3PubMed Central Citations
A new fluorine-doped porous carbon-decorated Fe3O4-FeF2 composite, referred to as Fe3O4-FeF2@CFx, was prepared for the first time. The formation mechanism is discussed, and a new concept of introducing double layers of FeF2 and CFx into the oxide-based anode is presented for lithium ion batteries. Varying the amount of fluorine precursor, derivatives of Fe3O4@CFx and FeF2@CFx were further obtained, allowing an original analysis of their electrochemical behaviors. As-prepared Fe3O4-FeF2@CFx can deliver a high capacity of 718 mAh g−1 at 50 mA g−1. Under a hash rate of 1600 mAg−1, the capacity of Fe3O4-FeF2@CFx (around 338 mAh g−1) is higher than that (200 mAh g−1) of FeF2@CFx. Further, its capacity retention of 97% over 100 cycles is much better than the 59.4% observed for Fe3O4@CFx. The positive effect of the CFx layer on the electronic conductivity and ionic diffusion ability was confirmed. The role of FeF2 in the stabilization of the structure of CFx and Fe3O4 is also discussed. Further, a new battery composed of Fe3O4-FeF2@CFx/LiNi0.5Mn1.5O4 with a robust rate capability was assembled and delivered a reversible capacity of 565 mAh g−1 (vs. anode) at 100 mA g−1 with a high potential of 3.3 V and a capacity retention of 81.5% over 50 cycles
Elementary sulphur (S) has been shown to be an excellent cathode material in energy storage devices such as Li–S batteries owing to its very high capacity. The major challenges associated with the sulphur cathodes are structural degradation, poor cycling performance and instability of the solid–electrolyte interphase caused by the dissolution of polysulfides during cycling. Tremendous efforts made by others have demonstrated that encapsulation of S materials improves their cycling performance. To make this approach practical for large scale applications, the use of low-cost technology and materials has become a crucial and new focus of S-based Li-ion batteries. Herein, we propose to use a low temperature spraying process to fabricate graphene/S electrode material, where the ink is composed of graphene flakes and the micron-sized S particles prepared by grinding of low-cost S powders. The S particles are found to be well hosted by highly conductive graphene flakes and consequently superior cyclability ([similar]70% capacity retention after 250 cycles), good coulombic efficiency ([similar]98%) and high capacity ([similar]1500 mA h g−1) are obtained. The proposed approach does not require high temperature annealing or baking; hence, another great advantage is to make flexible Li-ion batteries. We have also demonstrated two types of flexible batteries using sprayed graphene/S electrodes.
Jun Ming, Hai Ming, Wenjing Yang, Won-Jin Kwak, Jin-Bum Park, Junwei Zheng andYang-Kook Sun
One kind of porous carbon-Fe3O4 (e.g., PC-Fe3O4) composite with an industrial production was introduced in the sodium ion battery application for the first time. The PC-Fe3O4 composite, consisting of highly dispersed Fe3O4 nanocrystals within the porous carbon with a relative low percent of 45.5 wt%, could well demonstrate high capacities of 225, 168, 127, 103, 98 and 90 mAhg-1 under the current densities of 50, 100, 200, 300, 400 and 500 mA g-1 with a good stability over 400 cycles. The utilization co-efficient of Fe3O4 nanocrystals was proved to be much higher than most Fe3O4 nanoparticles reported recently under the study of capacity contribution of carbon originally. And also, the robust of electrode during the charge-discharge was well characterized by the ex-situ XRD and emission scanning electron microscopy (SEM). More importantly, a new concept of elemental iron-based sodium ion battery of PC-Fe3O4/Na2FeP2O7 was presented. This is the first example to introduce an element-rich configuration in sodium ion battery from the viewpoint of sustainability. The full battery demonstrated a superior capacity of 93 mAh g-1, high capacity retention of 93.3% over 100 cycles and work voltage around 2.28 V with the energy density of 203 Wh kg-1. Such configuration of iron-based sodium battery would be highly promising and sustainable owing to its low cost and high stability in grid storage.
