Preparation method and application of high-rate negative electrode material

Abstract

The application discloses a preparation method and application of a high-rate negative electrode material, and steps are as follows: (1) naphthalene tetracarboxylic dianhydride and 2,5-thiophene dicarboxylic acid are dissolved in an organic solvent to obtain an organic ligand product by heating; (2) the organic ligand product is added into a bimetallic salt solution to stir, and a bimetallic organic ligand solution is obtained; (3) multi-walled carbon nanotubes and sodium dodecyl benzene sulfonate are added into an organic solvent to obtain a mixed solution; (4) the solution of (2) and the solution of (3) are mixed, heated and reacted, filtered and dried, and calcined under an inert protective atmosphere at high temperature to obtain a double MOFs and multi-walled carbon nanotube composite material; the bimetallic salt solution contains two kinds of metal ions with different valences. The two kinds of metal ions are coordinated with the organic ligand to obtain a heterostructure combined and stacked by sheets and particles, and the multi-walled carbon nanotubes are introduced to effectively improve the conductivity of the electrode material, and the electrode material has excellent specific capacitance and rate performance as a negative electrode material.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, and more specifically, to a method for preparing and applying a high-rate anode material. Background Technology

[0002] Due to the continued consumption of traditional fossil fuels and global environmental problems, there is increasing focus on developing sustainable and clean energy. Rechargeable batteries, benefiting from their high energy conversion efficiency and portability, have become one of the most promising energy storage devices. Among them, lithium-ion batteries have advantages such as high energy density, low self-discharge rate, long cycle life, and light weight, and are therefore widely used in automobiles, power tools, energy storage, and other fields. Commercially available lithium-ion batteries consist of positive electrode materials, negative electrode materials, a separator, and an electrolyte.

[0003] Currently, the rate performance of lithium-ion batteries and capacitors is difficult to improve significantly due to limitations in anode materials. Graphite is a commonly used anode material, possessing a stable structure, good conductivity, and safety performance. However, graphite's theoretical specific capacity is only 372 mAh / g, and its solid-state electron diffusion capability is poor, failing to meet future demands for high-power and high-energy-density batteries. New anode materials need to be developed to address these issues. Metal-organic frameworks (MOFs) are porous network framework structures formed by the coordination of metal ions and organic ligands. Compared to traditional porous materials, MOFs offer advantages such as diverse structures, high porosity, large specific surface area, tunable pore volume, and easy functionalization of pore surface area, making them promising for energy storage applications. While MOF materials exhibit high theoretical specific capacity as anode materials, their conductivity and stability during cycling are poor, and they suffer from severe volume expansion, significantly limiting their cycle performance.

[0004] In view of the above, this application is hereby submitted. Summary of the Invention

[0005] The technical problem this invention aims to solve is that existing metal MOF materials suffer from poor conductivity and stability, as well as volume expansion, during cycling when used as a negative electrode material, which limits their cycling performance. The goal is to provide a method for preparing and applying a high-rate negative electrode material. This method involves using naphthalenetetracarboxylic dianhydride and 2,5-thiophene dicarboxylic acid to form a special organic ligand, which is then compounded with a bimetallic solution. The resulting bimetallic MOF product is further reacted with multi-walled carbon nanotubes (MWCNTs). The resulting composite material has a rich pore structure and a large specific surface area, which can alleviate the volume expansion phenomenon during charge and discharge, improving stability. The coordination of the two metal ions with the organic ligands yields a heterogeneous structure combining sheet-like and granular stacks. The simultaneous introduction of MCCNTs effectively improves the conductivity of the electrode material. As a negative electrode material, it exhibits excellent specific capacitance and rate performance, thus demonstrating superior electrochemical and cycling performance.

[0006] This invention is achieved through the following technical solution:

[0007] In a first aspect, the present invention provides a method for preparing a high-rate anode material, comprising the following steps:

[0008] Step (1): Dissolve naphthalene tetracarboxylic acid dianhydride and 2,5-thiophene dicarboxylic acid in an organic solvent and heat to react to obtain an organic ligand product;

[0009] Step (2): The organic ligand product is added to a bimetallic salt solution and stirred to obtain a bimetallic organic ligand solution;

[0010] Step (3): Multi-walled carbon nanotubes and sodium dodecylbenzenesulfonate are added to an organic solvent and dispersed evenly to obtain a mixed solution;

[0011] Step (4): The bimetallic organic ligand solution from step (2) and the mixed solution from step (3) are heated and reacted. After the reaction, the mixture is filtered and dried. The dried mixture is calcined at high temperature under an inert protective atmosphere to obtain a composite material of bimetallic MOFs and multi-walled carbon nanotubes.

