Preparation process of low-residual-alkali high-performance ternary positive electrode material

Abstract

The application discloses a preparation process of a low-residual-alkali high-performance ternary positive electrode material, and belongs to the technical field of ternary positive electrode material preparation. The preparation process comprises the following steps: adding the ternary positive electrode material into an alcohol solution of polyphosphoric acid for acid pickling; adding a composite coating agent into the reaction solution after the acid pickling, sealing and stirring after constant volume of the alcohol solvent, so as to obtain a mixed solution; and sintering the mixed solution after suction filtration, so as to obtain the low-residual-alkali high-performance ternary positive electrode material. The preparation process can form a double-layer coating structure on the surface of the ternary positive electrode material, remove the residual alkali on the surface of the ternary positive electrode material, and improve the chargeable capacity, stability and charge-discharge specific capacity performance of the ternary positive electrode material.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery technology, specifically relating to a preparation process for a ternary cathode material with low residual alkali and high performance. Background Technology

[0002] Ternary cathode materials, as a type of cathode material for lithium-ion batteries, belong to the category of multi-metal composite oxides, mainly including lithium nickel cobalt manganese oxide (NCM) and lithium nickel cobalt aluminum oxide (NCA). They possess significant advantages such as low production cost, high capacity, and high volumetric energy density, and are currently primarily used in passenger vehicle power batteries. Among these, high-nickel ternary cathode materials, by increasing the nickel content and decreasing the cobalt content, can effectively improve the material's energy density while reducing costs; therefore, high-nickel ternary materials have become a current research hotspot. However, high-nickel ternary cathode materials suffer from severe Li-related degradation. + / Ni 2+ Defects such as mixed arrangement, surface air sensitivity, poor interface stability, and intergranular / intragranular cracks severely affect its application and development. In the synthesis and sintering process of high-nickel ternary cathode materials, in order to compensate for the sintering volatilization of Li salt and ensure the high charge-discharge specific capacity performance of the material, the ratio of lithium salt to nickel-cobalt-manganese metal salt is increased. However, this also leads to a high residual alkali problem in the sintered material, further aggravating the air instability of the material.

[0003] Chinese patent application CN114927664A discloses a process for reducing residual alkali in ternary cathode materials by acid washing with a mixed aqueous solution of boron and phosphate sources. The process involves pressure filtration and low-temperature vacuum sintering at 200-400℃ to prepare a boron / phosphate co-coated cathode material. This method effectively reduces the problem of residual alkali in high-nickel ternary cathodes, and the low-temperature vacuum sintering process improves the material's cycle performance. However, this method still uses deionized water as a washing solvent. While water washing in high-nickel ternary cathode production effectively reduces residual alkali, it requires strict control of the water volume and washing time. Furthermore, it easily causes microcrack propagation, intensified cation mixing, structural instability, and erosion from interfacial side reactions during charge and discharge. In addition, washing with deionized water significantly exacerbates the harmful phase transformation from layered structures to disordered spinel and rock salt phase structures, reducing the material's structural stability. Therefore, many manufacturers are striving to find a method that removes residual alkali from high-nickel ternary cathode materials efficiently without introducing water. Currently, some methods exist for removing residual alkali without introducing moisture. These methods involve dissolving the phosphate source in an organic solvent to form a solution, thoroughly stirring the ternary cathode material for lithium-ion batteries, and then drying it until the organic solvent is completely evaporated. This forms a lithium phosphate coating layer on the surface of the ternary cathode material, thus removing residual alkali. However, this method has two drawbacks. First, the lithium phosphate reacts with the test reagents during the residual alkali testing of the synthesized product, interfering with the test results. Second, this method is only suitable for coating small amounts of phosphate, which limits the effectiveness of phosphate in improving the performance of ternary cathode materials. Summary of the Invention

[0004] In view of this, the present invention needs to provide a low residual alkali and high performance ternary cathode material preparation process. This preparation process can effectively overcome the above problems and improve the rechargeable capacity, stability and charge-discharge specific capacity performance of the ternary cathode material while removing residual alkali from the surface of the ternary cathode material.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] The first aspect of this invention provides a process for preparing a low-residue, high-performance ternary cathode material, comprising the following steps:

[0007] The ternary cathode material was added to an alcohol solution of polyphosphoric acid for acid washing;

[0008] Add a composite coating agent to the acid-washed reaction solution, dilute to volume with alcohol solvent, seal and stir to obtain a mixed solution;

[0009] After filtration, the mixed solution is sintered to obtain a ternary cathode material with low residual alkali and high performance.

[0010] This invention firstly reduces the residual alkali content on the surface of the ternary cathode material by reacting a polyphosphoric acid alcohol solution with residual LiOH and Li₂CO₃ on the surface of the ternary cathode material to generate lithium phosphate and lithium hydrogen phosphate, without introducing water as a solvent. Furthermore, a composite coating agent is added to the liquid phase solution to generate a secondary coating layer, thereby improving the material's capacity, stability, and energy density performance.

[0011] The ternary cathode material used in the preparation process described in this invention is a conventional choice in the art, and specific examples include, but are not limited to, lithium nickel cobalt manganese oxide (NCM) or lithium nickel cobalt aluminum oxide (NCA).

