WO2017113125A1

WO2017113125A1 - V2o5-c-sno2 hybrid nanobelt as anode material for lithium ion battery and preparation method therefor

Info

Publication number: WO2017113125A1
Application number: PCT/CN2015/099581
Authority: WO
Inventors: 程春; 张林飞; 张圣亮
Original assignee: 南方科技大学
Priority date: 2015-12-29
Filing date: 2015-12-29
Publication date: 2017-07-06
Also published as: CN108475768A; CN108475768B

Abstract

Disclosed are a V₂O₅-C-SnO₂ hybrid nanobelt used in an anode material for a lithium ion battery and a preparation method therefor, wherein the hybrid nanobelt is an ultra-dispersed SnO₂ nanocrystal connected on the V₂O₅ surface via amorphous carbon. The preparation method comprises loading SnO₂ onto the V₂O₅ ultra-thin nanobelt via a glucose connection. The V₂O₅-carbon-SnO₂ hybrid nanobelt anode material of the present invention shows a highly stable cyclicity. In the present invention, a simple two-step hydrothermal method is used for preparing an ultra-thin V₂O₅-carbon-SnO₂ hybrid nanobelt, and the difficulty of poor interaction between SnO₂ and V₂O₅ is overcome by introducing glucose as a special connecting and carburizing agent.

Description

V2O5-C-SnO2 hybrid nanobelt as anode material of lithium ion battery and preparation method thereof

Technical field

The present invention belongs to the field of lithium ion battery, particularly to a high-performance V as an anode material for lithium ion batteries _₂ O ₅ -C-SnO ₂ (i.e., V ₂ O ₅ - carbon -SnO ₂₎ hybrid nanoribbons.

Background technique

As one of the most important energy storage devices, due to the many advantages of lithium ion batteries (LIB), such as high energy density, environmental friendliness and light weight, it has been studied in depth in recent years ^1-3 . Although graphite is the primary anode material for commercial LIB, its relatively low theoretical capacity (372 mA h g ^-1 ) greatly hampers the development of LIB with high energy density ^4,5 . When used as an anode in lithium ion batteries, transition metal oxides have attracted more attention than commercial graphite due to their high theoretical capacity and abundant source of raw materials ^6-12 . In order to be used as the cathode or anode of LIB, the nanostructured active material has a short lithium ion diffusion distance, easy strain relaxation during electrochemical cycling, and a very large surface to volume ratio when in contact with the electrode, which can improve LIB Capacity and cycle life ^13-16 .

However, in ordinary batteries, nanomaterials often self-aggregate due to high surface energy, which reduces the effective contact area of the active material, the conductive agent, and the electrolyte. How to maintain the effective contact area and make full use of the advantages of nano-active materials remains a challenge and is of great significance.

V ₂ O ₅ due to its high specific capacity, the natural abundance and relatively low cost material for a lithium anode is applied ^{17, 18} in-depth study. In addition, V ₂ O ₅ is also an ideal material for high energy anodes. If V ⁵⁺ can be reduced to V ⁰ , it exhibits a high theoretical capacity of 1472 mA h g ^{-1 and} a maximum capacity of ^19-22 among all metal oxides. However, limited data is available for the V ₂ O ₅ anode, where the potential high capacity cannot be achieved ^{22-24 with} stable cycle performance. For example, Liu et al. Reported that V _₂ O ₅ -SnO ₂ nanocapsule double-shell, which shows a reversible capacity 600mA h ^g-1 at ¹⁶ after 50 cycles 250mA g ^-1. Recent studies of vanadium oxide airgel displays only 30 cycles at a high capacity rate of 118mA g ^-1 to ²² 1000mA h g ^-1. In addition, structural degradation, poor electrochemical kinetics, and low electronic conductivity have severely hampered their further development. For example, Sun et al. applied graphene to amorphous V ₂ O ₅ by atomic layer deposition to enhance electronic conductivity and electrochemical activity ¹⁹ .

SnO ₂ because of its abundance secure lithiated potential and a high theoretical capacity (782mA h g ^-1) is one of the most intensively studied of the anode material ^25. However, SnO ₂ is usually due to alloying Li- / alloying process to the large volume expansion (up to 250%) and agglomerated, pulverized lead electrodes ²⁶ and rapid capacity fade. One of the mitigation strategies is to establish a heterostructure of SnO ₂ with other materials that can buffer excessive volume changes. Due to the low volume change during lithiation/delithiation, V ₂ O ₅ has been proposed as a promising candidate for the mechanical support of SnO ₂ by forming nanocapsules ¹⁶ , nanosheets ²⁷ , and core-shell nanowires ²⁸ .

Inspired by previous research, we have developed a simple strategy for coating SnO ₂ onto V ₂ O ₅ nanoribbons via glucose bonding to achieve high power density and high energy density LIB.

Summary of the invention

One of the objects of the present invention is to provide a V ₂ O ₅ -C-SnO ₂ (i.e., V ₂ O ₅ -carbon-SnO ₂ ) hybrid nanobelt as a high performance anode for a lithium ion battery. The hybrid nanoribbon provided by the present invention, when used as an anode material for a lithium ion battery (LIB), exhibits a much higher reversible capacity and structural stability than the carbon-V ₂ O ₅ hybrid nanobelt.

