Preparation method of lithium ion battery material

Abstract

The invention relates to the technical field of lithium ion battery positive electrode materials, in particular to a preparation method of a lithium ion battery material, which comprises the following specific steps: step 1, ball-milling and mixing a precursor and ethanol according to a mass ratio of 1: 3 for 4 hours, and drying to obtain uniformly dispersed matrix powder; 2, the matrix powder is subjected to coating treatment, and a coating material is obtained; 3, placing the coating material in a tubular furnace, annealing for 2 hours in an argon / hydrogen atmosphere, and inducing surface oxygen vacancies to form a sintered material; the lanthanum aluminate buffer layer, the Zr-doped transition layer and the lithium phosphate fast ion conductor of the gradient coating layer enable the interface impedance to be reduced from 65 ohm to 28 ohm, the reduction amplitude is 57%, and the electrolyte decomposition gas production rate is reduced by 70%; and the lanthanum aluminate buffer layer increases the oxygen evolution initial voltage from 4.35 V to 4.5 V by anchoring lattice oxygen.

Description

Technical Field

[0001] The present invention relates to the technical field of cathode materials for lithium-ion batteries, and particularly to a preparation method of a lithium-ion battery material. Background Art

[0002] With the rapid development of technology, lithium-ion batteries have become an important energy solution in fields such as portable electronic devices, electric vehicles, and energy storage systems due to their high energy density, long cycle life, and environmental friendliness. The performance of lithium-ion batteries depends to a large extent on the performance of their cathode materials.

[0003] However, traditional high-nickel materials are prone to lattice oxygen evolution during high-voltage cycling, which triggers electrolyte decomposition and transition metal dissolution, resulting in a sharp increase in interfacial impedance and capacity attenuation. Traditional coating technologies, such as single alumina or lithium phosphate layers, are difficult to balance ion conduction and interfacial passivation, and the difference in thermal expansion coefficients between the coating layer and the substrate will cause the coating layer to crack during cycling, exacerbating side reactions. In view of this, we propose a preparation method of a lithium-ion battery material. Summary of the Invention

[0004] The purpose of the present invention is to solve the deficiencies mentioned in the above background art and provide a preparation method of a lithium-ion battery material.

[0005] To solve the above technical problems, the present invention adopts the following technical solutions: A preparation method of a lithium-ion battery material, the specific steps of the preparation method are as follows: Step 1: Ball-mill and mix the precursor and ethanol at a mass ratio of 1:3 for 4 hours, and obtain uniformly dispersed matrix powder after drying; Step 2: Perform coating treatment on the matrix powder to obtain a coated material; Step 3: Place the coated material in a tube furnace and anneal it for 2 hours in an argon / hydrogen atmosphere to induce the formation of surface oxygen vacancies to form a sintered material; Step 4: Mix the material with molten salt, sinter at 850 °C for 6 hours, cool and wash with water to remove the molten salt to obtain a lithium-ion battery material.

[0006] Preferably, the specific steps of the coating treatment of the coated material in Step 2 are as follows: S1. Mix the matrix powder with lanthanum nitrate and aluminum nitrate in a molar ratio of 1:1, add citric acid, irradiate in a microwave reactor at a frequency of 2.45 GHz and a power of 800 W for 5 minutes, and heat up to 300 °C to form a coated powder; S2. Mix the coated powder with a doping element, and achieve gradient diffusion of Zr element under microwave irradiation to obtain a Zr-doped material; S3. Then, by using atomic layer deposition technology on the Zr-doped material, with lithium phosphate as the precursor, perform 50 cycles at 150 °C to form a fast ion conductor layer, and the coated material can be obtained. Preferably, the material of the fast ion conductor layer is any one of lithium phosphate, lithium aluminate, or lithium silicate, and the thickness is 3 - 10 nm.

[0007] Preferably, the power of the microwave irradiation is 500 - 1000 W, and the irradiation time is 3 - 10 minutes.

[0008] Preferably, the doping element is any one of Zr, Ti, or Nb, and the doping amount is 0.2% - 1% of the mass of the matrix powder.

[0009] Preferably, the molten salt medium is , or any one of them, and the sintering temperature is 800 - 900 °C.

[0010] Preferably, the precursor is any one of high-nickel ternary materials or lithium-rich manganese-based materials.

[0011] A lithium-ion battery material prepared by using the preparation method of the lithium-ion battery material.

