Search

To inhibit the aggregation of TiO2 nanoparticles and to improve the electrochemical kinetics of TiO2 electrode, a hybrid material of ultrasmall TiO2 nanoparticles in situ grown on rGO nanosheets was obtained by ultraphonic and reflux methods. The size of the TiO2 particles was controlled about 10 nm, and these particles were evenly distributed across the rGO nanosheets. When used for the anode of a sodium ion battery, the electrochemical performance of this hybrid TiO2@rGO was much improved. A capacity of 186.6 mAh g(-1) was obtained after 100 cycles at 0.1 A g(-1), and 112.2 mAh g(-1) could be maintained at 1.0 A g(-1), showing a high capacity and good rate capability. On the basis of the analysis of cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), the achieved excellent electrochemical performance was mainly attributed to the synergetic effect of well-dispersed ultrasmall TiO2 nanoparticles and conductive graphene network and the improved electrochemical kinetics. The superior electrochemical performance of this hybrid material on lithium storage further confirmed the positive effect of rGO.

Small amount of reduce graphene oxide (rGO) nanosheets modified Li 4 Ti 5 O 12 nanoparticles composite has been synthesized by a facile and environmental in-situ hydrothermal reaction with subsequent annealing. The small amount of rGO (only 1.2 wt. %) greatly improves the whole morphology and electrochemical performance of composite. The nanoparticles uniformly grow on the rGO nanosheets effective suppressing the agglomeration and enhancing the specific surface area. Meanwhile, the special discharge capacity is 187 mAh g −1 at 1 C and the high rates discharge capacity is 128 mAh g −1 at 80 C (discharge-charge time only 33s). In particular, the cells remain in good work condition after 2000 cycles at 80 C, which credibly evidence the excellent electrochemical performance as an anode for high-power LIBs.

Electrochemical performances of LiCoO2 as a candidate material for supercapacitor are systematically investigated. LiCoO2 nanomaterials are synthesized via hydrothermal reaction with consequent calcination process. And the particle size increases as the calcination temperature rises. LCO-650 sample with the largest particle size displays the maximum capacitances of 817.5 F·g−1 with the most outstanding capacity retention rate of 96.8% after 2000 cycles. It is shown that large particle size is beneficial to the electrochemical and structural stability of LiCoO2 materials. We speculate that the micron-sized waste LiCoO2 materials have great potential for supercapacitor application. It may provide a novel recovered approach for spent LIBs and effectively relieve the burdens on the resource waste and environment pollution.

Although transition metal oxide electrodes have large lithium storage capacity, they often suffer from low rate capability, poor cycling stability, and unclear additional capacity. In this paper, CoO nanowire clusters (NWCs) composed of ultra-small nanoparticles (≈10 nm) directly grown on copper current collector are fabricated and evaluated as an anode of binder-free lithium-ion batteries, which exhibits an ultra-high capacity and good rate capability. At a rate of 1 C (716 mA g−1), a reversible capacity as high as 1516.2 mA h g−1 is obtained, and even when the current density is increased to 5 C, a capacity of 1330.5 mA h g−1 could still be maintained. Importantly, the origins of the additional capacity are investigated in detail, with the results suggesting that pseudocapacitive charge and the higher-oxidation-state products are jointly responsible for the large additional capacity. In addition, nanoreactors for the CoO nanowires are fabricated by coating the CoO nanowires with amorphous silica shells. This hierarchical core–shell CoO@SiO2 NWC electrode achieves an improved cycling stability without degrading the high capacity and good rate capability compared to the uncoated CoO NWCs electrode.

Monocrystal LiMn0.6Fe0.4PO4 cathode material was obtained via hydrothermal method at 180 °C for 10 h without any surfactant. The effects of hydrothermal time on the phase and morphology of the material were discussed. By controlling the reaction solutions, the rodlike, flowerlike, and strawlike LiMn0.6Fe0.4PO4 cathode materials were synthesized. Electrochemical performances show that the rodlike LiMn0.6Fe0.4PO4 has the best electrochemical properties. The initial discharge capacity of the rodlike structure is 106.4 mAh·g−1, which is higher than those of flowerlike and strawlike materials.

Hierarchical porous ZnCo2O4 microspheres have been successfully synthesized via a solvothermal method followed by an annealing process. The ZnCo2O4 electrode shows a high specific capacitance of 647.1 F g−1 at 1 A g−1 and 440.6 F g−1 at 10 A g−1 in 2 M KOH. After 2000 cycles, the capacity loss is only 8.5%.

Designed as a high-capacity, high-rate, and long-cycle life anode for sodium ion batteries, exfoliated-SnS2 restacked on graphene is prepared by the hydrolysis of lithiated SnS2 followed by a facile hydrothermal method. Structural and morphological characterizations demonstrate that ultrasmall SnS2 nanoplates (with a typical size of 20–50 nm) composed of 2–5 layers are homogeneously decorated on the surface of graphene, while the hybrid structure self-assembles into a three-dimensional (3D) network architecture. The obtained SnS2/graphene nanocomposite delivers a remarkable capacity as high as 650 mA h g−1 at a current density of 200 mA g−1. More impressively, the capacity can reach 326 mA h g−1 even at 4000 mA g−1 and remains stable at ∼610 mA h g−1 without fading up to 300 cycles when the rate is brought back to 200 mA g−1. The excellent electrochemical performance is attributed to the synergetic effects between the ultrasmall SnS2 and the highly conductive graphene network. The unique structure can simultaneously facilitate Na+ ion diffusion, provide more reaction sites, and suppress aggregation and volume fluctuation of the active materials during prolonged cycling.

