Ultra-high Cycle Research Articles

One-Step Synthesis of Three-Dimensional Na3V2(PO4)3/Carbon Frameworks as Promising Sodium-Ion Battery Cathode.

Sodium-ion batteries (SIBs) are essential for large-scale energy storage attributed to the high abundance of sodium. Polyanion Na3V2(PO4)3 (NVP) is a dominant cathode candidate for SIBs because of its high-voltage and sodium superionic conductor (NASICON) framework. However, the electrochemical performance of NVP is hindered by the inherently poor electronic conductivity, especially for extreme fast charging and long-duration cycling. Herein, we develop a facile one-step in-situ polycondensation method to synthesize the three-dimensional (3D) Na3V2(PO4)3/holey-carbon frameworks (NVP@C) by using melamine as carbon source. In this architecture, NVP crystals intergrown with the 3D holey-carbon frameworks provide rapid transport pathways for ion/electron transmission to increase the ultrahigh rate ability and cycle capability. Consequently, the NVP@C cathode possesses a high reversible capacity of 113.9 mAh g-1 at 100 mA g-1 and delivers an outstanding high-rate capability of 75.3 mAh g-1 at 6000 mA g-1. Moreover, it shows that the NVP@C cathode is able to display a volumetric energy density of 54 Wh L-1 at 6000 mA g-1 (31 Wh L-1 for NVP bulk), as well as excellent cycling performance of 65.4 mAh g-1 after 1000 cycles at 2000 mA g-1. Furthermore, the NVP@C exhibits remarkable reversible capabilities of 81.9 mAh g-1 at a current density of 100 mA g-1 and 60.2 mAh g-1 at 1000 mA g-1 even at a low temperature of -15 °C. The structure of porous carbon frameworks combined with single crystal materials by in-situ polycondensation offers general guidelines for the design of sodium, lithium and potassium energy storage materials.

Fretting Fatigue Test and Simulation Analysis of Steam Generator Heat Transfer Tube

In a steam generator, the heat transfer tubes are supported by the contact with support plates and anti-vibration bars. The two-phase flow flows over the tubes and causes a vibration when operating. In fatigue analysis, the heat transfer tube is simplified to a beam model, and the contacts with the support plates and the anti-vibration bars are simplified as simple-supported boundary conditions. This linear simplification improves the computational efficiency but cannot simulate the actual situation of the contact area. In consideration of this situation, in the actual analysis, a downwards modified S–N fatigue curve is used to envelop the fretting. For different materials and contact pressure, this modification needs to be obtained through experimental and computational analysis. In this paper, the effect of fretting on fatigue performance of heat transfer tube material 690 alloy is discussed by means of high cycle fretting fatigue test of tube specimen in room temperature air, low cycle fretting fatigue test of sheet specimen in high temperature water environment, and SWT (Smith–Watson–Topper) fretting fatigue predicting simulation, and the conservatism of design fatigue curve is discussed. It is shown that, in range of low cycle and high cycle, the fatigue strength is lower than the mean curve, but it can still be enveloped by the design curve of ASME (the American Society of Mechanical Engineers). However, under the condition of ultra-high cycle, the design curve of ASME can no longer envelop the effect of fretting on fatigue performance, so a further downward modification is necessary to ensure the safety of design.

Phase Evolution of VC‐VO Heterogeneous Particles to Facilitate Sulfur Species Conversion in Li−S Batteries

AbstractLithium−sulfur (Li−S) batteries with ultrahigh theoretical energy densities have thus far attracted significant attention as the next‐generation energy storage systems. However, the presence of the polysulfide shuttle effect and sluggish reaction kinetics have critically hindered their research progress. Herein, the fabrication of novel VC‐VO heterogeneous particles supported on a hierarchical porous carbon matrix (VC‐VO/HPC) is reported that regulate the disordered motion of lithium polysulfides (LiPSs); these particles can simultaneously achieve powerful anchoring, fast diffusion, and high‐efficiency conversion of LiPSs. Moreover, the in situ characterization of VC‐VO/HPC@S provides a rational inference for their phase evolution in the galvanostatic charge/discharge process. The formation of the V5S8 phase during electrochemical cycling primarily facilitates the interconversion of liquid‐phase polysulfides. Consequently, the VC‐VO/HPC@S cathodes exhibit excellent capacity performance (1484 mAh g−1 at 0.1 C) and ultrahigh cycle stability (0.045% decay rate per cycle at 5 C). The pouch cell exhibits a high energy density of 358 Wh kg−1. This approach explores the phase evolution of VC‐VO particles in an electrochemical environment and is valuable for the development of Li−S batteries with high area capacity and long cycle life.

