Electrospun CuFe_2O_4 nanotubes as anodes for high-performance lithium-ion batteries

Herein,we report on the synthesis and lithium storage properties of electrospun one-dimensional(1D) CuFe_2O_4 nanomaterials.1D CuFe_2O_4nanotubes and nanorods were fabricated by a single spinneret electrospinning method followed by thermal decomposition for removal of polymers from the precursor fibers.The as-prepared CuFe_2O_4 nanotubes with wall thickness of ~50 nm presented diameters of ~150 nm and lengths up to several millimeters.It was found that phase separation between the electrospun composite materials occured during the electrospinning process,while the as-spun precursor nanofibers composed of polyacrylonitrile(PAN),polyvinylpyrrolidone(PVP) and metal salts might possess a core-shell structure(PAN as the core and PVP/metal salts composite as the shell) and then transformed to a hollow structure after calcination.Moreover,as a demonstration of the functional properties of the 1D nanostructure.CuFe_2O_4 nanotubes and nanorods were investigated as anodes for lithium ion batteries(LIBs).It was demonstrated that CuFe_2O_4 nanotubes not only delivered a high reversible capacity of ~816 mAh·g~(-1) at a current density of 200 mA·g~(-1)over 50 cycles,but also showed superior rate capability with respect to counterpart nanorods.Probably,the enhanced electrochemical performance can be attributed to its high specific surface areas as well as the unique hollow structure.     

Synthesis of FeS2/CoS heterostructure microspheres as anodes for high-performance Li-ion batteries

Journal of Solid State Electrochemistry - FeS2/CoS and FeS2/CoS/C composites were synthesized by solvothermal method and following vapor phase vulcanization at mild temperature with binary oxide...     

Electrospun CuFe2O4 nanotubes as anodes for high-performance lithium-ion batteries

Herein,we report on the synthesis and lithium storage properties of electrospun one-dimensional(1D) CuFe_2O_4 nanomaterials.1D CuFe_2O_4nanotubes and nanorods were fabricated by a single spinneret electrospinning method followed by thermal decomposition for removal of polymers from the precursor fibers.The as-prepared CuFe_2O_4 nanotubes with wall thickness of ~50 nm presented diameters of ~150 nm and lengths up to several millimeters.It was found that phase separation between the electrospun composite materials occured during the electrospinning process,while the as-spun precursor nanofibers composed of polyacrylonitrile(PAN),polyvinylpyrrolidone(PVP) and metal salts might possess a core-shell structure(PAN as the core and PVP/metal salts composite as the shell) and then transformed to a hollow structure after calcination.Moreover,as a demonstration of the functional properties of the 1D nanostructure.CuFe_2O_4 nanotubes and nanorods were investigated as anodes for lithium ion batteries(LIBs).It was demonstrated that CuFe_2O_4 nanotubes not only delivered a high reversible capacity of ~816 mAh·g~(-1) at a current density of 200 mA·g~(-1)over 50 cycles,but also showed superior rate capability with respect to counterpart nanorods.Probably,the enhanced electrochemical performance can be attributed to its high specific surface areas as well as the unique hollow structure.     

Rational design of robust nano-Si/graphite nanocomposites anodes with strong interfacial adhesion for high-performance lithium-ion batteries

The nano-Si/graphite nanocomposites are the promising anodes candidates for high-energy lithium-ion batteries because of their high theoretical capacities and low volume variations.However,the nano-Si has a severe tendency to separate from the graphite substrate due to the inherently weak bonding between them,thus leading to the deteriorated cycling performance and low Coulombic efficiency.Herein,we design a robust nano-Si/graphite nanocomposite structure with strong interfacial adhesion caused by the Si—Ti and Ti—C covalent bonds.The abundant Si—Ti and Ti—C bonds formed between nano-Si and graphite greatly enhance the interfacial adhesion force,resulting in the highly stabilized and integrated electrode structure during battery cycling.Consequently,the as-obtained nano-Si/graphite anodes deliver a high capacity retention of 90.0% after 420 cycles at 0.5 C with an average Coulombic efficiency of 99.5%;moreover,a high initial Coulombic efficiency of 90.2% is achieved.Significantly,this work provides a novel strategy to address the poor interfacial adhesion between nano-Si and graphite,which can be applied to other nano-Si based composites anodes.     

