Multicomponent Copper-Zinc Alloy Layer Enabling Ultra-Stable Zinc Metal Anode of Aqueous Zn-ion Battery.

Constructing stable surface modification layer is an effective strategy to suppress dendrite growth and side reactions of Zinc (Zn) metal anode in aqueous Zn-ion battery. Herein, a multicomponent Cu-Zn alloy interlayer with superior Zn affinity, high toughness and effective inhibition effect on lattice distortion is constructed on Zn foil (Cu-Zn@Zn) to fabricate ultra-stable Zn metal anode. Owning to the advantages of high binding energy of Cu-Zn alloy layer with Zn atoms and less contact area between metallic Zn and electrolyte, the as-prepared Cu-Zn@Zn electrode not only restricts the aggregation of Zn atoms, but also suppresses the pernicious hydrogen evolution and corrosion, leading to homogeneous Zn deposition and outstanding electrochemical performances. Accordingly, the symmetric battery with Cu-Zn@Zn electrode exhibits an ultra-long cycle life of 5496 h at 1 mA cm-2 for 1 mAh cm-2 , and the Cu-Zn@Zn//V2 O5 pouch cell demonstrates excellent cycling stability with a capacity retention of 88 % after 600 cycles.

Enabling Multi-Chemisorption Sites on Carbon Nanofibers Cathodes by an In-situ Exfoliation Strategy for High-Performance Zn-Ion Hybrid Capacitors.

Carbon nanofibers films are typical flexible electrode in the field of energy storage, but their application in Zinc-ion hybrid capacitors (ZIHCs) is limited by the low energy density due to the lack of active adsorption sites. In this work, an in-situ exfoliation strategy is reported to modulate the chemisorption sites of carbon nanofibers by high pyridine/pyrrole nitrogen doping and carbonyl functionalization. The experimental results and theoretical calculations indicate that the highly electronegative pyridine/pyrrole nitrogen dopants can not only greatly reduce the binding energy between carbonyl group and Zn2+ by inducing charge delocalization of the carbonyl group, but also promote the adsorption of Zn2+ by bonding with the carbonyl group to form N-Zn-O bond. Benefit from the multiple highly active chemisorption sites generated by the synergy between carbonyl groups and pyridine/pyrrole nitrogen atoms, the resulting carbon nanofibers film cathode displays a high energy density, an ultralong-term lifespan, and excellent capacity reservation under commercial mass loading (14.45 mg cm‒2). Particularly, the cathodes can also operate stably in flexible or quasi-solid devices, indicating its application potential in flexible electronic products. This work established a universal method to solve the bottleneck problem of insufficient active adsorption sites of carbon-based ZIHCs.Imoproved should be changed into Improved.

Flexible Sb-graphene-carbon nanofibers as binder-free anodes for potassium-ion batteries with enhanced properties.

Potassium-ion batteries (KIBs) are emerging as attractive alternatives to lithium-ion batteries for the large scale energy storage and conversion systems, in view of the natural abundance and low cost of potassium resources. However, the lack of applicable anodes for reversible accommodation to the large K+ limits the application of KIBs. Herein, porous Sb-graphene-carbon (Sb-G-C) nanofibers are fabricated via a scalable and facile electrospinning approach. As an attempt, the nanofibers weaving into flexible mats are introduced as binder-free anode materials of KIBs, presenting a great cycle life (204.95 mAh g-1 after 100 cycles at 100 mA g-1), as well as the excellent rate capability (120.83 mAh g-1 at 1 A g-1). The superior performances of the Sb-G-C anodes can be derived from the dispersed graphene, which offers enhanced tolerance to the volume change and promotes the electron transportation, accounting for the outstanding cyclability and rate capability. Furthermore, the extrinsic pseudocapacitance created from the 1D porous nanostructure of the Sb-G-C also boosts the K+ storage capacity. The presented results may pave a new pathway for future high-performance KIBs.

Sulfur-Rich (NH4)2Mo3S13 as a Highly Reversible Anode for Sodium/Potassium-Ion Batteries.

Sodium-ion batteries (SIBs) and potassium-ion batteries (PIBs) have attracted much attention owing to the inexpensive Na/K metal and satisfactory performance. Currently, there are still difficulties in research anode materials that can insert/extract Na/K ions quickly and stably. Herein, the sulfur-rich (NH4)2Mo3S13 is proposed as the anode for SIBs/PIBs and is obtained by a hydrothermal method. The sulfur-rich (NH4)2Mo3S13 with a three-dimensional structure shows a high capacity and long lifespans for Na+ (at 10 A g-1 the capacity of 165.2 mAh g-1 after 1100 cycles) and K+ (120.7 mAh g-1 at 1 A g-1 retained after 500 cycles) storage. In addition, the (NH4)2Mo3S13 electrode exhibits excellent electrochemical performance at low temperatures (0 °C). The mechanism of Na+ storage in (NH4)2Mo3S13 can be innovatively revealed through the combined use of electrochemical kinetic analysis and a series of ex situ characterization tests. It is believed that the present work identifies (NH4)2Mo3S13 as a promising anode for the SIBs/PIBs and will be of broad interest in research on engineering sulfur-rich transition metal sulfide and on energy storage devices.

