Main Aging Mechanisms Research Articles

Cycling Aging in Different State of Charge Windows in Lithium-Ion Batteries with Silicon-Dominant Anodes

Reducing the capacity utilization of silicon-containing anodes and choosing the optimal full-cell voltage window improve the lifetime significantly. In this study, we investigate how different voltage windows affect the aging modes with a common 50% cycling depth. First, the cyclic stability, the anode potentials, and the polarization increase are analyzed for the different voltage windows using 70 wt% microscale silicon anodes and NCA cathodes with a lithium metal reference electrode to investigate the electrode-specific characteristics. Further, the underlying aging modes are quantified in the post-mortem analysis. Finally, the anode thickness increase is quantified using a dilatometer setup for different anode lithiations. In contrast to the literature, the highest voltage window is most beneficial for the lifetime since high anode delithiation potentials and high surface increases are avoided. The anode potential at the end-of-discharge, the charge-averaged full-cell potentials, and the resistance increase are a function of the state of health (SoH). The common underlying main aging mechanism is the loss of lithium inventory, followed by the loss of anode active material. In contrast, the loss of cathode active materials only plays a minor role.

Assessment of leak-tightness for nuclear reactor containment under overpressure conditions considering aging effects

This paper assesses the aging effects on the leak-tightness of containment under overpressure conditions. A global containment model and the detailed sub-models for the three main penetration regions in the containment are established. The main aging forms and mechanisms of containment are clarified, and corresponding simulation schemes are provided. Through numerical simulation, the impacts of different aging forms on the failure pressure of containment are discussed from a deterministic perspective. Finally, the fragility and functional failure probability of containment under different aging conditions are evaluated. When 60 years of concrete degradation and prestress loss are considered, the pressure capacities of equipment hatch, personnel airlock, and pipe penetration are reduced by approximately 5%. Upon further considering steel liner corrosion, when the corrosion degree reaches 30%, the pressure capacities of these regions are reduced by 24.37%, 25.52%, and 22.83%, respectively. Within the scope of this study, the impact of steel liner corrosion on the risk of containment leakage is the most pronounced, whereas the impact of concrete degradation is minimal. If steel liner corrosion occurs simultaneously in three penetration regions, the whole containment will fail to meet the probabilistic performance goal when the corrosion degree reaches 30%.

Experimental and simulation studies of degraded EPDM composite in the coupled gamma radiation-thermal environments

The degradation behaviors, mechanisms and compatibility are not well understood and hard to be harnessed for EPDM composite in the coupled gamma radiation-thermal environments. This contribution performs a thorough study accordingly with 0 ∼ 200 kGy dose under temperatures varying from room temperature to 90 °C in N2/O2 mixture atmosphere. Radiation-thermal aging leads to annealing effect and chemi-crystallization that rebuilds the semi-crystalline structure and invokes competitive filler migration, reconfiguration and loss. Crosslinking reactions prevail the scission during the investigated conditions. However, the surface oxidation and damage are not severe. In-situ nondestructive gas-phase FTIR sensitively find the formed various gaseous products, whose generation kinetics behaviors are temperature and dose dependent. Most surprisingly, the radiolysis caused carbonyl sulfide and carbon disulfide are discovered with indispensable gamma radiation, which manifest temperature reined conversion thermodynamics and kinetics behavior. The qualitative and quantitative analysis of gas products is also validated by GC and GC-MS tests. The evolved semi-crystalline structure, macromolecular chain network and filler network significantly impact the mechanical property, but the barrier property and hydrophobic property are slightly influenced. The inverse temperature effect occurred at 50 °C for the mechanical properties, which show abnormal rejuvenation behavior due to the counteraction between aging induced change in molecular structure, aggregation structure and filler reconfiguration, migration and loss. The multiscale structure-property-behavior relationships possess good interdependency, indicating the main aging mechanism and failure mode are almost invariant. By ReaxFF simulation, the complex degradation mechanism for EPDM composite at atomic scale is revealed for the first time.

