Monocrystal ternary positive electrode material, preparation method thereof and lithium ion battery

Abstract

The invention belongs to the technical field of lithium ion batteries, and particularly relates to a single-crystal ternary positive electrode material, a preparation method thereof and a lithium ion battery, and the preparation method comprises the following steps: providing a mixed solution of water-soluble nickel salt, cobalt salt and manganese salt; preparing precursor powder from the mixed solution; weighing lithium hydroxide and lithium phosphate, and mixing to obtain a mixed lithium salt; mixing the precursor powder with a mixed lithium salt, and heating for primary sintering to obtain a prefabricated material; and performing secondary sintering on the prefabricated material to obtain the single-crystal ternary positive electrode material. According to the preparation method, the mixed lithium salt is adopted to overcome the defect that a ternary material prepared by a single lithium salt is disordered, the sintering temperature can be reduced and the specific capacity and the sintering morphology of the material can be improved through step-by-step sintering, relative independence exists among particles of the single crystal ternary positive electrode material prepared in the mode, microcracks can be relieved, and the service life of the single crystal ternary positive electrode material is prolonged. Higher mechanical strength and compaction density are achieved, and capacity loss caused by the polarization effect can be reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium - ion batteries, and particularly relates to a single - crystal ternary cathode material, a preparation method thereof, and a lithium - ion battery. Background Art

[0002] Currently, as one of the most feasible energy storage technologies for electric vehicles, lithium - ion batteries have been continuously innovated with related new high - performance cathode materials. Among them, nickel - based ternary cathode materials are regarded as one of the most promising cathode materials. However, disadvantages such as low cycle life and insufficient rate performance have always restricted their industrial development.

[0003] However, the ternary material prepared by a single molten salt has strong disorder, which easily leads to the transformation of the material structure from a layered structure to a rock - salt structure, resulting in a low variable capacity of the battery. And when oxides of Ni, Co, and Mn are introduced into the lithium salt as a flux, it is difficult to control the growth morphology of the crystal, which is not conducive to industrial preparation.

[0004] Therefore, how to provide a single - crystal ternary cathode material with a controllable crystal morphology for industrial production is a technical problem that urgently needs to be solved in this field.

[0005] It should be noted that the above information disclosed in this background - art section is only used to understand the background technology of the concept of this application. Therefore, the above description is not considered as information on the prior art. Summary of the Invention

[0006] The embodiments of the present disclosure at least provide a single - crystal ternary cathode material, a preparation method thereof, and a lithium - ion battery.

[0007] In a first aspect, the embodiments of the present disclosure provide a preparation method of a single - crystal ternary cathode material, including the following steps: using deionized water as a solvent, providing a mixed solution of water - soluble nickel salt, cobalt salt, and manganese salt; preparing a precursor powder from the mixed solution; weighing lithium hydroxide and lithium phosphate and mixing them to obtain a mixed lithium salt; mixing the precursor powder with the mixed lithium salt and performing a first - stage sintering by heating to obtain a pre - formed material; performing a second - stage sintering on the pre - formed material to obtain a single - crystal ternary cathode material.

[0008] In an optional embodiment, the molar ratio of the water - soluble nickel salt, cobalt salt, and manganese salt satisfies n(Ni):n(Co):n(Mn)=(70 - 80):(7 - 13):(10 - 20).

[0009] In an alternative embodiment, the preparation of the precursor powder from the mixed solution specifically includes: using deionized water as a solvent, providing a phosphoric acid solution as a complexing agent and a sodium hydroxide solution as a precipitating agent; adding the mixed solution, the complexing agent, and the precipitating agent to deionized water respectively, and continuously stirring to obtain the precursor powder; wherein, the concentration range of the complexing agent is 1-5 mol / L; the concentration range of the precipitating agent is 4-10 mol / L.

[0010] In an alternative embodiment, the pH range maintained in the reaction vessel after adding the precipitating agent is 10-12.

[0011] In an alternative embodiment, the molar ratio of lithium hydroxide to lithium phosphate is (0.35~0.40):(0.60~0.70).

[0012] In an alternative embodiment, the first sintering is specifically carried out at 450-500 °C for 3.5-4.5 h in an O2 environment, and then at 850-900 °C for 8-10 h.

[0013] In an alternative embodiment, the molar ratio of the precursor powder to the mixed lithium salts is 1:(1~5).

[0014] In an alternative embodiment, the second sintering is specifically carried out at 750-800 °C for 4-6 h in a vacuum environment.

