JP6708326B2 - Positive electrode material for sodium secondary batteries - Google Patents
Positive electrode material for sodium secondary batteries Download PDFInfo
- Publication number
- JP6708326B2 JP6708326B2 JP2015225767A JP2015225767A JP6708326B2 JP 6708326 B2 JP6708326 B2 JP 6708326B2 JP 2015225767 A JP2015225767 A JP 2015225767A JP 2015225767 A JP2015225767 A JP 2015225767A JP 6708326 B2 JP6708326 B2 JP 6708326B2
- Authority
- JP
- Japan
- Prior art keywords
- sodium
- iron
- positive electrode
- manganese
- secondary battery
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
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- 239000011734 sodium Substances 0.000 title claims description 164
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 title claims description 146
- 229910052708 sodium Inorganic materials 0.000 title claims description 146
- 239000007774 positive electrode material Substances 0.000 title claims description 96
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 293
- PXHVJJICTQNCMI-UHFFFAOYSA-N nickel Substances [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 claims description 206
- 239000011572 manganese Substances 0.000 claims description 115
- 229910052742 iron Inorganic materials 0.000 claims description 106
- 229910052759 nickel Inorganic materials 0.000 claims description 72
- 238000010438 heat treatment Methods 0.000 claims description 63
- 150000001875 compounds Chemical class 0.000 claims description 53
- 239000000203 mixture Substances 0.000 claims description 42
- 229910052748 manganese Inorganic materials 0.000 claims description 41
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 claims description 34
- 239000013078 crystal Substances 0.000 claims description 29
- WPBNNNQJVZRUHP-UHFFFAOYSA-L manganese(2+);methyl n-[[2-(methoxycarbonylcarbamothioylamino)phenyl]carbamothioyl]carbamate;n-[2-(sulfidocarbothioylamino)ethyl]carbamodithioate Chemical compound [Mn+2].[S-]C(=S)NCCNC([S-])=S.COC(=O)NC(=S)NC1=CC=CC=C1NC(=S)NC(=O)OC WPBNNNQJVZRUHP-UHFFFAOYSA-L 0.000 claims description 27
- 238000000034 method Methods 0.000 claims description 21
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 claims description 20
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 19
- 229910052760 oxygen Inorganic materials 0.000 claims description 19
- 239000001301 oxygen Substances 0.000 claims description 19
- 238000004519 manufacturing process Methods 0.000 claims description 17
- 239000007864 aqueous solution Substances 0.000 claims description 10
- 150000004649 carbonic acid derivatives Chemical class 0.000 claims description 10
- 229910000029 sodium carbonate Inorganic materials 0.000 claims description 10
- 150000004679 hydroxides Chemical class 0.000 claims description 9
- 239000000243 solution Substances 0.000 claims description 7
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 claims description 3
- 229910002651 NO3 Inorganic materials 0.000 claims description 3
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 claims description 3
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 claims description 3
- 239000010406 cathode material Substances 0.000 claims description 3
- 229910001854 alkali hydroxide Inorganic materials 0.000 claims description 2
- 150000008044 alkali metal hydroxides Chemical class 0.000 claims description 2
- 239000002131 composite material Substances 0.000 description 54
- 229910052596 spinel Inorganic materials 0.000 description 28
- 239000011029 spinel Substances 0.000 description 28
- 230000000052 comparative effect Effects 0.000 description 27
- 229910017120 Fe—Mn—Ni Inorganic materials 0.000 description 22
- 230000015572 biosynthetic process Effects 0.000 description 22
- 239000000463 material Substances 0.000 description 22
- 239000002994 raw material Substances 0.000 description 22
- 238000003786 synthesis reaction Methods 0.000 description 22
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 18
- 229910052751 metal Inorganic materials 0.000 description 17
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N iron oxide Inorganic materials [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 description 15
- 239000002184 metal Substances 0.000 description 15
- 238000002156 mixing Methods 0.000 description 15
- 229910001415 sodium ion Inorganic materials 0.000 description 15
- VZSRBBMJRBPUNF-UHFFFAOYSA-N 2-(2,3-dihydro-1H-inden-2-ylamino)-N-[3-oxo-3-(2,4,6,7-tetrahydrotriazolo[4,5-c]pyridin-5-yl)propyl]pyrimidine-5-carboxamide Chemical compound C1C(CC2=CC=CC=C12)NC1=NC=C(C=N1)C(=O)NCCC(N1CC2=C(CC1)NN=N2)=O VZSRBBMJRBPUNF-UHFFFAOYSA-N 0.000 description 14
- FKNQFGJONOIPTF-UHFFFAOYSA-N Sodium cation Chemical compound [Na+] FKNQFGJONOIPTF-UHFFFAOYSA-N 0.000 description 14
- 238000012360 testing method Methods 0.000 description 12
- AFCARXCZXQIEQB-UHFFFAOYSA-N N-[3-oxo-3-(2,4,6,7-tetrahydrotriazolo[4,5-c]pyridin-5-yl)propyl]-2-[[3-(trifluoromethoxy)phenyl]methylamino]pyrimidine-5-carboxamide Chemical compound O=C(CCNC(=O)C=1C=NC(=NC=1)NCC1=CC(=CC=C1)OC(F)(F)F)N1CC2=C(CC1)NN=N2 AFCARXCZXQIEQB-UHFFFAOYSA-N 0.000 description 11
- URQWOSCGQKPJCM-UHFFFAOYSA-N [Mn].[Fe].[Ni] Chemical compound [Mn].[Fe].[Ni] URQWOSCGQKPJCM-UHFFFAOYSA-N 0.000 description 10
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 9
- 229910052744 lithium Inorganic materials 0.000 description 9
- 229910021314 NaFeO 2 Inorganic materials 0.000 description 8
- PPNAOCWZXJOHFK-UHFFFAOYSA-N manganese(2+);oxygen(2-) Chemical compound [O-2].[Mn+2] PPNAOCWZXJOHFK-UHFFFAOYSA-N 0.000 description 8
- 239000002245 particle Substances 0.000 description 8
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 7
- 238000002441 X-ray diffraction Methods 0.000 description 7
- 230000033228 biological regulation Effects 0.000 description 7
- 238000007599 discharging Methods 0.000 description 7
- BAUYGSIQEAFULO-UHFFFAOYSA-L iron(2+) sulfate (anhydrous) Chemical compound [Fe+2].[O-]S([O-])(=O)=O BAUYGSIQEAFULO-UHFFFAOYSA-L 0.000 description 7
- 229910000359 iron(II) sulfate Inorganic materials 0.000 description 7
- SQQMAOCOWKFBNP-UHFFFAOYSA-L manganese(II) sulfate Chemical compound [Mn+2].[O-]S([O-])(=O)=O SQQMAOCOWKFBNP-UHFFFAOYSA-L 0.000 description 7
- 229910000357 manganese(II) sulfate Inorganic materials 0.000 description 7
- LGQLOGILCSXPEA-UHFFFAOYSA-L nickel sulfate Chemical compound [Ni+2].[O-]S([O-])(=O)=O LGQLOGILCSXPEA-UHFFFAOYSA-L 0.000 description 7
- 229910000363 nickel(II) sulfate Inorganic materials 0.000 description 7
- 230000003247 decreasing effect Effects 0.000 description 6
- RAQDACVRFCEPDA-UHFFFAOYSA-L ferrous carbonate Chemical compound [Fe+2].[O-]C([O-])=O RAQDACVRFCEPDA-UHFFFAOYSA-L 0.000 description 6
- 235000013980 iron oxide Nutrition 0.000 description 6
- VASIZKWUTCETSD-UHFFFAOYSA-N manganese(II) oxide Inorganic materials [Mn]=O VASIZKWUTCETSD-UHFFFAOYSA-N 0.000 description 6
- BFDHFSHZJLFAMC-UHFFFAOYSA-L nickel(ii) hydroxide Chemical compound [OH-].[OH-].[Ni+2] BFDHFSHZJLFAMC-UHFFFAOYSA-L 0.000 description 6
- 239000011255 nonaqueous electrolyte Substances 0.000 description 6
- 229910018661 Ni(OH) Inorganic materials 0.000 description 5
- 229910052799 carbon Inorganic materials 0.000 description 5
- 239000006258 conductive agent Substances 0.000 description 5
- XLYOFNOQVPJJNP-UHFFFAOYSA-M hydroxide Chemical compound [OH-] XLYOFNOQVPJJNP-UHFFFAOYSA-M 0.000 description 5
- 235000014413 iron hydroxide Nutrition 0.000 description 5
- NCNCGGDMXMBVIA-UHFFFAOYSA-L iron(ii) hydroxide Chemical compound [OH-].[OH-].[Fe+2] NCNCGGDMXMBVIA-UHFFFAOYSA-L 0.000 description 5
- 150000002739 metals Chemical class 0.000 description 5
- -1 sodium carbonate) Chemical class 0.000 description 5
- 239000007784 solid electrolyte Substances 0.000 description 5
- 239000002904 solvent Substances 0.000 description 5
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 description 4
- UIIMBOGNXHQVGW-UHFFFAOYSA-M Sodium bicarbonate Chemical compound [Na+].OC([O-])=O UIIMBOGNXHQVGW-UHFFFAOYSA-M 0.000 description 4
- 229910052782 aluminium Inorganic materials 0.000 description 4
- 239000011230 binding agent Substances 0.000 description 4
- 229910017052 cobalt Inorganic materials 0.000 description 4
- 239000010941 cobalt Substances 0.000 description 4
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 description 4
- 239000012535 impurity Substances 0.000 description 4
- IPJKJLXEVHOKSE-UHFFFAOYSA-L manganese dihydroxide Chemical compound [OH-].[OH-].[Mn+2] IPJKJLXEVHOKSE-UHFFFAOYSA-L 0.000 description 4
- NUJOXMJBOLGQSY-UHFFFAOYSA-N manganese dioxide Chemical compound O=[Mn]=O NUJOXMJBOLGQSY-UHFFFAOYSA-N 0.000 description 4
- AMWRITDGCCNYAT-UHFFFAOYSA-L manganese oxide Inorganic materials [Mn].O[Mn]=O.O[Mn]=O AMWRITDGCCNYAT-UHFFFAOYSA-L 0.000 description 4
- 238000003701 mechanical milling Methods 0.000 description 4
- 229910000480 nickel oxide Inorganic materials 0.000 description 4
- 229910012851 LiCoO 2 Inorganic materials 0.000 description 3
- WMFOQBRAJBCJND-UHFFFAOYSA-M Lithium hydroxide Chemical compound [Li+].[OH-] WMFOQBRAJBCJND-UHFFFAOYSA-M 0.000 description 3
- MKYBYDHXWVHEJW-UHFFFAOYSA-N N-[1-oxo-1-(2,4,6,7-tetrahydrotriazolo[4,5-c]pyridin-5-yl)propan-2-yl]-2-[[3-(trifluoromethoxy)phenyl]methylamino]pyrimidine-5-carboxamide Chemical compound O=C(C(C)NC(=O)C=1C=NC(=NC=1)NCC1=CC(=CC=C1)OC(F)(F)F)N1CC2=C(CC1)NN=N2 MKYBYDHXWVHEJW-UHFFFAOYSA-N 0.000 description 3
- NIPNSKYNPDTRPC-UHFFFAOYSA-N N-[2-oxo-2-(2,4,6,7-tetrahydrotriazolo[4,5-c]pyridin-5-yl)ethyl]-2-[[3-(trifluoromethoxy)phenyl]methylamino]pyrimidine-5-carboxamide Chemical compound O=C(CNC(=O)C=1C=NC(=NC=1)NCC1=CC(=CC=C1)OC(F)(F)F)N1CC2=C(CC1)NN=N2 NIPNSKYNPDTRPC-UHFFFAOYSA-N 0.000 description 3
- 239000003125 aqueous solvent Substances 0.000 description 3
- 239000003792 electrolyte Substances 0.000 description 3
- 229910000625 lithium cobalt oxide Inorganic materials 0.000 description 3
- BFZPBUKRYWOWDV-UHFFFAOYSA-N lithium;oxido(oxo)cobalt Chemical compound [Li+].[O-][Co]=O BFZPBUKRYWOWDV-UHFFFAOYSA-N 0.000 description 3
- 230000014759 maintenance of location Effects 0.000 description 3
- 229910000008 nickel(II) carbonate Inorganic materials 0.000 description 3
- 229920000642 polymer Polymers 0.000 description 3
- 239000002244 precipitate Substances 0.000 description 3
- 230000002441 reversible effect Effects 0.000 description 3
- 238000006467 substitution reaction Methods 0.000 description 3
- YLZOPXRUQYQQID-UHFFFAOYSA-N 3-(2,4,6,7-tetrahydrotriazolo[4,5-c]pyridin-5-yl)-1-[4-[2-[[3-(trifluoromethoxy)phenyl]methylamino]pyrimidin-5-yl]piperazin-1-yl]propan-1-one Chemical compound N1N=NC=2CN(CCC=21)CCC(=O)N1CCN(CC1)C=1C=NC(=NC=1)NCC1=CC(=CC=C1)OC(F)(F)F YLZOPXRUQYQQID-UHFFFAOYSA-N 0.000 description 2
- 101100513612 Microdochium nivale MnCO gene Proteins 0.000 description 2
- 239000004743 Polypropylene Substances 0.000 description 2
- 239000011149 active material Substances 0.000 description 2
- 239000006229 carbon black Substances 0.000 description 2
- 239000003575 carbonaceous material Substances 0.000 description 2
- 239000002800 charge carrier Substances 0.000 description 2
- 238000000975 co-precipitation Methods 0.000 description 2
- 239000000571 coke Substances 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 229910002804 graphite Inorganic materials 0.000 description 2
- 239000010439 graphite Substances 0.000 description 2
- 230000001771 impaired effect Effects 0.000 description 2
- 239000011656 manganese carbonate Substances 0.000 description 2
- 235000006748 manganese carbonate Nutrition 0.000 description 2
- 229910000016 manganese(II) carbonate Inorganic materials 0.000 description 2
- XMWCXZJXESXBBY-UHFFFAOYSA-L manganese(ii) carbonate Chemical compound [Mn+2].[O-]C([O-])=O XMWCXZJXESXBBY-UHFFFAOYSA-L 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- ZULUUIKRFGGGTL-UHFFFAOYSA-L nickel(ii) carbonate Chemical compound [Ni+2].[O-]C([O-])=O ZULUUIKRFGGGTL-UHFFFAOYSA-L 0.000 description 2
- GNRSAWUEBMWBQH-UHFFFAOYSA-N oxonickel Chemical compound [Ni]=O GNRSAWUEBMWBQH-UHFFFAOYSA-N 0.000 description 2
- 229920001155 polypropylene Polymers 0.000 description 2
- 239000000047 product Substances 0.000 description 2
- 235000017557 sodium bicarbonate Nutrition 0.000 description 2
- 229910000030 sodium bicarbonate Inorganic materials 0.000 description 2
- 229910001220 stainless steel Inorganic materials 0.000 description 2
- 239000010935 stainless steel Substances 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 229910052723 transition metal Inorganic materials 0.000 description 2
- 150000003624 transition metals Chemical class 0.000 description 2
- HMUNWXXNJPVALC-UHFFFAOYSA-N 1-[4-[2-(2,3-dihydro-1H-inden-2-ylamino)pyrimidin-5-yl]piperazin-1-yl]-2-(2,4,6,7-tetrahydrotriazolo[4,5-c]pyridin-5-yl)ethanone Chemical compound C1C(CC2=CC=CC=C12)NC1=NC=C(C=N1)N1CCN(CC1)C(CN1CC2=C(CC1)NN=N2)=O HMUNWXXNJPVALC-UHFFFAOYSA-N 0.000 description 1
