CN116387492A - Co-coated modified cathode material, preparation method thereof and lithium ion battery - Google Patents
Co-coated modified cathode material, preparation method thereof and lithium ion battery Download PDFInfo
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- 238000002360 preparation method Methods 0.000 title claims abstract description 23
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 title claims abstract description 18
- 229910001416 lithium ion Inorganic materials 0.000 title claims abstract description 18
- 239000010406 cathode material Substances 0.000 title claims description 60
- 239000007774 positive electrode material Substances 0.000 claims abstract description 100
- 239000000463 material Substances 0.000 claims abstract description 52
- 239000011247 coating layer Substances 0.000 claims abstract description 37
- 239000011248 coating agent Substances 0.000 claims abstract description 32
- 239000011159 matrix material Substances 0.000 claims abstract description 28
- 238000000576 coating method Methods 0.000 claims abstract description 23
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims abstract description 19
- 239000001301 oxygen Substances 0.000 claims abstract description 19
- 229910052760 oxygen Inorganic materials 0.000 claims abstract description 19
- 238000002156 mixing Methods 0.000 claims abstract description 8
- 239000010405 anode material Substances 0.000 claims abstract description 7
- 229910052712 strontium Inorganic materials 0.000 claims abstract description 3
- 238000004519 manufacturing process Methods 0.000 claims abstract 6
- 238000010304 firing Methods 0.000 claims description 19
- KGBXLFKZBHKPEV-UHFFFAOYSA-N boric acid Chemical compound OB(O)O KGBXLFKZBHKPEV-UHFFFAOYSA-N 0.000 claims description 13
- 239000004327 boric acid Substances 0.000 claims description 13
- 229910052782 aluminium Inorganic materials 0.000 claims description 12
- 239000000126 substance Substances 0.000 claims description 12
- MULYSYXKGICWJF-UHFFFAOYSA-L cobalt(2+);oxalate Chemical compound [Co+2].[O-]C(=O)C([O-])=O MULYSYXKGICWJF-UHFFFAOYSA-L 0.000 claims description 9
- RXSHXLOMRZJCLB-UHFFFAOYSA-L strontium;diacetate Chemical compound [Sr+2].CC([O-])=O.CC([O-])=O RXSHXLOMRZJCLB-UHFFFAOYSA-L 0.000 claims description 9
- 150000001875 compounds Chemical class 0.000 claims description 6
- 238000000354 decomposition reaction Methods 0.000 claims description 5
- 238000000034 method Methods 0.000 claims description 5
- 239000003792 electrolyte Substances 0.000 abstract description 17
- 238000006243 chemical reaction Methods 0.000 abstract description 3
- 230000002349 favourable effect Effects 0.000 abstract description 3
- 238000005265 energy consumption Methods 0.000 abstract 1
- 230000000052 comparative effect Effects 0.000 description 53
- 238000012360 testing method Methods 0.000 description 20
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 19
- 239000000843 powder Substances 0.000 description 19
- 238000005253 cladding Methods 0.000 description 13
- 229910052759 nickel Inorganic materials 0.000 description 12
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 11
- 229910052744 lithium Inorganic materials 0.000 description 11
- 230000014759 maintenance of location Effects 0.000 description 11
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 10
- 239000011888 foil Substances 0.000 description 10
- -1 lithium hexafluorophosphate Chemical compound 0.000 description 10
- 238000007873 sieving Methods 0.000 description 10
- 230000000694 effects Effects 0.000 description 9
- 229910052751 metal Inorganic materials 0.000 description 7
- 239000002184 metal Substances 0.000 description 7
- 239000002245 particle Substances 0.000 description 7
- 238000010438 heat treatment Methods 0.000 description 6
- 239000010410 layer Substances 0.000 description 5
- 239000000758 substrate Substances 0.000 description 5
- 239000000203 mixture Substances 0.000 description 4
- 230000001681 protective effect Effects 0.000 description 4
- 230000002195 synergetic effect Effects 0.000 description 4
- 229910013716 LiNi Inorganic materials 0.000 description 3
- 238000012512 characterization method Methods 0.000 description 3
- 229910013184 LiBO Inorganic materials 0.000 description 2
- 230000002411 adverse Effects 0.000 description 2
- MORCTKJOZRLKHC-UHFFFAOYSA-N lithium;oxoboron Chemical compound [Li].O=[B] MORCTKJOZRLKHC-UHFFFAOYSA-N 0.000 description 2
- BAEKJBILAYEFEI-UHFFFAOYSA-N lithium;oxotungsten Chemical class [Li].[W]=O BAEKJBILAYEFEI-UHFFFAOYSA-N 0.000 description 2
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 description 1
- 229910021503 Cobalt(II) hydroxide Inorganic materials 0.000 description 1
- MYMOFIZGZYHOMD-UHFFFAOYSA-N Dioxygen Chemical compound O=O MYMOFIZGZYHOMD-UHFFFAOYSA-N 0.000 description 1
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 229910052796 boron Inorganic materials 0.000 description 1
- ASKVAEGIVYSGNY-UHFFFAOYSA-L cobalt(ii) hydroxide Chemical compound [OH-].[OH-].[Co+2] ASKVAEGIVYSGNY-UHFFFAOYSA-L 0.000 description 1
- 238000009831 deintercalation Methods 0.000 description 1
- 229910001882 dioxygen Inorganic materials 0.000 description 1
- 238000004146 energy storage Methods 0.000 description 1
- 238000000445 field-emission scanning electron microscopy Methods 0.000 description 1
- 239000000446 fuel Substances 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- BDAGIHXWWSANSR-NJFSPNSNSA-N hydroxyformaldehyde Chemical compound O[14CH]=O BDAGIHXWWSANSR-NJFSPNSNSA-N 0.000 description 1
- 238000009830 intercalation Methods 0.000 description 1
- 230000002687 intercalation Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000011056 performance test Methods 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 238000005245 sintering Methods 0.000 description 1
