JP4707950B2 - Method for producing positive electrode active material for lithium battery, positive electrode active material for lithium battery, electrode for lithium battery, and lithium battery - Google Patents
Method for producing positive electrode active material for lithium battery, positive electrode active material for lithium battery, electrode for lithium battery, and lithium battery Download PDFInfo
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- JP4707950B2 JP4707950B2 JP2003432271A JP2003432271A JP4707950B2 JP 4707950 B2 JP4707950 B2 JP 4707950B2 JP 2003432271 A JP2003432271 A JP 2003432271A JP 2003432271 A JP2003432271 A JP 2003432271A JP 4707950 B2 JP4707950 B2 JP 4707950B2
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- lithium
- lithium battery
- positive electrode
- iron
- active material
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- 229910052744 lithium Inorganic materials 0.000 title claims description 110
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 title claims description 96
- 239000007774 positive electrode material Substances 0.000 title claims description 61
- 238000004519 manufacturing process Methods 0.000 title claims description 24
- 239000002243 precursor Substances 0.000 claims description 76
- 239000010450 olivine Substances 0.000 claims description 64
- 229910052609 olivine Inorganic materials 0.000 claims description 64
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 61
- 150000003839 salts Chemical class 0.000 claims description 43
- 229910052742 iron Inorganic materials 0.000 claims description 30
- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical compound [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 claims description 30
- -1 lithium organic acid salt Chemical class 0.000 claims description 28
- 239000003125 aqueous solvent Substances 0.000 claims description 27
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 claims description 24
- 239000000203 mixture Substances 0.000 claims description 19
- 229910000147 aluminium phosphate Inorganic materials 0.000 claims description 12
- LFVGISIMTYGQHF-UHFFFAOYSA-N ammonium dihydrogen phosphate Chemical compound [NH4+].OP(O)([O-])=O LFVGISIMTYGQHF-UHFFFAOYSA-N 0.000 claims description 10
- 229910000387 ammonium dihydrogen phosphate Inorganic materials 0.000 claims description 10
- 235000019837 monoammonium phosphate Nutrition 0.000 claims description 10
- 239000007864 aqueous solution Substances 0.000 claims description 9
- MNNHAPBLZZVQHP-UHFFFAOYSA-N diammonium hydrogen phosphate Chemical compound [NH4+].[NH4+].OP([O-])([O-])=O MNNHAPBLZZVQHP-UHFFFAOYSA-N 0.000 claims description 7
- XGZVUEUWXADBQD-UHFFFAOYSA-L lithium carbonate Chemical group [Li+].[Li+].[O-]C([O-])=O XGZVUEUWXADBQD-UHFFFAOYSA-L 0.000 claims description 5
- 229910052808 lithium carbonate Inorganic materials 0.000 claims description 5
- 229910000388 diammonium phosphate Inorganic materials 0.000 claims description 4
- 235000019838 diammonium phosphate Nutrition 0.000 claims description 4
- XIXADJRWDQXREU-UHFFFAOYSA-M lithium acetate Chemical group [Li+].CC([O-])=O XIXADJRWDQXREU-UHFFFAOYSA-M 0.000 claims description 4
- QGZKDVFQNNGYKY-UHFFFAOYSA-O Ammonium Chemical compound [NH4+] QGZKDVFQNNGYKY-UHFFFAOYSA-O 0.000 claims description 3
- 239000011149 active material Substances 0.000 claims description 3
- 229910052739 hydrogen Inorganic materials 0.000 claims description 3
- NBIIXXVUZAFLBC-UHFFFAOYSA-L Phosphate ion(2-) Chemical group OP([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-L 0.000 claims description 2
- OWZIYWAUNZMLRT-UHFFFAOYSA-L iron(2+);oxalate Chemical group [Fe+2].[O-]C(=O)C([O-])=O OWZIYWAUNZMLRT-UHFFFAOYSA-L 0.000 claims description 2
- LNOZJRCUHSPCDZ-UHFFFAOYSA-L iron(ii) acetate Chemical compound [Fe+2].CC([O-])=O.CC([O-])=O LNOZJRCUHSPCDZ-UHFFFAOYSA-L 0.000 claims description 2
- 150000008442 polyphenolic compounds Chemical class 0.000 claims 2
- 235000013824 polyphenols Nutrition 0.000 claims 2
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims 1
- 239000001257 hydrogen Substances 0.000 claims 1
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 46
- 239000013078 crystal Substances 0.000 description 45
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 description 44
- 239000003638 chemical reducing agent Substances 0.000 description 44
- 238000010438 heat treatment Methods 0.000 description 43
- 229910052757 nitrogen Inorganic materials 0.000 description 22
- 238000000034 method Methods 0.000 description 18
- GHMLBKRAJCXXBS-UHFFFAOYSA-N resorcinol Chemical compound OC1=CC=CC(O)=C1 GHMLBKRAJCXXBS-UHFFFAOYSA-N 0.000 description 16
- 230000000052 comparative effect Effects 0.000 description 15
- 239000000243 solution Substances 0.000 description 14
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 14
- 238000002156 mixing Methods 0.000 description 13
- 239000002994 raw material Substances 0.000 description 12
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 10
- 229910010707 LiFePO 4 Inorganic materials 0.000 description 10
- CWYNVVGOOAEACU-UHFFFAOYSA-N Fe2+ Chemical class [Fe+2] CWYNVVGOOAEACU-UHFFFAOYSA-N 0.000 description 9
- 239000012298 atmosphere Substances 0.000 description 9
- 229910052799 carbon Inorganic materials 0.000 description 9
- NPLZZSLZTJVZSX-UHFFFAOYSA-L iron(2+);oxalate;dihydrate Chemical compound O.O.[Fe+2].[O-]C(=O)C([O-])=O NPLZZSLZTJVZSX-UHFFFAOYSA-L 0.000 description 9
- 239000004570 mortar (masonry) Substances 0.000 description 9
- 229910052698 phosphorus Inorganic materials 0.000 description 9
- 239000011574 phosphorus Substances 0.000 description 9
- WQGWDDDVZFFDIG-UHFFFAOYSA-N pyrogallol Chemical compound OC1=CC=CC(O)=C1O WQGWDDDVZFFDIG-UHFFFAOYSA-N 0.000 description 8
- 239000002904 solvent Substances 0.000 description 8
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 7
- 238000002441 X-ray diffraction Methods 0.000 description 7
- 239000011230 binding agent Substances 0.000 description 7
- 230000000694 effects Effects 0.000 description 6
- IAQLJCYTGRMXMA-UHFFFAOYSA-M lithium;acetate;dihydrate Chemical compound [Li+].O.O.CC([O-])=O IAQLJCYTGRMXMA-UHFFFAOYSA-M 0.000 description 6
- 150000002989 phenols Chemical class 0.000 description 6
- VTLYFUHAOXGGBS-UHFFFAOYSA-N Fe3+ Chemical class [Fe+3] VTLYFUHAOXGGBS-UHFFFAOYSA-N 0.000 description 5
- 238000002425 crystallisation Methods 0.000 description 5
- 230000008025 crystallization Effects 0.000 description 5
- 229910052751 metal Inorganic materials 0.000 description 5
- 239000002184 metal Substances 0.000 description 5
- 239000000126 substance Substances 0.000 description 5
- CIWBSHSKHKDKBQ-JLAZNSOCSA-N Ascorbic acid Chemical compound OC[C@H](O)[C@H]1OC(=O)C(O)=C1O CIWBSHSKHKDKBQ-JLAZNSOCSA-N 0.000 description 4
- QIGBRXMKCJKVMJ-UHFFFAOYSA-N Hydroquinone Chemical compound OC1=CC=C(O)C=C1 QIGBRXMKCJKVMJ-UHFFFAOYSA-N 0.000 description 4
- 238000009835 boiling Methods 0.000 description 4
- 238000010304 firing Methods 0.000 description 4
- 229940079877 pyrogallol Drugs 0.000 description 4
- WMFOQBRAJBCJND-UHFFFAOYSA-M Lithium hydroxide Chemical compound [Li+].[OH-] WMFOQBRAJBCJND-UHFFFAOYSA-M 0.000 description 3
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 description 3
- 239000002202 Polyethylene glycol Substances 0.000 description 3
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 3
- 230000015572 biosynthetic process Effects 0.000 description 3
- 239000002482 conductive additive Substances 0.000 description 3
- 239000007772 electrode material Substances 0.000 description 3
- 239000007789 gas Substances 0.000 description 3
- 229910000398 iron phosphate Inorganic materials 0.000 description 3
- WBJZTOZJJYAKHQ-UHFFFAOYSA-K iron(3+) phosphate Chemical compound [Fe+3].[O-]P([O-])([O-])=O WBJZTOZJJYAKHQ-UHFFFAOYSA-K 0.000 description 3
- 239000001301 oxygen Substances 0.000 description 3
- 229910052760 oxygen Inorganic materials 0.000 description 3
- 229920001223 polyethylene glycol Polymers 0.000 description 3
- 229920001343 polytetrafluoroethylene Polymers 0.000 description 3
- 239000004810 polytetrafluoroethylene Substances 0.000 description 3
- 230000008569 process Effects 0.000 description 3
- 230000001603 reducing effect Effects 0.000 description 3
- 230000009467 reduction Effects 0.000 description 3
- 238000005979 thermal decomposition reaction Methods 0.000 description 3
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- 229910013870 LiPF 6 Inorganic materials 0.000 description 2
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 2
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 description 2
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 2
- MCMNRKCIXSYSNV-UHFFFAOYSA-N Zirconium dioxide Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-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
- 229960005070 ascorbic acid Drugs 0.000 description 2
- 235000010323 ascorbic acid Nutrition 0.000 description 2
- 239000011668 ascorbic acid Substances 0.000 description 2
- 150000001875 compounds Chemical class 0.000 description 2
- WQKHTJFZNMYFQC-UHFFFAOYSA-L dichloroiron;hydrate Chemical compound O.Cl[Fe]Cl WQKHTJFZNMYFQC-UHFFFAOYSA-L 0.000 description 2
- 238000007580 dry-mixing Methods 0.000 description 2
- 239000011888 foil Substances 0.000 description 2
