Gel Polymer Electrolyte for High-Salt Li-Ion Conductivity
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Solution Overview
Problem
Lithium secondary batteries face challenges in maintaining ionic conductivity and mechanical strength while improving output characteristics and high-temperature safety, particularly when using high-concentration lithium salts that increase viscosity and reduce ion mobility.
Innovation Solution
An electrolyte composition for lithium secondary batteries is developed, incorporating a lithium salt concentration of 1.6 M to 5 M, an oligomer mixture with specific units, and an organic solvent, along with a halogenated benzene compound, to enhance lithium ion dissociation, mechanical strength, and thermal safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high-concentration lithium salt is used to improve output characteristics and high-temperature safety, then lithium ion dissociation and safety are improved, but viscosity increases and ionic conductivity decreases
Solution Approach 1:
The patent uses a composite electrolyte system combining lithium salt, siloxane-based oligomer, and polyalkylene carbonate-based oligomer. This composite approach allows the system to achieve both high lithium salt concentration for safety and low viscosity for conductivity through synergistic interactions between components.
Solution Approach 2:
The patent optimizes specific parameters including lithium salt concentration (1.3-4.0 M), siloxane oligomer content (5-50 wt%), and polyalkylene carbonate oligomer content (5-50 wt%). By precisely controlling these parameters, the electrolyte achieves the optimal balance between safety and conductivity.
2Productivity
If high-concentration lithium salt is used to improve output characteristics, then lithium ion yield increases, but ionic conductivity decreases due to increased viscosity
Solution Approach 1:
The siloxane-based oligomer acts as an intermediary component that facilitates lithium ion transport. Its molecular structure with oxygen atoms provides coordination sites for lithium ions, enabling efficient ion conduction even at high lithium salt concentrations where viscosity would normally hinder conductivity.
Solution Approach 2:
The patent adjusts the lithium salt concentration to an optimal range (1.3-4.0 M) rather than using maximum concentration, and combines it with specific ratios of oligomers. This parameter optimization ensures high lithium ion yield while maintaining adequate ionic conductivity.
3Strength
If gel polymer electrolyte is used to improve mechanical strength, then safety is maintained, but ionic conductivity may be compromised
Solution Approach 1:
The electrolyte forms a gel polymer composite by combining lithium salt with siloxane-based oligomer and polyalkylene carbonate-based oligomer. This composite structure provides both mechanical strength from the polymer network and ionic conductivity through the oligomer channels that facilitate lithium ion transport.
Solution Approach 2:
The gel polymer electrolyte exhibits different properties in different regions: the polymer network provides mechanical strength and structural integrity, while the oligomer-rich regions provide ionic conduction pathways. This local differentiation allows simultaneous achievement of strength and conductivity.
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 electrolyte composition improves the battery's output characteristics, capacity retention, and high-temperature safety by maintaining ionic conductivity and mechanical strength, while the oligomer mixture and halogenated benzene compound contribute to better wetting and interfacial properties, respectively.
Implementation Method 1
a degree of dissociation of the lithium ions using an electrolyte containing a high-concentration lithium salt
Implementation Method 2
viscosity of the electrolyte is increased. In this case, since mobility of ions in the electrolyte is inversely proportional to the viscosity of the electrolyte based on Stokes' law
Implementation Method 3
the oxygen radicals generated in this case have very high reactivity, the oxygen radicals may react with the free solvent, which does not bind with the lithium ions, to cause an exothermic reaction
Data Source
AI summary
An electrolyte for a lithium secondary battery is disclosed herein. In some embodiments, an electrolyte includes a lithium salt present in a concentration of 1.6 M to 5 M, an oligomer mixture including a first oligomer containing a unit represented by Formula 1 and a second oligomer containing a unit represented by Formula 2, and an organic solvent.