Cylindrical Cell Research Articles

Elastic instability and inflation modeling of an axially-loaded hyperelastic cylindrical thin shell

ABSTRACT While inflating the thin-walled hyperelastic cylindrical cell, a localized type of instability occurs. After some deformation, the localization forms a bulge along the tube length. When a bulge reaches a specific diameter, it begins to spread axially. Such a phenomenon occurs at a single pressure value much lower than the pressure required to initiate the bulge. In this paper, we model such a phenomenon by predicting the effect of axial load on the value of limit pressure and bulge propagation pressure. In conjunction with existing experiments, we develop the model and determine the conditions that cause bulges to form and spread in an inflated thin cylindrical shell in the presence of an axial force. Using a newly proposed energy function, we demonstrate how axial tensile load influences bulge initiation and steady-state propagation in a thin cylindrical rubber shell. Experimental data and alternative models have both been used to validate the proposed mathematical model.

Rate of Emergence and Mortality of Sceliphron caementarium (Hymenoptera: sphecidae) as a Result of Parasitoids to Endogenous Factors in Ahmadu Bello University Zaria, Kaduna, Nigeria.

The nests of Sceliphron caementarium were studied to ascertained the rate of emergence and mortality cause of S. caementarium before emergence. Ten (10) nests of S. caementarium were taken from the various Faculties of Ahmadu Bello University main campus, located in Zaria, Kaduna, Nigeria and analyzed. The greatest width of the head (GWH) was employed to estimate the size and sex ratio of emerged adult wasps. The nests of S. caementarium collected and examined from the study consists of 1-23 vertically arranged cylindrical allantoid-shaped cells. The average length and width of the male and female wasp cells was (l = 24.8mm, w = 7.0mm) and (l = 25.5mm, w = 7.8mm) respectively. The mean fecundity of the female S. caementarium from the study was calculated at 15.1 eggs per female. The sex ratio of the emerged adult S. caementarium obtained from the nests was 1 male : 1.28 female. With respect to size, the females black-and-yellow mud dauber wasp were observed to be significantly bigger than the males (p < 0.05). The highest rate of Mortality observed in the nest of S. caementarium in the study area was due to an endogenous factor 64.15% (which may be a developmental failure, pathogenic or fungal infection) followed by parasitoids accounting for about 24.52% deaths in the cells and accidental cell damage (11.32%) was the least cause of mortality in the cells.

A lithium-ion battery equivalent circuit model based on a hybrid parametrization approach

This paper proposes an improved lithium-ion battery equivalent circuit model that can simulate the current-voltage characteristics of the battery under various operating conditions. Specifically, a hybrid parametrization approach is adopted by combining the electrochemical impedance spectroscopy and the hybrid pulse power characterization techniques for the identification and quantification of all loss contributions in a lithium-ion battery cell, for a wide operating frequency range. Moreover, the proposed equivalent circuit model considers the variation of the state of charge, the temperature and the charging-discharging current, and since it can be easily realized by utilizing the existing hardware for the cell equalization, it can be a useful tool for a wide range of real-time applications. The above are realized based on analytical equations of the battery performance with respect to the aforementioned operating parameters' variations. The effectiveness and feasibility of the proposed model is experimentally verified on a commercial, high energy capacity cylindrical lithium-ion battery cell of 3.25 Ah by comparing the model voltage performance with the real voltage of the cell during dynamic operating conditions and with variable surface temperature values.

Cylindrical helical cell metamaterial with large strain zero Poisson’s ratio for shape morphing analysis

In this paper, a novel cylindrical metamaterial with helical cell exhibiting zero Poisson’s ratio (ZPR) in two different directions is introduced. Detailed Computer-aided design modelling of a curved optimised spring element is demonstrated for numerical and experimental analysis. High fidelity finite element models are developed to assess the homogenisation study of Poisson’s ratios, normalised Young’s modulus and torsion behaviour, demonstrating the curvature effect and independency of mechanical behaviour of cylindrical optimised spring element metamaterial from tessellation numbers. Buckling and frequency analysis of the cylindrical metamaterial with spring element are compared with equivalent shell cylinders. Moreover, experimental analysis is performed to validate the large strain ZPR and deformation mechanism demonstrated in numerical simulations. Finally, radical shape morphing analysis under different bending conditions for cylindrical metamaterial with helical cell is investigated, including deformation and actuation energy and compared with positive and negative Poisson’s ratio cylinders formed by honeycomb and auxetic cells.