- WXEICPMZIKLINJ-UHFFFAOYSA-L iron(2+) diacetate tetrahydrate Chemical compound O.O.O.O.[Fe+2].CC([O-])=O.CC([O-])=O WXEICPMZIKLINJ-UHFFFAOYSA-L 0.000 description 2
- SURQXAFEQWPFPV-UHFFFAOYSA-L iron(2+) sulfate heptahydrate Chemical compound O.O.O.O.O.O.O.[Fe+2].[O-]S([O-])(=O)=O SURQXAFEQWPFPV-UHFFFAOYSA-L 0.000 description 2
- 150000002641 lithium Chemical class 0.000 description 2
- 229910003002 lithium salt Inorganic materials 0.000 description 2
- 159000000002 lithium salts Chemical class 0.000 description 2
- 229910001463 metal phosphate Inorganic materials 0.000 description 2
- 239000012071 phase Substances 0.000 description 2
- 239000000843 powder Substances 0.000 description 2
- 230000002194 synthesizing effect Effects 0.000 description 2
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- 229920002943 EPDM rubber Polymers 0.000 description 1
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 1
- KMTRUDSVKNLOMY-UHFFFAOYSA-N Ethylene carbonate Chemical compound O=C1OCCO1 KMTRUDSVKNLOMY-UHFFFAOYSA-N 0.000 description 1
- 229910012851 LiCoO 2 Inorganic materials 0.000 description 1
- 229910013290 LiNiO 2 Inorganic materials 0.000 description 1
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 1
- 239000002033 PVDF binder Substances 0.000 description 1
- 239000004743 Polypropylene Substances 0.000 description 1
- 239000006230 acetylene black Substances 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 238000010669 acid-base reaction Methods 0.000 description 1
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- 239000012300 argon atmosphere Substances 0.000 description 1
- 125000003118 aryl group Chemical group 0.000 description 1
- 239000000919 ceramic Substances 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 238000000576 coating method Methods 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
- 229910052802 copper Inorganic materials 0.000 description 1
- 239000010949 copper Substances 0.000 description 1
- 230000007547 defect Effects 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
- YNQRWVCLAIUHHI-UHFFFAOYSA-L dilithium;oxalate Chemical compound [Li+].[Li+].[O-]C(=O)C([O-])=O YNQRWVCLAIUHHI-UHFFFAOYSA-L 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 238000007606 doctor blade method Methods 0.000 description 1
- 239000008151 electrolyte solution Substances 0.000 description 1
- JBTWLSYIZRCDFO-UHFFFAOYSA-N ethyl methyl carbonate Chemical compound CCOC(=O)OC JBTWLSYIZRCDFO-UHFFFAOYSA-N 0.000 description 1
- 230000001747 exhibiting effect Effects 0.000 description 1
- 229920001973 fluoroelastomer Polymers 0.000 description 1
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 1
- 229910052737 gold Inorganic materials 0.000 description 1
- 239000010931 gold Substances 0.000 description 1
- 238000000227 grinding Methods 0.000 description 1
- CUPFNGOKRMWUOO-UHFFFAOYSA-N hydron;difluoride Chemical compound F.F CUPFNGOKRMWUOO-UHFFFAOYSA-N 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 239000011261 inert gas Substances 0.000 description 1
- 150000002505 iron Chemical class 0.000 description 1
- BDSLJORKWHZTAU-UHFFFAOYSA-M iron(2+);acetate;tetrahydrate Chemical compound O.O.O.O.[Fe+2].CC([O-])=O BDSLJORKWHZTAU-UHFFFAOYSA-M 0.000 description 1
- LEAMSPPOALICQN-UHFFFAOYSA-H iron(2+);diphosphate;octahydrate Chemical compound O.O.O.O.O.O.O.O.[Fe+2].[Fe+2].[Fe+2].[O-]P([O-])([O-])=O.[O-]P([O-])([O-])=O LEAMSPPOALICQN-UHFFFAOYSA-H 0.000 description 1
- PVFSDGKDKFSOTB-UHFFFAOYSA-K iron(3+);triacetate Chemical compound [Fe+3].CC([O-])=O.CC([O-])=O.CC([O-])=O PVFSDGKDKFSOTB-UHFFFAOYSA-K 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 150000002642 lithium compounds Chemical class 0.000 description 1
- 229910001416 lithium ion Inorganic materials 0.000 description 1
- 229910001386 lithium phosphate Inorganic materials 0.000 description 1
- 229910052748 manganese Inorganic materials 0.000 description 1
- 239000011572 manganese Substances 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 239000002905 metal composite material Substances 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 238000000465 moulding Methods 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 239000011255 nonaqueous electrolyte Substances 0.000 description 1
- 150000004689 octahydrates Chemical class 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 230000001590 oxidative effect Effects 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 229920001155 polypropylene Polymers 0.000 description 1
- 229920002981 polyvinylidene fluoride Polymers 0.000 description 1
- 239000000376 reactant Substances 0.000 description 1
- 230000009257 reactivity Effects 0.000 description 1
- 239000004576 sand Substances 0.000 description 1
- 229920006395 saturated elastomer Polymers 0.000 description 1
- 238000007650 screen-printing Methods 0.000 description 1
- 239000007790 solid phase Substances 0.000 description 1
- 238000003746 solid phase reaction Methods 0.000 description 1
- 230000006641 stabilisation Effects 0.000 description 1
- 238000011105 stabilization Methods 0.000 description 1
- 239000000758 substrate Substances 0.000 description 1
- 229920001897 terpolymer Polymers 0.000 description 1
- 150000004685 tetrahydrates Chemical class 0.000 description 1
- 229910052723 transition metal Inorganic materials 0.000 description 1
- 150000003624 transition metals Chemical class 0.000 description 1
- TWQULNDIKKJZPH-UHFFFAOYSA-K trilithium;phosphate Chemical compound [Li+].[Li+].[Li+].[O-]P([O-])([O-])=O TWQULNDIKKJZPH-UHFFFAOYSA-K 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
Description
本発明は、リチウム電池用正極活物質の製造方法とリチウム電池用正極活物質及びリチウム電池用電極並びにリチウム電池に関し、更に詳しくは、ＬｉＦｅＰＯ４の様なオリビン型リチウム鉄リン酸塩の正極活物質を合成する際に、３価の鉄の生成による放電容量の低下を防止することにより、優れた放電容量を有するリチウム電池用正極活物質の製造方法、このリチウム電池用正極活物質の製造方法により得られたリチウム電池用正極活物質、このリチウム電池用正極活物質を含むリチウム電池用電極、及びこのリチウム電池用電極を正電極として備えたリチウム電池に関するものである。 The present invention relates to a method for producing a positive electrode active material for a lithium battery, a positive electrode active material for a lithium battery, an electrode for a lithium battery, and a lithium battery, and more specifically, a positive electrode active material of an olivine type lithium iron phosphate such as LiFePO 4 . In the method for producing a positive electrode active material for a lithium battery having an excellent discharge capacity by preventing a decrease in the discharge capacity due to the production of trivalent iron, the method for producing the positive electrode active material for a lithium battery The present invention relates to an obtained positive electrode active material for a lithium battery, an electrode for a lithium battery containing the positive electrode active material for a lithium battery, and a lithium battery including the electrode for a lithium battery as a positive electrode.
近年、携帯用電子機器やハイブリット自動車等に用いるための電池として二次電池の開発が進められている。
代表的な二次電池としては鉛蓄電池、アルカリ蓄電池、リチウム電池等が知られているが、特に、リチウム電池は、小型化、軽量化、高容量化が可能であり、しかも、高出力、高エネルギー密度を有していることから、大いに期待されている。
このリチウム電池は、リチウムイオンを可逆的に脱挿入可能な活物質を有する正極と、負極と、非水系の電解質から構成されている。
この正極自体は、正極活物質、導電助剤およびバインダーを含む電極材料により構成され、この電極材料を集電体と呼ばれる金属箔の表面に塗布することにより正極とされている。
In recent years, secondary batteries have been developed as batteries for use in portable electronic devices, hybrid automobiles, and the like.
As typical secondary batteries, lead storage batteries, alkaline storage batteries, lithium batteries, and the like are known. In particular, lithium batteries can be reduced in size, weight, and capacity, and have high output and high capacity. It is highly expected because of its energy density.
This lithium battery is composed of a positive electrode having an active material capable of reversibly inserting and removing lithium ions, a negative electrode, and a non-aqueous electrolyte.
The positive electrode itself is composed of an electrode material containing a positive electrode active material, a conductive additive, and a binder, and is formed into a positive electrode by applying this electrode material to the surface of a metal foil called a current collector.
正極活物質としては、コバルト酸リチウム（ＬｉＣｏＯ２）、ニッケル酸リチウム（ＬｉＮｉＯ２）、マンガン酸リチウム（Ｌｉ２ＭｎＯ４）等のリチウムと遷移金属の複合酸化物がよく知られている。しかしながら、これらの物質は、コバルトやニッケルの様に資源量の少ない貴重で高価な金属を含むものであったり、使用中にマンガンが溶出するために寿命が短い等の欠点がある。
そこで、最近では、このような欠点を補う目的で、資源的に豊富かつ安価な金属である鉄を用いたＬｉＦｅＰＯ４のようなオリビン型金属リン酸塩の正極活物質が提案されている。
As the positive electrode active material, lithium and transition metal composite oxides such as lithium cobaltate (LiCoO 2 ), lithium nickelate (LiNiO 2 ), and lithium manganate (Li 2 MnO 4 ) are well known. However, these substances have disadvantages such as those containing precious and expensive metals with a small amount of resources such as cobalt and nickel, and short life because manganese elutes during use.
Therefore, recently, a positive electrode active material of an olivine type metal phosphate such as LiFePO 4 using iron, which is a resource-rich and inexpensive metal, has been proposed for the purpose of compensating for such drawbacks.
ＬｉＦｅＰＯ４のようなＦｅ含有リチウム化合物は、金属Ｌｉに対して３．３Ｖ程度の電位を有することから、充放電可能な正極材料として注目されている（例えば、非特許文献１参照）。
通常、このようなオリビン型金属リン酸塩の正極活物質は、原料のリチウム塩、２価の鉄塩およびリン化合物を混合したものを焼成し、これらの間に固相反応を生じさせることにより作製される（特許文献１参照）。
Usually, such a positive electrode active material of olivine type metal phosphate is obtained by firing a mixture of a raw material lithium salt, a divalent iron salt and a phosphorus compound, and causing a solid phase reaction therebetween. It is manufactured (see Patent Document 1).
