Ultrafine ordered L1_(2)-Pt-Co-Mn ternary intermetallic nanoparticles as high-performance oxygen-reduction electrocatalysts for practical fuel cells

The long-range periodically ordered atomic structures in intermetallic nanoparticles(INPs)can significantly enhance both the electrocatalytic activity and electrochemical stability toward the oxygen reduction reaction(ORR)compared to the disordered atomic structures in ordinary solid-solution alloy NPs.Accordingly,through a facile and scalable synthetic method,a series of carbon-supported ultrafine Pt_3Co_(x)Mn_(1-x)ternary INPs are prepared in this work,which possess the"skin-like"ultrathin Pt shells,the ordered L1_(2) atomic structure,and the high-even dispersion on supports(L1_(2)-Pt_3Co_(x)Mn_(1-x)/~SPt INPs/C).Electrochemical results present that the composition-optimized L1_(2)-Pt_3Co_(0.7)Mn_(0.3)/~SPt INPs/C exhibits the highest electrocata lytic activity among the series,which are also much better than those of the pristine ultrafine Pt/C.Besides,it also has a greatly enhanced electrochemical stability.In addition,the effects of annealing temperature and time are further investigated.More importantly,such superior ORR electrocatalytic performance of L1_(2)-Pt_3Co_(0.7)Mn_(0.3)/~SPt INPs/C are also well demonstrated in practical fuel cells.Physicochemical characterization analyses further reveal the major origins of the greatly enhanced ORR electrocata lytic performance:the Pt-Co-Mn alloy-induced geometric and ligand effects as well as the extremely high L1_(2) atomic-ordering degree.This work not only successfully develops a highly active and stable ordered ternary intermetallic ORR electrocatalyst,but also elucidates the corresponding"structure-function"relationship,which can be further applied in designing other intermetallic(electro)catalysts.

Hybrid co-based MOF nanoboxes/CNFs interlayer as microreactors for polysulfides-trapping in lithium-sulfur batteries

Lithium-sulfur battery is desirable for the future potential electrochemical energy storage device with advantages of high theoretical energy density,low cost and environmental friendliness.However,some natural hindrances,particularly fast capacity degradation resulting from the migration of dissolved polysulfide intermediates,remain to be significant challenges prior to the practical applications.In this work,a composite interlayer of carbon nanofibers(CNFs)which are enriched by Co-based metal organic frameworks(ZIF-67)growth in-situ is exploited.Notably,physical blocking and chemical trapping abilities are obtained synergistically from the ZIF/CNFs interlayer,which enables to restrain the dissolution of polysulfides and alleviate shuttle effect.Moreover,the three-dimensional fiber networks provide an interconnected conductive framework between each ZIF microreactor to promote fast electron transfer during cycling,thus contributing to excellent rate and cycling performance.As a result,Li-S cells with ZIF/CNFs interlayer show a high specific capacity of 1334 mAh g^(-1) at 1 C with an excellent cycling stability over 300 cycles.Besides,this scalable and affordable electrospinning fabrication method provides a promising approach for the design of MOFs-derived carbon materials for high performance Li-S batteries.

ZrO_(2) and Nitrogen-doped Carbon Co-coated LiFePO_(4) Cathode with Improved Cycling Stability and Rate Performance for Lithium Batteries

LiFePO_(4)cathode was successfully co-coated by ZrO_(2)and N-doped carbon layer based on the coprecipitation of Zr species and polydopamine on the LiFePO_(4)surfaces.The mutual promotion between the hydrolyzation of ZrO_(2)precursor and the self-polymerization of dopamine was realized in the one-step synthesis.After being used in the coin battery as cathode material,the ZrO_(2)and N-doped carbon co-coated LiFePO_(4)displayed improved cycling stability(97.0%retention at 0.2 C after 200 cycles)and enhanced rate performance(130.7 mAh·g^(−1) at 1 C)due to its higher electrochemical reactivity and reversibility compared with those of commercial LiFePO_(4).

