Synthesis and Electrochemical Characterization of Nickel Germanate as an Electrode Material for Lithium-Ion Batteries

Here, we report on a study of nickel germanate formation in the Ni(OH)₂-GeO₂ system under solid-phase synthesis conditions in the 500-800°C temperature range and on the research of electrochemical performance of Ni₂GeO₄-based electrodes. It is shown that the Ni₂GeO₄ formation occurred at temperatures around 700°C, and the process began with the melting of the nonautonomous phase GeO₂ at T_m2n = 725 ± 112°C. The nickel germanate-based electrodes showed a rapid decrease in capacity over 40 cycles. However, starting from the 80^th cycle, a gradual increase in capacity was observed from 190 to 528 mAh/g at the 270^th cycle. We attribute this increase in capacity to evolution in the specific surface area and porosity of the electrode material during long-term cycling.