The Preparation And Electrochemical Property Research Of Germanium On Three-dimensional Nanostructured Copper Current Collector

Germanium has been investigated intensively for its high specific capacity, which make it a promising candidate anode for high energy lithium-ion batteries. Unfortunately, Ge also undergoes a huge volume expansion(370%) during lithiation, which leads to electrode pulverization. Therefore, severe capacity fade is generally observed for Ge-based anodes, it is not conducive to maintaining the stability of the battery capacity. Herein, the rational design of a germanium electrode with enhanced electrochemical performances is still a big challenge for the scientists around the world. The current collector with 3D structure can provide a buffer space for the volume expansion of Ge and to avoid shed off from the current collector during charging and discharging. In this paper, we investigate the electrochemical properties of different 3D germanium electrode which was made by electrodepositing germanium on diffrenrent 3D structure of copper current collector.In this paper, dendritic copper collector is prepared by plating firstly. Then germanium film were prepared by the method of ionic liquid electrodeposition on the copper collector. A Cu/Ge composite was investigated as an anode material for Li-ion batteries. The discharge and charge capacities of the Cu/Ge composite for the first cycle were 1700.6m Ah/g and 1171.3m Ah/g at the rate of C/10, respectively, which corresponded to an initial Coulombic Efficiency of 68.88%, After100 charge/discharge cycles, the electrode displayed a reversible capacity of 821.1m Ah/g and 856.1m Ah/g, indicative of a better cycling stability than commercial copper collector. At the same time the rate performance of dendritic copper collector has been significantly improved.Furthermore, 3D porous copper collector is prepared by electrochemical deposition with the template of hydrogen bubbles, the better parameters of 3D porous copper collector were obtained in this paper. And then germanium film was electrodeposited on the copper collector, after annealing with high temperature, a special 3D porous nanostructure Cu/Ge electrode with high specific surface area and conductivity was obtained. The discharge and charge capacities of the Cu/Ge composite for the first cycle were 1351.6m Ah/g and 1767.5m Ah/g at the rate of C/10, the initial Coulombic Efficiency was 76.47%. After100 charge/discharge cycles, the electrode displayed a reversible discharge capacity of 1260 m Ah/g, indicative of a better cycling stability. Even if the electrode was cycled at a very high rate of 5 C, a discharge capacity of 632.2m Ah /g was acquired. It holds excellent rate capability.At last, club-shaped copper collector was prepared by the method of ionic liquid electrodeposition. And cauliflower-like copper collector was prepared through changing the deposition potential in the ionic liquid. After the germanium film was electrodeposited on the copper collector, the Cu /Ge electrode with high stability and chemical resistance was obtained. We study the electrochemical properties of clubshaped copper collector, the pulverization of Cu /Ge electrode was serious due to the copper collector can not provide a buffer space for Ge during its charging and discharging. While the cauliflower-like copper collector made in the deposition potential of-1.4V show good electrochemical properties. The discharge capacities of the Cu/Ge composite for the first cycle were 1776.8m Ah/g at the rate of C/10, After100 charge/discharge cycles, the electrode still has discharge capacity of 655.6m Ah/g, the Cu /Ge electrode demonstrate a good cycling stability.