In-situ cation-inserted MnO_(2) with selective accelerated intercalation of individual H^(+) or Zn^(2+) ions in aqueous zinc ion batteries

The recognized energy storage mechanism of neutral aqueous zinc-manganese batteries is the co-insertion/extrusion of H^(+) and Zn^(2+) ions.However,modulating the kinetics of a single H^(+) or Zn^(2+) ion is scarce,which can provide meaningful insights into the energy storage mechanism of Zn ion batteries.Herein,a distinctive doubly electric field in-situ induced cationic anchoring of two-dimensional layered MnO_(2) is successfully constructed to modulate the insertion/extrusion of a single H^(+) or Zn^(2+) ion.As a result,regulating the intercalation of different metal ions can precisely achieve the accelerated induction for the individual H^(+) or Zn^(2+) ions intercalation/deintercalation.Moreover,the introduction of metal ions stabilizes the lattice distortion and alleviates the irreparable structural collapse,leading to an increase in the H^(+)/Zn^(2+) storage sites,efficiently diminishing the stagnation of the ordered structure and creating the more open channels,which is conducive to facilitating the diffusion of ions.This work delivers some innovative insights into pre-embedding strategies,and also serves as a precious reference for the cathode development of advanced aqueous batteries.

PIM-1 as an artificial solid electrolyte interphase for stable lithium metal anode in high-performance batteries

Lithium metal anode is a promising electrode with high theoretical specific capacity and low electrode potential.However,its unstable interface and low Coulombic efficiency,resulting from the dendritic growth of lithium,limits its commercial application.PIM-1(PIM:polymer of intrinsic microporosity),which is a polymer with abundant micropores,exhibits high rigidity and flexibility with contorted spirocenters in the backbone,and is an ideal candidate for artificial solid electrolyte interphases(SEI).In this work,a PIM-1 membrane was synthesized and fabricated as a protective membrane on the surface of an electrode to facilitate the uniform flux of Li ions and act as a stable interface for the lithium plating/stripping process.Nodule-like lithium with rounded edges was observed under the PIM-1 membrane.The Li@PIM-1 electrode delivered a high average Coulombic efficiency(99.7%),excellent cyclability(80%capacity retention rate after 600 cycles at 1 C),and superior rate capability(125.3 m Ah g-1 at 10 C).Electrochemical impedance spectrum(EIS)showed that the PIM-1 membrane could lower the diffusion rate of Li+significantly and change the rate-determining step from charge transfer to Li+diffusion.Thus,the PIM-1 membrane is proven to act as an artificial SEI to facilitate uniform and stable deposition of lithium,in favor of obtaining a compact and dense Li-plating pattern.This work extends the application of PIMs in the field of lithium batteries and provides ideas for the construction of artificial SEI.

Facile synthesis of spinel LiNi_(0.5)Mn_(1.5)O_(4) as 5.0 V-class high-voltage cathode materials for Li-ion batteries

LiNi_(0.5)Mn_(1.5)O_(4) and LiMn_(2)O_(4) with novel spinel morphology were synthesized by a hydrothermal and postcalcination process.The synthesized LiMn_(2)O_(4) particles(5–10 lm)are uniform hexahedron,while the LiNi_(0.5)Mn_(1.5)O_(4) has spindle-like morphology with the long axis 10–15 lm,short axis 5–8 lm.Both LiMn_(2)O_(4) and LiNi_(0.5)Mn_(1.5)O_(4) show high capacity when used as cathode materials for Li-ion batteries.In the voltage range of 2.5–5.5 V at room temperature,the LiNi_(0.5)Mn_(1.5)O_(4) has a high discharge capacity of 135.04 mA·h·g^(-1) at 20 mAg^(-1),which is close to 147 mA·h·g^(-1)(theoretical capacity of LiNi_(0.5)Mn_(1.5)O_(4)).The discharge capacity of LiMn_(2)O_(4) is 131.08 mA·h·g^(-1) at 20 mAg^(-1).Moreover,the LiNi_(0.5)Mn_(1.5)O_(4) shows a higher capacity retention(76%)compared to that of LiMn_(2)O_(4)(61%)after 50 cycles.The morphology and structure of LiMn_(2)O_(4) and LiNi_(0.5)Mn_(1.5)O_(4) are well kept even after cycling as demonstrated by SEM and XRD on cycled LiMn_(2)O_(4) and LiNi_(0.5)Mn_(1.5)O_(4) electrodes.

