A single-crystal ternary material, a preparation method and application thereof

Abstract

The application discloses a single-crystal ternary material and a preparation method and application thereof. x Co y M 1‑x‑y O2, wherein 0.6<=x<1, y<=0.05, and M is Al and / or Mn; the single-crystal ternary material has a rest angle less than 30 degrees, a sphericity greater than 0.75, an aspect ratio of 0.7-1, and a particle size D50 of 2.5-4.5 microns. The preparation method comprises the following steps: S1) mixing a single-crystal ternary positive electrode base material A with petrolatum containing nano additives, and immersing in a vacuum environment to obtain an intermediate product B; S2) subjecting the intermediate product B to high-speed hot gas treatment, and then to cold treatment to obtain an intermediate product C; S3) mixing the intermediate product C with a surface modifier, and then adding nano graphene sheets to perform ultrasonic dispersion and heat treatment to obtain a final product D, and grinding to obtain the single-crystal ternary material. The single-crystal ternary positive electrode material can be used for preparing a positive electrode material, and effectively solves the problems of gas release, poor long cycle performance and poor thermal stability.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of new energy, and relates to a single-crystal ternary material and a preparation method and application thereof. BACKGROUND

[0002] With more and more attention paid to carbon emission and related climate problems, new energy vehicles account for a larger and larger proportion in the automobile market. At present, one of the main obstacles to the development of new energy vehicles is the endurance problem, that is, the energy density problem of the automobile battery. The energy density of the battery is mainly determined by the positive electrode material. Among them, the layered structure ternary material (LiNi 1-x- y Co x Mn y O2, 1-x-y is greater than 0.6) combines the advantages of three transition metal oxide lithium salts, has high energy density, good cycle performance and low cost, and is considered as one of the most promising positive electrode materials for new energy vehicles.

[0003] Traditional ternary materials are mainly agglomerated ternary materials, which are secondary particles formed by agglomeration of primary particles. The agglomerated secondary particles are prone to pulverization under multiple cycles and high voltage, which directly leads to the exposure of fresh interfaces, increases the electrolyte side reaction, increases the interface impedance, increases the polarization, and causes the capacity to drop sharply in the later cycle stage, and even causes the battery to expand and even explode, thereby affecting the safety performance of the battery. The breakage of the polycrystalline particles after long cycle is due to the repeated embedding and de-embedding of Li + in the charging and discharging process, which causes anisotropic changes in the crystal lattice, and the micro-strain generated gradually diffuses along the gaps or grain boundaries between the primary particles, and finally forms cracks to make the primary particles fall off until the secondary particles are completely broken. In addition, due to the existence of gaps between the primary particles of the secondary spherical particles, the surfaces of some primary particles in the gaps between the secondary spherical particles cannot be uniformly coated when the surface coating treatment is performed on the positive electrode material; this inevitably leads to poor overall electronic conductivity of the secondary particles, and the capacity retention rate of the battery manufactured using the positive electrode material will decrease after a certain period of cycle. The crystal structure of the single-crystal particles has anisotropy, which can effectively relieve the micro-strain generated when the crystal lattice changes; at the same time, the good mechanical strength of the single-crystal particles can effectively inhibit the expansion of micro-cracks during long cycle, so that the single-crystal ternary positive electrode material has excellent cycle stability in a long cycle period. Therefore, during the long cycle charging and discharging process, the single-crystal particles with high mechanical strength can significantly improve the cycle stability of the ternary positive electrode material. For LiNi 1-x-y Co x Mn yO2, the positive electrode material, is very easy to react with CO2 and H2O in an air atmosphere, generating Li2CO3 and LiOH on the surface of the positive electrode material, which is easy to cause the ternary positive electrode material to easily decompose to produce a large amount of gas when working at high voltage or storing at high temperature, not only causing the soft package lithium ion battery to swell, bulge and other phenomena, but also the generated bubbles cannot be discharged, causing edge lithium precipitation in the cell, which significantly reduces the capacity of the lithium ion battery. Since the original particles of the single-crystal ternary positive electrode material have no voids and are a complete crystal form, the side reaction between the single-crystal ternary positive electrode material and the electrolyte can be greatly reduced, thereby effectively alleviating the gas production problem of the lithium ion battery during high-temperature storage.

[0004] With the development and progress of science and technology, ternary single-crystal materials are the preferred positive electrode materials for lithium batteries due to their high compaction rate, low alkali content, and excellent battery expression performance. The common method for crushing single-crystal materials is air flow crushing. During the air flow crushing process, the dust-containing air obtains a large flow speed and generates strong turbulence, greatly increasing the collision and friction opportunities between dust particles. Micron particles move at high speed in a narrow space, and particles collide with each other and with obstacles to acquire positive or negative charges. During sieving, ternary single-crystal products are prone to form large particle agglomerates on the sieve surface. The accumulation of large particle agglomerates can seriously affect the sieving speed and production capacity, and in severe cases, it can also cause the material to be unable to sieve. In the existing production process, the treatment method for the agglomerated material on the sieve surface is generally as follows: every two hours, the vibrating sieve is disassembled and manually cleaned after stopping. The large particle agglomerates on the sieve surface are manually cleaned and recovered in bags. When the accumulation reaches a certain amount, it is re-put into the bin and re-sieved. This treatment method has the problems of delaying production capacity, introducing metal impurities at the breakpoint, and poor material flowability, which can cause pipe blockage in the automatic mixing process, poor dispersion of the stirrer, high energy consumption, long stirring time, and other problems.

