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For practical implementation of high-capacity silicon anodes, porous silicon (pSi) structures have demonstrated outstanding cycling stability against the large volume changes typical of solid silicon particles. The conventional magnesiothermic reduction (MR) of silica under static conditions limits the yield of pSi and sometimes produces low-purity of pSi owing to limited mass transfer and many side reactions. Hence, we devise a rotational MR (R-MR) system with rapid magnesium transport in which a uniform Mg/SiO2 molar ratio is readily achievable, and a short reaction time can be applied. Compared to conventional MR, the R-MR process has an extremely high yield (∼90 wt%) of pSi at almost complete conversion of precursor, whereas side reactions are substantially suppressed. Mg 2p X-ray photoelectron spectroscopy analysis of the reduction product reveals that pSi yield is well correlated with the conversion of Mg to MgO. The carbon-coated pSi/C samples and their hybrids with graphite (pSi/C@Gr) composites demonstrate stable cycling performance for 300−600 cycles at high capacity with high cycling efficiency (∼99.9%). Therefore, high-conversion R-MR can be a very efficient and scalable process for obtaining pSi for use in carbon composites (such as pSi/C and pSi/C@Gr) that offer outstanding cycling performance in high-capacity anodes for high-energy LIBs.

Despite its highest theoretical capacity, the practical applications of the silicon anode are still limited by severe capacity fading, which is due to pulverization of the Si particles through volume change during charge and discharge. In this study, silicon nanoparticles are embedded in micron-sized porous carbon spheres (Si-MCS) via a facile hydrothermal process in order to provide a stiff carbon framework that functions as a cage to hold the pulverized silicon pieces. The carbon framework subsequently allows these silicon pieces to rearrange themselves in restricted domains within the sphere. Unlike current carbon coating methods, the Si-MCS electrode is immune to delamination. Hence, it demonstrates unprecedented excellent cyclability (capacity retention: 93.5% after 500 cycles at 0.8 A g–1), high rate capability (with a specific capacity of 880 mAh g–1 at the high discharge current density of 40 A g–1), and high volumetric capacity (814.8 mAh cm–3) on account of increased tap density. The lithium-ion...

The widespread use of lithium–sulfur (Li–S) batteries is still hindered by the low electrochemical activity of sulfur-species, and a short cycle life owing to anode instability coupled with polysulfide shuttle effects. As a first measure to counteract these issues, a new and simple sulfur-loading method consisting of solution impregnation and subsequent melt-diffusion (IM) is demonstrated and compared to the conventional method of physical mixing followed by melt-diffusion (PM). Using the IM method, sulfur is well encapsulated and highly dispersed in conducting mesoporous carbons (MCs) that possess an ideal pore diameter (around 10 nm) and a large pore volume (∼2.8 cm3 g−1). S/MC cathodes prepared by the IM method deliver much higher capacities, better rate responses and cycling stabilities up to 300 cycles (the fading rate was as low as −0.037% per cycle) with less concerns in lithium polysulfide (LPS) shuttling and impedance build up than S/MC cathodes prepared by the PM method. The S/MC cathodes prepared by the IM method has a pseudo-optimum sulfur content of 65 wt%, and when coupled with a new type of carbon-coated separator (CCS), a high areal capacity of >2.5 mA h cm−2 is successfully achieved, combined with excellent cycling stability and rate capability.

A series of Si/graphene sheet/carbon (Si/GS/C) composites was prepared by electrostatic self-assembly between amine-grafted silicon nanoparticles (SiNPs) and graphene oxide (GO). The Si/GS derived from carbonization of Si/GO assemblies showed limited cycling stability owing to loose cohesion between SiNPs and graphene, and increased impedances during cycling. To counteract the cycling instability of Si/GS, an additional carbon-gel coating was applied to the Si/GO assemblies in situ in solution followed by carbonization to yield dense three-dimensional particulate Si/GS/C composite with many internal voids. The obtained Si/GS/C composites showed much better electrochemical performances than the Si/GS owing to enhanced cohesion between the SiNPs and the carbon structures, which reduced the impedance buildup and protected the SiNPs from direct exposure to the electrolyte. A strategy for practical use of a high-capacity Si/GS/C composite was also demonstrated using a hybrid composite prepared by mixing it with commercial graphite. The hybrid composite electrode showed specific and volumetric capacities that were 200% and 12% larger, respectively, than those of graphite, excellent cycling stability, and CEs (>99.7%) exceeding those of graphite. Hence, electrostatic self-assembly of SiNPs and GO followed by in situ carbon coating can produce reliable, high-performance anodes for high-energy LIBs.

