Synergistic Alloying of Na and P in <scp>LiMnSi</scp> <i>Half</i> ‐Heusler Alloy for Improved Metal‐Ion Battery Performance

ABSTRACT The quest for high‐performance, robust electrode materials with higher theoretical specific capacities and improved structural stability is a prominent area of research worldwide. This work explores the half ‐Heusler alloy LiMnSi as a novel electrode material using first‐principles density functional theory (DFT) calculations implemented in the WIEN2k code to investigate the electronic structure, open‐circuit voltage ( OCV ), and theoretical specific capacity. The pristine cubic lattice of LiMnSi undergoes a gradual structural change upon alloying (cubic → tetragonal → orthorhombic) and, eventually, the cubic phase reappears upon complete swapping. The formation energy, phonon dispersion, and elastic parameters determine the stability of the host structure and the alloyed phases. The band‐structure results for the host structure and its alloyed phases indicates a metallic nature. For Na x Li 1 − x MnSi, the calculated theoretical specific capacity increases from 33.64 to 225.04 as Na concentration in the alloy increases. A similar trend is observed for LiMnSi 1 − x P x , where the specific capacity increases from 37.08 to 253.55 mAh/g over the investigated composition range. OCV attains its maximum value at 87.5% substitution of Na and P, reaching 2.56 and 3.91 V, respectively. These findings suggest that optimal OCV and specific capacity can be tailored for these alloys, making them a potential candidate for electrodes in metal‐ion batteries.