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Master Mindmap PTFE decomposition - Coggle Diagram
Master Mindmap PTFE decomposition
Goal mindmap
Determine why my PTFE containing sulfide electrolyte film keeps short circuiting
Film properties
How do the film properties change as function of the PTFE content and fabrication method
Mechanical properties
Tensile strength improves with PTFE content, calender loops and fibrillation temperature
Ionic conductivity
Decreases with PTFE content, but quite stable with the number of calender loops
PTFE decomposition
Mechanism
(CF2 − CF2)n + 4n Li+⇒ − (C ≡ C)n + 4n LiF
PTFE is unstable against 1V vs Li/Li+ and thus also against lithium metal
Effect
Low initial coulombic efficiency and loss in mechanical strength
Electronic conductivity solid electrolyte increases due to conductive carbon forming inside the solid electrolyte, can result in short-circuiting of the cells
The higher the fibrillation degree the more electronically conductive the membrane becomes
Also result in the solid electrolyte turning black and looses mechanical strength because of this reactivity with the anode
Prevention
Use an additional liquid electrolyte that can form a stable SEI layer on top of the PTFE
Use a low wt% of PTFE at the anode sides, while still have a high Wt% at the cathode side
To do list
Can add PTFE together with Li metal inside a solid state cell and observe the colour change
Ask Tom or valerio about if this short circuiting was also common for their cells.
Make sure in my cell to distuingish mechanical short circuit with electrochemical short circuit by having a much thicker solid electrolyte piece myself first.