Co3V2O8催化剂的合成表征及其催化性能研究

采用共沉淀法制备了Co₃V₂O₈催化剂,并对催化剂进行了BET、XRD、H₂-TPR、XPS、和 TEM等技术表征,研究了其丙烷氧化脱氢 (ODH) 制丙烯反应的催化性能。H₂-TPR和XPS实验结果表明,Co₃V₂O₈催化剂中晶格氧可以较容易转换成可动氧物种(即未完全还原氧物种),使催化剂内各种价态的钒之间易于进行氧化还原反应并形成氧缺位,催化剂的表面含有较多未充分还原氧物种O^-和V⁴⁺ 物种。催化活性结果显示,在425℃和475℃,丙烯选择性分别为49.45%和33.74%,表现了较好的催化性能。     

Facile hydrothermal construction of Nb_2CT_x/Nb_2O_5 as a hybrid anode material for high-performance Li-ion batteries

Herein,a simple yet efficient hydrothermal strategy is developed to in-situ convert multi-layered niobium-based MXene(Nb₂ CT_x) to hierarchical Nb2 CTx/Nb₂O₅ composite.In the hybrid,the Nb₂O₅ nanorods are well dispersed in and/or on the Nb₂ CTx.Thanks to the synergetic contributions from the high capacity of Nb₂O₅ and superb electrical conductivity of the two-dimensional Nb₂ CT_x     

Electrochemical reaction mechanism of porous Zn2Ti3O8 as a high-performance pseudocapacitive anode for Li-ion batteries

Zn₂Ti₃O₈, as a new type of anode material for lithium-ion batteries, is attracting enormous attention because of its low cost and excellent safety. Though decent capacities have been reported, the electrochemical reaction mechanism of Zn₂Ti₃O₈ has rarely been studied. In this work, a porous Zn₂Ti₃O₈ anode with considerably high capacity (421 mAh/g at 100 mA/g and 209 mAh/g at 5000 mA/g after 1500 cycles) was reported, which is even higher than ever reported titanium-based anodes materials including Li₄Ti₅O₁₂, TiO₂ and Li₂ZnTi₃O₈. Here, for the first time, the accurate theoretical capacity of Zn₂Ti₃O₈ was confirmed to be 266.4 mAh/g. It was also found that both intercalation reaction and pseudocapacitance contribute to the actual capacity of Zn₂Ti₃O₈, making it possibly higher than the theoretical value. Most importantly, the porous structure of Zn₂Ti₃O₈ not only promotes the intercalation reaction, but also induces high pseudocapacitance capacity (225.4 mAh/g), which boosts the reversible capacity. Therefore, it is the outstanding pseudocapacitance capacity of porous Zn₂Ti₃O₈ that accounts for high actual capacity exceeding the theoretical one. This work elucidates the superiorities of porous structure and provides an example in designing high-performance electrodes for lithium-ion batteries.     

Nanostructured Sn/TiO2/C composite as a high-performance anode for Li-ion batteries

A nanostructured Sn/TiO₂/C composite was prepared from SnO, Ti, and carbon powders using a mechanochemical reduction method and evaluated as an anode material in rechargeable Li-ion batteries. The Sn/TiO₂/C nanocomposite was composed of uniformly dispersed nanocrystalline Sn and rutile TiO₂ in amorphous carbon matrix. In addition, electrochemical Li insertion/extraction in rutile TiO₂ was examined by ex situ XRD and extended X-ray absorption fine structure. The Sn/TiO₂/C nanocomposite exhibited excellent electrochemical performance, which highlights its potential as a new alternative anode material in Li-ion batteries.     

