Double-doped single-crystal ultrahigh-nickel positive electrode material as well as preparation method and application thereof

Abstract

The invention discloses a double-doped single-crystal ultrahigh-nickel positive electrode material and a preparation method and application thereof, and the positive electrode material is mainly prepared by the following method: (1) carrying out ball milling on nano nickel oxide or nano cobaltosic oxide, nano manganese dioxide, a boron source and an aluminum source, and uniformly mixing to obtain mixed powder; and (2) uniformly mixing the mixed powder obtained in the step (1) with a lithium source, carrying out two-stage microwave sintering in an oxidizing atmosphere, cooling to room temperature along with a furnace, and grinding to obtain the double-doped single-crystal ultrahigh-nickel positive electrode material. A positive pole piece prepared from the double-doped single-crystal ultrahigh-nickel positive pole material is applied to the field of lithium ion batteries. The positive electrode material is compact in grain, stable in structure, high in crystallinity and low in Li / Ni mixed arrangement, and a battery assembled by a prepared electrode plate is excellent in high rate performance and cycle performance. The method disclosed by the invention is simple in process, rapid, green, environment-friendly, energy-saving, consumption-reducing, low in cost and suitable for industrial production.

Description

Technical Field

[0001] The present invention relates to a single-crystal ultra-high nickel cathode material, its preparation method and application, and specifically relates to a double-doped single-crystal ultra-high nickel cathode material, its preparation method and application. Background Art

[0002] High-nickel single-crystal cathode materials (such as LiNi x Co y Mn 1-x-y O2, 0.9 ≤ x < 1.0, 0 ≤ y ≤ 0.1) as the core material for lithium-ion batteries to achieve a high energy density of 400 Wh / kg have received much attention in recent years. Its single-crystal structure significantly improves the cycle stability by eliminating grain boundary cracks and interfacial side reactions in polycrystalline materials. However, traditional preparation technologies face severe challenges: The high-temperature solid-phase method requires multi-stage calcination (>12 h) and multi-step preparation (first preparing the precursor and then the cathode material), with high energy consumption and prone to Li / Ni mixing (>4%) and grain coarsening (>5 μm); Although the co-precipitation-calcination method can control the particle morphology, the process is complex, the wastewater treatment cost is high, and the secondary particles are prone to cracking along the grain boundaries during cycling.

[0003] CN110112403A discloses a high specific capacity lithium nickel cobalt manganese oxide cathode material and its preparation method, which is to mix and dissolve nickel sulfate, cobalt sulfate, manganese sulfate, and aluminum sulfate in proportion to prepare a metal sulfate solution; then add NaOH and NH3·H2O to the solution to adjust the pH = 11, stir the solution, collect the precipitate by centrifugation, and vacuum dry to obtain an aluminum-doped nickel cobalt manganese hydroxide precursor; further ball-mill and mix the precursor with LiOH·H2O with 5% excess lithium, 1 wt% B2O3, and 0.5 wt% SiO2, and sinter the mixture at 850°C for 12 h, and after natural cooling, obtain a lithium nickel cobalt manganese oxide cathode material. Although this method can effectively improve the cycle performance of lithium manganese oxide batteries and inhibit the self-discharge phenomenon, this method requires co-precipitation combined with solid-phase sintering preparation, with a long process time and high energy consumption.

[0004] CN114400320A discloses a high-temperature stable cathode material, its preparation method and application, which uses lithium nickel cobalt manganese oxide as the matrix, and sequentially coats a composite oxide layer containing two or more metal elements and a difluorophosphate layer on the surface, and prepares the cathode material through a step-by-step process of high-temperature sintering the matrix, medium-temperature oxidation composite coating, and low-temperature solvothermal deposition of difluorophosphate. Although the material obtained by this method has both high voltage capacity and high-temperature cycle stability, this method requires step-by-step high-temperature sintering, composite oxide coating, and difluorophosphate deposition, with a cumbersome process and strict control of parameters such as temperature gradient and atmosphere switching, increasing the industrialization difficulty and energy consumption cost.

[0005] CN114656000A discloses a nickel-cobalt-manganese-oxide lithium material and a preparation method thereof, a positive electrode material and a lithium ion battery. The material is made of a lithium source, a nickel-cobalt-manganese precursor and a trivalent / pentavalent antimony source (molar ratio 1:0.9-1.1) as raw materials, and a step-by-step double-platform sintering method is used to achieve directional doping of antimony elements. The pentavalent antimony source is first mixed and sintered at high temperature to make Sb 5+ Embedded in transition metal sites, then introduced trivalent antimony source for secondary step sintering, using Sb 3+ Ions with larger radii preferentially occupy lithium sites, and the bulk and surface structures are stabilized through a multi-stage temperature control strategy with a temperature difference of >200°C and a time difference of >1h. Although the material obtained by this method can effectively inhibit electrolyte side reactions and transition metal dissolution, and significantly improve lithium ion diffusion efficiency, high temperature safety, and long cycle capacity retention, this method is still a traditional step-by-step solid-phase sintering method with a long process time and high energy consumption.

