Review on Multi-Scale Models of Solid-Electrolyte Interphase Formation

Electrolyte reduction products form the solid-electrolyte interphase (SEI) on negative electrodes of lithium-ion batteries. Even though this process practically stabilizes the electrode-electrolyte interface, it results in continued capacity-fade limiting lifetime and safety of lithium-ion batteries. Recent atomistic and continuum theories give new insights into the growth of structures and the transport of ions in the SEI. The diffusion of neutral radicals has emerged as a prominent candidate for the long-term growth mechanism, because it predicts the observed potential dependence of SEI growth.Comment: 8 pages, 4 figure

Modeling Nucleation and Growth of Zinc Oxide During Discharge of Primary Zinc-Air Batteries

Metal-air batteries are among the most promising next-generation energy storage devices. Relying on abundant materials and offering high energy densities, potential applications lie in the fields of electro-mobility, portable electronics, and stationary grid applications. Now, research on secondary zinc-air batteries is revived, which are commercialized as primary hearing aid batteries. One of the main obstacles for making zinc-air batteries rechargeable is their poor lifetime due to the degradation of alkaline electrolyte in contact with atmospheric carbon dioxide. In this article, we present a continuum theory of a commercial Varta PowerOne button cell. Our model contains dissolution of zinc and nucleation and growth of zinc oxide in the anode, thermodynamically consistent electrolyte transport in porous media, and multi-phase coexistance in the gas diffusion electrode. We perform electrochemical measurements and validate our model. Excellent agreement between theory and experiment is found and novel insights into the role of zinc oxide nucleation and growth and carbon dioxide dissolution for discharge and lifetime is presented. We demonstrate the implications of our work for the development of rechargeable zinc-air batteries.Comment: 16 pages, 8 figures, Supplementary Information uploaded as ancillary fil

Modellierung und Simulation Primärer Zink-Luft-Knopfzellen

Primäre Zink-Luft-Knopfzellen werden bereits erfolgreich in Hörgeräten eingesetzt. Für Anwendungen in portablen Geräten, sowie im Rahmen der Elektromobilität und der Energiewende, werden allerdings elektrisch wiederaufladbare Energiespeicher benötigt, weshalb an sekundären Zink-Luft-Zellen geforscht wird. Diese haben allerdings zum aktuellen Stand der Forschung noch eine sehr geringe Lebensdauer. In dieser Arbeit stellen wir ein thermodynamisch konsistentes, eindimensionales Modell für die Transportvorgänge in Zink-Luft-Knopfzellen, unter Berücksichtigung der Reaktionen und porösen Elektroden, auf. Die Modellgleichungen diskretisieren wir mit der Finite-Volumen-Methode und implementieren diese in Matlab und erhalten so eine Simulation der Zelle. Wir rechtfertigen unsere Ortsdiskretisierung durch eine Fehlerabschätzung, die auf Dreiecksgittern auch in zwei Dimensionen gilt. Die Zeitschritte berechnen wir mit dem Solver ode15i. Um dieses Verfahren numerisch zu validieren, berechnen wir die experimentelle Konvergenzordnung an Hand der Wärmeleitungsgleichung als Testproblem. Wir untersuchen das Entladeverhalten von Zink-Luft-Knopfzellen bei konstanter Stromstärke experimentell und vergleichen die Resultate mit denen unserer Simulation. Durch die Analyse der Ergebnisse erhalten wir einen guten Einblick in die Prozesse beim Entladevorgang in der Batterie. Außerdem untersuchen wir die Selbstentladung der Zelle durch die Wechselwirkung mit Kohlendioxid aus der Luft experimentell und führen eine entsprechende Simulation durch. Die Ergebnisse stimmen qualitativ gut überein und liefern eine Aussage über die Lebensdauer der Zelle

Localization of cold atoms in state-dependent optical lattices via a Rabi pulse

We propose a novel realization of Anderson localization in non-equilibrium states of ultracold atoms trapped in state-dependent optical lattices. The disorder potential leading to localization is generated with a Rabi pulse transfering a fraction of the atoms into a different internal state for which tunneling between lattice sites is suppressed. Atoms with zero tunneling create a quantum superposition of different random potentials, localizing the mobile atoms. We investigate the dynamics of the mobile atoms after the Rabi pulse for non-interacting and weakly interacting bosons, and we show that the evolved wavefunction attains a quasi-stationary profile with exponentially decaying tails, characteristic of Anderson localization. The localization length is seen to increase with increasing disorder and interaction strength, oppositely to what is expected for equilibrium localization.Comment: 4 pages, 4 figure

