Preparation method and energy storage application of hard carbon material

Abstract

The invention provides a preparation method and energy storage application of a phenolic resin-based hard carbon material, and relates to the field of sodium ion battery electrode materials. The closed pore volume of the material is 0.15-0.35 cm < 3 > / g, and the specific surface area is 5-15 m < 2 > / g. According to the hard carbon material, phenolic resin is used as a precursor, C60 is used as an additive, directional crystallization of a graphite micro-domain of the hard carbon material is realized by using the C60 as a template in a phenolic resin pyrolysis stage, and an extra sodium storage site is introduced by structural recombination of the C60 in a phenolic resin carbonization stage, so that regulation and control of the graphite micro-domain and a closed pore structure of the hard carbon material are realized; when used as a sodium-ion battery negative electrode material, the composite material shows high sodium storage capacity and high cycle stability.

Description

Technical Field

[0001] The present invention relates to the field of sodium ion battery electrode materials, and in particular to a sodium ion battery electrode material having a C 60 The invention relates to a preparation method of a phenolic resin-based hard carbon material with a rich closed-pore structure as an additive and its application in the negative electrode of a sodium ion battery. Background Art

[0002] At present, lithium-ion batteries have been widely used in electric vehicles, mobile devices and other fields. However, the limited reserves of lithium resources have caused people to worry about the future energy market. Sodium has similar physical and chemical properties to lithium, and sodium reserves are abundant. Sodium-ion batteries have more cost advantages than lithium-ion batteries. Therefore, sodium-ion batteries are a strong competitor to lithium-ion batteries.

[0003] One of the main factors limiting the further development of sodium-ion batteries is the negative electrode material. This is due to the large radius of sodium ions, which hinders the application of graphite materials widely used in lithium-ion batteries as their negative electrode materials. Hard carbon has a large interlayer spacing, highly disordered graphite microdomains, a large number of defects and pore structures, and is regarded as the most promising negative electrode material for the commercialization of sodium-ion batteries. The charge and discharge curve of hard carbon sodium storage includes two stages, namely the slope zone with a voltage greater than 0.1V and the platform zone with a voltage less than 0.1V. Among them, the increase in the capacity of the platform zone is conducive to the development and commercial application of high energy density sodium-ion batteries. Therefore, the improvement of the platform capacity of hard carbon materials for sodium storage has profound practical significance.

[0004] Existing studies have shown that the platform capacity of hard carbon for sodium storage mainly comes from the filling of sodium ions in closed pores. Therefore, the design of the closed-pore structure of hard carbon is a current research hotspot. At present, the most effective method for regulating the closed-pore structure of hard carbon is to add pore-forming agents. For example, Hu et al. published an article entitled "Tuning Closed Pore Structure of Hard Carbons with Highest Na Storage Capacity" in "ACS Energy Letters" (2019, 4 (11): 2608-2612), using ethanol as a pore-forming agent and regulating the closed-pore structure of hard carbon by hydrothermal method. He et al. published an article entitled "Dual-Interfering Chemistry for Soft-Hard Carbon Translation toward Fast and Durable Sodium Storage" in "Advanced Energy Materials" (2023, 13, 2300357), using zinc gluconate as a pore-forming agent, and removing the decomposed solid products by acid washing to form pores, thereby achieving an increase in the platform capacity of hard carbon.

[0005] All of the methods reported above have some problems in their practical applications. First, these methods involve complex experimental steps, such as the need for hydrothermal method before carbonization, or acid washing and multiple carbonization. Second, these experimental steps are dangerous. Third, a large amount of pore-forming agents, complex steps and equipment increase the cost burden. Therefore, the regulation of the closed-pore structure of hard carbon through simple and effective methods is of great significance for the preparation of high-performance sodium-ion battery negative electrode materials and the promotion of the commercialization of sodium-ion batteries. Summary of the invention

[0006] In order to overcome the problems existing in the above-mentioned technologies, the present invention aims to provide a C 60 Preparation method and energy storage application of phenolic resin-based hard carbon materials as additives. 60 It is a face-centered cubic molecular crystal composed of 60 carbon atoms, with a spherical geometric structure of 20 hexagonal faces and 12 pentagonal faces. 60 When used as an additive, the hard carbon preparation process is simple, avoiding the complex impurity removal steps and equipment required for pore-forming agents such as alkalis and metal salts. 60 The special cage structure enables it to act as a template during the pyrolysis of phenolic resin, inducing the directional crystallization of graphite microdomains in hard carbon materials. 60 During the high-temperature carbonization process, the carbon structure will be reorganized and hard carbon materials will gradually form. 60 The reaction occurring during the carbonization stage of the phenolic resin will introduce additional sodium storage sites, thereby achieving the regulation of the graphite microdomain and closed-cell structure of the phenolic-based hard carbon material. 60 The phenolic resin-based hard carbon material as an additive is characterized by:

[0007] The closed pore volume of the material obtained by the present invention is 0.15-0.35cm 3 / g, with a specific surface area of ​​5-15m 2 / g, and is a hard carbon material with high-curvature graphite microdomains and rich closed-pore structure inside.

