Novel composite separators containing metal–organic‐framework (MOF) particles and poly(vinyl alcohol) are fabricated by the electrospinning process. The MOF particles containing opened metal sites ...can spontaneously adsorb anions while allowing effective transport of lithium ions in the electrolyte, leading to dramatically improved lithium‐ion transference number tLi+ (up to 0.79) and lithium‐ion conductivity. Meanwhile, the incorporation of the MOF particles alleviates the decomposition of the electrolyte, enhances the electrode reaction kinetics, and reduces the interface resistance between the electrolyte and the electrodes. Implementation of such composite separators in conventional lithium‐ion batteries leads to significantly improved rate capability and cycling durability, offering a new prospective toward high‐performance lithium‐ion batteries.
An electrospun composite separator comprising metal–organic frameworks with open metal sites (OMSs) is developed for high‐rate lithium‐ion batteries, where the OMSs can efficiently immobilize anions in the electrolyte and afford highly mobile lithium ions. This work opens up new opportunities for functional separators aiming at regulating ion transport in the electrolyte and achieving a high rate capability of batteries.
Abstract
The sluggish electrochemical kinetics of sulfur species has impeded the wide adoption of lithium-sulfur battery, which is one of the most promising candidates for next-generation energy ...storage system. Here, we present the electronic and geometric structures of all possible sulfur species and construct an electronic energy diagram to unveil their reaction pathways in batteries, as well as the molecular origin of their sluggish kinetics. By decoupling the contradictory requirements of accelerating charging and discharging processes, we select two pseudocapacitive oxides as electron-ion source and drain to enable the efficient transport of electron/Li
+
to and from sulfur intermediates respectively. After incorporating dual oxides, the electrochemical kinetics of sulfur cathode is significantly accelerated. This strategy, which couples a fast-electrochemical reaction with a spontaneous chemical reaction to bypass a slow-electrochemical reaction pathway, offers a solution to accelerate an electrochemical reaction, providing new perspectives for the development of high-energy battery systems.
Despite the progress made on the production of graphene using liquid‐phase exfoliation methods, the fabrication of graphene with both high conductivity and dispersibility remains challenging. Through ...catalytic exfoliation of graphite, an effective synthesis method for graphene with large lateral size (≈10 µm), high conductivity (926 S cm–1), and excellent water solubility (≈10 mg mL–1) is reported herein. Such graphene can be used broadly for applications such as lithium ion batteries, where both high conductivity and dispersibility are required. As an example, the synthesis of graphene and lithium‐iron‐phosphate composites is demonstrated, which leads to electrodes with dramatically improved cycling stability and rate performance. Adaption of such material leads to electrodes with volumetric energy density as high as 658.7 and 287.6 W h L–1 under 0.5 and 20 C, respectively, which is significantly higher than that of commercial LiFePO4 (394.7 and 13.5 W h L–1 at 0.5 and 20 C, respectively). This work provides a new method of making high‐conductivity–dispersibility graphene for various applications.
This work reports an effective synthesis of graphene with a large lateral size, high conductivity, and excellent water solubility through catalytic exfoliation of graphite. To examine its use in lithium ion batteries, such a graphene is further assembled with LiFePO4 through spray drying to form a composite cathode, which leads to a dramatically improved cycling stability and rate performance.
Sulfurized hematite for photo-Fenton catalysis Zhang, Yaping; Dong, Kaituo; Liu, Zheng ...
Progress in Natural Science/Progress in natural science,
08/2017, Volume:
27, Issue:
4
Journal Article
Peer reviewed
Open access
A hematite/amorphous sulfur composite was prepared via simple heating hematite and α-sulfur in Teflon-lined autoclave at low temperature. The composite was characterized by X-ray diffraction (XRD), ...Raman spectrum, Thermal Gravity Analysis (TGA), Transmission Electron Microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The results revealed that an allotrope sulfur at 5–37% weight percent was found in the composite. After sulfuration, Sn2- or S22- was doped in the lattice of hematite, large amounts of OH and SO4 were adsorbed on the surface of hematite. Hematite/amorphous sulfur composite had superior photo-Fenton activities than pure hematite. This work also demonstrated that amorphous sulfur also had the activity of photo-Fenton catalysis. OH- and SO4 radicals facilitated dye adsorption and acted as a bridge to link H2O2. Moreover, SO4 radicals on hematite served as electron trapping center that can receive photo-induced electron from conduction band of hematite and transfer it to the adsorbed H2O2, increasing the rate of photo-Fenton reaction eventually.
