Growth of single-crystal copper sulfide thin films via electrodeposition in ionic liquid media for lithium ion batteries

By exploiting the ability of ionic liquids to solubilize molecular sulfur at the melting point, we report the electrodeposition of CuS in an [EMIm]TFSI (1-ethyl-3-methylimidazolium bis (trifluoromethanesulfonyl) imide) electrolytic bath containing Cu(TFSI)2 salt and elemental sulfur. Single-crystal and preferentially oriented covellite CuS thin films with flake morphology have been successfully obtained. Li/CuS coin cells using the deposits after carbon coating as the positive electrode show a discharge capacity of 350 mA h g−1 with capacity retention of 54.4% after 20 cycles.