Simulation and Measurement of Local Potentials of Modified Commercial Cylindrical Cells

Erhard, Simon V.; Oßwald, Patrick; Wilhelm, Jörn; Rheinfeld, Alexander; Kosch, Stephan; Jossen, Andreas

doi:10.1149/2.0431514jes

Cited by 50 publications

(69 citation statements)

References 45 publications

(91 reference statements)

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“…Nearly no error occurs at 0.5C as well as 1C and 2C. This result is a distinct improvement to our previous study, 4 where thermal gradients within the cell superimposed the electrochemical cell performance and larger deviations between simulation and measurement remained. With a single-layered pouch cell approach, the assumption of negligible thermal gradients simplifies the investigation of model and parameter quality.…”

Section: Temperature Dependency-insupporting

confidence: 55%

“…Only the main equations are shown, for more details the reader is referred to our previous publication. 4 assuming common literature values for specific conductivities of copper and aluminum. 30 Compared to the measured values in Figs.…”

Section: Resultsmentioning

confidence: 99%

“…Often, this corresponds to thicker electrodes or larger form factors leading to capacities of up to 100 Ah per cell. In these large format cells, severe gradients in current density and temperature distribution can occur along the electrode stack, [3][4][5][6][7][8][9] which might provoke a performance loss during operation due to inhomogeneous utilization. Also non-properly adapted thermal conditioning can have a crucial impact on the performance of larger cells.…”

mentioning

confidence: 99%

“…A general study on the current density distribution within that cell during discharge derived from measuring local potentials and their deviation at varying C-rates and temperatures is presented here. In the second part of this work, we apply our multi-dimensional modeling framework 4 to reproduce the measured data and investigate the To assure mechanical stiffness, the cell is mounted on an acrylic back plate which is fixed to an aluminum frame. The reference tabs are connected by cable shoes which are screwed to the tabs whereas the potential measurement tabs are connected by alligator clips (bottom).…”

mentioning

confidence: 99%

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Simulation and Measurement of the Current Density Distribution in Lithium-Ion Batteries by a Multi-Tab Cell Approach

Erhard

Oßwald

Keil

et al. 2017

J. Electrochem. Soc.

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A single-layered NMC/graphite pouch cell is investigated by means of differential local potential measurements during various operation scenarios. 44 tabs in total allow for a highly resolved potential measurement along the electrodes whilst the single layer configuration guarantees the absence of superimposed thermal gradients. By applying a multi-dimensional model framework to this cell, the current density and SOC distribution are analyzed quantitatively. The study is performed for four C-rates (0.1C, 0.5C, 1C, 2C) at three temperatures (5 • C, 25 • C, 40 • C). The maximum potential drop as well the corresponding SOC deviation are characterized.The results indicate that cell inhomogeneity is positively coupled to temperature, i.e. the lower the temperature, the more uniform the electrodes will be utilized. Within the past decades, demand for lithium-ion batteries in mobile applications has significantly increased. Due to their well proven performance as well as their stability in long-term usage, lithium-ion batteries became the technology of choice for electrochemical energy storage devices.1,2 Still, the specific energy density as well as cycle life are constantly being optimized by either commercializing new active materials, electrolytes and additives or by reducing the fraction of non-active parts within a battery. Often, this corresponds to thicker electrodes or larger form factors leading to capacities of up to 100 Ah per cell. In these large format cells, severe gradients in current density and temperature distribution can occur along the electrode stack, 3-9 which might provoke a performance loss during operation due to inhomogeneous utilization. Also non-properly adapted thermal conditioning can have a crucial impact on the performance of larger cells. [10][11][12] Modeling of internal distributions of potential and temperature along the electrodes is quite challenging, since even to calculate only a few cycles, a lot of computational resources are required for fully resolved models. In literature, there are many examples for spatially resolved multi-dimensional modeling approaches, 8,9,[13][14][15][16] which aim at representing the cell's internal behavior in terms of potential, current density, state of charge (SOC) and temperature distribution. Unfortunately, all of these examples lack a detailed, i.e. spatially resolved experimental validation, which is capable of tracking internal variables instead of measuring the surface temperature at a few spots and considering the overall battery's terminal voltage. Also, only a few examples of direct measurements of the internal current density distribution were published so far. Zhang et al.6,7 built a specific LFP/graphite prototype cell for this purpose. A segmented cathode was used for analyzing the current distribution during discharge at varying C-rates and temperatures. This setup allows for a precise monitoring of the current of each electrode element individually. Large deviations in SOC of up to several percent were identified during the process...

