Ternary positive electrode material, preparation method thereof and battery

Abstract

The invention provides a ternary positive electrode material, a preparation method thereof and a battery. The preparation method comprises the steps of pre-sintering, doping and mixing, primary sintering, secondary sintering and tertiary sintering. By introducing the dopant and optimizing the sintering process, the problems of wide product particle distribution, serious agglomeration and high metal ion dissolution rate in the traditional method are solved, and the consistency and stability of the material are improved. The ternary positive electrode material has excellent electrochemical performance, the 1C discharge capacity under 4.5 V high voltage can reach 195mAh / g, the 100-cycle cycle capacity retention ratio can exceed 90%, the energy density of the lithium ion battery is remarkably improved, the cycle life of the lithium ion battery is remarkably prolonged, and the problem that a traditional ternary positive electrode material is poor in cycle stability in practical application is solved.

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to a ternary cathode material, its preparation method, and a battery. Background Technology

[0002] Ternary cathode materials (such as NCM) have become key materials for power batteries due to their high specific capacity. Currently, the mainstream method used in the industry is the hydroxide coprecipitation method to prepare precursors, but this process requires real-time monitoring and control of the reaction pH and ammonia concentration, which is time-consuming and costly. In contrast, the carbonate coprecipitation method is simple and inexpensive, making it a highly promising alternative.

[0003] However, carbonate co-precipitation precursors are typically directly mixed with lithium salts and sintered, resulting in ternary cathode materials with severe agglomeration, poor dispersibility, high difficulty in subsequent fragmentation, and wide particle size distribution with poor uniformity. Furthermore, this material also suffers from high metal ion dissolution rates. While existing modification methods can improve metal dissolution to some extent, they may negatively impact the material's electrochemical performance. Summary of the Invention

[0004] In view of this, this application proposes a method for preparing ternary cathode materials to solve the problems of severe agglomeration, wide particle size distribution, high metal ion dissolution rate and poor electrical performance of existing ternary cathode materials prepared from carbonate coprecipitation precursors.

[0005] Furthermore, it is necessary to propose a ternary cathode material prepared by this preparation method and a battery including the ternary cathode material.

[0006] A method for preparing a ternary cathode material includes the following steps: pre-sintering: sintering a carbonate co-precipitation precursor at 500℃~800℃ for 5h~8h to obtain a pre-sintered product; doping and mixing: mixing and grinding the pre-sintered product, a lithium source, and a dopant to obtain a mixture; primary sintering: subjecting the mixture to stepwise heating sintering, first heating to 650℃~750℃ and holding for 3h~8h, then heating to 900℃~1000℃ and holding for 1h~3h, and then... The temperature is lowered to 650℃~750℃ and held for 3h~5h to obtain the primary sintering product; secondary sintering: the primary sintering product is mixed with the first coating agent, and then sintered at 700℃~800℃ for 7h~12h, and then the temperature is lowered to 400℃~500℃ and held for 3h~5h to obtain the secondary sintering product; tertiary sintering: the secondary sintering product is mixed with the second coating agent, and then sintered at 350℃~550℃ for 4h~8h to obtain the ternary cathode material.

[0007] In one embodiment, the dopant includes one or more of MoO3, B2O3, and V2O5, and the mass percentage of the dopant to the carbonate coprecipitation precursor is 0.03% to 0.3%.

[0008] In one embodiment, the first coating agent includes one or more of TiNbO7, Ti2Nb 10 O 29 、TiNb 24 O 62 、LiPON、Li7La3Zr2O 12 and the addition amount of the first coating agent is 0.05 wt.% to 0.5 wt.% of the primary sintered product.

[0009] In one embodiment, the second coating agent includes Al2O3 and / or ZrO2, and the addition amount of the second coating agent is 0.03 wt.% to 0.5 wt.% of the primary sintered product.

[0010] In one embodiment, in the primary sintering step, the first heating rate from room temperature to 650 °C to 750 °C is 3 °C / min to 5 °C / min, the second heating rate from 650 °C to 750 °C to 900 °C to 1000 °C is 3 °C / min to 10 °C / min, and the cooling rate from 900 °C to 1000 °C to 650 °C to 750 °C is 3 °C / min to 10 °C / min.

