Preparation and characterization of Silicon-carbon composite powders using recycled Silicon from solar cells as anode material in Li-ion batteries

Currently, silicon (Si) coming from the recycling of solar cells is a non-valued fraction. The principal aim
of this work is the development of silicon recovered during the dismantling of solar panels as electrode
material for Li-ion batteries. The main technological challenge associated with the use of silicon in this
type of application is to control the volume expansion during charge/discharge cycles. This drawback
could be avoided through the formation of Silicon/carbon composites in which the size of the silicon
particles and their dispersion must be controlled.
In this research, we develop a carbon matrix consisting of graphene or carbon nanotubes (CNT) that
allow the incorporation of silicon particles coated with a carbon layer (Si@C/C). The process is divided
in two main steps : I) the grinding of leached Si wafer pieces in order to extract pure Si powder and then
a mixed aqueous suspension of this recycled Si and an organic carbon source (Acetic acid, Ascorbic acid
or Lactose) is spray-dried followed by heat treatment to generate the coating of silicon particles with
carbon (Si@C). Then, II) aqueous suspension of Si@C and graphene/CNT is spray dried and calcined to
obtain the final composite structure (Si@C/C).
The morphology of composite materials is analyzed by scanning electron microscopy (SEM) and
transmission electron microscopy (TEM). Electrochemical performance of Si@C/C composites are
characterized by galvanostatic charge-discharge cycling and electrochemical impedance spectroscopy
(EIS).