A method for modifying a single-crystal high-nickel ternary positive electrode material
A three-stage heat treatment method was used to form a continuous transition structure of single-crystal high-nickel ternary cathode material, which solved the problem of insufficient control gradient between the surface layer and the main structure, and improved the chemical stability and cycle performance of the material.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- DEZHOU UNIV
- Filing Date
- 2026-04-07
- Publication Date
- 2026-06-26
AI Technical Summary
In the existing technology, the modification methods of single-crystal high-nickel ternary cathode materials are prone to insufficient control gradient between the surface layer and the main body, resulting in discontinuous structural connection and difficulty in simultaneously stabilizing the surface layer and maintaining the layered structure of the main body.
A three-stage heat treatment method is adopted, including a first-stage heat treatment, a second-stage state-tuning treatment, and a third-stage solidification treatment. By controlling the contact between the components and the single-crystal high-nickel ternary cathode material, a continuous transition is formed between the surface in-situ conversion region, the near-surface partitioned control region, and the main layered structure region.
It achieves high chemical stability of the particle surface and good stress buffering capacity of the near-surface layer, while maintaining the integrity of the main layered structure and the continuity of lithium-ion transport channels, thereby improving the material's cycle stability and high-temperature storage performance.
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Figure CN122279756A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of lithium battery cathode material modification technology, and in particular to a method for isotropic modification of a single-crystal high-nickel ternary cathode material. Background Technology
[0002] With the development of high-energy-density lithium-ion batteries, single-crystal high-nickel ternary cathode materials have become an important development direction for cathode materials in power and energy storage batteries due to their high compaction density, fewer particle boundaries, and better structural integrity during cycling. The industry continues to conduct research on composition control, heat treatment optimization, surface modification, and interface stabilization for these materials, aiming to balance capacity utilization, structural stability, and processing adaptability under high-nickel conditions.
[0003] In existing technologies, the modification methods for single-crystal high-nickel materials are mostly focused on external coating or surface monolayer reaction. Although these methods can improve the surface state of particles to some extent, they can easily lead to insufficient control gradient between the surface layer and the main body, and discontinuous structural connection. Consequently, it is difficult to simultaneously meet the requirements for surface stabilization and the requirements for maintaining the layered structure of the main body. Summary of the Invention
[0004] In view of this, this application provides a method for isotropic modification of single-crystal high-nickel ternary cathode materials.
[0005] According to one aspect of this disclosure, a method for isotropic modification of a single-crystal high-nickel ternary cathode material is provided, comprising: providing a single-crystal high-nickel ternary cathode material, wherein the single-crystal high-nickel ternary cathode material is a layered single-crystal particle; The single-crystal high-nickel ternary cathode material is brought into contact with the precursor state control component and subjected to a first-stage heat treatment. The temperature of the first-stage heat treatment is 120℃~350℃, the time is 5 minutes~10 hours, and the atmosphere is an inert atmosphere, vacuum or a restrictive atmosphere with an oxygen content of less than 5% by volume. The layered single crystal particles after the first stage heat treatment are further subjected to the second stage state tuning treatment. The temperature of the second stage state tuning treatment is 180℃~500℃ and the time is 10 minutes~12 hours to obtain the precursor state partitioned particles. The precursor-state partitioned particles are subjected to a third-stage curing treatment. The temperature of the third-stage curing treatment is 250℃~650℃, the time is 10 minutes~20 hours, and the atmosphere is an oxygen-containing atmosphere or an regulated atmosphere with an oxygen partial pressure higher than that of the first-stage heat treatment atmosphere, so as to obtain a monocrystalline high-nickel ternary cathode material after isotropic modification. The particles of the isotropically modified single-crystal high-nickel ternary cathode material include, from the outside to the inside, a surface in-situ conversion region, a near-surface partitioned control region, and a main layered structure region. The surface in-situ conversion region and the near-surface partitioned control region are continuously connected, and the near-surface partitioned control region and the main layered structure region are continuously transitioned.
