Accelerated Life Cycle Research Articles

Life cycle testing and reliability analysis of prismatic lithium-iron-phosphate cells

ABSTRACT A cell’s ability to store energy, and produce power is limited by its capacity fading with age. This paper presents the findings on the performance characteristics of prismatic Lithium-iron phosphate (LiFePO4) cells under different ambient temperature conditions, discharge rates, and depth of discharge. The accelerated life cycle testing results depicted a linear degradation pattern of up to 300 cycles. Linear extrapolation reveals that at 25°C temperature, an increase in the discharge rate from 0.5 C to 0.8 C reduces the cycle life significantly by 52.9%. On the other hand, at a constant discharge rate, an increase in temperature reduced predicted cycle life in the range of 23.2–41.36%. Lithium-ion cells’ reliability modeling and analysis was carried out using an exponential distribution showing the increasing failure rate with age, with the temperature significantly reducing the expected life of the cells.

Application of particle filter variants to estimate the remaining useful life

Dynamic loadings encountered by clutch motor of an Automated manual transmission (AMT) passenger vehicle require apposite assessment of nonlinear characteristic of the degrading system to accurately predict the remaining useful life (RUL) for implementation of condition based maintenance (CBM) schedule. The present study involves the application of three variants of particle filter (PF) with various resampling techniques to account for heavy tailed observations and non-Gaussian characteristic of noise to improve the accuracy of RUL estimation. Degradation dataset was generated using accelerated life cycle test (ALCT) on hardware-in-loop (HIL) laboratory of a large Indian automotive company. A comparative analysis of the results showed 91.5, 93.2, and 94.9% enhancement in the efficacy of RUL estimation due to canonical, unscented, and improved unscented particle filters (i-UPF) vis-a-vis the ordinarily fitted exponential degradation model.

Sugars and the speed of life-Metabolic signals that determine plant growth, development and death.

Plant growth and development depend on the availability of carbohydrates synthesised in photosynthesis (source activity) and utilisation of these carbohydrates for growth (sink activity). External conditions, such as temperature, nutrient availability and stress, can affect source as well as sink activity. Optimal utilisation of resources is under circadian clock control. This molecular timekeeper ensures that growth responses are adjusted to different photoperiod and temperature settings by modulating starch accumulation and degradation accordingly. For example, during the night, starch degradation is required to provide sugars for growth. Under favourable growth conditions, high sugar availability stimulates growth and development, resulting in an overall accelerated life cycle of annual plants. Key signalling components include trehalose‐6‐phosphate (Tre6P), which reflects sucrose availability and stimulates growth and branching when the conditions are favourable. Under sink limitation, Tre6P does, however, inhibit night‐time starch degradation. Tre6P interacts with Sucrose‐non‐fermenting1‐Related Kinase1 (SnRK1), a protein kinase that inhibits growth under starvation and stress conditions and delays development (including flowering and senescence). Tre6P inhibits SnRK1 activity, but SnRK1 increases the Tre6P to sucrose ratio under favourable conditions. Alongside Tre6P, Target of Rapamycin (TOR) stimulates processes such as protein synthesis and growth when sugar availability is high. In annual plants, an accelerated life cycle results in early leaf and plant senescence, thus shortening the lifespan. While the availability of carbohydrates in the form of sucrose and other sugars also plays an important role in seasonal life cycle events (phenology) of perennial plants, the sugar signalling pathways in perennials are less well understood.

Cycle‐life prediction model of lithium iron phosphate‐based lithium‐ion battery module

The aging rate of Li-ion batteries depends on temperature and working conditions and should be studied to ensure an efficient supply and storage of energy. In a battery module, the thermal energy released by the exothermic reaction occurring within each cell is transferred to its adjacent cells, thus leading to a higher internal temperature than that of a single cell. Therefore, there exists a considerable difference between the internal and external temperatures of the module. Thus, it is essential to study the battery module temperature when developing its cycle life (capacity fade) model. In this study, an accelerated cycle life experiment is conducted on an 8-cell LiFePO4 battery. Eight thermocouples were placed internally and externally at selected points to measure the internal and external temperatures within the battery module. This model is developed based on the Arrhenius equation, which explains the effect of temperature according to its spatial position. The models are developed according to the ambient, external, internal, and total average temperatures generated in the battery module, which are verified with the collected experimental results. The results indicate that the total average temperature–based model exhibits the lowest average percentage error when compared with the experimental data.

