Large Interlayer Distance Research Articles

A novel layered birnessite-type sodium molybdate as dual-ion electrodes for high capacity battery

A birnessite-type Na1/3MoO2•H2O with a large interlayer distance has been synthesized by solid-state reaction and water treatment for the first time. The obtained Na1/3MoO2•H2O is phase-pure and well-crystallized as determined by X-ray structure refinement and presents a typical plate-like microstructure. Surprisingly, the Na1/3MoO2•H2O can be used as both anode and cathode electrodes for Li-ion batteries (LIBs), which shows long cycle life ((anode, 500 cycles~650 mAh g−1), and high capacity of 300 mAh g−1 (cathode). This high performance is ascribed to the PF6− intercalation mechanism of Na1/3MoO2•H2O based on the density functional theory (DFT) calculations. This work offers an efficient way for the design of electrode materials and sheds light on the application of the Na1/3MoO2•H2O for high capacity dual-ion batteries (DIBs).

Potassium-ion storage mechanism of MoS2-WS2-C microspheres and their excellent electrochemical properties

Potassium-ion batteries are receiving increasing interest as a new type of secondary batteries because of their low redox potentials. In particular, two-dimensional transition metal dichalcogenides are being widely studied because they possess a layered structure with a large interlayer distance; these structural characteristics are favorable for hosting potassium-ions. However, capacity decay occurs and the intercalation of potassium-ions is hindered due to the huge volume expansion during the cycling process. Here, MoS2-WS2-C microspheres containing highly porous structure and heterogeneous interfaces are synthesized through facile spray pyrolysis. Benefiting from the unique structure and hetero-interfaces, the composite microspheres exhibit stable cycle performance and an outstanding rate performance. Meanwhile, a reversible capacity of 350 mA h g−1 is achieved after 100 cycles at the current density of 100 mA g−1, and even at the high current density of 5.0 A g−1, it maintains a capacity of 176 mA h g−1. The potassium-ion storage mechanism of MoS2-WS2-C microspheres is also systematically explored via ex-situ transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). With the advantages of highly reversible intercalation from WS2 and high specific capacity of conversion from MoS2, the MoS2-WS2-C microspheres achieve high rate performance and specific capacity.

Wide interlayer spacing ammonium vanadate (NH4)0.37V2O5.0.15(H2O) cathode for rechargeable aqueous zinc-ion batteries

Recently, aqueous zinc-ion batteries (AZIBs) have been gaining widespread academic interest in the energy-storage field owing to their high energy density, enhanced safety of electrochemical operation, and low cost, as well as the abundance of zinc on earth. The ammonium vanadate group contains compounds that are considered efficient energy-storage materials because they provide two-dimensional (2D) layered structures with large interlayer distances that promote the intercalation of metal ions during electrochemical processes. Here, we report a hydrated form of ammonium vanadate (NH4)0.37V2O5·0.15(H2O) with a highly crystalline rose-like microstructure, which is used as the positive electrode material in AZIBs. The ammonium vanadate cathode delivered an initial capacity of 400mAh g−1 with 2M ZnSO4 at the current density of 0.5 Ag−1 in a voltage range from 0.2V to 1.4V vs Zn2+/Zn. At a higher current density (10 A g−1), the material retained 84% of the initial discharge capacity after 1000 cycles, while displaying an excellent rate capability. Cyclic voltammetry and ex-situ XRD and XPS are used to study the reaction mechanism of ammonium vanadate cathode in the AZIBs. Unlike other ammonium vanadate’s, (NH4)0.37V2O5·0.15(H2O) undergoes co-intercalation of Zn2+ and H+ along with water molecules. There is no intermediate irreversible crystal phase formation during the discharge/charge cycles due to expandable interlaying distance. This report suggests that (NH4)0.37V2O5·0.15(H2O) can be an alternative highly stable cathode material for use in AZIBs, and it can be promising for the intercalation of the cathode in larger-sized metal-ion storage systems.

