CN116864662A - Lithium-rich positive electrode material and preparation method and application thereof - Google Patents
Lithium-rich positive electrode material and preparation method and application thereof Download PDFInfo
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- CN116864662A CN116864662A CN202310905104.6A CN202310905104A CN116864662A CN 116864662 A CN116864662 A CN 116864662A CN 202310905104 A CN202310905104 A CN 202310905104A CN 116864662 A CN116864662 A CN 116864662A
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- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 title claims abstract description 338
- 229910052744 lithium Inorganic materials 0.000 title claims abstract description 338
- 239000007774 positive electrode material Substances 0.000 title claims abstract description 145
- 238000002360 preparation method Methods 0.000 title claims abstract description 34
- 150000004706 metal oxides Chemical class 0.000 claims abstract description 72
- 229910044991 metal oxide Inorganic materials 0.000 claims abstract description 71
- 229910052751 metal Inorganic materials 0.000 claims abstract description 69
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims abstract description 55
- 229910052760 oxygen Inorganic materials 0.000 claims abstract description 55
- 239000001301 oxygen Substances 0.000 claims abstract description 55
- 229910052752 metalloid Inorganic materials 0.000 claims abstract description 54
- 239000002184 metal Substances 0.000 claims description 60
- 239000010406 cathode material Substances 0.000 claims description 47
- 239000000872 buffer Substances 0.000 claims description 45
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 claims description 43
- 238000005245 sintering Methods 0.000 claims description 43
- 229910001416 lithium ion Inorganic materials 0.000 claims description 42
- 238000000034 method Methods 0.000 claims description 34
- 239000010416 ion conductor Substances 0.000 claims description 27
- 239000002245 particle Substances 0.000 claims description 22
- 239000011164 primary particle Substances 0.000 claims description 22
- 239000011163 secondary particle Substances 0.000 claims description 17
- 239000011258 core-shell material Substances 0.000 claims description 16
- 239000010405 anode material Substances 0.000 claims description 14
- 238000011065 in-situ storage Methods 0.000 claims description 14
- 229910052796 boron Inorganic materials 0.000 claims description 9
- 239000000126 substance Substances 0.000 claims description 9
- 229910052723 transition metal Inorganic materials 0.000 claims description 9
- 150000003624 transition metals Chemical class 0.000 claims description 9
- 229910052726 zirconium Inorganic materials 0.000 claims description 9
- 239000002994 raw material Substances 0.000 claims description 8
- 239000012298 atmosphere Substances 0.000 claims description 7
- 239000003513 alkali Substances 0.000 claims description 5
- 239000003575 carbonaceous material Substances 0.000 claims description 3
- 229910052721 tungsten Inorganic materials 0.000 claims description 3
- 229910052720 vanadium Inorganic materials 0.000 claims description 3
- 230000014759 maintenance of location Effects 0.000 claims description 2
- 239000013078 crystal Substances 0.000 abstract description 10
- 239000010410 layer Substances 0.000 description 139
- PXHVJJICTQNCMI-UHFFFAOYSA-N nickel Substances [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 129
- 239000011162 core material Substances 0.000 description 86
- 229910052759 nickel Inorganic materials 0.000 description 60
- 239000000463 material Substances 0.000 description 50
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 36
- WMFOQBRAJBCJND-UHFFFAOYSA-M Lithium hydroxide Chemical compound [Li+].[OH-] WMFOQBRAJBCJND-UHFFFAOYSA-M 0.000 description 33
- 229910002804 graphite Inorganic materials 0.000 description 33
- 239000010439 graphite Substances 0.000 description 33
- 238000002156 mixing Methods 0.000 description 26
- 239000012299 nitrogen atmosphere Substances 0.000 description 25
- 230000008569 process Effects 0.000 description 24
- 230000000052 comparative effect Effects 0.000 description 23
- 230000009286 beneficial effect Effects 0.000 description 12
- 230000002829 reductive effect Effects 0.000 description 12
- 239000011247 coating layer Substances 0.000 description 10
- 229910000480 nickel oxide Inorganic materials 0.000 description 9
- GNRSAWUEBMWBQH-UHFFFAOYSA-N oxonickel Chemical compound [Ni]=O GNRSAWUEBMWBQH-UHFFFAOYSA-N 0.000 description 9
- 239000003792 electrolyte Substances 0.000 description 8
- 239000011267 electrode slurry Substances 0.000 description 7
- 238000010298 pulverizing process Methods 0.000 description 7
- 230000009471 action Effects 0.000 description 6
- 230000015572 biosynthetic process Effects 0.000 description 6
- 238000006138 lithiation reaction Methods 0.000 description 6
- 230000008859 change Effects 0.000 description 5
- 238000009831 deintercalation Methods 0.000 description 5
- 239000011248 coating agent Substances 0.000 description 4
- 238000000576 coating method Methods 0.000 description 4
- 239000013067 intermediate product Substances 0.000 description 4
- 150000002739 metals Chemical class 0.000 description 4
- 239000011149 active material Substances 0.000 description 3
- 230000005540 biological transmission Effects 0.000 description 3
- 150000002500 ions Chemical class 0.000 description 3
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 description 2
- OIFBSDVPJOWBCH-UHFFFAOYSA-N Diethyl carbonate Chemical compound CCOC(=O)OCC OIFBSDVPJOWBCH-UHFFFAOYSA-N 0.000 description 2
- KMTRUDSVKNLOMY-UHFFFAOYSA-N Ethylene carbonate Chemical compound O=C1OCCO1 KMTRUDSVKNLOMY-UHFFFAOYSA-N 0.000 description 2
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 description 2
- 229910002651 NO3 Inorganic materials 0.000 description 2
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 description 2
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 description 2
- 238000005054 agglomeration Methods 0.000 description 2
- 230000002776 aggregation Effects 0.000 description 2
- 229910052787 antimony Inorganic materials 0.000 description 2
- WATWJIUSRGPENY-UHFFFAOYSA-N antimony atom Chemical compound [Sb] WATWJIUSRGPENY-UHFFFAOYSA-N 0.000 description 2
- 230000008901 benefit Effects 0.000 description 2
- 239000011230 binding agent Substances 0.000 description 2
- 239000006258 conductive agent Substances 0.000 description 2
- 238000005336 cracking Methods 0.000 description 2
- 238000009792 diffusion process Methods 0.000 description 2
- 238000001035 drying Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- JBTWLSYIZRCDFO-UHFFFAOYSA-N ethyl methyl carbonate Chemical compound CCOC(=O)OC JBTWLSYIZRCDFO-UHFFFAOYSA-N 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-M hydroxide Chemical compound [OH-] XLYOFNOQVPJJNP-UHFFFAOYSA-M 0.000 description 2
- 230000002401 inhibitory effect Effects 0.000 description 2
- 230000037427 ion transport Effects 0.000 description 2
- 238000011031 large-scale manufacturing process Methods 0.000 description 2
- 230000000670 limiting effect Effects 0.000 description 2
- XGZVUEUWXADBQD-UHFFFAOYSA-L lithium carbonate Chemical compound [Li+].[Li+].[O-]C([O-])=O XGZVUEUWXADBQD-UHFFFAOYSA-L 0.000 description 2
- 229910052808 lithium carbonate Inorganic materials 0.000 description 2
- 229910021450 lithium metal oxide Inorganic materials 0.000 description 2
- 150000002738 metalloids Chemical class 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 229910052757 nitrogen Inorganic materials 0.000 description 2
- 238000011056 performance test Methods 0.000 description 2
- 229910052710 silicon Inorganic materials 0.000 description 2
- 239000002904 solvent Substances 0.000 description 2
- -1 transition metals Chemical class 0.000 description 2
- QTBSBXVTEAMEQO-UHFFFAOYSA-M Acetate Chemical compound CC([O-])=O QTBSBXVTEAMEQO-UHFFFAOYSA-M 0.000 description 1
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 description 1
- 239000006173 Good's buffer Substances 0.000 description 1
- 229910010093 LiAlO Inorganic materials 0.000 description 1
- 229910001290 LiPF6 Inorganic materials 0.000 description 1
- 239000002033 PVDF binder Substances 0.000 description 1
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
- 150000001242 acetic acid derivatives Chemical class 0.000 description 1
- 239000006230 acetylene black Substances 0.000 description 1
- 239000000853 adhesive Substances 0.000 description 1
- 230000001070 adhesive effect Effects 0.000 description 1
- 229910052783 alkali metal Inorganic materials 0.000 description 1
- 150000001340 alkali metals Chemical class 0.000 description 1
- 229910052784 alkaline earth metal Inorganic materials 0.000 description 1
- 150000001342 alkaline earth metals Chemical class 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 150000001450 anions Chemical class 0.000 description 1
- 239000006256 anode slurry Substances 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- 229910052785 arsenic Inorganic materials 0.000 description 1
- RQNWIZPPADIBDY-UHFFFAOYSA-N arsenic atom Chemical compound [As] RQNWIZPPADIBDY-UHFFFAOYSA-N 0.000 description 1
- 229910052789 astatine Inorganic materials 0.000 description 1
- RYXHOMYVWAEKHL-UHFFFAOYSA-N astatine atom Chemical compound [At] RYXHOMYVWAEKHL-UHFFFAOYSA-N 0.000 description 1
- 230000002238 attenuated effect Effects 0.000 description 1
- 230000003139 buffering effect Effects 0.000 description 1
- 239000006229 carbon black Substances 0.000 description 1
- 239000002041 carbon nanotube Substances 0.000 description 1
- 229910021393 carbon nanotube Inorganic materials 0.000 description 1
- 238000012512 characterization method Methods 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 230000001351 cycling effect Effects 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 238000010586 diagram Methods 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
- 239000006185 dispersion Substances 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 238000000840 electrochemical analysis Methods 0.000 description 1
- 239000011888 foil Substances 0.000 description 1
- 230000006870 function Effects 0.000 description 1
- SCCCLDWUZODEKG-UHFFFAOYSA-N germanide Chemical compound [GeH3-] SCCCLDWUZODEKG-UHFFFAOYSA-N 0.000 description 1
- 229910052732 germanium Inorganic materials 0.000 description 1
- GNPVGFCGXDBREM-UHFFFAOYSA-N germanium atom Chemical compound [Ge] GNPVGFCGXDBREM-UHFFFAOYSA-N 0.000 description 1
