The lithium-ion battery is currently the most important type of battery among the rechargeable high-performance batteries. While small lithium-ion batteries are already being used commercially in consumer electronics, electrical tools, hybrid vehicles, and electric cars, the commercial use of larger energy storage units is still in its early stages. The maximum storage capacity of conventional lithium-ion batteries has, however, nearly been reached. In order to achieve advances in performance, it is therefore necessary to press ahead with the development of new storage material and approaches. New electrochemical pairings and new ideas for an even more compact design are needed to achieve another significant jump in energy density.