Electrochemical activation of a diatom-derived SiO2/C composite anode and its implementation in a lithium ion battery

Nano-architectured silica is extracted from algae harvested in the ocean. Its electrochemical properties are investigated as an anode material for lithium ion batteries. The beneficial effect of a carbon coating formed by pyrolysis of glucose at 850 °C in Ar(g) onto the surface of the SiO2 particles is demonstrated. The SiO2 and SiO2/C composites are characterized by means of SEM, EDX, XRD, FT-IR and Raman spectroscopy, TGA, gas sorption analysis and laser diffraction, in order to verify the structure, morphology and composition of the materials. A procedure for the electrochemical activation of SiO2- and SiO2/C-based electrodes in Li half cells is devised to fully maximize their utility as a host material for Li-ions. The activated SiO2/C composite reversibly delivers delithiation capacities of ≈800 mAhg−1 at 50 mAg−1 and ≈450 mAhg−1 at 2000 mAg−1 in a LiPF6‑carbonate electrolyte. The properties of an electrochemically activated, algae-derived silica-based electrode (SiO2/C) is investigated in a full cell configuration using a commercially available LiNi0.4Mn0.4Co0.2O2 (NMC442) cathode material. Such a cell operates at an average discharge voltage of 3 V while delivering capacities up to ≈150 mAhg−1 (NMC), which translate into a specific energy density of ≈390 mWhg−1, based on the active materials.