Biomass carbon sodium ion battery negative electrode material and preparation method thereof

Abstract

The invention relates to the technical field of sodium ion battery negative electrode materials, in particular to a biomass carbon sodium ion battery negative electrode material and a preparation method thereof. The preparation method comprises the following steps: step 1, cleaning and cutting solidago canadensis into sections, freezing and freeze-drying to obtain biomass carbon; and 2, mixing the biomass carbon and nano graphite, pre-carbonizing, carbonizing at high temperature, sequentially grinding and sieving for the first time, treating in an alkaline solution, treating in an acid solution after suction filtration, cleaning in water to be neutral after suction filtration, drying, and grinding and sieving for the second time to obtain the biomass carbon sodium ion battery negative electrode material. According to the invention, resource application of alien invasive plants is realized. According to the invention, the solidago canadensis is used as a biomass material to prepare the biomass carbon, and the biomass carbon is modified by using the nano-graphite, so that the prepared sodium ion battery negative electrode material has relatively high practical application value.

Description

Technical Field

[0001] The present invention relates to the technical field of sodium ion battery negative electrode materials, and in particular to a biomass carbon sodium ion battery negative electrode material improved by using nanographite and a preparation method thereof. Background Art

[0002] In the energy storage field, lithium-ion batteries are widely used due to their high energy density, high specific capacity, and excellent cycle performance. However, due to the limited availability of lithium resources and the high cost of lithium battery manufacturing, there is an urgent need to find alternative energy sources. Sodium and lithium belong to the same main group of alkali metal elements and have similar physical and chemical properties. Researchers are working to identify more performant cathode and anode materials for sodium-ion batteries. Currently, the major limitation to the development of sodium-ion batteries is the lack of anode materials with high storage capacity, excellent cycle stability, and a green, non-toxic, and low-cost performance. Research has identified hard carbon as the most promising anode material for sodium-ion batteries, offering advantages such as high electrical conductivity, low cost, and excellent cycle performance. Hard carbon materials are largely derived from the high-temperature pyrolysis of biomass, including materials such as straw, fruit peels, and plant tissue. In recent years, the prevalence of invasive alien plants has become severe, causing serious damage to the ecological environment. Finding appropriate resource utilization methods has become an advantageous option for their control. Therefore, using invasive plants to create efficient sodium-ion battery anode materials can not only solve the problem of invasive plant control and protect the ecological environment, but also provide new methods and ideas for the development of sodium-ion batteries. However, although invasive plants have good electrochemical properties and a wide range of pore sizes, the material suffers from significant capacity loss, which hinders its practical application. Summary of the Invention

[0003] Based on the above content, the present invention provides a biomass carbon sodium ion battery negative electrode material improved by nanographite and a preparation method thereof.

[0004] To achieve the above object, the present invention provides the following solutions:

[0005] One of the technical solutions of the present invention is a method for preparing a biomass carbon sodium ion battery negative electrode material, comprising the following steps:

[0006] Step 1, washing and cutting the Canada solidago into sections, freezing, and freeze-drying the sections to obtain biomass carbon;

[0007] Step 2: The biomass carbon is mixed with nano-graphite for pre-carbonization and high-temperature carbonization, and then the mixture is ground and sieved for the first time, placed in an alkaline solution for treatment, filtered and placed in an acid solution for treatment, filtered and placed in water for washing until neutral, dried, and ground and sieved for the second time to obtain the biomass carbon sodium ion battery negative electrode material.

[0008] In a preferred embodiment of the present invention, in step 1, the freeze-drying step further includes a grinding step.

[0009] In a preferred embodiment of the present invention, the pre-carbonization temperature is 500-700° C. and the time is 2-4 hours.

[0010] In a preferred embodiment of the present invention, the high-temperature carbonization temperature is 1200° C. and the time is 2 hours.

[0011] In a preferred embodiment of the present invention, the treatment in an alkaline solution is specifically placing the substrate in a KOH solution with a mass concentration of 10%, stirring for 2 hours, and then heating at 70° C. for 2 hours.

[0012] In a preferred embodiment of the present invention, the treatment in an acid solution is specifically placing the sample in a 3 mol / L HCl solution and stirring for 2 hours, followed by heating at 50° C. for 2 hours.

[0013] In a preferred embodiment of the present invention, the first grinding and screening is specifically grinding through a 60-mesh sieve; the second grinding and screening is specifically grinding through a 200-mesh sieve.

[0014] The second technical solution of the present invention is a biomass carbon sodium ion battery negative electrode material prepared according to the above-mentioned preparation method.