The effects of laser peening treatment on the very high cycle fatigue properties for AA2024-T351 alloy using a crystal plasticity framework

The effects of laser shot peening (LSP) on very high cycle fatigue (VHCF) properties of AA2024-T351 alloy were investigated using the combination of experiment and modified crystal plasticity finite element (CPFE) method. The experimental observation found a contradictable result that the fatigue life decreased after laser peening with relatively high pulse energy in this work. The fatigue fracture observation shows that there are obvious facets and refined grains on the shot peening surface, which are not uniform and their aspect ratio is obviously larger than that of the matrix material. In particular, the fracture surface of the sample treated with 20 J pulse energy shows a highly distorted zig-zag crack propagation path. In order to further understand the ultra-high cycle fatigue failure mechanism of aluminum alloy treated with laser shot peening, a modified crystal plasticity (CP) model was applied to find a possible explanation for the contradictable experimental results. In this model, the critical resolved shear stress (CRSS) evolution of the deformation systems in the CP model was variable due to the refined average grain size after different laser peening conditions using the Hall-Petch type relationship. Additionally, the effects of grain morphology characterized by aspect ratio were considered after LSP of AA2024-T351. The fatigue indicator parameters (FIPs) were calculated based on the modified CPFE model under cyclic low stress amplitudes to estimate the fatigue driving force for fatigue crack initiation and microstructural small crack propagation. It is found that the LSP treatment has a beneficial effect on the fatigue properties only considering the refined influence of grain size. However, LSP has a detrimental effect on VHCF properties when considering the combined influences of grain refinement and the changing of grain aspect ratio due to the laser peening surface treatment with relative high pulse energy in this work.

Effect of microstructural heterogeneity on fatigue strength predicted by reinforcement machine learning

AbstractThe posterior statistical distributions of fatigue strength are determined using Bayesian inferential statistics and the Metropolis Monte Carlo method. This study explores how structural heterogeneity affects ultrahigh cycle fatigue strength in additive manufacturing. Monte Carlo methods and procedures may assist estimate fatigue strength posteriors and scatter. The acceptable probability in Metropolis Monte Carlo relies on the Markov chain's random microstructure state. In addition to commonly studied variables, the proportion of chemical composition was demonstrated to substantially impact fatigue strength if fatigue lifetime in crack propagation did not prevail due to high threshold internal notches. The study utilizes an algorithm typically used for quantum mechanics to solve the complicated multifactorial fatigue problem. The inputs and outputs are modified by fitting the microstructural heterogeneities into the Metropolis Monte Carlo algorithm. The main advantage here is applying a general‐purpose nonphenomenological model that can be applied to multiple influencing factors without high numerical penalty.

Tuning discrete growth of ultrathin nonstoichiometric Li2−xO2 discs to achieve high cycling performance Li–O2 battery

AbstractLi–O2 batteries (LOBs) with high theoretical energy density are regarded as promising next‐generation energy storage devices. However, the electrochemical performance of LOBs is significantly impacted by the sluggish reaction kinetics of the insulative discharge product, Li2O2. It is envisaged that nonstoichiometric lithium peroxide (Li2−xO2) with an increased charge transfer rate would address this issue. Herein, Ketjen black modified by highly stable polyarylimide was employed as the cathode material for LOBs. As revealed by time‐of‐flight secondary ion mass spectrometry and O K‐edge X‐ray absorption near‐edge structure analyses, nonstoichiometric Li2−xO2, primarily composed of LiO2 and Li2O3, is distributed homogeneously within the discharge products. The formation of nonstoichiometric Li2−xO2 is attributed to the strong interaction of the functional group C═O toward Li ions. In addition, the thickness of the discharge product is well controlled to less than 10 nm, providing a shortened charge transport path and increasing the decomposition kinetics. Consequently, ultrahigh cycle stability (>130 cycles) is achieved with a cutoff capacity of 1000 mAh g−1 at a current density of 400 mA g−1. This study provides a novel strategy for the development of sustainable and durable rechargeable LOBs.

