阅读说明：本技术 一种锂硫电池正极与隔膜一体化结构及其制备方法 (Lithium-sulfur battery anode and diaphragm integrated structure and preparation method thereof ) 是由 张力 吕晓雪 熊杰 雷天宇 陈伟 胡音 李政翰 张淼 邬春阳 王显福 于 2019-08-30 设计创作，主要内容包括：本发明提供一种锂硫电池正极与隔膜一体化结构及其制备方法,属于锂硫电池技术领域。发明提供一种隔膜与正极一体的新型结构,该结构具有纳米纤维状的隔膜直接覆盖在正极表面,使在电池制备中,由原来需在隔膜两面滴加电解液减少为仅需滴加在一次电解液,大大降低了电解液的用量,从而降低了E/S,提升电池的能量密度；基于本发明一体化结构组装的扣式CR2025电池,E/S可降低至5。(The invention provides a lithium-sulfur battery anode and diaphragm integrated structure and a preparation method thereof, and belongs to the technical field of lithium-sulfur batteries. The invention provides a novel structure integrating a diaphragm and an anode, which has the advantages that the nano-fibrous diaphragm directly covers the surface of the anode, so that in the preparation of a battery, electrolyte needing to be dripped on two sides of the diaphragm is reduced to only be dripped in one time, the using amount of the electrolyte is greatly reduced, the E/S is reduced, and the energy density of the battery is improved; based on the button type CR2025 battery assembled by the integrated structure, the E/S can be reduced to 5.)

1. The lithium-sulfur battery anode and diaphragm integrated structure is characterized by comprising an anode and a diaphragm directly grown on the surface of the anode by adopting an electrostatic spinning method, wherein the diaphragm has a nanofiber mesh structure, the area of the diaphragm is larger than that of the anode, and the thickness of the diaphragm is 30-70 mu m.

2. The method for preparing the lithium-sulfur battery positive electrode and separator integrated structure according to claim 1, comprising the steps of:

step 1: dissolving polyacrylonitrile in N-methyl pyrrolidone, and stirring in a water bath at 40-60 ℃ to obtain an electrostatic spinning precursor solution, wherein the mass fraction of the polyacrylonitrile in the precursor solution is 10-20%;

step 2: absorbing the electrostatic spinning precursor solution obtained in the step (1) by using an injection needle tube, using the positive electrode of the lithium-sulfur battery as an electrostatic spinning receiving substrate, and spinning by using an electrostatic spinning instrument;

and step 3: and (3) putting the receiving substrate with the diaphragm obtained in the step (2) into a vacuum oven for drying, and taking out the substrate after drying is finished, so that the diaphragm and anode integrated structure can be obtained.

3. The method for preparing the lithium-sulfur battery positive electrode and separator integrated structure according to claim 2, wherein the method for preparing the lithium-sulfur battery positive electrode in step 2 comprises the following steps: mixing acetylene black, sulfur and polyvinylidene fluoride, adding N-methyl pyrrolidone for grinding, uniformly coating on a carbon-coated aluminum foil, and drying to obtain the anode.

4. The method for preparing the integrated structure of the positive electrode and the diaphragm of the lithium-sulfur battery according to claim 2, wherein the specific parameters of the electrostatic spinning in the step 2 are as follows: diameter of the spinning nozzle: 0.5 mm-1 mm; spinning negative voltage: 5kV to 7 kV; spinning positive voltage: 5kV to 7 kV; spinning receiving speed: 20-50 r/min; spinning translation speed: 300-500 mm/min; the bolus injection speed: 0.01-0.02 mm/min; spinning time: 8-16 h.

5. The method for preparing the lithium-sulfur battery cathode and separator integrated structure according to claim 2, wherein the drying conditions in step 3 are as follows: drying for 12-24 h at 50-60 ℃.

Technical Field

The invention belongs to the technical field of lithium-sulfur batteries, and particularly relates to a lithium-sulfur battery anode and diaphragm integrated structure and a preparation method thereof.

Background

At present, more than 90% of world energy sources come from fossil energy sources such as coal, petroleum and natural gas, and the like, but the excessive consumption of the fossil energy sources can cause environmental problems such as greenhouse effect and the like; meanwhile, as a non-renewable energy source, large-scale consumption inevitably leads to resource exhaustion. Thus, clean energy sources such as solar energy and wind energy attract a lot of attention, but the utilization of the energy sources needs to be matched with a proper energy storage system. Among the numerous electrochemical energy storage systems, the Li-S battery is a new type of energy storage system, which has a theoretical specific capacity (1675mAhg-1) and energy density (2500Whkg-1) much higher than those of the current commercial lithium ion batteries, and has attracted much attention. In addition, sulfur has the advantages of low price, abundant natural reserves (almost accounting for 3 percent of the mass of the earth), environmental friendliness, no pollution and the like, so that the Li-S battery becomes an energy storage technology with low cost and great attraction.

Research on Li-S batteries began in the sixties of the twentieth century and, through decades of development, researchers have addressed three major problems in lithium-sulfur batteries: the research on the shuttle effect, the volume expansion problem in the charge-discharge cycle process and the poor conductivity of the elemental sulfur and the lithium polysulfide thereof has been greatly developed, so that the capacity, the cycle performance and the like of the battery are greatly improved. However, there still remains a significant problem that hinders the commercialization of Li-S batteries, i.e., the magnitude of the E/S (electrolyte to sulfur content) value: the larger the E/S, the lower the energy density; if the E/S exceeds 20, the calculated energy density is not much more advantageous than the existing ternary lithium ion battery. Therefore, how to reduce the E/S and make full use of the electrolyte is an urgent problem to be solved in the current lithium-sulfur battery research.

