Phosphorus-tungsten co-doped positive electrode precursor material and preparation method and application thereof

Abstract

The invention provides a phosphorus-tungsten co-doped positive electrode precursor material as well as a preparation method and application thereof. The preparation method comprises the following steps: mixing a tungsten source, a phosphorus source, a nickel-cobalt-manganese mixed salt and a solvent to obtain a mixed solution, and performing spray pyrolysis on the mixed solution to obtain the phosphorus-tungsten co-doped positive electrode precursor material. According to the preparation method, specific positive and negative ions of phosphorus and tungsten are cooperatively matched with spray pyrolysis, so that on the premise of ensuring that the ternary positive electrode material has high energy density, the effects of inhibiting lithium-nickel mixing, reducing an irreversible phase change process, stabilizing a lattice structure and improving the diffusion efficiency of lithium ions are achieved; therefore, the energy density, the cycle performance and the rate capability of the battery are improved.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion electrochemical device technology, and relates to a phosphorus-tungsten co-doped cathode precursor material, its preparation method and application. Background Technology

[0002] With the rapid development of the electronics industry, the battery technology required for its operation is also constantly evolving. Lithium-ion batteries, due to their high operating voltage, high energy density, and long cycle life, are widely used in electric vehicles, smartphones, laptops, and mobile energy storage. With the rapid development of lithium-ion batteries, consumers are placing higher demands on their energy density, cycle performance, and safety. Among the four main materials of lithium-ion batteries—positive electrode, negative electrode, separator, and electrolyte—the positive electrode material has the greatest impact on both performance and cost.

[0003] In terms of cathode materials, the most widely used materials on the market are LiCoO2, LiNiO2, LiMnO2, spinel-structured LiMn2O4, olivine-structured LiFePO4, or layered ternary LiNi. x Co y Mn z O2 (x > 0, y > 0, x + y + z = 1), etc. Among them, layered ternary LiNi... x Co y Mn z O2 cathode materials have attracted much attention in the market due to their high energy density, high cost performance, and good safety. Currently, ternary cathode materials are being mass-produced by major domestic companies and are the dominant cathode materials in the market.

[0004] Despite the numerous advantages exhibited by ternary cathode materials, their inherent defects hinder further development. Common degradation mechanisms in ternary cathode materials include: lithium-nickel mixing, harmful phase transitions, microcracks and particle breakage, the influence of residual lithium, and interfacial side reactions. To address these issues, a common approach is to add doped metal or non-metal elements during the co-precipitation preparation of the precursor. However, the improvement effect of a single doping method is limited. Furthermore, the co-precipitation method has a long preparation cycle and complex steps.

[0005] Furthermore, in order to improve the energy density of ternary materials, the frequency of use of high-nickel ternary materials is gradually increasing. However, while high nickel content can bring higher reversible discharge capacity, it will accelerate the degradation of material stability. This is due to the instability of its surface properties, the phase transition induced by cation mixing, and the reduced cycle stability caused by intergranular cracks due to micro-strain.

[0006] Therefore, how to solve the above-mentioned problems of ternary cathode materials and reduce the production cost is an urgent issue that needs to be addressed. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the present invention aims to provide a phosphorus-tungsten co-doped cathode precursor material, its preparation method, and its applications. This invention employs a specific spray pyrolysis preparation method involving the synergistic combination of phosphorus and tungsten cations and anions. While ensuring the high energy density of the ternary cathode material, it effectively suppresses lithium-nickel mixing, reduces irreversible phase transitions, stabilizes the crystal structure, and improves lithium-ion diffusion efficiency, thereby enhancing the battery's energy density, cycle performance, and rate performance.

[0008] To achieve this objective, the present invention adopts the following technical solution:

[0009] In a first aspect, the present invention provides a method for preparing a phosphorus-tungsten co-doped cathode precursor material, the method comprising the following steps:

[0010] A mixed solution is obtained by mixing a tungsten source, a phosphorus source, a nickel-cobalt-manganese mixed salt, and a solvent. The mixed solution is then subjected to spray pyrolysis to obtain the phosphorus-tungsten co-doped cathode precursor material.

