Modified high-nickel NCA positive electrode material and preparation method and application thereof
By modifying high-nickel NCA cathode materials with hafnium doping and double-layer coating, the structural degradation problem of the material during charge and discharge processes was solved, achieving high capacity, long cycle life and excellent rate performance.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-02-28
- Publication Date
- 2026-05-05
AI Technical Summary
High-nickel NCA cathode materials are prone to side reactions during charge and discharge, leading to structural degradation and short cycle life. Existing modification strategies cannot effectively improve capacity, rate performance and structural stability.
The core is a hafnium-doped lithium nickel cobalt aluminum oxide, with copper oxide and a fast lithium-ion conductor layer coated on the outside. The hafnium doping stabilizes the crystal structure, the copper oxide layer improves electronic conductivity, and the fast lithium-ion conductor layer promotes lithium-ion migration. The synergistic effect of the double coating improves the interface stability.
Significantly improves cycle performance, rate performance and thermal stability, reduces side reactions and extends battery life.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of lithium-ion battery cathode material technology, specifically to a modified high-nickel NCA cathode material, its preparation method, and its application. Background Technology
[0002] High-nickel NCA materials (such as LiNi) 0.88 Co 0.09 Al 0.03 O2 (Ni2+) is considered a core cathode material for next-generation lithium-ion batteries due to its high energy density (theoretical specific capacity up to 274 mAh / g), and has broad application prospects in electric vehicles and energy storage systems. However, high nickel content also brings a series of technical challenges: First, highly active Ni... 4+ It is prone to side reactions with the electrolyte, leading to an increase in residual lithium compounds (LiOH and Li2CO3) on the surface, which causes gas generation and capacity decay. Secondly, during charge and discharge, the H2-H3 phase transition causes lattice contraction in the c-axis direction, generating microcracks and accelerating structural degradation. In addition, cation mixing and interfacial instability also limit its cycle life and safety.
[0003] Currently, in the modification strategies of high-nickel NCA cathode materials, surface coating technology is widely used to isolate the electrolyte from direct contact with the material surface, thereby suppressing interfacial side reactions, reducing residual lithium compounds, and enhancing structural stability. However, while traditional single-component coatings have certain physical isolation effects and chemical stability, they are usually electronic insulators or semiconductors, which hinder interfacial charge transfer and lead to a decrease in battery rate performance. While some conductive polymers or carbon materials can improve electronic conductivity, they lack the ability to promote lithium-ion migration, and their structural stability and thermal expansion coefficient matching with the high-nickel matrix are poor, affecting the battery's long cycle life. Furthermore, elemental doping can enhance crystal structure stability, but it cannot effectively solve the above problems, and its use alone is still insufficient to improve battery capacity and rate performance.
[0004] Therefore, developing a comprehensive modification scheme that can improve the capacity, long cycle life, and rate performance of high-nickel NCA materials has become an urgent research need. Summary of the Invention
[0005] This invention provides a modified high-nickel NCA cathode material, its preparation method, and its application, which features high capacity, long cycle life, and excellent rate performance.
[0006] In a first aspect, the present invention provides a modified high-nickel NCA cathode material, comprising a core, a first coating layer, and a second coating layer arranged sequentially from the inside out;
[0007] The core comprises hafnium-doped lithium nickel cobalt aluminum oxide; The first coating layer includes copper oxide; The second coating layer includes a lithium fast ion conductor.
[0008] In one optional embodiment, the modified high-nickel NCA cathode material satisfies at least one of the following conditions: (1) The mass of the first coating layer is 0.1wt%-0.5wt% of the core mass; (2) The mass of the second coating layer is 0.5wt%-2wt% of the sum of the mass of the first coating layer and the core. (3) The molar amount of hafnium in the hafnium-doped lithium cobalt aluminum oxide accounts for 0.2%-1% of the total molar amount of hafnium, nickel, cobalt and aluminum in the hafnium-doped lithium cobalt aluminum oxide; the molar amount of nickel accounts for 80%-95% of the total molar amount of hafnium, nickel, cobalt and aluminum in the hafnium-doped lithium cobalt aluminum oxide; the molar amount of cobalt accounts for 2%-15% of the total molar amount of hafnium, nickel, cobalt and aluminum in the hafnium-doped lithium cobalt aluminum oxide; and the molar amount of aluminum accounts for 1%-5% of the total molar amount of hafnium, nickel, cobalt and aluminum in the hafnium-doped lithium cobalt aluminum oxide. (4) The lithium fast ion conductor includes one or more of LiAlO2, Li2ZrO3, Li2TiO3, Li3PO4, lithium lanthanum zirconium oxide (LLZO), and lithium lanthanum titanate (LLTO).
