Fluoride-coated precursor, preparation method thereof and single-crystal positive electrode material

Abstract

The invention relates to a fluoride-coated precursor, a preparation method thereof and a single-crystal positive electrode material. The preparation method comprises the following steps: carrying out parallel flow mixing on a first metal salt solution, a complexing agent solution and a precipitant solution, and carrying out first coprecipitation reaction to a target particle size; and then stopping introducing the first metal salt solution, introducing the fluorine source solution and the second metal salt solution at the same time, and carrying out a second coprecipitation reaction to obtain the fluoride-coated precursor. The cladding fluoride grows on the surface of the precursor and can be used as a fluxing agent during preparation of a single-crystal positive electrode material, so that the single-crystal material can be prepared at a relatively low temperature; meanwhile, fluoride can serve as a doping agent, and through composite doping of second metal and fluorine, the structural stability and the cycle performance of the single-crystal positive electrode material are improved; and an additional impurity removal process is not needed.

Description

Technical Field

[0001] The present invention belongs to the technical field of batteries and relates to a lithium-ion battery precursor material, in particular to a fluoride-coated precursor and a preparation method thereof and a single crystal positive electrode material. Background Art

[0002] Ternary cathode materials have been widely used in lithium batteries for new energy vehicles and consumer electronics due to their high energy density and good cycle performance. The ternary cathode materials prepared by traditional two-stage high-temperature sintering are mainly secondary spherical polycrystalline materials formed by the accumulation of nano-scale primary particles. Polycrystalline structures usually have a high specific surface area and can provide more active sites, thereby exhibiting higher energy density and good rate performance. However, under the polycrystalline stacking method, the anisotropic volume change caused by the irreversible phase change can easily lead to structural degradation problems such as intercrystalline microcracks. These microcracks expand the contact area between the active material and the electrolyte, aggravate the side reactions, and form an additional interfacial film (CEI) at the interface between the positive electrode and the electrolyte, significantly increasing the charge transfer resistance, and the electrochemical performance also decreases significantly. It can be said that the above-mentioned chain reaction caused by intercrystalline microcracks is one of the key reasons for the deterioration of the performance of current high-nickel ternary cathode materials.

[0003] Single-crystal materials have a complete crystal structure and lack grain boundaries, making them less susceptible to microcracks during charge and discharge. This significantly improves the material's structural strength, compaction density, and interfacial stability, and has shown promising application prospects in high-voltage and solid-state battery applications. Currently, single-crystal ternary materials are primarily prepared by increasing the sintering temperature of the high-temperature solid-phase method and the molten salt method. For materials of the same composition, the synthesis temperature of single-crystal cathode materials is typically 60-100°C higher than that of polycrystalline cathode materials. The high-temperature lithiation process can easily cause Li and O losses, leading to stoichiometric imbalance and layered structural degradation. The molten salt method typically involves adding a flux during the lithiation calcination of the cathode. The introduction of the flux lowers the melting point, forming a liquid phase, increasing the diffusion rate of lithium ions or other cations, and promoting close contact between particles, thereby lowering the sintering temperature and increasing density. However, the sintering aid in this method requires thorough mixing with the precursor and lithium salt to ensure uniform dispersion, otherwise it will affect the sintering effect.

[0004] In view of the shortcomings of the existing technology, it is necessary to provide a fluoride-coated precursor and a preparation method thereof and a single crystal positive electrode material. Summary of the Invention

[0005] In view of the deficiencies in the prior art, the object of the present invention is to provide a fluoride-coated precursor, a preparation method thereof, and a single-crystal positive electrode material. The preparation method of the fluoride-coated precursor can grow and coat fluoride on the surface of the precursor, so that the fluoride acts as a flux when preparing the single-crystal positive electrode material, thereby enabling the preparation of the single-crystal material at a lower temperature; at the same time, the fluoride can act as a dopant, and through the composite doping of a second metal and fluorine, the structural stability and cycle performance of the single-crystal positive electrode material are improved; and no additional impurity removal process is required.