Aging Mechanism For Calendar Aging of Li-Ion Cells With Si/Graphite Anodes

Calendar aging of Li-ion batteries with Si/graphite electrodes was investigated within this study. A total of 121 single-layer pouch full cells with either graphite or Si/graphite (3.0 wt−%, 5.8 wt−% and 20.8 wt−% Si) anodes and NMC622 cathodes with the same N/P ratio were built on pilot-scale. Calendar aging was studied at SoC 30%, 60%, and 100%, as well as temperature (25 °C, 45 °C, 60 °C) and time dependence. The aging data was analyzed in terms of capacity fade and a square-root behavior was observed. Differential voltage analysis (DVA) has been performed as a function of aging time. The observed temperature and time dependence is best described by time dependent, 3D Arrhenius plots. Post-Mortem analysis (SEM, EDX, GD-OES) is applied to investigate the changes on electrode and material level. Conclusions are drawn on the main aging mechanisms for calendar aging of Li-ion cells with Si/graphite anodes and differences between Si/graphite and pure graphite anodes are discussed. The Si-containing cells show a combination of lithium inventory loss and a loss of accessible Si active material, both caused by SEI growth.

Change of safety by main aging mechanism – A multi-sensor accelerating rate calorimetry study with commercial Li-ion pouch cells

The safety of Li-ion batteries is the most critical of many important characteristics and must be carefully considered. However, depending on the aging conditions, safety of batteries can change drastically. We had recently introduced ARC-MS as a new tool for safety investigations, which is an updated accelerating rate calorimeter (ARC) combined with a mass spectrometer (MS). Additionally, our ARC-MS setup is equipped by seven more low cost sensors (temperature, voltage, resistance, audio, strain, and transmitted and reflected ultrasound). In this paper, the dependence of safety on the dominant aging mechanism as a function of aging temperature, and state-of-health (SOH) is investigated on the example of 3.3 Ah commercial pouch cells. The ambient temperature during aging has a strong influence on the dominant aging mechanism (Li plating or SEI growth) of this cell as shown by Arrhenius plots of the aging rate and Post-Mortem analyses (ICP-OES, SEM, EDX, Hg porosimetry, STA) of aged cells. Our in-depth evaluation shows that different sensors can provide indications of safety relevant events (onset of swelling, onset of self-heating, cell venting, stable exothermic reactions, separator melting, and thermal runaway) in the cells independently. Combining these low-cost sensors might be a solution for detection of unsafe cells in applications.

Natural aging mechanism of buried polyethylene pipelines during long-term service

Currently, accelerated aging tests are widely used to study the aging process of polyethylene pipelines. However, this approach can only simulate one or several main influencing factors in the natural environment, which are often quite different from the actual environment of the buried pipelines. In this study, five types of PE80 buried pipelines in service for 9–18 years were taken as the research object, while new PE80 pipelines were taken as the reference group. The aging process and mechanism of polyethylene buried pipelines were studied through mechanical and chemical property tests and microstructural analysis. The results showed that the pipeline exhibited cross-linking as the main aging mechanism after being in service for 0–18 years. The aging degree and law of the inner and outer surface of the pipeline were compared, and the observed mechanism of both surfaces was explained. After 18 years in service, the elongation at the break of the pipe decreased by 16.2%, and the toughness of the matrix in the main collapse area of the tensile sample was the fundamental reason responsible for changes in the mechanical properties. Finally, after 18 years in service, the oxidation induction time of the pipeline was 25.7 min, which was 28.5% higher than the national standard value. There were no potential safety hazards during continuous long-term service. The results of this paper provide reference data and theoretical guidance for the aging process study of buried polyethylene pipelines.