[0015] The third technical solution of the present invention is a sodium ion battery, comprising a negative electrode, a positive electrode, a separator and an electrolyte; the negative electrode comprises the above-mentioned biomass carbon sodium ion battery negative electrode material.

[0016] The present invention discloses the following technical effects:

[0017] The method of the invention is simple, uses Canada goldenrod as a raw material, and realizes resource utilization of alien invasive plants.

[0018] The present invention uses Canada goldenrod as a biomass material to prepare biomass carbon, and uses nanographite to modify the biomass carbon. The prepared sodium ion battery negative electrode material has high first discharge capacity and high first coulombic efficiency, good cycle stability, and high practical application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0020] Figure 1The SEM images of the biomass carbon sodium ion battery negative electrode materials prepared with different nanographite doping ratios (0%, 5%, 10% and 15%) in Example 1 are as follows: Figure 1 As shown; wherein, (a) represents 0%, (b) represents 5%, (c) represents 10%, and (d) represents 15%.

[0021] Figure 2 (a) XRD, (b) Raman spectra, (c) N2 adsorption-desorption isotherms and (d) BET pore size distribution of biomass carbon sodium ion battery anode materials prepared with different nanographite doping ratios (0%, 5%, 10% and 15%) in Example 1.

[0022] Figure 3 This is the XPS total spectrum of the biomass carbon sodium ion battery negative electrode material prepared with different nanographite doping ratios (0%, 5%, 10% and 15%) in Example 1; wherein (a) represents 0%, (b) represents 5%, (c) represents 10%, and (d) represents 15%.

[0023] Figure 4 These are the XPS fitting peaks of the biomass carbon sodium ion battery negative electrode materials prepared with different nanographite doping ratios (0%, 5%, 10% and 15%) in Example 1; where (a) represents 0%, (b) represents 5%, (c) represents 10%, and (d) represents 15%.

[0024] Figure 5 These are the XRD images of the biomass carbon sodium ion battery negative electrode materials prepared with different nanographite doping ratios (0%, 5%, 10% and 15%) after charge and discharge tests in Example 1.

[0025] Figure 6 Biomass carbon sodium ion battery negative electrode material prepared with different nanographite doping ratios (0%, 5%, 10% and 15%) in Example 1: (a) first charge and discharge curve at 20 mA / g, (b) ratio of platform capacity to slope capacity in the first charge and discharge curve, (c) short cycle test at a current density of 50 mA / g, and (d) long cycle test at a current density of 200 mA / g.

[0026] Figure 7 The pseudocapacitance ratio of the biomass carbon sodium ion battery negative electrode material prepared with different nanographite doping ratios (0%, 5%, 10% and 15%) in Example 1 at a scan rate of 0.5 mV / s; wherein, (a) represents a nanographite doping ratio of 0%, (b) represents a nanographite doping ratio of 5%, (c) represents a nanographite doping ratio of 10%, and (d) represents a nanographite doping ratio of 15%. DETAILED DESCRIPTION

[0027] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0028] It should be understood that the terms described herein are intended only to describe particular embodiments and are not intended to limit the present invention. In addition, for numerical ranges herein, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. The intermediate value within any stated value or stated range, and each smaller range between any other stated value or intermediate value within the stated range, is also encompassed within the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded within the scope.

[0029] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of any conflict with any incorporated document, the contents of this specification shall prevail.

[0030] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from the description of the invention. The description and examples are intended to be exemplary only.

[0031] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0032] Unless otherwise specified, the "%" in the present invention refers to mass percentage.

[0033] In view of the resource utilization of alien invasive plants and the application background of sodium ion battery materials, the present invention provides a plant resource solution and a preparation and improvement technology of sodium ion battery negative electrode materials. The present invention further optimizes the invasive plant pyrolysis carbon battery by modification experiments. Canada goldenrod has similar water pipes and special internal pores, and has great potential for use as electrode materials. Nanographite is a carbon material with special structure and properties. Its structure composed of a hexagonal lattice composed of a single layer of carbon atoms gives it excellent flexibility and strength, and exhibits excellent quantum Hall effect and unique electron transport properties. By utilizing the conductivity and structural characteristics of nanographite to complement the performance of biomass carbon, a larger initial battery capacity and reversible capacity can be achieved, thereby improving the efficiency of battery use.

