Lithium-air and lithium-sulfur batteries

Reducing our dependence on fossil fuels increases the demand for energy storage. Lithium-ion batteries have transformed portable electronics and will continue to be important but cannot deliver the step change in energy density required in the longer term in markets such as electric vehicles and the storage of electricity from renewables. There are a few alternatives. Here we describe two: Li-air and Li-sulfur batteries. We compare the energy densities of Li-ion, Li-air, and Li-S and discuss their differences and the challenges facing Li-air and Li-S, many of which are materials related.