JP5478693B2 - Positive electrode active material for secondary battery and method for producing the same - Google Patents
Positive electrode active material for secondary battery and method for producing the same Download PDFInfo
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- 239000007774 positive electrode material Substances 0.000 title claims description 40
- 238000004519 manufacturing process Methods 0.000 title claims description 11
- -1 silicate compound Chemical class 0.000 claims description 63
- 239000002131 composite material Substances 0.000 claims description 57
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 53
- 239000002245 particle Substances 0.000 claims description 49
- 229910052799 carbon Inorganic materials 0.000 claims description 44
- 239000011164 primary particle Substances 0.000 claims description 20
- 229910004283 SiO 4 Inorganic materials 0.000 claims description 14
- 239000010450 olivine Substances 0.000 claims description 13
- 229910052609 olivine Inorganic materials 0.000 claims description 13
- 239000011163 secondary particle Substances 0.000 claims description 9
- 238000002156 mixing Methods 0.000 claims description 7
- 239000000203 mixture Substances 0.000 claims description 6
- 238000010008 shearing Methods 0.000 claims description 6
- 230000002093 peripheral effect Effects 0.000 claims description 5
- 239000006229 carbon black Substances 0.000 claims description 3
- 239000006182 cathode active material Substances 0.000 claims 2
- 239000006185 dispersion Substances 0.000 description 17
- 239000011248 coating agent Substances 0.000 description 16
- 238000000576 coating method Methods 0.000 description 16
- 229910052723 transition metal Inorganic materials 0.000 description 13
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 11
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 11
- 229910001416 lithium ion Inorganic materials 0.000 description 11
- WMFOQBRAJBCJND-UHFFFAOYSA-M Lithium hydroxide Chemical compound [Li+].[OH-] WMFOQBRAJBCJND-UHFFFAOYSA-M 0.000 description 10
- 230000000052 comparative effect Effects 0.000 description 10
- 239000007788 liquid Substances 0.000 description 10
- 238000001027 hydrothermal synthesis Methods 0.000 description 9
- 238000000034 method Methods 0.000 description 9
- 238000003917 TEM image Methods 0.000 description 8
- 229910052782 aluminium Inorganic materials 0.000 description 8
- 239000003963 antioxidant agent Substances 0.000 description 8
- 230000003078 antioxidant effect Effects 0.000 description 8
- 150000002642 lithium compounds Chemical class 0.000 description 8
- 238000001878 scanning electron micrograph Methods 0.000 description 8
- 229910000385 transition metal sulfate Inorganic materials 0.000 description 8
- 150000003624 transition metals Chemical class 0.000 description 8
- 230000000704 physical effect Effects 0.000 description 7
- 239000000843 powder Substances 0.000 description 7
- 239000011734 sodium Substances 0.000 description 7
- 239000000243 solution Substances 0.000 description 7
- 239000011230 binding agent Substances 0.000 description 6
- 229910052742 iron Inorganic materials 0.000 description 6
- 239000003273 ketjen black Substances 0.000 description 6
- 229910052759 nickel Inorganic materials 0.000 description 6
- 150000007524 organic acids Chemical group 0.000 description 6
- 238000007086 side reaction Methods 0.000 description 6
- 238000007599 discharging Methods 0.000 description 5
- 239000008151 electrolyte solution Substances 0.000 description 5
- 230000001965 increasing effect Effects 0.000 description 5
- 229910052744 lithium Inorganic materials 0.000 description 5
- 150000003839 salts Chemical class 0.000 description 5
- 150000004760 silicates Chemical class 0.000 description 5
- 229910052720 vanadium Inorganic materials 0.000 description 5
- 229910052725 zinc Inorganic materials 0.000 description 5
- 229910052726 zirconium Inorganic materials 0.000 description 5
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 4
- 238000007600 charging Methods 0.000 description 4
- 238000006243 chemical reaction Methods 0.000 description 4
- 239000011888 foil Substances 0.000 description 4
- 229910052748 manganese Inorganic materials 0.000 description 4
- 239000000463 material Substances 0.000 description 4
- QTBSBXVTEAMEQO-UHFFFAOYSA-N Acetic acid Chemical compound CC(O)=O QTBSBXVTEAMEQO-UHFFFAOYSA-N 0.000 description 3
- MUBZPKHOEPUJKR-UHFFFAOYSA-N Oxalic acid Chemical compound OC(=O)C(O)=O MUBZPKHOEPUJKR-UHFFFAOYSA-N 0.000 description 3
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 3
- 239000006230 acetylene black Substances 0.000 description 3
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 3
- 239000003575 carbonaceous material Substances 0.000 description 3
- 239000003795 chemical substances by application Substances 0.000 description 3
- 238000001035 drying Methods 0.000 description 3
- 239000010419 fine particle Substances 0.000 description 3
- 239000003960 organic solvent Substances 0.000 description 3
- 229920000642 polymer Polymers 0.000 description 3
- 239000011541 reaction mixture Substances 0.000 description 3
- 239000007787 solid Substances 0.000 description 3
- VZCYOOQTPOCHFL-OWOJBTEDSA-N Fumaric acid Chemical compound OC(=O)\C=C\C(O)=O VZCYOOQTPOCHFL-OWOJBTEDSA-N 0.000 description 2
- 229910010707 LiFePO 4 Inorganic materials 0.000 description 2
- BPQQTUXANYXVAA-UHFFFAOYSA-N Orthosilicate Chemical compound [O-][Si]([O-])([O-])[O-] BPQQTUXANYXVAA-UHFFFAOYSA-N 0.000 description 2
- 239000002033 PVDF binder Substances 0.000 description 2
- 241000282320 Panthera leo Species 0.000 description 2
- 239000004743 Polypropylene Substances 0.000 description 2
- MCMNRKCIXSYSNV-UHFFFAOYSA-N Zirconium dioxide Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 description 2
- 238000010521 absorption reaction Methods 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 125000004432 carbon atom Chemical group C* 0.000 description 2
- 239000011267 electrode slurry Substances 0.000 description 2
- 230000002708 enhancing effect Effects 0.000 description 2
- 239000010439 graphite Substances 0.000 description 2
- 229910002804 graphite Inorganic materials 0.000 description 2
- 230000006872 improvement Effects 0.000 description 2
- 239000011261 inert gas Substances 0.000 description 2
- 229910017053 inorganic salt Inorganic materials 0.000 description 2
- JVTAAEKCZFNVCJ-UHFFFAOYSA-N lactic acid Chemical compound CC(O)C(O)=O JVTAAEKCZFNVCJ-UHFFFAOYSA-N 0.000 description 2
- XGZVUEUWXADBQD-UHFFFAOYSA-L lithium carbonate Chemical compound [Li+].[Li+].[O-]C([O-])=O XGZVUEUWXADBQD-UHFFFAOYSA-L 0.000 description 2
- 229920001155 polypropylene Polymers 0.000 description 2
- 229920002981 polyvinylidene fluoride Polymers 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- 235000012239 silicon dioxide Nutrition 0.000 description 2
- GEHJYWRUCIMESM-UHFFFAOYSA-L sodium sulfite Chemical compound [Na+].[Na+].[O-]S([O-])=O GEHJYWRUCIMESM-UHFFFAOYSA-L 0.000 description 2
- 239000002904 solvent Substances 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 description 1
- 238000012935 Averaging Methods 0.000 description 1
- 229920002134 Carboxymethyl cellulose Polymers 0.000 description 1
- KMTRUDSVKNLOMY-UHFFFAOYSA-N Ethylene carbonate Chemical compound O=C1OCCO1 KMTRUDSVKNLOMY-UHFFFAOYSA-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
- 229910014689 LiMnO 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
- 229910013870 LiPF 6 Inorganic materials 0.000 description 1
- 229910012424 LiSO 3 Inorganic materials 0.000 description 1
- 241000080590 Niso Species 0.000 description 1
- 239000004698 Polyethylene Substances 0.000 description 1
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 description 1
- QSNQXZYQEIKDPU-UHFFFAOYSA-N [Li].[Fe] Chemical compound [Li].[Fe] QSNQXZYQEIKDPU-UHFFFAOYSA-N 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
- 238000004220 aggregation Methods 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- QGZKDVFQNNGYKY-UHFFFAOYSA-N ammonia Natural products N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 1
- 229910003481 amorphous carbon Inorganic materials 0.000 description 1
- 229910021383 artificial graphite Inorganic materials 0.000 description 1
- BVKZGUZCCUSVTD-UHFFFAOYSA-N carbonic acid Chemical class OC(O)=O BVKZGUZCCUSVTD-UHFFFAOYSA-N 0.000 description 1
- 150000004649 carbonic acid derivatives Chemical class 0.000 description 1
- 238000003763 carbonization Methods 0.000 description 1
