Coupling Sb_(2)WO_(6)microflowers and conductive polypyrrole for efficient potassium storage by enhanced conductivity and K^(+) diffusivity

Although metal oxide compounds are considered as desirable anode materials for potassium-ion batteries(PIBs)due to their high theoretical capacity,the large volume variation remains a key issue in realizing metal oxide anodes with long cycle life and excellent rate property.In this study,polypyrroleencapsulated Sb_(2)WO_(6)(denoted Sb_(2)WO_(6)@PPy)microflowers are synthesized by a one-step hydrothermal method followed by in-situ polymerization and coating by pyrrole.Leveraging the nanosheet-stacked Sb_(2)WO_(6)microflower structure,the improved electronic conductivity,and the architectural protection offered by the PPy coating,Sb_(2)WO_(6)@PPy exhibits boosted potassium storage properties,thereby demonstrating an outstanding rate property of 110.3 m A h g^(-1)at 5 A g^(-1)and delivering a long-period cycling stability with a reversible capacity of 197.2 m A h g^(-1)after 500 cycles at 1 A g^(-1).In addition,the conversion and alloying processes of Sb_(2)WO_(6)@PPy in PIBs with the generation of intermediates,K_(2)WO_(4)and K_(3)Sb,is determined by X-ray photoelectron spectroscopy,transmission electron microscopy,and exsitu X-ray diffraction during potassiation/depotassiation.Density functional theory calculations demonstrate that the robust coupling between PPy and Sb_(2)WO_(6)endues it with a much stronger total density of states and a built-in electric field,thereby increasing the electronic conductivity,and thus effectively reduces the K^(+)diffusion barrier.

Coupling Ternary Selenide SnSb_(2)Se_(4) with Graphene Nanosheets for High-Performance Potassium-Ion Batteries

Although chalcogenide anodes possess higher potassium storage capacity than intercalated-based graphite,their drastic volume change and the irreversible electrochemical reactions still hinder the effective electron/ion transfer during the potassiation/depotassiation process.To solve the above problems,this article proposes the synthesis of a lamellar nanostructure where graphene nanosheets are embedded with SnSb_(2)Se_(4)nanoparticles(SnSb_(2)Se_(4)/GNS).In the product,fine monodisperse SnSb_(2)Se_(4)nanoparticles are coupled with graphene nanosheets to form a porous network framework,which can effectively mitigate the drastic volume changes during electrode reactions and guarantee efficient potassium-ion storage through the synergistic interactions among multiple elements.Various electrochemical analyses prove that SnSb_(2)Se_(4)inherits the advantages of the binary Sb2Se3 and SnSe while avoiding their disadvantages,confirming the synergistic effect of the ternary–chalcogenide system.When tested for potassium storage,the obtained composite delivers a high specific capacity of 368.5 mAh g^(-1)at 100 mA g^(-1)and a stable cycle performance of 265.8 mAh g^(-1)at 500 mA g^(-1)over 500 cycles.Additionally,the potassium iron hexacyanoferrate cathode and the SnSb_(2)Se_(4)/GNS anode are paired to fabricate the potassium-ion full cell,which shows excellent cyclic stability.In conclusion,this strategy employs atomic doping and interface interaction,which provides new insights for the design of high-rate electrode materials.

金属硫化物基钾离子电池负极:储存机制和合成策略

钾离子电池由于其低成本和丰富的钾矿产资源,在能量存储和转化领域极具应用潜力。金属硫化物理论容量高且材料种类丰富,在众多钾离子电池负极材料中表现突出。然而,金属硫化物存在的缺点,如导电性差、离子扩散率低、界面/表面传输动力学缓慢等,限制了其在储钾过程中的性能表现。在这篇综述中,我们系统的讨论和总结了金属硫化物作为钾离子电池负极的电化学反应机制、所面临的挑战和合成方法。其中,重点讨论了其常见的合成方法,包括模板法、溶剂热/水热法、固相反应法、静电纺丝法和离子交换法。这篇综述意在通过优化合成策略设计合成理想的组分和结构,来解决钾电负极材料存在的问题,最终得到高性能的钾离子电池负极材料。最后我们还对基于金属硫化物的钾离子电池负极的发展方向进行了展望。