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•Sulfur in composite exists in amorphous state;•Composites have superior photo-Fenton catalytic performance;•Amorphous sulfur also has the ability of photo-Fenton catalysis;
Black silicon co-hyperdoped with sulfur and nitrogen in different ratios is prepared by femtosecond laser-assisted chemical etching in the mixed atmosphere of SF6 and NF3 with varying gas pressure ...ratios. Their room-temperature NO2 gas sensing capability is studied systematically, in which the photocurrent as a readout signal is generated by the lateral photovoltaic effect of black silicon under an asymmetrical light illumination. These co-hyperdoped black silicon exhibits high response, fast response/recovery, ultrawide detection range from 29 ppb to 2000 ppm, excellent selectivity and acceptable long-term durability over 3 months. Moreover, NO2 gas sensing performances are effectively tuned or optimized by deliberately changing the co-doping ratio of sulfur and nitrogen, as different photovoltaic characteristics are induced by changes in morphology and structural defects resulting from different hyperdoping. Specifically, ultra-high relative gas response (∼3955%@20 ppm NO2) and superior selectivity are obtained at the SF6/NF3 pressure ratio of 56/14, while faster response/recovery time (17 s/ 47 s @ 20 ppm NO2) and response photocurrent with a weaker disturbance by humidity are given by the samples with SF6/NF3 of 7/63 and 63/7, respectively. Therefore, such black silicon material has good potential to meet different application needs.
•Co-hyperdoped black silicon targeting gas sensing was prepared by femtosecond laser-assisted chemical etching.•Photocurrent-based gas sensing mode was applied via the lateral photovoltaic effect (LPE).•NO2 gas sensing performances are effectively tuned or optimized via controlling co-doping ratio of sulfur and nitrogen.•The roles of supersaturated dopants in the LPE and gas sensing properties of black silicon are explored.
NO2 gas sensing properties of the nitrogen-hyperdoped black silicon (N-Si) modified at different annealing temperatures are studied. Owing to the abundant defects in the material and their changes ...with the annealing, the thermal modification brings a series of novel sensing behaviors and characteristics. Working as the sensitive material in a conductometric gas sensor, the pristine N-Si exhibits an undesirable n- to p-type response transition for higher NO2 concentration, which severely reduces its upper limit of detection (< 5 ppm). However, for the thermally modified N-Si after annealing at higher temperature (≥ 673 K), the abnormal response transition induced by higher concentration disappears. These modified N-Si show consistent p-type response to all tested NO2 concentrations, successfully breaking the detection limit. More interestingly, there is an optimal annealing temperature ~ 873 K, at which the sensor demonstrates outstanding sensing performances, including wide dynamic range spanning 5 orders of magnitude, rapid adsorption and desorption ability, high response and good selectivity, etc. Results indicate that through the thermal modification a novel N-Si gas-sensitive material is obtained. The mechanism for the thermally-induced response type conversion is discussed, in which the activation of acceptor energy levels provided by the complexes associated with substitutional nitrogen are considered.
•Nitrogen-hyperdoped silicon with p-type NO2 response are obtained.•Electrical and sensing properties of thermally modified nitrogen-hyperdoped silicon.•Excellent overall sensing performance at the optimal annealing temperature ~ 873 K.•Discussion for the conduction type conversion, variation in resistance and sensing behaviors.
