Doped bimetallic sulfide sodium ion negative electrode material, preparation method and application thereof, and sodium ion battery

Abstract

The invention discloses a doped bimetallic sulfide sodium ion negative electrode material, a preparation method and application thereof, and a sodium ion battery, and relates to the technical field of sodium batteries. The sodium ion negative electrode material has the following general formula: Cu < 3-x > Zn < x > Nb < 1-x > Ti < x > S4, x is greater than or equal to 0 and less than 0.5, the negative electrode material belongs to a tetragonal crystal system and has an ordered vacancy avendite structure, the sodium ion negative electrode material is granular, the average particle size is 0.2-20 microns, the specific capacity of the negative electrode material is 400-800 mAh / g, and the cycle life of 300-5000 times under the high current density of 1 A / g can be realized. The invention also provides a preparation method of the sodium ion negative electrode material, the sodium ion negative electrode material is mainly obtained by using a high-temperature solid-phase reaction, the method abandons the use of hazardous chemical reagents, the preparation condition requirements are simple, and the prepared sodium ion negative electrode material has the advantages of controllable structure and morphology, stable electrochemical performance and the like. The method can be used in the field of electrochemical sodium ion energy storage.

Description

Technical Field

[0001] The present invention relates to the technical field of sodium batteries, and in particular to a doped bimetallic sulfide sodium ion negative electrode material, a preparation method and application thereof, and a sodium ion battery. Background Art

[0002] With the widespread deployment of renewable energy and the rapid development of electric transportation, global demand for efficient, safe, and low-cost energy storage systems is growing. While lithium-ion batteries have been widely used in portable electronics and electric vehicles, their sustainable development in large-scale energy storage faces significant challenges due to the scarcity of lithium resources, rising prices, and uneven geographical distribution. In contrast, sodium-ion batteries, with their abundant sodium resources, low cost, and similar electrochemical properties to lithium batteries, are emerging as a potential technological alternative or supplement to lithium-ion batteries.

[0003] Compared to the mature lithium-ion battery system, the development of sodium-ion batteries still faces many challenges, especially in terms of anode materials. Currently, the anode material systems widely studied include hard carbon, metal oxides / sulfides, and alloy materials. Among them, hard carbon materials, as the most commercially promising anodes, generally have a reversible specific capacity of 250-300 mAh / g, but they suffer from low first-cycle coulombic efficiency, poor rate performance, and the risk of sodium precipitation under deep charging conditions on extremely low voltage platforms. In contrast, metal oxides / sulfides and alloy materials (such as Sn, Sb, and Bi) have higher theoretical capacities, but these materials generally suffer from severe volume expansion and structural pulverization during the sodium ion insertion and extraction process, resulting in a cycle life of less than 500 cycles. Therefore, the development of new anode materials that combine high capacity, good rate performance, and long cycle life is of great significance to promoting the development of sodium-ion batteries.

[0004] Cu3NbS4 is a typical bimetallic sulfide with a vanadium-copper structure. It is composed of [NbS4] and [CuS4] tetrahedra forming a three-dimensional edge-sharing / corner-sharing connection. It has high structural stability and theoretical capacity, making it a candidate material for sodium anodes that has attracted much attention in recent years. However, Cu3NbS4 itself has two major problems: first, the low electronic conductivity limits its rate performance; second, the insufficient stability of the crystal structure during the redox process makes it difficult to balance specific capacity and cycle stability as an electrode material. To address the above problems, studies have attempted to improve the electrochemical performance of Cu3NbS4 through nano-sizing, carbon coating, etc., but these methods generally have defects such as complex preparation process, insufficient structural stability or limited improvement in conductivity. Therefore, further improvement is needed. Summary of the Invention

[0005] To address the above shortcomings, the present invention provides a doped bimetallic sulfide sodium ion negative electrode material, its preparation method and application, and a sodium ion battery. This sodium ion negative electrode material has the characteristics of controllable structure and morphology, stable electrochemical performance, and a simple preparation method, and can be applied to the field of electrochemical sodium ion energy storage. The specific technical solution is as follows: A doped bimetallic sulfide sodium ion negative electrode material, the sodium ion negative electrode material has the following general formula: Cu 3-x Zn x Nb 1-x Ti x S4, wherein 0<x<0.5; the sodium ion negative electrode material belongs to the cubic crystal system, has an ordered vacancy vanadium sulfide structure and a sharp granular micromorphology, and its average particle size is 0.2~20μm.

