Composite capillary carbon tube Nb₁₈W₁₆O₉₃ as advanced anode material for aqueous ion capacitors

Abstract

Niobium-tungsten bimetal oxides have received wide attention due to their excellent lattice properties. In this work, Nb18W16O93 (NbWO) with a tetragonal tungsten bronze structure was synthesized by simple hydrothermal method. NbWO was modified to provide high specific surface area via combining with hollow carbon nanotubes. Meanwhile, NbWO grows along the tube wall of carbon nanotubes, thus buffering the volume effect of NbWO particles. Also, the migration distance of Li-ion is effectively shortened, as well as the improved ion transfer efficiency and the reaction kinetics. In addition, carbon tube can enhance conductivity of NbWO, contributing to outstanding charge storage capacity and rate energy. Precisely, NbWO@C as electrode possesses large specific capacity (249.6 F g-1 at 0.5 A g-1) and good rate performance (55.9 % capacity retention from 0.5 A g-1 to 2 A g-1). The aqueous Li-ion capacitor presents the advantages of high safety, low cost and good environmental friendliness. An asymmetric aqueous capacitor AC//NbWO@C, based on "water-in-salt" electrolyte with high concentration lithium acetate, exhibits a large energy density of 43.2Wh kg-1 and a power density of 9 kW kg-1. Generally, NbWO@C as anode materials shows superior application perspective.

Defect chemistry and physics in functional nanomaterials

“…The development of electrochemical energy storage devices has opened up a new avenue to address the energy crisis, and materials with defective structures provide distinct advantages. Chen et al [4] discovered that Nb 18 W 16 O 93 @C exhibits excellent electrochemical properties, including notable charge storage capacity, rate capability, and cycling performance, indicating its potential for promising applications. Heteroatoms can induce defects in carbon tubes, which contribute to enhancing pseudocapacitance.…”

Significantly enhanced supercapacitor performance of W3Nb14O44 by introducing serine and histidine-functionalized and boron-doped graphene quantum dots

“…The hybrid method introduces a conductive carbon material, such as carbon nanotubes, to the construction of a niobium tungsten oxide–based composite, 13 which can enhance the electronic conductivity and improve rate capacity. 17 However, a huge interface resistance considerably restricts the high-speed electron transfer between the niobium tungsten oxide nanocrystal and the carbon material. In fact, introducing the carbon material primarily improves the electronic conductivity of the environment surrounding the niobium tungsten oxide nanocrystal rather than the inherent electronic conductivity of the niobium tungsten oxide nanocrystal.…”