K2Nb8O21 nanotubes with superior electrochemical performance for ultrastable lithium storage

Abstract

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.