[0015] In a second aspect, the embodiments of the present disclosure further provide a single-crystal ternary cathode material, the chemical formula of the single-crystal ternary cathode material is LiNi x Co y Mn z O2, and it is obtained by using the preparation method as described above; wherein x is 0.7-0.8, y is 0.07-0.13, z is 0.1-0.2, and x + y + z = 1.

[0016] In a third aspect, the embodiments of the present disclosure further provide a lithium-ion battery, using the single-crystal ternary cathode material as described above as the cathode material of the battery.

[0017] The beneficial effects of the present invention are that the single-crystal ternary cathode material, its preparation method, and the lithium-ion battery use mixed lithium salts to overcome the defects of the disorder in the preparation of ternary materials by single lithium salts. By stepwise sintering, the sintering temperature can be reduced, the specific capacity and sintering morphology of the material can be improved. The particles of the single-crystal ternary cathode material prepared in the above manner have relative independence, which can alleviate the appearance of microcracks, and also have higher mechanical strength and tap density, which can reduce the capacity loss caused by polarization, providing a solution for the industrial production of single-crystal ternary cathode materials with controllable morphology.

[0018] Other features and advantages of the present invention will be set forth in the following description, and in part will be obvious from the description, or may be learned by practice of the present invention. The objectives and other advantages of the present invention are realized and attained by the structure particularly pointed out in the specification, claims and drawings.

[0019] To make the above objectives, features and advantages of the present invention more obvious and understandable, the following specific preferred embodiments are given, in conjunction with the accompanying drawings, and are described in detail as follows. Brief Description of the Drawings

[0020] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0021] Figure 1 SEM diagram of the single-crystal ternary cathode material provided by an embodiment of the present disclosure;

[0022] Figure 2 XRD diagram of the single-crystal ternary cathode material provided by an embodiment of the present disclosure;

[0023] Figure 3 Diagram of the initial discharge specific capacity (a) and cyclic discharge specific capacity (b) of the single-crystal ternary cathode material provided by an embodiment of the present disclosure. Specific Embodiments

[0024] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the drawings. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0025] As used herein, phrases such as "in one embodiment", "according to one embodiment", "in some embodiments", etc. generally refer to the fact that the particular feature, structure, or characteristic following the phrase can be included in at least one embodiment of the present disclosure. Thus, a particular feature, structure, or characteristic can be included in more than one embodiment of the present disclosure, such that these phrases do not necessarily refer to the same embodiment. As used herein, the terms "example", "exemplary", etc. are used "as an example, instance, or illustration. Any embodiment, aspect, or design described herein as "example" or "exemplary" is not necessarily to be construed as preferred or superior to other embodiments, aspects, or designs. Instead, the use of the terms "example", "exemplary", etc. is intended to present concepts in a concrete manner.

[0026] Herein, example embodiments of the present disclosure will be described in more detail with reference to the accompanying drawings. As used herein, expressions such as "at least one of..." modify the entire list of elements when following a list of elements, rather than modifying an individual element in the list. For example, the expression "at least one of a, b, and c" should be understood to include only a, only b, only c, both a and b, both a and c, both b and c, or all of a, b, and c.

[0027] The terms used herein are only for describing specific exemplary configurations and are not intended to be limiting. As used herein, the singular articles "a", "an", and "the" may also be intended to include the plural forms, unless it is clearly stated otherwise herein. The terms "comprising", "including", and "having" are inclusive and thus specify the presence of the specified features, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and / or their combinations. The method steps, processes, and operations described herein should not be construed as necessarily requiring them to be performed in the particular order discussed or shown, unless specifically identified as an order of performance. Additional or alternative steps may be employed.

[0028] The substances used herein are selected from industrial-grade raw materials. Thus, NiSO4 includes NiSO4 and NiSO4·6H2O, CoSO4 includes CoSO4 and CoSO4·7H2O, MnSO4 includes MnSO4 and MnSO4·H2O, and H3PO4 includes H3PO4 and H3PO4·H2O.

