High-nickel positive electrode material as well as preparation method and application thereof

Abstract

The invention discloses a high-nickel positive electrode material as well as a preparation method and application thereof, and belongs to the technical field of lithium ion batteries. The preparation method of the high-nickel positive electrode material comprises the following steps: (1) mixing a high-nickel ternary precursor, a lithium source and WO3, and carrying out pulse high-temperature sintering treatment to prepare the high-nickel ternary positive electrode material; and (2) mixing the high-nickel ternary positive electrode material with ammonium bicarbonate, and then carrying out sealed tube heating treatment to obtain the high-nickel positive electrode material. The low-cost and high-efficiency preparation of the single-crystal ternary positive electrode material is realized through a pulse high-temperature sintering technology, and a layer of uniform proton enrichment shell is formed on the surface of the positive electrode material through a sealed tube heating method, so that the cycling stability and the safety performance of the material are further improved.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium-ion batteries, and in particular to a high-nickel positive electrode material and a preparation method and application thereof. Background Art

[0002] With the growing global demand for clean energy and efficient energy storage technologies, lithium-ion batteries, as key energy storage devices, are playing an increasingly important role in applications such as electric vehicles, portable electronic devices, and large-scale energy storage systems. The performance of lithium-ion batteries depends largely on the properties of their cathode materials. In recent years, ultra-high nickel cathode materials have become a hot topic in lithium-ion battery research due to their high specific capacity and relatively low cost. However, while the capacity of NCM cathode materials gradually increases with increasing nickel content, high nickel content also leads to significant volume changes, increased intergranular microcracks, and enhanced interfacial side reactions, resulting in decreased battery cycling stability and safety. To overcome these drawbacks, single-crystal NCM cathode materials have emerged. By eliminating internal voids and grain boundaries within the cathode particles, reducing intergranular microcracks, and inhibiting side reactions with the electrolyte, single-crystal NCM cathode materials significantly improve battery cycling stability and safety.

[0003] Traditional methods for preparing single-crystal NCM cathode materials often suffer from severe lithium volatilization, the need for flux, and high costs. In recent years, pulsed high-temperature sintering technology has emerged as an effective method for preparing high-performance single-crystal NCM cathode materials, combining the advantages of high-temperature sintering, flux-assisted sintering, and ultra-fast sintering. This technology achieves high-temperature sintering in a short period of time, reduces lithium volatilization, eliminates the need for flux, and eliminates the need to modify existing production lines, thereby reducing production costs.

[0004] On the other hand, to further enhance the performance of ultra-high nickel cathode materials, surface modification technologies have also attracted widespread attention. Through surface coating and doping, the interfacial properties of cathode materials can be effectively stabilized, side reactions with the electrolyte can be suppressed, and the battery's cycle stability and rate performance can be improved. Among these, utilizing the chemical reactions of protons within the battery to transform them into inorganic F- and P-based interfacial layers that are beneficial to the long-term cycling stability of high-nickel single crystals is an innovative interface design approach. Summary of the Invention

[0005] In order to solve the problems of poor cycle stability and thermal stability of high-nickel ternary positive electrode materials in the existing technology, the present invention provides a high-nickel positive electrode material and its preparation method and application. The present invention combines pulse high-temperature sintering technology and surface proton enrichment technology to prepare a high-stability high-nickel positive electrode material.

[0006] The present invention first provides a method for preparing a high-nickel positive electrode material, comprising the following steps: (1) A high nickel ternary precursor, a lithium source and WO3 are mixed and subjected to a pulse high temperature sintering treatment to prepare a high nickel ternary positive electrode material; (2) The high-nickel ternary positive electrode material and ammonium bicarbonate are mixed, and then subjected to a sealed tube heating treatment to obtain the high-nickel positive electrode material.

[0007] The present invention achieves low-cost and efficient preparation of single-crystal ternary cathode materials through pulsed high-temperature sintering technology, and forms a uniform proton-enriched shell on the surface of the cathode material through a sealed tube heating method, further improving the material's cycle stability and safety performance.

[0008] In the above-mentioned method for preparing high nickel cathode material, the molecular formula of the high nickel ternary precursor is Ni x Co y Mn (1-x-y) (OH)2, wherein 0.9≤x≤0.95, 0.05≤y≤0.1, and x+y<1; specifically, the molecular formula of the high nickel ternary precursor is Ni 0.93 Co 0.06 Mn 0.01 (OH)2; The lithium source is at least one of lithium hydroxide, lithium carbonate, lithium dihydrogen phosphate, lithium oxide, lithium oxalate, lithium acetate and lithium nitrate; The molar ratio of the high-nickel ternary precursor, the lithium source and WO3 is 1:1.01-1.1:0.01-0.03, specifically 1:1.02:0.02.

