Adopting porous current collector is one of the most effective approaches to suppress the dendrite growth in alkaline metal batteries. In this invention, a flexible, lightweight, porous, and electronically conductive metal@polymer composite material was successfully developed as the current collector for rechargeable alkaline metal batteries. This material is comprised of an electrospun polyimide (PI) polymer matrix coated with electrically conductive copper (Cu) film. To achieve a durable, uniform, and firm Cu coating on the electrospun PI matrix, a unique synthesis route was designed. PI matrix was first etched with potassium hydroxide solution to introduce potassium ions (K+) into the polymer backbone of PI. The K+ was substituted by silver ions (Ag+) via ion exchange, which were subsequently reduced to silver (Ag) nanoparticles on the surface of PI to yield the Ag@PI composite. Thereafter, the Ag@PI composite was plated with a Cu electroless plating solution, where Ag nanoparticles serve as the seed for Cu to deposit. The final electrically conductive Cu@PI composite material with three dimensional (3D) porous structure was thus obtained. The Cu@PI composite material exhibits good flexibility, low density, high porosity as well as excellent electronic conductivity, making it a highly attractive material for being used as the current collector in alkaline metal based batteries.