[0008] The preparation method of the hard carbon material comprises the following steps:

[0009] Step 1): C 60 Dissolve in solvent 1, stir at 30°C for 30 minutes to obtain solution 1, dissolve phenolic resin in solvent 2, stir at 30°C for 30 minutes to obtain solution 2;

[0010] Step 2): mixing the two solutions, removing the solvent, and drying to obtain a mixed solid product;

[0011] Step 3): placing the mixed solid product into a high-temperature carbonization furnace and heating it to 1300-1500° C. in an argon atmosphere to obtain the desired hard carbon material.

[0012] The phenolic resin is a resol linear phenolic resin, the first solvent is selected from one or more of toluene, chlorobenzene, n-hexane, carbon disulfide, and carbon tetrachloride, and the second solvent is selected from one or more of ethanol, water, methanol, and acetone.

[0013] Solution C 60 The concentration of phenolic resin in solution 2 is 5-100 mg / ml, the concentration of phenolic resin in solution 2 is 0.1-0.5 g / ml, and in the mixed solution C 60 The mass of phenolic resin accounts for 0.1% to 15% of the mass of phenolic resin

[0014] The invention obtains a phenolic resin-based hard carbon and applies the phenolic resin-based hard carbon to a negative electrode material of a sodium ion battery.

[0015] Compared with the prior art, the invention has the advantage that C 60 As an additive, C 60 Molecular dissolution in the phenolic resin matrix. 60 In the phenolic pyrolysis stage, it will serve as a template to realize the high curvature directional crystallization of graphite microdomains in hard carbon materials; in the phenolic carbonization stage, C 60 The carbon structure will be reorganized to introduce additional sodium storage sites, and the above two points can be used to control the graphite microdomain and closed-pore structure of hard carbon materials. This scheme does not involve complicated experimental steps, and the preparation of high platform capacity and high cycle stability sodium ion battery negative electrode materials is achieved through one-step carbonization. In particular, the additive C 60 It also participates in carbonization and induces the formation of a rich closed-pore structure of phenolic carbon materials, and does not need to be removed after carbonization like most reported pore-forming agents. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Attached Figure 1 This is a scanning electron microscope image of the phenolic resin-based hard carbon of Example 1 of the present invention;

[0017] Attached Figure 2 This is a high-resolution transmission electron microscopy image of the phenolic resin-based hard carbon of Example 1 of the present invention;

[0018] Attached Figure 3 A rate performance diagram of a sodium ion battery provided in Example 4 of the present invention;

[0019] Attached Figure 4 A rate performance diagram of a sodium ion battery provided in Comparative Example 1 of the present invention; DETAILED DESCRIPTION

[0020] The present invention is described in detail below in conjunction with the accompanying drawings and examples, but the present invention is not limited to the following examples. The conditions for electrode testing when used as a negative electrode material for sodium ion batteries in the following examples are: the electrode composition is 80% of the hard carbon material of the present invention, 10% of acetylene black, and 10% of PVDF, and the electrolyte composition is 1 mol NaPF6 dissolved in a solvent with a volume ratio of EC and DEC of 1:1.

[0021] Example 1

[0022] Take 50mg C 60 Dissolve in toluene solution, stir at 30°C for 30 minutes to obtain solution 1, dissolve phenolic resin in ethanol, stir at 30°C for 30 minutes to obtain solution 2. Mix the two solutions, heat to 80°C under uniform stirring, and keep the temperature constant for 5 hours to obtain a cured product. Put the cured product into a high-temperature carbonization furnace and heat to 1500°C in an argon atmosphere to obtain the desired hard carbon material. The closed pore volume is 0.20cm 3 / g, with a specific surface area of ​​8.3m 2 / g.

[0023] The electrochemical performance test results show that when the electrode material is used as the negative electrode material of sodium ion batteries, the reversible specific capacity at a current density of 0.02A / g can reach 340mA h / g, and the platform capacity is 240mA h / g.

[0024] Example 2

[0025] Take 100 mg C 60 Dissolve in carbon tetrachloride solution, stir at 30°C for 30 minutes to obtain solution 1, dissolve phenolic resin in acetone, stir at 30°C for 30 minutes to obtain solution 2. Mix the two solutions, heat to 80°C under uniform stirring, and keep the temperature constant for 12 hours to obtain a cured product. Put the cured product into a high-temperature carbonization furnace and heat to 1500°C in an argon atmosphere to obtain the desired hard carbon material. The closed pore volume is 0.24cm 3 / g, with a specific surface area of ​​7.8m 2 / g.

[0026] The electrochemical performance test results show that when the electrode material is used as the negative electrode material of sodium ion battery, it can -1 The reversible specific capacity at the current density can reach 347 mA h / g, and the platform capacity is 257 mA h / g.

