Ten-Minute Synthesis of a New Redox-Active Aqueous Binder for Flame-Retardant Li-S Batteries

As a critical role in battery systems,polymer binders have been shown to efficiently suppress the lithium polysulfide shuttling and accommodate volume changes in recent years.However,preparation processes and safety,as the key criterions for Li-S batteries'practical applications,still attract less attention.Herein,an aqueous multifunction binder(named PEI-TIC)is prepared via an easy and fast epoxy-amine ring-opening reaction(10 min),which can not only give the sulfur cathode a stable mechanical property,a strong chemical adsorption and catalytic conversion ability,but also a fire safety improvement.The Li-S batteries based on the PEI-TIC binder display a high discharge capacity(1297.8 mAh g^(-1)),superior rate performance(823.0 mAh g^(-1)at 2 C),and an ultralow capacity decay rate of 0.035%over more than 800 cycles.Even under 7.1 mg cm^(-2)S-loaded,the PEI-TIC electrode can also achieve a high areal capacity of 7.2 mA h g^(-1)and excellent cycling stability,confirming its application potential.Moreover,it is also noted that TG-FTIR test is performed for the first time to explore the flame-retardant mechanism of polymer binders.This work provides an economically and environmentally friendly binder for the practical application and inspires the exploration of the flame-retardant mechanism of all electrode components.

A semi-immobilized sulfur-rich copolymer backbone with conciliatory polymer skeleton and conductive substrates for high-performance Li-S batteries

Sulfur-rich polymers have gained a great deal of attention as the next-generation active materials in lithium-sulfur(Li-S)batteries due to their low cost,environmental compatibility,naturally sulfur uniform dispersion,and distinctive structure covalently bonding with sulfur atoms.However,the poor electrical conductivity and undesirable additional shuttle effect still hinder the commercial application of sulfur-rich polymers.Herein,we report a flexible semi-immobilization strategy to prepare allylterminated hyperbranched poly(ethyleneimine)-functionalized reduced graphene oxide(A-PEI-EGO)as sulfur-rich copolymer backbone.The semi-immobilization strategy can effectively reconcile the demand for polymer skeleton and conductive substrates through forming quaternary ammonium groups and reducing oxygen-containing functional groups,resulting in enhanced skeleton adsorption capacity and substrate electronic conductivity,respectively.Furthermore,the stable covalent bonding connection based on polymer molecules(A-PEI)not only completely prevents the additional shuttle effect of lithiation organic molecules and even sulfur-rich oligomers,but provides more inverse vulcanization active sites.As a result,the as-prepared A-PEI-EGO-S cathodes display an initial discharge capacity of1338 m A h g^(-1)at a rate of 0.1 C and an outstanding cycling stability of 0.046%capacity decay per cycle over 600 cycles.Even under 6.2 mg cm^(-2)S-loaded and sparing electrolyte of 6μL mg^(-1),the A-PEI-EGO-S cathode can also achieve a superior cycling performance of 98%capacity retention after 60 cycles,confirming its application potential.

High-Performance and Flexible Co-Planar Integrated Microsystem of Carbon-Based All-Solid-State Micro-Supercapacitor and Real-Time Temperature Sensor

With the rapid development of flexible and portable microelectronics,the extreme demand for miniaturized,mechanically flexible,and integrated microsystems are strongly stimulated.Here,biomass-derived carbons(BDCs)are prepared by KOH activation using Qamgur precursor,exhibiting three-dimensional(3D)hierarchical porous structure.Benefiting from unobstructed 3D hierarchical porous structure,BDCs provide an excellent specific capacitance of 433 F g^(-1)and prominent cyclability without capacitance degradation after 50000 cycles at 50 A g^(-1).Furthermore,BDC-based planar micro-supercapacitors(MSCs)without metal collector,prepared by mask-assisted coating,exhibit outstanding areal-specific capacitance of 84 mF cm^(-2)and areal energy density of 10.6μWh cm^(-2),exceeding most of the previous carbon-based MSCs.Impressively,the MSCs disclose extraordinary flexibility with capacitance retention of almost 100%under extreme bending state.More importantly,a flexible planar integrated system composed of the MSC and temperature sensor is assembled to efficiently monitor the temperature variation,providing a feasible route for flexible MSC-based functional micro-devices.

