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

• Carbon-coated V2O5 particles were synthesized in a scalable and easy method using carboxylic acids such as oxalic acid, tartaric acid, and citric acid as a carbon source.
• V2O5 particles prepared with citric acid were coated with uniform carbon layers of about 4-5 nm thick.
• The carbon-coated V2O5 particles prepared with citric acid showed enhanced capacity retention and rate capabilities.

Vanadium pentoxide (V2O5) 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 LiCoO2 (140 mA h g−1) and LiFePO4 (170 mA h g−1). However, practical applications of V2O5 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 V2O5 nanoparticles were synthesized by facile thermal decomposition of a soluble intermediate product, namely (NH4)(VO)(C6H5O7) from a reaction of NH4VO3 with citric acid (C6H8O7); citric acid was used as both a carbon source and a chelating/reducing agent. The highly crystalline V2O5 nanoparticles were coated with a carbon layer of thickness approximately 4–5 nm. The carbon-coated V2O5 nanoparticles had better electrochemical performances than those of V2O5 nanoparticles synthesized using tartaric acid (C4H6O6) or oxalic acid (C2H2O4), 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.

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