Sodium-ion batteries are a cheaper alternative to lithium-ion (LiIon) batteries. Sodium has a negative potential of -2.71 V in the electrochemical voltage series. This means that the potential difference to other chemical elements such as copper, tin, lead
or cobalt is quite high. In terms of construction, sodium-ion batteries consist of a cathode and an anode between which there is a liquid electrolyte
in which the ion transport takes place. The electrolyte only allows positive ions to pass, i.e. atoms that are missing one or two electrons. Thecathode consists of sodium or a sodium alloy, the anode of calcium iron oxide or cobalt oxide. The
operating voltage of sodium ion batteries is lower than that of lithium ion batteries, which means that the energy density is considerably lower than that of lithium ion batteries.