阅读说明：本技术 一种锗掺杂超细二氧化锡石墨烯复合材料的制备方法及应用 (Preparation method and application of germanium-doped superfine tin dioxide graphene composite material ) 是由 赵永男 高海燕 黄志强 于 2019-04-02 设计创作，主要内容包括：本发明公开了一种锗掺杂超细二氧化锡石墨烯复合材料的制备方法,具体制备过程如下：将一定比例的锗源,锡源和氧化石墨烯溶解于去离子水和乙醇的混合溶液中,加入适量盐酸调节pH值。将溶解分散好的混合溶液装釜并在一定条件下进行水热反应。反应结束后,进行离心清洗和冷冻干燥得到一种锗掺杂超细二氧化锡石墨烯复合材料。本发明中所制备的锗掺杂超细二氧化锡石墨烯复合材料作为锂离子负极材料具有良好的循环稳定性,优异的倍率性能和高的放电比容量。(The invention discloses a preparation method of a germanium-doped superfine tin dioxide graphene composite material, which comprises the following specific preparation processes: dissolving a germanium source, a tin source and graphene oxide in a mixed solution of deionized water and ethanol according to a certain proportion, and adding a proper amount of hydrochloric acid to adjust the pH value. And filling the dissolved and dispersed mixed solution into a kettle, and carrying out hydrothermal reaction under certain conditions. After the reaction is finished, carrying out centrifugal cleaning and freeze drying to obtain the germanium-doped superfine tin dioxide graphene composite material. The germanium-doped superfine tin dioxide graphene composite material prepared by the invention has good cycling stability, excellent rate capability and high specific discharge capacity when being used as a lithium ion negative electrode material.)

1. A preparation method of a germanium-doped superfine tin dioxide graphene composite material is characterized by comprising the following steps:

(1) dissolving a tin source, a germanium source, graphene oxide and a proper amount of hydrochloric acid in a mixed solution of deionized water and ethanol according to a certain proportion, and placing the mixture in a reaction kettle for hydrothermal reaction after complete dissolution and dispersion.

(2) And (3) centrifugally cleaning a product obtained by hydrothermal preparation, and freeze-drying in a freeze dryer to obtain the germanium-doped superfine tin dioxide graphene composite material.

2. The method for preparing the germanium-doped ultrafine tin dioxide graphene composite material, according to the claim, wherein the molar ratio of the tin source to the germanium in the step (1) is 1: 0.01-1.

3. The method for preparing the germanium-doped ultrafine tin dioxide graphene composite material, according to the claim, wherein the addition amount of the graphene oxide in the step (1) is 0.1-2 g/L.

4. The method for preparing the germanium-doped ultrafine tin dioxide graphene composite material as claimed in claim, wherein the addition amount of hydrochloric acid in the step (1) is 0-2 mL.

5. The method for preparing the germanium-doped ultrafine tin dioxide graphene composite material, according to the claim, wherein the volume ratio of the deionized water to the ethanol mixed solution in the step (1) is as follows.

6. The method for preparing the germanium-doped ultrafine tin dioxide graphene composite material as claimed in claim, wherein the drying method adopted in the step (2) is freeze drying.

7. The germanium-doped ultrafine tin dioxide graphene composite material prepared according to the claims 1 to 6 has excellent rate performance, high specific discharge capacity and good cycling stability.

Technical Field

The invention relates to the field of preparation of lithium ion battery electrode materials, and particularly provides a preparation method of a germanium-doped tin dioxide graphene composite material.

Background

The lithium ion battery has the advantages of high energy density, light weight, long service life and the like, and is widely applied to portable functional electronic equipment such as mobile phones, notebook computers, unmanned planes and the like. With the advent of the 5G era, the performance requirements for lithium ion batteries have increased. At present, the negative electrode material of the commercial lithium ion battery is mainly made of graphite materials, but the low theoretical specific capacity (372mAh g)^-1) Limit the nextThe development of high-energy lithium ion batteries is replaced. Therefore, there is a need to develop a novel lithium ion battery electrode material that meets the requirements of high energy, high stability and safety.