Lithiophilic Zn-doped CuO/ZnO nanoarrays modified 3D scaffold inducing lithium lateral plating achieving highly stable lithium metal anode

Commercial applications of lithium (Li) metal anodes are limited by the continuous presence of Li dendrites and infinite volume variation during the plating/stripping process. Herein, the three-dimensional Zn-doped CuO/ZnO nanoarrays modified mesh (3D ZZCM) is prepared via redox electrochemistry method and Li/3D ZZCM composite anode is prepared by pressing 3D ZZCM on Li foil. The Li/3D ZZCM with uniformly distributed lithiophilic sites, induces Li lateral plating, which effectively suppresses the growth of Li dendrites and alleviates the volume expansion. The doping of zinc can further improve the charge transfer and reduce the interfacial resistance, promoting the redox reaction kinetics and reversibility of Li plating/stripping. Therefore, the Li/3D ZZCM composite anode achieves a stable cycle with low overpotential over 535 h even at 40 mA cm−2 with 10 mA h cm−2. And the dendrite-free uniform deposition process of Li/3D ZZCM anode is observed by in-situ optical dynamic test. When assembled with commercial LiCoO2, the Li/3D ZZCM||LiCoO2 full-cell demonstrates ultra-high cycle stability (81.8 % capacity retention after 600 cycles at 1C) and excellent rate performance, highlighting the great significance of Li/3D ZZCM anode for high energy density and safe Li metal batteries (LMBs).

Heat treatment for selective laser melting of Inconel 718 alloy with simultaneously enhanced tensile strength and fatigue properties

Inconel 718 alloy fabricated by selective laser melting (SLM) was used to investigate the evolution of precipitated phase from as-SLM to heat-treated (HT) samples. A heat treatment, including homogenization, solution and aging heat treatments, was proposed to obtain SLMed Inconel 718 alloy components for desirable mechanical performance. Post heat treatment process can reduce the number of original print defects due to grain boundary migration and grain growth. The solid solution plus double aging treatment (HT-1) results in the precipitation of large amounts of δ phase within the grain and at grain boundaries, as well as a small amount of massive MC. Homogenization, solid solution plus double aging (HT-2) eliminated a large amount of internal δ phases in the grain as well as needle-like δ phases at grain boundaries. However, the single aging (HT-3) still retains some of the needle-like δ phase. Heat-treated specimens increased tensile strength by 20–24% at room temperature and maintained high strength at 650 °C compared to the as-SLM. Further fatigue results also confirmed that the HT-2 treatment increases the fatigue life by an order of magnitude compared to the as-SLM to 10 8 cycles at a stress amplitude of 300 MPa. This work is anticipated to provide a potential route to obtaining attractive mechanical properties for SLM superalloy components. • The evolution of precipitated phase in SLMed Inconel 718 alloy under different heat treatment systems was studied. • Post heat treatment significantly improves strength of SLMed Inconel 718 alloy and maintains the high strength at 650 °C. • HT-2 heat treatment significantly increases the ultra-high cycle symmetric bending fatigue strength and life of the specimens .

Microwave-synthesized self-supporting CoSe2/carbon fiber felt electrode for ultra–high cycling life flexible supercapacitors

