High-performance long-cycle high-nickel ternary positive electrode material and preparation method thereof

Abstract

The invention belongs to the field of lithium ion batteries, and provides a preparation method of a high-performance long-cycle high-nickel ternary positive electrode material, which comprises the following steps: uniformly mixing a nickel-cobalt-manganese hydroxide precursor with barium strontium tungsten oxide and a lithium source to obtain a mixture; and sintering the mixture in an aerobic atmosphere to obtain the high-performance long-cycle high-nickel ternary positive electrode material. According to the invention, the additive Ba2O6SrW is introduced, so that the obtained high-nickel ternary positive electrode material shows relatively high specific discharge capacity and first charge-discharge efficiency, and relatively excellent cycle retention rate.

Description

Technical Field

[0001] The present invention belongs to the field of lithium-ion batteries, and relates to a high-performance long-cycle high-nickel ternary cathode material and a preparation method thereof. Background Art

[0002] Disclosing the information of this background art section is only intended to enhance the understanding of the overall background of the present invention, and is not necessarily regarded as an admission or an implication in any form that this information constitutes the prior art already known to those of ordinary skill in the art.

[0003] In recent years, with the popularization of electronic products, the demand for batteries, especially lithium-ion batteries, has been increasing. In addition, as cars enter families, air pollution in large and medium-sized cities mainly stems from vehicle exhaust emissions. One of the effective ways to solve the fuel and pollution problems of cars is to develop electric vehicles. The key to developing electric vehicles lies in battery technology. Although mass production technologies for electric vehicles have been achieved at home and abroad, due to the limitation of battery energy density, there is still a large gap in the cruising range compared with fuel vehicles. And the nickel-rich ternary material is one of the cathode materials for high-energy-density lithium-ion batteries at present.

[0004] The nickel-rich ternary cathode material has a relatively high reversible discharge specific capacity, but due to the high nickel content, the cycle performance is poor. The main reasons are as follows:

[0005] 1. Structural defects and lithium-nickel mixing. Limited by thermodynamic factors, it is difficult to prepare a nickel-rich ternary material with a stoichiometric composition. Part of Ni 2+ is prone to migrate to the lithium layer and occupy the lithium site, resulting in Li + / Ni 2+ cation mixing. Severe lithium-nickel mixing will affect the intercalation and deintercalation of lithium ions and electrochemical performance. Such structural defects will increase the internal resistance of the material and reduce the electrochemical activity.

[0006] 2. Unstable surface properties. The residual lithium on the surface of the nickel-rich ternary material is prone to form impurity phases such as Li2CO3 and LiOH when exposed to air, increasing the alkalinity of the material particles. This will not only bring difficulties to the subsequent coating process, but also the insulating impurity phases will increase the interfacial impedance of the material. In addition, in a deeper delithiated state, the high-valent transition metal ions on the particle surface have strong oxidizing properties and are prone to react with the electrolyte, resulting in capacity loss.

[0007] 3. Intergranular cracks and microstrain. In the electrochemical reaction, repeated phase transitions are usually accompanied by changes in lattice parameters and the generation of microstresses. The newly generated cracks are exposed to the electrolyte, and continuous side reactions will form an additional insulating film, and even cause pulverization of the electrode material, thereby increasing the impedance of the material and reducing the kinetic performance.

[0008] To solve the above problems, researchers have carried out a large amount of research work to prepare nickel-rich ternary cathode materials through modification. Currently, the modification strategies for nickel-rich ternary cathode materials mainly include: surface and interface engineering, bulk doping, and morphology control and other modification methods. For example: Patent CN114656000A discloses a lithium nickel cobalt manganese oxide material Li a Ni x Co y Mn z Q u R v T w O2 and the cathode material, and prepares a nickel-rich ternary cathode material through modification. Among them, T is selected from one or more of boron, fluorine, magnesium, aluminum, silicon, phosphorus, calcium, scandium, titanium, vanadium, chromium, iron, copper, zinc, gallium, germanium, tin, niobium, molybdenum, strontium, yttrium, zirconium, tungsten, hafnium, indium, bismuth, lanthanum, cerium, gadolinium, barium, and tantalum.

[0009] However, there is still an urgent need in the industry to find a simpler and more efficient method to solve the problems such as the inability to obtain high capacity and long cycle life of existing high-nickel cathode materials. Summary of the Invention

[0010] To solve the above problems, the present invention provides a high-performance long-cycle nickel-rich ternary cathode material and a preparation method thereof. The present invention introduces barium strontium tungsten Ba2O6SrW as an additive in the high-temperature solid-phase lithiation reaction stage of the lithium source and the precursor. Both Ba and Sr belong to the second main group and have the effect of reducing the grain boundary migration and fusion energy barrier, thereby promoting the nucleation and growth of grains, and further reducing the lattice distortion, crystal defects, and the degree of Li / Ni mixing, making the high-nickel cathode material have a high reversible specific capacity and good stability. At the same time, the Sr-O bond energy is relatively strong, which can effectively improve the lattice oxygen evolution of the high-nickel cathode material, reduce the reversible specific capacity loss in the deep discharge state, and improve the initial efficiency and capacity of the cathode material. However, due to the ionic radii of Ba, Sr, and W being much larger than those of lithium ions and transition metal ions, they cannot enter the lattice and thus accumulate on the crystal surface to form a stable coating film, thereby improving the cycle stability of the nickel-rich ternary cathode material.

