Polyionic liquid-coated bacterial cellulose diaphragm and preparation method thereof

Abstract

The invention discloses a bacterial cellulose diaphragm and a preparation method thereof. The surfaces of nanofibers of the bacterial cellulose diaphragm are coated with a layer of polyionic liquid, and the polyionic liquid is one or the combination of more of imidazolium salt polyionic liquid, pyrrolidine salt polyionic liquid, piperidine salt polyionic liquid and quaternary ammonium salt polyionic liquid. The preparation method comprises the following steps: the bacterial cellulose diaphragm is sequentially immersed in aqueous polyionic liquid solution for 2 to 48 hours, immersed in precipitator for 30 minutes to 24 hours and immersed in lithium salt solution for 2 to 48 hours, finally, a hot press is utilized to press the bacterial cellulose diaphragm to be thin, and after drying, the polyionic liquid-coated bacterial cellulose diaphragm is obtained. The advantages of the invention are as follows: (1) the polyionic liquid-coated bacterial cellulose diaphragm has the advantages of high mechanical strength, good thermal stability, good lyophilic property, high porosity and high ionic conductivity, and can increase the cyclic stability and safety of lithium ion batteries; (2) the preparation method is simple, has low requirement on equipment, and is suitable for mass production.

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 a polyionic liquid and a preparation method thereof, belonging to the technical field of electrochemistry. Background technique [0002] The diaphragm is a key component of lithium-ion batteries, and is a key factor affecting the safety, capacity, service life and cost of lithium-ion batteries. With the greenness, safety, long life and high power density of lithium-ion batteries, there is an urgent need to develop high-performance separators. [0003] Due to the disadvantages of low safety, low charge and discharge efficiency, and short service life, traditional lithium-ion battery separators cannot meet the performance requirements of new power batteries. Therefore, the research and development of high-performance new power battery separators has become a major technical field in which countries all ove...

AI Technical Summary

Problems solved by technology

[0004] At present, the separators for lithium-ion batteries on the market are mainly polyolefin porous membranes, which are made of polyethylene (PE) and polypropylene (PP) as raw materials. The preparation process is simple and the production efficiency is high, but the equipment is complicated. High production cost of diaphragm

[0005] In addition, and most importantly, this diaphragm has many disadvantages, such as:

[0006] 1. The heat resistance is not good, and heat shrinkage is easy to occur at high temperature (PP melting temperature is 165°C), resulting in low battery safety;

[0007] 2. The porosity is low, which leads to low liquid absorption rate and is not conducive to high current charging and discharging;

[0008] 3. The surface energy is low, which is not conducive to the combination with the positive and negative electrodes, 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

Fan Lingling and others make the bacterial cellulose membrane absorb nitrate and nano-oxide particles through the impregnation method (CN106531931A), and then decompose the nitrate to obtain a metal oxide-cellulose composite membrane with a step-by-step hot-press drying method, which is used for When used as a lithium-ion battery separator, the battery exhibits excellent performance and safety, but because the silica particles are 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 amount, resulting in poor performance of the diaphragm

[0014] When bacterial cellulose membrane is used as a lithium-ion battery separator, the hydroxyl groups on the surface of the cellulose membrane will cooperate with lithium ions, reducing the dissociation ability of lithium ions, resulting in low ion conductivity; and, for lithium metal as an electrode When using high-performance lithium-ion batteries, the active groups on the surface of the cellulose membrane may react with lithium metal, reducing the safety and long-term service life of the battery

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