CN114956200A - Electrochemical performance regulation and control method of anode material - Google Patents
Electrochemical performance regulation and control method of anode material Download PDFInfo
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- CN114956200A CN114956200A CN202210327023.8A CN202210327023A CN114956200A CN 114956200 A CN114956200 A CN 114956200A CN 202210327023 A CN202210327023 A CN 202210327023A CN 114956200 A CN114956200 A CN 114956200A
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- 238000000034 method Methods 0.000 title claims abstract description 40
- 239000010405 anode material Substances 0.000 title claims abstract description 32
- 239000002243 precursor Substances 0.000 claims abstract description 64
- 239000010406 cathode material Substances 0.000 claims abstract description 16
- 238000002156 mixing Methods 0.000 claims abstract description 13
- 230000001276 controlling effect Effects 0.000 claims abstract description 11
- 230000001105 regulatory effect Effects 0.000 claims abstract description 9
- 239000011164 primary particle Substances 0.000 claims abstract description 8
- 229910003002 lithium salt Inorganic materials 0.000 claims abstract description 7
- 159000000002 lithium salts Chemical class 0.000 claims abstract description 7
- 238000005245 sintering Methods 0.000 claims abstract description 7
- 239000013078 crystal Substances 0.000 claims description 65
- 239000011572 manganese Substances 0.000 claims description 61
- PXHVJJICTQNCMI-UHFFFAOYSA-N nickel Substances [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 claims description 50
- 239000007774 positive electrode material Substances 0.000 claims description 18
- 238000003756 stirring Methods 0.000 claims description 17
- 239000011259 mixed solution Substances 0.000 claims description 13
- 150000002500 ions Chemical class 0.000 claims description 10
- 238000006243 chemical reaction Methods 0.000 claims description 9
- 229910052748 manganese Inorganic materials 0.000 claims description 8
- 230000035484 reaction time Effects 0.000 claims description 8
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 claims description 7
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 claims description 7
- 235000011114 ammonium hydroxide Nutrition 0.000 claims description 7
- 239000008139 complexing agent Substances 0.000 claims description 7
- 239000002064 nanoplatelet Substances 0.000 claims description 6
- 229910052759 nickel Inorganic materials 0.000 claims description 6
- 238000000975 co-precipitation Methods 0.000 claims description 5
- 239000012716 precipitator Substances 0.000 claims description 3
- 238000007086 side reaction Methods 0.000 abstract description 5
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 abstract description 4
- 239000011248 coating agent Substances 0.000 abstract description 4
- 238000000576 coating method Methods 0.000 abstract description 4
- 229910052744 lithium Inorganic materials 0.000 abstract description 4
- 238000007709 nanocrystallization Methods 0.000 abstract description 3
- 239000002135 nanosheet Substances 0.000 description 40
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 20
- 229910001416 lithium ion Inorganic materials 0.000 description 20
- 239000000463 material Substances 0.000 description 20
- 239000002245 particle Substances 0.000 description 19
- 238000012360 testing method Methods 0.000 description 16
- 229910013716 LiNi Inorganic materials 0.000 description 12
- WMFOQBRAJBCJND-UHFFFAOYSA-M Lithium hydroxide Chemical compound [Li+].[OH-] WMFOQBRAJBCJND-UHFFFAOYSA-M 0.000 description 11
- 238000009792 diffusion process Methods 0.000 description 10
- 238000004458 analytical method Methods 0.000 description 9
- 230000008569 process Effects 0.000 description 9
- 239000000243 solution Substances 0.000 description 8
- 238000001069 Raman spectroscopy Methods 0.000 description 6
- 238000009826 distribution Methods 0.000 description 6
- 239000003792 electrolyte Substances 0.000 description 6
- 239000012467 final product Substances 0.000 description 6
- 239000011163 secondary particle Substances 0.000 description 6
- 229910002099 LiNi0.5Mn1.5O4 Inorganic materials 0.000 description 5
- 230000008859 change Effects 0.000 description 5
- 230000001351 cycling effect Effects 0.000 description 5
- 238000010586 diagram Methods 0.000 description 5
- 230000000694 effects Effects 0.000 description 5
- 239000000203 mixture Substances 0.000 description 5
- 229910052596 spinel Inorganic materials 0.000 description 5
- 239000011029 spinel Substances 0.000 description 5
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 4
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 description 4
- 230000009286 beneficial effect Effects 0.000 description 4
- 230000015572 biosynthetic process Effects 0.000 description 4
- 150000001768 cations Chemical class 0.000 description 4
- 230000002349 favourable effect Effects 0.000 description 4
- 229910021645 metal ion Inorganic materials 0.000 description 4
- 238000007254 oxidation reaction Methods 0.000 description 4
- 238000001878 scanning electron micrograph Methods 0.000 description 4
- MUBZPKHOEPUJKR-UHFFFAOYSA-N Oxalic acid Chemical compound OC(=O)C(O)=O MUBZPKHOEPUJKR-UHFFFAOYSA-N 0.000 description 3
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 3
- 230000009471 action Effects 0.000 description 3
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- 238000009616 inductively coupled plasma Methods 0.000 description 3
- 230000001788 irregular Effects 0.000 description 3
- IPJKJLXEVHOKSE-UHFFFAOYSA-L manganese dihydroxide Chemical compound [OH-].[OH-].[Mn+2] IPJKJLXEVHOKSE-UHFFFAOYSA-L 0.000 description 3
- 125000004430 oxygen atom Chemical group O* 0.000 description 3
- 238000011056 performance test Methods 0.000 description 3
- 238000002360 preparation method Methods 0.000 description 3
- 239000000047 product Substances 0.000 description 3
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- 238000003786 synthesis reaction Methods 0.000 description 3
- NQTSTBMCCAVWOS-UHFFFAOYSA-N 1-dimethoxyphosphoryl-3-phenoxypropan-2-one Chemical compound COP(=O)(OC)CC(=O)COC1=CC=CC=C1 NQTSTBMCCAVWOS-UHFFFAOYSA-N 0.000 description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 2
- 238000002441 X-ray diffraction Methods 0.000 description 2
- 229910021529 ammonia Inorganic materials 0.000 description 2
- 125000004429 atom Chemical group 0.000 description 2
- 238000010835 comparative analysis Methods 0.000 description 2
- 238000004090 dissolution Methods 0.000 description 2
- 238000001035 drying Methods 0.000 description 2
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- 238000010894 electron beam technology Methods 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-M hydroxide Chemical compound [OH-] XLYOFNOQVPJJNP-UHFFFAOYSA-M 0.000 description 2
- 238000003780 insertion Methods 0.000 description 2
- 230000037431 insertion Effects 0.000 description 2
- 238000009830 intercalation Methods 0.000 description 2
- IIPYXGDZVMZOAP-UHFFFAOYSA-N lithium nitrate Chemical compound [Li+].[O-][N+]([O-])=O IIPYXGDZVMZOAP-UHFFFAOYSA-N 0.000 description 2
- AMWRITDGCCNYAT-UHFFFAOYSA-L manganese oxide Inorganic materials [Mn].O[Mn]=O.O[Mn]=O AMWRITDGCCNYAT-UHFFFAOYSA-L 0.000 description 2
- PPNAOCWZXJOHFK-UHFFFAOYSA-N manganese(2+);oxygen(2-) Chemical class [O-2].[Mn+2] PPNAOCWZXJOHFK-UHFFFAOYSA-N 0.000 description 2
- 229910000000 metal hydroxide Inorganic materials 0.000 description 2
- 150000004692 metal hydroxides Chemical class 0.000 description 2
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- 235000002639 sodium chloride Nutrition 0.000 description 2
- 239000011780 sodium chloride Substances 0.000 description 2
