CN106654221A - Three-dimensional porous carbon-coated zinc selenide material for lithium ion battery anodes and preparation method of material - Google Patents

Abstract

The invention belongs to the technical field of materials and energy, and specifically relates to a three-dimensional porous carbon-coated zinc selenide material used for a negative electrode of a lithium-ion battery and a preparation method thereof. Specifically, zinc-based zeolite imidazolate metal-organic framework (ZIF‑8) is used as a precursor or template, and selenium powder is sintered at high temperature for a certain period of time under the protection of an inert atmosphere. Through the simultaneous selenization and carbonization process, the final Carbon-coated ZnSe composites were prepared. The composite material method prepared by the present invention realizes the effective compounding of zinc selenide and graphite carbon, forms a strong interfacial coupling effect between the components, and can effectively alleviate and inhibit the volume expansion effect of the zinc selenide material in the charging and discharging process, The conductivity of the material is improved, so when the composite material is used as an anode material for a lithium-ion battery, it has both very high specific capacity and excellent cycle stability and rate performance. The preparation process of the invention is simple, the preparation condition is moderate, and the cost is low.

Description

Three-dimensional porous carbon-coated zinc selenide material for lithium-ion battery anode and its preparation method

technical field

The invention belongs to the technical field of materials and energy, and in particular relates to a three-dimensional porous carbon-coated zinc selenide material used for a negative electrode of a lithium-ion battery and a preparation method thereof.

Background technique

With the development of the economy, the demand for energy is also increasing. People have discovered a variety of available clean energy, and the development of energy conversion and storage technology is also very important. Removable cyclic charge-discharge batteries are currently the most widely used energy storage methods. Lithium-ion batteries are widely used in various portable electronic devices due to their advantages of high energy density, long cycle life and environmental friendliness. With the increase in demand, people have higher and higher requirements for the performance of lithium-ion batteries. How to increase battery capacity, prolong cycle life, and improve rate performance are the main goals of researching lithium-ion batteries. Lithium-ion batteries mainly include battery case, negative electrode material, positive electrode material, diaphragm and electrolyte, and the improvement of its performance mainly depends on the improvement of the performance of positive and negative electrode materials.

At present, the negative electrodes of commercially produced lithium-ion batteries are mainly graphite materials. However, the theoretical capacity of graphite-based negative electrode materials is only 372mAh/g, which cannot meet people's demand for high capacity. However, silicon-based materials and transition metal oxides with high theoretical capacity have a large volume change during the lithium-deintercalation process and poor conductivity, resulting in low life, easy attenuation, and poor cycle stability. Therefore, there is an urgent need to find anode materials for lithium-ion batteries that satisfy both high capacity and good cycle stability.

Elemental selenium has a high theoretical specific capacity (weight specific capacity is 675mAh/g, volume specific capacity is 3268mAh/g), high electrical conductivity (10 ^-5 S/cm, much higher than sulfur 10 ^-30 S/cm) Caused widespread concern. Amine et al. (J.Am.Chem.Soc.2012, 134, 4505-4508) first reported a preparation method for lithium-selenium batteries. However, due to the large size of selenium particles, they cannot be effectively recombined, resulting in low capacity during cycling. fast decay. Guo et al. (Angew.Chem.Int.ed.2013, 52, 8363-8367) used the melt-diffusion method to prepare cyclic or chain selenium molecules. The Coulombic efficiency was close to 100%, but the capacity was only 657mAh/g.

The study found that alloying with selenium can effectively buffer the volume change in the process of lithium intercalation and deintercalation, and improve cycle performance. In recent years, metal selenides have been widely used as anode materials for lithium-ion batteries. Zhang et al. (ELECTROCHIMICAACTA . 2016, 209, 423-429) reported a one-dimensional nanowire-like SnSe/C composite anode material, which can maintain the initial 840mAh/g after 100 cycles at a rate of 200mA/g. capacity. Although the rate performance is outstanding, its capacity still needs to be improved.

