Polyurethane sponge-derived nitrogen-doped carbon-encapsulation composite for enhanced lithium-ion battery performances

Surface coating is an efficient strategy for interfacial modification and functionalization to boost the physical and chemical properties of materials, especially in energy conversion storage and catalysis. Herein, a robust strategy toward nitrogen (N)-doped carbonaceous coating was developed through hydrothermal treatment of polyurethane (PU) sponge. Small molecules originated from the pyrolysis of PU sponge would reassemble and polymerize again, which not only can realize surface-adherent coating for different types of materials from 3D bulk structure to tiny nanoparticles with a controllable thickness, but also obtain well-defined carbon materials with hollow structure through self-template method. What is more, N atoms can be in-situ introduced during hydrothermal procedure owning to the nitrogen-rich in PU sponge. As a proof of concept, the prepared N-doped carbon encapsulated Fe3O4 (Fe3O4@N-C) composite manifested excellent lithium storage properties with stable cycling performance and rate capability. The capacity of 714.8 mA h g−1 could be obtained after 200 cycles at current density of 500 mA g−1. Indeed, our results described here not only can provide an easy surface engineering technique so as to design N-doped carbon-encapsulation composite, but also provide an eco-friendly and efficient way to make better use of PU sponge.