Dopamine Surface Functionalized 1D Titania Lepidocrocite Porous Mesostructured Particles for Improved Polysulfide Anchoring in Lithium Sulfur Cells

Lithium-sulfur (Li-S) batteries offer high specific capacities but their development is hindered by several issues, most notably polysulfide shuttle. Previously, a new form of titania nanomaterial, 1D lepidocrocite (1DL) nanofilaments was shown to serve as a sulfur (S) host for Li-S batteries. In this work, porous mesostructured particles are introduced as a new morphology of the titania 1DL to improve its performance as a S host. Furthermore, employing a facile, aqueous, one-step surface functionalization with dopamine enhances 1DL interactions with S, as confirmed by changes in infrared spectroscopy peaks and an increase in d-spacing via X-ray diffraction. This surface functionalization results in a reduction of 1DL band gap energy (E_g) from 3.62 to ≈2.29 eV, resulting in a 2.6-fold increase in electrical conductivity. Additionally, the surface functionalization renders a more conformal coating of S on the 1DL, leading to increased S utilization and interaction with the 1DL. Electrochemical testing shows a 20% reduction in the polysulfide shuttle current in comparison to base 1DL and 560 mAh g^-1 at 0.5 C at a S-loading of 2 mg cm^-2. Postmortem X-ray photoelectron spectroscopy analysis also reveals stronger thiosulfate signals in the dopamine-functionalized 1DLs, further confirming improved S interactions compared to untreated 1DL.