[0029] 1. Kim et al. prepared single-crystalline LiNi 0.8 Co 0.1 Mn 0.1 O2 materials using KCl or NaCl as a flux for sintering. However, the melting points of NaCl and KCl are relatively high (801 °C and 770 °C respectively), and sintering at a higher temperature results in the escape of Li and O from the material;

[0030] 2. Satyanarayana et al. prepared single-crystal LiNi 0.4 Co 0.2 Mn 0.4 O2 material by sintering with LiNO3-LiCl as a flux. At 0.1C and 2.5-4.4V, the discharge specific capacity of this material reached 155 mAh / g. However, the method of simply introducing a lithium salt as a flux to sinter and prepare single-crystal materials is difficult to control the growth morphology of crystals, has a long sintering time, and is prone to waste of lithium salt.

[0031] Regarding the defects existing in the above solutions, they are all the results obtained by the inventors through practice and careful research. Therefore, the discovery process of the above problems and the solutions proposed by the present disclosure for the above problems in the following text should all be the contributions made by the inventors to the present disclosure during the process of the present disclosure.

[0032] It should be noted that similar reference numerals and letters represent similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0033] The following will describe in detail some embodiments of the present invention with reference to the drawings. Without conflict, the following embodiments and the features in the embodiments can be combined with each other.

[0034] The embodiments of the present disclosure provide a method for preparing a single-crystal ternary cathode material, including the following steps: using deionized water as a solvent to provide a mixed solution of water-soluble nickel salt, cobalt salt, and manganese salt; preparing precursor powder from the mixed solution; weighing lithium hydroxide and lithium phosphate and mixing them to obtain a mixed lithium salt; mixing the precursor powder with the mixed lithium salt and performing a first sintering by heating to obtain a preform; and performing a second sintering on the preform to obtain the single-crystal ternary cathode material.

[0035] Specifically, to avoid the poor mechanical stability of spherical particles, microcracks are generated inside the particles during repeated expansion and contraction, resulting in hindered ion and electron transport. The single-crystal particle manufacturing method is adopted, and the single-crystal particles have relative independence, which can greatly alleviate the appearance of microcracks to a large extent. Compared with spherical particles, single-crystal particles have higher mechanical strength and higher tap density, which is beneficial to reducing the capacity loss caused by polarization. Therefore, preparing single-crystal particles with micron size can effectively solve many problems of secondary spherical particles.

[0036] Specifically, the ternary material prepared by using a single molten salt has strong disorder, resulting in the transformation of the material structure from a layered structure to a rock salt structure. Therefore, the specific capacity of the prepared cathode material is low. Compared with the solution using a single molten salt, using a mixed lithium salt as a flux is beneficial to reducing the sintering temperature, improving the specific capacity and sintering morphology of the material.

[0037] Specifically, lithium hydroxide is used as the molten salt and lithium phosphate as the flux. Compared with lithium carbonate, when lithium hydroxide is used as the lithium source, materials with excellent performance can be obtained only by low-temperature sintering; as the number of cycles increases, the cycling curve of the materials prepared with lithium hydroxide as the lithium source is smoother, and the charge-discharge performance is more stable. At the same time, PO4 3- in lithium phosphate can enter the Li + solvation structure to regulate the formation of the SEI film. And the reduction product of PO4 3- such as Li3P is an excellent Li + conductor, which can accelerate the Li + deposition / stripping behavior. Moreover, Li3PO4 is usually used in combination with other solvents or active substances to strengthen the SEI film and inhibit the growth of lithium dendrites. In addition to Li3PO4, other metal phosphates also contribute to the formation of a good SEI film and improve the cycling performance of lithium metal batteries.

[0038] In some embodiments, specifically, the molar ratio of the water-soluble nickel salt, cobalt salt, and manganese salt satisfies n(Ni):n(Co):n(Mn) = (70 - 80):(7 - 13):(10 - 20); the water-soluble nickel salt, cobalt salt, and manganese salt are preferably NiSO4, CoSO4, and MnSO4, respectively.

[0039] In some embodiments, specifically, the preparation of the precursor powder from the mixed solution specifically includes: using deionized water as the solvent, providing a phosphoric acid solution as the complexing agent and a sodium hydroxide solution as the precipitating agent; adding the mixed solution, complexing agent, and precipitating agent to deionized water respectively and continuously stirring to obtain the precursor powder; wherein, the concentration range of the complexing agent is 1 - 5 mol / L; the concentration range of the precipitating agent is 4 - 10 mol / L.

[0040] In some embodiments, specifically, the pH in the reaction vessel is maintained in the range of 10 - 12 after adding the precipitating agent.

[0041] In some embodiments, specifically, the molar ratio of the lithium hydroxide and lithium phosphate is (0.35 - 0.40):(0.60 - 0.70).

