A negative electrode material, a preparation method therefor, and an application thereof

Abstract

The application relates to the technical field of fast-charging lithium battery materials, and particularly discloses a negative electrode material, a preparation method and application thereof. The negative electrode material is composed of disordered rock salt materials and carbon nanofibers, and the disordered rock salt materials contain lithium-rich transition metal oxides. The negative electrode material provided by the application has three-dimensional lithium ion migration channels provided by the disordered rock salt phase, supports fast charging, and has carbon nanofibers as high-conductivity frameworks and buffer layers, which not only improve the overall conductivity and the electrochemical performance of lithium batteries, but also relieve the influence of volume change on the structural stability in the charging and discharging process. After the two are combined, the lithium-rich transition metal oxides can provide additional lithium sources, which helps to improve the first coulomb efficiency.

Description

Technical Field

[0001] This invention relates to the field of fast-charging lithium battery materials technology, and in particular to a negative electrode material, its preparation method, and its application. Background Technology

[0002] Lithium-ion batteries typically achieve charging and discharging based on the migration of lithium ions between the positive and negative electrodes. During charging, lithium ions are extracted from the positive electrode and inserted into the negative electrode, and vice versa during discharging. Currently, most commercially available lithium-ion batteries typically use two types of negative electrode active materials. The most common is graphite, which has a high energy density, but during fast charging, lithium metal easily deposits on the negative electrode side, forming lithium dendrites, which poses extremely serious safety hazards. The second type is lithium titanate, a safer alternative that allows for fast charging, but usually results in a significant decrease in energy density. Therefore, there is an urgent need to develop a fast-charging lithium battery negative electrode material that offers both high safety and high energy density.

[0003] Lithium-rich disordered rock salt (DRS) oxides are promising battery materials due to their rapid lithium migration via an octahedral-tetrahedral-octahedral permeation network. Studies have shown that when the discharge cutoff voltage is increased to 1.9V, three lithium ions can be intercalated into transition metal oxides (such as vanadium pentoxide, V₂O₅) to form Li₃V₂O₅, which has a disordered rock salt phase structure. Furthermore, the lithiation plateau below 1V indicates that Li… + It can be further inserted into Li3V2O5, thus indicating its potential as a lithium-ion anode material. Summary of the Invention

[0004] Based on this, the purpose of this invention is to provide an anode material, its preparation method and application. The anode material is composed of disordered rock salt material and carbon nanofibers. During the lithium intercalation process, the redistribution of lithium causes the optimal conduction path of lithium ions to change, resulting in rapid lithium ion conduction characteristics.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: The present invention provides an anode material composed of disordered rock salt material and carbon nanofibers, wherein the disordered rock salt material contains lithium-rich transition metal oxides.

[0006] The negative electrode material provided by this invention utilizes a disordered rock salt phase to provide three-dimensional lithium-ion migration channels, supporting fast charging. Carbon nanofibers, acting as a highly conductive framework and buffer layer, not only improve overall conductivity and the electrochemical performance of the lithium battery, but also mitigate the impact of volume changes on structural stability during charging and discharging. The combination of these two components, along with the lithium-rich transition metal oxide, provides an additional lithium source, contributing to improved initial coulombic efficiency.

[0007] As a further improvement to the above-described scheme of the present invention, the disordered rock salt material comprises Li3V2O5 or LiCoO2.

[0008] The present invention also provides a method for preparing the negative electrode material as described above, which includes the following steps: S1. Disperse the polymer in solvent A to obtain an electrospinning solution; S2. The electrospinning solution is electrospinned to obtain a nanofiber membrane, and the nanofiber membrane is pre-oxidized and then carbonized to obtain a carbon nanofiber membrane. S3. A transition metal oxide is grown on the carbon nanofiber membrane and then electrochemically lithiated to obtain the negative electrode material.

