Abstract
Porous Si/Cu6Sn5/C composite containing native oxides was prepared via solid state mechanical milling and wet chemical etching. This composite was used as anode material for Li-ion batteries. X-ray diffraction, electron microscopy, 119 Sn Mössbauer spectroscopy and X-ray photoelectron spectroscopy show that the composite has a pitaya-like morphology based on porous Si and embedded Cu6Sn5 nonporous microparticles with surface native oxides. Both Si and Cu6Sn5 are electrochemically active and the activation process during the first charge-discharge cycles improves the nanostructuration of the composite that helps to buffer the volume variations of the Li-Si and Li-Sn alloying reactions. The porous composite delivers a reversible and stable capacity of 900 mAh.g-1 at a galvanostatic current density of 422 mA.g-1 with a retention of 90% for 100 cycles, which is higher than porous Si (53%). The stability during cycling is explained by buffering effects, enhanced electrode conductivity and stable SEI due to the presence of native oxides and the use of FEC-containing electrolyte.