JP5709136B2 - Method for producing lithium iron phosphate and method for producing lithium iron phosphate-based positive electrode active material - Google Patents
Method for producing lithium iron phosphate and method for producing lithium iron phosphate-based positive electrode active material Download PDFInfo
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- JP5709136B2 JP5709136B2 JP2011192456A JP2011192456A JP5709136B2 JP 5709136 B2 JP5709136 B2 JP 5709136B2 JP 2011192456 A JP2011192456 A JP 2011192456A JP 2011192456 A JP2011192456 A JP 2011192456A JP 5709136 B2 JP5709136 B2 JP 5709136B2
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- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical compound [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 title claims description 45
- 239000007774 positive electrode material Substances 0.000 title claims description 20
- 238000004519 manufacturing process Methods 0.000 title claims description 13
- -1 phosphoric acid compound Chemical class 0.000 claims description 27
- 150000002506 iron compounds Chemical class 0.000 claims description 24
- 239000000203 mixture Substances 0.000 claims description 24
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 23
- 150000002642 lithium compounds Chemical class 0.000 claims description 19
- 238000001027 hydrothermal synthesis Methods 0.000 claims description 16
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 15
- 229910001873 dinitrogen Inorganic materials 0.000 claims description 15
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 12
- NBIIXXVUZAFLBC-UHFFFAOYSA-N phosphoric acid Substances OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 claims description 12
- 239000002994 raw material Substances 0.000 claims description 12
- 229910052799 carbon Inorganic materials 0.000 claims description 11
- 229910000147 aluminium phosphate Inorganic materials 0.000 claims description 10
- 238000006243 chemical reaction Methods 0.000 claims description 9
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 9
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical group N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 claims description 8
- 238000010304 firing Methods 0.000 claims description 7
- 238000002156 mixing Methods 0.000 claims description 6
- 239000011261 inert gas Substances 0.000 claims description 5
- 150000001412 amines Chemical class 0.000 claims description 3
- 229910021529 ammonia Inorganic materials 0.000 claims description 3
- 238000002360 preparation method Methods 0.000 claims 1
- 238000003756 stirring Methods 0.000 description 21
- 239000002245 particle Substances 0.000 description 16
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 15
- 229910001416 lithium ion Inorganic materials 0.000 description 15
- 238000000034 method Methods 0.000 description 15
- 239000013078 crystal Substances 0.000 description 13
- 229910010707 LiFePO 4 Inorganic materials 0.000 description 9
- 229910019142 PO4 Inorganic materials 0.000 description 9
- 239000010452 phosphate Substances 0.000 description 9
- 235000011007 phosphoric acid Nutrition 0.000 description 9
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 8
- 239000000843 powder Substances 0.000 description 8
- 238000001878 scanning electron micrograph Methods 0.000 description 8
- 229910052744 lithium Inorganic materials 0.000 description 7
- CIWBSHSKHKDKBQ-JLAZNSOCSA-N Ascorbic acid Chemical compound OC[C@H](O)[C@H]1OC(=O)C(O)=C1O CIWBSHSKHKDKBQ-JLAZNSOCSA-N 0.000 description 6
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 6
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 6
- 230000000052 comparative effect Effects 0.000 description 6
- 239000001301 oxygen Substances 0.000 description 6
- 229910052760 oxygen Inorganic materials 0.000 description 6
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 5
- 229920002472 Starch Polymers 0.000 description 5
- 239000003963 antioxidant agent Substances 0.000 description 5
- 235000006708 antioxidants Nutrition 0.000 description 5
- 229910052786 argon Inorganic materials 0.000 description 5
- 238000007599 discharging Methods 0.000 description 5
- 239000008151 electrolyte solution Substances 0.000 description 5
- 238000010438 heat treatment Methods 0.000 description 5
- 239000000463 material Substances 0.000 description 5
- 239000008107 starch Substances 0.000 description 5
- 235000019698 starch Nutrition 0.000 description 5
- 230000003078 antioxidant effect Effects 0.000 description 4
- 238000007600 charging Methods 0.000 description 4
- 239000007789 gas Substances 0.000 description 4
- 239000001257 hydrogen Substances 0.000 description 4
- 229910052739 hydrogen Inorganic materials 0.000 description 4
- 150000003839 salts Chemical class 0.000 description 4
- 238000007086 side reaction Methods 0.000 description 4
- 239000002002 slurry Substances 0.000 description 4
- 239000000243 solution Substances 0.000 description 4
- WMFOQBRAJBCJND-UHFFFAOYSA-M Lithium hydroxide Chemical compound [Li+].[OH-] WMFOQBRAJBCJND-UHFFFAOYSA-M 0.000 description 3
- RWRDLPDLKQPQOW-UHFFFAOYSA-N Pyrrolidine Chemical compound C1CCNC1 RWRDLPDLKQPQOW-UHFFFAOYSA-N 0.000 description 3
- 235000010323 ascorbic acid Nutrition 0.000 description 3
- 239000011668 ascorbic acid Substances 0.000 description 3
- KRKNYBCHXYNGOX-UHFFFAOYSA-N citric acid Chemical compound OC(=O)CC(O)(C(O)=O)CC(O)=O KRKNYBCHXYNGOX-UHFFFAOYSA-N 0.000 description 3
- 238000009833 condensation Methods 0.000 description 3
- 230000005494 condensation Effects 0.000 description 3
- XGZVUEUWXADBQD-UHFFFAOYSA-L lithium carbonate Chemical compound [Li+].[Li+].[O-]C([O-])=O XGZVUEUWXADBQD-UHFFFAOYSA-L 0.000 description 3
- 229910052808 lithium carbonate Inorganic materials 0.000 description 3
- 239000003960 organic solvent Substances 0.000 description 3
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 description 2
- 229920002134 Carboxymethyl cellulose Polymers 0.000 description 2
- WQZGKKKJIJFFOK-GASJEMHNSA-N Glucose Natural products OC[C@H]1OC(O)[C@H](O)[C@@H](O)[C@@H]1O WQZGKKKJIJFFOK-GASJEMHNSA-N 0.000 description 2
- YNAVUWVOSKDBBP-UHFFFAOYSA-N Morpholine Chemical compound C1COCCN1 YNAVUWVOSKDBBP-UHFFFAOYSA-N 0.000 description 2
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 description 2
- NQRYJNQNLNOLGT-UHFFFAOYSA-N Piperidine Chemical compound C1CCNCC1 NQRYJNQNLNOLGT-UHFFFAOYSA-N 0.000 description 2
- 239000004743 Polypropylene Substances 0.000 description 2
- JUJWROOIHBZHMG-UHFFFAOYSA-N Pyridine Chemical compound C1=CC=NC=C1 JUJWROOIHBZHMG-UHFFFAOYSA-N 0.000 description 2
- 229960005070 ascorbic acid Drugs 0.000 description 2
- 239000003575 carbonaceous material Substances 0.000 description 2
