CN113113722A

CN113113722A - Lithium-sulfur battery diaphragm and preparation method thereof

Info

Publication number: CN113113722A
Application number: CN202110313838.6A
Authority: CN
Inventors: 李仕琦; 王�锋; 冷丹; 汶飞; 李丽丽
Original assignee: Hangzhou Dianzi University
Current assignee: Hangzhou Dianzi University
Priority date: 2021-03-24
Filing date: 2021-03-24
Publication date: 2021-07-13

Abstract

The invention discloses a lithium-sulfur battery diaphragm and a preparation method thereof, and the preparation method comprises the following steps: step S1, stretching the plastic bag at room temperature to a maximum extent in the transverse and longitudinal directions to nearly rupture; step S2, a thin needle is used to pierce as many small holes as possible uniformly without overlapping on the stretched plastic bag. By adopting the technical scheme of the invention, the biggest bright point is that the materials are simple and easy to obtain, waste can be turned into wealth, and the problem of white pollution is solved. The technical scheme can provide a novel preparation method of the battery diaphragm.

Description

Lithium-sulfur battery diaphragm and preparation method thereof

Technical Field

The invention belongs to the technical field of lithium-sulfur battery diaphragms, and relates to a lithium-sulfur battery diaphragm and a preparation method thereof.

Background

Modern society develops rapidly, and people's demand for energy is constantly increasing. The ever-emerging environmental problems and the continuing consumption of fossil energy have led to the advent of new energy storage systems and chemical power sources. Since sony corporation developed successful lithium ion batteries in the 90 th of the 20 th century, lithium ion batteries have rapidly developed with excellent electrical properties such as high energy density, long cycle life, and high voltage. The method is widely applied to the field of electronic products such as mobile phones, portable computers, cameras, video cameras and the like. The lithium ion battery consists of positive and negative electrodes, electrolyte and a diaphragm. The diaphragm has the important functions of isolating the positive electrode and the negative electrode, preventing electrons in the battery from passing through, and allowing ions to pass through, so that the lithium ions are rapidly transferred between the positive electrode and the negative electrode in the electrochemical charge-discharge process. The quality of the separator performance directly affects the discharge capacity and cycle life of the battery, and thus, sufficient attention is paid to the research and application of the separator material.

The function of the diaphragm is as follows:

1. the diaphragm material must have electronic insulation, so that the two poles are mechanically isolated, the positive pole and the negative pole are prevented from being contacted with each other, the internal short circuit of the lithium ion battery can be caused if the two poles are contacted, the battery is damaged, and even if the battery is serious, an explosion and fire accident can occur.

2. Electrolyte can be moisturized, the loss of the electrolyte is greatly reduced, the permeability is good in the transmission process of lithium ions, and the diaphragm material needs to have strong permeability.

3. If the temperature of the lithium ion battery is too high, the diaphragm has an automatic turn-off protection function.

The traditional diaphragm preparation method is divided into a dry method and a wet method, and although the two methods are widely used, the two methods have advantages and disadvantages. The aperture and the pore of the dry method are difficult to control, and only longitudinal stretching is carried out, so that the transverse strength of the membrane is poor; the wet process requires a complicated process flow, and a large amount of solvent is required in the preparation process, thereby causing environmental pollution.

Disclosure of Invention

Aiming at the defects in the prior art, the invention provides the lithium-sulfur battery diaphragm and the preparation method thereof, the method is simple and easy to operate, and the defects of the traditional method can be well avoided only by stretching the plastic bag transversely and longitudinally as much as possible and then pricking holes with fine needles, so that a novel structure for preparing the battery diaphragm by using the plastic bag can be provided.

In order to solve the technical problems in the prior art, the technical scheme of the invention is as follows:

a preparation method of a lithium-sulfur battery diaphragm comprises the following steps:

step S1, stretching the plastic bag at room temperature to a maximum extent in the transverse and longitudinal directions to nearly rupture;

step S2, a thin needle is used to pierce as many small holes as possible uniformly without overlapping on the stretched plastic bag.

As a preferred solution, in step S1, the plastic bag is stretched as uniformly and over the entire surface as possible.