[0006] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides a method for preparing a fluoride-coated precursor, the preparation method comprising the following steps:

[0008] mixing the first metal salt solution, the complexing agent solution, and the precipitant solution in parallel, and performing a first coprecipitation reaction to a target particle size; then stopping the introduction of the first metal salt solution, and simultaneously introducing a fluorine source solution and a second metal salt solution, and performing a second coprecipitation reaction to obtain the fluoride-coated precursor;

[0009] The first metal salt in the first metal salt solution includes nickel salt, cobalt salt and manganese salt;

[0010] The second metal salt in the second metal salt solution includes any one or a combination of at least two of lithium salt, aluminum salt, cerium salt, magnesium salt, lanthanum salt, zinc salt, calcium salt, lead salt or zirconium salt;

[0011] The general chemical formula of the fluoride-coated precursor is Ni a Co b Mn 1-a-b (OH)2@MF c , wherein M is any one of the metals Li, Al, Ce, Mg, La, Zn, Ca, Pb, and Zr, or a combination of at least two thereof, 0.5≤a<1, 0.01≤b≤0.3, and 1≤c≤4.

[0012] The present invention grows and coats fluoride on the surface of the precursor, which can act as a flux when preparing single-crystal positive electrode materials, thereby enabling the preparation of single-crystal materials at lower temperatures; at the same time, the fluoride can act as a dopant, and through the composite doping of the second metal and fluorine, the structural stability and cycle performance of the single-crystal positive electrode material are improved; and no additional impurity removal process is required.

[0013] Preferably, the complexing agent in the complexing agent solution includes any one of ammonia water, citric acid or oxalic acid, or a combination of at least two thereof, preferably ammonia water.

[0014] The present invention does not impose any further restrictions on the concentration of the complexing agent solution, as long as the concentration of the complexing agent in the system during the coprecipitation reaction meets the process requirements.

[0015] Preferably, the precipitant in the precipitant solution comprises sodium hydroxide and / or potassium hydroxide.

[0016] The present invention does not impose any further restrictions on the concentration of the precipitant solution, and it is sufficient that the pH value in the system during the coprecipitation reaction meets the process requirements.

[0017] Preferably, the fluorine source in the fluorine source solution includes sodium fluoride and / or potassium fluoride.

[0018] Preferably, the concentration of the fluorine source solution is 0.1 mol / L-2 mol / L, for example, 0.1 mol / L, 0.5 mol / L, 1 mol / L, 1.5 mol / L or 2 mol / L, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0019] Preferably, the second metal salt is any one of sulfate, chloride or nitrate, or a combination of at least two of them.

[0020] For example, taking the second metal salt as an aluminum salt, the second metal salt is any one of aluminum sulfate, aluminum chloride or aluminum nitrate, or a combination of at least two of them. Typical but non-limiting combinations include a combination of aluminum sulfate and aluminum chloride, a combination of aluminum sulfate and aluminum nitrate, a combination of aluminum chloride and aluminum nitrate, or a combination of aluminum sulfate, aluminum chloride and aluminum nitrate.

[0021] Preferably, the concentration of the second metal salt solution is 0.1 mol / L-0.5 mol / L, for example, it can be 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L or 0.5 mol / L, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0022] Preferably, in the fluoride-coated precursor, the second metal in the second metal salt accounts for 0.1wt%-10wt% of the total metal amount in the fluoride-coated precursor, for example, it can be 0.1wt%, 1wt%, 3wt%, 5wt%, 8wt% or 10wt%, but is not limited to the listed values. The remaining values not listed within the numerical range are also applicable, preferably 1wt%-5wt%.

