Nitrogen-doped graphene nano-metal negative electrode material and preparation method thereof, battery negative electrode and battery

Abstract

The invention provides a nitrogen-doped graphene nano-metal negative electrode material and a preparation method thereof, a battery negative electrode and a battery. The preparation method comprises the following steps: mixing graphene with a nitrogen source, and performing high-temperature pyrolysis to obtain nitrogen-doped graphene; nano metal particles and the nitrogen-doped graphene are mixed, an organic solvent and a binder solution are added, and slurry is obtained; and coating a substrate with the slurry, and drying to obtain the nitrogen-doped graphene nano-metal negative electrode material attached to the substrate. The nitrogen-doped graphene nano-metal negative electrode material provided by the invention has a larger specific surface area and lower resistance, especially has excellent electrochemical performance for high current density, and can keep higher coulombic efficiency in a long period.

Description

Technical Field

[0001] This invention belongs to the field of lithium battery technology, specifically relating to a nitrogen-doped graphene nanometal anode material and its preparation method, as well as a battery anode and a battery. Background Technology

[0002] The theoretical specific capacity of traditional graphite anodes is 372 mAh / g. After years of research and optimization, their actual specific capacity has approached the theoretical value, leaving limited room for further improvement. With the increasing demand for high-energy-density batteries in portable electronic devices, electric vehicles, and other fields, the energy density of graphite anodes is insufficient to meet the requirements of long-lasting and miniaturized devices. Furthermore, in applications with extremely high energy density requirements, such as drones and electric aircraft, the low energy density of graphite anodes prevents batteries from providing enough energy to support long-term operation, thus limiting technological development in these areas.

[0003] Lithium metal anodes have a much higher specific capacity than graphite anodes. Batteries using lithium metal anodes can store more energy in a lighter and smaller volume, significantly improving battery energy density. Furthermore, the low electrochemical potential of lithium metal anodes helps increase the battery's output voltage, further increasing energy density and extending device battery life. However, lithium metal batteries also face a series of problems, such as lithium dendrite growth, poor interface compatibility, and significant volume changes, which seriously hinder their development.

[0004] Therefore, how to provide a negative electrode material with better electrochemical performance and cycle life is an urgent problem to be solved. Summary of the Invention

[0005] To address the aforementioned technical problems, the present invention aims to provide a nitrogen-doped graphene nanomaterial anode, its preparation method, a battery anode, and a battery. This nitrogen-doped graphene nanomaterial anode achieves high conductivity and exhibits good stability.

[0006] To achieve the above objectives, the present invention provides a method for preparing nitrogen-doped graphene nanometal anode materials, wherein the preparation method includes:

[0007] S1. Graphene is mixed with a nitrogen source and subjected to high-temperature pyrolysis to obtain nitrogen-doped graphene.

[0008] S2. Mix the nano-metal particles with the nitrogen-doped graphene, and add an organic solvent and a binder solution to obtain a slurry;

[0009] S3. The slurry is coated onto the substrate and dried to obtain a nitrogen-doped graphene nanometal anode material attached to the substrate.

[0010] The mass ratio of graphene to nitrogen source is (1-10): (0.1-1); the mass ratio of nano-metal particles to nitrogen-doped graphene is (0.1-1): (1-10).

[0011] In some specific embodiments, preferably, the mass ratio of graphene to nitrogen source is (1-2):(0.1-0.5), more preferably 1:0.1.

[0012] In some specific embodiments, preferably, the mass ratio of the nano-metal particles to nitrogen-doped graphene is (0.5-1):(1-3), more preferably 1:3.

[0013] According to a specific embodiment of the present invention, preferably, the particle size of the nano-metal particles is 20-500 nm, more preferably 20-100 nm.

[0014] According to a specific embodiment of the present invention, preferably, the nano-metal particles include one or more of silver, gold, platinum, and rhodium, more preferably silver.

