Doped high-nickel single-crystal positive electrode material as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of batteries, and provides a doped high-nickel single-crystal positive electrode material and a preparation method and application thereof.The doped high-nickel single-crystal positive electrode material comprises strontium element doped single-crystal particles, the doping amount of the strontium element is 0.3%-3% of the total molar weight of nickel, cobalt and manganese elements, and the positive electrode material has the small average particle size of 1-3 m. The doping of the strontium element can change the crystal structure of the NCM, and is beneficial to improving the ion mixing and enhancing the stability of the structure, thereby improving the cycling stability. Meanwhile, the small-size single crystal particles are beneficial to further effectively inhibiting formation of microcracks, electrolyte is effectively prevented from permeating into the particles, and side reaction is inhibited. In addition, the increase of the oxygen vacancy formation energy and the reduction of the migration energy barrier in the strontium-doped high-nickel single-crystal NCM positive electrode material are both helpful for improving the electrochemical performance.

Description

Technical Field

[0001] This invention belongs to the field of battery technology and relates to a doped high-nickel single-crystal cathode material, its preparation method, and its applications. Background Technology

[0002] Currently, lithium-ion batteries, with their high energy density, long cycle life, and low self-discharge rate, have become the core power source driving the development of electric vehicles, portable electronic devices, and large-scale energy storage systems. In the overall cost structure of batteries, cathode materials account for as much as 30% to 40%, and their performance directly determines the battery's energy density, safety, and economy. Therefore, the research and development of cathode materials has always been key to the advancement of lithium-ion battery technology. Among many cathode systems, layered ternary oxides (LiNi) are... x Co y Mn 1-x-y O2 (NCM) is widely used due to its adjustable elemental ratio, high specific capacity, and excellent overall electrochemical performance. In particular, high-nickel-content (≥0.8%) NCM materials (such as NCM811) have theoretical specific capacities exceeding 200 mAh / g, demonstrating significant advantages in improving battery energy density and becoming the mainstream choice for high-energy-density battery cathode materials. However, high-nickel NCM materials still face several key technical bottlenecks in practical applications, severely restricting their cycle stability and safety.

[0003] Among them, the formation of microcracks is related to the mixing of lithium-nickel cations (Li... + / Ni 2+ Mixed arrangement (Ni) are two core issues. High-nickel materials exhibit significant anisotropic lattice strain during charge and discharge, especially in the deep delithiation state. The H2→H3 phase transition triggers severe c-axis contraction, leading to stress concentration within the primary particles and inducing microcracks. These microcracks not only disrupt the particle structure but also continuously expose fresh surfaces to the electrolyte, accelerating interfacial side reactions, transition metal dissolution, and impedance growth, ultimately causing rapid capacity decay. Simultaneously, due to Ni... 2+ (0.69Å) and Li + The ionic radii are similar (0.76 Å), and the Ni content in high-nickel materials is... 2+ The content increases with increasing nickel content, and Ni is highly susceptible to oxidation during synthesis or recycling. 2+ The phenomenon of cation mixing occupying Li layer sites. This mixing not only hinders the diffusion channels of lithium ions between layers and reduces rate performance, but also destroys the long-range order of the layered structure, induces phase transitions or even structural collapse, and further deteriorates electrochemical performance.

[0004] To address these challenges, single-crystalization is widely considered an effective solution. Compared to traditional polycrystalline secondary pellets (formed by the aggregation of primary nanoparticles), single-crystal NCM materials possess a complete crystal structure and lack internal grain boundaries, significantly suppressing the initiation and propagation of microcracks and reducing the contact interface with the electrolyte, thereby improving structural stability and cycle life. Furthermore, the compactness of single-crystal particles helps reduce specific surface area and mitigate surface side reactions. However, existing single-crystal growth processes generally rely on high-temperature solid-state reactions, typically requiring prolonged calcination at temperatures approaching 900°C to promote grain growth and improve crystallinity. But this high-temperature environment exacerbates lithium volatilization and Ni… 2+ The formation of these cations leads to severe Li / Ni cation mixing, which in turn impairs the electrochemical reversibility of the material. Especially with high nickel content, the material is more sensitive to synthesis temperature; excessively high temperatures, while beneficial for grain growth, significantly deteriorate cation order. Furthermore, prolonged high-temperature processing results in high energy consumption, significant equipment wear and tear, and poor batch-to-batch consistency, hindering industrial scale-up. While simply lowering the calcination temperature can suppress mixing, it is insufficient to drive sufficient grain growth, making it difficult to obtain uniformly sized, fully crystalline single crystals.

