Abstract
The preparation of binder and carbon-free electrodes is of great interest owing to higher energy density. In this scope, electrodeposition is a suitable method that can be easily scale up providing that suitable chemical reactants are used. In this work, we used highly soluble Sn precursor based on TFSI counter ion dissolved in [EMIm + ][TFSI-] ionic liquid. The use of similar anionic groups in both Sn precursor and solvent allowed to avoid impurities typically encoureted when using Sn chloride precursor. The resulting solution was characterized by cyclic voltametry using either inert (Mo) and reactive substrate (Cu). In both cases, the electrodeposition occured in a diffusion controlled process. In the case of Cu, however, a Cu-Sn alloy that is η-Cu6Sn5 phase was identified. A FIB cross section revealed that Cu and Sn interdiffused and that no epitaxial growth occured. Prolonging the electrodeposition time favored the formation of β-Sn because Cu could no longer diffuse within the deposited structure. This resulted in a mixed β-Sn/η-Cu6Sn5 composite whose proportions depended on the deposition duration time. The deposited samples were directly assembled in lithium coin cells to characterize the capacity and cyclability of binder and carbon-free electrodes. Increasing the mass of deposited sample degraded the capacity and reversility of the system which was explained by a lower ability to accommodate the volume variation occurring during the electrochemical lithiation/delithiation process.