Tri-Block Battery Polymers for Cathode Adhesion and Volume Change
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Solution Overview
Problem
Existing rechargeable lithium-ion batteries face challenges in maintaining physical particle-particle contact of solid components without applying impractical pressures due to volume changes in cathode materials, leading to battery performance deterioration, and current polymers lack the necessary elasticity and adhesion to inorganic electrode materials.
Innovation Solution
Development of a tri-block copolymer with a polycarbonate and polyether structure, prepared via ring-opening copolymerization, which provides enhanced elasticity and adhesion, suitable for use in electrolytes and cathodes, accommodating volume changes and maintaining mechanical integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If elastomers such as styrenic block copolymers (SBS and SEBS) are used to improve capacity retention, then elasticity and adhesion are enhanced, but poor attachment to inorganic electrode materials occurs due to low polarity
Solution Approach 1:
The patent uses a block copolymer composite structure combining poly(ethylene oxide) blocks (providing polarity and adhesion to inorganic electrodes) with polybutadiene blocks (providing elasticity and mechanical flexibility). This composite approach allows the material to simultaneously achieve strong attachment to electrode materials and accommodate volume changes during cycling.
2Use of energy by moving object
If poly(ethylene oxide) (PEO) is used as polymer electrolyte, then ion transport is facilitated by high chain flexibility, but semi-crystalline nature limits room-temperature ionic conductivity and mechanical properties
Solution Approach 1:
The patent creates local amorphous regions within the block copolymer structure where ion transport occurs. The polybutadiene blocks form amorphous domains that prevent crystallization of the PEO segments, creating localized regions with high ionic conductivity while maintaining overall material stability. This local quality approach allows ion transport without the limitations of bulk semi-crystalline structure.
3Use of energy by moving object
If higher-voltage cathode materials (>3.5V) are used to enhance battery capacities, then energy density is improved, but safety requirements become stricter
Solution Approach 1:
The patent employs the block copolymer as an intermediary protective layer between the high-voltage cathode material and the electrolyte. The poly(ethylene oxide) blocks provide chemical stability and compatibility with high-voltage materials, while the polybutadiene blocks provide mechanical flexibility to accommodate volume changes. This intermediary structure enables safe operation at higher voltages by preventing direct harmful interactions.
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 tri-block copolymer enhances battery safety and performance by maintaining mechanical integrity and adhesion, allowing for higher energy densities and improved cycle stability through phase-separated domains that accommodate volume changes without requiring high pressures.
Implementation Method 1
ion transport by hopping between oxygen sites being facilitated by the high chain flexibility of PEO related with its low glass transition (Tg ̃-64° C.)
Implementation Method 2
growing a polycarbonate on both ends of the polyether by ring-opening copolymerisation of: (i) an epoxide or an oxetane, and (ii) carbon dioxide
Data Source
AI summary
New block polymers are described, as well as processes for preparing them using a ring-opening copolymerisation technique. Also described are electrolytes, cathodes and batteries comprising the polymers.