CN115148945A - Modification method of high-nickel ternary cathode material - Google Patents
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Abstract
The invention provides a method for modifying a high-nickel ternary cathode material, which relates to the technical field of electrode materials of lithium ion batteries and comprises the following steps: (1) The prepared carbon content is 60-80%, the oxygen content is 20-40%, and the specific surface area is more than or equal to 300m 2 Graphene oxide powder per gram; (2) Adding the graphene oxide powder, a dispersing agent, a binder and a high-nickel ternary cathode material into an organic solvent, uniformly stirring, and then carrying out spray granulation and drying to obtain a high-nickel ternary cathode material coated by graphene oxide; (3) And controlling the sintering temperature and the sintering time, and sintering and reducing the high-nickel ternary cathode material coated by the graphene oxide to obtain the high-nickel ternary cathode material coated by the graphene oxide. The invention relates to aThe graphene is uniformly coated on the surface of the high-nickel ternary cathode material, so that the problems that the high-nickel ternary cathode material is easy to absorb moisture in air, low in conductivity and poor in cycle life can be effectively solved, and the processing, multiplying power and cycle performance of the high-nickel ternary cathode material are improved.
Description
Technical Field
The invention relates to the technical field of lithium ion battery electrode materials, in particular to a method for modifying a high-nickel ternary cathode material.
Background
With the rapid development of new energy vehicles, portable electronic devices and energy storage system technologies, the requirements of the market on the cycle performance, energy density and safety performance of lithium ion batteries are also increasing. The cathode material is used as a key material of the lithium ion battery and plays an important role in the capacity, cycle, safety performance and the like of the battery. Among the current lithium ion battery cathode materials, the high-nickel ternary cathode material has attracted attention due to the fact that the high-nickel ternary cathode material has high specific capacity (0.1C is larger than or equal to 180 mAh/g), a high discharge platform, good safety performance, relatively low raw material cost and the like. However, the high-nickel ternary cathode material still has the following problems to be solved when used in large-scale batch: (1) The material is easy to react with H in the air 2 O and CO 2 React to form LiOH and Li 2 CO 3 The surface alkalinity of the battery is increased, and the battery has poor high-temperature gas production, multiplying power and cycle performance; (2) The nickel ion with the valence of +4, which appears in the high delithiation state, has strong oxidizing property and reacts with the electrolyte to release O 2 Leading to collapse of the structure of the positive electrode material, thereby leading to rapid capacity fade and deterioration of safety; (3) The high-nickel ternary cathode material has some phase changes in the circulation process, and the phase changes can cause the material to have larger volume expansion and contraction, and then microcracks occur. And the occurrence of the microcracks can generate side reactions with the electrolyte again, and finally the electrode material is pulverized and the battery fails. The effective carbon coating on the surface of the high-nickel ternary cathode material can be used as an effective method for improving the electrochemical performance of the ternary material, and two process routes of physical coating and chemical coating are generally adopted at present. The physical coating process flow is simple, mass production is easy to realize, but the problems of non-uniform and discontinuous carbon coating, and poor binding force and batch stability exist; the chemical coating has good uniformity and strong binding force, but water is mainly used as a solvent, and the high-temperature sintering at the temperature of more than 400 ℃ is usually carried out after the drying, so that on one hand, the water solvent can influence the content of lithium in the high-nickel ternary cathode material, destroy the structure of the high-nickel ternary cathode material, cause the loss of a lithium source and reduce the capacity; the other partyAnd when the material is sintered at a high temperature of more than 400 ℃, the reducibility of carbon can promote the reduction of the + 3-valent nickel in the high-nickel ternary cathode material, so that the capacity and the first effect are reduced.
Disclosure of Invention
In view of the above, there is a need to select a new and effective surface coating method to further improve the electrochemical performance of the nickel ternary cathode material without affecting the structure of the high nickel ternary itself. The invention aims to provide a modification method of a high-nickel ternary cathode material, which can be used for uniformly and compactly coating graphene on the particle surface of the high-nickel ternary cathode material, the coated graphene has the advantages of controllable thickness, good electronic conductivity and stable chemical and thermodynamic structures, and the high-nickel ternary cathode material prepared by the method has good rate capability, cycle performance and high-temperature storage performance.
