CN117199336A - Surface gradient doped lithium-rich manganese-based positive electrode material with composite structure and preparation method thereof - Google Patents
Surface gradient doped lithium-rich manganese-based positive electrode material with composite structure and preparation method thereof Download PDFInfo
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- CN117199336A CN117199336A CN202311246309.4A CN202311246309A CN117199336A CN 117199336 A CN117199336 A CN 117199336A CN 202311246309 A CN202311246309 A CN 202311246309A CN 117199336 A CN117199336 A CN 117199336A
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- 239000011572 manganese Substances 0.000 title claims abstract description 159
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 title claims abstract description 148
- 229910052744 lithium Inorganic materials 0.000 title claims abstract description 148
- 229910052748 manganese Inorganic materials 0.000 title claims abstract description 108
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 title claims abstract description 107
- 239000007774 positive electrode material Substances 0.000 title claims abstract description 92
- 239000002131 composite material Substances 0.000 title claims abstract description 70
- 238000002360 preparation method Methods 0.000 title abstract description 27
- 238000000034 method Methods 0.000 claims abstract description 38
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims abstract description 31
- 239000001301 oxygen Substances 0.000 claims abstract description 31
- 229910052760 oxygen Inorganic materials 0.000 claims abstract description 31
- 229910052596 spinel Inorganic materials 0.000 claims abstract description 26
- 239000011029 spinel Substances 0.000 claims abstract description 26
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical group [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 claims abstract description 13
- 150000001875 compounds Chemical class 0.000 claims description 151
- 239000000463 material Substances 0.000 claims description 68
- 239000000203 mixture Substances 0.000 claims description 58
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 47
- 239000007791 liquid phase Substances 0.000 claims description 43
- 238000003756 stirring Methods 0.000 claims description 38
- 238000010438 heat treatment Methods 0.000 claims description 35
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 claims description 29
- 239000011261 inert gas Substances 0.000 claims description 29
- 238000002156 mixing Methods 0.000 claims description 27
- 238000001035 drying Methods 0.000 claims description 26
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 24
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 20
- 239000007864 aqueous solution Substances 0.000 claims description 20
- 238000005406 washing Methods 0.000 claims description 20
- XLYOFNOQVPJJNP-UHFFFAOYSA-M hydroxide Chemical compound [OH-] XLYOFNOQVPJJNP-UHFFFAOYSA-M 0.000 claims description 18
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 claims description 16
- 229910002651 NO3 Inorganic materials 0.000 claims description 16
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 claims description 16
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 claims description 16
- 239000010405 anode material Substances 0.000 claims description 16
- 239000012071 phase Substances 0.000 claims description 16
- 238000001354 calcination Methods 0.000 claims description 15
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 14
- 238000001704 evaporation Methods 0.000 claims description 14
- 238000001914 filtration Methods 0.000 claims description 13
- 238000000498 ball milling Methods 0.000 claims description 12
- CDBYLPFSWZWCQE-UHFFFAOYSA-L sodium carbonate Substances [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 claims description 12
- 238000005303 weighing Methods 0.000 claims description 12
- 229910052757 nitrogen Inorganic materials 0.000 claims description 10
- ATRRKUHOCOJYRX-UHFFFAOYSA-N Ammonium bicarbonate Chemical compound [NH4+].OC([O-])=O ATRRKUHOCOJYRX-UHFFFAOYSA-N 0.000 claims description 9
- WMFOQBRAJBCJND-UHFFFAOYSA-M Lithium hydroxide Chemical compound [Li+].[OH-] WMFOQBRAJBCJND-UHFFFAOYSA-M 0.000 claims description 9
- 239000001099 ammonium carbonate Substances 0.000 claims description 9
- 238000001816 cooling Methods 0.000 claims description 9
- 239000003513 alkali Substances 0.000 claims description 8
- 239000000843 powder Substances 0.000 claims description 8
- 239000000126 substance Substances 0.000 claims description 8
- 229910052786 argon Inorganic materials 0.000 claims description 7
- NLXLAEXVIDQMFP-UHFFFAOYSA-N Ammonia chloride Chemical compound [NH4+].[Cl-] NLXLAEXVIDQMFP-UHFFFAOYSA-N 0.000 claims description 6
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 claims description 6
- UIIMBOGNXHQVGW-UHFFFAOYSA-M Sodium bicarbonate Chemical compound [Na+].OC([O-])=O UIIMBOGNXHQVGW-UHFFFAOYSA-M 0.000 claims description 6
- 235000012501 ammonium carbonate Nutrition 0.000 claims description 6
- 235000011114 ammonium hydroxide Nutrition 0.000 claims description 6
- ROOXNKNUYICQNP-UHFFFAOYSA-N ammonium persulfate Chemical compound [NH4+].[NH4+].[O-]S(=O)(=O)OOS([O-])(=O)=O ROOXNKNUYICQNP-UHFFFAOYSA-N 0.000 claims description 6
- 239000011248 coating agent Substances 0.000 claims description 6
- 238000000576 coating method Methods 0.000 claims description 6
- XGZVUEUWXADBQD-UHFFFAOYSA-L lithium carbonate Chemical compound [Li+].[Li+].[O-]C([O-])=O XGZVUEUWXADBQD-UHFFFAOYSA-L 0.000 claims description 6
- 229910052808 lithium carbonate Inorganic materials 0.000 claims description 6
- IIPYXGDZVMZOAP-UHFFFAOYSA-N lithium nitrate Chemical compound [Li+].[O-][N+]([O-])=O IIPYXGDZVMZOAP-UHFFFAOYSA-N 0.000 claims description 6
- 239000002244 precipitate Substances 0.000 claims description 6
- 229910000029 sodium carbonate Inorganic materials 0.000 claims description 6
- 235000017550 sodium carbonate Nutrition 0.000 claims description 5
- BFNBIHQBYMNNAN-UHFFFAOYSA-N ammonium sulfate Chemical compound N.N.OS(O)(=O)=O BFNBIHQBYMNNAN-UHFFFAOYSA-N 0.000 claims description 4
- 229910052921 ammonium sulfate Inorganic materials 0.000 claims description 4
- 235000011130 ammonium sulphate Nutrition 0.000 claims description 4
- LCPVQAHEFVXVKT-UHFFFAOYSA-N 2-(2,4-difluorophenoxy)pyridin-3-amine Chemical compound NC1=CC=CN=C1OC1=CC=C(F)C=C1F LCPVQAHEFVXVKT-UHFFFAOYSA-N 0.000 claims description 3
- 229910000013 Ammonium bicarbonate Inorganic materials 0.000 claims description 3
- 235000012538 ammonium bicarbonate Nutrition 0.000 claims description 3
- BIGPRXCJEDHCLP-UHFFFAOYSA-N ammonium bisulfate Chemical compound [NH4+].OS([O-])(=O)=O BIGPRXCJEDHCLP-UHFFFAOYSA-N 0.000 claims description 3
- 235000019270 ammonium chloride Nutrition 0.000 claims description 3
- 229910001870 ammonium persulfate Inorganic materials 0.000 claims description 3
- XYXNTHIYBIDHGM-UHFFFAOYSA-N ammonium thiosulfate Chemical compound [NH4+].[NH4+].[O-]S([O-])(=O)=S XYXNTHIYBIDHGM-UHFFFAOYSA-N 0.000 claims description 3
- FGRVOLIFQGXPCT-UHFFFAOYSA-L dipotassium;dioxido-oxo-sulfanylidene-$l^{6}-sulfane Chemical compound [K+].[K+].[O-]S([O-])(=O)=S FGRVOLIFQGXPCT-UHFFFAOYSA-L 0.000 claims description 3
- 230000008020 evaporation Effects 0.000 claims description 3
- FUJCRWPEOMXPAD-UHFFFAOYSA-N lithium oxide Chemical compound [Li+].[Li+].[O-2] FUJCRWPEOMXPAD-UHFFFAOYSA-N 0.000 claims description 3
