CN114551862B - Cobalt-free binary single crystal material and preparation method thereof - Google Patents
Cobalt-free binary single crystal material and preparation method thereof Download PDFInfo
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- 239000000463 material Substances 0.000 title claims abstract description 94
- 239000013078 crystal Substances 0.000 title claims abstract description 45
- 238000002360 preparation method Methods 0.000 title claims abstract description 25
- 238000005245 sintering Methods 0.000 claims abstract description 57
- 239000002131 composite material Substances 0.000 claims abstract description 28
- 238000000034 method Methods 0.000 claims abstract description 27
- 229910052726 zirconium Inorganic materials 0.000 claims abstract description 27
- WMFOQBRAJBCJND-UHFFFAOYSA-M Lithium hydroxide Chemical compound [Li+].[OH-] WMFOQBRAJBCJND-UHFFFAOYSA-M 0.000 claims abstract description 24
- 239000002243 precursor Substances 0.000 claims abstract description 24
- 229910052721 tungsten Inorganic materials 0.000 claims abstract description 23
- QCWXUUIWCKQGHC-UHFFFAOYSA-N Zirconium Chemical compound [Zr] QCWXUUIWCKQGHC-UHFFFAOYSA-N 0.000 claims abstract description 17
- 238000005253 cladding Methods 0.000 claims abstract description 17
- 229910044991 metal oxide Inorganic materials 0.000 claims abstract description 12
- 150000004706 metal oxides Chemical class 0.000 claims abstract description 12
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims abstract description 11
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 claims abstract description 11
- 239000010937 tungsten Substances 0.000 claims abstract description 11
- 229910052782 aluminium Inorganic materials 0.000 claims abstract description 10
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 claims abstract description 7
- 229910052723 transition metal Inorganic materials 0.000 claims abstract description 6
- 238000007670 refining Methods 0.000 claims abstract description 5
- 239000000126 substance Substances 0.000 claims abstract description 5
- 239000000047 product Substances 0.000 claims description 26
- 238000000576 coating method Methods 0.000 claims description 15
- 239000011248 coating agent Substances 0.000 claims description 14
- 229910052760 oxygen Inorganic materials 0.000 claims description 12
- 239000001301 oxygen Substances 0.000 claims description 12
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 11
- 238000002156 mixing Methods 0.000 claims description 10
- 239000006185 dispersion Substances 0.000 claims description 9
- 239000000843 powder Substances 0.000 claims description 7
- 238000004519 manufacturing process Methods 0.000 claims description 5
- 229910052751 metal Inorganic materials 0.000 claims description 5
- 239000002184 metal Substances 0.000 claims description 5
- 239000012467 final product Substances 0.000 claims description 4
- 229910017052 cobalt Inorganic materials 0.000 abstract description 21
- 239000010941 cobalt Substances 0.000 abstract description 21
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 abstract description 20
- 239000007774 positive electrode material Substances 0.000 abstract description 13
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 abstract description 3
- 229910052744 lithium Inorganic materials 0.000 abstract description 3
- 230000000052 comparative effect Effects 0.000 description 22
- 230000008569 process Effects 0.000 description 11
- PXHVJJICTQNCMI-UHFFFAOYSA-N nickel Substances [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 10
- 239000002245 particle Substances 0.000 description 7
- 238000004321 preservation Methods 0.000 description 6
- 229910052759 nickel Inorganic materials 0.000 description 5
- 238000000227 grinding Methods 0.000 description 4
- 239000000203 mixture Substances 0.000 description 4
- 229910013716 LiNi Inorganic materials 0.000 description 3
- 239000010405 anode material Substances 0.000 description 3
- 239000010406 cathode material Substances 0.000 description 3
- 238000010438 heat treatment Methods 0.000 description 3
- 230000006872 improvement Effects 0.000 description 3
- 239000002994 raw material Substances 0.000 description 3
- 230000009467 reduction Effects 0.000 description 3
- 230000007547 defect Effects 0.000 description 2
- 238000011161 development Methods 0.000 description 2
- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical compound [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 description 2
- 229910003002 lithium salt Inorganic materials 0.000 description 2
