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Aqueous lithium‐ion batteries (ALIBs) have attracted extensive interest since the safety problems of traditional lithium‐ion batteries are waived. Although the energy density of ALIBs is improved, their rate capability and power density are still poor due to the slow Li+ diffusivity of the existing anode materials, and their cyclic stability is also poor. Here, W7Nb4O31 nanorods with very fast‐ and stable‐charging capability are explored as a new anode material for ALIBs for the first time. This material owns different tetragonal tungsten bronze (TTB) structures together with 4 × 4 ReO3‐type blocks confined by TTB matrices, allowing abundant pentagonal and quadrangular tunnels for Li+ transport. These large‐sized tunnels combine with the large interlayer spacing (≈3.95 Å) not only lead to extremely fast Li+ diffusivity but also small unit‐cell volume variations (maximum 2.1%) during lithiation/delithiation, thereby enabling the LiMn2O4//W7Nb4O31 full cell to possess excellent rate capability with a 50C versus 1C capacity ratio of 68.3%, ultrahigh power density of 9854 W kg–1, and superior cyclic stability with capacity retention of 89.7/66.7/72.0% at 1C/5C/50C over 1000/10 000/10 000 cycles. This comprehensive study demonstrates that the W7Nb4O31 nanorods are highly promising for fast‐ and stable‐charging ALIBs. [ABSTRACT FROM AUTHOR]

Two-dimensional molybdenum disulfide (MoS2) is considered as a highly promising anode material for lithium-ion batteries (LIBs) due to its unique layer structure, large plane spacing, and high theoretical specific capacity; however, the overlap of MoS2 nanosheets and inherently low electrical conductivity lead to rapid capacity decay, resulting in poor cycling stability and low multiplicative performance. This severely limits its practical application in LIBs. To overcome the above problems, composite fibers with a core//sheath structure have been designed and fabricated. The sheath moiety of MoS2 nanosheets is uniformly anchored by the hydrothermal treatment of the axial of carbon nanofibers derived from an electrospinning method (CNFs//MoS2). The quantity of the MoS2 nanosheets on the CNFs substrates can be tuned by controlling the amount of utilized thiourea precursor. The influence of the MoS2 nanosheets on the electrochemical properties of the composite fibers has been investigated. The synergistic effect between MoS2 and carbon nanofibers can enhance their electrical conductivity and ionic reversibility as an anode for LIBs. The composite fibers deliver a high reversible capacity of 866.5 mA h g−1 after 200 cycles at a current density of 0.5 A g−1 and maintain a capacity of 703.3 mA h g−1 after a long cycle of 500 charge–discharge processes at 1 A g−1. [ABSTRACT FROM AUTHOR]

Niobates are very promising anode materials for Li+-storage rooted in their good safety and high capacities. However, the exploration of niobate anode materials is still insufficient. In this work, we explore ~1 wt% carbon-coated CuNb13O33 microparticles (C-CuNb13O33) with a stable shear ReO3 structure as a new anode material to store Li+. C-CuNb13O33 delivers a safe operation potential (~1.54 V), high reversible capacity of 244 mAh g−1, and high initial-cycle Coulombic efficiency of 90.4% at 0.1C. Its fast Li+ transport is systematically confirmed through galvanostatic intermittent titration technique and cyclic voltammetry, which reveal an ultra-high average Li+ diffusion coefficient (~5 × 10–11 cm2 s−1), significantly contributing to its excellent rate capability with capacity retention of 69.4%/59.9% at 10C/20C relative to 0.5C. An in-situ XRD test is performed to analyze crystal-structural evolutions of C-CuNb13O33 during lithiation/delithiation, demonstrating its intercalation-type Li+-storage mechanism with small unit-cell-volume variations, which results in its capacity retention of 86.2%/92.3% at 10C/20C after 3000 cycles. These comprehensively good electrochemical properties indicate that C-CuNb13O33 is a practical anode material for high-performance energy-storage applications. [ABSTRACT FROM AUTHOR]

In this study, a facile method is developed for preparing porous microspheres of lithium titanate (Li4Ti5O12 [LTO]) nanocrystals for use as anode materials of lithium-ion batteries (LIBs). Spray drying combined with solid-state calcination have been applied for the preparation. A sol of TiO2 nanoparticles of several nanometers has been obtained through the quaternary-ammonium-hydroxide-assisted sol–gel process. TiO2 sol is used as a precursor for LTO to ensure a stable mixture of a TiO2 sol with the LiOH aqueous solution, which is crucial for spray drying. Microspheres of 0.5 and 3 μm consisting of LTO nanocrystals of approximately 200 nm are obtained by calcining the spray drying samples. The phase, composition, microstructure, porosity, and electrochemical properties of the obtained samples are investigated. When used as an anode material for LIBs, LTO microspheres exhibit a reversible capacity of 174.7 mAhg−1 at 0.1 C and an excellent cycling stability with capacity retention of 98.6% after 100 cycles at 1 C rate. Furthermore, a remarkable rate capacity of 57.8% is retained at 20 C (vs 0.1 C). [ABSTRACT FROM AUTHOR]

