High-power-density positive electrode material and preparation method thereof

Abstract

The invention provides a high-power-density positive electrode material and a preparation method thereof. The molecular formula of the high-power-density positive electrode material is Li1 + aNixMyAzO2, a is more than or equal to 0 and less than or equal to 0.2, x is more than or equal to 0.45 and less than or equal to 0.95, y is more than 0 and less than or equal to 0.5, z is more than 0 and less than or equal to 0.2, and x + y + z is equal to 1; wherein the M element comprises at least one of Co, Mn, Al, Nb and Sb elements; the element A comprises at least one of Ti, Mo, Zr, Sr, Re, P, B, La, Ta and C. Compared with the prior art, the high-power-density positive electrode material disclosed by the invention works under high voltage and high magnification, the discharge capacity is stably exerted, the platform voltage attenuation rate is low, the temperature change is controlled within a safe range, and meanwhile, the high-power-density positive electrode material disclosed by the invention can be used for preparing the high-power-density positive electrode material in a low-temperature environment or a high-temperature environment. And the battery can be charged and discharged well.

Description

Technical Field

[0001] The present invention relates to the technical field of secondary battery positive electrode materials, and in particular to a high power density positive electrode material and a preparation method thereof. Background Art

[0002] Against the backdrop of the attention and development of the low-altitude economy, the demand for low-cost, high-energy-density, sustainable high-power-density, and low-temperature-rise lithium-ion batteries for low-altitude aircraft is gradually increasing. For the battery system, on the positive electrode material side, positive electrode materials with high energy density and high-rate discharge capability are required. The existing material system is mainly developed for passenger cars and energy storage fields, and cannot fully meet all the requirements for use in low-altitude aircraft under high-rate conditions (5C and above). The reason is that the bulk and interfacial lithium-ion transport and diffusion capabilities of the existing material system cannot support charge balance under high-power conditions, resulting in severe polarization, capacity utilization and platform voltage attenuation, inability to maintain sustained high power density, and severe heat generation.

[0003] Taking into account the material's elemental composition, particle size and other characteristics, the present invention provides a positive electrode material that can be charged and discharged at a high rate. It has a cut-off voltage of 4.35V to 4.6V, high energy density, and high power density, and can be suitable for batteries used in low-altitude aircraft such as drones. Summary of the Invention

[0004] One of the objectives of the present invention is to address the deficiencies of the prior art and provide a high power density cathode material to improve the problems of decreased energy density and severe heat generation of the current cathode material at high rates.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A high power density cathode material with the molecular formula Li 1+a Ni x M y A z O2, 0≤a≤0.2, 0.45≤x≤0.95, 0<y≤0.5, 0≤z≤0.2, x+y+z=1; wherein the M element includes at least one of Co, Mn, Al, Nb, and Sb; and the A element includes at least one of Ti, Mo, Zr, Sr, Re, P, B, La, Ta, and C.

[0007] Preferably, the high power density positive electrode material has the following diffraction peaks in its XRD pattern under Cu Kα1 rays: characteristic peak A: 18°~20°, characteristic peak B: 36°~37.4°, characteristic peak C: 37.4°~39.5°, characteristic peak D: 37.4°~39.5°, characteristic peak E: 43°~46°, characteristic peak F: 63°~66°, and characteristic peak G: 63°~66°.

[0008] Preferably, the diffraction peak intensity ratio between the characteristic peak A and the characteristic peak E is ≥1.1, and the half-peak width of the characteristic peak A: 18° to 20° is <0.2.

[0009] Preferably, the high power density positive electrode material is primary particles and / or secondary particles formed by aggregation of primary particles, the D50 of the primary particles is 1 to 4 μm, and the D50 of the secondary particles is 3 to 8 μm, wherein the maximum particle size of the primary particles and the secondary particles are both ≤15 μm.

[0010] Preferably, the high power density positive electrode material has a powder conductivity of 0.00001 to 0.05 S / cm at 100 MPa and a specific surface area of ​​0.2 to 20 m 2 / g; its liquid phase density is 4.2~5.2g / mL.

[0011] Preferably, the high power density positive electrode material has a capacity of 170 to 220 mAh / g at a voltage of 4.35 to 4.6 V (2032 button half-cell) at 0.1C; the high power density positive electrode material has an energy density of 650 Wh / kg to 860 Wh / kg at a platform voltage of 3.84 to 3.92 V and 0.1C.

[0012] Preferably, in its differential capacity curve (dQ / dV curve), there is at least one set of redox peaks between 3.4V and 4.6V.

[0013] Preferably, the compacted density of the positive electrode sheet made of the high power density positive electrode material can be 3.2 to 4.2 g / cm 3 , and the temperature rise of the assembled battery cell is less than 30℃ when discharged at 15C at 20-25℃.

[0014] Preferably, the compacted density of the positive electrode sheet made of the high power density positive electrode material can be 3.2 to 4.2 g / cm 3 , and the temperature rise of the assembled battery cell is less than 30℃ when discharged at 15C at 20-25℃.

[0015] Preferably, the compacted density of the positive electrode sheet made of the high power density positive electrode material can be 3.2 to 4.2 g / cm 3 , and the assembled battery cell is at 4.35~4.6V, compared with 1C discharge;

[0016] When discharging at 5C rate, 5C / 1C rate>95%;

[0017] and / or, when discharging at a rate of 10C, the 10C / 1C rate is greater than 97%;

[0018] And / or, when discharging at a rate of 15C, the 10C / 1C rate is greater than 100%.

[0019] Preferably, the compacted density of the positive electrode sheet made of the high power density positive electrode material can be 3.2 to 4.2 g / cm 3 , and the assembled battery cell is at 4.35~4.6V, compared with 1C discharge;

[0020] When discharging at a rate of 5C, the platform voltage decay rate is less than 5%;

[0021] and / or, when discharged at a rate of 10C, the platform voltage decay is less than 8%;

[0022] And / or, when discharging at a rate of 15C, the platform voltage decay is less than 10%.

[0023] Preferably, the compacted density of the positive electrode sheet made of the high power density positive electrode material can be 3.2 to 4.2 g / cm 3 , and the assembled battery cell has a capacity retention rate of >90% after 4000 cycles of 1C charge and discharge cycles at 4.35-4.6V, and / or a capacity retention rate of >85% after 500 cycles of 3C charge and discharge cycles.

[0024] A second object of the present invention is to provide a method for preparing the above-mentioned high power density positive electrode material, comprising the following steps:

[0025] A1: Weigh the lithium source, nickel source, and M source, mix them evenly, then add an organic acid and deionized water to obtain a clear solution. Ammonia water is then added while stirring the clear solution to obtain a sol. The mixing method used may include at least one of mechanical dispersion, shearing, shaking, crushing, and emulsification. A dispersant such as an organic polyacid, dispersant, or defoaming agent may be added during the mixing process.

[0026] A2: drying the mixture obtained in step A1 and then granulating it;

[0027] A3: placing the particles obtained in step A2 in a sintering device and sintering them in an oxygen-containing atmosphere; after cooling to room temperature in the furnace, grinding or crushing the obtained material;

[0028] A4: The material obtained in step A3 is surface coated with a material containing source A, and then subjected to secondary sintering after drying to obtain a high power density positive electrode material.

[0029] Preferably, in step A1, the water content of the mixture is controlled during mixing, wherein the mass percentage of water to the total weight is ≤50%.

[0030] Preferably, in step A1, the mixing method used during mixing is preferably high-speed emulsification or high-speed shearing.

[0031] Preferably, in step A1, an appropriate amount of one or more of citric acid, malic acid, hydroxypropyl cellulose or polyvinyl alcohol (PVA), polyvinyl pyrrolidone (PVP), oleyl amino oleate, silicone resins, polyethers, etc. can be added as an auxiliary agent.

[0032] Preferably, in step A2, the mixture needs to be pulverized to obtain a uniform powder after being dried under a negative pressure environment.

[0033] Preferably, in step A2, the mixture is dried to obtain a uniform powder, which is then granulated to obtain particles with a diameter of 0.5 mm to 10 mm.

[0034] Preferably, in step A2, the granulation equipment may be a disc granulator, a drum granulator, a pillow granulator, etc.

[0035] Preferably, the sintering conditions of step A3 are: in an oxygen-containing atmosphere with an oxygen partial pressure ≥ 0.21 atm, heating to 250-350°C at a rate of 1-6°C / min, and keeping warm for 1-3 hours; then heating to 500-700°C at a rate of 1-6°C / min, keeping warm for 3-5 hours, and then heating to 750-960°C at a rate of 1-6°C / min, and keeping warm for 8-20 hours.

