Composite positive electrode material and preparation method thereof, lithium ion battery and electric equipment
By combining bulk doping and surface coating, the problems of lattice expansion, electrolyte decomposition and thermal stability of Ni90 material under high nickel content were solved through the preparation method of composite cathode material. This achieved a balance between high capacity, stability and rate performance, and improved the overall performance of lithium-ion batteries.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- GEM WUXI ENERGY MATERIAL CO LTD
- Filing Date
- 2025-12-17
- Publication Date
- 2026-05-01
AI Technical Summary
Existing Ni90 single-crystal and polycrystalline cathode materials suffer from problems such as lattice volume expansion, electrolyte decomposition, poor thermal stability, low lithium-ion conduction efficiency, and poor cycle stability under high nickel content, making it difficult to simultaneously meet the requirements of high capacity and high stability.
By employing a composite treatment of bulk dopants and surface coating agents, and through sequential sintering and coating processes, a composite cathode material is formed. Combining the advantages of single-crystal and polycrystalline structures, the dopants enhance lattice stability, while the coating agents form physical barriers and lithium-ion transport channels.
It achieves a balance between high capacity, stability and excellent rate performance, improves the cycle life and thermal safety of the material, and solves the performance bottleneck that is difficult to achieve with a single doping or coating method.
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Abstract
Description
A composite cathode material and its preparation method, a lithium-ion battery, and an electrical device thereof. Technical Field
[0001] This invention relates to the field of lithium-ion battery technology, specifically to a composite cathode material and its preparation method, a lithium-ion battery, and electrical equipment. Background Technology
[0002] Ternary lithium-ion batteries, with their excellent high energy density characteristics, have become the mainstream technology for power batteries in new energy vehicles and are leading the future direction of technological development. In the ternary cathode material system, high-nickel, low-cobalt ternary materials have become one of the core directions of current cathode material research and development due to their higher theoretical specific capacity. Among them, ultra-high nickel NCM cathode materials with a Ni content of not less than 90% (hereinafter referred to as Ni90 materials) have shown significant performance potential, with a theoretical specific capacity exceeding 220 mAh / g. Power batteries built based on this material are expected to have an energy density exceeding 800 Wh / kg, and are therefore widely recognized as a key cathode material for next-generation high-energy-density power batteries. However, Ni90 materials currently face insurmountable technical bottlenecks in both single-crystal and polycrystalline structural forms. For Ni90 single-crystal materials, the main problems are as follows: First, when the Ni content is increased to 90%, the H2-H3 phase transition effect during charging and discharging is significantly enhanced, leading to excessive expansion of the lattice volume and inducing microcracks internally; second, the high oxidation state of Ni on the particle surface... 4+ The ions have extremely high catalytic activity, which can easily promote the decomposition reaction of the electrolyte to generate HF, thereby accelerating the battery capacity decay. Furthermore, the high nickel content leads to a significant reduction in the stability of the lattice oxygen, and the thermal decomposition temperature of the material drops to below 210°C, increasing the risk of thermal runaway of the power battery. In addition, the size of single crystal particles is usually large, which limits the conduction efficiency of lithium ions and makes it difficult to meet the requirements of high-rate fast charging performance.
[0003] For Ni90 polycrystalline materials, the main problems lie in two aspects: cycle stability and batch consistency. During cycling, due to the accumulation of volume changes, the grain boundaries between primary particles are prone to peeling, leading to the breakage of secondary particle structures, poor material structural stability, and limited cycle life. Simultaneously, its agglomeration structure easily causes uneven particle morphology and excessively wide particle size distribution, making it difficult to guarantee batch-to-batch consistency in industrial production. In existing technologies, doping modification, surface coating, or structural optimization methods implemented individually for Ni90 single-crystal or polycrystalline materials are insufficient to simultaneously meet the performance requirements of high capacity and high stability. For example, while spinel phase coating of Ni90 single-crystal materials helps improve thermal safety, it increases lithium-ion migration resistance and reduces ion conduction rate. Surface modification with a lithium-rich layer can improve cycle performance but causes a decrease in initial coulombic efficiency. While optimizing primary particle size by controlling the sintering process can improve cycle stability for Ni90 polycrystalline materials, the extended lithium-ion diffusion path leads to a significant deterioration in the material's electrochemical performance under high-rate conditions.
[0004] Therefore, developing an ultra-high nickel composite cathode material that combines the advantages of polycrystalline and single-crystal structures and achieves complementary performance through the construction of a composite system has become a key research direction for breaking through current technological bottlenecks. Summary of the Invention
[0005] This invention provides a composite cathode material and its preparation method, a lithium-ion battery, and an electrical device to solve the above-mentioned problems.
