Hybridisation of battery systems for stationary energy storage The objective is to develop and demonstrate optimised innovative battery storage systems based on hybridisation. The resulting storage system can be engineered either by the twinning of distinct systems, or internal hybridisation of cells and control systems. Focus should be on cell and stack design, on advanced battery management systems and on high-level, hybrid storage control systems. The hybrid storage systems may for example be optimised for one or more of the following applications:Stand-alone provision of services to the interconnected pan-European gridProvision of services to island gridsProvision of services in weak distribution gridsProvision of services in private grids such as industrial parksProvision of load levelling for EV charging service stations. The activities are expected to bring the technologies from TRL 4 to TRL 6 (please see part G of the General Annexes). The battery systems should have optimal sustainability throughout the entire supply chain, including the substitution of critical raw materials. The systems should be demonstrated in a relevant environment and at a scale that allows future business cases to be developed.The Commission considers that proposals requesting a contribution from the EU of EUR 3 to 4 million would allow this specific challenge to be addressed appropriately. Nonetheless, this does not preclude submission and selection of proposals requesting other amounts. Advanced batteries are expected to play a major role in electricity grid management in systems with a high share of renewable electricity. The need for simultaneously providing multiple services (e.g. artificial inertia, frequency regulation, renewables balancing, load levelling, backup power and longer-term energy storage) requires compromises between power needs and energy needs. Hybrid battery systems can provide the ability to optimise power/energy performances by the combination of different technologies. Such hybrid systems would reach better business cases by mixing the contribution to different services and/or products. This challenge is in line with the identified priorities in the context of the SET-Plan [[https://setis.ec.europa.eu/sites/default/files/set_plan_batteries_implementation_plan.pdf]]. Increased competitiveness of electrical energy storage by balancing power needs with energy needs, providing a more efficient system with a longer and better performing lifespan, and by optimising balance-of-plant and installation costs. Project results should put the energy storage cost on the path to fall below 0.05 €/kWh/cycle by 2030.