A flexible design strategy to modify Ti3C2Tx MXene surface terminations via nucleophilic substitution for long-life Li-S batteries

MXene-based materials have gained considerable attention for lithium-sulfur(Li-S)batteries cathode materials due to their superior electric conductivity and high affinitive to polysulfides.However,there are still challenges in modifying the surface functional groups of MXene to further improve the electrochemical performance and increase the structure variety for MXene-based sulfur host.Herein,we report an efficient and flexible nucleophilic substitution(S_(N))strategy to modify the Ti_(3)C_(2)T_(x) surface terminations and purposefully designed Magnolol-modified Ti_(3)C_(2)T_(x)(M-Ti_(3)C_(2)T_(x))as powerful cathode host materials.Benefiting from more C-Ti-O bonds forming and diallyl groups terminations reducing after the dehalogenation and nucleophilic addition reactions,the given M-Ti_(3)C_(2)T_(x) electrode could effectively suppress the lithium polysulfides shuttling via chemisorption and C—S covalent bond formation.Besides,the Magnolol-modified Ti_(3)C_(2)T_(x) significantly accelerates polysulfide redox reaction and reduces the activation energy of Li_(2) S decomposition.As a result,the as-prepared M-Ti_(3)C_(2)T_(x) electrode displays an excellent rate capability and a high reversible capacity of 7.68 mAh cm^(-2)even under 7.2 mg cm^(-2)S-loaded with a low decay rate of 0.07%(from 2 nd cycle).This flexible surface-modified strategy for MXene terminations is expected to be extended to other diverse MXene applications.

A Novel Strategy of In Situ Trimerization of Cyano Groups Between the Ti3C2Tx(MXene) Interlayers for High-Energy and High-Power Sodium-Ion Capacitors

2D MXenes are attractive for energy storage applications because of their high electronic conductivity.However,it is still highly challenging for improving the sluggish sodium(Na)-ion transport kinetics within the MXenes interlayers.Herein,a novel nitrogen-doped Ti3C2Tx MXene was synthesized by introducing the in situ polymeric sodium dicyanamide(Na-dca)to tune the complex terminations and then utilized as intercalation-type pseudocapacitive anode of Na-ion capacitors(NICs).The Na-dca can intercalate into the interlayers of Ti3C2 Tx nanosheets and simultaneously form sodium tricyanomelaminate(Na3TCM)by the catalyst-free trimerization.The as-prepared Ti3C2Tx/Na3TCM exhibits a high N-doping of 5.6 at.%in the form of strong Ti-N bonding and stabilized triazine ring structure.Consequently,coupling Ti3C2Tx/Na3 TCM anode with different mass of activated carbon cathodes,the asymmetric MXene//carbon NICs are assembled.It is able to deliver high energy density(97.6 Wh kg-1),high power output(16.5 kW kg-1),and excellent cycling stability(≈82.6%capacitance retention after 8000 cycles).

The maize late embryogenesis abundant protein Zm DHN13 positively regulates copper tolerance in transgenic yeast and tobacco

Late embryogenesis abundant (LEA) proteins accumulate in the late stage of plant seed development, and are upregulated in most plants during drought, cold, heat, or salinity stress. LEA proteins can be classified by amino-acid sequence into seven groups. Dehydrins belong to LEA protein group Ⅱ. In previous studies, the maize KS type dehydrin ZmDHN13 increased the tolerance of transgenic tobacco to oxidative stress. In the present study, ZmDHN13 was identified under copper stress conditions, and the protein was then characterized using transgenic yeast and tobacco plants to investigate its functions. ZmDHN13 bound Cu2+. Its overexpression in transgenic tobacco conferred tolerance to copper stress by binding metals and reducing the accumulation of reactive oxygen species (ROS). Three conserved domains displayed a cooperative effect under copper stress conditions.

