Fabrication of vulcanized cross-linked polystyrene grafted on carbon nanotubes for use as an advanced lithium host

Abstract

We report the fabrication of vulcanized cross-linked polystyrene grafted on carbon nanotubes (CNTs) for use as an advanced three-dimensional Li host. First, polystyrene was grafted from Br-modified CNTs to form brush-like structure by surface-initiated atom-transfer radical polymerization. Polystyrene grafted on carbon nanotubes was then cross-linked using a Friedel-Crafts reaction and finally vulcanized with sulfur. Vulcanized cross-linked polystyrene grafted on carbon nanotubes was used as a support for the Li metal, and its macro-, meso- and microporous structure increased Li ion transport, buffered the volume changes of the Li anode, and provided a high specific surface area to reduce local current density, which assisted rapid and uniform Li plating/stripping. At the same time, the homogenously distributed sulfur in the support reacted with Li to produce a Li₂S-containing SEI layer, while the CNTs provided conductive pathways for the rapid transmission of electrons. As a result, a Li|Li symmetric cell using this anode material and a Cu current collector had a stable cycling performance of more than 500 h at a current density of 1 mA cm⁻². When LiFePO₄ was used as the cathode, a full cell had a high discharge capacity of 101 mAh g⁻¹ with a capacity retention of 77% after 600 cycles at 1 C.