Preferably, in step S2, the pinholes formed by the needle are not overlapped as much as possible, so that the pore size and porosity are not uniform.

The invention discloses a novel battery diaphragm, which adopts a plastic bag with synthetic resin as a main component.

Compared with the prior art, the invention has the following beneficial effects:

(1) when the battery system is abnormal, the temperature rises, and in order to prevent danger, when the temperature of rapid heat generation (120-140 ℃) begins, the diaphragm is melted, the micropores are closed, and the diaphragm becomes an insulator to prevent electrolyte from passing through, so that the aim of cutting off current is fulfilled.

(2) The electrolyte has good wettability, enough imbibition and moisture retention capacity, reduced electrolyte loss, electrolyte corrosion resistance and enough chemical stability.

Drawings

FIG. 1 is a flow chart of the steps of a method of making a battery separator according to the present invention;

fig. 2 is a cycle capacity curve of the lithium sulfur battery assembled in example 1 of the present invention at a charge and discharge current of 0.2C;

the following specific embodiments will further illustrate the invention in conjunction with the above-described figures.

Detailed Description

In order to better explain the process and scheme of the present invention, the following invention is further described with reference to the accompanying drawings and examples. The specific embodiments described herein are merely illustrative of the invention and do not delimit the invention.

Referring to fig. 1, the present invention provides a method for preparing a battery separator using a plastic bag, comprising the steps of:

EXAMPLE 1

The plastic bag is stretched to a maximum extent in the transverse and longitudinal directions at 50-60 ℃ to near rupture, and then cut into multiple portions with scissors. Taking out one part, pricking uniformly and with small holes on the stretched plastic bag with fine needle, and processing the rest parts.

Instantiation 2

The plastic bag is stretched laterally to its maximum extent at room temperature to near rupture, and then cut into multiple portions with scissors. Taking out one part, pricking uniformly and with small holes on the stretched plastic bag with fine needle, and processing the rest parts.

Instantiation 3

The plastic bag is stretched to a maximum extent at room temperature in both the transverse and longitudinal directions to approximate the break, and then cut into multiple portions with scissors. Taking out one part, overlapping the stretched plastic bag with a fine needle, and pricking many small holes, and processing the rest parts by the method.

Instantiation 4

The plastic bag is stretched to a maximum extent at room temperature in both the transverse and longitudinal directions to approximate the break, and then cut into multiple portions with scissors. Taking out one part, pricking small holes uniformly on the stretched plastic bag with fine needle, and processing the other parts.

Fig. 2 is a cyclic capacity curve of the lithium-sulfur battery assembled in instantiation 1 of the present invention at a charge-discharge current of 0.2C, the specific capacity of the lithium-sulfur battery can reach 571mAh/g, and the attenuation rate of each cycle of 500 times is only 0.033%.

Further, the battery separator material obtained above was sandwiched between the positive and negative electrodes of the battery with tweezers to assemble the battery.

From the above analysis, it can be seen that the battery separator has strong electronic insulation, prevents the positive and negative electrodes from contacting each other, and when the assembled battery is cycled 500 times at a charge-discharge rate of 0.2C, the attenuation rate of each cycle is only 0.033%. The rate performance of the diaphragm material is stable, and when the charge and discharge rate is recovered, the specific capacity of the diaphragm material can be well recovered, which indicates that the battery assembled by the diaphragm material has good cycle performance.

The above description of the embodiments is only intended to facilitate the understanding of the method of the invention and its core idea. It should be noted that, for those skilled in the art, it is possible to make various improvements and modifications to the present invention without departing from the principle of the present invention, and those improvements and modifications also fall within the scope of the claims of the present invention.

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A novel battery diaphragm is characterized in that the battery diaphragm adopts a plastic bag which takes synthetic resin as a main component.

2. A preparation method of a lithium-sulfur battery diaphragm is characterized by comprising the following steps:

in step S2, a plurality of small holes are uniformly punched on the stretched plastic bag without overlapping with each other with fine needles.

3. The method of manufacturing a separator for a lithium-sulfur battery according to claim 2, wherein the plastic bag is uniformly and entirely stretched in step S1.