In order to achieve the above object, the present invention adopts the following technical solutions:

A V ₂ O ₅ -C-SnO ₂ hybrid nanobelt for a lithium ion battery anode material, the ultra-dispersed SnO ₂ nanocrystal is tightly attached to the V ₂ O ₅ surface by amorphous carbon. In the hybrid nanobelt of the present invention, the nanostructured V ₂ O ₅ functions not only as a support matrix but also as an active electrode component, and when used as an anode material of a lithium ion battery (LIB), exhibits a specific ratio of carbon-V ₂ O _{5 .} The nanoribbons have much higher reversible capacity and structural stability. The cycle performance of the excellent VCSN can be attributed to the synergistic effect of SnO ₂ and V ₂ O ₅ .

Preferably, the SnO 2 nanocrystals have a diameter of less than 10 nm, preferably 3-6 nm.

Preferably, the hybrid nanobelt has a lattice period of 0.33±0.02 nm.

Preferably, the hybrid nanobelt has a thickness of 5 to 20 nm, for example, 8 nm, 13 nm, 18 nm or the like, and preferably 7 to 15 nm. The ultra-thin features of the hybrid nanoribbons of the present invention can increase electron transfer and shorten the lithium diffusion path, resulting in increased power density.

Preferably, the mass ratio of the SnO ₂ , V ₂ O ₅ , and carbon is: 0.015-0.045:0.065-0.2:0.08-0.25, for example, 0.015-0.04:0.07-0.2:0.1-0.2, 0.02-0.03 : 0.07-0.15: 0.15-0.25, 0.03-0.04: 0.15-0.2: 0.08-0.15, and the like. Selecting the ratio of this range, the hybrid nanobelt has good dispersibility and is ideal for use as an electrode material. Beyond this range, the electrical properties are gradually attenuated, and the nanoribbon structure also begins to decompose and fracture.

It is also an object of the present invention to provide a method for preparing a V ₂ O ₅ -C-SnO ₂ hybrid nanobelt for a lithium ion battery, which supports loading SnO ₂ to V ₂ O ₅ nm through a glucose linkage. Bring it.

Preferably, the method first dissolves SnCl _{2 in a} solution of V ₂ O ₅ nanobelts to culture the seed crystal; then, the seed crystal is adsorbed onto the surface of the V ₂ O ₅ nanobelt by means of glucose.

Advantageously, the method comprises the steps of:

(1) dissolving SnCl _{2 in a} solution of V ₂ O ₅ nanobelts, and then adding an aqueous glucose solution;

(2) after the occurrence of suspended solids, the resulting mixture is sealed and heated;

(3) The black product was collected after cooling; then washed and dried.

Glucose plays an important role in the formation of hybrid nanoribbons with ideal morphology. The reaction in the absence of glucose results in irregular and broken nanoribbons. When glucose is replaced with a conventional nanomaterial synthesis additive such as polyethylene glycol 2000 (PEG2000), the resulting nanobelts appear as small, agglomerated blocks having a length of 10 nm to 500 nm. Therefore, the introduction of glucose not only immobilizes the SnO ₂ seed on the V ₂ O ₅ nanobelt, which enables the in-situ growth of the superdisperse SnO ₂ nanocrystals, but also serves as an effective physical support for V ₂ O ₅ has the form of nanoribbons integrity.

Wherein, the V ₂ O ₅ nanobelts can be prepared using methods in the prior art. For example, the method ²⁹ using the modified Zhu is synthesized from a V ₂ O ₅ powder. Briefly, V ₂ O ₅ powder, H ₂ O ₂ and deionized water were mixed until a clear solution was obtained, and then the mixture was placed in a reactor and maintained at 150-250 ° C for 15 hours or more to form V ₂ O ₅ nm. band. The resulting brick red floc was collected by separation and washed with absolute ethanol. Finally, the resulting V ₂ O ₅ nanobelts were dispersed in deionized water for later use.

_{_{_{Advantageously, SnCl 2, V 2 O 5}}} , as the mass ratio of the three glucose: 0.01-0.06:0.05-0.208:0.2-0.8, for example 0.01-0.05:0.1-0.208:0.4-0.8,0.02-0.06:0.05 -0.108: 0.2-0.5, 0.03-0.05: 0.15-0.208: 0.3-0.6, and the like. By selecting the ratio of this range, the final product obtained by the synthesis has good dispersibility, and the nanobelt is uniform and intact, and is not damaged, and is preferably used as an electrode material. Beyond this range, the electrical properties are gradually attenuated, and the nanoribbon structure also begins to decompose and fracture.

Preferably, the mass concentration of V ₂ O ₅ in the solution of the V ₂ O ₅ nanobelt in the step (1) is 5-20 mg/mL, for example, 8 mg/mL, 13 mg/mL, 16 mg/mL, and 19 mg/mL. Etc., preferably 10-15 mg/mL, more preferably 12 mg/mL.

Preferably, the concentration of glucose in the aqueous glucose solution in the step (1) is 0.02-0.10 mol/L, for example, 0.03 mol/L, 0.07 mol/L, 0.095 mol/L, etc., preferably 0.04-0.06 mol/L. More preferably, it is 0.05 mol/L.

