A porous nanofibrous ge / geo2 / nc sodium-ion battery anode material and a preparation method thereof

Abstract

The application relates to the field of sodium ion battery negative electrode materials, and discloses a porous nanofibrous Ge / GeO2 / NC sodium ion battery negative electrode material, the material is internally provided with a Ge / GeO2 nano structure, and externally provided with a porous carbon nanofiber structure, has the advantages of simple preparation process and unique morphology, and shows good specific capacity and cycle stability.

Description

Technical Field

[0001] This invention relates to the field of sodium-ion battery anode materials, specifically a porous nanofiber-like Ge / GeO2 / NC sodium-ion battery anode material and its preparation method. Background Technology

[0002] Current research indicates that morphology engineering is one of the important methods to significantly improve the performance of sodium-ion battery anode materials. For example, Hu et al. (Hu L, Shang C, Huang L, Wang X, Zhou G. Cu3Ge coated by nitrogen-doped carbon nanorods as advanced sodium-ion battery anodes[J]. Ionics 26(2020)719-726.) prepared Cu3Ge@C anode material with carbon coating protection, which showed that it was effective at 0.1 Ag -1 After 500 cycles at a current density, 160 mAh g can be obtained. -1 The specific capacity; 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 encapsulated in a carbon framework. Due to their unique nanostructure and the protection of the carbon coating, they exhibited high specific capacity at 1.5 A g when used as a negative electrode material for sodium-ion batteries. -1 It can still maintain 201mAh g after 5000 cycles at a current density. -1 The specific capacity. Although some progress has been made in improving the performance of Ge-based composite materials, the modification processes and preparation methods of Ge-based anode materials in the prior art are relatively complex, and their low capacity hinders practical applications. Therefore, this application proposes a porous nanofiber-like Ge / GeO2 / NC sodium-ion battery anode material and its preparation method. Summary of the Invention

[0003] The purpose of this invention is to provide a porous nanofiber-like Ge / GeO2 / NC sodium-ion battery anode material and its preparation method, so as to solve the problems mentioned in the background art.

[0004] To achieve the above objectives, the present invention provides the following technical solution: a porous nanofiber-like Ge / GeO2 / NC sodium-ion battery anode material, wherein the material is composed of nanofibers, and nitrogen-doped porous carbon nanofibers are arranged around and protected on the outside of the Ge / GeO2, and the material is used as a sodium-ion battery anode.

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

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

[0007] The preparation method of the porous nanofiber-like Ge / GeO2 / NC sodium-ion battery anode material described above includes the following steps:

[0008] 1) Dissolve germanium oxide in a mixed solution of deionized water and ammonia, and mix sodium borohydride solution dissolved in deionized water with the above solution. After magnetic stirring, a homogeneous solution is obtained.

[0009] 2) The homogeneous solution obtained in step 1) is filtered, and the resulting sample is dried and then mixed with a polyacrylonitrile solution dissolved in N,N-dimethylformamide. After thorough magnetic stirring, a homogeneous spun film is obtained using electrospinning technology.

[0010] 3) After vacuum drying the spun membrane obtained in step 2), a two-step calcination technique is used to obtain porous nanofiber-like Ge / GeO2 / NC sodium-ion battery anode material.

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

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

[0013] Compared with the prior art, the beneficial effects of this invention are as follows:

[0014] This invention employs electrospinning and calcination techniques to prepare high-performance porous nanofiber-like Ge / GeO2 / NC materials. The unique structure refers to the nanoscale porous structure of the prepared material. This unique structure is achieved through the retention of the nanofiber structure and the emergence of the porous structure during electrospinning and appropriate calcination temperatures. Furthermore, the presence of nitrogen-doped carbon in this structure enhances electrical conductivity and significantly improves the reaction kinetics of the composite material, thereby increasing its rate performance. The porous nanofiber-like Ge / GeO2 / NC materials synthesized using this method exhibit excellent morphology and superior electrochemical performance.