- 235000002639 sodium chloride Nutrition 0.000 description 1
- 239000011780 sodium chloride Substances 0.000 description 1
- 239000007858 starting material Substances 0.000 description 1
- 229910000018 strontium carbonate Inorganic materials 0.000 description 1
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/362—Composites
- H01M4/366—Composites as layered products
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- 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
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
- H01M4/485—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy
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- 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
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- H01—ELECTRIC ELEMENTS
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- 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
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- 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
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- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
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Abstract
The invention discloses a co-coating modified positive electrode material, a preparation method thereof and a lithium ion battery, wherein the co-coating modified positive electrode material can be used for manufacturing the lithium ion battery and comprises a positive electrode material matrix and a coating layer coated on the surface of the positive electrode material matrix, and the coating layer comprises MB 2 O 4 M is at least one of Sr and Co; the preparation method comprises the following steps: (1) Mixing a positive electrode material matrix and a coating agent to obtain a mixed material; (2) Roasting the mixed material for a set time under the condition of introducing oxygen. The positive electrode material has stable surface, and is favorable for relieving the surface of the positive electrode materialThe phenomenon of being corroded by electrolyte improves the electrochemical performance of the anode material, and the preparation method is simple, easy and convenient to operate, mild in reaction condition, low in preparation energy consumption and low in cost, and is suitable for large-scale industrialized production.
Description
Technical Field
The invention relates to the field of positive electrode materials of lithium ion batteries, in particular to a co-cladding modified positive electrode material, a preparation method thereof and a lithium ion battery using the positive electrode material.
Background
The lithium ion battery is widely applied to the fields of 3C, EV and electric energy storage nowadays, and has the advantages of high energy density, high working voltage, long cycle time, small occupied space and the like, so that the lithium ion battery has great advantages in application compared with a nickel-hydrogen battery and a fuel battery, and becomes an indispensable functional application in the life of mankind nowadays.
The positive electrode material of the lithium ion battery is an important component, and the performance of the positive electrode material determines the final performance of the lithium ion battery. Today, with the demand for high energy density for lithium ion batteries, high nickel ternary cathode materials are the preferred choice. However, although the high-nickel ternary material has the advantage of high energy density, the surface structure is unstable in the circulation process, electrolyte is easy to erode the surface of the material, so that the surface structure is declined and converted to a rock salt phase, and the adverse effects of rapid energy attenuation, increased impedance, reduced circulation life and the like are caused.
The prior art generally adopts a coating process to improve the problems, wherein the coating process is to form a coating layer on the surface of the high-nickel ternary material, and the method not only can reduce the residual lithium on the surface, but also can isolate the surface of the high-nickel ternary material from electrolyte to avoid contact between the surface and the electrolyte, thereby further improving the electrochemical performance of the high-nickel material. Some studies have shown that the B-containing coating has good effect on high nickel ternary materials, for example, CN115440952A discloses the use of a boron-containing substance LiBO on the surface of ternary cathode materials 2 、Li 2 B 4 O 7 、Li 3 BO 3 And H 3 BO 3 The technical proposal for sintering and coating is that the coating layer formed by the proposal contains LiBO 2 , Li 2 B 4 O 7 Can effectively reduceThe impedance of lithium ions transmitted at the grain boundary is improved cooperatively, so that the efficiency of lithium ion intercalation and deintercalation is improved cooperatively, and the stability of the ternary positive electrode material is improved effectively; for another example, CN114079043a discloses a double-clad structure of a lithium tungsten oxide layer and a lithium boron oxide layer to improve the high-temperature cycle performance of a lithium ion battery. However, the improvement of the high-temperature cycle performance of the single coating layer containing the B element is limited, the double coating layers of the lithium tungsten oxide layer and the lithium boron oxide layer are mutually independent, the coating structure components are not uniform, the synergistic advantage is difficult to develop, and the maximization of the improvement effect of the coating layer on the battery performance cannot be realized.
