Porous carbon-coated silica macroparticles as anode materials for lithium ion batteries: Effect of boric acid

• Gradual increase in charge retention of carbon-coated silica anode was demonstrated.
• Complex phases were detected after carbonization of porous silica with boric acid.
• Carbon-coated silica formed with boric acid show improved capacity of 500 mAh g−1.

We report carbon-coated porous silica macroparticles (SiO2@C) prepared using polymeric templates and subsequent carbonization with sucrose for improved electrochemical energy storage in lithium-ion batteries (LIBs). In addition, boron is introduced to improve the stability of electrochemical cells by pyrolyzing mixtures of sucrose and boric acid (SiO2@C + B) under inert atmosphere. The initially large surface area of porous SiO2 (SBET ∼ 658 m2 g−1) is reduced to 102 m2 g−1 after carbonization and introduction of boric acid. Surface of both SiO2@C and SiO2@C + B are covered with amorphous carbon. In particular, SiO2@C + B particles containing borosilicate (Si–O–B) phase and B–O bondings and Si–C–O bondings are also detected from the X-ray photoelectron spectra. The SiO2@C + B macroparticles shows high reversible charge capacity up to 503 mAh g−1 after 103 cycles of Li intercalation/de-intercalation although initial capacity was 200 mAh g−1. The improved charge capacity of SiO2@C + B is attributed to formation of advantageous microstructures induced from boric acid.