High-Branched Natural Polysaccharide Flaxseed Gum Binder for Silicon-Based Lithium-Ion Batteries with High Capacity.

Silicon-based anodes heavily depend on the binder to preserve the unbroken electrode structure. In the present work, natural flaxseed gum (FG) is used as a binder of silicon nanoparticles (SiNPs) anode for the first time. Owing to a large number of polar groups and a rich branched structure, this material not only anchors tightly to the surface of SiNPs through bonding interactions but also formed a hydrogen bonding network structure among molecules. As a result, the FG binder can endow the silicon electrode with stable interfacial adhesion and outstanding mechanical properties. In addition, FG with a high viscosity facilitates the homogeneous dispersion of the electrode components. When FG is used as a binder, the cycling performance of the Si anode is greatly improved. After one hundred cycles at an applied current density of 1 A g-1, the electrode continues to display remarkable electrochemical properties with a significant cyclic capacity (2213 mA h g-1) and initial Coulombic efficiency (ICE) of 89.7%.

Self-Powered Disinfection Using Triboelectric, Conductive Wires of Metal-Organic Frameworks.

Efficient water disinfection is vitally needed in rural and disaster-stricken areas lacking power supplies. However, conventional water disinfection methods strongly rely on external chemical input and reliable electricity. Herein, we present a self-powered water disinfection system using synergistic hydrogen peroxide (H2O2) assisted electroporation mechanisms driven by triboelectric nanogenerators (TENGs) that harvest electricity from the flow of water. The flow-driven TENG, assisted by power management systems, generates a controlled output with aimed voltages to drive a conductive metal-organic framework nanowire array for effective H2O2 generation and electroporation. The injured bacteria caused by electroporation can be further damaged by facile diffused H2O2 molecules at high throughput. A self-powered disinfection prototype enables complete disinfection (>99.9999% removal) over a wide range of flows up to 3.0 × 104 L/(m2 h) with low water flow thresholds (200 mL/min; ∼20 rpm). This rapid, self-powered water disinfection method is promising for pathogen control.

A General Synthesis of Mesoporous Hollow Carbon Spheres with Extraordinary Sodium Storage Kinetics by Engineering Solvation Structure.

Porous and hollow carbon materials have great superiority and prospects in electrochemical energy applications, especially for surface charge storage due to the high active surface. Herein, a general strategy is developed to synthesize mesoporous hollow carbon spheres (MHCS) with controllable texture and compositions by the synergistic effect of dopamine polymerization and metal catalysis (Cu, Bi, Zn). Mesoporous MHCS-Cu and MHCS-Bi are regular spheres, while mesoporous MHCS-Zn possesses an inward concave texture, and simultaneously has a very high surface area of 1675.5 m2 g-1 and lower oxygen content through the catalytic deoxygenation effect. MHCS-Zn displays an exceptional sodium storage kinetics and excellent long cycling life with 171.9 mAh g-1 after 2500 cycles at 5 A g-1 in compatible ether-based electrolytes. Such electrolyte enables enhanced solvated Na+ transport kinetics with appropriate electrostatic interactions at the surface of carbon anode as revealed by molecular dynamics simulations and molecular surface electrostatic potential calculations. Such an anode also displays basically constant capacity working at 0 °C, and still delivers 140 mAh g-1 at 3 A g-1 under -20 °C. Moreover, MHCS-Zn anode is coupled with Na3 V2 (PO4 )3 cathode to construct a hybrid capacitor, which exhibits a high energy density of 145 Wh Kg-1 at a very high power of 8009 W kg-1 .

Self-Optimizing Effect in Lithium Storage of GeO2 Induced by Heterointerface Regulation.

Herein, a heterostructural hexagonal@tetragonal GeO2 (HT-GeO2 ) composite has been designed based on density functional theory (DFT) calculations and synthesized via an acidic-heating route dealt with rapid cooling, where the inner hexagonal GeO2 (H-GeO2 ) phase is covered by a porous layer of tetragonal GeO2 (T-GeO2 ) owing to HF etching. Interestingly, the HT-GeO2 electrode has a self-optimizing effect in lithium storage induced by heterointerface regulation, where the porous T-GeO2 layer on the surface of HT-GeO2 can act as not only a Li+ /electron conducting layer, but also a buffer layer, while the inner H-GeO2 phase can react preferentially with Li ions owing to lower intercalation energy, which is confirmed by operando XRD measurement contributing to thorough lithiation for HT-GeO2 . Moreover, the heterointerface can enhance the pseudocapacitance effect, which can boost the Li storage and accelerate the discharge-charge process. As a result, a large capacity of 984 mAh g-1 after 500 cycles at 2 A g-1 and a capacity of 430 mAh g-1 at a high current density of 20 A g-1 are delivered. This work provides an easy and efficient way to improve the cycling stability of the GeO2 anode, and the T-GeO2 phase would be a novel anode material in energy storage devices.