[0006] In a first aspect, the present invention provides a method for preparing a composite cathode material, comprising the following steps: S1, mixing a bulk dopant, a lithium source, and a ternary precursor to obtain a mixture I; taking a portion of the mixture I for a first sintering to obtain sintered material I-1; and taking another portion of the mixture I for a second sintering to obtain sintered material I-2; the temperature of the first sintering is 815-830℃ and the time is 12-14h; the temperature of the second sintering is 760-770℃ and the time is 8-10h; S2, mixing a first coating agent and a second coating agent with sintered material I-1 and then performing a coating treatment to obtain sintered material II-1; S3, mixing the first coating agent and the second coating agent with sintered material I-2 and then performing a coating treatment to obtain sintered material II-2; S4, mixing sintered material II-1 and sintered material II-2 to obtain the composite cathode material.
[0007] In one optional embodiment, in step S1, the mass ratio of bulk dopant, lithium source, and ternary precursor is (0.6-0.8):(65-75):(195-205); optionally, in step S1, the mass ratio of bulk dopant, lithium source, and ternary precursor is 0.6:70:200; in one optional embodiment, the amount of mixture I used for the first sintering accounts for 45%-55% of the total mass of mixture I; optionally, the amount of mixture I used for the first sintering accounts for 50% of the total mass of mixture I.
[0008] In one optional embodiment, in step S2, the mass ratio of the first coating agent, the second coating agent, and sintered material I-1 is (0.8-1.3):(0.5-0.8):(95-105); optionally, in step S2, the mass ratio of the first coating agent, the second coating agent, and sintered material I-1 is 0.8:0.6:100; in one optional embodiment, in step S3, the mass ratio of the first coating agent, the second coating agent, and sintered material I-2 is (0.8-1.3):(0.5-0.8):(95-105); optionally, in step S3, the mass ratio of the first coating agent, the second coating agent, and sintered material I-2 is 0.8:0.6:100; in one optional embodiment, in step S3, the mass ratio of sintered material II-1 to sintered material II-2 is 7:3-3:7.
[0009] Optionally, in S4, the mass ratio of sintering material II-1 to sintering material II-2 is 6:4.
[0010] In one optional embodiment, in step S1, the temperature of the first sintering is 820°C and the time is 12 hours; in another optional embodiment, the atmosphere of the first sintering includes a pure oxygen atmosphere.
[0011] In one optional embodiment, the second sintering temperature is 765°C and the time is 10 hours; in another optional embodiment, the atmosphere of the second sintering includes a pure oxygen atmosphere.
[0012] In one optional embodiment, the ternary precursor is a nickel-cobalt-manganese ternary precursor; optionally, the general formula of the nickel-cobalt-manganese ternary precursor includes LiNi. x Co y Mn z (OH)₂, where 0.9 ≤ x < 1, x + y + z = 1, preferably Ni 0.90 Co 0.06 Mn 0.04 (OH)2.
[0013] In one optional embodiment, in S1, the atmosphere of the first sintering and the second sintering is independently pure oxygen; in another optional embodiment, in S2 and S3, the temperature of the coating treatment is independently 620-650°C, the holding time is independently 4-7h, and the atmosphere of the coating treatment is independently air.
[0014] Optionally, in S2 and S3, the coating treatment temperature is independently 640°C and the coating treatment time is independently 5 hours.
[0015] In one optional embodiment, the coating process further includes crushing and sieving; it should be noted that the sieving is mainly to remove foreign impurities, and the particle size D50 after sieving is generally 3-4 μm.
[0016] In one optional embodiment, the bulk dopant comprises a Group IIIB metal oxide; optionally, the Group IIIB metal oxide comprises at least one of scandium oxide, zirconium oxide, and yttrium oxide; in one optional embodiment, the lithium source comprises at least one of lithium hydroxide and lithium carbonate; in one optional embodiment, the first coating agent comprises at least one of Group IIIA metal oxide and Group IVB metal oxide; optionally, the Group IIIA metal oxide comprises aluminum oxide; optionally, the Group IVB metal oxide comprises at least one of zirconium oxide and titanium oxide; in one optional embodiment, the second coating agent comprises an inorganic lithium acid salt; optionally, the inorganic lithium acid salt comprises at least one of lithium aluminate and lithium phosphate.
[0017] The second invention provides a composite cathode material prepared by the above-described preparation method.
[0018] Thirdly, the present invention provides a lithium-ion battery comprising the above-mentioned composite cathode material.
