Preparation and application of a sodium ion battery negative electrode material

Abstract

The present invention discloses a preparation method and application of a sodium ion battery negative electrode material. The method adopts an oxide and doped carbon coating method to improve the capacity of the battery. At the same time, the interaction between the oxide and the doped carbon is utilized to give the battery ideal cycle stability, solving the problem that the existing technology has not yet produced an ideal sodium ion battery negative electrode material suitable for commercial use.

Description

Technical field:

[0001] The present invention relates to the technical field of sodium ion battery negative electrode materials, and in particular to a preparation method and application of a sodium ion battery negative electrode material. Background technology:

[0002] Currently, lithium-ion batteries face challenges such as uneven lithium resource distribution and high lithium salt prices, and are unable to meet future energy storage development needs. Therefore, developing low-cost, high-performance, and sustainable electrochemical energy storage systems is of great significance.

[0003] Given that lithium and sodium are adjacent elements in the first main group and have similar physical and chemical properties, sodium is abundant, evenly distributed, and low-cost, and most importantly, sodium-ion batteries and lithium-ion batteries have very similar operating principles. Therefore, based on existing research on lithium-ion batteries, the development of sodium-ion batteries has great prospects. Although sodium-ion batteries have many advantages, the larger radius of sodium ions compared to lithium ions causes them to encounter greater resistance when intercalating and deintercalating in electrode materials than lithium-ion batteries, resulting in lower energy density and power density of sodium-ion batteries. Therefore, at this stage, relatively mature sodium-ion battery materials are relatively few and their performance is poor, making them unsuitable for large-scale commercial needs.

[0004] The internal structure and working mechanism of sodium-ion batteries are similar to those of lithium-ion batteries. They are primarily composed of negative electrode materials, positive electrode materials, electrolytes, and separators. Their working mechanism is achieved through the intercalation and deintercalation of sodium ions between the positive and negative electrodes, enabling the battery's charge and discharge processes. The charging process of a sodium-ion battery involves extracting sodium ions from the positive electrode and embedding them into the negative electrode through the electrolyte. Simultaneously, the compensating charge of electrons is transferred to the negative electrode through an external circuit, thereby ensuring charge balance between the positive and negative electrodes. The discharge process involves extracting sodium ions from the negative electrode and reinserting them into the positive electrode through the electrolyte.

[0005] As the core component of sodium-ion batteries, the anode material directly determines the key to battery performance. Developing anode materials with excellent comprehensive performance is one of the key issues in the development of sodium-ion batteries. To date, anode materials are mainly divided into alloys, metal compounds, organic matter, and carbon-based. Alloy-based anode materials refer to alloys of sodium metal and one or more other metals or non-metals. Although alloyed materials have relatively high theoretical specific capacities, incomplete alloying of sodium with other metals results in low reversible capacity and coulombic efficiency. At the same time, the alloy anode is prone to volume expansion and structural destruction during the charge / discharge process, resulting in poor cycle stability. Therefore, the capacity of alloy-based materials is relatively low in actual use. Metal compounds mainly refer to metal oxides or sulfides, such as SnO2, TiO2, MoS2, FeS2, etc. Although this type of negative electrode material has good safety and energy density, there is a phase transition reaction during the charging and discharging process, which makes the metal oxides or sulfides destroy the stability of the material structure due to the volume effect, resulting in poor cycle stability; organic matter has become a sodium ion negative electrode material due to its many types, abundant and renewable raw materials, low cost, and high first efficiency. However, its development is limited by problems such as poor conductivity, many side reactions, and easy decomposition of the electrolyte.

[0006] Compared with other negative electrode materials for sodium-ion batteries, carbon-based materials are considered to be the most promising negative electrode materials due to their abundant sources, low cost, and good overall performance. Currently, carbon-based materials mainly include graphite and hard carbon. Although graphite has been widely used in lithium-ion batteries, due to the large radius of sodium ions, graphite has problems with low sodium storage capacity and poor reversibility in sodium-ion batteries. Hard carbon is a carbon material that is difficult to graphitize at high temperatures. Although hard carbon has shown good sodium storage performance, its low initial efficiency and poor long-term cycle stability still hinder its application in sodium-ion batteries.