Three-Dimensional Self-assembled Hairball-Like VS4 as High-Capacity Anodes for Sodium-Ion Batteries.

Sodium-ion batteries (SIBs) are considered to be attractive candidates for large-scale energy storage systems because of their rich earth abundance and consistent performance. However, there are still challenges in developing desirable anode materials that can accommodate rapid and stable insertion/extraction of Na+ and can exhibit excellent electrochemical performance. Herein, the self-assembled hairball-like VS4 as anodes of SIBs exhibits high discharge capacity (660 and 589 mAh g-1 at 1 and 3 A g-1, respectively) and excellent rate property (about 100% retention at 10 and 20 A g-1 after 1000 cycles) at room temperature. Moreover, the VS4 can also exhibit 591 mAh g-1 at 1 A g-1 after 600 cycles at 0 °C. An unlike traditional mechanism of VS4 for Na+ storage was proposed according to the dates of ex situ characterization, cyclic voltammetry, and electrochemical kinetic analysis. The capacities of the final stabilization stage are provided by the reactions of reversible transformation between Na2S and S, which were considered the reaction mechanisms of Na-S batteries. This work can provide a basis for the synthesis and application of sulfur-rich compounds in fields of batteries, semiconductor devices, and catalysts.

An in situ electrospinning route to fabricate NiO-SnO2 based detectors for fast H2S sensing.

Hydrogen sulfide (H2S) is a toxic and flammable chemical, even in low concentration. In this study, an in situ electrospinning strategy was developed to directly deposit the sensitive materials of nickel oxide (NiO)-doped SnO2 nanofiber on alumina substrates, resulting in the fast H2S detection. The electrospun fiber could be deposited on to the alumina tube directly, and remain there during calcination. Using this method, the NiO-doped SnO2 nanofibers fabricated and manifested a fast response, fast recovery, and high selectivity at a low temperature (150 °C). A 15% atom NiO-doped SnO2 nanofiber-containing H2S detector presented a high response (1352), low response time (23 s), and low recovery time (38 s) while detecting a concentration of 50 ppm H2S at 150 °C. Compared to conventional methods, the H2S detector based on the in situ electrospinning method showed a higher sensitivity, faster response, and faster recovery. Furthermore, the superior performance of the detector can be ascribed to the thinner film and non-interrupted fiber structure. Additionally, the transformation of NiO to Ni3S2, confirmed by the x-ray photoelectron spectroscopy under a H2S atmosphere, suggested the main reason for the detector's high performance. The high performance of the NiO-doped SnO2 suggests a strategy for gas detectors, biodetectors, and semiconductor devices.

S-Doped Carbon Fibers Uniformly Embedded with Ultrasmall TiO2 for Na+ /Li+ Storage with High Capacity and Long-Time Stability.

Building a rechargeable battery with high capacity, high energy density, and long lifetime contributes to the development of novel energy storage devices in the future. Although carbon materials are very attractive anode materials for lithium-ion batteries (LIBs), they present several deficiencies when used in sodium-ion batteries (SIBs). The choice of an appropriate structural design and heteroatom doping are critical steps to improve the capacity and stability. Here, carbon-based nanofibers are produced by sulfur doping and via the introduction of ultrasmall TiO2 nanoparticles into the carbon fibers (CNF-S@TiO2 ). It is discovered that the introduction of TiO2 into carbon nanofibers can significantly improve the specific surface area and microporous volume for carbon materials. The TiO2 content is controlled to obtain CNF-S@TiO2 -5 to use as the anode material for SIBs/LIBs with enhanced electrochemical performance in Na+ /Li+ storage. During the charge/discharge process, the S-doping and the incorporation of TiO2 nanoparticles into carbon fibers promote the insertion/extraction of the ions and enhance the capacity and cycle life. The capacity of CNF-S@TiO2 -5 can be maintained at ≈300 mAh g-1 over 600 cycles at 2 A g-1 in SIBs. Moreover, the capacity retention of such devices is 94%, showing high capacity and good stability.

Encapsulation of MoSe2 in carbon fibers as anodes for potassium ion batteries and nonaqueous battery-supercapacitor hybrid devices.

Potassium ion batteries (PIBs) are considered as promising alternatives to sodium-ion batteries (SIBs) and lithium-ion batteries (LIBs), which can be ascribed to the rich abundance of potassium resources, low cost and high safety. Currently, the development of anode materials for PIBs is still confronted with many serious problems, such as low capacity and poor cycling performance. In this work, sheet-like MoSe2 implanted on the surfaces of carbon nanofibers is successfully synthesized through a simple electrospinning and selenization route. MoSe2/C-700 (selenization at 700 °C) maintains high structural stability and facilitates the intercalation/deintercalation of K+, which benefits from one-dimensional nanofibers with good structural stability and MoSe2 with an expanded interlayer spacing. As a whole, MoSe2/C-700 as an anode for PIBs shows a high reversible capacity of 316 mA h g-1 at 100 mA g-1 over 100 cycles. It also displays a specific capacity of 81 mA h g-1 at 100 mA g-1 over 100 cycles when it first serves as an electrode material for nonaqueous potassium-based battery-supercapacitor hybrid (BSH) devices.

