Porous carbon-based sodium battery negative electrode material and preparation method thereof

Abstract

The invention relates to the technical field of sodium ion batteries, and discloses a sodium battery negative electrode material based on porous carbon and a preparation method thereof.The negative electrode material is composed of a porous carbon-based active substance, acetylene black and a cementing agent, and the porous carbon-based active substance is an element-doped porous carbon material coated with manganese oxide; the active substance with the structure can combine the advantages of the porous carbon material and the metal oxide material, not only can solve the problem of low specific capacity of the porous carbon material, but also can solve the problem of easy volume expansion of the metal oxide, so that the prepared negative electrode material can show excellent specific capacity, cycling stability and rate capability. In addition, the cementing agent is excellent in bonding performance, and the problems that pores of the porous carbon are blocked and the advantages of the pore structure are difficult to play efficiently due to the fact that excessive cementing materials are used can be avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of sodium ion batteries, and particularly relates to a sodium battery anode material based on porous carbon and a preparation method thereof. Background Art

[0002] With the increasingly severe energy crisis and environmental problems, the demand for new battery technologies is becoming increasingly urgent. As a potential new battery technology, sodium ion batteries (SIBs) have become an ideal alternative to lithium ion batteries due to their high energy density, low cost, and rich resources. In sodium ion batteries, the anode material is one of the key factors determining its performance. Porous carbon materials are known for their large specific surface area, rich pore structure, and high conductivity. These characteristics endow porous carbon materials with unique advantages in the field of energy storage. Firstly, the large specific surface area can provide more active sites, enhancing the adsorption and storage capacity of sodium ions; secondly, the rich pore structure can effectively alleviate the volume change of sodium ions during charge and discharge, improving the cycle stability of the battery; finally, the high conductivity can ensure the rapid transmission of charges inside the battery, improving the power density of the battery. Therefore, porous carbon materials show great application potential in the field of sodium battery anode materials.

[0003] However, porous carbon materials lack a high specific capacity performance, making it difficult to meet the requirements of high energy density sodium batteries. Although metal oxides such as manganese oxide have a high theoretical specific capacity, they have poor conductivity and also exhibit a large volume change during the charge and discharge process of the battery, eventually pulverizing and causing serious attenuation of the battery capacity. Therefore, using porous carbon materials or metal oxide materials alone as the anode material of sodium batteries has defects in practical applications.

[0004] Based on this, the present invention provides a composite electrode material of metal oxide and porous carbon material, which can be used as the anode material of sodium ion batteries and exhibits excellent electrochemical performance. Summary of the Invention

[0005] In order to solve the problems mentioned in the background art, the purpose of the present invention is to provide a sodium battery anode material based on porous carbon and a preparation method thereof.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] A preparation method of a sodium battery anode material based on porous carbon, comprising the following steps:

[0008] Step S1, ingredient preparation

[0009] Weigh porous carbon-based active material, acetylene black, and binder according to a mass ratio of 8 - 8.5:1:0.5 - 1, and set aside;

[0010] Step S2: Prepare the anode material for the sodium battery

[0011] Mix the binder with purified water, stir evenly, then add the porous carbon-based active material and acetylene black and stir. Control the stirring rate at 300 - 500 r / min, stir and mix until a uniform material is formed, discharge the material, and obtain the anode material for the sodium battery.

[0012] As a further solution of the present invention, the preparation method of the porous carbon-based active material is as follows:

[0013] Step A: Prepare sulfonic acid cross-linked polyvinylidene chloride

[0014] Add polyvinylidene chloride to tetrahydrofuran, stir and mix evenly, then add a sulfonic acid group-functional cross-linking agent to the formed mixed solution. After adding, start heating, control the temperature at 60 - 70 °C, and continuously stir at this temperature for 2 - 4 h. Then add triethylamine. After adding, keep the temperature for 1 - 2 h, cool down and discharge the material to obtain sulfonic acid cross-linked polyvinylidene chloride;

