Sodium-ion battery negative electrode material and preparation method and application thereof

Abstract

The application discloses a kind of sodium ion battery negative electrode material and its preparation method and application, belong to sodium ion battery technical field, solve the poor universality of the modification method of sodium ion battery negative electrode material in prior art.The preparation method includes: the surface oxygen-rich oxidation treatment of carbon negative electrode;Two-step thermal reaction is carried out in inert atmosphere;Among them, the first step is to use nitrogen / sulfur-containing small molecules to carry out heteroatom doping;The second step is to carry out calcination treatment, remove heteroatom, and obtain the carbon negative electrode material with surface topological defect modification after natural cooling to 25-30 DEG C;The carbon negative electrode material with surface topological defect modification is physically mixed with active heteroatom-containing small molecules, and then heat-treated in inert atmosphere to obtain a sodium ion battery negative electrode material.The negative electrode material prepared by the preparation method provided by the application significantly improves the performance of sodium ion battery, especially the rate performance, high active material loading and capacity at low temperature.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of sodium ion batteries, and more particularly to a sodium ion battery negative electrode material and a preparation method and application thereof. BACKGROUND

[0002] In recent years, the continuous development of large-scale industries, electric vehicles and portable electronic devices has put forward higher requirements for the performance of energy storage devices. Lithium ion batteries have the advantages of high energy density and long cycle life, and are the main power supply for the above-mentioned devices. Sodium resources are widely distributed in the earth's crust and are low in cost. Emerging sodium ion batteries, as low-cost substitutes for lithium ion batteries, have begun to make a name for themselves in the field of electrochemical energy storage. However, the diffusion rate of the traditional graphite negative electrode of lithium ion batteries is slow, especially the lithium ion intercalation / deintercalation kinetics process at high rates. The ionic radius of sodium ions is larger, and the intercalation / deintercalation in graphite is more difficult, which inevitably leads to a large volume expansion of the electrode material during the charging and discharging cycle, resulting in a serious capacity decay at high rates. Therefore, the rate performance of the traditional graphite negative electrode for sodium ion batteries is not satisfactory, which limits the further application of sodium ion batteries. In view of the problem of slow storage kinetics caused by the ionic radius in sodium ion batteries, in recent years, other carbon materials have been developed as negative electrode materials for sodium ion batteries, such as hard carbon, soft carbon and graphene. Although these materials have alleviated the above-mentioned problems to some extent, there is still a lot of room for improvement.

[0003] Developing new high-performance negative electrode materials is one of the keys to promoting the development of sodium ion batteries. With the in-depth study of sodium ion battery negative electrode materials, it is realized that the formation and structure of the solid electrolyte interface (SEI) on the negative electrode surface are particularly important for the first-cycle coulombic efficiency, capacity, rate performance and cycle stability of sodium ion batteries. The formation and structure of the SEI are related to many factors, such as the composition of the electrolyte, the charging and discharging process, and the structure of the electrode material. Among them, the surface structure of the negative electrode material will affect the decomposition behavior of the electrolyte and thus affect the formation of the SEI, so adjusting the surface structure of the material is a key strategy to improve the performance of sodium ion batteries. In recent years, heteroatom modification has been proven to be one of the effective strategies to improve the SEI formation of carbon material negative electrodes. The introduction of nitrogen, oxygen, phosphorus and other heteroatoms into the carbon skeleton can change the electronegativity of the material, thereby affecting the adsorption and decomposition of the electrolyte components on the material surface. However, most of the currently reported heteroatom modification strategies adopt a "bottom-up" design approach, i.e. by designing the structure of the carbon precursor to control the configuration of the heteroatoms in the product. This modification strategy often has difficulty in adjusting the intrinsic structure of the material. Moreover, the idea of modifying existing materials through a "post-modification" strategy is limited by the surface groups of carbon materials, and has poor universality for carbon materials of different structures, making it difficult to be applied on a large scale. SUMMARY

[0004] The application provides a sodium ion battery negative electrode material and a preparation method and application thereof, and aims at solving the poor universality of the modification method of the sodium ion battery negative electrode material in the prior art.

