Progress on Transition Metal Ions Dissolution Suppression Strategies in Prussian Blue Analogs for Aqueous Sodium-/Potassium-Ion Batteries

Aqueous sodium-ion batteries(ASIBs)and aqueous potassium-ion batteries(APIBs)present significant potential for large-scale energy storage due to their cost-effectiveness,safety,and environmental compatibility.Nonetheless,the intricate energy storage mechanisms in aqueous electrolytes place stringent require-ments on the host materials.Prussian blue analogs(PBAs),with their open three-dimensional framework and facile synthesis,stand out as leading candidates for aqueous energy storage.However,PBAs possess a swift capacity fade and limited cycle longevity,for their structural integrity is compromised by the pronounced dis-solution of transition metal(TM)ions in the aqueous milieu.This manuscript provides an exhaustive review of the recent advancements concerning PBAs in ASIBs and APIBs.The dissolution mechanisms of TM ions in PBAs,informed by their structural attributes and redox processes,are thoroughly examined.Moreover,this study delves into innovative design tactics to alleviate the dissolution issue of TM ions.In conclusion,the paper consolidates various strategies for suppressing the dissolution of TM ions in PBAs and posits avenues for prospective exploration of high-safety aqueous sodium-/potassium-ion batteries.

Chloride ion battery:A new emerged electrochemical system for next-generation energy storage

In the scope of developing new electrochemical concepts to build batteries with high energy density,chloride ion batteries(CIBs)have emerged as a candidate for the next generation of novel electrochemical energy storage technologies,which show the potential in matching or even surpassing the current lithium metal batteries in terms of energy density,dendrite-free safety,and elimination of the dependence on the strained lithium and cobalt resources.However,the development of CIBs is still at the initial stage with unsatisfactory performance and several challenges have hindered them from reaching commercialization.In this review,we examine the current advances of CIBs by considering the electrode material design to the electrolyte,thus outlining the new opportunities of aqueous CIBs especially combined with desalination,chloride redox battery,etc.With respect to the developing road of lithium ion and fluoride ion batteries,the possibility of using solid-state chloride ion conductors to replace liquid electrolytes is tentatively discussed.Going beyond,perspectives and clear suggestions are concluded by highlighting the major obstacles and by prescribing specific research topics to inspire more efforts for CIBs in large-scale energy storage applications.

Bi nanoparticles encapsulated in nitrogen-doped carbon as a long-life anode material for magnesium batteries

Bismuth has garnered significant interest as an anode material for magnesium batteries(MBs) because of its high volumetric specific capacity and low working potential. Nonetheless, the limited cycling performance(≤100 cycles) limits the practical application of Bi as anode for MBs. Therefore, the improvement of Bi cycling performance is of great significance to the development of MBs and is also full of challenges. Here, Bi nanoparticles encapsulated in nitrogen-doped carbon with single-atom Bi embedded(Bi@NC) are prepared and reported as an anode material for MBs. Bi@NC demonstrates impressive performance, with a high discharge capacity of 347.5 mAh g^(-1) and good rate capability(206.4 mAh g^(-1)@500 mA g^(-1)) in a fluoride alkyl magnesium salt electrolyte. In addition, Bi@NC exhibits exceptional long-term stability, enduring 400 cycles at 500 mA g^(-1). To the best of our knowledge, among reported Bi and Bi-based compounds for MBs, Bi@NC exhibits the longest cycle life in this work. The magnesium storage mechanism of Bi@NC is deeply studied through X-ray diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy. This work provides some guidance for further improving the cycling performance of other alloy anodes in MBs.