Preferably, the aqueous glucose solution is added to the step (1) with stirring.

Preferably, the heating temperature in the step (2) is 170-200 ° C, for example, 170 ° C, 175 ° C, 189 ° C, 195 ° C, etc., preferably 170-180 ° C, more preferably 170 ° C; heating time It is 4h or more, for example, 4.5h, 5.5h, 6.0h, 8.5h, 10h, 15h, etc., Preferably it is 5-12h, More preferably, it is 8h.

Preferably, the cooling in step (3) is to cool to room temperature.

Preferably, the collection in step (3) is carried out by centrifugation.

Preferably, the rotational speed of the centrifugation is 4,000-8000 rpm, preferably 6000 rpm; the time of centrifugation is 3 min or more, preferably 4-6 min, more preferably 5 min.

Preferably, the washing in the step (3) is carried out sequentially using distilled water and absolute ethanol to remove ions and possible residues, preferably 2 times or more, more preferably 3-6 times, particularly preferably 4 times.

Preferably, the drying in step (3) is carried out under vacuum.

Preferably, the drying temperature in the step (3) is 50-100 ° C, for example, 55 ° C, 70 ° C, 85 ° C, 92 ° C, 98 ° C, etc., preferably 60-90 ° C, more preferably 80 ° C; The drying time is 3 h or more, for example, 3.6 h, 4.5 h, 5.5 h, 6.0 h, 8.5 h, 10 h, 15 h, etc., preferably 6-12 h, more preferably 8 h.

Advantageously, the method comprises the steps of:

(1) Dissolving SnCl _{2 in a} solution of 5-20 mg/mL of V ₂ O ₅ nanobelts, and then adding a glucose aqueous solution having a concentration of 0.02-0.10 mol/L; SnCl ₂ , V ₂ O ₅ , and glucose. The mass ratio is: 0.01-0.06:0.05-0.208:0.2-0.8;

(2) After the brown suspension appears, the resulting mixture is transferred to an autoclave and heated at 170-200 ° C for more than 4 h;

(3) After cooling to room temperature, the black product was collected by centrifugation; then washed with distilled water and absolute ethanol at least four times in sequence, and dried at 50-100 ° C for more than 3 h under vacuum.

The present invention provides a simple two-step hydrothermal process for the preparation of ultra-thin V ₂ O ₅ -C-SnO ₂ hybrid nanoribbons (denoted as VCSN). Incorporated by excellent carbonate linking agent and agent interaction glucose overcome the difference between the _₂ O ₅ SnO ₂ and V. The resulting VCSN showed a highly stable cycle with a highly reversible capacity of 800 mA h g ^-1 after 100 cycles at a current density of 200 mA g ^-1 . The improved cycle stability and rate performance of these hybrid nanoribbons can be attributed to their unique structural design and synergistic effects between SnO ₂ and V ₂ O ₅ . In addition, the ultra-thin features of VCSN can increase electron transfer and shorten the lithium diffusion path, resulting in increased power density.

The ultrathin V ₂ O ₅ -carbon-SnO ₂ hybrid nanobelts of the present invention can be prepared by a solution-based method having a high yield. These nanoribbons provide a short lithium ion path with a stable structure and high electron and ion conductivity. This property is achieved by using glucose as a carbonic acid agent for the formation of monodisperse SnO ₂ nanocrystals on the surface of the V ₂ O ₅ nanobelt and the linker which delays structural fracture. As anode materials for LIB, these hybrid nanobelts exhibit extremely high reversible capacity, excellent cycle performance, and good rate performance. The controlled growth strategy of the multicomponent metal oxides of the present invention can motivate new ways to fabricate nanostructures for functional nanocomposites with improved performance in applications such as solar light conversion, energy storage, and water splitting. Reasonable design of the material.

DRAWINGS

Figure 1 (A) is a TEM image of ultra-thin V ₂ O ₅ nanobelts dispersed in water; (B) is an XRD pattern of pure V ₂ O ₅ nanoribbons;

Figure 2 is a glucose-induced transformation pathway for preparing VCSN;

In Fig. 3, (A) is a TEM image of VCSN, (B) and (C) are HRTEM images of VCSN, and (D) is a V ₂ O ₅ -based nanocomposite synthesized by hydrothermal method at 170 ° C for 8 hours. XRD image;

Figure 4 is a TEM image of a sample synthesized by adding different amounts of SnCl ₂ ; wherein, (A) 10 mg, (B) 60 mg, (C) 80 mg, (D) 100 mg;

Figure 5 (A) shows the cyclic voltammetry curve of VCSN at 0.01-3.0 V at a scan rate of 0.2 mV s ^-1 ; (B) is the charge-discharge curve, (C) is the cycle of the VCSN base electrode at 200 mAg ^-1 Performance, (D) is the rate performance of VCSN at different current densities;

(A) and (B) of FIG. 6 are TEM images of different magnifications of the VCSN base electrode after complete discharge at 200 mAg ^-1 ;

Figure 7 is a low magnification TEM image of VCSN synthesized in the absence of glucose;

Figure 8 is an EDX spectrum of VCSN;

Figure 9 is a nitrogen adsorption/desorption isotherm of VCSN, and V ₂ O ₅ /SnO ₂ samples;

