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

Abstract

The invention discloses a biomass-derived carbon aerogel sodium ion battery negative electrode material and a preparation method thereof, and the preparation process comprises the following steps: cleaning and drying a biomass precursor, cutting the biomass precursor into blocks (sheets) with proper sizes, and carrying out hydrothermal treatment at 180 DEG C for a period of time to obtain biomass hydrogel; further freeze-drying for a period of time to obtain biomass aerogel; heating the obtained biomass aerogel to a certain temperature in an inert atmosphere, and keeping the temperature for 2-5 hours to obtain a biomass carbon material; and soaking the obtained biomass carbon material in an HCl solution with a certain concentration for a certain time, cleaning to be neutral, and drying to obtain the biomass-derived carbon aerogel material. According to the biomass derived carbon aerogel negative electrode material for the sodium ion battery prepared in the embodiment 1, the first discharge capacity reaches 520 mAh g <-1 > under the current density of 50 mA g <-1 >, the reversible capacity reaches 382 mAh g <-1 > after 50 times of circulation, and excellent electrochemical performance is shown.

Description

Technical Field

[0001] The present invention relates to the technical field of sodium ion batteries, in particular to battery negative electrode materials, and specifically provides a biomass-derived carbon aerogel sodium ion battery negative electrode material and a preparation method thereof. Background Art

[0002] Among the existing electrochemical energy storage devices, lithium-ion batteries have been widely studied due to their high theoretical specific capacity and long cycle life. However, the scarcity, uneven distribution and high cost of lithium resources have hindered the further development of lithium-ion batteries. In contrast, sodium-ion batteries are expected to become a candidate for the development of large-scale energy storage systems due to their abundant resources and low cost.

[0003] The key to realizing the application of sodium-ion battery energy storage system is to develop negative electrode materials with low development cost, high theoretical specific capacity and good stability. Similar to the graphite negative electrode of lithium-ion battery, the negative electrode side of sodium-ion battery requires a sodium ion carrier with a stable low-potential charge and discharge platform. Due to the large size of sodium ions, the graphite negative electrode suitable for lithium-ion intercalation cannot accommodate sodium ions. Hard carbon materials with larger interlayer spacing are considered to be one of the most promising negative electrode materials for sodium-ion batteries. Summary of the invention

[0004] The object of the present invention is to provide a biomass-derived carbon aerogel negative electrode material for use in sodium ion batteries and a preparation method thereof. The carbon aerogel material prepared by the method of the present invention has abundant raw material resources, low cost, and simple preparation process. The sodium ion battery assembled using the carbon aerogel material as the negative electrode active material of the sodium ion battery has high reversible specific capacity, excellent cycle performance and rate performance.

[0005] According to a first aspect of the present invention, a method for preparing a biomass-derived carbon aerogel sodium ion battery negative electrode material is provided, comprising the following steps: Step 1: Wash and dry the biomass precursor, cut it into blocks or sheets of suitable size, transfer it to a hydrothermal reactor, and perform hydrothermal treatment at 180° C. for a period of time to obtain a biomass hydrogel; Step 2, freeze-drying the biomass hydrogel obtained in step 1 at a certain temperature for several days to obtain biomass aerogel; Step 3, heating the biomass aerogel obtained in step 2 to a certain temperature at a certain heating rate under an inert atmosphere, and keeping the temperature for 2 to 5 hours to obtain a biomass carbon material; Step 4, soaking the biomass carbon material obtained in step 3 in a certain concentration of HCl for a certain period of time to remove impurities; Step 5: Wash the biomass carbon material from which impurities have been removed with deionized water and anhydrous ethanol until it becomes neutral, and then dry it to obtain the biomass carbon aerogel as the negative electrode active material of the sodium ion battery.

[0006] In step 1 of the preparation method of the present invention, the biomass precursor is one of loquat leaves, peanut shells, coconut shells, and wheat straw.

[0007] In step 1 of the preparation method of the present invention, the hydrothermal treatment time is 1 h to 24 h.

[0008] In step 2 of the preparation method of the present invention, the freeze-drying temperature is -45°C to -70°C, and the time is 3 to 7 days.

[0009] In step 3 of the preparation method of the present invention, the inert atmosphere is one of argon, nitrogen and helium.

[0010] In step 3 of the preparation method of the present invention, the heating rate is 1 °C min -1 ~5 ℃ min -1 , the temperature is 800~1200 ℃.

[0011] In step 4 of the preparation method of the present invention, the HCl concentration is 1-2 M, and the soaking time is 12-48 h.

[0012] The biomass-derived carbon aerogel material prepared above was applied as an active material to the negative electrode of a sodium ion battery. Tests showed that the biomass-derived carbon aerogel had excellent electrochemical properties.

