Facile Synthesis and Electrochemical Performance of Carbon-Coated V2O5 Cathode Materials Using Carboxylic Acids as Carbon Source

Abstract Vanadium pentoxide (V 2 O 5 ) with a layered structure is considered an attractive cathode material for lithium-ion batteries (LIBs) because of its low cost, abundance, and relatively high theoretical capacity (294 mA h g −1 with two lithium insertion/extractions per unit formula) as compared with more commonly used cathode materials such as LiCoO 2 (140 mA h g −1 ) and LiFePO 4 (170 mA h g −1 ). However, practical applications of V 2 O 5 are limited by its poor structural stability, low electrical conductivity, and slow electrochemical kinetics, leading to poor long-term cycling stability and rate performance. In this study, carbon-coated V 2 O 5 nanoparticles were synthesized by facile thermal decomposition of a soluble intermediate product, namely (NH 4 )(VO)(C 6 H 5 O 7 ) from a reaction of NH 4 VO 3 with citric acid (C 6 H 8 O 7 ); citric acid was used as both a carbon source and a chelating/reducing agent. The highly crystalline V 2 O 5 nanoparticles were coated with a carbon layer of thickness approximately 4–5 nm. The carbon-coated V 2 O 5 nanoparticles had better electrochemical performances than those of V 2 O 5 nanoparticles synthesized using tartaric acid (C 4 H 6 O 6 ) or oxalic acid (C 2 H 2 O 4 ), which are commonly used as reducing agents. They exhibited a high initial discharge capacity of 293 mA h g −1 between 2.1 and 4.0 V at a rate of 0.1 C, and good capacity retention of 90% after 30 cycles. At high current densities of 0.5–5 C, excellent rate capabilities and cycling stabilities were achieved.