Preparation method of polyvinylidene fluoride-polyvinyl alcohol composite proton exchange membrane

Abstract

The invention discloses a preparation method of a polyvinylidene fluoride-polyvinyl alcohol composite proton exchange membrane and belongs to the field of a battery electrolyte material. The preparation method comprises the following steps of: firstly preparing a polymer solution by dissolving polyvinyl alcohol in mixed liquid of dimethyl sulfoxide and water; adding silicon tetrachloride and sodium tungstate to the polymer solution; heating, stirring, and then adding polyvinylidene fluoride; carrying out oil bath in vacuum, heating and stirring so as to form a solution; pouring the solution on a polytetrafluoroethylene glass plate and drying to form a membrane, thus obtaining the needed silicotungstic acid and silicon dioxide doped polyvinylidene fluoride-polyvinyl alcohol composite proton exchange membrane. The proton exchange membrane prepared by the method has very good proton electrical conductivity, low methyl alcohol permeability and relatively low swelling degree and is favorable for large-scale production.

Description

[0001] technical field [0002] The invention relates to a method for preparing a polyvinylidene fluoride-polyvinyl alcohol composite proton exchange membrane doped with silicotungstic acid and silicon dioxide, and belongs to the field of battery electrolyte materials. Background technique [0003] Direct methanol fuel cell (DMFC) has broad application prospects as a portable mobile power supply in the fields of communication, military and emergency rescue. As the core material of direct methanol fuel cells, the proton exchange membrane acts as a selective conductor from the cathode to the anode, while it blocks fuel and oxidant. The performance of the proton exchange membrane determines the performance of the fuel cell. [0004] Most of the proton exchange membranes currently used in DMFC are hydrated perfluorosulfonic acid membranes such as Nafion. Nafion membranes have good chemical and mechanical stability and excellent proton conductivity, but there are also the follow...

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Problems solved by technology

[0004] Most of the proton exchange membranes currently used in DMFC are hydrated perfluorosulfonic acid membranes such as Nafion. Nafion membranes have good chemical and mechanical stability and excellent proton conductivity, but there are also the following defects: (1) Synthesis of perfluorinated substances , sulfonation, and film formation are very difficult and costly; (2) High requirements on temperature and water content, hydration of sulfonic acid membranes exceeding the boiling point of water will cause a sharp drop in water content and a rapid drop in conductivity; (3) a certain Some hydrocarbons (such as methanol, etc.) have high permeability in this type of membrane

The key issue in preparing silicotungstic acid-doped polyvinyl alcohol composite membrane is to reduce the swelling rate of the membrane and to distribute the added nano-silicotungstic acid particles evenly in the polyvinyl alcohol matrix. However, due to the strong water absorption of polyvinyl alcohol, Even if the doped inorganic substances are evenly distributed in the polyvinyl alcohol matrix, the swelling degree of the obtained film is still relatively large, and the film becomes brittle due to the recrystallization of polyvinyl alcohol after standing for a period of time, so This membrane needs to be improved to become a Nafion membrane replacement membrane

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