Starch-based sodium-ion battery anode material and its preparation method

Abstract

This invention relates to the field of hard carbon anode material technology, and discloses a starch-based sodium-ion battery anode material and its preparation method. The preparation method of the starch-based sodium-ion battery anode material of this invention includes the following steps: pretreatment: mixing and dissolving starch, sodium monofluorophosphate, sodium carbonate, and water to obtain a pretreatment solution; spray drying: spray drying the pretreatment solution under an inert atmosphere to obtain a particulate mixture; prestabilization: calcining the particulate mixture under an inert atmosphere to obtain a prestabilized product; template removal: grinding the prestabilized product and adding a dissolving solution to dissolve and remove sodium carbonate, obtaining a hard carbon precursor; high-temperature carbonization: calcining the hard carbon precursor under an inert atmosphere to obtain the starch-based sodium-ion battery anode material. The starch-based sodium-ion battery anode material of this invention is prepared by the above-described preparation method. This invention effectively improves the gelatinization and foaming problems that occur during high-temperature carbonization of starch.

Description

Technical Field

[0001] This application relates to the technical field of hard carbon anode materials, and in particular to starch-based sodium-ion battery anode materials and their preparation methods. Background Technology

[0002] Carbon-based materials are a class of materials primarily composed of carbon, including graphite, soft carbon, hard carbon, and carbon nanotubes. Due to their wide availability, abundant resources, diverse structures, renewability, and non-toxicity, carbon-based materials can be used as anode materials for sodium-ion batteries. In related technologies, hard carbon is commonly used as the electrode material for sodium-ion batteries. Hard carbon possesses a highly disordered structure, large interlayer distances, and abundant surface defects, enabling the formation of sufficient active sites for sodium ion storage. This results in minimal volume deformation after sodium intercalation and exhibits low-temperature performance and excellent fast-charging capabilities.

[0003] Among numerous hard carbon precursors, starch is widely available, inexpensive, environmentally friendly, and readily adaptable to various material processing methods, making it a suitable carbon source for hard carbon anode materials. Starch is processed through carbonization to form hard carbon. Current high-temperature carbonization methods for starch primarily involve calcining starch at a specific temperature to prepare hard carbon materials.

[0004] However, starch is prone to gelatinization and foaming during high-temperature carbonization. Starch particles adhere to each other, fuse together, and expand to form a foamy, fluffy structure. This gelatinization leaves numerous pores inside the hard carbon anode material. These pores disrupt the microstructure of the hard carbon anode material, thereby impairing the conduction pathways of electrons and sodium ions within it, resulting in poor electrical performance of the assembled sodium-ion battery. Summary of the Invention

[0005] To address the aforementioned issues, the first aspect of this application aims to provide a method for preparing a starch-based sodium-ion battery anode material. This method helps to suppress the fusion between starch particles, thereby improving the gelatinization and foaming problems that occur during high-temperature carbonization of starch. It also enables the formation of well-developed nanopores within the starch, thereby enhancing the sodium storage capacity of the hard carbon material and resulting in superior electrical performance of the hard carbon material.

[0006] The second aspect of this application aims to provide a starch-based sodium-ion battery anode material.

[0007] To achieve the above objectives, the present invention provides the following technical solution: In a first aspect, the present invention provides a method for preparing a starch-based sodium-ion battery anode material, comprising the following steps: Pretreatment: Mix starch, sodium monofluorophosphate, sodium carbonate and water, heat to dissolve, and obtain a pretreatment solution; Spray drying: The pretreated liquid is spray-dried under an inert atmosphere at a drying air velocity of 15–40 m / s. 3 The heating temperature is 110–280 °C / h to obtain a particulate mixture; Prestabilization: The particulate mixture is calcined in an inert atmosphere to obtain a prestabilized product; Template removal: The pre-stabilized product is ground and dissolved in a solvent to remove sodium carbonate, thereby obtaining a hard carbon precursor; High-temperature carbonization: Hard carbon precursors are calcined in an inert atmosphere to obtain starch-based sodium-ion battery anode materials.

[0008] In some embodiments, in the pretreatment step, the mass ratio of the starch, the sodium monofluorophosphate, and the sodium carbonate is 1:(0.1-2):(0.1-1).

[0009] In some embodiments, the particle size of the particulate mixture is 0.5 to 100 μm.

