Enhancing the electrochemical properties of a Si anode by introducing cobalt metal as a conductive buffer for lithium-ion batteries

Abstract

Silicon anodes have attracted extensive attention due to their high theoretical capacities (3579 mAh g−1) and low working potential (<0.5 V). However, Si suffers from low electrical conductivity (6.7 × 10−4 S cm−1) and pulverization of silicon particles during charging/discharging. To prevent the degradation of Si anodes, many approaches, such as introducing a mechanical buffer, have been conducted to reduce the mechanical stress on Si. Among these approaches, introducing electrically conductive materials is desirable in that it can also reduce the internal resistance of the Si electrode. In this work, we synthesized a Si/SiOx/Co composite using a conversion reaction of CoO and Si at 900 °C under continuous nitrogen flow. Co metal with face-centered cubic (fcc) structure in the Si/SiOx/Co composite can act as a mechanical buffer as well as a conductive agent due to its high ductility. As a result, the Si/SiOx/Co anode exhibited a high specific capacity of 1602 mAh g−1 Si/SiOx after 200 cycles at a current of 2 A g−1. The Si/SiOx/Co composite is suitable for lithium-ion batteries (LIBs) due to its facile synthetic method and high electrochemical performance.