Ternary positive electrode material, preparation method thereof and electrochemical device

Abstract

A ternary cathode material, its preparation method, and an electrochemical device are disclosed. The preparation method includes: providing a doped and modified nickel-cobalt-manganese precursor, the precursor comprising a core and a shell layer on the surface of the core, the shell layer comprising multiple primary particles containing dopant ions, the primary particles being radially arranged on the surface of the core away from the core; mixing the nickel-cobalt-manganese precursor and a lithium source and performing a first sintering to obtain a matrix material; spraying a first coating material onto the surface of the matrix material, mixing, and performing a second sintering to form a first coating layer on the surface of the matrix material, obtaining an intermediate material; spraying a second coating material onto the surface of the intermediate material, mixing, and performing a third sintering to form a second coating layer on the surface of the first coating layer, obtaining the ternary cathode material. This application can improve the capacity of the ternary cathode material while simultaneously enhancing its safety.

Description

Technical Field

[0001] This application relates to the field of new energy technology, specifically to a ternary cathode material and its preparation method, and an electrochemical device. Background Technology

[0002] In recent years, the rapid development of new energy vehicles and energy storage has placed higher demands on the performance and cost of lithium-ion batteries. Compared with cathode materials such as lead dioxide, nickel hydroxide, lithium iron phosphate, and lithium manganese iron phosphate, ternary cathode materials have higher energy density, providing a longer driving range. Furthermore, ternary cathode materials have a higher charge-discharge rate, enabling them to complete the charging or discharging process in a shorter time, thus improving the user experience. Ternary cathode materials also have a long cycle life, maintaining stable performance even after multiple charge-discharge cycles.

[0003] However, under extreme conditions such as sustained high temperatures and violent collisions, batteries made from ternary cathode materials still pose a risk of thermal runaway, which could lead to safety accidents such as fires or even explosions. Therefore, how to improve the safety performance of ternary cathode materials while maintaining high capacity has become a current research hotspot. Summary of the Invention

[0004] In view of this, in order to solve at least one of the above technical problems, this application provides a method for preparing a ternary cathode material.

[0005] In addition, embodiments of this application also provide a ternary cathode material and an electrochemical device.

[0006] In a first aspect, embodiments of this application provide a method for preparing a ternary cathode material, the method comprising the following steps: providing a doped and modified nickel-cobalt-manganese precursor, the nickel-cobalt-manganese precursor comprising a core and a shell layer located on the surface of the core, the shell layer comprising a plurality of primary particles containing doped ions, the plurality of primary particles being radially stacked on the surface of the core in a direction away from the core; mixing the nickel-cobalt-manganese precursor and a lithium source and performing a first sintering to obtain a matrix material; spraying a first coating material onto the surface of the matrix material, mixing and performing a second sintering to form a first coating layer on the surface of the matrix material, obtaining an intermediate material, wherein the first coating material comprises lithium cobalt oxide, a first solid electrolyte and a metal compound; and spraying a second coating material onto the surface of the intermediate material, mixing and performing a third sintering to form a second coating layer on the surface of the first coating layer, obtaining the ternary cathode material, wherein the second coating material comprises a second solid electrolyte, a phosphate cathode material and a carbon source.

[0007] Based on the first aspect, in some possible embodiments, the preparation method of the nickel-cobalt-manganese precursor includes: mixing a mixed metal salt solution containing nickel, cobalt, and manganese, a precipitant, and a complexing agent and carrying out a first-stage reaction to form a core, thereby obtaining a first slurry containing the core; and continuing to add a precipitant, a complexing agent, and a dopant containing the dopant ions to the first slurry to obtain a second slurry, and carrying out a second-stage reaction in the second slurry to radially deposit multiple primary particles containing dopant ions on the surface of the core in a direction away from the core, thereby forming a shell layer on the surface of the core, thereby obtaining a doped and modified nickel-cobalt-manganese precursor.

[0008] Based on the first aspect, in some possible embodiments, the dopant ions include Mg. 2+ Ca 2+ 、Sr 2+ Ba 2+ Cu 2+ Zn 2+ Al 3+ Y 3+ Ga 3+ 、Ge 4+ Se 4+ Sn 4+ Zr 4+ Ti 4+ 、Nb 5+ V 5+ Ta 5+ P 5+ F - Mo 6+ and W 6+ At least one of the following; and / or in the nickel-cobalt-manganese precursor, the mass ratio of the nickel-cobalt-manganese precursor to each element in the dopant ion is 1:(0.0005~0.008).

[0009] Based on the first aspect, in some possible embodiments, in the first stage reaction, the pH of the first slurry is adjusted to 11.6~12.1, and the concentration of the complexing agent in the first slurry is adjusted to 0.5mol / L~0.8mol / L; and / or in the second stage reaction, the pH of the second slurry is adjusted to 11.4~11.7, and the concentration of the complexing agent in the second slurry is adjusted to 0.3mol / L~0.5mol / L.

[0010] Based on the first aspect, in some possible embodiments, the median particle size Dv50 of the first coating material is 20nm~50nm; and / or the median particle size Dv50 of the second coating material is 20nm~50nm.

[0011] Based on the first aspect, in some possible embodiments, the first solid electrolyte comprises at least one of lithium lanthanum zirconium tantalum oxide, lithium lanthanum zirconium niobium oxide, lithium lanthanum zirconium oxide, lithium lanthanum titanium oxide, lithium titanium aluminum phosphate, lithium niobate, lithium phosphate, and lithium borate; and / or the metal compound contains metal ions, the metal ions including Mg. 2+ Ca 2+ 、Sr 2+ Ba 2+ Cu 2+ Zn 2+ Al 3+ Y 3+ Ga 3+ 、Ge 4+ Se 4+ Sn 4+ Zr 4+ Ti 4+ 、Nb 5+ V 5+ Ta 5+ Mo 6+ and W 6+ At least one of them.

[0012] Based on the first aspect, in some possible embodiments, the metal compound further contains non-metal ions, including P 5+ and F - At least one of them.

[0013] Based on the first aspect, in some possible embodiments, the second solid electrolyte includes at least one of lithium lanthanum zirconium tantalum oxide, lithium lanthanum zirconium niobium oxide, lithium lanthanum zirconium oxide, lithium lanthanum titanium oxide, lithium titanium aluminum phosphate, lithium niobate, lithium phosphate, and lithium borate; and / or the phosphate cathode material includes at least one of lithium cobalt phosphate, lithium vanadium phosphate, lithium iron phosphate, and lithium nickel iron phosphate; and / or the carbon source includes at least one of conductive carbon black, graphite, graphene, and carbon nanotubes.

[0014] Secondly, this application provides a ternary cathode material, which is prepared by the aforementioned preparation method. The ternary cathode material includes a matrix material, a first coating layer located on the surface of the matrix material, and a second coating layer located on the surface of the first coating layer away from the matrix material. The matrix material includes a ternary cathode active material. The first coating layer includes lithium cobalt oxide, a first solid electrolyte, and a metal compound. The second coating layer includes a second solid electrolyte, a phosphate cathode material, and a carbon source.

