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Hard carbon is promising anode for potassium-ion batteries (PIBs), however, the poor rate capability hinders its development as potential anode. To address this question, we design a sulfur-doped porous hard carbon (S-HC) for PIBs through the combination of structural design and composition adjustment. The as-designed S-HC exhibits a long cycling life with ∼191 mA h/g after 300 cycles at 1 A/g, and an excellent rate capability with ∼100 mA h/g at 5 A/g, which was attributed to its structural characteristics and compositions. The S-HC demonstrates to be promising anode in the future.

One-dimensional nano-structured materials have attracted attention due to its unique properties afforded such as the across-linked structures and large aspect ratios. In this work, one-dimensional CoSe@N-doped carbon nanofibers (CoSe@NC NFs) are successfully by combining the techniques of electrospinning and annealing. Selenium powder are directly dispersed in the polyacrylonitrile /N,N-Dimethylformamide (DMF) solution containing cobalt salt to form the product. The performance of these materials was investigated in Li-ion batteries after the annealing at different temperatures. The CoSe@NC nanofibers annealed at 550 °C (CoSe@NC-550) and displayed excellent storage properties, affording a high capacity of 796 mAh·g−1 at a current density of 1 A·g−1 for 100 cycles. Moreover, it is confirmed that the pseudocapacitive contribution of CoSe@NC-550 is up to 72.8% at the scan rate of 1 mV/s through the cyclic voltammetry analysis.

As a promising material for sodium-ion batteries, molybdenum disulphide (MoS2) affords excellent electrochemical performance owing to its large surface area and the accelerated electron transport within individual layers. However, it suffers from slow reaction kinetics and agglomeration owing to low conductivity and high surface energy. In this work, nitrogen-doped carbon nanofiber@MoS2 nanosheets arrays with S-vacancies (NC@MoS2-VS) are developed via a process involving electrospining, hydrothermal and annealing. When served as an anode material for SIBs, this material displays a superior capacity of 495 mAh g−1 over 100 charge/discharge cycles at a current density of 100 mA g−1, and the pseudocapacitive contribution is up to 74.4% as revealed by the cyclic voltammogram (CV) at 1 mV s−1. The theoretical calculations show that the presence of sulfur vacancies facilitates the adsorption of Na+ and enhances the conductivity of MoS2. This work may pave a new avenue to develop other types of metal sulfides for high-performance SIBs.

The NASICON-type NaTi2(PO4)3 has drawn much attention as anode material for sodium-ion batteries owing to its stable structural characteristics and low cost. Nevertheless, the insulating property of NaTi2(PO4)3 and the high working potential of about 2.1 V vs. Na+/Na lead to its poor cycling stability, low rate performance as well as inferior capacity. In this work, we synthesize the porous NaTi2(PO4)3@C nanocubes by hydrothermal method and a subsequent coating process with using oleic acid as the carbon source. When utilized as the anode for sodium-ion battery in the voltage range between 0.01 V and 3.0 V, The as-synthesized porous NaTi2(PO4)3@C nanocubes deliver a discharge capacity of 201 mAh·g−1 at the current density of 100 mA g−1 after 100 cycles. Additionally, the reserved capacity of 140 mAh·g−1 could be achieved at the current density of 1 A g−1 after 1000 cycles.

MoO2@N-doped C nanofibers (MoO2@NC NFs) were synthesized by electrospinning with polyacrylonitrile as carbon source. The in situ formed MoO2 nanocrystals are completely embedded in the carbon nanofibers, which can not only accelerate ion transition, but also act as a buffer to avoid the mechanical degradation of active material due to the volume changes during charge/discharge cycling. When used as the anode material for both Li/Na-ion batteries, the as-synthesized MoO2@NC NFs displayed excellent Li+/Na+ storage properties. As the anode for Li-ion battery, the MoO2@NC NFs display a high discharge capacity of 930 mA h g−1 at a current density of 200 mA g−1 for 100 cycles, and 720 mA h g−1 at a current density of 1 A g−1 for 600 cycles. Moreover, the discharge capacity of 350 mA h g−1 could be realized at a current density of 100 mA g−1 for 200 cycles for Na-ion battery.

