A kind of asphalt-based sodium ion battery negative electrode material and preparation method thereof

Abstract

The present invention proposes an asphalt-based sodium ion battery negative electrode material and a preparation method thereof, which belongs to the technical field of energy storage batteries and can solve the technical problems of low carbon yield and high comprehensive cost in traditional asphalt modification methods. The preparation method of the asphalt-based sodium ion battery negative electrode material comprises: crushing and screening the asphalt to obtain crushed asphalt; pre-oxidizing the crushed asphalt in an air atmosphere to obtain oxidized asphalt; after the oxidized asphalt is cooled to room temperature, the cooled oxidized asphalt and unoxidized asphalt are mixed and heated and coated in a certain proportion, and the unoxidized asphalt is coated on the outside of the oxidized asphalt to obtain a coated material; after the coated material is cooled to room temperature, a high-temperature carbonization treatment is performed to obtain an asphalt-based sodium ion battery negative electrode material. The asphalt-based sodium ion battery negative electrode material of the present invention has the characteristics of high carbon yield and low comprehensive cost.

Description

Technical Field

[0001] The present invention belongs to the technical field of energy storage batteries, and in particular relates to an asphalt-based sodium ion battery negative electrode material and a preparation method thereof. Background Art

[0002] Sodium-ion batteries have the advantages of abundant resources, low cost, and environmental friendliness. They are considered to be one of the most likely to replace lithium-ion batteries and become one of the ideal power sources for large-scale energy storage applications. The performance of sodium-ion batteries is mainly determined by the sodium storage positive and negative electrode materials, and the sodium storage negative electrode material is an important component. Among the sodium storage negative electrode materials currently studied, the carbon-based negative electrode not only has a lower sodium insertion platform, higher capacity and good cycle stability, but also has the advantages of abundant resources and simple preparation. It is currently the most promising sodium storage negative electrode material. At present, the precursors used to prepare carbon materials are mainly biomass and resins. The carbon yield of biomass precursors is very low, and the cost of resin precursors is relatively high. Therefore, the use of these two types of precursors to prepare carbon materials is not conducive to the low-cost advantage of sodium-ion batteries. As a by-product of the petroleum industry, asphalt has a low price and a high carbon yield, making it an ideal precursor for preparing carbon materials.

[0003] However, the electrochemical performance of the carbon-based negative electrode of the sodium ion battery prepared by direct carbonization of asphalt is very poor. This is because asphalt is a soft carbon precursor. During the high-temperature carbonization process, it melts and rearranges in an orderly manner, the degree of graphitization increases, and a highly ordered carbon layer structure is formed. Usually, the asphalt needs to be modified and coated to improve the overall performance. For example, Chinese patent CN108878774B discloses a method of coating asphalt with natural cotton as a substrate to form a soft and hard composite material to improve material performance, but the low carbon yield of cotton hard carbon increases the cost; Chinese patent CN109148838B discloses a method of coating asphalt with charcoal and bamboo charcoal as a substrate, which also has the problem of low carbon yield using biomass materials such as charcoal.

[0004] It can be seen that how to improve the performance and carbon yield of asphalt-based sodium-ion battery negative electrodes and reduce costs is a key challenge currently facing this field. Summary of the invention

[0005] In view of the technical problems of low carbon yield and high comprehensive cost in traditional asphalt modification methods, the present invention proposes an asphalt-based sodium ion battery negative electrode material and a preparation method thereof. The asphalt-based sodium ion battery negative electrode material is prepared by using oxidized asphalt as a coated inner core and unoxidized asphalt as an outer coating layer. The asphalt-based sodium ion battery negative electrode material has the characteristics of high carbon yield and low cost.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] A method for preparing an asphalt-based sodium ion battery negative electrode material comprises the following steps:

[0008] Raw material crushing: crushing and screening the asphalt to obtain crushed asphalt;

[0009] Pre-oxidation treatment: the crushed asphalt is pre-oxidized in an air atmosphere to obtain oxidized asphalt;

[0010] Heating and coating treatment: after the oxidized asphalt is cooled to room temperature, the cooled oxidized asphalt and unoxidized asphalt are mixed in a certain proportion and heated and coated, and the unoxidized asphalt is coated on the outside of the oxidized asphalt to obtain a coated material;

[0011] High-temperature carbonization treatment: After the coated material cools to room temperature, a high-temperature carbonization treatment is performed to obtain an asphalt-based sodium ion battery negative electrode material.