[0009] In the preparation method of the above-mentioned high-nickel positive electrode material, in step (1), the pulse high-temperature sintering treatment is as follows: the atmosphere of the pulse high-temperature sintering treatment is oxygen, and the oxygen flow rate is maintained at 50-150 mL / min. The temperature is first raised to 450-550°C at a heating rate of 3-7°C / min, and pretreated for 3-6 hours. Then, the temperature is raised to 730-830°C at a heating rate of 1-5°C / min, and kept warm for 3-7 hours. The oxygen flow rate is adjusted to 30-70 mL / min, and the temperature is raised to 950-1150°C at a rate of 5-9°C / min, and kept warm for 8-12 minutes. The temperature is then lowered to 730-820°C at a rate of 5-9°C / min. At this time, the oxygen flow rate is adjusted back to 70-130 mL / min, and kept warm at 730-820°C for 3-7 hours.

[0010] In the above-mentioned method for preparing the high-nickel positive electrode material, the mass ratio of the high-nickel ternary positive electrode material to ammonium bicarbonate is 50-200:1; preferably 100:1.

[0011] In the above-mentioned method for preparing high nickel positive electrode materials, in step (2), the vacuum pressure of the sealed tube during heating treatment is 0.5×10 -3 -1.5×10-3 pa, can be 1.0×10 -3 pa; The sealing tube is heated at a temperature of 150-250°C, specifically 200°C; The sealing tube is heated for 8-12 minutes, specifically 10 minutes. The heating rate of the sealed tube during heating is 5-15°C / min, specifically 10°C / min.

[0012] The above-mentioned method for preparing high-nickel positive electrode materials includes the steps of cooling to room temperature and crushing and screening after the pulse high-temperature sintering treatment in step (1).

[0013] The present invention also provides a high-nickel positive electrode material prepared by the above preparation method.

[0014] The application of the above-mentioned high nickel positive electrode material in the preparation of lithium ion battery positive electrodes also falls within the protection scope of the present invention.

[0015] Furthermore, the present invention provides a positive electrode plate, the active component of which is the high-nickel positive electrode material.

[0016] A lithium-ion battery comprises the positive electrode plate.

[0017] Compared with the prior art, the present invention has the following advantages: (1) The present invention develops a W-doped high-nickel ternary cathode material. W-doping can reduce the unit cell parameters, optimize the lithium ion diffusion channel, and improve the rate performance of the material.

[0018] (2) In the present invention, the high-temperature thermal melting and subsequent cooling crystallization process of pulse high-temperature sintering are conducive to the fusion and recrystallization of single crystal particles, thereby promoting the single crystalization of the ternary material. This method not only reduces the volatilization of lithium during the sintering process, but also does not require the addition of additional flux or water washing treatment, and can prepare a ternary positive electrode material with a single crystal morphology, and can improve the cycle stability and safety performance of the material. (3) The pulse high-temperature sintering method adopted by the present invention shortens the production cycle, improves production efficiency, and has universal applicability; (4) The present invention forms a uniform proton-enriched shell on the ultra-high nickel ternary positive electrode material. During the first charging process of the battery, the protons released by the proton-enriched shell react with lithium hexafluorophosphate (LiPF6) in the electrolyte and are in situ converted into sub-nanometer lithium fluoride (LiF) and lithium phosphate (Li3PO4) particles, forming a dense inorganic masking agent. The masking agent forms a protective layer on the surface of the positive electrode material, effectively resisting the erosion of the electrolyte, reducing the loss of lattice oxygen and the dissolution of transition metals, thereby improving the surface stability of the material; (5) The preparation process of the present invention is simple and the electrical performance is significantly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is the SEM image of the high-stability high-nickel positive electrode material of Example 2.

[0020] Figure 2 This is the TEM image of the high-stability high-nickel positive electrode material of Example 2.

[0021] Figure 3 This is the SEM image of the high-nickel ternary positive electrode material of comparative example 2.

[0022] Figure 4 DSC graphs of button cells prepared with the positive electrode materials of Example 2 and Comparative Example 1. DETAILED DESCRIPTION

[0023] The present invention will be further described in detail below in conjunction with specific embodiments. The examples given are only for illustrating the present invention, not for limiting the scope of the present invention.

[0024] The experimental methods in the following examples are conventional methods unless otherwise specified.

[0025] The quantitative tests in the following examples were performed in triplicate unless otherwise specified, and the results were averaged.

[0026] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0027] The electrochemical performance testing methods used in the following examples are as follows: CR2032 batteries were fabricated in an argon-filled glove box using the cathode material from the examples or comparative examples as the positive electrode, a lithium metal sheet as the negative electrode, a polypropylene microporous membrane as the separator, and 1 mol / L LiPF6 as the electrolyte. 0.2C constant current charge and discharge tests were conducted at room temperature, with charge and discharge cutoff voltages ranging from 2.8V to 4.35V.

