Preparation method of negative electrode material, negative electrode material and application of negative electrode material
By preparing cobalt phosphide/nickel phosphide@carbon nanoparticle anode materials, a "nickel phosphide particle-cobalt phosphide nanoparticle-3D carbon coating framework" structure was constructed, which solved the problems of low capacity of traditional graphite anode materials and high volume expansion rate and cycle performance decay of high-capacity materials, and achieved high energy density and long-term stability.
Patent Information
- Application Number
- CN202511348759.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-22
- Publication Date
- 2026-01-13
AI Technical Summary
Traditional graphite anode materials have a low theoretical specific capacity. High-capacity anode materials, such as silicon-based and Prussian blue materials, suffer from high volume expansion, cycle performance degradation, and insufficient conductivity during charge and discharge, making it difficult to meet the requirements of high-endurance and high-power lithium-ion batteries.
A three-step method of coordination assembly-pyrolysis to carbon-gas phase phosphating was adopted to prepare cobalt phosphide/nickel phosphide@carbon nanoparticle anode material. By forming a composite structure of "nickel phosphide particles-cobalt phosphide nanoparticles-3D carbon coating framework", the nitrogen-doped carbon network was used to improve the electron/ion conduction efficiency and alleviate the volume expansion.
It achieves a synergistic improvement in high capacity and cycle stability, solves the problems of cycle decay and insufficient conductivity of traditional high-capacity materials, and improves the energy density and long-term stability of the battery.
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Figure CN121331784A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the field of lithium ion batteries, in particular to a preparation method of a negative electrode material, the negative electrode material and application thereof. BACKGROUND
[0002] As a key device in the field of electrochemical energy storage, lithium ion batteries have been widely used in consumer electronics, electric vehicles and energy storage systems. With the development of high integration and high energy density of the battery, the traditional graphite negative electrode material gradually fails to meet the demand of high endurance and high power devices in the market due to its low theoretical specific capacity.
[0003] To improve the energy density of the negative electrode, the prior art mainly adopts a double-layer coating process: a high-capacity negative electrode material (such as silicon-based, transition metal compound, etc.) is coated on the bottom layer, and graphite is coated on the upper layer to balance the cycle stability. However, the existing high-capacity negative electrode material has significant defects: for example, although the silicon-based material has high theoretical capacity, it has high volume expansion rate during charging and discharging, which easily leads to electrode cracking and cycle performance degradation; the Prussian blue type material has poor cycle stability and limited theoretical capacity improvement. In addition, although some transition metal oxides or sulfides have high capacity, the conductivity is insufficient and the volume expansion problem has not been completely solved, which limits their practical application. SUMMARY
[0004] In order to overcome the defects in the prior art, the first object of the present application provides a preparation method of a negative electrode material, the second object of the present application provides a negative electrode material, the third object of the present application provides a lithium ion battery, and the fourth object of the present application provides an electric device.
[0005] To achieve the above objects, the technical scheme adopted by the present application is as follows:
[0006] In a first aspect, a preparation method of a lithium ion battery negative electrode material comprises the following steps:
[0007] Dissolve sodium citrate and a nickel source compound in deionized water, and stir to form a first solution;
[0008] Dissolve sodium citrate and a cobalt source compound in deionized water, and stir to form a second solution;
[0009] Mix the first solution and the second solution, and after stirring, standing, separating and drying, a precursor is obtained;
[0010] Anneal the precursor in an inert atmosphere to prepare a nickel-cobalt@modified nanocarbon skeleton;
[0011] Carry out a gas phase phosphorization reaction on the nickel-cobalt@modified nanocarbon skeleton and a phosphorus source in an inert atmosphere to obtain a cobalt phosphide / nickel phosphide@nanocarbon negative electrode material.
[0012] The preparation method of this anode material achieves synergistic optimization of structure and performance through the following steps:
[0013] Precursor preparation stage: Sodium citrate, as a ligand, reacts with nickel and cobalt sources in an aqueous solution to form a nickel-cobalt modified Prussian blue nanocube precursor, which self-assembles into a uniform nanostructure during the standing process.
[0014] Annealing and transformation stage: During annealing under an inert atmosphere, the organic ligands in the Prussian blue nanocubes decompose into a nitrogen-doped carbon network, and nickel and cobalt ions are uniformly dispersed in the carbon framework to form a 3D carbon coating framework structure of "nickel cobalt@modified nano carbon".
[0015] Phosphating Regulation Stage: During gas-phase phosphating, the active phosphorus produced by the decomposition of the phosphorus source reacts with nickel and cobalt elements uniformly dispersed in the carbon framework. By significantly exceeding the phosphorus source, sufficient thermodynamic driving force is provided for the reaction, ensuring that nickel and cobalt elements are phosphated simultaneously and fully, generating nickel phosphide particles and cobalt phosphide nanoparticles respectively, ultimately constructing a composite structure of "nickel phosphide particles-cobalt phosphide nanoparticles-3D carbon coating framework".
