A sodium-ion battery anode material

Abstract

This invention relates to a sodium-ion battery anode material, belonging to the field of battery material technology. The invention introduces a microwave-absorbing agent or partially reduced graphene oxide to obtain a microwave-absorbing precursor, promoting microwave absorption and enabling the simultaneous crystallization of metal salts into active anode materials and microwave irradiation reduction of graphene oxide. During microwave irradiation, the metal salts can crystallize in situ on the graphene network substrate, growing a large number of ultrafine nanocrystalline active anode material particles. These ultrafine nanocrystalline active anode material particles are directly bonded to the graphene substrate. Because graphene provides abundant internal space and anchors the main active anode material particles through bonding, the volume change of the active anode material during service can be accommodated by the pores between the graphene networks, thus maintaining the structural stability of the anode material, fully utilizing its theoretical specific capacity, and maintaining the reversibility of the electrochemical process.

Description

Technical Field

[0001] This invention relates to a sodium-ion battery anode material, belonging to the field of battery material technology. Background Technology

[0002] In recent years, due to increasing attention to renewable energy, lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs) have received growing interest. While pure lithium or sodium metal has the highest theoretical specific capacity as the negative electrode in lithium or sodium-ion batteries, it reacts strongly with the electrolyte, leading to battery failure and safety concerns, making it difficult to use in practical battery technologies.

[0003] Since Sony commercialized graphite lithium-ion battery anodes in 1991, graphite has successfully served as the benchmark anode for lithium-ion batteries, becoming a crucial pillar for their widespread adoption. However, lithium-ion resources are limited, making sodium, with its more abundant resources, a key direction for battery technology development. Unfortunately, graphite anodes are unsuitable for sodium-ion batteries because sodium ions are difficult to transport in graphite, resulting in extremely low specific capacity. To date, hard carbon is the best candidate carbon material for sodium-ion batteries, defined as a non-crystallizable carbon material typically composed of amorphous carbon, bent amorphous graphene-like sheets, and the surrounding pores. Hard carbon can be synthesized by pyrolysis of various carbon precursors at temperatures above 1000°C. As anodes, they can typically achieve peak specific capacities of 250–300 mAh / g, but due to complex manufacturing processes and low reliability, the stable cycle capacity of practical hard carbon anodes is far below 200 mAh / g. Clearly, further improving the anode capacity is essential for competitive sodium-ion batteries.

[0004] Unfortunately, currently known anode materials with higher theoretical specific capacity are all conversion-type elements or compounds involving chemical reactions and phase transitions. Competitive conversion-type anode materials include metal elements, oxides, sulfides, and selenides. Although these conversion-type anode materials have higher theoretical capacity, the volume change during charge-discharge processes exceeds 100% due to phase changes, leading to anode breakage and battery structural failure. Utilizing carbon-based materials combined with conversion-type materials has become an important measure to maintain the structural stability of battery anodes. Graphene, due to its good mechanical properties, excellent metal ion and electronic conductivity, and extremely large specific surface area, is one of the most promising composite substrates and is expected to become a high-specific-capacity anode material system with a large amount of nano-conversion material crystals loaded. Although there are reports of using composites of metal elements, metal oxides, sulfides, and selenides with reduced graphene oxide (RGO) as anodes for sodium-ion batteries, these methods typically require harsh process conditions such as high temperature and high pressure, resulting in low efficiency and high energy consumption, making them unsuitable for the requirements of low-carbon and environmentally friendly energy storage technologies. Summary of the Invention

[0005] The purpose of this invention is to provide a sodium-ion battery anode material that solves the problems of harsh preparation process conditions, low efficiency, and high energy consumption when using composites of elemental metals / metal oxides / sulfides / selenides with reduced graphene oxide (RGO) as anodes for sodium-ion batteries.

[0006] To achieve the above objectives, the technical solution adopted by the sodium-ion battery anode material of the present invention is as follows:

[0007] A sodium-ion battery anode material is prepared by a method comprising the following steps: subjecting a microwave absorbing precursor to microwave irradiation to obtain a microwave reactant, and then pulverizing the microwave reactant.

[0008] The microwave absorbing precursor includes a metal salt and component A; the metal element in the metal salt is a metal element found in conversion-type negative electrode materials for sodium-ion batteries; component A is a combination of graphene oxide and a microwave absorbing agent or component A is partially reduced graphene oxide.

[0009] The absorbing precursor may or may not include a non-metallic source; the non-metallic source is selected from one or any combination of sulfur, selenium, and phosphorus.

[0010] When the microwave absorbing precursor includes a non-metallic source, the microwave irradiation treatment is carried out in an inert atmosphere;

[0011] When the microwave absorbing precursor does not include a non-metallic source, the microwave irradiation treatment is carried out in an oxidizing atmosphere or an inert atmosphere.

[0012] The sodium-ion battery anode material of this invention is prepared by a simple, energy-saving, and environmentally friendly method. By introducing a microwave-absorbing agent or partially reduced graphene oxide, a microwave-absorbing precursor is obtained, which promotes microwave absorption, thereby activating the formation and rapid epitaxial growth of the reduced graphene crystal core. This promotes the simultaneous and coordinated crystallization of metal salts into active anode materials and microwave irradiation of reduced graphene oxide (GO), directly preparing the sodium-ion battery anode material. During microwave irradiation, metal salts can crystallize and grow in situ on the graphene network substrate to form active anode material crystal particles (conversion-type anode materials). The active anode material particles are directly bonded to the graphene substrate. Because graphene provides abundant internal space and anchors the main active anode material particles through bonding, the volume change of the active anode material during service can be accommodated by the pores between the graphene networks, thus maintaining the structural stability of the anode material, fully utilizing its theoretical specific capacity, and maintaining the reversibility of the electrochemical process. Microwave-reduced graphene possesses a crystalline structure, thus fully leveraging its outstanding mechanical properties and excellent transport capabilities for sodium ions and electrons, thereby effectively accelerating the electrochemical process in the negative electrode region. Sodium-ion batteries employing the negative electrode material of this invention exhibit significant advantages such as high structural stability and high specific capacity.

