阅读说明：本技术 一种锂硫电池用多功能隔膜涂层的制备方法 (Preparation method of multifunctional diaphragm coating for lithium-sulfur battery ) 是由 卢红斌 刘意成 赵则栋 郭屹轩 胡波 于 2021-05-25 设计创作，主要内容包括：本发明涉及一种锂硫电池用多功能隔膜涂层的制备方法,该多功能隔膜涂层由硒化镍铁/石墨烯复合物组成。采用抽滤的方法将石墨烯/原位生长的纳米立方笼硒化镍铁复合物修饰到朝向正极隔膜一侧,解决传统隔膜不能有效阻止多硫化物向锂金属负极扩散这一难题。具有催化活性的硒化镍铁可加速多硫化物和硫化锂之间的相互转化,提高活性物质的利用率的同时防止放电产物硫化锂阻塞孔道。此外,笼状镍铁硒化物的多孔结构有利于锂离子快速传输。此种复合设计使得具备硒化镍铁隔膜涂层的电池表现出高的比容量和出色的倍率性能。(The invention relates to a preparation method of a multifunctional diaphragm coating for a lithium-sulfur battery, wherein the multifunctional diaphragm coating is composed of a nickel-iron selenide/graphene compound. A suction filtration method is adopted to modify the graphene/in-situ grown nano cubic cage ferronickel selenide compound to one side facing the anode diaphragm, so that the problem that polysulfide cannot be effectively prevented from diffusing to the lithium metal cathode by the traditional diaphragm is solved. The nickel-iron selenide with catalytic activity can accelerate the mutual conversion between polysulfide and lithium sulfide, improve the utilization rate of active substances and prevent the discharge product lithium sulfide from blocking pore channels. In addition, the porous structure of the cage-shaped nickel iron selenide is beneficial to the rapid transmission of lithium ions. The composite design enables the battery with the nickel-iron selenide diaphragm coating to show high specific capacity and excellent rate capability.)

1. A preparation method of a multifunctional diaphragm coating for a lithium-sulfur battery is characterized by comprising the following specific steps:

(1) adding 1-10 mmol of divalent nickel salt and 1-20 mmol of sodium citrate into 100-1000 ml of graphene oxide solution to prepare solution A, and preparing 1-10 mmol of potassium hexacyanoferrate into solution B; slowly dripping the solution B into the solution A, and reacting for 3-24 hours at a certain temperature to obtain a mixed solution;

(2) putting the mixed solution obtained in the step (1) into a reaction kettle, carrying out hydrothermal reaction for 3 hours, and washing and drying by using a screen to obtain a nickel iron prussian blue/graphene compound;

(3) placing the ferronickel prussian blue/graphene compound and the selenium powder obtained in the step (2) at the downstream and upstream of the porcelain boat respectively, and calcining at high temperature for 3 hours in a tube furnace under a specific atmosphere to obtain a ferronickel selenide/graphene compound; wherein: the mass ratio of the ferronickel Prussian blue to the graphene to the selenium powder is 1 (1-20);

(4) mixing the ferronickel selenide/graphene compound obtained in the step (3) with an adhesive solution, performing suction filtration on the mixture to obtain a ferronickel selenide/graphene diaphragm coating after drying; wherein: the mass ratio of the nickel iron selenide/graphene compound to the adhesive solution is 10 (0.1-10).

2. The method for preparing a multifunctional separator coating for a lithium-sulfur battery according to claim 1, wherein the divalent nickel ion salt solution in step (1) is any one of nickel sulfate, nickel nitrate, nickel acetate, or nickel chloride.

3. The method for preparing the multifunctional separator coating for the lithium-sulfur battery according to claim 1, wherein the method for preparing the graphene oxide in the step (1) comprises the following specific steps: the preparation method comprises the steps of taking crystalline flake graphite as a raw material, adding potassium permanganate and concentrated sulfuric acid, preparing graphite oxide in a mild stirring-free mode, and obtaining graphene oxide through stripping.

4. The method for preparing a multifunctional separator coating layer for a lithium sulfur battery according to claim 1, wherein the concentration of the graphene oxide in the step (1) is 0.1 to 8 mg/ml.