[0005] In summary, although single crystallization is widely recognized as an effective direction for improving the performance of high-nickel NCM materials, existing synthesis strategies still have fundamental limitations in balancing temperature control, crystal growth kinetics, and cation order. There is an urgent need to develop a new preparation method for high-crystallinity, low-mixing-degree single-crystal high-nickel cathode materials under relatively mild conditions to overcome the current bottlenecks in performance and process. Summary of the Invention

[0006] In view of the problems existing in the prior art, the purpose of this invention is to provide a doped high-nickel single-crystal cathode material, its preparation method, and its uses. The doped high-nickel single-crystal cathode material comprises strontium-doped single-crystal particles, with the strontium doping amount being 0.3% to 3% of the total molar amount of nickel, cobalt, and manganese, and having a small average particle size of 1 to 3 µm. Strontium doping can alter the crystal structure of NCM, which is beneficial for improving ion mixing and enhancing structural stability, thereby improving cycle stability. Simultaneously, the smaller size of the single-crystal particles further helps to effectively suppress microcrack formation, prevent electrolyte penetration into the particle interior, and suppress side reactions. Furthermore, the increased oxygen vacancy formation energy and decreased migration energy barrier in the strontium-doped high-nickel single-crystal NCM cathode material both contribute to improved electrochemical performance.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a doped high-nickel single-crystal cathode material, wherein the doped high-nickel single-crystal cathode material is a single-crystal particle and the doping element includes strontium, the average particle size is 1µm~3µm, and the chemical formula is LiNi. a Co b Mn c Sr d O2, where 0.8≤a<1, 0<b<0.2, 0<c<0.2, a+b+c=1, d=0.003~0.03.

[0009] This invention selects strontium as a dopant. Strontium doping can alter the crystal structure of NCM, improve ion mixing, and optimize ion diffusion paths, thus promoting lithium-ion migration within the particles. Strontium doping strengthens the crystal structure, enhancing structural stability and minimizing structural changes and lattice distortion during charge-discharge cycles, thereby improving cycle stability. Simultaneously, strontium doping facilitates control over the size of single-crystal grains and promotes a more uniform particle size distribution. Smaller single-crystal particles effectively suppress microcrack formation, prevent electrolyte infiltration into the particle interior, and inhibit side reactions. Furthermore, the increased oxygen vacancy formation energy and reduced migration barrier in the strontium-doped high-nickel single-crystal NCM cathode material both contribute to improved electrochemical performance.

[0010] The doped high-nickel single-crystal cathode material of the present invention has an average particle size of 1µm to 3µm, for example, it can be 1µm, 1.2µm, 1.4µm, 1.6µm, 1.8µm, 2µm, 2.2µm, 2.4µm, 2.6µm, 2.8µm or 3µm, etc., preferably 1.8µm to 2.2µm.

[0011] The chemical formula of the heterogeneous high-nickel single-crystal cathode material described in this invention is LiNi. a Co b Mn c Sr dO2, where 0.8 ≤ a < 1, for example, a can be 0.8, 0.82, 0.84, 0.86, 0.88, 0.9, 0.92, 0.94, 0.96, or 0.98, etc.; 0 < b < 0.2, for example, b can be 0.01, 0.02, 0.05, 0.08, 0.1, 0.12, 0.15, or 0.18, etc.; 0 < c < 0.2, for example, c can be 0.01, 0.02, 0.05, 0.08, 0.1, or 0. 12, 0.15 or 0.18, etc.; a+b+c=1, for example a=0.8, b=0.1, c=0.1 or a=0.9, b=0.05, c=0.05, etc.; d=0.003~0.03, for example d can be 0.003, 0.005, 0.008, 0.01, 0.012, 0.014, 0.016, 0.018, 0.02, 0.022, 0.024, 0.026, 0.028 or 0.03, etc.

