The Helios project brings together two research institutes (CEA, ICMMO –Université Paris saclay) and an innovative SME (Nanomakers). Two laboratories of CEA (NIMBE and LITEN) will be involved, located respectively in Saclay and Grenoble. The project aims to develop a high capacity Li-Ion battery using nanostructured silicon as the anode material for mobile applications. It targets two strategic objectives for the battery: a lifespan exceeding 500 cycles and energy density of 300 Wh/kg corresponding to a specific capacity of the active material of 1000 mAhG-1 (about 3 times higher than the graphite batteries currently on the market). Despite being the focus of scientific activity for over 10 years, the use of silicon based anodes have not yet been realized because the performance of these materials degrades rapidly during cycling. The innovative solution proposed here is to use at the anode nanoparticles of Si@C synthesized in a single step by a scalable continuous gas phase method particularly interesting for industrial production. These nanoparticles exhibit very interesting electrochemical performances with stable cycling over several hundred cycles and a remarkable coulombic efficiency, of the order of 99.9% in coin cell configuration. These performances are obtained because the silicon core gives high capacity while the carbon shell stabilizes the solid/electrolyte interface (SEI) for several hundred cycles. The remaining hurdles to achieving a proof of concept high energy density Li-ion prototype are the large Li loss during SEI formation in the initial cycles control of the SEI that is developed during cycling. To address these challenges the project will have a two-fold focus. In order to reduce initial cycle lithium loss, methods to decrease the reactive anode surface area by aggregation of the nanoparticles with graphite and amorphous carbon will be investigated. To develop improved stability of the SEI, studies will be performed to understand the changes in the stability of SEI and the morphology of the active material and the electrode with impedance spectroscopy (EIS). Different types of carbon-coated nanoparticles will be prepared (varying crystallinity and core size, thickness and structure of carbon shell, etc.) then agglomeration methods will be compared it includes dispersion of nanoparticles in an organic precursor in the presence of graphite, followed by pyrolysis. The electrochemical performance of these materials will be evaluated in electrodes adapted to the characteristics of materials with different electrolytes in order to correlate the morphology and structure of the composite with degradation mechanisms. The final outcome will be a proof of concept device produced at pilot scale for mobile applications (e.g., cellular phones). Such a demonstration will be of interest for industrial companies in this market, providing a commercial outlet for the Nanomakers SME which will provide the active material. The predicted business growth is projected to provide 50 french jobs in Nanomakers by 2020.
Madame Nathalie Herlin Boime (Commissariat à l'Energie Atomique et aux Energie Alternatives)
The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.
ICMMO Institut de Chimie Moléculaire et des Matériaux d'Orsay
CEA Commissariat à l'Energie Atomique et aux Energie Alternatives
Help of the ANR 456,720 euros
Beginning and duration of the scientific project: September 2016 - 36 Months