Ternary positive electrode material, preparation method thereof and electrochemical device

Abstract

The invention provides a ternary positive electrode material, a preparation method thereof and an electrochemical device. The chemical general formula of the ternary positive electrode material is LiNixCoyAzMwO2, the element A is at least one of Mn and Al, the element M comprises Nb < 5 + >, Ta < 5 + > and Mo < 6 + >, x is larger than or equal to 0.6 and smaller than or equal to 0.8, y is larger than or equal to 0.05 and smaller than or equal to 0.2, z is larger than or equal to 0.05 and smaller than or equal to 0.2, and w is larger than or equal to 0.005 and smaller than or equal to 0.03. According to the ternary positive electrode material disclosed by the invention, Li < + > / Ni < 2 + > mixed arrangement in the ternary positive electrode material can be inhibited through multi-element synergistic doping, a crystal layered structure is stabilized, the electronic conductivity is improved, and the thermal decomposition temperature of the ternary positive electrode material is improved, so that the structural stability, the thermal safety and the conductivity of the ternary positive electrode material are synchronously improved; and the balance of high capacity, long circulation and high safety of the ternary positive electrode material is realized.

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] Ternary cathode material (LiNi) x Co y Mn Z O2 (x+y+z=1) has become a core material for power batteries due to its high specific capacity. Among them, the medium-nickel ternary cathode material (x≥0.6) has attracted widespread attention due to its high energy density.

[0003] However, the poor structural stability and insufficient thermal safety of ternary cathode materials limit their widespread application. 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 ternary cathode material.

[0005] In addition, this application also provides a method for preparing a ternary cathode material and an electrochemical device.

[0006] In a first aspect, embodiments of this application provide a ternary cathode material, wherein the general chemical formula of the ternary cathode material is LiNi. x Co y A z M w O2, wherein element A is at least one of Mn and Al, and element M includes Nb. 5+ Ta 5+ And Mo 6+ , 0.6≤x≤0.8, 0.05≤y≤0.2, 0.05≤z≤0.2, 0.005≤w≤0.03.

[0007] Based on the first aspect, in some possible embodiments, the M element is Nb 5+ Ta 5+ And Mo 6+ The combination of .

[0008] Based on the first aspect, in some possible embodiments, in the M element, Nb 5+ Ta 5+ And Mo 6+ The molar ratio is (0.5~2):(0.5~2):(0.3~1).

[0009] Based on the first aspect, in some possible embodiments, in the M element, Nb 5+ Ta5+ And Mo 6+ The molar ratio is (1~2):(1~2):(0.5~1).

[0010] Based on the first aspect, in some possible embodiments, in the M element, Nb 5+ Ta 5+ And Mo 6+ The molar ratio is 1:1:0.5.

[0011] Secondly, this application provides a method for preparing a ternary cathode material, comprising: dissolving a lithium source, a nickel source, a cobalt source, an A source, and an M source in a solvent in a certain proportion to obtain a precursor solution, wherein the A source contains at least one of Mn and Al, and the M source contains Nb. 5+ Ta 5+ And Mo 6+ A complexing agent is added to the precursor solution and stirred to obtain a sol; the sol is then dried and sintered to obtain the ternary cathode material, the chemical formula of which is LiNi. x Co y A z M w O2, where 0.6≤x≤0.8, 0.05≤y≤0.2, 0.05≤z≤0.2, and 0.005≤w≤0.03.

[0012] Based on the second aspect, in some possible embodiments, the M source consists of an Nb source, a Ta source, and a Mo source.

[0013] Based on the second aspect, in some possible embodiments, in the M source, Nb 5+ Ta 5+ And Mo 6+ The molar ratio is (0.5~2):(0.5~2):(0.3~1).

[0014] Based on the second aspect, in some possible embodiments, the sintering includes pre-sintering and formal sintering.

[0015] Based on the second aspect, in some possible embodiments, the pre-sintering temperature is 450℃~500℃, and the pre-sintering time is 3h~5h; the formal sintering temperature is 750℃~850℃, and the formal sintering time is 8h~12h.

