CN114628675B - Ternary lithium battery anode material and preparation method thereof - Google Patents
Ternary lithium battery anode material and preparation method thereof Download PDFInfo
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- 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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Abstract
The invention relates to the field of lithium ion battery anode materials, and discloses a ternary lithium battery anode material and a preparation method thereof, wherein the ternary lithium battery anode material comprises a ternary material and a coating agent coated on the surface of the ternary material, the coating agent comprises composite carbon, and the preparation method comprises the following steps: firstly preparing COFs, and then sintering the COFs step by step to prepare composite carbon; calcining the ternary material precursor, a lithium source and a doping agent to obtain primary calcined powder, soaking the primary calcined powder and the composite carbon in a lithium hydroxide solution, and finally carrying out secondary calcination on the composite carbon soaked with the lithium hydroxide and the primary calcined powder to obtain a ternary anode material; the composite carbon prepared by sintering the COFs is coated on the ternary material, and the lithium hydroxide is infiltrated into the ternary material by the composite carbon and the ternary material, so that the lithium ion transmission rate and the electronic conductivity of the ternary positive electrode material are remarkably improved, the side reaction between the ternary positive electrode material and the electrolyte is effectively slowed down, and the battery capacity, the conductivity and the cycle life of the ternary material lithium battery are improved.
Description
Technical Field
The invention relates to the field of lithium ion battery anode materials, in particular to a ternary lithium battery anode material and a preparation method thereof.
Background
Lithium batteries are a research hotspot in the field of new energy, so that the research of electrodes of the lithium batteries is also attracting attention; the lithium battery electrode comprises a lithium battery anode and a lithium battery cathode, the development of the lithium battery cathode is relatively mature and stable, and the common cathode material is graphite; the lithium battery anode has a complex structure and high development difficulty, and the current development direction mainly focuses on high capacity, long service life, low cost, safety, environmental protection and the like; the current commonly used lithium battery anode materials mainly comprise lithium cobaltate, ternary materials and lithium manganate and lithium iron phosphate, wherein the ternary materials have the performances of high specific capacity, high energy density and high power density, are considered as anode materials with great development potential in the field, but have lower electrochemical performance, thermal stability and structural stability under high-temperature or high-potential test environments, and the problems are more prominent along with the improvement of nickel content, so that the ternary materials need to be modified during use; in the prior art, the ternary material is coated, and the coating layer is utilized to improve the structural stability, the thermal stability, the multiplying power performance and the cycling stability of the ternary anode.
For example, publication No. CN111162249a discloses a positive electrode material for improving the first discharge capacity and a method for preparing the same, wherein the positive electrode material is prepared from a positive electrode material matrix, a lithium source and a coating agent, and the coating agent is one or more of boric acid, lithium borate, aluminum borate, sodium borate, potassium borate, aluminum oxide, titanium oxide, zirconium oxide and yttrium oxide.
For another example, publication number CN202010442120.2 discloses a high voltage lithium cobaltate material, which is mainly prepared by reacting the following raw materials: a cobalt source, a lithium source, an additive, a coating agent A and a coating agent B; the coating agent A is at least one of a Al, ti, co, mg, sn nanoscale oxide, nanoscale hydroxide or salt; the coating agent B is at least one of boric acid, lithium tetraborate, boron oxide, boron phosphate, titanium diboride or titanium metaborate; the mass ratio of the lithium source to the cobalt source is (1.03-1.07): 1.00.
in the prior art, a boron-containing material is often used as a coating agent, but the lithium ion conductivity and the conductivity of a lithium battery can be reduced after the ternary material is coated by the boron-containing material; therefore, it is necessary to provide a ternary lithium battery positive electrode material and a preparation method thereof to improve the performance of a lithium battery.
Disclosure of Invention
The invention aims to solve the problem that the lithium ion conductivity and the conductivity of a lithium battery can be reduced when a ternary positive electrode material is coated and modified by using a coating agent in the prior art, and provides the ternary positive electrode material and the preparation method thereof; meanwhile, the composite carbon coating layer can effectively slow down side reaction between the ternary material and the electrolyte, improve the cycle performance of the ternary material and prolong the service life of the battery.