Wolbachia-infected ant colonies have increased reproductive investment and an accelerated life cycle.

Wolbachia is a widespread genus of maternally transmitted endosymbiotic bacteria that often manipulates the reproductive strategy and life history of its hosts to favor its own transmission. Wolbachia-mediated phenotypic effects are well characterized in solitary hosts, but effects in social hosts are unclear. The invasive pharaoh ant, Monomorium pharaonis, shows natural variation in Wolbachia infection between colonies and can be readily bred under laboratory conditions. We previously showed that Wolbachia-infected pharaoh ant colonies had more queen-biased sex ratios than uninfected colonies, which is expected to favor the spread of maternally transmitted Wolbachia Here, we further characterize the effects of Wolbachia on the short- and longer-term reproductive and life history traits of pharaoh ant colonies. First, we characterized the reproductive differences between naturally infected and uninfected colonies at three discrete time points and found that infected colonies had higher reproductive investment (i.e. infected colonies produced more new queens), particularly when existing colony queens were 3 months old. Next, we compared the long-term growth and reproduction dynamics of infected and uninfected colonies across their whole life cycle. Infected colonies had increased colony-level growth and early colony reproduction, resulting in a shorter colony life cycle, when compared with uninfected colonies.

Food availability modulates temperature-dependent effects on growth, reproduction, and survival in Daphnia magna.

Reduced body size and accelerated life cycle due to warming are considered major ecological responses to climate change with fitness costs at the individual level. Surprisingly, we know little about how relevant ecological factors can alter these life history trade‐offs and their consequences for individual fitness. Here, we show that food modulates temperature‐dependent effects on body size in the water flea Daphnia magna and interacts with temperature to affect life history parameters. We exposed 412 individuals to a factorial manipulation of food abundance and temperature, tracked each reproductive event, and took daily measurements of body size from each individual. High temperature caused a reduction in maximum body size in both food treatments, but this effect was mediated by food abundance, such that low food conditions resulted in a reduction of 20% in maximum body size, compared with a reduction of 4% under high food conditions. High temperature resulted in an accelerated life cycle, with pronounced fitness cost at low levels of food where only a few individuals produced a clutch. These results suggest that the mechanisms affecting the trade‐off between fast growth and final body size are food‐dependent, and that the combination of low levels of food and high temperature could potentially threaten viability of ectotherms.

Galvanic Corrosion of Automotive Mixed Metal Substrates: Fundamental Understanding

Dissimilar metal joining is of increasing interest in many structural applications due to its potential to enable light weighting. Light-weight substrates such as aluminum alloys, magnesium alloys and carbon-fiber reinforced polymer (CFRP) are increasingly used in place of conventional steels due to their high strength-to-weight ratios. Two of the main challenges associated with the increased usage of mixed metal systems are galvanic corrosion and challenges with classical joining methods. 1,2. Most joining methods such as riveting, mechanical fasteners, and welding, results in electrical connection between the joined metals, which poses galvanic corrosion issues. Even galvanic isolation approaches such as the use of adhesives can cause galvanic corrosion problems due to the complexity of mixed metal assemblies. In galvanic coupling scenarios, the less noble material experiences severe corrosion and more noble material is protected. It is important to build a fundamental understanding of this phenomenon relative to the metallurgy and electrochemistry of the substrates, as well as the coupling method, to provide effective corrosion mitigation solutions. Electrochemical test techniques such as zero resistance ammeter measurements, open circuit potential measurements, and potentiodynamic polarization were utilized to understand effect of substrate type and solution pH on galvanic corrosion. In addition to the substrate effect, the effect of fastener type on galvanic corrosion between substrate and fasteners was also investigated for selected systems. The influence of joining methods such as self-piercing rivets, adhesives, and mechanical fasteners on galvanic corrosion was also studied. Galvanic and self-coupled coupons were exposed to standard laboratory accelerated life cycle test methods. Wedging by corrosion products, scribe creep, and corrosion volume loss were each characterized to quantify the extent of galvanic corrosion after environmental testing. Preliminary results indicated that galvanic coupling enhanced the wedging of substrate by corrosion products when aluminum alloy 6111-T4 (AA 6111-T4) is coupled with cold rolled steel (CRS). In addition, the pitting corrosion of AA 6111-T4 increased when it is coupled with CRS (Figure 1). Although hot dip galvanized (HDG) based galvanic coupons showed no significant wedging by corrosion products, galvanic coupling of CRS with HDG aggravate the scribe creep of HDG. Galvanic isolation methods such as coating before joining or utilizing adhesives significantly reduced galvanic corrosion in the model mixed-material systems. Figure 1. Average pit depth of AA 6111-T4 substrate coupled with different mixed-metal substrates after various exposure times in neutral and acidic cyclic corrosion tests (CCT). Acknowledgements: Research was sponsored by the Army Research Laboratory, the Tank Automotive Research Design Engineering Center, and Drexel University under Cooperative Agreement W911NF-13-2-0046 and related sub awards.