- 229910001947 lithium oxide Inorganic materials 0.000 claims description 3
- USHAGKDGDHPEEY-UHFFFAOYSA-L potassium persulfate Chemical compound [K+].[K+].[O-]S(=O)(=O)OOS([O-])(=O)=O USHAGKDGDHPEEY-UHFFFAOYSA-L 0.000 claims description 3
- 229910000030 sodium bicarbonate Inorganic materials 0.000 claims description 3
- 235000017557 sodium bicarbonate Nutrition 0.000 claims description 3
- CHQMHPLRPQMAMX-UHFFFAOYSA-L sodium persulfate Substances [Na+].[Na+].[O-]S(=O)(=O)OOS([O-])(=O)=O CHQMHPLRPQMAMX-UHFFFAOYSA-L 0.000 claims description 3
- AKHNMLFCWUSKQB-UHFFFAOYSA-L sodium thiosulfate Chemical compound [Na+].[Na+].[O-]S([O-])(=O)=S AKHNMLFCWUSKQB-UHFFFAOYSA-L 0.000 claims description 3
- 235000019345 sodium thiosulphate Nutrition 0.000 claims description 3
- 238000001556 precipitation Methods 0.000 abstract description 6
- PXHVJJICTQNCMI-UHFFFAOYSA-N nickel Substances [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 56
- 239000010936 titanium Substances 0.000 description 40
- 239000011777 magnesium Substances 0.000 description 34
- 230000000052 comparative effect Effects 0.000 description 26
- 150000002500 ions Chemical class 0.000 description 15
- 239000010406 cathode material Substances 0.000 description 13
- 238000010532 solid phase synthesis reaction Methods 0.000 description 12
- KLARSDUHONHPRF-UHFFFAOYSA-N [Li].[Mn] Chemical compound [Li].[Mn] KLARSDUHONHPRF-UHFFFAOYSA-N 0.000 description 8
- 230000001351 cycling effect Effects 0.000 description 8
- 239000002344 surface layer Substances 0.000 description 8
- 238000012360 testing method Methods 0.000 description 8
- 239000002245 particle Substances 0.000 description 7
- 239000002243 precursor Substances 0.000 description 7
- 238000000967 suction filtration Methods 0.000 description 7
- NUJOXMJBOLGQSY-UHFFFAOYSA-N manganese dioxide Chemical compound O=[Mn]=O NUJOXMJBOLGQSY-UHFFFAOYSA-N 0.000 description 6
- 239000000047 product Substances 0.000 description 6
- 239000002002 slurry Substances 0.000 description 6
- 238000010998 test method Methods 0.000 description 6
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 5
- 239000000395 magnesium oxide Substances 0.000 description 5
- CPLXHLVBOLITMK-UHFFFAOYSA-N magnesium oxide Inorganic materials [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 description 5
- AXZKOIWUVFPNLO-UHFFFAOYSA-N magnesium;oxygen(2-) Chemical compound [O-2].[Mg+2] AXZKOIWUVFPNLO-UHFFFAOYSA-N 0.000 description 5
- OGIDPMRJRNCKJF-UHFFFAOYSA-N titanium oxide Inorganic materials [Ti]=O OGIDPMRJRNCKJF-UHFFFAOYSA-N 0.000 description 5
- 229910008555 Li1.2Mn0.6Ni0.2O2 Inorganic materials 0.000 description 4
- CSNNHWWHGAXBCP-UHFFFAOYSA-L Magnesium sulfate Chemical compound [Mg+2].[O-][S+2]([O-])([O-])[O-] CSNNHWWHGAXBCP-UHFFFAOYSA-L 0.000 description 4
- 239000002585 base Substances 0.000 description 4
- 229910001416 lithium ion Inorganic materials 0.000 description 4
- 229910052719 titanium Inorganic materials 0.000 description 4
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 3
- QGZKDVFQNNGYKY-UHFFFAOYSA-N ammonia Natural products N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 3
- 239000008367 deionised water Substances 0.000 description 3
- 229910021641 deionized water Inorganic materials 0.000 description 3
- 238000000227 grinding Methods 0.000 description 3
- 238000012986 modification Methods 0.000 description 3
- 230000004048 modification Effects 0.000 description 3
- 229910000480 nickel oxide Inorganic materials 0.000 description 3
- GNRSAWUEBMWBQH-UHFFFAOYSA-N oxonickel Chemical compound [Ni]=O GNRSAWUEBMWBQH-UHFFFAOYSA-N 0.000 description 3
- 239000002994 raw material Substances 0.000 description 3
- 239000011780 sodium chloride Substances 0.000 description 3
- 239000007787 solid Substances 0.000 description 3
- 238000001694 spray drying Methods 0.000 description 3
- 241000234314 Zingiber Species 0.000 description 2
- 235000006886 Zingiber officinale Nutrition 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 150000004649 carbonic acid derivatives Chemical class 0.000 description 2
- 238000009792 diffusion process Methods 0.000 description 2
- 238000004090 dissolution Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 235000008397 ginger Nutrition 0.000 description 2
- 229910052749 magnesium Inorganic materials 0.000 description 2
- 229910052943 magnesium sulfate Inorganic materials 0.000 description 2
- 235000019341 magnesium sulphate Nutrition 0.000 description 2
- DCKVFVYPWDKYDN-UHFFFAOYSA-L oxygen(2-);titanium(4+);sulfate Chemical compound [O-2].[Ti+4].[O-]S([O-])(=O)=O DCKVFVYPWDKYDN-UHFFFAOYSA-L 0.000 description 2
- 230000001376 precipitating effect Effects 0.000 description 2
- 238000005245 sintering Methods 0.000 description 2
- 229910000348 titanium sulfate Inorganic materials 0.000 description 2
- 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 1
- 229910016087 LiMn0.5Ni0.5O2 Inorganic materials 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 239000007772 electrode material Substances 0.000 description 1
- 239000003792 electrolyte Substances 0.000 description 1
- 238000000605 extraction Methods 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 150000004679 hydroxides Chemical class 0.000 description 1
- 238000010348 incorporation Methods 0.000 description 1
- 230000002401 inhibitory effect Effects 0.000 description 1
- 229910001425 magnesium ion Inorganic materials 0.000 description 1
- 230000014759 maintenance of location Effects 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 239000007773 negative electrode material Substances 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 238000007086 side reaction Methods 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
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- Battery Electrode And Active Subsutance (AREA)
- Inorganic Compounds Of Heavy Metals (AREA)
Abstract
The invention relates to a surface gradient doped lithium-rich manganese-based positive electrode material with a composite structure and a preparation method thereof, and belongs to the technical field of lithium-rich manganese-based positive electrode materials. The technical problems of poor rate capability, lattice oxygen precipitation in the circulation process and the like of the lithium-rich manganese-based positive electrode material in the prior art are solved. The surface gradient doped lithium-rich manganese-based positive electrode material with the composite structure comprises the following components in percentage by weight 1+ x Mg a Ti b Mn c Ni d O 2 Wherein x is more than 0 and less than 0.2, a is more than 0 and less than or equal to 0.1, b is more than 0 and less than or equal to 0.1, c is more than 0.5 and less than or equal to 0.9, d is more than or equal to 0.1 and less than or equal to 0.5, and x+a+b+c+d=1; the structure is composed of a composite layered structure, a spinel structure and a rock salt structure which are sequentially arranged from inside to outside. The surface gradient doped lithium-rich manganese-based positive electrode material has the advantages of excellent first coulombic efficiency, rate capability and long-cycle stability, low cost and easy preparation.
Description
Technical Field
The invention belongs to the technical field of lithium-rich manganese-based cathode materials, and particularly relates to a surface gradient doped lithium-rich manganese-based cathode material with a composite structure and a preparation method thereof.
