A ternary blended cathode material, its preparation method and a battery

Abstract

The present invention relates to a ternary blended cathode material, a preparation method thereof and a battery. The preparation method comprises the following steps: mixing a ternary material, a lithium iron manganese phosphate material and a coating material, and performing high-energy ball milling on the obtained mixture to obtain the ternary blended cathode material; the coating material comprises a polyphosphazene intermediate. The ternary material and the lithium iron manganese phosphate material are uniformly mixed together by high-energy ball milling. Due to the high ball milling efficiency, the ball milling particle size is finer and the mixing is more uniform, thereby improving the compactness of the ternary material and the lithium iron manganese phosphate material and improving the conductivity of the material. At the same time, a polyphosphazene intermediate is used as the coating material, and the ternary blended cathode material with an ultrathin coating layer is obtained to isolate the direct contact between the electrolyte and the cathode material during the cycle, providing stability.

Description

Technical Field

[0001] The present invention belongs to the technical field of ternary cathode material preparation, and relates to a preparation method of a ternary blended cathode material, in particular to a ternary blended cathode material and its preparation method and battery. Background Art

[0002] Advanced energy storage materials are the trend of future development. Lithium-ion batteries have excellent energy density and cycle durability, and are lightweight, and these qualities can meet our growing energy needs. The research on lithium batteries is also a hot topic in current research in physics, chemistry, materials and other disciplines. Currently, the commonly used cathode materials for lithium batteries in the market include lithium cobaltate, ternary, lithium iron phosphate, lithium manganese iron phosphate, etc.

[0003] Lithium manganese iron phosphate is a new type of phosphate-based lithium-ion battery cathode material formed by doping a certain proportion of manganese on the basis of lithium iron phosphate. Lithium manganese iron phosphate maintains the stable olivine-type structure of lithium iron phosphate, and the structure is more stable during charge and discharge. Even if all lithium ions are extracted during the charging process, the structure will not collapse, so the safety is better and the cost is lower. The application of pure lithium manganese iron phosphate has the advantages of lower cost and higher safety performance compared with ternary materials. The main limitations are low conductivity and low energy density. In order to balance performance and safety, the ternary and lithium manganese iron phosphate materials are compounded, which can further integrate the advantages of the materials, achieve complementary short boards through compounding, improve the energy density, and have more comprehensive and comprehensive battery performance.

[0004] CN 107546379A discloses a lithium manganese iron phosphate-ternary material composite cathode material and its preparation method. The nanoparticles of lithium manganese iron phosphate are fixed on the surface of the ternary material particles by a mechanical fusion method to form a dense porous coating layer, which solves the problem that the ternary material and the lithium manganese iron phosphate cathode material are prone to segregation due to different densities when obtaining a mixed slurry of the ternary material and the lithium manganese iron phosphate cathode material during the slurry mixing stage; by achieving a tight coating of the ternary material surface with lithium manganese iron phosphate, a stable core-shell structure is obtained, so that the lithium manganese iron phosphate material can protect the surface of the ternary material, prevent the ternary material from absorbing moisture in the environment and deteriorating, reduce the direct contact between the ternary material and the electrolyte in the battery, and improve the stability and cycle performance of the ternary material.

[0005] CN 111864198A provides a preparation method of a ternary material composite lithium iron manganese phosphate cathode material. S1: Mix PVDF and NMP, and disperse them with a nano-disperser at a dispersion speed of 1100 - 1300 rpm for 5.5 - 6.5 h at a temperature of 30 - 40 °C to obtain material A. S2: Add SP and disperse it with a nano-disperser at a dispersion speed of 1900 - 2100 rpm for 1 - 2 h at a temperature of 20 - 30 °C to obtain material B. S3: Mix material A and material B, add CNT, and disperse it with a nano-disperser at a dispersion speed of 1900 - 2100 rpm for 1.5 - 2.5 h at a temperature of 20 - 30 °C to obtain material C. S4: Mix lithium nickel cobalt manganese oxide and lithium iron manganese phosphate evenly and divide them into 3 portions, add them to material C in 3 times, and disperse it with a nano-disperser at a dispersion speed of 1400 - 1600 rpm for 5 - 15 min at a temperature of 20 - 30 °C to obtain material D. S5: Disperse material D with a nano-disperser at a dispersion speed of 1700 - 1900 rpm for 2 - 3 h at a temperature of 20 - 30 °C and a vacuum degree greater than 0.085 MPa to obtain material E. This material has high safety.