- 239000001768 carboxy methyl cellulose Substances 0.000 description 2
- 235000010948 carboxy methyl cellulose Nutrition 0.000 description 2
- 239000008112 carboxymethyl-cellulose Substances 0.000 description 2
- 150000001875 compounds Chemical class 0.000 description 2
- MNNHAPBLZZVQHP-UHFFFAOYSA-N diammonium hydrogen phosphate Chemical compound [NH4+].[NH4+].OP([O-])([O-])=O MNNHAPBLZZVQHP-UHFFFAOYSA-N 0.000 description 2
- 238000009826 distribution Methods 0.000 description 2
- 239000011267 electrode slurry Substances 0.000 description 2
- 238000001914 filtration Methods 0.000 description 2
- 239000011888 foil Substances 0.000 description 2
- 239000008103 glucose Substances 0.000 description 2
- 229910017053 inorganic salt Inorganic materials 0.000 description 2
- 229910052742 iron Inorganic materials 0.000 description 2
- AMXOYNBUYSYVKV-UHFFFAOYSA-M lithium bromide Chemical compound [Li+].[Br-] AMXOYNBUYSYVKV-UHFFFAOYSA-M 0.000 description 2
- KWGKDLIKAYFUFQ-UHFFFAOYSA-M lithium chloride Chemical compound [Li+].[Cl-] KWGKDLIKAYFUFQ-UHFFFAOYSA-M 0.000 description 2
- PQXKHYXIUOZZFA-UHFFFAOYSA-M lithium fluoride Chemical compound [Li+].[F-] PQXKHYXIUOZZFA-UHFFFAOYSA-M 0.000 description 2
- HSZCZNFXUDYRKD-UHFFFAOYSA-M lithium iodide Chemical compound [Li+].[I-] HSZCZNFXUDYRKD-UHFFFAOYSA-M 0.000 description 2
- 230000003647 oxidation Effects 0.000 description 2
- 238000007254 oxidation reaction Methods 0.000 description 2
- 229920000642 polymer Polymers 0.000 description 2
- 229920001155 polypropylene Polymers 0.000 description 2
- 238000010532 solid phase synthesis reaction Methods 0.000 description 2
- 238000005406 washing Methods 0.000 description 2
- 239000004254 Ammonium phosphate Substances 0.000 description 1
- CIWBSHSKHKDKBQ-DUZGATOHSA-N D-isoascorbic acid Chemical compound OC[C@@H](O)[C@H]1OC(=O)C(O)=C1O CIWBSHSKHKDKBQ-DUZGATOHSA-N 0.000 description 1
- 229920001353 Dextrin Polymers 0.000 description 1
- 239000004375 Dextrin Substances 0.000 description 1
- KMTRUDSVKNLOMY-UHFFFAOYSA-N Ethylene carbonate Chemical compound O=C1OCCO1 KMTRUDSVKNLOMY-UHFFFAOYSA-N 0.000 description 1
- 229930091371 Fructose Natural products 0.000 description 1
- 239000005715 Fructose Substances 0.000 description 1
- RFSUNEUAIZKAJO-ARQDHWQXSA-N Fructose Chemical compound OC[C@H]1O[C@](O)(CO)[C@@H](O)[C@@H]1O RFSUNEUAIZKAJO-ARQDHWQXSA-N 0.000 description 1
- 102100031416 Gastric triacylglycerol lipase Human genes 0.000 description 1
- 101000941284 Homo sapiens Gastric triacylglycerol lipase Proteins 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
- 229910012851 LiCoO 2 Inorganic materials 0.000 description 1
- 229910015643 LiMn 2 O 4 Inorganic materials 0.000 description 1
- 229910013385 LiN(SO2C2F5)2 Inorganic materials 0.000 description 1
- 229910013392 LiN(SO2CF3)(SO2C4F9) Inorganic materials 0.000 description 1
- 229910013290 LiNiO 2 Inorganic materials 0.000 description 1
- 229910013870 LiPF 6 Inorganic materials 0.000 description 1
- 229910012424 LiSO 3 Inorganic materials 0.000 description 1
- UEZVMMHDMIWARA-UHFFFAOYSA-N Metaphosphoric acid Chemical compound OP(=O)=O UEZVMMHDMIWARA-UHFFFAOYSA-N 0.000 description 1
- 239000002033 PVDF binder Substances 0.000 description 1
- 239000004698 Polyethylene Substances 0.000 description 1
- 239000002202 Polyethylene glycol Substances 0.000 description 1
- 239000004372 Polyvinyl alcohol Substances 0.000 description 1
- 229930006000 Sucrose Natural products 0.000 description 1
- CZMRCDWAGMRECN-UGDNZRGBSA-N Sucrose Chemical compound O[C@H]1[C@H](O)[C@@H](CO)O[C@@]1(CO)O[C@@H]1[C@H](O)[C@@H](O)[C@H](O)[C@@H](CO)O1 CZMRCDWAGMRECN-UGDNZRGBSA-N 0.000 description 1
- LSNNMFCWUKXFEE-UHFFFAOYSA-N Sulfurous acid Chemical compound OS(O)=O LSNNMFCWUKXFEE-UHFFFAOYSA-N 0.000 description 1
- YDHWWBZFRZWVHO-UHFFFAOYSA-N [hydroxy(phosphonooxy)phosphoryl] phosphono hydrogen phosphate Chemical compound OP(O)(=O)OP(O)(=O)OP(O)(=O)OP(O)(O)=O YDHWWBZFRZWVHO-UHFFFAOYSA-N 0.000 description 1
- 238000005054 agglomeration Methods 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- 150000001299 aldehydes Chemical class 0.000 description 1
- 150000003973 alkyl amines Chemical class 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 229910000148 ammonium phosphate Inorganic materials 0.000 description 1
- 235000019289 ammonium phosphates Nutrition 0.000 description 1
- 229910003481 amorphous carbon Inorganic materials 0.000 description 1
- 150000004982 aromatic amines Chemical class 0.000 description 1
- 229940072107 ascorbate Drugs 0.000 description 1
- WQZGKKKJIJFFOK-VFUOTHLCSA-N beta-D-glucose Chemical compound OC[C@H]1O[C@@H](O)[C@H](O)[C@@H](O)[C@@H]1O WQZGKKKJIJFFOK-VFUOTHLCSA-N 0.000 description 1
- 239000011230 binding agent Substances 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 230000005587 bubbling Effects 0.000 description 1
- 150000004649 carbonic acid derivatives Chemical class 0.000 description 1
- 239000012295 chemical reaction liquid Substances 0.000 description 1
- 235000015165 citric acid Nutrition 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 229940126214 compound 3 Drugs 0.000 description 1
- 239000006258 conductive agent Substances 0.000 description 1
- 238000010277 constant-current charging Methods 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 235000019425 dextrin Nutrition 0.000 description 1
- 125000005265 dialkylamine group Chemical group 0.000 description 1
- 235000013681 dietary sucrose Nutrition 0.000 description 1
- XPPKVPWEQAFLFU-UHFFFAOYSA-N diphosphoric acid Chemical compound OP(O)(=O)OP(O)(O)=O XPPKVPWEQAFLFU-UHFFFAOYSA-N 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 230000005518 electrochemistry Effects 0.000 description 1
- 235000010350 erythorbic acid Nutrition 0.000 description 1
- 150000002170 ethers Chemical class 0.000 description 1
- JBTWLSYIZRCDFO-UHFFFAOYSA-N ethyl methyl carbonate Chemical compound CCOC(=O)OC JBTWLSYIZRCDFO-UHFFFAOYSA-N 0.000 description 1
- VEPSWGHMGZQCIN-UHFFFAOYSA-H ferric oxalate Chemical compound [Fe+3].[Fe+3].[O-]C(=O)C([O-])=O.[O-]C(=O)C([O-])=O.[O-]C(=O)C([O-])=O VEPSWGHMGZQCIN-UHFFFAOYSA-H 0.000 description 1
- 238000005187 foaming Methods 0.000 description 1
- 235000001727 glucose Nutrition 0.000 description 1
- 239000010439 graphite Substances 0.000 description 1
- 229910002804 graphite Inorganic materials 0.000 description 1
- 150000008282 halocarbons Chemical class 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 238000009830 intercalation Methods 0.000 description 1
- FBAFATDZDUQKNH-UHFFFAOYSA-M iron chloride Chemical compound [Cl-].[Fe] FBAFATDZDUQKNH-UHFFFAOYSA-M 0.000 description 1
- 229910000358 iron sulfate Inorganic materials 0.000 description 1