[0016] Based on the second aspect, in some possible embodiments, the pH of the stirring is 4.5 to 5.5, the stirring temperature is 60°C to 70°C, and the stirring time is 2 to 4 hours.

[0017] 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 or a ternary positive electrode material prepared by the aforementioned preparation method.

[0018] Compared to existing technologies, the ternary cathode material provided in this application, through Nb 5+ Ta 5+ And Mo 6+ Multi-element synergistic doping, with the total amount of composite element doping controlled between 0.005 and 0.03, can suppress Li in ternary cathode materials. + / Ni 2+ Mixed arrangement stabilizes the layered crystal structure, improves electronic conductivity, and increases the thermal decomposition temperature of ternary cathode materials. This leads to a simultaneous improvement in the structural stability, thermal safety, and conductivity of ternary cathode materials, achieving a balance between "high capacity, long cycle life, and high safety" in ternary cathode materials. Attached Figure Description

[0019] Figure 1 This is a process flow diagram of the preparation method of the ternary cathode material provided in an embodiment of this application. Detailed Implementation

[0020] 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.

[0021] This study found that as the nickel content increases, the Li in the ternary cathode material... + / Ni 2+ The mixing of materials intensifies, and the layered structure is prone to transforming into the spinel / rock salt phase during cycling, leading to rapid capacity decay. Furthermore, the ternary cathode material reacts violently with the electrolyte during charging, resulting in a low thermal decomposition temperature and a high risk of thermal runaway. Existing technologies often employ single-element doping to improve these defects in ternary cathode materials; however, this only improves a single property and makes it difficult to simultaneously optimize multiple properties of ternary cathode materials.

[0022] Therefore, embodiments of this application provide a ternary cathode material with the general chemical formula LiNi. x Co y Az M w O2, wherein element A is at least one of Mn and Al, and element M includes Nb. 5+ Ta 5+ And Mo 6+ , 0.6≤x≤0.8, 0.05≤y≤0.2, 0.05≤z≤0.2, 0.005≤w≤0.03. Through Nb 5+ Ta 5+ And Mo 6+ Multi-element synergistic doping, with the total amount of composite element doping controlled between 0.005 and 0.03, can suppress Li + / Ni 2+ Mixed arrangement stabilizes the layered structure, improves electronic conductivity, and increases the thermal decomposition temperature of ternary cathode materials. This leads to a simultaneous improvement in the structural stability, thermal safety, and conductivity of ternary cathode materials, achieving a balance between "high capacity, long cycle life, and high safety" in ternary cathode materials.

[0023] Nb 5+ The ionic radius of Ta is 0.64 Å. 5+ The ionic radius of Ni is 0.64 Å. 3+ The ionic radius of Nb is 0.60 Å. 5+ and Ta 5+ with Ni 3+ The ionic radii are close and the size matching is high, Nb 5+ and Ta 5+ They can be co-embedded in the ternary cathode material lattice to form strong MO bonds, suppressing Li + / Ni 2+ Mixing prevents the collapse of the layered structure, thereby improving the structural stability of the ternary cathode material.

[0024] Mo 6+ Having d 0 Electronic configuration, doped with Mo 6+ It can reduce the band gap of ternary cathode materials from 3.2 eV to 2.5 eV. The reduction in band gap is conducive to electron transition, thereby increasing the electronic conductivity of ternary cathode materials by 1-2 orders of magnitude. The rate performance of ternary cathode materials is also improved, with the capacity retention rate of ternary cathode materials at 10C rate increasing from 60% to over 85%.

[0025] Nb 5+ Ta 5+ And Mo 6+The composite doping forms a "lattice anchoring effect," which restricts the escape of lattice oxygen, thereby delaying the oxygen release of the charged ternary cathode material. This can increase the thermal decomposition temperature of the ternary cathode material from 210℃ to over 250℃, reduce the risk of thermal runaway by 40%, and thus enhance the thermal safety of the ternary cathode material.

