Elucidating the Electrochemical Properties of LiFe_0.5Mn_1.5O₄ as a High-Voltage, Low-Cost Material

Abstract

In this article, key electrochemical features of LiFe 0.5 Mn 1.5 O 4 (LFMO) such as phase stability, voltage behavior, and redox process during delithiation are investigated using density functional theory calculations implementing both PBE + U and SCAN functionals. Our findings indicate that numerous equally likely intermediates can be formed, regardless of the metallic distribution across all lithium compositions, thereby excluding a biphasic mechanism between LFMO and FMO. The shape of the experimental voltage−composition curve is well reproduced by both functionals predicting a voltage step in the half-lithiated LFMO, and the PBE + U functional is more accurate in predicting quantitatively the Mn and Fe plateaus, while SCAN underestimates them. The redox activity of Li x Fe 0.5 Mn 1.5 O 4 is primarily governed by the Mn 3+/4+ redox couple in the range of 0.5 ≤ x ≤ 1, whereas the Fe 3+/4+/(3.x+) couple operates in the region of 0 ≤ x ≤ 0.5, aligned with the experimental voltage−composition curves. The investigation of the redox process suggests the possibility of an anionic contribution that may be reversible in the case of the SCAN functional. This discovery paves the path for the next generation of high-voltage, environmentally friendly lithium-ion batteries with remarkable stability, enhanced performance, and cost-effective potential.