Silicon has attracted a lot of attention as a potential anode material for next-generation lithium ion batteries (LIBs) because of its high energy density, high theoretical capacity, and abundance. Herein, we introduce an effortless synthesis of coral-like silicon powders with a three-dimensional (3D) interlinked network using a scalable method that consist of magnesiothermic reduction and chemical vapor deposition. The porous structure achieved by silicon nanospheres can create room for the volume expansion and alleviate the built strain that would occur upon lithiation. In addition, intertwined coral-like framework provides a shortened path for lithium ion diffusion, which can improve the ionic conductivity of the cells. At a high current rate of C/2, a reversible capacity of 3172mAhg(-1) was delivered by the silicon-carbon nanocomposite electrode, and the capacity still remains as high as 1018mAhg(-1) after 500cycles, while the Columbic efficiency is higher than 99%. The inexpensive, effective, and scalable fabrication of porous silicon-carbon nanocomposite spheres possessing a 3D interlinked network could establish a basis for developing high energy density anode materials to be used in next-generation LIBs.

This paper demonstrates cooling of the center-of-mass motion of 10 $\mu$m-diameter optically levitated silica spheres to an effective temperature of $50\pm22 \mu$K, achieved by minimizing the technical pointing noise of the trapping laser. This low noise leads to an acceleration and force sensitivity of $95\pm41$ n$g/\sqrt{\mathrm{Hz}}$ ($g = 9.8$ m/s$^2$) and $0.95\pm0.11$ aN$/\sqrt{\mathrm{Hz}}$, respectively, at frequencies near 50 Hz. This force sensitivity is comparable to that demonstrated for optically levitated nanospheres that are $10^4$ times less massive, corresponding to an acceleration sensitivity that is several orders of magnitude better. It is further shown that under these conditions the spheres remain stably trapped at pressures of $\sim 10^{-7}$ mbar with no active cooling for periods longer than a day. Feedback cooling is still necessary in the moderate-pressure regime, motivating a comprehensive study of the loss mechanisms of the microspheres and providing better understanding of the requirements for feedback-free optical trapping in vacuum. This work can enable high-sensitivity searches for accelerations and forces acting on micron-sized masses, including those that could be produced by new physics beyond the Standard Model.

Chemical vapor deposition and phase stability of pyrite crystals on SiO2at temperatures up to 600 °C have been studied.

Light-weight graphite foam decorated with carbon nanotubes (dia. 20-50 nm) is utilized as an effective electrode without binders, conductive additives, or metallic current collectors for supercapacitors in aqueous electrolyte. Facile nitric acid treatment renders wide operating potentials, high specific capacitances and energy densities, and long lifespan over 10 000 cycles manifested as 164.5 and 111.8 F g-1 , 22.85 and 12.58 Wh kg-1 , 74.6% and 95.6% capacitance retention for 2 and 1.8 V, respectively. Overcharge protection is demonstrated by repetitive cycling between 2 and 2.5 V for 2000 cycles without catastrophic structural demolition or severe capacity fading. Graphite foam without metallic strut possessing low density (≈0.4-0.45 g cm-3 ) further reduces the total weight of the electrode. The thorough investigation of the specific capacitances and coulombic efficiencies versus potential windows and current densities provides insights into the selection of operation conditions for future practical devices.

Carbonaceous materials are intensively used as additives or active electrode materials in lithium-ion battery (LIB) industry due to their stable chemical and physical properties. Compared to developing next-generation high-capacity non-carbonaceous anode materials, improvement on current carbonaceous materials could lead to instant commercial values due to less process modifications to the battery manufacturing. Here, we report a facile approach to synthesize carbon nanotubes (CNTs) with controlled assemblies: well-dispersed CNTs vs. bundled CNTs. Furthermore, we incorporated these CNTs onto three-dimensional (3D) graphite foams as free-standing anodes for LIBs. This hierarchical 3D network provided high surface area and ultra-high conductivity with enhanced battery capacity. With controlled growth conditions, the assembly of CNTs can be changed from bundled state to dispersed state, resulting in a significant improvement in electrochemical performance. The dispersed CNTs showed a higher specific capacity of above 800 mAhg−1 over 120 cycles, while CNT bundles exhibited a specific capacity of 500 mAhg−1. The loose structure of well-dispersed CNTs provides sufficient active interfaces between electrolyte and materials, as well as shortened ion transport path. Insights can be gained in improving state-of-the-art battery performance by controlling the bulk assemblies of CNT additives.