[0006] The beneficial effects of this invention are as follows: Through the second-stage state tuning process, based on the surface precursor state formed in the first stage, the regulatory components are promoted to undergo controlled rearrangement and partitioned distribution from the outer layer of the particle to the near-surface region, enabling the regulatory elements to establish a continuous transition structure decreasing radially from the outside to the inside. This step helps to effectively couple the in-situ transformation trend of the surface layer with the near-surface structure regulation process, forming a stable near-surface partitioned regulatory region, and providing a uniform and inheritable precursor state basis for the subsequent third-stage solidification process. This allows the particle surface to obtain higher chemical stability, and the near-surface layer to possess better stress buffering and defect passivation capabilities, while maintaining the crystal integrity of the main layered structure region and the continuity of lithium-ion transport channels. Attached Figure Description
[0007] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0008] Figure 1 This is a schematic diagram comparing the in-situ transformation zone on the material surface with the near-surface zone control structure.
[0009] Figure 2 This is a comparison chart of the overall electrochemical performance of the examples and comparative examples. Detailed Implementation
[0010] To make the objectives, technical solutions, and advantages of the embodiments of this disclosure clearer, the technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this disclosure. All other embodiments obtained by those skilled in the art based on the described embodiments of this disclosure without creative effort are within the scope of protection of this disclosure.
[0011] This application provides a method for isotropic modification of a single-crystal high-nickel ternary cathode material, which includes: providing a single-crystal high-nickel ternary cathode material, wherein the single-crystal high-nickel ternary cathode material is a layered single-crystal particle.
[0012] The single-crystal high-nickel ternary cathode material is brought into contact with the precursor-state control component and subjected to a first-stage heat treatment. The temperature of the first-stage heat treatment is 120℃~350℃, the time is 5 minutes~10 hours, and the atmosphere is an inert atmosphere, vacuum, or a restrictive atmosphere with an oxygen content of less than 5% by volume.
[0013] The layered single-crystal particles after the first stage of heat treatment are further subjected to a second stage of state conditioning treatment. The temperature of the second stage of state conditioning treatment is 180℃~500℃ and the time is 10 minutes~12 hours, to obtain precursor state partitioned particles.
[0014] The precursor-state partitioned particles are subjected to a third-stage curing treatment. The temperature of the third-stage curing treatment is 250℃~650℃, the time is 10 minutes~20 hours, and the atmosphere is an oxygen-containing atmosphere or an regulated atmosphere with an oxygen partial pressure higher than that of the first-stage heat treatment atmosphere, so as to obtain the isotropic modified single-crystal high-nickel ternary cathode material.
[0015] The particles of the isotropically modified single-crystal high-nickel ternary cathode material include, from the outside to the inside, a surface in-situ conversion region, a near-surface partitioned control region, and a main layered structure region. The surface in-situ conversion region and the near-surface partitioned control region are continuously connected, and the near-surface partitioned control region and the main layered structure region are continuously transitioned.
[0016] In some embodiments of this application, the single-crystal high-nickel ternary cathode material is a layered oxide single-crystal material containing nickel, cobalt, manganese and / or aluminum, and the molar percentage of nickel in the transition metal elements is 60% to 98%.
[0017] The D50 of the layered oxide single crystal material is 1 μm to 12 μm.
[0018] In some embodiments of this application, the precursor state control component includes a lithium supplementation component and at least one of a fluorine-containing control component and a boron-containing control component.
[0019] The lithium supplementing component is lithium hydroxide and / or lithium dihydrogen phosphate, the fluorine-containing regulating component is lithium fluoride, and the boron-containing regulating component is boric acid.
[0020] In some embodiments of this application, the amount of lithium supplementation component added to the precursor state regulation component is 0.01% to 1.50% of the mass of the single-crystal high-nickel ternary cathode material, calculated based on lithium element.
[0021] The total amount of fluorine-containing and boron-containing control components added is 0.01% to 3.00% of the mass of the single-crystal high-nickel ternary cathode material, calculated based on non-lithium elements.
[0022] The mass ratio of the lithium supplement component to the fluorine-containing regulating component and / or the boron-containing regulating component is 1:(0.1-20).
[0023] In some embodiments of this application, the contacting of the single-crystal high-nickel ternary cathode material with the precursor-state control component is carried out in a system with a water content of less than 5% by mass, including any of the following methods: Dry mixing: The precursor-state control component is brought into contact with the single-crystal high-nickel ternary cathode material in the form of solid powder.
