Passivation is a chemical phenomenon affecting lithium battery performance. It is a film that forms on the negative electrode, serving to prevent discharge after removal of load.
What is passivation in a lithium thionyl chloride battery cell?
Passivation in a lithium thionyl chloride battery cell is a chemical reaction between the solid metallic lithium metal and the liquid catholyte (cathode and electrolyte) in the cell. It is a self-assembled, thin, highly resistant layer of lithium chloride crystals on the surface of the lithium metal.
Where does passivation occur in a lithium battery?
Since passivation begins to occur as soon as the lithium metal battery cell is manufactured, it occurs anywhere the cell or battery pack using the cell is located. Thus passivation is occurring naturally in the battery while in transit, in storage, at the shop, at the rig, or downhole even while operating, if current loads are very low. Why?
What is a lithium passivation layer?
It is a self-assembled, thin, highly resistant layer of lithium chloride crystals on the surface of the lithium metal. This passivation layer partially blocks the chemical reaction between the solid lithium (anode) and the liquid thionyl chloride (cathode), inhibiting the battery chemical reaction from generating the electrons (electrical current).
How does temperature affect the passivation layer of a battery?
Higher temperature causes a thicker passivation layer, thus storing at cooler (room) temperature helps mitigate passivation layer growth. Consequently, using fresher batteries helps assure a less resistive passivation layer has formed in the battery. The passivation layer is diminished by appropriate electrical current flow through the cell.
What is battery de-passivation?
Battery de-passivation is a process that “conditions” the battery for proper operation.
Why is the passivation layer important?
This layer is important because it protects the anode from reaction while the cell is dormant – resulting in a long shelf-life. During low rate discharge (5-10 microamps/cm2), the lithium ions that allow the cell to operate can migrate through the passivation layer.