[0028] Example 1 (1) According to the commercial precursor Ni 0.93 Co 0.06 Mn 0.01 The precursor Ni was weighed in a molar ratio of (OH)2, LiOH·H2O, and WO3 of 1:1.02:0.02. 0.93 Co 0.06 Mn 0.01(OH)2, LiOH·H2O and WO3 are mixed and mechanically ground, then placed in a tubular furnace and calcined at high temperature in an oxygen atmosphere. The oxygen flow rate is maintained at 100mL / min. The tubular furnace is first heated to 500℃ at a heating rate of 5℃ / min, pretreated for 5h, then heated to 780℃ at a heating rate of 3℃ / min, kept warm for 5h, and the oxygen flow is adjusted to 50mL / min. The furnace is heated to 1050℃ at a heating rate of 7℃ / min, kept warm for 10min, and cooled to 780℃ at a rate of 7℃ / min. At this time, the oxygen flow is adjusted back to 100mL / min, and the furnace is kept warm at 780℃ for 5h and then cooled to room temperature. The high-nickel ternary positive electrode material is crushed and sieved.

[0029] (2) The high nickel ternary cathode material obtained in step (1) was mixed with ammonium bicarbonate at a mass ratio of 50:1. The resulting mixture was transferred to a quartz tube and vacuumed to 1.0×10 -3 The sealed quartz tube was heat treated at 200°C for 10 min at a heating rate of 10°C / min. After cooling and sieving, a high-stability high-nickel cathode material was obtained.

[0030] Example 2-3 Except that the mass ratio of the high-nickel ternary positive electrode material to ammonium bicarbonate in step (2) is different, that is, 100:1 in Example 2 and 200:1 in Example 3, the other synthesis conditions are the same as those in Example 1, and a high-stability high-nickel positive electrode material is obtained.

[0031] The SEM image of the high-stability high-nickel cathode material of Example 2 is shown in FIG. Figure 1 ,Depend on Figure 1 It can be seen that the high-stability high-nickel positive electrode material prepared in this embodiment is a coating layer uniformly coated on the surface of the ternary material particles.

[0032] Figure 2 TEM image of the high-stability high-nickel cathode material of Example 2, Figure 2 It can also be seen that the surface of the ternary material particles of the high-stability and high-nickel positive electrode material prepared in this embodiment has a coating layer.

[0033] Comparative Example 1 (Conventionally sintered high nickel ternary cathode material) According to the commercial precursor Ni 0.93 Co 0.06 Mn 0.01 (OH)2, LiOH·H2O, WO3 molar ratio 1:1.02:0.02 weigh Ni 0.93 Co 0.06 Mn 0.01(OH)2, LiOH·H2O, and WO3 were mixed and mechanically ground, and then the mixture was placed in a tubular furnace, and the oxygen flow was maintained at 100 mL / min throughout the process. The tubular furnace was first heated to 500°C at a heating rate of 5°C / min, pretreated for 5 hours, and then heated to 750°C at a heating rate of 3°C / min, kept warm for 15 hours, and cooled to room temperature to obtain a conventionally sintered high-nickel ternary positive electrode material.

[0034] Comparative Example 2 (High-nickel ternary positive electrode material sintered by pulse method) According to the commercial precursor Ni 0.93 Co 0.06 Mn 0.01 (OH)2, LiOH·H2O, WO3 molar ratio 1:1.02:0.02 weigh Ni 0.93 Co 0.06 Mn 0.01 (OH)2, LiOH·H2O, WO3, mix them and grind them mechanically, then place the mixture in a tubular furnace and calcine at high temperature in an oxygen atmosphere. The oxygen flow rate is maintained at 100 mL / min. The tubular furnace is first heated to 500°C at a heating rate of 5°C / min, pretreated for 5h, then heated to 780°C at a heating rate of 3°C / min, kept warm for 5h, and the oxygen flow is adjusted to 50mL / min. The furnace is heated to 1050°C at a heating rate of 7°C / min, kept warm for 10min, and then cooled to 780°C at a cooling rate of 7°C / min. At this time, the oxygen flow is adjusted back to 100mL / min, and the furnace is kept warm at 780°C for 5h and then cooled to room temperature. The high-nickel ternary positive electrode material is obtained by crushing and sieving. The SEM image of the high-nickel ternary positive electrode material is shown in Figure 3 ,Depend on Figure 3 It can be seen that the surface of the high-nickel ternary positive electrode material particles prepared in this comparative example is smooth and does not have any coating layer.