A Composite of Two Dimensional GeSe2 /Nitrogen-Doped Reduced Graphene Oxide for Enhanced Capacitive Lithium-Ion Storage.

A composite of two-dimensional (2D) GeSe2 nanosheets dispersed on N-doped reduced graphene oxide (GeSe2 /N-rGO) is fabricated via a simple hydrothermal method combined with post-selenization process. The high electronic conductivity and the substantial void spaces of the wrinkled N-rGO can improve the electrical conductivity of the active material and accommodate the volume evolution of GeSe2 nanosheets during the (de)lithiation processes, while GeSe2 nanosheets can reduce ion diffusion length effectively. Meanwhile, the unique layered structure is beneficial to the contact of the active material and electrolyte, and the reversibility of conversion reaction has also been improved. Furthermore, kinetics analysis reveals a pseudocapacitance-dominated Li+ -storage mechanism at high rates. In-situ X-ray diffraction analysis discloses that the conversion reaction has played a certain part in Li+ -storage. Thus, the GeSe2 /N-rGO composite delivers excellent rate capability and good long-term stability with a high reversible capacity of 711.0 mA h g-1 after 2000 cycles at 1 A g-1 .

Structure Engineering of BiSbSx Nanocrystals Embedded within Sulfurized Polyacrylonitrile Fibers for High Performance of Potassium-Ion Batteries.

Potassium-ion batteries (PIBs) are regarded as promising candidates in next-generation energy storage technology; however, the electrode materials in PIBs are usually restricted by the shortcomings of large volume expansion and poor cycling stability stemming from a high resistance towards diffusion and insertion of large-sized K ions. In this study, BiSbSx nanocrystals are rationally integrated with sulfurized polyacrylonitrile (SPAN) fibres through electrospinning technology with an annealing process. Such a unique structure, in which BiSbSx nanocrystals are embedded inside the SPAN fibre, affords multiple binding sites and a short diffusion length for K+ to realize fast kinetics. In addition, the molecular structure of SPAN features robust chemical interactions for stationary diffluent discharge products. Thus, the electrode demonstrates a superior potassium storage performance with an excellent reversible capacity of 790 mAh g-1 (at 0.1 A g-1 after 50 cycles) and 472 mAh g-1 (at 1 A g-1 after 2000 cycles). It's one of the best performances for metal dichalcogenides anodes for PIBs to date. The unusual performance of the BiSbSx @SPAN composite is attributed to the synergistic effects of the judicious nanostructure engineering of BiSbSx nanocrystals as well as the chemical interaction and confinement of SPAN fibers.

General Synthesis of Sulfonate-Based Metal-Organic Framework Derived Composite of Mx Sy @N/S-Doped Carbon for High-Performance Lithium/Sodium Ion Batteries.

A general and simple strategy is realized for the first time for the preparation of metal sulfide (Mx Sy ) nanoparticles immobilized into N/S co-doped carbon (NSC) through a one-step pyrolysis method. The organic ligand 1,5-naphthalenedisulfonic acid in the metal-organic framework (MOF) precursor is used as a sulfur source, and metal ions are sulfurized in situ to form Mx Sy nanoparticles, resulting in the formation of Mx Sy /NSC (M=Fe, Co, Cu, Ni, Mn, Zn) composites. Benefiting from the Mx Sy nanoparticles and conductive carbon, a synergistic effect of the composite is achieved. For instance, the composite of Fe7 S8 /NSC as an anode displays excellent long-term cycling stability in lithium/sodium ion batteries. At 5 A g-1 , large capacities of 645 mA h g-1 and 426.6 mA h g-1 can be retained after 1500 cycles for the lithium-ion battery and after 1000 cycles for the sodium-ion battery, respectively.

Valence Engineering via Selective Atomic Substitution on Tetrahedral Sites in Spinel Oxide for Highly Enhanced Oxygen Evolution Catalysis.