Assembling Co_9S_8 nanoflakes on Co_3O_4 nanowires as advanced core/shell electrocatalysts for oxygen evolution reaction

Rational design of advanced cost-effective electrocatalysts is vital for the development of water electrolysis. Herein, we report a novel binder-free efficient Co_9S_8@Co_3O_4 core/shell electrocatalysts for oxygen evolution reaction(OER) via a combined hydrothermal-sulfurization method. The sulfurized net-like Co_9S_8 nanoflakes are strongly anchored on the Co_3O_4 nanowire core forming self-supported binder-free core/shell electrocatalysts. Positive advantages including larger active surface area of Co_9S_8 nanoflakes,and reinforced structural stability are achieved in the Co_9S_8@Co_3O_4 core/shell arrays. The OER performances of the Co_9S_8@Co_3O_4 core/shell arrays are thoroughly tested and enhanced electrocatalytic performance with lower over-potential(260 m V at 20 m A cm~(-2)) and smaller Tafel slopes(56 mV dec-1) as well as long-term durability are demonstrated in alkaline medium. Our proposed core/shell smart design may provide a new way to construct other advanced binder-free electrocatalysts for applications in electrochemical catalysis.     

Synthesis of NiS/carbon composites as anodes for high-performance sodium-ion batteries

Journal of Solid State Electrochemistry - We demonstrate a general solid-state synthesis of nickel sulfide (NiS) and carbon-based composites (NiS/C) via simple thermal decomposition of nickel...     

Achieving high-performance Li2ZnTi3O8 anode for advanced Li-ion batteries by molybdenum doping

The Li₂ZnTi_3-xMo_xO₈ (x = 0, 0.05, 0.1 and 0.15) anode materials are successfully synthesized through a simple solid-state method, and few Li₂MoO₄ phase can be found in Li₂ZnTi_3-xMo_xO₈ (x = 0.1 and 0.15). All samples are composed of nanocrystalline particles and irregular micron-sized particles with a relatively uniform particle size of 100–200 nm Li₂ZnTi_2.9Mo_0.1O₈ shows the best electrochemical properties among all samples. The Li₂ZnTi_2.9Mo_0.1O₈ delivers a charge/discharge capacity of 188.1/188.2 mA h/g at 1 A/g after 400 cycles, but the corresponding capacity of pristine Li₂ZnTi₃O₈ is only 104.5 (102.2) mA h/g. The Mo⁶⁺ doping enhances the reversible capacity, rate performance, and cycling stability of Li₂ZnTi₃O₈, especially at large current densities. The improved electrochemical performance of Li₂ZnTi_3-xMo_xO₈ can be ascribed to the enhanced electrical conductivity, improved intercalation/de-intercalation reversibility of Li ions, increased lithium-ion diffusion coefficients, and reduced charge-transfer resistance. This work provides an effective strategy to construct high-performance anode materials for advanced lithium-ion battery; this effective design strategy may be used to enhance the reversible specific capacity, and rate the performance and cycle stability of other insertion-host anode materials.     

Rational design of self-sacrificial template derived quasi-Cu-MOF composite as anodes for high-performance lithium-ion batteries

MOF-based composites have aroused widespread concern due to their controllable morphology and pore characteristics. Nevertheless, the poor conductivity and volume expansion hinder its practical application in LIBs. Herein a classical structure HKUST-1, as the precursor, was used to fabricate quasi-Cu-MOF composite through a facile thermal decomposition strategy. The results showed that quasi-Cu-MOF composite had superior reversible specific capacity (627.5 mAh/g at 100 mA/g) and outstanding cycle stability (514.6 mAh/g at 500 mA/g after 400 cycles) as anodes for LIBs. The results demonstrated that the low-temperature calcination strategy played a significant role in morphology retaining during cycling and the derived copper framework play a crucial part in conductivity improvement. This work is helpful to the design of high-performance electrodes with advanced three-dimensional hierarchical structures.     

