N‐Doping and Defective Nanographitic Domain Coupled Hard Carbon Nanoshells for High Performance Lithium/Sodium Storage

WS2 nanosheets–carbon composites (WS2/C) were synthesized through a simple two‐step process including ball‐milling and sulfidation. When applied as anode materials for sodium‐ion batteries and lithium‐ion batteries, WS2/C composites deliver a high reversible sodium storage capacity of 270 mA h g−1 at 100 mA g−1 and a high reversible lithium storage capacity of 322 mA h g−1 at 200 mA g−1 after 100 cycles. The improved electrochemical performance of WS2/C compared with the bare WS2 can be attributed to the synergic effects between WS2 and Super P carbon black matrix, which can offer a beneficial conductivity environment for electron transfer and accommodate stress from the volume change during cycling.

High reversible lithium storage capacity is obtained from novel SnO2/ZnWO4 core-shell nanorods. At C/20 (20 h per half cycle) rate, the reversible capacity of SnO2/ZnWO4 core-shell nanorods is as high as 1000 mA h g(-1), much higher than that of pure ZnWO4, SnO2, or the traditional theoretical result of the simple mixture. Such performance can be attributed to the synergistic effect between the nanostructured SnO2 and ZnWO4. The distinct electrochemical activity of ZnWO4 nanorods probably activates the irreversible capacity of the SnO2 nanoparticles. These results indicate that high-performance lithium ion batteries can be realized by introducing the synergistic effect of one-dimensional core-shell nanocomposites.

Tandem plasma reactions for Sn/C composites with tunable structure and high reversible lithium storage capacity

Conductive carbon networks in surface coating of GeP rods toward high-performance lithium/sodium-ion battery anode

In this paper, we report a facile ultrasonic method to synthesize well-dispersed CoO quantum dots (3-8 nm) on graphene nanosheets at room temperature by employing Co(4)(CO)(12) as cobalt precursor. The prepared CoO/graphene composites displayed high performance as an anode material for lithium-ion battery, such as high reversible lithium storage capacity (1592 mAh g(-1) after 50 cycles), high Coulombic efficiency (over 95%), excellent cycling stability, and high rate capability (1008 mAh g(-1) with a total retention of 77.6% after 50 cycles at a current density of 1000 mA g(-1), dramatically increased from the initial 50 mA g(-1)). The extraordinary performance arises from the structure advantages of the composites: the nanosized CoO quantum dots with high dispersity on conductive graphene substrates supply not only large quantity of accessible active sites for lithium-ion insertion but also good conductivity and short diffusion length for lithium ions, which are beneficial for high capacity and rate capability. Meanwhile, the isolated CoO quantum dots anchored tightly on the graphene nanosheets can effectively circumvent the volume expansion/contraction associated with lithium insertion/extraction during discharge/charge processes, which is good for high capacity as well as cycling stability. Moreover, regarding the anomalous behavior of capacity increase with cycles (activation effect) observed, we proposed a tentative hypothesis stressing the competition between the conductivity increase and the amorphorization of the composite electrodes during cycling in determining the trends of the capacity, in the hope to gain a fuller understanding of the inner working of the novel nanostructured electrode-based lithium-ion batteries.

Carbon polyhedra encapsulated Si derived from Co-Mo bimetal MOFs as anode materials for lithium-ion batteries

Cage-like MnSe@PPyC/rGO as superior dual anode materials in Li/Na-ions storage

In this study, we demonstrated a facile method to prepare a novel SnO2 microporous rod with various microstructures by controlling NaOH molarities in precursor synthesis processes. Four different molarities of NaOH solution (0.005 M, 0.048 M, 0.12 M and 0.5 M) were used together with o-phthalic acid in Sn-MOF synthesis to determine the effect of ligand [o-C6H4 CO222− ] concentration on microstructure evolution. It was found that increasing NaOH molarity can effectively decrease the size of Sn-MOF rods. Then, the SnO2 microporous rods were obtained by calcinating the as-prepared Sn-MOF as microstructures. Under an optimized experimental condition (NaOH molarity of 0.12 M), the SnO2 rods shows a modest initial coulombic efficiency of 61.3% with a high reversible sodium storage capacity of 503 mAh g−1 after 150 cycles at 50 mA g−1. Moreover, an impressive reversible sodium storage capacity of 206 mAh g−1 can be obtained at long-term cycling performance (800 cycles at current density of 2 A g−1). Effects of morphologies to electrochemical performances have been further discussed in aspects of intrinsic resistance, pseudocapacitive contribution, surface area and porous structure and microstructural stability, and the enhanced electrochemical performance could be attributed to factors of enhanced pseudocapacitive charge contribution, optimized microstructures, and structural stability, which ensure the SnO2−0.12 M to have a good rate performance and cyclability. This nanoscale-engineering method adopted here could be a promising path to fabricate SnO2-based anodes with novel microstructures for sodium storage applications.