- LDXJRKWFNNFDSA-UHFFFAOYSA-N 2-(2,4,6,7-tetrahydrotriazolo[4,5-c]pyridin-5-yl)-1-[4-[2-[[3-(trifluoromethoxy)phenyl]methylamino]pyrimidin-5-yl]piperazin-1-yl]ethanone Chemical compound C1CN(CC2=NNN=C21)CC(=O)N3CCN(CC3)C4=CN=C(N=C4)NCC5=CC(=CC=C5)OC(F)(F)F LDXJRKWFNNFDSA-UHFFFAOYSA-N 0.000 description 1
- WZFUQSJFWNHZHM-UHFFFAOYSA-N 2-[4-[2-(2,3-dihydro-1H-inden-2-ylamino)pyrimidin-5-yl]piperazin-1-yl]-1-(2,4,6,7-tetrahydrotriazolo[4,5-c]pyridin-5-yl)ethanone Chemical compound C1C(CC2=CC=CC=C12)NC1=NC=C(C=N1)N1CCN(CC1)CC(=O)N1CC2=C(CC1)NN=N2 WZFUQSJFWNHZHM-UHFFFAOYSA-N 0.000 description 1
- DEXFNLNNUZKHNO-UHFFFAOYSA-N 6-[3-[4-[2-(2,3-dihydro-1H-inden-2-ylamino)pyrimidin-5-yl]piperidin-1-yl]-3-oxopropyl]-3H-1,3-benzoxazol-2-one Chemical compound C1C(CC2=CC=CC=C12)NC1=NC=C(C=N1)C1CCN(CC1)C(CCC1=CC2=C(NC(O2)=O)C=C1)=O DEXFNLNNUZKHNO-UHFFFAOYSA-N 0.000 description 1
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 1
- 229910021260 NaFe Inorganic materials 0.000 description 1
- 229910015228 Ni1/3Mn1/3CO1/3 Inorganic materials 0.000 description 1
- VEQPNABPJHWNSG-UHFFFAOYSA-N Nickel(2+) Chemical compound [Ni+2] VEQPNABPJHWNSG-UHFFFAOYSA-N 0.000 description 1
- 239000004677 Nylon Substances 0.000 description 1
- 229920003171 Poly (ethylene oxide) Polymers 0.000 description 1
- 239000004698 Polyethylene Substances 0.000 description 1
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 description 1
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 1
- KEAYESYHFKHZAL-UHFFFAOYSA-N Sodium Chemical compound [Na] KEAYESYHFKHZAL-UHFFFAOYSA-N 0.000 description 1
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 1
- UCKMPCXJQFINFW-UHFFFAOYSA-N Sulphide Chemical compound [S-2] UCKMPCXJQFINFW-UHFFFAOYSA-N 0.000 description 1
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 description 1
- FHKPLLOSJHHKNU-INIZCTEOSA-N [(3S)-3-[8-(1-ethyl-5-methylpyrazol-4-yl)-9-methylpurin-6-yl]oxypyrrolidin-1-yl]-(oxan-4-yl)methanone Chemical compound C(C)N1N=CC(=C1C)C=1N(C2=NC=NC(=C2N=1)O[C@@H]1CN(CC1)C(=O)C1CCOCC1)C FHKPLLOSJHHKNU-INIZCTEOSA-N 0.000 description 1
- RMZMFASTOVOJPY-UHFFFAOYSA-N [Fe].[Mn].[Ni].[Na] Chemical compound [Fe].[Mn].[Ni].[Na] RMZMFASTOVOJPY-UHFFFAOYSA-N 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical group [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 239000004760 aramid Substances 0.000 description 1
- 229920003235 aromatic polyamide Polymers 0.000 description 1
- 125000003118 aryl group Chemical group 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 239000010949 copper Substances 0.000 description 1
- 238000003795 desorption Methods 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 150000002170 ethers Chemical class 0.000 description 1
- 239000004744 fabric Substances 0.000 description 1
- MSNWSDPPULHLDL-UHFFFAOYSA-K ferric hydroxide Chemical compound [OH-].[OH-].[OH-].[Fe+3] MSNWSDPPULHLDL-UHFFFAOYSA-K 0.000 description 1
- 239000012467 final product Substances 0.000 description 1
- 238000010304 firing Methods 0.000 description 1
- 239000011888 foil Substances 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- 230000033444 hydroxylation Effects 0.000 description 1
- 238000005805 hydroxylation reaction Methods 0.000 description 1
- 238000011065 in-situ storage Methods 0.000 description 1
- 239000011261 inert gas Substances 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- DALUDRGQOYMVLD-UHFFFAOYSA-N iron manganese Chemical compound [Mn].[Fe] DALUDRGQOYMVLD-UHFFFAOYSA-N 0.000 description 1
- KEBVLXZBNYKBFW-UHFFFAOYSA-J iron(2+);manganese(2+);tetrahydroxide Chemical class [OH-].[OH-].[OH-].[OH-].[Mn+2].[Fe+2] KEBVLXZBNYKBFW-UHFFFAOYSA-J 0.000 description 1
- VBMVTYDPPZVILR-UHFFFAOYSA-N iron(2+);oxygen(2-) Chemical class [O-2].[Fe+2] VBMVTYDPPZVILR-UHFFFAOYSA-N 0.000 description 1
- 230000001678 irradiating effect Effects 0.000 description 1
- 229910001416 lithium ion Inorganic materials 0.000 description 1
- ZAUUZASCMSWKGX-UHFFFAOYSA-N manganese nickel Chemical compound [Mn].[Ni] ZAUUZASCMSWKGX-UHFFFAOYSA-N 0.000 description 1
- MMIPFLVOWGHZQD-UHFFFAOYSA-N manganese(3+) Chemical compound [Mn+3] MMIPFLVOWGHZQD-UHFFFAOYSA-N 0.000 description 1
- ACNRYARPIFBOEZ-UHFFFAOYSA-K manganese(3+);trihydroxide Chemical compound [OH-].[OH-].[OH-].[Mn+3] ACNRYARPIFBOEZ-UHFFFAOYSA-K 0.000 description 1
- 239000012528 membrane Substances 0.000 description 1
- 229910000000 metal hydroxide Inorganic materials 0.000 description 1
- 239000012982 microporous membrane Substances 0.000 description 1
- 239000004570 mortar (masonry) Substances 0.000 description 1
- 238000003823 mortar mixing Methods 0.000 description 1
- 239000007773 negative electrode material Substances 0.000 description 1
- 229910001453 nickel ion Inorganic materials 0.000 description 1
- AIBQNUOBCRIENU-UHFFFAOYSA-N nickel;dihydrate Chemical compound O.O.[Ni] AIBQNUOBCRIENU-UHFFFAOYSA-N 0.000 description 1
- 150000002825 nitriles Chemical class 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 239000004745 nonwoven fabric Substances 0.000 description 1
- 229920001778 nylon Polymers 0.000 description 1
- 230000001590 oxidative effect Effects 0.000 description 1
- 229920000573 polyethylene Polymers 0.000 description 1
- 229920005672 polyolefin resin Polymers 0.000 description 1
- 239000004810 polytetrafluoroethylene Substances 0.000 description 1
- 229920001343 polytetrafluoroethylene Polymers 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 230000009257 reactivity Effects 0.000 description 1
- 238000006479 redox reaction Methods 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- PFUVRDFDKPNGAV-UHFFFAOYSA-N sodium peroxide Chemical compound [Na+].[Na+].[O-][O-] PFUVRDFDKPNGAV-UHFFFAOYSA-N 0.000 description 1
- 239000007858 starting material Substances 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- 229910052717 sulfur Inorganic materials 0.000 description 1
- 239000011593 sulfur Substances 0.000 description 1
- 230000002194 synthesizing effect Effects 0.000 description 1
- 239000011135 tin Substances 0.000 description 1
- 229910052718 tin Inorganic materials 0.000 description 1
- 229910052719 titanium Inorganic materials 0.000 description 1
- 229910000314 transition metal oxide Inorganic materials 0.000 description 1
- 239000002759 woven fabric Substances 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
Landscapes
- Inorganic Compounds Of Heavy Metals (AREA)
- Secondary Cells (AREA)
- Battery Electrode And Active Subsutance (AREA)
Description
本発明は、ナトリウム二次電池用正極材料及びその製造方法に関する。 The present invention relates to a positive electrode material for sodium secondary batteries and a method for manufacturing the same.
リチウムイオン二次電池は高いエネルギー密度を有する二次電池であることから、携帯電話、ノートパソコン等の小型電源の他、電気自動車等の大型電源等としても実用化されており、今後もさらに需要の拡大が期待される。 Since the lithium-ion secondary battery is a secondary battery with high energy density, it has been put to practical use not only as a small power source for mobile phones, notebook computers, etc., but also as a large power source for electric vehicles, etc. Is expected to expand.
リチウム二次電池において、リチウムは電荷担体として使用されており、また、リチウム及びコバルトは、正極材料として通常使用されているコバルト酸リチウム（ＬｉＣｏＯ２）を構成する材料である。これらリチウム及びコバルトは、希少金属であり、その資源は南米、中国等に偏在しており、原料価格が高く、原料の安定供給にも不安がある。 In a lithium secondary battery, lithium is used as a charge carrier, and lithium and cobalt are materials constituting lithium cobalt oxide (LiCoO 2 ) which is usually used as a positive electrode material. These lithium and cobalt are rare metals, and their resources are unevenly distributed in South America, China, etc., the raw material price is high, and there is concern about stable supply of raw materials.
この課題を解決するため、これらリチウム、コバルト等の希少金属の使用量を低減できる次世代二次電池として、ナトリウム二次電池の検討がなされている。ナトリウム二次電池の電荷担体であるナトリウムは資源量が豊富で且つ安価な材料である。また、ナトリウム二次電池の正極材料として通常使用される鉄酸ナトリウム（ＮａＦｅＯ２）を構成するナトリウム及び鉄も、資源量が豊富で且つ安価な材料である。このため、近年、ナトリウム二次電池の実用化が期待されている。特に、鉄酸ナトリウム（ＮａＦｅＯ２）は、リチウム二次電池用酸化物正極材料では達成が困難であったＦｅイオンの酸化還元反応を利用する事が可能で、希少金属を一切含まない材料として注目されている。 In order to solve this problem, a sodium secondary battery has been studied as a next-generation secondary battery that can reduce the amount of rare metals such as lithium and cobalt used. Sodium, which is a charge carrier of a sodium secondary battery, is a resource-rich and inexpensive material. In addition, sodium and iron, which constitute sodium ferrate (NaFeO 2 ) that is usually used as a positive electrode material for sodium secondary batteries, are also resource-rich and inexpensive materials. Therefore, in recent years, commercialization of sodium secondary batteries is expected. In particular, sodium ferrate (NaFeO 2 ) is capable of utilizing the oxidation-reduction reaction of Fe ions, which was difficult to achieve with oxide positive electrode materials for lithium secondary batteries, and is noted as a material that does not contain any rare metals. Has been done.
例えば、特許文献１には、主に鉄とナトリウムとを含有し、六方晶の結晶構造を有し、かつ２．２０Åのピークの強度を面間隔５．３６Åのピークの強度で除した値が２以下である複合酸化物からなる正極活物質が記載されているが、充放電の可逆容量はせいぜい６０ｍＡｈ／ｇ程度に過ぎず、また、容量維持率も十分ではない。 For example, in Patent Document 1, a value mainly containing iron and sodium, having a hexagonal crystal structure, and dividing the intensity of the peak of 2.20Å by the intensity of the peak of the interplanar spacing 5.36Å is Although a positive electrode active material composed of a composite oxide having a ratio of 2 or less is described, the reversible capacity of charge/discharge is at most about 60 mAh/g, and the capacity retention rate is not sufficient.
このように、鉄酸ナトリウム（ＮａＦｅＯ２）を正極材料として用いたナトリウム二次電池は、十分な充放電容量及び容量維持率が得られていない。そのため、正極材料の結晶性の改善、Ｆｅの一部又は全部を異種元素で置換する事等によって、特性改善が試みられている。 As described above, the sodium secondary battery using sodium ferrate (NaFeO 2 ) as the positive electrode material does not have sufficient charge/discharge capacity and capacity retention rate. Therefore, attempts have been made to improve the characteristics by improving the crystallinity of the positive electrode material and substituting a part or all of Fe with a different element.
例えば、非特許文献１には、リチウム二次電池において既に実用化されているＬｉ（Ｎｉ１／３Ｍｎ１／３Ｃｏ１／３）Ｏ２におけるＬｉをＮａに置き換えたＮａ（Ｎｉ１／３Ｍｎ１／３Ｃｏ１／３）Ｏ２を正極材料に用いることが記載されている。 For example, in Non-Patent Document 1, Na(Ni 1/3 ) obtained by replacing Li in Na(Ni 1/3 Mn 1/3 Co 1/3 )O 2 which has already been put into practical use in a lithium secondary battery with Na(Ni 1/3) It is described that Mn 1/3 Co 1/3 )O 2 is used as a positive electrode material.
非特許文献２にはＮａＦｅＯ２のＦｅをＭｎ及びＮｉで置換したＮａＦｅ１−ｘＭｎｘ／２Ｎｉｙ／２Ｏ２を正極材料に用いることによって、高容量化が可能であることが記載されている。 Non-Patent Document 2 describes that high capacity can be achieved by using NaFe 1-x Mn x/2 Ni y/2 O 2 obtained by substituting Fe of NaFeO 2 with Mn and Ni as a positive electrode material. ing.
しかしながら、非特許文献１では、Ｎｉ、Ｃｏ等の希少金属が多く使用されており、原料の安定供給の根本解決には至っていない。また、非特許文献２では、Ｆｅの４割以上を置換した材料しか電極特性が示されておらず、置換量を低減した材料の特性は明らかになっていない。また、非特許文献２には、ＭｎとＮｉが同量置換された材料の特性のみが記載されており、ＭｎとＮｉの置換量を独立に変化させた材料の特性については検討されていない。さらに、非特許文献２では、ＮａＦｅＯ２のＦｅをＭｎ及びＮｉで置換した材料は、８００℃及び２４時間という長時間の熱処理がされており、結晶子サイズが大きいことが示唆され、充放電サイクル特性が不十分であることが示唆される。 However, in Non-Patent Document 1, rare metals such as Ni and Co are often used, and a fundamental solution to stable supply of raw materials has not been reached. Further, in Non-Patent Document 2, only the material in which 40% or more of Fe is substituted is shown as electrode characteristics, and the characteristics of the material in which the substitution amount is reduced are not clear. Further, Non-Patent Document 2 describes only the characteristics of a material in which Mn and Ni are substituted in the same amount, and the characteristics of a material in which the substitution amounts of Mn and Ni are independently changed are not examined. Further, in Non-Patent Document 2, a material obtained by substituting Fe of NaFeO 2 with Mn and Ni is subjected to a heat treatment for a long time of 800° C. and 24 hours, suggesting that the crystallite size is large, and the charge-discharge cycle is shown. It is suggested that the properties are insufficient.
本発明は、上記した従来技術の現状に鑑みてなされたものであり、その主な目的は、希少金属使用量が少なく、従来の鉄酸ナトリウムと比べて高容量で且つ、鉄の重量分率容量に優れ、充放電サイクル特性にも優れたナトリウム二次電池用正極材料を提供することである。鉄の重量分率容量とは下記に示される式で算出されるもので、充放電容量への鉄の寄与を示す指標として用いた。この値が高いほど、充放電容量に対して、鉄が有効に利用されているものと考えられる。 The present invention has been made in view of the above-mentioned conventional state of the art, and its main purpose is to use a small amount of a rare metal, have a higher capacity than conventional sodium ferrate, and a weight fraction of iron. An object of the present invention is to provide a positive electrode material for sodium secondary batteries, which has excellent capacity and excellent charge/discharge cycle characteristics. The weight fraction capacity of iron is calculated by the formula shown below and used as an index showing the contribution of iron to the charge/discharge capacity. It is considered that the higher this value is, the more effectively iron is used for the charge/discharge capacity.
