The increasingly demand on secondary batteries with higher specific energy densities requires the replacement of the actual electrode materials. With a very high theoretical capacity (4200mAhg−1) at low voltage, silicon is presented as a very interesting potential candidate as negative electrode for lithium-ion microbatteries. For the first time, the electrochemical lithium alloying/de-alloying process is proven to occur, respectively, at 0.15V/0.45V vs. Li+/Li with Si nanowires (SiNWs, 200–300nm in diameter) synthesized by chemical vapour deposition. This new three-dimensional architecture material is well suited to accommodate the expected large volume expansion due to the reversible formation of Li–Si alloys. At present, stable capacity over ten to twenty cycles is demonstrated. The storage capacity is shown to increase with the growth temperature by a factor 3 as the temperature varies from 525 to 575°C. These results, showing an attractive working potential and large storage capacities, open up a new promising field of research.