Sodium-phosphorus modified high-nickel ternary positive electrode material and preparation method thereof
By modifying high-nickel ternary cathode materials with sodium and phosphorus, and using Na+ doping and coating methods, the problems of lithium-nickel mixing and capacity decay were solved, the electrochemical performance and structural stability of the materials were improved, and the process operation was simplified.
Patent Information
- Application Number
- CN202510999206.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-21
- Publication Date
- 2025-11-18
AI Technical Summary
Traditional high-nickel ternary cathode materials suffer from severe lithium-nickel mixing, rapid capacity decay, and poor rate performance at high nickel content. Single doping or coating modification has limited effect, and complex modification methods may increase costs.
A sodium-phosphorus modification method was used to dope and coat high-nickel ternary cathode materials with Na+. Sodium phosphate was generated by dispersing sodium and phosphorus sources in an alcohol solvent to uniformly adhere to the material surface, forming a core-shell structure, which simplifies the process and improves electrochemical performance.
It improves the initial coulombic efficiency, capacity retention and rate performance of high-nickel ternary cathode materials. The material particles are uniform, well dispersed, highly crystallized, and have a uniform surface coating, which reduces lithium-nickel mixing and electrolyte corrosion.
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Figure CN120964898A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of lithium-ion battery technology, and in particular to a sodium-phosphorus modified high-nickel ternary cathode material and its preparation method. Background Technology
[0002] With the increasing depletion of primary energy sources and the worsening environment, the development of renewable energy and the realization of more efficient and convenient energy conversion and storage are urgently needed. New energy vehicles, due to their significant environmental advantages, are expected to completely replace traditional gasoline-powered vehicles in the future. As the core of new energy vehicles, the development of high-performance lithium-ion batteries has become paramount. However, traditional cathode materials such as lithium iron phosphate are limited by capacity and can no longer meet the range requirements of electric vehicles, making the development of higher-capacity cathode materials imperative.
[0003] Ternary cathode material (LiNi) x Co y Mn z O2 (x+y+z=1) has attracted widespread attention due to its high energy density and discharge platform, low cost, and safety and environmental friendliness. The higher the nickel content, the greater the energy density, making it easier to achieve a longer driving range. However, when the nickel content is too high (x≥0.8), LiNi... x Co y Mn z O2 exhibits significant lithium-nickel mixing, rapid capacity decay, and poor rate performance. Doping and coating are important means to improve these shortcomings. However, single doping or coating has limited effect on improving the electrochemical performance of the material. Improper selection of doping elements or protective layers may also affect the capacity utilization of the material. At the same time, complex modification methods are often accompanied by increased costs. Therefore, developing a doping-coating dual modification method for high-nickel ternary cathode materials that is simple to operate and produces products with excellent electrochemical performance is of great practical significance. Summary of the Invention
[0004] The purpose of this invention is to provide a sodium-phosphorus modified high-nickel ternary cathode material and its preparation method, so as to solve the problems in the background art.
[0005] The technical solution adopted in this invention includes: a method for preparing a sodium-phosphorus modified high-nickel ternary cathode material, comprising the following steps:
[0006] The lithium source and polycrystalline high-nickel precursor were mixed and sintered in an atmosphere furnace to obtain a sintered material.
[0007] The calcined material, sodium source, and phosphorus source are dispersed in an alcohol solvent, stirred, and the alcohol solvent is evaporated to obtain a modified precursor.
[0008] The modified precursor was sintered in an atmosphere furnace to obtain a sodium-phosphorus modified high-nickel ternary cathode material.
[0009] The molar ratio of the sodium source to the phosphorus source is (2-12):1, and the two can be converted into sodium phosphate after the alcohol solvent is evaporated.
[0010] Preferably, the phosphorus source includes at least one of H3PO4, NH4H2PO4, (NH4)2HPO4 and NaH2PO4.
[0011] Preferably, the sodium source includes at least one of CH3ONa, NaOH, CH3COONa, and Na2CO3.
[0012] Preferably, the molar ratio of the calcined material to the sodium source is 1:(0.036 to 0.120).
[0013] Preferably, the alcohol solvent contains ethanol and ethylene glycol in a mass ratio of (1-4):1.
