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Core-shell structured Ni-ZIF-67@ZIF-8 derived bimetal selenides encapsulating into a 3D interpenetrating dual-carbon framework (Ni

In this study, nano-sized SnO2 decorated on carbon cloth (SnO2/CC) is prepared through a simple and facile solid method. The nano-sized SnO2 is uniformly distributed on the surface of carbon fibers in carbon cloth, providing sufficient free space to relieve volume expansion and reduce electrode pulverization during cycling. The as-prepared SnO2/CC as a flexible, self-supporting and additive-free anode electrode for sodium-ion/lithium-ion batteries (SIBs/LIBs) can demonstrate outstanding electrochemical performance. SnO2/CC after annealing at 350 °C (SC-350) as an anode for SIBs can deliver a reversible capacity of 0.587 mA h cm−2 at the current density of 0.3 mA cm−2 after 100 cycles. In addition, when cycling at 1.5 mA cm−2, SC-350 can maintain 1.69 mA h cm−2 after 500 cycles when used as LIB anode. These results illustrate that the as-prepared SnO2/CC can be a promising flexible anode material for flexible SIBs/LIBs and provide a simple and practical method for designing new flexible electrode materials.

Ternary transition metal oxides have attracted increasing attention due to their many merits, and will enhance electrochemical performance via the synergistic effects of the different single metal oxides. Herein, ZnCo2O4 nanoparticles encapsulated in nitrogen-doped carbon (ZnCo2O4@NC) polyhedrons have been successfully prepared through a facile two-step method. The as-prepared products had a uniform size and consisted mainly of interconnected ZnCo2O4 nanoparticles (NPs), which were uniformly distributed in the materials. As a result, the ZnCo2O4@NC polyhedrons of ZnCo-700 show a superb specific capacity of approximately 1601 mA h g−1 over 50 cycles at 0.1 A g−1. A reversible capacity of 1082 mA h g−1 was retained after 300 cycles at 1 A g−1, and a superb reversible capacity of 775 mA h g−1 was attained even when the current density was increased to 5 A g−1. These distinguished electrochemical properties could be ascribed mainly to the uniquely advantageous structural and compositional features.

Spinel ZnCo2O4/ZnO/C hierarchically porous structures were successfully synthesized by two-step annealing of cyanide-bridged coordination polymer precursors. Such hierarchically porous structures exhibit a regular cube structure and provide a large surface area, which provides excellent charge transport kinetics by promoting the charge transfer into the inside of the electrode materials. When used as the anode material of lithium ion batteries, the spinel ZnCo2O4/ZnO/C porous structures exhibit high capacity and excellent cycling stability with a capacity of 1100 mA h g-1 at a current density of 0.1 A g-1 and maintain 800 mA h g-1 after 400 cycles at a current density of 1 A g-1. Meanwhile, the spinel ZnCo2O4/ZnO/C porous structures also exhibit an excellent pseudocapacitive contribution ratio of 86% at a scan rate of 1 mV s-1.

Nanocavity-enriched Co3O4@ZnCo2O4@NC porous nanowires have been successfully prepared by a two-step annealing process of one-dimensional (1D) coordination polymer precursors. Such unique nanowires with nanocavity-based porous channels can provide a large specific surface area, which allows fast electron/ion transfer and alleviates the volume expansion caused by strain during the charge/discharge processes. While used as the anode material of lithium-ion batteries (LIBs), Co3O4@ZnCo2O4@NC electrodes exhibit outstanding rate capacity and cycling stability, such as a high reversible capacity of 931 mA h g-1 after 50 cycles at a current density of 0.1 A g-1 and a long-term cycling efficiency of 649 mA h g-1 after 600 cycles at 1 A g-1. This coordination polymer template method lays a solid foundation for the design and preparation of bimetal oxide materials with outstanding electrochemical performance for LIBs.

Spinel ZnCo2O4/ZnO/C hierarchically porous structures were successfully synthesized by two-step annealing of cyanide-bridged coordination polymer precursors. Such hierarchically porous structures exhibit a regular cube structure and provide a large surface area, which provides excellent charge transport kinetics by promoting the charge transfer into the inside of the electrode materials. When used as the anode material of lithium ion batteries, the spinel ZnCo2O4/ZnO/C porous structures exhibit high capacity and excellent cycling stability with a capacity of 1100 mA h g-1 at a current density of 0.1 A g-1 and maintain 800 mA h g-1 after 400 cycles at a current density of 1 A g-1. Meanwhile, the spinel ZnCo2O4/ZnO/C porous structures also exhibit an excellent pseudocapacitive contribution ratio of 86% at a scan rate of 1 mV s-1.