しかしながら、従来のリチウム塩、２価の鉄（以下、鉄（II）と称する）塩およびリン化合物を混合し焼成するという方法で作製されたオリビン型リチウム鉄リン酸塩をリチウム電池の正極活物質に適用した場合、満足できる充放電容量が得られていない。
その原因としては、原料に含まれる鉄（II）が焼成時に原料に付着している空気や水分により一部が酸化され、正極活物質として機能しない３価の鉄（以下、鉄（III）と称する）に変化してしまうために、焼成後に得られた固相反応物がオリビン型鉄リン酸塩以外の鉄（III）化合物をも含むものとなり、オリビン型リチウム鉄リン酸塩の純度が低下した分、充放電容量が低下するからである。
However, an olivine type lithium iron phosphate prepared by mixing and baking a conventional lithium salt, divalent iron (hereinafter referred to as iron (II)) salt and a phosphorus compound is used as a positive electrode active material for a lithium battery. When applied to, satisfactory charge / discharge capacity has not been obtained.
The cause is that iron (II) contained in the raw material is partially oxidized by air or moisture adhering to the raw material during firing, and trivalent iron that does not function as a positive electrode active material (hereinafter referred to as iron (III)). The solid-phase reactant obtained after firing also contains iron (III) compounds other than olivine type iron phosphate, and the purity of olivine type lithium iron phosphate is reduced. This is because the charge / discharge capacity is reduced accordingly.
また、鉄（II）の原料として比較的安価に入手可能でかつ工業的に利用可能なものは、しゅう酸鉄（II）２水和物（ＦｅＣ２Ｏ４・２Ｈ２Ｏ、リン酸鉄（II）８水和物（Ｆｅ３（ＰＯ４）２・８Ｈ２Ｏ）、塩化鉄（II）水和物（ＦｅＣｌ２・ｎＨ２Ｏ）、硫酸鉄（II）７水和物（ＦｅＳＯ４・７Ｈ２Ｏ）、酢酸鉄（II）４水和物（Ｆｅ（ＣＨ３ＣＯＯ）２・４Ｈ２Ｏ）等のように結晶水を含む状態で安定なものであるから、酸化を防ぐために原料の表面に付着している空気や水分を何らかの方法で除去したとしても、実質的に完全に水分を除去するのは不可能である。 In addition, iron (II) oxalate dihydrate (FeC 2 O 4 .2H 2 O, iron phosphate ( II) octahydrate (Fe 3 (PO 4 ) 2 · 8H 2 O), iron (II) chloride hydrate (FeCl 2 · nH 2 O), iron (II) sulfate heptahydrate (FeSO 4 · 7H 2 O), iron (II) acetate tetrahydrate (Fe (CH 3 COO) 2 · 4H 2 O), etc., which are stable in a state containing crystal water, Even if air or moisture adhering to the surface is removed by some method, it is impossible to remove moisture substantially completely.
また、これらの塩は、いずれも結晶水を含む水和物の形態で安定であるから、もし結晶水を含まない状態で使用や保管をする場合、特殊な容器あるいは環境が必要となる。さらに、安定な塩として存在する期間も比較的短いため、工業的に利用するのは難しい。
このように、鉄（II）の原料としては結晶水を含む化合物を使用する必要があるが、この化合物に含まれる鉄（II）は焼成時に鉄（III）に変化するのを防止することが難しく、したがって、オリビン型リチウム鉄リン酸塩中の鉄（II）の比率をこれ以上上げることが難しく、リチウム電池の充放電容量をさらに向上させることは難しい。
In addition, since these salts are all stable in the form of hydrate containing water of crystallization, special containers or environments are required if they are used and stored in a state not containing water of crystallization. Furthermore, since the period of existence as a stable salt is relatively short, it is difficult to use industrially.
Thus, it is necessary to use a compound containing water of crystallization as the raw material of iron (II), but iron (II) contained in this compound can be prevented from changing to iron (III) during firing. Therefore, it is difficult to further increase the ratio of iron (II) in the olivine type lithium iron phosphate, and it is difficult to further improve the charge / discharge capacity of the lithium battery.
本発明は、上記の課題を解決するためになされたものであって、ＬｉＦｅＰＯ４の様なオリビン型リチウム鉄リン酸塩の正極活物質を合成する際に、鉄（III）化合物の生成を防止することができ、したがって、鉄（III）化合物を含まないオリビン型リチウム鉄リン酸塩を容易に作製することができ、充放電容量、特に放電容量に優れたリチウム電池用正極活物質を作製することができるリチウム電池用正極活物質の製造方法とリチウム電池用正極活物質及びリチウム電池用電極並びにリチウム電池を提供することを目的とする。 The present invention has been made to solve the above problems, and prevents the formation of an iron (III) compound when synthesizing a positive electrode active material of olivine type lithium iron phosphate such as LiFePO 4 . Therefore, an olivine-type lithium iron phosphate not containing an iron (III) compound can be easily produced, and a positive electrode active material for a lithium battery excellent in charge / discharge capacity, particularly discharge capacity, is produced. It is an object to provide a method for producing a positive electrode active material for a lithium battery, a positive electrode active material for a lithium battery, an electrode for a lithium battery, and a lithium battery.
本発明者は、鋭意検討を行った結果、ＬｉＦｅＰＯ４の様なオリビン型リチウム鉄リン酸塩の正極活物質を製造する際に、リチウムを含有する塩と、鉄を含有する塩と、リン酸を含有する塩とを含む混合物を３２０℃以上かつ４８０℃以下の温度にて加熱して前駆体を生成し、得られた前駆体に、多価フェノール類を添加し、さらに６００℃以上かつ８００℃以下の温度にて加熱すれば、鉄（III）化合物の生成を防止することができ、したがって、オリビン型リチウム鉄リン酸塩を容易に作製することができ、リチウム電池の充放電容量をさらに向上させることができることを見出し、本発明を完成するに至った。 As a result of intensive studies, the inventor has produced a lithium-containing salt, an iron-containing salt, and phosphoric acid when producing a positive electrode active material of olivine-type lithium iron phosphate such as LiFePO 4 . A mixture containing a salt containing a salt is heated at a temperature of 320 ° C. or higher and 480 ° C. or lower to produce a precursor , polyhydric phenols are added to the obtained precursor , and 600 ° C. or higher and 800 ° C. or higher. When heated at a temperature of ℃ or less, the formation of iron (III) compound can be prevented, and therefore olivine-type lithium iron phosphate can be easily produced, further increasing the charge / discharge capacity of the lithium battery. The present inventors have found that it can be improved and have completed the present invention.
すなわち、本発明のリチウム電池用正極活物質の製造方法は、リチウムを含有する塩と、鉄を含有する塩と、リン酸を含有する塩とを混合し、３２０℃以上かつ４８０℃以下の温度にて加熱して前駆体を生成し、得られた前駆体と多価フェノール類を非水系溶媒に分散または溶解させた非水系溶液とを混合し、この非水系溶媒を除去した後、さらに、６００℃以上かつ８００℃以下の温度にて加熱し、オリビン型リチウム鉄リン酸塩を生成することを特徴とする。 That is, in the method for producing a positive electrode active material for a lithium battery according to the present invention, a salt containing lithium, a salt containing iron, and a salt containing phosphoric acid are mixed, and the temperature is 320 ° C. or higher and 480 ° C. or lower. A precursor is produced by heating at, and after mixing the obtained precursor and a non-aqueous solution in which polyhydric phenols are dispersed or dissolved in a non-aqueous solvent and removing this non-aqueous solvent, Heating at a temperature of 600 ° C. or more and 800 ° C. or less to produce olivine type lithium iron phosphate.
前記リチウムを含有する塩はリチウム有機酸塩またはリチウム無機酸塩が好ましく、前記鉄を含有する塩は鉄（II）有機酸塩が好ましく、前記リン酸を含有する塩はリン酸水素アンモニウムが好ましい。
前記リチウム有機酸塩は酢酸リチウムが好ましく、前記リチウム無機酸塩は炭酸リチウムが好ましく、前記鉄（II）有機酸塩はシュウ酸鉄（II）または酢酸鉄（II）が好ましく、前記リン酸水素アンモニウムはリン酸２水素アンモニウムまたはリン酸水素２アンモニウムが好ましい。
前記多価フェノール類の添加量は、前記前駆体の質量に対して５質量％以上かつ３０質量％以下であることが好ましい。
The lithium-containing salt is preferably a lithium organic acid salt or a lithium inorganic acid salt, the iron-containing salt is preferably an iron (II) organic acid salt, and the phosphoric acid-containing salt is preferably ammonium hydrogen phosphate .
The lithium organic acid salt is preferably lithium acetate, the lithium inorganic acid salt is preferably lithium carbonate, the iron (II) organic acid salt is preferably iron (II) oxalate or iron (II) acetate, and the hydrogen phosphate The ammonium is preferably ammonium dihydrogen phosphate or diammonium hydrogen phosphate.
The addition amount of the polyhydric phenols is preferably 5% by mass or more and 30% by mass or less with respect to the mass of the precursor.
本発明のリチウム電池用正極活物質は、本発明のリチウム電池用正極活物質の製造方法により得られたことを特徴とする。 The positive electrode active material for a lithium battery of the present invention is obtained by the method for producing a positive electrode active material for a lithium battery of the present invention.
本発明のリチウム電池用電極は、本発明のリチウム電池用正極活物質を含むことを特徴とする。 The electrode for lithium batteries of the present invention is characterized by including the positive electrode active material for lithium batteries of the present invention.
本発明のリチウム電池は、本発明のリチウム電池用電極を正電極として備えてなることを特徴とする。 The lithium battery of the present invention comprises the lithium battery electrode of the present invention as a positive electrode.