Figure 10 is a TEM image of a V ₂ O ₅ /SnO ₂ nanocomposite synthesized without glucose (A) and with PEG2000 (B);

Figure 11 is a graph showing the charge and discharge capacity versus cycle number of a V ₂ O ₅ /SnO ₂ nanocomposite at a current density of 200 mAg ^-1 ;

Fig. 12(A) shows the charge-discharge voltage distribution, and (B) shows the carbon-V ₂ O ₅ core-shell under the voltage range of 0.01-3.0 V at a current density of 200 mAg ^-1 and a cycle number of 100 times. Cyclic performance of nanobelts;

Figure 13 is an impedance diagram of an electrode composed of a VCSN and a V ₂ O ₅ /SnO ₂ composite material;

Figure 14 is an XPS spectrum of complete discharge ((A) and (B)) and full charge ((C) and (D)) of VCSN.

detailed description

To facilitate an understanding of the invention, the invention is set forth below. It should be understood by those skilled in the art that the present invention is only to be construed as a

All chemicals in the present invention were of analytical grade and were used without further purification.

Example 1

Synthesis of ultra-thin V ₂ O ₅ nanobelts

First, the V ₂ O ₅ thin nanoribbons using a modified method of synthesizing Zhu ²⁹ from V ₂ O ₅ powder. Mix 0.36 g of V ₂ O ₅ powder, 5 mL of 30% H ₂ O ₂ , and 30 mL of deionized water until a clear solution is obtained, then place 35 mL of this mixture in a 100 mL Teflon autoclave and hold at 190 ° C for 20 hours. To form a V ₂ O ₅ nanobelt. The resulting brick red floes were collected by centrifugation (8,000 rpm for 5 min) and washed three times with absolute ethanol. Finally, the resulting V ₂ O ₅ nanobelts were dispersed in 70 mL of deionized water for later use.

Synthesis of V ₂ O ₅ -C-SnO ₂ Hybrid Nanobelts (VCSN)

VCSN is prepared by simple hydrothermal action. In a typical synthesis, 0.04 g of SnCl ₂ ·2H ₂ O was dissolved in a solution of 30 mL of V ₂ O ₅ nanobelts, and then 40 mL of a 0.05 mol/L aqueous glucose solution was added with stirring. After 30 minutes, a brown suspension appeared, which was transferred to a 100 mL lined Teflon autoclave, sealed in an oven at 170 ° C for 8 hours, and then naturally cooled to room temperature. The obtained black product was collected by centrifugation (6,000 rpm for 5 min), and then washed with distilled water and absolute ethanol at least four times in order to remove ions and possible residues, and finally, dried at 80 ° C for 6 hours under vacuum.

Comparative example 1

Synthesis of V ₂ O ₅ /SnO ₂ Hybrid

The V ₂ O ₅ /SnO ₂ hybrid preparation process was similar to the above VCSN synthesis except that glucose was not introduced into the final reaction solution.

Material characterization

Use of Ni-filtered Cu K α radiation (

An X-ray diffraction (XRD) pattern was performed on a Bruker D8 advanced X-ray diffractometer at 40 kV and 25 mA. Transmission electron microscopy images (TEM), high-resolution transmission electron microscopy images (HRTEM), and energy dispersive X-ray spectroscopy (EDS) analysis were captured by a JEOL-2010 microscope with an acceleration voltage of 200 kV. Nitrogen adsorption measurements were performed using a Micromeritics ASAP 2020 system at 77 K using Barrett-Emmett-Teller (BET) to calculate surface area. Nitrogen adsorption measurements were taken on Autosorb 6B at liquid nitrogen temperature.

Electrochemical characterization

Electrochemical testing was performed in a 2032 button cell. The working electrode consisted of 80 wt% active material, 10 wt% conductive carbon black (Super-P-Li), and 10 wt% polymer binder (polyvinylidene fluoride, PVDF). The electrolyte was 1 M LiPF ₆ in a mixture of ethylene carbonate and diethyl carbonate (1:1 by volume). Lithium foil is used as a counter electrode which is separated from the working electrode by glass fibers. Battery assembly was performed in a glove box with a humidity and oxygen concentration below 1.0 ppm. The charge and discharge test was performed on the NEWARE battery detector. For anode performance measurements, the cells were charged/discharged in voltage windows of 0.01-3.0 V at different current densities. Cyclic voltammogram (CV) measurements were performed on a CH instrument model 600C electrochemical workstation at a scan rate of 0.2 mV s ^-1 . Electrochemical impedance spectroscopy (EIS) measurements were performed on the working electrode in the frequency range of 100 kHz to 0.01 Hz with 5 mV AC disturbance. The EIS data is analyzed using a Nyquist map representing the virtual portion (Z') and the real portion (Z") of the impedance.