[0007] Given the many problems with the current negative electrodes of sodium-ion batteries, there is no ideal material suitable for commercial use. Summary of the invention:

[0008] The purpose of the present invention is to provide a preparation method and application of a sodium ion battery negative electrode material, which adopts an oxide and doped carbon coating method to improve the capacity of the battery. At the same time, the interaction between the oxide and the doped carbon is utilized to give the battery ideal cycle stability, thereby solving the problem that the existing technology has not yet produced an ideal sodium ion battery negative electrode material suitable for commercial use.

[0009] The present invention is achieved through the following technical solutions:

[0010] A method for preparing a negative electrode material for a sodium ion battery, the method comprising the following steps:

[0011] 1) Using tetraethyl orthosilicate (TEOS) as a raw material, ammonia as a catalyst for the hydrolysis of TEOS, and a mixed solution of deionized water and ethanol as a solvent, stirring for a certain period of time, centrifuging, and drying to obtain white SiO2 powder;

[0012] 2) Using any natural polymer such as cellulose (CN) or starch as a carbon source, dissolving it in deionized water, and rapidly stirring under inert gas protection until a uniform carbon source solution A is formed;

[0013] 3) adding the white SiO2 powder obtained in step 1) to the uniform carbon source solution A obtained in step 2) and stirring them uniformly under an inert atmosphere to form a solution B in which the mass fraction of SiO2 is 50-70%. Placing solution B in an autoclave and reacting at a temperature of 160-200°C for 12-24 hours, the solution is centrifuged and dried to obtain a black powder;

[0014] 4) The black powder obtained in step 3) is placed in a tube furnace and heated to 800-1100° C. under inert gas protection. The inert gas is continuously introduced into a gas bottle containing an organic compound at a flow rate of 5-10 L / min for 10-30 minutes to obtain a SiO2 / doped carbon negative electrode material; the organic compound is one of ethylenediamine, triethylamine, ethanol and a mixture of boric acid.

[0015] Preferably, in step 1), the volume ratio of deionized water to ethanol is 1:1 to 1:5, and the volume ratio of ammonia water to tetraethyl orthosilicate is 2:1 to 1:1.

[0016] Preferably, the mass fraction of the natural polymer in step 2) is 1.0 to 5.0 wt%.

[0017] Preferably, the inert gas is one of argon and nitrogen.

[0018] The sodium-ion battery anode material obtained by the above-mentioned preparation method is a SiO2 / doped carbon composite sodium-ion anode material. The carbon layer is produced using two raw materials: a natural polymer and an organic compound, respectively, through two processes: hydrothermal deposition and vapor deposition. This method not only increases the specific capacity but also improves the conductivity of the anode material, further contributing to improved overall battery performance.

[0019] The specific capacity of the material can reach 280mAh / g.

[0020] The present invention also protects the sodium ion battery negative electrode material obtained by the preparation method. The carbon layer thickness of the material obtained by the present invention is 5-10nm, and the doping atoms of the doped carbon are mainly nitrogen and boron.

[0021] The present invention also protects the application of the sodium ion battery negative electrode material in sodium ion batteries. A sodium ion battery is constructed with the oxide / doped carbon as the negative electrode and the sodium sheet as the positive electrode. The specific capacity can reach 280 mAhg -1 After 1000 cycles, the capacity can still be maintained at 240mAhg -1 .

[0022] The present invention also provides a sodium ion battery, which uses the oxide / doped carbon as a negative electrode and a sodium sheet as a positive electrode.

[0023] The beneficial effects of the present invention are as follows:

[0024] 1) The SiO2 / doped carbon composite sodium ion negative electrode material prepared in this invention, due to the presence of heteroatoms in the carbon layer, facilitates the adsorption of sodium ions, significantly improving the battery's specific capacity. Simultaneously, the coating effect between the oxide and the carbon material significantly enhances the negative electrode material's structural stability during charge and discharge, improving long-term cycle stability. Because the oxide and doped carbon exist in a coated form, the bonding between the functional groups on the oxide surface and the doped atoms in the carbon layer significantly maintains the material's structural stability during the battery's long-term charge and discharge processes.

[0025] 2) The carbon layer in the SiO2 / doped carbon composite sodium-ion negative electrode material of this invention is produced using two raw materials: a natural polymer and an organic compound, respectively, through two processes: hydrothermal deposition and vapor deposition. This approach not only increases the specific capacity but also enhances the conductivity of the negative electrode material, further contributing to improved overall battery performance.