[0012] In a further embodiment, the acid washing process using an alcoholic solution of polyphosphoric acid in this invention ensures high safety and a simple procedure (using conventional stirring and vacuum / pressure filtration methods). In some typical embodiments of this invention, the alcoholic solution of polyphosphoric acid is obtained by completely and uniformly mixing polyphosphoric acid and an alcohol solvent under sealed conditions. The concentration of polyphosphoric acid in the alcoholic solution is 1 wt%-5 wt%. The alcohol solvent can be a common alcohol-based solvent in the art, specifically including at least one of ethanol and isopropanol. The preparation of the alcoholic solution of polyphosphoric acid uses conventional mixing methods to ensure complete and uniform mixing of the polyphosphoric acid and the alcohol solvent. Preferably, the mixing is performed using magnetic stirring for 30-40 minutes.

[0013] In a further embodiment, the amount of polyphosphoric acid used is adjusted or selected according to the mass of the ternary cathode material. In some specific embodiments of the present invention, the amount of polyphosphoric acid used is 5%-15% of the mass of the ternary cathode material.

[0014] In a further embodiment, the pickling operation described in this invention is simple, employing a sealed stirring method. The amount and time of pickling can be adjusted according to the concentration of the polyphosphoric acid alcohol solution. Specifically, the amount of pickling solution is inversely proportional to its concentration, and the pickling time increases as the concentration of the polyphosphoric acid alcohol solution decreases. In some specific embodiments of this invention, the pickling time is 0.5-2 hours.

[0015] In a further embodiment, the composite coating agent is composed of a first coating agent and a second coating agent, with different specific modes of action and effects.

[0016] The first coating agent is a metal salt of metal element A, wherein metal element A is selected from at least one of Zr, Y, Co, La, and V. The metal salt reacts with phosphoric acid to generate the corresponding phosphate. Specifically, the first coating agent reacts with excess phosphoric acid in the solution, consuming the excess phosphoric acid and generating the corresponding metal phosphate salt. Specific examples of the first coating agent include at least one of ZrOCl2, YCl2, Y2(CO3)3, YCl3, Co(OH)2, CoO(OH), and La(NO3)3. It is understood that the specific amount used can be adjusted according to the amount of ternary cathode material and polyphosphoric acid. In some specific embodiments of the present invention, the amount of the first coating agent is 0.05%-2% of the mass of the ternary cathode material.

[0017] The second coating agent is a metal oxide of metal element B, wherein metal element B is selected from at least one of Al, Ti, Mg, W, Nb, Mo, and Ta. This metal oxide does not react with phosphoric acid, thereby allowing an oxide coating layer to continue forming on the surface of the phosphate metal salt coating layer formed by the first coating agent, improving the stability of the material. The second coating agent is at least one of Al₂O₃, Ti₂O₃, Mg₂O₃, WO₃, Nb₂O₃, Mo₂O₃, and Ta₂O₃. The amount of the second coating agent can be adjusted according to the desired material performance and requirements. In some specific embodiments of the present invention, the amount of the second coating agent is 0.05%-2% of the mass of the ternary cathode material.

[0018] In a further embodiment, after adding the composite coating agent, the alcohol solvent is adjusted to a mass ratio with the ternary cathode material ranging from 2:1 to 5:1 to ensure uniform dispersion of the ternary cathode material in the alcohol solvent.

[0019] In a further embodiment of the present invention, the sintering is a staged sintering process, with an added low-temperature pre-sintering step to thoroughly remove organic solvents and excess gases from the material. In some specific embodiments of the present invention, the first stage involves holding at 200-400°C for 2-4 hours, and the second stage involves holding at 500-700°C for 3-6 hours; the heating rate during the sintering process is 3-10°C / min.

[0020] A second aspect of this invention provides a low-alkali-residue, high-performance ternary cathode material, prepared using the process described in the first aspect of this invention. This low-alkali-residue, high-performance ternary cathode material exhibits low surface alkali content and excellent electrochemical performance.

[0021] A third aspect of the present invention provides a lithium-ion battery comprising a positive electrode, wherein the positive electrode active material is a low-residue, high-performance ternary positive electrode material as described in the second aspect of the present invention.

[0022] This lithium-ion battery has the same or similar advantages as "low residual alkali and high performance ternary cathode materials", which will not be elaborated here.

[0023] It is understood that the composition of lithium-ion batteries (positive electrode, negative electrode, separator, electrolyte, etc.) and the specific battery assembly described in this article can all adopt conventional choices and methods in this field, and will not be elaborated here.

[0024] The beneficial effects of this invention are:

[0025] This invention first involves thoroughly mixing a polyphosphoric acid alcohol solution with a ternary cathode material without introducing water as a solvent. The ternary cathode material is then acid-washed to react with residual LiOH and Li₂CO₃ on the material surface, consuming residual alkali to generate lithium phosphate and lithium hydrogen phosphate, effectively reducing the amount of residual alkali on the material surface. Because lithium phosphate has a more stable P=O bond, it improves the stability of the ternary material and simultaneously delays the corrosion of the cathode material by HF during battery charging and discharging, thereby increasing the material's rechargeable capacity. Furthermore, by adding a composite coating agent to the liquid phase solution, the capacity, stability, and energy density performance of the material are further enhanced.

