Phenolic resin hard carbon microspheres as well as preparation method and application thereof

Abstract

The invention relates to the field of sodium ion battery negative electrode materials, and discloses phenolic resin hard carbon microspheres as well as a preparation method and application thereof. The preparation method specifically comprises the following steps: by using copper gluconate as an active site, inducing resorcinol and a formaldehyde solution to polymerize on the surface of the copper gluconate, so as to obtain phenolic resin rich in copper components, and after high-temperature carbonization, obtaining the phenolic resin hard carbon microspheres with rich ultra-micropores and a small amount of small-size mesopores by using escape of ultra-small copper particles. The preparation process route is simple, raw materials are cheap and easy to obtain, and industrial production is easy. The prepared phenolic resin-based hard carbon negative electrode material has the advantages of low cost, high reversible capacity, high initial coulombic efficiency, excellent cycle performance and the like.

Description

Technical Field

[0001] This invention belongs to the field of sodium-ion battery electrode materials, specifically relating to a phenolic resin hard carbon microsphere, its preparation method, and its application. Background Technology

[0002] Sodium-ion batteries, with their advantages of abundant sodium resources and low cost, have shown great application potential in areas such as grid-connected energy storage for renewable energy sources like wind and solar power, electric two-wheelers / low-speed electric vehicles, and 5G communication base stations. Developing hard carbon anode materials that combine low cost and high performance is key to driving sodium-ion batteries into the consumer market. Hard carbon, as a carbon material that is difficult to graphitize, is characterized by numerous defect sites, high disorder, and large interlayer spacing. Precursors for hard carbon materials mainly include biomass, polymers, coal, and resins. Compared to biomass and coal precursors, phenolic resin precursors have advantages such as high carbon yield, low ash content, and easier structural control. However, phenolic resins decompose during high-temperature pyrolysis, producing a large amount of volatile gases, forming hard carbon materials with excessive micropores and poor conductivity, resulting in lower initial coulombic efficiency and poor cycle stability.

[0003] To improve the microstructure of phenolic resin-based hard carbon, pretreatment or heteroatom doping modification processes are commonly used. For example, patent application CN112125295B involves a solvothermal reaction of phenolic resin, sucrose, and deionized water, followed by high-temperature carbonization to obtain a hard carbon material exhibiting high initial coulombic efficiency but low specific capacity. Patent application CN118099421A involves uniformly stirring hexachlorotriphosphazene in a phenolic resin solution, then adding an organic base and phloroglucinol for polymerization, followed by freeze-drying and carbonization with sodium molybdate to obtain hard carbon. While this doping and crosslinking modification method effectively improves electrochemical performance, it is costly, cumbersome, and difficult to scale up. Therefore, developing a simple process for preparing high-performance phenolic resin hard carbon materials is crucial for accelerating the industrialization of sodium-ion batteries and enhancing market competitiveness. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to overcome the shortcomings of the prior art and provide a phenolic resin hard carbon microsphere, its preparation method and application.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows: In a first aspect, the present invention provides a method for preparing phenolic resin hard carbon microspheres, comprising the following steps: Step 1: Add resorcinol, formaldehyde aqueous solution and copper gluconate to deionized water, and stir thoroughly to form a homogeneous solution; Step 2: The solution obtained in Step 1 is heated and stirred, then filtered and baked to obtain copper-containing phenolic resin microspheres; Step 3: Carbonize the copper-containing phenolic resin microspheres obtained in Step 2 under an inert atmosphere to obtain phenolic resin hard carbon microspheres.

[0006] Furthermore, the concentration of the formaldehyde aqueous solution in step 1 is 37 wt%.

[0007] Further, in step 1, the mass ratio of hydroquinone, formaldehyde aqueous solution, and copper gluconate is 0.5~1.5:1.5:0.5~3.

[0008] Furthermore, in step 2, the heating and stirring temperature is 80~95℃, and the time is 0.5~2 hours.

[0009] Furthermore, in step 2, the baking temperature is 60~90℃ and the baking time is 2~10 hours.

[0010] Furthermore, the inert atmosphere in step 3 includes any one of argon, nitrogen, helium, and neon.

[0011] Furthermore, in step 3, the carbonization treatment temperature is 1200~1600℃, and the time is 1~5 hours.

[0012] Secondly, the present invention provides phenolic resin hard carbon microspheres prepared by the preparation method described in the first aspect.

[0013] Thirdly, the present invention provides the application of phenolic resin hard carbon microspheres prepared by the preparation method described in the first aspect in sodium-ion battery electrode materials.