[0011] In one embodiment, in the secondary sintering step, the heating rate is 3 °C / min to 5 °C / min, and the cooling rate is 3 °C / min to 5 °C / min; in the tertiary sintering step, the heating rate is 3 °C / min to 5 °C / min.

[0012] A ternary cathode material includes a core and a composite coating layer covering the surface of the core. The chemical general formula of the core is LiNi x Co y Mn z M a O2, where x + y + z = 1, 0.5 ≤ x ≤ 0.9, 0 < y ≤ 0.3, 0 < z ≤ 0.4. M is a doping element, and the doping element includes one or more of Mo, B, and V. The doping amount of the doping element in the core is 100 ppm to 3000 ppm. The composite coating layer includes a first coating layer and a second coating layer. The first coating layer is located on the surface of the core, and the first coating layer includes TiNbO7, Ti2Nb 10 O 29 、TiNb 24 O 62LiPON, Li7La3Zr2O 12 One or more of the following. The second coating layer is located on the surface of the first coating layer and / or the second coating layer, and the second coating layer includes Al2O3 and / or ZrO2.

[0013] In one embodiment, the mass of the first coating layer is 0.05% to 0.5% of the mass of the core.

[0014] In one embodiment, the mass of the second coating layer is 0.03% to 0.5% of the mass of the core.

[0015] A battery includes a positive electrode sheet, said positive electrode sheet comprising a ternary positive electrode material as described above.

[0016] This application addresses the problems of wide particle distribution, severe agglomeration, and high metal ion dissolution rate in traditional methods by introducing dopants and optimizing the sintering process, thereby improving the uniformity and stability of the material. The ternary cathode material of this application exhibits excellent electrochemical performance, achieving a 1C discharge capacity of 195 mAh / g at a high voltage of 4.5V and a capacity retention rate exceeding 90% after 100 cycles. This significantly improves the energy density and cycle life of lithium-ion batteries and solves the problem of poor cycle stability in practical applications of traditional ternary cathode materials. Attached Figure Description

[0017] Figure 1 These are scanning electron microscope (SEM) images of the ternary cathode materials prepared in the embodiments and comparative examples of this application, wherein... Figure 1 (a) is a SEM image of the ternary cathode material of Example 1. Figure 1 (b) is a SEM image of the ternary cathode material in Comparative Example 1. Figure 1 Image (c) is a SEM image of the ternary cathode material in Comparative Example 2. Figure 1 (d) is the SEM image of the ternary cathode material of Comparative Example 3.

[0018] Figure 2 The diagram shows the percentage of transition metal ions dissolved in the ternary cathode materials prepared in Example 1 and Comparative Examples 1-3 of this application.

[0019] Figure 3 The diagram shows the rate performance of the button cells in Examples 1-6 and Comparative Examples 1-3 of this application.

[0020] Figure 4 The diagram shows the cycle performance of the button cells in Examples 1-6 and Comparative Examples 1-3 of this application.

[0021] The following detailed description, in conjunction with the accompanying drawings, further illustrates the embodiments of this application. Detailed Implementation

[0022] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field to which the embodiments of this application belong. The terms used herein are for the purpose of describing specific embodiments only and are not intended to limit the embodiments of this application. Where no specific conditions are noted in the embodiments, they are carried out under conventional conditions or conditions recommended by the manufacturer. Where the manufacturers of the reagents or instruments used are not specified, they are all conventional products that can be obtained through commercial purchase.

[0023] Some embodiments of this application will be described in detail below. Without conflict, the following embodiments and the features in the embodiments can be combined with each other.

[0024] This application provides a method for preparing a ternary cathode material, including steps S1 to S5.

[0025] S1, presintering: sinter the carbonate co-precipitation precursor at 500°C to 800°C for 5h to 8h to obtain a presintered product.

[0026] Among them, the carbonate co-precipitation precursor is a composite carbonate particle synthesized by the carbonate co-precipitation method and containing nickel (Ni), cobalt (Co), and manganese (Mn) elements. The molar ratio of Ni, Co, and Mn satisfies: Ni:Co:Mn = x:y:z, and x + y + z = 1, 0.5 ≤ x ≤ 0.9, 0 < y ≤ 0.3, 0 < z ≤ 0.4. The carbonate co-precipitation precursor may contain a small amount of crystal water. The purpose of presintering is to decompose the carbonate co-precipitation precursor in advance and release H2O and CO2.