[0019] Those skilled in the art will understand that the lithium-ion battery provided by this invention includes structural components such as an electrolyte, a positive electrode, a negative electrode, a separator, and a casing. During the charging and discharging process, lithium ions repeatedly insert and extract between the positive and negative electrode. The electrolyte acts as a conductor between the positive and negative electrode. The composite separator is disposed between the positive and negative electrode, primarily to prevent short circuits between the positive and negative electrodes, while simultaneously allowing lithium ions to pass through.
[0020] As an example, the positive electrode sheet includes a positive current collector and a positive active layer. The positive current collector has two surfaces opposite each other in its own thickness direction, and the positive active layer is disposed on either or both of the opposite surfaces of the positive current collector. The materials, composition, and manufacturing methods of the positive electrode sheet used in the lithium-ion battery of the present invention may include any techniques disclosed in the prior art.
[0021] As an example, the negative electrode sheet includes a negative electrode current collector and a negative electrode active layer. The negative electrode current collector has two opposing surfaces in its own thickness direction, and the negative electrode active layer is disposed on either or both of the opposing surfaces of the negative electrode current collector. The materials, composition, and manufacturing methods of the negative electrode sheet used in the lithium-ion battery of the present invention may include any techniques disclosed in the prior art.
[0022] The material and shape of the separator used in the lithium-ion battery of the present invention are not particularly limited, and may include any technology disclosed in the prior art.
[0023] The electrolyte used in the lithium-ion battery of the present invention may also include any technology disclosed in the prior art.
[0024] This invention does not specifically limit the preparation method of lithium-ion batteries; lithium-ion batteries can be prepared using conventional preparation methods in the art. For example, positive electrode sheets, separators, and negative electrode sheets are stacked sequentially, with the separator located between the positive and negative electrode sheets. A cell is obtained through stacking or winding processes, and then the lithium-ion battery of this invention is obtained through baking, electrolyte injection, formation, and packaging.
[0025] Fourthly, the present invention provides an electrical device comprising the aforementioned lithium-ion battery.
[0026] It is understood that in the electrical equipment provided by the present invention, the lithium-ion battery can be used as a power source for the electrical equipment, or as an energy storage unit for the electrical equipment. The electrical equipment may be, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.
[0027] The technical solution of the present invention has the following advantages: 1. The present invention provides a method for preparing a composite cathode material, comprising the following steps: mixing a bulk dopant, a lithium source, and a ternary precursor to obtain a mixture I; taking a portion of the mixture I and performing a first sintering at 815-830℃ for 12-14 hours to obtain sintered material I-1; performing a second sintering at 760-770℃ for 8-10 hours to obtain sintered material I-2; mixing a first coating agent and a second coating agent with sintered material I-1 and performing a coating treatment to obtain sintered material II-1; mixing the first coating agent and the second coating agent with sintered material I-2 and performing a coating treatment to obtain sintered material II-2; mixing sintered material II-1 and sintered material II-2 to obtain the composite cathode material. The preparation method provided by this invention first adds a bulk dopant to dope a ternary precursor core layer, and then adds a first coating agent and a second coating agent to synthesize a surface functional layer on the surface of the sintered material. The two work synergistically to make the composite cathode material have both high capacity and stability (better rate performance and cycle performance). In addition, mixing the sintered material I-1 formed by the first sintering, i.e., the single crystal material, with the sintered material I-2 formed by the second sintering, i.e., the polycrystalline material, can overcome the problems that traditional single doping, coating, or structural design cannot balance high capacity and stability. For example, it balances the problems that single polycrystalline cathode materials have high first-cycle coulombic efficiency and good rate performance but poor stability, and single crystal materials have good cycle performance but low initial discharge capacity and low rate performance.
[0028] 2. The present invention provides a method for preparing a composite cathode material, wherein the bulk dopant includes at least one of scandium oxide, zirconium oxide, and yttrium oxide. The bond energy between the metal element and oxygen ions in the bulk dopant is higher than that of Ni-O, which can enhance the stability of the crystal framework, suppress lattice distortion during lithium-ion insertion / extraction, and reduce cation mixing. The first coating agent includes at least one of alumina, zirconium oxide, and titanium oxide, which can form a physical barrier on the surface of the cathode material, blocking the direct contact between the electrolyte and the core, reducing HF corrosion and side reactions of residual Li, and improving the thermal stability of the material. The second coating agent includes at least one of lithium aluminate and lithium phosphate. Lithium aluminate and lithium phosphate have high lithium-ion conductivity, which can construct a continuous lithium-ion transport channel, solve the problem of traditional coating layers hindering ion transport, and improve rate performance. Detailed Implementation
[0029] The following embodiments are provided to better understand the present invention, but the following embodiments do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the scope of protection of the present invention.