[0016] This process involves a three-step method: coordination assembly, pyrolysis to carbon, and gas-phase phosphating. This method directionally transforms the raw materials into functional structures: a 3D carbon coating framework acts as a buffer matrix to effectively mitigate the volume expansion of nickel phosphide, while the nitrogen-doped carbon network enhances electron / ion conduction efficiency (shortening the Li...). + (Diffusion pathway), heterostructure provides high lithium storage active sites. The entire process uses an aqueous reaction system, avoiding the use of organic solvents, and there are no toxic gas emissions during the annealing process; the tail gas generated during the phosphating process meets environmental protection requirements after effective treatment.
[0017] Optionally, the nickel source compound is nickel nitrate hexahydrate, and the molar ratio of sodium citrate to nickel nitrate hexahydrate is (1.5-2):1. Nickel nitrate hexahydrate is chosen as the nickel source because of its high solubility in water, which helps to provide stable Ni. 2+ Nitrate ions, and nitrate ions can decompose into gas and escape during subsequent annealing, thereby reducing the introduction of impurities. Sodium citrate acts as a complexing agent, reacting with Ni through the carboxyl group. 2+ Forming stable coordination bonds helps control the release rate of metal ions and reduces the risk of particle aggregation caused by rapid precipitation.
[0018] Regarding the raw material ratio, the molar ratio of sodium citrate to nickel nitrate hexahydrate should be controlled at (1.5-2):1. This range is primarily based on the following considerations: an appropriate excess of sodium citrate helps ensure sufficient coordination of nickel ions, forming a stable complex to reduce hydrolysis and precipitation; if the ratio is too high, it may lead to an increase in residual carbon during subsequent annealing, potentially affecting the material's conductivity; if the ratio is too low, insufficient coordination of nickel ions may increase the risk of precursor inhomogeneity.
[0019] In terms of operation, when dissolving sodium citrate and nickel source compound in deionized water and stirring to form the first solution, the stirring time can be set to 30-60 minutes to promote the full dissolution of sodium citrate and nickel nitrate hexahydrate, ensure that the two are uniformly mixed at the molecular level, provide a stable ionic environment for subsequent coordination reactions, and reduce the problem of uneven crystal growth caused by excessively high local concentrations.
[0020] Optionally, the cobalt source compound is potassium hexacyanocobaltate, and the molar ratio of sodium citrate to potassium hexacyanocobaltate is (2.2-2.6):1. Using potassium hexacyanocobaltate as the cobalt source is advantageous because its cyano ligand has strong coordination ability, which helps to form a stable complex with cobalt ions, and it is easily decomposed during subsequent annealing, reducing harmful residues. Preferably, the molar ratio of sodium citrate to potassium hexacyanocobaltate is 2.4:1. An appropriate excess of sodium citrate helps to ensure sufficient complexation of cobalt ions and reduce free Co. 3+ This reduces the risk of heterogeneous phase formation; simultaneously, the release rate of metal ions can be regulated through the synergistic effect of carboxyl and cyano ligands, facilitating subsequent interaction with Ni in the first solution. 2+ The coordination reaction provides a uniform ionic environment, avoiding excessive accumulation of cyano ligands and complying with experimental safety procedures.
[0021] When preparing the second solution, sodium citrate and potassium hexacyanocobaltate are dissolved in deionized water and stirred for 30-60 minutes to promote the full dissolution of the solutes and reduce the problem of uneven crystal growth caused by excessively high local concentrations.
[0022] Optionally, after mixing the first and second solutions, the mixture should be stirred for 15-30 minutes to allow for a thorough reaction, ensuring uniform contact between the nickel and cobalt sources in the sodium citrate coordination system. This facilitates the formation of a nickel-cobalt modified Prussian blue nanocube precursor through a synergistic coordination reaction. After stirring, the mixture is allowed to stand overnight at room temperature. This slow self-assembly process promotes the orderly growth of the nanocube structure and reduces crystal defects. The precipitate is then collected by centrifugation and washed 3-5 times alternately with deionized water and ethanol to remove unreacted free ions and residual organic matter, improving the precursor purity. Finally, the precipitate is dried in a vacuum oven at 60-65°C for 10-12 hours. The vacuum environment lowers the solvent boiling point, preventing precursor oxidation while achieving rapid dehydration, laying the foundation for the uniform formation of the carbon framework during subsequent annealing.