[0012] The bimetallic salt solution contains two metal ions with different valence states.

[0013] In one specific embodiment, the multi-walled carbon nanotubes are hydroxylated carbon nanotubes.

[0014] In one specific embodiment, the bimetallic salt solution uses cobalt salt and iron salt.

[0015] This invention first involves heating naphthalenetetracarboxylic dianhydride and 2,5-thiophene dicarboxylic acid to form a specific organic ligand structure. This structure retains the carboxyl functional groups of 2,5-thiophene dicarboxylic acid, enabling it to effectively complex with metal ions, forming a metal MOF with abundant pores and a large specific surface area. This invention then combines this ligand with a bimetallic salt, utilizing the different coordination modes of divalent cobalt salt and trivalent iron salt with the organic ligand. Specifically, divalent cobalt ions form a sheet-like structure with the organic ligand, while trivalent iron ions form a particulate structure. Therefore, the simultaneous coordination of both metal ions with the specially structured organic ligand results in a composite structure with a particulate internal matrix and stacked sheet-like external layers. The granular matrix structure provides internal fixation, preventing structural collapse due to volume expansion during discharge and improving the stability of the electrode material. Meanwhile, the sheet-like nanosheets provide shorter charge transfer paths, enhancing the material's specific capacitance and rate performance. This invention further introduces multi-walled carbon nanotubes into the bimetallic MOF structure. Multi-walled carbon nanotubes have good conductivity and stability, which can significantly improve the conductivity of electrode materials, thereby improving electrochemical performance and cycling performance. Moreover, by using hydroxylated multi-walled carbon nanotubes, they can react with carboxyl groups of special ligand structures, exert the conductivity of thiophene groups, and compete with metal ions for carboxyl groups, so that the organic ligands are in an unsaturated state, promoting the nucleation of bimetallic crystals.

[0016] In a specific embodiment, the molar ratio of naphthalenetetracarboxylic dianhydride and 2,5-thiophene dicarboxylic acid in step (1) is 1:1.2~1.5, the heating reaction is at 150~180℃, and the reaction time is 10~12h.

[0017] In a specific embodiment, in step (2), the molar ratio of the organic ligand product, cobalt salt, and iron salt is 1:1.5~2:1~1.2.

[0018] In one specific embodiment, in step (3), the molar ratio of multi-walled carbon nanotubes and sodium dodecylbenzenesulfonate is 10:1~3.

[0019] In one specific embodiment, in step (4), the bimetallic organic ligand solution from step (2) and the mixed solution from step (3) are mixed at a solute molar ratio of 2:1.

[0020] In a specific embodiment, in step (4), the heating reaction temperature is 150~180℃, the reaction time is 10~12h, and the high-temperature calcination temperature is 400-700℃.

[0021] Secondly, the present invention provides a high-rate anode material, which is prepared by the above-described preparation method.

[0022] Thirdly, the present invention provides a lithium-ion battery or lithium-ion capacitor, comprising a negative electrode material, wherein the negative electrode material is prepared by the above-described preparation method.

[0023] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0024] 1. The present invention provides a method for preparing and applying a high-rate anode material. By using naphthalenetetracarboxylic dianhydride and 2,5-thiophene dicarboxylic acid to form a special organic ligand, and then compounding it with a bimetallic solution, the obtained bimetallic MOF product is further reacted with multi-walled carbon nanotubes. The resulting composite material has a rich pore structure and a large specific surface area, which can alleviate the volume expansion phenomenon during charging and discharging and improve stability. The coordination of the two metal ions with the organic ligand can obtain a heterogeneous structure of sheet-like and granular stacked structures. At the same time, the introduction of multi-walled carbon nanotubes can effectively improve the conductivity of the electrode material. As an anode material, it has both excellent specific capacitance and rate performance, thus exhibiting excellent electrochemical performance and cycle performance.

[0025] 2. The present invention provides a method for preparing a high-rate negative electrode material and its application. Naphthalene tetracarboxylic dianhydride and 2,5-thiophene dicarboxylic acid are heated to form a specific organic ligand structure. This structure retains the carboxyl functional groups of 2,5-thiophene dicarboxylic acid, which can well complex with metal ions to form a metal MOF with rich pore structure and large specific surface area.

