No abstract

No abstract

A NiSb−Al 2 O 3 −C nanocomposite alloy anode has been synthesized by high-energy mechanical milling, involving the mechanochemical reduction of Sb 2 O 3 by metallic Al and Ni in the presence of acetylene black carbon. X-ray diffraction and X-ray photoelectron spectroscopy confirm the presence of crystalline NiSb and amorphous Al 2 O 3 in the final nanocomposite. Transmission electron microscopy analysis shows the distribution of nanoscale crystalline NiSb particles in the matrix of Al 2 O 3 and carbon. The presence of reinforcing Al 2 O 3 and nanoscale active particles give this nanocomposite excellent cycle life with demonstrated capacity of 280 mAh g −1 to 1000 cycles. While the as-synthesized sample suffers from low coulombic efficiency of 55% in the first cycle and a large irreversible loss of roughly 350 mAh g −1 , post-heat-treatment processes dramatically reduce the irreversible loss to 150 mAh g −1 with a coulombic efficiency of 73%. Combined with good rate capability and a tap density of 1.3 g cm −3 , NiSb−Al 2 O 3 −C has significant potential as an alternative to graphite anodes in Li-ion batteries.

First-cycle irreversibility is a major problem that plagues many next-generation nanoscale anode materials which form solidelectrolyte interphase (SEI) layers. Without a method to compensate for this irreversible capacity loss, the full cells will face serious problems. The concept of a lithium reservoir in spinel cathodes was proposed in the early 90s to combat the irreversibility of graphite anodes, but chemical techniques to lithiate spinel have been complex or hazardous. We present in this study (i) a new facile microwave-assisted chemical lithiation technique for spinel oxide cathodes which is capable of inserting one extra lithium per formula unit using less expensive, readily available lithium hydroxide in polyol and (ii) two new advanced lithium-ion batteries combining a prelithiated 5 V spinel Li 1 + x Mn 1.5 Ni 0.5 O 4 or a 4 V spinel Li 1.05 + x Ni 0.05 Mn 1.9 O 4 cathode and a carbon-free FeSb-TiC alloy anode that has a high first-cycle irreversible capacity loss. We show that the extra chemically inserted lithium is necessary to achieve a complete utilization of the cathode capacity. The battery employing the 5 V spinel cathode exhibits good rate capability with an energy density of 260 Wh/kg based on total active mass.

High-density, high-rate FeSb-TiC-C nanocomposite alloy anodes composed of varying amounts of FeSb, TiC, and conductive carbon black have been synthesized by heating the metallic precursors first followed by high-energy mechanical milling (HEMM) of the product with carbon black. The synthesis method allows for a systematic variation of the TiC and carbon contents within the electrode so that the effects of each component on the electrochemical performance can be understood. The FeSb-TiC-C samples display high tap density (2.9 g cm À3 ), high reversible specific capacity (450 mA h g À1 ), superior volumetric capacity (1300 mA h cm À3 ), and high rate capability (89% retention of the C/5 capacity at 10 C rate).However, realizing a cycle life of >500 cycles requires increased contents of carbon and TiC, which lead to a reduction in reversible capacity and tap density. Incorporation of additives, such as fluoroethylene carbonate (FEC) or vinylene carbonate (VC), into the electrolyte provides moderate improvements in cycle life. The FeSb-TiC-C nanocomposite anodes with a high volumetric capacity at a moderate operating voltage offer an attractive alternative to graphite anodes with safety advantages.