[0009] Secondly, the present invention provides a method for preparing the modified high-nickel NCA cathode material, comprising the following steps: S1. Prepare a mixed solution by mixing soluble salts of nickel, cobalt, aluminum and hafnium in stoichiometric ratio. React the mixed solution with a precipitant and a complexing agent, and control the pH to 10.5-11.5 to obtain a hafnium-doped precursor. S2. Mix the hafnium-doped precursor with a lithium source, pre-calcine it, and then calcine it to obtain hafnium-doped lithium nickel cobalt aluminum oxide. S3. Disperse hafnium-doped lithium nickel cobalt aluminum oxide in a copper-containing salt solution, spray dry it, and then perform a first heat treatment to obtain hafnium-doped lithium nickel cobalt aluminum oxide coated with a first coating layer. S4. The hafnium-doped lithium nickel cobalt aluminum oxide coated with the first coating layer obtained in S3 is mixed with the M source and subjected to a second heat treatment to obtain the modified high-nickel NCA cathode material containing the second coating layer. The M element in the M source includes one or more of Al, Zr, Ti, P, and La.
[0010] In one optional embodiment, the precipitant in S1 includes one or more of NaOH, KOH, Na2CO3, and NH4HCO3, preferably at least one of NaOH and Na2CO3; And / or, the complexing agent in S1 includes one or more of NH3·H2O, citric acid, ethylenediaminetetraacetic acid, and tartaric acid, preferably NH3·H2O.
[0011] In one optional embodiment, the reaction temperature in S1 is 50-70°C, and the reaction time is 20-50 h.
[0012] In one alternative implementation, S1 satisfies at least one of the following conditions: (1) Soluble salts of nickel include one or more of NiSO4, Ni(NO3)2, and NiCl2; (2) Soluble salts of cobalt include one or more of CoSO4, Co(NO3)2, and CoCl2; (3) Soluble salts of aluminum include one or more of Al2(SO4)3, Al(NO3)3, and AlCl3; (4) Soluble salts of hafnium include at least one of Hf(NO3)4 and HfOCl2; (5) The general chemical formula of the hafnium-doped precursor in S1 is Ni x Co y Al z Hf w (OH)2, where 0.8≤x≤0.95, 0.02≤y≤0.15, 0.01≤z≤0.05, 0.002≤w≤0.01, and x+y+z+w=1.
[0013] In one alternative implementation, S2 satisfies at least one of the following conditions: (1) The ratio of the molar amount of lithium in the lithium source in S2 to the total molar amount of metal elements in the hafnium-doped precursor is (1.03-1.08):1; (2) The pre-firing temperature in S2 is 400-600℃, and the pre-firing time is 3-5h; (3) The calcination temperature in S2 is 750-850℃ and the calcination time is 15-20h.
[0014] In an optional embodiment, the copper salt in the copper salt solution in S3 includes one or more of CuSO4, Cu(NO3)2, and CuCl2, preferably CuSO4; And / or, the temperature of the first heat treatment in S3 is 350-550℃, and the time of the first heat treatment is 3-6h.
[0015] In one alternative implementation, S4 satisfies at least one of the following conditions: (1) The M source in S4 includes one or more of Al(NO3)3, Al2(SO4)3, AlCl3, Al(C3H7O)3, ZrOCl2, Zr(NO3)4, tetrabutyl titanate, TiCl4, (NH4)2HPO4, H3PO4, La(NO3)3, LaCl3, La(CH3COO)3, and La2(SO4)3; (2) The molar ratio of element M in source M in S4 to residual LiOH on the surface of hafnium-doped lithium nickel cobalt aluminum oxide prepared in S2 is (2-2.4):1; (3) The temperature of the second heat treatment in S4 is 450-600℃ and the time of the second heat treatment is 4-8h.