[0034] The first aspect of the present invention provides a method for preparing a biomass carbon sodium ion battery negative electrode material, comprising the following steps:

[0035] Step 1, washing and cutting the Canada solidago into sections, freezing, and freeze-drying the sections to obtain biomass carbon;

[0036] Step 2: The biomass carbon is mixed with nano-graphite and pre-carbonized and high-temperature carbonized, and then the mixture is ground and screened for the first time, placed in an alkaline solution for treatment, filtered and placed in an acid solution for treatment, filtered and placed in water for washing until neutral, dried, and ground and screened for the second time to obtain the biomass carbon sodium ion battery negative electrode material.

[0037] In the present invention, the effects of freeze-drying are as follows:

[0038] 1. Protect the structural integrity of biomass carbon

[0039] Avoiding high-temperature damage: Unlike traditional drying methods (such as hot air drying), the freeze-drying process is carried out at low temperatures, which can effectively avoid high-temperature damage to the biomass carbon structure. This helps to preserve the original pore structure and surface properties of the biomass carbon, providing a good foundation for the subsequent carbonization and activation processes.

[0040] Maintaining pore structure: During the freeze-drying process, the water in the biomass sublimes directly at low temperatures, avoiding pore collapse caused by water evaporation. This intact pore structure is crucial for increasing the specific surface area and adsorption performance of biomass carbon.

[0041] 2. Improve the electrochemical performance of biomass carbon

[0042] Enhanced conductivity: Freeze-dried biomass carbon exhibits better conductivity in electrochemical applications. This is because the internal structure of the biomass carbon is better protected during the freeze-drying process, reducing the increase in resistance caused by structural damage.

[0043] 3. Facilitate subsequent processing and application

[0044] Improved material uniformity: Freeze-dried biomass carbon has a more uniform particle size distribution and structure, which makes subsequent grinding and mixing processes easier and more efficient. Uniform material properties help achieve better performance consistency when preparing electrodes or other composite materials.

[0045] Enhanced material stability: Freeze-dried biochar is more stable during storage and transportation, and is less likely to undergo structural changes or performance degradation due to environmental changes (such as humidity and temperature).

[0046] In a preferred embodiment of the present invention, in step 1, the freeze-drying step further comprises a grinding step. The present invention has no particular requirements on the particle size of the powder obtained by grinding in step 1.

[0047] In a preferred embodiment of the present invention, the pre-carbonization temperature is 500-700° C. and the time is 2-4 hours.

[0048] In a preferred embodiment of the present invention, the high-temperature carbonization temperature is 1200° C. and the time is 2 hours.

[0049] If the temperature of high-temperature carbonization is too high or too low, the cycle performance will decrease, or the long cycle capacity / short cycle capacity will decrease, which is not conducive to battery discharge.

[0050] In a preferred embodiment of the present invention, the treatment in an alkaline solution is specifically placing the substrate in a KOH solution with a mass concentration of 10%, stirring for 2 hours, and then heating at 70° C. for 2 hours.

[0051] The purpose of placing it in an alkaline solution is as follows: on the one hand, it is to remove some tar-like substances in the biomass carbon and remove impurities; on the other hand, it is to perform etching and increase ion channels.

[0052] In a preferred embodiment of the present invention, the treatment in an acid solution is specifically placing the sample in a 3 mol / L HCl solution and stirring for 2 hours, followed by heating at 50° C. for 2 hours.

[0053] In a preferred embodiment of the present invention, the first grinding and screening is specifically grinding through a 60-mesh sieve; the second grinding and screening is specifically grinding through a 200-mesh sieve.

[0054] The second aspect of the present invention provides a biomass carbon sodium ion battery negative electrode material prepared according to the above preparation method.

[0055] The third aspect of the present invention provides a sodium ion battery, comprising a negative electrode, a positive electrode, a separator and an electrolyte; the negative electrode comprises the above-mentioned biomass carbon sodium ion battery negative electrode material.

[0056] Unless otherwise specified, the technical solutions described in the present invention are all conventional solutions in the field, and the reagents or raw materials used, unless otherwise specified, are purchased from commercial channels or have been disclosed.

[0057] The nanographite used in the embodiments of the present invention has a purity of ≥99.9%, D50 <600 nm, and CAS No. 7782-42-5.

[0058] The technical solutions provided by the present invention are described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0059] Example 1

[0060] Step 1, biomass carbon preparation: clean and cut the stems of Canada goldenrod into segments with a length of 2-5 cm, place them in a -20°C refrigerator, freeze them for 24 hours, then place them in a freeze dryer and vacuum freeze-dry them for 48 hours, and then grind them into powder for later use.

