The passivation layer on the anode surface is crucial to the electrochemical capacity and lifetime of a lithium-ion battery becauseit is highly stressed with every charging cycle.
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.
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?
Battery de-passivation is a process that “conditions” the battery for proper operation.
Lithium thionyl chloride batteries will passivate continuously, with more increasing level of passivation both as battery temperatures increase and as time extends longer. Operating tools need current pulses to not be adversely inhibited by this natural passivation layer.
Battery de-passivation should be conducted just prior to tool assembly at the job shop, rig, or end use application sight. In some rare cases as mentioned above, battery de-passivation may be appropriate while operating downhole and between tool runs.