Preparation method of size-controllable phenolic resin-based spherical carbon material for potassium ion battery

Abstract

The invention relates to the field of chemical synthetic resin carbon microspheres, in particular to a preparation method of size-controllable phenolic resin-based carbon microspheres. The preparation method comprises the following steps: controlling the volume fraction of ammonia water in a solvent and the heating temperature to obtain phenolic resin microsphere precursors with different sizes; and carbonizing the phenolic resin microspheres at high temperature to obtain hard carbon materials with different sizes. Compared with a traditional preparation method, the phenolic resin-based carbon microspheres with the controllable particle size range can be prepared, and the preparation method is simple, convenient and easy to implement. The phenolic resin-based carbon microspheres prepared by the method have excellent potassium storage capacity and high first-week coulombic efficiency when being used for a potassium ion battery, and particularly have relatively high low-voltage potassium storage capacity.

Description

Technical Field

[0001] The present invention relates to the technical field of negative electrode materials for potassium ion batteries, and in particular to a size-controllable phenolic resin-based hard carbon negative electrode material and a preparation method and application thereof. Background Art

[0002] As the demand for energy storage continues to grow, the need for high energy density devices is also increasing. Over the past few decades, lithium-ion batteries (LIBs) have faced a shortage of lithium resources, which has led to an urgent need to find "next-generation ion batteries". Potassium-ion batteries (PIBs) can complement lithium-ion batteries in large-scale energy storage applications due to their similar redox chemistry and lower material cost. However, the limited energy density of potassium-ion batteries has seriously hindered their practical applications.

[0003] Carbon anode is considered to be an important role in breaking the bottleneck of low energy density of PIB. High energy density devices require high output voltage and high capacity, which depends on the presence of low potential platform (LPP) region in carbon anode materials. Therefore, improving the low potential performance of carbon anode is crucial for the development of high energy density PIB. Among them, hard carbon (HC) with curved carbon layer and closed pore structure is considered to be one of the most promising anode materials. The outstanding low voltage platform capacity (LPP) of HC plays a key role in improving the output voltage and energy density of the whole battery. Therefore, the development of advanced HC anode with excellent LPP performance is crucial to achieve high energy density PIB.

[0004] Phenolic resin material is a commonly used polymer material with the advantages of stable performance, high carbon yield and low cost. It is an excellent potassium ion negative electrode material. However, the synthesis process of spherical phenolic resin-based hard carbon materials is cumbersome. The traditional preparation method often uses a mixture of thermosetting phenolic resin and a curing agent, and then undergoes a process of crushing, curing and crushing before preparing resin microspheres by carbonization. The process is not only cumbersome and time-consuming, but the size of the prepared microspheres is often higher than 100μm and uneven, and the specific capacity is low at low voltage. Although phenolic resin microspheres below 50μm can be prepared by hydrothermal autoclave, the reaction conditions require high temperature and high pressure, and the reaction time is too long, and the cost of industrial production is too high. These problems limit its application in potassium ion batteries. How to improve the low-voltage potassium storage capacity while controlling the size of carbon microspheres is a problem that needs to be solved urgently by technicians in this field. Summary of the invention

[0005] The purpose of the present invention is to provide a method for preparing a size-controllable phenolic resin-based spherical carbon material for potassium ion batteries, so as to solve the problems that the existing phenolic resin-based hard carbon material preparation method is complicated and has poor low-voltage electrochemical performance, which affects its commercial use.

[0006] In order to achieve the above object, the present invention provides a method for preparing a size-controllable phenolic resin-based spherical carbon material for potassium ion batteries, characterized in that it comprises the following steps:

[0007] 1) Mix ethanol and ultrapure water in a flask and stir evenly; then add resorcinol, formaldehyde and ammonia water of different volume fractions (in the solvent) to the solution respectively, then transfer to a heating table, and stir continuously for 24 hours at different temperatures to obtain a light yellow mixed solution; wash the mixed solution with ultrapure water by centrifugation for 3 times, and dry it in an oven at 60°C for 24 hours to obtain a phenolic resin ball precursor;

[0008] 2) The phenolic resin microsphere precursor is carbonized at high temperature to obtain a phenolic resin-based spherical hard carbon material.