[0026] Furthermore, the preparation process in this invention is simple, and subsequent steps only require filtration followed by direct sintering, eliminating the need for drying or solvent removal. This process is highly safe, optimizes the process flow, reduces energy consumption, and is suitable for large-scale applications. Attached Figure Description

[0027] Figure 1 The modified ternary cathode materials of Example 1 and Comparative Example 1, and the untreated Li(Ni) 0.88 Co 0.07 Mn 0.05 XRD pattern of O2;

[0028] Figure 2 The low residual alkali and high performance ternary cathode material and untreated Li(Ni) in Example 1 0.88 Co 0.07 Mn 0.05 SEM image of O2;

[0029] Figure 3 The modified ternary cathode material in Example 4 and Comparative Example 1, and the untreated Li(Ni) 0.88 Co 0.07 Mn 0.05 Cyclic performance test curves of O2. Detailed Implementation

[0030] The embodiments of the present invention are described in detail below. The embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0031] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. Furthermore, unless otherwise specified, methods not specifically describing conditions or steps are conventional methods, and the reagents and materials used are commercially available.

[0032] Example 1

[0033] This embodiment discloses a process for preparing a low-residue, high-performance ternary cathode material, the specific steps of which are as follows:

[0034] Acid washing: Weigh 2.5g of polyphosphoric acid and dissolve it in 50g of ethanol. Stir magnetically at room temperature for 30min to obtain a polyphosphoric acid alcohol solution with an acid concentration of 5wt%. Under magnetic stirring, add 10g of ternary cathode material Li(Ni) 0.88 Co 0.07 Mn 0.05 O2 was slowly added to the polyphosphoric acid alcohol solution and stirred for 30 seconds to ensure that the ternary cathode material was free from particle agglomeration and sedimentation, thus preventing uneven washing. Then, magnetic stirring was continued for 20 minutes under sealed conditions. During this process, the polyphosphoric acid consumed Li(Ni) 0.88 Co 0.07 Mn 0.05 O2 surface residual alkali, in Li(Ni) 0.88 Co 0.07 Mn 0.05 A lithium phosphate and lithium hydrogen phosphate coating layer is formed on the O2 surface.

[0035] Coating: Add 0.05g Co(OH)2 and 0.02g Al2O3 as the first coating agent and magnetically stir for 1 hour after the acid washing reaction is completed to the solution, and form a mixed solution. The addition of metal salts in this process has two main effects: (1) Co(OH)2 consumes excess phosphoric acid and forms Li3PO4 and LiCoPO4 coating layers to improve the material capacity, energy density and air stability; (2) Alumina coating forms AlPO4 and Al2O3 in the subsequent sintering process, which improves the material stability.

[0036] Filtration and sintering: The above mixed solution was filtered and then sintered. The sintering process was carried out in an oxygen sintering atmosphere at a heating rate of 3℃ / min. The first stage was held at 200℃ for 2 hours, and the second stage was held at 500℃ for 5 hours. After cooling, the mixture was ground to obtain Li(Ni) coated with inner layers of Li3PO4 and LiCoPO4 and outer layers of AlPO4 and Al2O3. 0.88 Co 0.07 Mn 0.05 O2 ternary cathode material.

[0037] Example 2

[0038] This embodiment discloses a low-residue, high-performance ternary cathode material preparation process, which adopts the same implementation method as in Example 1, except that: during the acid washing process, the acid concentration of the polyphosphoric acid alcohol solution is 2 wt%, and the washing time is 40 min. All other processes are the same as in Example 1. The specific steps are as follows:

[0039] Acid washing: Weigh 1g of polyphosphoric acid and dissolve it in 50g of ethanol. Stir magnetically at room temperature for 30min to obtain a polyphosphoric acid alcohol solution with an acid concentration of 2wt%. Under magnetic stirring, add 10g of ternary cathode material Li(Ni) 0.88 Co 0.07 Mn 0.05 O2 was slowly added to the polyphosphoric acid alcohol solution, and the mixture was manually stirred for 30 seconds to ensure that there was no particle agglomeration or sedimentation of the ternary cathode material, which would cause uneven washing. Then, magnetic stirring was continued for 40 minutes under sealed conditions. During this process, the polyphosphoric acid consumed Li(Ni) 0.88 Co 0.07 Mn 0.05 O2 surface residual alkali, in Li(Ni) 0.88 Co 0.07 Mn 0.05 A lithium phosphate and lithium hydrogen phosphate coating layer is formed on the O2 surface.

[0040] Coating: After adding 0.05g Co(OH)2 and 0.02g Al2O3 as the first coating agent to the solution after the acid washing reaction, the mixture is sealed and magnetically stirred for 1 hour to form a mixed solution. The addition of metal salts in this process has two main effects: (1) Co(OH)2 consumes excess phosphoric acid and forms Li3PO4 and LiCoPO4 coating layers to improve the material capacity, energy density and air stability; (2) Alumina coating forms AlPO4 and alumina coating layers in the subsequent sintering process to improve the material stability and cycle performance.