A robust interface enabled by electrospun membrane with optimal resistance in lithium metal batteries

A uniform diffusion layer is essential for non-dendritic deposition of lithium in high-density lithium batteries.However,natural pristine solid electrolyte interface(SEI)is always porous and inhomogeneous because of repeated breakdown and repair cycles,whereas ideal materials with excellent mechanical property for artificial SEIs remain a challenge.Herein,a robust and stable interface is achieved by spinning soft polymer associated with few MoO_(3) into fibers,and thus mechanical property of fibers other than materials determines mechanical performance of the interface which can be optimized by adjusting parameters.Furthermore,lithium deposited underneath the layer is enabled by constructing an optimal resistance to make the membrane serve as an artificial SEI rather than lithium host.As a result,dendritefree lithium was observed underneath the membrane,and stable interface for long-term cycling was also indicated by EIS measurements.The lithium iron phosphate(LiFePO_(4))full-cell with coated electrode demonstrated an initial capacity of 155.2 m Ah g^(-1),and 80%of its original capacity was retained after 500 cycles at 2.0℃ without any additive in carbonate-based electrolyte.

Stable and Fast Lithium–Sulfur Battery Achieved by Rational Design of Multifunctional Separator

Lithium–sulfur(Li-S) battery is considered as one of the most promising candidates for future portable electronics and electric vehicles due to high energy density and potentially low cost. However, the severe polysulfides shuttling in Li-S battery always causes low Coulombic efficiency, capacity fading, and hindering its practical commercialization. Herein, a dualfunctional PEI@MWCNTs-CB/MWCNTs/PP(briefly denoted as PMS)separator is assembled through Langmuir–Blodgett–Scooping(LBS) technique for improvement of Li-S battery performance, that is, rational integrating conductive MWCNTs multilayer on a routine PP separator with polyethyleneimine(PEI) polymer. Owing to "proton-sponge"-based PEI feature with the abundant amino/imine groups and branched structures, the PMS separator can provide strong affinity to immobilize the negatively charged polysulfides via electrostatic interaction. Simultaneously,incorporated with the conductive MWCNTs multilayers for the electron transportation, the Li-S cells assembled with PMS separators achieve exceptional high delivery capacity, good rate performance(~550 m Ah g-1 at a current density of 9 A g-1), and stable cycling retention(retention of84.5% at a current density of 1 A g-1) even over 120 cycles, especially in the case of high-loading sulfur cathode(80 wt% of S content). This multifunctional separator with dual-structural architectures via self-assembly LBS method paves new avenues to develop high-performance Li-S batteries.

Weakly solvated electrolytes conducive to uniform lithium deposition

Rechargeable lithium metal batteries(LMBs)meet the demands of high-energy applications in electric vehicles and truck transportation[1-4].Yet,the low coulombic efficiency(CE)hinders the widespread application of Li anode,which is closely related to the electrolytes[5-7].The CE of traditional electrolytes for Li anodes is closely related to the speciation of the plated Li during cycling,where fluorinated solvents with weakly solvated Li+usually exhibit larger Li deposition particles with higher CE[8,9].But the relationship between the morphological difference and CE in different electrolytes is less studied[10,11].There are three relationships between the deposition kinetics of interface Li and the cycling of the battery,no correlation,positive correlation[12,13],and negative correlation[14,15]have been reported on active Li anodes,which neglects the reactivity of Li metal in kinetics.Solid electrolyte interphase(SEl)was formed by the electrolytes reacting with Li,and Li deposition can occur on the Li/SEl interface or the fresh Li/electrolyte interface[16,17].Each pathway has different deposition kinetics.Therefore,in order to understand the relationship between electrolyte kinetics and lithium deposition morphology,it is important to solve the kinetics of the two ways in the electrolyte.