[0012] Compared with the prior art, the beneficial effects of the present invention are: 1. For the preparation method of the lithium-ion battery material, the lanthanum aluminate buffer layer + Zr-doped transition layer + lithium phosphate fast ion conductor of the gradient coating layer reduce the interfacial impedance from 65 Ω to 28 Ω, a decrease of 57%, and the gas generation amount of electrolyte decomposition is reduced by 70%; and the lanthanum aluminate buffer layer anchors the lattice oxygen and raises the oxygen evolution onset voltage from 4.35 V to 4.5 V; 2. The Zr-doped layer of the present invention buffers the thermal mismatch stress between the matrix and the lithium phosphate layer, and the crack density after cycling is reduced by 83%; the core-shell - porous structure design reduces the volume expansion rate from 3.8% to 1.2%, and the compaction density retention rate after 500 cycles is ≥97%; 3. The microwave dielectric heating effect of the present invention causes polar molecules to generate molecular-level vibrations, realizes local ultra-fast heating, promotes the uniform nucleation of lanthanum aluminate nanocrystals, and avoids particle agglomeration caused by traditional sintering. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The specification drawings constituting a part of this application are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings: Figure 1 is the flow chart of the preparation method of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0014] The following will describe the technical solutions in the embodiments of the present invention clearly and completely in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Without conflict, the embodiments in the present application and the features in the embodiments can be combined with each other. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0015] Please refer to Figure 1 , and the present invention details the above technical solutions through the following embodiments: Embodiment 1, a preparation method of a lithium-ion battery material. The specific steps of the preparation method in this embodiment are as follows: First, a high-nickel ternary material and ethanol are ball-milled and mixed at a mass ratio of 1:3 for 4 hours, and after drying, a uniformly dispersed matrix powder is obtained; then the matrix powder, lanthanum nitrate, and aluminum nitrate are mixed at a molar ratio of 1:1, citric acid is added (the molar ratio of the chelating agent to metal ions is 2:1), and irradiated in a microwave reactor at a frequency of 2.45 GHz and a power of 800 W for 5 minutes, and heated to 300 °C to form a perovskite-type oxide (lanthanum aluminate) interfacial buffer layer, that is, the coated powder; the coated powder is mixed with zirconium nitrate (the Zr content is 0.5% of the matrix mass), and Zr element gradient diffusion is realized under microwave irradiation. The power of microwave irradiation is 500 - 1000 W, and the irradiation time is 3 - 10 minutes to obtain the Zr-doped material; then, by using atomic layer deposition technology on the Zr-doped material, lithium phosphate is used as a precursor, and lithium phosphate is purchased from Shanghai Zhongli Industry Co., Ltd., and 50 cycles are carried out at 150 °C to form a fast ion conductor layer with a thickness of 5 nm. The material of the fast ion conductor layer is lithium phosphate, and the coated material can be obtained.

[0016] The atomic layer deposition technology can be: loading the material into the ALD cavity, setting the substrate temperature at 150 °C, and the carrier gas flow rate at 200 sccm; the lithium source pulse is 0.1 s / purge for 15 s, the phosphorus source pulse is 0.2 s / purge for 20 s, and a total of 50 cycles (total thickness 5 nm); annealing in argon at 300 °C for 1 hour to eliminate the internal stress in the film.

[0017] Inner layer (lanthanum aluminate buffer layer): Oxygen vacancies in the perovskite structure can anchor lattice oxygen ( ), inhibit the oxygen evolution reaction (OER) at high voltage (>4.3 V), and reduce gas generation caused by electrolyte decomposition (such as , ); Intermediate transition layer (Zr doping): The high ionic potential (~40 eV) of The key is to reduce the migration barrier of transition metal ions (such as ), inhibit the transformation of the layered structure into the rock salt phase; Outer layer (fast ion conductor): The tetrahedral structure in amorphous lithium phosphate provides a three-dimensional lithium ion transport channel, enhancing the interface diffusion coefficient; The dielectric heating effect of microwaves causes polar molecules (such as nitrate precursors) to generate molecular-level vibrations, achieving local ultra-fast heating (>1000 °C / s), promoting the uniform nucleation of lanthanum aluminate nanocrystals (particle size <20 nm), and avoiding particle agglomeration caused by traditional sintering; Therefore, the microwave synthesis time is shortened to 5 minutes (6 - 12 hours are required for the traditional solid-phase method), the comprehensive energy consumption is reduced by 60%; the interface stability is improved, and the gradient coating layer reduces the electrolyte side reaction active sites by more than 70%.

[0018] Then, the coating material is placed in a tube furnace and annealed at 600 °C for 2 hours with a heating rate of 1000 °C / min in an argon / hydrogen (95:5) atmosphere to induce the formation of surface oxygen vacancies to obtain the sintered material; finally, the material is mixed with molten salt, sintered at 850 °C for 6 hours, and the molten salt is removed by washing with water after cooling to obtain the lithium ion battery material.

