All-inorganic solid-state sodium–sulfur batteries (ASSBs) are promising technology for stationary energy storage due to their high safety, high energy, and abundant resources of both sodium and sulfur. However, current ASSB shows poor cycling and rate performances mainly due to the huge electrode/electrolyte interfacial resistance arising from the insufficient triple-phase contact among sulfur active material, ionic conductive solid electrolyte, and electronic conductive carbon. Herein, we report an innovative approach to address the interfacial problem using a Na3PS4–Na2S–C (carbon) nanocomposite as the cathode for ASSBs. Highly ionic conductive Na3PS4 contained in the nanocomposite can function as both solid electrolyte and active material (catholyte) after mixing with electronic conductive carbon, leading to an intrinsic superior electrode/electrolyte interfacial contact because only a two-phase contact is required for the charge transfer reaction. Introducing nanosized Na2S into the nanocomposite cathode can effectively improve the capacity. The homogeneous distribution of nanosized Na2S, Na3PS4, and carbon in the nanocomposite cathode could ensure a high mixed (ionic and electronic) conductivity and a sufficient interfacial contact. The Na3PS4-nanosized Na2S–carbon nanocomposite cathode delivered a high initial discharge capacity of 869.2 mAh g–1 at 50 mA g–1 with great cycling and rate capabilities at 60 °C, representing the best performance of ASSBs reported to date and therefore constituting a significant step toward high-performance ASSBs for practical applications.Keywords: all-inorganic; all-solid-state; electrode design; nanocomposite; sodium−sulfur battery;

A nickel hexacyanoferrate (NiHCF)/carbon composite is prepared to realize reduced structure vacancies and enhanced conductivity simultaneously. The resultant composite as a cathode material exhibits good capacity retentions both for rate capability (93% of that at 0.1 A g−1 for 2 A g−1) and cycle stability (94% after 900 cycles at 0.5 A g−1). This feature is also kept in an aqueous hybrid energy storage device, after coupling with rGO as the anode. After 5000 cycles at 2 A g−1, 94% of the initial capacity is preserved, exhibiting extraordinary stability at high rates.

MoSe2 grown on N,P-co-doped carbon nanosheets is synthesized by a solvothermal reaction followed with a high-temperature calcination. This composite has an interlayer spacing of MoSe2 expanded to facilitate sodium-ion diffusion, MoSe2 immobilized on carbon nanosheets to improve charge-transfer kinetics, and N and P incorporated into carbon to enhance its interaction with active species upon cycling. These features greatly improve the electrochemical performance of this composite, as compared to all the controls. It presents a specific capacity of 378 mAh g−1 after 1000 cycles at 0.5 A g−1, corresponding to 87% of the capacity at the second cycle. Ex situ Raman spectra and high-resolution transmission electron microscopy images confirm that it is element Se, rather than MoSe2, formed after the charging process. The interaction of the active species with modified carbon is simulated using density functional theory to explain this excellent stability. The superior rate capability, where the capacity at 15 A g−1 equals ≈55% of that at 0.5 A g−1, could be associated with the significant contribution of pseudocapacitance. By pairing with homemade Na3V2(PO4)3/C, this composite also exhibits excellent performances in full cells.

Development of high energy/power density and long cycle life of anode materials is highly desirable for sodium ion batteries, because graphite anode cannot be used directly. Sb stands out from the potential candidates, due to high capacity, good electronic conductivity, and moderate sodiation voltage. Here, one-dimensional yolk–shell Sb@Ti–O–P nanostructures are synthesized by reducing core–shell Sb2O3@TiO2 nanorods with NaH2PO2. This structure has Sb nanorod as the core to increase the capacity and Ti–O–P as the shell to stabilize the interface between electrolyte and electrode material. The gap between the core and the shell accommodates the volume change during sodiation/desodiation. These features endow the structure outstanding performances. It could deliver a capacity of about 760 mA h g–1 after 200 cycles at 500 mA g–1, with a capacity retention of about 94%. Even at 10 A g–1, the reversible capacity is still at 360 mA h g–1. The full battery of Sb@Ti–O–P//Na3V2(PO4)3–C presents a high output voltage (∼2.7 V) and a capacity of 392 mA h g–1anode after 150 cycles at 1 A g–1anode.Keywords: antimony; composite; full cells; nanostructures; sodium ion batteries;

High-capacity anode materials are highly desirable for sodium ion batteries. Here, a porous Sb/Sb2O3 nanocomposite is successfully synthesized by the mild oxidization of Sb nanocrystals in air. In the composite, Sb contributes good conductivity and Sb2O3 improves cycling stability, particularly within the voltage window of 0.02–1.5 V. It remains at a reversible capacity of 540 mAh·g–1 after 180 cycles at 0.66 A·g–1. Even at 10 A·g–1, the reversible capacity is still preserved at 412 mAh·g–1, equivalent to 71.6% of that at 0.066 A·g–1. These results are much better than Sb nanocrystals with a similar size and structure. Expanding the voltage window to 0.02–2.5 V includes the conversion reaction between Sb2O3 and Sb into the discharge/charge profiles. This would induce a large volume change and high structure strain/stress, deteriorating the cycling stability. The identification of a proper voltage window for Sb/Sb2O3 paves the way for its development in sodium ion batteries.

