The conductivity of Nb2O5 enhanced by the triple effect of fluorine doping, oxygen vacancy, and carbon modification for improving the lithium storage performance

In view of the inherent pseudocapacitance, rich redox pairs (Nb 5+ /Nb 4+ and Nb 4+ /Nb 3+ ), and high lithiation potential (1.0–3.0 V vs Li/Li + ), Nb 2 O 5 is considered a promising anode material. However, the inherent low electronic conductivity of Nb 2 O 5 limits its lithium storage performance, and the rate performance after carbon modification is still unsatisfactory because the intrinsic conductivity of Nb 2 O 5 has not been substantially improved. In this experiment, taking the improvement of the intrinsic electrical conductivity of Nb 2 O 5 as the guiding ideology, we prepared F-doped Nb 2 O 5 @fluorocarbon composites (F–Nb 2 O 5 @FC) with a large number of oxygen vacancies by one-step annealing. As the anode electrode of lithium-ion batteries, the reversible specific capacity of F–Nb 2 O 5 @FC reaches 150 mA g −1 at 5 A g −1 after 1100 cycles, and the rate performance is particularly outstanding, with a capacity up to 130 mA g −1 at 16 A g −1 , which is far superior to other Nb 2 O 5 @carbon-based anode electrodes. Compared with other single conductivity sources of Nb 2 O 5 @carbon-based composites, the electrical conductivity of F–Nb 2 O 5 @FC composites is greatly improved in many aspects, including the introduction of free electrons by F − doping, the generation of oxygen vacancies, and the provision of a three-dimensional conductive network by FC. Through analytical chemistry (work function, UV–Vis diffuse reflectance spectroscopy, and EIS) and theoretical calculations, it is proved that F–Nb 2 O 5 @FC has high electrical conductivity and realizes rapid electron transfer.