WO2019128644A1

WO2019128644A1 - Aluminum-sulfur composite material, preparation method, and positive electrode material for lithium-sulfur battery

Info

Publication number: WO2019128644A1
Application number: PCT/CN2018/119158
Authority: WO
Inventors: 柯菲; 苗力孝
Original assignee: 桑德集团有限公司; 桑顿新能源科技有限公司
Priority date: 2017-12-28
Filing date: 2018-12-04
Publication date: 2019-07-04
Also published as: CN108134071A; CN108134071B

Abstract

An aluminum-sulfur composite material. The aluminum-sulfur composite material comprises a hollow aluminum ball shell and elemental sulfur encapsulated in the hollow aluminum ball shell; pores are distributed on the hollow aluminum ball shell. The aluminum-sulfur composite material has a composite type microstructure with elemental sulfur encapsulated in a porous hollow aluminum ball shell; a positive electrode of a lithium-sulfur battery is prepared by using the composite material having said structure, and thus the sulfur utilization rate of the battery can be increased, and the rate performance and the cycle performance can be improved.

Description

Aluminum-sulfur composite material, preparation method and cathode material of lithium sulfur battery

The present application claims priority to Chinese Patent Application No. JP-A No. No. No. No. No. No. No. No. No. No. No.

Technical field

The invention relates to the technical field of battery materials, in particular to an aluminum-sulfur composite material, a preparation method thereof and a cathode material for a lithium-sulfur battery.

Background technique

Due to the theoretical specific capacity of 1675mA h g ^-1 and the theoretical energy density of 2600Whkg ^-1 , the sulfur element is widely used as a safe and non-toxic source. It is considered to be a promising next-generation lithium battery cathode material. However, when the sulfur element is used alone as a positive electrode material, the following problems still exist:

(1) The conductivity of sulfur element is very low (5*10-30Scm ^-1 at 25°C);

(2) The rate of volume change during charging and discharging is large (up to 80%);

(3) The lithium polysulfide (Li ₂ S _X , 4 ≤ _X ≤ 8), which is an intermediate product formed during the charge and discharge process, is easily dissolved in the electrolyte, thereby forming a shuttle effect between the positive and negative electrodes. The shuttle effect refers to the phenomenon that the intermediate product lithium polysulfide is dissolved in the electrolyte during the discharge process of the lithium-sulfur battery, and the electrode reciprocates back and forth between the electrodes under the dual action of the concentration difference and the electric field. This phenomenon will significantly increase the migration resistance of electrolyte ions, and will deposit lithium sulfide and lithium sulfide in the poorly soluble final product of the positive and negative electrodes. On the one hand, it will cause the loss of active sulfur, on the other hand, it will also produce a certain amount of negative lithium. The corrosion damage hinders the further reaction of the positive sulfur. Therefore, the shuttle effect is one of the most important factors that drag down the cycle performance of lithium-sulfur batteries.

These problems make the sulfur element alone as the positive electrode material, and there are problems such as low sulfur utilization rate, poor rate performance, and excessive decay of the circulation process. In general, the method of relieving the shuttle effect is also adsorbed and intercepted by modification of the separator or the barrier layer, and few considerations are made to find a solution to the problem by directly changing the direction in which the cathode material itself limits sulfur loss.

Summary of the invention

In order to solve the above problems of the prior art, an object of the present invention is to provide an aluminum-sulfur composite material having a porous microstructure of a porous hollow aluminum spherical shell coated with sulfur, which can be used as a positive electrode material for a lithium-sulfur battery. The outstanding electrical conductivity of the aluminum improves the conductivity of the electrode, suppresses the change of the electrode volume, limits the sulfur loss, and alleviates the shuttle effect, so that the battery has better electrochemical performance, cycle performance and rate performance. Another object of the present invention is to provide a method of preparing the aluminum-sulfur composite.

In view of the above, the present application provides an aluminum-sulfur composite material comprising: a hollow aluminum spherical shell and a sulfur element coated in the hollow aluminum spherical shell, the hollow aluminum spherical shell having pores distributed thereon.

