Energy storage devices that can deliver high powers have many applications, including hybrid vehicles and renewable energy. Much research has focused on increasing the power output of lithium batteries by reducing lithium-ion diffusion distances, but outputs remain far below those of electrochemical capacitors and below the levels required for many applications. Here, we report an alternative approach based on the redox reactions of functional groups on the surfaces of carbon nanotubes. Layer-by-layer techniques are used to assemble an electrode that consists of additive-free, densely packed and functionalized multiwalled carbon nanotubes. The electrode, which is several micrometres thick, can store lithium up to a reversible gravimetric capacity of approximately 200 mA h g(-1)(electrode) while also delivering 100 kW kg(electrode)(-1) of power and providing lifetimes in excess of thousands of cycles, both of which are comparable to electrochemical capacitor electrodes. A device using the nanotube electrode as the positive electrode and lithium titanium oxide as a negative electrode had a gravimetric energy approximately 5 times higher than conventional electrochemical capacitors and power delivery approximately 10 times higher than conventional lithium-ion batteries.

High-Power Lithium Batteries from Functionalized Carbon Nanotube Electrodes

As one important component of sulfur cathodes, the carbon host plays a key role in the electrochemical performance of lithium-sulfur (Li-S) batteries. In this paper, a mesoporous nitrogen-doped carbon (MPNC)-sulfur nanocomposite is reported as a novel cathode for advanced Li-S batteries. The nitrogen doping in the MPNC material can effectively promote chemical adsorption between sulfur atoms and oxygen functional groups on the carbon, as verifi ed by X-ray absorption near edge structure spectroscopy, and the mechanism by which nitrogen enables the behavior is further revealed by density functional theory calculations. Based on the advantages of the porous structure and nitrogen doping, the MPNC-sulfur cathodes show excellent cycling stability (95% retention within 100 cycles) at a high current density of 0.7 mAh cm −2 with a high sulfur loading (4.2 mg S cm −2 ) and a sulfur content (70 wt%). A high areal capacity (≈3.3 mAh cm −2 ) is demonstrated by using the novel cathode, which is crucial for the practical application of Li-S batteries. It is believed that the important role of nitrogen doping promoted chemical adsorption can be extended for development of other high performance carbon-sulfur composite cathodes for Li-S batteries.

Nitrogen-Doped Mesoporous Carbon Promoted Chemical Adsorption of Sulfur and Fabrication of High-Areal-Capacity Sulfur Cathode with Exceptional Cycling Stability for Lithium-Sulfur Batteries

Lithium-ion batteries have witnessed meteoric advancement the last two decades. The anode area has seen unprecedented research activity on Si and Sn, the two anode alternatives to currently used carbon following the initial seminal work by Fuji on tin oxide nanocomposites. Recent reports on silicon nanowires, porous Si, and amorphous Si coatings on graphite nanofibers (GNF) have been very encouraging. High capacity and long cycle life anodes are still, however, elusive and much needed to meet the ever increasing energy storage demands of modern society. Herein, we report for the first time the synthesis of novel 1D heterostructures comprising vertically aligned multiwall CNTs (VACNTs) containing nanoscale amorphous/nanocrystalline Si droplets deposited directly on VACNTs with clearly defined spacing using a simple two-step liquid injection CVD process. A hallmark of these single reactor derived heterostructures is an interfacial amorphous carbon layer anchoring the nanoscale Si clusters directly to the VACNTs. The defined spacing of nanoscale Si combined with their tethered CNT architecture allow for the silicon to undergo reversible electrochemical alloying and dealloying with Li with minimal loss of contact with the underlying CNTs. The novel heterostructures thus exhibit impressive reversible stable capacities approximately 2050 mAh/g with very good rate capability and an acceptable first cycle irreversible loss approximately 20% comparable to graphitic anodes indicating their promise as high capacity Li-ion anodes. Although warranting further research, particularly with regard to long-term cycling, it can be envisaged that optimization of this simple approach could lead to reversible high capacity next generation Li-ion anodes.

http://ma.ecsdl.org/content/MA2010-01/5/352.full.pdf

Nanostructured Hybrid Silicon/Carbon Nanotube Heterostructures: Novel Reversible High-Capacity Lithium-Ion Anodes

