Future storage systems for the energy transition: Polymer-based redox-flow batteries

Introduction

The efficient storage of electric energy represents a major challenge for a successful energy transition, enabling the utilization of fluctuating renewable resources also as base load. Redox-flow batteries (RFBs) are the only type of battery where intrinsically power and capacity can be varied independently from each other, making this type of battery perfectly suited for scalable stationary applications.

Potential of Aqueous Electrolytes

RFBs based on aqueous electrolytes with organic/polymer active materials have the potential to be suitable alternatives for commercial metal-based RFBs, with a low CO2 footprint perfectly fitting the goals of the EU Green Deal.

Advantages of Polymer-Based RFB Systems

In particular, polymer-based RFB systems enable the use of cost-efficient dialysis membranes together with pH neutral table salt solutions as electrolytes. Nevertheless, systems still reveal restrictions in terms of:

1. Capacity
2. Lifetime
3. Temperature stability

FutureBAT Objectives

FutureBAT targets a breakthrough in the development of novel organic active materials for RFBs. This will be achieved by:

• Combining the search for new active entities with the improvement of current polymeric materials on the molecular level.
• Providing new functions/properties.

The key question will be how far polymeric electrolytes can be tuned by adjusting the molecular structure.

Advanced Polymer Structures

Advanced polymer structures (including (hyper-) branched structures) and colloidal systems (with varied morphologies) as well as novel hybrid organic systems will provide access to hitherto unknown properties, such as:

• New photo-rechargeable RFBs
• RFBs having all charged species within one single tank

New Sensor Systems

Furthermore, new sensor systems (SOC and SOH) will be applied, which will also form the basis for novel 3D-printed lab cells for (high-throughput) screening.

Expected Outcomes

As the outcome, pioneering breakthroughs in the field of polymer-based RFBs will be enabled, surely targeting high risk/high gain step-changing research but built upon the know-how of one of the leading international research teams in this rather new field.