Fei-Fei Cao

Cu-Si nanocable arrays as high-rate anode materials for lithium-ion batteries.

There is a surge in developing rechargeable lithium-ion batteries (LIBs) with higher energy densities and higher rate performance for application in powering future advanced communications equipment and electric vehicles (EVs). [ 1–6 ] The development of the electrode materials is essential for the improvement of the electrochemical properties of LIBs. [ 7–10 ] Among various anode materials tested for LIBs, Si has triggered signifi cant research effort because of its low Li-uptake potential and the high theoretical capacity (4200 mA h g − 1 ). [ 6 , 11–19 ] However, the main disadvantage that restricts the application of Si is the large volume changes of Si during Li + insertion and extraction, which results in a pulverization of the Si particles, a peeling off the current connection network, and, consequently, a rapid capacity decline upon cycling. [ 11–17 ] To overcome this issue, Si nanostructures, such as Si nanowires and nanotubes, have been fabricated. [ 6 , 11 , 18–23 ] The procedures for the fabrication of the Si nanostructures have also been well developed. [ 24–26 ] These nanostructures can provide spaces to accommodate the large volume variation during charge and discharge processes and thus allow for facile strain relaxation, which prevents pulverization upon lithium insertion. [ 11–19 , 27 ] The cycle stability of the Si anode has been signifi cantly improved by using these nanostructures. [ 11–17 , 27 ] Nevertheless, the rate capability of these materials highly needed for EVs is still not satisfying. This is possibly due to the lack of favorable electronic conductivity and the continuous growth of the unstable solid electrolyte interphase (SEI) at the Si/electrolyte interface upon cycling. Therefore, a new design for the structure of the Si anode is in high demand to achieve both longer cycling life and higher rate capability. Our previous work suggested that the application of nanocable structures in LIBs electrodes can signifi cantly improve the batteries’ electrochemical performance, especially the high

Better lithium-ion batteries with nanocable-like electrode materials

Lithium-ion battery constitutes one of the most popular energy sources which powers current electronic instruments. It is also a promising candidate to be used in future electric devices. To fulfil its potential in future battery market, the better properties of lithium-ion batteries, e.g., higher capacity, better rate performance, are undoubtedly required. The development of nanotechnology has greatly advanced the frontier of lithium-ion battery research. Recently, it was realized that the application of nanocable-like structure in the design of electrodes can significantly improve the properties of lithium-ion batteries. Here we give an overiew of the design, synthesis, and applications of such structures in lithium-ion batteries and highlight some of the latest achievements in this area. It is exciting that the future of lithium-ion batteries is quite bright in view of the high specific capacity, much improved rate performance, as well as superior cycling stability brought by the nanocable-like electrode materials.

Photocatalytic CO2 Reduction by Carbon-Coated Indium-Oxide Nanobelts

Indium-oxide (In2O3) nanobelts coated by a 5-nm-thick carbon layer provide an enhanced photocatalytic reduction of CO2 to CO and CH4, yielding CO and CH4 evolution rates of 126.6 and 27.9 μmol h-1, respectively, with water as reductant and Pt as co-catalyst. The carbon coat promotes the absorption of visible light, improves the separation of photoinduced electron-hole pairs, increases the chemisorption of CO2, makes more protons from water splitting participate in CO2 reduction, and thereby facilitates the photocatalytic reduction of CO2 to CO and CH4.

Facile Synthesis of Carbon-Coated Spinel Li4Ti5O12/Rutile-TiO2 Composites as an Improved Anode Material in Full Lithium-Ion Batteries with LiFePO4@N-Doped Carbon Cathode

The spinel Li4Ti5O12/rutile-TiO2@carbon (LTO-RTO@C) composites were fabricated via a hydrothermal method combined with calcination treatment employing glucose as carbon source. The carbon coating layer and the in situ formed rutile-TiO2 can effectively enhance the electric conductivity and provide quick Li+ diffusion pathways for Li4Ti5O12. When used as an anode material for lithium-ion batteries, the rate capability and cycling stability of LTO-RTO@C composites were improved in comparison with those of pure Li4Ti5O12 or Li4Ti5O12/rutile-TiO2. Moreover, the potential of approximately 1.8 V rechargeable full lithium-ion batteries has been achieved by utilizing an LTO-RTO@C anode and a LiFePO4@N-doped carbon cathode.

