[en] We have studied the electrochemical and thermal properties of Li_4/3T_5/3O₄ spinel as a promising anode material for lithium ion batteries. The spinel/rock-salt two-phase transition process was interpreted using a core-shell model, which provided a good explanation of the different area-specific impedance behaviors during the charge and discharge processes. The constant dE/dT during the spinel/rock-salt phase transition was calculated from the heat-flow profile by isothermal microcalorimeter results and found to be around -0.04 mV/K. This very low and constant entropy change indicates that Li_4/3T_5/3O₄ is a good anode material in terms of thermal stability. Also, we propose that there is a new phase generation when more than one lithium atom is inserted into Li_4/3T_5/3O₄. According to the discontinuity of dE/dT results, the order/disorder transition at the low-voltage region (around 0.6 V vs Li) occurs during further lithium insertion