[0005] In a first aspect, the application provides a preparation method of a sodium ion battery negative electrode material, including the following steps: performing surface oxygen-rich treatment on a carbon negative electrode; performing two-step thermal reaction in an inert atmosphere; wherein the first step is to perform heteroatom doping by using a nitrogen / sulfur-containing small molecule; the second step is to perform calcination treatment to remove the heteroatom, and then naturally cool to 25-30 DEG C to obtain a carbon negative electrode material with surface topological defect modification; and then physically mixing the carbon negative electrode material with surface topological defect modification and an active heteroatom-containing small molecule, and performing thermal treatment in an inert atmosphere to obtain the sodium ion battery negative electrode material.

[0006] As a possible implementation manner, the thermal treatment in the inert atmosphere includes the following steps: physically mixing the carbon negative electrode material with surface topological defect modification and the active heteroatom-containing small molecule, and then heating to 130-180 DEG C in the inert atmosphere, and keeping the temperature for 6-24 h; then heating to 200-900 DEG C again, and keeping the temperature for 1-20 h; then naturally cooling to 25-30 DEG C, and then dispersing the obtained product in a good solvent of the active heteroatom-containing small molecule, and then purifying to obtain the sodium ion battery negative electrode material.

[0007] As a possible implementation manner, the carbon negative electrode is any one of hard carbon or soft carbon; and / or, the nitrogen / sulfur-containing small molecule is one or a combination of several of melamine, urea, thiourea, monocyannide and dicyannide; and / or, the active heteroatom-containing small molecule is one or a combination of several of carbon disulfide, hydrogen sulfide, sodium thiosulfate, melamine, urea, thiourea, monocyanide, dicyannide and sodium borohydride.

[0008] As a possible implementation manner, the surface oxygen-rich treatment is one or a combination of several of oxygen plasma treatment, acid solution thermal treatment and air thermal treatment; and / or, in the heteroatom doping, the mass ratio of the carbon negative electrode to the nitrogen / sulfur-containing small molecule is 1:0.5-10, the temperature condition is 600-800 DEG C, and the time length is 1-4 h; and / or, the calcination treatment has a temperature condition of 900-1400 DEG C and a time length of 1-4 h; and / or, the thermal treatment has a temperature condition of 130-900 DEG C and a treatment time length of 2-20 h; and / or, the inert atmosphere is one or a combination of several of nitrogen, argon and helium, and the gas flow rate of the inert atmosphere is 100-300 mL·min -1 .

[0009] As a possible implementation manner, in the heteroatom doping, the heating rate is 2-5 DEG C·min -1; and / or, the calcining process, the heating rate is 2-5℃·min -1 ; and / or, the heating under inert atmosphere, the heating rate is 2-5℃·min -1 ; and / or, the re-heating, the heating rate is 2-5℃·min -1 .

[0010] In a second aspect, the present application provides a sodium-ion battery negative electrode material, which is prepared by the preparation method of any possible implementation manner of the first aspect.

[0011] In a third aspect, the present application provides an application of the sodium-ion battery negative electrode material prepared by the preparation method of any possible implementation manner of the first aspect or the sodium-ion battery negative electrode material of any possible implementation manner of the second aspect in a sodium-ion battery.

[0012] In a fourth aspect, the present application provides a sodium-ion battery, which comprises the sodium-ion battery negative electrode material prepared by the preparation method of any possible implementation manner of the first aspect or the sodium-ion battery negative electrode material of any possible implementation manner of the second aspect.

[0013] As a possible implementation manner, the sodium-ion battery negative electrode material, the binder and the conductive agent are mixed in a mass ratio of 8:1:1 to prepare a slurry; the slurry is coated on a current collector to obtain an electrode sheet; and the electrode sheet is cut into an appropriate size to serve as a negative electrode sheet of the sodium-ion battery.

[0014] As a possible implementation manner, the application condition is: the current density is 0.05-10A·g -1 , and the temperature is-20-30℃.