MnO@C nanocomposites are synthesized by annealing MnO microspheres treated with oleic acid as carbon source. The obtained MnO@C nanocomposites exhibit a discharge capacity of 1075 mAh/g for the initial cycle, and show the excellent cycling performance with a discharge capacity of 421 mAh/g after 100 cycles at a current density of 100 mA/g. The total specific capacity of MnO@C nanocomposites is higher than those of pure MnO microspheres in our experiments. Owing to the superior electrochemical behavior, the as-obtained MnO@C nanocomposites are potentially applied as next-generation anode material for lithium-ion batteries.

A three-dimensional flower-shaped iron molybdate microsphere (3D-FIMMS) and a zero-dimensional iron molybdate nanoparticle (0D-IMNP) were successfully synthesized by a rapid and environment friendly microwave irradiation method. The 3D-FIMMS crystal growth was investigated by changing the microwave heating time. The gas sensing performances of various morphologies of iron molybdate were studied. The results showed that 3D-FIMMS sensors exhibited excellent gas sensing properties compared with the 0D-IMNP sensors, in which response value reached 13.5 for 50 ppm H 2 S gas. Meanwhile, the 3D-FIMMS sensors displayed high selectivity to H 2 S. The experimental results indicated an efficient and eco-friendly approach to realize promising sensing performance to H 2 S gas.

NaTi2(PO4)3 has attracted great interest as anode material for sodium ion batteries owing to its open three-dimensional framework structure and almost unchanged volume during the charge and discharge process. However, the poor intrinsic electronic conductivity of NaTi2(PO4)3 still needs to be improved. In this work, porous NaTi2(PO4)3 nanocubes anchored on porous carbon nanosheets (NaTi2(PO4)3/C) are designed to improve the electrical conductivity. This material exhibit a large discharge capacity and good rate capacity: The first discharge capacity can reach 485 mAh g-1 at a current density of 0.1 A g-1; A capacity of 98 mAh g-1 can be retained at a high rate of 4 A g-1 even after 2,000 cycles. These results suggest that NaTi2(PO4)3/C is a promising anode material for sodium-ion batteries.

V2O5-decorated α-Fe2O3 composite nanorods were synthesized successfully by electrospinning and an environmentally-friendly soak-calcination method. The composite showed high selectivity and stability to diethylamine gas as well as ultra fast response times within 2 s to 100 ppm diethylamine gas.

SnSb alloys with high theoretical capacities for lithium-ion batteries always suffer from the quick capacity fading owing to their huge volume change. In this study, SnSb nanoparticles are fixed in the nanochannels of flexible mats composed of graphene, and multichannel porous carbon nanofiber mats which are prepared by electrospinning and subsequent thermal treatment at 700 °C in Ar/H 2 . The flexible mats can be bent for 180 degree without any crack and can be unfolded as usual. As binder-free anodes, the mats with suitable ratio of GO in precursor solution show discharge capacity of 617 mA h/g at 300th cycle at a current density of 100 mA/g, much higher than those similar nanofibers added with more or less GO. The flexible mats can deliver a rate capacity of 369 mA h/g at a current density of 2 A/g, also higher than those similar nanofibers. The electronic tests show that the graphene asrising from GO can linearly improve the conductivity of the mats. The enhanced properties of Sn x Sb-graphene-carbon flexible mats can be attributed to the improved conductivity and mechanical property due to the presence of graphene, the multichannels to accommodate the volume change of Sn x Sb during lithiation/delithiation, and carbon nanofiber mats to provide high-way and diffusion channels for electrons and ions. It is believed that the electrospinning method combined with graphene could be a useful approach to prepare flexible mats for supercapacitors, lithium-ion batteries, and fuel cells.

It is urgent to solve the problems of the dramatic volume expansion and pulverization of SnO2 anodes during cycling process in battery systems. To address this issue, we design a hybrid structure of N-doped carbon fibers@SnO2 nanoflowers (NC@SnO2) to overcome it in this work. The hybrid NC@SnO2 is synthesized through the hydrothermal growth of SnO2 nanoflowers on the surface of N-doped carbon fibers obtained by electrospinning. The NC is introduced not only to provide a support framework in guiding the growth of the SnO2 nanoflowers and prevent the flower-like structures from agglomeration, but also serve as a conductive network to accelerate electronic transmission along one-dimensional structure effectively. When the hybrid NC@SnO2 was served as anode, it exhibits a high discharge capacity of 750 mAh g−1 at 1 A g−1 after 100 cycles in Li-ion battery and 270 mAh g−1 at 100 mA g−1 for 100 cycles in Na-ion battery, respectively. Electronic supplementary material The online version of this article (10.1007/s40820-017-0172-2) contains supplementary material, which is available to authorized users.