Lithium flow between active area and overhang of graphite anodes as a function of temperature and overhang geometry

Hüfner, T.; Oldenburger, Marc; Bedürftig, Benjamin; Gruhle, A.

doi:10.1016/j.est.2019.100790

Cited by 26 publications

(26 citation statements)

References 13 publications

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“…The anode overhang equalization is already well documented in the literature for capacity and CE measurements, where typically full cycling 29,30 or at least significant SOC changes are investigated. 25,27,28 In summary, considering the time-scale of both mechanisms, voltage relaxation leads to short-term disturbances in self-discharge measurements and dominates them. In contrast, anode overhang equalization causes long-term disturbances that decline over a longer period.…”

Section: Theorymentioning

confidence: 99%

“…While shortterm relaxation is mostly attributed to voltage relaxation, long-term relaxation effects are increasingly attributed to anode overhang equalization. 25,26 The effect of anode overhang areas on capacity 27,28 and coulombic efficiency (CE) 29,30 has been investigated in regard to cell quality parameters. The anode overhang also strongly affected self-discharge measurements, 12,31 but the mechanism and the implications for self-discharge measurements have not been fully explored.…”

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confidence: 99%

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Relaxation Effects in Self-Discharge Measurements of Lithium-Ion Batteries

Roth

Streck

Oberbauer

et al. 2023

J. Electrochem. Soc.

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In order to determine the quality of newly produced lithium-ion cells, self-discharge measurements are performed after manufacturing during the so-called aging step. The aging step is a time-consuming and cost-intensive process due to relaxation effects disturbing the self-discharge measuremtens. Relaxation effects are mainly attributed to voltage relaxation and anode overhang equalization. In this work, different methods for electrical self-discharge measurement, such as the voltage decay method, the voltage hold method, and the capacity loss method, were investigated using commercial Samsung INR21700-50E cylindrical cells (NCA/silicon-graphite) and non-commercial pouch-cells (NMC622/graphite). Various preconditioning methods allowed a distinction to be made between undisturbed, short-term, and long-term disturbed cells. While short-term disturbances subsided after several hours, long-term disturbances due to anode overhang were found to significantly disturb all electrical self-discharge measurements for several weeks. A theoretical explanation was introduced, describing the lithium inventory change due to anode and coupled side reactions being measured differently by voltage- and capacity-based methods. Experimental results confirmed this notion and showed that voltage-based self-discharge measurements underestimated the anode overhang equalization. A comparison to the initial cell aging data indicated that the self-discharge measurement performed shortly after cell formation was disturbed by the anode overhang equalization.

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Section: Theorymentioning

confidence: 99%

mentioning

confidence: 99%

Relaxation Effects in Self-Discharge Measurements of Lithium-Ion Batteries

Roth

Streck

Oberbauer

et al. 2023

J. Electrochem. Soc.

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“…Afterward, lithium ions can diffuse from the active anode part into the overhang or vice versa because of the potential difference between these two regions. The diffusion speed increases with higher temperatures and potential differences between the active and passive areas [73]. move back reversibly to the active part because the driving potential is now reversed [74].…”

Section: Reversible Effectsmentioning

confidence: 99%

A Review on Aging-Aware System Simulation for Plug-In Hybrids

Frambach

Liedtke

Dechent

et al. 2022

IEEE Trans. Transp. Electrific.

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The lithium-ion battery is a vital powertrain component in plug-in hybrid electric vehicles (PHEVs). The fuel reduction potential and cost-effectiveness of these vehicles depend on the sizing of the powertrain components as well as on their utilization, which is defined by the energy management system (EMS). The battery is affected by power and capacity reduction over the lifetime of the vehicle, which needs to be considered during the design process to ensure the performance goals throughout the vehicle lifetime. Current literature regarding battery aging usually contains experimental results, which are not transformed into a useful aging model for system simulations. Consequently, battery aging is often neglected, which is why this paper intends to help researchers understand the degradation process of batteries in PHEVs and consider this in their simulation and dimensioning process. First, PHEV powertrain topologies and components are presented. Afterward, battery degradation mechanisms and recent findings are explained, followed by appropriate modeling approaches for different simulation targets. Finally, current aging-aware EMS literature is systematically reviewed and the integration of the aging models is analyzed, so researchers in system simulation areas can improve their powertrain models.

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“…[38] As known from LIBs, the cell design can also play a crucial role, for example apparently inconspicuous aspects like a larger geometric area of the anode (relative to the cathode). [39][40][41][42] The resulting "overhang" area is advantageous for electrode stacking (alignment) and cell processing, but, at least for LIB cells, disadvantageous for the capacity during charge-discharge cycling, thus has a significant impact on operation performance. [43] Similar to LIBs, proper alignment of electrodes is beneficial also for LMBs.…”

Section: Introductionmentioning

confidence: 99%

“…To reproduce the performance of LMBs for given materials, several conditions and performance‐influencing factors need to be highlighted and reported (e. g., temperature, voltage range, specific current, SPE thickness) [38] . As known from LIBs, the cell design can also play a crucial role, for example apparently inconspicuous aspects like a larger geometric area of the anode (relative to the cathode) [39–42] . The resulting “overhang” area is advantageous for electrode stacking (alignment) and cell processing, but, at least for LIB cells, disadvantageous for the capacity during charge–discharge cycling, thus has a significant impact on operation performance [43] …”

Section: Introductionmentioning

confidence: 99%

Area Oversizing of Lithium Metal Electrodes in Solid‐State Batteries: Relevance for Overvoltage and thus Performance?

et al. 2021

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Systematic and systemic research and development of solid electrolytes for lithium batteries requires a reliable and reproducible benchmark cell system. Therefore, factors relevant for performance, such as temperature, voltage operation range, or specific current, should be defined and reported. However, performance can also be sensitive to apparently inconspicuous and overlooked factors, such as area oversizing of the lithium electrode and the solid electrolyte membrane (relative to the cathode area). In this study, area oversizing is found to diminish polarization and improves the performance in LiNi 0.6 Mn 0.2 Co 0.2 O 2 (NMC622) j j Li cells, with a more pronounced effect under kinetically harsh conditions (e. g., low temperature and/or high current density). For validity reasons, the polarization behavior is also investigated in Li j j Li symmetric cells. Given the mathematical conformity of the characteristic overvoltage behavior with the Sand's equation, the beneficial effect is attributed to lower depletion of Li ions at the electrode/ electrolyte interface. In this regard, the highest possible effect of area oversizing on the performance is discussed, that is when the accompanied decrease in current density and overvoltage overcomes the Sand's threshold limit. This scenario entirely prevents the capacity decay attributable to Li + depletion and is in line with the mathematically predicted values.

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Lithium flow between active area and overhang of graphite anodes as a function of temperature and overhang geometry

Cited by 26 publications

References 13 publications

Relaxation Effects in Self-Discharge Measurements of Lithium-Ion Batteries

Relaxation Effects in Self-Discharge Measurements of Lithium-Ion Batteries

A Review on Aging-Aware System Simulation for Plug-In Hybrids

Area Oversizing of Lithium Metal Electrodes in Solid‐State Batteries: Relevance for Overvoltage and thus Performance?

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