Search

[Display omitted] • P/S/N co-doping and carbon-coating of yolk-shelled CoMoO 4 nanospheres are realized in one-pot. • PSN-C@CoMoO 4 displays high lithium storage capacity and excellent cycle/rate performance. • PSN-C@CoMoO 4 shows enhanced electronic conductivity and robust structural stability. Transition metal oxides as potential anodes of lithium-ion batteries (LIBs) possess high theoretical capacity but suffer from large volume expansion and poor conductivity. To overcome these drawbacks, we designed and fabricated polyphosphazene-coated yolk-shelled CoMoO 4 nanospheres, in which polyphosphazene with abundant C/P/S/N species was readily converted into carbon shells and provided P/S/N dopants. This resulted in the formation of P/S/N co-doped carbon-coated yolk-shelled CoMoO 4 nanospheres (PSN-C@CoMoO 4). The PSN-C@CoMoO 4 electrode exhibits superior cycle stability of 439.2 mA h g−1 at 1000 mA g−1 after 500 cycles and rate capability of 470.1 mA h g−1 at 2000 mA g−1. The electrochemical and structural analyses reveal that PSN-C@CoMoO 4 with yolk-shell structure, coated with carbon and doped with heteroatom not only greatly enhances the charge transfer rate and reaction kinetics, but also efficiently buffers the volume variation upon lithiation/delithiation cycling. Importantly, the use of polyphosphazene as coating/doping agent can be a general strategy for developing advanced electrode materials. [ABSTRACT FROM AUTHOR]

Spinel ferrites have been widely used in various fields, among which nickel‐zinc (NiZn) ferrites have drawn much attention due to their high electrical resistivity as well as low eddy current loss. To accommodate highly‐integrated modern electronic devices, the preparation methods for nano/micro‐sized NiZn ferrites have been widely discussed. Nevertheless, these current synthesis routes are usually cost/time‐consuming, which hinders their large‐scale production for practical applications. Herein, we present a facile, low‐cost synthesis strategy for NiZn ferrites (NixZn1−xFe2O4, x=0, 0.25, 0.5, 0.75 and 1) through a blowing‐combustion method. The effect of Ni/Zn molar concentration on the structure, morphology as well as magnetic properties has been thoroughly investigated through X‐ray diffraction, Raman spectroscopy, scanning electron microscopy and vibrating sample magnetometer. Thanks to the synergetic effect of the pure phase and moderate Ni molar concentration, the Ni0.75Zn0.25Fe2O4 shows an enhanced saturation magnetization of 44.98 emu/g. More importantly, this blowing‐combustion method may also be commonly applied to other spinel ferrites with different stoichiometric ratios and heteroatom doping. [ABSTRACT FROM AUTHOR]

[Display omitted] • V-dopants were successfully incorporated into MIL-125 via solvothermal method. • V-doped TiO2@carbon was prepared by carbonizing the V-doped MIL-125. • V-doped TiO2@carbon showed much enhanced sodium storage performance. • V-doping of TiO2 enhanced the electronic/ionic transfer rate. Titanium dioxide (TiO 2) as a potential anode material for sodium-ion batteries (SIBs) suffers from the intrinsic poor electronic conductivity and sluggish ionic diffusivity, thus usually leading to the inferior electrochemical performance. Herein, we demonstrate a facile strategy to enhance the sodium storage performance of TiO 2 via vanadium (V) doping, using the pre-synthesized V-doped Ti-based metal–organic framework (MOF, MIL-125) as the precursor, which can be converted into the V-doped TiO 2 with simultaneous carbon hybridization and controlled V-doping amount (denote as V x TiO 2 @C, where × represents the V/Ti molar ratio (R V/Ti)). V-doping not only affects the morphology of the MIL-125 changing from thick to thin nanotablets, but also greatly enhances the electrochemical performance of the V x TiO 2 @C. When used as an anode for SIBs, the V 0.1 TiO 2 @C exhibits a much higher reversible capacity of 211 mAh/g than that for the undoped TiO 2 @C (only 156 mAh/g) after 150 cycles at 100 mA/g. Even after high-rate long-term cycling, the V 0.1 TiO 2 @C can still display a capacity of 180 mAh/g with a high capacity retention of 137% at 1000 mA/g after 4500 cycles. Structural/electrochemical measurements reveal that V-doping induces the formation of oxygen vacancies as well as Ti3+ species, which efficiently improve the electric conductivity and the ion diffusivity of the electrode. Meanwhile, the thinner V 0.1 TiO 2 @C nanotablets with porous structure and carbon hybridization could facilitate the ion/electron transfer with shortened diffusion pathways. [ABSTRACT FROM AUTHOR]

• Amorphous LiV 3 O x was encapsulated into carbon nanofibers via electrospinning and subsequent annealing. • The amorphous LVO@CNFs demonstrated superior lithium storage performance compared with the crystalline LiV 3 O 8. • The amorphous structure and carbon hybridization contributed to the enhanced electrochemical properties. We design and fabricate a novel hybrid with amorphous lithium vanadate (LiV 3 O x , LVO for short) uniformly encapsulated into carbon nanofibers (denoted as LVO@CNFs) via an easy electrospinning strategy followed by proper postannealing. When examined for use as anode materials for lithium-ion batteries (LIBs), the optimized LVO@CNFs present a high discharge capacity of 603 mAh g−1 with a capacity retention as high as 90% after 200 cycles at 0.5 A g−1 and a high rate capacity of 326 mAh g−1 after 400 cycles even at a high rate of 5 A g−1. The superior electrochemical performance with excellent cycling stability and rate capability is attributed to the full encapsulation of the amorphous LVO into the conductive carbon nanofibers, which hold enlarged electrochemically active sites for lithium storage, facilitate the charge transfer, and efficiently alleviate the volume changes upon lithium insertion/extraction. More importantly, the current synthesis can be a general strategy to fabricate various alkaline earth metal vanadates, which is promising for developing advanced electrochemical energy storage devices. [ABSTRACT FROM AUTHOR]

