Cross-Linked Polymer Electrolyte for Dendrite-Resistant LMP Batteries
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Solution Overview
Problem
Lithium metal polymer batteries face issues with insufficient mechanical strength, low ion conductivity, and dendrite formation due to the use of poly(ethylene oxide)-based electrolytes, leading to reduced performance and safety concerns at elevated temperatures.
Innovation Solution
A cross-linked copolymer comprising poly(alkylene oxide) and lithium polystyrene-sulfonyl(trifluoromethylsulfonyl)imide units, formed through a triblock copolymer with controlled radical polymerization, enhances mechanical strength and ion conductivity, limiting dendrite growth and improving electrochemical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If PEO-based electrolytes are used to ensure lithium ion conductivity, then ion conductivity is improved, but mechanical strength deteriorates at elevated temperatures
Solution Approach 1:
The patent employs a triblock copolymer composite structure comprising PEO blocks for ion conduction and PSTFSILi blocks for mechanical reinforcement. This composite material approach allows simultaneous achievement of high ion conductivity and mechanical strength at operating temperatures, resolving the fundamental trade-off between these two properties in single-component PEO electrolytes
Solution Approach 2:
The patent modifies the chemical structure parameters of the electrolyte by introducing cross-linkable functional groups (acrylate or methacrylate) on the PSTFSILi blocks and utilizing specific block length ratios. These parameter changes enable post-synthesis cross-linking that enhances mechanical properties while preserving ion conductivity pathways through the PEO segments
2Reliability
If plasticizers are added to improve ion conductivity of PEO, then ion conductivity is improved, but mechanical properties deteriorate
Solution Approach 1:
Instead of adding external plasticizers that compromise mechanical integrity, the patent incorporates plasticizing functionality directly into the copolymer structure through the PSTFSILi blocks. The flexible alkyl chains and polar sulfonyl groups within the copolymer itself provide plasticizing effects, maintaining high ion conductivity without sacrificing mechanical strength
Solution Approach 2:
The PSTFSILi blocks act as an intermediary component that mediates between the conflicting requirements of ion conductivity and mechanical strength. These blocks contain both plasticizing moieties (for conductivity) and cross-linkable groups (for mechanical reinforcement), serving as a bridge that reconciles the opposing properties
3Strength
If cross-linking is introduced to enhance mechanical strength, then mechanical strength is improved, but ion conductivity may be reduced due to restricted polymer chain mobility
Solution Approach 1:
The patent segments the copolymer into distinct PEO and PSTFSILi blocks, with cross-linking localized primarily in the PSTFSILi regions. This segmentation ensures that cross-links reinforce the mechanical framework without blocking the ion conduction pathways within the PEO blocks, maintaining high ion conductivity while achieving enhanced mechanical strength
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 cross-linked copolymer achieves high cation transport number, excellent ion conductivity, and mechanical strength, enabling safe and efficient operation of lithium metal polymer batteries at reduced temperatures, with improved power performance and reduced dendrite formation.
Implementation Method 1
Ion conductivity is ensured by the dissolution of the lithium salt in the PEO... the fraction of the charge carried by the lithium ions (also called cation transport number) is low... the cross-linked copolymer achieves high cation transport number, excellent ion conductivity
Implementation Method 2
a cross-linked copolymer comprising at least repeating units of poly(alkylene oxide) and at least repeating units of lithium polystyrene-sulfonyl(trifluoromethylsulfonyl)imide (PSTFSILi)... PEO does not have a sufficient mechanical strength at the temperatures usually implemented in an LMP battery (60-80° C.), since it becomes a viscous liquid and loses its dimensional stability at these temperatures
Implementation Method 3
limiting dendrite growth and improving electrochemical performance... improved power performance and reduced dendrite formation
Data Source
AI summary
A cross-linked copolymer is provided, including at least repeating units of poly(alkylene oxide) and at least repeating units of lithium polystyrene-sulfonyl(trifluoromethylsulfonyl)imide (PSTFSILi), as well as the use of such a cross-linked copolymer for preparing a solid polymer electrolyte, a solid polymer electrolyte having the cross-linked copolymer, and a battery, for example a lithium metal polymer (LMP) battery, including the solid polymer electrolyte.