Background
The lithium-rich layered oxide with high capacity and low cost is likely to be widely used as a positive electrode material of a high specific energy lithium ion battery. However, the series of materials have the problems of poor multiplying power performance, lattice oxygen precipitation in the circulation process and the like, which are unfavorable for large-scale practical application. Since oxygen precipitation of lithium-rich materials mainly occurs on the surface layer of the material, much research work has been focused on improving the unstable surface layer structure of lithium-rich materials.
Chinese patent (publication No. 106711439B) discloses a preparation method of a Mg and Ti composite doped lithium-rich manganese-based positive electrode material, which comprises the steps of firstly introducing Mg and Ti ions into a precursor of the lithium-rich material and preparing the composite doped lithium-rich manganese-based positive electrode material through high-temperature sintering. However, mg and Ti ions are easy to diffuse into the particles at high temperature, so that the composite doping method has limited improvement range on the structural stability of the surface layer of the lithium-rich material.
Chinese patent publication No. 103311532B discloses a nano-scale layered-spinel composite structure lithium-rich cathode material X (Li) 2 MnO 3 ·LiMn 0.5 Ni 0.5 O 2 )-YLiMn 1.5 Ni 0.5 O 4 The spinel phase in the lithium-rich cathode material is favorable for the diffusion of lithium ions in the composite material, but the problem of oxygen precipitation of the lamellar phase under high voltage and the ginger Taylor effect of the spinel phase are still to be further inhibited.
Therefore, it is necessary to develop a lithium-rich material having excellent rate performance and stable surface layer structure, which can be prepared by a simple method.
Disclosure of Invention
The invention aims to provide a surface gradient doped lithium-manganese-based positive electrode material with a composite structure and a preparation method thereof.
In order to achieve the above purpose, the present invention adopts the following technical scheme:
the invention provides a surface gradient doped lithium-rich manganese-based anode material with a composite structure,
the composition is Li 1+x Mg a Ti b Mn c Ni d O 2 Wherein x is more than 0 and less than 0.2, a is more than 0 and less than or equal to 0.1, b is more than 0 and less than or equal to 0.1, c is more than 0.5 and less than or equal to 0.9, d is more than or equal to 0.1 and less than or equal to 0.5, and x+a+b+c+d=1;
the structure is composed of a composite layered structure, a spinel structure and a rock salt structure which are sequentially arranged from inside to outside, wherein the composite layered structure is formed by a layered phase belonging to an R-3m space group and a layered phase belonging to a C2/m space group, the spinel structure is attributed to an Fd-3m space group and an I41/amd space group, and the rock salt structure is attributed to an Fm-3m space group.
Preferably, the composite lamellar structure accounts for 70-98wt%, the spinel structure accounts for 1-25wt%, and the rock salt structure accounts for 1-5wt%.
Preferably, in the composite layered structure, the mass ratio of the layered phase belonging to the R-3m space group to the layered phase belonging to the C2/m space group is 1:100 to 100:1.
Preferably, in the spinel structure, the mass ratio of the spinel structure belonging to Fd-3m space group to the spinel structure belonging to I41/amd space group is 1:100-100:1.
The invention also provides a preparation method of the surface gradient doped lithium-rich manganese-based positive electrode material with the composite structure, which comprises the following steps:
(1) Weighing Li compound, mg compound, ti compound, mn compound and Ni compound according to the stoichiometric ratio of each element in the composition of the surface gradient doped lithium-rich manganese-based positive electrode material;
(2) When the Li compound, the Ni compound and the Mn compound are one or more of oxide, hydroxide and carbonate respectively and independently, uniformly mixing the Li compound, the Ni compound and the Mn compound, ball milling the mixture, presintering and calcining the obtained mixture in a mixed atmosphere consisting of inert gas and oxygen, and cooling the mixture to obtain the lithium-rich manganese-based oxide anode material;
when the Li compound, the Ni compound and the Mn compound are respectively and independently soluble in water, firstly dissolving the Ni compound and the Mn compound in water to obtain a liquid phase mixture, then adding excessive soluble alkali aqueous solution or soluble carbonate aqueous solution into the liquid phase mixture under stirring, filtering, washing and drying the obtained precipitate to obtain a dried material, finally uniformly mixing the dried material and the Li compound, presintering and calcining the obtained mixture under a mixed atmosphere composed of inert gas and oxygen, and cooling to obtain the lithium-rich manganese-based oxide positive electrode material;
(3) Pre-coating a pre-delithiated compound on the surface of a lithium-rich manganese-based oxide positive electrode material, performing heat treatment on the pre-coated lithium-rich manganese-based oxide positive electrode material in a mixed atmosphere consisting of inert gas and oxygen, and washing, filtering and drying the powder after heat treatment to obtain the lithium-rich material with the pre-delithiated surface;
or dispersing the lithium-rich manganese-based oxide anode material in an aqueous solution with a pH value of 1-11, stirring for 0.1-100 h at 0-90 ℃, and filtering, washing and drying the obtained liquid phase mixture to obtain the lithium-rich material with the surface pre-delithiated;
(4) When the compound of Mg and the compound of Ti are each independently one or more of an oxide, a hydroxide, and a carbonate, (4 a) or (4 b) is used;
when the compound of Mg and the compound of Ti are each independently nitrate, (4 a) or (4 c) is used;
when the compound of Mg and the compound of Ti are respectively and independently one or more of sulfate and chloride, (4 c) is adopted;
(4a) Uniformly mixing a Mg compound, a Ti compound and a lithium-rich material with a surface pre-delithiated structure, and performing heat treatment on the obtained mixture in a mixed atmosphere consisting of inert gas and oxygen to obtain a lithium-rich manganese-based anode material with a surface gradient doping type composite structure;
(4b) Dispersing a Mg compound and a Ti compound in water, dispersing a lithium-rich material with a surface pre-delithiated in the water, evaporating the liquid phase mixture under stirring, and carrying out heat treatment on the material obtained after evaporation to obtain a lithium-rich manganese-based positive electrode material with a surface gradient doped composite structure;
(4c) Firstly, dissolving a Mg compound and a Ti compound in water, and dispersing a lithium-rich material with the surface pre-delithiated in the water to obtain a liquid phase mixture; and adding excessive soluble alkali aqueous solution or soluble carbonate aqueous solution into the liquid phase mixture under stirring, filtering, washing and drying the obtained precipitate to obtain a dry material, and finally performing heat treatment on the dry material under the mixed atmosphere consisting of inert gas and oxygen to obtain the lithium-manganese-rich anode material with the surface gradient doped composite structure.
Preferably, in the step (1),
the Li compound is one or more of lithium carbonate, lithium oxide, lithium hydroxide and lithium nitrate;
the Mg compound is one or more of Mg oxide, mg hydroxide, mg carbonate, mg nitrate, mg chloride and Mg sulfate;
the Ti compound is one or more of Ti oxide, ti hydroxide, ti carbonate, ti nitrate, ti chloride and Ti sulfate;
the Mn compound is one or more of Mn oxide, mn hydroxide, mn carbonate, mn nitrate, mn chloride and Mn sulfate;
the compound of Ni is one or more of oxide of Ni, hydroxide of Ni, carbonate of Ni, nitrate of Ni, chloride of Ni and sulfate of Ni.
Preferably, in the step (2), a high-speed mixer is adopted for uniform mixing; more preferably, the rotating speed of the high-speed mixer is 500-10000 r/min, and the mixing time is 1-72 h.
Preferably, in the step (2), ball milling is performed by adopting a ball mill; more preferably, the rotating speed of the ball mill is 200-800 r/min, the ball milling time is 1-72 h, and the weight ratio of the ball materials is 5-50: 1.
preferably, in step (2), the soluble carbonate comprises ammonium carbonate, ammonium bicarbonate, sodium bicarbonate or sodium carbonate, and the soluble base comprises aqueous ammonia or sodium hydroxide.
