Natural graphite with a high capacity for lithium-ion cells is obtained by the chemical flaking of natural graphite along cleavage planes. Flaking of graphite (foliated graphite) is obtained via: (i) formation of expanded graphite from natural graphite by acid treatment, and (ii) mechanical and ultrasonic powdering of expanded graphite. This treatment is useful even for natural graphite, that contains a large ash content, which shows very poor capacity and large polarization.