Electroless Copper Plating on Polyimide Using Environmentally Friendly Glyoxylic Acid for PI@Cu Composite Current Collectors

Due to the requirements of high energy density and safety in lithium‐ion batteries, the development of composite current collectors is highlydesirable. Polyimide (PI) that possesses excellent thermal stability, mechanical properties, intrinsic flame retardancy, and chemical stability is a highly promising substrate material for high‐performance composite current collectors. Generally, physical vapor deposition, electroplating technology, and electroless plating are employed to complete surface metallization on the PI surface. Among them, the electroless plating does not require an external power source, but typically involves the use of formaldehyde, which poses environmental and safety risks. Herein, we employ environmentally friendly glyoxylic acid as a substitute for formaldehyde. Through optimizing the electroless plating processes, high‐quality PI@Cu composite film is obtained with low sheet resistance of 7.54 mΩ sq –1 , high bonding strength between PI and copper layer, and favorable wettability for electrode slurry. The introduction of PI@Cu composite current collector into lithium‐ion battery leads to significant initial capacity of 362.5 mAh g –1 , representing an improvement of 3.3 mAh g –1 compared to a conventional copper foil current collector. The energy density of the electrode using the PI@Cu composite current collector has increased to 197% in contrast with that of Cu foil current collector.