[0042] In some embodiments, specifically, the primary sintering is specifically carried out by sintering at 450 - 500 °C for 3.5 - 4.5 h in an O2 environment, and then sintering at 850 - 900 °C for 8 - 10 h; first, medium-temperature calcination is carried out to preferentially prepare the prefabricated mixed lithium salt, and then the sintering temperature is increased to accelerate the ion diffusion rate, thereby promoting the growth of single crystals.

[0043] In some embodiments, specifically, the molar ratio of the precursor powder to the mixed lithium salts is 1:(1 - 5), specifically the ratio of the sum of Ni, Co, and Mn in the precursor powder to the molecular weight of Li in the mixed lithium salts.

[0044] In some embodiments, specifically, the secondary sintering is specifically carried out at 750 - 800 °C for 4 - 6 h in a vacuum environment.

[0045] The embodiments of the present disclosure also provide a single-crystalline ternary cathode material, and the chemical formula of the single-crystalline ternary cathode material is LiNi x Co y Mn z O2, and it is obtained by using the preparation method described above; where x is 0.7 - 0.8, y is 0.07 - 0.13, z is 0.1 - 0.2, and x + y + z = 1.

[0046] The embodiments of the present disclosure also provide a lithium-ion battery, which uses the single-crystalline ternary cathode material described above as the cathode material of the battery.

[0047] Example 1

[0048] (1) First, weigh the corresponding masses of NiSO4·6H2O, CoSO4·7H2O, and MnSO4·H2O according to the molar ratio n(Ni):n(Co):n(Mn) = 75:10:15, and prepare an aqueous solution with a certain concentration.

[0049] (2) Then, using deionized water as the solvent respectively, prepare 2.8 mol / L H3PO4·H2O solution and 5.5 mol / L NaOH solution as complexing agent and precipitating agent.

[0050] (3) Drop the three solutions obtained in steps (1) and (2) into a reaction kettle with appropriate deionized water simultaneously, and continuously stir, control the dropping rate of the NaOH solution to make the pH value in the reaction kettle 11, and finally obtain the precursor powder.

[0051] (4) Weigh LiOH·H2O and Li3PO4 with a molar ratio of 0.38:0.62 for mixing to prepare mixed lithium salts.

[0052] (5) Grind the materials obtained in steps (3) and (4) for 0.5 hours according to the molar ratio of the precursor powder to the mixed lithium salts of 1:1, then sinter at 480 °C for 4 h in an O2 environment, and then sinter at 860 °C for 10 h.

[0053] (6) Wash the product obtained in step (5) three times with high-purity deionized water to remove the excessive lithium salts, vacuum dry and then sinter at 760 °C for 5 h to obtain LiNi 0.75 Co0.10 Mn 0.15 O2 sample. It is named LNCM-1 according to the different amounts of the mixed salts used.

[0054] Example 2

[0055] The difference between this embodiment and Example 1 is that in step (5), the molar ratio of the precursor powder to the mixed lithium salts is 1:2, and the final product LiNi 0.75 Co 0.10 Mn 0.15 O2 powder is denoted as LNCM-2 according to the different amounts of the precursor and the mixed lithium salts used. Other steps and parameters are the same as those in Example 1.

[0056] Example 3

[0057] The difference between this embodiment and Example 1 is that in step (5), the molar ratio of the precursor powder to the mixed lithium salts is 1:3, and the final product LiNi 0.75 Co 0.10 Mn 0.15 O2 powder is denoted as LNCM-3 according to the different amounts of the precursor and the mixed lithium salts used. Other steps and parameters are the same as those in Example 1.

[0058] Example 4

[0059] The difference between this embodiment and Example 2 is that the molar ratio of the precursor powder to the mixed lithium salts is 1:2, and they are mixed and ball-milled for 0.5 hours, sintered at 480 °C for 4 h in a muffle furnace under O2 conditions, and then sintered at 840 °C for 10 h, and the final product LiNi 0.75 Co 0.10 Mn 0.15 O2 powder is denoted as LNCM-2-840 according to the different high-temperature sintering conditions. Other steps and parameters are the same as those in Example 2.

[0060] Example 5

[0061] The difference between this embodiment and Example 2 is that the molar ratio of the precursor powder to the mixed lithium salts is 1:2, and they are mixed and ball-milled for 0.5 hours, sintered at 480 °C for 4 h in a muffle furnace under O2 conditions, and then sintered at 850 °C for 10 h, and the final product LiNi 0.75 Co 0.10 Mn 0.15 O2 powder is denoted as LNCM-2-850 according to the different high-temperature sintering conditions. Other steps and parameters are the same as those in Example 2.

