Li–O2 and Li–S batteries with high energy storage

The amount of energy that can be stored in Li-ion batteries is insufficient for the long-term needs of society, for example, for use in extended-range electric vehicles. Here, the energy-storage capabilities of Li–O2 and Li–S batteries are compared with that of Li-ion, their performances are reviewed, and the challenges that need to be overcome if such batteries are to succeed are highlighted. Li-ion batteries have transformed portable electronics and will play a key role in the electrification of transport. However, the highest energy storage possible for Li-ion batteries is insufficient for the long-term needs of society, for example, extended-range electric vehicles. To go beyond the horizon of Li-ion batteries is a formidable challenge; there are few options. Here we consider two: Li–air (O2) and Li–S. The energy that can be stored in Li–air (based on aqueous or non-aqueous electrolytes) and Li–S cells is compared with Li-ion; the operation of the cells is discussed, as are the significant hurdles that will have to be overcome if such batteries are to succeed. Fundamental scientific advances in understanding the reactions occurring in the cells as well as new materials are key to overcoming these obstacles. The potential benefits of Li–air and Li–S justify the continued research effort that will be needed.