- 239000012798 spherical particle Substances 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 230000002194 synthesizing effect Effects 0.000 description 2
- 238000000101 transmission high energy electron diffraction Methods 0.000 description 2
- 229910002483 Cu Ka Inorganic materials 0.000 description 1
- KMTRUDSVKNLOMY-UHFFFAOYSA-N Ethylene carbonate Chemical compound O=C1OCCO1 KMTRUDSVKNLOMY-UHFFFAOYSA-N 0.000 description 1
- 229910015645 LiMn Inorganic materials 0.000 description 1
- 229910015643 LiMn 2 O 4 Inorganic materials 0.000 description 1
- 229910018584 Mn 2-x O 4 Inorganic materials 0.000 description 1
- 229910018663 Mn O Inorganic materials 0.000 description 1
- 229910003176 Mn-O Inorganic materials 0.000 description 1
- 241000080590 Niso Species 0.000 description 1
- 229910018553 Ni—O Inorganic materials 0.000 description 1
- 239000002033 PVDF binder Substances 0.000 description 1
- 238000003991 Rietveld refinement Methods 0.000 description 1
- XSQUKJJJFZCRTK-UHFFFAOYSA-N Urea Chemical compound NC(N)=O XSQUKJJJFZCRTK-UHFFFAOYSA-N 0.000 description 1
- 239000011149 active material Substances 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 150000003863 ammonium salts Chemical class 0.000 description 1
- 239000011230 binding agent Substances 0.000 description 1
- 230000000903 blocking effect Effects 0.000 description 1
- 239000004202 carbamide Substances 0.000 description 1
- 150000004649 carbonic acid derivatives Chemical class 0.000 description 1
- 238000012512 characterization method Methods 0.000 description 1
- 239000007795 chemical reaction product Substances 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 238000010668 complexation reaction Methods 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 239000006258 conductive agent Substances 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- RKTYLMNFRDHKIL-UHFFFAOYSA-N copper;5,10,15,20-tetraphenylporphyrin-22,24-diide Chemical compound [Cu+2].C1=CC(C(=C2C=CC([N-]2)=C(C=2C=CC=CC=2)C=2C=CC(N=2)=C(C=2C=CC=CC=2)C2=CC=C3[N-]2)C=2C=CC=CC=2)=NC1=C3C1=CC=CC=C1 RKTYLMNFRDHKIL-UHFFFAOYSA-N 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
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- 238000001514 detection method Methods 0.000 description 1
- 230000002542 deteriorative effect Effects 0.000 description 1
- YNQRWVCLAIUHHI-UHFFFAOYSA-L dilithium;oxalate Chemical compound [Li+].[Li+].[O-]C(=O)C([O-])=O YNQRWVCLAIUHHI-UHFFFAOYSA-L 0.000 description 1
- IEJIGPNLZYLLBP-UHFFFAOYSA-N dimethyl carbonate Chemical compound COC(=O)OC IEJIGPNLZYLLBP-UHFFFAOYSA-N 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 238000007323 disproportionation reaction Methods 0.000 description 1
- 230000005611 electricity Effects 0.000 description 1
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- 239000011261 inert gas Substances 0.000 description 1
- 230000037427 ion transport Effects 0.000 description 1
- XIXADJRWDQXREU-UHFFFAOYSA-M lithium acetate Chemical compound [Li+].CC([O-])=O XIXADJRWDQXREU-UHFFFAOYSA-M 0.000 description 1
- XGZVUEUWXADBQD-UHFFFAOYSA-L lithium carbonate Chemical compound [Li+].[Li+].[O-]C([O-])=O XGZVUEUWXADBQD-UHFFFAOYSA-L 0.000 description 1
- 229910052808 lithium carbonate Inorganic materials 0.000 description 1
- FUJCRWPEOMXPAD-UHFFFAOYSA-N lithium oxide Chemical compound [Li+].[Li+].[O-2] FUJCRWPEOMXPAD-UHFFFAOYSA-N 0.000 description 1
- 229910001947 lithium oxide Inorganic materials 0.000 description 1
- 229940071125 manganese acetate Drugs 0.000 description 1
- 229940099596 manganese sulfate Drugs 0.000 description 1
- 239000011702 manganese sulphate Substances 0.000 description 1
- 235000007079 manganese sulphate Nutrition 0.000 description 1
- UOGMEBQRZBEZQT-UHFFFAOYSA-L manganese(2+);diacetate Chemical compound [Mn+2].CC([O-])=O.CC([O-])=O UOGMEBQRZBEZQT-UHFFFAOYSA-L 0.000 description 1
- MIVBAHRSNUNMPP-UHFFFAOYSA-N manganese(2+);dinitrate Chemical compound [Mn+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O MIVBAHRSNUNMPP-UHFFFAOYSA-N 0.000 description 1
- SQQMAOCOWKFBNP-UHFFFAOYSA-L manganese(II) sulfate Chemical compound [Mn+2].[O-]S([O-])(=O)=O SQQMAOCOWKFBNP-UHFFFAOYSA-L 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 238000001000 micrograph Methods 0.000 description 1
- 230000005012 migration Effects 0.000 description 1
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- 238000012986 modification Methods 0.000 description 1
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- 230000000877 morphologic effect Effects 0.000 description 1
- 239000002086 nanomaterial Substances 0.000 description 1
- 239000002105 nanoparticle Substances 0.000 description 1
- LGQLOGILCSXPEA-UHFFFAOYSA-L nickel sulfate Chemical compound [Ni+2].[O-]S([O-])(=O)=O LGQLOGILCSXPEA-UHFFFAOYSA-L 0.000 description 1
- 229910000363 nickel(II) sulfate Inorganic materials 0.000 description 1
- AIYYMMQIMJOTBM-UHFFFAOYSA-L nickel(ii) acetate Chemical class [Ni+2].CC([O-])=O.CC([O-])=O AIYYMMQIMJOTBM-UHFFFAOYSA-L 0.000 description 1
- KBJMLQFLOWQJNF-UHFFFAOYSA-N nickel(ii) nitrate Chemical compound [Ni+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O KBJMLQFLOWQJNF-UHFFFAOYSA-N 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 239000003960 organic solvent Substances 0.000 description 1
- 235000006408 oxalic acid Nutrition 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 229920002981 polyvinylidene fluoride Polymers 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 230000027756 respiratory electron transport chain Effects 0.000 description 1
- 238000001338 self-assembly Methods 0.000 description 1
- 238000009751 slip forming Methods 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 230000008719 thickening Effects 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
- 230000032258 transport Effects 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Images
Classifications
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
- C01G53/00—Compounds of nickel
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
- C01G53/00—Compounds of nickel
- C01G53/40—Nickelates
- C01G53/42—Nickelates containing alkali metals, e.g. LiNiO2
- C01G53/44—Nickelates containing alkali metals, e.g. LiNiO2 containing manganese
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
- H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
- H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/20—Particle morphology extending in two dimensions, e.g. plate-like
- C01P2004/22—Particle morphology extending in two dimensions, e.g. plate-like with a polygonal circumferential shape
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
- H01M2004/028—Positive electrodes
-
- 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
Abstract
The invention belongs to the field of lithium battery anode materials, and particularly relates to an electrochemical performance regulation and control method of an anode material. The method comprises the following steps: obtaining a precursor of the cathode material, wherein the precursor is (Ni) 0.5 Mn 1.5 )(OH) 4 The primary particles of the precursor are of a sheet structure with a predetermined thickness; and carrying out first mixing on the precursor and lithium salt, and sintering to obtain the anode material with a specified morphology so as to realize regulation and control on the electrochemical performance of the anode material. The shape of the anode material is accurately regulated to be a specified shape by controlling the thickness of primary particles of the precursor, and the anode material has the specified shape, so that the anode material has corresponding electrochemical performance, the electrochemical performance of the anode material can be regulated, and coating, doping and nanocrystallization are avoidedAnd the like, loss of energy density or occurrence of side reactions.