[0013] It is understandable that the conversion-type anode materials used in sodium-ion batteries belong to the category of anode materials involving chemical reaction phase transitions, including metal oxide type conversion-type anode materials, elemental metal type conversion-type anode materials, alloy type conversion-type anode materials, metal sulfide type conversion-type anode materials, metal phosphide type conversion-type anode materials, and metal selenide type conversion-type anode materials.

[0014] When the absorbing precursor does not include a non-metallic source, microwave irradiation of metal salts in an oxidizing atmosphere can form metal oxides, resulting in a composite material composed of a metal oxide-type conversion anode material and graphene. Microwave irradiation of metal salts in an inert atmosphere can form elemental metals, resulting in a composite material composed of elemental metal conversion anode materials and graphene. When the absorbing precursor includes a non-metallic source, the non-metallic source can react with metals to form metal compound (metal sulfide / selenide / phosphide) type conversion anode materials, resulting in a composite material composed of a metal compound-type conversion anode material and graphene.

[0015] Preferably, the mass fraction of graphene in the sodium-ion battery anode material is 10-60%. For example, the mass fraction of graphene in the sodium-ion battery anode material is 15-37%. When the mass fraction of graphene in the sodium-ion battery anode material is 10-60%, it can more effectively mitigate the volume change of the main active anode material and provide higher capacity. In sodium-ion battery anode materials, the higher the graphene content, the larger the overall specific surface area and internal space, making it easier to buffer volume changes and resulting in better conductivity; if the graphene content is too low, not only is the conductivity relatively poor, but the smaller specific surface area and internal space cannot buffer the volume change of the active anode material, leading to battery failure. Since the capacity of graphene itself is much lower than that of the main active anode material (metal element, metal oxide, etc.), an excessively high graphene content leads to a low overall capacity. Therefore, the mass fraction of graphene in the sodium-ion battery anode material is controlled to be 10-60%.

[0016] Preferably, when component A is a combination of graphene oxide and a microwave absorbing agent, the mass fraction of the microwave absorbing agent in the microwave absorbing precursor is 1-5%.

[0017] Preferably, the microwave absorbing precursor is composed of a metal salt, graphene oxide, and a microwave absorbing agent, and is prepared by method I, which includes the following steps: freeze-drying a dispersion of the metal salt, graphene oxide, and microwave absorbing agent to obtain the microwave absorbing precursor. Preferably, in method I, the microwave irradiation treatment is carried out in an oxidizing atmosphere.

[0018] Preferably, the microwave absorbing precursor is composed of a metal salt and partially reduced graphene oxide. The precursor is prepared using method II, which includes the following steps: freeze-drying a dispersion of metal salt and graphene oxide to obtain a composite aerogel; then, heating and reducing the graphene oxide in the composite aerogel to obtain the microwave absorbing precursor. Preferably, in method II, the heating and reducing treatment temperature is 100–600°C, and the heating and reducing treatment time is 1–24 hours. For example, the heating and reducing treatment temperature is 200°C, and the heating and reducing treatment time is 1 hour. Preferably, in method II, the microwave irradiation treatment is performed in an oxidizing atmosphere. Heating and reducing the graphene oxide in the composite aerogel can partially reduce graphene oxide material that does not have electromagnetic wave absorption capabilities, obtaining a material with high electromagnetic wave absorption capabilities. During microwave irradiation treatment, microwaves can be absorbed and converted into heat energy, promoting further high-level reduction of the partially reduced graphene oxide, as well as the decomposition and conversion of the metal salt to form a sodium-ion battery anode material. The heating and reducing treatment can be performed in an inert atmosphere or in air.

[0019] Preferably, the microwave absorbing precursor is composed of a metal salt, graphene oxide, a microwave absorbing agent, and a non-metallic source. The microwave absorbing precursor is prepared using method III, which includes the following steps: freeze-drying a dispersion of the metal salt, graphene oxide, and the microwave absorbing agent to obtain a composite aerogel; then ball-milling the composite aerogel with a non-metallic source to obtain the microwave absorbing precursor. Preferably, in method III, the mass ratio of the composite aerogel to the non-metallic source is 10:(1-2). For example, when the non-metallic source is S, the mass ratio of the composite aerogel to the non-metallic source is 10:1; when the non-metallic source is Se, the mass ratio is 10:2; when the non-metallic source is P, the mass ratio is 10:1; when the non-metallic source is composed of S and Se in a mass ratio of 1:2, the mass ratio of the composite aerogel to the non-metallic source is 10:1.5. Preferably, in method III, the microwave irradiation treatment is performed in an inert atmosphere.

[0020] It is understandable that the metal salt dissolves in the dispersion, meaning the metal salt is dissolved in the dispersant of the dispersion. During the preparation of the microwave absorbing precursor, the metal salt, existing in a dissolved state, can be uniformly distributed on the surface and within the pores of graphene oxide after contact. During microwave irradiation, the uniformly distributed metal salt can crystallize in situ on the graphene network substrate, precipitating a large number of ultrafine nanocrystalline active anode material particles. These ultrafine nanocrystalline active anode material particles directly bond to the graphene substrate, resulting in a composite material composed of nanocrystalline active anode material and graphene.

