Block Copolymer Electrolytes for High-Temperature Lithium Battery Stability
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Solution Overview
Problem
Current block copolymer electrolytes face challenges in providing sufficient physical resistance to lithium intrusion and maintaining high ionic conductivity, especially at elevated temperatures, due to limitations in the thermomechanical properties of the 'hard' block polymers like polystyrene, which are often expensive and difficult to process.
Innovation Solution
Development of a nanostructured electrolyte material with ionically-conductive domains made of polyethylene oxide and structural domains composed of cross-linked polystyrene and hydrogenated polystyrene, which are covalently bonded to form block copolymers, enhancing mechanical strength and ionic conductivity while allowing operation at higher temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If polystyrene is used as the hard block in block copolymer electrolytes, then good physical resiliency and high glass transition temperature are achieved, but the modulus and resistance to lithium intrusion are insufficient at elevated temperatures
Solution Approach 1:
The patent combines polystyrene with poly(2,6-dimethyl-1,4-phenylene oxide) (PXE) to create a composite hard block material. PXE has a higher glass transition temperature (∼200°C) than polystyrene (∼100°C), and the composite provides superior high-temperature mechanical properties and modulus while maintaining processability. This composite approach resolves the contradiction by achieving both adequate strength and extended temperature range.
Solution Approach 2:
The patent modifies the chemical composition and molecular structure parameters of the hard block by incorporating aromatic ether linkages in PXE, which increase the glass transition temperature and thermal stability. This parameter change enables the electrolyte to maintain its modulus and physical resistance at higher operating temperatures.
2Strength
If crosslinking is applied to the hard block polymer, then physical properties and resistance to lithium intrusion are improved, but processing difficulty and risk of premature crosslinking increase
Solution Approach 1:
The patent incorporates crosslinkable functional groups (such as epoxide, oxetane, or vinyl groups) into the hard block polymer structure during synthesis, but the actual crosslinking reaction is postponed until after electrolyte fabrication. This preliminary preparation allows easy processing of the uncrosslinked polymer, then enables controlled crosslinking later to achieve the desired physical resistance without premature gelation.
Solution Approach 2:
The patent separates the crosslinking function from the main polymer chain by using pendant functional groups that can undergo crosslinking reactions. This extraction allows the polymer to be processed in its uncrosslinked state and then crosslinked in situ or during a separate step, avoiding processing difficulties associated with pre-crosslinked materials.
3Temperature
If engineering thermoplastics with better high-temperature properties are used as the hard block, then high-temperature performance is improved, but cost increases and processability decreases
Solution Approach 1:
The patent modifies the chemical structure of the hard block by incorporating aromatic ether linkages and adjusting molecular weight and composition to achieve high glass transition temperature (above 100°C) while maintaining compatibility with polyethylene oxide and processability. This parameter optimization provides high-temperature performance comparable to expensive engineering thermoplastics but with better manufacturability.
Solution Approach 2:
The patent introduces specific functional groups (crosslinkable groups such as epoxide, oxetane, or vinyl) at localized positions on the polymer chain rather than throughout the entire structure. This local modification provides high-temperature stability and crosslinking capability while maintaining the bulk polymer's processability and compatibility with the soft block.
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 proposed electrolyte material achieves a modulus greater than 1×107 Pa at 80° C and ionic conductivity of 10−4 Scm−1 at 25° C, providing improved resistance to lithium intrusion and enabling higher temperature operation with increased reliability and durability in lithium batteries.
Implementation Method 1
The first phase forms an ionically-conductive domain in the electrolyte material
Implementation Method 2
At least some of the first polymers are covalently bonded to at least some of the second polymers to form first block copolymers
Implementation Method 3
The second phase may be cross-linked
Data Source
AI summary
Polymer electrolytes incorporating PS-PEO block copolymers, PXE additives, and lithium salts provide improved physical properties relative to PS-PEO block copolymers and lithium salt alone, and thus provide improved battery performance.