[0012] In one embodiment, the asphalt is selected from any one or a combination of petroleum asphalt, coal asphalt, and natural asphalt.

[0013] In one embodiment, the particle size of the crushed asphalt ranges from 3 to 10 microns in D50.

[0014] In one embodiment, the oxidation temperature of the pre-oxidation treatment is 300-500° C., and the oxidation time is 3-12 hours.

[0015] In one embodiment, the mass ratio of the oxidized asphalt to the unoxidized asphalt is 1:(0.05-0.35).

[0016] In one embodiment, the temperature for the mixed heating coating treatment of the oxidized asphalt and the unoxidized asphalt is 200-300° C. and the time is 0.5-1.5 h.

[0017] In one embodiment, the high temperature carbonization temperature is 900-1600° C., and the carbonization time is 2-8 hours.

[0018] The present invention also provides an asphalt-based sodium ion battery negative electrode material, which is prepared using the preparation method described in any of the above embodiments.

[0019] In one embodiment, the coated inner core of the asphalt-based sodium ion battery negative electrode material is oxidized asphalt, the outer coating layer is unoxidized asphalt, and the thickness of the outer coating layer is 10-50 nanometers.

[0020] Compared with the prior art, the advantages and positive effects of the present invention are:

[0021] 1. The present invention provides a method for preparing an asphalt-based sodium ion battery negative electrode material, wherein the asphalt is pre-oxidized to obtain oxidized asphalt, and the oxidized asphalt and unoxidized asphalt are mixed and heated in a certain proportion to coat the mixture, so that the unoxidized asphalt is coated on the outside of the oxidized asphalt, and finally an asphalt-based sodium ion battery negative electrode material with oxidized asphalt as the coated core and unoxidized asphalt as the outer coating layer is prepared. The negative electrode material has a high yield, and the asphalt coating the core is oxidized to cross-link the internal structure, increase the interlayer spacing, and is more conducive to sodium storage, effectively solving the difficulty of sodium ions being difficult to embed into the carbon layer due to their large radius. At the same time, conventional asphalt is used for coating the outside to improve the overall conductivity of the material, prevent the co-embedding of the electrolyte, and reduce the loss of reversible capacity. In addition, asphalt has a wide source and is cheap, and can solve the technical problems of low yield and high comprehensive cost in the current use of resin and biomass charcoal to prepare the negative electrode of sodium ion batteries;

[0022] 2. The present invention provides a method for preparing an asphalt-based sodium ion battery negative electrode material. When pre-oxidizing the asphalt, air oxidation cross-linking is used. Asphalt is a composite material of hydrocarbons and related non-metallic derivatives. The pre-oxidation process can introduce oxygen functional groups, promote extensive cross-linking formation, prevent the degree of graphitization, and do not require the use of a cross-linking agent, which can further control costs.

[0023] 3. The present invention provides an asphalt-based sodium ion battery negative electrode material having the characteristics of high carbon yield and low cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is the XRD spectrum of the asphalt-based sodium ion battery negative electrode material provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0025] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] The embodiment of the present invention provides a method for preparing an asphalt-based sodium ion battery negative electrode material, comprising the following steps:

[0027] S1. Crushing raw materials: crushing and screening the asphalt to obtain crushed asphalt;

[0028] In the above step S1, the asphalt is specifically selected from any one or a combination of petroleum asphalt, coal asphalt, and natural asphalt. This raw material has a wide source, is cheap, and can effectively control production costs; the particle size range of the crushed asphalt is 3-10 microns in D50, and specifically 3 microns, 4 microns, 5 microns, 6 microns, 7 microns, 8 microns, 9 microns, 10 microns or any value in the above limited range can be selected, all of which fall within the protection scope of the present invention. If the particle size range of the crushed asphalt is lower than 3-10 microns, the internal cross-linked structure of the peroxidized material will collapse easily and the sodium storage structure will be destroyed; if it exceeds 3-10 microns, it will lead to insufficient oxidation, it is difficult to introduce oxygen inside, and it is impossible to form a cross-linked structure. The internal structure will tend to be orderly and it is difficult to store sodium.