In order to realize the purpose of the invention, the technical scheme comprises the following steps:
(1) Preparing graphene oxide: dispersing and stripping the graphene oxide solution by adopting nano sand grinding and high-pressure homogenizing equipment to obtain the graphene oxide solution with uniform particle size distribution; then carrying out spray granulation and drying to obtain graphene oxide powder;
(2) Coating with graphene oxide: adding a dispersing agent, a binder, graphene oxide powder and a high-nickel ternary cathode material into an organic solvent in proportion, uniformly stirring, and then carrying out spray granulation and drying to obtain a high-nickel ternary cathode material coated by graphene oxide;
(3) And (3) reducing graphene oxide: and sintering and reducing the high-nickel ternary cathode material coated by the graphene oxide under the inert atmosphere condition to obtain the high-nickel ternary cathode material coated by the graphene oxide.
(4) And (4) crushing the graphene-coated high-nickel ternary positive electrode material obtained in the step (3) to obtain a final product.
Specifically, in the step 1, the mass concentration of the graphene oxide solution is 0.5% -3%, and the solvent is pure water; the carbon content of the graphene oxide powder is 60-80%, the oxygen content is 20-40%, and the specific surface area is more than or equal to 300m 2 G, its D50 is between 3 and 10um. Carbon content < (R) > of graphene oxide60%, the oxidation degree is higher, the content of functional groups carried on the surface of the catalyst is high, and the subsequent sintering reduction is not facilitated; and the carbon content of the graphene oxide is more than 80%, the oxidation degree is low, the specific surface area of the graphene oxide is small, and the coating of the graphene oxide is not facilitated.
The size of the nano-sand-milled ball is 0.6-2um, the rotating speed is 1000-3000rpm, and the sand milling time is more than or equal to 2h; the pressure of the high-pressure homogenizing equipment is more than or equal to 800bar, and the homogenizing circulation is more than or equal to 3 times. Spray drying uses spray granulation equipment, the temperature of a feed inlet of the equipment is controlled to be 190-210 ℃, the temperature of a discharge outlet of the equipment is controlled to be 90-100 ℃, and the atomization frequency is 50-55Hz.
In the step 2, the organic solvent is one of N-methyl pyrrolidone, alcohol and acetone; the dispersing agent is polyvinylpyrrolidone; the binder is polyvinylidene fluoride; the chemical formula of the high-nickel ternary cathode material is LiNi x Co y Mn z O 2 Wherein, the content of nickel is more than or equal to 50 percent, x is more than or equal to 0.5 and less than 1, y is more than 0 and less than 0.5, z is more than 0 and less than 0.5, and x + y + z =1. The mass ratio of the dispersing agent to the binder to the graphene oxide to the high-nickel ternary material is as follows: 0.5-5% of dispersant, 0.5-5% of binder, 2-10% of graphene oxide and 80-97% of high nickel ternary.
The high nickel ternary material is modified in an organic solvent, so that the influence of an aqueous solution on the content of lithium in the high nickel ternary cathode material can be avoided.
The dispersant polyvinylpyrrolidone is a high molecular material rich in benzene rings, can form pi-pi bond interaction with six-membered rings of graphene to improve the dispersion effect of the graphene, and is complexed with a plurality of substances, particularly substances containing hydroxyl, carboxyl and the like, so that the thermodynamic activity of the material is reduced, and the stability is improved.
The adhesive polyvinylidene fluoride has large molecular weight and higher viscosity at normal temperature, is beneficial to playing a role in connection between the graphene oxide and the high-nickel ternary cathode material, can avoid layering between the graphene oxide and the high-nickel ternary cathode particles, and prevents the slurry from causing the problems of secondary agglomeration and unstable viscosity. The graphene oxide sheet layer contains rich oxygen-containing functional groups, such as carboxyl, hydroxyl, epoxy and the like, and the surface of the graphene oxide sheet layer can carry positive and negative group charges, so that the graphene oxide sheet layer has good self-assembly and film-forming functions and can well coat the high-nickel ternary positive electrode material.
In the selected high-nickel ternary material, the content of nickel is more than or equal to 50%, generally speaking, the higher the content of nickel is, the larger the specific capacity of the material is, the higher the energy density of the battery is, and the specific capacity of the material can be effectively increased by adopting the ternary material with the content of nickel more than or equal to 50%.