[0006] In the above technical solution, lithium iron manganese phosphate and ternary materials are compounded. However, the poor binding between the two materials will affect their conductivity, and the numerous steps of the preparation method increase the process preparation cost. How to improve the binding tightness between ternary materials and lithium iron manganese phosphate on the basis of simplifying the process is a technical problem urgently to be solved in the field of cathode materials. Summary of the Invention

[0007] To solve the above technical problems, the present invention provides a ternary blended cathode material, its preparation method and a battery. The ternary material and the lithium iron manganese phosphate material are uniformly mixed together by high-energy ball milling. Due to the high ball milling efficiency, the ball milling particle size is finer and the mixing is more uniform, thereby improving the tightness between the ternary material and the lithium iron manganese phosphate material and enhancing the conductivity of the material. At the same time, a polyphosphazene intermediate is used as a coating material to obtain a ternary blended cathode material with an ultra-thin coating layer to isolate the direct contact between the electrolyte and the cathode material during the cycle, providing stability.

[0008] To achieve this purpose, the present invention adopts the following technical solutions:

[0009] In the first aspect, the present invention provides a preparation method of a ternary blended cathode material. The preparation method includes the following steps:

[0010] Mix the ternary material, the lithium iron manganese phosphate material and the coating material, and perform high-energy ball milling on the obtained mixture to obtain the ternary blended cathode material;

[0011] The coating material includes a polyphosphazene intermediate.

[0012] In the present invention, the ternary material and the lithium iron manganese phosphate material are uniformly mixed by high-energy ball milling. Due to the high ball milling efficiency, the ball milling particle size is finer and the mixing is more uniform, thereby improving the compactness of the ternary material and the lithium iron manganese phosphate material and enhancing the conductivity of the material. At the same time, a polyphosphazene intermediate is used as the coating material to obtain a ternary-doped cathode material with an ultrathin coating layer, which isolates the direct contact between the electrolyte and the cathode material during the cycling process and provides stability.

[0013] Preferably, the median particle size of the ternary material is 8 - 20 μm, for example, it can be 8 μm, 10 μm, 12 μm, 15 μm, 18 μm or 20 μm, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0014] Preferably, the particle size distribution of the ternary material is 0.6 - 1.2, for example, it can be 0.6, 0.8, 1, 1.1 or 1.2, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0015] The particle size range Dspan = (D90 - D10) / D50.

[0016] Preferably, the ternary material includes NCM523 (LiNi 0.5 Co 0.2 Mn 0.3 O2), NCM622 (LiNi 0.6 Co 0.2 Mn 0.2 O2), NCM712 (LiNi 0.7 Co 0.1 Mn 0.2 O2), NCM811 (LiNi 0.8 Co 0.1 Mn 0.1 O2) or NCM90505 (LiNi 0.9 Co 0.05 Mn 0.05Any one or at least two combinations of the above, typical but non-limiting combinations include the combination of NCM523 and NCM622, the combination of NCM622 and NCM712, the combination of NCM712 and NCM811, the combination of NCM811 and NCM90505, the combination of NCM523, NCM622 and NCM712, the combination of NCM622, NCM712 and NCM811, the combination of NCM712, NCM811 and NCM90505, the combination of NCM523, NCM622, NCM712 and NCM811, the combination of NCM622, NCM712, NCM811 and NCM90505, or the combination of NCM523, NCM622, NCM712, NCM811 and NCM90505.

[0017] Preferably, the median particle size of the lithium iron manganese phosphate material is 1 - 2 μm, for example, it can be 1 μm, 1.2 μm, 1.4 μm, 1.6 μm, 1.8 μm or 2 μm, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0018] Preferably, the particle size distribution of the lithium iron manganese phosphate material is 0.2 - 0.4, for example, it can be 0.2, 0.25, 0.3, 0.35 or 0.4, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0019] Preferably, the polyphosphazene intermediate includes phosphoryl chloride trimer (P3N3Cl6, PNCL).