- 159000000002 lithium salts Chemical class 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 238000011160 research Methods 0.000 description 2
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 1
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 description 1
- 208000012868 Overgrowth Diseases 0.000 description 1
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 1
- 235000011114 ammonium hydroxide Nutrition 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 238000000975 co-precipitation Methods 0.000 description 1
- 238000006731 degradation reaction Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000010304 firing Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-M hydroxide Chemical compound [OH-] XLYOFNOQVPJJNP-UHFFFAOYSA-M 0.000 description 1
- 230000002401 inhibitory effect Effects 0.000 description 1
- 230000000977 initiatory effect Effects 0.000 description 1
- 230000002427 irreversible effect Effects 0.000 description 1
- 229910001416 lithium ion Inorganic materials 0.000 description 1
- 229910052748 manganese Inorganic materials 0.000 description 1
- 231100000252 nontoxic Toxicity 0.000 description 1
- 230000003000 nontoxic effect Effects 0.000 description 1
- -1 oxygen anions Chemical class 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 238000012827 research and development Methods 0.000 description 1
- 230000000087 stabilizing effect Effects 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 238000012360 testing method Methods 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
- 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
- H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
- H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Abstract
The application relates to the technical field of lithium battery materials, and discloses a cobalt-free binary single crystal material and a preparation method thereof. The preparation method comprises the following steps: the method comprises the steps of sequentially carrying out pre-cladding sintering, refining treatment, cladding metal oxide and post-cladding sintering on a mixed material containing cobalt-free binary precursor, lithium hydroxide and composite doping elements; the chemical formula of the cobalt-free binary precursor is Ni x Mn 1‑x (OH) 2 X is more than or equal to 0.6 and less than or equal to 1.0, the molar ratio of lithium element to transition metal element in cobalt-free binary precursor in the mixed material is 1.03-1.05:1, the composite doping element comprises zirconium, aluminum and tungsten with the mass ratio of 4:2.5-3.5:5.5-6.5, and zirconium accounts for 1-3 per mill of the total mass of the mixed material. The cobalt-free binary single crystal material is prepared by adopting the method. The preparation method can prepare the cobalt-free binary single crystal material with performance being comparable to that of the cobalt-containing ternary positive electrode material in the same series, and the cobalt-free material has low cost.
Description
Technical Field
The application relates to the technical field of lithium battery materials, in particular to a cobalt-free binary single crystal material and a preparation method thereof.
Background
As the power battery is turned from the lithium iron phosphate battery dominated by commercial vehicles to the ternary battery of passenger vehicles, starting in 2018, the power battery industry has more than 80% of enterprises which are originally dominated by lithium iron phosphate batteries begin to lay out routes to the ternary battery. From the market share ratio situation of different types of ternary materials in China in recent years, the market share ratio of high-nickel low-cobalt or cobalt-free materials is gradually increased, and the ternary materials are the positive electrode materials with the most application prospects.
Currently, cobalt ores are scarce, the price is getting higher, and the improvement of nickel content and the reduction of cobalt content are the necessary trend of the research and development of high-specific-energy power batteries. The cobalt-free high-nickel anode material is known to be high in specific capacity, low in cost, nontoxic and environment-friendly, and is one of candidate anode materials of future lithium ion batteries. However, the current cobalt-free high-nickel anode material has poor cycle stability and safety performance, and limits the commercialization process. Therefore, the research on cobalt-free positive electrode materials with high capacity and safety performance is significant, and the research is also the development direction of comprehensive consideration of cost and capacity performance.
