Size Effects in the Electrochemical Alloying and Cycling of Electrodeposited Aluminum with Lithium

The electrochemical alloying and cycling of electrodeposited aluminum films, electron-beam deposited aluminum films, and template-synthesized aluminum nanorods with lithium is presented here. Electrodeposition of aluminum is performed at room temperature using ionic liquid solutions and is shown to exhibit high faradaic efficiency. To study the dependence of lithium-aluminum cycling on size, the thickness of these films is varied between 0.25 μm and 6.2 μm by varying the electrodeposition time. Electrochemical alloying and de-alloying of these films with lithium is observed in lithium half-cells at room temperature. The films reach theoretical capacity for the formation of LiAl (1 Ah g −1 ). The performance of electrodeposited aluminum films is dependent on film thickness, and the thinnest films exhibit the worst cycling behavior. Cycling of aluminum films formed by electron-beam deposition is in quantitative agreement with that of films formed by electrodeposition, and the two types of films have a similar appearance in SEM images taken after cycling. Synthesis of aluminum nanorod arrays on stainless steel substrates is also demonstrated using electrodeposition into anodic aluminum oxide templates followed by template dissolution. Unlike nanostructures of other lithium-alloying materials, the electrochemical performance of these aluminum nanorod arrays is worse than that of bulk aluminum.