Self-doped V4+–V2O5 nanoflake for 2 Li-ion intercalation with enhanced rate and cycling performance

Abstract Orthorhombic V 2 O 5 has been considered as one of the most promising cathode materials for new lithium ion batteries (LIBs) due to its high specific capacity, easy synthesis and good safety. However, the poor rate and cycling performance of V 2 O 5 electrodes significantly impede their applications in high-power and long-life LIBs. The present work reports facile synthesis of self-doped V 4+ –V 2 O 5 nanoflakes through combusting the NH 4 V 4 O 10 and VO 2 (B) mixture in the presence of 2-ethylimidazole. The resulting V 4+ –V 2 O 5 exhibited superior rate capability (a reversible capacity of 293, 268, 234, 214, 196 and 139 mA h g −1 at 100, 300, 600, 1000, 2000 and 4000 mA g −1 , respectively) and remarkable cycling performance (95% capacity retention after 100 discharge/charge cycles at 2000 mA g −1 ). The outstanding performance is derived from the uniform nanoflake structure, which offers more surface area and reaction sites for lithium ion intercalation, and the presence of tetravalent vanadium ions accompanied with oxygen vacancies, which might promote and catalyze the electrochemical reactions at the surface, in addition to improve the intrinsic electrical conductivity and Li ion diffusion coefficient, as reflected by the smaller polarization and more reversible and easier phase transitions than those of V 2 O 5 without detectable V 4+ and oxygen vacancies.