[0011] In the preparation method of this invention, a specific phosphorus-tungsten dual-ion synergistic spray pyrolysis method is used to achieve bulk doping of phosphorus and tungsten in a nickel-cobalt-manganese oxide precursor material. Tungsten, with its high valence state, stabilizes the ternary layered structure, reduces irreversible phase transitions during charge-discharge processes, and delays capacity decay. Furthermore, tungsten's strong oxygen affinity enhances the transition metal (TM)-O bond, inhibits Ni²⁺ migration to the Li layer, and improves Li⁺ diffusion efficiency. Tungsten preferentially occupies lithium sites to suppress Ni²⁺ diffusion. 2+ Migration can balance Ni 2+ The resulting defects, and by preventing Ni 2+ Migration indirectly suppresses mixing and can stabilize the crystal structure by forming strong metal-oxygen bonds through lattice oxygen; P is a common non-metallic element in nature with abundant sources. Non-metallic phosphorus forms PO bonds with oxygen with strong chemical bonding ability, which helps stabilize lattice oxygen and can effectively suppress the escape of O during charging and discharging, thereby reducing irreversible phase transition processes; while spray pyrolysis process can achieve uniform doping of tungsten and phosphorus in a short time and reduce the number of preparation steps, reduce production costs, thereby improving the energy density, cycle performance and rate performance of the battery.

[0012] For the technical solution of this invention, the phosphorus source, tungsten source, the appropriate timing of their addition, and the spray pyrolysis method must work together in a coordinated manner; none of them can be omitted. If any one of these conditions is missing, the stability of the lattice oxygen in the cathode material will decrease significantly, and the escape of O during the charging and discharging process will be aggravated, thereby reducing the energy density, cycle performance, and rate performance of the material.

[0013] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. The technical objectives and beneficial effects of the present invention can be better achieved and realized through the following preferred technical solutions.

[0014] Preferably, based on the total molar amount of the nickel-cobalt-manganese mixed salt being 100%, the amount of tungsten source added is 0.1% to 0.3%, such as 0.1%, 0.13%, 0.15%, 0.18%, 0.2%, 0.23%, 0.25%, 0.28%, or 0.3%, etc., but not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0015] Preferably, based on the total molar amount of the nickel-cobalt-manganese mixed salt being 100%, the amount of phosphorus source added is 0.3% to 0.5%, such as 0.3%, 0.33%, 0.35%, 0.38%, 0.4%, 0.43%, 0.45%, 0.48%, or 0.5%, etc., but not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0016] In the mixing process of the mixed solution, the present invention further controls the addition amount of the tungsten source to 0.1% to 0.3% and / or the addition amount of the phosphorus source to 0.3% to 0.5%. While suppressing the escape of lattice oxygen and reducing lithium-nickel mixing, the high energy density advantage of the ternary material is not reduced.

[0017] Preferably, the tungsten in the tungsten source has a +6 valence.

[0018] The valence state of tungsten in the tungsten source is crucial for this invention. This invention selects a high-valence (+6) tungsten source, which can stabilize the layered structure of nickel-cobalt-manganese oxide precursor materials during bulk doping. 6+ It has a stronger oxygen affinity, which can enhance the transition metal (TM)-O bond and inhibit Ni. 2+ Migrating to the Li layer further indirectly suppressed lithium-nickel mixing and improved Li... + Diffusion efficiency.

[0019] Furthermore, the tungsten source for the +6 valent tungsten in this application includes, but is not limited to, at least one of ammonium tungstate, tungstic acid, metatungstic acid, sodium tungstate, calcium tungstate, or tungsten trioxide.

[0020] Phosphorus sources include, but are not limited to, at least one of phosphoric acid, ammonium dihydrogen phosphate, or diamine hydrogen phosphate.