Carbonates/bicarbonates (FeCO3, CoCO3 and Ni(HCO3)2) supported on reduced graphene oxide (rGO) are prepared by a simple method and examined as anode materials for sodium-ion batteries for the first time. Although carbonates in the composite are of the order of micrometers, they show fair electrochemical activities, particularly for FeCO3/rGO. It delivers a capacity of 247 mA h g−1 after 500 cycles at 500 mA g−1, corresponding to a capacity retention of 87% relative to the capacity at the second cycle. It also shows a superior rate capability with a capacity of 176 mA h g−1 at 2 A g−1. Ex situ XPS spectra, HRTEM images and SAED patterns demonstrate that the sodium uptake/extraction in FeCO3, CoCO3 and Ni(HCO3)2 is via M0/M2+-engaged redox reaction.

VS4 as an electrode material in lithium-ion batteries holds intriguing features like high content of sulfur and one-dimensional structure, inspiring the exploration in this field. Herein, VS4 submicrospheres have been synthesized via a simple solvothermal reaction. However, they quickly degrade upon cycling as an anode material in lithium-ion batteries. So, three conductive polymers, polythiophene (PEDOT), polypyrrole (PPY), and polyaniline (PANI), are coated on the surface to improve the electron conductivity, suppress the diffusion of polysulfides, and modify the interface between electrode/electrolyte. PANI is the best in the polymers. It improves the Coulombic efficiency to 86% for the first cycle and keeps the specific capacity at 755 mAh g–1 after 50 cycles, higher than the cases of naked VS4 (100 mAh g–1), VS4@PEDOT (318 mAh g–1), and VS4@PPY (448 mAh g–1). The good performances could be attributed to the improved charge-transfer kinetics and the strong interaction between PANI and VS4 supported by theoretical simulation. The discharge voltage ∼2.0 V makes them promising cathode materials.

•CuCo2O4 microflowers assembled by porous nanosheets are synthesized.•Porous structure and 2D morphology make them excellent in Li-ion/Li-O2 batteries.•In Li-ion batteries, the capacity is ∼612 mA h g−1 after 500 cycles at 1 A g−1.•In Li-O2 batteries, the life lasts 120 cycles by limiting capacity to 1000 mAh g−1.Hierarchical CuCo2O4 microflowers (CCFs) self-assembled by thin and porous nanosheets were synthesized by a simple solvothermal reaction followed by a low-temperature calcination. The porous nanosheets not only shorten the Li-ion diffusion distances and tolerate the volume variation upon cycling, but also enhance the transportation of oxygen and Li+ ions, and have abundance of active sites on the surface. Thus, it has been explored as the superior anode material in Li-ion batteries and as the cathode catalyst in Li-O2 batteries. Both of applications exhibit the remarkable electrochemical properties. In lithium ion batteries, CuCo2O4 micro-flowers deliver a specific lithium storage capacity of 871 mA h g−1, after 300 cycles at 100 mA g−1. Even at a high rate of 1 A g−1, the reversible capacity of the CuCo2O4 microflowers still remains at 612 mA h g−1 after 500 cycles. In Li-O2 batteries, CuCo2O4 microflowers as the cathode catalyst last 120 cycles, much longer than highly aggregated CuCo2O4 and pure carbon.

P2-type Na0.6Ni0.2Co0.2Mn0.5Ti0.1O2 powders are successfully synthesized by a solid state reaction. Ex situ XRD reveals the phase transition process from P2 to O2 occurs at 4.1 V. As they are cycled in a narrow voltage window (4.2–2 V), they exhibit excellent cycling stability and high rate capability. Even at 5C for 250 cycles, the reversible capacity could be kept at 66.0 mA h g−1.

Gold nanorods coated by oxygen-deficient TiO2 are synthesized by slow hydrolysis followed with high-temperature annealing in a reducing atmosphere. This does not alter the morphology of the nanorods, but produces Ti3+ species and oxygen vacancies in the shell. These nanorods show superior photocatalytic ability in hydrogen generation. The enhanced performance may be attributed to the synergistic effect of Ti3+ species, oxygen vacancies and Au, which effectively enhance light absorption, reduce charge recombination and increase charge-transfer across the interface between the electrolyte and electrode.

