New aqueous ‘all Vanadium-Solid-Liquid redox flow batteries for conversion and storage of renewable energies – V-S-L

The present PRC deals with the Redox Flow Batteries (RFB) used for the conversion and the storage of renewable electrical energies under chemical form, as well as the reversal procedure.
The project, based on the knowledge acquired into the RFB “all-liquid-all-Vanadium/V-RFB” and the Semi-Solid lithium based RFB, introduces an entirely new (no works find bibliography) concept: “all-aqueous, all-Vanadium, Solid(crystalized V salts)-Liquid(dissolved V salts) Redox Flow Battery (VSL-RFB)”. It expects to overcome the limitations of the V-RFB (specifically ‘the low solubility->low stored energy ~40 kWh/m3), by “scientific” and “technological” actions enabling to i) bring new knowledge in the field, ii) to design, manufacture and optimize a VSL-RFB able to deliver 100 W.
The scientific and technical actions consist:
-to elaborate and characterize concentrated flowing suspensions containing more than 500 g/L of VSL, in order to increase the energy stored up to 350 kWh/m3, as well as to reduce the stored volume (ratio: 10mol/L/~1.6M=~6),
-to introduce nano-metric carbon black additive (KB) into the formulation, expecting to create: a) electronic percolation into the bulk, thus enhancing the electrochemical surface area of the collector (×5 Sgeom.) and consequently the answer in current of the reactor, and b) catalytic seeds for the ‘rapid’ V salts dissolution and precipitation,
-to intensify the electrochemical reactor by:
i) the optimization of the geometry, the shape and the structure of the electrolytic compartments enabling to control the non-Newtonian fluid flow, avoiding dead zones (uniform distribution of the residence time),
ii) the use of three dimensions electronic collectors (porous or milli/micro-metric scale grooved plates) enabling the increase of the electrochemical surface area (×5 Sgeom.).
The expected current density is 2 kA/m², (instead 0.6kA/m² for V-RFB).

The proposal is structured into two parts, each one constituted by two tasks, and each task leaded by a partner from a specific scientific domain. Fundamental characterization of the system is the target of the first part (Tasks 1 and 2).
Task 1 leaded by NAVIER/Coussot, focuses on the rheological and electrochemical characterizations of the above described formulations of V+ KB, and expects to propose the corresponding laws to help for the building of the battery. Specifically will be treated: a) the elaboration of the suspensions, b) the study of their electrochemical properties, c) their rheological behavior in defined reactor geometry.
The task T2 leaded by the LGC-INPT/Biscans, focuses on the kinetics of the V salts (Vs) phases-change i.e. Dissolution/Crystallization (D/C); it expects to understanding the mechanisms and to define the laws providing the D/C rates. The effect of the KB on the rate of the Vs (D/C) as well as the favored D/C locations in the reactor, will be examined.
The second part concerns more the innovative technological actions: Task 3, leaded by the LGC/UTIII-PS/ Tzedakis aims to design, and to optimize one module of the electrochemical reactor and then to build the prototype (100 W); Task 4, leaded by the LEPMI/Bultel, focuses on the modelling of the electrolytic compartments in order to access to the concentration profiles of all the V species, as well as the current density in the reactor.
The strategy chosen in order to achieve the objectives of the project consists of two points:
-The full treatment of the whole process of the VSL-RFB, which justifies the choice of the multidisciplinary and complementary consortium.
-The structuration of the skeleton of the project (mixing of the partners into the tasks) which, in addition to the planned meetings, enables high interactivity and favors ‘easy, significant and permanent’ exchanges.
Finally, this project, involves 247.5 person.month, for an overall duration of 42 months and presents a financial demand of 606 k€ on a total budget of 1.8M€.