Porous nanofiber Ge / GeO2 / NC sodium ion battery negative electrode material and preparation method thereof

Abstract

The invention relates to the field of sodium ion battery negative electrode materials, and discloses a porous nanofiber-shaped Ge / GeO2 / NC sodium ion battery negative electrode material, the interior of the material is a Ge / GeO2 nanostructure, the exterior of the material is a porous carbon nanofiber structure, and the porous nanofiber-shaped Ge / GeO2 / NC sodium ion battery negative electrode material has the advantages of simple and convenient preparation process and unique morphology, and shows better specific capacity and cycling stability.

Description

Technical Field

[0001] The present invention relates to the field of sodium ion battery negative electrode materials, and in particular to a porous nanofiber-shaped Ge / GeO 2 / NC sodium ion battery negative electrode material and preparation method thereof. Background Art

[0002] Current research shows that morphology engineering is one of the important means to significantly improve the performance of negative electrode materials for sodium ion batteries. 3 Cu Ge coated by nitrogen-doped carbon nanorods as advanced sodium-ion battery anodes[J].Ionics 26(2020)719-726.) 3 Ge@C negative electrode material, it is 0.1Ag -1 After 500 cycles at a current density of 160 mAh g -1 Wei et al. (Wei W, Zhang Y, Liang L, Wang K, Zhou Q, Zhou Y, Wang H. Highly-dispersed Ge quantum dots in carbon frameworks for ultra-long-life sodium ion batteries[J]. Mater. Chem. Front. 5 (2021) 7778-7786.) prepared highly dispersed Ge quantum dots wrapped in carbon frameworks. Due to their unique nanostructure and the protection of carbon coating, they are used as negative electrode materials for sodium ion batteries at 1.5A g -1 After 5000 cycles, it can still maintain 201mAh g -1 Although some progress has been made in improving the performance of Ge-based composite materials, the modification process and preparation method of Ge-based negative electrode materials in the prior art are relatively complicated, and their low capacity hinders practical application. Therefore, this application proposes a porous nanofiber Ge / GeO 2 / NC sodium ion battery negative electrode material and preparation method thereof. Summary of the invention

[0003] The present invention aims to provide a porous nanofiber Ge / GeO 2 / NC sodium ion battery negative electrode material and its preparation method to solve the problems raised in the above background technology.

[0004] To achieve the above object, the present invention provides the following technical solution: a porous nanofiber-shaped Ge / GeO 2 / NC sodium ion battery negative electrode material, the material is composed of nano-scale nanofibers, Ge / GeO 2 The outside is surrounded by nitrogen-doped porous carbon nanofibers for protection, and the material is applied to the negative electrode of a sodium ion battery.

[0005] Preferably: the surface of the material has a porous structure.

[0006] Preferably, the nanofibers have distinct morphological features and are evenly distributed.

[0007] According to the porous nanofiber Ge / GeO 2 / NC sodium ion battery negative electrode material preparation method, comprising the following steps,

[0008] 1) dissolving germanium oxide in a mixed solution of deionized water and ammonia water, and mixing a sodium borohydride solution dissolved in deionized water with the solution, and obtaining a uniform solution after magnetic stirring;

[0009] 2) filtering the uniform solution obtained in step 1), drying the obtained sample, mixing it with a polyacrylonitrile solution dissolved in N,N-dimethylformamide, stirring it magnetically, and then using electrostatic spinning technology to obtain a uniform spinning membrane;

[0010] 3) After vacuum drying the spinning membrane obtained in step 2), a two-step calcination technique is used to obtain a porous nanofiber-shaped Ge / GeO 2 / NC sodium-ion battery negative electrode materials.

[0011] Preferably, in step 3), the annealing temperature of the second step of the two-step calcination is 400-600°C.

[0012] Preferably: the negative electrode material prepared by the above method is 0.1Ag -1 After 300 cycles at a current density of 500 mAh g -1 The specific capacity at 10Ag -1 After 20,000 cycles at a high current density, 188 mAh g -1 Specific capacity.

[0013] Compared with the prior art, the present invention has the following beneficial effects:

[0014] The present invention adopts electrospinning technology and calcination method to prepare Ge / GeO nanofibers with high performance. 2 / NC material, this special structure mainly refers to the prepared material is a nano-scale porous structure, this special structure is due to the electrospinning and high temperature calcination process of the appropriate calcination temperature so that the nanofiber structure is retained and the porous structure appears, at the same time, the structure contains a certain amount of nitrogen doped carbon, improves the conductivity, greatly increases the reaction kinetics of the composite material, thereby improving the rate performance; the porous nanofiber-shaped Ge / GeO synthesized by this synthesis method 2 / NC materials have good morphology and excellent electrochemical properties.