[0021] Preferably, with the total molar amount of nickel, cobalt, and manganese in the nickel-cobalt-manganese mixed salt being 100%, the molar amount of nickel accounts for ≥60%, preferably ≥80%, for example 60%, 63%, 65%, 68%, 70%, 73%, 75%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99%, etc., but not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0022] In the nickel-cobalt-manganese ternary cathode material system, as the nickel content increases, the energy density of the material also increases, but the material stability will be relatively worse. In this invention, a nickel-cobalt-manganese mixed salt with a relatively high nickel content is selected as the raw material, which can better exert the synergistic effect with tungsten source, phosphorus source and spray pyrolysis method, improve energy density and achieve synergistic improvement of other electrochemical performance.

[0023] Preferably, the concentration of the nickel-cobalt-manganese mixed salt in the mixed solution is 80 g / L to 120 g / L, such as 80 g / L, 85 g / L, 90 g / L, 95 g / L, 100 g / L, 105 g / L, 110 g / L, 115 g / L or 120 g / L, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0024] Preferably, during the spray pyrolysis process, the pyrolysis temperature is 600℃~800℃, such as 600℃, 625℃, 650℃, 675℃, 700℃, 725℃, 750℃, 775℃ or 800℃, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0025] Preferably, during the spray pyrolysis process, the top of the pyrolysis furnace is set to a negative pressure state.

[0026] Preferably, the negative pressure in the negative pressure state is -130Pa to -150Pa, such as -130Pa, -133Pa, -135Pa, -138Pa, -140Pa, -143Pa, -145Pa, -148Pa or -150Pa, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0027] In the spray pyrolysis process, this invention ensures that the top of the pyrolysis furnace is under negative pressure, that is, the gas pressure in the furnace top area is lower than the atmospheric pressure. This allows the aerosol of the mixed solution to pass through the furnace heating zone and be heated evenly. Furthermore, by controlling the negative pressure to be between -130 Pa and -150 Pa, it is even more beneficial to the complete decomposition of the mixed solution by heat.

[0028] It should be noted that:

[0029] The type of salt in the nickel-cobalt-manganese mixed salt of this invention is not unique. Without departing from the technical concept of this invention, any type of soluble salt is applicable to this invention. For example, the salt includes at least one of nitrate, oxalate, or chloride.

[0030] Optionally, the solvent includes water.

[0031] Optionally, the present invention does not impose excessive limitations on the atomization process in the spray pyrolysis process, and the present invention is applicable to atomization conditions that can achieve atomization of mixed solution droplets without causing side reactions.

[0032] In a second aspect, the present invention provides a phosphorus-tungsten co-doped cathode precursor material, wherein the cathode precursor material is prepared by the preparation method described in the first aspect;

[0033] The cathode precursor material includes nickel cobalt manganese oxide material and phosphorus and tungsten doped in the nickel cobalt manganese oxide material.

[0034] Thirdly, the present invention provides a cathode material, which is obtained by mixing and sintering a phosphorus-tungsten co-doped cathode precursor material as described in the second aspect with a raw material containing at least a lithium source.

[0035] The cathode material obtained from the cathode precursor material in the second aspect is a ternary layered cathode material.

[0036] This invention does not further limit the specific manufacturing method of the cathode material. In principle, any method for obtaining cathode material from corresponding oxide precursor materials that is reasonably known to those skilled in the art without departing from the technical concept of this invention is applicable to this invention.

[0037] Optionally, the lithium source includes, but is not limited to, at least one of lithium hydroxide, lithium carbonate, lithium nitrate, or lithium acetate.

[0038] Optionally, the ratio of the total molar amount of nickel, cobalt, and manganese in the cathode precursor material to the molar amount of lithium in the lithium source is 1:(1 to 1.3), such as 1:1, 1:1.05, 1:1.1, 1:1.15, 1:1.2, 1:1.25, or 1:3, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0039] Optionally, the sintering atmosphere is not unique, and those skilled in the art can make adaptive selections and adjustments according to actual needs. For example, it can be a protective atmosphere or an oxygen-containing atmosphere. The protective atmosphere includes nitrogen and / or inert gases (argon or helium), and the oxygen-containing atmosphere includes air, oxygen, or a mixture of oxygen and non-reactive gases.