Preferably, in the step (2), the pre-sintering temperature is 200-700 ℃ and the calcining time is 0.5-10 h.
Preferably, in the step (2), the calcination temperature is 500-1000 ℃ and the calcination time is 2-25 h.
Preferably, in the step (2), the molar ratio of the inert gas to the oxygen is 1 (0.001-100); more preferably, the inert gas is one or more of nitrogen and argon.
Preferably, in the step (3), the pre-delithiated compound is one or more of ammonium sulfate, ammonium bisulfate, ammonium thiosulfate, ammonium persulfate, sodium thiosulfate, sodium persulfate, potassium thiosulfate, potassium persulfate and ammonium chloride.
Preferably, in the step (3), the amount of the substance of the pre-delithiated compound is 0.1% to 30% of the amount of the substance of the lithium-rich manganese-based oxide positive electrode material.
Preferably, in the step (3), a method of pre-coating the surface of the lithium-rich manganese-based oxide positive electrode material with a pre-delithiated compound;
uniformly mixing the pre-delithiated compound with the lithium-rich manganese-based oxide positive electrode material to obtain a pre-coated lithium-rich manganese-based oxide positive electrode material;
or dissolving the pre-delithiated compound in water, dispersing the lithium-rich manganese-based oxide positive electrode material in the water to obtain a liquid phase mixture, and evaporating the liquid phase mixture under stirring to obtain the pre-coated lithium-rich manganese-based oxide positive electrode material.
Preferably, in the step (3), the temperature of the heat treatment is 150-850 ℃, and the time of the heat treatment is 10 min-20 h.
Preferably, in the step (3), the drying temperature is 80-300 ℃ and the drying time is 10 min-20 h.
Preferably, in the step (3), the stirring rotation speed is 100-800 rmp/min.
Preferably, in the step (3), the molar ratio of the inert gas to the oxygen is 1 (0.001-100), more preferably, the inert gas is one or more of nitrogen and argon.
Preferably, in the step (4), a high-speed mixer is adopted for uniform mixing; more preferably, the rotating speed of the high-speed mixer is 500-10000 r/min, and the mixing time is 1-72 h.
Preferably, in step (4), the soluble carbonate comprises ammonium carbonate or sodium carbonate and the soluble base comprises aqueous ammonia or sodium hydroxide.
Preferably, in the step (4), the temperature of the heat treatment is 300-1000 ℃, and the time of the heat treatment is 2-25 hours.
Preferably, in the step (4), the molar ratio of the inert gas to the oxygen is 1 (0.001-100), more preferably, the inert gas is one or more of nitrogen and argon.
The principle of the invention is as follows: firstly preparing a lithium-rich manganese-based oxide positive electrode material, and then carrying out pre-delithiation treatment on the lithium-rich manganese-based oxide positive electrode material to enable part of Li in the surface layer structure of the lithium-rich manganese-based oxide positive electrode material + Ion extraction followed by uniform introduction of M on the surface of the resulting surface pre-delithiated lithium-rich materialg 2+ And Ti is 4+ Ions and heat-treating. During the heat treatment, mg 2+ And Ti is 4+ Ions will diffuse into the surface structure of the particles. Wherein the outer surface layer Li + Less ion and Mg 2+ And Ti is 4+ Ions are more, so that a rock salt structure is formed; the rock salt structure can inhibit micro-cracks from forming on the particles in the long circulation process, inhibit precipitation of lattice oxygen on the surface layers of the particles, inhibit side reactions between Ni ions in the particles and electrolyte in a high-charge state, and inhibit dissolution of Mn in the particles in the circulation process. While the inner surface layer has relatively more Li + Ions and relatively little Mg 2+ And Ti is 4+ Ions, thus forming a doped spinel structure; the doped spinel structure has a three-dimensional lithium ion diffusion channel which is beneficial to the multiplying power performance of the material, mg 2+ And Ti is 4+ The incorporation of ions can inhibit Mn in the spinel phase 3+ The problems of particle breakage and Mn ion dissolution caused by the Taylor effect of the ginger, and further plays a role in inhibiting microcrack and oxygen precipitation. While the inner layered structure also has a small amount of Mg 2+ And Ti is 4+ The ion doping improves the stability of the positive electrode material in a high charging state.
Compared with the prior art, the invention has the following beneficial effects:
the first coulomb efficiency, multiplying power, circulation and thermal stability of the lithium-rich manganese-based positive electrode material with the surface gradient doped composite structure are obviously improved.
The preparation method of the lithium-rich manganese-based positive electrode material with the surface gradient doped composite structure has the advantages that the used Ti, mg and Mn elements are low in price, rich in reserves and environment-friendly, so that the preparation method has cost advantages.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are needed in the embodiments will be briefly described below, and it is apparent that the drawings in the following description are only some embodiments of the present invention and that other drawings can be obtained without inventive effort for a person skilled in the art.
FIG. 1 is a schematic structural diagram of a lithium-rich manganese-based positive electrode material with a surface gradient doped composite structure; in the figure, 1. Composite layered structure, 2. Spinel structure, 3. Rock salt structure.
Detailed Description
For a thorough understanding of the present invention, the preferred embodiments of the present invention will be described to further illustrate the features and advantages of the present invention, and any changes or modifications that do not depart from the gist of the present invention will be understood by those skilled in the art to which the present invention pertains, the scope of which is defined by the appended claims.
The surface gradient doped lithium-rich manganese-based positive electrode material with the composite structure comprises the following components in percentage by weight 1+ x Mg a Ti b Mn c Ni d O 2 Wherein x is more than 0 and less than 0.2, a is more than 0 and less than or equal to 0.1, b is more than 0 and less than or equal to 0.1, c is more than 0.5 and less than or equal to 0.9, d is more than or equal to 0.1 and less than or equal to 0.5, and x+a+b+c+d=1; the structure is composed of a composite layered structure, a spinel structure and a rock salt structure which are sequentially arranged from inside to outside, as shown in figure 1, wherein the composite layered structure is formed by a layered phase belonging to an R-3m space group and a layered phase belonging to a C2/m space group, the spinel structure is attributed to an Fd-3m space group and an I41/amd space group, and the rock salt structure is attributed to an Fm-3m space group.
According to the technical scheme, the preferable composite lamellar structure accounts for 70-98wt%, the spinel structure accounts for 1-25wt%, and the rock salt structure accounts for 1-5wt%.
In the above technical scheme, in the preferable composite lamellar structure, the mass ratio of lamellar phase belonging to R-3m space group to lamellar phase belonging to C2/m space group is 1:100-100:1.
In the above technical scheme, preferably, in the spinel structure, the mass ratio of the spinel structure belonging to Fd-3m space group to the spinel structure belonging to I41/amd space group is 1:100-100:1.