Co3O4/CNTs samples are synthesized via different methods and investigated as negative materials for alkaline rechargeable batteries for the first time. The reasons for performance difference of those Co3O4/CNTs electrodes and the impact of CNTs additive amount on cycling properties are explored in detail. CNTs can remarkably enhance the electrochemical activity of Co3O4 materials, leading to a notable improvement of discharge capacity, cycle stability and rate capability. Co3O4/CNTs-C composites via the one-pot reflux method exhibit the desirable electrochemical capability. Co3O4/CNTs-C8 sample (mass ratio of CNTs is 8%) shows the highest discharge capacity of 526.1 mA h g−1. Meanwhile, Co3O4/CNTs-C11 electrode (mass ratio of CNTs is 11%) displays the most outstanding cycle performance with a capacity retention rate of over 97.3% after 200 cycles. A properly electrochemical reaction mechanism of Co3O4/CNTs electrode is also constructed in detail.

Na-ion batteries have emerged in recent years, due to their advantages of natural abundance, low cost and environmental friendliness. In this article, we review the up-to-date research progress on anode materials for Na-ion batteries from five respects: carbon-based materials, alloy-based materials, metal oxides and sulfides based on conversion reaction, titanium-based compounds with insertion mechanism, and organic composites. In particular, we not only summarize the Na-storage mechanism of these anodes, but also discuss the failure mechanism. The problems and challenges associated with these anodes are pointed out. Furthermore, on the basis of extensive reports and our experimental studies, feasible strategies are suggested for designing high performance anode materials. After further in-depth exploration and investigation, we believe that Na-ion batteries are promising alternative to lithium-ion batteries for low cost and large-scale energy storage systems in the near future.

Novel NaV3O8 nanosheet@polypyrrole core-shell composites have been successfully prepared for the first time via a chemical oxidative polymerization method. Based on the morphological and microstructural characterization, it was found that polypyrrole (PPy) was uniformly wrapped on the surfaces of the NaV3O8 nanosheets. When used as a cathode for Na-ion batteries, the as-synthesized NaV3O8@10% PPy composite showed significantly improved cycling performance (with a discharge capacity of 99 mA h g(-1) after 60 cycles at 80 mA g(-1)) and better rate capacity (with a discharge capacity of 63 mA h g(-1) at a high current density of 640 mA g(-1)) than pristine NaV3O8 nanosheets. The greatly enhanced performance benefits from the unique core-shell structure, where the PPy coating not only prevents the pulverization and aggregation of the lamellar NaV3O8 nanosheets during cycling, which can improve the cycling stability, but also enhances the electrical conductivity of the composite, which can facilitate Na(+) ion diffusion.

One-dimensional porous Co 3 O 4 nanowires with different length have been successfully synthesized by thermal decomposition of Co-NA polymer precursors at various hydrothermal reaction times. The positive effects of longer nanowires and larger surface area on electrochemical performance of Co 3 O 4 samples were investigated systematically. All the as-prepared Co 3 O 4 samples display excellent discharge capacities and cycle stability on account of large surface area and porous structure, indicating great potential application of porous Co 3 O 4 nanowires for alkaline rechargeable batteries. The Co 3 O 4 -24 h sample with the longest length shows the most outstanding electrochemical performance, and displays the maximum discharge capacity of 450.1 mAh g −1 with the capacity retention of 90.4% after 100 cycles at a current density of 100 mA g −1 . Electrochemical reactions between Co and Co(OH) 2 occurring on the Co 3 O 4 electrodes are investigated by XRD, cyclic voltammetry (CV) and charge–discharge measurements.

A potential negative electrode material Co3O4@rGO is synthesized via a facile reflux condensation route. The electrochemical performances of Co3O4@rGO composite for alkaline rechargeable Ni/Co batteries have been systemically investigated for the first time. The reduced-graphene can remarkably enhance the electrochemical activity of Co3O4 materials, leading to a notable improvement of discharge capacity, cycle stability and rate capability. Interestingly, the maximum discharge capacity of Co3O4@rGO-20 (additive amount of GO is 20 mg) electrode can reach 511.4 mAh g−1 with the capacity retention of 89.1% after 100 cycles at a discharge current of 100 mA g−1. A properly electrochemical reaction mechanism of Co3O4@rGO electrode is also constructed in detail.

In this paper, porous Ni-substituted Co 3 O 4 (ternary NiCo 2 O 4 ) nanowires are synthesized via a simple microemulsion technique combined with a post thermal treatment. The as-prepared NiCo 2 O 4 exhibits porous one-dimensional (1D) nanostructure, which preserves the morphology of the precursor. Moreover, the NiCo 2 O 4 nanowires possess large surface area (53.6 m 2 g −1 ), pore volume (0.241 cm 3 g −1 ) and pore size (16.5 nm). The porous 1D nanostructures and large surface area have huge benefits for practical applications in supercapacitors. Due to the well-aligned 1D nanowire microstructure and a higher electrical conductivity, these ternary NiCo 2 O 4 electrodes possess high specific capacities of 1197 F g −1 at 1 A g −1 and capacitance retentions of 625 F g −1 at 8 A g −1 . After 2000 cycles, the NiCo 2 O 4 electrode can maintain 91.4% of its highest value, which demonstrates its superior cyclic stability performance. Also, the NiCo 2 O 4 electrode exhibits high capacity retention when fast charging. These results show that the porous NiCo 2 O 4 nanowires may be a promising electrode material for high performance electrochemical capacitors.