Description
Technical Field
The invention belongs to the field of lithium battery anode materials, and particularly relates to an electrochemical performance regulation and control method of an anode material.
Background
Lithium ion batteries are one of the most competitive products in the field of energy storage and Electric Vehicles (EV) due to their high energy density. Spinel LiNi x Mn 2-x O 4 (0. ltoreq. x. ltoreq.1), especially LiNi 0.5 Mn 1.5 O 4 (LNMO) is considered the most competitive candidate for the next generation as a lithium ion battery electrode material, since it provides LiMn that is more competitive than manganese alone 2 O 4 Higher capacity and discharge voltage of spinel. However, the bulk positive electrode material still has some disadvantages, such as: 1) with LiMn 2 O 4 Compared with the material, the material has poorer rate capability due to smaller unit cell parameters; 2) due to disproportionation of Mn (2 Mn) 3+ →Mn 2+ +Mn 4+ ) The capacity fade during cycling is severe. The traditional electrochemical performance improving methods include coating, doping, nanocrystallization and the like. However, these methods bring new problems, such as the introduction of electrochemically inert materials that reduce the energy density and the high activity of nanomaterials that pose potential risks of side reactions.
Disclosure of Invention
The application provides an electrochemical performance regulation and control method of a positive electrode material, which aims to solve the problem that the conventional precursor can not accurately regulate and control LiNi with adjustable generation performance 0.5 Mn 1.5 O 4 The technical problem of the anode material.
The application provides a method for regulating and controlling the electrochemical performance of a cathode material, which comprises the following steps:
obtaining a precursor of the cathode material, wherein the precursor is (Ni) 0.5 Mn 1.5 )(OH) 4 Primary particles of the precursor are of a sheet structure with a preset thickness;
and carrying out first mixing on the precursor and lithium salt, and sintering to obtain the anode material with a specified morphology so as to realize regulation and control on the electrochemical performance of the anode material.
Optionally, the predetermined thickness includes a first thickness and a second thickness, the first thickness is 0 to 0.05 μm, and the second thickness is 0.1 to 2 μm.
Optionally, the specified morphology includes regular octahedra and hexagonal nanosheets.
Optionally, the hexagonal nanosheet includes an exposed (110) crystal plane and an exposed (100) crystal plane, and/or the regular octahedron is an exposed (111) crystal plane.
Optionally, the generation time of the hexagonal nanosheet is more than or equal to 12 h.
Optionally, the obtaining of the precursor of the cathode material specifically includes:
secondly, mixing the precipitator, ammonia water, a complexing agent, a nickel source and a manganese source to obtain a mixed solution;
and carrying out coprecipitation reaction on the mixed solution to obtain a precursor of the anode material.
Optionally, NH in said ammonia water 4 + The molar concentration of the ions is 0.75-1mol dm -3 。
Optionally, the pH of the mixed solution is 10-11.
Optionally, the stirring speed during the second mixing is 800-1200 rpm.
Optionally, in the mixed solution, the molar ratio of Mn to Ni is 2.5-3.5: 1.
Compared with the prior art, the technical scheme provided by the embodiment of the application has the following advantages:
according to the method provided by the embodiment of the application, the precursor of the cathode material is obtained, and the precursor is (Ni) 0.5 Mn 1.5 )(OH) 4 The primary particles of the precursor are hexagonal nanosheet structures with a predetermined thickness; carrying out first mixing on the precursor and lithium salt, and sintering to obtain the anode material with the specified morphology; by controlling the thickness of the primary particles of the precursor, the morphology of the anode material is accurately regulated to be in a specified shapeThe positive electrode material has a specified shape, so that the positive electrode material has corresponding electrochemical performance, the electrochemical performance of the positive electrode material can be adjusted, and energy density loss or side reaction caused by methods such as coating, doping and nanocrystallization is avoided.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and together with the description, serve to explain the principles of the invention.
In order to more clearly illustrate the embodiments or technical solutions in the prior art of the present invention, the drawings used in the description of the embodiments or prior art will be briefly described below, and it is obvious for those skilled in the art to obtain other drawings without inventive exercise.
FIG. 1 is a schematic diagram of analysis of precursors synthesized under different conditions as provided in the examples of the present application;
FIG. 2 is a LiNi film provided by an embodiment of the present application 0.5 Mn 1.5 O 4 A flow schematic diagram of an electrochemical performance regulation method of the anode material;
fig. 3 is a schematic diagram illustrating a synthesis analysis of cathode materials with different morphologies according to an embodiment of the present disclosure;
FIG. 4 is a micrograph of different crystal plane structures of the cathode material provided by the embodiment of the present application;
FIG. 5 is a graph of the electrical performance of the LNMO-HP and LNMO-OH samples provided in the examples herein;
FIG. 6 is an EIS plot and corresponding lithium ion diffusion factor plot of the LNMO-HP and LNMO-OH samples provided in the examples herein at different charge states;
FIG. 7 is a graph of cycle performance of samples prepared from precursors of different cathode materials provided in the examples of the present application;
fig. 8 is an EIS diagram and a crystal plane schematic diagram of samples prepared from precursors of different cathode materials before and after cycling, provided by an embodiment of the present application.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are some embodiments of the present application, but not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
Throughout the specification, unless otherwise specifically noted, terms used herein should be understood as having meanings as commonly used in the art. Accordingly, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. If there is a conflict, the present specification will control. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of the present invention. For example, the room temperature may be a temperature within a range of 10 to 35 ℃.
