Combinatorial Study of the Sn–Cu–C System for Li-Ion Battery Negative Electrode Materials

Abstract

Thin-film combinatorial sputter-deposited Sn–Cu–C alloys for negative electrodes of Li-ion batteries were characterized using electron microprobe (energy-dispersive spectroscopy), X-ray diffraction, electrochemical methods, and Mössbauer effect spectroscopy. Combinatorial libraries with nominal compositions with , , and and with were investigated. The addition of carbon was responsible for a decrease in grain size and an increase in specific capacity, which approached the calculated value (based on ). Mössbauer effect spectra were compared with differential capacity ( vs ) and it was determined that the sample with the best capacity retention most closely resembled nanostructured grains embedded in a C matrix, yielding over 90% capacity retention after 30 cycles. However, changes in vs suggested that regions of were steadily growing or aggregating as Li was cycled, which may be a limiting factor in later cycles.