Better lithium batteries boost electric vehicles

Development of EVs for the transport sector is high on the list of EU priorities for economic recovery within the framework of the Green Car Initiative. Important hurdles to overcome include increasing durability and safety, and reducing the weight, volume and cost of batteries.

Conventional Li-ion cells have become widespread; however, for some, energy density remains too low for transport applications, while others are either too expensive or do not meet environmental or safety standards. The EU-funded EUROLIION (High energy density Li-ion cells for traction) project therefore developed novel Li-ion batteries that combine high energy density, low cost and enhanced safety.

Benefits were obtained through a change in materials. The new cell has an innovative silicon (Si) anode (negative electrode), novel low-cost salts, and a modified iron or manganese/nickel-based cathode (positive electrode). These electrode materials are cheaper and can store higher charge densities than the conventional electrodes. In addition, they require a higher operating voltage to increase cell energy density.

Project partners defined new formulations for synthesising nano-Si materials for the negative electrode, and different binders and additives. They produced Li-ion cells with a positive electrode comprising lithium, nickel and manganese. With a novel, well-purified salt as an electrolyte, the nano-Si electrodes showed satisfactory capacity retention. Additional lithium salts were also synthesised, tested and further purified since some were found to degrade the positive electrode.

Researchers produced and tested 20 cylindrical cells with commercial lithium iron phosphate (LFP) and graphite electrodes, and 20 cells with LFP and nano-Si electrodes. These tests were conducted for cell modelling, while a safety assessment was carried out according to the test procedure. Finally, a full vehicle simulation was performed.

EUROLIION has paved the way for widespread use of EVs by developing higher-efficiency, cheaper and safer rechargeable batteries made from widely available raw material. This could provide the basis for a world-class European automotive battery industry and help to increase the EV market around the world.