Porous Si/Cu6Sn5/C composite containing native oxides as anode material for lithium-ion batteries

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, scanning electron microscopy, Sn-119 Mossbauer spectroscopy, and X-ray photoelectron spectroscopy show that the composite has a pitaya-like morphology based on porous Si and embedded Cu6Sn5 non-porous microparticles with surface native oxides. Both Si and Cu6Sn5 are electrochemically active, and the activation process during the first charge-discharge improves the nanostructuration of the composite that helps 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 effect, enhanced electrode conductivity, and stable SEI due to the presence of native oxides and the use of FEC-containing electrolyte.