Sn_(4)P_(3)nanoparticles confined in multilayer graphene sheets as a high-performance anode material for potassium-ion batteries

Phosphorus-based anodes are highly promising for potassium-ion batteries(PIBs)because of their large theoretical capacities.Nevertheless,the inferior potassium storage properties caused by the poor electronic conductivity,easy self-aggregation,and huge volumetric changes upon cycling process restrain their practical applications.Now we impregnate Sn_(4)P_(3)nanoparticles within multilayer graphene sheets(Sn_(4)P_(3)/MGS)as the anode material for PIBs,greatly improving its potassium storage performance.Specifically,the graphene sheets can efficiently suppress the aggregation of Sn_(4)P_(3)nanoparticles,enhance the electronic conductivity,and sustain the structural integrity.In addition,plenty of Sn_(4)P_(3)nanoparticles impregnated in MGS offer a large accessible area for the electrolyte,which decreases the diffusion distance for K^(+)and electrons upon K^(+)insertion/extraction,resulting in an improved rate capability.Consequently,the optimized Sn_(4)P_(3)/MGS containing 80 wt%Sn_(4)P_(3)(Sn_(4)P_(3)/MGS-80)exhibits a high reversible capacity of 378.2 and 260.2 m Ah g;at 0.1 and 1 A g^(-1),respectively,and still delivers a large capacity retention of 76.6%after the 1000th cycle at 0.5 A g^(-1).

Ultrafine SnSSe/multilayer graphene nanosheet nanocomposite as a high-performance anode material for potassium-ion half/full batteries

Layer-structured Shsse attracts much attention as an anode material for potassium storage due to its la rge theoretical capacity.Unfortunately,their practical application is severely restrained by the dramatic volumetric variation of SnSSe.Herein,we synthesize ultrafine SnSSe/multilayer graphene nanosheet(SnSSe/MGS) by a vacuum solid-phase reaction and subsequent ball milling.Owing to the strong synergistic effect between the two components,the obtained SnSSe/MGS nanocomposite exhibits a high reversible capacity(423 mAh g^(-1) at 100 mA g^(-1)),excellent rate property(218 mAh g^(-1) at 5 A g^(-1)),and stable cycling performance(271 mAh g^(-1) after 500 cycles at 100 mA g^(-1)) in potassium-ion half batteries.Moreover,the full cell assembled by the SnSSe/MGS anode and the potassiated 3,4,9,10-perylene-tetracar boxylic aciddianhydride cathode shows excellent electrochemical performance between 0.2 and 3.3 V(209 mAh g^(-1) at 50 mA g^(-1) after 100 cycles).The presented two-step synthesis strategy of SnSSe/MGS may also provide ideas to craft other alloy-type anode materials.

Synthesis of multicore-shell FeS_(2)@C nanocapsules for stable potassiumion batteries

Transition-metal sulfides are widely used as anodes for potassium-ion batteries(PIBs) due to their low cost and high theoretical capacity.The practical application of such materials,however,is still impeded by their inherent low conductivity and obvious volume change during cycling.Herein,a flexible etchassisted sulfidation strategy is reported.According to the strategy,the multicore-shell(MCS) nanocapsule structure is constructed,and then mesoporous FeS2 nanoparticles are encapsulated in the hollow carbon shell with adjustable interior space.The product,MCS-FeS2@C-20,not only features optimized inner space,but also delivers a large reversible capacity(519 mAh g^(-1) at a current density of 50 mA g^(-1)),good rate capability(107 mAh g^(-1) at a high current density of 5 A g^(-1)) and excellent cycling stability(capacity retention rate of 84.2% over 500 cycles at 0.5 A g^(-1)),making it the promising anode material for PIBs.Notably,potassium-ion full cells(MCS-FeS_(2)@C-20//K_(0.4)CoO_(2)) also show an improved potassium storage performance.