Promoted porous Co_3O_4-Al_2O_3 catalysts for ammonia decomposition

Transition metal catalysts have been considerably used for NH_3 decomposition because of the potential application in CO_x-free H_2 generation for fuel cells.However,most transition metal catalysts prepared via traditional synthetic approaches performed the inferior stability due to the agglomeration of active components.Here,we adopted an efficient method,aerosol-assisted selfassembly approach(AASA),to prepare the optimized cobalt-alumina(Co_3O_4-Al_2O_3)catalysts.The Co_3O_4-Al_2O_3catalysts exhibited excellent catalytic performance in the NH_3 decomposition reaction,which can reach 100%conversion at 600°C and maintain stable for 72 h at a gaseous hourly space velocity(GHSV)of 18000 cm~3g~(-1)_(cat)h~(-1).The catalysts were characterized by various techniques including transmission electron microscope(TEM),scanning electron microscope(SEM),nitrogen sorption,temperature-programmed reduction by hydrogen(H_2-TPR),ex-situ/in-situ Raman and ex-situ/in-situ X-ray diffraction(XRD)to obtain the information about the structure and property of the catalysts.H_2-TPR and in-situ XRD results show that there is strong interaction between the cobalt and alumina species,which influences the redox properties of the catalysts.It is found that even a low content of alumina(10 at%)is able to stabilize the catalysts due to the adequate dispersion and rational interaction between different components,which ensures the high activity and superior stability of the cobalt-alumina catalysts.     

MOF-template derived hollow CeO_2/Co_3O_4 polyhedrons with efficient cathode catalytic capability in Li-O_2 batteries

Li-O_2 batteries(LOBs) have been perceived as the most potential clean energy system for fast-growing electric vehicles by reason of their environmentally friendlier,high energy density and high reversibility.However,there are still some issues limiting the practical application of LOBs,such as the large gap between the actual capacity level and the theoretical capacity,low rate performance as well as short cycle life.Herein,hollow CeO_2/Co_3 O_4 polyhedrons have been synthesized by MOF template with a simple method.And it is was further served as a cathode catalyst in Li-O_2 batteries.By means of the synergistic effect of two different transition metal oxides,nano-sized hollow porous CeO_2/Co_3 O_4 cathode obtained better capacity and cycle performance.As a result,excellent cyclability of exceeding 140 and 90 cycles are achieved at a fixed capacity of 600 and 1000 mAh/g,respectively.The successful application of this catalyst in LOBs offers a novel route in the aspect of the synthesis of other hollow porous composite oxides as catalysts for cathodes in LOBs systems by the MOF template method.     

SO_2对Co_3O_4/Al_2O_3选择性催化氧化NO的影响

采用流动态原位IR ,TPD及XPS技术研究了NO及SO2 在Co3 O4 /Al2 O3 金属氧化物催化剂表面上的吸附及脱附行为 ,并与该催化剂上模拟烟道气中NO的选择性催化氧化活性相关联 ,考察了SO2 对该反应过程的影响及作用机理 .     

超微粒CO3O4的合成与表征

本文用胶溶法合成了纳米级超微粒Co_3O_4,初步探讨了合成Co_3O_4超微粒的最佳实验条件,对产品的结构性能测试表明,所得超微粒子Co_3O_4粒度均匀,平均粒度为4.0nm.200℃热处理时,产品为无定形,在许多有机溶剂中具有良好的分散性和透明性;400℃热处理得到立方Co_3O_4纳米晶体,平均粒度为6.0nm,热稳定性好。     

3D-structured carbon-coated MnO/graphene nanocomposites with exceptional electrochemical performance for Li-ion battery anodes

