How can you determine if a voltaic cell is reversible (rechargeable) before testing it?

Asked by PhiNotPi (12686

) January 10th, 2013

To jog your memory, a voltaic cell is formed by two half-cells connected by a salt bridge. Electrodes are placed in the half-cells, and the electrodes are made of two different metals. When the electrodes are connected by a wire, one of the metals oxidizes and is dissolved in the solution, while the other is reduced and removed from the solution. Ions can flow across the salt bridge, but the fact that the two metals do not touch forces electricity to flow through the circuit, instead of simply producing heat.

To reverse this reaction, electricity is applied in the opposite direction. The cathode becomes the anode, and vice-versa. However, not are cells are reversible. How can I tell if a cell is reversible without simply testing it?

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1 Answer

I don’t know the answer but I like the question.
As far as I know you can’t put much reverse current into a non-rechargeable cell of common type/chemistry without inviting a problem with leakage, fire, explosion.

I will guess that a very slow and small charge in reverse, with a suitable survey of the state of the battery before and after might be able to get away with it.
I.e. if you have some voltage and current capability at time A, send measurable but slight reverse current (too small to cause a fire or explosion), and re-assess the voltage and current capability, that could tell you a lot. If the output capabilities don’t change, then Don’t Charge, if they improve then for safety’s sake re-test a few times with slightly larger reverse currents.
It’s not practical to do that manually on a regular basis, but an automated state-machine controller on a charger could do that evaluation for you.

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