Conversion‐type transition metal oxide MoO3 has attracted considerable interest as a promising anode material for lithium ion batteries (LIBs), but it suffers from the low electronic conductivity and the large volume changes upon lithiation/delithiation. To overcome these drawbacks, we herein report the full encapsulation of core‐shelled MoO3‐TiO2 into the carbon nanofibers (CNFs) via a facile coaxial electrospinning followed by a two‐step annealing process. TiO2 shells and MoO3 cores were coaxially integrated into the porous CNFs (denote the composite as TiO2/MoO3@CNFs). The two‐step annealing strategy (carbonization in Ar and then oxidization in air) allows the readily encapsulation of MoO3 into CNFs. When applied as anode materials for LIBs, the coaxial TiO2/MoO3@CNFs demonstrate superior lithium storage performance, delivering a high reversible capacity of 561 mAh/g after 300 cycles at 1000 mA/g with a much higher capacity retention of 70.8% than that of the MoO3@CNFs without TiO2 layers (only 42.3%). The results clearly demonstrate that the CNFs matrices and the TiO2 shells together efficiently enhance the electrode conductivity and buffer the volume changes of MoO3 upon cycling. [ABSTRACT FROM AUTHOR]

Tin dioxide (SnO 2) has attracted extensive attention as an anode for lithium-ion batteries (LIBs) due to its high theoretical specific capacity, however, it suffers from the severe volume changes upon lithiation/delithiation cycling, thus leading to fast capacity fading. To overcome the drawbacks, we herein report a facile one-pot self-templating fabrication of Ti-doped SnO 2 @carbon nanotubes (Ti-SnO 2 @CNTs), via annealing the electrospun precursor nanofibers of tetrabutyl titanate (TBT), tetraethyl orthosilicate (TEOS), polyvinylidene difluoride (PVDF), polyvinylpyrrolidone (PVP), and stannous chloride (SnCl 2). Interestingly, the introduction of TBT or not can lead to the controlled fabrication of the tubular or solid fibrous structure. During the annealing process, the chemical reaction between PVDF, TEOS, and TBT in-situ leads to the formation of tubular structure, while the SnCl 2 converts into ultrafine SnO 2 nanoparticles, embedding into the PVP-derived N-doped carbon nanotubes. When employed as anode materials for LIBs, the Ti-SnO 2 @CNTs deliver high reversible capacities of 868.6/495.9 mAh g−1 at 0.2/1.0 A g−1 after 200/500 cycles, higher than those for the fibrous SnO 2 @CNFs counterpart (654.9/391.08 mAh g−1). The better lithium storage performance is related to the unique carbon nanotube structure and the Ti-doping, which bring improved electrical conductivity, enhanced structural stability, and shortened ion diffusion path. More importantly, we demonstrate the facile electrospinning fabrication of tubular nanostructured hybrid electrodes for high-performance energy storage applications. [Display omitted] • Ultrafine SnO 2 nanoparticles are uniformly embedded into PVP-derived N-doped carbon nanotubes though electrospinning and subsequent calcination. • Tubular structure was formed using TBT/TEOS-derivates as templates, HF released by PVDF as the etching agent. • The unique tubular structure and ultrafine SnO 2 nanoparticles synergistically contributed to enhanced pseudocapacitive behavior and shortened lithium diffusion path. [ABSTRACT FROM AUTHOR]

An atomic layer deposition (ALD) of aluminum-doped zinc oxide (AZO) onto MoO 3 nanorods (denoted as MoO 3 @AZO) was developed to enhance the lithium storage performance of MoO 3 anode. Thanks to the highly conductive and robust AZO layer, the MoO 3 @AZO electrode demonstrated high pseudocapacitive contribution (76.2 % at 1.0 mV s −1), enhanced electron/ion transferability, outstanding rate performance (708 mAh g −1 at 2 A g −1) and excellent cycling stability (973 mAh g −1 after 100 cycles at 0.2 A g −1 with a high capacity retention of 92.8 %) when applied as an anode for lithium-ion batteries. Ex-situ transmission electron microscopy analysis revealed that the rod feature of MoO 3 @AZO was well retained with the protection of the AZO layer even after 100 cycles. Moreover, the ALD-AZO coating may also be commonly used for other metal oxides to enhance their electron conductivity and structural stability. [Display omitted] [ABSTRACT FROM AUTHOR]

Titanium dioxide (TiO2) is a promising anode for lithium‐ion batteries (LIBs) due to its long lifespan and high rate capability, arising from its excellent structural stability upon lithium intercalation‐deintercalation, but suffers from low conductivity and diffusivity. In contrast, germanium (Ge) possesses high specific theoretical capacity (1600 mA h g−1) as well as high electrical conductivity and high Li+ diffusivity, but the large volume changes upon cycling and the high price still impede its practical application. Herein, with the objective to overcome the drawbacks of TiO2‐based anode materials, Ge/TiO2@C nanotablets with a small amount of Ge content are successfully prepared by annealing C4H12GeO4/MIL‐125 mixtures in Ar/H2 atmosphere. Benefiting from the well‐dispersion of Ge nanoparticles within the TiO2@C matrices, the composites exhibit superior electrochemical performance when examined as a LIB anode material, delivering high reversible capacities of 502/258 mA h g−1 after 200/500 cycles at current densities of 200/500 mA g−1, respectively. Notably, the Ge/TiO2@C shows enhanced surface/pore features and demonstrates improved conductivity, lithium diffusion and specific capacities, owing to the introduction of Ge component. [ABSTRACT FROM AUTHOR]

