A nano Sn-C composite material for sodium ion battery negative electrode and preparation method

Abstract

The application discloses a kind of nano Sn-C composite material for sodium ion battery negative electrode and preparation method, belong to electrochemical energy storage material field.The application simultaneously realizes the preparation of nano Sn particles, direct reduction of graphene oxide and uniform dispersion of Sn nanoparticles on the surface of graphene by one-step chemical co-reduction method.Due to the small Sn particles and uniform dispersion on the surface of graphene carrier, the Sn-C composite material shows very high electrochemical sodium storage capacity, and good cycle stability.The raw materials used in the application are cheap and easy to obtain, the process is simple and does not require high-temperature treatment process, with low energy consumption and no pollution.

Description

Technical Field

[0001] The invention relates to a nano Sn-C composite material for a sodium ion battery negative electrode and a preparation method thereof, belonging to the field of electrochemical energy storage materials. Background Art

[0002] The negative electrode material is one of the key materials that determines the overall performance of sodium-ion batteries. Sn-based materials have the advantages of being non-toxic, having high capacity and good safety. As a promising negative electrode material for sodium-ion batteries, they have attracted widespread attention from researchers. However, the main problem with Sn-based materials is that sodium ions undergo huge volume changes during the alloying and dealloying reactions with Sn, which leads to easy pulverization and deactivation of the material and poor cycle performance. Nano-sizing Sn and compounding it with carbon materials can significantly improve this volume change problem. The principle is that the absolute volume change generated by the volume change of nano-sized particles is small, and the particles are not easy to break. The carbon material, as a continuous matrix with a certain elasticity, can effectively prevent the agglomeration of nano-Sn particles and effectively buffer the volume change of Sn, which greatly improves the stability of the material.

[0003] Among existing Sn-based materials, derivative Sn compounds such as Sn oxides and sulfides are difficult to apply in practice due to their poor electrical conductivity. However, nano-Sn-C composites, formed by combining metallic Sn nanoparticles with carbon materials, have greater practical application potential due to their improved electrical conductivity, which helps reduce charge transfer resistance during charge and discharge. However, currently reported nano-Sn-C composites are mostly used in lithium-ion batteries, and their preparation methods are relatively complex. They not only require structural barriers such as polyvinyl pyrrolidone, but also require energy-intensive processes such as high-temperature reducing atmosphere treatment to treat the carbon source to obtain a carbon matrix with a conductive network for buffering and simultaneously achieve Sn reduction. However, due to the low melting point of Sn (223°C), nano-Sn particles easily aggregate and grow to micrometer-sized sizes during high-temperature treatment. Due to the large absolute volume change during charge and discharge, the grown Sn particles experience significant internal stress, which leads to particle pulverization and deactivation due to detachment from the current collector. This can easily lead to poor cycling performance of the material, making it difficult to meet the requirements of application and promotion. Therefore, how to develop a new preparation method to avoid high-temperature treatment process, realize the efficient synthesis of nano-Sn-C composite materials, achieve a stable structure with high dispersion of ultrafine nano-Sn particles on a carbon matrix with good conductivity, and at the same time achieve a great improvement in the sodium storage cycle capacity and cycle life of the material, is an important research direction for Sn-C composite materials for sodium ion battery negative electrodes. Summary of the Invention

[0004] The application aims to provide a nano Sn-C composite material for a sodium ion battery negative electrode and a preparation method.

[0005] In order to achieve the above-mentioned purpose, the application adopts the following technical scheme:

[0006] A preparation method of a nano Sn-C composite material for a sodium ion battery negative electrode comprises the following steps:

[0007] Step 1: tin source is dissolved in water to obtain solution 1, and a ligand compound is dissolved in water to obtain solution 2;

[0008] Step 2: solution 1 and solution 2 are mixed and stirred;

[0009] Step 3: an aqueous graphene oxide solution is added to the mixed solution of solution 1 and 2 and stirred, and a reducing agent solution is further added to perform a reduction reaction;

[0010] Step 4: after the reaction is completed, the obtained product is subjected to centrifugation, washing and freeze-drying to obtain a nano Sn-C composite material.

[0011] The aqueous graphene oxide solution is prepared by a Hummers method.

[0012] Further, the tin source is tin dichloride dihydrate or anhydrous tin dichloride; the ligand compound is ethylenediaminetetraacetic acid (EDTA) or ethylenediaminetetraacetic acid disodium salt; and the reducing agent solution is a mixed solution of sodium borohydride and sodium citrate.

[0013] Further, the concentration of the tin source solution is 2-2000 mmol / L; the concentration of the ligand compound solution is 2-2000 mmol / L; and the concentration of the aqueous graphene oxide solution is 2-50 g / L.

[0014] Further, the mass of the tin source in step 1 is 0.045-0.7 g, and the mass of the ligand compound is 0.058-0.67 g.

[0015] Further, the volume of water in step 1 is 2-100 mL.

[0016] Further, the stirring time in step 2 is 0.5 h, and the stirring time in step 3 is 0.5 h.

[0017] Further, the reduction reaction time in step 3 is 1-50 min, and the freeze-drying time in step 4 is 12 h.