- 229910021389 graphene Inorganic materials 0.000 description 1
- 229910021385 hard carbon Inorganic materials 0.000 description 1
- 229910052734 helium Inorganic materials 0.000 description 1
- 239000001307 helium Substances 0.000 description 1
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 230000003993 interaction Effects 0.000 description 1
- 230000002427 irreversible effect Effects 0.000 description 1
- XIXADJRWDQXREU-UHFFFAOYSA-M lithium acetate Chemical compound [Li+].CC([O-])=O XIXADJRWDQXREU-UHFFFAOYSA-M 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
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 1
- 239000012982 microporous membrane Substances 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 229910052754 neon Inorganic materials 0.000 description 1
- GKAOGPIIYCISHV-UHFFFAOYSA-N neon atom Chemical compound [Ne] GKAOGPIIYCISHV-UHFFFAOYSA-N 0.000 description 1
- 229910052755 nonmetal Inorganic materials 0.000 description 1
- 230000036961 partial effect Effects 0.000 description 1
- 229910052699 polonium Inorganic materials 0.000 description 1
- HZEBHPIOVYHPMT-UHFFFAOYSA-N polonium atom Chemical compound [Po] HZEBHPIOVYHPMT-UHFFFAOYSA-N 0.000 description 1
- 230000001681 protective effect Effects 0.000 description 1
- 230000002441 reversible effect Effects 0.000 description 1
- 238000005096 rolling process Methods 0.000 description 1
- 238000007790 scraping Methods 0.000 description 1
- 238000007086 side reaction Methods 0.000 description 1
- 229910021332 silicide Inorganic materials 0.000 description 1
- FVBUAEGBCNSCDD-UHFFFAOYSA-N silicide(4-) Chemical compound [Si-4] FVBUAEGBCNSCDD-UHFFFAOYSA-N 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- 230000001502 supplementing effect Effects 0.000 description 1
- XSOKHXFFCGXDJZ-UHFFFAOYSA-N telluride(2-) Chemical compound [Te-2] XSOKHXFFCGXDJZ-UHFFFAOYSA-N 0.000 description 1
- 229910052714 tellurium Inorganic materials 0.000 description 1
- PORWMNRCUJJQNO-UHFFFAOYSA-N tellurium atom Chemical compound [Te] PORWMNRCUJJQNO-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- 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
- H01M4/485—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy
-
- 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
- H01M4/362—Composites
- H01M4/366—Composites as layered products
-
- 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
- H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
- H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
-
- 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
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- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Inorganic Chemistry (AREA)
- Composite Materials (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Manufacturing & Machinery (AREA)
- Battery Electrode And Active Subsutance (AREA)
- Secondary Cells (AREA)
Abstract
The application belongs to the technical field of batteries, and particularly relates to a lithium-rich positive electrode material, and a preparation method and application thereof. The lithium-rich positive electrode material comprises a lithium-rich metal oxide, wherein at least part of lithium positions of the lithium-rich metal oxide are doped with metal elements M, and the metal elements M comprise one or more of IB-VIIIB elements, IIA elements, IIIA elements, IVA elements and VA elements; at least part of the oxygen sites of the lithium-rich metal oxide are doped with a metalloid element. The application can lead the crystal lattice of the lithium-rich positive electrode material to be difficult to deform, effectively improve the structural stability of the lithium-rich positive electrode material and further improve the cycle performance of the lithium-rich positive electrode material.
Description
Technical Field
The application belongs to the technical field of batteries, and particularly relates to a lithium-rich positive electrode material, and a preparation method and application thereof.
Background
A lithium-rich positive electrode material is a lithium metal oxide having an atomic ratio of Li to other metals of more than 1, and such positive electrode material has been receiving attention because of its high specific capacity. However, more lithium-rich cathode materials continuously expand and contract in the unit cell volume in the long-time charge-discharge cycle process, so that large-area microcracks can appear at particle interfaces, and therefore, the cathode plate is broken and pulverized, side reactions of the lithium-rich cathode materials and electrolyte are increased, the internal resistance of the battery is increased, and the electrochemical performance of the battery is reduced.
Disclosure of Invention
The application aims to provide a lithium-rich positive electrode material, a preparation method and application thereof, and aims to solve the problems of cracks, even breakage and pulverization of the lithium-rich positive electrode material in the charge-discharge cycle process.
In order to achieve the purposes of the application, the technical scheme adopted by the application is as follows:
in a first aspect, the present application provides a lithium-rich cathode material, including a lithium-rich metal oxide, at least a lithium site of the lithium-rich metal oxide being doped with a metal element M, where the metal element M includes one or more of group IB to VIIIB elements, group IIA elements, group IIIA elements, group IVA elements, and group VA elements; at least the oxygen sites of the lithium-rich metal oxide are doped with a metalloid element.
According to the embodiment of the application, the lithium site and the oxygen site of the lithium-rich metal oxide are doped with specific elements at the same time, wherein the metal element M doped with the lithium site can prevent layer sliding and phase structure change of the lithium-rich oxide, for example, the formation of O1 phase stacking faults or O1 phases in O3 phase is prevented, so that the material can not undergo phase change even under high pressure, and the cycle performance of the lithium-rich positive electrode material is improved. In addition, the metal element M doped with lithium can form a lithium ion conductor material with the residual lithium in the lithium-rich positive electrode material on the surface of the lithium-rich positive electrode material in situ, so that on one hand, the surface of the lithium-rich positive electrode material can be coated, and the exposure of the lithium-rich positive electrode material in electrolyte in the charge and discharge processes is reduced, thereby improving the structural stability of the lithium-rich positive electrode material, ensuring that crystal lattices are not easy to deform, and being beneficial to improving the cycle performance of a battery; on the other hand, the lithium ion conductor coating layer can also rapidly realize the conduction of lithium ions and promote the deintercalation of lithium ions in the battery, thereby being beneficial to improving the capacity of the battery.
At the same time, the oxygen-site doped metalloid element can increase the energy of formation of oxygen vacancies in the lithium-rich metal oxide, thereby enabling O in the lithium-rich metal oxide 2- Can exist stably, and is not easy to generate oxygen escape (oxygen escape forms oxygen vacancies), which is beneficial to inhibiting the generation of cracks of the lithium-rich positive electrode material in the charge-discharge cycle process, thereby improving the cycle stability and the thermal stability of the lithium-rich positive electrode material. Meanwhile, the oxygen-site doped metalloid element can increase the exchange energy between Li and transition metal of the lithium-rich metal oxide, so that the tendency of mixed discharge of Li and transition metal is reduced. Therefore, under the action of oxygen-site doping elements, the crystal lattice of the lithium-rich positive electrode material is not easy to causeDeformation and improved structural stability.
Therefore, under the combined action of the metal element M doped with lithium and the metalloid element doped with oxygen, the crystal lattice of the lithium-rich positive electrode material is not easy to deform, the structural stability of the lithium-rich positive electrode material is effectively improved, and the cycle performance of the lithium-rich positive electrode material is further improved.
In a second aspect, the present application provides a method for preparing a lithium-rich cathode material, comprising:
adding a metal element M source and a metalloid element source into a preparation raw material of the lithium-rich metal oxide, and performing sintering treatment in an inert atmosphere; wherein the metal element M comprises one or more of IB-VIIIB element, IIA element, IIIA element, IVA element and VA element.
According to the embodiment of the application, the metal element M source and the metalloid element source are added into the preparation raw materials of the lithium-rich metal oxide for co-sintering, so that the metal element M can be doped on at least part of lithium positions of the lithium-rich metal oxide, and meanwhile, the metalloid element is doped on oxygen positions, so that the co-doping of the lithium positions and the oxygen positions of the lithium-rich metal oxide is realized, the crystal lattice of the lithium-rich positive electrode material is not easy to deform, and the structural stability of the lithium-rich positive electrode material is improved; the preparation method is simple, easy to implement and easy for large-scale production.
In a third aspect, the present application provides a positive electrode comprising the lithium-rich positive electrode material of the first aspect described above or the lithium-rich positive electrode material prepared by the method of the second aspect described above.
The lithium-rich positive electrode material provided by the embodiment of the application has good mechanical properties, and can reduce the problem of stress non-concentration caused by lithiation reaction of the lithium-rich metal oxide in the charge-discharge process, and the problems of cracking, even breaking, pulverization and the like are not easy to occur in the charge-discharge cycle process. Therefore, the positive electrode containing the lithium-rich positive electrode material is not easy to pulverize and has good structural stability.