[0040] Optionally, the sintering can be a single-stage sintering or a multi-stage sintering. The specific sintering process can be adapted and adjusted by those skilled in the art according to actual needs.

[0041] Optionally, the sintering temperature is 600℃ to 1000℃, such as 600℃, 650℃, 700℃, 750℃, 800℃, 850℃, 900℃, 950℃ or 1000℃, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0042] Fourthly, the present invention also provides an electrochemical device comprising the positive electrode material as described in the third aspect.

[0043] The electrochemical device includes lithium-ion electrochemical devices, such as lithium-ion batteries and / or lithium-ion capacitors; the present invention does not specifically limit the application of cathode materials in electrochemical devices, and those skilled in the art can make adaptive selections and adjustments according to actual needs.

[0044] Furthermore, in the specific electrochemical device, apart from the cathode material, the other raw materials, structures, and preparation processes are all conventional technical solutions. Without violating the technical concept of this invention, any known specific application process is applicable in principle to this invention.

[0045] Compared with the prior art, the present invention has the following beneficial effects:

[0046] In the preparation method of this invention, a specific phosphorus-tungsten dual-ion synergistic spray pyrolysis method is used to achieve bulk doping of phosphorus and tungsten in a nickel-cobalt-manganese oxide precursor material. Tungsten, with its high valence state, can stabilize the ternary layered structure, reduce irreversible phase transitions during charge-discharge processes, and delay capacity decay. Furthermore, tungsten's strong oxygen affinity can enhance transition metal (TM)-O bonds and suppress Ni... 2+ migrate to the Li layer, improving Li+ diffusion efficiency; tungsten preferentially occupies lithium sites to suppress Ni. 2+ Migration can balance Ni 2+ The resulting defects, and by preventing Ni 2+ Migration indirectly suppresses mixing and can stabilize the crystal structure by forming strong metal-oxygen bonds through lattice oxygen; P is a common non-metallic element in nature with abundant sources. Non-metallic phosphorus forms PO bonds with oxygen with strong chemical bonding ability, which helps stabilize lattice oxygen and can effectively suppress the escape of O during charging and discharging, thereby reducing irreversible phase transition processes; while spray pyrolysis process can achieve uniform doping of tungsten and phosphorus in a short time and reduce the number of preparation steps, reduce production costs, thereby improving the energy density, cycle performance and rate performance of the battery. Detailed Implementation

[0047] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0048] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this application; the terms “comprising” and “having” and any variations thereof in this application are intended to cover non-exclusive inclusion.

[0049] In the description of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary or secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0050] Example 1

[0051] This embodiment provides a method for preparing a phosphorus-tungsten co-doped cathode precursor material, the preparation method comprising:

[0052] Step 1: Prepare a ternary metal mixed nitrate aqueous solution with a total concentration of 100 g / L based on the Ni:Co:Mn molar ratio of 0.60:0.10:0.30; add ammonium tungstate and ammonium dihydrogen phosphate to the ternary solution to obtain a mixed solution.

[0053] Based on a total molar amount of nickel-cobalt-manganese ternary metal mixed nitrate of 100%, the molar amount of ammonium tungstate is 0.3%, and the molar amount of ammonium dihydrogen phosphate is 0.5%.

[0054] Step 2: Heat the furnace chamber of the pyrolysis furnace to 600°C;

[0055] Step 3: The mixed solution from Step 1 is atomized by a spray gun and then pyrolyzed in a furnace at 600°C. During the pyrolysis process, the negative pressure at the top of the furnace is -130Pa, resulting in a phosphorus-tungsten co-doped nickel-cobalt-manganese oxide cathode precursor material.