[0029] S2. Pre-oxidation treatment: in an air atmosphere, the crushed asphalt is pre-oxidized to obtain oxidized asphalt;

[0030] In the above step S2, asphalt is a composite material of hydrocarbons and related non-metallic derivatives, and air oxidation cross-linking is used. The pre-oxidation process can introduce oxygen functional groups to promote extensive cross-linking formation. The asphalt is oxidized by air to form a cross-linked state. After carbonization, the interlayer spacing is larger, which is more conducive to sodium storage. At the same time, it can prevent the degree of graphitization, and no cross-linking agent is required, which further controls the cost. The oxidation temperature of the pre-oxidation treatment is 300-500°C, and specifically 300°C, 350°C, 400°C, 450°C, 500°C or any numerical value in the above-defined range can be selected, all of which fall within the protection scope of the present invention. The oxidation time is 3-12h, and specifically 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h or any numerical value in the above-defined range can be selected, all of which fall within the protection scope of the present invention.

[0031] S3, heating and coating treatment: after the oxidized asphalt is cooled to room temperature, the cooled oxidized asphalt and unoxidized asphalt are mixed in a certain proportion and heated and coated, so that the unoxidized asphalt is coated on the outside of the oxidized asphalt to obtain a coated material;

[0032] In the above-mentioned S3 step, oxidized asphalt and unoxidized asphalt are mixed in a certain proportion and heated and coated, so that the unoxidized asphalt is coated on the outside of the oxidized asphalt, thereby obtaining a coated material with oxidized asphalt as the coated inner core and unoxidized asphalt as the outer coating layer; wherein the asphalt coating the inner core is oxidized to cross-link the internal structure, and the interlayer spacing is increased, which is more conducive to sodium storage, and effectively solves the difficulty of sodium ions being difficult to embed into the carbon layer due to their large radius. At the same time, conventional asphalt is used for coating on the outside to improve the overall conductivity of the material, prevent the co-embedding of the electrolyte, and reduce the loss of reversible capacity. In addition, asphalt is widely available and inexpensive, which can solve the technical problems of low yield and high comprehensive cost in the current preparation of sodium ion negative electrodes using resins and biomass charcoal.

[0033] Furthermore, the mass ratio of oxidized asphalt to unoxidized asphalt is 1:(0.05-0.35), specifically 1:0.05, 1:0.10, 1:0.15, 1:0.20, 1:0.25, 1:0.30, 1:0.35 or any value within the above-defined range may be selected, all of which fall within the protection scope of the present invention; the temperature for the mixed heating coating treatment of oxidized asphalt and unoxidized asphalt is 200-300°C, specifically 200°C, 220°C, 260°C, 280°C, 300°C or any value within the above-defined range may be selected, and the time is 0.5-1.5h, specifically 0.5h, 1.0h, 1.5h or any value within the above-defined range may be selected, all of which fall within the protection scope of the present invention.

[0034] S4. High-temperature carbonization treatment: After the coated material cools to room temperature, a high-temperature carbonization treatment is performed to obtain an asphalt-based sodium ion battery negative electrode material.

[0035] In the above-mentioned step S4, the coating material is subjected to high-temperature carbonization treatment to finally prepare an asphalt-based sodium ion battery negative electrode material with oxidized asphalt as the coating core and unoxidized asphalt as the outer coating layer. The asphalt in the coating core of the negative electrode material is oxidized to cross-link the internal structure, and the interlayer spacing is increased, which is more conducive to sodium storage and effectively solves the difficulty of sodium ions being difficult to embed into the carbon layer due to their large radius. At the same time, conventional asphalt is used for external coating to improve the overall conductivity of the material, prevent the co-embedding of the electrolyte, and reduce the loss of reversible capacity.

