Potato-shaped graphite particles with low impurity rate at the surface, method for preparing same

modified graphite particles obtained from graphite based or graphite, said particles having impurities in their internal structure and having on the surface a low or even zero for one or more impurities. These particles further have at least one of the following: a tab density between 0.3 and 1.5 g / cc; the form of a potato-shaped; and a granulometric dispersion such that the D90 / D10 ratio varies between 2 and 5 and the particles have a size between 1 and 50 .mu.m. These particles are useful for fuel cells, electrochemical generator or as a moisture sensor and / or oxygen absorbers and they possess useful electrochemical properties. Electrochemical cells and batteries thus obtained are safe and stable.