Characterization of cobalt monoxide thin film modified with silicon dioxide prepared by the cathodic deposition for lithium-ion battery

• The growth of CoO grain size was inhibited by SiO2 within CoO thin film.
• The capacity activation rate of CoO was effectively promoted by SiO2.
• The CoO capacity fading was significantly decreased for CoO modified by SiO2.
• The maximum capacity of CoO modified with SiO2 was 1583 mAh/g.

The precursor (cobalt hydroxide, Co(OH)2) of cobalt oxide (CoO) is cathodically electrodeposited on copper foil in cobalt nitrate and sodium nitrated aqueous solution. CoO can be obtained by calcinating Co(OH)2 for the temperature greater than 500 °C in N2 atmosphere. For the preparation of Co(OH)2 in the presence of silicon rubber as the sealant to define the electrodepositing area, some co-deposited components dissolved from silicon rubber are converted to SiO2 in the calcination process. The charge/discharge performances of CoO thin film are enhanced by the presence of SiO2. When the TEOS (tetraethyl orthosilicate) is added into the solution for electrodepositing the precursor of CoO at pH 3.30–3.14, the grain size of CoO decreases from 33.47 to 8.85 nm by increasing the concentration of TEOS from 0 to 0.005 M. When 0.01 M TEOS is added to prepare the precursor of CoO, the irreversible discharge capacity at the first cycle can be completely recovered in the activation period with the activation rate of 16.50 mAh/g cycle, and the capacity fading fraction at 80th cycle is found to be 16.7%.