[0013] According to a second aspect of the present invention, a biomass-derived carbon aerogel prepared according to the above method is provided for use as a negative electrode active material for a sodium ion battery.

[0014] Compared with the prior art, the present invention has the following significant advantages: 1. The biomass-derived carbon aerogel sodium ion battery negative electrode of the present invention uses biomass as a precursor of carbon aerogel, and the raw material source is wide. Its components contain cellulose, protein, alkaloids and other substances. It is used as a precursor, and it contains elements such as O, N, P, S, etc. The porous hard carbon material derived from it has self-doping characteristics. These heteroatoms can be self-doped into the carbon material during the carbonization process, thereby increasing the interlayer spacing, improving the conductivity, and increasing the sodium storage active sites, which is helpful to improve the reversible specific capacity and rate performance of the battery; 2. The preparation process of the present invention can make the carbon aerogel inherit the natural hierarchical porous structure of the precursor itself, which is beneficial to the penetration of electrolytes and the diffusion of sodium ions, and the preparation process is simple, low-cost, and green and environmentally friendly; the biomass-derived carbon aerogel of the present invention has a good hierarchical porous structure and abundant pores, good mechanical properties, ultra-low density and excellent conductivity and electrochemical stability. The sodium ion battery assembled as the negative active material has the advantages of low operating voltage, high specific capacity, good cycle and rate performance, etc. The biomass-derived carbon aerogel material proposed by the present invention exhibits more excellent electrochemical properties than the directly carbonized biomass hard carbon material. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 : This is the X-ray diffraction pattern of the loquat leaf-derived carbon aerogel (Example 1) according to an embodiment of the present invention.

[0016] Figure 2 : is the cyclic voltammetry curve of the loquat leaf derived carbon aerogel (Example 1) according to an embodiment of the present invention, wherein the abscissa is voltage (V), the ordinate is current (mA), and the scan rate is 0.1 mV s -1 .

[0017] Figure 3 : is the rate performance curve of the loquat leaf derived carbon aerogel (Example 1) according to an embodiment of the present invention, wherein the abscissa is the number of cycles (n) and the ordinate is the discharge specific capacity (mAh g -1 ), current densities of 25, 50, 100, 200, 500, 1000, and 25 mA g -1 .

[0018] Figure 4 : is the cycle stability curve of the loquat leaf derived carbon aerogel (Example 1) according to an embodiment of the present invention, wherein the abscissa is the cycle number (n) and the ordinate is the discharge specific capacity (mAh g -1 ), the current density is 50 mA g -1 DETAILED DESCRIPTION

[0019] In order to better understand the technical content of the present invention, specific embodiments are given and described as follows in conjunction with the accompanying drawings.

[0020] Various aspects of the invention are described in this disclosure with reference to the accompanying drawings. It is worth noting that the embodiments of the present disclosure are not intended to include all aspects of the invention. It should be appreciated that the concepts and embodiments mentioned above and described in more detail below can be implemented in any manner.

[0021] The present invention is further described below in conjunction with the examples. The following examples are only illustrative, and all changes within the scope of the present invention or equivalent to the present invention are included in the present invention.

[0022] According to an embodiment of the present invention, a method for preparing a biomass-derived carbon aerogel sodium ion battery negative electrode material is provided, comprising the following steps: Step 1: Wash and dry the biomass precursor, cut it into blocks or sheets of suitable size, transfer it to a hydrothermal reactor, and perform hydrothermal treatment at 180° C. for a period of time to obtain a biomass hydrogel; Step 2, freeze-drying the biomass hydrogel obtained in step 1 at a certain temperature for several days to obtain biomass aerogel; Step 3, heating the biomass aerogel obtained in step 2 to a certain temperature at a certain heating rate under an inert atmosphere, and keeping the temperature for 2 to 5 hours to obtain a biomass carbon material; Step 4, soaking the biomass carbon material obtained in step 3 in a certain concentration of HCl for a certain period of time to remove impurities; Step 5: Wash the biomass carbon material from which impurities have been removed with deionized water and anhydrous ethanol until it becomes neutral, and then dry it to obtain the biomass carbon aerogel as the negative electrode active material of the sodium ion battery.

[0023] In step 1 of the preparation method of the present invention, the biomass precursor is one of loquat leaves, peanut shells, coconut shells, and wheat straw.

[0024] In step 1 of the preparation method of the present invention, the hydrothermal treatment time is 1 h to 24 h.

[0025] In step 2 of the preparation method of the present invention, the freeze-drying temperature is -45°C to -70°C, and the time is 3 to 7 days.

[0026] In step 3 of the preparation method of the present invention, the inert atmosphere is one of argon, nitrogen and helium.

