dimethyl formamide and 20 g of polyacrylonitrile were added into a mixer and stirred to obtain a clear polymer solution the polymer solution was added into the barrel of an electrospinning device the collector was a copper plate the nozzles and the barrel were heated with a heating band to maintain the temperature of the polymer solution at 90 u00b0 c a voltage of 10 kv was applied to the nozzles to discharge the polymer solution onto the collector from a predetermined height and at a predetermined discharge rate thereby obtaining a polymer web being about 90 u03bcm thick the polymer web was processed into a carbon web through an oxidization furnace and a carbonization furnace 20 g of dimethylacetamide and 60 g of acetone were added into a mixer after adding 20 g of polyacrylonitrile the mixture was stirred to obtain a clear polymer solution the polymer solution was added into the barrel of an electrospinning device the height from the nozzles to the collector was 20 cm a voltage of 18 kv was applied to the nozzles to discharge the polymer solution onto the collector at a predetermined discharge rate a high porosity polymer web having a thickness of about 30 u03bcm was isolated from the collector the porous polymer web thus obtained.