Theoretical investigation of cycling stability in TiS₂ anode for zinc-ion rechargeable batteries

Abstract To advance the development of aqueous zinc-ion batteries (ZIBs), which are considered a promising alternative for sustainable energy storage, it is a crucial step to explore zinc-free metal anodes to prevent zinc-dendrite formation. Titanium disulfide (TiS₂) has emerged as a potential anode material for ZIBs, due to its sizeable interlayer spacing and favorable electrochemical properties. However, its stability during battery cycles must be thoroughly investigated to assess its feasibility from a theoretical perspective. Herein, the first-principles calculations are performed to theoretically investigate the stability during the cycles of zinc-intercalated TiS₂ (Zn _x TiS₂). Despite its formation energies lying above the thermodynamic convex hull, Zn _x TiS₂ demonstrates robust mechanical and dynamical stabilities over the entire range of zinc-ion intercalation, suggesting its ability to maintain structural integrity under cycling conditions of ZIBs. Our evaluation of structural, elastic, electrochemical, and electronic properties reveals significant changes during the zinc-ion intercalated process, such as the reduction of the open-circuit voltage and changes in the interlayer spacing. These findings indicate that while TiS₂ shows promise as an anode material from a theoretical aspect, addressing the irreversible structural changes observed experimentally is essential. Our insights into the mechanism of zinc-ion intercalation in TiS₂ provide valuable guidance for future design and optimization of zinc-free metal anodes.