[0011] To achieve the above object, the present invention adopts the following technical solutions:

[0012] In the first aspect of the present invention, a preparation method of a high-performance long-cycle nickel-rich ternary cathode material is provided, including:

[0013] Mixing a nickel cobalt manganese hydroxide precursor, barium strontium tungsten, and a lithium source uniformly to obtain a mixed material;

[0014] Sintering the mixed material in an aerobic atmosphere to obtain a high-performance long-cycle nickel-rich ternary cathode material.

[0015] Further, in the barium strontium tungsten oxide, the mass fraction of strontium in the total mass of the cathode material is 1000-1500 ppm.

[0016] Further, the nickel cobalt manganese hydroxide precursor is Ni x Co y Mn 1-x-y (OH)2, 0.5 ≤ x ≤ 1.0, 0 < y ≤ 0.5.

[0017] Further, the lithium source is selected from at least one of lithium carbonate, lithium hydroxide, lithium oxalate, and lithium nitrate.

[0018] Further, the sintering includes: pre-sintering at 300-600 °C for 5-8 h, and then raising the temperature to 680-930 °C for sintering for 10-15 h.

[0019] Further, in the lithium source and the nickel cobalt manganese hydroxide precursor, the molar ratio of lithium to the total molar amount of nickel, cobalt, and manganese is 1.03-1.06.

[0020] In the second aspect of the present invention, a high-performance long-cycle high-nickel ternary cathode material prepared by the above method is provided.

[0021] Advantages of the present invention

[0022] (1) In the present invention, barium strontium tungsten Ba2O6SrW is introduced in the high-temperature solid-phase lithiumation reaction stage of the lithium source and the precursor, and multi-element co-doping is utilized. Both Ba and Sr belong to the second main group and have the effect of reducing the grain boundary migration and fusion energy barriers, thereby promoting the nucleation and growth of grains, and further reducing the lattice distortion, crystal defects, and the degree of Li / Ni mixing, so that the high-nickel cathode material has a high reversible specific capacity and good stability. At the same time, the Sr-O bond energy is relatively strong, which can effectively improve the lattice oxygen evolution of the high-nickel cathode material, reduce the reversible specific capacity loss in the deep discharge state, and improve the first efficiency and capacity of the cathode material. However, since the ionic radii of Ba, Sr, and W are much larger than those of lithium ions and transition metal ions, they cannot enter the lattice and thus accumulate on the crystal surface to form a stable coating film, thereby improving the cycle stability of the high-nickel ternary cathode material.

[0023] (2) The introduction method of the present invention is different from the traditional method, which changes the spatial sites of each element inside the material, and the functions played are also slightly different. Brief description of the drawings

[0024] The specification drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention.

[0025] Figure 1SEM schematic diagram of the positive electrode material in Example 1;

[0026] Figure 2 First charge-discharge curves of the positive electrode materials prepared in Example 1 and Comparative Example 1;

[0027] Figure 3 Cycling performance comparison chart of the positive electrode materials prepared in Example 1 and Comparative Example 1. Detailed Description of the Invention

[0028] It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

[0029] The present invention will be further described in detail below with reference to specific embodiments. It should be noted that the specific embodiments are explanations rather than limitations of the present invention.

[0030] Example 1

[0031] 1. Weigh the hydroxide precursor Ni 0.9 Co 0.05 Mn 0.05 (OH)2, the lithium source LiOH·H2O, and the additive Ba2O6SrW. The molar ratio of Li / (Ni + Co + Mn) is 1.04, and the addition amount of the additive Ba2O6SrW is 1000 ppm (calculated based on the mass fraction of strontium element in the final product). Mix them evenly with a high-speed mixer at a rotation speed of 500 r / min for 30 min to obtain a uniformly mixed mixture;

[0032] 2. Sinter the mixture in an oxygen atmosphere in a box-type atmosphere furnace. The sintering regime is to increase the temperature at a rate of 3 °C / min to 500 °C, sinter for 5 h, then increase the temperature to 730 °C, and keep it warm for 12 h. After the sintering is completed, cool it to room temperature with the furnace, and obtain a high-nickel ternary positive electrode material after pulverizing, sieving, and removing magnetism.

