Synthesis at Low Cost and Large Scale of Silicon Powder Suitable for Li-Ion Anodes

Silicon is considered as one of the most promising materials to replace graphite in Li-ion batteries. The main inconvenient of that material is its huge volume expansion during lithiation which induces the disintegration of the electrode architecture with cycling. Nanosized Si materials (nanoparticles, nanowires, nanocomposites…) better accommodate large volume variation without cracking. However, the use of such materials by industries is unlikely because of their high synthesis cost, handling difficulties and low tapping density.  

We have recently demonstrated that Si powder produced by high-energy ball milling (using a laboratory vibratory-type miller) present the same benefits of nanometric Si in terms of performance but not the drawbacks¹. Milled Si powder is constituted of micrometric agglomerates (median size of ca. 10 µm), made of submicrometric cold-welded particles with a crystallite size of ca. 10 nm. The micrometric particle size provides handling and non-toxicity advantages compared to nanometric powders, as well as four times higher tap density. The nanocrystalline structure of the ball-milled Si powder is assumed to induce a smoother phase transition upon cycling.^1,2

In the present study, ball-milled Si powder is produced at larger scale (500 g/batch compared to 5g/batch in previous work) using a pilot-scale attritor (Fig. 1).  Using optimal milling parameters and appropriate composite electrode formulation, this material displays very good electrochemical performance (see Fig. 2). Various analyses will be presented in order to understand the influence of the milling time on the physicochemical characteristics and electrochemical behavior of the Si powder. During these investigations, we noticed that the storage conditions of the electrodes prior to assembling the cell have also a major influence on the electrochemical performance. This aspect will be also discussed.

References

1. M. Gauthier, D. Mazouzi, D. Reyter, B. Lestriez, P. Moreau, B. Lestriez, D. Guyomard, L. Roué. A low-cost and high-performance Si-based electrode for Li-ion batteries. Energy Environ. Sci. 6 (2013) 2145–2155.

2. M. Gauthier, D. Reyter, D. Mazouzi, P. Moreau, D. Guyomard, B. Lestriez, L. Roué. From Si wafers to cheap and efficient Si electrodes for Li-ion batteries. J. Power Sources 256 (2014) 32-36.