[0026] Nb 5+ Ta 5+ And Mo 6+ Composite doping can also improve the cycle performance of ternary cathode materials through mechanisms such as suppressing crystal phase transitions, reducing crystal structure decay, reducing internal resistance and improving ionic conductivity. This allows the capacity retention rate of ternary cathode materials to increase from 80% to over 92% after 100 cycles at 1C rate, and the capacity retention rate to remain above about 85% after 500 cycles, thus extending the cycle life of ternary cathode materials.

[0027] Nb 5+ Ta 5+ And Mo 6+ Appropriate composite doping has enabled the simultaneous improvement of the structural stability, thermal safety, conductivity and cycle performance of ternary cathode materials, providing a feasible solution for the industrialization of ternary cathode materials.

[0028] In some embodiments, the M element can be Nb 5+ Ta 5+ And Mo 6+ Compared to single / dual element doping, the ternary cathode material of this application can simultaneously improve multiple performance aspects. Compared to doping with simple listing and random combination of multiple elements, the random combination cannot predict the specific synergistic effect between different elements, and may lead to performance degradation due to mutual constraints between elements. However, the ternary cathode material of this application has a reasonable combination of doping elements to construct a multi-level and multi-functional doping system. This fixed combination method can achieve the simultaneous improvement of structural stability, thermal safety, conductivity and cycle performance of ternary cathode material without introducing other doping elements, achieving a synergistic effect of "1+1+1>3".

[0029] In some embodiments, in the M element, Nb 5+ Ta 5+ And Mo 6+ The molar ratio can be (0.5~2):(0.5~2):(0.3~1), and this application limits Nb 5+ Ta 5+ And Mo 6+A molar ratio satisfying the aforementioned suitable range is beneficial for achieving a synergistic improvement in the bulk structure, electrochemical performance, and interfacial stability of ternary cathode materials. This better addresses the pain points of cycle degradation and poor thermal safety caused by high-voltage operation, and further enhances the functional complementarity and synergistic effect among the doping elements. Examples of such molar ratios include 0.5:05:0.3, 0.5:0.5:0.6, 0.5:0.5:0.7, 0.5:0.5:0.8, 0.5:0.5:0.9, 0.5:0.5:1, 1:1:0.5, 1:1:0.8, 1:1:1, 1:1.2:0.5, 1:1.2:0.8, 1:1.2:1, 1:1.5:0.5, 1:1.5:0.8, 1:1.5:1, and 1:2: 0.5, 1:2:0.8, 1:2:1, 1.2:1:0.5, 1.2:1:0.8, 1.2:1:1, 1.2:1.2:0.5, 1.2:1.2:0.8, 1.2:1.2:1, 1.2:1.5:0.5, 1.2:1.5:0.8, 1.2:1.5:1, 1.2:2:0.5, 1.2:2:0.8, 1.2:2:1, 1.5:1:0.5, 1.5:1:0.8 1.5:1:1, 1.5:1.2:0.5, 1.5:1.2:0.8, 1.5:1.2:1, 1.5:1.5:0.5, 1.5:1.5:0.8, 1.5:1.5:1, 1.5:2:0.5, 1.5:2:0.8, 1.5:2:1, 2:1:0.5, 2:1:0.8, 2:1:1, 2:1.2:0.5, 2:1.2:0.8, 2:1.2:1, 2:1.5:0.5, 2:1.5:0.8, 2:1.5:1, 2:2:0.5, 2:2:0.8, or any value within the range (1~2):(1~2):(0.5~1). In the M element, Nb 5+ Ta 5+ And Mo 6+ The molar ratio can be (1~2):(1~2):(0.5~1). This molar ratio can further be 1:1:0.5.

[0030] Please see Figure 1 As shown, based on the same inventive concept, this application also provides a method for preparing a ternary cathode material, specifically including the following steps: Step S1: Dissolve lithium source, nickel source, cobalt source, A source and M source in a solvent in a certain proportion to obtain a precursor solution, wherein the A source contains at least one of Mn and Al, and the M source contains Nb. 5+ Ta 5+ And Mo 6+ .

