Carbon coating and oxygen vacancies modulated WNb12O33 for high-efficient lithium-ion storage

Niobium tungsten oxides possess Wadsley-Roth phase with 3D open tunnel structures and multiple reversible redox (W6+/W5+, Nb5+/Nb4+, Nb4+/Nb3+), which have been explored in the field of electrochemical energy storage devices because of fast ion exchange and high cycling stability. However, the restricted ion diffusivity and poor intrinsic conductivity hinder their application in the devices with high-power output and long lifespan. This study presents a selenization method with high performance WNb12O33@N-C co-modified by oxygen vacancies and carbon coating. The oxygen vacancies resulting from nitrogen-doped carbon layer in WNb12O33 provide additional active sites for electrochemical reactions in addition to improving the electric conductivity and electrochemical kinetics. Meanwhile, the carbon layer can accelerate electric conductivity and structure stability simultaneously. The common effect of oxygen vacancies and carbon layer improve the ion transport and electronic conductivity of the materials. Accordingly, WNb12O33@N-C exhibits excellent cycling stability (81.4 % capacity retention at 5 A/g after 1000 cycles), and superior rate capacity (158 mAh/g at 10 A/g). This work could be considered as a substantial approach for practical implementation of niobium-based oxides toward nextgeneration lithium-ion batteries (LIBs).