Disclosure of Invention
The invention provides a co-cladding modified positive electrode material and a preparation method thereof, which are used for solving the technical problems of limited effect on improving high-temperature cycle performance and non-uniformity of cladding components of the existing positive electrode material cladding layer.
In order to solve the technical problems, the invention adopts the following technical scheme:
a co-coating modified positive electrode material comprises a positive electrode material matrix and a coating layer coated on the surface of the positive electrode material matrix, wherein the coating layer comprises MB 2 O 4 M is at least one of Sr and Co.
The invention introduces another specific coating element M into the coating layer on the basis of the conventional coating process containing B element, selects the compound containing the element M with lower decomposition temperature to react with boric acid in a synergistic way at low temperature, and retains the effects of M and B to form MB 2 O 4 The coating layer has higher mechanical strength, can protect particles, is favorable for relieving the phenomenon that the surface of the positive electrode material is corroded by electrolyte, improves the cycle performance, is uniform in composition, can exert the synergistic advantage of each element to the greatest extent, ensures that the surface of the positive electrode material, particularly the ternary positive electrode material with high nickel content is more stable, and obviously improves the electrochemical performance of the positive electrode material from multiple aspects.
As a further preferable mode of the technical scheme, the mass of the coating layer is 1% -4% of the total mass of the co-coated modified cathode material. The coating layer with the quality ratio too low cannot form effective protection on the anode material; too high a coating mass ratio increases the possibility of unreacted starting materials remaining, thereby affecting the electrochemical performance of the cathode material.
As a further preferable aspect of the above-described technical solution, the positive electrode material matrix has a chemical formula of Li a Ni x Mn y Co z M’ b O 2 Wherein, the element M' is one or more of Al, ti, mg, ba, ca, zr, ta, nb, mo, a is more than or equal to 0.9 and less than or equal to 1.1, b is more than or equal to 0 and less than or equal to 0.1, x is more than or equal to 0.5 and less than or equal to 1.0, y is more than or equal to 0 and less than or equal to 0.5, z is more than or equal to 0 and less than or equal to 0.5, and x+y+z+b=1. Because the surface structure of the high-nickel ternary positive electrode material is unstable in the circulating process, electrolyte is easy to erode the surface of the material, and adverse effects such as rapid energy attenuation, increased impedance, reduced circulating life and the like are easily caused, the performance improving effect of the coating layer of the invention on the high-nickel ternary positive electrode material is more obvious compared with other positive electrode materials.
Based on the same technical conception, the invention also provides a preparation method of the co-cladding modified cathode material, which comprises the following steps:
(1) Mixing the positive electrode material matrix with a coating agent to obtain a mixed material, wherein the coating agent comprises boric acid and a compound containing M element;
(2) And roasting the mixed material at 280-320 ℃ for a set time under the condition of introducing oxygen to obtain the co-coated modified anode material.
As a further preferable aspect of the above technical solution, the decomposition temperature of the coating agent is lower than 400 ℃. The decomposition temperature of the coating agent (the temperature at which the compound starts to decompose during the temperature increase at atmospheric pressure) is MB 2 O 4 One of the important effects of coating layer formation is that too high a decomposition temperature of the coating agent will result in MB 2 O 4 The difficulty in forming the coating layer is increased, and the expected protective effect on the cathode material cannot be obtained.
As a further preferable aspect of the above technical scheme, the compound containing M element includes at least one of strontium acetate and cobalt oxalate.
As a further preferable aspect of the above technical solution, the molar ratio of M to B in the coating agent is (0.1 to 1): 2; more preferably, the molar ratio of M to B in the coating agent is (0.1 to 0.5): 2.
as a further preferable mode of the technical scheme, the roasting temperature in the step (2) is 300 ℃, and the roasting time is 4-12 hours.
As a further preferable mode of the technical scheme, the oxygen gas inlet flow rate in the step (2) is 10-60 mL/min.
