Preparation method of all-solid-state positive electrode material and all-solid-state positive electrode material

Abstract

The invention relates to the technical field of solid-state batteries, in particular to a preparation method of an all-solid-state positive electrode material and the all-solid-state positive electrode material. The preparation method of the all-solid-state positive electrode material comprises the following steps: refining original particles; the refined product is subjected to fluidization, so that the refined product reaches a fluidization or quasi-fluidization state; introducing a precursor to form a coating layer on the surface of the fluidized product; sintering the coated product, and then naturally cooling; and mixing and screening the sintered product.

Description

Technical Field

[0001] This invention relates to the field of solid-state battery technology, and in particular to a method for preparing an all-solid-state cathode material and the all-solid-state cathode material itself. Background Technology

[0002] Solid-state batteries, with their advantages of high specific energy, high operating voltage, fast charge and discharge speed, long cycle life, and safety without pollution, are gradually replacing traditional liquid lithium batteries. In recent years, research on high-capacity lithium-rich cathode materials has become a focus of solid-state battery development. However, extensive market experience has shown that the interfacial instability of lithium-rich cathodes generally hinders improvements in the cycle performance and safety of solid-state batteries. For example, ternary lithium-rich materials are an important type of solid-state battery cathode material, with advantages such as high specific energy and high energy density, but also many drawbacks: poor cycle stability, continuous voltage decay during cycling, low capacity retention; insufficient rate performance, significant capacity decay at high currents; and unstable interfacial states, leading to gas generation and numerous interfacial side reactions. Therefore, there is an urgent need to develop a novel lithium-rich cathode material that can simultaneously possess high capacity and high safety performance. Summary of the Invention

[0003] This invention provides a method for preparing an all-solid-state cathode material, comprising the following steps: Refine the original lithium-containing particles; The refined product is fluidized to achieve a fluidized or quasi-fluidized state. The precursor is introduced to form a coating layer on the surface of the fluidized product; The product is sintered and solidified, then allowed to cool naturally. The sintered product is mixed and sieved to obtain the cathode material.

[0004] Furthermore, the molecular formula of the original particle is LiNi. x Co y Mn z O2.

[0005] Furthermore, the specific surface area of ​​the original particles is greater than or equal to 0.5 m². 2 / g, loose bulk density less than or equal to 2.5g / cm³ 3 The capacity is greater than 220mAh / g.

[0006] Furthermore, during fluidization, the refined product is fed into a fluidized bed coating device, and then an inert gas is directionally and continuously fed into the fluidized bed coating device to make the micron-sized particles reach a fluidized or quasi-fluidized state.

[0007] Furthermore, the thickness of the coating layer is 10-100 nm.

[0008] Furthermore, the precursor is a polymeric carbon source, preferably an alkyne-based carbon source, an olefin-based carbon source, a resin-based carbon source, or a solid-liquid phase pitch-based carbon source.

[0009] Furthermore, the precursor is a transition metal oxide.

[0010] Furthermore, during sintering, the temperature profile is such that the temperature rises at a rate of 5-10°C per minute to the maximum temperature of 500-600°C.

[0011] Furthermore, during natural cooling, inert gas is introduced continuously for 24-36 hours.

[0012] Furthermore, the present invention also includes an all-solid-state cathode material, which is prepared by the aforementioned method for preparing all-solid-state cathode materials.

[0013] The method for preparing all-solid-state cathode materials provided by this invention involves refining the original particles, fluidizing them, and then introducing a precursor to form a coating layer. This allows for more precise and uniform coating of the particles by the precursor, avoiding problems such as poor contact between particles and substrates, localized shading during coating, and particle wear caused by accumulation and collisions in conventional techniques. It also avoids localized over- or under-coating in subsequent steps, preventing excessive agglomeration and granulation. Using a precursor amount far lower than the industry average, the precursor is uniformly and thinly coated on the material surface, effectively coating the material while preserving the inherent capacity of the lithium-rich manganese base, and reducing costs. The precursor used in this invention is a high-molecular carbon source or transition metal oxide, which plays a role in surface stabilization after the coating layer is formed, and also enhances the rate performance. This results in a uniformly deposited and thinly structured coating layer on the particle surface, leading to excellent cycle performance and high-temperature performance of the prepared cathode material. Attached Figure Description

[0014] Figure 1 This is a schematic diagram illustrating the preparation method of the all-solid-state cathode material provided by the present invention. Detailed Implementation

[0015] To further illustrate the technical means and effects adopted by the present invention in order to achieve the intended purpose, the present invention will be described in detail below with reference to the accompanying drawings and preferred embodiments.

[0016] It should be noted that the terms "first," "second," "third," "fourth," etc., in the specification and claims of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence.