[0023] By combining the processes of "stirring and mixing - static self-assembly - separation and purification - vacuum drying", the morphology and structural uniformity of the precursor can be effectively controlled: too short a stirring time may lead to insufficient coordination of metal ions and the generation of amorphous impurities; insufficient static time will result in incomplete growth of nanocubes, affecting the integrity of the 3D carbon framework after subsequent annealing; and strict washing and drying conditions can prevent residual impurities from generating gas cracks during high-temperature treatment, ensuring the stability of the electrochemical performance of the final material.
[0024] Optionally, the annealing temperature is 390-400℃, such as 390℃, 395℃, 400℃, or any value between 390-400℃. The holding time is 2-2.5 hours, such as 2 hours, 2.2 hours, 2.5 hours, or any value between 2-2.5 hours. Controlling the annealing temperature at 390-400℃ ensures that the organic ligands (such as sodium citrate and cyano groups) in the precursor (nickel-cobalt modified Prussian blue nanocubes) are completely decomposed into gases such as CO2 and H2O, while promoting the uniform dispersion of nickel and cobalt ions and the formation of a stable nickel-cobalt@modified nano-carbon skeleton with carbon. If the temperature is too high, the carbon skeleton may become too graphitized, reducing porosity; if the temperature is too low, the organic ligands will not decompose completely, and residual impurities will affect the conductivity of the material. Holding for 2-2.5 hours ensures that the reaction proceeds fully, resulting in a stable structure and uniform particle size of the nickel-cobalt@modified nano-carbon skeleton.
[0025] Optionally, the annealing treatment needs to be carried out in an inert atmosphere, which can be nitrogen or argon. An inert atmosphere isolates the precursor from air, preventing oxidation at high temperatures (avoiding the conversion of nickel and cobalt ions into insulating impurities such as NiO and Co3O4), while providing a stable environment for the decomposition of organic ligands. It also prevents oxidizing gases (such as oxygen) from reacting with the carbon skeleton to generate byproducts such as CO, ensuring the integrity of the 3D framework structure and laying a pure precursor foundation for the subsequent gas-phase phosphating reaction.
[0026] Optionally, the phosphorus source is hypophosphite powder, with a mass ratio of 10:1 between hypophosphite powder and nickel-cobalt@modified nano-carbon powder. Hypophosphite powder is chosen as the phosphorus source because it easily decomposes at high temperatures to produce PH3 gas, which can undergo a gas-phase phosphating reaction with the nickel-cobalt@modified nano-carbon framework, achieving uniform doping of phosphorus. The decomposition products of hypophosphite are pollution-free, and the phosphorus content is easy to control. The 10:1 mass ratio ensures sufficient phosphating of nickel and cobalt to form high-purity nickel phosphide. Insufficient hypophosphite will result in incomplete reaction, leading to residual metal elements and reducing the electrochemical performance of the material.
[0027] Optionally, the gas-phase phosphating reaction needs to be carried out in an inert atmosphere (such as nitrogen). An inert atmosphere can effectively isolate air, prevent the nickel-cobalt@modified nano-carbon skeleton and phosphating products from oxidizing at high temperatures, and at the same time provide a stable environment for uniform contact between PH3 gas and nickel-cobalt@modified nano-carbon skeleton, avoid interference from oxidizing gases in the reaction process, and ensure the directional progress of the phosphating reaction.
[0028] Optionally, in the gas-phase phosphating reaction, the inert atmosphere gas flow rate is 100-110 sccm, such as any value between 100 sccm, 105 sccm, 110 sccm, or 100-110 sccm. The heating rate is 3-4℃ / min, such as any value between 3℃ / min, 3.5℃ / min, 4℃ / min, or 3-4℃ / min. After heating to 400-410℃, the temperature is held for 2-2.5 hours. Controlling the gas flow rate can both remove air to prevent oxidation and ensure that the PH3 gas flows uniformly through the reaction area to improve the uniformity of phosphating; the heating rate of 3-4℃ / min can avoid structural breakage caused by a sudden temperature rise; the reaction temperature of 400-410℃ provides better thermodynamic conditions for nickel phosphide formation; and holding for 2-2.5 hours ensures complete reaction.
[0029] Secondly, a lithium-ion battery anode material is provided, wherein the anode material is cobalt phosphide / nickel phosphide@nanocarbon prepared by the above-mentioned preparation method. In the anode material, cobalt phosphide and nickel phosphide jointly contribute to high specific capacity and form a highly conductive network; the nanocarbon framework effectively alleviates volume expansion and further improves the conductivity of the electrode.
