Investigation on Lithiated Half-Heusler Alloy CoMnSi for Lithium-Ion Batteries

Abstract

In this work, we report on CoMnSi half-Heusler alloy as a cathode material for secondary lithium-ion batteries using ab initio methodology based on the density functional theory. The first-principle calculations have been performed via the Wien2k package, which utilizes the full potential linearized augmented plane wave (FP-LAPW) method to estimate the stability of the proposed structures and electronic characteristics while considering the exchange and correlation effects within the generalized gradient approximation. This alloy is found structurally stable with better electronic properties and with the alloying of lithium (Li) into the host lattice of CoMnSi, the metallic character is attained for Li_xCo_1−xMnSi (0.125 ≤ x ≤ 1). We propose possible reactions at electrodes during the electrochemical lithiation. The addition of Li in place of the Co atom is found to be an endothermic process. With the increase in lithium concentration, a substantial change in the total and atom projected density of states around the Fermi level is observed. The theoretical maximum specific capacity (C_M) and theoretical open circuit voltage (OCV) increase with the increase of lithium concentration in CoMnSi. The C_M and OCV values attain a maximum value of around 297 mAh/g and 2.4 Volts for x ≥ 0.75, which means towards the complete conversion of CoMnSi into LiMnSi. The LiMnSi exhibits a similar structure as CoMnSi, which is also advantageous for the overall performance of lithium-ion batteries to avoid any volumetric change during the charging and discharging cycles. Hence, the proposed half-Heusler alloys have great potential to be used as a cathode material for lithium-ion batteries.