Lithium Battery Electrolyte Additive for Dendrite-Suppressing SEI
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Solution Overview
Problem
The formation of lithium dendrites in lithium secondary batteries leads to degradation of the negative electrode, causing internal short circuits and reduced lifetime, particularly in lithium-sulfur batteries.
Innovation Solution
Incorporating alkyl trifluoroacetate as an additive in the electrolyte solution to form a protective film on the lithium surface, suppressing dendrite formation and enhancing the stability of lithium polysulfides through chemical interaction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If lithium metal is used as the negative electrode material to achieve high capacity and low density, then the energy density is improved, but dendrite formation occurs leading to internal short circuits and reduced stability
Solution Approach 1:
The patent introduces a fluorinated cyclic carbonate additive as an intermediary substance in the electrolyte that mediates between the lithium metal negative electrode and the electrolyte solution. This additive preferentially decomposes to form a protective fluorinated SEI film that acts as a mediator, preventing direct harmful interactions between lithium metal and the electrolyte, thereby suppressing dendrite formation while maintaining the high energy density benefits of lithium metal.
Solution Approach 2:
The patent changes the chemical composition parameters of the electrolyte by incorporating fluorinated cyclic carbonate compounds (specifically fluorinated 1,3-propanedione derivatives) at controlled concentrations (0.01-5 wt%). This parameter change modifies the properties of the SEI film formed on the lithium surface, transforming it from a dendrite-promoting structure to a dendrite-suppressing protective layer, thus resolving the contradiction between energy density and stability.
2Quantity of substance
If lithium metal is used as the negative electrode to achieve high capacity of 3,860mAh/g, then the battery capacity is improved, but degradation occurs due to reactions with positive electrode active material or electrolyte solution
Solution Approach 1:
The patent applies preliminary action by having the fluorinated cyclic carbonate additive decompose first during initial charging cycles to form a stable protective SEI film on the lithium metal surface before the lithium can react with the electrolyte solution or positive electrode materials. This preliminary protective layer prevents subsequent degradation reactions, allowing the lithium metal to maintain its high capacity (3,860mAh/g) over extended battery lifetimes.
3Device complexity
If conventional electrolyte solutions are used to maintain simplicity, then the device complexity is reduced, but uniform lithium deposition and peeling cannot be achieved leading to dendrite formation
Solution Approach 1:
The patent applies local quality by introducing a specific fluorinated cyclic carbonate additive that locally modifies the SEI film properties at the lithium-electrolyte interface. This localized modification creates a uniform protective layer with consistent fluorine distribution, ensuring uniform lithium deposition and peeling behavior without requiring complex changes to the overall electrolyte system composition.
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 additive improves the lifetime and efficiency of lithium secondary batteries by uniformly depositing and peeling lithium, reducing dendrite formation and increasing the solubility of lithium polysulfides, thereby enhancing battery stability and performance.
Implementation Method 1
enhancing the stability of lithium polysulfides through chemical interaction
Implementation Method 2
uniformly depositing (plating) and peeling (stripping) lithium on the surface of the negative electrode
Data Source
Figure 1
AI summary
The present invention relates to an electrolyte solution for a lithium secondary battery comprising a lithium salt, an organic solvent and an additive, wherein the additive comprises an alkyl trifluoroacetate, which is a compound represented by Formula 1, and a lithium secondary battery comprising the same.