[0006] In summary, it is urgent to find a positive electrode material with dense grains, stable structure, high crystallinity, low Li / Ni mixing, and the high rate performance and cycle performance of the battery assembled with the prepared electrode pole pieces, simple and fast process, green and environmentally friendly, energy-saving and consumption-reducing, low cost, suitable for industrial production of dual-doped single crystal ultra-high nickel positive electrode materials and their preparation methods and applications. Summary of the invention

[0007] The technical problem to be solved by the present invention is to overcome the above-mentioned defects of the prior art and provide a double-doped single crystal ultra-high nickel positive electrode material having dense grains, stable structure, high crystallinity, low Li / Ni mixing, and the high rate performance and cycle performance of the battery assembled with the prepared electrode pole pieces. The process is simple and fast, green and environmentally friendly, energy-saving and consumption-reducing, low cost, and suitable for industrial production, as well as a preparation method and application thereof.

[0008] The technical solution adopted by the present invention to solve the technical problem is as follows: A double-doped single crystal ultra-high nickel positive electrode material is mainly made by the following method: (1) Mixing nano nickel oxide or nano cobalt tetroxide, nano manganese dioxide, boron source and aluminum source by ball milling to obtain mixed powder; (2) After the mixed powder obtained in step (1) is evenly mixed with the lithium source, two-stage microwave sintering is performed in an oxidizing atmosphere, the mixture is cooled to room temperature in the furnace, and then ground and pulverized to obtain a dual-doped single crystal ultra-high nickel positive electrode material.

[0009] The inventive concept of the present invention is: the present invention prepares high nickel positive electrode materials by synergistic effect sintering of nano-oxides in one step by microwave-assisted method, thereby avoiding the selective precipitation deviation of metal ions in co-precipitation. 3+ 、Al 3+Double doping is carried out in the bulk of the high-nickel cathode material to inhibit lattice distortion, synergistically regulate the lattice structure of the material, and enhance the structural stability. At the same time, the boron source and the aluminum source can also act as sintering aids to promote the reaction. Combining with the advantages of microwave bulk heating, rapid and low-energy consumption synthesis can be achieved. The obtained material has the characteristics of high crystallinity, low Li / Ni mixing, stable cycling, and excellent high-rate performance, and is suitable for high-energy density scenarios such as power batteries.

[0010] Preferably, in step (1), the average particle size of the nano-nickel oxide, nano-cobalt tetroxide, and nano-manganese dioxide is 30-100 nm. The one-step method of nano-oxides skips the co-precipitation step by directly using nano-scale precursors (NiO, Co3O4, MnO2). Its technical breakthroughs are as follows: 1) Atomic-level uniform doping can be achieved: The high specific surface energy of nano-particles promotes the bulk diffusion of dopants such as B 3 + , Al 3+ etc., to form a gradient solid solution structure and relieve the H2-H3 phase transition stress; 2) Controllability of single-crystal nucleation: The high surface energy of nano-precursors reduces the sintering activation energy, and combined with the rapid microwave heating to inhibit the agglomeration of secondary particles, the consistency of single-crystal size can be achieved (deviation < 10%); 3) Process simplification and environmental protection: Omit processes such as co-precipitation and washing, reduce wastewater discharge by > 70%, and are suitable for the development of cobalt-free / low-cobalt systems.

[0011] Preferably, in step (1), the molar ratio of nickel element in the nano-nickel oxide, cobalt element in the nano-cobalt tetroxide, and manganese element in the nano-manganese dioxide is 90-95:0-10:0-10 (more preferably 90-95:1-9:1-9, and even more preferably 90-95:2-6:2-6).

[0012] Preferably, in step (1), the mass ratio of the sum of the masses of the nano-nickel oxide or also the nano-cobalt tetroxide and nano-manganese dioxide to the sum of the masses of the boron source and the aluminum source is 94-99:1-6. A small amount of doping can effectively adjust the electronic structure of the material and inhibit lattice distortion, while excessive doping will damage the crystal structure of the main material, form an inactive phase, hinder ion diffusion, and reduce the battery energy density.

[0013] Preferably, in step (1), the mass ratio of the boron source to the aluminum source is 1-4:1-4. If there is too much boron source, it may overly inhibit grain growth, resulting in insufficient mechanical strength of the material. If there is too much aluminum source, it may reduce the conductivity and affect the performance of the material.

[0014] Preferably, in step (1), the boron source includes one or more of boric acid, boron oxide, lithium borate, etc. Since boric acid has a low high-temperature decomposition temperature, is easy to mix with the precursor, and has a low cost, more preferably, the boron source is boric acid.

[0015] Preferably, in step (1), the aluminum source includes one or more of aluminum fluoride, aluminum oxide, lithium aluminate, etc. Due to the synergistic effect between Al 3+ and F - in aluminum fluoride, it can not only stabilize the lattice structure through Al 3+ but also passivate the surface and inhibit oxygen activity through F - , thereby comprehensively improving the thermal stability, cycle life and safety of the high-nickel single crystal material. More preferably, the aluminum source is aluminum fluoride.