[0015] The present application provides a kind of by in commercial sodium ion battery negative material (such as hard carbon, soft carbon etc.) surface successively introducing defect and active small molecule to obtain modified negative material technology.For the convenience of expressing the principle of the present application, the following is taken as an example with commercial hard carbon, melamine (nitrogen / sulfur-containing small molecules) and sulfur powder (active heteroatom-containing small molecules) as raw materials. First, oxygen plasma pre-oxidation technology is used to introduce oxygen-rich groups on the surface of commercial hard carbon, increasing the reaction sites of melamine during nitrogen atom doping. Then, the melamine is physically mixed with the oxygen-enriched hard carbon by grinding, and two-step heat treatment is carried out under inert atmosphere protection, realizing low-temperature nitrogen atom doping and high-temperature nitrogen atom removal on the surface of the material, and obtaining topological defect modified hard carbon. Subsequently, the elemental sulfur is physically mixed with the topological defect modified hard carbon by grinding, and heat treatment is carried out under inert atmosphere protection, and the active short-chain sulfur is modified to the surface of the hard carbon by using the bonding effect of the surface topological defects and the elemental sulfur, and the surface active short-chain sulfur modified hard carbon is prepared. The commercial hard carbon modified by this method can basically retain the original internal structure of the hard carbon (such as micropores for storing sodium metal), and the active short-chain sulfur on the surface can participate in the formation of the solid electrolyte interface, so that a more ideal solid electrolyte interface can be formed on the surface of the electrode when used as the negative electrode of the sodium ion battery, and the original characteristics of the hard carbon are retained, so that sodium ions can be transmitted in the optimized solid electrolyte interface, thereby improving the performance of the sodium ion battery, especially the rate capability, high active material loading and capacity at low temperature.

[0016] The sodium ion battery negative material prepared by the present application has significant performance advantages in the application of sodium ion battery. The relatively low temperature heat treatment ensures that the internal structure of the material is not damaged, and the active small molecules on the surface of the material participate in the formation of the solid electrolyte interface during charging and discharging, which helps to form a more ideal solid electrolyte interface and promote ion transmission. The above structural advantages improve the ion transmission kinetics of the electrode material without sacrificing the original structural advantages, which is beneficial to improve the electrochemical performance of the sodium ion battery, especially the capacity and rate capability. The present application uses topological defect construction strategy to introduce active small molecules on the surface of the carbon negative electrode material without damaging the structure of the carbon negative electrode material, which significantly improves the first cycle coulomb efficiency, rate capability and cycle stability of the sodium ion battery, especially the high active material loading and capacity at low temperature.

[0017] The sodium ion battery negative material provided by the present application takes the commonly used commercial hard carbon negative electrode as an example, compared with the material before modification, the modified material has about 5% improvement of the first cycle coulomb efficiency, 5A·g -1 and 10A·g -1 Current density has about 10% capacity retention rate improvement, and also has good low temperature performance (such as-20℃) and capacity under high active material loading (such as 4mg·cm -2), and has good capacity and cycle stability when used as a negative electrode material of a sodium ion battery. In addition, the sodium ion battery negative electrode material can be applied to negative electrode materials of different brands and different types, and different modified carbon negative electrode materials with different properties can be obtained on demand by changing the types and proportions of active small molecules, while the original structure of the negative electrode material is not damaged; the sodium ion battery negative electrode material is convenient to scale up, and has good universality and scaling potential.

[0018] The preparation strategy of the fast-charging carbon negative electrode material provided by the application can directly use commercially available materials on the market, has simple preparation steps and low material cost, and has good cost-effectiveness and scaling potential. BRIEF DESCRIPTION OF DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are only some embodiments of the application, and for those skilled in the art, other drawings can also be obtained without creative labor on the basis of these drawings.

[0020] Figure 1 The first cycle charge-discharge curve diagrams of the sodium ion battery negative electrode material I and the commercial hard carbon I provided by the embodiments of the application as the negative electrode materials of sodium ion batteries, respectively, wherein the current density is 0.05 A·g -1 , the temperature is 30 DEG C, the active material loading is 0.5-0.8 mg·cm -2 , Voltage represents voltage, and Specific capacity represents specific capacity.

[0021] Figure 2 The rate performance diagrams of the sodium ion battery negative electrode material I and the commercial hard carbon I provided by the embodiments of the application as the negative electrode materials of sodium ion batteries, respectively, wherein the current density is 0.05-10 A·g -1 , the temperature is 30 DEG C, the active material loading is 0.5-0.8 mg·cm -2 , Specific capacity represents specific capacity, Cycle number represents cycle number, and Current density represents current density.

[0022] Figure 3 The rate performance diagrams of the sodium ion battery negative electrode material I and the commercial hard carbon I provided by the embodiments of the application as the negative electrode materials of sodium ion batteries, respectively, wherein the current density is 0.05-10 A·g -1 , the temperature is 30 DEG C, the active material loading is 3.3-3.5 mg·cm -2Specific capacity indicates specific capacity, Cycle number indicates cycle number, and Current density indicates current density.

