462 research outputs found
Addressing the voltage and energy fading of Al-air batteries to enable seasonal/annual energy storage
No full textAl-air batteries are promising candidates for seasonal and annual energy storage. However, severe voltage decay upon discharge limits their practical specific energy. Herein, we first explore the effect of different Al(OH)4 - concentrations in alkaline electrolytes on the electrochemical oxidation of Al metal anodes (AMAs). Simulation analysis on the electrochemical impedance spectra of AMAs reveals that the formation of Al(OH)4 - reduces the OH- concentration and negatively affects the reaction kinetics of AMAs, which is responsible for increased potentials of AMAs and the consequent voltage decay of Al-air batteries. Subsequently, a seeded precipitation process taking advantage of the lower solubility of Al(OH)4 - at 20 °C than at 50 °C is proposed to recover the voltage decay of Al-air batteries. Inductively coupled plasma atomic emission spectroscopy demonstrates that more than 70 wt% of Al(OH)4 - in the electrolyte can be removed via this process. Raman spectra and ionic conductivity tests of the electrolyte, together with X-ray diffraction of the precipitate, reveal that the removed is converted into insoluble Al(OH)3 with release of OH-. Making use of the precipitation process, Al-air prototypes of Ah-level delivering 3.95 kWh/kg at 50 mA cm-2 and 3.52 kWh/kg at 100 mA cm-2 are demonstrated
Explaining the Voltage Hysteresis and Slow Relaxation of Silicon Nanoparticles with a Chemo-Mechanical Particle-SEI Model
No full textSilicon is widely considered to be a promising next-generation anode material, primarily due to its remarkably high theoretical capacity. Furthermore, silicon is an abundant, cheap, and widely spread material. However, a major challenge for the commercialization of silicon anodes is the significant voltage hysteresis reducing efficiency and leading to detrimental heat generation during fast-charging. Additionally, the hysteresis causes an unclear state-of-charge (SOC) to voltage relation impeding precise SOC estimation.
The voltage hysteresis behavior of silicon anodes is addressed in literature with three different arguments: phase transformations, plastic flow of silicon, and slow diffusion. These approaches can interpret the voltage hysteresis of crystalline silicon, thin films, and large anode particles, respectively. Nevertheless, we show that they cannot explain the hysteresis observed for silicon anodes consisting of amorphous nanoparticles, the relevant material for next-generation lithium-ion batteries.
Our investigation highlights the chemo-mechanical interplay between the silicon nanoparticle and the covering Solid-Electrolyte Interphase (SEI) as the underlying cause for the significant voltage hysteresis. The SEI, a thin passivating layer, forms on negative electrode particles due to electrolyte decomposition [1]. In the case of silicon particles, the volume changes during lithiation and delithiation result in massive strains and plastic deformation occurring within the SEI [2]. Our chemo-mechanical particle-SEI description successfully replicates the observed open-circuit voltage hysteresis in experiments and aligns with the Plett model [3]. Moreover, our visco-elastoplastic SEI model reproduces the voltage difference between slow cycling and the relaxed open-circuit voltage. In our recent work, we show that a sophisticated mechanical model explains the slow voltage relaxation observed for silicon nanoparticles as well as the observed C rate dependence [4].
To conclude, we explain the voltage hysteresis and the slow voltage relaxation of silicon nanoparticles with a visco-elastoplastic particle-SEI model and discuss options to mitigate the size of the voltage hysteresis. This detailed physical understanding can improve the performance of all-silicon anodes and contribute to their commercialization.
[1] Köbbing, L.; Latz, A.; Horstmann, B. J. Power Sources 2023, DOI: 10.1016/j.jpowsour.2023.232651.
[2] Kolzenberg, L.; Latz, A.; Horstmann, B. Batter. Supercaps 2022, DOI: 10.1002/batt.202100216.
[3] Köbbing, L.; Latz, A.; Horstmann, B. Adv. Funct. Mater. 2024, DOI: 10.1002/adfm.202308818.
[4] Köbbing, L.; Latz, A.; Horstmann, B. (in preparation).
[1] Köbbing, L.; Latz, A.; Horstmann, B. J. Power Sources 2023, DOI: 10.1016/j.jpowsour.2023.232651.