Modelling and Simulation of Zinc-Air Batteries with Aqueous Electrolytes

Primary zinc-air batteries have long been an industry standard for low-power applications like hearing aids. Their high theoretical specific energy (1086 Wh ∙ kg-1), use of cheap and non-hazardous materials, and superior operational safety make secondary zinc-air batteries desirable for emerging markets such as electric vehicles or grid storage. But effects including poor cycling stability of the anode, carbonate formation in the alkaline electrolyte, and the lack of a suitable bi-functional air catalyst have limited their use. The Horizon 2020 project Zinc Air Secondary (ZAS!) aims to develop a high-performance rechargeable zinc-air battery capable of achieving more than 1000 cycles. Modelling and simulation of novel cell materials and architectures provides crucial support towards achieving this goal. We have developed a 1D finite volume continuum model implemented in MATLAB. Our model includes a thermodynamically consistent description of mass transport in concentrated ternary electrolytes, multi-phase coexistence in porous media, and reaction kinetics with considerations for anode passivation due to types I and II ZnO, among other effects. Within this framework, we simulate cell performance and lifetime considering various material com-positions and cell architectures. Initial results show that inhomogeneous Zn dissolution and ZnO precipitation in 32 wt% KOH may lead to significant mass transport limitations, particularly at higher current densi-ties. Furthermore, under certain operating conditions type II ZnO may form on the zinc elec-trode surface, permanently shutting down the cell. To address these issues and improve overall performance the effect

Modeling Zinc-Air Batteries with Aqueous Electrolytes

Emerging markets such as electric mobility and renewable power generation are driving a demand for high-performance electrochemical energy storage. Zinc-air batteries are a promising technology due to their high theoretical specific energy, use of cheap materials, and superior operational safety. But they suffer from effects such as poor cycling stability and self-discharge due to carbonate formation in the alkaline electrolyte. The EU Horizon 2020 project Zinc Air Secondary (ZAS!) aims to overcome these limitations and develop a high-performance rechargeable zinc-air battery. Modelling and simulation of novel electrolytes provide crucial support towards achieving this goal. We have developed a 1D finite volume continuum model implemented in MATLAB. Our model includes a thermodynamically consistent description of mass transport in concentrated electrolytes, multi-phase coexistence in porous media, and reaction kinetics with considerations for anode passivation due to types I and II ZnO, among other effects. Within this framework, we simulate performance on mesoscopic and macroscopic scales. Zinc-air batteries have long been commercialized as primary batteries for hearing-aids. The contamination of potassium hydroxide electrolyte due to carbon dioxide from ambient air is known to limit the lifetime of alkaline zinc-air batteries to just a few months. This reaction is irreversibly forms carbonate species and degrades cell performance by consuming hydroxide. Our simulations show that as carbonate species form, the hydroxide concentration decreases linearly with time. The depletion of hydroxide decreases the ionic conductivity and in combination with the logarithmic dependence of anode overpotential on hydroxide concentration, this effect leads to a marked decrease in cell potential over time. Carbon dioxide reactions do not occur in non-alkaline electrolytes. Near-neutral chloride aqueous electrolytes have been proposed to improve zinc-air battery lifetime. These electrolytes do exhibit superior lifetime performance, but also have lower nominal conductivity values. This inhibits ionic transport in the electrolyte, and can be rate-limiting for large geometries. We present the first model-based analysis of zinc-air batteries with near-neutral electrolytes proposed to solve carbon dioxide poisoning

Modeling Secondary Zinc-Air Batteries with Advanced Aqueous Electrolytes

Advances in electric mobility and renewable power generation are driving a demand for high-performance electrochemical energy storage. Zinc-air batteries are a promising technology due to their high theoretical specific energy, use of cheap materials, and superior operational safety. But they suffer from effects such as poor cycling stability and self-discharge due to carbonate formation in the alkaline electrolyte. Modelling and simulation of zinc air batteries with novel electrolytes provide crucial support towards achieving this goal. We have developed a 1D finite volume continuum model implemented in MATLAB. Our model includes a thermodynamically consistent description of mass transport in concentrated electrolytes, multi-phase coexistence in porous media, and reaction kinetics with considerations for anode passivation due to types I and II ZnO, among other effects. Within this framework, we simulate performance on mesoscopic and macroscopic scales. The contamination of potassium hydroxide electrolyte due to carbon dioxide from ambient air is known to limit the lifetime of alkaline zinc-air batteries to just a few months. This reaction irreversibly forms carbonate species and degrades cell performance by consuming hydroxide. Our simulations and experimental results show that as carbonate species form, the hydroxide concentration decreases linearly with time. The depletion of hydroxide decreases the ionic conductivity and slows down zinc dissolution leading to a marked decrease in cell potential over time. Carbon dioxide reactions do not occur in non-alkaline electrolytes. Near-neutral chloride aqueous electrolytes have been proposed to improve zinc-air battery lifetime. These electrolytes utilize an ammonium chloride buffer solution to stabilize the pH during discharge. However, even small changes in pH may significantly alter the dominant aqueous zinc species. Due to this effect, the final discharge product may shift from ZnO to Zn(NH3)2Cl2 or Zn(OH)1.6Cl0.4∙(H2O)0.2, causing serious losses in the conductivity of the electrolyte and theoretical specific energy of the cell. We present the first model-based analysis of zinc-air batteries with near-neutral electrolytes. This work was supported by the EU Horizon 2020 project Zinc Air Secondary (ZAS!