Recharging Batteries: Electolytic Reactions Explained

[Beasticly]

I understand that a battery works as a series of electrolytic cells when discharging, so would it be true than when it recharges, and undoes the electrolytic reactions, it acts as electrolysis reaction so that the anode can be replenished?

Thanks in advance, would love some clarity on the issue.

 

[Integral]

This is really a chemistry question, not my forte. I have moved this to the chemistry forum in hopes that one of our chemists will answer.

 

[Borek]

I understand that a battery works as a series of electrolytic cells when discharging, so would it be true than when it recharges, and undoes the electrolytic reactions, it acts as electrolysis reaction so that the anode can be replenished?

Thanks in advance, would love some clarity on the issue.

It depends on the battery type, but your thinking is basically OK. That's the general idea. Note, that it is not anode or cathode that is replenished, but whole system - you need both red and ox part of the system.

 

[Beasticly]

Doh, I probably should've realized this was more a chemistry orientated question. Thanks for moving it Integral!

It depends on the battery type, but your thinking is basically OK. That's the general idea. Note, that it is not anode or cathode that is replenished, but whole system - you need both red and ox part of the system.

Ah, ok, so for the anode to be reduced the cathode has to be oxidised. Cool. :)

So that'd mean that there'd only be a transfer of electrons from within the battery and that the charger would only be providing a current but not actually giving any electrons up to the battery?

Thanks.

 

[mrjeffy321]

A battery is not a capacitor where there is a certain amount of stored free charge contained within it. The voltage, and in turn the current of moving charges, is generated by the electrochemical reaction taking place inside the battery (reduction / oxidization of the chemicals at the cathode / anode). The electrochemical reaction will continue to run as long as there is sufficient supply of the proper substances at each electrode (whether that is Copper / Zinc, or Pb / PbO2, or whatever combination that particular battery uses). As the battery discharges these chemicals are chemically changed into a different form which will not generate a current. When you recharge the battery you are running the RedOx reaction in reverse (still a redox reaction though) in order to revert the chemicals at the electrodes back to their states when the battery was fresh.

 

[Borek]

To add to mrjeffy321 post - battery, while called "charged" or "discharged", doesn't carry any electric charge in both states, it is electrically neutral. "Charged" battery stores energy, not the electrical charge. Whether it is used or charged, same amount of electrons goes in as goes out.