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Section: Temperature Dependency-insupporting

confidence: 55%

Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Simulation and Measurement of the Current Density Distribution in Lithium-Ion Batteries by a Multi-Tab Cell Approach

Erhard

Oßwald

Keil

et al. 2017

J. Electrochem. Soc.

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“…The distinct difference being that the TMM treats the electrolyte transport in the electrode in multiple dimensions to include spatial effects. [10][11][12][13][14][15] In contrast, the DM connects a set of 0D 2,[16][17][18][19][20][21] or 1D 1,[22][23][24][25][26][27] electrochemical sub-models electrically in parallel through the resistance-network which models the current collectors. Interestingly, few recent works have been conducted to provide experimental validation of the internal current distributions within a cell during operation, and even fewer have explicitly studied the effects caused by non-uniform temperatures.…”

mentioning

confidence: 99%

Current Distribution Measurements in Parallel-Connected Lithium-Ion Cylindrical Cells under Non-Uniform Temperature Conditions

Klein

Park

2017

J. Electrochem. Soc.

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Understanding internal state non-uniformity that occurs across the electrodes in large-format Lithium-ion batteries, and among parallel-connected cells, is a critical part of the cell and battery module design process. Two separate groups of parallel-connected 18650 cells were tested using LiFePO 4 /C 6 (LFP), and LiNiMnCoO 2 /C 6 (NMC) chemistries. Pulse and full-capacity discharges were performed at various States of Charge (SOC), C-rates, average temperatures, and levels of temperature non-uniformity. Current nonuniformity for the pulse testing was always lower for the LFP group compared to the NMC group. The hottest cell in the LFP group produced up to 40% more current than average, while this was up to 80% for NMC. Conversely, under charge depleting conditions the NMC group experienced less current non-uniformity, and in certain cases provided a nearly uniform current distribution in the presence of non-uniform temperature. The results indicate that higher temperature sensitivity in the impedance of a cell will cause larger current non-uniformity under pulse conditions. However, due to the presence of non-uniform SOC for charge depleting, the Open Circuit Voltage (OCV) versus SOC gradient plays a significant role in dictating the current distribution behavior, where steeper OCVs provide a corrective action that minimizes the effect of the non-uniform impedance. Understanding the evolution of non-uniform current and temperature that occurs either across the electrodes in Lithium-ion cells and/or among sets of interconnected cells is a critical part of the cell and module design process for Lithium-ion battery packs.1-3 The issues of non-uniform current and temperature cause a two-way coupled problem. For example, non-uniform current density can cause non-uniform heating, and therefore non-uniform temperature. 4 Additionally, nonuniform temperature causes non-uniform electrochemical impedance across the electrodes of individual cells and/or across cells in a module which will generate non-uniform current density and therefore non-uniform heating. [5][6][7] Several studies, particularly at high charge/discharge rates (i.e., above 1C), show single cell temperature differences greater than 20• C. 3,4,8,9 As a result battery thermal management systems (BTMS) must be incorporated into large scale battery packs, particularly in automotive applications where high C-rates are common. Traditionally, the BTMS is designed in such a way that thermal non-uniformity is kept below 5• C throughout the cell, module, and pack. 4 In order to optimize the BTMS to ensure efficient packaging, thermal performance, and proper electrochemical performance, a thermally-coupled spatially-resolved electrochemical model must be used to understand the coupled effects between the BTMS and the electrochemical performance.In recent years much progress has been accomplished to model the inhomogeneous behavior of large-format cells. Generally, these can be classified as either True Multidimensional Models (TMM) or Distributed Models (DM). The d...

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In Situ Measurement of Current Distribution in Large-Format Li-Ion Cells

Zhang

Shaffer

Yang

et al. 2023

Modern Aspects of Electrochemistry

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Simulation and Measurement of Local Potentials of Modified Commercial Cylindrical Cells

Cited by 50 publications

References 45 publications

Simulation and Measurement of the Current Density Distribution in Lithium-Ion Batteries by a Multi-Tab Cell Approach

Simulation and Measurement of the Current Density Distribution in Lithium-Ion Batteries by a Multi-Tab Cell Approach

Current Distribution Measurements in Parallel-Connected Lithium-Ion Cylindrical Cells under Non-Uniform Temperature Conditions

In Situ Measurement of Current Distribution in Large-Format Li-Ion Cells

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