Conductive Carbon Network inside a Sulfur-Impregnated Carbon Sponge: A Bioinspired High-Performance Cathode for Li–S Battery

A highly conductive sulfur cathode is crucial for improving the kinetic performance of a Li-S battery. The encapsulation of sulfur in porous nanocarbons is expected to benefit the Li(+) migration, yet the e(-) conduction is still to be improved due to a low graphitization degree of a conventional carbon substrate, especially that pyrolyzed from carbohydrates or polymers. Aiming at facilitating the e(-) conduction in the cathode, here we propose to use ketjen black, a highly graphitized nanocarbon building block to form a conductive network for electrons in a biomass-derived, hierarchically porous carbon sponge by a easily scaled-up approach at a low cost. The specifically designed carbon host ensures a high loading and good retention of active sulfur, while also provides a faster electron transmission to benefit the lithiation/delithiation kinetics of sulfur. The sulfur cathode prepared from the carbon network shows excellent cycling and rate performance in a Li-S battery, rendering its practicality for emerging energy storage opportunities such as grids or automobiles.

Improved Electrochemical Performance of LiFePO4@N-Doped Carbon Nanocomposites Using Polybenzoxazine as Nitrogen and Carbon Sources

Polybenzoxazine is used as a novel carbon and nitrogen source for coating LiFePO4 to obtain LiFePO4@nitrogen-doped carbon (LFP@NC) nanocomposites. The nitrogen-doped graphene-like carbon that is in situ coated on nanometer-sized LiFePO4 particles can effectively enhance the electrical conductivity and provide fast Li+ transport paths. When used as a cathode material for lithium-ion batteries, the LFP@NC nanocomposite (88.4 wt % of LiFePO4) exhibits a favorable rate performance and stable cycling performance.

Nitrogen and Sulfur Codoped Reduced Graphene Oxide as a General Platform for Rapid and Sensitive Fluorescent Detection of Biological Species

Nitrogen (N) and sulfur (S) codoped reduced graphene oxide (N,S-rGO) was synthesized through a facile solvothermal process. The introduction of N and S heteroatoms into GO effectively activated the sp(2)-hybridized carbon lattice and made the material an ideal electron/energy acceptor. Such unique properties enable this material to perform as a general platform for rapid and sensitive detection of various biological species through simple fluorescence quenching and recovering. When quantum dot (QD)-labeled HBV (human being disease-related gene hepatitis B virus DNA) and HIV (human being disease-related gene human immunodeficiency virus DNA) molecular beacon probes were mixed with N,S-rGO, QD fluorescence was quenched; when target HBV and HIV DNA were added, QD fluorescence was recovered. By the recovered fluorescence intensity, the target virus DNA detection limits were reduced to 2.4 nM for HBV and 3.0 nM for HIV with detection time of less than 5 min. It must be stressed out that different viruses in the same homogeneous aqueous media could be discriminated and quantified simultaneously through choosing diverse QD probes with different colors. Moreover, even one mismatched target DNA could be distinguished using this method. When altering the molecular beacon loop domain to protein aptamers, this sensing strategy was also able to detect thrombin and IgE in 5 min with detection limits of 0.17 ng mL(-1) and 0.19 ng mL(-1), respectively, which was far more rapid and sensitive than bare GO-based fluorescence detection strategy.

Co nanoparticles/Co, N, S tri-doped graphene templated from in-situ formed Co, S co-doped g-C3N4 as an active bifunctional electrocatalyst for overall water splitting

The development of high-performance electrocatalyst with earth-abundant elements for water-splitting is a key factor to improve its cost efficiency. Herein, a noble metal-free bifunctional electrocatalyst was synthesized by a facile pyrolysis method using sucrose, urea, Co(NO3)2 and sulfur powder as raw materials. During the fabrication process, Co, S co-doped graphitic carbon nitride (g-C3N4) was first produced, and then this in-situ-formed template further induced the generation of a Co, N, S tri-doped graphene coupled with Co nanoparticles (NPs) in the following pyrolysis process. The effect of pyrolysis temperature (700, 800, and 900 °C) on the physical properties and electrochemical performances of the final product was studied. Thanks to the increased number of graphene layer encapsulated Co NPs, higher graphitization degree of carbon matrix and the existence of hierarchical macro/meso pores, the composite electrocatalyst prepared under 900 °C presented the best activity for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) with outstanding long-term durability. This work presented a facile method for the fabrication of non-noble-metal-based carbon composite from in-situ-formed template and also demonstrated a potential bifunctional electrocatalyst for the future investigation and application.