The cobalt-free layered cathode material is a material which does not contain cobalt element but only Ni and Mn elements, and can be expressed as LiNi in general formula x Mn y O 2 (x is more than 0 and less than 1, y is more than 0 and less than 1, and x+y=1) when the layered binary material is, generally, x is more than or equal to 0.5, y is less than or equal to 0.5, and common cobalt-free binary materials are NM9010, NM8020, NM5050 and the like. Compared with NCM ternary materials, the current NM binary materials have the following advantages: 1. the NM binary material has certain advantages in raw material cost because of no cobalt element; 2. the literature reports that NM binary materials are slightly better than NCM ternary materials in terms of safety. The main disadvantages of the current NM binary materials are represented by: 1. the multiplying power, circulation and capacity performance of the material are generally inferior to those of NCM positive electrode materials, so that the process of doping, coating, crushing and the like is required to be optimized more carefully. 2. The current NM materials are still in the development stage, and knowledge of the material structure and direction of improvement are still in the exploration stage.
In view of this, the present application has been made.
Disclosure of Invention
The application aims to provide a preparation method of a cobalt-free binary single crystal material and the cobalt-free binary single crystal material.
The application is realized in the following way:
in a first aspect, the application provides a method for preparing a cobalt-free binary single crystal material, comprising the following steps:
the method comprises the steps of sequentially carrying out pre-cladding sintering, refining treatment, cladding metal oxide and post-cladding sintering on a mixed material containing cobalt-free binary precursor, lithium hydroxide and composite doping elements;
the chemical formula of the cobalt-free binary precursor is Ni x Mn 1-x (OH) 2 X is more than or equal to 0.6 and less than or equal to 1.0, the molar ratio of lithium element in the mixed material to transition metal element in the cobalt-free binary precursor is 1.03-1.05:1, and the composite doping element comprises the following components in mass ratio of 4:2.5-3.5:5.56.5 of zirconium, aluminum and tungsten, wherein the zirconium accounts for 1 to 3 per mill of the total mass of the mixed material.
In an alternative embodiment, the pre-cladding sintering includes primary sintering, uniform dispersion, and secondary sintering, the uniform dispersion being a mixture of the primary sintering products uniformly dispersed.
In an alternative embodiment, the uniform dispersion mode is that the product after primary sintering is placed in a mixer, the rotating speed is set to be 250-350 rpm, the mixing is carried out for 4-6 min, then the rotating speed is set to be 500-700 rpm, and the mixing is carried out for 20-30 min.
In an alternative embodiment, the primary sintering is carried out in the presence of oxygen, the pressure in the furnace is 5-20 Pa, the temperature is 450-650 ℃ and the time is 4-7 hours;
preferably, the atmosphere of the primary sintering is an air atmosphere or an oxygen atmosphere.
In an alternative embodiment, the secondary sintering is performed in an environment with an oxygen concentration of greater than 95% at a furnace pressure of 5 to 20Pa, a temperature of 850 to 950 ℃ and a time of 10 to 14 hours.
In an alternative embodiment, the metal oxide is at least one of Mg, al, zn, ti, cr, W and an oxide of Zr;
preferably, the metal in the metal oxide accounts for 2 to 3 per mill of the mass of the final product.
In an alternative embodiment, the pressure in the sintering furnace after cladding is 5-20 Pa, the temperature is 450-600 ℃ and the time is 5-8 h;
preferably, the three-time sintering atmosphere is an air atmosphere.
In an alternative embodiment, the refinement process is: the sintered product before coating is coarsely crushed to a grain diameter not larger than 3mm, and then the coarsely crushed product is finely crushed into powder with a grain diameter of 3.2+/-0.3 mu m.
In an alternative embodiment, the coarse crushing is to crush the secondary sintering product in jaw and then to pair rollers, the gap between the pair rollers is 1-3 mm, the fine crushing is to grind the secondary sintering product by adopting air flow, the air pressure of a grinding body is 0.4-0.5 MPa, and the frequency of a classifying wheel is 130-160 Hz.
In a second aspect, the present application provides a cobalt-free binary single crystal material prepared by a method according to any one of the preceding embodiments.
