<p>We present an integrated computational and experimental study of the structural and functional properties of LiX₅Sb₁₁(<i>X</i> = Fe, Mn) skutterudite compounds. X-ray diffraction analysis verifies the crystal structure for both materials, with LiMn₅Sb₁₁ displaying a contracted unit cell compared to LiFe₅Sb₁₁, consistent with the smaller ionic radius of Mn²⁺. Advanced mBJ electronic structure calculations reveal direct bandgaps of 1.7&#xa0;eV and 1.5&#xa0;eV for the Fe and Mn compounds, respectively. The materials exhibit fundamentally different charge transport characteristics, with LiFe₅Sb₁₁ demonstrating superior electrical conductivity, while LiMn₅Sb₁₁ shows enhanced thermopower attributable and phonon dispersion calculations, indicating stronger rattling modes in the Mn variant, leading to a 22% reduction in lattice thermal conductivity relative to an exceptional thermoelectric figure-of-merit (ZT = 0.95) for LiMn₅Sb₁₁. Optical characterization reveals distinct absorption profiles, with LiFe₅Sb₁₁ exhibiting broadband absorption suitable for photovoltaic applications, while LiMn₅Sb₁₁ displays sharp excitonic features advantageous for optoelectronic devices.</p>