[0005] The flowability of ternary single crystal particles is related to the shape, size, surface state, density, porosity and other factors of the particles, and the complex relationship between the adhesion, friction, van der Waals force and electrostatic force between the particles hinders the free flow of the particles and affects the flowability of the ternary single crystal particles, and the flowability of the ternary single crystal particles cannot be expressed by a single value. The flowability of the ternary single crystal particles is usually represented by the rest angle and the flow rate. In order to weaken the interaction between the particles, the following measures are taken. 1. Increase the particle size: round the particles of the adhesive powder to reduce the point contact between the particles and reduce the adhesion and cohesion between the particles. 2. Particle morphology and surface roughness: the smooth surface of the spherical particles can reduce the number of contact points and reduce the friction. 3. Moisture content: due to the hygroscopicity of the powder, the moisture adsorbed on the surface of the particles increases the adhesion between the particles, and therefore appropriate drying is beneficial to weaken the interaction between the particles. 4. The effect of adding a flow aid: the addition of a flow aid in the powder can greatly improve the flowability of the powder. The rough surface of the particles is filled and a smooth surface is formed, the resistance is reduced, and the electrostatic force is reduced, but attention should be paid to the amount, and too much flow aid will increase the resistance.

[0006] Therefore, it is necessary to provide a single crystal ternary material with good flowability, high working voltage, chargeable and dischargeable and good cycle stability. SUMMARY

[0007] In view of the above technical problems of poor flowability of the existing single crystal ternary material, the purpose of the present application is to provide a single crystal ternary material and a preparation method and application thereof.

[0008] The single crystal ternary positive electrode material can effectively solve the problems of gas release, poor long cycle performance and poor thermal stability; the single crystal particles with good flowability have good dispersibility, and when used for preparing a battery positive electrode, the conductive agent is uniformly dispersed in the slurry preparation process, which is beneficial to the transmission of lithium ions.

[0009] The present application provides a single crystal ternary material with a chemical formula of LiNi x Co y M 1-x-y O2, wherein 0.6≤x<1, y≤0.05, M is Al and / or Mn;

[0010] The rest angle of the single crystal ternary material is less than 30°, the sphericity is greater than 0.75, the aspect ratio is 0.7-1, and the particle size D50 is 2.5-4.5 μm.

[0011] In the present application, D50 refers to Dv50, also known as median diameter or median particle size, which refers to the particle size value corresponding to the cumulative percentage of 50%.

[0012] In the above-mentioned single crystal ternary material, the bulk density of the single crystal ternary material is greater than 1.6 g / cm3 while the tap density is > 2.0 g / cm 3 and the tap density / loose density < 1.3.

[0013] The application also provides a preparation method of the single-crystal ternary material, comprising the following steps:

[0014] S1) mixing the single-crystal ternary positive electrode matrix material A with petrolatum containing nano additives, and immersing in a vacuum environment to obtain an intermediate product B;

[0015] S2) treating the intermediate product B by high-speed hot gas, and then by cold treatment to obtain an intermediate product C;

[0016] S3) mixing the intermediate product C with a surface modifier, and then adding nano graphene sheets for ultrasonic dispersion and heat treatment to obtain a final product D, and grinding to obtain the single-crystal ternary material.

[0017] In the step S1) of the preparation method, the mass ratio of the single-crystal ternary positive electrode matrix material A to petrolatum in the petrolatum containing nano additives can be 2-10:1, specifically 5:1, 8:1, 2-5:1, 2-8:1, 5-8:1; the mass ratio of the nano additives to the single-crystal ternary positive electrode matrix material A can be 0.02-0.5:100, specifically 0.1:100, 0.2:100, 0.1-0.2:100, 0.1-0.5:100.

[0018] The chemical formula of the single-crystal ternary positive electrode matrix material A is LiNi x Co y M 1-x-y O2, wherein 0.6≤x<1, y≤0.05, and M is Al and / or Mn.

[0019] The longest crystal size of the mineral number of petrolatum in the petrolatum containing nano additives is less than 5 μm, the drop melting point is 35-70℃, the nano additives are selected from at least one of Al2O3, ZrO2, Y2O3, Nb2O5, WO3, TiO2, MoO3, and La2O3; and the particle size of the nano additives is less than 50 nm.

[0020] In the application, the longest crystal size of the mineral number of the petrolatum is the longest diameter, i.e. the Feret diameter.

[0021] The mixing method with the petrolatum in step S1) of the above preparation method adopts mechanical ball milling, the ball milling rotation speed can be 50-300 rpm / min, specifically can be 50 rpm / min, 100 rpm / min, 50-100 rpm / min, 100-300 rpm / min or 50-200 rpm / min, the ball milling time is 2-10 h, specifically can be 3 h, 10 h, 2-3 h, 3-10 h or 2.5-7.5 h, and the ball milling reaction temperature is room temperature;

[0022] The vacuum degree of the vacuum environment can be -0.06 to -0.1 MPa, specifically can be -0.06 MPa, -0.07 MPa, -0.1 MPa, -0.06 to -0.07 MPa, -0.07 to -0.1 MPa or -0.06 to -0.09 MPa, the impregnation time can be 30-120 min, specifically can be 60 min, 120 min, 30-60 min, 60-120 min or 50-100 min, and the impregnation temperature can be 35-100℃, specifically can be 35℃, 50℃, 100℃, 35-50℃, 50-100℃, 40-60℃ or 40-70℃.

[0023] In the present application, the room temperature is the common sense known in the art, generally refers to 10-30℃.

[0024] In the present application, the mechanical ball milling can grind the sharp corners of the particles to a flat surface, and modify the irregular particle morphology to a spherical particle, so that the material particles are round and have better flowability, which is beneficial to further improve the compaction density of the material;

[0025] The nano additive can form a chimeric structure with the surface of the single-crystal ternary positive electrode matrix material A after grinding, and the petrolatum has an adhesive effect, which can make the nano additive and the single-crystal ternary positive electrode matrix material A combine more closely. The Mohs hardness value of the abrasive particles of the mechanical ball milling should be not less than 6, and the selected noble metal oxide is zirconium oxide, gallium oxide, cerium oxide or tungsten carbide; preferably, the abrasive particles include metal oxide particles such as cerium dioxide, and the average particle size is 1-10 mm;

[0026] During the impregnation process in the vacuum environment, the petrolatum softens and enters the pores of the particle body phase, the nano additive and the single-crystal ternary positive electrode matrix material A further contact the body phase, not only the surface layer, and have an excellent multi-level structure.