鉄の重量分率容量（ｍＡｈ／ｇ）
= 材料の充放電容量（ｍＡｈ／ｇ） × 材料中に含まれる鉄の重量分率（％）
Weight fraction capacity of iron (mAh/g)
= Charge/discharge capacity of material (mAh/g) × Weight fraction of iron contained in material (%)
本発明者らは、上記した目的を達成すべく鋭意研究を重ねてきた。その結果、Ｏ３型層状構造を主相とし、特定の組成を有するナトリウム−鉄−マンガン−ニッケル系複合酸化物が、希少金属使用量が少なく、高容量で且つ、鉄の重量分率容量に優れていることを見出した。この複合酸化物を含有する正極材料は、ナトリウム、鉄、マンガン、ニッケル及び酸素を含む混合物を７００℃以上（特に結晶粒の大きさが特定の大きさとなる条件）で加熱する加熱工程を備える方法により得られる。本発明は、これらの知見に基づいて更に研究を重ねた結果、完成されたものである。即ち、本発明は、以下の構成を包含するものである。
項１．Ｏ３型層状構造を主相とし、一般式（１）：
Ｎａ１±δＦｅ１−ｘ−ｙＭｎｘＮｉｙＯ２
［式中、δは０〜０．１０；ｘ及びｙは同じか又は異なり、ｘは０．０５〜０．２３、ｙは０．０５〜０．２３である。］
で示される組成を有し、結晶子サイズが平均で３０〜６０ｎｍである結晶粒を有する化合物を含有する、ナトリウム二次電池用正極材料。
項２．前記一般式（１）において、０．１０≦ｘ＋ｙ＜０．４０である、項１に記載のナトリウム二次電池用正極材料。
項３．充電時にＯ３型層状構造から単斜晶系結晶構造への構造変化のない、項１又は２に記載のナトリウム二次電池用正極材料。
項４．Ｏ３型層状構造を８０モル％以上有する、項１〜３のいずれかに記載のナトリウム二次電池用正極材料。
項５．項１〜４のいずれかに記載のナトリウム二次電池用正極材料の製造方法であって、
ナトリウム、鉄、マンガン、ニッケル及び酸素を含む混合物を加熱する加熱工程
を備える、製造方法。
項６．前記加熱工程の加熱温度が７００〜１０００℃である、項５に記載の製造方法。
項７．前記ナトリウム、鉄、マンガン、ニッケル及び酸素を含む混合物が、鉄、マンガン及びニッケルを含む酸化物、水酸化物及び炭酸塩よりなる群から選ばれる少なくとも１種と、ナトリウム含有化合物との混合物である、項５又は６に記載の製造方法。
項８．前記ナトリウム、鉄、マンガン、ニッケル及び酸素を含む混合物が、鉄、マンガン及びニッケルを含む酸化物と、ナトリウム炭酸塩との混合物である、項５〜７のいずれかに記載の製造方法。
項９．前記鉄、マンガン及びニッケルを含む酸化物が、鉄、マンガン及びニッケルを含む硫酸塩、硝酸塩又は塩化物の水溶液をアルカリ水酸化物水溶液に滴下することにより得られる、項８に記載の製造方法。
項１０．項１〜４のいずれかに記載のナトリウム二次電池用正極材料を含有する、ナトリウム二次電池用正極。
項１１．項１０に記載のナトリウム二次電池用正極を備えるナトリウム二次電池。
項１２．項１１に記載のナトリウム二次電池を用いることを特徴とする電気機器。
項１３．ナトリウム二次電池の充電時に、ナトリウム二次電池用正極材料がＯ３型層状構造から単斜晶系結晶構造への構造変化を抑制する方法であって、
Ｏ３型層状構造を主相とし、一般式（１）：
Ｎａ１±δＦｅ１−ｘ−ｙＭｎｘＮｉｙＯ２
［式中、δは０〜０．１０；ｘ及びｙは同じか又は異なり、ｘは０．０５〜０．２３、ｙは０．０５〜０．２３である。］
で示される組成を有し、結晶子サイズが平均で３０〜６０ｎｍである結晶粒を有する化合物を含有するナトリウム二次電池用正極材料を使用する、方法。
The inventors of the present invention have conducted extensive studies to achieve the above-mentioned object. As a result, the sodium-iron-manganese-nickel composite oxide having an O3 type layered structure as a main phase and having a specific composition has a small amount of rare metals used, a high capacity, and an excellent iron weight fraction capacity. I found that. The positive electrode material containing this composite oxide is provided with a heating step of heating a mixture containing sodium, iron, manganese, nickel and oxygen at 700° C. or higher (particularly under the condition that the crystal grain size becomes a specific size). Is obtained by The present invention has been completed as a result of further research based on these findings. That is, the present invention includes the following configurations.
Item 1. The O3 type layered structure is the main phase, and the general formula (1):
Na 1 ±δ Fe 1-x-y Mn x Ni y O 2
[In formula, (delta) is 0-0.10; x and y are the same or different, x is 0.05-0.23, y is 0.05-0.23. ]
A positive electrode material for a sodium secondary battery, which comprises a compound having a composition shown by and having a crystal grain having an average crystallite size of 30 to 60 nm.
Item 2. Item 2. The positive electrode material for a sodium secondary battery according to Item 1, wherein 0.10≦x+y<0.40 in the general formula (1).
Item 3. Item 3. The positive electrode material for a sodium secondary battery according to Item 1 or 2, which has no structural change from an O3 type layered structure to a monoclinic crystal structure during charging.
Item 4. Item 4. The positive electrode material for a sodium secondary battery according to any one of Items 1 to 3, which has an O3-type layered structure of 80 mol% or more.
Item 5. Item 5. A method for producing a positive electrode material for a sodium secondary battery according to any one of Items 1 to 4,
A manufacturing method comprising a heating step of heating a mixture containing sodium, iron, manganese, nickel and oxygen.
Item 6. Item 6. The manufacturing method according to Item 5, wherein the heating temperature in the heating step is 700 to 1000°C.
Item 7. The mixture containing sodium, iron, manganese, nickel and oxygen is a mixture of at least one selected from the group consisting of oxides, hydroxides and carbonates containing iron, manganese and nickel and a sodium-containing compound. Item 5 or the manufacturing method according to Item 6.
Item 8. Item 8. The method according to any one of Items 5 to 7, wherein the mixture containing sodium, iron, manganese, nickel and oxygen is a mixture of an oxide containing iron, manganese and nickel and sodium carbonate.
Item 9. Item 9. The production method according to Item 8, wherein the oxide containing iron, manganese, and nickel is obtained by dropping an aqueous solution of a sulfate, nitrate, or chloride containing iron, manganese, and nickel into an aqueous alkali hydroxide solution.
Item 10. Item 4. A positive electrode for sodium secondary batteries, which contains the positive electrode material for sodium secondary batteries according to any one of Items 1 to 4.
Item 11. Item 11. A sodium secondary battery comprising the positive electrode for a sodium secondary battery according to Item 10.
Item 12. Item 12. An electric device using the sodium secondary battery according to item 11.
Item 13. A method for suppressing a structural change of a positive electrode material for a sodium secondary battery from an O3 type layered structure to a monoclinic crystal structure when the sodium secondary battery is charged,
The O3 type layered structure is the main phase, and the general formula (1):
Na 1 ±δ Fe 1-x-y Mn x Ni y O 2
[In formula, (delta) is 0-0.10; x and y are the same or different, x is 0.05-0.23, y is 0.05-0.23. ]
A method for using a positive electrode material for a sodium secondary battery, which comprises a compound having a composition represented by, and having a compound having crystal grains having an average crystallite size of 30 to 60 nm.
本発明のナトリウム二次電池用正極材料によれば、従来のリチウム二次電池用正極材料であるコバルト酸リチウム（ＬｉＣｏＯ２）に対して、希少金属であるリチウムを資源が豊富なナトリウムに置換しているとともに、希少金属であるコバルトの多くを資源が豊富な鉄に置換しているため、希少金属の使用量を低減することができ、原料価格及び原料の安定供給の観点から好ましい。 According to the positive electrode material for a sodium secondary battery of the present invention, lithium, which is a rare metal, is replaced with sodium, which is rich in resources, in contrast to lithium cobalt oxide (LiCoO 2 ) which is a conventional positive electrode material for a lithium secondary battery. In addition, since most of the rare metal, cobalt, is replaced with iron, which is rich in resources, the amount of rare metal used can be reduced, which is preferable from the viewpoint of raw material price and stable supply of raw material.
本発明のナトリウム二次電池用正極材料は、高容量で、且つ、鉄の重量分率容量に優れ、充放電サイクル特性にも優れているため、ナトリウム二次電池を高容量化しつつ、鉄の性能を十分生かし切ることが可能である。 The positive electrode material for a sodium secondary battery of the present invention has a high capacity, excellent weight fraction capacity of iron, and excellent charge/discharge cycle characteristics. It is possible to make full use of the performance.
また、本発明の製造方法によれば、この様な優れた性能を有する複合酸化物からなるナトリウム二次電池用正極活物質を、比較的容易に製造することができる。さらに、本発明のナトリウム二次電池用正極材料を、鉄、マンガン及びニッケルを含む酸化物、水酸化物及び炭酸塩等と、ナトリウムを含む酸化物、水酸化物及び炭酸塩等とを混合して加熱することにより製造した場合には、充放電サイクル特性を向上させることも可能である。 Further, according to the production method of the present invention, it is possible to relatively easily produce the positive electrode active material for sodium secondary batteries, which is made of such a complex oxide having excellent performance. Furthermore, the positive electrode material for a sodium secondary battery of the present invention is prepared by mixing an oxide, hydroxide, carbonate or the like containing iron, manganese and nickel with an oxide, hydroxide or carbonate, etc. containing sodium. When manufactured by heating by heating, it is possible to improve the charge/discharge cycle characteristics.
１．ナトリウム二次電池用正極材料
本発明のナトリウム二次電池用正極材料は、Ｏ３型層状構造を主相とし、一般式（１）：
Ｎａ１±δＦｅ１−ｘ−ｙＭｎｘＮｉｙＯ２
［式中、δは０〜０．１０；ｘ及びｙは同じか又は異なり、ｘは０．０５〜０．２３、ｙは０．０５〜０．２３である。］
で示される組成を有し、結晶子サイズが平均で３０〜６０ｎｍである結晶粒を有する。
1. Positive Electrode Material for Sodium Secondary Battery The positive electrode material for sodium secondary battery of the present invention has an O3 type layered structure as a main phase and has the general formula (1):
Na 1 ±δ Fe 1-x-y Mn x Ni y O 2
[In formula, (delta) is 0-0.10; x and y are the same or different, x is 0.05-0.23, y is 0.05-0.23. ]
And has a crystal grain having an average crystallite size of 30 to 60 nm.
本発明のナトリウム二次電池用正極材料は、Ｏ３型層状構造を主相とする。このＯ３型層状構造は、一般式（１）：
Ｎａ１±δＦｅ１−ｘ−ｙＭｎｘＮｉｙＯ２
［式中、δは０〜０．１０；ｘ及びｙは同じか又は異なり、ｘは０．０５〜０．２３、ｙは０．０５〜０．２３である。］
で示され、コバルト酸リチウムＬｉＣｏＯ２と同じ結晶構造モデルであり、充電時にナトリウムの脱離とともにＯ３型層状構造からＰ３型層状構造に変化し、その後Ｐ３型層状構造からＯ３型層状構造に変化する。この本発明のナトリウム二次電池用正極材料（ナトリウム二次電池用正極材料がＯ３型層状構造の化合物以外の化合物を有する場合はＯ３型層状構造の化合物）は、充電時にＯ３型層状構造から単斜晶系結晶構造への構造変化はしない材料である。このような構造変化を経る複合酸化物を含有する正極材料を採用することで、ナトリウム二次電池は高電位領域でも高い放電容量を示し、放電容量維持率に優れる。Ｏ３型層状構造が主相であるか否かは、ナトリウム二次電池用正極材料（上記複合酸化物を含有する化合物）のＸ線回析測定により確認する。Ｏ３型層状構造の存在量は特に限定的ではないが、該複合酸化物全体を基準として８０モル％以上が好ましく、９０モル％以上がより好ましい。
The positive electrode material for a sodium secondary battery of the present invention has an O3 type layered structure as a main phase. This O3 type layered structure has the general formula (1):
Na 1 ±δ Fe 1-x-y Mn x Ni y O 2
[In formula, (delta) is 0-0.10; x and y are the same or different, x is 0.05-0.23, y is 0.05-0.23. ]
It is the same crystal structure model as lithium cobalt oxide LiCoO 2, and changes from the O3 type layered structure to the P3 type layered structure with the desorption of sodium during charging, and then changes from the P3 type layered structure to the O3 type layered structure. .. The positive electrode material for a sodium secondary battery of the present invention (a compound having an O3 type layered structure when the positive electrode material for a sodium secondary battery has a compound other than the compound having an O3 type layered structure) is used as a single substance from the O3 type layered structure during charging. It is a material that does not change its structure to the orthorhombic crystal structure. By adopting the positive electrode material containing the complex oxide that undergoes such a structural change, the sodium secondary battery exhibits a high discharge capacity even in a high potential region and is excellent in the discharge capacity retention rate. Whether or not the O3 type layered structure is the main phase is confirmed by X-ray diffraction measurement of the positive electrode material for sodium secondary batteries (compound containing the above complex oxide). The amount of the O3 type layered structure is not particularly limited, but is preferably 80 mol% or more, and more preferably 90 mol% or more, based on the entire composite oxide.
本発明のナトリウム二次電池用正極材料は、単相のＯ３型層状構造、つまり、Ｏ３型層状構造のみからなる材料であってもよいが、本発明の効果を損なわない範囲で、他の結晶構造を有していてもよい。具体的には、β−ＮａＦｅＯ２型やＰ２型層状構造等の結晶構造を、該複合酸化物の２０モル％以下程度、特に１０モル％以下含有していてもよい。 The positive electrode material for a sodium secondary battery of the present invention may be a single-phase O3 type layered structure, that is, a material consisting of only an O3 type layered structure, but other crystals may be used as long as the effects of the present invention are not impaired. It may have a structure. Specifically, a crystal structure such as β-NaFeO 2 type or P2 type layered structure may be contained in an amount of about 20 mol% or less, particularly 10 mol% or less of the composite oxide.
一般式（１）において、δはナトリウム二次電池用正極材料（特にＯ３型層状構造の複合酸化物）中のナトリウムの含有割合に関し、０〜０．１０、好ましくは０〜０．０５である。δが０．１０を超えると、材料中のナトリウム量が少なくなりすぎたり多くなりすぎたりして、十分な可逆容量が得られなくなる。 In the general formula (1), δ is 0 to 0.10, preferably 0 to 0.05 with respect to the content ratio of sodium in the positive electrode material for sodium secondary batteries (particularly, the composite oxide having the O3 type layered structure). .. When δ exceeds 0.10, the amount of sodium in the material becomes too small or too large, and a sufficient reversible capacity cannot be obtained.
一般式（１）において、ｘはナトリウム二次電池用正極材料（特にＯ３型層状構造の複合酸化物）中のマンガンの含有割合に関し、０．０５〜０．２３、好ましくは０．０５〜０．２０、より好ましくは０．０８〜０．２０、さらに好ましくは０．１０〜０．２０、特に好ましくは０．１０〜０．１７である。ｘが０．０５未満では、容量が低下するのみならず、相対的に鉄の含有割合が上昇することから、鉄の重量分率容量が著しく低下してしまう。ｘが０．２３を超えると、容量は向上するものの、相対的に鉄の含有割合が減少することから、鉄の重量分率容量が著しく低下してしまう。 In the general formula (1), x is 0.05 to 0.23, preferably 0.05 to 0, with respect to the content ratio of manganese in the positive electrode material for sodium secondary batteries (particularly, the composite oxide having an O3 type layered structure). .20, more preferably 0.08 to 0.20, further preferably 0.10 to 0.20, and particularly preferably 0.10 to 0.17. When x is less than 0.05, not only the capacity is decreased, but also the iron content ratio is relatively increased, so that the weight fraction capacity of iron is significantly decreased. When x exceeds 0.23, the capacity is improved, but the iron content ratio is relatively decreased, so that the weight fraction capacity of iron is significantly decreased.
一般式（１）において、ｙはナトリウム二次電池用正極材料（特にＯ３型層状構造の複合酸化物）中のニッケルの含有割合に関し、０．０５〜０．２３、好ましくは０．０５〜０．２０、より好ましくは０．０８〜０．２０、さらに好ましくは０．１０〜０．２０、特に好ましくは０．１０〜０．１７である。ｙが０．０５未満では、容量が低下するのみならず、相対的に鉄の含有割合が上昇することから、鉄の重量分率容量が著しく低下してしまう。ｙが０．２３を超えると、容量は向上するものの、均一混合することが困難になり、また、鉄の重量分率容量が著しく低下してしまう。 In the general formula (1), y is 0.05 to 0.23, preferably 0.05 to 0, with respect to the content ratio of nickel in the positive electrode material for sodium secondary batteries (particularly, the complex oxide having an O3 type layered structure). .20, more preferably 0.08 to 0.20, further preferably 0.10 to 0.20, and particularly preferably 0.10 to 0.17. When y is less than 0.05, not only the capacity is decreased, but also the iron content ratio is relatively increased, so that the weight fraction capacity of iron is significantly decreased. When y exceeds 0.23, the capacity is improved, but uniform mixing becomes difficult, and the weight fraction capacity of iron is significantly reduced.