[0016] Thirdly, the present invention provides a lithium-ion battery that uses the modified high-nickel NCA cathode material or the modified high-nickel NCA cathode material prepared according to the preparation method described above.
[0017] The technical solution of this invention has the following advantages: 1. The modified high-nickel NCA cathode material provided by the present invention includes a core, a first coating layer and a second coating layer arranged sequentially from the inside out; the core includes hafnium-doped lithium nickel cobalt aluminum oxide; the first coating layer includes copper oxide; and the second coating layer includes a lithium fast ion conductor.
[0018] The modified high-nickel NCA cathode material provided by this invention has the following advantages: significantly improved cycle performance, excellent rate performance, controlled residual lithium, and enhanced thermal stability. The specific principle is as follows: (1) Hafnium doping microstructure control: Hafnium (Hf) is incorporated into the lattice as a high-valence cation (4+), partially replacing nickel sites and inducing primary particles to be short rod-shaped and arranged radially. This structure effectively disperses the internal stress generated by the H2-H3 phase transition and inhibits the formation of microcracks. At the same time, the strong Hf-O bond energy stabilizes the lattice oxygen, reduces the formation of oxygen vacancies, and improves thermal stability.
[0019] (2) Synergistic mechanism of doping and double-layer coating: The copper oxide layer consumes residual LiOH to generate lithium copper oxide, reducing surface alkalinity; the copper oxide layer increases the interfacial electron transport rate, and its own electronic conductivity reduces interfacial impedance, suppressing side reactions during charging and discharging. The outer layer of the lithium fast ion conductor acts as a lithium fast ion conductor to promote Li + Migration, thereby improving rate performance and cycle stability. The lithium fast-ion conductor layer also blocks direct contact between the electrolyte and the core, reducing Ni migration. 4+ Oxidative decomposition of the electrolyte. The double-layer coating compensates for the shortcomings of a single coating, improving interfacial stability.
[0020] In summary, hafnium doping can stabilize the crystal structure from a bulk perspective, while the synergistic coating of the copper oxide layer and the lithium fast ion conductor layer can suppress the occurrence of side reactions from an interface perspective. The two work together to solve the problem of bulk-interface synergistic degradation of NCA materials.
[0021] 2. The method for preparing the modified high-nickel NCA cathode material provided by the present invention includes the following steps: S1. Mixing soluble salts of nickel, cobalt, aluminum, and hafnium in stoichiometric ratio to form a mixed solution, reacting the mixed solution with a precipitant and a complexing agent, controlling the pH to 10.5-11.5, to obtain a hafnium-doped precursor; S2. Mixing the hafnium-doped precursor with a lithium source, pre-calcining, and then calcining to obtain hafnium-doped lithium nickel cobalt aluminum oxide; S3. Dispersing the hafnium-doped lithium nickel cobalt aluminum oxide in a copper-containing salt solution, spray drying, and then performing a first heat treatment to obtain hafnium-doped lithium nickel cobalt aluminum oxide coated with a first coating layer; S4. Mixing the hafnium-doped lithium nickel cobalt aluminum oxide coated with the first coating layer obtained in S3 with an M source, and performing a second heat treatment to obtain the modified high-nickel NCA cathode material containing a second coating layer; the M element in the M source includes one or more of Al, Zr, Ti, P, and La.
[0022] Double-layer wrapping design: First coating layer: A uniform and dense coating is formed on the surface of hafnium-doped lithium nickel cobalt aluminum oxide material by spray drying, which serves as an electronic conductive layer to improve the interfacial electron transport rate; at the same time, it reacts with the residual LiOH on the surface of hafnium-doped lithium nickel cobalt aluminum oxide to generate lithium copper oxide, thereby reducing the interfacial impedance.
