CN113346071B - Phosphorus-doped ternary precursor, preparation method thereof and ternary cathode material - Google Patents

Phosphorus-doped ternary precursor, preparation method thereof and ternary cathode material Download PDF

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CN113346071B
CN113346071B CN202110651324.1A CN202110651324A CN113346071B CN 113346071 B CN113346071 B CN 113346071B CN 202110651324 A CN202110651324 A CN 202110651324A CN 113346071 B CN113346071 B CN 113346071B
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CN113346071A (en
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张宝
邓鹏�
林可博
邓梦轩
丁瑶
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Zhejiang Power New Energy Co Ltd
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Abstract

The invention belongs to the field of preparation of anode materials, and particularly discloses a phosphorus-doped ternary precursor, a preparation method thereof and a ternary anode material, wherein the chemical general formula of the doped precursor is as follows: ni x Co y Mn (1‑x‑y) O 2‑z P z ，0.6<x<0.8，0.05<y<0.1，0.02<z<0.07, in the preparation process of the doped ternary precursor, firstly carrying out coprecipitation reaction in a low-oxygen atmosphere to prepare a ternary precursor material, then taking phosphide capable of releasing phosphine gas as a phosphorus source, decomposing the phosphide and the hydrogen in the calcining process to generate phosphine and hydrogen, and forming holes on the surface of the material, so that the specific surface area of the material is high, and the gradient doping of the phosphorus can form a directional internal electric field on the surface of the material. Therefore, the precursor and the lithium source can be sufficiently mixed during the lithium mixing and calcination, and the residual lithium on the surface of the cathode material can be reduced. The formation of the internal electric field is beneficial to the directional movement in the lithium ion de-intercalation process, and the length of a migration path is reduced. The structure of the anode material obtained by the invention is beneficial to releasing the stress of the material in the circulation process, and finally the circulation stability and the rate capability of the material are improved.

Description

Phosphorus-doped ternary precursor, preparation method thereof and ternary cathode material
Technical Field
The invention relates to the field of preparation of anode materials, in particular to a phosphorus-doped ternary precursor and a preparation method thereof.
Background
The ternary cathode material has the advantages of low cost, high energy density, environmental friendliness and the like, and is a hotspot in the research of the lithium ion cathode material at present. However, with the rapid development of the current electric vehicles, people have higher and higher requirements on the charge-discharge specific capacity, the cycle life and the stability of the lithium ion battery, which also puts higher requirements on the ternary cathode material. The prior ternary cathode material mainly has the following problems: (1) the high-nickel ternary positive electrode material can expand and contract in volume in the process of lithium intercalation and deintercalation to form microcracks, which can cause the immersion of electrolyte and a series of side reactions, thereby influencing the cycling stability of the material; (2) the residual lithium on the surface of the anode material is higher, and the process and the performance of the ternary material are adversely affected, such as capacity attenuation, blockage of lithium ion diffusion and the like. In addition, in the crystal structure, the relationship between the lithium ion migration path and the primary particle arrangement mode is large, and the migration path may have various meanders, so that the effective lithium ion migration path is prolonged. If an oriented internal electric field can be arranged in the material, the driving force for lithium ion extraction can be accelerated, the lithium ion migration rate can be accelerated, and the rate capability of the anode material can be improved.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides a phosphorus-doped ternary precursor and a preparation method thereof.
The specific scheme of the invention is as follows:
a phosphorus-doped ternary precursor, wherein the chemical formula of the doped precursor is as follows: ni x Co y Mn (1-x-y) O 2-z P z ，0.6<x<0.8，0.05<y<0.1，0.02<z<0.07, the surface of the doped ternary precursor is in a loose porous structure.