[0026] 3) The SiO2 / doped carbon composite sodium ion negative electrode material prepared by the present invention has a carbon layer thickness of 5-10nm and a specific capacity of up to 280mAhg -1 .

[0027] 4) The SiO2 / doped carbon composite sodium ion negative electrode material prepared by the present invention can maintain a capacity of 240 mAh g after 1000 cycles due to the coating of the carbon layer. -1 .

[0028] 5) The SiO2 / doped carbon composite material prepared by the present invention has abundant raw materials, is simple to prepare, and has excellent comprehensive performance, which can better meet the development needs of future sodium ion batteries. Description of the drawings:

[0029] Figure 1 is a transmission electron microscope image of the oxide / doped carbon negative electrode material prepared in Example 1;

[0030] Figure 2 is an X-ray spectrum of the oxide / doped carbon negative electrode material prepared in Example 1;

[0031] Figure 3 The performance of the battery with the oxide / doped carbon negative electrode material prepared in Example 1 as the negative electrode;

[0032] Figure 4 This is the long cycle stability of the sodium ion battery with the oxide / doped carbon negative electrode material prepared in Example 1 as the negative electrode. Specific implementation method:

[0033] The following is a further description of the present invention, but not a limitation of the present invention.

[0034] Example 1: Preparation of oxide / doped carbon negative electrode materials

[0035] It is completed in the following process:

[0036] (1) Using tetraethyl orthosilicate (TEOS) as the raw material, ammonia as the catalyst for TEOS hydrolysis, and a mixed solution of deionized water and ethanol as the solvent, the mixture is stirred for a certain period of time, centrifuged, and dried to obtain white oxide SiO2 powder. The volume ratio of deionized water to ethanol is 1:5, and the volume ratio of ammonia to TEOS is 2:1.

[0037] (2) Dissolve cellulose (CN) in deionized water and stir rapidly under inert gas protection until a uniform solution A is formed, wherein the mass fraction of cellulose is 5.0 wt % and the inert gas is argon.

[0038] (3) The white SiO2 powder obtained in step (1) is added to the homogeneous solution A obtained in step (2) in a certain proportion, and stirred evenly under an inert atmosphere of argon to form a solution B. The mass fraction of SiO2 is 50%. Solution B is placed in an autoclave and reacted at 200°C for 12 hours. After centrifugation and drying, a black powder is obtained.

[0039] (4) The black powder obtained in step (3) is placed in a tube furnace and heated to 1100° C. under inert gas protection. The inert gas is continuously introduced into a gas bottle containing an organic compound at a flow rate of 5 L / min. After 10 minutes of introduction, the preparation of the SiO2 / doped carbon negative electrode material is completed in the tube furnace. The organic compound is triethylamine.

[0040] The sodium ion battery negative electrode prepared above was characterized and its performance analyzed. Figure 1The transmission electron microscope image of the oxide / doped carbon negative electrode material shows that there is a 5nm thick carbon layer on the surface of the oxide SiO2, and part of the carbon layer is 10nm thick. This shows that the oxide / doped carbon negative electrode material can be prepared by the present invention. The components of the oxide / doped carbon negative electrode material were analyzed by X-ray spectroscopy. Figure 2 As shown in the spectrum, it can be seen that there are three elements Si, O, C, and N in the sample, among which Si and O come from the oxide SiO2, and C and N mainly come from the wrapped carbon layer. A sodium ion battery is constructed with oxide / doped carbon as the negative electrode and sodium sheet as the positive electrode. Its specific capacity is as follows Figure 3 As shown in the figure, it can be seen that the voltage window of the battery is 0~3.0V, and the specific capacity of the battery is 280mAhg -1 . Figure 4 The long cycle stability of the sodium ion battery with oxide / doped carbon as the negative electrode. As can be seen from the figure, after 1000 cycles, the specific capacity of the battery is 240mAhg -1 , the specific capacity attenuation is small.

[0041] Example 2:

[0042] Refer to Example 1, except that in step (2), cellulose (CN) is replaced by starch.

[0043] Example 3:

[0044] Refer to Example 1, except that the time for introducing the organic compound in step (4) is replaced by 30 min from 10 min.

[0045] Example 4:

[0046] Refer to Example 1, except that the organic compound introduced in step (4) is replaced by triethylamine with a mixture of ethanol and boric acid.

[0047] Comparative Example 1:

[0048] Refer to Example 1, except that there is no step (4), the carbon raw material is mainly natural high molecular weight cellulose, and the process only has a hydrothermal step.