Single-Atom Lithiophilic Sites Confined within Ordered Porous Carbon for Ultrastable Lithium Metal Anodes

Attributing to the high specific capacity and low electrochemical reduction potential,lithium(Li)metal is regarded as the most promising anode for high-energy Li batteries.However,the growth of lithium dendrites and huge volume change seriously limit the development of lithium metal batteries.To overcome these challenges,an ordered mesoporous N-doped carbon with lithiophilic single atoms is proposed to induce uniform nucleation and deposition of Li metal.Benefiting from the synergistic effects of interconnected three-dimensional ordered mesoporous structures and abundant lithiophilic single-atom sites,regulated local current density and rapid mass transfer can be achieved,leading to the uniform Li deposition with inhibition of dendrites and buffered volume expansion.As a result,the as-fabricated anode exhibits a high CE of 99.8%for 200 cycles.A stable voltage hysteresis of 14 mV at 5 mA cm^(−2)could be maintained for more than 1330 h in the symmetric cell.Furthermore,the full cell coupled with commercial LiFePO_(4)exhibits high reversible capacity of 108 mAh g^(−1)and average Coulombic efficiency of 99.8%from 5th to 350th cycles at 1 C.The ordered mesoporous carbon host with abundant lithiophilic single-atom sites delivers new inspirations into rational design of high-performance Li metal anodes.

Three dimensional porous frameworks for lithium dendrite suppression

Lithium metal is a promising anode material owing to its very low electrochemical potential and ultrahigh specific capacity.However,the growth of lithium dendrites could result in a short lifespan,low coulombic efficiency,and potential safety hazards during the progress of lithium plating/stripping.These factors drastically hinder its application in lithium metal batteries.This review focuses on the use of three dimensional(3D)porous host frameworks to improve Li plating/stripping behaviors,accommodate the change in volume,and suppress or block lithium dendrite growth.Various 3D porous frameworks,including the conductive carbon-based,metal-based,and lithiophilic inorganic-compound frameworks are introduced and summarized in detail.The particular functions,relative developments,and optimized strategies of various 3D porous frameworks for lithium deposition/dissolution behaviors are discussed.Moreover,the challenges and promising developments in the field of Li metal anodes will be discussed at the end of this review.

Fast, green microwave-assisted synthesis of single crystalline Sb_2Se_3 nanowires towards promising lithium storage

In this work, a fast(0.5 h), green microwave-assisted synthesis of single crystalline Sb_2Se_3 nanowires was developed. For the first time we demonstrated a facile solvent-mediated process, whereby intriguing nanostructures including antimony selenide(Sb_2Se_3) nanowires and selenium(Se) microrods can be achieved by merely varying the volume ratio of ethylene glycol(EG) and H_2O free from expensive chemical and additional surfactant. The achieved uniform Sb_2Se_3 nanowire is single crystalline along [001]growth direction with a diameter of 100 nm and a length up to tens of micrometers. When evaluated as an anode of lithium-ion battery, Sb_2Se_3 nanowire can deliver a high reversible capacity of 650.2 m Ah g^(-1) at 100 mA g^(-1) and a capacity retention of 63.8% after long-term 1000 cycles at 1000 mA g^(-1), as well as superior rate capability(389.5 m Ah g^(-1) at 2000 mA g^(-1)). This easy solvent-mediated microwave synthesis approach exhibits its great universe and importance towards the fabrication of high-performance metal chalcogenide electrode materials for future low-cost, large-scale energy storage systems.

Rechargeable metal(Li, Na, Mg, Al)-sulfur batteries: Materials and advances

Energy and environmental issues are becoming more and more severe and renewable energy storage technologies are vital to solve the problem.Rechargeable metal(Li,Na,Mg,Al)-sulfur batteries with low-cost and earth-abundant elemental sulfur as the cathode are attracting more and more interest for electrical energy storage in recent years.Lithium-sulfur(Li-S),room-temperature sodium-sulfur(RT Na-S),magnesium-sulfur(Mg-S)and aluminum-sulfur(Al-S)batteries are the most prominent candidates among them.Many obvious obstacles are hampering the developments of metal-sulfur batteries.Li-S and Na-S batteries are encumbered mainly by anode dendrite issues,polysulfides shuttle and low conductivity of cathodes.Mg-S and Al-S batteries are short of suitable electrolytes.In this review,relationships between various employed nanostructured materials and electrochemical performances of metal-sulfur batteries have been demonstrated.Moreover,the selections of suitable electrolytes,anode protection,separator modifications and prototype innovations are all crucial to the developments of metal-sulfur batteries and are discussed at the same time.Herein,we give a review on the advances of Li-S,RT Na-S,Mg-S and Al-S batteries from the point of view of materials,and then focus on perspectives of their future developments.

