Long Qie

Nitrogen-doped porous carbon nanofiber webs as anodes for lithium ion batteries with a superhigh capacity and rate capability.

Nitrogen-doped carbon nanofiber webs (CNFWs) with high surface areas are successfully prepared by carbonization-activation of polypyrrole nanofiber webs with KOH. The as-obtained CNFWs exhibit a superhigh reversible capacity of 943 mAh g(-1) at a current density of 2 A g(-1) even after 600 cycles, which is ascribed to the novel porous nanostructure and high-level nitrogen doping.

Synthesis of functionalized 3D hierarchical porous carbon for high-performance supercapacitors

Functionalized three-dimensional hierarchical porous carbon (THPC) is prepared via a facile modified chemical activation route with polypyrrole microsheets as precursor and KOH as activating agent. The as-obtained THPC presents a large specific surface area (2870 m2 g−1), high-level heteroatom doping (N: 7.7 wt%, O: 12.4 wt%), excellent electrical conductivity (5.6 S cm−1), and hierarchical porous nano-architecture containing macroporous frameworks, mesoporous walls and microporous textures. Such unique features make the THPC an ideal electrode material for electrochemical energy storage. As the electrode material for a supercapacitor, the THPC exhibits a high capacitance, excellent rate performance and long-term stability in both aqueous and organic electrolytes.

MOF‐Derived Porous ZnO/ZnFe2O4/C Octahedra with Hollow Interiors for High‐Rate Lithium‐Ion Batteries

Novel porous ZnO/ZnFe2O4/C octahedra with hollow interiors are fabricated by a facile self-sacrificing template method involving the refluxing synthesis of hollow, metal-organic framework octahedra in solution and subsequent thermal annealing in N2 . When evaluated as an anode material for lithium-ion batteries, these porous hollow ZnO/ZnFe2O4/C octahedra exhibit significantly enhanced electrochemical performances with high rate capability, high capacity, and excellent cycling stability.

Biomass derived hard carbon used as a high performance anode material for sodium ion batteries

A porous hard carbon material was synthesized by the simple pyrolysis of H3PO4-treated biomass, i.e., pomelo peels, at 700 °C in N2. The as-obtained hard carbon had a 3D connected porous structure and a large specific surface area of 1272 m2 g−1. XPS analysis showed that the carbon material was functionalized by O-containing and P-containing groups. The porous hard carbon was used as an anode for sodium ion batteries and exhibited good cycling stability and rate capability, delivering a capacity of 181 mA h g−1 at 200 mA g−1 after 220 cycles and retaining a capacity of 71 mA h g−1 at 5 A g−1. The sodium storage mechanisms of the porous hard carbon can be explained by Na+ intercalation into the disordered graphene layers, redox reaction of the surface O-containing functional groups and Na+ storage in the nanoscale pores. However, the porous hard carbon demonstrated a low coulombic efficiency of 27%, resulting from the formation of a solid electrolyte interphase film and the side reactions of surface phosphorus groups.

Flexible Membranes of MoS2/C Nanofibers by Electrospinning as Binder-Free Anodes for High-Performance Sodium-Ion Batteries

A flexible membrane consisting of MoS2/carbon nanofibers has been fabricated by a simple electrospinning method. MoS2 nanosheets are uniformly encapsulated in the inter-connected carbon nanofibers with diameters of ~150 nm. When evaluated as a binder-free electrode for sodium-ion batteries, the as-obtained electrode demonstrates high performances, including high reversible capacity of 381.7 mA h g−1 at 100 mA g−1 and superior rate capability (283.3, 246.5 and 186.3 mA h g−1 at 0.5, 1 and 2 A g−1, respectively). Most importantly, the binder-free electrode made of MoS2 and carbon nanofibers can still deliver a charge capacity of 283.9 mA h g−1 after 600 cycles at a current density of 100 m A g−1, indicating a very promising anode for long-life SIBs.

Sulfur‐Doped Carbon with Enlarged Interlayer Distance as a High‐Performance Anode Material for Sodium‐Ion Batteries

S‐doped carbon is investigated as a high‐performance anode material for sodium‐ion batteries. Due to the introduction of a high‐content of S atoms, the as‐obtained S‐doped carbon shows an enlarged interlayer distance. As an anode, a high specific capacity of up to 303 mAh g−1 is achieved, even after 700 cycles at 0.5 A g−1.

Microwave‐Induced In Situ Synthesis of Zn2GeO4/N‐Doped Graphene Nanocomposites and Their Lithium‐Storage Properties

Zn2GeO4/N-doped graphene nanocomposites have been synthesized through a fast microwave-assisted route on a large scale. The resulting nanohybrids are comprised of Zn2GeO4 nanorods that are well-embedded in N-doped graphene sheets by in situ reducing and doping. Importantly, the N-doped graphene sheets serve as elastic networks to disperse and electrically wire together the Zn2GeO4 nanorods, thereby effectively relieving the volume-expansion/contraction and aggregation of the nanoparticles during charge and discharge processes. We demonstrate that an electrode that is made of the as-formed Zn2GeO4/N-doped graphene nanocomposite exhibits high capacity (1463 mA h g(-1) at a current density of 100 mA g(-1)), good cyclability, and excellent rate capability (531 mA h g(-1) at a current density of 3200 mA g(-1)). Its superior lithium-storage performance could be related to a synergistic effect of the unique nanostructured hybrid, in which the Zn2GeO4 nanorods are well-stabilized by the high electronic conduction and flexibility of N-doped graphene sheets. This work offers an effective strategy for the fabrication of functionalized ternary-oxide-based composites as high-performance electrode materials that involve structural conversion and transformation.

Controllable Synthesis of Hollow Bipyramid β-MnO2 and Its High Electrochemical Performance for Lithium Storage

Three types of MnO2 nanostructures, viz., α-MnO2 nanotubes, hollow β-MnO2 bipyramids, and solid β-MnO2 bipyramids, have been synthesized via a simple template-free hydrothermal method. Cyclic voltammetry and galvanostatic charge/discharge measurements demonstrate that the hollow β-MnO2 bipyramids exhibit the highest specific capacity and the best cyclability; the capacity retains 213 mAh g(-1) at a current density of 100 mA g(-1) after 150 cycles. XRD patterns of the lithiated β-MnO2 electrodes clearly show the expansion of lattice volume caused by lithiation, but the structure keeps stable during lithium insertion/extraction process. We suggest that the excellent performance for β-MnO2 can be attributed to its unique electrochemical reaction, compact tunnel-structure and hollow architecture. The hollow architecture can accommodate the volume change during charge/discharge process and improve effective diffusion paths for both lithium ions and electrons.

VO2/TiO2 Nanosponges as Binder-Free Electrodes for High-Performance Supercapacitors.

VO2/TiO2 nanosponges with easily tailored nanoarchitectures and composition were synthesized by electrostatic spray deposition as binder-free electrodes for supercapacitors. Benefiting from the unique interconnected pore network of the VO2/TiO2 electrodes and the synergistic effect of high-capacity VO2 and stable TiO2, the as-formed binder-free VO2/TiO2 electrode exhibits a high capacity of 86.2 mF cm−2 (~548 F g−1) and satisfactory cyclability with 84.3% retention after 1000 cycles. This work offers an effective and facile strategy for fabricating additive-free composites as high-performance electrodes for supercapacitors.