Based on the same technical conception, the invention also provides a lithium ion battery, and the positive electrode material of the lithium ion battery is the co-cladding modified positive electrode material according to the technical scheme or the co-cladding modified positive electrode material prepared by the preparation method according to the technical scheme.
Compared with the prior art, the invention has the advantages that:
(1) The invention introduces another specific coating element M on the basis of the coating layer of the positive electrode material containing B element, thereby ensuring the capacity improvement effect after the B element is coated on one hand and forming MB on the basis 2 O 4 The coating layer has higher mechanical strength, can effectively protect particles, relieves the breakage of the particles in the charge and discharge process, improves the cycle performance, maximizes the synergistic advantage of each element, ensures that the surface of the positive electrode material is more stable, is favorable for relieving the phenomenon that the surface of the positive electrode material is corroded by electrolyte, and improves the electrochemical performance, particularly the high-temperature cycle performance, of the positive electrode material;
(2) The preparation method of the co-coated modified cathode material of the invention preferably selects the coating agents with low-temperature decomposable coating raw materials on one hand, and designs the roasting temperature in the coating process to be about 300 ℃ on the other hand, thereby ensuring the smooth preparation of the cathode material with the coating layer of the specific component.
Drawings
FIG. 1 is an XRD contrast pattern of the co-coated modified cathode material of example 1 and the cathode material of comparative example 1;
FIG. 2 is an XRD contrast pattern of the co-coated modified cathode material of example 2 and the cathode material of comparative example 1;
FIG. 3 is an XRD contrast pattern of the co-coated modified cathode material of example 3 and the cathode material of comparative example 1;
fig. 4 is an XFE-SEM comparison of the cathode material of comparative example 1 and the co-coated modified cathode materials of examples 1, 2, and 3.
Detailed Description
The present invention will be described in further detail with reference to specific examples.
Example 1
The co-coated modified cathode material of the embodiment comprises a cathode material matrix and a coating layer coated on the surface of the cathode material matrix, wherein the chemical formula of the coating layer is SrB 2 O 4 The positive electrode material matrix selects a high nickel ternary positive electrode material, and the chemical formula of the positive electrode material matrix is LiNi 0.9 Mn 0.05 Co 0.04 Y 0.01 O 2 The mass of the coating layer is 2% of that of the co-coating modified cathode material. XRD characterization contrast of the Co-coated modified cathode Material of this example and the cathode Material of comparative example 1 As shown in FIG. 1, it can be confirmed by combining FIG. 1 with the XRDpdf Standard card that the Co-coated modified cathode Material of this example has a SrB as the main component 2 O 4 。
The preparation method of the co-cladding modified cathode material comprises the following steps:
(1) 500 g of positive electrode material matrix, 2.86 g of boric acid powder and 1.17 g of strontium acetate powder are taken and added into a wall breaking machine for mechanical mixing, so as to obtain a mixed material.
(2) The mixed material was placed in a firing bowl, the firing bowl was placed in a box furnace, and the temperature was raised to 300℃at a rate of 1℃per minute under the oxygen-introducing condition (oxygen-introducing flow rate: 60 ml/min), and the reaction was maintained for 8 hours.
(3) And taking out the materials after the temperature of the box-type furnace is naturally cooled to be lower than 150 ℃, and sieving the materials through a 300-mesh sieve to obtain the co-cladding modified anode material of the embodiment.
The positive electrode material of comparative example 1 and examples 1, 2 and 3The FE-SEM comparison of the co-coated modified cathode material is shown in fig. 4, and it can be observed in fig. 4 that the particle surface of the co-coated modified cathode material of this example has a significant coating substance. Because at a certain temperature strontium acetate can react with boric acid as follows: sr (C) 2 H 3 O 2 ) 2 +2xH 3 BO 3 →SrB 2x O 3x+1 +H 2 O+CO 2 。
The co-coated modified cathode material of this example was coated on an aluminum foil of a cathode current collector with metallic lithium as a negative electrode, lithium hexafluorophosphate as an electrolyte, and a separator was added and assembled into a button cell, and the button cell was subjected to an electrical property test at 25 ℃ using a blue electric test system, the results are shown in table 1, and the results show that the button cell prepared using the co-coated modified cathode material of this example had a first discharge capacity of 218.1mAh/g and a capacity retention of 95.5% after 50 cycles at high temperature, at 3.0-4.3V, which proves that the invention adopts SrB 2 O 4 After the coating layer coats the positive electrode material, the coating layer has a protective effect on the surface of the positive electrode material, and the cycle performance of the positive electrode material can be improved.