[0017] Please see Figure 1The method for preparing all-solid-state cathode materials provided by this invention is used to prepare lithium-rich manganese-based cathode materials, and includes the following steps: Step S1: Refine the original lithium-containing particles.

[0018] Specifically, the initial particles in step S1 are preferably ternary cathode materials. When selecting a ternary cathode material, the main parameters considered include specific surface area, loose packing density, and specific capacity utilization. Specific surface area is related to the severity of interfacial side reactions. When the specific surface area is small, the severity of interfacial side reactions decreases, and the material stability is improved. Loose packing density reflects the material's packing efficiency and affects its volumetric energy density. Specific capacity utilization is the ratio of reversible specific capacity to theoretical specific capacity, determined by the material's chemical composition. Higher specific capacity utilization results in higher utilization of active lithium. Therefore, in one embodiment of the present invention, the preferred molecular formula is LiNi. x Co y Mn z O2-rich lithium-manganese-based cathode particles are used as the initial particles. Lithium-rich manganese-based materials have numerous advantages, such as: ultra-high energy density, with a specific capacity of 250–300 mAh / g, more than 1.5 times that of other common commercial cathode materials, and a theoretical energy density exceeding 1000 Wh / kg; significant cost advantage: primarily composed of inexpensive manganese, not dependent on cobalt and nickel, with a theoretical cost close to that of lithium iron phosphate; and compatibility with solid-state battery systems: solid electrolytes can suppress interfacial side reactions under high voltage, solving the stability problem in liquid systems. In other preferred embodiments of the invention, a specific surface area greater than or equal to 0.5 m² is preferred. 2 / g, loose density less than or equal to 2.5g / cm³ 3 The raw particles are ternary cathode materials with a specific capacity greater than 220 mAh / g. In step S1 of this invention, the raw particles are refined into micron-sized particles using a dedicated refining device to meet the process and performance requirements of subsequent steps.

[0019] Step S2: Fluidize the product obtained in step S1 to achieve a fluidized or quasi-fluidized state.

[0020] Specifically, fluidization in step S2 is achieved through a fluidized bed coating device. More specifically, micron-sized particles are first introduced into the fluidized bed coating device, and then an inert gas, such as nitrogen or helium, is introduced into the fluidized bed coating device in a directional and constant flow to achieve a fluidized or quasi-fluidized state for the micron-sized particles. The purpose of step S2 is to fully fluidize and disperse the micron-sized particles to meet the process requirements of subsequent steps. In this invention, step S2 fluidizes the micron-sized particles through a fluidized bed coating device, enabling the micron-sized particles to be completely coated by the precursor in subsequent steps. This avoids poor contact, local obstruction, and particle wear caused by accumulation and collision in conventional techniques. On the one hand, it avoids local over-coating or under-coating in subsequent steps, preventing excessive agglomeration and granulation. On the other hand, it allows for the rapid recovery and processing of unattached precursors, avoiding static retention and waste of precursors on micron-sized particles, resulting in more precise and uniform coating of micron-sized particles by the precursor.

[0021] Step S3: Introduce the precursor to form a coating layer on the surface of the product obtained in step S2.

[0022] Specifically, the introduction of the precursor in step S3 is carried out using equipment such as a coating reactor and a rotary kiln. More specifically, the precursor is continuously introduced into the micron-sized particles within the aforementioned equipment, causing the precursor to form a layered deposition or atomic layer, which is then deposited onto the material surface. In a preferred embodiment of the present invention, the thickness of the coating layer is 10-100 nm, varying slightly depending on the size of the original material to be coated, process fluctuations, performance requirements, and the choice of equipment. The coating layer formed in step S3 can be a layered deposition obtained from outside to inside or an atomic layer deposition obtained from inside to outside, wherein the layered deposition has a larger thickness and the atomic layer deposition has a smaller thickness. After the fluidization treatment in step S2, the coating amount of the coating layer formed in step S3 is easily and precisely controlled, resulting in a coating process yield close to 100%, extremely low loss costs during the process, and almost no agglomeration or granulation after coating. The resulting coating layer allows for a uniform and thin coverage of the precursor on the material surface using a significantly lower amount than the industry average. This effectively coats the material while preserving the inherent capacity of the lithium-rich manganese base, and the reduced precursor usage further lowers costs. The choice of precursor can be based on performance requirements. In one embodiment, the precursor is a polymeric carbon source, preferably an alkyne-based, olefin-based, resin-based, or solid-liquid phase pitch-based carbon source. Alkyne and olefin-based carbon sources are layered, while resin and solid-liquid phase pitch-based carbon sources are amorphous. Choosing a polymeric carbon source as the precursor results in better kinetic performance. In another embodiment, the precursor is a transition metal oxide. Choosing a transition metal oxide as the precursor provides high-temperature performance benefits, improves the high-temperature stability of the cathode material, and further reduces interfacial side reactions. Both polymeric carbon sources and transition metal oxides can stabilize the surface after the coating layer is formed on the coated particles and also enhance their rate performance. Step S3 of this invention involves coating the surface of lithium-rich manganese-based cathode particles with transition metal oxides or polymeric carbon sources, resulting in a uniformly deposited and thinly structured coating layer. This allows the prepared cathode material to exhibit excellent cycle performance and high-temperature performance, and meets the safety requirements of solid-state batteries, including high-temperature discharge capacity testing, hot box testing, and nail penetration testing. Furthermore, mass spectrometry analysis can be used to monitor the content of coating elements during the coating process.

