Rational design, convenient fabrication, and application of double-shelled hollow architectures with well-defined morphology and multicompositions as electrodes for rechargeable batteries still remain great challenges. Herein, double-shelled Ni− Fe−P/N-doped carbon nanoboxes (defined as Ni−Fe−P/NC) were synthesized and then applied as electrode materials for potassiumion batteries (KIBs) and Li−S batteries, first. The unique architectures could not only alleviate volume changes and prevent aggregation of Ni−Fe−P/NC during cycling but could also provide efficient surface areas for infiltration of electrolyte. Additionally, nitrogen-doped carbon could improve the conductivity of the electrode. Hence, when these Ni−Fe−P/NC nanoboxes were applied as anode materials for KIBs, they delivered enhanced cycling stability (172.9 mA h g −1 after 1600 cycles at 500 mA g −1 and 115 mA h g −1 after 2600 cycles at 1000 mA g −1 ). Meanwhile, the Ni−Fe−P/NC could also be used as the sulfur host material for Li−S batteries; benefiting from its unique hollow structure, it can accommodate high sulfur loading and have strong chemical adsorption ability to polysulfides.

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Uniform hierarchical porous MnCo2O4 and CoMn2O4 microspheres (3-6 µm) were fabricated through solvothermal process followed by a post annealing treatment. Fascinatingly, these porous MnCo2O4 and CoMn2O4 microspheres are composed of numerous polyhedral nanoparticles with diameters in the range of 200-500 nm. The porous structure is believed beneficial for improving the lithium-storage performance of the products, which can effectively buffer the volume expansion during Li + insertion/extraction process and shorten the Li + diffusion lengths. Polyhedral structure can enhance the electrolyte/electrode contact area and increase the Li + insertion/extraction sites. When used as anode materials for lithiumion batteries, the porous MnCo2O4 and CoMn2O4 microspheres exhibited excellent long-life cycling performance at high rate density. At current density of 1000 mA g -1 , the MnCo2O4 and CoMn2O4 exhibite initial capacity of 1034 and 1107 mAh g -1 and the capacity maintain at 740 and 420 mAh g -1 after 1000 cycles. Furthermore, the growth mechanism of porous microspheres is proposed based on many contrast experiments. The relationship between morphology evolution and annealing time is particular investigated in detail. It is find that the annealing time plays an important role to get products with different morphologies. Through controlled annealing time, porous microspheres, yolk-shell microspheres and solid microspheres could be selectively obtained.