Contents of the invention

In order to overcome the shortcomings of the above-mentioned technologies that cannot satisfy high capacity, long life and excellent rate performance at the same time, the present invention provides a three-dimensional porous carbon-coated zinc selenide material that is cost-effective, stable in performance, and industrially-producible and its preparation method and in Applications in the field of lithium-ion batteries.

The preparation method of the three-dimensional polyhedral porous carbon-coated zinc selenide material provided by the present invention is to use zinc-based metal-organic framework (ZIF-8) as a template, use hydrogen-argon mixed gas as a protective atmosphere, and conduct selenium selenide with selenium powder at high temperature. The three-dimensional porous carbon-coated zinc selenide material was prepared in situ. In the prepared material, zinc selenide quantum dots are embedded in porous carbon, which has a mesoporous structure and a high specific surface area, and maintains the polyhedral morphology of ZIF-8 very completely. It is used as a negative electrode material for lithium-ion batteries. In the process, it shows excellent performance.

The preparation method of the three-dimensional polyhedral porous carbon-coated zinc selenide material of the present invention, the specific steps are:

(1) Weigh 1.35-1.66 grams of zinc nitrate hexahydrate and 1.45-1.85 grams of 2-methylimidazole, dissolve them in 15-35 ml of methanol solution, stir to dissolve, then pour the 2-methylimidazole solution into nitric acid In the zinc solution; mix and stir until uniform (5-10 minutes), let stand at room temperature for 18-24 hours, centrifuge the product, wash it with ethanol solution 2-4 times, and finally place it in a drying oven at 55-80 degrees Celsius. The obtained product is polyhedral ZIF-8; the product is white, mostly in the shape of rhombic dodecahedron, and the particle size is mainly distributed between 600 and 900 nanometers;

(2) Three-dimensional porous carbon-coated zinc selenide material and its preparation: Weigh 100 to 300 mg of ZIF-8 and 100 to 300 mg of selenium powder and place them on both ends of the porcelain boat, and put the porcelain boat into the tube furnace , into a hydrogen-argon mixture, heated to 400-600 degrees Celsius at a rate of 1-3 degrees Celsius per minute, and kept at this temperature for 2 to 4 hours to obtain a three-dimensional porous carbon-coated zinc selenide material.

The three-dimensional porous zinc selenide material prepared by the present invention has a microporous structure and a relatively high specific surface area, and can be used as an anode active material for a lithium ion battery. The material has a relatively high capacity, and the three-dimensional porous structure can effectively buffer the process of deintercalating lithium The volume change in the medium improves the cycle performance. A lithium sheet was used as the positive electrode, a polypropylene microporous membrane (Celgard 2400) was used as the separator, and a commercial electrolyte (LiPF ₆ as the electrolyte, EC and DMC as the solvent with a volume ratio of 1:1) was used to assemble a CR2032 battery for testing.

The advantages of the present invention are: (1) The three-dimensional porous zinc selenide material well maintains the three-dimensional polyhedral morphology of the original ZIF-8, and has a microporous structure and a large specific surface area, showing excellent performance in lithium-ion batteries and other fields. It is obviously better than the capacity and cycle performance of known zinc selenide materials; (2) The raw materials only involve zinc nitrate hexahydrate, 2-methylimidazole, selenium powder, methanol, ethanol and other common reagents, which are safe, non-toxic and low cost. The method is cheap and the product has high purity; (3) the three-dimensional porous zinc selenide material is prepared by a one-step method, and the process is simple and easy for industrial production; (4) the method has good applicability and can be extended to the preparation methods of other metal selenides.

In summary, the present invention provides a method for preparing a three-dimensional porous zinc selenide material with high capacity, good stability and cycle performance, simple operation, good safety, low cost, high efficiency and easy industrial production.