[2] Kolzenberg, L.; Latz, A.; Horstmann, B. Batter. Supercaps 2022, DOI: 10.1002/batt.202100216.
[3] Köbbing, L.; Latz, A.; Horstmann, B. Adv. Funct. Mater. 2024, DOI: 10.1002/adfm.202308818.
[4] Köbbing, L.; Latz, A.; Horstmann, B. ArXiv 2024, DOI: 10.48550/arXiv.2408.0110
Description of the Silicon Voltage Hysteresis with a Visco-Elastoplastic SEI Model
No full textThe solid-electrolyte interphase (SEI) plays a crucial role in the performance and lifespan of lithium-ion batteries. Despite ongoing research, key aspects of this passivation layer remain unclear. Our study focuses on understanding SEI growth mechanisms and the mechanical behavior to improve battery lifetime and performance, contributing to more sustainable energy storage.
In advanced lithium-ion batteries, capacity fade during open-circuit storage results mainly from SEI growth. We investigate electron and solvent diffusion mechanisms to describe SEI growth, considering the observed capacity loss depending on state-of-charge (SOC) and time. Our simulations reveal that electron diffusion explains both SOC dependence and time behavior, while solvent diffusion reproduces only one aspect [1]. This detailed understanding, including self-discharge effects, can also describe experiments with significant capacity fades.
Looking ahead to applications such as aviation, the development of next-generation of lithium-ion batteries with increased storage capacity is imperative. Silicon, with its high theoretical capacity, is a promising candidate for future anodes. However, silicon anodes undergo substantial volume expansion that the SEI has to withstand. Consequently, significant strains and plastic flow emerge within the SEI [2]. Moreover, silicon exhibits an open-circuit voltage hysteresis, posing challenges due to detrimental heat generation and for accurately estimating the state-of-charge. While previous explanations focused on plastic models for silicon thin films and large particles, amorphous silicon nanoparticles were not considered. Our chemo-mechanical model of a silicon nanoparticle and SEI successfully replicates the observed open-circuit potential hysteresis in experiments [3]. In addition, viscous behavior of the SEI explains the voltage difference between slow cycling and the relaxed voltage in GITT experiments.
1. Köbbing, L.; Latz, A.; Horstmann, B. J. Power Sources 2023, DOI: 10.1016/j.jpowsour.2023.232651.
2. Kolzenberg, L.; Latz, A.; Horstmann, B. Batter. Supercaps 2022, 5, DOI: 10.1002/batt.202100216.
3. Köbbing, L.; Latz, A.; Horstmann, B. ArXiv Preprint. 2023, DOI: 10.48550/arXiv.2305.17533
Modeling solid-electrolyte interphase Formation on silicon interfaces
No full textLithium-ion batteries combine good long-term stability and performance. These properties have
made Lithium-ion batteries the benchmark energy storage for hand-held electronics and electric
vehicles. Nevertheless, there is an industrial urge to further push the technology towards higher
capacities and longer battery life. Increasing the lifetime of Lithium-ion batteries is currently a
fundamental challenge for battery research. Due to the growth of a solid-electrolyte interphase (SEI)
during storage and cycling, capacity is irreversibly lost.
Silicon anodes are a promising approach for further increasing the capacity of Lithium-ion batteries,
as they show the tenfold theoretical specific capacity of the currently used graphite anodes.
However, the SEI growth is even more severe for silicon anodes: large volume expansions of
~300% exert high mechanical stresses and fracture the SEI. The resulting cracks subsequently
expose the pristine electrode leading to SEI reformation and thereby continuous capacity decrease.
In order to further understand SEI growth, our group developed a model describing SEI growth on
graphite during storage [1-4]. Additionally, a thermodynamical framework was developed to
describe the coupling of different physical effects [5]. Based on these theories, we include
mechanical stresses and study their impact on SEI stability and growth during battery operation.
Understanding these relationships identifies critical operating conditions and aid in the design of
new electrodes. Thereby, batteries with higher capacity and long-term stability can be developed.