[0030] Optionally, the cobalt phosphide / nickel phosphide@carbon nanoparticles have a 3D carbon framework structure with a particle size of 100-150 nanometers. The 3D carbon framework structure is formed through precursor annealing and vapor-phase phosphating. The particle size is controlled within this range of 100-150 nanometers, which balances the material's specific surface area and structural stability: excessively small particle size easily leads to agglomeration, reducing ion diffusion efficiency; excessively large particle size prolongs the electron transport path, affecting rate performance.
[0031] Thirdly, a lithium-ion battery, wherein the negative electrode of the lithium-ion battery comprises cobalt phosphide / nickel phosphide@nanocarbon prepared by the above preparation method.
[0032] Optionally, the negative electrode adopts a double-layer coating structure. The active component of the lower coating is the cobalt phosphide / nickel phosphide@nanocarbon negative electrode material, and the active component of the upper coating is graphite. In the entire active material of the negative electrode coating, the mass ratio of the lower active material to the upper active material is 2.3:96.4. The lower layer uses high-capacity cobalt phosphide / nickel phosphide@nanocarbon material to provide high energy density; the upper layer uses graphite, which utilizes its good cycle stability and low volume expansion characteristics to protect the lower material and improve interfacial contact.
[0033] Fourthly, an electrical device comprising the aforementioned lithium-ion battery. Specifically, the electrical device may be an electric vehicle, an electric bicycle, an energy storage power station, a drone, a portable electronic device, etc.
[0034] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art:
[0035] 1. This application utilizes a three-step method—coordination assembly, pyrolysis to carbon formation, and gas-phase phosphating—to construct a composite structure of "nickel phosphide particles, cobalt phosphide nanoparticles, and a 3D carbon coating framework," achieving a synergistic improvement in both high capacity and cycling stability. The 3D carbon framework effectively mitigates volume expansion during electrochemical reactions, the nitrogen-doped carbon network shortens the Li⁺ diffusion path, and the heterostructure provides abundant lithium storage sites, solving the problems of rapid cycle decay and insufficient conductivity in traditional high-capacity materials.
[0036] 2. The preparation method of this application uses an aqueous reaction system throughout, avoiding the use of organic solvents. No toxic gases are emitted during the annealing process; the tail gas generated during the phosphating process is effectively treated to meet environmental protection requirements. All key parameters (such as annealing temperature and phosphating gas flow rate) are precisely controllable, ensuring batch-to-batch product stability and reducing the difficulty of large-scale production.
[0037] 3. The negative electrode adopts a double-layer coating structure, with the lower high-capacity material and the upper graphite layer working synergistically. This allows for direct adaptation to existing lithium-ion battery manufacturing processes without requiring major modifications to the production line. The material is suitable for various electrical devices such as electric vehicles, energy storage power stations, and portable electronic devices, and has broad market application prospects.
[0038] 4. Compared with the prior art, the negative electrode material prepared by this invention has made breakthroughs in specific capacity, cycle life and rate performance, which can improve the energy density of the battery cell while ensuring long-term stability, and provide key material support for high-endurance and high-power devices.
[0039] To make the above and other objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description
[0040] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0041] Figure 1 This embodiment of the invention uses transmission electron microscopy to analyze cobalt phosphide / nickel phosphide@nano carbon. Detailed Implementation
[0042] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.
[0043] In a first aspect, embodiments of the present invention provide a method for preparing a lithium-ion battery anode material, comprising the following steps:
[0044] S101, Preparation of the first solution and the second solution
[0045] Specifically, sodium citrate and a nickel source compound are dissolved in deionized water and stirred to form a first solution. Sodium citrate and a cobalt source compound are dissolved in deionized water and stirred to form a second solution.
[0046] In an optional embodiment, the nickel source compound is nickel nitrate hexahydrate, and the molar ratio of sodium citrate to nickel nitrate hexahydrate is (1.5-2):1. Preferably, the molar ratio of sodium citrate to nickel nitrate hexahydrate is 3:2. Within the above ratio range, a slight excess of sodium citrate helps ensure sufficient coordination of nickel ions, forming a stable complex to reduce hydrolysis precipitation. Nickel nitrate hexahydrate is chosen as the nickel source because of its high solubility in water, which helps to provide stable Ni. 2+ Nitrate ions, and nitrate ions can decompose into gas and escape during subsequent annealing, thereby reducing the introduction of impurities. Sodium citrate acts as a complexing agent, reacting with Ni through the carboxyl group. 2+ Forming stable coordination bonds helps control the release rate of metal ions and reduces the risk of particle aggregation caused by rapid precipitation.
[0047] In an optional embodiment, during the preparation of the first solution, when sodium citrate and the nickel source compound are dissolved in deionized water and stirred to form the first solution, the stirring time can be set to 30-60 minutes to promote the full dissolution of sodium citrate and nickel nitrate hexahydrate, ensure that the two are uniformly mixed at the molecular level, provide a stable ionic environment for subsequent coordination reactions, and reduce the problem of uneven crystal growth caused by excessively high local concentrations.