[0015] According to a specific embodiment of the present invention, preferably, the high-temperature pyrolysis temperature is 500-1000℃ and the high-temperature pyrolysis time is 0.5-4h; more preferably, the high-temperature pyrolysis temperature is 500-600℃ and the high-temperature pyrolysis time is 0.5-1h.

[0016] According to a specific embodiment of the present invention, preferably, the nitrogen source includes one or more of urea, melamine, nitrate, and amino acids; more preferably, it is urea.

[0017] In some specific embodiments, preferably, the graphene is prepared by the Hummers process using graphite as a raw material to produce graphene oxide, followed by reduction with a reducing agent (e.g., hydrazine hydrate). This invention uses graphene as the carbon framework for lithium-ion battery anode materials, which helps to construct a porous three-dimensional framework and provides high porosity (up to approximately 90%) and high lithium loading capacity (theoretical lithium loading capacity up to 30 mAh / cm³). 2 In addition, graphene sp 2 The hybrid structure exhibits excellent chemical inertness, ensuring long-term stability under complex and harsh electrochemical conditions.

[0018] According to a specific embodiment of the present invention, preferably, the organic solvent includes one or more of N-methylpyrrolidone, tetrahydrofuran, methanol, and acetone, more preferably N-methylpyrrolidone.

[0019] According to a specific embodiment of the present invention, preferably, the adhesive comprises one or more of polyvinylidene fluoride (PVDF), carboxymethyl cellulose (CMC), and lithium polyacrylate (PAALi), more preferably polyvinylidene fluoride.

[0020] According to a specific embodiment of the present invention, preferably, the amount of binder added is 5%-12% of the total mass of the nano-metal particles and nitrogen-doped graphene; more preferably, the concentration of the binder solution is 1wt%-10wt%, and the solvent is an organic solvent. Even more preferably, the solvent in the binder solution includes one or a combination of two or more of N-methylpyrrolidone, tetrahydrofuran, methanol, and acetone.

[0021] According to a specific embodiment of the present invention, preferably, in step S2, an organic solvent is added dropwise under stirring to dissolve the nano-metal particles and nitrogen-doped graphene in the organic solvent, and a binder solution is added dropwise under stirring to obtain a uniformly mixed slurry; more preferably, the stirring speed is 100-1000 r / min (more preferably 500-600 r / min), and the stirring time is 0.5-5 h.

[0022] In some specific implementations, preferably, the drying process involves first drying in air at 80-100°C for 20-40 minutes, and then drying in a vacuum at 100-120°C for 12-15 hours.

[0023] This invention also provides a nitrogen-doped graphene nanometal anode material, which is prepared by the above-described method. Preferably, the thickness of the nitrogen-doped graphene nanometal anode material on the substrate is 8-12 micrometers. The nitrogen-doped graphene nanometal anode material of this invention exhibits a long cycle life, effectively solving the problems of lithium dendrite growth, dead lithium stripping, and severe volume changes. Through the synergistic effect of nitrogen doping and nanometal, this anode material performs particularly well at high current densities, demonstrating practical commercial potential.

[0024] The present invention also provides a battery negative electrode, which is prepared from the above-mentioned nitrogen-doped graphene nanometal negative electrode material.

[0025] According to a specific embodiment of the present invention, preferably, the battery negative electrode is obtained by attaching the nitrogen-doped graphene nanomaterial to the surface of a copper foil and then cutting it. The diameter of the battery negative electrode is 10-16 mm.

[0026] The present invention also provides a battery, wherein the battery includes a positive electrode, a negative electrode, and an electrolyte, wherein the negative electrode is the negative electrode of the battery.

[0027] According to a specific embodiment of the present invention, preferably, the battery is a lithium battery.

[0028] According to a specific embodiment of the present invention, preferably, the electrolyte of the lithium battery includes a LiPF6 solution and / or a LiClO4 solution with a concentration of 0.5-2M, and the solvent of the electrolyte includes one or more of diethyl ether, propylene carbonate, and ethylene carbonate.