[0014] Fourthly, the present invention provides a sodium-ion battery electrode material comprising phenolic resin hard carbon microspheres prepared by the preparation method described in the first aspect of claim.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) Using inexpensive copper gluconate as the polymerization site, efficient polymerization of phenolic resin in aqueous solution at a relatively low temperature was achieved. The polymerization process is simple to operate, takes less time, and is easy to scale up. The obtained phenolic hard carbon exhibits a regular spherical morphology with a particle size of a few micrometers, which can promote sodium ion diffusion and increase compaction density.

[0016] (2) The copper-containing organic components are uniformly dispersed at the molecular level within the phenolic resin by ingeniously utilizing an in-situ polymerization strategy. During the pyrolysis-low-temperature carbonization (<600℃) stage, the copper-containing organic components are simultaneously carbothermally reduced to copper nanoparticles. Due to the poor affinity between carbon and copper, during the high-temperature carbonization stage (>600℃), as the carbonization temperature increases, the copper nanoparticles gradually escape from the interior of the phenolic carbon spheres to the surface. In this process, the copper nanoparticles act as templates, inducing the formation of abundant pores, especially ultramicropores and smaller mesopores, within the phenolic carbon spheres, thereby significantly improving the sodium storage performance of phenolic hard carbon in terms of specific capacity and rate capability. Attached Figure Description

[0017] Figure 1 The X-ray diffraction pattern is shown for the phenolic resin hard carbon microspheres prepared in Example 1 of this invention.

[0018] Figure 2 This is a scanning electron microscope image of the phenolic resin hard carbon microspheres prepared in Example 1 of the present invention.

[0019] Figure 3 This is a high-resolution transmission electron microscope image of the phenolic resin hard carbon microspheres prepared in Example 1 of the present invention.

[0020] Figure 4 The image shows the Raman spectrum of the phenolic resin hard carbon microspheres prepared in Example 1 of this invention.

[0021] Figure 5 The small-angle X-ray scattering curves are those of the phenolic resin hard carbon microspheres prepared in Example 1 of this invention.

[0022] Figure 6 The small-angle X-ray scattering curves are shown for the phenolic resin hard carbon microspheres prepared in Comparative Example 1 of this invention.

[0023] Figure 7 The charge-discharge curve of the phenolic resin hard carbon microspheres prepared in Example 1 of this invention is shown.

[0024] Figure 8 This is a charge-discharge curve of the phenolic resin hard carbon microspheres prepared in Comparative Example 1 of this invention. Detailed Implementation

[0025] To facilitate understanding of the present invention, a more comprehensive description will be given below. 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 thorough and complete understanding of the disclosure of the present invention.

[0026] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0027] 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. Example 1

[0028] Step 1: Add resorcinol, 37wt% formaldehyde aqueous solution and copper gluconate to deionized water in a mass ratio of 1:1.5:1, and stir thoroughly to form a homogeneous solution.

[0029] Step 2: Stir the solution obtained in Step 1 at 80°C for 1 hour, filter it, and then bake the solid product in a forced-air oven at 80°C for 6 hours to obtain copper-containing phenolic resin microspheres.

[0030] Step 3: The copper-containing phenolic resin microspheres obtained in Step 2 are subjected to high-temperature carbonization treatment at 1400℃ for 2 hours under a nitrogen atmosphere, and then cooled to room temperature to obtain phenolic resin hard carbon microspheres.

[0031] Figure 1 The image shows the X-ray diffraction pattern of the phenolic resin hard carbon microspheres prepared in Example 1 of this invention. The image reveals broad diffraction peaks on the 002 and 100 crystal planes, indicating a low degree of graphitization and a large interlayer spacing, typical characteristics of hard carbon materials.

[0032] Figure 2 This is a scanning electron microscope image of the phenolic resin hard carbon microspheres prepared in Example 1 of the present invention. The image shows that the hard carbon material exhibits a regular spherical morphology with a particle size of less than 4 micrometers.

[0033] Figure 3 This is a high-resolution transmission electron microscope (TEM) image of the phenolic resin hard carbon microspheres prepared in Example 1 of this invention. The image shows that the graphite crystallites in this hard carbon material are small in size, with disordered and chaotic lattice fringes, indicating low crystallinity.

[0034] Figure 4 The image shows the Raman spectrum of the phenolic resin hard carbon microspheres prepared in Example 1 of this invention. As can be seen from the image, this hard carbon material exhibits numerous defects and a high degree of disorder.

[0035] Figure 5 The figure shows the small-angle X-ray scattering curve of the phenolic resin hard carbon microspheres prepared in Example 1 of this invention. As can be seen from the figure, this hard carbon material has a large number of closed-pore structures with small pore diameters.

