Abstract: Silicon-containing composite particles, the process comprising the steps of: (a) providing a plurality of porous particles comprising micropores and/or mesopores, wherein the D50 particle diameter of the porous particles from 0.5 to 200 ?m; the total pore volume of micropores and mesopores is from 0.4 to 2.2 cm3/g; and the PD50 pore diameter is no more than 30 nm; c (b) combining a charge of the porous particles with a charge of a silicon-containing precursor in a batch pressure reactor, wherein the charge of porous particles has a volume of at least 20 cm3 per litre of reactor volume (cm3/LRV), and wherein the charge of the silicon-containing precursor comprises at least 2 g of silicon per litre of reactor volume (g/LRV); and (c) heating the reactor to a temperature effective to cause deposition of silicon in the pores of the porous particles, thereby providing the silicon-containing composite particles.