Introduction Lithium-sulfur batteries are considered as a promising candidate for next-generation secondary batteries because of their high theoretical capacit y, safe operating voltage (2.15 V vs. Li/Li ), and low cost. Nevertheless, lithium-sulfur batteries suffer from capacity fading, which limits their widespread application, due to the insulating nature of sulfur and its reduced pro ducts and the dissolution of intermediate lithium polysul fides. To address these problems, carbon-based materials have been integrated with sulfur to enhance the conductivity and inhibit the polysulfide dissolutio n. Recently, graphene, a single-atom-thick carbon mate rial with superior electrical conductivity and mechanica l flexibility, has been successfully applied in lithi um-sulfur batteries. While graphene-sulfur composite cathodes  demonstrate promising electrochemical performance, their synthesis is usually complicated and challeng ing for large-scale application. On the other hand, the sol utionbased synthesis without heat treatment produces lar ge crystalline sulfur particles, resulting in low util ization of active materials and poor rate performance. Herein, we report hydroxylated graphene nanosheets as a substr ate to produce graphene-amorphous sulfur nanocomposites, exhibiting superior cyclability at high rates, by a facile in situ deposition method at room temperature.

Hydroxylated Graphene-Sulfur Nanocomposites for High-Rate Lithium-Sulfur Batteries

Photo/Electrochemical Applications of Metal Sulfide/TiO2 Heterostructures

Promotional role of nano TiO2 for pomegranate-like SnS2@C spheres toward enhanced sodium ion storage

FeSb2S4 anchored on amine-modified graphene towards high-performance anode material for sodium ion batteries

TiNb2O7/carbon nanotubes composite (TNO/CNTs) was successfully synthesized by ultrasonic dispersion and a facile solvothermal method. Its physical properties were investigated by X-ray diffraction (XRD), thermogravimetric analysis (TG), and scanning microscopy (SEM). As the anode material of sodium ion battery, its electrochemical performances including cyclic voltammograms (CVs), electrochemical impedance spectra (EIS), and galvanostatic charge-discharge cycles were detected and analyzed for the first time. Compared with pure TiNb2O7, a high-reversible capacity reaches 261.1 mAh g−1 at 50 mA g−1 after 200 cycles. In addition, a prominent rate capability maintains ~ 110 mAh g−1 at 500 mA g−1 with over 1000 cycles. The improvements have been explained by the corresponding kinetics analysis which demonstrates that the pseudocapacitive behavior in TNO/CNTs contributes a lot to the enhanced sodium storage capacities and rate performance. The results show the great potential of TNO/CNTs composites for sodium-ion battery with a long cycle life.

TiNb2O7/carbon nanotube composites as long cycle life anode for sodium-ion batteries

Sb embedded TiO2/C spheres as high cyclability anode for lithium ion battery

Sb6O13/carbon nanotube (Sb6O13/CNT) composite prepared via a facile method has been evaluated as anode material for sodium-ion batteries. Its physical properties were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Its electrochemical characteristics were studied via cyclic voltammetry (CV), electrochemical impedance spectra (EIS), and galvanostatic charge/discharge. Compared with Sb6O13, Sb6O13/CNTs showed an obviously enhanced electrochemical performance with an initial discharge capacity of 1048.7 mA h g−1, a reversible capacity of 308.7 mA h g−1 at 100 mA g−1 after 350 cycles. Even at 1000 mA g−1, a capacity of 158 mA h g−1 was obtained for Sb6O13/CNTs compared to 47 mA h g−1 of Sb6O13, which showed a good rate performance of Sb6O13/CNTs. In addition, the calculated sodium-ion diffusion coefficients of Sb6O13/CNTs reached 6.70 × 10−14 cm2 s−1, which was almost 47 times as much as that of Sb6O13.

Xun Jiao

Papers

Promotional role of nano TiO2 for pomegranate-like SnS2@C spheres toward enhanced sodium ion storage

FeSb2S4 anchored on amine-modified graphene towards high-performance anode material for sodium ion batteries

TiNb2O7/carbon nanotube composites as long cycle life anode for sodium-ion batteries

Sb embedded TiO2/C spheres as high cyclability anode for lithium ion battery

Carbon nanotubes enhanced Sb 6 O 13 as a new anode material for sodium-ion batteries