Polydopamine-coated bacterial cellulose membrane and preparation method thereof

Abstract

The invention discloses a polydopamine-coated bacterial cellulose membrane and a preparation method thereof. The preparation method comprises the following steps: firstly placing a bacterial cellulosegel film in dopamine water solution to enable dopamine to be adsorbed on the surfaces of nanofibers; secondly placing the nanofibers in weak alkali solution for dipping; thirdly placing the nanofibers in an organic solvent for solvent exchange; fourthly utilizing a hot press to thin the nanofibers; and finally drying the nanofibers. The invention has the beneficial effects that (1) the preparation method is simple, low in equipment requirement and suitable for large-scale production; (2) the surface of the nanofiber is coated with a layer of polydopamine, so that the combination of cellulosehydroxyl and lithium ions can be overcome, the conductivity and the rapid migration capability of the lithium ions in the electrolyte are improved, and the diaphragm is suitable for being used as a novel high-power power lithium ion battery diaphragm; and (3) the polydopamine is loaded by utilizing the bacterial cellulose which is low in cost and rich in yield, so that the preparation cost is reduced, and the market prospect of industrial popularization is achieved.

Description

technical field [0001] The invention relates to a bacterial cellulose membrane and a preparation method thereof, in particular to a bacterial cellulose membrane coated with polydopamine and a preparation method thereof, belonging to the technical field of electrochemistry. Background technique [0002] The separator, the positive electrode, the negative electrode, and the electrolyte together constitute the key components of the lithium-ion battery. Among them, the structural stability and temperature resistance of the separator affect the safety of the lithium-ion battery. In addition, the separator acts as an ion conductor and a barrier for the electrode. It also has a serious impact on the capacity and service life of lithium-ion batteries. With the continuous improvement of the performance of the positive and negative electrode materials of lithium-ion batteries, the specific capacity and energy density of lithium-ion batteries have been significantly improved. High-cap...

AI Technical Summary

Problems solved by technology

[0006] 1. The heat resistance stability is not good, and high temperature is prone to thermal shrinkage. For example, due to the cold crystallization of the PP separator, the size of the PP separator begins to change significantly at 80°C, and the dimensional shrinkage in the stretching direction increases significantly, which is easy to cause battery damage. Internal short circuit, resulting in a decrease in battery safety;

[0007] 2. The porosity is low. The porosity of this type of diaphragm is usually below 50%, especially for dry stretched membranes, the porosity is below 40%, which leads to low liquid absorption and is not conducive to high-current charging and discharging;

[0008] 3. Since polyethylene and polypropylene are typical non-polar materials, the surface energy of the film is low, the electrolyte is difficult to wet on the surface of the film, and the interface resistance is large, which affects the energy density of the battery;

[0009] 4. The hydrophilicity is not good, and the wetting and maintenance of the electrolyte is not enough, which affects the migration of lithium ions and the safety of the battery

However, since inorganic nanoparticles (such as silica particles) are mainly dispersed in the pores of the bacterial cellulose membrane, it cannot effectively increase the porosity of the cellulose membrane, but may reduce the adsorption of the electrolyte, resulting in poor performance of the separator. good performance

[0014] When the bacterial cellulose membrane is used as a lithium-ion battery separator, the surface hydroxyl groups of the fiber bundles cooperate with lithium ions, which may reduce the dissociation ability of lithium ions, resulting in a decrease in ion conductivity.

In addition, the polarity of the bacterial cellulose surface and the polarity of the electrolyte are not well matched, and the infiltration of the bacterial cellulose and the electrolyte and the ability to retain the electrolyte are not ideal.

Images