本発明のリチウム電池用正極活物質の製造方法によれば、リチウムを含有する塩と、鉄を含有する塩と、リン酸を含有する塩とを混合し、３２０℃以上かつ４８０℃以下の温度にて加熱して前駆体を生成し、得られた前駆体と多価フェノール類を非水系溶媒に分散または溶解させた非水系溶液とを混合し、この非水系溶媒を除去した後、さらに、６００℃以上かつ８００℃以下の温度にて加熱するので、鉄（III）化合物の生成を防止することができ、オリビン型リチウム鉄リン酸塩を容易に作製することができる。したがって、充放電容量、特に放電容量に優れたリチウム電池用正極活物質を作製することができる。
According to the method for producing a positive electrode active material for a lithium battery of the present invention, a salt containing lithium, a salt containing iron, and a salt containing phosphoric acid are mixed, and the temperature is 320 ° C. or higher and 480 ° C. or lower. A precursor is produced by heating at, and after mixing the obtained precursor and a non-aqueous solution in which polyhydric phenols are dispersed or dissolved in a non-aqueous solvent and removing this non-aqueous solvent, Since it heats at the temperature of 600 degreeC or more and 800 degrees C or less, the production | generation of an iron (III) compound can be prevented and an olivine type lithium iron phosphate can be produced easily. Therefore, a positive electrode active material for a lithium battery excellent in charge / discharge capacity, particularly discharge capacity can be produced.
本発明のリチウム電池用正極活物質によれば、本発明のリチウム電池用正極活物質の製造方法により得られたので、鉄（III）化合物を含まないものとなり、充放電容量、特に放電容量を大幅に向上させることができる。 According to the positive electrode active material for a lithium battery of the present invention, since it was obtained by the method for producing a positive electrode active material for a lithium battery of the present invention, it does not contain an iron (III) compound, and has a charge / discharge capacity, particularly a discharge capacity. It can be greatly improved.
本発明のリチウム電池用電極は、本発明のリチウム電池用正極活物質を含むので、充放電容量、特に放電容量を大幅に向上させることができ、リチウム電池用電極の高品質化、小型化を図ることができる。 Since the electrode for a lithium battery of the present invention contains the positive electrode active material for a lithium battery of the present invention, the charge / discharge capacity, particularly the discharge capacity, can be greatly improved, and the quality and size of the lithium battery electrode can be improved. Can be planned.
本発明のリチウム電池は、本発明のリチウム電池用電極を正電極として備えたので、充放電容量、特に放電容量を大幅に向上させることができ、電池としての出力を高めることができる。したがって、各種電気特性に優れたリチウム電池を提供することができる。 Since the lithium battery of the present invention includes the lithium battery electrode of the present invention as a positive electrode, the charge / discharge capacity, particularly the discharge capacity, can be greatly improved, and the output as the battery can be increased. Therefore, it is possible to provide a lithium battery excellent in various electric characteristics.
本発明のリチウム電池用正極活物質の製造方法とリチウム電池用正極活物質及びリチウム電池用電極並びにリチウム電池の最良の形態について説明する。
なお、この形態は、発明の趣旨をより良く理解させるために具体的に説明するものであり、特に指定のない限り、本発明を限定するものではない。
The manufacturing method of the positive electrode active material for lithium batteries of this invention, the positive electrode active material for lithium batteries, the electrode for lithium batteries, and the best form of a lithium battery are demonstrated.
This embodiment is specifically described for better understanding of the gist of the invention and does not limit the present invention unless otherwise specified.
本発明のリチウム電池用正極活物質の製造方法は、リチウムを含有する塩と、鉄を含有する塩と、リン酸を含有する塩とを混合し、３２０℃以上かつ４８０℃以下の温度にて加熱し（第１の加熱工程）、さらに、有機還元剤を添加し、６００℃以上かつ８００℃以下の温度にて加熱する（第２の加熱工程）方法である。 In the method for producing a positive electrode active material for a lithium battery according to the present invention, a salt containing lithium, a salt containing iron, and a salt containing phosphoric acid are mixed and at a temperature of 320 ° C. or higher and 480 ° C. or lower. It is a method of heating (first heating step), further adding an organic reducing agent, and heating at a temperature of 600 ° C. to 800 ° C. (second heating step).
第１の加熱工程では、リチウムを含有する塩と、鉄を含有する塩と、リン酸を含有する塩とを混合して得られた混合物を、３２０〜４８０℃で加熱する。すなわち、第１の加熱工程で上記の混合物を一旦加熱することにより、熱分解により表面に付着している水分や酸素を除去する。さらに、原料塩として、結晶水を含むものを用いる場合には、熱分解により結晶水を除去することができる。
この加熱工程により、結晶水を含まなくても安定に存在できるオリビン型の結晶構造を有する前駆体（生成物）を合成することができる。
In the first heating step, a mixture obtained by mixing a salt containing lithium, a salt containing iron, and a salt containing phosphoric acid is heated at 320 to 480 ° C. That is, once the above mixture is heated in the first heating step, moisture and oxygen attached to the surface are removed by thermal decomposition. Further, when a raw material salt containing crystallization water is used, the crystallization water can be removed by thermal decomposition.
By this heating step, it is possible to synthesize a precursor (product) having an olivine-type crystal structure that can exist stably without containing crystal water.
この前駆体に有機還元剤を添加した後、６００〜８００℃の範囲で加熱する第２の加熱工程を施す。
このように、上記の前駆体に有機還元剤を添加し、第２の加熱工程にて更に加熱することにより、前駆体合成時（第１の加熱工程時）および再加熱時（第２の加熱工程時）に生成する鉄（III）を有機還元剤により鉄（II）に還元することができ、優れた放電容量を示すリチウム電池用正極活物質を得ることができる。
After adding an organic reducing agent to this precursor, the 2nd heating process heated in the range of 600-800 degreeC is given.
Thus, by adding an organic reducing agent to the precursor and further heating in the second heating step, the precursor is synthesized (during the first heating step) and reheated (second heating). Iron (III) produced during the process) can be reduced to iron (II) with an organic reducing agent, and a positive electrode active material for a lithium battery exhibiting excellent discharge capacity can be obtained.
次に、本発明のリチウム電池用正極活物質の製造方法について、より具体的に説明する。
「混合工程」
まず、本発明で得られるリチウム電池用正極活物質の原料となる各種の塩を、所定の配合比になるように秤量し、これらを混合する。混合方法としては、ボールミルや振動ミル等を用いた湿式混合、自動乳鉢等を用いた乾式混合のいずれでもかまわない。
ここで、原料となる各種の塩としては、リチウムを含有する塩、鉄を含有する塩、リン酸を含有する塩の３種類の塩が少なくとも必要である。
Next, the manufacturing method of the positive electrode active material for lithium batteries of this invention is demonstrated more concretely.
"Mixing process"
First, various salts used as raw materials for the positive electrode active material for a lithium battery obtained in the present invention are weighed so as to have a predetermined blending ratio and mixed. As a mixing method, either wet mixing using a ball mill or a vibration mill, or dry mixing using an automatic mortar or the like may be used.
Here, as various salts used as raw materials, at least three kinds of salts including a salt containing lithium, a salt containing iron, and a salt containing phosphoric acid are necessary.
リチウムを含有する塩としては、例えば、酢酸リチウム、蓚酸リチウム等のリチウム有機酸塩、炭酸リチウム、水酸化リチウム、リン酸リチウム等のリチウム無機酸塩が挙げられるが、吸水性が小さい等の取り扱いの容易さから酢酸リチウムあるいは炭酸リチウムが好ましい。 Examples of the salt containing lithium include lithium organic acid salts such as lithium acetate and lithium oxalate, and lithium inorganic acid salts such as lithium carbonate, lithium hydroxide, and lithium phosphate. Lithium acetate or lithium carbonate is preferred because of its ease.
鉄を含有する塩としては、例えば、蓚酸鉄（II）２水和物、リン酸鉄（II）８水和物、塩化鉄（II）水和物、硫酸鉄（II）７水和物、酢酸鉄（II）４水和物等の鉄（II）有機酸塩が挙げられるが、比較的低温で有害ガスを出さずに熱分解することから、蓚酸鉄（II）２水和物あるいは酢酸鉄（II）４水和物が好ましい。 Examples of the salt containing iron include iron (II) oxalate dihydrate, iron (II) phosphate octahydrate, iron (II) chloride hydrate, iron (II) sulfate heptahydrate, Iron (II) organic acid salts such as iron acetate (II) tetrahydrate can be mentioned, but since it decomposes at a relatively low temperature without producing harmful gases, iron (II) oxalate dihydrate or acetic acid Iron (II) tetrahydrate is preferred.
リン酸を含有する塩としては、例えば、リン酸２水素アンモニウム、リン酸水素２アンモニウム等のリン酸水素アンモニウム、あるいはリン酸鉄等が挙げられるが、比較的純度が高く組成制御が行い易いことから、リン酸２水素アンモニウムあるいはリン酸水素２アンモニウムが好ましい。 Examples of the salt containing phosphoric acid include ammonium hydrogen phosphate such as ammonium dihydrogen phosphate and di-ammonium hydrogen phosphate, and iron phosphate. However, the purity is relatively high and the composition can be easily controlled. Therefore, ammonium dihydrogen phosphate or diammonium hydrogen phosphate is preferable.
「第１の加熱工程」
次に、上記の混合物を３２０℃以上かつ４８０℃以下の温度にて加熱する。これにより、オリビン型の結晶構造を有する前駆体が形成される。
ここで、オリビン型の結晶構造を有する前駆体とは、Ｘ線回折チャートにおいてオリビン構造の最大強度の回折線である（３１１）面の強度が最も強く検知される状態、すなわちオリビン構造に該当しない原料塩の全ての他のピーク強度よりも生成物であるオリビン構造の最大強度の回折線における強度が強くなる状態をいう。
"First heating process"
Next, the above mixture is heated at a temperature of 320 ° C. or higher and 480 ° C. or lower. Thereby, a precursor having an olivine type crystal structure is formed.
Here, the precursor having an olivine type crystal structure is a state in which the intensity of the (311) plane, which is the diffraction line with the maximum intensity of the olivine structure, is detected in the X-ray diffraction chart, that is, does not correspond to the olivine structure. This refers to a state in which the intensity at the diffraction line having the maximum intensity of the olivine structure as a product is stronger than all other peak intensities of the raw material salt.
