Synthesis and electrochemical properties of Na-doped Li 3V 2(PO 4) 3 cathode materials for Li-ion batteries

• Published in: Journal of power sources Vol. 196; no. 23; pp. 10169 - 10175
• Main Authors: Kuang, Quan, Zhao, Yanming, Liang, Zhiyong
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 2011
• Subjects: Cathode materials; Li-ion batteries; Lithium vanadium phosphate; Na doping; Sol–gel method; Na doping; Sol–gel method; Cathode materials; Li-ion batteries; Lithium vanadium phosphate
• ISSN: 0378-7753; 1873-2755
• DOI: 10.1016/j.jpowsour.2011.08.044

► Li 3− x Na x V 2(PO 4) 3/C cathodes have been synthesized by using sol–gel method for the first time. ► The Na doping in Li site by Na would be favorable to expanding the lattices and enhancing the electronic conductivities. ► The short Li-Li distance and wide Li-O contact of Li 2.97Na 0.03V 2(PO 4) 3 improve Li-ion diffusion. ► The partial substitution of Li with Na ( x = 0.03) is favorable for rate performance and cyclic ability. Na-doped Li 3− x Na x V 2(PO 4) 3/C ( x = 0.00, 0.01, 0.03, and 0.05) compounds have been prepared by using sol–gel method. The Rietveld refinement results indicate that single-phase Li 3− x Na x V 2(PO 4) 3/C with monoclinic structure can be obtained. Among three Na-doped samples and the undoped one, Li 2.97Na 0.03V 2(PO 4) 3/C sample has the highest electronic conductivity of 6.74 × 10 −3 S cm −1. Although the initial specific capacities for all Na-doped samples have no much enhancement at the current rate of 0.2 C, both cycle performance and rate capability have been improved. At the 2.0 C rate, Li 2.97Na 0.03V 2(PO 4) 3/C presents the highest initial capacity of 118.9 mAh g −1 and 12% capacity loss after 80 cycles. The partial substitution of Li with Na ( x = 0.03) is favorable for electrochemical rate and cyclic ability due to the enlargement of Li 3V 2(PO 4) 3 unit cells, optimizing the particle size and morphology, as well as resulting in a higher electronic conductivity.