Engineering Mesoporous Structure in Amorphous Carbon Boosts Potassium Storage with High Initial Coulombic Efficiency

Amorphous carbon shows great potential as an anode material for high-performance potassium-ion batteries;however,its abundant defects or micropores generally capture K ions,thus resulting in high irreversible capacity with low initial Coulombic efficiency(ICE)and limited practical application.Herein,pore engineering via a facile self-etching strategy is applied to achieve mesoporous carbon(meso-C)nanowires with interconnected framework.Abundant and evenly distributed mesopores could provide short K^+ pathways for its rapid diffusion.Compared to microporous carbon with highly disordered structure,the meso-C with Zn-catalyzed short-range ordered structure enables more K^+to reversibly intercalate into the graphitic layers.Consequently,the mesoC shows an increased capacity by ~100 mAh g^-1 at 0.1 A g^-1,and the capacity retention is 70.7% after 1000 cycles at 1 A g^-1.Multiple in/ex situ characterizations reveal the reversible structural changes during the charging/discharging process.Particularly,benefiting from the mesoporous structure with reduced specific surface area by 31.5 times and less defects,the meso-C generates less irreversible capacity with high ICE up to 76.7%,one of the best reported values so far.This work provides a new perspective that mesopores engineering can effectively accelerate K^+ diffusion and enhance K^+ adsorption/intercalation storage.

High‑Energy and High‑Power Pseudocapacitor–Battery Hybrid Sodium‑Ion Capacitor with Na^(+) Intercalation Pseudocapacitance Anode

High-performance and low-cost sodium-ion capacitors(SICs)show tremendous potential applications in public transport and grid energy storage.However,conventional SICs are limited by the low specific capacity,poor rate capability,and low initial coulombic efficiency(ICE)of anode materials.Herein,we report layered iron vanadate(Fe5V15O39(OH)9·9H2O)ultrathin nanosheets with a thickness of~2.2 nm(FeVO UNSs)as a novel anode for rapid and reversible sodium-ion storage.According to in situ synchrotron X-ray diffractions and electrochemical analysis,the storage mechanism of FeVO UNSs anode is Na+intercalation pseudocapacitance under a safe potential window.The FeVO UNSs anode delivers high ICE(93.86%),high reversible capacity(292 mAh g^−1),excellent cycling stability,and remarkable rate capability.Furthermore,a pseudocapacitor–battery hybrid SIC(PBH-SIC)consisting of pseudocapacitor-type FeVO UNSs anode and battery-type Na3(VO)2(PO4)2F cathode is assembled with the elimination of presodiation treatments.The PBH-SIC involves faradaic reaction on both cathode and anode materials,delivering a high energy density of 126 Wh kg^−1 at 91 W kg^−1,a high power density of 7.6 kW kg^−1 with an energy density of 43 Wh kg−1,and 9000 stable cycles.The tunable vanadate materials with high-performance Na+intercalation pseudocapacitance provide a direction for developing next-generation highenergy capacitors.

Surface pseudocapacitance of mesoporous Mo_(3)N_(2) nanowire anode toward reversible high-rate sodium-ion storage

Sodium-ion storage devices are highly desirable for large-scale energy storage applications owing to the wide availability of sodium resources and low cost.Transition metal nitrides(TMNs)are promising anode materials for sodium-ion storage,while their detailed reaction mechanism remains unexplored.Herein,we synthesize the mesoporous Mo3N2 nanowires(Meso-Mo_(3)N_(2)-NWs).The sodium-ion storage mechanism of Mo3N2 is systematically investigated through in-situ XRD,ex-situ experimental characterizations and detailed kinetics analysis.Briefly,the Mo_(3)N_(2) undergoes a surface pseudocapacitive redox charge storage process.Benefiting from the rapid surface redox reaction,the Meso-Mo_(3)N_(2)-NWs anode delivers high specific capacity(282 m Ah g^(-1) at 0.1 A g^(-1)),excellent rate capability(87 m Ah g^(-1) at 16 A g^(-1))and long cycling stability(a capacity retention of 78.6%after 800 cycles at 1 A g^(-1)).The present work highlights that the surface pseudocapacitive sodium-ion storage mechanism enables to overcome the sluggish sodium-ion diffusion process,which opens a new direction to design and synthesize high-rate sodiumion storage materials.

