A lanthanide modification strategy with surface coating and interlayer-like doping dual effects

Abstract

The application aims to develop a lanthanide series modification strategy with wide application potential, which can form Q 1‑x‑y M x N y O 1.9 Lanthanide oxide coating layer, and form coherent nano precipitated phase between material layers, so as to realize the double modification effect of surface coating and interlayer-like doping. Due to this double modification, the cycle stability of the material is significantly improved, the voltage drop is effectively inhibited, and the structural stability is significantly enhanced.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery materials and electrochemical technology, specifically relating to a modification strategy with dual effects of surface coating and interlayer doping. Background Technology

[0002] Lithium-ion batteries have achieved significant application success in communications and consumer electronics, and are gradually expanding into electric vehicles and renewable energy storage. Faced with the ever-increasing demand for high energy density, the research of novel high-capacity electrode materials, especially Zhengji materials, has become a focus of scientific research. However, the structural instability of cathode materials during long-term cycling severely affects their cycle life. Therefore, achieving structural stability of materials is crucial for improving their electrochemical performance.

[0003] Taking lithium-rich manganese-based cathode materials (LLOs) as an example, their reversible capacity exceeding 250 mAh·g−1 makes them potential candidate materials for meeting high energy density requirements. Studies have shown that the high capacity of LLOs originates not only from cation redox reactions but also from anion redox reactions. These anion redox reactions mainly manifest as reversible bulk anodic redox and irreversible surface oxygen loss. Surface oxygen loss reduces the electrochemical performance of LLOs, triggering electrolyte decomposition and structural reconstruction, leading to the formation of a non-conductive SEI film, which in turn induces a phase transition from a layered structure to a spinel structure, hindering lithium-ion diffusion and causing capacity reduction, voltage decay, and deterioration of kinetic performance. Previous atomic structure and chemical observations indicate that the phase transition in LLOs begins at the surface and gradually extends inward during cycling. Therefore, achieving structural stability, especially surface stability, in LLO materials to mitigate lattice oxygen release is crucial for developing superior cathode materials and promoting the development of next-generation lithium-ion batteries.

[0004] To achieve structural stability in cathode materials, various modification strategies have been widely studied and applied, including doping, coating, and structural design. While traditional methods of surface coating battery cathode materials can improve cycle stability and durability to some extent, they often suffer from problems such as uneven coating thickness, increased interfacial impedance, and easy peeling of the coating. Furthermore, traditional coating methods struggle to optimize the overall performance of the material, providing only limited surface protection. Therefore, combining various modification strategies and developing novel modification methods to enhance the structural stability of cathode materials, thereby improving their cycle life and other electrochemical properties, has become an important research direction. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to develop a lanthanide modification strategy with broad application potential, which can form oxygen-vacancy-rich Q-type structures on the surface of cathode materials. ,

[0012] M x N y O 1.9 A lanthanide oxide coating layer, where 0 < x < 1, 0 < y < 1, Q, M, and N are a composition of one or more of La, Ce, Pr, Nd, Pm, Sm, Sc, Y, and Yb, and a coherent nano-precipitation phase is formed between the material layers, thereby achieving the dual modification effects of surface coating and interlayer pseudo-doping. Thanks to this dual modification, the cycle stability of the material is significantly improved, the voltage drop is effectively suppressed, and the structural stability is significantly enhanced.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A lanthanide-coated and doped dual-modified cathode composite material, characterized in that it can form a Q rich in oxygen vacancies on the surface of the cathode material of a lithium-ion battery 1-x-y M x N y O 1.9 A lanthanide oxide coating layer, where 0 < x < 1, 0 < y < 1, Q, M, and N are a composition of one or more of La, Ce, Pr, Nd, Pm, Sm, Sc, Y, and Yb. The lanthanide elements in the oxygen vacancy lanthanide oxide coating layer are doped into the layered structure of the cathode material, and a coherent nano-precipitation phase is formed between the material layers, achieving the dual modification of surface coating and interlayer pseudo-doping.

[0008] Furthermore, in the lanthanide-coated and doped dual-modified cathode composite material, Q is Ce, M is La, and N is Yb.

[0009] Furthermore, in the lanthanide-coated and doped dual-modified cathode composite material, 0 < x < 0.35 and 0 < y < 0.35.