In the proportion of the dispersing agent, the binder, the graphene oxide and the high-nickel ternary material, the proportion of the dispersing agent to the binder is 0.5-5%, because the dispersing agent and the binder belong to organic high polymer materials, electrons are not conductive, and the content is too high, which is not beneficial to the promotion of the electronic conductivity of the high-nickel material and increases the internal resistance of the material; if the content is too low, dispersion and coating of graphene are not facilitated. The proportion of the graphene oxide is 2-10%, because the graphene oxide loses part of weight after reduction, and the actual coating mass of the graphene is between 1% and 5%, so that the electronic conductivity and the cycle performance of the high-nickel ternary material are improved. And if the graphene is coated too high, the specific surface area of the material is too large, the slurry is not easy to disperse and process, and the loss of the specific capacity of the material per unit is increased. If the amount of the coating is too low, the coating is not uniform, and the particles are exposed, so that the electronic conductivity among the material particles is not uniformly distributed, the rate performance of the material is not exerted, and the actual use of the material is influenced.
Meanwhile, the graphene oxide solution shows weak acidity, while the high-nickel ternary positive electrode has alkaline compounds such as LiOH and Li remained on the surface 2 CO 3 Etc., which are predominantly alkaline. Therefore, carboxyl in the graphene oxide can spontaneously react with an alkaline compound in the high-nickel ternary material to generate an organic ester lithium salt compound, and the compound has higher conductivity than an inorganic compound, so that direct contact between particles of the high-nickel ternary positive electrode material and an electrolyte can be avoided, and the stability of the high-nickel ternary positive electrode material is improved.
Spray drying uses spray granulation equipment, the temperature of a feed inlet of the equipment is controlled to be 190-210 ℃, the temperature of a discharge outlet of the equipment is controlled to be 90-100 ℃, and the atomization frequency is 55Hz.
In step 3, the inert atmosphere refers to an atmosphere of one or a mixture of nitrogen and argon. The sintering temperature of the high-nickel ternary cathode material coated by the graphene oxide is 300-400 ℃, the sintering time is 10-24 hours, and the carbon content is more than or equal to 98 percent, the oxygen content is less than or equal to 2 percent, and the specific surface area is more than or equal to 200m 2 The graphene-coated high-nickel ternary cathode material is used for preparing the cathode material. The sintering temperature is lower than 300 ℃, the reduction of the graphene oxide is insufficient, the electronic conductivity is poor, and the rate capability of the high-nickel ternary cathode material is influenced; the sintering temperature is higher than 400 ℃, the graphene oxide is reduced and then undergoes an oxidation-reduction reaction with 3+ nickel ions in the high-nickel ternary cathode material, and the gram volume and the first effect of the high-nickel ternary cathode material are obviously affected. Generally speaking, graphene oxide needs to be reduced into graphene with carbon content not less than 98%, and high-temperature sintering at 400 ℃ is needed, at the temperature, the reduction property of carbon can promote the reduction of + 3-valent nickel in the high-nickel ternary cathode material, so that the capacity and the first effect are reduced, in the scheme, the carbon content of the raw material graphene oxide powder is controlled to be 60% -80%, the oxidation degree of the raw material is relatively low, the required reduction temperature is also low, and the graphene oxide can be reduced to an ideal state at the temperature of 300 ℃ -400 ℃.
The second aspect of the invention provides a graphene-coated high-nickel ternary cathode material prepared by the method.
Compared with the prior art, the invention has the following advantages:
1. the organic solvent system is adopted to coat the graphene on the high-nickel ternary cathode material, so that the problem that the specific capacity of the material is reduced and the cycle performance is reduced due to the loss of a lithium source caused by the side reaction of water and the high-nickel ternary cathode material under the aqueous solvent system is avoided. The organic solvent system can keep the original particle structure and form of the high-nickel ternary cathode material, is beneficial to uniform coating of graphene on the particle surface, can control the thickness of a coating layer, and greatly improves the electronic conductivity, the circulation stability and the rate capability of the material.
2. Adopts a lower temperature sintering process to carry out high nickel ternary sinteringAnd coating the positive electrode material. The graphene oxide mainly carries hydroxyl functional groups, so that the graphene oxide can be reduced at a lower sintering temperature, and has good electronic conductivity; meanwhile, the graphene oxide has certain oxidability, so that the condition that the + 3-valent nickel is reduced in the sintering process of the high-nickel ternary positive electrode material is avoided, and NI is reduced +2 With Li + The mixed discharging degree of the high-nickel ternary cathode material fundamentally improves the specific capacity and the first efficiency of the high-nickel ternary cathode material. In addition, by adopting the coating mode, the water absorption of the high-nickel ternary material can be reduced, and the adaptability under different moisture environments is improved.