Graphene-Encapsulated FeS2 in Carbon Fibers as High Reversible Anodes for Na+ /K+ Batteries in a Wide Temperature Range.

Developing low cost, long life, and high capacity rechargeable batteries is a critical factor towards developing next-generation energy storage devices for practical applications. Therefore, a simple method to prepare graphene-coated FeS2 embedded in carbon nanofibers is employed; the double protection from graphene coating and carbon fibers ensures high reversibility of FeS2 during sodiation/desodiation and improved conductivity, resulting in high rate capacity and long-term life for Na+ (305.5 mAh g-1 at 3 A g-1 after 2450 cycles) and K+ (120 mAh g-1 at 1 A g-1 after 680 cycles) storage at room temperature. Benefitting from the enhanced conductivity and protection on graphene-encapsulated FeS2 nanoparticles, the composites exhibit excellent electrochemical performance under low temperature (0 and -20 °C), and temperature tolerance with stable capacity as sodium-ion half-cells. The Na-ion full-cells based on the above composites and Na3 V2 (PO4 )3 can afford reversible capacity of 95 mAh g-1 at room temperature. Furthermore, the full-cells deliver promising discharge capacity (50 mAh g-1 at 0 °C, 43 mAh g-1 at -20 °C) and high energy density at low temperatures. Density functional theory calculations imply that graphene coating can effectively decrease the Na+ diffusion barrier between FeS2 and graphene heterointerface and promote the reversibility of Na+ storage in FeS2 , resulting in advanced Na+ storage properties.

Improved Na+/K+ Storage Properties of ReSe2-Carbon Nanofibers Based on Graphene Modifications.

Rhenium diselenide (ReSe2) has caused considerable concerns in the field of energy storage because the compound and its composites still suffer from low specific capacity and inferior cyclic stability. In this study, ReSe2 nanoparticles encapsulated in carbon nanofibers were synthesized successfully with simple electrospinning and heat treatment. It was found that graphene modifications could affect considerably the microstructure and electrochemical properties of ReSe2-carbon nanofibers. Accordingly, the modified compound maintained a capacity of 227 mAh g-1 after 500 cycles at 200 mA g-1 for Na+ storage, 230 mAh g-1 after 200 cycles at 200 mA g-1, 212 mAh g-1 after 150 cycles at 500 mA g-1 for K+ storage, which corresponded to the capacity retention ratios of 89%, 97%, and 86%, respectively. Even in Na+ full cells, its capacity was maintained to 82% after 200 cycles at 1C (117 mA g-1). The superior stability of ReSe2-carbon nanofibers benefitted from the extremely weak van der Waals interactions and large interlayer spacing of ReSe2, in association with the role of graphene-modified carbon nanofibers, in terms of the shortening of electron/ion transport paths and the improvement of structural support. This study may provide a new route for a broadened range of applications of other rhenium-based compounds.

Enhanced electrochemical properties of SnO2-graphene-carbon nanofibers tuned by phosphoric acid for potassium storage.

Potassium-ion batteries (KIBs) are considered as attractive alternatives to commercial lithium-ion batteries. However, the lack of suitable electrodes to host large K+ for rapid as well as reversible insertion/extraction hinders the developments of KIBs. As an attempt, the phosphoric acid doped SnO2-graphene-carbon (P-SGC) nanofibers synthesized with a facile electrospinning method are introduced and applied as anode materials for KIBs. The P-SGC anodes present a reversible capacity of 285.9 mAh g-1 over 60 cycles at the current density of 100 mA g-1, and the high rate capacity of 208.53 mAh g-1 at 1 A g-1 as well. Emphasis is placed on enhancing the electrochemical properties of the SGC nanofibers by phosphoric acid modification through more active sites and higher electrical conductivity, accounting for improved K+ diffusion kinetics. Meanwhile, the coated carbon matrix and dispersive graphene buffer the structural changes and protect the active materials from destruction, leading to the good structural stability. With the presented results, these P-SGC nanofibers show attractive potential for future energy storage application of KIBs.

ZnO-carbon nanofibers for stable, high response, and selective H2S sensors.

Hydrogen sulfide (H2S), as a typical atmospheric pollutant, is neurotoxic and flammable even at a very low concentration. In this study, we design stable H2S sensors based on ZnO-carbon nanofibers. Nanofibers with 30.34 wt% carbon are prepared by a facial electrospinning route followed by an annealing treatment. The resulting H2S sensors show excellent selectivity and response compared to the pure ZnO nanofiber H2S sensors, particularly the response in the range of 102-50 ppm of H2S. Besides, they exhibited a nearly constant response of approximately 40-20 ppm of H2S over 60 days. The superior performance of these H2S sensors can be attributed to the protection of carbon, which ensures the high stability of ZnO, and oxygen vacancies that improve the response and selectivity of H2S. The good performance of ZnO-carbon H2S sensors suggests that composites with oxygen vacancies prepared by a facial electrospinning route may provide a new research strategy in the field of gas sensors, photocatalysts, and semiconductor devices.