Porous Carbon Architecture Assembled by Cross-Linked Carbon Leaves with Implanted Atomic Cobalt for High-Performance Li–S Batteries

The practical application of lithium–sulfur batteries is severely hampered by the poor conductivity, polysulfide shuttle effect and sluggish reaction kinetics of sulfur cathodes. Herein, a hierarchically porous three-dimension (3D) carbon architecture assembled by cross-linked carbon leaves with implanted atomic Co–N4 has been delicately developed as an advanced sulfur host through a SiO2-mediated zeolitic imidazolate framework-L (ZIF-L) strategy. The unique 3D architectures not only provide a highly conductive network for fast electron transfer and buffer the volume change upon lithiation–delithiation process but also endow rich interface with full exposure of Co–N4 active sites to boost the lithium polysulfides adsorption and conversion. Owing to the accelerated kinetics and suppressed shuttle effect, the as-prepared sulfur cathode exhibits a superior electrochemical performance with a high reversible specific capacity of 695 mAh g−1 at 5 C and a low capacity fading rate of 0.053% per cycle over 500 cycles at 1 C. This work may provide a promising solution for the design of an advanced sulfur-based cathode toward high-performance Li–S batteries.

Improve the Performance of SONOS Type UV TD Sensors Using IOHAOS with Enhanced UV Transparency ITO Gate

This research demonstrates that an indium tin oxide–silicon oxide–hafnium aluminum oxide‒silicon oxide–silicon device with enhanced UV transparency ITO gate (hereafter E-IOHAOS) can greatly increase the sensing response performance of a SONOS type ultraviolet radiation total dose (hereafter UV TD) sensor. Post annealing process is used to optimize UV optical transmission and electrical resistivity characterization in ITO film. Via nano-columns (NCols) crystalline transformation of ITO film, UV transparency of ITO film can be enhanced. UV radiation causes the threshold voltage VT of the E-IOHAOS device to increase, and the increase of the VT of E-IOHAOS device is also related to the UV TD. The experimental results show that under UV TD irradiation of 100 mW·s/cm2, ultraviolet light can change the threshold voltage VT of E-IOHAOS to 12.5 V. Moreover, the VT fading rate of ten-years retention on E-IOHAOS is below 10%. The VT change of E-IOHAOS is almost 1.25 times that of poly silicon–aluminum oxide–hafnium aluminum oxide–silicon oxide–silicon with poly silicon gate device (hereafter SAHAOS). The sensing response performance of an E-IOHAOS UV TD sensor is greatly improved by annealed ITO gate.

Low-temperature Liquid Exfoliation of Milligram-scale Single Crystalline Few-layer β12-Borophene Sheets as Efficient Electrocatalysts for Lithium–Sulfur Batteries

Two-dimensional (2D) borophene is predicted as an ideal electrode material for lithium sulfur (Li-S) batteries because of low-density, metallic conductivity, high Li-ion surface mobility and strong interface bonding energy to polysulfide. But until now, 2D borophene-based Li-S batteries have not yet been achieved due to the absence of massive synthesis method. Herein, we developed a novel low-temperature liquid exfoliation (LTLE) method for scalable synthesis of single crystalline 2D few-layer β12-borophene sheets with a \(P\stackrel{-}{6}m2\) symmetry. The as-synthesized 2D sheets were used as the polysulfide immobilizers and electrocatalysts of Li-S batteries for the first time. The resulting Li-S cells employing borophene sheets delivered a strikingly high areal capacity of 5.2 mAh cm− 2 at a high sulfur loading of 7.8 mg cm− 2 with an ultralow capacity fading rate (0.039 % per cycle) in 1000 cycles, outperforming most of the Li-S batteries employing other 2D materials. Under the help of few-layer β12-borophene, their high-activity behaviors should be attributed to the significant enhancement of both the Li-ion’s surface migration and the adsorption energy for Li2Sn clusters based on density functional theory (DFT) models. Our research reveals great potential of 2D β12-borophene sheets in future high-performance Li-S batteries.

