Fast-charging type sodium ion battery negative electrode material based on thermoelectric effect and preparation method thereof

Abstract

The application discloses a fast-charging type sodium ion battery negative electrode material based on a thermoelectric effect and a preparation method thereof, and belongs to the field of electrochemical energy storage devices.The fast-charging type sodium ion battery negative electrode material comprises a hard carbon matrix material and a nano thermoelectric material coating layer, and the nano thermoelectric material coating layer is coated on the surface of the hard carbon matrix material.Joule heat and reaction heat generated in the battery working process are utilized to form a micro area temperature gradient at a heterojunction interface, and a built-in electric field driving directional migration of sodium ions is generated based on the Seebeck effect.The self-driving mechanism significantly improves the transport dynamics of sodium ions in the hard carbon, and the hetero electric field of the thermoelectric material can homogenize the sodium ion flow, effectively inhibiting the growth of sodium dendrites.The application firstly combines the thermoelectric effect and the structural advantages of the spherical hard carbon, utilizes the temperature gradient to drive the sodium ion diffusion rate, realizes a uniform electric field to improve the stability of the negative electrode, and improves the kinetic performance and electrochemical performance of the hard carbon negative electrode as a whole.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical energy storage devices, specifically relating to a fast-charging sodium-ion battery anode material based on the thermoelectric effect and its preparation method. Background Technology

[0002] Sodium-ion batteries are considered a key candidate for next-generation large-scale energy storage technology due to the abundance and low cost of sodium resources. Hard carbon materials, with their wide availability, low cost, and suitable sodium storage potential, are currently the most promising anode materials for sodium-ion batteries. The sodium storage mechanism of hard carbon materials is mainly achieved through adsorption, intercalation, and pore filling. However, the commercial application of hard carbon anodes still faces many challenges.

[0003] First, the initial coulombic efficiency of the hard carbon anode is low. This is mainly because during the first charge and discharge process, the electrolyte decomposes on the large specific surface area and active sites of the hard carbon, forming a solid electrolyte interface film. This irreversibly consumes a large amount of sodium ions and active sodium from the positive electrode, resulting in a significant decrease in the actual energy density and capacity of the entire battery. Simultaneously, the solid-phase diffusion rate of sodium ions in hard carbon is slow, leading to poor rate performance and failing to meet the demands of high-power fast charging. Second, the hard carbon anode interface is unstable, especially under high-current charging or low-temperature conditions. Sodium ions may deposit unevenly on the hard carbon surface, forming sodium dendrites. Dendrites can pierce the separator, causing a short circuit and posing a serious safety hazard. They also continuously damage and regenerate the SEI film, consuming electrolyte and accelerating capacity decay.

[0004] Current strategies for improving the fast-charging performance of hard carbon materials mainly focus on material nanostructuring, pore structure control, and surface modification. For example, constructing porous structures to shorten ion transport paths or introducing heteroatom doping to enhance interfacial reaction kinetics. However, these methods often come at the cost of sacrificing material tap density and first-cycle efficiency, and cannot fundamentally solve the kinetic bottleneck of ion transport.

[0005] In recent years, thermoelectric materials have attracted attention due to their unique Seebeck effect, which can directly convert thermal energy into electrical energy. In battery systems, the Joule heat and reaction heat generated during charging and discharging are generally considered unfavorable factors. If this thermal energy can be cleverly utilized and converted into additional driving force for ion migration through the thermoelectric effect, it will provide a completely new approach to solving the kinetic limitations of hard carbon anodes. Summary of the Invention

[0006] Based on the aforementioned problems with hard carbon anode materials for sodium-ion batteries, this invention develops a temperature gradient-driven fast-charging sodium-ion battery anode material and its preparation method based on thermoelectric effect. By controlling the heat energy generated by the thermoelectric effect, the ion diffusion process is promoted, improving the dynamic performance of the anode. At the same time, the generated electric field can homogenize the sodium ion flow, suppress sodium dendrite growth, and significantly improve the cycle stability and safety of the battery, exhibiting electrochemical characteristics such as fast charging and high stability.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] The fast-charging sodium-ion battery anode material based on the thermoelectric effect includes a hard carbon matrix material and a nano-thermoelectric material coating layer, wherein the nano-thermoelectric material coating layer is coated on the surface of the hard carbon matrix material.

