Journal of Power Sources Advances最新文献

A quasi-steady, CFD-based modeling approach is employed to investigate the heat loading within a small package of twenty-five 18650 Li-ion cells. The quasi-steady approach allows for computationally efficient simulations to capture the compressible and turbulent flow field through the safety vent structure and out into the space surrounding a failing cell. Combustion of vent gases leads to high heat loading on neighboring cells and nearby surfaces. Heat transfer mechanisms within the enclosure include convection from hot gases, radiation from the participating medium, and radiation exchange between surfaces. Simulations provide insight into the magnitude of each heat transfer mechanism, and the spatial distribution of heat flux on nearby cells and surfaces within the pack. The complex geometry of the safety vent geometry resulted in an asymmetric jet flow pattern, which induces highly localized impingement heat transfer on specific cells within the enclosure. Radiation from hot surfaces was more significant than radiation from hot gases and soot to neighboring cells. The quasi-steady simulations may be used in the future to develop reduced-order heat transfer models that include the effects of venting and combustion on propagating failure.

We report a new type of polymer blend electrolyte based on the principle of thermoplastic vulcanizates (TPV). TPV materials have been extensively used in the automotive and manufacturing sectors. However, to the best of our knowledge, TPV-based electrolytes have yet to be produced. These electrolytes, obtained via melt-processing, combine the high ionic conductivity and processibility of a thermoplastic phase with the improved mechanical strength of a crosslinked elastomeric phase. TPV electrolytes prepared with poly(caprolactone) (PCL) (thermoplastic phase) and hydrogenated nitrile butadiene rubber (HNBR) (elastomeric phase) are presented in this work. These materials deliver promising results in terms of ionic conductivity, electrochemical stability and mechanical strength. Further improvements in ionic conductivity are obtained by doping the TPV electrolyte with a flame-retardant solvent, triethyl phosphate. The crosslinked nature of the TPV allows both mechanical strength and electrochemical stability to be conserved upon doping which is not possible in non-crosslinked polymer blend electrolytes prepared with PCL and HNBR.

Recently, the first sodium-ion cells have been commercialized and have become available for consumers. Given, moreover, the exciting announcements by several producers of such battery cells, it is of great interest to analyze these first commercial cells in order to understand which materials are used and how these cells are designed. Herein, two types of commercially available sodium-ion battery cells (cylindrical 1.5 Ah 18650 and 3.5 Ah 26700 cells) are investigated regarding (i) their electrode chemistry, (ii) their thermal properties upon discharge as a function of the applied C rate, (iii) the available specific energy, and (iv) their cell impedance. The data are correlated with the electrode thickness and electrode area obtained from an ex situ (ante-mortem) analysis of the 18650 cells, and discussed in comparison with the performance metrics reported for commercial lithium-ion cells. This comparison reveals that the herein studied 18650 sodium-ion cells (hard carbon⎪⎪Na_xNi_yFe_zMn_1-y-zO₂) provide a comparable or even higher specific energy (∼128 Wh kg⁻¹) than that of graphite⎪⎪LiFePO₄ lithium-ion cells.

Nickel-rich cathode materials are a popular cathode for high energy lithium ion batteries in the current and next generation of electric vehicles. While nickel-rich cathodes offer high energy density, their cycle-life is compromised due to several factors directly related to their (de)lithiation behavior. At high state of charge the nickel-rich cathode experiences a hexagonal-hexagonal transition which is accompanied by drastic changes in the unit cell parameters. This phenomenon is detrimental for cycle-life of a battery cell. This work elucidates on the effect of storing LiNi_0.8Mn_0.1Co_0.1O₂‖Graphite cells at 95 % state of charge corresponding to the above-mentioned transition for 10 h every six cycles. The results are compared to cells cycled without a rest at high state of charge and cells cycled to 100 % state of charge. Analysis of the obtained cycling data shows that resting lithium ion cells based nickel-rich cathode based cells is detrimental leading to higher impedance growth and capacity decay than cycling to 100 % state of charge.

The novel trajectory correction hysteresis model (TCH) is based on measuring the first-order reversal branches (FORBs). As the enormous measurement effort required for parameterisation hinders a real-world application, this paper presents the data-efficient transfer fit (TF) method. The TF methodology is validated through two application cases: ageing update and cell chemistry adaptation. Remarkably, using only 12 measurement points on the open-circuit voltage (OCV) envelopes instead of hundreds of measurement data points, the ageing update TF model attains a mean absolute error (mae) of 4.1 mV, closely approaching the accuracy of a newly parameterised target model (3.6 mV mae). Similarly, adapting an NCA cell model to an NMC target cell using selected OCV envelope points yields a 5.3 mV mae, which further reduces to 3.2 mV with an additional discharge FORB starting at 10% SOC. In addition to the selective model adjustment using continuous OCV measurement trajectories, the much more realistic adaptation by measurement points randomly distributed within the hysteresis window was successfully demonstrated. The presented TF methodology overcomes the hurdle of data efficiency while maintaining model accuracy and paves the way for the future application of the TCH model for voltage-based SOC correction.