A Post-Mortem Study Case of a Dynamically Aged Commercial NMC Cell

Lithium-ion batteries are currently the pioneers of green transition in the transportation sector. The nickel-manganese-cobalt (NMC) technology, in particular, has the largest market share in electric vehicles (EVs), offering high specific energy, optimized power performance, and lifetime. The aging of different lithium-ion battery technologies has been a major research topic in the last decade, either to study the degradation behavior, identify the associated aging mechanisms, or to develop health prediction models. However, the lab-scale standard test protocols are mostly utilized for aging characterization, which was deemed not useful since batteries are supposed to age dynamically in real life, leading to aging heterogeneity. In this research, a commercial NMC variation (4-4-2) was aged with a pragmatic standard-drive profile to study aging behavior. The characterized measurable parameters were statistically investigated before performing an autopsy on the aged battery. Harvested samples of negative and positive electrodes were analyzed with Scanning Electron Microscopy (SEM) and the localized volumetric percentile of active materials was reported. Loss of lithium inventory was found to be the main aging mechanism linked to 20% faded capacity due to heavy electrolyte loss. Sparsely distributed fluorine from the lithium salt was found in both electrodes as a result of electrolyte decomposition.

Health prognostics for lithium-ion batteries: mechanisms, methods, and prospects

Critical review of main aging mechanisms and health prognostic methods for lithium-ion batteries. Comprehensive summary of challenges and prospects for future trends with potential solutions.

Preface to the theme issue 'Durability and ageing of composite materials'.

The issue focuses on ageing and durability of composite materials for industrial applications. Ageing and durability are two fundamental topics within the context of design and optimization of materials and structures: ageing may induce degradation and leads to premature failure. Therefore, understanding the main ageing mechanisms is of paramount importance for predicting material durability. These topics are still barely studied systematically and the main related issues are debated within mechanical, chemical, and solid-state physics research communities. This issue aims to update the current research state of the art, clarifying the interplay between chemical and physical mechanisms involved in degradation processes, and providing test protocols and design rules that account for ageing and durability. This article is part of the theme issue 'Ageing and durability of composite materials'.

Detection of Li Deposition on Si/Graphite Anodes from Commercial Li-Ion Cells - a Post-Mortem GD-OES Depth Profiling Study

A new semi-quantitative method based on Post-Mortem glow discharge optical emission spectroscopy (GD-OES) depth profiling was developed to detect Li deposition on Si/graphite anodes. By means of the detected amounts of Li, Si and O in the GD-OES depth profiles, a corridor is determined, in which the minimum amount of Li deposition is found. Three different commercially available 18650 cell types containing Si/graphite as anode active material were acquired to evaluate the newly developed method. Those three cell types were initially characterized in detail by means of SEM/EDX, GD-OES, ICP-OES, and Hg porosimetry regarding their cell chemistry and electrode properties. One cell type was a high-power cell due to its high anode porosity and low anode coating thickness. The other two cell types were high-energy cells, which have thick anode coatings and low porosities.We aged the cells at 45 °C until their SOH was 80% and analysed the aging behaviour using SEM, DVA, GD-OES, and in coin half-cells. GD-OES depth profiling revealed that no Li plating occurs during cycling aging at 45 °C. Contrary to this, Li plating was detected on the anodes of all three cell types by the new GD-OES method after the high-power cell was aged at -20 °C and the high-energy cells were aged to 0 °C.Cells, which were previously aged at 45 °C until 80% SOH have afterwards been cycled under the same conditions, which led to Li plating in the fresh cells. Cell types exhibiting predominantly loss of anode active material (LAAM) as aging mechanism during the first aging at 45 °C, still suffered from Li plating during the second aging. However, if the main aging mechanism during the initial aging was loss of cyclable Li inventory (LLI), the cells did show a significantly reduced tendency for Li plating, even though the same conditions caused Li plating in the fresh cells.Analysis of the aged anodes using coin half-cells revealed that the loss of anode material was caused by the deactivation of Si anode material. SEM images of the anode cross-section indicate that the deactivation is most likely mainly induced by the formation of a thick film surrounding the Si particles.In combination with complementary methods like SEM, ICP-OES, and coin half-cell analysis, the newly developed GD-OES method yields in profound understanding of the aging behaviour of state-of-the-art Li-ion cells contain Si/graphite anodes. Figure 1

An Efficient Electrochemical State of Health Model for Lithium-Ion Batteries

Capacity fade experienced by the battery will affect the lifetime of the battery pack as well as the residual value of an electric vehicle. Developing a degradation model that can prognosis state of health for the given operating condition is critical for developing an algorithm to maximize the remaining useful lifetime of the systems. It is known that the electrochemical degradation model has superior predictability to other data-driven models, but still needs improvement in terms of computational efficiency. We reduced the electrochemical degradation model which considers three main aging mechanisms that can predict the state of health at various calendric aging conditions. The parameterization procedure and its prediction capability will be also discussed.