[0009] Furthermore, the nanothermoelectric materials constituting the coating layer of the nanothermoelectric material include Bi2Te3, SnSe, or Cu2Se.

[0010] Furthermore, the thickness of the nano-thermoelectric material coating layer is 5-100 nm.

[0011] A method for preparing a fast-charging sodium-ion battery anode material based on thermoelectric effect includes the following steps: growing a nano-thermoelectric material coating layer in situ on the surface of a hard carbon matrix material using a solvothermal method to obtain a heterostructure of hard carbon and thermoelectric material; after washing and drying, the product is annealed to optimize crystallinity and interfacial bonding strength, thereby obtaining a fast-charging sodium-ion battery anode material based on thermoelectric effect.

[0012] Furthermore, the preparation method of the hard carbon matrix material is as follows: using biomass raw materials as a carbon source, a hard carbon matrix material with a regular spherical morphology and a high degree of graphitization is prepared through hydrothermal carbonization combined with high-temperature pyrolysis; preferably, the biomass raw materials include one or more combinations of glucose, sucrose, phenolic resin, starch, lignin, and cellulose. The biomass raw materials are prepared into a 5-10 mol / L aqueous solution, and a surfactant is added to adjust the surface tension. The hydrothermal carbonization temperature is 180-220℃, and the time is 6-12 h, forming a carbon microsphere precursor after hydrothermal carbonization; the parameters of the high-temperature pyrolysis are: the carbon microsphere precursor is subjected to high-temperature pyrolysis under an inert atmosphere, the heating rate is controlled at 2-5℃ / min, the final temperature is 1200-1400℃, and the holding time is 2-6 hours. Before use, the hard carbon matrix material is refluxed in concentrated nitric acid with surfactant to improve its surface coating effect.

[0013] Furthermore, the hard carbon matrix material is dispersed in an organic solvent and subjected to ultrasonic treatment to ensure thorough dispersion. Then, a thermoelectric material precursor is added to the solvent for a solvothermal reaction. The organic solvent is ethanol, and the mass fraction ratio of the hard carbon matrix material to the thermoelectric material precursor is 1:0.01-1:0.1.

[0014] Furthermore, the thermoelectric material precursor is a combination of Bi(NO3)3·5H2O and Na2TeO3, used for the preparation of the Bi2Te3 coating layer; the thermoelectric material precursor is a combination of SnCl2·2H2O and Se powder, used for the preparation of the SnSe coating layer; the thermoelectric material precursor is a combination of Se and Cu(NO3)2, used for the preparation of the Cu2Se coating layer.

[0015] Furthermore, the solvothermal reaction is carried out at a temperature of 160-200℃ for 12-24 hours. The molar ratio and concentration of the thermoelectric material precursor are controlled, and the thickness of the nano-thermoelectric material coating layer is controlled by adjusting the reaction parameters.

[0016] Furthermore, the annealing conditions are as follows: treatment at 200-500°C for 1-2 hours in a protective atmosphere.

[0017] The core innovation of this invention lies in utilizing the Joule heat and reaction heat generated during battery operation to form a micro-temperature gradient at the heterojunction interface, thereby generating a built-in electric field based on the Seebeck effect to drive the directional migration of sodium ions. This self-driven mechanism significantly enhances the transport kinetics of sodium ions in hard carbon, while the heterogeneous electric field of the thermoelectric material homogenizes the sodium ion flow and effectively suppresses sodium dendrite growth. This invention is the first to combine the thermoelectric effect with the structural advantages of spherical hard carbon, using a temperature gradient to accelerate the sodium ion diffusion rate and achieve a uniform electric field to improve the stability of the anode, thus improving the overall kinetic and electrochemical performance of the hard carbon anode. The fabrication process is simple and cost-controllable, providing an innovative material design strategy for developing high-performance fast-charging sodium-ion batteries.

