In this work, we investigated lithium-ion diffusion in spinel Li(4)Ti(5)O(12) nano-particles with carbon coating by electrochemical impedance spectroscopy (EIS), and proposed a hybrid model of the unsymmetrical lithium-ion pathway between charge and discharge processes. In this hybrid model, the charge process still follows the core-shell model, but in the discharge process, the phase transition evolves by growth of a few nuclei on the surface. And this hybrid model is possibly attributed to the nonuniform electron conductivity inside the Li(4)Ti(5)O(12) particles. Additionally, the relaxation process and the particle morphology are also carefully discussed in the experiment to show that this hybrid model is quite practical. Thereby, this investigation presents an unsymmetrical lithium-ion pathway in Li(4)Ti(5)O(12) particles, which could be extended to other active materials in lithium ion batteries.