[0006] Preferably, the Zn has a valence of +2, the Ti has a valence of +4, and the introduction of doping does not change the main crystal structure of the material.

[0007] The present invention also provides a method for preparing the above-mentioned doped bimetallic sulfide sodium ion negative electrode material, comprising: first weighing a copper source, a zinc source, a niobium source, a titanium source, and a sulfur source according to a certain molar ratio, mixing the mixture, grinding the mixture into powder, adding the powder into a tablet pressing mold, pressing the powder into a sheet, then evacuating the mixture and sealing the mixture in a glass tube, and performing a high-temperature solid-phase reaction in a muffle furnace, namely, first heating the mixture to 400°C to 1200°C at a rate of 0.1°C / min to 10°C / min, holding the temperature for 0.2 hour to 72 hours, and then cooling the mixture to room temperature at a rate of 2°C / min to 100°C / min, to obtain the sodium ion negative electrode material; The total molar ratio of copper, zinc, niobium, titanium and sulfur elements in the sodium ion negative electrode material is 3-x:x:1-x:x:4, wherein 0<x<0.5.

[0008] Preferably, the copper source is one or more of elemental copper and copper sulfide.

[0009] Preferably, the zinc source is one or more of elemental zinc and zinc sulfide.

[0010] Preferably, the niobium source is one or more of elemental niobium and niobium sulfide.

[0011] Preferably, the titanium source is one or more of elemental titanium and titanium sulfide.

[0012] Preferably, the sulfur source is elemental sulfur.

[0013] The present invention also provides a sodium ion battery, which comprises the above-mentioned doped bimetallic sulfide sodium ion negative electrode material.

[0014] The present invention also provides the application of the above-mentioned doped bimetallic sulfide sodium ion negative electrode material in the field of sodium ion batteries.

[0015] This study constructs a novel Cu3-xZnxNb1-xTixS4 solid solution system by controllably introducing heterovalent metal ions Zn2+ and Ti4+ into a Cu3NbS4 matrix. While maintaining the stability of the primary crystalline phase, vanadium sulfide, this system introduces electron and hole carriers through heterovalent doping, significantly improving the electronic structure and sodium ion diffusion kinetics. It also effectively mitigates the structural stress accumulation and crystal distortion caused by volume changes during sodium ion insertion and extraction. Specifically, Zn2+ (~0.74 Å) partially replaces Cu1+ (~0.77 Å) sites, and Ti4+ (~0.605 Å) partially replaces Nb5+ (~0.64 Å) sites, resulting in charge-equivalent substitution and maintaining local charge neutrality in the crystal. On the one hand, the coordinated doping of Zn2+ / Ti4+ heterovalent ions effectively modulates the material's band structure, reducing the band gap and improving electron mobility, resulting in an increase in the material's electronic conductivity by more than an order of magnitude compared to the original Cu3NbS4. On the other hand, the substitution of Ti4+ for Nb5+ weakens the strong Coulomb repulsion between high-valent Nb cations in the crystal. Furthermore, the higher valence of the Ti-S bond compared to the Nb-S bond makes the [TiS4] tetrahedron more stable, thereby enhancing the material's distortion resistance and effectively alleviating the local stress accumulation caused by sodium insertion and extraction during charge and discharge, resulting in the material exhibiting excellent structural retention over long cycles. This material design overcomes the problems of poor electronic conductivity, low rate capability, and insufficient cycling stability found in existing Cu3NbS4 materials.

