Theoretical investigation of lithium ions’ nucleation performance on metal-doped Cu surfaces

Lithium metal batteries(LMBs)of an ultrahigh theoretical energy density have attracted lots of attentions for a wide range of practical applications.However,there are still numerous challenges in LMBs system,such as poor cycling performance,complicated interfacial reactions,low Coulombic efficiency,and uncontrollable lithium dendrites.Understanding Li^+ions’nucleation mechanism is essential to tackle the uncontrolled growth of lithium dendrites.However,the nucleation behavior of Li+ions is interfered by the structural complexities of existing substrates during the reduplicative plating/stripping process and the rational mechanism of uniform nucleation of Li^+ions has not been clearly understood from the theoretical point of view.In our work,first-principles theoretical calculations are carried out to investigate the Li^+ions nucleation performance on metal-doped Cu surfaces(MDCSs)and the key descriptors that determines the properties of various MDCSs are systematically summarized.It is found that the introduction of heterogeneous doping Ag and Zn atoms will induce a gradient adsorption energy on MDCSs,and such gradient deposition sites can reduce the diffusion barriers and accelerate the diffusion rates of Li+ions dynamically.By maneuvering the Li+ions nucleation on MDCSs,a dendrite-free lithium metal anode can be achieved without the use of porous matrixes and complex synthesis process,which can be attributed to suppress the uncontrollable lithium dendrites for realizing the high-efficiency LMBs.

2D-layered Sn/Ge anodes for lithium-ion batteries with high capacity and ultra-fast Li ion diffusivity

As a new type of green energy, lithium-ion battery(LIB) has been widely used in various electric portable devices because of its high-voltage, large specific capacity, long cycle life and environmental friendliness [1,2]. However, today’s anode materials of commercial LIBs cannot meet the further development requirements of smart devices and electric car due to the limitations of the electrode capacity(e.g. 372 mAh g-1 for graphite).

Orbital symmetry matching:Achieving superior nitrogen reduction reaction over single-atom catalysts anchored on Mxene substrates

The nitrogen reduction reaction(NRR)under ambient conditions is still challenging due to the inertness of N2.Herein,we report a series of superior NRR catalysts identified by examining Ti2NO2 MXenes embedded with 28 different single-atom catalysts using first-principles calculations.The stability of this system was first verified using formation energies,and it is discovered that N2 can be effectively adsorbed due to the synergistic effect between single atom catalysis and the Ti atoms.Examination of the electronic structure demonstrated that this design satisfies orbital symmetry matching where“acceptor-donor”interaction scenario can be realized.A new“enzymatic-distal”reaction mechanism that is a mixture of the enzymatic and distal pathways was also discovered.Among all of the candidates,Ni anchored on MXene system achieves an onset potential as low as–0.13 V,which to the best of our knowledge is the lowest onset potential value reported to date.This work elucidates the significance of orbital symmetry matching and provides theoretical guidance for future studies.

Interface effect on promoting reversible conversion for Na2Se in the metal selenide as sodium ion batteries

The rapid development of modern electronic devices has promoted more research in the field of high energy-density storage devices[1].Lithium ion batteries(LIBs)have been widely used in electronic devices and hybrid electric vehicles since their successful commercialization by Sony[2,3].

A Janus separator towards dendrite-free and stable zinc anodes for long-duration aqueous zinc ion batteries

Critical issues of Zn anodes including undesirable dendrites formation and parasitic reactions severely limit the reversibility and cyclability of Zn anodes.To address these issues,a functional Janus separator with the structure of a mechanically strong sulfonated poly(arylene ether sulfone)(SPAES)dense layer composited on a porous glass fiber(GF)substrate is designed.The SPAES dense layer that faces the Zn anode containing abundant sulfonic acid groups effectively promotes the desolvation process of hydrated Zn ions,guides uniform Zn ion transfer,and blocks anions and water,contributing to dendrite-free and highly reversible Zn plating/stripping cycles,while the porous GF substrate retains high electrolyte uptake.As a result,the Zn symmetric cell with the Janus separator demonstrates an ultralong cycling lifespan of over 2000 h at the areal capacity of 1 m A h cm^(-2),which is 23-fold superior to that with a pristine glass fiber separator(<90 h).More impressively,the as-prepared Janus separator enables outstanding rate performance and excellent cycling stability of full Zn ion batteries with diverse cathode materials.For instance,when paired with the V_2O_(5)cathode,the full battery with a Janus separator attains an ultrahigh initial specific capacity of 416.3 m A h g^(-1)and capacity retention of 60%over 450 cycles at 1 A g^(-1),exceeding that with a glass fiber separator.Hence,this work provides a facile yet effective approach to mitigating the dendrites formation and ameliorating the parasitic reactions of Zn metal anodes for high-performance Zn ion batteries.