[0020] The melting point of PNCL is about 115 °C and the boiling point is 127 °C. Under the action of high-energy ball milling, PNCL easily becomes in a molten state. After stopping the ball milling and cooling, it uniformly coats on the surface of the ternary material and lithium iron manganese phosphate, forming a stable and uniform ultra-thin PNCL coating layer. The high energy of high-energy ball milling enables PNCL to perfectly and uniformly coat on the surface of the host materials (ternary material and lithium iron manganese phosphate). During the cycling process, the PNCL coating layer isolates the direct contact between the electrolyte and the positive electrode material, reducing the occurrence of side reactions, thereby improving the cycling stability of the material.

[0021] In addition to isolating the side reactions at the interface between the positive electrode and the electrolyte during the cycling process, the PNCL coating layer can also enhance the structural stability of the ternary blended positive electrode material, and enhance the diffusion of lithium ions at the electrode / electrolyte interface, prevent the pulverization of the ternary blended positive electrode material particles during the cycling process, and at the same time prevent the HF generated by the decomposition in the electrolyte from eroding the material, improving the cycling performance of the material.

[0022] Preferably, the mass ratio of the ternary material to lithium iron manganese phosphate is (1.5 - 4.5):(8.5 - 5.5), for example, it can be 1.5:8.5, 2:8, 3:7, 4:6 or 4.5:5.5, but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0023] Preferably, the mass of the coating material is 0.7 - 1.0 wt% of the total mass of the ternary material and lithium iron manganese phosphate. For example, it can be 0.7 wt%, 0.8 wt%, 0.9 wt%, 0.95 wt% or 1.0 wt%, but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0024] Preferably, the time of high-energy ball milling is 1 - 2 h. For example, it can be 1 h, 1.2 h, 1.4 h, 1.6 h, 1.8 h or 2 h, but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0025] Preferably, the ball-to-material ratio of the high-energy ball milling is (8 - 12):1. For example, it can be 8:1, 9:1, 10:1, 11:1, 12:1, but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0026] Preferably, the revolution speed of the high-energy ball milling is 800 - 1200 r / min. For example, it can be 800 r / min, 900 r / min, 1000 r / min, 1100 r / min or 1200 r / min, but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0027] Preferably, the rotation speed of the high-energy ball milling is 2200 - 2500 r / min. For example, it can be 2200 r / min, 2250 r / min, 2300 r / min, 2400 r / min or 2500 r / min, but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0028] Preferably, the preparation method of the ternary material includes:

[0029] Mixing nickel cobalt manganese hydroxide precursor, lithium source and additive, and performing high-temperature sintering to obtain the ternary material;

[0030] Preferably, the molar ratio of Ni:Co:Mn in the nickel cobalt manganese hydroxide precursor is 5:2:3 - 9.5:0.25:0.25. For example, it can be 5:2:3, 6:2:2, 7:1:2, 8:1:1 or 9.5:0.25:0.25, but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0031] Preferably, the lithium source includes any one or a combination of at least two of lithium hydroxide, lithium carbonate, lithium nitrate, or lithium acetate. Typical but non-limiting combinations include a combination of lithium hydroxide and lithium carbonate, a combination of lithium carbonate and lithium nitrate, a combination of lithium nitrate and lithium acetate, a combination of lithium hydroxide, lithium carbonate, and lithium nitrate, a combination of lithium carbonate, lithium nitrate, and lithium acetate, or a combination of lithium hydroxide, lithium carbonate, lithium nitrate, and lithium acetate.

[0032] Preferably, the additive includes any one or a combination of at least two of strontium carbonate, alumina, zirconium hydroxide, lanthanum sesquioxide, zirconia, lithium nitrate, magnesium oxide, niobium oxide, yttrium sesquioxide, aluminum phosphate, tungsten trioxide, lithium phosphate, or lithium silicate. Typical but non-limiting combinations include a combination of strontium carbonate and alumina, a combination of alumina and zirconium hydroxide, a combination of zirconium hydroxide and lanthanum sesquioxide, a combination of lanthanum sesquioxide and zirconia, a combination of lithium nitrate, magnesium oxide, and niobium oxide, a combination of niobium oxide, yttrium sesquioxide, and aluminum phosphate, a combination of aluminum phosphate, tungsten trioxide, and lithium phosphate, a combination of tungsten trioxide, lithium phosphate, and lithium silicate, a combination of strontium carbonate, alumina, zirconium hydroxide, and lanthanum sesquioxide, a combination of lanthanum sesquioxide, zirconia, lithium nitrate, magnesium oxide, and niobium oxide, a combination of lithium nitrate, magnesium oxide, niobium oxide, yttrium sesquioxide, and aluminum phosphate, or a combination of niobium oxide, yttrium sesquioxide, aluminum phosphate, tungsten trioxide, lithium phosphate, and lithium silicate.

