Mechanistic enhanced cell voltage based on halides doped metal oxide fullerenes for use in Li-ion batteries: Insights from DFT intuition

Designing of anode nanomaterials with an optimum cell voltage is an important challenge for high-performance lithium (Li) ion batteries. In this study, we have investigated the electrochemical potential of pristine and Li-doped magnesium oxide (Mg₁₂O₁₂) and zinc oxide (Zn₁₂O₁₂) fullerenes through density functional theory (DFT) simulations, with a focus on their potential applications in lithium-ion batteries. Specifically, we investigated the halide ion encapsulated oxide nanocages as a means to achieve this improvement. We examined both unaltered and halide encapsulated Mg₁₂O₁₂ and Zn₁₂O₁₂ with Li atom/lithium cation (Li/Li⁺). Our investigation delves into the geometric and electrochemical characteristics of Li/Li⁺ interactions with Mg₁₂O₁₂ and Zn₁₂O₁₂ nanocages. We analyzed adsorption energies (E_ad) and frontier molecular orbitals (FMOs) of Li/Li⁺ ions with these nanocages to gain insights into how neutral or ionic Li affects their geometric and electrochemical properties. The initial cell voltages of bare Mg₁₂O₁₂ and Zn₁₂O₁₂ are found to be 0.61 and 0.57 V, primarily due to marginal distinctions in the adsorption energies of Li and Li⁺ bound systems. Notably, the encapsulation of various halides into Mg₁₂O₁₂ and Zn₁₂O₁₂ nanocages significantly enhanced the cell voltage. Among the considered halides, the encapsulation of fluoride anion (F⁻) into Mg₁₂O₁₂ and Zn₁₂O₁₂ stands out, leading to a remarkable increase in cell voltage of 4.05 and 3.55 V for lithium-ion batteries, respectively. Moreover, the use of toluene solvent further increased the E_ad values of Li cation with pure and halides encapsulated oxides (Mg₁₂O₁₂ and Zn₁₂O₁₂) nanocages. Ultimately, the Gibb's free also decreased along with the decrease in the cell voltage which is encountered in the acceptable range. The most suitable anode nanomaterial is suggested to be Li doped F⁻@Mg₁₂O₁₂ which has the most acceptable cell voltage of 1.59 V. The work also leads to more research work on the designing of halides encapsulated oxides fullerenes based secondary batteries for use in electrochemical energy storage devices. This work is a full-length guideline for the experimentalist to synthesize such systems to overcome the energy crises.