A completely new compound of Na0.89Fe1.8(SO4)3 was prepared by the chemical oxidation of alluaudite Na2.4Fe1.8(SO4)3 phase and its electrochemical performance in lithium battery application was investigated for the first time.•A high capacity of 110 mAhg–1 at 0.1 C was obtained with a good rate kinetics and reversibility within a range of 0.1-10 C (1C = 118 mAhg- 1) involving a high Fe3 +/Fe2 + redox potential of 3.75 V (vs. Li/Li+).
The lithium storage capacity of an iron oxide-based anode of porous carbon–Fe3O4 (i.e., PC–Fe3O4) was investigated by varying the initial current and mass density of the electrode to achieve a good utilization coefficient of the oxide. It was confirmed that these factors largely affected the capacity of PC–Fe3O4 and a certain mass density of the electrode was key to achieve a high area capacity (μAh cm−2). Moreover, the chemical and electrochemical lithiation of PC–Fe3O4 were related to the lithiation time and pressure and both were both systemically studied. After optimization, a new battery of PC–Fe3O4/Li[Ni0.59Co0.16Mn0.25]O2 with a high area capacity of 748 μAh cm−2 (≈150 mAh g−1) and superior energy density of 483 Wh kg−1 (work voltage≈3.2 V) was developed. The battery showed reversible work ability in the rate window of 50–800 mA g−1, and also it could be charged/discharged for well over 1000 cycles with a capacity retention of 63.8 % under the high current value of 0.505 mA (current density, 50 mA g−1).
Journal of Materials Chemistry A
A new and simple strategy was developed to well disperse TiO2 nanocrystals into the porous carbon (i.e., PC), and a series of hierarchical PC-TiO2 composite with different architectural structures were synthesized. Varying the amount of TiO2, the lithium storage capacity of PC-TiO2 (from 30 wt% TiO2 to 64 wt%) could be controlled from 546 mAh g-1 to 446 mAh g-1 under the current density of 50 mA g-1. And also, a very stable cycling performances and rate capabilities could also be obtained at the rate of 50 mA g-1 to 1600 mA g-1. Further increasing the content of TiO2 to 93%, another new composite of TiO2-C was also prepared and it demonstrated a high capacity of 352 mAh g-1 at 50 mA g-1, which was much higher than most reported TiO2 materials. Based on above results, new full cells versus cathode of LiNi0.5Mn1.5O4, such as PC-TiO2/LiNi0.5Mn1.5O4, was successfully assembled and investigated. This full battery not only delivered a high energy density of 413 Wh kg-1 but also showed good rate capability and an energy retention of 90.5% over 100 cycles.
ACS Appl Mater Interfaces
A simple surfactant-assisted reflux method was used in this study for the synthesis of cocklebur-shaped Fe2O3 nanoparticles (NPs). With this strategy, a series of nanostructured Fe2O3 NPs with a size distribution ranging from 20 to 120 nm and a tunable surface area were readily controlled by varying reflux temperature and the type of surfactant. Surfactants such as cetyltrimethylammonium bromide (CTAB), polyvinylpyrrolidone (PVP), poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) (F127) and sodium dodecyl benzene sulfonate (SDBS) were used to achieve large-scale synthesis of uniform Fe2O3 NPs with a relatively low cost. A new composite of Fe3O4@CFx was prepared by coating the primary Fe2O3 NPs with a layer of F-doped carbon (CFx) with a one-step carbonization process. The Fe3O4@CFx composite was utilized as the anode in a lithium ion battery and exhibited a high reversible capacity of 900 mAh g-1 at a current density of 100 mA g-1 over 100 cycles with 95% capacity retention. In addition, a new Fe3O4@CFx/LiNi0.5Mn1.5O4 battery with a high energy density of 371 Wh kg-1 (vs. cathode) was successfully assembled, and more than 300 cycles were easily completed with 66.8% capacity retention at 100 mA g-1. Even cycled at the high temperature of 45 oC, this full cell also exhibited a relatively high capacity of 91.6 mAh g-1 (vs. cathode) at 100 mA g-1 and retained 54.6% of its reversible capacity over 50 cycles. Introducing CFx chemicals to modify metal oxide anodes and/or any other cathode is of great interest for advanced energy storage and conversion devices.
Porous TiO2 nanoribbons and TiO2 nanoribbon/carbon dot composites with excellent performances in lithium-ion batteries were prepared via a simple and efficient method.
