A kind of preparation method of inorganic composite separator assisted by water-soluble polymer

Abstract

The invention discloses a method for preparing a water-soluble polymer-assisted inorganic composite diaphragm, which belongs to the technical field of preparation and modification of lithium-ion battery diaphragms. The invention uses water-soluble polymers for the first time to improve the stability of inorganic composite diaphragms prepared by water-based systems And it is helpful for the complete film removal. The key points of the technical scheme are: mix and stir the ultrafine inorganic powder, water-based binder and water-soluble polymer in distilled water for 2 hours. Then spread the mixed slurry evenly on the glass substrate with a scraper and place it in a blast drying oven at 55°C to dry for 4 hours, soak the diaphragm and the glass substrate in distilled water for 1 hour to remove the water-soluble polymer, obtain a wet film, and take it out and dry it to obtain Inorganic composite membrane. The inorganic composite membrane prepared by the invention has high porosity, good wettability, strong stability, simple process and easy production, and the inorganic composite membrane can be widely used in portable electronic equipment, electric vehicles and lithium ion batteries for large energy storage.

Description

technical field [0001] The invention belongs to the technical field of preparation and modification of lithium-ion battery diaphragms, and in particular relates to a preparation method of an inorganic composite diaphragm assisted by a water-soluble polymer. Background technique [0002] Lithium-ion batteries are mainly composed of positive electrodes, negative electrodes, electrolytes, separators and battery casing packaging materials. The separator is one of the most critical parts of the lithium-ion battery. It plays an important role in separating the positive and negative electrodes, preventing electrons from passing through, but allowing ions to pass through freely to complete the electrochemical charge and discharge process. The performance of the separator determines the interface structure and internal resistance of the battery, which affects key characteristics such as the capacity, cycle performance, and charge-discharge current density of the battery. Commercial ...

AI Technical Summary

Problems solved by technology

Chen Chuan et al. (publication number: CN104269507A) used alumina as a substrate, treated with hydrochloric acid to make the surface have active hydroxyl groups, used aluminate coupling agent to make it capable of grafting polyethylene resin, and then grafted polyethylene on The modified alumina is finally biaxially stretched to produce pores, and the alumina-polyethylene microporous composite diaphragm is prepared. The diaphragm is resistant to high temperatures, has high puncture strength and tensile strength, but the porosity of the diaphragm is lower than that of commercial polyolefin diaphragms. The porosity is low, which limits the transmission of lithium ions in the separator and affects battery performance

Li Haibin et al. (publication number: CN102790195) added inorganic materials into the organic polymer solution, uniformly mixed, heated, and ball milled, and the resulting product mixture was poured on the substrate, and the inorganic / organic composite diaphragm was dried, and the obtained diaphragm had porosity and flexibility. , high mechanical strength, good stability, good uniformity, and good heat resistance, but organic solvents are toxic and pollute the air, affecting the environment and human health. In addition, the increase in the price of organic solvents increases energy consumption, making water-based The preparation of composite diaphragms with binder systems has been widely studied and applied at present.

[0004] Ultrafine inorganic powder is easy to agglomerate in water because of its small particle size, large specific surface area and surface energy, and the existence of agglomeration will greatly reduce the dispersion uniformity of inorganic powder particles in the water-based system

Liu Jin et al. (publication number: CN103311486A) obtained a composite separator by coating the slurry of inorganic particles, high molecular polymer precursors and water on the substrate to initiate a polymerization reaction, dry it, and then peel off the film, which has good mechanical properties, lithium ion Conductivity and excellent safety performance, but the polymerization reaction time is long, and the inorganic particles and polymers are easy to settle during the process of preparing the diaphragm, which reduces the uniformity of the diaphragm and affects the mechanical strength of the diaphragm. At the same time, the deposition of the binder on the substrate It is not easy to peel off the film after film formation

Zhang et al. (S.S.Zhang, K.Xu, T.R.Jow, J.PowerSources140(2005) 361-364) used polytetrafluoroethylene emulsion and CaCO 3 The self-supporting inorganic composite diaphragm is prepared by compounding particles. The preparation process is simple. The diaphragm exhibits good electrolyte wettability and liquid retention rate, good rate performance and cycle performance, but in order to obtain basic strength, the thickness of the diaphragm obtained 175-190 microns, which is too thick compared to the widely used polymer membranes (20-60 microns)

Therefore, in the past research work, due to the sedimentation and aggregation of inorganic and organic particles, it is difficult to form a stable suspension of the composite diaphragm with inorganic substances as the main body, and there are problems such as high organic binder content, poor mechanical strength, and large thickness.

Images