Example 2
The co-coated modified cathode material of the embodiment comprises a cathode material matrix and a coating layer coated on the surface of the cathode material matrix, wherein the chemical formula of the coating layer is SrB 2 O 4 The positive electrode material matrix selects a high nickel ternary positive electrode material, and the chemical formula of the positive electrode material matrix is LiNi 0.9 Mn 0.05 Co 0.04 Y 0.01 O 2 The mass of the coating layer is 3% of the mass of the co-coating modified cathode material. As can be confirmed by combining the XRD characterization comparison patterns of the co-coated modified cathode material of this example and the cathode material of comparative example 1 shown in FIG. 2 with the standard card of XRDpdf, the co-coated modified cathode material of this example has a coating material of CoB as the main component 2 O 4 。
The preparation method of the co-cladding modified cathode material comprises the following steps:
(1) 500 g of positive electrode material matrix, 2.86 g of boric acid powder and 1.55 g of cobalt oxalate powder are taken and added into a wall breaking machine for mechanical mixing, so as to obtain a mixed material.
(2) The mixed material was placed in a firing bowl, the firing bowl was placed in a box furnace, and the temperature was raised to 320℃at a rate of 1℃per minute under oxygen introduction (oxygen introduction flow rate: 60 ml/min), and the temperature was maintained for 4 hours.
(3) And taking out the materials after the temperature of the box-type furnace is naturally cooled to be lower than 150 ℃, and sieving the materials through a 300-mesh sieve to obtain the co-cladding modified anode material of the embodiment.
As can be seen in fig. 4, the particle surface of the co-coated modified cathode material of this example has a significant coating substance. Because at a certain temperature, cobalt oxalate can react with boric acid as follows: coC (CoC) 2 O 4 +H 3 BO 3 →CoB 2 O 4 +H 2 O+CO 2 。
The co-coated modified cathode material of this example was coated on an aluminum foil of a cathode current collector with metallic lithium as a negative electrode, lithium hexafluorophosphate as an electrolyte, and a separator was added and assembled into a coin cell, and the above-mentioned coin cell was subjected to an electrical property test at 25 ℃ using a blue electric test system, the results are shown in table 1, and the results show that the coin cell prepared using the co-coated modified cathode material of this example had a first discharge capacity of 218.6mAh/g and a capacity retention of 95.3% after 50 cycles at high temperature, at 3.0-4.3V, which proves that the present invention adopts CoB 2 O 4 After the coating layer coats the positive electrode material, the coating layer has a protective effect on the surface of the positive electrode material, and the cycle performance of the positive electrode material can be improved.
Example 3
The co-coated modified cathode material of the embodiment comprises a cathode material matrix and a coating layer coated on the surface of the cathode material matrix, wherein the coating layer comprises SrB 2 O 4 And CoB 2 O 4 The positive electrode material matrix selects a high nickel ternary positive electrode material, and the chemical formula of the positive electrode material matrix is LiNi 0.9 Mn 0.05 Co 0.04 Y 0.01 O 2 The mass of the coating layer is the mass of the co-coated modified cathode material2%. As can be confirmed by combining the XRD characterization comparison patterns of the co-coated modified cathode material of this example and the cathode material of comparative example 1 shown in FIG. 3 with the standard card of FIG. 3 and XRDpdf, the main component of the co-coated modified cathode material of this example is SrB 2 O 4 And CoB 2 O 4 。
The preparation method of the co-cladding modified cathode material comprises the following steps:
(1) 500 g of positive electrode material matrix, 2.86 g of boric acid powder, 0.59 g of strontium acetate powder and 0.78 g of cobalt oxalate powder are taken, added into a wall breaking machine, and mechanically mixed to obtain a mixed material.
(2) The mixed material was placed in a firing bowl, the firing bowl was placed in a box furnace, and the temperature was raised to 280℃at a rate of 1℃per minute under oxygen introduction (oxygen introduction flow rate: 60 ml/min), and the reaction was maintained for 12 hours.
(3) And taking out the materials after the temperature of the box-type furnace is naturally cooled to be lower than 150 ℃, and sieving the materials through a 300-mesh sieve to obtain the co-cladding modified anode material of the embodiment.
As can be seen in fig. 4, the particle surface of the co-coated modified cathode material of this example has a significant coating substance, because strontium acetate and cobalt oxalate can react with boric acid at a certain temperature.