[0024] Quasi-dry mixing: The precursor-state control components are attached to the surface of the single-crystal high-nickel ternary cathode material in the form of slurry, suspension or atomized droplets and then the solvent is removed.
[0025] Gas-solid contact: At least one component of the precursor-state control components is contacted with the single-crystal high-nickel ternary cathode material in the form of vapor, atomized aerosol or thermal decomposition gas.
[0026] It should be noted that the system with a water content of less than 5% by mass means that the free water content in the overall contact system is controlled within this range when the precursor-state control component comes into contact with the single-crystal high-nickel ternary cathode material, so as to reduce the side reactions on the surface of the high-nickel single-crystal particles and improve the effective adhesion and uniformity of the control component on the particle surface.
[0027] In some embodiments of this application, during the first stage of heat treatment, at least a portion of the lithium replenishment component, the fluorine-containing regulating component, and the boron-containing regulating component react with the residual lithium component on the surface of the single-crystal high-nickel ternary cathode material particles to form a surface precursor conversion layer.
[0028] It should be noted that the purpose of the first stage of heat treatment is to enable at least a portion of the lithium-replenishing components, fluorine-containing control components, and / or boron-containing control components to preferentially undergo a restricted reaction on the particle surface, and to form an inheritable surface precursor state conversion layer together with the residual lithium components on the particle surface, thereby providing an initial reaction interface for subsequent near-surface zonal control.
[0029] The surface precursor conversion layer is distributed in a discontinuous island-like pattern, a continuous thin layer, or both on the particle surface.
[0030] The thickness of the surface precursor state conversion layer is 1 nm to 80 nm.
[0031] In some embodiments of this application, the second stage state tuning process includes pre-tuning the layered single crystal particles after the first stage heat treatment at 180°C to 350°C, and performing partition rearrangement processing on the particles after the pre-tuning process at 300°C to 500°C.
[0032] It should be noted that the second stage state tuning process includes pre-tuning process and partition rearrangement process. The pre-tuning process is used to stabilize the surface precursor state transformation layer formed in the first stage and suppress its disordered diffusion. The partition rearrangement process is used to promote the controlled migration of the control elements from the particle surface to the near-surface region, so as to form a partitioned distribution that decreases from the outside to the inside.
[0033] The pre-tuning process and the partition rearrangement process are performed continuously or at intervals not exceeding 4 hours.
[0034] It should be noted that the pre-tuning process and the partition rearrangement process are carried out continuously or at intervals not exceeding 4 hours in order to avoid compositional fluctuations or interface instability caused by environmental exposure during the long-term storage of the surface precursor structure formed in the first stage, thereby ensuring the continuity and repeatability of the partition rearrangement process.
[0035] After the second stage of state tuning, the control elements in the precursor state partitioned particles form a distribution that decreases from the outside to the inside along the radial direction of the particles.
[0036] In some embodiments of this application, the third-stage curing process is carried out in an oxygen-containing atmosphere with an oxygen content of 10% to 100% by volume.
[0037] It should be noted that the function of the third-stage curing treatment is to perform structural curing of the precursor-state partitioned particles formed in the second stage under an oxygen-containing environment, so as to form a surface in-situ transformation zone on the particle surface and maintain a continuous transition relationship between the near-surface partitioned control zone and the main layered structure zone, so as to obtain a stable isotropic modified structure.
[0038] The third stage employs an oxygen-containing atmosphere or a conditioning atmosphere with an oxygen partial pressure higher than that of the first stage heat treatment atmosphere. This is to maintain and restore the oxygen coordination stability of the surface to near-surface region of the high-nickel layered oxide particles during the curing process, and to promote the formation of a stable modified region that connects with the main layered structure.
[0039] After the third stage of curing treatment, the thickness of the surface in-situ conversion zone is 1 nm to 50 nm, and the thickness of the near-surface partitioned control zone is 5 nm to 500 nm.
[0040] In some embodiments of this application, the precursor state regulating component is a combination of a lithium-supplementing component and a fluorine-containing regulating component, or a combination of a lithium-supplementing component and a boron-containing regulating component, or a combination of a lithium-supplementing component, a fluorine-containing regulating component, and a boron-containing regulating component.