[0062] Example 6

[0063] The difference between this embodiment and Example 2 is that the molar ratio of the precursor powder to the mixed lithium salts is 1:2, and they are mixed and ball-milled for 0.5 h. Then, they are sintered at 480 °C for 4 h in a muffle furnace under O2 conditions, and then sintered at 870 °C for 10 h to obtain the final product LiNi 0.75 Co 0.10 Mn 0.15 O2 powder, which is denoted as LNCM-2-870 according to different high-temperature sintering conditions. Other steps and parameters are the same as those in Example 2.

[0064] Prepare the electrode and assemble the battery with LNCM-2 obtained in Example 2. Weigh the active material, binder (polyvinylidene fluoride) with a content of 5%, and acetylene black according to a mass ratio of 8:1:1, and then add N-methylpyrrolidone as a solvent and mix them evenly. Coat the prepared slurry evenly on the aluminum foil. After vacuum drying for 3 h, punch it into a 10-mm electrode sheet, and then put it into a vacuum drying oven and dry it at 110 °C for 5 h to obtain the positive electrode sheet. Stack the obtained positive electrode sheet, Celgand (2500), separator, and lithium metal negative electrode in sequence for assembly, and drop 1.0 mol / L LiPF6 (EC+DEC) as the electrolyte on both sides of the separator, and finally seal it to assemble a coin cell.

[0065] Please refer to Figure 1 , Figure 1 , which are SEM images of LNCM-1, LNCM-2, and LNCM-3 materials prepared by calcining at 860 °C with three different ratios of mixed lithium salts. As can be seen from the figure, the morphologies of the three materials are single-crystalline, and the particle sizes are 0.5–1.5 μm, 1.0–2.0 μm, and 1.0–2.5 μm, respectively. With the increase in the amount of lithium salts, the agglomeration of small particles is weakened to a certain extent, the particle size of the single crystal gradually increases, and the dispersion degree also improves. In the high-temperature calcination stage, when the concentration of the supersaturated melt is relatively high, the nucleation rate is greater than the crystal growth rate, and it is easy to obtain small-particle crystals, and the agglomeration of the crystals is more serious; when the concentration of the supersaturated melt is relatively low, the nucleation rate is less than the crystal growth rate, and it is easier to obtain large-particle single crystals.

[0066] Please refer to Figure 2 , Figure 2XRD patterns of the LNCM materials in Examples 1 to 3 and Example 6. It can be seen that the XRD patterns of the prepared samples correspond to the LiNiO2 PDF card (98-003-4490). The diffraction peaks of all samples are clear, sharp, and there are no impurity peaks. This indicates that the four prepared LNCM materials are all pure phases. It can also be clearly seen from the figure that all four materials have obvious diffraction peaks at (003), (101), and (104), and the diffraction peaks corresponding to the (018) and (110) crystal planes show obvious splitting, proving that the prepared materials all have a typical layered structure.

[0067] Table 1: Lattice parameters of LiNi 0.75 Co 0.10 Mn 0.15 O2 materials

[0068]

[0069] Specifically, Table 1 shows the Rietveld refinement results of the XRD data of the LNCM materials in the above Examples 1 to 3. It can be seen that the degree of Ni / Li mixing in samples LNCM-1, LNCM-2, and LNCM-3 is 2.78%, 2.64%, and 2.51% respectively. This is because the mixed lithium salt flux, which also serves as the lithium source, can compensate for the loss of Li during the calcination process when the mass ratio to the precursor powder is slightly greater than 1:1, reduce the generation of Li vacancies, and lower the + / Ni 2+ mixing degree, thereby improving the crystallization performance of the material; however, too much lithium source may cause lithium ions to occupy the positions of transition metal ions, instead increasing the mixing degree to a certain extent.

[0070] Please refer to Figure 3 , Figure 3 Button cells prepared from the cathode materials synthesized in Examples 1 to 3 and Example 6. As Figure 3 (a) shows, the discharge specific capacities of LNCM-3, LNCM-2, LNCM-1, and LNCM-2-870 materials are 183.3 mA·h / g, 197.7 mA·h / g, 179.3 mA·h / g, and 167.5 mA·h / g respectively. That is, when the molar ratio of the precursor to the mixed lithium salt is 1:2 and the sintering temperature is 860 °C, the synthesized material LNCM-2 has the largest discharge specific capacity of 197.7 mA·h / g.