The preparation method of the lithium-rich manganese-based positive electrode material with the surface gradient doped composite structure comprises the following steps:
(1) Weighing raw materials
Lithium-rich manganese-based positive electrode material composition (Li) with surface gradient doping type composite structure 1+x Mg a Ti b Mn c Ni d O 2 Wherein x is more than 0 and less than 0.2, a is more than 0 and less than or equal to 0.1, b is more than 0 and less than or equal to 0.1, c is more than 0.5 and less than or equal to 0.9, d is more than or equal to 0.1 and less than or equal to 0.5, and the stoichiometric ratio of each element in x+a+b+c+d=1) is used for weighing Li compound, mg compound, ti compound, mn compound and Ni compound;
(2) Preparation of lithium-rich manganese-based oxide anode material by solid phase method or liquid phase method
Solid phase method: ball-milling and uniformly mixing a Li compound, a Ni compound and a Mn compound, presintering and calcining the obtained mixture in a mixed atmosphere consisting of inert gas and oxygen, and cooling to obtain a lithium-rich manganese-based oxide anode material;
in the solid phase method, the Li compound, the Ni compound, and the Mn compound each independently refer to one or more of an oxide, a hydroxide, and a carbonate of the corresponding element;
liquid phase method: dissolving a Ni compound and a Mn compound in water to obtain a liquid phase mixture, adding (dropwise) excessive soluble alkali or soluble carbonate into the liquid phase mixture under stirring, completely precipitating Ni ions and Mn ions, filtering, washing and drying the obtained precipitate to obtain a dry material, and finally uniformly mixing the dry material and the Li compound (a solid phase method), presintering and calcining the obtained mixture under a mixed atmosphere consisting of inert gas and oxygen, and cooling to obtain the lithium-rich manganese-based oxide anode material;
in the liquid phase method, the Li compound, the Ni compound, and the Mn compound refer to water-soluble compounds of the corresponding elements, such as one or more of nitrate, chloride, or sulfate, respectively;
(3) Pre-delithiation treatment of lithium-rich manganese-based oxide positive electrode material by using solid phase method or liquid phase method
Solid phase method: pre-coating a pre-delithiated compound on the surface of a lithium-rich manganese-based oxide positive electrode material, performing heat treatment on the pre-coated lithium-rich manganese-based oxide positive electrode material in a mixed atmosphere consisting of inert gas and oxygen, and washing, filtering and drying the powder after heat treatment to obtain the lithium-rich material with the pre-delithiated surface;
liquid phase method: dispersing the lithium-rich manganese-based oxide anode material in an aqueous solution with a pH value of 1-11, stirring for 0.1-100 h at 0-90 ℃, and filtering, washing and drying the obtained liquid phase mixture to obtain the lithium-rich material with the surface pre-delithiated;
(4) Preparing the lithium-rich manganese-based anode material with the surface gradient doping type composite structure by using a solid phase method or a liquid phase method: when the compound of Mg and the compound of Ti are each independently one or more of an oxide, a hydroxide, and a carbonate, (4 a) or (4 b) is used; when the compound of Mg and the compound of Ti are each independently nitrate, (4 a) or (4 c) is used; when the compound of Mg and the compound of Ti are respectively and independently one or more of sulfate and chloride, (4 c) is adopted;
(4a) Uniformly mixing a Mg compound, a Ti compound and a lithium-rich material with a surface pre-delithiated structure, and performing heat treatment on the obtained mixture in a mixed atmosphere consisting of inert gas and oxygen to obtain a lithium-rich manganese-based anode material with a surface gradient doping type composite structure;
(4b) Dispersing a Mg compound and a Ti compound in water, dispersing a lithium-rich material with a surface pre-delithiated in the water, evaporating the liquid phase mixture under stirring, and carrying out heat treatment on the material obtained after evaporation to obtain a lithium-rich manganese-based positive electrode material with a surface gradient doped composite structure;
(4c) Firstly, dissolving a Mg compound and a Ti compound in water, and dispersing a lithium-rich material with the surface pre-delithiated in the water to obtain a liquid phase mixture; and adding excessive soluble alkali aqueous solution or soluble carbonate aqueous solution into the liquid phase mixture under stirring, completely precipitating Mg ions and Ti ions, filtering, washing and drying the obtained precipitate to obtain a dry material, and finally performing heat treatment on the dry material under the mixed atmosphere consisting of inert gas and oxygen to obtain the lithium-rich manganese-based anode material with the surface gradient doped composite structure.
In the above technical scheme, in the step (1), the Li compound is one or more of lithium carbonate, lithium oxide, lithium hydroxide and lithium nitrate; the compound of Mg is one or more of Mg oxide, mg hydroxide, mg carbonate, mg nitrate, mg chloride and Mg sulfate; the Ti compound is one or more of Ti oxide, ti hydroxide, ti carbonate, ti nitrate, ti chloride and Ti sulfate; the Mn compound is one or more of Mn oxide, mn hydroxide, mn carbonate, mn nitrate, mn chloride and Mn sulfate; the compound of Ni is one or more of oxide of Ni, hydroxide of Ni, carbonate of Ni, nitrate of Ni, chloride of Ni and sulfate of Ni.
In the technical scheme, in the step (2), a ball mill is adopted for ball milling, the rotating speed of the ball mill is 200-800 r/min, the ball milling time is 1-72 h, and the weight ratio of ball materials is 5-50: 1. uniformly mixing by a high-speed mixer; the rotating speed of the high-speed mixer is 500-10000 r/min, and the mixing time is 1-72 h. The presintering temperature is 200-700 ℃, and the calcining time is 0.5-10 h. The calcination temperature is 500-1000 ℃ and the calcination time is 2-25 h. The molar ratio of the inert gas to the oxygen is 1 (0.001-100); the inert gas is one or more of nitrogen and argon. The soluble carbonate comprises ammonium carbonate or sodium carbonate, and the soluble base comprises ammonia water or sodium hydroxide.
In the above technical scheme, in the step (2), theoretically, if the raw materials meet the conditions of both the solid phase method and the liquid phase method, the raw materials may be prepared by either the solid phase method or the liquid phase method, but since the oxides, hydroxides, and carbonates of Mn are insoluble in water, the conditions of both the solid phase method and the liquid phase method are not satisfied.
In the above technical scheme, in the step (3), the pre-delithiated compound is one or more of ammonium sulfate, ammonium bisulfate, ammonium thiosulfate, ammonium persulfate, sodium thiosulfate, sodium persulfate, potassium thiosulfate, potassium persulfate and ammonium chloride. The amount of the substances of the pre-delithiated compound is 0.1% -30% of the amount of the substances of the lithium-rich manganese-based oxide positive electrode material. The temperature of the heat treatment is 150-850 ℃, and the time of the heat treatment is 10 min-20 h. The drying temperature is 80-300 ℃ and the drying time is 10 min-20 h. The stirring speed is 100-800 rmp/min. The molar ratio of the inert gas to the oxygen is 1 (0.001-100), and the inert gas is one or more of nitrogen and argon. The method for pre-coating the pre-delithiated compound on the surface of the lithium-rich manganese-based oxide positive electrode material is a solid-phase method or a liquid-phase method; solid phase method: uniformly mixing the pre-delithiated compound with the lithium-rich manganese-based oxide positive electrode material to obtain a pre-coated lithium-rich manganese-based oxide positive electrode material; liquid phase method: dissolving a pre-delithiated compound in water, dispersing the lithium-rich manganese-based oxide positive electrode material in the water to obtain a liquid phase mixture, and evaporating the liquid phase mixture under stirring to obtain the pre-coated lithium-rich manganese-based oxide positive electrode material.
In the technical scheme, in the step (4), a high-speed mixer is adopted for uniform mixing; the rotating speed of the high-speed mixer is 500-10000 r/min, and the mixing time is 1-72 h. The heat treatment temperature is 300-1000 ℃, and the heat treatment time is 2-25 h. The molar ratio of the inert gas to the oxygen is 1 (0.001-100), and the inert gas is one or more of nitrogen and argon. Soluble carbonates include ammonium carbonate, ammonium bicarbonate, sodium bicarbonate or sodium carbonate, and soluble bases include aqueous ammonia or sodium hydroxide.
The terms used in the present invention generally have meanings commonly understood by those of ordinary skill in the art unless otherwise indicated.
In order that those skilled in the art will better understand the technical scheme of the present invention, the present invention will be further described in detail with reference to examples and comparative examples.
In the following examples and comparative examples, various processes and methods, which are not described in detail, are conventional methods well known in the art. Materials, reagents, devices, instruments, equipment and the like used in the following examples and comparative examples are commercially available unless otherwise specified.
