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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.

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Galvanostatic intermittent titration technique ͑GITT͒ at 25 and 50°C and electrochemical impedance spectroscopy ͑EIS͒ at 25°C as a function of cell voltage and cycle number were performed on the layered oxide cathode, Li͑Ni 1/3 Co 1/3 Mn 1/3 )O 2 . The Li-ion diffusion coefficient D Li ͑GITT) obtained for GITT was stable with a value of ϳ3 ϫ 10 Ϫ10 cm 2 /s in the voltage range, 3.8 -4.4 V vs. Li. The D Li ͑EIS) was higher by an order of magnitude than the D Li ͑GITT) in the above voltage range. A minimum in the D Li vs. voltage curve was observed at ϳ3.7 V coinciding with the voltage-plateau region in the charge-discharge cycling curves, indicating a possible reversible structural phase transition or order-disorder transition in the compound. EIS studies as a function of cycle number show that the surface film and the bulk contribution to the cell resistances remain stable with cycling. The proportional increase in charge-transfer resistance (R ct ) with cycling observed when charged to 50 mAh/g ͑ϳ3.7 V͒ and charged to 4.4 V of the cell indicate the possible influence of phase transition on the charge-transfer kinetics. The variation of D Li derived from GITT and EIS as a function of cell voltage and D Li ͑EIS) with the cycle number and the kinetic parameters obtained from the impedance plots were correlated with the electrochemical performance.

Giving in to templation: Lithium‐containing nanostructured transition metal oxides have been prepared by a templating route with preservation of the nanostructure. Both one‐dimensional nanowire and three‐dimensional mesoporous samples of low‐temperature (LT)‐LiCoO2 with highly crystalline structures (see image) have been obtained, and these perform better than “normal” LT‐LiCoO2 as intercalation electrodes in lithium batteries.