The Mo/β (beta zeolite) catalyst was prepared by wet-impregnation and modified with cobalt promoter. The catalytic activity of monometallic Mo/β catalyst in selective hydrocracking of tetralin into monocyclic aromatic hydrocarbons (MAH) such as benzene, toluene and xylene (BTX) was investigated in fixed bed reactor and compared its activity with bimetallic CoMo/β catalyst. The catalytic results indicates that, incorporation of promoter (Co) not only improved their catalytic activity in hydrocracking reactions but also showed long term stability as compared with Mo/β. Effect of different SiO 2 /Al 2 O 3 ratio (25, 75, 150) in beta zeolite was investigated on catalytic activity of CoMo/β. CoMo/β with SiO 2 /Al 2 O 3 of 25, gave highest 62.6% of desired MAH yield at 99.5% conversion of tetralin for more than 140 h of reaction time. Likely, CoMo/β catalyst was also found to be effective for the conversion of pyrolysis fuel oil (PFO) into MAH. Crude PFO was distilled out at 170 °C and total amount of 55 wt.% PFO was received after distillation. In the PFO hydrocracking, it produced 43.3% of MAH product yield at 70% conversion of PFO, which is significantly higher than the conversion (48%) and MAH yield (34.2%) obtained from monometallic Mo/β catalysts. CoMo/β catalyst was found to be more stable as well as active for longer reaction time (140 h).

A mesoporous MnOx network (MMN) structure and MMN/C composites were prepared and evaluated as anodes for high-energy and high-rate lithium-ion batteries (LIB) in comparison to typical manganese oxide nanoparticle (MnNP) and graphite anodes, not only in a half-cell but also in a full-cell configuration (assembled with an NCM523, LiNi0.5Co0.2Mn0.3O2, cathode). With the mesoporous features of the MMN, the MMN/C exhibited a high capacity (approximately 720 mAh g−1 at 100 mA g−1) and an excellent cycling stability at low electrode resistance compared to the MnNP/C composite. The MMN/C composite also showed much greater rate responses than the graphite anode. Owing to the inherent high discharge (de-lithiation) voltage of the MMN/C than graphite as anodes, however, the MMN║NCM523 full cell showed approximately 87.4% of the specific energy density of the Gr║NCM523 at 0.2 C. At high current density above 0.2 C, the MMN║NCM523 cell delivered much higher energy than the Gr║NCM523 mainly due to the excellent rate capability of the MMN/C anode. Therefore, we have demonstrated that the stabilized and high-capacity MMN/C composite can be successfully employed as anodes in LIB cells for high-rate applications.

In order to fabricate high-energy and stable lithium-ion batteries (LIB), herein, mesoporous silicon (mpSi-Y) microparticles were prepared via a facile magnesiothermic reduction of commercial zeolite Y. The electrochemical characteristics of carbon-coated mpSi-Y (mpSi-Y/C) were evaluated in a lithium-ion battery full cell as well as a half-cell configuration and compared with those of silicon nanoparticle-carbon composite (SiNP/C) and graphite (Gr) anodes. With the mesoporous structural features of mpSi-Y, the high-capacity mpSi-Y/C (1200 mAh.g − 1 at 0.05 C) in a half-cell showed a much better cycling stability at a much less impedance build-up and electrode thickness increase than SiNP/C composite. It also presented much faster charging/discharging kinetics than does the graphite anode. A pretreated mpSi-Y/C was paired with a NCM (LiNi0.6Co0.2Mn0.2O2) cathode to fabricate a full cell, mpSi∥NCM. The mpSi∥NCM cell exhibited a comparable cycling performance to that of the Gr∥NCM cell at 0.5 C for 200 cycles. More importantly, detail analysis revealed that the size of the mpSi∥NCM cell can be smaller than that of the Gr∥NCM by more than 50%. The gain in specific energy density of the mpSi∥NCM cell over the Gr∥NCM was about 33%. Thus, the mpSi-Y/C can be promising anodes for stable and high-energy lithium-based batteries.

