxide. However, as is apparent from FIG. 3, when an electrolytic solution containing PC (propylene carbonate) is used, the present battery A3 in which niobium oxide is dissolved is compared with the comparative battery X3 that does not contain niobium oxide. The operating voltage did not rise much at low temperatures of -20 ° C to 0 ° C, and no improvement in low temperature characteristics was observed.
[0034]
This experimental result is considered to be due to the following reasons.
That is, in the battery system, an electrolytic solution such as EC or PC forms a film on the surface of the positive electrode particles, but a niobium compound such as niobium oxide dissolved in lithium cobaltate is present on the surface of the cobalt particles and exhibits a catalytic action. In order to do this, the electrolyte coating film by EC is decomposed. Therefore, it becomes difficult to form the electrolyte coating, and the surface resistance at the particle interface is reduced, and the ionic conductivity is improved. On the other hand, since the catalytic effect of such a niobium compound is not sufficiently exhibited in the decomposition of the electrolytic solution film by PC, it is considered that the ionic conductivity is not improved when an electrolytic solution containing PC is used. .
[0035]
In addition, when the negative electrode is graphite, it is generally known that PC will decompose the negative electrode. Therefore, no experiment was conducted on a battery using an electrolyte containing graphite and the negative electrode is graphite. .
In addition, it has been confirmed by experiments that the same effect as described above is exhibited even when the positive electrode active materials manufactured in the first and second embodiments in the embodiment of the invention are used.
[0036]
[Experiment 2]
Producing positive electrode active materials in which x in LiCo 1-x Nb x O 2 is 0, 0.00001, 0.0001, 0.01, 0.02, 0.03, 0.05, and 0.1, respectively. Then, a positive electrode using this positive electrode active material and a reference electrode made of metallic lithium are immersed in an electrolytic solution similar to the electrolytic solution shown in Example 1, and x in LiCo 1-x Nb x O 2 and the positive electrode Since the relationship with the discharge capacity per unit weight of the active material (hereinafter simply referred to as discharge capacity) was examined, the results are shown in FIGS.
[0037]
As is apparent from FIGS. 4 and 5, the discharge capacity decreases as x in LiCo 1-x Nb x O 2 increases (that is, the weight energy density when a battery is produced using a positive electrode active material). It is recognized that Therefore, from the viewpoint of weight energy density, x in LiCo 1-x Nb x O 2 is preferably in the range of x ≦ 0.05 (particularly, x ≦ 0.03).
[0038]
[Experiment 3]
Since the present invention batteries A1 and A4 to A8 and comparative batteries X1 and X4 were used, the relationship between x in LiCo 1-x Nb x O 2 and the discharge capacity at −10 ° C. and −20 ° C. was examined. The results are shown in FIGS. 6 to 9 (FIGS. 6 and 7 are −10 ° C., FIGS. 8 and 9 are −20 ° C.).
As is apparent from FIGS. 6 to 9, it is recognized that the discharge capacity increases as x in LiCo 1-x Nb x O 2 increases. Here, when a battery is actually used for a portable device, the initial capacity is 40% or more (480 mAh × 0.4 = 192 mAh) under the condition at −10 ° C., and the initial condition under the condition at −20 ° C. It is desirable to have a capacity of 20% or more (480 mAh × 0.2 = 96 mAh) with respect to the capacity. Therefore, from the viewpoint of obtaining a sufficient discharge capacity even at a low temperature, it is desirable that x in LiCo 1-x Nb x O 2 is in the range of 0.00001 ≦ x (particularly 0.0001 ≦ x).
[0039]
From the results of Experiment 2 and Experiment 3, in order to obtain a sufficient discharge capacity even at a low temperature while increasing the weight energy density, x in LiCo 1-x Nb x O 2 is 0.00001 ≦ x ≦ 0.05 ( In particular, it can be seen that a range of 0.0001 ≦ x ≦ 0.03) is desirable.
[0040]
[Experiment 4]
Various batteries were produced while changing the substances added to lithium cobaltate (including the case where they were not added), the solvent of the electrolytic solution, and the solute of the electrolytic solution, and the gas after storing these batteries at 80 ° C. for 96 hours. Since the generation amount was examined, the results are shown in Tables 1 to 3 below. In addition, a graphite-based carbon material is used for the negative electrode, and an electrolytic solution in which each solute is dissolved at a rate of 1 mol / l in a two-component equal volume mixed solvent containing EC as a main component is used. It was.
[0041]
[Table 1]
[Table 2]
[Table 3]
As is apparent from Tables 1 to 3 above, when any substance is added to lithium cobaltate, the substance acts as a catalyst during charge / discharge or high-temperature storage, and thus reacts with the solvent and solute of the electrolyte. To generate gas. When the gas is generated in this way, not only the battery performance deteriorates, but in the battery using the soft laminate outer casing that has been actively developed in recent years, it is a result of direct rupture or leakage due to deformation of the battery, Problems such as reduced safety occur.
[0045]
However, although the cause is not clear, lithium cobaltate in which niobium oxide is dissolved is used as a positive electrode active material, and an imide salt represented by LiN (SO 2 C 2 F 5 ) 2 is used as a solute of an electrolytic solution. In the conventional battery, it was found that the solvent and solute of the electrolytic solution have a function of suppressing decomposition in a high potential state or a high temperature state. Therefore, since the amount of gas generated in such a battery is remarkably reduced, the battery using the soft laminate outer casing as described above can suppress rupture and leakage due to deformation of the battery, and as a result, safety is dramatically increased. Improve.