The invention discloses a preparation method of the phosphorus-doped ternary precursor, which comprises the following steps:
s1, preparing a metal salt solution A of nickel, cobalt and manganese; preparing a precipitant solution B; preparing an ammonia water solution C;
s2, injecting the solution B and the solution C obtained in the step S1 into a reaction kettle as a base solution, then adding the solution A, the solution B and the solution C into the reaction kettle for reaction, and controlling in the reaction process: the pH value is 8.0-13.0, the ammonia concentration is 5-20 g/L, the oxygen content in the reaction kettle is 3-5%, when the materials in the reaction kettle reach the target granularity, the reaction is stopped to obtain ternary precursor slurry, and the ternary precursor slurry is subjected to solid-liquid separation, washing, drying and screening to obtain a ternary precursor;
and S3, taking phosphide capable of releasing phosphine gas as a phosphorus source, mixing the ternary precursor obtained in the step S2 with the phosphorus source, grinding, calcining for a period of time at the temperature of 250-400 ℃ in a protective atmosphere, cooling, washing and drying the product to obtain the phosphorus-doped ternary precursor with a loose porous structure on the surface and doped with phosphorus in a gradient manner.
Further, in the step S1, the total molar concentration of the metal ions in the metal salt solution a is 0.2 to 5mol/L, the molar concentration of the precipitant solution B is 3 to 20mol/L, and the concentration of the ammonia water solution C is 4 to 20 g/L.
Further, in step S1, the prepared nickel, cobalt, and manganese salts of the metal salt solution a are selected from at least one of sulfate, halide, and nitrate, and the precipitant solution B is NaOH, KOH, and KHCO 3 、Ba(OH) 2 Or Na 2 CO 3 At least one of (1).
Further, in step S2, the control in the reaction kettle: the pH value of the prepared base solution is 8.0-12.0, the base solution is 1/6-2/3 of the volume of the reaction kettle, the reaction temperature is 45-75 ℃, and the stirring speed is 100-800 rpm.
Further, in step S2, inert gas or nitrogen is introduced into the reaction kettle to control the oxygen content in the reaction kettle, so that the precursor material prepared by the present invention can form a loose surface structure more easily in a suitable low-oxygen atmosphere.
Further, in the step S2, adding the solution A, the solution B and the solution C into the reaction kettle for reaction, wherein the flow rate of the metal salt solution A is 10-250 mL/min, and the flow rate of the precipitant solution B and the flow rate of the ammonia water solution C are regulated and controlled according to the required condition parameters in the reaction kettle.
Further, in step S2, the precursor slurry is subjected to solid-liquid separation, washing, drying and screening, preferably washing with a centrifuge, and washing is performed sequentially with alkali and water, wherein the alkali for washing is low-concentration sodium hydroxide solutionThe washing water is pure water, and the temperature is 55-75 ℃ during washing until Na is contained in the materials + When the content is less than or equal to 150ppm, the washing is stopped, the drying temperature is 120-160 ℃, and a 200-400-mesh screen is adopted for screening.
Further, in step S3, the phosphorus source is an inorganic phosphide capable of releasing phosphine gas, such as NaH 2 PO 2 ·H 2 O、KH 2 PO 2 ·H 2 O、NH 4 H 2 PO 2 ·H 2 At least one of O. The phosphorus source of the invention is phosphide capable of releasing phosphine gas, which can generate phosphine and hydrogen after calcination, and the overflow of hydrogen can form holes on the surface of the material, so that the specific surface area of the material is high. Meanwhile, the phosphorus doping amount from the surface layer to the inside of the material is gradually reduced to form a gradient, and the gradient doping of the phosphorus can form a directional internal electric field on the surface of the material.
Further, in step S3, the mass ratio of the phosphorus source to the precursor is 0.2 to 1: 1. the protective atmosphere is nitrogen or inert gas, the heating speed is 2-10 ℃ per min, the calcining time is 0.5-3 h, and the cooling mode is natural cooling.
The invention also discloses a phosphorus-doped ternary cathode material, which has a chemical general formula as follows: li [ Ni ] x Co y Mn (1-x-y) ]O 2-z P z ，0.6<x<0.8，0.05<y<0.1，0.02<z<0.07, the surface of the ternary cathode material is in a loose porous structure.
Further, the anode material is obtained by uniformly mixing the phosphorus-doped ternary precursor prepared by the preparation method of the phosphorus-doped ternary precursor with a lithium source and then roasting.
