Silicon nanoparticles (SiNPs) can be synthesized by the hydrothermal method. This study synthesized silicon nanoparticles from rice husk ash using the hydrothermal method with ratios SiO2:Mg of 1:1.5, 1:2, and 1:2.5. A ratio of SiO2:Mg of 1:2.5 (SiNPs2.5) is the optimum for SiNPs synthesized, with a surface area and pore size of 41.69 m2/g and 8.28 nm, respectively. SiNPs2.5 was applied to a lithium-ion battery, yielding a capacity of 2101 mAh/g. © 2025 Elsevier B.V.