The co-coated modified cathode material of this example was coated on an aluminum foil of a cathode current collector with metallic lithium as a negative electrode, lithium hexafluorophosphate as an electrolyte, and a separator was added and assembled into a button cell, and the electrical properties of the button cell were tested by using a blue electric test system at 25 ℃ as shown in table 1, and the results showed that the button cell prepared by using the co-coated modified cathode material of this example had a first discharge capacity of 220.7mAh/g and a capacity retention rate of 96.0% after 50 cycles at high temperature, and the results demonstrated that the invention adopted SrB at 3.0-4.3V 2 O 4 And CoB 2 O 4 After the coating layer coats the positive electrode material, the coating layer has a protective effect on the surface of the positive electrode material, and the cycle performance of the positive electrode material can be improved.
Comparative example 1
The preparation method of the positive electrode material of the comparative example comprises the following steps:
(1) 500 g of the positive electrode material substrate (consistent with example 1) was taken, placed in a pot, placed in a box furnace, and heated to 300℃at a rate of 1℃per minute under the oxygen-introducing condition (oxygen-introducing flow rate: 60 ml/min), and maintained for 8 hours.
(2) And taking out the materials after the temperature of the box-type furnace is naturally cooled to be lower than 150 ℃, and sieving the materials through a 300-mesh sieve to obtain the positive electrode material of the comparative example.
XRD testing was performed on the positive electrode material of this comparative example, and the results can be seen in FIGS. 1 to 3.
As shown in fig. 4, it can be observed that the surface of the positive electrode material particles of this comparative example is clean and smooth, without coating substances.
The positive electrode material of the comparative example was coated on a positive electrode current collector aluminum foil, and a metal lithium was used as a negative electrode, lithium hexafluorophosphate was used as an electrolyte, and a separator was added and assembled to form a coin cell, and the above-mentioned coin cell was subjected to an electrical property test using a blue electric test system at 25 deg.c, and the results are shown in table 1, and the results show that the coin cell prepared using the positive electrode material of the comparative example had a first discharge capacity of 213.3mAh/g and a capacity retention rate of 84.1% after 50 cycles at a high temperature.
Comparative example 2
The preparation method of the positive electrode material of the comparative example comprises the following steps:
(1) 500 g of a positive electrode material matrix (consistent with example 1) and 2.86 g of boric acid powder were taken and added to a wall breaking machine, and mechanical mixing was performed to obtain a mixed material.
(2) The mixed material is put into a firing pot, the firing pot is put into a box-type furnace, and the temperature is raised to 300 ℃ at a heating rate of 1 ℃/min under the condition of introducing oxygen (the oxygen introducing flow is 60 ml/min), and the temperature is kept for 8 hours.
(3) And taking out the materials after the temperature of the box-type furnace is naturally cooled to be lower than 150 ℃, and sieving the materials through a 300-mesh sieve to obtain the positive electrode material of the comparative example.
The positive electrode material of the comparative example was coated on a positive electrode current collector aluminum foil, and a metal lithium was used as a negative electrode, lithium hexafluorophosphate was used as an electrolyte, and a separator was added and assembled to form a coin cell, and the above-mentioned coin cell was subjected to an electrical property test using a blue electric test system at 25 deg.c, and the results are shown in table 1, and the results show that the coin cell prepared using the positive electrode material of the comparative example had a first discharge capacity of 220.5mAh/g and a capacity retention rate of 94.2% after 50 cycles at a high temperature.
Comparative example 3
The preparation method of the positive electrode material of the comparative example comprises the following steps:
(1) 500 g of a positive electrode material matrix (consistent with example 1) and 1.17 g of strontium acetate powder were taken and added to a wall breaking machine, and mechanical mixing was performed to obtain a mixed material.
(2) The mixed material is put into a firing pot, the firing pot is put into a box-type furnace, and the temperature is raised to 300 ℃ at a heating rate of 1 ℃/min under the condition of introducing oxygen (the oxygen introducing flow is 60 ml/min), and the temperature is kept for 8 hours.
(3) And taking out the materials after the temperature of the box-type furnace is naturally cooled to be lower than 150 ℃, and sieving the materials through a 300-mesh sieve to obtain the positive electrode material of the comparative example.
The positive electrode material of the comparative example was coated on a positive electrode current collector aluminum foil, and a metal lithium was used as a negative electrode, lithium hexafluorophosphate was used as an electrolyte, and a separator was added and assembled to form a coin cell, and the above-mentioned coin cell was subjected to an electrical property test using a blue electric test system at 25 deg.c, and the results are shown in table 1, and the results show that the coin cell prepared using the positive electrode material of the comparative example had a first discharge capacity of 215.3mAh/g and a capacity retention rate of 95.1% after 50 cycles at high temperature.