[0012] In a second aspect, the present invention provides a method for preparing the doped high-nickel single-crystal cathode material described in the first aspect, the method comprising:

[0013] A nickel source, a cobalt source, a manganese source, and a strontium source are prepared into a mixed solution; in the mixed solution, the molar amount of nickel accounts for at least 80% of the total molar amount of nickel, cobalt, and manganese.

[0014] The mixed solution was subjected to spray pyrolysis to obtain strontium-doped ternary precursor powder;

[0015] Strontium-doped ternary precursor powder was mixed with a lithium source and calcined to obtain a doped high-nickel single-crystal cathode material.

[0016] The preparation method involves preparing a solution of strontium source as a dopant with other raw materials, followed by spray pyrolysis and lithiation calcination to obtain a doped high-nickel single-crystal cathode material. This invention combines strontium doping with spray pyrolysis, which helps to lower the calcination temperature and overcomes defects caused by excessively high single-crystal growth temperatures. Specifically, it enables low-temperature, efficient, and uniform strontium doping to obtain high-nickel single-crystal cathode materials with controlled particle size, facilitating the acquisition of smaller single-crystal grain sizes.

[0017] In the mixed solution described in this invention, the molar amount of nickel accounts for at least 80% of the total molar amount of nickel, cobalt and manganese, for example, it can be 80%, 82%, 84%, 86%, 88%, 90%, 92%, 94%, 96% or 98%, etc.

[0018] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. The technical objectives and beneficial effects of the present invention can be better achieved and realized through the following technical solutions.

[0019] As a preferred embodiment of the present invention, the nickel source, cobalt source and manganese source include nitrates of the corresponding metal elements.

[0020] Preferably, the strontium source includes strontium nitrate.

[0021] Preferably, in the mixed solution, the molar amount of strontium accounts for 0.3% to 3% of the total molar amount of nickel, cobalt, and manganese. For example, it can be 0.3%, 0.5%, 0.8%, 1%, 1.2%, 1.4%, 1.6%, 1.8%, 2%, 2.2%, 2.4%, 2.6%, 2.8%, or 3%, etc.

[0022] Preferably, the total concentration of the nickel source, cobalt source, manganese source, and strontium source in the mixed solution is 50 g / L to 500 g / L. For example, it can be 50 g / L, 80 g / L, 100 g / L, 130 g / L, 150 g / L, 180 g / L, 200 g / L, 230 g / L, 250 g / L, 280 g / L, 300 g / L, 330 g / L, 350 g / L, 380 g / L, 400 g / L, 430 g / L, 450 g / L, 480 g / L, or 500 g / L, etc.

[0023] As a preferred technical solution of the present invention, the spray pyrolysis process includes first spraying and atomizing the mixed solution to obtain atomized droplets, and then drying and pyrolyzing the atomized droplets.

[0024] As a preferred technical solution of the present invention, the spray atomization device includes a two-fluid atomizer.

[0025] Preferably, the gas used for spray atomization includes a mixture of carrier gas and compressed air.

[0026] Preferably, the carrier gas includes nitrogen.

[0027] Preferably, the flow ratio of the carrier gas to the compressed air is (2~4):1. For example, it can be 2:1, 2.2:1, 2.4:1, 2.6:1, 2.8:1, 3:1, 3.2:1, 3.4:1, 3.6:1, 3.8:1, or 4:1, etc.