[0023] Second coating layer: The second coating layer is in contact with the first coating layer and is bonded to the hafnium-doped lithium nickel cobalt aluminum oxide matrix through a chemical reaction. The first coating layer (copper oxide) is formed by spray drying and heat treatment, and lithium ions (Li... + With a small ionic radius (0.076 nm), it can penetrate the voids or grain boundaries of the first coating layer during heat treatment and react with the external M source to form a second coating layer. This design utilizes Li + The migration properties enable in-situ formation of the second coating layer. Therefore, the second coating layer exhibits good structural compatibility with the substrate, thus preventing the formation of microcracks; simultaneously, as a fast lithium-ion conductor, it promotes the formation of Li-ion bonds. + Migration improves rate performance. Detailed Implementation
[0024] 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.
[0025] 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.
[0026] Example 1 This embodiment provides a method for preparing a modified high-nickel NCA cathode material, including the following steps: S1. NiSO4·6H2O, CoSO4·7H2O, Al2(SO4)3·18H2O, and HfOCl2·8H2O were dissolved in deionized water at a metal element molar ratio of 0.85:0.12:0.028:0.002, and a solution was prepared with a total molar concentration of metal ions (Ni, Co, Al, Hf) of 2 mol / L. Under nitrogen protection, the mixed solution was added to the reactor in parallel with 4 mol / L NaOH solution and 1 mol / L ammonia solution. The pH was controlled at 11.0, the temperature at 60℃, and the reaction was carried out for 30 h to obtain the precursor Ni. 0.85 Co 0.12 Al 0.028 Hf 0.002 (OH)2.
[0027] S2. Mix LiOH·H2O with the precursor at a ratio of 1.05:1 of the total molar amount of lithium element in LiOH·H2O to the total molar amount of metal element in the precursor, pre-calcine at 500℃ for 4 hours in an oxygen atmosphere, and then calcine at 800℃ for 18 hours to obtain hafnium-doped lithium nickel cobalt aluminum oxide. S3. Disperse 10g of hafnium-doped lithium nickel cobalt aluminum oxide in 0.1mol / L CuSO4 solution, spray dry, and then heat treat in oxygen at 450℃ for 4h to form copper oxide-coated hafnium-doped lithium nickel cobalt aluminum oxide (coating amount 0.3wt% (mass ratio of copper oxide to hafnium-doped lithium nickel cobalt aluminum oxide)).
[0028] S4. The copper oxide-coated hafnium-doped nickel cobalt aluminum oxide was ball-milled and mixed with Al(NO3)3·9H2O (the mass of Al(NO3)3·9H2O was weighed according to the molar ratio of aluminum in Al(NO3)3·9H2O to residual LiOH on the surface of the hafnium-doped nickel cobalt aluminum oxide prepared in S2 of 2.2:1). The mixture was then heat-treated in oxygen at 500℃ for 6 hours to generate a modified high-nickel NCA cathode material with a LiAlO2 coating layer (coating amount 1.5wt% (coating amount is the mass of LiAlO2: copper oxide-coated hafnium-doped nickel cobalt aluminum oxide)).
[0029] Example 2: This embodiment provides a method for preparing a modified high-nickel NCA cathode material, including the following steps: S1. NiSO4·6H2O, CoSO4·7H2O, Al2(SO4)3·18H2O, and HfOCl2·8H2O were dissolved in deionized water at a metal element molar ratio of 0.85:0.12:0.025:0.005, and a solution was prepared with a total molar concentration of metal ions (Ni, Co, Al, Hf) of 2 mol / L. Under nitrogen protection, the mixed solution was added to the reactor in parallel with 4 mol / L NaOH solution and 1 mol / L ammonia solution. The pH was controlled at 11.0, the temperature at 60℃, and the reaction was carried out for 30 h to obtain the precursor Ni. 0.85 Co 0.12 Al 0.025 Hf 0.005 (OH)2.
[0030] S2. Mix LiOH·H2O with the precursor at a ratio of 1.05:1 of the total molar amount of lithium element in LiOH·H2O to the total molar amount of metal element in the precursor, pre-calcine at 500℃ for 4 hours in an oxygen atmosphere, and then calcine at 800℃ for 18 hours to obtain hafnium-doped lithium nickel cobalt aluminum oxide. S3. Disperse 10g of hafnium-doped lithium nickel cobalt aluminum oxide in 0.1mol / L CuSO4 solution, spray dry, and then heat treat in oxygen at 450℃ for 4h to form copper oxide-coated hafnium-doped lithium nickel cobalt aluminum oxide (copper oxide coating amount 0.5wt% (mass ratio of copper oxide to hafnium-doped lithium nickel cobalt aluminum oxide)).