The phosphorus-doped ternary precursor obtained by the preparation method of the phosphorus-doped ternary precursor has a loose surface structure due to a proper pH value, ammonia concentration and low oxygen atmosphere, the loose structure is further strengthened due to the generation of hydrogen when the phosphorus-doped ternary precursor is calcined with a phosphorus source, and the pore diameter is formed on the surface. The structure is beneficial to full contact in the process of calcining the mixed lithium, so that residual lithium on the surface of the prepared anode material is less, and the loose and porous appearance is beneficial to the stress release of the anode material in the circulating process. In addition, the anode material inherits the directional internal electric field, which is beneficial to directional migration of lithium ions and reduces unnecessary migration paths. Finally, the cycle stability and the rate capability of the anode material are improved.
The principle of the internal electric field is as follows: the 2P orbit of P and the 2P orbit of O carry out the hybridization, will promote the promotion of its energy band, form the anti-quantum well, according to the gradual reduction from the top layer to inside doping volume, the energy band promotes the level and is different to interior electric field from inside to outside has been formed in the material.
Compared with the prior art, the invention has the beneficial effects that:
the method creatively carries out coprecipitation reaction in an environment with proper pH value, ammonia concentration and low oxygen to prepare a ternary precursor material with a loose surface, then takes phosphide capable of releasing phosphine gas as a phosphorus source, mixes the phosphorus source with the ternary precursor material, slowly calcines the mixture at the temperature of 250-400 ℃, dopes the released phosphine into the surface of the loose ternary precursor, forms a phosphorus-doped concentration gradient which decreases from outside to inside, forms a directional internal electric field in the material, and can release hydrogen in the reaction process to enable the surface of the material to form a loose and porous structure. Therefore, the two can be sufficiently mixed at the time of firing of the lithium mixed, and the residual lithium on the surface of the positive electrode material can be reduced. The directional internal electric field can promote the effective migration in the lithium ion migration process, and realize the rapid de-intercalation. The structure of the anode material obtained by the invention is beneficial to releasing the stress of the material in the circulating process, and finally the circulating stability and the rate capability of the material are improved.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention, illustrate embodiments of the invention and together with the description serve to explain the invention and do not constitute a limitation of the invention.
Fig. l is a morphology diagram of the doped precursor obtained in step S3 under an electron microscope of 20000 times in example 1 of the present invention.
Fig. 2 is a graph showing cycle curves of the positive electrode material prepared in example 1 and the positive electrode material prepared in comparative example 1.
Detailed Description
The present invention will now be described in detail with reference to the drawings, which are given by way of illustration and explanation only and should not be construed to limit the scope of the present invention in any way. Furthermore, features from embodiments in this document and from different embodiments may be combined accordingly by a person skilled in the art from the description in this document.
Example 1
The embodiment provides a preparation method of a phosphorus-doped ternary cathode material, which specifically comprises the following steps:
s1, using nickel sulfate hexahydrate, cobalt sulfate heptahydrate and manganese sulfate monohydrate according to the proportion of Ni: co: molar ratio of Mn 0.7: 0.1: 0.2 preparing a metal salt mixed solution A with the total concentration of 2.0 mol/L; preparing a potassium hydroxide aqueous solution B with the concentration of 8 mol/L; preparing an ammonia water solution C with the concentration of 12 g/L;
s2, introducing 1/3 volume of base solution into a 50L reaction kettle, wherein the base solution is a potassium hydroxide aqueous solution containing certain ammonia water and having a pH value of 11.5. And then, introducing the solution A at the flow rate of 20mL/min, simultaneously introducing the solution C and the solution B for reaction, adjusting the introduction flow rates of the solution C and the solution B in real time, and simultaneously controlling reaction parameters in the reaction process as follows: the stirring speed is 500rpm, the ammonia concentration is 6-12 g/L, the pH is 11.3-11.5, the temperature of the reaction kettle is 65 ℃, nitrogen is introduced into the reaction kettle to control the oxygen content to be 3-5%, and the reaction is continued for a period of time. Stopping the reaction after the granularity reaches the requirement.
