CN114256457B - Lithium-rich manganese-based positive electrode material with homogeneous composite coating layer and preparation method thereof - Google Patents
Lithium-rich manganese-based positive electrode material with homogeneous composite coating layer and preparation method thereof Download PDFInfo
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- CN114256457B CN114256457B CN202111671583.7A CN202111671583A CN114256457B CN 114256457 B CN114256457 B CN 114256457B CN 202111671583 A CN202111671583 A CN 202111671583A CN 114256457 B CN114256457 B CN 114256457B
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- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 title claims abstract description 108
- 229910052744 lithium Inorganic materials 0.000 title claims abstract description 108
- 239000011572 manganese Substances 0.000 title claims abstract description 105
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 title claims abstract description 98
- 229910052748 manganese Inorganic materials 0.000 title claims abstract description 97
- 239000011247 coating layer Substances 0.000 title claims abstract description 55
- 239000007774 positive electrode material Substances 0.000 title claims abstract description 42
- 239000002131 composite material Substances 0.000 title claims abstract description 31
- 238000002360 preparation method Methods 0.000 title claims abstract description 9
- 239000000463 material Substances 0.000 claims abstract description 62
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 31
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 31
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 claims abstract description 26
- 239000010416 ion conductor Substances 0.000 claims abstract description 26
- 229910001416 lithium ion Inorganic materials 0.000 claims abstract description 26
- 238000000034 method Methods 0.000 claims abstract description 20
- 239000002345 surface coating layer Substances 0.000 claims abstract description 6
- VYFYYTLLBUKUHU-UHFFFAOYSA-N dopamine Chemical compound NCCC1=CC=C(O)C(O)=C1 VYFYYTLLBUKUHU-UHFFFAOYSA-N 0.000 claims description 106
- 239000011259 mixed solution Substances 0.000 claims description 80
- 229960003638 dopamine Drugs 0.000 claims description 53
- 239000000243 solution Substances 0.000 claims description 41
- 239000007787 solid Substances 0.000 claims description 34
- 238000003756 stirring Methods 0.000 claims description 28
- 238000000576 coating method Methods 0.000 claims description 26
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 25
- 239000011248 coating agent Substances 0.000 claims description 24
- 239000002994 raw material Substances 0.000 claims description 23
- 238000010438 heat treatment Methods 0.000 claims description 22
- LENZDBCJOHFCAS-UHFFFAOYSA-N tris Chemical compound OCC(N)(CO)CO LENZDBCJOHFCAS-UHFFFAOYSA-N 0.000 claims description 22
- GQYHUHYESMUTHG-UHFFFAOYSA-N lithium niobate Chemical compound [Li+].[O-][Nb](=O)=O GQYHUHYESMUTHG-UHFFFAOYSA-N 0.000 claims description 20
- 239000010405 anode material Substances 0.000 claims description 15
- UYLYBEXRJGPQSH-UHFFFAOYSA-N sodium;oxido(dioxo)niobium Chemical compound [Na+].[O-][Nb](=O)=O UYLYBEXRJGPQSH-UHFFFAOYSA-N 0.000 claims description 15
- 238000001035 drying Methods 0.000 claims description 13
- 238000001914 filtration Methods 0.000 claims description 13
- 238000005406 washing Methods 0.000 claims description 13
- 238000001816 cooling Methods 0.000 claims description 12
- 238000002156 mixing Methods 0.000 claims description 11
- 239000012298 atmosphere Substances 0.000 claims description 10
- 230000001681 protective effect Effects 0.000 claims description 7
- 229910052759 nickel Inorganic materials 0.000 claims description 6
- 239000002253 acid Substances 0.000 claims description 5
- 229910001386 lithium phosphate Inorganic materials 0.000 claims description 5
- 239000000126 substance Substances 0.000 claims description 5
- MVGWWCXDTHXKTR-UHFFFAOYSA-J tetralithium;phosphonato phosphate Chemical compound [Li+].[Li+].[Li+].[Li+].[O-]P([O-])(=O)OP([O-])([O-])=O MVGWWCXDTHXKTR-UHFFFAOYSA-J 0.000 claims description 5
- TWQULNDIKKJZPH-UHFFFAOYSA-K trilithium;phosphate Chemical compound [Li+].[Li+].[Li+].[O-]P([O-])([O-])=O TWQULNDIKKJZPH-UHFFFAOYSA-K 0.000 claims description 5
- 239000003792 electrolyte Substances 0.000 claims description 4
- LWIHDJKSTIGBAC-UHFFFAOYSA-K tripotassium phosphate Chemical compound [K+].[K+].[K+].[O-]P([O-])([O-])=O LWIHDJKSTIGBAC-UHFFFAOYSA-K 0.000 claims description 4
- 150000001450 anions Chemical class 0.000 claims description 3
- MNNHAPBLZZVQHP-UHFFFAOYSA-N diammonium hydrogen phosphate Chemical compound [NH4+].[NH4+].OP([O-])([O-])=O MNNHAPBLZZVQHP-UHFFFAOYSA-N 0.000 claims description 3
- 230000001105 regulatory effect Effects 0.000 claims description 3
- 238000005245 sintering Methods 0.000 claims description 3
- FQENQNTWSFEDLI-UHFFFAOYSA-J sodium diphosphate Chemical compound [Na+].[Na+].[Na+].[Na+].[O-]P([O-])(=O)OP([O-])([O-])=O FQENQNTWSFEDLI-UHFFFAOYSA-J 0.000 claims description 3
- 229940048086 sodium pyrophosphate Drugs 0.000 claims description 3
- 235000019818 tetrasodium diphosphate Nutrition 0.000 claims description 3
- 239000001577 tetrasodium phosphonato phosphate Substances 0.000 claims description 3
- 239000004254 Ammonium phosphate Substances 0.000 claims description 2
- 229910015118 LiMO Inorganic materials 0.000 claims description 2
- LFVGISIMTYGQHF-UHFFFAOYSA-N ammonium dihydrogen phosphate Chemical compound [NH4+].OP(O)([O-])=O LFVGISIMTYGQHF-UHFFFAOYSA-N 0.000 claims description 2
- 229910000387 ammonium dihydrogen phosphate Inorganic materials 0.000 claims description 2
- 229910000148 ammonium phosphate Inorganic materials 0.000 claims description 2
- 235000019289 ammonium phosphates Nutrition 0.000 claims description 2
- 235000019837 monoammonium phosphate Nutrition 0.000 claims description 2
- 229910000160 potassium phosphate Inorganic materials 0.000 claims description 2
- 235000011009 potassium phosphates Nutrition 0.000 claims description 2
- UKDIAJWKFXFVFG-UHFFFAOYSA-N potassium;oxido(dioxo)niobium Chemical compound [K+].[O-][Nb](=O)=O UKDIAJWKFXFVFG-UHFFFAOYSA-N 0.000 claims description 2
- 239000001488 sodium phosphate Substances 0.000 claims description 2
- 229910000162 sodium phosphate Inorganic materials 0.000 claims description 2
- 235000011008 sodium phosphates Nutrition 0.000 claims description 2
- RYCLIXPGLDDLTM-UHFFFAOYSA-J tetrapotassium;phosphonato phosphate Chemical compound [K+].[K+].[K+].[K+].[O-]P([O-])(=O)OP([O-])([O-])=O RYCLIXPGLDDLTM-UHFFFAOYSA-J 0.000 claims description 2
- 229910052718 tin Inorganic materials 0.000 claims description 2