[0015] Thirdly, embodiments of this application also provide an electrochemical device, the electrochemical device including a positive electrode sheet, the positive electrode sheet including a positive electrode material, the positive electrode material being the aforementioned ternary positive electrode material.

[0016] Compared to existing technologies, the ternary cathode material preparation method provided in this application improves the structure of the nickel-cobalt-manganese precursor. The nickel-cobalt-manganese precursor has a core-shell structure with radially arranged primary particles in the shell, enhancing the uniformity of the lithiation reaction between the precursor and the lithium source and reducing cracking of the ternary cathode material caused by uneven lithiation. Simultaneously, doping the shell of the nickel-cobalt-manganese precursor improves the stability of the ternary cathode material, increases its thermal runaway temperature, and reduces heat release. Furthermore, by spraying, mixing, and sintering, a first coating material and a second coating material are uniformly coated onto the surface of the substrate material to form a first coating layer and a second coating layer. The first coating material contains a first solid electrolyte, lithium cobalt oxide, and a carbon source, which improve the lithium-ion diffusion rate and electron diffusion rate of the ternary cathode material, enhancing its capacity and rate performance. The second coating material contains a second solid electrolyte, a phosphate cathode material, and a metal compound, which improves the thermal stability of the ternary cathode material. This application can improve the capacity and safety of ternary cathode materials by synergistically improving the precursor structure, doping ions, and composite coating. Attached Figure Description

[0017] Figure 1 This is a process flow diagram of a method for preparing a ternary cathode material according to an embodiment of this application.

[0018] Figure 2 This is a scanning electron microscope image of the nickel-cobalt-manganese precursor in Example 1 of this application.

[0019] Figure 3 This is a scanning electron microscope image of the ternary cathode material in Embodiment 1 of this application.

[0020] Figure 4 This is a scanning electron microscope image of the ternary cathode material in Embodiment 2 of this application.

[0021] Figure 5 This is a scanning electron microscope image of the ternary cathode material in Comparative Example 1 of this application.

[0022] Figure 6 This is a scanning electron microscope image of the ternary cathode material in Comparative Example 2 of this application.

[0023] Figure 7 The high-temperature cycling performance of batteries prepared from ternary cathode materials in Examples 1-2 and Comparative Examples 1-2 of this application is shown in the figure.

[0024] Figure 8 Thermogravimetric analysis (TGA) diagrams of the ternary cathode materials in Examples 1-2 and Comparative Examples 1-2 of this application are shown. Detailed Implementation

[0025] The embodiments of this application are described in detail below. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application; it should be noted that, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; where there is no conflict, the implementation methods and features of the implementation methods of this application can be combined with each other; many specific details are set forth in the following description to provide a full understanding of this application, and the described implementation methods are only a part of the implementation methods of this application, and not all of the implementation methods.

[0026] Please see Figure 1 As shown in the figure, this application provides a novel method for preparing a ternary cathode material, specifically including the following steps:

[0027] Step S1: Provide a doped and modified nickel-cobalt-manganese precursor, the nickel-cobalt-manganese precursor including a core and a shell layer located on the surface of the core, the shell layer including a plurality of primary particles containing doped ions, the plurality of primary particles being radially stacked on the surface of the core in a direction away from the core.

[0028] Specifically, a doped and modified nickel-cobalt-manganese precursor is provided. This precursor has a core-shell structure, with dopant ions in the shell. The shell is formed by multiple primary particles radially stacked on the surface of the core in a direction away from the core. The radial stacking of numerous primary particles creates uniformly distributed, loose pores, effectively improving the uniformity of the subsequent lithiation reaction between the nickel-cobalt-manganese precursor and the lithium source, and reducing cracking of the ternary cathode material caused by uneven lithiation. Simultaneously, doping the shell of the nickel-cobalt-manganese precursor improves the stability of the ternary cathode material, increases its thermal runaway temperature, and reduces heat release.

[0029] The preparation method of the nickel-cobalt-manganese precursor in step S1 may specifically include:

[0030] Step S11: Mix the mixed metal salt solution containing nickel, cobalt, and manganese, the precipitant, and the complexing agent, and carry out the first stage reaction to form a core, thereby obtaining a first slurry containing a core.

[0031] Specifically, a mixed metal salt solution of Ni, Co, and Mn, a precipitant, and a complexing agent are mixed and subjected to a first-stage reaction to nucleate and grow, resulting in a precursor core with a disordered structure.

[0032] In the first stage of the reaction, the pH of the first slurry can be adjusted to 11.6~12.1, and the concentration of the complexing agent in the first slurry can be adjusted to 0.5mol / L~0.8mol / L. The aforementioned higher pH values ​​are beneficial for promoting the reaction of metal ions (Ni... 2+ Co2+ Mn 2+ The complexing agent binds uniformly with the precipitant to form crystal nuclei. The higher concentration of the complexing agent mentioned above helps to slow down the precipitation rate, making the nucleation more uniform and reducing particle agglomeration or component segregation caused by excessively rapid precipitation.

[0033] In some embodiments, the complexing agent may be ammonia, and the precipitant may be sodium hydroxide solution.

[0034] In step S12, a precipitant, a complexing agent, and a dopant containing doped ions are added to the first slurry to obtain a second slurry. The second slurry undergoes a second-stage reaction to radially deposit multiple primary particles containing doped ions on the surface of the core in a direction away from the core, thereby forming a shell on the surface of the precursor core to obtain a nickel-cobalt-manganese precursor.

[0035] In the second-stage reaction, the addition of dopants promotes the preferential growth of primary particles along the I(001) crystal plane, forming multiple primary particles containing doped ions on the surface of the core. These primary particles are radially stacked on the surface of the core to form a shell, and the radially stacked primary particles construct a large number of uniformly distributed pores on the core surface. This radial structure of the nickel-cobalt-manganese precursor is beneficial for lithiation of the nickel-cobalt-manganese precursor and improves the uniformity of lithiation. In addition, dopants can improve the stability of ternary cathode materials, effectively increase the thermal runaway temperature and reduce the heat release, thereby improving the safety of ternary cathode materials.

[0036] In some embodiments, the dopant ions may include Mg 2+ Ca 2+ 、Sr 2+ Ba 2+ Cu 2+ Zn 2+ Al 3+ Y 3+ Ga 3+ 、Ge 4+ Se 4+ Sn 4+ Zr 4+ Ti 4+ 、Nb 5+ V 5+ Ta 5+ P 5+ F - Mo 6+ and W 6+ At least one of the above doping ions. All of the above doping ions can improve the crystal structure of ternary cathode materials, enhance the stability of ternary cathode materials under high temperature and high voltage conditions, reduce structural collapse or phase transition during charge and discharge, and thus further improve the safety of ternary cathode materials.

[0037] In some embodiments, the dopant may include a salt solution containing doped ions.

[0038] In the nickel-cobalt-manganese precursor, the mass ratio of each element in the nickel-cobalt-manganese precursor and the dopant ion can be 1:(0.0005~0.008). Moderate doping is beneficial to effectively improve the crystal structure of the nickel-cobalt-manganese precursor without reducing the capacity of the ternary cathode material. The mass ratio of each element in the nickel-cobalt-manganese precursor and the dopant ion can, for example, be 1:0.0005, 1:0.001, 1:0.002, 1:0.003, 1:0.004, 1:0.005, 1:0.006, 1:0.007, 1:0.008, or any value within the range of any two of the above values. The mass ratio of each element in the nickel-cobalt-manganese precursor and the dopant ion can further be 1:(0.003~0.005).