Early Questing by Lone Star Tick Larvae, New York and Massachusetts, USA, 2018.

Subtropical lone star tick larvae typically emerge in late summer. We found clusters of host-seeking lone star tick larvae during early June 2018 in New York and Massachusetts, USA. Invasion and persistence of this tick in more northern locations may have been promoted by adaptation to an accelerated life cycle.

Accelerated cycle life testing and capacity degradation modeling of LiCoO2-graphite cells

Accelerated cycle life testing of lithium-ion batteries is conducted as a means to assess whether a battery will meet its life cycle requirements. This paper presents a study to identify optimal accelerated cycle testing conditions for LiCoO2-graphite cells. A full factorial design of experiment with three stress factors—ambient temperature (10 °C, 25 °C, 45 °C, 60 °C), discharge current rate (C-rate, 0.7C, 1C, 2C), and charge cut-off C-rate (C/5, C/40)—is used to study the effects of these stress factors on battery capacity fade and to obtain the data necessary for decision making. An empirical accelerated degradation model is then developed to capture the characteristics of the two-stage capacity degradation process, along with an accelerated test planning approach.

Durability of Low Melt Alloys as Thermal Interface Materials

This study investigates the reliability of low melt alloys (LMAs) containing gallium (Ga), indium (In), bismuth (Bi), and tin (Sn) for the application as Thermal interface materials (TIMs). The analysis described herein involved the in situ thermal performance of the LMAs as well as performance evaluation after accelerated life cycle testing, which included high temperature aging at 130 °C and thermal cycling from −40 °C to 80 °C. Three alloys (75.5Ga & 24.5In, 100Ga, and 51In, 32.5Bi & 16.5Sn) were chosen for testing the thermal performance. Testing methodologies used follow ASTM D5470 protocols and the performance of LMAs is compared with some high-performing commercially available TIMs. Results show that LMAs can offer extremely low (<0.01 cm2 °C/W) thermal resistance compared to any commercial TIMs. The LMA–substrate interactions were explored using different surface treatments (copper and tungsten). Measurements show that depending on the substrate–alloy combinations, the proposed alloys survive 1500 hrs of aging at 130 °C and 1000 cycles from −40 °C to 80 °C without significant performance degradation. The obtained results indicate the LMAs are very efficient as TIMs.

Thermal performance of low melting temperature alloys at the interface between dissimilar materials

This paper describes the thermal performance and practical concerns of using a variety of thermal interface materials (traditional: greases, phase change materials, gels, and thermal pads; emerging: carbon nanotubes, graphene, low melt alloys, and metallic nanosprings) and investigated the reliability of low melt alloys (LMAs) containing gallium, indium, bismuth, and tin as thermal interface materials (TIMs). The analysis presented herein involved the thermal performance evaluation of LMAs placed between different surfaces (copper and nickel) after accelerated life cycle testing, which included high temperature aging at 130 °C and thermal cycling from −40 °C to 80 °C. Three alloys (75.5 Ga and 24.5 In, 100 Ga, and 51 In, 32.5 Bi, and 16.5 Sn) were chosen as candidate LMA TIMs. The testing methodologies followed ASTM D5470 protocols. Measurements showed that the proposed alloys survived as long as 3000 hours of aging at 130 °C and 1500 cycles from −40 °C to 80 °C without significant thermal performance degradation. The obtained results show that the performance of LMAs is significant as TIMs.