- RYFMWSXOAZQYPI-UHFFFAOYSA-K trisodium phosphate Chemical compound [Na+].[Na+].[Na+].[O-]P([O-])([O-])=O RYFMWSXOAZQYPI-UHFFFAOYSA-K 0.000 claims description 2
- 229910052720 vanadium Inorganic materials 0.000 claims description 2
- 238000004519 manufacturing process Methods 0.000 claims 2
- 239000005696 Diammonium phosphate Substances 0.000 claims 1
- 229910000388 diammonium phosphate Inorganic materials 0.000 claims 1
- 235000019838 diammonium phosphate Nutrition 0.000 claims 1
- 239000006012 monoammonium phosphate Substances 0.000 claims 1
- 230000008569 process Effects 0.000 abstract description 12
- 230000000694 effects Effects 0.000 abstract description 7
- 239000011159 matrix material Substances 0.000 abstract description 7
- 150000002500 ions Chemical class 0.000 abstract description 6
- 238000005580 one pot reaction Methods 0.000 abstract description 2
- 230000000052 comparative effect Effects 0.000 description 22
- 239000008367 deionised water Substances 0.000 description 21
- 229910021641 deionized water Inorganic materials 0.000 description 21
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 20
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 16
- 239000010410 layer Substances 0.000 description 13
- 238000005303 weighing Methods 0.000 description 10
- 230000005540 biological transmission Effects 0.000 description 9
- 230000014759 maintenance of location Effects 0.000 description 8
- 239000012299 nitrogen atmosphere Substances 0.000 description 8
- 238000006116 polymerization reaction Methods 0.000 description 7
- 239000007864 aqueous solution Substances 0.000 description 6
- 230000015572 biosynthetic process Effects 0.000 description 5
- 229910017052 cobalt Inorganic materials 0.000 description 5
- 239000010941 cobalt Substances 0.000 description 5
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 description 5
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 4
- 238000011065 in-situ storage Methods 0.000 description 4
- XGZVUEUWXADBQD-UHFFFAOYSA-L lithium carbonate Chemical compound [Li+].[Li+].[O-]C([O-])=O XGZVUEUWXADBQD-UHFFFAOYSA-L 0.000 description 4
- 229910052808 lithium carbonate Inorganic materials 0.000 description 4
- 229920000447 polyanionic polymer Polymers 0.000 description 4
- KMTRUDSVKNLOMY-UHFFFAOYSA-N Ethylene carbonate Chemical compound O=C1OCCO1 KMTRUDSVKNLOMY-UHFFFAOYSA-N 0.000 description 3
- 230000001276 controlling effect Effects 0.000 description 3
- -1 diamine hydrogen phosphate Chemical class 0.000 description 3
- 230000006872 improvement Effects 0.000 description 3
- 238000012986 modification Methods 0.000 description 3
- 230000004048 modification Effects 0.000 description 3
- 239000000047 product Substances 0.000 description 3
- 229910052596 spinel Inorganic materials 0.000 description 3
- 239000011029 spinel Substances 0.000 description 3
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- 229910019142 PO4 Inorganic materials 0.000 description 2
- 239000007983 Tris buffer Substances 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 239000007853 buffer solution Substances 0.000 description 2
- 239000013590 bulk material Substances 0.000 description 2
- 238000003763 carbonization Methods 0.000 description 2
- 230000015556 catabolic process Effects 0.000 description 2
- 239000010406 cathode material Substances 0.000 description 2
- 238000006731 degradation reaction Methods 0.000 description 2
- 238000009792 diffusion process Methods 0.000 description 2
- QHGJSLXSVXVKHZ-UHFFFAOYSA-N dilithium;dioxido(dioxo)manganese Chemical compound [Li+].[Li+].[O-][Mn]([O-])(=O)=O QHGJSLXSVXVKHZ-UHFFFAOYSA-N 0.000 description 2
- IEJIGPNLZYLLBP-UHFFFAOYSA-N dimethyl carbonate Chemical compound COC(=O)OC IEJIGPNLZYLLBP-UHFFFAOYSA-N 0.000 description 2
- XPPKVPWEQAFLFU-UHFFFAOYSA-J diphosphate(4-) Chemical compound [O-]P([O-])(=O)OP([O-])([O-])=O XPPKVPWEQAFLFU-UHFFFAOYSA-J 0.000 description 2
- 235000011180 diphosphates Nutrition 0.000 description 2
- 239000012528 membrane Substances 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 229910052757 nitrogen Inorganic materials 0.000 description 2
- 239000010452 phosphate Substances 0.000 description 2
- 239000002244 precipitate Substances 0.000 description 2
- 229940048084 pyrophosphate Drugs 0.000 description 2
- 239000002002 slurry Substances 0.000 description 2
- 238000003786 synthesis reaction Methods 0.000 description 2
- WSMQKESQZFQMFW-UHFFFAOYSA-N 5-methyl-pyrazole-3-carboxylic acid Chemical compound CC1=CC(C(O)=O)=NN1 WSMQKESQZFQMFW-UHFFFAOYSA-N 0.000 description 1
- 208000019901 Anxiety disease Diseases 0.000 description 1
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- 102000004310 Ion Channels Human genes 0.000 description 1
- 229910018119 Li 3 PO 4 Inorganic materials 0.000 description 1
- 229910010093 LiAlO Inorganic materials 0.000 description 1
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 description 1
- 239000002033 PVDF binder Substances 0.000 description 1
- 239000006230 acetylene black Substances 0.000 description 1
- 230000004913 activation Effects 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
- 229910003481 amorphous carbon Inorganic materials 0.000 description 1
- 230000036506 anxiety Effects 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- 239000000872 buffer Substances 0.000 description 1
- 239000003575 carbonaceous material Substances 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 125000004122 cyclic group Chemical group 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 239000002001 electrolyte material Substances 0.000 description 1
- 230000002708 enhancing effect Effects 0.000 description 1
- 239000012467 final product Substances 0.000 description 1
- 239000011888 foil Substances 0.000 description 1
- 238000005087 graphitization Methods 0.000 description 1
- 239000001307 helium Substances 0.000 description 1
- 229910052734 helium Inorganic materials 0.000 description 1
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- MRVHOJHOBHYHQL-UHFFFAOYSA-M lithium metaphosphate Chemical compound [Li+].[O-]P(=O)=O MRVHOJHOBHYHQL-UHFFFAOYSA-M 0.000 description 1
- 238000003760 magnetic stirring Methods 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- 238000010907 mechanical stirring Methods 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 229910021645 metal ion Inorganic materials 0.000 description 1
- 239000002120 nanofilm Substances 0.000 description 1
- 238000011056 performance test Methods 0.000 description 1
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 description 1
- 229920001690 polydopamine Polymers 0.000 description 1