[0030] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention; the terms “comprising” and “having” and any variations thereof in the text of this invention are intended to cover non-exclusive inclusion.
[0031] The term "embodiment" as used herein means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of the invention. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments. The "scope" disclosed in this invention is defined in the form of a lower limit and an upper limit, a given scope being defined by selecting a lower limit and an upper limit, which define the boundaries of a particular scope. A scope defined in this way may include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a scope. In this invention, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" represents all real numbers between "0-5" listed herein; "0-5" is merely a shortened representation of these numerical combinations. Furthermore, when a parameter is described as an integer greater than or equal to 2, it is equivalent to disclosing that the parameter can be, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.
[0032] In the description of the embodiments of the present invention, the term "and / or" is merely a description of the relationship between associated objects, indicating that there can be three relationships. For example, A and / or B can represent three situations: A exists alone, A and B exist simultaneously, and B exists alone.
[0033] In the description of the embodiments of the present invention, the term "at least one" refers to one or more (including two).
[0034] Unless otherwise specified, all steps of the present invention may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.
[0035] Unless otherwise specified, all experimental steps or conditions in the examples were performed according to conventional experimental procedures and conditions in the art. Reagents or instruments whose manufacturers are not specified are all commercially available products.
[0036] Example 1 This example provides a method for preparing a composite cathode material. The specific steps and parameter settings are as follows: S1, 0.6g scandium oxide, 70g lithium hydroxide, and 200g Ni 0.90 Co 0.06 Mn 0.04 (OH)2 is mixed to obtain mixture I; 135.3g of mixture I is placed in a muffle furnace and subjected to a first sintering treatment at 825℃ in a pure oxygen atmosphere for 12h, and then pulverized and sieved to obtain sintered material I-1; another 135.3g of mixture I is placed in a muffle furnace and subjected to a second sintering treatment at 763℃ in a pure oxygen atmosphere for 8h, and then pulverized and sieved to obtain sintered material I-2.
[0037] S2, take 1g of alumina and 0.5g of lithium aluminate, mix with 100g of sinter material I-1, and place in a muffle furnace. Coating treatment is carried out in air atmosphere at 650℃ for 5h. After crushing and sieving, sinter material II-1 with D50=3μm is obtained.
[0038] S3, take 1g of alumina and 0.5g of lithium aluminate, mix with 100g of sinter material I-2, and place in a muffle furnace. Coating treatment is carried out in air atmosphere at 650℃ for 5h. After crushing and sieving, sinter material II-2 with D50=3μm is obtained.
[0039] S4. Take 70g of sintered material II-1 and 30g of sintered material II-2, mix them evenly to obtain the composite cathode material.
[0040] Example 2 This example provides a method for preparing a composite cathode material. The specific steps and parameter settings are as follows: S1, 0.8g zirconium oxide, 70g lithium hydroxide, and 200g Ni 0.90 Co 0.06 Mn 0.04 (OH)2 is mixed to obtain mixture I; 135.4g of mixture I is placed in a muffle furnace and subjected to a first sintering treatment at 820℃ in a pure oxygen atmosphere for 12h, and then pulverized and sieved to obtain sintered material I-1; another 135.4g of mixture I is placed in a muffle furnace and subjected to a second sintering treatment at 765℃ in a pure oxygen atmosphere for 8h, and then pulverized and sieved to obtain sintered material I-2.
[0041] S2, take 1.2g zirconium oxide and 0.8g lithium phosphate, mix with 100g sinter material I-1, and place in a muffle furnace. Coating treatment is carried out in air atmosphere at 650℃ for 5h. After crushing and sieving, sinter material II-1 with D50=3μm is obtained.
[0042] S3, take 1.2g zirconium oxide and 0.8g lithium phosphate, mix with 100g sinter material I-2, and place in a muffle furnace. Coating treatment is carried out in air atmosphere at 650℃ for 5h. After crushing and sieving, sinter material II-2 with D50=3μm is obtained.
[0043] S4. Take 60g of sintering material II-1 and 40g of sintering material II-2, mix them evenly to obtain the composite cathode material.
[0044] Example 3 This example provides a method for preparing a composite cathode material. The specific steps and parameter settings are as follows: S1, 0.6g of yttrium oxide, 70g of lithium hydroxide, and 200g of Ni 0.90 Co 0.06 Mn 0.04 (OH)2 is mixed to obtain mixture I; 135.3g of mixture I is placed in a muffle furnace and subjected to a first sintering treatment at 820℃ in a pure oxygen atmosphere for 12h, and then pulverized and sieved to obtain sintered material I-1; another 135.3g of mixture I is placed in a muffle furnace and subjected to a second sintering treatment at 765℃ in a pure oxygen atmosphere for 8h, and then pulverized and sieved to obtain sintered material I-2.
