Promoting lithium-ion battery performance by application of crystalline cathodes LixMn1−zFezPO4

Abstract

LiMnPO4 (LMP) is known as a typical cathode for application in lithium-ion-batteries (LIB), since this cathode produces higher voltage. However, the diffusivity of Li+ into LMP crystalline structure is not sufficiently high and its application accompanies a large energy waste due to hysteresis loss in the charge-discharge cycle. Therefore, in this work, it is intended to show that partial substitution of Mn with Fe, as a dopant to obtain a crystal with a general formula of LixMn1−zFezPO4 for application as a cathode in LIB, not only can increase the diffusivity of Li+ but also can improve other electrochemical properties of the resulting crystal, as a cathode, compared with pristine LMP or with similar cathodes such as LiFePO4 (LFP). To study the properties of this cathode, a multiscale procedure consisting of quantum mechanical (QM) approach at picoscale level and by recourse to density functional theory (DFT) calculations along with molecular dynamics(MD) simulation at the nanoscale level as well as pseudo-two-dimensional (P2D) electrochemical model at the macroscale level, the parameters affecting the performance of LIBs due to employing the cathodes LMP, LFP, and LixMn0.75Fe0.25PO4 (LMFP) are investigated and the obtained results, in comparison with the available experimental data are validated, justified, and interpreted. It is found that the cathode LMFP, if used as a cathode in a LIB, would results in higher efficiency and lower voltage drop compared with the commonly used cathode LMP as well as producing higher voltage power in comparison to LFP.