Synthesis process for new particles of Li4Ti5O12, Li(4-α)ZαTi5O12 or Li4ZβTi(5-β)O12, wherein β is >0 and ≦0.5, α is a number >0 and ≦0.33, Z is 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. The process may involve the steps of a) preparing a dispersion of a mixture of TiOx—LizY-carbon, wherein x is a number between 1 and 2, z is 1 or 2, and Y is a radical chosen among CO3, OH, O and TiO3 or a mixture thereof; and 2) heating of the dispersion, preferably to a temperature of between about 400° C. and about 1000° C.