In this work, Li2NaV2(PO4)(3) is successfully synthesized by using a simple solid-state reaction method. Structural analysis shows that this sample is a hybrid product consisted of rhombohedral Li3V2(PO4)(3) phase and rhombohedral Na3V2(PO4)(3) phase As a cathode material for lithium ion batteries, Li2NaV2(PO4)(3) exhibits an initial reversible capacity of 108.9 mAh g(-1) at 35 mA g(-1) in the potential range between 3.0 and 4.3 V, with an average working potential at 3.75 V. The lithium-ion diffusion coefficient in Li2NaV2(PO4)(3) is measured to be 1.86-3.27 x 10(-15) cm(2) s(-1). In addition, the electrochemical reaction between Li2NaV2(PO4)(3) and Li is also investigated by various in-situ and ex-situ techniques. Viewed from the in-situ and ex-situ results, it is concluded that the electrochemical reactions of Li2NaV2(PO4)(3) with Li are associated with the formation of rhombohedral LiV2(PO4)(3) phase and rhombohedral NaV2(PO4)(3) phase during the lithium ion extraction process and its reverse lithium insertion process is reversible for structural evolution. The highly stable structure ensures the electrochemical reversibility of Li2NaV2(PO4)(3) cathode material in lithium ion batteries. (C) 2015 Elsevier Ltd. All rights reserved.