Safety assessment of flow battery electrolytes - SABATLE

The problem addressed

Redox flow batteries are an emerging technology for medium and large-scale stationary energy storage and are considered as a viable option to buffer fluctuations in the energy grid. These fluctuations are caused by the increasing share of renewable energy (e.g. solar and wind energy) whose production is dependent on weather and seasonal conditions. The core elements of a redox flow battery (RFB) are two tanks filled with the electrolytes. Currently used electrolytes feature several issues such as limited regional availability, stability, volatile price, lack of sustainability and – often neglected – significant toxicity. In SABATLE, we aim at investigating the safety and (nano)toxicity aspects of current and emerging electrolytes in redox flow batteries as well as the corresponding environmental impacts by performing a life cycle assessment of the whole life cycle from resource extraction to the end-of-life.

Keywords: ecotoxicity nanotechnology lifecycle assessment

Research questions

The project focuses on toxicity aspects of an emerging technology, namely redox-flow batteries. This topic has not been addressed in scientific literature so far. In particular, we screen the toxicity and environmental impacts of currently available redox flow battery electrolytes (e.g. vanadium) and compare them to organic electrolytes (derived from 2-methoxyquinones) from a renewable feedstock (lignin) currently being developed at some of the partners. We follow a holistic approach using different tools, databases and extensive toxicity testing (human toxicity, ecotoxicity, nanotoxicity) which never has been applied to redox flow battery electrolytes so far. In SABATLE, we explore the whole value chain of the electrolytes - from raw materials to electrolyte production to after-end-of-life and provide a detailed assessment of the involved processes and materials. We will perform life cycle analysis and impact assessment to reveal the environmental performance of the lignin-based system compared to its conventional counterparts as well as to highlight hotspots in life cycle stages and processes. Further, the inclusion of SaSbD in organic redox flow battery design is an innovative aspect and unprecedented in the field of redox flow battery electrolytes. In contrast to current redox flow battery electrolytes where environmental and hazard assessments have not been addressed, this project offers an opportunity to reduce potential hazards and environmental impact of an emerging technology.

Scientific disciplines: chemistry/chemical engineering

Expected outputs

The main objective of the proposal is to assess currently used and emerging electrolytes in redox flow batteries towards their (nano)safety and sustainability aspects and to provide design guidelines to make such electrolytes inherently safe throughout the whole value chain. The specific objectives (O1-O4) are aligned with the call objectives (safety of the energy storage system; risk assessment of impacts on human health and the environment; safety of the production process; SaSbD principles; public concerns, governance, standardization) O1: SaSbD concept development to inherently improve both, the safety of the electrolytes and the sustainability approach throughout the whole value chain (→WP2, WP5). O2: Testing of electrolyte solutions in zebrafish, algae and daphnia to assess their human toxicity and ecotoxicity, including consideration of accidents and after end-of-life scenarios including nanotoxicity (→WP3). O3: Life cycle assessment of the electrolytes from production to after end of life including recycling issues (→WP4). O4: Provide results for the governance of advanced materials/nano-materials, considering and contributing to OECD-testing guidelines and standardization (→WP5, WP6). The project will generate outputs of relevance to the following stakeholders:
  • Regulatory bodies: Real-life relevant knowledge on the applicability and/or identify the need for electrolyte modifications, as well as a blueprint for applying the SaSbD-concept to nano-enabled electrolytes will be established.
  • Energy suppliers: The development of safe, sustainable RFB electrolytes gives them an opportunity to extend the renewable energy production towards sustainable energy storage in the form of RFB systems.
  • Public bodies (e.g. municipalities), the results will provide the opportunity to assure supply security for critical infrastructure using safe and sustainable RFB technology with lowest possible environmental impacts. This will also increase acceptance on a socio-political and community level.
  • Redox-flow battery (RFB) manufacturers: the results provide a guideline to improve their environmental impact of their technology in both production and operation, thereby creating unique selling points over non-sustainable competitors.