[0041] Filtration and sintering: The above mixed solution was filtered and then sintered. The sintering process was carried out in an oxygen sintering atmosphere at a heating rate of 3℃ / min. The first stage was held at 200℃ for 2 hours, and the second stage was held at 500℃ for 5 hours. After cooling, the mixture was ground to obtain Li(Ni) coated with inner layers of Li3PO4 and LiCoPO4 and outer layers of AlPO4 and Al2O3. 0.88 Co 0.07 Mn 0.05 O2 ternary cathode material.

[0042] Example 3

[0043] This embodiment discloses a preparation process for a low-residue, high-performance ternary cathode material, which adopts the same implementation method as in Example 1, except that the first coating agent used in the coating process is 0.02g ZrOCl2 and the second coating agent is 0.02g V2O5. All other processes are the same as in Example 1. The specific steps are as follows:

[0044] Acid washing: Obtain a polyphosphoric acid alcohol solution with an acid concentration of 5 wt%; under magnetic stirring, add 10 g of ternary cathode material Li(Ni) 0.88 Co 0.07 Mn 0.05 O2 was slowly added to the polyphosphoric acid alcohol solution and stirred for 30 seconds to ensure that the ternary cathode material was free from particle agglomeration and sedimentation, thus preventing uneven washing. Then, magnetic stirring was continued for 20 minutes under sealed conditions. During this process, the polyphosphoric acid consumed Li(Ni) 0.88 Co 0.07 Mn 0.05 O2 surface residual alkali, in Li(Ni) 0.88 Co 0.07 Mn 0.05 A lithium phosphate and lithium hydrogen phosphate coating layer is formed on the O2 surface.

[0045] Coating: After adding 0.02g of the first coating agent ZrOCl2 and 0.02g of the second coating agent V2O5 to the solution after the acid washing reaction is completed, the mixture is sealed and magnetically stirred for 1 hour to form a mixed solution. The addition of metal salts in this process has two main effects: (1) ZrOCl2 consumes excess phosphoric acid and forms Li3PO4 and LiZrPO4 coating layers to improve the material capacity, surface electronic conductivity and stability; (2) V2O5 coating forms Li3V2(PO4)3 and V2O5 coating layers in the subsequent sintering process, which improves the stability of the material.

[0046] Filtration and sintering: The above mixed solution was filtered and then sintered. The sintering process was carried out in an oxygen sintering atmosphere at a heating rate of 3℃ / min. The first stage was held at 200℃ for 2 hours, and the second stage was held at 500℃ for 5 hours. After cooling, the mixture was ground to obtain Li(Ni) coated with inner layers of Li3PO4 and LiZrPO4 and outer layers of Li3V2(PO4)3 and V2O5. 0.88 Co 0.07 Mn 0.05 O2 ternary cathode material.

[0047] Example 4

[0048] This embodiment discloses a preparation process for a low-residue, high-performance ternary cathode material, which adopts the same implementation method as in Example 1, except that the first coating agent used in the coating process is 0.03g YCl3 and the second coating agent is 0.02g WO3. All other processes are the same as in Example 1. The specific steps are as follows:

[0049] Acid washing: Obtain a polyphosphoric acid alcohol solution with an acid concentration of 5 wt%; under magnetic stirring, add 10 g of ternary cathode material Li(Ni) 0.88 Co 0.07 Mn 0.05 O2 was slowly added to the polyphosphoric acid alcohol solution and stirred for 30 seconds to ensure that the ternary cathode material was free from particle agglomeration and sedimentation, thus preventing uneven washing. Then, magnetic stirring was continued for 20 minutes under sealed conditions. During this process, the polyphosphoric acid consumed Li(Ni) 0.88 Co 0.07 Mn 0.05 O2 surface residual alkali, in Li(Ni) 0.88 Co 0.07 Mn 0.05 A lithium phosphate and lithium hydrogen phosphate coating layer is formed on the O2 surface.

[0050] Coating: Add 0.03g YCl3 as the first coating agent and 0.02g WO3 as the second coating agent to the solution after the acid washing reaction is completed, and then seal and magnetically stir for 1 hour to form a mixed solution; the addition of metal salts in this process has two main effects: (1) YCl3 consumes excess phosphoric acid to form Li3PO4 and YPO4 coating layers to improve the material capacity, improve the electronic conductivity and stability of the material surface; (2) WO3 coating forms a WO3 coating layer in the subsequent sintering process to improve the material stability, cycle performance and specific capacity.

[0051] Filtration and sintering: The above mixed solution was filtered and then sintered. The sintering process was carried out in an oxygen sintering atmosphere at a heating rate of 3℃ / min. The first stage was held at 200℃ for 2 hours, and the second stage was held at 500℃ for 5 hours. After cooling, the mixture was ground to obtain Li(Ni) coated with an inner layer of Li3PO4 and YPO4 and an outer layer of WO3.0.88 Co 0.07 Mn 0.05 O2 ternary cathode material.