[0010] Furthermore, a Q rich in oxygen vacancies is formed on the surface 1-x-y M x N y O 1.9 The stoichiometric ratio of each lanthanide element in the lanthanide oxide is 1:1:1, and the thickness of the coating layer is 1 - 5 nm. If the thickness of the coating layer is too thin, the coating effect of the coating layer cannot be fully presented. If the thickness of the coating layer is too thick, it will affect the entry of ions and electrons into the active material and affect the electrochemical performance of the material. Therefore, it is preferably within this range, which can ensure both the strength and effect of the coating layer and also take into account the electrochemical performance.

[0011] On the other hand, the present invention also provides a preparation method for the lanthanide-coated and doped dual-modified cathode composite material, characterized by including the following steps:

[0012] 1) Dissolve different lanthanide sources in a certain amount of N,N-dimethylformamide (DMF) according to stoichiometric ratio to form a homogeneous solution;

[0013] 2) Take a certain mass of the original positive electrode material powder and dissolve it in a certain amount of the above solution. Place it in a vacuum environment and mix it evenly. Then wash the evenly mixed product multiple times with DMF solution.

[0014] 3) The product obtained in the previous step is dried in a vacuum oven, and then the dried product is sintered to obtain the modified cathode composite material.

[0015] Furthermore, in step 1), the lanthanide source in step 1) is one or more of the lanthanide nitrates, acetates, sulfates, and chlorides.

[0016] Furthermore, in step 2), the final mixed solution has a concentration of 0.1-1 mol / L.

[0017] Furthermore, in step 2), the original cathode material powder includes primary particles synthesized by sol-gel method and secondary particles synthesized by coprecipitation-solid phase method, with a stirring temperature of 50-120℃ and a stirring time of 5-12 h; the DMF solution is subjected to three repeated filtration and washing.

[0018] Furthermore, in step 3), the drying conditions are drying at 120-140 ℃ in a vacuum oven for 12 h; the sintering conditions are heating to 600-800 ℃ at a heating rate of 5 ℃ / min, holding at that temperature for 6-12 h, and then naturally cooling to room temperature.

[0019] A third aspect of the present invention is to provide the use of a lanthanide-coated doped dual-modified cathode composite material or a lanthanide-coated doped dual-modified cathode composite material prepared by the above method in a battery, wherein the battery includes a lithium-ion battery, a sodium-ion battery, and a potassium-ion battery.

[0020] The beneficial effects of this invention are as follows:

[0021] This invention discloses an effective lanthanide modification strategy that can form oxygen-vacancy-rich Q-type structures on the surface of lithium-ion battery cathode materials. 1-x-y M x N y O 1.9A lanthanide oxide coating layer is formed, and a coherent nano-precipitated phase is formed between the material layers, thus achieving a dual modification effect of surface coating and interlayer doping. The lanthanide oxide coating layer with certain oxygen vacancies formed on the surface after lanthanide modification can effectively suppress the release of lattice oxygen and reduce the occurrence of side reactions. Furthermore, the precipitated nano-phase generated in the interlayer has a doping effect, which helps maintain the stability of the layered structure. The lanthanide-modified material exhibits significantly improved cycle stability, effectively suppressed voltage drop, and significantly enhanced structural stability. Attached Figure Description

[0022] Figure 1 The images are (a) XRD patterns and (b) SEM images of the lithium-rich material LLO-L after lanthanide modification in Example 1 and the original lithium-rich material LLO.

[0023] Figure 2 These are (a) HAADF-STEM images and (b) EDS mapping images of the lithium-rich material LLO-L after lanthanide modification in Example 1.

[0024] Figure 3 This is an atomic-level HAADF-STEM image of the lithium-rich material LLO-L after lanthanide modification in Example 1.

[0025] Figure 4 This is a comparison chart of the cycling performance of the lithium-rich material LLO-L after lanthanide modification in Example 1 and the original lithium-rich material LLO at a rate of 0.2 C.

[0026] Figure 5 This is a comparison chart of the cycling performance of the lithium-rich material LLO-L after lanthanide modification in Example 1 and the original lithium-rich material LLO at a 1 C rate.

[0027] Figure 6 This is a high-magnification HAADF-STEM image of the original lithium-rich material in Example 1 after 200 LLO cycles.

[0028] Figure 7 This is a high-magnification HAADF-STEM image of the lithium-rich material LLO-L after lanthanide modification in Example 1.

[0029] Figure 8 This is a SEM image of the original secondary particle cobalt-free lithium-rich material LRNM in Example 2.

[0030] Figure 9 This is a SEM image of L-LRNM, a cobalt-free lithium-rich secondary particle material after lanthanide modification in Example 2.

