CN105680016B - One kind contains addition of C o3O4Lithium sulfur battery anode material and preparation method - Google Patents

Abstract

The invention discloses a lithium-sulfur battery cathode material containing an additive Co ₃ O ₄ , which is doped by KS-6, Co ₃ O ₄ and sulfur, wherein Co ₃ O ₄ and sulfur are evenly filled in the KS-6 In the sheet, the mass ratio of KS-6 to Co ₃ O ₄ is 1:0.1-0.25, and the mass ratio of Co ₃ O ₄ -KS-6 to sulfur is 1:1-2. _The invention also discloses a preparation method of the lithium _- sulfur battery cathode material containing the additive Co3O4. The preparation method of the present invention adopts wet mixing and high-temperature calcination to obtain the Co ₃ O ₄ -KS-6 composite product, which is mixed and ground with sulfur to obtain a lithium-sulfur battery cathode composite material, which is low in cost, simple in operation, and easy to improve The production efficiency is conducive to the realization of industrialized production; the positive electrode composite material prepared by the invention has high discharge specific capacity and strong cycle stability, and can be widely used in the field of energy storage as a lithium-sulfur battery positive electrode material.

Description

A lithium-sulfur battery cathode material containing additive Co3O4 and its preparation method

technical field

The invention belongs to the technical field of lithium _- sulfur battery preparation, and relates to a lithium _- sulfur battery positive electrode material containing an additive Co3O4, and also relates to a preparation method _of the lithium _- sulfur battery positive electrode material containing an additive Co3O4.

Background technique

At present, fossil fuels play a leading role in human energy demand, however, the resources of fossil fuels are limited, and the burning of fossil fuels causes serious environmental pollution. Therefore, the development of clean and renewable energy, such as wind energy and solar energy, is imminent, and these energy sources need to be transformed by electrochemical energy storage before they can be used by people, which requires reliable, low-cost, and environmentally friendly large-scale energy Storage System. The theoretical specific capacity of elemental sulfur is 1675mAh/g, and the theoretical specific energy reaches 2600Wh/kg, which is the highest among all known lithium-ion battery cathode materials, and sulfur reserves are abundant, cheap, low-toxic, and environmentally friendly, so sulfur The base material is the positive electrode material of lithium-ion batteries, and has development potential.

However, the following problems still exist in the application of lithium-sulfur batteries to practice: first, sulfur is a highly insulating material for electrons and ions; Third, due to the difference in density between sulfur and Li ₂ S, there is a serious volume expansion (about 80%) in the sulfur cathode during the lithiation process. This series of problems will lead to low utilization of electrode active materials and poor battery cycle performance.

In recent years, researchers have taken different measures to suppress the shuttle effect and improve the performance of lithium-sulfur batteries. Confining sulfur in the pores of conductive materials has become the most direct and effective method. For example, different methods are used to confine sulfur in the pores of mesoporous carbon, carbon nanotubes, hollow carbon spheres, graphene or conductive polymer spherical shells to limit the dissolution and shuttling of lithium polysulfide, an intermediate discharge product, in the electrolyte. The above method can improve battery performance to a certain extent, but there are disadvantages such as difficult preparation of carrier materials and high price. Utilizing the properties and high specific surface area of metal nano-oxides, lithium polysulfide can be adsorbed to prevent it from dissolving and shuttling in the electrolyte. Therefore, the composite electrode material prepared by metal nano-oxide and sulfur can improve the conductivity of sulfur, inhibit the shuttle effect, and improve the cycle performance to a certain extent. Co ₃ O ₄ is a positive electrode material with good chemical stability, which can inhibit the oxidation activity of the battery surface and reduce the interface reaction between the electrode and the electrolyte. At the same time, Co ₃ O ₄ reacts with sulfur to form CoS _X without the shuttle effect, thereby Improve the cycle stability and discharge specific capacity of lithium-sulfur batteries, improve the electrochemical performance of battery cathode materials, and prolong battery life.

Contents of the invention

_The purpose of the present invention is to provide a lithium _- sulfur battery positive electrode material containing additive Co3O4, which solves the problems of low utilization rate of electrode active materials and poor battery cycle performance when elemental sulfur is used as positive electrode material in the prior art.