High and ultra-stable energy storage from all-carbon sodium-ion capacitor with 3D framework carbon as cathode and carbon nanosheet as anode

Sodium-ion capacitors(SICs)are extremely promising due to the combined merits of high energy-power characteristics and considerable price advantage.However,it is still difficult to achieve high energypower outputs and cycle stability in a typical configuration of the metal-based battery-type anode and activated carbon capacitor-type cathode due to the kinetic mismatching.In this work,a carbon nanosheet(PSCS-600)with large interlayer spacing of 0.41 nm derived from the bio-waste pine cone shell was prepared.Besides,the covalent triazine framework derived carbon(OPDN-CTF-A)was obtained through ionothermal synthesis strategy,exhibiting beneficial hierarchical pores(0.5-6 nm)and high heteroatoms(5.6 at%N,6.6 at%O).On this basis,the all-carbon SICs were fabricated by the integration of PSCS-600 anode and OPDN-CTF-A cathode.The device delivered high energy density 111 Wh kg^(-1),high power output of 14,200 W kg^(-1) and ultra-stable cycling life(~90.7%capacitance retention after 10,000 cycles).This work provides new ideas in fabricating carbon-carbon architectural SICs with high energy storage for practical application.

Carbon spheres with rational designed surface and secondary particle-piled structures for fast and stable sodium storage

The electrochemical performance of hard carbon in sodium storage is still limited by its poor cycling stability and rate capability because of the sluggish kinetics process.In this study,we use a simple and effective method to accelerate the kinetics process by engineering the structure of the electrode to promote its surface and near-surface reactions.This goal is realized by the use of slightly aggregated ultra-small carbon spheres.The large specific surface area formed by the small spheres can provide abundant active sites for electrochemical reactions.The abundant mesopores and macropores derived from the secondary particle piled structure of the carbon spheres could facilitate the transport of electrolytes,shorten the diffusion distance of Na^(+)and accommodate the volume expansion during cycling.Benefiting from these unique structure features,PG700-3(carbon spheres with the diameters of 40-60 nm carbonized at 700℃)exhibits high performance for sodium storage.A high reversible capacity of 163 mAh g^(-1) could be delivered at a current density of 1.0 A g^(-1) after 100 cycles.Interestingly,at a current density of 10.0 A g^(-1),the specific capacity of PG700-3 gradually increases to 140 mAh g^(-1) after 10000 cycles,corresponding to a capacity retention of 112%.Given the enhanced kinetics of SIBs reactions,PG700-3 exhibits an excellent rate capability,i.e.,230 and 138 mAh g^(-1) at 0.1 and 5.0 A g^(-1),respectively.This study provides a facile method to attain high performance anode materials for SIBs.The design strategy and improvement mechanism could be extended to other materials for high rate applications.

A lightweight nitrogen/oxygen dual-doping carbon nanofiber interlayer with meso-/micropores for high-performance lithium-sulfur batteries

Lithium-sulfur(Li-S) batteries are promising energy-storage devices for future generations of portable electronics and electric vehicles because of the outstanding energy density,low cost,and nontoxic nature of S.In the past decades,various novel electrodes and electrolytes have been studied to improve the performance of Li-S batteries.However,the very limited lifespan and rate performance of Li-S batteries originating from the dissolution and diffusion of long-chain polysulfides in liquid electrolytes,and the intrinsic poor conductivity of S severely hinder their practical application.Herein,an electrospinning method was developed to fabricate a thin conductive interlayer consisting of meso-/microporous N/O dual-doping carbon nanofiber(CNF).The freestanding 3 D interwoven structure with conductive pathways for electrons and ions can enhance the contact between polysulfides and N/O atoms to realize the highly robust trapping of polysulfides via the extremely polar interaction.Consequently,combining the meso-microporous N/O dual-doping CNF interlayer with a monodispersed S nanoparticle cathode results in a superior electrochemical performance of 862.5 mAh/g after 200 cycles at 0.2 C and a cycle decay as low as 0.08% per cycle.An area specific capacity of 5.22 mAh/cm^(2) can be obtained after 100 cycles at 0.1 C with a high S loading of 7.5 mg/cm^(2).

