CN102522542A - Elemental sulfur composite material containing graphene and preparation method thereof - Google Patents

Abstract

The invention provides a graphene-containing elemental sulfur composite material and a preparation method thereof. This kind of composite material is a binary material A _x By _y , wherein A is graphene, B is elemental sulfur, 1%≤x≤90%, 10%≤y≤99%, and x+y=100%, and B is The nano state is uniformly dispersed on the surface of A. The preparation method is to use elemental sulfur and graphene oxide to perform hydrothermal treatment between 50 and 500 degrees, and the elemental sulfur will reduce the graphene oxide to graphene, and at the same time obtain a graphene-containing elemental sulfur compound with nanometer sulfur uniformly dispersed on the surface of the graphene. Material. The composite material is used to prepare a positive electrode and a metal lithium or metal sodium negative electrode to form a lithium-sulfur battery or a sodium-sulfur battery. The lithium-sulfur battery is charged and discharged at room temperature, and the reversible specific capacity of the graphene-containing sulfur-based composite material reaches 1480mAh/g.

Description

Elemental sulfur composite material containing graphene and preparation method thereof

technical field

The invention relates to a positive electrode material for a secondary battery and a preparation method thereof, in particular to an elemental sulfur composite positive electrode material for a secondary battery and a preparation method thereof.

Background technique

With the increasing global energy shortage and the deterioration of the environmental climate, people's demand for clean energy is becoming more and more urgent. As an energy storage and conversion device, batteries play an irreplaceable role in the process of clean energy utilization. Compared with other commonly used secondary batteries, lithium-ion batteries have attracted extensive attention because of their high mass-specific energy and volume-specific energy. Low cost, high energy density, high safety, long cycle life, and green secondary batteries are the hotspots in the development of next-generation lithium batteries.

The current commercial positive electrode materials are mainly layered or spinel-structured lithium transition metal oxides (such as lithium cobaltate, lithium manganate) and olivine-structured lithium iron phosphate. However, due to the structure and composition of these positive electrode materials, they have the disadvantages of low capacity, high price and poor safety, which cannot meet the requirements of the next generation of high energy density secondary batteries. Elemental sulfur reacts with lithium as a positive electrode material to form lithium sulfide (Li ₂ S), the theoretical capacity can be as high as 1672mAh/g, which is more than 6 times that of traditional transition metal oxides or phosphate positive electrode materials, and elemental sulfur is cheap, safe and non-toxic , is a new positive electrode active material with great development potential.

For decades, elemental sulfur and sulfur-containing inorganic sulfides, organic disulfides, polyorganodisulfides, organic polysulfides, polysulfides, and carbon-sulfur polymers have been widely used as high-capacity cathode materials. attention, but there are still many problems with these materials. First of all, the conductivity of elemental sulfur and sulfide itself is very poor, and a large amount of conductive agent must be added to increase its conductivity. Secondly, for the positive electrode with elemental sulfur as the active material, although the elemental sulfur existing on the positive electrode when fully charged and the _Li2S existing when fully discharged are insoluble in polar organic electrolytes, the positive electrode contains Lithium polysulfides are easily soluble in polar organic electrolytes. Similarly, the small molecular sulfides produced during discharge of polyorganosulfides are also easily soluble in organic electrolytes and deposited on the negative electrode, which affects the cycle performance of batteries (Kolosnitsyn, VS, Karaseva, EVRussian Journal of Electrochemistry 2008, 44(5), pp.506-509). Therefore, how to improve the conductivity of materials, solve the problem of dissolution of charge-discharge intermediate products, and improve battery cycle performance are the research focus of sulfur-based cathode materials.

Graphene is an electronic and thermal conductor with high specific surface area, high chemical stability, and high mechanical strength. Combining graphene with elemental sulfur is an effective means to overcome the above-mentioned shortcomings of elemental sulfur. By dispersing elemental sulfur particles on the surface of graphene, the high specific surface area of graphene can play a role in adsorbing sulfur, and the high electronic conductivity can overcome the problem of elemental sulfur insulation. Recently, papers have reported the synthesis method of graphene-sulfur composites (Hailiang Wang, Yuan Yang, Yi Cui, and Hongjie Dai. Nano Letters 2011, 11, 2644-2647; JiazhaoWang, Lin Lu, Xun Xu, Huakun Liu. Journal of Power Sources 2011, 196, 7030-7034), compared with elemental sulfur, the cycle performance has been improved to a certain extent, but there are also many shortcomings such as complicated preparation process and uneven compounding, which need to be improved and improved.

Contents of the invention

Aiming at the above-mentioned deficiencies in the prior art, the present invention provides a graphene-containing elemental sulfur composite material and a preparation method thereof.

The present invention is achieved through the following technical solutions.

A graphene-containing elemental sulfur composite material, the composite material is a binary composite material A _x By _y , wherein A is graphene, B is elemental sulfur, and B is uniformly dispersed on the surface of A in a nanometer state, wherein x , y are the contents of graphene and elemental sulfur respectively, the 1%≤x≤90%, the 10%≤y≤99%, and x+y=100%.