The application has the following beneficial effects:
in the process of preparing the cobalt-free binary single crystal material, due to the addition of proper amounts of composite doping elements of zirconium, aluminum and tungsten, the three elements play roles from different angles in reasonable proportion, so that the prepared cobalt-free binary single crystal material has better capacity, first-circle coulomb efficiency and cycle performance under the condition of no cobalt, and can be matched with the cobalt-containing same-series ternary positive electrode material. The preparation method provided by the application greatly reduces the manufacturing cost because the preparation raw materials do not contain cobalt.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present application more clear, the technical solutions of the embodiments of the present application will be clearly and completely described below. The specific conditions are not noted in the examples and are carried out according to conventional conditions or conditions recommended by the manufacturer. The reagents or apparatus used were conventional products commercially available without the manufacturer's attention.
The inventor finds that the related prior art also records the preparation of cobalt-free binary materials at present, but all have certain defects, so that the prepared product has obviously poorer performance than a cobalt-containing ternary positive electrode material, and the main aspects are as follows:
1. cobalt is important for the positive electrode material of the battery, and the lack of cobalt can lead to unstable crystal lattice of the material, resulting in capacity reduction and poor cycle rate performance.
2. The solubility of hydroxide precipitation of excessive elements is different when the precursor is prepared, ammonia water must be used to control co-precipitation, if one or more elements are doped in the precursor, the precursor preparation is difficult, and the material cost is increased.
3. The precursor and the lithium salt are directly sintered, so that the contact area of the lithium salt and the precursor is reduced, and the primary grain growth is uneven.
4. When coating a metal oxide without a firing treatment (air flow mill control of particle size), coating may be uneven.
In view of the above problems found by the inventors, the cobalt-free binary single crystal material and the preparation method thereof of the present application are provided.
The cobalt-free binary single crystal material and the preparation method thereof provided by the application are specifically described below.
The preparation method of the cobalt-free binary single crystal material provided by the embodiment of the application comprises the following steps:
the method comprises the steps of sequentially carrying out pre-cladding sintering, refining treatment, cladding metal oxide and post-cladding sintering on a mixed material containing cobalt-free binary precursor, lithium hydroxide and composite doping elements;
the chemical formula of the cobalt-free binary precursor is Ni x Mn 1-x (OH) 2 X is more than or equal to 0.6 and less than or equal to 1.0, the molar ratio of lithium element to transition metal element in cobalt-free binary precursor in the mixed material is 1.03-1.05:1 (for example, 1.03:1 or 1.06:1), the composite doping element comprises zirconium, aluminum and tungsten with the mass ratio of 4:2.5-3.5:5.5-6.5 (for example, 4:2.5:6.5, 4:3:6 or 4:3.5:5.5), and zirconium accounts for 1-3 per mill (for example, 1 per mill, 2 per mill or 3 per mill) of the total mass of the mixed material.
The cobalt-free binary single crystal material has unstable crystal structure, which can lead to the problems of capacity reduction and poor cycle rate performance, and zirconium in the composite doping element can play a role in stabilizing the crystal structure of the material (inhibiting Mn) 3+ Is produced according to the following steps); aluminum in the composite doping element increases the cycle performance of the material (since Al is only Al 3+ The average valence state of Mn is improved; tungsten in the composite doping element has fluxing effect to promote grain growth, increase c/a value and improve Li + And the transmission rate stabilizes oxygen anions and inhibits oxygen loss of the positive electrode material in a charged state. The three elements are doped into the binary single crystal material in reasonable proportion to perform the cooperation from different angles, so that the problems of unstable structure, low initial effect, small capacity and poor circularity caused by the lack of cobalt in the material can be effectively solved. In particular, the contents and proportions of the three elements are required to be within the proper range of the application, and if the contents and proportions are not within the range of the application, the following situations may occur: 1. assuming that the zirconium element is excessively doped, overgrowth of grains is caused, so that Li + Difficulty in drag and embedding, increased impedance, reduced capacity, etcThe method comprises the steps of carrying out a first treatment on the surface of the 2. Assuming that the aluminum element is excessively doped, al 3+ Substitution of too much transition metal element may result in capacity degradation (refer to lower capacity to NCM ratio for NCA-like materials); 3. if the tungsten element is excessively doped, the crystal lattice is easy to generate irreversible change in the circulation process, and the problems of reduced circulation performance, increased material cost and the like are caused. The preparation method of the cobalt-free binary single crystal material provided by the application does not use cobalt element, greatly reduces the manufacturing cost, and can solve the defect caused by the existence of cobalt-free binary single crystal material by adding the composite doping element, so that the preparation method provided by the application has low cost, and the cobalt-free binary single crystal material with capacity, initial coulomb efficiency and cycle performance equivalent to those of a cobalt-containing ternary positive electrode material can be prepared.