Understanding the electrochemical properties and phase transformations of layered VOPO4⋅H2O as a potassium-ion battery cathode

Layered oxovanadium phosphate hydrate (VOPO4·xH2O) is considered to be a promising cathode material for potassium-ion batteries. However, its correlation between electrochemical properties and structural changes during electrochemical processes still need further exploration. Herein, monohydrate VOPO4·H2O is used as an alkali ion (Li+, Na+, K+) host material that gives superior electrochemical performances in potassium-ion batteries. It has a high discharge capacity of 90 mA h g−1 with a high average potential of 3.5 V and a lifespan of over 650 cycles with 61% retention at 1C rate. Three phase transitions during the potassiation/depotassiation process are observed: KxVOPO4 (0 < x < 0.12, d = 7.06 Å) → αI-KxVOPO4 (0.12 < x < 0.48, d = 6.73 Å) → αII-KxVOPO4 (0.30 < x < 0.55, d = 6.55 Å). The small structural change (≤6% on the c-axis) and the full reversibility of the structural transformation ensure the stable cycling; the large interlayer distance allows a fast K-ion diffusion (10−9–10−11 cm2 s−1). This study provides a comprehensive understanding on electrochemical performances and structural evolutions of VOPO4·H2O. Meanwhile, the small volume variation, high operating potential, and excellent cycling stability of VOPO4·H2O can attract more attention to develop other layered materials beyond transition metal oxides.

In Operando Synchrotron Studies of NH4+ Preintercalated V2O5·nH2O Nanobelts as the Cathode Material for Aqueous Rechargeable Zinc Batteries.

NH4+ preintercalated V2O5·nH2O nanobelts with a large interlayer distance of 10.9 Å were prepared by the hydrothermal method. The material showed a large specific capacity of 391 mA·h·g-1 at the 500 mA·g-1 current density in aqueous rechargeable zinc batteries. In operando synchrotron X-ray diffraction demonstrated that the material experienced reversible solid-solution reaction and two-phase transition during charge-discharge cycling, accompanied by the reversible formation/decomposition of a ZnSO4Zn3(OH)6·5H2O byproduct. In operando X-ray absorption spectroscopy confirmed the reversible reduction/oxidation of V, together with small changes in the VO6 local structure. The formation of byproduct was attributed to the dehydration of [Zn(H2O)6]2+, which concurrently improved the desolvation of [Zn(H2O)6]2+ into Zn2+. Bond valence sum map analysis and electrochemical impedance spectroscopy demonstrated that the byproduct improved the charge transfer kinetics of the electrode. Cyclic voltammetry and galvanostatic intermittent titration technique showed that the electrode reaction was dominated by ionic intercalation where the discharge capacity in the voltage window of 1.4-0.85 V was attributed to the intercalation of [Zn(H2O)6]2+, followed by the intercalation of Zn2+ at 0.85-0.4 V.

Binding hierarchical MoSe2 on MOF-derived N-doped carbon dodecahedron for fast and durable sodium-ion storage

Molybdenum diselenide (MoSe2) has drawn a lot of attention for high-performance sodium ion batteries (SIBs) as anode material, for its high theoretical capacity as well as large interlayer distance. Nevertheless, the low capacity and the poor cycling stability greatly hinder their application. Herein, a facile strategy to improve the storage performance of sodium was proposed by the in-situ growth of MoSe2 on zeolitic imidazolate framework-8 (ZIF-8)-derived nitrogen doped porous carbon dodecahedron (MoSe2/N-PCD). The N-PCD can provide a fast electron transfer route for the MoSe2, and the robust interface between MoSe2 and N-PCD can relief the structure changes of the electrode during the sodiation/desodiation. When used as an anode for SIBs, the prepared MoSe2/N-PCD electrode displays a large initial specific capacity of 464 mA h g−1 at 0.2 A g−1, and the capacity maintains at 437 mA h g−1 after 500 cycles. Furthermore, at a high current density of 2 A g−1, the electrode can still show a capacity of 223 mA h g−1 after 1000 cycles (capacity retention∼83%). This work demonstrates an effective way to prepare high performance MoSe2 based anode materials for sodium-ion battery.

Sandwich-like SnS/N, S co-doped rGO/SnS structure with pseudocapacitance for high-performance Li- and Na–ion batteries

SnS is considered as a promising anode candidate for next-generation Li- and Na-ion batteries due to its high theoretical capacity and large interlayer distance, which provides excessive space for intercalation of Li- and Na-ions. However, the low electronic conductivity and large volumetric changes during charge/discharge process lead to its poor rate capability and severe capacity degradation. Herein, a sandwich-like SnS/N, S co-doped rGO/SnS structure is delicately tailored by using selective vulcanization and in situ decomposition processes. The unique sandwich-like SnS/rGO/SnS structure provides open channels for ion storage and ameliorates the electrical conductivity. RGO substrate and chemical bonds between SnS and rGO improves the electronic conductivity and furnishes additional ions/electrons transport routes. Moreover, the co-doping of N and S renders abundant sites for ions adsorption, inducing a strong pseudocapacitance effect and favoring fast electrochemical kinetics. Therefore, at the current density of at 1 A g−1, the sandwich-like SnS/rGO/SnS electrode delivered a high reversible capacity of 797.9 mAh g−1 and 359.2 mAh g−1 as an anode material in Li- and Na-ion batteries, respectively.