[0036] Preferably, the surface coating process in step A4 is: mixing the surface coating material with the positive electrode material. The coating material can be in the form of nanopowder, emulsion, sol or slurry.

[0037] Preferably, the surface coating process in step A4 is: preparing the surface coating material into an emulsion, a sol or a slurry, then adding the positive electrode material obtained in step A3, and sintering the obtained mixture at 250-1000° C. after drying to obtain the positive electrode material.

[0038] Preferably, when the surface coating material is prepared into an emulsion, sol or slurry in step A4, a dispersant, thickener or the like may be used. Specifically, the dispersant, thickener or the like may be sodium carboxymethyl cellulose (CMC), hydroxyethyl cellulose (HEC), hydroxypropyl cellulose or polyvinyl alcohol (PVA), polyvinyl pyrrolidone (PVP), oleyl amino oleate or the like.

[0039] Preferably, in step A4, the surface coating material accounts for 0.02% to 5% of the mass of the positive electrode material after coating.

[0040] Preferably, when the surface coating material in step A4 is element C, the sintering temperature is 250-500°C.

[0041] Preferably, when the surface coating material in step A4 is element C, the coating material is one or more of carbon nanotubes, carbon fibers, or graphene sheets.

[0042] Preferably, when the surface coating material in step A4 is a fast ion conductor, the sintering temperature is 450-960°C.

[0043] Preferably, when the surface coating material in step A4 is a fast ion conductor, the coating material can be one or more of lithium titanate, lithium lanthanum titanate, lithium lanthanum zirconate, lithium titanium aluminum phosphate, lithium phosphate, lithium zirconium phosphate, lithium titanium aluminum phosphate, etc.

[0044] Preferably, step A4 may include 2 or more coating processes, and correspondingly include 2 or more sintering processes.

[0045] The present invention also provides a method for preparing a high power density positive electrode material, comprising the following steps:

[0046] S1: Weigh a lithium source, a nickel source, and an M source, prepare a solution, add a precipitant and a pH adjuster, and co-precipitate to obtain a precursor. Depending on the amount of lithium in the prepared solution, the resulting precursor may or may not contain lithium.

[0047] S2: The obtained precursor is uniformly mixed with lithium salt, and the uniformly mixed powder is placed in a muffle furnace and sintered under an oxygen-containing air atmosphere; after cooling to room temperature with the furnace, the obtained material is ground or crushed; if the lithium content in the precursor meets the requirements, the precursor and lithium salt are not required to be uniformly mixed, and the precursor can be directly sintered, crushed, etc.

[0048] S3: The positive electrode material obtained in S2 is coated on the surface, dried, and then subjected to secondary sintering to obtain the positive electrode material.

[0049] Preferably, the precursor obtained in step S1 contains sufficient lithium element, and can be directly sintered in step S2 to obtain the positive electrode material.

[0050] Preferably, the M and A elements in S1 can be incorporated into the positive electrode material through thermal sintering in S2.

[0051] Preferably, the sintering conditions of step S2 are: in an oxygen-containing atmosphere with an oxygen partial pressure ≥ 0.21 atm, heating to 250-350°C at a rate of 1-6°C / min, and keeping warm for 1-3 hours; then heating to 500-700°C at a rate of 1-6°C / min, keeping warm for 3-5 hours, and then heating to 750-960°C at a rate of 1-6°C / min, and keeping warm for 8-20 hours.

[0052] Preferably, the surface coating process in step S3 is: mixing the surface coating material with the positive electrode material. The coating material can be in the form of nanopowder, emulsion, sol or slurry.

[0053] Preferably, the surface coating process in step S3 is: preparing the surface coating material into an emulsion, a sol or a slurry, then adding the positive electrode material obtained in step S3, and sintering the mixture obtained after drying at 250-1000° C. to obtain the positive electrode material.

[0054] Preferably, when the surface coating material in S3 is prepared into an emulsion, sol or slurry, a dispersant, a thickener, etc. can be selected. Specifically, they can be sodium carboxymethyl cellulose (CMC), hydroxyethyl cellulose (HEC), hydroxypropyl cellulose or polyvinyl alcohol (PVA), polyvinyl pyrrolidone (PVP), oleyl amino oleate, etc.

[0055] Preferably, the surface coating material in S3 accounts for 0.02% to 5% of the mass of the positive electrode material after coating.

[0056] Preferably, when the surface coating material in step S3 is element C, the sintering temperature is 250-500°C.

[0057] Preferably, when the surface coating material in step S3 is element C, the coating material is one or more of carbon nanotubes, carbon fibers, graphene sheets, and the like.

[0058] Preferably, when the surface coating material in step S3 is a fast ion conductor, the sintering temperature is 450-960°C.

[0059] Preferably, when the surface coating material in step S3 is a fast ion conductor, the coating material can be one or more of lithium titanate, lithium lanthanum titanate, lithium lanthanum zirconate, lithium titanium aluminum phosphate, lithium phosphate, lithium zirconium phosphate, lithium titanium aluminum phosphate, etc.

[0060] Preferably, step S3 may include 2 or more coating processes, and correspondingly include 2 or more sintering processes.

[0061] Compared with the prior art, the beneficial effects of the present invention are as follows: the layered positive electrode material provided by the present invention forms an anion and / or cation multi-element bulk doping structure through a solid-phase sintering reaction, thereby improving the bulk lithium ion transmission channel; a continuous fast ion conductor coating layer and / or conductive layer is in situ constructed on the positive electrode surface, thereby optimizing the surface charge distribution of the positive electrode material and improving the interfacial lithium ion diffusion performance, reducing the interfacial polarization impedance, and being able to normally exert the energy density and control the temperature change within a safe range under high voltage and high rate. At the same time, the layered positive electrode material of the present invention can enable the battery to be well charged and discharged regardless of whether it is in a low temperature environment or a high temperature environment, and the platform voltage decay rate is low. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] Figure 1 This is the SEM image of the high power density positive electrode material of Example 1 of the present invention.

[0063] Figure 2 This is the XRD diagram of the high power density positive electrode material of Example 1 of the present invention.

[0064] Figure 3 This is the SEM image of the high power density positive electrode material of Example 2 of the present invention.

[0065] Figure 4 This is the XRD diagram of the high power density positive electrode material of Example 2 of the present invention.

[0066] Figure 5 This is a charge and discharge cycle curve of the high power density positive electrode material of Example 1 of the present invention at a 1C rate.

[0067] Figure 6 The discharge curves of the battery cell of Example 1 of the present invention at different rates in the range of 3.0V to 4.35V are shown.

[0068] Figure 7 This is the differential capacity curve of the high power density positive electrode material of Example 1 of the present invention.

[0069] Figure 8 This is the charge and discharge cycle curve of the high power density positive electrode material of Example 1 of the present invention at a voltage range of 3.0V to 4.5V and a rate of 3C.

[0070] Figure 9 3C charge-discharge curves of the high power density positive electrode material of Example 1 of the present invention at different cycle times in the voltage range of 3.0V to 4.5V.

[0071] Figure 10 This is an SEM image of the high power density positive electrode material of Example 4 of the present invention. DETAILED DESCRIPTION

[0072] To make the technical solutions and advantages of the present invention more clear, the present invention and its beneficial effects will be further described in detail below in conjunction with specific implementation methods, but the implementation methods of the present invention are not limited thereto.

[0073] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature specified as "first" or "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, "plurality" means two or more, unless otherwise specifically defined.

[0074] In the first aspect of the present invention, a high power density cathode material is provided, the molecular formula of which is Li 1+a Ni x M y A z O2, 0≤a≤0.2, 0.45≤x≤0.95, 0<y≤0.5, 0≤z≤0.2, x+y+z=1; wherein the M element includes at least one of Co, Mn, Al, Nb, and Sb; and the A element includes at least one of Ti, Mo, Zr, Sr, Re, P, B, La, Ta, and C.

[0075] The high power density positive electrode material of the present invention may contain M and A elements, and their functions in the positive electrode material are as follows. As doping elements, the doping elements can change the lattice structure of the positive electrode material or adjust the lattice parameters, increase the lattice defects and impurity sites of the material, thereby improving the ion transmission rate and diffusion coefficient of the positive electrode material. At the same time, the doping elements can also change the electronic structure of the positive electrode material, improve the electron migration rate, and improve the electrical conductivity of the positive electrode material and the reaction kinetics during the electrochemical reaction; as coating elements, a fast ion conductor coating layer is formed on the surface of the positive electrode material, optimizing the surface charge distribution of the positive electrode material, improving the wettability of the surface electrolyte, and reducing the interface polarization impedance. The C element in the A element is derived from one or more of single-walled carbon nanotubes, multi-walled carbon nanotubes, carbon fibers, graphene, and conductive carbon, and it can also have the function of increasing the amount of electrolyte absorbed by the surface of the positive electrode material, further improving the ionic conductivity at the interface.