[0048] In an optional embodiment, the cobalt source compound is potassium hexacyanocobalaminate, and the molar ratio of sodium citrate to potassium hexacyanocobalaminate is (2.2-2.6):1. Preferably, the molar ratio of sodium citrate to potassium hexacyanocobalaminate is 12:5. Within the above ratio range, a suitable excess of sodium citrate helps to ensure sufficient complexation of cobalt ions and reduce free Co. 3+ This reduces the risk of heterogeneous phase formation; simultaneously, the release rate of metal ions can be regulated through the synergistic effect of carboxyl and cyano ligands, facilitating subsequent interaction with Ni in the first solution. 2+ The coordination reaction provides a uniform ionic environment. Excessive accumulation of cyano ligands is avoided, complying with experimental safety protocols. Potassium hexacyanocobalaminate is chosen as the cobalt source because its cyano ligands have strong coordination ability, facilitating the formation of stable complexes with cobalt ions, and are easily decomposed during subsequent annealing, reducing harmful residues.
[0049] In an optional embodiment, when preparing the second solution, sodium citrate and potassium hexacyanocobaltate are dissolved in deionized water and stirred for 30-60 minutes, such as any value between 30, 40, 50, and 60 minutes. Stirring promotes the complete dissolution of sodium citrate and potassium hexacyanocobaltate, reducing the problem of uneven crystal growth caused by excessively high local concentrations.
[0050] S102, Preparation of precursor
[0051] Specifically, the first solution and the second solution are mixed, stirred, allowed to stand, separated, and dried to obtain the precursor.
[0052] In one optional embodiment, the first solution and the second solution are first mixed. After mixing, the mixture is stirred for 15-30 minutes, such as any value between 15, 20, 25, 30 minutes, or 15-30 minutes. Stirring ensures a thorough reaction, allowing the nickel and cobalt sources to contact uniformly in the sodium citrate coordination system, forming a nickel-cobalt modified Prussian blue nanocube precursor through a synergistic coordination reaction.
[0053] In an optional embodiment, after stirring, the mixed solution formed by mixing the first and second solutions is allowed to stand overnight at room temperature. This allows for the slow self-assembly process, promoting the orderly growth of nanocube structures and reducing crystal defects. The precipitate is then collected by centrifugation and washed alternately with deionized water and ethanol 3-5 times to remove unreacted free ions and residual organic matter, improving precursor purity. Finally, the precipitate is dried in a vacuum drying oven at 60-65°C for 10-12 hours. The vacuum environment lowers the solvent boiling point, achieving rapid dehydration while preventing precursor oxidation, laying the foundation for the uniform formation of the carbon framework during subsequent annealing.
[0054] S103, Preparation of Nickel-Cobalt@Modified Nanocarbon Framework
[0055] Specifically, the precursor is annealed in an inert atmosphere to prepare nickel-cobalt@modified nano-carbon framework.
[0056] In one optional embodiment, the annealing temperature is 390-400℃, such as 390℃, 395℃, 400℃, or any value between 390-400℃. The holding time is 2-2.5 hours, such as 2 hours, 2.2 hours, 2.5 hours, or any value between 2-2.5 hours. Controlling the annealing temperature at 390-400℃ ensures that the organic ligands (such as sodium citrate and cyano groups) in the precursor (nickel-cobalt modified Prussian blue nanocubes) are completely decomposed into gases such as CO2 and H2O, while promoting uniform dispersion of nickel and cobalt ions and the formation of a stable nickel-cobalt@modified nano-carbon skeleton with carbon. If the temperature is too high, the carbon skeleton may become too graphitized, reducing porosity; if the temperature is too low, the organic ligands will not decompose completely, and residual impurities will affect the conductivity of the material. Holding for 2-2.5 hours ensures that the reaction proceeds fully, resulting in a stable structure and uniform particle size of the nickel-cobalt@modified nano-carbon skeleton.
[0057] In an optional embodiment, the annealing process is performed in an inert atmosphere, which can be nitrogen or argon. An inert atmosphere isolates the precursor from air, preventing oxidation at high temperatures (avoiding the conversion of nickel and cobalt ions into insulating impurities such as NiO and Co3O4), while providing a stable environment for the decomposition of organic ligands. This prevents oxidizing gases (such as oxygen) from reacting with the carbon skeleton to generate byproducts such as CO, ensuring the integrity of the 3D framework structure and laying a pure precursor foundation for subsequent gas-phase phosphating reactions.