[0035] The positive electrode materials from the above examples and comparative examples were fabricated into positive electrode sheets and assembled into CR2032 batteries. The specific steps were as follows: Using the positive electrode materials from the examples and comparative examples as the active material, SP as the conductive agent, PVDF as the binder, and N-methyl-2-pyrrolidone (NMP) as the dispersant, a ternary positive electrode material: SP:PVDF slurry was prepared at a mass ratio of 90:5:5, and the resulting mixture was coated onto aluminum foil to form the electrode sheet. A lithium metal sheet was used as the negative electrode, a polypropylene microporous membrane as the separator, and 1 mol / L LiPF6 as the electrolyte (the solvent was a mixture of EC, DEC, and DMC in a volume ratio of 1:1:1). The CR2032 batteries were fabricated in an argon-filled glove box. 0.2C constant current charge and discharge tests were conducted at room temperature, with charge and discharge cutoff voltages ranging from 2.8V to 4.35V.

[0036] The assembled CR2032 battery was subjected to charge and discharge tests. The results are shown in Table 1. The DSC graphs of the button batteries prepared with the positive electrode materials of Example 2 and Comparative Example 1 are shown in Table 1. Figure 4 .

[0037] Table 1 is a summary of the buckling performance data of the positive electrode materials prepared in the examples and comparative examples

[0038] As can be seen from Table 1, the first discharge capacity of the button cell with high-stability high-nickel cathode material prepared in Example 2 of the present invention is 221.9 mAh g -1 The first charge and discharge efficiency is 87.9%, and the cycle retention rate after 100 cycles is 97.1% at a current of 1C. The method of the present invention greatly improves the first efficiency, rate performance and cycle stability of the positive electrode material. Figure 4 It can be seen that compared with Comparative Example 1, the ternary material prepared in Example shows a shift in the exothermic reaction peak and an increase in the thermal stability temperature by 10° C., indicating that the safety of the positive electrode material of the present invention is improved.

Claims

1. A method for preparing a high-nickel positive electrode material, characterized in that: The preparation method comprises the following steps: (1) A high nickel ternary precursor, a lithium source and WO3 are mixed and subjected to a pulse high temperature sintering treatment to prepare a high nickel ternary positive electrode material; (2) The high-nickel ternary positive electrode material and ammonium bicarbonate are mixed, and then subjected to a sealed tube heating treatment to obtain the high-nickel positive electrode material.

2. The method for preparing a high-nickel cathode material according to claim 1, wherein: The molecular formula of the high nickel ternary precursor is Ni x Co y Mn (1-x-y) (OH)2, where 0.9≤x≤0.95, 0.05≤y≤0.1, and x+y<1; The lithium source is at least one of lithium hydroxide, lithium carbonate, lithium dihydrogen phosphate, lithium oxide, lithium oxalate, lithium acetate and lithium nitrate; The molar ratio of the high-nickel ternary precursor, the lithium source and WO3 is 1:1.01-1.1:0.01-0.

03.

3. The method for preparing a high-nickel cathode material according to claim 1, wherein: In step (1), the pulse high temperature sintering treatment is as follows: the atmosphere of the pulse high temperature sintering treatment is oxygen, and the oxygen flow rate is maintained at 50-150mL / min. The temperature is first raised to 450-550℃ at a heating rate of 3-7℃ / min, and pretreated for 3-6h. Then, the temperature is raised to 730-830℃ at a heating rate of 1-5℃ / min, and kept warm for 3-7h. The oxygen flow rate is adjusted to 30-70mL / min, and the temperature is raised to 950-1150℃ at a rate of 5-9℃ / min, and kept warm for 8-12min. The temperature is then lowered to 730-820℃ at a rate of 5-9℃ / min. At this time, the oxygen flow rate is adjusted back to 70-130mL / min, and kept warm at 730-820℃ for 3-7h.

4. The method for preparing a high-nickel cathode material according to claim 1, wherein: The mass ratio of the high-nickel ternary positive electrode material to ammonium bicarbonate is 50-200:

1.

5. The method for preparing a high-nickel cathode material according to claim 4, wherein: The mass ratio of the high-nickel ternary positive electrode material to ammonium bicarbonate is 100:

1.

6. The method for preparing a high-nickel cathode material according to claim 1, wherein: In step (2), the vacuum pressure of the sealed tube during heating is 0.5×10 -3 -1.5×10 -3 pa; The sealing tube is heated at a temperature of 150-250°C; The sealing tube is heated for 8-12 minutes. The heating rate of the sealed tube heating treatment is 5-15°C / min.

7. A high-nickel positive electrode material prepared by the preparation method according to any one of claims 1 to 6.

8. Use of the high-nickel positive electrode material according to claim 7 in preparing a positive electrode for a lithium-ion battery.

9. A positive electrode plate, the active ingredient of which is the high-nickel positive electrode material according to claim 7.

10. A lithium-ion battery comprising the positive electrode sheet according to claim 9.

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