[0076] In an embodiment of the present invention, the XRD pattern of the high power density positive electrode material under Cu Kα1 rays has the following diffraction peaks: characteristic peak A: 18°~20°, characteristic peak B: 36°~37.4°, characteristic peak C: 37.4°~39.5°, characteristic peak D: 37.4°~39.5°, characteristic peak E: 43°~46°, characteristic peak F: 63°~66°, and characteristic peak G: 63°~66°.

[0077] In the embodiment of the present invention, the diffraction peak intensity ratio between characteristic peak A and characteristic peak E is ≥1.1, and the half-peak width of characteristic peak A: 18° to 20° is less than 0.2, ensuring that the obtained positive electrode material has good crystallinity and unobstructed ion transmission channels inside.

[0078] In an embodiment of the present invention, the high power density positive electrode material is primary particles and / or secondary particles formed by aggregation of primary particles, the D50 of the primary particles is 1 to 4 μm, and the D50 of the secondary particles is 3 to 8 μm, wherein the maximum particle size of the primary particles and the secondary particles are both ≤15 μm.

[0079] In some embodiments, the high power density cathode material has a powder conductivity of 0.00001 to 0.05 S / cm at 100 MPa; its specific surface area is 0.2 to 20 m 2 / g; its liquid phase density is 4.2~5.2g / mL.

[0080] In some embodiments, the high power density cathode material has a capacity of 170 to 220 mAh / g at 4.35 to 4.6 V (2032 button half-cell) at 0.1C, and an energy density of 650 Wh / kg to 860 Wh / kg at a platform voltage of 3.84 to 3.92 V at 0.1C.

[0081] In some embodiments, the differential capacity curve (dQ / dV curve) exhibits at least one redox peak between 3.4V and 4.6V. This peak reflects the electrochemical process during the charge and discharge of the cathode material. The changes in the positions of the redox peaks can be used to reflect the electrochemical reaction kinetics of the cathode material.

[0082] In some embodiments, at 4.35-4.6V, compared to 1C discharge; at 5C rate discharge, the platform voltage decay rate is less than 5%; and / or, at 10C rate discharge, the platform voltage decay rate is less than 8%; and / or, at 15C rate discharge, the platform voltage decay rate is less than 10%. Compared with existing positive electrode materials, the high power density positive electrode material of the present invention has a lower platform voltage decay rate at high voltage and high rate, indicating that the positive electrode material of the present invention has better ionic conductivity, more stable structure, low polarization effect, and can effectively maintain the discharge efficiency, energy density and power density of the material. It can be applied to batteries and has the ability to meet the use requirements of low-altitude aircraft and other application scenarios such as high voltage and high rate.

[0083] A second aspect of the present invention provides a method for preparing the above-mentioned high power density positive electrode material, comprising the following steps:

[0084] A1: Weigh the lithium source, nickel source, and M source, mix them evenly, then add an organic acid and deionized water to obtain a clear solution. Ammonia water is then added while stirring the clear solution to obtain a sol. The mixing method used may include at least one of mechanical dispersion, shearing, shaking, crushing, and emulsification. A dispersant, such as an organic polyacid, dispersant, or defoaming agent, may be added during mixing.

[0085] A2: drying the mixture obtained in step A1 and then granulating it;

[0086] A3: Place the particles obtained in step A2 in a sintering device and sinter them in an oxygen-containing atmosphere with an oxygen partial pressure of ≥ 0.21 atm; after cooling to room temperature with the furnace, grind or crush the obtained material to obtain a positive electrode material.

[0087] A4: The positive electrode material obtained in A3 is coated on the surface of the source material A, dried, and then sintered twice to obtain a high power density positive electrode material.

[0088] Specifically, in the embodiment, in step A1, the lithium source, nickel source and M source are mixed in a designed molar ratio to obtain a uniform mixture. The specific molar ratio is (1+a):x:y to obtain a uniform mixture. Wherein 0≤a≤0.2, 0.45≤x≤0.95, 0<y≤0.5,

[0089] Specifically, in the embodiment, the lithium salt in step A1 is one of lithium chloride, lithium nitrate, lithium sulfate, lithium acetate, and lithium carbonate, preferably lithium carbonate, lithium acetate, or lithium hydroxide; the nickel salt is one of nickel chloride, nickel nitrate, nickel sulfate, nickel carbonate, and nickel acetate, preferably nickel carbonate; the cobalt salt is one of cobalt chloride, cobalt nitrate, cobalt sulfate, cobalt carbonate, cobalt hydroxide, and cobalt trioxide, preferably cobalt carbonate; the manganese salt is one of manganese chloride, manganese nitrate, manganese sulfate, manganese oxalate, manganese dioxide, manganese tetraoxide, manganese trioxide, and manganese carbonate, preferably manganese carbonate.

[0090] Specifically, in some embodiments, the compound containing Al, Nb, and Sb elements in the M source may be one or more of oxides, sulfates, nitrates, acetates, hydroxides, phosphates, chlorides, carbonates, and the like.

[0091] Specifically, in some embodiments, the compound containing elements such as Ti, Mo, Zr, Sr, Re, P, B, La, Ta in source A may be one or more of oxides, sulfates, nitrates, acetates, hydroxides, phosphates, chlorides, carbonates, etc.

[0092] Specifically, in some embodiments, the C element in the A-containing source is one or more of single-walled carbon nanotubes, multi-walled carbon nanotubes, carbon fibers, graphene, and conductive carbon.

[0093] Specifically, in some embodiments, the water content of the mixture during mixing in step A1 is controlled to be ≤50% by weight of the total weight, which may be 20%, 25%, 30%, 35%, 40%, 45%, and 50%, including but not limited to the above percentages.

[0094] Specifically, in some embodiments, the mixing method used in step A1 can be a high-speed disperser, a high-speed emulsifier, a high-speed shearing machine, a planetary ball mill, etc.

[0095] Specifically, in some embodiments, during the mixing in step A1, an appropriate amount of one or more of citric acid, malic acid, hydroxypropyl cellulose or polyvinyl alcohol (PVA), polyvinyl pyrrolidone (PVP), oleyl amino oleate, silicone resin, polyether, etc. can be added to improve the dispersion effect.

[0096] Specifically, in some embodiments, the drying process of the mixture in step A2 can be carried out under normal pressure or under negative pressure. The drying process can be carried out in a static drying mode or a dynamic drying mode. The drying temperature is 85°C to 250°C.

[0097] Specifically, in some embodiments, the mixture in step A2 is dried to obtain a uniform powder, which is then granulated to obtain granules with a diameter of 0.5 mm to 10 mm. The granulation equipment used can be a disc granulator, a rotary drum granulator, a pillow granulator, etc.

[0098] Specifically, in some embodiments, the sintering conditions of step A3 are as follows: heating to 250-350°C at a rate of 1-6°C / min, holding for 1-3 hours; then heating to 500-700°C at a rate of 1-6°C / min, holding for 3-5 hours, and then heating to 750-960°C at a rate of 1-6°C / min, holding for 8-20 hours. More specifically, the temperature may be first increased to 300°C at a rate of 6°C / min, holding for 2 hours; then heated to 550°C at a rate of 6°C / min, holding for 4 hours, and then heated to 950°C at a rate of 6°C / min, holding for 10 hours.

[0099] Specifically, in some embodiments, the surface coating process of step A4 is to mix the surface coating material with the positive electrode material. The surface coating material is first made into an emulsion, a sol or a slurry, and then the positive electrode material obtained in step A3 is added, and the mixture obtained after drying is sintered at 250 to 1000°C to obtain the positive electrode material. Among them, when the surface coating material is made into an emulsion, a sol or a slurry, a dispersant, a thickener, etc. can be selected. Specifically, it can be sodium carboxymethyl cellulose (CMC), hydroxyethyl cellulose (HEC), hydroxypropyl cellulose or polyvinyl alcohol (PVA), polyvinyl pyrrolidone (PVP), oleyl amino oleate, etc. The surface coating material accounts for 0.05% to 10% of the mass ratio of the positive electrode material after coating.

[0100] Specifically, in some embodiments, when the surface coating material in step A4 is element C, it can be one or more of single-walled carbon nanotubes, multi-walled carbon nanotubes, carbon fibers, graphene, and conductive carbon, with a mass fraction of 0.01% to 5% of the total weight of the positive electrode material, and the sintering temperature is 250°C to 500°C.