Characterization of aging mechanisms and state of health for second-life 21700 ternary lithium-ion battery

This paper focuses on the identification of aging mechanisms and the estimation of the state of health (SOH) for second-life 21700 nickel–cobalt–aluminum (NCA) lithium-ion batteries. NCA battery is aged at 1/2 C-rate in the laboratory until its SOH value reaches about 60%. Incremental capacity (IC) and different voltage (DV) and probability density function (PDF) analyses are used to explore the aging mechanisms of NCA battery and build SOH estimation models with and without multicollinearity. The results show that the capacity decays almost linearly throughout the aging cycle and the loss of lithium inventory (LLI) and the loss of active material (LAM) on anode are the main aging mechanisms. The equivalence between PDF and IC/DV analyses is proved by NCA battery. Peak (valley) features from IC, DV and PDF curves are extracted as health factors (HFs), which have good correlation with battery SOH. Principal component analysis (PCA) is employed to reduce the multicollinearity and more accurate SOH evaluation models are built based on principal component regression (PCR). The verification results show that the ICA-PCR, DVA-PCR and PDF-PCR models all have good evaluation accuracy.

Thickness change and jelly roll deformation and its impact on the aging and lifetime of commercial 18650 cylindrical Li-ion cells with silicon containing anodes and nickel-rich cathodes

Two types of commercial cylindrical cells in the format 18650 both with NCA cathode and anodes containing different silicon materials were electrochemically long-term cycled. Two voltage windows and their influence on the aging of the cells were investigated. Multiple CT images after a pre-determined number of completed cycles reveal volume expansion and jelly roll deformation during the aging of the cells. With an optical micrometer, the reversible and irreversible thickness change was studied in operando. Furthermore the electrode expansion was investigated with an electrochemical dilatometer. Depending on the type of silicon active material used, differences in the aging behavior of the cells were observed. These findings were linked to the rest of the non-destructive, destructive and post-mortem analyses. With the help of differential voltage analysis, pulse tests and different evaluations using the generated CT data, the inhomogeneous thickness change of the cells especially at critical spots could thus be revealed and reasons for capacity degradation or resistance increase can be directly seen. Due to post-mortem analysis a much better understanding of the underlying aging mechanisms was generated. With SEM/EDX analysis, ICP-OES and TGA, the formation of passivation layers on the electrodes was observed. By comparing the results with new cells, individual causes of failure were revealed. It was found that the main aging mechanism is the loss of lithium from the cathode together with the volume change of the anode. Cells with pure Si instead of SiOx have exhibited a faster degradation because of the additionally higher thickness change during charging and discharging. Delamination of the electrode coating because of particle swelling, binder failure and jelly roll deformation is seen after unrolling the aged cells. Limiting the voltage range leads to longer lifetime, less resistance increase and overall less aging of silicon in all tested cells.

A Comprehensive Review on the Characteristics and Modeling of Lithium-Ion Battery Aging

Battery aging is one of the critical problems to be tackled in battery research, as it limits the power and energy capacity during the battery’s life. Therefore, optimizing the design of battery systems requires a good understanding of aging behavior. Due to their simplicity, empirical and semiempirical models (EMs) are frequently used in smart charging studies, feasibility studies, and cost analyses studies, among other uses. Unfortunately, these models are prone to significant estimation errors without appropriate knowledge of their inherent limitations and the interdependence between stress factors. This article presents a review of empirical and semiempirical modeling techniques and aging studies, focusing on the trends observed between different studies and highlighting the limitations and challenges of the various models. First, we summarize the main aging mechanisms in lithium-ion batteries. Next, empirical modeling techniques are reviewed, followed by the current challenges and future trends, and a conclusion. Our results indicate that the effect of stress factors is easily oversimplified, and their correlations are often not taken into account. The provided knowledge in this article can be used to evaluate the limitations of aging models and improve their accuracy for various applications.