Awakening the oxygen evolution activity of MoS_(2) by oxophilic-metal induced surface reorganization engineering

Although molybdenum disulfide (MoS_(2))-based materials are generally known as active electrocatalysts for the hydrogen evolution reaction (HER), the inert performance for the oxygen evolution reaction (OER) seriously limits their wide applications in alkaline electrolyzers due to there exists too strong metal-sulfur (M−S) bond in MoS_(2). Herein, by means of surface reorganization engineering of bimetal Al, Co-doped MoS_(2) (devoted as AlCo_(3)-MoS_(2)) through in situ substituting partial oxidation, we successfully significantly activate the OER activity of MoS_(2), which affords a considerably low overpotential of 323 mV at −30 mA cm^(−2), far lower than those of MoS_(2), Al-MoS_(2) and Co-MoS_(2) catalysts. Essentially, the AlCo_(3)-MoS_(2) substrate produces lots of M−O (M=Al, Co and Mo) species with oxygen vacancies, which trigger the surface self-reconstruction of pre-catalysts and simultaneously boost the electrocatalytic OER activity. Moreover, benefiting from the moderate M−O species formed on the surface, the redistribution of surface electron states is induced, thus optimizing the adsorption of OH* and OOH* intermediates on metal oxyhydroxides and awakening the OER activity of MoS_(2).

Synthesis of carbon dots with predictable photoluminescence by the aid of machine learning

Carbon dots(CDs)have wide application potentials in optoelectronic devices,biology,medicine,chemical sensors,and quantum techniques due to their excellent fluorescent properties.However,synthesis of CDs with controllable spectrum is challenging because of the diversity of the CD components and structures.In this report,machine learning(ML)algorithms were applied to help the synthesis of CDs with predictable photoluminescence(PL)under the excitation wavelengths of 365 and 532 nm.The combination of precursors was used as the variable.The PL peaks of the strongest intensity(λ_(s))and the longest wavelength(λ_(l))were used as target functions.Among six investigated ML models,the random forest(RF)model showed outstanding)performance in the prediction of the PL peaks.

Microfluidic synthesis of hollow CsPbBr_(3) perovskite nanocrystals through the nanoscale Kirkendall effect

All inorganic metal halide perovskite nanocrystals(NCs)have attracted much attention for their outstanding optoelectronic properties,which can be tuned by the composition,surface,size and morphology in nanoscale.Herein,we report the microfluidic synthesis of hollow CsPbBr_(3)perovskite NCs through the nanoscale Kirkendall effect.The formation mechanism of the hollow structure(Kirkendall void)controlled by the temperature,flow rate,ratios of precursors and ligands was investigated.Compared with the solid CsPbBr_(3)NCs of the same size,the hollow CsPbBr_(3)NCs exhibit blue shifts in ultraviolet-visible(UV-vis)absorption and photoluminescence(PL)spectra,and remarkably longer PL average lifetime(~98.2 ns).Quantum confinement effect,inner surface induced additional trap states and lattice strain of the hollow CsPbBr_(3)NCs were discussed in understanding their unique optoelectronic properties.The hollow CsPbBr_(3)NC based photodetector exhibits an outstanding negative photoconductivity(NPC)detectivity of 8.9×10^(12)Jones.They also show potentials in perovskite NC based photovoltaic and light emitting diodes(LEDs).

Ligand-controlled synthesis of high density and ultra-small Ru nanoparticles with excellent electrocatalytic hydrogen evolution performance

