66 / 2021-06-30 11:27:41

Effect of electrolyte concentration and discharge voltage on the electrochemical performance of TiO2/SiO2 anode prepared by PEO

Ti foil; plasma electrolytic oxidation; electrolyte concentration; discharge voltage; lithium ion battery anode

Abstract: The electrolyte concentration and discharge voltage are critical parameters  of plasma electrolytic oxidation (PEO) technology. In this paper, PEO was employed to prepare a TiO₂/SiO₂ composite film on Ti foil by one-step process. The composite films with different SiO₂ contents were obtained by adjusting the concentration of Na₂SiO₃ in the electrolyte and the discharge voltage. The composite films were used as the anode of the lithium-ion batteries (LIBs) and a Li foil was used as the counter electrode. The capacity, rate capability, cycling stability, cyclic voltammetry curves and electrochemical impedance spectra were measured by the battery test system and electrochemical workstation. The results showed that the capacity of the TiO₂/SiO₂ composite film anode prepared in the electrolyte with the mass ratio of KOH to Na₂SiO₃ of 1:6 at the discharge voltage of 450 V was about 200 mAh g^-1 under a current density of 100 μA/cm² after 100 cycles, while in the electrolyte with the KOH:Na₂SiO₃=1:9, the measured capacity can reach 400 mAh g^-1. When the concentration of Na₂SiO₃ was increased to KOH:Na₂SiO₃=1:12, the discharge voltage was adjusted to 420 V accordingly, and the measured capacity was about 300 mAh g^-1. The high capacity should be ascribed to the SiO₂ generated by the decomposition of Na₂SiO₃, and TiO₂ mainly played the role of supporting carrier to buffer the volume change of SiO₂ during lithiation process. The high discharge voltage could promote the decomposition of Na₂SiO₃, so as to significantly increase the battery capacity. However, at the low discharge voltage, even if the concentration of Na₂SiO₃ was greatly increased, the capacity of the battery was improved with a limited extent. In addition, the three composite films showed the typical Li-TiO₂ and Li-SiO₂ redox peaks in the cyclic voltammograms. After cycling under a high current density of 800 μA/cm2, the composite films presented the reversible capacities with the good rate performance.