Fe/Fe3C modified C@Si/SiOx anodes to achieve significantly enhanced lithium storage performance

Abstract

The development of high-performance silicon/silicon oxide (Si/SiO_x) anodes has attracted great attention in the field of next-generation high-energy lithium-ion batteries (LIBs). However, preparing effective Si/SiO_x composite materials to address issues such as poor cycling stability, subpar initial coulombic efficiency (ICE), and subpar interface compatibility remains a challenge. This work proposes a simple strategy for preparing Fe/Fe₃C particle modified thin-layer carbon-coated Si/SiO_x composite materials using a mixture of resorcinol formaldehyde (RF) precursor pyrolysis and ultrasonic treatment (referred to as C@Si/SiO_x-Fe/Fe₃C, abbreviated as CSSO-Fe/Fe₃C). These composite materials are used as anodes for LIBs. Exploiting the benefits of its structure and composition, the CSSO-Fe/Fe₃C anode offers a high ICE value of 68.7% and maintains a capacity of 563.2 mAh g⁻¹ even after 1200 cycles at a current density of 2.5 A g⁻¹. Comprehensive characterization and electrochemical studies have elucidated the interface compatibility and structural stability mechanisms induced by the small amount of Fe/Fe₃C doping and carbon coating, which explain the high capacity and stable cycling performance. Furthermore, when paired with LiCoO₂ cathode, the assembled LiCoO₂||CSSO-Fe/Fe₃C coin-type full battery has a capacity of 80.7 mAh g⁻¹ and a capacity retention rate of 76.6% after 200 cycles at 1.0 C. This synthesis approach offers valuable insights for designing high-performance Si/SiO_x electrode materials.