[0018] Further, the amount of the graphene oxide aqueous solution added in step 3 is 2-100 mL; and the amount of the reducing agent solution added is 2-100 mL.

[0019] Further, the concentration of the sodium borohydride and the sodium citrate is 2-1000 mmol / L.

[0020] A preparation method of a nano Sn-C composite material for a sodium ion battery negative electrode.

[0021] Compared with the prior art, the present application has the following advantages:

[0022] 1. The size of the Sn particles obtained by the method of the present application is 2-100 nm, the particle size is uniform, the dispersibility is good, and the particle size can be controlled by the reaction conditions.

[0023] 2. The nano Sn-C composite material prepared by the present application utilizes the excellent properties of graphene, such as high electrical conductivity and large specific surface area, and carries ultrafine nano Sn particles on the graphene nanosheet layer structure, which can effectively alleviate the huge volume change during the charging and discharging process of Sn, maintain the stability of the material and a high cycle reversible capacity.

[0024] 3. The material used in the present application is inexpensive and easy to obtain, the process is simple, the processing process is efficient and energy-saving, and there is no pollution. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 It is a transmission electron microscope image of the nano Sn-C composite material in Example 1;

[0026] Figure 2 It is a scanning electron microscope image of the nano Sn-C composite material in Example 1;

[0027] Figure 3 It is a sodium ion cycle performance graph of the nano Sn-C composite material in Example 1. DETAILED DESCRIPTION

[0028] Example 1

[0029] (1) 0.045 g of tin dichloride dihydrate was dissolved in 100 mL of water to obtain solution 1, and 0.058 g of EDTA was dissolved in 100 mL of water to obtain solution 2;

[0030] (2) Solution 1 and solution 2 were mixed and stirred for 0.5 h;

[0031] (3) 10 mL of 2 g / L graphene oxide aqueous solution was added to the mixed solution of solution 1 and 2, stirred for 0.5 h, and 5 mL of reducing agent solution with a concentration of 10 mmol / L of sodium citrate and sodium borohydride was added for reduction reaction;

[0032] (4) After the reaction is completed, the obtained product is centrifuged, washed, and freeze-dried for 12 h to obtain the nano Sn-C composite material.

[0033] The sample is observed by transmission and scanning electron microscopy, and it is found that the size of the Sn nanoparticles ranges from 30 to 60 nm and is uniformly dispersed on the surface of the graphene carrier, as shown in FIGS. 1 and 2. Figure 1 and Figure 2 After the sodium storage charge-discharge test of the half battery, the cycle capacity after 100 times is 445 mAh / g, as shown in FIG. 3. Figure 3

[0034] Example 2

[0035] (2) 0.35 g of tin dichloride dihydrate is dissolved in 10 mL of water to obtain solution 1, and 0.48 g of EDTA is dissolved in 10 mL of water to obtain solution 2;

[0036] (2) The solution 1 and the solution 2 are mixed and stirred for 0.5 h;

[0037] (3) 15 mL of 20 g / L graphene oxide aqueous solution is added to the mixed solution of solution 1 and 2, stirred for 0.5 h, and 50 mL of a reducing agent solution with a sodium borohydride concentration of 200 mmol / L and a sodium citrate concentration of 30 mmol / L is added for reduction reaction;

[0038] (4) After the reaction is completed, the obtained product is centrifuged, washed, and freeze-dried for 12 h to obtain the nano Sn-C composite material.

[0039] The sample is subjected to a sodium storage charge-discharge test of a half battery, and the cycle capacity after 100 times is 343 mAh / g.

[0040] Example 3

[0041] (1) 0.20 g of anhydrous tin dichloride is dissolved in 20 mL of water to obtain solution 1, and 0.23 g of EDTA is dissolved in 20 mL of water to obtain solution 2;

[0042] (2) The solution 1 and the solution 2 are mixed and stirred for 0.5 h;

[0043] (3) 10 mL of 15 g / L graphene oxide aqueous solution is added to the mixed solution of solution 1 and 2, stirred for 0.5 h, and 20 mL of a reducing agent solution with a sodium borohydride concentration of 100 mmol / L and a sodium citrate concentration of 2 mmol / L is added for reduction reaction;

[0044] (4) After the reaction is completed, the obtained product is centrifuged, washed, and freeze-dried for 12 h to obtain the nano Sn-C composite material.

[0045] ​The sample underwent half-cell sodium storage charge and discharge tests, and the cycle capacity was 398mAh / g after 100 cycles.

[0046] Example 4

[0047] (1) Dissolve 0.70 g of anhydrous tin dichloride in 20 mL of water to obtain solution 1, and dissolve 0.63 g of EDTA in 20 mL of water to obtain solution 2;

[0048] (2) Solution 1 and solution 2 were mixed and stirred for 0.5 h;

[0049] (3) 50 mL of a 30 g / L graphene oxide aqueous solution was added to the mixed solution of solutions 1 and 2, stirred for 0.5 h, and 80 mL of a reducing agent solution with a sodium borohydride concentration of 100 mmol / L and a sodium citrate concentration of 180 mmol / L was added to carry out a reduction reaction;

[0050] (4) After the reaction is completed, the obtained product is centrifuged, washed, and freeze-dried for 12 hours to obtain a nano-Sn-C composite material.