In-situ surface self-reconstruction in ternary transition metal dichalcogenide nanorod arrays enables efficient electrocatalytic oxygen evolution

Water splitting has received more and more attention because of its huge potential to generate clean and renewable energy.The highly active and durable oxygen evolution reaction(OER)catalysts play a decisive factor in achieving efficient water splitting.The identification of authentic active origin under the service conditions can prompt a more reasonable design of catalysts together with well-confined micro-/nano-structures to boost the efficiency of water splitting.Herein,Fe,Co,and Ni ternary transition metal dichalcogenide(FCND)nanorod arrays on Ni foam are purposely designed as an active and stable low-cost OER pre-catalyst for the electrolysis of water in alkaline media.The optimized FCND catalyst demonstrated a lower overpotential than the binary and unary counterparts,and a 27-fold rise in kinetic current density at the overpotential of 300 m V compared to the nickel dichalcogenide counterpart.Raman spectra and other structural characterizations at different potentials reveal that the in-situ surface self-reconstruction from FCND to ternary transition metal oxyhydroxides(FCNOH)on catalyst surfaces initiated at about 1.5 V,which is identified as the origin of OER activity.The surface selfreconstruction towards FCNOH also enables excellent stability,without fading upon the test for 50 h.

Structural properties and electrochemical performance of different polymorphs of Nb_(2)O_(5) in magnesium-based batteries

The selection of the most suitable crystal structure for ions storage and the investigation of the corresponding reaction mechanism is still an ongoing challenge for the development of Mg-based batteries.In this article,high flexible graphene network supporting different crystal structures of Nb2 O5(TTNb_(2)O_(5)@rGO and T-Nb_(2)O_(5)@rGO) are successfully synthesized by a spray-drying-assisted approach.The three-dimensional graphene framework provides high conductivity and avoids the aggregation of Nb2 O5 nanoparticles.When employed as electrode materials for energy storage applications,TT-Nb_(2)O_(5) delivers a higher discharge capacity of 129.5 mAh g^(-1), about twice that of T-Nb_(2)O_(5) for Mg-storage,whereas,T-Nb_(2)O_(5) delivers a much higher capacity(162 mAh g^(-1)) compared with TT-Nb_(2)O_(5)(129 mAh g^(-1)) for Li-storage.Detailed investigations reveal the Mg intercalation mechanism and lower Mg^(2+) migration barriers,faster Mg^(2+) diffusion kinetics of TT-Nb_(2)O_(5) as cathode material for Mg-storage,and the faster Li+ diffusion kinetics,shorter diffusion distance of T-Nb_(2)O_(5) as cathode material for Li-storage.Our work demonstrates that exploring the proper crystal structure of Nb2 O5 for different ions storage is necessary.

Niobium oxyphosphate nanosheet assembled two-dimensional anode material for enhanced lithium storage

The development of high-capacity and high-rate anodes has become an attractive endeavor for achieving high energy and power densities in lithium-ion batteries(LIBs).Herein,a new-type anode material of reduced graphene oxide(rGO) supported niobium oxyphosphate(NbOPO_4) nanosheet assembled twodimensional composite material(NbOPO_4/rGO) is firstly fabricated and presented as a promising highperformance LIB anode material.In-depth electrochemical analyses and in/ex situ characterizations reveal that the intercalation-conversion reaction takes place during the first discharge process,followed by the reversible redox process between amorphous NbPO_4 and Nb which contributes to the reversible capacity in the subsequent cycles.Meanwhile,the lithiation-generated Li3 PO_4,behaving as a good lithium ion conductor,facilitates ion transport.The rGO support further regulates the structural and electron/ion transfer properties of NbOPO_4/rGO composite compared to neat NbOPO_4, resulting in greatly enhanced electrochemical performances.As a result,NbOPO_4/rGO as a new-type LIB anode material achieves a high capacity of 502.5 mAh g^(-1) after 800 cycles and outstanding rate capability of 308.4 mAh g^(-1) at 8 A g^(-1).This work paves the way for the deep understanding and exploration of phosphate-ba sed high-efficiency anode materials for LIBs.