[0027] In step S2) of the above preparation method, the high-speed hot gas is composed of CO2 and N2, and the volume ratio of the CO2 and N2 can be 0.1-0.5:1, specifically can be 0.1:1, 0.2:1 or 0.5:1.

[0028] The high-speed hot gas treatment is as follows: the gas flow rate can be 200-400 m / s, the gas temperature can be 1000-1500 DEG C, and the treatment time can be 0.05-0.5 h; the specific treatment conditions are as follows: the gas flow rate is 250 m / s or 400 m / s, the high-speed hot gas temperature is 1000 DEG C, 1050 DEG C or 1500 DEG C, and the treatment time is 0.05 h, 0.1 h or 0.05-0.1 h.

[0029] The cold treatment is as follows: the intermediate product B after the high-speed hot gas treatment is subjected to a cold gas treatment at a temperature of not higher than -0 DEG C, the cold gas is high-purity nitrogen, and the cold treatment time can be 0.5-1.5 h; specifically, the high-purity nitrogen can be at -5 DEG C or -10 DEG C, and the cold treatment time can be 0.5 h or 1.5 h.

[0030] The preparation method further comprises a step of cyclically performing the high-speed hot gas treatment and the cold treatment in step S2).

[0031] In the present application, the number of cycles of the high-speed hot gas treatment and the cold treatment in step S2) is determined according to the performance of the final material, and the principle of less quantity and more times is followed; too many cycles are not good for the performance, and the capacity will decrease.

[0032] In step S3) of the preparation method, the mass ratio of the intermediate product C to the surface modifier can be 1:0.05-0.5, specifically 1:0.1 or 1:0.5.

[0033] The surface modifier is a mixture of sodium dioctyl sulfosuccinate and amino-modified silicone oil, and the mass ratio is 1-5:1, specifically 2:1 or 5:1.

[0034] The mass ratio of the nanographene sheet to the intermediate product C can be 0.005-0.1:100, specifically 0.005:100, 0.05:100 or 0.1:100.

[0035] The ultrasonic dispersion conditions are as follows: the power is 1-4 KW, and the frequency is 10 Hz-100 KHz; the ultrasonic dispersion temperature is 40-60 DEG C, and the time is 10-60 min; specifically, the ultrasonic dispersion power can be 1 KW, 3 KW or 4 KW, the frequency can be 100 KHz or 50 KHz, the dispersion treatment temperature can be 50 DEG C or 60 DEG C, and the treatment time can be 10 min, 20 min or 60 min.

[0036] In the preparation method step S3) above, the heat treatment is as follows: heat treatment at 60-120 DEG C for 1-3 hours in the presence of nitrogen and / or inert gas; specifically, 3 hours of nitrogen heat treatment at 120 DEG C, 1 hour of nitrogen heat treatment at 120 DEG C, or 1 hour of nitrogen heat treatment at 100 DEG C.

[0037] In the present application, the inert gas is the inert gas commonly used in the art, such as argon, helium (He), neon (Ne), etc.

[0038] The present application further provides a lithium ion battery positive electrode, which comprises a positive electrode material, and the positive electrode material comprises the single-crystal ternary material described above.

[0039] In the lithium ion battery positive electrode described above, the lithium ion battery positive electrode is used under high-voltage conditions, and the capacity retention rate is greater than 97% after 100 cycles at 2.8-4.5 V and 1C rate, and the discharge median voltage platform is improved.

[0040] The present application further provides a lithium ion battery, which comprises a positive electrode, and the positive electrode is the lithium ion battery positive electrode described above.

[0041] Compared with the prior art, the scheme provided by the present application has the following benefits:

[0042] 1. On the basis of the conventional lithium nickel cobalt manganese oxide ternary material, the present application fully combines the nano additive and the matrix by using the petrolatum impregnation technology, trims the particle edges and corners by using the strong mechanical grinding technology, and then performs cold-heat alternating treatment, and finally obtains the single-crystal lithium nickel cobalt manganese oxide ternary material with good fluidity by using the modifier to locally recrystallize the material surface layer.

[0043] 2. The material modification process in the present application is performed by body doping and surface coating, which reduces the residual alkali content on the material surface, is suitable for application in the field of high-voltage lithium ion batteries, improves the safety performance of the material under high voltage, and improves the high specific capacity and excellent cycle stability of the single-crystal ternary positive electrode material and other electrochemical performances.

[0044] 3. The morphology of the single-crystal particles is tested to characterize the particle size information, sphericity, average particle size, aspect ratio and other information. The particles are round and smooth, and the particle size consistency is good.

[0045] 4. The present application discloses the relationship between the fluidity of the single-crystal ternary material with excellent electrochemical performance and the basic properties of the material, including the rest angle, tap density and specific surface area of the tested material. BRIEF DESCRIPTION OF DRAWINGS

[0046] Figure 1 is the SEM picture of the sample obtained in Example 1 of the present application;

[0047] Figure 2 is the charge-discharge curve of the sample obtained in Example 1 of the present application;

[0048] Figure 3 is the XRD of the sample obtained in Example 1 of the present application, the XRD test result of the final product shows that the crystal structure of the final product is a typical α-NaFeO2 type layered structure, belonging to R-3m space group. It is shown that the positive electrode material obtained by the present application has a good layered structure, and the materials obtained by other examples also have the same α-NaFeO2 type layered structure. DETAILED DESCRIPTION

[0049] The experimental methods used in the following examples are conventional methods unless otherwise specified.

[0050] The materials, reagents, etc. used in the following examples can be obtained from commercial channels unless otherwise specified.