[0021] In Methods I, II, and III, freeze drying can prevent graphene oxide from stacking, thereby maintaining the morphology of graphene oxide.

[0022] To reduce costs, the oxidizing atmosphere is preferably air. Preferably, the inert atmosphere is one or any combination of argon, nitrogen, and helium. Microwave irradiation in an oxidizing atmosphere enables in-situ crystallization growth of oxide nanocrystals on a graphene substrate; while microwave irradiation in an inert atmosphere yields non-oxide nanocrystal-supported graphene materials.

[0023] Preferably, in methods I, II and III, the dispersant in the dispersion is water.

[0024] Preferably, in method I, the dispersion is prepared by a method comprising the following steps: first, mixing a metal salt with a graphene oxide suspension to obtain a mixed solution; then, adding water to the mixed solution until the sum of the concentrations of the metal salt and graphene oxide is 3–10 mg / mL; then, adding a microwave absorbing agent and mixing thoroughly. Preferably, in method I, the concentration of the graphene oxide suspension is 5–15 mg / mL, and the mass ratio of the metal salt to the graphene oxide suspension is (163–350):(100–300). For example, in method I, the dispersion is prepared by a method comprising the following steps: first, mixing a metal salt with a graphene oxide suspension to obtain a mixed solution; then, adding water to the mixed solution until the sum of the concentrations of the metal salt and graphene oxide is 5–10 mg / mL; then, adding a microwave absorbing agent and mixing thoroughly.

[0025] Preferably, in method II, the dispersion is prepared by a method comprising the following steps: first, mixing the metal salt with a graphene oxide suspension to obtain a mixed solution; then, adding water to the mixed solution until the sum of the concentrations of the metal salt and graphene oxide is 3-10 mg / mL; and mixing thoroughly. Preferably, in method II, the concentration of the graphene oxide suspension is 5 mg / mL, and the mass ratio of the metal salt to the graphene oxide suspension is 350:300. For example, in method II, the dispersion is prepared by a method comprising the following steps: first, mixing the metal salt with a graphene oxide suspension to obtain a mixed solution; then, adding water to the mixed solution until the sum of the concentrations of the metal salt and graphene oxide is 5 mg / mL; and mixing thoroughly.

[0026] Preferably, in method III, the dispersion is prepared by a method comprising the following steps: first, mixing a metal salt with a graphene oxide suspension to obtain a mixed solution; then, adding water to the mixed solution until the sum of the concentrations of the metal salt and graphene oxide is 3–10 mg / mL; then, adding a microwave absorbing agent and mixing thoroughly. Preferably, in method III, the concentration of the graphene oxide suspension is 5–15 mg / mL, and the mass ratio of the metal salt to the graphene oxide suspension is 350:200. For example, in method III, the dispersion is prepared by a method comprising the following steps: first, mixing a metal salt with a graphene oxide suspension to obtain a mixed solution; then, adding water to the mixed solution until the sum of the concentrations of the metal salt and graphene oxide is 6–10 mg / mL; then, adding a microwave absorbing agent and mixing thoroughly.

[0027] Preferably, in methods I, II, and III, the solvent in the graphene oxide suspension is water.

[0028] In methods I, II, and III, the metal salt is first mixed with the graphene oxide suspension, and then diluted with water. This allows the metal salt to better bind with the high concentration of graphene oxide (metal salts can bind with various functional groups on graphene oxide), avoiding excessive dissolution and dilution by water, thus resulting in a more uniform distribution on the surface and within the pores of the graphene oxide. Adding water further improves the dispersion of the metal salt-graphene oxide complex.

[0029] Preferably, the metal element in the metal salt is selected from one or any combination of Sn, Fe, Mn, Ni, and Cu.

[0030] Preferably, the metal element in the metal salt is selected from one or any combination of Sn, Fe, and Mn.

[0031] Preferably, the metal salt is selected from one or any combination of metal hydrochloride, metal nitrate, metal phosphate, and metal acetate. For example, the metal hydrochloride is SnCl4·5H2O and / or FeCl3; the metal acetate is manganese acetate tetrahydrate.

[0032] Preferably, when the absorbing precursor is composed of a metal salt, graphene oxide, and an absorbing agent, or when the absorbing precursor is composed of a metal salt and partially reduced graphene oxide, the metal element in the metal salt is Sn and / or Fe. For example, when the absorbing precursor is composed of a metal salt, graphene oxide, and an absorbing agent, or when the absorbing precursor is composed of a metal salt and partially reduced graphene oxide, the metal salt is SnCl4·5H2O and / or FeCl3.

[0033] Preferably, when the microwave absorbing precursor is composed of a metal salt, graphene oxide, a microwave absorbing agent, and a non-metal source, the metal element in the metal salt is Mn. For example, when the microwave absorbing precursor is composed of a metal salt, graphene oxide, a microwave absorbing agent, and a non-metal source, the metal salt is manganese acetate tetrahydrate.

[0034] Preferably, during microwave irradiation treatment, the microwave frequency is 915 MHz and 2450 MHz; the microwave power is 0.1–100 kW; and the microwave irradiation treatment time is greater than 5 s. For example, the microwave power is 1 kW, and the microwave irradiation treatment time is 5–15 s.

[0035] Preferably, the microwave absorbing agent is a dielectric loss type microwave absorber and / or a magnetic loss type microwave absorber. Preferably, the dielectric loss type microwave absorber is selected from one or any combination of graphene, graphite, carbon black, carbon fiber, carbon nanotubes, and silicon carbide. Preferably, the magnetic loss type microwave absorber is a magnetic metal and / or a magnetic metal oxide. Preferably, the magnetic metal is selected from one or any combination of iron, nickel, and cobalt. Preferably, the magnetic metal oxide is one or any combination of iron oxide, nickel oxide, and cobalt oxide.