[0016] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention utilizes copper, zinc, niobium, titanium, and sulfur sources as raw materials to produce a sodium-ion negative electrode material using a high-temperature solid-phase reaction. This negative electrode material exhibits controllable structure and morphology, stable electrochemical performance, and is suitable for electrochemical sodium-ion energy storage. The negative electrode material has a conductivity of 60 S / m to 200 S / m, a specific capacity of 400 to 800 mAh / g, and a cycle life of 300 to 5000 cycles at a high current density of 1 A / g.

[0017] 2. The preparation method of the present invention abandons the use of hazardous chemicals and reagents. The doping method and synthesis process adopted are simple and controllable, and are suitable for large-scale preparation. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments.

[0019] Figure 1 This is a SEM morphology image of the sodium ion negative electrode material of the doped bimetallic sulfide prepared in Example 1 of the present invention; Figure 2 Specific capacity and coulombic efficiency diagram of the sodium ion negative electrode material of the doped bimetallic sulfide prepared in Example 1 of the present invention at different current densities; Figure 3 The sodium ion negative electrode material of the doped bimetallic sulfide prepared in Example 1 of the present invention is -1 Specific capacity and Coulombic efficiency diagram below; Figure 4 Specific capacity and coulombic efficiency diagram of the sodium ion negative electrode material of the bimetallic sulfide prepared in Comparative Example 1 of the present invention at different current densities; Figure 5 The sodium ion negative electrode material of the bimetallic sulfide prepared in Comparative Example 1 of the present invention is 1 A g -1 Specific capacity and Coulombic efficiency diagram below. DETAILED DESCRIPTION

[0020] The specific embodiments of the present invention are described in detail below, but it should be understood that the protection scope of the present invention is not limited by the specific embodiments.

[0021] Example 1 Elemental copper powder, zinc powder, niobium powder, titanium powder and sulfur powder were weighed in a molar ratio of 2.8:0.2:0.8:0.2:4. The ground raw material powders were added to a tablet pressing mold and pressed into discs. After evacuation, the discs were sealed in a glass tube and placed in a muffle furnace. The pellets were heated to 600°C at a rate of 3°C / min, kept at this temperature for 12 hours, and cooled to room temperature at a rate of 5°C / min to obtain a doped bimetallic sulfide sodium ion negative electrode material Cu2.8Zn0.2Nb0.8Ti0.2S4 with an ordered vacancy vanadium copper structure and a sharp angular granular micromorphology. The average particle size was 2.8μm ( Figure 1 ), the conductivity is 78.56 S / m. The specific capacity of the sodium ion negative electrode material of the doped bimetallic sulfide prepared in this embodiment is 570 mAh / g ( Figure 2 ), achieving a capacity retention rate of 96% after 1200 cycles at a high current density of 1 A / g ( Figure 3 ).

[0022] Comparative Example 1 Elemental copper powder, niobium powder and sulfur powder were weighed in a molar ratio of 3.0:1.0:4. The ground raw material powder was added to a tablet pressing mold and pressed into a disc. After vacuuming, it was sealed in a glass tube and placed in a muffle furnace. It was heated to 600°C at a rate of 3°C / min, kept warm for 12 hours, and cooled to room temperature at a rate of 5°C / min to obtain a doped bimetallic sulfide sodium ion negative electrode material Cu3NbS4 with a sharp angular granular micromorphology, an average particle size of 2.7 μm, and a conductivity of 5.73 S / cm. The specific capacity of the doped bimetallic sulfide sodium ion negative electrode material prepared in this comparative example is 515 mAh / g ( Figure 4 ), achieving a capacity retention rate of 65% after 700 cycles at a high current density of 1A / g ( Figure 5 ).

[0023] It can be seen from Example 1 and Comparative Example 1 that the sodium ion negative electrode material of the doped bimetallic sulfide prepared by the present invention exhibits higher specific capacity and cycle life in sodium ion batteries.