[0029] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0030] The method for preparing nitrogen-doped graphene nanometal anode material provided by this invention provides a foundation for the establishment of lithium deposition structure by selecting graphene carbon framework, thus establishing a three-dimensional conductive framework structure. Furthermore, by combining it with nanometal particles, it can provide induction sites for lithium deposition, promote lithium deposition on the surface of nanometal, reduce the risk of lithium dendrite formation, and greatly improve the safety and lithium capacity of lithium deposition. At the same time, the synergistic effect of nitrogen doping can significantly improve the conductivity of graphene, enhancing its conductivity and stability.

[0031] The nitrogen-doped graphene nanometal anode material provided by this invention has a larger specific surface area and lower resistance, and can exhibit higher electrochemical performance in lithium battery anodes, including higher specific capacity, fast charge and discharge capability and longer cycle life, especially under high current conditions, and can still maintain high coulombic efficiency over long periods of time. Attached Figure Description

[0032] Figure 1 The lithium batteries in Example 1 and Comparative Examples 1-2 are at 1 mA / cm 2 1 mAh / cm 2 The first charge-discharge diagram under the given conditions.

[0033] Figure 2 The lithium batteries in Example 1 and Comparative Examples 1-2 are at 1 mA / cm 2 1 mAh / cm 2 Charge and discharge diagrams under the specified conditions.

[0034] Figure 3 The lithium batteries in Example 1 and Comparative Examples 1-2 were at 3 mA / cm 2 1 mAh / cm 2 Charge and discharge diagrams under the specified conditions.

[0035] Figure 4 The lithium batteries in Example 1 and Comparative Examples 1-2 are at 1 mA / cm 2 Charge and discharge diagrams under varying deposition conditions.

[0036] Figure 5The images show the electrochemical impedance spectroscopy of the lithium batteries in Example 1 and Comparative Examples 1-2. Detailed Implementation

[0037] In order to provide a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention will now be described in detail below, but it should not be construed as limiting the scope of implementation of the present invention.

[0038] It should be noted that, unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0039] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0040] It should be understood that the terms “comprising,” “including,” and / or “containing” as used herein specify the presence of the stated features, integers, steps, components, or combinations thereof, but do not exclude the presence or addition of one or more other features, integers, steps, components, or combinations thereof.

[0041] The endpoints and any values ​​of the ranges disclosed in this invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this invention.

[0042] Example 1:

[0043] This embodiment provides a method for preparing nitrogen-doped graphene nanomaterials as a negative electrode, the specific steps of which are as follows:

[0044] S0. Using graphite as raw material, graphene oxide is prepared by the Hummers method. After reduction with hydrazine hydrate, filtration, washing and drying, graphene raw material is obtained.

[0045] S1. Mix graphene and urea at a mass ratio of 1:0.1, place them in a tube furnace, and pyrolyze them at a rate of 5℃ / min to 600℃ for 0.5h under a protective atmosphere of argon gas at 0.1 L / min. Then, cool them down and remove them to obtain nitrogen-doped graphene.

[0046] S2. Mix nano-silver powder (D50 = 100 nm) and nitrogen-doped graphene at a mass ratio of 1:3. During the mixing process, add NMP dropwise as a solvent with an equal weight of solids to promote mixing. Magnetic stirring is turned on during the mixing process, and the stirring speed is 500 r / min. Then, add NMP solution containing 5 wt% PVDF, controlling the amount of PVDF added to be 10% of the total mass of nano-metal particles and nitrogen-doped graphene. After the addition is completed, continue stirring until the resulting slurry is in a uniform and stable state. The stirring time is 0.5 h.

[0047] S3. The slurry is coated onto the surface of the copper foil using an automatic coating machine, and then dried in the air at 80°C for 20 minutes, followed by vacuum drying at 100°C for 12 hours to obtain a nitrogen-doped graphene nanometal anode material attached to the copper foil, namely the Ag-C nanocomposite layer, with a thickness of 10 micrometers.