[0026] 3. The present invention provides a method for preparing and applying a high-rate negative electrode material. The ligand is compounded with a bimetallic salt. The two metals, divalent cobalt salt and trivalent iron salt, are used to coordinate with the organic ligand in different ways. Specifically, divalent cobalt ions form a sheet-like structure with the organic ligand, while trivalent iron ions form a particulate structure with the organic ligand. Therefore, the two metal ions coordinate with the organic ligand with the special structure at the same time, which can form a composite structure with particulate stacking as the internal matrix and sheet-like stacking on the outside. The matrix structure formed by the particulate stacking can play a fixing role inside, avoiding structural collapse caused by volume expansion during discharge, and improving the stability of the electrode material. The sheet-like nanosheets provide a shorter path for charge transfer, improving the specific capacitance and rate performance of the material.

[0027] 4. The present invention provides a method for preparing and applying a high-rate negative electrode material, which further introduces multi-walled carbon nanotubes into the bimetallic MOF structure. Multi-walled carbon nanotubes have good conductivity and stability, which can significantly improve the conductivity of the electrode material, thereby improving electrochemical performance and cycle performance.

[0028] 5. The present invention provides a method for preparing and applying a high-rate negative electrode material, which uses hydroxylated multi-walled carbon nanotubes that can react with carboxyl groups of special ligand structures to exert the conductivity of thiophene groups, while competing with metal ions for carboxyl groups, so that the organic ligands are in an unsaturated state, promoting the nucleation of bimetallic crystals. Attached Figure Description

[0029] Figure 1 The material SEM image obtained in an embodiment of the present invention;

[0030] Figure 2 This is a rate performance test diagram of the electrode materials assembled into a battery according to Embodiment 3 of the present invention;

[0031] Figure 3 This is a cycle life test diagram of the electrode materials in Embodiment 3 of the present invention after they are assembled into a battery. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the embodiments. The illustrative embodiments and descriptions of this invention are only used to explain this invention and are not intended to limit this invention.

[0033] In the following description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be apparent to those skilled in the art that these specific details are not necessary to practice the invention. In other embodiments, well-known methods have not been specifically described in order to avoid obscuring the invention.

[0034] Throughout this specification, references to "an embodiment," "an example," or "an example" mean that a particular feature, structure, or characteristic described in connection with that embodiment or example is included in at least one embodiment of the invention. Therefore, the phrases "an embodiment," "an example," "an example," or "an example" appearing in various places throughout the specification do not necessarily refer to the same embodiment or example. Furthermore, specific features, structures, or characteristics can be combined in one or more embodiments or examples in any suitable combination and / or sub-combination. Example 1

[0035] The present invention provides a method for preparing a high-rate anode material, comprising the following steps:

[0036] Step (1): Dissolve naphthalene tetracarboxylic acid dianhydride and 2,5-thiophene dicarboxylic acid in N,N-dimethylformamide, heat the reaction at 150~180℃ for 10~12h to obtain the organic ligand product;

[0037] Step (2): The organic ligand product is added to a bimetallic salt solution and stirred to obtain a bimetallic organic ligand solution;

[0038] Step (3): Hydroxylated multi-walled carbon nanotubes and sodium dodecylbenzenesulfonate are added to an ethanol solution and dispersed evenly to obtain a mixed solution;

[0039] Step (4): The bimetallic organic ligand solution from step (2) and the mixed solution from step (3) are heated to react at a temperature of 150-180℃ for 10-12 hours. After the reaction, the mixture is filtered and dried. The dried mixture is then calcined at a high temperature of 400-700℃ under an inert protective atmosphere to obtain a composite material of double MOFs and multi-walled carbon nanotubes.

[0040] The bimetallic salt solution contains cobalt salt and iron salt;

[0041] The molar ratio of naphthalenetetracarboxylic dianhydride to 2,5-thiophene dicarboxylic acid is 1:1.2; the molar ratio of organic ligand product, cobalt salt, and iron salt is 1:1.5:1; the molar ratio of multi-walled carbon nanotubes to sodium dodecylbenzenesulfonate is 10:1; the bimetallic organic ligand solution and the mixed solution are mixed with a solute molar ratio of 2:1. Example 2

[0042] The present invention provides a method for preparing a high-rate anode material, comprising the following steps:

[0043] Step (1): Dissolve naphthalene tetracarboxylic acid dianhydride and 2,5-thiophene dicarboxylic acid in N,N-dimethylformamide, heat the reaction at 150~180℃ for 10~12h to obtain the organic ligand product;

[0044] Step (2): The organic ligand product is added to a bimetallic salt solution and stirred to obtain a bimetallic organic ligand solution;

[0045] Step (3): Hydroxylated multi-walled carbon nanotubes and sodium dodecylbenzenesulfonate are added to an ethanol solution and dispersed evenly to obtain a mixed solution;

[0046] Step (4): The bimetallic organic ligand solution from step (2) and the mixed solution from step (3) are heated to react at a temperature of 150-180℃ for 10-12 hours. After the reaction, the mixture is filtered and dried. The dried mixture is then calcined at a high temperature of 400-700℃ under an inert protective atmosphere to obtain a composite material of double MOFs and multi-walled carbon nanotubes.

