Helios :  Description of the project

Battery reliability and safety are the key issues for the commercialisation of Electric and Hybrid Electric Vehicles (HEV) for the private customers. For High Energy (HE) applications, requiring a large amount of energy stored on board, the lack of long-term visibility on the battery performances is limiting the commercial availability of Electric Vehicles and Plug-in HEV.

The main goal of the project is to evaluate 4 electrochemical couples of lithium–ion cells whose lower voltage window matches perfectly with the stability window of the electrolyte, which should guarantee an excellent safety & performances.

These active materials are listed below:

Active materials (cathode / anode) Common name (cathode / anode)
Li(NiCoAl)O2 / C (reference) Lithium Nickel Cobalt Oxide / Graphite
Li(NiMnCo)O2 / C Lithium Nickel Manganese Cobalt Oxide / Graphite
LiMn2O4 / C Lithium Manganese spinel / Graphite
LiFePO4 / C Lithium Iron Phosphate / Graphite

 The project Helios will evaluate both electrical performances and their evolution in time – life, and their behaviour under abuse test conditions – safety. The key point of the organisation of the project is that a dedicated Work Package (WP) focused on the interpretation of the tests results by post mortem analysis of aged cells, thus correlating life and safety with the specific properties of the active materials. Recycling & cost estimation are also being studied..

Another specific aim of the project is to focus such tests and their interpretation on real size HE cells, with a capacity of approximately 40Ah, produced industrially by Saft.

The quantitative assessment of these four issues (safety, life, recycling and cost) is a key point for car manufacturers to evaluate the potential of these chemistries. It will be performed at cell level, but the results will supply the basis for an evaluation at system level. In particular the system level implications are :

  • The consequence of safety tests results on the battery pack concept: impact on safety devices (valves, balancing, safety devices, fuse,).
  • Impact of fast charge on battery packs specifications.
  • Estimation of extra recycling needs when treating modules or large battery packs: comparison between manual dismantling and one-step thermal treatment.

These inputs will be taken into account for the global estimation of global battery pack cost for each defined application.

Another issue addressed by the project is the definition of an European standard for safety and life (cycle/storage) tests, adapted to High Energy applications such as EV, PHEV and Heavy Duty Hybrid Truck (hereby called HEV-APU). It is fundamental to define an European standard for safety tests, taking into account the different realities of High Power and High Energy type Li-ion cells.