Another object of the present invention is to provide a preparation method of the lithium-sulfur battery cathode material containing the additive Co ₃ O ₄ .

The technical solution adopted in the present invention is a lithium-sulfur battery positive electrode material containing additive Co ₃ O ₄ , which is doped by KS-6, Co ₃ O ₄ and sulfur, wherein Co ₃ O ₄ and sulfur are evenly filled In the KS-6 sheet, the mass ratio of KS-6 to Co ₃ O ₄ is 1:0.1-0.25, and the mass ratio of Co ₃ O ₄ -KS-6 to sulfur is 1:1-2.

Another technical solution adopted in the present invention is a preparation method of a lithium _- sulfur battery cathode material containing an additive _Co3O4 , which is specifically implemented according to the following steps:

Step 1) Put KS-6 and Co(NO ₃ ) ₂ ·6H ₂ O into a ball milling jar at a mass ratio of 1:0.5~1, add an appropriate amount of ethanol, and wet mix for 1.5-2 hours, then dry in an oven at 70°C Dry for 12-15 hours;

Step 2) Calcining the mixture obtained in step 1) at a high temperature in a tube furnace at 250° C. to 400° C. under protective gas conditions for 4 to 7 hours. The mass ratio of KS-6 to Co ₃ O ₄ in the product obtained after calcination is 1: 0.1～0.25;

Step 3) Mix and grind the calcined product of step 2) with sulfur at a ratio of 1:1~2, place it in a hydrothermal reaction kettle, and put argon gas into it for 20-30 minutes, then place the reaction kettle at 150-160°C to keep warm After 10-12 hours, a lithium-sulfur battery cathode material containing the additive Co ₃ O ₄ is obtained.

The beneficial effect of the present invention is that the composite product of Co ₃ O ₄ -KS-6 can be obtained after high-temperature calcination by wet mixing, which is mixed and ground with sulfur to obtain a lithium-sulfur battery cathode composite material, which is low in cost, simple in operation, and easy to Improve production efficiency, which is conducive to the realization of industrial production; the additive Co ₃ O ₄ has good chemical stability, can inhibit the oxidation activity of the electrode surface, reduce the interface reaction between the electrode and the electrolyte, thereby improving the cycle stability and actual specific capacity of the lithium-sulfur battery, and improving Electrochemical properties of battery materials to prolong battery life. The positive electrode composite material prepared by the invention has high discharge specific capacity and strong cycle stability, and can be widely used in the field of energy storage as a lithium-sulfur battery positive electrode material.

Description of drawings

Fig. 1 is the scanning electron micrograph of the Co ₃ O ₄ -KS-6/S cathode composite material prepared in Example 1;

Fig. 2 is the X-ray diffraction pattern of the Co ₃ O ₄ -KS-6/S cathode composite material prepared in Example 1;

Figure 3 is the first charge and discharge curves of the Co ₃ O ₄ -KS-6/S cathode composite material prepared in Example 1 and the KS-6/S cathode composite material without Co ₃ O ₄ at 0.1C;

Fig. 4 is a diagram of cycle performance and coulombic efficiency of the Co ₃ O ₄ -KS-6/S cathode composite material prepared in Example 1 at 0.1C.

detailed description

The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments.

The lithium-sulfur battery positive electrode material containing the additive Co ₃ O ₄ (abbreviated positive electrode composite material) of the present invention is formed by doping KS-6, Co ₃ O ₄ and sulfur, wherein Co ₃ O ₄ and sulfur are uniformly filled in KS- In 6 sheets, the mass ratio of KS-6 to Co ₃ O ₄ is 1:(0.1~0.25), and the mass ratio of Co ₃ O ₄ -KS-6 to sulfur is 1:(1~2).

The preparation method of the positive electrode material of the lithium _- sulfur battery containing the additive Co3O4 _of the present invention is specifically implemented according to the following steps:

Step 1) Put KS-6 and Co(NO ₃ ) ₂ ·6H ₂ O into a ball mill at a mass ratio of 1:(0.5~1), add an appropriate amount of ethanol, and wet mix for 1.5-2 hours. ℃ oven drying for 12-15h.