[0047] The bimetallic salt solution contains cobalt salt and iron salt;

[0048] The molar ratio of naphthalenetetracarboxylic dianhydride to 2,5-thiophene dicarboxylic acid is 1:1.5; the molar ratio of organic ligand product, cobalt salt, and iron salt is 1:2:1.2; the molar ratio of multi-walled carbon nanotubes to sodium dodecylbenzenesulfonate is 10:3; the bimetallic organic ligand solution and the mixed solution are mixed with a solute molar ratio of 2:1. Example 3

[0049] The present invention provides a method for preparing a high-rate anode material, comprising the following steps:

[0050] Step (1): Dissolve naphthalene tetracarboxylic acid dianhydride and 2,5-thiophene dicarboxylic acid in N,N-dimethylformamide, heat the reaction at 150~180℃ for 10~12h to obtain the organic ligand product;

[0051] Step (2): The organic ligand product is added to a bimetallic salt solution and stirred to obtain a bimetallic organic ligand solution;

[0052] Step (3): Hydroxylated multi-walled carbon nanotubes and sodium dodecylbenzenesulfonate are added to an ethanol solution and dispersed evenly to obtain a mixed solution;

[0053] Step (4): The bimetallic organic ligand solution from step (2) and the mixed solution from step (3) are heated to react at a temperature of 150-180℃ for 10-12 hours. After the reaction, the mixture is filtered and dried. The dried mixture is then calcined at a high temperature of 400-700℃ under an inert protective atmosphere to obtain a composite material of double MOFs and multi-walled carbon nanotubes.

[0054] The bimetallic salt solution contains cobalt salt and iron salt;

[0055] The molar ratio of naphthalenetetracarboxylic dianhydride to 2,5-thiophene dicarboxylic acid is 1:1.4; the molar ratio of organic ligand product, cobalt salt, and iron salt is 1:1.8:1~1.1; the molar ratio of multi-walled carbon nanotubes to sodium dodecylbenzenesulfonate is 10:2; the bimetallic organic ligand solution and the mixed solution are mixed with a solute molar ratio of 2:1.

[0056] Comparative Example 1

[0057] The comparative example provides a method for preparing a negative electrode material, which includes the following steps:

[0058] Step (1): Dissolve naphthalene tetracarboxylic acid dianhydride and 2,5-thiophene dicarboxylic acid in N,N-dimethylformamide, heat the reaction at 150~180℃ for 10~12h to obtain the organic ligand product;

[0059] Step (2): The organic ligand product is added to the bimetallic salt solution and stirred. The reaction is heated at 150-180°C for 10-12 hours. After the reaction, the product is filtered and dried to obtain the double MOF material.

[0060] The bimetallic salt solution contains cobalt salt and iron salt;

[0061] The molar ratio of naphthalenetetracarboxylic dianhydride to 2,5-thiophene dicarboxylic acid is 1:1.4; the molar ratio of organic ligand product, cobalt salt, and iron salt is 1:1.8:1~1.1.

[0062] Comparative Example 2

[0063] The present invention provides a method for preparing a high-rate anode material, comprising the following steps:

[0064] Step (1): Dissolve 2,5-thiophene dicarboxylic acid and cobalt salt in anhydrous ethanol to obtain a metal-organic ligand solution;

[0065] Step (2): Hydroxylated multi-walled carbon nanotubes and sodium dodecylbenzenesulfonate are added to an ethanol solution and dispersed evenly to obtain a mixed solution;

[0066] Step (3): The metal-organic ligand solution from step (1) and the mixed solution from step (2) are heated to react at a temperature of 150-180℃ for 10-12 hours. After the reaction, the mixture is filtered and dried. The dried mixture is then calcined at a high temperature of 400-700℃ under an inert protective atmosphere to obtain MOFs and multi-walled carbon nanotube composite materials.

[0067] The molar ratio of multi-walled carbon nanotubes to sodium dodecylbenzenesulfonate was 10:2; the organometallic ligand solution and the mixed solution were mixed at a solute molar ratio of 2:1.