[0036] Preferably, the grinding process involves milling. To remove excessively large particles, the material is sieved after grinding. The sieve mesh size is preferably 200 mesh. Attached Figure Description

[0037] Figure 1 The images show the appearance of the mixture and dispersion prepared in Example 1; wherein, Figure 1 a is an appearance diagram of the mixture prepared in Example 1. Figure 2 a is an appearance diagram of the dispersion prepared in Example 1;

[0038] Figure 2 The X-ray diffraction (XRD) patterns of the sodium-ion battery anode materials in Examples 1-5 and Comparative Examples 1-2 are shown below; Figure 2 a shows the X-ray diffraction (XRD) patterns of the sodium-ion battery anode materials of Examples 1-3 and Comparative Examples 1-2. Figure 2 b is the X-ray diffraction (XRD) pattern of the sodium-ion battery anode material in Example 4. Figure 2 c is the X-ray diffraction (XRD) pattern of the sodium-ion battery anode material in Example 5;

[0039] Figure 3 The X-ray absorption spectra (XPS) of the metal-ion battery anode materials of Examples 2 and Comparative Examples 1-2 are shown, along with the high-resolution C 1s XPS and high-resolution O 1s XPS spectra of the metal-ion battery anode materials of Examples 2 and Comparative Example 1; wherein, Figure 3 a shows the X-ray absorption spectrum (XPS) of the metal-ion battery anode materials of Example 2 and Comparative Examples 1-2. Figure 3 b is the high-resolution C 1s XPS spectrum of the metal-ion battery anode materials of Example 2 and Comparative Example 1. Figure 3 c is the high-resolution O 1s XPS spectrum of the metal-ion battery anode material of Example 2 and Comparative Example 1;

[0040] Figure 4 This is a schematic diagram showing the specific capacity of sodium-ion batteries assembled with the sodium-ion battery anode materials of Examples 1-3 and Comparative Examples 1-2 under different cycle numbers and different current densities.

[0041] Figure 5 This is a schematic diagram showing the specific capacity and coulombic efficiency of a sodium-ion battery assembled with the sodium-ion battery anode material of Example 2, tested under different cycle numbers and current densities of 5 A / g.

[0042] Figure 6The sodium-ion battery assembled using the sodium-ion battery anode material of Example 2 operates at a high load (3.4 mg / cm³). 2 ), Schematic diagram of the areal capacity, specific capacity and coulombic efficiency obtained under different cycle numbers and current density of 0.2 A / g. Detailed Implementation

[0043] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0044] Example 1

[0045] The sodium-ion battery anode material of this embodiment is prepared by a method including the following steps:

[0046] SnCl4·5H2O was mixed with a 5 mg / mL graphene oxide (GO) suspension (water as the solvent) at a mass ratio of 350:100 to obtain a mixture. Deionized water was then added to the mixture until the sum of the SnCl4·5H2O and GO concentrations reached 5 mg / mL. Then, an absorbing agent (RGO powder) was added, and the mixture was stirred until a dispersion was obtained. The dispersion was then freeze-dried to obtain an absorbing precursor. This precursor was then placed in a microwave oven (2450 MHz, 1000 W) and subjected to microwave irradiation for 10 seconds at room temperature and in an air atmosphere (a violent flash was observed) to obtain a microwave reactant. The microwave reactant was ground and sieved (200 mesh) to obtain a sodium-ion battery anode material, labeled SnO2 / 100MWG.

[0047] In this embodiment, the absorbing agent in the microwave absorbing precursor has a mass fraction of 1%. The graphene in the sodium-ion battery anode material prepared in this embodiment has a mass fraction of 15.4%.

[0048] Example 2

[0049] The sodium-ion battery anode material of this embodiment is prepared by a method including the following steps:

[0050] SnCl4·5H2O was mixed with a 5 mg / mL graphene oxide (GO) suspension (water as the solvent) at a mass ratio of 350:200 to obtain a mixture. Deionized water was then added to the mixture until the sum of the SnCl4·5H2O and GO concentrations reached 5 mg / mL. Then, a microwave absorbing agent (graphite powder) was added, and the mixture was stirred until homogeneous to obtain a dispersion. The dispersion was then freeze-dried to obtain a microwave absorbing precursor. This precursor was then placed in a microwave oven (2450 MHz, 1000 W) and subjected to microwave irradiation for 10 seconds at room temperature and in an air atmosphere (a violent flash was observed) to obtain a microwave reactant. The microwave reactant was ground and sieved (200 mesh) to obtain a sodium-ion battery anode material, labeled SnO2 / 200MWG.

[0051] In this embodiment, the absorbing agent in the microwave absorbing precursor has a mass fraction of 2%. The graphene in the sodium-ion battery anode material prepared in this embodiment has a mass fraction of 28.6%.

[0052] Example 3

[0053] The sodium-ion battery anode material of this embodiment is prepared by a method including the following steps:

[0054] SnCl4·5H2O was mixed with a 5 mg / mL graphene oxide (GO) suspension (water was used as the solvent in the suspension) at a mass ratio of 350:300 to obtain a mixture. Deionized water was then added to the mixture until the sum of the concentrations of SnCl4·5H2O and GO was 5 mg / mL to obtain a dispersion. The dispersion was then freeze-dried to obtain a composite aerogel. The composite aerogel was then heated at 200°C in an argon atmosphere for 1 h to obtain a microwave absorbing precursor. The microwave absorbing precursor was then placed in a microwave oven (microwave frequency 2450 MHz, microwave power 1000 W) and microwave irradiated for 8 s at room temperature and in an air atmosphere (a violent flash was observed) to obtain a microwave reactant. The microwave reactant was ground and sieved (sieve size 200 mesh) to obtain a sodium-ion battery anode material, labeled SnO2 / 300MWG.

