Investigation of multi-step fast charging protocol and aging mechanism for commercial NMC/graphite lithium-ion batteries

Fast charging is considered a promising protocol for raising the charging efficiency of electric vehicles.However,high currents applied to Lithium-ion(Li-ion)batteries inevitably accelerate the degradation and shorten their lifetime.This work designs a multi-step fast-charging method to extend the lifetime of LiNi0.5Co0.2Mn0.3O2(NMC)/graphite Li-ion batteries based on the studies of half cells and investigates the aging mechanisms for different charging methods.The degradation has been studied from both full cell behaviour and materials perspectives through a combination of non-destructive diagnostic methods and post-mortem analysis.In the proposed multi-step charging protocol,the state-of-charge(SOC)profile is subdivided into five ranges,and the charging current is set differently for different SOC ranges.One of the designed multi-step fast charging protocols is shown to allow for a 200 full equivalent cycles longer lifetime as compared to the standard charging method,while the charging time is reduced by 20%.From the incremental capacity analysis and electrical impedance spectroscopy,the loss of active materials and lithium inventory on the electrodes,as well as an increase in internal resistance for the designed multistep constant-current-constant-voltage(MCCCV)protocol have been found to be significantly lower than for the standard charging method.Post-mortem analysis shows that cells aged by the designed MCCCV fast charging protocol exhibit less graphite exfoliation and crystallization damage,as well as a reduced solid electrolyte interphase(SEI)layer growth on the anode,leading to a lower Rseiresistance and extended lifetime.

Aging Mechanism and Life Estimation of Photovoltaic Inverter DC-link Capacitors in Alternating Humid and Thermal Environment

DC-link capacitors play a vital role in managing ripple voltage and current in converters and various devices.This study focuses on exploring the aging characteristics of DC-link capacitors in alternating humid and thermal environments aligned with the operational conditions in photovoltaic and wind power applications.Adhering to relevant power equipment standards,we designed a 24-h alternating humid and thermal aging environment tailored to the requirements of DC-link capacitors.An aging test platform is established,and 20 widely used metallized polypropylene film capacitors are selected for evaluation.Parameters such as the capacitance,equivalent series resistance(ESR),and phase angle are assessed during aging,as well as the onset time and extent of aging at various intervals.This study focuses on the aging mechanisms,analyzing electrode corrosion,the self-healing process,and dielectric aging.Fitting the aging characteristics enabled us to calculate the lifespan of the capacitor and predict it under different degrees of capacitance decay.The results show that under alternating humid and thermal conditions,capacitance attenuation and ESR increase exhibit exponential nonlinearity,influenced by factors such as the oxidation and self-healing of capacitive metal electrodes,dielectric main-chain fracture,and crystal transformation.This study underscores the pivotal role of encapsulation in determining the aging decay time.

Review of the influencing factors of secondary organic aerosol formation and aging mechanism based on photochemical smog chamber simulation methods

The formation and aging mechanism of secondary organic aerosol(SOA)and its influencing factors have attracted increasing attention in recent years because of their effects on climate change,atmospheric quality and human health.However,there are still large errors between air quality model simulation results and field observations.The currently undetected components during the formation and aging of SOA due to the limitation of current monitoring techniques and the interactions among multiple SOA formation influencing factors might be the main reasons for the differences.In this paper,we present a detailed review of the complex dynamic physical and chemical processes and the corresponding influencing factors involved in SOA formation and aging.And all these results were mainly based the studies of photochemical smog chamber simulation.Although the properties of precursor volatile organic compounds(VOCs),oxidants(such as OH radicals),and atmospheric environmental factors(such as NOx,SO2,NH3,light intensity,temperature,humidity and seed aerosols)jointly influence the products and yield of SOA,the nucleation and vapor pressure of these products were found to be the most fundamental aspects when interpreting the dynamics of the SOA formation and aging process.The development of techniques for measuring intermediate species in SOA generation processes and the study of SOA generation and aging mechanism in complex systems should be important topics of future SOA research.

