Ionic Liquid Secondary Battery Electrolyte for Dendrite-Stable Cycling
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Solution Overview
Problem
Post-lithium ion batteries face challenges in achieving both high energy density and durable life performance, with issues such as dendrite formation in metal negative electrodes and redox-decomposition of ionic liquids.
Innovation Solution
A secondary battery design incorporating a negative electrode with lithium metal or alloys, a nonaqueous electrolyte containing an ionic liquid and a specific range of a urea compound, which forms a film with high ion conductivity to suppress redox-decomposition and enhance cycle life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If Li metal is used for the negative electrode to increase energy density, then energy density is improved, but dendrite deposition occurs causing short circuits
Solution Approach 1:
The patent introduces an ionic liquid as an intermediary substance between the Li metal negative electrode and the conventional electrolyte. This ionic liquid forms a protective interface layer that prevents direct contact between Li metal and the electrolyte, thereby suppressing dendrite formation while maintaining high energy density benefits
Solution Approach 2:
The patent changes the physical and chemical parameters of the electrolyte system by incorporating ionic liquid components. This modifies the electrochemical window, viscosity, and interfacial properties to enable stable Li metal operation without dendrite formation, resolving the reliability issue while preserving energy density
2Reliability
If ionic liquid is used as electrolytic solution to improve safety, then safety is improved, but redox-decomposition occurs causing large cycle deterioration
Solution Approach 1:
The patent creates a composite electrolyte system combining ionic liquid with specific additives and co-solvents. This composite structure leverages the safety benefits of ionic liquid while the additional components suppress redox-decomposition reactions, thereby extending cycle life
Solution Approach 2:
The patent converts the potential harm of ionic liquid redox-decomposition into a beneficial protective mechanism. The controlled decomposition products form stable surface films on electrodes that actually protect against further decomposition and improve long-term cycling stability
3Use of energy by moving object
If Mg metal is used for the negative electrode to increase energy density, then energy density is improved, but overvoltage is large making charge and discharge difficult
Solution Approach 1:
The patent modifies the electrolyte composition parameters to match the electrochemical characteristics of Mg metal. By adjusting ionic liquid type, concentration, and additives, the electrolyte's viscosity, conductivity, and electrochemical window are optimized to reduce overvoltage and enable smooth Mg ion insertion/extraction
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 solution enhances the charge-discharge reaction efficiency, improves cycle life and discharge rate performance, and increases energy density while suppressing self-discharge and corrosion.
Implementation Method 1
the ionic liquid is easily redox-decomposed. Therefore, a secondary battery including an ionic liquid as an electrolytic solution has problems of large cycle deterioration
Implementation Method 2
a nonaqueous electrolyte containing an ionic liquid and 0.5 wt % or more and 30 wt % or less of a urea compound
Data Source
AI summary
In general, according to one embodiment, a secondary battery including a positive electrode, a negative electrode, and a nonaqueous electrolyte. The negative electrode includes at least one selected from the group consisting of lithium metal, a lithium alloy, and a compound capable of allowing Li to be inserted and extracted. The nonaqueous electrolyte includes an ionic liquid and 0.5 wt % or more and 30 wt % or less of a urea compound.