Fluorinated Vinylene Ether Electrolyte for Lithium Battery Cycle Life
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Solution Overview
Problem
Lithium secondary batteries experience a decrease in discharge capacity when charge/discharge cycles are repeated, due to side reactions at the negative electrode surface and non-aqueous electrolyte interactions, which limits their cycle characteristics.
Innovation Solution
Incorporating a non-aqueous electrolyte with a fluorinated vinylene ether compound A, such as CF2═CH—O—CF2—CF2H, that reacts and polymerizes at the negative electrode surface to form a protective coating, suppressing side reactions and improving cycle characteristics, along with a suitable alkyl ether compound X as the main solvent component to enhance lithium ion conductivity and solubility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional electrolyte compositions are used, then the battery structure is simple, but charge/discharge cycle characteristics deteriorate due to side reactions at the negative electrode surface
Solution Approach 1:
The fluorinated vinylene ether compound acts as an intermediary substance that mediates between the negative electrode and the electrolyte. It preferentially reacts with the negative electrode surface to form a protective coating layer, preventing direct contact and harmful side reactions between the electrolyte and electrode, thereby improving cycle characteristics while maintaining electrolyte composition simplicity
Solution Approach 2:
The fluorinated vinylene ether compound performs preliminary action by reacting first during initial charging cycles to form a stable coating layer on the negative electrode surface before the main electrolyte components can cause harmful side reactions. This preliminary protective action prevents capacity fade during subsequent charge/discharge cycles
2Productivity
If the battery undergoes repeated charge/discharge cycles, then the battery operates continuously, but discharge capacity decreases due to side reactions at the negative electrode surface
Solution Approach 1:
The invention converts the potentially harmful side reactions into a beneficial process. The fluorinated vinylene ether compound intentionally reacts with the negative electrode surface under controlled conditions to form a protective coating, transforming what would be capacity-degrading side reactions into a beneficial protective mechanism that preserves discharge capacity during continuous operation
Solution Approach 2:
The invention changes the chemical composition parameter of the electrolyte by introducing the fluorinated vinylene ether compound with specific molecular structure (containing —CF2—O— or —CF2—CF2—O— groups). This parameter change alters the reaction behavior at the electrode surface, reducing harmful side reactions and maintaining discharge capacity during repeated cycles
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 fluorinated vinylene ether compound A forms an effective coating on the negative electrode surface, significantly improving charge/discharge cycle characteristics by reducing side reactions and maintaining high discharge capacity over repeated cycles.
Implementation Method 1
the fluorinated vinylene ether compound A in the non-aqueous electrolyte reacts and polymerizes at an initial stage of charging at the negative electrode surface, and may form an excellent coating on the negative electrode surface
Data Source
AI summary
A lithium secondary battery includes a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and a non-aqueous electrolyte, wherein the non-aqueous electrolyte includes a fluorinated vinylene ether compound A having a —CF═CH—O— bond, and a non-aqueous solvent.