Interface enhanced well-dispersed Co9S8 nanocrystals as an efficient polysulfide host in lithium–sulfur batteries

The high specific capacity and energy density of lithium-sulfur batteries have attracted strong considerations on their fundamental mechanism and energy applications.However,polysulfide shuttle is still the key issue that impedes the development of Li-S batteries.Exploring nanocrystal hosts for polysulfide immobilization and conversion is a promising way.In this contribution,we have investigated well-dispersed Co9S8 nanocrystals grown on graphene oxide(GO)nanosheets with different degrees of dispersion as cathode host materials for Li-S batteries.The Co9S8-GO composite with 1 wt%GO(GCS1)has an average crystal size of 76 nm and shows the strongest adsorption capability toward lithium polysulfides.When used as the host material for the cathode of Li-S batteries,the GCS1-sulfur composite exhibits an initial specific capacity of^-1000 mAh g^-1 at 0.5 C and shows an average decay rate of 0.11%for 500 cycles.This work on the dispersion control of Co9S8 nanocrystals may inspire more investigations on well-dispersed nanocrystal based hosts for Li-S batteries.

Ultrathin Metal Silicate Hydroxide Nanosheets with Moderate Metal-Oxygen Covalency Enables Efficient Oxygen Evolution

Exploring efficient,cost-effective,and durable electrocatalysts for electrochemical oxygen evolution reaction(OER)is pivotal for the large-scale application of water electrolysis.Recent advance has demonstrated that the activity of electrocatalysts exhibits a strong dependence on the surface electronic structure.Herein,a series of ultrathin metal silicate hydroxide nanosheets(UMSHNs)M_(3)Si_(2)O_(5)(OH)_(4)(M=Fe,Co,and Ni)synthesized without surfactant are introduced as highly active OER electrocatalysts.Cobalt silicate hydroxide nanosheets show an optimal OER activity with overpotentials of 287 and 358 m V at 1 and 10 m A cm^(-2),respectively.Combining experimental and theoretical studies,it is found that the OER activity of UMSHNs is dominated by the metal-oxygen covalency(MOC).High OER activity can be achieved by having a moderate MOC as reflected by aσ^(*)-orbital(e_(g))filling near unity and moderate[3d]/[2p]ratio.Moreover,the UMSHNs exhibit favorable chemical stability under oxidation potential.This contribution provides a scientific guidance for further development of active metal silicate hydroxide catalysts.

Pancake-Like MOF Solid-State Electrolytes with Fast Ion Migration for High-Performance Sodium Battery

Solid-state electrolyte(SSE)of the sodium-ion battery have attracted tremendous attention in the next generation energy storage materials on account of their wide electrochemical window and thermal stability.However,the high interfacial impedance,low ion transference number and complex preparation process restrict the application of SSE.Herein,inspired by the excellent sieving function and high specific surface area of red blood cells,we obtained a solid-like electrolyte(SLE)based on the combination of the pancake-like metal-organic framework(MOF)with liquid electrolyte,possessing a high ionic conductivity of 6.60×10^(-4) S cm^(−1),and excellent sodium metal compatibility.In addition,we investigated the ion restriction effect of MOF’s apertures size and special functional groups,and the ion transference number increased from 0.16 to 0.33.Finally,the assembled Na_(0.44)MnO_(2)//SLE//Na full batteries showed no obvious capacity decrease after 160 cycles.This material design of SLE in our work is an important key to obtain fast ion migration SLE for high-performance sodium-ion batteries.