Co 3 O 4 nanoparticles are successfully synthesized from Cobalt bis (4-pyridine carboxylate) tetrahydrate (Co-INA) precursors through the solvothermal method followed by thermal treatment in air. The morphologies of Co 3 O 4 products varies with the amount of ethanol in the solvent. What's more, the phenomenon of aggregation becomes more unobvious with increasing the amount of ethanol to 15 mL ethanol, the corresponding Co 3 O 4 nanoparticles show a better dispersion and more excellent cycling performance. This electrode provides a specific discharge capacity of 712 mA h g -1 after 100 cycles at the current density of 200 mA g -1 . Therefore, the Co 3 O 4 nanoparticles can be deemed to be potential candidates as anode materials for further investigation.

The nanostructured CoB of morphologies, being rod-like, flake-like, chain-like, waxberry-like and mulberry-like, was synthesized, and then doped into LiBH 4 by ball milling. CoB played as pure catalyst facilitating de/rehydrogenation of LiBH 4 , and its morphology greatly influenced the catalytic activity. The catalytic effect of CoB is approximately in the order of mulberry-like>waxberry-like>chain-like>flake-like>rod-like, in accordance with their specific surface area from high to low. For dehydrogenation at 200 °C, mulberry-like and waxberry-like CoB dramatically enhanced the dehydrogenation of LiBH 4 , but not other CoB catalysts. 4.6 and 4.8 wt% hydrogen was released from LiBH 4 catalyzed by those two CoB, respectively, and the later showed reversibility of >2 wt%. For dehydrogenation at 350 °C, mulberry-like CoB showed the best catalytic effect. 10.4 wt% hydrogen was liberated from LiBH 4 with almost full reversibility under 400 °C and 10 MPa rehydrogenation conditions, remaining 9.6 wt% at the fourth cycle.

The effects of NaAlH 4 , TiF 3 and NaAlH 4 -TiF 3 co-additive on dehydriding reaction of Mg(AlH 4 ) 2 are systematically investigated. The onset dehydrogenation temperature of the co-doped Mg(AlH 4 ) 2 composites decreased to 74 °C, which is about 59 °C lower than that of pure Mg(AlH 4 ) 2 . The dehydrogenation kinetics of NaAlH 4 -TiF 3 co-doped Mg(AlH 4 ) 2 sample was also improved, which released about 94% hydrogen within 48 min, but no visible hydrogen was released from pure Mg(AlH 4 ) 2 under the same conditions. The activation energy of co-doped Mg(AlH 4 ) 2 was 85.6 kJ-mol −1 , which was significantly lower than that of additive-free Mg(AlH 4 ) 2 sample. The synergetic effects of NaAlH 4 and TiF 3 on the dehydrogenation performance of Mg(AlH 4 ) 2 were confirmed. In addition, a possible catalytic mechanism is discussed, regarding the different roles of NaAlH 4 and TiF 3 on Mg(AlH 4 ) 2 .

Designed as a high-capacity, high-rate, and long-cycle life anode for sodium-ion batteries, ultrasmall Sn nanoparticles (≈8 nm) homogeneously embedded in spherical carbon network (denoted as 8-Sn@C) is prepared using an aerosol spray pyrolysis method. Instrumental analyses show that 8-Sn@C nanocomposite with 46 wt% Sn and a BET surface area of 150.43 m2 g−1 delivers an initial reversible capacity of ≈493.6 mA h g−1 at the current density of 200 mA g−1, a high-rate capacity of 349 mA h g−1 even at 4000 mA g−1, and a stable capacity of ≈415 mA h g−1 after 500 cycles at 1000 mA g−1. The remarkable electrochemical performance of 8-Sn@C is owing to the synergetic effects between the well-dispersed ultrasmall Sn nanoparticles and the conductive carbon network. This unique structure of very-fine Sn nanoparticles embedded in the porous carbon network can effectively suppress the volume fluctuation and particle aggregation of tin during prolonged sodiation/desodiation process, thus solving the major problems of pulverization, loss of electrical contact and low utilization rate facing Sn anode.

Both kinetics and thermodynamics properties of MgH2 are significantly improved by the addition of Mg(AlH4)2. The as-prepared MgH2–Mg(AlH4)2 composite displays superior hydrogen desorption performances, which starts to desorb hydrogen at 90 °C, and a total amount of 7.76 wt% hydrogen is released during its decomposition. The enthalpy of MgH2-relevant desorption is 32.3 kJ mol−1 H2 in the MgH2–Mg(AlH4)2 composite, obviously decreased than that of pure MgH2. The dehydriding mechanism of MgH2–Mg(AlH4)2 composite is systematically investigated by using x-ray diffraction and differential scanning calorimetry. Firstly, Mg(AlH4)2 decomposes and produces active Al∗. Subsequently, the in-situ formed Al∗ reacts with MgH2 and forms Mg–Al alloys. For its reversibility, the products are fully re-hydrogenated into MgH2 and Al∗, under 3 MPa H2 pressure at 300 °C for 5 h.