[0015] The advantages of using the above method to prepare porous nanofiber-like Ge / GeO2 / NC materials are:

[0016] 1) A special morphology of porous nanofiber-like Ge / GeO2 / NC material was prepared. The large number of porous structures on its surface provided active sites, thereby enhancing its reaction kinetics as a sodium-ion battery anode material.

[0017] 2) The outer surface of the prepared composite material is nitrogen-doped carbon nanofibers, which greatly improves the electrical conductivity of the composite material, thereby enabling the composite material to obtain excellent electrochemical performance.

[0018] 3) The porous nanofiber-like Ge / GeO2 / NC material prepared by this method has nitrogen-doped carbon nanofibers on the outside and a protected Ge / GeO2 composite material on the inside. The outer carbon nanofibers can effectively act as a buffer layer to alleviate the large volume expansion of the inner Ge / GeO2 during repeated charge and discharge, thereby enabling the composite material to obtain excellent cycle stability.

[0019] 4) The negative electrode material prepared by this invention has good reproducibility in morphology and electrochemical performance, and excellent structural stability.

[0020] 5) The prepared anode material can obtain a specific capacity of 500 mAh g-1 after 300 cycles at a current density of 0.1 A g-1, and a specific capacity of 188 mAh g-1 after 20,000 cycles at a high current density of 10 A g-1. Attached Figure Description

[0021] Figure 1 This is a SEM image of the porous nanofiber-like Ge / GeO2 / NC synthesized by the method of this invention;

[0022] Figure 2 This is a TEM image of the porous nanofiber-like Ge / GeO2 / NC synthesized by the method of this invention;

[0023] Figure 3 These are the XRD test results of Ge / GeO2 / NC synthesized by the method of this invention;

[0024] Figure 4 This is an electrochemical performance diagram of the Ge / GeO2 / NC anode material synthesized by the method of this invention.

[0025] Figure 5 This is a graph showing the electrochemical performance of the Ge / GeO2 / NC anode material synthesized by the method of this invention. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] Example 1

[0028] The porous nanofiber-like Ge / GeO2 / NC composite material was prepared through the following steps:

[0029] (1) Dissolve 0.5g GeO2 in 20ml deionized water and 5ml ammonia water, and denote it as solution A. Then dissolve 0.3g sodium borohydride in 15ml 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 60℃ constant temperature drying oven to dry and obtain the precursor.

[0030] (2) Dissolve 1g of polyacrylonitrile in 10ml 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 syringe with a volume of 10ml and perform electrospinning at a positive pressure of 12KV and a negative pressure of -2.6KV. Dry the spun membrane under vacuum conditions for 12 hours.

[0031] (3) The dried electrospun membrane was placed on a ceramic boat and transferred into a corundum tube furnace. It was heated at 280°C for 3 hours in air at a heating rate of 1°C / min, and then heated at 500°C for 3 hours in argon at a heating rate of 2°C / min to obtain the sample.

[0032] Figure 1 , Figure 2SEM and TEM images of the porous nanofiber-like Ge / GeO2 / NC show that the morphology synthesized by this method is porous nanofiber-like, and neither the internal Ge / GeO2 nor the external carbon fibers have obvious lattice fringes, proving its amorphous structure. Figure 3 The XRD pattern of the porous nanofiber-like Ge / GeO2 / NC sample shows that there are no obvious diffraction peaks, which proves its amorphous structure.