[0041] When the precursor-state regulating component contains a fluorine-containing regulating component, the first-stage heat treatment temperature is 120℃~280℃.
[0042] When the precursor state regulating component contains a boron-containing regulating component, the temperature for the second-stage state tuning process is 250℃~500℃.
[0043] In some embodiments of this application, the isotropically modified single-crystal high-nickel ternary cathode material satisfies the following structural limitations: The main peak of the layered α-NaFeO2 structure is preserved in the X-ray diffraction pattern.
[0044] In X-ray photoelectron spectroscopy depth profiling, the atomic percentage of the modulating element in the particle surface to near-surface range is higher than the atomic percentage of the corresponding position inside the particle.
[0045] It should be noted that the atomic percentage of the control element in the X-ray photoelectron spectroscopy depth profile, which is higher than the atomic percentage of the corresponding position inside the particle, is used to characterize that the control element in the particle obtained by the present invention is not uniformly distributed in bulk, but forms a gradient partition control structure from the surface to the inside.
[0046] In transmission electron microscopy characterization, there is no independently separated dense outer coating layer between the surface in-situ transformation zone and the near-surface regional regulation zone.
[0047] It should be noted that the absence of an independently separated dense outer coating layer in the transmission electron microscope characterization refers to the in-situ and continuous structural relationship between the outermost modified region of the particle and the near-surface zoned control region, rather than an additional coating layer with a clearly separated interface attached to the outside of the main particle.
[0048] Example 1: 100g of a single-crystal lithium nickel cobalt manganese ternary layered oxide cathode material with a D50 of 4.8μm and a nickel, cobalt, and manganese molar ratio of 0.90:0.05:0.05 was selected as the substrate. It was first vacuum dried at 115℃ for 5 hours. Then, 0.58g of lithium hydroxide and 0.16g of lithium fluoride were added, and the mixture was mixed for 35 minutes using a V-type mixer in a dry environment with a dew point below -30℃, allowing the precursor conditioning components to contact the substrate via a low-water dry method. The resulting mixture underwent a first-stage heat treatment at 225℃ for 2 hours in a nitrogen atmosphere with an oxygen content of 0.4% by volume. A pre-conditioning treatment was then performed at 305℃ for 1.5 hours, followed by a partition rearrangement treatment at 415℃ for 3 hours. Finally, the mixture was switched to an oxygen-containing atmosphere with an oxygen content of 30% by volume and cured at 525℃ for 4 hours. After cooling and sieving, the isotropic modified material was obtained. Characterization revealed that the in-situ conversion region on the surface of the material is continuous and relatively uniform, with a clear gradient control region near the surface, effectively controlling the residual lithium level. The material maintained a relatively stable capacity output under cycling conditions at 45℃, making it suitable as a preferred option with balanced overall performance.
[0049] Example 2: 100g of a single-crystal lithium nickel cobalt manganese ternary layered oxide cathode material with a D50 of 5.3μm and a nickel, cobalt, and manganese molar ratio of 0.88:0.06:0.06 was selected as the substrate. After vacuum drying at 110℃ for 6 hours, 0.71g of lithium hydroxide and 0.54g of boric acid were added and mixed in a sealed drying mixing tank for 40 minutes to ensure uniform adhesion of the control components to the particle surface. Subsequently, a first-stage heat treatment was performed at 240℃ for 70 minutes under a 300Pa vacuum, followed by a pre-conditioning treatment at 320℃ for 1 hour, and a zone rearrangement treatment at 438℃ for 2.5 hours. Finally, a third-stage curing treatment was completed at 505℃ for 5 hours in an atmosphere with an oxygen content of 45% by volume. The resulting material showed a relatively complete near-surface zone control region, and a smoother structural transition between the surface and the main body region. Especially during high-temperature long-cycle testing, the capacity decay was slower, indicating that boron-containing control is more conducive to the stable construction of the near-surface region.