1. Single, F., Latz, A. & Horstmann, B. Identifying the Mechanism of Continued Growth of the Solid-Electrolyte Interphase. ChemSusChem 1–7
(2018). doi:10.1002/cssc.201800077
2. Single, F., Horstmann, B. & Latz, A. Revealing SEI Morphology: In-Depth Analysis of a Modeling Approach. J. Electrochem. Soc. 164, E3132–
E3145 (2017).
3. Single, F., Horstmann, B. & Latz, A. Revealing SEI Morphology: In-Depth Analysis of a Modeling Approach. J. Electrochem. Soc. 164, E3132–
E3145 (2017).
4. Single, F., Horstmann, B. & Latz, A. Dynamics and morphology of solid electrolyte interphase (SEI). Phys. Chem. Chem. Phys. 18, 17810–17814
(2016).
5. Latz, A. & Zausch, J. Multiscale modeling of lithium ion batteries: thermal aspects. Beilstein J. Nanotechnol. 6, 987 (2015)
Understanding the Silicon Voltage Hysteresis by considering the impact of the Solid-Electrolyte Interphase (SEI)
No full textLong-range Battery Electric Vehicles (BEVs) and electric planes require the development of next-generation lithium-ion batteries (LIBs) with increased storage capacity. Silicon stands out as the most promising next candidate for the anode, primarily due to its remarkably high theoretical capacity. Furthermore, silicon is an abundant, cheap, and widely spread material.
A major challenge for the implementation is detrimental heat generation during fast-charging due to the significant voltage hysteresis of silicon anodes. The hysteresis leads to an unclear state-of-charge (SOC) to voltage relation impeding precise SOC estimation.
The voltage hysteresis behavior of silicon anodes was rationalized before by three approaches: phase transformations, plastic flow of silicon, and slow diffusion. They explain the voltage hysteresis of crystalline silicon, thin films, and large anode particles. Nevertheless, these approaches are not able to explain the hysteresis observed for silicon anodes consisting of amorphous nanoparticles, the commercially relevant materials.
Our research identifies the chemo-mechanical coupling of silicon and the Solid-Electrolyte Interphase (SEI) as the reason for the substantial voltage hysteresis. The SEI is a thin passivating layer that grows on negative electrode particles due to electrolyte decomposition [1]. For silicon particles, volume change leads to significant strains and plastic deformation occurring within the SEI [2]. We demonstrate that our chemo-mechanical model agrees with the Plett model and reproduces the observed open-circuit voltage hysteresis in experiments [3]. Furthermore, our visco-elastoplastic SEI model reproduces the voltage difference between slow cycling and the relaxed open-circuit voltage.
To summarize, we for the first time explain the silicon hysteresis with a visco-elastoplastic particle-SEI model and discuss options to mitigate the related heat generation. This detailed understanding can improve battery management systems.
1. Köbbing, L.; Latz, A.; Horstmann, B. J. Power Sources 2023, 561, 232651.
2. Kolzenberg, L.; Latz, A.; Horstmann, B. Batter. Supercaps 2022, 5, e202100216.
3. Köbbing, L.; Latz, A.; Horstmann, B. Adv. Funct. Mater. 2024, 34, 2308818
Chemical-mechanical modeling of SEI on Silicon particles
No full textLithium-ion batteries combine good long-term stability and performance. These properties havemade Lithium-ion batteries the benchmark energy storage for hand-held electronics and electricvehicles. Nevertheless, there is an industrial urge to further push the technology towards highercapacities and longer battery life. Increasing the lifetime of Lithium-ion batteries is currently afundamental challenge for battery research. One important mechanism contributing to the capacity loss isthe growth of a solid-electrolyte interphase (SEI) during storage and cycling.Silicon anodes are a promising approach for further increasing the capacity of Lithium-ion batteries,as they show the tenfold theoretical specific capacity of the currently used graphite anodes.However, the SEI growth is even more severe for silicon anodes: large volume expansions of~300% exert high mechanical stresses and fracture the SEI. The resulting cracks subsequentlyexpose the pristine electrode leading to SEI reformation and thereby continuous capacity decrease.In order to further understand SEI growth, our group developed a model describing SEI growth ongraphite during