In this work, we performed ab initio calculations within the density-functional theory framework to study the electrochemical and kinetic properties of silicate materials with the olivine morphology, that can be suitable for the cathode of rechargeable Li-ion batteries. Our study shows that the migration barriers for polaron-Li complex diffusion in the multicomponent silicates are in a reasonable range (227-248 meV), compared to similar systems. The results show that, although the Li vacancies are strongly bounded to polarons, these materials might not be as insulating as previously assumed, provided that an adequate carrier concentration can be achieved. The effects of the different transition metals on the local structure, electrochemical and electronic properties and on the kinetic mobility of the polaron-Li ion complex are discussed, showing a useful strategy to tailor the electrochemical properties of this family of silicate cathode materials, in order to enhance the energy density and rate capability of the Li-ion battery. (C) 2014 The Electrochemical Society. All rights reserved.