[0036] The obtained phenolic resin hard carbon microspheres were uniformly mixed with sodium carboxymethyl cellulose at a mass ratio of 9:0.5:0.5. The mixture was then ground into a slurry using deionized water as a solvent and coated onto aluminum foil. The slurry was dried in a vacuum oven at 100°C for 10 hours to form an electrode sheet. This electrode was then assembled into a CR2025 coin cell. A sodium metal sheet was used as the counter electrode, a glass fiber felt as the separator, and a 1 mol / L sodium perchlorate / ethylene carbonate / dimethyl carbonate solution as the electrolyte. Half-cell tests at room temperature showed that the material achieved a first-cycle reversible specific capacity of 346 mAh / g at a current density of 0.1 C, with an initial coulombic efficiency of 88.3%. Figure 7 This is a charge-discharge curve of the phenolic resin hard carbon microspheres prepared in Example 1 of this invention. As can be seen from the figure, this hard carbon material exhibits typical electrochemical sodium storage characteristics of hard carbon materials when used in sodium-ion batteries. It possesses a high low-voltage plateau, and the capacity contribution from the slope region is also relatively high. Example 2

[0037] Step 1: Add resorcinol, 37wt% formaldehyde aqueous solution and copper gluconate to deionized water in a mass ratio of 0.5:1.5:0.5 and stir thoroughly to form a homogeneous solution.

[0038] Step 2: Stir the solution obtained in Step 1 at 95°C for 0.5 hours, filter it, and then bake the solid product in a forced-air oven at 90°C for 2 hours to obtain copper-containing phenolic resin microspheres.

[0039] Step 3: The copper-containing phenolic resin microspheres obtained in Step 2 are subjected to high-temperature carbonization treatment at 1200℃ for 5 hours under an argon atmosphere, and then cooled to room temperature to obtain phenolic resin hard carbon microspheres.

[0040] Sodium-ion button half-cells were assembled according to the same process and conditions as in Example 1. The test results showed that the material achieved a first-cycle reversible specific capacity of 326.2 mAh / g at a current density of 0.1C and an initial coulombic efficiency of 83.1%. Example 3

[0041] Step 1: Add resorcinol, 37wt% formaldehyde aqueous solution and copper gluconate to deionized water in a mass ratio of 1.5:1.5:3 and stir thoroughly to form a homogeneous solution.

[0042] Step 2: Stir the solution obtained in Step 1 at 80°C for 2 hours, filter it, and then bake the solid product in a forced-air oven at 60°C for 10 hours to obtain copper-containing phenolic resin microspheres.

[0043] Step 3: The copper-containing phenolic resin microspheres obtained in Step 2 are subjected to high-temperature carbonization treatment at 1600℃ for 1 hour under a helium atmosphere, and then cooled to room temperature to obtain phenolic resin hard carbon microspheres.

[0044] Sodium-ion button half-cells were assembled according to the same process and conditions as in Example 1. The test results showed that the material achieved a first-cycle reversible specific capacity of 324.4 mAh / g at a current density of 0.1C and an initial coulombic efficiency of 82.2%. Example 4

[0045] Step 1: Add resorcinol, 37wt% formaldehyde aqueous solution and copper gluconate to deionized water in a mass ratio of 0.7:1.5:1 and stir thoroughly to form a homogeneous solution.

[0046] Step 2: Stir the solution obtained in Step 1 at 85°C for 1.5 hours, filter it, and then bake the solid product in a forced-air oven at 85°C for 4 hours to obtain copper-containing phenolic resin microspheres.

[0047] Step 3: The copper-containing phenolic resin microspheres obtained in Step 2 are subjected to high-temperature carbonization treatment at 1500℃ for 1.5 hours under an argon atmosphere, and then cooled to room temperature to obtain phenolic resin hard carbon microspheres.

[0048] Sodium-ion button half-cells were assembled according to the same process and conditions as in Example 1. The test results showed that the material achieved a first-cycle reversible specific capacity of 315 mAh / g at a current density of 0.1C and an initial coulombic efficiency of 81.8%. Example 5

[0049] Step 1: Add resorcinol, 37wt% formaldehyde aqueous solution and copper gluconate to deionized water in a mass ratio of 1.3:1.5:1 and stir thoroughly to form a homogeneous solution.

[0050] Step 2: Stir the solution obtained in Step 1 at 90°C for 0.5 hours, filter it, and then bake the solid product in a forced-air oven at 70°C for 8 hours to obtain copper-containing phenolic resin microspheres.

[0051] Step 3: The copper-containing phenolic resin microspheres obtained in Step 2 are subjected to high-temperature carbonization treatment at 1300℃ for 4 hours under a nitrogen atmosphere, and then cooled to room temperature to obtain phenolic resin hard carbon microspheres.