[0048] This embodiment also provides a lithium battery, which is prepared using the negative electrode material prepared in this embodiment. The specific steps are as follows:

[0049] (1) Cutting; The copper foil with the above-mentioned negative electrode material attached is cut using a slicing machine to form a CR2032 button cell negative electrode with a diameter of 16 mm;

[0050] (2) Assemble the battery: Place the obtained negative electrode of the battery into the glove box and assemble it into a lithium battery with the positive electrode shell, separator, lithium sheet, gasket, spring sheet and negative electrode shell, and drop 200μL of electrolyte in the middle; wherein the electrolyte is a 1.0M LiPF6 diethyl ether solution.

[0051] Example 2:

[0052] This embodiment provides a method for preparing nitrogen-doped graphene nanomaterials as a negative electrode, the specific steps of which are as follows:

[0053] S0. Graphene raw material was prepared using the same method as step S0 in Example 1.

[0054] S1. Mix graphene and melamine in a mass ratio of 2:1, place them in a tube furnace, and pyrolyze them at a rate of 5℃ / min to 500℃ for 1 hour under a protective atmosphere of argon gas at 0.1 L / min. Then cool them down and remove them to obtain nitrogen-doped graphene.

[0055] S2. Mix nano-silver powder (D50 = 100nm) and nitrogen-doped graphene at a mass ratio of 1:1. During the mixing process, add an appropriate amount of tetrahydrofuran as a solvent to promote mixing, so that the solid-liquid ratio of the mixture is 1:1. Magnetic stirring is turned on during the mixing process, and the stirring speed is 500 r / min. Then, NMP solution containing 5wt% PVDF is added dropwise, and the amount of PVDF added is controlled to be 10% of the total mass of nano-metal particles and nitrogen-doped graphene. After the addition is completed, continue stirring until the resulting slurry is in a uniform and stable state. The stirring time is 1 hour.

[0056] S3. The slurry is coated onto the surface of the copper foil using an automatic coating machine, and then dried in the air at 80°C for 20 minutes, followed by vacuum drying at 100°C for 12 hours to obtain a nitrogen-doped graphene nanometal anode material attached to the copper foil, namely the Ag-C nanocomposite layer, with a thickness of 10 micrometers.

[0057] This embodiment also provides a lithium battery. The steps for preparing the battery are basically the same as those in Embodiment 1, except that the negative electrode material used is replaced with the negative electrode material prepared in this embodiment.

[0058] Example 3:

[0059] This embodiment provides a method for preparing nitrogen-doped graphene nanomaterials as a negative electrode, the specific steps of which are as follows:

[0060] S0. Graphene raw material was prepared using the same method as step S0 in Example 1.

[0061] S1. Graphene and lysine are mixed in a mass ratio of 1:1 and placed in a tube furnace. Under the protective atmosphere of argon gas at 0.1 L / min, the temperature is increased to 800℃ for 2 hours at a rate of 5℃ / min. The mixture is then cooled and removed to obtain nitrogen-doped graphene.

[0062] S2. Mix nano-silver powder (D50 = 100nm) and nitrogen-doped graphene at a mass ratio of 1:10. During the mixing process, add an appropriate amount of methanol as a solvent to promote mixing and make the solid-liquid ratio of the mixture 1:1. Magnetic stirring is turned on during the mixing process at a speed of 500 r / min. Then, NMP solution containing 5wt% PVDF is added dropwise, and the amount of PVDF added is controlled to be 10% of the total mass of nano-metal particles and nitrogen-doped graphene. After the addition is completed, continue stirring until the resulting slurry is in a uniform and stable state. The stirring time is 2h.

[0063] S3. The slurry is coated onto the surface of the copper foil using an automatic coating machine, and then dried in the air at 80°C for 20 minutes, followed by vacuum drying at 100°C for 12 hours to obtain a nitrogen-doped graphene nanometal anode material attached to the copper foil, namely the Ag-C nanocomposite layer, with a thickness of 10 micrometers.