[0056] Example 2

[0057] This embodiment provides a method for preparing a phosphorus-tungsten co-doped cathode precursor material, the preparation method comprising:

[0058] Step 1: Prepare a nickel-cobalt-manganese ternary metal mixed nitrate aqueous solution with a total concentration of 100 g / L according to the Ni:Co:Mn molar ratio of 0.75:0.10:0.25; add ammonium tungstate and ammonium dihydrogen phosphate to the ternary solution to obtain a mixed solution.

[0059] Based on a total molar amount of nickel-cobalt-manganese ternary metal mixed nitrate of 100%, the molar amount of ammonium tungstate is 0.2%, and the molar amount of ammonium dihydrogen phosphate is 0.4%.

[0060] Step 2: Heat the furnace chamber of the pyrolysis furnace to 700°C;

[0061] Step 3: The mixed solution from Step 1 is atomized by a spray gun and then pyrolyzed in a furnace at 700°C. During the pyrolysis process, the negative pressure at the top of the furnace is -140Pa, resulting in a phosphorus-tungsten co-doped nickel-cobalt-manganese oxide cathode precursor material.

[0062] Example 3

[0063] This embodiment provides a method for preparing a phosphorus-tungsten co-doped cathode precursor material, the preparation method comprising:

[0064] Step 1: Prepare a mixed nitrate aqueous solution of nickel, cobalt, and manganese ternary metals with a total concentration of 100 g / L, based on the Ni:Co:Mn molar ratio of 0.85:0.05:0.15; add ammonium tungstate and ammonium dihydrogen phosphate to the ternary solution to obtain a mixed solution.

[0065] Based on a total molar amount of nickel-cobalt-manganese ternary metal mixed nitrate of 100%, the molar amount of ammonium tungstate is 0.1%, and the molar amount of ammonium dihydrogen phosphate is 0.3%.

[0066] Step 2: Heat the furnace chamber of the pyrolysis furnace to 800℃;

[0067] Step 3: The mixed solution from Step 1 is atomized by a spray gun and then pyrolyzed in a furnace at 800°C. During the pyrolysis process, the negative pressure at the top of the furnace is -150Pa, resulting in a phosphorus-tungsten co-doped nickel-cobalt-manganese oxide cathode precursor material.

[0068] Example 4

[0069] The difference between this embodiment and Embodiment 1 is that in step 1 of this embodiment, the molar ratio of Ni:Co:Mn is 0.75:0.10:0.25.

[0070] All other conditions remain the same as in Example 1.

[0071] Example 5

[0072] The difference between this embodiment and Embodiment 1 is that in step 1 of this embodiment, the molar ratio of Ni:Co:Mn is 0.85:0.05:0.15.

[0073] All other conditions remain the same as in Example 1.

[0074] Example 6

[0075] The difference between this embodiment and embodiment 1 is that the pyrolysis temperature in steps 2 and 3 of this embodiment is 700℃.

[0076] All other conditions remain the same as in Example 1.

[0077] Example 7

[0078] The difference between this embodiment and Embodiment 1 is that the pyrolysis temperature in steps 2 and 3 of this embodiment is 800℃.

[0079] All other conditions remain the same as in Example 1.

[0080] Example 8

[0081] The difference between this embodiment and Embodiment 1 is that in step 1 of this embodiment, with the total molar amount of nickel-cobalt-manganese ternary metal mixed nitrate being 100%, the molar amount of ammonium tungstate added is 0.1%, and the molar amount of ammonium dihydrogen phosphate added is 0.3%.

[0082] All other conditions remain the same as in Example 1.

[0083] Example 9

[0084] The difference between this embodiment and embodiment 1 is that in step 3 of this embodiment, the negative pressure at the top of the furnace is -140Pa.

[0085] All other conditions remain the same as in Example 1.

[0086] Example 10

[0087] The difference between this embodiment and embodiment 1 is that in step 3 of this embodiment, the negative pressure at the top of the furnace is -150Pa.