[0023] Step S4: Sinter and solidify the product obtained in step S3, and then allow it to cool naturally.

[0024] Specifically, during sintering, the temperature profile involves heating at a rate of 5-10°C per minute to a maximum temperature of 500-600°C. During natural cooling, an inert gas is introduced for 24-36 hours. In a preferred embodiment of the invention, the heating rate is 5°C per minute, the maximum achievable temperature is 580°C, and the natural cooling duration is 24 hours.

[0025] Step S5: Mix and sieve the product obtained in step S4 to obtain the cathode material.

[0026] Specifically, the sieving in step S5 includes classifying the product obtained in step S4 using a sieve. The undersize material obtained from sieving can be used directly, while the oversize material needs to be depolymerized before use.

[0027] Furthermore, the present invention also includes an all-solid-state cathode material, which is prepared by the aforementioned method for preparing all-solid-state cathode materials.

[0028] In summary, the method for preparing all-solid-state cathode materials provided by this invention, through steps such as refining the original particles, fluidizing them, and then introducing a precursor to form a coating layer, allows for more precise and uniform coating of the particles by the precursor. This avoids the problems of poor contact between particles and the precursor caused by accumulation and collision in conventional techniques, local shading during the coating process, and collision wear between particles. It also avoids local over- or under-coating in subsequent steps, and prevents excessive agglomeration and granulation. While using a precursor amount far lower than the industry average, it achieves a uniform and thin coating of the precursor on the material surface, effectively coating the material while preserving the inherent capacity of the lithium-rich manganese base, and reducing costs. The precursor used in this invention is a high-molecular carbon source or transition metal oxide, which plays a role in surface stabilization after the coating layer is formed on the particles, and also enhances its rate performance. This results in a uniformly deposited and thinly structured coating layer on the particle surface, leading to excellent cycle performance and high-temperature performance of the prepared cathode material.

[0029] The above are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for preparing an all-solid-state cathode material, characterized in that: Includes the following steps: Refine and refine the original lithium-containing particles; Fluidization: Fluidizing the refined product to achieve a fluidized or quasi-fluidized state; The precursor is coated and introduced to form a coating layer on the surface of the fluidized product; The product is sintered, solidified and coated, and then cooled naturally. The sintered product is mixed and sieved to obtain the cathode material.

2. The method for preparing the all-solid-state cathode material as described in claim 1, characterized in that: The molecular formula of the original particles is LiNi. x Co y Mn z O2.

3. The method for preparing the all-solid-state cathode material as described in claim 1, characterized in that: The specific surface area of ​​the original particles is greater than or equal to 0.5 m². 2 / g, loose bulk density less than or equal to 2.5g / cm³ 3 The capacity is greater than 220mAh / g.

4. The method for preparing the all-solid-state cathode material as described in claim 1, characterized in that: During fluidization, the refined product is fed into a fluidized bed coating device, and then an inert gas is directionally and continuously fed into the fluidized bed coating device to make the micron-sized particles reach a fluidized or quasi-fluidized state.

5. The method for preparing the all-solid-state cathode material as described in claim 1, characterized in that: The thickness of the coating layer is 10-100 nm.

6. The method for preparing the all-solid-state cathode material as described in claim 1, characterized in that: The precursor is a polymeric carbon source, preferably an alkyne-based carbon source, an olefin-based carbon source, a resin-based carbon source, or a solid-liquid phase pitch-based carbon source.

7. The method for preparing the all-solid-state cathode material as described in claim 1, characterized in that: The precursor is a transition metal oxide.

8. The method for preparing the all-solid-state cathode material as described in claim 1, characterized in that: During sintering, the temperature curve is such that the temperature is increased at a rate of 5-10℃ per minute to the maximum temperature of 500-600℃.

9. The method for preparing the all-solid-state cathode material as described in claim 8, characterized in that: During natural cooling, inert gas is introduced continuously for 24-36 hours.

10. An all-solid-state cathode material, characterized in that: It is prepared by the method for preparing all-solid-state cathode material according to any one of claims 1 to 9.

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