[Display omitted] Ti 2 Nb 10 O 29 , as one of the most promising anode materials for lithium-ion batteries (LIBs), possesses excellent structural stability during lithiation/delithiation cycling and higher theoretical capacity. However, Ti 2 Nb 10 O 29 faces some challenges, such as insufficient ion diffusion coefficient and poor electronic conductivity. To overcome these problems, this study investigates the effect of applying nanostructure engineering on Ti 2 Nb 10 O 29 and the lithium storage behaviors. We successfully synthesized hollow Ti 2 Nb 10 O 29 nanospheres (h-TNO NSs) via solvothermal method using phenolic resin nanospheres as the template. The effects of using a template or not and the annealing atmospheres on the microstructures of the as-prepared Ti 2 Nb 10 O 29 are investigated. Different nanostructures (porous Ti 2 Nb 10 O 29 nanoaggregates (p-TNO NAs) without a template and core-shelled Ti 2 Nb 10 O 29 @C nanospheres (cs-TNO@C NSs)) were formed through annealing in Ar. When examined as anodes for LIBs, the h-TNO NSs electrode with hollow spherical structure displayed a better lithium storage performance. Compared to its counterparts, p-TNO NAs and cs-TNO@C NSs, h-TNO NSs electrode exhibited a higher reversible capacity of 282.5 mAh g−1 at 1C, capacity retention of 79.5% (i.e. , 224.6 mAh g−1) after 200 cycles, and a higher rate capacity of 173.1 mAh g−1 at 10C after 600 cycles. The excellent electrochemical performance of h-TNO NSs is attributed to the novel structure. The hollow nanospheres with cavities and thin shells not only exposed more active sites and improved ion diffusion, but also buffered the volume variation upon cycling and facilitated electrolyte penetration. This consequently enhanced the lithium storage performance of the electrode and its high pseudocapacitive contribution (90% at 1.0 mV s−1). [ABSTRACT FROM AUTHOR]

Sodium-ion capacitors (SICs) have been viewed as promising energy storage devices because of their high power/energy density, cycling stability and cost-efficiency, but they are also restricted by the unmatched reaction kinetics between the battery-type anode and capacitor-type cathode. Herein, we present a novel way to enhance the pseudocapacitive storage behavior and reaction kinetics of TiO 2 -based anode via Mo-doping and carbon hybridization, using the Mo-doped titanium metal-organic framework (Ti-MOF, MIL-125) as the precursor. Appropriate amount of Mo-doping (Mo:Ti = 1:9) induces the shape evolution from the round MIL-125 nanotablets to square Mo-MIL-125 nanocubes, which can be readily converted to Mo-doped TiO 2-x @carbon composite with conformal morphology (namely, Mo 0.1 -TiO 2-x @C). Mo-doping increases the concentration of Ti3+/oxygen vacancy and decreases its crystallinity, which greatly enhances the reaction kinetics and sodium storage performance. When examined in half-cells, the Mo 0.1 -TiO 2-x @C anode exhibits higher pseudocapacitive contribution (∼85%), higher reversible capacity (216 mAh g−1 at 0.5 A g−1), and better cycling and rate capability (185 mAh g−1 even after 3000 cycles at 1 A g−1). When paired with commercial activated carbon (AC) as cathode, the Mo 0.1 -TiO 2-x @C//AC SICs deliver a maximum energy density of 269.37 Wh kg−1 at a power density of 80.4 W kg−1 and 61.75 Wh kg−1 even at a high power density of 5421.95 W kg−1. [Display omitted] • Approximate Mo-doping induces the morphology change of MIL-125 from round tablet-like to square cube-like shapes. • Mo-doping TiO 2-x @C nanocubes display more defective Ti3+ species and increased oxygen vacancies. • Mo 0.1- TiO 2-x @C nanocubes display predominantly pseudocapacitive sodium storage behavior. • Mo 0.1- TiO 2-x @C//AC SIC displays a high operating voltage of 4 V and a maximum energy density of 80.4 Wh kg−1. [ABSTRACT FROM AUTHOR]

Bimetal oxides possess high electronic conductivity and multiple electrochemically active sites owing to their stepwise electrochemical reactions compared with the single metal oxides. However, bimetal oxides still suffer from the severe volume changes upon lithium insertion/delithiation processes, thus leading to poor cycle stability. Herein, we demonstrate the growth of novel CoMoO 3 nanosheets on the cage-like carbon nanoflakes (c-CNFs) through a facile in-situ thermal decomposition strategy. The phase and morphology structures of CoMoO 3 can be readily controlled by adjusting the sintering temperature under the argon atmosphere, changing from 0D CoMoO 4 nanoparticles@c-CNFs (350 ℃, denoted as CoMoO 4 @C) to 0D CoMoO 4 nanoparticles and 2D CoMoO 3 nanosheets co-existed nanohybrids@c-CNFs (450 ℃, denoted as CoMoO x @C) and 2D CoMoO 3 nanosheets@c-CNFs (550 ℃, denoted as CoMoO 3 @C). When examined as anode materials for LIBs, the CoMoO 3 @C electrode exhibited excellent lithium storage performance. The superior performance of the CoMoO 3 @C electrode could be attributed to the novel CoMoO 3 nanosheet structure combined with the reduced volume change from well-fitted CoMoO 3 @c-CNFs, which delivered a reversible capacity of ~706 mA h/g for 360 cycles at 500 mA/g, higher than that of the CoMoO 4 @C and CoMoO x @C electrodes. Facile co-engineering on phases and morphology structures based on CoMoO 3 through in-situ thermal decomposition. The optimized strategy enabled the construction of novel CoMoO 3 nanosheets@cage-like carbon nanoflakes (c-CNFs) with different temperature-dependent phases. With the novel nanosheet-to-nanosheet structure , such CoMoO 3 @C electrode demonstrate superior cycle stability as an anode material for lithium-ion batteries. [Display omitted] • We developed a facile in-situ thermal decomposition strategy to successfully grow novel CoMoO 3 nanosheets on c-CNFs. • The phases and morphology structures of CoMoO 3 can be readily controlled by adjusting the sintering temperature. • The unique nanosheet-to-nanosheet structure benefited for the superior cycle stability and excellent rate capability. • This opens an avenue for the development of advanced practical electrochemical energy storage in the future. [ABSTRACT FROM AUTHOR]