[0051] The sample underwent half-cell sodium storage charge and discharge tests, and the cycle capacity was 318mAh / g after 100 cycles.

[0052] Example 5

[0053] (1) Dissolve 0.1 g of tin dichloride dihydrate in 2 mL of water to obtain solution 1, and dissolve 0.12 g of EDTA in 2 mL of water to obtain solution 2;

[0054] (2) Solution 1 and solution 2 were mixed and stirred for 0.5 h;

[0055] (3) 10 mL of 50 g / L graphene oxide aqueous solution was added to the mixed solution of solution 1 and 2, stirred for 0.5 h, and 2 mL of a reducing agent solution with a sodium borohydride concentration of 1000 mmol / L and a sodium citrate concentration of 1000 mmol / L was added to carry out a reduction reaction;

[0056] (4) After the reaction is completed, the obtained product is centrifuged, washed, and freeze-dried for 12 hours to obtain a nano-Sn-C composite material.

[0057] The sample underwent half-cell sodium storage charge and discharge tests, and the cycle capacity was 151mAh / g after 100 cycles.

[0058] Example 6

[0059] (1) Dissolve 0.09 g of tin dichloride dihydrate in 10 ml of water to obtain solution 1, and dissolve 0.11 g of EDTA in 10 ml of water to obtain solution 2;

[0060] (2) Solution 1 and solution 2 were mixed and stirred for 0.5 h;

[0061] (3) 100 ml of a 2 g / L graphene oxide aqueous solution was added to the mixed solution of solutions 1 and 2, stirred for 0.5 h, and 100 mL of a reducing agent solution with a sodium borohydride concentration of 2 mmol / L and a sodium citrate concentration of 2 mmol / L was added to carry out a reduction reaction;

[0062] (4) After the reaction is completed, the obtained product is centrifuged, washed, and freeze-dried for 12 hours to obtain a nano-Sn-C composite material.

[0063] The sample underwent half-cell sodium storage charge and discharge tests, and the cycle capacity was 136mAh / g after 100 cycles.

[0064] Any matters not described in detail in this specification are prior art known to those skilled in the art. Although the above description of the present invention is based on specific embodiments to facilitate understanding of the present invention by those skilled in the art, it should be understood that the present invention is not limited to the scope of the specific embodiments. As long as various modifications are within the spirit and scope of the present invention as defined and determined by the appended claims, such modifications will be obvious to those skilled in the art, and all inventions and creations utilizing the concepts of the present invention are protected.

Claims

1. A method for preparing a nano Sn-C composite material for a sodium ion battery negative electrode, characterized in that: The following steps are involved: Step 1, dissolving a tin source in water to obtain solution 1, and dissolving a ligand compound in water to obtain solution 2; Step 2, mixing solution 1 and solution 2; Step 3, adding the graphene oxide aqueous solution to the mixed solution of solutions 1 and 2 and stirring, and then adding the reducing agent solution to carry out a reduction reaction; Step 4: After the reaction is completed, the obtained product is centrifuged, washed, and freeze-dried to obtain a negative electrode material for a sodium ion battery; the tin source is tin dichloride dihydrate or anhydrous tin dichloride; the ligand compound is ethylenediaminetetraacetic acid or ethylenediaminetetraacetic acid disodium salt; and the reducing agent solution is a mixed solution of sodium borohydride and sodium citrate; The concentration of the tin source solution is 2 to 2000 mmol / L; the concentration of the ligand compound solution is 2 to 2000 mmol / L; the concentration of the graphene oxide aqueous solution is 2 to 50 g / L; The concentrations of the sodium borohydride and sodium citrate are both 2-1000 mmol / L.

2. The method for preparing a nano Sn-C composite material for a negative electrode of a sodium ion battery according to claim 1, wherein: In the step 1, the mass of the tin source is 0.045 to 0.7 g, and the mass of the ligand compound is 0.058 to 0.67 g.

3. The method for preparing a nano Sn-C composite material for a sodium ion battery negative electrode according to claim 1, characterized in that: The volume of water in step 1 is 2 to 100 mL.

4. The method for preparing a nano Sn-C composite material for a negative electrode of a sodium ion battery according to claim 1, wherein: The stirring time in step 2 is 0.5 h; the stirring time in step 3 is 0.5 h.

5. The method for preparing a nano Sn-C composite material for a negative electrode of a sodium ion battery according to claim 1, characterized in that: The reduction reaction time in step 3 is 1 to 50 minutes; the freeze-drying time in step 4 is 12 hours.

6. The method for preparing a nano Sn-C composite material for a negative electrode of a sodium ion battery according to claim 1, characterized in that: In step 3, the amount of graphene oxide aqueous solution added is 2 to 100 mL; the amount of reducing agent solution added is 2 to 100 mL.

7. The nano Sn-C composite material obtained by the method for preparing a nano Sn-C composite material for a negative electrode of a sodium ion battery according to any one of claims 1 to 6.

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