CN109167045B

CN109167045B - Method for preparing sulfur-based positive electrode material by applying reticular porous nano lanthanum oxide

Info

Publication number: CN109167045B
Application number: CN201811064314.2A
Authority: CN
Inventors: 张永光; 崔国梁
Original assignee: Zhaoqing South China Normal University Optoelectronics Industry Research Institute
Current assignee: Zhaoqing South China Normal University Optoelectronics Industry Research Institute
Priority date: 2018-09-12
Filing date: 2018-09-12
Publication date: 2021-07-27
Anticipated expiration: 2038-09-12
Also published as: CN109167045A

Abstract

The invention relates to a method for preparing a lithium-sulfur battery anode by using an active material, belonging to the field of material chemistry. According to the method, porous net-shaped nano lanthanum oxide is prepared by a spray drying technology, and then the composition of the porous net-shaped nano lanthanum oxide and sulfur is realized through a hydrothermal reaction to obtain a rare earth sulfur-based positive electrode material, wherein the first discharge capacity is up to 1095mAh/g after the rare earth sulfur-based positive electrode material is assembled into a battery. The method has high yield and industrial feasibility, the nano lanthanum oxide in the rare earth sulfur-based positive electrode material can ensure high conductivity so as to improve the transmission rate of electrons and ions and adsorb soluble polysulfide, and the mesh porous structure can not only provide rich active sites, but also effectively coat sulfur.

Description

Method for preparing sulfur-based positive electrode material by applying reticular porous nano lanthanum oxide

Technical Field

The invention relates to a method for preparing a lithium-sulfur battery anode by using an active material, belonging to the field of material chemistry.

Background

The rechargeable battery is undoubtedly one of the most important basic components closely related to human activities, and has been widely used in portable electronic products, such as mobile phones, notebook computers, automobiles, wearable sensors, medical devices, and the like, and people have made higher and higher demands on the performance thereof. At present, the traditional commercial lithium ion battery is limited by the theoretical specific capacity (300 mAh/g) and the safety problem, and the requirement of the lithium ion battery on the practical application quality is difficult to meet. Therefore, it is of great strategic importance to develop a new lithium ion secondary battery with high energy density, environmental protection and low cost in the next generation.

The theoretical specific capacity of the novel lithium-sulfur battery is 2600Wh/kg, which is about five times of that of the traditional commercial lithium ion battery, and the lithium-sulfur battery also has the advantages of rich sulfur resources, environmental friendliness, low price and the like, and is considered to be one of the high-performance batteries with the most development potential. However, commercialization of lithium sulfur batteries has a long way. Firstly, elemental sulfur is used as an insulator of electrons and ions at room temperature, so that the transmission efficiency of the electrons and the ions is low, and the coulomb efficiency is reduced; secondly, the reduction intermediate polysulfide is dissolved in the electrolyte, so that a severe shuttling effect is generated, and the cycle life of the lithium-sulfur battery is shortened; third, the initial lithiation of sulfur forms long chain lithium polysulfides (4. ltoreq. n.ltoreq.8) that are soluble in the organic electrolyte and can pass through the separator to the anode side. Subsequently, further lithiation into low-order short-chain lithium polysulfides (1. ltoreq. n.ltoreq.4) can be performed to deposit on the lithium surface, resulting in problems of continuous capacity fading and low utilization of active materials. Fourthly, the sulfur electrode can contract and expand correspondingly in the charging and discharging process, and the physical structure of the electrode is damaged to a certain extent. Therefore, how to improve the cycle life of the lithium-sulfur battery, improve the utilization rate of the positive active material, and improve the volume expansion problem becomes a hot research point of the lithium-sulfur battery.

