At month 36, the HELENA project has made substantial progress across its work packages.
WP1 continued overseeing project monitoring, quality control, and risk management. WP2 advanced testing and validation of HELENA battery cells for automotive and aerospace applications, integrating new aircraft concepts. WP3 focused on improving halide solid electrolytes, developing In-doped Li₃Y₀.₉₇In₀.₀₃Cl₄Br2 and selecting compatible cathodes (NMC622, NMC811). Several strategies were tested to stabilize the lithium–halide interface, but none fully succeeded. WP4 fabricated cell components and optimized extrusion processes, concentrating on 40 mAh monolayer pouch cells. WP5 defined handling conditions for raw materials and assessed humidity effects on electrolyte conductivity. WP6 developed testing protocols for EV and aeronautic use cases, coordinated with WP2 and WP7, and supported experimental setups for WP4. WP7 finalized modeling at atomistic, particle, and microstructural levels, linking experimental data to simulations. A physics-based cell-level model was developed and calibrated, awaiting pouch cell data for validation. WP8 demonstrated environmental and economic sustainability of halide-based batteries, achieving high recovery rates for lithium and copper, and over 80% for yttrium. A robust LCA framework was established, with ongoing emissions modeling and plans for a Social LCA. WP9 intensified dissemination through publications and events, and advanced the IPR strategy, identifying 12 Key Exploitation Results, including innovations in halide electrolytes, solid-state cells, and protective layers.
The project has entered Phase II, targeting large-format cell prototype manufacturing. Phase I achievements in material optimization have enabled the development of composite cathodes and solid electrolyte films meeting energy density goals. A key challenge remains: identifying a stable anode–electrolyte interface to ensure reliable cycling performance.