Bimetallic nanoframes and nanoboxes of Pd–Rh are synthesized by selective removal of Pd cores from different Pd–Rh nanocubes prepared by a hydrothermal reaction of PdCl2, RhCl3 and HCHO. HCHO in the procedure alters the reaction kinetics and the growth behavior of Pd and Rh, resulting in different nanocubes that determine the following hollow nanostructures, nanoframes or nanoboxes. The catalytic properties of the hollow nanostructures are investigated using the oxidation of o-phenylenediamine (OPDA) to 2,3-diaminophenazine (DAP) as a model reaction. The resulting bimetallic nanoframes and nanoboxes show enhanced conversion efficiencies compared to their solid counterparts. This method offers a convenient way for mass production of bimetallic hollow nanomaterials.

A one-dimensional MWCNT@a-C@Co9S8 nanocomposite has been prepared via a facile solvothermal reaction followed by a calcination process. The amorphous carbon layer between Co9S8 and MWCNT acts as a linker to increase the loading of sulfides on MWCNT. When evaluated as anode materials for lithium ion batteries, the MWCNT@a-C@Co9S8 nanocomposite shows the advantages of high capacity and long life, superior to Co9S8 nanoparticles and MWCNT@Co9S8 nanocomposites. The reversible capacity could be retained at 662 mA h g−1 after 120 cycles at 1 A g−1. The efficient synthesis and excellent performances of this nanocomposite offer numerous opportunities for other sulfides as a new anode for lithium ion batteries.

Triple-walled SnO2@N-doped carbon@SnO2 nanotubes are synthesized by a facile process with high-quality PPy nanotubes as the template. This structure has SnO2 nanoparticles closely attached to both the external and internal surfaces of N-doped carbon nanotubes, thus assuring good charge-transfer kinetics to all the SnO2 nanoparticles. Meanwhile, it doubles the loading density of SnO2 in the nanocomposite, and offers adequate room to accommodate the volume deformation of SnO2 on/in the nanotubes. All these features make the nanocomposite well fitted for lithium or sodium storage. It is found that this nanocomposite as an anode material for lithium ion batteries can deliver a reversible capacity of 935 mA h g−1 after 100 cycles at 200 mA g−1, or 658 mA h g−1 after 300 cycles at 2000 mA g−1. In the case of sodium ion batteries, its capacity could be still preserved at 492 mA h g−1 after 50 cycles at a current density of 25 mA g−1.

MnO nanorods encapsulated by N-doped carbon are prepared, using polypyrrole-coated MnOOH nanorods as both a template and a precursor. The resulting coaxial nanorods have a one-dimensional shape, nanoscale size and an N-doped carbon coating within one particle, which substantially improves their electrochemical performance. As an anode material for lithium-ion batteries, the coaxial nanorods of MnO/N-doped carbon deliver a specific capacity of 982 mA h g−1 at a current density of 500 mA g−1 after 100 cycles, higher than the values for pure MnO nanostructures and MnO/C nanocomposites. At a current density of 5000 mA g−1, the reversible capacity of the coaxial nanorods could be as high as 372 mA h g−1.

Tunnel-structured Na0.54Mn0.50Ti0.51O2 nanorods have been synthesized by a facile molten salt method. These nanorods are grown in the direction normal to the sodium-ion tunnels, greatly shortening the diffusion distance of sodium ions and benefiting the transfer kinetics. Thus, the nanorods show significant enhancements in terms of reversible capacity, cycling stability and rate capability. The electrochemical performance could be further promoted via carbon coating to ∼122 mA h g−1 after 150 cycles at 0.2 C or ∼85 mA h g−1 after 400 cycles at 1 C.

Rational design and delicate control on the component, structure, and surface of electrodes in lithium ion batteries are highly important to their performances in practical applications. Compared with various components and structures for electrodes, the choices for their surface are quite limited. The most widespread surface for numerous electrodes, a carbon shell, has its own issues, which stimulates the desire to find another alternative surface. Here, hydrogenated TiO2 is exemplified as an appealing surface for advanced anodes by the growth of ultrathin hydrogenated TiO2 branches on Mn3O4 nanorods. High theoretical capacity of Mn3O4 is well matched with low volume variation (∼4%), enhanced electrical conductivity, good cycling stability, and rate capability of hydrogenated TiO2, as demonstrated in their electrochemical performances. The proof-of-concept reveals the promising potential of hydrogenated TiO2 as a next-generation material for the surface in high-performance hybrid electrodes.Keywords: batteries; electrochemical properties; hybrid materials; nanostructures; oxygen vacancies;

•MnOx hierarchical microspheres are prepared by a template method.•MnOx hierarchical microspheres exhibit superior electrochemical properties.•MnO anode delivers a capacity of 810 mAh g-1 at 0.5 C after 100 cycles.Four type of MnOx (MnO2, Mn2O3, Mn3O4, MnO) hierarchical microspheres assembled by rod-like building blocks are synthesized by a facile hydrothermal process with/without a consequent calcination. The morphology and structure of these hierarchical microspheres are confirmed by XRD, SEM, TEM, HRTEM, XPS and BET measurements. The electrochemical properties of the four hierarchical microspheres are investigated in terms of cycling stability and rate capability. Specific capacities of 240, 396, 271 and 810 mAh g−1 can be achieved after 100 cycles at 0.5C for MnO2, Mn2O3, Mn3O4 and MnO, respectively. Even at a high rate of 2C, MnO microspheres can still deliver a reversible capacity of 406 mA h g−1. Their superior electrochemical properties might be attributed to the secondary nanostructure in the MnOx microspheres, which could effectively shorten the diffusion pathway of Li+, tolerate the structural stress caused by Li+ insertion/extraction, reduce the side reactions with electrolyte, and restrain the self-aggregation of nanomaterials.