- BAUYGSIQEAFULO-UHFFFAOYSA-L iron(2+) sulfate (anhydrous) Chemical compound [Fe+2].[O-]S([O-])(=O)=O BAUYGSIQEAFULO-UHFFFAOYSA-L 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
- GYCHYNMREWYSKH-UHFFFAOYSA-L iron(ii) bromide Chemical compound [Fe+2].[Br-].[Br-] GYCHYNMREWYSKH-UHFFFAOYSA-L 0.000 description 1
- BQZGVMWPHXIKEQ-UHFFFAOYSA-L iron(ii) iodide Chemical compound [Fe+2].[I-].[I-] BQZGVMWPHXIKEQ-UHFFFAOYSA-L 0.000 description 1
- SHXXPRJOPFJRHA-UHFFFAOYSA-K iron(iii) fluoride Chemical compound F[Fe](F)F SHXXPRJOPFJRHA-UHFFFAOYSA-K 0.000 description 1
- 229940026239 isoascorbic acid Drugs 0.000 description 1
- 239000003273 ketjen black Substances 0.000 description 1
- 150000002576 ketones Chemical class 0.000 description 1
- 150000002596 lactones Chemical class 0.000 description 1
- 229910021450 lithium metal oxide Inorganic materials 0.000 description 1
- 239000012046 mixed solvent Substances 0.000 description 1
- 150000002825 nitriles Chemical class 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 239000011255 nonaqueous electrolyte Substances 0.000 description 1
- 239000010450 olivine Substances 0.000 description 1
- 229910052609 olivine Inorganic materials 0.000 description 1
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 description 1
- 229940085991 phosphate ion Drugs 0.000 description 1
- 229910052698 phosphorus Inorganic materials 0.000 description 1
- 239000011574 phosphorus Substances 0.000 description 1
- 229920000573 polyethylene Polymers 0.000 description 1
- 229920001223 polyethylene glycol Polymers 0.000 description 1
- 229920000098 polyolefin Polymers 0.000 description 1
- 229920002451 polyvinyl alcohol Polymers 0.000 description 1
- 235000019422 polyvinyl alcohol Nutrition 0.000 description 1
- 229920002981 polyvinylidene fluoride Polymers 0.000 description 1
- 238000010298 pulverizing process Methods 0.000 description 1
- UMJSCPRVCHMLSP-UHFFFAOYSA-N pyridine Natural products COC1=CC=CN=C1 UMJSCPRVCHMLSP-UHFFFAOYSA-N 0.000 description 1
- 229940005657 pyrophosphoric acid Drugs 0.000 description 1
- 238000001694 spray drying Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 229960004793 sucrose Drugs 0.000 description 1
- 238000003786 synthesis reaction Methods 0.000 description 1
- 230000002194 synthesizing effect Effects 0.000 description 1
- 229920003002 synthetic resin Polymers 0.000 description 1
- 239000000057 synthetic resin Substances 0.000 description 1
- 125000005270 trialkylamine group Chemical group 0.000 description 1
- UNXRWKVEANCORM-UHFFFAOYSA-N triphosphoric acid Chemical compound OP(O)(=O)OP(O)(=O)OP(O)(O)=O UNXRWKVEANCORM-UHFFFAOYSA-N 0.000 description 1
- 229940048102 triphosphoric acid Drugs 0.000 description 1
- 238000001291 vacuum drying Methods 0.000 description 1
- 238000009777 vacuum freeze-drying Methods 0.000 description 1
Classifications
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Description
本発明は、リチウムイオン二次電池の正極材料として有用なリン酸鉄リチウム系正極活物質の製造法に関する。 The present invention relates to a method for producing a lithium iron phosphate-based positive electrode active material useful as a positive electrode material for a lithium ion secondary battery.
携帯電子機器、ハイブリッド自動車、電気自動車等に用いられる二次電池の開発が行われており、特にリチウムイオン二次電池が広く知られている。当該リチウムイオン電池は、基本的に正極、負極、非水電解質及びセパレータからなり、正極材料としてはＬｉＣｏＯ2が広く用いられ、さらにＬｉＮｉＯ2、ＬｉＭｎ2Ｏ4などが開発されている。しかし、これらのリチウム系金属酸化物は、高電圧ではあるが容量が低いという問題がある。 Secondary batteries used for portable electronic devices, hybrid cars, electric cars, and the like have been developed, and lithium ion secondary batteries are particularly widely known. The lithium ion battery basically includes a positive electrode, a negative electrode, a non-aqueous electrolyte, and a separator. LiCoO 2 is widely used as a positive electrode material, and LiNiO 2 , LiMn 2 O 4 and the like have been developed. However, these lithium metal oxides have a problem that the capacity is low although the voltage is high.
これらに対し、最近になって、オリビン構造を有するリン酸鉄リチウム等のリン酸化合物を正極に用いることが提案されている（特許文献１）。しかしながら、このリン酸鉄リチウムの合成法は固相法であり、不活性ガス雰囲気下で焼成と粉砕を行う必要があり、操作が複雑であった。 On the other hand, recently, it has been proposed to use a phosphate compound such as lithium iron phosphate having an olivine structure for the positive electrode (Patent Document 1). However, this method of synthesizing lithium iron phosphate is a solid phase method, which requires firing and pulverization in an inert gas atmosphere, and the operation is complicated.
そこで、リン酸鉄リチウムを水熱反応で製造する試みがなされている（特許文献２及び３、非特許文献１）。これらの方法は、リチウム化合物、鉄化合物、リン酸化合物を耐圧容器内で水熱反応させるというものである。 Therefore, attempts have been made to produce lithium iron phosphate by a hydrothermal reaction (Patent Documents 2 and 3, Non-Patent Document 1). In these methods, a lithium compound, an iron compound, and a phosphoric acid compound are hydrothermally reacted in a pressure resistant vessel.
これら従来の水熱反応によるリン酸鉄リチウムの製造法によれば固相法に比べて、粒径が均一なものが得られるものの、副反応が生じ生成物に不純物が混入する、高価なリチウム化合物を大過剰反応させる必要があるなどの問題があることが判明した。
従って、より微細で均一な粒径を有するリン酸鉄リチウムを高純度、高収率かつ安価に製造する方法が望まれていた。
According to these conventional methods for producing lithium iron phosphate by hydrothermal reaction, compared to the solid phase method, a product having a uniform particle size can be obtained, but an expensive lithium in which a side reaction occurs and impurities are mixed into the product. It has been found that there is a problem that the compound needs to undergo a large excess reaction.
Accordingly, there has been a demand for a method for producing lithium iron phosphate having a finer and more uniform particle size with high purity, high yield and low cost.
そこで本発明者は、鉄化合物、リン酸化合物及びリチウム化合物の水熱反応条件について種々検討した結果、リチウム化合物とリン酸化合物と水を最初に混合し、次いで２価の鉄化合物を添加して水熱反応させるに際し、塩基を添加して混合物のｐＨを３〜６に調整すれば、原料であるリチウム化合物の使用量を大過剰用いなくとも、反応途中の副反応や凝結もなく操作が容易であり、かつ微細で均一な粒径を有する高純度のリン酸鉄リチウムが高収率で得られること、また得られたリン酸鉄リチウムを正極材料として用いれば、高容量で充放電特性に優れたリチウムイオン二次電池が得られることを見出し、本発明を完成した。 Therefore, as a result of various studies on the hydrothermal reaction conditions of the iron compound, phosphate compound and lithium compound, the present inventor mixed lithium compound, phosphate compound and water first, and then added divalent iron compound. In the hydrothermal reaction, if a base is added and the pH of the mixture is adjusted to 3 to 6, operation is easy without side reactions or condensation during the reaction without using a large excess of the lithium compound used as a raw material. In addition, high purity lithium iron phosphate having a fine and uniform particle size can be obtained in a high yield, and if the obtained lithium iron phosphate is used as a positive electrode material, high capacity and charge / discharge characteristics can be obtained. The inventors have found that an excellent lithium ion secondary battery can be obtained and completed the present invention.