Novel CoNi binary metal oxide superstructures assembled with cross-stacked nanosheets (Co

In this study, a Co-rich Ni-rich layered material with a core–shell structure is designed, in which LiNi0.82Co0.12Mn0.06O2 (NCM-Ni82) is used as the core wrapped in the shell by doping Al into LiNi0.735Co0.15Mn0.1Al0.015O2 to form the hybrid particle LiNi0.795Co0.13Mn0.07Al0.005O2 (NCM-HA). NCM-HA is divided modularly into the core part NCM-Ni82 and the single hybrid part without doped Al (NCM-HS), and then all modules were compared with the pristine LiNi0.8Co0.1Mn0.1O2 via various characterization methods to reveal the superiority of the design. The core–shell structure, which prevents the diffusion of microcracks caused by the lattice shrinkage of a high content of cobalt, is used to improve the morphological strength of the material so that the cathode material is capable of fully playing the excellent stable cycling performance brought by the remarkable cationic order degree of Co-rich treatment. The excellent cathode material NCM-HA still has a capacity retention rate of 83.35% after 200 cycles, while the pristine material has a rate of 55.42%. Moreover, NCM-HA successfully inhibits the unsteady phase transition of layered materials at 4.2 V and reduces the degree of polarization during the cycling process. This study provides a new strategy for the modification of Cobalt-enriched Ni-rich layered materials.

Hybrid aerogel by dispersing Mo2C@C core-shell nanocrystals into three-dimensional (3D) graphene (Mo2C@C-GA) has been successfully prepared through two-step methods. Firstly, carbon-coated MoO2 nanocrystals uniformly anchor on 3D graphene aerogel (MoO2@C-GA) via hydrothermal reaction. Then the MoO2@C-GA precursor is transformed into Mo2C@C-GA after the following carbonization process. Furthermore, the freeze-drying step plays an important role in the resulting pore size distribution of the porous networks. Moreover, graphene aerogels exhibit extremely low densities and superior electrical properties. When evaluated as anode material for lithium ion battery, Mo2C@C-GA delivers excellent rate capability and stable cycle performance when compared with C-GA and Mo2C nanoparticles. Mo2C@C-GA exhibits the initial discharge capacity of 1461.4 mA h g−1 at the current density of 0.1 A g−1, and retains a reversible capacity of 1089.8 mA h g−1 after 100 cycles at a current density of 0.1 A g−1. Even at high current density of 5 A g−1, a discharge capacity of 623.5 mA h g−1 can be still achieved. The excellent performance of Mo2C@C-GA could be attributed to the synergistic effect of Mo2C@C nanocrystals and the 3D graphene conductive network.

Rhenium disulfide (ReS2) is a promising 2D-layered anode material for rechargeable batteries. However, this material suffers from severe agglomeration and volume expansion during ions insertion/extraction, leading to inferior battery performance. Building 3D hierarchical structure is an effective strategy to overcome these problems and simultaneously manifest synergistic effects. Herein, a one-pot hydrothermal method is introduced to construct N-doped carbon confined ReS2 ultrathin nanosheets anchored on few-layered Ti3C2Tx MXene substrate (MXene@ReS2@C). The MXene flakes can effectively reduce agglomeration of ReS2 nanosheets during charge/discharge process and generate chemical interaction with ReS2 nanosheets, thereby promoting charge transfer kinetic of hierarchical composite. Carbon incorporation not only stabilizes MXene from successive oxidation during hydrothermal procedure but also alleviates volume expansion of ReS2, ensuring cycling durability of electrode. When used as anode material of SIBs, this hierarchical MXene@ReS2@C hybrid with strong interfacial interactions demonstrates improved electrochemical performances with satisfying rate capability (138 mAh g-1 at 5.0 A g-1) and cycling stability (202 mAh g-1 at 2.0 A g-1 after 200 cycles). This work provides a new scope of synthesizing MXene-based transition metal sulfide composite for practical application in sodium ion batteries.

Metal-organic framework (MOF)-derived yolk-shell structures are one of the most potential nanoarchitectures applied in second batteries and electrocatalysis. In this manuscript, a multilayer yolk-shell structured CoSe2 has been fabricated via post carbonization and selenization processes of step-by-step crystal epitaxial growth of multilayer solid zeolitic imidazolate frameworks (ZIFs) precursor. When used as the anode of a sodium-ion half battery, the obtained multilayer yolk-shell structured CoSe2 materials can maintain a discharge capacity of 352.9 mAh g−1 after the 2000 cycles at the current density of 1 A g−1, which can be attributed to the special multilayer yolk-shell structure by providing the fast sodium ion transport. Besides, it also delivers excellent electrochemical performance in the sodium-ion full batteries, which further demonstrate the outstanding electrochemical property of the obtained multilayer yolk-shell structured CoSe2 electrode material.

