Abab-type multilayer lithium-ion battery separator with thermal shutdown function and preparation method thereof

Abstract

The invention belongs to the technical field of polymer materials, in particular to an ABAB type multilayer lithium-ion battery diaphragm with thermal shutdown function and a preparation method thereof. The present invention selects a polymer with a higher melting point as the A layer, selects a polymer with a lower melting point as the B layer, and combines the microlayer co-extrusion technology with the thermally induced phase separation technology to prepare an ABAB alternating multilayer lithium-ion battery diaphragm. The present invention utilizes the low melting point of the polymer B layer to obtain a lower diaphragm closed cell temperature to prevent the temperature from further increasing under high temperature conditions, and utilizes the high melting point of the polymer A layer to obtain a higher film deformation temperature to avoid the positive The short circuit caused by the contact of the negative electrode makes the diaphragm have a wider safety window and more effective thermal shutdown function; the diaphragm prepared by the present invention has uniform thickness, rich submicron porous structure, uniform and controllable pore structure, and thermal stability Excellent, with an effective thermal shutdown function, and has application prospects in the fields of lithium-ion battery separators and other fields.

Description

technical field [0001] The invention belongs to the technical field of polymer materials, and in particular relates to a lithium-ion battery diaphragm and a preparation method thereof. Background technique [0002] Lithium-ion batteries (LIB) are widely used in MP3, mobile phones, notebook computers and other fields due to their high working voltage, high energy density and long cycle life (Arora P, Zhang Z. Battery separators. Chemical Reviews, 2004, 104(10 ): 4419-4462). However, due to the existence of flammable electrolytes and oxidants in lithium-ion batteries, there are hidden dangers of fire and explosion during battery use. In order to promote the application of lithium-ion batteries in high energy density fields, it is necessary to further improve their safety and stability. Using a battery separator with thermal shutdown is an effective way to prevent catastrophic thermal failure during Li-ion battery life. From the consideration of safety performance, the diaphr...

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Problems solved by technology

The process route of the manufacturing process is relatively complicated, the investment in equipment is large, and the production efficiency is low (Deimede V, Elmasides C. Separators forlithium-ion batteries: A Review on the Production Processes and Recent Developments. Energy Technology, 2015, 3(5): 453-468)

In addition, the disadvantage of the current commercial multilayer separator is that the porous film prepared after multiple stretches has residual stress, which makes it easy to shrink greatly when encountering high temperature, resulting in poor thermal dimension. stability

In order to improve the poor thermal stability of the current commercial multilayer polyolefin separators, researchers are committed to reducing the thermal shrinkage of the separators through various modification methods

For example, the organic polymer / inorganic oxide with excellent thermal stability is coated on the surface of the diaphragm, but this process is complicated and difficult to produce in batches, which greatly increases the cost of the diaphragm

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