For this problem, there are two general solutions: (1) the electrolyte with low or insoluble polysulfide ion solubility is adopted to separate the charge transfer of the elemental sulfur from the dissolution process of the polysulfide ion, however, the electrolyte has poor reaction kinetics because the electrolyte has low solubility to the polysulfide ion, and cannot meet the requirement of effective transmission of the ion at room temperature; (2) the electrolyte with high dielectric constant is adopted to promote the dissolution of polysulfide, so that the kinetics of electrochemical reaction can be greatly accelerated. However, such an electrolyte requires a good SEI film to be formed on the surface of the lithium negative electrode to suppress the shuttle effect, and a conventional high dielectric constant electrolyte is unstable to lithium, and side reactions on the lithium negative electrode side limit the wide use of such an electrolyte.

The above solutions are all studied by modifying the constituent materials of the battery, but there is no measure for improving the battery structure itself to solve the E/S value. The structure of the current lithium-sulfur battery is composed of a positive electrode, a diaphragm, an electrolyte and a negative electrode, and the assembly sequence of the button battery is generally as follows: the battery needs to respectively drop the electrolyte on both sides of the diaphragm.

Disclosure of Invention

The invention aims to provide a lithium-sulfur battery anode and diaphragm integrated structure and a preparation method thereof, aiming at the problem of larger E/S ratio in the existing battery structure in the background art.

In order to achieve the purpose, the technical scheme of the invention is as follows:

the lithium-sulfur battery anode and diaphragm integrated structure comprises an anode and a diaphragm directly grown on the surface of the anode by adopting an electrostatic spinning method, wherein the diaphragm has a nanofiber mesh structure, the area of the diaphragm is larger than that of the anode, and the thickness of the diaphragm is 30-70 mu m.

A preparation method of a lithium-sulfur battery anode and diaphragm integrated structure comprises the following steps:

step 1: dissolving Polyacrylonitrile (PAN) in N-methylpyrrolidone (NMP), and stirring for 2-4 h in a water bath at 40-60 ℃ to obtain an electrostatic spinning precursor solution, wherein the mass fraction of the PAN in the precursor solution is 10-20%;

step 2: dissolving polyvinylidene fluoride (PVDF) in NMP, grinding for 5-10 min to obtain viscous thick liquid, and adhering the positive electrode of the lithium-sulfur battery to an aluminum foil by using the viscous thick liquid to obtain an electrostatic spinning receiving substrate;

and step 3: absorbing the electrostatic spinning precursor solution obtained in the step (1) by using an injection needle tube, using the electrostatic spinning receiving substrate obtained in the step (2), and spinning by using an electrostatic spinning instrument;

and 4, step 4: and (4) putting the receiving substrate with the diaphragm obtained in the step (3) into a vacuum oven for drying, and taking out the substrate after drying is finished, so that the diaphragm and anode integrated structure can be obtained.

Further, the concentration of the polyvinylidene fluoride in the viscous thick liquid in the step 2 is 0.15-0.2 mg/mu l.

Further, the preparation method of the lithium-sulfur battery positive electrode in the step 2 comprises the following steps: and mixing acetylene black, sulfur and PVDF, adding N MP for grinding, uniformly coating on the carbon-coated aluminum foil, and drying to obtain the anode.

Further, the specific parameters of electrostatic spinning in the step 3 are as follows: diameter of the spinning nozzle: 0.5 mm-1 mm; spinning negative voltage: 5kV to 7 kV; spinning positive voltage: 5kV to 7 kV; spinning receiving speed: 20-50 r/min; spinning translation speed: 300-500 mm/min; the bolus injection speed: 0.01-0.02 mm/min; spinning time: 8-16 h.

Further, the drying conditions in step 4 are as follows: drying for 12-24 h at 50-60 ℃.

In summary, due to the adoption of the technical scheme, the invention has the beneficial effects that:

1. the invention provides a novel structure integrating a diaphragm and an anode, wherein the nano-fibrous diaphragm directly grows on the surface of the anode, so that electrolyte is dropped on two sides of the diaphragm from the prior art in the preparation of a battery instead of dropping electrolyte once, the use amount of the electrolyte is greatly reduced, the E/S is reduced, and the energy density of the battery is improved; based on the button type CR2025 battery assembled by the integrated structure, the E/S can be reduced to 5.

2. The preparation process of the integrated structure is simple, the electrostatic spinning process is adopted, the diaphragm is directly spun on the surface of the anode, and compared with the prior art, the preparation method has the advantages of simple equipment, low preparation cost and large-scale production.

Drawings

Fig. 1 is a diagram of an integrated structure of a positive electrode and a separator according to example 1 of the present invention;

wherein (a) is with the membrane facing upward; (b) with the positive electrode facing upward.

Fig. 2 is an SEM image of a nanofiber separator in the cathode-separator integrated structure prepared in example 1 of the present invention.

Fig. 3 is a graph of electrochemical charge-discharge plateau of button cell assembled based on the integrated structure of positive electrode and separator prepared in example 1 of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail with reference to the following embodiments and accompanying drawings.