High Strength Nanotwinned Copper foils for PCB and Current Collectors in Lithium Ion Battery

Abstract

The demand for high density energy storage devices in electronic products is increasing. The application of various wearable devices in medical treatment, health management and promotion of convenience in life is also gradually emerging, which also requires high-performance power storage components. In addition, the various electric vehicles (including electric bicycles, electric motorcycles, electric cars) also have an urgent demand for high energy density batteries. High energy density means that with limited battery weight and battery volume, the mileage traveled after a single charge can be higher. For electric vehicles, the mastery of battery technology is extremely critical. In this study, we use a new type of electroplated nanotwinned copper foil as the negative electrode for current collectors. The electroplated nanotwinned copper foil has higher mechanical strength than the regular copped foil and also the ductility can be maintained within an acceptable range. By using electroplated nanotwinned copper foil in batteries, we can reduce the thickness, weight and volume comparing to the regular copper foil. After reducing its volume, the remaining space can be filled with more positive and negative electrode active materials. Finally, we can increase the overall weight energy density and volume energy density of the batteries. Recently, we have successfully electroplated nanotwinned copper foils with a titanium wheel, and their ultimate tensile strength can reach up to over 800 MPa. The conductivity of nanotwinned copper foil can reach more than 90% IACS (International Annealing Copper Standard). By changing electroplating parameters, we can control the mechanical properties of our nanotwinned copper foil to meet the needs for lithium ION batteries. The lifetime of lithium batteries is another serious issue. During the process of charging and discharging, the electrode substrate suffers from a volume change and mechanical stress. After several times of charging and discharging, cracks can be observed on the surface of the normal copper electrode substrate. Because of the high tensile strength of electroplated nanotwinned copper, when we use it as the electrode substrate it can stand the volume change and mechanical strength during charging and discharging cycle. Nanotwinned copper foil with high mechanical strength and conductivity not only enhance the weight energy density and volume energy density of the battery, it also solves the reliability issue during the charge and discharge cycle.