•Hollow nanospheres of mesoporous Co9S8 are synthesized by a simple process.•These nanospheres show a capacity of ~1400 mA h g−1 after 100 cycles at 100 mA g−1.•There is a significant capacity recovery upon this cycling.•This capacity recovery is associated with enhanced capacitive contribution.•Carbon coating on Co9S8 further stabilizes the capacity at high rates.Hollow nanospheres of mesoporous Co9S8 are successfully synthesized by a facile solvothermal reaction followed with a high-temperature annealing in Ar/H2. These hollow nanoparticles exhibit a reversible capacity of ~1414 mA h g−1 after 100 cycles at 100 mA g−1. In the course of this cycling, there is a significant capacity recovery, which is associated with enhanced capacitance caused by repeated electro-chemical milling. The growth of a carbon shell on the hollow nanospheres further improves the reversible capacities at high rates, ~896 mA h g−1 after 800 cycles at 2 A g−1. The excellent lithium-storage performances shed light on the promising potential of sulfides as a high capacity, high rate and long life anodes.

The use of manganese oxides as promising candidates for anode materials in lithium ion batteries has attracted a significant amount of attention recently. Here, we develop a general approach to synthesize hollow nanospheres of MnO2, Mn3O4 and MnO, using carbon nanospheres as a template and a reagent. Depending on the calcination temperature, time and atmosphere, hollow nanospheres of MnO2 assembled by randomly dispersed nanosheets, or hollow nanospheres of Mn3O4 and MnO composed of aggregated nanoparticles, are produced. The electrochemical properties of the three hollow nanoparticles are investigated in terms of cycling stability and rate capability. They deliver the specific capacities of 840, 1165 or 1515 mA h g−1 after 60 cycles at 100 mA g−1 for MnO2, Mn3O4 and MnO. Even at 500 mA g−1, the reversible capacities could be still kept at 637, 820, and 1050 mA h g−1 after 150 cycles. The outstanding performances might be related with their hollow structure, porous surface and nanoscale size.

Hierarchically porous NiO microtubes are synthesized by a high-temperature calcination of Ni(dmg)2 microtubes obtained by a simple precipitation method. The porous NiO microtubes as an anode material for lithium ion batteries exhibit excellent performances, ∼640 mA h g−1 after 200 cycles at 1 A g−1.

High-performance anode materials in lithium ion batteries greatly rely on the elaborate control of their size, shape, structure and surface. However, it is difficult to assemble all of the controls within one particle, due to difficulties in their synthesis. Here, hierarchical carbon-coated α-Fe2O3 nanotubes are prepared by a facile hydrothermal reaction between branched MnO2/Fe2O3 nanorods and glucose. The resulting nanotubes realize all these controls in one particle in terms of their nanoscale size, one-dimensional shape, hollow structure, hierarchical surface and carbon coating. Meanwhile, the thickness of the carbon layer could be easily controlled by the ratio between the different reactants. Electrochemical measurements show that the core–shell nanotubes with the thinnest carbon layer give the best cycling and rate performances. They deliver a specific capacity of 1173 mA h g−1 after 100 cycles at a current density of 0.2 A g−1, or 1012 mA h g−1 after 300 cycles at 1 A g−1. Even after 1000 cycles at a current density of 4 A g−1, the specific capacity could be still kept at 482 mA h g−1. The excellent lithium-storage performance could be attributed to the well-designed controls in this nanocomposite and a thin carbon layer, which increases the electron conductivity of the electrode and simultaneously keeps the carbon content lower.

Controlled growth of hybrid metallic nanocomposites for a desirable structure in a combination of selected components is highly important for their applications. Herein, the controllable growth of RhAg on the gold nanorods is achieved from the dumbbell-like RhAg-tipped nanorods to the brushy RhAg-coated nanorods, or the rod-like Au@Ag–Rh nanorattles. These different growth modes of RhAg on the gold nanorods are correlated with the reducing kinetics of RhCl3 and AgNO3. In view of the promising catalytic properties of Rh, the gold nanorods modified by RhAg in different structures are examined as catalysts for the oxidation of o-phenylenediamine. It is found that brushy RhAg-coated nanorods present a higher catalytic efficiency than dumbbell-like RhAg-tipped nanorods and rod-like Au@Ag–Rh nanorattles. These results would benefit the overgrowth control on the one-dimensional metallic nanorods and the rational design of new generation heterogeneous catalysts and optical devices.