[0068] Performance testing

[0069] The composite materials obtained in Examples 1-3 and Comparative Examples 1-2 were dissolved in N-methylpyrrolidone at a mass ratio of 8:1:1 with conductive carbon black and binder, stirred evenly, and coated onto copper foil to a thickness of 200 μm. After the electrode was dried, it was rolled to 90% of its dry thickness. The rolled electrode was then punched into small discs with a diameter of 1.6 cm and assembled with lithium foil to form coin cells for testing. The assembled cells were tested for electrochemical performance at 25°C with a set charge / discharge current density and a battery voltage test range (0.01-3.0 V (vs Na+ / Na)). Figure 2 The graph shows the rate performance test results of the electrode material assembled into a coin cell in Example 3. It can be seen that the negative electrode material prepared by the method of this embodiment has good rate performance.

[0070] The batteries assembled in Examples 1-3 and Comparative Examples 1-2 were cycled 200 times at a current density of 2 A / g within a voltage range of 0.01-3V. The results are shown in Table 1.

[0071]

[0072] As can be seen from Table 1, the composite anode material prepared by the method of the present invention has good conductivity, good electrochemical performance, and high capacity retention after 200 cycles, indicating that the composite anode material of the present invention has uniform pores, good cycle performance, and high battery capacity.

[0073] Figure 3 The graph shows the cycle life of the battery in Example 3 after 1000 cycles at a current density of 2A / g within a voltage range of 0.01-3V. The results show that the electrode material prepared in this embodiment still has a specific capacity of over 500 mAh / g after 1000 cycles.

[0074] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a high-rate negative electrode material, characterized by, Includes the following steps: Step (1): Dissolve naphthalene tetracarboxylic acid dianhydride and 2,5-thiophene dicarboxylic acid in an organic solvent and heat to react to obtain an organic ligand product; Step (2): The organic ligand product is added to a bimetallic salt solution and stirred to obtain a bimetallic organic ligand solution; Step (3): Multi-walled carbon nanotubes and sodium dodecylbenzenesulfonate are added to an organic solvent and dispersed evenly to obtain a mixed solution; Step (4): The bimetallic organic ligand solution from step (2) and the mixed solution from step (3) are heated and reacted. After the reaction, the mixture is filtered and dried. The dried mixture is calcined at high temperature under an inert protective atmosphere to obtain a composite material of bimetallic MOFs and multi-walled carbon nanotubes. The bimetallic salt solution contains two metal ions with different valence states. The bimetallic salt solution uses cobalt salt and iron salt, and the multi-walled carbon nanotubes are hydroxylated carbon nanotubes.

2. The method of claim 1, wherein the high-rate negative electrode material is prepared by the steps of: In step (1), the molar ratio of naphthalenetetracarboxylic acid dianhydride and 2,5-thiophene dicarboxylic acid is 1:1.2~1.5, the heating reaction is at 150~180℃, and the reaction time is 10~12h. ​ 3. The method of claim 1, wherein the high-rate negative electrode material is prepared by the steps of: preparing a mixture of a lithium metal oxide, a carbon material, and a binder; and coating the mixture on a current collector. In step (2), the molar ratio of the organic ligand product, cobalt salt, and iron salt is 1:1.5~2:1~1.

2.

4. The method of claim 1, wherein the high-rate negative electrode material is prepared by the steps of: preparing a mixture of a lithium metal oxide, a carbon material, and a binder; and coating the mixture on a current collector. In step (3), the molar ratio of multi-walled carbon nanotubes to sodium dodecylbenzenesulfonate is 10:1~3.

5. The method of claim 1, wherein the high-rate negative electrode material is prepared by the steps of: preparing a mixture of a lithium metal oxide, a carbon material, and a binder; and coating the mixture on a current collector. In step (4), the bimetallic organic ligand solution from step (2) and the mixed solution from step (3) are mixed at a solute molar ratio of 2:

1.

6. The method of claim 1, wherein the high-rate negative electrode material is prepared by the steps of: preparing a mixture of a lithium metal oxide, a carbon material, and a binder; and coating the mixture on a current collector. In step (4), the heating reaction temperature is 150~180℃ and the reaction time is 10~12h. In step (4), the high-temperature calcination temperature is 400-700℃.

7. A high-rate negative electrode material, characterized by, It is prepared by any one of the methods described in claims 1 to 6.

8. A lithium-ion battery or lithium-ion capacitor comprising a negative electrode material, characterized in that The negative electrode material is the high-rate negative electrode material described in claim 7.

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