Lithium-position nickel-doped positive electrode material as well as preparation method and application thereof

Abstract

The invention relates to the technical field of batteries, and discloses a lithium-position nickel-doped positive electrode material and a preparation method and application thereof, and the preparation method comprises the following steps: (1) carrying out first mixing on a first lithium source, a first nickel source and a solvent to obtain a mixed metal solution; (2) carrying out spray drying on the mixed metal solution, and calcining to obtain lithium-nickel composite oxide microspheres; and (3) carrying out second mixing on the lithium-nickel composite oxide microspheres, a positive electrode precursor material and a second lithium source, and then sequentially pre-sintering and sintering to obtain the lithium-position nickel-doped positive electrode material. The lithium-position nickel-doped positive electrode material with excellent performance is prepared through mutual cooperation of designed specific preparation processes, so that the obtained positive electrode material can simultaneously exert excellent capacity performance and crystal structure stability in the running process of the lithium ion battery.

Description

A lithium-nickel-doped cathode material, its preparation method and application Technical Field

[0001] This invention relates to the field of batteries, specifically to a lithium-nickel-doped cathode material, its preparation method, and its application. Background Technology

[0002] High-nickel ternary nickel-cobalt-aluminum cathode materials are widely recognized as one of the most promising cathode materials in the field of power batteries due to their high energy density, excellent cost-effectiveness, and good safety performance. However, these materials still face several technical challenges in practical applications, mainly including insufficient cycle stability, poor material-electrolyte interface stability, and stringent preparation process conditions. These factors collectively restrict further improvement in the electrochemical performance of high-nickel ternary nickel-cobalt-aluminum cathode materials. Therefore, how to improve their overall performance through precise control and optimization of crystal structure has become a key research direction.

[0003] In crystal structure regulation, the effective suppression of lithium / nickel disorder is particularly important. Precise control of lithium / nickel disorder can significantly alleviate irreversible phase transitions during cycling, enhance interfacial stability, optimize ion and electron transport dynamics, and reduce the accumulation of micro-stress within the material, thereby improving the rate performance and structural durability of the material. Currently, strategies for regulating lithium / nickel disorder mainly focus on element doping or surface coating techniques in the transition metal layer. However, doping mainly involves introducing heterogeneous elements into the bulk lattice of the cathode material, aiming to stabilize the crystal structure and improve electronic / ionic conductivity. These elements typically do not participate in electrochemical reactions (i.e., they are "inert"), which is the most direct cost of doping modification—trading some capacity for improved cycle life and stability. Conventional doping elements mostly enter the transition metal sites, having limited effect on suppressing nickel ion migration in the lithium layer. While surface coating can improve interfacial stability, it is difficult to solve the problem of structural degradation in the bulk phase of the material. Summary of the Invention

[0004] This invention provides a lithium-site nickel-doped cathode material, its preparation method, and its applications. This addresses the problem that existing cathode materials cannot simultaneously achieve both superior capacity performance and a stable crystal structure during battery operation.

[0005] In a first aspect, the present invention provides a method for preparing a lithium-nickel-doped cathode material, the method comprising the following steps: (1) mixing a first lithium source, a first nickel source and a solvent to obtain a mixed metal solution; (2) spray-drying the mixed metal solution and then calcining it to obtain lithium-nickel composite oxide particles; (3) mixing the lithium-nickel composite oxide particles, the cathode precursor material and the second lithium source in a second mixture and then pre-sintering and sintering them sequentially to obtain the lithium-nickel-doped cathode material.

[0006] As an optional implementation, in step (1), the molar ratio of the first lithium element in the first lithium source to the first nickel element in the first nickel source is x:y, where 0 < x ≤ 0.01 and 0 < y ≤ 0.01.

[0007] Optionally, in step (1), the first lithium source includes at least one of lithium nitrate, lithium carbonate, lithium acetate, and nickel sulfate.

[0008] Optionally, in step (1), the first nickel source includes at least one of nickel nitrate, nickel carbonate, nickel acetate, and nickel sulfate.