- 229920002981 polyvinylidene fluoride Polymers 0.000 description 1
- 230000002035 prolonged effect Effects 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 239000007858 starting material Substances 0.000 description 1
- 239000002344 surface layer Substances 0.000 description 1
- 230000007704 transition Effects 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
- H01M4/50—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
-
- 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
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
- H01M4/624—Electric conductive fillers
- H01M4/625—Carbon or graphite
-
- 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
A lithium-rich Mn-based positive electrode material with a multifunctional homogeneous composite coating layer and a preparation method thereof are provided. The lithium-rich manganese-based positive electrode material comprises a lithium-rich manganese-based material and a homogeneous composite coating layer, and is characterized in that the homogeneous composite coating layer is composed of fast ion conductors and three-dimensional carbon grids, and the fast ion conductors are uniformly loaded in the three-dimensional carbon grids to be crossed and interconnected to form a homogeneous composite surface coating layer. Namely, the lithium-rich manganese-based positive electrode material loads a fast ion conductor with high lithium ion conduction efficiency in a high-conductivity three-dimensional carbon network to form specific continuous lithium ions and electron channels, so that the ion conduction and the electron conduction of the matrix material are synchronously improved, and meanwhile, the interface impedance is effectively reduced. In addition, the preparation method can obtain the homogeneous film by adopting one-step reaction, and has simple process flow, mild condition and outstanding effect.
Description
Technical Field
The application relates to the field of lithium ion batteries, in particular to a lithium-rich manganese-based positive electrode material with a multifunctional homogeneous composite coating layer and a preparation method thereof.
Background
Mileage anxiety, safety and cost are major bottlenecks restricting the technical development of electric automobiles, wherein the cathode material is an important influencing factor thereof.
The lithium-rich manganese-based positive electrode material is considered as the preferred positive electrode material of the next-generation high-specific-energy battery because of the advantages of high specific capacity (more than 250 mAh/g), low cost, good thermal stability and the like. The lithium-rich manganese-based positive electrode material is mainly environment-friendly manganese element, has low nickel and cobalt content, can not contain cobalt, and can effectively avoid the problem of nickel and cobalt resources, meanwhile, compared with cobalt and nickel, manganese is low in price and rich in reserves, according to the American geological survey data in 2015, the Chinese manganese ore reserves account for 7.7% of the global reserves, and nickel ore and cobalt ore respectively account for 3.7% and 1.1% of the global reserves.
However, the lithium ion diffusion coefficient of the lithium-rich material is low, which results in poor rate performance, and metal ions migrate during charge and discharge cycles, gradually change from a layered structure to a spinel structure, and further result in specific capacity and dischargeThe voltage decays stepwise. Studies show that the structural phase transition of the lithium-rich manganese-based material gradually extends from the surface layer to the bulk phase. Therefore, it is important to construct a stable surface structure, and a proper surface coating layer can not only provide a rapid transmission channel for lithium ions/electrons, but also isolate the direct contact between electrolyte and positive electrode materials, so as to avoid the degradation of battery performance due to the reaction of the electrolyte and the positive electrode materials. Like Li 3 PO 4 、Li 2 SO 4 、LiAlO 2 And the like, the lithium ion transmission efficiency is better, and the lithium ion transmission efficiency is also a popular coating material at present. However, the single-structure coating layer cannot improve the ion conductivity and the electron conductivity of the matrix material at the same time, so researchers have developed a series of multi-layer coatings.
Such as:
chinese patent application CN113308080a discloses a double-coated lithium-rich material, the coating layer of which is sequentially a lithium metaphosphate base and a vulcanized carbon layer, and the cycle performance and rate performance of the material are significantly improved.
Chinese patent application CN113078315a discloses a double-conductive-layer coated lithium-rich manganese-based material, whose structure is, from inside to outside, a lithium-rich core, a spinel lithium manganate coating layer and a nitrogen-doped graphitized carbon coating layer in order, wherein the spinel lithium manganate has a higher lithium ion transmission capability, and the nitrogen-doped graphitized carbon coating layer can effectively improve the electron transmission capability of the material, and the material has the characteristics of high capacity, high multiplying power and high cycle.
Although the above multi-layer coating can improve ion conductivity, electron conductivity or enhance interface stability, the increase of the coating layer means that the interface is increased, the interface resistance is increased, and in general, a single coating layer has only one attribute, that is, the single coating layer may block the transmission of electrons while improving the ion conductivity, and influence the conductivity, and vice versa, for example, the carbon layer has good conductivity, but the lithium ion transmission capability is relatively poor. In addition, the multi-layer coating also means that the synthesis process is more complex, the bonding strength between each coating layer is difficult to ensure, and the separation of the coating layer and the matrix material can occur along with the progress of the circulation process, so that the performance is deteriorated.
Therefore, a new lithium-rich manganese-based positive electrode material and a preparation method thereof are needed to solve the technical problems.
Disclosure of Invention
Therefore, the application provides a lithium-rich manganese-based positive electrode material with a multifunctional homogeneous composite coating layer and a preparation method thereof.
