Battery technologies based on the use of monovalent ions (Na⁺) or multivalent ions (Mg⁺⁺, Ca⁺⁺...), or even both

Recently, Li-ion batteries have emerged as the best technology for electric vehicle applications, and as a serious option for stationary applications. However, the growing development of these markets raises the question of potential lithium reserves. Fears of a significant increase, particularly in price, due to limited resources located in a few producer countries, have led to the study of alternatives, among which the most interesting and mature is undoubtedly the use of sodium. Sodium resources are unlimited, distributed throughout the world and accessible at very low cost. What's more, while some criteria, notably mass, may appear penalizing, they are counterbalanced by the possibility of replacing the copper imposed as a current collector at the negative electrode in the case of lithium, by the lighter and cheaper aluminum, which does not form an alloy with sodium. Efforts in this field are divided between two systems, which differ in that one uses polyanionic compounds _Na3V2(_PO4)2F3, and the other lamellar compounds _{Na2/3Mn0.5Fe0.5O2} as the positive electrode respectively. The advantages and disadvantages of each of these systems, which currently use a negative carbon electrode but may in the longer term use NaxSb or even NaxPb intermetallic phases, were presented. To date, the _Na3V2(_PO4)2F3/C Na-ion system is the most attractive, with cycling and power performance on a par with Li-ion technology. Only high-temperature performance remains an issue.