First-Principles prediction of the structural stability, optoelectronic, magnetic properties and mechanical response of olivine type LiMPO4 (M = Ni, Cu) phosphate materials for energy storage applications

Abstract

The quest for the most suitable materials for energy storage applications is a pressing requirement in the current era of science and technology. In this article, we have performed first-principles calculation based on density functional theory (DFT) utilizing the CASTEP code to analyze LiMPO4 (M = Ni, Cu) for energy storage applications. The computed lattice parameters in the orthorhombic crystal structure for LiNiPO4 are determined to be a = 10.336 Å, b = 6.006 Å, c = 4.693 Å with cell angles α = β = γ = 90o and for LiCuPO4, its values are a = 10.042 Å, b = 6.122 Å, c = 5.123 Å with cell angles α = β = γ = 90o. The calculated negative cohesive energies, −6.21 eV/atom for LiNiPO4 and −6.13 eV/atom for LiCuPO4, confirm their structural stability. The energy band structure demonstrates the semi-metallic characteristics of both LiNiPO4 and LiCuPO4 materials with the energy gap of 1.80 eV and 3.84 eV, respectively. Additionally, both LiNiPO4 and LiCuPO4 exhibit a net magnetic moment of 2 μB. The calculated elastic constants for these materials meet Born’s stability criteria while confirming their mechanical stability and positioning them as highly appropriate materials for energy storage systems. Furthermore, LiNiPO4 and LiCuPO4 showcase remarkable optical conductivity measuring at 4.40 (fs)-1 and 5.24 (fs)-1, respectively, which asserts their suitability for applications in energy storage technology.