The spinel LiMn2O4was recognized as an appealing candidate cathode material for high rate Li-ionbattery, but it suffers from severe capacity fading, especially at a high temperature. In order to solvethis problem, we prepared V2O5coated LiMn2O4(LiMn2O4@V2O5) samples in this work and its structureand morphology were characterized by powder X-ray diffraction, scanning electron microscope, andtransmission electron microscope. The LiMn2O4@V2O5material delivers an excellent cycling ability andrate capability in lithium batteries, while sustaining a capacity of 75.5 mAh g−1after 200 cycles at 2 C witha high operating temperature (328 K). This performance are much better than that of LiMn2O4(35.4 mAhg−1) without V2O5coating, the capacity of which faded seriously. These results indicated that the surfacemodification of V2O5, which possess a relative lower operating potential (≤ 3.7 V, LixV2-x/5O5) compareto the LiMn2O4(∼ 3.9 and 4.1 V), can improve the electrochemical properties of LiMn2O4by endowing afast lithium diffusion and reasonable electronic conductivity which facilitates the transformation of theelectrons and ions. In addition, the acidic and isolated protective layer of V2O5can work as a HF inhibitorand/or HF scavenger and suppress the dissolution of manganese into electrolyte. Thus, we believe thatsuch a LiMn2O4@V2O5composite can be an economical and viable candidate cathode material for Li-ionbatteries.
Carbon and nitrogen, (C&N), co-modified hierarchical Li4Ti5O12(LTO) particles with excellent perfomancein lithium-ion batteries were prepared via a facile synthesis with the proper modifying of C and N suc-cessfully reducing the polarization and enhancing the conductivity of LTO while also giving rise to Ti3+sites due to the reduction ability of C&N. Together, with primary nanocrystals less than 10 nm and arelatively high specific surface area (16.9 m2g−1), as-prepared samples exhibit excellent electrochemicalperformance, such as a high capacity around 174.7 mAh g−1at the current rate of 0.1 C and reversiblecapacity over 171 and 150 mAh g−1after 100 cycles at the current rate of 1 and 10 C (1 C = 175 mAhg−1). More importantly, the optimal amount of C&N modifying in LTO was investigated for the first time.It was found that excessive modifying of C&N can introduce a lot of amorphous TiONxand also createundesirable Ti2+to induce a structural transformation of LTO, directly leading to a low rate capacity.
In this study, highly dispersive spherical Li-rich solid solution (Li1.2Mn0.54Ni0.13Co0.13O2) particles aresuccessfully synthesized by a co-precipitation method. Then these particles are treated with aluminumnitrates ethanol solution at 80◦C. The treatment can extract lithium (Li2O) from the Li2MnO3componentin the composite of Li1.2Mn0.54Ni0.13Co0.13O2. Simultaneously, a thin layer of Al2O3can be precipitatedon the surface of the electrode particles via direct thermal decomposition of aluminum nitrates. Aftertreatment, the first-cycle coulombic efficiency of the electrode increases from 72.1% to 93.6%, meanwhileit shows a superior cycling stability at 100 mA g−1with a discharge capacity of around 220 mAh g−1andretention of 92.5% after 100 cycles, which is much higher than that of the pristine electrode (83.2%). Evenat a high current density of 2 A g−1(10 C), the discharge capacity could still achieve and well maintain ashigh as 140 mAh g−1.
The salt effect of NaxA (A = SO4 2−, Cl−, NO3 −, etc.) on the hydrothermal carbonization of biomass is reported. It is a new catalyst and recyclable template to more simply and effectively prepare carbon-based materials, such as porous carbon-coated anode materials (e.g., Fe3 O4@porous-C) in lithium-ion battery applications with enhanced performance.
A new kind of metal oxide nanoparticle coated with a uniform layer of N-doped carbon (e.g., Fe3 O4@CNy, CoOx@CNy) was prepared readily in one-step. The nanoparticles show a high and stable lithium storage ability for lithium-ion battery applications.
