Flexible Graphene-Wrapped Carbon Nanotube/Graphene@MnO 3D Multilevel Porous Film for High-Performance Lithium-Ion Batteries.

The ingenious design of a freestanding flexible electrode brings the possibility for power sources in emerging wearable electronic devices. Here, reduced graphene oxide (rGO) wraps carbon nanotubes (CNTs) and rGO tightly surrounded by MnO nanosheets, forming a 3D multilevel porous conductive structure via vacuum freeze-drying. The sandwich-like architecture possesses multiple functions as a flexible anode for lithium-ion batteries. Micrometer-sized pores among the continuously waved rGO layers could extraordinarily improve ion diffusion. Nano-sized pores among the MnO nanosheets and CNT/rGO@MnO particles could provide vast accessible active sites and alleviate volume change. The tight connection between MnO and carbon skeleton could facilitate electron transportation and enhance structural stability. Due to the special structure, the rGO-wrapped CNT/rGO@MnO porous film as an anode shows a high capacity, excellent rate performance, and superior cycling stability (1344.2 mAh g over 630 cycles at 2 A g , 608.5 mAh g over 1000 cycles at 7.5 A g ). Furthermore, the evolutions of microstructure and chemical valence occurring inside the electrode after cycling are investigated to illuminate the structural superiority for energy storage. The excellent electrochemical performance of this freestanding flexible electrode makes it an attractive candidate for practical application in flexible energy storage.