New silicon-based alloys and composites for all-solid-state batteries: from combinatorial synthesis by magnetron sputtering to mechanosynthesis
All-solid state lithium-ion batteries using sulphide-based electrolytes are among the most studied at present in order to improve energy density, safety and fast charging. Although lithium metal was initially the preferred choice for the anode, the difficulties encountered in its implementation and the performance achieved suggest that alternatives should be proposed. Silicon offers an interesting compromise in terms of energy density and lifetime. However, it is necessary to look at anode materials developed for all-solid state batteries. To this end, we propose to collaborate with CEA Tech Nouvelle-Aquitaine, which has set up a combinatorial synthesis methodology using magnetron sputtering, in order to accelerate the identification of new compositions of silicon-based materials. Libraries of materials with compositions gradient in thin films will be prepared at CEA Tech Nouvelle-Aquitaine and then studied at CEA Grenoble. The most promising compositions will then be prepared by mechanosynthesis and characterised at CEA Grenoble. Significant work will be carried out on milling processes in order to optimise particle size and homogeneity, as well as structure and microstructure. Attention will also be paid to integration in all-solid state cells, drawing on the laboratory's expertise.
Simulation of heterogeneities in battery cells using materials with lower environmental impact
The electrification of vehicles to decarbonize our activities faces a dilemma concerning batteries, their environmental impact and the supply of materials needed to manufacture them. The low-environmental-impact materials being considered today to meet these needs (LF(M)P, sodium-ion technology, etc.) have specific electrochemical characteristics that need to be anticipated before they can be used in large-capacity batteries. These two- or multi-phase materials have an electrical potential that is only slightly dependent on the state of charge. This characteristic favors the appearance of a highly heterogeneous state of charge in the cell. The complex mechanism is linked in particular to fast charging, which is very important for vehicles, and which creates significant heating at the heart of the cells. These heterogeneities limit battery performance and shorten their lifespan. In addition, the flat voltage profile and heterogeneities make it extremely difficult to diagnose the cell's state of charge and state of health. Yet this information is crucial for battery management that maximizes battery life.
Our laboratory is developing advanced modeling tools that enable us to simulate these phenomena. Using a highly detailed numerical model of a large cell, applied to realistic cycling conditions, the candidate will highlight the internal state of cells, which is difficult to access experimentally, and show how cycling, thermal management or diagnostic strategies need to be adapted for the more sustainable chemistries envisaged today. To do this, he will use CEA's software platforms and supercomputers, and draw on CEA/LITEN's expertise covering all technological stages, from materials to real-life cell testing.