[0033] Preferably, the addition amount of the additive is 1000 - 1500 ppm. For example, it can be 1000 ppm, 1100 ppm, 1200 ppm, 1300 ppm, 1400 ppm, or 1500 ppm, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0034] Preferably, the temperature of the high-temperature sintering is 750 - 950 °C. For example, it can be 750 °C, 780 °C, 800 °C, 820 °C, or 850 °C, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0035] Preferably, the time of the high-temperature sintering is 8 - 18 h. For example, it can be 8 h, 10 h, 14 h, 15 h, or 18 h, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0036] Preferably, the preparation method of the lithium iron phosphate manganese material includes:

[0037] In a liquid phase system, sand-mix the lithium iron phosphate manganese precursor, lithium source, and carbon source, perform spray drying and then sintering to obtain the lithium iron phosphate manganese material.

[0038] Preferably, the liquid phase system is deionized water and / or ultrapure water.

[0039] Preferably, the carbon source is any one or a combination of at least two of glucose, starch, sucrose, citric acid, lactic acid, succinic acid, ethanol, methanol, or oil. Typical but non-limiting combinations include the combination of glucose and starch, the combination of starch and sucrose, the combination of sucrose and citric acid, the combination of citric acid and lactic acid, the combination of lactic acid and succinic acid, the combination of succinic acid and ethanol, the combination of ethanol, methanol, and oil, the combination of glucose, starch, sucrose, and citric acid, the combination of sucrose, citric acid, lactic acid, and succinic acid, the combination of citric acid, lactic acid, succinic acid, and ethanol, the combination of succinic acid, ethanol, methanol, and oil, the combination of glucose, starch, sucrose, citric acid, and lactic acid, the combination of sucrose, citric acid, lactic acid, succinic acid, and ethanol, or the combination of lactic acid, succinic acid, ethanol, methanol, and oil.

[0040] Preferably, the sintering temperature is 500 - 800 °C. For example, it can be 500 °C, 550 °C, 600 °C, 700 °C, or 800 °C, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0041] Preferably, the sintering time is 10 - 20 h. For example, it can be 10 h, 12 h, 15 h, 18 h, or 20 h, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0042] Preferably, the sintering is carried out in an inert atmosphere.

[0043] As a preferred technical solution of the preparation method described in the first aspect of the present invention, the preparation method includes the following steps:

[0044] Mix a ternary material, a lithium iron manganese phosphate material, and phosphoryl chloride trimer with an addition amount of 0.7 - 1.0 wt%. The mass ratio of the ternary material to the lithium iron manganese phosphate is (1.5 - 4.5):(8.5 - 5.5). Perform high-energy ball milling on the obtained mixture for 1 - 2 h with a ball-to-material ratio of (8 - 12):1, a revolution speed of 800 - 1200 r / min, and a rotation speed of 2200 - 2500 r / min to obtain the ternary-doped cathode material;

[0045] The ternary material is prepared by the following method:

[0046] Mix a nickel-cobalt-manganese hydroxide precursor, a lithium source, and an additive with an addition amount of 1000 - 1500 ppm, and perform high-temperature sintering at 750 - 950 °C for 8 - 18 h to obtain the ternary material;

[0047] The median particle size of the ternary material is 8-20 μm, and the particle size distribution of the ternary material is 0.6-1.2; the ternary material includes any one or at least two combinations of NCM523, NCM622, NCM712, NCM811 or NCM90505;

[0048] The lithium iron manganese phosphate material is prepared by the following method:

[0049] In a liquid phase system, the lithium iron manganese phosphate precursor, lithium source and carbon source are mixed by sand milling, and after spray drying, sintering is carried out at 500-800 °C for 10-20 h to obtain the lithium iron manganese phosphate material;

[0050] The median particle size of the lithium iron manganese phosphate material is 1-2 μm, and the particle size distribution of the lithium iron manganese phosphate material is 0.2-0.4.