[0045] S2, take 0.8g of titanium oxide and 0.6g of lithium aluminate, mix with 100g of sinter material I-1, and place in a muffle furnace. Coating treatment is carried out in air atmosphere at 640℃ for 5h. After crushing and sieving, sinter material II-1 with D50=3μm is obtained.
[0046] S3, take 0.8g of titanium oxide and 0.6g of lithium aluminate, mix with 100g of sinter material I-2, and place in a muffle furnace. Coating treatment is carried out in air atmosphere at 640℃ for 5h. After crushing and sieving, sinter material II-2 with D50=3μm is obtained.
[0047] S4. Take 60g of sintering material II-1 and 40g of sintering material II-2, mix them evenly to obtain the composite cathode material.
[0048] Example 4 This example provides a method for preparing a composite cathode material. The specific steps and parameter settings are as follows: S1, 0.3g scandium oxide, 0.4g zirconium oxide, 70g lithium hydroxide, and 200g Ni 0.90 Co 0.06 Mn 0.04(OH)2 is mixed to obtain mixture I; 135.35g of mixture I is placed in a muffle furnace and subjected to a first sintering treatment at 820℃ in a pure oxygen atmosphere for 12h, and then pulverized and sieved to obtain sintered material I-1; another 135.35g of mixture I is placed in a muffle furnace and subjected to a second sintering treatment at 765℃ in a pure oxygen atmosphere for 8h, and then pulverized and sieved to obtain sintered material I-2.
[0049] S2, take 1.3g of alumina and 0.7g of lithium phosphate, mix with 100g of sinter material I-1, and place in a muffle furnace. Coating treatment is carried out in air atmosphere at 640℃ for 5h. After crushing and sieving, sinter material II-1 with D50=3μm is obtained.
[0050] S3, take 1.3g of alumina and 0.7g of lithium phosphate, mix with 100g of sinter material I-2, and place in a muffle furnace. Coating treatment is carried out in air atmosphere at 640℃ for 5h. After crushing and sieving, sinter material II-2 with D50=3μm is obtained.
[0051] S4. Take 50g of sintering material II-1 and 50g of sintering material II-2, mix them evenly to obtain the composite cathode material.
[0052] Example 5 This example provides a method for preparing a composite cathode material. The specific steps and parameter settings are as follows: S1, 0.6g scandium oxide, 75g lithium hydroxide, and 195g Ni 0.90 Co 0.06 Mn 0.04 (OH)2 is mixed to obtain mixture I; 135.3g of mixture I is placed in a muffle furnace and subjected to a first sintering treatment at 830℃ in a pure oxygen atmosphere for 12h, and then pulverized and sieved to obtain sintered material I-1; another 135.3g of mixture I is placed in a muffle furnace and subjected to a second sintering treatment at 770℃ in a pure oxygen atmosphere for 8h, and then pulverized and sieved to obtain sintered material I-2.
[0053] S2, take 1.3g of alumina and 0.5g of lithium aluminate, mix with 105g of sinter material I-1, and place in a muffle furnace. Coating treatment is carried out in air atmosphere at 650℃ for 4h. After crushing and sieving, sinter material II-1 with D50=3μm is obtained.
[0054] S3, take 1.3g of alumina and 0.5g of lithium aluminate, mix with 105g of sinter material I-2, and place in a muffle furnace. Coating treatment is carried out in air atmosphere at 650℃ for 4h. After crushing and sieving, sinter material II-2 with D50=3μm is obtained.
[0055] S4. Take 70g of sintered material II-1 and 30g of sintered material II-2, mix them evenly to obtain the composite cathode material.
[0056] Example 6 This example provides a method for preparing a composite cathode material. The specific steps and parameter settings are as follows: S1, 0.8g scandium oxide, 71g lithium hydroxide, and 205g Ni 0.90 Co 0.06 Mn 0.04 (OH)2 is mixed to obtain mixture I; 135.4g of mixture I is placed in a muffle furnace and subjected to a first sintering treatment at 815℃ in a pure oxygen atmosphere for 14h, and then pulverized and sieved to obtain sintered material I-1; another 135.3g of mixture I is placed in a muffle furnace and subjected to a second sintering treatment at 760℃ in a pure oxygen atmosphere for 10h, and then pulverized and sieved to obtain sintered material I-2.