[0009] Optionally, the solvent in step (1) includes deionized water.

[0010] As an optional implementation, the total concentration of metal elements in the mixed metal solution in step (1) is 0.5-1.0 mol / L.

[0011] As an optional implementation, the inlet temperature of the spray dryer in step (2) is 250-270°C.

[0012] As an optional implementation, the outlet temperature of the spray dryer in step (2) is 100-120°C.

[0013] As an optional implementation, the rotation speed of the atomizer in the spray drying process of step (2) is 18000-22000 rpm.

[0014] As an optional implementation, the calcination temperature in step (2) is 400-500℃.

[0015] As an optional implementation, the calcination time in step (2) is 3-5 hours.

[0016] As an optional implementation, the calcination atmosphere in step (2) includes an oxygen-containing atmosphere.

[0017] Optionally, the oxygen-containing atmosphere includes an air atmosphere or an oxygen atmosphere.

[0018] As an optional implementation, the average particle size of the lithium-nickel composite oxide particles in step (2) is 8-15 μm.

[0019] As an optional implementation, the positive electrode precursor material in step (3) is a ternary nickel-cobalt-aluminum precursor material, which includes a second nickel element, a cobalt element and an aluminum element, and the molar ratio of the second nickel element, cobalt element and aluminum element is a:b:c, where a+b+c=1, 0.6<a<0.9, 0<b<0.2, 0<c<0.2.

[0020] Furthermore, as an optional implementation, the chemical formula of the ternary nickel-cobalt-aluminum precursor material is Ni a Co b Al c (OH)2, where a+b+c=1, 0.6<a<0.9, 0<b<0.2, 0<c<0.2.

[0021] As an optional implementation, the ratio of the total molar amount of metal elements in the positive electrode precursor material in step (3) to the total molar amount of the first lithium element and the first nickel element in the lithium-nickel composite oxide particles is 1:(x+y), where 0<x≤0.01 and 0<y≤0.01.

[0022] As an optional implementation, the ratio of the total molar amount of metal elements in the positive electrode precursor material in step (3) to the molar amount of the second lithium element in the second lithium source is 1:(1-xy), where 0<x≤0.01 and 0<y≤0.01.

[0023] Optionally, in step (3), the second lithium source includes at least one of lithium hydroxide, lithium nitrate, lithium carbonate, and lithium acetate.

[0024] As an optional implementation, step (3) the second mixing method includes ball milling.

[0025] Optionally, in the second mixing process, the ball milling media used in the ball milling includes zirconium oxide balls, the ball milling aid used in the ball milling includes ethanol, the ball-to-material ratio of the ball milling is (5-15):1, and the ratio of the total mass of the lithium-nickel composite oxide particles, the cathode precursor material and the second lithium source to the mass of the ball milling aid is (0.5-2):1.

[0026] As an optional implementation, in step (3), the rotation speed of the second mixing is 200-400 rpm.

[0027] As an optional implementation, the mixing time in step (3) is 4-6 hours.

[0028] As an optional implementation, the heating rate of the pre-sintering in step (3) is 1-5℃ / min.

[0029] As an optional implementation, the holding temperature for pre-sintering in step (3) is 400-600℃.

[0030] As an optional implementation, the heat preservation time for pre-sintering in step (3) is 4-6 hours.

[0031] As an optional implementation, the pre-sintering atmosphere in step (3) includes an oxygen-containing atmosphere.

[0032] As an optional implementation, the heating rate of the sintering in step (3) is 1-5℃ / min.

[0033] As an optional implementation, the holding temperature for sintering in step (3) is 760-780℃.

[0034] As an optional implementation, the holding time for sintering in step (3) is 10-20 hours.

[0035] As an optional implementation, the sintering atmosphere in step (3) includes an oxygen-containing atmosphere.

[0036] As an optional implementation, the product obtained after sintering in step (3) is further ground and sieved.

[0037] Optionally, the sieve used for sieving has a mesh size of 300-500.

[0038] Secondly, the present invention also provides a lithium-site nickel-doped cathode material, which is prepared by the preparation method described in the first aspect.

