Porous silicon and porous silicon particles are composite particles

Object of the present invention is to obtain a negative electrode material suitable for high capacity and good cycle characteristics of the lithium ion battery like porous silicon and porous silicon particles are composite particles. As a solution, the present invention is used as the porous silicon particle, which is (3) joining a plurality of silicon fine particles having a continuous porous silicon particle voids (1), wherein said silicon fine particles x standard deviation of the average diameter or diameter of struts 2nm ~ 2μm, or a particle diameter of the silicon pillar diameter [sigma] is 1 ~ 500nm, the mean x and the standard deviation [sigma] a ratio (σ / x) was 0.01 ~ 0.5. Further, porous silicon may be used as the composite particles, which are a plurality of silicon particles and the plurality of bonding the silicon compound particles having a continuous porous silicon voids composite particles, the apparatus comprising similar features.