Energy production and storage are great challenges to ensure the energetic transition. High energy density, low cost, with extended cycle life batteries must be developed to promote renewable stationary applications (solar and wind farm) and electrified transport. Since their market introduction in 1991, lithium (Li)-ion batteries are the dominant solutions to power small electronic portable devices and are now used in most of the modern hybrid and full electric cars. However, for all of these applications this accumulator is not fully adequate because its energy density should be increased by factor two at minimum to answer the demand of the market whereas their energy levels off at about 250 Wh/kg due to their maturity. In addition, the presence of flammable liquid electrolyte is a strong safety issue (fire, explosion). To overcome these limitations a solution is to replace the unsafe liquid electrolyte by an inherently non-flammable solid polymer electrolyte. In addition to safety, the other advantage of polymer electrolytes resides in their chemical and electrochemical stability toward metallic Li. This material is ideally suited as negative electrode because of its high specific capacity (3860 mAh/g). At the positive electrode side, an interesting active material is sulfur (S8). The specific capacity of sulfur is important (1675 mAh/g) and permits to envision Li-S8 batteries with a specific energy density in the order of 500 Wh/kg, roughly twice that of conventional Li-ion accumulator. However, many hurdles remain to be solved to favor this battery technology such as the lithium polysulfides dissolution in to the electrolyte upon cycling (redox shuttle effect) which impairs the delivered capacity and the faradaic efficiency, and the prevention of dendrite growth at the negative electrode leading to short-cut issues. In this context, the project proposes to design an all-Solid-state litHium sulfUr baTTery with a poLymer Electrolyte (SHUTTLE). The goal is to develop a reliable device based on a new generation of sulfur based accumulator in order to increase in the energy density and cyclability. One of the originality of the project corresponds to the investigation of the functioning and failure modes by operando analysis of batteries in order to optimize the positive electrode texture and the polymer electrolyte properties, and to deeply understand the dendrite growth processes at the negative electrode. As a perspective, the project will develop a test bench of microstructural and topological analysis of electrochemical energy storage devices during cycling by X-ray and Neutron tomography.

Gas separation by dense polymer membranes is a very promising alternative to the cryogenic distillation or adsorption separation processes due to its much lower energy costs. This is critical for chemical industries, where the separation of mixtures accounts for over 50% of the energy costs. More energy-efficient methods should improve economical viability and lower greenhouse gas emissions. In addition, membrane devices are compact and fairly easy to operate. Unfortunately, polymers do not perform well under harsh conditions since they tend to lose their structural integrity at high temperatures and pressures. The University of Twente, The Netherlands, has recently developed new hybrid ultrathin membranes based on inorganic POSS cross-linked with organic imides in order to improve the thermomechanical resistance while maintaining the gas-sieving properties. The synthesis is suited to large-scale production and these hybrid polyPOSS-imide networks are indeed able to perform under tougher conditions than conventional polymers. However, the aliphatic arms of the POSS precursors used so far are too flexible and prone to thermal degradation, which prevents their use above ~300°C. In addition, the gas sieving abilities are strongly dependent on the precursors, the cross-linking densities, the temperatures and the pressures. Furthermore, experiments under harsh conditions are difficult to carry out and it has not been possible to characterize them over a large range of high temperatures and pressures. The aim of MOLHYB is to exploit the possibilities opened up by this innovative class of materials in order to develop new hybrid membranes capable of performing at very high temperatures and pressures, based on a combined molecular modelling and experimental approach. During an initial collaboration with Twente, the LEPMI at the University Savoie Mont Blanc, France (LEPMI-USMB), has developed realistic molecular models of two polyPOSS-imides at one cross-linking density. We intend to design more robust materials within MOLHYB. Molecular dynamics simulations will be used at LEPMI-USMB to pre-screen a novel set of candidate polyPOSS-imides for improved thermomechanical resistance, i.e. up to at least 400°C, without compromising their gas separation function. Their physical and mechanical properties will be characterized at the molecular-level as a function of the precursors, the cross-linking densities and the temperature. Only the most promising structures will then