Recent progress in self-repairing coatings for corrosion protection on magnesium alloys and perspective of porous solids as novel carrier and barrier

Featuring low density and high specific strength, magnesium(Mg) alloys have attracted wide interests in the fields of portable devices and automotive industry. However, the active chemical and electrochemical properties make them susceptible to corrosion in humid, seawater, soil,and chemical medium. Various strategies have revealed certain merits of protecting Mg alloys. Therein, engineering self-repairing coatings is considered as an effective strategy, because they can enable the timely repair for damaged areas, which brings about long-term protection for Mg alloys. In this review, self-repairing coatings on Mg alloys are summarized from two aspects, namely shape restoring coatings and function restoring coatings. Shape restoring coatings benefit for swelling, shrinking, or reassociating reversible chemical bonds to return to the original state and morphology when coatings broken;function self-repairing coatings depend on the release of inhibitors to generate new passive layers on the damaged areas. With the advancement of coating research and to fulfill the demanding requirements of applications, it is an inevitable trend to develop coatings that can integrate multiple functions(such as stimulus response, self-repairing, corrosion warning,and so on). As a novel carrier and barrier, porous solids, especially covalent organic frameworks(COFs), have been respected as the future development of self-repairing coatings on Mg alloys, due to their unique, diverse structures and adjustable functions.

Identifying Hidden Li–Si–O Phases for Lithium-Ion Batteries via First-Principle Thermodynamic Calculations

SiO–based materials are promising alloys and conversion-type anode materials for lithium-ion batteries and are recently found to be excellent dendrite-proof layers for lithium-metal batteries.However,only a small fraction of the Li–Si–O compositional space has been reported,significantly impeding the understanding of the phase transition mechanisms and the rational design of these materials both as anodes and as protection layers for lithium-metal anodes.Herein,we identify three new thermodynamically stable phases within the Li–Si–O ternary system(Li_(2)SiO_(5),Li_(4)SiO_(6),and Li_(4)SiO_(8))in addition to the existing records via first-principle calculations.The electronic structure simulation shows that Li_(2)SiO_(5)and Li_(4)SiO_(8)phases are metallic in nature,ensuring high electronic conductivity required as electrodes.Moduli calculations demonstrate that the mechanical strength of Li–Si–O phases is much higher than that of lithium metal.The diffusion barriers of interstitial Li range from 0.1 to 0.6 eV and the interstitial Li hopping serves as the dominating diffusion mechanism in the Li–Si–O ternary systems compared with vacancy diffusion.These findings provide a new strategy for future discovery of improved alloying anodes for lithium-ion batteries and offer important insight towards the understanding of the phase transformation mechanism of alloy-type protection layers on lithium-metal anodes.

Recycling the spent electronic materials to construct a highperformance Cu_(1.94)S/ZnS heterostructure anode of sodium-ion batteries

Heterostructure engineering by coupling different nanocrystals has received extensive attention because it can enhance the reaction kinetics of the anode of sodium-ion batteries(SIBs).However,constructing high-quality heterostructure anode materials through green and environmentally friendly methods remains a challenge.Herein,we have proposed a simple one-step method by recycling the electronic waste metal materials to synthesize the Cu_(1.94)S/ZnS heterostructure materials.Combined with the experimental analysis and first principle calculations,we find that the synergistic effect of different components in heterostructure structures can significantly enhance the reversible capacity and rate performance of anode materials.Based on the constructed Cu_(1.94)S/ZnS anode,we obtain a superior reversible capacity of 440 mAh·g^(-1) at 100 mA·g^(-1) and 335 mAh·g^(-1) after 3000 cycles at 2000 mA·g^(-1).Our work sheds new light on designing high-rate and capacity anodes for SIBs through the greenness synthesis method.

