Redox Flow Hybrid Zinc / Manganese – REDZIM

In the current scenario of energy transition, batteries for large-scale grid storage require low cost, high safety, low maintenance, high number of charge/discharge cycles, and calendar life, and for some services high power. Redox Flow Batteries (RFB) are particularly well suited to meet these requirements since they cover a power/energy range from several kW/kWh up to tens of MW/MWh and they are designed for longer storage periods compared to most other storage technologies. However, installation and maintenance costs are still the main barriers for penetration of storage on the grid. In this context, research on new cell configurations and on the identification of new alternative redox partners and on the membrane separating them, is still needed.

REDZIM project aims to develop a hybrid Zinc/Manganate-Permanganate Redox-Flow system with volumetric energy densities up 30% higher than that of current vanadium-based systems (25-35 Wh/L - VRFB). This can be achieved thanks to a high discharge voltage (1.8V, 40% higher than VRFB), a very high energy density catholyte (theoretical is above 160 Wh/L) and a thick porous zinc anode. The system energy density can thus reach about 40Wh/L. In addition, the proposed system is also particularly respectful of environmental constraints and uses abundant, low cost and safe active materials like zinc and manganese dioxide.

The potential of the hybrid Redox Zn/Manganate-Permanganate system has been checked and confirmed through first proof of concept experiments. However, to reach the expected performance, LPPI/CY Cergy Paris Université, Sunergy and EDF will develop three key elements dedicated (1) a high-capacity rechargeable porous zinc anode (2) a new stable cathode in the optimized permanganate based-electrolyte and (3) a tailored ionic exchange membrane adapted to the chosen redox couple being able to decrease manganese cross-over, detrimental to the coulombic efficiency. These three elements will be then assembled in 70cm3 cells of 10Ah capacity with catholyte circulation to evaluate energy, power, and lifespan with different combinations of membrane and electrolytes. Finally, two 5V-10Ah 3 cell demonstrators (with and without anolyte circulation) will be built and tested to analyse intra-cell interactions.

Finally, the REDZIM battery aimed at stationary storage, is particularly respectful of environmental constraints, uses a non-toxic aqueous electrolyte and is safe. This ambitious but achievable project brings together two industrial partners (Sunergy and EDF), a battery manufacturer and an end-user, with an academic partner (LPPI). These three partners have previously worked together in ANR projects in addition to close bilateral collaborations, which shows the solidity of the partnership. The completion of a demonstrator evaluated at TRL4 will prepare the way to a demonstration at TRL5 and higher with an enlarged consortium.