[0010] In some embodiments, in the pretreatment step, the solid-liquid ratio of the pretreatment liquid is 10% to 60%, the heating temperature is 40 to 100°C, and the heating time is 1 to 30 minutes.

[0011] In some embodiments, the drying air velocity of the spray drying is 15–40 m / s. 3 / h, heating temperature is 110~280℃.

[0012] In some embodiments, an inert gas is introduced during the spray drying process, and the pressure of the inert gas is 0.01 to 0.8 MPa.

[0013] In some embodiments, the pre-stabilization includes low-temperature calcination and high-temperature calcination; The initial calcination temperature for pre-stabilization is 20–30°C; in the low-temperature calcination, the temperature is raised to 100–200°C and held for 20–100 hours; in the high-temperature calcination, the temperature is raised to 600–950°C and held for 1–5 hours.

[0014] In some embodiments, the heating rate of the low-temperature calcination is 0.1 to 10 °C / min, and the heating rate of the high-temperature calcination is 0.1 to 60 °C / min.

[0015] In some embodiments, the initial calcination temperature of the high-temperature carbonization is 20-50°C, the temperature is raised to 1000-1500°C, and the calcination time is 2-10 hours.

[0016] Secondly, the present invention provides a starch-based sodium-ion battery anode material, wherein the starch-based sodium-ion battery anode material is prepared by the above-described method for preparing starch-based sodium-ion battery anode materials.

[0017] Based on the above technical solution, the present invention has the following technical effects: 1. The present invention provides a method for preparing starch-based sodium-ion battery anode material, wherein starch is pretreated with sodium monofluorophosphate and sodium carbonate to form a pretreatment solution, and the pretreatment solution is pre-stabilized, template removed and high-temperature carbonized, which can effectively alleviate the problems of starch gelatinization and foaming.

[0018] Starch reacts with sodium monofluorophosphate to form fluorine-oxygen bonds, which interfere with the hydrogen bonding structure within starch molecules, disrupting the interactions between starch molecules and inhibiting the fusion of starch granules due to hydrogen bond breakage. Simultaneously, sodium carbonate blocks the excessive gas production that occurs after starch molecules bond together, effectively suppressing the gas production rate. Furthermore, sodium carbonate creates good venting channels within the starch, absorbing excess heat and thus inhibiting foaming. During preparation, spray drying facilitates the formation of hollow spherical particles from the pretreatment solution, reducing contact between starch particles and creating a synergistic effect with sodium monofluorophosphate and sodium carbonate. By adding sodium monofluorophosphate and sodium carbonate and then spray-drying the starch, gelatinization and foaming phenomena in starch-based sodium-ion battery anode materials during pre-stabilization and high-temperature carbonization can be improved, reducing the formation of numerous pores within the starch-based sodium-ion battery anode material during starch gelatinization.

[0019] 2. The starch-based sodium-ion battery anode material provided by this invention can effectively suppress the gelatinization and foaming problems of starch. The starch-based sodium-ion battery anode material is transformed into a closed-cell structure through high-temperature carbonization treatment. Abundant nanopores are formed inside the starch-based sodium-ion battery anode material, which is conducive to improving the effective sodium storage space of the starch-based sodium-ion battery anode material, thereby improving the capacity of the starch-based sodium-ion battery anode material. Attached Figure Description

[0020] Figure 1 This is a diagram showing the pre-stabilization effect of the starch-based sodium-ion battery anode material prepared in Example 1 of the present invention.

[0021] Figure 2 This is a diagram showing the pre-stabilization effect of the starch-based sodium-ion battery anode material prepared in Comparative Example 1 of the present invention.

[0022] Figure 3 This diagram shows the pre-stabilization effect of the starch-based sodium-ion battery anode material prepared in Comparative Example 2 of the present invention. Figure 4This is a diagram showing the pre-stabilization effect of the starch-based sodium-ion battery anode material prepared in Comparative Example 3 of the present invention.

[0023] Figure 5 This is a SEM image of the starch-based sodium-ion battery anode material prepared in Example 1 of the present invention.

[0024] Figure 6 This is a SEM image of the starch-based sodium-ion battery anode material prepared in Example 2 of the present invention.

[0025] Figure 7 The images show the XRD patterns of the starch-based sodium-ion battery anode materials prepared in Examples 1 and 2 of this invention.