A major challenge that prohibits the practical application of single/double-transition metal (3d-M) oxides as oxygen evolution reaction (OER) catalysts is the high overpotentials during the electrochemical process. Herein, our theoretical calculation shows that Fe will be more energetically favorable in the tetrahedral site than Ni and Co, which can further regulate their electronic structure of binary NiCo spinel oxides for optimal adsorption energies of OER intermediates and improved electronic conductivity and hence boost their OER performance. X-ray absorption spectroscopy study on the as-synthesized NiCoFe oxide catalysts indicates that Fe preferentially dopes into tetrahedral sites of the lattice, which induces high proportions of Ni3+ and Co2+ on the octahedral sites (the active sites in OER). Consequently, this material exhibits a significantly enhanced OER performance with an ultralow overpotential of 201 mV cm-2 at 10 mA cm-2 and a small Tafel slope of 39 mV dec-1, which are much superior to state-of-the-art Ni-Co based catalysts.

Hierarchical Composite of Rose-Like VS2 @S/N-Doped Carbon with Expanded (001) Planes for Superior Li-Ion Storage.

In the present work, a hierarchical composite of rose-like VS2 @S/N-doped carbon (VS2 @SNC) with expanded (001) planes is successfully fabricated through a facile synthetic route. Notably, the d-spacing of (001) planes is expanded to 0.92 nm, which is proved to dramatically reduce the energy barrier for Li+ diffusion in the composite of VS2 @SNC by density functional theory calculation. On the other hand, the S/N-doped carbon in the composite greatly promotes the electrical conductivity and enhances the structural stability. In addition, the hierarchical structure of VS2 @SNC facilitates rapid electrolyte diffusion and increases the contact area between the electrode and electrolyte simultaneously. Benefiting from the merits mentioned above, the VS2 @SNC electrode exhibits excellent electrochemical properties, such as a large reversible capacity of 971.6 mA h g-1 at 0.2 A g-1 , an extremely high rate capability of 772.1 mA h g-1 at 10 A g-1 , and a remarkable cycling stability up to 600 cycles at 8 A g-1 with a capacity of 684.5 mA h g-1 , making it a promising candidate as an anode material for lithium-ion batteries.

Facile Synthesis of Ultra-Small Few-Layer Nanostructured MoSe2 Embedded on N, P Co-Doped Bio-Carbon for High-Performance Half/Full Sodium-Ion and Potassium-Ion Batteries.

Sodium/potassium-ion batteries (SIBs/PIBs) arouse intensive interest on account of the natural abundance of sodium/potassium resources, the competitive cost and appropriate redox potential. Nevertheless, the huge challenge for SIBs/PIBs lies in the scarcity of an anode material with high capacity and stable structure, which are capable of accommodating large-size ions during cycling. Furthermore, using sustainable natural biomass to fabricate electrodes for energy storage applications is a hot topic. Herein, an ultra-small few-layer nanostructured MoSe2 embedded on N, P co-doped bio-carbon is reported, which is synthesized by using chlorella as the adsorbent and precursor. As a consequence, the MoSe2 /NP-C-2 composite represents exceedingly impressive electrochemical performance for both sodium-ion batteries (SIBs) and potassium-ion batteries (PIBs). It displays a promising reversible capacity (523 mAh g-1 at 100 mA g-1 after 100 cycles) and impressive long-term cycling performance (192 mAh g-1 at 5 A g-1 even after 1000 cycles) in SIBs, which are some of the best properties of MoSe2 -based anode materials for SIBs to date. To further probe the great potential applications, full SIBs pairing the MoSe2 /NP-C-2 composite anode with a Na3 V2 (PO4 )3 cathode also exhibits a satisfactory capacity of 215 mAh g-1 at 500 mA g-1 after 100 cycles. Moreover, it also delivers a decent reversible capacity of 131 mAh g-1 at 1 A g-1 even after 250 cycles for PIBs.

Hierarchical Cobalt-Based Metal-Organic Framework for High-Performance Lithium-Ion Batteries.

In the present work, a simple solvothermal method is developed for the synthesis of hierarchical Co-based metal-organic framework (H-Co-MOF) microflowers. These microflowers are composed of nanosheets, consisting of small nanoflakes. Upon application as an electrode material in Li-ion batteries, H-Co-MOF shows ultrahigh specific capacity and long cycling performance. For instance, a remarkably superior capacity of 1345 mA h g-1 can be achieved after 100 cycles at a current density of 0.1 A g-1 . Even at 2 A g-1 , a large capacity of 828 mA h g-1 is maintained after 700 cycles. This excellent electrochemical performance might be ascribed to the intrinsic properties and unique hierarchical structure of the Co-based MOF.