[0058] S104, Preparation of cobalt phosphide / nickel phosphide@carbon nano-anode materials
[0059] Specifically, the nickel-cobalt@modified nano-carbon framework is subjected to a gas-phase phosphating reaction with a phosphorus source in an inert atmosphere to obtain cobalt phosphide / nickel phosphide@nano-carbon anode material.
[0060] In an optional embodiment, the phosphorus source is hypophosphite powder, with a mass ratio of 10:1 between hypophosphite powder and nickel-cobalt@modified nano-carbon powder. Hypophosphite powder is chosen as the phosphorus source because it readily decomposes at high temperatures to produce PH3 gas, which can undergo a gas-phase phosphating reaction with the nickel-cobalt@modified nano-carbon framework, achieving uniform phosphorus doping. Furthermore, the decomposition products of hypophosphite are pollution-free, and the phosphorus content is easily controlled. The 10:1 mass ratio ensures sufficient phosphating of nickel and cobalt to form high-purity nickel phosphide. Insufficient hypophosphite will result in incomplete reaction, leading to residual metal elements and reducing the electrochemical performance of the material.
[0061] In an optional embodiment, the gas-phase phosphating reaction is carried out in an inert atmosphere (such as nitrogen). An inert atmosphere effectively isolates the air, preventing the nickel-cobalt@modified nanocarbon skeleton and phosphating products from oxidizing at high temperatures. Simultaneously, it provides a stable environment for uniform contact between PH3 gas and the nickel-cobalt@modified nanocarbon skeleton, avoiding interference from oxidizing gases and ensuring the directional conduction of the phosphating reaction.
[0062] In an optional embodiment, during the gas-phase phosphating reaction, the inert atmosphere gas flow rate is 100-110 sccm, such as 100 sccm, 105 sccm, 110 sccm, or any value between 100-110 sccm. The heating rate is 3-4 °C / min, such as 3 °C / min, 3.5 °C / min, 4 °C / min, or any value between 3-4 °C / min. After heating to 400-410 °C, the temperature is held for 2-2.5 hours. Controlling the gas flow rate both removes air to prevent oxidation and ensures that the PH3 gas flows uniformly through the reaction zone to improve phosphating uniformity; the heating rate of 3-4 °C / min avoids structural breakage caused by a sudden temperature rise; the reaction temperature of 400-410 °C provides optimal thermodynamic conditions for nickel phosphide formation; and holding for 2-2.5 hours ensures complete reaction. The exhaust gas generated by the gas-phase phosphating reaction needs to be absorbed and treated by passing it through an alkaline potassium permanganate solution or a dedicated exhaust gas treatment device to ensure operational safety and environmental friendliness.
[0063] This application's preparation method achieves precise control over the structure and performance of the anode material through a three-step process: coordination assembly, pyrolysis to carbon, and gas-phase phosphating. In the precursor preparation stage, the coordination and self-assembly of sodium citrate ensures the uniformity of the nanocubic structure. The 3D carbon framework formed during annealing provides a stable matrix for subsequent reactions. The gas-phase phosphating process, controlled by parameters such as gas flow rate and heating rate, achieves synergistic loading of nickel phosphide and cobalt phosphide nanoparticles. The entire process is controllable and environmentally friendly. The resulting cobalt phosphide / nickel phosphide@carbon nanomaterials possess high specific capacity, excellent cycle stability, and good conductivity, making them directly compatible with existing lithium-ion battery double-layer coating processes and providing a feasible path for the large-scale production of high-energy-density batteries.
[0064] Secondly, a lithium-ion battery anode material is provided, wherein the anode material is cobalt phosphide / nickel phosphide@nanocarbon prepared by the above-mentioned preparation method. In the anode material, cobalt phosphide and nickel phosphide jointly contribute to high specific capacity and form a highly conductive network; the nanocarbon framework effectively alleviates volume expansion and further improves the conductivity of the electrode.
[0065] In one optional embodiment, the cobalt phosphide / nickel phosphide@carbon nanoparticles have a 3D carbon framework structure with a particle size of 100-150 nanometers. The 3D carbon framework structure is formed through precursor annealing and a gas-phase phosphating reaction, with its particle size controlled within the 100-150 nanometer range. This size range balances the material's specific surface area and structural stability: excessively small particle sizes easily lead to agglomeration, reducing ion diffusion efficiency; excessively large particle sizes lengthen the electron transport path, affecting rate performance.
[0066] Thirdly, a lithium-ion battery, wherein the negative electrode of the lithium-ion battery comprises cobalt phosphide / nickel phosphide@nanocarbon prepared by the above preparation method.