In order to achieve the above purpose, the present invention adopts the following technical scheme:
the ternary lithium battery anode material comprises a ternary material and a coating agent coated on the surface of the ternary material, wherein the coating agent comprises composite carbon, and the composite carbon is prepared by sintering COFs.
According to the invention, the composite carbon obtained after the COFs sintering is used as a coating agent, so that the conductivity and the cycle performance of the ternary material are obviously improved; the COFs are light materials composed of C, H, N, F and other light elements, the light materials have the characteristics of high crystallinity, regular pore structure and large specific surface area, meanwhile, the structural aperture of the light materials can be designed manually.
Preferably, the mass ratio of the composite carbon accounts for 0.5-5% of the ternary positive electrode material.
Preferably, the preparation method of the composite carbon comprises the following steps:
(1) Preparation of polyamide COFs: preparing N-methyl-2-pyrrolidone (NMP), mesitylene and isoquinoline into a solution according to the volume ratio of 0.5-1.5:0.5-1.0:0.05-0.25; adding cyclobutane tetracarboxylic dianhydride and 2, 6-diaminonaphthalene into the solution according to the molar ratio of 1-2:0.5-1, uniformly mixing and heating, cooling to room temperature, filtering to obtain COFs, washing the COFs by using an organic solvent, and drying in vacuum; the reaction formula is:
(2) Preparing composite carbon: placing the prepared COFs into a ball mill for ball milling, sieving to obtain a composite carbon precursor, calcining the composite carbon precursor under an inert atmosphere, calcining the composite carbon precursor step by step, calcining the composite carbon precursor at 300-350 ℃ for 1h, heating the composite carbon precursor to 500-600 ℃ for 2-3h, heating the composite carbon precursor to 700-900 ℃ for 1-2h, and cooling the composite carbon precursor to obtain the composite carbon.
Preferably, the particle size of the composite carbon precursor is 2-2.5 μm.
Preferably, in the step (1), the heating temperature is 150-200 ℃, the heating time is 60-90min, the drying temperature is 70-90 ℃, and the drying time is 10-24h; the organic solvent in the step (1) is selected from one or more of absolute ethyl alcohol, methanol and isopropanol.
Preferably, in the step (2), the ball milling temperature is 20-30 ℃, the ball milling frequency is 30-50HZ, the ball milling time is 5-15min, the ball milling interval is 1-2min, and the ball milling times are 3-6 ℃.
The invention also provides a preparation method of the ternary lithium battery anode material, which comprises the following steps:
a. preparing a composite carbon material;
b. uniformly mixing a precursor, a lithium source and a doping agent to obtain powder to be burned, and then placing the powder to be burned in an inert atmosphere for primary calcination to obtain primary calcined powder;
c. uniformly dispersing the primary calcined powder and the composite carbon material in an alkaline solution, fully soaking, filtering, vacuum drying, and performing secondary calcination to obtain the ternary anode material with the surface coated with the composite carbon material.
According to the invention, the composite carbon and the ternary material are soaked in the lithium hydroxide alkaline solution and calcined, so that lithium hydroxide crystals are adhered to the inside of a gap of the composite carbon and the surface of the ternary material, the lithium ion exchange rate of the ternary positive electrode material is remarkably improved, the composite carbon has large specific surface area and developed pores, a large amount of lithium hydroxide can be adsorbed when the lithium hydroxide is soaked, after the lithium hydroxide is burned, the lithium hydroxide is adhered between the pores of the composite carbon in a crystalline state, after the ternary positive electrode material wrapped by the composite carbon is prepared, a large amount of lithium exists on the surfaces of the wrapping agent and the ternary material, the exchange rate of the lithium ions can be remarkably improved in the charging and discharging process, meanwhile, the dead lithium in the positive electrode and the negative electrode is increased, so that the cycle life of the battery is reduced.
Preferably, the molar ratio of the ternary material precursor to the lithium source in the step b is 1:1.0-1.5; the doping agent is one or more of zirconia, alumina, magnesia and strontium oxide, and the doping amount of the doping agent is 300-2000ppm of the mass of the ternary material precursor; the primary calcination temperature is 700-900 ℃ and the calcination time is 18-26 hours.