storage [1-4]. Thereby, the diffusion of neutral Li interstitials from the electrode to theelectrolyte was found to cause the long-term growth of the SEI [1,2]. Additionally, a thermodynamical framework was developed to describe the coupling of chemical,electrical and thermal effects [5]. We extend this model for mechanical effects and investigate how theinterplay of chemistry and mechanics impacts stability and growth of the SEI during battery operation.Understanding these relationships identifies critical operating conditions and aid in the design ofnew electrodes. Thereby, batteries with higher capacity and long-term stability can be developed.1. Horstmann, B., Single, F. & Latz, A. Review on Multi-Scale Models of Solid-Electrolyte InterphaseFormation. 13, 1\u20138 (2018). doi:10.1016/j.coelec.2018.10.0132. Single, F., Latz, A. & Horstmann, B. Identifying the Mechanism of Continued Growth of the Solid-Electrolyte Interphase. ChemSusChem 1\u20137 (2018). doi:10.1002/cssc.2018000773. Single, F., Horstmann, B. & Latz, A. Revealing SEI Morphology: In-Depth Analysis of a ModelingApproach. J. Electrochem. Soc. 164, E3132\u2013E3145 (2017). doi:10.1149/2.0121711jes4. Single, F., Horstmann, B. & Latz, A. Dynamics and morphology of solid electrolyte interphase (SEI).Phys. Chem. Chem. Phys. 18, 17810\u201317814 (2016). doi:10.1039/C6CP02816K5. Latz, A. & Zausch, J. Multiscale modeling of lithium ion batteries: Thermal aspects. Beilstein J.Nanotechnol. 6, 987\u20131007 (2015). doi:10.3762/bjnano.6.10
Modeling Crystal Growth and Multi-Phase Flow in Metal-Air Batteries
No full textWe contributed to research on lithium-air batteries with aqueous as well as non-aqueous electrolytes on the pore level and the cell level. Based on the developed modeling methodologies, we study silicon-air and zinc-air batteries.
In aqueous alkaline electrolytes, lithium ions react with oxygen to form lithium hydroxide in a gas diffusion electrode (GDE), where liquid and gas coexist in a porous structure. We model the electrochemical dynamics within a GDE including the effects of pressure-driven convection and multi-phase coexistence with continuum models and Lattice-Boltzmann theory [1,2]. The lithium hydroxide concentration in alkaline lithium-air batteries is accumulating during discharge until it precipitates. We rationalize that this precipitation is inhomogeneous due to fundamental transport effects in alkaline electrolytes and discuss adjusted cell designs [1]. On a microscopic level, we study the elementary kinetics of the oxygen reduction reaction on the active surfaces [3].
A second line of our research is devoted to aprotic solvents in lithium-air batteries. On a cell level, we found that slow oxygen transport in flooded electrodes is a limiting factor for power density [4]. On a pore level, we studied the nucleation of lithium peroxide on the active surfaces of the cathode [5]. The discharge product lithium peroxide is found in different morphologies inside lithium air batteries: either it forms films that passivate the active surface, or it forms particles that grow into the electrolyte pore space. We found out and explained that nucleation of lithium peroxide particles happens at discharge currents below the exchange current of the oxygen reduction reaction.
Furthermore, we are performing research on metal-air batteries based upon zinc- or silicon-ions [6]. Our model explains the experimentally observed dependence of cell capacity on water content in the electrolyte of silicon-air batteries. The addition of water to the electrolyte affects the spatial distribution of the precipitation reaction and thus the balance between anode and cathode capacity.
Parts of this research were performed in collaborations with Martin Z. Bazant, Volker P. Schulz, Wolfgang G. Bessler, Yasin Emre Durmus, Daniel Eberle, Johannes Stamm, Yang Shao-Horn, Betar Gallant, Robert Mitchell, Dennis Wittmaier, and Norbert Wagner.
[1] B. Horstmann, T. Danner, and W. G. Bessler, Energy Environ. Sci. 6, 1299–1314 (2013).
[2] T. Danner, B. Horstmann, D. Wittmaier, N. Wagner, and W. G. Bessler, J. Power Sources 264, 320–332 (2014).
[3] D. Eberle and B. Horstmann, Electrochim. Acta 137, 714–720 (2014).
[4] J. P. Neidhardt, D. N. Fronczek, T. Jahnke, T. Danner, B. Horstmann, and W. G. Bessler, J. Electrochem. Soc. 159, A1528 (2012).