The tin dioxide-based negative electrode material has high theoretical specific capacity (1494mAh g)^-1) The material has the advantages of low voltage platform, safety, low price and the like, and is expected to replace graphite materials to realize commercial cathode materials. However, during the charging and discharging process, the tin dioxide can generate huge volume change, so that the active substance is pulverized, and the current collector is stripped, so that the cycle performance and the reversible capacity of the tin dioxide are reduced. In addition, tin dioxide reacts with lithium in two steps during charging and discharging, as shown in the following formula:

for bulk tin dioxide materials, it is generally believed that the first step conversion reaction is irreversible and only the second alloying reaction provides reversible capacity. Thus, in previous studies, tin dioxide materials have not exhibited the advantages of high capacity as expected. However, recent studies have shown that the reversibility of the first-part conversion reaction can be improved to some extent by making the tin dioxide-based negative electrode material into a nano-size. In addition, the nano tin dioxide particles are loaded on the carbon material, so that the volume change of the tin dioxide-based composite material in the charging and discharging process can be relieved to a certain extent, and the cycle stability of the tin dioxide-based composite material is improved. However, in the current research, the reversibility of the first-step conversion reaction of tin dioxide is limited, so finding a method for making the conversion reaction of the tin dioxide negative electrode reversible during charge and discharge is the key point of the research on the tin dioxide-based negative electrode material.

The invention provides a simple method for preparing a germanium-doped superfine tin dioxide graphene composite material, wherein the size of tin dioxide nanoparticles is 3-5nm, and the germanium-doped superfine tin dioxide graphene composite material has good rate capability, high specific discharge capacity and stable cyclicity when used as a lithium ion negative electrode material. The preparation method has the advantages of simple preparation process, low energy consumption, low preparation cost and no pollution to the environment, and is expected to be commercially applied.

Disclosure of Invention

The invention provides a simple preparation method of a germanium-doped superfine tin dioxide graphene composite material, aiming at the problems of the existing tin dioxide-based negative electrode material.

The invention is realized by the following steps:

weighing a tin source and a germanium source according to a molar ratio of 1: 0.01-1, weighing a certain amount of graphene oxide, and dispersing and dissolving the graphene oxide and the germanium source in 60mL of deionized water and ethanol mixed solution, wherein the tin source is tin tetrachloride, stannous chloride or stannous sulfate, the germanium source is germanium dioxide, the addition amount of the graphene oxide is 0.1-2g/L, and the volume ratio of the deionized water and the ethanol mixed solution is 1: 0.5-2. Then adding a proper amount of hydrochloric acid to adjust the pH value of the mixed solution, stirring for 60min, putting the mixed solution into a kettle, and placing the kettle in an air-blast drying oven at 120-180 ℃ for hydrothermal reaction, wherein the reaction time is controlled to be 3-12 h. And centrifugally cleaning a product after the hydrothermal reaction, and freeze-drying the product in a freeze dryer to obtain the germanium-doped superfine tin dioxide graphene composite material.

Compared with other synthesis methods, the preparation method of the germanium-doped superfine tin dioxide graphene composite material provided by the invention has the advantages of simple preparation process, low energy consumption, low preparation cost, large-scale production and no environmental pollution, and the prepared composite material as a lithium ion negative electrode material shows excellent rate performance, good cycling stability and high discharge specific capacity. The method is mainly characterized in that the superfine tin dioxide in the prepared composite material is uniformly dispersed on the graphene substrate, the volume change of tin dioxide particles generated in the charging and discharging processes is effectively relieved in the long-cycle charging and discharging processes, the structural stability of the composite material is ensured, and meanwhile, the doped germanium element promotes the reversible conversion reaction of the tin dioxide in the charging and discharging processes, so that the high specific capacity is obtained. The preparation method has the advantages of simple preparation process, low energy consumption, low preparation cost and no pollution to the environment, and is expected to be commercially applied.

Drawings

Fig. 1 is an X-ray diffraction (XRD) pattern of the prepared germanium-doped ultrafine tin dioxide graphene composite material and undoped tin dioxide graphene composite material;

FIG. 2 is an X-ray photoelectron spectroscopy (XPS) of the prepared germanium-doped ultra-fine tin dioxide graphene composite material and undoped tin dioxide graphene composite material;

FIG. 3 shows that the germanium-doped ultrafine tin dioxide graphene composite material and the undoped tin dioxide graphene composite material are 0.1A g^-1A high current density cyclic charge-discharge diagram;

FIG. 4 shows that the prepared germanium-doped ultrafine tin dioxide graphene composite material is 0.1A g^-1Current density cycle charge-discharge diagram;

FIG. 5 shows that the prepared germanium-doped ultrafine tin dioxide graphene composite material is 0.5A g^-1Current density cycle charge-discharge diagram;

fig. 6 is a rate performance graph of the prepared germanium-doped ultrafine tin dioxide graphene composite material.