Dynamic crushing behaviors and failure of cylindrical lithium-ion batteries subjected to impact loading

The mechanical property and failure prediction play a significant role in engineering applications of lithium-ion batteries (LIBs), but with great difficulties due to their complicated internal structures. This paper mainly focused on dynamic crushing behaviors and internal failure mechanisms of cylindrical LIBs subjected to different impact loadings for the safety assessment and protection design. A series of dynamic experiments were conducted on typical 18650 LIBs using the drop weight impact test system. The force-electric-thermal responses and impact failure modes of the cells with state of charge (SOC) dependence were experimentally explored under different impactor types. The finite element (FE) model was also established to reveal the failure mechanisms of the battery under high-velocity impact, and its accuracy was validated by the comparison between the experimental and corresponding FE results. Furthermore, the dynamic failure mechanisms of cylindrical cells using the stress wave theory were also explored in this work. It was shown that except from impact velocities, there were significant effects of the SOCs and impactor types on dynamic responses and internal failure modes of LIBs. The failure displacement of the cell will decrease with the increase of impact velocity, but it was insensitive under low-velocity crushing. Based on the FE results, the relationships between failure displacement and impact velocity and impactor diameter were established under flat-end cylinder head impacting. This work can provide some references for multi-functional dynamic integrity design and safety assessment of LIBs.

Wire bond contact defect identification in battery modules of electric vehicles using pulses and differential voltage analysis

Automotive battery packs for electromobility applications consist of a large number of interconnected battery cells. Different cell-to-busbar joining techniques are utilized, with cylindrical cells frequently being contacted using wire bonding. Failure of individual connections can occur due to strong vibrations during operation and improper stress, making detection by the battery management system a necessity. This study investigates the identification of an electrical wire bond failure in a state-of-the-art electric vehicle module of a Lucid Air with 10 series-connected and 30 parallel-connected cells (10s30p). Four individual cells were characterized extensively in order to generate a simulation model taking into account parameter scatter. The failure case under investigation was simulatively incorporated in one parallel circuit and subsequently replicated in experimental validation measurements at the module level. The results show that this defect can be detected using pulses of C/3 or higher currents at various states of charge. An even more robust detection is achieved using differential voltage analysis of constant current C/20 discharge voltage trajectories. This defect identification method does not require any additional measurement sensors beyond the voltage taps and sensors provided by the manufacturer – with one voltage sensor per parallel circuit – and can therefore be implemented during electric vehicle usage, e.g. at dedicated service checks. A discussion on the applicability and scalability as well as the limitations of the method is provided. All measurement data of the state-of-the-art Lucid battery system is available as open source alongside the article.

P02.06.B DIELECTRIC PROPERTIES OF INTRACRANIAL TUMORS

Abstract BACKGROUND Recently, tumor treating fields (TTFields) were established for the treatment of newly diagnosed glioblastoma (GBM). One of the most crucial parameters defining the treatment efficacy of TTFields is the electric field intensity, which depends on the dielectric properties of the tumor tissue. In this study we determined the dieclectric properties of brain tumors by analyzing resected tissue following a fast acquisition protocol. In GBM patients, histological analysis for cellularity, vascularization and myelin content was performed. In addition, sensitivity analyses for specific parameters (tissue hydration, temperature, and saline irrigation) were conducted. MATERIAL AND METHODS A cohort of 130 patients with tumors of different histology and malignancy grade have been recruited (meningioma: n=36; brain metastases n=29; low grade glioma n=7; anaplastic glioma = 12; other= 7; glioblastoma n=39, all treated with TTFields). Tissue samples were placed into a cylindrical cell with a known diameter. The impedance was recorded at frequencies 20Hz-1MHz using a software specifically developed for this study. The measured impedance was translated into dielectric properties of the sample (conductivity and relative permittivity) based on the parallel plate model. Myelin, which is the most powerful electric isolator in the brain, was assessed in GBM samples by luxol fast blue staining, and quantified in a three-tier scale. To assess the impact of tissue conditions on the measurements, probes were warmed to 35 degree Celsius, dehydrated or irrigated with 0.9% saline solution. RESULTS We found significant differences between the conductivity of different types of tumors with meningiomas showing the lowest and GBM tissue exhibiting the highest conductivity values. GBM samples with very high median conductivity values displayed a consistently lower myelin content. In addition, GBM patients with particularly high conductivity had a significantly shorter overall survival (log rank analysis, p = 0.024). While tissue temperature had no detectable effects on the dielectric properties in GBM, saline irrigation tissue hydration significantly affected the results. CONCLUSION The dielectric properties of intracranial tumors depend on histological class and malignancy grade. GBM patients with high conductivity values showed a significantly poorer prognosis, indicating this parameter as potential marker for TTF efficacy.

