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Scientists from the University of Freiburg and colleagues replace a critical raw material used in redox flow batteries with a sustainable one.
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Schematic representation of the electrochemical reactions proceeding during charge/discharge of the all-MFB.

27th of May 2021

One of the biggest challenges of today and in the near future is the development of large‑scale electrical energy‑storage, which is important for the integration of intermittent renewable energy­ sources into the electrical grid.

Next to the well‑known lithium‑ion batteries (LIB), redox‑flow batteries (RFB) are an attractive alternative. However, regardless of the respective battery system it is important to replace critical and less abundant elements with elements that are sustainable. For this purpose, it is important to establish new electrochemical reactions that can be used in batteries. For these reactions, materials based on “green” elements have to be used, which also show a good performance regarding efficiency and lifetime.

The benchmark RFB shows an exceptionally long lifetime coupled with a very high energy efficiency. However, the respective chemistry is based on the critical element vanadium.

A team of scientists led by Prof. Dr. Ingo Krossing from the Institut für Anorganische und Analytische Chemie who is also a member of the Freiburger Materialforschungszentrum (FMF), together with Prof. Dr. Sebastian Riedel (Freie Universität Berlin) and the Fraunhofer ISE, successfully developed a new chemical system for an application in a redox‑flow battery. In this system the critical element vanadium was replaced with the sustainable element manganese. Although the respective electrochemistry is completely new in batteries, an acceptable efficiency and a long lifetime was achieved.

Behind the simple replacement of the active material (manganese instead of vanadium) lies a completely new approach for the utilization of the sustainable manganese. The deposition of elemental manganese is combined with the oxidation of Mn in the oxidation state +II toward Mn +III, which has not been used so far for the storage of electrical energy in batteries. In addition to the utilization of the sustainable manganese, the energy density is more than doubled compared to the benchmark RFB system based on vanadium.

The results of this new and sustainable research was now published in Advanced Energy Materials.

Krossing states that: „With the electrolytes published in our article it is possible to achieve energy densities up to 74 Wh L−1.” He further says: “This is especially remarkable, because we exclusively used the sustainable element manganese as active material”. Although further improvements of this battery system are necessary, according to the chemist from Freiburg, he also says: “This system describes a new and very promising design for sustainable large‑scale electrical energy‑storage”.

 

Original publication:

Schmucker, M. et al., Krossing, I. (2021): Investigations toward a Non‑Aqueous Hybrid Redox‑Flow Battery with a Manganese Based Anolyte and Catholyte. In: Advanced Energy Materials. DOI: 10.1002/aenm.202101261