5. The method for preparing a multifunctional separator coating layer for a lithium sulfur battery according to claim 1, wherein the certain temperature in the step (1) is 10 to 100 ℃.

6. The method for preparing a multifunctional separator coating for a lithium sulfur battery as defined in claim 1, wherein the hydrothermal reaction temperature in step (2) is 100-400 ℃.

7. The method for preparing a multifunctional separator coating layer for a lithium sulfur battery according to claim 1, wherein the specific atmosphere in the step (3) is any one of argon gas, nitrogen gas or hydrogen-argon mixture gas.

8. The method for preparing a multifunctional separator coating for a lithium sulfur battery as defined in claim 1, wherein the high-temperature calcination temperature in step (3) is 250-800 ℃.

9. The method for preparing the multifunctional separator coating for the lithium-sulfur battery according to claim 1, wherein the adhesive in the step (4) is any one or a mixture of polyvinylidene fluoride, sodium carboxymethyl cellulose, polyvinyl alcohol or acrylonitrile multipolymer.

10. The method for preparing a multifunctional separator coating for a lithium sulfur battery according to claim 1, wherein the thickness of the multifunctional separator coating obtained in the step (4) is 1 to 100 μm.

Technical Field

The invention belongs to the technical field of materials, and particularly relates to a preparation method of a multifunctional diaphragm coating for a lithium-sulfur battery.

Background

Lithium sulfur batteries have become a promising candidate for next generation energy storage systems due to the ultra high theoretical energy density (2600 watt-hours/kg) and the low cost advantage. However, the complex shuttling effect of lithium polysulfide due to the multi-step and multi-phase reaction behavior of sulfur will cause a series of problems in lithium sulfur batteries, such as loss of active material, severe capacity fade, and poor cycle life, thereby greatly hindering further commercialization.

The separator of the conventional lithium-sulfur battery functions to separate the positive electrode and the negative electrode and provide a transport channel for lithium ions, but cannot prevent the diffusion of lithium polysulfide into the negative electrode. One promising and simple strategy is to introduce a multifunctional coating between the positive electrode and the separator to block lithium polysulfide diffusion. There are generally two strategies for the construction of separator coatings: the first is a molecular sieve type and electrostatic repulsion type coating developed using differences in the radius and charge of polysulfide and lithium ions, which can effectively prevent the diffusion path of lithium polysulfide, but lithium polysulfide dissolved in an electrolyte or accumulated on a separator hardly participates in the subsequent electrochemical reaction, resulting in low utilization of sulfur. The second method is to capture and reuse lithium polysulfide in the electrolyte by using carbon materials, thereby improving the utilization rate of sulfur and simultaneously inhibiting the shuttle effect. Due to the weak affinity of the nonpolar carbon to polar lithium polysulfide, the shuttling of the lithium polysulfide in the charging and discharging process is not prevented; some polar oxides are incorporated into the separator coating to effectively immobilize the lithium polysulfide by physicochemical interactions. However, most metal oxides have poor conductivity, resulting in slow kinetics for the lithium polysulfide conversion reaction. In addition, separator coatings often impede lithium ion diffusion and negatively impact the cycling stability of lithium sulfur batteries. Therefore, there is an urgent need to design a multifunctional membrane coating which can not only effectively block polysulfide, but also catalyze the conversion of lithium polysulfide to increase the conversion rate of polysulfide without affecting ion transmission.

Disclosure of Invention

The invention aims to provide a lithium-sulfur battery diaphragm, aiming at the defect that the existing lithium-sulfur battery diaphragm cannot effectively regulate and control lithium polysulfideA method for preparing a multifunctional diaphragm coating for a sulfur battery. Cubic cage-shaped (Ni, Fe) Se prepared by the invention₂Graphene coatings can be used as effective polysulfide barriers for high performance lithium sulfur batteries. Graphene serves to block polysulfides by physical action on the one hand and to provide a good conductive network on the other hand; in addition, the transition metal selenide with high conductivity and polarity characteristics has a good catalytic conversion effect on polysulfide due to proper d electronic structure and catalytic activity. More critically, the porous structure of the caged nickel iron selenide ensures rapid transport of lithium ions. (Ni, Fe) Se having these characteristics₂The graphene diaphragm coated battery can realize excellent electrochemical performance.