Unless otherwise specifically stated, various raw materials, reagents, instruments, equipment and the like used in the present invention are commercially available or can be prepared by existing methods.
In order to solve the technical problems, the general idea of the embodiment of the application is as follows:
according to an exemplary embodiment of the present invention, there is provided a method for regulating electrochemical properties of a positive electrode material, as shown in fig. 2, the method including the steps of:
s1, obtaining a precursor of the anode material, wherein the precursor is (Ni) 0.5 Mn 1.5 )(OH) 4 Primary particles of the precursor are of a sheet structure with a preset thickness;
s2, carrying out first mixing on the precursor and a lithium salt, and sintering to obtain the anode material with a specified morphology so as to realize regulation and control on the electrochemical performance of the anode material.
Specifically, the specified morphology of the anode material is different except that the exposed crystal face, and the components, the grain size, the cation order degree, the rock salt impurity phase content and the like are basically consistent, so that a foundation is laid for the subsequent electrochemical performance comparative analysis and a precondition is provided. Because parameters such as components, particle size, cation order degree, rock salt impurity phase content and the like can influence the electrochemical performance of the material, the relation between the crystal face and the electrochemical performance can be objectively reflected under the condition of single factor change of the crystal face.
Specifically, lithium salts include, but are not limited to, lithium acetate, lithium oxalate, lithium oxide, lithium hydroxide, lithium carbonate, lithium nitrate.
In some embodiments, the predetermined thickness comprises a first thickness and a second thickness, the first thickness being 0-0.05 μm and the second thickness being 0.1-2 μm.
In particular, the first thickness represents that the sheet structure is ultra-thin; the second thickness represents that the sheet-like structure is thicker; the ultrathin precursor sheet is random in nature, and reacts with lithium hydroxide at high temperature, so that the ultrathin sheet structure is damaged to form a final product with the shape of an octahedron; the thicker hexagonal nanosheet precursor reacts with lithium hydroxide at high temperature, and the original morphology can be maintained, namely the final product with the morphology of the hexagonal nanosheet is formed.
In some embodiments, the hexagonal nanoplatelets have a generation time ≧ 12 h.
In the embodiment of the application, when the precursor is prepared, the coprecipitation reaction is carried out for less than 2 hours to generate an extremely thin and irregular precursor sheet structure, when the ammonia water ion concentration, the pH value and the stirring rate are the same and are in proper conditions, the hexagonal nanosheet structure with the second thickness can be prepared by controlling the time of the coprecipitation reaction to be more than or equal to 12 hours, and therefore the anode material is the hexagonal nanosheet structure with the exposed (100) crystal face and the exposed (110) crystal face.
In some embodiments, the defined morphology comprises regular octahedra and hexagonal nanoplatelets, and/or the regular octahedra are bare (111) facets.
Specifically, the regular octahedron is a naked (111) crystal face, and the cycle performance of the regular octahedron is better after testing.
In some embodiments, the hexagonal nanoplatelets comprise exposed (110) crystal planes and exposed (100) crystal planes.
Through electrochemical performance comparison research, the following results are found: (100) compared with the (111) crystal face, the (110) crystal face is more beneficial to lithium ion de-intercalation, the lithium ion diffusion coefficient is high, and the good rate performance is shown, namely the large-current charge and discharge performance of the hexagonal nanosheet is better, and the cycle performance of the regular octahedral material is better; (110) the crystal face is easy to be corroded compared with the (100) crystal face; (110) Mn/Ni ions of a crystal face are low in density and lack of protection of oxygen atoms, and are easy to corrode by hydrofluoric acid in electrolyte, so that side reaction occurs, impedance is rapidly increased, and cycle performance is deteriorated.
Therefore, hexagonal nanosheets with excellent rate performance and regular octahedral LiNi with excellent cycle performance can be obtained by regulating and controlling the reaction time of the precursor 0.5 Mn 1.5 O 4 . Furthermore, according to different application scenes, the final product LiNi can be realized by regulating and controlling the reaction time of the precursor 0.5 Mn 1.5 O 4 The proportion of the shapes of the medium-hexagonal nanosheets and the regular octahedrons finally achieves the purpose of comprehensively regulating and controlling the rate capability and the cycle performance of the final product.
In some embodiments, the obtaining of the precursor of the cathode material specifically includes:
secondly, mixing the precipitator, ammonia water, a complexing agent, a nickel source and a manganese source to obtain a mixed solution;
and carrying out coprecipitation reaction on the mixed solution to obtain a precursor of the anode material.
Specifically, precipitants include, but are not limited to, carbonates, hydroxides, oxalic acid; nickel sources include, but are not limited to, nickel sulfate, nickel nitrate, nickel acetate compounds; manganese sources include, but are not limited to, manganese sulfate, manganese nitrate, manganese acetate; sources of ammonia include, but are not limited to, ammonia, ammonium salts, and urea.
In some embodiments, the ammonia water is NH 4 + The molar concentration of the ions is 0.75-1mol dm -3 。
Controlling NH 4 + The molar concentration of the ions is 0.75-1mol dm -3 The reason for this is that: NH (NH) 4 + The molar concentration of the ion is out of the rangeUnfavorable to manganese hydroxide generation and NH can not be enabled 4 OH is favorable for synthesizing (Ni) with narrow particle size distribution and higher sphericity 0.5 Mn 1.5 )(OH) 4 The precursor is further favorable for obtaining powder materials with higher tap density.
In some embodiments, the pH of the mixed solution is 10 to 11.
The reason why the pH value of the mixed solution is controlled to 10 to 11 is that: when the pH is more than 11, the hydroxide of manganese is not easy to form or other manganese oxides are easy to form, and the utilization rate of raw materials is low.
In some embodiments, the second mixing is performed at a stirring rate of 800-.
The reason for controlling the stirring rate at 800-1200rpm is that: with the increase of the stirring speed, the particle size distribution of the sample is narrower, and at a lower stirring speed, the particles are composed of a plurality of small nano-sheets and are looser; along with the increase of the stirring speed, the particles gradually grow from the crystal nucleus to the outside to form a more compact spherical shape; increasing the stirring rate allows the precursor to grow into particles of uniform size and dense structure.
In some embodiments, the molar ratio of Mn to Ni in the mixed solution is 2.5 to 3.5: 1.