[0088] All other conditions remain the same as in Example 1.

[0089] Example 11

[0090] The difference between this embodiment and Embodiment 1 is that in step 1 of this embodiment, the total molar amount of nickel-cobalt-manganese ternary metal mixed nitrate is 100%, and the molar amount of ammonium tungstate added is 0.05%.

[0091] All other conditions remain the same as in Example 1.

[0092] Example 12

[0093] The difference between this embodiment and Embodiment 1 is that in step 1 of this embodiment, the total molar amount of nickel-cobalt-manganese ternary metal mixed nitrate is 100%, and the molar amount of ammonium tungstate added is 0.5%.

[0094] All other conditions remain the same as in Example 1.

[0095] Example 13

[0096] The difference between this embodiment and Embodiment 1 is that in step 1 of this embodiment, the total molar amount of nickel-cobalt-manganese ternary metal mixed nitrate is 100%, and the molar amount of ammonium dihydrogen phosphate added is 0.1%.

[0097] All other conditions remain the same as in Example 1.

[0098] Example 14

[0099] The difference between this embodiment and Embodiment 1 is that in step 1 of this embodiment, with the total molar amount of nickel-cobalt-manganese ternary metal mixed nitrate being 100%, the molar amount of ammonium dihydrogen phosphate added is 0.6%.

[0100] All other conditions remain the same as in Example 1.

[0101] Example 15

[0102] The difference between this embodiment and embodiment 1 is that the pyrolysis temperature in steps 2 and 3 of this embodiment is 400℃.

[0103] All other conditions remain the same as in Example 1.

[0104] Example 16

[0105] The difference between this embodiment and embodiment 1 is that in step 3 of this embodiment, the negative pressure at the top of the furnace is -200Pa.

[0106] All other conditions remain the same as in Example 1.

[0107] Comparative Example 1

[0108] The difference between this comparative example and Example 1 is that in step 1 of this example, ammonium dihydrogen phosphate is not added.

[0109] All other conditions remain the same as in Example 1.

[0110] Comparative Example 2

[0111] The difference between this comparative example and Example 1 is that ammonium tungstate is not added in step 1 of this example.

[0112] All other conditions remain the same as in Example 1.

[0113] Comparative Example 3

[0114] This comparative example provides a method for preparing a phosphorus-tungsten co-doped cathode precursor material, the method comprising:

[0115] NiSO4, CoSO4, and MnSO4 solutions were mixed uniformly in stoichiometric ratio to prepare a ternary solution. Phosphorus source and tungsten source with the same doping amount as in Example 1 were dissolved in the above ternary solution to obtain a mixed salt solution. A 30% NaOH solution was prepared as a precipitant solution and a 20% ammonia solution was prepared as a complexing agent solution.

[0116] A mixed salt solution, precipitant solution, and complexing agent solution were added concurrently to a reaction vessel for co-precipitation. During the reaction, the reaction temperature was 50°C, the stirring speed was 380 rpm, and the reaction pH was 10.5. Nitrogen gas was simultaneously introduced into the reaction vessel to protect against oxidation until precipitation was complete. The ternary hydroxide prepared in the above steps was washed and dried, and then calcined in an air atmosphere in a muffle furnace at 500°C for 20 hours to obtain a phosphorus-tungsten co-doped cathode precursor material.

[0117] Battery fabrication and performance testing

[0118] Lithium-ion batteries were prepared using the cathode precursor materials provided in Examples 1-16 and Comparative Examples 1-3, and their performance was tested.

[0119] I. Battery Manufacturing

[0120] The cathode precursor material and lithium carbonate powder provided in the examples and comparative examples were weighed and mixed evenly according to the molar ratio of Li / Me = 1.05:1, and then subjected to two-stage solid-state sintering in an oxygen atmosphere, namely the first sintering, the second sintering and the third sintering.