[0039] In the second stage reaction, the pH of the second slurry can be adjusted to 11.4~11.7, and the concentration of the complexing agent in the second slurry can be adjusted to 0.3mol / L~0.5mol / L. Lower pH and lower complexing agent concentration are beneficial for the formation of needle-like and strip-like primary particles, and also promote the formation of metal ions (Ni...). 2+ Co 2+ Mn 2+ Rapid precipitation increases the porosity of the shell, which is beneficial to further improve the uniformity of the lithiation reaction between the nickel-cobalt-manganese precursor and the lithium source.

[0040] In some embodiments, the median particle size Dv50 of the nickel-cobalt-manganese precursor is 3.0 μm to 4.0 μm.

[0041] In some embodiments, the specific surface area of ​​the nickel-cobalt-manganese precursor is 10 m². 2 / g~25m 2 / g.

[0042] The chemical formula of the nickel-cobalt-manganese precursor (this formula only indicates the proportion of nickel, cobalt, and manganese, and does not show the doping ions; the doping ions replace part of Ni, Co, and Mn) can be Ni α Co β Mn γ (OH)₂, wherein 0.8 > α ≥ 0.5, 0.2 ≥ β > 0.04, 0.3 ≥ γ > 0.1, and β + γ ≤ 0.5. The chemical formula of the nickel-cobalt-manganese precursor (without showing the dopant ions) can exemplarily be Ni. 0.6 Co 0.1 Mn 0.3 (OH)2, Ni 0.65 Co 0.15 Mn 0.2 (OH)2 and Ni 0.75 Co0.1 Mn 0.15 One of (OH)2.

[0043] Step S2: Mix the nickel-cobalt-manganese precursor and the lithium source and perform the first sintering to obtain the matrix material.

[0044] Specifically, in the first sintering, the nickel-cobalt-manganese precursor has a radial structure that creates a large number of uniformly distributed pores, which improves the uniformity of lithium source penetration into the nickel-cobalt-manganese precursor. This helps to reduce the problem of matrix material cracking after long-term cycling caused by uneven lithiation. In addition, the uniformly distributed dopants in the nickel-cobalt-manganese precursor can reduce the risk of thermal runaway of the matrix material, and the structural stability and safety of the matrix material are effectively improved.

[0045] In some embodiments, the lithium source may include at least one of lithium hydroxide, lithium hydroxide monohydrate, and lithium carbonate.

[0046] In some embodiments, the lithium source and the nickel-cobalt-manganese precursor are prepared according to a molar ratio of Li:Me (transition metal element in the nickel-cobalt-manganese precursor) of 1.02 to 1.06.

[0047] After the lithium source and nickel-cobalt-manganese precursor are uniformly mixed, a first sintering is performed. The first sintering temperature is 800℃~1050℃, and the time is 15h~20h. For example, the first sintering temperature can be 800℃, 850℃, 900℃, 950℃, 1000℃, 1050℃, or any value within the range of any two of the above values. The time can be 15h, 16h, 17h, 18h, 19h, 20h, or any value within the range of any two of the above values. When sintering the mixture of nickel-cobalt-manganese precursor and lithium source, controlling the temperature and time within the higher temperature range mentioned above is beneficial for controlling the crystallinity, particle morphology, and size of the matrix material, thereby facilitating the formation of a single-crystal matrix material with high crystallinity and uniform particle size.

[0048] In addition, the atmosphere for the first sintering can be an oxygen atmosphere, which is conducive to maintaining the high valence state of transition metal elements, thereby reducing cation mixing and phase transition.

[0049] Before the first sintering, the mixture of lithium source and nickel-cobalt-manganese precursor can be pre-sintered and dispersed, which helps to improve the uniformity and production capacity of the first sintering. The pre-sintering temperature is 450℃~750℃, and the time is 10h~15h. For example, the pre-sintering temperature can be 450℃, 500℃, 550℃, 600℃, 700℃, 750℃ or any value within the range of any two of the above values, and the time can be 10h, 11h, 12h, 13h, 14h, 15h or any value within the range of any two of the above values.

[0050] The matrix material can be a medium-nickel high-voltage single-crystal ternary material, exhibiting high energy density, good rate performance, and long cycle life. The chemical formula of the matrix material (this formula only indicates the nickel, cobalt, and manganese ratio and does not represent the doping ions; the doping ions replace some of Ni, Co, and Mn) can be LiNi. α Co β Mn γ O2, where 0.8 > α ≥ 0.5, 0.2 ≥ β > 0.04, 0.3 ≥ γ > 0.1, and β + γ ≤ 0.5. The chemical formula of the matrix material (without specifying dopant ions) can exemplarily be LiNi. 0.6 Co 0.1 Mn 0.3 O2, LiNi 0.65 Co 0.15 Mn 0.2 O2 and LiNi 0.75 Co 0.1 Mn 0.15 One of the components of O2.

[0051] Step S3: Spray the first coating material onto the surface of the substrate material, mix and sinter a second time to form a first coating layer on the surface of the substrate material, and obtain an intermediate material, wherein the first coating material includes lithium cobalt oxide, a first solid electrolyte and a metal compound.

[0052] Building upon the structural modification of the nickel-cobalt-manganese precursor to improve the stability and safety of the matrix material, this application further modifies the matrix material through coating to further enhance the thermal stability, capacity, and rate performance of the ternary cathode material. In the first coating material, lithium cobalt oxide exhibits good electronic conductivity and ion migration ability, while the first solid electrolyte possesses excellent lithium-ion conductivity. Lithium cobalt oxide and the first solid electrolyte effectively improve the lithium-ion diffusion rate and electron diffusion rate of the ternary cathode material, thereby increasing its capacity and rate performance. The metal compound forms a protective layer, effectively isolating the matrix material from external air or moisture, reducing pyrolysis reactions, and minimizing direct contact between the matrix material and the electrolyte. It also improves the mechanical strength of the ternary cathode material, thus comprehensively enhancing its thermal stability.

[0053] The mass ratio of the matrix material to lithium cobalt oxide can be 1:(0.001~0.05), which is beneficial for the ternary cathode material to maintain both good ionic conductivity and capacity. For example, this mass ratio can be 1:0.001, 1:0.005, 1:0.01, 1:0.02, 1:0.03, 1:0.04, 1:0.05, or any value within the range of any two of the above values. The mass ratio can further be 1:(0.005~0.02).

[0054] In some embodiments, the first solid electrolyte may include at least one of lithium lanthanum zirconium tantalum oxide, lithium lanthanum zirconium niobium oxide, lithium lanthanum zirconium oxide, lithium lanthanum titanium oxide, lithium titanium aluminum phosphate, lithium niobate, lithium phosphate, and lithium borate.