[0027] S2, doping and mixing: mix and grind the presintered product, lithium source, and dopant to obtain a mixture.

[0028] Among them, the presintered product, lithium source, and dopant can be placed in a ball mill for ball milling and mixing until the particle size distribution is uniform to ensure the uniformity of the above materials.

[0029] S3, first sintering: sinter the mixture by stepwise heating. First, heat it to 650°C to 750°C and hold for 3h to 8h, then heat it to 900°C to 1000°C and hold for 1h to 3h, and then cool it to 650°C to 750°C and hold for 3h to 5h to obtain a first sintered product.

[0030] Among them, after cooling to 650°C to 750°C and holding for 3h to 5h, it is naturally cooled to room temperature to obtain the first sintered product.

[0031] S4, Secondary sintering: The primary sintering product is mixed with the first coating agent, and then sintered at 700℃~800℃ for 7h~12h, and then cooled to 400℃~500℃ and held for 3h~5h to obtain the secondary sintering product.

[0032] The primary sintering product and the first coating agent can be mixed in a high-speed mixer to ensure thorough and uniform mixing, which helps improve the uniformity of the coating. After cooling to 400℃~500℃ and holding for 3h~5h, it is naturally cooled to room temperature to obtain the secondary sintering product.

[0033] S5, three-stage sintering: the product from the second sintering is mixed with the second coating agent, and then sintered at 350℃~550℃ for 4h~8h to obtain the ternary cathode material.

[0034] The secondary sintering product and the second coating agent can be mixed in a high-speed mixer to ensure thorough and uniform mixing, which is beneficial for improving the uniformity of coating. After sintering at 350℃~550℃ for 4h~8h, the material is naturally cooled to room temperature to obtain the ternary cathode material.

[0035] The carbonate co-precipitated precursor has a high surface energy, making it prone to agglomeration due to particle adhesion. To reduce system energy, this application introduces a dopant that inhibits grain fusion, thereby suppressing abnormal grain growth and particle fusion at high temperatures, thus refining the grains and alleviating agglomeration. The primary sintering step employs a sintering process of medium-low temperature holding-high temperature holding-medium-low temperature holding (slow cooling) to match the grain growth kinetics changes caused by the dopant. Specifically, the medium-low temperature stage (650℃~750℃) ensures sufficient decomposition of the precursor and formation of crystal nuclei, the high temperature stage (900℃~1000℃) promotes uniform grain growth, and the medium-low temperature stage (650℃~750℃, slow cooling) releases internal stress, stabilizes the crystal structure, and ultimately forms the nucleus.

[0036] The secondary sintering step employs a medium-temperature holding followed by a low-temperature holding (slow cooling) sintering process to allow the first coating agent to crystallize into a crystalline phase with excellent lithium-ion conductivity, forming a good bond with the primary sintering product (core), thereby forming the first coating layer on the core surface. Specifically, the medium-temperature range (700℃~800℃) ensures that the first coating agent forms a crystal structure with good crystallinity, few grain boundaries, and smooth ion channels, while also fusing with the core interface; the low-temperature range (400℃~500℃) is below the crystallization temperature, but it can further stabilize the crystal structure, ensure ionic conductivity, and reduce undesirable phase transformations caused by direct cooling to room temperature. The first coating layer (high conductivity layer) ensures efficient lithium-ion and electron transport and improves the interfacial contact between the electrolyte and the ternary cathode material.

[0037] The three-stage sintering process employs low-temperature sintering followed by natural cooling to ensure the formation of a continuous, dense, and crack-free second coating layer. The primary function of this second coating layer (dense barrier layer) is physical and chemical barrier protection, effectively preventing electrolyte penetration and improving the material's thermal stability and safety. At low temperatures (350℃~550℃), the second coating agent, through mechanisms such as surface diffusion and grain boundary diffusion of nanoparticles, is sufficient to flow, fill pores, and form a continuous second coating layer. Excessively high temperatures may lead to unnecessary violent reactions or grain cracking. Because the sintering temperature is inherently low and the resulting second coating layer is thin, the thermal stress between it and the internal structure is minimal, and rapid cooling is unlikely to cause cracking. Therefore, it can be directly cooled to room temperature without slow cooling.