[0031] S4. The copper oxide-coated hafnium-doped nickel cobalt aluminum oxide is ball-milled with Al(NO3)3·9H2O (the mass of Al(NO3)3·9H2O is weighed according to the molar ratio of aluminum in Al(NO3)3·9H2O to the residual LiOH on the surface of the hafnium-doped nickel cobalt aluminum oxide obtained in S2, which is 2.4:1). The mixture is then heat-treated in oxygen at 500℃ for 6 hours to generate a modified high-nickel NCA cathode material with a LiAlO2 coating layer (LiAlO2 coating amount 2wt% (coating amount is the mass of LiAlO2: copper oxide-coated hafnium-doped nickel cobalt aluminum oxide)).
[0032] Example 3 This embodiment provides a method for preparing a modified high-nickel NCA cathode material, including the following steps: S1. NiSO4·6H2O, CoSO4·7H2O, Al2(SO4)3·18H2O, and HfOCl2·8H2O were dissolved in deionized water at a metal element molar ratio of 0.9:0.05:0.04:0.01, and a solution was prepared with a total molar concentration of metal ions (Ni, Co, Al, Hf) of 2 mol / L. Under nitrogen protection, the mixed solution was added to the reactor in parallel with 4 mol / L NaOH solution and 1 mol / L ammonia solution. The pH was controlled at 10.5, the temperature at 50℃, and the reaction was carried out for 40 h to obtain the precursor Ni. 0.9 Co 0.05 Al 0.04 Hf 0.01 (OH)2.
[0033] S2.LiOH·H2O and the precursor were mixed at a ratio of 1.05:1 of the total molar amount of lithium element in LiOH·H2O to the total molar amount of metal element in the precursor. The mixture was pre-calcined at 450℃ for 5 hours in an oxygen atmosphere and then calcined at 800℃ for 20 hours to obtain hafnium-doped lithium nickel cobalt aluminum oxide. S3. Disperse 10g of hafnium-doped lithium nickel cobalt aluminum oxide in 0.1mol / L CuSO4 solution, spray dry, and then heat treat in oxygen at 450℃ for 4h to form copper oxide-coated hafnium-doped lithium nickel cobalt aluminum oxide (coating amount 0.4wt% (mass ratio of copper oxide to hafnium-doped lithium nickel cobalt aluminum oxide)).
[0034] S4. The copper oxide-coated hafnium-doped nickel cobalt aluminum oxide is ball-milled and mixed with Al(NO3)3·9H2O (the mass of Al(NO3)3·9H2O is weighed according to the molar ratio of aluminum in Al(NO3)3·9H2O to the residual LiOH on the surface of the hafnium-doped high-nickel NCA cathode material prepared in S2 is 2:1). The mixture is then heat-treated in oxygen at 550℃ for 5 hours to generate a modified high-nickel NCA cathode material with a LiAlO2 coating layer (coating amount 2wt% (coating amount is the mass of LiAlO2: copper oxide-coated hafnium-doped nickel cobalt aluminum oxide)).
[0035] Example 4 This embodiment provides a method for preparing a modified high-nickel NCA cathode material, including the following steps: S1. NiSO4·6H2O, CoSO4·7H2O, Al2(SO4)3·18H2O, and HfOCl2·8H2O were dissolved in deionized water at a metal element molar ratio of 0.88:0.1:0.015:0.005, and a solution was prepared with a total molar concentration of metal ions (Ni, Co, Al, Hf) of 2 mol / L. Under nitrogen protection, the mixed solution was added to the reactor in parallel with 4 mol / L NaOH solution and 1 mol / L ammonia solution. The pH was controlled at 11.5, the temperature at 70℃, and the reaction was carried out for 25 h to obtain the precursor Ni. 0.88 Co 0.1 Al 0.015 Hf 0.005 (OH)2.