MXenes for metal-ion and metal-sulfur batteries:Synthesis,properties,and electrochemistry

In 2011,a new class of 2D materials was discovered;after 2012,they began to be concerned;in 2017,the“gold rush”of the materials was triggered,and they are exactly MXenes.2D MXenes,a new class of transition metal carbides,carbonitrides and nitrides,have become the star and cutting-edge research materials in the field of emerging batteries systems due to their unique 2D structure,abundant surface chemistry,and excellent physical and electrochemical properties.This review focuses on the MXene materials and summarizes the recent advancements in the synthesis techniques and properties,in addition to a detailed discussion on the electrochemical energy storage applications,including alkali-ion(Li^(+),Na^(+),K^(+))storage,lithium-sulfur(Li–S)batteries,sodiumsulfur(Na–S)batteries,and metal anode protection.Special attentions are given to the elaborate design of nano-micro structures of MXenes for the various roles as electrodes,multifunctional components,S hosts,modified separators,and metal anode protective layers.The paper ends with a prospective summary of the promising research directions in terms of synthesis,structure,properties,analysis,and production on MXene materials.

An all-biomaterials-based aqueous binder based on adsorption redox-mediated synergism for advanced lithium–sulfur batteries

The complex multistep electrochemical reactions of lithium polysulfides and the solid–liquid–solid phase transformation involved in the S8 to Li2S reactions lead to slow redox kinetics in lithium–sulfur batteries(Li–S batteries).However,some targeted researches have proposed strategies requiring the introduction of significant additional inactive components,which can seriously affect the energy density.Whereas polymer binders,proven to be effective in suppressing shuttle effects and constraining electrode volume expansion,also have promising potential in enhancing Li–S batteries redox kinetics.Herein,a novel aqueous polymer binder is prepared by convenient amidation reaction of fully biomaterials,utilizing its inherent rich amide groups for chemisorption and redox mediating ability of thiol groups to achieve adsorption redox-mediated synergism for efficient conversion of polysulfides.Li–S batteries based on N-Acetyl-L-Cysteine-Chitosan(NACCTS)binder exhibit high initial discharge specific capacity(1260.1mAhg−1 at 0.2C)and excellent cycling performance over 400 cycles(capacity decay rate of 0.018%per cycle).In addition,the batteries exhibit great areal capacity and stable capacity retention of 83.6%over 80 cycles even under high sulfur loading of 8.4mgcm−2.This work offers a novel perspective on the redox-mediated functional design and provides an environmentally friendly biomaterials-based aqueous binder for practical Li–S battery.

Sulfur polymerization strategy based on the intrinsic properties of polymers for advanced binder-free and high-sulfur-content Li–S batteries

Lithium-sulfur(Li-S)batteries are the promising next-generation secondary energy storage systems,because of their advantages of high energy density and environmental friendliness.Among numerous cathode materials,organosulfur polymer materials have received extensive attentions because of their controllable structure and uniform sulfur distribution.However,the sulfur content of most organosulfur polymer cathodes is limited(S content<60%)due to the addition of large amounts of conductive agents and binders,which adversely affects the energy density of Li-S batteries.Herein,a hyperbranched sulfur-rich polymer based on modified polyethyleneimine(Ath-PEI)named carbon nanotubeentangled poly(allyl-terminated hyperbranched ethyleneimine-random-sulfur)(CNT/Ath-PEI@S)was prepared by sulfur polymerization and used as a Li-S battery cathode.The high intrinsic viscosity of Ath-PEI provided considerable adhesion and avoided the addition of PVDF binder,thereby increasing the sulfur content of cathodes to 75%.Moreover,considering the uniform distribution of elemental sulfur by the polymer,the utilization of sulfur was successfully improved,thus improving the rate capability and discharge capacity of the battery.The binder-free,sulfur-rich polymer cathode exhibited ultra-high initial discharge capacity(1520.7 mAh g^(−1) at 0.1 C),and high rate capability(804 mAh g^(−1) at 2.0 C).And cell-level calculations show that the electrode exhibits an initial capacity of 942.3 mAh g^(−1) electrode,which is much higher than those of conventional sulfur-polymer electrodes reported in the literature.

