Bio-enzymatic synthesis of nitrogen-doped porous carbon/SnO2/carbon microspheres as high-performance composite materials for lithium-ion and sodium-ion batteries

In this study, a nitrogen-doped 3D porous starch-derived carbon/SnO 2 /carbon (PSC/SnO 2 /C) composite is synthesized with porous starch as a carbon source by biological enzymatic hydrolysis . Compared with the traditional complex acid-base reagent method, the biological enzymatic method is more environmentally friendly and economical, and it can also naturally introduce nitrogen sources and dope the carbon layer . Many mesoporous nanostructures provide enough buffer space and promote the ions' and electrons’ transmission rate. The formation of the Sn– O –C bond between SnO 2 and carbon ensures the stability of the structure. As a result, the PSC/SnO 2 /C composite exhibits a high initial discharge capacity (1802 mAhg −1 at 0.2 A g −1 for LIBs and 549 mAh g −1 at 0.1 A g −1 for SIBs) and good cycle stability (701 mAh g −1 at 0.2 A g −1 after 100 cycles for LIBs and 271 mAh g −1 at 0.1 A g −1 after 100 cycles for SIBs). This synthesis method can prepare other energy storage systems such as fuel cells, supercapacitors , and metal ion batteries .