[0050] Example 3: 100g of a single-crystal lithium nickel cobalt aluminum layered oxide cathode material with a D50 of 4.1μm and a nickel, cobalt, and aluminum molar ratio of 0.92:0.04:0.04 was selected as the substrate and first vacuum dried at 120℃ for 4 hours. Separately, 0.49g of lithium hydroxide, 0.11g of lithium fluoride, and 0.31g of boric acid were dispersed in 16g of anhydrous ethanol to form a low-level dry adhesion system, which was then applied to the substrate surface via atomized spraying. The solvent was subsequently removed under reduced pressure at 85℃. The treated material underwent a first-stage heat treatment at 205℃ for 2.5 hours in a nitrogen atmosphere with an oxygen content of 0.6% by volume, followed by a pre-conditioning treatment at 285℃ for 1.8 hours, a partition rearrangement treatment at 395℃ for 3.8 hours, and finally a third-stage curing treatment at 538℃ for 3 hours in an oxygen-containing atmosphere with an oxygen content of 25% by volume. The resulting material has a thinner surface conversion zone and a more obvious enrichment gradient of elements in the near-surface layer. Without significantly sacrificing the first-cycle specific capacity, the growth of cycling impedance is well suppressed, making it suitable for demonstrating the synergistic optimization effect of F and B composite regulation on the surface and near-surface layers.
[0051] Example 4: 100g of a single-crystal lithium nickel cobalt manganese ternary layered oxide cathode material with a D50 of 4.4μm and a nickel, cobalt, and manganese molar ratio of 0.95:0.025:0.025 was selected as the substrate. It was first vacuum dried at 110℃ for 6 hours. 1.92g of lithium dihydrogen phosphate and 0.14g of lithium fluoride were added to the substrate, and the mixture was ball-mixed for 25 minutes under low humidity to obtain a precursor mixture. The precursor mixture underwent the first stage of heat treatment at 185℃ for 4 hours in a nitrogen atmosphere with an oxygen content of 0.2% by volume. It then underwent pre-conditioning treatment at 300℃ for 2 hours, followed by partition rearrangement treatment at 452℃ for 2 hours. Finally, it underwent the third stage of curing at 558℃ for 2.5 hours in an atmosphere with an oxygen content of 38% by volume. This embodiment corresponds to a system with higher nickel content. After treatment, the material still maintains a layered main structure, the surface modified region is continuously distinguishable, and the near-surface layer has certain buffering characteristics. It can maintain relatively stable cycling performance under high capacity output, indicating that the solution of the present invention is also applicable to single crystal materials with higher nickel content.
[0052] Example 5: 100g of a single-crystal lithium nickel cobalt manganese ternary layered oxide cathode material with a D50 of 6.1μm and a nickel, cobalt, and manganese molar ratio of 0.85:0.10:0.05 was selected as the substrate and vacuum dried at 105℃ for 5 hours. 1.56g of lithium dihydrogen phosphate and 0.63g of boric acid were dispersed in 18g of anhydrous ethanol, and after high-speed shearing to form a suspension, it was contacted with the substrate by fluidized bed spraying. Subsequently, the solvent was removed at 90℃ to obtain a low-water-contact precursor material. This precursor material underwent a first-stage heat treatment at 232℃ for 2 hours under a vacuum of 450Pa, followed by a pre-conditioning treatment at 332℃ for 1 hour, a partition rearrangement treatment at 425℃ for 3.5 hours, and finally a third-stage curing treatment at 510℃ for 5 hours in an atmosphere with an oxygen content of 60% by volume. The resulting material has a relatively thick near-surface zone control area, and a more complete transition between the particle surface and the main body area. It exhibits a low gas evolution level under 60°C high-temperature static conditions, indicating that this embodiment is more suitable as a solution with better high-temperature storage stability.
