One of the most abundant by-products from the photovoltaic industry is a sludge of Si micro-particles and sawing fluids, called “kerf”. Although it has been considered as a waste for a long time, many efforts are put into revalorization of this kerf. One possible application is to use it as active material in batteries because of the high theoretical capacity of silicon (3579 mAh g−1) compared to the conventionally used graphite (372 mAh g−1). The aim of this project is to investigate how the physical properties of the recycled Si kerf will affect their performance as active material in lithium-ion batteries. We have investigated several Si powders from various sources and they featured different amounts of amorphous Si, up to 50%, evidenced by X-ray powder diffraction, Raman spectroscopy, nuclear magnetic resonance and analytical electron microscopy with electron diffraction and electron energy loss spectroscopy. The presence and distribution of nano-crystallites within the amorphous Si matrix was analysed with high-resolution scanning transmission electron microscopy. Their particle size, morphology and surface chemistry were characterized with scanning electron microscopy and X-ray photoelectron spectroscopy. In addition, we have prepared silicon electrodes and investigated their electrochemical performance, especially focussing on the effect of the degree of crystallinity, by means of operando X-ray diffractometry.

Silicon: From kerf to anode material in lithium-ion batteries

ACS Fall 2021

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