Figure 1 (A) is a TEM image of the ultra-thin V ₂ O ₅ nanobelts dispersed in water prepared in Example 1; (B) is an XRD pattern of pure V ₂ O ₅ nanoribbons; (A in Figure 1) The TEM image shows that the newly prepared V ₂ O ₅ nanoribbon substrate has a width of 50-80 nm and a length of up to several tens of micrometers, and is characterized by flexibility, smoothness, thinness, and almost transparency. Figure 2 is a glucose-induced transformation pathway for the preparation of VCSN. Fig. 3 (A) is a TEM image of VCSN prepared in Example 1, (B) and (C) are HRTEM images of VCSN, and (D) is V ₂ synthesized by hydrothermal method at 170 ° C for 8 hours. An XRD image of the O ₅ -based nanocomposite; the thickness of the carbon coating as shown in (C) is about 2 nm. Figure 4 is a TEM image of a sample synthesized by adding different amounts of SnCl ₂ ; (A) 10 mg, (B) 60 mg, (C) 80 mg, (D) 100 mg. FIG. 5 (A) is prepared in Example 1 at a scan rate of 0.2mVs ^-1 0.01-3.0V VCSN in the cyclic voltammetry; (B) is a charge-discharge curve, (C) as 200mAg ^-1 The cycle performance of the lower VCSN base electrode, (D) is the rate performance of VCSN at different current densities. Fig. 6 (A) and (B) are TEM images of different magnifications of the base electrode prepared in VCSN Example 1 after complete discharge at 200 mAg ^-1 .

An ultrathin V ₂ O ₅ nanobelt synthesized by a hydrothermal method was used as a starting template material. Transmission electron microscopy (TEM) studies have shown that these V ₂ O ₅ nanoribbons are highly uniform, with a thickness of 4 nm and a length of 800 nm to several microns, which means a large aspect ratio of >200 ((A) of Figure 1) . Due to the high uniformity and relatively large aspect ratio, the V ₂ O ₅ nanobelts can be used as an excellent template to support the growth of SnO ₂ nanocrystals by a simple glucose-assisted hydrothermal method. As observed from the X-ray diffraction (XRD) pattern in (B) of Fig. 1, the XRD pattern shows a strong peak which can be classified as orthorhombic V ₂ O ₅ (JCPDS No. 40-1296). In order to grow the nanocrystals, SnCl _{2 is} first dissolved in a solution of V ₂ O ₅ nanobelts to culture the seed crystals. These seeds are then adsorbed onto the surface of the V ₂ O ₅ nanoribbon by means of glucose, which occurs due to the affinity of SnO ₂ and V ₂ O ₅ for the -OH group (Fig. 2) ^30,31 .

(A) of Fig. 3 shows a TEM image of the prepared VCSN. The hybrid nanoribbon has a length of a few microns and a width of 50-80 nm. The aggregate morphology of the hybrid nanoribbons as shown in Figure 7 shows excellent uniformity and dispersibility. Typical high resolution TEM (HRTEM) analysis ((B) and (C) of Figure 3) on these hybrid nanoribbons clearly shows the dense growth of SnO ₂ nanocrystals on the V ₂ O ₅ surface . The fixed SnO ₂ nanocrystals have a diameter of less than 5 nm. A lattice period of 0.33 nm, which corresponds to the intermediate wing pitch of the (110) crystal plane of the tetragonal SnO ₂ , is clearly observed in (B) of FIG. An enlarged TEM image recorded on the edge of the nanoribbon in (C) of Figure 3 indicates that the entire surface of the nanoribbon is covered with a continuous amorphous carbon layer having a thickness of about 2 nm. The X-ray diffraction (XRD) pattern of the hybrid nanobelts ((D) of Fig. 2) shows that all of the XRD peaks can be well indexed into a tetragonal SnO ₂ phase (JCPDS No. 41-1445) and orthorhombic V _{2 .} O ₅ phase (JCPDS No. 40-1296). Equivalently, the XRD peak of VCSN is relatively wider and weaker than the synthesized V ₂ O ₅ nanoribbon template (Fig. 1 (B)). And some peaks are incorporated into the background. This is attributable to the smaller size of the V ₂ O ₅ and SnO ₂ nanocrystals in the composite as determined by the TEM study above ((B) of Figure 3). The energy dispersive X-ray spectroscopy (EDS) pattern (Figure 8) shows that the hybrid nanoribbon consists of Sn, V, C, and O, which is consistent with the above TEM and XRD measurements, with a weight ratio of V to Sn of 10; EDS analysis confirmed There is a representative peak corresponding to the Sn and O elements and an atomic ratio of Sn/O of about 30:66. The surface area of the prepared hybrid nanoribbons was investigated using an N ₂ adsorption isotherm. As shown in FIG. 9, with having found that nano hybrid 132.9m ² / g of Barrett-Emmett-Teller (BET) surface area, than V _₂ O ₅ / SnO ₂ samples (28.3m ² / g) to about 4.7 times.

As a result, it was found that glucose plays an important role in the formation of a VCSN having a desired morphology (Fig. 7). The reaction in the absence of glucose causes irregular and broken nanoribbons ((A) in Figure 10). When glucose is replaced with a common nanomaterial synthesis additive such as polyethylene glycol 2000 (PEG2000), the resulting nanobelt appears as a small and entangled block having a length of 10 nm to 500 nm ((B) in Fig. 10). Therefore, the introduction of glucose not only immobilizes the SnO ₂ seed crystal on the V ₂ O ₅ nanobelt, which enables the in-situ growth of the ultra-dispersed SnO ₂ nanocrystals, but also serves as an effective physical support for V ₂ O _{The 5} nanoribbons have morphological integrity.