[0023] Preferably, the concentration of the first metal salt solution is 1 mol / L-2 mol / L, for example, it can be 1 mol / L, 1.2 mol / L, 1.5 mol / L, 1.6 mol / L, 1.8 mol / L or 2 mol / L, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0024] The molar ratio of nickel salt, cobalt salt and manganese salt in the first metal salt solution of the present invention is as follows: a Co b Mn 1-a-b (OH)2@MF c The values of a, b and 1-ab are determined.

[0025] Preferably, the nickel salt in the first metal salt solution includes any one or a combination of at least two of nickel sulfate, nickel chloride or nickel nitrate. Typical but non-limiting combinations include a combination of nickel sulfate and nickel chloride, a combination of nickel chloride and nickel nitrate, a combination of nickel sulfate and nickel nitrate, or a combination of nickel sulfate, nickel chloride and nickel nitrate.

[0026] Preferably, the cobalt salt in the first metal salt solution includes any one or a combination of at least two of cobalt sulfate, cobalt chloride or cobalt nitrate. Typical but non-limiting combinations include a combination of cobalt sulfate and cobalt chloride, a combination of cobalt chloride and cobalt nitrate, a combination of cobalt sulfate and cobalt nitrate, or a combination of cobalt sulfate, cobalt chloride and cobalt nitrate.

[0027] Preferably, the manganese salt in the first metal salt solution includes any one or a combination of at least two of manganese sulfate, manganese chloride or manganese nitrate. Typical but non-limiting combinations include a combination of manganese sulfate and manganese chloride, a combination of manganese chloride and manganese nitrate, a combination of manganese sulfate and manganese nitrate, or a combination of manganese sulfate, manganese chloride and manganese nitrate.

[0028] Preferably, the pH value of the first coprecipitation reaction is 10.5-12, for example, it can be 10.5, 11, 11.5 or 12, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0029] Preferably, the temperature of the first coprecipitation reaction is 45°C-70°C, for example, 45°C, 50°C, 55°C, 60°C, 65°C or 70°C, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0030] Preferably, the concentration of the complexing agent during the first coprecipitation reaction is 4 g / L-7 g / L, for example, 4 g / L, 5 g / L, 6 g / L or 7 g / L, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0031] Preferably, the first coprecipitation reaction is carried out under stirring conditions of 300rpm-400rpm, for example, 300rpm, 320rpm, 350rpm, 380rpm or 400rpm, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0032] Preferably, the target particle size refers to a median particle size D50 reaching 2.5 μm-3.5 μm, for example, it can be 2.5 μm, 2.8 μm, 3.0 μm, 3.2 μm or 3.5 μm, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0033] Preferably, the pH value of the second coprecipitation reaction is 8-9, for example, 8, 8.5 or 9, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0034] Preferably, the temperature of the second coprecipitation reaction is 45°C-70°C, for example, 45°C, 50°C, 55°C, 60°C, 65°C or 70°C, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0035] Preferably, the concentration of the complexing agent during the second coprecipitation reaction is 4 g / L-7 g / L, for example, 4 g / L, 5 g / L, 6 g / L or 7 g / L, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0036] Preferably, the second coprecipitation reaction is carried out under stirring conditions of 300rpm-400rpm, for example, 300rpm, 320rpm, 350rpm, 380rpm or 400rpm, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0037] The endpoint of the second coprecipitation reaction of the present invention is that the second metal in the fluoride-coated precursor accounts for 0.1 wt% to 10 wt% of the total amount of metal in the fluoride-coated precursor.

[0038] In a second aspect, the present invention provides a fluoride-coated precursor, wherein the fluoride-coated precursor is prepared by the preparation method described in the first aspect;

[0039] The general chemical formula of the fluoride-coated precursor is Ni a Co b Mn 1-a-b (OH)2@MF c, wherein M is any one of the metals Li, Al, Ce, Mg, La, Zn, Ca, Pb, and Zr, or a combination of at least two thereof, 0.5≤a<1, 0.01≤b≤0.3, and 1≤c≤4.

[0040] In a third aspect, the present invention provides a single crystal positive electrode material, which is prepared from the fluoride-coated precursor described in the second aspect.