[5] B. Horstmann, B. Gallant, R. Mitchell, W. G. Bessler, Y. Shao-Horn, and M. Z. Bazant, J. Phys. Chem. Lett. 4, 4217–4222 (2013).
[6] Y. E. Durmus, Modeling of Silicon Air-Batteries, University of Ulm, 2013
Physics-based inverse modeling of degradation in Li-ion batteries by using Bayesian methods
No full textModelling at the cell level aims at improving and predicting the lifetime of Lithium-ion batteries (LIBs). To this aim, we want to understand and parameterize the degradation mechanisms. However, the different degradation mechanisms interplay and their origin are even debated in relevant cases [1].
As example, we consider the growth of the Solid-Electrolyte Interphase (SEI). It is the dominant degradation mechanisms during storage of LIBs and plays a significant role during battery operation [2]. To differentiate between various proposed growth mechanisms, i.e., solvent diffusion, electron diffusion and electron migration, we utilize an automated parameterization routine based on Bayesian methods that is able to distinguish the different mechanisms [3].
We show how efficient Bayesian methods [3,4] parametrize and quantify uncertainties of physics-based models, within reasonable sample numbers, operate as a consistent model selection criterion, and give reliable correlations in the overall and feature specific parametrization [5]. We discuss that feature selection has a huge impact on the algorithmic performance and the correct identification of the physical features. By applying this routine to real data, we find that electron diffusion [6] is the dominant growth mechanism of the SEI during storage. In conclusion, our inverse model routine can help to identify and parametrize degradation mechanisms of LIBs and is generalizable to include more mechanisms. This automatable method is applicable to the analysis of battery data, model development and validation and can therefore accelerate battery research.
1. S. O’Kane et al., Phys. Chem. Chem. Phys, 2022, DOI: 10.1039/d2cp00417h
2. B. Horstmann et al., Current Opinion in Electrochemistry, 2019, DOI 10.1016/j.coelec.2018.10.013
3. Y. Kuhn, H. Wolf, A. Latz, B. Horstmann, Batteries & Supercaps. 2023, DOI: 10.1002/batt.202200374.
4. M. Adachi et al., IFAC-PapersOnLine, 2023, DOI: 10.1016/j.ifacol.2023.10.1073.
5. M. Philipp, Y. Kuhn, A. Latz, B. Horstmann, in prep.
6. L. Köbbing, A. Latz, B. Horstmann, J. Power Sources 2023, DOI: 10.1016/j.jpowsour.2023.232651
Modelling of lithium whisker growth
No full textLithium metal batteries are promising candidates for next-generation batteries due to their high specific energy [1]. However, lithium metal anodes show poor cycling stability in commercially available carbonate-based electrolytes. The cycling inefficiencies can be traced back to lithium whisker growth. This high surface-area lithium deposition type leads to accelerated solid electrolyte interphase (SEI) formation and the formation of dead lithium during stripping [2,3]. We investigate the emergence of lithium whiskers in the early stages of electroplating. After the nucleation phase, lithium is deposited underneath the SEI. The SEI stretches with the growing nucleus and may break eventually. We model lithium whisker growth as the extrusion of lithium through cracks in the SEI. In the expected stress conditions, lithium experiences significant creep deformation, which provides a material transport mechanism toward the whisker root. By modeling the flow of lithium as a Herschel-Bulkley fluid, we predict whisker growth rates consistent with experimental observations. The whisker diameter is determined by the crack size of the SEI. Engineering the SEI properties can mitigate whisker emergence and is the most promising approach to achieving safe lithium metal batteries.
[1] Horstmann, B., Werres, M. et al. Strategies towards enabling lithium metal in batteries: Interphases and electrodes. Energy Environ. Sci. 14, 5289-5314 (2021)
[2] von Kolzenberg, L., Werres, M., Tetzloff, J. and Horstmann, B. Transition between growth of dense and porous films: theory of dual-layer SEI. Phys. Chem. Chem. Phys. 24, 18469-18476 (2022)
[3] Werres, M. et al. Origin of Heterogeneous Stripping of Lithium in Liquid Electrolytes. ACS Nano 17, 10218-10228 (2023
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