[0009] Preferably, in step 1), the volume fraction of aqueous ammonia to the solvent is 8%, 2% and 0.5% respectively.

[0010] Preferably, the heating temperature in step 1) is 20 to 50°C.

[0011] Preferably, the process of high temperature carbonization treatment of the phenolic resin hard carbon in step 2) is to carbonize the phenolic resin microspheres obtained in step 1) at 1100° C. for 2 hours.

[0012] Compared with the prior art, the present invention has the following effective benefits:

[0013] (1) The present invention can not only maintain the spherical morphology of the phenolic resin by controlling the volume fraction of ammonia water and the reaction temperature, but also prepare a uniform and size-controlled phenolic resin microsphere precursor. The closed-cell structure in the carbon sphere is generated under high-temperature carbonization, further improving the specific capacity of the battery at low voltage.

[0014] (2) When the size-controllable phenolic resin-based hard carbon material described in the present invention is applied to the negative electrode material of potassium ion batteries, it can solve the problems of complicated synthesis and serious pollution of phenolic resin-based hard carbon materials, and can also improve the battery energy density, specific capacity and cycle performance.

[0015] (3) The entire preparation process is mild, green, and has low material costs. The microsphere yield is high and the sphere radius is controllable, making it suitable for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The SEM and particle size statistics of Example 1 (HCS-1) of the present invention;

[0017] Figure 2 The SEM and particle size statistics of Example 2 (HCS-2) of the present invention;

[0018] Figure 3The SEM and particle size statistics of Example 3 (HCS-3) of the present invention;

[0019] Figure 4 The charge and discharge curves of the potassium ion batteries of Examples 1 to 3 of the present invention at different numbers of cycles;

[0020] Figure 5 It is a comparison diagram of the charge and discharge curves of the 5th cycle of Examples 1 to 3 of the present invention. DETAILED DESCRIPTION

[0021] The present invention will be further described below in conjunction with specific examples. It should be understood that these examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention.

[0022] Example 1

[0023] First, measure 280 mL of ethanol and 40 mL of ultrapure water and mix them into a flask, and stir evenly. Then add 1.56 g of resorcinol, 2.25 mL of formaldehyde, and ammonia water (8% of the solvent volume fraction) to the solution, then transfer it to a heating table and stir it continuously at 25 ° C for 24 hours to obtain a light yellow mixed solution. Wash the mixed solution three times with ultrapure water by centrifugation, and dry it in an oven at 60 ° C for 24 hours to obtain phenolic resin balls. Transfer the resin balls to a tubular furnace and heat them at 5 ° C min in an argon atmosphere. -1 By heating to 1100℃ at a heating rate of 100℃ and keeping it at the specified temperature for 2h, the HCS-1 sample can be obtained, and its average diameter is 122nm.

[0024] The steps of preparing potassium ion battery using HCS-1 are as follows: 80wt% HCS-1, 10wt% carbon black and 10wt% carboxymethyl cellulose (CMC, 2%) binder are mixed into slurry, evenly coated on copper foil, and dried to obtain HCS-1 electrode sheet. When used to evaluate electrochemical potassium storage behavior, metal K is used as the counter electrode, glass fiber (Whatman GF / C) is used as the diaphragm, and the electrolyte is 0.8mol L -1 KPF6 was dissolved in ethylene carbonate (EC) and diethyl carbonate (DEC) (volume ratio of 1:1). The electrochemical performance of HCS-1 was tested, and it showed a first efficiency of 34.5%, and the platform capacity of its ramp charge-discharge curve (below 0.4V) was 34.0mAh g -1 .

[0025] Example 2

[0026] First, measure 280 mL of ethanol and 40 mL of ultrapure water and mix them in a flask, and stir evenly. Then add 1.56 g of resorcinol, 2.25 mL of formaldehyde, and ammonia water (2% of the solvent volume fraction) to the solution, then transfer it to a heating table and stir it continuously at 35 ° C for 24 hours to obtain a light yellow mixed solution. Wash the mixed solution three times with ultrapure water by centrifugation, and dry it in an oven at 60 ° C for 24 hours to obtain phenolic resin balls. Transfer the resin balls to a tubular furnace and heat them at 5 ° C min in an argon atmosphere. -1 By heating to 1100℃ at a heating rate and keeping it at the specified temperature for 2h, the HCS-2 sample can be obtained, and its average diameter is 248nm.