Li4Ti5O12 (LTO) is the most famous Li+‐storage anode material with fast‐ and stable‐charging capability, but suffers from several disadvantages, such as poor electron conduction, low energy density, and disappointing high‐temperature performance. Here, LaCeNb6O18 (LCNO) micrometer‐sized particles are explored as a fast‐ and stable‐charging anode material superior to LTO sub‐micrometer‐sized particles in terms of the working potential, rate capability, and high‐temperature performance. The conductive Ce3+ and Nb5+↔Nb3+ reactions in LCNO, respectively, enable its significantly larger electronic conductivity and lower working potential than those of LTO. LCNO owns a very open A‐site‐cation‐deficient perovskite structure, in which (vacancy/La/Ce)O12 layers with electrochemical inactivity and superior volume‐buffering capability locate between active NbO6 layers, leading to not only fast Li+ diffusivity but also low‐ and negative‐strain behavior at different temperatures. At 25 °C, LCNO exhibits higher rate capability (50 vs 0.1 C capacity ratio of 67.9%) than that of LTO, and excellent cyclability. At 60 °C, LCNO maintains excellent cyclability, and achieves larger reversible capacity and even higher rate capability, whereas the high temperature lowers all the electrochemical properties of LTO. Therefore, LCNO holds great promise for fast‐ and stable‐charging applications in a wide temperature range, even when its particle sizes are on the order of micrometers. [ABSTRACT FROM AUTHOR]

The application of Fe3O4 as anode material for lithium‐ion batteries is hindered by the capacity fade owing to its enormous volume expansion and the inherent low conductivity. Herein, carbon‐encapsulated Fe3O4 nanospheres anchored on carbon nanotubes (Fe3O4/CNTs@C) have been successfully fabricated. The obtained Fe3O4/CNTs@C composites show that numerous Fe3O4 nanospheres are held and connected by the CNT network, forming a composite of porous three‐dimensional structure. The unique structure improves the conductivity and structural stability of the Fe3O4/CNTs@C composite. The encapsulation with carbon enhances the contact between Fe3O4 nanospheres and carbon nanotubes and shortens the ion‐transport path. As a result, the Fe3O4/CNTs@C delivers a high capacity of 612 mA h g−1 at 1 A g−1, even after 200 cycles, and shows a superior rate performance of 523 mA h g−1 at 5 A g−1. This work provides a preparation strategy that could be easily applied to other functional materials for energy storage and/or catalysis. [ABSTRACT FROM AUTHOR]

Abstract Three-dimensional porous SnO 2 /rGO hollow spheres with abundant internal void space were designed to resolve the volume expansion problem of SnO 2 -based anode materials for sodium-ion batteries. The unique hollow spheres with a porous wall of SnO 2 decorated GO sheets were realized by a facile spray drying method. Nanosized SnO 2 particles, which uniformly anchored on graphene sheets, in situ formed at the hydrolysis stage. Ethanol was used as porosity tuning agent to achieve template free pore-forming. The hollow spheres of porous SnO 2 /rGO composite show superior sodium storage performance with large specific capacity, remarkable cycling stability and excellent rate capability. The as-prepared SnO 2 /rGO composite delivered a high initial discharge capacity of 821.6 mA h g−1 at 200 mA g−1, and even after 1500 charge/discharge cycles a discharge capacity of 204 mA h g−1 still can be obtained. The SnO 2 /rGO composite achieved a capacity of 213.1 mA h g−1 at 500 mA g−1 after 500 cycles. And maintained an enhanced rate capability of 231 mA h g−1 at 2000 mA g−1. The excellent cyclability and high-rate capability of the composite can be ascribed to its unique hollow/porous architecture and the synergistic effect between SnO 2 nanoparticles and the conductive matrix of rGOs. Graphical abstract Schematic illustration of the procedure for the synthesis of the SnO 2 /rGO composites (A). TEM image of Sn(OH) 4 nanoparticles decorated GO sheets (B). SEM image of Sn(OH) 4 microsphere (C). SEM image of SnO 2 /rGO microsphere (D). 3D Porous SnO 2 /rGO hollow spheres with abundant internal void space were prepared by a facile spray drying method. The unique hollow spheres with a porous wall of SnO 2 decorated GO sheets can efficiently resolve the volume expansion problem of SnO 2 -based anode materials for sodium-ion batteries. The as-prepared SnO 2 /rGO composites exhibited a high reversible capacity, a long cycle life and a good rate capability when used as anode for sodium-ion batteries. Unlabelled Image Highlights • 3D Porous SnO 2 /rGO hollow spheres with abundant internal void space were prepared by a facile spray drying method. • Nanosized SnO 2 particles, which uniformly anchored on graphene sheets, in situ formed at the hydrolysis stage. • Ethanol was used as porosity tuning agent to achieve template-free pore forming. • The 3D hollow spheres of porous SnO 2 /rGO composite show superior sodium storage performance. [ABSTRACT FROM AUTHOR]