[0049] Comparative Example 2:

[0050] Referring to Example 1, the difference is that there are no steps (2) and (3), the carbon raw material is mainly triethylamine, an organic compound, and the process is a vapor deposition step, comprising the following steps:

[0051] (1) Using tetraethyl orthosilicate (TEOS) as the raw material, ammonia as the catalyst for TEOS hydrolysis, and a mixed solution of deionized water and ethanol as the solvent, the mixture is stirred for a certain period of time, centrifuged, and dried to obtain white oxide SiO2 powder. The volume ratio of deionized water to ethanol is 1:5, and the volume ratio of ammonia to TEOS is 2:1.

[0052] (2) White oxide SiO2 powder is placed in a tube furnace and heated to 1100°C under inert gas protection. The inert gas is continuously introduced into a gas bottle containing an organic compound at a flow rate of 5 L / min. After 10 minutes of inert gas introduction, the preparation of the SiO2 / doped carbon anode material is completed in the tube furnace. The organic compound is triethylamine.

[0053] The performance of the SiO2 / doped carbon composite sodium ion negative electrode materials prepared in Example 1, Comparative Example 1, and Comparative Example 2 was compared. A sodium ion battery was constructed using oxide / doped carbon as the negative electrode and a sodium sheet as the positive electrode. The results are shown in Table 1:

[0054] Table 1 Performance comparison of SiO2 / doped carbon composite sodium ion negative electrode materials prepared by different processes

[0055] <![CDATA[Specific capacity of sodium-ion battery (mAh g -1 )]]> Conductivity (Ω) Example 1 280 96 Comparative Example 1 198 205 Comparative Example 2 221 183

[0056] From the comparative data in Table 1, it can be seen that the SiO2 / doped carbon composite sodium ion negative electrode material prepared by two raw materials and two processes in Example 1 has relatively excellent performance.

Claims

1. A method for preparing a negative electrode material for a sodium ion battery, characterized in that: The method comprises the following steps: 1) Using tetraethyl orthosilicate as raw material, ammonia as catalyst, and a mixed solution of deionized water and ethanol as solvent, stirring for a certain period of time, centrifuging, and drying to obtain white SiO2 powder; 2) Using any natural polymer such as cellulose or starch as a carbon source, dissolving it in deionized water, and rapidly stirring under inert gas protection until a uniform carbon source solution A is formed; 3) adding the white SiO2 powder obtained in step 1) to the uniform carbon source solution A obtained in step 2) and stirring them uniformly under an inert atmosphere to form a solution B in which the mass fraction of SiO2 is 50-70%. Placing solution B in an autoclave and reacting at a temperature of 160-200°C for 12-24 hours, the solution is centrifuged and dried to obtain a black powder; 4) The black powder obtained in step 3) is placed in a tube furnace and heated to 800-1100° C. under inert gas protection. The inert gas is continuously introduced into a gas bottle containing an organic compound at a flow rate of 5-10 L / min for 10-30 minutes to obtain a SiO2 / doped carbon negative electrode material; the doping atoms of the doped carbon are mainly nitrogen and boron; the organic compound is a mixture of ethylenediamine, triethylamine, or ethanol and boric acid.

2. The preparation method according to claim 1, characterized in that In step 1), the volume ratio of deionized water to ethanol is 1:1 to 1:5, and the volume ratio of ammonia water to tetraethyl orthosilicate is 2:1 to 1:

1.

3. The preparation method according to claim 1, characterized in that In step 2), the mass fraction of the natural polymer is 1.0 to 5.0 wt%.

4. The preparation method according to claim 1, characterized in that The inert gas is one of argon and nitrogen.

5. The sodium ion battery negative electrode material obtained by the preparation method according to claim 1.

6. The sodium ion battery negative electrode material according to claim 5, characterized in that The carbon layer thickness of the material is 5-10nm, and the doping atoms of the doped carbon are mainly nitrogen and boron.

7. Use of the sodium ion battery negative electrode material according to claim 5 in a sodium ion battery.

8. The use according to claim 7, characterized in that A sodium ion battery is constructed using the sodium ion battery negative electrode material as the negative electrode and the sodium sheet as the positive electrode.

9. A sodium ion battery, characterized in that: The sodium ion battery negative electrode material according to claim 5 is used as the negative electrode, and the sodium sheet is used as the positive electrode.

Images