Effects of transition metals for silicon-based lithium-ion battery anodes: A comparative study in electrochemical applications

Abstract

The strength, conductivity, elasticity, inactivity against lithium, and tunability properties of transition metals (TMs) are the major reasons these metals are used to synthesize silicon-based lithium-ion battery (LIBs) composite anodes. This is because TMs significantly influence and improve the overall electrochemical performance of LIB electrodes by mitigating the undesired expansion of silicon. The effects of different elemental transition metals copper (Cu), titanium (Ti), nickel (Ni), and iron (Fe) on the electrochemical performance of silicon-based composites were compared, and the phases formed during milling were correlated to the behavior of the composites in which they are present. The excellent performance of these electrodes was attributed to the reaction mechanism of transition metals after the first conversion reaction during lithiation and remained inactive during the ensuing cycles. It was found that the strength and ductile nature of nickel accounts for relieving mechanical stress induced on Silicon during the insertion and extraction of lithium ions. All copper-containing composites showed high stability in cycling but low capacity, which is attributed to the high amounts of copper, contained in these composites and the reaction of copper with silicon during milling. The presence of titanium improved the electrical conductivity and mechanical strength of the electrodes. Iron-containing composites were observed to highly withstand deformation due to the strength of the matrix. Moreover, the addition of 10 wt. percentage carbon improved the cycle performance and rate capability of Cu-Fe-Si-C, Cu-Ni-Si-C, Ni-Fe-Si-C, and Ni-Ti-Si-C. These composites showed stable cycling performance of 654.42 mAh g–1, 686.16 mAh g–1, 657.56 mAh g–1, and 643.29 mAh g–1 respectively after 100 cycles capacity at 1 C.