A novel and bottom-up approach has been applied to synthesize bi-metal Ni-Co coordination polymer@polydopamine (NiCoCP@PDA) core-shell nanocubes by polymerization of PDA layer on the surface of NiCoCP nanocubes. After thermally induced sulfurization processes, biactive NiS2@CoS2 hetero-nanocrystals encapsulated into N-doped carbon core-shell nanocubes has been successfully prepared. When used as anodes materials for lithium ion batteries (LIBs) and sodium ion batteries (SIBs), the novel bicontinuous carbon wrapped NiS2@CoS2 nanocrystals hierarchical structures show excellent lithium/sodium ion storage capacities with high specific capacities, good rate capabilities and stable cycling stability. The enhanced electrochemical performance is attributed to the interconnected porous structures and large amount of mesoporous structures, which effectively reduce the diffusion length for lithium ions and electrons, buffer volume expansion during the lithium/sodium ion insertion/extraction processes and retained structural integrity due to double carbon frameworks.

Ultrahigh level nitrogen and sulfur co-doped disordered porous carbon (NSDPC) was facilely synthesized and applied as anode materials for lithium-ion batteries (LIBs). Benefiting from high nitrogen (14.0 wt%) and sulfur (21.1 wt%) doping, electrode fabricated from NS 1/3 showed a high reversible capacity of 1188 mA h g −1 at 0.1 A g −1 in the first cycle with a high initial columbic efficiency (>75%). In addition, prolonged life over 500 cycles and excellent rate capability of 463 mA h g −1 at 5 A g −1 have been realized. The preeminent electrochemical performance is attributed to three effects: (1) the high level of sulfur and nitrogen; (2) the synergic effect of dual-doping heteroatoms in cooperation with each other; (3) the large quantity of edge defects and abundant micropores and mesopores that can provide extra Li storage regions. These unique features of NSDPC electrodes suggest that they can serve as a practical substitute for graphite as a high performance anode material in LIBs.

Novel nitrogen-doped porous molybdenum carbide (α-MoC1−x and β-Mo2C) architectures were prepared using Mo-based metal–organic frameworks (MOFs) as the precursor. The synthesized molybdenum carbides consist of numerous nanocrystals organized into micro-sized rods with interpenetrating mesoporous-channels and macroporous-tunnels along the axial direction. When employed as the cathode catalyst for Li-O2 batteries, this dual pore configuration offers abundant active sites for the electrochemical reaction and many nucleation sites for the discharge product of Li2O2; hence, decent performances were obtained. Among the two synthesized molybdenum carbides, the α-MoC1−x electrode stands out as being better due to its lower charge transfer resistance (395.8 Ω compared to 627.9 Ω) and better O2 adsorption (binding energy of −1.87 eV of α-(111)-Mo compared to −0.72 eV of β-(101)-Mo). It delivered a high full discharge of 20 212 mA h g−1 with a discharge voltage of 2.62 V at 200 mA g−1. A good cycling stability was also obtained: i.e. 100 stable cycles with a fixed capacity of 1000 mA h g−1 (at a current density of 200 mA g−1) with a charging voltage of 4.24 V and maintaining a respectable round-trip efficiency of ∼70%. NRF (Natl Research Foundation, S’pore) MOE (Min. of Education, S’pore)

In this study, the double transition metal selenide Ni1.5CoSe5 with cube-like nanoaggregate morphology was successfully embedded into a three-dimensional (3D) dual N-doped carbon network, developing an advanced anode material for sodium-ion batteries (SIBs). In the prepared composite, Ni1.5CoSe5 nanoparticles were first coated by N-doped carbon (NC), which further aggregated to form nanocubes, and finally embedded into interconnected N-doped reduced graphene oxide (rGO) nanosheets; hence, the material was abbreviated as Ni1.5CoSe5@NC@rGO. It delivered a reversible Na-storage capacity of 582.5 mA h g−1 at a low current density of 0.05 A g−1 and exhibited ultra-fast rate properties (e.g., with the specific capacities of 180.8 and 96.3 mA h g−1 at high current densities of 30 and 50 A g−1, respectively). The much enhanced Na-storage properties were ascribed to the highly conductive 3D network constructed by dual N-doped carbonaceous materials, which acted not only as a highway for ultrafast charge transfer but also as an effective protector for the active Ni1.5CoSe5 material and cube-like nanoaggregates with nanometer-sized primary particles. More significantly, the Ni1.5CoSe5@NC@rGO electrode also exhibited superior energy storage performance in sodium-ion full cells when coupled with a high-voltage Na3V2(PO4)2O2F cathode, making it a promising anode material for practical SIBs.

In this work, the epoxidized castor oil (ECO) with self-crosslinking structure is prepared and a series of PLA/ECO blends are fabricated via dynamic vulcanization. The effects of raw castor oil and ECO with different contents on the static and dynamic mechanical properties, rheological properties, crystalline properties were studied. FTIR NMR and GPC results indicate the generation of self-crosslinking structure and the interaction between the oil and PLA matrix. DSC and TGA results show a higher crystallinity and lower thermal stability for PLA/ECO blends. It is also shown the better rheological and dynamic mechanical properties are obtained in PLA/ECO blends in comparison with raw castor oil filled samples. The data of static mechanical properties exhibit that ECO leads a much better toughening effect than that of the raw castor oil, which is also proved by the morphology photos of SEM, showing a better dispersion and smaller droplet size of oil, as well as the toughening mechanism of shear yielding and internal cavitation in PLA. However, the structures are defected in PLA matrix with the ECO contents over 10 wt% due to the agglomeration of ECO in local areas, leading significant decrease in mechanical properties.

