Enhanced Li‐Storage of Ni3S2 Nanowire Arrays with N‐Doped Carbon Coating Synthesized by One‐Step CVD Process and Investigated Via Ex Situ TEM

In this work, a facile strategy for the construction of single crystalline Ni₃S₂ nanowires coated with N‐doped carbon shell (NC) forming Ni₃S₂@NC core/shell arrays by one‐step chemical vapor deposition process is reported. In addition to the good electronic conductivity from the NC shell, the nanowire structure also ensures the accommodation of large volume expansion during cycling, leading to pre‐eminent high‐rate capacities (470 mAh g^?1 at 0.05 A g^?1 and 385 mAh g^?1 at 2 A g^?1) and outstanding cycling stability with a capacity retention of 91% after 100 cycles at 1 A g^?1. Furthermore, ex situ transmission electron microscopy combined with X‐ray diffraction and Raman spectra are used to investigate the reaction mechanism of Ni₃S₂@NC during the charge/discharge process. The product after delithiation consists of Ni₃S₂ and sulfur, suggesting that the capacity of the electrode comes from the conversion reaction of both Ni₃S₂ and sulfur with Li₂S.     

Ti3+ Self‐Doped Li4Ti5O12 Anchored on N‐Doped Carbon Nanofiber Arrays for Ultrafast Lithium‐Ion Storage

Omnibearing acceleration of charge/ion transfer in Li₄Ti₅O₁₂ (LTO) electrodes is of great significance to achieve advanced high‐rate anodes in lithium‐ion batteries. Here, a synergistic combination of hydrogenated LTO nanoparticles (H‐LTO) and N‐doped carbon fibers (NCFs) prepared by an electrodeposition‐atomic layer deposition method is reported. Binder‐free conductive NCFs skeletons are used as strong support for H‐LTO, in which Ti³⁺ is self‐doped along with oxygen vacancies in LTO lattice to realize enhanced intrinsic conductivity. Positive advantages including large surface area, boosted conductivity, and structural stability are obtained in the designed H‐LTO@NCF electrode, which is demonstrated with preeminent high‐rate capability (128 mAh g^?1 at 50 C) and long cycling life up to 10 000 cycles. The full battery assembled by H‐LTO@NCFs anode and LiFePO₄ cathode also exhibits outstanding electrochemical performance revealing an encouraging application prospect. This work further demonstrates the effectiveness of self‐doping of metal ions on reinforcing the high‐rate charge/discharge capability of batteries.     

Precisely Controlling the Position of Bromine on the End Group Enables Well-Regular Polymer Acceptors for All-Polymer Solar Cells with Efficiencies over 15%

Recent advances in the development of polymerized A–D–A-type small-molecule acceptors (SMAs) have promoted the power conversion efficiency (PCE) of all-polymer solar cells (all-PSCs) over 13%. However, the monomer of an SMA typically consists of a mixture of three isomers due to the regio-isomeric brominated end groups (IC-Br(in) and IC-Br(out)). In this work, the two isomeric end groups are successfully separated, the regioisomeric issue is solved, and three polymer acceptors, named PY-IT, PY-OT, and PY-IOT, are developed, where PY-IOT is a random terpolymer with the same ratio of the two acceptors. Interestingly, from PY-OT, PY-IOT to PY-IT, the absorption edge gradually redshifts and electron mobility progressively increases. Theory calculation indicates that the LUMOs are distributed on the entire molecular backbone of PY-IT, contributing to the enhanced electron transport. Consequently, the PM6:PY-IT system achieves an excellent PCE of 15.05%, significantly higher than those for PY-OT (10.04%) and PY-IOT (12.12%). Morphological and device characterization reveals that the highest PCE for the PY-IT-based device is the fruit of enhanced absorption, more balanced charge transport, and favorable morphology. This work demonstrates that the site of polymerization on SMAs strongly affects device performance, offering insights into the development of efficient polymer acceptors for all-PSCs.     

Fused Benzothiadiazole: A Building Block for n‐Type Organic Acceptor to Achieve High‐Performance Organic Solar Cells

Narrow bandgap n‐type organic semiconductors (n‐OS) have attracted great attention in recent years as acceptors in organic solar cells (OSCs), due to their easily tuned absorption and electronic energy levels in comparison with fullerene acceptors. Herein, a new n‐OS acceptor, Y5, with an electron‐deficient‐core‐based fused structure is designed and synthesized, which exhibits a strong absorption in the 600–900 nm region with an extinction coefficient of 1.24 × 10⁵ cm^?1, and an electron mobility of 2.11 × 10^?4 cm² V^?1 s^?1. By blending Y5 with three types of common medium‐bandgap polymers (J61, PBDB‐T, and TTFQx‐T1) as donors, all devices exhibit high short‐circuit current densities over 20 mA cm^?2. As a result, the power conversion efficiency of the Y5‐based OSCs with J61, TTFQx‐T1, and PBDB‐T reaches 11.0%, 13.1%, and 14.1%, respectively. This indicates that Y5 is a universal and highly efficient n‐OS acceptor for applications in organic solar cells.     