In a fourth aspect, the present application provides a secondary battery comprising the above-described positive electrode.
The positive electrode contains the lithium-rich positive electrode material provided by the embodiment of the application, and has the advantages of difficult pulverization and good structural stability, so that the secondary battery comprising the positive electrode has good cycle performance.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are needed in the embodiments or the description of the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and that other drawings can be obtained according to these drawings without inventive effort for a person skilled in the art.
Fig. 1 is a schematic diagram of a core-shell structure in an embodiment of the present application.
Reference numerals:
01-inner core, 02-middle buffer layer and 03-shell layer.
Detailed Description
In order to make the technical problems, technical schemes and beneficial effects to be solved more clear, the application is further described in detail below with reference to the embodiments. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the application.
In the present application, the term "and/or" describes an association relationship of an association object, which means that three relationships may exist, for example, a and/or B may mean: a alone, a and B together, and B alone. Wherein A, B may be singular or plural. The character "/" generally indicates that the context-dependent object is an "or" relationship.
In the present application, "at least one" means one or more, and "a plurality" means two or more. "at least one of" or the like means any combination of these items, including any combination of single item(s) or plural items(s). For example, "at least one (individual) of a, b, or c," or "at least one (individual) of a, b, and c," may each represent: a, b, c, a-b (i.e., a and b), a-c, b-c, or a-b-c, wherein a, b, c may be single or multiple, respectively.
It should be understood that, in various embodiments of the present application, the sequence number of each process described above does not mean that the execution sequence of some or all of the steps may be executed in parallel or executed sequentially, and the execution sequence of each process should be determined by its functions and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.
The terminology used in the embodiments of the application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used in this application and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.
The weights of the relevant components mentioned in the description of the embodiments of the present application may refer not only to the specific contents of the components, but also to the proportional relationship between the weights of the components, so long as the contents of the relevant components in the description of the embodiments of the present application are scaled up or down within the scope of the disclosure of the embodiments of the present application. Specifically, the mass described in the specification of the embodiment of the application can be mass units known in the chemical industry field such as mu g, mg, g, kg.
The terms "first" and "second" are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated for distinguishing between objects such as substances from each other. For example, a first XX may also be referred to as a second XX, and similarly, a second XX may also be referred to as a first XX, without departing from the scope of embodiments of the application. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include one or more such feature.
The first aspect of the embodiment of the application provides a lithium-rich positive electrode material, which at least partially comprises a lithium-rich metal oxide, wherein a metal element M is doped on a lithium position of the lithium-rich metal oxide, and the metal element M comprises one or more of IB-VIIIB elements, IIA elements, IIIA elements, IVA elements and VA elements; at least part of the oxygen sites of the lithium-rich metal oxide are doped with a metalloid element.
Wherein, the lithium-rich metal oxide refers to a lithium metal oxide having an atomic ratio of Li to other metals (e.g., transition metals, various doping metals, etc.) of greater than 1. The lithium site of the lithium-rich metal oxide refers to the position of Li in the lithium-rich metal oxide lattice, and the oxygen site refers to the position of O in the lithium-rich metal oxide lattice. The doping of the metal element M on the lithium sites of at least part of the lithium-rich metal oxide means that the metal element M is doped on some or all of the lithium sites of the lithium-rich metal oxide. The oxygen sites of at least part of the lithium-rich metal oxide are doped with a metalloid element, meaning that part or all of the oxygen sites of the lithium-rich metal oxide are doped with a metalloid element. It can be understood that, for the lithium-rich metal oxide doped with the metal element M at the lithium site, the oxygen site may be doped with the metalloid element, or the oxygen site may be not doped with the metalloid element; in the lithium-rich metal oxide doped with a metalloid element at the oxygen site, the lithium site may be doped with the metal element M or may be not doped with the metal element M.
The metal element M includes one or more of group IB to VIIIB elements, group IIA elements, group IIIA elements, group IVA elements, group VA elements, mainly including alkaline earth metals, transition metals, and other metals, and in actual practice, metal elements other than alkali metals and radioactivity may be selected. Metalloid, which refers to a substance between metal and non-metal, whose exterior exhibits metallic properties, but chemically exhibits both metallic and non-metallic properties. For example, boron, silicon, arsenic, antimony, tellurium, polonium, astatine, germanium, antimony, and the like can be ascribed to metalloids.
According to the embodiment of the application, the lithium site and the oxygen site of the lithium-rich metal oxide are doped with specific elements at the same time, wherein the metal element M doped with the lithium site can prevent layer sliding and phase structure change of the lithium-rich oxide, for example, the formation of O1 phase stacking faults or O1 phases in O3 phase is prevented, so that the material can not undergo phase change even under high pressure, and the cycle performance of the lithium-rich positive electrode material is improved. In addition, the metal element M doped with lithium can form a lithium ion conductor material with the residual lithium in the lithium-rich positive electrode material on the surface of the lithium-rich positive electrode material in situ, so that on one hand, the surface of the lithium-rich positive electrode material can be coated, and the exposure of the lithium-rich positive electrode material in electrolyte in the charge and discharge processes is reduced, thereby improving the structural stability of the lithium-rich positive electrode material, ensuring that crystal lattices are not easy to deform, and being beneficial to improving the cycle performance of a battery; on the other hand, the lithium ion conductor coating layer can also rapidly realize the conduction of lithium ions and promote the deintercalation of lithium ions in the battery, thereby being beneficial to improving the capacity of the battery.
At the same time, the oxygen-site doped metalloid element can increase the energy of formation of oxygen vacancies in the lithium-rich metal oxide, thereby enabling O in the lithium-rich metal oxide 2- Can exist stably, and is not easy to generate oxygen escape (oxygen escape forms oxygen vacancies), which is beneficial to inhibiting the generation of cracks of the lithium-rich positive electrode material in the charge-discharge cycle process, thereby improving the cycle stability and the thermal stability of the lithium-rich positive electrode material. Meanwhile, the oxygen-site doped metalloid element can increase the exchange energy between Li and transition metal of the lithium-rich metal oxide, so that the tendency of mixed discharge of Li and transition metal is reduced. Therefore, under the action of oxygen-site doping elements, the crystal lattice of the lithium-rich anode material is not easy to deform, and the structural stability of the lithium-rich anode material is improved.
Therefore, under the combined action of the metal element M doped with lithium and the metalloid element doped with oxygen, the crystal lattice of the lithium-rich positive electrode material is not easy to deform, the structural stability of the lithium-rich positive electrode material is effectively improved, and the cycle performance of the lithium-rich positive electrode material is further improved.
In some embodiments, the chemical formula of the lithium-rich metal oxide includes [ Li 2+x M y ]M 0 a O 2-z A z X is more than or equal to 0.2 and less than or equal to 0.2, y is more than or equal to 0 and less than or equal to 1, a is more than or equal to 0 and less than or equal to 1, z is more than or equal to 0 and less than or equal to 2, wherein M 0 Comprises transition metal, A is a metalloid element doped on oxygen.
For example, x may be any one or a range between-0.2, -0.1,0,0.1,0.2; y may be any one or a range between any two of 0,0.001,0.005,0.01,0.05,0.1,0.5,1; a may be any one or a range between any two of 0.001,0.005,0.01,0.05,0.1,0.5,1; in some embodiments, y+a=1. z may be a number of times 0,0.001,0.005,0.01,0.05,0.1, 0.5,1,1.5,1.99, or a range therebetween; m is M 0 Including one or more of Ni, zr, cu, fe, mn, zn, co, cr, V, mo, W, ti, optionally including Ni.
It can be understood that in the lithium-rich positive electrode material of the present application, at least part of lithium sites of the lithium-rich metal oxide are doped with a metal element M, and at least part of oxygen sites of the lithium-rich metal oxide are doped with a metalloid element, so that y and z may be different from 0 at the same time; one of them may be 0 and the other may be other than 0; or both may be 0. Under the condition that y and z are not 0 at the same time, the lithium position of the part of the lithium-rich metal oxide is doped with a metal element M, and the oxygen position is doped with a metalloid element; in the case that one of y and z is 0 and the other is not 0, then the lithium site of the part of the lithium-rich metal oxide is doped with a metal element M, or the oxygen site is doped with a metalloid element; in the case where both y and z are 0, it means that the lithium site of the partial lithium-rich metal oxide is not doped with a metal element M, and the oxygen site is also not doped with a metalloid element; in this case, the lithium sites of the other part of the lithium-rich metal oxide should be doped with a metal element, and/or the oxygen sites should be doped with a metalloid element.
In some embodiments, the metallic element M comprises one or more of Zr, cu, mg, fe, mn, zn, co, cr, V, mo, W, ti, al.
In some embodiments, the metalloid element (a) comprises one or more of B, si, te, as, ge.
In some embodiments, the mass ratio of metal element M to metalloid element a is 1: (0.1 to 1), for example, 1:0.1,1:0.2,1:0.4,1:0.6,1:0.8,1:0.9,1:1 or a range between any one or both. The content of the metal element M doped in the lithium position is too low, so that a lithium ion conductor is not formed on the surface of the lithium-rich positive electrode material; too high a content of M in the metal element doped with lithium sites may result in too much inert M (e.g. Zr 4+ ) Occupying the Li site, thereby reducing the activity Li + And a specific discharge capacity. When the content of the oxygen-doped metalloid element A is too low, the number of A-O bonds (for example, B-O bonds) is insufficient,O 2- the anion frame is not stable enough, so that the cycle stability and the thermal stability of the lithium-rich cathode material are not high; if the content of the oxygen-site doped metalloid element A is too high, the crystal lattice of the lithium-rich cathode material is easy to deform, so that some capacity loss is caused.