Investigation of the Electrochemical and Thermal Characteristics of NCM811-21700 Cylindrical Lithium-Ion Battery: A Numerical Study and Model Validation

Recently, there has been growing recognition of the significance of energy and environmental challenges. Utilization of lithium-ion batteries in electric vehicles has shown considerable potential and benefits for tackling these issues. The effective management of battery temperature has become a crucial factor in the advancement and widespread adoption of lithium-ion batteries in electric vehicles. In this study, a thermo-coupled pseudo-two-dimensional (P2D) electrochemical model is employed to simulate the heat generation of the NCM811-21700 cylindrical battery cell at various discharge rates at an ambient temperature of 25 °C, and is validated by experimental data. The validation results demonstrate that the thermo-coupled P2D model can effectively predict the battery voltage curve during the discharge process with less than 4% errors. Although there is a slightly larger error in the temperature prediction during the battery 2C and 3C discharge processes, the maximum error approaches 10%, which is still generally within an acceptable range. In addition, the battery’s electrochemical and thermal characteristics during discharge are presented. The suggested thermo-coupled electrochemical model can be used for applications in the thermal management system of the NCM811-21700 battery.

A method to determine the specific heat capacity of lithium-ion battery cells using thermal insulation

Thermal simulations of lithium-ion batteries that contribute to improvements in the safety and lifetime of battery systems require precise thermal parameters, such as the specific heat capacity. In contrast to the vast number of lithium-ion batteries, the number of specific heat capacity results is very low. This work presents a new method for accurately and easily determining the specific heat capacity of battery cells of any form factor. Using an extruded polystyrene thermal resistor, temperature logging equipment, and two temperature chambers at different temperatures, the presented approach determines the specific heat capacity of cylindrical 18650 and 21700 cells, in addition to two pouch cells, through simple temperature changes. While the cylindrical cells have very similar specific heat capacities, both pouch cells have significantly higher specific heat capacities most likely due to their different material compositions. Linear approximations of the results agree well with a temperature sensitivity of all battery models between 1.6 and 2.0 JkgK per ∘C over the range of 0 ∘C to 40 ∘C. Compared to a reference material with a known specific heat capacity, validation measurements reveal an error between 1% and 3%.

Evaluating Long-Term Cycling Degradation in Cylindrical Li-Ion Batteries Using X-ray Tomography and Virtual Unrolling

Lithium-ion (Li-ion) batteries have undergone a multitude of improvements and achieved a high level of technological maturity. To further optimise cell performance, an understanding of the failure mechanisms is important. Forty-eight state-of-the-art cylindrical cells in the 21700 format, suitable for electric vehicles, are studied at the beginning-of-life (BOL) and end-of-life (EOL) by X-ray computed tomography (X-ray CT) and image analysis. The results indicate that shifting current collecting tabs closer to the centre of the cell and including a mandrel is likely to supress the propagation of capacity depleting deformations. It is recommended that manufacturers also try to improve cell assembly processes to form a more uniformly circular jelly roll and use tapered electrodes to minimise the nucleation of deformations.

Tracking the Lifecycle of a 21700 Cell: A 4D Tomography and Digital Disassembly Study

Extending the lifetime of commercial Li-ion cells is amongst the most important challenge to facilitate the continued electrification of transport as demonstrated by the substantial volume of literature dedicated to identifying degradation mechanisms in batteries. Here, we conduct a long-term study on a cylindrical Li-ion cell, tracking the evolution of the structure of the cell using X-ray computed tomography. By evaluating the internal geometry of the cell over several hundreds of cycles we show a causal relationship between changes in the electrode structure and the capacity fade associated with cell ageing. The rapid aging which occurs as cells reach their end-of-life condition is mirrored in a significant acceleration in internal architecture changes. This work also shows the importance of consistent and accurate manufacturing processes with small defects in the jelly-roll being shown to act as nucleation sites for the structural degradation and by extension capacity fade.