Combining the advantages of cobalt and zinc-based imidazolate frameworks (ZIF-67 and ZIF-8), CoS2/Sb2S3 hetero-structured nanocrystals encapsulated into interpenetrating dual-carbon framework of nitrogen-doped carbon and carbon nanotubes (CoS2/Sb2S3@NC/CNT) were successfully prepared by ion-exchange reaction between Co and Sb3+ and subsequent sulfidation reaction process. The supported dual carbon framework derived from ZIF-8 and ZIF-67 not only buffers volume expansion during repeated discharge/charge to prevent polyhedron from collapsing but also significantly enhances electronic conductivity which is beneficial to optimize rate performance and cycle stability. Besides, introducing of Sb2S3 to form heterostructure greatly improves electrochemical properties. As a result, the CoS2/Sb2S3@NC/CNT heterostructure exhibits favorable rate capability and cycle stability in both sodium-ion battery (SIBs) and potassium-ion battery (PIBs). The CoS2/Sb2S3@NC/CNT anode in SIBs delivers the reversible specific capacity of 360.1 mAh g−1 at the current density of 0.5 A g−1 after 200 cycles, while the CoS2/Sb2S3@NC/CNT anode in PIBs exhibits the specific capacity of 453.5 mAh g−1 at the current density of 0.2 A g−1 after 50 cycles. The complex heterostructure consisting of CoS2/Sb2S3 core and coated carbon shell easily promotes electrolyte penetration and further accelerates ions diffusion and electrochemical reaction kinetics. This material will provide a novel alternative method for the preparation of heterogeneous structure anode materials, paving the way for being applied in high-efficiency energy storage devices.

NaCl-type Ni-Co oxide solid solution is expected to be a promising alternative anode material for lithium-ion batteries. However, the synthesis of solid solutions with well-defined morphology and homogeneity is still challenging. Based on a novel NixCo1−x(OH)(OCH3)@polydopamine intermediate and its topotactic thermolysis, a unique synthetic route towards NixCo1−xO solid solution (0

In this paper, 1T’-ReS2@FeS2@NC heterostructure was successfully prepared by growing ReS2 nanosheet arrays on porous FeS2 nano-spindle by using metal-organic framework (MIL-88) as precursor. The heterostructure with external nanosheet array structure ensures sufficient contact between the electrolyte solution and the electrode material by shortening the ion transfer path. When 1T’-ReS2@FeS2@NC heterostructure was used as anode material of sodium ion battery, it delivered excellent rate performance and cycling stability, reaching a high specific capacity of 729 mAh g−1 at a current density of 0.1 A g−1. Meanwhile, the results of galvanostatic intermittent titration technique (GITT) and electrochemical impedance spectroscopy (EIS) tests can indicate that the heterostructure greatly enhances the Na+ diffusion kinetics through combining of three-dimensional porous FeS2 nano-spindle and two-dimensional nanosheet arrays. It is proved that 1T’-ReS2@FeS2@NC heterostructure is a promising anode material for sodium-ion batteries.

Uniform Ni3C nanodots dispersed in ultrathin N-doped carbon nanosheets were successfully prepared by carburization of the two dimensional (2D) nickel-cyanide coordination polymer precursors. The Ni3C based nanosheets have lateral length of about 200 nm and thickness of 10 nm. When doped with Fe, the Ni3C based nanosheets exhibited outstanding electrocatalytic properties for both hydrogen evolution reactions (HER) and oxygen evolution reactions (OER). For example, 2 at% Fe (atomic percent) doped Ni3C nanosheets depict a low overpotential (292 mV) and a small Tafel slope (41.3 mV dec-1) for HER in KOH solution. An outstanding OER catalytic property is also achieved with a low overpotential of 275 mV and a small Tafel slope of 62 mV dec-1 in KOH solution. Such nanodots incorporated 2D hybrid structures can serve as an efficient bifunctional electrocatalyst for overall water splitting.

NiFe2O4 porous nanorods/graphene composites are synthesized by a solvothermal method in combination with calcination at 400 °C. Uniform NiFe2O4 porous nanorods with a diameter of about 300 nm and a length of several micrometers are homogeneously anchored on graphene sheets. The close and firm contact between the two components assures the sound electrochemical properties. The lithium-ion battery performance of the composites anode is evaluated by galvanostatic and rate performance. NiFe2O4 porous nanorods/graphene composites electrode exhibit a superior lithium storage capability. The first discharge capacity of the composites electrode is 1115 mA h g−1 at a current density of 1 A g−1, and still maintains at 655 mA h g−1 even after 600 cycles. Even at a high current density of 5 A g−1, a high reversible specific capacity of 509 mA h g−1 can be achieved. The synergistic effect between graphene with excellent electrical conductivity and NiFe2O4 nanorods with porous structure makes a substantial contribution to the outstanding electrochemical performance.