Preferably, the alkali liquor in the step c is lithium hydroxide solution, and the concentration of the alkali liquor is 0.1-5mol/L; c, stirring for 0.5-5h, and vacuum drying at 100-150 ℃ for 10-24h; the secondary calcination temperature is 700-900 ℃ and the calcination time is 2-6h.
Therefore, the invention has the following beneficial effects:
(1) The composite carbon material obtained after the covalent organic material is sintered is used as a coating agent, so that the side reaction between the ternary positive electrode material and the electrolyte can be effectively slowed down, the cycle performance of the ternary positive electrode material is improved, and the service life of a battery is prolonged; the specific surface of the ternary material conductive network can be obviously increased, the electron transmission rate of the ternary material is increased, and the conductivity of the lithium battery is improved;
(2) The lithium hydroxide solution is soaked in the composite carbon and then calcined, so that active lithium crystals are attached to pores of the composite carbon, the exchange rate of lithium ions can be remarkably improved, the conductive efficiency of the battery is improved, and the effects of supplementing lithium ions, improving the battery capacity and prolonging the cycle life of the battery can be achieved.
Detailed Description
The invention is further described below in connection with the following detailed description.
In the present invention, all raw materials are commercially available or commonly used in the industry, and the methods in the following examples are conventional in the art unless otherwise specified.
Example 1:
a preparation method of a ternary lithium battery anode material comprises the following steps:
(1) NMP, mesitylene and isoquinoline are prepared into a solution according to the volume ratio of 0.5:0.5:0.05; adding cyclobutane tetracarboxylic dianhydride and 2, 6-diaminonaphthalene into the solution according to the molar ratio of 1:0.5, uniformly mixing and heating at 150 ℃ for 60min, cooling to room temperature, filtering to obtain COFs, washing the COFs with absolute ethyl alcohol, and vacuum drying at 70 ℃ for 10h;
(2) Placing the prepared COFs into a ball mill for ball milling, wherein the ball milling temperature is 20 ℃, the ball milling frequency is 30HZ, the ball milling time is 5min, the ball milling interval is 1min, the ball milling times are 3 times, screening is carried out after ball milling processing to obtain a composite carbon precursor with the particle size of 2 mu m, calcining the composite carbon precursor under an inert atmosphere, calcining the composite carbon precursor step by step, calcining at 300 ℃ for 1h, heating to 500 ℃ for continuous calcining for 2h, heating to 700 ℃ for calcining for 1h, and cooling to obtain composite carbon;
(3) Uniformly mixing NCM811 (Ni: co: mn molar ratio is 8:1:1), lithium carbonate and zirconia to obtain powder to be burned, wherein the molar ratio of NCM811 to lithium carbonate is 1:1, and the doping amount of zirconia is 300ppm of the mass of NCM 811; then placing the powder to be burned in an argon atmosphere for primary calcination to obtain primary calcined powder, wherein the calcination temperature is 700 ℃ and the calcination time is 18 hours;
(4) Uniformly dispersing the primary calcined powder and the composite carbon material in a lithium hydroxide solution with the concentration of 0.1mol/L, fully soaking, and then carrying out vacuum filtration and drying at the drying temperature of 100 ℃ for 10 hours; and then carrying out secondary calcination to obtain the ternary positive electrode material with the surface coated with the composite carbon material, wherein the calcination temperature is 700 ℃ and the calcination time is 2 hours.