[0101] Specifically, in some embodiments, when the surface coating material is made into an emulsion, sol or slurry in the A4 step, the elemental compound required for the element to be coated can be formed into a uniform emulsion, sol or slurry, and the coating process is achieved by directly mixing with the positive electrode material and drying and sintering. At this time, the coating process is achieved by uniformly mixing the positive electrode material and the coating material, and desorption of the solvent and drying and sintering. Emulsions, sols or slurries of different compositions can also be made according to the elemental composition, and mixed with the positive electrode material in batches. When mixing in batches, the components added later and the components added earlier can undergo gelation or precipitation reaction around the positive electrode material to achieve partial coating, and the complete coating process is achieved after drying and sintering.

[0102] Specifically, in some embodiments, when the surface coating material in step A4 is a fast ion conductor, it can be lithium titanate (LTO), lithium aluminate (LAO), lithium lanthanum titanate (LLTO), lithium lanthanum zirconate (LLZO), lithium aluminum titanium phosphate (LATP), etc., with its mass fraction accounting for 0.01% to 8% of the total weight of the positive electrode material. The sintering temperature is 450 to 960°C.

[0103] Specifically, in some embodiments, step A4 may include two or more coating processes, correspondingly including two or more sintering processes. That is, a coating process is performed once, followed by a sintering process. Then, a second coating process is performed, followed by a second sintering process. The first coating process may be a lithium fast ion conductor coating, and the second coating process may be a C element coating. Alternatively, the first coating process may be a one-type lithium fast ion conductor coating, and the second coating process may be a different lithium fast ion conductor coating.

[0104] One of the manufacturing methods in the present invention is to obtain a positive electrode material by mixing in a liquid phase and obtaining a dry powder, and then further granulating the powder and performing a solid phase sintering reaction and surface coating in an atmosphere.

[0105] In addition, the present invention also provides a second method for preparing the above-mentioned high power density positive electrode material, comprising the following steps:

[0106] S1: Weigh a lithium source, a nickel source, and an M source in a molar ratio of (1+a):x:y to form a solution, where 0≤a≤0.2, 0.45≤x≤0.95, 0<y≤0.5, 0<z≤0.2, and x+y+z=1. Add a precipitant and a pH adjuster, and co-precipitate to obtain a precursor.

[0107] S2: uniformly mix the obtained precursor with lithium salt, place the uniformly mixed powder in a muffle furnace, and sinter it under an oxygen-containing air atmosphere; after cooling to room temperature in the furnace, grind or crush the obtained material to obtain a layered positive electrode material.

[0108] S3: The positive electrode material obtained in S2 is coated with the surface of the A source material, dried, and then subjected to secondary sintering to obtain the positive electrode material.

[0109] Specifically, in some embodiments, S1 may contain a lithium source. When it contains sufficient lithium source, the obtained precursor can be directly sintered to prepare the positive electrode material. When S1 does not contain a lithium source or the lithium source content is insufficient, the obtained precursor needs to be mixed with sufficient lithium source and then sintered to prepare the positive electrode material.

[0110] Specifically, in some embodiments, the precipitant in S1 is a soluble compound containing one or more of carbonate, hydroxide, oxalate, and bicarbonate. Specifically, it may be sodium hydroxide solution, lithium hydroxide solution, lithium carbonate solution, lithium oxalate solution, etc. The pH adjuster is aqueous ammonia.

[0111] Specifically, in some embodiments, the M and A elements in S1 can be mixed with a precursor in S2 and then thermally sintered to enter the positive electrode material.

[0112] Specifically, in some embodiments, the sintering conditions of step S2 are: heating to 250-350°C at a rate of 1-6°C / min, holding for 1-3 hours; then heating to 500-700°C at a rate of 1-6°C / min, holding for 3-5 hours, and then heating to 750-960°C at a rate of 1-6°C / min, holding for 8-20 hours. More specifically, the oxygen partial pressure is 0.42 atm, the gas flow rate is 350 Nm 3 / h, first increase the temperature to 300℃ at a rate of 6℃ / min and keep it for 2h; then increase the temperature to 550℃ at a rate of 6℃ / min and keep it for 4h, and then increase the temperature to 940℃ at a rate of 6℃ / min and keep it for 10h.

[0113] Specifically, in some embodiments, the surface coating process of step S3 is to mix the surface coating material with the positive electrode material. The surface coating material is first made into an emulsion, a sol or a slurry, and then the positive electrode material obtained in step S2 is added, and the mixture obtained after drying is sintered at 250 to 1000°C to obtain the positive electrode material. Among them, when the surface coating material is made into an emulsion, a sol or a slurry, a dispersant, a thickener, etc. can be selected. Specifically, it can be sodium carboxymethyl cellulose (CMC), hydroxyethyl cellulose (HEC), hydroxypropyl cellulose or polyvinyl alcohol (PVA), polyvinyl pyrrolidone (PVP), oleyl amino oleate, etc. The surface coating material accounts for 0.05% to 10% of the mass ratio of the positive electrode material after coating.

[0114] Specifically, in some embodiments, when the surface coating material is made into an emulsion, sol or slurry in the S3 step, the elemental compound required for the element to be coated can be formed into a uniform emulsion, sol or slurry, and the coating process is achieved by directly mixing with the positive electrode material and drying and sintering. At this time, the coating process is achieved by uniformly mixing the positive electrode material and the coating material, and desorption of the solvent and drying and sintering. Emulsions, sols or slurries of different compositions can also be made according to the elemental composition, and mixed with the positive electrode material in batches. When mixing in batches, the components added later and the components added earlier can undergo gelation or precipitation reaction around the positive electrode material to achieve partial coating, and the complete coating process is achieved after drying and sintering.

[0115] Specifically, in some embodiments, when the surface coating material in step S3 is element C, it can be one or more of single-walled carbon nanotubes, multi-walled carbon nanotubes, carbon fibers, graphene, and conductive carbon. Its mass fraction accounts for 0.01% to 5% of the total weight of the positive electrode material. The sintering temperature is 250°C to 500°C.

[0116] Specifically, in some embodiments, when the surface coating material in step S3 is a fast ion conductor, it can be lithium titanate (LTO), lithium aluminate (LAO), lithium lanthanum titanate (LLTO), lithium lanthanum zirconate (LLZO), lithium aluminum titanium phosphate (LATP), etc., with its mass fraction accounting for 0.01% to 8% of the total weight of the positive electrode material. The sintering temperature is 450 to 960°C.

[0117] Specifically, in some embodiments, step S3 may include two or more coating processes, and correspondingly, two or more sintering processes. That is, a coating process is performed once, followed by a sintering process. Then, a second coating process is performed, followed by a second sintering process. The first coating process may be a lithium fast ion conductor coating, and the second coating process may be a C element coating. Alternatively, the first coating process may be a one-type lithium fast ion conductor coating, and the second coating process may be a different type of lithium fast ion conductor coating.

[0118] The capacity, platform voltage and mass energy density of the positive electrode material obtained by the present invention are obtained by assembling a button-type half-cell (coin-cell 2032). The assembly process of the button-type battery is as follows: after the sample to be tested is pretreated (baked in a vacuum oven at 85°C for 4h), the positive electrode material (weighing 20g) is weighed, and SP and PVDF are weighed according to the following weight ratio (positive electrode material: SP: PVDF = 90%: 5%: 5%), and an appropriate amount of NMP is added. The slurry is obtained by dispersing it at 2500rpm with a high-speed dispersant for 45min and passing it through a 150-mesh sieve. The pole piece is prepared using the 150μm end of a four-sided coater (the surface density of the single-sided pole piece is about 10-15mg / cm 2). Place the coated membrane in a 120℃ forced air drying oven and dry it for 30 minutes. The rolled electrode is sliced ​​by a punch. Weigh the circular electrode paper bag and place it in a vacuum drying oven to dry (at -97.5Kpa, 85℃, bake for 14 hours). After drying, put the paper bag with the membrane in a ziplock bag (exclude the air in the ziplock bag) and transfer it to the glove box. Assemble the button battery according to the "negative electrode shell-shrapnel-gasket-a drop of electrolyte-lithium sheet-45μL electrolyte-diaphragm-45μL electrolyte-membrane-positive electrode shell" and transfer it out of the glove box and let it stand for 3 hours.

[0119] The internal electrode sheet of the battery in the present invention is a laminated structure. The battery model is 554390, designed for 3Ah. The surface density of the positive electrode sheet is 20-24mg / cm 2 The compaction density is 2.9-3.5 g / cc, and the positive electrode material accounts for 96% of the coating layer; the negative electrode uses FT-1, and the negative electrode sheet density is 14-16 mg / cm 2 The compaction density is 1.3-1.5 g / cc. The negative electrode material accounts for 94.8% of the coating layer by mass; the designed N / P ratio is 1.1. The remaining materials are common battery materials. The initial electrolyte injection volume is 10 g. The basic formation process is charging at 0.05C for 1 hour, 0.1C for 1 hour, and 0.2C for 2 hours, followed by degassing and secondary sealing. The cell is charged at 0.2C to the cutoff voltage, and then discharged at 0.2C to the cutoff voltage to complete the capacity separation.