Preferably, the molar ratio of Mn to Ni is 3:1, the molar ratio of Mn to Ni is controlled to be 2.5-3.5:1, manganese sources and nickel sources can be saved, the material utilization rate is improved, and the generated LiNi can be generated 0.5 Mn 1.5 O 4 The structure of the cathode material is more stable.
According to the method, the nano thin sheet and the thicker hexagonal nano sheet are used as basic raw materials, and the positive electrode material with the regular octahedron shape and the hexagonal nano sheet shape is successfully prepared. The two samples are proved to have Fd-3m space group structures by means of characterization methods such as Raman, XRD and the like. SEM and TEM tests show that the diameter of the nano-sheet is about 1 μm, the exposed crystal face of the regular octahedron is (111), and the main exposed crystal faces of the hexagonal nano-sheet are (110) and (100). The first discharge curves of the two samples further illustrate that both samples belong to the Fd-3m space group structure and the degree of disorder is very close.
By grindingThe rate capability shows that the 40C/1C of the hexagonal nano-sheets with the (110) and (100) crystal faces can reach 71.4 percent, and the specific capacity of the regular octahedron with the exposed (111) crystal face is less than 20mAhg at 40C rate -1 However, the normal temperature and high temperature performance of the regular octahedron with the exposed (111) crystal face is much better than that of the hexagonal nanosheets with the (110) and (100) crystal faces. Through EIS and crystal structure analysis, compared with a (111) crystal face, the (100) crystal face and the (110) crystal face are more beneficial to lithium ion de-intercalation, the diffusion coefficient of lithium ions is high, and the good rate performance is shown, but the Mn/Ni ion density of the (110) crystal face is low, the protection of oxygen atoms is lacked, the corrosion of hydrofluoric acid in electrolyte is easier, the impedance is increased, and the cycle performance is deteriorated.
The process of the present invention will be described in detail below with reference to examples, comparative examples and experimental data.
Example 1
Preparing a precursor: NiSO is added according to the stoichiometric ratio of Ni to Mn being 1 to 3 4 And MnSO 4 Dissolving in water to obtain 2.0mol/L metal ion solution, and preparing 2.0mol/L NaOH solution and NH solution with certain concentration 4 And (3) simultaneously injecting the three solutions into a reaction kettle with the constant temperature of 60 ℃, protecting by using high-purity nitrogen, and controlling the dropping speed of each solution. Because the pH value, the concentration of the complexing agent and the stirring speed greatly influence the morphology of the precipitated product, different condition parameters are designed according to the table 1 to investigate the influence rule of the pH value, the concentration of the complexing agent and the stirring speed on the morphology, after the reaction is finished, the mixture is continuously stirred and aged for 24 hours, filtered and washed, and dried at the temperature of 80 ℃ to obtain (Ni) with different morphologies 0.5 Mn 1.5 )(OH) 4 And (3) precursor. Mixing a precursor with a specified morphology with a lithium salt (specifically LiOH) with a certain stoichiometric ratio, transferring the mixture into a muffle furnace, reacting for 12 hours at 900 ℃, and naturally cooling to obtain F-type LiNi with different exposed crystal faces 0.5 Mn 1.5 O 4 And (3) a positive electrode material.
TABLE 1 (Ni) 0.5 Mn 1.5 )(OH) 4 Preparation parameters of the precursor.
The prepared F-type LiNi with different exposed crystal faces 0.5 Mn 1.5 O 4 The positive electrode material mainly has 3 types after analysis, and LiNi can be prepared by selecting precursors distributed in HP1-2h and HP5 as templates 0.5 Mn 1.5 O 4 3 types of the positive electrode material were analyzed in detail.
Example 2
In the embodiment of the application, the X-ray diffraction pattern is a Bruker D8 type diffractometer, and the X-ray source is Cu-Ka
Scanning angle range: 10 to 80 degrees and the step length is 0.02 degrees s -1 (ii) a The electron scanning electron microscope and the transmission electron microscope are respectively completed by adopting Philip-XL30 and TecnaiG 2F 30; the Raman spectrometer is LabRAMHR800 type, and is excited by He-Ne to have 632.8nm wavelength for testing.
And (3) researching the influence rule of the change of the parameters in the table 1 on the morphology of the precursor material. The phase structures of all samples are firstly characterized by XRD, as shown in figure 1a, X-ray spectrograms of the precursors of the cathode materials prepared under different conditions and Mn (OH) 2 Compared with the standard card number (JCPDS- #12-0696), which shows a typical layered structure, the diffraction peaks at 2 θ ═ 19 ° are each slightly shifted toward a high angle, and the diffraction peaks at 2 θ ═ 38 ° are broadened because: as a result of the partial oxidation that occurs during drying. However, there was no significant difference in diffraction peaks for all samples, indicating that these conditions had no significant effect on the crystal structure of the precursor. After the morphology of the precursor prepared under different synthesis conditions is observed by using an electronic scanning electron microscope, the influence of the synthesis conditions on the morphology is found to be very large. As shown in fig. 1(b-c), when the reaction time is 2 hours, the morphology of the sample HP1-2h is an ultrathin nanosheet structure with an irregular morphology except a very small amount of hexagonal nanosheets, the ultrathin nanosheet structure gradually disappears with the extension of the reaction time (fig. 1c), the sample HP1 is completely a hexagonal nanosheet morphology, and the hexagonal nanosheets are self-assembled into a secondary spherical particle with a diameter of about 3-5 μm. In the preparation of the end product LiNi 0.5 Mn 1.5 O 4 When the positive electrode material is used, the studyThe influence of the chemical composition of the precursor on the anode material, and the Mn and Ni of the precursor are determined by performing ICP (inductively coupled plasma) test on the precursor synthesized under different preparation conditions. As shown in FIG. 1i, the Mn to Ni ratios of the samples are similar at different reaction times, indicating that the reaction time only affects the morphology of the hydroxide and not its chemical composition. Fig. 1(c-e) illustrates the change of the precursor morphology with pH, and at the same reaction time, when the pH is increased from 10 to 10.5, compared with the morphology of the sample HP1 (fig. 1c), the sample HP2 (fig. 1d) has a significantly deteriorated sphericity and a non-uniform thickness of the primary nanosheets, although the morphology of the primary nanosheets is also shown to be