Flexible electrodes are candidate for portable and wearable electronic storage devices. In this work, high-performance flexible self-supporting CoSe 2 /carbon fiber felt (CoSe 2 /CFF) electrode was prepared via the microwave method without any binder. The CoSe 2 /CFF electrodes exhibited superior electrochemical performance (621 F g −1 at 1 A g −1 ) and an ultra-high cycling life (84.7% capacitance retention after 100,000 cycles). When the CoSe 2 /CFF was used as the positive electrode for the flexible supercapacitor, the assembled device exhibited an outstanding energy density of 22.43 W h Kg −1 at a power density of 823.12 W kg −1 . Because of the excellent mechanical stability of the device, it maintained 91.3% of its initial C after bending from 0° to 180°. The CoSe 2 /CFF proposed in this work shows electrode promising applicability to a low-cost, small-sized wearable and portable energy storage device. • A flexible electrode of CoSe 2 -CFF was prepared at a 120 s heating time via microwave method. • The CoSe 2 -CFF electrodes exhibit superior specific capacitance of 621F g −1 at 1A g −1 . • The CoSe 2 -CFF electrodes shows ultra-high cycle life of 84.7% after 100,000 cycles. • The all-solid-state ASC delivers high energy density and outstanding mechanical flexibility.

Microstructural evolution and elastic–plastic accommodation of misfit strain in a γ′-richen Ni-based superalloy during ultra-high temperature thermal cycle

Microstructural evolution and elastic–plastic accommodation of misfit strain in a γ′-richen Ni-based superalloy during ultra-high temperature thermal cycle

Wear and leakage assessments of canted coil Spring–Energized polytetrafluoroethylene seals under Ultra-High cycle operations

Spring-energized polytetrafluoroethylene (PTFE) seals are typically utilized to meet requirements of long service life due to their excellent temperature and chemical resistance. After high-cycle operations, the contact pressure between the seal lip and the associated counterpart possibly decrease because of the wear on the contact surface and this eventually leads to loss of the sealing capability. Evaluations of the wear and resulting sealing performance of the seal are rather essential, however, the corresponding experiments are generally time consuming and costly. Simulation procedures for the seal based on the finite element analysis were therefore developed in the current study. Experimental and numerical investigations of mechanical behaviors of the canted coil spring and PTFE materials were first performed. A wear analysis model for the spring-energized PTFE seal used in a glue dispenser with reciprocating motions for semiconductor equipment was subsequently constructed. The modified Archard model was implemented into a self-coded user subroutine of commercial finite element software to assess the amount of wear on the seal. Simulation results revealed that the geometry dimensions of the worn seal are in fair agreement with those of the corresponding samples. Contact pressure distributions of the seal lip were also examined during the operations. Peak of the contact pressure was found to gradually decrease along with the increase of cycles due to the wear, and potential fluid leakage was then assessed via the Reynolds equation. Numerical calculations showed that no leakage would occur after ultra-high cycle operations which was consistent with practical observations.

Ultrahigh cycle fatigue of nanocrystalline NiTi tubes for elastocaloric cooling

Elastocaloric cooling using superelastic NiTi shape memory alloy with reversible phase transformation is a promising environmentally friendly technology, but the limited fatigue life of conventional coarse-grained NiTi remains a crucial bottleneck. Here, we report the ultrahigh fatigue life of nanocrystalline NiTi tubes, exceeding 120 million cycles under a compressive stress of 800 MPa. The NiTi tubes demonstrate stable cyclic stress-strain responses and a stable adiabatic temperature drop of 6.6 K in the lifespan. The material coefficient of performance increases from the initial 8.8 to 11.6 of the 108th compressive cycle. The high resistance to nucleation and growth of compression-parallel cracks results in the ultrahigh fatigue life of the tubes. Our research shows the great potentials of nanocrystalline NiTi tubes with both stable thermomechanical properties and long compressive fatigue lives for reliable elastocaloric cooling.

Simple electrodeposition of 3D NiCoFe-layered double hydroxide nanosheet assembled nanospheres/nanoflowers on carbon cloth for high performance hybrid supercapacitors

Although layered double hydroxides (LDHs), especially NiCo-based LDHs, have been verified to be a type of potential cathode material for supercapacitors with high specific capacity and electric conductivity, their lifespan and rate performance are still not satisfactory. Herein, a series of 3D NiCoFe-LDH samples with different molar ratio of Ni/Co/Fe are successfully fabricated on carbon cloth via an electrodeposition method. It is found that NiCoFe-LDH nanosheet assembled nanospheres/nanoflowers electrode delivers high specific capacity, electrical conductivity, and more importantly, more superior rate performance as well as cycle stability than pristine NiCo-LDH electrode without Fe introduction. Moreover, the as-assembled hybrid supercapacitor device with NiCoFe-LDH and activated carbon as the cathode and anode respectively displays a wide voltage window (0–1.5 V), large specific energy (65 W h kg−1 at the specific power of 83 W kg−1) together with an ultrahigh cycle stability (26% capacity increment after 5000 cycles). With the merits of ease to fabricate and outstanding energy storage property, the newly assembled hybrid supercapacitor delivers great potential for practical application in the near future.