- 239000001768 carboxy methyl cellulose Substances 0.000 description 1
- 235000010948 carboxy methyl cellulose Nutrition 0.000 description 1
- 239000008112 carboxymethyl-cellulose Substances 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 239000006231 channel black Substances 0.000 description 1
- 239000011246 composite particle Substances 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 239000002482 conductive additive Substances 0.000 description 1
- 239000006258 conductive agent Substances 0.000 description 1
- 238000010280 constant potential charging Methods 0.000 description 1
- 238000010277 constant-current charging Methods 0.000 description 1
- 238000000151 deposition Methods 0.000 description 1
- 150000001991 dicarboxylic acids Chemical class 0.000 description 1
- 235000014113 dietary fatty acids Nutrition 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
- 238000002296 dynamic light scattering Methods 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
- 239000000194 fatty acid Substances 0.000 description 1
- 229930195729 fatty acid Natural products 0.000 description 1
- 150000004665 fatty acids Chemical class 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 238000010304 firing Methods 0.000 description 1
- 238000004108 freeze drying Methods 0.000 description 1
- 239000001530 fumaric acid Substances 0.000 description 1
- 239000006232 furnace black Substances 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 150000008282 halocarbons Chemical class 0.000 description 1
- 238000009830 intercalation Methods 0.000 description 1
- 150000002576 ketones Chemical class 0.000 description 1
- 239000004310 lactic acid Substances 0.000 description 1
- 235000014655 lactic acid Nutrition 0.000 description 1
- 150000002596 lactones Chemical class 0.000 description 1
- 239000006233 lamp black Substances 0.000 description 1
- XIXADJRWDQXREU-UHFFFAOYSA-M lithium acetate Chemical compound [Li+].CC([O-])=O XIXADJRWDQXREU-UHFFFAOYSA-M 0.000 description 1
- 229910052808 lithium carbonate Inorganic materials 0.000 description 1
- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical compound [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 description 1
- 229910021450 lithium metal oxide Inorganic materials 0.000 description 1
- INHCSSUBVCNVSK-UHFFFAOYSA-L lithium sulfate Inorganic materials [Li+].[Li+].[O-]S([O-])(=O)=O INHCSSUBVCNVSK-UHFFFAOYSA-L 0.000 description 1
- 239000012046 mixed solvent Substances 0.000 description 1
- 229910021382 natural graphite Inorganic materials 0.000 description 1
- 239000007773 negative electrode material Substances 0.000 description 1
- 150000002825 nitriles Chemical class 0.000 description 1
- 239000011255 nonaqueous electrolyte Substances 0.000 description 1
- 235000005985 organic acids Nutrition 0.000 description 1
- 235000006408 oxalic acid Nutrition 0.000 description 1
- 229920000573 polyethylene Polymers 0.000 description 1
- 229920000098 polyolefin Polymers 0.000 description 1
- 229920001343 polytetrafluoroethylene Polymers 0.000 description 1
- 239000004810 polytetrafluoroethylene Substances 0.000 description 1
- 229920000915 polyvinyl chloride Polymers 0.000 description 1
- 239000004800 polyvinyl chloride Substances 0.000 description 1
- 238000010298 pulverizing process Methods 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 230000035484 reaction time Effects 0.000 description 1
- 238000010079 rubber tapping Methods 0.000 description 1
- 238000004904 shortening Methods 0.000 description 1
- 239000000377 silicon dioxide Substances 0.000 description 1
- JVBXVOWTABLYPX-UHFFFAOYSA-L sodium dithionite Chemical compound [Na+].[Na+].[O-]S(=O)S([O-])=O JVBXVOWTABLYPX-UHFFFAOYSA-L 0.000 description 1
- 235000010265 sodium sulphite Nutrition 0.000 description 1
- 238000010532 solid phase synthesis reaction Methods 0.000 description 1
- 239000003381 stabilizer Substances 0.000 description 1
- 229920003002 synthetic resin Polymers 0.000 description 1
- 239000000057 synthetic resin Substances 0.000 description 1
- RBTVSNLYYIMMKS-UHFFFAOYSA-N tert-butyl 3-aminoazetidine-1-carboxylate;hydrochloride Chemical compound Cl.CC(C)(C)OC(=O)N1CC(N)C1 RBTVSNLYYIMMKS-UHFFFAOYSA-N 0.000 description 1
- 239000006234 thermal black Substances 0.000 description 1
- VZCYOOQTPOCHFL-UHFFFAOYSA-N trans-butenedioic acid Natural products OC(=O)C=CC(O)=O VZCYOOQTPOCHFL-UHFFFAOYSA-N 0.000 description 1
- 229910021642 ultra pure water Inorganic materials 0.000 description 1
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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、二次電池用正極活物質及びその製造方法に関する。 The present invention relates to a positive electrode active material for a secondary battery and a method for producing the same.
リチウムイオン電池等の二次電池は、非水電解質電池の１種であり、携帯電話、デジタルカメラ、ノートＰＣ、ハイブリッド自動車、電気自動車等広い分野に利用されている。リチウムイオン電池は、正極材料としてリチウム金属酸化物を用い、負極材料としてグラファイトなどの炭素材を用いるものが主流となっている。 A secondary battery such as a lithium ion battery is a kind of non-aqueous electrolyte battery, and is used in a wide range of fields such as a mobile phone, a digital camera, a notebook PC, a hybrid vehicle, and an electric vehicle. Lithium ion batteries mainly use lithium metal oxide as a positive electrode material and a carbon material such as graphite as a negative electrode material.
この正極材料としては、コバルト酸リチウム（ＬｉＣｏＯ2）、マンガン酸リチウム（ＬｉＭｎＯ2）、リン酸鉄リチウム（ＬｉＦｅＰＯ4）、ケイ酸鉄リチウム（Ｌｉ2ＦｅＳｉＯ4）等が知られている。このうち、ＬｉＦｅＰＯ4やＬｉ2ＦｅＳｉＯ4等は、オリビン構造を有し、高容量のリチウムイオン電池用正極材料として有用であり、特にＬｉ2ＦｅＳｉＯ4等のいわゆるオリビン型シリケート化合物は、優れた正極材料として注目を浴びている。 As this positive electrode material, lithium cobaltate (LiCoO 2 ), lithium manganate (LiMnO 2 ), lithium iron phosphate (LiFePO 4 ), lithium iron silicate (Li 2 FeSiO 4 ) and the like are known. Among these, LiFePO 4 and Li 2 FeSiO 4 have an olivine structure and are useful as positive electrode materials for high-capacity lithium ion batteries. In particular, so-called olivine-type silicate compounds such as Li 2 FeSiO 4 are excellent positive electrodes. It is attracting attention as a material.
これらオリビン型シリケート化合物を用いて二次電池を製造するには、かかるオリビン型シリケート化合物をバインダー溶液とともに混合して塗工液を調製し、得られた塗工液をアルミ箔等の正極集電体上に塗布した後、乾燥工程等を経ることにより正極を得る。この際、オリビン型シリケート化合物は、そのもの単独では導電性が低いため、二次電池の正極材料として用いるには、予めこれに導電性を付与する処理を施す。 In order to manufacture a secondary battery using these olivine-type silicate compounds, the olivine-type silicate compound is mixed with a binder solution to prepare a coating solution, and the resulting coating solution is used as a positive electrode current collector such as an aluminum foil. After coating on the body, a positive electrode is obtained through a drying process and the like. At this time, since the olivine silicate compound itself has low conductivity, in order to use it as a positive electrode material for a secondary battery, a treatment for imparting conductivity to the olivine type silicate compound is performed in advance.
オリビン型シリケート化合物に導電性を付与する処理としては、例えば、特許文献１には、炭素源となる有機物をオリビン型シリケート化合物のような正極材料表面に堆積させ、炭化処理をする方法が開示されている。また、特許文献２には、正極材料とカーボンブラック等の導電性物質とを、遊星ボールミルを用いて粉砕・混合し、正極材料として用い得る複合体粒子を得る方法が開示されている。 As a treatment for imparting conductivity to an olivine-type silicate compound, for example, Patent Document 1 discloses a method of depositing an organic substance serving as a carbon source on the surface of a positive electrode material such as an olivine-type silicate compound and performing a carbonization treatment. ing. Patent Document 2 discloses a method of obtaining composite particles that can be used as a positive electrode material by pulverizing and mixing a positive electrode material and a conductive substance such as carbon black using a planetary ball mill.
しかしながら、塗工液を調製する際、上記文献に記載のような方法によって得られる正極材料を用いると、粒子の比表面積が高い上にタップ密度も低いため、粒子の凝集化が進行して塗工液中での分散性が低下する傾向にある。また、バインダーの吸収量が増大するため、塗工液中での固形分濃度を十分に高めることができない傾向にある。このような塗工液を用いるのでは、依然として得られる電池性能の向上を期待することができないため、良好な導電性が付与されてなるとともに、電池性能を十分に高めることのできる正極材料の実現が望まれている。 However, when preparing a coating liquid, if a positive electrode material obtained by a method as described in the above document is used, the particle surface area is high and the tap density is low. The dispersibility in the working liquid tends to decrease. Moreover, since the absorption amount of the binder increases, the solid content concentration in the coating liquid tends not to be sufficiently increased. By using such a coating solution, it is not possible to expect an improvement in battery performance that can still be obtained, so that good conductivity is imparted and a positive electrode material that can sufficiently enhance battery performance is realized. Is desired.