The preparation method provided by the application specifically comprises the following steps:
s1, preparing a mixed material
Adding the cobalt-free binary precursor, lithium hydroxide and the composite doping element into a high-speed mixer for uniform mixing to obtain a mixed material.
The chemical formula of the cobalt-free binary precursor is Ni x Mn 1-x (OH) 2 ，0.6≤x≤1.0。
Considering that lithium element can volatilize and lose in the sintering process, the lithium content is slightly increased during the batching, and lithium hydroxide and a cobalt-free binary precursor are added according to the molar ratio (Li/TM) of the lithium element in the mixed material to the transition metal element in the cobalt-free binary precursor of 1.03-1.05:1.
The composite doping element comprises zirconium, aluminum and tungsten with the mass ratio of 4:2.5-3.5:5.5-6.5, and the composite doping element is added according to the mass ratio of 1-3 per mill of the zirconium element in the total mass.
S2, one-time sintering
The mixed materials are placed in an atmosphere box-type furnace to be sintered once in oxygen atmosphere or air atmosphere, the pressure (gauge pressure) in the furnace is 5Pa to 20Pa, the temperature is 450 ℃ to 650 ℃ (for example, 450 ℃, 500 ℃, 550 ℃, 600 ℃ or 650 ℃), and the time is 4h to 7h (for example, 4h, 5h, 6h or 7 h).
S3, uniformly dispersing the primary sintering product
Because the sintering process can not achieve the identical sintering degree of each part of the mixed material, the products after primary sintering are placed in a mixer to ensure that the primary sintering products are uniformly mixed and dispersed, and the problem that the non-uniform sintering degree of each part causes non-uniform grain growth in the subsequent sintering process is avoided.
Preferably, the uniform dispersion process is carried out at a low rotation speed of 250-350 rpm (e.g. 250rpm, 300rpm or 350 rpm), mixing for 4-6 min (e.g. 4min, 5min or 6 min), and then at a high rotation speed of 500-700 rpm (e.g. 500rpm, 600rpm or 700 rpm), mixing for 20-30 min (e.g. 20min, 25min or 30 min) to ensure uniform dispersion of the primary sintered product.
The product is uniformly dispersed after primary sintering, so that the uniform growth of crystal grains in the subsequent sintering process can be effectively ensured, and the monocrystalline material with good performance is obtained.
S4, secondary sintering
The uniformly dispersed primary sintered product is placed in an atmosphere box furnace to be sintered in an environment with the oxygen concentration of more than 95%, the pressure (gauge pressure) in the furnace is 5-20 Pa, the temperature is 850-950 ℃ (for example, 850 ℃, 900 ℃ or 950 ℃), and the time is 10-14 h (for example, 10h, 11h, 12h or 14 h).
