Hollow Si/SiOx nanosphere/nitrogen-doped carbon superstructure with a double shell and void for high-rate and long-life lithium-ion storage

Abstract

Silicon (Si) is a promising anode candidate for lithium-ion batteries (LIBs) owing to its unprecedented theoretical capacity of 4200 mA h g⁻¹ and earth-abundant supply (26.2 wt%). Nevertheless, the huge volume expansion and unstable solid-electrolyte interface (SEI) of Si in multiple cycles make it very hard to simultaneously achieve high-energy and long-term cycle life for applications in large-scale renewable energy storage. Herein, we demonstrate a new class of Si/SiO_x@void@nitrogen-doped carbon double-shelled hollow superstructure (Si/SiO_x-DSHS) electrodes that are capable of accommodating huge volume changes without pulverization during cycling. Benefiting from the unique double-shelled hollow superstructure, Si/SiO_x-DSHSs can facilitate the formation of a highly stable SEI layer and provide superior kinetics toward Li⁺-ion storage. The diffusion-controlled process and the capacitance-type reaction can work together to endow Si/SiO_x-DSHSs with remarkable electrochemical characteristics, especially at high current density. These important characteristics make Si/SiO_x-DSHSs deliver a large reversible capacity (1290 mA h g⁻¹ at 0.1C), high first-cycle coulombic efficiency (71.7%), superior rate capability (360 mA h g⁻¹ at 10C), and excellent cycling behavior up to 1000 cycles with a small capacity decay of 10.2%. The Si/SiO_x-DSHSs are among the best Si-based anode materials for LIBs reported to date.