[0061] Step 2, Nanographite Doping: The biomass carbon powder and nanographite were mixed in proportions of 0%, 5%, 10%, and 15% of the biomass carbon powder mass, respectively. The resulting mixture was pre-carbonized in a tube furnace at 600°C for two hours under an argon atmosphere to remove tar and impurities. The mixture was then subjected to high-temperature carbonization at 1200°C for two hours for final carbonization. The carbonized material was taken out, ground, passed through a 60-mesh sieve, and then washed with 100 mL of KOH solution (10% mass fraction). It was placed on a magnetic stirrer and stirred for 2 hours, and then placed in an oven at 70°C for 2 hours. The filtrate was removed by suction, and HCl solution (100 mL, 3 mol / L) was added for washing to remove impurities and excess KOH. It was placed on a magnetic stirrer and stirred for 2 hours, and then placed in an oven at 70°C for 2 hours. The filtrate was removed by suction, and then 50 mL of ethanol was added for washing. This step is to remove excess HCl and other non-volatile impurities in the sample. It was placed on a magnetic stirrer for 2 hours and then placed in an oven at 50°C for 2 hours. The sample was further heated in the oven for 2 hours, then washed with deionized water until neutral, filtered and dried at 70°C for 24 hours, ground and passed through a 200-mesh sieve to obtain the final biomass carbon sodium ion battery negative electrode material, marked as G-SCL-X, where G- represents nanographite (Graphite), SCL represents the biomass carbon prepared in step 1, and X is the mass fraction of the doped nanographite; corresponding to the above-mentioned nanographite doping percentages of 0%, 5%, 10% and 15%, the biomass carbon sodium ion battery negative electrode materials are marked as G-SCL-0%, G-SCL-5%, G-SCL-10% and G-SCL-15%, respectively.

[0062] The physical structure of the biomass carbon sodium ion battery anode materials prepared with different nanographite doping ratios (0%, 5%, 10% and 15%) was characterized by SEM, XRD, Raman spectroscopy, XPS and other methods. In order to understand the electrochemical performance of Canada goldenrod after doping with nanographite, the materials were prepared into half-cells for charge and discharge tests. The test method is as follows:

[0063] The biomass carbon sodium ion battery negative electrode material prepared in step 2, the binder, and the conductive carbon black were ground and mixed in a mass ratio of 8:1:1 for 20 minutes. Deionized water was then added and ground again until a viscous liquid was prepared. The slurry was coated on a copper foil current collector using a coater and then dried in a vacuum drying oven at 60°C for 12 hours. The tablets were then pressed using a tablet press and dried in a vacuum drying oven for another 12 hours. The cells were then assembled in an argon-filled glove box. The separator used was a fiber film Whatman GF / D, and the electrolyte was a mixture of 1 mol / L NaClO4 and a 1:1 volume ratio of EC and PC. 5% fluoroethylene carbonate was used as an electrolyte additive. The cells were assembled in a glove box and allowed to stand for 12 hours to obtain a sodium ion button cell. Constant current charge and discharge tests and cycle performance tests were performed using a constant current potentiostat and an electrochemical workstation. The results are as follows:

[0064] Figure 1 SEM images of biomass carbon sodium ion battery anode materials prepared with different nanographite doping ratios (0%, 5%, 10% and 15%) are shown in Figure 2. Figure 1 As shown; wherein, (a) represents 0%, (b) represents 5%, (c) represents 10%, and (d) represents 15%.

[0065] Figure 2 (a) XRD, (b) Raman spectra, (c) N2 adsorption-desorption isotherms and (d) BET pore size distribution of biomass carbon sodium ion battery anode materials prepared with different nanographite doping ratios (0%, 5%, 10% and 15%).

[0066] Figure 3 XPS spectra of biomass carbon sodium ion battery anode materials prepared with different nanographite doping ratios (0%, 5%, 10% and 15%); (a) represents 0%, (b) represents 5%, (c) represents 10%, and (d) represents 15%.

[0067] Figure 4 XPS fitting peaks of biomass carbon sodium ion battery anode materials prepared with different nanographite doping ratios (0%, 5%, 10% and 15%); where (a) represents 0%, (b) represents 5%, (c) represents 10%, and (d) represents 15%.

[0068] Figure 5The XRD images of the biomass carbon sodium ion battery negative electrode material prepared with different nanographite doping ratios (0%, 5%, 10% and 15%) after cycling (100 cycles at a current density of 20 mA / g, for charge and discharge tests). Figure 1-5 The successful doping of biomass carbon with nanographite was observed, providing certain defect sites for ion adsorption. Compared with the SCL material, the GSCLX material had a smaller pore size, a higher degree of graphitization, and a higher degree of disorder. The 15% doped SCL (GSCL-15%) had the most disordered structure.

