First-principles study of the structural, electronic, mechanical, and thermodynamic properties of (P, Al, B)-doped Li2SiO3 system

Abstract

In this investigation, Li₂SiO₃, a promising candidate as an electrolyte compound in Li⁺-ion-based batteries, exhibits a distinctive orthorhombic crystal structure. The generalized gradient approximation (GGA-PBE) with the ultrasoft pseudopotential approach in density functional theory (DFT) is employed to gain significant insights into enhancing the performance and efficiency of Li-ion batteries utilizing silicon cathodes. The calculated bandgap values are 5.61 eV (Li₂SiO₃), 2.62 eV (Li₂Si_1.5P_0.5O₃), and 1.7 eV (Li₂Si_1.25P_0.75O₃) for the first doped material, 2.66 eV (Li_1.5Al_0.5SiO₃) and 2.16 eV (Li_1.25Al_0.75SiO₃) for the second material, and 3.71 eV (Li_1.5B_0.5SiO₃) and 3.16 eV (Li_1.25B_0.75SiO₃) for the third material. For Li–O bonds, the overlap between the 2 s state of lithium (Li) and the 2 s (2p_x, 2p_y, and 2p_z) states of oxygen (O) is analyzed. The obtained results indicate that these systems exhibit mechanical stability and doping induced stability. The material structures display anisotropic and ductile elastic responses. Additionally, due to their narrow bandgaps, these materials demonstrate excellent photon absorption capabilities, as evidenced by their distinctive optical responses. This analysis identifies four new thermodynamically stable systems within the Li-Si–O framework, encompassing both pristine and doped structures. This theoretical investigation aims to explore the essential properties of cathode and anode materials for next-generation Li-ion batteries.