[0067] In one optional embodiment, the negative electrode employs a double-layer coating structure. The active component of the lower coating is the cobalt phosphide / nickel phosphide@nanocarbon negative electrode material, and the active component of the upper coating is graphite. The mass ratio of the lower active material to the upper active material in the entire negative electrode coating is 2.3:96.4. The lower layer uses high-capacity cobalt phosphide / nickel phosphide@nanocarbon material to provide high energy density; the upper layer uses graphite, utilizing its good cycle stability and low volume expansion characteristics to protect the lower material and improve interfacial contact.
[0068] Fourthly, an electrical device comprising the aforementioned lithium-ion battery. Specifically, the electrical device may be an electric vehicle, an electric bicycle, an energy storage power station, a drone, a portable electronic device, etc.
[0069] The embodiments of the present invention employ the following testing methods to test the relevant performance:
[0070] Microstructure characterization: The microstructure of cobalt phosphide / nickel phosphide@carbon nanoparticles was observed by transmission electron microscopy (TEM, Tecnai F30) to clarify the particle size of the 3D carbon coating framework, the carbon layer encapsulation state, and the anchoring of nickel phosphide particles on cobalt phosphide nanoparticles.
[0071] Electrical performance testing: Charge and discharge tests were conducted using the Blue Battery Testing System. The test conditions were a charge / discharge range of 2.0-4.5V and a charge rate of 0.5C. The focus was on evaluating the 0.5C capacity and the capacity retention rate after 500 cycles at room temperature.
[0072] The features and performance of the present invention will be further described in detail below with reference to embodiments.
[0073] Example 1: A method for preparing a lithium-ion battery anode material, comprising the following steps:
[0074] S101, Preparation of the first solution and the second solution
[0075] Dissolve 4.8 mmol of sodium citrate and 3.2 mmol of nickel nitrate hexahydrate in 65 mL of deionized water and stir for 30 minutes to form a homogeneous first solution.
[0076] Dissolve 4.8 mmol of sodium citrate and 2 mmol of potassium hexacyanocobaltate in 35 mL of deionized water and stir for 30 minutes to form a homogeneous second solution.
[0077] S102, Preparation of precursor
[0078] The first and second solutions were mixed and stirred for 15 minutes, then the resulting mixture was allowed to stand overnight at room temperature. The product was then collected by centrifugation and washed several times with deionized water and ethanol. Finally, the precipitate was dried at 60°C for 12 hours to obtain the precursor.
[0079] S103, Preparation of Nickel-Cobalt@Modified Nanocarbon Framework
[0080] The obtained precursor was annealed in nitrogen at 400°C for 2 hours to prepare nickel-cobalt@modified nano-carbon framework.
[0081] S104, Preparation of cobalt phosphide / nickel phosphide@carbon nano-anode materials
[0082] 450 mg of hypophosphite powder and 45 mg of nickel-cobalt@modified nanocarbon framework powder were evenly sprinkled on a quartz boat and transferred to a tube furnace. The nickel-cobalt@modified nanocarbon framework powder was located on the downstream side of the tube furnace, and the hypophosphite powder was located on the upstream side. Under a nitrogen atmosphere with a gas flow rate of 100 sccm, the temperature was increased to 400 °C at a heating rate of 3 °C / min and held for 2 hours, then cooled to room temperature to obtain cobalt phosphide / nickel phosphide@nanocarbon anode material.
[0083] Comparative Example 1:
[0084] Prussian blue (Sigma-Aldrich, 99.9% analytical grade) was directly selected as the negative electrode material.
[0085] Comparative Example 2:
[0086] Silicon-carbon (Sigma-Aldrich, 99.9% analytical grade) was directly selected as the anode material.
[0087] Example of detection:
[0088] The performance of the negative electrode materials of Example 1 and Comparative Examples 1 and 2 was tested.
[0089] Battery formulation: Positive electrode (16.0 mg / cm² per side) 2 It is composed of LFP, Super P, PVDF 5130 and CNT in a weight ratio of 96:1.8:1.7:0.5; the negative electrode is coated (10.1 mg / cm² per layer). 2 The battery employs a double-layer coating structure, consisting of graphite, the aforementioned negative electrode material from the examples / comparative examples, LA136D, Super P, and CMC mixed in a weight ratio of 96.4:2.3:0.9:0.4. The upper layer is graphite, and the lower layer is the negative electrode material from the examples / comparative examples, with an overall N / P ratio controlled at 1.13. The electrolyte is 1 M LiPF6 / EC:EMC (volume ratio 3:7), the separator is a ceramic-coated polyethylene film, and the negative electrode current collector is a 6.0 μm thick copper foil. Charge-discharge tests were conducted on the Blue Battery testing system, with a test range of 2.0-4.5V and a charge rate of 0.5C.