A preparation method for preparing a graphene-containing elemental sulfur composite material according to claim 1, comprising the steps of:

Step 1, adding graphene oxide into deionized water to obtain a dispersion of graphene oxide;

Step 2, adding elemental sulfur to obtain a mixture slurry of graphene oxide and elemental sulfur;

Step 3: After the mixture slurry is heat-treated, it is washed with water and filtered to obtain a graphene-containing elemental sulfur composite material.

The thickness of the graphene oxide is 0.35-3.5nm, which contains 1-10 graphite sheets, and the length and width of the graphite sheets are respectively 10nm-10μm.

In step 1, the graphene oxide is 1 part by mass.

In step 1, the deionized water is 1-500 parts by mass.

In step 2, the elemental sulfur is 0.1-30 parts by mass.

In step 3, the heat treatment is hydrothermal treatment in a sealed polytetrafluoroethylene or stainless steel tank.

In step 3, the corresponding temperature of the heat treatment is 50-500°C.

In step 3, the corresponding time of the heat treatment is 1-72 hours.

The elemental sulfur composite material containing graphene provided by the invention has the following advantages:

In terms of structure, the binary composite material is evenly compounded, and the elemental sulfur is uniformly dispersed on the surface of the reduced graphene in a nanometer state. This structure is conducive to giving full play to the high conductivity of graphene and its impact on the material structure when used as a battery cathode material. The stabilizing effect of graphene improves the power characteristics of the battery; the high thermal conductivity of graphene is beneficial to the heat dissipation of the composite material, and the high specific surface area is beneficial to the adsorption of lithium polysulfide produced during the cycle. These properties play an important role in improving the cycle stability of the battery. . The size of nano-sulfur dispersed on the surface of graphene is small, which is conducive to the full utilization of sulfur and improves the utilization rate of elemental sulfur in the composite material, that is, increases the energy density of the composite material.

The preparation method of the elemental sulfur composite material containing graphene provided by the invention has the following advantages:

Graphene oxide is reduced in situ by using elemental sulfur in the hydrothermal method, and the elemental sulfur is evenly distributed on the surface of graphene in a nanometer state, which has the advantages of simple synthesis method and adjustable and controllable material morphology.

A lithium-sulfur secondary battery or a sodium-sulfur secondary battery is composed of the positive electrode prepared by the invention and the metal lithium or metal sodium negative electrode. Charged and discharged at room temperature, the reversible capacity of the single sulfur composite positive electrode material for lithium-sulfur secondary batteries can reach 1480mAh/g, and this material has good cycle performance.

Description of drawings

Fig. 1 is the SEM photograph of the elemental sulfur composite material containing graphene obtained by embodiment 3.

Fig. 2 is the charge-discharge curve of the simple sulfur composite material containing graphene obtained in Example 3.

Fig. 3 is the cycle performance curve of the elemental sulfur composite material containing graphene obtained according to Example 3.

Detailed ways

The embodiments of the present invention are described in detail below: the present embodiment is implemented under the premise of the technical solution of the present invention, and detailed implementation and specific operation process are provided, but the protection scope of the present invention is not limited to the following implementation example.

Example 1

This embodiment provides a graphene-containing elemental sulfur composite material, which is a binary composite material A _x By _y , wherein A is graphene, B is elemental sulfur, and B is evenly dispersed on the surface of A in a nanometer state , where 1%≤x≤90%, 10%≤y≤99%, and x+y=100%.

The following examples are examples of the preparation method of the graphene-containing elemental sulfur composite material provided in Example 1.

Example 2

This embodiment provides a method for preparing the graphene-containing elemental sulfur composite material provided in Example 1, comprising the following steps:

Step 1, adding graphene oxide into deionized water to obtain a graphene oxide dispersion; specifically, adding 1 mass part of graphene oxide to 1 mass part of deionized water to obtain a graphene oxide dispersion;

Step 2, adding elemental sulfur to obtain a mixture slurry of graphene oxide and elemental sulfur; specifically, adding 1 mass part of elemental sulfur to obtain a mixture slurry of graphene oxide and elemental sulfur;

Step 3, after heat-treating the mixture slurry, washing and filtering with water to obtain a graphene-containing elemental sulfur composite material; specifically, heat-treating the mixture slurry in a polytetrafluoroethylene sealed tank at 200°C for 24 hours, washing and filtering with water to obtain a graphene-containing elemental sulfur composite material; The elemental sulfur composite material of graphene, wherein the mass content of graphene is 50%, and the mass content of elemental sulfur is 50%.

Example 3

Embodiment 3 is a variation example of embodiment 2, specifically:

Step 1, adding 1 mass part of graphene oxide into 10 mass parts of deionized water to obtain a dispersion of graphene oxide;

Step 2, adding 3 parts by mass of elemental sulfur to obtain a mixture slurry of graphene oxide and elemental sulfur;

Step 3, after heat-treating the mixture slurry in a polytetrafluoroethylene sealed tank at 155°C for 48 hours, washing and filtering with water to obtain a graphene-containing elemental sulfur composite material, wherein the mass content of graphene is 20%, and the mass content of elemental sulfur is 80% %.