Comparative example 1
Lithium-rich manganese-based positive electrode material Li 1.2 Mn 0.6 Ni 0.2 O 2 The preparation method comprises the following steps:
according to the matters of each element of the lithium-rich manganese-based positive electrode materialWeighing nickel oxide, manganese dioxide and lithium carbonate according to the mass proportion, mixing for 8 hours in a mixer (stirring speed is 500-10000 r/min), adding deionized water according to the solid content of 20wt%, and pouring the slurry into a ball mill (ball milling speed is 200-800 r/min) for grinding until the medium granularity is less than 0.3 microns. And finally, spray drying the obtained slurry to obtain the precursor. The precursor is kept at 450 ℃ for 5 hours, and then the temperature is continuously raised to 950 ℃ for 20 hours; finally naturally cooling to room temperature to obtain Li 1.2 Mn 0.6 Ni 0.2 O 2 And (3) a lithium-rich manganese-based positive electrode material.
The prepared material is used as a positive electrode material, a lithium sheet is used as a negative electrode material, the lithium sheet is assembled into a button cell, a constant current charge and discharge test is carried out at 25 ℃, and the charge and discharge voltage ranges are as follows: 2-4.8V, and defines a current density of 200mA/g of 1C. The test results are shown in Table 1.
Comparative example 2
Doped lithium-rich manganese-based positive electrode material Li 1.2 Mn 0.59 Ti 0.01 Ni 0.19 Mg 0.01 O 2 The preparation method comprises the following steps:
weighing nickel oxide, manganese dioxide, magnesium oxide, titanium oxide and lithium carbonate according to the proportion of the substances of each element of the doped lithium-rich manganese-based positive electrode material, mixing for 8 hours in a mixer (stirring speed is 500-10000 r/min), adding deionized water according to the proportion of 20wt% of solid content, and pouring the slurry into a ball mill (ball milling speed is 200-800 r/min) for grinding until the medium granularity is less than 0.3 micron. And finally, spray drying the obtained slurry to obtain the precursor. The precursor is kept at 450 ℃ for 5 hours, and then the temperature is continuously raised to 950 ℃ for 20 hours; finally naturally cooling to room temperature to obtain doped Li 1.2 Mn 0.6 Ni 0.2 O 2 Doped lithium-rich manganese-based positive electrode material.
The first coulombic efficiency, rate capability and cycle stability of the material prepared in comparative example 2 were measured by the same method as in comparative example 1, and the measurement results are shown in table 1.
Comparative example 3
Layered-spinel-rock salt composite structure lithium-rich manganese basePositive electrode material Li 1.15 Mn 0.6 Ni 0.2 O 2 The preparation method comprises the following steps:
weighing nickel oxide, manganese dioxide and lithium carbonate according to the proportion of the mass of each element of the lithium-rich manganese-based positive electrode material with the layered-spinel-rock salt composite structure, mixing for 8 hours in a mixer (stirring speed is 500-10000 r/min), adding deionized water according to the proportion of 20wt% of solid content, and pouring the slurry into a ball mill (ball milling speed is 200-800 r/min) for grinding until the medium granularity is less than 0.3 micron. And finally, spray drying the obtained slurry to obtain the precursor. The precursor is kept at 450 ℃ for 5 hours, and then the temperature is continuously raised to 950 ℃ for 20 hours; finally naturally cooling to room temperature to obtain the layered-spinel-rock salt composite structure Li 1.15 Mn 0.6 Ni 0.2 O 2 And (3) a lithium-rich manganese-based positive electrode material.
The positive electrode material prepared in comparative example 3 was examined for initial coulombic efficiency, rate capability and cycling stability by the same method as in comparative example 1, and the examination results are shown in table 1.
Example 1
Surface gradient doping type composite structure lithium-rich manganese-based positive electrode material Li 1.15 Mn 0.59 Ti 0.01 Ni 0.19 Mg 0.01 O 2 The preparation method comprises the following steps:
(1) Weighing Li compound, mg compound, ti compound, mn compound and Ni compound according to the stoichiometric ratio of each element in the composition of the surface gradient doped lithium-rich manganese-based positive electrode material;
(2) Preparation of lithium-rich manganese-based cathode Material Li according to the method in comparative example 1 1.2 Mn 0.6 Ni 0.2 O 2 ；
(3) Dissolving 5% ammonium sulfate of the amount of the substance of the lithium-rich manganese-based positive electrode material in water, and dissolving the prepared Li 1.2 Mn 0.6 Ni 0.2 O 2 Dispersing the materials in the mixture, evaporating the liquid phase mixture under the condition of continuously stirring at 80 ℃, carrying out heat treatment (300 ℃ for 10 hours) on the obtained powder under the air atmosphere, and then carrying out water washing, suction filtration and drying (80-300 ℃) to obtain the surface pre-preparationLithium-rich material for lithium removal;
(4) Dissolving magnesium sulfate and titanium sulfate in water, dispersing a lithium-rich material with the surface pre-delithiated in the water, then dropwise adding excessive sodium hydroxide aqueous solution into the liquid-phase mixture under stirring, and carrying out suction filtration, water washing and drying to obtain a dry material; and (3) carrying out heat treatment on the mixture at 750 ℃ (6 h) in an air atmosphere to obtain a target product.
The first coulombic efficiency, the rate capability and the cycling stability of the lithium-manganese-rich positive electrode material with the surface gradient doped composite structure prepared in example 1 were tested, the test method was the same as that of comparative example 1, and the test results are shown in table 1.
TABLE 1 Primary coulombic efficiency, rate Performance and cycle stability Properties of the cathode materials prepared in comparative examples 1 to 3 and example 1
As can be seen from table 1, compared with the conventional layered lithium-rich material of comparative example 1: (1) Mg prepared in comparative example 2 2 + /Ti 4+ The cycle performance of the doped layered lithium-rich material is obviously improved, but the initial capacity and the rate performance are obviously reduced; (2) The first coulomb efficiency and the multiplying power performance of the lithium-rich material with the composite structure prepared in the comparative example 3 are obviously improved, but the capacity retention rate after 200 weeks of 1C circulation is not greatly improved; (3) The first coulombic efficiency, the rate capability and the cycling stability of the lithium-rich manganese-based positive electrode material with the surface gradient doped composite structure prepared in the embodiment 1 are all obviously improved.
Example 2
Surface gradient doping type composite structure lithium-rich manganese-based positive electrode material Li 1.16 Mn 0.58 Ti 0.02 Ni 0.18 Mg 0.02 O 2 The preparation method comprises the following steps:
(1) Weighing Li compound, mg compound, ti compound, mn compound and Ni compound according to the stoichiometric ratio of each element in the composition of the surface gradient doped lithium-rich manganese-based positive electrode material;
(2) Preparation of lithium-rich manganese-based cathode Material Li according to the method in comparative example 1 1.2 Mn 0.6 Ni 0.2 O 2 ；
(3) Li prepared 1.2 Mn 0.6 Ni 0.2 O 2 Dispersing the material in an aqueous solution with the pH value of 6, continuously stirring at 50 ℃ for 6 hours (stirring rotation speed is 100-800 rmp/min), and then carrying out suction filtration, water washing and drying (80-300 ℃), thus obtaining the lithium-rich material with the surface pre-delithiated;
(4) Dispersing magnesium oxide and titanium oxide in water, dispersing lithium-rich material with pre-delithiated surface in the water, and then evaporating the liquid phase mixture at 90 ℃ under continuous stirring; and (3) carrying out heat treatment on the evaporated powder at 750 ℃ (6 h) in an air atmosphere to obtain a target product.
The first coulombic efficiency, the rate capability and the cycling stability of the lithium-manganese-rich positive electrode material with the surface gradient doped composite structure prepared in example 2 were tested, the test method was the same as that of comparative example 1, and the test results are shown in table 2.
