CN106099066A - A kind of germanium dioxide/graphene composite material and preparation method thereof - Google Patents

Abstract

A germanium dioxide/graphene composite material relates to the technical field of negative electrode materials for lithium-ion batteries. The composite material is formed by wrapping germanium dioxide submicron particles with graphene nanosheets; wherein, the diameter of the germanium dioxide submicron particles is 400~900nm. In the present invention, germanium dioxide powder and graphene oxide are dissolved in distilled water, and then the water is completely evaporated at 25-45°C, and the evaporated powder is calcined at 200-300°C for 1-3 hours in an air atmosphere. The composite material is obtained. The germanium dioxide/graphene composite material prepared by the present invention is used as the negative electrode material of lithium ion battery, has higher charge-discharge specific capacity, better cycle stability and fast charge-discharge performance, and the preparation method is simple, pollution-free, and the reaction temperature Low, the resulting product has high purity and no by-products.

Description

A kind of germanium dioxide/graphene composite material and preparation method thereof

technical field

The invention belongs to the technical field of inorganic energy storage materials, and relates to lithium ion battery negative electrode materials, in particular to a germanium dioxide/graphene composite material and a preparation method thereof.

Background technique

With the advantages of high capacity, long cycle life, low self-discharge rate and no memory effect, lithium-ion batteries have become one of the most advanced secondary chemical energy storage devices. However, in order to meet the requirements of a new generation of green large vehicles such as electric vehicles and hybrid vehicles, its performance still needs to be further improved.

Electrodes are the core components of lithium-ion batteries, and electrode materials are the key factors that determine the performance of lithium-ion batteries. Traditional graphite anode materials have the problems of low specific capacity (theoretical capacity is 372 mAh/g), poor lithium extraction power and poor safety. Recently, the research on GeO ₂ anode materials is gradually rising, because GeO ₂ anode materials have low operating voltage (0 ~ 0.4 V) and high theoretical capacity (1100 mAh/g), suitable for replacing graphite. However, _GeO2 is a semiconductor material, and its conductivity cannot meet the requirements of fast charging and discharging of high-performance lithium-ion batteries. In addition, due to the repeated intercalation and extraction of lithium ions during the charging and discharging process, the dramatic volume change of the _GeO2 anode material will lead to a rapid decline in its cycle performance. Therefore, to use _GeO2 as an electrode material, its above two defects, namely poor electrical conductivity and cycle performance, must be compensated or resolved. Studies have shown that the electrochemical performance can be effectively improved by combining conductive buffer materials (graphene, amorphous carbon, carbon nanotubes, etc.) with _GeO2 nanoparticles. However, the method of synthesizing such materials has many problems such as cumbersome steps, many by-products, low product purity, and serious environmental pollution.

Contents of the invention

The purpose of the present invention is to provide a lithium ion battery negative electrode material with simple preparation method, green and pollution-free, high charge and discharge capacity, good cycle stability and fast charge and discharge performance.

In order to achieve the above object, the technical solution of the present invention is: a germanium dioxide/graphene composite material, which is composed of graphene nanosheets wrapped germanium dioxide submicron particles; wherein, germanium dioxide submicron The diameter of the particles is 400-900 nm.

The preparation method of germanium dioxide/graphene composite material of the present invention, its steps are as follows:

(1) Add germanium dioxide powder and graphene oxide into distilled water, stir to completely dissolve the two, and obtain a precursor solution; wherein, the mass ratio of germanium dioxide powder and graphene oxide is 1:0.1~2;

(2) Transfer the obtained precursor solution into a watch glass and evaporate at 25 ~ 45°C to completely evaporate the water to obtain a powder;

(3) Calcining the powder obtained in step (2) at 200-300° C. for 1-3 hours in an air atmosphere to obtain the germanium dioxide/graphene composite material.

Further, in step (1), the mass ratio of germanium dioxide powder to distilled water is 1:200-500.

In step (1), the stirring method is magnetic stirring, and the stirring time is 30-60 min.

Beneficial effect:

The invention uses commercial germanium dioxide and graphene oxide as raw materials, uses water as a solvent, and adopts a dissolution-recrystallization method to synthesize a graphene-wrapped germanium dioxide particle composite material. The preparation method has the advantages of simple operation, simple equipment, no environmental pollution, low reaction temperature, cheap raw materials, high purity of the obtained product, high yield and no by-products.