Comparative example 4
The preparation method of the positive electrode material of the comparative example comprises the following steps:
(1) 500 g of a positive electrode material substrate (consistent with example 1) and 1.55 g of cobalt oxalate powder were taken and added to a wall breaking machine, and mechanical mixing was performed to obtain a mixed material.
(2) The mixed material is put into a firing pot, the firing pot is put into a box-type furnace, and the temperature is raised to 300 ℃ at a heating rate of 1 ℃/min under the condition of introducing oxygen (the oxygen introducing flow is 60 ml/min), and the temperature is kept for 8 hours.
(3) And taking out the materials after the temperature of the box-type furnace is naturally cooled to be lower than 150 ℃, and sieving the materials through a 300-mesh sieve to obtain the positive electrode material of the comparative example.
The positive electrode material of the comparative example was coated on a positive electrode current collector aluminum foil, and a metal lithium was used as a negative electrode, lithium hexafluorophosphate was used as an electrolyte, and a separator was added and assembled to form a coin cell, and the above-mentioned coin cell was subjected to an electrical property test using a blue electric test system at 25 deg.c, and the results are shown in table 1, and the results show that the coin cell prepared using the positive electrode material of the comparative example had a first discharge capacity of 216.5mAh/g and a capacity retention rate of 94.8% after 50 cycles at a high temperature.
Comparative example 5
The preparation method of the positive electrode material of the comparative example comprises the following steps:
(1) 500 g of a positive electrode material substrate (consistent with example 1), 2.86 g of boric acid powder, 0.59 g of strontium acetate powder and 0.78 g of cobalt oxalate powder were taken, and added to a wall breaking machine to mechanically mix, thereby obtaining a mixed material.
(2) The mixed material is put into a firing pot, the firing pot is put into a box-type furnace, and the temperature is raised to 200 ℃ at a heating rate of 1 ℃/min under the condition of introducing oxygen (the oxygen introducing flow is 60 ml/min), and the temperature is kept for 8 hours.
(3) And taking out the materials after the temperature of the box-type furnace is naturally cooled to be lower than 150 ℃, and sieving the materials through a 300-mesh sieve to obtain the positive electrode material of the comparative example.
The positive electrode material of the comparative example was coated on a positive electrode current collector aluminum foil, and a metal lithium was used as a negative electrode, and lithium hexafluorophosphate was used as an electrolyte, and a separator was added and assembled to form a coin cell, and the above-mentioned coin cell was subjected to an electrical property test using a blue electric test system at 25 deg.c, and the results are shown in table 1, and the results show that the coin cell prepared using the positive electrode material of the comparative example had a first discharge capacity of 211.6mAh/g and a capacity retention rate of 92.1% after 50 cycles at a high temperature.
Comparative example 6
The preparation method of the positive electrode material of the comparative example comprises the following steps:
(1) 500 g of a positive electrode material substrate (consistent with example 1), 2.86 g of boric acid powder, 0.59 g of strontium acetate powder and 0.78 g of cobalt oxalate powder were taken, and added to a wall breaking machine to mechanically mix, thereby obtaining a mixed material.
(2) The mixed material is put into a firing pot, the firing pot is put into a box-type furnace, and the temperature is raised to 400 ℃ at a heating rate of 1 ℃/min under the condition of introducing oxygen (the oxygen inlet flow is 60 ml/min), and the temperature is kept for 8 hours.
(3) And taking out the materials after the temperature of the box-type furnace is naturally cooled to be lower than 150 ℃, and sieving the materials through a 300-mesh sieve to obtain the positive electrode material of the comparative example.
The positive electrode material of the comparative example was coated on a positive electrode current collector aluminum foil, and a metal lithium was used as a negative electrode, lithium hexafluorophosphate was used as an electrolyte, and a separator was added and assembled to form a coin cell, and the above-mentioned coin cell was subjected to an electrical property test using a blue electric test system at 25 deg.c, and the results are shown in table 1, and the results show that the coin cell prepared using the positive electrode material of the comparative example had a first discharge capacity of 213.0mAh/g and a capacity retention rate of 93.0% after 50 cycles at a high temperature.
Comparative example 7
The preparation method of the positive electrode material of the comparative example comprises the following steps:
(1) 500 g of a positive electrode material substrate (consistent with example 1), 2.86 g of boric acid powder, 0.42 g of strontium carbonate powder and 0.39 g of cobalt hydroxide powder were taken, and added to a wall breaking machine to mechanically mix, thereby obtaining a mixed material.