Journal of Materials Chemistry A
In this work, we have developed a new method to synthesize a Fe3O4@graphene (Fe3O4@GN) composite.First, the precursor was synthesized through the decomposition of ferric nitrate in the presence of graphene oxide in the mixed solvent of CO2–expanded ethanol. Then, the precursor was converted to the Fe3O4@GN composite via thermal treatment in N2 atmosphere. With the help of the CO2–expanded ethanol, Fe3O4 nanoparticles were coated on the surface of GN completely and uniformly with high loading. However, it is difficult to load Fe3O4 particles onto the surface of GN and most of the Fe3O4 particles were deviated away from GN and aggregated to form larger units in pure ethanol. When used as anode for Li-ion batteries (LIBs), the Fe3O4@GN composite with a graphene content of 25 wt% synthesized in CO2–expanded ethanol manifested excellent charge–discharge cycling stability and rate performance compared with the sample synthesized in ethanol. Such improved electrochemical performances should be attributed to the intimate contact between the GN and Fe3O4 nanoparticles in the composite. Since the present method does not need tedious pre-treatment, surfactant, or precipitate, it is a green or sustainable technology and the solvents could be recycled easily after simple phase separation. This facile method can be extended to the synthesis of other metal oxide composites, which are expected to have good performance as anode materials for LIBs and other applications.
Journal of Energy Chemistry
Li(Mn1/3Ni1/3Co1/3)O2 cathode materials were fabricated by a hydroxide precursor method. Al2O3 was coated on the surface of the Li(Mn1/3Ni1/3Co1/3)O2 through a simple and effective one-step electrostatic self-assembly method. In the coating process, a NaHCO3-H2CO3 buffer was formed spontaneously when CO2 was introduced into the NaAlO2 solution. Compared with bare Li(Mn1/3Ni1/3Co1/3)O2, the surface-modified samples exhibited better cycling performance, rate capability and rate capability retention. The Al2O3-coated Li(Mn1/3Ni1/3Co1/3)O2 electrodes delivered a discharge capacity of about 115 mAh·g−1 at 2 A·g−1, but only 84 mAh·g−1 for the bare one. The capacity retention of the Al2O3-coated Li(Mn1/3Ni1/3Co1/3)O2 was 90.7% after 50 cycles, about 30% higher than that of the pristine one.
Journal of Materials Chemistry A
In this work, we report a facile method for the synthesis of a Co3O4 functionalized carbon nanotube (Co3O4–f-CNT) composite via the growth of Co3O4 nanoparticles on the surface of functionalized carbon nanotubes (f-CNTs) by thermal decomposition of cobalt nitrate hexahydrate in ethanol. The composite consists of 13% carbon nanotubes and 87% Co3O4 nanoparticles by weight, and all the Co3O4 particles grew compactly along the carbon nanotube axis with a highly uniform dispersion.When used as an anode material for rechargeable lithium ion batteries, the composite manifested high capacities and excellent cycling performance at high and low current rates. The discharge capacity was 719 mA h g-1 at the 2nd cycle and 776 mA h g-1 at the 100th cycle. Even at a current density of 1 A g-1, the specific capacity still remained at about 600 mA h g-1. This superior electrochemical performance was attributed to the unique nanostructure of the composite. Because almost all of the Co3O4 nanoparticles were immobilized on the surface of f-CNTs, physical aggregation of nanoparticles was avoided during the charge–discharge processes. Furthermore, the good mechanical flexibility of f-CNTs can readily alleviate the massive volume expansion/shrinkage associated with a conversion reaction electrode. Finally, f-CNTs are highly conductive matrices for electrons due to their high conductivity, which can shorten the diffusion path for electrons.
Journal of Material Chemistry
In this study, an effective method of slow hydrolization of metal alkoxide (e.g., Ti(C4H9O)4) in an ethanol–water system was systematically investigated and used to finely control the deposition of titania on carbon colloids. A model of adsorption–hydrolization of precursors during the coating process was rationally built for the first time to interpret the usability of the method and facilitate its further extension. Using this strategy, titania in the form of supported nanocrystals or layers on carbon colloids (TiO2/C, C@TiO2) was successfully tailored. Meanwhile, finely dispersed hollow TiO2 nanoparticles with shells consisting of different crystalline structures were also prepared by varying the calcination conditions after removing the carbon cores. More importantly, the effects of the crystalline and nano/macrostructures of the as-prepared TiO2 samples in photocatalysis and lithium-ion battery applications were analyzed in detail. The preliminary results show that anatase–rutile TiO2 hollow particles demonstrate a higher catalytic activity in the photo-degradation of rhodamine B than anatase TiO2 hollow particles, powders, and P25. However, in the case of Li-ion battery applications, the anatase TiO2 hollow particles exhibited better performance as anode materials with high capacities of around 190 mA h g-1, 140 mA h g-1, and 120 mA h g-1 at current densities of 60 mA g-1, 120 mA g-1,and 300 mA g-11, respectively, accompanied by stable cyclability.