[0016] Preferably, in step (1), the mass ratio of the mixed powder to the ball milling beads is 1:5 to 20 (more preferably 1:5 to 15), the mixing rotation speed of ball milling is 200 to 800 rpm (more preferably 200 to 600 rpm), and the time is 5 to 20 h (more preferably 5 to 12 h). Ball milling can make the mixture more uniform.

[0017] Preferably, in step (2), the total molar number of nickel element in the nano-nickel oxide, cobalt element in the nano-cobalt ferrite, and manganese element in the nano-manganese dioxide is in a molar ratio of 1:1.03 to 1.20 to the lithium element in the lithium source.

[0018] Preferably, in step (2), the lithium source includes one or more of lithium hydroxide monohydrate, lithium carbonate, lithium nitrate, etc.

[0019] Preferably, in step (2), the flow rate of the oxidation atmosphere is 50 to 200 sccm.

[0020] Preferably, in step (2), the oxidation atmosphere includes oxygen and / or air, etc.

[0021] Preferably, in step (2), in the microwave sintering, the output power of the microwave is 200 to 2900 W (more preferably 800 to 1200 W), and the microwave frequency is 2.45 GHz.

[0022] Preferably, in step (2), the two-stage microwave sintering means: first, heat from room temperature to 400 to 600 °C at a rate of 50 to 100 °C / min and hold for 5 to 60 min (more preferably 20 to 60 min) for the first-stage microwave sintering, and then heat to 750 to 950 °C at a rate of 50 to 100 °C / min and hold for 5 to 60 min (more preferably 20 to 60 min) for the second-stage microwave sintering. Microwave sintering realizes bulk uniform heating through the dielectric loss of the material to the microwave (such as the ionic conduction and dipole polarization of NiO and LiOH). Its core advantages are reflected in three aspects: 1) Ultra-fast reaction kinetics: The heating rate can reach more than 100 °C / min, the sintering time is shortened to 1 / 5 of the traditional process, abnormal grain growth is inhibited, and sub-micron single crystals are obtained; 2) Precise structure regulation: The microwave electric field drives Li+ Migration reduces the Li / Ni mixing degree to less than 2%. Meanwhile, the dynamic regulation of the O2 atmosphere stabilizes Ni 3+ oxidation state and reduces oxygen vacancy defects; 3) Energy conservation and consumption reduction: The energy utilization rate reaches 80% (less than 40% for the traditional method), the lithium volatilization loss rate is less than 3%, and the comprehensive cost is reduced by 40%.

[0023] In summary, the synergistic effect of nanoscale raw materials and microwave sintering further releases the performance potential. The microwave field accelerates the densification of nanoparticles (for example, the synthesis of NCM single crystals can be completed at 850 °C / 30 min). At the same time, the grain boundary migration is optimized through the coupling of the electric field and the thermal field, greatly improving the cycle stability and rate performance of the material, providing an innovative path for the high safety and high energy density of power batteries. In the future, with the development of the large-scale of microwave equipment and the standardization of nano-precursors, this green synthesis technology is expected to promote the large-scale commercial application of high-nickel single crystal materials.

[0024] The technical solution adopted by the present invention to further solve its technical problems is as follows: An application of a double-doped single-crystal ultra-high nickel cathode material, using the cathode electrode sheet made of the double-doped single-crystal ultra-high nickel cathode material in the field of lithium-ion batteries.

[0025] The beneficial effects of the present invention are as follows: (1) The double-doped single-crystal ultra-high nickel cathode material of the present invention has dense grains, stable structure, high crystallinity, and low Li / Ni mixing. The battery assembled with the made electrode sheet has a first reversible discharge specific capacity as high as 222.82 mAh / g at a rate of 0.1C, and a first Coulomb efficiency as high as 85.67%; at rates of 1C, 2C, 3C, and 5C, the first discharge specific capacities are 193.3 mAh / g, 183.4 mAh / g, 174.1 mAh / g, and 153.4 mAh / g respectively; at 0.5C, after 200 cycles, the discharge capacity retention rate can still reach 83.15%, indicating that the double-doped single-crystal ultra-high nickel cathode material of the present invention has excellent high-rate performance and cycle performance; (2) The combination of nano-oxide and microwave sintering in one step in the method of the present invention becomes the key technology to break through the bottleneck in the preparation of high-nickel single crystal materials. The sintering activation energy is reduced by the high surface energy of nanoparticles, and the densification process is further accelerated by synergistic microwave heating. Moreover, the process is simple, fast, green and environmentally friendly, energy-saving and consumption-reducing, and low-cost, suitable for industrial production. Description of the Drawings

[0026] Figure 1 It is the SEM diagram of Example 1 of the double-doped single-crystal ultra-high nickel cathode material of the present invention; Figure 2 It is the first-cycle charge-discharge diagram of the battery assembled with the electrode sheet made of Example 1 of the double-doped single-crystal ultra-high nickel cathode material of the present invention; Figure 3 It is a comparison chart of the rate performance of the batteries assembled with the electrode sheets made from Example 1 and Comparative Example 1 of the double-doped single-crystal ultra-high nickel cathode material of the present invention; Figure 4 It is a comparison chart of the cycling performance of the batteries assembled with the electrode sheets made from Example 1 and Comparative Example 1 of the double-doped single-crystal ultra-high nickel cathode material of the present invention. Detailed implementation manners

[0027] The present invention will be further described below in conjunction with examples and drawings.