assembled into a secondary particle shape, and a small amount of flake morphology appears, when the pH is 11 (fig. 1e), the secondary spheroidal particles are hardly seen, and the crystal morphology is shown to be randomly distributed in nanosheets, and from the morphology analysis of HP1, HP2, and HP3, the larger the pH is, the spherical self-assembly effect of the secondary particles is worse, and the nanosheets are thinner. In addition, from their Mn to Ni ratios (FIG. 1i), the Mn to Ni of the samples are increasingly far from the theoretical value of 3.0 as the pH is increased, indicating that at high pH, manganese hydroxides do not readily form or other manganese oxides readily form. In the precipitation of the double metal hydroxide, if no complexing agent is added, Ni (OH) 2 And Mn (OH) 2 The compound precipitated out separately. The primary function of the complexing agent is to precipitate it as a homogeneous, single-phase metal hydroxide rather than separately as a separate phase. The pH was fixed at 10 and different NH were studied 4 Effect of OH concentration on particle size and morphology of the product. As is apparent from FIG. 1(f-h), NH 4 + Concentration vs. precursor (Ni) 0.5 Mn 1.5 )(OH) 4 The morphology, size and distribution of the particles have a great influence. NH (NH) 4 + At a concentration of 0.50mol -3 When this is the case, sample HP4 is a spherical-like secondary particle loosely packed from a large number of primary particles (nanosheets), but its particle size is very non-uniform. When the concentration increased to 0.75mol dm -3 In the process, irregular primary nano particles do not exist, and hexagonal nano sheets with uniform shapes are loosely self-assembled into uniform secondary spherical particles. The hexagonal nanosheet can be used as a morphology template to prepare a final product with the same morphology.Therefore, when the cathode material is prepared subsequently, the sample is used as a precursor to obtain the cathode material of the hexagonal nanosheet. Then, when NH 4 + To a concentration of 1.0mol dm -3 And the balling tendency is more obvious. Moreover, most of the secondary particles are composed of thick plate-like crystals crosslinked with each other, the secondary particle size is also increased to about 10 μm, and the particle size distribution is also made narrower. Similarly, from the Mn to Ni results in FIG. 1i, the ratios are all very close to the theoretical value of 3.0, with NH 4 + The ratio of (A) to (B) is slightly decreased, indicating high NH 4 + The formation of manganese hydroxide is also not favored at concentrations. NH 4 The complexation of OH is favorable for synthesizing (Ni) with narrow particle size distribution and higher sphericity 0.5 Mn 1.5 )(OH) 4 The precursor is favorable for obtaining powder material with higher tap density. Stirring speed ratio pair (Ni) 0.5 Mn 1.5 )(OH) 4 The morphology of the precursor also has a large influence, as shown in fig. 1(i-k), the particle size distribution of the sample is narrower with the increase of the stirring speed, and at the lower stirring speed, the particle is composed of many small nanosheets and is looser. With the increase of the stirring speed, the particles gradually grow from the crystal nucleus to the outside to form a more compact spherical shape. Increasing the stirring rate allows the precursor to grow into particles of uniform size and dense structure. The ICP test results (FIG. 1i) show that the stirring speed has no significant effect on the Mn: Ni values. The research shows that the secondary particles become spherical and have no direct influence on the crystal face of the anode material.
In fig. 1, fig. 1a is an XRD pattern of a precursor synthesized under different conditions; FIGS. 1b-1k are SEM images; FIG. 1l is a schematic view showing the control of the Mn/Ni molar ratio, wherein the bar line in FIG. 1a is Mn (OH) 2 Standard diffraction peaks of (JCPDS- #12-0696). SEM images (1b-1k) represent the following fractions, respectively: fig. 1b represents HP1-2h, fig. 1c represents HP1, fig. 1d represents HP2, fig. 1e represents HP3, fig. 1f represents HP4, fig. 1g represents HP5, fig. 1h represents HP6, fig. 1i represents HP7, fig. 1j represents HP8, and fig. 1k represents HP9, the dashed line in fig. 1l is the standard ratio of Mn: Ni ═ 3.0.
Example 3
Preparing a positive electrode material:
as shown in FIG. 3a, LiNi was prepared using HP1-2h and HP5 as templates 0.5 Mn 1.5 O 4 The anode material is called as LNMO for short and respectively named as: LNMO-OH and LNMO-HP. The classification into Fd-3m and P4 depending on the degree of order of Ni atoms in their crystal lattices 3 32 two space group structure materials. In order to determine the type of crystal structure of the synthesized cathode material, a raman spectroscopy test was performed, with the abscissa of fig. 3b being a raman shift and the ordinate being an intensity, and the abscissas of fig. 3c and 3d being an angle and the ordinate being an intensity. As shown in FIG. 3b, both LNMO-OH and LNMO-HP have similar Raman peaks at 636cm -1 (A 1g) The strong peak at (E) is attributed to Mn-O stretching vibration at 405 (E) 1g) And
the weak peak at (A) was attributed to Ni-O stretching vibration, and no P4 was observed 3 Fingerprint peak of 32 crystalline phases (585- -1 The interval is split into a plurality of peaks and 220cm -1 With additional peaks) indicating that LNMO-OH and LNMO-HP belong primarily to the Fd-3m crystalline phase structure. XRD tests of LNMO-OH and LNMO-HP showed that from FIG. 3(c-d), the major diffraction peaks of both LNMO-OH and LNMO-HP samples were highly matched with the cubic spinel phase (Fd-3m, JCPDS #80-2162), except for two weak diffraction peaks at 37.5 and 43.8 degrees 2 theta, which are part of the impure phase Li 1-x Ni x O or NiO x This phenomenon is also frequently observed in other studies. Rietveld refinement was performed on the XRD diffraction pattern of the sample in order to understand the crystal phase structure and the content of impure phase, and the related refinement results are shown in Table 2, R of LNMO-OH wp And R p R of 3.78 and 3.29, LNMO-HP, respectively wp And R p 3.78 and 3.27, respectively, indicating that the refinement result is consistent with the XRD test pattern. Furthermore, calculated lattice parameter of LNMO-HP
And percent impure phase (2.9%) compared to LNMO-OH sample: (
And 1.6%) which is slightly higher, as shown in table 2, it is probably due to the reason that Mn: Ni ═ 2.975 in the LNMO-HP precursor is slightly higher than that in the LNMO-OH precursor (Mn: Ni ═ 2.968), and overall, the difference in crystal structure is very small, and the influence on the subsequent electrochemical performance is not great, and the correlation between the comparative analysis morphology and the electrochemical performance is not influenced.
TABLE 2 LiNi with different crystal face structures 0.5 Mn 1.5 O 4 And (3) a positive electrode material.