MnO has a high theoretical capacity, moderate discharge plateau, and low polarization when it is used as the anode material in lithium battery. However, the issues that limit its application are its poor conductivity and large volume changes, which can easily result in the collapse of electrode structure during long-term cycling. In the present work, a carbon-coated MnO/graphene 3D-network anode material is synthesized by an electrostatic adsorption of dispersed precipitates precipitation method. The MnO nanoparticles coated by carbon are uniformly distributed on the surface of graphene nanosheets and form a 3D sandwich-like nanostructure. A carbon layer is coated on the surface of MnO nanoparticles, which slows down the volume expansion in the process of lithium intercalation. The graphene nanosheets are cross-linked through carbons in this 3D nanostructure, which provides mechanical support and effective electron conduction pathways during the charge-discharge. The electrochemical tests indicate that the prepared 3D carbon-coated MnO/graphene electrode exhibits an excellent rate capacity of 1247.3 and 713.2 mAh g^?1 at 100 and 1000 mA g^?1, respectively. The capacity is 792.2 mAh g^?1 after long cycle at a current density of 1000 mA g^?1. The specific capacity is higher than that of MnO-based composite lithium anode materials currently reported. The superior rate and cycling performances are attributed to the unique 3D-network structure, which provides an effectively conductive network, buffers volume expansion, and prevents falling and aggregation of MnO in the charge and discharge process of the electrode materials. The 3D-structured carbon-coated MnO/graphene anode material will have an excellent application prospect.

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Graphical abstract Cyclic performance at 1 A g^?1 and SEM images (inset) of the 3D-structured carbon-coated MnO/graphene nanocomposite.

     

Reversible 3-Li storage reactions of amorphous phosphorus as high capacity and cycling-stable anodes for Li-ion batteries

An amorphous phosphorus/carbon nanocomposite demonstrates a reversible 3-Li storage capacity of 2355 mAh g(-1) with an excellent capacity retention of 90% over 100 cycles and a superior power capability with 62% of its capacity realizable at a very high rate of 8000 mA g(-1), possibly serving as a high capacity and high rate alternative anode for next-generation Li-ion batteries.     

The Co_3O_4 nanosheet array as support for MoS_2 as highly efficient electrocatalysts for hydrogen evolution reaction

The electrochemical hydrogen evolution reaction(HER) on a non-precious electrocatalyst in an alkaline environment is of essential importance for future renewable energy. The design of advanced electrocatalysts for HER is the most important part to reduce the cost and to enhance the efficiency of water splitting. MoS_2 is considered as one of the most promising electrocatalysts to replace the precious Pt catalyst.Herein, for the first time, we have successfully loaded MoS_2 electrocatalysts onto the Co_3O_4 nanosheet array to catalyze HER with a low onset potential of ~76 mV. The high hydrogen evolution activity of MoS_2 supported on the Co_3O_4 nanosheet array may be attributed to the increased active sites and the electronic interactions between MoS_2 and Co_3O_4.     

Co_3O_4 modified Ag/g-C_3N_4 composite as a bifunctional cathode for lithium-oxygen battery

Rechargeable lithium-oxygen(Li-O_2)batteries have appeal to enormous attention because they demonstrate higher energy density than the state-of-the-art Li-ion batteries.Whereas,their practical application is impeded by several challenging problems,such as the low energy round trip efficiencies and the insufficient cycle life,due to the cathode passivation caused by the accumulation of discharge products.Developing efficient catalyst for oxygen reduction and evolution reactions is effective to reduce the overpotentials in Li-O_2cells.In our work,we report a Co_3O_4modified Ag/g-C_3N_4nanocomposite as a bifunctional cathode catalyst for Li-O_2cells.The g-C_3N_4substrate prevents the accumulation of Ag and Co_3O_4nanoparticles and the presence of Ag NPs improves the surface area of g-C_3N_4and electronic conductivity,significantly improving the oxygen reduction/evolution capabilities of Co_3O_4.Due to a synergetic effect,the Ag/g-C_3N_4/Co_3O_4nanocomposite demonstrates a higher catalytic activity than each individual constituent of Co_3O_4or Ag/g-C_3N_4for the ORR/OER on as catalysts in Li-O_2cells.As a result,the Ag/gC_3N_4/Co_3O_4composite shows impressive electrochemical performance in a Li-O_2battery,including high discharge capacity,small gap between charge and discharge potential,and high cycling stability.