For the practical use of high-capacity silicon anodes in high-energy lithium-based batteries, key issues arising from the large volume change of silicon during cycling must be addressed by the facile structural design of silicon. Herein, we discuss the zeolite-templated magnesiothermic reduction synthesis of mesoporous silicon (mpSi) (mpSi-Y, -B, and -Z derived from commercial zeolite Y, Beta, and ZSM-5, respectively) microparticles having large pore volume (0.4–0.5 cm3/g), wide open pore size (19–31 nm), and small primary silicon particles (20–35 nm). With these appealing mpSi particle structural features, a series of mpSi/C composites exhibit outstanding performance including excellent cycling stabilities for 500 cycles, high specific and volumetric capacities (1100–1700 mAh g–1 and 640–1000 mAh cm–3 at 100 mA g–1), high Coulombic efficiencies (approximately 100%), and remarkable rate capabilities, whereas conventional silicon nanoparticles (SiNP)/C demonstrate limited cycle life. These enhanced electro...

Silicon-based composites are very promising anode materials for boosting the energy density of lithium-ion batteries (LIBs). These silicon-based anodes can also replace the dendrite forming lithium metal anodes in lithium metal-free Li–O2 and Li–S batteries, which can offer energy content far beyond that of current LIBs. However, it is challenging to design silicon-based materials for use as anodes in real energy storage devices. In this review, we discuss how to boost the energy content of LIBs, the pros and cons of silicon-based anodes, and challenges associated with silicon-based anodes. A major focus of this review is on the rational design of silicon-based composite anodes to address the outstanding issues. In addition, high energy LIBs and Li–S batteries that employ silicon-based anodes are introduced and discussed.

FeF 3 microspheres/reduced graphene oxide (r-GO) composites were synthesized by a simple hydrothermal route with HF vapor. The size of the microspheres was controllable simply by adjusting the amount of graphene oxide in the precursor solution from about 1 to 10 wt%. The FeF 3 microspheres/r-GO composites showed improved discharge capacity and cycling stability in the voltage ranges of 1.5–4.5 V and 2.0–4.5 Vat room temperature compared to those of bulk FeF 3 . For example, the composites delivered an initial discharge capacity of about 196 mAhg −1 at a rate of 0.1C with 0.28% fading per cycle during 50 cycles in the range of 2.0–4.5 V. The composites also showed significantly enhanced rate capabilities in the range of 0.1–20C (e.g., about 170 mAhg −1 at a rate of 1C).

Iron trifluoride (FeF3 ) has been actively studied as an alternative cathode material due to its cost effectiveness, low toxicity, and high theoretical capacities of 237 and 712 mAhg −1 at 2.0−4.5 V and 1.5−4.5 V, respectively. In spite of these advantages, FeF3 has serious shortcomings of poor electronic conductivity and a slow diffusion rate of lithium ions, leading to a lower reversible specific capacity than its theoretical value. In this work, we prepared FeF3 /activated carbon foam (ACF) nanocomposites by impregnating FeF3 nanoparticles in the mesoporous ACF. The FeF3 /ACF nanocomposites showed improved electrochemical performances compared to bulk FeF3 . For example, the FeF3 /ACF nanocomposites showed an initial discharge capacity of 195 mAhg −1 at 0.1 C with a capacity retention of ~93% during 50 cycles in the voltage range 2.0−4.5 V. The cycling stability at 1.5−4.5 V was also superior to that of bulk FeF3 .

It is challenging to design silicon anodes exhibiting stable cycling behavior, high volumetric and specific capacity, and low volume expansion for Li-based batteries. Herein, we designed Si/C-IWGN composites (Si/C composites internally wired with graphene networks). For this purpose, we used simple aqueous sol–gel systems consisting of varying amounts of silicon nanoparticles, resorcinol–formaldehyde, and graphene oxide. We found that a small amount of graphene (1–10 wt%) in Si/C-IWGNs efficiently stabilized their cycling behavior. The enhanced cycling stability of Si/C-IWGNs could be ascribed to the following facts: (1) ideally dispersed graphene networks were formed in the composites, (2) these graphene networks also created enough void spaces for silicon to expand and contract with the electrode thickness increase comparable to that of graphite. Furthermore, properly designed Si/C-IWGNs exhibited a high volumetric capacity of ∼141% greater than that of commercial graphite. Finally, a hybrid sample, Si–Gr, consisting of a high capacity Si/C-IWGN and graphite was prepared to demonstrate a hybrid strategy for a reliable and cost-effective anode with a capacity level required for high-energy Li-ion cells. The Si–Gr hybrid exhibited not only high capacity (800–900 mA h g−1 at 100 mA g−1) but also a high electrode volumetric capacity of 161% greater than that of graphite.