Description of drawings

Fig. 1 is a scanning electron microscope (SEM) image of the three-dimensional porous zinc selenide material prepared in Example 1 of the present invention.

Fig. 2 is a transmission electron microscope (TEM) image of the three-dimensional porous zinc selenide material prepared in Example 1 of the present invention.

Fig. 3 is an X-ray diffraction (XRD) diagram of the three-dimensional porous zinc selenide material prepared in Example 1 of the present invention.

Fig. 4 is a specific surface area analysis (BET) diagram of the three-dimensional porous zinc selenide material prepared in Example 1 of the present invention.

Fig. 5 is a capacity curve of a lithium-ion battery prepared by using the three-dimensional porous zinc selenide material prepared in Example 1 of the present invention as the negative electrode active material.

6 is a rate performance curve of a lithium-ion battery prepared by using the three-dimensional porous zinc selenide material prepared in Example 1 of the present invention as the negative electrode active material.

detailed description

In order to further understand the present invention, the present invention will be further described below in conjunction with examples and accompanying drawings.

Embodiment 1: three-dimensional porous carbon-coated zinc selenide material and its preparation method and application, comprising the following steps:

(1) Preparation of ZIF-8 template with polyhedral morphology: Weigh 1.45 g of zinc nitrate hexahydrate and 1.66 g of 2-methylimidazole, dissolve them in 20 ml of methanol solution, stir and dissolve, and dissolve 2-methylimidazole Pour the imidazole solution into the zinc nitrate solution; stir for 5 minutes, let it stand at room temperature for 24 hours, centrifuge the product, wash it with ethanol solution for 4 times, and finally place it in a drying oven at 55 degrees Celsius. The obtained product is polyhedral ZIF -8; The product is white, mostly rhomboid dodecahedron, and the particle size is mainly distributed between 600 and 900 nanometers;

(2) Three-dimensional porous zinc selenide material and preparation: Weigh 200 mg of ZIF-8 and 200 mg of selenium powder and place them on both ends of the porcelain boat respectively, put the porcelain boat into a tube furnace, and inject a hydrogen-argon gas mixture , heated to 600 degrees Celsius at a heating rate of 3 degrees Celsius per minute, and kept at this temperature for 2 hours to obtain a three-dimensional porous carbon-coated zinc selenide material.

The three-dimensional porous carbon-coated zinc selenide material is used as the negative electrode active material of the lithium-ion battery, the lithium sheet is used as the positive electrode, the polypropylene microporous membrane (Celgard 2400) is used as the separator, and the commercial electrolyte (LiPF ₆ is used as the electrolyte, EC and DMC as a solvent and the volume ratio is 1:1), assembled into a CR2032 battery for testing. Its morphology and characteristics are shown in Figure 1-Figure 5.

The advantages of the present invention are: (1) The three-dimensional porous zinc selenide material well maintains the three-dimensional polyhedral morphology of the original ZIF-8, and has a microporous structure and a large specific surface area, showing excellent performance in lithium-ion batteries and other fields. It is obviously better than the capacity of the currently known zinc selenide materials (Figure 4, at a current density of 600mA/g, after 500 cycles, the capacity remains at 1134mAh/g) and cycle performance (Figure 5, at 200, 400, 800, 1600, 3200 , 6400, 12800 mA/g current density, the capacities are 1162, 1157, 1127, 1029, 811,696, and 474 mAh/g respectively); (2) The raw materials only involve zinc nitrate hexahydrate, dimethylimidazole, selenium Powder and common reagents such as methanol and ethanol are safe, non-toxic, low in cost, and high in product purity; (3) The three-dimensional porous zinc selenide material is prepared by a one-step method, and the process is simple and easy for industrial production.