Current research on vanadium oxides in lithium ion batteries (LIBs) considers them as cathode materials, whereas they are rarely studied for use as anodes in LIBs because of their low electrical conductivity and rapid capacity fading. In this work, hydrogenated vanadium oxide nanoneedles were prepared and incorporated into freeze-dried graphene foam. The hydrogenated vanadium oxides show greatly improved charge-transfer kinetics, which lead to excellent electrochemical properties. When tested as anode materials (0.005–3.0 V vs. Li/Li+) in LIBs, the sample activated at 600 °C exhibits high specific capacity (∼941 mA·h·g−1 at 100 mA·g−1) and high-rate capability (∼504 mA·h·g−1 at 5 A·g−1), as well as excellent cycling performance (∼285 mA·h·g−1 in the 1,000th cycle at 5 A·g−1). These results demonstrate the promising application of vanadium oxides as anodes in LIBs.

Three-dimensional nanoporous carbon frameworks encapsulated Sn nanoparticles (Sn@3D-NPC) are developed by a facile method as an improved lithium ion battery anode. The Sn@3D-NPC delivers a reversible capacity of 740 mAh g–1 after 200 cycles at a current density of 200 mA g–1, corresponding to a capacity retention of 85% (against the second capacity) and high rate capability (300 mAh g–1 at 5 A g–1). Compared to the Sn nanoparticles (SnNPs), such improvements are attributed to the 3D porous and conductive framework. The whole structure can provide not only the high electrical conductivity that facilities the electron transfer but also the elasticity that will suppress the volume expansion and aggregation of SnNPs during the charge and discharge process. This work opens a new application of metal–organic frameworks in energy storage.

3D ordered porous structures of MoxC are prepared with different Mo to C ratios and tested for two possible promising applications: hydrogen evolution reaction (HER) through water splitting and lithium ion batteries (LIBs). Mo2C and MoC with 3D periodic ordered structures are prepared with a similar process but different precursors. The 3D ordered porous MoC exhibits excellent cycling stability and rate performance as an anode material for LIBs. A discharge capacity of 450.9 mA h g-1 is maintained up to 3000 cycles at 10.0 A g-1. The Mo2C with a similar ordered porous structure shows impressive electrocatalytic activity for the HER in neutral, alkaline and acidic pH solutions. In particular, Mo2C shows an onset potential of only 33 mV versus a reversible hydrogen electrode (RHE) and a Tafel slope of 42.5 mV dec-1 in a neutral aqueous solution (1.0 M phosphate buffer solution), which is approaching that of the commercial Pt/C catalyst.

The orthorhombic layer structured vanadium oxide, V2O5, is an attractive material for many essential applications. Here, a series of vanadium pentoxide micro-/nanostructures were prepared via a simple solvothermal approach followed by an annealing process. Various morphological structures from core–shell microspheres, nanosheets, hierarchical microflowers to octahedron structures can be tuned by simply changing the solvent ratio among dimethylformamide (DMF), isopropyl alcohol (IPA) and acetic acid. V2O5 microflowers and octahedra were investigated as cathodes for LIBs and showed good cycling stabilities and excellent ultrahigh rate capabilities.

Tin disulfide (SnS2) has emerged as a promising anode material for lithium/sodium ion batteries (LIBs/SIBs) due to its unique layered structure, outstanding electrochemical properties and low cost. However, its poor cycling life and time-consuming synthesis as well as low-yield production hinder the practical utilization of nanostructured SnS2. In this work, we demonstrate a simple and reliable dissolution–regeneration strategy to construct a flexible SnS2/sulfur-doped reduced graphene oxide (S-rGO) composite as anodes for LIBs and SIBs, highlighting its mass-production feature. In addition, the robust affinity between SnS2 and S-rGO without interstitial volume is very beneficial for preventing the SnS2 particles from breaking themselves away from the rGO nanosheets into free nanoparticles. As a result, the SnS2/S-rGO composite as anodes delivers high reversible capacities of 1078 mA h g−1 and 564 mA h g−1 (at 0.1 A g−1) for LIBs and SIBs, respectively, and excellent rate capabilities and cycling stability (e.g. 532 mA h g−1 during the 600 cycles at 5.0 A g−1 for LIBs). Our proposed strategy may also possess great potential for the practical application of other electrochemically active metal sulfide composites for energy devices.