[0033] Example 2

[0034] 1. Weigh the hydroxide precursor Ni 0.9 Co 0.05 Mn 0.05(OH)2, lithium source LiOH·H2O, additive Ba2O6SrW, where the molar ratio of Li / (Ni+Co+Mn) is 1.03, and the addition amount of additive Ba2O6SrW is 1000 ppm (calculated based on the mass fraction of strontium element in the final product). Mix them evenly with a high-speed mixer at a rotation speed of 500 r / min for 30 min to obtain a uniformly mixed mixture;

[0035] 2. Sinter the mixture in an oxygen atmosphere in a box-type atmosphere furnace. The sintering regime is to increase the temperature at a rate of 3 °C / min to 600 °C, sinter for 3 h, then increase the temperature to 730 °C, hold for 15 h. After the sintering is completed, cool it to room temperature with the furnace, and obtain the high-nickel ternary cathode material after crushing, sieving, and demagnetization.

[0036] Example 3

[0037] 1. Weigh the hydroxide precursor Ni 0.9 Co 0.05 Mn 0.05 (OH)2, lithium source LiOH·H2O, additive Ba2O6SrW, where the molar ratio of Li / (Ni+Co+Mn) is 1.03, and the addition amount of additive Ba2O6SrW is 1000 ppm (calculated based on the mass fraction of strontium element in the final product). Mix them evenly with a high-speed mixer at a rotation speed of 500 r / min for 30 min to obtain a uniformly mixed mixture;

[0038] 2. Sinter the mixture in an oxygen atmosphere in a box-type atmosphere furnace. The sintering regime is to increase the temperature at a rate of 3 °C / min to 300 °C, sinter for 8 h, then increase the temperature to 730 °C, hold for 10 h. After the sintering is completed, cool it to room temperature with the furnace, and obtain the high-nickel ternary cathode material after crushing, sieving, and demagnetization.

[0039] Comparative Example 1

[0040] 1. Weigh the hydroxide precursor Ni 0.9 Co 0.05 Mn 0.05 (OH)2, lithium source LiOH·H2O, where the molar ratio of Li / (Ni+Co+Mn) is 1.03. Mix them evenly with a high-speed mixer at a rotation speed of 500 r / min for 30 min to obtain a uniformly mixed mixture;

[0041] 2. The mixture is subjected to high-temperature sintering in a box-type atmosphere furnace under an oxygen atmosphere. The sintering regime is as follows: heating at a rate of 3 °C / min to 500 °C, sintering for 5 h, then heating to 730 °C and holding for 12 h. After sintering, it is cooled to room temperature in the furnace. After pulverization, sieving, and magnetic removal, a high-nickel ternary cathode material is obtained.

[0042] Comparative Example 2

[0043] 1. Weigh the hydroxide precursor Ni 0.9 Co 0.05 Mn 0.05 (OH)2, lithium source LiOH·H2O, additives SrO, BaO, WO3. The molar ratio of Li / (Ni + Co + Mn) is 1.03. The addition amounts of additives SrO, BaO, and WO3 are 1000 ppm, 3100 ppm, and 2000 ppm respectively (calculated based on the mass fractions of strontium, barium, and tungsten elements in the final product). Mix them evenly with a high-speed mixer at a rotation speed of 500 r / min for 30 min to obtain a uniformly mixed mixture.

[0044] 2. The mixture is subjected to high-temperature sintering in a box-type atmosphere furnace under an oxygen atmosphere. The sintering regime is as follows: heating at a rate of 3 °C / min to 500 °C, sintering for 5 h, then heating to 730 °C and holding for 12 h. After sintering, it is cooled to room temperature in the furnace. After pulverization, sieving, and magnetic removal, a high-nickel ternary cathode material is obtained.

[0045] Comparative Example 3

[0046] 1. Weigh the hydroxide precursor Ni 0.9 Co 0.05 Mn 0.05 (OH)2, lithium source LiOH·H2O, additives SrO, BaO. The molar ratio of Li / (Ni + Co + Mn) is 1.03. The addition amounts of additives SrO and BaO are 1000 ppm and 3100 ppm respectively (calculated based on the mass fractions of strontium and barium elements in the final product). Mix them evenly with a high-speed mixer at a rotation speed of 500 r / min for 30 min to obtain a uniformly mixed mixture.

[0047] 2. The mixture is subjected to high-temperature sintering in a box-type atmosphere furnace under an oxygen atmosphere. The sintering regime is as follows: heating at a rate of 3 °C / min to 500 °C, sintering for 5 h, then heating to 730 °C and holding for 12 h. After sintering, it is cooled to room temperature in the furnace. After pulverization, sieving, and magnetic removal, an intermediate A of the high-nickel ternary cathode material is obtained.