すなわち、本発明は、リチウム化合物、リン酸化合物及び水を混合後、塩基を添加し、次いで２価の鉄化合物を原料組成比Ｌｉ／Ｆｅ＝１．５〜２．５の範囲で添加し、混合物のｐＨを３〜６に調整して水熱反応することを特徴とするリン酸鉄リチウムの製造法を提供するものである。
また、本発明は、リチウム化合物、リン酸化合物及び水を混合後、塩基及び炭素源を添加し、その後２価の鉄化合物を原料組成比Ｌｉ／Ｆｅ＝１．５〜２．５の範囲で添加し、混合物のｐＨを３〜６に調整して水熱反応を行い、次いで不活性ガス又は還元雰囲気下に焼成することを特徴とするリン酸鉄リチウム系正極活物質の製造法を提供するものである。
また、本発明は、上記の製造法により得られたリン酸鉄リチウムを正極材料として含有するリチウムイオン二次電池を提供するものである。
That is, in the present invention, after mixing a lithium compound, a phosphoric acid compound and water, a base is added, and then a divalent iron compound is added in a raw material composition ratio Li / Fe = 1.5 to 2.5, The present invention provides a method for producing lithium iron phosphate, characterized in that the pH of the mixture is adjusted to 3 to 6 to cause a hydrothermal reaction.
In the present invention, after mixing a lithium compound, a phosphoric acid compound and water, a base and a carbon source are added, and then a divalent iron compound is added in a raw material composition ratio Li / Fe = 1.5 to 2.5. And providing a method for producing a lithium iron phosphate-based positive electrode active material, characterized in that the pH of the mixture is adjusted to 3 to 6, a hydrothermal reaction is performed, and then firing is performed in an inert gas or a reducing atmosphere. Is.
Moreover, this invention provides the lithium ion secondary battery which contains the lithium iron phosphate obtained by said manufacturing method as a positive electrode material.
本発明方法によれば、高価なリチウム化合物を大過剰使用することなく、操作が容易であるとともに副反応が生じない。また本発明方法によれば、微細で均一な粒径を有する高純度のリン酸鉄リチウムが高収率で得られる。本発明方法により得られたリン酸鉄リチウムを正極材料として用いれば、高容量で充放電特性に優れたリチウムイオン二次電池が得られる。 According to the method of the present invention, the operation is easy and no side reaction occurs without using an excessive amount of an expensive lithium compound. Further, according to the method of the present invention, high purity lithium iron phosphate having a fine and uniform particle size can be obtained in high yield. When lithium iron phosphate obtained by the method of the present invention is used as a positive electrode material, a lithium ion secondary battery having a high capacity and excellent charge / discharge characteristics can be obtained.
本発明のリン酸鉄リチウムの製造法においては、まず、リチウム化合物、リン酸化合物及び水を混合する。 In the method for producing lithium iron phosphate of the present invention, first, a lithium compound, a phosphate compound and water are mixed.
リン酸鉄リチウムの合成原料は、基本的に２価の鉄化合物とリチウム化合物とリン酸化合物であるが、本発明においては、最初にリチウム化合物、リン酸化合物及び水の混合物を調製しておき、最後に２価の鉄化合物を添加することが、副反応を防止し、反応を容易に進行させるうえで重要である。２価の鉄化合物とリン酸化合物と水を最初に混合しておき、これに炭素源を加え、窒素ガスを導入した後に炭酸リチウムを加えると、反応中に凝結を生じ、撹拌できなくなり、特殊な撹拌装置を必要とする。一方、２価の鉄化合物と炭酸リチウムと水を最初に混合し、炭素源を加え、窒素ガスを導入した後にリン酸化合物を加えると、過度の発泡により撹拌が困難になり、凝結が生じる。これに対し、本発明のような順序で原料を添加すると、凝結が生じることなく、撹拌も容易であり、反応がスムーズに進行する。 The synthetic raw material of lithium iron phosphate is basically a divalent iron compound, a lithium compound and a phosphate compound. In the present invention, a mixture of a lithium compound, a phosphate compound and water is prepared first. Finally, the addition of a divalent iron compound is important for preventing side reactions and allowing the reaction to proceed easily. When a divalent iron compound, a phosphoric acid compound and water are mixed first, a carbon source is added to this, and nitrogen gas is added after introducing nitrogen gas, condensation occurs during the reaction, which makes stirring impossible and makes it special. A simple stirring device is required. On the other hand, when a divalent iron compound, lithium carbonate, and water are first mixed, a carbon source is added, a nitrogen gas is introduced, and then a phosphoric acid compound is added, stirring becomes difficult due to excessive foaming and condensation occurs. In contrast, when the raw materials are added in the order as in the present invention, no agglomeration occurs, stirring is easy, and the reaction proceeds smoothly.
原料として用いられるリチウム化合物としては、フッ化リチウム、塩化リチウム、臭化リチウム、ヨウ化リチウム等のリチウム金属塩、水酸化リチウム、炭酸リチウム等が挙げられるが、炭酸リチウムを使用するのが安価である点で好ましい。 Examples of the lithium compound used as a raw material include lithium metal salts such as lithium fluoride, lithium chloride, lithium bromide, and lithium iodide, lithium hydroxide, lithium carbonate, etc., but it is inexpensive to use lithium carbonate. It is preferable in a certain point.
リン酸化合物としては、オルトリン酸、メタリン酸、ピロリン酸、三リン酸、四リン酸、リン酸アンモニウム、リン酸水素アンモニウム等が用いられる。 As the phosphoric acid compound, orthophosphoric acid, metaphosphoric acid, pyrophosphoric acid, triphosphoric acid, tetraphosphoric acid, ammonium phosphate, ammonium hydrogen phosphate and the like are used.
リチウム化合物及びリン酸化合物の使用量はリチウムイオン及びリン酸イオンのモル比換算で１．５：１〜２．５：１が好ましく、略２．０：１〜２．５：１とするのがより好ましい。 The amount of the lithium compound and phosphate compound used is preferably 1.5: 1 to 2.5: 1 in terms of molar ratio of lithium ion and phosphate ion, and is approximately 2.0: 1 to 2.5: 1. Is more preferable.
水の使用量は、原料化合物の溶解性、撹拌の容易性、合成の効率等の点から、リン酸化合物のリンイオン１モルに対して１０〜５０モルが好ましく、さらに１３〜３０モルが好ましく、特に１５〜２０モルが好ましい。 The amount of water used is preferably 10 to 50 mol, more preferably 13 to 30 mol with respect to 1 mol of phosphorus ion of the phosphoric acid compound, from the viewpoints of solubility of the raw material compound, easiness of stirring, synthesis efficiency, and the like. 15-20 mol is particularly preferable.
リチウム化合物とリン酸化合物と水の添加順序は特に限定されず、またこれらの原料の混合時間も限定されない。これらの原料の混合は、室温、例えば１０〜３５℃で行えばよい。 The order of addition of the lithium compound, phosphate compound and water is not particularly limited, and the mixing time of these raw materials is not limited. These raw materials may be mixed at room temperature, for example, 10 to 35 ° C.
本発明方法においては、リチウム化合物、リン酸化合物及び水の混合物に、塩基を添加して２価の鉄化合物添加後のｐＨを３〜６に調整する。当該塩基添加によるｐＨの調整により、原料として用いるリチウム化合物の量が大過剰でなくとも、高純度のリン酸鉄リチウムが効率良く得られる。 In the method of the present invention, a base is added to a mixture of a lithium compound, a phosphoric acid compound and water to adjust the pH after addition of the divalent iron compound to 3-6. By adjusting the pH by the addition of the base, high-purity lithium iron phosphate can be obtained efficiently even if the amount of the lithium compound used as a raw material is not excessively large.