[0051] In a second aspect, the present invention provides a ternary blended cathode material, and the ternary blended cathode material is obtained by the preparation method as described in the first aspect.

[0052] In a third aspect, the present invention provides a battery, and the battery contains the ternary blended cathode material as described in the second aspect.

[0053] Compared with the prior art, the present invention has at least the following beneficial effects:

[0054] (1) In the present invention, the ternary material and the lithium iron manganese phosphate material are uniformly mixed together by high-energy ball milling. Due to the high ball milling efficiency, the ball milling particle size is finer and the mixing is more uniform, thereby improving the compactness of the ternary material and the lithium iron manganese phosphate material and improving the conductivity of the material; at the same time, a polyphosphazene intermediate is used as a coating material to obtain a ternary blended cathode material with an ultra-thin coating layer to isolate the direct contact between the electrolyte and the cathode material during the cycle, providing stability.

[0055] (2) The preparation method provided by the present invention is simple and easy to realize industrialization, and the cathode material of the ternary material doped with lithium iron manganese phosphate with PNCL ultra-thin coating can be obtained only by one high-energy ball milling method. Specific Embodiments

[0056] To facilitate the understanding of the present invention, the following examples are listed for the present invention. Those skilled in the art should understand that the examples are only for helping to understand the present invention and should not be regarded as specific limitations to the present invention.

[0057] Example 1

[0058] This example provides a preparation method for a ternary blended cathode material, and the preparation method includes the following steps:

[0059] The ternary NCM523 material and lithium iron manganese phosphate material with a mixing mass ratio of 3:7, and phosphorus oxychloride trimer with an addition amount of 0.85 wt% are used. The obtained mixture is subjected to high-energy ball milling at a ball-to-material ratio of 10:1 for 1 h, with a revolution speed of 1000 r / min and a rotation speed of 2300 r / min to obtain the ternary blended cathode material;

[0060] The ternary NCM523 material is prepared by the following method:

[0061] A nickel-cobalt-manganese hydroxide precursor with Ni:Co:Mn = 5:2:3, lithium carbonate, and strontium carbonate with an addition amount of 1200 ppm are mixed and sintered at a high temperature of 900 °C for 12 h to obtain the ternary material, with a median particle size of 12 μm and a particle size distribution of 0.8;

[0062] The lithium iron manganese phosphate material is prepared by the following method:

[0063] In a liquid phase system, a lithium iron manganese phosphate precursor, lithium carbonate, and citric acid are mixed by sand milling, spray-dried at 220 °C, and then sintered at 750 °C for 10 h under nitrogen conditions. After airflow crushing and screening, the lithium iron manganese phosphate material is obtained, with a median particle size of 1.5 μm and a particle size distribution of 0.3.

[0064] Example 2

[0065] This example provides a preparation method for a ternary blended cathode material. The preparation method includes the following steps:

[0066] The ternary NCM523 material, lithium iron manganese phosphate material, and phosphorus oxychloride trimer with an addition amount of 0.7 wt% are mixed. The obtained mixture is subjected to high-energy ball milling at a ball-to-material ratio of 8:1 for 2 h, with a revolution speed of 800 r / min and a rotation speed of 2200 r / min to obtain the ternary blended cathode material;

[0067] The ternary material is prepared by the following method:

[0068] A nickel-cobalt-manganese hydroxide precursor with Ni:Co:Mn = 5:2:3, lithium hydroxide, and lanthanum sesquioxide with an addition amount of 1000 ppm are mixed and sintered at 750 °C for 10 h. After mechanical crushing and screening, the ternary material is obtained, with a median particle size of 8 μm and a particle size distribution of 1.2;

[0069] The lithium iron manganese phosphate material is prepared by the following method:

[0070] In a liquid phase system, a lithium iron manganese phosphate precursor, lithium hydroxide, and starch are mixed by sand milling, spray-dried at 200 °C, and then sintered at 500 °C for 20 h. After airflow milling and screening, the lithium iron manganese phosphate material is obtained, with a median particle size of 1 μm and a particle size distribution of 0.4.