Furthermore, the initial amount of SnCl ₂ significantly affects the final morphology of the hybrid nanoribbon. Figure 4 shows the TEM image using the product prepared SnCl ₂ when other conditions remain unchanged plus different amounts. When the amount of SnCl ₂ is less than 60 mg, a hybrid nanobelt having a desired morphology can be obtained in high yield ((A) and (B) of Fig. 4). When the amount of SnCl ₂ is more than 60 mg ((C) and (D) of Fig. 4), a hybrid nanobelt having a pore diameter of 10 to 50 nm is formed, sometimes even broken. The formation of these high porosity hybrid nanoribbons can be attributed to the fact that the V ₂ O ₅ nanoribbons react with excess Sn ²⁺ cations by selective cation exchange. For hydrothermal exchange reaction Nano porous Cd _{_x} Zn _{_1-x} S nanosheet by cation reported similar phenomenon ^32.

We subsequently studied the electrochemical performance of these VCSNs as anode materials for LIB. (A) of Fig. 5 shows a cyclic voltammogram (CV) of the first 5 consecutive cycles in a voltage window of 0.01 - 3.0 V at a scanning rate of 0.2 mV s ^-1 . This CV characteristic is basically consistent with that reported in the literature ^33-35 , indicating the same electrochemical reaction pathway. (B) of FIG. 5 shows a charge and discharge curve of a Li/V ₂ O ₅ -carbon-SnO ₂ battery. At a current density of 200 mAg ^-1 , the first discharge and charge capacities were 2075 and 1205 mAh g ^{-1 , respectively} . During the initial cycle, a large irreversible capacity and an initial coulombic efficiency of 58% occurred, which is attributable to the formation of a solid electrolyte interface (SEI) layer on the surface of the VCSN electrode.

Due to the different redox reactions associated with lithium insertion/precipitation, multiple voltage platforms can be observed in the first charge and discharge curve ((A), (B) of Figure 5). Although SnO ₂ theoretically has a high capacity of 782 mAhg ^-1 of ²⁵ , most of these VCSNs are derived from V ₂ O ₅ because only 10% by weight of the composite material is SnO ₂ . If it is assumed that when the composite is discharged to 0 V and V ₂ O ₅ can be reduced to metal V, the theoretical capacity of the Li insertion reaction is 1472 mAhg ^-1 , which explains the high reversible capacity of the nanocomposite as an anode material ^{19- 22} .

(C) of Fig. 5 shows the cycle performance of the anode composite cycled 100 times at a current density of 200 mAg ^-1 . After 50 cycles, the hybrid nanoribbon still showed a high reversible capacity of 930 mAhg ^-1 and a capacity retention rate of 84.5% from the tenth cycle. After 100 cycles, the nanocomposite maintained a reversible capacity of 800 mAhg ^-1 , indicating excellent cycle stability of the VCSN. For comparison, the cycle performance of the V ₂ O ₅ /SnO ₂ composite without the carbon layer and the carbon-V ₂ O ₅ core-shell nanoribbon is provided in FIGS. 11 and 12. Under the same experimental conditions, the two samples exhibited much faster decay of its capacity, and holds only about 518mAhg ^-1 (for the V _₂ O ₅ / SnO ₂ composite) after 50 cycles and 200mAg ^-1 Capacity of 411 mAhg ^-1 (carbon-V ₂ O ₅ core-shell nanoribbon). VCSN was found to exhibit much lower resistance than the V ₂ O ₅ /SnO ₂ composite, as evidenced by a significant decrease in the diameter of the semicircle in the high frequency region in the electrochemical impedance spectroscopy (EIS) pattern (Fig. 13). Lower contact and charge transfer impedance facilitates Li ⁺ diffusion and electron transfer, which results in greatly improved electrochemical performance of VCSN.

To evaluate the rate performance, the VCSN was cycled at a voltage window of 0.01-3.0 V ((D) of Figure 5) at different current densities of 100 to 800 mAg ^-1 . As current density increases, VCSN only experiences a small drop in capacity. For example, at a high current density of 800mAg ^-1, VCSN still reversible capacity can be achieved in about 620mAhg ^-1. It is worth noting that VCN still maintains a reversible capacity of about 1005 mAhg ^-1 when the current rate drops back to 200 mAg ^-1 after more than 60 cycles, indicating excellent rate performance of VCSN. We also studied the valence states of V and Sn from full charge and discharge by XPS spectroscopy. As shown in (A) and (B) of Fig. 14, the XPS spectrum showed no significant V and Sn peaks in the complete discharge. However, in full charging, the binding energy of Sn 3d _5/2 at the center of 487.7 eV is attributed to Sn ⁴⁺ . Similarly, appendages of the V ⁵⁺ 2p _3/2 and 2p _1/2 bands at the binding energies of 516.9 and 525 eV appear, and it is clear that V ₂ O ₅ is formed in our anode material. SnO ₂ ((C) and (D) in Fig. 14) ³⁶ .