[0051] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application is further described in detail below in combination with examples. It should be understood that the specific examples described herein are only used to explain the present application and do not limit the present application.

[0052] Example 1

[0053] A single crystal type ternary material is prepared according to the following steps:

[0054] S1), the single crystal type ternary positive electrode matrix material A (LiNi 0.7 Co 0.05 Mn 0.25 O2) is mixed with petrolatum containing nano additive Nb2O5 uniformly, the mass ratio of A to petrolatum is 5:1, the amount of nano additive Nb2O5 is 0.1wt% of the mass of matrix material A, the average particle size of additive Nb2O5 is 50nm and the BET is 27m 2 / g, the ball milling speed is 100rpm / min, the ball milling time is 3h, the mechanical ball milling reaction temperature is room temperature (25℃, same below), the vacuum degree of vacuum environment is-0.07MPa, the immersion time is 60min, and the immersion temperature is 50℃, to obtain intermediate product B;

[0055] S2), the intermediate product B is treated under high-speed hot gas composed of CO2 and N2 (0.2:1), the gas flow rate is 250m / s, the high-speed hot gas temperature is 1050℃, and the treatment time is 0.1h. Then, the high-purity nitrogen gas at-5℃ is used for cold treatment, and the cold treatment time is 0.5h, to obtain intermediate product C.

[0056] S3), the intermediate product C was dispersed with a mixture of sodium dioctyl sulfosuccinate and amino-modified silicone oil at a mass ratio of 2:1, 0.05wt% of nano-graphene sheets were added, and ultrasonic dispersion was performed under the action of ultrasonic waves with a power of 3KW and a frequency of 50KHz, the dispersion treatment temperature was 50℃, and the treatment time was 20min; nitrogen heat treatment was performed at 120℃ for 1 hour; and then grinding treatment was performed to obtain the single-crystal ternary material LiNi 0.7 Co 0.05 Mn 0.25 O2.

[0057] The micro-morphology of the sample was tested by SEM (results are shown in FIG. 1), and the crystal structure was tested by XRD (as shown in FIG. 2). The tap density TD and the loose bulk density AD of the sample were tested, and the residual alkali content and the electrochemical performance were tested. The sphericity was 0.8, the aspect ratio was 0.71, and the particle size D50 was 3.5μm. Figure 1 Figure 3 The micro-morphology of the sample was tested by SEM (results are shown in FIG. 1), and the crystal structure was tested by XRD (as shown in FIG. 2). The tap density TD and the loose bulk density AD of the sample were tested, and the residual alkali content and the electrochemical performance were tested. The sphericity was 0.8, the aspect ratio was 0.71, and the particle size D50 was 3.5μm.

[0058] Example 2

[0059] S1), the single-crystal ternary positive electrode matrix material A (LiNi 0.83 Co 0.05 Al 0.12 O2) with poor fluidity was mixed with petrolatum containing nano-additive WO3, the mass ratio of A to petrolatum was 8:1, the amount of nano-additive Nb2O5 was 0.2wt% of the mass of the matrix material A, the average particle size of the additive WO3 was 40nm and the BET was 37m 2 / g, the ball milling speed was 50rpm / min, the ball milling time was 10h, the mechanical ball milling reaction temperature was room temperature, the vacuum degree of the vacuum environment was-0.06MPa, the immersion time was 120min, and the immersion temperature was 100℃, to obtain the intermediate product B;

[0060] S2), the intermediate product B was treated under high-speed hot gas composed of CO2 and N2 (0.5:1) at a gas flow rate of 400m / s and a high-speed hot gas temperature of 1000℃ for 0.1h. Then, high-purity nitrogen gas cold treatment was performed at-10℃ for 0.5h, and the cold and hot alternating cycle treatment was performed to obtain the intermediate product C.

[0061] ​S3), the intermediate product C and the mixture of sodium dioctyl sulfosuccinate and amino-modified silicone oil with a mass ratio of 5:1, 0.1wt% of nano-graphene sheets were added, and the dispersion treatment was carried out under the action of ultrasonic waves with a dispersion power of 4KW and a frequency of 100KHz, the dispersion treatment temperature was 60°C, and the treatment time was 10min; nitrogen heat treatment at 100°C for 1h; and then grinding treatment to obtain the single-crystal ternary material LiNi 0.83 Co 0.05 Al 0.12 O2.

[0062] Example 3

[0063] S1), the poor flowability single-crystal ternary positive electrode matrix material A (LiNi 0.65 Co 0.05 Mn 0.30 O2) was uniformly mixed with petrolatum containing nano-additive MoO3, the mass ratio of A to petrolatum was 5:1, the dosage of nano-additive MoO3 was 0.2wt% of the mass of the matrix material A, the average particle size of the additive MoO3 was 40nm and the BET was 40m 2 / g, the ball milling speed was 100rpm / min, the ball milling time was 3h, the mechanical ball milling reaction temperature was room temperature, the vacuum degree of the vacuum environment was-0.1MPa, the immersion time was 120min, and the immersion temperature was 35°C to obtain the intermediate product B;

[0064] S2), the intermediate product B was treated under high-speed hot gas composed of CO2 and N2 (0.5:1) at a gas flow rate of 250m / s and a high-speed hot gas temperature of 1500°C for a treatment time of 0.05h. Then, high-purity nitrogen cold treatment at-5°C for 1.5h was carried out, and the cold and hot alternating cycle treatment was carried out to obtain the intermediate product C.

[0065] S3), the intermediate product C and the mixture of sodium dioctyl sulfosuccinate and amino-modified silicone oil with a mass ratio of 2:1, 0.1wt% of nano-graphene sheets were added, and the dispersion treatment was carried out under the action of ultrasonic waves with a dispersion power of 3KW and a frequency of 50KHz, the dispersion treatment temperature was 50°C, and the treatment time was 20min; nitrogen heat treatment at 120°C for 1h; and then grinding treatment to obtain the single-crystal ternary material LiNi 0.65 Co 0.05 Mn 0.30 O2.