[0041] The numerical range described in the present invention includes not only the point values listed above, but also any point values between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values included in the range.

[0042] Compared with the prior art, the present invention has the following beneficial effects:

[0043] The present invention grows and coats fluoride on the surface of the precursor, which can act as a flux when preparing single-crystal positive electrode materials, thereby enabling the preparation of single-crystal materials at lower temperatures; at the same time, the fluoride can act as a dopant, and through the composite doping of the second metal and fluorine, the structural stability and cycle performance of the single-crystal positive electrode material are improved; and no additional impurity removal process is required. DETAILED DESCRIPTION

[0044] The technical solution of the present invention is further described below by way of specific embodiments. It should be understood by those skilled in the art that the embodiments are merely to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0045] The complexing agent solution used in the specific embodiment of the present invention is ammonia water, the precipitant solution is sodium hydroxide, and the molar ratio of nickel, cobalt and manganese in the first metal salt solution is 8:1:1. The above content is only for the purpose of clearly illustrating the technical solution of the present invention and is not regarded as further limitation of the technical solution of the present invention.

[0046] Example 1

[0047] This embodiment provides a method for preparing a fluoride-coated precursor, the preparation method comprising the following steps:

[0048] (1) Pure water, sodium hydroxide solution, and ammonia water were added to a reaction kettle to prepare a base solution with a temperature of 45°C, a pH value of 11.5, and an ammonia concentration of 6 g / L;

[0049] (2) a first metal salt solution, a sodium hydroxide solution, and aqueous ammonia are introduced into the base liquid in parallel, and a first coprecipitation reaction is performed under the conditions of a stirring speed of 350 rpm, a temperature of 45° C., a pH value of 11.5, and an aqueous ammonia concentration of 6 g / L until a median particle size of 3 μm is achieved;

[0050] The first metal salt solution includes nickel sulfate, cobalt sulfate and manganese sulfate, and the total concentration of metal ions is 1.5 mol / L;

[0051] (3) Stop the introduction of the first metal salt solution, and simultaneously introduce 1 mol / L sodium fluoride solution and 0.3 mol / L aluminum sulfate solution, and carry out a second coprecipitation reaction under the conditions of a stirring speed of 350 rpm, a temperature of 45°C, a pH value of 8.5 and an ammonia concentration of 6 g / L to obtain the fluoride-coated precursor Ni 0.8 Co 0.1 Mn 0.1 (OH)2@AlF3.

[0052] The endpoint of the second coprecipitation reaction is that the Al in the fluoride-coated precursor accounts for 2 wt % of the total metal content in the fluoride-coated precursor.

[0053] Example 2

[0054] This embodiment provides a method for preparing a fluoride-coated precursor, the preparation method comprising the following steps:

[0055] (1) Pure water, sodium hydroxide solution, and ammonia water were added to a reaction kettle to prepare a base solution with a temperature of 45°C, a pH value of 10.5, and an ammonia concentration of 4 g / L;

[0056] (2) a first metal salt solution, a sodium hydroxide solution, and aqueous ammonia are introduced into the base liquid in parallel, and a first coprecipitation reaction is performed under the conditions of a stirring speed of 300 rpm, a temperature of 45° C., a pH value of 10.5, and an aqueous ammonia concentration of 4 g / L until a median particle size of 2.5 μm is achieved;

[0057] The first metal salt solution includes nickel sulfate, cobalt sulfate and manganese sulfate, and the total concentration of metal ions is 1 mol / L;

[0058] (3) Stop the introduction of the first metal salt solution, and simultaneously introduce 0.1 mol / L sodium fluoride solution and 0.1 mol / L aluminum sulfate solution, and carry out a second coprecipitation reaction under the conditions of a stirring speed of 300 rpm, a temperature of 45°C, a pH value of 8, and an ammonia concentration of 4 g / L to obtain the fluoride-coated precursor Ni 0.8 Co 0.1 Mn 0.1 (OH)2@AlF3.

