Synthesis of fluorinated multimetallic cathodes for Lithium metal batteries

Lithium-ion batteries are widely used in the space industry to ensure the energy autonomy of satellites. However, there is a growing demand for higher energy densities for these devices. In this work, we took an interest in the development opportunity of so-called all solid lithium batteries (ASSB): indeed, these allow the use of metallic lithium in anode (capacity approximately 10 times greater than that of graphite currently) which could allow a significant gain in performance. In addition, this also enables the use of non-lithiated cathode materials, such as metal fluorides potentially doubling the theoretical capacities obtained with the best LiNi_xMn_yCo_zO₂ cathodes in current use. In this work, we considered an energy mix based on CuF₂ for its high redox potential, FeF₃ for its high theoretical capacity and MnF₂ for its cyclability. To improve the reversibility of these conversion materials, we have developed an innovative technique for preparing multimetallic fluorides by solid gas fluorination (multimetallic Template Fluorination MMTF) of templates such as Layered Double Hydroxides LDH as well as Prussian Blue and its Analogs PBA: this method can be generalized to other templates. This technique, proceeding by a structural (XRD, XAS) and thermal (TGA MS) preliminary study leading to a tuning of the fluorination protocol, enables the synthesis of fluorinated cathode materials which can maintain the initial template or mix fluorides intimately. The electrochemical properties are then improved both with respect to those of simple fluorides and those of ball milled fluorides with similar active redox sites composition. (author)