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In the present work, pellets of Li x Mn 2 O 4 polycrystalline powder samples with x = 0.8, 0.9, 1.0, 1.1, and 1.2 are analyzed to understand the effect of lithium concentration on the thermal and optical properties, and the electronic structure of Li x Mn 2 O 4 predicted in an earlier work using full-potential linear muffin-tin orbital ͑FP-LMTO͒ method is experimentally verified. The experimental tool used for the determination of the thermal and optical properties is the well-known photoacoustic technique. The variation of thermal diffusivity with changing x values in Li x Mn 2 O 4 is extensively studied to explain the influence of lithium concentration on the thermal properties, and has been correlated with the structural asymmetry and defects in Li x Mn 2 O 4 . The optical absorption spectrum, being the signature of the electronic structure of materials, is recorded in the visible range ͑350-800 nm͒. Six prominent absorption peaks associated with the O 2p-Mn t 2g , O 2p-Mn e g , and Mn t 2g -Mn e g band transitions for Li x Mn 2 O 4 , with x ഛ 1, are observed experimentally, substantiating the electronic structure predicted by the FP-LMTO method. However, it is observed that there are more absorption peaks in the case of Li 1.1 Mn 2 O 4 and Li 1.2 Mn 2 O 4 , which is attributed to the structural distortion from pure cubic spinel structure to a mixture of spinel and tetragonal structures, which is verified by the x-ray diffraction spectra.

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