A Zero-Strain P2-Layered Na0.66[Li0.22Ti0.78]O2 As New Anode Material for Room-Temperature Sodium-Ion Batteries

Abstract

Room-temperature sodium storage technology has attracted more and more interest in the electrical energy storage field, particularly for large-scale applications in renewable solar and wind power as well as smart grid. However, the development of suitable anode materials remains a big challenging issue for long-life sodium-ion batteries. In this presentation, we will introduce a new “zero-strain” anode, Na0.66[Li0.22Ti0.78]O2 with P2-layered structure, as a promising material for room-temperature long-life sodium-ion batteries. There are several significantly important results obtained in this work: the reversible capacity is ca. 110 mAh/g; the average sodium storage voltage is ca. 0.75 V; the volume change during sodium insertion and extraction is only 0.77%, showing the “zero-strain” characteristics; the material exhibits very long cycling performance, over 1200 cycles with a capacity retention of 75%; the measured apparent Na+ ion diffusion coefficient is ca. 1x10-10 cm2/s. It is also very interesting to find that the final discharge product is actually a mixture of several phases which also retain the P2-structure confirmed by in situ and ex situXRD. The difference in these several P2-phases lies in different sodium composition and occupation (2b, 2d) in the alkali layer. This contribution demonstrates that P2-Na0.66[Li0.22Ti0.78]O2is a promising anode material for the development of rechargeable long-life sodium-ion batteries.