なお、本発明において、マンガン及びニッケルは、従来からナトリウム二次電池の正極材料として使用されている鉄酸ナトリウム（ＮａＦｅＯ２）における鉄（３価）の置換元素としての位置付けである。これらの元素は理論上、ニッケルが２価、マンガンは平均価数３価〜４価で安定に存在することができる。鉄の一部が置換されたＮａ１±δＦｅ１−ｘ−ｙＭｎｘＮｉｙＯ２中においても遷移金属の平均価数は３価であることが好ましく、２価であるニッケルの置換による平均価数の低下をマンガンが４価となることで補償することができる。そのため、ｘとｙの範囲、具体的にはｘ／ｙが２以下であれば、遷移金属の価数が平均して３価となり、釣り合いを取ることができ、より高容量で、より鉄の重量分率容量に優れる正極材料が得られる。この観点から、ｘとｙは同程度とすることが好ましい。具体的には、ｘ／ｙは３．０／１．０〜１．０／１．０が好ましく、２．０／１．０〜１．０／１．０がより好ましい。 In the present invention, manganese and nickel are positioned as elements substituting iron (trivalent) in sodium ferrate (NaFeO 2 ) conventionally used as a positive electrode material for sodium secondary batteries. Theoretically, nickel can be stably present with divalent nickel and manganese with an average valence of three to four. Even in Na 1 ±δ Fe 1-x-y Mn x Ni y O 2 in which a part of iron is substituted, the average valence of the transition metal is preferably trivalent, and due to the substitution of divalent nickel. The decrease in the average valence can be compensated by making the manganese tetravalent. Therefore, when the range of x and y, specifically, x/y is 2 or less, the valence of the transition metal becomes trivalent on average, and the balance can be achieved, and the capacity is higher and the iron content is higher. A positive electrode material having an excellent weight fraction capacity can be obtained. From this viewpoint, it is preferable that x and y are substantially the same. Specifically, x/y is preferably 3.0/1.0 to 1.0/1.0, and more preferably 2.0/1.0 to 1.0/1.0.
一般式（１）において、ｘ＋ｙはナトリウム二次電池用正極材料（特にＯ３型層状構造の複合酸化物）中の鉄の含有割合に関する。上記のとおり、ｘが０．０５〜０．２３であり、ｙが０．０５〜０．２３であることから、ｘ＋ｙは０．１０〜０．４６であるが、容量及び鉄の重量分率容量の観点から、０．１０以上０．４０未満が好ましく、０．１６〜０．３８がより好ましく、０．２０〜０．３７がさらに好ましく、０．２０〜０．３５が特に好ましく、０．２０〜０．３０がさらに特に好ましい。 In the general formula (1), x+y relates to the content ratio of iron in the positive electrode material for sodium secondary batteries (particularly, the composite oxide having an O3 type layered structure). As described above, since x is 0.05 to 0.23 and y is 0.05 to 0.23, x+y is 0.10 to 0.46, but the capacity and the weight fraction of iron are From the viewpoint of capacity, it is preferably 0.10 or more and less than 0.40, more preferably 0.16 to 0.38, further preferably 0.20 to 0.37, particularly preferably 0.20 to 0.35, and 0. .20-0.30 is even more preferable.
本発明のナトリウム二次電池用正極材料は、上記一般式（１）で示される組成を有する化合物を含有しており、主相が上記一般式（１）で示されるＯ３型層状構造であるが、不可避不純物が含まれていてもよい。このような不可避不純物としては、原料によるものが考えられ、ナトリウム含有化合物としてＮａ２ＣＯ３、ＮａＯＨ等の他、Ｆｅ、Ｍｎ及びＮｉを１種類以上含む遷移金属酸化物及び水酸化物等が挙げられ、本発明の効果を損なわない範囲で、１０モル％以下程度、特に５モル％以下、さらには２モル％以下含有していてもよい。 The positive electrode material for sodium secondary batteries of the present invention contains the compound having the composition represented by the general formula (1), and the main phase thereof is the O3 type layered structure represented by the general formula (1). Inevitable impurities may be contained. As such unavoidable impurities, those due to the raw materials are considered, and examples of the sodium-containing compound include Na 2 CO 3 and NaOH, as well as transition metal oxides and hydroxides containing one or more kinds of Fe, Mn, and Ni. However, it may be contained in an amount of about 10 mol% or less, particularly 5 mol% or less, and further 2 mol% or less as long as the effect of the present invention is not impaired.
上記のような結晶構造及び組成を有する本発明のナトリウム二次電池用正極材料は、容量及び鉄の重量分率容量の観点から、結晶粒（特に、Ｏ３型層状構造を有する結晶粒）を有する。この結晶粒の平均結晶子サイズは、直径３０〜６０ｎｍ、好ましくは直径３５〜６０ｎｍである。結晶粒の平均結晶子サイズが３０ｎｍ未満の材料は、合成が困難である。また、結晶粒の平均結晶子サイズが６０ｎｍをこえると、充放電サイクル特性が悪化する。材料の結晶子サイズは、Ｘ線回折測定において、単相又は主相として観測されるＯ３型層状構造の（００３）面に帰属される回折ピークの半価幅から、Scherrerの式に基づいて算出した。 The positive electrode material for sodium secondary batteries of the present invention having the above crystal structure and composition has crystal grains (particularly, crystal grains having an O3 type layered structure) from the viewpoint of capacity and iron weight fraction capacity. .. The average crystallite size of the crystal grains is 30 to 60 nm in diameter, preferably 35 to 60 nm in diameter. A material having an average crystallite size of crystal grains of less than 30 nm is difficult to synthesize. If the average crystallite size of the crystal grains exceeds 60 nm, the charge/discharge cycle characteristics deteriorate. The crystallite size of the material is calculated based on the Scherrer formula from the half width of the diffraction peak attributed to the (003) plane of the O3 type layered structure observed as a single phase or a main phase in X-ray diffraction measurement. did.
２．ナトリウム二次電池用正極材料の製造方法
本発明のナトリウム二次電池用正極材料は、例えば、
ナトリウム、鉄、マンガン、ニッケル及び酸素を含む混合物を加熱する加熱工程
を備える製造方法により得ることができる。以下、この方法について具体的に説明する。
2. Method for producing positive electrode material for sodium secondary battery The positive electrode material for sodium secondary battery of the present invention is, for example,
It can be obtained by a manufacturing method including a heating step of heating a mixture containing sodium, iron, manganese, nickel and oxygen. Hereinafter, this method will be specifically described.
（１）原料化合物
本発明の製造方法においては、ナトリウム、鉄、マンガン、ニッケル及び酸素を含む混合物を加熱工程に供する。このナトリウム、鉄、マンガン、ニッケル及び酸素を含む混合物を得るための原料化合物としては、最終的に混合物中にナトリウム、鉄、マンガン、ニッケル及び酸素が所定割合で含まれていればよいが、例えば、ナトリウム含有化合物、鉄含有化合物、マンガン含有化合物、ニッケル含有化合物及び酸素含有化合物を用いることができる。
(1) Raw Material Compound In the production method of the present invention, a mixture containing sodium, iron, manganese, nickel and oxygen is subjected to a heating step. As a raw material compound for obtaining a mixture containing sodium, iron, manganese, nickel and oxygen, sodium, iron, manganese, nickel and oxygen may be finally contained in the mixture at a predetermined ratio, for example, , Sodium-containing compounds, iron-containing compounds, manganese-containing compounds, nickel-containing compounds and oxygen-containing compounds can be used.
ナトリウム含有化合物、鉄含有化合物、マンガン含有化合物、ニッケル含有化合物及び酸素含有化合物の各化合物の種類については特に限定的ではなく、ナトリウム、鉄、マンガン、ニッケル及び酸素の各元素を一種類ずつ含む５種類またはそれ以上の種類の化合物を混合して用いてもよく、あるいは、ナトリウム、鉄、マンガン、ニッケル及び酸素の内の２種類又はそれ以上の元素を同時に含む化合物を原料の一部として用い、５種類未満の化合物を混合して用いてもよい。 The kind of each compound of the sodium-containing compound, the iron-containing compound, the manganese-containing compound, the nickel-containing compound and the oxygen-containing compound is not particularly limited, and each of the elements of sodium, iron, manganese, nickel and oxygen is included 5 One or more kinds of compounds may be mixed and used, or a compound containing simultaneously two or more elements of sodium, iron, manganese, nickel and oxygen is used as a part of the raw material, You may mix and use less than 5 types of compounds.
これらの原料化合物は、ナトリウム、鉄、マンガン及びニッケル以外の金属元素（特に希少金属元素）を含まない化合物であることが好ましい。また、原料化合物中に含まれるナトリウム、鉄、マンガン、ニッケル及び酸素の各元素以外の元素については、後述する非酸化性雰囲気下での熱処理により離脱・揮発していくものが望ましい。 It is preferable that these raw material compounds are compounds that do not contain metal elements other than sodium, iron, manganese, and nickel (particularly rare metal elements). Further, it is desirable that elements other than the elements of sodium, iron, manganese, nickel and oxygen contained in the raw material compounds be released and volatilized by a heat treatment under a non-oxidizing atmosphere described later.
この様な原料化合物の具体例としては、ナトリウム含有化合物として、金属ナトリウム（Ｎａ）；水酸化ナトリウム（ＮａＯＨ）；炭酸ナトリウム（Ｎａ２ＣＯ３）、炭酸水素ナトリウム（ＮａＨＣＯ３）等のナトリウム炭酸塩等が例示でき、鉄含有化合物として、金属鉄（Ｆｅ）；酸化鉄（II）（ＦｅＯ）、酸化鉄（III）（Ｆｅ２Ｏ３）等の鉄酸化物；水酸化鉄（II）（Ｆｅ（ＯＨ）２）、水酸化鉄（III）（Ｆｅ（ＯＨ）３）等の鉄水酸化物；炭酸鉄（II）（ＦｅＣＯ３）、炭酸鉄（III）（Ｆｅ２（ＣＯ３）２）等の鉄炭酸塩；鉄−マンガン−ニッケル複合酸化物等の鉄、マンガン及びニッケルを含む酸化物；鉄−マンガン−ニッケル複合水酸化物等の鉄、マンガン及びニッケルを含む水酸化物；鉄−マンガン−ニッケル複合炭酸塩等の鉄、マンガン及びニッケルを含む炭酸塩等が例示でき、マンガン含有化合物として、金属マンガン（Ｍｎ）；酸化マンガン（II）（ＭｎＯ）、酸化マンガン（IV）（ＭｎＯ２）等のマンガン酸化物；水酸化マンガン（II）（Ｍｎ（ＯＨ）２）、水酸化マンガン（III）（Ｍｎ（ＯＨ）３）等のマンガン水酸化物；炭酸マンガン（II）（ＭｎＣＯ３）；鉄−マンガン−ニッケル複合酸化物等の鉄、マンガン及びニッケルを含む酸化物；鉄−マンガン−ニッケル複合水酸化物等の鉄、マンガン及びニッケルを含む水酸化物；鉄−マンガン−ニッケル複合炭酸塩等の鉄、マンガン及びニッケルを含む炭酸塩等が例示でき、ニッケル含有化合物として、金属ニッケル（Ｎｉ）；酸化ニッケル（ＮｉＯ）；水酸化ニッケル（I）（Ｎｉ（ＯＨ））、水酸化ニッケル（II）（Ｎｉ（ＯＨ）２）等のニッケル水酸化物；炭酸ニッケル（II）（ＮｉＣＯ３）；鉄−マンガン−ニッケル複合酸化物等の鉄、マンガン及びニッケルを含む酸化物；鉄−マンガン−ニッケル複合水酸化物等の鉄、マンガン及びニッケルを含む水酸化物；鉄−マンガン−ニッケル複合炭酸塩等の鉄、マンガン及びニッケルを含む炭酸塩等が例示でき、酸素含有化合物として、水酸化ナトリウム（ＮａＯＨ）；炭酸ナトリウム（Ｎａ２ＣＯ３）、炭酸水素ナトリウム（ＮａＨＣＯ３）等のナトリウム炭酸塩；酸化鉄（II）（ＦｅＯ）、酸化鉄（III）（Ｆｅ２Ｏ３）等の鉄酸化物；水酸化鉄（II）（Ｆｅ（ＯＨ）２）、水酸化鉄（III）（Ｆｅ（ＯＨ）３）等の鉄水酸化物；炭酸鉄（II）（ＦｅＣＯ３）、炭酸鉄（III）（Ｆｅ２（ＣＯ３）２）等の鉄炭酸塩；酸化マンガン（II）（ＭｎＯ）、酸化マンガン（IV）（ＭｎＯ２）等のマンガン酸化物；水酸化マンガン（II）（Ｍｎ（ＯＨ）２）、水酸化マンガン（III）（Ｍｎ（ＯＨ）３）等のマンガン水酸化物；炭酸マンガン（II）（ＭｎＣＯ３）；酸化ニッケル（ＮｉＯ）；水酸化ニッケル（I）（Ｎｉ（ＯＨ））、水酸化ニッケル（II）（Ｎｉ（ＯＨ）２）等のニッケル水酸化物；炭酸ニッケル（II）（ＮｉＣＯ３）；鉄−マンガン−ニッケル複合酸化物等の鉄、マンガン及びニッケルを含む酸化物；鉄−マンガン−ニッケル複合水酸化物等の鉄、マンガン及びニッケルを含む水酸化物；鉄−マンガン−ニッケル複合炭酸塩等の鉄、マンガン及びニッケルを含む炭酸塩等が例示できる。 Specific examples of such raw material compounds include sodium-containing compounds such as metal sodium (Na); sodium hydroxide (NaOH); sodium carbonate such as sodium carbonate (Na 2 CO 3 ), sodium hydrogen carbonate (NaHCO 3 ). And the like, and examples of the iron-containing compound include metallic iron (Fe); iron oxides such as iron oxide (II) (FeO) and iron oxide (III) (Fe 2 O 3 ); iron hydroxide (II) (Fe (OH) 2 ), iron hydroxide such as iron (III) hydroxide (Fe(OH) 3 ); iron carbonate (II) (FeCO 3 ), iron carbonate (III) (Fe 2 (CO 3 ) 2 ). Iron carbonates such as; oxides containing iron, manganese and nickel such as iron-manganese-nickel composite oxides; hydroxides containing iron, manganese and nickel such as iron-manganese-nickel composite hydroxides; iron- Examples thereof include iron, such as manganese-nickel composite carbonates, carbonates containing manganese and nickel, and examples of the manganese-containing compound include metal manganese (Mn); manganese (II) oxide (MnO) and manganese (IV) oxide (MnO 2 ). ) And other manganese oxides; manganese (II) hydroxide (Mn(OH) 2 ), manganese (III) hydroxide (Mn(OH) 3 ) and other manganese hydroxides; manganese (II) carbonate (MnCO 3 ) An oxide containing iron, manganese and nickel such as iron-manganese-nickel composite oxide; a hydroxide containing iron, manganese and nickel such as iron-manganese-nickel composite hydroxide; iron-manganese-nickel composite carbonate Examples of the salt include iron, manganese, and carbonates containing nickel. Examples of the nickel-containing compound include metallic nickel (Ni); nickel oxide (NiO); nickel hydroxide (I) (Ni(OH)) and nickel hydroxide. (II) (Ni(OH) 2 ) nickel hydroxide; nickel carbonate (II) (NiCO 3 ); iron-manganese-nickel composite oxide and other oxides containing iron, manganese and nickel; iron-manganese -Hydroxides containing iron, manganese and nickel such as nickel composite hydroxides; carbonates containing iron, manganese and nickel such as iron-manganese-nickel composite carbonates, and the like, and examples of oxygen-containing compounds include hydroxides. Sodium (NaOH); sodium carbonate such as sodium carbonate (Na 2 CO 3 ), sodium hydrogen carbonate (NaHCO 3 ); iron such as iron oxide (II) (FeO) and iron oxide (III) (Fe 2 O 3 ). Oxide; iron hydroxide (I Iron hydroxides such as I) (Fe(OH) 2 ) and iron hydroxide (III) (Fe(OH) 3 ); iron carbonate (II) (FeCO 3 ), iron carbonate (III) (Fe 2 (CO 3 ) 2 ) etc. iron carbonates; manganese oxides such as manganese (II) oxide (MnO) and manganese (IV) oxide (MnO 2 ); manganese hydroxide (II) (Mn(OH) 2 ), hydroxylation Manganese hydroxide such as manganese (III) (Mn(OH) 3 ); manganese (II) carbonate (MnCO 3 ); nickel oxide (NiO); nickel hydroxide (I) (Ni(OH)), nickel hydroxide (II) (Ni(OH) 2 ) nickel hydroxide; nickel carbonate (II) (NiCO 3 ); iron-manganese-nickel composite oxide and other oxides containing iron, manganese and nickel; iron-manganese Examples thereof include hydroxides containing iron, manganese and nickel such as nickel composite hydroxide; carbonates containing iron, manganese and nickel such as iron-manganese-nickel composite carbonate.