[0055] The mass ratio of the matrix material to the first solid electrolyte can be 1:(0.003~0.05), which is beneficial for the ternary cathode material to achieve both good ionic conductivity and electronic conductivity. For example, this mass ratio can be 1:0.003, 1:0.005, 1:0.01, 1:0.02, 1:0.03, 1:0.04, 1:0.05, or any value within the range of any two of the above values. The mass ratio can further be 1:(0.002~0.01).

[0056] In some embodiments, the metal compound contains a metal ion, which may include Mg. 2+ Ca 2+ 、Sr 2 + Ba 2+ Cu 2+ Zn 2+ Al 3+ Y 3+ Ga 3+ 、Ge 4+ Se 4+ Sn4+ Zr 4+ Ti 4+ 、Nb 5+ V 5+ Ta 5+ Mo 6+ and W 6+ At least one of the following. The metal ion may further include Al. 3+ Y 3+ Ti 4+ Mg 2+ Ta 5+ Mo 6+ At least one of them.

[0057] In some embodiments, the metal compound may also contain non-metal ions, which may include P 5+ and F - At least one of them.

[0058] The mass ratio of the matrix material to the metal compound can be 1:(0.0005~0.08), which is beneficial for the ternary cathode material to maintain both good conductivity and stability. For example, this mass ratio can be 1:0.0005, 1:0.001, 1:0.005, 1:0.001, 1:0.02, 1:0.03, 1:0.04, 1:0.05, 1:0.06, 1:0.07, 1:0.08, or any value within the range of any two of the above values. The mass ratio can further be 1:(0.003~0.005).

[0059] In this application, a spray coating method is used to modify the matrix material. Compared with dry mixing coating or wet grinding coating, spray coating can improve the uniformity of coating.

[0060] In some embodiments, the median particle size Dv50 of the first coating material can be 20 nm to 50 nm. A smaller particle size is beneficial for further improving the uniformity of the coating, forming a uniform, thin, and dense first coating layer. The median particle size Dv50 of the first coating material can, for example, be 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 47 nm, 49 nm, 50 nm, or any value within the range of any two of the above values. The median particle size Dv50 of the first coating material can further be 30 nm to 40 nm.

[0061] To control the median particle size Dv50 of the first coating material within the range of 20 nm to 50 nm, grinding can be employed, using a sand mill for grinding and ultrasonic dispersion. It is understood that methods for controlling the median particle size of the first coating material include, but are not limited to, the methods described above.

[0062] After the matrix material and the first coating material are uniformly mixed, a second sintering is performed under an oxygen atmosphere. The temperature of the second sintering can be 500℃~800℃, and the time can be 10h~15h. For example, the temperature of the second sintering can be 400℃, 450℃, 500℃, 550℃, 600℃, 650℃, 700℃, 750℃, 800℃, or any value within the range of any two of the above values, and the time can be 10h, 11h, 12h, 13h, 14h, 15h, or any value within the range of any two of the above values. Controlling the temperature and time of the second sintering within the above range is beneficial for improving the uniformity of the coating and enhancing the adhesion between the first coating layer and the matrix material, thereby further improving the safety, conductivity, and capacity performance of the ternary cathode material.

[0063] Step S4: Spray the second coating material onto the surface of the intermediate material, mix and perform a third sintering, so that the second coating material forms a second coating layer on the surface of the first coating layer, thereby obtaining a ternary cathode material, wherein the second coating material includes a second solid electrolyte, a phosphate cathode material and a carbon source.

[0064] A second coating layer is formed on the surface of the first coating layer to obtain a ternary cathode material with a composite coating layer, further improving the thermal stability, capacity, and rate performance of the ternary cathode material. In the second coating material, the second solid electrolyte has excellent lithium-ion conductivity and low interfacial impedance, effectively improving the lithium-ion diffusion rate of the ternary cathode material, thereby enhancing its capacity and rate performance. The carbon source has good conductivity, effectively improving the electron diffusion rate of the ternary cathode material, further enhancing its capacity and rate performance. The phosphate cathode material has good thermal stability and safety, as well as high voltage performance, capable of withstanding voltages above 4.5V, effectively improving the thermal stability of the ternary cathode material.

[0065] In some embodiments, the second solid electrolyte may include at least one of lithium lanthanum zirconium tantalum oxide, lithium lanthanum zirconium niobium oxide, lithium lanthanum zirconium oxide, lithium lanthanum titanium oxide, lithium titanium aluminum phosphate, lithium niobate, lithium phosphate, and lithium borate.

[0066] The mass ratio of the intermediate material to the second solid electrolyte can be 1:(0.003~0.05), which is beneficial for improving the ionic conductivity of the ternary cathode material. For example, this mass ratio can be 1:0.003, 1:0.005, 1:0.007, 1:0.01, 1:0.02, 1:0.03, 1:0.05, or any value within the range of any two of the above values. This mass ratio can further be 1:(0.005~0.01).

[0067] In some embodiments, the phosphate cathode material may include at least one of lithium cobalt phosphate, lithium vanadium phosphate, lithium iron phosphate, and lithium nickel iron phosphate. All of the above phosphate cathode materials have good high voltage performance and can withstand voltages above 4.5V, effectively improving the thermal stability of ternary cathode materials.

[0068] The mass ratio of intermediate material to phosphate cathode material can be 1:(0.003~0.08), which is beneficial for the ternary cathode material to achieve both good thermal stability and capacity performance. For example, this mass ratio can be 1:0.003, 1:0.005, 1:0.01, 1:0.02, 1:0.03, 1:0.04, 1:0.05, 1:0.06, 1:0.07, 1:0.08, or any value within the range of any two of the above values. This mass ratio can further be 1:(0.005~0.03).

[0069] In some embodiments, the carbon source may include at least one of conductive carbon black, graphite, graphene, and carbon nanotubes, which have good conductivity and structural elasticity, and are beneficial to improving the overall conductivity and cycle stability of the ternary cathode material.

[0070] The mass ratio of intermediate materials to carbon source can be 1:(0.003~0.08), which is beneficial for ternary cathode materials to maintain both good conductivity and stability. For example, this mass ratio can be 1:0.003, 1:0.005, 1:0.01, 1:0.02, 1:0.03, 1:0.04, 1:0.05, 1:0.06, 1:0.07, 1:0.08, or any value within the range of any two of the above values. This mass ratio can further be 1:(0.003~0.02).

[0071] The second coating material is also coated by spray coating. Compared with dry mixing coating or wet grinding coating, spray coating can improve the uniformity of coating.

[0072] In some embodiments, the median particle size Dv50 of the second coating material can be 20 nm to 50 nm. A smaller particle size is beneficial for further improving the uniformity of the coating, forming a uniform, thin, and dense second coating layer. The median particle size Dv50 of the second coating material can, for example, be 20 nm, 25 nm, 30 nm, 35 nm, 37 nm, 40 nm, 42 nm, 45 nm, 46 nm, 50 nm, or any value within the range of any two of the above values. The median particle size Dv50 of the second coating material can further be 30 nm to 40 nm.

[0073] To control the median particle size (Dv50) of the second coating material within the range of 20 nm to 50 nm, grinding can be employed, specifically grinding with a sand mill and dispersing using ultrasound. It is understood that methods for controlling the median particle size of the first coating material include, but are not limited to, the methods described above.