(2) The mixed material is put into a firing pot, the firing pot is put into a box-type furnace, and the temperature is raised to 300 ℃ at a heating rate of 1 ℃/min under the condition of introducing oxygen (the oxygen introducing flow is 60 ml/min), and the temperature is kept for 8 hours.
(3) And taking out the materials after the temperature of the box-type furnace is naturally cooled to be lower than 150 ℃, and sieving the materials through a 300-mesh sieve to obtain the positive electrode material of the comparative example.
The positive electrode material of the comparative example was coated on a positive electrode current collector aluminum foil, and a metal lithium was used as a negative electrode, and lithium hexafluorophosphate was used as an electrolyte, and a separator was added and assembled into a coin cell, and the above-mentioned coin cell was subjected to an electrical property test using a blue electric test system at 25 deg.c, and the results are shown in table 1, and the results show that the coin cell prepared using the positive electrode material of the comparative example had a first discharge capacity of 208.3mAh/g and a capacity retention rate of 86.6% after 50 cycles at a high temperature.
TABLE 1 Performance test results of batteries prepared from the cathode materials of examples and comparative examples
| B/ppm | Sr/ppm | Co/ppm | Coating temperature/. Degree.C | Discharge capacity (mAh/g) | High temperature cycle retention/% | |
| Example 1 | 1000 | 1000 | / | 300 | 218.1 | 95.5 |
| Example 2 | 1000 | / | 1000 | 320 | 218.6 | 95.3 |
| Example 3 | 1000 | 500 | 500 | 280 | 220.7 | 96.0 |
| Comparative example 1 | / | / | / | 300 | 213.3 | 84.1 |
| Comparative example 2 | 1000 | / | / | 300 | 220.5 | 94.2 |
| Comparative example 3 | / | 1000 | / | 300 | 215.3 | 95.1 |
| Comparative example 4 | / | / | 1000 | 300 | 216.5 | 94.8 |
| Comparative example 5 | 1000 | 500 | 500 | 200 | 211.6 | 92.1 |
| Comparative example 6 | 1000 | 500 | 500 | 400 | 213.0 | 93.0 |
| Comparative example 7 | 1000 | 500 | 500 | 300 | 208.3 | 86.6 |
The above description is merely a preferred embodiment of the present invention, and the scope of the present invention is not limited to the above examples. Modifications and variations which would be obvious to those skilled in the art without departing from the spirit of the invention are also considered to be within the scope of the invention.
Claims (9)
1. The co-coating modified positive electrode material is characterized by comprising a positive electrode material matrix and a coating layer coated on the surface of the positive electrode material matrix, wherein the coating layer comprises MB 2 O 4 M is at least one of Sr and Co.
2. The co-coated modified cathode material according to claim 1, wherein the mass of the coating layer is 1% -4% of the total mass of the co-coated modified cathode material.
3. The co-coated modified cathode material according to claim 1 or 2, wherein the cathode material matrix has a chemical formula of Li a Ni x Mn y Co z M’ b O 2 Wherein, the element M' is one or more of Al, ti, mg, ba, ca, zr, ta, nb, mo, a is more than or equal to 0.9 and less than or equal to 1.1, b is more than or equal to 0 and less than or equal to 0.1, x is more than or equal to 0.5 and less than or equal to 1.0, y is more than or equal to 0 and less than or equal to 0.5, z is more than or equal to 0 and less than or equal to 0.5, and x+y+z+b=1.
4. A method for preparing the co-coated modified cathode material according to any one of claims 1 to 3, comprising the steps of:
(1) Mixing the positive electrode material matrix with a coating agent to obtain a mixed material, wherein the coating agent comprises boric acid and a compound containing M element;
(2) And roasting the mixed material at 280-320 ℃ for a set time under the condition of introducing oxygen to obtain the co-coated modified anode material.
5. The method for producing a co-coated modified cathode material according to claim 4, wherein the decomposition temperature of the coating agent is lower than 400 ℃.
6. The method for producing a co-coated modified cathode material according to claim 5, wherein the compound containing M element comprises at least one of strontium acetate and cobalt oxalate.
7. The method for producing a co-coated modified positive electrode material according to claim 4, wherein the molar ratio of M to B in the coating agent is (0.1 to 1): 2.
8. the method for producing a co-coated modified cathode material according to any one of claims 4 to 7, wherein the firing time in the step (2) is 4 to 12 hours.
9. A lithium ion battery, characterized in that the positive electrode material of the lithium ion battery is the co-coated modified positive electrode material according to any one of claims 1 to 3 or the co-coated modified positive electrode material prepared by the preparation method according to any one of claims 4 to 8.
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