[0028] The average particle size of the nickel oxide nanoparticles used in the examples of the present invention is 30 nm, the average particle size of the cobalt tetroxide nanoparticles is 50 nm, and the average particle size of the manganese dioxide nanoparticles is 100 nm, all of which are purchased from Aladdin Chemical Reagent Network; the raw materials or chemical reagents used in the examples and comparative examples of the present invention are obtained through conventional commercial channels without special instructions.

[0029] Example 1 of a double-doped single-crystal ultra-high nickel cathode material It is mainly made by the following method: (1) 2.017 g (27 mmol) of nickel oxide nanoparticles, 0.120 g (0.5 mmol) of cobalt tetroxide nanoparticles, and 0.130 g (1.5 mmol) of manganese dioxide nanoparticles are mixed with 0.0398 g of H3BO3 and 0.0796 g of AlF3. At a mass ratio of the mixed powder to the milling beads of 1:5 and a mixing rotation speed of 200 rpm, ball milling is carried out for 5 h until evenly mixed to obtain a mixed powder; (2) After the mixed powder obtained in step (1) is mixed evenly with 1.322 g (31.50 mmol) of LiOH·H2O, in an oxygen atmosphere with a flow rate of 50 sccm, a microwave output power of 900 W, and a microwave frequency of 2.45 GHz, two-stage microwave sintering is carried out: first, it is heated from room temperature to 400 °C at a rate of 50 °C / min and kept warm for 60 min for the first-stage microwave sintering, and then it is heated to 850 °C at a rate of 50 °C / min and kept warm for 60 min for the second-stage microwave sintering. It is cooled to room temperature with the furnace and ground and pulverized to obtain the double-doped single-crystal ultra-high nickel cathode material LiNi 0.9 Co 0.05 Mn 0.05 O2.

[0030] As Figure 1 shown, the double-doped single-crystal ultra-high nickel cathode material obtained in the examples of the present invention is micron-sized blocky particles with a particle size of 1 - 6 μm.

[0031] Example 1 of the application of a double-doped single-crystal ultra-high nickel cathode material The positive electrode sheet made of the double-doped single-crystal ultra-high nickel cathode material obtained in the embodiment of the present invention is used to assemble a button-type lithium-ion battery.

[0032] Preparation method of the positive electrode sheet: In a dew point room, 0.8 g of the double-doped single-crystal ultra-high nickel cathode material obtained in the embodiment of the present invention, 0.1 g of conductive carbon black, and 0.1 g of polyvinylidene fluoride are ground until there are no obvious particles. Further, 1 mL of N-methylpyrrolidone solution is added to the above mixture, and grinding is continued until a homogeneous paste-like material is obtained; the prepared paste-like material is coated on the current collector aluminum foil so that the slurry adheres evenly to the surface of the current collector; finally, after drying at 120 °C for 6 h, it is punched into an SNCM positive electrode with a diameter of 12 mm.

[0033] Assembly of the button-type lithium-ion battery: The obtained SNCM positive electrode sheet is placed in the positive electrode case, and an appropriate amount of electrolyte is dropped to wet the electrode; then a separator is covered, a lithium sheet is placed, and a spacer and a spring sheet are stacked; finally, the negative electrode case is aligned and pressed and sealed with a sealer; after assembly, it needs to be left standing for 18 h to allow the electrolyte to fully infiltrate, and then charge-discharge tests are carried out.

[0034] Battery test: The button-type lithium-ion battery assembled in the application embodiment of the present invention is tested for its first charge-discharge specific capacity at 0.1 C under the conditions that the discharge cut-off voltage is 2.75 V and the charge cut-off voltage is 4.4 V. The test results are shown in Table 1, Figure 2 as shown; its rate performance is tested at rates of 0.1 C, 0.2 C, 0.3 C, 0.5 C, 1 C, 2 C, 3 C, and 5 C, and the test results are as Figure 3 shown; after activation at 0.1 C for 3 cycles, it is charged at 0.5 C and discharged at 0.5 C for 200 cycles, and its cycle performance is tested. The test results are shown in Table 1, Figure 4 as shown.

[0035] As Figure 2 shown, the first charge-discharge specific capacities of the button-type lithium-ion battery assembled in the application embodiment of the present invention at 0.1 C are 259.04 mAh / g and 213.80 mAh / g respectively, and the Coulomb efficiency is 82.54%.