The invention provides a preparation method of a multifunctional diaphragm coating for a lithium-sulfur battery, which comprises the following specific steps:

(1) adding 1-10 mmol of divalent nickel salt and 1-20 mmol of sodium citrate into 100-1000 ml of graphene oxide solution to prepare solution A, and preparing 1-10 mmol of potassium hexacyanoferrate into solution B. Slowly dripping the solution B into the solution A, and reacting for 3-24 hours at a certain temperature to obtain a mixed solution;

(2) putting the mixed solution obtained in the step (1) into a reaction kettle, carrying out hydrothermal reaction for 3 hours, and washing and drying by using a screen to obtain a nickel iron prussian blue/graphene compound;

(3) placing the ferronickel prussian blue/graphene compound and the selenium powder obtained in the step (2) at the downstream and upstream of the porcelain boat respectively, and calcining at high temperature for 3 hours in a tube furnace under a specific atmosphere to obtain a ferronickel selenide/graphene compound; wherein: the mass ratio of the ferronickel Prussian blue to the graphene to the selenium powder is 1 (1-20);

(4) mixing the ferronickel selenide/graphene compound obtained in the step (3) with an adhesive solution, performing suction filtration on the mixed mixture to obtain a commercial diaphragm, and drying the commercial diaphragm to obtain a ferronickel selenide/graphene diaphragm coating; wherein: the mass ratio of the nickel iron selenide/graphene compound to the adhesive solution is 10 (0.1-10).

In the invention, the divalent nickel ions in the step (1) are any one of nickel sulfate, nickel nitrate, nickel acetate or nickel chloride.

In the invention, the preparation method of the graphene oxide in the step (1) comprises the following specific steps: the preparation method comprises the steps of taking crystalline flake graphite as a raw material, adding potassium permanganate and concentrated sulfuric acid, preparing graphite oxide in a mild stirring-free mode, and obtaining graphene oxide through stripping.

In the invention, the concentration of the graphene oxide in the step (1) is 0.1-8 mg/ml.

In the invention, the temperature in the step (1) is 10-100 ℃.

In the invention, the hydrothermal reaction temperature in the step (2) is 100-400 ℃.

In the present invention, the specific atmosphere in the step (3) is any one of argon gas, nitrogen gas, and a hydrogen-argon mixed gas.

In the invention, the high-temperature calcination temperature in the step (3) is 250-800 ℃.

In the invention, the adhesive in the step (4) is any one of polyvinylidene fluoride, sodium carboxymethyl cellulose, polyvinyl alcohol and acrylonitrile multipolymer or mixture thereof.

In the invention, the thickness of the coating of the diaphragm obtained in the step (4) is 1-100 microns.

The invention has the advantages that: aiming at the defects of the existing diaphragm of the lithium-sulfur battery and the related technology, the technical scheme of the invention is provided through long-term research, and the scheme realizes the low-cost preparation of the multifunctional nickel-iron selenide/graphene diaphragm coating material under the controllable reaction condition. The diaphragm coating prepared by the invention can reasonably regulate and control lithium polysulfide to realize a high-performance lithium-sulfur battery. Catalytically active nickel-iron-selenide can accelerate the interconversion between lithium polysulphide and lithium sulphide. In addition, nickel iron selenide from the prussian blue porous structure facilitates the transport of lithium ions. The invention overcomes the main limitation of the diaphragm coating related to the non-active material and provides an effective solution for the practicability of the lithium-sulfur battery.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention.

Fig. 1 is X-ray diffraction spectrum of nickel iron selenide/graphene composite material.

Fig. 2 is a scanning electron microscope and a transmission electron microscope of the ferronickel selenide/graphene composite material (a) and (b).

Fig. 3 is a constant current charging and discharging curve of the battery with the ferronickel selenide/graphene composite material modified diaphragm prepared in embodiment 1 of the invention at 0.1C.

Fig. 4 is a rate characteristic curve of the lithium-sulfur battery with a diaphragm modified by a nickel-iron selenide/graphene composite material prepared in embodiment 1 of the invention at 0.1-5C.