Example 2:
a preparation method of a ternary lithium battery anode material comprises the following steps:
(1) NMP, mesitylene and isoquinoline are prepared into a solution according to the volume ratio of 1:1:0.15; adding tetracarboxylic dianhydride and 2, 6-diaminonaphthalene into the solution according to the molar ratio of 1.5:0.75, uniformly mixing and heating at 175 ℃ for 75min, cooling to room temperature, filtering to obtain COFs, washing the COFs with absolute ethyl alcohol, and vacuum drying at 80 ℃ for 18h;
(2) Ball milling the prepared COFs in a ball mill at 20-30 ℃ with a ball milling frequency of 40HZ for 10min at a ball milling interval of 1.5min and a ball milling frequency of 4 times, sieving to obtain a composite carbon precursor with a particle size of 2.25 mu m, ball milling the prepared COFs in the ball mill, sieving to obtain a composite carbon precursor, calcining the composite carbon precursor under an inert atmosphere, calcining the composite carbon precursor stepwise, calcining at 325 ℃ for 1h, heating to 550 ℃ for 2h, calcining at 800 ℃ for 2h, and cooling to obtain the composite carbon;
(3) Uniformly mixing NCM811 (Ni: co: mn molar ratio is 8:1:1), lithium carbonate and zirconia to obtain powder to be burned, wherein the molar ratio of NCM811 to lithium carbonate is 1:1.25, and the doping amount of zirconia is 1000ppm of the mass of NCM 811; then placing the powder to be burned in an argon atmosphere for primary calcination to obtain primary calcined powder, wherein the calcination temperature is 800 ℃ and the calcination time is 24 hours;
(4) Uniformly dispersing the primary calcined powder and the composite carbon material in a lithium hydroxide solution with the concentration of 2.5mol/L, fully soaking, and then carrying out vacuum filtration and drying at the drying temperature of 125 ℃ for 18 hours; and then carrying out secondary calcination to obtain the ternary anode material with the surface coated with the composite carbon material, wherein the calcination temperature is 800 ℃ and the calcination time is 4 hours.
Example 3:
a preparation method of a ternary lithium battery anode material comprises the following steps:
(1) NMP, mesitylene and isoquinoline are prepared into a solution according to the volume ratio of 1.5:1.0:0.25; uniformly mixing tetracarboxylic dianhydride and 2, 6-diaminonaphthalene in a solution with a molar ratio of 2:1, heating at 200 ℃ for 90min, cooling to room temperature, filtering to obtain COFs, washing the COFs with absolute ethyl alcohol, and vacuum drying at 90 ℃ for 24h;
(2) Placing the prepared COFs into a ball mill for ball milling, wherein the ball milling temperature is 30 ℃, the ball milling frequency is 50HZ, the ball milling time is 15min, the ball milling interval is 2min, the ball milling times are 6 times, screening is carried out after ball milling processing to obtain a composite carbon precursor with the particle size of 2.5 mu m, and the composite carbon precursor is calcined under the argon atmosphere to obtain the composite carbon material, wherein the calcining temperature is 500 ℃, the calcining time is 4h, and the heating rate is 5 ℃/min;
(3) Uniformly mixing NCM811 (Ni: co: mn molar ratio is 8:1:1), lithium carbonate and zirconia to obtain powder to be burned, wherein the molar ratio of NCM811 to lithium carbonate is 1:1.5, and the doping amount of zirconia is 2000ppm of the mass of NCM 811; then placing the powder to be calcined in an argon atmosphere for primary calcination to obtain primary calcined powder, wherein the calcination temperature is 900 ℃ and the calcination time is 26 hours;
(4) Uniformly dispersing the primary calcined powder and the composite carbon material in a lithium hydroxide solution with the concentration of 5mol/L, fully soaking, and then carrying out vacuum filtration and drying for 24 hours at the drying temperature of 150 ℃; and then carrying out secondary calcination to obtain the ternary positive electrode material with the surface coated with the composite carbon material, wherein the calcination temperature is 900 ℃ and the calcination time is 6 hours.
Comparative example 1 (without coating NCM):
and (3) calcining the powder material at 900 ℃ for 24 hours, and crushing to obtain the ternary cathode material. A preparation method of a ternary positive electrode material of a lithium ion battery comprises the following steps:
(1) Mixing NCM811 (Ni: co: mn molar ratio is 8:1:1) which is an NCM ternary material precursor with lithium carbonate and zirconia, and uniformly stirring to obtain a powder material, wherein the molar ratio of NCM811 to lithium carbonate is 1:1.1, and the doping amount of zirconia is 1000ppm of the mass of NCM 811; will be
Comparative example 2 (only lithium hydroxide coated):
a preparation method of a ternary lithium battery anode material comprises the following steps:
(1) Mixing NCM811 (Ni: co: mn molar ratio is 8:1:1) which is an NCM ternary material precursor with lithium carbonate and zirconia, and uniformly stirring to obtain a powder material, wherein the molar ratio of NCM811 to lithium carbonate is 1:1.1, and the doping amount of zirconia is 1000ppm of the mass of NCM 811; the powder material is subjected to primary calcination at 800 ℃ for 24 hours, and primary calcination sample powder is obtained after crushing;
(2) And soaking the primary calcined sample powder in a lithium hydroxide solution with the concentration of 2.5mol/L, sufficiently soaking, performing vacuum filtration, drying at the drying temperature of 125 ℃ for 18 hours, and performing secondary calcination to obtain the ternary positive electrode material, wherein the calcination temperature is 900 ℃ and the calcination time is 24 hours.