用いられる塩基としては、２価の鉄化合物添加後の混合物のｐＨを３〜６に調整できる塩基であればよいが、非金属系であることが必要であり、アンモニア又は有機アミンが好ましい。有機アミンとしては、アルキルアミン、ジアルキルアミン、トリアルキルアミン、アルカノールアミン、ジアルカノールアミン、トリアルカノールアミン、ピペリジン、ピロリジン、モルホリン等の環状アミン、ピリジン等の芳香族アミン等が挙げられる。これらの塩基のうち、アンモニアが特に好ましい。
これらの塩基の使用量は、２価の鉄化合物添加後の混合物のｐＨを３〜６にする量であればよく、さらにｐＨ３〜５にする量であるのがより好ましい。
The base to be used may be any base that can adjust the pH of the mixture after addition of the divalent iron compound to 3 to 6, but is required to be non-metallic and is preferably ammonia or organic amine. Examples of organic amines include alkylamines, dialkylamines, trialkylamines, alkanolamines, dialkanolamines, trialkanolamines, cyclic amines such as piperidine, pyrrolidine, and morpholine, and aromatic amines such as pyridine. Of these bases, ammonia is particularly preferred.
The amount of these bases used may be an amount that makes the pH of the mixture after addition of the divalent iron compound 3 to 6, more preferably an amount that makes the pH 3 to 5.
本発明方法においては、２価の鉄化合物を添加する前に、混合物に窒素ガスを導入するのが好ましい。窒素ガスの導入は、反応液中の溶存酸素量を低下させ、後に添加する２価の鉄化合物の酸化を防止する点、酸化防止剤の添加量を低減する点から好ましい。窒素ガスの導入量は、溶液中の溶存酸素濃度が１．０ｍｇ／Ｌ以下になるまで行うのが好ましく、特に０．５ｍｇ／Ｌ以下となるまで行うのがさらに好ましい。窒素ガスの導入手段としては、溶液中に窒素ガスをバブリングすることにより行うのが好ましい。 In the method of the present invention, it is preferable to introduce nitrogen gas into the mixture before adding the divalent iron compound. The introduction of nitrogen gas is preferable from the viewpoint of reducing the amount of dissolved oxygen in the reaction solution, preventing oxidation of a divalent iron compound to be added later, and reducing the amount of antioxidant added. The amount of nitrogen gas introduced is preferably carried out until the dissolved oxygen concentration in the solution is 1.0 mg / L or less, more preferably 0.5 mg / L or less. Nitrogen gas is preferably introduced by bubbling nitrogen gas into the solution.
また、本発明方法においては、後に添加する２価の鉄化合物の酸化を防止するために、この時点で酸化防止剤を添加してもよい。酸化防止剤の添加時期は、窒素ガスの導入と当時でもよいし、これらの操作の前でも中間でも後でもよい。酸化防止剤としては、アスコルビン酸、アスコルビン酸エステル、アスコルビン酸塩、イソアスコルビン酸、アルデヒド類、水素ガス、亜硫酸塩等が挙げられる。これらの酸化防止剤の使用量は、２価の鉄化合物の鉄イオン１モルに対して０．００１モル〜０．1モルが好ましく、０．００５モル〜０．０５モルがさらに好ましい。 In the method of the present invention, an antioxidant may be added at this point in order to prevent oxidation of a divalent iron compound added later. The antioxidant may be added at the time of introduction of nitrogen gas and at that time, or before, during or after these operations. Examples of the antioxidant include ascorbic acid, ascorbic acid ester, ascorbate, isoascorbic acid, aldehydes, hydrogen gas, sulfite and the like. The amount of these antioxidants to be used is preferably 0.001 mol to 0.1 mol, and more preferably 0.005 mol to 0.05 mol, per 1 mol of iron ions of the divalent iron compound.
また、本発明方法においては、炭素源の添加は、水熱反応後でもよいが、水熱反応前に添加しておくのが、均一な正極活物質を得る点で好ましい。ここで炭素源としては、グルコース、フルクトース、ポリエチレングリコール、ポリビニルアルコール、カルボキシメチルセルロース、サッカロース、デンプン、デキストリン、クエン酸が挙げられるが、安価である点から、デンプン、グルコースが特に好ましい。炭素源の使用量は、得られるリン酸鉄リチウムを正極材料として使用した場合の充放電特性の点から、リチウム化合物とリン酸化合物、２価の鉄化合物及び水の混合物重量に対して０．１重量％〜１５重量％が好ましく、さらに０．５重量％〜１０重量％が好ましく、特に１．５重量％〜５重量％が好ましい。 In the method of the present invention, the carbon source may be added after the hydrothermal reaction, but it is preferable to add it before the hydrothermal reaction from the viewpoint of obtaining a uniform positive electrode active material. Here, examples of the carbon source include glucose, fructose, polyethylene glycol, polyvinyl alcohol, carboxymethylcellulose, saccharose, starch, dextrin, and citric acid, and starch and glucose are particularly preferable from the viewpoint of low cost. The amount of the carbon source used is 0. 0 with respect to the mixture weight of the lithium compound, phosphate compound, divalent iron compound and water from the viewpoint of charge / discharge characteristics when the obtained lithium iron phosphate is used as the positive electrode material. It is preferably 1 to 15% by weight, more preferably 0.5 to 10% by weight, and particularly preferably 1.5 to 5% by weight.
なお、塩基の添加、窒素ガスの導入及び炭素源の添加の順序は問わず、同時でもよい。 The order of adding the base, introducing nitrogen gas, and adding the carbon source is not limited and may be simultaneous.
本発明方法においては、次に２価の鉄化合物を添加する。用いられる２価の鉄化合物としては、フッ化鉄、塩化鉄、臭化鉄、ヨウ化鉄等のハロゲン化鉄、硫酸鉄、シュウ酸鉄、酢酸鉄等が挙げられる。２価の鉄化合物の使用量は、Ｌｉ／Ｆｅ＝１．５〜２．５とするのが、高純度のリン酸鉄リチウムを得る点で好ましい。Ｌｉ／Ｆｅ比が３以上では高価なリチウムを大過剰使用することになり非経済的である。また、Ｌｉ／Ｆｅ比が１．５未満では高純度のリン酸鉄リチウムを得ることが困難である。当該２価の鉄化合物添加後の混合物のｐＨは、前記塩基の添加により３〜６になっているのが望ましい。 Next, in the method of the present invention, a divalent iron compound is added. Examples of the divalent iron compound used include iron halides such as iron fluoride, iron chloride, iron bromide, and iron iodide, iron sulfate, iron oxalate, and iron acetate. The amount of the divalent iron compound used is preferably Li / Fe = 1.5 to 2.5 in terms of obtaining high purity lithium iron phosphate. If the Li / Fe ratio is 3 or more, expensive lithium is excessively used, which is uneconomical. Further, when the Li / Fe ratio is less than 1.5, it is difficult to obtain high purity lithium iron phosphate. The pH of the mixture after the addition of the divalent iron compound is desirably 3 to 6 due to the addition of the base.
本発明方法においては、次に前記混合物を微細で均一な粒径を有するリン酸鉄リチウムを得る点から撹拌することが好ましく、さらに３０分以上混合することがより好ましい。混合に際しては、撹拌することが好ましい。この撹拌時間は３０分以上、さらに３０〜１２０分が好ましく、さらにまた６０〜１２０分が好ましい。撹拌反応は、室温で行えばよく、１０〜３５℃で行うのが好ましい。撹拌は、通常の撹拌手段、例えばプロペラ撹拌、ポンプ循環撹拌により行うことができる。 In the method of the present invention, the mixture is preferably stirred from the viewpoint of obtaining lithium iron phosphate having a fine and uniform particle size, and more preferably mixed for 30 minutes or more. In mixing, it is preferable to stir. The stirring time is 30 minutes or more, preferably 30 to 120 minutes, and more preferably 60 to 120 minutes. The stirring reaction may be performed at room temperature, and is preferably performed at 10 to 35 ° C. Stirring can be performed by ordinary stirring means such as propeller stirring and pump circulation stirring.