Diffusive and convective dissolution of carbon dioxide in a vertical cylindrical cell

Diffusive and convective dissolution of carbon dioxide in a vertical cylindrical cell

Comparative Testing of Li-Ion Battery Chemistries for Stationary Energy Storage

Li-ion batteries are the most widely deployed battery energy storage system (BESS) today but understanding the benefits and cost-effectiveness for a wide range of grid services needs to be fully validated to further expand the market. Hence, various Li-ion battery chemistries currently deployed must be evaluated and compared in terms of performance, lifecycle, economics, and safety under grid services using standardized testing protocols. In this work, commercially available cylindrical cells with four different chemistries from major Li-ion battery manufacturers are subjected to standardized tests developed by the U.S. Department of Energy Office of Electricity (DOE-OE) for frequency regulation, peak shaving, and electric vehicle drive cycles. The results of 15 months of continuous grid service tests on different chemistries are presented, analyzed, and compared in terms of capacity retention, resistance, open-circuit voltage (OCV), cyclic voltammetry (CV), incremental capacity (dQ/dV), differential voltage (dV/dQ), and AC impedance

Safety Componentry for Mitigating Catastrophic Failure in Lithium-Ion Cylindrical Cells

The lithium-ion cylindrical cell is designed as a thin-walled pressure vessel, with various engineering controls to mitigate catastrophic failure. With an increase in pressure inside the cell, given suitable can wall thickness, the cell will fail through the header componentry. A tear down and inspection method has been developed to observe the header design and componentry of cells. A range of cylindrical cells were investigated - from 18650 to 46950 in size. This involved visual inspection, x-ray tomography, chemical analysis and microscopy. The presence of safety componentry, thickness and material type is discussed; factors which affect the propensity of the cell to fail at this location. Commonly observed was the Current Interrupt Device (CID) vent disc which is designed to mechanically deform in response to pressure increase within the cell. This in turn disconnects the cell circuitry and ruptures, initiating the venting process. Furthermore, cells typically contained a Positive Temperature Coefficient (PTC) device which protects the battery from external short circuits and electrical abuse conditions by limiting current flow when the cell reaches a particular temperature. This approach clearly outlines the safety componentry and their respective functions used within these cell sizes, allowing for a better understanding of battery safety. Additionally, we expect this work to disseminate new developments in larger format lithium-ion batteries as they are being sought for better system performance.

(Invited) Development of Commercial-Scale High Energy Density Aqueous Zinc Manganese Dioxide Alkaline Batteries for Long Duration Storage

Alkaline zinc manganese dioxide batteries are attractive for grid related energy storage applications but have been limited to relatively low utilization of the active materials to assure good cycling performance. Zinc anodes tend to deteriorate due to shape change, passivation, and dendrite formation during charge/discharge cycles. Manganese dioxide cathodes also deteriorate due to formation of inactive crystalline polymorphs during cycling. Recent work using additives in both the anodes and the cathodes has mitigated these issues and enabled access of much higher active material utilization levels, up to 50% of the two-electron capacity of the zinc and over 75% of the two-electron capacity of the manganese dioxide electrodes. Commercial-scale cylindrical (jelly roll) cells of 150 to 200 Wh, particularly suitable for long duration energy storage with discharge periods from a day to a week, have been manufactured on a pilot line. Their performance and various deployments will be discussed indicating areas where future developments would be of importance.

(Invited) Operando Observation of Fast Charging in Li-Ion Cells

Fast charging (<15 min) of lithium-ion batteries (LIBs) for electrical vehicles (EVs) is widely seen as the key factor that will greatly stimulate the EV markets, and its realization is mainly hindered by the sluggish diffusion of Li+. To have a mechanistic understanding of Li+ diffusion within LIBs, in this study, structural evolutions of electrodes for a Ni-rich LiNi0.6Mn0.2Co0.2O2 (NMC622) || graphite cylindrical cell with high areal loading (2.78 mAh cm−2) are developed for operando neutron powder diffraction study at different charging rates. Via sequential Rietveld refinements, changes in structures of NMC622 and Li x C6 are obtained during moderate and fast charging (from 0.27 C to 4.4 C). NMC622 exhibits the same structural evolution regardless of C-rates. For phase transitions of Li x C6, the stage I (LiC6) phase emerges earlier during the stepwise intercalation at a lower state of charge when charging rate is increased. It is also found that the stage II (LiC12) → stage I (LiC6) transition is the rate-limiting step during fast charging. The LiC12 → LiC6 transition mechanism is further analyzed using the Johnson–Mehl–Avrami–Kolmogorov model. It is concluded as a diffusion-controlled, 1D phase transition with decreasing nucleation kinetics under increasing charging rates.