[0023] Figure 4 The rate performance graph of the sodium ion battery negative electrode material I and the commercial hard carbon I provided by the embodiment of the present application as the sodium ion battery negative electrode material, wherein the current density is 0.05-10 A·g -1 , the temperature is -20 DEG C, and the active material loading is 0.5-0.8 mg·cm -2 , Specific capacity indicates specific capacity, Cycle number indicates cycle number, and Current density indicates current density.

[0024] Figure 5 The first cycle charge-discharge curve graph of the sodium ion battery negative electrode material II and the commercial hard carbon II provided by the embodiment of the present application as the sodium ion battery negative electrode material, wherein the current density is 0.05 A·g -1 , the temperature is 30 DEG C, and the active material loading is 0.5-0.8 mg·cm -2 , Voltage indicates voltage, and Specific capacity indicates specific capacity.

[0025] Figure 6 The rate performance graph of the sodium ion battery negative electrode material II and the commercial hard carbon II provided by the embodiment of the present application as the sodium ion battery negative electrode material, wherein the current density is 0.05-10 A·g -1 , the temperature is 30 DEG C, and the active material loading is 0.5-0.8 mg·cm -2 , Specific capacity indicates specific capacity, Cycle number indicates cycle number, and Current density indicates current density.

[0026] Figure 7 The first cycle charge-discharge curve graph of the sodium ion battery negative electrode material III and the commercial hard carbon I provided by the embodiment of the present application as the sodium ion battery negative electrode material, wherein the current density is 0.05 A·g -1 , the temperature is 30 DEG C, and the active material loading is 0.5-0.8 mg·cm -2 , Voltage indicates voltage, and Specific capacity indicates specific capacity.

[0027] Figure 8 The rate performance graph of the sodium ion battery negative electrode material III and the commercial hard carbon I provided by the embodiment of the present application as the sodium ion battery negative electrode material, wherein the current density is 0.05-10 A·g-1 at 30℃ with an active material loading of 0.5-0.8 mg·cm -2 , Specific capacity indicates specific capacity, Cycle number indicates cycle number, and Current density indicates current density. DETAILED DESCRIPTION

[0028] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative labor fall within the scope of protection of the present application.

[0029] To solve the poor universality of the modification method for the negative electrode material of the sodium-ion battery in the prior art, the embodiments of the present application provide a preparation experiment of a negative electrode material of a sodium-ion battery, and the target product is prepared under different conditions.

[0030] Further, the embodiments of the present application provide a performance test experiment of the negative electrode material of the sodium-ion battery, and the raw material before modification and the corresponding product prepared are respectively used as the active negative electrode material to be tested to prepare a half battery. The performance results of the corresponding active negative electrode material are obtained by testing the electrochemical performance of the half battery. It can be known that, compared with before modification, the material after modification has higher initial capacity, first-cycle coulombic efficiency and better rate performance, and can still maintain higher initial capacity and better rate performance under the condition of higher active material loading or low temperature.

[0031] The technical solutions of the present application will be further described below with reference to specific embodiments.

[0032] Embodiment 1

[0033] The present embodiment provides a preparation experiment of a negative electrode material of a sodium-ion battery.

[0034] 1.0 g of commercial hard carbon I (Kylin, type-2) was placed in a small beaker, and an oxygen plasma treatment machine was used with the following treatment conditions: the vacuum degree was kept below 20 Pa, the treatment power was 150 W, and the treatment time was 4 min. After each treatment, the powder was stirred uniformly, and the treatment was performed 4 times to obtain the surface oxygen-enriched hard carbon I. The surface oxygen-enriched hard carbon I was ground and mixed uniformly with 1.0 g of melamine powder, and was placed in a 200 mL·min -1 of nitrogen atmosphere, and was heated at a heating rate of 5℃·min -1 to 700℃ for 2 h, and then was heated to 1050℃ for 2 h. After natural cooling to room temperature, the surface topological defect-modified hard carbon I was taken out.