[0038] By adopting a gradient multilayer composite coating structure design, the coating layer includes an outer dense barrier layer (second coating layer) and an inner highly conductive layer (first coating layer), thereby achieving the best balance between efficient barrier to electrolyte and lithium-ion conduction performance.

[0039] The introduction of dopants can stabilize the crystal structure, increase the lattice energy, and make it difficult for transition metal ions (Ni, Co, Mn) to escape. Furthermore, when the material comes into contact with the electrolyte, the electrolyte preferentially undergoes a slight, stable passivation reaction with the first coating layer, consuming aggressive substances (such as H₂). + This protects the core and reduces the dissolution of transition metal ions. The second coating layer directly isolates the electrolyte from the core, blocking most corrosive substances (such as HF), further reducing the probability of the corrosive substances reacting with the transition metal ions and causing the transition metal ions to dissolve.

[0040] In some embodiments, the D50 particle size of the carbonate coprecipitation precursor is 3.0 μm to 5.0 μm.

[0041] In some embodiments, the dopant may be one or more of MoO3, B2O3, and V2O5, but not limited to. These dopant ions can enter the crystal lattice or segregate at grain boundaries, effectively pinning grain boundary migration, suppressing abnormal grain growth and interparticle fusion at high temperatures, thereby refining grains and alleviating agglomeration.

[0042] In some embodiments, the mass percentage of the dopant co-precipitated precursor with carbonate is 0.03% to 0.3%. For example, the mass percentage can be 0.03%, 0.1%, 0.2%, 0.3%, or any value between any two adjacent values ​​mentioned above. This ensures both stable suppression of abnormal grain growth and grain refinement, while preventing negative effects caused by excessive doping (such as blocking lithium-ion diffusion channels and increasing interfacial impedance).

[0043] In some embodiments, the lithium source may be one or more of Li2CO3, LiOH, and Li2O, with Li2CO3 being preferred. The molar ratio (Li:Me) of the amount of lithium in the lithium source to the amount of metal elements (Ni, Co, Mn) in the carbonate coprecipitation precursor may be 1.01 to 1.10, preferably 1.03 to 1.06.

[0044] In some embodiments, during a single sintering step, the first stage heating rate from room temperature to 650°C to 750°C is 3°C / min to 5°C / min, the second stage heating rate from 650°C to 750°C to 900°C to 1000°C is 3°C / min to 10°C / min, and the cooling rate from 900°C to 1000°C to 650°C to 750°C is 3°C / min to 10°C / min.

[0045] In some embodiments, the first coating agent may be, but is not limited to, TiNbO7 or Ti2Nb. 10 O 29 TiNb 24 O 62 LiPON, Li7La3Zr2O 12 One or more of the following: titanium niobium oxides (TiNbO7, Ti2Nb). 10 O 29 TiNb 24 O 62 Lithium phosphine oxide (LiPON) possesses an open, interconnected crystal structure (such as bronze or tungsten bronze), providing ample lithium-ion transport channels. Lithium phosphine oxide (LiPON) exhibits good interfacial adhesion, providing uniform and stable interfacial protection, and also possesses high ionic conductivity. Lithium lanthanum zirconium oxide (Li7La3Zr2O) 12 LLZO (Lithium-ion-rich oxide) possesses extremely high ionic conductivity, along with excellent mechanical strength and chemical inertness. In summary, the aforementioned first coating agents are all fast ion conductors, which can significantly reduce the diffusion barrier of lithium ions on the surface of cathode material particles, improve interfacial ion conduction kinetics, and enhance rate performance.

[0046] In some embodiments, the amount of the first coating agent added is 0.05 wt.% to 0.5 wt.% of the primary sintering product to form a uniform first coating layer on the surface of the core. The amount of the first coating agent added can be 0.05 wt.%, 0.1 wt.%, 0.2 wt.%, 0.3 wt.%, 0.4 wt.%, 0.5 wt.%, or any value between any two adjacent values ​​mentioned above.

[0047] In some embodiments, in the secondary sintering step, the heating rate is 3°C / min to 5°C / min, and the cooling rate is 3°C / min to 5°C / min. Thus, it is possible to avoid uneven decomposition, volatilization or out-of-control reaction with the core caused by too fast heating; slow cooling allows the lattice to adjust slowly, releasing the internal stress generated by the difference in thermal expansion coefficient with the core at high temperature.

