Lithium transfer dynamics and storage capacity/cyclability properties of Ni and Ru dual-doped two-dimensional FePS₃ nanoflakes

Despite owning a high theoretical lithium ion capacity, the iron phosphorus trisulfide FePS₃ writhes from inferior cyclability and lower reaction kinetics to be employed as a potential anode in lithium ion batteries. Herein, we demonstrate a dual-doping approach with nickel and ruthenium in optimal quantities leading to the formation of Ni_0.07Ru_0.03-FePS₃ two dimensional layers (flakes) having high electrochemical conductivity and increased cyclability. This comprehensive investigation unravels the influence of single and dual doping of isovalent (Ni²⁺) and aliovalent (Ru³⁺) ions on the lithium intercalation/deintercalation kinetics in FePS₃. The Ni increases active intercalation sites and enhances electrical conductivity while Ru influences the Li⁺ ion kinetics by increasing the channel width, termed as pillar effect. Theoretical calculations indicate the improved binding of lithium on Ni and Ru dual-doped FePS₃. Ni_0.07Ru_0.03-FePS₃ based anode offers a high discharge-capacity ∼600mAhg⁻¹ (∼450 mAhg⁻¹) at a high current rate of 1 Ag⁻¹ (10 Ag⁻¹) showcasing an approximate six-fold improvement from FePS₃ (∼104 mAhg⁻¹). The high coulombic efficiency (∼95 %) and high rate performance with improved cyclability obtained with the LiFePO₄/Ni_0.07Ru_0.03-FePS₃ full-cell indicate the synergistic effects of dual doping. This opens a plethora of opportunities in developing high-capacity and high-cyclability anodes by engineering the metal trichalcogenides through dual doping.