A facile and effective approach to prepare Co 3 O 4 /CoFe 2 O 4 hollow cubes with uniform size and complex interior architectures is proposed via annealing of metal-cyanide-bridged hybrid coordination polymers (HCPs). The synergistic effect of the hybrid metal oxides and the rational design of the architecture endow these heterostructures with good lithium storage property and charge carrier transfer kinetics. In the hybrid materials, CoFe 2 O 4 offers high theoretical capacity and Co 3 O 4 provides stability at high current densities, leading to the significant enhancement in lithium storage properties comparing to the pure CoFe 2 O 4 . For example, Co 3 O 4 /CoFe 2 O 4 heterostructures annealed at 800 °C exhibit a high capacity of 511 mA h g −1 at a current density of 8.0 A g −1 and a reversible capacity of 515 mA h g −1 during the 500th cycle at a current density of 5.0 A g −1 .

Rechargeable alkali metal-Se batteries have attracted a lot of attention due to their high capacity and low cost. However, the shuttle effect and volume change during charge/discharge are the main obstacles for further development of high-performance alkali-Se rechargeable batteries. In order to solve these issues, herein a biomass-derived 3D interconnected foam-like N-doped porous carbon (FNDPC) is synthesized as a Se-container for metal-Se batteries. In this FNDPC@Se structure, stable porous carbon hosts can serve as chambers for Se reacting with Li+, Na+ or K+. As expected, the FNDPC@Se electrode exhibits an ultrahigh rate performance and excellent cycling stability during the reversible storage of alkali metal ions. For Na-Se batteries, the high specific capacity of 354.9 mAh g−1 is achieved even at a high current density of 20 A g−1 and there is 90.7% capacity retention after 500 cycles at 2.0 A g−1. For Li-Se batteries, FNDPC@Se can offer an impressive rate capability with specific capacities of 653.1 mAh g−1 at 0.1 A g−1 and 350.4 mAh g−1 at 20 A g−1. In contrast, the performance of FNDPC@Se in K-Se batteries is relatively lower than that in Li-Se and Na-Se batteries. Moreover, different energy-storage mechanisms for three types of ions are also revealed by cycling voltammetry (CV). Therefore, FNDPC is considered to be a promising carbon host for alkali-Se batteries, and our reported method provides possibilities for mass production of alkali-Se battery through the cheap raw materials.

We establish a unique bottom-up route to fabricate well-defined two-dimensional (2D) carbon coated CoS2 (CoS2@C) nanoplatelets as anode materials for highly reversible lithium ion batteries (LIBs). A novel platelet-like Co(OH)(OCH3) precursor is firstly prepared with a solvothermal method, and subsequently immersed in dopamine aqueous solution to generate a Co(OH)(OCH3)/polydopamine composite. Finally, 2D CoS2@C nanoplatelets are obtained through the topotactic sulfurization of Co(OH)(OCH3) into CoS2 nanoplatelets and the simultaneous carbonization of polydopamine coating by thermal annealing at 450 °C. The 2D porous CoS2 nanoplatelet cores offer abundant active sites for Li storage and shorten transport lengths of lithium ions and electrons, while the amorphous carbon shells increase the electronic conductivity, retard the dissolution of intermediate reactants in the electrolyte, and accommodate volume change during the charge-discharge process. As a result, the hierarchical CoS2@C nanoplatelets deliver a high reversible specific capacity of 1100 mAh g−1 at 0.2 A g−1 and maintain 740 mAh g−1 after 400 cycles at 1.0 A g−1. Moreover, the rate capability is also significantly improved relative to the bare CoS2. This work offers a new strategy for the synthesis of 2D transition metal sulfide nanoplatelets and their rational design to achieve desirable electrochemical performances for LIBs.

Novel nitrogen-doped porous molybdenum carbide (α-MoC1-x and β-Mo2C) architectures were prepared using Mo-based metal-organic frameworks (MOFs) as the precursor. The synthesized molybdenum carbides consist of numerous nanocrystals organized into micro-sized rods with interpenetrating mesoporous-channels and macroporous-tunnels along the axial direction. When employed as the cathode catalyst for Li-O2 batteries, this dual pore configuration offers abundant active sites for the electrochemical reaction and many nucleation sites for the discharge product of Li2O2; hence, decent performances were obtained. Among the two synthesized molybdenum carbides, the α-MoC1-x electrode stands out as being better due to its lower charge transfer resistance (395.8 Ω compared to 627.9 Ω) and better O2 adsorption (binding energy of -1.87 eV of α-(111)-Mo compared to -0.72 eV of β-(101)-Mo). It delivered a high full discharge of 20 212 mA h g-1 with a discharge voltage of 2.62 V at 200 mA g-1. A good cycling stability was also obtained: i.e. 100 stable cycles with a fixed capacity of 1000 mA h g-1 (at a current density of 200 mA g-1) with a charging voltage of 4.24 V and maintaining a respectable round-trip efficiency of ∼70%.

