Most batteries used in mobile but also on electric vehicles applications rely on graphite anode.

Si storage capacity can be as high 3579 mAh/g. This is almost 10 times higher than graphite’s theoretical capacity of 372 mAh/g.

An active material containing 20% Si and 80% graphite would then have a capacity of 1000 mAh/g, which has the potential to increase battery capacity notably.

So the large and still increasing markets energy supply and mobility run into resource scarcity. This resource scarcity will become even more relevant in future if we do not find efficient and sustainable substitutes for those materials. Furthermore, graphite anodes have reached their limits in terms of performances, that’s why current market expects new anodes alternatives. Due to the promising scientific results, batteries using Si based anodes have been announced several times and multiple companies are working on their development. However, up to now there are few industrially developed materials. SiO or Si alloys are or are going to be commercialized but there are severe limitations including large initial capacity losses and poor cycling stability.

 

The goal of the SiRIUS project is to develop high capacity silicon – carbon composites anodes for lithium ion batteries targeting high energy density applications (> 300 Wh/kg & > 700 Wh/L) and intermediate cycle life (> 500 cycles) to meet requirements of portable electronic and au-tomotive markets. The high energy density requirements give the following specifications at the material level:

- Specific capacity: 1000 mAh/g

- Capacity retention: 70% @ 500 cycles

- Initial irreversible capacity: < 15%

 

These new generations of advanced materials will be built from carbon-coated silicon nanoparticles produced by Nanomakers using SGL’s composite preparation process. Material will be evaluated in commercial design Li-ion cells by VMI to validate the interest and part of the characterization will be performed by CEA and UU.

The use of these new silicon composite anodes enables benefits for battery characteristics and will help solving supply bottlenecks of critical resources for batteries at the same time:

 -The proposed approach will help to secure raw materials supply by working on two aspects. On one hand the use of silicon gas precursor to obtain silicon metal and the partial substitution of graphite. On the other hand the development of high capacity anodes is a way to reduce the anode materials quantity in batteries

- The novelty of the proposed approach is based on the use of high efficient carbon coated silicon nanoparticles. The original one step synthesis process (using laser pyrolysis) allows to avoid the detrimental excessive oxidation which could happen during aggregation step. In addition the carbon surface will improve contact with graphite and amorphous carbon.

 

At this level of the state of the art, a breakthrough in energy performances concerning the world of mobile computing and hybrid/electrical vehicle is still possible using silicon – carbon composites approach as proposed here.

 

At the end of the project the TRL level is targeted to be 7, which means that a prototype demonstration will be realized under operational environment. This prototype will consist of a new high energy lithium-ion battery cell based on sustainable and high-performance silicon based anodes materials.

 

 

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