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.

Lithium-sulfur (Li–S) batteries have emerged as a next-generation battery technology owing to their prospects of high capacity and energy density. They, however, suffer from rapid capacity decay due to the shuttling of reaction intermediate species: Li polysulfides (LiPSs). One of the more important and intriguing PSs is the tri-sulfur radical ($S_3^{•-}$), observed mainly in high-donor number (DN) solvent-based electrolytes. Although this radical has been proposed to be crucial to full active material (AM) utilization, there is currently no direct evidence of the impact of $S_3^{•-}$ on cycling stability. To gain more insight into the role of the $S_3^{•-}$, we studied the use of radical traps in low and high DN solvent-based electrolytes by operando Raman spectroscopy. The traps were based on nitrone and iminium cation, and $S_3^{•-}$ was indeed successfully trapped in ex situ analysis. However, it was the ionic liquid-based trap, specifically pyridinium, that effectively suppressed $S_3^{•-}$ during battery operation. Overall, the PS formation was altered in the presence of the traps and we confirmed the impact of $S_3^{•-}$ formation on the Li–S battery redox reactions and show how the trapping correlates with Li–S battery performance. Therefore, stabilization of the $S_3^{•-}$ might be a path to improved Li–S batteries.

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.

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.

Finding a correlation between the rheology of an electrode slurry and the mixing variables is challenging due to the complex interactions among the materials in the suspension. Here, we report a systematic study of the mixing speed and how this variable impacts the slurry rheology of the Nickel Manganese Cobalt Oxide (NMC622) positive electrode at 2000, 3000, and 4000 rpm and maintaining constant the other mixing parameters. We partially combined the slurry components and compared the rheology results with the complete formulation. This systematic study shows differences in viscosity depending on mixing speed and the slurry component combination. In addition, frequency oscillatory sweeps were used to obtain information on the slurry microstructure, showing changes depending on the nature of component interactions. The slurries were also casted, dried, and calendered. Numerical simulations were also performed to analyze the experimental findings. Understanding the slurry rheology and the interaction of the formulation components is fundamental for further engineering electrode manufacturing and analysis of the dried electrode's output properties.

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.

Li-ion batteries (LIBs), thanks to high efficiencies and energy density, represent the mainstream technology to replace traditional internal combustion vehicles with electric ones. However, LIBs state of health (SoH) should be investigated to avoid fast degradation due to fast-charging, electrical, mechanical and thermal factors. Therefore, SoH prediction and monitoring for battery electric vehicles is necessary for extending LIB lifespan and avoiding failures. In this paper, an accurate real-time SoH prediction and monitoring method, based on discrete wavelet (DWT) analysis, is investigated through an extensive experimental campaign considering the effect of temperature variation. Specifically, moving from cycle aging performed on Li-ion NCR 18650 cells and applying two typical US test drive cycles at different SoHs, three different operating temperatures (i.e., 0 °C, 20 °C and 30 °C) were investigated. Applying DWT on the gathered LIB voltage profiles, it is demonstrated that temperature effect on the implemented method is easily recognizable from the one of cycle aging. Moreover, suitable linearized functions are identified to refer DWT outcomes assessed at the operative temperature to a reference temperature, at which a suitable equation is previously identified to assess capacity fading. Due to its general validity the method can be extended to stationary applications.

We demonstrate, as proof of concept, a materials design path that allows us to exploit thermal deposition technique to fabricate sodium (Na) metal anodes at the microscale. Our study reveals that Na thin anodes <10 μm, directly coated on a stainless-steel current collector, reduces the energy barrier of Na nucleation during plating process. Likewise, evaporated thin-film sodium anodes enable achieving a cycling in a full battery configuration as stable as with bulk Na anode, and considerably more stable than the here presented anode-less case. These insights may lead to practical design changes toward the efficient use of metallic Na, alleviating weight and costs. In addition, they provide a solid starting point for future developments that focus on improving the stability and extending the life of Na-metal batteries. All this paves the way for the next-generation of sodium-based energy storage technologies, where energy density and cost are key factors.

The need for high-energy and safe batteries is more and more urgent, and a possible approach is to use solid polymer electrolyte with high conductivity combined with lithium metal anode. Poly (1,3-dioxolane)-based electrolytes are promising, and the feasibility to polymerize 1,3-dioxolane (DOL) in situ makes this approach very attractive. In this paper, we present the in situ electro-initiated polymerization of DOL in polyacrylonitrile nanofibrous mats, without using initiator or crosslinking agents. The amount of monomer loaded in the porous scaffold, the electrochemical technique used to initiate the polymerization and the salt amount were investigated as important parameters that affect the ion conductivity and the performance of the obtained polymer electrolyte. Particular attention was directed towards minimizing the presence of residual monomer in the resulting polymer, with the aim of progressing towards the development of a real solid-state polymer electrolyte. The results of the thermal, morphological, and electrochemical characterization are reported and discussed.