ここで、加熱温度を３２０℃以上かつ４８０℃以下の範囲に限定した理由は、加熱温度が３２０℃未満では、原料中における元素の移動が不十分で、オリビン型の結晶構造を有する前駆体の生成が不十分なものとなるからであり、また、加熱温度が４８０℃を超えると、オリビン型の結晶構造を有する前駆体の成長が大きくなり過ぎ、表面に付着する有機還元剤の効果が粒子の内部まで届かなくなるからである。 Here, the reason why the heating temperature is limited to the range of 320 ° C. or more and 480 ° C. or less is that when the heating temperature is less than 320 ° C., the movement of the element in the raw material is insufficient and the precursor having an olivine type crystal structure is used. If the heating temperature exceeds 480 ° C., the growth of the precursor having an olivine type crystal structure becomes too large, and the effect of the organic reducing agent adhering to the surface becomes particles. It is because it will not reach the inside.
加熱時間は、３時間以上かつ１０時間以下が好ましい。その理由は、加熱時間が３時間未満では、原料中の元素の移動が不十分で、オリビン型の結晶構造を有する前駆体の生成が不十分なものとなり易く、また、１０時間を超えると、オリビン型の結晶構造を有する前駆体が成長し過ぎてしまい、良好な前駆体が得られなくなるからである。 The heating time is preferably 3 hours or more and 10 hours or less. The reason is that if the heating time is less than 3 hours, the movement of elements in the raw material is insufficient, and the production of a precursor having an olivine type crystal structure tends to be insufficient, and if it exceeds 10 hours, This is because a precursor having an olivine type crystal structure grows too much and a good precursor cannot be obtained.
また、加熱時の雰囲気は、窒素（Ｎ２）ガス等の不活性雰囲気、あるいは５ｖ／ｖ％Ｈ２−Ｎ２等の還元性雰囲気が好ましい。
その理由は、得られた前駆体が２価の鉄を含むものであるから、酸素または大気雰囲気とすると、２価の鉄が酸化して３価の鉄を含む前駆体となってしまい、その後、この前駆体を焼成してもＬｉＦｅＰＯ４の様なオリビン型リチウム鉄リン酸塩が得られないからである。
The atmosphere during heating is preferably an inert atmosphere such as nitrogen (N 2 ) gas or a reducing atmosphere such as 5 v / v% H 2 —N 2 .
The reason is that since the obtained precursor contains divalent iron, when it is made into oxygen or air atmosphere, the divalent iron is oxidized to become a precursor containing trivalent iron. This is because an olivine-type lithium iron phosphate such as LiFePO 4 cannot be obtained even if the precursor is fired.
「有機還元剤添加工程」
この様にして得られたオリビン型の結晶構造を有するリチウム鉄リン酸塩の前駆体に、さらに有機還元剤を添加し、この前駆体の表面に有機還元剤を付着させる。
有機還元剤を添加する方法としては、ボールミルや振動ミル等を用いた湿式混合法、自動乳鉢等を用いた乾式混合法のどちらでも良いが、オリビン型の結晶構造を有する前駆体と有機還元剤が均一に混合されるという点では、湿式混合法の方が優れているので好ましい。
"Organic reducing agent addition process"
An organic reducing agent is further added to the thus obtained precursor of lithium iron phosphate having an olivine type crystal structure, and the organic reducing agent is attached to the surface of the precursor.
As a method for adding the organic reducing agent, either a wet mixing method using a ball mill or a vibration mill or a dry mixing method using an automatic mortar may be used, but a precursor having an olivine type crystal structure and an organic reducing agent In terms of being uniformly mixed, the wet mixing method is preferable because it is superior.
湿式混合法としては、有機還元剤を非水系溶媒中に分散または溶解させた非水系溶液中に、前駆体を混合、分散した後、非水系溶媒を除去する方法が好ましい。この混合、分散の際に、オリビン型の結晶構造を有する前駆体の表面に有機還元剤を付着させることが好ましい。
ここで、非水系溶媒が好ましい理由は、第１の加熱工程により原料塩中の結晶水や付着水を除去して水分のない前駆体を生成したため、この前駆体に水分を導入しない方がよいからである。
As the wet mixing method, a method in which the non-aqueous solvent is removed after the precursor is mixed and dispersed in a non-aqueous solution in which an organic reducing agent is dispersed or dissolved in the non-aqueous solvent is preferable. At the time of mixing and dispersing, it is preferable to attach an organic reducing agent to the surface of the precursor having an olivine type crystal structure.
Here, the reason why the non-aqueous solvent is preferable is that it is preferable not to introduce moisture into the precursor because the precursor without water is generated by removing crystal water and adhering water in the raw material salt in the first heating step. Because.
非水系溶媒としては、有機還元剤が溶解するものであり、かつ、加熱による除去が可能な低沸点溶媒、例えば、アセトン、無水メタノール、無水エタノール等が好ましい。非水系溶媒の量としては、オリビン型の結晶構造を有する前駆体の重量に対して３倍〜５倍の重量が好ましい。その理由は、３倍未満では、溶媒が少な過ぎるために有機還元剤が完全に溶解しきれず、あるいは十分に分散しきれないからであり、５倍を超えると、後の工程における溶媒の除去に時間と手間がかかるからである。 The non-aqueous solvent is preferably a low-boiling solvent that dissolves the organic reducing agent and can be removed by heating, such as acetone, anhydrous methanol, and anhydrous ethanol. The amount of the non-aqueous solvent is preferably 3 to 5 times the weight of the precursor having an olivine type crystal structure. The reason is that if the ratio is less than 3 times, the organic reducing agent cannot be completely dissolved or sufficiently dispersed because the solvent is too small. If the ratio exceeds 5 times, removal of the solvent in a later step is not possible. It takes time and effort.
有機還元剤としては、非水系溶媒に溶解するものが好ましい。また、芳香族系の還元剤が好ましい。特に、多価フェノール類は、非水系溶媒に溶解し易く、有機物の中でも特に還元性が強く、さらに、加熱分解すると炭素しか残留しないことから好ましい。多価フェノール類としては、例えば、レゾルシノール、キノール、ピロガロール等が好ましい。
ここで、有機還元剤を用いる理由は、無機還元剤を用いた場合、無機還元剤は大部分がイオン性であるから、非水系溶媒に溶解しないあるいは溶解し難いものが多く、また、無機還元剤はリチウムとの反応性が高く、オリビンの結晶構造を有する前駆体を酸塩基反応で分解してしまう虞があるからである。
As the organic reducing agent, those which are soluble in a non-aqueous solvent are preferable. An aromatic reducing agent is preferred. In particular, polyhydric phenols are preferable because they are easily dissolved in a non-aqueous solvent, have a particularly strong reducibility among organic substances, and further, only carbon remains upon thermal decomposition. As polyhydric phenols, for example, resorcinol, quinol, pyrogallol and the like are preferable.
Here, the reason for using an organic reducing agent is that when an inorganic reducing agent is used, the inorganic reducing agent is mostly ionic, so it is not soluble or difficult to dissolve in a non-aqueous solvent. This is because the agent has high reactivity with lithium, and there is a possibility that the precursor having the olivine crystal structure may be decomposed by an acid-base reaction.
有機還元剤の添加量は、処理するオリビンの結晶構造を有する前駆体の質量に対して５質量％以上かつ３０質量％以下が好ましい。その理由は、５質量％未満では、前駆体の表面への付着量が少なく、還元剤としての効果にばらつきが生じるからであり、また、３０質量％を越えると、還元剤としての効果が飽和してしまい、それ以上添加しても効果に変わりがないからである。 The addition amount of the organic reducing agent is preferably 5 % by mass or more and 30 % by mass or less with respect to the mass of the precursor having the crystal structure of olivine to be treated. The reason is that if the amount is less than 5 % by mass , the amount of the precursor deposited on the surface is small and the effect as a reducing agent varies. If the amount exceeds 30 % by mass , the effect as a reducing agent is saturated. This is because the effect does not change even if it is added more.
この有機還元剤を含む非水系溶液と上記の前駆体とを混合し、上記の前駆体を有機還元剤を含む非水系溶液中に均一分散させる。
例えば、上記の前駆体を有機還元剤を溶解した非水系溶媒中に分散する方法としては、ボールミルやサンドミル等の媒体分散ミルで処理すればよい。特に前駆体の酸化を防ぐためには、上記の前駆体と有機還元剤を溶解した非水系溶媒とをアルミナやジルコニア等のセラミックスボールのような粉砕メディアとともにボールミル中に密封し、このボールミルを所定時間回転させることにより、上記の前駆体を有機還元剤を含む非水系溶液中に均一分散させることが好ましい。
The non-aqueous solution containing the organic reducing agent and the precursor are mixed, and the precursor is uniformly dispersed in the non-aqueous solution containing the organic reducing agent.
For example, as a method of dispersing the precursor in a non-aqueous solvent in which an organic reducing agent is dissolved, the precursor may be treated with a medium dispersion mill such as a ball mill or a sand mill. In particular, in order to prevent oxidation of the precursor, the above-mentioned precursor and a non-aqueous solvent in which an organic reducing agent is dissolved are sealed in a ball mill together with a grinding medium such as a ceramic ball such as alumina or zirconia, and this ball mill is kept for a predetermined time. It is preferable that the precursor is uniformly dispersed in a non-aqueous solution containing an organic reducing agent by rotating.
ここで「分散する」とは、上記の前駆体粉末の表面全てが有機還元剤を溶解した非水系溶媒によって濡れることであり、ミル等により処理した後は固液分離してしまってもかまわない。
上記の前駆体を有機還元剤を含む非水系溶液中に均一分散させた後は、非水系溶媒を除去し、その後、この有機還元剤を添加した前駆体に第２の加熱工程を施すのが好ましい。
Here, “dispersing” means that the entire surface of the precursor powder is wetted by a non-aqueous solvent in which an organic reducing agent is dissolved, and may be solid-liquid separated after being processed by a mill or the like. .
After the above precursor is uniformly dispersed in a non-aqueous solution containing an organic reducing agent, the non-aqueous solvent is removed, and then the precursor to which the organic reducing agent is added is subjected to a second heating step. preferable.