S5, refining treatment
The sintered product before coating is coarsely crushed to a grain diameter not larger than 3mm, and then the coarsely crushed product is finely crushed into powder with a grain diameter of 3.2+/-0.3 mu m. The method specifically comprises the following steps:
sequentially carrying out jaw breaking on the secondary sintering product, then carrying out twin rollers, wherein the gap between the twin rollers is 1-3 mm (for example, 1mm, 2mm or 3 mm) to obtain particles with the particle size not more than 3mm, then carrying out fine crushing on the obtained particles by adopting an air flow mill, wherein the air pressure (gauge pressure) of a grinding body is 0.4-0.5 MPa (for example, 0.4MPa or 0.5 MPa), and the frequency of a classifying wheel is 130-160 Hz (for example, 130Hz, 140Hz or 160 Hz) to obtain powder with the particle size of 3.2+/-0.3 mu m.
The coarse crushing and fine crushing are carried out, so that the particle size of the powder before coating is strictly controlled, and the uniform coating can be ensured.
S6, coating
And (5) coating the metal oxide on the powder obtained in the step S5 by adopting a conventional coating process.
Specifically, the metal oxide is at least one of Mg, al, zn, ti, cr, W and an oxide of Zr. Preferably, the metal in the metal oxide comprises 2 to 3 (e.g. 2 or 3) per mill of the mass of the final product.
S7, sintering after coating
And (3) placing the product after the S6 coating in an atmosphere box-type furnace to sinter under the air atmosphere, wherein the pressure (gauge pressure) in the furnace is 5-20 Pa, the temperature is 450-600 ℃ (e.g. 450 ℃, 500 ℃ or 600 ℃), and the sintering time is 5-8 h (e.g. 5h, 7h or 8 h). And sintering to obtain the cobalt-free binary single crystal material.
The cobalt-free binary single crystal material provided by the embodiment of the application is prepared by adopting the preparation method provided by the embodiment of the application.
The features and capabilities of the present application are described in further detail below in connection with the examples.
Example 1
(1) Ni as binary cobalt-free precursor 0.75 Mn 0.25 (OH) 2 And placing the lithium hydroxide and the composite doping element into a high-speed mixer, and uniformly mixing to obtain a mixed material. Li/TM=1.03 in the lithium hydroxide and cobalt-free binary precursor, wherein the mass ratio of Zr, al and W in the composite doping element is 4:3:6, and the added composite doping element takes Zr as a base line, and the Zr accounts for 1 per mill of the mass content of the mixed material.
(2) And (3) sintering the mixture in an atmosphere box furnace for one time, wherein the sintering atmosphere is air, the temperature of a heat preservation area is 550 ℃, the heating rate is 3 ℃/min, and the heat preservation time is 6 hours.
(3) Placing the materials sintered at one time (presintered) in a high-speed mixer, setting the rotating speed to 300rpm, mixing for 5min, setting the rotating speed to 600rpm, and mixing for 25min to uniformly disperse the materials.
(4) Placing the dispersed materials in an atmosphere box-type furnace for secondary sintering, wherein the temperature of a heat preservation area is 890 ℃, the heating rate is 3 ℃/min, the sintering atmosphere is oxygen, the oxygen concentration is more than 95%, and the heat preservation time is 12h;
(5) Coarse crushing and fine crushing are carried out on the secondary sintering material, jaw crushing and roller pair are sequentially carried out on the coarse crushing, the roller pair clearance is 2mm, air flow grinding is adopted for fine crushing, the air pressure of a grinding body is 0.4-0.5 Pa, and the frequency of a classifying wheel is 130, so that powder with the particle size of 3.2+/-0.3 mu m is obtained.
(6) Coating metal nano oxide Al 2 O 3 Coating according to the mass of Al metal accounting for 2 per mill of the final product.
(7) Sintering the alumina-coated material for three times under the condition that the sintering atmosphere is air, the temperature of a heat preservation area is 550 ℃, the heating rate is 3 ℃/min, and the heat preservation time is 8 hours, thereby finally obtaining the product LiNi 0.75 Mn 0.25 O 2 。
Example 2
This embodiment is substantially the same as embodiment 1, except that: zr accounts for 2 per mill of the mass of the mixture.
