Lithium Salt Mixtures for Battery Electrolyte Corrosion
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Solution Overview
Problem
Lithium-ion battery electrolytes face safety issues due to the degradation of lithium hexafluorophosphate (LiPF6) into hydrofluoric acid gas and corrosion with aluminum current collectors, while alternative salts like LiTFSI and LiTDI have limitations in cost and stability.
Innovation Solution
A mixture of lithium salts, specifically combining LiPF6 or LiTFSI with lithium salts of the R1-SO2-NLi-SO2-R2 type, dissolved in solvents such as carbonates, glymes, or fluorinated nitriles, to achieve enhanced ionic conductivity, electrochemical stability, and capacity retention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lithium hexafluorophosphate (LiPF6) is used as electrolyte salt, then ionic conductivity is improved, but safety deteriorates due to degradation into hydrofluoric acid gas and corrosion with aluminum current collectors
Solution Approach 1:
The patent combines LiPF6 with at least one alternative lithium salt (such as LiTFSI, LiFSI, LiTDI, or LiPDI) in a mixture where LiPF6 constitutes 1-99 wt% of the total salt content. This merging approach allows the electrolyte to benefit from the high ionic conductivity of LiPF6 while the alternative salts mitigate its harmful degradation products and corrosion effects, resolving the contradiction between conductivity and safety.
Solution Approach 2:
The electrolyte uses a composite salt system rather than a single salt, creating a multi-component lithium salt mixture. This composite approach combines the advantageous properties of different salts (conductivity from LiPF6, stability from alternative salts) while eliminating their individual disadvantages, achieving both high ionic conductivity and improved safety profile.
2Stability of the object's composition
If lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) is used as electrolyte salt, then stability with respect to hydrolysis is improved, but corrosion with aluminum current collectors worsens
Solution Approach 1:
The patent combines LiTFSI with LiPF6 or other complementary lithium salts in a mixture. LiTFSI provides hydrolysis stability and forms protective passivation layers on aluminum current collectors, while the co-salts enhance ionic conductivity and further reduce corrosion, resolving the contradiction between stability and corrosion resistance.
3Object-affected harmful factors
If lithium bis(fluorosulfonyl)imide (LiFSI) is used as electrolyte salt, then corrosion with aluminum current collectors is reduced, but cost worsens
Solution Approach 1:
The patent combines LiFSI with more cost-effective salts like LiPF6 in a mixture where LiFSI constitutes 1-99 wt% of the total salt content. This blending approach reduces the overall cost compared to using pure LiFSI while maintaining its key benefits of reduced corrosion and improved stability, resolving the contradiction between corrosion resistance and manufacturing cost.
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 mixture overcomes the drawbacks of individual salts by providing maximum ionic conductivity, electrochemical stability, and capacity retention while minimizing irreversible capacity and corrosion, forming a stable passivation layer on aluminum current collectors.
Implementation Method 1
A subject of the invention is also the mixture of salts dissolved in a solvent
Implementation Method 2
these salts have conductivities of the order of 6 mS/cm, a very good dissociation between the imidazolate anion and the lithium cation
Implementation Method 3
forming a stable passivation layer on aluminum current collectors
Data Source
AI summary
The present invention relates to mixtures of lithium salts. It also relates to these mixtures of salts dissolved in solvents, suitable for use as electrolytes for Li-ion type batteries.