A one-step high-temperature solvothermal approach to the synthesis of monolayer or bilayer MoS2 anchored onto reduced graphene oxide (RGO) sheet (denoted as MoS2/RGO) is described. It was found that single-layered or double-layered MoS2 were synthesized directly without an extra exfoliation step and well dispersed on the surface of crumpled RGO sheets with random orientation. The prepared MoS2/RGO composites delivered a high reversible capacity of 900 mAhg − 1 after 200 cycles at a current density of 200 mAg − 1 as well as good rate capability as anode active material for lithium ion batteries. This one-step high-temperature hydrothermal strategy provides a simple, cost-effective and eco-friendly way to the fabrication of exfoliated MoS2 layers deposited onto RGO sheets. Monolayer or bilayer MoS2 anchored onto reduced graphene oxide (RGO) sheet (denoted as MoS2/RGO) has been successfully fabricated by a one-step high-temperature solvothermal approach up to 350∘C. The as-synthesized MoS2/RGO composites delivered a high reversible capacity of 900 mAhg−1 after 200 cycles at a current density of 200 mAg−1 as well as good rate capability as anode active material for lithium ion batteries. [ABSTRACT FROM AUTHOR]

Ni3S2 nanocrystals wrapped by thin carbon layer and anchored on the sheets of reduced graphene oxide (Ni3S2@C/RGO) have been synthesized by a spray-coagulation assisted hydrothermal method and combined with a calcination process. Cellulose, dissolved in Thiourea/NaOH aqueous solution is chosen as carbon sources and mixed with graphene oxide via a spray-coagulation method using graphene suspension as coagulation bath. The resulted cellulose/graphene suspension is utilized as solvent for dissolving of Ni(NO3)2 and then used as raw materials for hydrothermal preparation of the Ni3S2@C/RGO composites. The structure of the composites has been investigated and their electrochemical properties are evaluated as anode material for lithium-ion batteries. The Ni3S2@C/RGO sample exhibits increasing reversible capacities upon cycles and shows a superior rate performance as well. Such kinds of promising performance have been ascribed to the wrapping effect of carbon layer which confines the dislocation of the polycrystals formed upon cycles and the enhanced conductivity as the integration of RGO conductive substrate. Discharge capacities up to 850 and 630 mAh·g−1 at current densities of 200 and 5000 mA·g−1, respectively, are obtained. The evolution of electrochemical performance of the composites with structure variation of the encapsulated Ni3S2 nanocrystals has been revealed by ex-situ TEM and XRD measurements. [ABSTRACT FROM AUTHOR]

[Display omitted] • Flexible microspheres consisting of Si nanoparticles, CNTs and amorphous carbon are prepared. • The mass producible spray-drying method is used for building the stable composite microspheres. • The carbon nanotubes and amorphous carbon act as conductive pathway and relieve internal stresses. • The interpenetrating structure improves the performance of Si nanoparticles as anode materials. The huge volumetric expansion (> 300 %) of Si that occurs during the charge–discharge process makes it to have poor cycling ability and weak stable structure. These factors are considered as critical obstacles to the further development of Si as anode for lithium-ion batteries (LIBs). Herein, novel 3D interpenetrating microspheres, i.e., Si@C-CNTs, which consist of silicon nanoparticles interpenetrated with carbon nanotubes (CNTs) and stuck with amorphous carbon (C) have been designed and prepared via a spray-drying assisted approach. As anode of LIBs, Si@C-CNTs microspheres can achieve high silicon loadings of around 86 % and a high initial coulomb efficiency of 80.8 %. The electrodes maintain a reversible specific capacity of 1585.9mAh/g at 500 mA g−1 after 200 cycles, and deliver an excellent rate capability of 756.4 mAh/g at 5 A g−1. The outstanding performance of Si@C-CNTs can be due to their 3D interpenetrating structure and the synergy effect between the CNTs network and amorphous carbon therein. They synergistically act as conductive matrices which significantly improve the conductivity of the composite; they also act binders and reinforcing skeleton which help the composite spheres to have stable structure. Especially, the latter (reinforcing skeleton) alleviates the volumetric effect induced by the expansion and shrinkage of silicon particles during lithiation. The unique architecture provides an ideal model that can be used to design Si-based composite anode for advanced LIBs. [ABSTRACT FROM AUTHOR]

