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Abstract Searching for advanced anode materials with exceptional electrochemical performance is essential for next-generation rechargeable batteries. The selection and structural design of anode materials are pivotal in the development of high-performance batteries. Herein, we demonstrate the preparation of uniform NiCo 2 O 4 nanotubes via a simple and cost-effective electrospinning technique followed by calcination in the air. Impressively, the advantages and importance of NiCo 2 O 4 nanotubes as an anode in lithium-ion batteries (LIBs) is demonstrated, which surpass their respective monometallic oxides in terms of electrochemical performance. Encouragingly, the as-obtained NiCo 2 O 4 nanotubes as an anode for sodium-ion batteries (SIBs) exhibit appealing electrochemical performance, such as high initial discharge capacity (879 mAh g−1 at 100 mA g−1), good rate capability, and excellent cycling stability. Moreover, a reversible capacity of 420 mAh g−1 at a current density of 100 mA g−1 can be maintained even after 100 cycles, corresponding to around 72% of the second cycle discharge capacity (584 mAh g−1). It is worth noting that this facile technique may provide a feasible way for the preparation of other functional materials with tube-like architectures for application in energy-storage device. Graphical abstract An advanced NiCo 2 O 4 nanotubes anode has been successfully prepared through a simple and cost-effective electrospinning technique followed by calcination in air. The as-obtained NiCo 2 O 4 nanotubes exhibits appealing electrochemical performance, such as high initial discharge capacity, good rate capability, and excellent cycling stability. Image 1 Highlights • NiCo 2 O 4 nanotubes are prepared through an electrospinning technique. • The NiCo 2 O 4 nanotubes surpass their respective monometallic oxides in terms of electrochemical performance in LIBs. • The NiCo 2 O 4 nanotubes as anode for SIBs present excellent electrochemical properties. • The electrospinning technique can be extended to prepare other functional materials in energy-storage devices. [ABSTRACT FROM AUTHOR]

Ni xZn1− xFe2O4 ( x=0, 0.25, 0.5, 0.75, 1) compounds were prepared by a hydrothermal method and subsequent heat treatment. The physical characteristics of the samples were investigated by field-emission SEM, XRD, X-ray photoelectron spectroscopy, and TEM. The electrochemical properties of Ni xZn1− xFe2O4 ( x=0, 0.25, 0.5, 0.75, 1) as anode materials were tested for lithium-ion batteries. The lithium-storage properties of the electrodes were assessed by cyclic voltammetry and galvanostatic cycling. Among the five samples, Ni0.25Zn0.75Fe2O4 shows good electrochemical performance with a discharge capacity of 1488 mAh g−1 in the initial cycle and 856 mAh g−1 after 100 cycles. [ABSTRACT FROM AUTHOR]

Single-phase Na1.2V3O8 materials with single and hierarchical nanobelt morphologies were prepared by using a versatile electrospinning technique by altering the sintering profiles. On the basis of characterization by field-emission scanning electron microscopy and high-resolution transmission electron microscopy, the formation mechanisms of products with tunable morphologies are discussed. The products obtained are employed as cathode materials for lithium-ion batteries. Their electrochemical activities are demonstrated through galvanostatic cycling and cyclic voltammetry. The non-agglomerated, single nanobelts with exposed (100) facets, which serve as channels for facile lithium diffusion, are capable of exhibiting higher maximum capacities of approximately 218 mAh g−1 compared to hierarchical nanobelts with a maximum capacity of approximately 197 mAh g−1 versus Li/Li+ at a current density of 200 mA g−1. Their associated reversible capacities are approximately 207 and 173 mAh g−1, respectively, after 100 cycles. Single nanobelts with individual belt-like structures and preferred facet orientation also exhibit better rate capabilities. [ABSTRACT FROM AUTHOR]

Hierarchical CaCo2O4 nanofibers (denoted as CCO-NFs) with a unique hierarchical structure have been prepared by a facile electrospinning method and subsequent calcination in air. The as-prepared CCO-NFs are composed of well-defined ultrathin nanoplates that arrange themselves in an oriented manner to form one-dimensional (1D) hierarchical structures. The controllable formation process and possible formation mechanism are also discussed. Moreover, as a demonstration of the functional properties of such hierarchical architecture, the 1D hierarchical CCO-NFs were investigated as materials for lithium-ion batteries (LIBs) anode; they not only delivers a high reversible capacity of 650 mAh g−1 at a current of 100 mA g−1 and with 99.6 % capacity retention over 60 cycles, but they also show excellent rate capability with respect to counterpart nanoplates-in-nanofibers and nanoplates. The high specific surface areas as well as the unique feature of hierarchical structures are probably responsible for the enhanced electrochemical performance. Considering their facile preparation and good lithium storage properties, 1D hierarchical CCO-NFs will hold promise in practical LIBs. [ABSTRACT FROM AUTHOR]