Ускоренные ресурсные испытания опор контактной сети железных дорог

Ускоренные ресурсные испытания опор контактной сети железных дорог

Live Fast, Die Young: Experimental Evidence of Population Extinction Risk due to Climate Change.

Evidence has accumulated in recent decades on the drastic impact of climate change on biodiversity. Warming temperatures have induced changes in species physiology, phenology, and have decreased body size. Such modifications can impact population dynamics and could lead to changes in life cycle and demography. More specifically, conceptual frameworks predict that global warming will severely threaten tropical ectotherms while temperate ectotherms should resist or even benefit from higher temperatures. However, experimental studies measuring the impacts of future warming trends on temperate ectotherms' life cycle and population persistence are lacking. Here we investigate the impacts of future climates on a model vertebrate ectotherm species using a large-scale warming experiment. We manipulated climatic conditions in 18 seminatural populations over two years to obtain a present climate treatment and a warm climate treatment matching IPCC predictions for future climate. Warmer temperatures caused a faster body growth, an earlier reproductive onset, and an increased voltinism, leading to a highly accelerated life cycle but also to a decrease in adult survival. A matrix population model predicts that warm climate populations in our experiment should go extinct in around 20 y. Comparing our experimental climatic conditions to conditions encountered by populations across Europe, we suggest that warming climates should threaten a significant number of populations at the southern range of the distribution. Our findings stress the importance of experimental approaches on the entire life cycle to more accurately predict population and species persistence in future climates.

Accelerated aging and thermal cycling of low melting temperature alloys as wet thermal interface materials

This paper focuses on developing an effective thermal interface material (TIM) using low melt alloys (LMAs) containing gallium (Ga), indium (In), bismuth (Bi) and tin (Sn). The investigation described herein involved the thermal performance evaluation of LMAs after accelerated life cycle testing, which included isothermal aging at 130°C and thermal cycling from -40°C to 80°C. Three alloys (75.5Ga/24.5In, 100Ga, and 51In/32.5Bi/16.5Sn) were chosen as candidate LMA TIMs. The testing methodologies followed ASTM D5470 protocols and the performance of the alloys was compared to commercially available thermal grease and liquid metal TIMs. To understand the LMA-substrate interactions, the alloys were applied to different surfaces (bare copper, nickel coated copper and tungsten coated copper). It was found that the proposed alloys between bare copper substrates were able to survive as long as 2700h of aging at 130°C and 1400cycles from −40°C to 80°C without significant performance degradation.

Investigation into the application of low melting temperature alloys as wet thermal interface materials

The application of low melt alloys (LMAs) containing In, Ga, Sn, and Bi as compliant high performance thermal interface material (TIM) is investigated. The investigation described herein involves in situ thermal performances of the LMAs as a function of applied pressure and interface temperature, performance evaluation after accelerated life cycle testing, and guidelines to improve the cycle life. Testing methodologies follow ASTM D5470 protocols, and measurements are validated by testing well established, commercially available TIMs and comparisons are made to values reported in open literature as well as manufacturers’ data. Measurement shows that LMAs can offer thermal interfacial resistances as low as 0.005cm2°C/W, and their performance is highly contingent upon the quality of the mating surfaces. The issue of LMA containment and dewetting are discussed along with the solutions to mitigate them.