Electrospinning has been used as a convenient technology to produce high-energy and self-standing anodes for lithium-ion batteries (LIBs) by encapsulating silicon nanoparticles (Si/NPs) into carbon nanofibers (CNF). However, the inhomogeneous distribution of Si/NPs in CNF results in low coulombic efficiency, rapid capacity decay and slow kinetics during cycling process which hinder the practical application of this promising composite anode. In this work, a principle of universal design is applied to the manufacture of Si-CNF composites, in this way, a self-standing electrode with homogeneous distribution of Si/NPs in CNF (Si//PCNF-15) is developed by introducing triblock copolymer Pluronic P123 (polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer) as dispersant and pore directing agent. As anode of LIBs, the Si//PCNF-15 exhibits outstanding electrochemical performance and considerable flexibility due to the homogeneous dispersion of Si nanoparticles and high graphitization of the carbon network. As results, a specific capacity of 1074.8 mAh g−1 at 0.3 A g−1 and a rate capacity of 236.1 mAh g−1 at 10 A g−1 have been delivered when it is explored as a self-standing anode for LIBs. This work provides a universal approach for developing self-standing anodes of composite fibers with nanoparticles dispersed homogeneously in CNF. [Display omitted] • Composite fibers of carbon encapsulated Si nanoparticles are got by electrospinning. • P123 surfactant play dual-role as Si dispersant and pore director of carbon nanofibers. • Even dispersion of Si nanoparticles and formation of mesopores are achieved by P123. • The composite is used as self-standing anode for high-performance lithium-ion battery. [ABSTRACT FROM AUTHOR]

• A facile annealing-followed solvothermal process was developed to prepare size controllable Co 3 O 4 cubes. • Diverse morphologies from microflowers to cubes can be acquired by reconciling the mass of precursors. • The sample of CC-3 exhibits high discharge capacity and cycling stability as anode both for LIBs and SIBs. C-doped Co 3 O 4 assemblies with porous character and morphologies from microflowers to cubes have been obtained by an annealing-followed solvothermal strategy. These features can achieve fast ion/electron transport and structural integrity upon repeated ion insertion/extraction. As a consequence, the porous Co 3 O 4 superstructure exhibits high discharge capacity and long-life cycling stability both as anode for LIBs and SIBs. Furthermore, the electrode shows excellent electrochemical performance when used as anode for full cell of SIBs as well. [Display omitted] Co 3 O 4 microflowers and size controllable porous cubes are synthesized through a facile solvothermal process followed by annealing. The Co 3 O 4 microflowers and porous cubes range in size from 3 to 10 µm, which consist of Co 3 O 4 particles of a few tens of nanometers, can be obtained by adjusting the amount of urea precursor during the preparation. The porous structure of Co 3 O 4 cubes can provide abundant diffusion paths for lithium or sodium ions and void space to accommodate volume variation during the repeated ion insertion/extraction process significantly. In addition, the uniform carbon-doping could effectively enhance the conductivity of the composites. As a result, the CC-3 sample exhibits a high specific capacity of 539.2 mAh g−1 after 500 cycles at a current density of 1000 mA g−1 as an anode for LIBs and 176.1 mAh g−1 after 1000 cycles at 2000 mA g−1 for SIBs. Meanwhile, the sample delivers an excellent cycle performance of 130.2 mAh g−1 after 160 cycles at 500 mA g−1 when used as an anode for the full cell of a sodium-ion battery. The superior electrochemical performance can be attributed to the unique cube shape with a porous structure, appropriate sample size, and carbon-doping, which have been discussed based on the morphology, construction, phase, and electrochemical properties. [ABSTRACT FROM AUTHOR]

Hierarchically structured microspheres consisting of carbon coated porous silicon have been prepared by a spray drying assisted magnesiothermic reduction using gelatin as carbon precursor and SiO 2 as silicon source. Gelatin is deposited on the surface of SiO 2 nanospheres during spray drying, which plays also as binder in assembling SiO 2 nanospheres to form the microspheres. After the magnesiothermic reduction, gelatin is carbonized and deposited in-situ on the surface of nanospheres and porous silicon nanospheres wrapped with a carbon layer are derived. The thickness of carbon coating and the porosity of obtained Si/C composite nanospheres can be modified by tuning the content of gelatin in the suspension. Two desired purposes, i.e. downsizing of Si particles and in-situ carbon coating of the nanoparticles have been achieved by this preparation. The resulted Si/C composite microspheres show superior electrochemical performance and high structure stability as anode materials for Li-ion batteries. An initial reversible capacity of 1638 mAh g−1 and excellent capacity retention of 523 mAh g−1 after 300 cycles can be achieved at a current density of 200 mA g−1. The formation mechanism of the hierarchically structured microspheres and the variation of porosity for the individual Si nanospheres have been investigated and discussed in details. Image 1 [ABSTRACT FROM AUTHOR]