[0048] In some embodiments, the second coating agent may be, but is not limited to, one or more of Al2O3, ZrO2. Al2O3 has extremely strong densification ability, can sinter to form a dense film with low porosity, continuous and crack-free at a relatively low temperature, and has excellent chemical inertness, hardly reacting with electrolyte components (including HF). ZrO2 has high hardness and mechanical strength, and can provide strong physical protection. The combination of ZrO2 and Al2O3 can make the second coating layer more dense and may produce a synergistic protection effect.

[0049] In some embodiments, the addition amount of the second coating agent is 0.03wt.% to 0.5wt.% of the primary sintering product to form a uniform, dense and continuous second coating layer. The addition amount of the second coating agent can be 0.03wt.%, 0.035wt.%, 0.04wt.%, 0.045wt.%, 0.5wt.% or any value between any two adjacent of the above values.

[0050] In some embodiments, in the tertiary sintering step, the heating rate is 3°C / min to 5°C / min.

[0051] The present application also provides a ternary cathode material prepared by the above preparation method, which includes a core and a composite coating layer coated on the surface of the core. The chemical general formula of the core is LiNi x Co y Mn z M a O2, where x + y + z = 1, 0.5 ≤ x ≤ 0.9, 0 < y ≤ 0.3, 0 < z ≤ 0.4. M is a doping element, and the doping element may be, but is not limited to, one or more of Mo, B, V. The doping amount of the doping element in the core is 100ppm to 3000ppm.

[0052] The composite coating layer includes a first coating layer and a second coating layer. The first coating layer is located on the surface of the core, and the first coating layer may be, but is not limited to, TiNbO7, Ti2Nb 10 O 29 、TiNb 24 O 62 、LiPON、Li7La3Zr2O 12One or more of the following. The second coating layer is located on the surface of the first coating layer and / or the second coating layer; that is, the second coating layer can be located on the surface of the first coating layer away from the core, or it can be located on the surface of the core. The second coating layer can be, but is not limited to, one or more of Al2O3 and ZrO2.

[0053] In some embodiments, the D50 particle size of the ternary cathode material is 3.0 μm to 4.0 μm.

[0054] In some embodiments, the mass of the first coating layer is 0.05% to 0.5% of the core mass.

[0055] In some embodiments, the mass of the second coating layer is 0.03% to 0.5% of the core mass.

[0056] In some embodiments, the thickness of the second coating layer is 50nm~80nm, and the porosity is ≤5%.

[0057] This application also provides a battery, which may be, but is not limited to, a lithium-ion battery. The battery includes a positive electrode, a negative electrode, and an electrolyte, wherein the positive electrode includes the ternary positive electrode material described above.

[0058] The present application will be further described below with reference to specific embodiments and comparative examples.

[0059] Example 1 S1, co-precipitate the sodium carbonate precursor Ni 0.6 Co 0.1 Mn 0.3 CO3 (commercially available product) was sintered at 600℃ for 6 hours to obtain a pre-sintered product.

[0060] S2, the pre-sintered product, Li2CO3 (lithium source), and MoO3 (dopant) are mixed to obtain a mixture. The molar ratio of Li2CO3 to the metal element in the precursor (Li:Me) is 1.05:1, and the mass of MoO3 is 0.1% of the precursor mass. The mixture is ball-milled to obtain particles with a uniform particle size distribution to ensure the homogeneity of the mixing of the lithium source, dopant, and precursor.

[0061] S3. The mixture is sintered once. First, the temperature is raised to 700℃ at a rate of 3℃ / min and held for 5h. Then, the temperature is raised to 930℃ at a rate of 5℃ / min and held for 2h. Next, the temperature is lowered to 700℃ at a rate of 5℃ / min and held for 4h. Finally, it is naturally cooled to room temperature to obtain the sintered product.

[0062] S4. The primary sintering product, along with the first coating agent TiNbO7 and LiPON, is mixed in a high-speed mixer at 700 rpm for 45 minutes until homogeneous. The mixture is then held at 750°C for 10 hours, followed by a second holding at 450°C for 4 hours to obtain the secondary sintering product. The weight ratio of the primary sintering product to TiNbO7 and LiPON is 1:0.2%:0.2%.