[0014] Preferably, when sintering the modified precursor, the sintering temperature is 550–850°C, the heating rate is 1–5°C / min, and the sintering time is 6–12 h.
[0015] Preferably, the chemical formula of the calcined material is LiNi. x Co y Mn z O2, x+y+z=1, x≥0.8.
[0016] Preferably, when sintering the mixture of the lithium source and the polycrystalline high-nickel precursor: the sintering temperature is 340-660°C, the heating rate is 1-5°C / min, and the sintering time is 4-8h.
[0017] Preferably, the sintering atmosphere of the lithium source and the polycrystalline high-nickel precursor mixture and the sintering atmosphere of the modified precursor are independently selected from an oxygen atmosphere and an air-oxygen mixture atmosphere, respectively.
[0018] The technical solution of the present invention also includes: a sodium-phosphorus modified high-nickel ternary cathode material prepared by the above preparation method.
[0019] The beneficial effects of the present invention include at least the following:
[0020] (1) This invention involves simultaneously performing Na2O4 on high-nickel ternary cathode materials. + Doping and Encapsulation, Na + Doping is used to widen the lithium interlayer spacing, reduce lithium-nickel mixing, and improve lithium-ion diffusion. Coating reduces the corrosion of the cathode material by the electrolyte, stabilizes the crystal structure of the cathode material, optimizes the modification process, and comprehensively improves the electrochemical performance of the cathode material.
[0021] (2) The present invention selects a phosphorus source that is easily soluble in alcohol solvents and uses a specially formulated alcohol solvent to dissolve and disperse the sodium source, phosphorus source and calcined material. This simplifies the process operation and avoids the introduction of water solvents, thus avoiding damage to the electrochemical performance of the high-nickel ternary cathode material.
[0022] (3) The sodium-phosphorus modified high-nickel ternary cathode material prepared by this invention has uniform particles, good dispersibility, high crystallinity, and uniform surface coating. + Doping The dual-modification coating synergistically improves the first coulombic efficiency, capacity retention, and rate performance of high-nickel ternary cathode materials. Attached Figure Description
[0023] Figure 1 These are SEM images of the sodium-phosphorus modified high-nickel ternary cathode material prepared in Example 1 of this invention and the high-nickel ternary cathode material prepared in the comparative example;
[0024] Figure 2 The charge-discharge curves of coin cells assembled using the sodium-phosphorus modified high-nickel ternary cathode material prepared in Example 1 of this invention and the high-nickel ternary cathode material prepared in the comparative example are shown at a 0.1C rate.
[0025] Figure 3 The graph shows the charge-discharge curves of coin cells assembled using the sodium-phosphorus modified high-nickel ternary cathode material prepared in Example 1 of this invention and the high-nickel ternary cathode material prepared in the comparative example at a rate of 0.3C. Detailed Implementation
[0026] The embodiments of the present invention are described in detail below.
[0027] This invention provides a sodium-phosphorus modified high-nickel ternary cathode material and its preparation method, which involves simultaneously modifying the high-nickel ternary cathode material with sodium phosphorus. + Doping and Encapsulation, Na + Doping is used to widen the lithium interlayer spacing, reduce lithium-nickel mixing, and improve lithium-ion diffusion. Coating reduces the corrosion of the cathode material by the electrolyte, stabilizes the crystal structure of the cathode material, optimizes the modification process, and comprehensively improves the electrochemical performance of the cathode material.
[0028] The method for preparing sodium-phosphorus modified high-nickel ternary cathode material provided in this invention includes the following steps:
[0029] (1) The lithium source and the polycrystalline high-nickel precursor are mixed and sintered in an atmosphere furnace to obtain a sintered material.
[0030] (2) Disperse the calcined material, sodium source and phosphorus source in alcohol solvent, stir and evaporate the alcohol solvent to obtain the modified precursor; wherein the molar ratio of sodium source to phosphorus source is (2~12):1, and the two can be converted into sodium phosphate after evaporating the alcohol solvent.
[0031] (3) The modified precursor was placed in an atmosphere furnace for sintering to obtain sodium-phosphorus modified high-nickel ternary cathode material.