次に前記混合物を水熱反応に付す。水熱反応は、混合物中に水が存在するので、耐圧容器中で密封して１５０℃以上に加熱すればよい。より好ましい反応温度は１５０〜２００℃であり、さらに好ましくは１８０〜２００℃である。圧力は、耐圧容器中密封して加熱するのみでよく、理論上１．０〜１．５ＭＰａ程度になる。加熱時間は１〜１０時間が好ましく、さらに２〜５時間が好ましい。なお、水熱反応中は、反応液を撹拌しておくのが好ましい。 The mixture is then subjected to a hydrothermal reaction. In the hydrothermal reaction, since water is present in the mixture, it may be sealed in a pressure vessel and heated to 150 ° C. or higher. A more preferable reaction temperature is 150 to 200 ° C, and further preferably 180 to 200 ° C. The pressure only needs to be sealed and heated in a pressure-resistant container, and is theoretically about 1.0 to 1.5 MPa. The heating time is preferably 1 to 10 hours, more preferably 2 to 5 hours. In addition, it is preferable to stir the reaction liquid during the hydrothermal reaction.
水熱反応終了後、生成したリン酸鉄リチウムをろ過により採取し、洗浄するのが好ましい。洗浄は、ケーキ洗浄機能を有したろ過装置を用いて水で行うのが好ましい。得られた結晶は、必要により乾燥する。乾燥手段は、噴霧乾燥、真空乾燥、凍結乾燥等が挙げられる。 After completion of the hydrothermal reaction, the produced lithium iron phosphate is preferably collected by filtration and washed. Washing is preferably performed with water using a filtration device having a cake washing function. The obtained crystals are dried if necessary. Examples of the drying means include spray drying, vacuum drying, freeze drying and the like.
得られたリン酸鉄リチウムは、不活性ガス又は還元雰囲気下で焼成することにより、正極材料として有用なリン酸鉄リチウムとなる。水熱反応前に炭素源を添加しなかった場合は、ここで炭素源を添加する。不活性ガスとしては、Ａｒ、Ｎ2等が挙げられる。また還元雰囲気下とするには水素ガスを導入すればよい。焼成条件は６００℃以上が好ましく、さらに６００〜９００℃が好ましく、特に６００〜８００℃が好ましい。焼成時間は０．５時間〜５時間が好ましく、さらに１時間〜３時間が好ましい。 The obtained lithium iron phosphate becomes a lithium iron phosphate useful as a positive electrode material by firing in an inert gas or a reducing atmosphere. If the carbon source is not added before the hydrothermal reaction, the carbon source is added here. Examples of the inert gas include Ar and N 2 . In addition, hydrogen gas may be introduced to obtain a reducing atmosphere. Firing conditions are preferably 600 ° C. or higher, more preferably 600 to 900 ° C., and particularly preferably 600 to 800 ° C. The firing time is preferably 0.5 hours to 5 hours, more preferably 1 hour to 3 hours.
本発明方法により得られるリン酸鉄リチウムは、化学組成がＬｉＦｅＰＯ4で示されるものであり、炭素によりコーティングされていることから正極活物質として有用である。得られるリン酸鉄リチウムは、平均粒子径が１μｍ以下と微細であり、かつその粒度分布がせまいという特徴がある。ＳＥＭ像から計算された平均粒子径は１０００ｎｍ以下であり、粒度分布は１００〜８００ｎｍが好ましく、さらに２００〜６００ｎｍが好ましく、特に３００〜５００ｎｍが好ましい。平均粒子径は、６００ｎｍ以下が好ましく、特に５００ｎｍ以下が好ましい。 The lithium iron phosphate obtained by the method of the present invention has a chemical composition represented by LiFePO 4 and is useful as a positive electrode active material because it is coated with carbon. The obtained lithium iron phosphate has a feature that the average particle size is as fine as 1 μm or less and the particle size distribution is narrow. The average particle size calculated from the SEM image is 1000 nm or less, and the particle size distribution is preferably 100 to 800 nm, more preferably 200 to 600 nm, and particularly preferably 300 to 500 nm. The average particle size is preferably 600 nm or less, and particularly preferably 500 nm or less.
本発明方法により得られるリン酸鉄リチウム系正極活物質は、粒径が微細で均一であることから、リチウムイオン二次電池の正極材料として有用である。次に本発明方法で得られたリン酸鉄リチウム系正極活物質を正極材料として含有するリチウムイオン二次電池について説明する。 The lithium iron phosphate-based positive electrode active material obtained by the method of the present invention is useful as a positive electrode material for lithium ion secondary batteries because the particle size is fine and uniform. Next, a lithium ion secondary battery containing the lithium iron phosphate positive electrode active material obtained by the method of the present invention as a positive electrode material will be described.
本発明の正極材料を適用できるリチウムイオン二次電池としては、正極と負極と電解液とセパレータを必須構成とするものであれば特に限定されない。 The lithium ion secondary battery to which the positive electrode material of the present invention can be applied is not particularly limited as long as it has a positive electrode, a negative electrode, an electrolytic solution, and a separator as essential components.
ここで、負極については、リチウムイオンを充電時には吸蔵し、かつ放電時には放出することができれば、その材料構成で特に限定されるものではなく、公知の材料構成のものを用いることができる。たとえば、リチウム金属、グラファイト又は非晶質炭素等の炭素材料等である。そしてリチウムを電気化学的に吸蔵・放出し得るインターカレート材料で形成された電極、特に炭素材料を用いることが好ましい。 Here, as long as lithium ions can be occluded at the time of charging and released at the time of discharging, the material structure is not particularly limited, and a known material structure can be used. For example, a carbon material such as lithium metal, graphite, or amorphous carbon. It is preferable to use an electrode formed of an intercalating material capable of electrochemically inserting and extracting lithium, particularly a carbon material.
電解液は、有機溶媒に支持塩を溶解させたものである。有機溶媒は、通常リチウムイオン二次電池の電解液の用いられる有機溶媒であれば特に限定されるものではなく、例えば、カーボネート類、ハロゲン化炭化水素、エーテル類、ケトン類、ニトリル類、ラクトン類、オキソラン化合物等を用いることができる。 The electrolytic solution is obtained by dissolving a supporting salt in an organic solvent. The organic solvent is not particularly limited as long as it is an organic solvent that is usually used for an electrolyte solution of a lithium ion secondary battery. For example, carbonates, halogenated hydrocarbons, ethers, ketones, nitriles, lactones An oxolane compound or the like can be used.
支持塩は、その種類が特に限定されるものではないが、ＬｉＰＦ6、ＬｉＢＦ4、ＬｉＣｌＯ4及びＬｉＡｓＦ6から選ばれる無機塩、該無機塩の誘導体、ＬｉＳＯ3ＣＦ3、ＬｉＣ（ＳＯ3ＣＦ3）2及びＬｉＮ（ＳＯ3ＣＦ3）2、ＬｉＮ（ＳＯ2Ｃ2Ｆ5）2及びＬｉＮ（ＳＯ2ＣＦ3）（ＳＯ2Ｃ4Ｆ9）から選ばれる有機塩、並びに該有機塩の誘導体の少なくとも１種であることが好ましい。 The type of the supporting salt is not particularly limited, but an inorganic salt selected from LiPF 6 , LiBF 4 , LiClO 4 and LiAsF 6 , a derivative of the inorganic salt, LiSO 3 CF 3 , LiC (SO 3 CF 3 ) 2 and LiN (SO 3 CF 3 ) 2 , LiN (SO 2 C 2 F 5 ) 2 and LiN (SO 2 CF 3 ) (SO 2 C 4 F 9 ), and organic salt derivatives It is preferable that it is at least 1 type of these.