[0064] This embodiment also provides a lithium battery. The steps for preparing the battery are basically the same as those in Embodiment 1, except that the negative electrode material used is replaced with the negative electrode material prepared in this embodiment.

[0065] Example 4:

[0066] This embodiment provides a method for preparing nitrogen-doped graphene nanomaterials as a negative electrode, the specific steps of which are as follows:

[0067] S0. Graphene raw material was prepared using the same method as step S0 in Example 1.

[0068] S1. Graphene and sodium nitrate were mixed in a mass ratio of 10:0.1 and placed in a tube furnace. Under the protective atmosphere of argon gas at 0.1 L / min, the temperature was increased to 1000℃ for 4 hours at a rate of 5℃ / min. The mixture was then cooled and removed to obtain nitrogen-doped graphene.

[0069] S2. Mix nano-silver powder (D50 = 100nm) and nitrogen-doped graphene at a mass ratio of 0.1:5. During the mixing process, add an appropriate amount of acetone as a solvent to promote mixing, so that the solid-liquid ratio of the mixture is 1:1. Magnetic stirring is turned on during the mixing process at a speed of 500 r / min. Then, NMP solution containing 5wt% PVDF is added dropwise, and the amount of PVDF added is controlled to be 10% of the total mass of nano-metal particles and nitrogen-doped graphene. After the addition is completed, continue stirring until the resulting slurry is in a uniform and stable state. The stirring time is 5h.

[0070] S3. The slurry is coated onto the surface of the copper foil using an automatic coating machine, and then dried in the air at 80°C for 20 minutes, followed by vacuum drying at 100°C for 12 hours to obtain a nitrogen-doped graphene nanometal anode material attached to the copper foil, namely the Ag-C nanocomposite layer, with a thickness of 10 micrometers.

[0071] This embodiment also provides a lithium battery. The steps for preparing the battery are basically the same as those in Embodiment 1, except that the negative electrode material used is replaced with the negative electrode material prepared in this embodiment.

[0072] Comparative Example 1:

[0073] This comparative example provides a method for preparing a negative electrode material. The negative electrode material is the graphene raw material prepared in step S0 of Example 1. It is not nitrogen-doped and is not combined with silver powder. The graphene raw material is directly mixed with NMP and NMP solution of 5wt% PVDF to obtain a slurry.

[0074] The remaining steps and parameters are consistent with those in Example 1, resulting in a negative electrode material attached to copper foil.

[0075] This comparative example also provides a lithium battery. The battery preparation steps are basically the same as those in Example 1, except that the negative electrode material used is replaced with the negative electrode material prepared in this comparative example.

[0076] Comparative Example 2:

[0077] This comparative example provides a method for preparing a negative electrode material, which is basically the same as the preparation process in Example 1, except that nitrogen doping is not performed.

[0078] Step S1 is omitted, and the nano-silver powder is directly mixed with graphene raw material. The remaining steps and parameters are consistent with those in Example 1 to obtain the negative electrode material attached to the copper foil.

[0079] This comparative example also provides a lithium battery. The battery preparation steps are basically the same as those in Example 1, except that the negative electrode material used is replaced with the negative electrode material prepared in this comparative example.

[0080] Comparative Example 3:

[0081] This comparative example provides a method for preparing a negative electrode material, which is basically the same as the preparation process in Example 1, except that it is not combined with silver powder.

[0082] In step S2, nitrogen-doped graphene is directly mixed with NMP and a 5wt% PVDF NMP solution to obtain a slurry; the remaining steps and parameters are consistent with those in Example 1 to obtain a negative electrode material attached to copper foil.

[0083] This comparative example also provides a lithium battery. The battery preparation steps are basically the same as those in Example 1, except that the negative electrode material used is replaced with the negative electrode material prepared in this comparative example.