これらのなかでも、鉄、マンガン及びニッケルを含む酸化物、水酸化物及び炭酸塩よりなる群から選ばれる少なくとも１種（なかでも鉄、マンガン及びニッケルを含む酸化物、さらには鉄−マンガン−ニッケル複合酸化物、特にスピネル構造を有する複合酸化物）を原料化合物としてナトリウム含有化合物（特にナトリウム炭酸塩）との混合物を使用することにより、得られる本発明のナトリウム二次電池用正極活物質の充放電サイクル特性をより向上させることができる。 Among these, at least one selected from the group consisting of oxides, hydroxides and carbonates containing iron, manganese and nickel (among others, oxides containing iron, manganese and nickel, and further iron-manganese-nickel). By using a mixture of a complex oxide, particularly a complex oxide having a spinel structure) as a starting compound with a sodium-containing compound (particularly sodium carbonate), the obtained positive electrode active material for a sodium secondary battery of the present invention can be charged. The discharge cycle characteristics can be further improved.
なお、本発明において、上記した原料化合物は、市販品を使用してもよいし、別途合成して用いてもよい。 In the present invention, the above raw material compounds may be commercially available products or may be separately synthesized and used.
原料化合物を合成する場合、例えば、鉄、マンガン及びニッケルを含むスピネル酸化物は、特に制限されないが、共沈法により合成することができる。具体的には、鉄、マンガン及びニッケルのイオンを含む水溶液（硫酸塩、硝酸塩、塩化物等の水溶液）をアルカリ水溶液中に滴下し沈殿物を生成することにより、鉄、マンガン及びニッケルを含むスピネル酸化物を得ることができる。 When synthesizing the raw material compound, for example, the spinel oxide containing iron, manganese, and nickel is not particularly limited, but can be synthesized by a coprecipitation method. Specifically, a spinel containing iron, manganese, and nickel is prepared by dropping an aqueous solution containing iron, manganese, and nickel ions (aqueous solution of sulfate, nitrate, chloride, etc.) into an alkaline aqueous solution to form a precipitate. An oxide can be obtained.
鉄、マンガン及びニッケルを含む混合物は、上記説明した原料化合物のうち、必要な材料を混合して得ることができる。 The mixture containing iron, manganese, and nickel can be obtained by mixing necessary materials among the raw material compounds described above.
鉄、マンガン及びニッケルを含む混合物における鉄、マンガン及びニッケルの含有割合は、特に制限されないが、容量及び鉄の重量分率容量の観点から、例えば、９０〜５４モル％：５〜２３モル％：５〜２３モル％（マンガン及びニッケルの合計含有量は１０モル％以上４０モル％未満）が好ましく、９０〜６０モル％：５〜２０モル％：５〜２０モル％（マンガン及びニッケルの合計含有量は１６〜３８モル％）がより好ましく、８４〜６０モル％：８〜２０モル％：８〜２０モル％（マンガン及びニッケルの合計含有量は２０〜３７モル％）がさらに好ましく、８０〜６０モル％：１０〜２０モル％：１０〜２０モル％（マンガン及びニッケルの合計含有量は２０〜３５モル％）が特に好ましく、８０〜６３モル％：１０〜２０モル％：１０〜１７モル％（マンガン及びニッケルの合計含有量は２０〜３０モル％）がさらに特に好ましい。 The content ratio of iron, manganese and nickel in the mixture containing iron, manganese and nickel is not particularly limited, but from the viewpoint of the capacity and the weight fraction capacity of iron, for example, 90 to 54 mol%: 5 to 23 mol%: 5 to 23 mol% (total content of manganese and nickel is 10 mol% or more and less than 40 mol%) is preferable, 90 to 60 mol%: 5 to 20 mol%: 5 to 20 mol% (total content of manganese and nickel The amount is more preferably 16 to 38 mol %, more preferably 84 to 60 mol %: 8 to 20 mol %: 8 to 20 mol% (the total content of manganese and nickel is 20 to 37 mol %), and 80 to 60 mol%:10-20 mol%:10-20 mol% (the total content of manganese and nickel is 20-35 mol%) is particularly preferable, and 80-63 mol%:10-20 mol%:10-17 mol % (The total content of manganese and nickel is 20 to 30 mol %) is particularly preferable.
アルカリ水溶液としては、特に制限はないが、鉄、マンガン及びニッケルを含むスピネル酸化物の合成のしやすさの観点から、水酸化ナトリウム水溶液、炭酸ナトリウム水溶液、水酸化リチウム水溶液、水酸化カリウム水溶液等が挙げられる。これらのアルカリ水溶液は、単独で用いてもよいし、２種以上を組合せて用いてもよい。 The alkaline aqueous solution is not particularly limited, but from the viewpoint of ease of synthesis of spinel oxide containing iron, manganese, and nickel, aqueous sodium hydroxide solution, aqueous sodium carbonate solution, aqueous lithium hydroxide solution, aqueous potassium hydroxide solution, etc. Is mentioned. These alkaline aqueous solutions may be used alone or in combination of two or more.
この場合、鉄、マンガン及びニッケルを含む混合物を、攪拌しながら、アルカリ水溶液を、１０〜５０℃（特に２０〜３０℃）程度の温度で、ｐＨが９〜１４（特に１２〜１４）となるように少しずつ添加し、沈殿物を生成させることが好ましい。アルカリ水溶液を２種以上使用する場合、各水溶液は、別途添加してもよいし、同時に添加してもよい。 In this case, while stirring the mixture containing iron, manganese and nickel, the pH of the alkaline aqueous solution becomes 9 to 14 (particularly 12 to 14) at a temperature of about 10 to 50°C (particularly 20 to 30°C). It is preferable that the precipitates are formed by adding them little by little as described above. When two or more alkaline aqueous solutions are used, each aqueous solution may be added separately or may be added simultaneously.
これら原料化合物の形状については特に限定はないが、取り扱い性の観点から、粉末状であることが好ましい。また反応性の観点から粒子は微細である方がよく平均粒子径が１μｍ以下（特に６０〜８０ｎｍ程度）の粉末状であることが好ましい。原料化合物の平均粒子径は、電子顕微鏡観察（ＳＥＭ）により測定する。 The shape of these raw material compounds is not particularly limited, but powdery form is preferable from the viewpoint of handleability. From the viewpoint of reactivity, the particles are preferably fine, and are preferably powdery with an average particle diameter of 1 μm or less (particularly about 60 to 80 nm). The average particle size of the raw material compound is measured by electron microscope observation (SEM).
各原料化合物の混合割合については、特に限定的ではないが、最終生成物であるナトリウム二次電池用正極材料（複合酸化物）が有する組成となるように混合することが好ましい。原料化合物の混合割合については、原料化合物に含まれる各元素の比率が、目的とする複合酸化物中の各元素の比率と同一となるようにすればよい。 The mixing ratio of the respective raw material compounds is not particularly limited, but it is preferable to mix them so that the composition of the final product positive electrode material for a sodium secondary battery (composite oxide) has. Regarding the mixing ratio of the raw material compounds, the ratio of each element contained in the raw material compound may be the same as the ratio of each element in the target composite oxide.
（２）製造方法
ナトリウム、鉄、マンガン、ニッケル及び酸素を含む混合物を製造するための混合方法としては、特に制限されるわけではなく、各原料化合物を均一に混合できる方法を採用すればよい。例えば、乳鉢混合、メカニカルミリング処理、各成分を溶媒中に分散させた後に混合する方法、各成分を溶媒中で一度に分散させて混合する方法等を採用することができる。各成分の溶媒への分散及び混合を行う場合には、対象物に超音波を照射する方法が、分散性の向上と均一な混合の観点からより好ましい。これらのなかでも、より均一に混合できる観点から、メカニカルミリング処理が好ましい。
(2) Manufacturing method The mixing method for manufacturing the mixture containing sodium, iron, manganese, nickel and oxygen is not particularly limited, and a method capable of uniformly mixing each raw material compound may be adopted. For example, mortar mixing, mechanical milling treatment, a method of dispersing each component in a solvent and then mixing, a method of dispersing each component in the solvent at once and mixing can be adopted. When each component is dispersed and mixed in a solvent, a method of irradiating an object with ultrasonic waves is more preferable from the viewpoint of improving dispersibility and uniform mixing. Among these, the mechanical milling treatment is preferable from the viewpoint of more uniform mixing.
混合手段としてメカニカルミリング処理を行う場合、メカニカルミリング装置としては、例えば、ボールミル、振動ミル、ターボミル、ディスクミル等を用いることができ、中でもボールミルが好ましい。また、この際には、混合と加熱処理を同時に施すことが好ましい。 When mechanical milling treatment is performed as the mixing means, for example, a ball mill, a vibration mill, a turbo mill, a disc mill or the like can be used as the mechanical milling device, and the ball mill is preferable. Further, at this time, it is preferable to perform the mixing and the heat treatment at the same time.
混合時の雰囲気は特に制限はないが、例えば、Ａｒ、Ｎ２等の不活性ガス雰囲気、大気雰囲気等が採用できる。 The atmosphere at the time of mixing is not particularly limited, but, for example, an atmosphere of an inert gas such as Ar or N 2 or an air atmosphere can be adopted.
ナトリウム、鉄、マンガン、ニッケル及び酸素を含む混合物を加熱処理するに際して、加熱温度は、得られるナトリウム二次電池用正極材料（特にＯ３型層状構造の複合酸化物）の結晶性及び電極特性（容量、鉄の含有分率当たりの容量）をより向上させるためには高温が好ましいが、高温にするほど結晶粒が大きくなる。結晶粒内のナトリウムの拡散距離を程度な範囲とし、ナトリウム正極材料の反応速度を維持するため、結晶粒の大きさは適切な範囲に留めた方がよく、高温にしすぎないことが好ましい。つまり、結晶性及び電極特性（容量、鉄の含有分率当たりの容量）の双方の観点から、加熱処理後に存在する結晶粒の大きさを適度に調整することが好ましい。具体的には、加熱処理後に存在する結晶粒の平均粒子径が３０〜６０ｎｍ、特に５０〜６０ｎｍとなるような温度及び時間加熱処理することが好ましい。 When heat-treating a mixture containing sodium, iron, manganese, nickel and oxygen, the heating temperature depends on the crystallinity and the electrode characteristics (capacity) of the obtained positive electrode material for sodium secondary batteries (particularly, the complex oxide having an O3 type layered structure). In order to further improve the iron content capacity, the high temperature is preferable, but the higher the temperature, the larger the crystal grains become. In order to keep the diffusion distance of sodium in the crystal grains within a certain range and maintain the reaction rate of the sodium positive electrode material, it is preferable to keep the size of the crystal grains within an appropriate range, and it is preferable that the temperature is not too high. That is, it is preferable to appropriately adjust the size of the crystal grains present after the heat treatment, from the viewpoints of both the crystallinity and the electrode characteristics (capacity, capacity per iron content fraction). Specifically, it is preferable to perform heat treatment at a temperature and for a time such that the average particle diameter of the crystal grains present after the heat treatment is 30 to 60 nm, particularly 50 to 60 nm.
具体的には、加熱温度を、７００℃以上、特に７００〜１０００℃、さらには８００〜９５０℃とすることが好ましい。なお、鉄含有量が多い場合（一般式（１）において、０．１０≦ｘ＋ｙ≦０．１５の場合）は、加熱温度は低温、特に６００〜８００℃（特に７００〜７５０℃）とすることが好ましく、鉄含有量がやや多い場合（一般式（１）において、０．１５≦ｘ＋ｙ≦０．２５の場合）は、加熱温度はやや低温、特に６００〜９００℃（特に６５０〜８５０℃）とすることが好ましく、鉄含有量がやや少ない場合（一般式（１）において、０．２５≦ｘ＋ｙ≦０．３５の場合）は、加熱温度はやや高温、特に７００〜１０００℃（特に７５０〜９５０℃）とすることが好ましく、鉄含有量が少ない場合（一般式（１）において、０．３５≦ｘ＋ｙ≦０．４の場合）は、加熱温度は高温、特に７５０〜１０００℃（特に８００〜９５０℃）とすることが好ましい。 Specifically, the heating temperature is preferably 700° C. or higher, particularly 700 to 1000° C., and more preferably 800 to 950° C. When the iron content is high (in the general formula (1), 0.10≦x+y≦0.15), the heating temperature is low, particularly 600 to 800° C. (particularly 700 to 750° C.). Is preferred, and when the iron content is slightly high (in the general formula (1), 0.15≦x+y≦0.25), the heating temperature is rather low, particularly 600 to 900° C. (especially 650 to 850° C.). When the iron content is slightly low (in the general formula (1), 0.25≦x+y≦0.35), the heating temperature is rather high, particularly 700 to 1000° C. (especially 750 to 750° C.). 950° C.), and when the iron content is low (in the general formula (1), 0.35≦x+y≦0.4), the heating temperature is high, particularly 750 to 1000° C. (especially 800° C.). Up to 950° C.) is preferable.
加熱時間については、特に限定的ではないが、例えば、５〜２０時間が好ましく、 １０〜１５時間がより好ましい。 The heating time is not particularly limited, but is, for example, preferably 5 to 20 hours, more preferably 10 to 15 hours.
３．ナトリウム二次電池用正極及びナトリウム二次電池
本発明のナトリウム二次電池用正極材料（特にＯ３型層状構造の複合酸化物）は、上記した優れた特性（容量及び鉄の重量分率容量）を利用して、ナトリウムイオン二次電池、金属ナトリウム二次電池等ナトリウム二次電池の正極活物質として有効に利用できる。特に、本発明のナトリウム二次電池用正極材料（特にＯ３型層状構造の複合酸化物）は、構造中にナトリウムを含有する材料であるため、充電から充放電を行うことができる材料であり、しかも、高容量及び高い鉄の重量分率容量を有することから、ナトリウムイオン二次電池用の正極活物質として有用である。本発明のナトリウム二次電池用正極材料（特にＯ３型層状構造の複合酸化物）を正極活物質として使用するナトリウムイオン二次電池は、電解質として非水溶媒系電解液を用いる非水電解質ナトリウムイオン二次電池であってもよく、或いは、ナトリウムイオン伝導性の固体電解質を用いる全固体型ナトリウムイオン二次電池であってもよい。
3. Positive Electrode for Sodium Secondary Battery and Sodium Secondary Battery The positive electrode material for sodium secondary battery of the present invention (particularly, the composite oxide having an O3 type layered structure) has the above-described excellent properties (capacity and weight fraction capacity of iron). By utilizing it, it can be effectively used as a positive electrode active material for sodium secondary batteries such as sodium ion secondary batteries and metallic sodium secondary batteries. In particular, the positive electrode material for a sodium secondary battery of the present invention (particularly, the composite oxide having an O3 type layered structure) is a material that contains sodium in the structure, and thus can be charged and discharged. Moreover, since it has a high capacity and a high weight fraction capacity of iron, it is useful as a positive electrode active material for a sodium ion secondary battery. A sodium ion secondary battery using the positive electrode material for a sodium secondary battery of the present invention (particularly, a composite oxide having an O3 type layered structure) as a positive electrode active material is a non-aqueous electrolyte sodium ion using a non-aqueous solvent electrolyte as an electrolyte. It may be a secondary battery, or may be an all-solid-state sodium ion secondary battery using a sodium ion conductive solid electrolyte.
非水電解質ナトリウムイオン二次電池、全固体型ナトリウムイオン二次電池及び金属ナトリウム二次電池の構造は、本発明のナトリウム二次電池用正極材料（特にＯ３型層状構造の複合酸化物）を正極活物質として用いること以外は、公知のナトリウム二次電池と同様とすることができる。 The structure of the non-aqueous electrolyte sodium ion secondary battery, the all-solid-state sodium ion secondary battery, and the metal sodium secondary battery is the positive electrode material for the sodium secondary battery of the present invention (particularly, the composite oxide having the O3 type layered structure) as a positive electrode. It may be the same as a known sodium secondary battery except that it is used as an active material.