Preferably, the hollow aluminum spherical shell has a particle diameter of 1 um to 10 μm.

Preferably, the mass ratio of the hollow aluminum spherical shell to the sulfur element is (20-30): (80-70).

The application also provides a method for preparing an aluminum-sulfur composite material, which comprises:

(1) Preparation of hollow aluminum spherical shell: the aluminum ball is placed in an acidic aqueous solution to be immersed, and after the bubbles are uniformly escaped, the aluminum ball is separated to obtain a hollow aluminum spherical shell with pores on the surface;

(2) Preparation of composite material of hollow aluminum spherical shell coated with sulfur element: the hollow aluminum spherical shell obtained in step (1) and the sulfur element are mixed in a certain mass ratio, and then heated to make the sulfur element in a molten state, thereby obtaining a hollow aluminum spherical shell. A composite material coated with sulfur.

Preferably, in the step (2), the hollow aluminum spherical shell obtained in the step (1) and the sulfur element are mixed and ground in a certain mass ratio, and then heated to a temperature of 113 ° C - 170 ° C and kept warm to obtain a hollow aluminum spherical shell package. A composite material coated with sulfur.

At present, the melting point of sulfur is 112.8 ° C, 115.2 ° C, etc., and the melting point of different sulfur elements is slightly different, but usually above 113 ° C, the sulfur element will melt into a liquid state, in a molten state, and along the hollow aluminum ball. The pores on the surface of the shell further penetrate into the interior of the hollow aluminum spherical shell, so that the hollow aluminum spherical shell can better combine and load the sulfur element. However, the temperature of the molten sulfur element should not be too high, especially not higher than the flash point of the sulfur element (the data indicates that the flash point temperature of the sulfur element is slightly less than 170 ° C), otherwise it is prone to fire or explosion. And in this temperature range, the hollow aluminum spherical shell is still solid and does not melt.

Preferably, the acidic aqueous solution used in the step (1) is a dilute aqueous hydrochloric acid solution having a concentration of 0.1 mol/L to 1 mol/L.

Among them, the aluminum ball used in the step (1) has an aluminum oxide film on the surface in a natural environment.

Preferably, in the step (1), the time during which the aluminum ball is placed in the acidic aqueous solution is 2-4 hours.

Preferably, in the step (1), the aluminum sphere has a particle diameter of 1 um to 10 um.

Preferably, in the step (1), the separation method is suction filtration separation, and the separated aluminum balls are washed with water to remove residual acid liquid on the aluminum balls.

Preferably, in the step (2), the hollow aluminum spherical shell and the sulfur element are mixed in a mass ratio of (20 to 30): (80 to 70).

Preferably, in the step (2), the mixture of the hollow aluminum spherical shell and the sulfur simple substance is ground for 2 to 4 hours. Preferably, the mixture of the hollow aluminum spherical shell and the sulfur element is homogeneously mixed and ground using a high energy ball mill.

Preferably, in the step (2), the heating is carried out to a temperature of from 130 ° C to 170 ° C, preferably from 150 ° C to 170 ° C, more preferably from 160 ° C to 170 ° C.

Preferably, in the step (2), the holding time is 4 to 10 hours.

The present invention also provides an aluminum-sulfur composite material obtained by the above method.

The invention also provides a lithium sulfur battery cathode material, comprising the aluminum sulfur composite material provided by the invention.

The invention has the beneficial effects that the aluminum-sulfur composite material of the invention has a composite microstructure of a porous hollow aluminum spherical shell coated with sulfur, and the positive electrode of the lithium-sulfur battery is fabricated by using the composite material having the structure, and the following technology can be achieved. effect:

(1) The electrical conductivity of the electrode can be significantly improved by utilizing the conductive property of the aluminum protrusion.