[0057] S2, take 0.8g of alumina and 0.8g of lithium aluminate, mix with 95g of sinter material I-1, and place in a muffle furnace. Coating treatment is carried out in air atmosphere at 620℃ for 7h. After crushing and sieving, sinter material II-1 with D50=3μm is obtained.
[0058] S3, take 0.8g of alumina and 0.8g of lithium aluminate, mix with 95g of sinter material I-2, and place in a muffle furnace. Coating treatment is carried out in air atmosphere at 620℃ for 7h. After crushing and sieving, sinter material II-2 with D50=3μm is obtained.
[0059] S4. Take 30g of sintered material II-1 and 70g of sintered material II-2, mix them evenly to obtain the composite cathode material.
[0060] Example 7 This example provides a method for preparing a composite cathode material. The only difference from Example 1 is that in S1, the first sintering temperature is 820°C and the time is 12h, after which the material is crushed and sieved to obtain sintered material I-1; the second sintering temperature is 765°C and the time is 10h; the remaining steps are the same as in Example 1.
[0061] Comparative Example 1 This comparative example provides a method for preparing a composite cathode material. The specific steps and parameter settings are as follows: S1, 0.6g scandium oxide, 70g lithium hydroxide, and 200g Ni 0.90 Co 0.06 Mn 0.04 (OH)2 is mixed to obtain mixture I, which is placed in a muffle furnace and subjected to a first sintering treatment at 820°C in a pure oxygen atmosphere for 12 hours. After that, it is crushed and sieved to obtain sintered material I-1. S2, 1g of alumina and 0.5g of lithium aluminate are mixed with 100g of sintered material I-1 and placed in a muffle furnace. It is subjected to a coating treatment at 650°C in an air atmosphere for 5 hours. After that, it is crushed and sieved to obtain sintered material II-1 with D50=3μm, which is the composite cathode material.
[0062] Comparative Example 2 This comparative example provides a method for preparing a composite cathode material. The specific steps and parameter settings are as follows: S1, 0.6g scandium oxide, 70g lithium hydroxide, and 200g Ni 0.90 Co 0.06 Mn 0.04 (OH)2 is mixed to obtain mixture I, which is placed in a muffle furnace and subjected to a second sintering treatment at 765°C for 8 hours in a pure oxygen atmosphere. After that, it is crushed and sieved to obtain sintered material I-2.
[0063] S2, take 1g of alumina and 0.5g of lithium aluminate, mix with 100g of sinter material I-2, and place in a muffle furnace. Coating treatment is carried out in air atmosphere at 650℃ for 5h. After crushing and sieving, sinter material II-2 with D50=3μm is obtained, which is the composite cathode material.
[0064] Comparative Example 3 provides a method for preparing a composite cathode material. The specific steps and parameter settings are as follows: S1, 0.6g scandium oxide, 70g lithium hydroxide, and 200g Ni 0.90 Co 0.06 Mn 0.04 (OH)2 is mixed to obtain mixture I; 135.3g of mixture I is placed in a muffle furnace and sintered at 820℃ for 12h in a pure oxygen atmosphere, and then pulverized and sieved to obtain sintered material I-1; another 135.3g of mixture I is placed in a muffle furnace and sintered at 765℃ for 8h in a pure oxygen atmosphere, and then pulverized and sieved to obtain sintered material I-2.
[0065] S2, take 2g of alumina, 1g of lithium aluminate, 100g of sinter material I-1, and 100g of sinter material I-2, mix them, and place them in a muffle furnace. Coating treatment is carried out in air atmosphere at 650℃ for 5h. After crushing and sieving, sinter material II with D50=3μm is obtained.
[0066] Comparative Example 4 provides a method for preparing a composite cathode material. The only difference from Example 1 is that in S1, scandium oxide is replaced with an equal mass of ternary precursor; the remaining steps are the same as in Example 1.
[0067] Comparative Example 5 provides a method for preparing a composite cathode material, which differs from Example 1 only in that: in S2, lithium aluminate and alumina are replaced with sintering material I-1 of equal mass; in S3, lithium aluminate and alumina are replaced with sintering material I-2 of equal mass; the remaining steps are the same as in Example 1.
[0068] Comparative Example 6 provides a method for preparing a composite cathode material, which differs from Example 1 only in that: in S2, alumina is replaced with an equal mass of sintering material I-1; in S3, alumina is replaced with an equal mass of sintering material I-2; the remaining steps are the same as in Example 1.
[0069] Comparative Example 7 provides a method for preparing a composite cathode material, which differs from Example 1 only in that: in S2, lithium aluminate is replaced with an equal mass of sintering material I-1; in S3, lithium aluminate is replaced with an equal mass of sintering material I-2; the remaining steps are the same as in Example 1.
