Chemical reactions are the limiting factor for the lifetime of batteries. In batteries, there are two different materials used as the electrodes, one for the anode and the other for the cathode. The electrolyte reacts with both electrodes and provides the chemical reactions, which produce protons (positive ions) at the positive electrode and electrons (negative ions) at the negative electrode. This causes different chemical reactions to occur at the electrons, one that gives up ions and the other that accepts ions. Once this electrolyte is
used up, no chemical reactions can occur, and the battery stops working because it cannot store or discharge any longer. The number of cycles is much smaller than that of supercapacitors because capacitors do not rely on chemical reactions to store energy making the lifetime of supercapacitors much longer than batteries.
Supercapacitors have a much higher up-front cost than batteries, which causes many designs to use batteries instead. Given the differences in lifetime of supercapacitors and batteries, the long-term cost of supercapacitors may be a cheaper option even with the higher initial cost. It all depends on the lifetime needed for the specific application.
In many applications, the differences mentioned previously rule out replacing batteries with supercapacitors. Some applications do not have the space to add as many supercapacitors as it takes to reach the energy density that batteries contain. Other applications need the supercapacitors to hold the charge longer or they have to be recharged more often than batteries, which is not always an option. There are advancements in supercapacitor technologies that allow a higher energy density, but this capability is still not within the range of a battery’s energy density. In some applications though, a hybrid configuration prove to be the most useful. The supercapacitors provide the quick burst of energy for an application, while the batteries handle the long-term energy needs.