Lithium Metal Battery Electrolyte Composition for Cyclability
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Solution Overview
Problem
Current lithium-ion battery electrolytes face challenges in achieving high performance while maintaining cost-effectiveness, with existing electrolytes often being costly, having limited cyclability, and presenting thermostability issues.
Innovation Solution
The use of a liquid electrolyte system comprising two or more lithium salts, such as lithium bis(fluorosulfonyl)imide and lithium perchlorate, dissolved in a solvent mixture of fluoroethylene carbonate and ethylmethylcarbonate, with a specific volumetric ratio, and optionally including additional lithium salts, to enhance conductivity and cyclability, along with a solid electrolyte interface layer and surface-modified separators to improve capacity retention and reduce capacity fade.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high concentration lithium bis(fluorosulfonyl)imide (LIFSI) electrolyte is used, then cyclability and shelf life are improved, but conductivity and wettability are reduced
Solution Approach 1:
The patent changes the concentration parameter of LIFSI from high (4M) to low (0.1M-0.9M), and combines it with lithium perchlorate to achieve both improved cyclability and maintained conductivity through parameter optimization
Solution Approach 2:
The patent creates a composite electrolyte system by combining lithium bis(fluorosulfonyl)imide and lithium perchlorate in a mixed salt configuration, where each salt contributes different properties to achieve synergistic performance in cyclability, conductivity, and wettability
2Reliability
If fluorinated ether co-solvents are added to improve conductivity, then cyclability is improved, but flash point is reduced causing thermostability issues
Solution Approach 1:
The patent extracts and removes fluorinated ether co-solvents from the electrolyte system, replacing them with alternative solvents that do not compromise thermostability while maintaining improved cyclability characteristics
Solution Approach 2:
The patent replaces expensive and thermostability-compromising fluorinated ether co-solvents with more stable, cost-effective solvent alternatives that provide sufficient cyclability improvement without the thermal hazards
3Loss of energy
If lithium hexafluorophosphate with fluoroethylene carbonate and ethylmethylcarbonate is used, then conductivity and wettability are improved, but capacity retention is limited
Solution Approach 1:
The patent creates a composite electrolyte combining lithium bis(fluorosulfonyl)imide and lithium perchlorate with optimized solvent composition, where the mixed salt system provides both high conductivity and superior capacity retention through complementary mechanisms
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
This configuration improves the cycle life and reduces capacity fade of lithium-ion batteries, achieving better performance and cost-effectiveness by optimizing the electrolyte composition and separator modifications.
Implementation Method 1
The electrolyte is suitable for conducting lithium ions between the electrodes
Implementation Method 2
Liquid electrolytes may include one or more lithium salts dissolved in an organic solvent or a mixture of organic solvents
Data Source
AI summary
The present disclosure relates to electrolyte systems and/or separators for electrochemical cells that cycle lithium ions and which may have lithium metal electrodes. The electrochemical cell includes a liquid electrolyte system that fills voids and pores within the electrochemical cell. The electrolyte system includes two or more lithium salts and two or more solvents. The two or more lithium salts include bis(fluorosulfonyl)imide (LiN(FSO2)2) (LIFSI) and lithium perchlorate (LiClO4). The two or more solvents include a first solvent and a second solvent. The first solvent may be a fluorinated cyclic carbonate. The second solvent may be a linear carbonate. A volumetric ratio of the first solvent to the second solvent may be 1:4. The electrochemical cell may include a surface-modified separator that has one or more coatings or fillers.