Uniform lithium deposition induced by copper phthalocyanine additive for durable lithium anode in lithium-sulfur batteries

Abstract

Copper phthalocyanine (CuPc) is adopted as an electrolyte additive to stabilize lithium anode for lithium-sulfur (Li-S) batteries. CuPc with a planar molecular structure and lithiophilic N-containing group, is likely to be adsorbed on the surface of Li anode to form a coating layer, which can restrict the direct contact between Li anode and solvents, and guide the uniform deposition of Li+ ions. The Li||Li symmetric cells demonstrate a stable cycle performance, and Li||Cu cells show high Coulombic efficiencies. In Li-S batteries, the formed stable solid-electrolyte interface (SEI) film containing copper sulfides can protect Li anode from the polysulfide corrosion and side reactions with the electrolyte, leading to the compact and smooth surface morphology of Li anode. Therefore, the Li-S batteries with CuPc additive deliver much higher capacity, better cycle performance and rate capability as compared to the one without CuPc additive.