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This study reports the synthesis of hierarchical NiCoO2 nanosheets growing on hollow carbon spheres (denoted as NiCoO2 NSs@HCS) via a facile and low‐cost process. When evaluated as anode materials for lithium‐ion batteries, the as‐prepared NiCoO2 NSs@HCS exhibits high specific capacity, enhanced cycling stability, and good rate capability. A high discharge capacity of 631.7 mA h g−1 is delivered even after 200 cycles at a current density of 400 mA g−1, corresponding to approximately 92 % of the second reversible discharge capacity. The hierarchical and hollow structure of NiCoO2 NSs@HCS plays a role in its excellent performance. Advanced architecture: A new hierarchical material consisting of NiCoO2 nanosheets grown on hollow carbon spheres was used as the anode material in lithium‐ion batteries (see figure). This material not only buffers the large volume change during the charging–discharging processes, but also provides more active sites for lithium‐ion storage. Even after 200 cycles at a current density of 400 mA g−1, a high discharge capacity of 631.7 mAh g−1 is retained. [ABSTRACT FROM AUTHOR]

We report the synthesis and application of ordered mesoporous TiNb6O17 microspheres (M-TNO) using a one-step solvothermal method for the first time in lithium-ion batteries. The diameters of TiNb6O17 microspheres are in the range from 2.2 to 2.4 μm with a mesopore size of about 35 nm, which promotes the electron and ion migration in charge/discharge processes. M-TNO shows a high specific capacitance (307.2 mA h g−1) at a low current density of 0.2 C and a long-term cycle life over 500 cycles as an electrode. The retentive capacity of the batteries is 77% of the initial cycle after 500 cycles. It is worth noting that M-TNO exhibits excellent rate capacity, which decreases slowly from 265.7 to 172.4 mA h g−1 with the current density increasing from 1 C to 30 C. The retentive capacity at a current density of 30 C is 65% compared to that at 1 C. [ABSTRACT FROM AUTHOR]

Hierarchical hybrid nanostructures based on flexible graphene sheets and ternary transition metal oxides have attracted special attention as high-performance electrode materials for next-generation lithium-ion batteries (LIBs) yet their practical application is often beset with challenges. In this work, we report a hierarchical hybrid nanocomposite of reduced graphene oxide supported mesoporous Co3V2O8 nanoparticles (rGO@Co3V2O8 NPs) through a simple hydrothermal synthesis and post-calcination. This unique hybrid architecture when used as an anode in LIBs would effectively facilitate charge transfer, maintain structural integrity and accommodate the volume variation of the electrode materials during the repeated charge/discharge processes. As a result, the hybrid rGO@Co3V2O8 NPs manifest a very stable high reversible capacity of 1050 mA h g−1 over 200 cycles at a current density of 50 mA g−1 and excellent rate capability. Importantly, even when cycled at a higher current density of 200 mA g−1, a stable reversible capacity of 899 mA h g−1 and a remarkable cycling stability could also be achieved after 600 cycles. These results indicate the potential suitability of such mesoporous nanoparticles on graphene nanostructures for high-rate and long cycle life anode materials. [ABSTRACT FROM AUTHOR]

Ultrathin CoMn2O4 nanosheets supported on reduced graphene oxide (rGO) are successfully synthesized through a simple co-precipitation method with a post-annealing treatment. With the assistance of citrate, the free-standing CoMn2O4 ultrathin nanosheets can form porous overlays on both sides of the rGO sheets. Such a novel hybrid nanostructure can effectively promote charge transport and accommodate volume variation upon prolonged charge/discharge cycling. When evaluated as a promising electrode for supercapacitors in a 6 M KOH solution electrolyte, the hybrid nanocomposites demonstrate highly enhanced capacitance and excellent cycling stability. [ABSTRACT FROM AUTHOR]

Hybrid nanosheet structures based on carbon coated metal oxides still attract promising interest as high-performance electrode materials for next-generation lithium-ion batteries (LIBs). In this study, we develop a simple one-pot solution method to synthesize large-scale flat Fe3O4 nanosheet hybrid structures coated with an amorphous carbon overlayer (denoted as Fe3O4@C NSs) followed by a thermal annealing treatment. It is found that the refluxing temperature plays an important role in adjusting the morphology of the Fe3O4@C hybrid. Increasing the temperature from 140 °C to 200 °C will lead to flower-like hybrid structures constructed by Fe3O4 nanoflakes gradually growing, rupturing, and finally evolving into flat and completely separate nanoflakes with large size at 200 °C. When evaluated as an anode material for LIBs, the hybrid Fe3O4@C NSs demonstrate a high reversible capacity of 1232 mA h g−1 over 120 cycles at a current density of 200 mA g−1, and remarkable rate capability. [ABSTRACT FROM AUTHOR]

The growth of ultrathin ZnCo2O4 nanosheets on reduced graphene oxide (denoted as rGO/ZnCo2O4) via a facile low‐temperature solution method combined with a subsequent annealing treatment is reported. With the assistance of citrate, interconnected ZnCo2O4 nanosheets can assemble into hierarchically porous overlays on both sides of rGO sheets. Such a hybrid nanostructure would effectively faciliate the charge transport and accommodate volume variation upon prolonged charge/discharge cycling for reversible lithium storage. As a result, the rGO/ZnCo2O4 nanocomposite manifests a very stable high reversible capacity of around 960 mAh g−1 over 100 cycles at a low current density of 90 mA g−1 and excellent rate capability. [ABSTRACT FROM AUTHOR]