[0039] As an optional implementation, the lithium-nickel-doped cathode material has the chemical formula Li. 1-y Ni a+ y Co b Al c O2, where 0 < y ≤ 0.01, 0.6 < a < 0.9, 0 < b < 0.2, 0 < c < 0.2, and a + b + c = 1.

[0040] Thirdly, the present invention also provides a lithium-ion battery, the lithium-ion battery comprising a positive electrode sheet, the positive electrode sheet comprising a positive electrode material, the positive electrode material comprising the lithium-site nickel-doped positive electrode material described in the second aspect.

[0041] The technical solution of the present invention has the following advantages: The preparation method of the lithium nickel doped cathode material provided by the present invention includes the following steps: (1) mixing the first lithium source, the first nickel source and the solvent to obtain a mixed metal solution; (2) spray drying the mixed metal solution and then calcining it to obtain lithium nickel composite oxide particles; (3) mixing the lithium nickel composite oxide particles, the cathode precursor material and the second lithium source to obtain the lithium nickel doped cathode material. The preparation method provided by this invention first mixes and spray-dries a first nickel source and a first lithium source to form lithium-nickel composite salt microspheres with highly uniform composition. Then, the spray-dried microspheres are calcined to completely decompose the metal salts, forming lithium-nickel composite oxide particles with uniform elemental distribution and appropriate size. Further, the lithium-nickel composite oxide particles are mixed a second time with a positive electrode precursor material and a second lithium source to prevent particle agglomeration and achieve uniform mixing. After this mixing, a pre-sintering process is performed to remove the water of crystallization from the mixed product and initiate an initial solid-state reaction, forming amorphous or semi-crystalline structures. A crystalline layered structure framework prepares for subsequent crystal growth. Following this, a sintering process is performed to form a lithium-doped nickel-coated cathode material. Introducing nickel as a dopant at the lithium sites avoids affecting the electrochemically active elements at the transition metal sites in the cathode material and ensures unimpeded lithium-ion diffusion. The lithium-doped nickel interacts with the transition metal nickel through a 180° Ni-O-Ni pathway, promoting antiferromagnetic coupling and pinning the structure, effectively suppressing phase transitions and improving the stability of the cathode material's crystal structure. Furthermore, the lithium-doped nickel-coated cathode material provided in this application exhibits a significant advantage over inert dopants introduced at transition metal sites during battery cycling, where a small amount of lithium substitution does not affect the number of reversibly inserted / extracted lithium ions. This invention, through a specifically designed synergistic preparation process, yields a high-performance lithium-doped nickel-coated cathode material, enabling it to simultaneously exhibit excellent capacity performance and crystal structure stability during lithium-ion battery operation. Attached Figure Description

[0042] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0043] Figure 1 shows the X-ray diffraction (XRD) patterns of the cathode materials provided in Embodiments 1, 4, 5 and 6 of this invention. Detailed Implementation

[0044] The following embodiments are provided to better understand the present invention, but the following embodiments do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the scope of protection of the present invention.

[0045] Unless otherwise specified, all experimental steps or conditions in the examples were performed according to conventional experimental procedures and conditions in the art. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0046] Example 1 This example provides a method for preparing a lithium-site nickel-doped cathode material, specifically including the following steps: S1. Dissolve LiNO3 and NiNO3·6H2O in deionized water at a molar ratio of Li to Ni of 0.005:0.005 to prepare a mixed metal solution with a concentration of 0.75 mol / L.

[0047] S2. The mixed metal solution obtained in step S1 is transported to a spray dryer by a peristaltic pump for spray drying. The parameters are set as follows: inlet temperature 260℃, outlet temperature 110℃, and atomizer speed 20000rpm. Then, the product obtained by spray drying is calcined in air at 450℃ for 4 hours to obtain lithium nickel composite oxide particles with an average particle size of 10μm.