Preparation of a Si/SiO2 -Ordered-Mesoporous-Carbon Nanocomposite as an Anode for High-Performance Lithium-Ion and Sodium-Ion Batteries.

In this work, an Si/SiO2 -ordered-mesoporous carbon (Si/SiO2 -OMC) nanocomposite was initially fabricated through a magnesiothermic reduction strategy by using a two-dimensional bicontinuous mesochannel of SiO2 -OMC as a precursor, combined with an NaOH etching process, in which crystal Si/amorphous SiO2 nanoparticles were encapsulated into the OMC matrix. Not only can such unique porous crystal Si/amorphous SiO2 nanoparticles uniformly dispersed in the OMC matrix mitigate the volume change of active materials during the cycling process, but they can also improve electrical conductivity of Si/SiO2 and facilitate the Li+ /Na+ diffusion. When applied as an anode for lithium-ion batteries (LIBs), the Si/SiO2 -OMC composite displayed superior reversible capacity (958 mA h g-1 at 0.2 A g-1 after 100 cycles) and good cycling life (retaining a capacity of 459 mA h g-1 at 2 A g-1 after 1000 cycles). For sodium-ion batteries (SIBs), the composite maintained a high capacity of 423 mA h g-1 after 100 cycles at 0.05 A g-1 and an extremely stable reversible capacity of 190 mA h g-1 was retained even after 500 cycles at 1 A g-1 . This performance is one of the best long-term cycling properties of Si-based SIB anode materials. The Si/SiO2 -OMC composites exhibited great potential as an alternative material for both lithium- and sodium-ion battery anodes.

Plasmonic Effects of Silver Nanoparticles Embedded in the Counter Electrode on the Enhanced Performance of Dye-Sensitized Solar Cells.

The plasmonic effects of silver (Ag) nanoparticles (NPs) with various morphologies (sphere, rod, and prism) embedded into the platinum (Pt) counter electrodes (CEs) of dye-sensitized solar cells (DSCs) were systematically investigated. It was shown that the power conversion efficiencies (PCEs) of the incorporated devices are notably improved from 7.60%, for the reference device without Ag NPs, to 8.10, 8.68, and 8.55% with Ag nanospheres, nanorods, and nanoprism devices, respectively. Moreover, the photocurrent and fill factor enhancement is attributed to the better optical and electrical properties of the integrated devices. Among all of the NP morphologies studied, Ag nanorods offer the best improvement to the device efficiency, as they have longitudinal localized surface plasmon resonance (L-LSPR) and strong scattering effects correlate within the morphology.

Layered Structural Co-Based MOF with Conductive Network Frames as a New Supercapacitor Electrode.

Layered structural Co-MOF nanosheets were synthesized and then used as an electrode material for supercapacitors for the first time. This material exhibited a high specific capacitance, a good rate capability, and an excellent cycling stability. A maximum capacitance of 2564 F g-1 can be achieved at a current density of 1 Ag-1 . Moreover, the capacitance retention can be kept at 95.8 % respectively of its initial value after 3000 cycles. To the best of our knowledge, both the specific capacitance and the capacitance retention were the highest values reported for MOF materials as supercapacitor electrodes until now. Such a high supercapacitive performance might be attributed to the intrinsic characteristics of this kind of Co-MOF material, including its layered structure, conductive network frame, and thin nanosheet.

Rutile TiO2 Mesocrystals as Sulfur Host for High-Performance Lithium-Sulfur Batteries.

Although lithium-sulfur (Li-S) batteries are among the most promising rechargeable batteries in the field of energy-storage devices, their poor cycling performance restricts their potential applications. Polar materials can improve the cycling stability owing to their inherent strong chemical interaction with polysulfides. Herein, novel rutile TiO2 mesocrystals (RTMs) are employed as the host for sulfur in Li-S batteries; the RTMs display a stable cycling performance with a capacity retention of 64 % and a small average capacity decay rate of 0.12 % per cycle over 300 cycles at 1 C rate. The good electrochemical properties are attributed to the interior ordered nanopores of the RTMs, which can effectively limit the dissolution of polysulfides, and the ultrafine nanowires in RTMs, which shorten the path for lithium-ion transport effectively.

