Li-doped SiO-negative active material (Li x SiO) has been successfully synthesized by chemical method with immersion in Li-organic complex solution obtained by dissolving naphthalene and metallic Li into butyl methyl ether (BME) solvent. The rest potential of resultant Li x SiO electrode drastically shifts to less noble value at the beginning of immersion and tends to be stable at around 0.21V versus Li/Li+, which means the progress of Li-doping into SiO-negative active material. Furthermore, this chemical Li-doping process proceeds by the catalysis function of naphthalene and leads to reduce the irreversible capacity of SiO-negative electrode caused by consumption of Li sources provided from positive electrode.