したがって、本発明の課題は、オリビン型シリケート化合物を用いつつ、優れた導電性を有するとともに、電池性能をも十分に高めることのできる正極材料を提供することにある。 Therefore, the subject of this invention is providing the positive electrode material which can fully improve battery performance while having the outstanding electroconductivity, using an olivine type | mold silicate compound.
そこで本発明者らは、特定の平均粒径を有するオリビン型シリケート化合物と導電性炭素とを用いて、高い嵩密度と特定の平均粒径とを有する複合体を得れば、電池性能を十分に高めることのできる正極材料として用いることができることを見出し、本発明を完成させるに至った。 Therefore, the present inventors have sufficient battery performance if a composite having a high bulk density and a specific average particle size is obtained using an olivine-type silicate compound having a specific average particle size and conductive carbon. The present invention has been completed by finding that it can be used as a positive electrode material that can be improved.
すなわち、本発明は、２０〜２００ｎｍの平均粒径Ｘを有する一次粒子であるオリビン型シリケート化合物、及び平均粒径Ｘ以下の平均粒径Ｙを有する導電性炭素から得られ、
タップ密度が０．８〜２．５ｇ／ｃｍ3であり、かつ
５〜５０μｍの平均粒径Ｚを有する二次粒子であることを特徴とする、二次電池用正極活物質複合体を提供するものである。
That is, the present invention is obtained from an olivine-type silicate compound that is a primary particle having an average particle diameter X of 20 to 200 nm, and conductive carbon having an average particle diameter Y equal to or less than the average particle diameter X.
Provided is a positive electrode active material composite for a secondary battery, which is a secondary particle having a tap density of 0.8 to 2.5 g / cm 3 and an average particle size Z of 5 to 50 μm. Is.
また、本発明は、２０〜２００ｎｍの平均粒径Ｘを有する一次粒子であるオリビン型シリケート化合物、及び平均粒径Ｘ以下の平均粒径Ｙを有する導電性炭素を、周速２５〜４０ｍ／ｓで回転するインペラを備える密閉容器内に投入して、圧縮力及びせん断力を付加しながら混合することを特徴とする、上記二次電池用正極活物質複合体の製造方法を提供するものである。 The present invention also provides an olivine-type silicate compound, which is a primary particle having an average particle diameter X of 20 to 200 nm, and conductive carbon having an average particle diameter Y equal to or less than the average particle diameter X, at a peripheral speed of 25 to 40 m / s. The method for producing a positive electrode active material composite for a secondary battery is provided, wherein the mixture is introduced into a closed container having an impeller rotating at a time and mixed while applying a compressive force and a shearing force. .
本発明の二次電池用正極活物質複合体は、オリビン型シリケート化合物と導電性炭素とが極めて均一に分散されてなる空隙が低減された二次粒子であるため、かかる粒子間の凝集を抑制しながら塗工液中での分散性を高めることができるとともに、バインダーの吸収量を低減して塗工液中での固形分濃度を十分に高めることもできる。したがって、得られる二次電池において、電池物性の向上を図ることが可能となる。 The positive electrode active material composite for a secondary battery according to the present invention is a secondary particle with reduced voids in which an olivine-type silicate compound and conductive carbon are dispersed extremely uniformly, thereby suppressing aggregation between the particles. While dispersibility in a coating liquid can be improved, the amount of absorption of a binder can be reduced and solid content concentration in a coating liquid can also be fully raised. Therefore, in the obtained secondary battery, it is possible to improve battery physical properties.
以下、本発明について詳細に説明する。
本発明で用いるオリビン型シリケート化合物は、２０〜２００ｎｍの平均粒径Ｘを有する一次粒子である。このような微細な粒子を有するオリビン型シリケート化合物を一次粒子として用いることにより、かかる粒子と粒子の間隙に後述する平均粒径Ｙを有する導電性炭素が効率的に配置されて、空隙が低減された均一な二次粒子、すなわち二次電池用正極活物質複合体を得ることができる。
Hereinafter, the present invention will be described in detail.
The olivine-type silicate compound used in the present invention is primary particles having an average particle diameter X of 20 to 200 nm. By using the olivine-type silicate compound having such fine particles as the primary particles, conductive carbon having an average particle diameter Y, which will be described later, is efficiently arranged in the gap between the particles and the voids are reduced. Uniform secondary particles, that is, a positive electrode active material composite for a secondary battery can be obtained.
オリビン型シリケート化合物が有する平均粒径Ｘは、複合体の均一性を高めて得られる電池物性の向上を図る観点から、２０〜２００ｎｍであって、好ましくは２０〜１５０ｎｍであり、より好ましくは２０〜１００ｎｍである。なお、かかる平均粒径Ｘは、試料を溶媒によって均一分散させ、動的光散乱法の粒度分析計（ナノトラックUPA-EX150、日機装株式会社製）により測定される値を意味する。 The average particle size X of the olivine-type silicate compound is 20 to 200 nm, preferably 20 to 150 nm, more preferably 20 from the viewpoint of improving battery properties obtained by increasing the uniformity of the composite. ~ 100 nm. The average particle diameter X means a value measured by a dynamic light scattering particle size analyzer (Nanotrack UPA-EX150, manufactured by Nikkiso Co., Ltd.) after uniformly dispersing the sample with a solvent.
オリビン型シリケート化合物としては、遷移金属Ｍ（Ｍは、Ｆｅ、Ｎｉ、Ｃｏ、Ａｌ、Ｚｎ、Ｖ、Ｚｒ又はＭｎを示す）を含むのが好ましい。かかる遷移金属Ｍを含むオリビン型シリケート化合物は、具体的には下記式（１）〜（５）のいずれかで表わされる。
Ｌｉ2Ｍ'ＳｉＯ4 ・・・（１）
（式中、Ｍ'はＦｅ、Ｎｉ、Ｃｏ及びＭｎから選ばれる１種又は２種以上を示す。）
Ｌｉa'ＦｅxＭｎyＡｌzＳｉＯ4 ・・・（２）
（式中、ａ'、ｘ、ｙ及びｚは、１＜ａ'≦２、０≦ｘ＜１、０≦ｙ＜１、０＜ｚ＜２／３、ａ'＋２ｘ＋２ｙ＋３ｚ＝４、及びｘ＋ｙ≠０を満たす数を示す。）
Ｌｉa"ＦｅxＭｎyＶz'ＳｉＯ4 ・・・（３）
（式中、ａ"、ｘ、ｙ及びｚ'は、１＜ａ"≦２、０≦ｘ＜１、０≦ｙ＜１、０＜ｚ'＜１、ａ"＋２ｘ＋２ｙ＋（２〜５）ｚ'＝４、及びｘ＋ｙ≠０を満たす数を示す。）
Ｌｉa"ＦｅxＭｎyＺｒz"ＳｉＯ4 ・・・（４）
（式中、ａ"、ｘ、ｙ及びｚ"は、１＜ａ"≦２、０≦ｘ＜１、０≦ｙ＜１、０＜ｚ"＜０．５、ａ"＋２ｘ＋２ｙ＋４ｚ"＝４、及びｘ＋ｙ≠０を満たす数を示す。）
Ｌｉ2ＦｅxＭｎyＺｎqＳｉＯ4 ・・・（５）
（式中、ｘ、ｙ及びｑは、０≦ｘ＜１、０≦ｙ＜１、０＜ｑ＜１、ｘ＋ｙ＋ｑ＝１、及びｘ＋ｙ≠０を満たす数を示す。）
The olivine-type silicate compound preferably contains a transition metal M (M represents Fe, Ni, Co, Al, Zn, V, Zr or Mn). The olivine-type silicate compound containing such a transition metal M is specifically represented by any of the following formulas (1) to (5).
Li 2 M'SiO 4 (1)
(In the formula, M ′ represents one or more selected from Fe, Ni, Co and Mn.)
Li a 'Fe x Mn y Al z SiO 4 ··· (2)
(Where, a ′, x, y and z are 1 <a ′ ≦ 2, 0 ≦ x <1, 0 ≦ y <1, 0 <z <2/3, a ′ + 2x + 2y + 3z = 4, and x + y ≠ Indicates a number satisfying 0.)
Li a "Fe x Mn y V z 'SiO 4 ··· (3)
(Where a " , x, y and z 'are 1 <a " ≤2, 0≤x <1, 0≤y <1, 0 <z'<1, a " + 2x + 2y + (2-5) z '= 4 and a number satisfying x + y ≠ 0.)
Li a "Fe x Mn y Zr z" SiO 4 ··· (4)
(Where a " , x, y and z " are 1 <a " ≤2, 0≤x <1, 0≤y <1, 0 <z " <0.5, a " + 2x + 2y + 4z " = 4, And a number satisfying x + y ≠ 0.)
