Abstract
The rapid growth of the electric vehicle market as well as the increasing demand for energy storage worldwide involve the development of high energy density batteries. Increasing the energy density of batteries requires, for example, the use of metallic lithium (specific capacity ≈ 3860 mAh.g-1) at the negative electrode. In this regard, "all-solid" technologies based on solid sulphur-containing electrolytes, such as argyrodite Li6PS5Cl, are considered very promising. Major scientific barriers have been identified for this new technology. For example, when brought into contact with lithium metal, argyrodite (Li6PS5Cl) is reduced to Li2S, LiCl and Li3P, leading to the formation of an uncontrolled resistive interphase. In addition to chemical stability, the mechanical stability of this interface is also a major problem, which can lead to the formation of dendrites during electrochemical cycling. The main aim of the research work in this thesis, carried out in collaboration with Renault Group, was to understand and control the Li6PS5Cl /lithium metal interface. First, the mechanical stability of this interface and the impact of pressure on electrochemical performance were studied. These studies demonstrated the importance of the manufacturing pressure, as well as the pressure applied during cycling, on the ionic conductivity, as well as on the electrochemical stability in symmetrical cells and all-solid-state batteries. In a second step, using a solution coating method, the use of a protective layer of lithium chloride (LiCl), stable against metallic lithium and argyrodite, showed very promising results. Indeed, XPS analyses show a decrease in the chemical degradation of argyrodite towards metallic lithium. Atomic Layer Deposition of Al2O3 or Li3PO4 on argyrodite pellets also demonstrated a reduction in the chemical degradation of argyrodite at zero current