非水系溶媒の除去方法としては、窒素やアルゴン等の不活性ガス雰囲気中にて加熱することが好ましい。加熱温度は、使用した非水系溶媒及び有機還元剤の種類にもよるが、例えば、有機還元剤としてレゾルシノールを、非水系溶媒としてアセトン（沸点（ｂ．ｐ．）＝５６．５℃）をそれぞれ用い、レゾルシノールをアセトンに溶解した場合、６０℃にて２〜３時間程度加熱すればよい。
なお、ここでは、非水系溶媒の沸点以上の温度にて加熱処理することにより非水系溶媒を除去し、その後、第２の加熱工程を施すこととしたが、第２の加熱工程の加熱初期に、非水系溶媒の沸点以上の温度を一定時間保持する温度領域を設けることにより、非水系溶媒の除去と前駆体及び有機還元剤の加熱処理とを１つの温度プロファイル上で行うこととしてもよい。
As a method for removing the non-aqueous solvent, it is preferable to heat in an inert gas atmosphere such as nitrogen or argon. The heating temperature depends on the type of the non-aqueous solvent and the organic reducing agent used. For example, resorcinol is used as the organic reducing agent, and acetone (boiling point (bp) = 56.5 ° C.) is used as the non-aqueous solvent. When resorcinol is dissolved in acetone, it may be heated at 60 ° C. for about 2 to 3 hours.
Here, the non-aqueous solvent is removed by heat treatment at a temperature equal to or higher than the boiling point of the non-aqueous solvent, and then the second heating step is performed, but at the initial heating stage of the second heating step. In addition, by providing a temperature region that maintains a temperature equal to or higher than the boiling point of the non-aqueous solvent for a certain period of time, the removal of the non-aqueous solvent and the heat treatment of the precursor and the organic reducing agent may be performed on one temperature profile.
「第２の加熱工程」
次に、上記の非水系溶媒が除去された有機還元剤を添加した前駆体を、６００℃以上かつ８００℃以下の温度にて加熱する。
この加熱により、有機還元剤を添加した前駆体は、オリビン型リチウム鉄リン酸塩の正極活物質となる。
"Second heating process"
Next, the precursor to which the organic reducing agent from which the non-aqueous solvent has been removed is added is heated at a temperature of 600 ° C. or higher and 800 ° C. or lower.
By this heating, the precursor to which the organic reducing agent is added becomes a positive electrode active material of olivine type lithium iron phosphate.
ここで、加熱温度を６００℃以上かつ８００℃以下としたのは、６００℃未満では、各元素の移動速度が遅く、オリビン型結晶構造の単一相とするためには長時間を要し、工業的に非効率であるからであり、また、有機還元剤を熱分解して完全に飛散させてしまうためには、６００℃以上の温度で加熱処理する必要があるからである。また、加熱温度が８００℃を越えると、リチウム元素の蒸発が生じ、オリビン型の結晶構造が分解し始めるからである。 Here, the heating temperature is set to 600 ° C. or more and 800 ° C. or less. If the heating temperature is less than 600 ° C., the movement speed of each element is slow, and it takes a long time to obtain a single phase of the olivine type crystal structure, This is because it is industrially inefficient, and in order to thermally decompose and completely disperse the organic reducing agent, it is necessary to perform a heat treatment at a temperature of 600 ° C. or higher. Further, when the heating temperature exceeds 800 ° C., the lithium element evaporates and the olivine type crystal structure starts to decompose.
加熱時間は、７〜２４時間が好ましい。７時間未満では、各元素の移動が不十分のためオリビン型結晶構造単一相の生成が不十分になり易く、また、２４時間を超えると、リチウム元素の蒸発が生じ、オリビン型の結晶構造が分解し始めるからである。 The heating time is preferably 7 to 24 hours. If it is less than 7 hours, the movement of each element is insufficient, so that the generation of a single phase of the olivine-type crystal structure tends to be insufficient. Because it begins to decompose.
また、加熱時の雰囲気は、窒素（Ｎ２）ガス等の不活性雰囲気、あるいは５ｖ／ｖ％Ｈ２−Ｎ２等の還元性雰囲気が好ましい。
その理由は、得られた前駆体が鉄（II）を含むものであるから、酸素または大気雰囲気とすると、鉄（II）が酸化して鉄（III）を含む前駆体となってしまい、その後、この前駆体を焼成してもＬｉＦｅＰＯ４の様なオリビン型リチウム鉄リン酸塩が得られないからである。
The atmosphere during heating is preferably an inert atmosphere such as nitrogen (N 2 ) gas or a reducing atmosphere such as 5 v / v% H 2 —N 2 .
The reason is that since the obtained precursor contains iron (II), when it is oxygen or air atmosphere, iron (II) is oxidized to become a precursor containing iron (III). This is because an olivine-type lithium iron phosphate such as LiFePO 4 cannot be obtained even if the precursor is fired.
この有機還元剤は加熱後に一部が炭素として残留するが、リチウム電池の正極は導電助剤として炭素を含むために、有機還元剤に起因する炭素が残留していることは、正極活物質の表面に導電助剤としての炭素がよく密着した状態で存在しているという点で、むしろ好ましいことである。
さらに、そのような正極活物質の表面によく密着した炭素は、オリビン型のリチウム鉄リン酸塩の粒成長を抑制するため、微細で活性の高い粉末状の正極活物質を合成することができる。
This organic reducing agent partially remains as carbon after heating. However, since the positive electrode of the lithium battery contains carbon as a conductive additive, the carbon resulting from the organic reducing agent remains. It is rather preferable in that carbon as a conductive additive is in close contact with the surface.
Furthermore, since carbon closely adhered to the surface of such a positive electrode active material suppresses the grain growth of olivine-type lithium iron phosphate, a fine and highly active powdered positive electrode active material can be synthesized. .
本発明の製造方法によれば、リチウム電池用正極活物質に用いて好適なオリビン型の結晶構造を有するリチウム鉄リン酸塩を製造することができる。
また、このリチウム鉄リン酸塩は、基本的にはＬｉＦｅＰＯ４なる化学式で表わされるが、オリビン型の結晶構造を維持したままでＬｉやＦｅの一部を他元素で置換したもの、あるいはオリビン型の結晶構造にて一部の元素が欠落して格子欠陥が生じ、組成がＬｉＦｅＰＯ４からずれて非化学量論組成となっているものも含む。ＬｉやＦｅの一部を他元素で置換した組成のものを得るには、本発明の製造方法において、原料として、リチウムを含有する塩と、鉄を含有する塩と、リン酸を含有する塩に加えて、他元素を含む塩等を加えればよい。
According to the production method of the present invention, it is possible to produce a lithium iron phosphate having an olivine type crystal structure suitable for use as a positive electrode active material for a lithium battery.
Further, this lithium iron phosphate is basically represented by the chemical formula LiFePO 4 , but with a part of Li or Fe substituted with other elements while maintaining the olivine type crystal structure, or the olivine type In this crystal structure, some elements are missing and lattice defects are generated, and the composition deviates from LiFePO 4 and has a non-stoichiometric composition. In order to obtain a composition in which a part of Li or Fe is substituted with another element, in the production method of the present invention, as a raw material, a salt containing lithium, a salt containing iron, and a salt containing phosphoric acid In addition to the above, a salt containing other elements may be added.
このリチウム電池用正極活物質が高い容量を示す理由は、有機還元剤添加工程において、非水系溶媒を除去することにより有機還元剤を前駆体の表面に付着させるとともに、有機還元剤の一部が溶媒除去時の加熱によって鉄（III）を鉄（II）に還元するからである。また、表面に有機還元剤が付着したオリビンの結晶構造を有する前駆体を６００℃以上かつ８００℃以下の温度で加熱することにより、鉄（III）が有機還元剤により還元され、高容量を示すオリビン型リチウム鉄リン酸塩の正極活物質となるからである。 The reason why this positive electrode active material for lithium batteries shows a high capacity is that, in the organic reducing agent addition step, the organic reducing agent is attached to the surface of the precursor by removing the non-aqueous solvent, and part of the organic reducing agent is It is because iron (III) is reduced to iron (II) by heating at the time of solvent removal. In addition, by heating a precursor having an olivine crystal structure with an organic reducing agent attached to the surface at a temperature of 600 ° C. or higher and 800 ° C. or lower, iron (III) is reduced by the organic reducing agent and exhibits a high capacity. It is because it becomes a positive electrode active material of olivine type lithium iron phosphate.
以上により、本発明のリチウム電池用正極活物質の製造方法により得られたオリビン型リチウム鉄リン酸塩の正極活物質は、鉄（III）化合物を含まないものであるから、充放電容量、特に放電容量を大幅に向上させることができる。
また、このリチウム電池用正極活物質と、炭素と、適当なバインダーとを混合したものを用いて、基材上にオリビン型リチウム鉄リン酸塩と炭素とバインダーとからなる層を形成することにより、本発明のリチウム電池用正極（電極）を作製することができる。
As described above, since the positive electrode active material of the olivine-type lithium iron phosphate obtained by the method for producing a positive electrode active material for a lithium battery of the present invention does not contain an iron (III) compound, the charge / discharge capacity, particularly The discharge capacity can be greatly improved.
In addition, by using a mixture of the positive electrode active material for lithium battery, carbon, and a suitable binder, a layer composed of olivine type lithium iron phosphate, carbon and binder is formed on the base material. The positive electrode (electrode) for a lithium battery of the present invention can be produced.
バインダーとしては、通常用いられているものでよく、例えば、ポリテトラフルオロエチレン、ポリフツ化ビニリデンフルオライト、フッ素ゴム、エチレン−プロピレン−ジエンモノマー三元共重合体等が用いられる。
バインダーを混合する際に、必要により溶媒を添加してもよい。溶媒としては、例えば、Ｎ−メチル−２−ピロリドン、アセトン等が用いられる。
As the binder, those commonly used may be used. For example, polytetrafluoroethylene, polyvinylidene fluoride fluoride, fluororubber, ethylene-propylene-diene monomer terpolymer, and the like are used.
When mixing the binder, if necessary, a solvent may be added. As the solvent, for example, N-methyl-2-pyrrolidone, acetone or the like is used.
基材としては、例えば、アルミニウム、鉄、銅、金等の金属箔からなる集電体が用いられる。
形成方法としては、特に限定されず、通常用いられる方法を適用することができる。例えば、リチウム鉄リン酸塩と炭素とバインダーとを溶媒と共に混練しペースト化して集電体の表面に塗布し、正極とする。
塗布方法としては、ペーストをへらで直接塗りつける方法でもよいが、膜厚を制御するためには、ドクターブレード法、スクリーン印刷法等を用いるのが好ましい。
As the substrate, for example, a current collector made of a metal foil such as aluminum, iron, copper, or gold is used.