セパレータは、正極及び負極を電気的に絶縁し、電解液を保持する役割を果たすもので
ある。たとえば、多孔性合成樹脂膜、特にポリオレフィン系高分子（ポリエチレン、ポリ
プロピレン）の多孔膜を用いればよい。
The separator plays a role of electrically insulating the positive electrode and the negative electrode and holding the electrolytic solution. For example, a porous synthetic resin film, particularly a polyolefin polymer (polyethylene, polypropylene) porous film may be used.
次に実施例を挙げて、本発明をさらに詳細に説明するが、本発明はこれに限定されるものではない。 EXAMPLES Next, although an Example is given and this invention is demonstrated further in detail, this invention is not limited to this.
実施例１
Ｌｉ2ＣＯ3 １０．０ｇ、Ｈ3ＰＯ4 １７．６ｇ及び水６０．０ｇを混合した。これに２８％アンモニア水１５．５ｇ、デンプン３．０ｇを加え、次いで窒素ガスをバブリングし、溶存酸素濃度が０．１ｍｇ／Ｌ未満になったことを確認した。これにＦｅＳＯ4・７Ｈ2Ｏ ５０．０ｇを混合し、２３±２℃でプロペラ式撹拌装置で６０分間撹拌した。このとき、スラリーのｐＨは３．３であった。
６０分間撹拌した混合物をオートクレーブに入れ、２００℃で３時間加熱した。加熱中も撹拌を続けた。オートクレーブの内圧は１．５ＭＰａであった。生成した結晶をろ過し、次いで水により洗浄した。結晶を６０℃、１Torrの条件で真空乾燥した。得られた結晶をアルゴンガスに水素を３％導入した管状電気炉中で７００℃、１時間焼成し、リン酸鉄リチウムの微細粉末を得た。得られた粉末のＳＥＭ像を図１にＸＲＤチャートを図２示す。得られたリン酸鉄リチウムの粒子径は３００〜５００ｎｍの範囲であり、高純度のリン酸鉄リチウムが得られたことが確認できた。
Example 1
Li 2 CO 3 10.0g, was mixed with H 3 PO 4 17.6 g, and water 60.0 g. To this, 15.5 g of 28% aqueous ammonia and 3.0 g of starch were added, and then nitrogen gas was bubbled to confirm that the dissolved oxygen concentration was less than 0.1 mg / L. This was mixed with 50.0 g of FeSO 4 .7H 2 O and stirred at 23 ± 2 ° C. with a propeller type stirring device for 60 minutes. At this time, the pH of the slurry was 3.3.
The mixture stirred for 60 minutes was placed in an autoclave and heated at 200 ° C. for 3 hours. Stirring was continued during heating. The internal pressure of the autoclave was 1.5 MPa. The formed crystals were filtered and then washed with water. The crystals were vacuum dried at 60 ° C. and 1 Torr. The obtained crystal was baked at 700 ° C. for 1 hour in a tubular electric furnace in which 3% of hydrogen was introduced into argon gas to obtain a fine powder of lithium iron phosphate. FIG. 1 shows an SEM image of the obtained powder, and FIG. 2 shows an XRD chart. The particle diameter of the obtained lithium iron phosphate was in the range of 300 to 500 nm, and it was confirmed that high purity lithium iron phosphate was obtained.
実施例２
Ｌｉ2ＣＯ3 １６．６ｇ、Ｈ3ＰＯ4 １７．６ｇ及び水６０．０ｇを混合した。これに２８％アンモニア水７．９ｇ、デンプン３．０ｇを加え、次いで窒素ガスをバブリングし、溶存酸素濃度が０．１ｍｇ／Ｌ未満になったことを確認した。これにＦｅＳＯ4・７Ｈ2Ｏ ５０．０ｇを混合し、２３±２℃でプロペラ式撹拌装置で６０分間撹拌した。このとき、スラリーのｐＨは３．７であった
６０分間撹拌した混合物をオートクレーブに入れ、２００℃で３時間加熱した。加熱中も撹拌を続けた。オートクレーブの内圧は１．５ＭＰａであった。生成した結晶をろ過し、次いで水により洗浄した。結晶を６０℃、１Torrの条件で真空乾燥した。得られた結晶をアルゴンガスに水素を３％導入した管状電気炉中で７００℃、１時間焼成し、リン酸鉄リチウムの微細粉末を得た。得られた粉末のＳＥＭ像を図３にＸＲＤチャートを図４示す。得られたリン酸鉄リチウムの粒子径は３００〜１０００ｎｍの範囲であり、高純度のリン酸鉄リチウムが得られたことが確認できた。
Example 2
16.6 g of Li 2 CO 3 , 17.6 g of H 3 PO 4 and 60.0 g of water were mixed. To this, 7.9 g of 28% aqueous ammonia and 3.0 g of starch were added, and then nitrogen gas was bubbled to confirm that the dissolved oxygen concentration was less than 0.1 mg / L. This was mixed with 50.0 g of FeSO 4 .7H 2 O and stirred at 23 ± 2 ° C. with a propeller type stirring device for 60 minutes. At this time, the pH of the slurry was 3.7. The mixture stirred for 60 minutes was placed in an autoclave and heated at 200 ° C. for 3 hours. Stirring was continued during heating. The internal pressure of the autoclave was 1.5 MPa. The formed crystals were filtered and then washed with water. The crystals were vacuum dried at 60 ° C. and 1 Torr. The obtained crystal was baked at 700 ° C. for 1 hour in a tubular electric furnace in which 3% of hydrogen was introduced into argon gas to obtain a fine powder of lithium iron phosphate. FIG. 3 shows an SEM image of the obtained powder, and FIG. 4 shows an XRD chart. The particle diameter of the obtained lithium iron phosphate was in the range of 300 to 1000 nm, and it was confirmed that high purity lithium iron phosphate was obtained.
比較例１
Ｌｉ2ＣＯ3 １０．０ｇ、Ｈ3ＰＯ4 １７．６ｇ及び水６０．０ｇを混合した。これにデンプン３．０ｇを加え、次いで窒素ガスをバブリングし、溶存酸素濃度が０．１ｍｇ／Ｌ未満になったことを確認した。これにＦｅＳＯ4・７Ｈ2Ｏ ５０．０ｇを混合し、２３±２℃でプロペラ式撹拌装置で６０分間撹拌した。このとき、スラリーのｐＨは２．１であった。
６０分間撹拌した混合物をオートクレーブに入れ、２００℃で３時間加熱した。加熱中も撹拌を続けた。オートクレーブの内圧は１．５ＭＰａであった。生成した結晶をろ過し、次いで水により洗浄した。結晶を６０℃、１Torrの条件で真空乾燥した。得られた結晶をアルゴンガスに水素を３％導入した管状電気炉中で７００℃、１時間焼成し、リン酸鉄リチウムの微細粉末を得た。得られた粉末のＳＥＭ像を図５にＸＲＤチャートを図６示す。得られたリン酸鉄リチウムの粒子径は１０００〜５０００ｎｍの範囲であり、粒子径の大きなリン酸鉄リチウムが得られた。
Comparative Example 1
Li 2 CO 3 10.0g, was mixed with H 3 PO 4 17.6 g, and water 60.0 g. To this, 3.0 g of starch was added, and then nitrogen gas was bubbled to confirm that the dissolved oxygen concentration was less than 0.1 mg / L. This was mixed with 50.0 g of FeSO 4 .7H 2 O and stirred at 23 ± 2 ° C. with a propeller type stirring device for 60 minutes. At this time, the pH of the slurry was 2.1.
