What is needed to reverse a reaction in a rechargeable cell?

In a rechargeable cell, reversing the chemical reaction that occurs during discharge is achieved by applying an external electric current. This process is known as electrolysis, where the electrical energy supplied to the cell is converted back into chemical energy, restoring the original reactants and allowing the cell to be reused.

When an external electric current is applied, it forces the reaction to occur in the opposite direction, allowing the materials within the cell to be recharged. This ability to reverse the reaction is what distinguishes rechargeable cells from non-rechargeable cells, where the chemical reactions are irreversible.

The other options do not achieve the same effect: disconnecting the electrodes would halt any flow of current and stop the reaction entirely, changing the temperature may affect the reaction rate but does not necessarily reverse the reaction, and the addition of a new electrolyte may alter the cell's chemistry but does not directly facilitate the reversal of the existing reaction. Therefore, connecting to an external electric current is essential for the recharging process in a rechargeable cell.