Beyond lithium ion batteries: Higher energy density battery systems based on lithium metal anodes

Environmental pollution and energy shortage lead to a continuous demand for battery energy storage systems with a higher energy density. Due to its lowest mass-density among metals, ultra-high theoretical capacity, and the most negative reduction potential, lithium (Li) is regarded as one of the most promising anode materials. Li–sulfur (Li–S) and Li–oxygen (Li–O₂) batteries based on lithium metal anode possess a much higher theoretical energy density in comparison to the present lithium ion batteries. Nevertheless, some severe issues, such as the formation of Li dendrites on the metallic anode, Li polysulfide shuttle effect from the sulfur cathode, and oxygen/moisture erosion from the oxygen cathode, critically hinder their practical applications. Herein, general strategies to address these problems of Li metal anodes are introduced and the special issues for the cathodes in Li–S and Li–O₂ batteries are discussed respectively. Finally, the perspectives on the next-generation Li metal batteries are presented.