Titanium Sulfides as Intercalation-Type Cathode Materials for Rechargeable Aluminum Batteries

We report the electrochemical intercalation–extraction of aluminum (Al) in the layered TiS₂ and spinel-based cubic Cu_0.31Ti₂S₄ as the potential cathode materials for rechargeable Al-ion batteries. The electrochemical characterizations demonstrate the feasibility of reversible Al intercalation in both titanium sulfides with layered TiS₂ showing better properties. The crystallographic study sheds light on the possible Al intercalation sites in the titanium sulfides, while the results from galvanostatic intermittent titration indicate that the low Al³⁺ diffusion coefficients in the sulfide crystal structures are the primary obstacle to facile Al intercalation–extraction

Correlating Li⁺‑Solvation Structure and its Electrochemical Reaction Kinetics with Sulfur in Subnano Confinement

Combining theoretical and experimental approaches, we investigate the solvation properties of Li⁺ ions in a series of ether solvents (dimethoxyethane, diglyme, triglyme, tetraglyme, and 15-crown-5) and their subsequent effects on the solid-state lithium–sulfur reactions in subnano confinement. The <i>ab initio</i> and classical molecular dynamics (MD) simulations predict Li⁺ ion solvation structures within ether solvents in excellent agreement with experimental evidence from electrospray ionization-mass spectroscopy. An excellent correlation is also established between the Li⁺-solvation binding energies from the <i>ab initio</i> MD simulations and the lithiation overpotentials obtained from galvanostatic intermittent titration techniques (GITT). These findings convincingly indicate that a stronger solvation binding energy imposes a higher lithiation overpotential of sulfur in subnano confinement. The mechanistic understanding achieved at the electronic and atomistic level of how Li⁺-solvation dictates its electrochemical reactions with sulfur in subnano confinement provides invaluable guidance in designing future electrolytes and electrodes for Li-sulfur chemistry