3. The carbon content of the graphene oxide powder serving as a raw material is controlled to be 60% -80%, and the oxygen content is controlled to be 20% -40%, so that the graphene oxide can be reduced to an ideal state at the temperature of 300-400 ℃.
Drawings
FIG. 1 is an SEM of a graphene-coated high-nickel ternary positive electrode material
FIG. 2 is a graph of the rate discharge performance of the high nickel ternary positive electrode material before graphene coating and uncoated in example 1
FIG. 3 is a 1C charge-discharge cycle performance curve of examples 1-3 and comparative examples 1-2
Detailed Description
The technical solutions of the present invention will be described clearly and completely with reference to the following embodiments, and it should be understood that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention is further illustrated by the following examples. The materials in the examples are prepared according to known methods or are directly commercially available, unless otherwise specified.
Example 1
The invention provides a method for modifying a high-nickel ternary cathode material, which comprises the following steps:
(a) Preparing graphene oxide:
and (3) taking 10Kg of GO aqueous solution with the concentration of 2.5% at room temperature, and carrying out nano sanding and high-pressure homogenization treatment to obtain a uniformly dispersed graphene oxide solution with the particle size D50 of 3-10um. And then carrying out spray drying treatment on the graphene oxide powder to obtain the graphene oxide powder. The size of balls used by the sanding equipment is 0.6-0.8mm, the balls are made of zirconia, the sanding speed is 2000rpm, the sanding time is 3 hours, and the temperature of the sanding cavity slurry is controlled at 20-45 ℃; the pressure used in the homogenizing device is 900-1000bar, and the circulation homogenizing is performed for 5 times. The temperature of a feed inlet of the spray drying equipment is 195 ℃, the temperature of a discharge outlet of the spray drying equipment is 90 ℃, and the atomization frequency is 50Hz, so that the graphene oxide powder with 68.2% of carbon content and 31.8% of oxygen content is prepared.
(b) Coating with graphene oxide:
at room temperature, in 4.5Kg of N-methylpyrrolidone solvent, according to the mass ratio of 1:1:5:93 sequentially adding 5g of dispersing agent polyvinylpyrrolidone, 5g of binder polyvinylidene fluoride, 25g of graphene oxide powder and 465g of high-nickel ternary positive electrode material to prepare mixed slurry with the concentration of 10%; after the mixture is uniformly stirred, the mixture is subjected to secondary spray drying to obtain the high-nickel ternary cathode material coated by the graphene oxide. The chemical formula of the high-nickel ternary cathode material is LiNi 0.8 Co 0.1 Mn 0.1 O 2 . The temperature of the feed inlet of the spray drying equipment is 195 ℃, the temperature of the discharge outlet is 90 ℃, and the atomization frequency is 50Hz. The powder prepared by spray drying is called precursor.
(c) And (3) reducing graphene oxide:
and (3) putting the precursor into a crucible, sintering at 350 ℃ in a nitrogen atmosphere, and keeping the temperature for 8h to finally obtain the graphene-coated high-nickel ternary cathode material. The temperature rise speed in the whole process is controlled at 8 ℃/min. The high-temperature heating equipment is a tube furnace.
Example 2
The present example differs from example 1 in that:
in the graphene oxide coating in the step (b) of the embodiment, the mass ratio of: 1:8:90, adding 5g of dispersant polyvinylpyrrolidone, 5g of binder polyvinylidene fluoride, 40g of graphite oxide powder and 450g of high-nickel ternary cathode material in sequence to prepare mixed slurry with the concentration of 10%.
And the rest is the same as that in the embodiment 1, so that the high-nickel ternary cathode material coated by the graphene is obtained.
Example 3
The difference between the present embodiment and embodiment 1 is that the temperature for reducing graphene oxide in step (c) of the present embodiment is adjusted to 400 ℃;
the rest is the same as that in the embodiment 1, and the high-nickel ternary cathode material coated by the graphene is obtained.
Comparative example 1
The difference between the comparative example and the example 1 is that in the step (2) of the comparative example, pure water is used as a solvent in the graphene oxide coating;
and the rest is the same as that in the embodiment 1, so that the high-nickel ternary cathode material coated by the graphene is obtained.