[0036] Furthermore, the present invention also limits the carbonization temperature and carbonization time in the process of preparing the asphalt-based sodium ion battery negative electrode material, that is, the high-temperature carbonization temperature is 900-1600°C, and specifically 900°C, 1000°C, 1100°C, 1200°C, 1300°C, 1400°C, 1500°C, 1600°C or any numerical value in the above-defined range falls within the protection scope of the present invention, and the carbonization time is 2-8h, and specifically 2h, 3h, 4h, 5h, 6h, 7h, 8h or any numerical value in the above-defined range falls within the protection scope of the present invention.

[0037] Furthermore, in order to ensure that the performance of the asphalt-based sodium ion battery negative electrode material reaches the expected level, the present invention also clearly defines the thickness of the unoxidized asphalt coated on the outer layer, that is, the thickness of the unoxidized asphalt coated on the outer layer is 10-50 nanometers, and specifically, 10 nanometers, 15 nanometers, 20 nanometers, 25 nanometers, 30 nanometers, 35 nanometers, 40 nanometers, 45 nanometers, 50 nanometers or any value within the above-defined range can be selected, all of which fall within the protection scope of the present invention. If it is too thick, it will hinder the transmission of sodium ions and affect the performance of capacity; if it is too thin, it will not be able to repair the structural defects such as cracks and holes formed during the oxidation of asphalt, and the internal core structure will still be partially in direct contact with the electrolyte, resulting in an irreversible increase in capacity and a decrease in performance.

[0038] It should also be noted that the asphalt-based sodium ion battery negative electrode material provided by the present invention is a negative electrode material with "oxidized asphalt as the coated core and unoxidized asphalt as the outer coating layer". The order of oxidized asphalt as the coated core and unoxidized asphalt as the outer coating layer cannot be changed. The reason is that the external unoxidized asphalt mainly fills the pores of the internal oxidized asphalt, that is, prepares a closed-pore structure for sodium storage, while reducing the specific surface area of ​​the material to reduce the side reactions of contact with the electrolyte, and can also improve the conductivity of the material. Once the oxidized asphalt is replaced, the specific surface area is large and the open-pore structure on the surface will contact the electrolyte, causing a large amount of irreversible capacity loss.

[0039] The present invention also provides an asphalt-based sodium ion battery negative electrode material, which is prepared using the preparation method described in any of the above embodiments.

[0040] In a specific embodiment, the coated inner core of the asphalt-based sodium ion battery negative electrode material is oxidized asphalt, the outer coating layer is unoxidized asphalt, and the thickness of the outer coating layer is 10-50 nanometers.

[0041] In order to more clearly and in detail introduce an asphalt-based sodium ion battery negative electrode material and a preparation method thereof provided in an embodiment of the present invention, a description will be given below in conjunction with specific embodiments.

[0042] Example 1

[0043] This embodiment provides a method for preparing an asphalt-based sodium ion battery negative electrode material, specifically:

[0044] (1) Raw material crushing: crush and screen the asphalt and take 30 g of the material to obtain unoxidized asphalt with a particle size of 10 μm;

[0045] (2) Pre-oxidation treatment: The unoxidized asphalt was pre-oxidized at 300°C for 3 h in an air atmosphere to obtain oxidized asphalt;

[0046] (3) Heating and coating treatment: After the oxidized asphalt is cooled to room temperature, the cooled oxidized asphalt and unoxidized asphalt are heated and mixed in a mass ratio of 1:0.05 for coating treatment, the mixing time is 0.5 h, the heating temperature is 200°C, and the unoxidized asphalt is coated on the outside of the oxidized asphalt to obtain a coated material;

[0047] (4) High temperature carbonization treatment: After the coated material is cooled to room temperature, a high temperature carbonization treatment is performed at 900°C for 2h to finally prepare an asphalt-based sodium ion battery negative electrode material with a yield of 50%, a D002 of 0.371nm, a coating thickness of unoxidized asphalt of 30nm, a half-cell reversible capacity of 258.4mAh / g, and a first efficiency of 73%. The figure shows the XRD spectrum of the asphalt-based sodium ion battery negative electrode material provided in Example 1.