Nickel-copper-zinc (NiCuZn) ferrites are widely used in high-frequency fields due to their low eddy current losses as well as high resistivity, but which are greatly affected by their microstructures, such as porosity, grain size. Herein, we report a novel synthesis of shuttle-shaped NiCuZn ferrites through electrospinning and subsequent sintering. The microstructural evolution and its effect on magnetic properties upon annealing at temperatures ranging from 500 to 1000 °C are systematically investigated through X-ray diffraction, Raman spectroscopy, scanning electron microscopy, and vibrating sample magnetometry. The results demonstrate that the average crystallite size of NiCuZn ferrites decreases and the grain size rises with increasing the sintering temperature. Meanwhile, the saturation magnetization shows an upward trend upon increasing the sintering temperature and reaches the highest value of 68.07 emu g−1 at 900 °C. However, when further increasing the sintering temperature to 1000 °C, the crystalline structure, as well as the morphology of the NiCuZn ferrite, change a lot with coarse particle growth/aggregation, thus resulting in lowered saturation magnetization. Inductively coupled plasma mass spectrometer analysis shows that the stoichiometric ratios of NiCuZn ferrite change with the sintering temperature, which also affects the magnetic properties. More importantly, this study demonstrates that electrospinning is promising to fabricate well-defined nanostructured ferrites with tunable components, morphologies, and magnetic properties. [ABSTRACT FROM AUTHOR]

• Novel 3D ordered porous MoS 2 /C hierarchies are fabricated via a template method. • MoS 2 /C demonstrates excellent high-rate long-life sodium storage performance. • MoS 2 /C architecture displays extraordinary pseudocapacitive energy storage behavior. • Carbon hybridization enhances the charge transfer and sodium diffusion rates. Pseudocapacitive energy storage offers short charging time, long-term cycling stability and high-rate capability, but developing nanostructured electrodes with high pseudocapacitance is still challenging. Herein, we present a facile template-assisted nanocasting method to fabricate three-dimensional (3D) ordered porous MoS 2 /C hierarchical nanostructures through simultaneous thermal decomposition of the (NH 4) 2 MoS 4 /(C 6 H 9 NO) n /SiO 2 mixture by annealing and subsequent template removal. The interplanar spacing along (0 0 2) plane of MoS 2 is greatly expanded owing to the incorporation of the PVP-derived carbon species, which also effectively enhance the structural stability of the overall hierarchies composing of interconnected hollow MoS 2 /C spheres with ultrathin shells and vast macro/mesoporous structure. These novel structure characteristics endow the as-prepared MoS 2 /C hierarchies with many advantages for sodium storage, ex. , lower Na+ intercalation barrier, higher penetration of electrolyte and larger surface active sites. When applied as anode materials for sodium ion batteries (SIBs), the as-prepared MoS 2 /C exhibits outstanding electrochemical properties, delivering a high reversible capacity of 412 mAh/g after 500 cycles at 2 A/g, and remarkably excellent rate capacities of 156/128/76 mAh/g at 10/20/50 A/g after 5000 cycles, respectively. The excellent cycle stability and rate capability are attributed to the unique 3D ordered porous nanostructure, in which the conductive carbon matrices and the enlarged van der Waals gaps in the layered MoS 2 synergistically result in the ultrahigh pseudocapacitance contribution in sodium storage. [ABSTRACT FROM AUTHOR]

In order to overcome the poor electrical conductivity of titania (TiO2) and silica (SiO2) anode materials for lithium ion batteries (LIBs), we herein report a facile preparation of integrated titania–silica–carbon (TSC) nanofibers via electrospinning and subsequent heat-treatment. Both titania and silica are successfully embedded into the conductive N-doped carbon nanofibers, and they synergistically reinforce the overall strength of the TSC nanofibers after annealing (Note that titania–carbon or silica–carbon nanofibers cannot be obtained under the same condition). When applied as an anode for LIBs, the TSC nanofiber electrode shows superior cycle stability (502 mAh/g at 100 mA/g after 300 cycles) and high rate capability (572, 518, 421, 334, and 232 mAh/g each after 10 cycles at 100, 200, 500, 1000 and 2000 mA/g, respectively). Our results demonstrate that integration of titania/silica into N-doped carbon nanofibers greatly enhances the electrode conductivity and the overall structural stability of the TSC nanofibers upon repeated lithiation/delithiation cycling. [ABSTRACT FROM AUTHOR]

[Display omitted] Tin dioxide (SnO 2) is a promising alternative material to graphite anode, but the large volume change induced electrode pulverization issue has limited its application in lithium-ion batteries (LIBs). In contrast, titanium dioxide (TiO 2) anode shows high structure stability upon lithium insertion/extraction, but with low specific capacity. To overcome their inherent disadvantages, combination of SnO 2 with TiO 2 and highly conductive carbon material is an effective way. Herein, we report a facile fabrication method of carbon-coated SnO 2 /TiO 2 nanowires (SnO 2 /TiO 2 @C) using tin titanate nanowires as precursor, which are prepared by reacting SnCl 2 ·2H 2 O with layered sodium titanate (Na 2 Ti 3 O 7) nanowires in the aqueous solution though the ion exchange between Sn2+ and Na+. After annealing under argon atmosphere, the hydrothermally carbon-coated tin-titanate nanowires decompose, forming a unique hybrid structure, where ultrafine SnO 2 nanoparticles are uniformly embedded within the TiO 2 substrate with carbon coating. Consequently, the SnO 2 /TiO 2 @C nanowires demonstrate excellent lithium storage capacity with high pseudocapacitance contribution, excellent reversible capacity, and long-term cycling stability (673.7/510.5 mAh/g at 0.5/1.0 A/g after 250/800 cycles), owing to the unique hybrid structure, as the well-dispersion of ultra-small SnO 2 within TiO 2 nanowire substrate with simultaneous carbon coating efficiently suppresses the volume changes of SnO 2 , provides abundant reactive sites for lithium storage, and enhances the electrical conductivity with shortened ion transport distance. [ABSTRACT FROM AUTHOR]