Analysis of Lithium-ion Battery Micro-overcharge Cycle Damage Mechanism Based on Electrochemical Impedance Spectroscopy

Electrochemical impedance spectroscopy (EIS) was used to study the micro-overcharge cycle damage mechanism of Lithium-ion batteries (LIBs). Micro-overcharge cycle experiments of LIBs were carried out, and the capacity fading of LIBs under different charging cut-off voltages were analyzed. It was found that the capacity fading rate of LIBs increased with the rising of overcharge cut-off voltages and the increasing of cycle numbers. The EIS results show that the main damage pattern of LIBs during micro-overcharge cycle is the active lithium loss when the cut-off voltage is between 4.3 V and 4.4 V. Lithium loss accounts for more than 80% damage proportion when LIBs cycling for more than 20 cycles.

Synthesis and Electrochemical Properties of MoS2/rGO/S Composite as a Cathode Material for Lithium–Sulfur Batteries

To develop the next-generation energy storage systems, lithium-sulfur batteries represent an attractive option due to its high theoretical capacity, and energy density. In this work, MoS2/rGO (reduced graphene oxide) was prepared by hydrothermal synthesis and sulfur added by the melt diffusion method. The as-prepared MoS2/rGO has strong polysulfides entrapping, high conductivity, large surface area, and high catalytic activity, consequently resulting in enhanced rate performance and cycling capability of Li-S batteries. The coin cells were constructed with the MoS2/rGO/S cathode material, exhibit a high reversible capacity of nearly 1380 mAh/g at 0.1 C, outstanding cycling stability with a low capacity fading rate. Present work reveals that the hierarchal MoS2/rGO/S cathodes are potential candidate materials for future high-performance lithium-sulfur batteries.

Lithium-Rich Cobalt-Free Manganese-Based Layered Cathode Materials for Li-Ion Batteries: Suppressing the Voltage Fading

Lithium-rich layered oxides are recognized as promising materials for Li-ion batteries, owing to higher capacity than the currently available commercialized cathode, for their lower cost. However, their voltage decay and cycling instability during the charge/discharge process are problems that need to be solved before their practical application can be envisioned. These problems are mainly associated with a phase transition of the surface layer from the layered structure to the spinel structure. In this paper, we report the AlF3-coating of the Li-rich Co-free layered Li1.2Ni0.2Mn0.6O2 (LLNMO) oxide as an effective strategy to solve these problems. The samples were synthesized via the hydrothermal route that insures a very good crystallization in the layered structure, probed by XRD, energy-dispersive X-ray (EDX) spectroscopy, and Raman spectroscopy. The hydrothermally synthesized samples before and after AlF3 coating are well crystallized in the layered structure with particle sizes of about 180 nm (crystallites of ~65 nm), with high porosity (pore size 5 nm) determined by Brunauer–Emmett–Teller (BET) specific surface area method. Subsequent improvements in discharge capacity are obtained with a ~5-nm thick coating layer. AlF3-coated Li1.2Ni0.2Mn0.6O2 delivers a capacity of 248 mAh g−1 stable over the 100 cycles, and it exhibits a voltage fading rate of 1.40 mV per cycle. According to the analysis from galvanostatic charge-discharge and electrochemical impedance spectroscopy, the electrochemical performance enhancement is discussed and compared with literature data. Post-mortem analysis confirms that the AlF3 coating is a very efficient surface modification to improve the stability of the layered phase of the Li-rich material, at the origin of the significant improvement of the electrochemical properties.

Electrodeposited Sulfur and CoxS Electrocatalyst on Buckypaper as High-Performance Cathode for Li–S Batteries

Lithium–sulfur batteries (LSBs) are considered as the next generation of advanced rechargeable batteries because of their high energy density. In this study, sulfur and CoxS electrocatalyst are deposited on carbon nanotube buckypaper (S/CoxS/BP) by a facile electrodeposition method and are used as a binder-free high-performance cathode for LSBs. Elemental sulfur is deposited on buckypaper by electrooxidation of a polysulfide solution (~ S62−). This approach substantially increased the current and time efficiency of sulfur electrochemical deposition on conductive material for LSBs. S/CoxS/BP cathode could deliver an initial discharge capacity as high as 1650 mAh g−1 at 0.1 C, which is close to the theoretical capacity of sulfur. At current rate of 0.5 C, the S/CoxS/BP has a capacity of 1420 mAh g−1 at the first cycle and 715 mAh g−1 after 500 cycles with a fading rate of 0.099% per cycle. The high capacity of S/CoxS/BP is attributed to both the homogeneous dispersion of nanosized sulfur within BP and the presence of CoxS catalyst. The sodium dodecyl sulfate (SDS) pretreatment of BP renders it polarity to bind polysulfides and thus facilitates the good dispersibility of nanosized sulfur within BP. CoxS catalyst accelerates the kinetics of polysulfide conversion and reduces the presence of polysulfide in the cathode, which suppresses the polysulfide diffusion to anode, i.e., the shuttle effect. The mitigation of the active material loss improves not only the capacity but also the cyclability of S/CoxS/BP. Graphic Abstract