Bio-inspired co-deposited preparation of GO composite loose nanofiltration membrane for dye contaminated wastewater sustainable treatment

The fully separation of dye/salt through loose nanofiltration membranes is of great significance for the sustainable development paradigm of textile wastewater. However, the current loose nanofiltration membranes suffer low separation efficiency and complex preparation. Herein, by one-step co-deposition, we develop graphene oxide (GO) composite loose nanofiltration membranes with low negatively charged surface. Our membrane possesses unconventional high pure water permeation of 71.7 LMH/bar, 92.9 % rejection for Methyl blue (MB) and 98.8 % rejection for Congo red (CR). Benefiting from the large interlayer distance of GO nanosheets and low negatively charged surface, membrane achieves high dyes/salts separation with satisfactory permeation to salts (94.3 % of Na2SO4, 97.6 % of MgSO4, 98.3 % of MgCl2 and 99.0 % of NaCl). The CR/salt mixed solutions exhibit similar removal rates to their constituents’ single dye or salt solutions (CR rejection is up to more than 97 % and the permeations of all salts are above 93 %). At the same time, binary dyes mixtures (Congo red and Methyl orange) can also be effectively separated. Furthermore, the membrane shows a relatively desirable antifouling property. The flux recovery still remains at 85.9 % after three cycling filtrations. This study provides a facile approach to prepare highly-efficient loose nanofiltration membranes for wastewater sustainable remediation.

Aluminum vanadate hollow spheres as zero-strain cathode material for highly reversible and durable aqueous zinc-ion batteries

The intercalation and conversion compounds have long been exploited in aqueous zinc-ion batteries such as Prussian blue, VS2, Zn0.25V2O5, MnO2 and so on. However, the lattice distortion of host materials during Zn ions insertion is the major issue with cycling stability. Metastable-phase vanadium oxide with bilayer structure, low crystallinity and interstitial water molecules may decrease lattice distortion, leading to long cycle stability. Herein we demonstrate H11Al2V6O23.2 (HAVO) microspheres with large interlayer distance (d001 ​= ​1.336 ​nm) as cathode materials for zinc-ion batteries. The Zn ions insertion/extraction behaviors are investigated deeply. Ex-situ XRD and Raman spectra of HAVO collected at various states show no shift during battery operation, indicating the lattice distortion is nearly negligible. In addition, the lattice structure is well maintained even after 1000 cycles and the HAVO delivers an outstanding reversibility (88.6% capacity retention after 7000 cycles).

Codoped Holey Graphene Aerogel by Selective Etching for High‐Performance Sodium‐Ion Storage

AbstractThe pursuit of more efficient carbon‐based anodes for sodium‐ion batteries (SIBs) prepared from facile and economical methods is a very important endeavor. Based on the crystallinity difference within carbon materials, herein, a low‐temperature selective burning method is developed for preparing oxygen and nitrogen codoped holey graphene aerogel as additive‐free anode for SIBs. By selective burning of a mixture of graphene and low‐crystallinity carbon at 450 °C in air, an elastic porous graphene monolith with abundant holes on graphene sheets and optimized crystallinity is obtained. These structural characteristics lead to an additive‐free electrode with fast charge (ions and electrons) transfer and more abundant Na+ storage active sites. Moreover, the heteroatom oxygen/nitrogen doping favors large interlayer distance for rapid Na+ insertion/extraction and provides more active sites for high capacitive contribution. The optimized sample exhibits superior sodium‐ion storage capability, i.e., high specific capacity (446 mAh g−1 at 0.1 A g−1), ultrahigh rate capability (189 mAh g−1 at 10 A g−1), and long cycle life (81.0% capacity retention after 2000 cycles at 5 A g−1). This facile and economic strategy might be extended to fabricating other superior carbon‐based energy storage materials.

K+ alkalization promoted Ca2+ intercalation in V2CT MXene for enhanced Li storage

Abstract Although MXenes is highly attractive as anode materials of lithium ion batteries, it sets a bottleneck for higher capacity of the V2CTx MXene due to the limited interlayer space and the derived surface terminations. Herein, the cation intercalation and ion-exchange were well employed to achieve a K+ and Ca2+ intercalated V2CTx MXene. A larger interlayer distance and low F surface terminations were thereof obtained, which accelerates the ion transport and promotes the delicate surface of V2CTx MXene. As a result, a package of enhanced capacity, rate performance and cyclability can be achieved. Furthermore, the ion exchange approach can be extended to other 2D layered materials, and both the interlayer control and the surface modification will be achieved.