In the prior art, the scheme for improving the performance of the lithium-sulfur battery is mainly optimization and modification of a sulfur-based positive electrode structure, and elemental sulfur and a porous material with a high pore structure are mechanically compounded by a filling, mixing or coating method to form a positive electrode composite material, so that the lithium ion conductivity of the sulfur-based positive electrode and the cycle performance of the battery are improved. The prior art on the study of metal oxide/sulfur composite positive electrode materials has also been reported: CN201510606994 reports a preparation method of a metal-coated sulfur/nickel-cobalt-manganese-lithium oxide electrode material, weighing sulfur and nickel-cobalt-manganese-lithium oxides according to a certain proportion, mechanically ball-milling for 2-20 hours in an argon atmosphere, dispersing the obtained product in a soluble metal salt solution, adding a surfactant, stirring for 1-10 hours, slowly dropwise adding an alkali solution, stirring for 2-5 hours, filtering and drying, standing for 1-10 hours at 60-120 ℃ to obtain a metal-oxide-coated sulfur/nickel-cobalt-manganese-lithium oxide electrode material, heating the metal-oxide-coated sulfur/nickel-cobalt-manganese-lithium oxide electrode material to 60-120 ℃ in an atmosphere protection mode, introducing alcohol vapor of C1-C4, and reducing to obtain the metal-coated sulfur/nickel-cobalt-manganese-lithium oxide electrode material.

Disclosure of Invention

Aiming at the problems, the invention provides a preparation method of a lithium-sulfur battery positive electrode material, which is characterized in that porous reticular nano lanthanum oxide is prepared by a spray drying technology, and then the compounding of the porous reticular nano lanthanum oxide and sulfur is realized through a hydrothermal reaction to obtain the rare earth sulfur-based positive electrode material. The method comprises the following specific steps:

step one, preparing porous reticular nano lanthanum oxide:

according to the volume ratio of 1:1, mixing 0.1mol/L lanthanum nitrate and 0.9mol/L urea, then carrying out ultrasonic dispersion on the mixed solution for 1-5 h by using an ultrasonic cell crusher under the power of 300-650W, and carrying out spray drying treatment on the obtained uniform mixed solution. The temperature is kept at 400-500 ℃ during spray drying, the air flow rate is kept at 8-10 cc/min, the feeding rate is 0.5-1 ml/min, and the needle passing rate is 1 time/5-30 seconds. Because lanthanum nitrate and urea can generate chemical reaction at 400 ℃ to generate lanthanum oxide, nitrogen, carbon dioxide and water vapor, pure porous reticular nano lanthanum oxide can be obtained after spray drying is finished;

secondly, preparing the porous reticular nano lanthanum oxide/sulfur anode material:

according to the mass ratio of 1: weighing the porous net-shaped nano lanthanum oxide and nano sulfur obtained in the step one according to the proportion of 1-10, placing the mixture in a mortar, grinding the mixture into uniform and fine powder, dropwise adding carbon disulfide into the mixture in the mortar, then fully grinding again, collecting the obtained powder, placing the powder into a reaction kettle, and carrying out hydrothermal reaction under the conditions that the heating temperature is 155 ℃ and the heat preservation time is 12 hours to obtain the porous net-shaped nano lanthanum oxide/sulfur composite material.

The assembly and application of the lithium-sulfur battery can be completed by adopting the obtained porous reticular nano lanthanum oxide/sulfur cathode material.

The raw materials involved in the above steps are all commercially available.

The invention has the following beneficial effects:

(1) the lanthanum oxide prepared by adopting a spray drying method is of a net-shaped porous structure, so that the efficiency of a sulfur inlet hole structure in a sulfur loading process is improved, the electrochemical performance of a lithium-sulfur battery anode material is obviously improved, the discharge capacity attenuation in a circulating process is small, and the circulating stability is obviously improved.

(2) The reticular porous nano lanthanum oxide modified lithium sulfur battery has the advantages that lanthanum oxide has unique properties as a rare earth oxide, the conductivity is high, the molecular adsorption capacity of a surface structure is strong, the active surface area is large, the shuttle effect of polysulfide can be effectively prevented, a good stable network structure can be provided for active substance sulfur, the transmission path of electrons and particles can be shortened, the electrochemical activity of elemental sulfur is improved, and the overall performance of the lithium sulfur battery is further improved.

(3) The spray drying and hydrothermal methods adopted in the preparation of the porous reticular nano lanthanum oxide/sulfur composite anode are the simplest and most convenient and high-yield synthesis means, and the spray drying and hydrothermal strategies are easy and effective, so that the large-scale and low-cost industrialization of the preparation of the porous reticular nano lanthanum oxide/sulfur composite anode is easy to realize.