Li 2 Fe x Mn y Zn q SiO 4 ··· (5)
(In the formula, x, y, and q represent numbers satisfying 0 ≦ x <1, 0 ≦ y <1, 0 <q <1, x + y + q = 1, and x + y ≠ 0.)
上記オリビン型シリケート化合物は、例えば、遷移金属（Ｍ）源として、ＭＳＯ4（式中、Ｍは、Ｆｅ、Ｎｉ、Ｃｏ、Ａｌ、Ｚｎ、Ｖ、Ｚｒ又はＭｎを示す）で表される遷移金属硫酸塩又は（Ｒ）2Ｍ（式中、Ｒは有機酸残基を示し、Ｍは、Ｆｅ、Ｎｉ、Ｃｏ、Ａｌ、Ｚｎ、Ｖ、Ｚｒ又はＭｎを示す）で表される有機酸遷移金属塩を用い、リチウム化合物、ケイ酸化合物及び酸化防止剤を含有する塩基性水分散液を水熱反応させることにより製造することができる。 The olivine-type silicate compound is, for example, a transition metal represented by MSO 4 (wherein M represents Fe, Ni, Co, Al, Zn, V, Zr, or Mn) as a transition metal (M) source. Organic acid transition metal represented by sulfate or (R) 2 M (wherein R represents an organic acid residue, M represents Fe, Ni, Co, Al, Zn, V, Zr or Mn) It can be produced by hydrothermal reaction of a basic aqueous dispersion containing a lithium compound, a silicate compound and an antioxidant, using a salt.
リチウム化合物としては、水酸化リチウム（例えばＬｉＯＨ・Ｈ2Ｏ）、炭酸リチウム（Ｌｉ2ＣＯ3）、硫酸リチウム、酢酸リチウムが挙げられるが、水酸化リチウム、炭酸リチウムが特に好ましい。水分散液中のリチウム化合物の濃度は、０．３０〜３．００ｍｏｌ／ｌが好ましく、さらに１．００〜１．５０ｍｏｌ／ｌが好ましい。 Examples of the lithium compound include lithium hydroxide (for example, LiOH.H 2 O), lithium carbonate (Li 2 CO 3 ), lithium sulfate, and lithium acetate, and lithium hydroxide and lithium carbonate are particularly preferable. The concentration of the lithium compound in the aqueous dispersion is preferably 0.30 to 3.00 mol / l, more preferably 1.00 to 1.50 mol / l.
ケイ酸化合物としては、反応性のあるシリカ化合物であれば特に限定されず、非晶質シリカ、Ｎａ4ＳｉＯ4（例えばＮａ4ＳｉＯ4・Ｈ2Ｏ）が好ましい。このうちＮａ4ＳｉＯ4を用いた場合、水分散液が塩基性になるので、より好ましい。水分散液中のケイ酸化合物の濃度は、０．１５〜１.５０ｍｏｌ／ｌが好ましく、さらに０．５０〜０．７５ｍｏｌ／ｌが好ましい。 The silicic acid compound is not particularly limited as long as it is a reactive silica compound, and amorphous silica and Na 4 SiO 4 (for example, Na 4 SiO 4 .H 2 O) are preferable. Of these, the use of Na 4 SiO 4 is more preferable because the aqueous dispersion becomes basic. The concentration of the silicate compound in the aqueous dispersion is preferably 0.15 to 1.50 mol / l, more preferably 0.50 to 0.75 mol / l.
さらに、この分散液には副反応を防止する点から、酸化防止剤を添加することが好ましい。酸化防止剤としては、ハイドロサルファイトナトリウム（Ｎａ2Ｓ2Ｏ4）、アンモニア水、亜硫酸ナトリウム等を使用することができる。水分散液中の酸化防止剤の含有量は、多量に添加するとオリビン型シリケート化合物の生成を抑制してしまうため、遷移金属（Ｍ）に対して等モル量以下が好ましく、遷移金属（Ｍ）に対してモル比で０．５以下がさらに好ましい。 Furthermore, it is preferable to add an antioxidant to the dispersion from the viewpoint of preventing side reactions. As the antioxidant, hydrosulfite sodium (Na 2 S 2 O 4 ), aqueous ammonia, sodium sulfite and the like can be used. The content of the antioxidant in the aqueous dispersion is preferably equal to or less than the transition metal (M) because the formation of the olivine-type silicate compound is suppressed when added in a large amount. More preferably, the molar ratio is 0.5 or less.
遷移金属源として遷移金属硫酸塩ＭＳＯ4（式中、Ｍは、Ｆｅ、Ｎｉ、Ｃｏ、Ａｌ、Ｚｎ、Ｖ、Ｚｒ又はＭｎを示す）を用いる場合、副反応を抑制する点から、遷移金属硫酸塩とは別に、リチウム化合物及びケイ酸化合物を含有する塩基性水分散液を予め調製しておくのが好ましい。この場合、該水分散液と遷移金属硫酸塩及び酸化防止剤とを混合し、水熱反応に付す。該水分散液の調製にあたって、リチウム化合物及びケイ酸化合物の添加順序は特に限定されず、これらの２成分を同時に水に添加してもよい。 When transition metal sulfate MSO 4 (wherein M represents Fe, Ni, Co, Al, Zn, V, Zr or Mn) is used as the transition metal source, transition metal sulfate from the viewpoint of suppressing side reactions. Apart from the salt, a basic aqueous dispersion containing a lithium compound and a silicate compound is preferably prepared in advance. In this case, the aqueous dispersion, transition metal sulfate and antioxidant are mixed and subjected to a hydrothermal reaction. In preparing the aqueous dispersion, the order of addition of the lithium compound and the silicate compound is not particularly limited, and these two components may be simultaneously added to water.
遷移金属硫酸塩ＭＳＯ4の具体例としては、ＦｅＳＯ4、ＮｉＳＯ4、ＣｏＳＯ4、Ａｌ2（ＳＯ4）3、ＺｎＳＯ4、Ｖ2（ＳＯ4）3、Ｚｒ（ＳＯ4）2又はＭｎＳＯ4が挙げられ、これらは１種でも２種以上を混合して用いてもよい。これらのうち、ＦｅＳＯ4、ＭｎＳＯ4がより好ましく、ＦｅＳＯ4がさらに好ましい。遷移金属硫酸塩を用いる場合、副反応を抑制する点から、遷移金属硫酸塩とは別に、リチウム化合物及びケイ酸化合物を含有する塩基性水分散液を予め調製しておくのが好ましい。この場合、該水分散液と遷移金属硫酸塩及び酸化防止剤とを混合し、水熱反応に付す。遷移金属硫酸塩の添加量は、反応混合液中０．１５〜１.５０ｍｏｌ／ｌとなる量が好ましく、さらに０．５０〜０．７５ｍｏｌ／ｌとなる量が好ましい。
なお、この場合における反応混合液中のＬｉの含有量は、Ｍに対して２モル以上が好ましい。
Specific examples of the transition metal sulfate MSO 4 include FeSO 4 , NiSO 4 , CoSO 4 , Al 2 (SO 4 ) 3 , ZnSO 4 , V 2 (SO 4 ) 3 , Zr (SO 4 ) 2 or MnSO 4. These may be used alone or in combination of two or more. Of these, FeSO 4 and MnSO 4 are more preferable, and FeSO 4 is more preferable. In the case of using a transition metal sulfate, it is preferable to prepare a basic aqueous dispersion containing a lithium compound and a silicate compound separately from the transition metal sulfate in terms of suppressing side reactions. In this case, the aqueous dispersion, transition metal sulfate and antioxidant are mixed and subjected to a hydrothermal reaction. The amount of transition metal sulfate added is preferably 0.15 to 1.50 mol / l in the reaction mixture, and more preferably 0.50 to 0.75 mol / l.
In this case, the Li content in the reaction mixture is preferably 2 mol or more with respect to M.
遷移金属源として有機酸遷移金属塩（Ｒ）2Ｍ（式中、Ｒは有機酸残基を示し、Ｍは、Ｆｅ、Ｎｉ、Ｃｏ、Ａｌ、Ｚｎ、Ｖ、Ｚｒ又はＭｎを示す）を用いる場合には、リチウム化合物、ケイ酸化合物及び酸化防止剤を含有し、さらに有機酸遷移金属塩を含有する塩基性水分散液を調製する。この場合、リチウム化合物、ケイ酸化合物、酸化防止剤及び有機酸遷移金属塩の添加順序は特に限定されない。また、大気条件下でもよい。通常、有機酸塩は固相法に用いられる原料であるが、水熱反応に用いることにより副反応を抑制することができる。
なお、この場合における反応混合液中のＬｉは、遷移金属に対してモル比で２倍以上用いることが好ましく、Ｌｉ：Ｍが２．５：１〜３：１程度がより好ましい。
An organic acid transition metal salt (R) 2 M (wherein R represents an organic acid residue, and M represents Fe, Ni, Co, Al, Zn, V, Zr, or Mn) is used as a transition metal source. In some cases, a basic aqueous dispersion containing a lithium compound, a silicate compound and an antioxidant and further containing an organic acid transition metal salt is prepared. In this case, the order of addition of the lithium compound, silicic acid compound, antioxidant and organic acid transition metal salt is not particularly limited. Moreover, atmospheric conditions may be sufficient. Usually, an organic acid salt is a raw material used in a solid phase method, but side reactions can be suppressed by using it in a hydrothermal reaction.