The application provides a lithium-rich manganese-based anode material with a multifunctional homogeneous composite coating layer, which comprises a lithium-rich manganese-based material and a surface coating layer and is characterized in that the homogeneous composite coating layer is composed of fast ion conductors and three-dimensional carbon grids, and the fast ion conductors are uniformly loaded in the three-dimensional carbon grids to be crossed and interconnected to form the homogeneous composite surface coating layer.
Wherein the chemical general formula of the lithium-rich manganese-based material is xLi 2 MnO 3 ·(1-x)LiMO 2 Wherein x is more than or equal to 0.1 and less than or equal to 0.9, and M is one or more of Ni, co, mn, cr, fe, ti, mo, ru, V, nb, zr and Sn.
Wherein the fast ion conductor is any one of lithium phosphate, lithium niobate and lithium pyrophosphate.
Wherein the thickness of the homogeneous composite coating layer is 5-50nm, and the content of the fast ion conductor is more than 0-10mol% of the content of the lithium-rich manganese-based material.
The application also provides a preparation method of the lithium-rich manganese-based positive electrode material with the multifunctional homogeneous composite coating layer, which is characterized by comprising the following steps of:
(1) Adding a certain amount of lithium-rich manganese-based material and tris (hydroxymethyl) aminomethane into deionized water to form a mixed solution A;
(2) Dissolving a certain amount of dopamine and coating raw materials in deionized water to form a solution B;
(3) Mixing the solution B and the solution A under the stirring condition to form a mixed solution C, regulating the pH value range of the mixed solution C to 8-10, preferably 8.5-9.5 by using acid, continuously stirring for 10-24 hours, and then filtering, washing and drying to obtain a solid D;
(4) And (3) placing the solid D in a sintering furnace, performing heat treatment in a protective atmosphere, and cooling to obtain the lithium-rich manganese-based anode material with the multifunctional surface coating layer.
Wherein in the step (3), the acid is hydrochloric acid.
In the step (1), the addition amount of the lithium-rich manganese-based material is such that the mass percentage of the lithium-rich manganese-based material in the mixed solution A is >0-10%, and the addition amount of the tris (hydroxymethyl) aminomethane) is such that the concentration of the tris (hydroxymethyl) aminomethane in the mixed solution A is 0-1mol/L.
In the step (2), the adding amount of the dopamine is controlled so that the mass ratio of the dopamine to the lithium-rich manganese-based material in the mixed solution A is more than 0-0.5.
In the step (2), the raw material of the coating comprises one or more of ammonium phosphate, diamine hydrogen phosphate, ammonium dihydrogen phosphate, potassium phosphate, sodium phosphate, potassium niobate, sodium niobate, potassium pyrophosphate and sodium pyrophosphate.
In the step (2), the raw materials of the coating are as follows: so that the ratio of the mole number of anions in the raw material of the coating to the mole number of the lithium-rich manganese-based material added in the mixed solution A in the step (1) is>0 to 0.1, more preferably 0.01 to 0.05, wherein the number of moles of anions in the starting material of the coating is the number of moles of acid groups, e.g. NaNbO for the coating 3 In the sense of NbO 3 - Calculated in moles for the coating NH 4 H 2 PO 4 In PO 4 6- Calculated in moles (mol).
In the step (3), the stirring mode is one or more of mechanical stirring and magnetic stirring, and the stirring temperature is room temperature.
In the step (4), the protective atmosphere includes a reducing atmosphere or an inert atmosphere, and may specifically be one of argon, helium, nitrogen and hydrogen.
Wherein in the step (4), the heat treatment condition is that the temperature is raised to 500-1000 ℃ at a heating rate of 3-10 ℃/min, and the temperature is kept for 3-15 hours.
The application also provides a lithium ion battery, which comprises a positive electrode, a negative electrode and an electrolyte, wherein the positive electrode comprises the lithium-rich manganese-based positive electrode material with the multifunctional homogeneous composite coating layer.
From the above, the technical scheme adopted by the application is as follows: adding a lithium-rich manganese-based material and tris (hydroxymethyl) aminomethane into deionized water, controlling the pH range of the mixed solution to 8-10, preparing an aqueous solution containing dopamine and a soluble coating raw material, uniformly mixing the two mixed solutions, continuously stirring, filtering, washing and drying after a certain time to form a solid C. And C is placed in a muffle furnace for heat treatment under protective atmosphere, so that the lithium-rich manganese-based anode material with the multifunctional homogeneous coating layer can be obtained.
The mechanism of the application is as follows: trace lithium carbonate remains on the surface of the lithium-rich manganese-based material, and when the material is placed in a polyanion aqueous solution, the surface lithium carbonate is dissolved, and the dissolved lithium ions and polyanion in the solution generate water-insoluble lithium fast ion conductors (lithium phosphate, lithium niobate, lithium tantalate, lithium pyrophosphate and the like) in situ. On the other hand, lithium carbonate is alkaline (pH > 8) when dissolved in aqueous solution, and dopamine can be polymerized on the surface of solid to form a polydopamine nano film when contacting air under the weak alkaline condition (pH > 8.5), and particularly, self-polymerization reaction is easier to occur in hydrochloric acid solution of tris. Adding dopamine into a polyanion-containing lithium-rich manganese-based material aqueous solution, controlling process conditions to enable formation of a lithium fast ion conductor and polymerization reaction of dopamine to be carried out synchronously, and forming a homogeneous lithium fast ion conductor/dopamine film on the surface of the lithium-rich manganese-based material. Furthermore, dopamine is used as a carbon source, heat treatment is carried out in protective atmosphere, the dopamine is carbonized to form a three-dimensional carbon network structure, and in-situ carbonization is beneficial to enhancing the bonding strength of the carbon network and the fast ion conductor as well as the carbon network and the matrix material.
Therefore, the application has the following beneficial technical effects:
(1) According to the application, a homogeneous composite coating layer is designed and constructed on the surface of a lithium-rich material, a fast ion conductor with high lithium ion conduction efficiency is loaded in a high-conductivity three-dimensional carbon network, a specific continuous lithium ion channel and an electron channel are formed, and as shown in a figure 1, the ion conduction and the electron conduction of a matrix material are synchronously improved. Compared with the conventional multilayer coating, the interface impedance is effectively reduced, and the problems of poor transmission capacity of electrons in a fast ion body coating layer and lithium ions in a conductive coating layer are avoided.
