Ion beam-mixed Ge electrodes for high capacity Li rechargeable batteries

Ion beam modification to effect ion beam mixing without changing morphology was investigated as a means to improve the electrochemical performance of Ge thin film electrodes for rechargeable Li batteries. As a result of a minimum tenfold increase in the strength of adhesion of the Ge film to the current collector (substrate), the ion beam-mixed electrodes exhibited stable specific capacities of ∼1500 mAh g ^-1 (close to the theoretical maximum of 1623 mAh g ^-1) for galvanostatic cycling rates of 0.2C-1.6C using both single- and multi-rate testing schemes. Electron microscopy investigations showed that the ion beam-mixed electrodes transform from a flat, continuous, nonporous microstructure in the virgin state to a rough, cracked, porous microstructure as a result of electrochemical cycling, but remain in excellent electrical contact with the current collector. The results suggest that ion beam mixing could be used to produce inexpensive, high capacity conversion electrodes for rechargeable Li batteries.