[0074] After the intermediate material and the second coating material are mixed evenly, a third sintering is performed under an oxygen atmosphere. The temperature of the third sintering can be 300℃~450℃, and the time can be 10h~15h. For example, the temperature of the third sintering can be 300℃, 350℃, 400℃, 450℃, or any value within the range of any two of the above values, and the time can be 10h, 11h, 12h, 13h, 14h, 15h, or any value within the range of any two of the above values. Controlling the temperature and time of the third sintering within the above range is beneficial to improving the uniformity of the coating, thereby further improving the safety, conductivity, and capacity performance of the ternary cathode material.

[0075] Compared with existing technologies, the preparation method of the ternary cathode material in this application has the following advantages:

[0076] 1. By improving the structure of the nickel-cobalt-manganese (NiCoMn) precursor, dopants are used to form primary particles on the core surface, creating a radial structure and constructing a large number of uniformly distributed pores. This improves the uniformity of the lithiation reaction between the NiCoMn precursor and the lithium source, reducing cracking in the ternary cathode material caused by uneven lithiation and enhancing its stability and safety. Simultaneously, the dopant ions introduced into the NiCoMn precursor also improve the lattice parameters of the ternary cathode material, increasing its thermal runaway temperature and reducing heat release, thereby further enhancing its stability and safety.

[0077] 2. A composite coating layer containing a first coating layer and a second coating layer is formed on the surface of the substrate material: wherein, in the first coating layer, the first solid electrolyte and lithium cobalt oxide can improve the conductivity of the ternary cathode material, and the metal compound can improve the thermal stability of the ternary cathode material; in the second coating layer, the second solid electrolyte and carbon source can improve the conductivity of the ternary cathode material, and the phosphate cathode material can improve the thermal stability of the ternary cathode material.

[0078] 3. By modifying the structure and doping of nickel-cobalt-manganese precursors to improve the stability and safety of the matrix material, and then combining this with composite coating modification of the matrix material, the thermal stability, capacity and rate performance of the ternary cathode material are synergistically improved.

[0079] Based on the same inventive concept, this application also provides a ternary cathode material, which is prepared by the aforementioned preparation method. The ternary cathode material includes a matrix material, a first coating layer located on the surface of the matrix material, and a second coating layer located on the surface of the first coating layer away from the matrix material. The matrix material includes a ternary cathode active material, the first coating layer includes lithium cobalt oxide, a first solid electrolyte, and a metal compound, and the second coating layer includes a second solid electrolyte, a phosphate cathode material, and a carbon source.

[0080] Compared with existing technologies, the ternary cathode material of this application has both high capacity and high safety, as well as good rate performance and cycle stability.

[0081] This application also provides an electrochemical device (e.g., a secondary battery) that includes a positive electrode plate, the positive electrode plate including a positive electrode material, wherein the positive electrode material is the aforementioned ternary positive electrode material.

[0082] Compared with the prior art, the electrochemical device provided in this application has higher safety and higher capacity.

[0083] The present application's solution will be explained below with reference to embodiments. Those skilled in the art will understand that the following examples are for illustrative purposes only and should not be construed as limiting the scope of the application. Unless otherwise stated, reagents, software, and instruments involved in the following embodiments that are not specifically described are all conventional commercially available products or publicly disclosed.

[0084] Example 1

[0085] Step S1: Provide a doped and modified nickel-cobalt-manganese precursor, which includes a core and a shell layer on the surface of the core. The shell layer includes a plurality of primary particles containing doped ions, and the plurality of primary particles are radially stacked on the surface of the core in a direction away from the core. The preparation steps of this nickel-cobalt-manganese precursor include: mixing a mixed metal salt solution containing nickel, cobalt, and manganese, a precipitant sodium hydroxide, and a complexing agent ammonia to obtain a first slurry; performing a first-stage reaction to form a core, resulting in a slurry containing the core; adjusting the pH of the first slurry to 11.6~12.1 and the concentration of the complexing agent in the first slurry to 0.5mol / L~0.8mol / L during the first-stage reaction; adding a precipitant, a complexing agent, and a dopant containing doped ions to the first slurry containing the core to obtain a second slurry; and performing a second-stage reaction to form multiple primary particles containing doped ions on the surface of the core. These primary particles are radially arranged away from the core to form a shell on the surface of the core, resulting in a doped and modified nickel-cobalt-manganese precursor Ni with a Dv50 of 3.5μm. 0.6 Co 0.1 Mn 0.3(OH)₂ (doped ions not shown), where the dopant is a salt solution of the doped ion, and the doped ion is Al. 3+ Y 3+ Ti 4+ Mg 2+ Ta 5+ And Mo 6+ In the second stage reaction, the pH of the second slurry is 11.4~11.7, the concentration of the complexing agent in the second slurry is 0.3mol / L~0.5mol / L, and the mass ratio of each element in the nickel-cobalt-manganese precursor and dopant ions is 1:0.003.

[0086] Step S2: The nickel-cobalt-manganese precursor and lithium source lithium hydroxide are mixed evenly in a high-speed mixer at a ratio of Li:Me=1.05. The mixture is then pre-sintered in an air furnace at a temperature of 700°C for 12 hours. After being evenly dispersed in a mixer, the mixture is then sintered for the first time in an oxygen atmosphere in a kiln at a temperature of 1000°C for 18 hours to obtain the matrix material.

[0087] Step S3: The matrix material is mechanically pulverized using a high-speed airflow pulverizer. A first coating material with a Dv50 of 35 nm is sprayed onto the surface of the treated matrix material. The mixture is then homogenized using a high-speed mixer, dried, and placed in a crucible for a second sintering at 800°C for 12 hours under an oxygen atmosphere. This allows the first coating material to form a first coating layer on the surface of the matrix material, resulting in an intermediate material. The first coating material includes lithium cobalt oxide, lithium lanthanum zirconium tantalum oxide, lithium lanthanum zirconium niobium oxide, aluminum oxide, niobium oxide, magnesium oxide, and zirconium oxide. The mass ratio of the matrix material to each of the above materials in the first coating material is 1:0.005. Among them, lithium lanthanum zirconium tantalum oxide and lithium lanthanum zirconium niobium oxide are the first solid electrolytes, while aluminum oxide, niobium oxide, magnesium oxide, and zirconium oxide are metal compounds. The first coating material is ground using a sand mill and dispersed using ultrasound to control the particle size Dv50 to 35 nm.

[0088] Step S4: A second coating material with a Dv50 of 40 nm is sprayed onto the surface of the intermediate material. The mixture is then mixed evenly using a high-speed mixer. After drying, the mixture is placed in a crucible and sintered for 12 hours at 210°C under an oxygen atmosphere. This allows the second coating material to form a second coating layer on the surface of the first coating layer, resulting in a ternary cathode material. The second coating material includes lithium titanium aluminum phosphate, lithium phosphate, lithium iron vanadium phosphate, lithium nickel iron phosphate, and single-walled carbon nanotubes. The mass ratio of each of the above materials in the intermediate material to the second coating material is 1:0.005. Among them, lithium titanium aluminum phosphate and lithium phosphate are the second solid electrolyte, lithium iron vanadium phosphate and lithium nickel iron phosphate are phosphate cathode materials, and single-walled carbon nanotubes are the carbon source. The second coating material is ground using a sand mill and dispersed using ultrasound to control the particle size Dv50 to 40 nm.