•α-Fe2O3 nanotubes and nanorods with close sizes are obtained by hydrothermal methods.•The nanotubes show better cycling stability and rate capability than the nanorods.•The nanotubes show a high capacity of 810 mAh g−1 at 1 A g−1 after 60 cycles.α-Fe2O3 nanotubes and nanorods are obtained via a hydrothermal method without further annealing. Both of them are characterized by X-ray powder diffraction, scanning electron microscopy, and high-resolution transmission electron microscopy. The lithium-storage performances of the nanostructures are measured and compared in terms of reversible capacity, cycling stability, and rate capability. The electrode based on the nanotubes delivers the reversible capacities of 1200 mAh g−1 at 100 mA g−1, 1000 mAh g−1 at 500 mA g−1, and 810 mAh g−1 at 1000 mA g−1 after 60 cycles, much higher than those based on the nanorods. The better performances of the nanotubes could be assigned to their tubular morphology that tolerates the huge volume change during the discharge/charge processes and possesses the large surface area to increase the contact between the electrode and the electrolyte. These insights will be of benefits in the design of other anode materials for lithium ion batteries.

•Novel mesoporous silicon nanorods have been prepared.•Magnesiothermic reduction method was adopted in the preparation process.•The reversible capacity can maintain 1038 mAh g−1 after 170 cycles.•The reversible capacity can retain 664 mAh g−1 at a high rate of 2000 mA g−1.Mesoporous silicon nanorods assembled by small nanocrystals were successfully prepared using multi-walled carbon nanotubes (MWCNTs) as a template via a facile magnesiothermic reduction process. The obtained product was characterized by X-ray diffraction, Raman spectroscopy, transmission electron microscopy, nitrogen adsorption-desorption measurement and electrochemical measurements. The resulting mesoporous silicon nanorods as an anode exhibit a significantly improved electrochemical performance compared with the porous silicon networks and bulk silicon. The reversible capacity can retain 1038 mAh g−1 at 200 mA g−1 after 170 cycles. Even at a high rate of 2000 mA g−1, a reversible capacity of 664 mAh g−1 can still be obtained. All these results suggest that the mesoporous silicon nanorods are a promising candidate for the next generation of lithium ion batteries.

•Porous ZnMn2O4 microspheres composed of interconnected nanoparticles have been prepared by a two-step process.•ZnMn2O4 microspheres exhibit a reversible capacity of 800 mAh g−1 at 500 mA g−1 over 300 cycles.•Even at 2 A g−1, ZnMn2O4 microspheres deliver a capacity of 395 mAh g−1, higher than the theoretical capacity of graphite.•The superior electrochemical performances can be associated with the porous structure and nanoscale building blocks.High-quality porous ZnMn2O4 microspheres composed of interconnected nanoparticles have been achieved by calcination of metal carbonates synthesized by a solvothermal reaction. The porous microspheres are characterized by XRD patterns, SEM, TEM, and HRTEM images to reveal the crystal phase and particle morphology. The porous structure and nanoscale building blocks of ZnMn2O4 microspheres make them a promising anode material for lithium ion batteries. After 300 cycles at a current density of 500 mA g−1, they still preserve a reversible capacity of 800 mAh g−1. Even at 2 A g−1, the reversible capacity could be 395 mAh g−1, higher than the theoretical capacity of graphite. The superior electrochemical performances can be associated with the porous structure and nanoscale building blocks, which promote the contacting between electrolyte and electrode, accommodate volume change during discharge/charge processes, and provide a large number of active surface sites for lithium storage.

Binary transition metal oxides have been attracting extensive attention as promising anode materials for lithium-ion batteries, due to their high theoretical specific capacity, superior rate performance and good cycling stability. Here, loaf-like ZnMn2O4 nanorods with diameters of 80–150 nm and lengths of several micrometers are successfully synthesized by annealing MnOOH nanorods and Zn(OH)2 powders at 700 °C for 2 h. The electrochemical properties of the loaf-like ZnMn2O4 nanorods as an anode material are investigated in terms of their reversible capacity, and cycling performance for lithium ion batteries. The loaf-like ZnMn2O4 nanorods exhibit a reversible capacity of 517 mA h g−1 at a current density of 500 mA g−1 after 100 cycles. The reversible capacity of the nanorods still could be kept at 457 mA h g−1 even at 1000 mA g−1. The improved electrochemical performance can be ascribed to the one-dimensional shape and the porous structure of the loaf-like ZnMn2O4 nanorods, which offers the electrode convenient electron transport pathways and sufficient void spaces to tolerate the volume change during the Li+ intercalation. These results suggest the promising potential of the loaf-like ZnMn2O4 nanorods in lithium-ion batteries.