The present invention uses graphene nanosheets and germanium dioxide particles to compound, utilizes the synergistic effect between the two (that is, uses graphene to improve the conductivity of germanium dioxide, and alleviates the problem of severe volume change of germanium dioxide during charging and discharging ), to improve the charge-discharge capacity, cycle stability and fast charge-discharge performance of germanium dioxide.

As a lithium ion battery negative electrode material, the germanium dioxide/graphene composite material prepared by the invention exhibits a higher charge-discharge specific capacity, better cycle stability and fast charge-discharge performance. After testing, the composite material of the present invention has an initial discharge capacity of 3053-3072 mAh/g at a current density of 200 mA/g, and an initial charge capacity (ie, reversible capacity) of 1623-1641 mAh/g. After 100 cycles, the composite material The capacity retention rate is about 90%.

Description of drawings

FIG. 1 is an XRD pattern of the germanium dioxide/graphene composite material of Example 1 of the present invention.

Fig. 2 is a _GeO2 particle size distribution diagram of the germanium dioxide/graphene composite material of Example 1 of the present invention.

3 is an SEM image of the germanium dioxide/graphene composite material of Example 1 of the present invention.

Fig. 4 is the first charge and discharge curve of the germanium dioxide/graphene composite material in Example 1 of the present invention.

Fig. 5 is the cycle performance curve of the germanium dioxide/graphene composite material of Example 1 of the present invention.

FIG. 6 is the charging and discharging performance curves of the germanium dioxide/graphene composite material in Example 1 of the present invention under different currents.

detailed description

Example 1

A preparation method of germanium dioxide/graphene composite material, the steps are as follows:

(1) Add 0.1 g of commercial germanium dioxide powder and 0.03 g of graphene oxide (GO) into 30 ml of distilled water, and magnetically stir the solution for 50 minutes, so that both germanium dioxide and graphene oxide are completely dissolved in distilled water;

(2) Transfer the obtained solution into a watch glass, put the watch glass into an electric heating constant temperature blast drying oven, keep a constant temperature of 35°C until the water evaporates completely;

(3) Calcining the black powder obtained after drying in step (2) at 300° C. for 1.5 hours in an air atmosphere, and finally obtaining a germanium dioxide/graphene composite material.

As shown in Figure 1, the X-ray powder diffraction of the product obtained in this example shows that the product is germanium dioxide in the hexagonal phase, corresponding to the JCPDS card number (36-1463). As shown in Figure 2, in the product obtained in this embodiment, the particle size distribution of germanium dioxide particles is uniform, ranging from 400 to 900 nm. As shown in Figure 3, the product obtained in this embodiment consists of graphene nanosheets wrapped germanium dioxide particles. The resulting product has a purity of 100%.

The germanium dioxide/graphene composite material prepared in this example was used as the negative electrode material of lithium ion battery, and its electrochemical performance was tested. The specific method is as follows: uniformly mix the germanium dioxide/graphene composite material with the conductive agent (acetylene black) and the adhesive (PVDF) according to the mass ratio of 80:15:5. Put the above mixture in an agate mortar and grind it carefully for 30 minutes, add the N-methylpyrrolidone solution to the ground mixture, stir well until the mixture is a uniform viscous paste, and then spread the slurry evenly Clothed on a copper sheet with a diameter of 14 mm, put the copper sheet in a blast drying oven at 60°C and dry for 10 hours to make the electrode to be tested. A 2016-type button battery was assembled in a vacuum glove box with a lithium metal sheet as the counter electrode (reference electrode), cell guard 2400 made in the United States as the diaphragm, and 1 M LiPF ₄ EC/DMC solution as the electrolyte. The LandBT2013A charge and discharge instrument produced by Wuhan Landian was used to test the charge and discharge performance of the battery. As shown in Figure 4, the first discharge capacity of the germanium dioxide/graphene composite material prepared in this example can reach 3053 mAh/g, and the charge (ie reversible) capacity is 1637 mAh/g, which is much higher than the current commercial graphite anode material capacity (theoretical value is 372 mAh/g). As shown in Figure 5, after 100 cycles, the reversible charge capacity of the composite can still be as high as 1473 mAh/g, with a capacity retention rate of 90%. As shown in Figure 6, the composite material has a capacity of 1637, 1414, 956, 763, 496 mAh/g at current densities of 200, 500, 1000, 2000 and 5000 mA/g, respectively. When the current density is lowered to 200 mA/g, the capacity can still recover to 1580mAh/g.