Dynamic patterns of industry convergence: Evidence from a large amount of unstructured data

Because of the accelerated life cycle in technology and correspondingly rapid technological saturation in markets, firms are not only accelerating the rate of technological innovation but also expanding the scope of their products or services by combining product or service features of other markets, which eventually leads to industry convergence. However, despite the significant impact of industry convergence on the economy, our understanding of the phenomenon is still limited because previous studies explored only a few cases and come largely from the technological perspective. Therefore, it is still questionable whether industry convergence is a general phenomenon that is prevalent across entire industries. In this paper, we analyze the phenomenon in entire U.S. industries, focusing on its trends and patterns. To do so, we conduct a co-occurrence-based analysis of text mining for a large volume of unstructured data – 2 million newspaper articles from 1989 to 2012 – and suggest using an industry convergence (IC) index based on normalized pointwise mutual information (PMI). We find that overall industry convergence is increasing over time. Moreover, the rate of the increase has been greater within industry than between industries at a given industry level. However, when we cluster the dynamic patterns of industry convergence among industry pairs, the patterns are mixed, and, while some industry groups are converging over time, others are stationary. These findings suggest that significant transformation is under way in the economy, but this phenomenon is not yet prevalent across entire industries. In addition, this study provides a method for anticipating the future direction of industry convergence.

A high-performance three-dimensional micro supercapacitor based on ripple-like ruthenium oxide–carbon nanotube composite films

A micro-supercapacitor with a three-dimensional configuration has been fabricated using an inductively coupled plasma etching technique. A ruthenium oxide–carbon nanotube (CNT) composite with a ripple-like morphology is successfully synthesized using a cathodic deposition technique while using silica-based three-dimensional microstructures as a template. The desired network of carbon nanotubes in the composite facilitates electrolyte penetration and proton exchange/diffusion. A single three dimensional microelectrode is studied using cyclic voltammetry, and a specific capacitance of 272mF·cm−2 is observed at 5mVs−1 in a neutral Na2SO4 solution. The accelerated cycle life is tested at 80mVs−1, and a satisfactory cyclability is observed. When placed on a chip, the symmetric cell exhibits good supercapacitor properties, the specific capacitance up to 37.23mFcm−2 and specific power density up to 19.04mWcm−2 were obtained at 50mAcm−2.

Cycle Life of Commercial Lithium-Ion Batteries with Lithium Titanium Oxide Anodes in Electric Vehicles

The lithium titanium oxide (LTO) anode is widely accepted as one of the best anodes for the future lithium ion batteries in electric vehicles (EVs), especially since its cycle life is very long. In this paper, three different commercial LTO cells from different manufacturers were studied in accelerated cycle life tests and their capacity fades were compared. The result indicates that under 55 °C, the LTO battery still shows a high capacity fade rate. The battery aging processes of all the commercial LTO cells clearly include two stages. Using the incremental capacity (IC) analysis, it could be judged that in the first stage, the battery capacity decreases mainly due to the loss of anode material and the degradation rate is lower. In the second stage, the battery capacity decreases much faster, mainly due to the degradation of the cathode material. The result is important for the state of health (SOH) estimation and remaining useful life (RUL) prediction of battery management system (BMS) for LTO batteries in EVs.

EMC Management in HEV/EV Applications

EMC Management in HEV/EV Applications

Fabrication of a symmetric micro supercapacitor based on tubular ruthenium oxide on silicon 3D microstructures

A micro-supercapacitor with a three-dimensional configuration has been fabricated using an ICP etching technique. Hydrous ruthenium oxide with a tubular morphology is successfully synthesized using a cathodic deposition technique with a Si micro prominence as a template. The desired tubular RuO2·xH2O architecture facilitates electrolyte penetration and proton exchange/diffusion. A single MEMS electrode is studied using cyclic voltammetry, and a specific capacitance of 99.3 mF cm−2 and 70 F g−1 is presented at 5 mV s−1 in neutral Na2SO4 solution. The accelerated cycle life is tested at 80 mV s−1, and satisfactory cyclability is observed. When placed on a chip, the symmetric cell exhibits good supercapacitor properties, and a specific capacitance as high as 23 mF cm−2 is achieved at 10 mA cm−2. Therefore, 3D MEMS microelectrode arrays with electrochemically deposited ruthenium oxide films are promising candidates for on-chip electrochemical micro-capacitor applications.