Rational synthesis of flexible electrodes is crucial to rapid growth of functional materials for energy-storage systems. Herein, a controllable fabrication is reported for the self-supported structure of CuCo

Two types of porous cobalt manganese oxide nanowires (MnCo2O4 and CoMn2O4) with different structures have been successfully synthesized by thermal decomposition of organometallic compounds for the first time. Nitrilotriacetic acid (NA) was used as a chelating agent to coordinate Co(II) and Mn(II) ions in various molar ratios, in a hydrothermal condition. The microstructure of as-synthesized cobalt manganese oxides, composed of numerous nanoparticles, completely retains the 1D network structure of the Co–Mn–NA coordination precursors without structure collapse. Electrochemical properties of the cobalt manganese oxide materials have been tested for supercapacitors at room temperature. Both the MnCo2O4 and CoMn2O4 electrodes display the outstanding capacitive behaviors and superior electrochemical properties. The CoMn2O4 nanowire shows excellent capacitance and desirable rate performance (2108 F g−1 at 1 A g−1 and 1191 F g−1 at 20 A g−1) compared to that of the MnCo2O4 nanowire (1342 F g−1 at 1 A g−1 and 988 F g−1 at 20 A g−1). Electrochemical impedance spectra (EIS) results also reconfirm that the CoMn2O4 nanowires display more facile electrolyte diffusion and higher capacitor response frequency than MnCo2O4 nanowires. This can be ascribed to the facile electrolyte/OH− ion penetration and better Faradaic utilization of the electroactive surface sites that generated by the smaller particle size and higher surface area.

Bimetallic NiCo functional graphene (NiCo/rGO) was synthesized by a facile one-pot method. During the coreduction process, the as-synthesized ultrafine NiCo nanoparticles (NPs), with a typical size of 4-6 nm, were uniformly anchored onto the surface of reduced graphene oxide (rGO). The NiCo bimetal-supported graphene was found to be more efficient than their single metals. Synergetic catalysis of NiCo NPs and rGO was confirmed, which can significantly improve the hydrogen-storage properties of MgH2. The apparent activation energy (E(a)) of the MgH2-NiCo/rGO sample decreases to 105 kJ mol(-1), which is 40.7% lower than that of pure MgH2. More importantly, the as-prepared MgH2-NiCo/rGO sample can absorb 5.5 and 6.1 wt% hydrogen within 100 and 350 s, respectively, at 300 °C under 0.9 MPa H2 pressure. Further cyclic kinetics investigation indicates that MgH2-NiCo/rGO nanocomposites have excellent cycle stability.

Highly crumpled graphene nanosheets (GS) with a BET surface area as high as 722.1 m2 g−1 is prepared by a thermal exfoliation method. A systematical investigation is performed on the electrochemical performances of porous Ni2P/GS nanocomposite synthesized by the low temperature solid state reaction method. It is shown that Ni2P nanoparticles anchor on graphene sheets producing a porous structure and GS have beneficial effects on the electrochemical properties of Ni2P nanoparticles when investigated as pseudocapacitor materials. The novel Ni2P/GS composite electrode exhibits a superior specific capacitance of 1912 F g−1 and 888 F g−1 at current densities of 5 and 50 mA cm−2, respectively. The specific capacitance decreases to 1473 F g−1 after 2500 cycles, suggesting its excellent cycling stability. It is confirmed that the GS with good electrical conductivity serve as a conducting network for fast electron transfer between the active materials and charge collector, as well as buffered spaces to accommodate the volume expansion/contraction during cycling, thus, leading to enhancement of the electrochemical properties of the Ni2P electrode.

2LiBH 4 /MgH 2 system is a representative and promising reactive hydride composite for hydrogen storage. However, the high desorption temperature and sluggish desorption kinetics hamper its practical application. In our present report, we successfully introduce CoNiB nanoparticles as catalysts to improve the dehydrogenation performances of the 2LiBH 4 /MgH 2 composite. The sample with CoNiB additives shows a significant desorption property. Temperature programmed desorption (TPD) measurement demonstrates that the peak decomposition temperatures of MgH 2 and LiBH 4 are lowered to be 315 °C and 417 °C for the CoNiB-doped 2LiBH 4 /MgH 2 . Isothermal dehydrogenation analysis demonstrates that approximately 10.2 wt% hydrogen can be released within 360 min at 400 °C. In addition, this study gives a preliminary evidence for understanding the CoNiB catalytic mechanism of 2LiBH 4 /MgH 2

The catalytic effects of few-layer, highly wrinkled graphene nanosheet (GNS) addition on the dehydrogenation/rehydrogenation performance of MgH2 were investigated. It was found that MgH2-5 wt %GNSs nanocomposites prepared by ball milling exhibit relatively lower sorption temperature, faster sorption kinetics, and more stable cycling performance than that of pure-milled MgH2. The dehydrogenation step confirms that the Avrami exponent n increases from 1.22 to 2.20 by the Johnson-Mehl-Avrami (JMA) formalism when the desorption temperature is reduced from 350 °C to 320 °C and 300 °C, implying that a change in the decomposition temperature can alter the mechanism during the dehydrogenation process. For rehydrogenation, the Avrami value n is close to 1; further study by several models coincident with n = 1 reveals that the absorption process of the MgH2-5 wt %GNSs sample conforms to the Mampel equation formulated through the random nucleation approach and that the nature of the absorption mechanism does not change within the temperature range studied. Furthermore, microstructure analysis demonstrated that the defective GNSs are distributed uniformly among the MgH2 particles and that the grain size of the MgH2-5 wt %GNSs nanocomposite is approximately 5-9 nm. The efficient metal-free catalytic dehydrogenation/rehydrogenation of MgH2 can be attributed to the coupling of the nanosize effect and defective GNSs.