[0026] Figure 8 This is a schematic diagram illustrating the mechanism by which sodium monofluorophosphate reacts with starch to inhibit starch foaming in a specific embodiment of the present invention. Detailed Implementation

[0027] To facilitate understanding of the present invention, a more comprehensive description will be provided below with reference to specific embodiments. Preferred embodiments are given herein. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the present invention.

[0028] Before further describing in more detail the various embodiments of the compounds / compositions and methods of this disclosure through exemplary descriptions, examples, and results, it should be understood that the embodiments of this disclosure are not limited in application to the details of the methods and compositions described below. The descriptions provided herein are for illustrative purposes only and are not intended to be interpreted in a limiting sense. The inventive concept of this disclosure can have other embodiments or can be practiced or implemented in various ways. Therefore, the language used herein is intended to give the broadest scope and meaning; and the embodiments are intended to be exemplary, not exhaustive, and are not intended to limit this disclosure to these particular embodiments. Moreover, it should be understood that the wording and terminology used herein are for descriptive purposes and should not be considered limiting unless otherwise stated. Furthermore, numerous specific details are set forth in the following detailed description to provide a more thorough understanding of this disclosure.

[0029] However, it will be apparent to those skilled in the art that embodiments of this disclosure can be practiced without these specific details. In other instances, features well-known to those skilled in the art have not been described in detail to avoid unnecessary complexity. It is intended that all substitutions, replacements, modifications, and equivalents that are apparent to those skilled in the art are included within the scope of this disclosure. Based on this disclosure, all compounds / compositions disclosed herein, their preparation methods, applications, and uses can be prepared and implemented without excessive experimentation.

[0030] Therefore, although the compounds / compositions and methods of this disclosure have been described with reference to specific embodiments, it will be apparent to those skilled in the art that variations may be made to the formulations, compounds or compositions and / or methods, as well as the steps or sequence of steps of the methods described herein, without departing from the spirit and scope of the inventive concept of this disclosure.

[0031] As used herein, any reference to "an embodiment" or "an embodiment" means that a particular element, feature, structure, or characteristic described in connection with that embodiment is included in at least one embodiment. The phrase "in an embodiment" appearing in multiple places throughout the specification does not necessarily refer to the same embodiment.

[0032] Unless otherwise defined herein, scientific and technical terms used in connection with this disclosure shall have the meanings commonly understood by one of ordinary skill in the art. Furthermore, unless the context requires otherwise, singular terms shall include plural forms, and plural terms shall include singular forms.

[0033] The following provides a further detailed description of this application.

[0034] The present invention discloses a method for preparing a starch-based sodium-ion battery anode material, comprising the following steps: Pretreatment: Starch, sodium monofluorophosphate, sodium carbonate, and water are mixed and dissolved. In a preferred embodiment, the starch is a soluble starch, such as corn starch or potato starch. In some preferred embodiments, the mass ratio of starch, sodium monofluorophosphate, and sodium carbonate is 1:(0.1-2):(0.1-1), such as 1:0.1:1, 1:2:0.1, 1:1.5:0.5, etc.