[0063] S5. The secondary sintering product and the second coating agents Al2O3 and ZrO2 are mixed in a high-speed mixer at 700 rpm for 45 minutes to ensure uniform mixing. The mixture is then heated to 350℃ and held for 8 hours, followed by natural cooling to obtain the finished product (ternary cathode material). The weight ratio of Al2O3, ZrO2 to the primary sintering product is 0.1%:0.1%:1.

[0064] Example 2 The main differences between Example 2 and Example 1 are as follows: In S1, the pre-sintering temperature is 500℃ and the sintering time is 8h; in S2, the mass of MoO3 is 0.03% of the precursor mass; in S3, the first sintering involves heating to 650℃ and holding for 8h, then heating to 900℃ and holding for 3h, and then cooling to 650℃ and holding for 5h; in S4, the addition amount of the first coating agent TiNbO7 and LiPON is 0.25%, and the second sintering involves heating to 700℃ and holding for 12h, then cooling to 400℃ and holding for 5h; in S5, the addition amount of the second coating agent Al2O3 and ZrO2 is 0.03%, and the third sintering temperature is 450℃ and the holding time is 6h. All other aspects are the same as in Example 1 and will not be repeated here.

[0065] Example 3 The main differences between Example 3 and Example 1 are as follows: In S1, the pre-sintering temperature is 800℃ and the sintering time is 5h; in S2, the mass of MoO3 is 0.2% of the precursor mass; in S3, the first sintering involves heating to 750℃ and holding for 3h, then heating to 1000℃ and holding for 1h, and then cooling to 750℃ and holding for 3h; in S4, the addition amount of the first coating agent TiNbO7 and LiPON is 0.05%, and the second sintering involves heating to 800℃ and holding for 7h, then cooling to 500℃ and holding for 3h; in S5, the addition amount of the second coating agent Al2O3 and ZrO2 is 0.25%, and the third sintering temperature is 550℃ and the holding time is 4h. All other aspects are the same as in Example 1 and will not be repeated here.

[0066] Example 4 The main difference between Example 4 and Example 1 is that in S2, the dopants are MoO3 and B2O3, with MoO3 accounting for 0.07% of the precursor mass and B2O3 accounting for 0.03% of the precursor mass. All other aspects are the same as in Example 1 and will not be repeated here.

[0067] Example 5 The main difference between Example 5 and Example 1 is that in S4, the first coating agent is Ti2Nb. 10 O 29 and Li7La3Zr2O 12 (LLZO), a product of primary sintering and Ti2Nb 10 O 29 Li7La3Zr2O 12 The weight ratio is 1:0.2%:0.2%. Everything else is the same as in Example 1, and will not be repeated here.

[0068] Example 6 The main difference between Example 6 and Example 1 is that in S5, the second coating agent is Al2O3, and the weight ratio of the primary sintering product to Al2O3 is 1:0.2%. All other aspects are the same as in Example 1 and will not be repeated here.

[0069] Comparative Example 1 The main difference between Comparative Example 1 and Example 1 is that steps S2 and S3 are omitted, i.e., no doping is performed. The rest are the same as in Example 1, and will not be repeated here.

[0070] Comparative Example 2 The main difference between Comparative Example 2 and Example 1 is that in S3, the temperature was increased to 940°C at a rate of 3°C / min and held for 8 hours, then naturally cooled to room temperature. All other steps were the same as in Example 1 and will not be repeated here.

[0071] Comparative Example 3 The main difference between Comparative Example 3 and Example 1 is that step S4 is omitted, i.e., no coating is performed. All other aspects are the same as in Example 1 and will not be repeated here.

[0072] The main experimental parameters for the above embodiments and comparative examples are shown in Table 1.

[0073] Table 1 The ternary cathode materials prepared in Example 1 and Comparative Examples 1-3 were photographed using a scanning electron microscope (SEM) at 3Kx magnification. See attached SEM images. Figure 1 .in, Figure 1 (a) is a SEM image of the ternary cathode material of Example 1. Figure 1 (b) is a SEM image of the ternary cathode material in Comparative Example 1. Figure 1 Image (c) is a SEM image of the ternary cathode material in Comparative Example 2. Figure 1 (d) is the SEM image of the ternary cathode material of Comparative Example 3.