In this case, Li in the reaction mixture is preferably used in a molar ratio of 2 times or more with respect to the transition metal, and Li: M is more preferably about 2.5: 1 to 3: 1.
有機酸遷移金属塩（Ｒ）2ＭのＲで示される有機酸としては、炭素数１〜２０の有機酸が好ましく、炭素数２〜１２の有機酸がより好ましい。より具体的な有機酸としては、シュウ酸、フマル酸等のジカルボン酸、乳酸等のヒドロキシカルボン酸、酢酸等の脂肪酸が挙げられる。 The organic acid represented by an organic acid transition metal salt (R) of 2 M R, preferably an organic acid having 1 to 20 carbon atoms, more preferably an organic acid having 2 to 12 carbon atoms. More specific organic acids include dicarboxylic acids such as oxalic acid and fumaric acid, hydroxycarboxylic acids such as lactic acid, and fatty acids such as acetic acid.
該水分散液は塩基性とするのが、副反応を防止し、ケイ酸化合物を溶解するうえで重要である。具体的には、該水分散液のｐＨが１２．０〜１３．５であるのが副反応（Ｆｅ3Ｏ4の生成）の防止、ケイ酸化合物の溶解性及び反応の進行の点で特に好ましい。該水分散液のｐＨの調整は、塩基、例えば、水酸化ナトリウムを添加することにより行ってもよいが、ケイ酸化合物としてＮａ4ＳｉＯ4を用いるのが特に好ましい。 Making the aqueous dispersion basic is important in preventing side reactions and dissolving the silicate compound. Specifically, the pH of the aqueous dispersion is 12.0 to 13.5, particularly in terms of preventing side reactions (formation of Fe 3 O 4 ), solubility of silicate compounds, and progress of the reaction. preferable. The pH of the aqueous dispersion may be adjusted by adding a base such as sodium hydroxide, but it is particularly preferable to use Na 4 SiO 4 as the silicate compound.
水熱反応は、１００℃以上であればよく、１３０〜２００℃が好ましく、さらに１４０〜１８０℃が好ましい。水熱反応は耐圧容器中で行うのが好ましく、１３０〜２００℃で反応を行う場合この時の圧力は０．３〜１．５ＭＰａとなり、１４０〜１８０℃で反応を行う場合の圧力は０．４〜１．０ＭＰａとなる。水熱反応時間は１〜２４時間が好ましく、さらに３〜１２時間が好ましい。 Hydrothermal reaction should just be 100 degreeC or more, 130-200 degreeC is preferable and 140-180 degreeC is more preferable. The hydrothermal reaction is preferably performed in a pressure vessel. When the reaction is performed at 130 to 200 ° C, the pressure at this time is 0.3 to 1.5 MPa, and the pressure when the reaction is performed at 140 to 180 ° C is 0. 4 to 1.0 MPa. The hydrothermal reaction time is preferably 1 to 24 hours, more preferably 3 to 12 hours.
当該水熱反応により、オリビン型シリケート化合物が高収率で得られ、その結晶度も高い。得られたオリビン型シリケート化合物は、ろ過後、乾燥することにより単離できる。乾燥手段は、凍結乾燥、真空乾燥が用いられる。 By the hydrothermal reaction, an olivine-type silicate compound is obtained in high yield, and its crystallinity is also high. The obtained olivine-type silicate compound can be isolated by drying after filtration. As the drying means, freeze drying or vacuum drying is used.
本発明で用いる導電性炭素は、オリビン型シリケート化合物が有する平均粒径Ｘ以下の平均粒径Ｙを有する。導電性炭素がこのような平均粒径を有することにより、かかる導電性炭素がオリビン型シリケート化合物の粒子と粒子の間隙に効率的に配置されて、空隙が低減された均一性の高い二次粒子の複合体を得ることができる。 The conductive carbon used in the present invention has an average particle size Y equal to or less than the average particle size X of the olivine-type silicate compound. Since the conductive carbon has such an average particle size, the conductive carbon is efficiently arranged in the gap between the particles of the olivine-type silicate compound, and the highly uniform secondary particles with reduced voids. The complex can be obtained.
オリビン型シリケート化合物が有する平均粒径Ｘと導電性炭素が有する平均粒径Ｙとの比（Ｘ／Ｙ）は、より効率的にオリビン型シリケート化合物の粒子と粒子の間隙に配置される観点、及び得られる電池物性の向上を図る観点から、好ましくは１〜２０であり、より好ましくは１．５〜１０である。また、導電性炭素が有する平均粒径Ｙは、同様の観点から、好ましくは１０〜１００ｎｍであり、より好ましくは１０〜５０ｎｍである。かかる平均粒径Ｙは、上記オリビン型シリケート化合物の平均粒径Ｘと同様の方法により測定される値を意味する。 The ratio (X / Y) of the average particle diameter X possessed by the olivine type silicate compound and the average particle diameter Y possessed by the conductive carbon is a viewpoint that is more efficiently arranged in the gap between the particles of the olivine type silicate compound, And from a viewpoint of aiming at the improvement of the battery physical property obtained, Preferably it is 1-20, More preferably, it is 1.5-10. Moreover, the average particle diameter Y which electroconductive carbon has becomes like this. Preferably it is 10-100 nm, More preferably, it is 10-50 nm. The average particle size Y means a value measured by the same method as the average particle size X of the olivine type silicate compound.
このような導電性炭素としては、カーボンブラックが好ましく、具体的には、例えば、アセチレンブラック、ケッチェンブラック、チャンネルブラック、ファーネスブラック、ランプブラック、サーマルブラック等が挙げられる。なかでも、良好な導電性を付与する観点から、アセチレンブラック、ケッチェンブラックが好ましい。また、これら導電性炭素の形状としては、後述するように一次粒子の少なくとも一部の表面を導電性炭素からなる層で被覆させて得られる電池物性をより高める観点から、中空形状を呈するもの、又は空隙を含む形状を呈するものであるのが好ましい。 As such conductive carbon, carbon black is preferable, and specific examples include acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black. Of these, acetylene black and ketjen black are preferred from the viewpoint of imparting good conductivity. Further, as the shape of these conductive carbon, from the viewpoint of further improving the physical properties of the battery obtained by coating at least a part of the surface of the primary particles with a layer made of conductive carbon, as described later, a hollow shape, Or it is preferable to exhibit the shape containing a space | gap.
本発明の二次電池用正極活物質複合体は、これらオリビン型シリケート化合物及び導電性炭素から得られ、タップ密度が０．８〜２．５ｇ／ｃｍ3である。したがって、極めて空隙が低減されてなり、これらオリビン型シリケート化合物と導電性炭素とが非常に均一に分散してなる二次粒子である。そのため、これを用いて塗工液を調製すれば、かかる塗工液中での複合体の分散性や固形分濃度を高めることができ、得られる電池物性の向上を容易に図ることが可能となる。本発明の二次電池用正極活物質複合体のタップ密度は、得られる電池物性を高める観点から、０．８〜２．５ｇ／ｃｍ3であって、好ましくは１．０〜２．５ｇ／ｃｍ3であり、より好ましくは１．２〜２．５ｇ／ｃｍ3である。なお、二次電池用正極活物質複合体のタップ密度は、重量既知の粉体試料ｍ（g）を入れた測定用容器を機械的にタップし、体積変化が認められなくなった時の粉体体積Ｖ（ｃｍ3）を読み取り、式 ｍ/Ｖ を用いて計算された値を平均したものを意味する。 The positive electrode active material composite for a secondary battery of the present invention is obtained from these olivine-type silicate compounds and conductive carbon, and has a tap density of 0.8 to 2.5 g / cm 3 . Therefore, the voids are extremely reduced, and secondary particles are obtained by dispersing these olivine-type silicate compounds and conductive carbon very uniformly. Therefore, if a coating liquid is prepared using this, it is possible to increase the dispersibility and solid content concentration of the composite in such a coating liquid, and to easily improve the physical properties of the battery obtained. Become. The tap density of the positive electrode active material composite for a secondary battery of the present invention is 0.8 to 2.5 g / cm 3 , preferably 1.0 to 2.5 g / cm, from the viewpoint of improving the physical properties of the obtained battery. cm 3 , more preferably 1.2 to 2.5 g / cm 3 . The tap density of the positive electrode active material composite for the secondary battery is determined by mechanically tapping a measuring container containing a powder sample m (g) of known weight, and the powder when no volume change is observed. It means a value obtained by reading the volume V (cm 3 ) and averaging the values calculated using the formula m / V.