[0048] 3. Weigh intermediate A and additive WO3. The mass fraction of additive WO3 to intermediate A is 2000 ppm (calculated based on the mass fraction of tungsten element to the final product mass). Mix them evenly with a high-speed mixer at a rotation speed of 500 r / min for 30 min to obtain a uniformly mixed mixture. Sinter the mixture in a box-type atmosphere furnace under an oxygen atmosphere. The sintering regime is to heat it up to 400 °C at a heating rate of 3 °C / min, hold for 8 h, and then cool it to room temperature with the furnace. After sieving and magnetic separation, a high-nickel ternary cathode material is obtained.

[0049] Preparation of button battery: Apply the high-nickel ternary cathode materials prepared in the examples and comparative examples to button batteries for electrochemical performance testing. The battery assembly process is as follows: Mix the high-nickel ternary cathode material, polyvinylidene fluoride (PVDF), and conductive carbon black in a mass ratio of 8:1:1 and dissolve them in N-methylpyrrolidone (NMP) solvent to make a positive electrode slurry without particulate matter inside. Coat the slurry evenly on aluminum foil with a coater to make a pole piece. Put the coated pole piece into a vacuum drying oven at 120 °C for 12 hours of vacuum drying, take out the pole piece and roll it on a roll press for standby. Cut the pole piece into a circular pole piece with a diameter of 12 mm with a cutter, take it out after drying in a vacuum drying oven at 60 °C for 12 h, weigh it with an electronic balance, and finally assemble the positive electrode pole piece, lithium piece, spring piece, gasket, positive electrode shell, negative electrode shell, separator, and electrolyte into a CR2025-type button half-cell in a glove box filled with argon. The electrolyte is an electrolyte formed by dissolving 1M NaPF6 in a mixture of EC (ethylene carbonate) and DMC (dimethyl carbonate) (in a volume ratio of EC:DMC = 1:1), and the metallic lithium piece is the counter electrode. The charge-discharge voltage range is 2.8 - 4.4 V, the first charge-discharge rate is 0.1 C, and the nominal specific capacity is 1 C = 200 mAh / g. The charge-discharge rate for the cycle performance test is 1 C for 50 cycles.

[0050] Table 1 Comparison of electrical properties of examples and comparative examples

[0051]

[0052] From the comparison of physicochemical analysis results, after introducing the additive Ba2O6SrW, compared with Comparative Example 1, the high-nickel cathode material shows a higher discharge specific capacity, first charge-discharge efficiency, and better cycle retention rate.

[0053] From Comparative Example 2, it can be seen that compared with the mixture of SrO, BaO, and WO3 added, when using Ba2O6SrW as the additive, the high-nickel cathode material shows a higher discharge specific capacity, first charge-discharge efficiency, and better cycle retention rate.

[0054] As can be seen from Comparative Example 3, compared with the stepwise addition of SrO, BaO, and WO3, when using the method of introducing Ba2O6SrW as an additive in the present invention, the high-nickel cathode material exhibits a higher discharge specific capacity, first charge-discharge efficiency, and better cycle retention rate.

[0055] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a high-performance, long-cycle, high-nickel ternary cathode material, characterized in that: include: The nickel-cobalt-manganese hydroxide precursor is uniformly mixed with barium-strontium-tungsten oxide and a lithium source to obtain a mixture; The mixed material is sintered in an oxygen atmosphere to obtain a high-performance, long-cycle, high-nickel ternary positive electrode material.

2. The method for preparing a high-performance, long-cycle, high-nickel ternary cathode material according to claim 1, characterized in that: In the barium strontium tungsten oxide, the mass fraction of strontium in the total mass of the positive electrode material is 1000-1500ppm.

3. The method for preparing a high-performance, long-cycle, high-nickel ternary cathode material according to claim 1, characterized in that: The nickel-cobalt-manganese hydroxide precursor is Ni x Co y Mn 1-x-y (OH)2, 0.5≤x≤1.0, 0<y≤0.

5.

4. The method for preparing a high-performance, long-cycle, high-nickel ternary cathode material according to claim 1, characterized in that: The lithium source is selected from at least one of lithium carbonate, lithium hydroxide, lithium oxalate and lithium nitrate.

5. The method for preparing a high-performance, long-cycle, high-nickel ternary cathode material according to claim 1, characterized in that: The sintering comprises: pre-sintering at 300-600° C. for 5-8 hours, and then heating to 680-930° C. for sintering for 10-15 hours.

6. The method for preparing a high-performance, long-cycle, high-nickel ternary cathode material according to claim 1, characterized in that: In the lithium source and the nickel-cobalt-manganese hydroxide precursor, the ratio of lithium to the total molar amount of nickel-cobalt-manganese is 1.03-1.

06.

7. A high-performance, long-cycle, high-nickel ternary positive electrode material prepared by the method described in any one of claims 1 to 6.

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