Non-Aqueous Electrolyte Additives for Cathode Passivation in Li-Ion Cells
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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, thereby reducing degradation and improving battery performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional electrolytes are used, then battery capacity is achieved, but energy retention deteriorates and internal resistance increases due to electrolyte degradation and cathode structure instability
Solution Approach 1:
The electrolyte additives (LiTFSI, LiDFSI, LiMFSI) perform preliminary action by forming a stable passivation layer on the cathode surface before degradation can occur. This pre-formed protective layer prevents subsequent electrolyte decomposition and cathode structure collapse during cycling, thereby improving both energy retention and cycling life simultaneously
Solution Approach 2:
The invention uses composite electrolyte formulations combining multiple lithium salts (LiTFSI, LiDFSI, LiMFSI, LiBF4) with conventional additives (FEC, LiDFOB) in specific ratios. This composite approach creates synergistic effects where the fluorinated imide salts provide superior passivation while working complementarily with traditional additives to achieve both high energy retention and extended cycling life
2Power
If conventional electrolytes are used, then initial performance is achieved, but internal resistance increases due to electrolyte degradation
Solution Approach 1:
The fluorinated lithium imide salts form a stable passivation layer on the cathode surface during initial cycles, creating a protective barrier that prevents subsequent electrolyte decomposition. This preliminary protective action maintains low internal resistance throughout the battery's operational life, addressing both power delivery and cycling durability
3Reliability
If conventional electrolytes are used, then battery operation is achieved, but cathode structure deteriorates due to instability
Solution Approach 1:
The electrolyte additives (LiTFSI, LiDFSI, LiMFSI) perform preliminary action by forming a stable passivation layer on the cathode surface before degradation can occur. This pre-formed protective layer prevents subsequent electrolyte decomposition and cathode structure collapse during cycling, thereby improving both energy retention and cycling life simultaneously
Solution Approach 2:
The invention changes the chemical composition parameters of the electrolyte by introducing fluorinated lithium imide salts with specific molecular structures. These parameter changes in electrolyte chemistry lead to fundamentally different interfacial properties on the cathode, creating more stable solid electrolyte interfaces that protect the cathode structure throughout cycling
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, reduces internal resistance, and minimizes battery swelling at high temperatures, leading to improved cycling life and overall performance of lithium-ion batteries.
Implementation Method 1
helps in forming a passivation layer at the cathode active material, thereby 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.