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.

In France, water electrolysis using renewable energy is nowadays considered a promising solution for producing hydrogen without dependencies on fossil fuels. Among different types, polymer electrolyte membrane water electrolysers (PEMWE) are considered the most favourable technology for hydrogen generation from renewable sources. However, the lifetime of current PEMWE technology is generally much shorter than the target value in Europe. Optimizing PEMWE operating parameters has been considered a potential approach to mitigate material degradation and extend the PEMWE lifetime, but it has been difficult so far because PEMWE degradation and its correlation to the performance and operating parameters involves complex multiscale physicochemical phenomena. Project DuraPEME contributes to improve the durability of PEMWE by developing an artificial intelligence (AI)-accelerated multiscale degradation model. In parallel and in connection with the models developed, it will also propose accelerated stress tests for PEMWE. We will achieve this goal by 1) characterizing degradations from multiple scales; 2) developing and accelerating a multiscale degradation model 3) generalizing the model in different uses and powers. The project will adopt a highly interdisciplinary approach by integrating methods in PEMWE multiphysics, material science, numerical calculation, and machine learning. As outcomes, project DuraPEME will empower PEMWE technology with an efficient multiscale degradation model. The model will enable optimizing PEMWE operating parameters to mitigate degradations.

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.

Every year, more than 200 000 orthopaedic prostheses (knee, hip) and a huge (but unknown) number of dental implants are implanted in France. For an optimal efficiency, these implants have to be well integrated in bone. To favour osseointegration, dental implants rely on modification of their surface morphology, while a Calcium-Phosphate coating is often required on the surface of orthopaedic implants. Traditionally, these coatings are fabricated by plasma-spray, leading to well crystallized films in the most stable phases (mainly hydroxyapatite).Even though these plasma-sprayed coatings are commonly used on stems and metal-backs of hip prostheses, their efficiency is subject to controversy because of several drawbacks such as the excessive thickness of the coatings, their possible delamination leading to local inflammations, and the overly stable nature of the constitutive materials that do not favour reactivity. DECaP project aims at developing alternative coating techniques, less costly and leading more efficient coatings (with higher adhesion to substrate, more reactive to allow faster bone ongrowth and faster healing of the patient) potentially applicable to both dental and orthopaedic implants. The consortium will thus use ElectroSpinning (ES) and Electrostatic Spray Deposition (ESD) to fabricate (and characterize) osseoconductive coatings of optimized architectures, compositions and structures (amorphous or crystalline), on biomedical grade titanium substrates. We will aim at biologically reactive coatings such as out-of-equilibrium or amorphous calcium phosphates (highly difficult to stabilize as coatings by any other technique, thus their potential as osseoconductive coatings could never be assessed) or bioactive glasses (whose synthesis has never been attempted using ESD). Moreover, we will look for architectures that promote reactivity and mechanical adhesion to bone tissues: dense coatings with arborescent surface, and porous coatings with a large amount of porosity (easily obtained with ES), or even with a multiscale architecture (network of tubular pores inside a coral-like dense matrix). As a proof of concept, these findings will be applied to a real dental implant. The expected outputs of this project are: - Scientific: obtaining stable over time, out-of-equilibrium, reactive CaP or bioactive glass phases is a scientific challenge. Understanding how these phases are stabilized during the process could open the way to new materials with original properties (reactivity, transport…) - Industrial: after further development, the findings of DECaP project will allow biomaterial companies to implement new processes leading to innovative and efficient coatings for improved osseoconductivity of biomedical implants. - Societal: the improved osseoconductiviy of these implants will allow faster healing of the patients, thus better comfort, shorter treatments thus lower treatment cost and hopefully better long term success. Besides these cheaper coatings will help reduce the price of implants. DECaP consortium combines the competencies of three laboratories: MATEIS will bring its knowledge of calcium phosphates and extensive, in-situ characterization. LEPMI will use its in-depth understanding and practice of Electrostatic Spray Deposition, already applied with great success to the fabrication of Solid Oxide Fuel Cell components. LMI masters Electro Spinning, that was used (combined with sol-gel chemistry) to fabricate original and architectured materials.The synergy between the three laboratories will allow reaching our ambitious goals.

The challenge of the DURACELL project is to improve the durability of PEM fuel cells by optimizing the mechanical properties of the interfaces within the membrane-electrode assemblies (MEAs), where the electrochemical reactions take place. The latter are subjected to complex and variable mechanical stresses depending on the hygrothermal conditions related to the operation of the fuel cell, which can lead to the damage of its components and the shutdown of the system. The initial objective of the project will be to measure, identify and control the manufacturing parameters of the MEA that impact the adhesion between its layers. To that goal, specific mechanical characterizations will be implemented in order to quantify the level of adhesion at the interfaces of MEAs manufactured within the DURACELL project consortium. The measured properties will then be implemented in a numerical model in order to contribute to the prediction of the optimal physical properties of the MEA and its assembly conditions to limit the mechanical damage of its components. These results will be verified by comparing the lifetime of MEAs assembled under these different adhesion conditions, via in situ and ex situ accelerated stress tests (hygrothermal cycling and coupled mechanical/chemical degradation). These different tests will provide a better understanding of the mechanical/chemical degradation synergies that occur in the membrane and at the membrane|electrode|gas diffusion layers interfaces. They will also allow to unbundle the different mechanisms responsible for the degradation of MEAs in a system environment. The analysis of the results of the DURACELL project will lead to recommendations to be shared with the scientific and industrial community to limit the level of mechanical stresses undergone by the different components of a PEMFC, thus contributing to the increase of its life span in operation.