Blooming growth of durable carbon nanotubes bundles from graphite interlayer seeds for free-standing lithium-oxygen battery electrodes

Abstract

Lithium‑oxygen batteries (LOBs) have attracted considerable attention as promising high energy density batteries. One of the common reasons for LiO2 cell failure is the collapse of the free-standing electrode owing to inadequate mechanical stability, resulting in a battery with poor cycle life. It remains challenging to prepare structurally stable electrode materials to enable long and efficient operation of batteries. Herein, we report three-dimensional hierarchical carbon nanotubes/graphene (CNTs/Gr) bundles as mechanically durable free-standing electrodes for high-performance LOBs. We introduce a novel chemical vapor deposition method for fabricating CNTs foam that can be grown on Fe catalyst seeds embedded in the graphite intercalation compound (FeCl3-GIC). The inner CNTs act as pillars between graphene layers to absorb compressive forces, ensuring excellent mechanical strength. In addition, countless CNTs blooms grown from graphene layers provide numerous reaction sites for LiO2 reaction. The hierarchical CNTs/Gr bundles exhibit 100% mechanical recovery properties and 5–6 times better electrochemical cyclability than the reference CNTs bundles without graphene. This new structure and fabrication strategy could provide a new approach to prepare high-performance carbon-based free-standing electrode alternatives.