Ultra-small size metal nanoparticles(u-MNPs)have broad applications in the fields of catalysis,biomedicine and energy conversion.Herein,by means of a ligand-controlled synthesis strategy,series of Ru-based NPs with high dispersity and ultra-small size(marked as u-Ru/C),or sparse and aggregated state(marked as a-Ru/C)anchored on the surface of hollow porous carbon shells are prepared.Systematical in-situ thermogravimetry-mass spectrometry-Fourier transform infrared spectra tests suggest that the different ligands in these Ru-based precursors can regulate the nucleation,growth and fixation of metal sites during the pyrolysis process,thus contributing to Ru NPs with various size and dispersity.As a result,when applied to hydrogen evolution reaction,the u-Ru-1/C catalyst displays a low Tafel slope of 26 mV dec-1,overpotential of 31 mV(at 10 mA cm^(-2))and a large exchange current density of 1.7 mA cm^(-2) in 1.0 M KOH,significantly better than that of the a-Ru-2/C,hollow carbon and even commercial 20%Pt/C.This is mainly because that the u-Ru-1/C sample owns both smaller particle size,more electrochemical active sites,higher intrinsic activity and optimized surface H adsorption ability than that of the a-Ru-2/C counterpart.Such ligand-modulated growth strategy is not only applicable to Ru,but also can be extended to other similar metals,offering a step forward in the design and synthesis of highly dispersed u-MNPs.

Confining ultrafine SnS nanoparticles in hollow multichannel carbon nanofibers for boosting potassium storage properties

SnS has been extensively investigated as a potential anode material in potassium-ion batteries (PIBs) for its high theoretical capacity.Nonetheless,it suffers a limited cyclic lifespan owing to its poor electronic conductivity and huge volume expansion.This work proposed a facile approach where SnS nanocrystals are confined in the walls of hollow multichannel carbon nanofibers (denoted SnS@HMCFs) to tackle the issues above.In contrast to previous studies,impregnated ultrafine SnS nanocrystals in HMCFs compactly can increase the SnS loading number per unit area of the carbon matrix.Furthermore,the unique hollow multichannel carbon nanofibers are used as a robust carrier to uniformly distribute the SnS nanocrystals.This can significantly accelerate K;/electron transport,resulting in large specific capacity,outstanding rate performance,and steady cycling property for PIBs.High reversible capacities of 415.5 mAh g^(-1)at0.1 A g^(-1)after 300 cycles and 245.5 mAh g^(-1)at 1 A g^(-1)after 1000 cycles are retained,suggesting great potential of SnS@HMCFs as a negative electrode material for PIBs.Additionally,when the SnS@HMCF anode is assembled with the KVPO_(4)F cathode,the obtained full cell shows a large discharge capacity of165.3 m Ah g^(-1)after 200 cycles at 0.1 A g^(-1).

Robust carbon nanotube-interwoven KFeSO_(4)F microspheres as reliable potassium cathodes

Orthorhombic iron-based fluorosulfate KFeSO_(4)F represents one of the most promising cathode materials due to its high theoretical capacity,high voltage plateau,unique three-dimensional conduction pathway for potassium ions,and low cost.Yet,the poor thermostability and intrinsic low electronic conductivity of KFeSO_(4)F challenge its synthesis and electrochemical performance in potassium-ion batteries(PIBs).Herein,we report,for the first time,judicious crafting of carbon nanotubes(CNTs)-interwoven KFeSO_(4)F microspheres in diethylene glycol(DEG)(denoted KFSF@CNTs/DEG)as the cathode to render high-performance PIBs,manifesting an outstanding reversible capacity of 110.9 m Ah g^(-1) at 0.2 C,a high working voltage of 3.73 V,and a long-term capacity retention of 93.9%after 2000 cycles at 3 C.Specifically,KFSF@CNTs/DEG microspheres are created via introducing CNTs into the precursors DEG solution at relatively low temperature.Notably,the strong binding of the ether groups in DEG retards the nucleation and growth of KFSF,leading to in situ formation of microspheres with CNTs interwoven within KFSF crystals,thereby greatly enhancing electronic conductivity of KFSF.Intriguingly,the remarkable electrochemical performance of KFSF@CNTs/DEG cathode is found to stem from the massively exposed(100)plane and uniform interpenetration of CNTs inside KFSF microsphere.More importantly,in situ X-ray diffraction and electrochemical kinetics study unveil outstanding structural stability and high K+diffusion rate of KFSF@CNTs/DEG.Finally,the KFSF@CNTs/DEG//graphite full cell displays a large energy density of~243 Wh kg^(-1).Such simple route to KFSF@CNTs/DEG highlights the robustness of creating inexpensive CNTs-interwoven polyanionic cathodes for high-performance PIBs.