(2) The lithium-rich manganese-based material has trace lithium carbonate remained on the surface, lithium ions are dissolved in the aqueous solution and are alkaline, dopamine is polymerized to form a film when contacting air under the weak alkaline condition, dopamine and specific polyanion (which reacts with lithium to form a fast ion conductor insoluble substance) are simultaneously added into the aqueous solution of the lithium-rich material, and the formation of a fast ion conductor and the polymerization of the dopamine simultaneously occur by controlling the process conditions, so that a homogeneous and compact fast ion conductor/dopamine coating layer can be formed. The application combines the characteristics of lithium-rich manganese-based surface characteristics, dopamine properties, fast ion conductor properties and the like, and can obtain the homogeneous membrane by adopting one-step reaction, and the application has simple process flow, mild conditions and outstanding effect.
(3) The dopamine has multiple functions, firstly, a homogeneous film is formed on the surface of the lithium-rich manganese-based material by utilizing the self-polymerization reaction of the dopamine, then the homogeneous film is used as a carbon source, and the dopamine is carbonized into a three-dimensional amorphous carbon network structure through heat treatment of protective atmosphere, compared with the traditional coating process, the in-situ polymerization and in-situ carbonization can obviously improve the bonding strength of a coating layer and a matrix material, avoid the coating layer from falling off and performance degradation caused by uneven stress in the circulation process, obviously improve the circulation life of the material, and improve the 600-week capacity retention rate from 49% of the original material to 89.1% at most, and is better than 72.1-76.1% after the coating by the conventional process.
Brief description of the drawings
Fig. 1 is a schematic structural diagram of a lithium-rich manganese-based positive electrode material with a multifunctional homogeneous composite coating layer according to the present application.
Fig. 2 shows the first charge-discharge curves of the batteries prepared from the lithium-rich manganese-based positive electrode materials prepared in examples 1-2 and comparative example 1.
Fig. 3 shows the rate performance of batteries made from the lithium-rich manganese-based positive electrode materials prepared in examples 1-2 and comparative example 1.
Fig. 4 shows the cycle capacity retention rates of the batteries made from the lithium-rich manganese-based positive electrode materials prepared in examples 1-2 and comparative example 1.
Fig. 5 shows discharge medium voltage retention rates of batteries made from the lithium-rich manganese-based positive electrode materials prepared in examples 1-2 and comparative example 1.
Detailed Description
The present application will be described in further detail with reference to specific examples. It is to be understood that these examples are for illustration only and are not intended to limit the scope of the application. Further, it is understood that various changes and modifications may be made by those skilled in the art after reading the teachings of the present application, and such equivalents are intended to fall within the scope of the application as defined in the claims. The specific techniques or conditions are not identified in the examples and are described in the literature in this field or are carried out in accordance with the product specifications. The equipment and other manufacturers are not noted, and the conventional products can be purchased through regular channel providers. The chemical raw materials used in the application can be conveniently purchased in the domestic chemical product market.
Example 1
5g of lithium-rich manganese-based raw material autonomously synthesized by the company (number: GM5, molecular formula Li) 1.2 Mn 0.52 Ni 0.13 Co 0.13 O 2 ) Adding GM5 into 100mL deionized water to form a mixed solution A with the mass fraction of 5%, adding a certain amount of tris (hydroxymethyl) aminomethane into the mixed solution A to make the concentration of the tris (hydroxymethyl) aminomethane be 0.1mol/L, and uniformly stirring for later use; and (2) weighing a certain amount of dopamine and sodium niobate, dissolving the dopamine and sodium niobate in deionized water to form a solution B, enabling the mass ratio of the dopamine content in the solution B to the lithium-rich manganese-based material in the mixed solution A to be 0.2 and the mole number ratio of the niobate to the lithium-rich manganese-based material in the mixed solution A to be 0.028, mixing the mixed solution A and the solution B to form a mixed solution C, adding a proper amount of hydrochloric acid to regulate the pH value of the mixed solution C to be 8.5, stirring the mixed solution C for 15 hours at room temperature, filtering, washing and drying the mixed solution C to obtain a solid D with a lithium niobate and dopamine homogeneous coating layer, placing the solid D in a muffle furnace to be subjected to heat treatment in a nitrogen atmosphere, preserving the heat for 5 hours at 750 ℃, and cooling the solid D to the room temperature to obtain the lithium-rich manganese-based anode material containing the lithium niobate/carbon network composite homogeneous coating layer, namely the anode material 1.
Mixing the anode material 1, acetylene black, polyvinylidene fluoride and N-methyl pyrrolidone to form slurry, and uniformly coating the slurry on the surface of an aluminum foil sheet to obtain an anode sheet; and then, taking a lithium sheet as a negative electrode sheet, taking 1mol/L of Ethylene Carbonate (EC) and dimethyl carbonate (DMC) solution of lithium hexafluorophosphate (the volume ratio of EC to DMC is 1:1) as electrolyte, and assembling in a glove box to obtain the lithium ion battery.
The lithium ion battery was tested for cycle performance using an electrochemical tester at 25 ℃ and at a current density of 0.1C (1c=200 mAg -1 ) The first charge and discharge performance of the battery is tested within the charge and discharge voltage range of 4.8-2V. The rate performance of the cells was tested at 0.1C, 0.2C, 0.5C, 1C, 3C rates. The cycle performance was tested at 2.0-4.7V, after the first 0.1C activation, under a 1C/1C regime. The results are shown in tables 2-3.
Example 2
5g of lithium-rich manganese-based raw material autonomously synthesized by the company (number: GM5, molecular formula Li) 1.2 Mn 0.52 Ni 0.13 Co 0.13 O 2 ) Adding GM5 into 100mL deionized water to form a mixed solution A with the mass fraction of 5%, adding a certain amount of tris (hydroxymethyl) aminomethane into the mixed solution A to make the concentration of the tris (hydroxymethyl) aminomethane be 0.1mol/L, and uniformly stirring for later use; and (2) weighing a certain amount of dopamine and sodium pyrophosphate, dissolving in deionized water to form a solution B, enabling the mass ratio of the dopamine content in the solution B to the lithium-rich manganese-based material in the mixed solution A to be 0.2 and the mole number ratio of pyrophosphate to the lithium-rich manganese-based material in the mixed solution A to be 0.024, mixing the mixed solution A and the solution B to form a mixed solution C, adding a proper amount of hydrochloric acid to regulate the pH value of the mixed solution C system to be 8.5, stirring at room temperature for 15 hours, filtering, washing and drying the mixed solution C to obtain a solid matter D with a lithium pyrophosphate and dopamine homogeneous coating layer, placing the solid matter D in a muffle furnace to perform heat treatment in a nitrogen atmosphere, preserving heat for 5 hours at 750 ℃, and cooling to room temperature to obtain the lithium-rich manganese-based positive electrode material containing the lithium pyrophosphate/carbon network composite homogeneous coating layer, namely the positive electrode material 2.
