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Controllable synthesis of uniform graphene–metal oxide nanocomposites is of great interest in energy storage applications, due to the combination of their merits and the synergistic effects on the enhancement of their electrochemical performance. Herein, we report a controllable synthesis of uniform mesoporous H-Nb2O5/rGO nanocomposites, which exhibit higher reversible specific capacity (∼190 mA h g−1), and better rate capability and cycling stability (the capacitance retention is 96.5% over 500 cycles) than pristine H-Nb2O5 microflowers, attributed to their large specific surface area (364.17 m2 g−1), porous structure, and intimate interface. More remarkably, the H-Nb2O5/rGO-based lithium ion hybrid supercapacitor (LIHS) delivered a high energy density of 100.2 W h kg−1 at 50 W kg−1 and still retained 18.3 W h kg−1 at an ultrahigh power density of 20 000 W kg−1, as well as an excellent cycling stability. It is worth noting that some other nanocomposites, including Zn2Ti3O8/rGO, Si/rGO, NaNbO3/rGO, Nb4N5/rGO, and H-Nb2O5/2D g-C3N4, have also been successfully synthesized by this method, demonstrating that it can be extended to prepare other functional nanocomposites for applications in energy conversion and storage, photocatalytic hydrogen production, sensors, and so on. [ABSTRACT FROM AUTHOR]

Micro-/nano-structured spherical intergrown LiMn2O4–LiNi0.5Mn1.5O4 (LMO–LNMO I, LiNi0.25Mn1.75O4) particles as a cathode material have been synthesized by an impregnation method with highly reactive chestnut-like MnO2 nano-spheres as a manganese source and structural template. The LMO–LNMO I consisted of aggregates of nano-sized particles with a well-defined cubic spinel structure. The electrochemical performance and thermostability of LMO–LNMO I are better than those of a simple mechanical mixture of LiMn2O4 and LiNi0.5Mn1.5O4 (LMO–LNMO M), and much better than those of individual LiMn2O4 and LiNi0.5Mn1.5O4 monomers. Within this special structure, LNMO acts as a skeleton to stabilize the structure of LMO and enables more lithium ions in LMO to participate in the charge–discharge process along with those in LNMO, leading to high specific discharge capacities. In addition, this material exhibits excellent cycle stabilities at room temperature (25 °C) as well as at elevated temperature. It presented a discharge capacity of 130 mA h g−1, with 96.2% capacity retention after 100 cycles at 25 °C at 1 C. When the temperature and rate are increased to 55 °C and 5 C, it still delivers a discharge capacity of 131 mA h g−1, with a capacity retention of 95% after 100 cycles. Being synthesized by a special impregnation method, LMO–LNMO I shows a more homogeneous ion mixing of Ni and Mn in the structure at the atomic level with a more enhanced thermostability due to its high Mn content compared to LNMO. The structural stability and high electrical conductivity of LMO–LNMO I are responsible for the excellent electrochemical performance and outstanding thermal stability. [ABSTRACT FROM AUTHOR]