Transition metal oxides/selenides as anodes for sodium-ion batteries (SIBs) suffer from the insufficient conductivity and large volumetric expansion, which leads to the poor electrochemical performance. To address these issues, we herein demonstrate a facile selenization method to enhance the sodium storage capability of CoMoO 4 nanoparticles which are encapsulated into the electrospun carbon nanofibers (CMO@carbon for short). The partially and fully selenized CoMoO 4 within carbon nanofibers (denote as CMOS@carbon and CMS@carbon, respectively) can be readily obtained by controlling the annealing temperature (at 400 and 600 °C, correspondingly). When examined as anode materials for SIBs, the CMOS@carbon nanofibers display an outstanding electrochemical performance with a higher reversible capacity of 396 mA h g−1 after 200 cycles at 0.2 A g−1 and a high-rate capacity of 365 mA h g−1 at 2 A g−1, as compared with the CMO@carbon and CMS@carbon counterparts. The enhanced sodium storage performance of the CMOS@carbon can be owing to the partial selenization of the CoMoO 4 nanoparticles which are rooted into the porous electrospun carbon nanofibers, thus endowing them with superior ionic/electronic charge transfer efficiencies and a cushion against the electrode pulverization during cycling. Moreover, this work proposed a useful strategy to enhance the sodium storage performance of metal oxides via controlled selenization, which is promising for exploiting the advanced anode materials for SIBs. [ABSTRACT FROM AUTHOR]

Alloy-/conversion-type metal oxides usually exhibit high theoretical lithium storage capacities but suffer from the large volume change induced electrode pulverization and the poor electric conductivity, which limit their practical applications. Hybrid/mixed metal oxides with different working mechanisms/potentials can display advantageous synergistic enhancement effect if delicate structure engineering is performed. Herein, atomically hybridized SnO 2 /Co 3 O 4 nanocomposites with amorphous nature are successfully cast onto the porous N -doped carbon (denoted as NC) nanoflakes through facile pyrolysis of the tin (II) 2-ethylhexanoate (C 16 H 30 O 4 Sn) and cobalt (II) 2-ethylhexanoate (C 16 H 30 O 4 Co) mixture within NC nanoflakes in air at 300 °C for 1 h. The Sn/Co atomic ratio and the loading amount of SnO 2 /Co 3 O 4 can be readily controlled, whose effect on lithium storage are investigated as anodes for lithium ion batteries (LIBs). Notably, SnO 2 /Co 3 O 4 @NC (R Sn/Co = 1.25) nanoflakes exhibit the most excellent lithium storage properties, delivering a reversible capacity of 1450.3 mA h g−1 after 300 cycles at 200 mA g−1, which is much higher than that of the single metal oxide SnO 2 @NC and Co 3 O 4 @NC electrodes. [ABSTRACT FROM AUTHOR]

CoMoO 4 nanoparticles have been successfully in-situ formed and simultaneously embedded within the porous carbon nanofibers (CoMoO 4 /CNFs) via a facile electrospinning-annealing strategy. The porous CoMoO 4 /CNFs exhibit a specific surface area of 255.3 m2/g and a pore volume of 0.52 cc/g with average pore diameter of 43.5 nm. The carbon content in the CoMoO 4 /CNFs can be readily controlled by adjusting the annealing temperature. When examined as anode materials for lithium ion batteries (LIBs), the CoMoO 4 /CNFs demonstrate superior electrochemical performance, delivering a high reversible capacity of 802 mA h/g after 200 cycles at 200 mA/g and a high-rate capacity of 574 mA h/g at 2000 mA/g. The excellent lithium storage behavior can be attributed to the incorporation of CoMoO 4 nanoparticles into the porous N -doped graphitic carbon nanofibers, which efficiently buffer the volume changes of CoMoO 4 upon lithiation/delithiation and maintain the overall electrode conductivity/integrity. [ABSTRACT FROM AUTHOR]

We report an amorphorization-hybridization strategy to enhance lithium storage by casting atomically mixed amorphorized SnO 2 /MoO 3 into porous foam-like carbon nanoflakes (denote as SnO 2 /MoO 3 @CNFs, or SMC in short), which are simply prepared by annealing tin(II)/molybdenum(IV) 2-ethylhexanoate within CNFs under ambient atmosphere at a low temperature (300 °C). The SnO 2 /MoO 3 loading amount within CNFs can be easily adjusted by controlling the Sn/Mo/C precursors. When examined as lithium ion battery (LIB) anode materials, the amorphorized SnO 2 /MoO 3 @CNFs with carbon content of 32 wt% (also denote as SMC-32, in which the number represents the carbon content) deliver a high reversible capacity of 1120.5 mA h/g after 200 cycles at 200 mA/g and then 651.5 mA h/g after another 300 cycles at 2000 mA/g, which is much better than that of the crystalline SnO 2 /CNFs (carbon content of 34 wt%), MoO 3 /CNFs (carbon content of 22.7 wt%), or SnO 2 /MoO 3 @CNFs (with lower carbon contents of 11 and 25 wt%). The electrochemical measurements as well as the ex situ structure characterization clearly suggest that combination of amorphorization and hybridization of SnO 2 /MoO 3 with CNFs synergistically contributes to the superior lithium storage performance with high pseudocapacitive contribution. [ABSTRACT FROM AUTHOR]