[0048] Example 2

[0049] This embodiment provides a method for preparing an asphalt-based sodium ion battery negative electrode material, specifically:

[0050] (1) Raw material crushing: crush and screen the asphalt and take 35 g of the material to obtain unoxidized asphalt with a particle size of 10 μm;

[0051] (2) Pre-oxidation treatment: The unoxidized asphalt was pre-oxidized at 300°C for 6 h in an air atmosphere to obtain oxidized asphalt;

[0052] (3) Heating and coating treatment: After the oxidized asphalt is cooled to room temperature, the cooled oxidized asphalt and unoxidized asphalt are heated and mixed in a mass ratio of 1:0.08 for coating treatment, the mixing time is 0.5 h, the heating temperature is 200° C., and the unoxidized asphalt is coated on the outside of the oxidized asphalt to obtain a coated material;

[0053] (4) High-temperature carbonization treatment: After the coated material is cooled to room temperature, it is subjected to high-temperature carbonization treatment at 900°C for 2 h to finally prepare an asphalt-based sodium ion battery negative electrode material with a yield of 54%, a D002 of 0.374 nm, a coating thickness of unoxidized asphalt of 35 nm, a half-cell reversible capacity of 261.7 mAh / g, and an initial efficiency of 75%.

[0054] Example 3

[0055] This embodiment provides a method for preparing an asphalt-based sodium ion battery negative electrode material, specifically:

[0056] (1) Raw material crushing: crush and screen the asphalt and take 35 g of the material to obtain unoxidized asphalt with a particle size of 8 μm;

[0057] (2) Pre-oxidation treatment: The unoxidized asphalt was pre-oxidized at 300°C for 12 h in an air atmosphere to obtain oxidized asphalt;

[0058] (3) Heating and coating treatment: After the oxidized asphalt is cooled to room temperature, the cooled oxidized asphalt and unoxidized asphalt are heated and mixed in a mass ratio of 1:0.10 for coating treatment, the mixing time is 1 hour, the heating temperature is 200°C, and the unoxidized asphalt is coated on the outside of the oxidized asphalt to obtain a coated material;

[0059] (4) High-temperature carbonization treatment: After the coated material is cooled to room temperature, it is subjected to high-temperature carbonization treatment at 1000°C for 2 h to finally prepare an asphalt-based sodium ion battery negative electrode material with a yield of 52%, a D002 of 0.378 nm, a coating thickness of unoxidized asphalt of 45 nm, a half-cell reversible capacity of 261.2 mAh / g, and an initial efficiency of 78%.

[0060] Example 4

[0061] This embodiment provides a method for preparing an asphalt-based sodium ion battery negative electrode material, specifically:

[0062] (1) Raw material crushing: crush and screen the asphalt and take 45 g of the material to obtain unoxidized asphalt with a particle size of 5 μm;

[0063] (2) Pre-oxidation treatment: In an air atmosphere, the unoxidized asphalt is pre-oxidized at 450°C for 6 h to obtain oxidized asphalt;

[0064] (3) Heating and coating treatment: After the oxidized asphalt is cooled to room temperature, the cooled oxidized asphalt and unoxidized asphalt are heated and mixed in a mass ratio of 1:0.08 for 1 h at a heating temperature of 220°C, and the unoxidized asphalt is coated on the outside of the oxidized asphalt to obtain a coated material;

[0065] (4) High-temperature carbonization treatment: After the coated material is cooled to room temperature, it is subjected to high-temperature carbonization treatment at 1200°C for 2 h to finally prepare an asphalt-based sodium ion battery negative electrode material with a yield of 52%, a D002 of 0.395 nm, a coating thickness of unoxidized asphalt of 15 nm, a half-cell reversible capacity of 303.5 mAh / g, and an initial efficiency of 89%.

