Electrode reaction cannot be reversed, and the identities of the anode and cathode are therefore fixed. The anode is always the negative electrode. The cell can be discharged but not recharged. A secondary cell, for example a rechargeable battery, is a cell in which the chemical reactions are reversible. When the cell is being charged, the anode becomes the positive (+) and the cathode the negative (−) electrode. This is also the case in an electrolytic cell. When the cell is being discharged, it behaves like a primary cell, with the anode as the negative and the cathode as the positive
Electrode potential that only the magnitude expressed according to the convention (2) be called "the electrode potential". To avoid possible ambiguities, the electrode potential thus defined can also be referred to as "Gibbs–Stockholm electrode potential". In both conventions, the standard hydrogen electrode is defined to have a potential of 0 V. Both conventions also agree on the sign of "E" for a half-cell reaction when it is written as a reduction. The main difference between the two conventions is that upon reversing the direction of a half-cell reaction "as written", according to convention (1) the sign of "E" also switches, whereas in