Core-shelled NiFe 2 O 4 /NiO@Fe 2 O 3 nanocubes were synthesized based on Prussian blue analogues. The core-shelled structure was built through ion-exchange process in aqueous solution, and was remained after calcination. Different concentrations of ferrous affect the size and surface states of PBA precursors and its successor. Fabricated core-shelled NiFe 2 O 4 /NiO@Fe 2 O 3 nanocubes produced with the PBA precursor that soaked in the solution of ferrous ion with the highest concentration in this work appears the most stable capacity during cycles, because of its more homogeneous Fe 2 O 3 layer surface and more complete crystal. At the current density of 100 mA/g, it offers an initial capacity of 1587.96 mA h/g, and the second capacity of 967.91 mA h/g, that was remained as 806.1 mA h/g after 50 cyles. At 500 mA/g, it performs a capacity of 472.5 mA h/g after 500 cycles with a strong stability. • Core-shelled structure is built through ion exchange process. • Ion concentrations in ion exchange process sever different surfaces. • Complete Fe 2 O 3 shell layer permits more stability during cycling. • Suitable calcined temperature is detected for high performance material. [ABSTRACT FROM AUTHOR]

A facile two-step method is developed to synthesize three dimensional (3D) hierarchical CaCo 2 O 4 architectures as high-performance electrode materials for lithium ion batteries (LIBs) and oxygen evolution reaction (OER). Our strategy involves a simple poly(vinylpyrolidone) (PVP)-assisted hydrothermal route and subsequent thermal treatment to produce flowerlike CaCo 2 O 4 nanostructures with a size of ∼500 nm, which is constructed by some neighboring vertical nanoplates. Whereas, the absence of PVP results in the formation of CaCo 2 O 4 microspheres, further indicating the vital role of PVP in favor of the oriented crystal growth of Co-based oxides. Benefited from the unique structural features, the resultant CaCo 2 O 4 nanoflower presents excellent cycling stability (∼560 mAh g−1 after 100 cycles at 50 mA g−1) and remarkable rate capability. Apart from superior lithium storage properties, more strikingly, CaCo 2 O 4 nanoflower demonstrates a promising candidate as a noble metal-free electrocatalyst for oxygen evolution reaction, which will spur us to find more novel functional nanomaterials for wide applications. • 3D hierarchical CaCo 2 O 4 architectures have been synthesized. • CaCo 2 O 4 nanoflower presents high lithium-storage performance. • CaCo 2 O 4 nanoflower presents high oxygen evolution reaction performance. [ABSTRACT FROM AUTHOR]

Flexible and highly conductive single-walled carbon nanotube/polycellulose papers (SWCNT/PPs) were developed as current collectors for lithium-ion batteries by a simple and scalable process. The flexible electrodes based on SWCNT/PP conductors consisted of a unique three-dimensional interwoven structure of electrode materials and cellulose fibers with CNTs and exhibited flexibility, good electrochemical performance and excellent cyclic stability. Full cells using Li4Ti5O12 and LiFePO4 electrodes based on SWCNT/PPs showed a first discharge capacity of 153.5 mA h g−1 with Coulombic efficiencies of 90.6% at 0.1 C and discharge capacity of 102.6 mA h g−1 at high rate (10 C). Full cells based SWCNT/PP conductors showed higher capacities and lower electrochemical interfacial resistance compared to metallic current collectors. Half cells using anatase TiO2 hierarchical spheres based on SWCNT/PP conductors also exhibited outstanding electrochemical performance, verifying the stability of SWCNT/PP conductors to various electrode materials. Our results demonstrated the potential versatility of composite electrodes and conductive SWCNT/PPs for flexible and portable micropower devices. [ABSTRACT FROM AUTHOR]

Sodium-ion batteries are considered a top alternative to lithium-ion batteries for large-scale renewable energy storage units due to their low cost and the abundance of sodium-bearing precursors in the earth's mineral deposits. However, the absence of a suitable negative electrode material hinders their development. In this contribution, we report the preparation of nitrogen and phosphorous co-doped carbon microspheres through a hydrothermal process followed by heat treatment in presence of (NH 4 ) 2 HPO 4 and investigate their electrochemical performance as anode in sodium-ion batteries. Benefiting from the N, P co-doping, the obtained N, P co-doped carbon microspheres demonstrates high specific capacity, excellent cycle stability as well as good rate performance. The as prepared N, P co-doped carbon microspheres can deliver a reversible capacity of 305 mAh g −1 at a current density of 0.1 A g −1 and even deliver a capacity of 136 mAh g −1 at 5 A g −1 . This superior sodium storage performance of N, P co-doped carbon makes it as a promising low-cost anode candidate for sodium-ion batteries. [ABSTRACT FROM AUTHOR]

