Integrated battery and electrolyser; Combining electricity storage and Power2Gas for a renewable future


To accommodate increasing amounts of renewable electricity from wind and solar power, grid scale electricity storage on daily (diurnal) and seasonal scales is required.1 The daily electricity storage would be most energy efficient in batteries, while seasonal storage scales require the conversion to synthetic fuels. These two directions have generally been treated as separate or even competing solutions. Here we study storage of electricity in a novel integrated battery electrolyser that is based on the extremely durable nickel iron ‘Edison battery’2, and the durable alkaline electrolyser. Initial results show that the overall energy efficiency in storing electricity in the Ni-Fe battery and in the electrolytic hydrogen gas can reach > 81% up to 90%. Since this is a new device we indicate it here for convenience as ‘Battolyser’. When becoming charged the battery forms in the positive electrode nanostructured NiOOH and at the negative electrode nanostructured metallic Fe that then start acting as efficient oxygen and hydrogen evolution catalysts respectively. Being both battery and electrolyser, our results demonstrate fast current switching capabilities. The novel battery-electrolyser urgently requires further research and development to reach its full potential for energy and power density. Here we propose to investigate the following aspects: 1) optimize electrode design for the novel dual purpose, 2) increase energy densities of the battery aspect, 3) the further enhancement of catalytic water splitting, 4) the quality of H2 and O2 separation under varying conditions, 5) the feasibility of electrochemical compression of the produced gasses, and 6) the potential reversible operation as a low cost iron-battery-electrolyser-O2 cell that minimises the Ni demand.

Important advances of the Battolyser are that now an extremely robust Ni-Fe battery technology becomes energy efficient by enabling the co-produced hydrogen to become a regular valuable product, and by integrating flexible amounts of hydrogen production. Furthermore the infrastructure costs are shared by two applications and the ‘capacity factor’ of the device is thus much larger than the separate functionalities. The users see this capacity factor, and the possibility to support the business case with both electricity and hydrogen supply, and grid stabilisation, as very important assets. Please see the Support Letters for additional remarks. We anticipate the integrated battery-electrolyser/battolyser to be a starting point for designing a robust, flexible, grid scale energy storage solution without precious metals. The novel device has close to full time applicability: as unlimited switchable power storage and hydrogen producer and as battery electricity source.


Project number


Main applicant

Prof. dr. F.M. Mulder

Affiliated with

Technische Universiteit Delft, Faculteit Technische Natuurwetenschappen, Chemical Engineering

Team members

Dr. A. Iranzo, R. Möller-Gulland MSc, Dipl.-Ing. B.M.H Weninger MSc


01/02/2017 to 03/08/2020