A high-rate cathode material based on potassium-doped Na3V2(PO4)3 for high/low-temperature sodium-ion batteries

Abstract

Na3V2(PO4)3, with its three-dimensional NASICON structure and an excellent reversible capacity, is one of the most promising cathode materials for sodium-ion batteries. To overcome the poor rate performance of the Na3V2(PO4)3 electrode caused by the structural damage during Na ion insertion/extraction at low-temperature, an appropriate amount of K ions has been doped into Na3V2(PO4)3 by a rational design to enlarge the unit cell volume, which broadens the Na ion migration channel and ensures a significant improvement in the rate performance of the Na3V2(PO4)3 electrode under all-climate (−25 °C–40 °C). The results indicate that the as-prepared Na3-xKxV2(PO4)3 not only provides rapid molecular dynamics of sodium ions but also improves the structural stability. A remarkable electrochemical performance of the Na2.95K0.05V2(PO4)3 cathode electrode can be obtained even at high current densities (a reversible capacity 80.2 mAh/g at 100 C with a temperature of 40 °C). Moreover, Na2.95K0.05V2(PO4)3 can still maintain a capacity of 72 mAh/g at 2 C under a low temperature of −25 °C, while the undoped Na3V2(PO4)3 has almost no capacity. This article provides a promising strategy to cope with the long-standing inherent all-climate issues of sodium ion batteries and broaden the application of rechargeable batteries.