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The high resistance protective film on the lithium anode surface (which provides the long shelf life) can be a problem at low temperatures and even at room temperature. This is often a consequence of poor quality control, particularly with respect to trace water contamination.
| This problem is termed
the voltage delay effect and is illustrated in this
Figure. This is a delay in
reaching normal operating voltage after discharging has begun, which is worst at
low temperatures following prolonged storage at high temperature. The film
causes the cell's internal resistance to high, until it has been broken up and
removed by the discharge reaction.
Voltage delay is a problem when the film is thicker than usual, trace water often being the culprit. Voltage delay is typically worse for liquid cathode systems because of the lithium being in direct contact with the cathode material. To counter voltage delay sonobuoys, for example, are ed to take a large current pulse during descent from an aircraft to precondition the battery before it hits the water. Otherwise, quality control is the answer. |
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