[0015] In the above technical solution, the halogen substituents in the polyvinylidene chloride structure can undergo substitution with the primary amine groups in the sulfonic acid group-functional cross-linking agent structure, thereby realizing the cross-linking of polyvinylidene chloride to obtain sulfonic acid cross-linked polyvinylidene chloride;

[0016] Step B: Prepare the precursor of the porous carbon-based active material

[0017] Add sulfonic acid cross-linked polyvinylidene chloride to N,N-dimethylformamide, control the temperature at 70 - 80 °C, stir evenly, then add the manganese salt aqueous solution to the formed mixed solution, and treat it at an ultrasonic frequency of 60 - 80 kHz for 2 - 4 h. Then stop heating, separate the material, and obtain the precursor of the porous carbon-based active material;

[0018] Since the sulfonic acid groups in the sulfonic acid cross-linked polyvinylidene chloride structure carry negative charges, they can adsorb the manganese ions ionized from the manganese salt through electrostatic interaction. At the same time, the sulfonic acid groups can also adsorb the manganese ions in the polyvinylidene chloride molecular chain through complexation and be surrounded by the molecular chain to form manganese-loaded polyvinylidene chloride, that is, the precursor of the porous carbon-based active material;

[0019] Step C: Prepare the porous carbon-based active material

[0020] Mix the precursor of the porous carbon-based active material and the activator evenly, then place them in a tube furnace and perform calcination treatment under the protection of a nitrogen atmosphere to obtain the porous carbon-based active material.

[0021] The cross-linked polyvinylidene chloride in the porous carbon-based active material precursor can provide a carbon source, and the sulfonic acid group-functional cross-linking agent can provide a nitrogen source and an oxygen source. During the high-temperature calcination process, the nitrogen source can be introduced into the carbon material matrix in the form of element doping and form defect sites, and the oxygen source can combine with manganese to form an element-doped porous carbon material coated with manganese oxide.

[0022] Polyvinylidene chloride with a cross-linked structure has a higher carbonization rate, which is beneficial to the formation of pore structures. With the pore-making activation of the activator, a porous carbon material with rich and uniformly distributed pores can be prepared.

[0023] As a further scheme of the present invention, in step A, the sulfonic acid group-functional cross-linking agent is 4,4'-diaminostilbene-2,2'-disulfonic acid.

[0024] As a further scheme of the present invention, in step B, the manganese salt is at least one of manganese chloride, manganese sulfate or manganese acetate.

[0025] As a further scheme of the present invention, in step B, the concentration of the manganese salt aqueous solution is 0.5-1.5 mg / mL.

[0026] As a further scheme of the present invention, in step C, the activator is zinc chloride.

[0027] As a further scheme of the present invention, in step C, the calcination temperature is 700-750 °C and the time is 1-3 h.

[0028] As a further scheme of the present invention, the preparation method of the binder is as follows:

[0029] Mix citric acid, triethylene glycol and purified water, stir into a uniform solution, then add p-toluenesulfonic acid, control the temperature to 90-95 °C, keep stirring for 1-3 h, then add hydroxypropyl methylcellulose. After adding, continue to keep warm for 4-6 h under stirring conditions, and cool down and discharge to obtain the binder.

[0030] In the above technical scheme, using citric acid and triethylene glycol as raw materials, and by controlling the amounts of citric acid and triethylene glycol, a branched bridging agent with a terminal carboxyl hyperbranched structure is formed through an esterification condensation reaction. Using this branched bridging agent to bridge hydroxypropyl methylcellulose, a highly cross-linked hydroxypropyl methylcellulose, that is, the binder, can be prepared.

[0031] As a further scheme of the present invention, the molar ratio of malic acid to triethylene glycol is 1:0.8-1.

[0032] A sodium battery negative electrode material based on porous carbon is prepared by using the above preparation method.

