RECHARGEABLE OR DISPOSABLE

Batteries run out of power when the chemical reactions inside them stop. The anode no longer releases ions, and the cathode no longer wants to take them. But that’s not always the end. Some types of battery let you run the reactions in reverse. If you connect them up to a power source, you can force the ions back. The electrolyte returns positive ions to the anode, and the cathode lets go of the negative ions it has collected. This makes it possible to use the battery again. However, this reversal isn’t perfect. Electrodes start out as neat stacks of crystals, but when they discharge and recharge they become untidy. This affects their ability to store power in the future.