[0015] The porous nanofibrous Ge / GeO prepared by the above method 2 / The advantages of NC materials are:

[0016] 1) Preparation of Ge / GeO with special porous nanofiber morphology 2 / NC materials, whose large amount of porous structures on the surface provide active sites, thus enhancing their reaction kinetics when used as negative electrode materials for sodium-ion batteries;

[0017] 2) The prepared composite material has nitrogen-doped carbon nanofibers on the outside, which greatly improves the electrical conductivity of the composite material, thereby enabling the composite material to obtain excellent electrochemical properties;

[0018] 3) Porous nanofibrous Ge / GeO prepared by this method 2 The outer part of the NC material is nitrogen-doped carbon nanofibers, and the inner part is protected Ge / GeO 2 Composite materials, the outer carbon nanofibers can effectively act as a buffer layer to relieve the internal Ge / GeO 2 The large volume expansion problem during repeated charge and discharge makes the composite material have excellent cycle stability;

[0019] 4) The morphology and electrochemical performance of the negative electrode material prepared by the inventive method have good repeatability, and the structural stability is excellent;

[0020] 5) The prepared negative electrode material can obtain a specific capacity of 500 mAh g-1 after 300 cycles at a current density of 0.1 Ag-1, and a specific capacity of 188 mAh g-1 after 20,000 cycles at a high current density of 10 Ag-1. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The porous nanofiber Ge / GeO synthesized by the method of the present invention 2 / SEM image of NC;

[0022] Figure 2 The porous nanofiber Ge / GeO synthesized by the method of the present invention2 / TEM image of NC;

[0023] Figure 3 The Ge / GeO synthesized by the method of the present invention 2 / NC XRD test results;

[0024] Figure 4 The Ge / GeO synthesized by the method of the present invention 2 Electrochemical performance diagram of / NC negative electrode materials.

[0025] Figure 5 The Ge / GeO synthesized by the method of the present invention 2 Electrochemical performance diagram of / NC negative electrode materials. DETAILED DESCRIPTION

[0026] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] Example 1

[0028] Porous Nanofiber Ge / GeO 2 / NC composite material, prepared by the following steps:

[0029] (1) 0.5gGeO 2 Dissolve in a solution of 20 ml of deionized water and 5 ml of ammonia water, recorded as solution A, then dissolve 0.3 g of sodium borohydride in 15 ml of deionized water, and add the solution to solution A, and stir magnetically for 24 hours until the solution reacts completely; centrifuge the mixed solution and wash it five times with deionized water, and place the obtained sample in a 60°C constant temperature drying oven to dry to obtain a precursor;

[0030] (2) dissolving 1 g of polyacrylonitrile in 10 ml of N,N-dimethylformamide solution and stirring magnetically until the solute is completely dissolved, adding the precursor powder collected in step (1) to the above solution and stirring magnetically for 12 hours to obtain a precursor solution, transferring the solution to a 10 ml syringe and performing electrostatic spinning at a positive pressure of 12 KV and a negative pressure of -2.6 KV, and drying the obtained spinning membrane under vacuum conditions for 12 hours;

[0031] (3) placing the obtained dried electrospun membrane on a porcelain boat and transferring it into a corundum tube furnace, and keeping it at 280° C. for 3 hours at a heating rate of 1° C. / min in an air atmosphere, and then keeping it at 500° C. for 3 hours at a heating rate of 2° C. / min in an argon atmosphere to obtain a sample,

[0032] Figure 1 , Figure 2 Porous nanofiber Ge / GeO 2 The SEM and TEM images of / NC show that the morphology of the synthesized nanofibers is porous and the Ge / GeO 2 There are no obvious lattice fringes on the carbon fiber inside and outside, proving its amorphous structure. Figure 3 Porous nanofiber Ge / GeO 2 From the XRD spectrum of the / NC sample, it can be seen that there is no obvious diffraction peak, which proves its amorphous structure.

[0033] The porous nanofiber Ge / GeO 2 / NC was made into 2032 type half-cells according to the following method for electrochemical performance testing:

[0034] Weigh Ge / GeO in a mass ratio of 7:2:1 2 / NC, Ketjen black and polyvinylidene fluoride were put into a mortar, and a certain amount of N-methylpyrrolidone was added. After sufficient grinding, it was coated on a copper foil and vacuum dried for 12 hours. After sufficient drying, it was punched into a circular piece with a diameter of 10 mm. The copper foil coated with active material was used as the negative electrode, 5% fluoroethylene carbonate was used as an additive, diethyl carbonate dissolved with 1 mol sodium hexafluorophosphate and ethylene carbonate solution (1:1 volume ratio) were used as electrolytes, glass fiber was used as a diaphragm, sodium was used as a counter electrode, and a 2032 type half-cell was made in a glove box filled with argon. All performance tests were carried out on two devices, LANHE 3001A and CHI-760E. The sample with the highest performance was calcined at 500°C. Its electrochemical performance at lower currents and cycle performance at high currents are shown in Figure 2. Figure 4 and 5 As shown, it can obtain a specific capacity of 500 mAh / g after 300 cycles at a current density of 0.1 A / g, and a specific capacity of 188 mAh / g after 20,000 cycles at a high current density of 10 A / g.

