Hierarchical nanostructure of three-dimensional Au/carbon nanotube-graphene foam for high performance lithium metal anode

Abstract

Owing to the large specific capacity and low electrochemical potential, lithium metal anodes have attracted much attentions. However, owing to lithium metal's high reactivity and infinite volume change, the lithium dendrite formation is uncontrollable and even causes serious safety concerns. In this work, three-dimensional (3D) carbon nanotubes-foam graphene (CNT-GF) nanostuctures were synthesized using a chemical vapor deposition approach, followed by sputtering Au nanoparticles (Au NPs) onto CNT-GF surface to prepare Au/CNT-GF hierarchical structure. The lithium metal deposition behavior onto Au/CNT-GF was investigated by in-situ optical microscope characterization, and the current density distribution over the Au/CNT-GF electrode surface was explored by simulation. The electrochemical meaurements show that Au/CNT-GF exhibits excellent performance, including long cycle stability with high Coulombic efficiency (CE). For example, Au/CNT-GF electrode can cycle stably for more than 1100 h with a CE of higher than 99% when evaluated at a current density of 1 mA cm−2 with a capacity of 1 mAh cm−2. It can even stably cycle more than 300 cycles at a high current density of 5 mA cm−2 with 1 mAh cm−2. The results show that the improvement of electrochemical performance is attributed to the 3D structure with large specific surface area and the lithiophilic interface constructed by Au NPs. Finally, a full cell with LiFePO4 (LFP) as cathode and Li@Au/CNT-GF as anode is assembled. After 500 cycles at 100 mA g−1, the full cell can deliver a capacity of 105.8 mAh g−1 with a high capacity retention of 92%.