Evolution of Microstructure and Mechanical Property during Long-Term Aging in Udimet 720Li

Thermal stabilities of microstructure and mechanical property have been investigated on super- alloy U72OLi, which is of great interest of application for jet engine and land-based turbine disc. The results showed that, the primary and secondary γ’?particles maintain good thermal stability at 650 and 7000C with aging time up to 3000 h, while the tertiary γ’?is apparently dependent on aging temperature and time. The tertiary γ’?particles undergo a procedure of coarsening, dissolution and eventually complete disappearance with the increasing of aging time and temper- ature. They exhibit unusual high sensibility upon aging temperature, which is attributed to the lattice misfit between the γ’?precipitates and the matrix in the alloy. The grain boundary phase M23C6 remains stable without forming of sigma phase even with aging time up to 3000 h at 700℃. Microhardness decreases apparently with increasing aging time and aging temperature. Theoretical analysis based on dislocation mechanism indicates that the change of microhardness should be attributed to the evolution of the tertiary γ’?during aging.

Effect of aging temperature on the microstructures and mechanical properties of ZG12Cr9Mo1Co1NiVNbNB ferritic heat-resistant steel

The effect of aging on the mechanical properties and microstructures of a new ZG12Cr9 MolColNiVNbNB ferritic heat resistant steel was investigated in this work to satisfy the high steam parameters of the ultra-supercritical power plant.The results show that the main precipitates during aging are Fe（Cr,Mo）23C6,V（Nb）C,and（Fe2Mo） Laves in the steel.The amounts of the precipitated phases increase during aging,and correspondingly,the morphologies of phases are similar to be round.Fe（Cr,Mo）23C6 appears along boundaries and grows with increasing temperature.In addition,it is revealed that the martensitic laths are coarsened and eventually happen to be polygonization.The hardness and strength decrease gradually,whereas the plasticity of the steel increases.What＇s more,the hardness of this steel after creep is similar to that of other 9%-12%Cr ferritic steels.Thus,ZG12Cr9 MolColNiVNbNB can be used in the project.

Aging effects on rheological properties of high viscosity modified asphalt

This work investigated the aging effects on the rheological properties of high viscosity modified asphalt(HVMA).First,the high-and low-temperature rheological properties were measured by a dynamic shear rheometer and a bending beam rheometer,respectively.The aging mechanism was then tested using an Fourier transform infrared spectroscopy and a scanning electron microscope.Besides,a study was performed to compare the aging effects on the rheological properties of HVMA,crumb rubber modified asphalt(CRMA),and neat asphalt(SK-90).The experimental results showed that the effects of the long-term aging on HVMA exceeded those of short-term aging.The complex shear modulus of the HVMA was improved by the aging in the whole frequency range.The complex shear modulus of the HVMA after the long-term aging was larger than after the short-term aging.Thus,the aging improved the high-temperature viscoelastic performance of HVMA.With a decrease in temperature from-12℃to-24℃,the low-temperature viscoelastic performance of HVMA decreased since its stiffness modulus and low continuous grading temperature increase.Both of the short-and long-term aging of HVMA were caused by an oxidation reaction,while modifier swelling also happened after long-term aging.Compared to CRMA and SK-90,aging had a limited influence on the high-and low-temperature rheological properties of HVMA.

Diagnosing Battery Degradation via Gas Analysis

Interfacial reactions in lithium-ion batteries often involve gaseous reaction products.Mechanistic investigation of material degradation processes requires a technique to identify and quantify these gases in battery cells.Online electrochemical mass spectrometry(OEMS)is an operando gas analysis method that continuously samples the headspace of a custom battery cell.Real-time gas analysis by quantitative OEMS was used to create mechanistic understanding of battery degradation reactions,some of which will be highlight in this article.

Understanding and quantifying capacity loss in storage aging of Ah-level Li metal pouch cells

Promoting industry applications of high-energy Li metal batteries(LMBs)is of vital importance for accelerating the electrification and decarbonization of our society.Unfortunately,the time-dependent storage aging of Ah-level Li metal pouch cells,a ubiquitous but crucial practical indicator,has not yet been revealed.Herein,we first report the storage behaviors and multilateral synergistic aging mechanism of Ah-level NCM811jjLi pouch cells during the 120-day long-term storage under various conditions.Contrary to the conventional belief of Li-ion batteries with graphite intercalation anodes,the significant available capacity loss of 32.8%on average originates from the major electrolyte-sensitive anode corrosion and partial superimposed cathode degradation,and the irreversible capacity loss of 13.3%is essentially attributed to the unrecoverable interface/structure deterioration of NCM with further hindrance of the aged Li.Moreover,principles of alleviating aging have been proposed.This work bridges academia and industry and enriches the fundamental epistemology of storage aging of LMBs,shedding light on realistic applications of high-energy batteries.