be synthesized and characterized experimentally by Twente. In parallel, single-gas sorption and transport in the selected model polyPOSS-imides will be studied at LEPMI-USMB for penetrants with different plasticizing capabilities, i.e. N2, CH4, CO2 and H2S, under a full set of both normal and harsh conditions. The latter are industrially-relevant conditions that are difficult to attain safely in the laboratory. Twente will carry out single-gas permeation experiments under a limited set of conditions to validate the model results. This will provide ideal selectivities for CO2/CH4, N2/CH4, CO2/N2, H2S/CH4 and CO2/H2S separations under a large range of conditions. To assess the influence of mixed-gas reservoirs, LEPMI-USMB will also consider CO2+CH4+H2S mixtures. The novel polyPOSS-imide membranes showing both improved thermoresistance and optimized gas separation properties will then be assembled at Twente atop inorganic porous hollow fibres in order to obtain supported materials that can be used for upscaling. Based on this combined approach, MOLHYB should lead to better materials for selective separations under harsh conditions, i.e. with mixed-gas reservoirs at high temperatures and pressures. Since The Netherlands are not part of the countries selected for PRCI, Twente will entirely provide its own funding. The ANR demand only concerns the French partner LEPMI-USMB and is mainly aimed at funding a Ph. D. student.

All solid-state batteries based on thiosulfate solid electrolyte hold the promise of safer and more energetic batteries, especially once coupled to Li metal anode and high voltage cathodes. Unfortunately, it was demonstrated in the literature that their electrochemical stability window is far from optimal being very narrow (less than 1V). This is causing severe chemical degradation upon oxidation/reduction of the solid electrolyte, showing that the solid electrolyte is a very active player in the solid-state batteries. The decomposition products generated during oxidation/reduction are causing drastic increase in cell resistance as well as some structural/chemical changes both hindering the long-term cycling of solid-state batteries. On top of that, the mechanical stability of the solid-state batteries is also questioned, as during cycling, the electrode breathing will lead to volume changes generating stress i) in the composite electrode materials, ii) at the interfaces, and iii) in the electrolyte. The stress propagation will be soon translated into fractures at all pre-cited levels, affecting the lithium transport mechanism within the cell causing premature cell failure. As described in the literature, this chemo-mechanical degradation looks unavoidable. However, the literature is relying on the investigation of half-cells/full-cells to explain the chemo-mechanical degradation, but the solid electrolyte alone and especially its sintering/shaping could also be the main responsible of most of the pre-cited issues. Poor sintering, as an example, promotes chemical degradation and voids propagation, thus, getting a deep understanding of the sintering process prior to any electrochemical cycling is of utmost importance. We propose a multiscale approach based in operando characterizations at the laboratory scale and at large scale facilitate (synchrotron and neutrons) to fully understand the sintering process of the electrolyte and in particular to establish the relationship between structural/chemical/morphological/electrochemical parameters as a function of the pressure/temperature. To apply this methodology, novel special electrochemical cells will be developed to perform advanced operando-based techniques. Neutron diffraction will be used to follow the structural evolution during sintering process as a function of temperature/pressure, whereas X-ray tomography and FIB-SEM will be employed to follow the evolution of the porosity as a function of the pressure/temperature. Quasi elastic neutron scattering (QENS) owing to the contrast of lithium isotopes will provide information about Li ion transport whereas chemical decomposition will be investigated by X-ray absorption spectroscopy, etc. Once the sintering process will be fully understood, the solid electrolyte fully optimized will be then transferred to half-cell configuration (vs. Li metal) and the same methodology will be applied. Neutron imaging technique will be added to the pool of operando techniques to follow the Li ion transport as a function of cell cycling. Results from morphology/structure/chemistry gathered at this stage will be used to develop proper coating strategy and buffer layer to ensure electrochemical/chemical/morphological/structural stability. Again, once this goal will be reached, full cell investigation combining high voltage cathode vs. Li metal will be undertaken following the same operando-based approach. The results collected and obtained through this OpInSolid project will shed light on a forgotten player, the solid electrolyte. Based on the outcome, several strategies will be developed to tackle chemo-mechanical issues in sulfide-based solid state batteries.

