阅读说明：本技术 一种离子电池隔膜及其制备方法 (Ion battery diaphragm and preparation method thereof ) 是由 田子钦 黄恒辉 谢嘉宜 徐睿杰 雷彩红 于 2019-09-26 设计创作，主要内容包括：本申请属于电池隔膜的技术领域,尤其涉及一种离子电池隔膜及其制备方法。本申请提供了一种离子电池隔膜的制备方法,包括步骤1、将聚乳酸与有机溶剂混合,制得油相溶液；将分散剂与水混合,制得水相溶液；步骤2、将所述油相溶液与所述水相溶液进行乳化,制得乳酸微球,然后将所述乳酸微球干燥得到乳酸微球粉末；步骤3、将所述乳酸微球粉末、水与粘结剂混合,制得涂敷浆料；步骤4、将所述涂敷浆料涂敷在电池隔膜的表面,然后真空烘干后制得离子电池隔膜。本申请提供了一种离子电池隔膜及其制备方法,能有效解决目前离子电池隔膜存在的保液性差、浸润性差的技术缺陷。(The application belongs to the technical field of battery diaphragms, and particularly relates to an ion battery diaphragm and a preparation method thereof. The application provides a preparation method of an ion battery diaphragm, which comprises the following steps of 1, mixing polylactic acid with an organic solvent to prepare an oil phase solution; mixing a dispersant with water to prepare a water phase solution; step 2, emulsifying the oil phase solution and the water phase solution to prepare lactic acid microspheres, and drying the lactic acid microspheres to obtain lactic acid microsphere powder; step 3, mixing the lactic acid microsphere powder, water and a binder to prepare coating slurry; and 4, coating the coating slurry on the surface of the battery diaphragm, and then drying in vacuum to obtain the ionic battery diaphragm. The application provides an ion battery diaphragm and a preparation method thereof, which can effectively overcome the technical defects of poor liquid retention and poor wettability of the conventional ion battery diaphragm.)

1. The preparation method of the ion battery diaphragm is characterized by comprising the following steps:

step 1, mixing polylactic acid and an organic solvent to prepare an oil phase solution; mixing a dispersant with water to prepare a water phase solution;

step 2, emulsifying the oil phase solution and the water phase solution to prepare lactic acid microspheres, and drying the lactic acid microspheres to obtain lactic acid microsphere powder;

step 3, mixing the lactic acid microsphere powder, water and a binder to prepare coating slurry;

and 4, coating the coating slurry on the surface of the battery diaphragm, and then drying in vacuum to obtain the ionic battery diaphragm.

2. The method according to claim 1, wherein in step 1, the polylactic acid is selected from poly-L-lactic acid; the molar mass of the poly-L lactic acid is 100-200 kg/mol.

3. The method according to claim 1, wherein the organic solvent is selected from dichloromethane and/or chloroform in step 1.

4. The method according to claim 1, wherein in step 1, the dispersant is one or more selected from polyvinyl alcohol PVA, sodium polyacrylate and sodium sulfonate salt.

5. The method according to claim 4, wherein the polyvinyl alcohol PVA is present in an amount of 0.5 to 5% by mass.

6. The method according to claim 1, wherein the temperature of the emulsification in the step 2 is 25 to 60 ℃; the stirring speed of the emulsification is 600-1200 r/min.

7. The method according to claim 1, wherein the emulsifying step 2 further comprises ultrasonic treatment for 0-10 min.

8. The preparation method according to claim 1, wherein in the step 2, the drying temperature is 50-110 ℃; the drying time is 2-8 h.

9. The method according to claim 1, wherein in step 3, the binder is selected from polyvinyl alcohol PVA and/or oxidized cyclodextrin, the latter being oxidized by 5% hydrogen peroxide.

10. An ion battery separator, comprising the ion battery separator produced by the production method according to any one of claims 1 to 9.

Technical Field

The application belongs to the technical field of battery diaphragms, and particularly relates to an ion battery diaphragm and a preparation method thereof.

Background

In the construction of lithium batteries, the separator is one of the key internal components. The performance of the diaphragm determines the interface structure, internal resistance and the like of the battery, directly influences the capacity, circulation, safety performance and other characteristics of the battery, and the diaphragm with excellent performance plays an important role in improving the comprehensive performance of the battery. The separator has a main function of separating the positive electrode and the negative electrode of the battery to prevent short circuit due to contact between the two electrodes, and also has a function of allowing electrolyte ions to pass therethrough. The separator material is non-conductive, and the physical and chemical properties of the separator have a great influence on the performance of the battery.

For ion battery series, because the electrolyte is an organic solvent system, a diaphragm material resistant to organic solvent is needed, a PE film is generally adopted, but the melting point of the existing PE film is 120-140 ℃, so the heat shrinkage performance is not good; the PE film has a structure of-CH₂-CH₂Since the PE film and the electrolyte are similar and compatible, the wettability of the PE film and the electrolyte is poor, the electrolyte is very easy to volatilize, the resistance of the battery is increased, and the performance and the service life of the battery are influenced.

Disclosure of Invention

In view of this, the application provides an ion battery diaphragm and a preparation method thereof, which can effectively solve the technical defects of poor liquid retention and poor wettability of the existing ion battery diaphragm.