[0031] Figure 10 This is a HAADF-STEM image of L-LRNM, a cobalt-free lithium-rich secondary particle material after lanthanide modification in Example 2.

[0032] Figure 11 This is a comparison chart of the cycling performance of L-LRNM, a cobalt-free lithium-rich material with secondary particles after lanthanide modification in Example 2, and the original cobalt-free lithium-rich material LRNM at a 1 C rate. Detailed Implementation

[0033] To make the technical solutions and advantages of the present invention clearer, the present invention and its beneficial effects will be described in further detail below with reference to specific embodiments and accompanying drawings. However, the embodiments of the present invention are not limited thereto. For ease of understanding, the present invention will be described more comprehensively and meticulously below with reference to the accompanying drawings and preferred embodiments. However, the scope of protection of the present invention is not limited to the following specific embodiments.

[0034] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0035] Unless otherwise specified, all reagents and raw materials used in this invention are commercially available products or products that can be prepared by known methods.

[0036] To better understand the present invention, the following embodiments further illustrate the content of the present invention, but the content of the present invention is not limited to the following embodiments.

[0037] In this invention, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can both represent: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0038] Example 1:

[0039] 1) Dissolve 1.737 g of cerium nitrate hexahydrate, 1.732 g of lanthanum nitrate hexahydrate and 1.797 g of ytterbium nitrate pentahydrate in 40 ml of DMF solution and mix thoroughly to form a homogeneous solution of 0.1 mol / L.

[0040] 2) Take 0.2 g of lithium-rich material powder (LLO) prepared by sol-gel method and dissolve it in 4 ml of the solution prepared above. Place it in a vacuum environment and stir at 50 °C for 12 h to mix thoroughly. The subsequent product is washed by vacuum filtration three times with DMF solution.

[0041] 3) The product obtained in the previous step was dried in a vacuum oven at 120 °C for 12 h to remove excess DMF. Then the dried product was placed in a muffle furnace and heated to 675 °C at a heating rate of 5 °C / min. The temperature was held for 6 h and then cooled naturally to room temperature to complete the lanthanide modification (LLO-L).

[0042] Taking the lithium-rich material powder (LLO) of primary particles in this embodiment as an example, lanthanide modification (LLO-L) was performed on it to verify the effectiveness of this strategy in modifying primary particle Zhengji material samples.

[0043] Figure 1 XRD results showed that the lanthanide-modified (LLO-L) sample retained the characteristic peaks of lithium-rich LLO while exhibiting additional small peaks at diffraction angles of 30-35° and 47°. Magnified observation of the (003) peak revealed a shift towards lower angles in the LLO-L sample, further indicating successful doping of lanthanides into the material's crystal lattice. SEM image analysis showed that the LLO particles had a relatively clean and smooth surface structure, while the LLO-L particles exhibited a distinct coating layer, indicating successful lanthanide coating.

[0044] Figure 2 The HAADF-STEM image and EDS mapping also demonstrate the success of the lanthanide modification strategy.

[0045] pass Figure 3 Atomic-level HAADF-STEM images, after lanthanide modification, confirm the presence of significant Ce on its surface. 1-x- y La x Yb y O 1.9 A lanthanide oxide coating layer is formed, and a coherent nanoprecipitate phase is formed between the material layers.

[0046] Figure 4 The graph shows a comparison of the cycling performance of the lanthanide-modified lithium-rich material LLO-L and the original lithium-rich material LLO at a rate of 0.2 C. After 200 cycles, LLO only retained 73.54% of its capacity, while the lanthanide-modified LLO-L still retained 87.75% of its capacity, demonstrating superior cycling stability compared to LLO.

[0047] Figure 5The graph shows a comparison of the cycling performance of the two at a 1 C rate. After 500 cycles, LLO only retains 69.81% of its capacity, while LLO-L, after lanthanide modification, still retains 80.39% of its capacity, demonstrating extremely high cycling stability.

[0048] Figure 6 The structure of the original lithium-rich material after 200 LLO cycles is characterized. After the original LLO cycle, a large number of black pores appeared on the surface, accompanied by lattice distortion and severe phase transition. The loss of lattice oxygen was very serious, and the structure was greatly damaged, thus exhibiting poor cycling stability.