[0120] Example 1

[0121] The preparation method of the high power density positive electrode material of this embodiment is:

[0122] A1: According to the molar ratio of Li:Ni:Co:Mn=1.04:0.5:0.2:0.3, anhydrous lithium acetate (213.7g), nickel acetate tetrahydrate (391.3g), cobalt hydroxide (57.6g), and manganese carbonate (108.5g) were weighed, 250g of deionized water were added, and the mixture was dispersed by homogeneous emulsification. During the dispersion process, 77g of citric acid was added to obtain a paste mixture.

[0123] A2: The paste mixture was placed in a vacuum oven at 200°C until dry. After cooling, it was ground through a 300-mesh sieve to obtain a powder of a uniformly dispersed lithium-nickel-cobalt-manganese mixture. The resulting powder was granulated using a disc granulator, using a dilute polyvinyl alcohol solution as a binder, to obtain a particle size of 1-3 mm.

[0124] A3: The particles in A2 were placed in a sagger in a muffle furnace under an oxygen-containing air atmosphere with an oxygen partial pressure of 0.21 atm and a gas flow rate of 350 Nm 3 / h, first heat to 300℃ at a rate of 6℃ / min and keep warm for 2h; then heat to 550℃ at a rate of 6℃ / min and keep warm for 4h, then heat to 930℃ at a rate of 6℃ / min and keep warm for 10h to complete sintering; after cooling to room temperature with the furnace, the obtained material is ground or crushed to D50 of 4.5μm, and a total of about 290g is collected.

[0125] A4: Weigh 2.14 g of tetraisopropyl titanate, add an appropriate amount of deionized water and stir vigorously, then add an appropriate amount of tetramethylammonium hydroxide to obtain a transparent titanium sol, add the material obtained in A3 to the titanium sol, and stir to disperse the slurry evenly. Weigh 0.99 g of anhydrous lithium acetate, add an appropriate amount of deionized water to obtain a solution. Add the lithium acetate solution to the slurry of the above-mentioned titanium sol and the positive electrode material, and stir and knead continuously. In this process, the titanium sol gels to form a lithium-titanium gel-coated positive electrode material. After drying at 350°C, the powder is placed in a sagger and placed in a muffle furnace. Under the conditions of an oxygen-containing air atmosphere, the oxygen partial pressure is 0.21 atm, and the gas flow rate is 350 Nm 3 / h, first heat to 550℃ at a rate of 6℃ / min, keep warm for 2h, then heat to 800℃ at a rate of 6℃ / min, keep warm for 6h, complete sintering, and obtain positive electrode material after crushing and sieving.

[0126] Battery Assembly:

[0127] Positive electrode sheet preparation: The prepared high-power density positive electrode material, conductive carbon, carbon nanotubes, and PVDF binder were premixed at a mass ratio of 96:2:1:1 for 45 minutes. NMP was then added and kneaded to achieve a slurry with a solids content between 55% and 70% and a viscosity between 4,000 and 10,000 mPas. The slurry was then coated onto aluminum foil to form a positive electrode sheet.

[0128] Negative electrode sheet preparation: Weigh the negative electrode active material, conductive carbon, binder SBR, and sodium carboxymethyl cellulose (CMC) in a mass ratio of 95:2:1.5:1.5. Premix the negative electrode active material and conductive carbon for 45 minutes. Add deionized and dissolved CMC and continue kneading for 60 minutes. Then add SBR and continue kneading to ensure that the solid content of the slurry is between 50% and 60% and the viscosity is between 4000 and 6000 mPas. The slurry is coated on copper foil to form the negative electrode sheet.

[0129] The positive electrode sheet, diaphragm, negative electrode sheet and separator are die-cut, and the positive electrode sheet, diaphragm, negative electrode sheet and separator are stacked in order to obtain the battery cell. The battery cell is sent to the dryer and baked at a temperature of 110-120℃ for 12 hours. After baking, the positive and negative electrode ears are welded.

[0130] The battery cell is injected with electrolyte and packaged to obtain a secondary battery.

[0131] Example 2

[0132] S1: Weigh nickel sulfate, cobalt sulfate and manganese sulfate according to the molar ratio of Ni:Co:Mn=0.6:0.1:0.3 and prepare a 2 mol / L solution. In addition, prepare sodium hydroxide solution as a precipitant and ammonia water as a pH regulator. 0.6 Co 0.1 Mn 0.3 The (OH)2-type precursor is controlled to have a D50 of 4 to 6 μm. The obtained precursor is uniformly mixed with lithium carbonate, wherein the molar ratio of lithium to nickel, cobalt and manganese is 1.04:1.

[0133] S2: The precursor mixed with lithium carbonate powder is put into a sagger and placed in a muffle furnace under the conditions of oxygen-containing air atmosphere, oxygen partial pressure of 0.42atm, gas flow rate of 350Nm 3 / h, first heat to 300℃ at a rate of 6℃ / min and keep warm for 2h; then heat to 550℃ at a rate of 6℃ / min and keep warm for 4h, then heat to 880℃ at a rate of 6℃ / min and keep warm for 10h to complete sintering; after cooling to room temperature with the furnace, grind or crush the obtained material to D50 of 3-5μm to obtain the positive electrode material.

[0134] S3: Weigh 13.9 g of aluminum nitrate nonahydrate and add an appropriate amount of deionized water to obtain a solution. Weigh 1.55 g of lithium hydroxide monohydrate and add an appropriate amount of deionized water to obtain a solution. Add the lithium hydroxide solution dropwise into the aluminum nitrate solution and stir vigorously. Add an appropriate amount of tetramethylammonium hydroxide as needed to obtain a lithium aluminate sol. Weigh 500 g of the positive electrode material obtained in S2 and mix it evenly with the lithium aluminate sol, and dry it in a blast oven at 150 ° C. Then put the obtained powder into a sagger and place it in a muffle furnace. Under the conditions of an oxygen-containing air atmosphere, the oxygen partial pressure is 0.21 atm, and the gas flow rate is 350 Nm 3 / h, first heat to 550℃ at a rate of 6℃ / min, keep warm for 2h, then heat to 740℃ at a rate of 6℃ / min, keep warm for 6h, complete sintering, and obtain positive electrode material after crushing and sieving.

[0135] Positive electrode sheet preparation: Weigh the positive electrode active material, conductive carbon, carbon nanotubes, and PVDF binder at a mass ratio of 96:2:1:1 and premix for 45 minutes. Then, add NMP and knead the slurry. The weight of NMP added ensures that the solid content of the slurry is between 55% and 70%, and the viscosity of the slurry is between 4000 and 10000 mPas. The slurry is coated on aluminum foil to form the positive electrode sheet.

[0136] Negative electrode sheet preparation: Weigh the negative electrode active material, conductive carbon, binder SBR, and sodium carboxymethyl cellulose (CMC) in a mass ratio of 95:2:1.5:1.5. Premix the negative electrode active material and conductive carbon for 45 minutes. Add deionized and dissolved CMC and continue kneading for 60 minutes. Then add SBR and continue kneading to ensure that the solid content of the slurry is between 50% and 60% and the viscosity is between 4000 and 6000 mPas. The slurry is coated on copper foil to form the negative electrode sheet.

[0137] The rest is the same as in Example 1 and will not be described again here.

[0138] Example 3

[0139] S1: Weigh nickel sulfate, cobalt sulfate and manganese sulfate according to the molar ratio of Ni: Co: Mn = 0.7: 0.1: 0.2, and prepare a 2 mol / L mixed solution. Weigh an appropriate amount of oxalic acid to prepare a solution as a precipitant, and weigh an appropriate amount of ammonia water as a pH regulator. Add the above mixed solution, oxalic acid solution and ammonia water into the reactor through a peristaltic pump, and stir at a rate of 600-800 rpm. After the reaction is completed, age for 12 hours. The precipitate is washed, filtered and dried to obtain a precursor. Ni 0.7 Co 0.1 Mn 0.2 A C2O4 precursor is prepared with a D50 of 5 to 8 μm. The obtained precursor is uniformly mixed with lithium carbonate, wherein the molar ratio of lithium to nickel, cobalt, and manganese is 1.04:1.

[0140] S2: The obtained precursor was placed in a sagger and placed in a muffle furnace under the conditions of an oxygen-containing air atmosphere with an oxygen partial pressure of 0.80 atm and a gas flow rate of 350 Nm 3 / h, first heat to 300℃ at a rate of 6℃ / min, keep warm for 2h; then heat to 550℃ at a rate of 6℃ / min, keep warm for 4h, and then heat to 840℃ at a rate of 6℃ / min, keep warm for 10h to complete sintering; after cooling to room temperature with the furnace, grind or crush the obtained material to D50 of 5.0-6.0μm to obtain the positive electrode material.