[0027] In step 3 of the preparation method of the present invention, the heating rate is 1 °C min -1 ~5 ℃ min -1 , the temperature is 800~1200 ℃.

[0028] In step 4 of the preparation method of the present invention, the HCl concentration is 1-2 M, and the soaking time is 12-48 h.

[0029] Through the preparation process of the present invention, one of loquat leaves, peanut shells, coconut shells or wheat straw is used as a precursor, which has the characteristics of self-doping, so that the carbon aerogel can inherit the natural hierarchical porous structure of the precursor itself, which is conducive to the penetration of electrolytes and the diffusion of sodium ions. The biomass-derived carbon aerogel of the present invention has a good hierarchical porous structure and abundant pores, good mechanical properties, ultra-low density and excellent conductivity and electrochemical stability. The sodium ion battery assembled as the negative active material has the advantages of low operating voltage, high specific capacity, good cycle and rate performance, etc. The biomass-derived carbon aerogel material proposed by the present invention shows more excellent electrochemical properties than the directly carbonized biomass hard carbon material.

[0030] [Example 1] The loquat leaves were washed and dried, and cut into slices of appropriate size. The sliced ​​loquat leaves were transferred to a hydrothermal reactor and hydrothermally treated at 180 °C for 12 h to obtain loquat leaf hydrogel. Subsequently, the loquat leaf aerogel was freeze-dried at -56 °C for 5 days to obtain loquat leaf aerogel. The loquat leaf aerogel was heated at 5 °C min under a nitrogen atmosphere. -1 The samples were heated to 1200 °C at a heating rate of 100 °C, kept warm for 2 h, soaked in 1 M hydrochloric acid for 48 h, washed with deionized water and anhydrous ethanol until neutral, and then dried in a vacuum drying oven to obtain loquat leaf-derived carbon aerogel material.

[0031] [Example 2] The peanut shells were washed and dried, and cut into blocks of appropriate size. The blocks of peanut shells were transferred to a hydrothermal reactor and hydrothermally treated at 180 °C for 24 h to obtain peanut shell hydrogel. Peanut shell aerogel was then freeze-dried at -56 °C for 5 days to obtain peanut shell aerogel. Peanut shell aerogel was heated at 3 °C min under a nitrogen atmosphere. -1 The material was heated to 1000°C at a heating rate of 1000°C, kept warm for 3 h, soaked in 1 M hydrochloric acid for 48 h, washed with deionized water and anhydrous ethanol until neutral, and then dried in a vacuum drying oven to obtain a peanut shell-derived carbon aerogel material.

[0032] [Example 3] The coconut shell was washed and dried, and cut into blocks of appropriate size. The blocks were transferred to a hydrothermal reactor and hydrothermally treated at 180 °C for 12 h to obtain coconut shell hydrogel. Subsequently, coconut shell aerogel was obtained by freeze drying at -70 °C for 3 days. The coconut shell aerogel was heated at 1 °C min under an argon atmosphere. -1 The carbon aerogel material derived from coconut shell was obtained by heating the carbon aerogel to 800 °C at a heating rate of 100 °C and keeping the temperature for 5 h. Then, the carbon aerogel was immersed in 2 M hydrochloric acid for 24 h, washed with deionized water and anhydrous ethanol until neutral, and then dried in a vacuum drying oven.

[0033] [Example 4] The wheat straw was washed and dried, and cut into blocks of appropriate size. The blocks of wheat straw were transferred to a hydrothermal reactor and hydrothermally treated at 180 °C for 24 h to obtain wheat straw hydrogel. Subsequently, wheat straw aerogel was freeze-dried at -48 °C for 6 days to obtain wheat straw aerogel. The wheat straw aerogel was heated at 1 °C min under an argon atmosphere. -1 The material was heated to 800 °C at a heating rate of 100 °C, kept warm for 5 h, soaked in 1 M hydrochloric acid for 12 h, washed with deionized water and anhydrous ethanol until neutral, and then dried in a vacuum drying oven to obtain wheat straw-derived carbon aerogel material.

[0034] The following is combined with Figure 1-4 As shown, the phase composition and electrochemical performance test results of the loquat leaf-derived carbon aerogel material prepared in Example 1 are further illustrated.

[0035] Figure 1 This is the X-ray diffraction pattern of the carbon aerogel material derived from loquat leaves. Two broad diffraction peaks appear at about 23° and 43°, corresponding to the (002) and (100) crystal planes of the graphite structure, respectively. The broad diffraction peaks indicate that the prepared carbon aerogel material derived from loquat leaves has poor crystallinity.