In-situ MOFs coating on 3D-channeled separator with superior electrolyte uptake capacity for ultrahigh cycle stability and dendrite-inhibited lithium-ion batteries

Lithium-ion batteries have been regarded as the most potential energy storage system due to their high energy density and theoretical capacity. However, conventional separators suffer from low electrolyte absorption, poor thermal and cycling stability, short circuits caused by dendrite growth. Herein, an effective approach was proposed to explore MOFs-based 3D-channeled separator via in-situ growth of ZIF-8 coating, which could significantly improve cycle stability and inhibit dendrite growth. Specifically, PLA membrane with 3D-channels was prepared by directional electrospinning and dopamine-induced assembling of MOFs in-situ growth onto the specified surface. By manipulating solvents, the desirable robustness of MOFs coatings could be accomplished through morphological assembly. Based on MOFs-architectured coating and microporosity, the excellent thermal stability (no change in size at 120 °C) and superior electrolyte uptake ability (290%) were finally obtained for the biobased separator. The assembled Li-ion battery exhibited ultrahigh cycle stability (capacity retention rate, 98.78% after 200 cycles at 1C rate) and preferable resistance to dendritic penetration, higher than those of the publicly reported. The excellent performance was attributed to the multiple 3D-channeled pathways for Li+ provided by MOFs and coating morphology. This study shows the potential for the development of next generation energy storage devices with excellent cycle stability.

Research on ultra-high cycle fatigue performance and reliability life analysis of TC4 by laser shock peening

The ultra-high cycle fatigue performance of TC4 titanium alloy specimens under different laser power densities was carried out by an ultrasonic fatigue testing machine. The fatigue fracture mechanism was analyzed by scanning electron microscope (SEM), and the reliability of ultra-high cycle fatigue life was analyzed. The results show that the specimen fatigue performance is obviously improved after laser shock peening, and the fatigue fracture surface shows a transgranular quasi-cleavage cracking mode with facets on the surface or subsurface, corresponding to high cycle fatigue and ultra-high cycle fatigue, respectively. At the same time, the position of the crack origin zone shifts sideways. The ultra-high cycle fatigue life obeys both lognormal distribution and three-parameter Weibull distribution, and the influence of reliability and confidence on reliability life depends on the sensitivity of unilateral tolerance confidence factor to both. According to the p-γ-S-N fitting curves, it was concluded that the fatigue life is higher and the scatter is smaller under the power density of 3.42 GW/cm2, so it is the best impact parameter.

Highly stable electrochromism and electrofluorochromism derived from a bi-functional polyamide containing conjugated bis(diphenylamine-spirodifluorene) moieties

A polyamide containing bis(diphenylamine-spirodifluorene) moieties was designed and synthesized. Owing to the stable electroactive amine center of conjugated system and loose interchain packing of twisted double triphenylamine-fluorophore moieties, the resulting polyamide revealed good overall properties, especially ultra-high cycle stability (less than 11.0% of fluorescence contrast loss after 800 cycles), as well as rapid switching speed (2.9/1.8 s) and high fluorescence/color contrast (111/69.2%). The study will promote their practical applications in the near future.