[0031] Specifically, lithium source, nickel source, cobalt source, and A source are dissolved in a solvent (e.g., deionized water) and stirred until transparent. Then, source M is added and mixed thoroughly to obtain a precursor solution, wherein source M contains Nb. 5+ Ta 5+ And Mo 6+ The amount of each metal source is added according to the chemical formula of the target ternary cathode material.

[0032] In some embodiments, the M source comprises an Nb source, a Ta source, and a Mo source. The Nb source may include at least one of niobium pentachloride, niobium pentoxide, niobium carbide, and ammonium niobium oxalate; the Ta source may include at least one of tantalum pentoxide, tantalum pentachloride, tantalum carbide, and ammonium tantalum oxalate, and the tantalum source may be first dissolved in hydrofluoric acid before use; the Mo source may include at least one of ammonium molybdate, molybdenum trioxide, molybdenum pentachloride, and molybdenum carbide.

[0033] In some embodiments, in source M, Nb 5+ Ta 5+ And Mo 6+ The molar ratio can be (0.5~2):(0.5~2):(0.3~1), which can form the same doping element ratio in ternary cathode materials, further improving the functional complementarity and synergistic effect among the doping elements. In the M source, Nb 5+ Ta 5+ And Mo 6+ The molar ratio can be further expressed as (1~2):(1~2):(0.5~1). This molar ratio can be further expressed as 1:1:0.5.

[0034] In some embodiments, the total concentration of doped elements in the M source in the precursor solution can be 0.01 mol / L to 0.05 mol / L, which is beneficial for effective doping of nickel, cobalt, and manganese, and for adjusting the doped element content in the final ternary cathode material.

[0035] In some embodiments, the lithium source may include at least one of lithium nitrate, lithium hydroxide, and lithium carbonate.

[0036] In some embodiments, the nickel source may include at least one of nickel nitrate, nickel sulfate, and nickel chloride.

[0037] In some embodiments, the cobalt source may include at least one of cobalt nitrate, cobalt sulfate, and cobalt chloride.

[0038] Step S2: Add a complexing agent to the precursor solution and stir to obtain a sol.

[0039] Specifically, a complexing agent is added to the precursor solution and stirred to form a viscous sol, wherein the complexing agent can be citric acid.

[0040] In some embodiments, the pH during stirring can be 4.5 to 5.5, which is beneficial for maintaining the ionic state of the dopant elements, thereby forming a more uniform doping distribution in the ternary cathode material. The pH can exemplary be 4.5, 4.6, 4.7, 4.8, 4.9, 5.0, 5.1, 5.2, 5.3, 5.4, 5.5, or any value within the range of any two of the above values. The pH can be adjusted by adding an alkaline solution, which can be ammonia.

[0041] In some embodiments, the stirring temperature is 60℃~70℃ and the stirring time is 2h~4h. By adjusting the stirring temperature and time, it is beneficial to fully form a gel with uniform elements.

[0042] Step S3 involves drying and sintering the sol to obtain a ternary cathode material with the general chemical formula LiNi. x Co y A z M w O2, where 0.6≤x≤0.8, 0.05≤y≤0.2, 0.05≤z≤0.2, and 0.005≤w≤0.03.

[0043] Specifically, the sol is first dried in an oven or other drying device to remove impurities such as solvent and moisture, resulting in a dry gel. The dry gel is then sintered, naturally cooled, pulverized, and sieved to obtain a ternary cathode material.

[0044] In some embodiments, drying includes drying at 80°C to 100°C for 12-16 hours, which can slowly and uniformly remove moisture from the inside of the gel, helping the gel to form a more stable network structure, reducing cracks and shrinkage, and maintaining the uniformity of the gel.

[0045] In some embodiments, sintering includes pre-sintering and formal sintering, which is beneficial for doping elements (Nb). 5+ Ta 5+ And Mo 6 + The gel fully penetrates the ternary cathode material lattice and is evenly distributed within it. Furthermore, pre-sintering removes some residual organic impurities, promotes the initial sintering and densification of the dry gel, alleviates thermal stress and reduces cracks, and improves the mechanical strength of the ternary cathode material. Formal sintering then promotes grain growth and phase transformation through high temperature to form the ternary cathode material.