[0032] Since phosphates (such as lithium phosphate and sodium phosphate) are poorly soluble in alcohol but soluble in water, some existing liquid-phase coating processes involve mixing an aqueous solution of phosphate with the high-nickel ternary cathode material, evaporating the water, grinding and mixing it with a lithium source, and then sintering it to avoid the reaction of the aqueous solution with the high-nickel ternary precursor and thus deteriorating its electrochemical performance. However, this method is not only complex, but the addition of lithium source after evaporating the water and grinding the material will inevitably damage the phosphate adhesion layer on the high-nickel ternary precursor, affecting the final coating effect. In this embodiment, a phosphorus source that is easily soluble in alcohol solvents is selected, and a specially formulated alcohol solvent is used to dissolve and disperse the sodium source, phosphorus source, and sintered material. This simplifies the process and avoids the introduction of aqueous solvents, thus preventing damage to the electrochemical performance of the high-nickel ternary cathode material. In addition, an excess of sodium source is used in this process. Part of the sodium source reacts with the phosphorus source to generate sodium phosphate, which is used to coat the high-nickel ternary cathode material, while the remaining sodium source is used for bulk doping of the high-nickel ternary cathode material, further simplifying the process. + Doping The coating process involves dual modification, and compared to the point-distributed coating obtained by the dry mixing coating process, in this embodiment, the sodium source and phosphorus source react in the liquid phase system and directly adhere to the surface of the calcined material, forming a uniformly distributed, more densely coated planar coating layer (i.e., forming a core-shell structure, with the core being doped with Na). + High-nickel ternary cathode material, shell is (Coating layer) can more effectively improve the electrochemical performance of cathode materials.
[0033] The polycrystalline high-nickel precursor used in step (1) is a commercially available finished product and can be Ni x Co y Mn z (OH)₂, 0.80≤x≤0.98, 0≤y<0.2, and x+y+z=1; the preferred ratio of the molar number of lithium elements in the lithium source to the total molar number of transition metal elements in the polycrystalline high-nickel precursor is (1.010~1.040):1, to obtain the chemical formula LiNi x Co y Mn z O2 is a burning material, where x+y+z=1, x≥0.8.
[0034] When sintering a mixture of lithium source and polycrystalline high-nickel precursor: the preferred sintering temperature is 340–660℃, the heating rate is 1–5℃ / min, and the sintering time is 4–8h.
[0035] Through research, experimentation, and verification by the inventors, it was found that when the molar ratio of the calcined material to the sodium source in step (2) is 1:(0.036~0.120), the Na... + Doping amount and The coating amount is controlled at a relatively optimal level, which has a better effect on improving the electrochemical performance of high-nickel ternary cathode materials. The phosphorus source can be any one or more of H3PO4, NH4H2PO4, (NH4)2HPO4 and NaH2PO4, and the sodium source can be any one or more of sodium methoxide, NaOH, CH3COONa and Na2CO3.
[0036] To ensure efficient dispersion of each substance and control To improve the uniformity of adhesion, the alcohol solvent in this embodiment is configured to contain ethanol and ethylene glycol in a mass ratio of (1-4):1. By adjusting the ratio of ethanol and ethylene glycol, the average boiling point of the alcohol solvent is adjusted to a suitable level to prevent the alcohol solvent from evaporating too quickly and causing uneven coating.
[0037] It is worth noting that, in order to ensure To ensure uniform adhesion, one of the phosphorus source and sodium source should be dissolved in the alcohol solvent last, so that the sodium phosphate particles generated by the reaction of the phosphorus source and sodium source are uniformly attached to the surface of the calcined material. That is, in step (2), the calcined material, sodium source and phosphorus source should be added to the alcohol solvent in steps, and the next material should be added after the previous material is evenly dispersed. The order of dissolution of the aforementioned materials can be calcined material, sodium source, phosphorus source, calcined material, phosphorus source, sodium source, sodium source, calcined material, phosphorus source, or phosphorus source, calcined material, sodium source. Considering Na + For efficient doping, the above order can be further optimized to: sodium source added before phosphorus source.
[0038] In step (3), when sintering the modified precursor, the preferred sintering temperature is 550-850℃, the heating rate is 1-5℃ / min, and the sintering time is 6-12h.