[0055] In this embodiment, the mass fraction of graphene in the sodium-ion battery anode material is 36.3%.

[0056] Example 4

[0057] The sodium-ion battery anode material of this embodiment is prepared by a method including the following steps:

[0058] Manganese acetate tetrahydrate (C4H) 14MnO8 was mixed with a 10 mg / mL suspension of graphene oxide (GO) (water as the solvent) at a mass ratio of 245:100 to obtain a mixture. Deionized water was then added to the mixture until the sum of the concentrations of manganese acetate tetrahydrate and GO reached 5 mg / mL. Then, a microwave absorbing agent (carbon black powder) was added, and the mixture was stirred until homogeneous to obtain a dispersion. The dispersion was then freeze-dried to obtain a microwave absorbing precursor. This precursor was then placed in a microwave oven (2450 MHz, 1000 W) and subjected to microwave irradiation for 10 seconds at room temperature and in an air atmosphere (a violent flash was observed) to obtain a microwave reactant. The microwave reactant was ground and sieved (200 mesh) to obtain a sodium-ion battery anode material, labeled Mn3O4 / 200MWG.

[0059] In this embodiment, the mass fraction of the absorbing agent in the absorbing precursor is 2%.

[0060] Example 5

[0061] The sodium-ion battery anode material of this embodiment is prepared by a method including the following steps:

[0062] FeCl3 was mixed with a 15 mg / mL graphene oxide (GO) suspension (water as the solvent) at a mass ratio of 163:100 to obtain a mixture. Deionized water was then added to the mixture until the sum of the FeCl3 and GO concentrations reached 5 mg / mL. A microwave absorbing agent (carbon nanotube powder) was then added, and the mixture was stirred until homogeneous to obtain a dispersion. The dispersion was then freeze-dried to obtain a microwave absorbing precursor. This precursor was then placed in a microwave oven (2450 MHz, 1000 W) and subjected to microwave irradiation for 10 seconds at room temperature and in an air atmosphere (a violent flash was observed) to obtain a microwave reactant. The microwave reactant was ground and sieved (200 mesh) to obtain a sodium-ion battery anode material, labeled Fe2O3 / 100MWG.

[0063] In this embodiment, the mass fraction of the absorbing agent in the absorbing precursor is 3%.

[0064] Example 6

[0065] The sodium-ion battery anode material of this embodiment is prepared by a method including the following steps:

[0066] SnCl4·5H2O was mixed with a 5 mg / mL graphene oxide (GO) suspension (water as the solvent) at a mass ratio of 350:200 to obtain a mixture. Deionized water was then added to the mixture until the sum of the SnCl4·5H2O and GO concentrations reached 5 mg / mL. A microwave absorbing agent (nano-nickel powder) was then added, and the mixture was stirred until homogeneous to obtain a dispersion. The dispersion was then freeze-dried to obtain a microwave absorbing precursor. This precursor was then placed in a microwave oven (2450 MHz, 1000 W) and irradiated for 10 seconds at room temperature under an inert atmosphere (argon) (a violent flash was observed) to obtain a microwave reactant. The microwave reactant was ground and sieved (200 mesh) to obtain a sodium-ion battery anode material, labeled Sn / 200MWG.

[0067] In this embodiment, the mass fraction of the absorbing agent in the absorbing precursor is 5%.

[0068] Example 7

[0069] The sodium-ion battery anode material of this embodiment is prepared by a method including the following steps:

[0070] SnCl4·5H2O was mixed with a 10 mg / mL graphene oxide (GO) suspension (water was used as the solvent in the suspension) at a mass ratio of 350:200 to obtain a mixture. Deionized water was then added to the mixture until the sum of the concentrations of SnCl4·5H2O and GO was 8 mg / mL. Then, microwave absorbing agent (RGO powder) was added and stirred until a dispersion was obtained. The dispersion was then freeze-dried to obtain a composite aerogel. The composite aerogel with elemental sulfur at a mass ratio of 10:1 was then ball-milled and mixed evenly to obtain a microwave absorbing precursor. The microwave absorbing precursor was then placed in a microwave oven (microwave frequency of 2450MHz, microwave power of 1000W) and subjected to microwave irradiation treatment for 10s at room temperature and inert atmosphere (nitrogen) (intense flashes could be observed) to obtain a microwave reactant. The microwave reactant was then ground and sieved (sieve size of 200 mesh) to obtain a sodium-ion battery anode material, labeled SnS / 200MWG.

[0071] In this embodiment, the mass fraction of the absorbing agent in the absorbing precursor is 2%.

[0072] Example 8

[0073] The sodium-ion battery anode material of this embodiment is prepared by a method including the following steps:

[0074] SnCl4·5H2O was mixed with a 5 mg / mL graphene oxide (GO) suspension (water was used as the solvent in the suspension) at a mass ratio of 350:200 to obtain a mixture. Deionized water was then added to the mixture until the sum of the concentrations of SnCl4·5H2O and GO reached 6 mg / mL. Then, a microwave absorbing agent (graphite powder) was added, and the mixture was stirred evenly to obtain a dispersion. The dispersion was then freeze-dried to obtain a composite aerogel. The composite aerogel with a mass ratio of 10:2 was then ball-milled with elemental Se and mixed evenly to obtain a microwave absorbing precursor. The microwave absorbing precursor was then placed in a microwave oven (microwave frequency of 2450MHz, microwave power of 1000W) and microwave irradiated for 10s at room temperature and inert atmosphere (helium) (a violent flash can be observed) to obtain a microwave reactant. The microwave reactant was ground and sieved (sieve size of 200 mesh) to obtain a sodium-ion battery anode material, labeled SnSe / 200MWG.