And carrying out morphology and crystal face structure analysis on the samples LNMO-OH and LNMO-HP. In FIG. 4, 4a-4b are Scanning Electron Microscope (SEM) images, 4c-4d are Transmission Electron Microscope (TEM) images, and 4e-4f are High Resolution Transmission Electron Microscope (HRTEM) images; as is evident from the SEM images (FIGS. 4a-b), LNMO-OH exhibits a typical regular octahedral shape with a diameter of about 1-2 μm, while LNMO-HP exhibits a hexagonal nanosheet shape with a diameter of about 1-2 μm and a thickness of 100 nm-2 μm. Compared with a thicker regular nanosheet precursor, the ultrathin nanosheet precursor is less prone to maintaining the morphology in the subsequent sintering process, and the morphology of the ultrathin nanosheet precursor is more prone to being damaged and generating an octahedral final product due to huge surface energy in the high-temperature sintering process. The morphology of LNMO-OH and LNMO-HP was further confirmed using TEM and HRTEM tests. As shown in FIGS. 4(c-d), LNMO-OH and LNMO-HP show well-angled octahedral and hexagonal nanosheet morphologies, respectively, consistent with the results of SEM image analysis. Furthermore, it can be seen from the HRTEM image, FIG. 4(e-f), that when the electron beam is irradiated to the edge of the LNMO-OH octahedral surface, a clear lattice fringe can be obtained, and the lattice spacing value is
With the {111} interplanar spacing observed in XRD diffraction spectrumThe values match. And for the LNMO-HP sample, when an electron beam irradiates from the front side direction of the LNMO-HP hexagonal nanometer sheet, the lattice spacing value is
Matching the {220} interplanar spacing values.
Analysis by the electron diffraction method (SAED) was performed separately and found that both samples did not have superlattice diffraction spots around the bright diffraction spots, indicating that both belong to Fd-3m space group crystalline phase structure, which is consistent with the XRD and Raman test results in FIG. 3. In summary, combining SEM, TEM, HRTEM and SAED analysis, one can conclude that: LNMO-OH exposes the {111} crystal plane, while LNMO-HP exposes the {110} and {100} crystal planes.
Performance detection
The electrical properties were measured as follows: mixing LiNi as active material 0.5 Mn 1.5 O 4 The positive electrode material, the binder PVDF and the conductive agent AB are mixed according to the weight ratio of 8:1:1, then a proper amount of NMP solvent is added, and the mixture is fully and uniformly stirred to prepare uniform and viscous slurry. And then uniformly coating the slurry on an aluminum foil, and drying to obtain the electrode plate for later use. Cutting the pole piece to be used into a wafer, moving the wafer into a glove box protected by inert gas, and placing the wafer in the glove box O 2 And H 2 O is controlled to be less than 1ppm, a metal lithium sheet is used as a negative electrode, and the electrolyte is 1MLiPF 6 Dissolving in ethylene carbonate by volume ratio: in a mixed organic solvent with dimethyl carbonate of 3:7, a diaphragm adopts Celgard2320, and a battery is assembled by taking the electrode as a positive electrode. The electrochemical performance test is carried out on a Wuhan blue electricity CT2001A battery tester, and the test voltage range is 4.9-3.5V. When the multiplying power test is carried out, the charging current is stabilized at 1C (147 mAg) -1 ) The magnitude of the discharge current was varied from 1C to 40C. The charging and discharging current of the normal temperature cycle performance test is 1C. The EIS test adopts PGSTAT302N type instrument, the amplitude is 0.02V, and the frequency interval is 50 mHz-10 5 Hz。
FIG. 5a is the first discharge curve between 5.0V and 1.9V for NMO-HP and LNMO-OH samples. From the figure, 5 distinct discharge plateaus can be seen, 2 discharge plateaus at about 4.7V respectively represent lithium ion intercalationNi induced by the position of 8a of cubic spinel phase 4+ →Ni 3+ And Ni 3+ →Ni 2+ Reduction of the couple, and a 4.0V discharge plateau represents insertion of lithium ions into the cubic spinel phase 8a sites causing Mn 4+ →Mn 3+ The reduced couple can be seen in the figure, the shapes of the discharge curves of LNMO-HP and LNMO-OH are similar, which indicates that the valence states of metal ions in two morphological samples are similar; in FIG. 5a, the discharge capacity is plotted on the abscissa and the voltage is plotted on the ordinate, and it can be seen from FIG. 5a that the discharge capacity ratio of the LNMO-HP and LNMO-OH samples on the two voltage plateaus is 63.4 and 67.1%, respectively, which indicates that the cation order degrees of the two samples are very close and both are crystal phases mainly based on Fd-3m space group. In addition, comparing the discharge curves of 3.0V or less, about 2.7V and 2.1V are Mn caused by insertion of lithium ions into 16c octahedral sites 4+ →Mn 3+ Reduction and cubic phase to tetragonal phase conversion are carried out, and the capacity ratio of the two discharge platforms is another effective method for measuring the cation order degree, so that the test results of XRD, Raman, SEM, TEM and first discharge curves are combined to prove that the crystal phase structure, the impurity phase content and the particle size of LNMO-HP and LNMO-OH samples are very close, and only the micro-morphology is different, namely: LNMO-HP is a hexagonal nanosheet morphology with bare (110) and (001) crystal faces, and LNMO-O is an octahedral morphology with only bare (111) crystal faces. Rate capability is very important for battery materials. All cells were re-discharged 5 times at 0.2C and then tested for rate performance by fixing the charge current at 1C and then cycling 5 times at 1C, 5C, 10C, 15C, 20C, 25C, 30C, 35C, 40C rates, respectively. As shown in FIG. 5b, the specific discharge capacities of the LNMO-HP and LNMO-OH samples were very close to each other, about 140mAhg, when discharged at 1C -1 Along with the increase of the discharge rate, the specific discharge capacity difference of the two samples is gradually increased, and the specific discharge capacity of the LNMO-HP can be maintained at 100mAhg under 40C discharge current -1 About 71.4% of 1C, while LNMO-OH is less than 20mAhg -1 Specific discharge capacity of (2). In addition, it can be seen from their corresponding discharge graphs that, as shown in fig. 5(C-d), when the two are discharged at 1C rate, there is no obvious difference in discharge plateau, but as the discharge rate increases, both LNMO-HP can be increasedWhile maintaining a high discharge voltage plateau, e.g., 40C, the average discharge voltage plateau is about 4.0V, and correspondingly, the average voltage plateau of LNMO-OH discharged at 40C rate is less than 3.5V, so rate performance tests show that: compared with an LNMO-OH material only exposing a (111) crystal face, LNMO-HP exposing a (110) crystal face and an (001) crystal face has better rate performance, and the (110) crystal face has a diffusion channel which is more beneficial to lithium ion deintercalation.