[0084] Comparative Example 4:

[0085] This comparative example provides a method for preparing a negative electrode material, which is basically the same as the preparation process in Example 1, except that the ratio of graphene to nitrogen source is not suitable.

[0086] In step S1, the mass ratio of graphene to nitrogen source is adjusted to 1:0.01;

[0087] The remaining steps and parameters are consistent with those in Example 1, resulting in a negative electrode material attached to copper foil.

[0088] This comparative example also provides a lithium battery. The battery preparation steps are basically the same as those in Example 1, except that the negative electrode material used is replaced with the negative electrode material prepared in this comparative example.

[0089] Comparative Example 5:

[0090] This comparative example provides a method for preparing a negative electrode material, which is basically the same as the preparation process in Example 1, except that the ratio of nano-metal particles to nitrogen-doped graphene is not suitable.

[0091] In step S1, the mass ratio of nano-metal particles to nitrogen-doped graphene is adjusted to 1:30;

[0092] The remaining steps and parameters are consistent with those in Example 1, resulting in a negative electrode material attached to copper foil.

[0093] This comparative example also provides a lithium battery. The battery preparation steps are basically the same as those in Example 1, except that the negative electrode material used is replaced with the negative electrode material prepared in this comparative example.

[0094] Test Example 1:

[0095] This test example measures the specific surface area of ​​the negative electrode material in the above embodiments and comparative examples, as follows:

[0096] The specific surface area of ​​each negative electrode material sample was determined by BET gas adsorption method, and the results are shown in Table 1.

[0097] Table 1. Results of specific surface area measurement

[0098]

[0099] As shown in Table 1, the specific surface areas of Examples 1-4 are all higher than those of Comparative Examples 1-5. Comparative Example 1 has the lowest specific surface area, at only 217 m² / g, while Comparative Example 3 shows a slight increase compared to Comparative Example 1. This indicates that nitrogen doping can effectively expand the interlayer spacing of graphene, exposing more surface area, but the increase is small. The significantly increased specific surface areas of Examples 1-4 demonstrate that, based on nitrogen doping of graphene, the loading of silver nanoparticles can further expand the exposed surface, thereby increasing the space for lithium deposition. These results indicate that the examples successfully constructed an effective nitrogen-doped graphene-silver nanomaterial system, with Example 1 exhibiting the highest specific surface area, reaching 385 m² / g. 2 / g.

[0100] Test Example 2:

[0101] This test example measures the electrochemical performance of lithium batteries assembled with the negative electrode materials in the above embodiments and comparative examples, as detailed below:

[0102] The test used Wuhan Landian CT3004A, and the current and voltage were controlled by a program to test the battery performance.

[0103] Figure 1 The lithium batteries in Example 1, Comparative Example 1, and Comparative Example 2 are shown to operate at 1 mA / cm². 2 1 mAh / cm 2 The first charge and discharge performance under the conditions, by Figure 1 It can be seen that, due to the lack of a lithium storage platform at low potential in Comparative Example 1, the lithium storage capacity curve is mainly concentrated at the ramp end, indicating that it does not have the ability to adsorb lithium ions and form lithium deposition. In Comparative Example 2, after adding nano-silver to the anode material, the assembled lithium battery showed obvious lithium deposition and stripping platforms at low potential, proving that nano-silver had successfully attached to the graphene carbon framework, forming lithiophilic sites. However, the test results were still not as good as in Example 1. In contrast, the anode material prepared by combining nitrogen-doped graphene and nano-silver in Example 1 can further improve the lithium deposition performance of the lithium battery, thus exhibiting a higher lithium deposition platform capacity and reducing the generation of ineffective dead lithium.