R&D on anion exchange membrane fuel cells (AEMFCs) has shown tremendous progress in recent years, AEMFCs reaching now high power densities with catalysts based on platinum group metals (PGMs). While AEMFCs offer the long-term perspective to switch to PGM-free catalysts due to the high-pH environment, high performance AEMFCs with PGM-free catalysts at both the cathode and anode still needs to be realized. In addition, the chemical stability of AEMs and anion-exchange ionomers is still insufficient. In the DEEP project, novel AEMs and ionomers with improved stability will be developped as well as novel anode and cathode catalysts free of PGM. Down-selected materials will be tested in AEMFC for their initial performance and also for durability testing. DEEP is a collaborative project between 2 academic partners and one partner from the private sector.

Emission-free transport is a fundamental pillar for the energy transition towards a green energy landscape. Proton Exchange Membrane Fuel Cells (PEMFCs), using hydrogen (H2) and oxygen (O2), are at the forefront of the portfolio of practical solutions that are emerging on the market. However, Europe, and a fortiori France and Germany, has to develop a strategic positioning for research and development to maintain in-house the manufacturing of advanced and strategic technologies involved in the energy transition and thus preserve its independence; unlike as, e.g., batteries and solar panels production in spite of large investments. The present project proposal aims at identifying and unlocking obstacles limiting the implementation of promising O2 reduction reaction (ORR) catalyst materials, identified after fundamental and model investigations in well-controlled laboratory conditions, into efficient PEMFC cathodes. To this goal, a library of materials composed of state-of-the-art ORR nanocatalysts (octahedral, cubic, hollow, nanowires and spongy) will be built, and the synthesis processes will be scaled-up in a stepwise manner to reach volumetric quantities allowing MEAs manufacturing. The (i) structure and the chemistry of these nanocatalysts and (ii) the ionomer content and distribution within the cathode structure will be determined at each step of the membrane-electrodes assembly (MEA) manufacturing to rationalize changes of performance in model and real PEMFC systems. A specific diagnostic toolbox, combining advanced experimental techniques and modelling, will be specifically developed and the output of this toolbox will be used to adapt the ink formulation from which the MEAs are manufactured (catalyst content and chemistry, ionomer content and chemistry, solvent composition, use of additives). Strategies to mitigate issues related to low density of catalytic sites (highly-active ORR nanocatalysts usually feature large crystallite size), incomplete wetting of the catalyst by the ionomer and poor accessibility for O2 to the catalytic sites will be also developed. Finally, accelerated stress tests (ASTs) will be carried out. After characterisation, the results of these tests will help rationalizing why the degradation mechanisms may be different in simulated and real PEMFC operating conditions. Ultimately, the key findings of the project will be transferred to Heraeus and Symbio for industrial development. The ambitious research program proposed in the frame of the BRIDGE project requires efforts of scientific teams with broad interdisciplinary expertise in chemistry and physics, materials science and engineering. Therefore, this proposal brings together two groups at LEPMI/CNRS and ZSW, and two industrial partners Heraeus and Symbio. LEPMI/CNRS will use its expertise in the synthesis of ORR nanocatalysts and electrocatalysis using model electrodes to understand the structural, compositional and morphological changes occurring during elaboration of MEAs, while the ZSW group will engineer them to implement them in real-life PEMFC. The two industrial partners, Heraeus and Symbio, are a well-established catalyst materials manufacturer and an automotive equipment supplier designing and developing a large range of PEMFC related products, from specifically designed MEAs to a few hundreds kW systems, for electric vehicles, respectively. The BRIDGE project thus covers all the facets of a critical technology that is expected to grow further for the development of independent European-based solutions in the field of sustainable energy transition. It also intends to setup solid foundations for future original contributions from the French-German consortium in the field of PEMFCs electrodes technology/concepts, and its transfer towards the European industry.