[0035] A pretreatment solution is obtained by mixing starch, sodium monofluorophosphate and water. In some preferred embodiments, the solid-liquid ratio of the pre-stabilized solution is 10% to 60%, such as 10%, 30%, 45%, 50%, 60%, etc. The pre-stabilized liquid is heated at a constant temperature. In some preferred embodiments, the heating temperature is 40-100°C, such as 40°C, 50°C, 60°C, 80°C, or 10°C, and the heating time is 1-30 min, such as 1 min, 5 min, 10 min, 15 min, 20 min, or 30 min. Spray drying: The pretreated liquid is spray-dried under an inert atmosphere at a drying air velocity of 15–40 m / s. 3 / h, in some specific embodiments, the drying air velocity is preferably, but not limited to, 15m / h. 3 / h、18 m 3 / h、20 m 3 / h、25 m 3 / h、27m 3 / h、30 m 3 / h, 40m 3 / h. The heating temperature for spray drying is 110–280°C. In some specific embodiments, the heating temperature is preferably, but not limited to, 110°C, 120°C, 160°C, 180°C, 200°C, 260°C, and 280°C. The pretreatment liquid is spray dried to obtain a particulate mixture. In some preferred embodiments, the particle size of the particulate mixture is 0.5–100 μm, such as 0.5 μm, 10 μm, 20 μm, 60 μm, 80 μm, and 100 μm. Starch reacts with sodium monofluorophosphate to form fluorine-oxygen bonds, which interfere with the hydrogen bonding structure within starch molecules, leading to the fusion of starch particles. Simultaneously, the addition of sodium carbonate creates effective venting channels within the starch to suppress foaming. The synergistic effect between spray drying and sodium monofluorophosphate and sodium carbonate promotes the formation of hollow spherical particle mixtures in the pretreatment solution, reducing contact between starch particles. Spray drying of starch after adding sodium monofluorophosphate and sodium carbonate improves the gelatinization and foaming phenomena of starch-based sodium-ion battery anode materials during pre-stabilization and high-temperature carbonization. Pre-stabilization: The particle mixture is calcined under an inert atmosphere; pre-stabilization includes low-temperature calcination and high-temperature calcination. In some preferred embodiments, the initial calcination temperature for pre-stabilization is 20-30°C, such as 20°C, 22°C, 24°C, 26°C, 28°C, 30°C, etc. In low-temperature calcination, it is preferred to raise the temperature to 100-200°C, such as 100°C, 130°C, 160°C, 190°C, 200°C, etc., and the holding time is preferably 20-100h, such as 20h, 40h, 60h, 80h, 100h, etc. In high-temperature calcination, the temperature is preferably raised to 600-950℃, such as 600℃, 650℃, 700℃, 750℃, 800℃, 950℃, etc., and the holding time is preferably 1-5h, such as 1h, 2h, 4h, 5h, etc. The particulate mixture is pre-stabilized to obtain a pre-stabilized product. Template removal: The pre-stabilized product is ground and dissolved in a solvent to remove sodium carbonate, thereby obtaining a hard carbon precursor; High-temperature carbonization: The hard carbon precursor is calcined in an inert atmosphere. In a preferred embodiment, the initial calcination temperature of high-temperature carbonization is 20-50°C, such as 20°C, 25°C, 30°C, 40°C, 50°C, etc. Further, the temperature is preferably raised to 1000-1500°C, such as 1000°C, 1200°C, 1400°C, 1500°C, etc., and the calcination time is preferably 2-10h, such as 2h, 4h, 6h, 8h, 10h, etc. The hard carbon precursor is carbonized at high temperature to obtain starch-based sodium-ion battery anode material.

[0036] Example 1 A method for preparing a starch-based sodium-ion battery anode material includes the following steps: Pretreatment: Weigh out 20g of starch, sodium monofluorophosphate, and sodium carbonate, with a mass ratio of 1:0.1:1. Mix and dissolve the starch, sodium monofluorophosphate, and sodium carbonate in 200ml of ultrapure water to obtain the pretreatment solution. Specifically, the solid-liquid ratio of the pretreatment solution is 21%.

[0037] The pretreatment solution was placed in a heater and heated in a constant temperature water bath at 80°C for 15 minutes. The pretreatment solution was stirred with a magnetic stirrer during heating until it turned red and transparent for 10 minutes. Spray drying: An inert gas is introduced into the spray dryer to create an inert atmosphere. The pressure of the inert gas is 0.2 MPa. Specifically, argon or nitrogen is preferred, but not limited to, the inert gas. The pretreated liquid is spray-dried through the spray dryer at a drying air velocity of 40 m / s. 3 / h, heating temperature is 180℃, to obtain a particulate mixture, the particulate mixture is spherical and the particle size of the particulate mixture is 0.5μm; Pre-stabilization: First, the particulate mixture is placed in a graphite box, and then the graphite box is placed in a tube furnace. An inert gas is introduced into the tube furnace. Specifically, the inert gas is preferably, but not limited to, argon or nitrogen. The particulate mixture is calcined in an inert atmosphere to obtain a pre-stabilized product.

[0038] Pre-stabilization includes low-temperature calcination and high-temperature calcination. The initial calcination temperature is 30℃. During low-temperature calcination, the temperature is gradually increased to 100℃ at a rate of 5℃ / min, and the holding time is 60 hours. During high-temperature calcination, the temperature is gradually increased to 600℃ at a rate of 10℃ / min, and the holding time is 4 hours. Template removal: The pre-stabilized product is ground and a dissolving solution is added to dissolve and remove sodium carbonate. In some specific embodiments shown, the dissolving solution may be ultrapure water, and the solid-liquid ratio of the dissolving solution to the pre-stabilized product is 12.5%.