Lithium ion batteries were prepared and tested for performance as described in example 1, with the results shown in tables 2-3.
Example 3
5g of lithium-rich manganese-based raw material autonomously synthesized by the company (number: GM5, molecular formula Li) 1.2 Mn 0.52 Ni 0.13 Co 0.13 O 2 ) Adding GM5 into 100mL deionized water to form a mixed solution A with the mass fraction of 5%, adding a certain amount of tris (hydroxymethyl) aminomethane into the mixed solution A to make the concentration of the tris (hydroxymethyl) aminomethane be 0.1mol/L, and uniformly stirring for later use; and (3) weighing a certain amount of dopamine and diamine hydrogen phosphate, dissolving in deionized water to form a solution B, enabling the mass ratio of the dopamine content in the solution B to the lithium-rich manganese-based material in the mixed solution A to be 0.2 and the mole ratio of phosphate radical to the lithium-rich manganese-based material in the mixed solution A to be 0.028, mixing the mixed solution A and the solution B to form a mixed solution C, adding a proper amount of hydrochloric acid to regulate the pH value of the mixed solution C to be 8.5, stirring at room temperature for 15 hours, filtering, washing and drying the mixed solution C to obtain a solid matter D with a lithium phosphate and dopamine homogeneous coating layer, placing the solid matter D in a muffle furnace to perform heat treatment in a nitrogen atmosphere, preserving heat for 5 hours at 750 ℃, and cooling to room temperature to obtain the lithium-rich manganese-based positive electrode material containing the lithium phosphate/carbon network composite homogeneous coating layer, and marking as the positive electrode material 3.
Lithium ion batteries were prepared and tested for performance as described in example 1, with the results shown in tables 2-3.
Example 4
5g of lithium-rich manganese-based raw material autonomously synthesized by the company (number: GM5, molecular formula Li) 1.2 Mn 0.52 Ni 0.13 Co 0.13 O 2 ) Adding GM5 into 100mL deionized water to form a mixed solution A with the mass fraction of 5%, and uniformly stirring for later use; weighing a certain amount of dopamine and sodium niobate, dissolving in deionized water to form a solution B, enabling the mass ratio of the dopamine content in the solution B to the lithium-rich manganese-based material in the mixed solution A to be 0.2 and the mole number ratio of the niobate to the lithium-rich manganese-based material in the mixed solution A to be 0.028, mixing the mixed solution A and the solution B to form a mixed solution C, adding a proper amount of hydrochloric acid to regulate the pH value of the mixed solution C system to be 8.5, stirring at room temperature for 15 hours, filtering, washing and drying the mixed solution C to obtain a solid D with a homogeneous coating layer of lithium niobate and dopamine, and placing the solid D in a muffle furnace to enter in a nitrogen atmospherePerforming heat treatment, preserving heat for 5 hours at 750 ℃, and cooling to room temperature to obtain the lithium-rich manganese-based positive electrode material containing the lithium niobate/carbon network composite homogeneous coating layer, which is denoted as positive electrode material 4.
Lithium ion batteries were prepared and tested for performance as described in example 1, with the results shown in tables 2-3.
Example 5
5g of lithium-rich manganese-based raw material autonomously synthesized by the company (number: GM5, molecular formula Li) 1.2 Mn 0.52 Ni 0.13 Co 0.13 O 2 ) Adding GM5 into 100mL deionized water to form a mixed solution A with the mass fraction of 5%, adding a certain amount of tris (hydroxymethyl) aminomethane into the mixed solution A to make the concentration of the tris (hydroxymethyl) aminomethane be 0.999mol/L, and uniformly stirring for later use; and (2) weighing a certain amount of dopamine and sodium niobate, dissolving the dopamine and sodium niobate in deionized water to form a solution B, enabling the mass ratio of the dopamine content in the solution B to the lithium-rich manganese-based material in the mixed solution A to be 0.2 and the mole number ratio of the niobate to the lithium-rich manganese-based material in the mixed solution A to be 0.028, mixing the mixed solution A and the solution B to form a mixed solution C, adding a proper amount of hydrochloric acid to regulate the pH value of the mixed solution C system to be 8.5, stirring the mixed solution C for 15 hours at room temperature, filtering, washing and drying the mixed solution C to obtain a solid D with a lithium niobate and dopamine homogeneous coating layer, placing the solid D in a muffle furnace to perform heat treatment in a nitrogen atmosphere, preserving the heat for 5 hours at 750 ℃, and cooling to the room temperature to obtain the lithium-rich manganese-based positive electrode material containing the lithium niobate/carbon network composite homogeneous coating layer, namely the positive electrode material 5.
Lithium ion batteries were prepared and tested for performance as described in example 1, with the results shown in tables 2-3.
Example 6
5g of lithium-rich manganese-based raw material autonomously synthesized by the company (number: GM5, molecular formula Li) 1.2 Mn 0.52 Ni 0.13 Co 0.13 O 2 ) Adding GM5 into 100mL deionized water to form a mixed solution A with the mass fraction of 5%, adding a certain amount of tris (hydroxymethyl) aminomethane into the mixed solution A to make the concentration of the tris (hydroxymethyl) aminomethane be 0.1mol/L, and uniformly stirring for later use; weighing a certain amount of dopamine and sodium niobate, dissolving in deionized water to form solution B, and making the dopamine content and the sodium niobate content in the solution BThe mass ratio of the lithium-rich manganese-based material in the mixed solution A is 0.5, the mole ratio of the niobate to the lithium-rich manganese-based material in the mixed solution A is 0.028, the mixed solution A and the solution B are mixed to form a mixed solution C, a proper amount of hydrochloric acid is added to regulate the pH value of the mixed solution C system to 8.5, the mixed solution C is stirred for 15 hours at room temperature, then the mixed solution C is filtered, washed and dried to obtain a solid D with a lithium niobate and dopamine homogeneous coating layer, the solid D is placed in a muffle furnace to be subjected to heat treatment in nitrogen atmosphere, the temperature is kept at 750 ℃ for 5 hours, and the solid D is cooled to the room temperature to obtain the lithium-rich manganese-based anode material containing the lithium niobate/carbon network composite homogeneous coating layer, which is denoted as an anode material 6.
Lithium ion batteries were prepared and tested for performance as described in example 1, with the results shown in tables 2-3.