[0028] Preferably, the flow rate of the carrier gas is 20m³. 3 / h~30m 3 / h. For example, it could be 20m. 3 / h、21m 3 / h、22m 3 / h、23m 3 / h、24m 3 / h, 25m 3 / h、26m3 / h、27m 3 / h、28m 3 / h、29m 3 / h or 30m 3 / h etc.

[0029] Preferably, the gas pressure for atomization is 0.2 MPa to 1.2 MPa. For example, it can be 0.2 MPa, 0.4 MPa, 0.6 MPa, 0.8 MPa, 1 MPa, or 1.2 MPa, etc.

[0030] Preferably, the size of the atomized droplets is 10µm to 100µm. For example, it can be 10µm, 20µm, 30µm, 40µm, 50µm, 60µm, 70µm, 80µm, 90µm or 100µm, etc.

[0031] As a preferred embodiment of the present invention, the drying pyrolysis equipment includes a drying tower.

[0032] Preferably, the inlet temperature of the drying tower is 200℃~300℃. For example, it can be 200℃, 220℃, 240℃, 260℃, 280℃ or 300℃, etc.

[0033] Preferably, the outlet temperature of the drying tower is 600℃~750℃. For example, it can be 600℃, 620℃, 640℃, 660℃, 680℃, 700℃, 720℃ or 750℃, etc.

[0034] Preferably, the average residence time of the atomized droplets in the drying tower is 10s to 20s. For example, it can be 10s, 11s, 12s, 13s, 14s, 15s, 16s, 17s, 18s, 19s, or 20s.

[0035] As a preferred embodiment of the present invention, the lithium source includes LiOH·H2O.

[0036] Preferably, the dosage is controlled according to a ratio of (1~1.03):1 between the molar amount of lithium in the lithium source and the total molar amount of metal elements in the strontium-doped ternary precursor powder. For example, it can be 1:1, 1.01:1, 1.02:1, or 1.03:1, etc.

[0037] As a preferred technical solution of the present invention, the calcination includes first performing a first calcination at a first temperature to completely remove moisture and melt the lithium source, and then performing a second calcination at a second temperature in a pure oxygen atmosphere.

[0038] Preferably, the first temperature is 500℃~600℃. For example, it can be 500℃, 510℃, 520℃, 530℃, 540℃, 550℃, 560℃, 570℃, 580℃, 590℃ or 600℃, etc.

[0039] Preferably, the holding time for the first calcination is 4h to 6h. For example, it can be 4h, 4.3h, 4.5h, 4.8h, 5h, 5.3h, 5.5h, 5.8h, or 6h, etc.

[0040] Preferably, the heating temperature of the second calcination is 3℃ / min to 8℃ / min. For example, it can be 3℃ / min, 4℃ / min, 5℃ / min, 6℃ / min, 7℃ / min or 8℃ / min, etc.

[0041] Preferably, the second temperature is 700℃~800℃. For example, it can be 700℃, 710℃, 720℃, 730℃, 740℃, 750℃, 760℃, 770℃, 780℃, 790℃ or 800℃, etc.

[0042] Preferably, the holding time for the second calcination is 8h to 15h. For example, it can be 8h, 9h, 10h, 11h, 12h, 13h, 14h or 15h, etc.

[0043] Thirdly, the present invention provides a battery comprising the doped high-nickel single-crystal cathode material described in the first aspect or the doped high-nickel single-crystal cathode material obtained by the preparation method described in the second aspect.

[0044] It should be noted that, due to space limitations and to avoid redundancy, this invention does not exhaustively list all point values ​​within the above numerical range, but it is not limited to the listed values ​​either; other unlisted values ​​within the above numerical range are also applicable.