[0024] Example 2 Elemental copper powder, zinc powder, niobium powder, titanium powder, and sulfur powder were weighed in a molar ratio of 2.95:0.05:0.95:0.05:4. The ground raw powders were added to a tableting mold and pressed into discs. After evacuation, the discs were sealed in a glass tube and placed in a muffle furnace. The tubes were heated to 700°C at a rate of 10°C / min, held at that temperature for 36 hours, and then cooled to room temperature at a rate of 20°C / min. This resulted in a doped bimetallic sulfide sodium ion anode material, Cu2.95Zn0.05Nb0.95Ti0.05S4, with a sharp angular granular micromorphology, an average particle size of 3.5μm, and a conductivity of 125 S / m. The doped bimetallic sulfide sodium ion anode material prepared in this embodiment had a specific capacity of 550 mAh / g and achieved a capacity retention rate of 85% after 3000 cycles at a high current density of 1 A / g.

[0025] Example 3 Elemental copper powder, zinc powder, niobium powder, titanium powder, and sulfur powder were weighed in a molar ratio of 2.85:0.15:0.85:0.15:4. The ground raw powders were added to a tableting mold and pressed into discs. After evacuation, the discs were sealed in a glass tube and placed in a muffle furnace. The tubes were heated to 900°C at a rate of 1°C / min, held at that temperature for 48 hours, and then cooled to room temperature at a rate of 50°C / min. This resulted in a doped bimetallic sulfide sodium ion anode material, Cu2.85Zn0.15Nb0.85Ti0.15S4, with a sharp angular granular micromorphology, an average particle size of 3.2 μm, and a conductivity of 145 S / m. The doped bimetallic sulfide sodium ion anode material prepared in this embodiment had a specific capacity of 560 mAh / g, and achieved a capacity retention rate of 82% after 5000 cycles at a high current density of 1 A / g.

[0026] Example 4 Cuprous sulfide, zinc sulfide, niobium pentasulfide, and titanium disulfide were weighed in a molar ratio of 1.35:0.3:0.35:0.3. The ground raw material powders were added to a tableting mold and pressed into discs. After evacuation, the discs were sealed in a glass tube and placed in a muffle furnace. The tubes were heated to 950°C at a rate of 5°C / min, held for 40 hours, and then cooled to room temperature at a rate of 100°C / min. This resulted in a doped bimetallic sulfide sodium ion anode material, Cu2.7Zn0.3Nb0.7Ti0.3S4, with a sharp angular granular micromorphology, an average particle size of 1.2 μm, and a conductivity of 165 S / m. The doped bimetallic sulfide sodium ion anode material prepared in this embodiment had a specific capacity of 740 mAh / g, and achieved a capacity retention rate of 82% after 2000 cycles at a high current density of 1 A / g.

[0027] Example 5 Cuprous sulfide, zinc sulfide, niobium pentasulfide, and titanium disulfide were weighed in a molar ratio of 1.3:0.4:0.6:0.4. The ground raw material powders were added to a tableting mold and pressed into discs. After evacuation, the discs were sealed in a glass tube and placed in a muffle furnace. The tubes were heated to 500°C at a rate of 2°C / min, held at that temperature for 72 hours, and then cooled to room temperature at a rate of 2°C / min. This resulted in a doped bimetallic sulfide sodium ion anode material, Cu2.6Zn0.4Nb0.6Ti0.4, with a sharp-edged granular micromorphology, an average particle size of 3.0 μm, and a conductivity of 189 S / m. The doped bimetallic sulfide sodium ion anode material prepared in this embodiment had a specific capacity of 780 mAh / g, and achieved a capacity retention rate of 84% after 1000 cycles at a high current density of 1 A / g.