J Colloid Interface Sci 2012 Jul 23;377(1):322-7. Epub 2012 Mar 23.
State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, People's Republic of China.
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Journal of Catalysis
Water as a green solvent to replace the conventional organic solvent presents many advantages in the organic synthesis. The hydrogenation of nitrobenzene in water has been investigated by using Ni/TiO2 catalyst in this work, and our main purpose was focused on the Ni/TiO2 catalyst activity and its stability improvement. The experimental results and analysis from the data of XRD, XPS, ICP revealed that the formation of nickel hydroxide from metallic nickel reacting with water caused a rapid deactivation of Ni/TiO2 catalyst. Based on these, we designed a catalyst with hydrophobic property to prevent the nickel active species to contact with water; thus, a hydrophobic carbon layer was coated on the surface of Ni/TiO2. As expected, the hydrophobic carbon was successfully coated on Ni/TiO2 catalysts by a hydrothermal method and they presented higher reactivity and improved stability in the present aqueous reaction system; nickel hydroxide was not detected on the used and water treated carbon-coated Ni/TiO2 samples. The improved abilities were attributed to the increased hydrophobicity of catalysts modified by carbon, which not only prevents water to contact with nickel catalytic species, but also protects the metallic nickel to be oxidized as it exposed to air.
Journal of Materials Chemistry
In this contribution, monodisperse porous hollow bi-phase g-/a-Fe2O3 nanoparticles were successfully fabricated based on hard-template method with using carbon colloids as sacrificial templates. A new concept of assembling one kind of metal oxide with different crystalline structures into a single shell was presented for the first time. The critical procedure of coating carbon cores with a uniform layer of oxide was performed in CO2-expanded ethanol, which is a versatile way to produce high-quality hollow oxide nanoparticles. The formation of the novel bi-phase shell was achieved through combining the reduction ability of carbon cores under inert calcination atmosphere and the unique chemical composition of intermediate-shell formed in CO2-expanded ethanol. The porous hollow g-/a-Fe2O3 nanoparticles with an average diameter of 99 nm not only possess combined properties of g-Fe2O3 and a-Fe2O3, but also have a large specific surface area of 93.7 m2 g1 and a high pore volume of 1.056 cm3 g1, enabling them to have widespread applications in sensors, catalysis, magnetic and electrochemical areas, etc. Herein,such hollow bi-phase g-/a-Fe2O3 nanoparticles were utilized to prepare a sensor device, and intriguingly it shows higher sensitivity and selectivity to ethanol than g-Fe2O3 powders and many other porous a-Fe2O3 materials reported recently. The probable sensor mechanism of hollow g-/a-Fe2O3 nanoparticles was discussed in detail.
Chem Commun (Camb) 2011 May 22;47(18):5223-5. Epub 2011 Mar 22.
State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, PR China.
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Journal of Materials Chemistry
In this work, we presented a new way for the functionalization of carbon nanotubes (CNTs) with the use of biomass as starting materials and introduced a novel concept of knitting process in the chemistry of CNTs for the first time. A mixture of aromatic compounds obtained from the hydrothermal treatment of biomass, rather than the traditional polymer monomers, was used as the nanoscale building blocks to knit an oxygenated network-coat on the CNTs layer-by-layer. It is an effective, mild, green and easily-controlled method for the functionalization of CNTs. The obtained f-CNTs were proved to be a promising catalyst support for metal catalysts, such as Ru/f-CNTs, showed high activity and selectivity for the hydrogenation of citral to unsaturated alcohol. More importantly, we opened a pioneering way for the conversion of low-cost, abundant and renewable biomass into a hydrophilic/chemical reactive network-coat on the inert surface of a wide range of sp2 carbon materials, such as prevalent fullerene, carbon nanotubes, carbon nanohorns and hot graphene etc.