Fig. 5 shows the discharge specific capacity and coulombic efficiency of the lithium-sulfur battery with a ferronickel selenide/graphene composite modified diaphragm prepared in example 1 of the present invention at 1C for 800 cycles.

Detailed Description

The following detailed description of embodiments of the invention refers to the accompanying drawings. It is to be understood that one or more of the steps referred to herein do not exclude the presence of other methods or steps before or after the combined steps, or that other methods or steps may be intervening between the explicitly mentioned steps. It should also be understood that these examples are intended only to illustrate the invention and are not intended to limit the scope of the invention. Unless otherwise indicated, the numbering of the method steps is only for the purpose of identifying the steps, and is not intended to limit the order of arrangement of each method or the scope of the implementation of the invention, and changes or modifications in the relative relationship thereof, without substantial technical changes, should also be considered as the scope of the implementation of the invention.

Example 1

(1) 7.5 mmol of nickel nitrate and 11.25 mmol of sodium citrate are added to 500 ml of a 1.5 mg/ml graphene oxide solution to prepare a solution A, and 5 mmol of potassium hexacyanoferrate is added to 500 ml of a solution B. Slowly dripping the solution B into the solution A, and reacting for 24 hours at 30 ℃;

(2) putting the mixed solution obtained in the step (1) into a reaction kettle, carrying out hydrothermal reaction at 130 ℃ for 3 hours, and washing and drying by using a screen to obtain a nickel iron prussian blue/graphene compound;

(3) respectively placing the ferronickel prussian blue/graphene compound (100 mg) and the selenium powder (700 mg) obtained in the step (2) at the downstream and upstream of a porcelain boat, and calcining at the high temperature of 350 ℃ for 3 hours in a tube furnace under argon gas to obtain a ferronickel selenide/graphene compound;

(4) mixing the ferronickel selenide/graphene compound obtained in the step (3) with a polyvinylidene fluoride adhesive solution, then performing suction filtration on the mixed solution to obtain a membrane coating of the ferronickel selenide/graphene; wherein the mass ratio of the nickel iron selenide/graphene compound to the adhesive solution is 10: 1.

The X-ray diffraction pattern (fig. 1) confirms that the method successfully prepares the nickel iron selenide/graphene composite. The field emission scanning electron microscope (fig. 2 a) and the transmission electron microscope (fig. 2 b) show that the nickel iron selenide prepared by the method has a porous cubic cage structure and is uniformly distributed in the graphene frame. And (3) assembling the button lithium-sulfur battery by taking the carbon nano tube/sulfur material as a positive electrode, the lithium sheet as a negative electrode and the diaphragm modified by the nickel-iron selenide/graphene composite coating as a diaphragm. From the constant current charge and discharge curve, it can be seen that the lithium sulfur battery with the separator coating shows a distinct two-stage discharge plateau (fig. 3). At 0.1C (1C = 1675 mA g^{- 1}) The cell exhibited 1462 mAh g^-1High initial capacity. While 1050, 870, 772 and 584 mAh g are maintained when the current density is increased to 0.2, 0.5, 1.0, 2.0 and 5.0C, respectively^{- 1}High reversible capacity (fig. 4). In addition, the battery with the separator coating showed good cycle performance at a current density of 1C, and the discharge capacity remained at 507mAh g after 800 cycles^-1The capacity fade per revolution was 0.033% (fig. 5).

Example 2

(1) 7.5 mmol of nickel nitrate and 11.25 mmol of sodium citrate are added to 500 ml of graphene oxide solution with the concentration of 2 mg/ml to prepare solution A, and 5 mmol of potassium hexacyanoferrate is prepared to 500 ml of solution B. Slowly dripping the solution B into the solution A and reacting for 24 hours at 30 ℃;

(2) putting the mixed solution obtained in the step (1) into a reaction kettle, carrying out hydrothermal reaction for 2 hours at 150 ℃, and washing and drying by using a screen to obtain a nickel iron prussian blue/graphene compound;

(3) respectively placing the ferronickel prussian blue/graphene compound (100 mg) and the selenium powder (700 mg) obtained in the step (2) at the downstream and upstream of a porcelain boat, and calcining at the high temperature of 350 ℃ for 3 hours in a tube furnace under the argon atmosphere to obtain a ferronickel selenide/graphene compound;

(4) mixing the ferronickel selenide/graphene compound obtained in the step (3) with a polyvinylidene fluoride adhesive solution, then performing suction filtration on the mixed solution to obtain a membrane coating of the ferronickel selenide/graphene; wherein the mass ratio of the nickel iron selenide/graphene compound to the adhesive solution is 10: 1.