[0053] Example 6: 100g of a single-crystal lithium nickel cobalt aluminum layered oxide cathode material with a D50 of 3.8μm and a nickel, cobalt, and aluminum molar ratio of 0.94:0.03:0.03 was selected as the substrate. It was first vacuum dried at 118℃ for 4 hours. Subsequently, 0.61g of lithium hydroxide, 0.10g of lithium fluoride, and 0.28g of boric acid were added, and the mixture was mixed for 45 minutes using a double-cone mixer under a dry nitrogen atmosphere. The mixture underwent a first-stage heat treatment at 218℃ for 2 hours in a nitrogen atmosphere with an oxygen content of 0.5% by volume, followed by a pre-setting treatment at 302℃ for 1.6 hours, a partition rearrangement treatment at 432℃ for 2.8 hours, and finally, a third-stage curing treatment at 532℃ for 4 hours in an atmosphere with an oxygen content of 35% by volume. The resulting material forms a continuous modified region in the high-nickel aluminum doped system, achieving a good balance between surface stability and near-surface buffering capacity. This is manifested in a slower impedance increase during cycling and more stable gas generation control, indicating that the method of this invention also has good adaptability to high-nickel NCA type single crystal materials.
[0054] Comparative Example 1: Using the same substrate, the same amount of lithium hydroxide and lithium fluoride as in Example 1, and mixed under the same low-water dry method conditions; then, the first stage heat treatment was performed at 225°C for 2 hours in a nitrogen atmosphere with an oxygen content of 0.4% by volume. However, instead of a second stage state-conditioning treatment, the subsequent treatment was performed directly at 525°C for 4 hours in an oxygen-containing atmosphere with an oxygen content of 30% by volume. The resulting material still showed some reaction zones on the surface, indicating that the first stage treatment itself could bring some surface improvement. However, due to the lack of pre-conditioning and partition rearrangement processes, the near-surface layer reduction distribution was insufficient, resulting in limited improvement in interfacial stability during subsequent cycles. The overall effect was weaker than that of Example 1. Figure 1 As shown, after adopting the three-stage isotropic modification process of the present invention, the particles form a hierarchical feature from the surface to the inside, consisting of an in-situ transformation zone on the surface, a near-surface partitioned control zone, and a continuous transition of the main structure. Compared with the comparative sample that has not undergone complete state tuning and partition rearrangement, the near-surface gradient region of the sample of the present invention is more complete and the structural connection is more continuous, which better reflects the design concept of the present invention to establish a continuous gradient modified structure through staged heat treatment.
[0055] Comparative Example 2: Using the same substrate and the same amounts of lithium hydroxide, lithium fluoride, and boric acid as in Example 3, but dispersing the regulating components in an ethanol-water mixed solvent with a high water content, resulting in a free water content in the contact stage significantly higher than 5% by mass. After stirring and adhesion and drying at 120°C, the three-stage heat treatment was no longer distinguished; instead, a one-time treatment was performed directly at 520°C for 5 hours in an atmosphere with an oxygen content of 30% by volume. The resulting material showed enrichment of regulating elements on its surface, but the distribution uniformity was poor, and there were relatively more side reactions on the particle surface. The residual lithium reduction effect and subsequent cycling performance were inferior to those of Example 3, indicating that the low-water contact system has a significant effect on the controllable formation of the precursor layer.
[0056] Comparative Example 3: 100g of a single-crystal lithium nickel cobalt manganese ternary layered oxide cathode material with a nickel, cobalt, and manganese molar ratio of 0.88:0.06:0.06 was used as the substrate. 0.58g of boric acid was dissolved in deionized water to form a coating solution, which was then mixed with the substrate and dried at 110°C. The mixture was then calcined at 500°C for 6 hours in a pure oxygen atmosphere to simulate a conventional external coating process. The material obtained in this comparative example forms a relatively independent modified layer on the outer surface, providing some surface protection. However, under TEM, the interface between the surface layer and the substrate is relatively clear, and the near-surface region lacks the continuous partitioned transition described in this invention. Therefore, under long-term cycling and high-temperature static conditions, its overall stability is still inferior to the solution of this invention corresponding to Example 2. Figure 2 As shown, the embodiments of the present invention maintain a relatively high discharge specific capacity in the first cycle while the cycle capacity retention rate is significantly better than that of the comparative example. Furthermore, the DC internal resistance growth rate and the high-temperature storage gas production are significantly lower. This indicates that the present invention can achieve a synergistic improvement in capacity output, cycle stability, and high-temperature storage performance through the isotropic modified structure formed by precursor state construction, pre-tuning, partition rearrangement, and oxygen-containing curing.
