The left side of the lithium iron phosphate battery is a positive electrode composed of an olivine structure LiFePO4 material, which is connected to the positive electrode of the battery by an aluminum foil. On the right is the negative electrode of the battery composed of carbon (graphite), which is connected to the negative electrode of the battery by a copper foil. In the middle is a polymer separator, which separates the positive and negative electrodes, through which lithium ions can pass but electrons cannot. The interior of the battery is filled with electrolyte, and the battery is hermetically sealed by a metal casing.