[0045] Compared with existing technical solutions, the present invention has at least the following beneficial effects:

[0046] This invention selects strontium as a dopant. Strontium doping can alter the crystal structure of NCM, improve ion mixing, and optimize ion diffusion paths, thus promoting lithium-ion migration within the particles. Strontium doping strengthens the crystal structure, enhancing structural stability and minimizing structural changes and lattice distortion during charge-discharge cycles, thereby improving cycle stability. Simultaneously, strontium doping facilitates control over the size of single-crystal grains and promotes a more uniform particle size distribution. Smaller single-crystal particles effectively suppress microcrack formation, prevent electrolyte infiltration into the particle interior, and inhibit side reactions. Furthermore, the increased oxygen vacancy formation energy and reduced migration barrier in the strontium-doped high-nickel single-crystal NCM cathode material both contribute to improved electrochemical performance.

[0047] The preparation method involves preparing a solution of strontium source as a dopant with other raw materials, followed by spray pyrolysis and lithiation calcination to obtain a doped high-nickel single-crystal cathode material. This invention combines strontium doping with spray pyrolysis, which helps to lower the calcination temperature and overcomes defects caused by excessively high single-crystal growth temperatures. Specifically, it enables low-temperature, efficient, and uniform strontium doping to obtain high-nickel single-crystal cathode materials with controlled particle size, facilitating the acquisition of smaller single-crystal grain sizes. Detailed Implementation

[0048] The technical solution of the present invention will be further illustrated below through specific embodiments.

[0049] Those skilled in the art will understand that the embodiments described are merely illustrative of the invention and should not be construed as limiting the invention.

[0050] Example 1

[0051] This embodiment provides a doped high-nickel single-crystal cathode material. The doped high-nickel single-crystal cathode material is a single-crystal particle and the doping element includes strontium. The average particle size is 2µm, and the chemical formula is LiNi. 0.9 Co 0.05 Mn 0.05 Sr 0.015 O2.

[0052] This embodiment also provides a method for preparing the doped high-nickel single-crystal cathode material, the method comprising the following steps:

[0053] Step 1: Prepare the mixed solution:

[0054] Nickel nitrate (Ni(NO3)2), cobalt nitrate (Co(NO3)2), manganese nitrate (Mn(NO3)2), and strontium nitrate (Sr(NO3)2) were dissolved in deionized water in the molar ratio Ni:Co:Mn:Sr = 0.90:0.05:0.05:0.015 to prepare a mixed solution with a concentration of 400 g / L.

[0055] Step 2: Preparation of Strontium-doped ternary precursor powder by spray pyrolysis

[0056] A two-fluid atomizer was used to spray and atomize the mixed solution. The gas pressure was controlled at 0.2~1.2 MPa, and the flow ratio of the carrier gas nitrogen to compressed air was adjusted to 3:1, with a carrier gas flow rate of 25 m³ / h. 3 / h, the mixed solution is atomized into 10~100µm atomized droplets and sprayed into the drying tower (inlet temperature controlled at 260℃, outlet temperature at 680℃) for drying and pyrolysis, with an average residence time of 16s, and strontium-doped ternary precursor powder.

[0057] Step 3: Low-temperature lithiation calcination

[0058] Uniformly doped strontium-doped ternary precursor powder was mixed with lithium source LiOH·H2O at an elemental molar ratio of Li:(Ni+Co+Mn+Sr)=1.02:1. The mixture was first calcined at 550℃ for 5 hours to completely remove moisture and melt the lithium source. Then, the mixture was calcined again in a pure oxygen atmosphere at a rate of 5℃ / min to 750℃ and held for 12 hours to obtain a doped high-nickel single-crystal cathode material.

[0059] Example 2

[0060] This embodiment provides a doped high-nickel single-crystal cathode material. The difference from Embodiment 1 is that the doping amount of strontium is adjusted. Specifically, in step 1 of the method, the molar ratio of the elements is adjusted from Ni:Co:Mn:Sr=0.90:0.05:0.05:0.015 to 0.90:0.05:0.05:0.003 to control the amount of raw materials used. Apart from the above, the other conditions are exactly the same as in Embodiment 1.