[0059] The endpoint of the second coprecipitation reaction is that the Al in the fluoride-coated precursor accounts for 1 wt % of the total metal content in the fluoride-coated precursor.

[0060] Example 3

[0061] This embodiment provides a method for preparing a fluoride-coated precursor, the preparation method comprising the following steps:

[0062] (1) Pure water, sodium hydroxide solution, and ammonia water were added to a reaction kettle to prepare a base solution with a temperature of 70°C, a pH value of 12, and an ammonia concentration of 7 g / L;

[0063] (2) a first metal salt solution, a sodium hydroxide solution, and aqueous ammonia are introduced into the base liquid in parallel, and a first coprecipitation reaction is performed under the conditions of a stirring speed of 400 rpm, a temperature of 70° C., a pH value of 12, and an aqueous ammonia concentration of 7 g / L until a median particle size of 3.5 μm is achieved;

[0064] The first metal salt solution includes nickel sulfate, cobalt sulfate and manganese sulfate;

[0065] (3) Stop the introduction of the first metal salt solution, and simultaneously introduce 2 mol / L sodium fluoride solution and 0.5 mol / L aluminum sulfate solution, and carry out a second coprecipitation reaction under the conditions of a stirring speed of 400 rpm, a temperature of 70°C, a pH value of 9 and an ammonia concentration of 7 g / L to obtain the fluoride-coated precursor Ni 0.8 Co 0.1 Mn 0.1 (OH)2@AlF3.

[0066] The endpoint of the second coprecipitation reaction is that the Al in the fluoride-coated precursor accounts for 5 wt % of the total metal content in the fluoride-coated precursor.

[0067] Example 4

[0068] This embodiment provides a method for preparing a fluoride-coated precursor, which is the same as that of Example 1 except that the endpoint of the second coprecipitation reaction is such that Al in the fluoride-coated precursor accounts for 0.1 wt % of the total metal content in the fluoride-coated precursor.

[0069] Example 5

[0070] This embodiment provides a method for preparing a fluoride-coated precursor, which is the same as that of Example 1 except that the endpoint of the second coprecipitation reaction is such that Al in the fluoride-coated precursor accounts for 10 wt % of the total metal content in the fluoride-coated precursor.

[0071] Comparative Example 1

[0072] This comparative example provides a method for preparing a precursor, which is the same as Example 1 except that the second coprecipitation reaction is not performed, that is, the fluoride coating is not performed.

[0073] Comparative Example 2

[0074] This comparative example provides a method for preparing a precursor, which comprises the following steps:

[0075] (1) Pure water, sodium hydroxide solution, and ammonia water were added to a reaction kettle to prepare a base solution with a temperature of 45°C, a pH value of 11.5, and an ammonia concentration of 6 g / L;

[0076] (2) a first metal salt solution, a sodium hydroxide solution, aqueous ammonia, and a 0.3 mol / L aluminum sulfate solution were introduced into the base liquid in parallel, and a coprecipitation reaction was carried out under the conditions of a stirring speed of 350 rpm, a temperature of 45° C., a pH value of 11.5, and an aqueous ammonia concentration of 6 g / L to a median particle size of 3 μm;

[0077] The first metal salt solution includes nickel sulfate, cobalt sulfate and manganese sulfate, and the total concentration of metal ions is 1.5 mol / L;

[0078] The amount of aluminum sulfate solution used is such that when the coprecipitation reaction is completed, Al in the precursor accounts for 2 wt % of the total amount of metal in the precursor.