Detection of Li Deposition on Si/Graphite Anodes from Commercial Li-Ion Cells: A Post-Mortem GD-OES Depth Profiling Study

A new semi-quantitative method was developed to detect Li deposition on Si/graphite anodes. This method is based on Post-Mortem glow discharge optical emission spectroscopy (GD-OES) depth profiling. Based on the contents of Si, Li, and O in the GD-OES depth profiles, we define a corridor, in which the minimum amount of metallic Li on the anode is located. This method was applied to three types of commercial 18650 cells with Si/graphite anodes in the fresh state and with Li plating intentionally produced by cycling at low temperatures. Additional cells were cycling aged at 45 °C to 80% SOH. The main aging mechanisms at 45 °C were determined using differential voltage analysis (DVA), SEM, and half cell experiments. Subsequently, the cells aged at 45 °C were further cycled under the conditions that had led to Li deposition for the fresh cells. Furthermore, the anode coating thickness for 18 types of commercial Li-ion cells are correlated with the specific energy, while distinguishing between graphite anodes and Si/graphite anodes. Our extensive Post-Mortem study gives deep insights into the aging behavior of state-of-the-art Li-ion cells with Si/graphite anodes.

Quantitative analysis of aging and detection of commercial 18650 lithium-ion battery under slight overcharging cycling

Lithium-ion batteries are widely used in electric vehicles to solve the problems of greenhouse gas emission. However, overcharging occurs due to the inconsistency of lithium-ion batteries, malfunction of charge control and inappropriate battery management. In order to solve the safety and cycle life problems of batteries suffering slight overcharging, quantitative analysis of the aging behavior, aging mechanisms and detection of slight overcharging cycling are studied in this manuscript. The results indicate that the cycle life of battery decreases linearly and exponentially with the upper cut-off voltage increasing when capacity and resistance are used as the threshold of the end of life respectively. The batteries have tolerance to slight overcharging with voltage lower than 4.6 V. The generated gas is not the main aging mechanism. Loss of active material is the main aging mechanism when the batteries are cycled at 4.4 V. Charging stress is the key factor triggering the loss of active material. The main aging mechanism becomes to be loss of lithium with the increase of voltage and cycle number due to the electrolyte oxidation, reduction and lithium plating. The differential voltage, coulombic efficiency and fast resistance increase are used as warming parameters of slight overcharging cycling.

Impact of low temperature and charge profile on the aging of lithium-ion battery: Non-invasive and post-mortem analysis

In this paper, the low temperature performance of lithium-ion batteries under various charge rates ranged from 0.2 C to 1 C were studied. To shed some light on the degradation modes and aging mechanism, non-invasive and post-mortem analysis were adopted. The results reveal that there is a considerable reversible capacity loss and internal resistance increase with the increase in charge rate. Particularly, the relative capacity of 1C charged cell after 150 cycles is below 0.8, indicating the end of life is achieved. In addition, the increased internal resistance will lead to a substantial increase in heat generation rate, which is an important factor to the thermal safety control of battery related to the design of thermal management strategy. Besides the resistance increase, two major degradation modes i.e., loss of lithium inventory and loss of active material are demonstrated according to the differential voltage and incremental capacity analysis. It is found that lithium plating is regarded as the main aging mechanism. The anode material of cycled cell display distinct deterioration even exfoliated from the copper foil upon a macroscopic check, and a thick deposited layer morphology and cracking of the layer is visible from a micro point of view through cell opening. During the low temperature charging, lithium plating could be triggered due to the limitation of charge transfer resulted from high-rate charge as well as the limitation of solid-state diffusion resulted from low temperature. The continuous lithium-consuming during cycling will lead to secondary SEI formation, which may result in dead lithium and stripping, eventually reversible capacity loss.