[0039] As mentioned above, the sintering atmosphere of the lithium source and polycrystalline high-nickel precursor mixture and the sintering atmosphere of the modified precursor are independently selected from oxygen atmosphere and air-oxygen mixed atmosphere, respectively.
[0040] It is worth noting that when modifying high-nickel ternary cathode materials using the above methods, the state of the products at each stage should be observed and analyzed. If the particle size is too large or there is local agglomeration, it can be ground and dispersed at an appropriate stage. For example, the sintered products at each stage can be ground and dispersed after being cooled to 40°C to ensure the quality of modification or to make the particle size of the final product meet the application requirements. Another example is that when evaporating the alcohol solvent, there may be local agglomeration. After evaporating the alcohol solvent, the modified precursor can be shaken and dispersed before sintering.
[0041] The sodium-phosphorus modified high-nickel ternary cathode material prepared by the above method has uniform particle size, good dispersibility, high crystallinity, and uniform surface coating. The high-nickel ternary cathode material achieves Na… + Doping and Coated double-modified structure, Na + Doping can widen the lithium interlayer spacing, reduce lithium-nickel mixing, and improve lithium-ion diffusion. Coating can reduce the corrosion of the positive electrode material by the electrolyte and stabilize the crystal structure of the positive electrode material. + Doping The dual-modification coating synergistically improves the first coulombic efficiency, capacity retention, and rate performance of high-nickel ternary cathode materials.
[0042] The present technical solution is further illustrated below through examples and comparative examples. Unless otherwise specified, the raw materials, reagents or apparatus used in the examples and comparative examples can be obtained from conventional commercial channels.
[0043] Example 1:
[0044] (1) Mix 22.9g of LiOH·H2O (lithium source) and 50g of Ni 0.92 Co 0.06 Mn 0.02 (OH)2 (polycrystalline high-nickel precursor) is added to a mixer and mixed evenly. Then it is transferred to an atmosphere furnace and heated to 500°C at a heating rate of 5°C / min under an oxygen atmosphere. It is then sintered at this temperature for 4 hours. After cooling down to 40°C, the sintered product is crushed into powder to obtain a sintered material.
[0045] (2) Add 1.853g of NaOH (sodium source), 50g of calcined material, and 0.896g of H3PO4 (phosphorus source) to 120g of alcohol solvent in sequence (add the next one after the previous one is evenly dispersed). The alcohol solvent contains ethanol and ethylene glycol in a mass ratio of 2:1. Sonicate and stir to disperse evenly.
[0046] (3) Heat and stir the mixture obtained in step (2) at 60°C until the alcohol solvent is completely evaporated, and then transfer the remaining material to a drying oven at 80°C for drying to obtain the modified precursor.
[0047] (4) The modified precursor was added to the mixer and dispersed at a speed of 1000 r / min (to break up local agglomerates). Then it was transferred to an atmosphere furnace and heated to 750°C at a heating rate of 3°C / min under an oxygen atmosphere. The product was sintered at this temperature for 12 h. After cooling down to 40°C, the sintered product was ground and dispersed to obtain sodium phosphorus modified high nickel ternary cathode material (hereinafter referred to as NCM-1).
[0048] Example 2:
[0049] (1) Mix 23.29g of LiOH·H2O (lithium source) and 50g of Ni 0.92 Co 0.06 Mn 0.02 (OH)2 (polycrystalline high-nickel precursor) is added to a mixer and mixed evenly. Then it is transferred to an atmosphere furnace and heated to 500°C at a heating rate of 5°C / min under an oxygen atmosphere. It is then sintered at this temperature for 4 hours. After cooling down to 40°C, the sintered product is crushed into powder to obtain a sintered material.
[0050] (2) Add 1.570g of CH3ONa (sodium source), 50g of calcined material, and 0.597g of H3PO4 (phosphorus source) to 120g of alcohol solvent (add the next one after the previous one is evenly dispersed). The alcohol solvent contains ethanol and ethylene glycol in a mass ratio of 2:1. Sonicate and stir to disperse evenly.
[0051] (3) Heat and stir the mixture obtained in step (2) at 65°C until the alcohol solvent is completely evaporated, and then transfer the remaining material to a drying oven at 85°C for drying to obtain the modified precursor.