In some embodiments, the total mass content of both metallic element M and metalloid element a in the lithium-rich cathode material is in a range between any one or any two of 0.1% -6%, for example 0.1%,0.5%,1%,2%,3%,4%,5%, 6%. The structural stability of the lithium-rich cathode material cannot be improved if the content of the doping element is too low; too high doping levels may result in severe lattice distortion of the material, thereby reducing the structural stability of the lithium-rich cathode material.
In some embodiments, the lithium-rich cathode material has a core-shell structure comprising a core and a shell, each of the core and the shell independently comprising a lithium-rich metal oxide; the metal element M is distributed in the core, the shell and the surface of the shell; the metalloid element a is distributed in the core and/or shell layer.
Wherein, the core-shell structure refers to an orderly assembled structure similar to a shell and a kernel, which is formed by coating one (or a group of) materials with the other (or another group of) materials through chemical bonds or other acting forces. In the core-shell structure, the types of materials of the core include, but are not limited to, one or more than one type, and the number of layers of the core include, but are not limited to, one or more than one layer; similarly, the types of materials of the shell layer also include, but are not limited to, one or more than one type, and the number of layers of the shell layer includes, but is not limited to, one or more than one type.
The inner core and the shell of the lithium-rich positive electrode material comprise lithium-rich metal oxides, and the element types and the element contents of a metal element M doped with lithium positions and a metalloid element A doped with oxygen positions in the lithium-rich metal oxides of the inner core and the shell can be the same or different. When the metal element M doped with lithium bits and the metalloid element A doped with oxygen bits in the core and the shell are the same, the introduction of heterogeneous elements can be reduced; when the metal element M doped by the lithium position and the metalloid element A doped by the oxygen position of the inner core and the shell are different, the structural stability and the capacity of the lithium-rich positive electrode material can be improved. When the content of the metal element M doped with the lithium position is the same as that of the metalloid element A doped with the oxygen position, the stress of the lithium-rich anode material can be uniformly dispersed in the lithiation process; when the content of the metal element M doped with the lithium position is different from that of the metalloid element A doped with the oxygen position, the reversible capacity/irreversible capacity (lithium supplementing amount) of the lithium-rich positive electrode material can be improved.
By setting the lithium-rich anode material as a core-shell structure, the oxygen-site doped elements and the lithium-site doped elements of the lithium-rich anode material can have different distributions, wherein the oxygen-site doped metalloid element A is concentrated in the inner core and/or the shell layer, and the lithium-site doped metal element M is distributed in the inner core and the shell layer and also migrates to the surface of the shell layer, thereby being beneficial to combining with residual lithium on the surface of the shell layer to form a lithium ion conductor.
In some embodiments, the lithium-rich cathode material further comprises an intermediate buffer layer between the core and the shell layer. At this time, as shown in fig. 1, the structure of the lithium-rich cathode material sequentially includes, from inside to outside, a core 01, an intermediate buffer layer 02, and a shell layer 03, where the intermediate buffer layer 02 is coated on the surface of the core 01, and the shell layer 03 is coated on the surface of the intermediate buffer layer 02. The kind of material of the intermediate buffer layer 02 may include, but is not limited to, one or more, and the number of layers of the intermediate buffer layer 02 may include, but is not limited to, one or more.
The intermediate buffer layer is arranged between the inner core and the shell layer, so that the overall mechanical property of the positive electrode material can be effectively improved, the problem of stress unconcentration caused by lithiation reaction of lithium-rich metal oxides of the inner core and the shell layer in the charge-discharge process is solved, and the problems of cracks, even breakage, pulverization and the like of lithium-rich positive electrode material particles in the charge-discharge cycle process are solved.
In some embodiments, the shell layer includes a lithium ion conductor layer bonded in situ to an outer surface of the lithium-rich cathode material. Since the outer surface of the lithium-rich cathode material, that is, the outer surface of the shell layer, the lithium ion conductor layer is in-situ bonded to the outer surface of the lithium-rich cathode material, it is also understood that the lithium ion conductor layer is in-situ bonded to the outer surface of the shell layer. A lithium ion conductor is an ion conductor capable of conducting lithium ions. The lithium ion conductor coating layer can be formed by transferring metal elements M doped with lithium-rich metal oxide lithium sites in the inner core and the shell from the inner core and the shell to the outside and combining the metal elements M with residual lithium elements on the surface of the lithium-rich positive electrode material. On the one hand, the lithium ion conductor layer can be used for coating the lithium-rich metal oxide serving as an active material, so that the exposure of the active material in electrolyte in the charge-discharge process is reduced, the stability of the lithium-rich positive electrode material is improved, and the cycle performance of the battery is improved. On the other hand, the lithium ion conductor layer can also rapidly realize the conduction of lithium ions and promote the deintercalation of lithium ions in the battery, thereby being beneficial to improving the capacity of the battery.
In some embodiments, the mass ratio of the core to the shell is 0.1 to 2:1, optionally 0.5 to 1.5:1, for example 0.1:1,0.2:2,0.4:1,0.5:1,0.6:1,0.8:1,1:1,1.2:1,1.4:1,1.5:1,1.6:1,1.8:1,2:1 or a range between any one or both. Under the proper mass ratio of the core and the shell, the problem of stress non-concentration caused by lithiation reaction of the lithium-rich positive electrode material in the charge and discharge process is solved, and the stability of the lithium-rich positive electrode material is improved.
In some embodiments, the thickness of the intermediate buffer layer is in the range of 1 to 500nm, for example, any one or between any two of 1nm,10nm,50nm,100nm,150nm,200nm,250nm,300nm,350nm,400nm,450nm,500 nm. If the middle layer is too thin, the acting force on the inner core and the shell layer is weak, which is not beneficial to improving the structural stability of the lithium-rich anode material; too thick an intermediate layer affects ion transport of the lithium-rich positive electrode material.
In some embodiments, the intermediate buffer layer comprises a carbon material; the carbon material comprises one or more of graphene, carbon black, hard carbon, acetylene black, graphite and carbon nano-tubes. The material has good structural stability, good flexibility and high strength, so that the material can generate good buffer effect on volume expansion of the inner core and the shell layer, and the problem of stress unconcentration caused by lithiation reaction of lithium-rich metal oxides in the inner core and the shell layer in the charge-discharge process is solved, so that the problems of cracks, even breakage, pulverization and the like of lithium-rich positive electrode material particles in the charge-discharge cycle process are solved. Meanwhile, the materials have excellent conductivity, and can smoothly carry out electron transmission between the inner core and the shell layer without reducing the conductivity of the lithium-rich cathode material.
In some embodiments, the mass content of the intermediate buffer layer in the lithium-rich cathode material is in a range of 0.1% to 10%, for example 0.0.1%,0.5%,1%,2%,3%,4%,5%,6%,7%,8%,9%,10% or any range therebetween. The intermediate layer has too low mass content to play a role in buffering stress impact; and if the mass content of the intermediate layer is too large, the ratio of the lithium-rich positive electrode material in the battery can be influenced, and the capacity of the battery can be further influenced.
In some embodiments, the thickness of the lithium ion conductor layer is in the range of 1 to 200nm, for example, any one or between any two of 1nm,10nm,50nm,100nm,150nm,200 nm. The lithium ion conductor layer is too thin, so that the binding force with the inner core, the middle layer and the shell layer inside the lithium-rich positive electrode material is weak, and the structure stability of the lithium-rich positive electrode material is not facilitated; too thick a lithium ion conductor layer can affect the lithium ion transport rate of the lithium-rich positive electrode material.
In some embodiments, the lithium ion conductor layer includes Li b MO c B is more than 0 and less than or equal to 6, c is more than 0 and less than or equal to 15. Alternatively, 1.ltoreq.b.ltoreq.4. For example b may include, but is not limited to, any one or range between any two of 1,2,3,4,5, 6. Alternatively, 2.ltoreq.c.ltoreq.12. For example, c may include, but is not limited to, a range between any one or both of 1,2,3,4,5,6,7,8,9, 10, 11, 12, 13, 14, 15. Exemplary lithium ion conductor layers include LiAlO 2 、Li 2 ZrO 3 、Li 2 MnO 3 、Li 2 TiO 3 、Li 4 TiO 4 、Li 4 Ti 5 O 12 、Li 2 WO 4 、Li 5 FeO 4 、Li 2 MoO 3 One or more of the following. The lithium ion conductor layer can be generated by the reaction of lithium-site doping elements M in the core and the shell layer with residual Li in the lithium-rich positive electrode material.
In some embodiments, the mass content of the lithium ion conductor layer in the lithium-rich cathode material is in a range between any one or both of 0.1% -3%, e.g., 0.1%,0.2%,0.3%,0.4%,0.5%,1%,1.5%,2%,2.5%, 3%. If the content of the coating layer is too low, the formed coating layer is discontinuous, so that part of the surface of the active material is exposed to electrolyte, and the improvement on the battery circulation is limited; too high a coating layer content can make the coating layer too thick, preventing the diffusion of lithium during the deintercalation process, resulting in poor performance.