Washing a reaction product in the reaction kettle by using a centrifugal machine, wherein alkali for washing is a low-concentration sodium hydroxide solution, water for washing is pure water, the temperature of the alkali for washing and the pure water is controlled to be 70 ℃, and the washing is stopped when the Na content of a finished product is less than 150 ppm; drying the washed solid particle material at 130 ℃, and sieving the dried solid particle material by a 200-mesh sieve to obtain a ternary precursor;
s3, grinding the sodium hypophosphite and the ternary precursor prepared in the step S2 by using a mortar, wherein the weight ratio of the sodium hypophosphite to the ternary precursor is 0.3: 1, transferring the mixture after grinding to a porcelain boat and in a tube furnace under argon atmosphere at 3 ℃/minThe speed is increased to 300 ℃, the mixture is calcined for 1h, and then the mixture is naturally cooled, washed and dried to obtain a doping precursor with loose and porous surface, wherein the chemical of the doping precursor is as follows: ni 0.7 Co 0.1 Mn 0.2 O 1.98 P 0.02 Referring to fig. 1, it is a topography of the obtained doped precursor under an electron microscope of 20000 times;
s4, the doped precursor prepared in the step S3 is sintered in a tubular furnace at the speed of 5 ℃/min to 800 ℃, the sintering time is 8h, and then the sintered precursor is naturally cooled to obtain the ternary cathode material with the surface gradient doped with phosphorus and containing the directional internal electric field, wherein the chemical formula of the ternary cathode material is as follows: li [ Ni ] 0.7 Co 0.1 Mn 0.2 ]O 1.98 P 0.02 。
Example 2
The embodiment provides a preparation method of a phosphorus-doped ternary cathode material, which specifically comprises the following steps:
s1, using nickel sulfate hexahydrate, cobalt sulfate heptahydrate and manganese nitrate according to the proportion of Ni: co: molar ratio of Mn 0.72: 0.05: 0.23 preparing a metal salt mixed solution A with the total concentration of 1.5 mol/L; preparing a sodium hydroxide aqueous solution B with the concentration of 6 mol/L; preparing an ammonia water solution C with the concentration of 10 g/L;
s2, introducing 1/4 volume of base solution into a 50L reaction kettle, wherein the base solution is a sodium hydroxide aqueous solution containing certain ammonia water and having a pH value of 11.8. And then, introducing the solution A at the flow rate of 15mL/min, simultaneously introducing the solution C and the solution B for reaction, adjusting the introduction flow rates of the solution C and the solution B in real time, and simultaneously controlling reaction parameters in the reaction process as follows: the stirring speed is 600rpm, the ammonia concentration is 6-12 g/L, the pH is 11.6-11.8, the temperature of the reaction kettle is 60 ℃, nitrogen is introduced into the reaction kettle to control the oxygen content to be 3-5%, and the reaction is continued for a period of time. Stopping the reaction after the granularity reaches the requirement. Washing a reaction product in the reaction kettle by using a centrifugal machine, wherein alkali for washing is a low-concentration sodium hydroxide solution, water for washing is pure water, the temperature of the alkali for washing and the pure water is controlled to be 75 ℃, and the washing is stopped when the Na content of a finished product is less than 150 ppm; drying the washed solid particle material at 140 ℃, and sieving the dried solid particle material by a 200-mesh sieve to obtain a ternary precursor;
s3, grinding by using mortarGrinding sodium hypophosphite and the ternary precursor prepared in the step S2, wherein the weight ratio of the sodium hypophosphite to the ternary precursor is 0.4: 1, transferring the mixture into a porcelain boat after grinding, raising the temperature to 350 ℃ at a speed of 4 ℃/min in a tube furnace under the argon atmosphere, calcining for 0.75h, naturally cooling, washing and drying to obtain a doped precursor with a loose and porous surface, wherein the chemical of the doped precursor is as follows: ni 0.72 Co 0.05 Mn 0.23 O 1.94 P 0.06 ；
S4, the doped precursor prepared in the step S3 is sintered in a tube furnace at the temperature of 900 ℃ at the speed of 4 ℃/min for 6h, and then natural cooling is carried out to obtain the ternary cathode material with the surface gradient doped with phosphorus and containing the directional internal electric field, wherein the chemical formula of the ternary cathode material is as follows: li [ Ni ] 0.72 Co 0.05 Mn 0.23 ]O 1.94 P 0.06 。
Example 3
The embodiment provides a preparation method of a phosphorus-doped ternary cathode material, which specifically comprises the following steps:
s1, using nickel sulfate hexahydrate, cobalt sulfate heptahydrate and manganese sulfate monohydrate according to the proportion of Ni: co: molar ratio of Mn 0.75: 0.10: 0.15 preparing a metal salt mixed solution A with the total concentration of 1.0 mol/L; preparing a sodium hydroxide aqueous solution B with the concentration of 6 mol/L; preparing an ammonia water solution C with the concentration of 6 g/L;
s2, introducing 1/5-volume base solution into a 50L reaction kettle, wherein the base solution is a sodium hydroxide aqueous solution containing certain ammonia water and having a pH value of 12.0. And then, introducing the solution A at the flow rate of 18mL/min, simultaneously introducing the solution C and the solution B for reaction, adjusting the introduction flow rates of the solution C and the solution B in real time, and simultaneously controlling reaction parameters in the reaction process as follows: the stirring speed is 400rpm, the ammonia concentration is 8-14 g/L, the pH is 11.7-12.0, the temperature of the reaction kettle is 65 ℃, nitrogen is introduced into the reaction kettle to control the oxygen content to be 3-5%, and the reaction is continued for a period of time. Stopping the reaction after the granularity reaches the requirement. Washing a reaction product in the reaction kettle by using a centrifugal machine, wherein alkali for washing is a low-concentration sodium hydroxide solution, water for washing is pure water, the temperature of the alkali for washing and the pure water is controlled to be 60 ℃, and the washing is stopped when the Na content of a finished product is less than 150 ppm; drying the washed solid particle material at 130 ℃, and sieving the dried solid particle material by a 200-mesh sieve to obtain a ternary precursor;
s3, grinding the potassium hypophosphite and the ternary precursor prepared in the step S2 by using a mortar, wherein the weight ratio of the potassium hypophosphite to the ternary precursor is 0.6: 1, transferring the mixture into a porcelain boat after grinding, raising the temperature to 320 ℃ at a speed of 5 ℃/min in a tube furnace under an argon atmosphere, calcining for 0.8h, naturally cooling, washing and drying to obtain a doped precursor with a loose and porous surface, wherein the chemical of the doped precursor is as follows: ni 0.75 Co 0.10 Mn 0.15 O 1.97 P 0.03 ；
S4, the doped precursor prepared in the step S3 is sintered in a tubular furnace at the temperature of 850 ℃ at the speed of 6 ℃/min for 7h, and then natural cooling is carried out to obtain the ternary cathode material with the surface gradient doped with phosphorus and containing the directional internal electric field, wherein the chemical formula of the ternary cathode material is as follows: li [ Ni ] 0.75 Co 0.10 Mn 0.15 ]O 1.97 P 0.03 。
Example 4
The embodiment provides a preparation method of a phosphorus-doped ternary cathode material, which specifically comprises the following steps:
s1, using nickel sulfate hexahydrate, cobalt sulfate heptahydrate and manganese sulfate monohydrate according to the proportion of Ni: co: molar ratio of Mn 0.7: 0.1: 0.2 preparing a metal salt mixed solution A with the total concentration of 0.5 mol/L; preparing a sodium hydroxide aqueous solution B with the concentration of 6 mol/L; preparing an ammonia water solution C with the concentration of 12 g/L;
s2, introducing 1/4 volume of base solution into a 50L reaction kettle, wherein the base solution is a sodium hydroxide aqueous solution containing certain ammonia water and having a pH value of 11.3. And then, introducing the solution A at the flow rate of 15mL/min, simultaneously introducing the solution C and the solution B for reaction, adjusting the introduction flow rates of the solution C and the solution B in real time, and simultaneously controlling reaction parameters in the reaction process as follows: the stirring speed is 400rpm, the ammonia concentration is 6-12 g/L, the pH is 11.0-11.3, the temperature of the reaction kettle is 65 ℃, nitrogen is introduced into the reaction kettle to control the oxygen content to be 3-5%, and the reaction is continued for a period of time. And stopping the reaction after the granularity meets the requirement. Washing a reaction product in the reaction kettle by using a centrifugal machine, wherein alkali for washing is a low-concentration sodium hydroxide solution, water for washing is pure water, the temperature of the alkali for washing and the pure water is controlled to be 70 ℃, and the washing is stopped when the Na content of a finished product is less than 150 ppm; drying the washed solid particle material at 140 ℃, and sieving the dried solid particle material by a 200-mesh sieve to obtain a ternary precursor;