Nickel‐copper‐zinc (NiCuZn) spinel ferrites have attracted intensive research owing to their unique magnetic properties and low co‐fire temperature. Combustion synthesis has been viewed as a promising protocol for the large‐scale fabrication of NiCuZn spinel ferrites. However, the spinel ferrites prepared by this method usually suffer from limited saturation magnetization and high coercivity due to their large size, which will impose detrimental harmonics on electrical equipment (e. g. transformer, motor, etc.). To address these issues, highly porous NiCuZn spinel ferrite hierarchies were prepared within several hours through a modified solution combustion method, using glucose and ammonium nitrate as the fuel and combustion enhancer, respectively. The as‐obtained NiCuZn spinel ferrite hierarchies show excellent magnetic properties with a high saturation magnetization up to 62.61 emu/g and a low coercivity of 9.6 Oe thanks to the rational distribution of cations and grain size. More importantly, this method also allows various modifications (heteroatom doping) and large‐scale applications, which may be promising for the fabrication of high‐performance soft magnets for electrical equipment. [ABSTRACT FROM AUTHOR]

Titanium dioxide (TiO 2) has been considered as a promising anode material for alkaline ion batteries (AIBs), yet the low electrical conductivity and sluggish reaction kinetics have restricted its practical applications, while rational structure design can significantly overcome these drawbacks. Herein, we report a one-step fabrication of ultrafine anatase TiO 2 nanoparticles within holely carbon nanofibers (denoted as A-TiO 2 @HCNFs) via a facile electrospinning method and subsequent annealing treatment. The chemical reaction between TEOS (Si(OC 2 H 5) 4) and PVDF ((CH 2 CF 2) n) in the precursor induces the generation of numerous holes (via 4HF + SiO 2 = SiF 4 ↑+ 2 H 2 O) during the carbonization process by annealing in Ar at 800 °C, leading to the formation of holely structure and the suppression of the anatase-to-rutile phase transformation. When employed as anode materials for AIBs, the A-TiO 2 @HCNFs exhibit a high sodium storage capacity of 206.8 mAh g−1 at 1.0 A g−1 after 500 cycles and a superior rate performance of 188.4 mAh g−1 at 5.0 A g−1, and a lithium storage capacity is 354.0/233.9 mAh g−1 at 0.2/1.0 A g−1 after 100/500 cycles with an excellent rate performance of 145.6 mAh g−1 at 5.0 A g−1. The superior electrochemical performance is related to the unique structure with integration of ultrafine anatase TiO 2 nanoparticles and holely carbon nanofibers, which bring many advantages including improved electrical conductivity, sufficient reaction sites and robust structure stability. [Display omitted] • Template-free one-pot hole generation within carbon nanofibers is realized through chemical reaction between TEOS and PVDF. • Ultrafine anatase TiO 2 nanoparticles were produced and uniformly distributed within the holely carbon nanofibers. • The anatase TiO 2 nanoparticles within holely carbon nanofibers demonstrate excellent sodium and lithium storage performances. [ABSTRACT FROM AUTHOR]

[Display omitted] • Mn 2 V 2 O 7 microspheres with solid or hollow interiors were realized via a facile solvothermal method followed by annealing. • The effects of PVP as controlling agent on the structure and electrochemical properties of Mn 2 V 2 O 7 were revealed. • Mn 2 V 2 O 7 microspheres demonstrated superior lithium storage performance owing to the favorable structure. We report the fabrication of well-defined phase-pure Mn 2 V 2 O 7 hollow microspheres (h-MVO), assembled from the porous plate-like building blocks, via a facile solvothermal method followed by annealing, with the assistance of polyvinylpyrrolidone (PVP) as the structure-regulating agent. The microstructure dependent electrochemical properties of h-MVO as anode materials for lithium ion batteries (LIBs) are investigated, and excellent lithium storage performance is obtained with a reversible capacity of 1707 mAh g−1 after 700 cycles at 0.5 A g−1, revealing that the unique hierarchical framework of the h-MVO microspheres with hollow interiors and porous building blocks could not only accelerate the transport of Li+ ions and electrolyte, but also efficiently suppress the electrode pulverization upon cycling. More importantly, we demonstrate that PVP can be an effective agent to tune the microstructures, which would be promising for the development of high-performance energy storage devices. [ABSTRACT FROM AUTHOR]

[Display omitted] • A uniform flower-like N, O-codoped carbon host is derived from a Ni-MOF. • The well distribution of Se in the host is realized by vapor-infiltration method. • The cathode fabricated by vapor-infiltration method shows a high Se utilization. Na-Se batteries have their drawbacks such as large volumetric expansion and shuttle effect related to generation of soluble sodium polyselenides. To address these issues, a nitrogen and oxygen codoped flower-like porous carbon host is derived from a Ni-based metal–organic framework (MOF) for Se storage. The use of 4,4′-oxybisbenzoic acid and 4,4′-dimethyl-2,2′-bipyridyl ligands ensure the in-situ doping of the carbon host with oxygen and nitrogen upon carbonization of MOF, which increases its polarity and restricts the diffusion of selenium. Highly porous microflower-like carbon morphology provides sufficient space for Se storage. To avoid undesirable aggregation of Se particles which happens when using conventional melt-diffusion method, we employed a vapor-infiltration method for Se loading, which ensures the homogeneous dispersion of selenium and high utilization of pores in the carbon host. Density functional theory calculations confirmed that the increased polarity of the carbon host due to N,O codoping promotes the adsorption of polyselenides. When tested as a cathode for sodium-selenium battery, the optimized carbon/selenium composite shows an excellent electrochemical performance. [ABSTRACT FROM AUTHOR]