In some embodiments, the lithium-rich cathode material includes primary particles and secondary particles, and a portion of the primary particles are filled in gaps of the secondary particles. "primary particles" refer to particles that do not agglomerate and are the smallest particle unit having a particle size. "secondary particles" refers to agglomerated particles. In general, individual fine grains are called primary particles; the primary particles are easy to be combined together due to weak interaction force due to small particle size and large specific surface energy, namely, agglomeration occurs, and secondary particles with larger particle size are formed; alternatively, the primary particles may agglomerate with each other under the action of the cohesive substance to form secondary particles.
The lithium-rich positive electrode material provided by the embodiment of the application contains the primary particles and the secondary particles, and part of the primary particles can be filled in gaps of the secondary particles with larger particle sizes, so that the tap density of the lithium-rich positive electrode material is improved.
In some embodiments, the primary particle to secondary particle mass ratio is 1: (5-20), for example 1:5,1:10,1:15,1:20 or a range therebetween. The primary particles and the secondary particles are in a proper proportion range, so that the diffusion of ions is facilitated, and the lithium-rich positive electrode material can be ensured to have higher energy density.
In some embodiments, the primary particles have an average particle size of from 10nm to 3 μm, alternatively from 25nm to 70nm, for example, any one or a range between 10nm,20nm,25nm,50nm,70nm,100nm,200nm,300nm,400nm,500nm,600nm,700nm,800nm,900nm,1000nm,1 μm,1.5 μm,2 μm,2.5 μm,3 μm.
The secondary particles consist of a plurality of primary particles having an average particle diameter of 5 to 60 μm, alternatively 5 to 20 μm, for example 5 μm,10 μm,15 μm,20 μm,25 μm,30 μm,35 μm,40 μm,45 μm,50 μm,55 μm,60 μm or a range between any one or both.
The lithium-rich positive electrode material contains lithium-site doping elements and oxygen-site doping elements, primary particles can be thinned, so that the primary particles have small particle sizes, the specific surface area of the material is increased, gaps between secondary particles can be filled, and the material in tap density is improved. However, too small a primary particle size results in too large a specific surface area of the material to agglomerate, thereby forming secondary particles having too large a particle size. The particle size of the lithium-rich positive electrode material is moderate, and the capacity of the lithium-rich positive electrode material can be fully exerted. Too small particle size is unfavorable for the dispersion of lithium-rich positive electrode material particles in positive electrode slurry, and too large particle size can influence the electron conduction and ion conduction of a positive electrode plate, thereby influencing the electrochemical performance of a secondary battery.
In some embodiments, the lithium-rich positive electrode material has a specific surface area of 0.3 to 100m 2 /g, optionally 10-40 m 2 /g, e.g. 0.3m 2 /g，1m 2 /g，5m 2 /g，10m 2 /g，20m 2 /g，30m 2 /g，40m 2 /g，50m 2 /g，60m 2 /g，70m 2 /g，80m 2 /g，90m 2 /g，100m 2 Either one or a range between either two of/g. The proper specific surface area is beneficial to improving the ion transmission and the stability of the lithium-rich positive electrode material. If the specific surface area is too low, the porosity is too low, and the transmission rate of lithium ions is reduced; if the specific surface area is too high, the porosity is too high, and the lithium-rich positive electrode material is easy to adsorb moisture in the external environment, so that the stability of the surface interface is reduced.
In some embodiments, the residual alkali mass content of the lithium-rich cathode material is in a range between any one or both of 0.03% to 0.15%, alternatively 0.03% to 0.1%, for example 0.03%,0.08%,0.1%,0.12%,0.14%, 0.15%. In the lithium-rich cathode material provided by the embodiment of the application, the main components of the residual alkali comprise alkaline substances such as lithium hydroxide, lithium carbonate and the like, and the main components are mainly derived from an unsintered lithium source in the process of preparing the lithium-rich cathode material by sintering or are decomposed in the sintering process to generate the alkaline substances.
In some embodiments, the lithium-rich positive electrode material has a tap density of 0.6 to 1.2g/cm 3 For example 0.6g/cm 3 ，0.8g/cm 3 ，1g/cm 3 ，1.2g/cm 3 Either or both.
In some embodiments, the lithium-rich positive electrode material has a first charge gram capacity of 390 to 450mAh/g, alternatively 395.1 to 445.2mAh/g, at a 1C rate and a charge capacity retention after 500 cycles of 70% to 85%, alternatively 78.4% to 83.7%.
The lithium-rich cathode material of the above-described embodiments of the application can be prepared by the following example method.
A second aspect of the embodiment of the present application provides a method for preparing a lithium-rich cathode material, including:
adding a metal element M source and a metalloid element source into a preparation raw material of the lithium-rich metal oxide, and performing sintering treatment in an inert atmosphere; wherein the metal element M comprises one or more of IB-VIIIB element, IIA element, IIIA element, IVA element and VA element.
According to the embodiment of the application, the metal element M source and the metalloid element source are added into the preparation raw materials of the lithium-rich metal oxide for co-sintering, so that the metal element M can be doped on at least part of lithium positions of the lithium-rich metal oxide, and meanwhile, the metalloid element is doped on oxygen positions, so that the co-doping of the lithium positions and the oxygen positions of the lithium-rich metal oxide is realized, the crystal lattice of the lithium-rich positive electrode material is not easy to deform, and the structural stability of the lithium-rich positive electrode material is improved; the preparation method is simple, easy to implement and easy for large-scale production.
In the above preparation method, the metal element M source includes one or more of hydroxide of M, carbonate of M, oxide of M, nitrate of M, sulfate of M, acetate of M. The metalloid element source includes one or more of boride, silicide, telluride, arsenide, germanide.
In some embodiments, the method of preparing a lithium-rich cathode material includes the steps of:
under inert atmosphere, lithium source, M 0 Sintering the source, the metal element M source and the metalloid element source; wherein M is 0 Including transition metals; wherein the lithium source, M 0 The element ratios in the source, the metal element M source and the metalloid element source satisfy [ Li 2+x M y ]M 0 a O 2-z A z ，-0.2≤x≤0.2，0≤y＜1，0＜a＜1，0≤z＜2。
Thus, a compound of the formula [ Li ] 2+x M y ]M 0 a O 2-z A z Contains lithium-rich metal oxide co-doped with lithium and oxygen.
Wherein, lithium source, M 0 The molar ratio of the source to the doping source (metal element Msource+metalloid element source) is (2-2.1): 1: (0.001 to 0.05), for example, (2 to 2.1): 1:0.001, (2 to 2.1): 1:0.02, (2-2.1): 1:0.03, (2 to 2.1): 1: a range of either or both of 0.05.
The lithium source comprises one or more of lithium hydroxide, lithium carbonate, lithium oxide, lithium acetate, and lithium oxalate. M is M 0 The source includes M 0 Oxide of (C), M 0 Hydroxide, M of 0 Carbonate, M of 0 Nitrate of (M) 0 Sulfate, M of (2) 0 One or more of the acetates of (a).
In some embodiments, the method of preparing a lithium-rich cathode material includes the steps of:
coating the lithium-rich metal oxide by adopting a buffer layer raw material to obtain an intermediate product; and coating the intermediate product by adopting lithium-rich metal oxide to obtain the lithium-rich anode material.
More specifically, the method comprises the following steps:
s1, under an inert atmosphere, a lithium source and M are subjected to 0 Sintering the source, the metal element M source and the metalloid element source to obtain a lithium-rich metal oxide;
s2, co-sintering the lithium-rich metal oxide and the buffer layer raw material in an inert atmosphere to obtain an intermediate product;
S3, sintering the intermediate product and the lithium-rich metal oxide in an inert atmosphere to obtain the lithium-rich anode material.
According to the embodiment of the application, the lithium-rich anode material with the core-shell structure can be obtained by sequentially carrying out sintering treatment, wherein after the treatment in the step S2, the lithium-rich metal oxide forms a core, and a buffer layer is formed on the surface of the core. After the treatment of the step S3, a shell layer containing lithium-rich metal oxide can be formed on the surface of the buffer layer; meanwhile, in step S3, the lithium-site doped element M in the lithium-rich metal oxide may migrate to the surface to combine with the remaining lithium element to form a lithium ion conductor. The lithium-rich metal oxide in step S2 and step S3 may be the same or different. When the lithium-rich metal oxides adopted in step S2 and step S3 are different, a step of preparing different lithium-rich metal oxides may be additionally added, and the added step of preparing different lithium-rich metal oxides may refer to step S1.
In some embodiments, the sintering treatment temperature in step S1 is in the range of 650-900 ℃, such as 650 ℃,700 ℃,750 ℃,800 ℃,850 ℃,900 ℃ or between any one or both; the sintering treatment time is in the range of 8 to 20 hours, for example, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, 15 hours, 16 hours, 17 hours, 18 hours, 19 hours, 20 hours or any two.
In some embodiments, the sintering treatment temperature in step S2 is in the range of 300-500 ℃, such as 300 ℃,350 ℃,400 ℃,450 ℃,500 ℃, either or both; the sintering treatment time is in the range of 1 to 8 hours, for example, any one or any two of 1h,2h,3h,4h,5h,6h,7h,8 h.
