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, ¹¹⁹Sn Mössbauer 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. [ABSTRACT FROM AUTHOR]