Fluorinated Electrolyte Additive for Stable High-Capacity Li-Ion Cells
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Solution Overview
Problem
Lithium secondary batteries face issues with electrolyte depletion, electrochemical performance deterioration, and the formation of resistive films due to oxygen gas generation and volume expansion in lithium-rich cathode and silicon-based anode materials.
Innovation Solution
The use of an electrolyte additive represented by Chemical Formulas 1 and 2, which are compounds that reduce reductive decomposition and form a uniform protective film on electrodes, is proposed. This additive is manufactured through a process involving hexafluorophosphate and 2-monofluoromalonic acid, with a HF scavenger added to the reaction mixture to enhance the synthesis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If lithium-rich cathode and silicon-based anode materials are used to increase energy density and capacity, then the battery capacity and voltage are improved, but oxygen gas is generated during charging and volume expansion occurs during discharging, causing electrolyte decomposition and performance deterioration
Solution Approach 1:
The patent introduces a fluorinated cyclic carbonate compound as an intermediary substance that mediates between the electrode materials and the electrolyte. This compound forms a protective interface layer that prevents direct harmful interactions between the electrolyte and electrode surfaces, thereby stabilizing the system while maintaining high capacity performance
Solution Approach 2:
The fluorinated cyclic carbonate compound performs preliminary protective action by forming a stable protective film on the electrode surfaces before the electrolyte can decompose. This pre-formed protective layer prevents subsequent electrolyte decomposition and electrode damage that would otherwise occur during normal battery operation
2Quantity of substance
If silicon-based anode material is used to improve capacity, then the battery capacity is increased, but serious volume expansion occurs during repeated charges and discharges forming cracks on the anode surface
Solution Approach 1:
The fluorinated cyclic carbonate compound forms a flexible thin protective film on the anode surface that can accommodate the volume expansion of silicon during charging without cracking. This flexible protective layer maintains structural integrity while allowing the underlying silicon to expand and contract during charge-discharge cycles
Solution Approach 2:
The protective film formed by the fluorinated cyclic carbonate compound provides beforehand cushioning for the silicon anode, absorbing mechanical stress from volume expansion before cracks can form. This pre-established protective layer prevents structural degradation during repeated cycling
3Power
If conventional electrolyte is used with lithium-rich cathode material, then the battery operates at high voltage, but oxygen gas generation causes electrolyte decomposition and formation of thick resistive films on electrode surfaces
Solution Approach 1:
The fluorinated cyclic carbonate compound acts as an intermediary layer between the high-voltage lithium-rich cathode and the electrolyte, preventing direct contact and chemical reactions. This protective interface allows high-voltage operation while blocking the pathway that would otherwise lead to electrolyte decomposition
Solution Approach 2:
The patent converts the potentially harmful high-voltage environment into a beneficial operating condition by using the fluorinated cyclic carbonate compound to stabilize the interface. The compound's fluorinated structure is specifically designed to withstand high voltage while protecting the electrolyte, turning what would be a damaging condition into a sustainable operating state
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 additive improves the stability of secondary batteries by reducing internal resistance and maintaining electrochemical performance even with high-voltage and high-capacity lithium-rich cathode and silicon-graphite anode materials.
Implementation Method 1
a compound represented by Chemical Formula 1 or Chemical Formula 2 below... which are compounds that reduce reductive decomposition and form a uniform protective film on electrodes
Data Source
AI summary
According to an embodiment of the present inventive concept, an electrolyte additive represented by the compounds of Chemical Formulas 1 to 4 may be provided. In addition, according to another embodiment of the present inventive concept, a method for preparing an electrolyte additive of the compounds of Chemical Formulas 1 to 4 may be provided, wherein the method for preparing the electrolyte additive includes reacting hexafluorophosphate and 2-monofluoromalonic acid, further adding an HF scavenger to the mixed solution produced by the reaction, and concentrating and drying the reaction solution obtained therefrom.