[0046] In some embodiments, pre-sintering includes holding at 450°C to 500°C in air for 3 to 5 hours. The pre-sintering temperature can, exemplarily, be 450°C, 460°C, 470°C, 480°C, 490°C, 500°C, or any value within the range of any two of the above values. The pre-sintering time can, exemplarily, be 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours, or any value within the range of any two of the above values. By controlling the pre-sintering temperature and time to meet the above ranges, this application facilitates further removal of organic impurities.

[0047] In some embodiments, the formal sintering includes holding at 750°C to 850°C for 8 to 12 hours in an oxygen atmosphere. The formal sintering temperature can, for example, be 750°C, 780°C, 800°C, 825°C, 850°C, or any value within the range of any two of the above values. The formal sintering time can, for example, be 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, or any value within the range of any two of the above values. This application, by controlling the formal sintering temperature and time to meet the above ranges, facilitates the formation of ternary cathode materials with uniform elemental distribution, high mechanical strength, and high crystallinity.

[0048] This application also provides an electrochemical device, which includes a positive electrode sheet, the positive electrode sheet including a positive electrode material, the positive electrode material being the aforementioned ternary positive electrode material or a ternary positive electrode material prepared by the aforementioned method. Compared with the prior art, the electrochemical device provided in this application has good capacity performance, cycle stability and thermal stability, achieving a multi-performance improvement of "high capacity-long cycle-high safety".

[0049] 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.

[0050] Example 1 Step S1: Dissolve 0.108 mol of lithium nitrate, 0.06 mol of nickel nitrate, 0.02 mol of cobalt nitrate, and 0.02 mol of manganese nitrate in 100 mL of deionized water. Add 0.0006 mol of niobium pentachloride, 0.0006 mol of tantalum pentoxide (dissolved in hydrofluoric acid), and 0.0003 mol of ammonium molybdate and stir until homogeneous to obtain the precursor solution. Nb 5+ Ta 5+ And Mo 6+ The total doping concentration is 1.5 mol%, Nb 5+ Ta 5+ Mo6+ The molar ratio is 1:1:0.5.

[0051] Step S2: Add 0.132 mol of citric acid to the precursor solution, adjust the pH to 5.0 with ammonia, and stir in a water bath at 65°C for 3 hours to obtain a sol.

[0052] Step S3: Dry the sol at 85°C for 14 hours, then pre-sinter it at 480°C in air for 4 hours, and finally sinter it at 800°C in oxygen for 10 hours to obtain the ternary cathode material.

[0053] Example 2: The difference from Example 1 is that in step S1, 0.108 mol of lithium nitrate, 0.06 mol of nickel nitrate, 0.02 mol of cobalt nitrate, and 0.02 mol of manganese nitrate are dissolved in 100 mL of deionized water. Then, 0.0012 mol of niobium pentachloride, 0.0006 mol of tantalum pentoxide (dissolved in hydrofluoric acid), and 0.0003 mol of ammonium molybdate are added and stirred until homogeneous to obtain a precursor solution. Nb 5+ Ta 5+ And Mo 6+ The total doping concentration is 2.1 mol%, Nb 5+ Ta 5+ Mo 6+ The molar ratio is 2:1:0.5. The preparation methods for the remaining ternary cathode materials are basically the same as in Example 1.

[0054] Example 3: The difference from Example 1 is that in step S1, 0.108 mol of lithium nitrate, 0.06 mol of nickel nitrate, 0.02 mol of cobalt nitrate, and 0.02 mol of manganese nitrate are dissolved in 100 mL of deionized water. Then, 0.0006 mol of niobium pentachloride, 0.0012 mol of tantalum pentoxide (dissolved in hydrofluoric acid), and 0.0003 mol of ammonium molybdate are added and stirred until homogeneous to obtain a precursor solution. Nb 5+ Ta 5+ And Mo 6+ The total doping concentration is 2.1 mol%, Nb 5+ Ta 5+ Mo 6+ The molar ratio is 1:2:0.5. The preparation methods for the remaining ternary cathode materials are basically the same as in Example 1.

