Electrodeposition of copper-tin nanowires on Ti foils for rechargeable lithium micro-batteries with high energy density

摘要

We report the optimized fabrication of copper-tin material in the form of nanowires perpendicular to the current collector with diameters ranging between 80 and 100 nm and 2 μm length via an electrochemical deposition process. This approach aims to validate fabrication of thin films containing nanoparticles by taking the advantage of using an additive-free route for potential application in 3D-Li micro-batteries. We have analyzed the importance of controlling pure phases to obtain a high first cycle reversibility in a series of Cu_6Sn_5-based films. The capacity is retained during a large number of cycles. In particular, a stable gravimetric capacity of 295 μA h g~(-1) or 70 μA h cm~(-2) areal capacity over 100 cycles is obtained for η'-Cu_6Sn_5 under 50 μA cm~(-2) rate. This behavior is mostly ascribable to the electrode nano-architec-ture and phase composition even though Cu content in the film decreased specific capacity. On decreas ing the nanowire size, the surface energy increases, thus minimizing particle agglomeration and volume variations in the Li-Sn alloy.