Mesoporous Polyimide Separators for Alkali Battery Dendrite Suppression
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Solution Overview
Problem
Lithium dendrites pose significant safety hazards in alkali metal batteries due to their ability to penetrate separators, leading to short circuits and potential fires, and existing separators with large macropores are susceptible to dendrite penetration.
Innovation Solution
Development of mesoporous polyimide separators with controlled pore sizes between 5 nm to 20 nm, achieved through the use of thermally labile block copolymers that self-assemble and decompose to form uniform mesopores, providing a strong physical barrier against dendrite penetration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If macroporous separators are used, then ion transport is facilitated, but dendrite penetration occurs leading to safety hazards
Solution Approach 1:
The patent applies porous materials by transitioning from macroporous to mesoporous structure with controlled pore sizes of 2-50 nm. This mesoporous configuration allows efficient ion transport while the smaller, controlled pore sizes prevent dendrite penetration, resolving the contradiction between ion transport speed and safety reliability
Solution Approach 2:
The patent changes the critical parameter of pore size from macroporous (>50 nm) to mesoporous (2-50 nm, specifically 2-20 nm in some embodiments). This parameter change enables the separator to maintain ion conductivity while providing a physical barrier against dendrites, simultaneously improving both ion transport and safety
2Reliability
If separator pore size is reduced to prevent dendrite penetration, then safety is improved, but ion transport efficiency decreases
Solution Approach 1:
The patent utilizes mesoporous materials with optimized pore sizes in the 2-50 nm range that strike a balance between being small enough to block dendrites while remaining large enough to allow efficient ion transport. The porous structure provides both safety and conductivity
Solution Approach 2:
The patent employs composite material strategies by combining mesoporous polyimide with specific pore size distributions and potentially multiple functional components. This composite approach optimizes both the mechanical barrier properties for dendrite blocking and the ionic conductivity for efficient transport
3Ease of manufacture
If conventional separators are used, then manufacturing is simple, but they cannot suppress dendrite growth effectively
Solution Approach 1:
The patent employs mesoporous polyimide materials that can be manufactured through established porous polymer techniques. The mesoporous structure is created through controlled phase separation or templating methods that are compatible with existing manufacturing processes, maintaining ease of production while achieving superior dendrite suppression
Solution Approach 2:
The patent changes the pore size parameter to the mesoporous range (2-50 nm) while maintaining manufacturing processes that are adaptations of conventional separator production. This parameter optimization enables dendrite suppression without requiring completely new manufacturing methodologies
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 mesoporous polyimide separators effectively suppress dendrite growth, ensuring safe operation and prolonged battery life by preventing dendrites from penetrating the separator, thereby enhancing safety and performance.
Implementation Method 1
achieved through the use of thermally labile block copolymers that self-assemble and decompose to form uniform mesopores
Implementation Method 2
heating the precursor film to a temperature from about 100° C. to about 300° C. for a time interval to form the polyimide membrane; wherein the mesoporous polyimide membrane comprises a plurality of mesopores
Data Source
AI summary
In various aspects, methods of preparing mesoporous polyimide membranes are provided. The polyimide membranes are useful as separators in various electrochemical devices, in particular in alkali metal batteries where the controllable pore size and high modulus of the membranes can prevent or suppress dendrite formation in alkali metal batteries. Electrochemical devices, and in particular alkali metal batteries, incorporating the polyimide membranes as separators are also provided.