[0055] Example 4: The difference from Example 1 is that in step S1, 0.108 mol of lithium nitrate, 0.06 mol of nickel nitrate, 0.02 mol of cobalt nitrate, and 0.02 mol of manganese nitrate are dissolved in 100 mL of deionized water. Then, 0.0003 mol of niobium pentachloride, 0.0006 mol of tantalum pentoxide (dissolved in hydrofluoric acid), and 0.0012 mol of ammonium molybdate are added and stirred until homogeneous to obtain a precursor solution. Nb 5+ Ta 5+ And Mo 6+ The total doping concentration is 2.1 mol%, Nb 5+ Ta 5+ Mo 6+ The molar ratio is 0.5:1:2. The preparation methods for the remaining ternary cathode materials are basically the same as in Example 1.

[0056] Example 5: The difference from Example 1 is that in step S1, 0.108 mol of lithium nitrate, 0.06 mol of nickel nitrate, 0.02 mol of cobalt nitrate, and 0.02 mol of manganese nitrate are dissolved in 100 mL of deionized water. Then, 0.0006 mol of niobium pentachloride, 0.0003 mol of tantalum pentoxide (dissolved in hydrofluoric acid), and 0.0012 mol of ammonium molybdate are added and stirred until homogeneous to obtain a precursor solution. Nb 5+ Ta 5+ And Mo 6+ The total doping concentration is 2.1 mol%, Nb 5+ Ta 5+ Mo 6+ The molar ratio is 1:0.5:2. The preparation methods for the remaining ternary cathode materials are basically the same as in Example 1.

[0057] Example 6: The difference from Example 1 is that in step S1, 0.108 mol of lithium nitrate, 0.06 mol of nickel nitrate, 0.02 mol of cobalt nitrate, and 0.02 mol of manganese nitrate are dissolved in 100 mL of deionized water. Then, 0.0006 mol of niobium pentachloride, 0.00048 mol of tantalum pentoxide (dissolved in hydrofluoric acid), and 0.00018 mol of ammonium molybdate are added and stirred until homogeneous to obtain a precursor solution. Nb 5+ Ta 5+ And Mo 6+ The total doping concentration is 1.26 mol%, Nb 5+ Ta 5+ Mo 6+ The molar ratio is 1:0.8:0.3. The preparation methods for the remaining ternary cathode materials are basically the same as in Example 1.

[0058] Example 7: The difference from Example 1 is that in step S1, 0.108 mol of lithium nitrate, 0.06 mol of nickel nitrate, 0.02 mol of cobalt nitrate, and 0.02 mol of manganese nitrate are dissolved in 100 mL of deionized water. Then, 0.001 mol of niobium pentachloride, 0.001 mol of tantalum pentoxide (dissolved in hydrofluoric acid), and 0.001 mol of ammonium molybdate are added and stirred until homogeneous to obtain a precursor solution. Nb 5+ Ta 5+ And Mo 6+ The total doping amount is 3 mol%, Nb 5+ Ta 5+ Mo 6+ The molar ratio is 1:1:1. The preparation methods of the remaining ternary cathode materials are basically the same as those in Example 1.

[0059] Example 8: The difference from Example 1 is that in step S1, 0.108 mol of lithium nitrate, 0.06 mol of nickel nitrate, 0.02 mol of cobalt nitrate, and 0.02 mol of manganese nitrate are dissolved in 100 mL of deionized water. Then, 0.0002 mol of niobium pentachloride, 0.0002 mol of tantalum pentoxide (dissolved in hydrofluoric acid), and 0.0001 mol of ammonium molybdate are added and stirred until homogeneous to obtain a precursor solution. Nb 5+ Ta 5+ And Mo 6+ The total doping amount is 0.5 mol%, Nb 5+ Ta 5+ Mo 6+ The molar ratio is 2:2:1. The preparation methods for the remaining ternary cathode materials are basically the same as in Example 1.