[Display omitted] TiNb 2 O 7 (TNO) as a promising candidate anode for lithium-ion batteries (LIBs) shows obvious advantages in terms of specific capacity and safety, but which undergoes the intrinsic poor electrical and ionic conductivity. Herein, we propose a simple synthesis strategy of mesoporous TNO via a polymeric surfactant-mediated evaporation-induced sol-gel method, using polyvinylpyrrolidone (PVP) with different molecular weights (average Mw: 10000/58000/1300000) as the regulating agent, which greatly affects the lithium storage performance of the as-prepared TNO. The optimized TNO (i.e., PVP of 58000) delivers a high reversible capacity of 303.1 mAh/g at 1 C, with a retention rate of 73.4% (222.5 mAh/g) after 300 cycles. Even at 5 C, a high reversible capacity of 185.6 mAh/g can be achieved, with a retention rate of 72.3% after 1000 cycles. The superior lithium storage behavior is attributed to the fine mesoporous framework consisting of interconnected TNO nanocrystallites with high specific surface area and high mesoporosity, which greatly increases the active sites, improves the Li+ diffusion kinetics and alleviates volume fluctuation induced by the repetitive Li+ insertion-extraction processes. [ABSTRACT FROM AUTHOR]

[Display omitted] Metal oxides are prospective alternative anode materials to the commercial graphite for lithium ion batteries (LIBs), while their practical application is seriously hampered by their poor conductivities and large volume changes. Herein, we report the controllable synthesis of amorphous/crystalline MnCo 2 O x nanoparticles within porous carbon nanofibers (marked as MCO@CNFs) through a facile electrospinning strategy and subsequent annealing reactions. The phase structures from Co/MnO X to amorphous MnCo 2 O x and crystalline MnCo 2 O 4.5 can be readily tuned by thermal reduction/oxidation under controlled atmosphere and temperature. When examined as anode for LIBs, the optimized MCO@CNFs delivers a high stable capacity of 780.3 mA h g−1 at 200 mA g−1 after 250 cycles, which is attributed to the synergistic effect of the distinctive amorphous structure and defective carbon nanofiber matrices. Specifically, the amorphous structure with rich defects offers more reactive sites and multiple pathways for the Li+ diffusion, while carbon hybridization sufficiently improves the electrode conductivities as well as buffers the volume changes. More importantly, we demonstrate a convenient synthesis strategy to control the metal-to-oxide structure evolution within carbon matrices, which is of great importance in exploring high-performance electrodes for next generation LIBs. [ABSTRACT FROM AUTHOR]

CoSe 2 -based anode materials are highly attractive for sodium-ion batteries (SIBs) due to their high theoretical specific capacity, but the weak rate capability and rapid capacity fading hinder their practical application. Herein, porous carbon nanofiber supported CoSe 2 nanoparticles (denoted as CS@PCNFs) are designed and fabricated through electrospinning and subsequent heat treatment with PAN (polyacrylonitrile) as the carbon source and PMMA (polymethyl methacrylate) as the pore-forming agent to design the porous architecture of the carbon nanofibers and control the amount of CoSe 2 grains anchored on the fiber surface. Benefiting from the desired structural features including the large specific surface area, appropriate pore volume and robust structure stability, when examined as anode materials for SIBs, the as-prepared CS@PCNFs demonstrated excellent sodium-ion storage performances. Experimental results show that the CS@PCNFs with an optimized PAN/PMMA mass ratio of 6:4 can deliver a high reversible capacity of 413.6 mA h g−1 at 0.2 A g−1 after 150 cycles and an excellent rate capability of 401.5 mA h g−1 at 2.0 A g−1. Image 1 • Porous carbon nanofiber supported CoSe 2 nanoparticles are designed and fabricated as anodes for SIBs. • PAN and PMMA are employed as the carbon source and the pore-forming agent, respectively. • Excellent electrochemical properties are demonstrated due to the ultra-high pseudocapacitive contribution. [ABSTRACT FROM AUTHOR]

To explore advanced anode materials with superior Li+/Na+/K+ storage performances for alkaline ion batteries (AIBs), a hybrid of amorphous vanadium oxide uniformly embedded into the highly defective carbon nanofibers (denoted as VO x @CNFs) was fabricated via a facile electrospinning method followed by proper heat treatment in this work. The integrated structure synergistically combines the advantages of the amorphous VO x and the defective carbon matrices, which can not only bring abundant active sites for ion storage and multi-channels for ion diffusion, but also well accommodate the structural change induced electrode pulverization. When evaluated as anode materials for AIBs, the optimized VO x @CNFs demonstrate excellent alkaline ion storage performances with high-specific capacities, long-cycling life and high-rate capabilities, delivering a Na+ storage capacity of 260 mAh g−1 at 1.0 A g−1 after 1000 cycles, a Li+ storage capacity of 556 mAh g−1 at 0.5 A g−1after 500 cycles, and a K+ storage capacity of 198 mAh g−1 at 0.5 A g−1 after 400 cycles. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Hydrogen (H 2) is the cleanest energy but also dangerous, thus the real-time detection of H 2 leakage is crucially important. Herein, we develop ultra-large micro-sized Sn 3 O 4 nanosheet hierarchies via a facile hydrothermal method using polyvinyl pyrrolidone as a regulating agent. Structural analyses reveal the as-prepared Sn 3 O 4 nanosheets are single-crystalline with {010}-facet exposure and Sn2+-deficiency. When examined as gas sensing materials, the {010}-faceted Sn2+-deficient Sn 3 O 4 nanosheets demonstrate highly efficient H 2 sensing with excellent selectivity/response (two times higher than those for NO 2 , SO 2 , H 2 S, and H 2 O) and stability upon long-term testing (over 37 days). The sensor displays fast response /recovery times of 9.4/24 s to 10 ppm H 2 at a low working temperature of 150 °C, and even well responds to 50 ppb H 2 with a theoretical limit of detection (LOD) of 0.54 ppb. The excellent H 2 sensing performance of the Sn 3 O 4 nanosheets has been verified by the first-principle calculation based on density functional theory (DFT), suggesting that the Sn2+-deficient {010} surface of Sn 3 O 4 provides abundant adsorption sites for hydrogen molecules. Moreover, we demonstrate the practical application of Sn 3 O 4 sensor embedded into a miniaturized deployable module, which realizes the real-time on-line H 2 monitoring with excellent repeatability and selectivity for long-term operation. [Display omitted] • We predicted that Sn 3 O 4 NSs with Sn2+ defect were sensitive to H 2 by DFT. • The Sn 3 O 4 NSs have been successfully synthesized by hydrothermal method. • H 2 -sensitive properties were tested comprehensively to verify the DFT calculation. • We fabricated a miniaturized deployable module to monitor the hydrogen leak. [ABSTRACT FROM AUTHOR]