(2) The composite microstructure of porous hollow aluminum spherical shell coated with sulfur elemental substance. On the one hand, the pore structure distributed on the hollow aluminum spherical shell provides a way for the electrolyte to enter the hollow aluminum spherical shell and fully contact with the sulfur element. The coating effect of the aluminum spherical shell can effectively fix sulfur, inhibit the sulfur element and the polysulfide escape from the hollow aluminum spherical shell dissolved in the electrolyte, reduce the loss of sulfur, thereby improving the utilization of sulfur and alleviating the shuttle effect.

(3) The hollow aluminum spherical shell is coated on the outside of the sulfur element, which has certain constraint on the expansion of sulfur volume during charging and discharging, so the volume change rate of the positive electrode material during charging and discharging can be reduced.

In summary, the aluminum-sulfur composite material of the present invention is used as a positive electrode of a lithium-sulfur battery, which can improve the sulfur utilization rate of the battery, improve the rate performance and the cycle performance.

In addition, the preparation method of the aluminum-sulfur composite material of the invention utilizes the certain corrosion resistance of the aluminum oxide film naturally existing on the surface of the aluminum ball, and the aluminum oxide film in a partial region when the aluminum ball is put into the dilute acid. It will be corroded, causing the acid to enter the inside of the aluminum ball. The internal aluminum will corrode much faster than the aluminum ball shell in which the aluminum oxide film is not corroded in the surface area. The contact between the parts and the acid is not the same, causing some parts to corrode quickly and some parts to corrode slowly. By this principle, the aluminum balls immersed in the dilute acid become hollow spherical shell structures with pores distributed on the surface. The process is fast and easy to operate. Then, by mixing and grinding with the sulfur element, the sulfur element is further mixed with the hollow aluminum ball to be more uniform, and has a more uniform and fine particle structure. In the heated reaction kettle, the sulfur element is melted at a high temperature. After the liquid is further infiltrated into the aluminum shell of the porous hollow sphere structure from the pores, not only the sulfur element is further uniformly distributed, but also the sulfur element is tightly combined with the aluminum shell of the porous hollow sphere structure, and the hollow aluminum spherical shell is coated with the sulfur element. Composite material. The preparation method of the aluminum-sulfur composite material of the invention is very suitable for industrial production.

DRAWINGS

1 is a flow chart of a method for preparing an aluminum-sulfur composite material of the present invention.

2 is a scanning electron microscope image of an aluminum-sulfur composite material prepared in Example 1 of the present invention at a low magnification.

Fig. 3 is a scanning electron microscope image of the aluminum-sulfur composite material prepared in Example 1 of the present invention at a high rate.

Detailed ways

The present invention will be described in detail with reference to the accompanying drawings,

The present application provides an aluminum-sulfur composite material comprising: a hollow aluminum spherical shell and a sulfur element coated in the hollow aluminum spherical shell, wherein the hollow aluminum spherical shell has pores distributed thereon.

Preferably, the hollow aluminum spherical shell has a particle size of from 1 μm to 10 μm, and typically, but not limited to, preferably 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, and 10 μm.

Preferably, the mass ratio of the hollow aluminum spherical shell to sulfur in the aluminum-sulfur composite material is (20-30): (80-70), typically but not limited to preferably 20:80, 22:78, 25:75 26:74, 27:73, 28:72, 29:71, 30:70.

The present application further includes a method for preparing the aluminum-sulfur composite material, as shown in FIG. 1, specifically comprising the following steps:

(1) Preparation of hollow aluminum spherical shell: The aluminum sphere with particle size of 1um-10um is placed in a dilute acid aqueous solution to be immersed, and after the bubbles are uniformly escaped, the aluminum sphere is separated to obtain a hollow aluminum spherical shell with pores on the surface;

(2) Preparation of composite material of hollow aluminum spherical shell coated with sulfur element: the hollow aluminum spherical shell obtained in step (1) and the elemental sulfur are mixed and ground in a certain mass ratio, and then the mixture is charged into the reaction kettle, and heated to make the reaction vessel The temperature is higher than the melting temperature of the sulfur element but lower than the flash point temperature (generally referred to as 113 ° C to 170 ° C in the present application) and is kept warm to obtain a composite material in which the hollow aluminum spherical shell is coated with sulfur.

