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/SnO2/carbon (PSC/SnO2/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 SnO2 and carbon ensures the stability of the structure. As a result, the PSC/SnO2/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.