[0061] Example 3

[0062] This embodiment provides a doped high-nickel single-crystal cathode material. The difference from Embodiment 1 is that the doping amount of strontium is adjusted. Specifically, in step 1 of the method, the molar ratio of the elements is adjusted from Ni:Co:Mn:Sr=0.90:0.05:0.05:0.015 to 0.90:0.05:0.05:0.03 to control the amount of raw materials used. Apart from the above, the other conditions are exactly the same as in Embodiment 1.

[0063] Example 4

[0064] This embodiment provides a doped high-nickel single-crystal cathode material. The difference from Embodiment 1 is that the average particle size of the doped high-nickel single-crystal cathode material is adjusted from 2µm to 1µm. Apart from the above, the other conditions are exactly the same as those in Embodiment 1.

[0065] Example 5

[0066] This embodiment provides a doped high-nickel single-crystal cathode material. The difference from Embodiment 1 is that the average particle size of the doped high-nickel single-crystal cathode material is adjusted from 2µm to 3µm. Apart from the above, the other conditions are exactly the same as those in Embodiment 1.

[0067] Example 6

[0068] This embodiment provides a doped high-nickel single-crystal cathode material. The difference from Embodiment 1 is that the ratio of nickel, cobalt, and manganese elements is adjusted. Specifically, in step 1 of the method, the molar ratio of the elements is adjusted from Ni:Co:Mn:Sr=0.90:0.05:0.05:0.015 to 0.80:0.10:0.10:0.015 to control the amount of raw materials. Apart from the above, the other conditions are exactly the same as in Embodiment 1.

[0069] Comparative Example 1

[0070] This comparative example provides a high-nickel single-crystal cathode material. The difference from Example 1 is that strontium or other elements are not doped. Specifically, in step 1 of the method, the molar ratio of the elements is adjusted from Ni:Co:Mn:Sr=0.90:0.05:0.05:0.015 to 0.90:0.05:0.05:0 to control the amount of raw materials. Apart from the above, the other conditions are exactly the same as in Example 1.

[0071] Comparative Example 2

[0072] This comparative example provides a doped high-nickel single-crystal cathode material. The difference from Example 1 is that the doping amount of strontium is adjusted. Specifically, in step 1 of the method, the molar ratio of the elements is adjusted from Ni:Co:Mn:Sr=0.90:0.05:0.05:0.015 to 0.90:0.05:0.05:0.001 to control the amount of raw materials used. Apart from the above, the other conditions are exactly the same as in Example 1.

[0073] Comparative Example 3

[0074] This embodiment provides a doped high-nickel single-crystal cathode material. The difference from Embodiment 1 is that the doping amount of strontium is adjusted. Specifically, in step 1 of the method, the molar ratio of the elements is adjusted from Ni:Co:Mn:Sr=0.90:0.05:0.05:0.015 to 0.90:0.05:0.05:0.04 to control the amount of raw materials used. Apart from the above, the other conditions are exactly the same as in Embodiment 1.

[0075] Comparative Example 4

[0076] This comparative example provides a doped high-nickel single-crystal cathode material. The difference from Example 1 is that the average particle size of the doped high-nickel single-crystal cathode material is adjusted from 2µm to 0.5µm. Apart from the above, the other conditions are exactly the same as those in Example 1.

[0077] Comparative Example 5

[0078] This comparative example provides a doped high-nickel single-crystal cathode material. The difference from Example 1 is that the average particle size of the doped high-nickel single-crystal cathode material is adjusted from 2µm to 4µm. Apart from the above, the other conditions are exactly the same as those in Example 1.

[0079] Comparative Example 6

[0080] This comparative example provides a high-nickel single-crystal cathode material. The difference from Example 6 is that strontium or other elements are not doped. Specifically, in step 1 of the method, the molar ratio of the elements is adjusted from Ni:Co:Mn:Sr=0.80:0.10:0.10:0.015 to 0.80:0.10:0.10:0 to control the amount of raw materials. Apart from the above, the other conditions are exactly the same as in Example 6.

