Electrochemical energy storage devices are destined to be key technologies to alleviating the intermittent and fluctuating nature of renewable energy sources (1). In particular, Redox Flow Batteries (RFB) have been recognized as a viable technology for the integration and balancing electricity grids due to their ability to decouple power and energy. However, wide-spread implementation of conventional RFBs is limited by some obstacles related to low abundance, toxicity and high cost of vanadium redox compounds, and the poor-performing and expensive ion exchange membranes used to separate catholyte and anolyte compartments (2).
Here, we present an innovative concept of Membrane-Free Battery which proposes to eliminate any separator or membrane in the cell by using immiscible redox electrolytes (Fig. 1). Moreover, the metal-based redox species are replaced by cheap and abundant organic redox molecules that can be specifically designed to provide high solubility and adequate redox potentials. As result, this disruptive technology is hugely versatile with respect to the nature of the electrolytes (aqueous / non-aqueous) as well as the type of organic redox species dissolved in each electrolyte (Fig. 1). To demonstrate the feasibility of this concept, we report here a spontaneous biphasic system formed by an acidic solution and an ionic liquid both containing dissolved quinoyl species that behaves as a reversible battery without any membrane or separator (3). The electrochemical performance of this Membrane-Free battery and the new challenges and future opportunities of the technology will be discussed.
Figure 1. a) Scheme of our Membrane-Free Battery concept. b) Versatility of this concept by using different combinations of immiscible electrolytes and their corresponding characteristics.
References:
- Z. Yang et al., Chem. Rev. 111, 3577–3613 (2011).
- a) H. Prifti, A. Parasuraman, S. Winardi, T. M. Lim, M. Skyllas-Kazacos, Membranes (Basel). 2, 275–306 (2012). b) W. Wang, V. Sprenkle, Nat. Chem. 8, 204–206 (2016). c) J. Winsberg, T. Hagemann, T. Janoschka, M. D. Hager, U. S. Schubert, Angew. Chemie - Int. Ed. 55, 2–28 (2016).
- P. Navalpotro, J. Palma, M. Anderson, R. Marcilla. Angew. Chem. Int. Ed. 56, 12460 –12465. 2017