[0048] S3. The lithium-nickel composite oxide particles obtained in step S2 are ball-milled with the cathode precursor material and lithium hydroxide. Zirconia balls are used as the grinding medium during the ball milling process, and anhydrous ethanol is added as a grinding aid. The ball-to-material ratio (the ratio of the mass of the zirconia balls to the total mass of the lithium-nickel composite oxide particles, cathode precursor material and lithium hydroxide) is 10:1, and the ratio of the total mass of the lithium-nickel composite oxide particles, cathode precursor material and lithium hydroxide to the mass of anhydrous ethanol is 0.5:1. The ball milling speed is 300 rpm and the time is 5 h.

[0049] The chemical formula of the positive electrode precursor material is Ni. 0.8 Co 0.1 Al 0.1 The ratio of the total molar amount of metal elements in the positive electrode precursor material to the total molar amount of lithium and nickel elements in the lithium-nickel composite oxide particles is 1:0.01, and the ratio of the total molar amount of metal elements in the positive electrode precursor material to the molar amount of lithium elements in lithium hydroxide is 1:0.99.

[0050] S4. Place the product from the ball milling mixture in step S3 into a high-temperature furnace filled with oxygen. First, heat the product to 500℃ at a heating rate of 2℃ / min and hold for 5 hours for pre-sintering. Then, heat the product to 760℃ at a heating rate of 3℃ / min and hold for 15 hours for sintering. Cool the sintered product to 25℃ with the furnace. Next, grind the sintered product and sieve it through a 400-mesh sieve to obtain a lithium-nickel-doped cathode material with the chemical formula Li. 0.995 Ni 0.805 Co 0.1 Al 0.1 O2.

[0051] Example 2 This example provides a method for preparing a lithium-site nickel-doped cathode material, which specifically includes the following steps: S1. Dissolve LiNO3 and NiNO3·6H2O in deionized water at a molar ratio of Li to Ni of 0.01:0.01 to prepare a mixed metal solution with a concentration of 0.5 mol / L.

[0052] S2. The mixed metal solution obtained in step S1 is transported to a spray dryer by a peristaltic pump for spray drying. The parameters are set as follows: inlet temperature 250℃, outlet temperature 100℃, and atomizer speed 18000rpm. Then, the product obtained by spray drying is calcined in air at 400℃ for 5h to obtain lithium nickel composite oxide particles with an average particle size of 8μm.

[0053] S3. The lithium-nickel composite oxide particles obtained in step S2 are ball-milled with the cathode precursor material and lithium hydroxide. Zirconia balls are used as the grinding medium during the ball milling process, and anhydrous ethanol is added as a grinding aid. The ball-to-material ratio (the ratio of the mass of the zirconia balls to the total mass of the lithium-nickel composite oxide particles, cathode precursor material and lithium hydroxide) is 10:1, and the ratio of the total mass of the lithium-nickel composite oxide particles, cathode precursor material and lithium hydroxide to the mass of anhydrous ethanol is 2:1. The ball milling speed is 200 rpm and the time is 6 hours.

[0054] The chemical formula of the positive electrode precursor material is Ni. 0.7 Co 0.15 Al 0.15 The ratio of the total molar amount of metal elements in the positive electrode precursor material to the total molar amount of lithium and nickel elements in the lithium-nickel composite oxide particles is 1:0.02, and the ratio of the total molar amount of metal elements in the positive electrode precursor material to the molar amount of lithium elements in lithium hydroxide is 1:0.98.

[0055] S4. Place the product from the ball milling mixture in step S3 into a high-temperature furnace filled with oxygen. First, heat the product to 400℃ at a heating rate of 1℃ / min and hold for 6 hours for pre-sintering. Then, heat the product to 780℃ at a heating rate of 5℃ / min and hold for 10 hours for sintering. Cool the sintered product to 25℃ with the furnace. Next, grind the sintered product and sieve it through a 300-mesh sieve to obtain a lithium-nickel-doped cathode material with the chemical formula Li. 0.99 Ni 0.71 Co 0.15 Al 0.15 O2.

[0056] Example 3 This example provides a method for preparing a lithium-site nickel-doped cathode material, specifically including the following steps: S1. Dissolve LiNO3 and NiNO3·6H2O in deionized water at a molar ratio of Li to Ni of 0.01:0.01 to prepare a mixed metal solution with a concentration of 1 mol / L.

