  In this study, we have employed a DFT+U calculation using quantum-espresso
(QE) code to investigate the structural, electronic, optical, and magnetic
properties of LiFePO$\rm_{4}$ cathode material for Li-ion batteries. Crystals
of LiFePO$\rm_{4}$ and related materials have recently received a lot of
attention due to their very promising use as cathodes in rechargeable
lithium-ion batteries. The structural optimization was performed and the
equilibrium parameters such as the lattice constants, and the bulk modulus are
calculated using QE code and found to be a=4.76 {\AA}, b=6.00 {\AA}, c=10.28
{\AA}, B=90.2 GPa, respectively. The projected density of states (PDOS) for the
LiFePO$\rm_{4}$ material is remarkably similar to experimental results in
literature showing the transition metal $3d$ states forming narrow bands above
the O $2p$ band. The results of the various spin configurations suggested that
the ferromagnetic configuration can serve as a useful approximation for
studying the general features of these systems. In the absence of Li, the
majority spin transition metal $3d$ states are well-hybridized with the O 2p
band in FePO$\rm_{4}$. The result obtained with a DFT + U showed that LiFePO4
is direct band gap materials with a band gap of 3.82 eV, which is within the
range of the experimental values. The PDOS analyses show qualitative
information about the crystal field splitting and bond hybridization and help
rationalize the understanding of the structural, electronic, optical, and
magnetic properties of the LiFePO$\rm_{4}$ as a novel cathode material. On the
basis of the predicted optical absorbance, reflection, refractive index, and
energy loss function, LiFePO$\rm_{4}$ is demonstrated to be viable and
cost-effective, which is very suitable as a cathode material for Li-ion
battery.