[0049] Figure 7 The structure of the lanthanide-modified lithium-rich material after 200 LLO-L cycles was characterized. The lanthanide coating and precipitated nanophases remained intact after cycling, maintaining a complete structure. Furthermore, only a small number of pores appeared on the surface after cycling, indicating a low degree of adverse phase transitions and no significant lattice distortion, demonstrating excellent suppression of lattice oxygen release. The lanthanide oxide coating with oxygen vacancies formed on the surface after lanthanide modification effectively suppresses lattice oxygen release and reduces side reactions. In addition, the precipitated nanophases generated between the layers exhibit a doping effect, contributing to the stability of the layered structure.

[0050] Example 2:

[0051] 1) Dissolve 1.737 g of cerium nitrate hexahydrate, 1.732 g of lanthanum nitrate hexahydrate and 1.797 g of ytterbium nitrate pentahydrate in 40 ml of DMF solution and mix thoroughly to form a homogeneous solution of 0.1 mol / L.

[0052] 2) Take 0.2 g of cobalt-free lithium-rich material powder (LRNM) prepared by coprecipitation-solid phase method and dissolve it in 4 ml of the solution prepared above. Place it in a vacuum environment and stir at 50 °C for 12 h to mix thoroughly. The subsequent product is washed by vacuum filtration three times with DMF solution.

[0053] 3) The product obtained in the previous step was dried in a vacuum oven at 120 °C for 12 h to remove excess DMF. Then the dried product was placed in a muffle furnace and heated to 675 °C at a heating rate of 5 °C / min. The temperature was held for 6 h and then cooled naturally to room temperature to complete the lanthanide modification (L-LRNM).

[0054] Taking the cobalt-free lithium-rich material powder (LRNM) of secondary particles in this embodiment as an example, lanthanide modification (L-LRNM) was performed on it to verify the effectiveness of this strategy in modifying secondary particle cathode material samples.

[0055] Figure 8 and Figure 9 SEM images show the original cobalt-free lithium-rich material powder LRNM and the lanthanide-modified L-LRNM, respectively. Both consist of spherical secondary particles of approximately 10 μm, composed of primary particles of tens of nanometers in size. After lanthanide modification, a coating layer is clearly present in L-LRNM, filling the gaps between the primary particles.

[0056] Figure 10 This is an atomic-level HAADF-STEM image of lanthanide-modified L-LRNM. A distinct coating layer is observed on the surface, and coherent nanoprecipitates are formed in the interlayer structure. This confirms the success of lanthanide modification and demonstrates the universality of lanthanide modification strategies in secondary particulate materials.

[0057] Figure 11 This chart compares the cycling stability of the original cobalt-free lithium-rich material powder LRNM and the lanthanide-modified L-LRNM at a 1 C rate. The original cobalt-free lithium-rich material LRNM only retained 70.96% of its capacity after 400 cycles, while the lanthanide-modified L-LRNM still maintained 93.19% of its capacity, demonstrating excellent cycling stability.

[0058] Example 3:

[0059] 1) Dissolve 1.737 g of cerium nitrate hexahydrate, 1.732 g of lanthanum nitrate hexahydrate and 1.797 g of ytterbium nitrate pentahydrate in 20 ml of DMF solution and mix thoroughly to form a homogeneous solution of 0.2 mol / L.

[0060] 2) Dissolve 0.2 g of single-crystal high-nickel NCM811 powder in 4 ml of the solution prepared above, place it in a vacuum environment, and stir at 80 °C for 10 h to ensure thorough mixing. The subsequent product is then subjected to three repeated vacuum filtration and washing with DMF solution.

[0061] 3) Place the product obtained in the previous step in a vacuum oven at 130 °C for 12 h to remove excess DMF. Then place the dried product in a muffle furnace and heat it to 700 °C at a heating rate of 5 °C / min. Hold it at this temperature for 6 h and allow it to cool naturally to room temperature to complete the lanthanide modification.

[0062] Example 4:

[0063] 1) Dissolve 1.737 g of cerium nitrate hexahydrate, 1.732 g of lanthanum nitrate hexahydrate and 1.797 g of ytterbium nitrate pentahydrate in 20 ml of DMF solution and mix thoroughly to form a homogeneous solution of 0.2 mol / L.

[0064] 2) Dissolve 0.2 g of secondary particle polycrystalline high-nickel NCM811 powder in 4 ml of the solution prepared above, place it in a vacuum environment, and stir at 80 °C for 8 h to mix thoroughly. The subsequent product is washed by vacuum filtration three times using DMF solution.