[0057] S2. The mixed metal solution obtained in step S1 is transported to a spray dryer by a peristaltic pump for spray drying. The parameters are set as follows: inlet temperature 270℃, outlet temperature 120℃, and atomizer speed 21000rpm. Then, the product obtained by spray drying is calcined in air at 500℃ for 3 hours to obtain lithium nickel composite oxide particles with an average particle size of 15μm.

[0058] S3. The lithium-nickel composite oxide particles obtained in step S2 are ball-milled with the cathode precursor material and lithium hydroxide. Zirconia balls are used as the grinding medium during the ball milling process, and anhydrous ethanol is added as a grinding aid. The ball-to-material ratio (the ratio of the mass of the zirconia balls to the total mass of the lithium-nickel composite oxide particles, cathode precursor material and lithium hydroxide) is 10:1, and the ratio of the total mass of the lithium-nickel composite oxide particles, cathode precursor material and lithium hydroxide to the mass of anhydrous ethanol is 1:1. The ball milling speed is 400 rpm and the time is 4 h.

[0059] The chemical formula of the positive electrode precursor material is Ni. 0.85 Co 0.1 Al 0.05 The ratio of the total molar amount of metal elements in the positive electrode precursor material to the total molar amount of lithium and nickel elements in the lithium-nickel composite oxide particles is 1:0.02, and the ratio of the total molar amount of metal elements in the positive electrode precursor material to the molar amount of lithium elements in lithium hydroxide is 1:0.98.

[0060] S4. Place the product from the ball milling mixture in step S3 into a high-temperature furnace filled with oxygen. First, heat the product to 600℃ at a heating rate of 5℃ / min and hold for 4 hours for pre-sintering. Then, heat the product to 760℃ at a heating rate of 1℃ / min and hold for 20 hours for sintering. Cool the sintered product to 25℃ with the furnace. Next, grind the sintered product and sieve it through a 500-mesh sieve to obtain a lithium-nickel-doped cathode material with the chemical formula Li. 0.99 Ni 0.86 Co 0.1 Al 0.05 O2.

[0061] Example 4 differs from Example 1 only in that: in step S1, the molar ratio of Li to Ni in LiNO3 and NiNO3·6H2O is 0.01:0.01; in step S3, the ratio of the total molar amount of metal elements in the cathode precursor material to the total molar amount of lithium and nickel in the lithium-nickel composite oxide particles is 1:0.02; the ratio of the total molar amount of metal elements in the cathode precursor material to the molar amount of lithium in lithium hydroxide is 1:0.98; and the chemical formula of the lithium-nickel-doped cathode material obtained in step S3 is Li 0.99 Ni 0.81 Co 0.1 Al 0.1 O2. All other contents are the same as in Example 1.

[0062] Example 5 differs from Example 1 only in that the holding temperature in step S4 of the sintering process is 770℃. All other aspects are the same as in Example 1.

[0063] Example 6 differs from Example 4 only in that the holding temperature in step S4 is 770℃. All other aspects are the same as in Example 4.

[0064] Example 7: The only difference between this example and Example 1 is that the holding temperature in step S4 of the sintering process is 780℃. All other contents are the same as in Example 1.

[0065] Example 8 differs from Example 4 only in that the holding temperature in step S4 is 780℃. All other aspects are the same as in Example 4.

[0066] Example 9 differs from Example 1 only in that the holding temperature in step S4 of the sintering process is 750°C. All other aspects are the same as in Example 1.

[0067] Example 10: The only difference between this example and Example 1 is that the holding temperature in step S4 of the sintering process is 790℃. All other contents are the same as in Example 1.