Anchoring ultrafine CoP and CoSb nanoparticles into rich N-doped carbon nanofibers for efficient potassium storage

Transition-metal compounds have received extensive attention from researchers due to their high reversible capacity and suitable voltage platform as potassium-ion battery anodes.However,these materials commonly feature a poor conductivity and a large volume expansion,thus leading to underdeveloped rate capability and cyclic stability.Herein,we successfully encapsulated ultrafine CoP and CoSb nanoparticles into rich N-doped carbon nanofibers(NCFs)via electrospinning,carbonization,and phosphorization(antimonidization).The N-doped carbon fiber prevents the aggregation of nanoparticles,buffers the volume expansion of CoP and CoSb during charging and discharging,and improves the conductivity of the composite material.As a result,the CoP/NCF anode exhibits excellent potassium-ion storage performance,including an outstanding reversible capacity of 335mAh g^(-1),a decent capacity retention of 79.3%after 1000 cycles at 1Ag^(-1)and a superior rate capability of 148mAh g^(-1)at 5Ag^(-1),superior to most of the reported transition-metalbased potassium-ion battery anode materials.

Double-Coated Fe_(2)N@TiO_(2)@C Yolk-Shell Submicrocubes as an Advanced Anode for Potassium-Ion Batteries

Main observation and conclusion Rationally designing inexpensive iron nitrides that have large conductivity,high theoretical capacity,and rapid ionic diffusion kinetics is of great importance for realizing their practical application in potassium-ion batteries.

Ternary phase diagram of all-inorganic perovskite CsPbCl_(a)Br_(b)I_(3−a−b)nanocrystals

All-inorganic lead halide perovskite CsPbX3(X=Cl,Br,and I)nanocrystals(NCs)have shown great application prospects in optoelectronic fields.Their properties can be feasibly tuned by the ratio of different halide ions.Post-synthesis halide anion exchange of Cl‒Br or Br‒I in CsPbX3 NCs allows getting any desired composition of CsPbClxBr3−x and CsPbBr_(x)I_(3−x)(0≤x≤3).However,due to the large difference of the Cl and I radii,they can only substitute each other in a limited ratio to form CsPbCl_(y)I_(3−y)(0<y<δor 3−δ'<y<3).To date,little has been known on the phase diagram of the ternary halide perovskite of CsPbCl_(a)Br_(b)I_(3−a−b)(0<a+b<3).In this work,the ternary halide perovskite phase diagram is constructed by the strategy of halide anion exchange between perovskite NCs.From the diagram,the composition and proportion of the perovskite NC final phases from any starting perovskite NC mixture can be calculated.Specifically,a two-phase perovskite NC system showing stable dual photoluminescence(PL)peaks is achieved.

General Preparation and Shaping of Multifunctional Nanowire Aerogels for Pressure/Gas/Photo‑Sensing

Nanowires(NWs)with ultrahigh aspect ratio are good one-dimensional(1D)nano scafolds for building functional aerogels.However,challenges still remain in exploring methods to prepare shape designable NW aerogels with high quality,and to reveal multi functions in a single NW aerogel monolith.Here,we report a general camphene freeze-drying method for preparation of various inorganic NW aerogels(e.g,Cu,hydroxylapatite,MnO_(2)and MnOOH NW aerogels),2D graphene oxide nanosheet aerogels,organic polymer aerogels of polystyrene(post-synthesis)and resin(in situ polymerization)aerogels,which can be freely shaped in the frozen monolith stage.The as prepared aerogels have even distributed porosity and smooth surface.Also camphene is cheap and can be efectively recycling collected for reuse.For the Cu NW aerogel with even porosity and low density of 20 mg cm^(−3),multifunctional pressure/gas/photo-sensing was demonstrated.A high pressure sensitivity of 1.7 kPa^(−1)was achieved.