[0104] Figure 2 The lithium batteries in Example 1, Comparative Example 1, and Comparative Example 2 were tested at 1 mA / cm². 2 1 mAh / cm 2 Performance after 100 cycles under certain conditions, by Figure 2 It can be seen that Comparative Example 1 exhibits the largest capacity fluctuation. This is because Comparative Example 1 only uses graphene to build a carbon framework, but graphene itself has poor affinity for lithium, thus easily leading to lithium deadness and capacity fluctuations. Adding silver as a lithium-affinity center in Comparative Example 2 significantly improves lithium battery performance and coulombic efficiency, but the overall coulombic efficiency is still lower than that of Example 1. In contrast, the anode material prepared by combining nitrogen-doped graphene with nano-silver in Example 1 has higher conductivity, which reduces the lithium transport barrier, thus exhibiting a higher coulombic efficiency of 99.8%.

[0105] Figure 3 The lithium batteries in Example 1, Comparative Example 1, and Comparative Example 2 were tested at 3 mA / cm². 2 1 mAh / cm 2 Performance after 100 cycles under certain conditions, by Figure 3It can be seen that under rapid deposition conditions, the performance of the anode material experienced more severe degradation and challenges. Comparative Example 1 showed drastic fluctuations and a downward trend during cycling, exhibiting significant degradation around cycle 90. Comparative Example 2, containing silver active centers, maintained stable battery cycling, but its overall coulombic efficiency was still lower than that of Example 1. Example 1, using nitrogen-doped graphene combined with nano-silver, achieved higher conductivity, further reducing deposition resistance and facilitating lithium deposition and stripping, while maintaining high coulombic efficiency even under rapid deposition.

[0106] Figure 4 The lithium batteries in Example 1, Comparative Example 1, and Comparative Example 2 were tested at 1 mA / cm². 2 The performance of 60 cycles under varying depositional conditions, from Figure 4 It can be seen that Example 1 has a very high lithium storage capacity, with the lithium level rising to 6 mAh / cm³. 2 Previously, Example 1 maintained fairly stable performance, indicating that the anode material prepared in Example 1 has a strong affinity for lithium and lithium storage capacity. When the lithium content exceeds 7 mAh / cm³, the performance remains stable. 2 At that time, the coulombic efficiency of Example 1 showed some fluctuation. This may be because at the lithium deposition concentration, the surface lithiophilic sites were completely covered by lithium, and a large number of them had already been deposited on the negative electrode support, leaving no new active sites exposed, thus resulting in a decrease in material performance. However, Comparative Examples 1 and 2 showed more drastic fluctuations at high rates, both far less stable than Example 1. Among them, Comparative Example 1 had the worst performance under high-rate testing conditions. The above results indicate that the present invention makes a significant contribution to the regulation of lithium deposition in graphene through nitrogen doping and the synergistic effect of composite with nano-silver.

[0107] Table 2 summarizes the battery performance test results of the above samples.

[0108] Table 2. Battery performance test results of the samples

[0109]

[0110] Furthermore, the lithium batteries assembled with the negative electrode materials prepared in Example 1, Comparative Example 1, and Comparative Example 2 were subjected to electrochemical impedance spectroscopy (EIS) testing, and the results are as follows: Figure 5 As shown, the intrinsic properties of the negative electrode material are demonstrated. The test used a 10 mV sinusoidal wave amplitude, with a frequency range of 100,000 Hz to 0.01 Hz. The results are as follows: Figure 5 As shown in Table 3.

[0111] Table 3. Electrochemical impedance spectroscopy results

[0112]

[0113] from Figure 5 As can be seen, the resistance of Comparative Example 1 is as high as 247Ω, while after adding silver, the resistance of Comparative Example 2 is reduced to 224Ω, but it is still at a high level. Furthermore, the examples demonstrate that the resistance of the anode material can be further reduced through nitrogen doping and the synergistic effect of composite with nano-silver. The resistance of Example 1 is only 108Ω. The above results show that the modification of the material by the present invention is of great significance. The electrochemical impedance test results echo the battery test results mentioned above, proving that the anode material has excellent electrochemical performance.