[0141] S3: Weigh 0.39g of lithium hydroxide monohydrate and add an appropriate amount of deionized water to form a solution. This solution is then added to 8g of tetraisopropyl titanate and an appropriate amount of tetramethylammonium hydroxide to form a lithium-titanium sol. Add 500g of the positive electrode material obtained in S2 to the lithium-titanium sol and stir to combine.

[0142] Weigh 5.76g of lanthanum acetate and dissolve it, and add the resulting solution to the mixture of the above-mentioned positive electrode material and lithium titanium sol. Continue stirring and kneading. During this process, the lithium titanium sol gels to form a positive electrode material coated with lithium titanium lanthanum gel. After drying at 350℃, the powder is placed in a sagger and placed in a muffle furnace under the conditions of an oxygen-containing air atmosphere with an oxygen partial pressure of 0.21atm and a gas flow rate of 350Nm 3 / h, first heat to 550℃ at a rate of 6℃ / min, keep warm for 2h, then heat to 820℃ at a rate of 6℃ / min, keep warm for 6h, complete sintering, and obtain positive electrode material after crushing and sieving.

[0143] The rest is the same as in Example 1 and will not be described again here.

[0144] Example 4

[0145] S1: Weigh nickel sulfate, cobalt sulfate and manganese sulfate according to the molar ratio of Ni:Co:Mn=0.7:0.1:0.2 and prepare a 2 mol / L solution. In addition, prepare sodium hydroxide solution as a precipitant and ammonia water as a pH regulator. 0.7 Co 0.1 Mn 0.2 The (OH)2-type precursor is controlled to have a D50 of 4 to 6 μm. The obtained precursor is uniformly mixed with lithium carbonate, wherein the molar ratio of lithium to nickel, cobalt and manganese is 1.04:1.

[0146] S2: The precursor mixed with lithium carbonate powder is put into a sagger and placed in a muffle furnace under the conditions of oxygen-containing air atmosphere, oxygen partial pressure of 0.42atm, gas flow rate of 350Nm 3 / h, first heat to 300℃ at a rate of 6℃ / min, keep warm for 2h; then heat to 550℃ at a rate of 6℃ / min, keep warm for 4h, and then heat to 840℃ at a rate of 6℃ / min, keep warm for 10h to complete sintering; after cooling to room temperature with the furnace, grind or crush the obtained material to D50 of 3-5μm to obtain the positive electrode material.

[0147] S3: Weigh 13.9 g of aluminum nitrate nonahydrate and add an appropriate amount of deionized water to obtain a solution. Weigh 1.55 g of lithium hydroxide monohydrate and add an appropriate amount of deionized water to obtain a solution. Add the lithium hydroxide solution dropwise into the aluminum nitrate solution and stir vigorously. Add an appropriate amount of tetramethylammonium hydroxide as needed to obtain a lithium aluminate sol. Weigh 500 g of the positive electrode material obtained in S2 and mix it evenly with the lithium aluminate sol, and dry it in a blast oven at 150 ° C. Then put the obtained powder into a sagger and place it in a muffle furnace. Under the conditions of an oxygen-containing air atmosphere, the oxygen partial pressure is 0.21 atm, and the gas flow rate is 350 Nm 3 / h, first raise the temperature to 550℃ at a rate of 6℃ / min, hold for 2h, then raise the temperature to 740℃ at a rate of 6℃ / min, hold for 6h, complete sintering, and obtain 495g of positive electrode material after crushing and sieving. Weigh 50g of carbon nanotube slurry (carbon nanotube content 5%), add an appropriate amount of polyvinyl pyrrolidone aqueous solution to disperse evenly, then add the aforementioned 495g of positive electrode material and knead evenly. After drying in a blast oven at 150℃, transfer to a muffle furnace and hold at 400℃ for 8h, and sieve to obtain the positive electrode material.

[0148] The remaining steps are the same as in Example 1 and will not be repeated here. Positive electrode sheet preparation: The positive electrode active material, conductive carbon, and PVDF binder were weighed and premixed at a mass ratio of 97:2:1 for 45 minutes. NMP was then added and kneaded to achieve a slurry with a solids content between 55% and 70% and a viscosity between 4000 and 10000 mPas. The slurry was then coated onto aluminum foil to form a positive electrode sheet.

[0149] Negative electrode sheet preparation: Weigh the negative electrode active material, conductive carbon, binder SBR, and sodium carboxymethyl cellulose (CMC) in a mass ratio of 95:2:1.5:1.5. Premix the negative electrode active material and conductive carbon for 45 minutes. Add deionized and dissolved CMC and continue kneading for 60 minutes. Then add SBR and continue kneading to ensure that the solid content of the slurry is between 50% and 60% and the viscosity is between 4000 and 6000 mPas. The slurry is coated on copper foil to form the negative electrode sheet.

[0150] The rest is the same as in Example 1 and will not be described again here.

[0151] Example 5

[0152] S1: Weigh 185.5g of lithium chloride monohydrate, 266.7g of nickel sulfate hexahydrate, 114.1g of cobalt sulfate heptahydrate, and 102.9g of manganese sulfate monohydrate in a molar ratio of Li:Ni:Co:Mn=1.0:0.5:0.2:0.3, add deionized water to dissolve, and prepare a mixed solution (total metal molar concentration is 2.5mol / L). Weigh 129g of lithium hydroxide monohydrate and dissolve it in deionized water as a precipitant, and weigh an appropriate amount of ammonia water as a pH regulator. The above mixed solution, lithium hydroxide solution, and ammonia water are added to the reactor (the bottom liquid contains 0.15g of polyacrylamide, and the reactor is filled with carbon dioxide atmosphere) through a peristaltic pump, with a stirring rate of 600-800rpm. After the reaction is completed, age for 12h. The precipitate is washed, filtered, and dried to obtain a precursor. Control D50 to be 5-6μm. The obtained precursor contains lithium element, and the molar ratio of lithium element to nickel, cobalt and manganese elements is 1.02:1.

[0153] S2: The obtained precursor was placed in a sagger and placed in a muffle furnace under the conditions of an oxygen-containing air atmosphere with an oxygen partial pressure of 0.30 atm and a gas flow rate of 350 Nm 3 / h, first heat to 300℃ at a rate of 6℃ / min, keep warm for 2h; then heat to 550℃ at a rate of 6℃ / min, keep warm for 4h, and then heat to 920℃ at a rate of 6℃ / min, keep warm for 10h to complete sintering; after cooling to room temperature with the furnace, grind or crush the obtained material to D50 of 4.0-5.0μm to obtain the positive electrode material.

[0154] S3: Weigh 1.54g of lithium hydroxide monohydrate and add an appropriate amount of deionized water to form a solution; weigh 13.7g of tetraisopropyl titanate and 3.2g of aluminum nitrate nonahydrate, add an appropriate amount of deionized water, and then add an appropriate amount of tetramethylammonium hydroxide to obtain aluminum titanium sol; add an appropriate amount of deionized water to 9.8g of ammonium dihydrogen phosphate to obtain a solution. Add the lithium hydroxide solution, aluminum titanium sol and ammonium dihydrogen phosphate solution to a homogenizer to obtain a uniformly dispersed emulsion. Add 500g of the positive electrode material obtained in the S2 stage to the obtained emulsion, and stir and knead evenly to form a positive electrode material coated with a lithium aluminum titanium phosphate precursor. After drying at 350°C, the powder is placed in a sagger and placed in a muffle furnace. Under the conditions of an oxygen-containing air atmosphere, the oxygen partial pressure is 0.21atm, and the gas flow rate is 350Nm 3 / h, first heat to 550℃ at a rate of 6℃ / min, keep warm for 2h, then heat to 750℃ at a rate of 6℃ / min, keep warm for 6h, complete sintering, and obtain positive electrode material after crushing and sieving.

[0155] The rest is the same as in Example 1 and will not be described again here.

[0156] Example 6

[0157] S1: Weigh 96.7g of lithium chloride monohydrate, 373.4g of nickel sulfate hexahydrate, 57.1g of cobalt sulfate heptahydrate, and 68.6g of manganese sulfate monohydrate in a molar ratio of Li:Ni:Co:Mn = 0.8:0.7:0.1:0.2, dissolve in deionized water, and prepare a mixed solution (total metal molar concentration of 2.5 mol / L). Weigh 129g of lithium hydroxide monohydrate and dissolve in deionized water as a precipitant, and weigh an appropriate amount of ammonia water as a pH adjuster. The mixed solution, lithium hydroxide solution, and ammonia water are added to a reactor (the bottom liquid contains 0.16g of polyacrylamide, and the reactor is filled with a carbon dioxide atmosphere) via a peristaltic pump, stirring at 600-800rpm. After completion of the reaction, age for 12h. The precipitate is washed, filtered, and dried to obtain a precursor. The D50 value is controlled to be 5-6μm. The resulting precursor contains some lithium, with a molar ratio of lithium to nickel, cobalt, and manganese of 0.8:1.