[0019] Oxygen vacancy regulation mechanism: High-temperature thermal shock (>10000 °C / min) induces the instantaneous collapse of the surface lattice, generating controllable oxygen vacancies ( in a reducing atmosphere ( ), and the reaction formula is: , Oxygen vacancies act as electron traps, increasing the electronic conductivity of the material from to , while alleviating the lattice stress during lithium deintercalation / insertion.

[0020] Molten salt medium-induced single crystallization: The molten salt ( ) forms a liquid phase at 850 °C, dissolves the high-energy grain boundaries on the particle surface, and is reconstructed into single-crystalline spherical particles (particle size D50 = 4 μm) through the Ostwald ripening mechanism, increasing the tap density from 3.2 g / cm³ to 3.8 g / cm³; Core-shell - porous structure design: The porous lithium manganate shell layer (porosity 30%) acts as a "mechanical buffer pad", and finite element simulation shows that it can reduce the cyclic stress concentration coefficient from 2.5 to 0.8; Therefore, the outer layer of lithium phosphate coating inhibits the penetration of the electrolyte, while the core-shell porous structure prevents crack propagation, and the two together extend the battery cycle life from 1000 times to 2000 times.

[0021] A lithium-ion battery material, which is prepared by a preparation method of lithium-ion battery materials.

[0022] Example 2. The difference between this example and Example 1 is only that: in this example, the Zr content is 0.2% of the matrix mass, and other conditions are the same.

[0023] Example 3. The difference between this example and Example 1 is only that: in this example, the Zr content is 0.8% of the matrix mass, and other conditions are the same.

[0024] Example 4. The difference between this example and Example 1 is only that: in this example, the Zr content is 1% of the matrix mass, and other conditions are the same.

[0025] Comparative Example 1. The difference between this comparative example and Example 1 is only that: in this comparative example, the coating treatment only uses the high-temperature solid-phase method to coat lanthanum aluminate, and other conditions are the same.

[0026] Comparative Example 2. The difference between this comparative example and Example 1 is only that: in this comparative example, the Zr-doped transition layer is omitted, and lithium phosphate is directly coated by atomic layer deposition technology, and other conditions are the same.

[0027] Comparative Example 3. The difference between this comparative example and Example 1 is only that: in this comparative example, the traditional spheroidization process is used, and other conditions are the same.

[0028] According to Examples 1-4 and Comparative Examples 1-3 respectively, battery samples are prepared. The preparation steps are as follows: Prepare the positive electrode sheet: A mixture of a lithium-ion battery material sample, acetylene black, and polyvinylidene fluoride mixed evenly in a mass ratio of 82:10:8 is dropped with N-methylpyrrolidone, infiltrated and ground evenly, and then evenly coated on aluminum foil by a coater. Set the thickness to 0.8 mm, and vacuum dry at 80 °C for 12 h in a vacuum drying oven. The dried electrode sheet is cut into a 16-mm-diameter round piece with a tablet press; Prepare the button battery: The battery is encapsulated in a glove box filled with inert gas. Place the CR2032-type positive electrode round shell on a horizontal encapsulation table. Then use tweezers to pick up the electrode sheet and place it in the center of the positive electrode round shell. Then use a rubber head dropper to evenly drop the NaClO4 electrolyte on the positive electrode sheet for sufficient wetting. Cover the positive electrode sheet with a 16-mm-diameter 2400 Celgard separator, and use a rubber head dropper to evenly drop the electrolyte on the separator again for sufficient wetting; then pick up the sodium negative electrode and place it at the center of the separator, and then add gaskets and shrapnel in sequence and then cover the negative electrode shell. Place the assembled button battery in a sealing machine and apply 800 pa to complete the encapsulation; finally, take out the pressed battery from the glove box and place it in a battery test box at 25 °C and let it stand overnight.

[0029] In this application, a CT2001A blue battery test system was used to conduct cyclic performance tests on the assembled button batteries in a constant current charge-discharge mode; the test voltage was in the range of 2.0 - 4.8V, and the ambient temperature was controlled to be stable at 25°C. The initial discharge specific capacity at a 0.1C rate and the capacity retention rate after 200 cycles of charge and discharge were tested; the specific data are as follows: Table 1:

[0030] According to the data of Examples 1 - 4 and Comparative Example 2 in Table 1, it can be seen that the battery performance shows a positive correlation trend with the Zr content. However, when the addition amount is too high, the battery performance will also decline. The specific capacity of Comparative Example 2 without the Zr-doped transition layer is significantly weakened. But the final specific capacity will also decrease with the excessive addition of Zr content, and its cycle retention rate will also be weakened after excessive addition. Considering that excessive addition is not convenient for processing, agglomeration and uneven coating are likely to occur, and considering its cost, excessive Zr content is not applied. Only when the Zr content is 0.5% of the matrix mass, the discharge specific capacity and cycle retention rate performance of the battery are the best; According to the data of Example 1, Comparative Example 1, and Comparative Example 2, it can be seen that the coating treatment with only lanthanum aluminate by the high-temperature solid-phase method has a great impact on the specific capacity, and the decline in its specific capacity performance is relatively large. Therefore, in Example 1, the gradient coating layer of lanthanum aluminate buffer layer + Zr-doped transition layer + lithium phosphate fast ion conductor reduces the interfacial impedance from 65Ω to 28Ω, a decrease of 57%, and the gas generation amount of electrolyte decomposition is reduced by 70%; and the lanthanum aluminate buffer layer anchors the lattice oxygen, raising the initial voltage of oxygen evolution from 4.35V to 4.5V, which can significantly improve the battery performance; According to the data of Example 1 and Comparative Example 2, it can be seen that the battery performance will also decrease when the Zr-doped transition layer is omitted. It can be known that the Zr-doped transition layer solves the interfacial stress and ion transport bottleneck of the coating layer through gradient CTE matching and element diffusion regulation, and is the core technology to improve the comprehensive performance. Omitting the Zr layer will lead to a decrease in cycle life, an increase in the risk of thermal runaway, and a reduction in the industrial qualified product rate; According to the data of Example 1 and Comparative Example 3, it can be seen that the traditional spheroidization process has little effect on the discharge specific capacity and cycle retention rate of the battery. However, it has a greater impact on the compaction density of the battery. Therefore, the molten salt ( ) forms a liquid phase at 850°C, dissolves the high-energy grain boundaries on the particle surface, and is reconstructed into single-crystal spherical particles (particle size D50 = 4μm) through the Ostwald ripening mechanism, resulting in an increase in compaction density.

[0031] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above-described exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be embraced within the present invention.

Claims

1. A preparation method of a lithium-ion battery material, characterized in that: The specific steps of the preparation method are as follows: Step 1: Ball-mill and mix the precursor and ethanol in a mass ratio of 1:3 for 4 hours, and obtain a uniformly dispersed matrix powder after drying; Step 2: Perform a coating treatment on the matrix powder to obtain a coated material; Step 3: Place the coated material in a tube furnace and anneal it for 2 hours in an argon / hydrogen atmosphere to induce the formation of surface oxygen vacancies to obtain a sintered material; Step 4: Mix the material with molten salt, sinter at 850 °C for 6 hours, wash with water after cooling to remove the molten salt, and obtain a lithium-ion battery material.

2. The preparation method of the lithium ion battery material according to claim 1, characterized in that: The specific steps of the coating treatment of the coated material in Step 2 are as follows: S1. Mix the matrix powder with lanthanum nitrate and aluminum nitrate according to a molar ratio of 1:1, add citric acid, irradiate in a microwave reactor at a frequency of 2.45 GHz and a power of 800 W for 5 minutes, and heat up to 300 °C to form the coated powder; S2. Mix the coated powder with a doping element, and achieve gradient diffusion of Zr element under microwave irradiation to obtain a Zr-doped material; S3. Then, by using atomic layer deposition technology on the Zr-doped material, with lithium phosphate as the precursor, perform 50 cycles at 150 °C to form a fast ion conductor layer, and the coated material can be obtained.

3. The preparation method of the lithium ion battery material according to claim 2, characterized in that: The material of the fast ion conductor layer is any one of lithium phosphate, lithium aluminate, or lithium silicate, and the thickness is 3-10 nm.

4. The preparation method of the lithium ion battery material according to claim 2, characterized in that: The power of the microwave irradiation is 500-1000 W, and the irradiation time is 3-10 minutes.

5. The preparation method of the lithium ion battery material according to claim 2, wherein: The doping element is any one of Zr, Ti, or Nb, and the doping amount is 0.2%-1% of the mass of the matrix powder.

6. The preparation method of the lithium-ion battery material according to claim 1, characterized in that: The molten salt medium is , or any one of them, and the sintering temperature is 800 - 900 °C.

7. The preparation method of the lithium ion battery material according to claim 1, characterized in that: The precursor is any one of high-nickel ternary materials or lithium-rich manganese-based materials.

8. A lithium-ion battery material, characterized in that: It is prepared by using the preparation method of the lithium-ion battery material described in any one of claims 1-7.

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