Using a green and effective method based on the solid state reaction between FePO4·2H2O and KBH4, high pure Fe2P nanoparticles are successfully prepared. The mass ratio of FePO4·2H2O to KBH4 has a decisive influence on the composition of the products. Moreover, Fe2P nanoparticles exhibit considerably high discharge capacities and excellent rate capability as the anode materials for nickel-based rechargeable batteries. The reversible discharge capacities are 413 and 343 mAh g−1 at currents of 100 and 500 mA g−1, respectively. It is expected that Fe2P nanoparticles have potential applications in nickel-based rechargeable batteries.

Assisted by graphene oxide (GO), nano-sized LiMn0.6Fe0.4PO4 with excellent electrochemical performance was prepared by a facile hydrothermal method as cathode material for lithium ion battery. SEM and TEM images indicate that the particle size of LiMn0.6Fe0.4PO4 (S2) was about 80 nm in diameter. The discharge capacity of LiMn0.6Fe0.4PO4 nanoparticles was 140.3 mAh·g−1 in the first cycle. It showed that graphene oxide was able to restrict the growth of LiMn0.6Fe0.4PO4 and it in situ reduction of GO could improve the electrical conductivity of LiMn0.6Feo.4PO4 material.

A simple solvent method is proposed for the recovery of waste LixCoO2 from lithium-ion batteries, which employs inexpensive DMF to remove the binder of PVDF. This method is convenient to manipulate and low-cost to apply. Electrochemical investigations indicate that recovered LixCoO2 materials with a small amount of S-doping exhibit excellent properties as negative materials for alkaline rechargeable Ni/Co batteries. At the discharge current density of 100 mA g−1, the LixCoO2 + 1% S electrode displays the max discharge capacity of 357 mAh g−1 and outstanding capacity retention rate of 85.5% after 100 cycles. It could overcome not only the sophisticated, energy-intensive shortcomings of conventional recycling methods, but also the high-cost restriction on alkaline rechargeable Ni/Co batteries.

Fe–B nanochains are prepared by a modified chemical reduction method by introducing the cyclohexane–water interface for reaction. Scanning electron microscopy and transmission electron microscopy tests show that this Fe–B is composed of several wire-like nanochains. X-ray diffraction pattern reveals that the Fe–B nanochains obtained are in amorphous form. The formation of these Fe–B nanochains is discussed and attributed to the self-assembly of magnetic Fe–B nanoparticles on the cyclohexane–water interface. Compared to Fe–B nanoparticles, Fe–B nanochains exhibit much higher magnetic and electrochemical activities.

Lithium aluminum hydride (LiAlH4) is considered as an attractive candidate for hydrogen storage owing to its favorable thermodynamics and high hydrogen storage capacity. However, its reaction kinetics and thermodynamics have to be improved for the practical application. In our present work, we have systematically investigated the effect of NiCo2O4 (NCO) additive on the dehydrogenation properties and microstructure refinement in LiAlH4. The dehydrogenation kinetics of LiAlH4 can be significantly increased with the increase of NiCo2O4 content and dehydrogenation temperature. The 2 mol% NiCo2O4-doped LiAlH4 (2% NCO–LiAlH4) exhibits the superior dehydrogenation performances, which releases 4.95 wt% H2 at 130 °C and 6.47 wt% H2 at 150 °C within 150 min. In contrast, the undoped LiAlH4 sample just releases

A bi-component catalyst TiB 2 /GNSs (GNSs is the abbreviation of graphene nanosheets) is synthesized by a solid-state method. Microstructural characterizations based on SEM (scanning electron microscopy), TEM (transmission electron microscopy) and N 2 physisorption show that the size of TiB 2 /GNSs catalyst is at nanoscale (20–30 nm) with a surface area of 84.69 m 2 g −1 . The TiB 2 /GNSs nanoparticles ball milled with MgH 2 and exhibit enhanced catalytic effects on the dehydrogenation properties of MgH 2 compares to TiB 2 and GNSs individually. DSC (differential scanning calorimetry) measurements confirm that the peak desorption temperature of MgH 2 -5 wt%TiB 2 /GNSs composites can be lowered more than 44 °C than the pure as-milled MgH 2 . And the dehydrogenation kinetics of TiB 2 /GNSs-doped MgH 2 is severalfold acceleration compares to the pure as-milled MgH 2 . It is proposed that the TiB 2 /GNSs nanoparticles could significantly enhance the intimate interface between TiB 2 /GNSs and hydride, therefore, provide more active “catalytic sites” and H “diffusion channels” to reduce the dehydrogenation temperature and improve the dehydrogenation kinetics of MgH 2 . The synergistic effect of nano-GNSs and TiB 2 nanoparticles contributes to the highly efficient for dehydrogenation of MgH 2 -5wt%TiB 2 /GNSs composites.

