Lithium Battery Safety with Bis(fluorosulfonyl)imide Ionic Liquid
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Lithium secondary batteries using conventional organic solvents face safety issues due to low flash points, leading to potential fires or explosions, and exhibit poor performance with high internal resistance and low lifetime characteristics when using graphitized carbon electrodes with ionic liquids.
Innovation Solution
A lithium secondary battery design incorporating a nonaqueous electrolytic solution with bis(fluorosulfonyl)imide anions and a lithium-manganese-nickel composite oxide positive electrode, which reduces internal resistance and enhances safety by using a flame-retardant ionic liquid, thereby preventing fires and explosions and improving charge and discharge characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional organic solvents are used as nonaqueous electrolytic solution, then the battery has good charge-discharge characteristics, but the battery has low safety due to low flash point causing fire or explosion
Solution Approach 1:
The patent changes the fundamental parameter of the electrolytic solution from conventional organic solvents to ionic liquids containing bis(fluorosulfonyl)imide anions. This parameter change fundamentally alters the safety characteristics by eliminating flammability while maintaining electrochemical performance, directly resolving the contradiction between safety and harmful factors.
Solution Approach 2:
The patent uses a composite ionic liquid system combining specific cations with bis(fluorosulfonyl)imide anions. This composite material approach creates an electrolytic solution that integrates both safety (nonflammability) and performance (good charge-discharge characteristics) properties that neither component could achieve alone.
2Reliability
If ionic liquid is used as nonaqueous electrolytic solution to improve safety, then the battery has high safety, but the battery has high internal resistance and poor output characteristics
Solution Approach 1:
The patent optimizes parameters of the ionic liquid system including anion selection (bis(fluorosulfonyl)imide), cation types, and their ratios to reduce internal resistance. This parameter optimization enables the ionic liquid-based battery to maintain high safety while improving output characteristics and charge-discharge performance.
Solution Approach 2:
The patent enhances local quality at the electrode-electrolyte interface by optimizing the ionic liquid composition to improve ion transport and reduce interfacial resistance. This localized optimization allows the battery to achieve better output characteristics without compromising the overall safety provided by the ionic liquid medium.
3Reliability
If ionic liquid is used as nonaqueous electrolytic solution, then the battery has high safety, but the battery has low lifetime characteristics due to deposition on electrode surface
Solution Approach 1:
The patent changes parameters of the ionic liquid composition to control deposition behavior on electrode surfaces. By optimizing the chemical composition and physical properties of the ionic liquid, the patent reduces harmful deposition while maintaining the safety advantages, thereby extending battery lifetime.
Solution Approach 2:
The ionic liquid acts as an intermediary between the electrodes and the electrolyte, mediating the interaction to prevent direct harmful contact and deposition. The specific ionic liquid composition serves as a protective intermediary layer that reduces degradation while maintaining safety.
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 battery achieves excellent safety and performance with a fully charged voltage of 4.4 V or more and average discharge voltage of 4.0 V or more, maintaining high energy density and voltage while preventing battery shorting and explosions, and showing improved charge and discharge characteristics in high potential regions.
Implementation Method 1
a nonaqueous electrolytic solution that contains a lithium salt dissolved in an ionic liquid as a supporting electrolyte
Implementation Method 2
polar nonprotonic organic solvents that easily dissolve lithium salts and that do not easily undergo electrolysis
Implementation Method 3
a lithium-manganese-nickel composite oxide positive electrode
Data Source
AI summary
A flame-retardant lithium secondary battery is provided that has better battery performance and higher safety than conventional batteries. The lithium secondary battery uses a positive electrode that includes a positive electrode active material of the general formula (1) below, and a nonaqueous electrolytic solution in which an ionic liquid that contains bis(fluorosulfonyl)imide anions as an anionic component is used as the solvent, LiNixMnyO4 (1). In the formula (1), x and y are values that satisfy the relations x + y = 2, and x:y = 27.5:72.5 to 22.5:77.5.