[0035] Example 2

[0036] Porous Nanofiber Ge / GeO 2 / NC, prepared by the following steps:

[0037] (1) 0.5gGeO 2 Dissolve it in a solution of 20 ml deionized water and 5 ml ammonia water, recorded as solution A. Then dissolve 0.3 g of sodium borohydride in 15 ml deionized water and add the solution to solution A. Stir magnetically for 24 hours until the solution reacts completely. Centrifuge the mixed solution and wash it five times with deionized water. Place the obtained sample in a constant temperature drying oven at 60°C and dry it to obtain a precursor.

[0038] (2) Dissolve 1 g of polyacrylonitrile in 10 ml of N,N-dimethylformamide solution and stir magnetically until the solute is completely dissolved. Add the precursor powder collected in step (1) to the above solution and stir magnetically for 12 hours to obtain a precursor solution. Transfer the solution to a 10 ml syringe and perform electrostatic spinning at a positive pressure of 12 KV and a negative pressure of -2.6 KV. The obtained spinning membrane is dried under vacuum conditions for 12 hours.

[0039] (3) The obtained dried electrospun membrane was placed on a porcelain boat and transferred into a corundum tube furnace, and kept at 280°C for 3 hours at a heating rate of 1°C min in an air atmosphere, and then kept at 400°C for 3 hours at a heating rate of 2°C / min in an argon atmosphere to obtain a sample.

[0040] Example 3

[0041] Porous Nanofiber Ge / GeO 2 / NC, prepared by the following steps:

[0042] (1) 0.5gGeO 2 Dissolve it in a solution of 20 ml deionized water and 5 ml ammonia water, recorded as solution A. Then dissolve 0.3 g of sodium borohydride in 15 ml deionized water and add the solution to solution A. Stir magnetically for 24 hours until the solution reacts completely. Centrifuge the mixed solution and wash it five times with deionized water. Place the obtained sample in a constant temperature drying oven at 60°C and dry it to obtain a precursor.

[0043] (2) Dissolve 1 g of polyacrylonitrile in 10 ml of N,N-dimethylformamide solution and stir magnetically until the solute is completely dissolved. Add the precursor powder collected in step (1) to the above solution and stir magnetically for 12 hours to obtain a precursor solution. Transfer the solution to a 10 ml syringe and perform electrostatic spinning at a positive pressure of 12 KV and a negative pressure of -2.6 KV. The obtained spinning membrane is dried under vacuum conditions for 12 hours.

[0044] (3) The obtained dried electrospun membrane was placed on a porcelain boat and transferred into a corundum tube furnace, and kept at 280°C for 3 hours at a heating rate of 1°C / min in an air atmosphere, and then kept at 600°C for 3 hours at a heating rate of 2°C / min in an argon atmosphere to obtain a sample.

[0045] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0046] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A porous nanofiber-shaped Ge / GeO2 / NC sodium ion battery negative electrode material, characterized in that: The material consists of nanometer-scale nanofibers, and the outside of Ge / GeO2 is surrounded and protected by nitrogen-doped porous carbon nanofibers. The material is applied to the negative electrode of a sodium ion battery.

2. The porous nanofibrous Ge / GeO2 / NC sodium ion battery negative electrode material according to claim 1, characterized in that: The surface of the material has a porous structure.

3. The porous nanofibrous Ge / GeO2 / NC sodium ion battery negative electrode material according to claim 2, characterized in that: The nanofibers have obvious morphological features and are evenly distributed.

4. A method for preparing a porous nanofibrous Ge / GeO2 / NC sodium ion battery negative electrode material according to any one of claims 1 to 3, characterized in that: The following steps are included: 1) dissolving germanium oxide in a mixed solution of deionized water and ammonia water, and mixing a sodium borohydride solution dissolved in deionized water with the solution, and obtaining a uniform solution after magnetic stirring; 2) filtering the uniform solution obtained in step 1), drying the obtained sample, mixing it with a polyacrylonitrile solution dissolved in N,N-dimethylformamide, stirring it magnetically, and then using electrostatic spinning technology to obtain a uniform spinning membrane; 3) After vacuum drying the spinning membrane obtained in step 2), a two-step calcination technique is used to obtain a porous nanofiber-shaped Ge / GeO2 / NC sodium ion battery negative electrode material.

5. The method for preparing a porous nanofibrous Ge / GeO2 / NC sodium ion battery negative electrode material according to claim 4, characterized in that: In the step 3), the annealing temperature of the second step of the two-step calcination is 400-600°C.

6. The method for preparing a porous nanofibrous Ge / GeO2 / NC sodium ion battery negative electrode material according to claim 5, characterized in that: The negative electrode material prepared by the above method is 0.1Ag -1 After 300 cycles at a current density of 500 mAh g -1 The specific capacity at 10Ag -1 After 20,000 cycles at a high current density, 188 mAh g -1 Specific capacity.

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