[0074] Depend on Figure 1 As can be seen from (a), the ternary cathode material of Example 1 of this application has good particle uniformity, high roundness, good dispersibility, and no obvious agglomeration. The particles are single crystal particles with regular morphology. The D50 of the ternary cathode material of Example 1 is about 3.0 μm to 4.0 μm.

[0075] Depend on Figure 1 As can be seen from (b), since no dopant was added during the preparation of Comparative Example 1, the single crystal particle size distribution of the finished product after sintering is wide, there are single crystal particles that failed to grow, and there are also large single crystals (more than 8μm) and agglomeration.

[0076] Depend on Figure 1 As can be seen from (c), since the first sintering of Comparative Example 2 did not adopt the gradient sintering method, there are a large number of ungrown single crystal particles in the finished product, which are polycrystalline or broken and have extremely irregular morphology.

[0077] Depend on Figure 1 As can be seen from (d), since Comparative Example 3 only has a second coating layer (dense barrier layer), its coating layer exhibits obvious discontinuity, cracks and island-like accumulation morphology, with a large number of fine, loose, and accumulated secondary particles covering the larger single crystal particles.

[0078] The ternary cathode materials of Example 1 and Comparative Examples 1-3 were subjected to transition metal ion dissolution tests. The test method was as follows: the ternary cathode material was immersed in a 1 wt% EDTA-2Na solution and kept at 60°C for 24 hours. The concentrations of Ni, Co, and Mn ions in the solution were then determined using ICP-OES. The test results are shown below. Figure 2 .Depend on Figure 2 It can be seen that the weight percentage of Ni, Co, and Mn ions dissolved in Example 1 is lower than that in Comparative Examples 1 to 3, indicating that the ternary cathode material prepared in this application has a reduced metal ion dissolution rate, which effectively confirms the interface protection effect of the dopant and the gradient coating layer.

[0079] The ternary cathode materials of Examples 1-6 and Comparative Examples 1-3 were used to fabricate coin cells (CR2032) for electrical performance testing. In the cathode sheet, the ratio of ternary cathode material: conductive carbon black: binder PVDF was 90:5:5 (mass ratio). The electrolyte was 1M LiPF6, and the solvent was EC:DMC:EMC (1:1:1 vol%). The testing equipment was a LAND battery testing system. During the testing, the initial discharge capacity test operating voltage range was 2.8V~4.3V, the charge / discharge rate was +0.1C / -0.1C, and the CV cutoff current was 0.01C. The test results are shown in [link to test results]. Figure 3The high-temperature cycling test operates within a voltage range of 2.8V to 4.3V, at a temperature of 45℃, with a charge / discharge rate of +1C / 1C and a CV cutoff current of 0.01C. Test results are available in the [link to test results]. Figure 4 .

[0080] Depend on Figure 3 It can be seen that, at a 0.1C rate, the initial charge specific capacity of all embodiments in the 2.8-4.5V voltage range is above 230 mAh / g, which is higher than that of Comparative Examples 1-3; at a 0.1C rate, the initial discharge specific capacity of all embodiments in the 2.8-4.5V voltage range is above 210 mAh / g, which is higher than that of Comparative Examples 1-3; at a 1C rate, the discharge specific capacity of all embodiments in the 2.8-4.5V voltage range is above 195 mAh / g, which is higher than that of Comparative Examples 1-3. This indicates that the ternary cathode material of all embodiments in this application has good rate performance.

[0081] Depend on Figure 4 It can be seen that after 100 cycles at 45°C and 1C, the capacity retention rates of Examples 1-6 are all higher than those of Comparative Examples 1-3, indicating that the ternary cathode material of this application has better high-temperature cycling performance. Example 1, after 100 cycles at 45°C and 1C, has a cycle capacity retention rate ≥90%. Comparative Example 1 (undoped), due to particle inhomogeneity, also has poor cycling stability, with a cycle retention rate of approximately 87.8% after 100 cycles. Comparative Example 2 lacks gradient sintering, and its cycle retention rate after 100 cycles is approximately 86%. Comparative Example 3 (without a first coating layer, i.e., without an inner high-conductivity layer), has a capacity retention rate that decays to approximately 85% after 100 cycles.