Selective Adsorption and Electrocatalysis of Polysulfides through Hexatomic Nickel Clusters Embedded in N-Doped Graphene toward High-Performance Li-S Batteries

The shuttle effect hinders the practical application of lithium-sulfur (Li-S) batteries due to the poor affinity between a substrate and Li polysulfides (LiPSs) and the sluggish transition of soluble LiPSs to insoluble Li2S or elemental S. Here, we report that Ni hexatomic clusters embedded in a nitrogen-doped three-dimensional (3D) graphene framework (Ni-N/G) possess stronger interaction with soluble polysulfides than that with insoluble polysulfides. The synthetic electrocatalyst deployed in the sulfur cathode plays a multifunctional role: (i) selectively adsorbing the polysulfides dissolved in the electrolyte, (ii) expediting the sluggish liquid-solid phase transformations at the active sites as electrocatalysts, and (iii) accelerating the kinetics of the electrochemical reaction of multielectron sulfur, thereby inhibiting the dissolution of LiPSs. The constructed S@Ni-N/G cathode delivers an areal capacity of 9.43 mAh cm-2 at 0.1 C at S loading of 6.8 mg cm-2, and it exhibits a gravimetric capacity of 1104 mAh g-1 with a capacity fading rate of 0.045% per cycle over 50 cycles at 0.2 C at S loading of 2.0 mg cm-2. This work opens a rational approach to achieve the selective adsorption and expediting of polysulfide transition for the performance enhancement of Li-S batteries.

Scintillation and Energy-Storage Properties of Micro-Pulling-Down Grown Crystals of Sc3+- and La3+-Doped YAlO3 Perovskite

The scintillation and energy-storage properties of YAlO3 (YAP) crystals doped with Sc3+ and La3+ isoelectronic dopants were investigated in this work. The YAP:Sc and YAP:La crystals were grown from the melt with a nominal Sc and La content in the 0.2–5.0 mol.% range using the novel micro-pulling-down method. We found that the segregation coefficient of Sc ions in YAP:Sc (0.2–1.0 mol.%) crystals is about of 0.35–0.4 and decreases to around 0.2 at Sc content of 5.0 mol.% when the segregation coefficient of La ions in YAP:La (1.0–5.0 mol.%) crystals is 0.008–0.01. The scintillation and stimulated luminescence phenomena, like thermo- and photoluminescence, were utilized for the property characterization of the studied materials. The cathodoluminescence and X-ray-excited luminescence were used for the imitation of scintillation in the YAP:Sc and YAP:La crystals. The influence of Sc3+ and La3+ dopant concentration on the CL and RL emission spectra, as well as the shape of the measured thermoluminescence (TL) glow-curves, was also investigated. The measured emission spectra showed dominant emission of Sc3+ and La3+ ions in the UV range. For this reason, the YAP:Sc and YAP:La crystals can be considered for creation of ultraviolet (UV)-emitting scintillators. For the undoped YAlO3 crystals, the main TL emission peak occurs in a low-temperature range at 375 K. Meanwhile, even a small addition of dopants causes a strong suppression of luminescence of the YAP host and high-temperature peaks become dominant in the TL glow-curves of YAP:Sc and YAP:La crystals. Moreover, the amplitude of emission does not change monotonically with increasing dopant content. The kinetic parameters of emission were also evaluated, and the first-order behavior was confirmed in all cases. The dosimetric properties of investigated materials such as dose response, fading rate, and the lowest measurable dose are also discussed. The obtained results tend to suggest that the YAlO3 perovskite host, apart from its application for the development of efficient scintillators, may also be considered as a promising matrix for the creation of energy-storage phosphors for dosimetric applications.