In some embodiments, the sintering treatment temperature in step S3 is in the range of 400-600 ℃, such as 400 ℃,450 ℃,500 ℃,550 ℃,600 ℃, either or both; the sintering treatment time is in the range of 0.1 to 9 hours, for example, 0.1 hours, 0.5 hours, 1 hours, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, or any one or any two of them.
In some embodiments, the protective atmospheres in step S1, step S2, and step S3 each independently comprise one or more of nitrogen, argon, neon, helium.
A third aspect of an embodiment of the present application provides a positive electrode comprising the lithium-rich positive electrode material of the first aspect described above or the lithium-rich positive electrode material prepared by the method of the second aspect described above.
The lithium-rich positive electrode material provided by the embodiment of the application has good mechanical properties, and can reduce the problem of stress non-concentration caused by lithiation reaction of the lithium-rich metal oxide in the charge-discharge process, and the problems of cracking, even breaking, pulverization and the like are not easy to occur in the charge-discharge cycle process. Therefore, the positive electrode containing the positive electrode material is not easy to pulverize and has good structural stability.
In some embodiments, the positive electrode includes a current collector and a positive electrode active layer disposed on a surface of the current collector, the positive electrode active layer including the above-described lithium-rich positive electrode material or the lithium-rich positive electrode material prepared as described above.
The positive electrode active layer also comprises a conductive agent, a binder and the like, wherein the conductive agent, the binder and the lithium-rich positive electrode material are mixed under the action of a solvent to form positive electrode slurry, the positive electrode slurry is coated on the surface of a current collector, and the positive electrode active layer is obtained through drying treatment.
A fourth aspect of the embodiment of the present application provides a secondary battery including the above-described positive electrode.
The positive electrode contains the lithium-rich positive electrode material provided by the embodiment of the application, and has the advantages of difficult pulverization and good structural stability, so that the secondary battery comprising the positive electrode has good cycle performance.
In some embodiments, the secondary battery further includes a negative electrode, and the positive electrode and the negative electrode form a circuit during charge and discharge of the secondary battery.
In some embodiments, the secondary battery further includes an electrolyte and a separator stacked between the positive electrode and the negative electrode.
In some embodiments, the secondary battery comprises a lithium ion battery.
The following description is made with reference to specific embodiments.
Example 1
The embodiment provides a lithium-rich nickel-containing positive electrode material and a preparation method thereof, wherein the lithium-rich nickel-containing positive electrode material has a core-shell structure and sequentially comprises a core, an intermediate buffer layer and a shell layer from inside to outside. Wherein the inner core and the shell each comprise [ Li ] 2.01 Zr 0.03 ]Ni 0.97 O 1.94 B 0.06 Wherein the mass ratio of Zr to B is 1:0.24, and the total mass content of Zr and B in the core and the shell is 3.2%; meanwhile, the shell layer also comprises a lithium-rich positive electrode material in-situ combined on the outer surface { also in the shell layer [ Li ] 2.01 Zr 0.03 ]Ni 0.97 O 1.94 B 0.06 Li of the outer surface } 2 ZrO 3 Layer, li 2 ZrO 3 The mass content of the layer in the lithium-rich nickel-containing positive electrode material is 0.44%, li 2 ZrO 3 The layer thickness was 29.7nm.
The intermediate buffer layer comprises graphite, the mass content of the graphite in the lithium-rich nickel-containing positive electrode material is 0.5%, and the thickness of the intermediate buffer layer is 5.6nm.
The preparation method of the lithium-rich nickel-containing positive electrode material of the embodiment comprises the following steps:
step one, lithium hydroxide: nickel oxide: zrB 2 Molar ratio = 2.01:1:0.03, mixing, sintering at 820 ℃ for 15 hours in nitrogen atmosphere, and obtaining the core material doped with Zr element at lithium position and B element at oxygen position.
And step two, adding graphite into the core material prepared in the step one, uniformly mixing, and sintering at 400 ℃ for 2 hours in a nitrogen atmosphere to obtain the core material with graphite on the surface.
Step three, the same step one.
Step four, taking the materials prepared in the step two and the step three, wherein the mass ratio of the materials is (60): 40, uniformly mixing, and sintering for 5 hours at 450 ℃ in nitrogen atmosphere to obtain the lithium-rich nickel-containing anode material.
Example 2
This embodiment differs from embodiment 1 in that: the elements doped at the lithium sites are different, specifically Zr is replaced by Mg.
Specifically, the embodiment provides a lithium-rich nickel-containing positive electrode material and a preparation method thereof, wherein the lithium-rich nickel-containing positive electrode material has a core-shell structure and sequentially comprises a core, an intermediate buffer layer and a shell layer from inside to outside. Wherein the inner core and the shell each comprise [ Li ] 2.05 Mg 0.03 ]Ni 0.97 O 1.94 B 0.06 Wherein the mass ratio of Mg to B is 1:0.89, and the total mass content of Mg and B in the core and the shell is 1.3 percent; meanwhile, the shell layer also comprises Li which is combined on the outer surface of the lithium-rich positive electrode material in situ 2 MgO 2 Layer, li 2 MgO 2 The mass content of the layer in the lithium-rich nickel-containing positive electrode material is 0.18%, li 2 MgO 2 The thickness of the layer was 11.8nm.
The intermediate buffer layer comprises graphite, the mass content of the graphite in the lithium-rich nickel-containing positive electrode material is 0.5%, and the thickness of the intermediate buffer layer is 5.3nm.
The preparation method of the lithium-rich nickel-containing positive electrode material of the embodiment comprises the following steps:
step one, lithium hydroxide: nickel oxide: mgB (MgB) 2 Molar ratio = 2.05:1:0.03, mixing, sintering for 10 hours at 880 ℃ in nitrogen atmosphere, and obtaining the core material doped with Mg element at lithium position and B element at oxygen position.
And step two, adding graphite into the core material prepared in the step one, uniformly mixing, and sintering for 4 hours at 450 ℃ in nitrogen atmosphere to obtain the core material with graphite on the surface.
Step three, the same step one.
Step four, taking the materials prepared in the step two and the step three, wherein the mass ratio of the materials is (60): 40, uniformly mixing, and sintering for 3 hours at 500 ℃ in nitrogen atmosphere to obtain the lithium-rich nickel-containing positive electrode material.
Example 3
This embodiment differs from embodiment 1 in that: the oxygen-site doped elements are different, specifically, B is replaced with Si.
Specifically, the embodiment provides a lithium-rich nickel-containing positive electrode material and a preparation method thereof, wherein the lithium-rich nickel-containing positive electrode material has a core-shell structure and sequentially comprises a core, an intermediate buffer layer and a shell layer from inside to outside. Wherein the inner part isThe core and the shell both comprise [ Li ] 2.05 Zr 0.03 ]Ni 0.97 O 1.94 Si 0.06 Wherein the mass ratio of Zr to Si is 1:0.62, and the total mass content of Zr and Si in the core and the shell is 4.1 percent; meanwhile, the shell layer also comprises Li which is combined on the outer surface of the lithium-rich positive electrode material in situ 2 ZrO 3 Layer, li 2 ZrO 3 The mass content of the layer in the lithium-rich nickel-containing positive electrode material is 0.37 percent, li 2 ZrO 3 The thickness of the layer was 24.4nm.
The intermediate buffer layer comprises graphite, the mass content of the graphite in the lithium-rich nickel-containing positive electrode material is 0.5%, and the thickness of the intermediate buffer layer is 5.6nm.
The preparation method of the lithium-rich nickel-containing positive electrode material of the embodiment comprises the following steps:
step one, lithium hydroxide: nickel oxide: zrSi 2 Molar ratio = 2.03:1:0.03, mixing, sintering for 8 hours at 700 ℃ in nitrogen atmosphere, and obtaining the core material doped with Zr element at lithium position and Si element at oxygen position.
And step two, adding graphite into the core material prepared in the step one, uniformly mixing, and sintering at 480 ℃ for 6 hours in a nitrogen atmosphere to obtain the core material with graphite on the surface.
Step three, the same step one.
Step four, taking the materials prepared in the step two and the step three, wherein the mass ratio of the materials is (60): 40, uniformly mixing, and sintering for 4 hours at 550 ℃ in nitrogen atmosphere to obtain the lithium-rich nickel-containing cathode material.
Example 4
This embodiment differs from embodiment 1 in that: there is no intermediate buffer layer.
Specifically, the embodiment provides a lithium-rich nickel-containing positive electrode material and a preparation method thereof, wherein the lithium-rich nickel-containing positive electrode material has a core-shell structure and sequentially comprises a core and a shell layer from inside to outside. Wherein the core comprises [ Li ] 2.01 Zr 0.03 ]Ni 0.97 O 1.94 B 0.06 Wherein the mass ratio of Zr to B is 1:0.24, the total mass content of Zr and B in the core being 3.2%; the shell layer comprises Li 2 ZrO 3 Layer, li 2 ZrO 3 Layer is rich in lithiumThe mass content of the nickel-containing positive electrode material is 0.4%, li 2 ZrO 3 The thickness of the layer was 26.8nm.
The preparation method of the lithium-rich nickel-containing positive electrode material of the embodiment comprises the following steps:
step one, lithium hydroxide: nickel oxide: zrB 2 Molar ratio = 2.01:1:0.03, mixing, sintering at 820 ℃ for 15 hours in nitrogen atmosphere to obtain a core material doped with Zr element at lithium position and B element at oxygen position; at the same time Zr and residual Li form Li on the surface of the kernel material in situ 2 ZrO 3 And a coating layer.
