OK, so what happens when cells are charged?
Well, in a nutshell, the inverse of the discharge. To charge, one is forcing current back into the cell (opposite of discharge current). Here, electrons are being taken out of the positive terminal, and forced into the negative terminal. This means that the material at the positive terminal is being oxidized (hence is now the anode — confusing, eh?) and material at the negative terminal is being reduced (now the cathode). In the NiCd system, the cadmium hydroxide is being re-converted into cadmium, and the nickelous hydroxide is being re-converted to nickelic hydroxide. Note that the electrolyte in both charge and discharge is a means to move the hydroxyl (OH-) ions around. Unlike the lead-acid system, the electrolyte really doesn’t change in composition too much between the charged and discharged state.
Well, in a nutshell, the inverse of the discharge. To charge, one is forcing current back into the cell (opposite of discharge current). Here, electrons are being taken out of the positive terminal, and forced into the negative terminal. This means that the material at the positive terminal is being oxidized (hence is now the anode — confusing, eh?) and material at the negative terminal is being reduced (now the cathode). In the NiCd system, the cadmium hydroxide is being reconverted into cadmium, and the nickelous hydroxide is being reconverted to nickelic hydroxide. Note that the electrolyte in both charge and discharge is a means to move the hydroxyl (OH-) ions around. Unlike the lead-acid system, the electrolyte really doesn’t change in composition too much between the charged and discharged state.
