3 V Cu–Al Rechargeable Battery Enabled by Highly Concentrated Aprotic Electrolyte

Cu and Al foils are commonly used in lithium-ion batteries as current collectors. They are inactive and do not participate in the charge–discharge reactions but take up resources and space within a cell. Herein, we demonstrate a proof of concept to turn the Cu and Al foils into active materials by constructing a Cu–Al full cell, with Cu undergoing stripping/deposition reactions at the cathode and Al alloying with lithium at the anode. Stable cycle performance is possible with the use of a highly concentrated electrolyte; a 3 V cell exhibits excellent cycle stability for more than 200 cycles in 6 M LiTFSI DMC electrolyte. Our Cu–Al battery can give a volumetric energy density in the range 79–156 Wh L^–1, comparable to that of state-of-the-art all-vanadium redox-flow batteries. The use of inexpensive Cu and Al as active materials can also potentially reduce the cost of energy storage.