Porous TiO2 micro-tubes were fabricated by a solvothermal method, and the effect of TiO2 micro-tubes on the hydrogen desorption properties of LiBH4 was systematically investigated. It was confirmed that LiBH4 nanoparticles were successfully incorporated into these TiO2 scaffolds via a chemical impregnation method. It was revealed by results of TPD, PCT and DSC that both the lowered desorption temperature and improved kinetics of the desorption rate were due to the synergistic effects of nanoconfinement and destabilization of TiO2. The LiBH4@2TiO2 mixture (the preparation mass ratio is 1 : 2) started to release hydrogen at 180 °C, and the apparent activation energy (Ea) had been reduced from 146 kJ mol−1 (pure LiBH4) to 121.9 kJ mol−1. Moreover, it is interesting that the onset desorption temperature of LiBH4@3TiO2 composite was below 100 °C, reduced by about 300 °C compared to that of pure LiBH4, which was lower than that in most of the current studies about LiBH4.

Three-dimensional flower-like NiCo2O4 hierarchitectures have been successfully prepared on a large scale via a facile solvothermal method followed by an annealing process. The as-synthesized NiCo2O4 flower-like architectures have uniform diameters of about 500 nm assembled by numerous nanosheets radially grown from the center. The possible growth mechanism of the unique structures has been investigated. Both the poly(vinylpyrrolidone) (PVP) surfactant and the formation of metal glycolate play important roles in the formation of these novel three-dimensional flower-like hierarchitectures. With a large surface specific area of 212.6 m2 g−1, this novel NiCo2O4 material exhibited a superior specific capacitance of 1191.2 F g−1 and 755.2 F g−1 at current densities of 1 and 10 A g−1, respectively, which suggests that 63.4% of the capacitance is still retained when the charge–discharge rate is increased from 1 A g−1 to 10 A g−1. This superior electrochemical performance of NiCo2O4 as an electrode material for supercapacitors can be ascribed to the synergetic effect of the porous structure and the small diffusion lengths in the nanosheet building blocks. The simple, versatile and cost-effective route reported here may provide a general methodology for the high-yield synthesis of metal cobaltite nanostructures featuring improved properties and structures.

The effects of NbN nanoparticles synthesized via a simple "urea glass" route on the dehydrogenation properties of LiAlH4 have been systematically investigated. The particle size of the as-synthesized NbN nanoparticles is determined to be about 10 nm. The surface configuration and dehydrogenation behaviors of the 2 mol% NbN-doped LiAlH4 (2% NbN-LiAlH4) system are also discussed. It is found that the 2% NbN-LiAlH4 sample starts to decompose at about 95 °C and releases a total of 7.10 wt% hydrogen, which is 55 °C lower than that of as-milled LiAlH4. The isothermal dehydrogenation kinetics shows that the 2% NbN-LiAlH4 sample could release approximately 6.10 wt% hydrogen in 150 min at 130 °C, whereas as-received LiAlH4 only releases about 0.63 wt% hydrogen under the same conditions, revealing that the enhancements arising upon adding NbN nanoparticles are almost 8-9 times that of as-milled LiAlH4. The activation energy (Ea) is calculated to be 71.91 and 90.87 kJ mol(-1) for the first and second hydrogen desorption of the NbN-LiAlH4 sample, a 38% and 32% reduction relative to as-received LiAlH4, respectively. A detailed modeling study shows that the first dehydrogenation step can be sufficiently interpreted with the nucleation and growth in a one-dimensional model based on the first-order reaction. More interestingly, the dehydrogenated LiAlH4 sample can recharge H2 under a 5.5 MPa hydrogen pressure. An SEM image of the dehydrogenated 8% NbN-LiAlH4 sample after HP-DSC under 5.5 MPa H2 shows that some nanorods appear.

An efficient core–shell Co@C catalyst is synthesized through a solvothermal and subsequent annealing process. The as-synthesized Co@C consists of an 11 nm Co core and a 3 nm amorphous carbon shell. Nitrogen sorption isothermals show that Co@C has a surface area of 112.6 m2 g−1 and a typical pore size of 4.8 nm. The catalytic effects of core–shell Co@C, which can significantly improve the dehydrogenation performance of MgH2, are systematically investigated. With increasing amounts of Co@C (0, 3, 5, 10, 15 wt%), the dehydrogenation temperature of MgH2 decreased. Its dehydrogenation kinetics are also improved, especially for the MgH2–10%Co@C sample, which starts to release hydrogen at 168 °C. In fact, about 6.00 wt% hydrogen is released during its decomposition, and the activation energy of MgH2–10%Co@C is determined to be 84.5 kJ mol−1, 46.2% less than that of pure MgH2. Mechanism analysis indicates that upon increasing the Co@C content, the decomposition of MgH2 gradually occurs along lower-dimensional nucleation and growth. Moreover, the excellent thermal conductivity of the carbon shell in Co@C also contributes to the enhanced dehydrogenation performance of MgH2.

In this article, we report on the preparation of a graphene-like MoS2/graphene nanocomposite by hydrolysis of lithiated MoS2 (LiMoS2) and its application as the anode material for lithium ion batteries. When the mass ratio of graphene/LiMoS2 is 15/100, the obtained composite (MoS2/GNS-15) displays a flower-like architecture composed of exfoliated nanosheets. The structure analyses further demonstrate that graphene-like MoS2 is supported on the surface of graphene nanosheets (GNS) and some of the interlayer spacings of MoS2 are enlarged with the intercalation of graphene. The reversible capacity of the MoS2/GNS-15 nanocomposite is ∼1400 mA h g−1 in the initial cycle and remains 1351 mA h g−1 after 200 cycles at 100 mA g−1. Furthermore, the capacity can reach 591 mA h g−1 even at a high current density of 1000 mA g−1. The excellent electrochemical performance of MoS2/GNS-15 is due to the synergetic effect between highly conductive GNS and graphene-like MoS2. On one hand, the GNS matrix can offer two-dimensional conductive networks and effectively suppress the aggregation of layered MoS2 during the lithiation/delithiation process. On the other hand, graphene-like MoS2 with an enlarged gallery can ensure the flooding of the electrolyte, provide more active sites and lower the diffusion energy barrier of Li+ ions.