[0036] S2. Mix LiOH·H2O with the precursor at a ratio of 1.05:1 of the total molar amount of lithium element in LiOH·H2O to the total molar amount of metal element in the precursor, pre-calcine at 550℃ for 3 hours in an oxygen atmosphere, and then calcine at 750℃ for 20 hours to obtain hafnium-doped lithium nickel cobalt aluminum oxide. S3. Disperse 10g of hafnium-doped lithium nickel cobalt aluminum oxide in 0.1mol / L CuSO4 solution, spray dry, and then heat treat in oxygen at 450℃ for 4h to form copper oxide-coated hafnium-doped lithium nickel cobalt aluminum oxide (coating amount 0.2wt% (mass ratio of copper oxide to hafnium-doped lithium nickel cobalt aluminum oxide)).
[0037] S4. The copper oxide-coated hafnium-doped lithium nickel cobalt aluminum oxide is ball-milled and mixed with Al(NO3)3·9H2O (the mass of Al(NO3)3·9H2O is weighed according to the molar ratio of aluminum in Al(NO3)3·9H2O to the residual LiOH on the surface of the hafnium-doped high-nickel NCA cathode material prepared in S2, which is 2.3:1). The mixture is then heat-treated in oxygen at 500℃ for 6 hours to generate a modified high-nickel NCA cathode material with a LiAlO2 coating layer (coating amount 1wt% (coating amount is the mass of LiAlO2: copper oxide-coated hafnium-doped lithium nickel cobalt aluminum oxide)).
[0038] Comparative Example 1: This comparative example provides a method for preparing a high-nickel NCA cathode material, including the following steps: S1. NiSO4·6H2O, CoSO4·7H2O, and Al2(SO4)3·18H2O were dissolved in deionized water at a metal element molar ratio of 0.85:0.12:0.03, and a solution was prepared with a total molar concentration of metal ions (Ni, Co, Al) of 2 mol / L. Under nitrogen protection, the mixed solution was added to the reactor in parallel with 4 mol / L NaOH solution and 1 mol / L ammonia solution. The pH was controlled at 11.0, the temperature at 60℃, and the reaction was carried out for 30 h to obtain the precursor Ni. 0.85Co 0.12 Al 0.03 (OH)2.
[0039] S2. The precursor was mixed with LiOH·H2O at a lithium metal molar ratio of 1.05, pre-calcined at 500℃ for 4 hours in an oxygen atmosphere, and then calcined at 800℃ for 18 hours to obtain NCA material LiNi. 0.85 Co 0.12 Al 0.03 O2; Comparative Example 2: This comparative example provides a method for preparing a modified high-nickel NCA cathode material, including the following steps: S1. NiSO4·6H2O, CoSO4·7H2O, Al2(SO4)3·18H2O, and HfOCl2·8H2O were dissolved in deionized water at a metal element molar ratio of 0.85:0.12:0.028:0.002, and a solution was prepared with a total molar concentration of metal ions (Ni, Co, Al, Hf) of 2 mol / L. Under nitrogen protection, the mixed solution was added to the reactor in parallel with 4 mol / L NaOH solution and 1 mol / L ammonia solution. The pH was controlled at 11.0, the temperature at 60℃, and the reaction was carried out for 30 h to obtain the precursor Ni. 0.85 Co 0.12 Al 0.028 Hf 0.002 (OH)2.
[0040] S2. Mix LiOH·H2O with the precursor at a ratio of 1.05:1 of the total molar amount of lithium element in LiOH·H2O to the total molar amount of metal element in the precursor, pre-calcine at 500℃ for 4 hours in an oxygen atmosphere, and then calcine at 800℃ for 18 hours to obtain hafnium-doped lithium nickel cobalt aluminum oxide. S3. Disperse 10g of hafnium-doped lithium nickel cobalt aluminum oxide in 0.1mol / L CuSO4 solution, spray dry, and then heat treat in oxygen at 450℃ for 4h to form copper oxide-coated hafnium-doped lithium nickel cobalt aluminum oxide (coating amount 0.3wt% (mass ratio of copper oxide to hafnium-doped lithium nickel cobalt aluminum oxide)).