[0027] The steps of preparing potassium ion battery using HCS-2 are as follows: 80wt% HCS-2, 10wt% carbon black and 10wt% carboxymethyl cellulose (CMC, 2%) binder are mixed into slurry, evenly coated on copper foil, and dried to obtain HCS-2 electrode sheet. When used to evaluate electrochemical potassium storage behavior, metal K is used as the counter electrode, glass fiber (Whatman GF / C) is used as the diaphragm, and the electrolyte is 0.8mol L -1 KPF6 was dissolved in ethylene carbonate (EC) and diethyl carbonate (DEC) (volume ratio of 1:1). The electrochemical performance of HCS-2 was tested, and the first efficiency was 53.6%, and the low voltage platform capacity (below 0.4V) was 129.9mAh g -1 .

[0028] Example 3

[0029] First, measure 280 mL of ethanol and 40 mL of ultrapure water and mix them in a flask, and stir evenly. Then add 1.56 g of resorcinol, 2.25 mL of formaldehyde, and ammonia water (0.5% of the solvent volume fraction) to the solution, then transfer it to a heating table and stir it continuously at 45 ° C for 24 hours to obtain a light yellow mixed solution. Wash the mixed solution three times with ultrapure water by centrifugation, and dry it in an oven at 60 ° C for 24 hours to obtain phenolic resin balls. Transfer the resin balls to a tubular furnace and heat them at 5 ° C min in an argon atmosphere. -1 By heating to 1100℃ at a heating rate and keeping it at the specified temperature for 2h, the HCS-3 sample can be obtained, and its average diameter is 914nm.

[0030] The steps of preparing potassium ion battery using HCS-3 are as follows: 80wt% HCS-3, 10wt% carbon black and 10wt% carboxymethyl cellulose (CMC, 2%) binder are mixed into slurry, evenly coated on copper foil, and dried to obtain HCS-3 electrode sheet. When used to evaluate electrochemical potassium storage behavior, metal K is used as the counter electrode, glass fiber (Whatman GF / C) is used as the diaphragm, and the electrolyte is 0.8mol L -1 KPF6 was dissolved in ethylene carbonate (EC) and diethyl carbonate (DEC) (volume ratio of 1:1). The electrochemical performance of HCS-3 was tested, and the first efficiency was 32.1%, and the platform capacity (below 0.4V) of its ramp charge-discharge curve was 19.0mAh g -1 .

[0031] Table 1 Statistics of carbon microsphere diameter and platform capacity

[0032]

Claims

1. A method for preparing a size-controllable phenolic resin-based spherical carbon material for potassium ion batteries, characterized in that: The following steps are involved: 1) Mix ethanol and ultrapure water in a flask and stir evenly; then add resorcinol, formaldehyde and ammonia water of different volume fractions (in the solvent) to the solution respectively, then transfer to a heating table, and stir continuously for 24 hours at different temperatures to obtain a light yellow mixed solution; wash the mixed solution with ultrapure water by centrifugation for 3 times, and dry it in an oven at 60°C for 24 hours to obtain a phenolic resin ball precursor; 2) The phenolic resin microsphere precursor is carbonized at high temperature to obtain a phenolic resin-based spherical hard carbon material.

2. The method for preparing a size-controllable phenolic resin-based spherical carbon material for potassium ion battery according to claim 1, characterized in that: In the step 1), the volume fractions of ammonia water to the solvent are 8%, 2% and 0.5% respectively.

3. The method for preparing a size-controllable phenolic resin-based spherical carbon material for potassium ion battery according to claim 1, characterized in that: The heating temperature in step 1) is 20 to 50°C.

4. The method for preparing a size-controllable phenolic resin-based spherical carbon material for a potassium ion battery according to claim 1, characterized in that: The process of high temperature carbonization treatment of phenolic resin hard carbon in step 2) is to carbonize the phenolic resin microspheres obtained in step 1) at 1100° C. for 2 hours.

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