Pressure Prediction Modeling and Validation for Lithium-Ion Pouch Cells in Buffered Module Assemblies

Hahn, Severin; Theil, Sebastian; Kroggel, Jan; Birke, Kai Peter

doi:10.1016/j.est.2021.102517

Cited by 17 publications

(27 citation statements)

References 67 publications

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“…Pressure has been applied to batteries with various methods, but it generally falls into two categories, using a fixed displacement with two parallel plates or using parallel plates but adding foam as a spring element to reduce the variance in pressure as the cell thickness changes [1,2]. Pressure has been shown to improve the surface area in the negative and positive electrode of the cell, but reaches a critical limit when electrode cracking occurs, reducing the performance of cells [3].…”

Section: Introductionmentioning

confidence: 99%

“…Pressure has been shown to improve the surface area in the negative and positive electrode of the cell, but reaches a critical limit when electrode cracking occurs, reducing the performance of cells [3]. Stack pressure varies during charging and discharging when using a fixed displacement constraint due to elastic swelling, and over time due to anode growth [1]. Applying a pressure that does not vary with thickness may provide further performance benefits by increasing the positive effects of pressure without causing cracking [1].…”

Section: Introductionmentioning

confidence: 99%

“…This increases stack pressure but also causes pressure to vary. Despite this, applying an initial stack pressure improves cell conductivity, as well as cell lifetime [1,2]. In this paper, a fixture was designed that applies constant pressure to the cell independent of displacement.…”

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confidence: 99%

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Investigation of Constant Stack Pressure on Lithium-Ion Battery Performance

Leonard¹,

Planden²,

Lukow³

2023

Preprint

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Current research involving applying stack pressure to lithium-pouch cells has shown both performance and lifetime benefits. Fixtures are used to mimic this at the cell level and conventionally prescribe a constant displacement onto the cell. This increases stack pressure but also causes pressure to vary. Despite this, applying an initial stack pressure improves cell conductivity, as well as cell lifetime [1, 2]. In this paper, a fixture was designed that applies constant pressure to the cell independent of displacement. Thefixture uses pneumatics to apply a constant stack pressure independent of elastic andplastic swelling. Cells constrained by the constant pressure fixture (CPF) fixture anda conventional fixture (MBPF) were evaluated using a Hybrid Pulse Power Characterization (HPPC) test, to measure internal resistance and maximum deliverable power. Multiple stack pressures were applied to investigate differences in pressure variation and performance between constant pressure and constant displacement, while all tests were additionally compared to control tests with no applied stack pressure. The CPF reduced pressure variation during charging and discharging. revealing the performance effects of maintaining uniform pressure. Applying constant stack pressure reduced the discharge impedance and improved discharged power of the tested cell but did not improve charge performance. Additionally, all constraining methods reported lower internal resistance with maximum current compared to 50% maximum current. Discharge performance benefits from constant pressure could influence pack design to improve vehicle performance.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Investigation of Constant Stack Pressure on Lithium-Ion Battery Performance

Leonard¹,

Planden²,

Lukow³

2023

Preprint

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“…Hahn et al. [ 44 ] and Wuensch et al. [ 26 ] investigated the effect of different types of bracing on automotive lithium‐ion pouch cells with a capacity of 40 Ah, respectively 37 Ah.…”

Section: Introductionmentioning

confidence: 99%

“…Most of the studies deal with either cylindrical- [39] or pouch cells [25,[40][41][42][43] with a small nominal capacity of <6 Ah. Hahn et al [44] and Wuensch et al [26] investigated the effect of different types of bracing on automotive lithium-ion pouch cells with a capacity of 40 Ah, respectively 37 Ah. There are a few reports about the aging effects in prismatic cells [45][46][47][48][49][50] but only little about the impact of bracing on the cells' cycling performance.To reduce the ecological footprint and to increase the lifetime of lithium-ion batteries (LIBs), it is necessary to understand aging phenomena inside the cells during cycling.…”

mentioning

confidence: 99%

Impact of Bracing on Large Format Prismatic Lithium‐Ion Battery Cells during Aging

Daubinger

Schelter²,

Petersohn³

et al. 2021

Advanced Energy Materials

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To reduce the ecological footprint and to increase the lifetime of lithium‐ion batteries (LIBs), it is necessary to understand aging phenomena inside the cells during cycling. In this study, the positive effect of external pressure through bracing the cells on aging is investigated for automotive battery cells with more than 7000 cycles. After cycling, the aged cells are studied by using post‐mortem analysis. It is shown that bracing does not affect the anode and cathode in the same manner. A lack of external pressure results in lithium plating due to contact losses on the anode. Such a loss of lithium inventory plays only a small role in the braced cells. However, the structural and morphological degradation, such as particle cracking at the cathode, is significant. Half‐cell tests of aged and unaged anode samples extracted from the automotive cells confirm the post‐mortem findings, where only minimal differences can be seen for the braced cell. In contrast, the aged cathodes from braced cells demonstrate substantial capacity fade in half‐cell measurements as compared to the cathodes extracted from the unbraced cell. Finally, a new concept of the mechanical state of health (mechanical SOH) is introduced to correlate mechanical effects with electrode degradation.

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