Al2O3-doped ZnO coating of carbon nanotubes as cathode material for lithium-sulfur batteries

Currently, lithium-sulfur (Li-S) batteries become increasingly attractive because of their high theoretical energy density and high theoretical specific capacity. In this work, high-sulfur-loading Al2O3 doping of a ZnO-modified carbon nanotube (AZO@S/CNT) composite is synthesized via the hydrothermal method and subsequent high temperature solid-state reaction. Al2O3-doped ZnO (AZO) induces a strong chemical interaction between poly-sulfides to restrain the shuttle effect. In addition, we use a novel method to enhance the electronic conductivity of the cathode material. The Al2O3 doping of ZnO can increase the electron density in ZnO, and thus enhance its electronic conductivity. The initial discharge capacity of the cathode with 60-wt.% S reaches 1100 mAh g(-1) and the recycle capacity still remains 700 mAh g(-1) after 200 cycles at 0.2 C with a capacity fade rate of 0.18% per cycle, offering a potential candidate for practical application of high-energy-density Li-S batteries in the future.