[0052] Sodium-ion button half-cells were assembled according to the same process and conditions as in Example 1. The test results showed that the material achieved a first-cycle reversible specific capacity of 322 mAh / g at a current density of 0.1C and an initial coulombic efficiency of 82.9%.

[0053] Comparative Example 1 Step 1: Add resorcinol, 37wt% formaldehyde aqueous solution and potassium gluconate to deionized water in a mass ratio of 1:1.5:1 and stir thoroughly to form a homogeneous solution.

[0054] Step 2: Stir the solution obtained in Step 1 at 80°C for 1 hour, filter it, and then bake the solid product in a forced-air oven at 80°C for 6 hours to obtain potassium-containing phenolic resin microspheres.

[0055] Step 3: The potassium-containing phenolic resin microspheres obtained in Step 2 are subjected to high-temperature carbonization treatment at 1400℃ for 2 hours under a nitrogen atmosphere, and then cooled to room temperature to obtain phenolic resin hard carbon microspheres.

[0056] Figure 6 The image shows the small-angle X-ray scattering curve of the phenolic resin hard carbon microspheres prepared in Comparative Example 1 of this invention. It can be observed that, compared with the hard carbon material obtained in Example 1, this hard carbon material has relatively fewer closed-pore structures and relatively larger closed-pore diameters.

[0057] Sodium-ion button half-cells were assembled according to the same process and conditions as in Example 1. The test results showed that the material had a first-cycle reversible specific capacity of only 213 mAh / g at a current density of 0.1C and an initial coulombic efficiency of 60.3%. Figure 8 This is a charge-discharge curve of the phenolic resin hard carbon microspheres prepared in Comparative Example 1 of this invention. The figure shows that, compared with the hard carbon material obtained in Example 1, the reversible specific capacity of this hard carbon material is significantly lower, and the capacity contribution in the low-voltage plateau region is significantly reduced.

[0058] Comparative Example 2 Step 1: Add resorcinol, 37wt% formaldehyde aqueous solution and zinc gluconate to deionized water in a mass ratio of 1:1.5:1 and stir thoroughly to form a homogeneous solution.

[0059] Step 2: Stir the solution obtained in Step 1 at 80°C for 1 hour, filter it, and then bake the solid product in a forced-air oven at 80°C for 6 hours to obtain zinc-containing phenolic resin microspheres.

[0060] Step 3: The zinc-containing phenolic resin microspheres obtained in Step 2 are subjected to high-temperature carbonization treatment at 1400℃ for 2 hours under a nitrogen atmosphere, and then cooled to room temperature to obtain phenolic resin hard carbon microspheres.

[0061] Sodium-ion button half-cells were assembled according to the same process and conditions as in Example 1. The test results showed that the material had a first-cycle reversible specific capacity of 277 mAh / g and an initial coulombic efficiency of 72.9% at a current density of 0.1C.

[0062] The above description is only for better explaining the embodiments of the present invention and is not intended to limit them. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention shall fall within the scope of the present invention.

Claims

1. A method for preparing phenolic resin hard carbon microspheres, characterized in that, Includes the following steps: Step 1: Add resorcinol, formaldehyde aqueous solution and copper gluconate to deionized water, and stir thoroughly to form a homogeneous solution; Step 2: The solution obtained in Step 1 is heated and stirred, then filtered and baked to obtain copper-containing phenolic resin microspheres; Step 3: Carbonize the copper-containing phenolic resin microspheres obtained in Step 2 under an inert atmosphere to obtain phenolic resin hard carbon microspheres.

2. The preparation method according to claim 1, characterized in that, The concentration of the formaldehyde aqueous solution in step 1 is 37 wt%.

3. The preparation method according to claim 2, characterized in that, In step 1, the mass ratio of hydroquinone, formaldehyde aqueous solution, and copper gluconate is 0.5~1.5:1.5:0.5~3.

4. The preparation method according to claim 1, characterized in that, In step 2, the heating and stirring temperature is 80~95℃, and the time is 0.5~2 hours.

5. The preparation method according to claim 1, characterized in that, In step 2, the baking temperature is 60~90℃ and the time is 2~10 hours.

6. The preparation method according to claim 1, characterized in that, The inert atmosphere in step 3 includes any one of argon, nitrogen, helium, and neon.

7. The preparation method according to claim 1, characterized in that, The carbonization process in step 3 is carried out at a temperature of 1200~1600℃ for 1~5 hours.

8. Phenolic resin hard carbon microspheres prepared by the preparation method according to any one of claims 1 to 7.

9. The application of the phenolic resin hard carbon microspheres prepared by the preparation method according to any one of claims 1 to 7 in sodium-ion battery electrode materials.

10. A sodium-ion battery electrode material, characterized in that, Including phenolic resin hard carbon microspheres prepared by the preparation method according to any one of claims 1 to 7.

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