Wherein the dilute acid aqueous solution used in the step (1) is a dilute hydrochloric acid aqueous solution having a concentration of 0.1 mol/L to 1 mol/L, and typically, but not limited to, preferably 0.1 mol/L, 0.2 mol/L, 0.3 mol/L, 0.4 mol/L, 0.5 mol/L, 0.6 mol/L, 0.7 mol/L, 0.8 mol/L, and 0.9 mol/L.

Preferably, the step (1) of placing the aluminum balls in the dilute acid aqueous solution for 2-4 hours, typically but not limited to preferably 2h, 2.5h, 3h, 3.5h and 4h, at this time, the bubbles A uniform rise of 0.5-1 h, typically but not limited to preferably 0.5 h, 0.6 h, 0.7 h, 0.8 h, 0.9 h, separates the aluminum spheres.

Preferably, the separation method in the step (1) is a suction filtration separation, and the separated aluminum balls are washed with water to remove the residual acid liquid on the aluminum balls.

Preferably, the step (2) is to mix and grind the mixture of the hollow aluminum spherical shell and the sulfur element by high energy ball milling, high energy ball milling for 2 to 4 hours, typically but not limited to preferably 2h, 3h, 3.5h and 4h. .

Preferably, the step (2) is specifically heated to bring the temperature in the reaction vessel to 130 ° C to 170 ° C, more preferably 150 ° C to 170 ° C, still more preferably 160 ° C to 170 ° C.

In the step (2), the temperature in the reaction vessel is typically, but not limited to, preferably 113 ° C, 115 ° C, 120 ° C, 125 ° C, 130 ° C, 135 ° C, 140 ° C, 145 ° C, 150 ° C, 155. °C, 160 ° C, 165 ° C and 170 ° C.

Preferably, the holding time in the step (2) is 4 to 10 hours, typically but not limited to 4h, 4.5h, 5h, 5.5h, 6h, 6.5h, 7h, 7.5h, 8h, 8.5h, 9h, 9.5h and 10h.

In the present invention, the aluminum-sulfur composite material obtained by the above preparation method is used as a positive electrode material of a lithium sulfur battery.

In order to help understand the solution of the present invention, several specific processes for preparing the aluminum-sulfur composite of the present invention are given below, and the present invention will be further explained in conjunction with the microscopic topography.

Embodiment 1

The aluminum ball with a particle size of 10 um was selected and placed in a 1 mol/L aqueous solution of hydrochloric acid. The aluminum ball was immersed for 2 hours, and the bubbles were uniformly allowed to escape for about 0.5 h, and the aluminum powder was taken out by suction filtration. Deionized water washing, suction filtration, drying, and a hollow aluminum spherical shell. The prepared hollow aluminum spherical shell and sulfur powder were ball milled at a mass ratio of 30:70 for 4 hours, and then the prepared powder was charged into a 200 ml reaction vessel, heated to 160 ° C, and kept for 4 hours to obtain a hollow. The aluminum spherical shell is coated with a sulfur-only composite material and used as a positive electrode material for a lithium-sulfur battery.

The hollow aluminum spherical shell obtained in the present embodiment is coated with a sulfur-only composite material, and the morphology is observed under a scanning electron microscope. As shown in FIG. 2, a scanning electron microscope image at a low magnification is observed, and the particles are uniform. The spherical structure, Figure 3 shows the scanning electron microscopy image at high magnification, each particle has a hollow spherical shell structure with several pores on the surface, and sulfur is coated in the pores.