[0075] In this embodiment, the mass fraction of the absorbing agent in the absorbing precursor is 3%.

[0076] Example 9

[0077] The sodium-ion battery anode material of this embodiment is prepared by a method including the following steps:

[0078] SnCl4·5H2O was mixed with a 15 mg / mL graphene oxide (GO) suspension (water was used as the solvent in the suspension) at a mass ratio of 350:200 to obtain a mixture. Deionized water was then added to the mixture until the sum of the concentrations of SnCl4·5H2O and GO reached 10 mg / mL. Then, microwave absorbing agent (RGO powder) was added and stirred until a dispersion was obtained. The dispersion was then freeze-dried to obtain a composite aerogel. The composite aerogel and elemental P at a mass ratio of 10:1 were then ball-milled and mixed evenly to obtain a microwave absorbing precursor. The microwave absorbing precursor was then placed in a microwave oven (microwave frequency of 2450MHz, microwave power of 1000W) and subjected to microwave irradiation treatment for 10s at room temperature and inert atmosphere (helium) (a violent flash can be observed) to obtain a microwave reactant. The microwave reactant was ground and sieved (sieve aperture size of 200 mesh) to obtain a sodium-ion battery anode material, labeled Sn4P3 / 200MWG.

[0079] In this embodiment, the mass fraction of the absorbing agent in the absorbing precursor is 2%.

[0080] Example 10

[0081] The metal-ion battery anode material of this embodiment is prepared by a method including the following steps:

[0082] SnCl4·5H2O was mixed with a 5 mg / mL graphene oxide (GO) suspension (water was used as the solvent in the suspension) at a mass ratio of 350:200 to obtain a mixture. Deionized water was then added to the mixture until the sum of the concentrations of SnCl4·5H2O and GO was 5 mg / mL. Then, microwave absorbing agent (RGO powder) was added and stirred until a dispersion was obtained. The dispersion was then freeze-dried to obtain a composite aerogel. The composite aerogel, elemental S, and elemental Se in a mass ratio of 10:0.5:1 were then ball-milled and mixed evenly to obtain a microwave absorbing precursor. The microwave absorbing precursor was then placed in a microwave oven (microwave frequency of 2450MHz, microwave power of 1000W) and microwave irradiated for 10s at room temperature and inert atmosphere (argon) (a violent flash can be observed) to obtain a microwave reactant. The microwave reactant was ground and sieved (sieve aperture size of 200 mesh) to obtain a metal ion battery anode material, labeled SnSe-SnS / 200MWG.

[0083] In this embodiment, the mass fraction of the absorbing agent in the absorbing precursor is 2%.

[0084] Comparative Example 1

[0085] The sodium-ion battery anode material of this comparative example was prepared by a method including the following steps:

[0086] SnCl4·5H2O was mixed with a 5 mg / mL graphene oxide (GO) suspension (water as the solvent) at a mass ratio of 350:200 to obtain a mixture. Deionized water was then added to the mixture until the sum of the SnCl4·5H2O and GO concentrations reached 5 mg / mL. The mixture was stirred until homogeneous to obtain a dispersion. The dispersion was then freeze-dried to obtain a microwave absorbing precursor. This precursor was then heat-treated at 600°C for 2 hours under an inert atmosphere (helium) to obtain a reactant. The reactant was then ground and sieved (200 mesh) to obtain a metal-ion battery anode material, labeled SnO2 / 200HT.

[0087] The sodium-ion battery anode material prepared in this embodiment contains 55.5% graphene by mass.

[0088] Comparative Example 2

[0089] The sodium-ion battery anode material of this comparative example was prepared by a method including the following steps:

[0090] SnCl4·5H2O was directly heat-treated in air at 600℃ for 2 hours to obtain the reactant. The reactant was then ground and sieved (sieve size 200 mesh) to obtain the sodium-ion battery anode material, labeled as SnO2.

[0091] For ease of comparison, the composition of the microwave absorbing precursors, the temperature and atmosphere used for microwave irradiation treatment, and the names of the products in Examples 1-10 and Comparative Examples 1-2 are listed in Table 1.

[0092] Table 1. Composition of the microwave absorbing precursors in Examples 1-10 and Comparative Examples 1-2, temperature and atmosphere used for microwave irradiation treatment, and names of the products.

[0093]

[0094] Experimental Example 1

[0095] The results of observing the mixture and dispersion prepared in Example 1 are as follows: Figure 1 As shown. By Figure 1 It can be seen that RGO is relatively uniformly dispersed in the mixture, which helps to quickly absorb and reflect microwaves throughout the material, promoting the reduction of graphene oxide and the crystal growth of metal compounds.

[0096] Experiment Example 2

[0097] The sodium-ion battery anode materials of Examples 1-5 and Comparative Examples 1-2 were characterized by XRD, and the results are as follows: Figure 2 As shown. The results indicate that the crystallinity of the sodium-ion battery anode materials in Examples 1-3 is better than that of the sodium-ion battery anode material in Comparative Example 1, and is close to that of the sodium-ion battery anode material in Comparative Example 2.