[0065] 3) Place the product obtained in the previous step in a vacuum oven at 130 °C for 10 h to remove excess DMF. Then place the dried product in a muffle furnace and heat it to 650 °C at a heating rate of 5 °C / min. Hold it at that temperature for 6 h and let it cool naturally to room temperature to complete the lanthanide modification.

[0066] Example 5:

[0067] 1) Dissolve 1.737 g of cerium nitrate hexahydrate, 1.732 g of lanthanum nitrate hexahydrate and 1.797 g of ytterbium nitrate pentahydrate in 40 ml of DMF solution and mix thoroughly to form a homogeneous solution of 0.1 mol / L.

[0068] 2) Dissolve 0.2 g of secondary particle polycrystalline high-nickel NCM523 powder in 4 ml of the solution prepared above, place it in a vacuum environment, and stir at 80 °C for 8 h to mix thoroughly. The subsequent product is washed by vacuum filtration three times using DMF solution.

[0069] 3) Place the product obtained in the previous step in a vacuum oven at 130 °C for 10 h to remove excess DMF. Then place the dried product in a muffle furnace and heat it to 750 °C at a heating rate of 5 °C / min. Hold it at this temperature for 6 h and allow it to cool naturally to room temperature to complete the lanthanide modification.

[0070] Based on the disclosure and teachings of the foregoing specification, those skilled in the art can make changes and modifications to the above embodiments. Therefore, the present invention is not limited to the specific embodiments described above, and any obvious improvements, substitutions, or modifications made by those skilled in the art based on the present invention are within the scope of protection of the present invention. Furthermore, although some specific terms are used in this specification, these terms are only for convenience of explanation and do not constitute any limitation on the present invention.

Claims

1. A lanthanide-coated doped dual-modified cathode composite material, characterized in that, Form Q rich in oxygen vacancies on the surface of the cathode material of the lithium-ion battery 1-x-y M x N y O 1.9 lanthanide oxide coating layer, where Q is Ce, M is La, N is Yb, 0 < x < 0.35, 0 < y < 0.35, and the Q rich in oxygen vacancies 1-x-y M x N y O 1.9 The lanthanide elements in the lanthanide oxide coating layer are doped into the layered structure of the coated cathode material of the lithium-ion battery, and coherent nanoprecipitation phases are formed in the layered structure, realizing double modification of surface coating and interlayer-like doping. The thickness of the coating layer is 1 - 5 nm.

2. The lanthanide-coated doped dual-modified cathode composite material according to claim 1, wherein the surface forms a Q-type structure rich in oxygen vacancies. 1-x-y M x N y O 1.9 The stoichiometric ratio of the lanthanide elements in lanthanide oxides is 1:1:

1.

3. A method for preparing a lanthanide-coated doped dual-modified cathode composite material as described in any one of claims 1-2, characterized in that, Includes the following steps: 1) Dissolve different lanthanide sources in a certain amount of N,N-dimethylformamide (DMF) according to stoichiometric ratio to form a homogeneous solution; 2) Take a certain mass of the original positive electrode material powder and dissolve it in a certain amount of the above solution. Place it in a vacuum environment and mix it evenly. Then wash the evenly mixed product multiple times with DMF solution. 3) The product obtained in the previous step is dried in a vacuum oven, and then the dried product is sintered. The sintering conditions are to raise the temperature to 600-800℃ at a heating rate of 5℃ / min, hold for 6-12 h, and then cool naturally to room temperature to obtain the modified cathode composite material.

4. The method according to claim 3, characterized in that: In step 1), the lanthanide source is one or more of the lanthanide nitrates, acetates, sulfates, and chlorides.

5. The method according to claim 3, wherein the concentration of the final mixed solution in step 2) is 0.1-1 mol / L.

6. The method according to claim 3, characterized in that: In step 2), the original cathode material powder includes primary particles synthesized by sol-gel method and secondary particles synthesized by coprecipitation-solid phase method. The stirring temperature is 50-120℃ and the time is 5-12 h. The DMF solution is subjected to three repeated filtration and washing.

7. The method according to claim 3, characterized in that: In step 3), the drying conditions are drying at 120-140℃ in a vacuum oven for 12 hours.

8. The use of the lanthanide-coated doped dual-modified cathode composite material according to any one of claims 1-2 or the lanthanide-coated doped dual-modified cathode composite material prepared by the method according to any one of claims 3-7 in a battery, wherein the battery includes a lithium-ion battery, a sodium-ion battery or a potassium-ion battery.

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