[0009] This invention involves obtaining a carbon nanofiber membrane from a polymer solution through electrospinning and subsequent high-temperature carbonization. A transition metal oxide is then grown on the carbon nanofiber membrane, and finally, disordered rock salt oxide lithium-ion battery fast-charging anode material is obtained through electrochemical lithiation. This method allows for the in-situ formation of disordered rock salt material on the carbon fiber surface. This approach improves the conductivity of the anode material, enhances electron conduction, and thus improves battery performance. It also features a high specific surface area, allowing for the accommodating of more lithium ions, which helps increase battery capacity and energy density. Furthermore, the high conductivity and electron conduction properties improve the battery's charge and discharge rates, thereby enhancing fast-charging performance.

[0010] As a further improvement to the above-mentioned solution of the present invention, in step S1, the polymer is selected from at least one of polyacrylonitrile, polyvinylidene fluoride, polyethylene oxide, polyamide, polyethersulfone resin, and polystyrene; the polymer content in the electrospinning solution is 5wt%~15wt%.

[0011] As a further improvement of the above-mentioned solution of the present invention, in step S2, during electrospinning, the electrospinning is performed at a flow rate of 0.5~1.5mL / h onto the target rotating collector, the voltage applied to the needle tip is 20~25 kV, the distance from the needle tip to the collector is 10~20cm, and the air humidity is 5%~8%.

[0012] As a further improvement to the above-mentioned scheme of the present invention, in step S2, the pre-oxidation is performed at 180~280℃ for 0.5~1.2h; and / or, the carbonization is performed at 900~1100℃ under a protective atmosphere for 1.5~2.5h.

[0013] Pre-oxidation can stabilize the cross-linking of polymer molecular chains and prevent melting deformation during high-temperature carbonization; carbonization can form carbon nanofibers with a high degree of graphitization, which ensures both conductivity and maintains the integrity of fiber morphology. Generally speaking, the higher the carbonization temperature and the higher the carbon content, the better the conductivity; however, further increases in temperature lead to increased fiber heat loss and a decrease in the retention rate of the final product. In this invention, the carbonization temperature is controlled at 900~1100℃.

[0014] As a further improvement to the above-mentioned scheme of the present invention, step S3, growing transition metal oxides on the carbon nanofiber membrane, includes: dissolving the transition metal oxides in solvent B to obtain a precursor solution; immersing the carbon nanofiber membrane in the precursor solution and performing a hydrothermal reaction; and cleaning, drying, and annealing after the reaction. By using a hydrothermal method to grow transition metal oxides on the carbon nanofiber membrane, and through hydrothermal reaction, cleaning, drying, and annealing, the transition metal oxide nanostructures can be uniformly attached to the carbon fiber surface, with a strong bond and controllable crystal structure, providing an ideal precursor morphology for subsequent electrochemical lithiation to generate a disordered rock salt phase.

[0015] As a further improvement to the above-mentioned scheme of the present invention, the transition metal oxide is one of Co2O3 and V2O5; the hydrothermal reaction is carried out at 190-200℃ for 8-10 hours; and the annealing is carried out at 250-300℃ for 0.5-1.2 hours.

[0016] As a further improvement to the above-described scheme of the present invention, the electrochemical lithiation cutoff voltage is 1.5V. By controlling the electrochemical lithiation cutoff voltage at 1.5V, the transition metal oxide can be quantitatively converted into a lithium-rich disordered rock salt phase, while avoiding metal precipitation or material structure damage caused by excessively low voltage, thereby obtaining a negative electrode material with both fast charging capability and cycle stability.

[0017] This invention also provides an application of the aforementioned anode material in lithium batteries. Using this anode material in lithium batteries allows for stable charging and discharging at high current densities, suppresses lithium dendrite growth, and offers superior safety compared to graphite anodes; simultaneously, its energy density is higher than that of lithium titanate anodes, meeting the requirements of fast-charging, high-safety energy storage devices. Attached Figure Description

[0018] Figure 1 Scanning electron microscope images of the transition metal oxide composite carbon nanofiber membranes prepared in Examples 1-4; Figure 2 This is the X-ray diffraction pattern of the transition metal oxide composite carbon nanofiber membrane prepared in Example 3; Figure 3 This is an electrochemical performance diagram of the disordered rock salt oxide lithium battery fast-charging negative electrode material prepared in Example 3. Detailed Implementation

[0019] To facilitate understanding of the present invention, a more comprehensive description will be given below with reference to specific embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of the present invention.