Transition metal sulfides (TMSs) with high theoretical sodium storage capacity have been regarded as one of the most competitive and promising anode materials for sodium-ion batteries. Nevertheless, great challenges still exist for TMS to achieve long-cycle life owing to the poor conductivity and volume expansion during the sodiation/desodiation process. The conventionally used pure carbon coating method can effectively solve the above problems. However, the low sodium ion storage capability of carbon will decrease the capacity of the anode. Thus the functionalization of well-designed carbon nanostructures with exotic elements (e.g., sulfur) or high-specific-capacity materials has been regarded as an efficient route to enhance sodium storage performance. Herein, we developed a facile strategy to incorporate covalent sulfur and CoS 2 nanoparticles into honeycomb-like carbon matrices (denoted as S/CoS 2 @C), where sulfur is vaporized under vacuum and reacted with the Co-decorated carbon hierarchies, leading to the formation of CoS 2 nanoparticles as well as the covalent C–S x –C bonds. Consequently, the as-prepared S/CoS 2 @C composite demonstrates excellent sodium storage performance, with high initial coulomb efficiency (ICE) of 83 % and capacity retention of 95 % (478.5 mAh g−1) after 700 cycles at 0.2 A g−1, and an outstanding high-rate long-term cycling stability with a high reversible capacity of 396.1 mAh g−1 after 5000 cycles at 2 A g−1 (an average decay rate of only 0.0014 %). Furthermore, electrochemical analyses reveal that both covalent sulfur and CoS 2 contribute to the sodium storage capacity via a predominantly surface-induced capacitive process, and the well-designed S/CoS 2 @C composite with encapsulation of covalent sulfur and CoS 2 into the highly interconnected porous carbon matrices efficiently buffer the volume changes and well maintain the electrode integrity/conductivity upon sodiation/desodiation cycling. [Display omitted] • Honeycomb-like Co@C hierarchies with highly interconnected porous structure was prepared. • Covalent S/CoS 2 were confined into the porous carbon framestructures. • S/CoS 2 @C displayed excellent sodium storage performance with ultra-long high-rate cycling stability. [ABSTRACT FROM AUTHOR]

[Display omitted] • Nickel-copper-zinc (NiCuZn) ferrites were prepared by a facile blowing-combustion method. • Variation of zinc content with temperature was investigated through inductive coupled plasma (ICP). • The effect of sintering temperatures on structural and magnetic properties of NiCuZn ferrites were investigated. We report the fabrication of nickel-copper-zinc (NiCuZn) ferrites via a facile blowing-combustion method, where the grain size and morphology can be readily controlled by adjusting the sintering temperature. The effect of sintering temperatures on the structural evolution as well as the magnetic properties of the NiCuZn ferrites was systematically studied. It's found that the Zn elemental content is highly dependent on the sintering temperature and would undergo evaporation when annealing at 800 °C, which consequently greatly affects the magnetic properties of NiCuZn ferrites. [ABSTRACT FROM AUTHOR]

Surface modification via atomic layer deposition (ALD) of metal oxides (ex. , TiO 2) has been suggested as an effective strategy to enhance the electrochemical performance of high-specific-capacity electrode materials. Herein, we study the lithium storage behavior of TiO 2 coated CoSe 2 nanorods (TiO 2 @CoSe 2), in which a thin layer of TiO 2 shell is deposited via a conventional ALD method. The effects of the TiO 2 deposition on the structural and electrochemical characteristics of the CoSe 2 nanorods are systematically investigated. When applied as anodes for LIBs, the TiO 2 @CoSe 2 electrode displays much enhanced lithium storage performance including higher specific capacity, better cycle stability and rate capability, delivering a discharge capacity of 999.2 mA h/g after 300 cycles at 200 mA/g and an exceptional capacity of 723.7 mA h/g after 430 cycles even at high current density of 500 mA/g, which is much higher than that of the bare CoSe 2 electrode (only 145.4 mA h/g after 220 cycles at 200 mA/g). Atomic layer deposition (ALD) of TiO 2 shells on CoSe 2 nanorods (TiO 2 @CoSe 2) allows much enhanced lithium storage performance including higher specific capacity, better cycling stability and rate capability, when used as an anode material for lithium ion batteries, owing to the efficient buffering effect on the electrode pulverization upon cycling. Image 1 • CoSe 2 nanorods were successfully prepared by a facile hydrothermal method. • TiO 2 shells with controlled thickness were coated on the CoSe 2 nanorods via a facile atomic layer depositon method. • TiO 2 @CoSe 2 demonstrated much enhanced lithium storage performance as anode for lithium ion batteries. • Deposition of TiO 2 shells greatly improved the structure stability of CoSe 2 electrode upon lithiation/delithiation cycling. [ABSTRACT FROM AUTHOR]