[0114] The test results in Tables 2 and 3 show that the addition of nano-silver in this invention effectively improves the cycle coulombic efficiency of the anode material, thus ensuring stable operation of the lithium battery during long-term cycling and avoiding lithium deadness and dendrite formation caused by repeated charging. Furthermore, the addition of silver also effectively improves the initial coulombic efficiency, preventing excessive lithium consumption and the formation of an irregular SEI film. Further, the nitrogen doping of graphene in this invention significantly reduces the diffusion barrier of the material, lowering the interfacial resistance by approximately 50%. This greatly improves the performance of the anode material under high-rate and high-deposition conditions, achieving higher cycle coulombic efficiency, indicating that the vast majority of lithium is loaded within the material, allowing for reversible charge-discharge cycling. Therefore, the anode material preparation method provided by this invention, utilizing the synergistic effect of nitrogen doping and composite with nano-metals, makes a significant contribution to further improving the electrochemical performance of lithium battery anodes.

[0115] The above embodiments illustrate and describe the main features and advantages of the present invention in detail. However, the present invention is not limited to the embodiments described. Those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of the present invention. All such equivalent modifications or substitutions are included within the scope defined by the claims of the present invention.

Claims

1. A method for preparing nitrogen-doped graphene nanomaterials as a negative electrode, wherein, The preparation method includes: S1. Graphene is mixed with a nitrogen source and subjected to high-temperature pyrolysis to obtain nitrogen-doped graphene. S2. Mix the nano-metal particles with the nitrogen-doped graphene, and add an organic solvent and a binder solution to obtain a slurry; S3. The slurry is coated onto the substrate and dried to obtain a nitrogen-doped graphene nanometal anode material attached to the substrate. The mass ratio of graphene to nitrogen source is (1-10): (0.1-1); The mass ratio of the nano-metal particles to nitrogen-doped graphene is (0.1-1):(1-10).

2. The preparation method according to claim 1, wherein, The particle size of the nano-metal particles is 20-500 nm; Preferably, the nano-metal particles include one or more of silver, gold, platinum, and rhodium.

3. The preparation method according to claim 1, wherein, The high-temperature pyrolysis temperature is 500-1000℃, and the high-temperature pyrolysis time is 0.5-4h.

4. The preparation method according to claim 1, wherein, The nitrogen source includes one or more of urea, melamine, nitrate, and amino acids.

5. The preparation method according to claim 1, wherein, The organic solvent includes one or more of N-methylpyrrolidone, tetrahydrofuran, methanol, and acetone.

6. The preparation method according to claim 1, wherein, The adhesive includes one or more of polyvinylidene fluoride, carboxymethyl cellulose, and lithium polyacrylate. Preferably, the amount of binder added is 5%-12% of the total mass of the nano-metal particles and nitrogen-doped graphene; Preferably, the concentration of the adhesive solution is 1wt%-10wt%, and the solvent is an organic solvent.

7. The preparation method according to claim 1, wherein, In step S2, an organic solvent is added dropwise under stirring to dissolve the nano-metal particles and nitrogen-doped graphene in the organic solvent, and a binder solution is added dropwise under stirring to obtain a uniformly mixed slurry. Preferably, the stirring speed is 100-1000 r / min and the stirring time is 0.5-5h.

8. A nitrogen-doped graphene nanometal anode material, which is prepared by the preparation method according to any one of claims 1-7.

9. A battery negative electrode, which is prepared from the nitrogen-doped graphene nanometal negative electrode material as described in claim 8; Preferably, the battery negative electrode is obtained by attaching the nitrogen-doped graphene nanometal negative electrode material to the surface of a copper foil and then cutting it.

10. A battery, wherein, The battery includes a positive electrode, a negative electrode, and an electrolyte, wherein the negative electrode is the negative electrode of the battery according to claim 9; Preferably, the battery is a lithium battery; Preferably, the electrolyte of the lithium battery includes a LiPF6 solution and / or a LiClO4 solution with a concentration of 0.5-2M, and the solvent of the electrolyte includes one or more of diethyl ether, propylene carbonate, and ethylene carbonate.

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