Embodiment 2: three-dimensional porous carbon-coated zinc selenide material and its preparation method and application, comprising the following steps:

(1) Preparation of ZIF-8 template with polyhedral morphology: Weigh 1.45 g of zinc nitrate hexahydrate and 1.66 g of 2-methylimidazole, dissolve them in 20 ml of methanol solution, stir and dissolve, and dissolve 2-methylimidazole Pour the imidazole solution into the zinc nitrate solution; stir for 5 minutes, let it stand at room temperature for 24 hours, centrifuge the product, wash it with ethanol solution for 4 times, and finally place it in a drying oven at 55 degrees Celsius. The obtained product is polyhedral ZIF -8; The product is white, mostly rhomboid dodecahedron, and the particle size is mainly distributed between 600 and 900 nanometers;

(2) Three-dimensional porous zinc selenide material and preparation: Weigh 200 mg of ZIF-8 and 200 mg of selenium powder and place them on both ends of the porcelain boat respectively, put the porcelain boat into a tube furnace, and inject a hydrogen-argon gas mixture , heated to 500 degrees Celsius at a heating rate of 3 degrees Celsius per minute, and kept at this temperature for 2 hours to obtain a three-dimensional porous carbon-coated zinc selenide material.

The three-dimensional porous carbon-coated zinc selenide material is used as the negative electrode active material of the lithium-ion battery, the lithium sheet is used as the positive electrode, the polypropylene microporous membrane (Celgard 2400) is used as the separator, and the commercial electrolyte (LiPF ₆ is used as the electrolyte, EC and DMC as a solvent and the volume ratio is 1:1), assembled into a CR2032 battery for testing. Its appearance and characteristics are similar to Example 1.

The advantages of the present invention are: (1) The three-dimensional porous zinc selenide material well maintains the three-dimensional polyhedral morphology of the original ZIF-8, and has a microporous structure and a large specific surface area, showing excellent performance in lithium-ion batteries and other fields. It is obviously better than the capacity and cycle performance of known zinc selenide materials; (2) The raw materials only involve zinc nitrate hexahydrate, dimethylimidazole, selenium powder, methanol, ethanol and other common reagents, which are safe, non-toxic and low in cost , the product has high purity; (3) The three-dimensional porous zinc selenide material is prepared by a one-step method, and the process is simple and easy for industrial production.

Claims (3)

1. A preparation method of a three-dimensional porous carbon-coated zinc selenide material, characterized in that, using zinc-based metal-organic framework (ZIF-8) as a template, using hydrogen-argon mixed gas as a protective atmosphere, and selenium powder at high temperature Carry out selenization reaction, prepare three-dimensional porous carbon-coated zinc selenide material in situ; the specific steps are: (1) Preparation of ZIF-8 template with polyhedral morphology: Weigh 1.35-1.66 grams of zinc nitrate hexahydrate and 1.45-1.85 grams of 2-methylimidazole, dissolve them in 15-35 ml of methanol solution, stir to dissolve, then pour the 2-methylimidazole solution into the zinc nitrate solution ; Mix and stir until uniform, let stand at room temperature for 18-24 hours, centrifuge the product, wash 2-4 times with ethanol solution, and finally place it in a drying oven at 55-80 degrees Celsius, and the obtained product is polyhedral ZIF-8 ; The product is white, mostly rhomboid dodecahedron, and the particle size is mainly distributed between 600 and 900 nanometers; (2) Polyhedral zinc selenide material and its preparation: Weigh 100 to 300 mg of ZIF-8 and 100 to 300 mg of selenium powder and place them on both ends of the porcelain boat respectively, put the porcelain boat into a tube furnace, and feed a mixed gas of hydrogen and argon at 1-3 degrees Celsius per minute The heating rate is heated to 500-600 degrees Celsius, and the temperature is kept at this temperature for 2-4 hours to obtain a three-dimensional porous carbon-coated zinc selenide quantum dot material. 2. A zinc selenide material coated with three-dimensional porous carbon obtained by the preparation method according to claim 1. 3. A zinc selenide material coated by the three-dimensional porous carbon according to claim 2, as an application of lithium ion battery electrode active material.