Throughout the project duration, key achievements were realised and they are listed below.
+ First direct visualisation of (O-O) peroxo-like dimers in high capacity layered Li-rich oxides by HRTEM is achieved (Science, 2016), hence ending the long remaining controversies about the role of the anionic network.
+ Provided a rationalisation of the anionic redox process by showing that a strong M–(O2) covalence is an absolute condition to ensure high electrochemical reversibility and to prevent O2 gas release from the structure at high states of charge, which is crucial application-wise (Nature Materials, 2016).
+ Studied the poor kinetics of anionic-driven redox process and understood the practical road-blocks of these materials (JES, 2016).
+ Demonstrated (Nature Materials 2017) the feasibility to trigger novel anionic redox process in oxides having three dimensional (3D) rather than two dimensional (2D) crystal structures, thus freeing the structural dimensionality constraints.
+ Designed a novel Li3IrO4 phase that push the limit of the anionic redox activity to 3.7 e- per transition metals – a record among all the cathodes so far investigated (Nature Energy 2016).
+ Uncovered “model” materials based on 4d or 5d metals, having either a 2 or 3 dimensional structures (ex: alpha or beta Li2IrO3). These compounds established a sound scientific platform for rationalizing the design of future anionic-redox-based cathodes and also helped unravelling the origins of practical roadblocks in Li-rich cathodes (Nature Materials, 2018, “Fundamental understanding and practical challenges of anionic redox activity in Li-ion batteries”).
+ Isolated a Na-rich phase Na2IrO3 phase which can reversibly cycle 1.5 Na+ per formula unit while not suffering from oxygen release nor cationic migrations. This work published in Chemistry of Materials turns out to be an impetus for the design of high energy Na-rich materials based on more sustainable elements than Ir as we are presently investigating.
+ Extended anionic redox to chalcogenides Li1.13Fe0.33Ti0.54S2 (LTFS) phase (Nature Energy 2020) with minimized voltage fade and hysteresis that presently serves as benchmark positive electrode materials for solid state batteries.
+ Successfully extended anionic redox to Na-based materials and prepared the first and unique so far O3-type NaLi1/3Mn2/3O2 layered oxide showing high sustained reversible capacity with no voltage fade while being moisture insensitive unlike other Na-based compounds (Nature Materials 2021).
+ Apart from battery materials, ARPEMA has shown the feasibility of extending the anionic redox process to catalysts for water splitting by establishing for the first time the correlation existing between the OER activity and stability for perovskites when triggering the surface oxygen redox (Nature Energy 2017).
+ Finally, beside materials and theoretical developments, innovative developments of new analytical techniques were also achieved. Some of them are as follows,
i) A new and versatile cell to conduct specific operando electrochemical quartz crystal microbalance (EQCM) measurements (Applied Materials & Interfaces (2020)).
ii) Demonstration for the first time of an optical calorimeter based on the use of optical Fiber Bragg Grating (FBGs) to monitor chemical and thermal events associated to the cycling of Li-rich oxides/sulfides based batteries (Nature Energy, (2020).
iii) The development of specific electrochemical cells for assembling and testing solid-state batteries. Some of these tools together with the help of an ERC-PoC-2016 had led to creation of a company, SPHERE ENERGY.
Altogether, these advances published in high impact journals (Nature materials, Science) have been widely cited and received unsolicited coverage in press worldwide.