例えば、非水電解質ナトリウムイオン二次電池については、上記したナトリウム二次電池用正極材料（特にＯ３型層状構造の複合酸化物）を正極活物質として使用する他は、基本的な構造は、公知の非水電解質ナトリウムイオン二次電池と同様とすることができる。 For example, regarding the non-aqueous electrolyte sodium ion secondary battery, the basic structure is known except that the above-mentioned positive electrode material for sodium secondary batteries (particularly, the composite oxide having an O3 type layered structure) is used as the positive electrode active material. The same can be applied to the non-aqueous electrolyte sodium ion secondary battery of.
正極としては、上記したナトリウム二次電池用正極材料（特にＯ３型層状構造の複合酸化物）を正極活物質として用い、導電剤及びバインダーと混合することで作製した正極合剤をＡｌ、Ｎｉ、ステンレス、カーボンクロス等の正極集電体に担持させることで製造することができる。導電剤としては、例えば、黒鉛、コークス類、カーボンブラック、針状カーボン等の炭素材料を用いることができる。 As the positive electrode, the above positive electrode material for sodium secondary batteries (particularly, a composite oxide having an O3 type layered structure) is used as a positive electrode active material, and a positive electrode mixture produced by mixing with a conductive agent and a binder is Al, Ni, It can be manufactured by supporting it on a positive electrode current collector such as stainless steel or carbon cloth. As the conductive agent, for example, carbon materials such as graphite, cokes, carbon black, and needle-shaped carbon can be used.
負極としては、ナトリウムを含有する材料とナトリウムを含有しない材料共に用いることが可能である。例えば、難焼結性炭素、ナトリウム金属、スズ及びこれらを含む合金等、ナトリウムと反応する物質であれば用いることができる。これらの負極活物質についても、必要に応じて、導電剤、バインダー等を用いて、Ａｌ、Ｃｕ、Ｎｉ、ステンレス、カーボン等からなる負極集電体に担持させて、負極を製造することができる。 As the negative electrode, both a material containing sodium and a material not containing sodium can be used. For example, any substance that reacts with sodium, such as non-sinterable carbon, sodium metal, tin and alloys containing these, can be used. Also for these negative electrode active materials, a negative electrode can be manufactured by using a conductive agent, a binder, etc., if necessary, and supporting them on a negative electrode current collector made of Al, Cu, Ni, stainless steel, carbon, or the like. ..
セパレータとしては、例えば、ポリエチレン、ポリプロピレン等のポリオレフィン樹脂；フッ素樹脂；ナイロン；芳香族アラミド；無機ガラス等の材質からなり、多孔質膜、不織布、織布等の形態の材料を用いることができる。 The separator is made of, for example, a polyolefin resin such as polyethylene or polypropylene; a fluororesin; nylon; an aromatic aramid; an inorganic glass or the like, and a material in the form of a porous membrane, a non-woven fabric, a woven fabric or the like can be used.
非水電解質の溶媒としては、カーボネート類、エーテル類、ニトリル類、含硫黄化合物等の非水溶媒系二次電池の溶媒として公知の溶媒を用いることができる。 As the solvent of the non-aqueous electrolyte, known solvents such as carbonates, ethers, nitriles, and sulfur-containing compounds for non-aqueous solvent secondary batteries can be used.
また、全固体型ナトリウムイオン二次電池についても、本発明のナトリウム二次電池用正極材料（特にＯ３型層状構造の複合酸化物）を正極活物質として用いる以外は、公知の全固体型ナトリウムイオン二次電池と同様の構造とすることができる。 Also, for all-solid-state sodium ion secondary batteries, all known solid-state sodium ions except that the positive electrode material for sodium secondary batteries of the present invention (particularly, the composite oxide having an O3 type layered structure) is used as the positive electrode active material. The structure can be similar to that of the secondary battery.
この場合、電解質としては、例えば、ポリエチレンオキサイド系の高分子化合物、ポリオルガノシロキサン鎖及びポリオキシアルキレン鎖の少なくとも一種を含む高分子化合物等のポリマー系固体電解質の他、硫化物系固体電解質、酸化物系固体電解質等を用いることができる。 In this case, as the electrolyte, for example, a polyethylene oxide-based polymer compound, a polymer-based solid electrolyte such as a polymer compound containing at least one of a polyorganosiloxane chain and a polyoxyalkylene chain, a sulfide-based solid electrolyte, an oxide A physical solid electrolyte or the like can be used.
全固体型ナトリウムイオン二次電池の正極としては、例えば、本発明のナトリウム二次電池用正極材料（特にＯ３型層状構造の複合酸化物）を正極活物質として用い、導電剤、バインダー、固体電解質等を含む正極合剤をＴｉ、Ａｌ、Ｎｉ、ステンレス等の正極集電体に担持させることで製造することができる。導電剤については、非水溶媒系二次電池と同様に、例えば、黒鉛、コークス類、カーボンブラック、針状カーボン等の炭素材料を用いることができる。 As a positive electrode of an all-solid-state sodium ion secondary battery, for example, a positive electrode material for a sodium secondary battery of the present invention (particularly a composite oxide having an O3 type layered structure) is used as a positive electrode active material, and a conductive agent, a binder, a solid electrolyte are used. It can be manufactured by supporting a positive electrode mixture containing, for example, Ti on a positive electrode current collector such as Ti, Al, Ni, or stainless. As the conductive agent, a carbon material such as graphite, cokes, carbon black, and acicular carbon can be used, as in the non-aqueous solvent-based secondary battery.
さらに、金属ナトリウム二次電池についても、本発明のナトリウム二次電池用正極材料（特にＯ３型層状構造の複合酸化物）を正極活物質として用いる以外は、公知の金属ナトリウム二次電池と同様の構造とすることができる。 Further, the metal sodium secondary battery is similar to the known metal sodium secondary battery, except that the positive electrode material for sodium secondary battery of the present invention (particularly, the composite oxide having an O3 type layered structure) is used as the positive electrode active material. It can be a structure.
非水電解質ナトリウムイオン二次電池、全固体型ナトリウムイオン二次電池及び金属ナトリウム二次電池の形状についても特に限定はなく、円筒型、角型等のいずれであってもよい。 The shape of the non-aqueous electrolyte sodium ion secondary battery, the all-solid-state sodium ion secondary battery, and the metallic sodium secondary battery is not particularly limited, and may be any of a cylindrical type and a square type.
以下、実施例及び比較例を示して本発明を具体的に説明するが、本発明は、これらのみに限定されないことは言うまでもない。 Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples, but it goes without saying that the present invention is not limited thereto.
［合成例１：Ｆｅ−Ｍｎ−Ｎｉ複合スピネル酸化物（Ｆｅ：Ｍｎ：Ｎｉ＝８０：１０：１０）］
共沈法により、Ｆｅ：Ｍｎ：Ｎｉ＝８０：１０：１０（モル比）の複合スピネル酸化物を合成した。具体的には、以下の処理を行った。
[Synthesis Example 1: Fe-Mn-Ni composite spinel oxide (Fe:Mn:Ni=80:10:10)]
A composite spinel oxide of Fe:Mn:Ni=80:10:10 (molar ratio) was synthesized by the coprecipitation method. Specifically, the following processing was performed.
市販の硫酸鉄（ＩＩ）、硫酸マンガン（ＩＩ）及び硫酸ニッケル（ＩＩ）を、Ｆｅ：Ｍｎ：Ｎｉ＝８０：１０：１０（モル比）となるように混合し、得られた混合物に、２０℃において、水酸化ナトリウム水溶液を、ｐＨが１０以上となるように少しずつ添加し、沈殿物を生成させた。その結果、平均粒子径が６０ｎｍで、Ｆｅ：Ｍｎ：Ｎｉ＝８０：１０：１０（モル比）であるＦｅ−Ｍｎ−Ｎｉ複合スピネル酸化物が得られた。 Commercially available iron(II) sulfate, manganese(II) sulfate and nickel(II) sulfate were mixed so that Fe:Mn:Ni=80:10:10 (molar ratio), and the resulting mixture was mixed with 20 At 0° C., an aqueous sodium hydroxide solution was added little by little so that the pH became 10 or more, and a precipitate was generated. As a result, an Fe-Mn-Ni composite spinel oxide having an average particle diameter of 60 nm and Fe:Mn:Ni=80:10:10 (molar ratio) was obtained.
［合成例２：Ｆｅ−Ｍｎ−Ｎｉ複合スピネル酸化物（Ｆｅ：Ｍｎ：Ｎｉ＝９０：５：５）］
市販の硫酸鉄（ＩＩ）、硫酸マンガン（ＩＩ）及び硫酸ニッケル（ＩＩ）を、Ｆｅ：Ｍｎ：Ｎｉ＝９０：５：５（モル比）となるように混合すること以外は合成例１と同様に、Ｆｅ：Ｍｎ：Ｎｉ＝９０：５：５（モル比）であるＦｅ−Ｍｎ−Ｎｉ複合スピネル酸化物が得られた。
[Synthesis Example 2: Fe-Mn-Ni composite spinel oxide (Fe:Mn:Ni=90:5:5)]
Same as Synthesis Example 1 except that commercially available iron(II) sulfate, manganese(II) sulfate and nickel(II) sulfate are mixed so that Fe:Mn:Ni=90:5:5 (molar ratio). In addition, a Fe-Mn-Ni composite spinel oxide having Fe:Mn:Ni=90:5:5 (molar ratio) was obtained.
［合成例３：Ｆｅ−Ｍｎ−Ｎｉ複合スピネル酸化物（Ｆｅ：Ｍｎ：Ｎｉ＝７０：１５：１５）］
市販の硫酸鉄（ＩＩ）、硫酸マンガン（ＩＩ）及び硫酸ニッケル（ＩＩ）を、Ｆｅ：Ｍｎ：Ｎｉ＝７０：１５：１５（モル比）となるように混合すること以外は合成例１と同様に、Ｆｅ：Ｍｎ：Ｎｉ＝７０：１５：１５（モル比）であるＦｅ−Ｍｎ−Ｎｉ複合スピネル酸化物が得られた。
[Synthesis Example 3: Fe-Mn-Ni composite spinel oxide (Fe:Mn:Ni=70:15:15)]
Same as Synthesis Example 1 except that commercially available iron (II) sulfate, manganese (II) sulfate and nickel (II) sulfate are mixed so that Fe:Mn:Ni=70:15:15 (molar ratio). In addition, Fe:Mn:Ni=70:15:15 (molar ratio), a Fe-Mn-Ni composite spinel oxide was obtained.
［合成例４：Ｆｅ−Ｍｎ−Ｎｉ複合スピネル酸化物（Ｆｅ：Ｍｎ：Ｎｉ＝６０：２０：２０）］
市販の硫酸鉄（ＩＩ）、硫酸マンガン（ＩＩ）及び硫酸ニッケル（ＩＩ）を、Ｆｅ：Ｍｎ：Ｎｉ＝６０：２０：２０（モル比）となるように混合すること以外は合成例１と同様に、Ｆｅ：Ｍｎ：Ｎｉ＝６０：２０：２０（モル比）であるＦｅ−Ｍｎ−Ｎｉ複合スピネル酸化物が得られた。
[Synthesis Example 4: Fe-Mn-Ni composite spinel oxide (Fe:Mn:Ni=60:20:20)]
Same as Synthesis Example 1 except that commercially available iron (II) sulfate, manganese (II) sulfate and nickel (II) sulfate are mixed so that Fe:Mn:Ni=60:20:20 (molar ratio). In addition, a Fe-Mn-Ni composite spinel oxide having an Fe:Mn:Ni ratio of 60:20:20 (molar ratio) was obtained.
［合成例５：Ｆｅ−Ｍｎ−Ｎｉ複合スピネル酸化物（Ｆｅ：Ｍｎ：Ｎｉ＝５０：２５：２５）］
市販の硫酸鉄（ＩＩ）、硫酸マンガン（ＩＩ）及び硫酸ニッケル（ＩＩ）を、Ｆｅ：Ｍｎ：Ｎｉ＝５０：２５：２５（モル比）となるように混合すること以外は合成例１と同様に、Ｆｅ：Ｍｎ：Ｎｉ＝５０：２５：２５（モル比）であるＦｅ−Ｍｎ−Ｎｉ複合スピネル酸化物が得られた。
[Synthesis Example 5: Fe-Mn-Ni composite spinel oxide (Fe:Mn:Ni=50:25:25)]
Same as Synthesis Example 1 except that commercially available iron (II) sulfate, manganese (II) sulfate and nickel (II) sulfate are mixed so that Fe:Mn:Ni=50:25:25 (molar ratio). In addition, Fe:Mn:Ni=50:25:25 (molar ratio), a Fe-Mn-Ni composite spinel oxide was obtained.
［合成例６：Ｆｅ−Ｍｎ−Ｎｉ複合スピネル酸化物（Ｆｅ：Ｍｎ：Ｎｉ＝７０：２０：１０）］
市販の硫酸鉄（ＩＩ）、硫酸マンガン（ＩＩ）及び硫酸ニッケル（ＩＩ）を、Ｆｅ：Ｍｎ：Ｎｉ＝７０：２０：１０（モル比）となるように混合すること以外は合成例１と同様に、Ｆｅ：Ｍｎ：Ｎｉ＝７０：２０：１０（モル比）であるＦｅ−Ｍｎ−Ｎｉ複合スピネル酸化物が得られた。
[Synthesis Example 6: Fe-Mn-Ni composite spinel oxide (Fe:Mn:Ni=70:20:10)]
Same as Synthesis Example 1 except that commercially available iron (II) sulfate, manganese (II) sulfate and nickel (II) sulfate are mixed so that Fe:Mn:Ni=70:20:10 (molar ratio). In addition, a Fe-Mn-Ni composite spinel oxide having a Fe:Mn:Ni ratio of 70:20:10 (molar ratio) was obtained.
［合成例７：Ｆｅ−Ｍｎ−Ｎｉ複合スピネル酸化物（Ｆｅ：Ｍｎ：Ｎｉ＝７０：１０：２０）］
市販の硫酸鉄（ＩＩ）、硫酸マンガン（ＩＩ）及び硫酸ニッケル（ＩＩ）を、Ｆｅ：Ｍｎ：Ｎｉ＝７０：１０：２０（モル比）となるように混合すること以外は合成例１と同様に、Ｆｅ：Ｍｎ：Ｎｉ＝７０：１０：２０（モル比）であるＦｅ−Ｍｎ−Ｎｉ複合スピネル酸化物が得られた。
[Synthesis Example 7: Fe-Mn-Ni composite spinel oxide (Fe:Mn:Ni=70:10:20)]
Same as Synthesis Example 1 except that commercially available iron (II) sulfate, manganese (II) sulfate and nickel (II) sulfate are mixed so that Fe:Mn:Ni=70:10:20 (molar ratio). In addition, a Fe-Mn-Ni composite spinel oxide having Fe:Mn:Ni=70:10:20 (molar ratio) was obtained.
［実施例１：Ｆｅ／Ｍｎ／Ｎｉ＝８０／１０／１０］
実施例１−１：加熱温度８５０℃
合成例１で得たＦｅ−Ｍｎ−Ｎｉ複合スピネル酸化物と、市販の炭酸ナトリウム（Ｎａ２ＣＯ３）とを、Ｎａ：Ｆｅ：Ｍｎ：Ｎｉ＝１００：８０：１０：１０（モル比）となるように、ボールミルで混合し、大気中８５０℃で１０時間加熱した。その結果、実施例１−１のナトリウム二次電池用正極材料が得られた。
[Example 1: Fe/Mn/Ni=80/10/10]
Example 1-1: Heating temperature 850°C
Fe—Mn—Ni composite spinel oxide obtained in Synthesis Example 1 and commercially available sodium carbonate (Na 2 CO 3 ) were used as Na:Fe:Mn:Ni=100:80:10:10 (molar ratio). The mixture was mixed with a ball mill so that it was heated in the air at 850° C. for 10 hours. As a result, the positive electrode material for a sodium secondary battery of Example 1-1 was obtained.