Detailed Description

The preparation method of the germanium-doped superfine tin dioxide graphene composite material comprises the following specific steps:

weighing 0.48mmol of stannic chloride, 0.48mmol of germanium dioxide and 90mg of graphene oxide, dispersing and dissolving in 60mL of deionized water and ethanol mixed solution, wherein the volume ratio of the deionized water to the ethanol is 1: 1, then adding 0.8mL of hydrochloric acid, magnetically stirring for 60min, loading the obtained mixed solution into a kettle, placing the kettle in an air-blast drying oven at 150 ℃ for hydrothermal reaction, and controlling the reaction time to be 3 h. And centrifugally cleaning a product after the hydrothermal reaction, and freeze-drying the product in a freeze dryer to obtain the germanium-doped superfine tin dioxide graphene composite material.

The research result of the germanium-doped superfine tin dioxide graphene composite material is as follows:

(1) structural analysis of materials

XRD characterization shows that the diffraction peak of the prepared composite material is completely consistent with the standard card PDF #41-1445 (as shown in figure 1)Show), the tin dioxide in the prepared composite material is a typical rutile phase, and the material is obtained by calculation through the Scherrer formula, and the germanium-doped superfine tin dioxide graphene composite material (Ge doped SnO)₂@ G) has a tin dioxide particle size of 3.7nm, while undoped germanium tin dioxide graphene composite (SnO)₂@ G) particle size was 4.2 nm.

(2) Analysis of the test results for the presence of germanium.

FIG. 2 shows Ge doped SnO prepared₂@ G and SnO₂XPS spectra of @ G. As can be seen in the figure, Ge dopedSnO₂The @ G composite material has a characteristic peak position of germanium at 33eV, and SnO₂@ G shows no peak at this position. According to the XRD spectrum, the prepared germanium-doped superfine tin dioxide graphene composite material is characterized in that germanium exists in tin dioxide in a doped mode.

(3) Analysis of electrochemical Properties

Figures 3-6 are electrochemical performance test charts of germanium-doped ultrafine tin dioxide graphene composite materials as lithium ion battery cathodes. In FIG. 3, it can be seen that the value is 0.1A g^-1Under the current density, the germanium-doped tin dioxide graphene composite material has higher specific discharge capacity than an undoped composite material. In FIG. 4, it can be seen that the Ge-doped ultra-fine tin dioxide graphene composite material is 0.1A g^-1Under the current density, after 30 cycles of charge and discharge, the capacity begins to rise, reaches the highest theoretical specific capacity value after 200 cycles, and after 400 cycles, the capacity is stabilized at 1387mAh g^-1. FIG. 5 shows that the temperature is 0.5A g^-1Under the current density, after 200 cycles of charge and discharge, the capacity is still maintained at 693.1mAh g^-1。

FIG. 6 is a graph of the rate capability of germanium-doped ultra-fine tin dioxide graphene composite material, which is 0.05A g^-1，0.1Ag^-1，0.2A g^-1，0.5A g^-1，1A g^-1，2A g^-1，，5A g^-1，10A g^-1At a current density, the capacity was 1172.2mAhg^-1，931.4mAh g^-1，843.7mAh g^-1，726.7mAh g^-1，638.4mAh g^-1，472.2mAh g^-1，319.1mAh g^-1，155.6mAh g^-1. The current density returns to 0.1A g^-1When the discharge capacity is increased, the discharge capacity can still be maintained at 1036.9mAh g^-1. The germanium-doped superfine tin dioxide graphene composite material shows excellent electrochemical performance mainly due to the fact that the prepared superfine tin dioxide nano particles are limited on the reduced graphene oxide, and meanwhile, the doped germanium element can effectively promote the reversibility of conversion reaction in the charging and discharging processes, so that the specific discharge capacity and the good rate capability of the composite material are improved.

The invention provides a simple method for preparing a germanium-doped superfine tin dioxide graphene composite material, wherein the size of tin dioxide nanoparticles is 3-5nm, germanium exists in the tin dioxide in a doped form, and the germanium-doped superfine tin dioxide graphene composite material used as a lithium ion negative electrode material has good rate performance, high specific discharge capacity and stable cyclicity. The preparation method has the advantages of simple preparation process, low energy consumption, low preparation cost and no pollution to the environment, and is expected to be commercially applied.