[0158] S2: Add an appropriate amount of lithium carbonate to the obtained precursor (ensure that the molar ratio of lithium to nickel, cobalt and manganese is 1.02-1.04:1) and mix well. Then put it into a sagger and place it in a muffle furnace under the conditions of oxygen-containing air atmosphere, oxygen partial pressure of 0.80 atm, gas flow rate of 350 Nm 3 / h, first heat to 300℃ at a rate of 6℃ / min, keep warm for 2h; then heat to 550℃ at a rate of 6℃ / min, keep warm for 4h, and then heat to 840℃ at a rate of 6℃ / min, keep warm for 10h to complete sintering; after cooling to room temperature with the furnace, grind or crush the obtained material to D50 of 5.0-6.0μm to obtain the positive electrode material.

[0159] S3: Weigh 30.9g of lanthanum nitrate hexahydrate, 14.7g of zirconium carbonate (ZrO2 content 40%) and 11g of anhydrous lithium acetate, add appropriate amount of deionized water and citric acid and stir vigorously to obtain lithium lanthanum zirconium sol. Weigh 500g of positive electrode material and mix with lithium lanthanum zirconium sol and stir and knead evenly to form a positive electrode material coated with lithium lanthanum zirconium precursor. After drying at 350℃, the powder is put into a sagger and placed in a muffle furnace. Under the conditions of oxygen-containing air atmosphere, the oxygen partial pressure is 0.21atm and the gas flow rate is 350Nm 3 / h, first heat to 550℃ at a rate of 6℃ / min, keep warm for 2h, then heat to 840℃ at a rate of 6℃ / min, keep warm for 6h, complete sintering, and obtain positive electrode material after crushing and sieving.

[0160] The rest is the same as in Example 1 and will not be described again here.

[0161] Comparative Example 1

[0162] The positive electrode material used in the comparative example is commercially available NCM333;

[0163] The rest is the same as in Example 1 and will not be described again here.

[0164] The above examples and comparative examples were subjected to performance tests, and the test results are shown in Tables 1 to 4 below:

[0165] The electrochemical performance test of button cells was carried out at room temperature (25°C) using a Xinwei test system (model: CT-ZWJ).

[0166] The test voltage ranges include 3.0V to 4.35V, 3.0V to 4.5V, and 3.0V to 4.6V. When charging, use a 0.1C constant current mode to the desired cutoff voltage, then switch to a constant voltage mode (equal to the cutoff voltage) until the current is less than 1 / 100C, and wait for 5 minutes. When discharging, use a 0.1C constant current mode to discharge to 3.0V.

[0167] The test cut-off voltages of all the cells in the present invention are: 3.0 V-4.35 V, 3.0 V-4.5 V and 3.0 V-4.60 V. The test environment is room temperature (25° C.) for conducting the electrical performance test.

[0168] Rate test: An Arbin tester (model: BT2000) was used to test the rate performance of the battery cells.

[0169] (1) Charging process: Use 0.5C current to charge the battery at a constant current until the battery voltage reaches the required cut-off voltage of 4.35V, 4.5V or 4.6V, and then use constant voltage charging. When the charging current is less than 1 / 20C, the charging is terminated.

[0170] (2) Discharge process: Discharge at the tested discharge current (1C / 5C / 8C / 10C / 15C) until the battery voltage drops to 3.0V.

[0171] Temperature test: When testing the battery cell, place the thermocouple probe close to the middle of the battery cell and use a HIOKI data acquisition instrument (model: LR8402-21) to collect the battery cell temperature rise data.

[0172] Cycling performance test: The battery was cycled under the following charge and discharge conditions using an Arbin machine (model: BT2000); charging: charging to the required cutoff voltage (4.35 V or 4.5 V or 4.6 V) according to the required constant current, standing for 10 minutes, and discharging with the required constant current until the battery voltage dropped to 3.0 V.

[0173] Conductivity test: Conductivity tests were performed on samples using a PRCD3100 (IEST - Yuanneng Technology). Pressure was applied up to 100 MPa and maintained for 10 seconds. Data were obtained.

[0174] Liquid density: Ultrasonicate deionized water at 25°C for 30 minutes. Take a 25mL flask (mass m0) and fill it with ultrasonicated deionized water (25°C). The weight of the flask and deionized water is m1. Dry the flask and cool it to room temperature in a desiccator. Add an appropriate amount of positive electrode material powder m2. Then add an appropriate amount of ultrasonicated deionized water to the full scale and ultrasonicate for 30 minutes. Finally, let it stand in a 25°C water bath for 30 minutes, keeping the flask full. Wipe it dry and weigh m3. Given that the density of pure water at standard atmospheric pressure and 25°C is ρ0, the liquid density of the powder is ρpowder = m2*ρ0 / (m0+m1+m2-m3).

[0175] The test results are summarized in Tables 1-4 below.

[0176] Table 1

[0177]

[0178] Table 2

[0179]

[0180]

[0181] Table 3

[0182]

[0183]

[0184] Table 4

[0185]

[0186]

[0187] Table 1 shows the button cell test results of the embodiments and comparative examples. As can be seen from Table 1, relative to comparative example 1, the discharge capacity and energy density of each embodiment at 0.1C when the maximum cut-off voltage is 4.35-4.5V are higher than those of comparative example 1. When the cut-off voltage is further increased to 4.6V, the capacity of comparative example 1 at 0.1C is significantly improved, and therefore the energy density is also significantly improved, reaching 795.53Wh / kg (see Table 1 for other data). This is because the elemental composition of the positive electrode material of comparative example 1 has a large resistance to lithium ion migration, and a higher voltage is required to allow lithium ions to obtain sufficient driving force for migration.

[0188] Table 2 shows the rate performance of all cells in the Examples and Comparative Examples. As can be seen from Table 2, the rate performance of the Examples is significantly superior to that of Comparative Example 1. Furthermore, during rate testing, each cell in the Examples exhibited a slight temperature rise, resulting in high-rate discharge capacities (8C, 10C, and 15C) exceeding the 1C discharge capacity, indicating a rate performance exceeding 100%.

[0189] Although the platform voltage of Comparative Example 1 at 0.1C is higher than that of the embodiment (see Table 1), during the high rate discharge (1C to 15C) process, the intrinsic impedance brought by the material composition of Comparative Example 1 leads to severe polarization. Therefore, the voltage decay of the embodiment is much smaller than that of Comparative Example 1, that is, the platform voltage of the embodiment has a higher voltage platform retention rate at the discharge rate of 1C to 15C. Based on the test data in Table 3, the platform voltage decay rate is calculated using the formula (discharge platform voltage at 1C - discharge platform voltage at the corresponding rate) / discharge platform voltage at 1C. It can be seen that the platform voltage decay rates of the embodiment at 5C, 10C and 15C discharge rates are less than 2%, 5% and 10%, respectively. The platform voltage decay rates of the comparative example at 5C, 10C and 15C discharge rates are 7% to 8%, 14.3% to 17% and 19.4% to 23.6%, respectively.

[0190] Table 4 shows the temperature rise data for full-cell batteries produced in the Examples and Comparative Examples during rate discharge. The test data shows that the absolute temperature rise for the Examples at discharge rates of 5C, 10C, and 15C is less than 10°C, 15°C, and 30°C, respectively, while the temperature rise for the Comparative Example at 5C, 10C, and 15C is 12-18°C, 30-35°C, and 36-42°C, respectively. The Examples have significantly lower absolute temperature rises than the Comparative Examples.

[0191] The test results in Tables 1 to 4 above demonstrate that, compared to Comparative Example 1, the high-power-density cathode material prepared by the present invention, through a combination of bulk element doping and surface coating processes within a specific elemental composition range, can maintain its energy density at high voltages (4.35-4.6V) and high rates (5-15°C) while maintaining a safe temperature range (absolute temperature rise less than 30°C). Based on this, the high-power-density cathode material of the present invention enables the battery to maintain excellent charge and discharge performance in both low and high temperature environments.