[0060] Comparative Example 1: The difference from Example 1 is that in step S1, only 0.108 mol of lithium nitrate, 0.06 mol of nickel nitrate, 0.02 mol of cobalt nitrate, and 0.02 mol of manganese nitrate are dissolved in 100 mL of deionized water to obtain the precursor solution, without adding source M. The preparation method of the remaining ternary cathode materials is basically the same as in Example 1.

[0061] Comparative Example 2: The difference from Example 1 is that in step S1, 0.108 mol of lithium nitrate, 0.06 mol of nickel nitrate, 0.02 mol of cobalt nitrate, and 0.02 mol of manganese nitrate were dissolved in 100 mL of deionized water, and 0.0015 mol of niobium pentachloride was added and stirred until homogeneous to obtain a precursor solution. The preparation methods of the remaining ternary cathode materials are basically the same as in Example 1.

[0062] Comparative Example 3: The difference from Example 1 is that in step S1, 0.108 mol of lithium nitrate, 0.06 mol of nickel nitrate, 0.02 mol of cobalt nitrate, and 0.02 mol of manganese nitrate were dissolved in 100 mL of deionized water, and 0.0015 mol of tantalum pentoxide (dissolved in hydrofluoric acid) was added and stirred until homogeneous to obtain a precursor solution. The preparation methods of the remaining ternary cathode materials are basically the same as those in Example 1.

[0063] Comparative Example 4: The difference from Example 1 is that in step S1, 0.108 mol of lithium nitrate, 0.06 mol of nickel nitrate, 0.02 mol of cobalt nitrate, and 0.02 mol of manganese nitrate were dissolved in 100 mL of deionized water, and 0.0015 mol of ammonium molybdate was added and stirred until homogeneous to obtain a precursor solution. The preparation methods of the remaining ternary cathode materials are basically the same as those in Example 1.

[0064] The ternary cathode materials obtained in Examples 1-8 and Comparative Examples 1-4 were subjected to the following tests.

[0065] 1. Electrical performance testing: Preparation of button half-cells: Ternary cathode material, conductive agent acetylene black and binder PVDF are weighed according to a mass ratio of 96.5∶1.5∶2, coated and rolled cathode sheets, and button cells are assembled in an argon atmosphere glove box.

[0066] First discharge specific capacity test: Under normal temperature battery laboratory conditions, the coin cell was charged at a constant current of 0.1C to a voltage of 4.3V, then charged at a constant voltage of 4.3V to a current of 0.02C, left to stand for 5 minutes, and the charging capacity was recorded; then the coin cell was discharged at a constant current of 0.1C to a voltage of 2.8V, and the discharge capacity was recorded. The first discharge specific capacity at 0.1C was calculated.

[0067] Rate performance test: Under normal temperature conditions of 25℃, the battery working voltage range is set to 2.8V-4.4V. The battery is charged and discharged at 1C / 10C current for 5 cycles respectively. Finally, a long cycle is performed at 0.2C current. The rate performance of the battery at 10C is recorded. Rate performance = 10C discharge specific capacity / 0.1C discharge specific capacity × 100%.

[0068] Cyclic performance test: At 45℃, charge and discharge cycles were performed for 100 and 500 cycles according to the charge and discharge conditions of the first discharge specific capacity test. The capacity retention rate after cycling was calculated as: Capacity retention rate = Discharge specific capacity after cycling / First discharge specific capacity × 100%.

[0069] 2. Thermal decomposition temperature test: Thermogravimetric analysis is used to precisely control the temperature of the heated material and monitor the change in mass of the material during the heating process to obtain the thermogravimetric curve and determine the thermal decomposition temperature.

[0070] The parameters of Examples 1-8 and Comparative Examples 1-4 are shown in Table 1, and the test results are shown in Table 2.