[0068] Example 11 differs from Example 1 only in that: in step S1, the molar ratio of Li to Ni in LiNO3 and NiNO3·6H2O is 0.02:0.02; in step S3, the ratio of the total molar amount of metal elements in the cathode precursor material to the total molar amount of lithium and nickel in the lithium-nickel composite oxide particles is 1:0.04; the ratio of the total molar amount of metal elements in the cathode precursor material to the molar amount of lithium in lithium hydroxide is 1:0.96; and the chemical formula of the lithium-nickel-doped cathode material obtained in step S4 is Li 0.98 Ni 0.82 Co 0.1 Al 0.1 O2. All other contents are the same as in Example 1.

[0069] Example 12: The only difference between this example and Example 1 is that the concentration of the mixed metal solution prepared in step S1 is 0.2 mol / L. All other aspects are the same as in Example 1.

[0070] Example 13: The only difference between this example and Example 1 is that the concentration of the mixed metal solution prepared in step S1 is 1.5 mol / L. All other aspects are the same as in Example 1.

[0071] Example 14: The only difference between this example and Example 1 is that the calcination temperature in step S2 is 350°C. All other contents are the same as in Example 1.

[0072] Example 15: The only difference between this example and Example 1 is that the calcination temperature in step S2 is 550°C. All other contents are the same as in Example 1.

[0073] Comparative Example 1 differs from Example 1 only in that the preparation of lithium-nickel composite oxide particles in steps S1 and S2 is omitted, and step S3 directly uses the material with the chemical formula Ni. 0.8 Co 0.1 Al 0.1 The positive electrode precursor material (OH)₂ and lithium hydroxide are mixed in a 1:1 ratio of the total molar amount of metal elements in the positive electrode precursor material to the molar amount of lithium elements in the lithium hydroxide, resulting in a positive electrode material with the chemical composition LiNi. 0.8 Co 0.1 Al 0.1 O2. All other contents are the same as in Example 1.

[0074] Comparative Example 2 differs from Example 5 only in that the preparation of lithium-nickel composite oxide particles in steps S1 and S2 is omitted, and step S3 directly uses the material with the chemical formula Ni. 0.8 Co 0.1 Al0.1 The positive electrode precursor material (OH)₂ and lithium hydroxide are mixed in a 1:1 ratio of the total molar amount of metal elements in the positive electrode precursor material to the molar amount of lithium elements in the lithium hydroxide, resulting in a positive electrode material with the chemical composition LiNi. 0.8 Co 0.1 Al 0.1 O2. The rest of the content is the same as in Example 5.

[0075] The only difference between Comparative Example 3 and Example 7 is that the preparation of lithium-nickel composite oxide particles in steps S1 and S2 is omitted, and step S3 directly uses the material with the chemical formula Ni. 0.8 Co 0.1 Al 0.1 The positive electrode precursor material (OH)₂ and lithium hydroxide are mixed in a 1:1 ratio of the total molar amount of metal elements in the positive electrode precursor material to the molar amount of lithium elements in the lithium hydroxide, resulting in a positive electrode material with the chemical composition LiNi. 0.8 Co 0.1 Al 0.1 O2. The rest of the content is the same as in Example 7.

[0076] The only difference between Comparative Example 4 and Example 1 is that the pre-sintering process in step S4 is omitted, and the product obtained after ball milling is directly heated to 760°C at a heating rate of 3°C / min and sintered for 15 hours. All other contents are the same as in Example 1.

[0077] The only difference between Comparative Example 5 and Example 1 is that the sintering process in step S4 is omitted, and the product obtained after ball milling is directly heated to 500°C for pre-sintering at a heating rate of 2°C / min for 5 hours. All other contents are the same as in Example 1.

[0078] The only difference between Comparative Example 6 and Example 1 is that the spray drying process in step S2 is replaced with a vacuum drying process at 260°C. All other aspects are the same as in Example 1.