[0020] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0021] Example 1 This embodiment proposes a method for preparing a disordered rock salt oxide lithium-ion battery fast-charging anode material, the specific steps of which are as follows: S1. Preparation of electrospinning solution: Accurately weigh polyacrylonitrile (relative molecular mass of 130,000) and dissolve it in dimethylformamide solution. Stir thoroughly to obtain a homogeneous electrospinning solution. Polyacrylonitrile accounts for 10% of the total weight of the electrospinning solution.

[0022] S2. Obtain nanofiber membranes using electrospinning technology: at 1.0 mL h -1 The electrospinning solution was electrospun onto the target rotating collector at a flow rate of 22 kV and 15 cm from the needle tip to the collector. The air humidity was 5%. The electrospinning process was completed in 5 hours, and a nanofiber membrane was obtained.

[0023] S3. The nanofiber membrane was pre-oxidized at 280 °C for 1 h, and then subjected to high-temperature carbonization at 1000 °C in an argon atmosphere for 2 h to obtain a carbon nanofiber membrane.

[0024] S4. Preparation of vanadium pentoxide composite carbon nanofiber membrane: Plate-like V₂O₅ is grown on the carbon nanofiber membrane, specifically including: S41. First, add 0.1 mL of triisopropanol vanadium oxide to 50 mL of isopropanol and stir thoroughly to dissolve, thus obtaining the precursor solution; S42. A carbon nanofiber membrane (4 cm × 4 cm) and the prepared precursor solution were transferred to a hydrothermal reactor for hydrothermal reaction. The mixture was sealed and kept at 200 °C for 10 hours to obtain the precursor membrane. S43. Remove the precursor membrane, rinse it 2-3 times in ethanol, and dry it overnight under vacuum at 60 °C; S44. The precursor membrane was annealed in air at a heating rate of 2 °C / min to 280 °C for 1 hour to obtain a vanadium pentoxide composite carbon nanofiber membrane with a vanadium pentoxide loading of approximately 0.5 mg cm⁻¹. -2 .

[0025] S5. Assemble the obtained vanadium pentoxide composite carbon nanofiber membrane into a button cell and discharge it to a cutoff voltage of 1.5V to obtain a disordered rock salt oxide lithium battery fast-charging anode material.

[0026] Example 2 The difference between this embodiment and Embodiment 1 is that: In this embodiment, step S41 specifically involves adding 0.2 mL of vanadium triisopropoxide to 50 mL of isopropanol and stirring thoroughly to dissolve it, thereby obtaining a precursor solution. In this embodiment, step S44 yields a vanadium pentoxide loading of approximately 1.00 mg / cm³ in the vanadium pentoxide composite carbon nanofiber membrane. -2 .

[0027] Example 3 The difference between this embodiment and embodiment 1 is that step S41 in this embodiment is specifically: 0.3 mL of vanadium triisopropoxide is added to 50 mL of isopropanol and stirred thoroughly to dissolve, thereby obtaining a precursor solution; In this embodiment, step S44 yields a vanadium pentoxide loading of approximately 1.50 mg / cm³ in the vanadium pentoxide composite carbon nanofiber membrane. -2 .

[0028] Example 4 The difference between this embodiment and embodiment 1 is that step S41 in this embodiment is specifically: 0.4 mL of vanadium triisopropoxide is added to 50 mL of isopropanol and stirred thoroughly to dissolve, thereby obtaining a precursor solution; In this embodiment, step S44 yields a vanadium pentoxide loading of approximately 2.0 mg / cm³ in the vanadium pentoxide composite carbon nanofiber membrane. -2 .