[0082] This application addresses the problems of wide particle distribution, severe agglomeration, and high metal ion dissolution rate in traditional methods by introducing dopants and optimizing the sintering process, thereby improving the uniformity and stability of the material. The ternary cathode material of this application exhibits excellent electrochemical performance, achieving a 1C discharge capacity of 195 mAh / g at a high voltage of 4.5V and a capacity retention rate exceeding 90% after 100 cycles. This significantly improves the energy density and cycle life of lithium-ion batteries and solves the problem of poor cycle stability in practical applications of traditional ternary cathode materials.

[0083] The above description describes some specific embodiments of this application, but in actual applications, the application should not be limited to these embodiments. For those skilled in the art, other modifications and alterations made based on the technical concept of this application should fall within the protection scope of this application.

Claims

1. A method for preparing a ternary cathode material, characterized in that, Includes the following steps: Pre-sintering: The carbonate coprecipitation precursor is sintered at 500℃~800℃ for 5h~8h to obtain the pre-sintered product; Doping and mixing: The pre-sintered product, lithium source and dopant are mixed and ground to obtain a mixture; One-time sintering: The mixture is subjected to step-by-step heating and sintering. First, the temperature is raised to 650℃~750℃ and held for 3h~8h, then raised to 900℃~1000℃ and held for 1h~3h, and then lowered to 650℃~750℃ and held for 3h~5h to obtain the one-time sintering product. Secondary sintering: The primary sintering product is mixed with the first coating agent, and then sintered at 700℃~800℃ for 7h~12h, and then cooled to 400℃~500℃ and held for 3h~5h to obtain the secondary sintering product; Three-stage sintering: The secondary sintering product is mixed with the second coating agent and then sintered at 350℃~550℃ for 4h~8h to obtain the ternary cathode material.

2. The preparation method according to claim 1, characterized in that, The dopant includes one or more of MoO3, B2O3, and V2O5, and the mass percentage of the dopant and the carbonate co-precipitated precursor is 0.03% to 0.3%.

3. The preparation method according to claim 1, characterized in that, The first coating agent includes TiNbO7 and Ti2Nb. 10 O 29 TiNb 24 O 62 LiPON, Li7La3Zr2O 12 One or more of the above, wherein the amount of the first coating agent added is 0.05 wt.% to 0.5 wt.% of the primary sintering product.

4. The preparation method according to claim 1, characterized in that, The second coating agent includes Al2O3 and / or ZrO2, and the amount of the second coating agent added is 0.03wt.% to 0.5wt.% of the primary sintering product.

5. The preparation method according to claim 1, characterized in that, In the first sintering step, the first stage heating rate from room temperature to 650℃~750℃ is 3℃ / min~5℃ / min, the second stage heating rate from 650℃~750℃ to 900℃~1000℃ is 3℃ / min~10℃ / min, and the cooling rate from 900℃~1000℃ to 650℃~750℃ is 3℃ / min~10℃ / min.

6. The preparation method according to claim 1, characterized in that, In the secondary sintering step, the heating rate is 3℃ / min~5℃ / min and the cooling rate is 3℃ / min~5℃ / min; in the tertiary sintering step, the heating rate is 3℃ / min~5℃ / min.

7. A ternary cathode material, characterized in that, Includes a core and a composite coating layer covering the surface of the core; The chemical general formula of the core is LiNi x Co y Mn z M a O2, where x + y + z = 1, 0.5 ≤ x ≤ 0.9, 0 < y ≤ 0.3, 0 < z ≤ 0.4, M is a doping element, the doping element includes one or more of Mo, B, V, and the doping amount of the doping element in the core is 100 ppm to 3000 ppm; The composite coating layer includes a first coating layer and a second coating layer. The first coating layer is located on the surface of the core and includes TiNbO7 and Ti2Nb. 10 O 29 TiNb 24 O 62 LiPON, Li7La3Zr2O 12 One or more of the following; the second coating layer is located on the surface of the first coating layer and / or the second coating layer, the second coating layer comprising Al2O3 and / or ZrO2.

8. The ternary cathode material as described in claim 7, characterized in that, The mass of the first coating layer is 0.05% to 0.5% of the mass of the core.

9. The ternary cathode material as described in claim 7, characterized in that, The mass of the second coating layer is 0.03% to 0.5% of the mass of the core.

10. A battery, comprising a positive electrode, characterized in that, The positive electrode sheet comprises a ternary positive electrode material as described in any one of claims 7 to 9.

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