Comparative example 3 (coating with lithium borate only)
A preparation method of a ternary lithium battery anode material comprises the following steps:
(1) Mixing NCM811 (Ni: co: mn molar ratio is 8:1:1) which is an NCM ternary material precursor with lithium carbonate and zirconia, and uniformly stirring to obtain a powder material, wherein the molar ratio of NCM811 to lithium carbonate is 1:1.1, and the doping amount of zirconia is 1000ppm of the mass of NCM 811; the powder material is subjected to primary calcination at 800 ℃ for 24 hours, and primary calcination sample powder is obtained after crushing;
(2) And uniformly mixing the primary calcined sample powder with lithium borate, and performing secondary calcination to obtain the ternary anode material, wherein the mass of the lithium borate is 500ppm of that of the secondary calcined sample powder, the calcination temperature is 900 ℃, and the calcination time is 24 hours.
Comparative example 4 (composite carbon non-impregnated lithium hydroxide):
a preparation method of a ternary lithium battery anode material comprises the following steps:
(1) NMP, mesitylene and isoquinoline are prepared into a solution according to the volume ratio of 1:1:0.15; adding tetracarboxylic dianhydride and 2, 6-diaminonaphthalene into the solution according to the molar ratio of 1.5:0.75, uniformly mixing and heating at 175 ℃ for 75min, cooling to room temperature, filtering to obtain COFs, washing the COFs with absolute ethyl alcohol, and vacuum drying at 80 ℃ for 18h;
(2) Placing the prepared COFs into a ball mill for ball milling, wherein the ball milling temperature is 25 ℃, the ball milling frequency is 40HZ, the ball milling time is 10min, the ball milling interval is 2min, the ball milling times are 5 times, screening is carried out after ball milling processing to obtain a composite carbon precursor with the particle size of 2.25 mu m, and the composite carbon precursor is calcined under the argon atmosphere to obtain the composite carbon material, wherein the calcining temperature is 400 ℃, the calcining time is 2.5h, and the heating rate is 3 ℃/min;
(3) Uniformly mixing NCM811 (Ni: co: mn molar ratio is 8:1:1), lithium carbonate and zirconia to obtain powder to be burned, wherein the molar ratio of NCM811 to lithium carbonate is 1:1.25, and the doping amount of zirconia is 1000ppm of the mass of NCM 811; then placing the powder to be calcined in an argon atmosphere for primary calcination to obtain primary calcined powder, wherein the calcination temperature is 900 ℃ and the calcination time is 24 hours;
(4) Uniformly dispersing the primary calcined powder in a lithium hydroxide solution with the concentration of 2.5mol/L, fully soaking, and then carrying out vacuum filtration and drying for 18 hours at the drying temperature of 125 ℃; and fully and uniformly mixing the dried primary calcined powder which is infiltrated with lithium hydroxide with the composite carbon material to prepare secondary to-be-calcined powder, and carrying out secondary calcination on the secondary to-be-calcined powder to prepare the ternary positive electrode material, wherein the calcination temperature is 900 ℃ and the calcination time is 4 hours.
