Direct insight into sulfiphilicity-lithiophilicity design of bifunctional heteroatom-doped graphene mediator toward durable Li-S batteries

The practical applications of lithium-sulfur(Li-S)battery have been greatly hindered by the severe polysulfide shuttle at the cathode and rampant lithium dendrite growth at the anode.One of the effective solutions deals with concurrent management of both electrodes.Nevertheless,this direction remains in a nascent stage due to a lack of material selection and mechanism exploration.Herein,we devise a temperature-mediated direct chemical vapor deposition strategy to realize the controllable synthesis of three-dimensional boron/nitrogen dual-doped graphene(BNG)particulated architectures,which is employed as a light-weighted and multi-functional mediator for both electrodes in Li-S batteries.Benefiting from the“sulfiphilic”and“lithiophilic”features,the BNG modified separator not only enables boosted kinetics of polysulfide transformation to mitigate the shuttle effect but also endows uniform lithium deposition to suppress the dendritic growth.Theoretical calculations in combination with electro-kinetic tests and operando Raman analysis further elucidate the favorable sulfur and lithium electrochemistry of BNG at a molecular level.This work offers direct insight into the mediator design via controllable synthesis of graphene materials to tackle the fundamental challenges of Li-S batteries.

A review in rational design of graphene toward advanced Li-S batteries

For lithium-sulfur(Li-S)batteries,the problems of polysulfides shuttle effect,slow dynamics of sulfur species and growth of lithium dendrite during charge/discharge processes have greatly impeded its practical development.Of core importance to advance the performances of Li-S batteries lies in the selection and design of novel materials with strong polysulfides adsorption ability and enhanced redox electrocatalytic behavior.Graphene,affording high electrical conductivity,superior carrier mobility,and large surface area,has presented great potentials in improving the performances of Li-S cells.However,the properties of intrinsic graphene are far enough to achieve the multiple management toward electrochemical catalysis of energy storage systems.In addition,a general and objective understanding of its role in Li-S systems is still lacking.Along this line,we summarize the design routes from three aspects,including defect engineering,dimension adjustment,and heterostructure modulation,to perfect the graphene properties.Thus-synthesized graphene materials are explored as multifunctional electrocatalysts targeting high-efficiency and long-lifespan Li-S batteries,based on which the regulating role of graphene is comprehensively analyzed.This project provides a perspective on the effective engineering management of graphene materials to boost Li-S chemistry,meanwhile promote the practical application process for graphene materials.

CO_(2)-promoted transfer-free growth of conformal graphene

Gaseous promotors have readily been adopted during the direct synthesis of graphene over insulators to enhance the growth quality and/or boost the growth rate.The understanding of the real functions of carbon-containing promotors has still remained elusive.In this study,we identify the critical roles of a representative CO_(2)promotor played in the direct growth of graphene.The comparative experimental trials validate CO_(2)as an effective modulator to decrease graphene nucleation density,improve growth kinetics,mitigate adlayer formation.The first-principles calculations illustrate that the generation of gas-phase OH species in CO_(2)-assisted system helps decrease the energy barriers of CH4 decomposition and carbon attachment to the growth front,which might be the key factor to allow high-quality direct growth.Such a CO_(2)-promoted strategy enables the conformal coating of graphene film over curved insulators,where the sheet resistance of grown graphene on quartz reaches as low as 1.26 kΩ·sq^(−1)at an optical transmittance of~95.8%.The fabricated endoscope lens based on our conformal graphene harvests an apoptosis of 82.8%for noninvasive thermal therapy.The work presented here is expected to motivate further investigations in the controllable growth of high-quality graphene on insulating substrates.

Decorating Vertically Oriented Graphene Arrays with Co-Doped NiTe_(2)Toward Al-Current-Collector-Free Li-S Batteries

Lithium-sulfur(Li-S)batteries are broadly regarded as one of the most promising energy storage systems owing to their high-energy and low-cost features.Nevertheless,their practical implementation is plagued by the notorious polysulfide shuttling and sluggish reaction kinetics.Transition metal telluride has emerged as a promising electrocatalyst to expedite sulfur redox kinetics,even though its controllable and precise fabrication remains quite elusive.Herein,we propose the employment of a chemical vapor deposition approach to achieve in situ growth of Co-doped NiTe_(2)(Co-NiTe_(2))on vertically oriented graphene coated carbon cloth(VG/CC)substrate,in the pursuit of high-performance sulfur host material(Co-NiTe_(2)@VG/CC)in Li-S realms.Electrokinetic analysis and operando Raman spectroscopy characterization reveal the effective regulation capability of Co-NiTe_(2)@VG/CC with respect to polysulfide capture/conversion and Li2S decomposition.As a result,the Al-currentcollector-free Co-NiTe_(2)@VG/CC-based cathodes with typical sulfur loading exhibit outstanding cycling stability(93.8% capacity retention over 100 cycles at 0.5 C).Moreover,an areal capacity of 4.27 mAh cm^(-2) at 0.2 C can be harvested even at an elevated sulfur loading of 7.2 mg cm^(-2).

