How rechargeable batteries are going green

The market for rechargeable batteries is growing at a rapid pace. It is currently dominated by lithium-ion batteries. There is, however, a limited supply of the raw materials required, such as lithium or graphite. The Centre for Solar Energy and Hydrogen Research Baden-Württemberg (Zentrum für Sonnenenergie- und Wasserstoff-Forschung Baden-Württemberg - ZSW) in Ulm has joined forces with other partners and is now developing an alternative without these scarce resources. The ORRCABATT project will focus on rechargeable zinc-manganese dioxide batteries for stationary applications. The advantage of this battery technology is that the only metals required are manganese and zinc. The metals are more eco-friendly than lithium and are also widely available. The ZSW wants to develop working battery prototypes in collaboration with universities, research institutions and industry partners and then prepare the ground to scale them up from the laboratory bench to the factory floor. The next step will be to run pilot tests. The Federal Ministry of Education and Research (Bundesministerium für Bildung und Forschung - BMBF) has earmarked 3.3 million euro in funds for the project over a period of three years.

One point in favour of zinc-manganese dioxide batteries is the global availability of zinc and manganese dioxide (brownstone), and another plus point is that recycling paths for these raw materials are already established. This means that the negative environmental impact is significantly lower compared to other types of batteries. The water-based electrolyte in the battery also guarantees a high level of safety. And they are cheap, with material costs of €15-50 per kilowatt-hour for such batteries undercutting the comparable values for lithium-ion batteries by a factor of two to three.

From battery to accumulator

Zinc-manganese dioxide batteries are now the global standard in non-rechargeable cells and can be purchased everywhere. They are not yet available, however, in rechargeable format as accumulators. The project partners now want to change this. This new type of battery could offer a cost-effective and eco-friendly storage solution for renewable sources of energy, such as solar power and wind energy, in the future.

With specific energy densities of up to 400 watt-hours per litre or 150 watt-hours per kilogramme, zinc-manganese dioxide batteries may store less energy than lithium-ion batteries but they can still be an efficient and inexpensive way of storing power. Other outstanding features are their extremely low susceptibility to thermal overheating and their non-combustibility, making them particularly safe for indoor applications.

The ORRCABATT project

ORRCABATT stands for “Optimised design for rechargeable and recyclable alkaline MnO2 batteries”. One key milestone in the project is the achievement of a prototype cell with a target energy density of over 100 watt-hours per kilogramme for more than 150 charge/discharge cycles. There are also plans to develop a demonstration battery with an energy capacity of over one kilowatt-hour. The project partners will also focus in their work on continuously improving the performance and service life of this zinc-manganese dioxide battery. The goal is to produce a scalable battery prototype which can then be put into mass production in industry.

The research scientists at the ZSW have already developed the first rechargeable zinc-manganese dioxide batteries with high energy content by means of innovative membrane technology and further system adaptations. These first prototypes boast exceptional cycle stability or – in other words – a long service life. The focal points of the research in the project in future will include intensive work on the further development of all the components of this first generation. In order to develop a deep understanding of the individual components, there will be an extensive characterisation of the battery components on a physical, chemical and electrochemical level.

The best materials will be identified in the project on the basis of life cycle assessments, and the right recycling routes will be developed with the specific requirements in mind. This holistic approach will enable a full assessment of the environmental impact right from the start and a recycling system fit for the future.

The project partners in the consortium are reputable institutions and enterprises, including the TU Braunschweig with the Institute of Energy and Process Systems Engineering and the Institute of Machine Tools and Production Technology, Chair of Sustainable Production & Life Cycle Engineering. Other partners include the Institute of Physical Chemistry at the Justus Liebig University of Gießen, the Institute for Decentralized Electrification, Entrepreneurship and Education, VARTA Microbattery, VARTA Consumer Batteries and, as associate partners, FUMATECH BWT and GRILLO-Werke.