[0057] Table 1. Characterization results of particle partitioning structure and surface state of the examples and comparative examples. As shown in Table 1, the materials obtained in the examples all exhibited obvious enrichment characteristics of regulatory elements in the particle surface to near-surface region, and the thickness combination of the surface in-situ conversion zone and the near-surface partitioned regulation zone was in a relatively coordinated range, indicating that the three-stage treatment can establish a homogeneous modified structure with a continuous transition from the outside to the inside while maintaining the main layered structure. Among them, different examples showed certain differences in the thickness of the surface region, the thickness of the near-surface region, and the residual lithium control level due to different combinations of regulatory components and treatment paths, demonstrating the controllability of the present invention. Although some samples in the comparative examples also showed certain modified layers or element enrichment on the surface, the near-surface partitioning was insufficient and the residual lithium was high, indicating that it was difficult to form the continuous gradient structure required by the present invention.
[0058] Table 2. Comparison of electrochemical performance and high-temperature storage effect between the examples and comparative examples. As shown in Table 2, the embodiments, while maintaining a high first-cycle discharge specific capacity, outperform the comparative embodiments in terms of 45°C cycle retention, DC internal resistance growth rate, and high-temperature storage gas generation. This demonstrates that the three-stage isotropic modification path combining precursor state construction, state tuning, and oxygen-containing curing can achieve synergistic optimization of capacity utilization and interface stability. The performance of different embodiments is not entirely consistent. For example, Embodiment 4 is more inclined towards high capacity output, Embodiments 2 and 6 show better cycle stability, and Embodiment 5 excels in high-temperature gas generation control. This also indicates that the present invention is not a random result under a single condition, but rather that verifiable performance improvements can be obtained under different preferred schemes.
[0059] The above description is only a specific embodiment of this disclosure, but the protection scope of this disclosure is not limited thereto. The protection scope of this disclosure should be determined by the protection scope of the claims.
Claims
1. A method for isotropic modification of a single-crystal high-nickel ternary cathode material, characterized in that, include: A single-crystal high-nickel ternary cathode material is provided, wherein the single-crystal high-nickel ternary cathode material is a layered single-crystal particle; The single-crystal high-nickel ternary cathode material is brought into contact with the precursor state control component and subjected to a first-stage heat treatment. The temperature of the first-stage heat treatment is 120℃~350℃, the time is 5 minutes~10 hours, and the atmosphere is an inert atmosphere, vacuum or a restrictive atmosphere with an oxygen content of less than 5% by volume. The layered single crystal particles after the first stage heat treatment are further subjected to the second stage state tuning treatment. The temperature of the second stage state tuning treatment is 180℃~500℃ and the time is 10 minutes~12 hours to obtain the precursor state partitioned particles. The precursor-state partitioned particles are subjected to a third-stage curing treatment. The temperature of the third-stage curing treatment is 250℃~650℃, the time is 10 minutes~20 hours, and the atmosphere is an oxygen-containing atmosphere or an regulated atmosphere with an oxygen partial pressure higher than that of the first-stage heat treatment atmosphere, so as to obtain a monocrystalline high-nickel ternary cathode material after isotropic modification. The particles of the isotropically modified single-crystal high-nickel ternary cathode material include, from the outside to the inside, a surface in-situ conversion region, a near-surface partitioned control region, and a main layered structure region. The surface in-situ conversion region and the near-surface partitioned control region are continuously connected, and the near-surface partitioned control region and the main layered structure region are continuously transitioned.
2. The isotropic modification method for single-crystal high-nickel ternary cathode material as described in claim 1, characterized in that, The single-crystal high-nickel ternary cathode material is a layered oxide single-crystal material containing nickel, cobalt, manganese and / or aluminum, and the molar proportion of nickel in the transition metal elements is 60% to 98%. The D50 of the layered oxide single crystal material is 1 μm to 12 μm.
3. The isotropic modification method for single-crystal high-nickel ternary cathode material as described in claim 1, characterized in that, The precursor state control component includes a lithium supplementation component and at least one of a fluorine-containing control component and a boron-containing control component. The lithium supplementing component is lithium hydroxide and / or lithium dihydrogen phosphate, the fluorine-containing regulating component is lithium fluoride, and the boron-containing regulating component is boric acid.