The mixture stirred for 60 minutes was placed in an autoclave and heated at 200 ° C. for 3 hours. Stirring was continued during heating. The internal pressure of the autoclave was 1.5 MPa. The formed crystals were filtered and then washed with water. The crystals were vacuum dried at 60 ° C. and 1 Torr. The obtained crystal was baked at 700 ° C. for 1 hour in a tubular electric furnace in which 3% of hydrogen was introduced into argon gas to obtain a fine powder of lithium iron phosphate. FIG. 5 shows an SEM image of the obtained powder, and FIG. 6 shows an XRD chart. The particle diameter of the obtained lithium iron phosphate was in the range of 1000 to 5000 nm, and lithium iron phosphate having a large particle diameter was obtained.
参考例
Ｌｉ2ＣＯ3 １９．９ｇ、Ｈ3ＰＯ4 １７．６ｇ及び水６０．０ｇを混合した。これにカルボキシメチルセルロース６．０ｇを加え、次いで窒素ガスをバブリングし、溶存酸素濃度が０．１ｍｇ／Ｌ未満になったことを確認した。これにＦｅＳＯ4・７Ｈ2Ｏ ５０．０ｇを混合し、２３±２℃でプロペラ式撹拌装置で６０分間撹拌した。このとき、スラリーのｐＨは３．９であった
６０分間撹拌した混合物をオートクレーブに入れ、２００℃で３時間加熱した。加熱中も撹拌を続けた。オートクレーブの内圧は１．５ＭＰａであった。生成した結晶をろ過し、次いで水により洗浄した。結晶を６０℃、１Torrの条件で真空乾燥した。得られた結晶をアルゴンガスに水素を３％導入した管状電気炉中で７００℃、１時間焼成し、リン酸鉄リチウムの微細粉末を得た。得られた粉末のＳＥＭ像を図７にＸＲＤチャートを図８に示す。得られたリン酸鉄リチウムの粒子径は３００〜５００ｎｍの範囲であり、高純度のリン酸鉄リチウムが得られたことが確認できた。
Reference Example 19.9 g of Li 2 CO 3 , 17.6 g of H 3 PO 4 and 60.0 g of water were mixed. To this, 6.0 g of carboxymethylcellulose was added, and then nitrogen gas was bubbled to confirm that the dissolved oxygen concentration was less than 0.1 mg / L. This was mixed with 50.0 g of FeSO 4 .7H 2 O and stirred at 23 ± 2 ° C. with a propeller type stirring device for 60 minutes. At this time, the pH of the slurry was 3.9. The mixture stirred for 60 minutes was placed in an autoclave and heated at 200 ° C. for 3 hours. Stirring was continued during heating. The internal pressure of the autoclave was 1.5 MPa. The formed crystals were filtered and then washed with water. The crystals were vacuum dried at 60 ° C. and 1 Torr. The obtained crystal was baked at 700 ° C. for 1 hour in a tubular electric furnace in which 3% of hydrogen was introduced into argon gas to obtain a fine powder of lithium iron phosphate. FIG. 7 shows an SEM image of the obtained powder, and FIG. 8 shows an XRD chart. The particle diameter of the obtained lithium iron phosphate was in the range of 300 to 500 nm, and it was confirmed that high purity lithium iron phosphate was obtained.
実施例３
実施例１、２、比較例１及び参考例で得られた材料を正極材料に用いて電池を作製した。
実施例１、２、及び比較例１及び参考例で得られた焼成物、ケッチェンブラック（導電剤）、ポリフッ化ビニリデン（粘結剤）を重量比７５：１５：１０の配合割合で混合し、これにＮ−メチル−２−ピロリドンを加えて充分混練し、正極スラリーを調製した。正極スラリーを厚さ２０μｍのアルミニウム箔からなる集電体に塗工機を用いて塗布し、８０℃で１２時間の真空乾燥を行った。その後、φ１４ｍｍの円盤状に打ち抜いてハンドプレスを用いて１６ＭＰａで２分間プレスし、正極とした。
次いで、上記の正極を用いてコイン型リチウムイオン二次電池を構築した。負極には、φ１５ｍｍに打ち抜いたリチウム箔を用いた。電解液には、エチレンカーボネート及びエチルメチルカーボネートを体積比１：１の割合で混合した混合溶媒に、ＬＩＰＦ6を１ｍｏｌ／ｌの濃度で溶解したものを用いた。セパレータには、ポリプロピレンなどの高分子多孔フィルムなど、公知のものを用いた。これらの電池部品を露点が−５０℃以下の雰囲気で常法により組み込み収容し、コイン型リチウム二次電池（ＣＲ−２０３２）を製造した。
製造したリチウムイオン二次電池を用いて定電流密度での充放電試験を行った。このときの充電条件は電流０．１ＣＡ（１７ｍＡ／ｇ）、電圧４．２Ｖの定電流充電とし、放電条件は電流０．１ＣＡ、終止電圧２．０Ｖの定電流放電とした。温度は全て３０℃とした。
充放電試験の結果の中から放電特性を図９に示す。その結果、実施例１、２及び参考例の正極材料を用いた電池は優れた充放電容量を示したが、比較例１の材料を用い電池の充放電容量は十分でなかった。
以上の結果より、本発明方法によれば、用いるリチウム化合物の量を減らしても、微細で均一なリン酸鉄リチウムが得られる。また、得られたリン酸鉄リチウムを用いれば優れた充放電容量を示すリチウムイオン二次電池が得られる。
Example 3
Batteries were fabricated using the materials obtained in Examples 1 and 2, Comparative Example 1 and Reference Example as positive electrode materials.
The fired products obtained in Examples 1 and 2 and Comparative Example 1 and Reference Example, ketjen black (conductive agent), and polyvinylidene fluoride (binder) were mixed at a weight ratio of 75:15:10. N-methyl-2-pyrrolidone was added thereto and kneaded sufficiently to prepare a positive electrode slurry. The positive electrode slurry was applied to a current collector made of an aluminum foil having a thickness of 20 μm using a coating machine, and vacuum dried at 80 ° C. for 12 hours. Thereafter, it was punched into a disk shape of φ14 mm and pressed at 16 MPa for 2 minutes using a hand press to obtain a positive electrode.
Next, a coin-type lithium ion secondary battery was constructed using the positive electrode. A lithium foil punched to φ15 mm was used for the negative electrode. As the electrolytic solution, a solution obtained by dissolving LIPF 6 at a concentration of 1 mol / l in a mixed solvent in which ethylene carbonate and ethyl methyl carbonate were mixed at a volume ratio of 1: 1 was used. As the separator, a known one such as a polymer porous film such as polypropylene was used. These battery components were assembled and housed in a conventional manner in an atmosphere with a dew point of −50 ° C. or lower to produce a coin-type lithium secondary battery (CR-2032).
A charge / discharge test at a constant current density was performed using the manufactured lithium ion secondary battery. Charging conditions at this time were constant current charging with a current of 0.1 CA (17 mA / g) and a voltage of 4.2 V, and discharging conditions were constant current discharging with a current of 0.1 CA and a final voltage of 2.0 V. All temperatures were 30 ° C.
FIG. 9 shows the discharge characteristics from the results of the charge / discharge test. As a result, the batteries using the positive electrode materials of Examples 1 and 2 and the reference example showed excellent charge / discharge capacity, but the charge / discharge capacity of the battery using the material of Comparative Example 1 was not sufficient.
From the above results, according to the method of the present invention, fine and uniform lithium iron phosphate can be obtained even if the amount of the lithium compound used is reduced. Moreover, if the obtained lithium iron phosphate is used, the lithium ion secondary battery which shows the outstanding charging / discharging capacity | capacitance will be obtained.
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