s3, grinding the potassium hypophosphite and the ternary precursor prepared in the step S2 by using a mortar, wherein the weight ratio of the potassium hypophosphite to the ternary precursor is 0.5: 1, transferring the mixture into a porcelain boat after grinding, and performing argon atmosphere
Raising the temperature to 280 ℃ in a tubular furnace at a speed of 3 ℃/min, calcining for 3h, naturally cooling, washing and drying to obtain a doped precursor with a loose and porous surface, wherein the chemical of the doped precursor is as follows: ni 0.7 Co 0.1 Mn 0.2 O 1.92 P 0.08 ；
S4, the doped precursor prepared in the step S3 is sintered in a tubular furnace at the temperature of 800 ℃ at the speed of 4 ℃/min for 10h, and then natural cooling is carried out to obtain the ternary cathode material with the surface gradient doped with phosphorus and containing the directional internal electric field, wherein the chemical formula of the ternary cathode material is as follows: li [ Ni ] 0.7 Co 0.1 Mn 0.2 ]O 1.92 P 0.08 。
Comparative example 1
The comparative example provides a preparation method of a ternary cathode material, which specifically comprises the following steps:
s1, using nickel sulfate hexahydrate, cobalt sulfate heptahydrate and manganese sulfate monohydrate according to the proportion of Ni: co: molar ratio of Mn 0.7: 0.1: 0.2 preparing a metal salt mixed solution A with the total concentration of 2.0 mol/L; preparing a potassium hydroxide aqueous solution B with the concentration of 8 mol/L; preparing an ammonia water solution C with the concentration of 12 g/L;
s2, introducing 1/3 volume of base solution into a 50L reaction kettle, wherein the base solution is a potassium hydroxide aqueous solution containing certain ammonia water and having a pH value of 11.5. And then, introducing the solution A at the flow rate of 20mL/min, simultaneously introducing the solution C and the solution B for reaction, adjusting the introduction flow rates of the solution C and the solution B in real time, and simultaneously controlling reaction parameters in the reaction process as follows: the stirring speed is 500rpm, the pH value is 11.3-11.5, the ammonia concentration is 6-12 g/L, the temperature of the reaction kettle is 65 ℃, nitrogen is introduced into the reaction kettle to control the oxygen content to be 3-5%, and the reaction is continued for a period of time. Stopping the reaction after the granularity reaches the requirement. Washing a reaction product in the reaction kettle by using a centrifugal machine, wherein alkali for washing is a low-concentration sodium hydroxide solution, water for washing is pure water, the temperature of the alkali for washing and the pure water is controlled to be 70 ℃, and the washing is stopped when the Na content of a finished product is less than 150 ppm; drying the washed solid particle material at 130 ℃, and sieving the dried solid particle material by a 200-mesh sieve to obtain a ternary precursor;
s3, grinding the ternary precursor prepared in the mortar step S2, transferring the mixture into a porcelain boat, raising the temperature to 300 ℃ at a speed of 3 ℃/min in a tube furnace under an argon atmosphere, calcining for 1h, naturally cooling, washing and drying to obtain the precursor, wherein the chemical formula of the precursor is as follows: ni 0.7 Co 0.1 Mn 0.2 O 2 ；
S4, sintering the precursor prepared in the step S3 in a tube furnace at a speed of 5/min to 800 ℃, wherein the sintering time is 8h, and naturally cooling to obtain a ternary cathode material, wherein the chemical formula of the ternary cathode material is as follows: li [ Ni ] 0.7 Co 0.1 Mn 0.2 ]O 2 。
The positive electrode materials of the embodiment 1 and the comparative example 1 are respectively uniformly mixed with carbon black and PVDF, coated on an aluminum foil to prepare a positive plate, and the positive plate, a lithium metal plate, a diaphragm and electrolyte are respectively assembled into a CR2025 button cell in a vacuum glove box.
The electrical properties of the two CR2025 button cells are detected, and as can be seen from fig. 2, the cycle performance of the test sample of the embodiment of the invention is obviously superior to the corresponding performance of the test sample of the comparative example in the voltage range of 3.0-4.3V and at the normal temperature of 25 ℃. The surface gradient doped phosphorus is used for constructing the ternary cathode material containing the directional internal electric field, and compared with the undoped cathode material, the ternary cathode material has more excellent cycle performance.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.