[0033] The beneficial effects of the present invention:

[0034] The present invention prepares an element-doped porous carbon material coated with manganese oxide as the active material of the negative electrode material. First, after the manganese oxide is embedded in the porous carbon material, the volume expansion effect can be effectively alleviated by the confinement effect of the carbon material, which can effectively solve the problem of battery capacity attenuation and exhibit better cycle stability. Second, due to the doping of nitrogen elements, a large number of defect structures such as graphitic nitrogen are generated in the porous carbon material, which can effectively improve the specific capacity and conductivity of the porous carbon material, making the negative electrode material exhibit more excellent electrochemical properties such as rate performance. Finally, since the prepared porous carbon material has a rich pore structure, it can exhibit a larger specific surface area, which is beneficial to improving the sodium storage performance of the carbon material. Moreover, the rich pore structure can also shorten the path for the transmission of sodium ions, accelerate the electron transmission rate, and thus increase the pseudocapacitance contribution of the negative electrode material, resulting in a higher specific capacity.

[0035] The present invention prepares a highly cross-linked hydroxypropyl methylcellulose as the binder in the negative electrode material. The high cross-linking degree gives it a higher cohesive energy, and a large number of ether bonds are contained in the triethylene glycol structure. At the same time, the ester bonds generated by the condensation reaction can all form hydrogen bonds with the adhered object. Therefore, the binder can exhibit more excellent adhesive properties, achieving the effect of bonding the active material to the current collector with a small amount of binder, avoiding the problem that excessive binder is used, resulting in the blockage of the pores of the porous carbon and making it difficult to efficiently utilize the advantages of the pore structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for describing the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0037] Figure 1 It is the electron microscope image of the porous carbon-based active material in the embodiment, where (1) is the scanning electron microscope image and (2) is the transmission electron microscope image. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0038] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0039] Example 1

[0040] A preparation method of a sodium battery anode material based on porous carbon, comprising the following steps:

[0041] Step S1, ingredient preparation

[0042] Weigh 8 g of porous carbon-based active material, 1 g of acetylene black, and 1 g of binder, and set aside;

[0043] Step S2, preparation of the sodium battery anode material

[0044] Mix the binder with purified water, stir evenly, then add the porous carbon-based active material and acetylene black and stir. Control the stirring rate at 400 r / min, stir and mix until a uniform material is formed, discharge, and obtain the sodium battery anode material.

[0045] Example 2

[0046] A preparation method of a sodium battery anode material based on porous carbon, comprising the following steps:

[0047] Step S1, ingredient preparation

[0048] Weigh 8.5 g of porous carbon-based active material, 1 g of acetylene black, and 0.5 g of binder, and set aside; Step S2, preparation of the sodium battery anode material

[0049] Mix the binder with purified water, stir evenly, then add the porous carbon-based active material and acetylene black and stir. Control the stirring rate at 400 r / min, stir and mix until a uniform material is formed, discharge, and obtain the sodium battery anode material.

[0050] Comparative Example 1

[0051] A preparation method of a sodium battery anode material based on porous carbon, comprising the following steps:

[0052] Step S1, ingredient preparation

[0053] Weigh 8.5 g of porous carbon-based active material, 1 g of acetylene black, and 0.5 g of hydroxypropyl methylcellulose, and set aside;

[0054] Step S2, preparation of the sodium battery anode material

[0055] Mix the binder with purified water, stir evenly, then add the porous carbon-based active material and acetylene black and stir. Control the stirring rate at 400 r / min, stir and mix until a uniform material is formed, discharge, and obtain the sodium battery anode material.

[0056] Comparative Example 2

[0057] A preparation method of a sodium battery anode material based on porous carbon, comprising the following steps:

[0058] Step S1, ingredient preparation

[0059] Weigh 8.5 g of commercially available activated carbon material, 1 g of acetylene black and 0.5 g of binder for standby;

[0060] Step S2: Prepare the anode material for sodium battery

[0061] Mix the binder with purified water, stir evenly, then add the porous carbon-based active material and acetylene black and stir. Control the stirring rate at 400 r / min, stir and mix until a uniform material is formed, and discharge to obtain the anode material for sodium battery.

[0062] The above-mentioned commercially available activated carbon material is selected from the first-grade bamboo charcoal of Anhui Xingheng Environmental Protection Technology Co., Ltd.