Example 3
Surface gradient doping type composite structure lithium-rich manganese-based positive electrode material Li 1.18 Mn 0.59 Ti 0.01 Ni 0.18 Mg 0.02 O 2 The preparation method comprises the following steps:
(1) Weighing Li compound, mg compound, ti compound, mn compound and Ni compound according to the stoichiometric ratio of each element in the composition of the surface gradient doped lithium-rich manganese-based positive electrode material;
(2) Preparation of lithium-rich manganese-based cathode Material Li according to the method in comparative example 1 1.2 Mn 0.6 Ni 0.2 O 2 ；
(3) Li prepared 1.2 Mn 0.6 Ni 0.2 O 2 Dispersing the material in an aqueous solution with the pH value of 5, continuously stirring at 60 ℃ for 2 hours (stirring speed is 100-800 rmp/min), and then carrying out suction filtration, water washing and drying (80-300 ℃), thus obtaining the lithium-rich material with the surface pre-delithiated;
(4) Dispersing magnesium oxide and titanium oxide in water, dispersing lithium-rich material with pre-delithiated surface in the water, and then evaporating the liquid phase mixture at 90 ℃ under continuous stirring; and (3) carrying out heat treatment on the evaporated powder at 750 ℃ (10 h) in a mixed atmosphere (the molar ratio of nitrogen to oxygen is 1:0.01), so as to obtain a target product.
The first coulombic efficiency, the rate capability and the cycling stability of the lithium-manganese-rich positive electrode material with the surface gradient doped composite structure prepared in example 3 were tested, the test method was the same as that of comparative example 1, and the test results are shown in table 2.
Example 4
Surface gradient doping type composite structure lithium-rich manganese-based positive electrode material Li 1.16 Mn 0.49 Ti 0.01 Ni 0.29 Mg 0.01 O 2 The preparation method comprises the following steps:
(1) Weighing Li compound, mg compound, ti compound, mn compound and Ni compound according to the stoichiometric ratio of each element in the composition of the surface gradient doped lithium-rich manganese-based positive electrode material;
(2) Preparation of lithium-rich manganese-based cathode Material Li according to the method in comparative example 1 1.2 Mn 0.5 Ni 0.3 O 2 ；
(3) Li prepared 1.2 Mn 0.5 Ni 0.3 O 2 Dispersing the material in an aqueous solution with the pH value of 6, continuously stirring at 50 ℃ for 6 hours (stirring speed is 100-800 rmp/min), and then carrying out suction filtration, water washing and drying (80-300 ℃), thus obtaining the lithium-rich material with the surface pre-delithiated;
(4) Dispersing magnesium oxide and titanium oxide in water, dispersing lithium-rich material with pre-delithiated surface in the water, and then evaporating the liquid phase mixture at 90 ℃ under continuous stirring; and (3) carrying out heat treatment on the evaporated powder at 750 ℃ (6 h) under a mixed atmosphere (the molar ratio of nitrogen to oxygen is 0.01:1), so as to obtain a target product.
The first coulombic efficiency, the rate capability and the cycling stability of the lithium-manganese-rich cathode material with the surface gradient doped composite structure prepared in example 4 were tested, the test method was the same as that of comparative example 1, and the test results are shown in table 2.
Example 5
Surface gradient doping type composite structure lithium-rich manganese-based positive electrode material Li 1.10 Mn 0.58 Ti 0.02 Ni 0.18 Mg 0.02 O 2 The preparation method comprises the following steps:
(1) Weighing Li compound, mg compound, ti compound, mn compound and Ni compound according to the stoichiometric ratio of each element in the composition of the surface gradient doped lithium-rich manganese-based positive electrode material;
(2) Preparation of lithium-rich manganese-based cathode Material Li according to the method in comparative example 1 1.2 Mn 0.6 Ni 0.2 O 2 ；
(3) Li prepared 1.2 Mn 0.6 Ni 0.2 O 2 Dispersing the material in an aqueous solution with the pH value of 5, continuously stirring at 50 ℃ for 10 hours (stirring speed is 100-800 rmp/min), and then carrying out suction filtration, water washing and drying (80-300 ℃), thus obtaining the lithium-rich material with the surface pre-delithiated;
(4) Dissolving magnesium sulfate and titanium sulfate in water, and dispersing a lithium-rich material with the surface pre-delithiated in the water to obtain a liquid phase mixture; then dropwise adding excessive sodium hydroxide aqueous solution into the liquid phase mixture under stirring, and then filtering, washing and drying to obtain a dried material; finally, the dry material is subjected to heat treatment at 800 ℃ (3 h) in air atmosphere, and a target product can be obtained.
The first coulombic efficiency, the rate capability and the cycling stability of the lithium-manganese-rich positive electrode material with the surface gradient doped composite structure prepared in example 5 were tested, the test method was the same as that of comparative example 1, and the test results are shown in table 2.
Example 6
Surface gradient doping type composite structure lithium-rich manganese-based positive electrode material Li 1.16 Mn 0.49 Ti 0.01 Ni 0.29 Mg 0.01 O 2 The preparation method comprises the following steps:
(1) Weighing Li compound, mg compound, ti compound, mn compound and Ni compound according to the stoichiometric ratio of each element in the composition of the surface gradient doped lithium-rich manganese-based positive electrode material;
(2) Preparation of lithium-rich manganese-based cathode Material Li according to the method in comparative example 1 1.2 Mn 0.5 Ni 0.3 O 2 ；
(3) Li prepared 1.2 Mn 0.5 Ni 0.3 O 2 Dispersing the material in an aqueous solution with the pH value of 6, continuously stirring at 50 ℃ for 6 hours (stirring speed is 100-800 rmp/min), and then carrying out suction filtration, water washing and drying (80-300 ℃), thus obtaining the lithium-rich material with the surface pre-delithiated;
(4) Dispersing magnesium oxide and titanium oxide in water, dispersing lithium-rich material with pre-delithiated surface in the water, and then evaporating the liquid phase mixture at 90 ℃ under continuous stirring; and (3) carrying out 700 ℃ (8 h) heat treatment on the evaporated powder under a mixed atmosphere (the molar ratio of oxygen to nitrogen is 0.05:0.95), so as to obtain a target product.
The first coulombic efficiency, the rate capability and the cycling stability of the lithium-manganese-rich positive electrode material with the surface gradient doped composite structure prepared in example 6 were tested, the test method was the same as that of comparative example 1, and the test results are shown in table 2.
TABLE 2 Primary coulombic efficiency, multiplying power Performance and cycle stability Properties of the cathode materials prepared in examples 2 to 6
It should be apparent that the above embodiments are merely examples for clarity of illustration and are not limiting of the embodiments. Other variations or modifications of the above teachings will be apparent to those of ordinary skill in the art. It is not necessary here nor is it exhaustive of all embodiments. And obvious variations or modifications thereof are contemplated as falling within the scope of the present invention.
Claims (10)
1. The surface gradient doped lithium-rich manganese-based positive electrode material with the composite structure is characterized in that,
the composition is Li 1+x Mg a Ti b Mn c Ni d O 2 Wherein x is more than 0 and less than 0.2, a is more than 0 and less than or equal to 0.1, b is more than 0 and less than or equal to 0.1, c is more than 0.5 and less than or equal to 0.9, d is more than or equal to 0.1 and less than or equal to 0.5, and x+a+b+c+d=1;
the structure is composed of a composite layered structure, a spinel structure and a rock salt structure which are sequentially arranged from inside to outside, wherein the composite layered structure is formed by a layered phase belonging to an R-3m space group and a layered phase belonging to a C2/m space group, the spinel structure is attributed to an Fd-3m space group and an I41/amd space group, and the rock salt structure is attributed to an Fm-3m space group.
2. The surface gradient doped composite structure lithium-rich manganese-based positive electrode material according to claim 1, wherein,
the composite lamellar structure accounts for 70-98wt%, the spinel structure accounts for 1-25wt%, and the rock salt structure accounts for 1-5wt%;
in the composite layered structure, the mass ratio of the layered phase belonging to the R-3m space group to the layered phase belonging to the C2/m space group is 1:100-100:1;
in the spinel structure, the mass ratio of the spinel structure belonging to Fd-3m space group to the spinel structure belonging to I41/amd space group is 1:100-100:1.