4. The isotropic modification method for single-crystal high-nickel ternary cathode material as described in claim 3, characterized in that, In the precursor state regulation component, the amount of lithium supplementation component added is 0.01% to 1.50% of the mass of the single-crystal high-nickel ternary cathode material, calculated based on lithium element. The total amount of fluorine-containing and boron-containing regulating components added is 0.01% to 3.00% of the mass of the single-crystal high-nickel ternary cathode material, calculated based on non-lithium elements. The mass ratio of the lithium supplement component to the fluorine-containing regulating component and / or the boron-containing regulating component is 1:(0.1-20).
5. The isotropic modification method for single-crystal high-nickel ternary cathode material as described in claim 1, characterized in that, The contacting of the single-crystal high-nickel ternary cathode material with the precursor-state control component in a system with a water content of less than 5% by mass includes any of the following methods: Dry mixing: The precursor-state control component is brought into contact with the single-crystal high-nickel ternary cathode material in the form of solid powder; Quasi-dry mixing: The precursor-state control components are attached to the surface of the single-crystal high-nickel ternary cathode material in the form of slurry, suspension or atomized droplets and then the solvent is removed. Gas-solid contact: At least one component of the precursor-state control components is contacted with the single-crystal high-nickel ternary cathode material in the form of vapor, atomized aerosol or thermal decomposition gas.
6. The isotropic modification method for single-crystal high-nickel ternary cathode material as described in claim 1, characterized in that, During the first stage of heat treatment, at least a portion of the lithium replenishment component, the fluorine-containing regulating component, and the boron-containing regulating component react with the residual lithium component on the surface of the single-crystal high-nickel ternary cathode material particles to form a surface precursor conversion layer. The surface precursor conversion layer is distributed in a discontinuous island-like pattern, a continuous thin layer, or both on the particle surface. The thickness of the surface precursor state conversion layer is 1 nm to 80 nm.
7. The isotropic modification method for single-crystal high-nickel ternary cathode material as described in claim 1 or 6, characterized in that, The second stage of state tuning process includes pre-tuning the layered single crystal particles after the first stage heat treatment at 180℃~350℃, and partitioning and rearranging the pre-tuned particles at 300℃~500℃. The pre-tuning process and the partition rearrangement process are performed continuously or at intervals not exceeding 4 hours. After the second stage of state tuning, the control elements in the precursor state partitioned particles form a distribution that decreases from the outside to the inside along the radial direction of the particles.
8. The isotropic modification method for single-crystal high-nickel ternary cathode material as described in claim 1, characterized in that, The third stage of curing is carried out in an oxygen-containing atmosphere with an oxygen content of 10% to 100% by volume. After the third stage of curing treatment, the thickness of the surface in-situ conversion zone is 1 nm to 50 nm, and the thickness of the near-surface partitioned control zone is 5 nm to 500 nm.
9. The isotropic modification method for single-crystal high-nickel ternary cathode material as described in claim 1 or 3, characterized in that, The precursor state regulating component is a combination of a lithium-supplementing component and a fluorine-containing regulating component, or a combination of a lithium-supplementing component and a boron-containing regulating component, or a combination of a lithium-supplementing component, a fluorine-containing regulating component, and a boron-containing regulating component; When the precursor-state regulating component contains a fluorine-containing regulating component, the first-stage heat treatment temperature is 120℃~280℃. When the precursor state regulating component contains a boron-containing regulating component, the temperature for the second-stage state tuning process is 250℃~500℃.
10. The isotropic modification method for single-crystal high-nickel ternary cathode material as described in claim 1, characterized in that, The isotropically modified single-crystal high-nickel ternary cathode material satisfies the following structural constraints: The main peak of the layered α-NaFeO2 structure is retained in the X-ray diffraction pattern; In X-ray photoelectron spectroscopy depth profiling, the atomic percentage of the modulating element in the particle surface to near-surface range is higher than the atomic percentage of the corresponding position inside the particle. In transmission electron microscopy characterization, there is no independently separated dense outer coating layer between the surface in-situ transformation zone and the near-surface regional regulation zone.