[0070] Comparative Example 8 provides a method for preparing a composite cathode material. The only difference from Example 1 is that in S1, the temperature of the first sintering treatment is 800°C and the time is 10h; the remaining steps are the same as in Example 1.
[0071] Comparative Example 9 provides a method for preparing a composite cathode material. The only difference from Example 1 is that in S1, the temperature of the first sintering treatment is 850°C and the time is 16h; the remaining steps are the same as in Example 1.
[0072] Comparative Example 10 provides a method for preparing a composite cathode material, which differs from Example 1 only in that: in S1, the temperature of the second sintering treatment is 800°C and the time is 12h.
[0073] The remaining steps are the same as in Example 1.
[0074] Comparative Example 11 provides a method for preparing a composite cathode material. The only difference from Example 1 is that in S1, the temperature of the second sintering treatment is 750°C and the time is 6 hours; the remaining steps are the same as in Example 1.
[0075] In Experiment 1, the composite cathode materials provided in each embodiment and comparative example were applied to a lithium-ion battery, and then their electrical performance was tested.
[0076] The method for preparing the lithium-ion battery includes the following steps: In an argon atmosphere within a glove box, a Celgard 2500 separator, a lithium metal sheet as the negative electrode, and an LBC3021C011 electrolyte are used. A CR2032 button cell is assembled in the order of negative electrode, electrolyte, separator, electrolyte, and positive electrode.
[0077] The specific method for the electrical performance test is as follows: (1) First-cycle charge and discharge performance test: At a temperature of 25°C, the assembled button cell is charged to 4.25V at a rate of 0.2C, and then discharged to 2.8V at a rate of 0.2C. The first-cycle charge capacity and the first-cycle discharge capacity are recorded, and the first-cycle coulombic efficiency (first efficiency) is calculated.
[0078] The Coulomb efficiency for the first lap is calculated as follows: .
[0079] Where: ICE is the initial coulombic efficiency; D1 is the initial discharge capacity at a specified rate (e.g., 0.1C); and C1 is the initial charge capacity at the same rate.
[0080] (2) Rate performance and cycle test: After completing the first two cycles, the charge and discharge regime was changed: the capacitor was charged to 4.25V with a constant current of 0.5 C and discharged with a constant current of 1 C, with a cutoff condition of 2.8V, for 50 consecutive cycles. The discharge specific capacity of the 3rd and 52nd cycles was recorded respectively.
[0081] The rate performance is characterized by the ratio of the discharge specific capacity of the 3rd cycle to that of the 2nd cycle; the cycle performance is characterized by the ratio of the discharge specific capacity of the 52nd cycle to that of the 3rd cycle.
[0082] Table 1 Electrical performance test data
[0083] As shown in Table 1, compared with Example 1 (first-cycle coulombic efficiency 90.7%, rate performance 97.2%, cycle performance 96.3%), Comparative Example 1 has better cycle performance (96.5%) but poorer rate performance (92.9%). This verifies that the kinetics of a single monocrystalline cathode material are limited. Comparative Example 2 has acceptable rate performance (96.3%) but extremely poor cycle performance (86.4%), verifying that the structure of a single polycrystalline cathode material is unstable. The coating effect of Comparative Example 3 (mixing before coating) is far inferior to that of the examples where the particles were coated separately and then mixed. Pre-mixing leads to uneven coating of the two particles with different surface properties, thus impairing performance (especially the rate performance of 91.0%). This demonstrates the importance of the preparation method of this invention. Comparative Example 4 (without dopant) showed a significant decrease in initial efficiency (87.0%), rate capability (90.6%), and cycle life (85.6%), indicating that even with dual-material mixing, the lack of bulk doping cannot achieve a stable structure, leading to increased side reactions, increased impedance, and structural collapse. Comparative Examples 5 (without any coating), 6 (without the first coating agent), and 7 (without the second coating agent) demonstrated that metal oxides and lithium salts are indispensable in the coating layer, respectively fulfilling the functions of "physical isolation" and "ion conduction". Comparative Examples 8-11 demonstrated that the precise control of the parameters of the first and second sintering processes in this invention determines the intrinsic properties of the material.