[0052] Example 5

[0053] This embodiment discloses a preparation process for a low-residue, high-performance ternary cathode material, which adopts the same implementation method as in Example 1, except that the first coating agent used in the coating process is 0.03g YCl3 and the second coating agent is 0.02g TiO2. All other processes are the same as in Example 1. The specific steps are as follows:

[0054] Acid washing: Obtain a polyphosphoric acid alcohol solution with an acid concentration of 5 wt%; under magnetic stirring, add 10 g of ternary cathode material Li(Ni) 0.88 Co 0.07 Mn 0.05 O2 was slowly added to the polyphosphoric acid alcohol solution and stirred for 30 seconds to ensure that the ternary cathode material was free from particle agglomeration and sedimentation, thus preventing uneven washing. Then, magnetic stirring was continued for 20 minutes under sealed conditions. During this process, the polyphosphoric acid consumed Li(Ni) 0.88 Co 0.07 Mn 0.05 O2 surface residual alkali, in Li(Ni) 0.88 Co 0.07 Mn 0.05 A lithium phosphate and lithium hydrogen phosphate coating layer is formed on the O2 surface.

[0055] Coating: Add 0.03g YCl3 as the first coating agent and 0.04g TiO2 as the second coating agent to the solution after the acid washing reaction is completed, and then seal and magnetically stir for 1 hour to form a mixed solution. The addition of metal salts in this process has two main effects: (1) YCl3 consumes excess phosphoric acid to form Li3PO4 and YPO4 coating layers to improve the material capacity, surface electronic conductivity and stability; (2) TiO2 coating forms LiTi2(PO4)3 and TiO2 coating layers in the subsequent sintering process to improve the material stability and cycle performance.

[0056] Filtration and sintering: The above mixed solution was filtered and then sintered. The sintering process was carried out in an oxygen sintering atmosphere at a heating rate of 3℃ / min. The first stage was held at 200℃ for 2 hours, and the second stage was held at 500℃ for 5 hours. After cooling, the mixture was ground to obtain Li(Ni) coated with inner layers of Li3PO4 and YPO4 and outer layers of LiTi2(PO4)3 and TiO2. 0.88 Co 0.07 Mn 0.05 O2 ternary cathode material.

[0057] Example 6

[0058] This embodiment discloses a preparation process for a low-residue, high-performance ternary cathode material, which adopts the same implementation method as in Example 1, except that the first coating agent used in the coating process is 0.02g LaCl2 and the second coating agent is 0.03g Nb2O5. All other processes are the same as in Example 1. The specific steps are as follows:

[0059] Acid washing: Obtain a polyphosphoric acid alcohol solution with an acid concentration of 5 wt%; under magnetic stirring, add 10 g of ternary cathode material Li(Ni) 0.88 Co 0.07 Mn 0.05 O2 was slowly added to the polyphosphoric acid alcohol solution and stirred for 30 seconds to ensure that the ternary cathode material was free from particle agglomeration and sedimentation, thus preventing uneven washing. Then, magnetic stirring was continued for 20 minutes under sealed conditions. During this process, the polyphosphoric acid consumed Li(Ni) 0.88 Co 0.07 Mn 0.05 O2 surface residual alkali, in Li(Ni) 0.88 Co 0.07 Mn 0.05 A lithium phosphate and lithium hydrogen phosphate coating layer is formed on the O2 surface.

[0060] Coating: Add 0.02g of the first coating agent LaCl2 and 0.03g of the second coating agent Nb2O5 to the solution after the acid washing reaction is completed, and then seal and magnetically stir for 1 hour to form a mixed solution; the addition of metal salts in this process has two main effects: (1) YCl3 consumes excess phosphoric acid and forms Li3PO4 and La3(PO4)2 coating layers to improve the material capacity, improve the electronic conductivity and stability of the material surface; (2) Nb2O5 coating forms an Nb2O5 coating layer in the subsequent sintering process, which improves the stability and cycle performance of the material.

[0061] Filtration and sintering: The above mixed solution was filtered and then sintered. The sintering process was carried out in an oxygen sintering atmosphere at a heating rate of 3℃ / min. The first stage was held at 200℃ for 2 hours, and the second stage was held at 500℃ for 5 hours. After cooling, the mixture was ground to obtain Li(Ni) oxide coated with inner layers of Li3PO4 and La3(PO4)2 and outer layers of Nb2O5. 0.88 Co 0.07 Mn 0.05 O2 ternary cathode material.

[0062] Comparative Example 1

[0063] This comparative example discloses a method for preparing a modified ternary cathode material, which adopts the same implementation method as Example 1, except that: no coating is performed, and the acid-washed solution is directly filtered and sintered. All other processes are the same as in Example 1. The specific steps are as follows:

[0064] Acid washing: Weigh 2.5g of polyphosphoric acid and dissolve it in 50g of ethanol. Stir magnetically at room temperature for 30min to obtain a polyphosphoric acid alcohol solution with an acid concentration of 5wt%. Under magnetic stirring, add 10g of ternary cathode material Li(Ni) 0.88 Co 0.07 Mn 0.05 O2 was slowly added to the polyphosphoric acid alcohol solution and stirred for 30 seconds to ensure that the ternary cathode material was free from particle agglomeration and sedimentation, thus preventing uneven washing. Then, magnetic stirring was continued for 20 minutes under sealed conditions. During this process, the polyphosphoric acid consumed Li(Ni) 0.88 Co 0.07 Mn 0.05 O2 surface residual alkali, in Li(Ni) 0.88 Co 0.07 Mn 0.05 A lithium phosphate and lithium hydrogen phosphate coating layer is formed on the O2 surface.

