Chris Lynness
The trouble with batteries: modelling electrochemical systems in a vehicle

Discussion around the challenge of understanding how internal mechanisms with battery cells can impact the behaviour of vehicles and how people drive.

Markus Schmuck
New upscaled charge transport equations for highly heterogeneous multiphase materials

includes joint works with P. Berg (NTNU) and M.Z. Bazant (MIT))
After motivating the complexity and high-dimensionality of nonlinear transport problems in systems for energy generation and storage [1,3], we introduce a rigorous mathematical upscaling technique based on asymptotic expansion techniques [4,5] and the two-scale convergence method [6]. Herewith, we rigorously and systematically derive effective macroscopic equations for the transport of dilute electrolytes in porous media [2,5,6] and for proton transport in catalyst layers in polymer electrolyte membrane fuel cells [3] as well as according extensions towards incompressible fluid flow [1]. We conclude with a result that shows how microscopic material properties can affect the transport characteristics on the macroscale [4].
References
[1] M. Schmuck, P. Berg, J ELECTROCHEM SOC, 161(8):E3323-E3327 (2014).
[2] M. Schmuck, M.Z. Bazant, SIAM J APPL MATH 75(3):1369-1401 (2015).
[3] M. Schmuck, P. Berg, APPL MATH RES EXPRESS, 2013(1):57-78 (2013).
[4] M. Schmuck, J MATH PHYS, 54(2):21 p.021504 (2013).
[5] M. Schmuck, ZAMM-Z ANGEW MATH ME, 92(4):304-319 (2012). [6] M. Schmuck, COMMUN MATH SCI, 9(3):685-710 (2011).

Michael Auinger
Near surface Ion distributions and buffer effects during electrochemical reactions

The near-surface ion distribution at the solid-liquid interface often defines the local corrosion behaviour of many electrochemical systems and may even lead to severe material degradation (corrosion) or battery failure. In this presentation, the Hydrogen Oxidation Reaction(HOR)/Hydrogen Evolution Reaction (HER) on a rotating platinum disc electrode is discussed. The relation between reaction rate, mass transport and the resulting surface pH-value is used to theoretically predict cyclic voltammetry behaviour using only thermodynamic and diffusion data obtained from the literature, which were confirmed by experimental measurements. The effect of buffer addition on the current signal, the surface pH and the ion distribution is quantitatively described by analytical solutions and the fragility of the surface pH during reactions that form or consume H+ in near-neutral unbuffered solutions or poorly buffered media is highlighted. While the ideal conditions utilized in this fundamental study cannot be directly applied to real scenarios, they do provide a basic understanding of the surface pH concept for more complex heterogeneous reactions, like the corrosion of Zinc surfaces.

Ashwin Rajan
Capacity fade modelling of Li-ion cells under cyclic loading condition

Lithium-ion batteries have been widely used in electric vehicles (EVs) and hybrid electric vehicles (HEVs) due to its high energy density, low energy-weight ratio and ease of operation. Thermal and electrochemical behaviour of Lithium-ion batteries have been the focus of research since it can predict ageing and fast charging capacity fade more accurately than simple network models. A pseudo two dimensional (P2D) electro-chemical Lithium-ion battery model is presented to study the effect of capacity fade under multiple charge-discharge conditions. The battery is cycled between two cut off voltage limits. The Newman's equations are modified to include a continuous solvent reduction reaction responsible for the capacity fade and power fade. The temperature variation inside the cell is accurately predicted using a distributed thermal model coupled with the internal chemical heat generation. The accuracy of model is further improved by linking the porosity variation with electrolyte partial molar concentration there by proving a stronger coupling between the battery performance and the chemical property of electrolyte. The SEI growth is quantified for different end of charging and discharge voltages as well as cell capacity rates. Results show that the convective heat transfer coefficient as well as the porosity variation greatly influences the Solid Electrolyte Interface (SEI) layer growth and life of the battery. The choice of an electrolyte decides the conductivity and partial molar concentration which is found to have strong influence on life of the battery. This model integrates all essential electro-chemical processes inside a lithium-ion battery under a strong implicit algorithm, useful for real time battery monitoring system.