[0079] The cathode materials prepared by the methods provided in the above embodiments and comparative examples were subjected to X-ray diffraction tests, and the obtained X-ray diffraction patterns (XRD patterns) were used to calculate I(003) / I(104). The results are shown in Table 1: Table 1

[0080] The cathode materials provided in the above embodiments and comparative examples are used in the preparation of lithium-ion batteries. The specific preparation process includes: mixing the cathode materials prepared in the above embodiments and comparative examples, polyvinylidene fluoride binder, and conductive carbon black in a mass ratio of 90:5:5, adding N-methylpyrrolidone for homogenization to obtain a cathode slurry, and then coating the cathode slurry onto aluminum foil (area density of 15 mg / cm³). 2 Next, the positive electrode sheet was dried at 80°C for 6 hours, pressed, and sliced ​​to obtain the positive electrode sheet. The lithium-ion coin cell was assembled using a polypropylene membrane as the separator, a lithium metal sheet as the negative electrode, and an electrolyte of 1 mol / L LiPF6 (solvent: ethylene carbonate and diethyl carbonate in a volume ratio of 1:1).

[0081] Electrochemical performance tests were conducted on lithium-ion batteries assembled using the cathode materials provided in the above embodiments and comparative examples, respectively, using a Wuhan Landian CT2001A battery tester. The specific testing process is as follows: First, under a constant temperature environment of 25°C, the battery was charged at a constant current of 0.2C to 4.3V, then charged at a constant voltage until the current dropped to 0.05C, and then allowed to stand for 10 minutes. Subsequently, it was discharged at a constant current of 0.2C to 3.0V, completing one charge-discharge cycle. This process was repeated twice to activate the battery cycle. Then, at a charge-discharge rate of 1C, continuous constant current charge-discharge cycle tests were performed within a voltage range of 3.0V-4.3V, for a total of 50 cycles. The discharge capacity of the 1st and 50th cycles was recorded, and the capacity retention rate (discharge capacity of the 50th cycle / discharge capacity of the 1st cycle × 100%) was calculated to evaluate the long-term service life of the battery, and the first-cycle discharge specific capacity and first-cycle coulombic efficiency at 0.2C were recorded.

[0082] The test results are shown in Table 2: Table 2

[0083] As shown in Table 1, the preparation method provided by this invention uses a mixing process of nickel source and part of lithium source, followed by a spray pyrolysis process combined with a calcination process to form lithium-nickel composite oxide particles. These particles are then mixed with a cathode precursor material and another part of the lithium source, followed by pre-sintering and sintering processes to form a lithium-nickel-doped cathode material. Part of the nickel element is doped into the lithium sites of the cathode material, replacing part of the lithium element in the lithium sites. Through the synergistic effect of a specifically designed preparation process, a high-performance lithium-nickel-doped cathode material is prepared, enabling the obtained cathode material to simultaneously exhibit excellent capacity performance and crystal structure stability during the operation of a lithium-ion battery.

[0084] Figure 1 shows the X-ray diffraction (XRD) patterns of the cathode materials prepared by the preparation methods provided in Examples 1, 4, 5 and 6. As can be seen from Figure 1, the cathode materials prepared by the preparation methods provided in Examples 1, 4, 5 and 6 have high crystallinity and a high value of I(003) / I(104), which effectively reduces the mixing of lithium and nickel.

[0085] By comparing Example 1 with Comparative Example 1, Example 5 with Comparative Example 2, and Example 7 with Comparative Example 3, it can be seen that if the lithium-nickel composite oxide microspheres and the nickel doping at the lithium sites are omitted, the resulting cathode material, when applied to a battery, will not effectively improve the battery's cycle performance.

[0086] The comparison between Example 1 and Comparative Examples 4-5 shows that if pre-sintering is omitted, it will affect the subsequent crystal growth, resulting in poor performance and crystal structure stability of the obtained cathode material, and a decrease in the cycle performance of the lithium-ion battery. If the sintering process is omitted, the cathode precursor material will not be completely converted into an active material with a regular layered structure, resulting in many lattice defects and poor material crystallinity, which will block the lithium-ion transport channel, resulting in low initial charge and discharge efficiency, and deterioration of battery capacity and cycle performance.

[0087] The comparison between Example 1 and Comparative Example 6 shows that if spray drying is replaced with conventional vacuum drying, the uniformity of lithium and nickel elements will be affected, thereby affecting the electrochemical performance of the battery.