また、本発明の二次電池用正極活物質複合体におけるオリビン型シリケート化合物及び導電性炭素は、これらの均一性及び分散性を高める観点、及び得られる電池物性をより高める観点から、オリビン型シリケート化合物の一次粒子の少なくとも一部の表面を、導電性炭素からなる層が被覆してなるのが好ましい。導電性炭素からなる層は、一次粒子の少なくとも一部の表面を被覆していてもよく、一次粒子のほぼ全表面を被覆していてもよい。これにより、オリビン型シリケート化合物の一次粒子及び導電性炭素の各々が凝集するのを抑制することができ、導電性炭素がより緻密かつ均一に分散した二次粒子が得られ、導電性をより高めることが可能となる。 In addition, the olivine silicate compound and the conductive carbon in the positive electrode active material composite for the secondary battery of the present invention are olivine silicate from the viewpoint of enhancing the uniformity and dispersibility thereof and the properties of the obtained battery. It is preferable that at least a part of the surface of the primary particles of the compound is covered with a layer made of conductive carbon. The layer made of conductive carbon may cover at least a part of the surface of the primary particles, or may cover almost the entire surface of the primary particles. As a result, the primary particles of the olivine-type silicate compound and the conductive carbon can be prevented from agglomerating, and secondary particles in which the conductive carbon is more densely and uniformly dispersed can be obtained, thereby further increasing the conductivity. It becomes possible.
導電性炭素からなる層の厚みは、好ましくは０．１〜５．０ｎｍであり、より好ましくは０．５〜３．０ｎｍである。 The thickness of the layer made of conductive carbon is preferably 0.1 to 5.0 nm, more preferably 0.5 to 3.0 nm.
本発明の二次電池用正極活物質複合体におけるオリビン型シリケート化合物の含有量と導電性炭素の含有量との質量比は、得られる電池物性を高める観点から、好ましくは９７：３〜８５：１５であり、より好ましくは９５：５〜８８：１２であり、さらに好ましくは９３：７〜９０：１０である。 The mass ratio between the content of the olivine-type silicate compound and the content of conductive carbon in the positive electrode active material composite for a secondary battery of the present invention is preferably 97: 3-85: from the viewpoint of enhancing the obtained battery properties. 15, more preferably 95: 5 to 88:12, and still more preferably 93: 7 to 90:10.
また、本発明の二次電池用正極活物質複合体が有する平均粒径Ｚは、５〜５０μｍである。このように、本発明の二次電池用正極活物質複合体は、均一に分散したオリビン型シリケート化合物と導電性炭素とを含有しつつも微細な二次粒子であるため、これから得られる塗工液を用いることにより、正極集電体上に形成する塗膜を薄膜化しながら優れた電池物性を有する二次電池を得ることができる。本発明の二次電池用正極活物質複合体の平均粒径Ｚは、得られる二次電池において優れた電池物性を保持しつつ軽量化を図る観点から、５〜５０μｍであって、好ましくは５〜３０μｍであり、より好ましくは５〜２０μｍである。なお、かかる平均粒径Ｚは、上記平均粒径Ｘ及びＹと同様の方法により測定される値を意味する。 Moreover, the average particle diameter Z which the positive electrode active material composite_body | complex for secondary batteries of this invention has is 5-50 micrometers. Thus, the positive electrode active material composite for a secondary battery of the present invention is a fine secondary particle containing a uniformly dispersed olivine-type silicate compound and conductive carbon, and thus a coating obtained from the same. By using the liquid, it is possible to obtain a secondary battery having excellent battery properties while reducing the thickness of the coating film formed on the positive electrode current collector. The average particle size Z of the positive electrode active material composite for a secondary battery of the present invention is 5 to 50 μm, preferably 5 from the viewpoint of reducing the weight while maintaining excellent battery properties in the obtained secondary battery. It is -30 micrometers, More preferably, it is 5-20 micrometers. In addition, this average particle diameter Z means the value measured by the method similar to the said average particle diameter X and Y.
本発明の二次電池用正極活物質複合体を製造するには、上記オリビン型シリケート化合物及び導電性炭素を、周速２５〜４０ｍ／ｓで回転するインペラを備える密閉容器内に投入して、圧縮力及びせん断力を付加しながら混合する。かかるインペラを備える密閉容器内では、インペラの回転によってこれらオリビン型シリケート化合物及び導電性炭素が均一に混合されるとともに、インペラと容器内壁との間で圧縮力を付加されながらせん断力も付加されることとなる。そのため、オリビン型シリケート化合物の一次粒子と一次粒子の間に導電性炭素が混入し、これらが均一に分散したまま堅固に凝集して二次粒子を形成することにより、空隙が低減された複合体を得ることができる。また、導電性炭素を変形又は延展させながら一次粒子の表面に付着させ、導電性炭素の層を形成させることもできる。インペラの周速は、得られる複合体のタップ密度を高める観点から、好ましくは２５〜４０ｍ／ｓであり、より好ましくは２７〜３５ｍ／ｓである。 In order to produce the positive electrode active material composite for a secondary battery of the present invention, the olivine-type silicate compound and conductive carbon are introduced into a sealed container equipped with an impeller rotating at a peripheral speed of 25 to 40 m / s, Mix while applying compressive and shear forces. In an airtight container equipped with such an impeller, the olivine-type silicate compound and conductive carbon are uniformly mixed by the rotation of the impeller, and a shearing force is also applied while a compressive force is applied between the impeller and the inner wall of the container. It becomes. Therefore, conductive carbon is mixed between the primary particles and the primary particles of the olivine type silicate compound, and these are uniformly dispersed to form secondary particles, thereby forming a composite with reduced voids. Can be obtained. Alternatively, the conductive carbon layer may be deposited on the surface of the primary particles while deforming or extending the conductive carbon layer. The peripheral speed of the impeller is preferably 25 to 40 m / s, more preferably 27 to 35 m / s, from the viewpoint of increasing the tap density of the resulting composite.
なお、得られる複合体の均一性を高める観点、およびインペラを備える密閉容器内での処理時間を短縮化する観点から、かかる密閉容器内へオリビン型シリケート化合物及び導電性炭素を投入する前に、予めこれらを混合してもよい。 In addition, from the viewpoint of increasing the uniformity of the resulting composite, and from the viewpoint of shortening the processing time in a closed container equipped with an impeller, before introducing the olivine-type silicate compound and conductive carbon into such a closed container, These may be mixed in advance.
このような圧縮力及びせん断力を付加しながら混合することのできる密閉容器を備える装置としては、高速せん断ミル、ブレード型混練機等が挙げられ、具体的には、例えば、微粒子複合化装置 ノビルタ（ホソカワミクロン社製）を好適に用いることができる。かかる装置を用いることにより、容易に所定の圧縮力とせん断力を付加しながらの混合処理を行うことができ、このような処理を施すのみで本願発明の二次電池用正極活物質複合体を得ることができる。
上記混合の処理条件としては、処理温度が、好ましくは５〜８０℃、より好ましくは１０〜５０℃であり、処理時間が、好ましくは５〜９０分、より好ましくは１０〜６０分である。処理雰囲気としては、特に限定されないが、不活性ガス雰囲気下、または還元ガス雰囲気下が好ましい。
Examples of the apparatus provided with a closed container that can be mixed while applying such compressive force and shearing force include a high-speed shear mill, a blade-type kneader, and the like. (Manufactured by Hosokawa Micron Corporation) can be preferably used. By using such an apparatus, it is possible to easily perform a mixing process while applying a predetermined compressive force and shearing force. By simply performing such a process, the positive electrode active material composite for a secondary battery of the present invention can be obtained. Can be obtained.
As the processing conditions for the mixing, the processing temperature is preferably 5 to 80 ° C., more preferably 10 to 50 ° C., and the processing time is preferably 5 to 90 minutes, more preferably 10 to 60 minutes. The treatment atmosphere is not particularly limited, but is preferably an inert gas atmosphere or a reducing gas atmosphere.
上記密閉容器内に投入するオリビン型シリケート化合物と導電性炭素との質量比は、得られる電池物性を高める観点から、好ましくは９７：３〜８５：１５であり、より好ましくは９５：５〜８８：１２であり、さらに好ましくは９３：７〜９０：１０である。 The mass ratio of the olivine-type silicate compound and the conductive carbon to be charged in the closed container is preferably 97: 3 to 85:15, more preferably 95: 5 to 88, from the viewpoint of improving the battery physical properties obtained. : 12, and more preferably 93: 7 to 90:10.
なお、電池物性をより高める観点から、得られた複合体を焼成してもよい。焼成条件は、不活性ガス雰囲気下又は還元条件下に４００℃以上、好ましくは４００〜８００℃で１０分〜３時間、好ましくは０．５〜１．５時間行うのが好ましい。 In addition, you may bake the obtained composite body from a viewpoint of improving battery physical property more. The firing conditions are 400 ° C. or higher, preferably 400 to 800 ° C. for 10 minutes to 3 hours, preferably 0.5 to 1.5 hours under an inert gas atmosphere or reducing conditions.
