This review introduces current research on materials and proposes future directions for sodium-ion batteries.

A critical overview of the latest developments in the lithium ion batteries technology is reported. We first describe the evolution in the electrolyte area with particular attention to ionic liquids, discussing the expected application of these room temperature molten salts and listing the issues that still prevent their practical implementation. The attention is then focused on the electrode materials presently considered the most promising for enhancing the energy density of the batteries. At the anode side a discussion is provided on the status of development of high capacity tin and silicon lithium alloys. We show that the morphology that is the most likely to ensure commercial exploitation of these alloy electrodes is that involving carbon-based nanocomposites. We finally touch on super-high-capacity batteries, discussing the key cases of lithium-sulfur and lithium-air and attempting to forecast their chances to eventually reach the status of practically appealing energy storage systems. We conclude with a brief reflection on the amount of lithium reserves in view of its large use in the case of global conversion from gasoline-powered cars to hybrid and electric cars.