MoS2, because of its layered structure and high theoretical capacity, has been regarded as a potential candidate for electrode materials in lithium secondary batteries. But it suffers from the poor cycling stability and low rate capability. Here, hierarchical hollow nanoparticles of MoS2 nanosheets with an increased interlayer distance are synthesized by a simple solvothermal reaction at a low temperature. The formation of hierarchical hollow nanoparticles is based on the intermediate, K2NaMoO3F3, as a self-sacrificed template. These hollow nanoparticles exhibit a reversible capacity of 902 mA h g–1 at 100 mA g–1 after 80 cycles, much higher than the solid counterpart. At a current density of 1000 mA g–1, the reversible capacity of the hierarchical hollow nanoparticles could be still maintained at 780 mAh g–1. The enhanced lithium storage performances of the hierarchical hollow nanoparticles in reversible capacities, cycling stability and rate performances can be attributed to their hierarchical surface, hollow structure feature and increased layer distance of S–Mo–S. Hierarchical hollow nanoparticles as an ensemble of these features, could be applied to other electrode materials for the superior electrochemical performance.Keywords: hierarchical surface; hollow structure; layered compounds; lithium secondary batteries; nanomaterials; solvothermal reaction;

The Li2MnSiO4/C nanocomposite has been successfully synthesized at a relatively low temperature of 650 °C by a facile solid-state reaction using citric acid as the carbon source. The highly crystalline Li2MnSiO4 nanoparticles in the size of 20–50 nm are coated by a uniform carbon layer in a thickness of 2–5 nm. At a rate of 0.05 C, the Li2MnSiO4/C nanocomposite exhibits a discharge specific capacity as high as 268 mAh g−1 for the first cycle and a reversible capacity of about 136 mAh g−1 after 140 cycles at room temperature. Meanwhile, an improved rate performance is achieved by the Li2MnSiO4/C nanocomposite. These superior electrochemical properties could be attributed to the nanoscale particle size and the enhanced electronic conductivity.Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Li2MnSiO4/C nanocomposite is synthesized by a facile solid-state reaction. ► The typical size of Li2MnSiO4 nanoparticles is in the range of 20–50 nm ► The nanocomposite exhibits a discharge capacity of 136 mAh g−1 after 140 cycles. ► The nanocomposite also shows a greatly improved rate performance.

•Pure cubic and tetragonal CuFe2O4 nanocrystals.•C- and t-CuFe2O4 exhibit similar electrode reactions except the first cycle.•C-CuFe2O4 shows superior capacity and rate capability.•FexCu1−x alloy in the discharged electrode were observed for the first time.Cubic CuFe2O4 (c-CuFe2O4) and tetragonal CuFe2O4 (t-CuFe2O4) nanoparticles were selectively prepared using a facile one-step solid state reaction route by ferrous oxalate and copper acetate as the reactants. As an anode material for Li-ion batteries, compared with c-CuFe2O4 and t-CuFe2O4 synthesized at 800 °C, c-CuFe2O4 synthesized at 400 °C with smaller particle size and larger surface area exhibited superior discharge capacities and better cycling performance (950 mAh g−1at 100 mA g−1 after 60 cycles), and higher rate capability. The influence of the two crystal phases on the electrochemical performance were only exhibited at the Li+ insertion process during the first discharge. The average particle size and the surface areas play an important role in effecting the lithium-ion storage capability and cycling ability. Through ex situ HRTEM analysis, we observed the existence of metastable FexCu1−x alloy in the discharged nanocomposition for the first time, which exhibits the interaction of metallic Cu particles with the adjacent iron ions.Cubic CuFe2O4 and tetragonal CuFe2O4 nanoparticles were selectively prepared and exhibit good performance for Li-ion batteries.

Successful doping of anisotropic semiconductor nanocrystals with impurities offers an effective pathway to manipulate their physical properties and enhance the application performances. However, such doping into anisotropic nanocrystals is seldom reported because it needs simultaneous controls in the crystal growth for a specific shape and composition engineering for transition-metal doping. Here, ultrathin Cu-doped ZnSe nanorods are synthesized by a growth–doping process. The doped nanorods are characterized by XRD and TEM techniques to reveal their crystal structure. Their optical properties are described in terms of UV-Vis absorption spectra and PL spectra. The tunable emission from 480 to 520 nm evidences the successful doping of Cu into ZnSe nanorods. The effects of the reaction time, the reaction temperature and the surface ligand on the optical properties are discussed in detail. After purification, the doped nanorods with a Cu/Zn ratio of 1% give a quantum yield of 7%. This emission could be retained for weeks in air, which is important for its future applications in many fields.

