Technical approach

Technical approach

HELENA proposes a disruptive technology to design batteries with high gravimetric and volumetric energy cells of at least 450 Wh/kg and 1200 Wh/l, enabled by a halide solid electrolyte and an optimized high-voltage cathode electrode for high C-rate capacity.

HELENA’s methodology consists of a series of R&D activities with the main objective to obtain a prototype of Li-metal halide solid state battery at the end of the project. Such activities begin with the synthesis of raw key materials for the battery that will be optimized to obtain high performance lab-scale devices and further upscaled to final prototypes. On the other hand, the battery modelling will allow for transversal development and for the improvement of materials and battery features.

The overall methodology of HELENA comprises three phases:

  • Phase I. Development, optimization, and upscaling of new materials.
  • Phase II. Halide based solid state battery development
  • Phase III. Testing, optimization and validation

Halide solid electrolytes

  • Lithium-ion superionic halide solid electrolyte (>2 mS/cm RT)
  • Mechanical deformable
  • Non-critical materials: safe and benign
  • Within 3 and 4 mS/cm at room temperature
  • High cathode stability
  • High anode stability
  • Improved moisture tolerance

Cathode active materials

  • High capacity Ni-rich cathode (NMC)
  • High areal loading (> 3 mAh cm-2)
  • High C-rate capacity

Li metal anode and interfaces

  • High-energy Li metal (LiM) anode
  • High reversibility
  • Li dendrite suppression
  • High Li conductivity
  • Stability through self-liming SEI layers



The high energy density of HELENA’s sustainable and safe advanced Li-on batteries will boost both the EV and aeronautic sectors.

Electric vehicle

Electric vehicle

In the automotive sector, the range is close to 500 km with 250 Wh/kg batteries. The replacement of liquid electrolytes by solid halide will have a major impact on cell degradation, resulting in longer cycle times (500,000 km).



For aeronautical applications, a target life in the range of 2000 to 5000 discharge cycles will be achieved, as well as an increase in range from the current 150 km to more than 500 km.

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