[0036] The electrode sheets were prepared and the sodium ion half-cell was assembled to test the electrochemical performance of the prepared loquat leaf-derived carbon aerogel material: First, 0.1 g of polytetrafluoroethylene (PVDF) was dissolved in an appropriate amount of N-methylpyrrolidone (NMP). Then, 0.7 g of loquat leaf-derived carbon aerogel and 0.2 g of conductive additive carbon black prepared in Example 1 were ground and added to the above solution. After fully stirring until viscous, the resulting slurry was coated on a copper foil and then vacuum dried at 70 °C for 12 h. The dried film was cut into electrode sheets with a diameter of 12 mm using a punch. In a glove box filled with high-purity argon (water and oxygen contents were both less than 1 ppm), sodium metal was used as the counter electrode and reference electrode, 1 M NaPF6 / diethylene glycol dimethyl ether was used as the electrolyte, and Glassfiber was used as the diaphragm to assemble a CR2032 button cell. The charge and discharge test was carried out in a constant current mode in the voltage range of 0~3 V.

[0037] Figure 2 The cyclic voltammetry curve of the carbon aerogel electrode derived from loquat leaves. A pair of obvious redox peaks can be observed around 0.02 V, which corresponds to Na + Insertion and extraction between graphene nanodomains or filling in pores. A weak reduction peak appears at around 0.5 V during the first discharge, but disappears in subsequent cycles, corresponding to the formation of a solid electrolyte interphase.

[0038] Figure 3 The loquat leaf-derived carbon aerogel electrode has a high conductivity at 50 mA g -1 The first discharge capacity of the loquat leaf-derived carbon aerogel material is 520 mAh g -1 After 50 cycles, the discharge capacity reached 382 mAh g -1 , showing high specific capacity and excellent cycle performance.

[0039] Figure 4 The loquat leaf derived carbon aerogel material has a high rate performance at 25, 50, 100, 200, 500, and 1000 mA g -1 The discharge specific capacities at the current densities are 337, 322, 314, 271, 196 and 124 mAh g -1 When the current density returns to 25 mA g −1 When the discharge capacity is restored to 386 mAh g −1 , showing excellent rate performance.

[0040] The above content is only a preferred embodiment of the present invention. It should be emphasized that for conventional practitioners in this technical field, it is still possible to implement multiple improvements and modifications without violating the core concept of the present invention. These improved and modified solutions should also be included in the protection scope of the present invention.

Claims

1. A method for preparing a biomass-derived carbon aerogel sodium ion battery negative electrode material, characterized in that: The method comprises the following steps: step 1, washing and drying the biomass precursor, cutting it into blocks or sheets of suitable size, transferring it to a hydrothermal reactor, and subjecting it to hydrothermal treatment at 180°C for a period of time to obtain a biomass hydrogel; Step 2, freeze-drying the biomass hydrogel obtained in step 1 at a certain temperature for several days to obtain biomass aerogel; Step 3, heating the biomass aerogel obtained in step 2 to a certain temperature at a certain heating rate under an inert atmosphere, and keeping the temperature for 2 to 5 hours to obtain a biomass carbon material; Step 4, soaking the biomass carbon material obtained in step 3 in a certain concentration of HCl for a certain period of time to remove impurities; Step 5: Wash the biomass carbon material from which impurities have been removed with deionized water and anhydrous ethanol until it becomes neutral, and then dry it to obtain the biomass carbon aerogel as the negative electrode active material of the sodium ion battery.

2. The method for preparing a biomass-derived carbon aerogel sodium ion battery negative electrode material according to claim 1, characterized in that: The biomass precursor is one of loquat leaves, peanut shells, coconut shells and wheat straw.

3. The method for preparing the biomass-derived carbon aerogel sodium ion battery negative electrode material according to claim 1, characterized in that: In step 1, the hydrothermal treatment time is 1 h to 24 h.

4. The method for preparing the biomass-derived carbon aerogel sodium ion battery negative electrode material according to claim 1, characterized in that: In step 2, the freeze-drying temperature is -45°C to -70°C, and the time is 3 to 7 days.

5. The method for preparing a biomass-derived carbon aerogel sodium ion battery negative electrode material according to claim 1, characterized in that: In step 3, the inert atmosphere is one of argon, nitrogen and helium.

6. The method for preparing the biomass-derived carbon aerogel sodium ion battery negative electrode material according to claim 1, characterized in that: In step 3, the heating rate is 1 °C min -1 ~5 ℃ min -1 , the temperature is 800~1200 ℃.

7. The method for preparing the biomass-derived carbon aerogel sodium ion battery negative electrode material according to claim 1, characterized in that: In step 4, the HCl concentration is 1-2 M, and the soaking time is 12-48 h.

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

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