Solid Polymer Electrolyte for Lithium Ion Battery
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Solution Overview
Problem
Current solid polymer electrolytes for lithium ion batteries face challenges in achieving high ionic conductivities and mechanical stability, with previous attempts resulting in materials with poor mechanical properties and minimal conductivity improvements.
Innovation Solution
A composition comprising polyoctahedral silsesquioxane-phenyl7(BF3Li)3 and high molecular weight poly(ethylene oxide) is self-assembled to form a solid polymer electrolyte with a two-phase morphology, where Si—O—BF3Li groups dissociate into Si—O—BF3− ions and Li+ ions are solvated by PEO, creating physical cross-links that enhance mechanical stability and ionic conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If plasticizers and nanoparticle fillers are added to PEO electrolytes to improve conductivity, then ionic conductivity is improved, but mechanical properties deteriorate
Solution Approach 1:
The patent uses a composite material system consisting of PEO polymer matrix combined with specific lithium salts (LiClO4, LiBF4, LiPF6) to create a solid polymer electrolyte that achieves both high ionic conductivity (4×10−4 S/cm) and good mechanical stability. The composite structure allows the polymer to provide mechanical integrity while the lithium salt complexes provide ionic conduction pathways.
Solution Approach 2:
The patent optimizes the molecular weight of PEO (using high molecular weight PEO with Mn ≥ 100,000) and controls the salt-to-polymer ratio to achieve the optimal balance between mechanical strength and ionic conductivity. By changing the molecular weight parameter and compositional ratios, the patent resolves the contradiction between conductivity and mechanical properties.
2Object-affected harmful factors
If PEO is used as solid polymer electrolyte to ensure safety and flexibility, then safety issues are eliminated, but ambient temperature ionic conductivities are lower than liquid or gel electrolytes
Solution Approach 1:
The patent uses high molecular weight PEO (Mn ≥ 100,000) and optimizes the salt-to-polymer ratio to achieve ambient temperature ionic conductivity of 4×10−4 S/cm, which is significantly higher than conventional solid polymer electrolytes. The specific composition and molecular weight parameters are tuned to maximize conductivity while maintaining the safety advantages of solid polymer electrolytes.
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 resulting solid polymer electrolyte exhibits high ambient temperature ionic conductivity (~4×10−4 S/cm) and high lithium ion transference number (0.6), with excellent interfacial stability and electrochemical stability window of 4.6 V, making it suitable for lithium battery applications.
Implementation Method 1
Si—O—BF3Li groups dissociate into Si—O—BF3− ions and Li+ ions
Implementation Method 2
Li+ ions are solvated by PEO
Implementation Method 3
A composition comprising polyoctahedral silsesquioxane-phenyl7(BF3Li)3 and at least one poly(ethylene oxide) is self-assembled to form a solid polymer electrolyte with a two-phase morphology
Data Source
AI summary
A composition suitable as a solid polymer electrolyte for a lithium ion battery comprises a mixture of polyoctahedral silsesquioxane-phenyl7(BF3Li)3 and a poly(ethylene oxide).