In order to improve the feasibility and accuracy of predicting the explosion power of fuel air mixture, a method of BP neural network prediction is proposed by combining factor analysis method with ...BP neural network. Using factor analysis method, the original data of 9 fuel air mixture explosion power factors were processed by dimensionality reduction data, 2 common factors were obtained, and 2 common factors were substituted for 9 fuel air mixtures as input layer parameters of BP neural network. A prediction model of coal and gas outburst with the combination of factor analysis method and BP Neural network is established to predict the explosion power of fuel air mixture. The prediction model of the explosion power of the fuel air mixture is selected to verify the improved BP neural network prediction models, and the final results are as follows: The relative error range of four prediction samples is 0.16%-7.58%, all less than 10%. The improved BP neural network prediction method is used to solve the problem of the traditional BP neural network because of the excessive number of input layer parameters, low data processing efficiency, slow iteration rate and low precision, which provides a new research way for predicting the explosion power of fuel air mixture.
Energy storage and conversion are key technologies in modern society, and they are becoming more and more important. This is mainly due to the severe future impact of fossil fuels on the world’s ...economy and ecology. So, there is an urgent need for alternative energy sources to address the depletion of fossil fuels and the environmental impact of their continued use. However, the large-scale development of renewable energy resources such as wind, solar, geothermal, biomass and hydropower, that are unpredictable and intermittent. Thus, these technologies require highly reliable electrical energy storage (EES) devices, which can store the excess produced electricity and release it on demand.Rechargeable batteries such as lithium-ion batteries, store energy through electrochemical reactions that typically occur throughout the bulk active materials, allowing comparatively large amount of energy to be stored compared with electric capacitors. The last decade has witnessed a tremendous growth in lithium-ion batteries for applications such as microelectronics and electric vehicles. However, the development of battery energy density has seriously lagged behind the demand growth of Li-ion batteries. Thus, high energy density electrode materials are extremely demanded in next-generation cutting-edge electronic devices. Parallel to this development, rechargeable batteries based on Na+, K+, Mg2+ and Al3+ ions have also attracted great interests due to their abundance and low cost.Such batteries generally employ flammable liquid electrolytes, which bring severe safety concerns. In this case, solid electrolytes are believed to be able to suppress Li dendrite growth because of their high mechanical strength and high Li+ transference number. In order to allow the implementation of high-specific-energy Li-metal batteries, both inorganic and organic solid electrolytes have been explored. Inorganic electrolytes may exhibit high ionic conductivity (e.g., > 10–4 S cm–1), whereas scale fabrication of solid batteries remains challenging. Polymeric electrolytes are less difficult to be integrated, whereas their ionic conductivity remains low at ambient temperature (e.g., < 10–5 S cm–1). Solid-like electrolytes, which are generally made by encapsulating liquid electrolytes within solid porous scaffolds, represent another direction with the merits of both liquid electrolyte and solid electrolyte.In this dissertation, we developed a novel family of solid-like electrolytes, which are made by infiltrating MIL-100(Al), a MOF with high porosity and excellent thermal, chemical and electrochemical stabilities, with a series of liquid electrolytes that contain cations from the 3rd period (Na+, Mg2+ and Al3+) and the 1st group (Li+, Na+, K+ and Cs+). Particularly, the Mg2+ solid-like electrolyte exhibits superionic conductivity (>10–3 S cm–1) with a low activation energy of 0.20 eV. From Li+, Na+, K+ to Cs+ with reducing Stokes radii and ionic solvation shell thickness, both the liquid electrolytes and solid-like electrolytes show a similar trend of increasing conductivity. This work investigates the ion-conduction mechanism of MOFs based solid-like electrolytes, providing reliable principles to the design of fast-conducting solid-like electrolytes for alkali or multivalent metal ions.Furthermore, we successfully employed MOF-based solid-like electrolytes in Na-metal batteries. Both MOF/polymer composite electrolytes on GF served as functional separator or directly as gel polymer electrolytes show advantages compared with commercial separators. The cell using solid-like electrolyte notably surpasses the cell using liquid electrolyte in terms of cycle stability and Coulombic efficiency. This work expands the application of MOF-based solid-like electrolytes from Li to Na metal batteries, offering the possibility for further applications in high energy density rechargeable batteries.
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