Metal foams are utilized in various applications, such as in the automotive industries and for electrochemical devices. Herein, a Ni nanofoam is synthesized using a facile method for Li-ion batteries. Self-aligned Ni wires or randomly linked webs are produced with or without magnetic field, respectively. Ni granular beads or spiky clusters form at 370 or 450 degrees C, respectively. The surface area of Ni wires is increased by oxalic acid etching at 80 degrees C using 5-30wt% water, leading to Ni oxalate nanosheets, nanowires (NWs), or nanoleaves. Metallic Ni NWs are obtained by reducing Ni oxalate NWs with H-2 at 350 degrees C in 10 min. Carbon-coated Si nanoparticles on Ni NW foam (C-SiNP/NiNWF) show 38% rate enhancement (1222 vs. 889mAhg(-1)) in comparison to C-SiNP/Cufoil. Higher stability of C-SiNP/NiNWF with a capacity retention of 91% is reached vs. 73% for C-SiNP/Cufoil over 180cycles. The ambient-pressure solution process with low temperature and fast reaction time could make large-scale production plausible for these nanoarchitectures.

Every year many tons of waste glass end up in landfills without proper recycling, which aggravates the burden of waste disposal in landfill. The conversion from un-recycled glass to favorable materials is of great significance for sustainable strategies. Recently, silicon has been an exceptional anode material towards large-scale energy storage applications, due to its extraordinary lithiation capacity of 3579 mAh g −1 at ambient temperature. Compared with other quartz sources obtained from pre-leaching processes which apply toxic acids and high energy-consuming annealing, an interconnected silicon network is directly derived from glass bottles via magnesiothermic reduction. Carbon-coated glass derived-silicon (gSi@C) electrodes demonstrate excellent electrochemical performance with a capacity of ~1420 mAh g −1 at C/2 after 400 cycles. Full cells consisting of gSi@C anodes and LiCoO 2 cathodes are assembled and achieve good initial cycling stability with high energy density.

To promote the energy density of lithium-ion battery, the sulfur-based cathode has attracted extensive attention because of its high specific capacity of 1672 mAh g(-1) and its high abundance. However, the sulfur shuttling effects and the loss of active material during lithiation hinder its commercial application. To tackle these issues, we synthesized a stable copolymer-sulfur composite by chemically binding sulfur. The composite with 86% sulfur content was prepared using 1,3-diethynylbenzen and sulfur particles via scalable invers vulcanization. The sulfur content in copolymer sulfur was achieved as high as 86%. Our copolymer-sulfur composite cathode showed excellent cycling performance with a specific capacity of 454 mAh g(-1) at 0.1 C after 300 cycles. We demonstrate that the organosulfur-DEB units in the copolymer-sulfur composite serve as the 'plasticizer' to effectively prevent the polysulfide shuttling.

Herein, facile synthesis of monodisperse silicon and carbon nanocomposite spheres (MSNSs) is achieved via a simple and scalable surface-protected magnesiothermic reduction with subsequent chemical vapor deposition (CVD) process. Li-ion batteries (LIBs) were fabricated to test the utility of MSNSs as an anode material. LIB anodes based on MSNSs demonstrate a high reversible capacity of 3207 mAh g −1 , superior rate performance, and excellent cycling stability. Furthermore, the performance of full cell LIBs was evaluated by using MSNS anode and a LiCoO 2 cathode with practical electrode loadings. The MSNS/LiCoO 2 full cell demonstrates high gravimetric energy density in the order of 850 Wh L −1 with excellent cycling stability. This work shows a proof of concept of the use of monodisperse Si and C nanocomposite spheres toward practical lithium-ion battery applications.

The kinetics and evolution of binary silicon–polymer systems have been systematically studied for electrochemical energy storage.