Summary form only given. The development of long-length, high current density Bi2Sr2CaCu2Ox wires and (RE)Ba2Cu3Oy coated conductors has now advanced New environmental regulations and oil crisis have induced the urgent adoption of electric vehicles and renewable energies. This will bring immense social and environmental benefits to the society, including reduced CO2 emissions, increased energy independence and energy security, and improved efficiency of transport. In this talk, I will report our research on electrode materials for lithium ion batteries, lithium-air batteries, lithium sulfur batteries and sodium ion batteries.A highly ordered mesoporous LiFePO4/C nanocomposite has been developed, in which LiFePO4 nanoparticles are embedded in conductive and interconnected carbon networks. This mesoporous nanoarchitecture ensures not only intimate contact between liquid electrolyte and active LiFePO4 nanoparticles, but also high electronic conductivity for both facile mass transfer and facile charge transfer. At the low current rate, mesoporous LiFePO4/C nanocomposite cathodes delivered a near theoretical capacity with ultrahigh coulombic efficiency and capacity retention. At high current rate, the cell also exhibited a satisfactory specific capacity with an excellent cyclability. Through material architecture design, LiFePO4 cathode material can meet the stringent requirements for high power applications such as electric vehicles and energy storage for smart grids. [1] Facet crystals with exposed highly reactive planes have attracted intensive investigations for applications such as hydrogen production, enhanced catalytic activity, and electrochemical energy storage and conversion. Herein, we report the synthesis of mesoporous NiO crystals with dominantly exposed {110} reactive facets by the thermal conversion of hexagonal Ni(OH)2 nanoplatelets. When applied as anode materials in lithium-ion batteries, mesoporous facet NiO crystals exhibit a high reversible lithium storage capacity of 700 mAh g-1 at 1 C rate in 100 cycles and an excellent cyclability. In particular, the dominantly exposed {110} reactive facets of NiO crystals lead to ultrafast lithium storage, which mimics the high power delivery of supercapacitors. [2] The synthesis of an effective cathode catalyst of ruthenium nanocrystals has been achieved by a surfactant assisting method. The as-prepared ruthenium nanocrystals exhibited an excellent catalytic activity as cathodes in Li-O2 batteries with a high reversible capacity of about 9,800 mAh g-1, a low charge-discharge over-potential (about 0.37 V), and an outstanding cycle performance up to 150 cycles (with a curtailing capacity of 1,000 mAh g-1). The electrochemical testing shows that ruthenium nanocrystals can significantly reduce the charge potential comparing to carbon black catalysts, which demonstrated that ruthenium based nanomaterials could be effective cathode catalysts for high performance lithium-O2 batteries.

One-pot synthesis of nanosized MnO incorporated into N-doped carbon nanosheets for high performance lithium storage

Hard carbon exhibits high theoretical capacity for sodium-ion batteries. However, its practical application suffers from low electric conductivity, poor electrochemical stability, and sluggish kinetics. To tackle these challenges, novel nitrogen-doped carbon spheres with mesopores, ultrathin nanostructure, and optimal graphitization are prepared by a three-step procedure. We find that the as-prepared sample (NMCSs-800) with an optimal structure and nitrogen content delivers a high reversible sodium storage capacity of 334.7 mA h/g at 50 mA/g and an ultrahigh rate performance of 93.9 mA h/g at 5 A/g, which is better than most state-of-the-art carbon materials. The improved energy storage capacity is attributed to its unique architecture and optimal nitrogen doping, which provide abundant active sites, defects, and voids. Moreover, kinetic analysis and in situ Raman spectroscopy results reveal adsorption and adsorption-intercalation mechanisms for Na+ storage in hard carbon at the slope region above 0.3 V and the other slope region of 0.3-0.02 V, respectively. We believe that our findings provide a novel tactic to design elaborate nanomaterials for the high-performance sodium-ion battery.

Exceptional electrochemical performance of two-year aged V2O5 nanowires for lithium storage