3. The method for preparing the lithium-rich manganese-based positive electrode material with the surface gradient doped composite structure according to claim 1 or 2, which is characterized by comprising the following steps:
(1) Weighing Li compound, mg compound, ti compound, mn compound and Ni compound according to the stoichiometric ratio of each element in the composition of the surface gradient doped lithium-rich manganese-based positive electrode material;
(2) When the Li compound, the Ni compound and the Mn compound are one or more of oxide, hydroxide and carbonate respectively and independently, uniformly mixing the Li compound, the Ni compound and the Mn compound, ball milling the mixture, presintering and calcining the obtained mixture in a mixed atmosphere consisting of inert gas and oxygen, and cooling the mixture to obtain the lithium-rich manganese-based oxide anode material;
when the Li compound, the Ni compound and the Mn compound are respectively and independently soluble in water, firstly dissolving the Ni compound and the Mn compound in water to obtain a liquid phase mixture, then adding excessive soluble alkali aqueous solution or soluble carbonate aqueous solution into the liquid phase mixture under stirring, filtering, washing and drying the obtained precipitate to obtain a dried material, finally uniformly mixing the dried material and the Li compound, presintering and calcining the obtained mixture under a mixed atmosphere composed of inert gas and oxygen, and cooling to obtain the lithium-rich manganese-based oxide positive electrode material;
(3) Pre-coating a pre-delithiation compound on the surface of a lithium-rich manganese-based oxide positive electrode material, performing heat treatment on the pre-coated lithium-rich manganese-based oxide positive electrode material in a mixed atmosphere consisting of inert gas and oxygen, washing, filtering and drying the powder after heat treatment to obtain the lithium-rich material with the pre-delithiation surface;
or dispersing the lithium-rich manganese-based oxide anode material in an aqueous solution with a pH value of 1-11, stirring for 0.1-100 h at 0-90 ℃, and filtering, washing and drying the obtained liquid phase mixture to obtain the lithium-rich material with the surface pre-delithiated;
(4) When the compound of Mg and the compound of Ti are each independently one or more of an oxide, a hydroxide, and a carbonate, (4 a) or (4 b) is used;
when the compound of Mg and the compound of Ti are each independently nitrate, (4 a) or (4 c) is used;
when the compound of Mg and the compound of Ti are respectively and independently one or more of sulfate and chloride, (4 c) is adopted;
(4a) Uniformly mixing a Mg compound, a Ti compound and a lithium-rich material with a surface pre-delithiated structure, and performing heat treatment on the obtained mixture in a mixed atmosphere consisting of inert gas and oxygen to obtain a lithium-rich manganese-based anode material with a surface gradient doping type composite structure;
(4b) Dispersing a Mg compound and a Ti compound in water, dispersing a lithium-rich material with a surface pre-delithiated in the water, evaporating the liquid phase mixture under stirring, and carrying out heat treatment on the material obtained after evaporation to obtain a lithium-rich manganese-based positive electrode material with a surface gradient doped composite structure;
(4c) Dissolving a Mg compound and a Ti compound in water, dispersing a lithium-rich material with a pre-delithiated surface in the water to obtain a liquid phase mixture, adding an excessive soluble alkali aqueous solution or soluble carbonate aqueous solution into the liquid phase mixture under stirring, filtering, washing and drying the obtained precipitate to obtain a dry material, and finally carrying out heat treatment on the dry material under a mixed atmosphere consisting of inert gas and oxygen to obtain the lithium-rich manganese-based anode material with the surface gradient doped composite structure.
4. The method for preparing a lithium-rich manganese-based positive electrode material with a surface gradient doped composite structure according to claim 3, wherein in the step (1),
the Li compound is one or more of lithium carbonate, lithium oxide, lithium hydroxide and lithium nitrate;
the Mg compound is one or more of Mg oxide, mg hydroxide, mg carbonate, mg nitrate, mg chloride and Mg sulfate;
the Ti compound is one or more of Ti oxide, ti hydroxide, ti carbonate, ti nitrate, ti chloride and Ti sulfate;
the Mn compound is one or more of Mn oxide, mn hydroxide, mn carbonate, mn nitrate, mn chloride and Mn sulfate;
the compound of Ni is one or more of oxide of Ni, hydroxide of Ni, carbonate of Ni, nitrate of Ni, chloride of Ni and sulfate of Ni.
5. The method for preparing a lithium-rich manganese-based positive electrode material with a surface gradient doped composite structure according to claim 3, wherein in the step (2),
uniformly mixing by a high-speed mixer, wherein the rotating speed of the high-speed mixer is 500-10000 r/min, and the mixing time is 1-72 h;
ball milling is carried out by adopting a ball mill, the rotating speed of the ball mill is 200-800 r/min, the ball milling time is 1-72 h, and the weight ratio of ball materials is 5-50: 1, a step of;
the soluble carbonate comprises ammonium carbonate, ammonium bicarbonate, sodium bicarbonate or sodium carbonate, and the soluble alkali comprises ammonia water or sodium hydroxide;
the presintering temperature is 200-700 ℃, and the calcining time is 0.5-10 h;
the calcination temperature is 500-1000 ℃ and the calcination time is 2-25 h.
6. The method for preparing a lithium-rich manganese-based positive electrode material with a surface gradient doped composite structure according to claim 3, wherein in the step (3), the pre-delithiated compound is one or more of ammonium sulfate, ammonium bisulfate, ammonium thiosulfate, ammonium persulfate, sodium thiosulfate, sodium persulfate, potassium thiosulfate, potassium persulfate and ammonium chloride, and the amount of the substance of the pre-delithiated compound is 0.1-30% of the amount of the substance of the lithium-rich manganese-based oxide positive electrode material.
7. The method for preparing a lithium-rich manganese-based positive electrode material with a surface gradient doped composite structure according to claim 3, wherein in the step (3),
the temperature of the heat treatment is 150-850 ℃, and the time of the heat treatment is 10 min-20 h;
the drying temperature is 80-300 ℃ and the drying time is 10 min-20 h;
the stirring rotating speed is 100-800 rmp/min.
8. The method for preparing the lithium-rich manganese-based positive electrode material with the surface gradient doped composite structure according to claim 3, wherein in the step (3), the method for pre-coating the surface of the lithium-rich manganese-based oxide positive electrode material with the pre-delithiated compound is as follows:
uniformly mixing the pre-delithiated compound with the lithium-rich manganese-based oxide positive electrode material to obtain a pre-coated lithium-rich manganese-based oxide positive electrode material;
or dissolving the pre-delithiated compound in water, dispersing the lithium-rich manganese-based oxide positive electrode material in the water to obtain a liquid phase mixture, and evaporating the liquid phase mixture under stirring to obtain the pre-coated lithium-rich manganese-based oxide positive electrode material.
9. The method for preparing a lithium-rich manganese-based positive electrode material with a surface gradient doped composite structure according to claim 3, wherein in the step (4),
uniformly mixing by a high-speed mixer, wherein the rotating speed of the high-speed mixer is 500-10000 r/min, and the mixing time is 1-72 h;
the soluble carbonate comprises ammonium carbonate or sodium carbonate, and the soluble alkali comprises ammonia water or sodium hydroxide;
the temperature of the heat treatment is 300-1000 ℃, and the time of the heat treatment is 2-25 h.
10. The method for preparing the lithium-rich manganese-based positive electrode material with the surface gradient doped composite structure according to claim 3, wherein in the steps (2) to (4), the molar ratio of the inert gas to the oxygen is 1 (0.001-100), and the inert gas is one or more of nitrogen and argon.
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