[0066] Example 4

[0067] S1), the poor flowability single-crystal ternary positive electrode matrix material A (LiNi 0.65Co 0.05 Mn 0.30 O2), mixed with petrolatum containing nano-additive La2O3, the mass ratio of A to petrolatum being 5:1, the amount of nano-additive La2O3 being 0.2wt% of the mass of base material A, the average particle size of additive La2O3 being 70nm and BET being 15m 2 / g, the ball milling rotation speed being 100rpm / min, the ball milling time being 3h, the mechanical ball milling reaction temperature being room temperature, the vacuum degree of the vacuum environment being -0.1MPa, the impregnation time being 120min, and the impregnation temperature being 35℃, to obtain intermediate product B;

[0068] S2), treating intermediate product B under high-speed hot gas composed of CO2 and N2(0.5:1) at a gas flow rate of 250m / s and a high-speed hot gas temperature of 1500℃ for 0.05h. Then, high-purity nitrogen gas at -5℃ is used for cold treatment for 1.5h, and the cold and hot alternating cycle treatment is performed to obtain intermediate product C.

[0069] S3), dispersing and treating intermediate product C with a mixture of succinyl dioctyl ester sodium sulfonate and amino-modified silicone oil at a mass ratio of 2:1, adding 0.1wt% of nano-graphene sheets, and dispersing and treating under the action of ultrasonic waves at an ultrasonic power of 3KW and a frequency of 50KHz, a dispersing and treating temperature of 50℃, and a treating time of 20min. Nitrogen gas heat treatment at 120℃ for 1h is then performed, and grinding treatment is performed to obtain single-crystal ternary material LiNi 0.65 Co 0.05 Mn 0.30 O2.

[0070] Example 5

[0071] S1), dispersing and treating single-crystal ternary positive electrode base material A (LiNi 0.65 Co 0.05 Mn 0.30 O2), mixed with petrolatum containing nano-additive Y2O3, the mass ratio of A to petrolatum being 5:1, the amount of nano-additive Y2O3 being 0.2wt% of the mass of base material A, the average particle size of additive Y2O3 being 80nm and BET being 10m 2 / g, the ball milling rotation speed being 100rpm / min, the ball milling time being 3h, the mechanical ball milling reaction temperature being room temperature, the vacuum degree of the vacuum environment being -0.1MPa, the impregnation time being 120min, and the impregnation temperature being 35℃, to obtain intermediate product B;

[0072] S2), the intermediate product B is treated under high-speed hot gas consisting of CO2 and N2 (0.1:1) at a gas flow rate of 200 m / s, a high-speed hot gas temperature of 1000°C, and a treatment time of 0.05 h. Then, the intermediate product is treated under high-purity nitrogen gas at -1°C for 1.5 h, and the cold and hot alternating cycle treatment is performed to obtain the intermediate product C.

[0073] S3), the intermediate product C is dispersed and treated with a mixture of sodium dioctyl sulfosuccinate and amino-modified silicone oil at a mass ratio of 2:1, 0.005wt% of nano graphene sheets, ultrasonic dispersion power of 1KW, ultrasonic frequency of 100KHz, dispersion treatment temperature of 50°C, and treatment time of 60 min; nitrogen heat treatment at 120°C for 3 hours; and then grinding treatment to obtain the single-crystal ternary material LiNi 0.65 Co 0.05 Mn 0.30 O2.

[0074] Comparative Example 1

[0075] The nano additive is omitted compared to Example 3.

[0076] S1), the single-crystal ternary positive electrode matrix material A (LiNi 0.65 Co 0.05 Mn 0.30 O2) with poor fluidity is mixed with petrolatum uniformly at a mass ratio of 5:1, ball milling speed of 100 rpm / min, ball milling time of 3 h, mechanical ball milling reaction temperature of room temperature, vacuum degree of the vacuum environment of -0.1 MPa, immersion time of 120 min, and immersion temperature of 35°C to obtain the intermediate product B.

[0077] S2), the intermediate product B is treated under high-speed hot gas consisting of CO2 and N2 (0.5:1) at a gas flow rate of 250 m / s, a high-speed hot gas temperature of 1500°C, and a treatment time of 0.05 h. Then, the intermediate product is treated under high-purity nitrogen gas at -5°C for 1.5 h, and the cold and hot alternating cycle treatment is performed to obtain the intermediate product C.

[0078] S3), the intermediate product C is dispersed and treated with a mixture of sodium dioctyl sulfosuccinate and amino-modified silicone oil at a mass ratio of 2:1, 0.1wt% of nano graphene sheets, ultrasonic dispersion power of 3KW, ultrasonic frequency of 50KHz, dispersion treatment temperature of 50°C, and treatment time of 20 min. Nitrogen heat treatment at 120°C for 1 hour. Then grinding treatment to obtain the single-crystal ternary material LiNi 0.65 Co 0.05 Mn0.30 O2.

[0079] Comparative Example 2

[0080] The vacuum impregnation process is omitted compared to Example 3.

[0081] S1), the poor flowability single-crystal ternary positive electrode base material A (LiNi 0.65 Co 0.05 Mn 0.30 O2) is mixed with petrolatum containing nano additive MoO3 uniformly, the mass ratio of A to petrolatum is 5:1, the dosage of nano additive MoO3 is 0.2wt% of the mass of base material A, the average particle size of additive MoO3 is 40nm and the BET is 40m 2 / g, the ball milling speed is 100rpm / min, the ball milling time is 3h, the mechanical ball milling reaction temperature is room temperature, to obtain intermediate product B;

[0082] S2), the intermediate product B is treated under high-speed hot gas composed of CO2 and N2 (0.5:1), the gas flow rate is 250m / s, the high-speed hot gas temperature is 1500℃, the treatment time is 0.05h. Then, high-purity nitrogen gas at-5℃ is used for cold treatment, the cold treatment time is 1.5h, and the cold and hot alternating cycle treatment is carried out to obtain intermediate product C.