[0041] Test Example 1 The preparation method of the coin cell is as follows: high-nickel NCA cathode material (cathode material prepared in Examples 1-4 and Comparative Examples 1-2), binder (polyvinylidene fluoride, PVDF), conductive agent (conductive carbon black, SP), and solvent (N-methylpyrrolidone, NMP) are mixed in a ratio of 95g:1g:4g:220mL, stirred to form a slurry, coated on copper foil, and dried and rolled to obtain a cathode sheet; lithium hexafluorophosphate (LiPF6) is used as the electrolyte, and a mixture of ethylene carbonate (EC) and diethyl carbonate (DEC) with a volume ratio of 1:1 is used as the solvent to prepare an electrolyte with a concentration of 1mol / L; a lithium metal sheet is used as the counter electrode, and a polypropylene (PP) membrane is used as the separator. The coin cell is assembled in an argon-filled glove box.
[0042] Electrochemical performance tests were conducted on coin cells containing high-nickel NCA cathode materials from Examples 1-4 and Comparative Examples 1-2, and the residual LiOH content on the surface of hafnium-doped lithium nickel cobalt aluminum oxide prepared by S2 was also tested.
[0043] Electrochemical performance testing methods: The Wuhan Landian CT2001A battery tester was used. The charge and discharge voltage range was 2.5-4.25V. The specific capacity of the first discharge at 0.1C, the capacity retention rate after 200 cycles at 1C, and the capacity at 10C rate were tested respectively. The test results are shown in Table 1.
[0044] Test method for residual LiOH content: Accurately weigh a certain mass (30.0 g) of hafnium-doped lithium nickel cobalt aluminum oxide material prepared by S2, add excess deionized water, stir, and filter. Titrate the filtrate with standard hydrochloric acid solution, using phenolphthalein as an indicator, record the volume of hydrochloric acid consumed at the titration endpoint, and calculate the residual LiOH content on the material surface. The test results are shown in Table 1.
[0045] Table 1
[0046] As shown in Table 1, the coin cells made from the ternary cathode materials obtained in Examples 1-4 of the present invention have higher initial discharge specific capacity, capacity retention rate after 200 cycles at 1C, and 10C rate capacity compared to Comparative Examples 1-2. This indicates that the cathode materials prepared by the present invention using the modification process of hafnium doping, first coating layer, and second coating layer have high capacity, long cycle life, and excellent rate performance.
[0047] 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 modified high-nickel NCA cathode material, characterized in that, It includes a kernel, a first wrapper layer, and a second wrapper layer arranged sequentially from the inside out; The core comprises hafnium-doped lithium nickel cobalt aluminum oxide; The first coating layer includes copper oxide; The second coating layer includes a lithium fast ion conductor.
2. The modified high-nickel NCA cathode material according to claim 1, characterized in that, At least one of the following conditions must be met: (1) The mass of the first coating layer is 0.1wt%-0.5wt% of the core mass; (2) The mass of the second coating layer is 0.5wt%-2wt% of the sum of the mass of the first coating layer and the core. (3) The molar amount of hafnium in the hafnium-doped lithium cobalt aluminum oxide accounts for 0.2%-1% of the total molar amount of hafnium, nickel, cobalt and aluminum in the hafnium-doped lithium cobalt aluminum oxide; the molar amount of nickel accounts for 80%-95% of the total molar amount of hafnium, nickel, cobalt and aluminum in the hafnium-doped lithium cobalt aluminum oxide; the molar amount of cobalt accounts for 2%-15% of the total molar amount of hafnium, nickel, cobalt and aluminum in the hafnium-doped lithium cobalt aluminum oxide; and the molar amount of aluminum accounts for 1%-5% of the total molar amount of hafnium, nickel, cobalt and aluminum in the hafnium-doped lithium cobalt aluminum oxide. (4) The fast lithium-ion conductor includes one or more of LiAlO2, Li2ZrO3, Li2TiO3, Li3PO4, lithium lanthanum zirconium oxide, and lithium lanthanum titanate.
