Simulation and Measurement of Local Potentials of Modified Commercial Cylindrical Cells

Oßwald, Patrick; Erhard, Simon V.; Wilhelm, Jörn; Hoster, Harry E.; Jossen, Andreas

doi:10.1149/2.0561510jes

Cited by 44 publications

(46 citation statements)

References 33 publications

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“…The reason is that large cells, develop temperature gradients 32,38,39 and differences in current density 39,40 during charging or discharging. For example in case of cylindrical cells, it was found that the temperature rise inside the jelly roll is usually significantly higher compared to the cell surface.…”

mentioning

confidence: 99%

Interplay of Operational Parameters on Lithium Deposition in Lithium-Ion Cells: Systematic Measurements with Reconstructed 3-Electrode Pouch Full Cells

Waldmann

Hogg

Kasper

et al. 2016

J. Electrochem. Soc.

142

111

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Deposition of metallic Li is a severe aging mechanism in Lithium-ion cells. This study evaluates the influence of the main operating parameters leading to deposition of Li: temperature, charging C-rate, and end-of-charge voltage. Therefore both, graphite anodes and NMC cathodes from commercial 16Ah pouch cells are reconstructed into 3-electrode full cells Due to their comparably high energy and power densities, Lithiumion batteries are currently used in state-of-the-art electric cars.1-3 In automotive applications, battery life-times of 10 years are expected for customer acceptance. However, it is known that life-time of Lithiumion batteries is limited by aging mechanisms.4-11 One of these aging mechanisms is deposition of metallic Li on anodes. 8,[12][13][14][15] Due to the high chemical reactivity of metallic Li, it readily reacts with electrolyte leading to capacity loss of the cell. 8,9,14,16 It is known that Li deposition mainly depends on (i) charging C-rate, 14,16,17 (ii) temperature, 8,9,12,14,[16][17][18] and (iii) end-of-charge voltage/state-of-charge.14,17 Several authors reported trends for variation of only one of these parameters respectively. E.g. low temperatures during charging are reported to lead to Li plating on graphite anodes. 8,9,14,16,19 However, there is a dearth of experimental results on the topic how specific combinations of operating conditions affect Li deposition. Since such experiments are highly interesting for extension of cycle life 14,20 and improvement of cell safety, 21 this is the topic of the present paper.The reason for deposition of Li on anodes are negative anode potentials E anode vs. (Li/Li + ). 8,12,14,20 Unfortunately, in commercial cells only the cell voltageand not the anode potential vs. (Li/Li + ) can be measured. The reason is that commercial cells do not contain a third reference electrode.Measurements of E anode in full cells would allow detection of Li deposition on anodes (condition: E anode vs. (Li/Li + ) < 0 V). Indeed, by introducing an additional reference electrode, such as metallic Li, the electrode potentials are accessible. 8,12,14,20,22,23 We note that such measurements are also not possible in a halfcell configuration with e.g. either only a graphite anode vs. a Li counter electrode or only a NMC cathode vs. a Li counter electrode, since the interaction between anode and cathode is not taken into account. Instead, 3-electrode full cells with the following electrodes are required to detect Li deposition correctly: (i) anode (e.g. graphite), (ii) cathode (e.g. NMC), and (iii) reference electrode (e.g. metallic Li).Furthermore, it is well-known that the reference electrode has to be positioned near the anode in order to minimize the Ohmic drop and to measure its potential accurately. 24 For example, in aqueous z E-mail: thomas.waldmann@zsw-bw.de systems, this is achieved by a Luggin-Haber capillary. 24 Simulations by Dees et al. also showed that the best position for a reference electrode in Lithium-ion cells is between anode and cathode. 25 The same...

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mentioning

confidence: 99%

Interplay of Operational Parameters on Lithium Deposition in Lithium-Ion Cells: Systematic Measurements with Reconstructed 3-Electrode Pouch Full Cells

Waldmann

Hogg

Kasper

et al. 2016

J. Electrochem. Soc.

142

111

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“…By monitoring 10 tab pairs at each edge of the single-layered NMC/graphite pouch cell, the quality and resolution in measuring local potentials 5 is maximized. Such a multi-tab cell can be used as measurement setup and validation tool for spatially resolved models in order to study effects related to electrode configuration and tab patterns, 6,[20][21][22][23] local relaxation processes 24,25 or local impedance effects.…”

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confidence: 99%

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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“…Although some attempts were made in this direction, in previous literature the studies fail to address the impact of the sensors on the stability of the electrochemical system. In‐situ application of thermocouples has been explored – however such systems are limited to measuring relative temperature changes and thus require a cold junction and analogue conditioning circuits to compensate for their poor sensitivity. Reference electrode incorporation was also attempted, however the methodologies developed were not representative of real‐world applications as significant post‐production modification or even permanent opening of the cell was required, significantly altering the electrochemical system under evaluation…”

Section: Introductionmentioning

confidence: 99%

Hybrid Thermo‐Electrochemical In Situ Instrumentation for Lithium‐Ion Energy Storage

Amietszajew

Fleming

Roberts

et al. 2019

Batteries & Supercaps

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Current "state-of-the-art" monitoring and control techniques for lithium-ion cells rely on full-cell potential measurement and occasional surface temperature measurements. However, Li-ion cells are complex multi-layer devices and as such these techniques have poor resolution, limiting applicability. In this work we develop hybrid thermo-electrochemical sensing arrays placed within the cell. The arrays are integrated into A5 pouch cells during manufacture and are used to create thermal maps in parallel with anode and cathode electrochemical data. The sensor array can be adapted to a range of cell formats and chemistries and installed into commercial or other industrially relevant cells, incorporating enhanced thermal and electrochemical diagnostic capability into a standard cell build.[a] Dr.

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Simulation and Measurement of Local Potentials of Modified Commercial Cylindrical Cells

Cited by 44 publications

References 33 publications

Interplay of Operational Parameters on Lithium Deposition in Lithium-Ion Cells: Systematic Measurements with Reconstructed 3-Electrode Pouch Full Cells

Interplay of Operational Parameters on Lithium Deposition in Lithium-Ion Cells: Systematic Measurements with Reconstructed 3-Electrode Pouch Full Cells

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

Hybrid Thermo‐Electrochemical In Situ Instrumentation for Lithium‐Ion Energy Storage

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