The forming method is not particularly limited, and a commonly used method can be applied. For example, lithium iron phosphate, carbon, and a binder are kneaded together with a solvent to form a paste, which is applied to the surface of the current collector to form a positive electrode.
As a coating method, a method of directly applying the paste with a spatula may be used, but in order to control the film thickness, it is preferable to use a doctor blade method, a screen printing method or the like.
このリチウム電池用正極は、本発明のリチウム電池用正極活物質を含むものであるから、放電容量を大幅に向上させることができ、リチウム電池用電極の高品質化、小型化を図ることができる。
さらに、本発明のリチウム電池は、本発明のリチウム電池用電極を正極としたものであるから、安価なオリビン型リチウム鉄リン酸塩を用いることで、正電極の放電容量を大幅に向上させることができ、電池としての出力を高めることができる。したがって、各種電気特性に優れたリチウム電池を提供することができる。
Since this positive electrode for a lithium battery contains the positive electrode active material for a lithium battery of the present invention, the discharge capacity can be greatly improved, and the quality and size of the lithium battery electrode can be improved.
Furthermore, since the lithium battery of the present invention uses the lithium battery electrode of the present invention as a positive electrode, the discharge capacity of the positive electrode can be greatly improved by using an inexpensive olivine type lithium iron phosphate. And the output as a battery can be increased. Therefore, it is possible to provide a lithium battery excellent in various electric characteristics.
以下、実施例１〜４及び比較例１〜３により本発明を具体的に説明するが、本発明はこれらの実施例によって限定されるものではない。
（実施例１）
酢酸リチウム２水和物、シュウ酸鉄（II）２水和物およびリン酸２水素アンモニウムを、リチウムと鉄とリンのモル比が１：１：１となる様に秤量し、乳鉢を用いて混合した。
その後、この混合物を窒素中、３５０℃にて５時間、熱処理した。
得られた生成物は、Ｘ線回折チャートで最も強度の強いピークはオリビン型結晶構造のものであり、本発明のオリビン型の結晶構造を有する前駆体であった。
EXAMPLES Hereinafter, although this invention is demonstrated concretely by Examples 1-4 and Comparative Examples 1-3, this invention is not limited by these Examples.
Example 1
Lithium acetate dihydrate, iron (II) oxalate dihydrate, and ammonium dihydrogen phosphate were weighed so that the molar ratio of lithium, iron, and phosphorus was 1: 1: 1, and a mortar was used. Mixed.
The mixture was then heat treated at 350 ° C. for 5 hours in nitrogen.
The obtained product was the precursor having the olivine type crystal structure of the present invention, with the strongest peak in the X-ray diffraction chart having the olivine type crystal structure.
このようにして得られたオリビン型の結晶構造を有する前駆体２ｇと、レゾルシノール０．３５ｇをアセトン７ｇに溶解した溶液とを、ボールミルにて４８時間混合し、次いで、この前駆体及びレゾルシノールを含むアセトン溶液を、窒素気流中、６０℃にて加熱してアセトンを除去した後、窒素中、６４０℃にて１０時間熱処理し、オリビン型のリチウム鉄リン酸塩正極活物質を得た。 2 g of the precursor having the olivine type crystal structure thus obtained and a solution obtained by dissolving 0.35 g of resorcinol in 7 g of acetone are mixed for 48 hours by a ball mill, and then the precursor and resorcinol are contained. The acetone solution was heated at 60 ° C. in a nitrogen stream to remove acetone, and then heat-treated at 640 ° C. for 10 hours in nitrogen to obtain an olivine type lithium iron phosphate positive electrode active material.
（実施例２）
炭酸リチウム、酢酸鉄（II）４水和物およびリン酸水素２アンモニウムを、リチウムと鉄とリンのモル比が１：１：１となる様に秤量し、乳鉢を用いて混合した。
その後、この混合物を窒素中、３８０℃にて５時間熱処理し、オリビン型の結晶構造を有する前駆体を得た。
(Example 2)
Lithium carbonate, iron (II) acetate tetrahydrate and diammonium hydrogen phosphate were weighed so that the molar ratio of lithium, iron and phosphorus was 1: 1: 1 and mixed using a mortar.
Thereafter, this mixture was heat-treated in nitrogen at 380 ° C. for 5 hours to obtain a precursor having an olivine type crystal structure.
このようにして得られたオリビン型の結晶構造を有する前駆体２ｇと、レゾルシノール０．５ｇをアセトン７ｇに溶解した溶液とを、ボールミルにて４８時間混合し、次いで、この前駆体及びレゾルシノールを含むアセトン溶液を、窒素気流中、６０℃にて加熱してアセトンを除去した後、窒素中、６７０℃にて１０時間熱処理し、オリビン型のリチウム鉄リン酸塩正極活物質を得た。 2 g of the precursor having the olivine type crystal structure thus obtained and a solution obtained by dissolving 0.5 g of resorcinol in 7 g of acetone are mixed for 48 hours by a ball mill, and then the precursor and resorcinol are contained. The acetone solution was heated at 60 ° C. in a nitrogen stream to remove acetone, and then heat-treated at 670 ° C. for 10 hours in nitrogen to obtain an olivine type lithium iron phosphate positive electrode active material.
（実施例３）
酢酸リチウム２水和物、シュウ酸鉄（II）２水和物およびリン酸２水素アンモニウムを、リチウムと鉄とリンのモル比が１：１：１となる様に秤量し、乳鉢を用いて混合した。
その後、この混合物を窒素中、３５０℃にて５時間熱処理した。
得られた生成物は、Ｘ線回折チャートで最も強度の強いピークはオリビン型結晶構造のものであり、本発明のオリビン型の結晶構造を有する前駆体であった。
(Example 3)
Lithium acetate dihydrate, iron (II) oxalate dihydrate, and ammonium dihydrogen phosphate were weighed so that the molar ratio of lithium, iron, and phosphorus was 1: 1: 1, and a mortar was used. Mixed.
The mixture was then heat treated at 350 ° C. for 5 hours in nitrogen.
The obtained product was the precursor having the olivine type crystal structure of the present invention, with the strongest peak in the X-ray diffraction chart having the olivine type crystal structure.
このようにして得られたオリビン型の結晶構造を有する前駆体２ｇと、キノール０．３５ｇをアセトン７ｇに溶解した溶液とを、ボールミルにて４８時間混合し、次いで、この前駆体及びキノールを含むアセトン溶液を、窒素気流中、６０℃にて加熱してアセトンを除去した後、窒素中、６４０℃にて１０時間熱処理し、オリビン型のリチウム鉄リン酸塩正極活物質を得た。 2 g of the precursor having the olivine type crystal structure thus obtained and a solution obtained by dissolving 0.35 g of quinol in 7 g of acetone are mixed for 48 hours by a ball mill, and then the precursor and the quinol are contained. The acetone solution was heated at 60 ° C. in a nitrogen stream to remove acetone, and then heat-treated at 640 ° C. for 10 hours in nitrogen to obtain an olivine type lithium iron phosphate positive electrode active material.
（実施例４）
酢酸リチウム２水和物、シュウ酸鉄（II）２水和物およびリン酸２水素アンモニウムを、リチウムと鉄とリンのモル比が１：１：１となる様に秤量し、乳鉢を用いて混合した。
その後、この混合物を窒素中、３５０℃にて５時間熱処理した。
得られた生成物は、Ｘ線回折チャートで最も強度の強いピークはオリビン型結晶構造のものであり、本発明のオリビン型の結晶構造を有する前駆体であった。
Example 4
Lithium acetate dihydrate, iron (II) oxalate dihydrate, and ammonium dihydrogen phosphate were weighed so that the molar ratio of lithium, iron, and phosphorus was 1: 1: 1, and a mortar was used. Mixed.
The mixture was then heat treated at 350 ° C. for 5 hours in nitrogen.
The obtained product was the precursor having the olivine type crystal structure of the present invention, with the strongest peak in the X-ray diffraction chart having the olivine type crystal structure.
このようにして得られたオリビン型の結晶構造を有する前駆体２ｇと、ピロガロール０．３５ｇをアセトン７ｇに溶解した溶液とを、ボールミルにて４８時間混合し、次いで、この前駆体及びピロガロールを含むアセトン溶液を、窒素気流中、６０℃にて加熱してアセトンを除去した後、窒素中、６４０℃にて１０時間熱処理し、オリビン型のリチウム鉄リン酸塩正極活物質を得た。 2 g of the precursor having the olivine type crystal structure thus obtained and a solution obtained by dissolving 0.35 g of pyrogallol in 7 g of acetone are mixed for 48 hours in a ball mill, and then the precursor and pyrogallol are contained. The acetone solution was heated at 60 ° C. in a nitrogen stream to remove acetone, and then heat-treated at 640 ° C. for 10 hours in nitrogen to obtain an olivine type lithium iron phosphate positive electrode active material.
（比較例１）
酢酸リチウム２水和物、シュウ酸鉄（II）２水和物およびリン酸２水素アンモニウムを、リチウムと鉄とリンのモル比が１：１：１となる様に秤量し、乳鉢を用いて混合した。
その後、この混合物を窒素中、３５０℃にて５時間、熱処理した。
得られた生成物は、Ｘ線回折チャートで最も強度の強いピークはオリビン型結晶構造のものであり、本発明のオリビン型の結晶構造を有する前駆体であった。
(Comparative Example 1)
Lithium acetate dihydrate, iron (II) oxalate dihydrate, and ammonium dihydrogen phosphate were weighed so that the molar ratio of lithium, iron, and phosphorus was 1: 1: 1, and a mortar was used. Mixed.
The mixture was then heat treated at 350 ° C. for 5 hours in nitrogen.
The obtained product was the precursor having the olivine type crystal structure of the present invention, with the strongest peak in the X-ray diffraction chart having the olivine type crystal structure.
このようにして得られたオリビン型の結晶構造を有する前駆体２ｇとアセトン７ｇとをボールミルにて４８時間混合し、次いで、この前駆体を含むアセトン溶液を、窒素気流中、６０℃にて加熱してアセトンを除去した後、窒素中、６４０℃にて１０時間熱処理し、オリビン型のリチウム鉄リン酸塩正極活物質を得た。 2 g of the precursor having the olivine type crystal structure thus obtained and 7 g of acetone were mixed in a ball mill for 48 hours, and then the acetone solution containing this precursor was heated at 60 ° C. in a nitrogen stream. After removing acetone, heat treatment was performed in nitrogen at 640 ° C. for 10 hours to obtain an olivine-type lithium iron phosphate positive electrode active material.