[0083] S3), the intermediate product C is dispersed and treated with the mixture of succinic acid dioctyl ester sodium sulfonate and amino-modified silicone oil with a mass ratio of 2:1, 0.1wt% of nano graphene sheets are added, and ultrasonic dispersion is carried out under the action of ultrasonic waves with a power of 3KW and a frequency of 50KHz, the dispersion treatment temperature is 50℃, the treatment time is 20min. Nitrogen heat treatment at 120℃ for 1h. Then, grinding treatment is carried out to obtain single-crystal ternary material LiNi 0.65 Co 0.05 Mn 0.30 O2.

[0084] Comparative Example 3

[0085] The high-speed cold and hot alternating treatment process is omitted compared to Example 3.

[0086] S1), the poor flowability single-crystal ternary positive electrode base material A (LiNi 0.65 Co 0.05 Mn 0.30 O2) is mixed with petrolatum containing nano additive MoO3 uniformly, the mass ratio of A to petrolatum is 5:1, the dosage of nano additive MoO3 is 0.2wt% of the mass of base material A, the average particle size of additive MoO3 is 40nm and the BET is 40m 2 / g, the ball milling rotation speed was 100 rpm / min, the ball milling time was 3 h, the mechanical ball milling reaction temperature was room temperature, the vacuum degree of the vacuum environment was-0.1 MPa, the impregnation time was 120 min, and the impregnation temperature was 35℃, to obtain intermediate product B;

[0087] S2), after drying the intermediate product B, to obtain intermediate product C.

[0088] S3), the intermediate product C was dispersed and treated under the action of ultrasonic waves with an ultrasonic dispersion power of 3 KW and a frequency of 50 KHz, the dispersion treatment temperature was 50℃, the treatment time was 20 min, 1 wt% of nano graphene sheets were added, and the mixture of sodium dioctyl succinate sulfonate and amino-modified silicone oil with a mass ratio of 2:1 was added. Nitrogen heat treatment at 120℃ for 1 hour. Then, grinding treatment was performed to obtain the single-crystal ternary material LiNi 0.65 Co 0.05 Mn 0.30 O2.

[0089] Comparative Example 4

[0090] The surface modifier use process was omitted compared to Example 3.

[0091] S1), the single-crystal ternary positive electrode matrix material A (LiNi 0.65 Co 0.05 Mn 0.30 O2) with poor fluidity was mixed with petrolatum containing nano additive MoO3, the mass ratio of A to petrolatum was 5:1, the dosage of nano additive MoO3 was 0.2 wt% of the mass of the matrix material A, the average particle size of the additive MoO3 was 40 nm and the BET was 40 m 2 / g, the ball milling rotation speed was 100 rpm / min, the ball milling time was 3 h, the mechanical ball milling reaction temperature was room temperature, the vacuum degree of the vacuum environment was-0.1 MPa, the impregnation time was 120 min, and the impregnation temperature was 35℃, to obtain intermediate product B;

[0092] S2), the intermediate product B was treated under high-speed hot gas composed of CO2 and N2 (0.5:1), the gas flow rate was 250 m / s, the high-speed hot gas temperature was 1500℃, and the treatment time was 0.05 h. Then, high-purity nitrogen cold treatment at-5℃ was performed for 1.5 h, and cold and hot alternating cycle treatment was performed, to obtain intermediate product C.

[0093] S3), the intermediate product C was dispersed and treated under the action of ultrasonic waves with an ultrasonic dispersion power of 3 KW and a frequency of 50 KHz, the dispersion treatment temperature was 50℃, the treatment time was 20 min, 1 wt% of nano graphene sheets were added, and the mixture of sodium dioctyl succinate sulfonate and amino-modified silicone oil with a mass ratio of 2:1 was added. Nitrogen heat treatment at 120℃ for 1 hour. Then, grinding treatment was performed to obtain the single-crystal ternary material LiNi0.65 Co 0.05 Mn 0.30 O2.

[0094] The single-crystal ternary material prepared in the above examples was tested, and the results were as follows:

[0095] (1) Electrochemical performance test:

[0096] Preparation of button cells: the positive active material, conductive carbon black and binder PVDF prepared in the examples and comparative examples were mixed in a weight ratio of 90:5:5 to disperse into a solvent N-methyl pyrrolidone (NMP) to obtain a positive electrode slurry; the slurry was coated on an aluminum foil, and then placed in a vacuum oven for drying at 120°C for 12 hours to obtain an electrode sheet with a surface density of 20 g / cm 2 The dried electrode sheet was rolled to a compacted density of 3.2 g / cm 3 The electrode sheet was cut to obtain a positive electrode sheet. Lithium metal was used as the negative electrode, EC, DEC and DMC were mixed in a volume ratio of 1:1:1 to obtain a solvent, and then LiPF6 was dissolved in the above-mentioned solvent to obtain an electrolyte, wherein the concentration of LiPF6 was 1 mol / L. Celgard 2400 (commercially available) was used as a separator, and in an argon-filled glove box, the positive electrode sheet, the separator and the lithium sheet were sequentially stacked and set, and the above-mentioned electrolyte was injected to assemble a 2016 type button cell.

[0097] The test conditions were as follows: tested on a blue electric tester in a 25°C constant temperature box; rate and discharge performance test, test current: 0.1C, 0.2C, 0.33C, 1C, 2C constant current constant voltage charging; 0.1C, 0.2C, 0.33C, 1C, 2C constant current discharge; constant voltage segment charging cutoff condition: current rate 0.05C; test voltage range: 2.8-4.5V. 1C rate charge-discharge cycle test, cycle 100 times, calculate the cycle capacity retention rate. Define 1C = 200 mA / g.

