Xuefang Chen

Cobalt fibers anchored with tin disulfide nanosheets as high-performance anode materials for lithium ion batteries

Well-designed hierarchical nanostructured composites consisting of one dimensional cobalt fibers and thin tin disulfide nanosheets were successfully synthesized for the first time through a hydrothermal method. The SnS2 nanosheets were uniformly grown onto the Co fibers and were almost perpendicular to the Co fibers. The composites as one kind anode materials exhibited more remarkable lithium ion storage properties than SnS2 nanosheets. The composites exhibited a capacity of 500.5mAh/g after 100 cycles even at 1000mA/g. The improved electrochemical performance could be assigned to the Co fiber substrate support, which could provide short lithium ion and electron pathways, alleviate large volume expansion, contribute to the capacity, and offer mechanical stability for the anode electrode. This special designing perhaps could lay a foundation for the preparation of high performance lithium ion battery anode materials.

Preparation and application of hollow ZnFe2O4@PANI hybrids as high performance anode materials for lithium-ion batteries

ZnFe2O4, a type of mixed transition metal oxide, is considered as one of the most attractive potential anode materials for LIBs due to its high reversible capacity and satisfactory structural stability. However, the low conductivity and the serious volume exchange during the electrochemical process are still two main issues for ZnFe2O4. In this study, we first designed conductive PANI layer coated hollow ZnFe2O4 nanospheres by micro emulsion polymerization. Two strategies of hollow structure and PANI coating were attempted to relieve expansion and increase conductivity. The results show that the as-designed hollow ZnFe2O4@PANI composites exhibited a large initial specific capacity of 1489.38 mA h g−1 with the first discharge that is maintained at over 607.3 mA h g−1 even after 50 charge–discharge cycles.

Cobalt nanofibers coated with layered nickel silicate coaxial core-shell composites as excellent anode materials for lithium ion batteries

A novel type of cobalt nanofibers coated with layered nickel silicate (Co nanofibers @ voids @ Ni3Si2O5(OH)4) coaxial core-shell composites were successfully prepared via a well-known Stöber process and two hydrothermal methods. In the composites, the international nanosheet structure of the nickel silicate provided interlayer spaces for lithium ions in the process of insertion and extraction. The cobalt nanofibers served as a mechanical support for the nickel silicate nanosheets, which increased the electrical conductivity of the whole electrode. In addition, one-dimensional coaxial structure was stable to buffer the volume change and avoid the destruction of the structure. Moreover, the voids provided effective channels for the transportation of lithium ions. The Co nanofibers @ voids @ Ni3Si2O5(OH)4) coaxial core-shell composites presented superior electrochemical properties compared with the published Ni3Si2O5(OH)4-related materials. With the advantages of exceptional performances and facile preparation, the composites show prospective application potential as advanced anode materials in lithium ion batteries.

Nitrogen-doped carbon nanotubes based on melamine-formaldehyde resin as highly efficient catalyst for oxygen reduction reaction

The preparation of highly efficient and cheap electrocatalysts toward oxygen reduction reaction is significant for many electrochemical cells. Here we facilely synthesized nitrogen doped carbon nanotube by pyrolyzing melamine formaldehyde resin and Fe loading on MgO. There were mainly three morphologies observed, slender bamboo-like CNT, thick bamboo-like CNT, surface smooth, hollow CNT. The content of Fe loading on MgO had little influence on morphologies of CNT, however, when no MgO as support, only carbon ribbon obtained. The MgO as support was also significant for the formation of CNT. The samples with CNT formed represented better catalytic activity than control samples with no-CNT obtained, the morphology of CNT was beneficial for catalytic process. The sample C1-CNT with lowest content of Fe on support represented best catalytic activity which was competitive with 20% Pt/C in half-wave potential. The C1-CNT also showed outstanding stability and improved selectivity towards ORR, making it a promising alternative to Pt in application of fuel cells and metal-air batteries.

Fabrication of porous nanosheets assembled from NiCo2O4/NiO electrode for electrochemical energy storage application

In this work, The NiCo2O4/NiO electrode materials are successfully synthesized via hydrothermal and following calcination approach. Due to the distinctive porous nanosheets assembled structure through controlling effectively the feeding amount of HMT, the NiCo2O4/NiO electrode possesses excellent specific surface area and reasonable pore size distribution, which hence minimizes the intrinsic electrode resistance and improves the morphology and structure stability. Therefore, the NiCo2O4/NiO electrode delivers a superior specific capacitance (Csp) (992.85Fg-1 at the current density of 1Ag-1), good rate capability (79.14% Csp retention even at 10Ag-1) and considerable cycle life (79.82% Csp retention at 10Ag-1 after 5000 times). Furthermore, the asymmetric supercapacitor is successfully assembled by NCN-0.1 as positive electrode and activated carbon (AC) as negative electrode. The NCN-0.1//AC device delivers a relatively excellent energy density of 47.43kWkg-1 at a power density of 0.389Whkg-1. Consequently, the outstanding performance and stability of the ASC device shows great potential for future energy storage application.

Controlled synthesis of hollow Si–Ni–Sn nanoarchitectured electrode for advanced lithium-ion batteries

A Sn-based intermetallic compound (hollow Si–Ni–Sn nanospheres) with a porous and hollow microspheric structure was fabricated via a versatile template synthesis approach followed by an in situ chemical reaction, and directly used as an anode material for lithium-ion batteries (LIBs). The hollow Si–Ni–Sn nanosphere anode with a unique architecture exhibits high initial discharge capacity and excellent cycling stability. The reversible capacity of hollow Si–Ni–Sn nanospheres is 1065 mA h g−1 and is maintained at 402 mA h g−1 after 50 cycles, which is much higher than that of hollow SiO2@Ni@SnO2 nanospheres. The unique configuration of the Sn-based intermetallic compound presents a beneficial approach to create efficient and practical electrodes for energy storage applications.