[0035] The surface topological defect modified hard carbon I and elemental sulfur were mixed uniformly at a mass ratio of 1:4, placed in a small glass bottle, sealed with aluminum foil paper, placed in a nitrogen atmosphere of 200 mL·min -1 at a heating rate of 5 ℃·min -1 -1 to 155 ℃ for 12 h, then to 200 ℃ for 6 h, and then naturally cooled to room temperature. The product was dispersed with carbon disulfide solution, centrifuged, and then placed in a vacuum oven at 40 ℃ for drying for 12 h to obtain a sodium ion battery negative electrode material I.

[0036] Example 2

[0037] This example provides a preparation experiment of a sodium ion battery negative electrode material.

[0038] 1.0 g of commercial hard carbon II (Kurufu, sodium ion battery hard carbon) was placed in a small beaker, and an oxygen plasma treatment machine was used with the following treatment conditions: vacuum degree maintained below 20 Pa, treatment power 150 W, and treatment time 4 min. After each treatment, the powder was stirred uniformly, and the treatment was repeated 4 times to obtain the surface oxygen-rich treated hard carbon II. The surface oxygen-rich treated hard carbon II and 1.0 g of melamine powder were mixed uniformly, placed in a nitrogen atmosphere of 200 mL·min -1 at a heating rate of 5 ℃·min -1 -1 to 700 ℃ for 2 h, and then to 1050 ℃ for 2 h. After naturally cooling to room temperature, the product was taken out to obtain the surface topological defect modified hard carbon II.

[0039] The surface topological defect modified hard carbon II and elemental sulfur were mixed uniformly at a mass ratio of 1:4, placed in a small glass bottle, sealed with aluminum foil paper, placed in a nitrogen atmosphere of 200 mL·min -1 at a heating rate of 5 ℃·min -1 -1 to 155 ℃ for 12 h, then to 200 ℃ for 6 h, and then naturally cooled to room temperature. The product was dispersed with carbon disulfide solution, centrifuged, and then placed in a vacuum oven at 40 ℃ for drying for 12 h to obtain a sodium ion battery negative electrode material II.

[0040] Example 3

[0041] This example provides a preparation experiment of a sodium ion battery negative electrode material.

[0042] 1.0 g of commercial hard carbon I (Nippon Carbon, type-2) was placed in a small beaker, and an oxygen plasma treatment machine was used with the following treatment conditions: the vacuum degree was maintained below 20 Pa, the treatment power was 150 W, and the treatment time was 4 min. After each treatment, the powder was stirred uniformly, and the treatment was performed 4 times to obtain the surface oxygen-enriched treated hard carbon I. The surface oxygen-enriched treated hard carbon I was uniformly ground and mixed with 1.0 g of melamine powder, and was placed in a 200 mL·min -1 nitrogen atmosphere at a heating rate of 5 ℃·min -1 -1 to 700 ℃ for 2 h, and then to 1050 ℃ for 2 h. After natural cooling to room temperature, the product was taken out, and the surface topological defect modified hard carbon I was obtained.

[0043] The surface topological defect modified hard carbon I was uniformly ground and mixed with elemental sulfur at a mass ratio of 1:4, and was placed in a small glass bottle and sealed with aluminum foil. It was placed in a 200 mL·min -1 nitrogen atmosphere at a heating rate of 5 ℃·min -1 -1 to 155 ℃ for 12 h, and then to 700 ℃ for 2 h at a heating rate of 5 ℃·min -1 -1. The product was taken out after natural cooling to room temperature, dispersed with carbon disulfide solution, and centrifuged and dried in a 40 ℃ vacuum oven for 12 h to obtain the sodium ion battery negative electrode material I.

[0044] Example 4

[0045] The present embodiment provides a preparation experiment of a sodium ion battery negative electrode material.

[0046] 1.0 g of commercial soft carbon IV (Koroch, BSC-3) was placed in a small beaker, and an oxygen plasma treatment machine was used with the following treatment conditions: the vacuum degree was maintained below 20 Pa, the treatment power was 150 W, and the treatment time was 4 min. After each treatment, the powder was stirred uniformly, and the treatment was performed 4 times to obtain the surface oxygen-enriched treated soft carbon IV. The surface oxygen-enriched treated soft carbon IV was uniformly ground and mixed with 1.0 g of melamine powder, and was placed in a 200 mL·min -1 nitrogen atmosphere at a heating rate of 5 ℃·min -1 -1 to 700 ℃ for 2 h, and then to 1050 ℃ for 2 h. After natural cooling to room temperature, the product was taken out, and the surface topological defect modified soft carbon IV was obtained.