[0098] The results are shown in Table 3. As can be seen from the results in Table 3, the sample treated by the method has higher specific capacity and higher first efficiency, better cycle performance, higher constant current charge-in rate and higher discharge median voltage compared with the comparative example. The single-crystal ternary positive electrode material has higher specific capacity and excellent cycle stability and other electrochemical properties.

[0099] (2) Residual alkali test:

[0100] Residual base test method: take the sample according to the table, accurate to 0.0001 g, put the sample in a 100 mL beaker, add 50 mL of deionized water, and put the magnetic beads into the beaker using a plastic wrap to seal, then put the beaker on a magnetic stirrer and stir for about 10-15 min; stand for 5 min, filter using a glass funnel, and the filtrate is the test solution. The specific method is shown in Table 1.

[0101] Table 1 Residual base test method

[0102]

[0103] Accurately take the test solution into a 100 mL beaker, put it into a stirring rotor, control the sample volume to about 50 mL (if less than 50 mL, add water to make up), put the beaker on the magnetic stirrer of the automatic potentiometric titrator, add 2d of phenolphthalein, select HCl standard solution according to the table, and titrate until the color changes from red to colorless. The instrument will record the volume of HCl standard solution consumed at the stoichiometric point Ep1(V1) and pH; then add 2d of methyl orange, continue to titrate until the color changes from yellow to orange, and the instrument will record the volume of HCl standard solution consumed at the stoichiometric point Ep2(V2) and pH.

[0104] Analysis result calculation: (1) when 2V1﹥V2, contains LiOH, Li2CO3, the calculation formula is as follows:

[0105]

[0106]

[0107] (2) when 2V1<V2, contains Li2CO3, LiHCO3, the calculation formula is as follows:

[0108]

[0109]

[0110] (3) when 2V1=V2, contains only Li2CO3, the calculation formula is as follows:

[0111]

[0112] In the above formula: c: concentration of the standard solution of HCl (mol / L); V1 (Ep1): volume of the standard solution of HCl consumed at the first equivalence point (mL); V2 (Ep2): volume of the standard solution of HCl consumed at the second equivalence point (including the first equivalence point) (mL); V': volume of the test solution (mL); V: volume of the sample (mL); 23.95: molar mass of LiOH (g / mol); 73.89: molar mass of Li2CO3 (g / mol); 67.96: molar mass of LiHCO3 (g / mol); m: mass of the sample (g).

[0113] The surface residual alkali mainly refers to substances such as LiOH and Li2CO3 on the surface of the positive material particles, and the source is mainly Li that is not burned in the sintering reaction or residual lithium generated by decomposition of the material due to high-temperature sintering, or is generated by the material being placed in the air for too long. The higher the Ni content, the more difficult it is to sinter the material to form a specific lithium metal ratio, resulting in more residual lithium in the sintered product. On the other hand, the higher the Ni content, the more likely it is to react with water and CO2 in the air to generate LiOH and Li2CO3, resulting in a high surface residual alkali.

[0114] (3) Particle micro-information test:

[0115] Select a 5K magnification SEM image with uniform and dispersed particles, no adhesion between particles, obvious boundaries, and obvious contrast between particles and background. The number of single-crystal ternary particles tested is not less than 100. ImageJ software is used to process the SEM morphology data to calculate the average particle size, circularity, and aspect ratio of the single-crystal ternary particles.

[0116] The particle sphericity is defined as the ratio of the equivalent diameter of the circumference of the particle to the equivalent diameter of the area of the particle. The secondary definition is limited to two-dimensional description of the SEM morphology of the present application, and it is more appropriate to be circularity. In this experiment, the particle morphology in the SEM image is used to calculate the circularity of the particle by ImageJ software. The circularity is the closeness of the projection of the particle to a circle. The calculation formula of the circularity is the projection area multiplied by 4π divided by the square of the circumference. That is, e = (4π x area) / (circumference x circumference) (e is the circularity). When e = 1, the particle is circular, and the smaller the e, the greater the difference between the particle and the circle.

[0117] The particle aspect ratio is defined as the ratio of the minimum Feret width to the maximum Feret length. The maximum Feret length and the minimum Feret width are the distances between two tangents parallel to opposite sides of the particle. The aspect ratio can represent the shape anisotropy of the particle, that is, its elongation. The aspect ratio is defined as the ratio of the maximum Feret length Lmax and the minimum Feret width Lmin. The aspect ratio reflects the elongation and symmetry of the particle, and the aspect ratio can represent the shape anisotropy of the particle. In combination with the sphericity of the particle, the microscopic information of the particle can be represented.

[0118] (4) Powder flowability test:

[0119] Flowability determination method: if the following three indexes are met at the same time, it is determined to be qualified, and if any index is not met, it is determined to be unqualified.

[0120] Test method reference: the provisions of GB / T16913 Dust Physical Property Test Method Part 5 Angle of Repose (Injection Limited Bottom Surface Method); GB / T1479.1 Metal Powder Loose Bulk Density Determination Part 1: Funnel Method; GB / T5162 Metal Powder Vibration Compaction Density Determination (ISO3953).

[0121] 1. The loose bulk density meets >1.6 g / cm 3 .

[0122] 2. The vibration compaction density meets >2.0 g / cm 3 .

[0123] 3. The rest angle is less than 30°. The angle of repose is synonymous with the rest angle.

[0124] The greater the ratio of the vibration compaction density to the loose bulk density, the better the flowability. If the vibration compaction density is a, the loose bulk density is b, a / b=n, the powder is in a loose state, and the flowability is better through vibration to the vibration compaction state. The vibration compaction effect is more significant, the a value is smaller, the b is unchanged, and the n value is smaller.

[0125] The specific results are shown in Table 2. As can be seen from the results in Table 2, the sample of the present application has a lower residual alkali content.