（比較例２）
酢酸リチウム２水和物、シュウ酸鉄（II）２水和物およびリン酸２水素アンモニウムを、リチウムと鉄とリンのモル比が１：１：１となる様に秤量し、乳鉢を用いて混合した。
その後、この混合物を窒素中、３５０℃にて５時間熱処理した。
得られた生成物は、Ｘ線回折チャートで最も強度の強いピークはオリビン型結晶構造のものであり、本発明のオリビン型の結晶構造を有する前駆体であった。
(Comparative Example 2)
Lithium acetate dihydrate, iron (II) oxalate dihydrate, and ammonium dihydrogen phosphate were weighed so that the molar ratio of lithium, iron, and phosphorus was 1: 1: 1, and a mortar was used. Mixed.
The mixture was then heat treated at 350 ° C. for 5 hours in nitrogen.
The obtained product was the precursor having the olivine type crystal structure of the present invention, with the strongest peak in the X-ray diffraction chart having the olivine type crystal structure.
このようにして得られたオリビン型の結晶構造を有する前駆体２ｇと、ポリエチレングリコール（平均分子量：２００）０．３５ｇをアセトン７ｇに溶解した溶液とを、ボールミルにて４８時間混合し、次いで、この前駆体及びポリエチレングリコールを含むアセトン溶液を、窒素気流中、１２０℃にて加熱してアセトンを除去した後、１２０℃にて乾燥させ、さらに、窒素中、６４０℃にて１０時間熱処理し、正極活物質を得た。 2 g of the thus obtained precursor having an olivine type crystal structure and a solution of 0.35 g of polyethylene glycol (average molecular weight: 200) dissolved in 7 g of acetone were mixed in a ball mill for 48 hours, The acetone solution containing this precursor and polyethylene glycol was heated at 120 ° C. in a nitrogen stream to remove acetone, then dried at 120 ° C., and further heat-treated at 640 ° C. for 10 hours in nitrogen. A positive electrode active material was obtained.
（比較例３）
酢酸リチウム２水和物、シュウ酸鉄（II）２水和物およびリン酸２水素アンモニウムを、リチウムと鉄とリンのモル比が１：１：１となる様に秤量し、乳鉢を用いて混合した。
その後、この混合物を窒素中、３５０℃にて５時間熱処理した。
得られた生成物は、Ｘ線回折チャートで最も強度の強いピークはオリビン型結晶構造のものであり、本発明のオリビン型の結晶構造を有する前駆体であった。
(Comparative Example 3)
Lithium acetate dihydrate, iron (II) oxalate dihydrate, and ammonium dihydrogen phosphate were weighed so that the molar ratio of lithium, iron, and phosphorus was 1: 1: 1, and a mortar was used. Mixed.
The mixture was then heat treated at 350 ° C. for 5 hours in nitrogen.
The obtained product was the precursor having the olivine type crystal structure of the present invention, with the strongest peak in the X-ray diffraction chart having the olivine type crystal structure.
このようにして得られたオリビン型の結晶構造を有する前駆体２ｇと、アスコルビン酸０．３５ｇを純水７ｇに溶解した溶液とを、ボールミルにて４８時間混合し、次いで、この前駆体及びアスコルビン酸を含む水溶液を、窒素気流中、１２０℃にて加熱して純水を除去した後、窒素中、６４０℃にて１０時間熱処理し、正極活物質を得た。 2 g of the precursor having an olivine type crystal structure thus obtained and a solution obtained by dissolving 0.35 g of ascorbic acid in 7 g of pure water were mixed for 48 hours in a ball mill, and then the precursor and ascorbine were mixed. The aqueous solution containing an acid was heated at 120 ° C. in a nitrogen stream to remove pure water, and then heat treated in nitrogen at 640 ° C. for 10 hours to obtain a positive electrode active material.
（リチウム電池の作製）
実施例１〜４および比較例１〜３で得られたそれぞれの正極活物質粉末６０ｍｇと、導電助剤としてアセチレンブラック３０ｍｇと、バインダーとしてポリテトラフルオロエチレン（ＰＴＦＥ）１０ｍｇを混練、圧延し、実施例１〜４および比較例１〜３それぞれの電極材料結合フィルムを得た。
(Production of lithium battery)
60 mg of each positive electrode active material powder obtained in Examples 1 to 4 and Comparative Examples 1 to 3, 30 mg of acetylene black as a conductive assistant, and 10 mg of polytetrafluoroethylene (PTFE) as a binder were kneaded and rolled, and then carried out. The electrode material binding films of Examples 1 to 4 and Comparative Examples 1 to 3 were obtained.
次いで、これらのフィルムを網目状のアルミニウムからなる集電体上に圧着後、成型機を用いて面積が２ｃｍ２の円板状に打ち抜き、実施例１〜４および比較例１〜３の正極とした。
これらの正極を真空乾燥器を用いて真空乾燥した後、乾燥したアルゴン雰囲気下にてＨＳ標準セル（宝泉株式会社製）を用いて実施例１〜４および比較例１〜３の電池を作製した。
Subsequently, these films were pressure-bonded onto a current collector made of mesh-like aluminum, and then punched into a disk shape having an area of 2 cm 2 using a molding machine, and the positive electrodes of Examples 1 to 4 and Comparative Examples 1 to 3 did.
After these positive electrodes were vacuum-dried using a vacuum dryer, the batteries of Examples 1 to 4 and Comparative Examples 1 to 3 were produced using an HS standard cell (manufactured by Hosen Co., Ltd.) under a dry argon atmosphere. did.
ここでは、負極として金属リチウムを、セパレータとして多孔質ポリプロピレン膜を、電解質溶液として１ｍｏｌ／ＬのＬｉＰＦ６溶液を、それぞれ用いた。
なお、このＬｉＰＦ６溶液に用いられる溶媒としては、炭酸エチレンと炭酸メチルエチルを体積％で１：１に混合したものを用いた。
Here, metallic lithium was used as the negative electrode, a porous polypropylene film was used as the separator, and a 1 mol / L LiPF 6 solution was used as the electrolyte solution.
As the solvent used in this LiPF 6 solution, 1 ethylene carbonate and methyl ethyl carbonate in a volume%: was a mixture in 1.
次に、上記の実施例１〜４及び比較例１〜３それぞれの電池に対して、室温（２５℃）にて電池充放電試験を行った。
この電池充放電試験においては、カットオフ電圧を３〜４Ｖとし、電流密度を次のように設定した。
充電時の電流密度については、まず、電極中の活物質含有量を実測し、この実測値とオリビン型リチウム鉄リン酸塩の理論容量（１７０ｍＡｈ／ｇ）を用いて１０時間で理論容量を充電できる電流量（レート：０．１Ｃ）の定電流とした。また、放電時の電流密度についても、同じ電流量（レート：０．１Ｃ）の定電流とした。
Next, a battery charge / discharge test was performed at room temperature (25 ° C.) for each of the batteries of Examples 1 to 4 and Comparative Examples 1 to 3.
In this battery charge / discharge test, the cutoff voltage was 3 to 4 V, and the current density was set as follows.
Regarding the current density during charging, first, the active material content in the electrode was measured, and the theoretical capacity was charged in 10 hours using this measured value and the theoretical capacity (170 mAh / g) of olivine type lithium iron phosphate. A constant current with a possible current amount (rate: 0.1 C) was used. The current density during discharge was also set to a constant current with the same amount of current (rate: 0.1 C).
上記の実施例１〜４及び比較例１〜３それぞれの初回放電特性を図１に示す。図１中、Ｅ１〜Ｅ４は実施例１〜４を、Ｒ１〜Ｒ３は比較例１〜３を、それぞれ示している。
この図によれば、実施例１〜４の電池は、オリビン型の結晶構造を有する前駆体をレゾルシノール、キノール、ピロガロールのような有機還元剤で処理することにより、比較例１の未処理のものを用いた電池より大きな放電容量を有することが分かった。
The initial discharge characteristics of each of Examples 1 to 4 and Comparative Examples 1 to 3 are shown in FIG. In FIG. 1, E1 to E4 show Examples 1 to 4, and R1 to R3 show Comparative Examples 1 to 3, respectively.
According to this figure, the batteries of Examples 1 to 4 were obtained by treating a precursor having an olivine type crystal structure with an organic reducing agent such as resorcinol, quinol, pyrogallol, and the untreated battery of Comparative Example 1. It has been found that the battery has a larger discharge capacity than the battery using.
また、比較例２の電池は、還元性がほとんどない有機物であるポリエチレングリコールを用いたために、オリビン型の結晶構造を有する前駆体の還元処理効果が認められなかった。
また、比較例３の電池は、強い還元性を有する有機物であるアスコルビン酸を純水中にて用いたために、水による酸化作用が強く、還元処理の効果が認められなかった。
In addition, since the battery of Comparative Example 2 used polyethylene glycol, which is an organic substance having almost no reducibility, the reduction treatment effect of the precursor having an olivine type crystal structure was not recognized.
Moreover, since the battery of Comparative Example 3 used ascorbic acid, which is an organic substance having a strong reducing property, in pure water, the oxidizing action by water was strong, and the effect of the reduction treatment was not recognized.
本発明は、ＬｉＦｅＰＯ４の様なオリビン型リチウム鉄リン酸塩の正極活物質を合成する際に、鉄（III）化合物の生成を防止することができることから、リチウム電池のさらなる充放電容量、特に放電容量の向上、充放電サイクルの安定化、高出力化はもちろんのこと、さらなる小型化、軽量化、高容量化が期待される二次電池の分野に適用することが可能である。 Since the present invention can prevent the formation of an iron (III) compound when synthesizing a positive electrode active material of olivine type lithium iron phosphate such as LiFePO 4, the charge / discharge capacity of the lithium battery, in particular, It can be applied to the field of secondary batteries where further reduction in size, weight and capacity are expected, as well as improvement in discharge capacity, stabilization of charge / discharge cycles, and higher output.
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