[0047] The surface topological defect modified soft carbon IV was uniformly ground and mixed with elemental sulfur at a mass ratio of 1:4, and was placed in a small glass bottle and sealed with aluminum foil. It was placed in a 200 mL·min -1 nitrogen atmosphere at a heating rate of 5 ℃·min -1The temperature was increased to 155℃ and held for 12 hours, then increased to 200℃ and held for 6 hours. After naturally cooling to room temperature, the product was taken out, dispersed with carbon disulfide solution, centrifuged, and then dried in a vacuum oven at 40℃ for 12 hours to obtain sodium-ion battery anode material IV.

[0048] Example 5

[0049] This embodiment provides an experimental preparation method for a sodium-ion battery anode material.

[0050] 1.0 g of commercial hard carbon I (Kuraray, type-2) was placed in a small beaker and treated with an oxygen plasma machine under the following conditions: vacuum maintained below 20 Pa, treatment power 150 W, and treatment time 4 min. The powder was stirred thoroughly after each treatment. This process was repeated four times to obtain hard carbon I with a richly oxide-treated surface. The oxide-treated hard carbon I was then ground and mixed thoroughly with 1.0 g of melamine powder and placed in a 200 mL / min jar. -1 In a nitrogen atmosphere, at 5℃·min -1 The temperature was increased to 700℃ and held for 2 hours, then increased to 1050℃ and held for 2 hours. After naturally cooling to room temperature, the material was removed to obtain hard carbon I with surface topological defects modified on the surface.

[0051] Hard carbon I modified with surface topological defects was ground and mixed with sodium thiosulfate at a mass ratio of 1:4. The mixture was then placed in a small glass bottle, sealed with aluminum foil, and incubated at 200 mL / min. -1 In a nitrogen atmosphere, at 5℃·min -1 The temperature was increased to 155℃ and held for 12 hours, then increased to 200℃ and held for 6 hours. After naturally cooling to room temperature, the product was taken out, dispersed in water / ethanol solution, centrifuged, and then dried in a vacuum oven at 40℃ for 12 hours to obtain sodium-ion battery anode material I.

[0052] Example 6

[0053] This embodiment provides a performance testing experiment for anode materials.

[0054] A coin cell, or sodium-carbon half-cell, was assembled using an electrode containing an active negative electrode material as the positive electrode and a sodium metal sheet as the negative electrode. The aim was to study the sodium storage performance of the active negative electrode material under conditions of sufficient sodium ions and to demonstrate its application potential in sodium-ion full cells.

[0055] The active negative electrode material to be tested, sodium carboxymethyl cellulose binder, and conductive carbon black Super P conductive agent were mixed at a mass ratio of 8:1:1. A small amount of deionized water was added, and the mixture was stirred to form a slurry with a certain viscosity. The slurry was uniformly coated onto the surface of the current collector copper foil using a coater, and then vacuum dried at 60°C. The coated electrode was then cut into 12mm diameter electrode sheets, and the batteries were assembled in a glove box under an argon atmosphere (water and oxygen content both less than 0.5ppm). Using the prepared electrode sheets as the positive electrode, the sodium metal sheet as the negative electrode, 1M NaPF6 dissolved in diethylene glycol dimethyl ether as the electrolyte, and Whatman glass microfiber filter paper as the separator, CR2032 button batteries were assembled in the appropriate order. The charge and discharge performance of the batteries was tested using a LandCT2001A battery testing system, with a charge and discharge termination range of 0.01–2.0V.

[0056] In this embodiment, commercial hard carbon I and sodium-ion battery anode material I from Example 1, commercial hard carbon II and sodium-ion battery anode material II from Example 2, and commercial hard carbon III and sodium-ion battery anode material III from Example 3 were used as the anode materials to be tested, and their performance was measured to obtain the following results: Figures 1-8 The results are shown.

[0057] Depend on Figure 1 It can be seen that when the active substance loading is 0.5–0.8 mg / cm³, -2 At a test temperature of 30°C, the half-cells assembled from sodium-ion battery anode material I and commercial hard carbon I in Example 1 respectively achieved a temperature of 0.05 A·g. -1 The first charge-discharge test was conducted at the current density, and the coulombic efficiencies for the first cycle were 86.5% and 82.5%, respectively.