[0039] The solution and pre-stabilized product were subjected to ultrasonic cleaning and agitation for 10 minutes. The solution and pre-stabilized product were then filtered through a vacuum funnel. After removing sodium carbonate from the pre-stabilized product, it was dried in an oven to obtain a hard carbon precursor at a temperature of 85°C for 2 hours. High-temperature carbonization: The hard carbon precursor is placed in a graphite crucible, and the graphite crucible and the hard carbon precursor it contains are placed in a tube furnace. An inert gas is introduced into the tube furnace; specifically, argon or nitrogen is preferred but not limited to the inert gas, and the pressure of the inert gas is 25 MPa. Under the inert atmosphere, the hard carbon precursor is calcined. The initial calcination temperature for high-temperature carbonization is 50°C, and the calcination temperature is gradually increased to 1300°C during the high-temperature carbonization process. The heating time is 260 min, and the calcination time is 3 h. When cooled to room temperature, starch-based sodium-ion battery anode material is obtained.

[0040] Example 2 A method for preparing a starch-based sodium-ion battery anode material includes the following steps: Pretreatment: Weigh 20g of starch, sodium monofluorophosphate and sodium carbonate. The mass ratio of starch, sodium monofluorophosphate and sodium carbonate is 1:0.1:0.5. Mix starch, sodium monofluorophosphate and sodium carbonate and dissolve them in 200ml of ultrapure water to obtain a pretreatment solution. The solid-liquid ratio of the pretreatment solution is 16%.

[0041] The pretreatment solution was placed in a heater and heated in a constant temperature water bath at 40°C for 15 minutes. The pretreatment solution was stirred with a magnetic stirrer during heating until it turned red and transparent for 10 minutes. Spray drying: Argon gas is introduced into the spray dryer to create an inert atmosphere. The argon gas pressure is 0.8 MPa. The pretreated liquid is spray-dried through the spray dryer at a drying air velocity of 15 m / s. 3 / h, heating temperature is 110℃, to obtain a particulate mixture, the particulate mixture is spherical and the particle size of the particulate mixture is 0.5μm; Prestabilization: The particulate mixture is first placed in a graphite box, then the graphite box is placed in a tube furnace, argon gas is introduced into the tube furnace, and the particulate mixture is calcined in an inert atmosphere to obtain a prestabilized product.

[0042] Pre-stabilization includes low-temperature calcination and high-temperature calcination. The initial calcination temperature is 20℃. During low-temperature calcination, the temperature gradually increases to 200℃ at a rate of 0.1℃ / min, and the holding time is 100h. During high-temperature calcination, the temperature gradually increases to 750℃ at a rate of 0.1℃ / min, and the holding time is 5h. Template removal: The pre-stabilized product is ground and a dissolving solution is added to dissolve and remove sodium carbonate. In some specific embodiments shown, the dissolving solution may be ultrapure water, and the solid-liquid ratio of the dissolving solution to the pre-stabilized product is 12.5%.

[0043] The solution and pre-stabilized product were subjected to ultrasonic cleaning and agitation for 10 minutes. The solution and pre-stabilized product were then filtered through a vacuum funnel. After removing sodium carbonate from the pre-stabilized product, it was dried in an oven to obtain a hard carbon precursor at a temperature of 85°C for 2 hours. High-temperature carbonization: The hard carbon precursor is placed in a graphite crucible, and the graphite crucible and the hard carbon precursor it contains are placed in a tube furnace. Argon gas is introduced into the tube furnace at a pressure of 25 MPa. Under an inert atmosphere, the hard carbon precursor is calcined. The initial calcination temperature for high-temperature carbonization is 50°C. During the high-temperature carbonization process, the calcination temperature is gradually increased to 1000°C, with a heating time of 180 min and a calcination time of 10 h. When cooled to room temperature, starch-based sodium-ion battery anode material is obtained.

[0044] Example 3 A method for preparing a starch-based sodium-ion battery anode material includes the following steps: Pretreatment: Weigh 20g of starch, sodium monofluorophosphate and sodium carbonate. The mass ratio of starch, sodium monofluorophosphate and sodium carbonate is 1:2:0.1. Mix starch, sodium monofluorophosphate and sodium carbonate and dissolve them in 200ml of ultrapure water to obtain a pretreatment solution. The solid-liquid ratio of the pretreatment solution is 31%.