The Journal of Supercritical Fluids
The fabrication of nanostructured materials from hydrous inorganic metal salt processed in supercritical CO2 (scCO2) expanded liquids has advantages to obtain good results. However, the behavior of the inorganic salts and the detailed reaction mechanism are still unknown up to now. In this work, the actual behavior of hydrous inorganic metal salts in CO2 expanded ethanol at the temperature of 50–200 ◦C, including the phase behavior, deposition mechanism, reaction rate and the effect of templates on the deposition were systematically investigated by using XRD, FTIR, CHN-analysis, TGA, ICP-AES. A series of experimental parameters such as CO2 flow rate, expand procedure, reaction temperature and time have been discussed, as well as the roles of CO2 and H2O (often originated from salts and/or solvent but always neglected) were studied in this contribution. Significantly, a coordination–decomposition (C–D) was proved to be the converting mechanism for the precipitation of the hydrous inorganic metal salts,rather than the fuzzy decomposition.
Highly concentrated microcrystalline cellulose was directly converted to isosorbide with yields of 35–50%, providing a new approach for producing important fine chemicals from biomass.
Journal of Materials Chemistry
In this contribution, we present an efficient, versatile and green strategy for finely controlling the metal(oxide) coating on core particles through in situ reaction of precursors in CO2 expanded ethanol without using any precipitants. It not only avoids the formation of free metal (oxide) and/or naked cores, but also permits individual dispersion of all the resultant particles without aggregation. With this method, the composition, thickness, uniformity, and structure of the metal (oxide) shell could be precisely controlled. A wide variety of unreported high-quality core-shell particles with a shell consisting of highly dispersed metal (oxide) nanocrystals or nanoalloys, such as C@Ni, CoO/C,C@Ni&Co and C@Ni&Pd particles have been fabricated, and the properties of the resultant particles were precisely tailored, such as the promising catalytic performance obtained over Ni/C and C@Ni particles in the hydrogenation of nitrobenzene. The present coating strategy is more simple and precisely controllable compared to the conventional deposition method and it is suitable for most precursors and even for multi-component materials, enabling the fabrication of nanostructured materials more easily and precisely.
CO2-in-Water (C/W) emulsion was formed by using a nonionic surfactant of poly (ethylene oxide)-poly (propylene oxide)-poly (ethylene oxide) (P123), and palladium nanoparticles were synthesized in situ in the present work. The catalytic performance of Pd nanoparticles in the C/W emulsion has been discussed for a selective hydrogenation of citral. Much higher activity with a turnover frequency (TOF) of 6313 h-1 has been obtained in this unique C/W emulsion compared to that in the W/C microemulsion (TOF, 23 h-1), since the reaction was taking place not only in the surfactant shell but also on the inner surface of the CO2 core in the C/W emulsion. Moreover,citronellal was obtained with a higher selectivity for that it was extracted to a supercritical carbon dioxide (scCO2) phase as formed and thus its further hydrogenation was prohibited. The Pd nanoparticles could be recycled several times and still retain the same selectivity, but it showed a little aggregation leading to a slight decrease in conversion.
Hydrogenation of a,b-unsaturated aldehydes (citral, 3-methyl-2-butenal, cinnamaldehyde) has been studied with tetrakis(triphenylphosphine) ruthenium dihydride (H2Ru(TPP)4) catalyst in a poly(ethylene glycol) (PEG)/compressed carbon dioxide biphasic system. The hydrogenation reaction was slow under PEG/H2 biphasic conditions at H2 4 MPa in the absence of CO2. When the reaction mixture was pressurized by a non-reactant of CO2, however, the reaction was significantly accelerated. As CO2 pressure was raised from 6 MPa to 12 MPa, the conversion of citral increased from 35% to 98%, and a high selectivity to unsaturated alcohols (geraniol and nerol) of 98% was obtained. The products were able to be extracted by high pressure CO2 stream and separated from the PEG phase, dissolving the Ru complex catalyst and the catalyst was recyclable without any post-treatment.