[0028] In summary, the present invention uses copper source, zinc source, niobium source, titanium source and sulfur source as raw materials, and utilizes high-temperature solid-phase reaction to obtain the sodium ion negative electrode material of the doped bimetallic sulfide. The negative electrode material has the advantages of controllable structure and morphology, stable electrochemical performance, etc., and can be used in the field of electrochemical sodium ion energy storage. Among them, the negative electrode material prepared by the present invention has an electrical conductivity of 60 S / m~200 S / m and a specific capacity of 400~800 mAh / g, and can achieve a cycle life of 300~5000 times at a high current density of 1 A / g. At the same time, the preparation method of the present invention abandons the use of hazardous chemical reagents, and the doping method and synthesis process adopted are simple and controllable, suitable for large-scale preparation.

[0029] The foregoing descriptions of specific exemplary embodiments of the present invention are for purposes of illustration and description. These descriptions are not intended to limit the invention to the precise forms disclosed, and it is apparent that many variations and modifications are possible in light of the foregoing teachings. The exemplary embodiments have been selected and described for the purpose of explaining the specific principles of the invention and their practical application, thereby enabling those skilled in the art to realize and utilize a variety of exemplary embodiments of the invention and various options and modifications. The scope of the invention is intended to be defined by the claims and their equivalents.

Claims

1. A doped bimetallic sulfide sodium ion negative electrode material, characterized in that: The sodium ion negative electrode material has the following general formula: Cu 3-x Zn x Nb 1-x Ti x S4, wherein 0<x<0.5; the sodium ion negative electrode material belongs to the cubic crystal system and has an ordered vacancy vanadium sulfide structure. The sodium ion negative electrode material is granular, and its average particle size is 0.2~20μm.

2. The sodium ion negative electrode material of a doped bimetallic sulfide according to claim 1, characterized in that: The Zn has a valence of +2, the Ti has a valence of +4, and the introduction of doping does not change the main crystal structure of the material.

3. A method for preparing the sodium ion negative electrode material of the doped bimetallic sulfide according to any one of claims 1 to 2, characterized in that: include: A copper source, a zinc source, a niobium source, a titanium source, and a sulfur source are weighed and mixed according to a certain molar ratio, and the mixture is ground into powder. The powder is added to a tablet pressing mold and pressed into a sheet. The sheet is then vacuumed and sealed in a glass tube. A high-temperature solid-phase reaction is carried out in a muffle furnace, that is, the temperature is first heated to 400°C to 1200°C at a rate of 0.1°C / min to 10°C / min, kept at this temperature for 0.2 hours to 72 hours, and then cooled to room temperature at a rate of 2°C / min to 100°C / min to obtain the sodium ion negative electrode material. The total molar ratio of copper, zinc, niobium, titanium and sulfur elements in the sodium ion negative electrode material is 3-x:x:1-x:x:4, wherein 0<x<0.

5.

4. The method for preparing a doped bimetallic sulfide sodium ion negative electrode material according to claim 3, characterized in that: The copper source is one or more of elemental copper and copper sulfide.

5. The method for preparing a doped bimetallic sulfide sodium ion negative electrode material according to claim 3, characterized in that: The zinc source is one or more of elemental zinc and zinc sulfide.

6. The method for preparing a doped bimetallic sulfide sodium ion negative electrode material according to claim 3, characterized in that: The niobium source is one or more of elemental niobium and niobium sulfide.

7. The method for preparing a doped bimetallic sulfide sodium ion negative electrode material according to claim 3, characterized in that: The titanium source is one or more of elemental titanium and titanium sulfide.

8. The method for preparing a doped bimetallic sulfide sodium ion negative electrode material according to claim 3, characterized in that: The sulfur source is elemental sulfur.

9. A sodium ion battery, characterized in that: The sodium ion battery comprises the negative electrode material according to any one of claims 1 to 8.

10. Use of the doped bimetallic sulfide sodium ion negative electrode material according to any one of claims 1 to 8 in the field of sodium ion batteries.

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