[0036] As Figure 3As shown, for the button-type lithium-ion battery assembled in the application embodiment of the present invention, at the rates of 0.1 C, 0.2 C, 0.3 C, 0.5 C, 1 C, 2 C, 3 C, and 5 C that increase step by step, the initial discharge specific capacities are 216.9 mAh / g, 212.3 mAh / g, 207.7 mAh / g, 201.9 mAh / g, 193.3 mAh / g, 183.4 mAh / g, 174.1 mAh / g, and 153.4 mAh / g respectively. When the rate returns to 0.1 C, the initial discharge specific capacity can still reach 203.2 mAh / g, showing excellent rate performance, indicating that the doping of boron and aluminum and the two-stage microwave sintering can promote the complete growth of single crystals, shorten the diffusion path of lithium-ion batteries, and improve the rate performance.

[0037] As Figure 4 shown, for the button-type lithium-ion battery assembled in the application embodiment of the present invention, at a rate of 0.5 C, the initial discharge specific capacity is 202.4 mAh / g. After 200 cycles, the discharge specific capacity can still reach 168.3 mAh / g, and the capacity retention rate is 83.15%.

[0038] Example 2 of a double-doped single-crystal ultra-high nickel cathode material It is mainly made by the following method: (1) Mix 2.062 g (27.6 mmol) of nano nickel oxide, 0.048 g (0.2 mmol) of nano cobalt tetroxide, and 0.156 g (1.8 mmol) of nano manganese dioxide with 0.0231 g of H3BO3 and 0.0231 g of AlF3. At a mass ratio of the mixed powder to the ball milling beads of 1:8 and a mixing rotation speed of 300 rpm, ball mill for 8 h until evenly mixed to obtain a mixed powder; (2) After evenly mixing the mixed powder obtained in step (1) with 1.385 g (33.0 mmol) of LiOH·H2O, in an oxygen atmosphere with a flow rate of 80 sccm, at a microwave output power of 800 W and a microwave frequency of 2.45 GHz, perform two-stage microwave sintering: first, heat from room temperature to 450 °C at a rate of 60 °C / min, hold for 50 min for the first-stage microwave sintering, then heat to 800 °C at a rate of 60 °C / min, hold for 50 min for the second-stage microwave sintering, and cool to room temperature with the furnace, grind and crush to obtain the double-doped single-crystal ultra-high nickel cathode material LiNi 0.92 Co 0.02 Mn 0.06 O2.

[0039] After testing, the double-doped single-crystal ultra-high nickel cathode material obtained in the embodiment of the present invention is micron-sized blocky particles with a particle size of 1 - 6 μm.

[0040] Application Example 2 of a Dual-Doped Single-Crystalline Ultra-High-Nickel Cathode Material The positive electrode sheet made of the dual-doped single-crystalline ultra-high-nickel cathode material obtained in the example of the present invention is used to assemble a button-type lithium-ion battery.

[0041] Preparation method of the positive electrode sheet: the same as that in Application Example 1.

[0042] Assembly of the button-type lithium-ion battery: the same as that in Application Example 1.

[0043] Battery test: The first charge-discharge specific capacity and cycle performance tests are the same as those in Application Example 1; the test results are shown in Table 1.

[0044] Example 3 of a Dual-Doped Single-Crystalline Ultra-High-Nickel Cathode Material It is mainly made by the following method: (1) 2.106 g (28.2 mmol) of nano nickel oxide, 0.048 g (0.2 mmol) of nano cobalt tetroxide, and 0.104 g (1.2 mmol) of nano manganese dioxide are mixed with 0.0466 g of H3BO3 and 0.0233 g of AlF3. At a mass ratio of the mixed powder to the ball milling beads of 1:10 and a mixing rotation speed of 400 rpm, ball milling is carried out for 10 h until evenly mixed to obtain a mixed powder; (2) After the mixed powder obtained in step (1) is mixed evenly with 1.448 g (34.5 mmol) of LiOH·H2O, in an oxygen atmosphere with a flow rate of 100 sccm, a microwave output power of 900 W, and a microwave frequency of 2.45 GHz, two-stage microwave sintering is carried out: first, it is heated from room temperature to 500 °C at a rate of 70 °C / min and held for 40 min for the first-stage microwave sintering, and then it is heated to 850 °C at a rate of 70 °C / min and held for 40 min for the second-stage microwave sintering. It is cooled to room temperature with the furnace and ground and pulverized to obtain the dual-doped single-crystalline ultra-high-nickel cathode material LiNi 0.94 Co 0.02 Mn 0.04 O2.

[0045] After detection, the dual-doped single-crystalline ultra-high-nickel cathode material obtained in the example of the present invention is micron-sized blocky particles with a particle size of 1 - 6 μm.

[0046] Application Example 3 of a Dual-Doped Single-Crystalline Ultra-High-Nickel Cathode Material The positive electrode sheet made of the dual-doped single-crystalline ultra-high-nickel cathode material obtained in the example of the present invention is used to assemble a button-type lithium-ion battery.

[0047] Preparation method of the positive electrode sheet: the same as that in Application Example 1.

[0048] Assembly of the button-type lithium-ion battery: the same as that in Application Example 1.

