Li-ion cells are probably the most appropriate technology for traction purposes of electric vehicles.
Considerable research and development is required. The EUROLIION project aims to develop a new Li-ion cell for traction purposes with the following characteristics:
- High energy density of at least 200 Wh/kg;
- Low costs i.e. a maximum of 150 Euro/kWh;
- Improved safety.
Note that the much-used LiFePO4 cells cannot reach the energy density criterion, and in addition, LiFePO4 is patented, which hampers worldwide commercialisation.
Many other materials are either too expensive or do not meet current safety, environmental standards (e.g. cobalt in LiCoO2). Thus, we propose a shift from carbon to the much higher capacity silicon-based anodes, and from cobalt-based to iron and/or manganese/nickel-based cathodes, and to use novel electrolyte salts.
To successfully develop a European Li-ion technology, the R&D will start at the anode side, i.e. Si, with a LiFePO4-C material at the cathode side. This requires a new electrode formulation with respect to binder, electrolyte salt, solvent, and composition. The change in formulation at the anode and electrolyte allows for a change in the cathode materials and a series of both novel (e. g. fluorosulfates, LiFeSO4F) and more established systems, will be investigated. New synthetic routes are proposed, along with an extensive characterization program. Scale-up, testing and benchmarking of optimum formulations will be performed. The outcome will be a newly developed cell, manufactured and tested by end-users. The new cell consists of:
- a newly formulated Si-negative electrode
- newly designed low cost salts, and
- modified positive electrodes.
The consortium includes renowned universities and knowledge institutes, a SME battery producer and the car industry as end-users. Thus, the composition of the consortium covers the whole spectrum of R&D, manufacturing and testing.
New materials to improve lithium batteries
Electric vehicles (EVs) offer many environmental benefits, yet they cannot cover great distances. An EU-funded project worked to produce cheaper and safer lithium-ion (Li-ion) batteries with energy densities approaching 200 watt-hours per kilogram.
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. Most work to date has focused on technical development and market analyses. Important challenges will also be faced in terms of durability, safety, cost and the required charging infrastructure.
Although conventional Li-ion cells have become widespread, some have too low energy density for transport applications. Others are either too expensive or do not meet environmental or safety standards. The EU-funded project 'High energy density Li-ion cells for traction' (http://www.euroliion.eu/ (EUROLIION)) focused on developing 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.
Scientists defined new formulations for synthesising nano-Si materials for the negative electrode, and different binders and additives. The produced Li-ion cells with a positive electrode that includes a combination of lithium, nickel and manganese demonstrated stable cycling. With a novel well-purified salt as an electrolyte, the nano-Si electrodes showed satisfactory capacity retention. More lithium salts were also synthesised, tested and even further purified since some were found to degrade the positive electrode.
Scientists 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 served for cell modelling. A safety assessment according to the test procedure was carried out. 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. The new technology should enhance the competitiveness of the EU while supporting its dedication to a low-carbon–output and sustainable economy.