Silicon monoxide carbonized by fluorocarbon as a composite material for anodes of lithium-ion batteries

Disperse composite materials based on silicon monoxide and carbon (SiO/C) have been obtained by thermal treatment of a powder mixture consisting of 40 wt.% SiO and 60 wt.% CF$_{0.8}$. Annealing has been performed in the argon atmosphere at temperatures 1000 – 1250$^\circ$C. It has been established using electron microscopy and Raman scattering that, at $T\ge$ 1100$^\circ$C, silicon carbide is formed in the solid-phase product, including in the form of nanowhiskers of cubic modification. Based on the data on the decrease of the reaction mixture weight, the composition of the formed products is calculated as a function of the annealing temperature. The anodes prepared from the composites obtained at a temperature above 1100$^\circ$C demonstrate a sharp decrease in the capacitance and in the Coulomb efficiency. It is shown that the observed changes are determined by an increase in the oxygen concentration in the matrix surrounding silicon precipitates, which have been formed as a result of SiO disproportionation, rather than by the formation of SiC. It is established that an optimal annealing temperature provides the highest values of the electrode capacitance, the Coulomb efficiency of the first cycle, and the ability to operate at high current densities is $T$ = 1050$^\circ$C.