(4) The porous reticular nano lanthanum oxide/sulfur composite lithium-sulfur battery anode material prepared by the method is used as a lithium-sulfur battery consisting of a working electrode of an anode pole piece, the first charge-discharge specific capacity of the battery reaches 1095mAh/g under 0.1 ℃, the battery has high discharge capacity and excellent cycling stability, and the electrochemical performance of the battery is obviously superior to that of the lithium-sulfur battery prepared by the prior art.

(5) The invention relates to a preparation method of a lithium-sulfur battery positive electrode material with the characteristics of high yield and industrial feasibility.

Drawings

FIG. 1 is an X-ray diffraction pattern of a reticulated porous lanthanum oxide/sulfur composite structure made in example 1.

Fig. 2 is a transmission electron microscope photograph of the lithium sulfur battery cathode material with a reticular porous lanthanum oxide/sulfur composite structure prepared in example 1.

Fig. 3 is an electrochemical charge-discharge curve of the lithium-sulfur battery positive electrode material with the reticular porous lanthanum oxide/sulfur composite structure prepared in example 1 after being assembled into a battery.

FIG. 4 is the electrochemical charge-discharge curve of the nano lanthanum oxide/sulfur composite structure lithium-sulfur battery anode material prepared by the comparative example after being assembled into a battery.

The specific implementation case is as follows:

the invention is further illustrated with reference to the following figures and examples.

Example 1:

step one, preparing porous reticular nano lanthanum oxide:

according to the volume ratio of 1:1, mixing 0.1mol/L lanthanum nitrate and 0.9mol/L urea, and then carrying out ultrasonic dispersion on the mixed solution for 3 hours by using an ultrasonic cell crusher under 500 power. The resulting homogeneous mixed solution was subjected to spray drying. The temperature was maintained at 400 ℃ during spray drying, the air flow rate was maintained at 8cc/min, the feed rate was 0.5ml/min, and the needle feed rate was 1 pass/5 sec. Because lanthanum nitrate and urea can generate chemical reaction to generate lanthanum oxide, nitrogen, carbon dioxide and water vapor under the condition of 400 ℃, pure porous reticular nano lanthanum oxide can be obtained after spray drying is finished.

according to the mass ratio of 1:2, placing the mixture in a mortar, grinding the mixture into uniform and fine powder, dropwise adding carbon disulfide into the mixture in the mortar, then fully grinding again, collecting the obtained powder, placing the powder in a reaction kettle, and carrying out hydrothermal reaction at the heating temperature of 155 ℃ for 12 hours to obtain the porous reticular nano lanthanum oxide/sulfur composite material.

FIG. 1 is an X-ray diffraction pattern of a reticulated porous lanthanum oxide/sulfur composite structure made in example 1. As can be seen from the figure, the characteristic peak of sulfur accompanied with the characteristic peak of lanthanum oxide in the reticular porous lanthanum oxide/sulfur composite structure is obvious, which shows that the sulfur in the composite material is rich and uniformly coated by the reticular porous lanthanum oxide to form a coating type structure, and also shows that the lanthanum oxide material with the structure has strong adsorption effect on the sulfur and high sulfur carrying capacity.

Fig. 2 is a transmission electron microscope photograph of the lithium sulfur battery cathode material with a reticular porous lanthanum oxide/sulfur composite structure prepared in example 1. In a transmission picture, the nano lanthanum oxide with the reticular porous structure designed by the invention is more visually displayed.

Fig. 3 is an electrochemical charge-discharge curve of the lithium-sulfur battery positive electrode material with the reticular porous lanthanum oxide/sulfur composite structure prepared in example 1 after being assembled into a battery. As can be seen from the figure, at the current density of 0.1C, the first discharge capacity of the material is up to 1095mAh/g, one reaction platform is arranged in the charging process (ascending curve), two reaction platforms are arranged in the discharging process (descending curve), and no redundant side reaction platform also shows that the positive electrode material has excellent charge-discharge stability in the circulating process.