[0052] (4) The modified precursor is added to the mixer and dispersed at a speed of 1000 r / min (to break up local agglomerates). Then it is transferred to an atmosphere furnace and heated to 700°C at a heating rate of 3°C / min under an oxygen atmosphere. It is sintered at this temperature for 10 h. After cooling down to 40°C, the sintered product is ground and dispersed to obtain sodium phosphorus modified high nickel ternary cathode material (hereinafter referred to as NCM-2).
[0053] Example 3:
[0054] (1) Mix 23.5g of LiOH·H2O (lithium source) and 50g of Ni 0.92 Co 0.06 Mn 0.02 (OH)2 (polycrystalline high-nickel precursor) is added to a mixer and mixed evenly. Then it is transferred to an atmosphere furnace and heated to 500°C at a heating rate of 5°C / min under an oxygen atmosphere. It is then sintered at this temperature for 4 hours. After cooling down to 40°C, the sintered product is crushed into powder to obtain a sintered material.
[0055] (2) Add 1.323g of CH3COONa (sodium source), 50g of calcined material, and 0.298g of H3PO4 (phosphorus source) to 120g of alcohol solvent (add the next one after the previous one is evenly dispersed). The alcohol solvent contains ethanol and ethylene glycol in a mass ratio of 2:1. Sonicate and stir to disperse evenly.
[0056] (3) Heat and stir the mixture obtained in step (2) at 65°C until the alcohol solvent is completely evaporated, and then transfer the remaining material to a drying oven at 85°C for drying to obtain the modified precursor.
[0057] (4) The modified precursor is added to the mixer and dispersed at a speed of 1000 r / min (to break up local agglomerates). Then it is transferred to an atmosphere furnace and heated to 700°C at a heating rate of 3°C / min under an oxygen atmosphere. It is sintered at this temperature for 10 h. After cooling down to 40°C, the sintered product is ground and dispersed to obtain sodium phosphorus modified high nickel ternary cathode material (hereinafter referred to as NCM-3).
[0058] Comparative example:
[0059] (1) Mix 23.7g of LiOH·H2O (lithium source) and 50g of Ni 0.92 Co 0.06 Mn 0.02 (OH)2 (polycrystalline high-nickel precursor) is added to a mixer and mixed evenly. Then it is transferred to an atmosphere furnace and heated to 500°C at a heating rate of 5°C / min under an oxygen atmosphere. It is then sintered at this temperature for 4 hours. After cooling down to 40°C, the sintered product is crushed into powder to obtain a sintered material.
[0060] (2) Transfer the sintered material to an atmosphere furnace and heat it to 700°C at a heating rate of 5°C / min under an oxygen atmosphere. Sinter it at this temperature for 10 hours. After cooling down to 40°C, grind and disperse the sintered product to obtain a high-nickel ternary cathode material.
[0061] Characterization and testing:
[0062] (1) SEM analysis was performed on the sodium-phosphorus modified high-nickel ternary cathode material prepared in Example 1 and the high-nickel ternary cathode material prepared in the comparative example to obtain the attached... Figure 1 .
[0063] (2) The sodium-phosphorus modified high-nickel ternary cathode material prepared in Example 1 and the high-nickel ternary cathode material prepared in the comparative example were respectively made into coin cells by the following methods:
[0064] The positive electrode material, conductive carbon black, and polyvinylidene fluoride were mixed evenly in the solvent N-methylpyrrolidone at a mass ratio of 8:1:1 to obtain a positive electrode slurry. The positive electrode slurry was coated onto carbon-coated aluminum foil to obtain a positive electrode sheet. The positive electrode sheet was dried in a vacuum drying oven at 110°C for 10 hours, then rolled on a rolling mill, and the rolled positive electrode sheet was punched into a circular electrode sheet.
[0065] Battery assembly was carried out in an argon-filled glove box. The electrolyte was 1 mol / L LiPF6, and the solvent contained EC, DEC, and DMC in a volume ratio of 1:1:1. The negative electrode was a lithium metal sheet.