This study analyzes the field performance of various solar cell designs. Most research and development efforts concerning solar cells aim to increase their efficiency or power under standard test conditions (STC). However, conducting an actual field performance analysis is crucial because of the various ambient conditions present in the field, including temperature, irradiance, PV system installation, and albedo. These conditions can result in different performance results compared to STC. This study compares and analyzes case studies to assess field performance. One particular case study compares the field performance of monofacial modules with a monofacial passivated emitter and rear cell (PERC) and bifacial PERC at a carport system in the ambient conditions of the Korean Peninsula during summer and winter. The module material properties (white EVA and white backsheet) can impact module performance owing to the transmittance spectra at longer wavelengths. Certain transmittance values also contribute to the bifaciality number. Although the monofacial cell demonstrates better STC results, the field performance of the bifacial cell is superior in terms of energy yield and cost-effectiveness. Therefore, this study highlights the importance of considering the field performance (energy yield), in addition to STC, when designing solar cells and modules.

Crystal orientation plays a crucial role in the performance of Sb₂S₃ thin-film solar cells (TFSCs). Among various deposition techniques, vapor transport deposition (VTD) stands out as a viable technique for producing scalable and uniformly deposited thin films, particularly in the solar industry. This study explores temperature-modulated VTD-Sb₂S₃ deposition to enable efficient carrier transport in photovoltaic cells. In the VTD process, the deposition temperature is altered between 480 °C and 540 °C. XRD, SEM, EDS, and AFM techniques are employed to obtain the characteristics of the Sb₂S₃ thin films at varying temperatures and evaluate critical features like crystal structure and orientation, surface morphology, composition, and roughness. The prominent crystal orientation changes from the (hk0) to the (hk1) plane after increasing the deposition temperature from 500 to 520 °C. The (211)- and (221)-planes become more prominent when the deposition temperature exceeds 520 °C. The device with the architecture SLG/Mo/Sb₂S₃/CdS/i-ZnO/AZO/Al, a substrate-configured TFSC, yields a maximum power conversion efficiency of 0.22% when the VTD-Sb₂S₃ absorber film is deposited at 520 °C. This study presents a promising approach to producing thin films with a preference for specific crystal orientations. The primary aim is to enhance the efficiency of solar cells that utilize VTD-Sb₂S₃ absorbers.

Sodium vanadium triphosphate (Na₃V₂(PO₄)₃, NVP) is a promising cathode material for Na-ion batteries. Due to its intrinsically low electronic conductivity, it is usually mixed or coated with carbon. However, so far there have been no systematic studies on the ionic and electronic conductivity of carbon-coated NVP particles. In this work, NVP with varying carbon contents are prepared. The powders are sintered as single pellets or sandwiched between a solid electrolyte for measurements in an ion blocking and non-ion blocking configuration. In these two different configurations, two different electrodes are attached and several electrochemical characterization techniques are applied such as impedance spectroscopy, chronoamperometry, and four-point measurements. The NVP/C composites with carbon content >0.1 wt% show a high degree of densification and an amorphous carbon network. The conductivity of NVP in composites with carbon content <0.1 wt% shows dominating ionic conduction with an average value of ∼2 × 10⁻⁶ S cm⁻¹. NVP/C samples with carbon contents >0.1 wt% show a dominance of electronic conduction in the range of 0.01–0.2 mS cm⁻¹ because of the percolated carbon network at the grain boundaries. The ionic conductivity, however, remains almost constant in the same order of magnitude (∼6 × 10⁻⁶ S cm⁻¹).

The dynamic behavior of potentials and currents in porous electrodes is crucial for optimizing the computational speed of lithium-ion battery models. Pseudo-two-dimensional (P2D) models, based on partial differential equations, offer insight but pose computational challenges. P2D equations are tackled with iterative algorithms, like the Newton or the shooting method. Yet, initiating the algorithm with random guesses for solid and electrolyte potentials can cause diverging ionic current values inside the electrolyte phase, increasing the computation time required to converge to the final solution. This study proposes a novel model order reduction using a galvanic pseudo-potential to prevent the occurrence of diverging currents. By sidestepping infinite values for ionic current inside the electrolyte phase, the method streamlines math and speeds up the shooting method used for solving battery model equations.

Lithium-metal anodes are promising electrodes for fabricating high-capacity all-solid-state batteries; however, lithium dendrite growth during charging limits their applicability. One method to suppress lithium dendrite growth is to insert a carbon interlayer between the solid electrolyte and the lithium-metal anode. There are many potential approaches for inserting a carbon interlayer. The optimal conditions for suppressing lithium dendrite growth and ensuring uniform lithium deposition have not yet been established. This study employs X-ray computed tomography to investigate anode-less all-solid-state batteries. Pressurized xenon is used to examine how the carbon interlayer functions and how uniformly lithium is deposited after various carbon interlayer insertion processes. Uniform deposition is observed following simultaneous pressure bonding of the carbon interlayer and compression of the solid electrolyte.