Example 3
This embodiment is substantially the same as embodiment 1, except that: zr accounts for 3 per mill of the mass of the mixture.
Example 4
This embodiment is substantially the same as embodiment 1, except that: the mass ratio of Zr, al and W is 4:2.5:6.5.
Example 5
This embodiment is substantially the same as embodiment 1, except that: the mass ratio of Zr, al and W is 4:3.5:5.5.
Example 6
This embodiment is substantially the same as embodiment 1, except that: after primary sintering, the primary sintering product is not uniformly dispersed and is directly subjected to secondary sintering.
Comparative example 1
This embodiment is substantially the same as embodiment 1, except that: no composite doping element is added.
Comparative example 2
This comparative example is substantially the same as example 1, except that: the added composite doping element takes zirconium as a base line, and Zr accounts for 5 per mill of the mass of the mixed material.
Comparative example 3
This comparative example is substantially the same as example 1, except that: the mass ratio of Zr, al and W elements is 4:1:6.
Comparative example 4
This comparative example is substantially the same as example 1, except that: the mass ratio of Zr, al and W elements is 4:5:6.
Comparative example 5
This comparative example is substantially the same as example 1, except that: the mass ratio of Zr, al and W elements is 4:3:4.
Comparative example 6
This comparative example is substantially the same as example 1, except that: the mass ratio of Zr, al and W elements is 4:3:8.
Comparative example 7
This comparative example is substantially the same as example 1, except that: the mass ratio of Zr, al and W elements is 2:3:6.
Comparative example 8
This comparative example is substantially the same as example 1, except that: the mass ratio of Zr, al and W elements is 6:3:6.
Comparative example 9
Ternary cathode material LiNi 0.75 Co 0.05 Mn 0.2 O 2 。
Experimental example
The positive electrode materials of examples 1 to 6 and comparative examples 1 to 9 were tested for performance. The results are recorded in the following table.
Table 1 Properties of Positive electrode materials of each Experimental group
As can be seen from the table, the cobalt-free binary single crystal material prepared by the embodiment of the application has better initial efficiency, capacity and circularity. Comparing each example with comparative example 1, the capacity and cycle of the composite element doped with the composite element are greatly improved, which shows that the capacity and cycle performance of the composite element doped can be greatly improved. Compared with the embodiment 1 and the embodiment 6, the embodiment 1 is dispersed and then sintered for the second time by introducing the same doped composite element, so that the growth of the precursor crystal grains is more uniform, and the capacity and the cycle performance of the embodiment 6 are improved compared with those of the embodiment 6. As can be seen from examples 1 to 3, when the mass content of Zr is 1 to 3% by weight, the capacity and the cycle performance are linearly increased with the increase of Zr element, but when the mass content reaches 3% by weight, the capacity and the cycle are reduced to some extent, so that 3% by weight is the upper limit value. From the test results of examples 1-3, it can be seen that the binary cobalt-free material can be almost comparable in capacity and cycle to the same series of ternary single crystal positive electrode materials (containing cobalt element) by adding the composite doping element and performing the primary sintering dispersion process. As can be seen by comparing example 1 with comparative example 2, the material properties of comparative example 2 are significantly inferior to example 1, indicating that it is not possible to obtain a product with properties close to those of the cobalt-containing co-series when the content of the complex doping element is outside the range required by the present application; comparing the positive electrode materials prepared in comparative examples 3 to 8, in which the contents of zirconium, aluminum and tungsten are not within the scope of the present application, are significantly worse than those prepared in comparative examples 3 to 8, indicating that the contents of zirconium, aluminum and tungsten in the composite doping element should be within the scope of the present application, and if they are not within the scope of the present application, materials having properties close to those of cobalt-containing co-series products cannot be prepared.