[0089] Example 2:

[0090] Step S1: Provide a doped and modified nickel-cobalt-manganese precursor, which includes a core and a shell layer on the surface of the core. The shell layer includes a plurality of primary particles containing doped ions, and the plurality of primary particles are radially stacked on the surface of the core in a direction away from the core. The preparation steps of this nickel-cobalt-manganese precursor include: mixing a mixed metal salt solution containing nickel, cobalt, and manganese, a precipitant sodium hydroxide, and a complexing agent ammonia to obtain a first slurry; performing a first-stage reaction to form a core, resulting in a slurry containing the core; adjusting the pH of the first slurry to 11.6~12.1 and the concentration of the complexing agent in the first slurry to 0.5mol / L~0.8mol / L during the first-stage reaction; adding a precipitant, a complexing agent, and a dopant containing doped ions to the first slurry containing the core to obtain a second slurry; and performing a second-stage reaction to form multiple primary particles containing doped ions on the surface of the core. These primary particles are radially arranged away from the core to form a shell on the surface of the core, resulting in a doped and modified nickel-cobalt-manganese precursor Ni with a Dv50 of 3.5μm. 0.75 Co 0.1 Mn 0.15 (OH)₂ (doped ions not shown), where the dopant is a salt solution of the doped ion, and the doped ion is Al. 3+ Y 3+ Ti 4+ Mg 2+ Ta 5+ And Mo 6+ In the second stage reaction, the pH of the second slurry is 11.4~11.7, the concentration of the complexing agent in the second slurry is 0.3mol / L~0.5mol / L, and the mass ratio of each element in the nickel-cobalt-manganese precursor and dopant ions is 1:0.003.

[0091] Step S2: The nickel-cobalt-manganese precursor and lithium source lithium hydroxide are mixed evenly in a high-speed mixer at a ratio of Li:Me=1.05. The mixture is then pre-sintered in an air furnace at a temperature of 700°C for 12 hours. After being evenly dispersed in a mixer, the mixture is then sintered for the first time in an oxygen atmosphere in a kiln at a temperature of 890°C for 18 hours to obtain the matrix material.

[0092] Step S3: The matrix material is mechanically pulverized using a high-speed airflow pulverizer. A first coating material with a Dv50 of 35 nm is sprayed onto the surface of the treated matrix material. The mixture is then homogenized using a high-speed mixer, dried, and placed in a crucible for a second sintering at 700°C for 12 hours under an oxygen atmosphere. This allows the first coating material to form a first coating layer on the surface of the matrix material, resulting in an intermediate material. The first coating material includes lithium cobalt oxide, lithium lanthanum zirconium tantalum oxide, lithium lanthanum zirconium niobium oxide, aluminum oxide, niobium oxide, magnesium oxide, and zirconium oxide. The mass ratio of the matrix material to each of the above materials in the first coating material is 1:0.005. Among them, lithium lanthanum zirconium tantalum oxide and lithium lanthanum zirconium niobium oxide are the first solid electrolytes, while aluminum oxide, niobium oxide, magnesium oxide, and zirconium oxide are metal compounds. The first coating material is ground using a sand mill and dispersed using ultrasound to control the particle size Dv50 to 35 nm.

[0093] Step S4: Spray a second coating material with a Dv50 of 30 nm onto the surface of the intermediate material, mix it evenly using a high-speed mixer, remove and dry it, and place it in a crucible for a second sintering at 310°C for 12 hours under an oxygen atmosphere. This allows the second coating material to form a second coating layer on the surface of the first coating layer, resulting in a ternary cathode material. The second coating material includes lithium titanium aluminum phosphate, lithium phosphate, lithium iron vanadium phosphate, lithium nickel iron phosphate, and single-walled carbon nanotubes. The mass ratio of each of the above materials in the intermediate material and the second coating material is 1:0.005. Among them, lithium titanium aluminum phosphate and lithium phosphate are the second solid electrolyte, lithium iron vanadium phosphate and lithium nickel iron phosphate are phosphate cathode materials, and single-walled carbon nanotubes are the carbon source. The second coating material is ground using a sand mill and dispersed using ultrasound to control the particle size Dv50 to 30 nm.

[0094] Comparative Example 1:

[0095] Step S1: Provide a nickel-cobalt-manganese precursor. The preparation steps of the nickel-cobalt-manganese precursor include: mixing a mixed metal salt solution containing nickel, cobalt, and manganese, a precipitant sodium hydroxide, and a complexing agent ammonia to obtain a first slurry; performing a first-stage reaction to form a core, obtaining a slurry containing the core; in the first-stage reaction, adjusting the pH of the first slurry to 11.6~12.1, and the concentration of the complexing agent in the first slurry to 0.5mol / L~0.8mol / L; continuing to add a precipitant and a complexing agent to the first slurry containing the core to obtain a second slurry; performing a second-stage reaction to obtain a nickel-cobalt-manganese precursor Ni with a Dv50 of 3.5μm. 0.6 Co 0.1 Mn 0.3 In the second stage reaction, the pH of the second slurry is 11.4~11.7, and the concentration of the complexing agent in the second slurry is 0.3mol / L~0.5mol / L.

[0096] Step S2: The nickel-cobalt-manganese precursor, lithium hydroxide source, and dopant are added to a high-speed mixer and mixed evenly. The nickel-cobalt-manganese precursor and lithium hydroxide are mixed at a ratio of Li:Me = 1.05. The dopant is a salt solution of dopant ions, and the dopant ion is Al. 3+ Y 3+ Ti 4+ Mg 2+ Ta 5+ And Mo 6+ The mass ratio of each element in the nickel-cobalt-manganese precursor and dopant ions is 1:0.003. After mixing, the mixture is first pre-sintered in an air furnace at 700℃ for 12 hours. Then, it is dispersed evenly in a mixer and subjected to a first sintering in an oxygen atmosphere in a kiln at 1000℃ for 18 hours to obtain the matrix material.

[0097] Step S3: The matrix material is mechanically pulverized using a high-speed airflow pulverizer. The first coating material is added to the treated matrix material and mixed evenly using a high-speed mixer. After drying, the material is placed in a crucible and sintered for 12 hours at 800°C under an oxygen atmosphere. This allows the first coating material to form a first coating layer on the surface of the matrix material, resulting in an intermediate material. The first coating material includes alumina, niobium oxide, magnesium oxide, and zirconium oxide. The mass ratio of each of the above materials in the matrix material to the first coating material is 1:0.005.

[0098] Step S4: Add the second coating material to the intermediate material, mix it evenly with a high-speed mixer, take it out and dry it, and place it in a crucible for a second sintering at 350°C for 12 hours under an oxygen atmosphere, so that the second coating material forms a second coating layer on the surface of the first coating layer, and obtain a ternary cathode material. The second coating material includes lithium cobalt oxide, aluminum oxide, niobium oxide, magnesium oxide and zirconium oxide. The mass ratio of the above materials in the intermediate material and the second coating material is 1:0.005.