Among various candidates to replace the low capacity graphitic carbon anode in current lithium ion batteries (LIBs), manganese oxides possess the advantages of high lithium storage capacity, low cost, high intrinsic density, environmental friendliness and low lithium storage voltage, i.e., 0.5 V Li+/Li. Manganese oxides, however, have to be incorporated with conducting and porous matrix due to poor electrical conductivity and large volume expansions associated with conversion reaction upon cycling. In this study, a facile one-pot route was attempted for the synthesis of MnO/C nanocomposite for which Mn3O4 nanoparticles were grown in aqueous medium followed by carbon gel formation in a one-pot reactor. Thus obtained Mn3O4/C carbon gel was transformed into MnO/C nanocomposite by thermal annealing in an Ar flow. The MnO nanoparticles (60wt%) of 20–50 nm in diameter were well dispersed throughout the MnO/C composite. The MnO/C composite delivered reversible capacity of 541mAh g−1 with an excellent cycling stability over 100 cycles, while parent Mn3O4 lost most of its capacity in 10 cycles. The MnO/C composite also exhibited much higher rate capability than a commercial graphite anode. Hence, the MnO/C composite based on low cost materials and facile synthetic process could be an attractive candidate for large-scale energy storage applications.

Magnetite, Fe3O4, is a promising anode material for lithium ion batteries due to its high theoretical capacity (924 mA h g−1), high density, low cost and low toxicity. However, its application as high capacity anodes is still hampered by poor cycling performance. To stabilize the cycling performance of Fe3O4 nanoparticles, composites comprising Fe3O4 nanoparticles and graphene sheets (GS) were fabricated. The Fe3O4/GS composite disks of mm dimensions were prepared by electrostatic self-assembly between negatively charged graphene oxide (GO) sheets and positively charged Fe3O4-APTMS [Fe3O4 grafted with (3-aminopropyl)trimethoxysilane (APTMS)] in an acidic solution (pH = 2) followed by in situ chemical reduction. Thus prepared Fe3O4/GS composite showed an excellent rate capability as well as much enhanced cycling stability compared with Fe3O4 electrode. The superior electrochemical responses of Fe3O4/GS composite disks assure the advantages of: (1) electrostatic self-assembly between high storage-capacity materials with GO; and (2) incorporation of GS in the Fe3O4/GS composite for high capacity lithium-ion battery application.

FeF3 is of great interest as a potential candidate cathode material because of its low cost, abundance, environmental friendliness, and high theoretical capacity of about 237 mAh·g–1 in the voltage range of 2.0–4.5 V. However, FeF3 has drawbacks of poor cycling stability and rate performance because of its low intrinsic electrical conductivity and slow diffusion of lithium ions. These issues should be improved for the practical application of FeF3 in lithium-ion battery systems. In this study, FeF3/ordered mesoporous carbon (OMC) nanocomposites were synthesized by an incipient-wetness impregnation technique in a facile and scalable method. The tubular shaped OMC was utilized as both a conductive agent and a hard template for the formation of nanosized FeF3 particles. The FeF3/OMC nanocomposites showed enhanced capacity, cycling stability, and rate performance compared to bulk FeF3 in the voltage range of 2.0–4.5 V at room temperature.