Two-dimensional (2D) graphene oxide/polypyrrole (GO/PPy) hybrid materials derived from in-situ polymerization are used as precursors for constructing functionalized three-dimensional (3D) porous nitrogen-doped carbon nanosheet frameworks (FT-PNCNFs) through a one-step activation strategy. In the formation process of FT-PNCNFs, PPY is directly converted into hierarchical porous nitrogen-doped carbon layers, while GO is simultaneously reduced to become electrically conductive. The complementary functions of individual components endow the FT-PNCNFs with excellent properties for both supercapacitors (SCs) and sodium ion batteries (SIBs) applications. When tested in symmetrical SC, the FT-PNCNFs demonstrate superior energy storage behaviour. At an extremely high scan rate of 3000 mV s −1 , the cyclic voltammetry (CV) curve retains an inspiring quasi-rectangle shape in KOH solution. Meanwhile, high capacitances (∼247 F g −1 at 10 mV s −1 ; ∼146 F g −1 at 3000 mV s −1 ) and good cycling stability (∼95% retention after 8000 cycles) are achieved. In addition, an attractive SIB anode performance could be achieved. The FT-PNCNFs electrode delivers a reversible capacity of 187 mAh g −1 during 160th cycle at 100 mA g −1 . Its reversible capacity retains 144 mAh g −1 after extending the number of cycles to 500 at 500 mA g −1 .

Traditional methods for the preparation of carbon aerogels, such as a sol–gel method, hydrothermal method, freeze-drying method and the direct carbonization of biomass materials, have been more and more limited in their applications due to their high cost, complex processes and the accompanying volume shrinkage in the preparation process. In this paper, we developed a novel air-expansion method for the preparation of porous carbonaceous aerogels with hierarchically macroporous, mesoporous and microporous structures from rice. The main advantages of an air-expansion method are large-scale preparation, low cost, a simple technique and most importantly it keeps the initial shape/structure and avoids shrinkage of the carbon aerogels owing to the air-expansion process of rice generating many macroporous structures for supporting the aerogel framework. When used as an anode for lithium ion batteries, rice-based carbonaceous aerogels exhibit a superior specific capacity and possess a good rate capability. This study gives a better insight into the preparation of carbonaceous aerogels from other grains as well as their potential applications in lithium ion batteries.

A general and simple approach for large-scale synthesis of porous hollow spinel AFe2O4 nanoarchitectures via metal organic framework self-sacrificial template strategy is proposed. By employing this method, we can successfully synthesize uniform NiFe2O4, ZnFe2O4, and CoFe2O4 hollow architectures that are hierarchically assembled by nanoparticles. When these hollow microcubes were tested as anode for lithium ion batteries, good rate capability and long-term cycling stability can be achieved. For example, high specific capacities of 636, 449, and 380 mA h g–1 were depicted by NiFe2O4, ZnFe2O4, and CoFe2O4, respectively, at a high current density of 8.0 A g–1. NiFe2O4 exhibits high specific capacities of 841 and 447 mA h g–1 during the 100th cycle when it was tested at current densities of 1.0 and 5.0 A g–1, respectively. Discharge capacities of 390 and 290 mA h g–1 were delivered by the ZnFe2O4 and CoFe2O4, respectively, during the 100th cycle at 5.0 A g–1. MOE (Min. of Education, S’pore) Published version

The synthesis of ZnO with tailorable shapes and point defects is important for its potential applications. Here, a facile approach is demonstrated to prepare ZnO nanocages with controllable porous shell structures though sintering a Zn-based cyanide-bridged coordination polymer under different temperatures. The transformation of ZnCP microspheres into ZnO nano cages is based on two types of nanoscale Kirkendall effect, which are related to low temperature solid-solid interfacial oxidation and high temperature solid-gas interfacial reaction, respectively. At low temperature (around 300 degrees C) and before the ZnCP decomposition, the novel "hierarchical ZnO bigger nanocages embedded with smaller nanocages with 10 nm nanocrystals" can be generated. By contrast, when coming to the total decomposition of ZnCP at 800 degrees C, ZnO nanocages with significantly increased sizes and large cavities are generated, and large amounts of oxygen vacancies (V-O) are created at the same time, leading to the dramatic increased luminescence intensities of the UV peak due to V-O at 540 nm. Thus, the luminescence intensities versus defect concentration in the prepared ZnO nanocages can also be controlled by tuning the sintering temperatures.

The composition and properties of silicone–hollow microsphere composites were studied in view of establishing a new type of maxillofacial prosthesis material. Two types of microspheres were used in different concentrations and were well dispersed in the silicone matrix. The mechanical properties of the composites were evaluated. Expancel hollow microspheres improve the density, Shore A hardness, and breaking elongation of the materials but degrade their tensile strength, tear strength, and dynamic mechanical properties, while opposite trends were observed with hollow SiO2 microspheres. Ideal properties for maxillofacial prosthetic applications can thereby be obtained by blending the two types of hollow microspheres in specific proportions.