Nanoporous nitrogen doped carbons with enhanced capacity for sodium ion battery anodes

Hard carbons with a disordered graphitic structure show promise as anode materials in next generation Na-ion batteries with stable and high sodiation/desodiation capacities. Since the mechanism of adsorption is not stoichiometric, as opposed to the case of Li-intercalation into graphite (LiC6), the search for an upper limit for the reversible capacity is an important task. We herein present a highly nanoporous nitrogen doped carbon obtained from ionothermal carbonization of a Zn-imidazolium framework that shows a stable cycling capacity of 496 ​mA ​h g-1 at 30 ​mA ​g-1 and 280 ​mA ​h g-1 at 5 ​A ​g-1 thus demonstrating exceptionally high capacity and outstanding rate performance. Although the reversible capacity was obtained only after extensive SEI formation, our results reveal the potential for much higher reversible capacities than usually observed today using carbons with a tailored porosity in Na-ion batteries. The electrochemical behavior is explained by improved utilization through a nanoscopic transport pore system and large graphitic interlayer distances. Initial SEI formation is herein used to passivate the carbon surface and obtain an ion-sieving coating. The ion sieving can allow for stable cycling at high capacity without further SEI formation because of a formed physical barrier between solvent molecules and metallic sodium.

Controllable Synthesis of Two-Dimensional Molybdenum Disulfide (MoS2 ) for Energy-Storage Applications.

Lamellar molybdenum disulfide (MoS2 ) has attracted a wide range of research interests in recent years because of its two-dimensional layered structure, ultrathin thickness, large interlayer distance, adjustable band gap, and capability to form different crystal structures. These special characteristics and high anisotropy have made MoS2 widely applicable in energy storage and harvesting. In this Minireview, a systematic and comprehensive introduction to MoS2 , as well as its composites, is presented. It is aimed to summarize the various synthetic methods of MoS2 -based composites and their application in energy-storage devices (lithium-ion batteries, sodium-ion batteries, lithium-sulfur batteries, and supercapacitors) in detail. Based on recent studies, this Minireview provides important and comprehensive guidelines for further study and development efforts in the MoS2 in energy-storage field.

Hollow Spheres Consisting of SnS Nanosheets Conformally Coated with S‐Doped Carbon for Advanced Lithium‐/Sodium‐Ion Battery Anodes

AbstractAlthough tin sulfide is a promising anode material for lithium‐ and sodium‐ion batteries due to the layered structure and high theoretical capacity, the large volume expansion and poor kinetics have seriously hindered further development and application. In this work, hollow spheres consisting of in situ generated SnS nanosheets (SnS@C HSs) conformally coated with S‐doped carbon are fabricated using polystyrene spheres as the self‐sacrifice template and carbon source. The SnS@C HSs with a large SnS interlayer distance, S‐doped carbon matrix, and hollow structure not only relieve the pressure caused by volume expansion during cycling, but also promote fast transfer of lithium/sodium ions leading to a high pseudocapacitance. The SnS@C HSs have excellent electrochemical properties in both LIBs and SIBs such as high capacity, high rate, and outstanding cycling stability. The use of a self‐sacrifice template is demonstrated to be a convenient and efficient strategy to design and prepare carbon‐coated metal hollow spheres for efficient energy storage and conversion.

Synergy of interlayer expansion and capacitive contribution promoting sodium ion storage in S, N-Doped mesoporous carbon nanofiber

Heteroatoms doping is proved to be an effective strategy to improve the electrochemical performance of carbon materials by adjusting its physical and chemical properties. In this work, sulfur, nitrogen co-doped carbon nanofiber (SNCNF) is prepared by electrospinning technique with the following heat and hydrothermal treatment route. Benefiting from the S, N co-doping, SNCNF demonstrates perfect pseudocapacitance characteristic improving rate performance (N-doping) and large interlayer distances promoting reversible insertion/extraction of Na+ (S-doping). SCNNF displays high charge-discharge specific capacity (290.3 mA h g−1 at 0.1 A g−1), superior cycling stability (247.4 mA h g−1 and 98.2% retention at 0.5 A g−1 over 600 cycles) and ultra-long circulation characteristics at high current rate (160.2 mA h g−1 at 10.0 A g−1 after 10,000 cycles), which can be served as a very promising material as anode for sodium ion batteries.