[0066] Example 5

[0067] This embodiment provides a method for preparing an asphalt-based sodium ion battery negative electrode material, specifically:

[0068] (1) Raw material crushing: crush and screen the asphalt and take 40 g of the material to obtain unoxidized asphalt with a particle size of 5 μm;

[0069] (2) Pre-oxidation treatment: In an air atmosphere, the unoxidized asphalt is pre-oxidized at 450°C for 9 hours to obtain oxidized asphalt;

[0070] (3) Heating and coating treatment: After the oxidized asphalt is cooled to room temperature, the cooled oxidized asphalt and unoxidized asphalt are heated and mixed in a mass ratio of 1:0.10, the mixing time is 0.5 h, the heating temperature is 200°C, and the unoxidized asphalt is coated on the outside of the oxidized asphalt to obtain a coated material;

[0071] (4) High-temperature carbonization treatment: After the coated material is cooled to room temperature, it is subjected to high-temperature carbonization treatment at 1200°C for 4 hours to finally prepare an asphalt-based sodium ion battery negative electrode material with a yield of 56%, a D002 of 0.383nm, a coating thickness of unoxidized asphalt of 45nm, a half-cell reversible capacity of 286.4mAh / g, and an initial efficiency of 87%.

[0072] Example 6

[0073] This embodiment provides a method for preparing an asphalt-based sodium ion battery negative electrode material, specifically:

[0074] (1) Raw material crushing: crush and screen the asphalt and take 30 g of the material to obtain unoxidized asphalt with a particle size of 8 μm;

[0075] (2) Pre-oxidation treatment: In an air atmosphere, the unoxidized asphalt is pre-oxidized at 500°C for 6 h to obtain oxidized asphalt;

[0076] (3) Heating and coating treatment: After the oxidized asphalt is cooled to room temperature, the cooled oxidized asphalt and unoxidized asphalt are heated and mixed in a mass ratio of 1:0.20, the mixing time is 0.5 h, the heating temperature is 200°C, and the unoxidized asphalt is coated on the outside of the oxidized asphalt to obtain a coated material;

[0077] (4) High-temperature carbonization treatment: After the coated material is cooled to room temperature, it is subjected to high-temperature carbonization treatment at 1200°C for 4 h to finally prepare an asphalt-based sodium ion battery negative electrode material with a yield of 55%, a D002 of 0.380 nm, a half-cell reversible capacity of 278.4 mAh / g, a coating thickness of unoxidized asphalt of 40 nm, and an initial efficiency of 82%.

[0078] Example 7

[0079] This embodiment provides a method for preparing an asphalt-based sodium ion battery negative electrode material, specifically:

[0080] (1) Raw material crushing: crush and screen the asphalt and take 45g of the material to obtain unoxidized asphalt with a particle size of 8 microns;

[0081] (2) Pre-oxidation treatment: The unoxidized asphalt was pre-oxidized at 500°C for 12 h in an air atmosphere to obtain oxidized asphalt;

[0082] (3) Heating and coating treatment: After the oxidized asphalt is cooled to room temperature, the cooled oxidized asphalt and unoxidized asphalt are heated and mixed in a mass ratio of 1:0.35, the mixing time is 0.5 h, the heating temperature is 200°C, and the unoxidized asphalt is coated on the outside of the oxidized asphalt to obtain a coated material;

[0083] (4) High-temperature carbonization treatment: After the coated material is cooled to room temperature, it is subjected to high-temperature carbonization treatment at 1400°C for 6 hours to finally prepare an asphalt-based sodium ion battery negative electrode material with a yield of 47%, a D002 of 0.387 nm, a coating thickness of unoxidized asphalt of 45 nm, a half-cell reversible capacity of 280.1 mAh / g, and an initial efficiency of 85%.