[0058] Depend on Figure 2 It can be seen that when the active substance loading is 0.5–0.8 mg / cm³, -2 At a test temperature of 30°C, the half-cells assembled from sodium-ion battery anode material I and commercial hard carbon I in Example 1 respectively achieved a temperature of 0.05 A·g. -1 The reversible specific capacities after stabilization at the current density were 314.4 and 287.6 mAh·g, respectively. -1 When the current density increases to 5 A·g -1 and 10A·g -1 At that time, the sodium-ion battery anode material I still had 198.9 and 112.4 mAh·g. -1 The reversible specific capacity, while commercial Hard Carbon I only retains 142.2 and 65.6 mAh·g. -1 The reversible specific capacity.

[0059] Depend on Figure 3 It can be seen that when the active substance loading is 3.3–3.5 mg·cm³, -2At a test temperature of 30°C, the half-cells assembled from sodium-ion battery anode material I and commercial hard carbon I in Example 1 respectively achieved a temperature of 0.02 A·g. -1 The reversible specific capacities after stabilization at the current density are 306.1 and 288.5 mAh·g, respectively. -1 When the current density increases to 1 A·g -1 At that time, sodium-ion battery anode material I still had 219.5 and 109.7 mAh·g. -1 The reversible specific capacity, while commercial Hard Carbon I only retains 180.9 and 83.3 mAh·g. -1 The reversible specific capacity.

[0060] Depend on Figure 4 It can be seen that when the active substance loading is 0.5–0.8 mg / cm³, -2 At a test temperature of -20°C, the half-cells assembled from sodium-ion battery anode material I and commercial hard carbon I in Example 1 respectively achieved a speed of 0.02 A·g -1 The reversible specific capacities after stabilization at the current density were 303.1 and 250.1 mAh·g, respectively. -1 When the current density increases to 1 A·g -1 and 2A·g -1 At that time, sodium-ion battery anode material I still had 74.1 and 32 mAh·g. -1 The reversible specific capacity, while commercial Hard Carbon I only retains 16.7 and 1.8 mAh·g. -1 The reversible specific capacity.

[0061] It is evident that sodium-ion battery anode material I has higher initial capacity, first-cycle coulombic efficiency, and better rate performance compared to commercial hard carbon I. Furthermore, it can maintain higher initial capacity and better rate performance even with higher active material loading or at low temperatures.

[0062] Depend on Figure 5 It can be seen that when the active substance loading is 0.5–0.8 mg / cm³, -2 At a test temperature of 30°C, the half-cells assembled from sodium-ion battery anode material II and commercially available hard carbon II in Example 2, respectively, achieved a temperature of 0.05 A·g. -1 The first charge-discharge test was conducted at the current density, and the coulombic efficiencies for the first cycle were 83.3% and 78.7%, respectively.

[0063] Depend on Figure 6 It can be seen that the half-cells assembled from sodium-ion battery anode material II and commercial hard carbon II in Example 2, respectively, have a performance of 0.05 A·g -1 The reversible specific capacities after stabilization at the current density were 308.7 and 276.6 mAh·g, respectively. -1 When the current density increases to 5 A·g -1 and 10A·g-1 At that time, the sodium-ion battery anode material II still had 138.8 and 66.9 mAh·g. -1 The reversible specific capacity, while the commercial Hard Carbon II only retains 44.7 and 19.7 mAh·g. -1 The reversible specific capacity.

[0064] It is evident that sodium-ion battery anode material II has higher initial capacity, first-cycle coulombic efficiency, and better rate performance compared to commercially available hard carbon II.

[0065] Depend on Figure 7 It can be seen that when the active substance loading is 0.5–0.8 mg / cm³, -2 At a test temperature of 30°C, the half-cells assembled from sodium-ion battery anode material III and commercial hard carbon I in Example 3 respectively achieved a temperature of 0.05 A·g. -1 The first charge-discharge test was conducted at the current density, and the coulombic efficiencies for the first cycle were 88.1% and 82.5%, respectively.