[0065] Filtration and sintering: The acid-washed solution was filtered and then sintered. The sintering process was carried out in an oxygen sintering atmosphere at a heating rate of 3℃ / min. The first stage was held at 200℃ for 2 hours, and the second stage was held at 500℃ for 5 hours. After cooling, the solution was ground to obtain lithium phosphate-coated Li(Ni) phosphate. 0.88 Co 0.07 Mn 0.05 O2 ternary cathode material.

[0066] Comparative Example 2

[0067] This comparative example discloses a method for preparing a modified ternary cathode material, which adopts the same implementation method as Example 1, except that polyphosphoric acid is not added during the acid washing process. All other processes are the same as in Example 1. The specific steps are as follows:

[0068] Alcohol washing: Under magnetic stirring, 10g of ternary cathode material Li(Ni) was washed... 0.88 Co 0.07 Mn 0.05 O2 was slowly added to the ethanol solution and stirred for 30 seconds to ensure that the ternary cathode material was free from particle agglomeration and sedimentation, which would cause uneven washing. Then, the mixture was sealed and magnetically stirred for another 20 minutes.

[0069] Coating: Add 0.05g of the first coating agent Co(OH)2 and 0.02g of the second coating agent Al2O3 to the solution after the alcohol washing reaction is completed, seal and stir magnetically for 1 hour to form a mixed solution.

[0070] Filtration and sintering: The above mixed solution was filtered and then sintered. The sintering process was carried out in an oxygen sintering atmosphere at a heating rate of 3℃ / min. The first stage was held at 200℃ for 2 hours, and the second stage was held at 500℃ for 5 hours. After cooling, the solution was ground to obtain Li(Ni) coated with Li2CO2 and Al2O3. 0.88 Co 0.07 Mn 0.05 O2 ternary cathode material.

[0071] Comparative Example 3

[0072] This comparative example discloses a method for preparing a modified ternary cathode material, which adopts the same implementation method as Example 1, except that polyphosphoric acid is not added and no coating is performed during the acid washing process. All other processes are the same as in Example 1.

[0073] The specific steps are as follows:

[0074] Alcohol washing: Under magnetic stirring, 10g of ternary cathode material Li(Ni) was washed... 0.88 Co 0.07 Mn 0.05 O2 was slowly added to the ethanol and stirred for 30 seconds to ensure that the ternary cathode material was free from particle agglomeration and sedimentation, which would cause uneven washing. Then, the mixture was sealed and magnetically stirred for another 20 minutes.

[0075] Filtration and sintering: The alcohol-washed solution was filtered and then sintered. The sintering process was carried out in an oxygen sintering atmosphere at a heating rate of 3℃ / min. The first stage was held at 200℃ for 2 hours, and the second stage was held at 500℃ for 5 hours. After cooling, Li(Ni) was obtained by grinding. 0.88 Co 0.07 Mn 0.05 O2 ternary cathode material.

[0076] Comparative Example 4

[0077] This comparative example discloses a method for preparing a modified ternary cathode material, which adopts the same implementation method as Example 1, except that the coating agent is entirely Co(OH)2. All other processes are the same as in Example 1. The specific steps are as follows:

[0078] Acid washing: Obtain a polyphosphoric acid alcohol solution with an acid concentration of 5 wt%. Under magnetic stirring, add 10 g of ternary cathode material Li(Ni) 0.88 Co 0.07 Mn 0.05 O2 was slowly added to the polyphosphoric acid alcohol solution and stirred for 30 seconds to ensure that the ternary cathode material was free from particle agglomeration and sedimentation, thus preventing uneven washing. Then, magnetic stirring was continued for 20 minutes under sealed conditions. During this process, the polyphosphoric acid consumed Li(Ni) 0.88 Co 0.07Mn 0.05 O2 surface residual alkali, in Li(Ni) 0.88 Co 0.07 Mn 0.05 A lithium phosphate and lithium hydrogen phosphate coating layer is formed on the O2 surface.

[0079] Coating: Add 0.07g of the first coating agent Co(OH)2 to the solution after the acid washing reaction is completed, seal and stir magnetically for 1 hour to form a mixed solution.

[0080] Filtration and sintering: The above mixed solution was filtered and then sintered. The sintering process was carried out in an oxygen sintering atmosphere at a heating rate of 3℃ / min. The first stage was held at 200℃ for 2 hours, and the second stage was held at 500℃ for 5 hours. After cooling, the mixture was ground to obtain Li(Ni) coated with Li3PO4 and LiCoPO4. 0.88 Co 0.07 Mn 0.05 O2 ternary cathode material.