[0049] Battery test: The first charge-discharge specific capacity and cycle performance tests were the same as those in Application Example 1; the test results are shown in Table 1.

[0050] Example 4 of a double-doped single-crystal ultra-high nickel cathode material It is mainly prepared by the following method: (1) 2.129 g (28.5 mmol) of nano-nickel oxide, 0.048 g (0.2 mmol) of nano-cobalt tetroxide, and 0.078 g (0.9 mmol) of nano-manganese dioxide were mixed with 0.0235 g of H3BO3 and 0.0705 g of AlF3. With the mass ratio of the mixed powder to the milling beads being 1:12 and the mixing rotation speed being 500 rpm, ball milling was carried out for 12 h until uniformly mixed to obtain a mixed powder. (2) After uniformly mixing the mixed powder obtained in step (1) with 1.511 g (36.0 mmol) of LiOH·H2O, in an oxygen atmosphere with a flow rate of 120 sccm, a microwave output power of 800 W, and a microwave frequency of 2.45 GHz, two-stage microwave sintering was carried out: first, it was heated from room temperature to 550 °C at a rate of 80 °C / min and held for 30 min for the first-stage microwave sintering, and then it was heated to 900 °C at a rate of 80 °C / min and held for 30 min for the second-stage microwave sintering. It was cooled to room temperature with the furnace and ground to obtain the double-doped single-crystal ultra-high nickel cathode material LiNi 0.95 Co 0.02 Mn 0.03 O2.

[0051] It was detected that the double-doped single-crystal ultra-high nickel cathode material obtained in the embodiment of the present invention was micron-sized blocky particles with a particle size of 1 - 6 μm.

[0052] Application Example 4 of a double-doped single-crystal ultra-high nickel cathode material The positive electrode sheet made of the double-doped single-crystal ultra-high nickel cathode material obtained in the embodiment of the present invention was used to assemble a button-type lithium-ion battery.

[0053] Method for preparing the positive electrode sheet: The same as Application Example 1.

[0054] Assembly of the button-type lithium-ion battery: The same as Application Example 1.

[0055] Battery test: The first charge-discharge specific capacity and cycle performance tests were the same as those in Application Example 1; the test results are shown in Table 1.

[0056] Example 5 of a double-doped single-crystal ultra-high nickel cathode material It is mainly prepared by the following method: (1) 2.084 g (27.9 mmol) of nickel oxide nanoparticles, 0.048 g (0.2 mmol) of cobalt tetroxide nanoparticles, and 0.130 g (1.5 mmol) of manganese dioxide nanoparticles were mixed with 0.0952 g of H3BO3 and 0.0239 g of AlF3. At a mass ratio of the mixed powder to the milling beads of 1:15 and a mixing rotation speed of 600 rpm, the mixture was ball-milled for 10 h until uniformly mixed to obtain a mixed powder; (2) After uniformly mixing the mixed powder obtained in step (1) with 1.385 g (33.0 mmol) of LiOH·H2O, in an oxygen atmosphere with a flow rate of 200 sccm, at a microwave output power of 900 W and a microwave frequency of 2.45 GHz, two-stage microwave sintering was carried out: first, it was heated from room temperature to 600 °C at a rate of 100 °C / min and held for 20 min for the first-stage microwave sintering, and then it was heated to 950 °C at a rate of 100 °C / min and held for 20 min for the second-stage microwave sintering. It was cooled to room temperature with the furnace and ground and pulverized to obtain the double-doped single-crystal ultra-high nickel cathode material LiNi 0.93 Co 0.02 Mn 0.05 O2.

[0057] After testing, the double-doped single-crystal ultra-high nickel cathode material obtained in the embodiment of the present invention is micron-sized blocky particles with a particle size of 1 - 6 μm.

[0058] Application Example 5 of a Double-Doped Single-Crystal Ultra-High Nickel Cathode Material The positive electrode sheet made of the double-doped single-crystal ultra-high nickel cathode material obtained in the embodiment of the present invention was used to assemble a button-type lithium-ion battery.

[0059] Preparation method of the positive electrode sheet: the same as Application Example 1.

[0060] Assembly of the button-type lithium-ion battery: the same as Application Example 1.

[0061] Battery testing: The first charge-discharge specific capacity and cycle performance tests were the same as those in Application Example 1; the test results are shown in Table 1.

[0062] Comparative Example 1 The difference between this comparative example and Example 1 is only that: in step (2), for the first-stage microwave sintering: it was heated from room temperature to 750 °C at a rate of 50 °C / min and held for 60 min. The rest was the same as in Example 1.

[0063] Preparation method of the positive electrode sheet: the same as Application Example 1.

[0064] Assembly of the button-type lithium-ion battery: the same as Application Example 1.

[0065] Battery testing: the same as Application Example 1; the test results are shown in Table 1,Figure 3 , 4 as shown.

