Composite Polyimide Separator With Controlled Pores for Safer Batteries
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Solution Overview
Problem
Polyimide separators in secondary batteries often cause micro-short circuits due to high-temperature imidization treatment, leading to safety issues like battery explosions and fires, and have unregulated surface pore sizes, which can result in internal short circuits.
Innovation Solution
A composite polyimide separator is prepared through an interfacial polymerization reaction on a porous polyamic acid film, followed by imidization in vapor, allowing for controlled pore size and reduced temperature processing to create a dense surface and loose bottom structure, enhancing safety and performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If high-temperature imidization treatment is applied to polyimide separator, then the thermal stability is improved, but micro-short circuits occur and safety deteriorates
Solution Approach 1:
The invention changes the imidization temperature parameter from conventional high temperature (300-500°C) to low temperature (60-120°C) by using vapor-phase imidization reagent treatment, thereby achieving thermal stability without causing micro-short circuits and safety issues
Solution Approach 2:
The invention introduces an imidization reagent (such as acetic anhydride, propionic anhydride, or butyric anhydride) as an intermediary substance that enables imidization reaction at low temperatures, replacing direct high-temperature heating and thus preventing safety accidents
2Productivity
If conventional imidization method is used, then the imidization reaction speed is fast, but the surface becomes cracked and manufacturing precision deteriorates
Solution Approach 1:
The imidization reagent acts as a mediator that enables rapid imidization reaction without direct high-temperature contact, preventing surface cracking while maintaining fast reaction speed through vapor-phase treatment
Solution Approach 2:
The invention replaces direct thermal heating (mechanical/thermal system) with chemical vapor-phase imidization (chemical system), achieving fast reaction speed without the harmful effects of high-temperature contact that cause surface cracking
3Temperature
If polyimide separator is used, then the thermal stability is improved, but micro-short circuits occur and reliability deteriorates
Solution Approach 1:
The invention changes the imidization temperature parameter to low temperature range (60-120°C) using vapor-phase reagent treatment, maintaining the thermal stability of polyimide material while preventing micro-short circuit formation that occurs with conventional high-temperature processing
4Productivity
If direct heating at high temperature is applied, then the imidization reaction is fast, but the separator develops cracks and manufacturing precision deteriorates
Solution Approach 1:
The invention replaces direct high-temperature heating (thermal/mechanical system) with vapor-phase chemical imidization (chemical system), achieving fast reaction kinetics through chemical catalysis while eliminating thermal stress that causes separator cracking
Solution Approach 2:
The imidization reagent vapor serves as an intermediary that facilitates rapid imidization reaction through chemical interaction without requiring direct high-temperature contact, thus preventing thermal degradation and cracking of the separator structure
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method reduces the occurrence of micro-short circuits, improves puncture strength, and achieves uniform pore distribution, thereby enhancing the safety and cycling performance of secondary batteries.
Implementation Method 1
subjecting a diamine aqueous solution and an acyl chloride organic solution to an interfacial polymerization reaction on a surface of the porous polyamic acid film to obtain a composite polyamic acid separator
Implementation Method 2
placing the composite polyamic acid separator in vapor of an imidization reagent for an imidization reaction to obtain the composite polyimide separator
Implementation Method 3
the imidization treatment is carried out by placing the composite polyamic acid separator in the vapor of the imidization reagent for reaction, rather than directly heating the separator at high temperature
Data Source
AI summary
A composite polyimide separator and a preparation method thereof, and a secondary battery are described. The preparation method of the composite polyimide separator comprises: providing a porous polyamic acid film; subjecting a diamine aqueous solution and an acyl chloride organic solution to an interfacial polymerization reaction on a surface of the porous polyamic acid film to obtain a composite polyamic acid separator; and placing the composite polyamic acid separator in vapor of an imidization reagent for imidization treatment to obtain the composite polyimide separator. In the present application, by controlling the parameters of the interfacial polymerization reaction, a composite polyamic acid separator with a dense surface, a loose bottom, and an adjustable surface pore size can be obtained.