[0066] The prepared button cells were subjected to charge-discharge tests at room temperature and a rate of 0.1C to obtain the results. Figure 2 The discharge curves shown are used to calculate the initial coulombic efficiency of the high-nickel ternary cathode material prepared in Comparative Example 1 as 90.6%, and the initial coulombic efficiency of the sodium-phosphorus modified high-nickel ternary cathode material prepared in Example 1 as 92.4%.
[0067] The prepared button cells were activated by cycling three times at room temperature at a rate of 0.1C, and then subjected to 100 charge-discharge cycles at room temperature at a charge-discharge rate of 0.3C / 0.3C. The results showed that... Figure 3 The discharge curves shown are used to calculate the capacity retention rate of the high-nickel ternary cathode material prepared in Comparative Example 1, which is 79.1%, and the capacity retention rate of the sodium-phosphorus modified high-nickel ternary cathode material prepared in Example 1, which is 88.3%.
[0068] It should be understood that the specific embodiments described above are merely illustrative or explanatory of the principles of the invention and do not constitute a limitation thereof. Therefore, any modifications, equivalent substitutions, improvements, etc., made without departing from the spirit and scope of the invention should be included within the protection scope of the invention. Furthermore, the appended claims are intended to cover all variations and modifications falling within the scope and boundaries of the claims, or equivalent forms of such scope and boundaries.
Claims
1. A method for preparing a sodium-phosphorus modified high-nickel ternary cathode material, characterized in that, Including the following steps: The lithium source and polycrystalline high-nickel precursor were mixed and sintered in an atmosphere furnace to obtain a sintered material. The calcined material, sodium source, and phosphorus source are dispersed in an alcohol solvent, stirred, and the alcohol solvent is evaporated to obtain a modified precursor. The modified precursor was sintered in an atmosphere furnace to obtain a sodium-phosphorus modified high-nickel ternary cathode material. The molar ratio of the sodium source to the phosphorus source is (2-12):1, and the two can be converted into sodium phosphate after the alcohol solvent is evaporated.
2. The method for preparing the sodium-phosphorus modified high-nickel ternary cathode material according to claim 1, characterized in that, The phosphorus source includes at least one of H3PO4, NH4H2PO4, (NH4)2HPO4 and NaH2PO4.
3. The method for preparing the sodium-phosphorus modified high-nickel ternary cathode material according to claim 2, characterized in that, The sodium source includes at least one of CH3ONa, NaOH, CH3COONa, and Na2CO3.
4. The method for preparing the sodium-phosphorus modified high-nickel ternary cathode material according to any one of claims 1-3, characterized in that, The molar ratio of the calcined material to the sodium source is 1:(0.036~0.120).
5. The method for preparing the sodium-phosphorus modified high-nickel ternary cathode material according to claim 4, characterized in that, The alcohol solvent contains ethanol and ethylene glycol in a mass ratio of (1-4):
1.
6. The method for preparing the sodium-phosphorus modified high-nickel ternary cathode material according to any one of claims 1-3 and 5, characterized in that, When sintering the modified precursor: the sintering temperature is 550-850℃, the heating rate is 1-5℃ / min, and the sintering time is 6-12h.
7. The method for preparing the sodium-phosphorus modified high-nickel ternary cathode material according to claim 6, characterized in that, The chemical formula of the calcined material is LiNi. x Co y Mn z O2, x+y+z=1, x≥0.
8.
8. The method for preparing the sodium-phosphorus modified high-nickel ternary cathode material according to claim 7, characterized in that, When sintering the mixture of the lithium source and the polycrystalline high-nickel precursor: the sintering temperature is 340-660℃, the heating rate is 1-5℃ / min, and the sintering time is 4-8h.
9. The method for preparing the sodium-phosphorus modified high-nickel ternary cathode material according to claim 7 or 8, characterized in that, The sintering atmosphere of the lithium source and the polycrystalline high-nickel precursor mixture and the sintering atmosphere of the modified precursor are independently selected from an oxygen atmosphere and an air-oxygen mixture atmosphere, respectively.
10. A sodium-phosphorus modified high-nickel ternary cathode material, characterized in that, The sodium-phosphorus modified high-nickel ternary cathode material is prepared by any one of the preparation methods described in claims 1-9.