[0027] Example 3

[0028] Take 100 mg C 60Dissolve in chlorobenzene solution, stir at 30°C for 30 minutes to obtain solution 1, and dissolve phenolic resin in methanol, stir at 30°C for 30 minutes to obtain solution 2. Mix the two solutions, heat to 100°C under uniform stirring, and keep the temperature constant for 12 hours to obtain a cured product. Put the cured product into a high-temperature carbonization furnace and heat to 1300°C in an argon atmosphere to obtain the desired hard carbon material. The closed pore volume is 0.21cm 3 / g, with a specific surface area of ​​8.3m 2 / g.

[0029] The electrochemical performance test results show that when the electrode material is used as the negative electrode material of sodium ion battery, it can -1 The reversible specific capacity at the current density can reach 354mA hg -1 , the platform capacity is 247mA h / g.

[0030] Example 4

[0031] Take 200 mg C 60 Dissolve in carbon disulfide solution, stir at 30°C for 30 minutes to obtain solution 1, dissolve phenolic resin in acetone, stir at 30°C for 30 minutes to obtain solution 2. Mix the two solutions, heat to 100°C under uniform stirring, and keep the temperature constant for 12 hours to obtain a cured product. Put the cured product into a high-temperature carbonization furnace and heat to 1500°C in an argon atmosphere to obtain the desired hard carbon material. The closed pore volume is 0.34cm 3 / g, with a specific surface area of ​​6.8m 2 / g.

[0032] The electrochemical performance test results show that when the electrode material is used as the negative electrode material of sodium ion battery, it can -1 The reversible specific capacity at the current density can reach 362 mA h / g, and the platform capacity is 269 mA h / g.

[0033] Comparative Example 1

[0034] The phenolic resin was heated to 100°C and kept at this temperature for 12 hours to obtain a cured product. The cured product was placed in a high-temperature carbonization furnace and heated to 1500°C in an argon atmosphere to obtain the desired hard carbon material. The closed pore volume was 0.16 cm 3 / g, with a specific surface area of ​​7.8m 2 / g.

[0035] The electrochemical performance test results show that when the electrode material is used as the negative electrode material of sodium ion battery, it can -1 The reversible specific capacity at the current density can reach 242 mA h / g, and the platform capacity is 193 mA h / g.

[0036] In order to more intuitively demonstrate the performance of the material prepared in the present invention, some preparation parameters and electrochemical properties of the negative electrode materials prepared in each embodiment are listed in Table 1 below.

[0037] Table 1

[0038]

[0039] The preferred embodiments of the present invention have been specifically described above, but the present invention is not limited to the embodiments. Those skilled in the art may make various equivalent modifications or substitutions without violating the spirit of the present invention. These equivalent modifications or substitutions are all included in the scope defined by the claims of this application.

Claims

1. A method for preparing a phenolic resin-based hard carbon material and its energy storage application, characterized in that: The closed cell volume is 0.15-0.35cm 3 / g, with a specific surface area of ​​5-15m 2 / g, is a hard carbon material with rich closed-pore structure inside; the hard carbon material uses phenolic resin as a precursor and C 60 As an additive, through C 60 The phenolic pyrolysis stage is used as a template to achieve directional crystallization of graphite microdomains in hard carbon materials, and C 60 The structural reorganization in the phenolic carbonization stage introduces additional sodium storage sites, realizing the regulation of graphite microdomains and closed-pore structures of hard carbon materials. When used as negative electrode materials for sodium-ion batteries, the platform capacity can be controlled, showing high sodium storage capacity and high cycle stability.

2. A method for preparing a phenolic resin-based hard carbon material and its energy storage application as claimed in claim 1, characterized in that Prepared by the following method: Step 1): C 60 Dissolve in solvent 1, stir at 30°C for 30 minutes to obtain solution 1, dissolve phenolic resin in solvent 2, stir at 30°C for 30 minutes to obtain solution 2; Step 2): mixing the two solutions, removing the solvent, and drying to obtain a mixed solid product; Step 3): placing the mixed solid product into a high-temperature carbonization furnace and heating it to 1300-1500° C. in an argon atmosphere to obtain the desired hard carbon material.

3. The method according to claim 2, characterized in that: The phenolic resin is a resol linear phenolic resin, the first solvent is selected from one or more of toluene, chlorobenzene, n-hexane, carbon disulfide, and carbon tetrachloride, and the second solvent is selected from one or more of ethanol, water, methanol, and acetone.

4. The method according to claim 2, characterized in that: Solution C 60 The concentration of phenolic resin in solution 2 is 5-100 mg / ml, the concentration of phenolic resin in solution 2 is 0.1-0.5 g / ml, and in the mixed solution C 60 The mass of phenolic resin accounts for 0.1% to 15% of the mass of phenolic resin.

5. Application of a phenolic resin-based hard carbon material with a rich closed-pore structure obtained by the method of claims 1 to 4 in a negative electrode material for a sodium ion battery.

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