Example 2-3

Synthesis of ultra-thin V ₂ O ₅ nanobelts

Mix 0.26 g of V ₂ O ₅ powder, 5 mL of 30% H ₂ O ₂ , and 30 mL of deionized water until a clear solution is obtained, then place 35 mL of this mixture in a 100 mL Teflon autoclave and hold at 190 ° C for 15 hours. To form a V ₂ O ₅ nanobelt. The resulting brick red floes were collected by centrifugation (8,000 rpm for 5 min) and washed three times with absolute ethanol. Finally, the resulting V ₂ O ₅ nanobelts were dispersed in 140 mL of deionized water for later use.

Synthesis of V ₂ O ₅ -C-SnO ₂ Hybrid Nanobelts (VCSN) in Example 2

0.015 g of SnCl ₂ ·2H ₂ O was dissolved in a solution of 30 mL of V ₂ O ₅ nanobelts, and then 40 mL of a 0.003 mol/L aqueous glucose solution was added with stirring. After 30 minutes, a brown suspension appeared, which was transferred to a 100 mL lined Teflon autoclave, sealed in an oven at 180 ° C for 10 hours, and then naturally cooled to room temperature. The obtained black product was collected by centrifugation (8,000 rpm for 3 min), and then washed with distilled water and absolute ethanol at least four times in order to remove ions and possible residues, and finally, dried at 50 ° C for 10 hours under vacuum.

Synthesis of V ₂ O ₅ -C-SnO ₂ Hybrid Nanobelts (VCSN) in Example 3

0.06 g of SnCl ₂ ·2H ₂ O was dissolved in a solution of 30 mL of V ₂ O ₅ nanobelts, and then 40 mL of a 0.1 mol/L aqueous glucose solution was added with stirring. After 30 minutes, brown suspension appeared, transferred to a 100 mL lined Teflon autoclave, sealed in an oven at 200 ° C for 4 hours, and then naturally cooled to room temperature. The obtained black product was collected by centrifugation (4,000 rpm for 8 min), and then washed with distilled water and absolute ethanol at least four times in order to remove ions and possible residues, and finally, dried at 100 ° C for 3 hours under vacuum.

Example 4-5

Synthesis of ultra-thin V ₂ O ₅ nanobelts

Mix 0.85 g of V ₂ O ₅ powder, 5 mL of 30% H ₂ O ₂ , and 30 mL of deionized water until a clear solution is obtained, then place 35 mL of this mixture in a 100 mL Teflon autoclave and hold at 150 ° C for 30 hours. To form a V ₂ O ₅ nanobelt. The resulting brick red floes were collected by centrifugation (8,000 rpm for 5 min) and washed three times with absolute ethanol. Finally, the resulting V ₂ O ₅ nanobelts were dispersed in 140 mL of deionized water for later use.

Synthesis of V ₂ O ₅ -C-SnO ₂ Hybrid Nanobelts (VCSN) in Example 4

0.02 g of SnCl ₂ ·2H ₂ O was dissolved in a solution of 30 mL of V ₂ O ₅ nanobelts, and then 40 mL of a 0.03 mol/L aqueous glucose solution was added with stirring. After 30 minutes, brown suspension appeared, transferred to a 100 mL lined Teflon autoclave, sealed in an oven at 190 °C for 5 hours, and then naturally cooled to room temperature. The obtained black product was collected by centrifugation (6,000 rpm for 5 min), and then washed with distilled water and absolute ethanol at least four times in order to remove ions and possible residues, and finally, dried at 70 ° C for 12 hours under vacuum.

Synthesis of V ₂ O ₅ -C-SnO ₂ Hybrid Nanobelts (VCSN) in Example 5

0.05 g of SnCl ₂ ·2H ₂ O was dissolved in a solution of 30 mL of V ₂ O ₅ nanobelts, and then 40 mL of a 0.08 mol/L aqueous glucose solution was added with stirring. After 30 minutes, brown suspension appeared, transferred to a 100 mL lined Teflon autoclave, sealed in an oven at 170 °C for 12 hours, and then naturally cooled to room temperature. The resulting black product was collected by centrifugation (6,000 rpm for 5 min), followed by washing with distilled water and absolute ethanol at least four times to remove ions and possible residue, and finally, dried at 90 ° C for 5 hours under vacuum.

The V ₂ O ₅ -C-SnO ₂ hybrid nanobelts prepared in the above Examples 2-5 have similar morphology and structure to the V ₂ O ₅ -C-SnO ₂ hybrid nanoparticle prepared in Example 1, and equivalent Electrochemical performance.

The improved cycle stability and rate performance of the hybrid nanoribbons of the present invention can be attributed to the unique design of the nanostructure compositions mentioned in the present invention. First, the ultrathin nanobelt subunit has a short distance for efficient Li ⁺ ion diffusion and a large electrode-electrolyte contact area for high Li ⁺ ion flux across the interface, resulting in improved rate performance ^35,37 . Secondly, it has been reported using pure V ₂ O ₅ nanometers anode material or the nano composite material structure and morphology tends to collapse, as Li ⁺ ions frequent insertion / release cycle process can cause serious stability decreased ^38. However, in this case, the soft carbon layer acts as an excellent physical support in which the ultra-thin nanobelt subunits are tightly attached or embedded. This effectively counteracts the fragmentation of the morphology and structure of the V ₂ O ₅ based nanocomposites. Therefore, the capacity of these VCSNs is significantly improved by ^39-42 compared to many other V ₂ O ₅ -based nanostructures. Further, Sn nanoparticles (produced during the reduction of SnO ₂ when the nanocomposite is used as an anode) are embedded in a V ₂ O ₅ matrix and form an ultrafine metal oxide electrode (Fig. 6). Electrode material made in this way may have some outstanding advantages, such as good cycle for the volume change resistance, and a high electron and ion conductivity ^43.