[0090] See Figure 1 As shown, the microstructure of cobalt phosphide / nickel phosphide@carbon nanoparticles was characterized by transmission electron microscopy (TEM, Tecnai F30). The results showed that it has a 3D carbon-coated framework structure with a particle size of approximately 120 nm, with a thin carbon layer encapsulating the surface of each individual particle. This structure can effectively alleviate the volume expansion of nickel phosphide particles during electrochemical reactions and improve electron / ion conduction efficiency. High-resolution TEM images further confirmed that nickel phosphide particles and cobalt phosphide nanoparticles are intercalated, and the two work together to provide high lithium storage active sites.
[0091] The performance test results are shown in the table below:
[0092] Test item Example 1 Comparative Example 1 Comparative Example 2 0.5 C gravimetric capacity 530 mAh / g 325 mAh / g 487 mAh / g 0.5 C ambient temperature cycling 96% / 500 cycles 88% / 500 cycles 92% / 500 cycles
[0093] The results show that, using a double-layer coating technique, the anode material with the material from Example 1 as the lower layer exhibits a high specific capacity of 530 mAh / g, significantly superior to Prussian blue (325 mAh / g) and silicon-carbon (487 mAh / g). Simultaneously, its cycle stability (96%@500 cycles) is better than that of silicon-carbon (92%@500 cycles) and Prussian blue (88%@500 cycles). This is attributed to the mitigating effect of the 3D carbon framework on volume expansion and the high stability of the heterostructure, verifying the synergistic advantages of this anode material in improving energy density and cycle performance.
[0094] Specific embodiments have been used to illustrate the principles and implementation methods of this invention. The descriptions of the embodiments above are only for the purpose of helping to understand the method and core ideas of this invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this invention. Therefore, the content of this specification should not be construed as a limitation of this invention.
Claims
1. A method for preparing a lithium-ion battery anode material, characterized in that, Includes the following steps: Sodium citrate and a nickel source compound were dissolved in deionized water and stirred to form a first solution; Sodium citrate and a cobalt source compound were dissolved in deionized water and stirred to form a second solution; The first and second solutions are mixed, stirred, allowed to stand, separated, and dried to obtain the precursor. The precursor was annealed in an inert atmosphere to prepare a nickel-cobalt@modified nano-carbon framework. The nickel-cobalt@modified nano-carbon framework was subjected to a gas-phase phosphating reaction with a phosphorus source in an inert atmosphere to obtain cobalt phosphide / nickel phosphide@nano-carbon anode material.
2. The preparation method according to claim 1, characterized in that, The nickel source compound is nickel nitrate hexahydrate, and the molar ratio of sodium citrate to nickel nitrate hexahydrate is (1.5-2):
1.
3. The preparation method according to claim 1, characterized in that, The cobalt source compound is potassium hexacyanocobalaminate, and the molar ratio of sodium citrate to potassium hexacyanocobalaminate is (2.2-2.6):
1.
4. The preparation method according to claim 1, characterized in that, The drying process involves vacuum drying at 60-65℃ for 10-12 hours.
5. The preparation method according to claim 1, characterized in that, The annealing temperature is 390-400℃, and the holding time is 2-2.5 hours.
6. The preparation method according to claim 1, characterized in that, The phosphorus source is hypophosphite powder, and the mass ratio of hypophosphite powder to nickel-cobalt@modified nano-carbon powder is 10:
1.
7. The preparation method according to claim 1, characterized in that, In the gas-phase phosphating reaction, the inert atmosphere has a gas flow rate of 100-110 sccm, a heating rate of 3-4℃ / min, and is heated to 400-410℃ and then held for 2-2.5 hours.
8. A lithium-ion battery anode material, characterized in that, The negative electrode material is cobalt phosphide / nickel phosphide@nano carbon prepared by the preparation method according to any one of claims 1-7.
9. The negative electrode material according to claim 8, characterized in that, The cobalt phosphide / nickel phosphide@carbon nanoparticles have a 3D carbon framework structure with a particle size of 100-150 nanometers.
10. A lithium-ion battery, characterized in that, The negative electrode of the lithium-ion battery comprises cobalt phosphide / nickel phosphide@nano carbon prepared by the preparation method according to any one of claims 1-7.
11. The lithium-ion battery according to claim 10, characterized in that, The negative electrode adopts a double-layer coating structure. The active component of the lower coating is the cobalt phosphide / nickel phosphide@nano-carbon negative electrode material, and the active component of the upper coating is graphite. In the active material of the entire negative electrode coating, the mass ratio of the lower active material to the upper active material is 2.3:96.
4.
12. An electrical appliance, characterized in that, The electrical device includes the lithium-ion battery as described in any one of claims 10-11.