Confining MOF-derived SnSe nanoplatelets in nitrogen-doped graphene cages via direct CVD for durable sodium ion storage

Tin-based compounds are deemed as suitable anode candidates affording promising sodium-ion storages for rechargeable batteries andhybrid capacitors.However,synergistically tailoring the electrical conductivity and structural stability of tin-based anodes to attain durablesodium-ion storages remains challenging to date for its practical applications.Herein,metal-organic framework(MOF)derived SnSe/C wrappedwithin nitrogen-doped graphene(NG@SnSe/C)is designed targeting durable sodium-ion storage.NG@SnSe/C possesses favorable electricalconductivity and structure stability due to the"inner"carbon framework from the MOF thermal treatment and"outer"graphitic cage from thedirect chemical vapor deposition synthesis.Consequently,NG@SnSe/C electrode can obtain a high reversible capacity of 650 mAh·g^-1 at 0.05 A·g^1,a favorable rate performance of 287.8 mAh·g^1 at 5 A·g^1 and a superior cycle stability with a negligible capacity decay of 0.016%percycle over 3,200 cycles at 0.4 A·g^1.Theoretical calculations reveal that the nitrogen-doping in graphene can stabilize the NG@SnSe/Cstructure and improve the electrical conductivity.The reversible Na-ion storage mechanism of SnSe is further investigated by in-situ X-raydiffraction/ex-s/tu transmission electron microscopy.Furthermore,assembled sodium-ion hybrid capacitor full-cells comprising our NG@SnSe/Canode and an active carbon cathode harvest a high energy/power density of 115.5 Wh·kg^-1/5,742 W·kg^-1,holding promise for next-generationen ergy storages.

基于化学气相沉积技术的粉体石墨烯的制备及能源领域应用

化学气相沉积技术(chemical vapor deposition,CVD)因其产物设计性强、反应途径灵活、层数均匀可控、衬底种类多样、批量化高品质制备等特点而广受关注.本文以CVD制备石墨烯为出发点,归纳利用模板法和非模板法合成具有特定形貌的高品质粉体石墨烯材料,其具有高电导率、大比表面积和良好的分散性.进一步地,基于CVD方法合成的粉体石墨烯,对其在能量存储领域的应用展开阐述.CVD技术所制备的粉体石墨烯在储能应用领域中展现出的巨大潜力,使其有望成为助力高能量长循环储能器件的理想材料.

6-inch uniform vertically-oriented graphene on soda-lime glass for photothermal applications

Vertically-oriented graphene （VG） has many advantages over flat lying graphene, including a large surface area, exposed sharp edges, and non-stacking three-dimensional geometry. Recently, VG nanosheets assembled on specific substrates have been used for applications in supersensitive gas sensors and high-performance energy storage devices. However, to realize these intriguing applications, the direct growth of high-quality VG on a functional substrate is highly desired. Herein, we report the direct synthesis of VG nanosheets on traditional soda-lime glass due to its low-cost, good transparency, and compatibility with many applications encountered in daily life. This synthesis was achieved by a direct-current plasma enhanced chemical vapor deposition （dc-PECVD） route at 580℃, which is right below the softening point of the glass, and featured a scale-up size - 6 inches. Particularly, the fabricated VG nanosheets/glass hybrid materials at a transmittance range of 97%-34% exhibited excellent solarthermal performances, reflected by a 70%-130% increase in the surface temperature under simulated sunlight irradiation. We believe that this graphene glass hybrid material has great potential for use in future transparent ＂green-warmth＂ construction materials.

Growth of 12-inch uniform monolayer graphene film on molten glass and its application in PbI2-based photodetector

Direct growth of large area uniform graphene on functional insulating materials is essential for engineering versatile applications of graphene. However, the existing synthesis approaches can hardly avoid the generation of non-uniform multilayer graphene along the gas flow direction, affording huge challenges for further scaling up. Herein, by exploiting the molten state of soda-lime glass, we have accomplished the direct growth of large area uniform (up to 30 cm × 6 cm) graphene via a facile chemical vapor deposition route on low cost soda-lime glass. The use of molten glass eliminates the chemically active sites (surface corrugations, scratches, defects), and improves the mobility of carbon precursors, affording uniform nucleation and growth of monolayer graphene. Intriguingly, thus-obtained graphene acts as an ideal coating layer for the surface crystallographic modification of soda-lime glass, making it epitaxy substrates for synthesizing high-quality PbI2 nanoplates and continues films. Accordingly, a prototype photodetector was fabricated to present excellent photoelectrical properties of high responsivity (~ 600 on/off current ratio) and fast response speed (18 μs). This work hereby paves ways for the batch production and the direct applications of graphene glass as platforms for constructing high performance electronic and optoelectronic devices.

Oxygen-assisted direct growth of large-domain and high-quality graphene on glass targeting advanced optical filter applications

Growing high quality graphene films directly on glass by chemical vapor deposition(CVD)meets a growing demand for constructing high-performance electronic and optoelectronic devices.However,the graphene synthesized by prevailing methodologies is normally of polycrystalline nature with high nucleation density and limited domain size,which significantly handicaps its overall properties and device performances.Herein,we report an oxygen-assisted CVD strategy to allow the direct synthesis of 6-inch-scale graphene glass harvesting markedly increased graphene domain size(from 0.2 to 1.8μm).Significantly,as-produced graphene glass attains record high electrical conductivity(realizing a sheet resistance of 900Ω·sq^(-1)at a visible-light transmittance of 92%)amongst the state-of-the-art counterparts,readily serving as transparent electrodes for fabricating high-performance optical filter devices.This work might open a new avenue for the scalable production and application of emerging graphene glass materials with high quality and low cost.