[0066] Depend on Figure 8 It can be seen that when the active substance loading is 0.5–0.8 mg / cm³, -2 At a test temperature of 30°C, the half-cells assembled from sodium-ion battery anode material III and commercial hard carbon I in Example 3 respectively achieved a temperature of 0.05 A·g. -1 The reversible specific capacities after stabilization at the current density are 328.1 and 287.6 mAh·g, respectively. -1 When the current density increases to 5 A·g -1 and 10A·g -1 At that time, sodium-ion battery anode material III still had 208.5 and 115.6 mAh·g. -1 The reversible specific capacity, while commercial Hard Carbon I only retains 142.2 and 65.6 mAh·g. -1 The reversible specific capacity.

[0067] It is evident that sodium-ion battery anode material III has higher initial capacity, first-cycle coulombic efficiency, and better rate performance compared to commercially available hard carbon I.

[0068] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the invention.

[0069] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for preparing a sodium-ion battery anode material, characterized in that, Includes the following steps: The carbon anode is subjected to a rich oxidation treatment on its surface. A two-step thermal reaction is carried out in an inert atmosphere. The first step involves heteroatom doping using nitrogen / sulfur-containing small molecules. The second step involves calcination to remove heteroatoms, followed by natural cooling to 25–30°C to obtain a carbon anode material with surface topological defects modified. The carbon anode material modified with the surface topological defects was physically mixed with active small molecules containing heteroatoms and then heat-treated under an inert atmosphere to obtain the sodium-ion battery anode material; The heat treatment under an inert atmosphere, Includes the following steps: The carbon anode material modified with the aforementioned surface topological defects was physically mixed with active heteroatom-containing small molecules, and heated to 130–180 °C under an inert atmosphere and held for 6–24 h; then heated again to 200–900 °C and held for 1–20 h; and then naturally cooled to 25–30 °C. The resulting product was dispersed in a good solvent containing active heteroatom small molecules and purified to obtain the sodium-ion battery anode material. The carbon negative electrode is either hard carbon or soft carbon; And / or, the nitrogen- / sulfur-containing small molecules are one or a combination of several of melamine, urea, thiourea, cyanamide, and dicyandiamide; And / or, the active heteroatom-containing small molecule is one or a combination of several of carbon disulfide, hydrogen sulfide, sodium thiosulfate, melamine, urea, thiourea, cyanamide, dicyandiamide, and sodium borohydride.

2. The preparation method according to claim 1, characterized in that, The surface rich oxidation treatment is one or a combination of oxygen plasma treatment, acid solution heat treatment, and air heat treatment. And / or, in the heteroatom doping, the mass ratio of the carbon anode to the nitrogen / sulfur-containing small molecules is 1:0.5 to 10, the temperature conditions are 600 to 800°C, and the duration is 1 to 4 hours; And / or, the calcination treatment is performed at a temperature of 900–1400°C for a duration of 1–4 hours; And / or, the heat treatment is performed at a temperature of 130–900°C for a duration of 2–20 hours; And / or, the inert atmosphere is one or a combination of nitrogen, argon, and helium, and the gas flow rate of the inert atmosphere is 100–300 mL / min. -1 .

3. The preparation method according to claim 1, characterized in that, The heteroatom doping is carried out at a heating rate of 2–5 °C·min. -1 ; And / or, the calcination treatment is performed at a heating rate of 2–5 °C / min. -1 ; And / or, the heating is carried out under an inert atmosphere at a rate of 2–5 °C / min. -1 ; And / or, the reheating, at a rate of 2–5 °C / min. -1 .

4. The sodium-ion battery anode material prepared by the preparation method according to any one of claims 1 to 3.

5. The application of the sodium-ion battery anode material prepared by the preparation method according to any one of claims 1 to 3 or the sodium-ion battery anode material according to claim 4 in a sodium-ion battery.

6. A sodium-ion battery, characterized in that, The sodium-ion battery anode material prepared by the preparation method according to any one of claims 1 to 3 or the sodium-ion battery anode material according to claim 4.

7. The sodium-ion battery according to claim 6, characterized in that, The sodium-ion battery anode material, binder, and conductive agent are mixed in a mass ratio of 8:1:1 to prepare a slurry. The slurry is coated onto the current collector to obtain an electrode sheet; The electrode is cut to a suitable size and used as the negative electrode of the sodium-ion battery.

8. The sodium-ion battery according to claim 6, characterized in that, Its application conditions are: current density 0.05 ~ 10 A·g -1 The temperature ranges from -20 to 30℃.

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