Fabricating ultralight and ultrathin copper current collectors for high-energy batteries

Improving cell-level gravimetric and volumetric energy density is essential to achieve high-performance batteries in the rapidly evolving field of energy storage technology, which requires consideration of all cell components. Traditional current collectors (CCs) made of metal foil, especially the copper (Cu) current collector of the anode, possess high mass and cost yet do not contribute to capacity. Reducing the weight of Cu CC with minimum thickness and desirable mechanical strength is critical in enhancing energy density but is technically challenging. Herein, we demonstrate a fast and scalable chemical coating method based on electroless plating for fabricating ultralight CC (∼1.72 mg cm−2) with a thin Cu layer (500 nm) on an ultrathin polyethylene (PE) polymer scaffold (5 μm). The ultralight and ultrathin CC possesses high metal purity, high mechanical strength, high thermal stability, and outstanding electrochemical performances in lithium-ion and lithium-metal battery systems. Our ultralight CC only exhibits ∼30% of the weight of 6 μm Cu foil, leading to a 5−10% improvement in cell-level gravimetric energy density without sacrificing volumetric energy density. Moreover, the simplicity and scalability of the chemical coating method make it a promising solution for the mass production of ultra-thin and lightweight current collectors.