Abstract

We consider an improved Nernst–Planck–Poisson model first proposed by Dreyer et al. in 2013 for compressible isothermal electrolytes in non-equilibrium. The elastic deformation of the medium, that induces an inherent coupling of mass and momentum transport, is taken into account. The model consists of convection–diffusion–reaction equations for the constituents of the mixture, of the Navier–Stokes equation for the barycentric velocity and of the Poisson equation for the electrical potential. Due to the principle of mass conservation, cross-diffusion phenomena must occur, and the mobility matrix (Onsager matrix) has a non-trivial kernel. In this paper, we establish the existence of a global-in-time weak solution, allowing for a general structure of the mobility tensor and for chemical reactions with fast nonlinear rates in the bulk and on the active boundary. We characterise the singular states of the system, showing that the chemical species can vanish only globally in space, and that this phenomenon must be concentrated in a compact set of measure zero in time.

Highlights

  • Increasing the efficiency of actual high-performance energy storage systems requires an exact understanding of their fundamental physical principles

  • In the neighbourhood of interfaces, the classical description using the Nernst–Planck theory is failing for various reasons: first of all, the Nernst–Planck model neglects the high pressures induced by the Lorentz force that affect the charge transport

  • Let us here mention the papers [31] and [34] where models of compressible mixtures with energy balance, but without electric field, were studied. These models are not derived from exactly the same thermodynamic principles that are used in our study: the constitutive equations for the pressure, for the diffusion fluxes and for the reaction terms, are different in [31] and in [12]

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Summary

Introduction

Increasing the efficiency of actual high-performance energy storage systems requires an exact understanding of their fundamental physical principles. Let us here mention the papers [31] and [34] where models of compressible mixtures with energy balance, but without electric field, were studied These models are not derived from exactly the same thermodynamic principles that are used in our study: the constitutive equations for the pressure, for the diffusion fluxes and for the reaction terms, are different in [31] and in [12]. The compactness question occurs there like in our analysis but is solved assuming a special structure of the viscosity tensor, called Bresch–Desjardins condition The latter allows to obtain estimates on the density gradient, a device which is not at our disposal here. The third part (Sects. 12, 13, 14) is concerned with the investigation of compactness properties, and with the proof of convergence of the approximation scheme

Improved Nernst–Planck–Poisson model
Balance equations in the bulk
Constitutive equations
Choice of the free energy function
The model for the boundary Γ
Summary of model equations
Notation
Mathematical assumptions on the data
Identification of natural variables in the equations of mass transfer
State-constraints
A ‘hyperbolic’ component
Vacuum oscillations
The solution class
Main theorems
Structure of the next sections
The natural variables: algebraic statements
The case of a general free energy
Special constitutive choice of the free energy
The regularisation strategy
Approximation scheme
Derivation of the global energy and mass balance identities
10. A priori estimates directly resulting from the energy equality
Conclusion
12. Compactness
12.1. Conditional compactness statements
12.2. Compactness of the total mass density
13. Existence of solutions
Full Text
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