Fluorine-Substituted Polymer Electrolyte for Lithium Battery Conductivity
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Solution Overview
Problem
Current polymer electrolytes for lithium secondary batteries have low ionic conductivity and limited electrochemical stability, which affects their performance and safety, especially at high temperatures and high voltages.
Innovation Solution
A polymer electrolyte comprising a copolymer with a fluorine-substituted or unsubstituted polyalkylene ether repeating unit, combined with a ceramic electrolyte and inorganic particles, to enhance ionic conductivity and electrochemical stability, while reducing interfacial resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a polymer electrolyte with polyethylene oxide or polyether is used, then the electrolyte provides ion dissociation ability, but it has low ionic conductivity at room temperature and low temperature
Solution Approach 1:
The patent modifies the chemical structure of the polymer electrolyte by introducing fluorine-substituted alkylene groups at specific positions in the repeating unit. This structural parameter change enhances the ionic conductivity while maintaining the ion dissociation ability, achieving a conductivity of 2.0×10^-4 S/cm or more at 25°C.
Solution Approach 2:
The patent creates a composite polymer electrolyte system that combines fluorine-substituted polyalkylene ether with ceramic electrolytes and inorganic particles. This composite structure synergistically improves ionic conductivity and electrochemical stability, resolving the contradiction between ion dissociation and conductivity.
2Reliability
If a polymer electrolyte with polyethylene oxide or polyether is used, then the electrolyte provides ion dissociation ability, but it has an oxidation stability of 4.0 V or less
Solution Approach 1:
The patent introduces fluorine atoms at specific positions (R1 and R2) in the polymer repeating unit, which fundamentally changes the electrochemical stability parameters. The fluorine substitution raises the oxidation stability above 4.0 V, enabling the electrolyte to withstand higher voltage conditions while maintaining ion dissociation capability.
Solution Approach 2:
The fluorine-substituted alkylene groups act as intermediary structures that mediate between the ion dissociation function and oxidation stability requirement. The specific positioning of fluorine atoms (with constraints on m1, n1, o1 values) creates an optimal balance, allowing the polymer to simultaneously achieve good ion transport and high voltage stability.
3Object-generated harmful factors
If the polymer electrolyte is composited with other conductive materials, then the ionic conductivity is improved, but lithium ion transfer numbers are different to cause non-uniform ion transport on the surface of the electrode
Solution Approach 1:
The patent achieves uniform ion transport by strategically placing fluorine atoms at specific local positions (R1 and R2) within the polymer chain structure. This local structural optimization ensures that the entire electrolyte surface maintains consistent ion transfer properties, preventing non-uniform transport while achieving high conductivity of 2.0×10^-4 S/cm or more.
4Object-generated harmful factors
If a liquid electrolyte is used, then the ionic conductivity is high, but the electrolyte is at high risk of leakage, fire, and explosion
Solution Approach 1:
The patent employs a solid polymer electrolyte structure that inherently eliminates the safety risks associated with liquid electrolytes (leakage, fire, explosion) while achieving comparable ionic conductivity through fluorine substitution. The solid structure provides intrinsic safety without sacrificing performance.
Solution Approach 2:
The patent creates a composite system combining fluorine-substituted polymer electrolyte with ceramic and inorganic components, achieving a material that has both the high ionic conductivity needed for performance and the solid-state safety features that eliminate leakage and fire risks.
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 solution achieves high ionic conductivity and improved electrochemical stability, leading to enhanced performance and safety of lithium secondary batteries, with ionic conductivity exceeding 2.0×10^-4 S/cm at 25°C and improved cycle life characteristics.
Implementation Method 1
a copolymer comprising a fluorine-substituted or unsubstituted polyalkylene ether repeating unit... a lithium salt; and a copolymer... wherein the copolymer includes a fluorine-substituted or unsubstituted polyalkylene ether repeating unit
Implementation Method 2
ionic conductivity exceeding 2.0×10^-4 S/cm at 25°C... improved ionic conductivity... low ionic conductivity at room temperature and low temperature
Implementation Method 3
electrochemical stability... improved cycle life characteristics... positive electrode and a negative electrode, which include electrode active materials capable of intercalating/deintercalating lithium ions
Data Source
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AI summary
The present invention relates to a polymer electrolyte, which includes a lithium salt and a copolymer including a fluorine-substituted or unsubstituted polyalkylene ether repeating unit, and a lithium secondary battery including the same.