Herein, silicon nanoparticles (SiNPs) are coated with conducting hydrogel and wrapped with reduced graphene oxide (rGO) sheets via a facile and scalable solution-based sol-gel process. The in-situ polymerized polypyrrole (PPy) hydrogel forms an interconnected three-dimensional (3D) fiber matrix. Amine and hydroxyl groups from the hydrogel assist the encapsulation of the SiNPs through hydrogen bonding. The electro-conductive PPy fiber network and the wrapping of rGO offer efficient electron and ion transport pathways. The PPy/SiNPs/rGO electrodes can produce highly reversible capacities of 1312, 1285 and 1066 mAh g(-1) at 100, 250 and 500 cycles at a current density of 2.1 A g(-1), respectively.

Herein, commercial Ni foam coated with self-assembled and linearly-aligned Ni wires is utilized as a cost-effective current collector for application in Li-O_2 battery. The Ni wires are furthered deposited with graphene layers (g-Ni wire) to improve electrical conductivity. Multivalent Mn oxides consisting of Mn_3O_4, Mn_2O_3 and MnCO_3 are used as effective oxygen reduction (ORR) and evolution reaction (OER) catalysts deposited on g-Ni wire current collectors. Specific capacities are respective ~100 and ~170 mAh g^-1 without or with O_2 introduction into the cell. The relative facile synthesis process requiring merely solution-based synthesis at ambient pressure, low temperature and short process time renders the Mn oxides/g-Ni wire electrode promising for Li-O_2 battery application.

Herein, NiO-decorated Ni nanowires with diameters ca. 30–150 nm derived from Ni wire backbone (ca. 2 μm in diameter) is directly synthesized on commercially available Ni foam as a renovated anode for Li-ion batteries. Excellent stability with capacity 680 mAh g−1 at 0.5C (1C = 718 mA g−1) is achieved after 1000 cycles. Superior rate capability is exhibited by cycling at extremely high current rates, such as 20C and 50C with capacities ca. 164 and 75 mAh g−1, respectively. The capacity can be recovered back to ca. 430 mAh g−1 in 2 cycles when lowered to 0.2C and stably cycled for 430 times with capacity 460 mAh g−1. The NiO nanowire foam anode possesses low equivalent series resistance ca. 3.5 Ω, resulting in superior power performance and low resistive losses. The NiO nanowire foam can be manufactured with bio-friendly chemicals and low temperature processes without any templates, binders and conductive additives, which possesses the potential transferring from lab scale to industrial production.

Flexible electrodes (C-Si/C) composed of Si/C fibers trapped in carbon fiber frames via double-nozzle electrospinning improve the cycling stability and rate capability of Si/C fabrics. Polyacrylonitrile (PAN) has been demonstrated as a superior carbon matrix for Si compared with polyvinylpyrrolidone (PVP) annealed using the same heat-treatment process.

A binder-less and carbon-free Ni nanofoam decorated with amorphous RuO2 nanoflakes was utilized as an innovative cathode in a Li–O2 battery.

Herein, Ni nanodendrite (ND) with diameter ≈30–100 nm directly synthesized on Ni foam is utilized as an effective support for hydrous RuO2 in symmetric supercapacitors operated at 1.6 V. Highest specific capacitance 678.57 F g−1 can be achieved with energy density 60.32 Wh kg−1. Even at large current density 100 A g−1, high energy density 19.73 Wh kg−1 can still be maintained with power density 40 kW kg−1 owing to the pristine metal nanostructure without any carbon additive and resistive binder. Long lifespan is shown with marginal performance improvement (≈4%) over 10 000 cycles. More importantly, the template‐less and self‐assembled Ni ND synthesis requires only low temperature and eco‐friendly chemicals, and can be simply dip‐coated with RuO2 nanoparticles. All of these render the RuO2‐Ni ND foam readily adapted into mass manufacturing without efforts.