Tin disulfide (SnS

Uniform Ni

3D ordered porous structures of Mo

Inspired by the remarkable adhesion of mussel, dopamine, a mimicking adhesive molecule, has been widely used for surface modification of various materials ranging from organic to inorganic. However, dopamine and its derivatives are expensive which impede their application in large scale. Herein, we replaced dopamine with low-cost catechol and polyamine (only 8% of the cost of dopamine), which could be polymerized in an alkaline solution and deposited on the surfaces of various materials. By using this cheap and simple modification method, polypropylene (PP) separator could be transformed from hydrophobic to hydrophilic, while the pore structure and mechanical property of the separator remained intact. The uptake of electrolyte increased from 80% to 270% after the hydrophilic modification. Electrochemical studies demonstrated that battery with the modified PP separator had a better Coulombic efficiency (80.9% to 85.3%) during the first cycle at a current density of 0.1 C, while the discharging current density increased to 15 C and the discharge capacity increased by 1.4 times compared to the battery using the bare PP separator. Additionally, the modification allowed excellent stability during manifold cycles. This study provides new insights into utilizing low-cost chemicals to mimic the mussel adhesion and has potential practical application in many fields.

A facile method was successfully established to construct 3D conductive network-based free-standing polyaniline/reduced graphene oxide/carbon nanotube ternary hybrid film, in which a 3D conductive network was synergistically assembled by MWNTs and GO. The synergistic assembly of carbon nanotubes and graphene oxide not only increased the basal spacing between graphene sheets but also effectively bridged the defects of reduced graphene oxide to form a 3D conductive network. Due to the 3D conductive network with high conductivity and the synergistic effect of polyaniline with carbon nanotubes and graphene, the as-prepared ternary hybrid film possessed high specific capacitance and good cycle stability as a flexible supercapacitor electrode. This study gives a better insight for the preparation of functional flexible hybrid film by combining conducting polymer with carbon materials of different dimensions.

Star-shaped and leaf-shaped polyaniline (PANI) hierarchical structures with interlaced nanofibers on the surface were successfully prepared by chemical polymerization of aniline in the presence of lithium triflate (LT). Chemical structure and composition of the star-like PANI obtained were characterized by FTIR and UV-vis spectra. PANI 2D architectures can be tailored from star-shaped to leaf-shaped structures by change the concentration of LT. The synthesized star-like and leaf-like polyaniline show good superhydrophobicity with water contact angles of both above 150° due to the combination of the rough nanoweb structure and the low surface tension of fluorinated chain of dopant. This method is a facile and applicable strategy for a large-scale fabrication of 2D PANI micro/nanostructures. Many potential applications such as self-cleaning and antifouling coating can be expected based on the superhydrophobic PANI micro/nanostructures.

3D hierarchical hollow nanocubes constructed by 1D FeSe2@C core-shell nanorods were successfully prepared by a thermally-induced selenization process of their Prussian blue microcubes precursor. Such novel nanorods-based FeSe2@C hollow structures exhibit high conductivity and special structural property which provide good charge transport kinetics by facilitating the charge transfer into the inner of FeSe2 nanorods. When used as anode materials for sodium ion batteries, the hierarchically hollow nanocubes showed excellent rate performance and ultra-stable long-term cycling stability at a high current density of 10 A g−1, suggesting a good sodium-ion storage material. This simple solid-phase process demonstrated in this work can be further used for the preparation of other metal selenide with unique and fascinating structure for the potential applications in the energy storage field. ASTAR (Agency for Sci., Tech. and Research, S’pore) MOE (Min. of Education, S’pore)

Carpenterworm-like multidimensional architectures of polyaniline/multi-walled carbon nanotubes (PANI–MWNTs), with a diameter of about 2.5 μm and consisting of many interlaced PANI nanorods on the surface of MWNTs, were successfully synthesized in a mixture of ethanol and water. Chemical structure and composition of the prepared PANI–MWNTs nanocomposites were characterized by Fourier transform infrared (FTIR) spectroscopy, ultraviolet and visible spectroscopy (UV–vis), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). It has been found that the concentration of ethanol in the solution plays a critical role in controlling the morphology of the resultant nanocomposites. The obtained carpenterworm-like PANI–MWNTs nanocomposites exhibit enhanced electrochemical behavior in comparison with MWNTs and PANI, indicating a potential application in electrode material of supercapacitors or secondary batteries.

A novel multidimensional architecture of tremella-like polyaniline (PANI) has been synthesized in the presence of oxalic acid (OA) by a template-free method. The PANI tremella is about 3–5 μm in average diameter and consist of petals of interlaced sheets with a thickness of about 20 nm. Chemical structures of obtained PANI were characterized by Fourier transform infrared spectroscopy (FTIR) and Ultraviolet and visible spectroscopy (UV–vis). It is found the micro-nanostructured PANI exhibits good electrochemical behavior in 0.1 M HCl electrolyte solution, indicating a potential application in sensors or electrochemical devices. In addition, the effect of OA concentration on the morphology of the tremella-like PANI was also investigated.

Uniform sized Co