Embodiment 2

The aluminum ball with a particle size of 1 um was selected and placed in a 0.1 mol/L-1 mol/L aqueous hydrochloric acid solution. The aluminum ball was immersed for 2 hours, and the bubbles were uniformly allowed to escape for about 1 hour, and the aluminum powder was taken out by suction filtration. Deionized water washing, suction filtration, drying, to obtain a hollow aluminum spherical shell. The prepared hollow aluminum spherical shell and sulfur powder were ball milled at a mass ratio of 30:70 for 2 h, and then the prepared powder was placed in a 200 ml reaction vessel, heated to 150 ° C, and kept for 4 h to obtain a hollow. The aluminum spherical shell is coated with a sulfur-only composite material and used as a positive electrode material for a lithium-sulfur battery.

Embodiment 3

The aluminum ball with a particle size of 1 um was selected and placed in a 0.1 mol/L-1 mol/L aqueous hydrochloric acid solution. The aluminum ball was immersed for 2 hours, and the bubbles were uniformly allowed to escape for about 1 hour, and the aluminum powder was taken out by suction filtration. Deionized water washing, suction filtration, drying, to obtain a hollow aluminum spherical shell. The prepared hollow aluminum spherical shell and sulfur powder were ball milled at a mass ratio of 20:80 for 4 hours, and then the prepared powder was charged into a 200 ml reaction vessel, heated to 160 ° C, and kept for 5 hours to obtain a hollow. The aluminum spherical shell is coated with a sulfur-only composite material and used as a positive electrode material for a lithium-sulfur battery.

Embodiment 4

The aluminum ball with a particle size of 5 um was selected and placed in a 0.1 mol/L-1 mol/L aqueous hydrochloric acid solution. The aluminum ball was immersed for 2 hours, and the bubbles were uniformly allowed to escape for about 1 hour, and the aluminum powder was taken out by suction filtration. Deionized water washing, suction filtration, drying, to obtain a hollow aluminum spherical shell. The prepared hollow aluminum spherical shell and sulfur powder were ball milled at a mass ratio of 30:70 for 2-4 hours, and then the prepared powder was charged into a 200 ml reaction vessel, heated to 170 ° C, and kept for 6 hours. A composite material of a hollow aluminum spherical shell coated with sulfur is obtained, which is used as a positive electrode material for a lithium-sulfur battery.

Embodiment 5

The aluminum ball with a particle size of 5 um was selected and placed in a 1 mol/L aqueous solution of hydrochloric acid. The aluminum ball was immersed for 4 hours, and the bubbles were uniformly allowed to escape for about 0.5 h, and the aluminum powder was taken out by suction filtration. Deionized water washing, suction filtration, drying, to obtain a hollow aluminum spherical shell. The prepared hollow aluminum spherical shell and sulfur powder were ball milled at a ratio of 20:80 by high energy for 2-4 hours, and then the prepared powder was charged into a 200 ml reaction vessel, heated to 150 ° C, and kept for 4 hours. A composite material of a hollow aluminum spherical shell coated with sulfur is obtained, which is used as a positive electrode material for a lithium-sulfur battery.

Embodiment 6

The aluminum ball with a particle size of 10 um was selected and placed in a 1 mol/L aqueous solution of hydrochloric acid. The aluminum ball was immersed for 4 hours, and the bubbles were uniformly allowed to escape for about 0.5 h, and the aluminum powder was taken out by suction filtration. Deionized water washing, suction filtration, drying, to obtain a hollow aluminum spherical shell. The prepared hollow aluminum spherical shell and sulfur powder were ball milled at a mass ratio of 20:80 for 4 hours, and then the prepared powder was charged into a 200 ml reaction vessel, heated to 140 ° C, and kept for 10 hours to obtain a hollow. The aluminum spherical shell is coated with a sulfur-only composite material and used as a positive electrode material for a lithium-sulfur battery.