Boosting the electrochemical performance and reliability of conducting polyme microelectrode via intermediate graphene for on-chip asymmetric micro-supercapacitor

High-performance anode is hurdle for on-chip planar microsupercapacitor(MSC).Polypyrrole(PPy)is a highly attractive pseudocapacitive material,but its low cycling stability,and low adhesion with current collector hinder its practicability.Herein we propose one-prong generic strategy to boost the cycling stability of PPy.For our strategy,the electrochemical deposition of multilayered reduced graphene oxide(rGO)on micropatterned Au is utilized,and the resultant rGO@Au pattern is then used for growing highly porous PPy nanostructures by facile electrochemical polymerization.The fabricated PPy anode on rGO@Au has quasi rectangular cyclic voltammetry curves up to-0.7 V and exceptional cycling stability,retaining82%of capacitance after 10,000 charge/discharge cycles in 2 M KCl electrolyte.The outstanding reliability of PPy on rGO@Au is due to the flexibility of rGO,accommodating structural pulverization and providing a promising background for the nucleation of highly porous nanostructure.Further,an all-polymer based asymmetric aqueous MSC(AMSC)is constructed with PPy anode and PEDOT cathode,which exhibited excellent electrochemical performance compared with conventional symmetric MSCs based on conducting polymers.The constructed AMSC delivered a maximum areal capacitance of 15.9 m F cm^-2(99.3 F cm^-3),high specific energy and power densities of 4.3μWh cm^-2(27.03 mWh cm^-3)and 0.36 W cm^-2(0.68 W cm^-3)at 1.4 V,respectively.The enhanced electrochemical performances can be illustrated by nucleation mechanism,in which surface topology of r GO generates a promising background for nucleation and electrochemical growth of nanoporous pseudocapacitive conducting polymers with superior interfacial contact and improved surface area.

Effect of Preparation Atmosphere on the Structure and Properties of Vanadium Pentoxide Xerogel Films

In this article, the vanadium pentoxide sols are synthesized by two different routes (melted and quenched in oxygenatmosphere or in air). The structure and properties of the vanadium pentoxide xerogel films are characterized byXRD, ESR, cyclic voltammograms curves and UV-visible transmittance analysis. The results show that the sampleprepared in oxygen has poorer crystallization. lower content of V^(4+) ions and higher Li^+ insertion capacity comparedwith that prepared in air.

Activating Inert Sites in Cobalt Silicate Hydroxides for Oxygen Evolution through Atomically Doping

Metal silicate hydroxides have been recognized as efficient oxygen evolution reaction(OER)electrocatalysts,yet tailoring of their intrinsic activity remains confused.Herein,Fe had been incorporated into cobalt silicate hydroxide nanosheets and the resulted material achieves a competitive OER catalytic activity.It is found that the doping state obviously affects the electrical transport property.Specifically,highly dispersed Fe atoms(low-concentration Fe doping)trigger slight electron transfer to Co atoms while serried Fe(highconcentration Fe doping)attract vast electrons.By introducing 6 at.%Fe doping,partial relatively inert Co sites are activated by atomically dispersed Fe,bearing an optimal metal 3d electronic occupation and adsorption capacity to oxygen intermediate.The introduced Co-O-Fe unit trigger the p-donation effect and decrease the number of electrons in p*-antibonding orbitals,which enhance the Fe-O covalency and the structural stability.As a result,the sample delivers a low overpotential of 293 mV to achieve a current density of 10 mA cm^(-2).This work clarifies the superiority of atomically dispersed doping state,which is of fundamental interest to the design of doped catalyst.

Three-Layer Structured SnO_(2)@C@TiO_(2)Hollow Spheres for High-Performance Sodium Storage

The unsatisfactory conductivity and large volume variation severely handicap the application of SnO_(2)in sodium-ion batteries(SIBs).Herein,we design unique three-layer structured SnO_(2)@C@TiO_(2)hollow spheres to tackle the above-mentioned issues.The hollow cavity affords empty space to accommodate the volume variation of SnO_(2),while the C and TiO_(2)protecting shells strengthen the structural integrity and enhances the electrical conductivity.As a result,the three-layer structured SnO_(2)@C@TiO_(2)hollow spheres demonstrate enhanced Na storage performances.The SnO_(2)@C@TiO_(2)manifests a reversible capacity two times to that of pristine SnO_(2)hollow spheres.In addition,Ex situ XRD reveals highly reversible alloying and conversion reactions in SnO_(2)@C@TiO_(2)hollow spheres.This study suggests the introduction of a hollow cavity and robust protecting shells is a promising strategy for constructing SIB anode materials.