Construction of WO3 nanowires artificial solid electrolyte interphase on silicon nanoparticles with sea urchin like structure for improving silicon anode stability

Giant volumetric variation of silicon during repeat lithiation/delethiation process leads to structure failure of silicon-based anodes and thus their initial high capacitance is hard to be maintained under long-run cyclic charging/discharging. Construction porous structure silicon composites and formation of artificial solid electrolyte interphase (SEI) coating on silicon particles are two effective ways to improve stability of silicon-based anodes. In this work, above two strategies are combined to construct a composite of inorganic artificial SEI WO₃ nanowires/Si nanoparticles with sea urchin like porous structure via simple hydrothermal method. The silicon nanoparticles act as seeds for around 70 nm average diameter WO₃ nanowires formation in compared with that of WO₃ nano-rods around 500 nm diameter without Si nanoparticle seeds. The WO₃ nanowire artificial SEI coating is found to be effective in preventing SEI overgrowth and their network provides spaces for volumetric variation of silicon nanoparticles in the bulk anode matrix during cyclic test, leading to reversible charging/discharging of stable bulk anode in compared with pure silicon anode of fast capacitance decay. The gravimetric capacitance of optimized composite reaches 1410.6 mAh·g⁻¹ and its capacity remains 1039 mAh·g⁻¹ after 200 cycles.