Dear Colleagues,

In recent decades, the development and continuous growth of the renewable energy production has pushed researchers to look for the optimum method to store and convert back energy to solve the problem of the intermittent energy generation and thus to guarantee the electrical grid stability. Among all the systems utilized, electrochemical energy storage and conversion (EESC) devices, such as batteries, fuel cells, capacitors, etc., are very promising. Their development and increasing performances are mandatory for an efficient management of energy. However, these devices have not yet reached complete maturity in terms of performance and cost reduction. Among all the components that are necessary for the operation of these devices, the ion-conducting electrolyte is fundamental. The so-called ionomer-based (i.e., polymers with grafted ionic groups ) electrolytes, often in the form of a solid membrane, can conduct cations, anions, or both, and they have to satisfy a lot of different requirements, which are sometimes very challenging. They have to accomplish the following:

• guarantee a high ionic conduction;
• be as thin as possible;
• guarantee the electrical insulation between the electrodes (resist high current densities and to possible perforations);
• be stable at different temperatures and/or different relative humidities and/or environments;
• be stable over a long period of operation;
• be safe for the suitable application;
• have a low cost.

Many ionomers are available on the market today, and even more are the subjects of research. It is for this reason that we are pleased to invite you to this Special Issue of Membranes that is focused on the recent advancements in ionomers used as electrolytes in EESC devices. Original research articles (based on lab or pilot scale experiments, simulations, or reviews) are welcome above all in the field of membranes (included reinforced membranes, membranes realised with polymer blends, and composite membranes) but also of gel or dispersion in liquid solution of ion-conducting polymers of the last generation. Research areas may include (but are not limited to) the following: batteries, fuel cells and biofuel cells, redox flow batteries, micro-EESC devices, and electrolysers.

I look forward to receiving your contributions.

Dr. Luca Pasquini
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Membranes is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2700 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

• polymer electrolyte
• ionomers
• polymer membranes
• ionic conduction
• fuel cells
• batteries