Claims (8)

1. A phosphorus-doped ternary precursor is characterized in that the chemical general formula of the doped precursor is as follows: ni x Co y Mn (1-x-y) O 2-z P z ，0.6<x<0.8，0.05<y<0.1，0.02<z<0.07, the surface of the doped ternary precursor is in a loose porous structure;
the preparation method of the doped precursor comprises the following steps:
s1, preparing a metal salt solution A of nickel, cobalt and manganese; preparing a precipitant solution B; preparing an ammonia water solution C;
s2, injecting the solution B and the solution C obtained in the step S1 into a reaction kettle as a base solution, then adding the solution A, the solution B and the solution C into the reaction kettle for reaction, and controlling in the reaction process: the pH value is 8.0-13.0, the ammonia concentration is 5-20 g/L, the oxygen content in the reaction kettle is 3-5%, when the materials in the reaction kettle reach the target granularity, the reaction is stopped to obtain ternary precursor slurry, and the ternary precursor slurry is subjected to solid-liquid separation, washing, drying and screening to obtain a ternary precursor;
and S3, taking phosphide capable of releasing phosphine gas as a phosphorus source, mixing and grinding the ternary precursor obtained in the step S2 and the phosphorus source, calcining for a period of time at the temperature of 250-400 ℃ in a protective atmosphere, cooling, washing and drying the product to obtain the phosphorus-doped ternary precursor with a loose porous structure on the surface and doped with phosphorus in a gradient manner.
2. The phosphorus-doped ternary precursor according to claim 1, wherein in step S1, the total molar concentration of metal ions in the metal salt solution a is 0.2-5 mol/L, the molar concentration of the precipitant solution B is 3-20 mol/L, and the concentration of the ammonia water solution C is 4-20 g/L.
3. The phosphorus-doped ternary precursor according to claim 1, wherein in step S1, the prepared metal salt solution a comprises at least one of nickel, cobalt and manganese salts selected from sulfate, halide and nitrate, and the precipitant solution B comprises NaOH, KOH and KHCO 3 、Ba(OH) 2 Or Na 2 CO 3 At least one of (1).
4. The phosphorus-doped ternary precursor of claim 1, wherein in step S2, the in-reactor controls: the pH value of the prepared base solution is 8.0-12.0, and the base solution is 1/6-2/3 of the volume of the reaction kettle; the temperature is 45-75 ℃ in the reaction process, the stirring speed is 100-800 rpm in the reaction process, and the oxygen content in the reaction kettle is controlled by introducing inert gas or nitrogen into the reaction kettle.
5. The phosphorus-doped ternary precursor according to claim 1, wherein in step S2, solution a, solution B and solution C are added to a reaction kettle for reaction, the flow rate of the metal salt solution a is controlled to be 10-250 mL/min, and the flow rate of the precipitant solution B and the flow rate of the ammonia water solution C are controlled according to the required condition parameters in the reaction kettle.
6. The phosphorus-doped ternary precursor according to claim 1, wherein in step S3, the phosphorus source is an inorganic phosphide capable of releasing phosphine gas, and contains NaH 2 PO 2 ·H 2 O、KH 2 PO 2 ·H 2 O、NH 4 H 2 PO 2 ·H 2 At least one of O.
7. The phosphorus-doped ternary precursor according to claim 1 or 6, wherein in step S3, the mass ratio of the phosphorus source to the ternary precursor obtained in step S2 is 0.2-1: 1, the protective atmosphere is nitrogen or inert gas, the heating speed is 2-10 ℃ per min, the calcining time is 0.5-3 h, and the cooling mode is natural cooling.
8. The phosphorus-doped ternary cathode material is characterized in that the chemical general formula of the cathode material is as follows: li [ Ni ] x Co y Mn (1-x-y) ]O 2-z P z ，0.6<x<0.8，0.05<y<0.1，0.02<z<0.07, the surface of the ternary cathode material is in a loose porous structure; the phosphorus is doped with IIIThe element material is obtained by uniformly mixing the phosphorus-doped ternary precursor disclosed by any one of claims 1-7 with a lithium source and then roasting.
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