[0081] The cathode materials obtained in the examples and comparative examples were tested as follows:

[0082] Battery assembly: The positive electrode materials prepared in all embodiments were mixed with conductive agent and binder in a ratio of 92:4:4 to form a slurry, which was then coated onto aluminum foil and dried to serve as the positive electrode. CR2032 button-type half-cells were assembled in an argon-filled glove box using lithium metal sheets as the negative electrode.

[0083] Test conditions: voltage range 2.8~4.3V, temperature 25℃.

[0084] Test content:

[0085] First-round performance: Tested at 0.1C rate, the first coulomb efficiency was recorded.

[0086] Cycling performance: Capacity retention was recorded after 200 cycles of continuous charge-discharge cycles at 1C rate.

[0087] Table 1

[0088]

[0089] As can be seen from Table 1:

[0090] A comparison of Examples 1 and 2-3 shows that the doping amount of strontium in the core of the doped high-nickel single-crystal cathode material of the present invention affects its performance. Controlling the strontium doping amount to 0.3 mol / %~3 mol / % yields a doped high-nickel single-crystal cathode material with better performance. If the strontium doping amount is too low, it cannot effectively suppress the migration of transition metal ions to Li sites, resulting in insufficient stability of the layered structure and easy structural collapse during cycling, affecting cycling performance. If the strontium doping amount is too high, it may occupy too many Li sites, hindering Li... + Diffusion reduces capacity.

[0091] A comparison of Examples 1 and 4-5 shows that in the core of the doped high-nickel single-crystal cathode material of the present invention, the particle size of the cathode material affects its performance. Controlling the particle size to 1µm~3µm results in a doped high-nickel single-crystal cathode material with better performance. If the particle size is too large, microcracks will form on the surface of the cathode material, and the electrolyte will penetrate into the particle to produce side reactions, reducing the life of the cathode material. If the particle size is too small, the material has a huge specific surface area, the interfacial impedance will continue to rise, lithium ion transport will be hindered, and the capacity will decay faster.

[0092] As can be seen from the comparison between Example 1 and Comparative Examples 1-3, strontium doping can alter the crystal structure of NCM, improve ion mixing, and optimize ion diffusion paths, which is beneficial for promoting lithium-ion migration within the particles. The strengthening of the crystal structure by strontium doping enhances structural stability, minimizing structural changes and lattice distortion during charge-discharge cycles, thereby improving cycle stability.

[0093] As can be seen from the comparison between Example 1 and Comparative Examples 4-5, single-crystal materials of suitable size can avoid interfacial side reactions with the electrolyte, thereby improving the lifespan of the cathode material.

[0094] As can be seen from the comparison between Example 6 and Comparative Example 6, strontium doping improves the performance of cathode materials for both high-nickel single crystals and ultra-high-nickel single crystals.

[0095] In summary, this invention selects strontium as a dopant. Strontium doping can alter the crystal structure of NCM, improve ion mixing, and optimize ion diffusion paths, thus promoting lithium-ion migration within the particles. Strontium doping strengthens the crystal structure, enhancing structural stability and minimizing structural changes and lattice distortion during charge-discharge cycles, thereby improving cycle stability. Simultaneously, strontium doping facilitates control over the size of single-crystal grains and promotes a more uniform particle size distribution. Smaller single-crystal particles effectively suppress microcrack formation, prevent electrolyte infiltration into the particle interior, and inhibit side reactions. Furthermore, the increased oxygen vacancy formation energy and reduced migration barrier in the strontium-doped high-nickel single-crystal NCM cathode material both contribute to improved electrochemical performance.

[0096] The preparation method involves preparing a solution of strontium source as a dopant with other raw materials, followed by spray pyrolysis and lithiation calcination to obtain a doped high-nickel single-crystal cathode material. This invention combines strontium doping with spray pyrolysis, which helps to lower the calcination temperature and overcomes defects caused by excessively high single-crystal growth temperatures. Specifically, it enables low-temperature, efficient, and uniform strontium doping to obtain high-nickel single-crystal cathode materials with controlled particle size, facilitating the acquisition of smaller single-crystal grain sizes.