Although not shown in Tables 1 to 3, when silicon, iron, aluminum, manganese, nickel, chromium, and zinc are used instead of niobium, addition is possible regardless of the solvent or solute of the electrolyte. Gas generation due to decomposition of the solvent and solute of the electrolyte due to the catalytic action of the product was observed. Further, when x in LiCo 1-x Nb x O 2 was changed to 0.0001, 0.001, 0.01 and 0.1 and the same experiment as described above was performed, the amount of gas generated was different (additional) As the amount of the product increased, the amount of gas generated also increased. However, as a tendency, it was confirmed that the tendency was the same as in Tables 1 to 3 above.
[0046]
(Second embodiment)
〔Example〕
As an example, a battery was manufactured by a method similar to the method shown in the fourth embodiment of the above-described embodiment. Note that x in LiCo 1-x Nb x O 2 is 0.01.
The battery thus produced is hereinafter referred to as the present invention battery B.
[0047]
[Comparative Example]
A battery was fabricated in the same manner as in the above example except that lithium cobaltate in which niobium oxide was not dissolved was used as the positive electrode active material.
The battery thus produced is hereinafter referred to as comparative battery Y.
[0048]
[Experiment]
Since the present invention battery B and comparative battery Y were subjected to a constant current charge / discharge test at temperatures of −20 ° C., −10 ° C., 0 ° C. and 25 ° C., the results are shown in FIG. The charge / discharge conditions are the same as those in
As is clear from FIG. 10, in the comparative battery Y, both the discharge operating voltage and the discharge capacity are significantly reduced, whereas in the battery B of the present invention, both the discharge operating voltage and the discharge capacity are not significantly reduced. The difference between the two in a low temperature region of −10 ° C. or lower is noticeable.
[0049]
This tends to increase the interfacial resistance in the low temperature region. This is more remarkable in the gel electrolyte than in the liquid electrolyte. However, as in the battery B of the present invention, lithium cobalt oxide in which niobium oxide is dissolved is used as the positive electrode. When used as a substance, it is considered that a decrease in low-temperature characteristics is suppressed in order to reduce the interface resistance.
[0050]
【The invention's effect】
As described above, according to the present invention, it is possible to increase the operating voltage of the battery, and to achieve excellent effects such as improving the low temperature characteristics and safety of the battery and reducing gas generation.
[Brief description of the drawings]
FIG. 1 is a graph showing the relationship between battery voltage and discharge capacity in the battery A1 of the present invention and a comparative battery X1.
FIG. 2 is a graph showing the relationship between battery voltage and discharge capacity in the battery A2 of the present invention and the comparative battery X2.
FIG. 3 is a graph showing the relationship between battery voltage and discharge capacity in the battery A3 of the present invention and the comparative battery X3.
FIG. 4 is a graph showing the relationship between x in LiCo 1-x Nb x O 2 and the discharge capacity per unit weight of the positive electrode active material.
FIG. 5 is a graph showing the relationship between x in LiCo 1-x Nb x O 2 and the discharge capacity per unit weight of the positive electrode active material.
FIG. 6 is a graph showing the relationship between x in LiCo 1-x Nb x O 2 and discharge capacity at −10 ° C. in the batteries A1 and A4 to A8 of the present invention and the comparative batteries X1 and X4.
FIG. 7 is a graph showing the relationship between x in LiCo 1-x Nb x O 2 and discharge capacity at −10 ° C. in the batteries A1 and A4 to A8 of the present invention and the comparative batteries X1 and X4.
FIG. 8 is a graph showing the relationship between x in LiCo 1-x Nb x O 2 and the discharge capacity at −20 ° C. in the batteries A1 and A4 to A8 of the present invention and the comparative batteries X1 and X4.
FIG. 9 is a graph showing the relationship between x in LiCo 1-x Nb x O 2 and discharge capacity at −20 ° C. in the batteries A1 and A4 to A8 of the present invention and the comparative batteries X1 and X4.
FIG. 10 is a graph showing the relationship between battery voltage and discharge capacity in the battery B of the present invention and the comparative battery Y.
Claims (8)
上記正極活物質として、ＬｉＣｏ1-x Ｎｂx Ｏ2 〔０．００００１≦ｘ≦０．０５〕で示されるリチウム含有複合酸化物が用いられ、
上記負極として黒鉛を主体とする材料が用いられ、
上記電解質としてエチレンカーボネートを主体とする混合溶媒が用いられている、
ことを特徴とする非水電解質電池。In a non-aqueous electrolyte battery in which a positive electrode including a positive electrode active material, a negative electrode, and an electrolyte are loaded in an exterior body,
As the positive electrode active material, a lithium-containing composite oxide represented by LiCo 1-x Nb x O 2 [0.00001 ≦ x ≦ 0.05 ] is used,
A material mainly composed of graphite is used as the negative electrode,
A mixed solvent mainly composed of ethylene carbonate is used as the electrolyte.
The nonaqueous electrolyte battery characterized by the above-mentioned.
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| JP31122398A JP4097337B2 (en) | 1998-10-30 | 1998-10-30 | Non-aqueous electrolyte battery |
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| JP31122398A JP4097337B2 (en) | 1998-10-30 | 1998-10-30 | Non-aqueous electrolyte battery |
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| JP4097337B2 true JP4097337B2 (en) | 2008-06-11 |
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| FI20060951A7 (en) * | 2004-04-30 | 2006-10-27 | Seimi Chem Kk | Method for preparing a lithium-containing composite oxide for a positive electrode for a lithium battery |
| JP5144944B2 (en) * | 2007-03-05 | 2013-02-13 | 三洋電機株式会社 | Non-aqueous electrolyte battery active material and non-aqueous electrolyte battery using the same |
| JP5215978B2 (en) | 2009-10-28 | 2013-06-19 | 信越化学工業株式会社 | Anode material for non-aqueous electrolyte secondary battery, method for producing the same, and lithium ion secondary battery |
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