Step 2) The mixture obtained in step 1) is calcined at a high temperature in a tube furnace at 250° C. to 400° C. under protective gas conditions for 4 to 7 hours. In the calcined product, KS-6 and Co ₃ O ₄ (formed by Co(NO ₃ ) ₂ ·6H ₂ O produced by decomposition) has a mass ratio of 1:(0.1-0.25).

Step 3) Mix and grind the calcined product of step 2) with sulfur at a ratio of 1: (1~2), place it in a hydrothermal reaction kettle, and put the reaction kettle at 150-160 ℃ for 10-12 hours to obtain a lithium-sulfur battery cathode material containing the additive Co ₃ O ₄ .

The wet ball milling solvent in the above step 1) is selected from one of water, ethanol or acetone with a low boiling point.

In the above step 2), at least one of nitrogen and inert gas is selected as the protective gas for calcination of the tube furnace.

Example 1

Step 1) Put KS-6 and Co(NO ₃ ) ₂ ·6H ₂ O into a ball mill at a mass ratio of 1:1, add an appropriate amount of ethanol, wet mix for 1.5 hours, and then dry in an oven at 70°C for 12 hours.

Step 2) The mixture obtained in step 1) was calcined in a tube furnace at 300°C under nitrogen for 5 hours at a high temperature, and KS-6 and Co ₃ O ₄ (from Co(NO ₃ ) ₂ ·6H ₂ O Decomposition) The mass ratio is 1:0.25.

Step 3) Mix and grind the calcined product of step 2) with sulfur at a ratio of 1:1, place it in a hydrothermal reaction kettle, and after passing argon gas for 20 minutes, place the reaction kettle at 156°C for 10 hours to obtain the additive containing Co ₃ O ₄ cathode material for lithium-sulfur batteries.

Example 2

Step 1) Put KS-6 and Co(NO ₃ ) ₂ ·6H ₂ O into a ball mill at a mass ratio of 1:0.5, add an appropriate amount of ethanol, wet mix for 2 hours, and then dry in an oven at 70°C for 15 hours.

Step 2) The mixture obtained in step 1) was calcined in a tube furnace at 400°C under nitrogen for 4 hours at a high temperature, and KS-6 and Co ₃ O ₄ (from Co(NO ₃ ) ₂ ·6H ₂ O The mass ratio of decomposition) is 1:0.1.

Step 3) Mix and grind the calcined product of step 2) with sulfur at a ratio of 1:1.5, place it in a hydrothermal reaction kettle, and after passing in argon for 25 minutes, place the reaction kettle at 155°C for 12 hours to obtain the additive-containing Co ₃ O ₄ cathode material for lithium-sulfur batteries.

Example 3

Step 1) Put KS-6 and Co(NO ₃ ) ₂ ·6H ₂ O into a ball mill jar at a mass ratio of 1:0.75, add an appropriate amount of acetone, wet mix for 1.5 hours, and then dry in an oven at 70°C for 12 hours.

Step 2) The mixture obtained in step 1) was calcined in a tube furnace at 250°C under nitrogen for 7 hours at a high temperature, and KS-6 and Co ₃ O ₄ (from Co(NO ₃ ) ₂ ·6H ₂ O The mass ratio of decomposition) is 1:0.23.

Step 3) Mix and grind the calcined product of step 2) with sulfur at a ratio of 1:2, place it in a hydrothermal reaction kettle, pass argon gas for 30 minutes, and place the reaction kettle at 156°C for 12 hours to obtain Co ₃ O ₄ cathode material for lithium-sulfur batteries.

Based on the above examples, the samples prepared in Examples 1-3 were further used for battery assembly, and the obtained lithium-sulfur battery cathode composite material was mixed with KS-6 and polyvinylidene fluoride (PVDF) according to the mass ratio of 7:2:1. Weighing, using N-methylpyrrolidone as a solvent to prepare a uniform slurry, drying and pressing after coating, cutting the pieces to make positive electrodes, lithium sheets as negative electrodes, and electrolyte solution containing 1% LiNO ₃ 1mol/ L LiTFSI/DOL–DME (1:1, V%), separator Celgard2300, assembled into a button-type CR2025 battery.

Figure 1 is the scanning electron microscope image of the Co ₃ O ₄ -KS-6/S cathode composite material prepared in Example 1. From Figure 1, it can be clearly seen that sulfur and Co ₃ O ₄ are evenly coated between the KS-6 sheets .