Olivine structured LiMnPO4 nanorods as an emerging cathode material for lithium ion batteries have recently triggered intensive interest. Herein, LiMnPO4 nanorods have been synthesized via a solvothermal route and then coated with a carbon layer from different carbon sources to improve their electrochemical performance. The LiMnPO4–C nanocomposite obtained from beta-cyclodextrin as the carbon source showed a reversible capacity of 153.4 mA h g−1 at a rate of 0.1 C and maintained it at 120 mA h g−1 after 50 cycles, which is much better than that obtained from ascorbic acid, citric acid, glucose and sucrose. This result can be attributed to the smaller electrode impedance in the nanocomposite obtained from beta-cyclodextrin, based on EIS measurements. Correlated to the molecule structure, it is believed that larger molecules with more oxygenous groups are beneficial to their uniform adsorption on the electrodes and then produce a better electron-conductive carbon layer after calcinations. This result would be very helpful in future work related to carbon coating on other electrodes.

General and simple methods for the syntheses of borides, carbides and nitrides are highly desirable, since those materials have unique physical properties and promising applications. Here, a series of boride (TiB2, ZrB2, NbB2, CeB6, PrB6, SmB6, EuB6, LaB6), carbide (SiC, TiC, NbC, WC) and nitride (TiN, BN, AlN, MgSiN2, VN) micro/nanocrystals were prepared from related oxides and amorphous boron/active carbon/NaN3 with the assistance of metallic Na and elemental S. In-situ temperature monitoring showed that the reaction temperature could increase quickly to ∼850 °C, once the autoclave was heated to 100 °C. Such a rapid temperature increase was attributed to the intense exothermic reaction between Na and S, which assisted the formation of borides, carbides and nitrides. The as-obtained products were characterized by XRD, SEM, TEM, and HRTEM techniques. Results in this report will greatly benefit the future extension of this approach to other compounds.Graphical abstractAn additive-assisted approach is successfully developed for the syntheses of borides, carbides and nitrides micro/nanocrystals with the assistance of the exothermic reaction between Na and S.Highlights► An additive-assisted synthesis strategy is developed for a number of borides, carbides and nitrides. ► The reaction mechanism is demonstrated by the case of SiC nanowires. ► The formation of SiC nanowires is initiated by the exothermic reaction of Na and S.

Structure tailoring of hybrid nanoparticles is highly desirable for a number of applications, due to their controllable physical properties. Here, a family of Ag–Fe3O4 nanohybrids is synthesized via a simple one-step reaction of silver acetate and iron acetylacetonate in the presence of 1,2-dodecanediol, oleylamine and oleic acid. The as-obtained Ag–Fe3O4 nanohybrid could be finely tuned from heterodimer nanoparticles to flower-like or core–shell nanoparticles, by controlling the experimental conditions. The structural differences between these nanohybrids greatly affect their optical properties. The intense surface plasmon resonance (SPR) peak allows the heterodimer nanoparticles to act as a superior surface-enhanced Raman scattering (SERS) substrate, which has been demonstrated by using 2-naphthalenethiol as a probe molecule. It is noted that the SERS signal of 2-naphthalenethiol on the heterodimer nanoparticles is much stronger than those on the core–shell nanohybrid and Ag nanoparticles alone, indicating its potential in the fields of ultrasensitive detection and biological imaging.

VS4 as an anode material is showing its glamour, due to its unique chain-like structure, the high content of sulfur, and distinctive electrochemical behaviours. Here, VS4 nanoparticles rooted by amorphous carbon coated multi-walled carbon nanotubes, are successfully synthesized via a simple solvothermal reaction. This unique structure enables modified carbon nanotubes to enhance the charge transportation not only inside the composite but also outside the composite, which is difficult to be achieved by other structures. These charge-transfer enhancements allow the composite to exhibit much better electrochemical performances than many transition metal sulfides, in terms of both cycling stability and rate capability. It delivers a reversible capacity of 922 mAh g-1 after 100 cycles at 0.5 A g-1. Even after cycled at 2 or 5 A g-1 for 1000 times, it still has a capacity of 576 or 401 mAh g-1. Besides in lithium ion batteries, this composite could be also used as an anode material in sodium ion batteries.Download high-res image (190KB)Download full-size image

Structure tailoring of hybrid nanoparticles is highly desirable for a number of applications, due to their controllable physical properties. Here, a family of Ag–Fe3O4 nanohybrids is synthesized via a simple one-step reaction of silver acetate and iron acetylacetonate in the presence of 1,2-dodecanediol, oleylamine and oleic acid. The as-obtained Ag–Fe3O4 nanohybrid could be finely tuned from heterodimer nanoparticles to flower-like or core–shell nanoparticles, by controlling the experimental conditions. The structural differences between these nanohybrids greatly affect their optical properties. The intense surface plasmon resonance (SPR) peak allows the heterodimer nanoparticles to act as a superior surface-enhanced Raman scattering (SERS) substrate, which has been demonstrated by using 2-naphthalenethiol as a probe molecule. It is noted that the SERS signal of 2-naphthalenethiol on the heterodimer nanoparticles is much stronger than those on the core–shell nanohybrid and Ag nanoparticles alone, indicating its potential in the fields of ultrasensitive detection and biological imaging.