A novel synthesis of Nb_(2)O_(5)@rGO nanocomposite as anode material for superior sodium storage

The development of novel anode materials,with superior rate capability,is of utmost significance for the successful realization of sodium-ion batteries(SIBs).Herein,we present a nanocomposite of Nb_(2)O_(5)and reduced graphene oxide(rGO)by using hydrothermal-assisted microemulsion route.The water-in-oil microemulsion formed nanoreactors,which restrained the particle size of Nb_(2)O_(5)and shortened the diffusion length of ions.Moreover,the rGO network prevented agglomeration of Nb_(2)O_(5)nanoparticles and improved electronic conductivity.Consequently,Nb_(2)O_(5)@rGO nanocomposite is employed as anode material in SIBs,delivering a capacity of 195 mAh/g after 200 charge/discharge cycles at 0.2 A/g.Moreover,owing to conductive rGO network,the Nb_(2)O_(5)@rGO electrode rende red a specific capacity of 76 mAh/g at high current density of 10 A/g and maintained 98 mAh/g after 1000 charge/discharge cycles at 2 A/g.The Nb_(2)O_(5)@rGO electrode material prepared by microemulsion method shows promising possibilities for application of SIBs.

层状镍铁双氢氧化物与金属磷化物耦合实现高效析氧和稳定的全解水

研制具有优良稳定性的高活性析氧反应(OER)电催化剂是一个巨大的挑战.这项工作构建了层状镍铁双氢氧化物修饰的磷化物(NiFe LDH@CoP/NiP_(3)),其在碱性介质中呈现出了令人满意的OER活性和良好的全解水稳定性.在300 mV的过电位下,NiFe LDH@CoP/NiP_(3)的电流密度为82 mA cm^(-2),分别是CoP/NiP3和NiFe LDH的9.1倍和2.3倍.通过X射线光电子能谱、拉曼和扫描电镜表征,研究了OER过程中的重构行为.氢析出性能测试也论证了NiFe LDH与CoP/NiP3之间的协同效应.此外,NiFe LDH@CoP/NiP_(3)同时作为阴极和阳极进行全解水时,可以维持100 mA cm^(-2)的高电流密度超过275小时.此外,在氙灯的照射下,太阳能驱动的水分解可以实现9.89%的光产氢效率.这项工作实现了不同活性成分间的耦合,为双功能电催化剂的设计提供了参考.

Porous and free-standing Ti3C2Tx-RGO film with ultrahigh gravimetric capacitance for supercapacitors

MXene-based electrode materials exhibit favorable supercapacitor performance in sulfuric acid due to praised pseudocapacitance charge storage mechanism.However,self-stacking of conventional MXene electrodes severely restricts their electrochemical performance,especially at high loading.Herein,a flexible cross-linked porous Ti3C2Tx-MXene-reduced graphene oxide(Ti3C2Tx-RGO)film is skillfully designed and synthesized by microscopic explosion of graphene oxide(GO)at sudden high te mperature.The generated chamber structure between layers could hold a few of electrolyte,leading to a close-fitting reaction at interlayer and avoiding complex ions transmission paths.The Ti3C2Tx-RGO film displayed a preferable rate performance than that of pure Ti3C2Tx film and a high capacitance of 505 F/g at 2 mV/s.Furthermore,the uniform intralayer structure and unique energy storage process lead to thicknessindependenct electrochemical performances.This work provides a simple and feasible improvement approach for the design of MXene-based electrodes,which can be spread other electrochemical systems limited by ions transport,such as metal ions batteries and catalysis.