Example 5
This embodiment differs from embodiment 1 in that: the mass ratio of Zr to B in the lithium-rich metal oxide is different.
Specifically, the embodiment provides a lithium-rich nickel-containing positive electrode material and a preparation method thereof, wherein the lithium-rich nickel-containing positive electrode material has a core-shell structure and sequentially comprises a core, an intermediate buffer layer and a shell layer from inside to outside. Wherein the inner core and the shell each comprise [ Li ] 2.03 Zr 0.02 ]Ni 0.98 O 1.92 B 0.08 Wherein the mass ratio of Zr to B is 1:0.47, wherein the total mass content of Zr and B in the core and the shell is 2.6%; meanwhile, the shell layer also comprises Li which is combined on the outer surface of the lithium-rich positive electrode material in situ 2 ZrO 3 Layer, li 2 ZrO 3 The mass content of the layer in the lithium-rich nickel-containing positive electrode material is 0.29%, li 2 ZrO 3 The thickness of the layer was 19.1nm.
The intermediate buffer layer comprises graphite, the mass content of the graphite in the lithium-rich nickel-containing positive electrode material is 0.5%, and the thickness of the intermediate buffer layer is 5.6nm.
The preparation method of the lithium-rich nickel-containing positive electrode material of the embodiment comprises the following steps:
step one, lithium hydroxide: nickel oxide: zrB 2 Molar ratio = 2.03:1:0.02, mixing, sintering for 12 hours at 900 ℃ in nitrogen atmosphere, and obtaining the core material doped with Zr element at lithium position and B element at oxygen position.
And step two, adding graphite into the core material prepared in the step one, uniformly mixing, and sintering at 500 ℃ for 8 hours in a nitrogen atmosphere to obtain the core material with graphite on the surface.
Step three, the same step one.
Step four, taking the materials prepared in the step two and the step three, wherein the mass ratio of the materials is (60): 40, uniformly mixing, and sintering at 600 ℃ for 8 hours in a nitrogen atmosphere to obtain the lithium-rich nickel-containing cathode material.
Example 6
This embodiment differs from embodiment 1 in that: the Zr and B contents in the positive electrode material are different.
Specifically, the embodiment provides a lithium-rich nickel-containing positive electrode material and a preparation method thereof, wherein the lithium-rich nickel-containing positive electrode material has a core-shell structure and sequentially comprises a core, an intermediate buffer layer and a shell layer from inside to outside. Wherein the inner core and the shell each comprise [ Li ] 2.1 Zr 0.05 ]Ni 0.95 O 1.9 B 0.1 Wherein the mass ratio of Zr to B is 1:0.24, wherein the total mass content of Zr and B in the core and the shell is 5.3%; meanwhile, the shell layer also comprises Li which is combined on the outer surface of the lithium-rich positive electrode material in situ 2 ZrO 3 Layer, li 2 ZrO 3 The mass content of the layer in the lithium-rich nickel-containing positive electrode material is 0.79%, li 2 ZrO 3 The thickness of the layer was 52.8nm.
The intermediate buffer layer comprises graphite, the mass content of the graphite in the lithium-rich nickel-containing positive electrode material is 0.5%, and the thickness of the intermediate buffer layer is 5.6nm.
The preparation method of the lithium-rich nickel-containing positive electrode material of the embodiment comprises the following steps:
step one, lithium hydroxide: nickel oxide: zrB 2 Molar ratio = 2.1:1:0.05, mixing, sintering for 12 hours at 860 ℃ in nitrogen atmosphere, and obtaining the core material doped with Zr element at lithium position and B element at oxygen position.
And step two, adding graphite into the core material prepared in the step one, uniformly mixing, and sintering at 460 ℃ for 8 hours in a nitrogen atmosphere to obtain the core material with graphite on the surface.
Step three, the same step one.
Step four, taking the materials prepared in the step two and the step three, wherein the mass ratio of the materials is (20): 80, mixing uniformly, and sintering for 9 hours at 580 ℃ in nitrogen atmosphere to obtain the lithium-rich nickel-containing anode material.
Comparative example 1
The difference between this comparative example and example 1 is that: the core and the shell do not contain B.
Specifically, the comparative example provides a lithium-rich nickel-containing cathode material and a preparation method thereof, wherein the lithium-rich nickel-containing cathode material has a core-shell structure and sequentially comprises a core, an intermediate buffer layer and a shell layer from inside to outside. Wherein the inner core and the shell each comprise [ Li ] 2.01 Zr 0.03 ]Ni 0.97 O 2 Wherein the total mass content of Zr in the core and the shell is 2.6%; meanwhile, the shell layer also comprises Li which is combined on the outer surface of the lithium-rich positive electrode material in situ 2 ZrO 3 Layer, li 2 ZrO 3 The mass content of the layer in the lithium-rich nickel-containing positive electrode material is 0.43%, li 2 ZrO 3 The thickness of the layer was 28.4nm.
The intermediate buffer layer comprises graphite, the mass content of the graphite in the lithium-rich nickel-containing positive electrode material is 0.5%, and the thickness of the intermediate buffer layer is 5.6nm.
The preparation method of the lithium-rich nickel-containing positive electrode material of the comparative example comprises the following steps:
step one, lithium hydroxide: nickel oxide: zrO (ZrO) 2 Molar ratio = 2.01:1:0.03, mixing, sintering for 12 hours at 780 ℃ in nitrogen atmosphere, and obtaining the lithium-doped Zr element core material.
And step two, adding graphite into the core material prepared in the step one, uniformly mixing, and sintering at 480 ℃ for 6 hours in a nitrogen atmosphere to obtain the core material with graphite on the surface.
Step three, the same step one.
Step four, taking the materials prepared in the step two and the step three, wherein the mass ratio of the materials is (60): 40, uniformly mixing, and sintering for 4 hours at 500 ℃ in nitrogen atmosphere to obtain the lithium-rich nickel-containing anode material.
Comparative example 2
The difference between this comparative example and example 1 is that: and replacing B elements in the core and the shell layer with N elements.
This comparative example provides a lithium-richThe nickel-containing positive electrode material has a core-shell structure, and sequentially comprises a core, an intermediate buffer layer and a shell layer from inside to outside. Wherein the inner core and the shell each comprise [ Li ] 2.01 Zr 0.05 ]Ni 0.95 O 1.95 N 0.05 Wherein the mass ratio of Zr to N is 1:0.15, wherein the total mass content of Zr and N in the core and the shell is 5%; meanwhile, the shell layer also comprises Li which is combined on the outer surface of the lithium-rich positive electrode material in situ 2 ZrO 3 Layer, li 2 ZrO 3 The mass content of the layer in the lithium-rich nickel-containing positive electrode material is 0.84%, li 2 ZrO 3 The thickness of the layer was 55.8nm.
The intermediate buffer layer comprises graphite, the mass content of the graphite in the lithium-rich nickel-containing positive electrode material is 0.5%, and the thickness of the intermediate buffer layer is 5.6nm.
The preparation method of the lithium-rich nickel-containing positive electrode material of the comparative example comprises the following steps:
step one, lithium hydroxide: nickel oxide: zrN in molar ratio = 2.01:1:0.05, mixing, sintering for 10 hours at 750 ℃ in nitrogen atmosphere, and obtaining the core material doped with Zr element at lithium position and N element at oxygen position.
And step two, adding graphite into the core material prepared in the step one, uniformly mixing, and sintering at 380 ℃ for 8 hours in a nitrogen atmosphere to obtain the core material with graphite on the surface.
Step three, the same step one.
Step four, taking the materials prepared in the step two and the step three, wherein the mass ratio of the materials is (50): 50, uniformly mixing, and sintering for 6 hours at 450 ℃ in nitrogen atmosphere to obtain the lithium-rich nickel-containing cathode material.
Comparative example 3
The difference between this comparative example and example 1 is that: the inner core and the shell layer are doped with B, but do not contain Zr, and the raw materials in the step one and the step three of the preparation method do not contain ZrB 2 But will be ZrB 2 Replaced by H 3 BO 3 . That is, the inner core and the shell of the lithium-rich nickel-containing positive electrode material of the comparative example are both Li 2.05 NiO 1.9 B 0.1 And the shell layer does not contain Li 2 ZrO 3 A layer.
Specifically, the comparative example provides a lithium-rich nickel-containing cathode material and a preparation method thereof, wherein the lithium-rich nickel-containing cathode material has a core-shell structure and sequentially comprises a core, an intermediate buffer layer and a shell layer from inside to outside. Wherein the inner core and the shell layer both comprise Li 2.05 NiO 1.9 B 0.1 Wherein the total mass content of B in the core and the shell is 1%; the intermediate buffer layer comprises graphite, the mass content of the graphite in the lithium-rich nickel-containing positive electrode material is 0.5%, and the thickness of the intermediate buffer layer is 5.6nm.
The preparation method of the lithium-rich nickel-containing positive electrode material of the comparative example comprises the following steps:
step one, lithium hydroxide: nickel oxide: h 3 BO 3 Molar ratio = 2.05:1:0.1, mixing, sintering for 10 hours at 880 ℃ in nitrogen atmosphere, and obtaining the oxygen-site-doped B element core material.
And step two, adding graphite into the core material prepared in the step one, uniformly mixing, and sintering at 500 ℃ for 5 hours in a nitrogen atmosphere to obtain the core material with graphite on the surface.
