Mechanistic understanding of lithium electrodeposition and morphology evolution is critical for lithium metal anodes. In this study, we deduce that Li deposition morphology evolution is determined by ...the mesoscale complexations that underlie due to local electrochemical reaction, Li surface self-diffusion, and Li-ion transport in the electrolyte. Li-ion depletion at the reaction front for higher reaction rates primarily accounts for dendritic growth with needlelike or fractal morphology. Large Li self-diffusion barrier, on the other hand, may lead to the formation of porous Li film for lower reaction rates. Enhanced ion transport in the electrolyte contributes to homogeneous deposition, thereby avoiding nucleation for Li dendrite formation. This study also demonstrates that the substrate surface roughness strongly affects dendritic growth localization over the protrusive surface features. A nondimensional electrochemical Damkohler number is further proposed, which correlates surface diffusion rate and reaction rate and allows constructing a comprehensive phase map for lithium electrodeposition morphology evolution.
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IJS, KILJ, NUK, PNG, UL, UM
Lithium metal, although attracting renewed interest for the next revolution in energy storage, continues to be challenged with the detrimental dendrite formation. Recent experimental reports have ...demonstrated the contrasting impact of thermal attributes on the electrodeposition morphology, showcasing the alleviation and/or aggravation of dendrite formation. Herein, we present a comprehensive discourse to discern the thermally activated physical mechanisms governing lithium electrodeposition morphology. We report that the synergistic effect of enhanced electrolyte transport and surface self-diffusion under a uniform thermal field (∼75 °C) enables adequate dendrite suppression, even at high reaction rates. However, in contrast to this, a localization of the thermal field substantially increases the exchange current density of the confined region, instigating the growth of needle dendrites. Based on our mesoscale analysis, we demarcate safety limits for such an event, beyond which dendrite growth is inevitably triggered. Therefore, though the operational strategy of elevating the cell temperature promises to resolve the challenge of stable electrodeposition, it comes along with the caveat. This fundamental study provides a detailed insight into underlying electrochemical-thermal complexations, critical to the performance and safety of metal-based rechargeable batteries.
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IJS, KILJ, NUK, PNG, UL, UM
Lithium-ion battery electrodes exhibit complex interplay among multiple electrochemically coupled transport processes, which rely on the underlying functionality and relative arrangement of different ...constituent phases. The electrochemically inactive solid phases (e.g., conductive additive and binder, referred to as the secondary phase), while beneficial for improved electronic conductivity and mechanical integrity, may partially block the electrochemically active sites and introduce additional transport resistances in the pore (electrolyte) phase. In this work, the role of mesoscale interactions and inherent stochasticity in porous electrodes is elucidated in the context of short-range (interface) and long-range (transport) characteristics. The electrode microstructure significantly affects kinetically and transport-limiting scenarios and thereby the cell performance. The secondary-phase morphology is also found to strongly influence the microstructure–transport-kinetics interactions. Apropos, strategies have been proposed for performance improvement via electrode microstructural modifications.
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IJS, KILJ, NUK, PNG, UL, UM
Despite progress in solid-state battery engineering, our understanding of the chemo-mechanical phenomena that govern electrochemical behaviour and stability at solid-solid interfaces remains limited ...compared to at solid-liquid interfaces. Here, we use operando synchrotron X-ray computed microtomography to investigate the evolution of lithium/solid-state electrolyte interfaces during battery cycling, revealing how the complex interplay among void formation, interphase growth and volumetric changes determines cell behaviour. Void formation during lithium stripping is directly visualized in symmetric cells, and the loss of contact that drives current constriction at the interface between lithium and the solid-state electrolyte (Li
SnP
S
) is quantified and found to be the primary cause of cell failure. The interphase is found to be redox-active upon charge, and global volume changes occur owing to partial molar volume mismatches at either electrode. These results provide insight into how chemo-mechanical phenomena can affect cell performance, thus facilitating the development of solid-state batteries.
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GEOZS, IJS, IMTLJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK, ZAGLJ
Lithium metal is an attractive negative electrode material for rechargeable lithium batteries because of its light weight and high electronegative redox potential. However, dendritic deposition of ...lithium during charging poses a safety concern. During discharging, some of the lithium may strip away from the electrode as the root of the dendrite is electrodissolved. This is referred to as dead lithium since it is not electrochemically active, which may result in low coulombic efficiency. In this work, a comprehensive understanding of the interface evolution leading to the formation of dead lithium is presented based on a mechanism-driven probabilistic analysis. A non-dendritic interface morphology is obtained under reaction and ionic transport controlled scenarios. Otherwise, this may evolve into mossy, dendritic, whisker or needle-like structures with the main characteristic being the propensity for undesirable vertical growth. During discharging, a pitted interface may be formed along with bulk dissolution. Surface diffusion is a key determinant controlling the extent of dead lithium formation, including a higher probability of the same when the effect of surface diffusion is comparable to that of ionic diffusion in the electrolyte and interface reaction.