Comparative example 5 (preparation of complex carbon using other COFs):
a preparation method of a ternary lithium battery anode material comprises the following steps:
(1) NMP, mesitylene and isoquinoline are prepared into a solution according to the volume ratio of 1:1:0.15; uniformly mixing PMDA and TAPA into the solution according to the molar ratio of 1:0.5, heating at 175 ℃ for 75min, cooling to room temperature, filtering to obtain PMDA-TAPA-COFs, washing the PMDA-TAPA-COFs with absolute ethyl alcohol, and vacuum drying at 80 ℃ for 18h;
(2) Placing the prepared PMDA-TAPA-COFs into a ball mill for ball milling at the temperature of 25 ℃, the ball milling frequency of 40HZ, the ball milling time of 10min, the ball milling interval of 2min, the ball milling times of 4 times, sieving after ball milling to obtain a composite carbon precursor with the particle size of 2.25 mu m, and calcining the composite carbon precursor in an argon atmosphere to obtain a composite carbon material, wherein the calcining temperature is 400 ℃, the calcining time is 2.5h, and the heating rate is 3 ℃/min;
(3) Uniformly mixing NCM811 (Ni: co: mn molar ratio is 8:1:1), lithium carbonate and zirconia to obtain powder to be burned, wherein the molar ratio of NCM811 to lithium carbonate is 1:1.25, and the doping amount of zirconia is 1000ppm of the mass of NCM 811; then placing the powder to be calcined in an argon atmosphere for primary calcination to obtain primary calcined powder, wherein the calcination temperature is 900 ℃ and the calcination time is 24 hours;
(4) Uniformly dispersing the primary calcined powder and the composite carbon material in a lithium hydroxide solution with the concentration of 2.5mol/L, fully soaking, and then carrying out vacuum filtration and drying at the drying temperature of 125 ℃ for 18 hours; and then carrying out secondary calcination to obtain the ternary positive electrode material with the surface coated with the composite carbon material, wherein the calcination temperature is 900 ℃ and the calcination time is 4 hours.
The ternary cathode materials obtained in the above examples and comparative examples were assembled into soft-pack lithium batteries, respectively, and performance test was performed, and the results are shown in table 1.
The soft-package lithium ion battery comprises a positive electrode material, a carbon black conductive agent, PVDF and carbon nanotubes, wherein the mass ratio of the positive electrode material to the carbon black conductive agent is 96:1.5:2:1, and the negative electrode material comprises artificial graphite, sodium carboxymethylcellulose (CMC), a synthetic rubber foam (SBR) and a carbon black conductive agent, wherein the mass ratio of the artificial graphite to the sodium carboxymethylcellulose (CMC) is 95.5:1.5:2:1;
the positive electrode material was prepared at 380g/m 2 Coating the surface density of the anode material on aluminum foil with the thickness of 12 mu m, rolling, punching and baking to obtain an anode plate, and carrying out 190g/m on the anode material 2 The surface density of the lithium ion battery is coated on copper foil with the thickness of 6 mu m, and the negative electrode plate is obtained after rolling, punching and baking, and the soft package lithium ion battery is prepared by adopting a lamination process and an aluminum plastic film packaging process.
Test conditions: test voltage: 2.8-4.3V; capacity test conditions: and 0.1C constant current charge and discharge test.
Table 1: battery performance test results.
As can be seen from Table 1, the initial discharge capacity of the NCM ternary positive electrode material obtained by adopting the coating agent and the preparation method in examples 1-3 is more than 200mAh/g, the cycle life is more than 330 times, and the 3C rate performance is more than 96%.
In the comparative example 1, the ternary material is not subjected to coating modification, and the battery capacity, the cycle life and the rate performance are obviously lower than those of the invention from the results; in comparative example 2, the ternary material was subjected to coating modification by using lithium hydroxide, but the battery capacity, cycle life and rate capability of the ternary material are still significantly lower than those of the ternary material, and in comparative example 3, the battery performance of the ternary material after modification by using lithium borate is still significantly lower than that of the ternary material, which indicates that the ternary positive electrode material prepared by the method can significantly improve the battery capacity, cycle life and conductivity of a lithium battery.
In comparative example 4, lithium hydroxide is not infiltrated into the composite material, and the cycle performance of the battery is obviously reduced compared with that of the example, which shows that after the composite carbon material is infiltrated, the cycle performance of the battery can be obviously increased, and the service life of the battery can be prolonged; the composite carbon prepared by using PMDA-TAPA-COFs in comparative example 5, however, the test result shows that the cycle life of the lithium battery prepared by the composite carbon is obviously reduced compared with that of the embodiment, because the high temperature resistance between the COFs used in the invention and the PMDA-TAPA-COFs used in the comparative example is different, when the composite carbon is prepared, the carbon content of the composite carbon after being burnt at high temperature is 67%, the carbon content of the PMDA-TAPA-COFs is only 7%, and the calcination temperature during coating modification is higher, so that the composite carbon material with lower high temperature resistance is decomposed, and the coating modification is incomplete; the composite carbon has high structural porosity and large specific surface area, can accommodate a large amount of active lithium, can obviously improve the lithium ion exchange rate after being prepared into a ternary positive electrode material, and can also supplement a large amount of lithium sources, thereby obviously improving the conductivity and the cycle life of the battery.