[0066] As Figure 3 shown, for the coin-type lithium-ion battery assembled in the comparative example of the present invention, at the increasing rates of 0.1 C, 0.2 C, 0.3 C, 0.5 C, 1 C, 2 C, 3 C, and 5 C, the initial discharge specific capacities are only 202.0 mAh / g, 193.6 mAh / g, 191.9 mAh / g, 181.9 mAh / g, 170.9 mAh / g, 158.0 mAh / g, 145.2 mAh / g, and 124.3 mAh / g in sequence. When the rate is restored to 0.1 C, the initial discharge specific capacity is only 181.2 mAh / g, and the rate performance is poor, indicating that one-stage sintering makes the decomposition rate of the precursor and the crystal nucleation rate too fast, resulting in chaotic crystal growth directions, easy formation of polycrystalline structures or secondary particles, and the existence of grain boundaries significantly hinders lithium-ion diffusion and reduces the rate performance.

[0067] As Figure 4 shown, for the coin-type lithium-ion battery assembled in the comparative example of the present invention, at a rate of 0.5 C, the initial discharge specific capacity is 181.5 mAh / g. After 200 cycles, the discharge specific capacity is only 137.2 mAh / g, and the discharge capacity retention rate is only 75.59%.

[0068] Comparative Example 2 The difference between this comparative example and Example 1 is only that: in step (1), 2.776 g (30 mmol) of Ni 0.9 Co 0.05 Mn 0.05 (OH)2, 0.0487 g of H3BO3, and 0.0974 g of AlF3 are ball-milled for 5 h until uniformly mixed at a mass ratio of the mixed powder to the ball-milling beads of 1:5 and a mixing rotation speed of 200 rpm to obtain a mixed powder. The rest is the same as in Example 1.

[0069] Comparative Example 3 After uniformly mixing 2.017 g (27 mmol) of nano-nickel oxide, 0.120 g (0.5 mmol) of nano-cobalt tetroxide, and 0.130 g (1.5 mmol) of nano-manganese dioxide with 1.322 g (31.50 mmol) of LiOH·H2O, two-stage microwave sintering is carried out in an oxygen atmosphere with a flow rate of 50 sccm: first, it is heated from room temperature to 400 °C at a rate of 50 °C / min and held for 60 min for one-stage microwave sintering, and then it is heated to 750 °C at a rate of 50 °C / min and held for 60 min for two-stage microwave sintering, and then cooled to room temperature with the furnace and ground and pulverized to obtain the single-crystal ultra-high nickel cathode material LiNi 0.9 Co0.05 Mn 0.05 O2。

[0070] Comparative Example 4 The difference between this comparative example and Example 1 is only that: in step (1), 0.0398 g of H3BO3 is not added; in step (2), the single-doped single-crystalline ultra-high nickel cathode material LiNi 0.90 Co 0.05 Mn 0.05 O2 is obtained. The rest is the same as in Example 1.

[0071] Comparative Example 5 The difference between this comparative example and Example 1 is only that: in step (1), 0.0796 g of AlF3 is not added; in step (2), the single-doped single-crystalline ultra-high nickel cathode material LiNi 0.90 Co 0.05 Mn 0.05 O2 is obtained. The rest is the same as in Example 1.

[0072] Preparation method of the cathode electrode sheets of Comparative Examples 2 to 5: the same as in Application Example 1.

[0073] Assembly of button-type lithium-ion batteries for Comparative Examples 2 to 5: the same as in Application Example 1.

[0074] Battery tests for Comparative Examples 2 to 5: The first charge-discharge specific capacity and cycle performance tests are the same as in Application Example 1; the test results are shown in Table 1.

[0075] Table 1 Comparison table of the electrochemical performances of the batteries assembled with the electrode sheets made in Examples 1 to 5 and Comparative Examples 1 to 5 of the present invention

[0076] As can be seen from Table 1, the batteries assembled with the electrode sheets made in Examples 1 to 5 of the present invention have a first reversible discharge specific capacity as high as 222.82 mAh / g and a first Coulombic efficiency as high as 85.67% at a 0.1C rate, while the first discharge specific capacity and the first Coulombic efficiency of the batteries assembled with the electrode sheets made in Comparative Examples 1 to 5 of the present invention are slightly reduced because the electrochemical performance is mainly determined by the performance of the ultra-high nickel cathode material itself.