[0084] Example 8

[0085] This embodiment provides a method for preparing an asphalt-based sodium ion battery negative electrode material, specifically:

[0086] (1) Raw material crushing: crush and screen the asphalt and take 30g of the material to obtain unoxidized asphalt with a particle size of 10 μm;

[0087] (2) Pre-oxidation treatment: In an air atmosphere, the unoxidized asphalt is pre-oxidized at 500°C for 6 h to obtain oxidized asphalt;

[0088] (3) Heating and coating treatment: After the oxidized asphalt is cooled to room temperature, the cooled oxidized asphalt and unoxidized asphalt are heated and mixed in a mass ratio of 1:0.35, the mixing time is 0.5 h, the heating temperature is 200°C, and the unoxidized asphalt is coated on the outside of the oxidized asphalt to obtain a coated material;

[0089] (4) High-temperature carbonization treatment: After the coated material is cooled to room temperature, it is subjected to high-temperature carbonization treatment at 1600°C for 6 hours to finally prepare an asphalt-based sodium ion battery negative electrode material with a yield of 45%, a D002 of 0.381 nm, a coating thickness of unoxidized asphalt of 50 nm, a half-cell reversible capacity of 269.9 mAh / g, and an initial efficiency of 79%.

[0090] Comparative Example 1

[0091] This comparative example provides a method for preparing an asphalt-based sodium ion battery negative electrode material, specifically:

[0092] After the asphalt is crushed and sieved, 30g of the material is taken, and the asphalt with a particle size of 10 microns is carbonized at 1200℃ for 2h under a nitrogen atmosphere. Finally, the asphalt-based sodium ion battery negative electrode material is prepared with a yield of 38%, D002 of 0.344nm, a half-cell reversible capacity of 87.6mAh / g, and an initial efficiency of 65%.

[0093] Comparative Example 2

[0094] This comparative example provides a method for preparing an asphalt-based sodium ion battery negative electrode material, specifically:

[0095] After the asphalt is crushed and sieved, 45g of the material is taken, and the asphalt with a particle size of 10 microns is carbonized at 1400℃ for 6 hours under a nitrogen atmosphere. Finally, the asphalt-based sodium ion battery negative electrode material is prepared with a yield of 35%, D002 of 0.341nm, a half-cell reversible capacity of 85.5mAh / g, and an initial efficiency of 62%.

[0096] Comparative Example 3

[0097] This comparative example provides a method for preparing an asphalt-based sodium ion battery negative electrode material, specifically:

[0098] After the asphalt is crushed and sieved, 43 g of the material is taken out, and the asphalt with a particle size of 12 microns is subjected to carbonization treatment at 1600°C for 6 hours under a nitrogen atmosphere to finally prepare an asphalt-based sodium ion battery negative electrode material.

[0099] Performance Testing

[0100] The present invention conducted multiple performance tests on the yield, D002, half-cell reversible capacity, and first efficiency of the asphalt-based sodium ion battery negative electrode materials prepared in the above embodiments and comparative examples. The test methods and test results are as follows:

[0101] Test method:

[0102] D002 interlayer spacing test: using XRD to detect materials, calculated according to the formula d002 = λ / (2sinθ);

[0103] Half-cell performance test: The prepared hard carbon negative electrode material was used as the electrode, the sodium sheet was used as the counter electrode, the ethylene carbonate (EC) / dimethyl carbonate (DEC) / propylene carbonate (PC) solution with a concentration of 1 mol / L NaPF6 was used as the electrolyte (the molar volume ratio of EC / DMC / PC was 1:1), and 1% fluoroethylene carbonate (FEC) was used as the electrolyte additive. The battery was assembled in an argon-filled glove box for charge and discharge tests.

[0104] Test results: See the table below.

[0105] Table 1 Performance test results of asphalt-based sodium ion battery negative electrode materials obtained in various embodiments and comparative examples

[0106]

[0107] The results show that the negative electrode materials prepared in Comparative Examples 1-3 are all prepared by high-temperature carbonization of oxidized asphalt, and the yield and other performance of such negative electrode materials are not ideal. The yield of the asphalt-based sodium ion battery negative electrode material prepared by the preparation process provided in Examples 1-8 is 52-56%, the D002 interlayer spacing is 0.371-0.395nm, the reversible specific capacity is 258.4-303.5mAh / g, and the first efficiency is 73-89%. It can be seen that the negative electrode material prepared by the present invention has the characteristics of high yield and low cost.