Tuning spatial distribution of graphene sheets composited with polyaniline nanofiber array on carbon cloth towards ultrahigh areal energy density flexible supercapacitors

Flexible supercapacitors with high areal energy density are promising energy storage devices to meet the increasing demands for wearable and portable electronic products. Herein, three kinds of flexible electrodes were fabricated electrochemically through tuning spatial distribution of graphene sheets composited with polyaniline (PANi) nanofiber array on carbon cloth, in which graphene sheets were used as the efficient growing substrate or protecting layer for the arrays and directly inserted into the arrays. It is found that the charge storage ability of all the PANi arrays could be enhanced significantly that depended greatly on the spatial distribution of graphene sheets composited with the array. The composite electrodes composing of graphene inserted PANi array on the graphene covered carbon cloth possesses the highest areal energy density among all the electrodes. More clearly, the corresponding all−solid−state supercapacitor devices can reach outstanding performances with a maximum energy density of 313 μWh cm−2 and capacitance retention of 92.7% after 5000 cycles could be achieved in the electrolyte containing Fe3+. This work is believed to provide a new thought for fabricating cost–effective and flexible electrodes with ultrahigh areal energy density, excellent flexibility and cycle stability endow for high−energy wearable/portable energy storage devices.

Magnetic and Optical Field Multi-Assisted Li-O2 Batteries with Ultrahigh Energy Efficiency and Cycle Stability.

The photoassisted lithium-oxygen (Li-O2 ) system has emerged as an important direction for future development by effectively reducing the large overpotential in Li-O2 batteries. However, the advancement is greatly hindered by the rapidly recombined photoexcited electrons and holes upon the discharging and charging processes. Herein, a breakthrough is made in overcoming these challenges by developing a new magnetic and optical field multi-assisted Li-O2 battery with 3D porous NiO nanosheets on the Ni foam (NiO/FNi) as a photoelectrode. Under illumination, the photogenerated electrons and holes of the NiO/FNi photoelectrode play a key role in reducing the overpotential during discharging and charging, respectively. By introducing the external magnetic field, the Lorentz force acts oppositely on the photogenerated electrons and holes, thereby suppressing the recombination of charge carriers. The magnetic and optical field multi-assisted Li-O2 battery achieves an ultralow charge potential of 2.73 V, a high energy efficiency of 96.7%, and good cycling stability. This external magnetic and optical field multi-assisted technology paves a new way of developing high-performance Li-O2 batteries and other energy storage systems.

Effects of laser shock peening on the ultra-high cycle fatigue performance of additively manufactured Ti6Al4V alloy

Although additive manufacturing (AM) allows to fabricate metallic parts with a high static strength comparable to their forged counterparts, the fatigue strength of an AM-ed part is generally inferior, restricting AM from many critical applications. In this study, laser shock peening (LSP) was applied to modify the surface properties of selective laser melting fabricated (SLM-ed) Ti6Al4V titanium alloy. This study performs systematic tests and analyses on the fabricated alloy specimens to characterize their microstructures and mechanical properties including residual stress, tensile strength, ultra-high cycle fatigue (UHCF) strength. The results reveal that LSP can refine microstructure, suppress residual stresses, and delay crack propagation in the affected area. However, the inherent defects in an SLM-ed part, such as unmelted powders, lack of fusion and clusters of α phase, dominate the fatigue failure of the specimens especially in the UHCF regime, resulting in their poor fatigue performance. Meanwhile, The LSP processed specimens showed a lower S-N curve than that of specimens without LSP processing especially in the UHCF regime, which not only results from the inherent defects, but also the increased surface roughness and non-uniform residual stresses.

High electrochemical performance of Ni-foam supported Ti3C2T x MXene/rGO nanocomposite

Two-dimensional (2D) materials have attracted extensive attention owing to their unique electronic/physiochemical properties, and wide application potential in energy storage and conversion. However, 2D materials are often tendency to aggregate due to the strong van der Waals interactions, leading to gradually decrease of an efficient mass transfer pathway and accessible surface area for the electrolyte. Here, we demonstrate an efficient approach for large-scale production of a hybrid nanostructures (Ti3C2T x /rGO) based on ultrathin MXene nanosheets anchored on layered reduced graphene (rGO) supported by porous Ni-foam via a plain chemical dipping method followed by high temperature annealing process. Ti3C2T x /rGO electrode exhibits a porous structure, excellent ionic and electrical conductivities, and remarkable specific capacitance. Furthermore, it shows ultra-high cycle stability, for example, 88.70% of its specific capacity can be maintained through 3000 cycles. This kind of porous nanostructure and integrated design idea is significant to design other energy storage modules.