K2Nb8O21 nanotubes with superior electrochemical performance for ultrastable lithium storage

High-performance lithium-ion batteries are important for developing sustainable energy. However, there is a shortage of advanced energy storage materials. K2Nb8O21 is a novel material for lithium storage which has not been investigated systematically. In this work, K2Nb8O21 nanotubes and microtubes were prepared facilely using electrospinning under different conditions. As an anode host, K2Nb8O21 nanotubes showed better long-term cycling, superior rate performance, and higher structural stability compared with microtubes. Electrochemical results showed that K2Nb8O21 nanotubes delivered a considerable lithium storage capacity of 213 mA h g(-1) after 5000 cycles at 1000 mA g(-1) with outstanding capacity retention of 80.3%. The nano/micro structured host could increase Li-ion transport to render high-rate capability and excellent cycling stability. In situ XRD, ex situ XPS and ex situ TEM revealed K2Nb8O21 nanotubes had high structural stability and reversibility as lithium storage anode materials. All of these advantages suggest that K2Nb8O21 nanotubes may be promising anode material for lithium-ion batteries.