[0099] Comparative Example 2:

[0100] Step S1: Provide a nickel-cobalt-manganese precursor. The preparation steps of the nickel-cobalt-manganese precursor include: mixing a mixed metal salt solution containing nickel, cobalt, and manganese, a precipitant sodium hydroxide, and a complexing agent ammonia to obtain a first slurry; performing a first-stage reaction to form a core, obtaining a slurry containing the core; in the first-stage reaction, adjusting the pH of the first slurry to 11.6~12.1, and the concentration of the complexing agent in the first slurry to 0.5mol / L~0.8mol / L; continuing to add a precipitant and a complexing agent to the first slurry containing the core to obtain a second slurry; performing a second-stage reaction to obtain a nickel-cobalt-manganese precursor Ni with a Dv50 of 3.5μm. 0.75 Co 0.1 Mn 0.15In the second stage reaction, the pH of the second slurry is 11.4~11.7, and the concentration of the complexing agent in the second slurry is 0.3mol / L~0.5mol / L.

[0101] Step S2: The nickel-cobalt-manganese precursor, lithium hydroxide source, and dopant are added to a high-speed mixer and mixed evenly. The nickel-cobalt-manganese precursor and lithium hydroxide are mixed at a ratio of Li:Me = 1.05. The dopant is a salt solution of dopant ions, and the dopant ion is Al. 3+ Y 3+ Ti 4+ Mg 2+ Ta 5+ And Mo 6+ The mass ratio of each element in the nickel-cobalt-manganese precursor and dopant ions is 1:0.003. After mixing, the mixture is first pre-sintered in an air furnace at 700℃ for 12 hours. Then, it is dispersed evenly in a mixer and subjected to a first sintering in an oxygen atmosphere in a kiln at 890℃ for 18 hours to obtain the matrix material.

[0102] Step S3: The matrix material is mechanically pulverized using a high-speed airflow pulverizer. The first coating material is added to the treated matrix material and mixed evenly using a high-speed mixer. After drying, the material is placed in a crucible and sintered for 12 hours at 700°C under an oxygen atmosphere. This allows the first coating material to form a first coating layer on the surface of the matrix material, resulting in an intermediate material. The first coating material includes alumina, niobium oxide, magnesium oxide, and zirconium oxide. The mass ratio of each of the above materials in the matrix material to the first coating material is 1:0.005.

[0103] Step S4: Add the second coating material to the intermediate material, mix it evenly with a high-speed mixer, take it out and dry it, and place it in a crucible for a second sintering at 350°C for 12 hours under an oxygen atmosphere, so that the second coating material forms a second coating layer on the surface of the first coating layer, and obtain a ternary cathode material. The second coating material includes lithium cobalt oxide, aluminum oxide, niobium oxide, magnesium oxide and zirconium oxide. The mass ratio of the above materials in the intermediate material and the second coating material is 1:0.005.

[0104] The following tests were conducted on the ternary cathode materials obtained in Examples 1-2 and Comparative Examples 1-2, and the batteries prepared from the ternary cathode materials.

[0105] 1. Scanning electron microscopy (SEM) test: Using a scanning electron microscope with high-resolution imaging capabilities, this type of instrument is used to observe the microscopic morphology and structural characteristics of materials.

[0106] 2. Particle size test: A Malvern 3000 particle size analyzer was used. After ultrasonic dispersion for 5 minutes, the particle size distribution was tested. Span is the width of the particle size distribution. Span = (Dv90-Dv10) / Dv50, which reflects the uniformity of particle size. The smaller the Span value (closer to 0), the more concentrated the particle size distribution and the better the particle uniformity.

[0107] 3. Specific surface area test: Using the nitrogen adsorption-desorption method, at liquid nitrogen temperature, the equilibrium adsorption amount of nitrogen on the surface of an object is related to its specific surface area and other characteristics. Combined with the law of the change of adsorption amount with relative pressure during the adsorption process, the specific surface area can be tested.

[0108] 4. Electrochemical performance testing:

[0109] Battery preparation: Ternary cathode material, conductive agent SP and binder PVDF are mixed evenly in a mass ratio of 90:5:5, and then subjected to slurry drawing, electrode coating, cutting, stamping and drying in sequence to assemble into a soft pack battery, wherein the lithium metal sheet is the negative electrode.

[0110] First-time efficiency and first-discharge specific capacity tests: The LAND battery testing system was used for constant current charge-discharge tests. During the test, the operating voltage range for the first-discharge capacity test was 2.8V~4.4V, the temperature was 25℃, and the charge-discharge rates were +0.1C / -0.1C, +0.33C / -0.33C, +0.5C / -0.5C, +1C / -1C, and +1C / -2C. The CV cutoff current was 0.01C. The first-time efficiency (fixed-capacity discharge specific capacity / total charge specific capacity) and the first-discharge specific capacity of the battery prepared by the ternary cathode material were measured.

[0111] High-temperature cycle performance test: The soft-pack battery was subjected to 1C / 1C charge-discharge cycles in a 45℃ constant temperature chamber. The cycle test range was 3%-97% SOC and the voltage range was 2.75-4.4V.

[0112] DC internal resistance (DCR) test: After calibrating the capacity at 25℃, the coin cell was intermittently discharged at a constant current of 155mA at 10℃ with a test interval of 10% SOC. The discharge time was 20 minutes, followed by a 5-minute rest. The voltage drop ΔU between the battery voltage before the discharge stopped and the battery voltage after the battery voltage stabilized, as well as the discharge current, were recorded. Then, the DC internal resistance was calculated using the formula R=ΔU / I (where: ΔU is the voltage difference, R is the DC resistance, and I is the discharge current) to obtain the DCR value.

[0113] 5. Thermogravimetric analysis (DSC) test: Differential scanning calorimetry is used to detect the effect of the battery positive electrode at 97% SOC at high temperature. The heat release curve of the positive electrode is measured, and the heat release and thermal runaway peak temperature are recorded to determine the thermal stability of the battery positive electrode material.

[0114] The test results of Examples 1-2 and Comparative Examples 1-2 are shown in Table 1 and 2. Figures 2 to 8 As shown.

[0115] Table 1

[0116]

[0117] The above results indicate that:

[0118] Figure 2 The image shows the SEM image of the nickel-cobalt-manganese precursor of Example 1. The core has a disordered structure, and the surface of the core forms a shell layer in which the particles are arranged radially outward. The nickel-cobalt-manganese precursor with a radial structure has more uniform lithium salt penetration in the first sintering, which can reduce the risk of cracking of the ternary cathode material after long-term cycling due to uneven lithiation. In combination with the dopants uniformly distributed in the nickel-cobalt-manganese precursor, the stability of the ternary cathode material can be effectively improved, the temperature at which thermal runaway occurs can be effectively increased, and the heat release can be reduced.

[0119] Figures 3 to 6 The images show SEM images of the ternary cathode materials from Examples 1, 2, 1 (Comparative Example), and 2 (Comparative Example 2). As can be seen from the images, the ternary cathode materials from Examples 1 and 2 are smooth single-crystal particles with relatively uniform coating. In contrast, the ternary cathode materials from Comparative Example 1 and 2 have rougher surfaces and poorer coating uniformity. This indicates that the spray coating method used in this application can effectively improve the coating effect.

