Large-scale production of silicon nanoparticles@graphene embedded in nanotubes as ultra-robust battery anodes

The nanosized silicon for lithium-ion batteries (LIBs) is mainly limited by cracking and pulverization caused by the large volume change during deep cycles. Here, we demonstrated a commercial viability (scalable synthesis) of Si nanoparticles@graphene encapsulated in titanium dioxide nanotubes (Si@G@TiO₂NTs) or carbon nanotubes (Si@G@CNTs) for the next generation of high-energy battery anodes. The nanotubes can not only provide strong protection and sufficient void space to buffer the huge volume expansion of Si nanoparticles during the charge/discharge process, but also enforce a most solid-electrolyte interphase to form on the outer surface of the nanotube instead of on individual Si nanoparticles, leading to ultrahigh coulombic efficiency and excellent cycling stability. The obtained Si@G@TiO₂NT and Si@G@CNT electrodes showed a high reversible capacity of 1919.2 mA h g⁻¹ (1.02 mA h cm⁻²) after 800 cycles and 2242.2 mA h g⁻¹ (1.19 mA h cm⁻²) after 1000 cycles (>1 year) at the constant current density of 500 mA g⁻¹, respectively. Furthermore, both Si@G@TiO₂NT and Si@G@CNT electrodes presented superior average coulombic efficiency more than 99.9% during the whole cycling process.