Pioneering Solid-State Innovation: HELENA, PSIONIC, and ADVAGEN Lead Europe’s Battery Revolution

30 October 2025

The first Horizon Europe projects focusing on battery research and innovation are entering their final stage since their launch. These projects are grouped under the BATT4EU Partnership, a public-private partnership between the European Commission and the Batteries European Partnership Association (BEPA), the private voice of research and innovation across the battery value chain.  

To date, BATT4EU counts 64 projects, which are delivering groundbreaking results. On September 29th, during the BATT4EU Success Stories webinar, BEPA showcased the achievements of HELENA, PSIONIC, and ADVAGEN. 

The HELENA project focuses on developing next-generation halide-based solid-state batteries for electric vehicles and aircraft. The project achieved significant breakthroughs in the development of new halide solid electrolytes (Li–Y-Br/Cl systems) with ionic conductivity up to 5 mS/cm, enhanced particle size control, and stability with active materials. It also developed advanced cathode materials. It also develops  NMC cathodes from 622 to high-voltage NMC 811, reaching 210 mAh/g and improved energy density through optimised coatings.  

HELENA successfully scaled up from coin cells to multilayer pouch cells (1–10Ah) using thin solid electrolyte membranes (~30 µm) and high-loading composite cathodes (~4 mAh/cm²). Interfacial stability was improved through protective sulphide coatings, extending cycle performance and achieving ~98% coulombic efficiency. Thanks to ab initio molecular dynamics simulations, they have been able to elucidate the reaction mechanism of lithium metal and the electrolyte interface, which is key for high-performance devices. In addition, HELENA validated recycling routes with >70–80% recovery of lithium and transition metals, demonstrating a clear roadmap toward sustainable, industrial-scale halide solid-state batteries.  

The PSIONIC project develops a polymer-based solid-state battery using an innovative solvent-free extrusion process. This approach eliminates the use of toxic solvents, offering a scalable and environmentally friendly route to battery manufacturing. PSIONIC optimised the composition of polymer electrolytes by blending polyethylene oxide (PEO) and polycarbonates (PPC and PEC) with lithium salts, achieving ionic conductivity of 4.6 × 10⁻⁵ S/cm at 40 °C and electrochemical stability at 4.58 V. A key achievement was the development of UV-cured crosslinked polymer membranes that are self-standing and flexible (~60 µm), enabling stable lithium plating and stripping for over 600 hours without short circuits. The project demonstrated cells with LFP cathodes delivering 168 mAh/g at C/20 and 99.8 % coulombic efficiency, while NMC-based cells reached 110 mAh/g at C/15 and 40 °C. They are currently studying how the addition of succinonitrile plasticisers could further improve room-temperature conductivity and stability by decreasing the crystallinity of the polymer. PSIONIC thus represents a strong step toward safe, sustainable, and industry-ready solid-state batteries manufactured through solvent-free processes. 

The ADVAGEN project focuses on hybrid oxide–sulphide solid-state batteries (LPSCl:LLZO, 80:20) based on European-sourced materials. The project synthesised high-purity LPSCl electrolytes with conductivities exceeding 1 mS/cm and optimised NMC 811 cathodes with precise temperature and oxygen control, achieving over 200 mAh/g. ADVAGEN developed innovative interface engineering solutions, including thin lithium metal deposition on copper and sputtering plasma for AlOx coatings, resulting in stable cycling at >0.1 mA/cm². Hybrid sulphide–oxide cells demonstrated robust compatibility and high energy density, while pouch cells exceeding 1 Ah are under fabrication. They developed multiscale modelling for the battery components, making the battery’s electrochemical working mechanism. These achievements show a fully European supply-chain approach to solid-state battery development, combining material innovation, modelling, and scalable cell prototyping. 

Together, HELENA, PSIONIC, and ADVAGEN illustrate the technological progress under the European BATT4EU partnership. From halide to polymer to hybrid solid-state systems, these projects are pushing the boundaries of safety, performance, and sustainability. They demonstrate that Europe is rapidly advancing toward industrially scalable, next-generation solid-state batteries that can power the electric mobility sectors of tomorrow. These are just a few examples of the BATT4EU projects that have been thriving and successful.  

These are just a few examples of the BATT4EU projects that have been thriving and successful. BEPA will continue to support these initiatives by highlighting more success stories on Thursday 13 November, 10:00-11:30, with the second webinar dedicated to the BATT4EU Success Stories, connect to hear about NoVOC, BatWoMan, and.