(Keynote) To Honor Michel Armand: Developments on New Electrode and Electrolyte Materials for Batteries at the IMN

Abstract

A selection of recent developments at IMN will be reviewed on several research directions dealing with new electrode and electrolyte materials for batteries. We focus on innovative surface modifications of electrode components, new electrode materials, compositions and architectures, and failure mechanism upon cycling by in-depth characterization through coupled advanced techniques. We cover the topics of silicon electrodes for Li-ion batteries, positive and negatives for Na batteries, renewable organic aqueous batteries, and all-solid-state ionogel Li-metal batteries. Surface derivatization of powder oxide materials by molecular grafting modifies their interfacial chemical reactivity, thus increasing cycle life and decreasing self-discharge. Molecular junctions through double-side grafting between non-carbon-coated LFP and multiwall carbon nanotubes (MWCNT) enables original electrode architecture, leading to higher specific capacity and better capacity retention. Our recently synthesized lithium-doped PANI shows excellent performance both as bulk material and as thin layer coating of bare LFP particles. We are also developing organic materials for bulk application in the new generation of renewable organic batteries. New results in the area of organic aqueous batteries for renewable energy storage will be disclosed. In the Na-FePO4 system, we identified the intermediate phase as a fully ordered Na2/3FePO4 composition showing a vacancy ordering along the channels coupled with a Fe(II)/Fe(III) charge ordering. Ab initio DFT total energy and molecular dynamics calculations lead to the optimized structure of the Li2/3FePO4 phase, and show the Na2/3FePO4 phase is thermodynamically stable while the Li2/3FePO4 phase is metastable. In the domain of negatives for non-aqueous Na-ion batteries, we found GaV4S8 is a new material with high cycled capacity of 500 mAh/g and an atypical reaction mechanism. In the field of silicon negative electrodes, we show some examples of nanoscale STEM-EELS imaging of the reaction mechanism upon cycling, and we describe an electrode maturation process that improves the performance whatever the type of silicon, binder and conductive agent. We also identify the end-of-life mechanism that is different in half cell and in full cell. Ionogels, which are confined ionic liquids within various host networks, are developed in order to fabricate self-standing solid-state membranes, all-solid-state Li metal batteries, and all-solid-state supercapacitors with good performance. We analyze as well what are the needed criteria to obtain good cycling efficiency and durability of the Li metal electrode in contact with these ionogel solid electrolytes.