[0120] Based on the analysis in Table 1, the pouch battery made with the ternary cathode material in Example 1 has an initial discharge specific capacity of 197.4 mAh / g, an initial efficiency of 91.55%, and a capacity of 174.5 mAh / g at 2C current. Comparative Example 1 uses a typical conventional 6-series nickel-based high-voltage ternary cathode material, with an initial discharge specific capacity of 195.7 mAh / g, an initial efficiency of 89.44%, and a capacity of 170.3 mAh / g at 2C current. The initial efficiency and capacity of Example 1 are both higher than those of Comparative Example 1. The pouch battery made with the ternary cathode material in Example 2 has an initial discharge specific capacity of 221.3 mAh / g (0.1C / 0.1C), an initial efficiency of 91.1%, and a capacity of 197.3 mAh / g at 2C current. Comparative Example 2 is a typical conventional 7-series nickel-based high-voltage ternary cathode material, with an initial discharge specific capacity of 220 mAh / g, an initial efficiency of 89.05%, and a capacity of 193.7 mAh / g at 2C current. Example 2 exhibits higher initial efficiency and capacity than Comparative Example 2. The results show that, under the same nickel-cobalt-manganese ratio, Examples 1-2 demonstrate superior initial capacity and rate performance compared to Comparative Examples 1-2.

[0121] Figure 7The results show the high-temperature cycling performance of Examples 1-2 and Comparative Examples 1-2. The results show that, under the same nickel-cobalt-manganese ratio, the high-temperature cycling performance of Examples 1-2 is better than that of Comparative Examples 1-2.

[0122] Figure 8 The results of thermal stability tests for Examples 1-2 and Comparative Examples 1-2 show that, under the same nickel-cobalt-manganese ratio, Examples 1-2 have a higher thermal runaway initiation temperature and are less prone to thermal runaway than Comparative Examples 1-2, thus exhibiting better safety.

[0123] It is understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of the present invention, and the present invention is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A method for preparing a ternary cathode material, characterized in that, include: A doped and modified nickel-cobalt-manganese precursor is provided, the nickel-cobalt-manganese precursor comprising a core and a shell layer located on the surface of the core, the shell layer comprising a plurality of primary particles containing dopant ions, the plurality of primary particles being radially stacked on the surface of the core in a direction away from the core; The nickel-cobalt-manganese precursor and lithium source are mixed and subjected to a first sintering to obtain the matrix material; A first coating material is sprayed onto the surface of the substrate material, mixed, and then sintered a second time to form a first coating layer on the surface of the substrate material, resulting in an intermediate material. The first coating material comprises lithium cobalt oxide, a first solid electrolyte, and a metal compound. A second coating material is sprayed onto the surface of the intermediate material, mixed, and sintered a third time to form a second coating layer on the surface of the first coating layer, thereby obtaining the ternary cathode material. The second coating material includes a second solid electrolyte, a phosphate cathode material, and a carbon source.

2. The preparation method according to claim 1, characterized in that, The preparation method of the nickel-cobalt-manganese precursor includes: A mixed metal salt solution containing nickel, cobalt, and manganese, a precipitant, and a complexing agent are mixed and subjected to a first-stage reaction to form a core, resulting in a first slurry containing the core; and A precipitant, a complexing agent, and a dopant containing the doped ions are added to the first slurry to obtain a second slurry. The second slurry undergoes a second-stage reaction to radially deposit multiple primary particles containing doped ions on the surface of the core in a direction away from the core, thereby forming a shell on the surface of the core to obtain the doped modified nickel-cobalt-manganese precursor.

3. The preparation method according to claim 2, characterized in that, The doping ions include Mg 2+ Ca 2+ 、Sr 2+ Ba 2+ Cu 2+ Zn 2+ Al 3+ Y 3+ Ga 3+ 、Ge 4+ Se 4+ Sn 4+ Zr 4+ Ti 4+ 、Nb 5+ V 5+ Ta 5+ P 5+ F - Mo 6+ and W 6+ At least one of them; and / or In the nickel-cobalt-manganese precursor, the mass ratio of the nickel-cobalt-manganese precursor to each element in the dopant ion is 1:(0.0005~0.008).

4. The preparation method according to claim 2, characterized in that, In the first stage of the reaction, the pH of the first slurry is adjusted to 11.6~12.1, and the concentration of the complexing agent in the first slurry is adjusted to 0.5mol / L~0.8mol / L; and / or In the second stage reaction, the pH of the second slurry is adjusted to 11.4~11.7, and the concentration of the complexing agent in the second slurry is adjusted to 0.3mol / L~0.5mol / L.

5. The preparation method according to claim 1, characterized in that, The median particle size Dv50 of the first coated material is 20nm~50nm; and / or The median particle size Dv50 of the second coating material is 20nm~50nm.

6. The preparation method according to claim 1, characterized in that, The first solid electrolyte comprises at least one of lithium lanthanum zirconium tantalum oxide, lithium lanthanum zirconium niobium oxide, lithium lanthanum zirconium oxide, lithium lanthanum titanium oxide, lithium titanium aluminum phosphate, lithium niobate, lithium phosphate, and lithium borate; and / or The metal compound contains metal ions, including Mg. 2+ Ca 2+ 、Sr 2+ Ba 2+ Cu 2+ Zn 2+ Al 3 + Y 3+ Ga 3+ 、Ge 4+ Se 4+ Sn 4+ Zr 4+ Ti 4+ 、Nb 5+ V 5+ Ta 5+ Mo 6+ and W 6+ At least one of them.

7. The preparation method according to claim 6, characterized in that, The metal compound also contains non-metal ions, including P. 5+ and F - At least one of them.

8. The preparation method according to claim 1, characterized in that, The second solid electrolyte includes at least one of lithium lanthanum zirconium tantalum oxide, lithium lanthanum zirconium niobium oxide, lithium lanthanum zirconium oxide, lithium lanthanum titanium oxide, lithium titanium aluminum phosphate, lithium niobate, lithium phosphate, and lithium borate; and / or The phosphate cathode material includes at least one of lithium cobalt phosphate, lithium vanadium phosphate, lithium iron phosphate, and lithium nickel iron phosphate; and / or The carbon source includes at least one of conductive carbon black, graphite, graphene, and carbon nanotubes.

9. A ternary cathode material, characterized in that, The ternary cathode material is prepared by any one of claims 1 to 8. The ternary cathode material includes a matrix material, a first coating layer located on the surface of the matrix material, and a second coating layer located on the surface of the first coating layer. The matrix material includes a ternary cathode active material. The first coating layer includes lithium cobalt oxide, a first solid electrolyte, and a metal compound. The second coating layer includes a second solid electrolyte, a phosphate cathode material, and a carbon source.

10. An electrochemical device, characterized in that, The electrochemical device includes a positive electrode plate, the positive electrode plate includes a positive electrode material, and the positive electrode material is the ternary positive electrode material as described in claim 9.

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