[0081] Comparative Example 5

[0082] This comparative example discloses a method for preparing a modified ternary cathode material, which adopts the same implementation method as Example 1, except that the coating agent is entirely Al2O3. All other processes are the same as in Example 1. The specific steps are as follows:

[0083] Acid washing: A 5 wt% polyphosphoric acid alcohol solution was obtained, and magnetically stirred at room temperature for 30 min to obtain a 2 wt% polyphosphoric acid alcohol solution; under magnetic stirring conditions, 10 g of ternary cathode material Li(Ni) 0.88 Co 0.07 Mn 0.05 O2 was slowly added to the polyphosphoric acid alcohol solution and stirred for 30 seconds to ensure that the ternary cathode material was free from particle agglomeration and sedimentation, thus preventing uneven washing. Then, magnetic stirring was continued for 20 minutes under sealed conditions. During this process, the polyphosphoric acid consumed Li(Ni) 0.88 Co 0.07 Mn 0.05 O2 surface residual alkali, in Li(Ni) 0.88 Co 0.07 Mn 0.05 A lithium phosphate and lithium hydrogen phosphate coating layer is formed on the O2 surface.

[0084] Coating: Add 0.07g of the second coating agent Al2O3 to the solution after the acid washing reaction is completed, seal and stir magnetically for 1 hour to form a mixed solution.

[0085] Filtration and sintering: The above mixed solution was filtered and then sintered. The sintering process was carried out in an oxygen sintering atmosphere at a heating rate of 3℃ / min. The first stage was held at 200℃ for 2 hours, and the second stage was held at 500℃ for 5 hours. After cooling, the solution was ground to obtain Li(Ni) coated with Li3PO and AlPO4. 0.88 Co 0.07 Mn 0.05 O2 ternary cathode material.

[0086] Performance testing

[0087] The modified ternary cathode materials and the untreated ternary cathode material Li(Ni) in Examples 1-6 and Comparative Examples 1-5 0.88 Co 0.07 Mn 0.05 O2 was subjected to XRD, SEM, residual alkali content testing, and nickel, cobalt, manganese, and lithium content detection. The residual alkali content was measured using the potentiometric titration method according to the national standard GB / T 11064.2-2023; the nickel, cobalt, manganese, and lithium content was measured using ICP-AES by measuring the digested and diluted finished solution.

[0088] Table 1 Results of residual alkali content test

[0089] serial number LiOH (wt%) <![CDATA[Li2CO3(wt%)]]> Example 1 0.0035 0.3709 Example 2 0.0534 0.3915 Example 3 0.0251 0.3706 Example 4 0.0233 0.3520 Example 5 0.0290 0.3601 Example 6 0.0297 0.3805 Comparative Example 1 0.0211 0.6735 Comparative Example 2 0.3072 0.6398 Comparative Example 3 0.4124 0.6219 Comparative Example 4 0.0073 0.4091 Comparative Example 5 0.0760 0.4121 <![CDATA[Li(Ni 0.88 What 0.07 Mn 0.05 )O2]]> 0.6617 0.5732

[0090] The test results in Table 1 show that the total residual alkali in Examples 1-6 and Comparative Examples 1-5 is lower than that in the untreated ternary cathode material, indicating that alcohol washing can remove excess residual alkali from the material surface during stirring, but its effect is significantly less than that of acid washing. Furthermore, a comparison of the data from Examples 1-6 reveals that higher acid concentration in the acid washing solution leads to better removal of residual alkali. A comparison of the data from Example 1 and Comparative Example 1 shows that acid washing without coating results in residual lithium phosphate, leading to a higher detection rate of Li2CO3 in the tested residual alkali. The data from Comparative Example 2 indicates that liquid-phase coating without acid washing only slightly reduces the residual alkali content. A comparison of the results from Comparative Examples 4-5 and Examples 1-6 shows that using two coating agents is more effective than using a single coating agent in reducing residual alkali on the material surface. The results in Table 1 demonstrate that simultaneous acid washing and liquid-phase coating can effectively reduce the residual alkali content on the surface of ternary cathode materials.

[0091] Table 2 Results of Nickel, Cobalt and Manganese Content Detection

[0092] serial number Li (wt%) Ni (mol%) Co (mol%) Mn (mol%) Example 1 6.99 87.73 7.06 5.20 Example 2 6.96 87.77 7.01 5.16 Example 3 6.98 88.02 6.80 5.17 Example 4 7.03 88.00 6.7 5.30 Example 5 6.97 87.98 6.75 5.27 Example 6 6.96 97.98 6.81 5.21 Comparative Example 1 7.05 87.98 6.76 5.18 Comparative Example 2 7.10 87.97 6.82 5.16 Comparative Example 3 7.18 88.05 6.76 5.19 Comparative Example 4 7.03 87.53 7.22 5.25 Comparative Example 5 7.06 88.04 6.77 5.19 <![CDATA[Li(Ni 0.88 What 0.07 Mn 0.05 )O2]]> 7.27 88.04 6.78 5.18

[0093] The test results in Table 2 show that the nickel, cobalt, and manganese data of Examples 1-6, Comparative Examples 1-5, and the untreated ternary cathode material indicate that acid washing or alcohol washing does not affect the proportion of main elements in the ternary material, while reducing the Li content. Adding Co salt during the coating process can adjust the cobalt content in the ternary material. Therefore, these test results demonstrate that the acid washing + liquid phase coating scheme is feasible and does not affect the proportion of main elements in the material.

