Nano-LiNi(0.5)Mn(1.5)O(4) spinel: a high power electrode for Li-ion batteries.

Disordered and ordered forms of nano-Li[Ni(0.5)Mn(1.5)]O(4) spinel, have been prepared by a one-pot resorcinol-formaldehyde synthesis. Lithium intercalation into disordered nano-Li[Ni(0.5)Mn(1.5)]O(4-delta) reveals good rate capability and cycling stability. It delivers 95.5% of the capacity at a rate of 10C (1500 mA g(-1)) and 88% at 20C (3000 mA g(-1)) compared with the capacity at low rate (0.2C). A capacity retention on cycling of 99.97% per cycle at 1C rate has also been observed. The superior electrochemical behaviour of disordered nano-Li[Ni(0.5)Mn(1.5)]O(4-delta) has been correlated with AC impedance data, which suggests a modified surface for the nanomaterial prepared using the resorcinol-formaldehyde route compared with micron sized materials prepared by conventional solid state synthesis.

Mesoporous and nanowire Co3O4 as negative electrodes for rechargeable lithium batteries.

The conversion reactions associated with mesoporous and nanowire Co(3)O(4) when used as negative electrodes in rechargeable lithium batteries have been investigated. Initially, Li is intercalated into Co(3)O(4) up to x approximately 1.5 Li in Li(x)Co(3)O(4). Thereafter, both materials form a nanocomposite of Co particles imbedded in Li(2)O, which on subsequent charge forms CoO. The capacities on cycling increase on initial cycles to values exceeding the theoretical value for Co(3)O(4) + 8 Li(+) + 8e(-) --> 4 Li(2)O + 3 Co, 890 mAhg(-1), and this is interpreted as due to charge storage in a polymer layer that forms on the high surface area of nanowire and mesoporous Co(3)O(4). After 15 cycles, the capacity decreases drastically for the nanowires due to formation of grains that are separated one from another by a thick polymer layer, leading to electrical isolation. In contrast, the mesoporous Co(3)O(4) losses its mesoporosity and forms a morphology similar to bulk Co(3)O(4) (Co particles imbedded in Li(2)O matrix) with which it exhibits a similar capacity on cycling. In contrast to mesoporous lithium intercalation compounds, which show superior capacity at high rates compared to bulk materials, mesoporosity does not seem to improve the capacity of conversion reactions on extended cycling. If, however, mesoporosity could be retained during the conversion reaction, then higher capacities could be obtained in such systems.