In this paper, we report a facile approach to the synthesis of one-dimension (1D) hierarchical NiCoO2 nanosheets (NSs)@amorphous CNT composites based on the templates and carbon source of polymeric nanotubes (PNTs). Importantly, these sulfonated PNTs can also be used to prepare many other functional 1D metal oxides@amorphous CNT nanostructures, such as TiO2, SnO2, CoO and NiO, etc. Due to the outstanding nanostructures and the synergistic effects of the NiCoO2 NSs and amorphous CNTs, an ultrahigh discharge capacity of 1309 mA h g-1 is delivered by the NiCoO2@CNT composites, even after 300 cycles at a current density of 400 mA g-1. The favorable improvements of the NiCoO2 based lithium-ion batteries (LIBs) reported in this work illustrate that the 1D amorphous carbon matrix offers significant benefits for high-capacity metal oxide anode nanomaterials. [ABSTRACT FROM AUTHOR]

One-dimensional nanostructures of ultrathin standing α-Ni(OH)2 nanosheets@halloysite nanotubes are synthesized through one-step facile precipitation method. The nanocomposites exhibit high capacitance (1677 F g-1) and excellent cycling stability (100% capacity retention after 2000 cycles) due to their ultrathin and standing nanosheets and intense cation/anion exchange performance of halloysite nanotubes. The remarkable electrochemical performance will undoubtedly make the hybrid structures attractive for high-performance supercapacitors. [ABSTRACT FROM AUTHOR]

The Ge-based compounds show great potential as replacements for traditional graphite anode in lithium-ion batteries (LIBs). However, large volume changes and low conductivity of such materials result in a poor electrochemical cycling and rate performance. Herein, we fabricate a self-supported and three-dimensional (3D) sponge-like structure of interlinked Zn 2 GeO 4 ultrathin nanosheets anchored vertically on a nickel foam (ZGO NSs@NF) via a simple hydrothermal process assisted by cetyltrimethyl ammonium bromide (CTAB). Such robust self-supported hybrid structures greatly improve the structural tolerance of the active materials and accommodate the volume variation that occurs during repeated electrochemical cycling. As expected, the self-supported ZGO NSs@NF composites demonstrate an excellent lithium storage with a high discharge capacity, a long cycling life, and a good rate capability when used as binder-free anodes for LIBs. A high reversible discharge capacity of 794 mA h g -1 is maintained after 500 cycles at 200 mA g -1 , corresponding to 81% capacity retention of the second cycle. Further evaluation at a higher current density (2 A g -1 ) also delivers a reversible discharge capacity (537 mA h g -1 ) for this binder-free anode. This novel 3D structure of the self-supported ultrathin nanosheets on a conductive substrate, with its volume buffer effect and good interfacial contacts, can stimulate the progress of other energy-efficient technologies.

Nickel hydroxide (Ni(OH) 2 ) has been regarded as a potential next-generation electrode material for supercapacitor owing to its attractive high theoretical capacitance. However, practical application of Ni(OH) 2 is hindered by its lower cycling life. To overcome the inherent defects, herein we demonstrate a unique interconnected honeycomb structure of g-C 3 N 4 and Ni(OH) 2 synthesized by an environmentally friendly one-step method. In this work, g-C 3 N 4 has excellent chemical stability and supports a perpendicular charge-transporting direction in charge-discharge process, facilitating electron transportation along that direction. The as-prepared composite exhibits higher specific capacities (1768.7 F g -1 at 7 A g -1 and 2667 F g -1 at 3 mV s -1 , respectively) compared to Ni(OH) 2 aggregations (968.9 F g -1 at 7 A g -1 ) and g-C 3 N 4 (416.5 F g -1 at 7 A g -1 ), as well as better cycling performance (∼84% retentions after 4000 cycles). As asymmetric supercapacitor, g-C 3 N 4 @Ni(OH) 2 //graphene exhibits high capacitance (51 F g -1 ) and long cycle life (72% retentions after 8000 cycles). Moreover, high energy density of 43.1 Wh kg -1 and power density of 9126 W kg -1 has been achieved. This attractive performance reveals that g-C 3 N 4 @Ni(OH) 2 with honeycomb architecture could find potential application as an electrode material for high-performance supercapacitors.

Ultrathin cobalt ferrite nanosheets have been successfully assembled on the surface of reduced graphene oxide (rGO) via only adjusting the volume ratio of ethanol and deionized (DI) water and a post calcination treatment. The perpendicular ultrathin cobalt ferrite nanosheets supported by rGO sheets (CoFe 2 O 4 NSs@rGO) can be obtained when the volume ratio of ethanol and DI water is 10:30. Correspondingly, the hierarchical porous films covering the total rGO sheets will be formed nanosheets. When evaluated as the electrodes for lithium ion batteries (LIBs) and supercapacitors (SCs), the resultant CoFe 2 O 4 NSs@rGO hybrids exhibit highly enhanced electrochemical performance. Even after 200 charge-discharge cycles at 400 mA g -1 , the electrodes as the anode material for LIBs still exhibit a reversible discharge capacity of 835.6 mAh g -1 . In addition, this electrode for SCs also exhibits specific capacitance of ca 1120 F g -1 after 3000 cycles. These superior results imply that CoFe 2 O 4 NSs with novel hybrid structure of rGO could potentially lead to an excellent electrochemical performance for energy storage.