In summary, in the preparation method of the cobalt-free binary single crystal material, due to the fact that the appropriate amount of composite doping elements zirconium, aluminum and tungsten are added in the preparation process of the cobalt-free binary single crystal material, the three elements play roles in different angles in reasonable proportion, and the prepared cobalt-free binary single crystal material can have better capacity, first-circle coulomb efficiency and cycle performance under the condition of no cobalt, and can be matched with cobalt-containing same-series ternary cathode materials. The preparation method provided by the application greatly reduces the manufacturing cost because the preparation raw materials do not contain cobalt.
The cobalt-free binary single crystal material provided by the application is prepared by adopting the preparation method provided by the application, so that the material has better performance and low cost.
The above is only a preferred embodiment of the present application, and is not intended to limit the present application, but various modifications and variations can be made to the present application by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the protection scope of the present application.
Claims (11)
1. The preparation method of the cobalt-free binary single crystal material is characterized by comprising the following steps of:
the method comprises the steps of sequentially carrying out pre-cladding sintering, refining treatment, cladding metal oxide and post-cladding sintering on a mixed material containing cobalt-free binary precursor, lithium hydroxide and composite doping elements;
the chemical formula of the cobalt-free binary precursor is Ni x Mn 1-x (OH) 2 X is more than or equal to 0.6 and less than or equal to 1.0, the molar ratio of lithium element in the mixed material to transition metal element in the cobalt-free binary precursor is 1.03-1.05:1, the composite doping element comprises zirconium, aluminum and tungsten in a mass ratio of 4:2.5-3.5:5.5-6.5, and zirconium accounts for 1-3 per mill of the total mass of the mixed material;
the refinement treatment is as follows: the sintered product before coating is coarsely crushed to a grain diameter not larger than 3mm, and then the coarsely crushed product is finely crushed into powder with a grain diameter of 3.2+/-0.3 mu m.
2. The method for preparing a cobalt-free binary single crystal material according to claim 1, wherein the pre-cladding sintering comprises primary sintering, uniform dispersion and secondary sintering, and the uniform dispersion is to uniformly disperse the primary sintering product.
3. The method for preparing the cobalt-free binary single crystal material according to claim 2, wherein the uniform dispersion mode is that a product after primary sintering is placed in a mixer, the rotation speed is set to be 250-350 rpm, the mixing speed is set to be 4-6 min, then the rotation speed is set to be 500-700 rpm, and the mixing speed is set to be 20-30 min.
4. The method for preparing the cobalt-free binary single crystal material according to claim 2, wherein the primary sintering is performed in an environment in which oxygen exists, the pressure in a furnace is 5-20 Pa, the temperature is 450-650 ℃, and the time is 4-7 hours.
5. The method for producing a cobalt-free binary single crystal material according to claim 4, wherein the atmosphere of primary sintering is an air atmosphere or an oxygen atmosphere.
6. The method for preparing the cobalt-free binary single crystal material according to claim 2, wherein the secondary sintering is performed in an environment with an oxygen concentration of more than 95%, wherein the pressure in a furnace is 5-20 Pa, the temperature is 850-950 ℃, and the time is 10-14 h.
7. The method for producing a cobalt-free binary single crystal material according to any one of claims 1 to 6, wherein the metal oxide is at least one of Mg, al, zn, ti, cr, W and Zr oxide.
8. The method for preparing a cobalt-free binary single crystal material according to claim 7, wherein the metal in the metal oxide accounts for 2-3 per mill of the mass of the final product.
9. The method for preparing a cobalt-free binary single crystal material according to any one of claims 1 to 6, wherein the pressure in a sintering furnace after cladding is 5 to 20Pa, the temperature is 450 to 600 ℃ and the time is 5 to 8 hours.
10. The method for preparing cobalt-free binary single crystal material according to claim 7, wherein,
the sintering atmosphere after cladding is air atmosphere.
11. A cobalt-free binary single crystal material, characterized in that it is prepared by the preparation method according to any one of claims 1 to 10.
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