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Owing to the abundant storage and environmentally benign of Na, Fe, and Mn elements, FeMn-based O3-type NaFe0.5Mn0.5O2 materials were considered to be a promising cathode for sodium-ion batteries. However, the poor rate performance was barely satisfactory to the commercial production. Here, different Na content O3-type NaxFe0.5Mn0.5O2 (x = 1, 0.9, 0.8) for sodium-ion batteries were synthesized by solid-state reaction. The results illustrated that Na-deficient compound was beneficial to improve the rate performance and discharge capacity. Due to the Na-deficient in the octahedral sites, O3-type Na0.8Fe0.5Mn0.5O2 achieved a discharge capacity of 179 mAh g−1 at 0.1 C, which is relatively higher than that of O3-type NaFe0.5Mn0.5O2 (145 mAh g−1). Besides, the O3-type Na0.8Fe0.5Mn0.5O2 exhibited an initial discharge capacity of 126 mAh g−1 and outstanding capacity retention of 82.6% after 60 cycles at 1C. The excellent performance indicates that nontoxic and earth-abundant Na-deficient O3-type cathode may be a promising cathode for large-scale application and development of sodium-ion batteries. [ABSTRACT FROM AUTHOR]

Although sheet-like materials have good electrochemical properties, they still suffer from agglomeration problems during the electrocatalytic process. Integrating two-dimensional building blocks into a hollow cage-like structure is considered as an effective way to prevent agglomeration. In this work, the hierarchical NiCo2O4 nanocages were successfully synthesized via coordinated etching and precipitation method combined with a post-annealing process. The nanocages are constructed through the interaction of two-dimensional NiCo2O4 nanosheets, forming a three-dimensional hollow hierarchical architecture. The three-dimensional supporting cavity effectively prevents the aggregation of NiCo2O4 nanosheets and the hollow porous feature provides amounts of channels for mass transport and electron transfer. As an electrocatalytic electrode for methanol, the NiCo2O4 nanocages-modified glassy carbon electrode exhibits a lower overpotential of 0.29 V than those of NiO nanocages (0.38 V) and Co3O4 nanocages (0.34 V) modified glassy carbon electrodes. The low overpotential is attributed to the prominent electrocatalytic dynamic issued from the three-dimensional hollow porous architecture and two-dimensional hierarchical feature of NiCo2O4 building blocks. Furthermore, the hollow porous structure provides sufficient interspace for accommodation of structural strain and volume change, leading to improved cycling stability. The NiCo2O4 nanocages-modified glassy carbon electrode still maintains 80% of its original value after 1000 consecutive cycles. The results demonstrate that the NiCo2O4 nanocages could have potential applications in the field of direct methanol fuel cells due to the synergy between two-dimensional hierarchical feature and three-dimensional hollow structure. [ABSTRACT FROM AUTHOR]

In this paper, a facile chemical bath deposition method was utilized to synthesize three-dimensional nanostructured CoNi 2 S 4 /Co 9 S 8 (CNSCS) composites as advanced electrode materials for high performance supercapacitors. CNSCS composites showed remarkable electrochemical performance owing to the high porosity, appropriate pore size distribution, novel architecture and synergistic effect of Ni/Co ions. The electrochemical tests revealed that CNSCS composites exhibited high specific capacitance (1183.3 Fg −1 at the current density of 2 Ag −1 ), excellent rate performance (74.9% retention with tenfold current density increase) and outstanding cycle life stability. Moreover, the effect of temperature on electrochemical performance of CNSCS composites was investigated and the results indicated the specific capacitance of CoNi 2 S 4 /Co 9 S 8 can keep relatively stable in a wide temperature from 0 °C to 50 °C. These results indicated that the synthesized CNSCS composites can be a promising electrode materials candidate for supercapacitors and chemical bath deposition is a promising processing route for CNSCS composites production. [ABSTRACT FROM AUTHOR]