[0063] The porous carbon-based active materials used in the above examples and comparative examples are prepared by the following method:

[0064] Step A: Prepare sulfonic acid cross-linked polyvinylidene chloride

[0065] Add 1.5 g of polyvinylidene chloride to tetrahydrofuran, stir and mix evenly, then add 0.6 g of 4,4'-diaminostilbene-2,2'-disulfonic acid to the formed mixed solution. After adding, start heating, control the temperature at 65 °C, and continuously stir at this temperature for 3 h. Then add 0.5 g of triethylamine. After adding, keep warm for 2 h, cool down and discharge to obtain sulfonic acid cross-linked polyvinylidene chloride;

[0066] Take out 0.2 g of sulfonic acid cross-linked polyvinylidene chloride as the test sample, use a Vario EL IIICHN type organic element analyzer to perform elemental analysis on it. The test results show that the carbon element content in the sample is 42.71%, the nitrogen element content is 2.52%, and the sulfur element content is 5.88%.

[0067] Step B: Prepare the precursor of porous carbon-based active material

[0068] Add 1.2 g of sulfonic acid cross-linked polyvinylidene chloride to 100 mL of N,N-dimethylformamide, control the temperature at 75 °C, stir evenly, then add 20 mL of manganese chloride aqueous solution with a concentration of 1 mg / mL to the formed mixed solution, and treat it at an ultrasonic frequency of 80 kHz for 3 h. Then stop heating, separate the material to obtain the precursor of porous carbon-based active material;

[0069] Step C: Prepare the porous carbon-based active material

[0070] Mix 1 g of the precursor of porous carbon-based active material and 3 g of zinc chloride evenly, place them in a tube furnace, and calcine them at a temperature of 750 °C for 2 h under the protection of a nitrogen atmosphere to obtain the porous carbon-based active material.

[0071] Figure 1 It is an electron micrograph of a porous carbon-based active material. Among them, (1) is a scanning electron micrograph. It can be observed that it has a rich pore structure, and the pore structure is very evenly distributed, with macropore and micropore structures. (2) is a transmission electron micrograph. It can be clearly observed that a large amount of manganese oxide is coated in the porous carbon material. Therefore, this porous carbon-based active material is a porous carbon material coated with manganese oxide.

[0072] The binder used in the above examples and comparative examples was prepared by the following method:

[0073] Mix 0.8 g of citric acid, 0.6 g of triethylene glycol and purified water, stir into a uniform solution, then add 0.1 g of p-toluenesulfonic acid, control the temperature at 90 °C, keep stirring for 2 h, then add 2.4 g of hydroxypropyl methylcellulose. After adding, continue to keep the temperature for 6 h under stirring conditions, cool down and discharge to obtain the binder.

[0074] Test Example

[0075] Apply the negative electrode materials in Examples 1 - 2 and Comparative Examples 1 - 2 on the surface of the copper foil, and dry them at 80 °C for 6 h, then punch them into copper foil discs with a size of 12 mm as the working electrode. The electrolyte uses a propylene carbonate solution of sodium perchlorate with a concentration of 1 mol / L, and the counter electrode uses a sodium metal sheet. Assemble them into a button battery. After standing for 4 h, perform battery performance tests. The results are shown in the following table:

[0076]

[0077]

[0078] Test results of rate performance:

[0079]

[0080] It can be concluded from the test results that Examples 1 and 2 use the porous carbon-based active material and binder prepared by the present invention as raw materials, and the prepared negative electrode material significantly has more excellent specific capacity, cycle stability and rate performance. After replacing the binder with conventional hydroxypropyl methylcellulose, due to the small amount used and poor binding performance, the active material falls off during charge and discharge, resulting in poor cycle stability and also poor rate performance. After replacing the porous carbon-based active material with a conventional commercially available activated carbon material, although it has good cycle stability, the specific capacity and rate performance are not good.

