Validation of an actively-controlled pneumatic press to simulate automotive module stiffness for mechanically representative lithium-ion cell aging

Deich, Tobias; Hahn, Severin; Both, Svenja; Birke, Kai Peter; Bund, Andreas

doi:10.1016/j.est.2020.101192

Cited by 30 publications

(22 citation statements)

References 30 publications

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“…A shared conclusion of these studies is the importance of monitoring and ideally controlling the external pressure. This is particularly important for automotive applications since battery packs are usually designed with several stacked cells, which means that due to irreversible expansion, the pressure on the cells can increase significantly and adversely impact the performance of the cells [16,17]. The evolution of the irreversible expansion also shows a strong dependency on the cycling conditions [18][19][20], further reinforcing the idea of the coupling between electrochemical and mechanical aging processes.…”

Section: Introductionmentioning

confidence: 81%

Reversible and Irreversible Expansion of Lithium-ion Batteries Under a Wide Range of Stress Factors

Mohtat¹,

Lee²,

Stefanopoulou³

et al. 2021

Preprint

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Lithium-ion batteries cell thickness changes as they degrade. These changes in thickness consist of a reversible intercalation-induced expansion and an irreversible expansion. In this work, we study the cell expansion evolution under variety of conditions such as temperature, charging rate, depth of discharge, and pressure.A specialized ?fixture was used to keep the cells at a constant pressure during cycling, while measuring the thickness change both within a cycle and the cumulative growth over many cycles. The changes in positive and negative electrode capacity and stoichiometric range can be diagnosed from the evolution of the reversible expansion. The changes in the reversible expansion if combined with the voltage, lead to a higher-confi?dence estimation of cell health parameters important for lifetime prediction and adoptive battery management such as asymmetric charge/discharge power limits. This study raises the importance of monitoring the expansion for enabling advanced and more-informed health diagnostics of lithium-ion batteries.

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Section: Introductionmentioning

confidence: 81%

Reversible and Irreversible Expansion of Lithium-ion Batteries Under a Wide Range of Stress Factors

Mohtat¹,

Lee²,

Stefanopoulou³

et al. 2021

Preprint

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“…Hence, the use of volume change to study aging or predict SoC, as indicated by different authors [9,12], requires special caution, since the expansion varies significantly depending on the measurement position and the measurement results may be biased depending on the measurement method.…”

Section: Discussionmentioning

confidence: 99%

“…Other factors influencing the cell volume are the Solid Electrolyte Interface (SEI) layer thickness growth due to electrolyte decomposition products forming a covering layer on the electrodes [11,12] and Li-plating (especially for Lithium Metal cells) [8,11]. These effects lead to a reduction in volume due to irreversible layer thickness growth and, together with the gassing that takes place due to side reactions [13,14], leads to an increase in pressure inside the cell on the housing, resulting in a measurable change of the cell thickness.…”

Section: Introductionmentioning

confidence: 99%

Non-Uniform Circumferential Expansion of Cylindrical Li-Ion Cells—The Potato Effect

Hemmerling

Guhathakurta²,

Dettinger

et al. 2021

Batteries

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This paper presents the non-uniform change in cell thickness of cylindrical Lithium (Li)-ion cells due to the change of State of Charge (SoC). Using optical measurement methods, with the aid of a laser light band micrometer, the expansion and contraction are determined over a complete charge and discharge cycle. The cell is rotated around its own axis by an angle of α=10° in each step, so that the different positions can be compared with each other over the circumference. The experimental data show that, contrary to the assumption based on the physical properties of electrode growth due to lithium intercalation in the graphite, the cell does not expand uniformly. Depending on the position and orientation of the cell coil, there are different zones of expansion and contraction. In order to confirm the non-uniform expansion around the circumference of the cell in 3D, X-ray computed tomography (CT) scans of the cells are performed at low and at high SoC. Comparison of the high resolution 3D reconstructed volumes clearly visualizes a sinusoidal pattern for non-uniform expansion. From the 3D volume, it can be confirmed that the thickness variation does not vary significantly over the height of the battery cell due to the observed mechanisms. However, a slight decrease in the volume change towards the poles of the battery cells due to the higher stiffness can be monitored.

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“…14 Separator pore closure, increased ion-path lengths, and mechanical degradation are the physical mechanisms responsible for this reduced performance. [15][16][17] Too low pressure levels, however, may lead to delamination and thus electrical disconnection of particles and gas generation, also resulting in reduced lifetime performance. 14,[18][19][20] For silicon-based chemistries, in particular, a certain amount of pressure seems necessary to fixate the expanding electrode layers and guarantee the required battery lifetime.…”

Section: List Of Symbolsmentioning

confidence: 99%

Electrochemical-Mechanical Parameterization and Modeling of Expansion, Pressure, and Porosity Evolution in NMC811∣SiOx-Graphite Lithium-Ion Cells

von Kessel,

Hoehl,

Heugel

et al. 2023

J. Electrochem. Soc.

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Mechanical changes in active materials with large volume expansion such as silicon and nickel not only affect the electrochemical performance of modern batteries but also pose a great challenge to their mechanical design due to pressure increase during operation. We show that the large expansion and consequently changing mechanical properties of silicon and nickel strongly affect the electrochemical and mechanical performance. A multi-scale electrochemical model is developed, parameterized, and validated for a pouch cell with a SiOx-graphite anode (22 wt.-% SiOx) and an NMC|811 cathode. Mechanical parameters such as expansion and compressive properties are determined experimentally using an in-house-developed high-precision cell press and electrode dilatometer, thus parameterizing a semi-empirical mechanical model. We employ a new characterization technique to measure mechanical changes in the cell in-operando and propose a phenomenological parameterization where physical modeling is not yet sufficient. Through electrode porosity, we show that mechanical and electrochemical performance are interdependent, as the latter is reduced upon expansion and pressure development. On the one hand, the active material of the anode seems to expand into the pores at increased pressure, and on the other hand, the mechanical deformation of the cell components can no longer be neglected.

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Validation of an actively-controlled pneumatic press to simulate automotive module stiffness for mechanically representative lithium-ion cell aging

Cited by 30 publications

References 30 publications

Reversible and Irreversible Expansion of Lithium-ion Batteries Under a Wide Range of Stress Factors

Reversible and Irreversible Expansion of Lithium-ion Batteries Under a Wide Range of Stress Factors

Non-Uniform Circumferential Expansion of Cylindrical Li-Ion Cells—The Potato Effect

Electrochemical-Mechanical Parameterization and Modeling of Expansion, Pressure, and Porosity Evolution in NMC811∣SiOx-Graphite Lithium-Ion Cells

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