The present invention provides a method for the processing of particles of metal phosphates or particles of mixed metal phosphates and in particular lithiated metal phosphates and mixed metal phosphates. The processing occurs, for example using a mechanofusion system as depicted in FIGS. 1 and 2. In general, the powder materials are placed in a rotary container and are subjected to centrifugal force and securely pressed against the wall of the container. The material then undergoes strong compression and shearing forces when it is trapped between the wall of the container and the inner piece of the rotor with a different curvature (FIG. 2). Particles of the material are brought together with such force that they adhere to one another. In the mechanofusion system, as indicated in FIG. 2, the powder material is delivered through slits on the rotary walls. It is carried up above the rotors by the rotor-mounted circulating blades. Subsequently, the material returns again to the rotors where it is are subjected to strong compression and shearing forces from the inner pieces of the rotor. This cycle of both three-dimensional circulation and effective compression/shearing of the powder material is repeated at high speeds, thereby forming it into a composite electroactive material (powder).