[0018] This invention aims to transform the waste heat generated during battery operation into an effective driving force for sodium ion migration by constructing a hard carbon-thermoelectric material heterostructure, thereby significantly improving the fast-charging performance and cycle stability of the hard carbon anode.

[0019] Compared with the prior art, the beneficial effects of the present invention are:

[0020] 1) This invention provides an additional driving force for sodium ion transport through a built-in electric field generated by the thermoelectric effect, significantly improving the fast-charging performance of hard carbon materials. This performance improvement is attributed to the built-in electric field generated by the thermoelectric material under the temperature gradient, which effectively reduces the diffusion barrier of sodium ions in hard carbon, ensuring that the hard carbon anode has good sodium ion transport speed and strong structural stability during charge-discharge cycles, thereby enabling the hard carbon material to have better rate performance and charge-discharge cycle performance.

[0021] 2) In this invention, the thermoelectric material coating layer homogenizes the sodium ion flow through the generated built-in electric field, effectively suppressing the growth of sodium dendrites. Simultaneously, the thermoelectric material coating layer not only generates an electric field that drives ion migration but also promotes the dissipation of interfacial heat, preventing localized overheating and exhibiting superior thermal stability.

[0022] 3) The preparation method adopted in this invention has the advantages of readily available raw materials, simple process and good repeatability. It maintains the cost advantage of biomass carbon source and achieves significant performance improvement through reasonable material design, and has good industrialization prospects. Attached Figure Description

[0023] Figure 1 This is a transmission electron microscope (TEM) image of the fast-charging sodium-ion battery anode material based on the thermoelectric effect prepared in Example 1 of the present invention.

[0024] Figure 2 This is a transmission electron microscope (TEM) image of the fast-charging sodium-ion battery anode material based on the thermoelectric effect prepared in Example 2 of the present invention.

[0025] Figure 3 The graph shows the cycling performance of a coin cell assembled with a sodium sheet and the fast-charging sodium-ion battery anode material based on thermoelectric effect prepared in Example 1 of this invention at a current density of 1 A / g.

[0026] Figure 4 The graph shows the cycling performance of a coin cell assembled with a sodium sheet and the fast-charging sodium-ion battery anode material based on thermoelectric effect prepared in Example 2 of this invention at a current density of 1 A / g. Detailed Implementation

[0027] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings and embodiments. Obviously, the described embodiments are only some embodiments of the invention, not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0028] Example 1:

[0029] A method for preparing a fast-charging sodium-ion battery anode material based on the thermoelectric effect includes the following steps:

[0030] 1 g of hard carbon powder was refluxed in concentrated nitric acid for 4 hours, washed and dried to obtain pretreated hard carbon; 0.5 g of pretreated hard carbon was dispersed in 70 mL of ethanol, and 0.485 g of Bi(NO3)3·5H2O and 0.200 g of Na2TeO3 were added sequentially, and the mixture was magnetically stirred for 2 hours; 1.0 g of NaOH and 0.5 g of hydrazine hydrate were added, and the mixture was stirred for another 30 minutes to control the morphology of the coating layer nano-thermoelectric material; the mixed solution was transferred to a 100 mL reactor and reacted at 160 °C for 18 hours to obtain Bi2Te3@hard carbon composite material; after washing, the product was annealed at 400 °C for 2 hours under an argon atmosphere to obtain a fast-charging sodium-ion battery anode material based on the thermoelectric effect.

[0031] The transmission electron microscope (TEM) image of the fast-charging sodium-ion battery anode material based on the thermoelectric effect obtained in this embodiment is shown below. Figure 1 As shown, Bi₂Te₃ is uniformly coated on the hard carbon anode. It is applied to sodium-ion batteries, specifically fast-charging sodium-ion batteries based on the thermoelectric effect, where a coin cell is assembled using a GF / D glass fiber separator and a 1 M NaPF₆in DEG electrolyte. The cycling performance of the prepared coin cell at a current density of 1 A / g is shown in the figure. Figure 3 As shown, the prepared thermoelectric effect-based fast-charging sodium-ion battery anode material can promote the insertion and extraction of sodium ions during the charging and discharging process, thereby improving the cycle stability of lithium-ion batteries.