Ni Single Atoms on MoS2 Nanosheets Enabling Enhanced Kinetics of Li-S Batteries

The practical application of Li-S batteries is seriously hindered due to its shuttle effect and sluggish redox reaction, which requires a better functional separator to solve the problems. Herein, polypropylene separators modified by MoS₂ nanosheets with atomically dispersed nickel (Ni-MoS₂) are prepared to prevent the shuttle effect and facilitate the redox kinetics for Li-S batteries. Compared with pristine MoS₂ nanosheets, Ni-MoS₂ nanosheets exhibit both excellent adsorption and catalysis performance for overcoming the shuttle effect. Assembled with this novel separator, the Li-S batteries exhibit an admirable cycling stability at 2 C over 400 cycles with 0.01% per cycle decaying. In addition, even with a high sulfur loading of 7.5 mg cm⁻², the battery still provides an initial capacity of 6.9 mAh cm⁻² and remains 5.9 mAh cm⁻² after 50 cycles because of the fast convention of polysulfides catalyzed by Ni-MoS₂ nanosheets, which is further confirmed by the density functional theory (DFT) calculations. Therefore, the proposed strategy is expected to offer a new thought for single atom catalyst applying in Li-S batteries.     

Solid-State Electrolytes in Lithium–Sulfur Batteries: Latest Progresses and Prospects

Solid-state lithium–sulfur batteries (SSLSBs) have attracted tremendous research interest due to their large theoretical energy density and high safety, which are highly important indicators for the development of next-generation energy storage devices. Particularly, safety and “shuttle effect” issues originating from volatile and flammable liquid organic electrolytes can be fully mitigated by switching to a solid-state configuration. However, their road to thecommercial application is still plagued with numerous challenges, most notably the intrinsic electrochemical instability of solid-state electrolytes (SSEs) materials and their interfacial compatibility with electrodes and electrolytes. In this review, a critical discussion on the key issues and problems of different types of SSEs as well as the corresponding optimization strategies are first highlighted. Then, the state-of-the-art preparation methods and properties of different kinds of SSE materials, and their manufacture, characterization and performance in SSLSBs are summarized in detail. Finally, a scientific outlook for the future development of SSEs and the avenue to commercial application of SSLSBs is also proposed.     

Quantification of Temperature-Dependent Charge Separation and Recombination Dynamics in Non-Fullerene Organic Photovoltaics

Transient optical spectroscopy is used to quantify the temperature-dependence of charge separation and recombination dynamics in P3TEA:SF-PDI₂ and PM6:Y6, two non-fullerene organic photovoltaic (OPV) systems with a negligible driving force and high photocurrent quantum yields. By tracking the intensity of the transient electroabsorption response that arises upon interfacial charge separation in P3TEA:SF-PDI₂, a free charge generation rate constant of ≈2.4 × 10¹⁰ s⁻¹ is observed at room temperature, with an average energy of ≈230 meV stored between the interfacial charge pairs. Thermally activated charge separation is also observed in PM6:Y6, and a faster charge separation rate of ≈5.5 × 10¹⁰ s⁻¹ is estimated at room temperature, which is consistent with the higher device efficiency. When both blends are cooled down to cryogenic temperature, the reduced charge separation rate leads to increasing charge recombination either directly at the donor-acceptor interface or via the emissive singlet exciton state. A kinetic model is used to rationalize the results, showing that although photogenerated charges have to overcome a significant Coulomb potential to generate free carriers, OPV blends can achieve high photocurrent generation yields given that the thermal dissociation rate of charges outcompetes the recombination rate.     

Method for Overflow Attack Defense of SDN Network Flow Table Based on Stochastic Differential Equation

In order to avoid the overflow problem of network flow table caused by hackers attacking the network in the process of using the network, a method for overflow attack defense of SDN network flow table based on stochastic differential equation is proposed. In this method, the stochastic differential equation is first proposed, and the drift coefficient and diffusion coefficient of the equation are expanded and adjusted by Taylor. By using the limit theorem, the spillover attack of SDN network is weakly converged to an approximate two-dimensional Markov diffusion process, and the improved stochastic differential equation is obtained. Then, according to the stochastic nature of SDN network attack, the stochastic differential equation is transformed into an amplitude equation, which is based on the amplitude. The equation establishes a SDN attack detection scheme based on flow table statistics, which detects the spillover attacks of SDN network flow tables. Finally, according to the test results, it is proposed to use other switches instead of network flow table overflow switches to control the data upload rate, thus reducing the possibility of network crash and meeting the attack defense requirements of flow table overflow. The simulation results show that the proposed method has better detection performance and shorter running time, and can provide help for network security related work.

     

JTE终端结构4H-SiC JBS二极管的击穿特性研究

研究了JTE终端结构4H-SiC JBS二极管的击穿特性。首先,理论模拟了JTE终端横向长度、离子注入剂量和界面电荷对击穿电压的影响。对工艺条件进行优化,制作了JTE终端结构4H-SiC JBS二极管。测试结果表明,器件的正向电压为1.52 V,特征导通电阻为2.12 mΩ·cm²,击穿电压为1 650 V。接着,研究器件的变温电流-电压特性发现,正向电流主要为热发射机制,而反向电流与电压、温度有很强的依赖关系。最后进行了高温反偏应力老化测试,结果表明,击穿电压呈下降趋势。     

磨粒厚度的测量研究

由于厚度在磨粒分类中具有重要作用,提出了用显微镜来测量磨粒的厚度的方法,并分析了引起测量误差的有关因素,计算了其可能的最大误差。实践表明用形状因子来区分层状磨粒与疲劳剥块是可行的。