One-step chemical vapor deposition synthesis of Si NWs@C core/shell anodes without additional catalysts by the oxide-assisted growth mechanism for lithium-ion batteries.

Si NWs@C core/shell anodes for lithium-ion batteries were synthesized via a one-step environmental-pressure chemical vapor deposition (CVD) process utilizing nano-silicon and methane as raw materials. In this structure, the silicon nanowire core is obtained by controlling the temperature above 900 °C to catalyze the growth of nano-silicon particles coated with a natural oxide layer according to the oxide-assisted growth (OAG) mechanism, while the carbon as a protective coating shell is derived from methane cracking. In contrast to the conventional nanowire catalytic approach, this method obviates the addition of metal catalysts while ensuring a straightforward and scalable process. This Si NWs@C electrode displayed excellent electrochemical performance, exhibiting high reversible capacity (745.8 mA h g-1) and excellent cycling stability (91.3% after 100 cycles at 0.5 A g-1).

Dual immobilization of porous Si by graphene supported anatase TiO2/carbon for high-performance and safe lithium storage.

Smart surface coatings have been proven to be an effective strategy to significantly enhance the electronic conductivity and cycling stability of silicon-based anode materials. However, the single/conventional coatings face critical challenges, including low initial Coulomb efficiency (ICE), poor cyclability, and kinetics failure, etc. Hence, we proposed a dual immobilization strategy to synthesize graphene supported anatase TiO2/carbon-coated porous silicon composite (denoted as PSi@TiO2@C/Graphene) using industrial-grade ferrosilicon as lithium storage raw materials through the simple etching, combined with sol-gel and hydrothermal coating processes. In this work, the dual immobilization from the "confinement effect" of the inner TiO2 shell and the "synergistic effect" of the outer carbon shell, improves the kinetics of the electrochemical reaction and ensures the integrity of the electrode material structure during lithiation. Furthermore, the introduction of the graphene substrate offers ample space for dispersing and anchoring the Si-based granules, which in turn provides a stable 3D conductive network between the particles. As a result, the PSi@TiO2@C/Graphene electrode delivers high reversible capacity of 1605.4 mAh g-1 with 93.65% retention at 0.5 A g-1 after 100 cycles (vs. 4th discharge), high initial Coulomb efficiency (82.30%), and superior cyclability of 1159.9 mAh g-1 after 250 cycles. The above results suggest that the particle structure has great potential for applications in Si-based anode and may provide some inspiration for the design of other energy storage materials.