[0071] In addition, the average voltage of these four single-crystal high-nickel materials is about 3.83 V. In the voltage range of 2.60 - 4.30 V, the above four button cells were tested for charge-discharge cycle performance at a 1C rate, and the results are as Figure 3(as shown in (b)). It can be seen from the figure that the initial discharge specific capacities of LNCM-3, LNCM-2, LNCM-1, and LNCM-2-870 materials are 160.2 mA·h / g, 173.6 mA·h / g, 156.6 mA·h / g, and 149.4 mA·h / g respectively, and the capacity retention rates after 100 cycles are 70.0%, 89.1%, 85.9%, and 58.3% respectively. Among them, LNCM-2 shows the highest 1C discharge specific capacity and the best cycle stability.

[0072] In summary, the present single-crystal ternary cathode material, its preparation method, and the lithium-ion battery use a mixed lithium salt to overcome the defect of disorder in the preparation of ternary materials by a single lithium salt. By stepwise sintering, the sintering temperature can be reduced, the specific capacity and sintering morphology of the material can be improved. The particles of the single-crystal ternary cathode material prepared in the above manner have relative independence, which can alleviate the appearance of microcracks, and also have higher mechanical strength and tap density, which can reduce the capacity loss caused by polarization, providing a solution for the industrial production of single-crystal ternary cathode materials with controllable morphology.

[0073] Taking the ideal embodiments of the present invention as the inspiration, through the above description, relevant workers can completely make various changes and modifications without departing from the technical idea of the present invention. The technical scope of the present invention is not limited to the content in the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. A method for preparing a single crystal ternary cathode material, characterized in that: The steps include: Providing a mixed solution of water-soluble nickel salt, cobalt salt and manganese salt; The mixed solution is used to prepare a precursor powder; Weigh lithium hydroxide and lithium phosphate and mix them to obtain a mixed lithium salt; The precursor powder is mixed with the mixed lithium salt, and the mixture is heated and sintered once to obtain a preform; The prefabricated material is sintered for a second time to obtain a single crystal ternary positive electrode material.

2. The method for preparing a single crystal ternary cathode material according to claim 1, characterized in that: The molar ratio of the water-soluble nickel salt, cobalt salt and manganese salt satisfies n(Ni):n(Co):n(Mn)=(70-80):(7-13):(10-20).

3. The method for preparing a single crystal ternary cathode material according to claim 1, characterized in that: The mixed solution is used to prepare the precursor powder, which specifically includes: providing a phosphoric acid solution as a complexing agent and a sodium hydroxide solution as a precipitating agent; The mixed solution, the complexing agent and the precipitant are added to deionized water respectively, and stirred continuously to obtain a precursor powder; wherein, The concentration range of the complexing agent is 1-5 mol / L; The concentration range of the precipitant is 4-10 mol / L.

4. The method for preparing a single crystal ternary cathode material according to claim 3, characterized in that: After the precipitant is added dropwise, the pH in the reaction container is maintained in the range of 10-12.

5. The method for preparing a single crystal ternary cathode material according to claim 1, characterized in that: The mass ratio of the lithium hydroxide to the lithium phosphate is (0.35-0.40):(0.60-0.70).

6. The method for preparing a single crystal ternary cathode material according to claim 1, characterized in that: The primary sintering is specifically sintering at 450-500° C. for 3.5-4.5 hours in an O2 environment, and then sintering at 850-900° C. for 8-10 hours.

7. The method for preparing a single crystal ternary cathode material according to claim 1, characterized in that: The mass ratio of the precursor powder to the mixed lithium salt is 1:(1-5).

8. The method for preparing a single crystal ternary cathode material according to claim 1, characterized in that: The secondary sintering is specifically sintering at 750-800° C. for 4-6 hours in a vacuum environment.

9. A single crystal ternary cathode material, characterized in that: The chemical formula of the single crystal ternary cathode material is LiNi x Co y Mn z O2, and is obtained by the preparation method according to any one of claims 1 to 8; in x is 0.7-0.8, y is 0.07-0.13, z is 0.1-0.2, and x+y+z=1.

10. A lithium ion battery, characterized in that: The single crystal ternary positive electrode material as claimed in claim 9 is used as the positive electrode material of the battery.

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