このようにして得られた本発明の二次電池用正極活物質複合体を用いて二次電池を製造する方法は特に限定されず、公知の方法をいずれも使用できる。例えば、かかる複合体を結着剤や溶剤等の添加剤とともに混合して塗工液を得る。この際、必要に応じて、さらに導電助剤を添加して混合してもよい。かかる結着剤としては、特に限定されず、公知の剤をいずれも使用できる。具体的には、ポリテトラフルオロエチレン、ポリビニリデンフルオライド、ポリビニルクロライド、エチレンプロピレンジエンポリマー等が挙げられる。また、かかる導電助剤としては、特に限定されず、公知の剤をいずれも使用できる。具体的には、アセチレンブラック、ケッチェンブラック、天然黒鉛、人工黒鉛、繊維状炭素等が挙げられる。次いで、かかる塗工液をアルミ箔等の正極集電体上に塗布し、乾燥させて正極とする。 The method for producing a secondary battery using the positive electrode active material composite for a secondary battery of the present invention thus obtained is not particularly limited, and any known method can be used. For example, such a composite is mixed with additives such as a binder and a solvent to obtain a coating liquid. At this time, if necessary, a conductive additive may be further added and mixed. The binder is not particularly limited, and any known agent can be used. Specific examples include polytetrafluoroethylene, polyvinylidene fluoride, polyvinyl chloride, and ethylene propylene diene polymer. Moreover, it does not specifically limit as this conductive support agent, Any well-known agent can be used. Specific examples include acetylene black, ketjen black, natural graphite, artificial graphite, and fibrous carbon. Next, such a coating solution is applied onto a positive electrode current collector such as an aluminum foil and dried to obtain a positive electrode.
本発明の二次電池用正極活物質複合体は、二次電池の正極として非常に優れた放電容量を発揮する点で有用である。かかる正極を適用できる二次電池としては、リチウムイオン二次電池であればよく、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 positive electrode active material composite for a secondary battery of the present invention is useful in that it exhibits a very excellent discharge capacity as a positive electrode of a secondary battery. The secondary battery to which such a positive electrode can be applied is not particularly limited as long as it is a lithium ion secondary battery and has a positive electrode, a negative electrode, an electrolyte 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.
以下、本発明について、実施例に基づき具体的に説明するが、本発明はこれら実施例に限定されるものではない。
なお、平均粒径及びタップ密度は、いずれも上記記載の方法にしたがって測定した。
EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited to these Examples.
The average particle diameter and the tap density were both measured according to the method described above.
［製造例１］
ＬｉＯＨ・Ｈ2Ｏ ４２．０ｇ（１．０ｍｏｌ）、Ｎａ4ＳｉＯ4・ｎＨ2Ｏ １４０．０ｇ（０．５ｍｏｌ）、Ｎａ2Ｓ2Ｏ4 ８．７ｇ（０．０５ｍｏｌ）に超純水４００ｃｍ3を加えて混合した（この時のｐＨは約１３）。この水分散液にＦｅＳＯ4・７Ｈ2Ｏ６２．６ｇ（０．２２５ｍｏｌ）、ＭｎＳＯ4・５Ｈ2Ｏ ５４．２ｇ（０．２２５ｍｏｌ）及びＺｒ（ＳＯ4）2・４Ｈ2Ｏ７．１ｇ（０．０２５ｍｏｌ）を添加し、混合した。得られた混合液をオートクレーブに投入し、１５０℃で１６ｈｒ水熱反応を行った。反応液をろ過後、凍結乾燥し（約１２時間）、粉末を得た。
得られた粉末の平均粒径は、７０ｎｍであった。
[Production Example 1]
LiOH.H 2 O 42.0 g (1.0 mol), Na 4 SiO 4 .nH 2 O 140.0 g (0.5 mol), Na 2 S 2 O 4 8.7 g (0.05 mol) and ultrapure water 400 cm 3 was added and mixed (the pH at this time was about 13). In this aqueous dispersion, 62.6 g (0.225 mol) of FeSO 4 .7H 2 O, 54.2 g (0.225 mol) of MnSO 4 .5H 2 O and 7.1 g (0.025 mol) of Zr (SO 4 ) 2 .4H 2 O were added. ) Was added and mixed. The obtained mixed liquid was put into an autoclave and subjected to a hydrothermal reaction at 150 ° C. for 16 hours. The reaction solution was filtered and freeze-dried (about 12 hours) to obtain a powder.
The average particle size of the obtained powder was 70 nm.
［実施例１］
製造例１で得られた粉末１８０ｇとケッチェンブラック（ライオン社製、平均粒径３０ｎｍ）２０ｇとを予め混合して混合物を得て、得られた混合物を微粒子複合化装置 ノビルタ（ホソカワミクロン社製）に投入し、２５〜３５℃で３０分間混合して、複合体Ａを得た。得られた複合体Ａの平均粒径は１５μｍであり、タップ密度は１．６ｇ／ｃｍ3であった。
得られた複合体ＡのＳＥＭ像を図１に示す。なお、図１（ａ）は複合体Ａの全体像を示す１０００倍のＳＥＭ像であり、図１（ｂ）は複合体Ａの断面図を示す１０００倍のＳＥＭ像である。
また、得られた複合体Ａの断面をさらに拡大したＴＥＭ像を図２に示す。図２（ａ）は複合体Ａの断面を示す２５０００倍のＴＥＭ像であり、図２（ｂ）は複合体Ａの断面において、一次粒子の表面の一部を拡大した５０万倍のＴＥＭ像である。図２より、一次粒子のほぼ全面に、厚み２ｎｍの導電性炭素からなる層が被覆されていることが確認された。
[Example 1]
180 g of the powder obtained in Production Example 1 and 20 g of ketjen black (Lion Corporation, average particle size 30 nm) are mixed in advance to obtain a mixture, and the resulting mixture is combined with a fine particle composite apparatus Nobilta (Hosokawa Micron Corporation). And mixed at 25 to 35 ° C. for 30 minutes to obtain a complex A. The obtained composite A had an average particle size of 15 μm and a tap density of 1.6 g / cm 3 .
The SEM image of the obtained composite A is shown in FIG. 1A is a 1000 × SEM image showing the entire composite A, and FIG. 1B is a 1000 × SEM image showing a cross-sectional view of the composite A.
Moreover, the TEM image which expanded the cross section of the obtained composite A further is shown in FIG. FIG. 2A is a 25,000 times TEM image showing a cross section of the composite A, and FIG. 2B is a 500,000 times TEM image obtained by enlarging a part of the surface of the primary particle in the cross section of the composite A. It is. From FIG. 2, it was confirmed that a layer made of conductive carbon having a thickness of 2 nm was coated on almost the entire surface of the primary particles.
［比較例１］
製造例１で得られた粉末９０ｇ、ケッチェンブラック（ライオン社製、平均粒径３０ｎｍ）１０ｇ及び分散安定化剤（カルボキシメチルセルロース、ダイセルファインケム社製）を加えた水１００ｇを、遊星ボールミル（遊星型ボールミルＰ−５、フリッチュ社製）のジルコニア製ポットにジルコニア製ボールとともに投入し、２５〜７０℃で２４０分間混合して乾燥し、複合体Ｂを得た。得られた複合体Ｂの平均粒径は、３５０ｎｍであり、タップ密度は０．６ｇ／ｃｍ3であった。
得られた複合体ＢのＳＥＭ像を図３に示す。なお、図３（ａ）は複合体Ｂの全体像を示す５０００倍のＳＥＭ像であり、図３（ｂ）は複合体Ｂの断面図を示す１００００倍のＳＥＭ像である。
また、得られた複合体Ｂの断面をさらに拡大した２５０００倍のＴＥＭ像を図４に示す。図４より、図４中の枠内に示すように、製造例１で得られた粉末が凝集し、導電性炭素からなる層が被覆されていないことが確認された。
[Comparative Example 1]
A planetary ball mill (planet type) was prepared by adding 90 g of the powder obtained in Production Example 1, 10 g of ketjen black (manufactured by Lion Corporation, average particle size 30 nm) and 100 g of water to which a dispersion stabilizer (carboxymethylcellulose, manufactured by Daicel Finechem) was added. Ball mill P-5, manufactured by Fritsch Co., Ltd.) was put together with zirconia balls, mixed at 25 to 70 ° C. for 240 minutes and dried to obtain composite B. The obtained composite B had an average particle size of 350 nm and a tap density of 0.6 g / cm 3 .
The SEM image of the obtained composite B is shown in FIG. 3A is a 5000 × SEM image showing an overall image of the composite B, and FIG. 3B is a 10,000 × SEM image showing a cross-sectional view of the composite B.
