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Multi-shell structured binary transition metal oxide powders with a Ni/Co mole ratio of 1:2 are prepared by a simple spray drying process. Precursor powder particles prepared by spray drying from a spray solution of citric acid and ethylene glycol have completely spherical shape, fine size, and a narrow size distribution. The precursor powders turn into multi-shell powders after a post heat-treatment at temperatures between 250 and 800 °C. The multi-shell structured powders are formed by repeated combustion and contraction processes. The multi-shell powders have mixed crystal structures of Ni 1− x Co 2 O 4− x and NiO phases regardless of the post-treatment temperature. The reversible capacities of the powders post-treated at 250, 400, 600, and 800 °C after 100 cycles are 584, 913, 808, and 481 mA h g −1 , respectively. The low charge transfer resistance and high lithium ion diffusion rate of the multi-shell powders post-treated at 400 °C with optimum grain size result in superior electrochemical properties even at high current densities. [ABSTRACT FROM AUTHOR]

Li2TiO3–LiCrO2 cathode powders of various compositions are prepared by spray pyrolysis. Pure Li2TiO3 powder and Li2TiO3–LiCrO2 composite cathode powder have a spherical shape, nonaggregated structure, and fine sizes even after post-treatment at 700 °C under nitrogen atmosphere. The optimum post-treatment temperature to obtain composite powders with high initial discharge capacity, high coulombic efficiency, and good cycle properties is 700 °C. The initial charge capacities increase when the LiCrO2 content of the composite increase. However, the 0.55Li2TiO3–0.45LiCrO2 composite cathode powders have the highest initial discharge capacity of 203 mAh g−1, in which the capacity retention after 30 cycles is 96%. The dQ/dV curve of the first charge curve has a distinct oxidation peak at approximately 3.9 V, which corresponds to Cr oxidation. The oxidation peak shifts to a lower voltage range at approximately 3.6 V after the first cycling because an irreversible reaction takes place in the initial charge process. The composite cathode powders with low LiCrO2 content have low initial charge/discharge capacities and good cycle properties because of the stabilizing effect of high amounts of an inactive Li2TiO3 component. [ABSTRACT FROM AUTHOR]

Pure LiCoO2 nanopowders and those coated with lithium boron oxide (LBO) glass are prepared directly using high-temperature flame spray pyrolysis. Prior to post-treatment, the LiCoO2 powders with nanometer-size particles have low discharge capacities and poor cycle properties, irrespective of the amount of glass material. Post-treatment at 500 °C does not improve these properties significantly; however, the LBO glass-modified LiCoO2 powders post-treated at 600 and 700 °C demonstrates good cycle performance. The discharge capacity of the 5 wt% glass-modified LiCoO2 powders post-treated at 600 °C with a mean particle size of 120 nm, decreases from 122 to 109 mAh g−1 after 50 cycles, with a capacity retention of 89%. The capacity retentions of the pure and 2, 5, and 10 wt% glass-modified LiCoO2 powders post-treated at 700 °C are 86, 96, 98, and 98% after 50 cycles, respectively. [ABSTRACT FROM AUTHOR]

Abstract: Li2O–2B2O3 glass-modified LiMn2O4 cathode powders are prepared using spray pyrolysis. The powders with 1 and 5wt% glass material have a spherical shape, dense structure, and large grain size. The BET surface areas of LiMn2O4 powders with 0 and 1wt% glass material are 15.0 and 5.9m2 g−1, and their mean crystallite sizes are 29 and 49nm. The lithium boron oxide (LBO) glass material improves the cycle properties as well as the initial discharge capacities of the LiMn2O4 powders at a constant current density of 1C. The discharge capacity of LiMn2O4 powders without any glass material decreases from 116.3 to 92.6mAhg−1 after 100 cycles, the reduced capacity being 80% of the initial capacity. However, the discharge capacity of the LiMn2O4 powders with 1wt% glass material decreases from 131.0 to 113.2mAhg−1 after 100 cycles; thus, the capacity retention is 86% of the initial capacity. [Copyright &y& Elsevier]

Abstract: Spherically shaped vanadium pentoxide (V2O5) cathode powders with porous or dense morphologies are prepared directly via spray pyrolysis by varying the preparation temperatures between 600 and 1000°C. The powders prepared at 600°C consist of nanometer-sized rod-shaped crystals with porous structures. The V2O5 powders prepared at 1000°C have spherical shapes, clean surfaces, and dense structures, because of complete melting of the powders that occurs inside the hot-wall reactor. The Brunauer–Emmett–Teller (BET) surface areas of the V2O5 powders decrease from 24.7 to 3.2m2 g−1 when the preparation temperature increases from 600 to 1000°C. The V2O5 powders prepared at 1000°C have better cycle properties than those prepared at 600 and 800°C. The discharge capacity of the V2O5 powders prepared at 1000°C decreases from 432mAhg−1 to 263mAhg−1 after 20 cycles, in which the capacity retention is 61%. [Copyright &y& Elsevier]