[0192] from Figure 1 and Figure 2 The size and XRD characteristics of the primary particles in Example 1 are shown. Figure 3 and Figure 4 The size and XRD characteristics of the secondary spheres in Example 2 are shown. The D50 of the primary particles is 1 to 4 μm, or the D50 of the secondary particles formed by the aggregation of primary particles is 3 to 8 μm, and the maximum particle size of the particles is ≤15 μm. Example 1 and Example 2 have almost the same XRD characteristics. That is, there are diffraction peaks at angles such as 18° to 20°, 36° to 37.4°, 37.4° to 39.5°, 37.4° to 39.5°, 43° to 46°, 63° to 66°, and 63° to 66°, among which the half-peak width at 18° to 20° is less than 0.2, and the ratio of the intensity of the diffraction peak at 18° to 20° to the intensity of the diffraction peak at 43° to 46° is greater than 1.1. Figure 10 This is the SEM of Example 4. The carbon nanotube coating layer can be seen after the coating process.

[0193] Figure 5 The capacity retention curve of Example 1 in the range of 3.0V to 4.35V using 1C / 1C charge and discharge is shown below: Figure 8 This is the capacity retention curve of Example 1 in the range of 3.0V to 4.5V, using 3C / 3C charge and discharge. As can be seen from the image, the positive electrode material using the invention solution has excellent cycle life under high cut-off voltage and high rate charge and discharge conditions. Figure 8 The fluctuation of the middle curve comes from the fluctuation of the test environment temperature.

[0194] Figure 6 The discharge rate curves of Example 1 in the range of 3.0V to 4.35V are shown at 1C / 5C / 8C / 10C / 15C discharge currents. It can be seen from the discharge curves that the positive electrode material prepared by the scheme of the present invention has excellent rate performance. Based on the 1C discharge capacity, there is almost no capacity decay during high-rate discharge. Furthermore, when the discharge rate reaches 8C or above, the discharge capacity is slightly higher than the capacity during 1C discharge due to the temperature effect (a moderate temperature rise improves the mobility of lithium ions).

[0195] Figure 7 The dQ / dV curve of Example 1 shows that there is at least one redox peak between 3.4 V and 4.6 V, which indicates that the positive electrode material has an obvious electrochemical reaction process between 3.4 V and 4.6 V.

[0196] Figure 9 The charge-discharge curves for Example 1 at the corresponding cycle numbers in the 3C / 3C charge-discharge capacity retention curve at a voltage range of 3.0V to 4.5V are shown. The positive electrode material prepared in this invention exhibits a capacity retention rate exceeding 88% after 500 cycles of 3C / 3C charge-discharge at a maximum cutoff voltage of 4.5V. The charge-discharge curves for different cycle numbers show a capacity retention rate approaching 90%. Furthermore, the material's coulombic efficiency approaches 100%.

[0197] Based on the disclosure and teachings of the above description, those skilled in the art will be able to make changes and modifications to the above embodiments. Therefore, the present invention is not limited to the above specific embodiments. Any obvious improvements, substitutions, or modifications made by those skilled in the art based on the present invention fall within the scope of protection of the present invention. In addition, although certain specific terms are used in this description, these terms are only for convenience of description and do not constitute any limitation to the present invention.

Claims

1. A high power density cathode material, characterized in that: Its molecular formula is Li 1+a Ni x M y A z O2, 0≤a≤0.2, 0.45≤x≤0.95, 0<y≤0.5, 0≤z≤0.2, x+y+z=1; wherein the M element includes at least one of Co, Mn, Al, Nb, and Sb; and the A element includes at least one of Ti, Mo, Zr, Sr, Re, P, B, La, Ta, and C.

2. A high power density cathode material according to claim 1, characterized in that: The positive electrode material has the following diffraction peaks in its XRD spectrum under Cu Kα1 rays: characteristic peak A: 18° to 20°, characteristic peak B: 36° to 37.4°, characteristic peak C: 37.4° to 39.5°, characteristic peak D: 37.4° to 39.5°, characteristic peak E: 43° to 46°, characteristic peak F: 63° to 66°, and characteristic peak G: 63° to 66°.

3. A high power density cathode material according to claim 2, characterized in that: The diffraction peak intensity ratio between the characteristic peak A and the characteristic peak E is ≥1.1, and the half-peak width of the characteristic peak A: 18° to 20° is less than 0.

2.

4. The high power density cathode material according to claim 1, characterized in that: The high power density positive electrode material is primary particles and / or secondary particles formed by aggregation of primary particles, the D50 of the primary particles is 1 to 4 μm, and the D50 of the secondary particles is 3 to 8 μm, wherein the maximum particle size of the primary particles and the secondary particles are both ≤15 μm.

5. The high power density cathode material according to claim 1, characterized in that: The high power density positive electrode material has a powder conductivity of 0.00001 to 0.05 S / cm at 100 MPa; its specific surface area is 0.2 to 20 m 2 / g; its liquid phase density is 4.2~5.2g / mL.

6. The high power density cathode material according to claim 1, characterized in that: The high power density positive electrode material has a capacity of 170 to 220 mAh / g at a voltage of 4.35 to 4.6 V at 0.1C; the high power density positive electrode material has an energy density of 650 Wh / kg to 860 Wh / kg at a platform voltage of 3.84 to 3.92 V at 0.1C.

7. The high power density cathode material according to claim 1, characterized in that: It is at a voltage of 4.35-4.6V, compared to 1C discharge; When discharging at a rate of 5C, the platform voltage decay rate is less than 5%; and / or, when discharged at a rate of 10C, the platform voltage decay is less than 8%; And / or, when discharging at a rate of 15C, the platform voltage decay is less than 10%.

8. The high power density cathode material according to claim 1, characterized in that: The compaction density of the positive electrode sheet made of the high power density positive electrode material is 3.2 to 4.2 g / cm 3 When the assembled battery cell is at 20-25℃ and discharged at 15C, the temperature rise is less than 30℃.

9. The high power density cathode material according to claim 1, characterized in that: The compaction density of the positive electrode sheet made of the high power density positive electrode material can be 3.2 to 4.2 g / cm 3 When the assembled battery cell is at 4.35-4.6V, compared with 1C discharge; when discharging at a 5C rate, the 5C / 1C rate is greater than 95%; and / or, when discharging at a 10C rate, the 10C / 1C rate is greater than 97%; and / or, when discharging at a 15C rate, the 10C / 1C rate is greater than 100%.

10. The high power density cathode material according to claim 1, characterized in that: In its differential capacity curve, there is at least one set of redox peaks between 3.4V and 4.6V.

11. The method for preparing a high power density positive electrode material according to any one of claims 1 to 10, characterized in that: The following steps are involved: A1: Weigh the lithium source, nickel source, and M source, mix them evenly, add the organic acid, and then add deionized water to obtain a clear solution. Then, add ammonia water while stirring the clear solution until a sol is obtained; A2: drying the sol obtained in step A1, and then granulating the dried product; A3: placing the particles obtained in step A2 in a sintering device and sintering them in an oxygen-containing atmosphere; after cooling to room temperature in the furnace, grinding or crushing the obtained material; A4: Weigh source A to coat the surface of the material obtained in step A3, dry it, and then perform secondary sintering to obtain a high power density positive electrode material.

12. The method for preparing a high power density positive electrode material according to claim 11, characterized in that: The sintering conditions of step A3 are as follows: heating to 250-350°C at a rate of 1-6°C / min and keeping warm for 1-3 hours; then heating to 500-700°C at a rate of 1-6°C / min and keeping warm for 3-5 hours; then heating to 750-960°C at a rate of 1-6°C / min and keeping warm for 8-20 hours.

13. The method for preparing a high power density positive electrode material according to any one of claims 1 to 10, characterized in that: The following steps are involved: S1: Weighing a lithium source, a nickel source, and an M source, and configuring them into a solution, adding a precipitant and a pH adjuster, and co-precipitating to obtain a precursor; depending on the amount of lithium contained in the prepared solution, the obtained precursor may contain lithium or may not contain lithium; S2: uniformly mixing the obtained precursor with the lithium salt, placing the uniformly mixed powder in a sintering device, and sintering it in an oxygen-containing atmosphere; after cooling to room temperature with the furnace, grinding or crushing the obtained material; if the lithium content in the precursor meets the requirements, the precursor and lithium salt uniform mixing step is not required, and the precursor is directly subjected to the sintering step; S3: The positive electrode material obtained in S2 is surface coated, dried, and then subjected to secondary sintering to obtain a high power density positive electrode material.

14. The method for preparing a high power density positive electrode material according to claim 13, characterized in that: The sintering conditions of step S2 are: heating to 250-350°C at a rate of 1-6°C / min, keeping warm for 1-3 hours; then heating to 500-700°C at a rate of 1-6°C / min, keeping warm for 3-5 hours, and then heating to 750-960°C at a rate of 1-6°C / min, keeping warm for 8-20 hours.

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