International audienceFerroelectrics materials have been tremendously attractive since the 40 s with the discovery of ferroelectricity in metal oxide perovskite materials and more precisely in barium titanate. Due to their high potential for industrial applications, intensive research has been carried out to better understand their behavior and develop processes to produce them. Trying to face the down scaling demand of high quality particles towards the nanometer range, some conventional methods such as the solid state one reach their limits. The development of other processes are thus required and the synthesis in supercritical fluids can be considered as a promising alternative. This technology exhibits very interesting characteristics such as fast continuous synthesis (few seconds) of high quality nanoparticles (well crystallized nanoparticles with narrow size distribution) with controlled composition (Ba1−xSrxTiO3 with 0 ⩽ x ⩽ 1) at intermediate synthesis temperatures (<400 °C) with the use of non-toxic solvents (water, ethanol). Reaching the nanometer size range, the intrinsic properties of ferroelectric materials change compared to the bulk. Consequently a deep study concerning the crystalline structure, the presence of defects and the surface chemistry of those nanoparticles has to be achieved to control their properties for further use in functional devices

The growing demand and production of lithium‐ion batteries (LIBs) have led to a critical concern regarding their resources and end‐of‐life management. Consequently, LIB recycling has emerged as a prominent topic in academia and in industries, driven by new worldwide governmental regulations and the increasing gap between the supply and demand of critical and strategic raw materials. Widely considered as a more sustainable and cheaper recycling method compared to pyrometallurgy and hydrometallurgy, direct recycling currently grabs the spotlight. This perspective provides insights and outlooks on the chemical and technological challenges of the innovative direct recycling approach for LIBs, addressing both the production scraps and batteries at their end‐of‐life (EOL). Technological advancements, changes in battery chemistry, along with the LIB market dynamics and collaborations between battery makers and recyclers, are key drivers of LIB waste recycling. While production scraps lend themselves well to direct recycling, EOL batteries encounter challenges in adopting this novel recycling technology. Besides, the need to assess novel direct recycling processes using Life Cycle Assessment (LCA) is also important for identifying eco‐design strategies and optimizing the processes, leading to a more sustainable energy storage system.

Supercritical fluid synthesis offers an attractive and unique method to produce metal oxide nanoparticles such as barium strontium titanate (Ba_1−xSr_xTiO₃ with 0 ≤ x ≤ 1). This synthesis pathway has the advantage of producing high quality, highly crystalline nanoparticles in a narrow size range, with accurate control of the elemental composition not easily afforded by other methods of production. Coupled with moderate reaction temperatures and short reaction times, this method could be an environmentally preferred synthesis route compared to conventional synthesis pathways. This paper examines the potential environmental impacts leading from the lab-scale supercritical synthesis of 1 kg of Ba_0.6Sr_0.4TiO₃ nanoparticles of an average size 16 nm using the approach of an anticipatory life-cycle assessment. A cradle-to-gate assessment was completed, estimating the impacts across resource extraction, material processing, and production of the nanoparticles, while excluding any associated use-phase or end-of-life considerations. The life-cycle assessment highlights a number of ways by which the environmental profile of the supercritical synthesis of barium strontium titanate nanoparticles could be improved. Lab-scale synthesis was bound by physical constraints of the reactor, whereby the precursor concentration was kept artificially low. Being able to synthesize nanoparticles with precursor concentrations of 0.1 and 1.0 molar would reduce the average life-cycle impacts by nearly 81% and 95%, respectively. Additionally, the recovery and reuse of solvents at high recycling rates (e.g. 90%) could reduce average life-cycle impacts by 56%. At high precursor concentrations and solvent recycling rates, the environmental performance was further limited by the precursors, namely barium and titanium alkoxides, which have high upstream life-cycle demands (i.e. isopropanol production and metal processing). General impact reductions were seen as the ratio of strontium : barium increased. Further reductions could be achieved by replacing the barium, strontium and titanium alkoxides with precursors having better life-cycle profiles such as barium and strontium acetates or barium and strontium hydroxides.