[0071] Example 3

[0072] This example provides a method for preparing a ternary blended cathode material, and the preparation method includes the following steps:

[0073] Mix the NCM523 ternary material, lithium iron manganese phosphate material, and phosphoryl chloride trimer with an addition amount of 1.0 wt%, and perform high-energy ball milling on the obtained mixture for 1 h with a ball-to-material ratio of 12:1, a revolution speed of 1200 r / min, and a rotation speed of 2500 r / min to obtain the ternary blended cathode material;

[0074] The ternary material is prepared by the following method:

[0075] Mix the nickel cobalt manganese hydroxide precursor with Ni:Co:Mn = 5:2:3, lithium nitrate, and aluminum phosphate with an addition amount of 1500 ppm, and perform high-temperature sintering at 950 °C for 8 h, followed by mechanical pulverization and screening to obtain the ternary material, with a median particle size of 20 μm and a particle size distribution of 0.6;

[0076] The lithium iron manganese phosphate material is prepared by the following method:

[0077] In a liquid phase system, sand-mill and mix the lithium iron manganese phosphate precursor, lithium nitrate, and lactic acid, perform spray drying, and then sinter at 800 °C for 10 h to obtain the lithium iron manganese phosphate material, with a median particle size of 2 μm and a particle size distribution of 0.2.

[0078] Example 4

[0079] This example provides a method for preparing a ternary blended cathode material, which is different from Example 1 in that the NCM523 ternary material is replaced by NCM811.

[0080] The NCM811 ternary material is prepared by the following method:

[0081] Mix the nickel cobalt manganese hydroxide precursor with Ni:Co:Mn = 8:1:1, lithium carbonate, and strontium carbonate, and perform high-temperature sintering at 900 °C for 12 h to obtain the ternary material, with a median particle size of 12 μm and a particle size distribution of 0.8.

[0082] Example 5

[0083] This example provides a method for preparing a ternary blended cathode material, which is different from Example 1 in that the NCM90505 ternary material is replaced by NCM811.

[0084] The NCM90505 ternary material is prepared by the following method:

[0085] Mix nickel cobalt manganese hydroxide precursor with Ni:Co:Mn = 9:0.5:0.5, lithium carbonate and strontium carbonate, and sinter them at a high temperature of 900 °C for 12 h to obtain the ternary material, with a median particle size of 12 μm and a particle size distribution of 0.8.

[0086] Example 6

[0087] This example provides a preparation method of a ternary blended cathode material, which is different from Example 1 in that the addition amount of phosphorus oxychloride trimer is 0.5 wt%.

[0088] Example 7

[0089] This example provides a preparation method of a ternary blended cathode material, which is different from Example 1 in that the addition amount of phosphorus oxychloride trimer is 1.2 wt%.

[0090] Example 8

[0091] This example provides a preparation method of a ternary blended cathode material, which is different from Example 1 in that the mass ratio of NCM523 ternary material to lithium iron manganese phosphate material is 5:5.

[0092] Example 9

[0093] This example provides a preparation method of a ternary blended cathode material, which is different from Example 1 in that the mass ratio of NCM523 ternary material to lithium iron manganese phosphate material is 1:9.

[0094] Comparative Example 1

[0095] This comparative example provides a preparation method of a ternary blended cathode material, which is different from Example 1 in that high-energy ball milling is replaced by mechanical fusion.

[0096] Comparative Example 2

[0097] This comparative example provides a preparation method of a ternary blended cathode material, which is different from Example 1 in that high-energy ball milling is replaced by dispersion machine mixing and dispersion.

[0098] The obtained ternary blended cathode material, binder, conductive agent, and dispersant are mixed and stirred evenly at a mass ratio of 97.5:0.3:2:0.2 to obtain a cathode slurry. The cathode slurry is coated on a 12-μm aluminum foil through a coating process, and after drying and cold pressing processes, a cathode sheet is obtained; a negative electrode slurry is prepared according to graphite:SP:CMC:SBR = 97:0.7:1.25:1.05 and coated on an 8-μm copper foil; a PP separator is used, and the electrolyte is EC:DEC:EMC = 4:3:3, and the mass ratio of the additive accounts for 10% of the total mass, where VC:PS:FEC:CHB = 3:2:1:1, and the concentration of lithium hexafluorophosphate in the electrolyte is 1 mol / L; the corresponding positive and negative electrode sheets and separator are wound or laminated to obtain a bare battery cell, and the bare battery cell is placed in an outer packaging aluminum-plastic film to assemble a 2-Ah soft-pack battery cell, and the electrolyte is injected, and after processes such as aging, formation, shaping, and encapsulation, a soft-pack lithium-ion battery is obtained for electrochemical testing.

