Rational design of germanium–copper based nanocomposite anodes for high-performance lithium-ion storage

Abstract

The rising energy demand in the 21st century has necessitated a shift from fossil fuels to irregular renewable sources for carbon neutrality. Therefore, energy-storage systems are crucial for storing intermittently produced energy. Electric vehicles (EVs), which are expected to replace internal combustion engines, are in high demand for achieving carbon neutrality. The development of efficient secondary batteries (such as lithium-ion batteries; LIBs) is vital for increasing the energy-storage capacity and driving range of EVs. Currently, the most commercialized carbon-based anode material has a capacity of 372 mAh g-1. However, this capacity is insufficient to produce the high-capacity batteries required in the current market. Therefore, in this study, GeO2, which can store 8.4 lithium atoms in one molecule, was selected as the target material. To enhance its electrochemical properties, conductive Cu and C were introduced into GeO2. The composites were synthesized via high-energy ball milling, a simple and easy method to scale up. Three types of GeO2/Cu@C composites, GeO2/Cu@C (10, 20, and 30wt%), were prepared by varying the carbon content. Among them, GeO2/Cu@C (20wt%) exhibited an average reversible capacity of 660.6 mAh g-1 after 200 cycles, with a capacity retention of 75.4% at a current density of 0.1Ag-1. Even at a high current density of 0.5Ag-1, its average capacity and capacity retention were 672.3 mAh g-1 and 99.5%, respectively, after 100 cycles. Moreover, galvanostatic intermittent titration technique analysis revealed that the Li+ diffusion coefficient of GeO2/Cu@C (20wt%) was higher than those of the other electrodes. The full-cell with the NCM622 cathode exhibited a high energy density of 284.9Whkg-1. Therefore, the GeO2/Cu@C (20wt%) electrode is anticipated to be a potential anode for long-term LIB cycling.