Degradation behavior of 21700 cylindrical lithium-ion battery cells during overdischarge cycling at low temperatures

Lithium-ion battery (LIB) cells are prone to overdischarge or overcharge when connected in series or parallel as a module or pack for large-format applications, such as electric vehicles (EVs) because of variations in battery capacities and difficulty in maintaining similar state-of-charge (SOC) of every single battery. However, the thermo-electrochemical behavior of LIBs during overdischarge has not been investigated at low temperatures. This study unveils the thermo-electrochemical behavior of overdischarged 21700 cylindrical LIB cells at −20 °C and 25 °C. Also, a thermo-electrochemical model was built to explain the heat generation within the cells and correlate them with the observed electrochemical characteristics. It was found that contrary to the severe cell degradation observed in the overdischarged cell compared to the standard cell at 25 °C, both cells show similar degradation behavior under low temperature cycling conditions. Thus, at low temperatures, overdischarge does not adversely affect cell degradation as observed at room temperature. This was attributed to the significant increase in the internal temperature, which results in improved electrochemical characteristics of the cell.

Liquid immersion thermal management of lithium-ion batteries for electric vehicles: An experimental study

The thermal and electrical performance of lithium-ion batteries subjected to liquid immersion cooling conditions in a dielectric fluid has been experimentally investigated in this study. A single 26650 LiFePO4 cylindrical cell is completely immersed in Novec 7000 and charged and discharged at onerous maximum rates of up to 4C and 10C, respectively, where C can be defined as the measure of the rate at which a cell is charged or discharged relative to its rated capacity. Immersion cooling offers high rates of heat transfer from the cell's surface, in particular when the saturation temperature of the fluid is exceeded, and two-phase conditions are established. At a preheated liquid pool temperature of 33 ± 0.5 °C for discharge rates ≥ 2C, subcooled boiling conditions develop, with the cell's temperature rise limited to 3.6 °C at the end of 10C discharge. Furthermore, for 4C charging under the same preheating conditions, the cell's temperature rise does not exceed 1 °C. Superior performance is observed under two-phase immersion cooling conditions in comparison to both single phase liquid immersion and natural convection air cooling for the same charge and discharge rates. Excellent thermal homogenisation across the cell is also determined, with a maximum axial temperature difference of 0.25 °C and 1 °C for 4C charging and 10C discharging respectively.

Large-scale production of 18650 cylindrical supercapacitors: Effects of separators, electrode thickness, electrolyte additives, and testing protocols

Although supercapcitors have been widely studied, large-scale 18650 cylindrical supercapacitor cells have been rarely investigated and reported. Here, we investigated the effects of polymer separators, electrode thickness, electrolyte additives, testing protocols, reproducibility, and stability of the supercapacitors at the large-scale pilot plant. The supercapacitor cells with polyethylene (PE) and Al2O3-coated PE separators are good at low and high specific currents, respectively. The Al2O3-coated PE exhibits better stability than the one with the PE separator. The supercapacitor with a thickness of 250 μm has a cell capacitance of over 120 F from 100 to 1000 mA, which is higher than that of the other cells studied in this work. Also, the cell capacitances of supercapacitors can be enhanced by having redox mediator additives. 25 mM hydroquinone and ferrocene methanol are the optimized concentrations. We also found that the cell capacitance and equivalent series resistance of the supercapacitors are sensitive to the testing protocol, for which the highest capacitance was observed using the IEC62391-1 standard method, followed by the Maxwell method and conventional galvanostatic charge discharge method without dwell time. High reproducibility and stability of the as-fabricated supercapacitors in this work may lead to the further development of practical large-scale supercapcitors in the future.

Rapid Estimation of Battery Storage Capacity through Multiple Linear Regression

Due to global warming issues, the rapid growth of electric vehicle sales is fully expected to result in a dramatic increase in returned batteries after the first use. Naturally, industries have shown great interest in establishing business models for retired battery reuse and recycling. However, they still have many challenges, such as high costs from the logistics of returned batteries and evaluating returned battery quality. One of the most important characteristics of a returned battery is the battery storage capacity. Conventionally, the battery’s energy capacity is measured through the low current full charging and discharging process. While this traditional measurement procedure gives a reliable estimate of battery storage capacity, the time required for a reliable estimate is unacceptably long to support profitable business models. In this paper, we propose a new algorithm to estimate battery storage capacity that can dramatically reduce the time for estimation through the partial discharging process. To demonstrate the applicability of the proposed algorithm, cylindrical and prismatic cells were used in the experiments. Initially, five indicators were selected from the voltage response curves that can identify battery storage capacity. Then, the five indicators were applied to principal component analysis (PCA) to extract dominant factors. The extracted factors were applied to a multiple linear regression model to produce a reliable estimation of battery storage capacity.