TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Powder: The pillars are formed from a material that, in use, undergoes volume expansion of at least 10% upon complete insertion into the material of the metal ions of the metal ion battery. The pillars comprise silicon. The core comprises silicon or carbon. The volume of the pillars is at least 20 (preferably at least 40)% of the total volume of the particles; A BET value of the pillared particles is less than 200 (preferably less than 100, especially less than 60, particularly less than 35) m2/g; and at least one dimension of the particle is less than 10 microns. An aspect ratio of the particle core is at least 2:1; an average pillar density of the pillars on the particle core is 10-80%; and mean average pillar diameter of less than 80 nm. Opposing surfaces of the particles carry pillars, where average length of the pillars is less than 5 (preferably less than 4) microns. Only one of two opposing surfaces of the particles carries pillars, where average length of the pillars is less than 10 (preferably less than 8) microns. The particles are discrete from one another. At least 50% or at least 90% of the total volume of the starting material powder is made up of starting material particles having a particle size of less than 15 microns or less than 25 microns respectively. The particle sizes are as measured by a laser diffraction method in which the particles being measured are assumed to be spherical, and in which particle size is expressed as a spherical equivalent volume diameter. Preferred Composition: The composition has a composite porosity, as a percentage of the total volume of the composite, which is at least the value given by the sum of the volume of pillars multiplied by 2 and the volume of particle cores multiplied by 1.2. Preferred Components: The additional component comprises at least one active component (preferably active carbon, especially graphite); at least one conductive, non-active component, optionally conductive non-active carbon; binder; and solvent. Preferred Method: In the method (M1), the pillars are grown on one surface only of the particles of the starting material powder. EXAMPLE - A powder comprising pillared particles was prepared by etching silicon granule starting material with BET of 0.67 m2/g; D10 size distribution of 8.2 mu m and D50 size distribution of 13.5 mu m, was prepared. Obtained pillared particles had BET of 32.9 m2/g.