Lithium-ion batteries (LIBs) have received increasing interest thank to their high potential for providing efficient energy storage and low environmental impact. However, there are still concerns about the safety of LIBs; the increased number of explosion and fire accidents has raised significant attention in LIBs safety, limiting their commercialization and applications.
A battery consists of anodic and cathodic compartments separated by an electrolyte. Usually this electrolyte is based on organic solvents dissolving suitable lithium salts, which guarantees the well-known high power densities and energies characteristic of LIBs. However, these organic electrolytes are volatile and flammable, posing a several safety issues for the LIBs use.
A strategy to reduce the safety hazard in these devices is the replacement of the conventional liquid electrolytes with solid polymer electrolytes (SPE).
Among all solid polymers studied, the ion exchange membrane can be considered an interesting choice due to its single-ion property which can facilitate the fast Li+ transport and guarantees a Li+ transference number equal to one. Besides, this type of membranes does not require the addition of lithium salts which are unstable and corrosive. In this field, perfluoro-sulfonated polymers, such as Nafion membrane (DuPont) widely used as electrolyte in low temperature Fuel Cells, could be an innovative approach for the development of future polymer electrolytes for LIBs.
In this project, particular efforts will be devoted to develop and characterize advanced Li+-conducting Nafion membrane with higher ionic conductivity and stability. Powerful physical chemical and electrochemical characterizations will be used. Composite Nafion-Li membranes, obtained by incorporating functional inorganic additives, will be also considered. The electrochemical performances of the proposed electrolytes will be studied in Li/Li symmetric cells and in secondary cells using LiFePO4 as cathode materials.
The increasing demand for energy storage systems and electrical devices has been the motivation for intensive research in lithium-ion batteries.
This project aims to respond to the some E.U. fundamental requirements (EC Proposal for a Regulation on batteries and waste batteries (Dec 2020) and Batteries Directive: DIRECTIVE 2006/66/EC) about the development of sustainable and safe batteries to support green mobility and drive the transition towards a decarbonised society. An international tendency is to consider the solid state technology as a solution to replace the current Li-ion technology based on liquid electrolytes. Higher energy density and inherently safe batteries are needed.
In this context, polymer-based lithium metal batteries are considered one of the most promising Li-based energy storage systems, especially for portable devices and flexible technologies because they can minimise the amount of hazardous components used in the available lithium batteries, without undermining their performance.
This project is going to present solutions beyond the current state of the art of polymer electrolyte, developing high performance single-lithium polymer conductor making this technology competitive in these new energy markets.
Till now, many efforts have been devoted to design novel polymer electrolytes in order to increase the lithium ion conductivity and stabilize the electrode-electrolyte interface. In particular, three strategies have been studied (i) developing new bi/multilayer-polymer for SPE, (ii) exploring additives for SPE and (iii) optimizing the microstructure of SPE[1].
In spite of a great potential, these polymer electrolytes suffer from various issues e.g. too low ion conductivity, too high electrode-electrolyte resistance and low electrochemical stability. Firstly, improve the ionic conductivity is one of the most important challenges.
More attention should be paid to the design of practical and efficient lithium membranes. Constructing single ion conductive polymer electrolyte is an interesting approach to achieve a good ionic conductivity.
One of the most known single ion conducting polymer is Nafion (Dupont) which is widely used for proton exchange membrane fuel cell devices. It is popular as selective proton electrolyte with higher ionic conductivity and high mechanical and thermal stabilities. Given these reasons, Nafion membrane is considered as a promising lithium polymer electrolyte; some prior studies[2,3]confirm the potentiality about the lithiated Nafion membrane as electrolyte in lithium batteries even though there are still many obstacles to overcome for their practical applications.
In this overview, the project aims to enhance the ionic conductivity of lithiated Nafion electrolyte materials as well as improve their stability and make more stable and efficient the interface electrode-electrolyte.
From our background and expertise in the field of hydrogen and fuel cells[4,5], we will address our competence in advanced manufacturing low-cost and durable lithiated Nafion membranes in order to achieve the EU's objectives.
In the search of high ionic conductive polymer electrolytes, we also propose novel organic-inorganic composite membranes, formed by the addition of inorganic nanoparticles within a Nafion polymer matrix. Furthermore, advanced physical-chemical and electrochemical characterizations will be carried out thank to the collaboration with universities and research centers highly specialized in the development of innovative materials for energy sector.
To expand our knowledge and facilitate the progress of our research, international and national conferences will be considered as the opportunity to get some and new ideas, feedbacks and new perspective useful for understanding and improving the functional materials here proposed.
[1]Kaihua W., Xin T., Tianhua C., Shimou C., Suojiang Z. "Fast Li-ion transport and uniform Li-ion flux enabled by a double-layered polymer electrolyte for high performance Li metal battery", Energy Storage Mater., 32 (2020) 55-64.
[2]Nicotera I., Simari C., Agostini M., Enotiadis A., Brutti B. "A Novel Li+-Nafion-Sulfonated Graphene Oxide Membrane as Single Lithium-Ion Conducting Polymer Electrolyte for Lithium Batteries", J. Phys. Chem. C 123, (2019) 27406-27416.
[3]Gao J., Shao Q., Chen J. "Lithiated Nafion-garnet ceramic composite electrolyte membrane forsolid-state lithium metal battery", J. Energy Chem. 46 (2020) 237-247.
[4]Mazzapioda L., Lo Vecchio C., Danyliv O., Baglio V., Martinelli A., Navarra M.A "Composite Nafion-CaTiO3-d Membranes as Electrolyte Component for PEM Fuel Cells", Polymers 12, (2020), 2019-2023
[5]Siracusano S., Oldani C., Navarra M.A, Tonella S., Mazzapioda L., Briguglio N., Aricò A.S. "Chemically stabilised extruded and recast short side chain Aquivion® proton exchange membranes for high current density operation in water electrolysis". J. Membr. Sci., 578 (2019), 136-148