Fluorinated Ionic Liquid Catholyte for Li-Ion Battery Stability
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Solution Overview
Problem
Lithium batteries face challenges in finding a single electrolyte that is chemically and electrochemically stable with both anode and cathode materials due to the extreme reactivity of lithium, requiring compromises that can compromise overall cell performance.
Innovation Solution
The use of different electrolytes in different portions of the lithium battery, with a block copolymer separator electrolyte and a fluorinated ionic liquid catholyte, each optimized for their specific functions, while being immiscible to prevent diffusion and maintain stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single electrolyte is used in the lithium battery, then the cell structure is simple, but the electrolyte cannot be optimized for both anode and cathode due to lithium's extreme reactivity
Solution Approach 1:
The battery cell is divided into two separate electrolyte compartments: an anode compartment containing a first electrolyte optimized for anode stability, and a cathode compartment containing a second electrolyte optimized for cathode stability. The separator layer acts as the boundary between these compartments, allowing each electrolyte to be independently optimized without compromising the other.
2Reliability
If different electrolytes are used for anode and cathode optimization, then electrolyte stability is improved, but the cell structure becomes more complex
Solution Approach 1:
The separator layer serves multiple functions simultaneously: it physically separates the two electrolyte compartments to prevent mixing, provides mechanical support for the electrodes, and enables ionic transport between compartments. This multi-functionality reduces the need for additional components, thereby limiting the increase in structural complexity.
3Ease of manufacture
If a single electrolyte is used, then manufacturing is simpler, but performance must be compromised for one electrode or the other
Solution Approach 1:
Each electrolyte compartment is designed with locally optimized properties: the anode compartment contains a first electrolyte with chemical composition tailored for anode compatibility and stability, while the cathode compartment contains a second electrolyte optimized for cathode stability. This local optimization allows each electrode to operate at peak performance without compromise.
4Productivity
If different electrolytes are used to optimize each electrode, then battery performance is improved, but manufacturing complexity increases
Solution Approach 1:
The patent introduces a vertical dimension to electrolyte placement by forming a raised first electrolyte compartment above a planar separator layer, then filling the cathode compartment around and above this raised structure. This three-dimensional arrangement allows both electrolytes to be filled through the same opening, simplifying the manufacturing process despite the complexity of having two different electrolytes.
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
This approach allows for high voltage electrochemical cells with improved cycling efficiency, reduced impedance, and minimal capacity loss over cycles, enabling optimized performance for both anode and cathode without compromising the cell's overall operation.
Implementation Method 1
a separator layer that has a block copolymer electrolyte and a second salt that contains the alkali metal. The separator layer is disposed between the negative electrode and the positive electrode and facilitates ionic communication therebetween
Implementation Method 2
The fluorinated ionic liquid catholyte is immiscible with the block copolymer electrolyte
Data Source
AI summary
Fluorinated ionic liquids have been prepared to be used as catholytes in lithium battery cells. Such ionic liquids are immiscible with polyethylene-oxide-based solid polymer electrolytes, which may be used as separators in such cells. Such catholytes can increase the lifetime and boost the performance of lithium battery cells.