Monodisperse and homogeneous SiCNO/C microspheres: A promising high-capacity and durable anode material for lithium-ion batteries

Silicon suboxide (SiOx, x < 2) shows promise as an anode material for lithium-ion batteries due to its high lithium-ion storage capacity. However, its low conductivity and substantial volume changes, similar to those observed in monolithic silicon, restrict its practical application. To address these challenges, this study focuses on designing and synthesizing SiCNO/C composite materials. Employing the St & ouml;ber sol-gel method, organopolysilazane oligomers (OPSZ) and resorcinol formaldehyde resin (RF) are co-hydrolyzed and condensed to create uniform OPSZ/RF nanoparticles. Subsequently, high-temperature ceramization produces nitrogen-doped carbon-silicon composites (SiCNO/C). This approach enables the preparation of composite nanomaterials with adjustable sizes (200-1000 nm) and controllable carbon content (20-60 wt%). Nitrogen doping levels range from 4-10 wt%, ensuring uniform distribution of C, Si, N, and O elements within the composite microspheres. Battery performance tests confirm that the presence of a substantial amount of free carbon and effective nitrogen doping increase the active sites on the material surface, resulting in SiCNO/C composites exhibiting high specific capacity and excellent cycling stability as anode materials for lithium-ion batteries. Specifically, the SiCNO/C-1 sample demonstrates an initial discharge capacity of 1309.0 mAh/g, retains 797.6 mAh/g after 100 cycles at 100 mA/g, and maintains 587.0 mAh/g after 400 cycles at 1 A/g. The composite also shows a low volume expansion of 47.7 % after 100 cycles. These results indicate that SiCNO/C microspheres are promising high-capacity and durable anode materials for lithium-ion batteries.