[0126] Table 2 Basic physical property data

[0127]

[0128]

[0129] Table 3 Electrochemical performance test

[0130]

[0131] Finally, it is to be explained that the above embodiments are only used to illustrate the technical solutions of the present application but not to limit the present application. Although the present application is described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the technical solutions of the present application can be modified or equivalently replaced without departing from the purpose and scope of the technical solutions of the present application, and all of them should be covered in the scope of the claims of the present application.

Claims

1. A single-crystal ternary material, characterized in that, The preparation method of this single-crystal ternary material includes the following steps: S1) A single-crystal ternary cathode substrate material A is mixed with mineral resin containing nano-additives and impregnated in a vacuum environment to obtain intermediate product B; the chemical formula of the single-crystal ternary cathode substrate material A is LiNi. x Co y M 1-x-y O2, wherein 0.6≤x<1, y≤0.05, and M is Al and / or Mn; the nano-additive is selected from at least one of Al2O3, ZrO2, Y2O3, Nb2O5, WO3, TiO2, MoO3, and La2O3; the particle size of the nano-additive is less than 50 nm; the mixing method with the petrolatum is mechanical ball milling; S2) The intermediate product B is treated with high-speed hot gas and then cooled to obtain intermediate product C; S3) The intermediate product C is mixed with a surface modifier, and then nano-graphene sheets are added for ultrasonic dispersion and heat treatment to obtain the final product D. Grinding yields the single-crystal ternary material. The surface modifier is a mixture of sodium dioctyl succinate sulfonate and amino-modified silicone oil. The single-crystal ternary material has an angle of repose of less than 30°, a sphericity of >0.75, an aspect ratio of 0.7~1, and a particle size D50 of 2.5~4.5μm.

2. The single-crystal ternary material according to claim 1, characterized in that, The loose packing density of the single-crystal ternary material is >1.6 g / cm³. 3 Meanwhile, the tapped density is >2.0 g / cm³. 3 Furthermore, the tapped density / loose packing density is less than 1.

3.

3. The method for preparing the single-crystal ternary material according to claim 1 or 2, characterized in that, Includes the following steps: S1) A single-crystal ternary cathode substrate material A is mixed with mineral resin containing nano-additives and impregnated in a vacuum environment to obtain intermediate product B; the chemical formula of the single-crystal ternary cathode substrate material A is LiNi. x Co y M 1-x-y O2, wherein 0.6≤x<1, y≤0.05, and M is Al and / or Mn; the nano-additive is selected from at least one of Al2O3, ZrO2, Y2O3, Nb2O5, WO3, TiO2, MoO3, and La2O3; the particle size of the nano-additive is less than 50 nm; the mixing method with the petrolatum is mechanical ball milling; S2) The intermediate product B is treated with high-speed hot gas and then cooled to obtain intermediate product C; S3) Mix the intermediate product C with a surface modifier, then add nano-graphene sheets for ultrasonic dispersion and heat treatment to obtain the final product D. Grind the product to obtain the single-crystal ternary material. The surface modifier is a mixture of sodium dioctyl succinate sulfonate and amino-modified silicone oil.

4. The preparation method according to claim 3, characterized in that, In step S1), the mass ratio of the single-crystal ternary cathode substrate material A to the petrolatum containing nano-additives is 2~10:1; the mass ratio of the nano-additives to the single-crystal ternary cathode substrate material A is 0.02~0.5:

100. The petrolatum containing nano-additives has a maximum crystal size of less than 5 μm and a dropping melting point of 35℃ to 70℃. The ball milling speed is 50~300 rpm / min, the ball milling time is 2~10 h, and the ball milling reaction temperature is room temperature; The vacuum level of the vacuum environment is -0.06 to -0.1 MPa, the immersion time is 30 to 120 minutes, and the immersion temperature is 35 to 100°C.

5. The preparation method according to claim 3 or 4, characterized in that, In step S2), the high-speed hot gas is composed of CO2 and N2, and the volume ratio of CO2 to N2 is 0.1~0.5:1; The conditions for the high-speed hot gas treatment are as follows: gas flow rate is 200-400 m / s, gas temperature is 1000-1500℃, and treatment time is 0.05-0.5 h; The cold treatment is as follows: the intermediate product B, which has been subjected to high-speed hot gas, is placed in a cold gas at a temperature not higher than -0°C. The cold gas is high-purity nitrogen, and the cold treatment time is 0.5~1.5h. Step S2) also includes the step of cyclically performing the high-speed hot gas treatment and the cold treatment.

6. The preparation method according to claim 3 or 4, characterized in that, In step S3), the mass ratio of the intermediate product C to the surface modifier is 1:0.05~0.5; The mass ratio of sodium dioctyl succinate sulfonate to amino-modified silicone oil is 1~5:1; The mass ratio of the nanographene sheet to the intermediate product C is 0.005~0.1:100; The conditions for ultrasonic dispersion are as follows: power is 1~4KW, frequency is 10Hz~100KHz; the temperature for ultrasonic dispersion is 40~60℃, and the time is 10~60min.

7. The preparation method according to claim 6, characterized in that, In step S3), the heat treatment is as follows: heat treatment at 60-120°C for 1-3 h in the presence of nitrogen and / or inert gas.

8. A lithium-ion battery positive electrode, the lithium-ion battery positive electrode comprising a positive electrode material, characterized in that, The cathode material includes the single-crystal ternary material as described in claim 1 or 2.

9. The lithium-ion battery positive electrode according to claim 8, characterized in that, The lithium-ion battery cathode is used under high voltage conditions, with a coin charge of 2.8~4.5V, and a capacity retention rate of more than 97% after 100 cycles at 1C rate, thus improving the median discharge voltage platform.

10. A lithium-ion battery, the lithium-ion battery comprising a positive electrode, characterized in that, The positive electrode is the positive electrode of the lithium-ion battery according to claim 8 or 9.

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