Fatigue behavior of direct laser deposited Ti-6.5Al-2Zr-1Mo-1V titanium alloy and its life distribution model

The present work aims to investigate the fatigue behavior of Direct Laser Deposition(DLD) Ti-6.5 Al-2 Zr-1 Mo-1 V titanium alloy under constant amplitude stress. 22 pieces of DLD Ti-6.5 Al-2 Zr-1 Mo-1 V titanium alloy standard cylinder specimens were tested under a stress level of 800 MPa with a stress ratio of 0.06. Fatigue fractography and fatigue life data were obtained.Through the fracture surface analysis, the specimens were divided into two categories in accordance with the location of crack initiation and defect types. Comparison of fatigue life and behavior between two specimen types was given, which was followed by a discussion about the impact of defect type, size and position on the fatigue life of the specimen. The fatigue test results also show a large variation of fatigue life. To illustrate the statistical characteristics of the fatigue life, probabilistic analysis was performed, and a novel bimodal lognormal model was established. The model has a good fit with the experimental data and can reduce the scatter of the fatigue life significantly.

Detail fatigue rating method based on bimodal Weibull distribution for DED Ti-6.5Al-2Zr-1Mo-1V titanium alloy

Previous studies have shown that the fatigue life distribution of metal materials fabricated with Additive Manufacturing(AM) methods, such as Direct Energy Deposited(DED) Ti-6.5Al-2Zr-1Mo-1V alloys, exhibits two peaks. To promote the application of AM in aerospace and other engineering fields, developing a fatigue strength evaluation method suitable for AM materials based on their unique fatigue behaviours and fatigue life distributions is necessary. In this paper, a novel Detail Fatigue Rating(DFR) method was developed to evaluate the fatigue strength of DED Ti-6.5Al-2Zr-1Mo-1V based on a bimodal Weibull distribution and the excessive restriction on the allowable stress of potential was improved. Meanwhile, a Bimodal Weibull distribution model for fatigue life and its parameter estimation method were established based on a twoparameter Weibull distribution. The fatigue life at a specific reliability level and confidence level was calculated by using the bootstrap method. The calculation results showed that fatigue life estimated by using the bimodal Weibull distribution at the high reliability level and high confidence level is higher than that estimated by using the two-parameter Weibull distribution. Furthermore,The S-N curve at the specified confidence level and reliability level was fitted.

Identifying the roles of Ce^(3+)-OH and Ce-H in the reverse water-gas shift reaction over highly active Ni-doped CeO_(2) catalyst

Nickel-CeO_(2)-based materials are commonly used for the thermal catalytic hydrogenation of CO_(2).However,high Ni loadings and low CO selectivity restrict their use in the reverse water–gas shift(RWGS)reaction.Herein,we demonstrate a highly active,robust,and low-Ni-doped(1.1 wt.%)CeO_(2) catalyst(1.0-Ni-CeO_(2)).The Ni-based-mass-specific CO formation rate reaches up to 1,542 mmol·gNi^(−1)·h^(−1) with 100%CO selectivity at 300°C for 100 h,among the best values reported in the literature.Density functional theory(DFT)and diffuse reflectance infrared Fourier transform spectroscopy(DRIFTS)results reveal that the enhanced catalytic activity is attributed to the abundant Ce–H species,while the high selectivity results from low CO affinity.More importantly,a new reaction mechanism is proposed,which involves the reduction of bicarbonate to generate formate intermediate and CO by the H−released from Ce–H species.The new findings in this work will benefit the design of economic,efficient,and robust catalysts for low-temperature RWGS reactions.

一种面向高稳定锂金属负极的具有仿生离子通道的人工界面层

锂金属具有氧化还原电位低、理论比容量大等优点,是下一代高比能电池极具发展前景的负极.然而,锂枝晶生长和低可逆性严重阻碍了高比能锂金属电池的发展.受启发于生物细胞膜结构,本文采用涂布法在锂金属表面成功构筑了一种具有仿生离子通道的人工界面固体电解质层(CAL).该CAL中大量带负电荷的离子通道可以促进锂离子均匀、快速的输运,有利于稳定、均匀地进行锂沉积/剥离.此外,在循环过程中,CAL底部与锂金属发生原位转化反应,生成了一层富含亲锂性无机组分的过渡层,促进了锂离子的扩散并抑制了锂金属与电解液的连续副反应.因此,形成的具有双面神结构的人工界面固体电解质层(CAJL)使得锂金属负极可以在10 mA cm^(-2)的高电流密度和10 mAh cm^(-2)的高面积容量下长期稳定循环.更重要的是,基于CAJL功能化锂金属负极的锂硫软包电池实现了429.2 Wh kg^(-1)的高能量密度.