YbMgGaO4: A Triangular‐Lattice Quantum Spin Liquid Candidate

AbstractResonating valence bond ground state, the prototype of a quantum spin liquid (QSL), had been first proposed by P. W. Anderson back in 1973 on the triangular lattice. In such a 2D QSL, spinons created as unpaired spins can propagate by locally rearranging the uncorrelated valence bonds. However, the corresponding candidate materials are still rare to date. YbMgGaO4, first proposed in 2015 may fill this gap: the magnetic rare‐earth Yb3+ ions arrange on the triangular lattice with the perfect R‐3m symmetries and with a large interlayer distance. No conventional spin freezing is observed down to 40 mK without residual magnetic entropy, despite the significant antiferromagnetic coupling of ≈2 K. This report reviews and classifies the relevant experimental and theoretical progress on some (effective) spin‐1/2 triangular antiferromagnets, especially on YbMgGaO4, followed by discussion and outlook on some of the pending issues.

Tunable Cloaking of Mexican-hat Confined States in Bilayer Silicene

We present the ballistic quantum transport of a p-n-p bilayer silicene junction in the presence of spin-orbit coupling and electric field using a four-band model in combination with the transfer-matrix approach. A Mexican-hat shape of low-energy spectrum is observed similarly to bilayer graphene under an interalayer bias. We show that while bilayer silicene shares some physics with bilayer graphene, it has many intriguing phenomena that have not been reported for the latter. First, the confined state producing a significantly non-zero transmission in Mexican hat. Second, the cloaking of the Mexican-hat confined state is found. Third, we observe that the Mexican-hat cloaking results in a strong oscillation of conductance when the incident energy is below the potential height. Finally, unlike monolayer silicene, the conductance at large interlayer distances increases with the rise of electric field when the incident energy is above the potential height.

Supercapacitors in Motion: Autonomous Microswimmers for Natural-Resource Recovery.

An electroadsorption technique similar to the ultrafast charging mechanism in supercapacitors is utilized to remove metals with different sizes and hydrophilicities from contaminated water using self-propelled microswimmers. The swimmers carry graphite fibre or bismuth with a layered crystal structure providing high electrostatic double-layer capacitances. Unlike previous methods, this electrochemical technique does not only utilize the surface of the swimmers, but due to the interlayer spacing of the graphite and bismuth, it is able to store metals in ≈400 layers, allowing removal and recovery of >50 ppm lithium in only 5 min. A larger interlayer distance between bismuth sheets allows the removal of bigger cations (sodium and calcium), expanding the application of this method to a large variety of natural elements. Finally, magnetic navigation of charged swimmers to an oxygen-saturated media causes oxidation and thus immediate release of the metal ions from the swimmers.

Supercapacitors in Motion: Autonomous Microswimmers for Natural‐Resource Recovery

AbstractAn electroadsorption technique similar to the ultrafast charging mechanism in supercapacitors is utilized to remove metals with different sizes and hydrophilicities from contaminated water using self‐propelled microswimmers. The swimmers carry graphite fibre or bismuth with a layered crystal structure providing high electrostatic double‐layer capacitances. Unlike previous methods, this electrochemical technique does not only utilize the surface of the swimmers, but due to the interlayer spacing of the graphite and bismuth, it is able to store metals in ≈400 layers, allowing removal and recovery of &gt;50 ppm lithium in only 5 min. A larger interlayer distance between bismuth sheets allows the removal of bigger cations (sodium and calcium), expanding the application of this method to a large variety of natural elements. Finally, magnetic navigation of charged swimmers to an oxygen‐saturated media causes oxidation and thus immediate release of the metal ions from the swimmers.

Synergistic effects of reduced graphene oxide with freeze drying tuned interfacial structure on performance of transparent and flexible supercapacitors

Transparent and flexible supercapacitors (TFSCs) could diversify the future wearable electronics owing to the fascinating optoelectronic and electrochemical performances. Herein, we report symmetric TFSCs assembled by reduced graphene oxide (rGO)@Ag nanowire/poly (ethylene terephthalate) (PET) transparent electrodes for capacitive storage, in which the interfacial structure of rGO film can be tuned by a facile freeze drying technique. The enlarged interlayer spacing of rGO film deteriorated the electronic migration derived from the loose layer structure, whereas about 33–52% of the areal capacitance of TFSCs was boosted as compared with the ones without freeze drying at the same transmittance. It is concluded that the enlarged inter-distance of rGO film could facilitate diffusion and transport of ions in the electrolyte, furthermore, the expanded rGO film could provide more interface to accommodate more ions for storage. The simulation results also confirmed the lower diffusion barrier and larger band gap of rGO with larger interlayer distance. The mechanically robust TFSCs exhibit the maximum energy density of 89.2 nWh cm−2, and the maximum power density of 4.63 μW cm−2 with remaining energy density of 41.1 nWh cm−2, as well as 3000 cyclic stability, demonstrating an efficient strategy toward high performance TFSCs.