Electrochemical energy systems, such as batteries and fuel cells, are being developed for applications ranging from portable devices and electric vehicles to large-scale grid storage. These advanced ...energy conversion and storage technologies will be a critical aspect of a sustainable energy future and promise to provide cleaner, more efficient energy. Computational modeling at various scales from nanoscale ab initio modeling to macroscale system and controls level modeling, has been a central part of the electrochemical energy research. Much of the complex interactions due to the electrochemistry coupled transport phenomena occur at the interfaces and within the porous electrode microstructures. This is often referred to as the mesoscale and plays a critical role in the operation and efficiency of electrochemical devices. In this critical perspective, we discuss the state-of-the-art, challenges and path forward in mesoscale modeling of electrochemical energy systems and their application to various design and operational issues in solid oxide fuel cells, polymer electrolyte membrane fuel cells, lithium ion batteries and metal-air batteries. Particular focus is given to particle-based methods and fine-scale computational fluid dynamics based direct numerical simulation techniques, along with the challenges and advantages of these methods. Notable results from mesoscale modeling are presented along with discussions of the advantages, disadvantages and challenges facing mesoscale model development. This in-depth perspective is envisioned to serve as a primer to the critical role mesoscale modeling is poised to play in advancing the science and engineering of electrochemical energy systems.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Lithium (Li)-metal anode has attracted renewed research interest due to its high specific capacity and the lowest negative potential. However, Li-metal batteries have safety issues and severe ...capacity fading. In this study, we demonstrate a facile and effective technique by adding an anodic aluminum oxide nanostructured interlayer onto the commercial polypropylene separator (PP) to create a novel architecture (AP). It is found that AP-based symmetric Li–Li cells and Li–NCM523 cells exhibit enhanced cycling performance and delayed capacity decay. Furthermore, compared with the cells with PP, the cells with AP show reduced overpotentials and improved cycle stability at low temperatures and various current densities, implying the wide applications of the designed architecture. The superior performance of AP is ascribed to its high electrolyte retention, high mechanical strength, and precisely ordered architecture, which contribute to uniform Li nucleation and growth. This unique separator architecture provides mechanistic insights into the design of rechargeable lithium-metal batteries, which are aimed at high energy density and cycling stability.
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IJS, KILJ, NUK, PNG, UL, UM
•Efficacy of nanofluids as an active thermal management strategy for Li-ion batteries.•Asses battery performance heat dissipation capability under high-stress.•Design considerations relevant to ...electric vehicle applications.•Thermo-electrochemical modeling and analysis.
Thermal implications related to heat generation and potential temperature excursions during operation in lithium-ion batteries are of critical importance for electric vehicle safety, performance and life. Concurrently, appropriate thermal management strategies for lithium-ion batteries are crucial to maintain cell temperatures within a desired range. Different battery thermal management strategies have been proposed, each with various advantages and disadvantages depending on the applications. This work proposes the use of nanofluids, colloidal suspensions of nanoparticles in a base fluid, as a heat transfer fluid for active thermal management. To analyze the efficacy of nanofluids for thermal management in lithium-ion batteries, different nanofluids and their effect on the temperature distribution within typical battery modules are investigated for two different flow configurations. In particular, the study is focused on battery performance, heat dissipation capability under high discharge rates and ambient temperatures, and design considerations relevant to electric vehicle applications. This study underscores the potential of this innovative thermal management technique toward effective thermal safety without performance penalty of lithium-ion batteries for vehicle electrification.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
While the energy and power density of lithium-ion batteries (LIBs) are steadily improving, thermal safety continues to remain a critical challenge. Under abuse conditions, exothermic reactions may ...lead to the release of heat that can trigger subsequent unsafe reactions. The situation worsens in a module configuration, as the released heat from an abused cell can activate a chain of reactions in the neighboring cells, causing catastrophic thermal runaway. This work focuses on experimental elucidation and analysis of different LIB module configurations to characterize the thermal behavior and determine safe practices. The abuse test consists of a heat-to-vent setting where a single cell in a module is triggered into thermal runaway via a heating element. The cell-to-cell thermal runaway propagation behavior has been characterized. Results have shown that increasing the inter-cell spacing in a module containing cylindrical cells significantly decreases the probability of thermal runaway propagation. Additionally, it was determined that appropriate tab configuration combined with cell form factors exhibit a major influence on thermal runaway propagation. Different thermal insulation materials have been analyzed to determine their ability to ameliorate and/or potentially mitigate propagation effects.
The stability and homogeneity of the solid electrolyte interphase (SEI) layer are critical toward understanding the root causes behind performance decay and safety concerns with lithium metal ...electrodes for energy storage. This study focuses on deducing mechanistic insights into the complexations between the Li metal electrode and SEI during electrodeposition. It is found that the formation of Li dendrite can be initiated by two distinct mechanisms: (i) aggressive Li-ion depletion near the anode–SEI interface at high reaction rates or low temperature attributed to transport limitations, and (ii) spatially varying reaction kinetics at the SEI–electrode interface due to SEI inhomogeneity even at low currents. Subsequent mechanical stability analyses reveal that significantly high stress is generated due to nonuniform Li electrodeposition which could lead to crack formation in the existing SEI layer, and consequently exposure of fresh lithium to the electrolyte resulting in enhanced capacity fading. Furthermore, a non-dimensional analysis relating the interfacial stress induced failure propensity to electrochemical Biot number and SEI heterogeneity factor is proposed, which delineates stable lithium deposition regimes.
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