[0032] Example 2

[0033] A method for preparing a fast-charging sodium-ion battery anode material based on the thermoelectric effect includes the following steps:

[0034] The hard carbon pretreatment was the same as in Example 1; 0.5 g of pretreated hard carbon was dispersed in 70 mL of ethylene glycol, and 0.351 g of SnCl2·2H2O and 0.173 g of Se powder were added sequentially, and the mixture was ultrasonically dispersed for 30 minutes; the mixed solution was transferred to a 100 mL reactor and reacted at 200 °C for 20 hours to obtain SnSe@hard carbon heterostructure material; after washing, the product was annealed at 450 °C for 3 hours under an argon atmosphere to obtain a thermoelectric fast-charging sodium-ion battery anode material.

[0035] The thermoelectric effect fast-charging sodium-ion battery anode material obtained in this embodiment is shown in the transmission electron microscope image below. Figure 2As shown, SnSe is uniformly coated on the hard carbon anode. It is applied to sodium-ion batteries, specifically fast-charging sodium-ion batteries based on the thermoelectric effect. A coin cell is assembled using a GF / D glass fiber separator and a 1 M NaPF6 in DEG electrolyte. The cycling performance of the prepared coin cell at a current density of 1 A / g is shown in the figure. Figure 4 As shown, the prepared thermoelectric effect-based fast-charging sodium-ion battery anode material can promote the insertion and extraction of sodium ions during the charging and discharging process, thereby improving the cycle stability of lithium-ion batteries.

[0036] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A fast-charging sodium-ion battery anode material based on the thermoelectric effect, characterized in that: It includes a hard carbon matrix material and a nano-thermoelectric material coating layer, wherein the nano-thermoelectric material coating layer coats the surface of the hard carbon matrix material; the nano-thermoelectric material constituting the nano-thermoelectric material coating layer includes Bi2Te3 or SnSe.

2. The fast-charging sodium-ion battery anode material based on thermoelectric effect according to claim 1, characterized in that: The thickness of the nano-thermoelectric material coating layer is 5-100 nm.

3. A method for preparing the fast-charging sodium-ion battery anode material based on the thermoelectric effect as described in claim 1 or 2, characterized in that, Includes the following steps: A nano-thermoelectric material coating layer was grown in situ on the surface of a hard carbon matrix material using a solvothermal method to obtain a heterostructure of hard carbon and thermoelectric material. Then, the material was annealed to obtain a fast-charging sodium-ion battery anode material based on the thermoelectric effect.

4. The preparation method according to claim 3, characterized in that: The preparation method of hard carbon matrix material is as follows: using biomass raw materials as carbon source, hard carbon matrix material is prepared by hydrothermal carbonization combined with high temperature pyrolysis.

5. The preparation method according to claim 4, characterized in that: The biomass raw materials include one or more combinations of glucose, sucrose, phenolic resin, starch, lignin, and cellulose; the hydrothermal carbonization temperature is 180-220℃, and the time is 6-12h; the parameters for high-temperature pyrolysis are: high-temperature pyrolysis is carried out under an inert atmosphere, the heating rate is controlled at 2-5℃ / min, the final temperature is 1200-1400℃, and the holding time is 2-6 hours.

6. The preparation method according to claim 3, characterized in that: A hard carbon matrix material is dispersed in an organic solvent, and then a thermoelectric material precursor is added to it for a solvothermal reaction. The mass fraction ratio of the hard carbon matrix material to the thermoelectric material precursor is 1:0.01-1:0.

1.

7. The preparation method according to claim 6, characterized in that: The thermoelectric material precursor includes a combination of Bi(NO3)3·5H2O and Na2TeO3 or a combination of SnCl2·2H2O and Se powder.

8. The preparation method according to claim 6, characterized in that: The solvothermal reaction is carried out at a temperature of 160-200℃ for 12-24 hours.

9. The preparation method according to claim 3, characterized in that: The annealing conditions are as follows: treatment at 200-500°C for 1-2 hours in a protective atmosphere.

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