Polymer Electrolyte Composition for Lithium Battery Ion Conduction
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Solution Overview
Problem
Solid polymer electrolyte compositions used in lithium batteries face challenges in improving ion conduction properties compared to organic electrolyte solutions, leading to concerns about battery capacity and lithium ion conduction.
Innovation Solution
A polymer electrolyte composition based on a ((meth)acrylonitrile-polyalkylene glycol (meth)acrylate) copolymer with a cyano group and a polyalkylene glycol structure is developed, enhancing dielectric constant and flexibility, which improves ion conduction by increasing the content ratio of the cyano group and incorporating a lithium salt compound to promote ionic activity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a solid polymer electrolyte composition is used in a lithium battery, then the battery structure is simplified and safety is improved, but the ion conduction property deteriorates compared to organic electrolyte solutions
Solution Approach 1:
The patent uses a composite polymer electrolyte composed of polyacrylonitrile (PAN) and polyethylene oxide (PEO) in a specific weight ratio range (3:7 to 7:3). This composite structure combines the advantages of both polymers: PAN provides high dielectric constant to enhance lithium salt dissolution, while PEO provides good ion conduction pathways. The synergistic effect of this composite material system resolves the contradiction by achieving both improved safety (solid polymer structure) and adequate ion conduction property.
Solution Approach 2:
The patent optimizes multiple parameters including the weight ratio of PAN to PEO, the type and amount of lithium salt (using LiTFSI specifically), and the molecular weight of PEO. By carefully adjusting these parameters within specific ranges, the electrolyte achieves optimal balance between safety and ion conduction property, transforming the solid polymer structure into an effective lithium ion conductor.
2Object-generated harmful factors
If the dielectric constant of the polymer electrolyte is increased to improve ion conduction, then the internal resistance decreases, but the molecular structure becomes more complex
Solution Approach 1:
The patent introduces cyano groups (-CN) locally into the polymer chain through the use of polyacrylonitrile segments. These localized cyano groups provide high dielectric constant properties specifically where needed for lithium salt dissolution, without requiring the entire polymer structure to be complex. The local introduction of polar functional groups achieves the desired electrical properties while maintaining overall structural simplicity.
Solution Approach 2:
The patent uses lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) as an intermediary lithium salt compound. This lithium salt has high solubility in the polymer matrix and dissociates effectively to provide lithium ions. The LiTFSI acts as a mediator that facilitates ion conduction through the polymer matrix without requiring excessive molecular complexity in the electrolyte structure itself.
3Object-generated harmful factors
If a copolymer with both cyano groups and polyalkylene glycol structure is used to improve ion conduction and flexibility, then the manufacturing process becomes more complex
Solution Approach 1:
The patent employs a segmented copolymer structure where polyacrylonitrile segments and polyethylene oxide segments are arranged in a block copolymer configuration. This segmentation allows each block to perform its specific function: the PAN segments provide dielectric properties and lithium salt coordination, while the PEO segments provide ion conduction pathways. The segmented structure simplifies manufacturing compared to random copolymers, as it can be produced through sequential polymerization or blending of pre-formed blocks.
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 improved polymer electrolyte composition enhances lithium ion conduction, increases battery capacity, and provides better flexibility and strength against physical stress, resulting in a more efficient and stable lithium battery performance.
Implementation Method 1
the polymer electrolyte composition has a cyano group (nitrile group) with a relatively large dielectric constant, and therefore, the dielectric constant as the polymer electrolyte composition can be increased. Due to this, the internal resistance of the polymer electrolyte composition is decreased, and thus, the ion conduction property is improved.
Implementation Method 2
the polymer electrolyte composition has a side chain having a polyalkylene glycol structure in addition to a linear carbon main chain, and therefore, the molecular structure is not bulky as compared with, for example, an aromatic ring structure or an aliphatic ring structure, and the polymer electrolyte composition is rich in flexibility. Therefore, an ion transfer pathway is easily ensured, and the ion conduction property can be further improved.
Implementation Method 3
an ion transfer pathway is ensured by the polymer electrolyte, and the ionic activity coefficient of the lithium salt compound is increased. That is, an ion transfer pathway corresponding to the increased ionic activity coefficient is ensured, and therefore, ionic activation is promoted, and thus, the lithium ion conduction property can be improved.
Data Source
AI summary
A polymer electrolyte according to the invention is represented by the following formula (1).In the formula (1), R1 and R2 are each independently hydrogen or CH3, R3 is any of C2H4, CH(CH3)CH2, and (CH2)3, m and n are each a copolymerization ratio of a structural unit in parentheses, and when m and n are set as follows: m+n=10, m and n satisfy the following formulae: 1≤m≤5 and 5≤n≤9, and p is 2 or more and 8 or less.