[0098] Experimental Example 3

[0099] XPS characterization was performed on the sodium-ion battery anode materials of Example 2 and Comparative Examples 1-2, respectively, and the results are as follows: Figure 3 As shown. The results indicate that the strength of the Sn-OC bond in the sodium-ion battery anode material of Example 2 is greater than that in the sodium-ion battery anode material of Comparative Example 1, thus demonstrating that microwave irradiation treatment is beneficial for the bonding of tin dioxide and graphene.

[0100] Experiment Example 4

[0101] The sodium-ion battery anode materials of Examples 1-3 and Comparative Examples 1-2 were used as anode materials in sodium-ion batteries (CR2032 coin cells), and the electrochemical performance of the prepared sodium-ion batteries was tested. The anode of the CR2032 coin cell was metallic sodium, the electrolyte was a 1 mol / L NaClO4 solution, and the separator was borosilicate microporous glass fiber (Whatman). The solvent in the electrolyte consisted of ethylene carbonate, dimethyl carbonate, and fluoroethylene carbonate, with a volume ratio of ethylene carbonate to dimethyl carbonate of 1:1, and the mass fraction of fluoroethylene carbonate in the electrolyte was 5%. The electrode sheet was prepared as follows: the sodium-ion battery anode material, conductive carbon black, and PVDF binder were mixed at a mass ratio of 8:1:1, and a uniform slurry was prepared with NMP. The slurry was then uniformly coated onto a copper foil current collector, and the copper foil coated with the slurry was dried under vacuum at 60°C for 12 hours. Finally, it was cut into electrode sheets with a diameter of 12 mm. The assembly of sodium-ion half-cells was carried out in a glove box under an argon atmosphere (water and oxygen content less than 0.1 ppm).

[0102] The constant current charge-discharge test of the battery was conducted using the Blue Electric (CT2001A) battery testing system, with a test voltage range of 0.01–3V. All tests were performed at room temperature (25℃).

[0103] The specific capacity of sodium-ion batteries assembled using the sodium-ion battery anode materials of Examples 1-3 and Comparative Examples 1-2 was tested at different cycle numbers and current densities as follows: Figure 4 As shown. By Figure 4 It can be seen that the rate performance of the sodium-ion battery anode materials in Examples 1-3 is much better than that of the sodium-ion battery anode materials in Comparative Examples 1-2.

[0104] The specific capacity and coulombic efficiency of the sodium-ion battery assembled using the metal-ion battery anode material of Example 2 were tested under different cycle numbers and a current density of 5 A / g, as shown below. Figure 5 As shown. By Figure 5 It can be seen that the metal-ion battery anode material of Example 2 has the ability to undergo long cycles under high current density, and the assembled battery has the potential for fast charging and fast discharging in practical applications.

[0105] The sodium-ion battery assembled using the sodium-ion battery anode material of Example 2 operates at high load (3.4 mg / cm³). 2 The areal capacity, specific capacity, and coulombic efficiency obtained under different cycle numbers and current densities of 0.2 A / g are as follows: Figure 6 As shown. By Figure 6It can be seen that the metal-ion battery anode material of Example 2 has the ability to undergo long cycles under high load, and the assembled battery has the potential to operate under high load in practical applications. The areal capacity and specific capacity are corresponding, and the specific calculation formulas are: areal capacity = total capacity / area; specific capacity = total capacity / total load; areal capacity = specific capacity × areal load.

Claims

1. A sodium-ion battery anode material, characterized in that, The microwave absorbing precursor is prepared by means of the following steps: microwave irradiation treatment is performed on the microwave absorbing precursor to obtain microwave reactant, and then the microwave reactant is crushed. The microwave absorbing precursor is composed of a metal salt, graphene oxide and a microwave absorbing agent. The microwave absorbing precursor is prepared by method I, which includes the following steps: freeze-drying a dispersion of the metal salt, graphene oxide and the microwave absorbing agent to obtain the microwave absorbing precursor. The microwave irradiation treatment was carried out in an oxidizing atmosphere; The metal element in the metal salt is the same metal element found in the conversion-type negative electrode material used in sodium-ion batteries. The microwave absorber is a dielectric loss type microwave absorber and / or a magnetic loss type microwave absorber; the dielectric loss type microwave absorber is selected from one or any combination of graphene, graphite, carbon black, carbon fiber, carbon nanotubes, and silicon carbide; the magnetic loss type microwave absorber is a magnetic metal and / or a magnetic metal oxide; the magnetic metal is selected from one or any combination of iron, nickel, and cobalt; the magnetic metal oxide is one or any combination of iron oxide, nickel oxide, and cobalt oxide.

2. The sodium-ion battery anode material as described in claim 1, characterized in that, The sodium-ion battery anode material contains 10-60% graphene by mass; the microwave absorbing precursor contains 1-5% microwave absorbing agent by mass.

3. The sodium-ion battery anode material as described in claim 2, characterized in that, The oxidizing atmosphere is air.

4. The sodium-ion battery anode material as described in claim 2, characterized in that, The dispersion is prepared by a method comprising the following steps: first, mixing the metal salt with the graphene oxide suspension to obtain a mixture; then, adding water to the mixture until the sum of the concentrations of the metal salt and the graphene oxide is 3-10 mg / mL; then, adding the microwave absorbing agent and mixing well to obtain the final product.

5. The sodium-ion battery negative electrode material according to any one of claims 1-4, characterized in that, The metal element in the metal salt is selected from one or any combination of Sn, Fe, and Mn.

6. The sodium-ion battery negative electrode material according to any one of claims 1-4, characterized in that, The metal salt is selected from one or any combination of metal hydrochloride, metal nitrate, metal phosphate, and metal acetate.

7. The sodium-ion battery anode material as described in claim 6, characterized in that, The metal hydrochloride is SnCl4·5H2O and / or FeCl3; the metal acetate is manganese acetate tetrahydrate.

