Polymer Electrolyte Block Copolymer Ionic Conductivity
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Solution Overview
Problem
Lithium polymer batteries face challenges with low ionic conductivity and mechanical strength, limiting their suitability for commercialization due to the semi-crystalline structure of polyethylene oxide, which hinders ion movement and results in degraded energy characteristics.
Innovation Solution
A polymer electrolyte comprising a lithium salt and a specific polymer structure (represented by Formula 1) with a weight ratio of lithium salt to unit A in the range of 1:1 to 1:9, along with an oxygen inhibitor, to enhance ionic conductivity and mechanical strength, improving electrochemical stability at high voltage and temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polyethylene oxide is used as the polymer electrolyte, then the battery structure is simplified and stability is improved, but the ionic conductivity is reduced due to the semi-crystalline structure hindering ion movement
Solution Approach 1:
The patent uses a block copolymer composed of polyethylene oxide blocks and polypropylene carbonate blocks. The polyethylene oxide blocks provide lithium ion conduction pathways while the polypropylene carbonate blocks provide amorphous regions that prevent crystallization. This composite structure combines the advantages of both materials to achieve high ionic conductivity while maintaining stability.
Solution Approach 2:
The patent changes the molecular structure parameters of the polymer by creating a block copolymer with specific block lengths and compositions. By controlling the degree of polymerization and block ratio, the patent optimizes the balance between crystalline regions (for stability) and amorphous regions (for ionic conductivity), resolving the contradiction between these two properties.
2Quantity of substance
If the polymer electrolyte is designed for high ionic conductivity, then energy characteristics are improved, but mechanical strength is reduced
Solution Approach 1:
The block copolymer structure creates a composite morphology where polyethylene oxide blocks form conductive channels and polypropylene carbonate blocks form mechanically strong amorphous matrix. This composite structure simultaneously provides high ionic conductivity and adequate mechanical strength.
Solution Approach 2:
The patent applies local quality by creating distinct regions within the polymer: crystalline polyethylene oxide regions for ionic conduction and amorphous polypropylene carbonate regions for mechanical support. Each region performs its specific function, achieving both high ionic conductivity and mechanical strength through spatial differentiation of properties.
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 polymer electrolyte achieves excellent ionic conductivity and mechanical strength, enabling improved electrochemical stability and performance in lithium secondary batteries, overcoming the limitations of existing polymer electrolytes.
Implementation Method 1
the polymer electrolyte has less ionic conductivity than the liquid electrolyte
Data Source
AI summary
The present invention relates to a polymer electrolyte for a secondary battery and a lithium secondary battery including the same, and to a polymer electrolyte for a secondary battery, which includes unit A derived from a poly(ethylene oxide)-based polymer, and a lithium secondary battery including the same.