[0108] XRD pattern analysis

[0109] The present invention takes the asphalt-based sodium ion battery negative electrode material prepared in Example 1 as an example, and performs X-ray diffraction analysis on the negative electrode material to obtain the following Figure 1 The XRD pattern shown in the figure is analyzed by Figure 1 It can be seen that two broad peaks appear near 23° and 43°, corresponding to the (002) diffraction peak and (100) diffraction peak of the material respectively. The two wider diffraction peaks in the figure indicate that the prepared hard carbon is in an amorphous state. The amorphous carbon material has good sodium storage capacity and high reversible specific capacity.

[0110] Outer Cover - Unoxidized Asphalt Thickness Screening Test

[0111] Since the thickness of the outer coating layer - unoxidized asphalt is closely related to the various properties of the asphalt-based sodium ion battery negative electrode material of the present invention, in order to optimize the most suitable thickness range, the present invention also conducted a screening test of the thickness of the outer coating layer - unoxidized asphalt. The specific test method and test results are as follows:

[0112] Experimental groups and methods:

[0113] Outer coating layer - unoxidized asphalt thickness: 5 nm, 10 nm, 15 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 60 nm;

[0114] Asphalt-based sodium ion battery negative electrode materials with different coating thicknesses were prepared according to the preparation method described in Example 1, and their electrochemical properties were tested.

[0115] Test results: See Table 2.

[0116] Table 2 Outer coating layer - unoxidized asphalt thickness screening test results

[0117]

[0118] By analyzing the data in the above table, it can be seen that when the thickness of the outer coating layer - unoxidized asphalt is in the range of 10-50 nanometers, the electrochemical performance of the asphalt-based sodium ion battery negative electrode material prepared by the method of Example 1 is relatively ideal, and when the thickness of the outer coating layer - unoxidized asphalt is lower than (for example, 5 nanometers) or exceeds (for example, 60 nanometers) the above range, the electrochemical performance of the prepared asphalt-based sodium ion battery negative electrode material cannot meet expectations. Therefore, the thickness of the outer coating layer - unoxidized asphalt has an important influence on the electrochemical performance of the asphalt-based sodium ion battery negative electrode material.

Claims

1. A method for preparing a negative electrode material for an asphalt-based sodium ion battery, characterized in that: The following steps are involved: Raw material crushing: crushing and screening the asphalt to obtain crushed asphalt; the particle size range of the crushed asphalt is D50 3-10 microns; Pre-oxidation treatment: In an air atmosphere, the crushed asphalt is pre-oxidized to obtain oxidized asphalt; the oxidation temperature of the pre-oxidation treatment is 300-500°C, and the oxidation time is 3-12h; Heating and coating treatment: after the oxidized asphalt is cooled to room temperature, the cooled oxidized asphalt and unoxidized asphalt are mixed and heated and coated in a certain proportion, and the unoxidized asphalt is coated on the outside of the oxidized asphalt to obtain a coated material; the temperature of the mixed heating and coating treatment of the oxidized asphalt and the unoxidized asphalt is 200-300°C, and the time is 0.5-1.5h; High-temperature carbonization treatment: After the coated material cools to room temperature, high-temperature carbonization treatment is performed to obtain an asphalt-based sodium ion battery negative electrode material; the high-temperature carbonization temperature is 900-1600° C., and the carbonization time is 2-8 hours; The mass ratio of the oxidized asphalt to the unoxidized asphalt is 1:(0.05-0.35).

2. The method for preparing the asphalt-based sodium ion battery negative electrode material according to claim 1, characterized in that: The asphalt is selected from any one or a combination of petroleum asphalt, coal asphalt, and natural asphalt.

3. A pitch-based sodium ion battery negative electrode material, characterized in that: The method is prepared by the method described in any one of claims 1 to 2.

4. The asphalt-based sodium ion battery negative electrode material according to claim 3, characterized in that: The coated inner core of the asphalt-based sodium ion battery negative electrode material is oxidized asphalt, the outer coating layer is unoxidized asphalt, and the thickness of the outer coating layer is 10-50 nanometers.

Images