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Ti-Fe-Si/C composites as anode materials for high energy li-ion batteries

ABSTRACT In this study, Ti-Fe-Si composites were prepared by one step ball-milling method as anode materials for Li-ion batteries. The effects of ball-milling speed and time were studied by X-ray diffraction, electron microscopy, and 57Fe Mössbauer spectroscopy. Changes in the composition and microstructure of the composites were observed and related to the electrochemical performance. Increasing ball-milling speed led to the formation of FeSix alloys that reduced the specific capacity while increasing the ball-milling time improved the particle size morphology and homogeneity. Discharge/charge profiles for the first two cycles were carried out at 0.05C current rate (1C = 1260 mAh.g−1for Li3.75Si). The first discharge for Ti-Fe-Si showed a LixSi reaction plateau of 1100 mAh.g−1, which were reversible and yielded columbic efficiency (CE) 77% and 90% in the first and second cycles, respectively. This capacity plateau indicated the insertion of about 3.25 Li into silicon. For the composite containing an additional 10% carbon SP, the theoretical capacity was about 1130 mAh.g−1, the discharge curve showed that the first discharge plateau reaches 1030 mAh.g−1 corresponding to 3.5 Li with the first CE was about 85%, and 98% for the second cycle. The addition of carbon to Ti-Fe-Si-C played a key role in capacity retention. The best results were obtained for the composite Fe/Ti/Si (1:1:2) with 10 wt% of carbon, ball-milled at 500 rpm for 48 hours. The specific capacities were about 900 mAh.g−1 at C/5 and 700 mAh.g−1 at 1C (C = 1200 mAg−1) with a capacity retention of about 90% for 100 cycles.