A DFT study on nano-voids enhanced lithium storage capacity in Li₄Ti₅O₁₂ anodes for lithium-ion batteries

The global imperative for high-energy-density lithium-ion batteries is increasing rapidly as it is essential for electrifying transport and the development of next-generation portable electronics. This demand places immense pressure on advancing electrode materials. Lithium titanate oxide stands out as an excellent anode material due to its exceptional electrochemical properties. However, having lower theoretical capacity limits is used in high-energy-density devices. This study is based on a novel strategy to overcome this limitation by introducing nano-voids in 0-D Li₄Ti₅O₁₂ nanocluster. Two nano-voids are engineered into the 2 × 2 × 2 supercell of Li₄Ti₅O₁₂ by removing 4 unit-cells. Geometry optimization confirmed the structural stability of the nano-voided structure. The density functional theory (DFT) simulations unveiled crucial aspects about diffusion, reaction kinetics, and adsorption in the Li₄Ti₅O₁₂ structure. Analysis of electronic properties revealed the transformative metallic nature of nano-voided Li₄Ti₅O₁₂, a significant contrast to the pristine Li₄Ti₅O₁₂ semiconducting nature. The most significant finding is the boosted theoretical capacity, reaching the value of 1348.40 mAh g⁻¹. This increase is attributed to the creation of nano-voids, providing expanded adsorption area and active sites. The voltage profile indicates a favorable open circuit voltage of 1.23 V/Li. Other properties including charge transfer kinetics and lithium-ion mobility have been improved. All these findings demonstrate that the introduction of nano-voids into Li₄Ti₅O₁₂ is an excellent approach to enhance theoretical capacity, ionic conductivity and other electrochemical properties of Li₄Ti₅O₁₂ as an anode for lithium-ion batteries.