Atomistic simulations of interfacial processes in energy materials
CECAM-FR-MOSER, Sorbonne University Pierre et Marie Campus Paris France
The energy transition aims at replacing fossil fuels by greenhouse-gas-free resources. Although the future energy mix is difficult to predict, it will certainly include larger shares of renewable sources, mainly wind and sun. Nuclear energy will continue to play an important role, not only because the current power plants may operate for several decades but also due to the emergence of new concepts of reactors. All these energy production involve the use of advanced materials: Wind farms extensively use magnetic materials, the next generation of solar cells will probably involve perovskites, and nuclear fuels are based on complex alloys to name a few. In addition, renewable energy sources suffer from strong intermittency. Even on a country scale, the fluctuations of wind and solar energy cannot phase well with the population needs, which induces the need to use large shares of coal or gas power plants to complement them. To solve this problem, the main solution would be to enable electricity storage using batteries or conversion towards hydrogen fuel through the use of fuel cells. In such electrochemical devices, the materials play a central role as well.
The long term stability of those materials is of particular importance. Nuclear reactors operate for half centuries, solar cells come with twenty-years guarantee and we would need batteries to cycle for >10,000 cycles to reduce their cost and their carbon fingerprint. This means that it would be necessary to account for the ageing of the materials, which is characterized by corrosion and chemical reaction issues.
In addition, energy storage materials (ESM) typically have to undergo some transformation between at least two metastable states (phase space domains of relatively high probability) of different thermodynamic potentials, one which stores the energy under chemical and/or mechanical form and the other one which releases it. All these problems involve the (trans)formation of solid-liquid and/or solid-solid interfaces.
Over the past decades, the development of simulation methods enabled the very efficient characterization of the equilibrium properties of materials. In particular, density functional theory and molecular dynamics have become essential tools for the interpretation of experimental results, and they are now involved at the initial stages for prediction purposes, with the development of consortiums such as the Materials Genome Initiative (https://www.mgi.gov/) or MARVEL (https://nccr-marvel.ch). The organisers of this workshop have recently created the MAESTRO (MAterials for Energy through STochastic sampling and high peRformance cOmputing) consortium, at the Institut des Sciences du Calcul et des Données (ISCD) of Sorbonne University in Paris, combining mathematicians, physicists, chemists, and computer scientists, precisely to provide multidisciplinary and transdisciplinary insights to these challenges.
In the case of energy applications, simulations have for example played a key role in:
-characterizing the electronic structure of Li-ion battery electrodes [1,2] and suggesting new cathode materials  or solid-state electrolytes 
-providing useful descriptors for ranking materials for catalyzing the reactions involved in the electrochemical production of fuels  and exploring the impact of the structure of the liquid on the energetics of water reduction 
-understanding the capacitive energy storage mechanisms in nanoporous carbon electrodes  and metal-organic-frameworks 
-identifying key chemical species involved in the transport of CO2 inside molten carbonate fuel cells 
Fabio Pietrucci (Sorbonne University) - Organiser
Benjamin Rotenberg (CNRS and Sorbonne Université) - Organiser
Antonino Marco Saitta (Sorbonne University) - Organiser
Mathieu Salanne (Sorbonne University) - Organiser
Rodolphe Vuilleumier (Sorbonne Université - ENS-PSL) - Organiser