Synthesis process for new particles of Li4Ti5O12, Li(4-α)ZαTi5O12 or Li4ZβTi(5-β)O12, preferably having a spinel structure, wherein β is greater than 0 and less than or equal to 0.5 (preferably having a spinel structure), α representing a number greater than zero and less than or equal to 0.33, Z representing a source of at least one metal, preferably chosen from the group made up of Mg, Nb, Al, Zr, Ni, Co. These particles coated with a layer of carbon notably exhibit electrochemical properties that are particularly interesting as components of anodes and/or cathodes in electrochemical generators.