The preparation method of the invention adopts dilute acid etching aluminum powder (microscopically spherical) to obtain a porous hollow aluminum spherical shell structure. The hollow aluminum spherical shell structure is used as a frame, and the sulfur simple substance is uniformly mixed with the porous hollow aluminum spherical shell, and the porous element is coated with sulfur by heating the elemental element of sulfur to a molten state and deep into the porous hollow aluminum spherical shell. The composite material is used for the positive electrode of the lithium-sulfur battery, which can increase the conductivity of the electrode, reduce the volume change rate of the positive electrode material during charge and discharge, hinder the dissolution of sulfur in the electrolyte, and reduce sulfur loss. The porous structure of the hollow aluminum spherical shell provides a passage for the electrolyte to enter the interior, but prevents the sulfur element from escaping the aluminum spherical shell and dissolves in the electrolyte, thereby improving the utilization efficiency of sulfur.

Claims

An aluminum-sulfur composite material, comprising: a hollow aluminum spherical shell and a sulfur element coated in the hollow aluminum spherical shell, wherein the hollow aluminum spherical shell has pores distributed thereon.
The aluminum-sulfur composite material according to claim 1, wherein the hollow aluminum spherical shell has a particle diameter of from 1 μm to 10 μm.
The aluminum-sulfur composite material according to claim 1, wherein a mass ratio of the hollow aluminum spherical shell to the sulfur simple substance is 20 to 30:80 to 70.
A method for preparing an aluminum-sulfur composite material, comprising the steps of:

(1) Preparation of hollow aluminum spherical shell: the aluminum ball is placed in an acidic aqueous solution to be immersed, and after the bubbles are uniformly escaped, the aluminum ball is separated to obtain a hollow aluminum spherical shell with pores on the surface;

(2) Preparation of composite material of hollow aluminum spherical shell coated with sulfur element: the hollow aluminum spherical shell obtained in step (1) and the sulfur element are mixed in a certain mass ratio, and then heated to make the sulfur element in a molten state, thereby obtaining a hollow aluminum spherical shell. A composite material coated with sulfur.
The method for producing an aluminum-sulfur composite according to claim 4, wherein the acidic aqueous solution used in the step (1) is a dilute aqueous hydrochloric acid solution having a concentration of 0.1 mol/L to 1 mol/L.
The method for producing an aluminum-sulfur composite according to claim 5, characterized in that, in the step (1), the time during which the aluminum balls are placed in the acidic aqueous solution is 2-4 hours.
The method for preparing an aluminum-sulfur composite material according to claim 4, wherein in the step (1), the separation method is separated by suction filtration, and the separated aluminum balls are washed with water to remove aluminum balls. Residual acid on the residue.
The method for producing an aluminum-sulfur composite according to claim 4, wherein in the step (1), the aluminum sphere has a particle diameter of from 1 μm to 10 μm.
The method for preparing an aluminum-sulfur composite material according to claim 4, wherein in the step (2), the hollow aluminum spherical shell obtained in the step (1) and the sulfur simple substance are mixed and ground in a certain mass ratio, and then heated to make The temperature reaches 113 ° C - 170 ° C and is kept warm, and a composite material of a hollow aluminum spherical shell coated with sulfur is obtained.
The method for producing an aluminum-sulfur composite material according to claim 4, wherein in the step (2), the hollow aluminum spherical shell and the sulfur simple substance are mixed at a mass ratio of 20 to 30:80 to 70.
The method for producing an aluminum-sulfur composite material according to claim 9, wherein in the step (2), the mixture of the hollow aluminum spherical shell and the sulfur simple substance is ground for 2 to 4 hours.
The method for producing an aluminum-sulfur composite according to claim 9, wherein in the step (2), heating is performed to bring the temperature to 130 ° C to 170 ° C.
The method for producing an aluminum-sulfur composite according to claim 12, wherein in the step (2), heating is performed to bring the temperature to 150 ° C to 170 ° C.
The method for preparing an aluminum-sulfur composite material according to claim 9, wherein in the step (2), the holding time is 4 to 10 hours.
An aluminum-sulfur composite material prepared by the method for producing an aluminum-sulfur composite material according to any one of claims 1-14.
A lithium-sulfur battery positive electrode material comprising the aluminum-sulfur composite material according to any one of claims 1-3 and 15.