The data show that the coating agent and the preparation method can effectively improve the capacity performance, the cycle life and the multiplying power performance of the battery.
Claims (8)
1. The ternary lithium battery anode material is characterized by comprising a ternary material and a coating agent coated on the surface of the ternary material, wherein the coating agent comprises composite carbon, and the composite carbon is prepared by sintering COFs;
the preparation method of the ternary lithium battery anode material comprises the following steps:
a. preparing a composite carbon material;
b. uniformly mixing a precursor, a lithium source and a doping agent to obtain powder to be burned, and then placing the powder to be burned in an inert atmosphere for primary calcination to obtain primary calcined powder;
c. uniformly dispersing the primary calcined powder and the composite carbon material in an alkaline solution, fully soaking, filtering, vacuum drying, and performing secondary calcination to obtain the ternary anode material with the surface coated with the composite carbon material, wherein the alkaline solution is one or more of a lithium hydroxide solution, a lithium carbonate solution and a lithium nitrate solution, and the concentration of the alkaline solution is 0.1-5mol/L.
2. The ternary lithium battery positive electrode material according to claim 1, wherein the mass ratio of the composite carbon material is 0.5-5% of the ternary positive electrode material.
3. The ternary lithium battery positive electrode material according to claim 1 or 2, wherein the preparation method of the composite carbon is as follows:
(1) Preparation of polyamide COFs: preparing N-methyl-2-pyrrolidone, mesitylene and isoquinoline into a solution according to the volume ratio of 0.5-1.5:0.5-1.0:0.05-0.25; adding cyclobutane tetracarboxylic dianhydride and 2, 6-diaminonaphthalene into the solution according to the mass ratio of 1-2:0.5-1, uniformly mixing, heating, cooling to room temperature, filtering to obtain COFs, washing the COFs by using an organic solvent, and drying in vacuum;
(2) Preparing composite carbon: placing the prepared COFs into a ball mill for ball milling, sieving to obtain a composite carbon precursor, calcining the composite carbon precursor under an inert atmosphere, calcining the composite carbon precursor step by step, calcining the composite carbon precursor at 300-350 ℃ for 1h, heating the composite carbon precursor to 500-600 ℃ for 2-3h, heating the composite carbon precursor to 700-900 ℃ for 1-2h, and cooling the composite carbon precursor to obtain the composite carbon.
4. A ternary lithium battery positive electrode material according to claim 3, wherein the particle size of the composite carbon precursor is 2-2.5 μm.
5. The ternary lithium battery positive electrode material according to claim 3, wherein in the step (1), the heating temperature is 150-200 ℃, the heating time is 60-90min, the drying temperature is 70-90 ℃, and the drying time is 10-24h; the organic solvent in the step (1) is selected from one or more of absolute ethyl alcohol, methanol and isopropanol.
6. The ternary lithium battery positive electrode material according to claim 3, wherein in the step (2), the ball milling temperature is 20-30 ℃, the ball milling frequency is 30-50HZ, the ball milling time is 5-15min, the ball milling interval is 1-2min, and the ball milling times are 3-6 ℃.
7. The method for preparing a ternary lithium battery positive electrode material according to claim 1, wherein the molar ratio of the ternary material precursor to the lithium source in the step b is 1:1.0-1.5; the doping agent is one or more of zirconia, alumina, magnesia and strontium oxide, and the doping amount of the doping agent is 300-2000ppm of the mass of the ternary material precursor; the primary calcination temperature is 700-900 ℃ and the calcination time is 18-26 hours.
8. The preparation method of the ternary lithium battery positive electrode material according to claim 1, wherein the stirring time in the step c is 0.5-5h, the vacuum drying temperature is 100-150 ℃, and the drying time is 10-24h; the secondary calcination temperature is 700-900 ℃ and the calcination time is 2-6h.
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