[0081] In this article, specific examples are used to elaborate on the principles and implementation modes of the present invention. The description of the above embodiments is only used to help understand the method and its core idea of the present invention, including the best mode, and also enables any person skilled in the art to practice the present invention, including manufacturing and using any device or system, and implementing any combined method. It should be noted that for those of ordinary skill in the art in this technical field, without departing from the principles of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention. The protection scope of the present invention patent is defined by the claims and may include other embodiments that can be conceived by those skilled in the art. If these other embodiments have structural elements similar to the literal description of the claims, or if they include equivalent structural elements that have no substantial difference from the literal description of the claims, then these other embodiments should also be included within the scope of the claims.

Claims

1. A method for preparing a sodium battery negative electrode material based on porous carbon, characterized in that: The following steps are involved: Step S1: Ingredients Weigh the porous carbon-based active material, acetylene black and binder in a mass ratio of 8-8.5:1:0.5-1 and set aside; Step S2: preparing negative electrode material for sodium battery The binder is mixed with purified water and stirred evenly, and then the porous carbon-based active material and acetylene black are added and stirred, and the stirring rate is controlled to be 300-500r / min, and the mixture is stirred and mixed until a uniform material is formed, and the material is discharged to obtain the negative electrode material of the sodium battery.

2. The method for preparing a sodium battery negative electrode material based on porous carbon according to claim 1, characterized in that: The preparation method of the porous carbon-based active material is as follows: Step A: Preparation of sulfonic acid cross-linked polyvinylidene chloride Add polyvinylidene chloride to tetrahydrofuran, stir and mix, then add sulfonic acid functional crosslinking agent to the formed mixed solution, turn on heating, control the temperature at 60-70°C, and continue stirring at this temperature for 2-4h, then add triethylamine, keep warm for 1-2h after adding, cool and discharge, and obtain sulfonic acid crosslinked polyvinylidene chloride; Step B: Preparation of porous carbon-based active material precursor Add sulfonic acid cross-linked polyvinylidene chloride to N,N-dimethylformamide, control the temperature to 70-80°C, stir evenly, then add a manganese salt aqueous solution to the formed mixed solution, treat at an ultrasonic frequency of 60-80kHz for 2-4h, then stop heating, separate the material, and obtain a porous carbon-based active material precursor; Step C: Preparation of porous carbon-based active material After the porous carbon-based active material precursor and the activator are evenly mixed, they are placed in a tubular furnace and calcined under the protection of a nitrogen atmosphere to obtain the porous carbon-based active material.

3. The method for preparing a sodium battery negative electrode material based on porous carbon according to claim 2, characterized in that: In step A, the sulfonic acid functional cross-linking agent is 4,4'-diaminobenzylbenzene-2,2'-disulfonic acid.

4. The method for preparing a sodium battery negative electrode material based on porous carbon according to claim 2, characterized in that: In step B, the manganese salt is at least one of manganese chloride, manganese sulfate or manganese acetate.

5. The method for preparing a sodium battery negative electrode material based on porous carbon according to claim 2, characterized in that: In step B, the concentration of the manganese salt aqueous solution is 0.5-1.5 mg / mL.

6. The method for preparing a sodium battery negative electrode material based on porous carbon according to claim 2, characterized in that: In step C, the activator is zinc chloride.

7. The method for preparing a sodium battery negative electrode material based on porous carbon according to claim 2, characterized in that: In step C, the calcination temperature is 700-750° C. and the calcination time is 1-3 hours.

8. The method for preparing a sodium battery negative electrode material based on porous carbon according to claim 1, characterized in that: The preparation method of the binder is as follows: Mix citric acid, triethylene glycol and purified water, stir to form a uniform solution, add p-toluenesulfonic acid, control the temperature to 90-95°C, keep warm and stir for 1-3 hours, then add hydroxypropyl methylcellulose, after the addition, continue to keep warm for 4-6 hours under stirring, cool and discharge to obtain a binder.

9. The method for preparing a sodium battery negative electrode material based on porous carbon according to claim 8, characterized in that: The molar ratio of malic acid to triethylene glycol is 1:0.8-1.

10. A sodium battery negative electrode material based on porous carbon, characterized in that: The method is prepared according to any one of claims 1 to 9.

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