実施例１−２：加熱温度８００℃
加熱温度を８００℃とすること以外は実施例１−１と同様に、実施例１−２のナトリウム二次電池用正極材料を得た。
Example 1-2: Heating temperature 800° C.
A positive electrode material for a sodium secondary battery of Example 1-2 was obtained in the same manner as in Example 1-1, except that the heating temperature was 800°C.
実施例１−３：加熱温度７５０℃
加熱温度を７５０℃とすること以外は実施例１−１と同様に、実施例１−３のナトリウム二次電池用正極材料を得た。
Example 1-3: Heating temperature 750°C
A positive electrode material for a sodium secondary battery of Example 1-3 was obtained in the same manner as in Example 1-1, except that the heating temperature was 750°C.
実施例１−４：加熱温度６５０℃
加熱温度を６５０℃とすること以外は実施例１−１と同様に、実施例１−４のナトリウム二次電池用正極材料を得た。
Example 1-4: Heating temperature 650° C.
A positive electrode material for a sodium secondary battery of Example 1-4 was obtained in the same manner as in Example 1-1, except that the heating temperature was 650°C.
［実施例２］
実施例１−１において、合成例１で得たＦｅ−Ｍｎ−Ｎｉ複合スピネル酸化物ではなく、合成例２〜４及び６〜７のいずれかで得たＦｅ−Ｍｎ−Ｎｉ複合スピネル酸化物を使用すること、加熱温度を７００℃、７５０℃、８００℃、８５０℃、９００℃、又は９５０℃とすること以外は同様に、種々の組成のナトリウム二次電池用正極材料を得た。具体的には、後述する表１において、Ｏ３型層状構造が「単相」となっている以下の試料を、実施例のナトリウム二次電池用正極材料として得た。
実施例２−１：Ｆｅ／Ｍｎ／Ｎｉ＝９０／５／５、加熱温度７５０℃
実施例２−２：Ｆｅ／Ｍｎ／Ｎｉ＝９０／５／５、加熱温度７００℃
実施例２−３：Ｆｅ／Ｍｎ／Ｎｉ＝７０／１５／１５、加熱温度９５０℃
実施例２−４：Ｆｅ／Ｍｎ／Ｎｉ＝７０／１５／１５、加熱温度９００℃
実施例２−５：Ｆｅ／Ｍｎ／Ｎｉ＝７０／１５／１５、加熱温度８５０℃
実施例２−６：Ｆｅ／Ｍｎ／Ｎｉ＝７０／１５／１５、加熱温度８００℃
実施例２−７：Ｆｅ／Ｍｎ／Ｎｉ＝７０／１５／１５、加熱温度７５０℃
実施例２−８：Ｆｅ／Ｍｎ／Ｎｉ＝６０／２０／２０、加熱温度９５０℃
実施例２−９：Ｆｅ／Ｍｎ／Ｎｉ＝６０／２０／２０、加熱温度９００℃
実施例２−１０：Ｆｅ／Ｍｎ／Ｎｉ＝６０／２０／２０、加熱温度８５０℃
実施例２−１１：Ｆｅ／Ｍｎ／Ｎｉ＝６０／２０／２０、加熱温度８００℃
実施例２−１２：Ｆｅ／Ｍｎ／Ｎｉ＝７０／２０／１０、加熱温度９５０℃
実施例２−１３：Ｆｅ／Ｍｎ／Ｎｉ＝７０／２０／１０、加熱温度９００℃
実施例２−１４：Ｆｅ／Ｍｎ／Ｎｉ＝７０／１０／２０、加熱温度９５０℃
実施例２−１５：Ｆｅ／Ｍｎ／Ｎｉ＝７０／１０／２０、加熱温度９００℃。
[Example 2]
In Example 1-1, the Fe-Mn-Ni composite spinel oxide obtained in any of Synthesis Examples 2 to 4 and 6 to 7 was used instead of the Fe-Mn-Ni composite spinel oxide obtained in Synthesis Example 1. Cathode materials for sodium secondary batteries of various compositions were obtained in the same manner except that they were used and the heating temperature was 700°C, 750°C, 800°C, 850°C, 900°C, or 950°C. Specifically, in Table 1 described later, the following samples having an O3 type layered structure of "single phase" were obtained as positive electrode materials for sodium secondary batteries of Examples.
Example 2-1: Fe/Mn/Ni=90/5/5, heating temperature 750° C.
Example 2-2: Fe/Mn/Ni=90/5/5, heating temperature 700° C.
Example 2-3: Fe/Mn/Ni=70/15/15, heating temperature 950° C.
Example 2-4: Fe/Mn/Ni=70/15/15, heating temperature 900° C.
Example 2-5: Fe/Mn/Ni=70/15/15, heating temperature 850° C.
Example 2-6: Fe/Mn/Ni=70/15/15, heating temperature 800° C.
Example 2-7: Fe/Mn/Ni=70/15/15, heating temperature 750° C.
Example 2-8: Fe/Mn/Ni=60/20/20, heating temperature 950° C.
Example 2-9: Fe/Mn/Ni=60/20/20, heating temperature 900° C.
Example 2-10: Fe/Mn/Ni=60/20/20, heating temperature 850° C.
Example 2-11: Fe/Mn/Ni=60/20/20, heating temperature 800° C.
Example 2-12: Fe/Mn/Ni=70/20/10, heating temperature 950° C.
Example 2-13: Fe/Mn/Ni=70/20/10, heating temperature 900° C.
Example 2-14: Fe/Mn/Ni=70/10/20, heating temperature 950° C.
Example 2-15: Fe/Mn/Ni=70/10/20, heating temperature 900° C.
［比較例１］
実施例１−１において、合成例１〜７と同様の沈殿法にてＦｅスピネル酸化物を作製し、過酸化ナトリウム（Ｎａ２Ｏ２）を瑪瑙性乳鉢にて混合し、大気中にて６５０℃、７００℃、７５０℃で１０時間加熱することにより種々の組成のナトリウム二次電池用正極材料を得た。具体的には、後述する表１において、Ｏ３型層状構造が「単相」又は「×」（単相ではない）となっている以下の試料を、比較例のナトリウム二次電池用正極材料として得た。
比較例１−１：Ｆｅ／Ｍｎ／Ｎｉ＝１００／０／０、加熱温度７５０℃
比較例１−２：Ｆｅ／Ｍｎ／Ｎｉ＝１００／０／０、加熱温度７００℃
比較例１−３：Ｆｅ／Ｍｎ／Ｎｉ＝１００／０／０、加熱温度６５０℃。
[Comparative Example 1]
In Example 1-1, Fe spinel oxide was prepared by the same precipitation method as in Synthesis Examples 1 to 7, sodium peroxide (Na 2 O 2 ) was mixed in an agate mortar, and the mixture was heated to 650 in the atmosphere. The positive electrode materials for sodium secondary batteries having various compositions were obtained by heating at 70° C., 700° C. and 750° C. for 10 hours. Specifically, in Table 1 described later, the following samples whose O3 type layered structure is "single phase" or "x" (not single phase) are used as positive electrode materials for sodium secondary batteries of Comparative Examples. Obtained.
Comparative Example 1-1: Fe/Mn/Ni=100/0/0, heating temperature 750° C.
Comparative Example 1-2: Fe/Mn/Ni=100/0/0, heating temperature 700° C.
Comparative Example 1-3: Fe/Mn/Ni=100/0/0, heating temperature 650° C.
［比較例２］
実施例１−１において、合成例１で得たＦｅ−Ｍｎ−Ｎｉ複合スピネル酸化物ではなく、合成例５で得たＦｅ−Ｍｎ−Ｎｉ複合スピネル酸化物を使用すること、加熱温度を８００℃又は９００℃とすること以外は同様に、種々の組成のナトリウム二次電池用正極材料を得た。具体的には、後述する表１において、Ｏ３型層状構造が「単相」となっている以下の試料を、比較例のナトリウム二次電池用正極材料として得た。
比較例２−１：Ｆｅ／Ｍｎ／Ｎｉ＝５０／２５／２５、加熱温度９００℃
比較例２−２：Ｆｅ／Ｍｎ／Ｎｉ＝５０／２５／２５、加熱温度８００℃。
[Comparative example 2]
In Example 1-1, the Fe-Mn-Ni composite spinel oxide obtained in Synthesis Example 5 was used instead of the Fe-Mn-Ni composite spinel oxide obtained in Synthesis Example 1, and the heating temperature was 800°C. Alternatively, cathode materials for sodium secondary batteries having various compositions were obtained in the same manner except that the temperature was set to 900°C. Specifically, in Table 1 described below, the following sample having an O3 type layered structure of "single phase" was obtained as a positive electrode material for a sodium secondary battery of a comparative example.
Comparative Example 2-1: Fe/Mn/Ni=50/25/25, heating temperature 900° C.
Comparative Example 2-2: Fe/Mn/Ni=50/25/25, heating temperature 800° C.
［比較例３］
実施例１−１において、合成例１又は２で得たＦｅ−Ｍｎ−Ｎｉ複合スピネル酸化物を使用すること、加熱温度を８００℃、９００℃又は９５０℃とすること以外は同様に、種々の組成のナトリウム二次電池用正極材料を得た。具体的には、後述する表１において、Ｏ３型層状構造が「×」となっている以下の試料を、比較例のナトリウム二次電池用正極材料として得た。
比較例３−１：Ｆｅ／Ｍｎ／Ｎｉ＝９０／５／５、加熱温度８００℃
比較例３−２：Ｆｅ／Ｍｎ／Ｎｉ＝８０／１０／１０、加熱温度９００℃。
[Comparative Example 3]
Similarly to Example 1-1, except that the Fe-Mn-Ni composite spinel oxide obtained in Synthesis Example 1 or 2 is used and the heating temperature is 800°C, 900°C, or 950°C, various kinds are similarly used. A positive electrode material for a sodium secondary battery having the composition was obtained. Specifically, in Table 1 described later, the following sample having an O3 type layered structure of "x" was obtained as a positive electrode material for a sodium secondary battery of a comparative example.
Comparative Example 3-1: Fe/Mn/Ni=90/5/5, heating temperature 800° C.
Comparative Example 3-2: Fe/Mn/Ni=80/10/10, heating temperature 900° C.
［比較例４］
実施例１−２において、加熱時間を２０時間とすること以外は同様に、種々の組成のナトリウム二次電池用正極材料を得た。具体的には、以下の試料を、比較例のナトリウム二次電池用正極材料として得た。
比較例４−１：Ｆｅ／Ｍｎ／Ｎｉ＝８０／１０／１０、加熱温度８００℃、焼成時間２０時間。
[Comparative Example 4]
In the same manner as in Example 1-2, except that the heating time was 20 hours, positive electrode materials for sodium secondary batteries having various compositions were obtained. Specifically, the following sample was obtained as a positive electrode material for a sodium secondary battery of Comparative Example.
Comparative Example 4-1: Fe/Mn/Ni=80/10/10, heating temperature 800° C., firing time 20 hours.
［実験例１：Ｘ線回折］
実施例１−１〜１−４で得られたナトリウム二次電池用正極材料について、ＣｕＫα線を用いたＸ線構造回折（ＸＲＤ）を測定した。結果を図１に示す。その他の試料についても同様に試験を行った。それら実施例の結果をまとめたものを表１に、比較例をまとめたものを表２に示す。表１及び２において、「×」は、Ｏ３型層状構造の不純物相が多く含まれていたことを意味し、「−」は未実施であることを意味する。また、「単相」はＯ３型層状構造のみからなることを意味し、「主相」はＯ３型層状構造以外にごく少量（５重量％以下）の不純物相が含まれていたことを意味する。
[Experimental Example 1: X-ray diffraction]
With respect to the positive electrode materials for sodium secondary batteries obtained in Examples 1-1 to 1-4, X-ray structural diffraction (XRD) using CuKα ray was measured. The results are shown in Figure 1. The other samples were also tested in the same manner. Table 1 shows a summary of the results of these Examples, and Table 2 shows a summary of the Comparative Examples. In Tables 1 and 2, "x" means that a large amount of the impurity phase of the O3 type layered structure was contained, and "-" means that it was not carried out. Further, "single phase" means that it is composed only of the O3 type layered structure, and "main phase" means that a very small amount (5% by weight or less) of an impurity phase was contained in addition to the O3 type layered structure. ..
［実験例２：結晶粒の結晶子サイズ］
上記実施例及び比較例にて得られた種々のナトリウム二次電池用正極材料中の結晶子サイズは、Ｘ線回折測定において、単相もしくは主相として観測されるＯ３型層状構造の（００３）面に帰属される回折ピークの半価幅から、Scherrerの式に基づいて算出した。実施例の結果を表１に、比較例の結果を表２に示す。なお、表１及び２において、結晶子サイズの単位は「ｎｍ」で結晶子の直径のことを示し、「−」は未実施であることを示す。
[Experimental Example 2: Crystallite size of crystal grains]
The crystallite sizes in the positive electrode materials for various sodium secondary batteries obtained in the above Examples and Comparative Examples are O003 type layered structure (003) observed as a single phase or a main phase in X-ray diffraction measurement. It was calculated based on the Scherrer's formula from the half width of the diffraction peak assigned to the plane. The results of Examples are shown in Table 1, and the results of Comparative Examples are shown in Table 2. In Tables 1 and 2, the unit of the crystallite size is "nm", which indicates the diameter of the crystallite, and "-" indicates that the crystallite size has not been measured.
［実験例３：充放電試験（その１）］
上記した実施例１−２で得られたナトリウム二次電池用正極材料を用いて、下記の方法で電気化学セルを作製し、充放電試験を行った。
[Experimental Example 3: Charge/Discharge Test (1)]
Using the sodium secondary battery positive electrode material obtained in Example 1-2 described above, an electrochemical cell was prepared by the following method, and a charge/discharge test was conducted.
電極組成は、活物質８４質量％、ＡＢ８質量％及びＰＴＦＥバインダー８質量％を混合した合剤を調製し、アルミニウムメッシュに密着接合させ、次いで、加熱処理（減圧中、２２０℃、１０時間以上）した。対極として、試験電極計算容量の約５０倍の容量を有している金属ナトリウム箔を用い、セパレータとしてポリプロピレン微多孔膜、電解液として１ｍｏｌ／Ｌ ＮａＰＦ６（ＥＣ：ＤＥＣ＝１：１（ｖｏｌ．％））を具備したコインセル（ＣＲ２０３２）を作製した。 The electrode composition was prepared by preparing a mixture in which 84% by mass of active material, 8% by mass of AB and 8% by mass of PTFE binder were mixed, adhered and bonded to an aluminum mesh, and then heat-treated (in reduced pressure, 220° C., 10 hours or more). did. A metal sodium foil having a capacity about 50 times the calculated capacity of the test electrode was used as a counter electrode, a polypropylene microporous membrane was used as a separator, and 1 mol/L NaPF 6 (EC:DEC=1:1 (vol. %)) was prepared as a coin cell (CR2032).
充放電試験は、まず、７０ｍＡｈ／ｇの容量規制をかけて（最大容量を７０ｍＡｈ／ｇとして）、行った。その結果、図２に示されるように、充電容量と放電容量はほとんど同じであり、７０ｍＡｈ／ｇの容量においては、ほぼ１００％の効率で充放電可能であることが確認できた。 The charge/discharge test was conducted by first applying a capacity regulation of 70 mAh/g (maximum capacity is 70 mAh/g). As a result, as shown in FIG. 2, it was confirmed that the charge capacity and the discharge capacity were almost the same, and that at a capacity of 70 mAh/g, charging/discharging was possible with an efficiency of almost 100%.
次に、８０ｍＡｈ／ｇの容量規制をかけて（最大容量を８０ｍＡｈ／ｇとして）、同様の試験を行ったところ、この場合も同様に、図２に示されるように、ほぼ１００％の効率で充放電可能であることが確認できた。 Next, a similar test was conducted by applying a capacity regulation of 80 mAh/g (maximum capacity is 80 mAh/g). In this case as well, as shown in FIG. 2, the efficiency is almost 100%. It was confirmed that charging/discharging was possible.