In summary, ultrathin V ₂ O ₅ -carbon-SnO ₂ hybrid nanoribbons were prepared by a solution-based process with high yield. These nanostructures provide a short lithium ion path with a stable structure and high electron and ion conductivity. This result was achieved by using glucose as a carbonic acid agent for the formation of monodisperse SnO ₂ nanocrystals on the surface of the V ₂ O ₅ nanobelt and the linker which retards structural fracture. As anode materials for LIB, these hybrid nanobelts exhibit extremely high reversible capacity, excellent cycle performance, and good rate performance. Our multi-component metal oxide controlled growth strategy can inspire new ways to fabricate nanostructures for functional nanocomposites with improved performance in applications such as solar light conversion, energy storage and water splitting. Reasonable design.

The Applicant declares that the present invention illustrates the detailed process equipment and process of the present invention by the above embodiments. The process, but the invention is not limited to the above detailed process equipment and process flow, that is, it does not mean that the invention must be implemented by relying on the detailed process equipment and process flow described above. It should be apparent to those skilled in the art that any modifications of the present invention, equivalent substitution of the various materials of the products of the present invention, addition of auxiliary components, selection of specific means, and the like, are all within the scope of the present invention.

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Claims

A V 2 O 5 -C-SnO 2 hybrid nanobelt for a lithium ion battery anode material, characterized in that the superdispersed SnO 2 nanocrystals are attached to the V 2 O 5 surface by amorphous carbon.
The hybrid nanobelt according to claim 1, wherein the SnO 2 nanocrystal has a diameter of less than 10 nm, preferably 3-6 nm;

Preferably, the hybrid nanobelt has a lattice period of 0.33±0.02 nm.
The hybrid nanobelt according to claim 1 or 2, wherein the hybrid nanobelt has a thickness of 5 to 20 nm, preferably 7 to 15 nm;

Preferably, the mass ratio of the SnO 2 , V 2 O 5 , and carbon is: 0.015-0.045:0.065-0.2:0.08-0.25.
A method for preparing a V 2 O 5 -C-SnO 2 hybrid nanobelt for a lithium ion battery anode material, characterized in that SnO 2 is supported on a V 2 O 5 nanobelt by a glucose linkage.
The preparation method according to claim 4, wherein the SnCl 2 is first dissolved in a solution of the V 2 O 5 nanobelt to culture the seed crystal; and then the seed crystal is adsorbed to V 2 O 5 nm by means of glucose. On the surface of the belt.
The preparation method according to claim 4 or 5, comprising the steps of:

(1) The SnCl 2 dissolved in a solution of V 2 O 5 nanometers belt, followed by addition of an aqueous glucose solution;

(2) after the flocculent suspension appears, the resulting mixture is sealed and heated;

(3) The black product was collected after cooling; then washed and dried.
The preparation method according to claim 5 or 6, wherein the mass ratio of SnCl 2 , V 2 O 5 and glucose is 0.01-0.06:0.05-0.208:0.2-0.8.
The preparation method according to claim 6 or 7, wherein the concentration of V 2 O 5 in the solution of the V 2 O 5 nanobelt in the step (1) is 5-20 mg/mL, preferably 10- 15mg/mL;

Preferably, the concentration of glucose in the aqueous glucose solution is 0.02-0.10 mol/L, preferably 0.04-0.06 mol/L;

Preferably, an aqueous dextrose solution is added with agitation.
The preparation method according to any one of claims 6 to 8, wherein the heating temperature in the step (2) is 170-200 ° C, preferably 170-180 ° C; the heating time is 4 h or more, preferably 8-12h;

Preferably, the cooling in step (3) is to cool to room temperature;

Preferably, said collecting is performed by centrifugation;

Preferably, the rotational speed of the centrifugation is 4,000-8000 rpm; the time of centrifugation is more than 3 min, preferably 4-6 min;

Preferably, the washing is carried out sequentially using distilled water and absolute ethanol, preferably 2 times or more, more preferably 3-6 times;

Preferably, said drying is carried out under vacuum;

Preferably, the drying temperature is 50-100 ° C, preferably 60-90 ° C; the drying time is 3 h or more, preferably 6-12 h.
The preparation method according to any one of claims 6 to 9, comprising the following steps:

(1) Dissolving SnCl 2 in a solution of 5-20 mg/mL of V 2 O 5 nanobelts, and then adding a glucose aqueous solution having a concentration of 0.02-0.10 mol/L; SnCl 2 , V 2 O 5 , and glucose. The mass ratio is: 0.01-0.06:0.05-0.208:0.2-0.8;

(2) After the brown suspension appears, the resulting mixture is transferred to an autoclave and heated at 170-200 ° C for more than 4 h;

(3) After cooling to room temperature, the black product was collected by centrifugation; then washed with distilled water and absolute ethanol at least four times in sequence, and dried at 50-100 ° C for more than 3 h under vacuum.