[0099] Test conditions: at 25 °C, 2.5 - 4.2 V, 1C / 1C cycle.

[0100] The test results are shown in Table 1.

[0101] Table 1

[0102]

[0103]

[0104] The following conclusions can be drawn from Table 1:

[0105] (1) As can be seen from Examples 1 - 5, in the present invention, the ternary material and lithium iron manganese phosphate material are uniformly mixed together by high-energy ball milling. Due to the high ball milling efficiency, the ball milling particle size is finer and the mixing is more uniform, thereby improving the compactness of the ternary material and lithium iron manganese phosphate material and enhancing the conductivity of the material; at the same time, using a polyphosphazene intermediate as a coating material, the obtained ternary blended cathode material with an ultra-thin coating layer isolates the direct contact between the electrolyte and the cathode material during the cycle, providing stability.

[0106] (2) As can be seen from the comparison between Examples 6 - 7 and Example 1, when the addition amount of the coating material is not within the preferred range of the present invention, the electrochemical performance of the prepared ternary blended cathode material will deteriorate;

[0107] (3) It can be seen from the comparison between Examples 8 and 9 and Example 1 that when the blending ratio of the ternary material and the lithium iron manganese phosphate material is within the preferred range provided by the present invention, a ternary blended cathode material with a compact and uniform structure can be obtained. When the proportion of the ternary material in the blending is too large, since the structural stability of the ternary material itself is poor, the cycling performance of the blended material deteriorates; when the proportion of the ternary in the blending is too small, a large amount of lithium iron manganese phosphate cannot come into good contact with the ternary material, and the lithium iron manganese phosphate itself has poor conductivity, so the electrical properties of the blended material will deteriorate.

[0108] (4) It can be seen from the comparison between Comparative Examples 1 and 2 and Example 1 that the high-energy ball milling provided by the present invention improves the compactness of the ternary material and the lithium iron manganese phosphate material compared with the traditional mixing in the prior art, improves the conductivity of the material, and at the same time is conducive to achieving uniform coating of the phosphorus oxychloride trimer.

[0109] In summary, in the present invention, the ternary material and the lithium iron manganese phosphate material are uniformly mixed together by high-energy ball milling. Due to the high ball milling efficiency, the ball milling particle size is finer and the mixing is more uniform, thereby improving the compactness of the ternary material and the lithium iron manganese phosphate material and improving the conductivity of the material; at the same time, a polyphosphazene intermediate is used as the coating material to obtain a ternary blended cathode material with an ultrathin coating layer to isolate the direct contact between the electrolyte and the cathode material during the cycling process, providing stability.

[0110] The present invention uses the above examples to illustrate the detailed process equipment and process flow of the present invention, but the present invention is not limited to the above detailed process equipment and process flow, that is, it does not mean that the present invention must rely on the above detailed process equipment and process flow to be implemented. Those skilled in the art should understand that any improvement to the present invention, the equivalent replacement of each raw material of the product of the present invention, the addition of auxiliary components, and the selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A preparation method of a ternary blended cathode material, characterized in that, The preparation method comprises the following steps: Mix a ternary material, a lithium iron manganese phosphate material, and a coating material, and perform high-energy ball milling on the obtained mixture to obtain the ternary blended cathode material; The coating material comprises a polyphosphazene intermediate; The polyphosphazene intermediate is phosphoryl chloride trimer; The particle size distribution of the lithium iron manganese phosphate material is 0.2 - 0.4; the particle size distribution of the ternary material is 0.6 - 1.2; The mass of the coating material is 0.7 - 1.0 wt% of the total mass of the ternary material and the lithium iron manganese phosphate; The revolution speed of the high-energy ball milling is 800 - 1200 r / min; the rotation speed of the high-energy ball milling is 2200 - 2500 r / min; The mass ratio of the ternary material to the lithium iron manganese phosphate is (1.5 - 4.5):(8.5 - 5.5).

2. The preparation method according to claim 1, characterized in that, The median particle size of the ternary material is 8 - 20 μm.

3. The preparation method according to claim 1, characterized in that, The ternary material comprises any one or at least two combinations of NCM523, NCM622, NCM712, NCM811, or NCM90505.