Among lithium alloy metals, silicon is an attractive candidate to replace commercial graphite anode because silicon possesses about ten times higher theoretical energy density than graphite. However, electrically nonconducting silicon undergoes a large volume changes during lithiation/delithiation reactions, which causes fast loss of storage capacity upon cycling due to electrode pulverization. To alleviate these problems, electrodes comprising Si nanoparticles (20 nm) and graphene platelets, denoted as SiGP-1 (Si = 35.5 wt%) and SiGP-2 (Si = 57.6 wt%), have been prepared with low cost materials and using easily scalable solution-dispersion methods. X-ray diffraction (XRD), scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HR-TEM) analyses indicated that Si nanoparticles were highly dispersed and encapsulated between graphene sheets that stacked into platelets in which portions of graphite phases were reconstituted. From the galvanostatic cycling test, SiGP-1 exhibited a reversible lithiation capacity of approximately 802 mAh/g with excellent capacity retention up to 30 cycles at 100 mA/g. Further cycling with a step-increase of current density (100-1,000 mA/g) up to 120 cycles revealed that it has an appreciable power capability as well, showing 520 mAh/g at 1,000 mA/g with capacity loss of 0.2-0.3% per cycle. The improved electrochemical performance is attributed to the robust electrical integrity provided by flexible graphene sheets that encapsulated dispersed Si nanopraticles and stacked into platelets with portions of reconstituted graphite phases in their structure.

Silicon nanoparticles have attracted a great deal of scientific interests due to its intense photoluminescence in the visible spectral region and its potential applications in biological fluorescence maker, RGB (red, green, blue) display, photonics and photovoltaics etc. Practical applications making use of optical and physicochemical properties of Si nanoparticles requires an efficient synthetic method which allows easy modulation of their size, size distribution as well as surface functionalities etc. In this study, a one-pot solution reduction scheme is attempted to prepare alkyl-terminated Si nanoparticles ( or mixture of (Octyl) and , containing alkyl-groups using Na(naphthalide) as reducing agent. The surface capping of Si nanoparticles with octyl-groups as well as Si nanoparticle formation was achieved in one-pot reaction. The hexane soluble Si nanoparticles with octyl-termination were in the range of 2-10 nm by TEM and some oxide groups (Si-O-Si) was present on the surface by EDS/FTIR analyses. The optical properties of Si nanoparticles measured by UV-vis and PL evidenced that photoluminescent Si nanoparticles with alkyl-termination was successfully synthesized by solution reduction of alkyl-containing Si precursors in one-pot reaction.

Spinel lithium manganese oxide was synthesized via co-precipitation. The prepared lithium manganese oxide powder was further heated at 700 ◦ C for 15 h under pressurized (3 bar) oxygen atmosphere. The resultant exhibited a highly crystalline cubic spinel phase with space group Fd3m, as confirmed by X-ray diffraction. The spinel compound exhibited a slightly smaller lattice constant than a conventional spinel compound, even though the cationic ratio of Li/Mn is the same for both compounds. Chemical titration of the Mn component showed that heat treatment under a 3 bar oxygen atmosphere resulted in slightly higher average Mn oxidation state, indicating that the amount of Mn4+ increased after the treatment. The Li1.05Mn1.95O3.99 electrode exhibited improved cycling performance, namely, 96.3% of capacity retention during 100 cycles at elevated temperature (60 ◦ C). The details of the structure and electrochemistry of the electrode are discussed.

Lithographic techniques were used to develop patterned silicone rubber membranes that provide 15 microm high microchannels for artificial lungs. Two types of devices were fabricated as a proof-of-concept: one has a series of parallel, straight, open rectangular channels that are each 300 microm wide, separated by 200-microm walls, and 3-mm long and the other is a wide rectangular channel with support posts, also 3- mm long. Experiments with 30% hematocrit, venous, bovine blood showed average oxygen fluxes ranging from 11 x 10(-7) moles/(min x cm(2)) at a residence time of 0.04 sec to 6.5 x 10(-7) moles/(min x cm(2)) at a residence time of 0.20 sec. The average oxygen flux vs. residence time, which is due to transverse molecular diffusion, follows the same relation for all membranes tested. The corresponding increase in hemoglobin saturation ranged from 9% at the residence time of 0.04 sec to 24% at the residence time of 0.20 sec. The support-post channel membranes are attractive for designers because they can be arbitrarily wide and would be less prone to blockage.

Nano-sized Cu-Sn and Cu oxide particles supported on ball-milled graphite were synthesized, and their electrochemical characteristics for use as anode active materials in lithium-ion batteries were investigated. The samples were also characterized via FE-SEM, XRD, and TGA. Most of the Cu oxides on BMG were monoclinic CuO crystals, whereas the Cu-Sn particles were composed of hexagonal Cu3Sn and tetragonal SnO2 crystals. These particles may contribute to an increase in the reversible capacity of lithium ion batteries.