Lithium Battery Electrolyte Composition for Viscosity-Safety Balance
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Solution Overview
Problem
Lithium secondary batteries face challenges in maintaining ionic conductivity while improving output and high-temperature safety using high-concentration lithium salts, as increased viscosity reduces ion mobility and poses safety risks.
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 control surface tension and enhance ionic conductivity and high-temperature safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high-concentration lithium salt is used in the electrolyte, then output characteristics and high-temperature safety are improved, but viscosity increases and ionic conductivity decreases
Solution Approach 1:
The patent changes the concentration parameter of lithium salt from conventional low concentrations (1.3-2.0 M) to high concentrations (2.5-5.0 M, preferably 3.0-4.5 M). This parameter change increases the amount of lithium ions available for transport, improving output characteristics and high-temperature safety by reducing free solvent that could participate in exothermic reactions.
Solution Approach 2:
The patent uses a composite electrolyte system combining high-concentration lithium salt with specific oligomer mixtures (containing fluorinated units and carbonate units) and organic solvents. This composite approach balances the high viscosity from high salt concentration with the low-viscosity properties of the organic solvent and the structural benefits of oligomers, maintaining ionic conductivity while achieving improved safety and output characteristics.
2Productivity
If high-concentration lithium salt is used to improve output characteristics, then lithium ion yield increases, but viscosity increases reducing ion mobility
Solution Approach 1:
The patent optimizes the lithium salt concentration parameter to a specific high-concentration range (2.5-5.0 M, preferably 3.0-4.5 M) rather than simply maximizing concentration. This optimized parameter range ensures sufficient lithium ion yield for high productivity while controlling viscosity to maintain acceptable ion mobility for the battery application.
Solution Approach 2:
The organic solvent acts as an intermediary that mediates between the high-concentration lithium salt and the ionic conductivity requirement. The organic solvent molecules solvate the lithium ions and facilitate their movement through the high-viscosity electrolyte medium, maintaining ion mobility despite the high salt concentration that provides high lithium ion yield.
3Object-affected harmful factors
If high-concentration lithium salt is used, then amount of free solvent is reduced improving safety, but viscosity increases
Solution Approach 1:
The patent changes the solvent-to-salt ratio parameter by using high-concentration lithium salt (2.5-5.0 M), which reduces the amount of free solvent available to participate in exothermic reactions with oxygen radicals. This parameter change improves safety by limiting the fuel for potential thermal runaway while the selected organic solvent maintains ionic 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 effectively maintains high ionic conductivity and improves initial capacity and high-temperature safety by controlling surface tension and suppressing exothermic reactions, while maintaining mobility of lithium ions.
Implementation Method 1
a method of improving the output characteristics of the battery by increasing a lithium ion yield (Li +
Implementation Method 2
the oxygen radicals may react with the free solvent, which does not bind with the lithium ions, to cause an exothermic reaction
Implementation Method 3
since mobility of ions in the electrolyte is inversely proportional to the viscosity of the electrolyte based on Stokes' law
Data Source
AI summary
The present invention provides an electrolyte for a lithium secondary battery which includes a lithium salt having a concentration of 1.6 M to 5 M, an oligomer mixture which includes 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.