Electrospinning provides a means to synthesize nanofibrous structures with very high surface area-to-volume ratio, which enhance the sensitivity of conductive polymer (CP)-based gas sensors in a cost effective manner. To enhance processability, insulating host polymers are often used with the CP for electrospinning. Unlike CPs, however, the contribution of insulating polymers on overall sensing performance of composites has not been systemically investigated. In this study, we examined the effects of insulating polymers in electrospun composite nanofibers on the sensitivity to various analytes. Different composition ratios of polyaniline (PANI)/poly(epsilon-caprolactone) (PCL) nanofibers were produced by electrospinning, and their structure and chemistry were characterized. The PANI/PCL electrospun composite nanofibers were configured in a chemiresistor and subjected to different analytes, including H2O vapor, NH3, and NO2. H2O vapor and NO2 showed a polarity change in sensitivity, having a compositional threshold of PANI-to-PCL ratio. To investigate this polarity change, the temperature dependence of electrical conductivity was examined. When H2O vapor was exposed to the composite with the highest PANI content at 20 wt%, there was a decrease in hopping distance; on the other hand, an increase in hopping distance was observed when H2O vapor was exposed to the composite with the lowest PANI content at 9 wt%. These results show an existence of competition between the conductive polymer, PANI, and the insulating host polymer, PCL, for analyte interaction, both of which integratively determine the overall sensitivity. The work demonstrates that the host polymer plays an important role in structural swelling as well as chemical interaction with analytes, which critically modulate sensing behavior. (C) 2014 Elsevier B.V. All rights reserved.

Electrospinning as a cost-effective process to synthesize nanofiber with controlled morphology and structure has regained attention in the last decade as result of rapid advancements in nanoscale science and engineering and their applications. Although there are a few works demonstrated the ability to fabricate nano gas sensor using electrospun nanofibers as sensing materials, there are limited works to show the optimization of the sensing performance by understanding the electron transport properties and their sensing mechanism. The overall objective of this work is to electrospun conducting polymer/insulating polymer composite nanofibers (i.e., (+)- camphor-10-sulfonic acid (HCSA) doped polyanline PANI (conductive) blended with PEO (non-conductive)) with different compositions (i.e., 12 to 68 wt.%) and apply them as chemiresistive sensing material to detect ammonia at room temperature. The diameter, defects, and morphology of nanofibers were adjusted by controlling solution composition, processing parameters and their effect toward the sensing performance were also investigated. Viscosity of electrospinning solutions was found to have a pronounced impact on fiber diameter and morphology of PANI/PEO nanofibers. Diameters around 350nm of different compositions of PANI/PEO nanofibers were achieved, where decreasing solution viscosity by increasing the PANI content resulted in a morphology changing from individual fibers to junctions. Although all the compositions of PANI/PEO nanofibers show semiconducting behavior and fit a three dimensional variable hopping range model, the activation energy and hopping distance increased as the PANI content decreased. The PANI/PEO nanofibers exhibited excellent sensitivity towards NH3 with fast response and recovery times where a low detection limit of 0.5 ppm with the sensitivity of 5.6 %/ppm of NH3 was achieved from 26 wt.% PANI/PEO nanofibers. Additionally, the PANI/PEO nanofibers response toward water vapor changed from positive to negative indicating the humidity independent ammonia gas sensor can be fabricated by controlling the composition of PANI/PEO nanofibers.

Electrospinning was utilized to synthesize a polyaniline (PANI)/poly(ε-caprolactone) (PCL) composite in the form of nanofibers to examine its gas sensing performance. Electrical conductivity of the composite nanofibers was tailored by secondary doping with protonic acids including hydrochloride (HCl) or camphorsulfonic acid (HCSA). FT-IR and diffuse reflectance UV-vis spectroscopy were utilized to examine doping-dependent changes in the chemical structure and the protonation state of the nanofibers, respectively. The oxidation and protonation state of the composite nanofibers were shown to strongly depend on the doping agent and duration, demonstrating a simple way of controlling the electrical conductivity of the composite. PANI/PCL electrospun nanofibers having various electrical conductivities via varying dopants and doping concentrations, were configured to chemiresistors for sensing various analytes, including water vapor, NH3, and NO2. Secondary doping with Cl(-) and CSA differentially affected sensing behaviors by having distinctive optimal sensitivities. Biphasic sensitivity with respect to electrical conductivity was observed, demonstrating a facile method to enhance gas sensitivity by optimizing secondary doping. A balance between Debye length of the nanofibers and overall charge conduction may play an important role for modulating such an optimal sensitivity.