[0079] Comparative Example 3

[0080] This comparative example provides a method for preparing a precursor, which comprises the following steps:

[0081] (1) Pure water, sodium hydroxide solution, and ammonia water were added to a reaction kettle to prepare a base solution with a temperature of 45°C, a pH value of 11.5, and an ammonia concentration of 6 g / L;

[0082] (2) a first metal salt solution, a sodium hydroxide solution, aqueous ammonia, and a 1 mol / L sodium fluoride solution were introduced into the base liquid in parallel, and a coprecipitation reaction was carried out under the conditions of a stirring speed of 350 rpm, a temperature of 45° C., a pH value of 11.5, and an aqueous ammonia concentration of 6 g / L to a median particle size of 3 μm;

[0083] The first metal salt solution includes nickel sulfate, cobalt sulfate and manganese sulfate, and the total concentration of metal ions is 1.5 mol / L;

[0084] The amount of sodium fluoride solution used is such that the proportion of F in the final precursor is the same as that in Example 1.

[0085] Performance Characterization

[0086] The precursors provided in the above embodiments and comparative examples were prepared into positive electrode materials: the precursor powder was mixed with lithium hydroxide in a molar ratio of 1:1.05, and heated to 600°C at a heating rate of 5°C / min under oxygen atmosphere and kept warm for 5 hours, and then heated to 900°C at a heating rate of 3°C / min and kept warm for 10 hours, and naturally cooled to obtain the positive electrode material.

[0087] The positive electrode material, conductive agent, and binder were uniformly mixed in nitrogen-methyl pyrrolidone at a mass ratio of 85:10:5. The mixture was then coated onto an aluminum foil current collector and dried at 120°C under vacuum to obtain a positive electrode sheet. The sheet was then punched into small discs with a diameter of 2 cm. A 2032-type button cell was assembled in a nitrogen atmosphere using a lithium metal sheet as the negative electrode, LiPF6 / EC+DMC as the electrolyte, and PP as the separator. The specific capacity, cycle capacity retention, and rate performance of the cell were then tested. The results are shown in Table 1.

[0088] The specific capacity test method is as follows: using the Blue Electric Battery Test System, at 25°C, the lithium-ion battery is charged and discharged three times in the voltage range of 2V to 4.3V at a charge and discharge rate of 0.04A / g (calculated based on the mass of the positive electrode material) to measure the battery specific capacity;

[0089] The test method for cycle capacity retention is as follows: at 25°C, cycle at a charge and discharge rate of 0.19 A / g (calculated based on the mass of the positive electrode material). After 100 cycles, the discharge capacity of the battery at this time is divided by the discharge capacity of the first cycle, which is the battery's 100-cycle capacity retention rate.

[0090] The test method for rate performance is as follows: at 25°C, charge and discharge three times in the voltage range of 2V to 4.3V at a charge and discharge rate of 0.04A / g (calculated based on the mass of the positive electrode material) to obtain the discharge capacity C0 of the last cycle; then, charge the battery to 4.3V at a charge rate of 0.04A / g (calculated based on the mass of the positive electrode material), and discharge the battery to 2V at a discharge rate of 0.12A / g (calculated based on the mass of the positive electrode material) to obtain the discharge capacity C2 of the last cycle; the ratio of C2 / C0 is the rate performance.

[0091] Table 1

[0092] Specific capacity (mAh / g) Cycle capacity retention rate (%) Rate performance (%) Example 1 205.5 94.3 92.6 Example 2 205.8 92.9 91.5 Example 3 199.4 93.8 92.2 Example 4 208.6 87.5 87.8 Example 5 192.5 91.4 89.1 Comparative Example 1 207.1 85.9 86.3 Comparative Example 2 203.2 88.1 88.2 Comparative Example 3 203.6 88.3 86.5

[0093] In summary, the present invention grows and coats fluoride on the surface of the precursor, which can act as a flux when preparing single-crystalline positive electrode materials, thereby enabling the preparation of single-crystalline materials at lower temperatures; at the same time, fluoride can act as a dopant, and through the composite doping of the second metal and fluorine, the structural stability and cycle performance of the single-crystalline positive electrode material are improved; and no additional impurity removal process is required.

[0094] The applicant declares that the above is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the scope of protection and disclosure of the present invention.