Comparative example 2
The difference between the comparative example and the example 1 is that in the step (3) of graphene oxide reduction of the comparative example, the thermal reduction temperature is 500 ℃.
And the rest is the same as that in the embodiment 1, so that the high-nickel ternary cathode material coated by the graphene is obtained.
Test examples
The mass ratio of the graphene-coated high-nickel ternary positive electrode material obtained in the embodiments 1-3 and the comparative examples 1-2 to SP and PVDF is 97:1.5, preparing a slurry in NMP solvent, wherein the mass of NMP is 1.2-1.5 times of the mass of solid. And coating the slurry on an aluminum foil with the thickness of 16um, and drying, rolling and punching to form a buckle type wafer. And assembling the button 2032 battery by using lithium foil as a counter electrode and the button wafer prepared above. The electrolyte used by the battery comprises the following main components: lithium hexafluorophosphate is adopted as lithium salt, and the concentration is 1.1mol/L; the solvent is ethylene carbonate, dimethyl carbonate and methyl ethyl carbonate, and the mass ratio is 1. The thickness of the diaphragm is 20um, and the polypropylene/polyethylene (PP/PE/PP) three-layer microporous diaphragm is formed. The first charge-discharge capacity of the battery is tested by adopting 0.1C multiplying power, the first coulomb efficiency of the battery is calculated, and the cycle performance is tested by adopting 1C multiplying power charge/discharge for 100 cycles (note: the specific capacity of the high-nickel ternary positive electrode is calculated according to 180 mAh/g). The cut-off voltage of the battery is 3.0-4.3V. In addition, slurry prepared by the high-nickel ternary cathode materials of the above examples 1-3, the comparative examples 1-2 and before modification is coated on a PET film, dried and punched into a round piece with the diameter of 12mm, and the resistivity of the round piece is tested. The test results are shown in Table 1.
TABLE 1 table of results of electrical property test of examples 1-3 and comparative examples 1-2
| Test object | Pole piece resistivity (omega/cm) | 0.1C first charge capacity (mAh/g) | 0.1C first discharge Capacity (mAh/g) | Initial coulomb efficiency (%) | Capacity retention (%) at week 100 (note: 1C cycle) |
| Example 1 | 2.38 | 226 | 194.3 | 85.8 | 97.8 |
| Example 2 | 1.89 | 231 | 192.8 | 83.4 | 96.3 |
| Example 3 | 2.16 | 224 | 191.9 | 85.5 | 95.2 |
| Comparative example 1 | 2.69 | 208 | 157.7 | 75.8 | 87.3 |
| Comparative example 2 | 1.95 | 213 | 171.0 | 80.3 | 90.8 |
| Before modification | 10.19 | 224 | 189.5 | 84.7 | 78.3 |
As can be seen from the above table 1, by adopting the method for modifying the graphene-coated high-nickel ternary cathode material, the resistivity of the pole piece is reduced to below 2.5 omega/cm from 10.19 omega/cm before modification; the 0.1C discharge specific capacity and the first effect are slightly improved compared with those before modification; the capacity retention rate of the button cell 1C in 100-cycle is improved from 78.3% before modification to more than 95%; the electronic conductivity and the cycle life of the high-nickel ternary cathode material coated by the graphene are obviously improved, and the high-nickel ternary cathode material has good electrochemical stability.
In the comparative examples 1-2, the pure water solvent and the higher reduction temperature are adopted, so the first effect is obviously reduced compared with that before modification, and the resistivity and the cycle performance of the pole piece are improved a little; the reduction in first effect is attributed to the loss of the lithium source and the high temperature reduction of the nickel ions, resulting in a decrease in capacity.