Example 7
The heat treatment temperature of the solid C was raised to 1000℃and the other conditions were the same as in example 1.
Example 8
The heat treatment time of solid C was prolonged to 12 hours, and the other conditions were the same as in example 1.
Example 9
The pH of the mixed liquor C system was adjusted to 8, and the other conditions were the same as in example 1.
Example 10
The pH of the mixed liquor C system was adjusted to 10, and the other conditions were the same as in example 1.
Example 11
The amount of sodium niobate added to the solution B was changed to 0.91g, and the other conditions were the same as those in example 1.
Table 1 below further lists some of the key process parameters of examples 1-11.
Comparative example 1
The lithium-rich manganese-based positive electrode material with the number GM5 prepared by the synthesis technology of the company is directly used as a positive electrode material, and a lithium ion battery is prepared and tested according to the method described in example 1, and the results are shown in tables 2-3.
Comparative example 2
And (3) weighing a certain amount of sodium niobate, dissolving the sodium niobate in 100mL of deionized water to form a solution, adding 5g of raw material GM5 in the stirring process, ensuring that the molar ratio of niobate to GM material is 0.028, stirring for 5 hours, filtering the mixture, washing and drying the precipitate to obtain a solid D of a lithium niobate coating layer, placing the solid D in a muffle furnace, performing heat treatment in an air atmosphere, preserving heat for 5 hours at 750 ℃, and cooling to room temperature to obtain the lithium-rich manganese-based anode material containing the lithium niobate coating layer.
Comparative example 3
1g of dopamine is weighed and dissolved in 100mL of deionized water to form a solution, 5g of raw material GM5 is added in the stirring process, the solution is heated and stirred until the solution is completely evaporated to dryness to obtain a solid, the solid is placed in a muffle furnace to be subjected to heat treatment in a nitrogen atmosphere, the temperature is kept at 750 ℃ for 5 hours, and the lithium-rich manganese-based anode material with carbon coated on the surface is obtained after cooling to room temperature.
Comparative example 4
Weighing a certain amount of sodium niobate, dissolving in 100mL of deionized water to form a solution, adding 5g of original material GM5 in the stirring process to ensure that the molar ratio of niobate to GM material is 0.028, stirring for 5 hours, filtering the mixture, washing and drying the precipitate to obtain a solid C of a lithium niobate coating layer; adding the obtained solid C with the surface coated with lithium niobate and a certain amount of tris (hydroxymethyl) aminomethane into 100mL of deionized water to form a mixed solution A, wherein the concentration of tris (hydroxymethyl) aminomethane in the mixed solution A is 0.1mol/L, additionally weighing a certain amount of dopamine, adding the solution A into the mixed solution A, ensuring that the mass ratio of the added amount of the dopamine to the originally added GM5 material is 0.2, adding a proper amount of hydrochloric acid to regulate the pH value of a system to be 8.5, stirring at room temperature for 15 hours, then filtering, washing and drying to obtain a solid D with the inner layer of lithium niobate and the outer layer of dopamine multi-layer coating, placing the solid D into a muffle furnace, carrying out heat treatment in a nitrogen atmosphere, preserving heat for 5 hours at 750 ℃, and cooling to room temperature to obtain the lithium-rich manganese-based anode material with the inner layer coated with lithium niobate and the outer layer coated with carbon.
Comparative example 5
5g of lithium-rich manganese-based raw material autonomously synthesized by the company (number: GM5, molecular formula Li) 1.2 Mn 0.52 Ni 0.13 Co 0.13 O 2 ) Adding GM5 into 100mL deionized water to form a mixed solution A with the mass fraction of 5%, adding a certain amount of tris (hydroxymethyl) aminomethane into the mixed solution A to make the concentration of the tris (hydroxymethyl) aminomethane be 0.1mol/L, and uniformly stirring for later use; and (3) weighing a certain amount of dopamine and sodium niobate, dissolving the dopamine and sodium niobate in deionized water to form a solution B, enabling the mass ratio of the dopamine content in the solution B to the lithium-rich manganese-based material in the mixed solution A to be 0.2, enabling the mole ratio of niobate to the lithium-rich manganese-based material in the mixed solution A to be 0.028, mixing the solution A and the solution B to form a mixed solution C, adding a proper amount of hydrochloric acid to regulate the pH value of the mixed solution C system to be 11.5, stirring the mixed solution C for 15 hours at room temperature, filtering, washing and drying the mixed solution C to obtain a solid D, placing the solid D in a muffle furnace, carrying out heat treatment in a nitrogen atmosphere, preserving heat for 5 hours at 750 ℃, and cooling to the room temperature to obtain the lithium-rich manganese-based anode material containing the lithium niobate coating.
Lithium ion batteries were prepared and tested according to the method described in example 1, taking the lithium-rich manganese-based cathode materials prepared in examples 1 to 11 and comparative examples 1 to 5, and the results are shown in tables 2 and 3. In addition, fig. 2 to 5 show the first charge-discharge curves, rate capability, cycle capacity retention and discharge medium voltage retention of the batteries prepared from the lithium-rich manganese-based positive electrode materials prepared in examples 1 to 2 and comparative example 1.
TABLE 2 rate performance of batteries prepared in examples 1 to 11 and comparative examples 1 to 5
TABLE 3 cycle and discharge Medium Voltage maintenance Rate of batteries prepared in examples 1 to 11 and comparative examples 1 to 5
As can be seen from the performance test results of examples 1-3, when the raw material is one of soluble niobate, pyrophosphate and phosphate, the lithium-rich manganese-based anode material with the surface being the fast ion conductor/carbon network homogeneous coating layer can be obtained by adopting the method disclosed by the application, and compared with the raw material (comparative example 1), the initial coulombic efficiency, the multiplying power performance, the capacity retention rate and the voltage attenuation performance are comprehensively and obviously improved.
Example 4, which is a buffer solution without adding tris, has electrochemical properties slightly lower than that of example 1, but still significantly higher than that of the comparative example, shows that in the absence of buffer solution, a homogeneous dopamine/fast ion conductor membrane can be formed as long as the pH of the system is controlled within a suitable range. The above results indicate that buffer is an unnecessary condition for the present application, and that too high a concentration of tris (hydroxymethyl) aminomethane further affects the film forming effect and electrochemical properties, and it can be seen from example 5 that the specific capacity and the cycle properties are reduced to some extent.
In the application, the addition of the dopamine serving as a carbon source is directly related to the thickness of the coating layer of the final product, and excessive addition can cause the thickness of the carbon network structure to exceed an optimal value, so that the lithium ion transmission efficiency can be affected, and the electrochemical performance can be reduced to a certain extent in embodiment 6.