Example 2

A preparation method of germanium dioxide/graphene composite material, the steps are as follows:

(1) Add 0.5 g of commercial germanium dioxide powder and 0.05 g of graphene oxide (GO) into 120 ml of distilled water, and magnetically stir the solution for 30 minutes, so that both germanium dioxide and graphene oxide are completely dissolved in distilled water;

(2) Transfer the obtained solution into a watch glass, put the watch glass into an electric heating constant temperature blast drying oven, and keep a constant temperature of 25°C until the water evaporates completely;

(3) Calcining the black powder obtained after drying in step (2) at 300° C. for 2.5 hours in an air atmosphere, and finally obtaining a germanium dioxide/graphene composite material. The resulting product has a purity of 100%.

The germanium dioxide/graphene composite material prepared in this example was used as the negative electrode material of lithium ion battery, and its electrochemical performance was tested. Specific method can refer to embodiment 1. The LandBT2013A charge and discharge instrument produced by Wuhan Landian was used to test the charge and discharge performance of the battery. The first discharge capacity of the germanium dioxide/graphene composite material prepared in this example can reach 3059 mAh/g, and the charge (ie reversible) capacity is 1641 mAh/g, which is much higher than the capacity of the current commercial graphite anode material (theoretical value is 372 mAh/g). After 100 cycles, the reversible charge capacity of the composite can still be as high as 1475 mAh/g with a capacity retention of 90%. The material has capacities of 1641, 1420, 961, 766, and 500 mAh/g at current densities of 200, 500, 1000, 2000, and 5000 mA/g, respectively. Then when the current density was lowered to 200 mA/g, the capacity could still recover to 1583 mAh/g.

Example 3

A preparation method of germanium dioxide/graphene composite material, the steps are as follows:

(1) Add 0.8 g of commercial germanium dioxide powder and 1.0 g of graphene oxide (GO) into 200 ml of distilled water, and magnetically stir the solution for 60 minutes, so that both germanium dioxide and graphene oxide are completely dissolved in distilled water;

(2) Transfer the obtained solution into a watch glass, put the watch glass into an electric heating constant temperature blast drying oven, and keep a constant temperature of 40°C until the water evaporates completely;

(3) Calcining the black powder obtained after drying in step (2) at 250° C. for 1 hour in an air atmosphere, and finally obtaining a germanium dioxide/graphene composite material. The resulting product has a purity of 100%.

The germanium dioxide/graphene composite material prepared in this example was used as the negative electrode material of lithium ion battery, and its electrochemical performance was tested. Specific method can refer to embodiment 1. The LandBT2013A charge and discharge instrument produced by Wuhan Landian was used to test the charge and discharge performance of the battery. The first discharge capacity of the germanium dioxide/graphene composite material prepared in this example can reach 3066 mAh/g, and the charge (ie reversible) capacity is 1633 mAh/g, which is much higher than the capacity of the current commercial graphite anode material (theoretical value is 372 mAh/g). After 100 cycles, the reversible charge capacity of the composite can still be as high as 1425 mAh/g with a capacity retention of 87%. The material exhibited capacities of 1633, 1410, 953, 761, and 490 mAh/g at current densities of 200, 500, 1000, 2000, and 5000 mA/g, respectively. When the current density is lowered to 200 mA/g, the capacity can still recover to 1580 mAh/g.

Example 4

A preparation method of germanium dioxide/graphene composite material, the steps are as follows:

(1) Add 1.0 g of commercial germanium dioxide powder and 2.0 g of graphene oxide (GO) into 200 ml of distilled water, and magnetically stir the solution for 60 minutes, so that both germanium dioxide and graphene oxide are completely dissolved in distilled water;

(2) Transfer the obtained solution into a watch glass, put the watch glass into an electric heating constant temperature blast drying oven, and keep a constant temperature of 38°C until the water evaporates completely;

(3) Calcining the black powder obtained after drying in step (2) at 200° C. for 1 hour in an air atmosphere, and finally obtaining a germanium dioxide/graphene composite material. The resulting product has a purity of 100%.