Example 4

Embodiment 4 is a variation example of embodiment 3, specifically:

Step 1, adding 1 mass part of graphene oxide into 500 mass parts of deionized water to obtain a dispersion of graphene oxide;

Step 2, adding 0.1 parts by mass of elemental sulfur to obtain a mixture slurry of graphene oxide and elemental sulfur;

Step 3, after heat-treating the mixture slurry in a polytetrafluoroethylene sealed tank at 50°C for 72 hours, washing and filtering with water to obtain a graphene-containing elemental sulfur composite material, wherein the mass content of graphene is 90%, and the mass content of elemental sulfur is 10% %.

Example 5

Embodiment 5 is a variation example of embodiment 4, specifically:

Step 1, adding 1 mass part of graphene oxide into 100 mass parts of deionized water to obtain a dispersion of graphene oxide;

Step 2, adding 30 parts by mass of elemental sulfur to obtain a mixture slurry of graphene oxide and elemental sulfur;

Step 3, heat-treat the mixture slurry in a stainless steel sealed tank at 500°C for 1 hour, wash and filter with water to obtain a graphene-containing elemental sulfur composite material, wherein the mass content of graphene is 1%, and the mass content of elemental sulfur is 99%.

In the above-mentioned embodiments, the graphene oxide has a thickness of 0.35-3.5 nm, which contains 1-10 graphite sheets, and the length and width of the graphite sheets are 10 nm-10 μm, respectively.

In the above-mentioned embodiments, the heat treatment is carried out by hydrothermal treatment in a sealed polytetrafluoroethylene or stainless steel tank.

The elemental sulfur composite material containing graphene was tested by SEM, and it can be seen that nano-sulfur particles are uniformly dispersed on the surface of graphene, as shown in Figure 1. The graphene-containing elemental sulfur composite material was mixed with the binder PTFE and the conductive agent Super P at a ratio of 8:1:1 to make a positive electrode sheet, with metallic lithium as the negative electrode, Cellgard 2400 as the diaphragm, and 1mol/L bistrifluoro The mixed solution of ethylene glycol dimethyl ether and dioxane (volume ratio 1:1) of lithium methylsulfonimide was used as the electrolyte, assembled into a CR2016 button battery in an argon glove box, and charged and discharged at room temperature Performance test, the specific capacity of the second discharge reaches 1480mAh/g, the charge-discharge curve is shown in Figure 2, and its cycle performance is shown in Figure 3.

Claims (9)

1. the elemental sulfur composite material of a graphitiferous alkene is characterized in that, said composite material is the binary composite A _xB _y, wherein, A is a Graphene, and B is an elemental sulfur, and B is dispersed in the A surface with the nanometer state, and wherein, x, y are respectively the content of Graphene and elemental sulfur, said 1%≤x≤90%, said 10%≤y≤99%, and x+y=100%.

2. a preparation method who prepares like the elemental sulfur composite material of graphitiferous alkene according to claim 1 is characterized in that, comprises the steps:

Step 1 adds graphene oxide in the deionized water, makes the dispersion liquid of graphene oxide;

Step 2 adds elemental sulfur, obtains the mixture paste of graphene oxide and elemental sulfur;

Step 3, mixture paste carried out heat treated after, washing filtering obtains the elemental sulfur composite material of graphitiferous alkene.

3. the preparation method of the elemental sulfur composite material of graphitiferous alkene according to claim 2; It is characterized in that in step 1, said graphene oxide thickness is 0.35～3.5nm; Wherein comprise 1～10 graphite flake layer, said graphite flake layer length and width is respectively 10nm～10 μ m.

4. the preparation method of the elemental sulfur composite material of graphitiferous alkene according to claim 2 is characterized in that, in step 1, said graphene oxide is 1 mass parts.

5. the preparation method of the elemental sulfur composite material of graphitiferous alkene according to claim 2 is characterized in that, in step 1, said deionized water is the 1-500 mass parts.

6. the preparation method of the elemental sulfur composite material of graphitiferous alkene according to claim 2 is characterized in that, in step 2, said elemental sulfur is the 0.1-30 mass parts.

7. the preparation method of the elemental sulfur composite material of graphitiferous alkene according to claim 2 is characterized in that, in step 3, said heat treated is handled in polytetrafluoroethylene that seals or stainless cylinder of steel, carrying out hydro thermal method.

8. according to the preparation method of the elemental sulfur composite material of claim 2 or 6 described graphitiferous alkene, it is characterized in that in step 3, said heat treated corresponding temperature is 50～500 ℃.

9. the preparation method of the elemental sulfur composite material of graphitiferous alkene according to claim 2 is characterized in that in step 3, and the corresponding time of said heat treated is 1～72 hour.

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