Ionic polymer film material and preparation method thereof, and lithium secondary battery

Abstract

The invention relates to an ionic polymer film material and a preparation method thereof, and a lithium secondary battery, belonging to the technical field of manufacturing of lithium batteries. The invention provides an ionic polymer film material consisting of polymer colloid particles with sulfonate groups on surfaces. A reactive sulfonate surfactant is taken as an emulsifier for synthesizing an acrylate polymer colloid emulsion with sulfonate groups on the surface, and a film is formed by performing curtain coating film forming on the emulsion. The film is formed by colloid particles, and is a pore-free dense film with a colloid particle structure; and when the battery is overheated, a diaphragm is free from remarkable thermal shrinkage. Moreover, a through ion conducting path is formed among colloid particles after a polymer film absorbs an electrolyte, and the ionic polymer film material can keep a colloid particle structure after absorbing an electrolyte solution or solvent; and through dense deposition of colloid particle sphere structures, the sinuosity of the ion conducting path is increased, and the electronic insulating performance of a poly-anion electrolyte film is enhanced.

Description

technical field [0001] The invention relates to a diaphragm material used for energy storage devices such as lithium-ion secondary batteries and a preparation method thereof, belonging to the field of lithium battery manufacturing. Background technique [0002] Separator is one of the important raw materials of batteries. Its microporous structure, physical properties, chemical properties, thermal properties, etc. are closely related to battery performance. For the diaphragm of lithium-ion batteries, since lithium-ion batteries have high operating voltage, the oxidation of positive electrode materials and the reducibility of negative electrode materials are relatively high, lithium-ion battery separator materials and high electrochemically active positive and negative electrode materials should have excellent compatibility. At the same time, it should have excellent stability, solvent resistance, ion conductivity, electronic insulation, good mechanical strength, high heat r...

AI Technical Summary

Problems solved by technology

[0011] The main problems of polyolefin microporous membranes: First, the microporous membranes have poor liquid absorption and liquid retention capabilities. PP or PE is a non-polar material, which has poor affinity with highly polar electrolyte solutions. The low affinity of the polyolefin microporous membrane leads to the poor ability of the microporous membrane to absorb and retain the electrolyte, and the strength of the liquid absorption and liquid retention of the microporous membrane is closely related to the charge-discharge cycle life of the battery. The second is that the thermal stability of the microporous membrane is poor. Because the polyolefin microporous membrane is mechanically stretched to cause pores, or mechanically stretched and then extracted with an organic solvent to cause pores, and the microporous membrane is heat-set. This preparation process makes the microporous membrane have residual stress, which makes the microporous membrane have a shape memory effect. When the polyolefin resin is heated to a temperature close to the softening point, the microporous membrane tends to recover the shape before stretching, and produces a large Shrinkage, thermal shrinkage of the microporous membrane must be accompanied by volume shrinkage, and the shrinkage of the membrane area will cause the microporous membrane to lose the barrier effect between the positive and negative electrodes, thereby short-circuiting the positive and negative electrodes inside the battery, causing safety problems such as battery combustion and explosion.

[0013] The inventor of the present invention believes that although the film has good battery performance and safety, it is obtained by modification on the basis of a microporous polyolefin diaphragm, which will inevitably increase the cost of the battery diaphragm, and is limited by the diaphragm in practice. Price constraints, in addition, the film needs to use a large amount of toluene as a solvent in the preparation process, which has pollution problems to the environment, and also increases the manufacturing cost of this polymer film

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