Claims

1. A method for preparing a fluoride-coated precursor, characterized in that: The preparation method comprises the following steps: mixing the first metal salt solution, the complexing agent solution, and the precipitant solution in parallel, and performing a first coprecipitation reaction to a target particle size; then stopping the introduction of the first metal salt solution, and simultaneously introducing a fluorine source solution and a second metal salt solution, and performing a second coprecipitation reaction to obtain the fluoride-coated precursor; The first metal salt in the first metal salt solution includes nickel salt, cobalt salt and manganese salt; The second metal salt in the second metal salt solution includes any one or a combination of at least two of lithium salt, aluminum salt, cerium salt, magnesium salt, lanthanum salt, zinc salt, calcium salt, lead salt or zirconium salt; The chemical formula of the fluoride-coated precursor is Ni a Co b Mn 1-a-b (OH)2@MF c , wherein M is any one of the metals Li, Al, Ce, Mg, La, Zn, Ca, Pb, and Zr, or a combination of at least two thereof, 0.5≤a<1, 0.01≤b≤0.3, and 1≤c≤4.

2. The preparation method according to claim 1, characterized in that The fluorine source in the fluorine source solution includes sodium fluoride and / or potassium fluoride; Preferably, the concentration of the fluorine source solution is 0.1 mol / L-2 mol / L.

3. The preparation method according to claim 1, characterized in that The second metal salt is any one of sulfate, chloride or nitrate, or a combination of at least two thereof; Preferably, the concentration of the second metal salt solution is 0.1 mol / L-0.5 mol / L.

4. The preparation method according to claim 1, characterized in that In the fluoride-coated precursor, the second metal in the second metal salt accounts for 0.1 wt%-10 wt% of the total amount of metal in the fluoride-coated precursor, preferably 1 wt%-5 wt%.

5. The preparation method according to claim 1, characterized in that The concentration of the first metal salt solution is 1 mol / L-2 mol / L; Preferably, the nickel salt in the first metal salt solution includes any one of nickel sulfate, nickel chloride or nickel nitrate, or a combination of at least two thereof; Preferably, the cobalt salt in the first metal salt solution includes any one of cobalt sulfate, cobalt chloride or cobalt nitrate, or a combination of at least two thereof; Preferably, the manganese salt in the first metal salt solution includes any one of manganese sulfate, manganese chloride or manganese nitrate, or a combination of at least two of them.

6. The preparation method according to claim 1, characterized in that The pH value of the first coprecipitation reaction is 10.5-12; Preferably, the temperature of the first coprecipitation reaction is 45°C-70°C; Preferably, the concentration of the complexing agent during the first coprecipitation reaction is 4 g / L-7 g / L; Preferably, the first coprecipitation reaction is carried out under stirring conditions of 300 rpm-400 rpm.

7. The preparation method according to claim 1, characterized in that The target particle size refers to a median particle size D50 reaching 2.5 μm-3.5 μm.

8. The preparation method according to any one of claims 1 to 7, characterized in that The pH value of the second coprecipitation reaction is 8-9; Preferably, the temperature of the second coprecipitation reaction is 45°C-70°C; Preferably, the concentration of the complexing agent during the second coprecipitation reaction is 4 g / L-7 g / L; Preferably, the second coprecipitation reaction is carried out under stirring conditions of 300 rpm-400 rpm.

9. A fluoride-coated precursor, characterized in that: The fluoride-coated precursor is prepared by the preparation method according to any one of claims 1 to 8; The chemical formula of the fluoride-coated precursor is Ni a Co b Mn 1-a-b (OH)2@MF c , wherein M is any one of the metals Li, Al, Ce, Mg, La, Zn, Ca, Pb, and Zr, or a combination of at least two thereof, 0.5≤a<1, 0.01≤b≤0.3, and 1≤c≤4.

10. A single crystal positive electrode material, characterized in that: The single crystal positive electrode material is prepared from the fluoride-coated precursor according to claim 9.