Li-Ion Electrolyte Composition for Heat-Stable Extrusion Processing
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Solution Overview
Problem
Commercial lithium-ion batteries face challenges with existing lithium salt and solvent components that decompose at elevated temperatures, are volatile, and sensitive to moisture, limiting processing techniques like extrusion and affecting manufacturing costs and throughput.
Innovation Solution
Development of a lithium-ion battery electrolyte composition comprising specific lithium salts, co-salts, additives, and solvents that are stable at high temperatures, passivate graphite, and maintain ionic conductivity, allowing for processing techniques like extrusion, with a composition of 5-35 wt % lithium salt, 2-10 wt % additive, and 55-93 wt % solvent, including lithium 2-trifluoromethyl-4,5-dicyanoimidazolide, lithium difluoro(oxalato)borate, and γ-butyrolactone.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If LiPF6 and linear carbonates (DEC/DMC/EMC) are used as electrolyte components, then ionic conductivity is achieved, but thermal decomposition and volatility occur at elevated temperatures
Solution Approach 1:
The patent changes the chemical composition parameters of the electrolyte by replacing LiPF6 with alternative lithium salts (LiBF4, LiDFB, LiBOB, LiTFSI, LiFSI) and modifying the solvent system to include cyclic carbonates (EC, PC) and chain carbonates (DMC, DEC, EMC) in specific ratios. This compositional parameter change enables the electrolyte to maintain stability at elevated processing temperatures while preserving ionic conductivity.
Solution Approach 2:
The patent creates a composite electrolyte system by combining multiple lithium salts and various carbonate solvents in specific proportions. This composite approach leverages the complementary properties of different components: cyclic carbonates provide high dielectric constant and ionic conductivity, while chain carbonates provide low viscosity and high thermal stability, achieving both conductivity and temperature resistance.
2Reliability
If LiPF6 is used as lithium salt source, then sufficient ionic conductivity is achieved, but moisture sensitivity and HF release occur
Solution Approach 1:
The patent extracts LiPF6 from the electrolyte composition and replaces it with alternative lithium salts that do not exhibit moisture sensitivity or HF release. Specifically, salts such as LiBF4, LiDFB, LiBOB, LiTFSI, and LiFSI are used, which are inherently more stable in the presence of moisture, thereby eliminating the harmful effects associated with LiPF6 while maintaining ionic conductivity.
Solution Approach 2:
The patent converts the limitation of alternative lithium salts (potentially lower conductivity compared to LiPF6) into a benefit by optimizing the solvent composition and ratios. The combined use of cyclic and chain carbonates in specific proportions compensates for any conductivity loss, while simultaneously providing the beneficial property of moisture stability and safety.
3Productivity
If elevated temperature processing (extrusion, hot rolling, hot pressing) is implemented, then manufacturing throughput and cost are improved, but thermal decomposition of electrolyte components occurs
Solution Approach 1:
The patent performs preliminary action by pre-stabilizing the electrolyte composition through careful selection and proportioning of thermal-stable components before the extrusion or hot pressing process. The electrolyte is formulated with salts and solvents that are inherently resistant to thermal decomposition, ensuring that when elevated temperature processing is applied, the composition remains stable and does not decompose, thereby enabling high-throughput manufacturing.
4Quantity of substance
If graphite is used as anode material, then capacity and performance are improved, but passivation issues occur with conventional electrolytes
Solution Approach 1:
The patent introduces an intermediary mechanism through the specific electrolyte composition that mediates the interaction between lithium ions and graphite anode. The combination of cyclic and chain carbonates, along with alternative lithium salts, creates a stable solid electrolyte interface (SEI) on the graphite surface that prevents further decomposition reactions while allowing lithium ion insertion and extraction, thereby enabling high capacity and long-term stability.
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 composition is stable at elevated temperatures, has low volatility, and provides sufficient ionic conductivity and rate performance, enabling the use of elevated temperature processing techniques while avoiding the limitations of LiPF6, such as thermal runaway and moisture sensitivity.
Implementation Method 1
have sufficient ionic conductivity
Implementation Method 2
cannot be processed at elevated temperatures due to thermal decomposition and/or their volatility
Implementation Method 3
cannot be processed at elevated temperatures due to thermal decomposition and/or their volatility
Data Source
AI summary
An electrolyte composition for a lithium ion battery. The composition including: (a) 5-35 wt % of lithium salt; (b) 2-10 wt % of additive; and (c) 55-93 wt % solvent. The lithium salt includes: (ai) a salt selected from lithium 2-trifluoromethyl-4,5-dicyanoimidazolide, lithium difluoro(oxalato)borate, lithium bis(oxalato) borate and lithium tetrafluroborate; (aii) and optionally, a co-salt selected from lithium bis(trifluoromethanesulfonyl)imide and/or lithium bis(fluorosulfonyl)imide. The molar ratio of the salt to co-salt is between 100:0 and 5:95. The composition does not include lithium bis(fluorosulfonyl)imide alongside lithium difluoro(oxalato)borate or lithium tetrafluroborate. The additive includes vinylene carbonate and optionally, fluoroethylene carbonate. The solvent includes either (ci) ethylene carbonate and 10-30 mol % propylene carbonate, or (cii) γ-butyrolactone and optionally ethylene carbonate.