[0094] also, Figure 1 Here are the XRD patterns of Example 1, Comparative Example 1, and the untreated sample. Figure 2 SEM images of Example 1 and the untreated sample. Figure 1 The XRD pattern shows that the phase and crystal structure of the sample were not affected after acid washing and coating treatment, proving that the coating additive was successfully coated onto the material surface. Figure 2 The SEM image shows that the surface of the material after pickling and coating treatment is covered with fine particles, which further proves that the additives formed a coating layer on the surface of the cathode material.

[0095] The CR2016 button cell materials from Examples 1-6, Comparative Examples 1-5, and untreated ternary cathode materials were assembled to test their electrochemical performance. All cells had a current density of 100 mA / g and a voltage range of 2.8–4.35 V. Cycling performance was tested at 1C@100 cycles at room temperature after initial activation at 0.2C. The test results are shown in Table 3.

[0096] Table 3 Electrical performance test results

[0097]

[0098] To more clearly observe the effect of acid pickling coating on the improvement of the cycling performance of ternary materials, Figure 3 Cyclic performance curves of some test samples are shown. Combined with the data in Table 3, it can be seen that the first discharge specific capacity of the ternary cathode material after acid washing and liquid phase coating is significantly improved, and the first efficiency and cycle performance are also significantly improved. At the same time, the electrical performance is also significantly improved compared with the samples that only undergo acid washing or coating. This indicates that the synergistic effect of liquid phase coating while acid washing is significantly better than that of acid washing or coating alone.

[0099] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0100] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A process for preparing a low-residue, high-performance ternary cathode material, characterized in that, Includes the following steps: The ternary cathode material was added to an alcohol solution of polyphosphoric acid for acid washing; Add a composite coating agent to the acid-washed reaction solution, dilute to volume with alcohol solvent, seal and stir to obtain a mixed solution; After the mixed solution is filtered, it is sintered to obtain a ternary cathode material with low residual alkali and high performance. The composite coating agent is composed of a first coating agent and a second coating agent; The first coating agent is at least one of ZrOCl2, Y2(CO3)3, YCl3, Co(OH)2, CoO(OH), and La(NO3)3, and the first coating agent can react with phosphoric acid to generate the corresponding metal phosphate salt; The second coating agent is a metal oxide of metal element B, wherein metal element B is selected from at least one of Al, Ti, W, Nb, Mo, Ta, and V, and the metal oxide continues to form an oxide coating layer on the surface of the phosphate metal salt coating layer formed by the first coating agent.

2. The preparation process according to claim 1, characterized in that, The ternary cathode material is selected from lithium nickel cobalt manganese oxide or lithium nickel cobalt aluminum oxide.

3. The preparation process according to claim 1, characterized in that, The polyphosphoric acid alcohol solution is obtained by completely and uniformly mixing polyphosphoric acid and an alcohol solvent under sealed conditions.

4. The preparation process according to claim 3, characterized in that, The concentration of polyphosphoric acid in the alcoholic solution is 1wt%-5wt%.

5. The preparation process according to claim 3, characterized in that, The alcohol solvent is at least one of ethanol and isopropanol.

6. The preparation process according to claim 3, characterized in that, The mixing is performed using magnetic stirring for 30-40 minutes.

7. The preparation process according to claim 1, characterized in that, The amount of polyphosphoric acid used is 5%-15% of the mass of the ternary cathode material.

8. The preparation process according to claim 1, characterized in that, The pickling process is carried out using a sealed stirring method, and the pickling time is 0.5-2 hours.

9. The preparation process according to claim 1, characterized in that, The amount of the first coating agent is 0.05%-2% of the mass of the ternary cathode material.

10. The preparation process according to claim 1, characterized in that, The second coating agent is at least one of Al2O3, TiO2, WO3, Nb2O5, Mo2O3, Ta2O3, and V2O5.

11. The preparation process according to claim 1, characterized in that, The amount of the second coating agent is 0.05%-2% of the mass of the ternary cathode material.

12. The preparation process according to claim 1, characterized in that, The alcohol solvent is brought to a final volume to achieve a mass ratio with the ternary cathode material ranging from 2:1 to 5:

1.

13. The preparation process according to claim 1, characterized in that, The sintering is a staged sintering process, wherein the first stage is held at 200-400℃ for 2-4 hours, and the second stage is held at 500-700℃ for 3-6 hours; the heating rate during the sintering process is 3-10℃ / min.

14. A low-residue, high-performance ternary cathode material, characterized in that, It is prepared using the preparation process described in any one of claims 1-13.

15. A lithium-ion battery comprising a positive electrode, characterized in that, The positive electrode active material in the positive electrode is the low residual alkali and high performance ternary positive electrode material as described in claim 14.

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