Figure 2 is the X-ray diffraction pattern of the Co ₃ O ₄ -KS-6/S cathode composite material prepared in Example 1. It can be seen from Figure 2 that the composite material has the characteristic diffraction peaks of Co ₃ O ₄ and S.

Fig. 3 is the first charge and discharge curves of the Co ₃ O ₄ -KS-6/S cathode composite material prepared in Example 1 and the KS-6/S cathode composite material without Co ₃ O ₄ added at 0.1C. The first discharge specific capacity of Co ₃ O ₄ -KS-6/S positive electrode composite material is 1260mAh/g, because the initial wettability of the electrolyte is not good, so the first discharge platform is low, the discharge platform is 2.0V, without adding Co ₃ O ₄ 's KS-6/S positive electrode composite has a first-time discharge specific capacity of 676mAh/g, which proves that the addition of Co ₃ O ₄ can significantly improve the first-time discharge specific capacity of the battery.

Fig. 4 is a diagram of cycle performance and coulombic efficiency of the Co ₃ O ₄ -KS-6/S cathode composite material prepared in Example 1 at 0.1C. It can be seen from Figure 4 that after 50 cycles, the discharge capacity is 539mAh/g, the capacity retention rate is 42.8%, and the coulombic efficiency is about 95%. The addition of Co ₃ O ₄ has a significant effect on the capacity retention rate and coulombic efficiency of the battery.

The battery obtained in Example 2 was charged and discharged 50 times under the condition of 0.1C. The specific capacity of the first discharge was 1176mAh/g, and the capacity remained at 450mAh/g after 50 cycles, with a capacity retention rate of 38.3%.

The battery obtained in Example 3 was charged and discharged 50 times under the condition of 0.1C, the specific capacity of the first discharge was 1054mAh/g, and the capacity remained at 432mAh/g after 50 cycles, and the capacity retention rate was 41.0%.

Through the method provided by the present invention, Co ₃ O ₄ and sulfur can be uniformly filled in the KS-6 sheet, which is more uniform than the Co ₃ O ₄ added by the ball milling method, so that the role of Co ₃ O ₄ can be fully exerted and the lithium Cycling stability and specific capacity of sulfur batteries.

Claims (3)

1. A preparation method of a lithium-sulfur battery cathode material containing additive Co ₃ O ₄ , the lithium-sulfur battery cathode material containing additive Co ₃ O ₄ is formed by doping KS-6, Co ₃ O ₄ and sulfur, The Co ₃ O ₄ and sulfur are evenly filled in the KS-6 sheet, the mass ratio of KS-6 to Co ₃ O ₄ is 1:0.1～0.25, the mass ratio of Co ₃ O ₄ -KS-6 to sulfur 1:1~2, It is characterized in that it is specifically implemented according to the following steps: Step 1) Put KS-6 and Co(NO ₃ ) ₂ ·6H ₂ O into a ball milling jar at a mass ratio of 1:0.5~1, add an appropriate amount of ethanol, and wet mix for 1.5-2 hours, then dry in an oven at 70°C Dry for 12-15 hours; Step 2) Calcining the mixture obtained in step 1) at a high temperature in a tube furnace at 250° C. to 400° C. under protective gas conditions for 4 to 7 hours. The mass ratio of KS-6 to Co ₃ O ₄ in the product obtained after calcination is 1: 0.1～0.25; Step 3) Mix and grind the calcined product of step 2) with sulfur at a ratio of 1:1~2, place it in a hydrothermal reaction kettle, and put argon gas into it for 20-30 minutes, then place the reaction kettle at 150-160°C to keep warm After 10-12 hours, a lithium-sulfur battery cathode material containing the additive Co ₃ O ₄ is obtained. 2. The preparation method of the lithium-sulfur battery cathode material containing the additive Co ₃ O ₄ according to claim 1, characterized in that: the wet ball milling solvent in the step 1) is selected from one of water, ethanol or acetone. 3. according to claim 1 containing additive Co ₃ O ₄ The preparation method of the lithium-sulfur battery cathode material is characterized in that: in the described step 2), the tube furnace calcining protection gas is selected from at least nitrogen and inert gases. A sort of.