Microstructure and Performance Analysis of Organic Coating under High Temperature and High CO_2 Partial Pressure

To evaluate the property of the organic coatings in oil and gas plants, the aging process was studied in high temperature and high CO_2 partial pressure environment. Correlations were developed between the macroscopic properties and microstructure of the organic coatings. The surface appearance, mechanical properties, and permeability of the organic coatings were measured. Furthermore, the crystal structure of the organic coatings was investigated through synchrotron radiation grazing incidence X-ray diffraction（GIXRD） on the BL14B1 beam line in Shanghai Synchrotron Radiation Facility. Combined with the Fourier transform infrared spectroscopy, the molecular structure of the organic coatings was investigated. The experimental results indicate that the thickness variation and weight loss of the organic coatings increase with the immersion time, and the penetration resistance of the coating obviously decreases as the temperature rises. Moreover, the degradation of the organic coatings with immersion time in high temperature and high CO_2 partial pressure environment is caused by the amorphization of the organic coatings as the groups and bonds of the organic coatings were not damaged.

Characterization of particulate products for aging of ethylbenzene secondary organic aerosol in the presence of ammonium sulfate seed aerosol

Aging of secondary organic aerosol（SOA） particles formed from OH– initiated oxidation of ethylbenzene in the presence of high mass（100–300 μg/m^3） concentrations of（NH_4）_2SO_4seed aerosol was investigated in a home-made smog chamber in this study.The chemical composition of aged ethylbenzene SOA particles was measured using an aerosol laser time-of-flight mass spectrometer（ALTOFMS） coupled with a Fuzzy C-Means（FCM） clustering algorithm.Experimental results showed that nitrophenol,ethyl-nitrophenol,2,4-dinitrophenol,methyl glyoxylic acid,5-ethyl-6-oxo-2,4-hexadienoic acid,2-ethyl-2,4-hexadiendioic acid,2,3-dihydroxy-5-ethyl-6-oxo-4-hexenoic acid,1H-imidazole,hydrated N-glyoxal substituted1H-imidazole,hydrated glyoxal dimer substituted imidazole,1H-imidazole-2-carbaldehyde,N-glyoxal substituted hydrated 1H-imidazole-2-carbaldehyde and high-molecular-weight（HMW） components were the predominant products in the aged particles.Compared to the previous aromatic SOA aging studies,imidazole compounds,which can absorb solar radiation effectively,were newly detected in aged ethylbenzene SOA in the presence of high concentrations of（NH_4）_2SO_4seed aerosol.These findings provide new information for discussing aromatic SOA aging mechanisms.

Effect of Different Aging Processes on the Microstructure and Mechanical Properties of a Novel Al–Cu–Li Alloy

The effects of different aging processes on the microstructure and mechanical properties of a novel Al-Cu-Li alloy have been investigated by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. It is found that the tensile properties of a novel Al-Cu-Li alloy are sensitive to aging processes, which correspond to different microstructures. σ（Al_5Cu_6Mg_2） and T_1（Al_2CuLi） phases are the major precipitates for the alloy in T6 aging condition（165 ℃/60 h）. After duplex aging condition（150 ℃/24 h ＋ 180 ℃/12 h）, σ, θ＇（Al_2Cu） and T_1 phases are detected. Only the T_1 phases can be found in the T8 state alloy（6% pre-strain＋135 ℃/60 h）. The failure modes of alloy in T6 and duplex aging conditions are dimple-intergranular fracture, while typical quasi-cleavage fracture in T8 condition.