The germanium dioxide/graphene composite material prepared in this example was used as the negative electrode material of lithium ion battery, and its electrochemical performance was tested. Specific method can refer to embodiment 1. The LandBT2013A charge and discharge instrument produced by Wuhan Landian was used to test the charge and discharge performance of the battery. The first discharge capacity of the germanium dioxide/graphene composite material prepared in this example can reach 3058 mAh/g, and the charge (ie reversible) capacity is 1623 mAh/g, which is much higher than the capacity of the current commercial graphite anode material (theoretical value is 372 mAh/g). After 100 cycles, the reversible charge capacity of the composite can still be as high as 1429 mAh/g, and the capacity retention rate is 88%. The material has capacities of 1623, 1399, 947, 759, 492 mAh/g at current densities of 200, 500, 1000, 2000 and 5000 mA/g, respectively. Then when the current density was lowered to 200 mA/g, the capacity could still recover to 1581 mAh/g.

Example 5

A preparation method of germanium dioxide/graphene composite material, the steps are as follows:

(1) Add 1.5 grams of commercial germanium dioxide powder and 2.0 grams of graphene oxide (GO) into 750 ml of distilled water, and magnetically stir the solution for 55 minutes, so that both germanium dioxide and graphene oxide are completely dissolved in distilled water;

(2) Transfer the obtained solution into a watch glass, put the watch glass into an electric heating constant temperature blast drying oven, and keep a constant temperature of 45°C until the water evaporates completely;

(3) Calcining the black powder obtained after drying in step (2) at 260° C. for 3 hours in an air atmosphere, and finally obtaining a germanium dioxide/graphene composite material. The resulting product has a purity of 100%.

The germanium dioxide/graphene composite material prepared in this example was used as the negative electrode material of lithium ion battery, and its electrochemical performance was tested. Specific method can refer to embodiment 1. The LandBT2013A charge and discharge instrument produced by Wuhan Landian was used to test the charge and discharge performance of the battery. The first discharge capacity of the germanium dioxide/graphene composite material prepared in this example can reach 3072 mAh/g, and the charge (ie reversible) capacity is 1639 mAh/g, which is much higher than the capacity of the current commercial graphite anode material (theoretical value 372 mAh/g). After 100 cycles, the reversible charge capacity of the composite can still be as high as 1463 mAh/g with a capacity retention of 89%. The material has capacities of 1663, 1428, 967, 778, 514 mAh/g at current densities of 200, 500, 1000, 2000 and 5000 mA/g, respectively. When the current density was lowered to 200 mA/g, the capacity could still recover to 1598 mAh/g.

Under the same conditions, the performance indicators of existing commercially available graphene negative electrode materials are measured: the first discharge capacity is 1034 mAh/g, the charge (ie reversible) capacity is 176 mAh/g, and after 100 cycles, the capacity is 169 mAh/g,

The capacity retention rate was 96%.

In the performance testing of the products prepared in the above five embodiments, the test results are better than the existing commercially available graphene negative electrode materials, and wherein the discharge capacity of the products prepared in Example 5 is the highest; the composite materials prepared in the five embodiments are passed through After 100 cycles, the capacity retention is around 90%.

Claims (4)

1. germanium dioxide/graphene composite material, it is characterised in that: this composite is to be wrapped up two by graphene nanometer sheet Germanium oxide submicron particles and constitute；Wherein, a diameter of 400 ~ 900 nm of germanium dioxide submicron particles.

The preparation method of a kind of germanium dioxide/graphene composite material the most as claimed in claim 1, it is characterised in that: step As follows:

(1), adding in distilled water by germanium dioxide powder and graphene oxide, stirring makes both be completely dissolved, and obtains presoma Solution；Wherein, the mass ratio of germanium dioxide powder and graphene oxide is 1:0.1 ~ 2；

(2), gained precursor solution is proceeded in surface plate, evaporate at 25 ~ 45 DEG C, moisture is evaporated completely, obtains powder End；

(3), the powder of step (2) gained is calcined 1 ~ 3 hour at 200 ~ 300 DEG C in air atmosphere, i.e. obtain described Germanium dioxide/graphene composite material.

The preparation method of a kind of germanium dioxide/graphene composite material the most as claimed in claim 2, it is characterised in that: step (1), in, germanium dioxide powder is 1:200 ~ 500 with the mass ratio of distilled water.

The preparation method of a kind of germanium dioxide/graphene composite material the most as claimed in claim 2, it is characterised in that: step (1) in, described alr mode is magnetic agitation, and mixing time is 30 ~ 60 min.