4. The preparation method according to claim 1, characterized in that, The median particle size of the lithium iron manganese phosphate material is 1 - 2 μm.

5. The preparation method according to claim 1, characterized in that, The time of the high-energy ball milling is 1 - 2 h.

6. The preparation method according to claim 1, characterized in that, The ball-to-material ratio of the high-energy ball milling is (8 - 12):

1.

7. The preparation method according to claim 1, wherein The preparation method of the ternary material comprises: Mix a nickel cobalt manganese hydroxide precursor, a lithium source, and an additive, and perform high-temperature sintering to obtain the ternary material.

8. The preparation method according to claim 7, characterized in that, The molar ratio of Ni:Co:Mn in the nickel cobalt manganese hydroxide precursor is 5:2:3 - 9.5:0.25:0.

25.

9. The preparation method according to claim 7, wherein, The lithium source comprises any one or at least two combinations of lithium hydroxide, lithium carbonate, lithium nitrate, or lithium acetate.

10. The preparation method according to claim 7, characterized in that, The additive comprises any one or at least two combinations of strontium carbonate, aluminum oxide, zirconium hydroxide, lanthanum sesquioxide, zirconium dioxide, lithium nitrate, magnesium dioxide, niobium oxide, yttrium sesquioxide, aluminum phosphate, tungsten trioxide, lithium phosphate, or lithium silicate.

11. The preparation method according to claim 7, characterized in that, The addition amount of the additive is 1000 - 1500 ppm.

12. The preparation method according to claim 7, characterized in that, The temperature of the high-temperature sintering is 750 - 950 °C.

13. The preparation method according to claim 7, wherein The time of the high-temperature sintering is 8 - 18 h.

14. The preparation method according to claim 1, characterized in that, The preparation method of the lithium iron manganese phosphate material comprises: In a liquid phase system, sand-mill and mix a lithium iron manganese phosphate precursor, a lithium source, and a carbon source, perform spray drying, and then perform sintering to obtain the lithium iron manganese phosphate material.

15. The preparation method according to claim 14, wherein, The carbon source comprises any one or at least two combinations of glucose, starch, sucrose, citric acid, lactic acid, succinic acid, ethanol, methanol, or grease.

16. The preparation method according to claim 14, characterized in that, The temperature of the sintering is 500 - 800 °C.

17. The preparation method according to claim 14, characterized in that, The time of the sintering is 10 - 20 h.

18. The preparation method according to claim 14, characterized in that, The sintering is carried out in an inert atmosphere.

19. The preparation method according to claim 1, characterized in that, The preparation method comprises the following steps: Mix a ternary material, a lithium iron manganese phosphate material, and phosphoryl chloride trimer with an addition amount of 0.7 - 1.0 wt%, wherein the mass ratio of the ternary material to the lithium iron manganese phosphate is (1.5 - 4.5):(8.5 - 5.5), perform high-energy ball milling on the obtained mixture for 1 - 2 h with a ball-to-material ratio of (8 - 12):1, a revolution speed of 800 - 1200 r / min, and a rotation speed of 2200 - 2500 r / min to obtain the ternary blended cathode material; The ternary material is prepared by the following method: Mix a nickel-cobalt-manganese hydroxide precursor, a lithium source, and an additive with an addition amount of 1000-1500 ppm, and sinter at a high temperature of 750-950 °C for 8-18 h to obtain the ternary material; The median particle size of the ternary material is 8-20 μm, and the particle size distribution of the ternary material is 0.6-1.2; the ternary material includes any one or a combination of at least two of NCM523, NCM622, NCM712, NCM811, or NCM90505; The lithium iron manganese phosphate material is prepared by the following method: In a liquid phase system, sand-mill and mix a lithium iron manganese phosphate precursor, a lithium source, and a carbon source, and after spray drying, sinter at 500-800 °C for 10-20 h to obtain the lithium iron manganese phosphate material; The median particle size of the lithium iron manganese phosphate material is 1-2 μm, and the particle size distribution of the lithium iron manganese phosphate material is 0.2-0.

4.

20. A ternary blended cathode material, characterized in that, The ternary blended cathode material is obtained by the preparation method described in any one of claims 1-19.

21. A battery, characterized in that, The battery contains the ternary blended cathode material described in claim 20.

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