Microstructure Evolution and Mechanical Properties of HR3C Steel during Long-term Aging at High Temperature

Microstructure evolution and the changes in mechanical properties of HR3 Csteel during long-term aging at650,700 and 750℃ were investigated.The precipitated phases of the aging steel included M23C6 carbides,Z-phase and a trace amount of Nb（C,N）.The M23C6 carbides were distributed mainly at the grain boundary,while Z-phase was mainly inside the grains.Amounts of both M23C6 carbides and Z-phase during the aging process increased with increasing aging period and temperature.Coarsening of M23C6 carbides was influenced significantly by aging time and temperature,while the size of the Z-phase was relatively less affected by the aging time and temperature,which had a steady strengthening effect.Coarsening of the M23C6 carbides was the main reason for the decline in high temperature yield strength during long-term aging at 750℃.The M23C6 carbides were linked into a continuous chain along the grain boundary which accounted for the decrease of toughness during aging.

Precipitation Behavior of Cu-1.9Be-0.3Ni-0.15Co Alloy During Aging

In this paper,the evolutions of microstructure and mechanical properties of Cu-l.9Be-0.3Ni-0.15Co alloy were studied.The alloys in the condition of the solution treated（soft state） and 37% cold rolled（hard state） were aged at 320 ℃for different time,respectively.The mechanical properties,electrical conductivity and microstructure of the alloy aged for different time were analyzed.Additionally,the precipitation kinetics of Cu-1.9Be-0.3Ni-0.15Co alloys was investigated.X-ray diffraction and transmission electron microscopy results reveal that both continuous precipitation and discontinuous precipitation existed in the hard-state Cu-l.9Be-0.3Ni-0.15Co alloy during the whole aging process;the sequence of continuous precipitation is G.P.zone →γ″→γ′→γ.Furthermore,the precipitation transformation mechanism of softstate alloy is homogeneous nucleation,while hard-state alloy shows the heterogeneous nucleation（interface nucleation）with the nucleation rate of both states decaying rapidly to zero during aging at 320 ℃.

Microstructure and properties of aging Cu–Cr–Zr alloy

The crystallography and morphology of precipitate particles in a Cu matrix were studied using an aged Cu–Cr–Zr alloy by transmission electron microscopy（TEM） and high-resolution transmission electron microscopy（HRTEM）. The tensile strength and electrical conductivity of this alloy after various aging processes were tested. The results show that two kinds of crystallographic structure associated with chromium-rich phases, fcc and bcc structure, exist in the peak-aging of the alloy. The orientation relationship between bcc Cr precipitate and the matrix exhibits Nishiyama–Wasserman orientation relationship. Two kinds of Zr-rich phases（Cu4Zr and Cu5Zr）can be identified and the habit plane is parallel to {111}Cu plane during the aging. The increase in strength is ascribed to the precipitation of Cr- and Zr-rich phase.

Long-term thermal-aging stability of oxide-dispersion-strengthened ferritic steels at 753 K

Oxide-dispersion-strengthened （ODS） ferritic steels are promising candidates for structural applications in the future nuclear reactors. The higher chromium contents of ODS ferritic steels, the better the corrosion resistance, which can meet the harsh corrosion environment of the advanced reactors. However, increasing the Cr content may also lead to the brittleness of the ODS steels when serving at high temperatures. The ODS ferritic steels with different Cr contents （12, 16 and 18 wt% Cr, respectively） were fabricated by mechanical alloying, hot isostatic pressing and forging. Mechanical properties and microstructure evolution of the ODS ferritic steels after aging at 753 K for 2000 h were investigated. It is found that both Vickers hardness and yield strength of 18%Cr ODS ferritic steel were strongly increased and the impact energy was decreased after aging at 753 K. In order to explore the reasons for changes in the mechanical properties, the fracture surfaces were characterized by scanning electron microscopy, and microstructures after aging were observed by transmission electron microscopy. The impact fracture of 18%Cr ODS ferritic steel belongs to quasi-cleavage facture, which is consistent with its very low impact energy. The grain size and dispersed oxide particles of different ODS steels are very stable. M23C6 carbide and M2C carbide were found in 12%Cr ODS steel and 16%Cr ODS steels, respectively.

