Active Membrane with Controlled Ion-Transport for Thermal Runaway Prevention
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Solution Overview
Problem
Current Li-ion batteries in electric vehicles are limited by short driving range, long recharge time, and capacity fade, while alternative energy storage devices like supercapacitors and redox flow batteries have poor energy density due to self-discharge, and existing separators in electrochemical cells are prone to thermal runaway, leading to safety issues and irreversible damage.
Innovation Solution
A membrane with a substrate and an ion-doped conductive polymer that allows controlled ion transport, featuring a tunable impedance to regulate ion flow, preventing thermal runaway and enabling high energy density and specific power in energy storage devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional separators are used in electrochemical cells, then ion transport is allowed, but thermal runaway occurs leading to safety issues and irreversible damage
Solution Approach 1:
The separator incorporates a shape memory polymer layer that dynamically changes its pore structure in response to temperature variations. At normal operating temperatures, the polymer maintains an open pore configuration that allows free ion transport. When thermal runaway conditions are detected, the polymer undergoes a phase transition to a closed configuration, automatically blocking ion transport and preventing further thermal escalation without requiring external control systems.
Solution Approach 2:
The invention utilizes temperature as a critical parameter to trigger the protective mechanism. The shape memory polymer is designed with a specific glass transition temperature (Tg) that is lower than the thermal runaway temperature but higher than normal operating temperatures. This parameter change approach allows the separator to distinguish between normal operation and dangerous conditions, activating the safety mechanism only when necessary while maintaining performance during normal use.
2Reliability
If multilayer separators are used to prevent thermal runaway, then ion transport is blocked during thermal events, but the membrane separator is irreversibly damaged and blocked
Solution Approach 1:
The shape memory polymer layer acts as a sacrificial protective element that can be reset. When thermal runaway occurs, the polymer undergoes a controlled structural change to block ion transport, protecting the underlying membrane separator from damage. After the thermal event subsides and the temperature returns to normal, the polymer can be reset to its original open configuration through controlled heating or other triggering mechanisms, restoring ion transport capability without permanent damage to the separator assembly.
3Quantity of substance
If Li-ion batteries are designed for high energy density, then driving range is improved, but recharge time increases and capacity fade occurs
Solution Approach 1:
The separator employs local quality differentiation through its multilayer structure, with each layer serving a specific function optimized for its role. The shape memory polymer layer is strategically positioned and designed with specific pore size distributions and thickness variations to optimize ion transport pathways. This localized optimization allows high ion conductivity in regions where it is most needed while maintaining overall separator integrity and safety performance.
4Productivity
If supercapacitors and redox flow batteries are used as alternatives, then rapid recharge is achieved, but energy density is poor due to self-discharge
Solution Approach 1:
The separator utilizes composite material construction combining the shape memory polymer with other functional layers that have complementary properties. This composite structure integrates the thermal-responsive protective functionality of the shape memory polymer with ion-conductive layers and mechanical support structures, creating a multi-functional separator that simultaneously addresses safety requirements and maintains high ion transport efficiency for rapid charging applications.
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 membrane effectively prevents thermal runaway, maintains device safety, and enhances the performance of energy storage devices by allowing reversible control of ion transport, thereby overcoming limitations in electric vehicle technology and improving energy storage capabilities.
Implementation Method 1
The ion-doped conductive polymer is formulated to have a change in at least one of a porosity and impedance in response to at least one of a reducing or an oxidizing voltage applied across the membrane
Data Source
AI summary
A membrane is provided that includes a membrane substrate defining a plurality of pores to allow ion transport therethrough; an ion-doped conductive polymer disposed on a surface of the membrane substrate; and a conductive material disposed between the membrane substrate and the ion-doped conductive polymer. The membrane may have an areal density from about 0.01 Coulombs per cm2 (C/cm2) to about 100 C/cm2. Such membranes provide for controlled bidirectional ion transport therethrough and may be used in electrochemical cells that includes such membranes as part of (or the entirety of) the separator. Such separators may be used to control charge transfer through the electrochemical cell and/or reversibly stop charge transfer therethrough to prevent thermal runaway.