[0045] The pretreatment solution was placed in a heater and heated in a constant temperature water bath at 100°C for 15 minutes. The pretreatment solution was stirred with a magnetic stirrer during heating until it turned red and transparent for 10 minutes. Spray drying: Argon gas is introduced into the spray dryer to create an inert atmosphere. The argon gas pressure is 0.5 MPa. The pretreated liquid is spray-dried through the spray dryer at a drying air velocity of 30 m / s. 3 / h, heating temperature is 200℃, to obtain a particulate mixture, the particulate mixture is spherical and the particle size of the particulate mixture is 0.5μm; Prestabilization: The particulate mixture is first placed in a graphite box, then the graphite box is placed in a tube furnace, argon gas is introduced into the tube furnace, and the particulate mixture is calcined in an inert atmosphere to obtain a prestabilized product.

[0046] Pre-stabilization includes low-temperature calcination and high-temperature calcination. The initial calcination temperature is 15℃. During low-temperature calcination, the temperature gradually increases to 200℃ at a rate of 5℃ / min, and the holding time is 60 hours. During high-temperature calcination, the temperature gradually increases to 950℃ at a rate of 10℃ / min, and the holding time is 4 hours. Template removal: The pre-stabilized product is ground and a dissolving solution is added to dissolve and remove sodium carbonate. In some specific embodiments shown, the dissolving solution may be ultrapure water, and the solid-liquid ratio of the dissolving solution to the pre-stabilized product is 12.5%.

[0047] The solution and pre-stabilized product were subjected to ultrasonic cleaning and agitation for 10 minutes. The solution and pre-stabilized product were then filtered through a vacuum funnel. After removing sodium carbonate from the pre-stabilized product, it was dried in an oven to obtain a hard carbon precursor at a temperature of 85°C for 2 hours. High-temperature carbonization: The hard carbon precursor is placed in a graphite crucible, and the graphite crucible and the hard carbon precursor it contains are placed in a tube furnace. Argon gas is introduced into the tube furnace at a pressure of 25 MPa. Under an inert atmosphere, the hard carbon precursor is calcined. The initial calcination temperature for high-temperature carbonization is 40°C. During the high-temperature carbonization process, the calcination temperature is gradually increased to 1300°C, with a heating time of 240 min and a calcination time of 6 h. After cooling to room temperature, starch-based sodium-ion battery anode material is obtained.

[0048] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that, in the pretreatment: 20g of starch was weighed and dissolved in 200ml of ultrapure water to obtain a pretreated solution. The pretreated solution was placed in a heater and heated in a constant temperature water bath at 80°C for 15 minutes. During heating, the pretreated solution was stirred with a magnetic stirrer until it became colorless and transparent for 10 minutes.

[0049] Comparative Example 2 The preparation method of a starch-based sodium-ion battery anode material of this comparative example includes the following steps: Weigh out 20g of starch; Prestabilization: The starch is placed in a graphite box, which is then placed in a tube furnace. Argon gas is introduced into the tube furnace, and the particulate mixture is calcined in an inert atmosphere to obtain a prestabilized product.

[0050] Pre-stabilization includes low-temperature calcination and high-temperature calcination. The initial calcination temperature for low-temperature calcination is 15℃, and the temperature is gradually increased to 200℃ at a rate of 5℃ / min, with a holding time of 60 hours. In the high-temperature calcination process, the temperature is gradually increased to 950℃ at a rate of 10℃ / min, with a holding time of 4 hours. High-temperature carbonization: The pre-stabilized product is placed in a graphite crucible, and the graphite crucible and the hard carbon precursor it holds are placed in a tube furnace. Argon gas is introduced into the tube furnace at a pressure of 25 MPa. Under an inert atmosphere, the hard carbon precursor is calcined. The initial calcination temperature for high-temperature carbonization is 40°C, and the calcination temperature is gradually increased to 1300°C during the high-temperature carbonization process. The heating time is 240 min, and the calcination time is 6 h. When cooled to room temperature, starch-based sodium-ion battery anode material is obtained.

[0051] Comparative Example 3 The difference between Comparative Example 3 and Example 1 is that sodium carbonate was not added to the pretreatment solution during the pretreatment process. The starch content was 20g, and the mass ratio of starch to sodium monofluorophosphate was 1:0.1.

[0052] The pretreatment solution was placed in a heater and heated in a constant temperature water bath at 40°C for 15 minutes. During heating, the pretreatment solution was stirred with a magnetic stirrer until it became colorless and transparent for 10 minutes.

[0053] The pretreatment process involves spray drying, pre-stabilization, and high-temperature carbonization to obtain starch-based sodium-ion battery anode material.

