Cu5Si–Si/C composites for lithium-ion battery anodes

Cu5Si–Si/C composites with precursor atomic ratio of Si:Cu = 1, 2 and 4.5 have been produced by high-energy ball-milling of a mixture of copper–silicon alloy and graphite powder for anode materials of lithium-ion battery. X-ray diffraction and scanning electron microscope measurements show that Cu5Si alloy is formed after the intensive ball milling and alloy particles along with low-crystallite Si are interspersed in graphite uniformly. Cu5Si–Si/C composite electrodes deliver a larger reversible capacity than commercialized graphite and better cyclability than silicon. The increase of copper amount in the composites decreases reversible capacity but improves cycling performance. Cu5Si–Si/C composite with Si:Cu = 1 demonstrates an initial reversible capacity of 612 mAh g−1 at 0.2 mA cm−2 in the voltage range from 0.02 to 1.5 V. The capacity retention is respectively 74.5 and 70.0% at the 40th cycle at the current density of 0.2 and 1 mA cm−2.