この後、容量規制（最大容量）を１０ｍＡｈ／ｇずつ増加させていき、ほぼ１００％の効率で充放電できなくなるまで試験を続けた。その結果、図２に示されるように、容量規制（最大容量）が１００ｍＡｈ／ｇまではほぼ１００％の効率で充放電することができ、容量規制（最大容量）が１１０ｍＡｈ／ｇとするとほぼ１００％の効率での充放電ができなくなった。このことから、ほぼ１００％の効率で充放電することができる最も大きな容量である１００ｍＡｈ／ｇを、実施例１−２のナトリウム二次電池用正極材料の容量とした。 Thereafter, the capacity regulation (maximum capacity) was increased by 10 mAh/g, and the test was continued until charging/discharging could not be performed at an efficiency of almost 100%. As a result, as shown in FIG. 2, charging/discharging can be performed with an efficiency of almost 100% up to a capacity regulation (maximum capacity) of 100 mAh/g, and when the capacity regulation (maximum capacity) is 110 mAh/g, it can be almost 100 It became impossible to charge and discharge with efficiency of %. From this, 100 mAh/g, which is the largest capacity capable of being charged/discharged at an efficiency of almost 100%, was set as the capacity of the positive electrode material for a sodium secondary battery of Example 1-2.
また、他の実施例及び比較例で得た種々のナトリウム二次電池用正極材料についても同様に試験を行い、容量を決定した。実施例の結果を表１に、比較例の結果を表２に示す。なお、表１及び２において、容量の単位はｍＡｈ／ｇである。 In addition, various positive electrode materials for sodium secondary batteries obtained in other examples and comparative examples were similarly tested to determine their capacities. The results of Examples are shown in Table 1, and the results of Comparative Examples are shown in Table 2. In Tables 1 and 2, the unit of capacity is mAh/g.
上記の表１及び２から、Ｆｅ：Ｍｎ：Ｎｉ＝１００：０：０（モル比）の場合における最大の容量は７０ｍＡｈ／ｇである。この場合、正極材料中の鉄の重量分率は５０．５重量％であることから、鉄の重量分率容量は、３５．３ｍＡｈ／ｇである。 From the above Tables 1 and 2, the maximum capacity in the case of Fe:Mn:Ni=100:0:0 (molar ratio) is 70 mAh/g. In this case, since the weight fraction of iron in the positive electrode material is 50.5% by weight, the weight fraction capacity of iron is 35.3 mAh/g.
上記の表１及び２から、Ｆｅ：Ｍｎ：Ｎｉ＝９０：５：５（モル比）の場合における最大の容量は８０ｍＡｈ／ｇである。この場合、正極材料中の鉄の重量分率は４５．４重量％であることから、鉄の重量分率容量は、３６．３ｍＡｈ／ｇである。 From the above Tables 1 and 2, the maximum capacity in the case of Fe:Mn:Ni=90:5:5 (molar ratio) is 80 mAh/g. In this case, since the weight fraction of iron in the positive electrode material is 45.4% by weight, the weight fraction capacity of iron is 36.3 mAh/g.
上記の表１及び２から、Ｆｅ：Ｍｎ：Ｎｉ＝８０：１０：１０（モル比）の場合における最大の容量は１００ｍＡｈ／ｇである。この場合、正極材料中の鉄の重量分率は４０．３重量％であることから、鉄の重量分率容量は、４０．３ｍＡｈ／ｇである。 From the above Tables 1 and 2, the maximum capacity in the case of Fe:Mn:Ni=80:10:10 (molar ratio) is 100 mAh/g. In this case, since the weight fraction of iron in the positive electrode material is 40.3% by weight, the weight fraction capacity of iron is 40.3 mAh/g.
上記の表１及び２から、Ｆｅ：Ｍｎ：Ｎｉ＝７０：１５：１５（モル比）の場合における最大の容量は１２０ｍＡｈ／ｇである。この場合、正極材料中の鉄の重量分率は３５．２重量％であることから、鉄の重量分率容量は、４２．３ｍＡｈ／ｇである。 From Tables 1 and 2 above, the maximum capacity in the case of Fe:Mn:Ni=70:15:15 (molar ratio) is 120 mAh/g. In this case, since the weight fraction of iron in the positive electrode material is 35.2% by weight, the weight fraction capacity of iron is 42.3 mAh/g.
上記の表１及び２から、Ｆｅ：Ｍｎ：Ｎｉ＝６０：２０：２０（モル比）の場合における最大の容量は１２０ｍＡｈ／ｇである。この場合、正極材料中の鉄の重量分率は３０．２重量％であることから、鉄の重量分率容量は、３６．２ｍＡｈ／ｇである。 From the above Tables 1 and 2, the maximum capacity in the case of Fe:Mn:Ni=60:20:20 (molar ratio) is 120 mAh/g. In this case, since the weight fraction of iron in the positive electrode material is 30.2% by weight, the weight fraction capacity of iron is 36.2 mAh/g.
上記の表１及び２から、Ｆｅ：Ｍｎ：Ｎｉ＝５０：２５：２５（モル比）の場合における最大の容量は１３０ｍＡｈ／ｇである。この場合、正極材料中の鉄の重量分率は２５．１重量％であることから、鉄の重量分率容量は、３２．７ｍＡｈ／ｇである。 From the above Tables 1 and 2, the maximum capacity in the case of Fe:Mn:Ni=50:25:25 (molar ratio) is 130 mAh/g. In this case, since the weight fraction of iron in the positive electrode material is 25.1% by weight, the weight fraction capacity of iron is 32.7 mAh/g.
上記の結果を図３にまとめた。その結果、Ｆｅ：Ｍｎ：Ｎｉ＝９０〜５６：５〜２２：５〜２２（モル比）の範囲においては、従来品であるＮａＦｅＯ２（Ｆｅ：Ｍｎ：Ｎｉ＝１００：０：０（モル比））と比較し、鉄の重量分率容量を向上させることができ、好ましいことが理解できる。なお、Ｆｅ：Ｍｎ：Ｎｉ＝８０〜７０：１０〜１５：１０〜１５（モル比）の範囲においては、鉄の重量分率容量を、特に顕著に向上させることができた。 The above results are summarized in FIG. As a result, in the range of Fe:Mn:Ni=90 to 56:5 to 22:5 to 22 (molar ratio), NaFeO 2 (Fe:Mn:Ni=100:0:0 (molar ratio), which is a conventional product, is used. It is understood that the weight fraction capacity of iron can be improved as compared with )) and it is preferable. In the range of Fe:Mn:Ni=80 to 70:10 to 15:10 to 15 (molar ratio), the weight fraction capacity of iron could be particularly remarkably improved.
なお、上記表１の実施例２−３〜２−７及び２−１２〜２−１５に示されるように、Ｍｎ及びＮｉの量を異なるものとした場合には、Ｍｎ及びＮｉの量を同一とした場合と同等又はそれに準ずる結果が得られた。Ｆｅ：Ｍｎ：Ｎｉ＝７０：２０：１０（モル比）の場合における最大の容量は１２０ｍＡｈ／ｇである。この場合、正極材料中の鉄の重量分率は３５．３重量％であることから、鉄の重量分率容量は、４２．３ｍＡｈ／ｇである。Ｆｅ：Ｍｎ：Ｎｉ＝７０：１０：２０（モル比）の場合における最大の容量は１１０ｍＡｈ／ｇである。この場合、正極材料中の鉄の重量分率は３５．２重量％であることから、鉄の重量分率容量は、３８．７ｍＡｈ／ｇである。 As shown in Examples 2-3 to 2-7 and 2-12 to 2-15 in Table 1 above, when the amounts of Mn and Ni were different, the amounts of Mn and Ni were the same. The result is equivalent to or similar to the case of. The maximum capacity in the case of Fe:Mn:Ni=70:20:10 (molar ratio) is 120 mAh/g. In this case, since the weight fraction of iron in the positive electrode material is 35.3% by weight, the weight fraction capacity of iron is 42.3 mAh/g. The maximum capacity in the case of Fe:Mn:Ni=70:10:20 (molar ratio) is 110 mAh/g. In this case, since the weight fraction of iron in the positive electrode material is 35.2% by weight, the weight fraction capacity of iron is 38.7 mAh/g.
［実験例４：充放電試験（その２）］
さらに、実施例２−４の試料を用いて、上記実験例３と同様の電気化学セルを用いて、電流密度１０ｍＡ／ｇにおいて、カットオフ１．５〜４．０Ｖにおける定電流測定（１１０ｍＡｈ／ｇ容量規制）で充電開始により繰り返し充放電試験を行い、充放電サイクル特性を評価した。
[Experimental Example 4: Charge/Discharge Test (Part 2)]
Furthermore, using the sample of Example 2-4 and the same electrochemical cell as in Experimental Example 3 above, at a current density of 10 mA/g, a constant current measurement at a cutoff of 1.5 to 4.0 V (110 mAh/ The charging/discharging cycle characteristics were evaluated by repeating the charging/discharging test by starting the charging under the g capacity regulation).
その結果、１サイクル目〜１３サイクル目まで容量１１０ｍＡｈ／ｇを維持しており、非常に優れた充放電サイクル特性が得られた。 As a result, the capacity was maintained at 110 mAh/g from the 1st cycle to the 13th cycle, and very excellent charge/discharge cycle characteristics were obtained.
一方、合成例１〜４で得られたＦｅ−Ｍｎ−Ｎｉ複合スピネル酸化物を使用するのではなく、市販の炭酸ナトリウム、市販の酸化鉄（Ｆｅ３Ｏ４；平均粒子径０．４μｍ）、市販の酸化マンガン（Ｍｎ３Ｏ４；平均粒子径１μｍ）、及び市販の水酸化ニッケル（Ｎｉ（ＯＨ）２；平均粒子径１μｍ）を、Ｎａ：Ｆｅ：Ｍｎ：Ｎｉ＝１００：７０：１５：１５（モル比）となるように、ボールミルで混合し、９００℃で１０時間加熱した場合（実施例３）には、容量１１０ｍＡｈ／ｇを維持できたのは７サイクル目までであった。この結果、実施例１〜２等のように、原料化合物として、Ｆｅ−Ｍｎ−Ｎｉ複合スピネル酸化物を使用することにより、さらに、充放電サイクル特性を向上させることができることが理解できた。 Meanwhile, instead of using the resulting Fe-Mn-Ni composite spinel oxide in Synthesis Example 1-4, a commercially available sodium carbonate, commercial iron oxide (Fe 3 O 4; average particle size 0.4 .mu.m), Commercially available manganese oxide (Mn 3 O 4 ; average particle size 1 μm) and commercially available nickel hydroxide (Ni(OH) 2 ; average particle size 1 μm) were used as Na:Fe:Mn:Ni=100:70:15: When mixed with a ball mill so as to be 15 (molar ratio) and heated at 900° C. for 10 hours (Example 3), the capacity of 110 mAh/g could be maintained until the 7th cycle. As a result, it was understood that the charge-discharge cycle characteristics can be further improved by using the Fe-Mn-Ni composite spinel oxide as the raw material compound as in Examples 1-2.
［実験例５：充放電試験（その３）］
さらに、実施例１−２の結晶子サイズの直径が４３ｎｍの試料を用いて、上記実験例３と同様の電気化学セルを用いて、電流密度１０ｍＡ／ｇにおいて、カットオフ１．５〜４．０Ｖにおける定電流測定（１００ｍＡｈ／ｇ容量規制）で充電開始により繰り返し充放電試験を行い、充放電サイクル特性を評価した。
[Experimental Example 5: Charge/Discharge Test (Part 3)]
Furthermore, using the sample having a crystallite size diameter of 43 nm of Example 1-2 and using the same electrochemical cell as in Experimental Example 3 above, at a current density of 10 mA/g, a cutoff of 1.5 to 4. The charge and discharge cycle characteristics were evaluated by conducting a repeated charge and discharge test by starting charging with constant current measurement (100 mAh/g capacity regulation) at 0 V.
その結果、１サイクル目〜２０サイクル目まで容量１００ｍＡｈ／ｇを維持しており、優れた充放電サイクル特性が得られた。 As a result, the capacity of 100 mAh/g was maintained from the first cycle to the 20th cycle, and excellent charge/discharge cycle characteristics were obtained.
一方、比較例４−１で得られた結晶子サイズの直径が１１０ｎｍの試料では、容量１００ｍＡｈ／ｇを維持できたのは１０サイクル目までであった。この結果より、合成試料の結晶子サイズは良好な充放電サイクル特性を得るために重要なパラメータであり、大きすぎると、特性が低下することが確認でした。 On the other hand, Comparative Example 4 - The diameter of a crystallite size obtained by the 1 in the 110nm sample, was able to maintain the capacity 100 mAh / g was up to the 10th cycle. From these results, it was confirmed that the crystallite size of the synthetic sample is an important parameter for obtaining good charge/discharge cycle characteristics, and that if it is too large, the characteristics deteriorate.
［実験例６］
比較例１−１の試料と実施例１−２の試料について充電過程における結晶構造の変化をin situ XRDによって、比較した結果を図４及び図５に示した。比較例１−１の鉄を他の元素で置換していない試料では、充電によりナトリウムを引き抜いていくと引き抜き量が０．３２ｍｏｌとなったところから、元のＯ３型層状構造から単斜晶系結晶構造への構造変化に由来するピークが新たに観察された。ナトリウム引き抜き量０．３２ｍｏｌを容量換算するとほぼ７７ｍＡｈ／ｇとなり、安定な可逆容量が得られるナトリウム引き抜き量と、構造変化が起こるナトリウム引き抜き量がほぼ一致することがわかった。一方、実施例１−２の試料では、充電によりナトリウムを引き抜いていっても、単斜晶系の構造に由来するピークは観察されず、比較例１−１のような構造変化が起こっていないことが確認された。
[Experimental Example 6]
4 and 5 show the results of comparison between the sample of Comparative Example 1-1 and the sample of Example 1-2 with respect to the change in crystal structure during the charging process by in situ XRD. In the sample of Comparative Example 1-1 in which iron was not replaced with another element, the amount of withdrawal was 0.32 mol as sodium was withdrawn from the charge, which indicates that the original O3 type layered structure was changed to the monoclinic system. A new peak derived from the structural change to the crystal structure was observed. When the sodium abstraction amount of 0.32 mol was converted into a volume, it was approximately 77 mAh/g, and it was found that the sodium abstraction amount at which a stable reversible capacity is obtained and the sodium abstraction amount at which the structural change occurs are substantially the same. On the other hand, in the sample of Example 1-2, no peak derived from the monoclinic structure was observed even when sodium was extracted by charging, and the structural change as in Comparative Example 1-1 did not occur. It was confirmed.
Claims (12)
Ｎａ１±δＦｅ１−ｘ−ｙＭｎｘＮｉｙＯ２
［式中、δは０〜０．１０；ｘ及びｙは同じか又は異なり、ｘは０．０５〜０．１０、ｙは０．０５〜０．１０である。］
で示される組成を有し、結晶子サイズが平均で３０〜６０ｎｍである結晶粒を有する化合物を含有する、ナトリウム二次電池用正極材料。 The O3 type layered structure is the main phase, and the general formula (1):
Na 1 ±δ Fe 1-x-y Mn x Ni y O 2
Wherein, [delta] is 0 to 0.10; x and y are the same or different, x is from 0.05 to 0.10, y is 0.05 to 0.10. ]
A positive electrode material for a sodium secondary battery, which comprises a compound having a composition shown by and having a crystal grain having an average crystallite size of 30 to 60 nm.
を備える、製造方法。 A method for producing a cathode material for a sodium secondary battery according to any one of claims 1 to 3, a sodium, iron, manganese, a heating step of heating the mixture containing nickel and oxygen, the manufacturing method.
Ｏ３型層状構造を主相とし、一般式（１）：
Ｎａ１±δＦｅ１−ｘ−ｙＭｎｘＮｉｙＯ２
［式中、δは０〜０．１０；ｘ及びｙは同じか又は異なり、ｘは０．０５〜０．１０、ｙは０．０５〜０．１０である。］で示される組成を有し、結晶子サイズが平均で３０〜６０ｎｍである結晶粒を有する化合物を含有するナトリウム二次電池用正極材料を使用する、方法。 A method for suppressing a structural change of a positive electrode material for a sodium secondary battery from an O3 type layered structure to a monoclinic crystal structure when the sodium secondary battery is charged,
The O3 type layered structure is the main phase, and the general formula (1):
Na 1 ±δ Fe 1-x-y Mn x Ni y O 2
Wherein, [delta] is 0 to 0.10; x and y are the same or different, x is from 0.05 to 0.10, y is 0.05 to 0.10. ] The method of using the positive electrode material for sodium secondary batteries containing the compound which has the composition shown by these, and contains the compound which has a crystal grain whose crystallite size is 30-60 nm on average.
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