Strain Hardening Associated with Dislocation,Deformation Twinning,and Dynamic Strain Aging in Fe–20Mn–1.3C–(3Cu) TWIP Steels

The effects of Cu on stacking fault energy,dislocation slip,mechanical twinning,and strain hardening in Fe–20Mn–1.3C twinning-induced plasticity（TWIP） steels were systematically investigated.The stacking fault energy was raised with an average slope of 2 mJ/m2 per 1 wt% Cu.The Fe–20Mn–1.3C–3Cu steel exhibited superior tensile properties,with the ultimate tensile strength reached at 2.27 GPa and elongation up to 96.9% owing to the high strain hardening that occurred.To examine the mechanism of this high strain hardening,dislocation density determination by XRD was calculated.The dislocation density increased with the increasing strain,and the addition of Cu resulted in a decrease in the dislocation density.A comparison of the strain-hardening behavior of Fe–20Mn–1.3C and Fe–20Mn–1.3C–3Cu TWIP steels was made in terms of modified Crussard–Jaoul（C–J） analysis and microstructural observations.Especially at low strains,the contributions of all the relevant deformation mechanisms—slip,twinning,and dynamic strain aging—were quantitatively evaluated.The analysis revealed that the dislocation storage was the leading factor to the increase of the strain hardening,while dynamic strain aging was a minor contributor to strain hardening.Twinning,which interacted with the matrix,acted as an effective barrier to dislocation motion.

锂离子电池加速老化:连接电池老化机制分析与寿命预测的桥梁

储能行业和新能源汽车的爆发式增长要求对锂离子电池的老化行为尤其是电池的寿命行为有更加深入的了解.准确地预测电池在各种工作条件下的使用寿命有助于优化电池的实际运行条件和延长电池的使用寿命,最终达到降低电池生命周期内总成本的目的.加速老化是一种经济高效的产品寿命评价方法,可以在短时间内获得大量的电池老化信息,快速预测锂离子电池在各种工作应力下的寿命特征.然而,基于加速老化进行电池寿命预测的前提是电池老化机理的一致性.本文综述了锂离子电池内各部件的老化机理和应力加速条件下的电池衰退机制以及相应的老化模式,为评价电池老化机理的一致性提供了参考.此外,本文还介绍了一些基于加速老化的电池寿命经验预测模型并为今后锂离子电池的加速老化研究提供了一些建议.

The Study on the Mechanical Properties of Optical Fiber With Long-Term Time Aging

The fiber properties depending on the coating thickness and long-term time aging were investigated. The coating strip forces of optical fiber were strongly increased with secondary coating thickness. But it did not change with time aging up to 90 days. The tensile strength and stress corrosion parameters of coated fiber were increased with time aging also but the increasing rate was quite different depending on the coating

Effect of Ageing at 700℃ on Microstructure and Mechanical Properties of S31042 Heat Resistant Steel

To investigate the effect of high temperature ageing on the microstructure and mechanical properties of S31042steel,solid solution treatment at 700℃ was carried out for various time from 10to 6 000h.Experimental results showed that the change of mechanical properties is closely related to the amount of precipitated phases.During ageing from 10to 300h,precipitation in the tested steel increases rapidly,and correspondingly,the high temperature yield strength and room temperature hardness of tested steel increase rapidly.Meanwhile,the thickness of the secondary phase on grain boundaries widens sharply and the room temperature Charpy impact absorb energy decreases.Ageing beyond 300h,the precipitation in the steel increases gradually and the precipitates coarsen to a certain extent.The high temperature yield strength of the steel keeps stable,and the room temperature Charpy impact energy and hardness decrease slowly.Ageing beyond 3 000h,the mechanical properties of the steel tend to be stable.The main precipitates are M23C6,NbCrN and NbC in the tested steel.

Microstructure Evolution and Mechanical Properties of Spray-deposited Al-21.47Si-4.73Fe-2.5Cu-0.9Mg Alloy

Al-Si-Fe-Cu-Mg alloy was prepared by spray deposition and was further processed by hot extrusion as well as T6heat-treatment.The results indicate that the microstructure of the deposited alloy is composed of primary Si particles with average size of less than 5μm,α-Al,Al_2CuMg,β-Al_5FeSi andδ-Al_4FeSi_2（rectangular shape）,and no eutectic silicon is found due to the special solidification behavior.The age hardening curves reveal two peaks.The uniform ultimate tensile strength（UTS）and the elongation of the peak-aged Al-Si-Fe-Cu-Mg alloy are 468.3 MPa,0.61% at 298 Kand 267.4MPa,6.42% at 573 K,respectively.The fracture surfaces display brittle fracture morphology at 298 K,whereas it varies to mixture of brittle and ductile failure with increasing the temperature.