Continuous Flow Synthesis of Carbon Coated Silicon/Iron Silicide Secondary Particles for Li-Ion Batteries.

The development of better Li-Ion battery (LIB) electrodes requires an orchestrated effort to improve the active materials, as well as the electron and ion transport in the electrode. In this paper, iron-silicide is studied as an anode material for LIBs because of its higher conductivity and lower volume expansion compared to pure Si particles. In addition, Carbon Nanotubes (CNTs) can be synthesised from the surface of iron-silicides using a continuous flow coating process where precursors are first spray dried into micrometer scale secondary particles and are then flown through a Chemical Vapour Deposition (CVD) reactor. The CNTs inside the secondary particles are important for short-range electrical transport and good utilisation of the active material. On the other hand, the CNTs on the surface of the secondary particles may help establishing a good long-range inter-particle conductivity. These spherical secondary particles allow for better electrode coating quality, cyclability, and rate performance than unstructured materials with the same composition. The electrodes showed 1150 mAh/g at 1A/g over 300 cycles, as well as a 43% capacity retention at a rate of 5 C. Further, blended electrodes with graphite delivered a 550 mAh/g with high electrode density (~1.6 g/cc) and areal capacity (~3.5 mAh/cm) with stable cycle performance.