Novel N-doped carbon encapsulation of nanoFe3O4 to improve electrochemical properties of lithium ion battery

To solve the volume expansion problem of Fe 3 O 4 nanoparticles (nmFe 3 O 4 ), a facile, green, and industrializable preparation of N-doped carbon–encapsulated nmFe 3 O 4 (nmFe 3 O 4 @N-doped C) is designed. This nmFe 3 O 4 @N-doped C is prepared through pyrolysis in nitrogen atmosphere of nmFe 3 O 4 encapsulated by polyaniline (PANI@nmFe 3 O 4 ) which is obtained through oxidative polymerization of aniline on the surface of nmFe 3 O 4 . In comparison with the capacity (113 mAh g −1 at 0.1C) of nmFe 3 O 4 , the nmFe 3 O 4 @N-doped C electrode exhibits a high reversible capacity of 400 mAh g −1 after 500 cycles. Even at 4C, the nmFe 3 O 4 @N-doped C electrode presents 160 mAh g −1 capacity, which is much higher than 30 mAh g −1 of the nmFe 3 O 4 electrode. The results suggest that the N-doped carbon shell layer obtained from PANI is effective to inhibit volume expansion of nmFe 3 O 4 core and maintain the electron and ion transport channels after long cycles.