[0077] From Table 1, Figure 4It can be seen that for the battery assembled with the electrode sheet prepared in Example 1 of the present invention, after 200 cycles at 0.5C, the discharge capacity retention rate can still reach 83.15%, and the cycling performance is stable. This indicates that the doping of boron and aluminum and the two-stage microwave sintering can inhibit the collapse of the cathode material structure and the generation of microcracks, while reducing cation mixing and maintaining the long-term stability of the layered structure, thereby improving the cycling stability. However, the discharge capacity retention rates of the batteries assembled with the electrode sheets prepared in Comparative Examples 1-5 of the present invention all decreased, and the cycling stability deteriorated. Among them, in Comparative Example 1, only one-stage microwave sintering was carried out, and the cycling stability of the obtained material deteriorated, indicating that the rapid temperature rise in one-stage sintering led to + disordered Li migration paths, and it was difficult for Ni 2+ to orderly migrate back to the transition metal layer, resulting in a significant increase in the degree of cation mixing. During cycling, the insertion and extraction of Li + triggered lattice distortion, accelerating particle cracking and capacity decay; in Comparative Example 2, the nano nickel cobalt manganese oxide raw material was replaced with a nickel cobalt manganese hydroxide precursor. First, the cycling stability of the obtained material deteriorated, indicating that the nano-oxide has a lower porosity, higher density, and lower degree of cation mixing compared to the hydroxide precursor, reducing side reactions and improving cycling stability. Second, the preparation process of the nickel cobalt manganese hydroxide precursor is complex, and its cost is also significantly higher than the nano-oxide material used in the present invention; in Comparative Example 3, boron and aluminum doping were not carried out, in Comparative Example 4, only aluminum was doped, and in Comparative Example 5, only boron was doped. The cycling stability of the obtained materials all deteriorated to varying degrees, indicating that the doped Al 3+ can partially replace the transition metal site, stabilize the layered structure and inhibit cation mixing, and the doped B 3+ can regulate the surface structure or occupy the interstitial site, optimizing the Li + diffusion kinetics. The co-doping of Al 3+ and B 3+ can combine the structural stability and surface / kinetic optimization capabilities to achieve a synergistic effect and improve the battery cycling stability.

[0078] In summary, the initial Coulomb efficiency of the double-doped single-crystalline high-nickel cathode materials obtained in Examples 1-5 of the present invention is high, and the rate performance and cycling performance are excellent. This indicates that the double-doped high-nickel cathode material obtained by the method of the present invention through boron and aluminum doping and two-stage microwave sintering can inhibit lattice distortion and enhance structural stability, greatly improving the cycling stability and rate performance, providing an innovative path for the high safety and high energy density of power batteries.

Claims

1. A dual-doped single crystal ultra-high nickel positive electrode material, characterized in that: Mainly made by the following methods: (1) Mixing nano nickel oxide or nano cobalt tetroxide, nano manganese dioxide, boron source and aluminum source by ball milling to obtain mixed powder; (2) After the mixed powder obtained in step (1) is evenly mixed with the lithium source, two-stage microwave sintering is performed in an oxidizing atmosphere, the mixture is cooled to room temperature in the furnace, and then ground and pulverized to obtain a dual-doped single crystal ultra-high nickel positive electrode material.

2. The dual-doped single crystal ultra-high nickel positive electrode material according to claim 1, characterized in that: In step (1), the average particle size of the nano nickel oxide, nano cobalt tetroxide and nano manganese dioxide is 30-100 nm; the molar ratio of the nickel element in the nano nickel oxide, the cobalt element in the nano cobalt tetroxide and the manganese element in the nano manganese dioxide is 90-95:0-10:0-10; the ratio of the mass sum of the nano nickel oxide or the nano cobalt tetroxide and the nano manganese dioxide to the mass sum of the boron source and the aluminum source is 94-99:1-6; the mass ratio of the boron source to the aluminum source is 1-4:1-4; the boron source includes one or more of boric acid, boric oxide or lithium borate; the aluminum source includes one or more of aluminum fluoride, aluminum oxide or lithium aluminate.

3. The dual-doped single crystal ultra-high nickel positive electrode material according to claim 1 or 2, characterized in that: In step (1), the mass ratio of the mixed powder to the ball milling beads is 1:5-20, the mixing speed of the ball mill is 200-800 rpm, and the time is 5-20 h.

4. The dual-doped single crystal ultra-high nickel positive electrode material according to any one of claims 1 to 3, characterized in that: In step (2), the molar ratio of the total molar number of nickel element in the nano nickel oxide, the cobalt element in the nano cobalt tetroxide, and the manganese element in the nano manganese dioxide to the lithium element in the lithium source is 1:1.03-1.20; and the lithium source includes one or more of lithium hydroxide monohydrate, lithium carbonate or lithium nitrate.

5. The dual-doped single crystal ultra-high nickel positive electrode material according to any one of claims 1 to 4, characterized in that: In step (2), the flow rate of the oxidizing atmosphere is 50 to 200 sccm; the oxidizing atmosphere includes oxygen and / or air; in the microwave sintering, the microwave output power is 200 to 2900 W, and the microwave frequency is 2.45 GHz; the two-stage microwave sintering refers to: first, heating from room temperature to 400 to 600°C at a rate of 50 to 100°C / min, keeping warm for 5 to 60 min, performing a first-stage microwave sintering, and then heating to 750 to 950°C at a rate of 50 to 100°C / min, keeping warm for 5 to 60 min, and performing a second-stage microwave sintering.

6. An application of the dual-doped single crystal ultra-high nickel positive electrode material as claimed in any one of claims 1 to 5, characterized in that: The positive electrode sheet made of the double-doped single crystal ultra-high nickel positive electrode material according to any one of claims 1 to 5 is used in the field of lithium-ion batteries.

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