Step three, the same step one.
Step four, taking the materials prepared in the step two and the step three, wherein the mass ratio of the materials is (60): 40, uniformly mixing, and sintering for 8 hours at 450 ℃ in nitrogen atmosphere to obtain the lithium-rich nickel-containing anode material.
The compositions of the lithium-rich nickel-containing positive electrode materials in each of the above examples and comparative examples are shown in the following table.
TABLE 1 composition of lithium-rich nickel-containing cathode materials
Characterization tests were performed on the structures of the lithium-rich nickel-containing positive electrode materials of the respective examples and comparative examples, and the results are shown in the following table.
TABLE 2 structural parameters of lithium-rich Nickel-containing cathode materials
It can be seen from examples 1 to 6 that doping of lithium and oxygen sites refines primary particles of the material, resulting in an increase in specific surface area (but agglomeration occurs when the primary particles have a small particle size and the surface energy of the material is too large, thereby forming secondary particles having a larger particle size); the smaller the primary particles, a portion of the primary particles can be filled into the gaps of the secondary particles, which is beneficial to improving the tap density of the material. As can be seen from comparative examples 1 and 3, the metal element doped with lithium sites can react with residual lithium in the material, thereby reducing the residual alkali amount of the material.
Electrochemical performance test:
the lithium-rich nickel-containing cathode materials prepared in each example and comparative example are applied to lithium ion batteries, and the preparation steps of the lithium ion batteries specifically comprise:
(1) preparation of a positive plate: the lithium-rich nickel-containing cathode materials prepared in each example and comparative example were mixed with SP (conductive carbon black), PVDF (polyvinylidene fluoride) and NMP (N-methylpyrrolidone) in a mass ratio of 93.5:2.5:4:100, stirring for 2 hours by using a ball mill stirrer, and uniformly mixing to obtain anode slurry; and (3) adding the prepared positive electrode slurry on an aluminum foil, uniformly scraping the positive electrode slurry by a scraper, drying the positive electrode slurry at 130 ℃, and rolling the positive electrode slurry to obtain the positive electrode plate.
(2) And (3) assembling a lithium ion battery: pasting the positive plate prepared in the step (1) on a positive metal shell by using a conductive adhesive, using a metal lithium plate as a negative electrode, using a Celgard 2400 microporous membrane as a diaphragm, and using a LiPF6 solution with the volume ratio of 1.0mol/L as an electrolyte, wherein the solvent of the electrolyte is as follows: 1:1, ethylene Carbonate (EC), diethyl carbonate (DEC) and ethylmethyl carbonate (EMC) were combined in a glove box to form a button lithium ion battery.
Each lithium ion battery assembled in the step (2) and containing the lithium-rich nickel-containing positive electrode material of the example or the comparative example is subjected to electrochemical performance test, including charge-discharge and cycle performance, under the following test conditions: 1C, 4.3-2.5V.
The test results are as follows.
TABLE 3 electrochemical test results
Table 3 shows that the charge-discharge capacity and cycle performance of the lithium-rich nickel-containing cathode materials of examples 1 to 6 are improved over those of comparative examples 1 to 3 when the materials are cycled for 500 cycles at 1C. The metal element M doped with lithium can react with residual alkali on the surface to form a coating layer on the surface of the material, so that the cycle performance of the material is improved, and on the other hand, the metal element M which does not react with residual lithium can prevent the sliding of the layer and the formation of O1 phase stacking faults or O1 phases in the O3 phase, so that the material cannot undergo phase change even under high pressure, and the cycle performance of the material is improved; the oxygen-site doped metalloid element can increase the formation energy of oxygen vacancies in the lithium-rich metal oxide and inhibit the generation of cracks in the charge-discharge process, thereby improving the cycling stability of the material.
It can be seen from example 4 that when the material has no buffer layer, the mechanical properties of the whole cathode material are reduced, cracks appear during charge and discharge cycles, and the properties are reduced compared with examples 1, 2, 3 and 5; but still exhibit better performance as a whole due to the presence of suitable doping elements at the lithium and oxygen sites. It can be seen from example 5 that the charge-discharge and cycle performance of the material is best when the doping of lithium and oxygen sites reaches an optimal value. As can be seen from example 6, when the doping of lithium and oxygen reaches a maximum, the coating layer on the surface of the material is too thick, which is unfavorable for the deintercalation of lithium ions, so that the charge-discharge capacity and the cycle performance of the material are attenuated compared with other examples.
In addition, it can be seen from comparative example 1 that if the oxygen site is not doped, or from comparative example 2 that if the oxygen site doping is not a metalloid element, or from comparative example 3 that if only the oxygen site doping is not pure, the charge-discharge capacity and cycle performance of the material are greatly reduced compared to those of the materials doped with lithium and oxygen sites (examples 1 to 6).
The foregoing description of the preferred embodiments of the application is not intended to be limiting, but rather is intended to cover all modifications, equivalents, and alternatives falling within the spirit and principles of the application.
Claims (10)
1. The lithium-rich positive electrode material is characterized by comprising a lithium-rich metal oxide, wherein at least part of lithium positions of the lithium-rich metal oxide are doped with metal elements M, and the metal elements M comprise one or more of IB-VIIIB elements, IIA elements, IIIA elements, IVA elements and VA elements; at least part of the oxygen sites of the lithium-rich metal oxide are doped with a metalloid element.
2. The lithium-rich positive electrode material of claim 1, wherein the chemical formula of the lithium-rich metal oxide comprises [ Li 2+x M y ]M 0 a O 2–z A z -0.2.ltoreq.x.ltoreq.0.2, 0.ltoreq.y.ltoreq.1, 0.ltoreq.a.ltoreq.1, 0.ltoreq.z.ltoreq.2, wherein M is the same as the above formula 0 Comprises transition metal, wherein A is a metalloid element doped on the oxygen site; and/or the number of the groups of groups,
the metal element M comprises one or more elements in Zr, cu, mg, fe, mn, zn, co, cr, V, mo, W, ti, al; and/or the number of the groups of groups,
the metalloid element comprises one or more of B, si, te, as, ge; and/or the number of the groups of groups,
the mass ratio of the metal element M to the metalloid element is 1: (0.1 to 1); and/or the number of the groups of groups,
the total mass content of the metal element M and the metalloid element in the lithium-rich positive electrode material is 0.1% -6%.
3. The lithium-rich cathode material according to claim 1 or 2, wherein the lithium-rich cathode material has a core-shell structure comprising a core and a shell, wherein the core and the shell each independently comprise the lithium-rich metal oxide; the metal element M is distributed in the inner core, the shell layer and the surface of the shell layer; the metalloid element is distributed in the core and/or in the shell.
4. The lithium-rich cathode material of claim 3, further comprising an intermediate buffer layer between the inner core and the shell layer; and/or the number of the groups of groups,
The shell layer comprises a lithium ion conductor layer, and the lithium ion conductor layer is combined on the outer surface of the lithium-rich positive electrode material in situ; and/or the number of the groups of groups,
the mass ratio of the inner core to the shell layer is 0.1-2: 1.
5. the lithium-rich cathode material according to claim 4, wherein the thickness of the intermediate buffer layer is 1 to 500nm; and/or the number of the groups of groups,
the intermediate buffer layer comprises a carbon material; and/or the number of the groups of groups,
the mass content of the intermediate buffer layer in the lithium-rich anode material is 0.1-10%; and/or the number of the groups of groups,
the thickness of the lithium ion conductor layer is 1-200 nm; and/or the number of the groups of groups,
the lithium ion conductor layer comprises Li b MO c B is more than 0 and less than or equal to 6, c is more than 0 and less than or equal to 15; and/or the number of the groups of groups,
the mass content of the lithium ion conductor layer in the lithium-rich positive electrode material is 0.1-3%.
6. The lithium-rich cathode material according to claim 1, wherein the lithium-rich cathode material comprises primary particles and secondary particles, and a part of the primary particles are filled in gaps of the secondary particles; and/or the number of the groups of groups,
the specific surface area of the lithium-rich positive electrode material is 0.3-100 m 2 /g; and/or，
The residual alkali mass content of the lithium-rich positive electrode material is 0.03% -0.15%; and/or the number of the groups of groups,
the tap density of the lithium-rich positive electrode material is 0.6-1.2 g/cm 3 The method comprises the steps of carrying out a first treatment on the surface of the And/or the number of the groups of groups,
the first charge gram capacity of the lithium-rich positive electrode material under the 1C multiplying power is 390-450 mAh/g, and the charge capacity retention rate after 500 times of circulation is 70-85%.
7. The lithium-rich cathode material according to claim 6, wherein the primary particles have an average particle diameter of 10nm to 3 μm and the secondary particles have an average particle diameter of 5 to 60 μm.
8. The preparation method of the lithium-rich cathode material is characterized by comprising the following steps of:
adding a metal element M source and a metalloid element source into a preparation raw material of the lithium-rich metal oxide, and performing sintering treatment in an inert atmosphere; wherein the metal element M comprises one or more of IB-VIIIB element, IIA element, IIIA element, IVA element and VA element.
9. A positive electrode comprising the lithium-rich positive electrode material according to any one of claims 1 to 7, or the lithium-rich positive electrode material produced by the method according to claim 8.
10. A secondary battery, characterized in that the secondary battery comprises the positive electrode of claim 9.
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