In addition, FIG. 4 shows a TEM image of 25,000 times in which the cross section of the obtained composite B is further enlarged. From FIG. 4, as shown in the frame in FIG. 4, it was confirmed that the powder obtained in Production Example 1 aggregated and the layer made of conductive carbon was not covered.
《充放電試験》
実施例１及び比較例１で得られた複合体を用い、リチウムイオン二次電池の正極を作製した。実施例１及び比較例１で得られた複合体、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。
《Charge / discharge test》
Using the composites obtained in Example 1 and Comparative Example 1, a positive electrode of a lithium ion secondary battery was produced. The composite obtained in Example 1 and Comparative Example 1, ketjen black (conductive agent), and polyvinylidene fluoride (binding agent) were mixed in a mixing ratio of 75:15:10, and this was mixed with N-methyl. -2-Pyrrolidone was added and sufficiently kneaded 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.
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。 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).
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い、充放電容量を測定した。このときの充電条件は電流０．１ＣＡ（３３ｍＡ／ｇ）、電圧４．５Ｖの定電流定電圧充電とし、放電条件は電流０．１ＣＡ、終止電圧１．５Ｖの定電流放電とした。温度は全て３０℃とした。得られた結果を表１に示す。 A charge / discharge test at a constant current density was performed using the manufactured lithium ion secondary battery, and a charge / discharge capacity was measured. The charging conditions at this time were constant current and constant voltage charging with a current of 0.1 CA (33 mA / g) and a voltage of 4.5 V, and the discharging conditions were constant current discharging with a current of 0.1 CA and a final voltage of 1.5 V. All temperatures were 30 ° C. The obtained results are shown in Table 1.
また、かかる充放電試験を４サイクル行ったときの充放電曲線を図５（実施例１）及び図６（比較例１）に示す。 Further, FIG. 5 (Example 1) and FIG. 6 (Comparative Example 1) show charge / discharge curves when the charge / discharge test is performed for 4 cycles.
図１〜６及び表１の結果より、実施例１で得られた複合体Ａは、比較例１で得られた複合体Ｂに比して、極めて均一性が高い上に空隙が低減されてなるため、これを用いた二次電池において優れた電池物性を示すことがわかる。なかでも、図２及び図４の結果によれば、比較例１の複合体Ｂ中では、オリビン型シリケート化合物や導電性炭素が一部凝集してなることが確認されるのに対し、実施例１の複合体Ａ中では、オリビン型シリケート化合物及び導電性炭素が非常に均一に分散しており、またオリビン型シリケート化合物の一次粒子の表面に導電性炭素の層が形成されていることが確認できる。 From the results shown in FIGS. 1 to 6 and Table 1, the composite A obtained in Example 1 has extremely high uniformity and reduced voids compared to the composite B obtained in Comparative Example 1. Therefore, it can be seen that a secondary battery using the same exhibits excellent battery properties. Especially, according to the result of FIG.2 and FIG.4, in the composite B of the comparative example 1, it is confirmed that the olivine type silicate compound and the conductive carbon are partly aggregated, whereas the example It is confirmed that the olivine-type silicate compound and the conductive carbon are very uniformly dispersed in the composite A of 1 and that a conductive carbon layer is formed on the surface of the primary particles of the olivine-type silicate compound. it can.
なお、比較例１で得られた複合体Ｂは、微細な粒子ではあるものの、十分な量の導電性炭素を含有していない上に空隙が多いため、電池物性の低下を招いたものと考えられる。 In addition, although the composite B obtained in Comparative Example 1 is a fine particle, it does not contain a sufficient amount of conductive carbon, and there are many voids. It is done.
Claims (9)
Ｌｉ a' Ｆｅ x Ｍｎ y Ａｌ z ＳｉＯ 4 ・・・（２）
（式（２）中、ａ'、ｘ、ｙ及びｚは、１＜ａ'≦２、０≦ｘ＜１、０≦ｙ＜１、０＜ｚ＜２／３、ａ'＋２ｘ＋２ｙ＋３ｚ＝４、及びｘ＋ｙ≠０を満たす数を示す。）
Ｌｉ a" Ｆｅ x Ｍｎ y Ｚｒ z" ＳｉＯ 4 ・・・（４）
（式（４）中、ａ " 、ｘ、ｙ及びｚ " は、１＜ａ " ≦２、０≦ｘ＜１、０≦ｙ＜１、０＜ｚ " ＜０．５、ａ " ＋２ｘ＋２ｙ＋４ｚ " ＝４、及びｘ＋ｙ≠０を満たす数を示す。）
で表されるオリビン型シリケート化合物、及び平均粒径Ｙを有するとともに平均粒径Ｘと平均粒径Ｙとの比（Ｘ／Ｙ）が１．５〜１０である導電性炭素を、周速２５〜４０ｍ／ｓで回転するインペラを備える密閉容器内に投入して、圧縮力及びせん断力を付加しながら混合することにより得られ、
タップ密度が０．８〜２．５ｇ／ｃｍ3であり、
０．５〜３．０ｎｍの導電性炭素からなる層が一次粒子の表面を被覆してなり、かつ
５〜５０μｍの平均粒径Ｚを有する二次粒子であることを特徴とする、二次電池用正極活物質複合体。 Formula I Oh a primary particle having an average particle diameter X of 20 to 200 nm (2) or (4):
Li a 'Fe x Mn y Al z SiO 4 ··· (2)
(In the formula (2), a ′, x, y and z are 1 <a ′ ≦ 2, 0 ≦ x <1, 0 ≦ y <1, 0 <z <2/3, a ′ + 2x + 2y + 3z = 4, And a number satisfying x + y ≠ 0.)
Li a "Fe x Mn y Zr z" SiO 4 ··· (4)
(In the formula (4), a " , x, y and z " are 1 <a " ≤2, 0≤x <1, 0≤y <1, 0 <z " <0.5, a " + 2x + 2y + 4z ". = 4, and a number satisfying x + y ≠ 0.)
In olivine silicate compound represented by the ratio (X / Y) is conductive carbon is 1.5 to 10 and the average particle diameter Y and the average particle diameter X and having an及beauty average particle diameter Y, the peripheral speed It is obtained by putting into an airtight container equipped with an impeller rotating at 25 to 40 m / s and mixing while adding compressive force and shearing force ,
The tap density is 0.8 to 2.5 g / cm 3 ,
A secondary battery comprising a layer made of conductive carbon of 0.5 to 3.0 nm covering the surface of primary particles and secondary particles having an average particle size Z of 5 to 50 μm Cathode active material composite.
Ｌｉ a' Ｆｅ x Ｍｎ y Ａｌ z ＳｉＯ 4 ・・・（２）
（式（２）中、ａ'、ｘ、ｙ及びｚは、１＜ａ'≦２、０≦ｘ＜１、０≦ｙ＜１、０＜ｚ＜２／３、ａ'＋２ｘ＋２ｙ＋３ｚ＝４、及びｘ＋ｙ≠０を満たす数を示す。）
Ｌｉ a" Ｆｅ x Ｍｎ y Ｚｒ z" ＳｉＯ 4 ・・・（４）
（式（４）中、ａ " 、ｘ、ｙ及びｚ " は、１＜ａ " ≦２、０≦ｘ＜１、０≦ｙ＜１、０＜ｚ " ＜０．５、ａ " ＋２ｘ＋２ｙ＋４ｚ " ＝４、及びｘ＋ｙ≠０を満たす数を示す。）
で表されるオリビン型シリケート化合物、及び平均粒径Ｙを有するとともに平均粒径Ｘと平均粒径Ｙとの比（Ｘ／Ｙ）が１．５〜１０である導電性炭素を、周速２５〜４０ｍ／ｓで回転するインペラを備える密閉容器内に投入して、圧縮力及びせん断力を付加しながら混合することを特徴とする、請求項１〜７のいずれか１項に記載の二次電池用正極活物質複合体の製造方法。 Formula I Oh a primary particle having an average particle diameter X of 20 to 200 nm (2) or (4):
Li a 'Fe x Mn y Al z SiO 4 ··· (2)
(In the formula (2), a ′, x, y and z are 1 <a ′ ≦ 2, 0 ≦ x <1, 0 ≦ y <1, 0 <z <2/3, a ′ + 2x + 2y + 3z = 4, And a number satisfying x + y ≠ 0.)
Li a "Fe x Mn y Zr z" SiO 4 ··· (4)
(In the formula (4), a " , x, y and z " are 1 <a " ≤2, 0≤x <1, 0≤y <1, 0 <z " <0.5, a " + 2x + 2y + 4z ". = 4, and a number satisfying x + y ≠ 0.)
In olivine silicate compound represented by the ratio (X / Y) is conductive carbon is 1.5 to 10 and the average particle diameter Y and the average particle diameter X and having an及beauty average particle diameter Y, the peripheral speed The mixture according to any one of claims 1 to 7, wherein the mixture is put into a closed container including an impeller rotating at 25 to 40 m / s and mixed while applying a compressive force and a shearing force. A method for producing a positive electrode active material composite for a secondary battery.
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