Battery Electrolyte Composition for SEI Stability and HF Removal
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Solution Overview
Problem
Lithium secondary batteries face challenges in maintaining lifespan and stability at high temperatures due to the decomposition of fluoroethylene carbonate, which produces hydrofluoric acid (HF), leading to potential swelling or explosion and electrode corrosion.
Innovation Solution
An electrolyte composition comprising a cyclic fluorocarbonate-based compound, such as fluoroethylene carbonate, and a propane sultone compound with specific substituents, which forms a stable SEI film and effectively removes HF, enhancing battery durability at room and high temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If cyclic fluorocarbonate-based compound (FEC) is used to form SEI film on negative electrode, then SEI film-forming ability is improved, but hydrofluoric acid (HF) is produced causing decomposition and safety issues
Solution Approach 1:
The patent introduces a boron-containing compound that reacts with the harmful HF produced by FEC decomposition to form beneficial compounds like LiF and boron-containing SEI film components. This converts the harmful HF byproduct into useful components that enhance SEI film stability and protect the electrode, directly applying the principle of converting harm into benefit.
Solution Approach 2:
The boron-containing compound acts as an intermediary substance that mediates between the harmful HF and the electrode/electrolyte system. It reacts with HF to form stable compounds, preventing HF from directly attacking the electrode or decomposing the electrolyte, thus serving as a protective intermediary that resolves the contradiction between SEI formation and HF generation.
2Reliability
If HF is produced during charging and discharging, then SEI film is formed, but swelling or explosion may be caused at high temperature
Solution Approach 1:
The boron-containing compound converts the harmful HF (which causes swelling and explosion) into beneficial LiF and stable boron compounds during charging and discharging. This transformation eliminates the swelling and explosion risks while maintaining the necessary SEI film formation for proper battery operation.
Solution Approach 2:
The boron-containing compound is introduced in advance to preemptively neutralize HF before it can accumulate to dangerous levels that cause swelling or explosion. By continuously reacting with HF during operation, it prevents the harmful accumulation that would lead to thermal runaway, applying preliminary anti-action against the potential danger.
3Reliability
If HF accumulates in electrolyte, then SEI film formation continues, but corrosion or decomposition of electrode occurs
Solution Approach 1:
The boron-containing compound converts the harmful HF that would cause electrode corrosion into beneficial LiF and stable boron compounds. This maintains continuous SEI film formation while protecting the electrode from corrosion, transforming the harmful acidic environment into a protective one.
Solution Approach 2:
The boron-containing compound serves as an intermediary that reacts with HF to form stable products, preventing HF from directly contacting and corroding the electrode. This intermediary action allows SEI film maintenance while simultaneously protecting electrode 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 improves the lifespan characteristic and stability of lithium secondary batteries by forming a stable SEI film and removing HF, ensuring enhanced durability and safety at elevated temperatures.
Implementation Method 1
the electrolyte composition and the material constituting the negative electrode active material react on the surface of the negative electrode active material to form a SEI (Solid Electrolyte Interface) film which is a kind of protective film
Implementation Method 2
lithium ions from a positive electrode active material such as lithium metal oxide migrate to a negative electrode active material
Implementation Method 3
The SEI film prevents the negative electrode structure from the destruction caused by the intercalation of organic solvent molecules having a large molecular weight which migrate together with lithium ions
Implementation Method 4
the amount of lithium ions in the electrolyte composition is reversibly maintained, thereby maintaining stable charging and discharging
Data Source
AI summary
An electrolyte composition contains a propane sultone compound substituted with a specific substituent, a cyclic fluorocarbonate-based compound and a nonaqueous solvent. A secondary battery containing the electrolyte composition is disclosed. The electrolyte composition has excellent SEI film-forming ability and HF-removing ability by containing the cyclic fluorocarbonate-based compound together with the propane sultone compound substituted with a specific substituent, so that the lifespan characteristic and stability at high temperature can be improved.