[0097] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0098] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0099] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A doped high-nickel single-crystal cathode material, characterized in that, The doped high-nickel single-crystal cathode material consists of single-crystal particles and is doped with strontium, with an average particle size of 1µm to 3µm, and is chemically denoted as LiNi. a Co b Mn c Sr d O2, where 0.8≤a<1, 0<b<0.2, 0<c<0.2, a+b+c=1, d=0.003~0.

03.

2. A method for preparing a doped high-nickel single-crystal cathode material, characterized in that, The preparation method includes: A nickel source, a cobalt source, a manganese source, and a strontium source are prepared into a mixed solution; in the mixed solution, the molar amount of nickel accounts for at least 80% of the total molar amount of nickel, cobalt, and manganese. The mixed solution was subjected to spray pyrolysis to obtain strontium-doped ternary precursor powder; Strontium-doped ternary precursor powder was mixed with a lithium source and calcined to obtain a doped high-nickel single-crystal cathode material.

3. The method for preparing doped high-nickel single-crystal cathode material according to claim 2, characterized in that, The nickel source, cobalt source, and manganese source include nitrates of the corresponding metal elements; Preferably, the strontium source includes strontium nitrate; Preferably, in the mixed solution, the molar amount of strontium accounts for 0.3% to 3% of the total molar amount of nickel, cobalt, and manganese. Preferably, the total concentration of nickel source, cobalt source, manganese source and strontium source in the mixed solution is 50 g / L to 500 g / L.

4. The method for preparing the doped high-nickel single-crystal cathode material according to claim 2 or 3, characterized in that, The spray pyrolysis process includes first spraying the mixed solution to obtain atomized droplets, and then drying and pyrolyzing the atomized droplets.

5. The method for preparing the doped high-nickel single-crystal cathode material according to claim 4, characterized in that, The spray atomization device includes a two-fluid atomizer; Preferably, the gas used for spray atomization includes a mixture of carrier gas and compressed air; Preferably, the carrier gas includes nitrogen; Preferably, the flow rate ratio of the carrier gas to the compressed air is (2~4):1; Preferably, the flow rate of the carrier gas is 20m³. 3 / h~30m 3 / h; Preferably, the gas pressure for atomization is 0.2 MPa to 1.2 MPa; Preferably, the size of the atomized droplets is 10~100µm.

6. The method for preparing the doped high-nickel single-crystal cathode material according to claim 4 or 5, characterized in that, The drying and pyrolysis equipment includes a drying tower; Preferably, the inlet temperature of the drying tower is 200℃~300℃; Preferably, the outlet temperature of the drying tower is 600℃~750℃; Preferably, the average residence time of the atomized droplets in the drying tower is 10s to 20s.

7. The method for preparing the doped high-nickel single-crystal cathode material according to any one of claims 2-6, characterized in that, The lithium source includes LiOH·H2O; Preferably, the dosage is controlled according to the ratio of the molar amount of lithium element in the lithium source to the total molar amount of metal elements in the strontium-doped ternary precursor powder as (1~1.03):

1.

8. The method for preparing the doped high-nickel single-crystal cathode material according to any one of claims 2-7, characterized in that, The calcination process includes a first calcination at a first temperature to completely remove moisture and melt the lithium source, followed by a second calcination at a second temperature in a pure oxygen atmosphere.

9. The method for preparing the doped high-nickel single-crystal cathode material according to claim 8, characterized in that, The first temperature is 500℃~600℃; Preferably, the holding time for the first calcination is 4h to 6h; Preferably, the heating temperature of the second calcination is 3℃ / min to 8℃ / min; Preferably, the second temperature is 700℃~800℃; Preferably, the heat preservation time for the second calcination is 8h to 15h.

10. A battery, characterized in that, The material contains the doped high-nickel single-crystal cathode material according to claim 1 or the doped high-nickel single-crystal cathode material obtained by the preparation method according to any one of claims 2-9.

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