Silicon/lithium titanate (Si/Li 2 TiO 3 ) nanocomposite is successfully prepared through the combination of a sol–gel approach with a high-temperature treatment as well as a high energy ball milling process. The structure and morphology of the composite are characterized by the X-ray diffraction (XRD), scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM) analysis reveals Si particles are coated by the uniform disordered Li 2 TiO 3 layer with a thickness of about 5 nm. The investigation in cycling performances demonstrates that Si/Li 2 TiO 3 exhibits the improved cycling stability, with specific capacity of 471.0 mA h g −1 after 50 cycles and the capacity retention is 31.5%, much higher than pure Si. Compared with pure Si, Si/Li 2 TiO 3 shows better rate-capability, a reversible capacity of 315.2 mA h g −1 at 0.8 A g −1 is maintained. The higher ionic conductivity of Li 2 TiO 3 is responsible for the improved rate performance. In addition, the results derived from XRD, the cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) indicate that lithium ions could react reversibly with Si, and electrochemically less active Li 2 TiO 3 turns into the Li–Ti–O ternary phase, which acts as a buffer matrix in the Si/Li 2 TiO 3 composite, thus improving the reversibility of electrode. [ABSTRACT FROM AUTHOR]

• Silicon is obtained from photovoltaic industrial waste through simple purification. • N-doped carbon ensures fast charge transfer and structural stabilization. • Si/NC electrode has a high specific capacity both in half-cell and full-cell. Silicon (Si) is considered to be one of the most promising anode materials for the next generation of lithium-ion batteries (LIBs). However, the practical application of Si anode is still high cost and hindered by huge volume change. It is significant to produce high-performance Si anode of LIBs inexpensively. Herein, we report the Si/N-doped carbon (Si/NC) composite anode materials constructed by recycling Si waste from the photovoltaic industry as raw materials after simple purification and polydopamine (PDA)-derived carbon coating. The Si micro/nano-plates coated with the NC can facilitate electron transfer and inhibit the volume expansion of Si to stabilize the structure of composites. The resulting Si/NC electrode exhibits a high discharge capacity of 1139 mAh g−1 at 1 A g−1 over 200 cycles. Moreover, the full-cell (LiFePO 4 //Si/NC) presents excellent cycling performance (108 mAh g−1 at 0.5 A g−1 over 200 cycles). This work not only offers a reasonable solution for the acquirement of Si anode from the photovoltaic industry but also provides a new strategy for the preparation of anodes for the next generation of LIBs, which may bring great economic benefits. [ABSTRACT FROM AUTHOR]

The as-prepared binder-free Co 1−x S/MCF anode exhibits the desirable electrochemical performance for LIBs and SIBs, which can be attributed to the unique hierarchical nanostructure which provides enough active sites and internal space for volume expansion. [Display omitted] • The flexible Co 1−x S/MCF electrode is prepared via the electrospinning technique. • The Co 1−x S/MCF presents hierarchically hollow and multichannel structures. • The Co 1−x S/MCF electrode can effectively ease the huge volume expansion. • The Co 1−x S/MCF electrode shows high electrochemical performance for LIBs and SIBs. The exploration of prospective electrode materials represents great challenges for remarkable lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs). Herein, we report a reliable synthetic approach for the in-situ growth of the Co-based zeolitic imidazolate framework (ZIF-67) on electrospun nanofibers, followed by carbonization and sulfurization with the formation of free-standing Co 1−x S hollow polyhedrons anchored on multichannel carbon nanofibers (Co 1−x S/MCF) for LIBs and SIBs. The Co 1−x S/MCF electrode displays a high reversible capacity (813 mAh g−1 over 180 cycles at 0.1 A g−1), and stable cycle performance (559 mAh g−1 for 300 cycles at 1 A g−1) in LIBs. For SIBs, Co 1−x S/MCF electrode exhibits a favorable Na-storage capacity (433 mAh g−1 over 120 cycles at 0.1 A g−1). The as-prepared binder-free Co 1−x S/MCF anode demonstrates the advanced electrochemical properties for LIBs and SIBs. It is attributed to the particular multichannel nanostructure and the Co 1−x S hollow polyhedrons (Co 1−x S HPs), which provide enough active sites, and the internal void space effectively reduces the structural strain and eases the volume expansion to maintain structural integrity. This work gives insights to design a unique structure for promising LIBs and SIBs. [ABSTRACT FROM AUTHOR]