[0071] Table 1 Table 2 The above results indicate that: As shown in Table 1, compared to Comparative Examples 1-4, the ternary cathode materials in Examples 1-8 are doped with Nb. 5+ Ta 5+ And Mo 6+ At that time, it can suppress Li in ternary cathode materials + / Ni 2+ By mixing and stabilizing the layered structure, improving electronic conductivity, and increasing the thermal decomposition temperature of the ternary cathode material, the structural stability, thermal safety, and conductivity of the ternary cathode material are simultaneously improved, resulting in electrochemical devices (batteries) with excellent capacity performance, cycle stability, rate performance, and thermal stability. Comparative Example 1, without doping, had an initial discharge specific capacity of only 190 mAh / g, and its capacity retention dropped to 79.8% after 100 high-temperature cycles. The thermal decomposition temperature of the ternary cathode material in Comparative Example 1 was only 208°C. Comparative Examples 2-4 were ternary cathode materials with single-doped metal elements, and their capacity performance, cycle stability, rate performance, and thermal stability were all lower than those of Examples 1-6.

[0072] As can be seen from Examples 1 to 6, when Nb 5+ Ta 5+ And Mo 6+ When the molar ratio satisfies (1~2):(1~2):(0.5~1), it is also beneficial to further improve the functional complementarity and synergistic effect among the dopants. Compared with Examples 4-6, the comprehensive performance of each ternary cathode material in Examples 1-3 is further improved, achieving a better balance of "high capacity-long cycle-high safety".

[0073] It is understood that the above embodiments are merely exemplary implementations 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 ternary cathode material, characterized in that, The general chemical formula of the ternary cathode material is LiNi. x Co y A z M w O2, wherein the element A is at least one of Mn and Al, and the element M includes Nb. 5+ Ta 5+ And Mo 6+ , 0.6≤x≤0.8, 0.05≤y≤0.2, 0.05≤z≤0.2, 0.005≤w≤0.

03.

2. The ternary cathode material as described in claim 1, characterized in that, The M element is Nb 5+ Ta 5+ And Mo 6+ The combination of .

3. The ternary cathode material as described in claim 1, characterized in that, In the M element, Nb 5+ Ta 5+ And Mo 6+ The molar ratio is (0.5~2):(0.5~2):(0.3~1).

4. The ternary cathode material as described in claim 1, characterized in that, In the M element, Nb 5+ Ta 5+ And Mo 6+ The molar ratio is (1~2):(1~2):(0.5~1).

5. The ternary cathode material as described in claim 1, characterized in that, In the M element, Nb 5+ Ta 5+ And Mo 6+ The molar ratio is 1:1:0.

5.

6. A method for preparing a ternary cathode material, characterized in that, include: A precursor solution is obtained by dissolving lithium, nickel, cobalt, A, and M sources in a solvent in a specific ratio, wherein the A source contains at least one of Mn and Al, and the M source contains Nb. 5+ Ta 5+ And Mo 6+ ; A complexing agent is added to the precursor solution and stirred to obtain a sol; and The sol is dried and sintered to obtain the ternary cathode material, the chemical formula of which is LiNi. x Co y A z M w O2, where 0.6≤x≤0.8, 0.05≤y≤0.2, 0.05≤z≤0.2, and 0.005≤w≤0.

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7. The preparation method according to claim 6, characterized in that, The M source consists of an Nb source, a Ta source, and a Mo source.

8. The preparation method according to claim 7, characterized in that, In the M source, Nb 5+ Ta 5+ And Mo 6+ The molar ratio is (0.5~2):(0.5~2):(0.3~1).

9. The preparation method according to claim 6, characterized in that, The sintering includes pre-sintering and formal sintering. The pre-sintering temperature is 450℃~500℃, and the pre-sintering time is 3h~5h. The formal sintering temperature is 750℃~850℃, and the formal sintering time is 8h~12h; and / or The pH of the stirring is 4.5~5.5, the stirring temperature is 60℃~70℃, and the stirring time is 2h~4h.

10. An electrochemical device, characterized in that, The electrochemical device includes a positive electrode plate, the positive electrode plate includes a positive electrode material, the positive electrode material is a ternary positive electrode material as described in any one of claims 1 to 5 or a ternary positive electrode material prepared by the preparation method as described in any one of claims 6 to 9.

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