[0054] Comparative Example 4 The difference between Comparative Example 4 and Example 1 is the pretreatment: starch and sodium carbonate were weighed, wherein the mass of starch was 20g and the mass ratio of starch to sodium carbonate was 1:1. The starch and sodium carbonate were mixed and dissolved in 200ml of ultrapure water to obtain a pretreated solution.

[0055] The pretreatment solution was placed in a heater and heated in a constant temperature water bath at 40°C for 15 minutes. During heating, the pretreatment solution was stirred with a magnetic stirrer until it turned red and transparent for 10 minutes.

[0056] Comparative Example 5 The difference between Comparative Example 5 and Example 1 is that starch, sodium monofluorophosphate, and sodium carbonate were weighed, with 20g of starch and a mass ratio of 1:0.1:1 for starch, sodium monofluorophosphate, and sodium carbonate. The starch, sodium monofluorophosphate, and sodium carbonate were mixed and stirred until homogeneous to obtain a raw material mixture. This mixture was then subjected to pre-stabilization, mold removal, and high-temperature carbonization treatment to finally obtain a starch-based sodium-ion battery anode material.

[0057] Performance testing Gelatinization and foaming detection: The gelatinization and foaming of the pre-stabilized products of Examples 1-3 and Comparative Examples 1-4 after pre-stabilization were observed, and the severity of gelatinization and foaming of the starch-based sodium-ion battery anode material was rated. Among them, the starch-based sodium-ion battery anode material showed the following: Spectroscopic detection: XRD detection was performed on the starch-based sodium-ion battery anode materials prepared in Example 1 and Example 2, respectively; Scanning electron microscopy (SEM) was performed on the starch-based sodium-ion battery anode materials prepared in Examples 1 and 2, respectively. Electrochemical performance testing: The starch-based sodium-ion battery anode materials prepared in Examples 1-3 were assembled into ten sodium-ion batteries. The sodium-ion batteries were subjected to charge-discharge tests using a high-performance battery testing system to determine the capacity and initial efficiency of the starch-based sodium-ion battery anode materials. The charge-discharge rate was 0.1C.

[0058] Table 1 Performance test results of starch-based sodium-ion battery anode materials prepared in Examples 1-3 and Comparative Examples 1-4

[0059] Reference Figure 7 As can be seen from the (002) and (100) diffraction peaks, both peaks have weak intensity and wide shape, indicating that the starch-based sodium-ion battery anode material has formed a short-range ordered structure, i.e., a microcrystalline structure. The basic structure within the starch-based sodium-ion battery anode material has formed sp 2 Carbon hexagonal network composed of carbon. (See reference) Figure 5 and Figure 6 The starch-based sodium-ion battery anode material has a spherical shape with depressions on each side and a small number of open pores. The short graphene in the starch-based sodium-ion battery anode material is arranged in an orderly manner, and the stacking and connection of graphitized carbon layers form a highly twisted structure with abundant nanopores, thus providing more space for sodium ion insertion.

[0060] The performance test results of the starch-based sodium-ion battery anode materials prepared in Examples 1-3 and Comparative Examples 1-4 show that there is a synergistic effect between sodium monofluorophosphate, sodium carbonate, and spray drying treatment, which can effectively improve the gelatinization and foaming phenomena of starch. Specifically, based on the performance test results of Examples 1-3 and Comparative Example 4, and referring to the appendix... Figure 8 It is known that during the preparation of starch-based sodium-ion battery anode materials, fluoride ions in sodium monofluorophosphate interact with hydroxyl groups in starch molecules to form fluoride-oxygen bonds. Starch is a polysaccharide composed of glucose molecules, usually existing in the form of α-glucan. Fluoride-oxygen bonds can interfere with the hydrogen bond structure within starch molecules and disrupt the interaction forces between starch molecules. When hydrogen bonds and van der Waals forces exist within starch molecules, the starch molecules exhibit certain crystallization properties, making them difficult to dissolve and gelatinize. The addition of sodium monofluorophosphate can inhibit the fusion and foaming of starch particles, thereby improving the electrochemical performance of starch-based sodium-ion battery anode materials.