[0069] Figure 6 For the biomass carbon sodium ion battery negative electrode material prepared with different nanographite doping ratios (0%, 5%, 10% and 15%) in Example 1, (a) the first charge and discharge curve at 20mA / g, (b) the ratio of the platform capacity to the slope capacity in the first charge and discharge curve, (c) the short cycle test at a current density of 50mA / g, and (d) the long cycle test at a current density of 200mA / g. Figure 6 As can be seen in (a) and (b), SCL doped with nanographite can improve the initial capacity of the battery. At a voltage of 0-3V and a current density of 20mA / g, the first discharge capacities of G-SCL-0%, G-SCL-5%, G-SCL-10%, and G-SCL-15% are 368.57, 379.77, 387.14, and 396.11mAh / g, and the first coulombic efficiency is 56.70%, 66.35%, 68.56%, and 67.01%, respectively. High coulombic efficiency means that more effective capacity can be retained in the first cycle, thereby improving the actual availability of the battery. Figure 6 As can be seen in (c) and (d), in the short cycle and long cycle tests, the doping of nanographite has a good effect on improving the cycle stability of the battery.

[0070] Figure 7 The pseudocapacitance ratio of the biomass carbon sodium ion battery negative electrode material prepared with different nanographite doping ratios (0%, 5%, 10% and 15%) in Example 1 at a scan rate of 0.5 mV / s; wherein, (a) represents a nanographite doping ratio of 0%, (b) represents a nanographite doping ratio of 5%, (c) represents a nanographite doping ratio of 10%, and (d) represents a nanographite doping ratio of 15%; cyclic voltammetry tests showed that with the increase of doped nanographite, the surface pseudocapacitance control process of the battery increased, thereby increasing part of the battery capacity.

[0071] On the basis of Example 1, different biomass materials were used to prepare biomass carbon sodium ion battery negative electrode materials (that is, the only difference from Example 1 is that Canada thistle was replaced with other biomass materials, and the other steps and parameters were the same as Example 1). The results are summarized in Table 1.

[0072] As can be seen from Table 1, the sodium ion negative electrode material prepared from Canada goldenrod pyrolysis carbon doped with different proportions of nanographite has good first charge and discharge capacity and reversible capacity, and shows superior electrochemical performance compared with existing biomass sodium ion batteries.

[0073] Table 1 Comparison of electrochemical performance of different biomass carbon batteries

[0074]

[0075] The embodiments described above are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by persons skilled in the art should fall within the scope of protection defined by the claims of the present invention.

Claims

1. A method for preparing a biomass carbon sodium ion battery negative electrode material, characterized in that: The following steps are involved: Step 1, washing and cutting the Canada solidago into sections, freezing, and freeze-drying the sections to obtain biomass carbon; Step 2: The biomass carbon is mixed with nano-graphite for pre-carbonization and high-temperature carbonization, and then the mixture is ground and sieved for the first time, placed in an alkaline solution for treatment, filtered and placed in an acid solution for treatment, filtered and placed in water for washing until neutral, dried, and ground and sieved for the second time to obtain the biomass carbon sodium ion battery negative electrode material.

2. The preparation method according to claim 1, characterized in that The freeze-drying step further includes a grinding step.

3. The preparation method according to claim 1, characterized in that The pre-carbonization temperature is 500-700° C. and the time is 2-4 hours.

4. The preparation method according to claim 1, characterized in that The temperature of the high-temperature carbonization is 1200° C. and the time is 2 hours.

5. The preparation method according to claim 1, characterized in that The treatment in the alkaline solution is specifically to place the product in a KOH solution with a mass concentration of 10% and stir for 2 hours, and then heat at 70° C. for 2 hours.

6. The preparation method according to claim 1, characterized in that The treatment in an acid solution specifically includes placing the sample in a 3 mol / L HCl solution and stirring for 2 hours, followed by heating at 50° C. for 2 hours.

7. The preparation method according to claim 1, characterized in that The first grinding and screening is specifically grinding through a 60-mesh sieve; the second grinding and screening is specifically grinding through a 200-mesh sieve.

8. A biomass carbon sodium ion battery negative electrode material prepared according to the preparation method according to any one of claims 1 to 7.

9. A sodium ion battery, characterized in that: It comprises a negative electrode, a positive electrode, a separator and an electrolyte; the negative electrode comprises the biomass carbon sodium ion battery negative electrode material according to claim 8.

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