[0121] The first sintering process involved raising the temperature from room temperature to 500°C at a rate of 4°C / min and holding it at that temperature for 6 hours. The second sintering process involved raising the temperature from 500°C to 900°C at a rate of 3°C / min and holding it at that temperature for 12 hours. After sintering, the sample was allowed to cool naturally to room temperature in the furnace. The sample was then pulverized and passed through a 300-mesh sieve to obtain the cathode material.

[0122] A positive electrode slurry was prepared according to the ratio of positive electrode material:SP:PVDF = 90:5:5, and the solid content of the slurry was 60%. Aluminum foil was placed on a coating machine, and a 150μm coating tool was placed on the aluminum foil. The single crystal slurry was poured in, and the equipment was turned on for coating. After coating, an electrode sheet was obtained. The electrode sheet was placed in a 110℃ oven for drying and then rolled to obtain the positive electrode sheet.

[0123] The positive electrode sheets provided in the examples and comparative examples were cut into circular pieces with a diameter of 15 mm using a stamping machine in a dry environment. In a glove box, a lithium metal sheet was used as the counter electrode, and a Ceglard composite membrane was selected as the separator. Electrolyte was added and assembled to obtain a coin cell. The electrolyte was an organic solution obtained by mixing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in a mass ratio of 30:50:20. The concentration of lithium salt (lithium hexafluorophosphate) in the electrolyte was 1.15 mol / L.

[0124] II Performance Testing

[0125] The performance of the coin cells provided in the examples and comparative examples was tested using the Wuhan Landian CT2001A system: the cells were activated three times at 0.1C rate / 2.7 to 4.3V, and then the electrochemical performance of the activated coin cells was tested at 2.7 to 4.3V@0.1C / 1C. The discharge specific capacity at 0.1C and 1C rates and the capacity retention rate after 100 cycles at 1C rate were obtained, respectively.

[0126] The test results are shown in Table 1.

[0127] Table 1

[0128]

[0129]

[0130] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing a phosphorus-tungsten co-doped cathode precursor material, characterized in that, The preparation method comprises the following steps: mixing a tungsten source, a phosphorus source, a nickel-cobalt-manganese mixed salt and a solvent to obtain a mixed solution, and performing spray pyrolysis on the mixed solution to obtain the phosphorus-tungsten co-doped positive electrode precursor material.

2. The production method according to claim 1, characterized by, The addition amount of the tungsten source is 0.1%-0.3% based on 100% of the total molar amount of the nickel-cobalt-manganese mixed salt. Preferably, the addition amount of the phosphorus source is 0.3%-0.5% based on 100% of the total molar amount of the nickel-cobalt-manganese mixed salt.

3. The production method according to claim 1 or 2, characterized by, The tungsten in the tungsten source is in +6 valence.

4. The production method according to claim 1, characterized by, The molar amount of nickel accounts for ≥60%, preferably ≥80%, based on 100% of the total molar amount of nickel-cobalt-manganese in the nickel-cobalt-manganese mixed salt.

5. The preparation method according to claim 1, characterized in that, The pyrolysis temperature in the spray pyrolysis process is 600-800°C.

6. The method of claim 1, wherein, In the spray pyrolysis process, the top of the pyrolysis furnace is set to a negative pressure state during pyrolysis.

7. The production method according to claim 6, wherein The pressure of the negative pressure in the negative pressure state is-130 Pa to-150 Pa.

8. A phosphorus-tungsten co-doped positive electrode precursor material, characterized in that, The positive electrode precursor material is prepared by the preparation method in any one of claims 1-7. The positive electrode precursor material comprises a nickel-cobalt-manganese oxide material and phosphorus and tungsten doped in the nickel-cobalt-manganese oxide material.

9. A positive electrode material, characterized by, The positive electrode material is obtained by mixing and sintering the phosphorus-tungsten co-doped positive electrode precursor material in claim 8 and raw materials containing at least a lithium source.

10. An electrochemical device, characterized by, The electrochemical device comprises the positive electrode material in claim 9.

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