密度泛函理论计算筛选锂硫电池用单原子催化剂

探索具有高催化作用的活性中心结构,对于开发锂硫电池用单原子催化剂(SACs)至关重要.基于密度泛函理论计算,本工作提出了一种新型吡咯氮配位结构,用于负载3d过渡金属原子,以设计出高性能SACs.相比于传统的吡啶氮配位结构,该吡咯氮配位结构可实现对多硫化物更高的吸附及催化转化作用,从而提升锂硫电池活性物质的利用率、循环稳定性及倍率性能.基于对不同配位结构中的金属原子d轨道与多硫化物中硫原子p轨道杂化方式的分析,本工作阐明了吡咯氮配位结构可对多硫化物实现更强吸附作用的原因.此外,采用数据驱动的研究手段,探索出影响多硫化物催化转化效率的本征因素.因此,本工作提出了新型锂硫电池用SACs活性中心结构,并揭示了SACs的性能调控机制,为锂硫电池用SACs的设计提供了新策略.

番茄果实早期发育的分子生理机制研究进展

番茄(Solanum lycopersicum)是目前世界上种植面积最广且最受欢迎的蔬菜作物之一,也是肉果及茄科的重要模式植物。番茄果实发育主要分为早期果实发育和果实成熟2个时期,但果实形态结构和大小主要决定于早期果实发育时期。该文围绕番茄早期果实发育时期植物激素、细胞周期、表观遗传和源库代谢等多方面调控的分子机制进行了综述,旨在认识植物生长与发育的基本生物学问题及促进基础理论研究成果在生产中应用。

Compositional and structural study of ash deposits spatially distributed in superheaters of a large biomass-fired CFB boiler

Recognizing the nature and formation progress of the ash deposits is essential to resolve the deposition problem hindering the wide application of large-scale biomass-fired boilers.Therefore,the ash deposits in the superheaters of a 220 t/h biomass-fired CFB boiler were studied,including the platen(PS),the high-temperature(HTS),the upper and the lower low-temperature superheaters(LTS).The results showed that the deposits in the PSs and HTSs were thin(several millimeters)and compact,consisting of a yellow outer layer and snow-white inner layer near the tube surface.The deposits in the upper LTS appeared to be toughly sintered ceramic,while those in the lower LTS were composed of dispersive coarse ash particles with an unsintered surface.Detailed characterization of the cross-section and the initial layers in the deposits revealed that the dominating compositions in both the PSs and the HTSs were Cl and K(approximately 70%)in the form of KCl.Interestingly,the cross-section of the deposition in the upper LTS exhibited a unique lamellar structure with a major composition of Ca and S.The contents of Ca and Si increased from approximately 10%to approximately 60%in the deposits from the high temperature surfaces to the low temperature ones.It was concluded that the vaporized mineral matter such as KCl played the most important role in the deposition progress in the PS and the HTS.In addition,although the condensation of KCl in the LTSs also happened,the deposition of ash particles played a more important role.

Replacing“Alkyl”with“Aryl”for inducing accessible channels to closed pores as plateau-dominated sodium-ion battery anode

Hard carbons are promising anodes for sodium-ion batteries.However,there is still considerable controversy regarding the sodium storage behaviors in hard carbons,which are mainly attributed to the varied precursors,confused pyrolysis mechanism,and different characterization methods.Herein,benefiting from the flexible molecular structure of polymers,a series of hard carbons with carefully tunedmicrostructures are fabricated by adjusting the ratio of aryl and alkyl groups in the epoxy resins.The results of dynamic mechanical analysis,insitu Fourier transform infrared spectra,and synchronous thermal gravimetricinfrared spectrum-gas chromatography/mass spectrometry reveal that replacing the alkyl with aryl groups in the resin can enhance the crosslink density,inhibit the degradation and rearrangement process,and further lead to a more disordered microstructure.In addition,it is suggested that accessible channels provided by sufficiently wide interlayer spacing are necessary for closed pore filling.The optimized anode delivers a high capacity of 375 mAh/g in half cell with an initial Coulombic efficiency of 80.61%,and an energy density of 252 Wh/kg is attained in full cell.Finally,a reliable relationship among precursor-pyrolysis mechanism-structure-performance is established,and the sodium storagemechanism of“adsorption-insertion-pore filling”iswell proved.