1. Introduction With rising interest in green electrode materials for lithium-ion batteries (LIBs), increasing attention has been paid to titanium dioxide (TiO2) anode material in recent years because of its long cycle life, low cost, and minimum environmental impact. Moreover, the relatively high lithium insertion /extraction voltage of a TiO2 anode (higher than 1.5 V vs Li+/Li) can efficiently avoid the formation of SEI layers and lithium plating on the anode, which improves the safety of the batteries as compared with its carbon-based counterparts. However, many potential electrode materials (e.g., TiO2) in Li-ion batteries are limited by poor electron transport, slow Li-ion diffusion in electrodes, and increased resistance at the interface of electrode/electrolyte at high chargedischarge rates. Graphene, which has exceptional electrical, mechanical, optical, and surface properties, is widely utilized to prepare various hybrid materials. The graphene substrate itself can be contributory to the improved electrochemical performance because it may enhance the electronic conductivity of the overall electrode[1]. It is noteworthy, on the other hand, that the size and dispersion of nanoparticles on graphene are crucial factors for improving cell performance because small particle size plus good dispersion (e.g., down to several nanometers) can endow the composite electrode a superior high surface area to buffer the volume change of the particles, but it could also bring the required conductivity to individual nanoparticles and shorten the diffusion length for Li ions, which are beneficial for high lithium storage and rate capability, respectively. However, most metal oxide/graphene composites prepared so far have the high level of metal oxides accompanied with the partial aggregation of particles may also result in the rapid capacity loss and poor cycle performance. Therefore, it remains a challenge to develop a facile and general approach for the synthesis of well-dispersed MOx (e.g., TiO2) Quantum Dots/Graphene composites with favored structures for high-performance lithium-ion batteries (LIBs). 2. Experimental Section 2.1 Synthesis of graphene oxide (GO) The graphite oxide was synthesized from natural graphite flake (Alfa Aesar, 325 mesh) by a modified Hummers method. As-prepared graphite oxide was dispersed in water by ultrasonication for 30 min, followed by a low-speed centrifugation to get rid of any aggregated GO.2.2 Preparation of TiO2 quantum dots /Graphene nanosheets (TiO2-QDs/GNs) Composites In a typical experimental procedure, 5.8 g of CTAB was dissolved in a mixture of 10 ml of n-pentanol and 60 ml of n-hexane; Then, the 10 ml GO aqueous dispersion (1 mg mL-1) was slowly poured and intensely stirred for 30 min at room temperature. Subsequently, with the formation of a golden water-in-oil emulsion. Then 0.8 ml of Titanium(III) chloride was added to golden water-in-oil emulsion while stirring. The achieved transparent microemulsions were poured into a Teflon-lined stainless steel autoclave (100 ml), and then placed in an oven maintaining 200°C for 6 h. The collected precipitates were treated under reduced pressure in a rotary evaporator to remove the volatile organic reagents and then repeatedly washed with water and ethanol to remove surfactants and other impurities. The final samples were dried at 80 °C for 2 h for further characterizations. 3. Results and Discussion In summary, we report a facile method to synthesize well-dispersed TiO2 quantum dots (6±2 nm) on graphene nanosheets (TiO2-QDs/GNs) in a water-in-oil (W/O) emulsion system (Figure 1). The prepared TiO2/graphene composites displayed high performance as an anode material for lithium-ion battery, such as high reversible lithium storage capacity (190 mA h g-1 after 100 cycles), high Coulombic efficiency (over 96%), excellent cycling stability and high rate capability (as high as 144 mA h g-1 at 10 C, 135 mA h g-1 at 20 C, 124 mA h g-1 at 30 C and 101 mA h g-1 at 50 C, respectively). Very significantly, the preparation method employed can be easily adapted and may offer an attractive alternative approach for preparation of the highly dispersed nanosized graphene-based nanostructured composites as promising applications in various energy-storage devices high performance electrodes for various energy-storage devices.Figure 1 Electrochemical measurements of (a) TiO2-QDs/GNs and (b) TiO2-QDs electrodes. Inset in Fiure 1 is the Schematic of synthesis steps for TiO2-QDs/GNs composite.

3D-hierarchical NiO–graphene nanosheet (GNS) composites as high performance anode materials for lithium-ion batteries (LIBs) were synthesized through a simple ultrasonic method, and characterized by X-ray diffraction, Raman spectrum, field emission scanning electron microscopy and transmission electron microscopy. The results show that the 3D-hierarchical NiO carnations with nanoplates as building blocks are homogeneously anchored onto GNS and act as spacers to reduce the stacking of GNS. Electrochemical performances reveal that the obtained 3D-hierarchical NiO–GNS composites exhibit remarkably high reversible lithium storage capacity, good rate capability and improved cycling stability, e.g. approximate 1065 mA h g−1 of reversible capacity is retained even after 50 cycles at a current density of 200 mA g−1. The remarkable improvement of electrochemical performances of the obtained composites could be attributed to the decrease of the volume expansion and contraction of NiO and the improvement of the electronic conductivity of composites during the cycling process.

Hard carbon, characterized by high ion storage capacity, low operating voltage, and excellent cycling stability, is considered an ideal negative electrode material for sodium‐ion batteries. However, the high cost and low carbon yield of thermosetting precursors limit their practical application in SIBs, while low‐cost and high‐yield raw materials exhibit highly ordered carbon structures and narrow interlayer spacing under high‐temperature carbonization. Discarded polyimide materials are inexpensive, which offer a high carbon yield and possess good thermal stability and thermoplasticity, with functional groups of imide rings (−CO−N−CO−) on their main chains. This study recycled and converted polyimide materials into hard carbon materials from discarded engineering plastics, investigating the influence of carbonization temperature on the degree of graphitization, interlayer spacing, and pore structure of the materials to achieve high reversible sodium storage capacity. After carbonization at 1300 °C, the polyimide material exhibited 319 mAh g −1 reversible capacity and excellent electrochemical performance (with a capacity retention of 91.92 % after 100 cycles at a 0.5 C current rate) and rate performance (up to 242.5 mAh g −1 at 2 C). This study provided a simple, high‐yield, and effective method for the reuse of discarded organic polymers, promoting the sustainable utilization of resources.