Hydrogen-Substituted Graphdiyne Ion Tunnels Directing Concentration Redistribution for Commercial-Grade Dendrite-Free Zinc Anodes

Current aqueous Zn batteries (ZBs) seriously suffer from dendrite issues caused by rough electrode surfaces. Despite significant efforts in prolonging lifespan of these batteries, little effort has been devoted to dendrite elimination in commercial-grade cathode loading mass. Instead, demonstrations have only been done at the laboratory level (≤2 mg cm⁻²). Additionally, new dilemmas regarding change of the proton-storage behavior and interface pulverization have emerged in turn. Herein, hydrogen-substituted graphdiyne (HsGDY), with sub-ångström level ion tunnels and robust chemical stability, is designed as an artificial interface layer to address these issues. This strategy prolongs the symmetric cell lifespan to >2400 h (100 days), which is 37 times larger than without protection (63 h). The simulation of dual fields reveals that HsGDY can redistribute the Zn²⁺ concentration field by spatially forcing Zn²⁺ to deviate from the irregular electric field. During practical use, the as-assembled full batteries deliver a long lifespan 50 000 cycles and remain stable even at a commercial-grade cathode loading mass of up to 22.95 mg cm⁻². This HsGDY-protection methodology represents great progress in Zn dendrite protection and demonstrates enormous potential in metal batteries.     

Twin crystal structured Al-10 wt.％ Mg alloy over broad velocity conditions achieved by high thermal gradient directional solidification

Twin crystal structured Al-10 wt.％ Mg alloys that were grown over a broad solidification velocity range were prepared and studied for the first time.The high thermal gradient (G) and growth velocity (V) of directional solidification resulted in the dominant solidification of twins: the twinned dendrite trunks at constant high Vs curved in the G direction with large angles in 7 mm diameter crucibles and invaded regular columnar grains because of a distinct kinetics growth advantage.Transitive deceleration experiments were designed to produce twin crystals that evolved with lower values of V (100,10,and 0.5 μm/s) and had a structural coarsening trend.Twin cell growth in the absence of arms occurred at a growth velocity of 10 μm/s.A coherency loss was observed at a growth velocity of 0.5 μm/s with straight coherent twin boundaries turning into curved incoherent boundaries.Linear theoretical analyses were performed to understand the structural evolution of the twins.These results demonstrate the possibility of producing dense and controlled twin crystals in the Al-Mg system under most industrial production conditions;thus,this approach can be a new structural choice for designing Al-Mg-based alloys that have widespread commercial applications.     

Tailoring Sodium Anodes for Stable Sodium–Oxygen Batteries

Sodium–oxygen batteries based on abundant sodium resource have caused increasing interest due to their high energy density and low cost. However, the reactive sodium anode always induces unpredictable side reactions especially in oxygen atmosphere and battery short circuit due to the uncontrolled formation of dendrites. Here, an accessible method to grow a durable protective passivation film on the surface of sodium anodes is reported. The sodium fluoride‐rich film efficiently suppresses O₂ crossover and electrolyte decay related side reactions on sodium anodes. Significantly, no dendrites form during long‐term stripping/plating cycles. Benefiting from these superiorities, sodium–oxygen batteries achieve impressive improvement of discharge–charge ability and reliable safety. These results enrich the approaches for stabilizing sodium anodes and allow researchers to focus on the investigations on the air cathode and the overall chemistry of sodium–oxygen batteries.     

Critical Current Density in Solid-State Lithium Metal Batteries: Mechanism,Influences, and Strategies

Solid-state lithium (Li) metal batteries (SSLMBs) have become a research hotspot in the energy storage field due to the much-enhanced safety and high energy density. However, the SSLMBs suffer from failures including dendrite-induced short circuits and contact-loss-induced high impedance, which are highly related to the Li plating/stripping kinetics and hinder the practical application of SSLMBs. The maximum endurable current density of lithium battery cycling without cell failure in SSLMB is generally defined as critical current density (CCD). Therefore, CCD is an important parameter for the application of SSLMBs, which can help to determine the rate-determining steps of Li kinetics in solid-state batteries. Herein, the theoretical and practical meanings for CCD from the fundamental thermodynamic and kinetic principles, failure mechanisms, CCD identifications, and influence factors for improving CCD performances are systematically reviewed. Based on these fundamental understandings, a series of strategies and outlooks for future researches on SSLMB are presented, endeavoring on increasing CCD for practical SSLMBs.     

Simulation of fluctuation effect on dendrite growth by phase field method

The dendrite growth process was simulated with the phase field model coupling with the fluctuation.The effect of fluctuation intensity on the dendrite morphology and that of the thermal fluctuation together with the phase field fluctuation on the forming of side branches were investigated.The results indicate that with the decrease of thermal fluctuation amplitude,the furcation of dendrite tip also decreases,transverse dendrites become stronger,longitudinal dendrites become degenerated,Doublon structure ...     

石墨烯层间距调控抑制锂枝晶生长的第一性原理研究

抑制锂枝晶生长是锂金属电池中亟需解决的关键问题之一。电极表面涂覆石墨烯可以有效抑制锂枝晶生长。然而,目前对石墨烯层间距影响锂枝晶生长的机制尚不明晰。采用第一性原理计算方法从吸附和扩散两个角度考察了石墨烯层间距对锂枝晶生长的影响。结果表明,石墨烯的层间距为0.45 ~ 0.55 nm时,电极表面对锂原子的吸附较弱,锂原子扩散性能最好,有利于抑制锂枝晶的生长。若小于该层间距,锂原子在层间的扩散较难。反之,锂原子则会在石墨烯层上吸附聚集,导致锂枝晶的快速生长。此外,在最佳层间距下,B掺杂和N掺杂改性的石墨烯,能促进锂原子在石墨烯层间的扩散,避免锂的不均匀沉积,从而抑制锂枝晶的形成。     

相场法模拟热耦合强度对纯Ni枝晶生长的影响

基于Karma的薄界面极限相场模型,研究了相场和温度场耦合强度对过冷纯Ni熔体中枝晶生长行为的影响。模拟结果表明:随着热耦合强度的减弱,相场受温度场的影响作用减弱,固-液相界面前沿扰动变大,主枝出现二次枝晶并逐渐发达粗化,其粗化方式由缩颈熔断向枝晶臂合并方式转变。同时,枝晶尖端的生长速率增大、曲率半径减小。瞬态过程中枝晶尖端生长速度大于稳态生长速度,随着生长过程的进行,枝晶尖端生长速度逐渐降低,直至达到稳态值,计算结果与微观可解理论吻合良好。     

含Hf镍基粉末高温合金快速凝固粉末颗粒特性

采用扫描电镜、透射电镜及其附带的能谱仪和碳复型萃取技术等多种手段研究了不同Hf含量的FGH96合金粉末颗粒显微组织、枝晶间合金元素偏析和析出相.发现Hf含量可以改变粉末颗粒内部树枝晶、胞状长大晶和微晶凝固组织的比例,粉末的快速凝固组织形态主要取决于冷却速率和固液界面前沿温度梯度与长大速度的比值.不同Hf含量的FGH96合金粉末颗粒中,Nb、Ti、Zr和Al均富集于枝晶间,Co、Cr、W和Ni均富集于枝晶轴.当Hf质量分数为0.3%时,Ti、Nb、Zr、Hf等强碳化物形成元素的枝晶偏析程度最小.在快速凝固粉末颗粒中,Hf对氧含量比碳含量更敏感,优先形成更稳定的氧化物HfO₂.