Armed lithium metal anodes with functional skeletons

Lithium (Li) metal, owing to its high theoretical capacity of 3860 mAh/g and the lowest reduction potential of −3.04 V, has promoted widespread interests in the development of Li metal batteries (LMBs). LMBs coupling Li metal anodes with industrially mature cathodes (LiNixCoyMn1-x-yO2) and novel cathodes (sulfur, O2) can in principle deliver higher energy density than commercial Li-ion batteries. However, practical applications of LMBs have been plagued by unstable solid electrolyte interphase, irreversible Li deposition, and uncontrollable dendrite growth. To overcome these challenges, numerous strategies have been proposed, and one particularly attractive approach is functional skeletons. In this contribution, we classify the types of skeletons on the basis of materials, examine the strengths and weaknesses of each type, and distinguish the underlying mechanisms for various designs. Particularly, we highlight the importance of architectures at various length scales and surface functionalization toward high-performance skeletons. Finally, we propose material design strategies that could eventually lead to practical applications of LMBs.