A synergistic effect of nanoconfinement and catalyzing is a new strategy to enhance the dehydrogenation properties of complex hydrides. Herein, LiBH4 has been infiltrated into a CoNiB-loaded carbon aerogels system (donated as LiBH4@CA@CoNiB). It is found that the desorption performances of LiBH4 are significantly strengthened. The onset desorption temperature of LiBH4@CA@CoNiB is decreased to 192 °C, and majority of the liberation occurs at about 320 °C, much lower than that of pure LiBH4. Also, about 15.9 wt% H2 could be released below 600 °C. Furthermore, LiBH4 doped with CA@CoNiB exhibits an excellent desorption kinetics, with a capacity of 9.33 wt% H2 released in 30 min at 350 °C, while only 2.13 wt% H2 is gained for bulk LiBH4. In addition, the apparent activation energy (Ea) is reduced sharply from 59.00 kJ/mol (pure LiBH4) to 46.39 kJ/mol.

A novel composite of magnetite (Fe 3 O 4 ) nanoparticles (NPs) grown on reduced graphene oxide (rGO) has been synthesized by a facile hydrothermal technique without any surfactants or templates. In this method, the growth of Fe 3 O 4 NPs and the reduction of graphene oxide (GO) are completed in one single step. Moreover, we have prepared Fe 3 O 4 microcubes and Fe 3 O 4 /carbon nanotubes (CNTs) composite under the same condition. The electrochemical properties of the as-prepared samples are investigated as advanced electrode materials for supercapacitors. It is found that the Fe 3 O 4 /rGO nanocomposite displays much higher specific capacitances and better cycle stability than those of pure Fe 3 O 4 and Fe 3 O 4 /CNTs composite. Specifically, it exhibits a high specific discharge capacitance of 220.1 F g −1 at 0.5 A g −1 and remains stable after 3000 charge/discharge cycles. The improvement of the electrochemical performances of Fe 3 O 4 /rGO may be attributed to the chemical interaction between rGO and Fe 3 O 4 , lower agglomeration and smaller particle size of Fe 3 O 4 .

In this communication, FeMnO

Developing low-cost, high-performance electrocatalysts to efficiently convert intermittent solar energy into hydrogen via water splitting is the key to realize sustainable energy cycle but remain challenges. Herein, the three dimensional core-branch CoP@NiFe–OH nanohybrids supported on surface-phosphatized Ni foam (CoP@NiFe–OH/SPNF) are facilely fabricated as the high-performance bifunctional electrocatalysts for alkaline water electrolysis. Theoretical calculation and electrochemical tests manifest that hybridizing CoP with NiFe–OH engenders strong synergistic catalytic effects, leading to fast hydrogen and oxygen evolution reaction kinetics. Meanwhile, hierarchical core-branch arrays and self-supported architecture also result in CoP@NiFe–OH/SPNF with multiple exposing active sites, faster ions, electron transport behavior and superior lifespan. Owing to these typical merits, the bifunctional CoP@NiFe–OH/SPNF electrode expedites overall water splitting with affording a current density of 10, 50 and 100 mA cm−2 only at 1.53, 1.63 and 1.68 V respectively, surpassing the performance of noble (+)IrO2/C//Pt/C(−) and most bifunctional electrocatalysts. As a practical application, a portable solar energy-driven water electrolyzer equipped with the bifunctional CoP@NiFe–OH/SPNF electrode can produce hydrogen at room temperature with a high gas evolution rate of 20.83 μL s−1.

Sodium-ion batteries (SIBs) have recently emerged as one of the favored contenders for use in medium and large-scale stationary energy storage owing to the abundance of the resources required to fabricate them, their low cost, and the fact that have properties similar to equivalent Li batteries. However, their development also faces challenges such as poor cycling stability and unsatisfying rate performance. In traditional electrodes, binders are commonly used to integrate individual active materials with conductive additives. Unfortunately, binders are generally electrochemically inactive and insulating, which reduces the overall energy density and leads to poor cycling stability. Therefore, binder-free electrodes provide great opportunity for high-performance SIBs in terms of both improved electronic conductivity and electrochemical reaction reversibility. This Progress Report provides an overview of the recent progress in binder-free electrodes for SIBs. It focuses on the current challenges of binder-free electrodes and provides an outlook for their future in energy conversion and storage.

Three-dimensional SnS2 hierarchitectures have been fabricated via a facile solvothermal method. A possible growth mechanism has been propounded based on the time-dependent experiments. As anode material for lithium-ion batteries, the SnS2 hierarchitectures display long-term cycle stability and excellent high-rate performance. A high specific capacity of 549.5 mA h g−1 is achieved at a current density of 100 mA g−1 after 100 discharge/charge cycles. The superior electrochemical performances of SnS2 as lithium-ion batteries anode material can be attributed to the synergistic effect of the specific porous structure and the thin nanosheets.

