Flame-Resistant Composite Separator for Lithium Dendrite Suppression
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Solution Overview
Problem
Rechargeable lithium metal batteries face challenges due to lithium metal dendrite formation and reactions with the electrolyte, leading to safety concerns, internal short circuits, and reduced cycle life, which have hindered their commercialization despite their high energy density potential.
Innovation Solution
A flame-resistant polymer composite separator with a porous structure and high lithium-ion conductivity is introduced, comprising a thermally stable first polymer and a second polymer that is either in situ polymerized or solidified within the pores, providing a stable and conductive barrier between the anode and cathode, preventing dendrite formation and electrolyte reactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If lithium metal is used as the anode active material to achieve high energy density, then the battery capacity is significantly improved, but lithium dendrite formation occurs during cycling leading to safety issues and reduced cycle life
Solution Approach 1:
A polymer electrolyte layer is introduced as an intermediary between the lithium metal anode and the liquid electrolyte. This polymer layer acts as a mediator that allows lithium ion transport while preventing direct contact between lithium metal and the liquid electrolyte, thereby eliminating dendrite formation and improving cycle stability while maintaining high capacity
Solution Approach 2:
The invention uses a composite structure combining lithium metal anode with a polymer electrolyte layer. This composite material approach integrates the high capacity benefit of lithium metal with the safety and stability benefits of the polymer electrolyte, resolving the contradiction between capacity and reliability
2Reliability
If conventional solid electrolytes are used to prevent dendrite formation, then safety is improved, but lithium-ion conductivity is low and the electrolyte is difficult to produce and implement
Solution Approach 1:
The polymer electrolyte is designed with a porous structure that facilitates lithium ion transport, achieving high ionic conductivity comparable to liquid electrolytes. The porous architecture allows easy infiltration of liquid electrolyte and simplifies the manufacturing process while maintaining safety benefits
Solution Approach 2:
The invention changes the physical and chemical parameters of the polymer electrolyte, specifically optimizing its ionic conductivity and porosity, to achieve performance levels that are easy to produce and implement while maintaining high safety standards
3Temperature
If a conventional ceramic separator is used between anode and cathode, then thermal stability is improved, but the separator has poor contact with the cathode layer when electrolyte is solid
Solution Approach 1:
The polymer electrolyte layer is designed to be dynamic and adaptable, changing its physical state to maintain optimal contact with both electrodes. When liquid, it flows to ensure complete contact; when solidified, it maintains intimate contact through its flexible nature, ensuring reliable electrical connection while providing thermal stability
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 solution significantly enhances the safety and cycle stability of lithium metal batteries by preventing dendrite penetration and electrolyte consumption, allowing for uniform lithium deposition and improved lithium-ion transport, thus extending the battery's life and maintaining high energy density.
Implementation Method 1
a first polymer comprising a flame-resistant or thermally stable polymer... having a lithium-ion conductivity no less than from 10−8 S/cm
Implementation Method 2
a second polymer permeating into or residing in these pores of the first polymer layer, wherein: (b) the second polymer comprises either a polymer that is obtained by in situ polymerizing and/or curing a reactive mass in the pores
Implementation Method 3
the first polymer comprises a flame-resistant or thermally stable polymer... (a) the first polymer comprises a flame-resistant or thermally stable polymer
Data Source
AI summary
A flame-resistant composite separator for use in a lithium battery, wherein the composite separator comprises a porous layer of a first polymer, having pores and a thickness from 50 nm to 200 μm, and a second polymer permeating into or residing in the pores, wherein: (a) the first polymer comprises a flame-resistant polymer or thermally stable polymer; (b) the second polymer comprises a polymer that is polymerized and/or cured in situ in the pores or is a polymer solidified from a polymer solution inside the pores of the first polymer layer; and (c) the first polymer or the second polymer has a lithium-ion conductivity from 10−8 S/cm to 2×10−2 S/cm at room temperature.