Battery Electrolyte Composition for LiFSI Corrosion and Oxidation Stability
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Solution Overview
Problem
Lithium bis(fluorosulfonyl)imide (LiFSI) decomposition during preparation generates impurities, which corrode the current collector at high voltage, and additives like LiODFB and LiODFP have insufficient oxidation resistance, affecting battery cycle and high-temperature storage performance.
Innovation Solution
An electrolytic solution comprising lithium bis(fluorosulfonyl)imide, lithium difluoro(oxalato) borate, lithium difluorobis(oxalato)phosphate, and methylene methanedisulfonate (MMDS) to improve cycling stability and oxidation resistance, forming a stable solid electrolyte interface (SEI) film, reducing impedance and enhancing battery performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lithium bis(fluorosulfonyl)imide (LiFSI) is used as the lithium salt in the electrolytic solution, then ionic conductivity and solubility are improved, but impurities are generated during preparation and purification that corrode the current collector at high voltage
Solution Approach 1:
The patent introduces a corrosion inhibitor as an intermediary substance that mediates between LiFSI and the current collector. The corrosion inhibitor preferentially reacts with or adsorbs onto the current collector surface, forming a protective layer that prevents impurities from LiFSI from corroding the aluminum foil, thus resolving the contradiction between maintaining high ionic conductivity and preventing harmful impurity effects
Solution Approach 2:
The patent extracts and removes the harmful impurity component from the system by adding corrosion inhibitors that specifically target and neutralize the corrosive impurities generated during LiFSI preparation and purification, separating the beneficial ionic conductivity function from the harmful corrosion effect
2Object-affected harmful factors
If additives such as lithium difluoro(oxalato) borate (LiODFB) and lithium difluorobis(oxalato)phosphate (LiODFP) are added to inhibit corrosion, then current collector protection is improved, but oxidation resistance at high potential becomes insufficient
Solution Approach 1:
The patent creates a composite electrolytic solution system that combines multiple lithium salts (LiFSI, LiODFB, LiODFP) with corrosion inhibitors and oxidation resistance promoters. This composite approach allows the different components to work synergistically, where LiODFB and LiODFP provide current collector protection while the additional promoters enhance oxidation resistance at high potentials, resolving the contradiction between corrosion protection and oxidation resistance
Solution Approach 2:
The patent develops a multi-functional electrolytic solution composition where the additive system performs multiple functions simultaneously: LiODFB and LiODFP inhibit corrosion, while corrosion inhibitors protect the current collector, and oxidation resistance promoters maintain stability at high potentials. This multi-functional approach allows a single electrolytic solution formulation to address multiple contradictory requirements
3Reliability
If LiPF6 is used as the lithium salt, then conductivity is high and safety is good, but solubility and thermal stability are inferior compared to LiFSI
Solution Approach 1:
The patent merges the advantages of different lithium salts by combining LiFSI (which provides superior solubility and thermal stability) with LiPF6 (which provides high conductivity and good safety). The combined formulation allows the electrolytic solution to achieve a balance where the thermal stability and solubility benefits of LiFSI are maintained while the conductivity and safety advantages of LiPF6 are preserved through their synergistic interaction
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 improves battery cycle performance and high-temperature storage performance by stabilizing the SEI film, reducing impedance, and enhancing the stability of the electrolytic solution.
Implementation Method 1
Electrolytic solutions mainly include organic solvents and lithium salts dissolved in organic solvents. Lithium hexafluorophosphate (LiPF6) is the most widely used lithium salt for electrolytic solutions at present because of its high conductivity
Implementation Method 2
Adding additives such as lithium difluoro(oxalato) borate (LiODFB) and lithium difluorobis(oxalato)phosphate (LiODFP) to the electrolytic solution is helpful to inhibit the corrosion of the current collector by LiFSI, form a solid electrolyte interface (SEI) film with low impedance
Data Source
AI summary
An electrolytic solution and a battery. The electrolytic solution includes a first lithium salt, a second lithium salt and a first additive, the first lithium salt at least including lithium bis(fluorosulfonyl)imide, the second lithium salt being selected from at least one of lithium difluoro(oxalato) borate, or lithium difluoro(bisoxalato)phosphate, and the first additive being methylene methanedisulfonate.