Co/CMK-3 composites are synthesized via a facile hydrothermal route. The electrochemical performances of Co/CMK-3 composite as the negative electrode material for alkaline rechargeable Ni/Co batteries have been systemically investigated. Electrochemical measurements show that the CMK-3 can remarkably enhance the electrochemical activity of Co, leading to a notable improvement of the discharge capacity, cycle stability and rate capability. Interestingly, the discharge capacity of Co/CMK-3 (25 mg CMK-3) electrode can reach 519.3 mAh g −1 and retains about 365.8 mAh g −1 after 100 cycles at discharge current of 100 mA g −1 . The electrochemical reaction mechanism of Co/CMK-3 composite electrode can be attributed to the electrochemical redox reaction between Co and Co(OH) 2 .

By directly introducing Ni–B into NaAlH4 system using a facile two-step synthesis method, the effects of Ni–B on NaAlH4 were systematically investigated. NaAlH4 can be completely formed after 30 h milling under 1 MPa hydrogen pressure. In addition, the dehydrogenation kinetics of as-prepared NaAlH4 after different milling times were investigated. As the dehydrogenation temperature rises, both the hydrogen desorption capacity and dehydrogenation rate quickly increase. The apparent activation energy E a for Ni–B-doped NaAlH4 is calculated to be 61.91 kJ·mol−1 for the first dehydrogenation step. More importantly, the dehydrogenation temperature of as-prepared NaAlH4 nanocrystalline can be reduced to about 100 °C.

Flower-like α-Ni(OH)2 microspheres composed of nanowires are prepared by a solvothermal method using triethylene glycol and water as the mixed solvent. The formation of this unique structure is attributed to the synergetic effect of dissolution-recrystallization procedure, Ostwald ripening, and aggregative lateral attachment. Experimental results indicate that the dielectric constant, viscosity, and the chain lengths of the alcohols in the solvent may greatly affect the morphology and size of the as-obtained α-Ni(OH)2 samples. Because of the high Brunauer, Emmett, and Teller (BET) nitrogen sorption surface area of 318 m(2) g(-1) and large pore volume, this sample displays a maximum discharge specific capacity of 1788.9 F g(-1) at a discharge current density of 0.5 A g(-1). Besides, rate performance of this sample is also excellent, indicating that this sample is promising in electrochemical supercapacitors.

The pristine Li 2 FeP 2 O 7 and Li 2 FeP 2 O 7 /C nanocomposites with different content of carbon have been successfully synthesized via a simple solid-state reaction, using cheap glucose as carbon source. XRD and EDS patterns demonstrate the high purity of the products. SEM images exhibit that the size of the particles is about 50–500 nm. Electrochemical measurements reveal that carbon coating and reducing particle size significantly enhance the electrochemical performances of Li 2 FeP 2 O 7 . Particularly, the Li 2 FeP 2 O 7 /C sample with a carbon content of 4.88 wt.% displays the best performance with a specific discharge capacity of 103.1 mAh g −1 at 0.1 C, which is 93.7% of its one-electron theoretical capacity, meaning 110 mAh g −1 . Meanwhile, it shows favorable cycling stability and excellent rate performance, indicating its potential applicability in Li-ion batteries in the long term.

Hydrogen storage properties of commercial NaAlH4 doped efficient TiN catalyst have been systematically investigated. The dehydrogenation and reversibility of the 2 mol% TiN-doped NaAlH4 (2%TiN–NaAlH4) system have been studied. It is found that TiN catalyst improves the dehydrogenation kinetics and decreases the dehydrogenation temperature of NaAlH4. Interestingly, the onset dehydrogenation temperature of 2%TiN–NaAlH4 system gets lowered to about 130.0 °C with a faster kinetics, and the dehydrogenation rate reaches a maximum value at 183.5 °C. The apparent activation energy for the first and the second dehydrogenation step of TiN–NaAlH4 system is estimated to be 91.70 kJ mol−1 and 99.93 kJ mol−1, respectively. The dehydrogenation and hydrogenation behaviors of 2%TiN–NaAlH4 are investigated under different hydrogen pressures using high-pressure differential scanning calorimetry (HP-DSC). The 2%TiN–NaAlH4 system exhibits excellent reversibility at moderate conditions. Moreover, the dehydrogenation and hydrogenation processes of the 2%TiN–NaAlH4 system are also discussed.

Hydrogen is a promising energy carrier in future energy systems. However, hydrogen storage is facing increasing challenges within the development of more environmentally friendly energy systems with high capacity, fast kinetics, favorable thermodynamics, controllable reversibility, especially for applications in vehicles with fuel cells that use proton–exchange membranes (PEMs). In this report, we present a critical review on catalyst modified and nanoconfined NaAlH4, focusing on their thermodynamics and kinetics behaviors. Catalyst is of increasing interest and may lead to significantly enhanced kinetics, higher degree of stability and/or more favorable thermodynamic properties. Thus, catalyst–doped NaAlH4 is expected to strongly contribute by the development of novel catalysts and synthesis methods. Additionally, nanoconfined NaAlH4 may also have a wide range of applications in the PEM fuel cells. Selected catalyst materials, porous scaffold materials, methods for preparation of NaAlH4 systems and their hydrogen storage properties are reviewed. This is the first review report on catalyst modified and nanoconfined NaAlH4.