[0088] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preparing a lithium-site nickel-doped cathode material, characterized in that, The preparation method includes the following steps: (1) mixing the first lithium source, the first nickel source and the solvent to obtain a mixed metal solution; (2) spray drying the mixed metal solution and then calcining it to obtain lithium-nickel composite oxide particles; (3) mixing the lithium-nickel composite oxide particles, the cathode precursor material and the second lithium source to obtain the lithium-nickel-doped cathode material by pre-sintering and sintering in sequence.

2. The preparation method according to claim 1, characterized in that, In step (1), the molar ratio of the first lithium element in the first lithium source to the first nickel element in the first nickel source is x:y, where 0 < x ≤ 0.01, 0 < y ≤ 0.01; and / or, the total concentration of metal elements in the mixed metal solution in step (1) is 0.5-1.0 mol / L.

3. The preparation method according to claim 1 or 2, characterized in that, The inlet temperature of the spray drying in step (2) is 250-270℃; and / or the outlet temperature of the spray drying in step (2) is 100-120℃; and / or the rotation speed of the atomizer in the spray drying process in step (2) is 18000-22000rpm.

4. The preparation method according to any one of claims 1-3, characterized in that, The calcination temperature in step (2) is 400-500℃; and / or the calcination time in step (2) is 3-5h; and / or the calcination atmosphere in step (2) includes an oxygen-containing atmosphere; and / or the average particle size of the lithium-nickel composite oxide particles in step (2) is 8-15μm.

5. The preparation method according to any one of claims 1-4, characterized in that, The positive electrode precursor material in step (3) is a ternary nickel-cobalt-aluminum precursor material, which includes a second nickel element, a cobalt element and an aluminum element. The molar ratio of the second nickel element, cobalt element and aluminum element is a:b:c, where a+b+c=1, 0.6<a<0.9, 0<b<0.2, 0<c<0.2; and / or, the ratio of the total molar amount of metal elements in the positive electrode precursor material in step (3) to the total molar amount of the first lithium element and the first nickel element in the lithium-nickel composite oxide particles is 1:(x+y), where 0<x≤0.01, 0<y≤0.01; and / or, the ratio of the total molar amount of metal elements in the positive electrode precursor material in step (3) to the molar amount of the second lithium element in the second lithium source is 1:(1-xy), where 0<x≤0.01, 0<y≤0.

01.

6. The preparation method according to any one of claims 1-5, characterized in that, Step (3) The second mixing method includes ball milling; and / or, in step (3) the rotation speed of the second mixing is 200-400 rpm; and / or, in step (3) the second mixing time is 4-6 h.

7. The preparation method according to any one of claims 1-6, characterized in that, The heating rate of the pre-sintering in step (3) is 1-5℃ / min; and / or, the holding temperature of the pre-sintering in step (3) is 400-600℃; and / or, the holding time of the pre-sintering in step (3) is 4-6h; and / or, the atmosphere of the pre-sintering in step (3) includes an oxygen-containing atmosphere; and / or, the heating rate of the sintering in step (3) is 1-5℃ / min; and / or, the holding temperature of the sintering in step (3) is 760-780℃; and / or, the holding time of the sintering in step (3) is 10-20h; and / or, the atmosphere of the sintering in step (3) includes an oxygen-containing atmosphere; and / or, after the sintering in step (3), the obtained product is further ground and sieved.

8. A lithium-site nickel-doped cathode material, characterized in that, The lithium-site nickel-doped cathode material is prepared by the preparation method described in any one of claims 1-7.

9. The lithium-nickel-doped cathode material according to claim 8, characterized in that, The chemical formula of the lithium-nickel-doped cathode material is Li. 1-y Ni a+y Co b Al c O2, where 0 < y ≤ 0.01, 0.6 < a < 0.9, 0 < b < 0.2, 0 < c < 0.2, and a + b + c = 1.

10. A lithium-ion battery, characterized in that, The lithium-ion battery includes a positive electrode sheet, the positive electrode sheet includes a positive electrode material, and the positive electrode material includes the lithium-site nickel-doped positive electrode material as described in claim 8 or 9.

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