Nb-Doped Rutile TiO2 Mesocrystals with Enhanced Lithium Storage Properties for Lithium Ion Battery.

A homogeneous Nb-doped rutile TiO2 mesocrystal material was synthesized successfully through a facile hydrothermal route. The incorporation of Nb5+ not only promotes the crystallization of the building subunits of the rutile TiO2 mesocrystal, but also improves the electrochemical performance at higher current rates. A capacity of 96.3 mAh g-1 at a current density as high as 40 C and an excellent long-term cycling stability with a capacity loss of approximately 0.006 % per cycle at 5 C could be achieved when an appropriate amount of Nb5+ was doped into rutile TiO2 mesocrystal. The reasons for the improvement of rate capability may be attributed to the enhancement of electronic conductivity, Li-ion diffusion kinetics, and the surface storage property for the Nb-doped rutile TiO2 mesocrystal.

The ZnSn(OH)6 nanocube-graphene composite as an anode material for Li-ion batteries.

ZnSn(OH)6 (ZSH) nanocubes with a uniform size of 40-80 nm were synthesized by using a simple hydrothermal route and then combined with graphene sheets (rGO) via the electrostatic interaction. The formed composite of ZnSn(OH)6 nanocube-graphene (ZSH-rGO) was used as an anode material for Li-ion batteries and it exhibited significantly enhanced electrochemical performance. For instance, a capacity of 540 mA h g(-1) at 500 mA g(-1) was retained after 40 cycles.

Understanding the growth and photoelectrochemical properties of mesocrystals and single crystals: a case of anatase TiO(2).

Anatase TiO2 mesocrystals and single crystals with dominant {101} facets were successfully synthesized without any additives using titanate nanowires as precursors under solvothermal and hydrothermal conditions, respectively. It is proposed that the oriented self-assembly process for the formation of TiO2 mesocrystals was controlled by the same thermodynamic principle as that of single crystals in this simple reaction system. Furthermore, the TiO2 mesocrystals were applied in photoelectrochemical (PEC) water splitting and demonstrated much enhanced photocurrent, almost 191% and 274% compared with that of TiO2 single crystals and commercial P25, respectively. Electrochemical impedance measurements under illumination revealed that the photocurrent increase was largely ascribed to the effective charge separation of electron-hole pairs and fast interfacial charge transfer. This could be attributed to the intrinsic characteristics of the mesostructured TiO2 composed of highly oriented nanocrystal subunits offering few grain boundaries, nanoporous nature and a short transport distance.

Compositing pine pollen derived carbon matrix with Na4FeV(PO4)3 nanoparticle for cost-effective sodium-ion batteries cathode.

Na super-ion conductor type material Na3V2(PO4)3 has been widely researched as the cathode of sodium-ion batteries (SIBs) in recent years, but the unsatisfying cost of Na3V2(PO4)3 impedes its wide application in SIBs. In this study, iron element is used to replace part of vanadium in Na3V2(PO4)3 to reduce its expense, and pine pollen is applied for the first time as a very effective carbon source to improve the performance of Na4FeV(PO4)3. The fabricated composite material achieves a capacity of 105 mA h g-1 under 0.2 C and fascinating cycling stability over 94 % under 2 C for 500 cycles and 98 % under 10 C for 1000 cycles. The excellent cycle performance is caused by the involvement of pine pollen that acts as a carbon matrix to enhance the electron conductivity and block the agglomeration of active material effectively, thus the well-dispersed nano sized Na4FeV(PO4)3 shortens the diffusion path of sodium ion and gains a remarkable rate capability. Moreover, the distinguished reversibility during the charge and discharge procedures is ascribed also to the robust structure of Na4FeV(PO4)3. This work provides an efficient route to realize the economic cathode material of SIBs with good performance.

F-doped TiO2(B)/reduced graphene for enhanced capacitive lithium-ion storage.

A composite of F-doped TiO2(B) and reduced graphene oxide (F-TiO2(B)/rGO) was successfully synthesized via a one-step hydrothermal route. It was found that the introduction of F ions in the synthetic process has led to the uniform dispersion of TiO2(B) on rGO nanosheets. The F ions have also been doped into the lattice of TiO2(B), which greatly improved the conductivity of the materials. Consequently, this composite delivered a large capacity of 249.4 mA h g-1 at 0.2 A/g. It also demonstrated a capacity of 203.1 mA h g-1 and an excellent capacity retention of 96% after 500 cycles even at a high current density of 2 A/g.