The graphene has excellent electronic conductivity, good electrochemical and thermal stability and small charge transfer impedance, and a continuous conductive network formed by a two-dimensional plane of the graphene can greatly reduce the resistivity of the high-nickel ternary cathode material and improve the rate capability of the high-nickel ternary cathode material. The graphene raw material adopted by the invention is graphene oxide, the graphene oxide sheet layer contains rich oxygen-containing functional groups, such as carboxyl, hydroxyl, epoxy and the like, and the surface of the graphene oxide sheet layer has positive and negative group charges, so that the graphene oxide sheet has good self-assembly and film-forming functions, and can well and uniformly coat the high-nickel ternary cathode material. The flexibility and the fold structure of the graphene oxide sheet layer can enable the high-nickel ternary cathode material to realize compact coating, and the improvement of the circulation stability of the material and the compatibility of the material with electrolyte is facilitated. Meanwhile, the graphene oxide solution is weakly acidic, and the high-nickel ternary positive electrode has alkaline compounds such as LiOH and Li remained on the surface 2 CO 3 Etc., which are predominantly alkaline. Therefore, carboxyl in the graphene oxide can spontaneously react with an alkaline compound in the high-nickel ternary material to generate an organic ester lithium salt compound, and the compound has higher conductivity than an inorganic compound, so that direct contact between particles of the high-nickel ternary positive electrode material and an electrolyte can be avoided, the stability of the high-nickel ternary positive electrode material is improved, the pH value of the high-nickel ternary positive electrode material is reduced, and the sensitivity to environmental moisture is slowed down. The organic solvent is adopted for coating, so that the structure change of the high-nickel ternary cathode material can be avoided, the self-lifting performance of the material can not be influenced, and meanwhile, the organic solvent can be recycled. In the aspect of graphene oxide reduction, due to the low oxidation degree and the main existence of the hydroxylated functional group, the graphene oxide can be reduced at a low heat treatment temperature, and the reduced graphene has good electronic conductivity.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and these modifications or substitutions do not depart from the spirit of the corresponding technical solutions of the embodiments of the present invention.
Claims (10)
1. A method for modifying a high-nickel ternary material is characterized by comprising the following steps:
(1) The prepared carbon content is 60-80%, the oxygen content is 20-40%, and the specific surface area is more than or equal to 300m 2 Per gram of graphene oxide powder;
(2) Adding the graphene oxide powder, a dispersing agent, a binder and a high-nickel ternary cathode material into an organic solvent, uniformly stirring, and then carrying out spray granulation and drying to obtain a high-nickel ternary cathode material coated with graphene oxide;
(3) Controlling sintering temperature and sintering time, and sintering and reducing the high-nickel ternary cathode material coated by the graphene oxide to obtain the high-nickel ternary cathode material coated by the graphene oxide, wherein the carbon content of the reduced graphene is more than or equal to 98%, the oxygen content is less than or equal to 2%, and the specific surface area is more than or equal to 200m 2 /g。
2. A method for modifying a high nickel ternary material according to claim 1, wherein:
the organic solvent is one or more of N-methyl pyrrolidone, alcohol and acetone, the dispersing agent is polyvinylpyrrolidone, and the binder is polyvinylidene fluoride.
3. A method for modifying a high nickel ternary material according to claim 1, wherein:
the chemical formula of the high-nickel ternary cathode material is LiNi x Co y Mn z O 2 Wherein the content of nickel is more than or equal to 50 percent, x is more than or equal to 0.5 and less than 1, y is more than 0 and less than 0.5,0＜z＜0.5，x+y+z=1。
4. A method for modifying a high nickel ternary material according to claim 1, wherein:
in the step (2), the graphene oxide powder, the dispersing agent, the binder and the high-nickel ternary cathode material are added in the following mass ratio: 2-10:0.5-5:0.5-5:80-97.
5. A method for modifying a high nickel ternary material according to claim 1, wherein:
the sintering temperature is 300-400 ℃, and the sintering time is 10-24 h.
6. The method for modifying a high-nickel ternary material according to claim 1, wherein the method comprises the following steps:
the sintering reduction treatment is carried out under the condition of inert atmosphere.
7. A method for modifying a high nickel ternary material according to claim 1, wherein:
and after the sintering reduction treatment, crushing the high-nickel ternary cathode material coated by the graphene.
8. A method for modifying a high nickel ternary material according to claim 1, wherein:
the preparation method of the graphene oxide powder comprises the following steps: and dispersing and stripping the graphene oxide solution by adopting nano sanding and high-pressure homogenizing equipment to obtain the graphene oxide solution with uniform particle size distribution, and then drying by spray granulation to obtain graphene oxide powder.
9. A method for modifying a high nickel ternary material according to claim 8, wherein:
the mass concentration of the graphene oxide solution is 0.5% -3%, and the solvent is pure water.
10. A method for modifying a high nickel ternary material according to claim 8, wherein:
the size of the nano-sand-milled ball is 0.6-2um, the rotating speed is 1000-3000rpm, and the sand milling time is more than or equal to 2h; the pressure of the high-pressure homogenizing equipment is more than or equal to 800bar, and the homogenizing circulation is more than or equal to 3 times.
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