Lithium-Ion Battery Electrolyte With Ionic Liquid for Temperature Stability
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Solution Overview
Problem
Lithium-ion batteries face degradation in high and low-temperature atmospheres due to volatility of organic solvents and increased resistance at the electrode interface, leading to performance degradation.
Innovation Solution
A lithium secondary battery design incorporating a positive electrode with a lithium transition metal oxide and a non-aqueous electrolyte solution containing a phosphonium salt-based ionic liquid additive, forming a stable film with low resistance and high flame retardancy to prevent degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a liquid electrolyte solution with organic solvent is used, then the battery can operate with good ionic conductivity, but the organic solvent has high volatility at high temperature, generates gas through side reactions, and shows low stability due to combustion
Solution Approach 1:
The patent changes the chemical composition parameters of the electrolyte by introducing ionic liquids with specific molecular structures ( Formula 2 with R as alkylene group having 1-5 carbon atoms and n as integer 0-3). This parameter change transforms the electrolyte from conventional organic solvent-based to ionic liquid-based, fundamentally altering its thermal stability and combustion resistance while maintaining ionic conductivity.
Solution Approach 2:
The patent creates a composite electrolyte system by combining ionic liquids with lithium salts and non-aqueous organic solvents in specific proportions. This composite approach leverages the thermal stability of ionic liquids while maintaining the solvation能力和ionic conductivity provided by the organic solvent components, achieving a balance between stability and performance.
2Reliability
If conventional electrolyte solutions are used, then the battery can function normally, but resistance at the electrode interface increases in low-temperature atmosphere, degrading overall performance
Solution Approach 1:
The patent modifies the electrolyte composition parameters by incorporating ionic liquids with specific structural parameters (R group length and n value in Formula 2). These parameter changes affect the viscosity, freezing point, and interfacial properties of the electrolyte, enabling it to maintain low resistance at low temperatures while preserving high-temperature stability.
3Use of energy by moving object
If high nickel content lithium transition metal oxide is used in positive electrode, then energy density is improved, but stability deteriorates at high temperature
Solution Approach 1:
The patent introduces ionic liquids as an intermediary substance between the high-nickel cathode material and the electrolyte. The ionic liquid forms a stable interfacial layer that mediates the interaction between the high-nickel cathode and conventional electrolytes, preventing direct harmful reactions and improving thermal stability while allowing the high energy density of nickel-rich materials to be realized.
Solution Approach 2:
The patent changes the chemical composition parameters of the electrolyte system by incorporating ionic liquids, which fundamentally alters the interfacial chemistry between the electrolyte and high-nickel cathode. This parameter change enables the system to tolerate higher nickel content by providing a more stable chemical environment at the electrode-electrolyte interface.
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 design achieves improved high-temperature storage characteristics and low-temperature performance by suppressing gas generation and resistance, enhancing overall battery stability and safety.
Implementation Method 1
a stable film with low resistance and high flame retardancy may be formed on a surface of the electrode
Implementation Method 2
a large amount of gas is generated by a side reaction with the electrode
Implementation Method 3
a non-aqueous electrolyte solution that becomes a medium for transferring lithium ions
Data Source
AI summary
The present invention provides a lithium secondary exhibiting battery excellent high-temperature storage characteristics and low-temperature storage characteristics. Specifically, the lithium secondary battery of the present invention includes a positive electrode including a lithium transition metal oxide of Formula 1 as a positive electrode active material; a negative electrode including a negative electrode active material; a separator disposed between the positive electrode and the negative electrode; and a non-aqueous electrolyte solution containing a lithium salt, a non-aqueous organic solvent, and an additive, wherein the additive may include an ionic liquid represented by Formula 2.