3. A method for preparing the modified high-nickel NCA cathode material according to claim 1 or 2, characterized in that, Includes the following steps: S1. Prepare a mixed solution by mixing soluble salts of nickel, cobalt, aluminum and hafnium in stoichiometric ratio. React the mixed solution with a precipitant and a complexing agent, and control the pH to 10.5-11.5 to obtain a hafnium-doped precursor. S2. Mix the hafnium-doped precursor with a lithium source, pre-calcine it, and then calcine it to obtain hafnium-doped lithium nickel cobalt aluminum oxide. S3. Disperse hafnium-doped lithium nickel cobalt aluminum oxide in a copper-containing salt solution, spray dry it, and then perform a first heat treatment to obtain hafnium-doped lithium nickel cobalt aluminum oxide coated with a first coating layer. S4. The hafnium-doped lithium nickel cobalt aluminum oxide coated with the first coating layer obtained in S3 is mixed with the M source and subjected to a second heat treatment to obtain the modified high-nickel NCA cathode material containing the second coating layer. The M element in the M source includes one or more of Al, Zr, Ti, P, and La.
4. The method for preparing the modified high-nickel NCA cathode material according to claim 3, characterized in that, The precipitant in S1 includes one or more of NaOH, KOH, Na2CO3, and NH4HCO3, preferably at least one of NaOH and Na2CO3; And / or, the complexing agent in S1 includes one or more of NH3·H2O, citric acid, ethylenediaminetetraacetic acid, and tartaric acid, preferably NH3·H2O.
5. The method for preparing the modified high-nickel NCA cathode material according to claim 3 or 4, characterized in that, The reaction temperature in S1 is 50-70℃, and the reaction time is 20-50h.
6. The method for preparing the modified high-nickel NCA cathode material according to claim 3 or 4, characterized in that, S1 satisfies at least one of the following conditions: (1) Soluble salts of nickel include one or more of NiSO4, Ni(NO3)2, and NiCl2; (2) Soluble salts of cobalt include one or more of CoSO4, Co(NO3)2, and CoCl2; (3) Soluble salts of aluminum include one or more of Al2(SO4)3, Al(NO3)3, and AlCl3; (4) Soluble salts of hafnium include at least one of Hf(NO3)4 and HfOCl2; (5) The general chemical formula of the hafnium-doped precursor in S1 is Ni x Co y Al z Hf w (OH)2, where 0.8≤x≤0.95, 0.02≤y≤0.15, 0.01≤z≤0.05, 0.002≤w≤0.01, and x+y+z+w=1.
7. The method for preparing the modified high-nickel NCA cathode material according to claim 3, characterized in that, S2 satisfies at least one of the following conditions: (1) The ratio of the molar amount of lithium in the lithium source in S2 to the total molar amount of metal elements in the hafnium-doped precursor is (1.03-1.08):1; (2) The pre-firing temperature in S2 is 400-600℃, and the pre-firing time is 3-5h; (3) The calcination temperature in S2 is 750-850℃ and the calcination time is 15-20h.
8. The method for preparing the modified high-nickel NCA cathode material according to claim 3 or 7, characterized in that, The copper salt in the copper salt solution in S3 includes one or more of CuSO4, Cu(NO3)2, and CuCl2, preferably CuSO4; And / or, the temperature of the first heat treatment in S3 is 350-550℃, and the time of the first heat treatment is 3-6h.
9. The method for preparing the modified high-nickel NCA cathode material according to claim 3 or 7, characterized in that, S4 satisfies at least one of the following conditions: (1) The M source in S4 includes one or more of Al(NO3)3, Al2(SO4)3, AlCl3, Al(C3H7O)3, ZrOCl2, Zr(NO3)4, tetrabutyl titanate, TiCl4, (NH4)2HPO4, H3PO4, La(NO3)3, LaCl3, La(CH3COO)3, and La2(SO4)3; (2) The molar ratio of element M in source M to residual LiOH on the surface of hafnium-doped lithium nickel cobalt aluminum oxide in S4 is (2-2.4):1; (3) The temperature of the second heat treatment in S4 is 450-600℃ and the time of the second heat treatment is 4-8h.
10. A lithium-ion battery, comprising the modified high-nickel NCA cathode material as described in claim 1 or 2, or the modified high-nickel NCA cathode material prepared by the preparation method according to any one of claims 3-9.