Example 2:

step one, preparing porous reticular nano lanthanum oxide:

according to the volume ratio of 1:1, mixing 0.1mol/L lanthanum nitrate and 0.9mol/L urea, and then carrying out ultrasonic dispersion on the mixed solution for 4 hours by using an ultrasonic cell crusher under 600 power. The resulting homogeneous mixed solution was subjected to spray drying. The temperature was maintained at 400 ℃ during spray drying, the air flow rate was maintained at 10cc/min, the feed rate was 1ml/min, and the needle feed rate was 1 pass/8 sec. Because lanthanum nitrate and urea can generate chemical reaction to generate lanthanum oxide, nitrogen, carbon dioxide and water vapor under the condition of 400 ℃, pure porous reticular nano lanthanum oxide can be obtained after spray drying is finished.

according to the mass ratio of 1: 4, weighing the required lanthanum oxide and nano sulfur, placing the mixture in a mortar, grinding the mixture into uniform and fine powder, dropwise adding carbon disulfide into the mixture in the mortar, then fully grinding again, collecting the obtained powder, placing the powder into a reaction kettle, and carrying out hydrothermal reaction under the conditions that the heating temperature is 155 ℃ and the heat preservation time is 12 hours to obtain the porous reticular nano lanthanum oxide/sulfur composite material. .

Comparative example:

firstly, preparing a precursor solution:

taking the required lanthanum chloride and nano sulfur according to the mass ratio of 1:2, mechanically ball-milling for 2 hours in an argon atmosphere, dispersing the obtained product in 50mL of deionized water, adding a surfactant, and stirring for 1 hour.

Step two, preparing a lanthanum hydroxide/sulfur anode material:

slowly dropwise adding a sodium hydroxide alkali solution into the precursor solution until the pH is =9, stirring for 2h, filtering and drying, and standing for 1h at 60 ℃ to obtain the lanthanum hydroxide coated nano sulfur composite material.

Thirdly, preparing the nano lanthanum oxide/sulfur anode material:

and heating the obtained lanthanum hydroxide coated nano sulfur composite material to 250 ℃ under the atmosphere protection, and thermally decomposing the lanthanum hydroxide to obtain the nano lanthanum oxide/sulfur anode material.

FIG. 4 is the electrochemical charge-discharge curve of the nano lanthanum oxide/sulfur composite structure lithium-sulfur battery anode material prepared by the comparative example after being assembled into a battery. As can be seen from the graph, the first discharge capacity of the material at a current density of 0.1C was 895mAh/g, which is lower than that of the porous network nano lanthanum oxide/sulfur cathode material prepared from example 1.

Claims

1. The method for preparing the sulfur-based positive electrode material by using the reticular porous nano lanthanum oxide is characterized in that the positive electrode material is formed by compounding the porous reticular nano lanthanum oxide and sulfur through a hydrothermal reaction;

the method comprises the following steps:

step one, preparing porous reticular nano lanthanum oxide:

mixing 0.1mol/L lanthanum nitrate and 0.9mol/L urea according to the volume ratio of 1:1, then carrying out ultrasonic dispersion on the mixed solution for 1-5 h by using an ultrasonic cell crusher under the power of 300-650W, and carrying out spray drying treatment on the obtained uniform mixed solution;

weighing the porous reticular nano lanthanum oxide and nano sulfur obtained in the step one according to the mass ratio of 1: 1-10, placing the mixture in a mortar, grinding the mixture into uniform fine powder, dropwise adding carbon disulfide into the mixture in the mortar, then fully grinding again, collecting the obtained powder, placing the powder into a reaction kettle, and carrying out hydrothermal reaction at the heating temperature of 155 ℃ for 12h to obtain the porous reticular nano lanthanum oxide/sulfur composite material.

2. The method for preparing the sulfur-based positive electrode material by using the reticular porous nano lanthanum oxide as claimed in claim 1, wherein the spray drying process comprises the steps of maintaining the temperature at 400-500 ℃, maintaining the air flow rate at 8-10 cc/min, maintaining the feeding rate at 0.5-1 ml/min, and maintaining the needle passing rate at 1 time/5-30 seconds.