Sustainable synthesis of Penicillium-derived highly conductive carbon film as superior binder-free electrode of lithium ion batteries

Fungi (Penicillium chrysogenum) were used as green and sustainable sources to fabricate free-standing binder-free carbon film through pyrolysis in inert atmosphere. The fungi before and after carbonization were characterized with scanning electron microscope (SEM), Fourier transformed infrared spectroscopy (FTIR), electron microprobe (EM), and Raman spectrum. The results showed that the fungi were composed of ultra-long microfibers around 3 μm in diameter, which can be readily transformed into membrane precursor. Abundant functional groups were detected on fungi. The carbon membrane from the pyrolysis of membrane precursor was constructed by the uniformly interconnected fibers. After carbonization, the functional groups disappeared, while the product was doped by O and N atoms. The conductivity of carbon film was as high as 29.4 S cm−1. Moreover, the carbon film was successfully applied as low-cost electrode in lithium ion batteries (LIBs). The capacity of the LIBs maintained 207 mA h g−1 with 89.6 % capacity retention after 80 cycles.