[0084] Example 1 successfully constructed a stable, integrated bulk-interface structure by employing a multi-strategy synergy of "gradient sintering to prepare single-crystal / polycrystalline composite materials," "separately coating to optimize the interface," and "bulk doping to stabilize the structure," thereby achieving a balance between high initial efficiency, excellent rate performance, and long cycle life. Furthermore, all examples (Examples 1-6) exhibited excellent key performance indicators after adjustments to dopant type, coating agent combination, sintering temperature, or mixing ratio, demonstrating the universality of this composite strategy across different process parameters. In summary, this invention effectively improves the structural and surface chemical stability of high-nickel ternary cathode materials through core layer doping and surface coating with functional layers, enhancing rate and cycle performance. The mixing of polycrystalline and single-crystal materials allows the material to simultaneously achieve excellent high capacity, cycle performance, and rate performance, overcoming the difficulty of balancing high capacity with high rate and cycle performance in traditional single-crystal or polycrystalline materials.
[0085] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.
Claims
1. A method for preparing a composite cathode material, characterized in that, The process includes the following steps: S1, mixing a bulk dopant, a lithium source, and a ternary precursor to obtain a mixture I; taking a portion of mixture I for a first sintering to obtain sintered material I-1; and taking another portion of mixture I for a second sintering to obtain sintered material I-2; the temperature of the first sintering is 815-830℃, and the time is 12-14h; the temperature of the second sintering is 760-770℃, and the time is 8-10h; S2, mixing a first coating agent and a second coating agent with sintered material I-1 and then performing a coating treatment to obtain sintered material II-1; S3, mixing a first coating agent and a second coating agent with sintered material I-2 and then performing a coating treatment to obtain sintered material II-2; S4, mixing sintered material II-1 and sintered material II-2 to obtain the composite cathode material.
2. The preparation method according to claim 1, characterized in that, In S1, the mass ratio of the bulk dopant, lithium source, and ternary precursor is (0.6-0.8):(65-75):(195-205); optionally, in S1, the mass ratio of the bulk dopant, lithium source, and ternary precursor is 0.6:70:200; and / or, the amount of the mixture I undergoing the first sintering accounts for 45%-55% of the total mass of the mixture I; optionally, the amount of the mixture I undergoing the first sintering accounts for 50% of the total mass of the mixture I.
3. The preparation method according to claim 1 or 2, characterized in that, In step S2, the mass ratio of the first coating agent, the second coating agent, and sintering material I-1 is (0.8-1.3):(0.5-0.8):(95-105); optionally, in step S2, the mass ratio of the first coating agent, the second coating agent, and sintering material I-1 is 0.8:0.6:100; and / or, in step S3, the mass ratio of the first coating agent, the second coating agent, and sintering material I-2 is (0.8-1.3):(0.5-0.8):(95-105); optionally, in step S3, the mass ratio of the first coating agent, the second coating agent, and sintering material I-2 is 0.8:0.6:100; and / or, in step S4, the mass ratio of sintering material II-1 and sintering material II-2 is 7:3-3:7; optionally, in step S4, the mass ratio of sintering material II-1 and sintering material II-2 is 6:
4.
4. The preparation method according to any one of claims 1-3, characterized in that, The ternary precursor is a nickel-cobalt-manganese ternary precursor; optionally, the general formula of the nickel-cobalt-manganese ternary precursor includes Ni. x Co y Mn z (OH)₂, where 0.9 ≤ x < 1, x + y + z = 1, preferably Ni 0.90 Co 0.06 Mn 0.04 (OH)2.
5. The preparation method according to any one of claims 1-4, characterized in that, In S1, the atmosphere for the first and second sintering is independently pure oxygen; and / or, in S2 and S3, the temperature of the coating treatment is independently 620-650°C, the time of the coating treatment is independently 4-7 h, and the atmosphere of the coating treatment is independently air; optionally, in S2 and S3, the temperature of the coating treatment is independently 640°C, and the time of the coating treatment is independently 5 h.
6. The preparation method according to any one of claims 1-5, characterized in that, The bulk dopant includes a Group IIIB metal oxide; optionally, the Group IIIB metal oxide includes at least one of scandium oxide, zirconium oxide, and yttrium oxide; and / or, the lithium source includes at least one of lithium hydroxide and lithium carbonate.
7. The preparation method according to any one of claims 1-6, characterized in that, The first coating agent includes at least one of Group IIIA metal oxides and Group IVB metal oxides; optionally, the Group IIIA metal oxide includes aluminum oxide; optionally, the Group IVB metal oxide includes at least one of zirconium oxide and titanium oxide; and / or, the second coating agent includes an inorganic lithium acid salt; optionally, the inorganic lithium acid salt includes at least one of lithium aluminate and lithium phosphate.
8. A composite cathode material prepared by the preparation method according to any one of claims 1-7.
9. A lithium-ion battery, characterized in that, It includes the composite cathode material as described in claim 8.
10. An electrical appliance, characterized in that, It includes the lithium-ion battery as described in claim 9.