The reason for the difference in the rate performance between LNMO-OH and LNMO-HP is that EIS tests were performed on batteries in different states of charge, as shown in fig. 6(a-b), with the abscissa Z' and the ordinate Z ″, which represent the impedance of the positive electrode material, except that the impedance curve immediately after charging appears as a semicircle, and the other curves consist of two semicircles and a diagonal line. The first semicircle in the high frequency region is the resistance (R) of lithium ion diffusion transport through the SEI film SEI ) The second half of the middle frequency region is the charge transfer resistance (R) representing the electrode interface reaction ct ) The low frequency region slope is associated with lithium ion transport within the electrode material. As can be seen from FIGS. 6(a-b), as charging proceeds, R SEI And R ct The overall impedance of the LNMO-HP is lower than that of the LNMO-OH. Further, the corresponding lithium ion diffusion coefficient is calculated from the formula (Eqn (1) andEqn (2)). As shown in fig. 6(c-d), the ordinate of the graph is voltage, and the diffusion coefficients of lithium ions of LNMO-OH and LNMO-HP change with the migration amount of lithium ions, which can be clearly divided into three parts: about 0.1 or less of lithium transference corresponds to Mn 3+ →Mn 4+ Oxidation reaction, 0.1-0.45 interval corresponding to Ni 2+ →Ni 3+ Oxidation reaction, 0.45 or more corresponds to Ni 3+ →Ni 4+ And (4) oxidation reaction. However, the diffusion coefficient values of lithium ions of the two materials are greatly different, and the LNMO-HP material is 10 -11 -10 -9 cm 2 s -1 While the LNMO-OH material is at 1 x 10 -11 -4×10 -10 cm 2 s -1 Meanwhile, the crystal face is obviously lower, which indicates that the (110) crystal face has a diffusion channel more beneficial to lithium ion deintercalation, and further can obtain better rate performance.
FIG. 6 EIS plots (a-b) of LNMO-HP and LNMO-OH samples at different charge states and correspondingLithium ion diffusion factor (c-d), with inset partial magnification. FIG. 7 is a graph of the 1C cycle performance of LNMO-OH and LNMO-HP at ambient and elevated temperatures. As shown in FIG. 7a, the specific capacity of LNMO-OH was from 140.5mAh g after 500 cycles at 25 deg.C -1 Reduced to 91.9mAhg -1 The average capacity attenuation rate per time is 0.069%, while the specific capacity of LNMO-HP attenuates very fast, and after 500 cycles, the specific capacity is only less than 30mAhg -1 . As shown in fig. 7(b-c), as the discharge curve is cycled, the discharge curve of LNMO-OH can basically keep the original shape, the discharge plateau is only slightly decreased, while the change of the discharge curve shape of LNMO-HP is large, especially when 400 cycles are cycled, the discharge plateau is represented as a slope, 3 distinct characteristic discharge plateaus during the first discharge are hardly seen, and the discharge voltage is decreased rapidly, which indicates that the impedance is increased significantly; the specific capacity decay of LNMO-OH was also significantly faster than LNMO-HP after 100 cycles at 55 deg.C (FIG. 7 d); as shown in FIG. 7(e-f), the discharge voltage plateau of LNMO-HP drops much faster than LNMO-OH as the high temperature cycle progresses. In the long cycle process, compared with the anode material only exposing the (111) crystal face, the hexagonal nanosheets exposing the (110) crystal face and the (100) crystal face are more susceptible to the influence of interface impedance, so that the cycle performance is poor.
The LNMO-OH and LNMO-HP materials with Fd-3m space groups were subjected to EIS testing before and after cycling at ambient and elevated temperatures. As shown in FIGS. 8(a-b), the abscissa is Z 'and the ordinate is Z', which represent the impedance of the positive electrode material, R of LNMO-OH and LNMO-HP before cycling SEI And R ct The values are very close, being around about 80 Ω and about 100 Ω, respectively. Delta R of LNMO-OH after 500 cycles at room temperature SEI And Δ R ct The values are increased by about 120 omega and about 190 omega, respectively, while the Δ R of LNMO-HP SEI And Δ R ct The values increase more significantly to around 280 Ω and 370 Ω, respectively. Likewise, the Δ R of LNMO-OH and LNMO-HP after 100 cycles at elevated temperature SEI And Δ R ct The variation trend is similar to that of the normal temperature cycle. The results show that: compared with the LNMO-OH material only exposing the (111) crystal face, the hexagonal nano-sheet LN with the (110) and (100) crystal faces can be exposed regardless of normal temperature or high temperature cycleMO-HP materials are more susceptible to series resistance caused by thickening of SEI films, and further the cycle performance of the MO-HP materials is deteriorated. FIG. 8c is a structural drawing of the (111), (110) and (100) crystallographic planes of Fd-3m space group LNMO, from which it can be seen that the (100) and (110) crystallographic planes have a higher lithium ion density than the (111) crystallographic planes, and exposure of these crystallographic planes facilitates lithium ion deintercalation, consistent with the results of FIG. 6, demonstrating that the rate capability of the LNMO-HP material is superior to that of LNMO-OH. However, the (100) crystal face cannot form a stable SEI film in the first cycle process, and surface atoms are more easily corroded by electrolyte; in addition, the Mn/Ni ions of the (110) crystal face have low density and lack the protection of oxygen atoms, so that the Mn/Ni ions are more sensitive to electrolyte and are easy to generate side reaction to dissolve metal ions, under long circulation, the dissolution of the metal ions causes a new SEI film to be continuously formed on a new interface, the electrolyte is consumed, the dissolution also causes the blocking of electron transfer channels among particles and between the particles and a current collector, and delta R before and after circulation can be caused SEI And Δ R ct The impedance increases rapidly, deteriorating the cycle performance.
It is noted that, in this document, relational terms such as "first" and "second," and the like, may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.
The foregoing are merely exemplary embodiments of the present invention, which enable those skilled in the art to understand or practice the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (10)
1. A method for regulating and controlling the electrochemical performance of a positive electrode material is characterized by comprising the following steps:
obtaining a precursor of the cathode material, wherein the precursor is (Ni) 0.5 Mn 1.5 )(OH) 4 Primary particles of the precursor are of a sheet structure with a preset thickness;
and carrying out first mixing on the precursor and lithium salt, and sintering to obtain the anode material with a specified morphology so as to realize regulation and control on the electrochemical performance of the anode material.
2. The method of claim 1, wherein the predetermined thickness comprises a first thickness and a second thickness, the first thickness being 0-0.05 μ ι η and the second thickness being 0.1-2 μ ι η.
3. The method of claim 1, wherein the specified morphologies comprise regular octahedra and hexagonal nanoplatelets.
4. The method of claim 1, wherein said hexagonal nanoplatelets comprise exposed (110) crystal planes and exposed (100) crystal planes; and/or the regular octahedron is a naked (111) crystal face.
5. The method of claim 4, wherein the reaction time of the hexagonal nanoplatelets is greater than or equal to 12 hours.
6. The method according to claim 1, wherein the obtaining of the precursor of the positive electrode material specifically comprises:
secondly, mixing the precipitator, ammonia water, a complexing agent, a nickel source and a manganese source to obtain a mixed solution;
and carrying out coprecipitation reaction on the mixed solution to obtain a precursor of the anode material.
7. The method of claim 5, wherein the ammonia water is NH 4 + The molar concentration of the ions is 0.75-1mol dm -3 。
8. The method according to claim 5, wherein the pH of the mixed solution is 10 to 11.
9. The method as claimed in claim 5, wherein the stirring rate during the second mixing is 800-1200 rpm.
10. The method according to claim 5, wherein the molar ratio of Mn to Ni in the mixed solution is 2.5-3.5: 1.
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