Abstract
To improve the performances of Li-Ion batteries, technological breakthroughs are required. This imposes that the fundamental aspects related to the operation of these electronic devices are reconsidered. Accordingly, the methods of quantum chemistry can bring a valuable help, in particular to rationalize the microscopic electronic phenomena at the origin of the energy storage. Establishing a direct relation between the nature of the chemical bond (microscopic) and the chemical properties (macroscopic) of materials is thus one of the main objectives of this thesis. The work explores both methodological aspects and applications. It aims at proposing simple methodologies of analysis, to study electrochemical reactions from a theoretical point of view, and to rationalize the microscopic mechanisms involved during the battery charge and discharge. The systems studied are the Li-intercalated graphite compounds (Li-GICs) and an hybrid material of MOFs type (”Metal Organic Framework”) based on ferric ions (MIL-53(Fe)). For Li-GICs, a new method coupling first principles DFT calculations with a statistical model derived from Bethe-Peierls was developed to account for the configuration entropy effects in the Li-GICs finite temperature phase diagram. The results obtained bring a new glance on the electrochemical processes induced by lithium, opening interesting technological prospects to cure the safety problems related to this electrode. For the MIL-53(Fe), the DFT+U method was used to account for electronic correlation effects and to reproduce the complex electronic ground-state of this system. The results obtained allowed us to determine the origin of the low capacity of this material with respect to lithium.