[0029] Figure 1 (a)-(d) are SEM images of the vanadium pentoxide composite carbon nanofiber membranes prepared in Examples 1-4, respectively. It can be seen that the vanadium pentoxide composite carbon nanofiber membranes prepared in Examples 1-4 all show carbon fiber as the substrate, with different contents of vanadium oxide precursor, and different morphologies of substances are grown on the carbon fiber substrate. Figure 1 (a) It can be seen that Example 1 only has smooth carbon nanofibers, which are thin and have no vanadium oxide active material loading on the surface, and lack electrochemical reaction active sites; Figure 1(b) It can be seen that the carbon fiber in Example 2 is significantly thicker, the vanadium oxide is only thinly coated on the fiber surface, the coating layer is dense without layering / sheet structure, the active material is tightly stacked, and the active sites are not sufficiently exposed. Figure 1 (c) It can be seen that the carbon nanofiber skeleton of Example 3 is completely preserved, and thin sheets of V2O5 are uniformly and vertically grown on the fiber surface. The sheets are interwoven and have a large number of pores. The sheet structure is thin and has a large specific surface area, which is an ideal electrochemical morphology. Figure 1 (d) It can be seen that in Example 4, the vanadium oxide was excessive, the sheet-like structure was excessively agglomerated and stacked, a large number of pores were blocked, the fiber skeleton was wrapped by thick oxide, and the structure was easy to pulverize and fall off.

[0030] Figure 2 This is the X-ray diffraction pattern of the vanadium pentoxide composite carbon nanofiber membrane prepared in Example 3. The characteristic diffraction peaks of the vanadium pentoxide composite carbon nanofiber membrane material were found to correspond one-to-one with the PDF#41-1426 card by XRD testing, which proved that sheet-like vanadium pentoxide was successfully grown on the carbon fiber membrane, and also corresponds to the scanning electron microscope image above.

[0031] Figure 3 The image shows the electrochemical performance of a lithium battery prepared using the disordered rock salt oxide lithium fast-charging negative electrode material obtained in Example 3. After 100, 200, and 300 cycles, the CV curves still showed good overlap with the first cycle, indicating that it has excellent electrochemical performance.

[0032] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0033] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A negative electrode material, characterized in that, It is composed of disordered rock salt material and carbon nanofiber composite, wherein the disordered rock salt material contains lithium-rich transition metal oxides.

2. The negative electrode material according to claim 1, characterized in that, The disordered rock salt material contains Li3V2O5 or LiCoO2.

3. A method for preparing a negative electrode material as described in any one of claims 1-2, characterized in that, It includes the following steps: S1. Disperse the polymer in solvent A to obtain an electrospinning solution; S2. The electrospinning solution is electrospinned to obtain a nanofiber membrane, and the nanofiber membrane is pre-oxidized and then carbonized to obtain a carbon nanofiber membrane. S3. A transition metal oxide is grown on the carbon nanofiber membrane and then electrochemically lithiated to obtain the negative electrode material.

4. The method for preparing the negative electrode material according to claim 3, characterized in that, In step S1, the polymer is selected from at least one of polyacrylonitrile, polyvinylidene fluoride, polyethylene oxide, polyamide, polyethersulfone resin, and polystyrene; the polymer content in the electrospinning solution is 5wt%~15wt%.

5. The method for preparing the negative electrode material according to claim 3, characterized in that, In step S2, during electrospinning, the electrospun fibers are electrospun onto the target rotating collector at a flow rate of 0.5~1.5 mL / h, the voltage applied to the needle tip is 20~25 kV, the distance from the needle tip to the collector is 10~20 cm, and the air humidity is 5%~8%.

6. The method for preparing the negative electrode material according to claim 3, characterized in that, In step S2, the pre-oxidation is performed at 180~280℃ for 0.5~1.2h; and / or, the carbonization is performed at 900~1100℃ under a protective atmosphere for 1.5~2.5h.

7. The method for preparing the negative electrode material according to claim 3, characterized in that, In step S3, growing transition metal oxides on the carbon nanofiber membrane includes: dissolving the transition metal oxides in solvent B to obtain a precursor solution; immersing the carbon nanofiber membrane in the precursor solution and performing a hydrothermal reaction; and washing, drying, and annealing after the reaction is completed.

8. The method for preparing the negative electrode material according to claim 7, characterized in that, The transition metal oxide is one of Co2O3 and V2O5; the hydrothermal reaction is carried out at 190-200℃ for 8-10 hours; the annealing is carried out at 250-300℃ for 0.5-1.2 hours.

9. The method for preparing the negative electrode material according to claim 3, characterized in that, The electrochemical lithiation cutoff voltage is 1.5V.

10. The application of a negative electrode material as described in any one of claims 1-2 in a lithium battery.

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