Non-Aqueous Electrolyte Composition for Li-Ion Cycling Stability
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Solution Overview
Problem
Existing lithium-ion batteries face challenges in achieving high energy retention and low internal resistance, leading to reduced battery cycling life due to instability of the cathode structure and electrolyte degradation.
Innovation Solution
The use of an electrolyte fluid comprising lithium bis(fluoromethanesulfonyl)imide, such as lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(difluoromethanesulfonyl)imide (LiDFSI), or lithium bis(monofluoromethanesulfonyl)imide (LiMFSI), in combination with other salts and additives like LiBF4, fluoroethylene carbonate (FEC), and lithium difluoro (oxalato) borate (LiDFOB), which helps in forming a passivation layer at the cathode active material, reducing degradation and improving battery performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional electrolytes are used, then the battery can operate, but energy retention deteriorates and internal resistance increases over cycling
Solution Approach 1:
The patent changes the chemical composition parameters of the electrolyte by introducing fluorinated cyclic carbonate components (fluorinated EC or fluorinated PC) at specific concentration ranges (1-50 wt%). This parameter change modifies the electrolyte's interaction with the cathode surface, forming a more stable passivation layer that reduces degradation and maintains energy retention over extended cycling, directly resolving the contradiction between energy retention and cycling life.
Solution Approach 2:
The patent creates a composite electrolyte system by combining fluorinated cyclic carbonate components with conventional cyclic carbonate solvents (EC, PC) and lithium salts. This composite approach leverages the beneficial properties of both the fluorinated additive (stability, passivation formation) and the conventional solvent (ion conductivity, solubility), achieving improved cycling life while maintaining reliable energy retention.
2Reliability
If conventional electrolytes are used, then the battery can operate, but internal resistance increases and energy retention decreases
Solution Approach 1:
The patent modifies the electrolyte composition by incorporating fluorinated cyclic carbonate components at optimized concentrations (1-50 wt%). This parameter change alters the chemical properties of the electrolyte, enabling it to form a stable passivation layer on the cathode that prevents harmful interactions, thereby suppressing internal resistance growth and maintaining high energy retention over cycling.
Solution Approach 2:
The patent converts the potentially harmful interaction between conventional electrolytes and cathode materials into a beneficial effect. The fluorinated cyclic carbonate components intentionally undergo controlled decomposition to form a stable passivation layer (SEI) on the cathode surface. This layer, initially formed through sacrificial decomposition, subsequently protects the cathode from further degradation, reducing internal resistance and improving energy retention.
3Stability of the object's composition
If cathode structure is modified through doping and coating, then stability improves, but electrolyte degradation continues
Solution Approach 1:
The patent introduces fluorinated cyclic carbonate components as an intermediary substance between the cathode and the bulk electrolyte. This intermediary forms a protective passivation layer on the cathode surface that mediates the interaction between the cathode structure and the electrolyte, preventing direct harmful contact. This approach complements cathode modifications by adding an additional protective interface, thereby reducing electrolyte degradation while maintaining cathode stability.
Solution Approach 2:
The patent changes the chemical parameters of the electrolyte system by incorporating fluorinated cyclic carbonate components. This parameter change creates a more chemically stable environment at the cathode-electrolyte interface, reducing the degradation rate of the electrolyte. The fluorinated components form a stable passivation layer that protects both the cathode structure and the bulk electrolyte from harmful reactions, addressing both cathode stability and electrolyte preservation simultaneously.
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 proposed electrolyte fluid composition enhances energy retention and reduces internal resistance, leading to improved battery cycling life and reduced swelling at high temperatures.
Implementation Method 1
helps in forming a passivation layer at the cathode active material, reducing degradation and improving battery performance
Data Source
AI summary
This disclosure relates generally to battery cells, and more particularly, electrolyte additives for use in lithium ion battery cells.