Examples 7 and 8 demonstrate that the heat treatment temperature and time are also critical factors affecting the homogeneous coating structure and the overall material properties, and that a high temperature and a long time on the one hand can lead to a high graphitization degree of the carbon network structure, and on the other hand can lead to the diffusion of elements in the fast ion conductor into the matrix material, and finally all affect the material properties, and that a moderate increase in temperature can lead to a further increase in the material cycle properties.
Examples 9-10 show that the polymerization of dopamine and the generation of fast ionic conductors can occur within the system pH range of 8-10, and the system has a certain performance improvement effect, but when the improvement effect is worse than pH=8.5, the cyclic capacity retention rate and the voltage retention rate are lower than those of example 1, but are obviously higher than those of the original materials and the comparative examples
Example 11 shows that if the amount of the raw material for the coating is too much, the molar ratio of the raw material for the coating to the lithium-rich manganese-based material in this example is 0.095, approaching the upper limit of the present application, but rather affecting the performance improvement effect may be caused by the fact that lithium is derived from the bulk material when the fast ion conductor is formed, and if the lithium loss of the bulk material is too much, the structure is deteriorated, thereby affecting the performance.
Comparative example 1 was an uncoated GM5 raw material, comparative example 2 was a single-clad lithium niobate fast ion conductor, comparative example 3 was a single-clad carbon material, comparative example 4 was a multilayer clad structure with an inner layer of lithium niobate and an outer layer of carbon network, and comparative example 5 had a pH too high to allow polymerization and film formation of dopamine, and it can be seen from tables 2 and 3 that the electrochemical properties of comparative examples 1 to 5 were significantly inferior to those of examples.
It is apparent that the above examples are given by way of illustration only and are not limiting of the embodiments. Other variations or modifications of the above teachings will be apparent to those of ordinary skill in the art. It is not necessary here nor is it exhaustive of all embodiments. While still being apparent from variations or modifications that may be made by those skilled in the art are within the scope of the application.
Claims (10)
1. The lithium-rich manganese-based positive electrode material with the multifunctional homogeneous composite coating layer comprises a lithium-rich manganese-based material and the homogeneous composite coating layer, and is characterized in that the homogeneous composite coating layer is composed of fast ion conductors and three-dimensional carbon grids, and the fast ion conductors are uniformly loaded in the three-dimensional carbon grids to be crossed and interconnected to form a homogeneous composite surface coating layer;
the preparation method of the lithium-rich manganese-based positive electrode material comprises the following steps of:
(1) Adding a certain amount of lithium-rich manganese-based material and tris (hydroxymethyl) aminomethane into water to form a mixed solution A;
(2) Dissolving a certain amount of dopamine and coating raw materials in water to form a solution B;
(3) Under the stirring condition, mixing the solution B and the solution A to form a mixed solution C, regulating the pH value range of the mixed solution C to 8-10 by using acid, stirring for a certain time, and then filtering, washing and drying to obtain a solid D;
(4) And (3) placing the solid D in a sintering furnace, performing heat treatment in a protective atmosphere, and cooling to obtain the lithium-rich manganese-based anode material with the multifunctional homogeneous composite coating layer.
2. The lithium-rich manganese-based positive electrode material according to claim 1, wherein the lithium-rich manganese-based material has a chemical formula of xLi 2 MnO 3 ·(1-x)LiMO 2 Wherein x is more than or equal to 0.1 and less than or equal to 0.9, and M is one or more of Ni, co, mn, cr, fe, ti, mo, ru, V, nb, zr and Sn; the fast ion conductor is any one of lithium phosphate, lithium niobate and lithium pyrophosphate.
3. The lithium-rich manganese-based positive electrode material according to claim 1 or 2, wherein the thickness of the homogeneous composite coating layer is 5-50nm, and the fast ion conductor content is 2.4-10 mol% of the lithium-rich manganese-based material content.
4. A method for preparing a lithium-rich manganese-based positive electrode material having a multifunctional homogeneous composite coating layer as set forth in any one of claims 1 to 3, comprising the steps of:
(1) Adding a certain amount of lithium-rich manganese-based material and tris (hydroxymethyl) aminomethane into water to form a mixed solution A;
(2) Dissolving a certain amount of dopamine and coating raw materials in water to form a solution B;
(3) Under the stirring condition, mixing the solution B and the solution A to form a mixed solution C, regulating the pH value range of the mixed solution C to 8-10 by using acid, stirring for a certain time, and then filtering, washing and drying to obtain a solid D;
(4) And (3) placing the solid D in a sintering furnace, performing heat treatment in a protective atmosphere, and cooling to obtain the lithium-rich manganese-based anode material with the multifunctional homogeneous composite coating layer.
5. The method for producing a lithium-rich manganese-based positive electrode material according to claim 4, wherein in the step (1), the lithium-rich manganese-based material is added in an amount such that the mass percentage of the lithium-rich manganese-based material in the mixed solution A is 5 to 10%, and the tris (hydroxymethyl) aminomethane is added in an amount such that the concentration thereof in the mixed solution A is 0 to 1mol/L.
6. The method for producing a lithium-rich manganese-based positive electrode material according to claim 4, wherein in the step (2), the addition amount of the dopamine is controlled so that the mass ratio of the dopamine to the lithium-rich manganese-based material in the mixed solution a is 0.2 to 0.5.
7. The method for preparing a lithium-rich manganese-based positive electrode material according to claim 4, wherein in the step (2), the coating material comprises one or more of ammonium phosphate, diammonium phosphate, monoammonium phosphate, potassium phosphate, sodium phosphate, potassium niobate, sodium niobate, potassium pyrophosphate, and sodium pyrophosphate.
8. The method for preparing a lithium-rich manganese-based positive electrode material according to claim 4, wherein in the step (2), the coating material is used in an amount of: so that the ratio of the mole number of anions in the raw material of the coating to the mole number of the lithium-rich manganese-based material added in the mixed solution A in the step (1) is 0.01-0.1.
9. The method for preparing a lithium-rich manganese-based positive electrode material according to claim 4, wherein in the step (4), the heat treatment temperature is 500 to 1000 ℃.
10. A lithium ion battery comprising a positive electrode, a negative electrode and an electrolyte, wherein the positive electrode comprises the lithium-rich manganese-based positive electrode material with a multifunctional homogeneous composite coating layer as claimed in any one of claims 1-3.
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