The application provides a preparation method of an ion battery diaphragm, which comprises the following steps:

step 1, mixing polylactic acid and an organic solvent to prepare an oil phase solution; mixing a dispersant with water to prepare a water phase solution;

step 2, emulsifying the oil phase solution and the water phase solution to prepare lactic acid microspheres, and drying the lactic acid microspheres to obtain lactic acid microsphere powder;

step 3, mixing the lactic acid microsphere powder, water and a binder to prepare coating slurry;

and 4, coating the coating slurry on the surface of the battery diaphragm, and then drying in vacuum to obtain the ionic battery diaphragm.

Specifically, the polylactic acid commercially available in the present application may be one or more of poly-D lactic acid, poly-L lactic acid, and poly-DL lactic acid.

It should be noted that after the lactic acid microspheres are obtained in step 2, conventional centrifugal washing (deionized water and acetone alternate washing) is not required, but the lactic acid microspheres are directly dried to obtain lactic acid microsphere powder, and the organic solvent contained in the lactic acid microspheres obtained in step 2 is volatilized by subsequent heating and drying.

Preferably, in step 1, the polylactic acid is selected from poly-L lactic acid; the molar mass of the poly-L lactic acid is 100-200 kg/mol, and preferably, the molar mass of the poly-L lactic acid is 150-200 kg/mol.

It should be noted that, the molar mass of the polylactic acid is selected to be favorable for forming the polylactic acid microspheres with hollow structures, and the lower the molar mass of the polylactic acid is, the shorter the molecular chain is, the worse the entanglement state is, and the more easily the polylactic acid is degraded and releases the coated solution. The ionic cell diaphragm is prepared by utilizing the polylactic acid microspheres, the degradation speed and the solution releasing speed of the polylactic acid microspheres are not too fast, and therefore the polylactic acid with proper molar mass is selected, and the polylactic acid with industrial extrusion injection molding grade is selected.

Preferably, in step 1, the organic solvent is selected from dichloromethane or/and chloroform.

Preferably, in the step 1, the dispersing agent is selected from one or more of polyvinyl alcohol PVA, sodium polyacrylate and sodium sulfonate; more preferably, the dispersant is PVA.

Preferably, the mass fraction of the polyvinyl alcohol PVA is 0.5 to 5 percent; more preferably 0.5 to 2%.

Preferably, in the step 2, the emulsifying temperature is 25-60 ℃; the stirring speed of the emulsification is 600-1200 r/min; more preferably 600 to 1000 r/min.

Preferably, in the step 2, the emulsification further comprises ultrasonic treatment, and the ultrasonic time is 0-10 min.

More preferably, the ultrasonic time is 3-10 min, and the ultrasonic time is 0-10 min.

Preferably, in the step 2, the drying temperature is 50-110 ℃; the drying time is 2-8 h; more preferably 4-6 h.

Preferably, in step 3, the binder is selected from polyvinyl alcohol PVA or/and oxidized cyclodextrin (oxidized by 5% hydrogen peroxide solution).

The application also provides an ion battery diaphragm which comprises the ion battery diaphragm prepared by the preparation method.

The battery diaphragm is applied to lithium ion batteries (the positive electrode comprises lithium cobaltate, lithium manganate, lithium iron phosphate and ternary materials), lithium sulfur batteries and sodium ion batteries.

The polylactic acid microspheres are creatively utilized as slurry of the ionic cell diaphragm, the glass transition temperature of the polylactic acid is 60 ℃, the melting point is 155-170 ℃, and the polylactic acid microspheres have the functions of heat resistance and slow release solution; because the glass transition temperature of the polylactic acid is 60 ℃, when the working temperature of the battery is 60 ℃ (for example, the temperature can be easily reached in summer) a common PE diaphragm can easily volatilize the electrolyte to cause the resistance of the battery to be increased, and the lactic acid microspheres can release part of the electrolyte, thereby compensating the electrolyte lost at high temperature (the glass transition temperature: the temperature at which the polymer chain segment starts to move). Finally, the ion battery diaphragm has good high-temperature electrochemical performance; a relatively high melting range; excellent electrolyte retention; the battery can be circulated, and the multiplying power performance is improved slightly; better thermal shrinkage resistance.

Drawings

In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below.

FIG. 1 shows a first magnification of a microtopography of lactic acid microspheres provided in example 1 of the present application;

FIG. 2 shows a second magnification microtopography of lactic acid microspheres provided in example 1 of the present application;

FIG. 3 shows a third magnified micro-topography of lactic acid microspheres provided in example 1 of the present application;

FIG. 4 shows a fourth magnification microtopography of lactic acid microspheres provided in example 1 of the present application;

fig. 5 illustrates a surface contact angle of a PE separator for a conventional ion battery;

fig. 6 shows the surface contact angle of the ion battery separator provided in example 1 of the present application.

Detailed Description

The application provides an ion battery diaphragm and a preparation method thereof, which can effectively overcome the technical defects of poor liquid retention and poor wettability of the conventional ion battery diaphragm.

The technical solutions in the embodiments of the present application will be described clearly and completely below, and it should be understood that the described embodiments are only a part of the embodiments of the present application, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

The reagents used in the following examples are commercially available or self-made.