Enhanced Lithium-Ion Diffusion Kinetics and Inhibition Volume Expansion via Sn-Bridged N-Doped Carbon and SiOx for Highly Reversible Lithium-Ion Storage

Abstract

Silicon oxide (SiO_x) is becoming a hot spot in the research of anode materials for lithium-ion batteries. However, the low initial coulombic efficiency (ICE), weak conductivity, unsatisfied rate performance, and significant volume changes during cycling of SiO_x have hindered its commercial application. Herein, a silicon–carbon composite material (SiO_x/C–Sn@NC) was synthesized, featuring metal tin that is embedded within and on the surface of the SiO_x framework. Additionally, a nitrogen-doped carbon layer was incorporated into the material to further mitigate volume changes. Benefitted from the discrepant lithiation/delithiation potentials of Sn and Si, the formed structure significantly limits the volume changes of the formed anode during the cycle, enhancing the cycle life and stability of the SiO_x/C–Sn@NC material. Additionally, multiple nodes are provided in the part where the bridged Sn is in contact with the N-doped carbon to enhance the Li⁺ diffusion during charge and discharge and overall conductivity, promoting the lithium-ion diffusion kinetics. The SiO_x/C–Sn@NC anode displays an ICE of 73.42% at 0.5 A g^–1, retaining a capacity of 680 mAh g^–1 after 500 cycles. In addition, this anode also exhibits excellent cycle performance of 591 mAh g^–1 after 500 cycles, with an ICE of 70.37% at a current of 2 A g^–1. The prominent cycle performance and electrochemical stability of SiO_x/C–Sn@NC far surpass those of commercial silicon–carbon and graphite, offering a new pathway for the commercial application of silicon oxide-based anodes.