Highly Reversible Li–Se Batteries with Ultra-Lightweight N,S-Codoped Graphene Blocking Layer

The desire for practical utilization of rechargeable lithium batteries with high energy density has motivated attempts to develop new electrode materials and battery systems. Here, without additional binders we present a simple vacuum filtration method to synthesize nitrogen and sulfur codoped graphene(N,S-G) blocking layer, which is ultra-lightweight, conductive, and free standing. When the N,S-G membrane was inserted between the catholyte and separator, the lithium–selenium(Li–Se)batteries exhibited a high reversible discharge capacity of 330.7 mAh g^(-1) at 1 C(1 C = 675 mA g^(-1)) after 500 cycles and high rate performance(over 310 mAh g^(-1) at 4 C) even at an active material loading as high as ～5 mg cm^(-2). This excellent performance can be ascribed to homogenous dispersion of the liquid active material in the electrode, good Li^+-ion conductivity, fast electronic transport in the conductive graphene framework, andstrong chemical confinement of polyselenides by nitrogen and sulfur atoms. More importantly, it is a promising strategy for enhancing the energy density of Li–Se batteries by using the catholyte with a lightweight heteroatom doping carbon matrix.

Robust S-doped TiO_(2)@N,S-codoped carbon nanotube arrays as free-binder anodes for efficient sodium storage

Titanium dioxide(TiO_2) has been investigated broadly as a stable,safe,and cheap anode material for sodium-ion batteries in recent years.However,the poor electronic conductivity and inherent sluggish sodium ion diffusion hinder its practical applications.Herein,a self-template and in situ vulcanization strategy is developed to synthesize self-supported hybrid nanotube arrays composed of nitrogen/sulfur-codoped carbon coated sulfur-doped TiO_2 nanotubes(S-TiO_2@NS-C) starting from H_2 Ti_2 O_5-H_2 O nanoarrays.The S-TiO_2@NS-C composite with one-dimensional nano-sized subunits integrates several merits.Specifically,sulfur doping strongly improves the Na~+ storage ability of TiO_2@C-N nanotubes by narrowing the bandgap of original TiO_2.Originating from the nanoarrays structures built from hollow nanotubes,carbon layer and sulfur doping,the sluggish Na~+ insertion/extraction kinetics is effectively improved and the volume variation of the electrode material is significantly alleviated.As a result,the S-TiO_2@NS-C nanoarrays present efficient sodium storage properties.The greatly improved sodium storage performances of S-TiO_2@NS-C nanoarrays confirm the importance of rational engineering and synthesis of hollow array architectures with higher complexity.

Biomass-Derived Nitrogen and Sulfur Co-Doped 3D Carbon Networks with Interconnected Meso-Microporous Structure for High-Performance Supercapacitors

Three-dimensional(3D)carbon networks have been explored as promising capacitive materials thanks to their unique structural features such as large ion-accessible surface area and interconnected porous networks,thus enhancing both ions and electrons transport.Here,sustainable bacterial cellulose(BC)is used both precursor and template for facile synthesis of free-standing N,S-codoped 3Dcarbon networks(a-NSC)by the pyrolysis and activation of polyrhodanine coated BC.The synthesized a-NSC shows highly conductive interconnected porous networks(24S·cm^(-1)),large surface area(1 420m^2·g^(-1))with hierarchical meso-microporosity,and high-level heteroatoms codoping(N:3.1%in atom,S:3.2%in atom).Benefitting from these,a-NSC as binder-free electrode exhibits an ultrahigh specific capacitance of 340F·g^(-1)(24μF·cm^(-2))at the current density of 0.5A·g^(-1)in 6MKOH electrolyte,high-rate capability(71%at 20A·g^(-1))and excellent cycle stability.Furthermore,the assembled symmetrical supercapacitor displays a much short time constant of 0.35sin 1MTEABF4/AN electrolyte,obtaining a maximum energy density of 32.1W·h·kg^(-1 )at power density of 637W·kg^(-1).The in situ multi-heteroatoms doping enables biocellulose-derived carbon networks to exploit its full potentials in energy storage applications,which can be extended to other dimensional carbon nanostructures.

Green-emissive carbon quantum dots with high fluorescence quantum yield:Preparation and cell imaging

High fluorescence quantum yield(QY),excellent fluorescence stability,and low toxicity are essential for a good cellular imaging fluorescent probe.Green-emissive carbon quantum dots(CQDs)with many advantages,such as unique fluorescence properties,anti-photobleaching,low toxicity,fine biocompatibility and high penetration depth in tissues,have been considered as a potential candidate in cell imaging fluorescent probes.Herein,N,S-codoped green-emissive CQDs(QY=64.03%)were synthesized by the one-step hydrothermal method,with m-phenylenediamine as the carbon and nitrogen source,and L-cysteine as the nitrogen and sulfur dopant,under the optimum condition of 200℃ reaction for 2 h.Their luminescence was found to originate from the surface state.In light of the satisfactory photobleaching resistance and the low cytotoxicity,CQDs were used as a cell imaging probe for HeLa cell imaging.The results clearly indicate that cells can be labeled with CQDs,which can not only enter the cytoplasm,but also enter the nucleus through the nuclear pore,showing their broad application prospect in the field of cell imaging.

在NaCl非水离子液体中制备类石墨烯状氮硫共掺杂生物质碳材料来提高锂硫电池的动力学研究（英文）

本论文通过结构设计利用简单方法成功制备了一种二维N,S共掺杂类石墨烯纳米片复合结构,即利用NaCl非水离子液体的剥离作用使生物质剥离得到二维片层类石墨烯结构.这种新的非水离子液体剥离技术较其他的碳材料剥离技术具有环境友好性、低成本、安全无毒性等优势,有利于实现量化制备锂硫电池电极材料.该材料采用大自然中广泛存在的紫菜作为原料,其内部富含的氨基酸为原位掺杂N,S元素提供了可能性.二维结构的纳米片能够提供有效的导电性和电解液浸润性的网络结构,同时还能够有效地降低电池在充放电循环过程中导致的体积膨胀效应,最终实现一种高机械性能、优异电化学活性的电极在锂硫电池储能领域中的应用.