[0061] According to the performance test results of Examples 1-3 and Comparative Example 3, sodium carbonate can prevent the fusion of starch particles during pre-stabilization treatment. Starch particles are prone to uneven heating during the heating process. At high temperatures, the hydroxyl bonds break, causing small molecule products and water vapor to escape from the starch, leading to fusion and gelatinization. After foaming, the starch expands in volume and leaves numerous pores. These pores disrupt the conduction pathways of electrons and sodium ions in the starch-based sodium-ion battery anode material, reducing the reversible sodium storage per unit volume. The addition of sodium carbonate creates good venting channels within the starch, facilitating the timely removal of water vapor during heating and carbonization, thus mitigating gelatinization. Simultaneously, sodium carbonate causes the short graphene layers in the starch-based sodium-ion battery anode material to arrange themselves in an orderly manner. The graphitized carbon layers stack and connect to form a highly twisted structure with numerous nanopores. The nanoscale voids constructed inside the starch-based sodium-ion battery anode material provide a foundation for subsequent Na... + Providing a transmission channel, the starch-based sodium-ion battery anode material is carbonized at high temperature to form a closed-pore structure. Sodium carbonate effectively increases the effective sodium storage space of the starch anode material, thereby improving the electrochemical performance of the starch anode material.

[0062] According to the performance test results of Examples 1-3 and Comparative Example 4, the spray drying process can maintain the initial ellipsoidal shape of starch granules. At this time, the granule mixture is spherical. The spherical shape of the granule mixture can reduce the mutual contact of starch molecules during carbonization, thereby effectively alleviating the problems of starch gelatinization and foaming.

[0063] The above description is merely an example and illustration of the structure of this invention, and while the description is specific and detailed, it should not be construed as limiting the scope of this invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this invention, and these obvious substitutions all fall within the protection scope of this invention.

Claims

1. A method for preparing a starch-based sodium-ion battery anode material, characterized in that, Includes the following steps: Pretreatment: Mix starch, sodium monofluorophosphate, sodium carbonate and water, heat to dissolve, and obtain a pretreatment solution; Spray drying: Under an inert atmosphere, the pretreatment liquid is spray dried to obtain a particulate mixture; Prestabilization: The particulate mixture is calcined in an inert atmosphere to obtain a prestabilized product; Template removal: The pre-stabilized product is ground and dissolved in a solvent to remove sodium carbonate and obtain a hard carbon precursor. High-temperature carbonization: Hard carbon precursors are calcined in an inert atmosphere to obtain starch-based sodium-ion battery anode materials. The initial calcination temperature for high-temperature carbonization is 20–50°C, then the temperature is increased to 1000–1500°C, and the calcination time is 2–10 hours.

2. The method for preparing the starch-based sodium-ion battery anode material according to claim 1, characterized in that, In the pretreatment step, the mass ratio of the starch, the sodium monofluorophosphate, and the sodium carbonate is 1:(0.1-2):(0.1-1).

3. The method for preparing the starch-based sodium-ion battery anode material according to claim 1, characterized in that, The particle size of the particulate mixture is 0.5 to 100 μm.

4. The method for preparing the starch-based sodium-ion battery anode material according to claim 1, characterized in that, In the pretreatment step, the solid-liquid ratio of the pretreatment liquid is 10% to 60%, the heating temperature is 40 to 100°C, and the heating time is 1 to 30 minutes.

5. The method for preparing the starch-based sodium-ion battery anode material according to claim 1, characterized in that, The drying air velocity of the spray drying is 15-40 m / s. 3 / h, heating temperature is 110~280℃.

6. The method for preparing the starch-based sodium-ion battery anode material according to claim 1, characterized in that, An inert gas is introduced during the spray drying process, and the pressure of the inert gas is 0.01 to 0.8 MPa.

7. The method for preparing the starch-based sodium-ion battery anode material according to claim 1, characterized in that, The pre-stabilization includes low-temperature calcination and high-temperature calcination; The initial calcination temperature for pre-stabilization is 20–30°C. In the low-temperature calcination, the temperature is raised to 100–200°C and held for 20–100 hours. In the high-temperature calcination, the temperature is raised to 600–950°C and held for 1–5 hours.

8. The method for preparing the starch-based sodium-ion battery anode material according to claim 7, characterized in that, The heating rate for the low-temperature calcination is 0.1–10 °C / min, and the heating rate for the high-temperature calcination is 0.1–60 °C / min.

9. A starch-based sodium-ion battery anode material, characterized in that, The starch-based sodium-ion battery anode material is prepared by the method for preparing starch-based sodium-ion battery anode material as described in any one of claims 1 to 8.

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