The approach is divided into 6 work packages that will cover all aspects and objectives (O1-O4) related to the safe redox flow batteries from an electrolyte point of view. This includes a coordination & management work package (WP1), 4 scientific work packages (WP2-WP5) and a dissemination & communication part (WP6). The expertise in the consortium covers the whole value chain starting from the raw material and its production (Mondi AG), the conversion into electrolytes including modification (TUG), toxicity testing (Biobide), LCA (UG) and development of safe and sustainable guidelines including interaction with regulatory bodies and stakeholders (BNN).

Associated deliverables

How Green are Redox Flow Batteries?
Journal publication Creative Commons BY-NC published on 2024-02-19
Providing sustainable energy storage is a challenge that must be overcome to replace fossil-based fuels. Redox flow batteries are a promising storage option that can compensate for fluctuations in energy generation from renewable energy production, as their main asset is their design flexibility in terms of storage capacity. Current commercial options for flow batteries are mostly limited to inorganic materials such as vanadium, zinc, and bromine. As environmental aspects are one of the main drivers for developing flow batteries, assessing their environmental performance is crucial. However, this topic is still underexplored, as researchers have mostly focused on single systems with defined use cases and system boundaries, making the assessments of the overall technology inaccurate. This review was conducted to summarize the main findings of life cycle assessment studies on flow batteries with respect to environmental hotspots and their performance as compared to that of other battery systems.

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Presentation at SAF€RA's 2022 symposium
Symposium presentation Creative Commons Attribution published on 2022-08-23
Sabatle project final report
Final report published on 2024-02-19
The SABATLE project was one of the first of its kind to adapt and employ the use of the Safe-and-Sustainable-by-Design approach to energy storage systems. As energy storage system we chose organic flow batteries, which aim at replacing the electrolyte, namely commercially available vanadium against biobased redox active molecules. The SSbD considerations included the value chain from cradle to grave, included social LCA impacts as well as toxicity testing of some compounds. Application of the SSbD approach showed that by analysis of all process steps, the safety of the overall process can be significantly increased. The main outcome of the project was a case study which was presented at the EuroNanoforum in Lund 2023 and submitted for publication in December 2023. It highlighted that the implementation of SSbD during technology development is capable to design better processes from both economic, ecologic and safety point of view. Another important outcome of the project was the analysis of current LCA methods to assess flow battery technoeconomic and environmental performance where we identified several methodological shortcomings which were summarized in a ChemSusChem Paper published in early 2023. In addition, the project was presented to a variety of stakeholders and was disseminated in many conferences on national and international level (e.g. American Chemical Society meeting). SABATLE also served as the seed for two more funding initiatives which both started in September 2023 (Safera SUESS, SSbD, LCA of post-lithium ion batteries and EIC VanillaFlow, toxicity of redox active molecules).

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Participating researchers

Stefan Spirk (Institute of Bioproducts and Paper Technology, Graz University of Technology, Austria) — project coordinator

Werner Schlemmer (Institute of Bioproducts and Paper Technology, Graz University of Technology, Austria)

Johanna Scheper (BioNanoNet Forschungsgesellschaft, Austria)

Susanne Resch (BioNanoNet Forschungsgesellschaft, Austria)

Claudia Mair-Bauernfeind (Institute of System Sciences, Innovation and Sustainability Research, University of Graz, Austria)

Tobias Stern (Institute of System Sciences, Innovation and Sustainability Research, University of Graz, Austria)

Leo Arpa (Mondi AG, Austria)

Arantza Muriana (Biobide, Spain)

Iñaki Iturria (Biobide, Spain)

Oihane Jaka (Biobide, Spain)

Ana Isabel Puertas (Biobide, Spain)

Juan Carlos Solis (Biobide, Spain)

Funding organizations

OSALAN (Spain)

BMK (Austria)

More details

Duration 2021-01 to 2022-12
Contact email
More information

Information last updated on 2021-03-22.

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