[0033] Electrochemical performance tests were conducted on a 2032-type half-cell prepared using the porous nanofiber-like Ge / GeO2 / NC obtained in Example 1 as follows:

[0034] Ge / GeO2 / NC, Ketjen Black, and polyvinylidene fluoride were weighed out in a mortar at a mass ratio of 7:2:1 and placed in a mortar. A certain amount of N-methylpyrrolidone was added gradually, and after thorough grinding, the mixture was coated onto copper foil and vacuum dried for 12 hours. After thorough drying, it was pressed into a circular sheet with a diameter of 10 mm. The copper foil coated with the active material was used as the negative electrode. A solution of diethyl carbonate and ethylene carbonate (1:1 volume ratio) containing 1 mol of sodium hexafluorophosphate was used as the electrolyte, with glass fiber as the separator and sodium as the counter electrode. A 2032 type half-cell was fabricated in an argon-filled glove box. All performance tests were conducted on LANHE 3001A and CHI-760E equipment. The sample with the highest performance was obtained by calcination at 500℃. Its electrochemical performance at lower currents and cycling performance at higher currents were as follows: Figure 4 and 5 As shown, it can achieve 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-like Ge / GeO2 / NC was prepared via the following steps:

[0037] (1) Dissolve 0.5g GeO2 in 20ml deionized water and 5ml ammonia water, and denote it as solution A. Then dissolve 0.3g sodium borohydride in 15ml 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 60℃ constant temperature drying oven to dry and obtain the precursor.

[0038] (2) Dissolve 1g of polyacrylonitrile in 10ml 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 syringe with a volume of 10ml and perform electrospinning at a positive pressure of 12KV and a negative pressure of -2.6KV. Dry the resulting spun membrane under vacuum conditions for 12 hours.

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

[0040] Example 3

[0041] Porous nanofiber-like Ge / GeO2 / NC was prepared via the following steps:

[0042] (1) Dissolve 0.5g GeO2 in 20ml deionized water and 5ml ammonia water, and denote it as solution A. Then dissolve 0.3g sodium borohydride in 15ml 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 60℃ constant temperature drying oven to dry and obtain the precursor.

[0043] (2) Dissolve 1g of polyacrylonitrile in 10ml 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 syringe with a volume of 10ml and perform electrospinning at a positive pressure of 12KV and a negative pressure of -2.6KV. Dry the resulting spun membrane under vacuum conditions for 12 hours.

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

[0045] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

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

Claims

1. A method for preparing a porous nanofiber-like Ge / GeO2 / NC sodium-ion battery anode material, characterized in that: Includes the following steps, 1) Dissolve germanium oxide in a mixed solution of deionized water and ammonia, and mix sodium borohydride solution dissolved in deionized water with the above solution. After magnetic stirring, a homogeneous solution is obtained. 2) The homogeneous solution obtained in step 1) is filtered, and the resulting sample is dried and then mixed with a polyacrylonitrile solution dissolved in N,N-dimethylformamide. After thorough magnetic stirring, a homogeneous spun film is obtained using electrospinning technology. 3) After vacuum drying the spun film obtained in step 2), a porous nanofiber-like Ge / GeO2 / NC sodium-ion battery anode material is obtained by using a two-step calcination technique. The annealing temperature of the second calcination step is 500℃. The material is composed of nanoscale nanofibers, with nitrogen-doped porous carbon nanofibers surrounding and protecting the exterior of the Ge / GeO2. The material is used as the negative electrode of a sodium-ion battery.

2. The method for preparing a porous nanofiber-like Ge / GeO2 / NC sodium-ion battery anode material according to claim 1, characterized in that: The anode material prepared by the above method can obtain a specific capacity of 500 mAh g⁻¹ after 300 cycles at a current density of 0.1 A g⁻¹, and a specific capacity of 188 mAh g⁻¹ after 20,000 cycles at a high current density of 10 A g⁻¹.

3. The method for preparing a porous nanofiber-like Ge / GeO2 / NC sodium-ion battery anode material according to claim 1, characterized in that: The surface of the material has a porous structure.

4. The method for preparing a porous nanofiber-like Ge / GeO2 / NC sodium-ion battery anode material according to claim 3, characterized in that: The nanofibers exhibit distinct morphological characteristics and are uniformly distributed.

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