Dual-carbon-confined hydrangea-like SiO cluster for high-performance and stable lithium ion batteries

Chemical Vapor Deposition Carbon Coating of SiO x Anode for Li-Ion Batteries: Significance of Carbon Precursor Selection and Deposition Temperature

Owing to the surge in the demand for lithium-ion batteries (LIBs) with high energy density, silicon suboxide (SiO x )-based materials with impressive theoretical capacities have garnered significant attention. However, challenges such as poor electrical conductivity and substantial volume expansion must be overcome. A common strategy for addressing these issues involves coating SiO x with carbon. During this process, the properties of the carbon layer and SiO x are strongly affected by the temperature and precursor choice. This study explores the impact of the temperature and precursor selection on the carbon coating layer deposited by chemical vapor deposition (CVD) and the phase of SiO x . Surprisingly, SiO x @C2H2, in which SiO x was coated with carbon using acetylene at low temperatures, exhibited lower cyclic stability than the uncoated SiO x . In contrast, SiO x @CH4, in which SiO x was coated with carbon at high temperatures, comprised a vertically grown carbon layer and SiO2 layer with optimal thickness. This configuration stabilized the growth of the solid electrolyte interphase (SEI) layer and enhanced the electrical contact. The optimized SiO x @CH4-1000 (methane-based CVD coating at 1000 °C) demonstrated excellent electrochemical performance, achieving a high capacity of 778 mAh g-1 at 0.75 A g-1 and a remarkable capacity retention of 92.8% after 100 cycles. This optimized CVD carbon coating process paves the way for industrialization of SiO x -based materials, positioning them for application in next-generation LIBs.

Realizing Sub-5 nm Red Phosphorus Dispersion in a SiOx/C Matrix for Enhanced Lithium Storage

With high capacity and suitable working plateau, silicon oxide (SiOx) has become a promising lithium-ion battery (LIB) anode material. However, bare SiOx usually suffers from sluggish electron transport and unsatisfactory cyclability. Composting SiOx with a second phase has become an efficient strategy to tackle the current drawbacks. Herein, a P/SiOx/C ternary composite, featuring sub-5 nm red phosphorus (P) clusters uniformly dispersed in a dense SiOx/C matrix has been constructed through an "inside-out" synthesis strategy. The nanosizing of bulk red P sealed in an organosilica matrix is realized by the high-temperature treatment-driven sublimation/diffusion. With the red P amount of ∼7.53 wt %, the P/SiOx/C ternary composite provides a stable discharge capacity of ∼950 mAh g-1 and also manifests a decent rate capability (510 mAh g-1 at 5 A g-1). This study affords a ternary compositing strategy for designing SiOx-based anode materials with desirable electrochemical performance for the next-generation LIBs.