The use of manganese oxides as promising candidates for anode materials in lithium ion batteries has attracted a significant amount of attention recently. Here, we develop a general approach to synthesize hollow nanospheres of MnO2, Mn3O4 and MnO, using carbon nanospheres as a template and a reagent. Depending on the calcination temperature, time and atmosphere, hollow nanospheres of MnO2 assembled by randomly dispersed nanosheets, or hollow nanospheres of Mn3O4 and MnO composed of aggregated nanoparticles, are produced. The electrochemical properties of the three hollow nanoparticles are investigated in terms of cycling stability and rate capability. They deliver the specific capacities of 840, 1165 or 1515 mA h g−1 after 60 cycles at 100 mA g−1 for MnO2, Mn3O4 and MnO. Even at 500 mA g−1, the reversible capacities could be still kept at 637, 820, and 1050 mA h g−1 after 150 cycles. The outstanding performances might be related with their hollow structure, porous surface and nanoscale size.

Hierarchically porous NiO microtubes are synthesized by a high-temperature calcination of Ni(dmg)2 microtubes obtained by a simple precipitation method. The porous NiO microtubes as an anode material for lithium ion batteries exhibit excellent performances, ∼640 mA h g−1 after 200 cycles at 1 A g−1.

High-performance anode materials in lithium ion batteries greatly rely on the elaborate control of their size, shape, structure and surface. However, it is difficult to assemble all of the controls within one particle, due to difficulties in their synthesis. Here, hierarchical carbon-coated α-Fe2O3 nanotubes are prepared by a facile hydrothermal reaction between branched MnO2/Fe2O3 nanorods and glucose. The resulting nanotubes realize all these controls in one particle in terms of their nanoscale size, one-dimensional shape, hollow structure, hierarchical surface and carbon coating. Meanwhile, the thickness of the carbon layer could be easily controlled by the ratio between the different reactants. Electrochemical measurements show that the core–shell nanotubes with the thinnest carbon layer give the best cycling and rate performances. They deliver a specific capacity of 1173 mA h g−1 after 100 cycles at a current density of 0.2 A g−1, or 1012 mA h g−1 after 300 cycles at 1 A g−1. Even after 1000 cycles at a current density of 4 A g−1, the specific capacity could be still kept at 482 mA h g−1. The excellent lithium-storage performance could be attributed to the well-designed controls in this nanocomposite and a thin carbon layer, which increases the electron conductivity of the electrode and simultaneously keeps the carbon content lower.

Triple-walled SnO2@N-doped carbon@SnO2 nanotubes are synthesized by a facile process with high-quality PPy nanotubes as the template. This structure has SnO2 nanoparticles closely attached to both the external and internal surfaces of N-doped carbon nanotubes, thus assuring good charge-transfer kinetics to all the SnO2 nanoparticles. Meanwhile, it doubles the loading density of SnO2 in the nanocomposite, and offers adequate room to accommodate the volume deformation of SnO2 on/in the nanotubes. All these features make the nanocomposite well fitted for lithium or sodium storage. It is found that this nanocomposite as an anode material for lithium ion batteries can deliver a reversible capacity of 935 mA h g−1 after 100 cycles at 200 mA g−1, or 658 mA h g−1 after 300 cycles at 2000 mA g−1. In the case of sodium ion batteries, its capacity could be still preserved at 492 mA h g−1 after 50 cycles at a current density of 25 mA g−1.

MnO nanorods encapsulated by N-doped carbon are prepared, using polypyrrole-coated MnOOH nanorods as both a template and a precursor. The resulting coaxial nanorods have a one-dimensional shape, nanoscale size and an N-doped carbon coating within one particle, which substantially improves their electrochemical performance. As an anode material for lithium-ion batteries, the coaxial nanorods of MnO/N-doped carbon deliver a specific capacity of 982 mA h g−1 at a current density of 500 mA g−1 after 100 cycles, higher than the values for pure MnO nanostructures and MnO/C nanocomposites. At a current density of 5000 mA g−1, the reversible capacity of the coaxial nanorods could be as high as 372 mA h g−1.

Tunnel-structured Na0.54Mn0.50Ti0.51O2 nanorods have been synthesized by a facile molten salt method. These nanorods are grown in the direction normal to the sodium-ion tunnels, greatly shortening the diffusion distance of sodium ions and benefiting the transfer kinetics. Thus, the nanorods show significant enhancements in terms of reversible capacity, cycling stability and rate capability. The electrochemical performance could be further promoted via carbon coating to ∼122 mA h g−1 after 150 cycles at 0.2 C or ∼85 mA h g−1 after 400 cycles at 1 C.