CoMn 2 O 4 nanomaterials are prepared by a low temperature precipitation route employing metal acetates and NaOH. Structural changes, induced by different annealing temperatures, are comprehensively analyzed by X-ray powder diffraction and Raman spectroscopy. With rising annealing temperature the crystal lattice of CoMn 2 O 4 undergoes changes; AO 4 tetrahedra expand due to thermally induced substitution of Co 2+ by larger Mn 2+ metal ions on the A-site of the spinel structure, while in contrast, BO 6 octahedra shrink since the B-site becomes partially occupied by smaller Co 3+ metal ions on account of the migrated Mn ions. CoMn 2 O 4 particle sizes are easily fine-tuned by applying different annealing temperatures; the particle size increases with increasing annealing temperature. During the battery operation, pulverization and reduction of particle sizes occurs regardless of the initial size of the particles, but the degree of division of the particles during the operation is dependent on the initial particle properties. Thus, contrary to the common assumption that nanostructuring of the anode material improves the battery performance, samples with the largest particle sizes exhibit excellent performance with a capacity retention of 104% after 1000 cycles (compared to the 2 nd cycle).

Characterization of nanocrystalline triple perovskites synthesized by a novel modified sol–gel route instead of bulk materials synthesized by a solid-state route.

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Cation distribution between tetrahedral and octahedral sites within the ZnMn2O4 spinel lattice, along with microstructural features, is affected greatly by the temperature of heat treatment. Inversion parameter can easily be tuned, from 5 to 19%, depending on the annealing temperature. The upper limit of inversion is found for T= 400 °C as confirmed by X-ray powder diffraction and Raman spectroscopy. Excellent battery behavior is found for samples annealed at lower temperatures; after 500 cycles the specific capacities for as-prepared ZnMn2O4 is 909 mAh/g, while ZnMn2O4 heat-treated at 300 °C shows 1179 mAh/g which amounts to 101 % of its initial capacity. Despite excellent performance of sample processed at 300 °C at lower charge/discharge rates (100 mAh/g), a drop in the specific capacity is observed with rate increase. This issue is solved by graphene oxide wrapping; specific capacity obtained after 400th cycle for graphene oxide wrapped ZnMn2O4 heat-treated at 300 °C is 799 mAh/g at charge/discharge rate 0.5 A/g, which is higher by factor 6 compared to sample without graphene oxide wrapping.