Eutectic Systems as Sustainable Electrolytes for Energy Storage

MIT PIs:
Donald R. Sadoway – John F. Elliott Professor of Materials Chemistry

PT PIs:
Hugo Gonçalo da Silva Cruz – Faculdade de Ciências e Tecnologia da Universidade Nova de Lisboa (FCT – UNL)

Abstract: Energy storage is at the core of the process and needs to meet the requisites of a decentralized zero carbon energy society. Conventional solutions “on the shelf” include batteries and carbon supercapacitors, fulfilling, respectively, the energy and power needs. Although the solution to meet simultaneously energy and power requirements is hybridization of batteries and capacitors, this is an expensive technology and imposes complex management systems and power electronics. Simpler plug-in devices are certainly much more attractive and flexible. Thus, the development of devices, like supercapacitors (SC), that combine increased energy density at high power, is essential. The discovery of sustainable electrolytes, all tailored to meet this requirement, are the key to enable the success of the next generation of electrochemical energy storage devices. Different roadmaps, including Battery 2030+, stress the need for novel systems, based on green chemistry routes, to improve electrochemical metrics and safety. The novelty of this project relies on the development of novel electrolytes based on eutectic systems and its gels tailored to be efficient integrated in redox SCs, while reaching increased capacitance and stability in the long run. The expected synergies established between our research group (expert in eutectic systems) and Prof. Sadoway group from MIT as expert in energy storage devices including SCs is crucial for the success of the project. The proposed eutectic systems or Deep eutectic solvents, DES (liquids or gels at room temperature) should present low viscosity, high conductivity (>10-3Scm-1) electrochemical potential window up to 3 V, large operational temperature range (-50ºC to 100ºC), low cost and high wettability on the electrode material. This can be achieved by chemical tuning taking advantage the characteristics of eutectic systems. DES are considered sustainable materials formed by the suitable mixture of hydrogen bond donors and acceptors and they can be very promising for application as electrolytes in energy devices. In this matter, a new and yet unexplored approach involves a hybrid system based on hydrophobic or hydrophilic DES and gel DES (development of gels by the combination of DES and different gellators such as polymers and silica nanoparticles), which can efficiently prevent competitive reactions, allowing higher wettability between the electrolyte/electrode will be explored. Their characteristics will be tailored to improve the capacitance of redox SCs based on selected electroactive materials. Our original concept goes far beyond the state of the art, and it is definitely high risk-high gain because: (i) it involves novel concepts at the level of engineering of the DES system to boost the response of specific electrodes. This concept also brings high potential to create disruptive impact on different electrode materials used either in SCs or modern batteries (this task will be done in strictly interaction with MIT group). (ii) the challenges inherent to ionic conductivity, viscosity and stability of the novel electrolytes to be placed in contact with electrodes, taking advantage the expertise of team members. We believe that our vision, skills and competences will deliver significant breakthroughs and innovative solutions to enable more reliable electrochemical energy storage SCs which are crucial devices in the energy transition. Finally, this team has outstanding experience in sustainable chemistry, material science and electrochemistry areas connected with strong expertise from MIT researchers in energy solutions showing an impressive track record in novel electrolytes and materials for SCs energy storage. No doubt, a unique highly skilled and collaborative team to drive this challenging project to success.