Post-Mortem Analysis of Lithium-Ion Capacitors after Accelerated Aging Tests

Lithium-ion Capacitors (LiCs) have recently emerged in the market of energy storage systems as a new technology having some of the advantages of Lithium-ion Batteries (LiBs) and Supercapacitors (SCs). As an important number of commercial LiCs combine the negative electrode of LiBs with the positive electrode of SCs, the lifetime of this new technology requires an effective analysis that can underlie degradation mechanisms related to each electrode. In order to evaluate the aging behavior of LiCs, calendar accelerated aging tests were applied to eighteen cells for twenty months in a previous study. Two temperatures, 60°C and 70°C, and three storage voltage values, 2.2 V, 3.0 V and 3.8 V were used to accelerate their aging. the The lifetime of LiCs was found to be particularly dependent on the storage voltage and the degradations of the cells were most pronounced at the highest temperature, 70°C. Therefore, in the current study, post-mortem analyses are applied to three cells that aged at different storage voltage values and 70°C. Considering the same aging mechanisms at high temperatures, only one high temperature was chosen. Two main aging mechanisms were observed: the pores blocking of activated carbon at the positive electrode and the loss of lithium ions from the negative electrode of pre-lithiated graphite. Elements responsible for these degradations were different at each voltage condition. Additional mechanisms were identified such as the degradation of the electrolyte and the decomposition of the positive current collector.

Thermal ageing of a silane-crosslinked polyethylene stabilised with a thiodipropionate antioxidant

The thermal ageing of a silane-crosslinked polyethylene stabilised with 1 wt% of distearyl thiodipropionate (Irganox PS802) was studied in air at three different temperatures: 87 °C, 110 °C, and 130 °C. FTIR spectroscopy and DSC under O2 were used in a complementary way to monitor the antioxidant (AO) depletion during thermal ageing, but also to detect the polymer oxidation. In particular, at the three ageing temperatures under study, it was observed that the physical loss of AO is the main ageing mechanism and is controlled by AO evaporation. However, the contribution of the AO chemical consumption in the overall kinetics of AO depletion was also estimated. In addition, the temperature dependences of the evaporation constant and the rate constant of the chemical consumption of AO were approximated with the usual Arrhenius law in the temperature range under investigation. Although the corresponding activation energies must be considered with caution, due to the limited amount of data acquired in this study, they were found to be in good agreement with the few results available in the literature.

Impact of Laboratory-Accelerated Aging Methods to Study Alkali-Silica Reaction and Reinforcement Corrosion on the Properties of Concrete.

This study focuses on two separate investigations of the main aging mechanisms: alkali–silica reactivity (ASR) and the corrosion of reinforcing steel (rebar) concrete, both of which may result in a premature failure to meet the serviceability or strength requirements of a concrete structure. However, these processes occur very slowly, spanning decades. The impact of direct chemical additives to fresh concrete to accelerate ASR and the corrosion of reinforcing steel on the fresh and hardened properties of the ensuing material are investigated to inform the potential use of chemicals in large-scale studies. The deterioration of reinforced concrete (RC) is determined by means of expansion, cracking, bulk diffusivity and surface resistivity measurements, and compressive, split tensile and flexural strength tests. The results indicate that the addition of sodium hydroxide and calcium chloride can effectively accelerate the crack formation and propagation in concrete due to ASR and the corrosion of rebar, respectively. The ASR-induced cracks maintained a constant crack width from 0.05 mm to 0.1 mm over the measurement period regardless of the intensity of aging acceleration. Adding 4% chloride by weight of cement for accelerating rebar corrosion resulted in an average crack that was 82% larger than in the case of ASR accelerated with the addition of sodium hydroxide. The addition of alkali resulted in an increase in early-age (7-day) strength. At a total alkali loading of 2.98 kg/m3, 3.84 kg/m3 and 5.57 kg/m3, the 28-day compressive strength of concrete decreased by 3%, 10% and 24%, respectively. Similarly, a higher early-age strength and a lower later-age strength was observed for the concrete in the presence of corrosive calcium chloride. The results from this research are expected to inform future studies on the long-term performance of RC structures under accelerated ASR and corrosion.