COordination complexes with Multi Electron Transfers as ion-battery Electrode – COMETE

Today, two different types of active materials are mainly used for Li-ion battery system: inorganic and organic compounds. By combining the advantage of both in a sole material, i.e. electron transfer centered on both the metal and the organic moieties, coordination polymers are a very interesting family of material to develop a new kind of cathode material. Their ability to present multiple reversible electron transfer will permit to reach a high specific capacity. Moreover, their huge versatility and their easy-to-tune redox properties are major advantages to control the potential windows (avoiding electrolyte degradation) and the solubility. The COMETE project will focus on earth-abundant-metal coordination complex polymers of Cu and Ni in redox-active ligand backbone. In our system, a theoretical capacity greater than 200 mAh.g-1 can be reached in a large potential window which does not penalize the overall energy of the device. Moreover, the insolubility of the material is ensured by integrating the coordination complex in a low mass host polymer as polyphosphazene, adding a safety flame retardant property. In a first step, complexes will be synthesized and characterized physiochemically and electrochemically, from the molecule up to the polymeric state. In parallel, ab initio calculations will permit to estimate the working potential(s), the local geometry changes of each complex coupled to the electron transfer(s). Electrochemical/ab initio investigations will enable to select the best candidate in terms of kinetics of the electron transfer (high C rate expected), high stability (durability) and energy (high E° values). Finally, the materials will be tested under battery conditions (Li, Na…) focusing on the durability of the system. Based on positive previous results, COMETE is an innovative project that allow to propose a new class of active high capacity and eco-friendly material for electrochemical energy storage device.