Example 3

(1) 7.5 mmol of nickel nitrate and 11.25 mmol of sodium citrate are added to 500 ml of graphene oxide solution with the concentration of 2 mg/ml to prepare solution A, and 5 mmol of potassium hexacyanoferrate is prepared to 500 ml of solution B. The solution B was slowly added dropwise to the solution A and the mixture was stirred at 30 deg.C^oC, reacting for 24 hours;

(2) putting the mixed solution obtained in the step (1) into a reaction kettle, carrying out hydrothermal reaction at 130 ℃ for 3 hours, and washing and drying by using a screen to obtain a nickel iron prussian blue/graphene compound;

(3) placing the ferronickel prussian blue/graphene compound (100 mg) and the selenium powder (1000 mg) in the step (2) at the downstream and upstream of a porcelain boat respectively, and calcining at 350 ℃ for 3 hours in a tube furnace under argon atmosphere to obtain a ferronickel selenide/graphene compound;

(4) mixing the ferronickel selenide/graphene compound obtained in the step (3) with a polyvinylidene fluoride adhesive solution, then performing suction filtration on the mixed solution to obtain a membrane coating of the ferronickel selenide/graphene; wherein the mass ratio of the nickel iron selenide/graphene compound to the adhesive solution is 10: 0.5.

Example 4

(1) 7.5 mmol of nickel nitrate and 22.5 mmol of sodium citrate are added to 500 ml of a 1.5 mg/ml graphene oxide solution to prepare a solution A, and 5 mmol of potassium hexacyanoferrate is added to 500 ml of a solution B. Slowly dripping the solution B into the solution A and reacting for 24 hours at 30 ℃;

(2) putting the mixed solution obtained in the step (1) into a reaction kettle, carrying out hydrothermal reaction for 2 hours at 150 ℃, and washing and drying by using a screen to obtain a nickel iron prussian blue/graphene compound;

(3) taking the nickel iron prussian blue/graphene compound (100 mg) and the selenium powder (700 mg) obtained in the step (2) to be respectively placed at the downstream and the upstream of a porcelain boat, and carrying out 350 ℃ reaction in a tube furnace under a hydrogen-argon mixed atmosphere^oCalcining at high temperature for 3 hours to obtain a nickel-iron selenide/graphene compound;

(4) mixing the ferronickel selenide/graphene compound obtained in the step (3) with an acrylonitrile multipolymer adhesive solution, then performing suction filtration on the mixture to obtain a ferronickel selenide/graphene diaphragm coating after drying; wherein the mass ratio of the nickel iron selenide/graphene compound to the adhesive solution is 10: 1.

Example 5

(1) 7.5 mmol of nickel nitrate and 11.25 mmol of sodium citrate are added to 500 ml of a graphene oxide solution with a concentration of 1 mg/ml to prepare a solution A, and 5 mmol of potassium hexacyanoferrate is added to 500 ml of a solution B. Slowly dripping the solution B into the solution A and reacting for 24 hours at 30 ℃;

(2) taking the mixed solution in the step (1) into a reaction kettle, and 140^oC, carrying out hydrothermal reaction for 3 hours, and washing and drying by using a screen to obtain a nickel iron prussian blue/graphene compound;

(3) taking the ferronickel Prussian blue/graphene compound (100 mg) and the selenium powder (800 mg) in the step (2) to be respectively placed at the downstream and the upstream of a porcelain boat, and carrying out 350 ℃ in a tube furnace under argon atmosphere^oCalcining at high temperature for 3 hours to obtain a nickel-iron selenide/graphene compound;

(4) mixing the ferronickel selenide/graphene compound obtained in the step (3) with a polyvinylidene fluoride adhesive solution, then performing suction filtration on the mixed solution to obtain a membrane coating of the ferronickel selenide/graphene; wherein the mass ratio of the nickel iron selenide/graphene compound to the adhesive solution is 10: 0.5.