8. The sodium-ion battery negative electrode material according to any one of claims 1-4, characterized in that, During microwave irradiation treatment, the microwave frequencies are 915 and 2450 MHz; the microwave power is 0.1–100 kW; and the microwave irradiation treatment time is greater than 5 seconds.

9. A sodium-ion battery anode material, characterized in that, The microwave absorbing precursor is prepared by means of the following steps: microwave irradiation treatment is performed on the microwave absorbing precursor to obtain microwave reactant, and then the microwave reactant is crushed. The microwave absorbing precursor is composed of a metal salt and partially reduced graphene oxide. The microwave absorbing precursor is prepared by method II, which includes the following steps: freeze-drying a dispersion of metal salt and graphene oxide to obtain a composite aerogel, and then heating and reducing the graphene oxide in the composite aerogel to obtain the microwave absorbing precursor; in method II, the temperature of the heating and reduction treatment is 100-600℃, and the time of the heating and reduction treatment is 1-24h. The microwave irradiation treatment was carried out in an oxidizing atmosphere; The metal element in the metal salt is the same metal element found in conversion-type negative electrode materials used in sodium-ion batteries.

10. The sodium-ion battery anode material as described in claim 9, characterized in that, The mass fraction of graphene in the sodium-ion battery anode material is 10-60%.

11. The sodium-ion battery anode material as described in claim 10, characterized in that, The oxidizing atmosphere is air.

12. The sodium-ion battery anode material as described in claim 10, characterized in that, The dispersion is prepared by a method comprising the following steps: first, mixing the metal salt with the graphene oxide suspension to obtain a mixture; then, adding water to the mixture until the sum of the concentrations of the metal salt and the graphene oxide is 3-10 mg / mL; and mixing thoroughly.

13. The sodium-ion battery anode material according to any one of claims 9-12, characterized in that, The metal element in the metal salt is selected from one or any combination of Sn, Fe, and Mn.

14. The sodium-ion battery anode material according to any one of claims 9-12, characterized in that, The metal salt is selected from one or any combination of metal hydrochloride, metal nitrate, metal phosphate, and metal acetate.

15. The sodium-ion battery anode material as described in claim 14, characterized in that, The metal hydrochloride is SnCl4·5H2O and / or FeCl3; the metal acetate is manganese acetate tetrahydrate.

16. The sodium-ion battery anode material according to any one of claims 9-12, characterized in that, During microwave irradiation treatment, the microwave frequencies are 915 and 2450 MHz; the microwave power is 0.1–100 kW; and the microwave irradiation treatment time is greater than 5 seconds.

17. A sodium-ion battery anode material, characterized in that, The microwave absorbing precursor is prepared by means of the following steps: microwave irradiation treatment is performed on the microwave absorbing precursor to obtain microwave reactant, and then the microwave reactant is crushed. The microwave absorbing precursor is composed of a metal salt, graphene oxide, a microwave absorbing agent, and a non-metallic source. The microwave absorbing precursor is prepared by method III, which includes the following steps: freeze-drying a dispersion of metal salt, graphene oxide, and microwave absorbing agent to obtain a composite aerogel, and then ball-milling the composite aerogel with a non-metallic source to obtain the microwave absorbing precursor. The microwave irradiation treatment was carried out in an inert atmosphere; The metal element in the metal salt is the same metal element found in the conversion-type negative electrode material used in sodium-ion batteries. The non-metallic source is selected from one or any combination of sulfur, selenium, and phosphorus. The microwave absorber is a dielectric loss type microwave absorber and / or a magnetic loss type microwave absorber; the dielectric loss type microwave absorber is selected from one or any combination of graphene, graphite, carbon black, carbon fiber, carbon nanotubes, and silicon carbide; the magnetic loss type microwave absorber is a magnetic metal and / or a magnetic metal oxide; the magnetic metal is selected from one or any combination of iron, nickel, and cobalt; the magnetic metal oxide is one or any combination of iron oxide, nickel oxide, and cobalt oxide.

18. The sodium-ion battery anode material as described in claim 17, characterized in that, The sodium-ion battery anode material contains 10-60% graphene by mass; the microwave absorbing precursor contains 1-5% microwave absorbing agent by mass.

19. The sodium-ion battery anode material as described in claim 18, characterized in that, The inert atmosphere is selected from one or any combination of argon, nitrogen, and helium.

20. The sodium-ion battery anode material as described in claim 18, characterized in that, The dispersion is prepared by a method comprising the following steps: first, mixing the metal salt with the graphene oxide suspension to obtain a mixture; then, adding water to the mixture until the sum of the concentrations of the metal salt and the graphene oxide is 3-10 mg / mL; then, adding the microwave absorbing agent and mixing well to obtain the final product.

21. The sodium-ion battery negative electrode material according to any one of claims 17-20, characterized in that, The metal element in the metal salt is selected from one or any combination of Sn, Fe, and Mn.

22. The sodium-ion battery negative electrode material according to any one of claims 17-20, characterized in that, The metal salt is selected from one or any combination of metal hydrochloride, metal nitrate, metal phosphate, and metal acetate.

23. The sodium-ion battery anode material as described in claim 22, characterized in that, The metal hydrochloride is SnCl4·5H2O and / or FeCl3; the metal acetate is manganese acetate tetrahydrate.

24. The sodium-ion battery negative electrode material according to any one of claims 17-20, characterized in that, During microwave irradiation treatment, the microwave frequencies are 915 and 2450 MHz; the microwave power is 0.1–100 kW; and the microwave irradiation treatment time is greater than 5 seconds.

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