A first-order transition at 290 K in LiMn 2 O 4 with a cubic spinel-type structure is known to degrade the electrochemical performance of the positive electrode of rechargeable lithium-ion batteries. Using firstprinciples density functional theory (DFT), we confirm that the phase transition is induced by chargeordering of Mn 3+ /Mn 4+ accompanied by orbital-ordering due to Jahn-Teller distortion, which is in agreement with the previous experimental results of RodrΓguez-Carvajal et al. [J. RodrΓguez-Carvajal, G. Rousse, C. Masquelier, M. Hervieu, Phys. Rev. Lett. 81 (1998) 4660]. The optimized structure of the lowtemperature (LT) phase has orthorhombic symmetry with five distinct crystallographic sites for Mn. The spin integration at each Mn site shows that Mn 3+ resides at three Mn sites and the remaining two sites are occupied by Mn 4+ ions. Total energy calculations indicate that the LT phase is about 0.23 eV/LiMn 2 O 4 more stable than cubic LiMn 2 O 4 (high-temperature phase). The electrochemical Li extraction reaction from the LT phase is also investigated using DFT calculations. The results indicate that the reaction is initially divided into two voltage regions. Electrostatic interactions in the LT phase are calculated using a point charge model, accounting for the features of the electronic configurations and electrochemical reactions.